drop the SG library completely.

8 files changed, 3 insertions, 51973 deletions

diff --git a/src/runtime/c/Makefile.am b/src/runtime/c/Makefile.am
index adec93e6d..0da14d204 100644
--- a/src/runtime/c/Makefile.am
+++ b/src/runtime/c/Makefile.am
@@ -1,7 +1,7 @@
-lib_LTLIBRARIES = libgu.la libpgf.la libsg.la
+lib_LTLIBRARIES = libgu.la libpgf.la
 
 pkgconfigdir = $(libdir)/pkgconfig
-pkgconfig_DATA = libgu.pc libpgf.pc libsg.pc
+pkgconfig_DATA = libgu.pc libpgf.pc
 
 configincludedir = $(libdir)/libgu/include
 
@@ -37,10 +37,6 @@ pgfinclude_HEADERS = \
 	pgf/pgf.h \
 	pgf/data.h
 
-sgincludedir=$(includedir)/sg
-sginclude_HEADERS = \
-	sg/sg.h
-
 libgu_la_SOURCES = \
 	gu/assert.c \
 	gu/bits.c \
@@ -92,12 +88,6 @@ libpgf_la_SOURCES = \
 libpgf_la_LDFLAGS = -no-undefined
 libpgf_la_LIBADD = libgu.la
 
-libsg_la_SOURCES = \
-	sg/sqlite3Btree.c \
-	sg/sg.c
-libsg_la_LDFLAGS = -no-undefined
-libsg_la_LIBADD = libgu.la libpgf.la
-
 bin_PROGRAMS =
 
 AUTOMAKE_OPTIONS = foreign subdir-objects dist-bzip2
@@ -105,5 +95,4 @@ ACLOCAL_AMFLAGS = -I m4
 
 EXTRA_DIST = \
 	libgu.pc.in \
-	libpgf.pc.in \
-	libsg.pc.in
+	libpgf.pc.in
diff --git a/src/runtime/c/configure.ac b/src/runtime/c/configure.ac
index f52479a5b..d8e55c164 100644
--- a/src/runtime/c/configure.ac
+++ b/src/runtime/c/configure.ac
@@ -58,7 +58,6 @@ AC_CONFIG_LINKS(pgf/lightning/asm.h:$cpu_dir/asm.h			dnl
 AC_CONFIG_FILES([Makefile
 	         libgu.pc
 		 libpgf.pc
-		 libsg.pc
 		 ])
 
 AC_OUTPUT
diff --git a/src/runtime/c/pgf/expr.c b/src/runtime/c/pgf/expr.c
index 92e92f04f..8580035b2 100644
--- a/src/runtime/c/pgf/expr.c
+++ b/src/runtime/c/pgf/expr.c
@@ -918,94 +918,6 @@ pgf_read_expr(GuIn* in, GuPool* pool, GuPool* tmp_pool, GuExn* err)
 	return expr;
 }
 
-PGF_API int
-pgf_read_expr_tuple(GuIn* in,
-                    size_t n_exprs, PgfExpr exprs[],
-                    GuPool* pool, GuExn* err)
-{
-	GuPool* tmp_pool = gu_new_pool();
-	PgfExprParser* parser =
-		pgf_new_parser(in, pgf_expr_parser_in_getc, pool, tmp_pool, err);
-	if (parser->token_tag != PGF_TOKEN_LTRIANGLE)
-		goto fail;
-	pgf_expr_parser_token(parser, false);
-	for (size_t i = 0; i < n_exprs; i++) {
-		if (i > 0) {
-			if (parser->token_tag != PGF_TOKEN_COMMA)
-				goto fail;
-			pgf_expr_parser_token(parser, false);
-		}
-
-		exprs[i] = pgf_expr_parser_expr(parser, false);
-		if (gu_variant_is_null(exprs[i]))
-			goto fail;
-	}
-	if (parser->token_tag != PGF_TOKEN_RTRIANGLE)
-		goto fail;
-	pgf_expr_parser_token(parser, false);
-	if (parser->token_tag != PGF_TOKEN_EOF)
-		goto fail;
-	gu_pool_free(tmp_pool);
-
-	return 1;
-	
-fail:
-	gu_pool_free(tmp_pool);
-	return 0;
-}
-
-PGF_API GuSeq*
-pgf_read_expr_matrix(GuIn* in,
-                     size_t n_exprs,
-                     GuPool* pool, GuExn* err)
-{
-	GuPool* tmp_pool = gu_new_pool();
-	PgfExprParser* parser =
-		pgf_new_parser(in, pgf_expr_parser_in_getc, pool, tmp_pool, err);
-	if (parser->token_tag != PGF_TOKEN_LTRIANGLE)
-		goto fail;
-	pgf_expr_parser_token(parser, false);
-
-	GuBuf* buf = gu_new_buf(PgfExpr, pool);
-	
-	if (parser->token_tag != PGF_TOKEN_RTRIANGLE) {	
-		for (;;) {
-			PgfExpr* exprs = gu_buf_extend_n(buf, n_exprs);
-
-			for (size_t i = 0; i < n_exprs; i++) {
-				if (i > 0) {
-					if (parser->token_tag != PGF_TOKEN_COMMA)
-						goto fail;
-					pgf_expr_parser_token(parser, false);
-				}
-
-				exprs[i] = pgf_expr_parser_expr(parser, false);
-				if (gu_variant_is_null(exprs[i]))
-					goto fail;
-			}
-
-			if (parser->token_tag != PGF_TOKEN_SEMI)
-				break;
-
-			pgf_expr_parser_token(parser, false);
-		}
-
-		if (parser->token_tag != PGF_TOKEN_RTRIANGLE)
-			goto fail;
-	}
-
-	pgf_expr_parser_token(parser, false);
-	if (parser->token_tag != PGF_TOKEN_EOF)
-		goto fail;
-	gu_pool_free(tmp_pool);
-
-	return gu_buf_data_seq(buf);
-
-fail:
-	gu_pool_free(tmp_pool);
-	return NULL;
-}
-
 PGF_API PgfType*
 pgf_read_type(GuIn* in, GuPool* pool, GuPool* tmp_pool, GuExn* err)
 {
diff --git a/src/runtime/c/pgf/expr.h b/src/runtime/c/pgf/expr.h
index b775bd9b5..2c960ac92 100644
--- a/src/runtime/c/pgf/expr.h
+++ b/src/runtime/c/pgf/expr.h
@@ -170,15 +170,6 @@ pgf_expr_unmeta(PgfExpr expr);
 PGF_API_DECL PgfExpr
 pgf_read_expr(GuIn* in, GuPool* pool, GuPool* tmp_pool, GuExn* err);
 
-PGF_API_DECL int
-pgf_read_expr_tuple(GuIn* in,
-                    size_t n_exprs, PgfExpr exprs[],
-                    GuPool* pool, GuExn* err);
-
-PGF_API_DECL GuSeq*
-pgf_read_expr_matrix(GuIn* in, size_t n_exprs,
-                     GuPool* pool, GuExn* err);
-
 PGF_API_DECL PgfType*
 pgf_read_type(GuIn* in, GuPool* pool, GuPool* tmp_pool, GuExn* err);
 
diff --git a/src/runtime/c/sg/sg.c b/src/runtime/c/sg/sg.c
deleted file mode 100644
index b5a473b99..000000000
--- a/src/runtime/c/sg/sg.c
+++ /dev/null
@@ -1,2408 +0,0 @@
-#include <stdlib.h>
-#include "sqlite3Btree.h"
-
-#include "sg/sg.h"
-#include "gu/mem.h"
-#include "pgf/data.h"
-
-#define SG_EXPRS       1
-#define SG_PAIRS       2
-#define SG_IDENTS      3
-#define SG_LITERALS    4
-#define SG_TOKENS      5
-#define SG_TRIPLES     6
-#define SG_TRIPLES_SPO 7
-#define SG_TRIPLES_PO  8
-#define SG_TRIPLES_O   9
-
-struct SgSG {
-	Btree *pBtree;
-	int exprsTNum;                /* The page number for the table of expressions */
-	int identsTNum;               /* The page number for the index on identifiers */
-	int literalsTNum;             /* The page number for the index on literals */
-	int pairsTNum;                /* The page number for the index on application pairs */
-	int tokensTNum;               /* The page number for the index on linearization tokens */
-	int triplesTNum;              /* The page number for the table of triples */
-	int triplesIdxTNum[3];        /* The page number for the three indexes on triples */
-	int autoCommit;
-};
-
-void
-sg_raise_sqlite(int rc, GuExn* err)
-{
-	const char *msg = sqlite3BtreeErrName(rc);
-
-	GuExnData* err_data = gu_raise(err, SgError);
-	if (err_data) {
-		err_data->data = gu_malloc(err_data->pool, strlen(msg)+1);
-		strcpy(err_data->data, msg);
-	}
-}
-
-void
-sg_raise_err(GuString msg, GuExn* err)
-{
-	GuExnData* err_data = gu_raise(err, SgError);
-	if (err_data) {
-		err_data->data = (char*) msg;
-	}
-}
-
-static int
-sg_create_table(Btree* pBtree, BtCursor* crsSchema, int tblKey, int* pTNum, int flags)
-{
-	int rc;
-	int file_format = sqlite3BtreeFileFormat(pBtree);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(crsSchema, 0, tblKey, 0, &res);
-	if (rc != SQLITE_OK) {
-		return rc;
-	}
-
-	Mem mem;
-	int serial_type;
-
-	if (res == 0) {
-		u32 payloadSize;
-		rc = sqlite3BtreeDataSize(crsSchema, &payloadSize);
-		if (rc != SQLITE_OK)
-			return rc;
-
-		u32 avail = 0;
-		const unsigned char* row = sqlite3BtreeDataFetch(crsSchema, &avail);
-		row++;
-
-		row += getVarint32(row, serial_type);
-		row += sqlite3BtreeSerialGet(row, serial_type, &mem);
-		assert(mem.flags & MEM_Int);
-
-		*pTNum = mem.u.i;
-	} else {
-		rc = sqlite3BtreeCreateTable(pBtree, pTNum, flags);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		mem.flags = MEM_Int;
-		mem.u.i = *pTNum;
-
-		unsigned char buf[32];
-		unsigned char *p;
-
-        buf[0] = 2;
-		serial_type = sqlite3BtreeSerialType(&mem, file_format);
-		buf[1] = serial_type;
-		
-		p = buf+2;
-		p += sqlite3BtreeSerialPut(buf+2, &mem, serial_type);
-
-		rc = sqlite3BtreeInsert(crsSchema, 0, tblKey,
-			                        buf, p-buf, 0,
-			                        0, 0);
-		if (rc != SQLITE_OK)
-			return rc;		
-	}
-
-	return SQLITE_OK;
-}
-
-SgSG*
-sg_open(const char *filename,
-        GuExn* err)
-{
-	int rc;
-
-	Btree* pBtree;
-    rc = sqlite3BtreeOpen(0, filename, &pBtree,
-                          0, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_MAIN_DB);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-
-	rc = sqlite3BtreeBeginTrans(pBtree, 1);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		sqlite3BtreeClose(pBtree);
-		return NULL;
-	}
-
-	BtCursor* crsSchema = NULL;
-	rc = sqlite3BtreeCursor(pBtree, 1, 1, 0, 0, &crsSchema);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		sqlite3BtreeClose(pBtree);
-		return NULL;
-	}
-
-	SgSG* sg = malloc(sizeof(SgSG));
-	sg->pBtree = pBtree;
-	sg->autoCommit = 1;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_EXPRS, &sg->exprsTNum, BTREE_INTKEY);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_IDENTS, &sg->identsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_LITERALS, &sg->literalsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_PAIRS, &sg->pairsTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TOKENS, &sg->tokensTNum, 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES, &sg->triplesTNum, BTREE_INTKEY);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_SPO, &sg->triplesIdxTNum[0], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_PO, &sg->triplesIdxTNum[1], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	rc = sg_create_table(pBtree, crsSchema, SG_TRIPLES_O, &sg->triplesIdxTNum[2], 0);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	sqlite3BtreeCloseCursor(crsSchema);
-
-	rc = sqlite3BtreeCommit(pBtree);
-	if (rc != SQLITE_OK)
-		goto fail;
-
-	return sg;
-	
-fail:
-	sg_raise_sqlite(rc, err);
-	if (crsSchema != NULL)
-		sqlite3BtreeCloseCursor(crsSchema);
-	sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	sqlite3BtreeClose(pBtree);
-	free(sg);
-	return NULL;
-}
-
-void
-sg_close(SgSG* sg, GuExn* err)
-{
-	sqlite3BtreeClose(sg->pBtree);
-}
-
-void
-sg_shutdown()
-{
-	sqlite3BtreeShutdown();
-}
-
-void
-sg_begin_trans(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 0;
-}
-
-void
-sg_commit(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeCommit(sg->pBtree);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 1;
-}
-
-void
-sg_rollback(SgSG* sg, GuExn* err)
-{
-	int rc = sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-	sg->autoCommit = 1;
-}
-
-typedef struct {
-	int n_cursors;
-	BtCursor* crsExprs;
-	BtCursor* crsIdents;
-	BtCursor* crsLiterals;
-	BtCursor* crsPairs;
-	SgId key_seed;
-} ExprContext;
-
-static int
-open_exprs(SgSG *sg, int wrFlag, bool identsOnly,
-           ExprContext* ctxt, GuExn* err)
-{
-	ctxt->n_cursors = 0;
-
-	int rc;
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, wrFlag, 0, 0, &ctxt->crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->identsTNum, wrFlag, 1, 1, &ctxt->crsIdents);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	if (!identsOnly) {
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->literalsTNum, wrFlag, 1, 1, &ctxt->crsLiterals);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->pairsTNum, wrFlag, 2, 0, &ctxt->crsPairs);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-	}
-
-	if (wrFlag) {
-		int res;
-		rc = sqlite3BtreeLast(ctxt->crsExprs, &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-
-		rc = sqlite3BtreeKeySize(ctxt->crsExprs, &ctxt->key_seed);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-	} else {
-		ctxt->key_seed = 0;
-	}
-
-	return SQLITE_OK;
-}
-
-static void
-close_exprs(ExprContext* ctxt)
-{
-	if (ctxt->n_cursors >= 4) {
-		sqlite3BtreeCloseCursor(ctxt->crsPairs);
-	}
-
-	if (ctxt->n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(ctxt->crsLiterals);
-	}
-
-	if (ctxt->n_cursors >= 2) {
-		sqlite3BtreeCloseCursor(ctxt->crsIdents);
-	}
-
-	if (ctxt->n_cursors >= 1) {
-		sqlite3BtreeCloseCursor(ctxt->crsExprs);
-	}
-	
-	ctxt->n_cursors = 0;
-}
-
-static int
-find_function_rowid(SgSG* sg, ExprContext* ctxt,
-                    GuString fun, SgId* pKey, int wrFlag)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	Mem mem[2];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(fun);
-	mem[0].z = (void*) fun;
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsIdents, 1, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(ctxt->crsIdents,
-									&idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		return rc;
-	}
-
-	if (res == 0) {
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsIdents, pKey);
-	} else {
-		if (wrFlag == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		*pKey = ++ctxt->key_seed;
-
-		int serial_type_fun = sqlite3BtreeSerialType(&mem[0], file_format);
-		int serial_type_fun_hdr_len = sqlite3BtreeVarintLen(serial_type_fun);
-
-		mem[1].flags = MEM_Int;
-		mem[1].u.i = *pKey;
-
-		int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-		int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-		unsigned char* buf = malloc(1+serial_type_fun_hdr_len+(serial_type_key_hdr_len > 1 ? serial_type_key_hdr_len : 1)+mem[0].n+8);
-		unsigned char* p = buf;
-		*p++ = 1+serial_type_fun_hdr_len+1;
-		p += putVarint32(p, serial_type_fun);
-		*p++ = 0;
-		memcpy(p, fun, mem[0].n);
-		p += mem[0].n;
-
-		rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-		                        buf, p-buf, 0,
-		                        0, 0);
-		if (rc != SQLITE_OK) {
-			goto free;
-		}
-
-		p = buf;
-		*p++ = 1+serial_type_fun_hdr_len+serial_type_key_hdr_len;
-		p += putVarint32(p, serial_type_fun);
-		p += putVarint32(p, serial_type_key);
-		memcpy(p, fun, mem[0].n);
-		p += mem[0].n;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-		rc = sqlite3BtreeInsert(ctxt->crsIdents, buf, p-buf,
-		                        0, *pKey, 0,
-		                        0, 0);
-
-free:
-		free(buf);
-	}
-
-	return rc;
-}
-
-static int
-store_expr(SgSG* sg,
-           ExprContext* ctxt, PgfExpr expr, SgId* pKey, int wrFlag)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-
-		Mem mem[3];
-
-		mem[0].flags = MEM_Int;
-		rc = store_expr(sg, ctxt, app->fun, &mem[0].u.i, wrFlag);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (wrFlag == 0 && mem[0].u.i == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		mem[1].flags = MEM_Int;
-		rc = store_expr(sg, ctxt, app->arg, &mem[1].u.i, wrFlag);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (wrFlag == 0 && mem[1].u.i == 0) {
-			*pKey = 0;
-			return SQLITE_OK;
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsPairs, 2, 0, mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->crsPairs,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		if (res == 0) {
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsPairs, pKey);
-		} else {
-			if (wrFlag == 0) {
-				*pKey = 0;
-				return SQLITE_OK;
-			}
-
-			*pKey = ++ctxt->key_seed;
-
-			unsigned char buf[32];  // enough for a record with three integers
-			buf[1] = 3;
-
-			u32 serial_type;
-			unsigned char* p = buf+4;
-
-			serial_type = sqlite3BtreeSerialType(&mem[0], file_format);
-			buf[2] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[0], serial_type);
-
-			serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-			buf[3] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-			rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-			                        buf+1, p-(buf+1), 0,
-			                        0, 0);
-			if (rc != SQLITE_OK) {
-				return rc;
-			}
-
-			buf[0] = 4;
-			buf[1] = buf[2];
-			buf[2] = buf[3];
-
-			mem[2].flags = MEM_Int;
-			mem[2].u.i = *pKey;
-			serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-			buf[3] = serial_type;
-			p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-			rc = sqlite3BtreeInsert(ctxt->crsPairs, buf, p-buf,
-			                        0, *pKey, 0,
-			                        0, 0);
-        }
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* elit = ei.data;
-
-		Mem mem[2];
-		size_t len = 0;
-
-		GuVariantInfo li = gu_variant_open(elit->lit);
-		switch (li.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = li.data;
-
-			len = strlen(lstr->val);
-
-			mem[0].flags = MEM_Str;
-			mem[0].n = len;
-			mem[0].z = lstr->val;
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = li.data;
-
-			mem[0].flags = MEM_Int;
-			mem[0].u.i = lint->val;
-			len = sizeof(mem[0].u.i);
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = li.data;
-
-			mem[0].flags = MEM_Real;
-			mem[0].u.r = lflt->val;
-			len = sizeof(mem[0].u.r);
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->crsIdents, 1, 0, mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->crsLiterals,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK) {
-			return rc;
-		}
-
-		if (res == 0) {
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->crsLiterals, pKey);
-		} else {
-			if (wrFlag == 0) {
-				*pKey = 0;
-				return SQLITE_OK;
-			}
-
-			*pKey = ++ctxt->key_seed;
-
-			mem[1].flags = MEM_Int;
-			mem[1].u.i = 0;
-
-			int serial_type_lit = sqlite3BtreeSerialType(&mem[0], file_format);
-			int serial_type_lit_hdr_len = sqlite3BtreeVarintLen(serial_type_lit);
-			int serial_type_arg = sqlite3BtreeSerialType(&mem[1], file_format);
-			int serial_type_arg_hdr_len = sqlite3BtreeVarintLen(serial_type_arg);
-
-			unsigned char* buf = malloc(1+serial_type_lit_hdr_len+(serial_type_arg_hdr_len > 1 ? serial_type_arg_hdr_len : 1)+len+8);
-			unsigned char* p = buf;
-			*p++ = 1+serial_type_lit_hdr_len+serial_type_arg_hdr_len;
-			p += putVarint32(p, serial_type_lit);
-			p += putVarint32(p, serial_type_arg);
-			p += sqlite3BtreeSerialPut(p, &mem[0], serial_type_lit);
-			p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_arg);
-
-			rc = sqlite3BtreeInsert(ctxt->crsExprs, 0, *pKey,
-			                        buf, p-buf, 0,
-			                        0, 0);
-			if (rc == SQLITE_OK) {
-				mem[1].flags = MEM_Int;
-				mem[1].u.i = *pKey;
-
-				int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-				int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-				p = buf;
-				*p++ = 1+serial_type_lit_hdr_len+serial_type_key_hdr_len;
-				p += putVarint32(p, serial_type_lit);
-				p += putVarint32(p, serial_type_key);
-				p += sqlite3BtreeSerialPut(p, &mem[0], serial_type_lit);
-				p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-				rc = sqlite3BtreeInsert(ctxt->crsLiterals, buf, p-buf,
-										0, *pKey, 0,
-										0, 0);
-			}
-
-			free(buf);
-		}
-		break;
-	}
-	case PGF_EXPR_META: {
-		gu_impossible();
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-		rc = find_function_rowid(sg, ctxt, fun->fun, pKey, wrFlag);
-        break;
-	}
-	case PGF_EXPR_VAR: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		PgfExprTyped* etyped = ei.data;
-		rc = store_expr(sg, ctxt, etyped->expr, pKey, wrFlag);
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* eimpl = ei.data;
-		rc = store_expr(sg, ctxt, eimpl->expr, pKey, wrFlag);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-
-	return rc;
-}
-
-SgId
-sg_insert_expr(SgSG *sg, PgfExpr expr, int wrFlag, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, wrFlag);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-	ExprContext ctxt;
-	rc = open_exprs(sg, wrFlag, false, &ctxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	SgId key;
-	rc = store_expr(sg, &ctxt, expr, &key, wrFlag);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-    return key;
-
-close:
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return 0;
-}
-
-static int
-load_expr(BtCursor* crsExprs, SgId key, PgfExpr *pExpr, GuPool* out_pool)
-{
-	int res;
-	int rc = sqlite3BtreeMovetoUnpacked(crsExprs, 0, key, 0, &res);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	if (res != 0) {
-		*pExpr = gu_null_variant;
-		return SQLITE_OK;
-	}
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsExprs, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsExprs, &avail);
-	row++;
-
-	int serial_type_fun, serial_type_arg;
-	row += getVarint32(row, serial_type_fun);
-	row += getVarint32(row, serial_type_arg);
-
-	Mem mem[2];
-	row += sqlite3BtreeSerialGet(row, serial_type_fun, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_arg, &mem[1]);
-
-	if (mem[1].flags & MEM_Null) {
-		u32 len = sqlite3BtreeSerialTypeLen(serial_type_fun);
-
-		PgfExprFun *efun =
-			gu_new_flex_variant(PGF_EXPR_FUN,
-			                    PgfExprFun,
-			                    fun, len+1,
-			                    pExpr, out_pool);
-		memcpy(efun->fun, mem[0].z, len);
-		efun->fun[len] = 0;
-	} else if (mem[1].u.i == 0) {
-		PgfExprLit *elit =
-			gu_new_variant(PGF_EXPR_LIT,
-			               PgfExprLit,
-			               pExpr, out_pool);
-
-		if (mem[0].flags & MEM_Str) {
-			u32 len = sqlite3BtreeSerialTypeLen(serial_type_fun);
-
-			PgfLiteralStr *lstr =
-				gu_new_flex_variant(PGF_LITERAL_STR,
-				                    PgfLiteralStr,
-				                    val, len+1,
-				                    &elit->lit, out_pool);
-			memcpy(lstr->val, mem[0].z, len);
-			lstr->val[len] = 0;
-		} else if (mem[0].flags & MEM_Int) {
-			PgfLiteralInt *lint =
-				gu_new_variant(PGF_LITERAL_INT,
-				               PgfLiteralInt,
-				               &elit->lit, out_pool);
-			lint->val = mem[0].u.i;
-		} else if (mem[0].flags & MEM_Real) {
-			PgfLiteralFlt *lflt =
-				gu_new_variant(PGF_LITERAL_FLT,
-				               PgfLiteralFlt,
-				               &elit->lit, out_pool);
-			lflt->val = mem[0].u.r;
-		} else {
-			gu_impossible();
-		}
-	} else {
-		PgfExprApp* papp =
-			gu_new_variant(PGF_EXPR_APP, PgfExprApp, pExpr, out_pool);
-
-		rc = load_expr(crsExprs, mem[0].u.i, &papp->fun, out_pool);
-		if (rc != SQLITE_OK)
-			return rc;
-
-		rc = load_expr(crsExprs, mem[1].u.i, &papp->arg, out_pool);
-		if (rc != SQLITE_OK)
-			return rc;
-	}
-
-	return SQLITE_OK;
-}
-
-PgfExpr
-sg_get_expr(SgSG *sg, SgId key, GuPool* out_pool, GuExn* err)
-{
-	int rc;
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return gu_null_variant;
-		}
-	}
-
-	BtCursor* crsExprs;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, 0, 0, 0, &crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	PgfExpr expr = gu_null_variant;
-	rc = load_expr(crsExprs, key, &expr, out_pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto rollback;
-		}
-	}
-
-    return expr;
-
-close:
-	sqlite3BtreeCloseCursor(crsExprs);
-
-rollback:
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return gu_null_variant;
-}
-
-// A query is compiled into a sequence of instructions with
-// the following codes:
-#define QI_PUSH   1
-#define QI_VAR    2
-#define QI_APPLY  3
-#define QI_RETURN 4
-
-typedef struct {
-	int  code;
-	SgId arg;
-} QueryInstr;
-
-struct SgQueryExprResult {
-	ExprContext ectxt;
-	GuBuf* instrs;
-	GuBuf* queue;
-	size_t iState;
-	PgfMetaId min_meta_id;
-	PgfMetaId max_meta_id;
-};
-
-typedef struct QueryArg QueryArg;
-struct QueryArg {
-	QueryArg* prev;
-	SgId arg;
-};
-
-typedef struct {
-	QueryArg* args;  // a stack of arguments
-	int pc;          // program counter
-} QueryState;
-
-static int
-build_expr_query(SgSG* sg,
-                 SgQueryExprResult* ctxt, PgfExpr expr)
-{
-	int rc = SQLITE_OK;
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-
-		rc = build_expr_query(sg, ctxt, app->fun);
-		if (rc != SQLITE_OK)
-			return rc;
-		QueryInstr* first =
-			gu_buf_index_last(ctxt->instrs, QueryInstr);
-
-		rc = build_expr_query(sg, ctxt, app->arg);
-		if (rc != SQLITE_OK)
-			return rc;
-		QueryInstr* second =
-			gu_buf_index_last(ctxt->instrs, QueryInstr);
-
-		if (first->code == QI_PUSH && second->code == QI_PUSH &&
-		    second - first == 1) {
-			// we could directly combine the two expressions
-
-			Mem mem[2];
-			mem[0].flags = MEM_Int;
-			mem[0].u.i   = first->arg;
-			mem[1].flags = MEM_Int;
-			mem[1].u.i   = second->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 2, 0, mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res != 0)
-				return SQLITE_DONE;
-
-			gu_buf_pop(ctxt->instrs, QueryInstr);
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &first->arg);
-   		} else if (gu_variant_tag(app->arg) != PGF_EXPR_META) {
-			QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-			instr->code = QI_APPLY;
-			instr->arg  = 0;
-		}
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* elit = ei.data;
-
-		Mem mem;
-
-		GuVariantInfo li = gu_variant_open(elit->lit);
-		switch (li.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = li.data;
-
-			mem.flags = MEM_Str;
-			mem.n = strlen(lstr->val);
-			mem.z = lstr->val;
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = li.data;
-
-			mem.flags = MEM_Int;
-			mem.u.i = lint->val;
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = li.data;
-
-			mem.flags = MEM_Real;
-			mem.u.r = lflt->val;
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		UnpackedRecord idxKey;
-		sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsIdents, 1, 0, &mem);
-
-		int res = 0;
-		rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsLiterals,
-		                                &idxKey, 0,  0, &res);
-		if (rc != SQLITE_OK)
-			return rc;
-		if (res != 0)
-			return SQLITE_DONE;
-
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_PUSH;
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsLiterals, &instr->arg);
-		break;
-	}
-	case PGF_EXPR_META: {
-		PgfExprMeta* emeta = ei.data;
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_VAR;
-		instr->arg  = emeta->id;
-		
-		if (ctxt->min_meta_id > emeta->id)
-			ctxt->min_meta_id = emeta->id;
-		if (ctxt->max_meta_id < emeta->id)
-			ctxt->max_meta_id = emeta->id;
-		break;
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_PUSH;
-		rc = find_function_rowid(sg, &ctxt->ectxt, fun->fun, &instr->arg, 0);
-		if (rc == SQLITE_OK && instr->arg == 0)
-			return SQLITE_DONE;
-        break;
-	}
-	case PGF_EXPR_VAR: {
-		gu_impossible();
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		PgfExprTyped* etyped = ei.data;
-		rc = build_expr_query(sg, ctxt, etyped->expr);
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* eimpl = ei.data;
-		rc = build_expr_query(sg, ctxt, eimpl->expr);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-
-	return rc;
-}
-
-static int
-run_expr_query(SgSG* sg, SgQueryExprResult* ctxt, GuPool* pool)
-{
-	int rc;
-
-	while (ctxt->iState < gu_buf_length(ctxt->queue)) {
-		QueryState* state =
-			gu_buf_index(ctxt->queue, QueryState, ctxt->iState);
-		QueryInstr* instr =
-			gu_buf_index(ctxt->instrs, QueryInstr, state->pc);
-
-		switch (instr->code) {
-		case QI_PUSH: {
-			QueryArg* arg = gu_new(QueryArg, pool);
-			arg->arg  = instr->arg;
-			arg->prev = state->args;
-			state->args = arg;
-			break;
-		}
-		case QI_VAR: {
-			assert(state->args != NULL);
-
-			Mem mem;
-			mem.flags = MEM_Int;
-			mem.u.i   = state->args->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 1, 1, &mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res < 0) {
-				rc = sqlite3BtreeNext(ctxt->ectxt.crsPairs, &res);
-			}
-			res = 0;
-
-			while (res == 0) {
-				i64 szData;
-				const unsigned char *zData;
-				rc = sqlite3BtreeKeySize(ctxt->ectxt.crsPairs, &szData);
-				if (rc != SQLITE_OK)
-					return rc;
-
-				u32 available = 0;
-				zData = sqlite3BtreeKeyFetch(ctxt->ectxt.crsPairs, &available);
-				if (szData > available)
-					gu_impossible();
-
-				idxKey.default_rc = 0;
-				res = sqlite3BtreeRecordCompare(available, zData, &idxKey);
-				if (res != 0)
-					break;
-
-				QueryArg* arg = gu_new(QueryArg, pool);
-				arg->prev = state->args->prev;
-
-				QueryState* state1 = gu_buf_extend(ctxt->queue);
-				state1->args = arg;
-				state1->pc   = state->pc+1;
-
-				rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &arg->arg);
-				if (rc != SQLITE_OK)
-					return rc;
-
-				sqlite3BtreeNext(ctxt->ectxt.crsPairs, &res);
-				if (rc != SQLITE_OK)
-					return rc;
-			}
-
-			ctxt->iState++;
-			break;
-		}
-		case QI_APPLY: {
-			assert(state->args != NULL && state->args->prev);
-
-			Mem mem[2];
-			mem[0].flags = MEM_Int;
-			mem[0].u.i   = state->args->prev->arg;
-			mem[1].flags = MEM_Int;
-			mem[1].u.i   = state->args->arg;
-
-			UnpackedRecord idxKey;
-			sqlite3BtreeInitUnpackedRecord(&idxKey, ctxt->ectxt.crsPairs, 2, 0, mem);
-
-			int res = 0;
-			rc = sqlite3BtreeMovetoUnpacked(ctxt->ectxt.crsPairs,
-											&idxKey, 0,  0, &res);
-			if (rc != SQLITE_OK)
-				return rc;
-			if (res != 0) {
-				ctxt->iState++;
-				continue;
-			}
-
-			state->args = state->args->prev;
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, ctxt->ectxt.crsPairs, &state->args->arg);
-			if (rc != SQLITE_OK)
-				return rc;
-			break;
-		}
-		case QI_RETURN:
-			return SQLITE_OK;
-		}
-
-		state->pc++;
-	}
-
-	return SQLITE_DONE;
-}
-
-SgQueryExprResult*
-sg_query_expr(SgSG *sg, PgfExpr expr, GuPool* pool, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgQueryExprResult* ctxt = gu_new(SgQueryExprResult, pool);
-	rc = open_exprs(sg, 0, false, &ctxt->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	ctxt->instrs = gu_new_buf(QueryInstr, pool);
-	ctxt->queue  = gu_new_buf(QueryState, pool);
-	ctxt->iState = 0;
-	ctxt->min_meta_id = INT_MAX;
-	ctxt->max_meta_id = INT_MIN;
-
-	rc = build_expr_query(sg, ctxt, expr);
-	if (rc == SQLITE_OK) {
-		QueryInstr* instr = gu_buf_extend(ctxt->instrs);
-		instr->code = QI_RETURN;
-		instr->arg  = 0;
-
-		QueryState* state = gu_buf_extend(ctxt->queue);
-		state->args = NULL;
-		state->pc   = 0;
-	} else if (rc != SQLITE_DONE) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-    return ctxt;
-
-close:
-	close_exprs(&ctxt->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return NULL;
-}
-
-PgfExpr
-sg_query_next(SgSG *sg, SgQueryExprResult* ctxt, SgId* pKey, GuPool* pool, GuExn* err)
-{
-	int rc;
-
-	rc = run_expr_query(sg, ctxt, pool);
-	if (rc == SQLITE_DONE)
-		return gu_null_variant;
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return gu_null_variant;
-	}
-
-	QueryState* state =
-		gu_buf_index(ctxt->queue, QueryState, ctxt->iState);
-	assert(state->args != NULL);
-	ctxt->iState++;
-
-	PgfExpr expr;
-	rc = load_expr(ctxt->ectxt.crsExprs, state->args->arg, &expr, pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return gu_null_variant;
-	}
-
-	*pKey = state->args->arg;
-
-	return expr;
-}
-
-void
-sg_query_close(SgSG* sg, SgQueryExprResult* ctxt, GuExn* err)
-{
-	int rc;
-
-	close_exprs(&ctxt->ectxt);
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-		}
-	}
-}
-
-static int
-insert_token(SgSG *sg, BtCursor* crsTokens, GuString tok, SgId key)
-{
-	int rc = SQLITE_OK;
-	int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-	Mem mem[2];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(tok);
-	mem[0].z = (void*) tok;
-
-	int serial_type_tok = sqlite3BtreeSerialType(&mem[0], file_format);
-	int serial_type_tok_hdr_len = sqlite3BtreeVarintLen(serial_type_tok);
-
-	mem[1].flags = MEM_Int;
-	mem[1].u.i = key;
-
-	int serial_type_key = sqlite3BtreeSerialType(&mem[1], file_format);
-	int serial_type_key_hdr_len = sqlite3BtreeVarintLen(serial_type_key);
-
-	unsigned char* buf = malloc(1+serial_type_tok_hdr_len+serial_type_key_hdr_len+mem[0].n+8);
-	unsigned char* p = buf;
-	*p++ = 1+serial_type_tok_hdr_len+serial_type_key_hdr_len;
-	p += putVarint32(p, serial_type_tok);
-	p += putVarint32(p, serial_type_key);
-	memcpy(p, tok, mem[0].n);
-	p += mem[0].n;
-	p += sqlite3BtreeSerialPut(p, &mem[1], serial_type_key);
-	rc = sqlite3BtreeInsert(crsTokens, buf, p-buf,
-	                        0, key, 0,
-	                        0, 0);
-	free(buf);
-
-	return rc;
-}
-
-static int
-insert_syms(SgSG *sg, BtCursor* crsTokens, PgfSymbols* syms, SgId key)
-{
-	int rc;
-	size_t n_syms = gu_seq_length(syms);
-	for (size_t sym_idx = 0; sym_idx < n_syms; sym_idx++) {
-		PgfSymbol sym = gu_seq_get(syms, PgfSymbol, sym_idx);
-		GuVariantInfo sym_i = gu_variant_open(sym);
-		switch (sym_i.tag) {
-		case PGF_SYMBOL_KS: {
-			PgfSymbolKS* ks = sym_i.data;
-			rc = insert_token(sg, crsTokens, ks->token, key);
-			if (rc != SQLITE_OK)
-				return rc;
-			break;
-		}
-		case PGF_SYMBOL_KP: {
-			PgfSymbolKP* kp = sym_i.data;
-			rc = insert_syms(sg, crsTokens, kp->default_form, key);
-			if (rc != SQLITE_OK)
-				return rc;
-				
-			for (size_t i = 0; i < kp->n_forms; i++) {
-				rc = insert_syms(sg, crsTokens, kp->forms[i].form, key);
-				if (rc != SQLITE_OK)
-					return rc;
-			}
-			break;
-		}
-		}
-	}
-	
-	return SQLITE_OK;
-}
-
-void
-sg_update_fts_index(SgSG* sg, PgfPGF* pgf, GuExn* err)
-{
-	int rc = SQLITE_OK;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	ExprContext ctxt;
-	rc = open_exprs(sg, 1, true, &ctxt, err);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-	
-	rc = sqlite3BtreeClearTable(sg->pBtree, sg->tokensTNum, NULL);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return;
-	}
-
-	BtCursor* crsTokens;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->tokensTNum, 1, 1, 1, &crsTokens);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-	}
-	ctxt.n_cursors++;
-
-	size_t n_concrs = gu_seq_length(pgf->concretes);
-	for (size_t i = 0; i < n_concrs; i++) {
-		PgfConcr* concr = gu_seq_index(pgf->concretes, PgfConcr, i);
-		
-		size_t n_funs = gu_seq_length(concr->cncfuns);
-		for (size_t funid = 0; funid < n_funs; funid++) {
-			PgfCncFun* cncfun = gu_seq_get(concr->cncfuns, PgfCncFun*, funid);
-
-			SgId key = 0;
-			rc = find_function_rowid(sg, &ctxt, cncfun->absfun->name, &key, 1);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			for (size_t lin_idx = 0; lin_idx < cncfun->n_lins; lin_idx++) {
-				PgfSequence* seq = cncfun->lins[lin_idx];
-				rc = insert_syms(sg, crsTokens, seq->syms, key);
-				if (rc != SQLITE_OK) {
-					sg_raise_sqlite(rc, err);
-					goto close;
-				}
-			}
-		}
-	}
-
-	if (ctxt.n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(crsTokens);
-		ctxt.n_cursors--;
-	}
-
-	close_exprs(&ctxt);
-	
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-		}
-	}
-
-    return;
-
-close:
-	if (ctxt.n_cursors >= 3) {
-		sqlite3BtreeCloseCursor(crsTokens);
-		ctxt.n_cursors--;
-	}
-
-	close_exprs(&ctxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-}
-
-GuSeq*
-sg_query_linearization(SgSG *sg, GuString tok, GuPool *pool, GuExn* err)
-{
-	int rc;
-
-	BtCursor* crsTokens;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->tokensTNum, 1, 1, 1, &crsTokens);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-
-	Mem mem[1];
-	mem[0].flags = MEM_Str;
-	mem[0].n = strlen(tok);
-	mem[0].z = (void*) tok;
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, crsTokens, 1, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(crsTokens,
-									&idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return NULL;
-	}
-	
-	GuBuf* ids = gu_new_buf(SgId, pool);
-
-	while (res == 0) {
-		SgId key;
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, crsTokens, &key);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		gu_buf_push(ids, SgId, key);
-
-		sqlite3BtreeNext(crsTokens, &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		i64 szData;
-		const unsigned char *zData;
-		rc = sqlite3BtreeKeySize(crsTokens, &szData);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			sqlite3BtreeClearCursor(crsTokens);
-			return NULL;
-		}
-
-		u32 available = 0;
-		zData = sqlite3BtreeKeyFetch(crsTokens, &available);
-		if (szData > available)
-			gu_impossible();
-
-		res = sqlite3BtreeRecordCompare(available, zData, &idxKey);
-		if (res != 0)
-			break;
-	}
-
-	sqlite3BtreeClearCursor(crsTokens);
-	return gu_buf_data_seq(ids);
-}
-
-typedef struct {
-	int n_cursors;
-	BtCursor* cursor[4];
-} TripleContext;
-
-static int
-open_triples(SgSG *sg, int wrFlag, TripleContext* ctxt, GuExn* err)
-{
-	int rc;
-
-	ctxt->n_cursors = 0;
-	while (ctxt->n_cursors < 3) {
-		rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesIdxTNum[ctxt->n_cursors], wrFlag, 3-ctxt->n_cursors, ctxt->n_cursors, &ctxt->cursor[ctxt->n_cursors]);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return rc;
-		}
-		ctxt->n_cursors++;
-	}
-
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesTNum, wrFlag, 0, 0, &ctxt->cursor[ctxt->n_cursors]);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return rc;
-	}
-	ctxt->n_cursors++;
-
-	return SQLITE_OK;
-}
-
-static void
-close_triples(TripleContext* ctxt)
-{
-	while (ctxt->n_cursors > 0) {
-		ctxt->n_cursors--;
-		sqlite3BtreeCloseCursor(ctxt->cursor[ctxt->n_cursors]);
-	}
-}
-
-SgId
-sg_insert_triple(SgSG *sg, SgTriple triple, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return 0;
-		}
-	}
-
-	TripleContext tctxt;
-	rc = open_triples(sg, 1, &tctxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	Mem mem[4];
-
-	ExprContext ectxt;
-	rc = open_exprs(sg, 1, false, &ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	for (size_t i = 0; i < 3; i++) {
-		mem[i].flags = MEM_Int;
-
-		rc = store_expr(sg, &ectxt, triple[i], &mem[i].u.i, 1);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-	UnpackedRecord idxKey;
-	sqlite3BtreeInitUnpackedRecord(&idxKey, tctxt.cursor[0], 3, 0, mem);
-
-	int res = 0;
-	rc = sqlite3BtreeMovetoUnpacked(tctxt.cursor[0],
-	                                &idxKey, 0,  0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	SgId key = 0;
-
-	if (res == 0) {
-		rc = sqlite3BtreeIdxRowid(sg->pBtree, tctxt.cursor[0], &key);
-	} else {
-		rc = sqlite3BtreeLast(tctxt.cursor[3], &res);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		rc = sqlite3BtreeKeySize(tctxt.cursor[3], &key);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-		key++;
-
-		u32 serial_type;
-		unsigned char buf[41];  // enough for a record with three integers
-		int file_format = sqlite3BtreeFileFormat(sg->pBtree);
-
-		unsigned char* p = buf+(buf[0] = 5);
-
-		serial_type = sqlite3BtreeSerialType(&mem[0], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[0], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[3] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		unsigned char* tmp = p;
-
-		mem[3].flags = MEM_Int;
-		mem[3].u.i = 1;
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[4] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[3], 0, key,
-								buf, p-buf, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		mem[3].flags = MEM_Int;
-		mem[3].u.i = key;
-
-		p = tmp;
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[4] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[0], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		p = buf+(buf[0] = 4);
-
-		serial_type = sqlite3BtreeSerialType(&mem[1], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[1], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[3] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[1], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-
-		p = buf+(buf[0] = 3);
-
-		serial_type = sqlite3BtreeSerialType(&mem[2], file_format);
-		buf[1] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[2], serial_type);
-
-		serial_type = sqlite3BtreeSerialType(&mem[3], file_format);
-		buf[2] = serial_type;
-		p += sqlite3BtreeSerialPut(p, &mem[3], serial_type);
-
-		rc = sqlite3BtreeInsert(tctxt.cursor[2], buf, p-buf,
-								0, key, 0,
-								0, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-close:
-	close_exprs(&ectxt);
-	close_triples(&tctxt);
-
-	if (sg->autoCommit) {
-		if (rc == SQLITE_OK || rc == SQLITE_DONE) {
-			rc = sqlite3BtreeCommit(sg->pBtree);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return 0;
-			}
-		} else {
-			sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-		}
-	}
-
-	return key;
-}
-
-static int
-load_triple(BtCursor* crsTriples, BtCursor* crsExprs, SgTriple triple,
-            GuPool* out_pool)
-{
-	int rc;
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsTriples, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsTriples, &avail);
-	row++;
-
-	int serial_type_subj, serial_type_pred, serial_type_obj;
-	row += getVarint32(row, serial_type_subj);
-	row += getVarint32(row, serial_type_pred);
-	row += getVarint32(row, serial_type_obj);
-	row++;
-
-	Mem mem[3];
-	row += sqlite3BtreeSerialGet(row, serial_type_subj, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_pred, &mem[1]);
-	row += sqlite3BtreeSerialGet(row, serial_type_obj,  &mem[2]);
-
-	for (int i = 0; i < 3; i++) {
-		if (gu_variant_is_null(triple[i])) {
-			rc = load_expr(crsExprs, mem[i].u.i, &triple[i], out_pool);
-			if (rc != SQLITE_OK)
-				return rc;
-		}
-	}
-
-	return SQLITE_OK;
-}
-
-int
-sg_get_triple(SgSG *sg, SgId key, SgTriple triple,
-              GuPool* out_pool, GuExn* err)
-{
-	triple[0] = gu_null_variant;
-	triple[1] = gu_null_variant;
-	triple[2] = gu_null_variant;
-
-	int rc;
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-	}
-
-	BtCursor* crsTriples;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->triplesTNum, 0, 0, 0, &crsTriples);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	BtCursor* crsExprs;
-	rc = sqlite3BtreeCursor(sg->pBtree, sg->exprsTNum, 0, 0, 0, &crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close1;
-	}
-
-	int res;
-	rc = sqlite3BtreeMovetoUnpacked(crsTriples, 0, key, 0, &res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close;
-	}
-
-	if (res == 0) {
-		rc = load_triple(crsTriples, crsExprs, triple, out_pool);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			goto close;
-		}
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsExprs);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto close1;
-	}
-
-	rc = sqlite3BtreeCloseCursor(crsTriples);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		goto rollback;
-	}
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeCommit(sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-	}
-
-	return (res == 0);
-
-close:
-	sqlite3BtreeCloseCursor(crsExprs);
-
-close1:
-	sqlite3BtreeCloseCursor(crsTriples);
-
-rollback:
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-	return false;
-}
-
-typedef struct {
-	TripleContext tctxt;
-
-	BtCursor* cursor;
-
-	int res;
-	Mem mem[3];
-	UnpackedRecord idxKey;
-}  SgTripleResultInt;
-
-struct SgTripleResult {
-	SgSG *sg;
-	SgTriple triple;
-	ExprContext ectxt;
-	
-	SgTripleResultInt i;
-};
-
-static int
-triple_result_init(SgSG *sg, SgTripleResultInt* tresi, GuExn* err)
-{
-	int rc;
-
-	rc = open_triples(sg, 0, &tresi->tctxt, err);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	int i = 0;
-	while (i < 3) {
-		if (tresi->mem[i].flags != MEM_Null)
-			break;
-		i++;
-	}
-
-	tresi->cursor = tresi->tctxt.cursor[i];
-	sqlite3BtreeInitUnpackedRecord(&tresi->idxKey, tresi->cursor, 0, 0, &tresi->mem[i]);
-	tresi->res = 0;
-
-	while (i+tresi->idxKey.nField < 3) {
-		tresi->idxKey.nField++;
-
-		if (tresi->mem[i+tresi->idxKey.nField].flags == MEM_Null)
-			break;
-	}
-
-	if (tresi->idxKey.nField > 0) {
-		tresi->idxKey.default_rc = 1;
-		rc = sqlite3BtreeMovetoUnpacked(tresi->cursor,
-										&tresi->idxKey, 0,  0, &tresi->res);
-		if (rc == SQLITE_OK) {
-			if (tresi->res < 0) {
-				rc = sqlite3BtreeNext(tresi->cursor, &tresi->res);
-			}
-			tresi->res = 0;
-		}
-	} else {
-		rc = sqlite3BtreeFirst(tresi->cursor, &tresi->res);
-	}
-
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-	}
-
-	return rc;
-}
-
-static bool
-triple_result_fetch(SgSG* sg,
-                    SgTripleResultInt* tresi,
-                    SgId* pKey, GuExn* err)
-{
-	while (tresi->res == 0) {
-		int rc;
-
-		if (tresi->idxKey.nField > 0) {
-			i64 szData;
-			const unsigned char *zData;
-			rc = sqlite3BtreeKeySize(tresi->cursor, &szData);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return false;
-			}
-
-			u32 available = 0;
-			zData = sqlite3BtreeKeyFetch(tresi->cursor, &available);
-			if (szData > available)
-				gu_impossible();
-
-			tresi->idxKey.default_rc = 0;
-			tresi->res = sqlite3BtreeRecordCompare(available, zData, &tresi->idxKey);
-			if (tresi->res != 0)
-				return false;
-
-			if (tresi->idxKey.aMem == &tresi->mem[0] &&
-			    tresi->idxKey.nField == 1 &&
-			    tresi->mem[2].flags != MEM_Null) {
-				int offset = 
-					zData[0] + 
-					sqlite3BtreeSerialTypeLen(zData[1]) + 
-					sqlite3BtreeSerialTypeLen(zData[2]);
-				zData+offset;
-				Mem mem;
-				sqlite3BtreeSerialGet(zData+offset, zData[3], &mem);
-				if (mem.u.i != tresi->mem[2].u.i) {
-					sqlite3BtreeNext(tresi->cursor, &tresi->res);
-					if (rc != SQLITE_OK) {
-						sg_raise_sqlite(rc, err);
-						return false;
-					}
-					continue;
-				}
-			}
-
-			rc = sqlite3BtreeIdxRowid(sg->pBtree, tresi->cursor, pKey);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				return false;
-			}
-
-			rc = sqlite3BtreeMovetoUnpacked(tresi->tctxt.cursor[3], 0, *pKey, 0, &tresi->res);
-		} else {
-			rc = sqlite3BtreeKeySize(tresi->cursor, pKey);
-		}
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return false;
-		}
-
-		return true;
-	}
-
-	return false;
-}
-
-SgTripleResult*
-sg_query_triple(SgSG *sg, SgTriple triple, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgTripleResult* tres = malloc(sizeof(SgTripleResult));
-	tres->sg = sg;
-	tres->triple[0] = triple[0];
-	tres->triple[1] = triple[1];
-	tres->triple[2] = triple[2];
-
-	rc = open_exprs(sg, 0, false, &tres->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	for (int i = 0; i < 3; i++) {
-		if (gu_variant_is_null(triple[i]))
-			tres->i.mem[i].flags = MEM_Null;
-		else {
-			tres->i.mem[i].flags = MEM_Int;
-			rc = store_expr(sg, &tres->ectxt, triple[i], &tres->i.mem[i].u.i, 0);
-			if (rc != SQLITE_OK)
-				goto close;
-			if (tres->i.mem[i].u.i == 0) {
-				tres->i.res = 1;
-				tres->i.tctxt.n_cursors = 0; // this is important since the triples are not initialized yet
-				return tres;
-			}
-		}
-	}
-
-	rc = triple_result_init(sg, &tres->i, err);
-	if (rc != SQLITE_OK) {
-		return NULL;
-	}
-
-	return tres;
-
-close:
-	close_exprs(&tres->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-
-	free(tres);
-	return NULL;
-}
-
-int
-sg_triple_result_fetch(SgTripleResult* tres, SgId* pKey, SgTriple triple,
-                       GuPool* out_pool, GuExn* err)
-{
-	int rc;
-
-	triple[0] = tres->triple[0];
-	triple[1] = tres->triple[1];
-	triple[2] = tres->triple[2];
-
-	bool found =
-		triple_result_fetch(tres->sg, &tres->i, pKey, err);
-	if (!found)
-		return 0;
-
-	rc = load_triple(tres->i.tctxt.cursor[3], tres->ectxt.crsExprs,
-		             triple, out_pool);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return 0;
-	}
-		
-	sqlite3BtreeNext(tres->i.cursor, &tres->i.res);
-	if (rc != SQLITE_OK) {
-		sg_raise_sqlite(rc, err);
-		return 0;
-	}
-
-	return 1;
-}
-
-void
-sg_triple_result_get_query(SgTripleResult* tres, SgTriple triple)
-{
-	triple[0] = tres->triple[0];
-	triple[1] = tres->triple[1];
-	triple[2] = tres->triple[2];
-}
-
-void
-sg_triple_result_close(SgTripleResult* tres, GuExn* err)
-{
-	close_exprs(&tres->ectxt);
-	close_triples(&tres->i.tctxt);
-
-	if (tres->sg->autoCommit) {
-		int rc = sqlite3BtreeCommit(tres->sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	free(tres);
-}
-
-typedef int SgPattern[3];
-
-struct SgQueryResult {
-	SgSG* sg;
-
-	size_t n_vars;
-	struct {
-		SgId id;
-		PgfExpr expr;
-	}* vars;
-
-	size_t n_sels;
-	int* sels;
-
-	ExprContext ectxt;
-	bool is_empty;
-
-	size_t n_results;
-	size_t n_patterns;
-	struct {
-		SgPattern pattern;
-		SgTripleResultInt result;
-	} triples[];
-};
-
-SgQueryResult*
-sg_query(SgSG *sg, size_t n_triples, SgTriple* triples, GuExn* err)
-{
-	int rc;
-
-	if (sg->autoCommit) {
-		rc = sqlite3BtreeBeginTrans(sg->pBtree, 0);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return NULL;
-		}
-	}
-
-	SgQueryResult* qres = malloc(GU_FLEX_SIZE(SgQueryResult, triples, n_triples));
-	qres->sg        = sg;
-	qres->is_empty  = false;
-	qres->n_results = 0;
-
-	qres->n_vars = 0;
-	qres->vars   = malloc(sizeof(qres->vars[0])*n_triples*3);
-
-	qres->n_sels = 0;
-	qres->sels   = malloc(sizeof(int)*n_triples*3);
-
-	rc = open_exprs(sg, 0, false, &qres->ectxt, err);
-	if (rc != SQLITE_OK)
-		goto close;
-
-	qres->n_patterns = n_triples;
-	for (size_t i = 0; i < n_triples; i++) {
-		for (int k = 0; k < 3; k++) {
-			PgfExpr expr = triples[i][k];
-
-			size_t j = 0;
-			while (j < qres->n_vars) {
-				if (pgf_expr_eq(expr, qres->vars[j].expr))
-					break;
-				j++;
-			}
-			if (j >= qres->n_vars) {
-				qres->vars[j].expr = expr;
-
-				if (gu_variant_tag(expr) == PGF_EXPR_META) {
-					qres->vars[j].id = 0;
-					qres->sels[qres->n_sels++] = j;
-					qres->triples[i].result.mem[k].flags = MEM_Null;
-				} else {
-					rc = store_expr(sg, &qres->ectxt, expr, &qres->vars[j].id, 0);
-					if (rc != SQLITE_OK) {
-						sg_raise_sqlite(rc, err);
-						goto close;
-					}
-
-					if (qres->vars[j].id == 0)
-						goto close;
-
-					qres->triples[i].result.mem[k].flags = MEM_Int;
-				}
-
-				qres->n_vars++;
-			} else {
-				qres->triples[i].result.mem[k].flags = MEM_Int;
-			}
-
-			qres->triples[i].pattern[k] = j;
-		}
-	}
-
-	return qres;
-
-close:
-	qres->is_empty = true;
-
-	close_exprs(&qres->ectxt);
-
-	if (sg->autoCommit) {
-		sqlite3BtreeRollback(sg->pBtree, SQLITE_ABORT_ROLLBACK, 0);
-	}
-
-	return qres;
-}
-
-size_t
-sg_query_result_columns(SgQueryResult* qres) {
-	return qres->n_sels;
-}
-
-static int
-load_vars(SgQueryResult* qres, BtCursor* crsTriples, SgPattern pattern)
-{
-	int rc;
-
-	u32 payloadSize;
-	rc = sqlite3BtreeDataSize(crsTriples, &payloadSize);
-	if (rc != SQLITE_OK)
-		return rc;
-
-	u32 avail = 0;
-	const unsigned char* row = sqlite3BtreeDataFetch(crsTriples, &avail);
-	row++;
-
-	int serial_type_subj, serial_type_pred, serial_type_obj;
-	row += getVarint32(row, serial_type_subj);
-	row += getVarint32(row, serial_type_pred);
-	row += getVarint32(row, serial_type_obj);
-	row++;
-
-	Mem mem[3];
-	row += sqlite3BtreeSerialGet(row, serial_type_subj, &mem[0]);
-	row += sqlite3BtreeSerialGet(row, serial_type_pred, &mem[1]);
-	row += sqlite3BtreeSerialGet(row, serial_type_obj,  &mem[2]);
-
-	for (int i = 0; i < 3; i++) {
-		qres->vars[pattern[i]].id = mem[i].u.i;
-	}
-
-	return SQLITE_OK;
-}
-
-int
-query_result_next(SgQueryResult* qres, GuExn* err)
-{
-	if (qres->is_empty)
-		return 0;
-
-	int rc;
-
-	SgId key;
-	size_t i = (qres->n_results == 0) ? 0 : qres->n_results-1;
-	while (i < qres->n_patterns) {
-		if (i >= qres->n_results) {
-			for (int k = 0; k < 3; k++) {
-				qres->triples[i].result.mem[k].u.i = qres->vars[qres->triples[i].pattern[k]].id;
-			}
-
-			rc = triple_result_init(qres->sg, &qres->triples[i].result, err);
-			if (rc != SQLITE_OK) {
-				goto close;
-			}
-
-			qres->n_results++;
-		}
-
-		bool found =
-			triple_result_fetch(qres->sg,
-								&qres->triples[i].result,
-								&key, err);
-		if (gu_exn_is_raised(err)) {
-			goto close;
-		}
-
-		if (found) {
-			rc = sqlite3BtreeNext(qres->triples[i].result.cursor, &qres->triples[i].result.res);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			rc = load_vars(qres, qres->triples[i].result.tctxt.cursor[3], qres->triples[i].pattern);
-			if (rc != SQLITE_OK) {
-				sg_raise_sqlite(rc, err);
-				goto close;
-			}
-
-			i++;
-		} else {
-			close_triples(&qres->triples[i].result.tctxt);
-
-			if (i == 0)
-				goto close;
-
-			i--;
-			qres->n_results--;
-		}
-	}
-
-close:
-	qres->is_empty = true;
-	return 0;
-}
-
-int
-sg_query_result_fetch(SgQueryResult* qres, PgfExpr* res, 
-                      GuPool* out_pool, GuExn* err)
-{
-	if (!query_result_next(qres, err))
-		return 0;
-
-	for (size_t i = 0; i < qres->n_sels; i++) {
-		int rc = load_expr(qres->ectxt.crsExprs,
-		                   qres->vars[qres->sels[i]].id,
-		                   &res[i], out_pool);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			qres->is_empty = true;
-			return 0;
-		}
-	}
-
-	return 1;
-}
-
-static PgfExpr
-instantiate_expr(SgQueryResult* qres, PgfExpr expr,
-                 GuPool* out_pool, GuExn* err)
-{
-	PgfExpr new_expr = gu_null_variant;
-
-	GuVariantInfo ei = gu_variant_open(expr);
-	switch (ei.tag) {
-	case PGF_EXPR_ABS: {
-		PgfExprAbs* abs = ei.data;
-
-		PgfExprAbs* new_abs =
-			gu_new_variant(PGF_EXPR_ABS,
-			               PgfExprAbs,
-			               &new_expr, out_pool);
-		new_abs->bind_type = abs->bind_type;
-		new_abs->id        = gu_string_copy(abs->id, out_pool);
-		new_abs->body      = instantiate_expr(qres, abs->body, out_pool, err);
-		break;
-	}
-	case PGF_EXPR_APP: {
-		PgfExprApp* app = ei.data;
-		
-		PgfExprApp* new_app =
-			gu_new_variant(PGF_EXPR_APP,
-			               PgfExprApp,
-			               &new_expr, out_pool);
-		new_app->fun = instantiate_expr(qres, app->fun, out_pool, err);
-		new_app->arg = instantiate_expr(qres, app->arg, out_pool, err);
-		break;
-	}
-	case PGF_EXPR_LIT: {
-		PgfExprLit* lit = ei.data;
-
-		PgfExprLit* new_lit =
-			gu_new_variant(PGF_EXPR_LIT,
-			               PgfExprLit,
-			               &new_expr, out_pool);
-
-		GuVariantInfo i = gu_variant_open(lit->lit);
-		switch (i.tag) {
-		case PGF_LITERAL_STR: {
-			PgfLiteralStr* lstr = i.data;
-
-			PgfLiteralStr* new_lstr =
-				gu_new_flex_variant(PGF_LITERAL_STR,
-				                    PgfLiteralStr,
-				                    val, strlen(lstr->val)+1,
-				                    &new_lit->lit, out_pool);
-			strcpy(new_lstr->val, lstr->val);
-			break;
-		}
-		case PGF_LITERAL_INT: {
-			PgfLiteralInt* lint = i.data;
-
-			PgfLiteralInt* new_lint =
-				gu_new_variant(PGF_LITERAL_INT,
-				               PgfLiteralInt,
-				               &new_lit->lit, out_pool);
-			new_lint->val = lint->val;
-			break;
-		}
-		case PGF_LITERAL_FLT: {
-			PgfLiteralFlt* lflt = i.data;
-
-			PgfLiteralFlt* new_lflt =
-				gu_new_variant(PGF_LITERAL_FLT,
-				               PgfLiteralFlt,
-				               &new_lit->lit, out_pool);
-			new_lflt->val = lflt->val;
-			break;
-		}
-		default:
-			gu_impossible();
-		}
-
-		break;
-	}
-	case PGF_EXPR_META: {
-		new_expr = expr;
-
-		size_t j = 0;
-		while (j < qres->n_vars) {
-			if (pgf_expr_eq(expr, qres->vars[j].expr)) {
-				
-				int rc = load_expr(qres->ectxt.crsExprs,
-		                           qres->vars[j].id,
-		                           &new_expr, out_pool);
-				if (rc != SQLITE_OK) {
-					sg_raise_sqlite(rc, err);
-					qres->is_empty = true;
-					return new_expr;
-				}
-				break;
-			}
-			j++;
-		}
-
-		break;
-	}
-	case PGF_EXPR_FUN: {
-		PgfExprFun* fun = ei.data;
-		
-		PgfExprFun *new_fun =
-			gu_new_flex_variant(PGF_EXPR_FUN,
-			                    PgfExprFun,
-			                    fun, strlen(fun->fun)+1,
-			                    &new_expr, out_pool);
-		strcpy(new_fun->fun, fun->fun);
-		break;
-	}
-	case PGF_EXPR_VAR: {
-		PgfExprVar* var = ei.data;
-
-		PgfExprVar* new_var =
-			gu_new_variant(PGF_EXPR_VAR,
-						   PgfExprVar,
-						   &new_expr, out_pool);
-		new_var->var = var->var;
-		break;
-	}
-	case PGF_EXPR_TYPED: {
-		break;
-	}
-	case PGF_EXPR_IMPL_ARG: {
-		PgfExprImplArg* impl = ei.data;
-		
-		PgfExprImplArg* new_impl =
-			gu_new_variant(PGF_EXPR_IMPL_ARG,
-			               PgfExprImplArg,
-			               &new_expr, out_pool);
-		new_impl->expr = instantiate_expr(qres, impl->expr, out_pool, err);
-		break;
-	}
-	default:
-		gu_impossible();
-	}
-	
-	return new_expr;
-}
-
-PgfExpr
-sg_query_result_fetch_expr(SgQueryResult* qres, PgfExpr expr,
-                           GuPool* out_pool, GuExn* err)
-{
-	if (!query_result_next(qres, err))
-		return gu_null_variant;
-
-	return instantiate_expr(qres, expr, out_pool, err);
-}
-
-void
-sg_query_result_close(SgQueryResult* qres, GuExn* err)
-{
-	while (qres->n_results > 0) {
-		close_triples(&qres->triples[qres->n_results-1].result.tctxt);
-		qres->n_results--;
-	}
-
-	close_exprs(&qres->ectxt);
-
-	if (qres->sg->autoCommit) {
-		int rc = sqlite3BtreeCommit(qres->sg->pBtree);
-		if (rc != SQLITE_OK) {
-			sg_raise_sqlite(rc, err);
-			return;
-		}
-	}
-
-	free(qres->vars);
-	free(qres->sels);
-	free(qres);
-}
diff --git a/src/runtime/c/sg/sg.h b/src/runtime/c/sg/sg.h
deleted file mode 100644
index 8e543a97c..000000000
--- a/src/runtime/c/sg/sg.h
+++ /dev/null
@@ -1,94 +0,0 @@
-#ifndef SG_SG_H_
-#define SG_SG_H_
-
-typedef long long int SgId;
-
-#include <gu/exn.h>
-#include <pgf/pgf.h>
-
-typedef struct SgSG SgSG;
-
-SgSG*
-sg_open(const char *filename, GuExn* err);
-
-void
-sg_close(SgSG *sg, GuExn* err);
-
-void
-sg_begin_trans(SgSG* sg, GuExn* err);
-
-void
-sg_commit(SgSG* sg, GuExn* err);
-
-void
-sg_rollback(SgSG* sg, GuExn* err);
-
-
-SgId
-sg_insert_expr(SgSG *sg, PgfExpr expr, int wrFlag, GuExn* err);
-
-PgfExpr
-sg_get_expr(SgSG *sg, SgId key, GuPool* out_pool, GuExn* err);
-
-typedef struct SgQueryExprResult SgQueryExprResult;
-
-SgQueryExprResult*
-sg_query_expr(SgSG *sg, PgfExpr expr, GuPool* pool, GuExn* err);
-
-PgfExpr
-sg_query_next(SgSG *sg, SgQueryExprResult* ctxt, SgId* pKey, GuPool* pool, GuExn* err);
-
-void
-sg_query_close(SgSG* sg, SgQueryExprResult* ctxt, GuExn* err);
-
-void
-sg_update_fts_index(SgSG* sg, PgfPGF* pgf, GuExn* err);
-
-GuSeq*
-sg_query_linearization(SgSG *sg, GuString tok, GuPool* pool, GuExn* err);
-
-
-typedef PgfExpr SgTriple[3];
-
-SgId
-sg_insert_triple(SgSG *sg, SgTriple triple, GuExn* err);
-
-int
-sg_get_triple(SgSG *sg, SgId key, SgTriple triple,
-                 GuPool* out_pool, GuExn* err);
-
-typedef struct SgTripleResult SgTripleResult;
-
-SgTripleResult*
-sg_query_triple(SgSG *sg, SgTriple triple, GuExn* err);
-
-int
-sg_triple_result_fetch(SgTripleResult* tres, SgId* pKey, SgTriple triple,
-                       GuPool* out_pool, GuExn* err);
-
-void
-sg_triple_result_get_query(SgTripleResult* tres, SgTriple triple);
-
-void
-sg_triple_result_close(SgTripleResult* tres, GuExn* err);
-
-typedef struct SgQueryResult SgQueryResult;
-
-SgQueryResult*
-sg_query(SgSG *sg, size_t n_triples, SgTriple* triples, GuExn* err);
-
-size_t
-sg_query_result_columns(SgQueryResult* qres);
-
-int
-sg_query_result_fetch_columns(SgQueryResult* qres, PgfExpr* res,
-                              GuPool* out_pool, GuExn* err);
-
-PgfExpr
-sg_query_result_fetch_expr(SgQueryResult* qres, PgfExpr expr,
-                           GuPool* out_pool, GuExn* err);
-
-void
-sg_query_result_close(SgQueryResult* qres, GuExn* err);
-
-#endif
diff --git a/src/runtime/c/sg/sqlite3Btree.c b/src/runtime/c/sg/sqlite3Btree.c
deleted file mode 100644
index 5271fef77..000000000
--- a/src/runtime/c/sg/sqlite3Btree.c
+++ /dev/null
@@ -1,48654 +0,0 @@
-/******************************************************************************
-** This file is an amalgamation of many separate C source files from SQLite
-** version 3.8.11.1.  By combining all the individual C code files into this 
-** single large file, the entire code can be compiled as a single translation
-** unit.  This allows many compilers to do optimizations that would not be
-** possible if the files were compiled separately.  Performance improvements
-** of 5% or more are commonly seen when SQLite is compiled as a single
-** translation unit.
-**
-** This file is all you need to compile SQLite.  To use SQLite in other
-** programs, you need this file and the "sqliteBtree.h" header file that defines
-** the programming interface to the SQLite library.  (If you do not have 
-** the "sqliteBtree.h" header file at hand, you will find a copy embedded within
-** the text of this file.  Search for "Begin file sqliteBtree.h" to find the start
-** of the embedded sqliteBtree.h header file.)
-*/
-#define SQLITE_CORE 1
-#define SQLITE_AMALGAMATION 1
-#ifndef SQLITE_PRIVATE
-# define SQLITE_PRIVATE static
-#endif
-/************** Begin file sqliteInt.h ***************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** Internal interface definitions for SQLite.
-**
-*/
-#ifndef _SQLITEINT_H_
-#define _SQLITEINT_H_
-
-/*
-** Include the header file used to customize the compiler options for MSVC.
-** This should be done first so that it can successfully prevent spurious
-** compiler warnings due to subsequent content in this file and other files
-** that are included by this file.
-*/
-/************** Include msvc.h in the middle of sqliteInt.h ******************/
-/************** Begin file msvc.h ********************************************/
-/*
-** 2015 January 12
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains code that is specific to MSVC.
-*/
-#ifndef _MSVC_H_
-#define _MSVC_H_
-
-#if defined(_MSC_VER)
-#pragma warning(disable : 4054)
-#pragma warning(disable : 4055)
-#pragma warning(disable : 4100)
-#pragma warning(disable : 4127)
-#pragma warning(disable : 4130)
-#pragma warning(disable : 4152)
-#pragma warning(disable : 4189)
-#pragma warning(disable : 4206)
-#pragma warning(disable : 4210)
-#pragma warning(disable : 4232)
-#pragma warning(disable : 4244)
-#pragma warning(disable : 4305)
-#pragma warning(disable : 4306)
-#pragma warning(disable : 4702)
-#pragma warning(disable : 4706)
-#endif /* defined(_MSC_VER) */
-
-#endif /* _MSVC_H_ */
-
-/************** End of msvc.h ************************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/*
-** Special setup for VxWorks
-*/
-/************** Include vxworks.h in the middle of sqliteInt.h ***************/
-/************** Begin file vxworks.h *****************************************/
-/*
-** 2015-03-02
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains code that is specific to Wind River's VxWorks
-*/
-#if defined(__RTP__) || defined(_WRS_KERNEL)
-/* This is VxWorks.  Set up things specially for that OS
-*/
-#include <vxWorks.h>
-#include <pthread.h>  /* amalgamator: dontcache */
-#define OS_VXWORKS 1
-#define SQLITE_OS_OTHER 0
-#define SQLITE_HOMEGROWN_RECURSIVE_MUTEX 1
-#define SQLITE_ENABLE_LOCKING_STYLE 0
-#define HAVE_UTIME 1
-#else
-/* This is not VxWorks. */
-#define OS_VXWORKS 0
-#endif /* defined(_WRS_KERNEL) */
-
-/************** End of vxworks.h *********************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/*
-** These #defines should enable >2GB file support on POSIX if the
-** underlying operating system supports it.  If the OS lacks
-** large file support, or if the OS is windows, these should be no-ops.
-**
-** Ticket #2739:  The _LARGEFILE_SOURCE macro must appear before any
-** system #includes.  Hence, this block of code must be the very first
-** code in all source files.
-**
-** Large file support can be disabled using the -DSQLITE_DISABLE_LFS switch
-** on the compiler command line.  This is necessary if you are compiling
-** on a recent machine (ex: Red Hat 7.2) but you want your code to work
-** on an older machine (ex: Red Hat 6.0).  If you compile on Red Hat 7.2
-** without this option, LFS is enable.  But LFS does not exist in the kernel
-** in Red Hat 6.0, so the code won't work.  Hence, for maximum binary
-** portability you should omit LFS.
-**
-** The previous paragraph was written in 2005.  (This paragraph is written
-** on 2008-11-28.) These days, all Linux kernels support large files, so
-** you should probably leave LFS enabled.  But some embedded platforms might
-** lack LFS in which case the SQLITE_DISABLE_LFS macro might still be useful.
-**
-** Similar is true for Mac OS X.  LFS is only supported on Mac OS X 9 and later.
-*/
-#ifndef SQLITE_DISABLE_LFS
-# define _LARGE_FILE       1
-# ifndef _FILE_OFFSET_BITS
-#   define _FILE_OFFSET_BITS 64
-# endif
-# define _LARGEFILE_SOURCE 1
-#endif
-
-/* What version of GCC is being used.  0 means GCC is not being used */
-#ifdef __GNUC__
-# define GCC_VERSION (__GNUC__*1000000+__GNUC_MINOR__*1000+__GNUC_PATCHLEVEL__)
-#else
-# define GCC_VERSION 0
-#endif
-
-/* Needed for various definitions... */
-#if defined(__GNUC__) && !defined(_GNU_SOURCE)
-# define _GNU_SOURCE
-#endif
-
-#if defined(__OpenBSD__) && !defined(_BSD_SOURCE)
-# define _BSD_SOURCE
-#endif
-
-/*
-** For MinGW, check to see if we can include the header file containing its
-** version information, among other things.  Normally, this internal MinGW
-** header file would [only] be included automatically by other MinGW header
-** files; however, the contained version information is now required by this
-** header file to work around binary compatibility issues (see below) and
-** this is the only known way to reliably obtain it.  This entire #if block
-** would be completely unnecessary if there was any other way of detecting
-** MinGW via their preprocessor (e.g. if they customized their GCC to define
-** some MinGW-specific macros).  When compiling for MinGW, either the
-** _HAVE_MINGW_H or _HAVE__MINGW_H (note the extra underscore) macro must be
-** defined; otherwise, detection of conditions specific to MinGW will be
-** disabled.
-*/
-#if defined(_HAVE_MINGW_H)
-# include "mingw.h"
-#elif defined(_HAVE__MINGW_H)
-# include "_mingw.h"
-#endif
-
-/*
-** For MinGW version 4.x (and higher), check to see if the _USE_32BIT_TIME_T
-** define is required to maintain binary compatibility with the MSVC runtime
-** library in use (e.g. for Windows XP).
-*/
-#if !defined(_USE_32BIT_TIME_T) && !defined(_USE_64BIT_TIME_T) && \
-    defined(_WIN32) && !defined(_WIN64) && \
-    defined(__MINGW_MAJOR_VERSION) && __MINGW_MAJOR_VERSION >= 4 && \
-    defined(__MSVCRT__)
-# define _USE_32BIT_TIME_T
-#endif
-
-#include "sqlite3Btree.h"
-
-#include <stdio.h>
-#include <stdarg.h>     /* Needed for the definition of va_list */
-
-/*
-** Provide the ability to override linkage features of the interface.
-*/
-#ifndef SQLITE_EXTERN
-# define SQLITE_EXTERN extern
-#endif
-#ifndef SQLITE_API
-# define SQLITE_API
-#endif
-#ifndef SQLITE_CDECL
-# define SQLITE_CDECL
-#endif
-#ifndef SQLITE_STDCALL
-# define SQLITE_STDCALL
-#endif
-
-/*
-** CAPI3REF: Compile-Time Library Version Numbers
-**
-** ^(The [SQLITE_VERSION] C preprocessor macro in the sqlite3.h header
-** evaluates to a string literal that is the SQLite version in the
-** format "X.Y.Z" where X is the major version number (always 3 for
-** SQLite3) and Y is the minor version number and Z is the release number.)^
-** ^(The [SQLITE_VERSION_NUMBER] C preprocessor macro resolves to an integer
-** with the value (X*1000000 + Y*1000 + Z) where X, Y, and Z are the same
-** numbers used in [SQLITE_VERSION].)^
-** The SQLITE_VERSION_NUMBER for any given release of SQLite will also
-** be larger than the release from which it is derived.  Either Y will
-** be held constant and Z will be incremented or else Y will be incremented
-** and Z will be reset to zero.
-**
-** Since version 3.6.18, SQLite source code has been stored in the
-** <a href="http://www.fossil-scm.org/">Fossil configuration management
-** system</a>.  ^The SQLITE_SOURCE_ID macro evaluates to
-** a string which identifies a particular check-in of SQLite
-** within its configuration management system.  ^The SQLITE_SOURCE_ID
-** string contains the date and time of the check-in (UTC) and an SHA1
-** hash of the entire source tree.
-**
-** See also: [sqlite3_libversion()],
-** [sqlite3_libversion_number()], [sqlite3_sourceid()],
-** [sqlite_version()] and [sqlite_source_id()].
-*/
-#define SQLITE_VERSION        "3.8.11.1"
-#define SQLITE_VERSION_NUMBER 3008011
-#define SQLITE_SOURCE_ID      "2015-07-29 20:00:57 cf538e2783e468bbc25e7cb2a9ee64d3e0e80b2f"
-
-/*
-** CAPI3REF: Device Characteristics
-**
-** The xDeviceCharacteristics method of the [sqlite3_io_methods]
-** object returns an integer which is a vector of these
-** bit values expressing I/O characteristics of the mass storage
-** device that holds the file that the [sqlite3_io_methods]
-** refers to.
-**
-** The SQLITE_IOCAP_ATOMIC property means that all writes of
-** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
-** mean that writes of blocks that are nnn bytes in size and
-** are aligned to an address which is an integer multiple of
-** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
-** that when data is appended to a file, the data is appended
-** first then the size of the file is extended, never the other
-** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
-** information is written to disk in the same order as calls
-** to xWrite().  The SQLITE_IOCAP_POWERSAFE_OVERWRITE property means that
-** after reboot following a crash or power loss, the only bytes in a
-** file that were written at the application level might have changed
-** and that adjacent bytes, even bytes within the same sector are
-** guaranteed to be unchanged.  The SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
-** flag indicate that a file cannot be deleted when open.  The
-** SQLITE_IOCAP_IMMUTABLE flag indicates that the file is on
-** read-only media and cannot be changed even by processes with
-** elevated privileges.
-*/
-#define SQLITE_IOCAP_ATOMIC                 0x00000001
-#define SQLITE_IOCAP_ATOMIC512              0x00000002
-#define SQLITE_IOCAP_ATOMIC1K               0x00000004
-#define SQLITE_IOCAP_ATOMIC2K               0x00000008
-#define SQLITE_IOCAP_ATOMIC4K               0x00000010
-#define SQLITE_IOCAP_ATOMIC8K               0x00000020
-#define SQLITE_IOCAP_ATOMIC16K              0x00000040
-#define SQLITE_IOCAP_ATOMIC32K              0x00000080
-#define SQLITE_IOCAP_ATOMIC64K              0x00000100
-#define SQLITE_IOCAP_SAFE_APPEND            0x00000200
-#define SQLITE_IOCAP_SEQUENTIAL             0x00000400
-#define SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN  0x00000800
-#define SQLITE_IOCAP_POWERSAFE_OVERWRITE    0x00001000
-#define SQLITE_IOCAP_IMMUTABLE              0x00002000
-
-/*
-** CAPI3REF: File Locking Levels
-**
-** SQLite uses one of these integer values as the second
-** argument to calls it makes to the xLock() and xUnlock() methods
-** of an [sqlite3_io_methods] object.
-*/
-#define SQLITE_LOCK_NONE          0
-#define SQLITE_LOCK_SHARED        1
-#define SQLITE_LOCK_RESERVED      2
-#define SQLITE_LOCK_PENDING       3
-#define SQLITE_LOCK_EXCLUSIVE     4
-
-/*
-** CAPI3REF: Synchronization Type Flags
-**
-** When SQLite invokes the xSync() method of an
-** [sqlite3_io_methods] object it uses a combination of
-** these integer values as the second argument.
-**
-** When the SQLITE_SYNC_DATAONLY flag is used, it means that the
-** sync operation only needs to flush data to mass storage.  Inode
-** information need not be flushed. If the lower four bits of the flag
-** equal SQLITE_SYNC_NORMAL, that means to use normal fsync() semantics.
-** If the lower four bits equal SQLITE_SYNC_FULL, that means
-** to use Mac OS X style fullsync instead of fsync().
-**
-** Do not confuse the SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags
-** with the [PRAGMA synchronous]=NORMAL and [PRAGMA synchronous]=FULL
-** settings.  The [synchronous pragma] determines when calls to the
-** xSync VFS method occur and applies uniformly across all platforms.
-** The SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL flags determine how
-** energetic or rigorous or forceful the sync operations are and
-** only make a difference on Mac OSX for the default SQLite code.
-** (Third-party VFS implementations might also make the distinction
-** between SQLITE_SYNC_NORMAL and SQLITE_SYNC_FULL, but among the
-** operating systems natively supported by SQLite, only Mac OSX
-** cares about the difference.)
-*/
-#define SQLITE_SYNC_NORMAL        0x00002
-#define SQLITE_SYNC_FULL          0x00003
-#define SQLITE_SYNC_DATAONLY      0x00010
-
-/*
-** CAPI3REF: OS Interface Open File Handle
-**
-** An [sqlite3_file] object represents an open file in the 
-** [sqlite3_vfs | OS interface layer].  Individual OS interface
-** implementations will
-** want to subclass this object by appending additional fields
-** for their own use.  The pMethods entry is a pointer to an
-** [sqlite3_io_methods] object that defines methods for performing
-** I/O operations on the open file.
-*/
-typedef struct sqlite3_file sqlite3_file;
-struct sqlite3_file {
-  const struct sqlite3_io_methods *pMethods;  /* Methods for an open file */
-};
-
-/*
-** CAPI3REF: OS Interface File Virtual Methods Object
-**
-** Every file opened by the [sqlite3_vfs.xOpen] method populates an
-** [sqlite3_file] object (or, more commonly, a subclass of the
-** [sqlite3_file] object) with a pointer to an instance of this object.
-** This object defines the methods used to perform various operations
-** against the open file represented by the [sqlite3_file] object.
-**
-** If the [sqlite3_vfs.xOpen] method sets the sqlite3_file.pMethods element 
-** to a non-NULL pointer, then the sqlite3_io_methods.xClose method
-** may be invoked even if the [sqlite3_vfs.xOpen] reported that it failed.  The
-** only way to prevent a call to xClose following a failed [sqlite3_vfs.xOpen]
-** is for the [sqlite3_vfs.xOpen] to set the sqlite3_file.pMethods element
-** to NULL.
-**
-** The flags argument to xSync may be one of [SQLITE_SYNC_NORMAL] or
-** [SQLITE_SYNC_FULL].  The first choice is the normal fsync().
-** The second choice is a Mac OS X style fullsync.  The [SQLITE_SYNC_DATAONLY]
-** flag may be ORed in to indicate that only the data of the file
-** and not its inode needs to be synced.
-**
-** The integer values to xLock() and xUnlock() are one of
-** <ul>
-** <li> [SQLITE_LOCK_NONE],
-** <li> [SQLITE_LOCK_SHARED],
-** <li> [SQLITE_LOCK_RESERVED],
-** <li> [SQLITE_LOCK_PENDING], or
-** <li> [SQLITE_LOCK_EXCLUSIVE].
-** </ul>
-** xLock() increases the lock. xUnlock() decreases the lock.
-** The xCheckReservedLock() method checks whether any database connection,
-** either in this process or in some other process, is holding a RESERVED,
-** PENDING, or EXCLUSIVE lock on the file.  It returns true
-** if such a lock exists and false otherwise.
-**
-** The xFileControl() method is a generic interface that allows custom
-** VFS implementations to directly control an open file using the
-** [sqlite3_file_control()] interface.  The second "op" argument is an
-** integer opcode.  The third argument is a generic pointer intended to
-** point to a structure that may contain arguments or space in which to
-** write return values.  Potential uses for xFileControl() might be
-** functions to enable blocking locks with timeouts, to change the
-** locking strategy (for example to use dot-file locks), to inquire
-** about the status of a lock, or to break stale locks.  The SQLite
-** core reserves all opcodes less than 100 for its own use.
-** A [file control opcodes | list of opcodes] less than 100 is available.
-** Applications that define a custom xFileControl method should use opcodes
-** greater than 100 to avoid conflicts.  VFS implementations should
-** return [SQLITE_NOTFOUND] for file control opcodes that they do not
-** recognize.
-**
-** The xSectorSize() method returns the sector size of the
-** device that underlies the file.  The sector size is the
-** minimum write that can be performed without disturbing
-** other bytes in the file.  The xDeviceCharacteristics()
-** method returns a bit vector describing behaviors of the
-** underlying device:
-**
-** <ul>
-** <li> [SQLITE_IOCAP_ATOMIC]
-** <li> [SQLITE_IOCAP_ATOMIC512]
-** <li> [SQLITE_IOCAP_ATOMIC1K]
-** <li> [SQLITE_IOCAP_ATOMIC2K]
-** <li> [SQLITE_IOCAP_ATOMIC4K]
-** <li> [SQLITE_IOCAP_ATOMIC8K]
-** <li> [SQLITE_IOCAP_ATOMIC16K]
-** <li> [SQLITE_IOCAP_ATOMIC32K]
-** <li> [SQLITE_IOCAP_ATOMIC64K]
-** <li> [SQLITE_IOCAP_SAFE_APPEND]
-** <li> [SQLITE_IOCAP_SEQUENTIAL]
-** </ul>
-**
-** The SQLITE_IOCAP_ATOMIC property means that all writes of
-** any size are atomic.  The SQLITE_IOCAP_ATOMICnnn values
-** mean that writes of blocks that are nnn bytes in size and
-** are aligned to an address which is an integer multiple of
-** nnn are atomic.  The SQLITE_IOCAP_SAFE_APPEND value means
-** that when data is appended to a file, the data is appended
-** first then the size of the file is extended, never the other
-** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
-** information is written to disk in the same order as calls
-** to xWrite().
-**
-** If xRead() returns SQLITE_IOERR_SHORT_READ it must also fill
-** in the unread portions of the buffer with zeros.  A VFS that
-** fails to zero-fill short reads might seem to work.  However,
-** failure to zero-fill short reads will eventually lead to
-** database corruption.
-*/
-typedef struct sqlite3_io_methods sqlite3_io_methods;
-struct sqlite3_io_methods {
-  int iVersion;
-  int (*xClose)(sqlite3_file*);
-  int (*xRead)(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
-  int (*xWrite)(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
-  int (*xTruncate)(sqlite3_file*, sqlite3_int64 size);
-  int (*xSync)(sqlite3_file*, int flags);
-  int (*xFileSize)(sqlite3_file*, sqlite3_int64 *pSize);
-  int (*xLock)(sqlite3_file*, int);
-  int (*xUnlock)(sqlite3_file*, int);
-  int (*xCheckReservedLock)(sqlite3_file*, int *pResOut);
-  int (*xFileControl)(sqlite3_file*, int op, void *pArg);
-  int (*xSectorSize)(sqlite3_file*);
-  int (*xDeviceCharacteristics)(sqlite3_file*);
-  /* Methods above are valid for version 1 */
-  int (*xShmMap)(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
-  int (*xShmLock)(sqlite3_file*, int offset, int n, int flags);
-  void (*xShmBarrier)(sqlite3_file*);
-  int (*xShmUnmap)(sqlite3_file*, int deleteFlag);
-  /* Methods above are valid for version 2 */
-  int (*xFetch)(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp);
-  int (*xUnfetch)(sqlite3_file*, sqlite3_int64 iOfst, void *p);
-  /* Methods above are valid for version 3 */
-  /* Additional methods may be added in future releases */
-};
-
-/*
-** CAPI3REF: Standard File Control Opcodes
-** KEYWORDS: {file control opcodes} {file control opcode}
-**
-** These integer constants are opcodes for the xFileControl method
-** of the [sqlite3_io_methods] object and for the [sqlite3_file_control()]
-** interface.
-**
-** <ul>
-** <li>[[SQLITE_FCNTL_LOCKSTATE]]
-** The [SQLITE_FCNTL_LOCKSTATE] opcode is used for debugging.  This
-** opcode causes the xFileControl method to write the current state of
-** the lock (one of [SQLITE_LOCK_NONE], [SQLITE_LOCK_SHARED],
-** [SQLITE_LOCK_RESERVED], [SQLITE_LOCK_PENDING], or [SQLITE_LOCK_EXCLUSIVE])
-** into an integer that the pArg argument points to. This capability
-** is used during testing and is only available when the SQLITE_TEST
-** compile-time option is used.
-**
-** <li>[[SQLITE_FCNTL_SIZE_HINT]]
-** The [SQLITE_FCNTL_SIZE_HINT] opcode is used by SQLite to give the VFS
-** layer a hint of how large the database file will grow to be during the
-** current transaction.  This hint is not guaranteed to be accurate but it
-** is often close.  The underlying VFS might choose to preallocate database
-** file space based on this hint in order to help writes to the database
-** file run faster.
-**
-** <li>[[SQLITE_FCNTL_CHUNK_SIZE]]
-** The [SQLITE_FCNTL_CHUNK_SIZE] opcode is used to request that the VFS
-** extends and truncates the database file in chunks of a size specified
-** by the user. The fourth argument to [sqlite3_file_control()] should 
-** point to an integer (type int) containing the new chunk-size to use
-** for the nominated database. Allocating database file space in large
-** chunks (say 1MB at a time), may reduce file-system fragmentation and
-** improve performance on some systems.
-**
-** <li>[[SQLITE_FCNTL_FILE_POINTER]]
-** The [SQLITE_FCNTL_FILE_POINTER] opcode is used to obtain a pointer
-** to the [sqlite3_file] object associated with a particular database
-** connection.  See the [sqlite3_file_control()] documentation for
-** additional information.
-**
-** <li>[[SQLITE_FCNTL_SYNC_OMITTED]]
-** No longer in use.
-**
-** <li>[[SQLITE_FCNTL_SYNC]]
-** The [SQLITE_FCNTL_SYNC] opcode is generated internally by SQLite and
-** sent to the VFS immediately before the xSync method is invoked on a
-** database file descriptor. Or, if the xSync method is not invoked 
-** because the user has configured SQLite with 
-** [PRAGMA synchronous | PRAGMA synchronous=OFF] it is invoked in place 
-** of the xSync method. In most cases, the pointer argument passed with
-** this file-control is NULL. However, if the database file is being synced
-** as part of a multi-database commit, the argument points to a nul-terminated
-** string containing the transactions master-journal file name. VFSes that 
-** do not need this signal should silently ignore this opcode. Applications 
-** should not call [sqlite3_file_control()] with this opcode as doing so may 
-** disrupt the operation of the specialized VFSes that do require it.  
-**
-** <li>[[SQLITE_FCNTL_COMMIT_PHASETWO]]
-** The [SQLITE_FCNTL_COMMIT_PHASETWO] opcode is generated internally by SQLite
-** and sent to the VFS after a transaction has been committed immediately
-** but before the database is unlocked. VFSes that do not need this signal
-** should silently ignore this opcode. Applications should not call
-** [sqlite3_file_control()] with this opcode as doing so may disrupt the 
-** operation of the specialized VFSes that do require it.  
-**
-** <li>[[SQLITE_FCNTL_WIN32_AV_RETRY]]
-** ^The [SQLITE_FCNTL_WIN32_AV_RETRY] opcode is used to configure automatic
-** retry counts and intervals for certain disk I/O operations for the
-** windows [VFS] in order to provide robustness in the presence of
-** anti-virus programs.  By default, the windows VFS will retry file read,
-** file write, and file delete operations up to 10 times, with a delay
-** of 25 milliseconds before the first retry and with the delay increasing
-** by an additional 25 milliseconds with each subsequent retry.  This
-** opcode allows these two values (10 retries and 25 milliseconds of delay)
-** to be adjusted.  The values are changed for all database connections
-** within the same process.  The argument is a pointer to an array of two
-** integers where the first integer i the new retry count and the second
-** integer is the delay.  If either integer is negative, then the setting
-** is not changed but instead the prior value of that setting is written
-** into the array entry, allowing the current retry settings to be
-** interrogated.  The zDbName parameter is ignored.
-**
-** <li>[[SQLITE_FCNTL_PERSIST_WAL]]
-** ^The [SQLITE_FCNTL_PERSIST_WAL] opcode is used to set or query the
-** persistent [WAL | Write Ahead Log] setting.  By default, the auxiliary
-** write ahead log and shared memory files used for transaction control
-** are automatically deleted when the latest connection to the database
-** closes.  Setting persistent WAL mode causes those files to persist after
-** close.  Persisting the files is useful when other processes that do not
-** have write permission on the directory containing the database file want
-** to read the database file, as the WAL and shared memory files must exist
-** in order for the database to be readable.  The fourth parameter to
-** [sqlite3_file_control()] for this opcode should be a pointer to an integer.
-** That integer is 0 to disable persistent WAL mode or 1 to enable persistent
-** WAL mode.  If the integer is -1, then it is overwritten with the current
-** WAL persistence setting.
-**
-** <li>[[SQLITE_FCNTL_POWERSAFE_OVERWRITE]]
-** ^The [SQLITE_FCNTL_POWERSAFE_OVERWRITE] opcode is used to set or query the
-** persistent "powersafe-overwrite" or "PSOW" setting.  The PSOW setting
-** determines the [SQLITE_IOCAP_POWERSAFE_OVERWRITE] bit of the
-** xDeviceCharacteristics methods. The fourth parameter to
-** [sqlite3_file_control()] for this opcode should be a pointer to an integer.
-** That integer is 0 to disable zero-damage mode or 1 to enable zero-damage
-** mode.  If the integer is -1, then it is overwritten with the current
-** zero-damage mode setting.
-**
-** <li>[[SQLITE_FCNTL_OVERWRITE]]
-** ^The [SQLITE_FCNTL_OVERWRITE] opcode is invoked by SQLite after opening
-** a write transaction to indicate that, unless it is rolled back for some
-** reason, the entire database file will be overwritten by the current 
-** transaction. This is used by VACUUM operations.
-**
-** <li>[[SQLITE_FCNTL_VFSNAME]]
-** ^The [SQLITE_FCNTL_VFSNAME] opcode can be used to obtain the names of
-** all [VFSes] in the VFS stack.  The names are of all VFS shims and the
-** final bottom-level VFS are written into memory obtained from 
-** [sqlite3_malloc()] and the result is stored in the char* variable
-** that the fourth parameter of [sqlite3_file_control()] points to.
-** The caller is responsible for freeing the memory when done.  As with
-** all file-control actions, there is no guarantee that this will actually
-** do anything.  Callers should initialize the char* variable to a NULL
-** pointer in case this file-control is not implemented.  This file-control
-** is intended for diagnostic use only.
-**
-** <li>[[SQLITE_FCNTL_PRAGMA]]
-** ^Whenever a [PRAGMA] statement is parsed, an [SQLITE_FCNTL_PRAGMA] 
-** file control is sent to the open [sqlite3_file] object corresponding
-** to the database file to which the pragma statement refers. ^The argument
-** to the [SQLITE_FCNTL_PRAGMA] file control is an array of
-** pointers to strings (char**) in which the second element of the array
-** is the name of the pragma and the third element is the argument to the
-** pragma or NULL if the pragma has no argument.  ^The handler for an
-** [SQLITE_FCNTL_PRAGMA] file control can optionally make the first element
-** of the char** argument point to a string obtained from [sqlite3_mprintf()]
-** or the equivalent and that string will become the result of the pragma or
-** the error message if the pragma fails. ^If the
-** [SQLITE_FCNTL_PRAGMA] file control returns [SQLITE_NOTFOUND], then normal 
-** [PRAGMA] processing continues.  ^If the [SQLITE_FCNTL_PRAGMA]
-** file control returns [SQLITE_OK], then the parser assumes that the
-** VFS has handled the PRAGMA itself and the parser generates a no-op
-** prepared statement if result string is NULL, or that returns a copy
-** of the result string if the string is non-NULL.
-** ^If the [SQLITE_FCNTL_PRAGMA] file control returns
-** any result code other than [SQLITE_OK] or [SQLITE_NOTFOUND], that means
-** that the VFS encountered an error while handling the [PRAGMA] and the
-** compilation of the PRAGMA fails with an error.  ^The [SQLITE_FCNTL_PRAGMA]
-** file control occurs at the beginning of pragma statement analysis and so
-** it is able to override built-in [PRAGMA] statements.
-**
-** <li>[[SQLITE_FCNTL_BUSYHANDLER]]
-** ^The [SQLITE_FCNTL_BUSYHANDLER]
-** file-control may be invoked by SQLite on the database file handle
-** shortly after it is opened in order to provide a custom VFS with access
-** to the connections busy-handler callback. The argument is of type (void **)
-** - an array of two (void *) values. The first (void *) actually points
-** to a function of type (int (*)(void *)). In order to invoke the connections
-** busy-handler, this function should be invoked with the second (void *) in
-** the array as the only argument. If it returns non-zero, then the operation
-** should be retried. If it returns zero, the custom VFS should abandon the
-** current operation.
-**
-** <li>[[SQLITE_FCNTL_TEMPFILENAME]]
-** ^Application can invoke the [SQLITE_FCNTL_TEMPFILENAME] file-control
-** to have SQLite generate a
-** temporary filename using the same algorithm that is followed to generate
-** temporary filenames for TEMP tables and other internal uses.  The
-** argument should be a char** which will be filled with the filename
-** written into memory obtained from [sqlite3_malloc()].  The caller should
-** invoke [sqlite3_free()] on the result to avoid a memory leak.
-**
-** <li>[[SQLITE_FCNTL_MMAP_SIZE]]
-** The [SQLITE_FCNTL_MMAP_SIZE] file control is used to query or set the
-** maximum number of bytes that will be used for memory-mapped I/O.
-** The argument is a pointer to a value of type sqlite3_int64 that
-** is an advisory maximum number of bytes in the file to memory map.  The
-** pointer is overwritten with the old value.  The limit is not changed if
-** the value originally pointed to is negative, and so the current limit 
-** can be queried by passing in a pointer to a negative number.  This
-** file-control is used internally to implement [PRAGMA mmap_size].
-**
-** <li>[[SQLITE_FCNTL_TRACE]]
-** The [SQLITE_FCNTL_TRACE] file control provides advisory information
-** to the VFS about what the higher layers of the SQLite stack are doing.
-** This file control is used by some VFS activity tracing [shims].
-** The argument is a zero-terminated string.  Higher layers in the
-** SQLite stack may generate instances of this file control if
-** the [SQLITE_USE_FCNTL_TRACE] compile-time option is enabled.
-**
-** <li>[[SQLITE_FCNTL_HAS_MOVED]]
-** The [SQLITE_FCNTL_HAS_MOVED] file control interprets its argument as a
-** pointer to an integer and it writes a boolean into that integer depending
-** on whether or not the file has been renamed, moved, or deleted since it
-** was first opened.
-**
-** <li>[[SQLITE_FCNTL_WIN32_SET_HANDLE]]
-** The [SQLITE_FCNTL_WIN32_SET_HANDLE] opcode is used for debugging.  This
-** opcode causes the xFileControl method to swap the file handle with the one
-** pointed to by the pArg argument.  This capability is used during testing
-** and only needs to be supported when SQLITE_TEST is defined.
-**
-** <li>[[SQLITE_FCNTL_WAL_BLOCK]]
-** The [SQLITE_FCNTL_WAL_BLOCK] is a signal to the VFS layer that it might
-** be advantageous to block on the next WAL lock if the lock is not immediately
-** available.  The WAL subsystem issues this signal during rare
-** circumstances in order to fix a problem with priority inversion.
-** Applications should <em>not</em> use this file-control.
-**
-** <li>[[SQLITE_FCNTL_ZIPVFS]]
-** The [SQLITE_FCNTL_ZIPVFS] opcode is implemented by zipvfs only. All other
-** VFS should return SQLITE_NOTFOUND for this opcode.
-**
-** <li>[[SQLITE_FCNTL_RBU]]
-** The [SQLITE_FCNTL_RBU] opcode is implemented by the special VFS used by
-** the RBU extension only.  All other VFS should return SQLITE_NOTFOUND for
-** this opcode.  
-** </ul>
-*/
-#define SQLITE_FCNTL_LOCKSTATE               1
-#define SQLITE_FCNTL_GET_LOCKPROXYFILE       2
-#define SQLITE_FCNTL_SET_LOCKPROXYFILE       3
-#define SQLITE_FCNTL_LAST_ERRNO              4
-#define SQLITE_FCNTL_SIZE_HINT               5
-#define SQLITE_FCNTL_CHUNK_SIZE              6
-#define SQLITE_FCNTL_FILE_POINTER            7
-#define SQLITE_FCNTL_SYNC_OMITTED            8
-#define SQLITE_FCNTL_WIN32_AV_RETRY          9
-#define SQLITE_FCNTL_PERSIST_WAL            10
-#define SQLITE_FCNTL_OVERWRITE              11
-#define SQLITE_FCNTL_VFSNAME                12
-#define SQLITE_FCNTL_POWERSAFE_OVERWRITE    13
-#define SQLITE_FCNTL_PRAGMA                 14
-#define SQLITE_FCNTL_BUSYHANDLER            15
-#define SQLITE_FCNTL_TEMPFILENAME           16
-#define SQLITE_FCNTL_MMAP_SIZE              18
-#define SQLITE_FCNTL_TRACE                  19
-#define SQLITE_FCNTL_HAS_MOVED              20
-#define SQLITE_FCNTL_SYNC                   21
-#define SQLITE_FCNTL_COMMIT_PHASETWO        22
-#define SQLITE_FCNTL_WIN32_SET_HANDLE       23
-#define SQLITE_FCNTL_WAL_BLOCK              24
-#define SQLITE_FCNTL_ZIPVFS                 25
-#define SQLITE_FCNTL_RBU                    26
-
-/*
-** CAPI3REF: Mutex Handle
-**
-** The mutex module within SQLite defines [sqlite3_mutex] to be an
-** abstract type for a mutex object.  The SQLite core never looks
-** at the internal representation of an [sqlite3_mutex].  It only
-** deals with pointers to the [sqlite3_mutex] object.
-**
-** Mutexes are created using [sqlite3_mutex_alloc()].
-*/
-typedef struct sqlite3_mutex sqlite3_mutex;
-
-/*
-** CAPI3REF: OS Interface Object
-**
-** An instance of the sqlite3_vfs object defines the interface between
-** the SQLite core and the underlying operating system.  The "vfs"
-** in the name of the object stands for "virtual file system".  See
-** the [VFS | VFS documentation] for further information.
-**
-** The value of the iVersion field is initially 1 but may be larger in
-** future versions of SQLite.  Additional fields may be appended to this
-** object when the iVersion value is increased.  Note that the structure
-** of the sqlite3_vfs object changes in the transaction between
-** SQLite version 3.5.9 and 3.6.0 and yet the iVersion field was not
-** modified.
-**
-** The szOsFile field is the size of the subclassed [sqlite3_file]
-** structure used by this VFS.  mxPathname is the maximum length of
-** a pathname in this VFS.
-**
-** Registered sqlite3_vfs objects are kept on a linked list formed by
-** the pNext pointer.  The [sqlite3_vfs_register()] interface manages
-** this list in a thread-safe way.  The [sqlite3_vfs_find()] interface
-** searches the list.  Neither the application code nor the VFS
-** implementation should use the pNext pointer.
-**
-** The pNext field is the only field in the sqlite3_vfs
-** structure that SQLite will ever modify.  SQLite will only access
-** or modify this field while holding a particular static mutex.
-** The application should never modify anything within the sqlite3_vfs
-** object once the object has been registered.
-**
-** The zName field holds the name of the VFS module.  The name must
-** be unique across all VFS modules.
-**
-** [[sqlite3_vfs.xOpen]]
-** ^SQLite guarantees that the zFilename parameter to xOpen
-** is either a NULL pointer or string obtained
-** from xFullPathname() with an optional suffix added.
-** ^If a suffix is added to the zFilename parameter, it will
-** consist of a single "-" character followed by no more than
-** 11 alphanumeric and/or "-" characters.
-** ^SQLite further guarantees that
-** the string will be valid and unchanged until xClose() is
-** called. Because of the previous sentence,
-** the [sqlite3_file] can safely store a pointer to the
-** filename if it needs to remember the filename for some reason.
-** If the zFilename parameter to xOpen is a NULL pointer then xOpen
-** must invent its own temporary name for the file.  ^Whenever the 
-** xFilename parameter is NULL it will also be the case that the
-** flags parameter will include [SQLITE_OPEN_DELETEONCLOSE].
-**
-** The flags argument to xOpen() includes all bits set in
-** the flags argument to [sqlite3_open_v2()].  Or if [sqlite3_open()]
-** or [sqlite3_open16()] is used, then flags includes at least
-** [SQLITE_OPEN_READWRITE] | [SQLITE_OPEN_CREATE]. 
-** If xOpen() opens a file read-only then it sets *pOutFlags to
-** include [SQLITE_OPEN_READONLY].  Other bits in *pOutFlags may be set.
-**
-** ^(SQLite will also add one of the following flags to the xOpen()
-** call, depending on the object being opened:
-**
-** <ul>
-** <li>  [SQLITE_OPEN_MAIN_DB]
-** <li>  [SQLITE_OPEN_MAIN_JOURNAL]
-** <li>  [SQLITE_OPEN_TEMP_DB]
-** <li>  [SQLITE_OPEN_TEMP_JOURNAL]
-** <li>  [SQLITE_OPEN_TRANSIENT_DB]
-** <li>  [SQLITE_OPEN_SUBJOURNAL]
-** <li>  [SQLITE_OPEN_MASTER_JOURNAL]
-** <li>  [SQLITE_OPEN_WAL]
-** </ul>)^
-**
-** The file I/O implementation can use the object type flags to
-** change the way it deals with files.  For example, an application
-** that does not care about crash recovery or rollback might make
-** the open of a journal file a no-op.  Writes to this journal would
-** also be no-ops, and any attempt to read the journal would return
-** SQLITE_IOERR.  Or the implementation might recognize that a database
-** file will be doing page-aligned sector reads and writes in a random
-** order and set up its I/O subsystem accordingly.
-**
-** SQLite might also add one of the following flags to the xOpen method:
-**
-** <ul>
-** <li> [SQLITE_OPEN_DELETEONCLOSE]
-** <li> [SQLITE_OPEN_EXCLUSIVE]
-** </ul>
-**
-** The [SQLITE_OPEN_DELETEONCLOSE] flag means the file should be
-** deleted when it is closed.  ^The [SQLITE_OPEN_DELETEONCLOSE]
-** will be set for TEMP databases and their journals, transient
-** databases, and subjournals.
-**
-** ^The [SQLITE_OPEN_EXCLUSIVE] flag is always used in conjunction
-** with the [SQLITE_OPEN_CREATE] flag, which are both directly
-** analogous to the O_EXCL and O_CREAT flags of the POSIX open()
-** API.  The SQLITE_OPEN_EXCLUSIVE flag, when paired with the 
-** SQLITE_OPEN_CREATE, is used to indicate that file should always
-** be created, and that it is an error if it already exists.
-** It is <i>not</i> used to indicate the file should be opened 
-** for exclusive access.
-**
-** ^At least szOsFile bytes of memory are allocated by SQLite
-** to hold the  [sqlite3_file] structure passed as the third
-** argument to xOpen.  The xOpen method does not have to
-** allocate the structure; it should just fill it in.  Note that
-** the xOpen method must set the sqlite3_file.pMethods to either
-** a valid [sqlite3_io_methods] object or to NULL.  xOpen must do
-** this even if the open fails.  SQLite expects that the sqlite3_file.pMethods
-** element will be valid after xOpen returns regardless of the success
-** or failure of the xOpen call.
-**
-** [[sqlite3_vfs.xAccess]]
-** ^The flags argument to xAccess() may be [SQLITE_ACCESS_EXISTS]
-** to test for the existence of a file, or [SQLITE_ACCESS_READWRITE] to
-** test whether a file is readable and writable, or [SQLITE_ACCESS_READ]
-** to test whether a file is at least readable.   The file can be a
-** directory.
-**
-** ^SQLite will always allocate at least mxPathname+1 bytes for the
-** output buffer xFullPathname.  The exact size of the output buffer
-** is also passed as a parameter to both  methods. If the output buffer
-** is not large enough, [SQLITE_CANTOPEN] should be returned. Since this is
-** handled as a fatal error by SQLite, vfs implementations should endeavor
-** to prevent this by setting mxPathname to a sufficiently large value.
-**
-** The xRandomness(), xSleep(), xCurrentTime(), and xCurrentTimeInt64()
-** interfaces are not strictly a part of the filesystem, but they are
-** included in the VFS structure for completeness.
-** The xRandomness() function attempts to return nBytes bytes
-** of good-quality randomness into zOut.  The return value is
-** the actual number of bytes of randomness obtained.
-** The xSleep() method causes the calling thread to sleep for at
-** least the number of microseconds given.  ^The xCurrentTime()
-** method returns a Julian Day Number for the current date and time as
-** a floating point value.
-** ^The xCurrentTimeInt64() method returns, as an integer, the Julian
-** Day Number multiplied by 86400000 (the number of milliseconds in 
-** a 24-hour day).  
-** ^SQLite will use the xCurrentTimeInt64() method to get the current
-** date and time if that method is available (if iVersion is 2 or 
-** greater and the function pointer is not NULL) and will fall back
-** to xCurrentTime() if xCurrentTimeInt64() is unavailable.
-**
-** ^The xSetSystemCall(), xGetSystemCall(), and xNestSystemCall() interfaces
-** are not used by the SQLite core.  These optional interfaces are provided
-** by some VFSes to facilitate testing of the VFS code. By overriding 
-** system calls with functions under its control, a test program can
-** simulate faults and error conditions that would otherwise be difficult
-** or impossible to induce.  The set of system calls that can be overridden
-** varies from one VFS to another, and from one version of the same VFS to the
-** next.  Applications that use these interfaces must be prepared for any
-** or all of these interfaces to be NULL or for their behavior to change
-** from one release to the next.  Applications must not attempt to access
-** any of these methods if the iVersion of the VFS is less than 3.
-*/
-typedef struct sqlite3_vfs sqlite3_vfs;
-typedef void (*sqlite3_syscall_ptr)(void);
-struct sqlite3_vfs {
-  int iVersion;            /* Structure version number (currently 3) */
-  int szOsFile;            /* Size of subclassed sqlite3_file */
-  int mxPathname;          /* Maximum file pathname length */
-  sqlite3_vfs *pNext;      /* Next registered VFS */
-  const char *zName;       /* Name of this virtual file system */
-  void *pAppData;          /* Pointer to application-specific data */
-  int (*xOpen)(sqlite3_vfs*, const char *zName, sqlite3_file*,
-               int flags, int *pOutFlags);
-  int (*xDelete)(sqlite3_vfs*, const char *zName, int syncDir);
-  int (*xAccess)(sqlite3_vfs*, const char *zName, int flags, int *pResOut);
-  int (*xFullPathname)(sqlite3_vfs*, const char *zName, int nOut, char *zOut);
-  void *(*xDlOpen)(sqlite3_vfs*, const char *zFilename);
-  void (*xDlError)(sqlite3_vfs*, int nByte, char *zErrMsg);
-  void (*(*xDlSym)(sqlite3_vfs*,void*, const char *zSymbol))(void);
-  void (*xDlClose)(sqlite3_vfs*, void*);
-  int (*xRandomness)(sqlite3_vfs*, int nByte, char *zOut);
-  int (*xSleep)(sqlite3_vfs*, int microseconds);
-  int (*xCurrentTime)(sqlite3_vfs*, double*);
-  int (*xGetLastError)(sqlite3_vfs*, int, char *);
-  /*
-  ** The methods above are in version 1 of the sqlite_vfs object
-  ** definition.  Those that follow are added in version 2 or later
-  */
-  int (*xCurrentTimeInt64)(sqlite3_vfs*, sqlite3_int64*);
-  /*
-  ** The methods above are in versions 1 and 2 of the sqlite_vfs object.
-  ** Those below are for version 3 and greater.
-  */
-  int (*xSetSystemCall)(sqlite3_vfs*, const char *zName, sqlite3_syscall_ptr);
-  sqlite3_syscall_ptr (*xGetSystemCall)(sqlite3_vfs*, const char *zName);
-  const char *(*xNextSystemCall)(sqlite3_vfs*, const char *zName);
-  /*
-  ** The methods above are in versions 1 through 3 of the sqlite_vfs object.
-  ** New fields may be appended in figure versions.  The iVersion
-  ** value will increment whenever this happens. 
-  */
-};
-
-/*
-** CAPI3REF: Flags for the xAccess VFS method
-**
-** These integer constants can be used as the third parameter to
-** the xAccess method of an [sqlite3_vfs] object.  They determine
-** what kind of permissions the xAccess method is looking for.
-** With SQLITE_ACCESS_EXISTS, the xAccess method
-** simply checks whether the file exists.
-** With SQLITE_ACCESS_READWRITE, the xAccess method
-** checks whether the named directory is both readable and writable
-** (in other words, if files can be added, removed, and renamed within
-** the directory).
-** The SQLITE_ACCESS_READWRITE constant is currently used only by the
-** [temp_store_directory pragma], though this could change in a future
-** release of SQLite.
-** With SQLITE_ACCESS_READ, the xAccess method
-** checks whether the file is readable.  The SQLITE_ACCESS_READ constant is
-** currently unused, though it might be used in a future release of
-** SQLite.
-*/
-#define SQLITE_ACCESS_EXISTS    0
-#define SQLITE_ACCESS_READWRITE 1   /* Used by PRAGMA temp_store_directory */
-#define SQLITE_ACCESS_READ      2   /* Unused */
-
-/*
-** CAPI3REF: Flags for the xShmLock VFS method
-**
-** These integer constants define the various locking operations
-** allowed by the xShmLock method of [sqlite3_io_methods].  The
-** following are the only legal combinations of flags to the
-** xShmLock method:
-**
-** <ul>
-** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_SHARED
-** <li>  SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE
-** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED
-** <li>  SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE
-** </ul>
-**
-** When unlocking, the same SHARED or EXCLUSIVE flag must be supplied as
-** was given on the corresponding lock.  
-**
-** The xShmLock method can transition between unlocked and SHARED or
-** between unlocked and EXCLUSIVE.  It cannot transition between SHARED
-** and EXCLUSIVE.
-*/
-#define SQLITE_SHM_UNLOCK       1
-#define SQLITE_SHM_LOCK         2
-#define SQLITE_SHM_SHARED       4
-#define SQLITE_SHM_EXCLUSIVE    8
-
-/*
-** CAPI3REF: Maximum xShmLock index
-**
-** The xShmLock method on [sqlite3_io_methods] may use values
-** between 0 and this upper bound as its "offset" argument.
-** The SQLite core will never attempt to acquire or release a
-** lock outside of this range
-*/
-#define SQLITE_SHM_NLOCK        8
-
-SQLITE_PRIVATE int sqlite3_os_init(void);
-SQLITE_PRIVATE int sqlite3_os_end(void);
-
-/*
-** CAPI3REF: Configuring The SQLite Library
-**
-** The sqlite3_config() interface is used to make global configuration
-** changes to SQLite in order to tune SQLite to the specific needs of
-** the application.  The default configuration is recommended for most
-** applications and so this routine is usually not necessary.  It is
-** provided to support rare applications with unusual needs.
-**
-** <b>The sqlite3_config() interface is not threadsafe. The application
-** must ensure that no other SQLite interfaces are invoked by other
-** threads while sqlite3_config() is running.</b>
-**
-** The sqlite3_config() interface
-** may only be invoked prior to library initialization using
-** [sqlite3BtreeInitialize()] or after shutdown by [sqlite3BtreeShutdown()].
-** ^If sqlite3_config() is called after [sqlite3BtreeInitialize()] and before
-** [sqlite3BtreeShutdown()] then it will return SQLITE_MISUSE.
-** Note, however, that ^sqlite3_config() can be called as part of the
-** implementation of an application-defined [sqlite3_os_init()].
-**
-** The first argument to sqlite3_config() is an integer
-** [configuration option] that determines
-** what property of SQLite is to be configured.  Subsequent arguments
-** vary depending on the [configuration option]
-** in the first argument.
-**
-** ^When a configuration option is set, sqlite3_config() returns [SQLITE_OK].
-** ^If the option is unknown or SQLite is unable to set the option
-** then this routine returns a non-zero [error code].
-*/
-SQLITE_PRIVATE int sqlite3_config(int, ...);
-
-/*
-** CAPI3REF: Memory Allocation Routines
-**
-** An instance of this object defines the interface between SQLite
-** and low-level memory allocation routines.
-**
-** This object is used in only one place in the SQLite interface.
-** A pointer to an instance of this object is the argument to
-** [sqlite3_config()] when the configuration option is
-** [SQLITE_CONFIG_MALLOC] or [SQLITE_CONFIG_GETMALLOC].  
-** By creating an instance of this object
-** and passing it to [sqlite3_config]([SQLITE_CONFIG_MALLOC])
-** during configuration, an application can specify an alternative
-** memory allocation subsystem for SQLite to use for all of its
-** dynamic memory needs.
-**
-** Note that SQLite comes with several [built-in memory allocators]
-** that are perfectly adequate for the overwhelming majority of applications
-** and that this object is only useful to a tiny minority of applications
-** with specialized memory allocation requirements.  This object is
-** also used during testing of SQLite in order to specify an alternative
-** memory allocator that simulates memory out-of-memory conditions in
-** order to verify that SQLite recovers gracefully from such
-** conditions.
-**
-** The xMalloc, xRealloc, and xFree methods must work like the
-** malloc(), realloc() and free() functions from the standard C library.
-** ^SQLite guarantees that the second argument to
-** xRealloc is always a value returned by a prior call to xRoundup.
-**
-** xSize should return the allocated size of a memory allocation
-** previously obtained from xMalloc or xRealloc.  The allocated size
-** is always at least as big as the requested size but may be larger.
-**
-** The xRoundup method returns what would be the allocated size of
-** a memory allocation given a particular requested size.  Most memory
-** allocators round up memory allocations at least to the next multiple
-** of 8.  Some allocators round up to a larger multiple or to a power of 2.
-** Every memory allocation request coming in through [sqlite3_malloc()]
-** or [sqlite3_realloc()] first calls xRoundup.  If xRoundup returns 0, 
-** that causes the corresponding memory allocation to fail.
-**
-** The xInit method initializes the memory allocator.  For example,
-** it might allocate any require mutexes or initialize internal data
-** structures.  The xShutdown method is invoked (indirectly) by
-** [sqlite3BtreeShutdown()] and should deallocate any resources acquired
-** by xInit.  The pAppData pointer is used as the only parameter to
-** xInit and xShutdown.
-**
-** SQLite holds the [SQLITE_MUTEX_STATIC_MASTER] mutex when it invokes
-** the xInit method, so the xInit method need not be threadsafe.  The
-** xShutdown method is only called from [sqlite3BtreeShutdown()] so it does
-** not need to be threadsafe either.  For all other methods, SQLite
-** holds the [SQLITE_MUTEX_STATIC_MEM] mutex as long as the
-** [SQLITE_CONFIG_MEMSTATUS] configuration option is turned on (which
-** it is by default) and so the methods are automatically serialized.
-** However, if [SQLITE_CONFIG_MEMSTATUS] is disabled, then the other
-** methods must be threadsafe or else make their own arrangements for
-** serialization.
-**
-** SQLite will never invoke xInit() more than once without an intervening
-** call to xShutdown().
-*/
-typedef struct sqlite3_mem_methods sqlite3_mem_methods;
-struct sqlite3_mem_methods {
-  void *(*xMalloc)(int);         /* Memory allocation function */
-  void (*xFree)(void*);          /* Free a prior allocation */
-  void *(*xRealloc)(void*,int);  /* Resize an allocation */
-  int (*xSize)(void*);           /* Return the size of an allocation */
-  int (*xRoundup)(int);          /* Round up request size to allocation size */
-  int (*xInit)(void*);           /* Initialize the memory allocator */
-  void (*xShutdown)(void*);      /* Deinitialize the memory allocator */
-  void *pAppData;                /* Argument to xInit() and xShutdown() */
-};
-
-/*
-** CAPI3REF: Configuration Options
-** KEYWORDS: {configuration option}
-**
-** These constants are the available integer configuration options that
-** can be passed as the first argument to the [sqlite3_config()] interface.
-**
-** New configuration options may be added in future releases of SQLite.
-** Existing configuration options might be discontinued.  Applications
-** should check the return code from [sqlite3_config()] to make sure that
-** the call worked.  The [sqlite3_config()] interface will return a
-** non-zero [error code] if a discontinued or unsupported configuration option
-** is invoked.
-**
-** <dl>
-** [[SQLITE_CONFIG_SINGLETHREAD]] <dt>SQLITE_CONFIG_SINGLETHREAD</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Single-thread.  In other words, it disables
-** all mutexing and puts SQLite into a mode where it can only be used
-** by a single thread.   ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to change the [threading mode] from its default
-** value of Single-thread and so [sqlite3_config()] will return 
-** [SQLITE_ERROR] if called with the SQLITE_CONFIG_SINGLETHREAD
-** configuration option.</dd>
-**
-** [[SQLITE_CONFIG_MULTITHREAD]] <dt>SQLITE_CONFIG_MULTITHREAD</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Multi-thread.  In other words, it disables
-** mutexing on [database connection] and [prepared statement] objects.
-** The application is responsible for serializing access to
-** [database connections] and [prepared statements].  But other mutexes
-** are enabled so that SQLite will be safe to use in a multi-threaded
-** environment as long as no two threads attempt to use the same
-** [database connection] at the same time.  ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to set the Multi-thread [threading mode] and
-** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
-** SQLITE_CONFIG_MULTITHREAD configuration option.</dd>
-**
-** [[SQLITE_CONFIG_SERIALIZED]] <dt>SQLITE_CONFIG_SERIALIZED</dt>
-** <dd>There are no arguments to this option.  ^This option sets the
-** [threading mode] to Serialized. In other words, this option enables
-** all mutexes including the recursive
-** mutexes on [database connection] and [prepared statement] objects.
-** In this mode (which is the default when SQLite is compiled with
-** [SQLITE_THREADSAFE=1]) the SQLite library will itself serialize access
-** to [database connections] and [prepared statements] so that the
-** application is free to use the same [database connection] or the
-** same [prepared statement] in different threads at the same time.
-** ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** it is not possible to set the Serialized [threading mode] and
-** [sqlite3_config()] will return [SQLITE_ERROR] if called with the
-** SQLITE_CONFIG_SERIALIZED configuration option.</dd>
-**
-** [[SQLITE_CONFIG_MALLOC]] <dt>SQLITE_CONFIG_MALLOC</dt>
-** <dd> ^(The SQLITE_CONFIG_MALLOC option takes a single argument which is 
-** a pointer to an instance of the [sqlite3_mem_methods] structure.
-** The argument specifies
-** alternative low-level memory allocation routines to be used in place of
-** the memory allocation routines built into SQLite.)^ ^SQLite makes
-** its own private copy of the content of the [sqlite3_mem_methods] structure
-** before the [sqlite3_config()] call returns.</dd>
-**
-** [[SQLITE_CONFIG_GETMALLOC]] <dt>SQLITE_CONFIG_GETMALLOC</dt>
-** <dd> ^(The SQLITE_CONFIG_GETMALLOC option takes a single argument which
-** is a pointer to an instance of the [sqlite3_mem_methods] structure.
-** The [sqlite3_mem_methods]
-** structure is filled with the currently defined memory allocation routines.)^
-** This option can be used to overload the default memory allocation
-** routines with a wrapper that simulations memory allocation failure or
-** tracks memory usage, for example. </dd>
-**
-** [[SQLITE_CONFIG_MEMSTATUS]] <dt>SQLITE_CONFIG_MEMSTATUS</dt>
-** <dd> ^The SQLITE_CONFIG_MEMSTATUS option takes single argument of type int,
-** interpreted as a boolean, which enables or disables the collection of
-** memory allocation statistics. ^(When memory allocation statistics are
-** disabled, the following SQLite interfaces become non-operational:
-**   <ul>
-**   <li> [sqlite3_memory_used()]
-**   <li> [sqlite3_memory_highwater()]
-**   <li> [sqlite3_soft_heap_limit64()]
-**   <li> [sqlite3_status64()]
-**   </ul>)^
-** ^Memory allocation statistics are enabled by default unless SQLite is
-** compiled with [SQLITE_DEFAULT_MEMSTATUS]=0 in which case memory
-** allocation statistics are disabled by default.
-** </dd>
-**
-** [[SQLITE_CONFIG_SCRATCH]] <dt>SQLITE_CONFIG_SCRATCH</dt>
-** <dd> ^The SQLITE_CONFIG_SCRATCH option specifies a static memory buffer
-** that SQLite can use for scratch memory.  ^(There are three arguments
-** to SQLITE_CONFIG_SCRATCH:  A pointer an 8-byte
-** aligned memory buffer from which the scratch allocations will be
-** drawn, the size of each scratch allocation (sz),
-** and the maximum number of scratch allocations (N).)^
-** The first argument must be a pointer to an 8-byte aligned buffer
-** of at least sz*N bytes of memory.
-** ^SQLite will not use more than one scratch buffers per thread.
-** ^SQLite will never request a scratch buffer that is more than 6
-** times the database page size.
-** ^If SQLite needs needs additional
-** scratch memory beyond what is provided by this configuration option, then 
-** [sqlite3_malloc()] will be used to obtain the memory needed.<p>
-** ^When the application provides any amount of scratch memory using
-** SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary large
-** [sqlite3_malloc|heap allocations].
-** This can help [Robson proof|prevent memory allocation failures] due to heap
-** fragmentation in low-memory embedded systems.
-** </dd>
-**
-** [[SQLITE_CONFIG_PAGECACHE]] <dt>SQLITE_CONFIG_PAGECACHE</dt>
-** <dd> ^The SQLITE_CONFIG_PAGECACHE option specifies a static memory buffer
-** that SQLite can use for the database page cache with the default page
-** cache implementation.  
-** This configuration should not be used if an application-define page
-** cache implementation is loaded using the [SQLITE_CONFIG_PCACHE2]
-** configuration option.
-** ^There are three arguments to SQLITE_CONFIG_PAGECACHE: A pointer to
-** 8-byte aligned
-** memory, the size of each page buffer (sz), and the number of pages (N).
-** The sz argument should be the size of the largest database page
-** (a power of two between 512 and 65536) plus some extra bytes for each
-** page header.  ^The number of extra bytes needed by the page header
-** can be determined using the [SQLITE_CONFIG_PCACHE_HDRSZ] option 
-** to [sqlite3_config()].
-** ^It is harmless, apart from the wasted memory,
-** for the sz parameter to be larger than necessary.  The first
-** argument should pointer to an 8-byte aligned block of memory that
-** is at least sz*N bytes of memory, otherwise subsequent behavior is
-** undefined.
-** ^SQLite will use the memory provided by the first argument to satisfy its
-** memory needs for the first N pages that it adds to cache.  ^If additional
-** page cache memory is needed beyond what is provided by this option, then
-** SQLite goes to [sqlite3_malloc()] for the additional storage space.</dd>
-**
-** [[SQLITE_CONFIG_HEAP]] <dt>SQLITE_CONFIG_HEAP</dt>
-** <dd> ^The SQLITE_CONFIG_HEAP option specifies a static memory buffer 
-** that SQLite will use for all of its dynamic memory allocation needs
-** beyond those provided for by [SQLITE_CONFIG_SCRATCH] and
-** [SQLITE_CONFIG_PAGECACHE].
-** ^The SQLITE_CONFIG_HEAP option is only available if SQLite is compiled
-** with either [SQLITE_ENABLE_MEMSYS3] or [SQLITE_ENABLE_MEMSYS5] and returns
-** [SQLITE_ERROR] if invoked otherwise.
-** ^There are three arguments to SQLITE_CONFIG_HEAP:
-** An 8-byte aligned pointer to the memory,
-** the number of bytes in the memory buffer, and the minimum allocation size.
-** ^If the first pointer (the memory pointer) is NULL, then SQLite reverts
-** to using its default memory allocator (the system malloc() implementation),
-** undoing any prior invocation of [SQLITE_CONFIG_MALLOC].  ^If the
-** memory pointer is not NULL then the alternative memory
-** allocator is engaged to handle all of SQLites memory allocation needs.
-** The first pointer (the memory pointer) must be aligned to an 8-byte
-** boundary or subsequent behavior of SQLite will be undefined.
-** The minimum allocation size is capped at 2**12. Reasonable values
-** for the minimum allocation size are 2**5 through 2**8.</dd>
-**
-** [[SQLITE_CONFIG_MUTEX]] <dt>SQLITE_CONFIG_MUTEX</dt>
-** <dd> ^(The SQLITE_CONFIG_MUTEX option takes a single argument which is a
-** pointer to an instance of the [sqlite3_mutex_methods] structure.
-** The argument specifies alternative low-level mutex routines to be used
-** in place the mutex routines built into SQLite.)^  ^SQLite makes a copy of
-** the content of the [sqlite3_mutex_methods] structure before the call to
-** [sqlite3_config()] returns. ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** the entire mutexing subsystem is omitted from the build and hence calls to
-** [sqlite3_config()] with the SQLITE_CONFIG_MUTEX configuration option will
-** return [SQLITE_ERROR].</dd>
-**
-** [[SQLITE_CONFIG_GETMUTEX]] <dt>SQLITE_CONFIG_GETMUTEX</dt>
-** <dd> ^(The SQLITE_CONFIG_GETMUTEX option takes a single argument which
-** is a pointer to an instance of the [sqlite3_mutex_methods] structure.  The
-** [sqlite3_mutex_methods]
-** structure is filled with the currently defined mutex routines.)^
-** This option can be used to overload the default mutex allocation
-** routines with a wrapper used to track mutex usage for performance
-** profiling or testing, for example.   ^If SQLite is compiled with
-** the [SQLITE_THREADSAFE | SQLITE_THREADSAFE=0] compile-time option then
-** the entire mutexing subsystem is omitted from the build and hence calls to
-** [sqlite3_config()] with the SQLITE_CONFIG_GETMUTEX configuration option will
-** return [SQLITE_ERROR].</dd>
-**
-** [[SQLITE_CONFIG_LOOKASIDE]] <dt>SQLITE_CONFIG_LOOKASIDE</dt>
-** <dd> ^(The SQLITE_CONFIG_LOOKASIDE option takes two arguments that determine
-** the default size of lookaside memory on each [database connection].
-** The first argument is the
-** size of each lookaside buffer slot and the second is the number of
-** slots allocated to each database connection.)^  ^(SQLITE_CONFIG_LOOKASIDE
-** sets the <i>default</i> lookaside size. The [SQLITE_DBCONFIG_LOOKASIDE]
-** option to [sqlite3_db_config()] can be used to change the lookaside
-** configuration on individual connections.)^ </dd>
-**
-** [[SQLITE_CONFIG_PCACHE2]] <dt>SQLITE_CONFIG_PCACHE2</dt>
-** <dd> ^(The SQLITE_CONFIG_PCACHE2 option takes a single argument which is 
-** a pointer to an [sqlite3_pcache_methods2] object.  This object specifies
-** the interface to a custom page cache implementation.)^
-** ^SQLite makes a copy of the [sqlite3_pcache_methods2] object.</dd>
-**
-** [[SQLITE_CONFIG_GETPCACHE2]] <dt>SQLITE_CONFIG_GETPCACHE2</dt>
-** <dd> ^(The SQLITE_CONFIG_GETPCACHE2 option takes a single argument which
-** is a pointer to an [sqlite3_pcache_methods2] object.  SQLite copies of
-** the current page cache implementation into that object.)^ </dd>
-**
-** [[SQLITE_CONFIG_LOG]] <dt>SQLITE_CONFIG_LOG</dt>
-** <dd> The SQLITE_CONFIG_LOG option is used to configure the SQLite
-** global [error log].
-** (^The SQLITE_CONFIG_LOG option takes two arguments: a pointer to a
-** function with a call signature of void(*)(void*,int,const char*), 
-** and a pointer to void. ^If the function pointer is not NULL, it is
-** invoked by [sqlite3_log()] to process each logging event.  ^If the
-** function pointer is NULL, the [sqlite3_log()] interface becomes a no-op.
-** ^The void pointer that is the second argument to SQLITE_CONFIG_LOG is
-** passed through as the first parameter to the application-defined logger
-** function whenever that function is invoked.  ^The second parameter to
-** the logger function is a copy of the first parameter to the corresponding
-** [sqlite3_log()] call and is intended to be a [result code] or an
-** [extended result code].  ^The third parameter passed to the logger is
-** log message after formatting via [sqlite3_snprintf()].
-** The SQLite logging interface is not reentrant; the logger function
-** supplied by the application must not invoke any SQLite interface.
-** In a multi-threaded application, the application-defined logger
-** function must be threadsafe. </dd>
-**
-** [[SQLITE_CONFIG_URI]] <dt>SQLITE_CONFIG_URI
-** <dd>^(The SQLITE_CONFIG_URI option takes a single argument of type int.
-** If non-zero, then URI handling is globally enabled. If the parameter is zero,
-** then URI handling is globally disabled.)^ ^If URI handling is globally
-** enabled, all filenames passed to [sqlite3_open()], [sqlite3_open_v2()],
-** [sqlite3_open16()] or
-** specified as part of [ATTACH] commands are interpreted as URIs, regardless
-** of whether or not the [SQLITE_OPEN_URI] flag is set when the database
-** connection is opened. ^If it is globally disabled, filenames are
-** only interpreted as URIs if the SQLITE_OPEN_URI flag is set when the
-** database connection is opened. ^(By default, URI handling is globally
-** disabled. The default value may be changed by compiling with the
-** [SQLITE_USE_URI] symbol defined.)^
-**
-** [[SQLITE_CONFIG_COVERING_INDEX_SCAN]] <dt>SQLITE_CONFIG_COVERING_INDEX_SCAN
-** <dd>^The SQLITE_CONFIG_COVERING_INDEX_SCAN option takes a single integer
-** argument which is interpreted as a boolean in order to enable or disable
-** the use of covering indices for full table scans in the query optimizer.
-** ^The default setting is determined
-** by the [SQLITE_ALLOW_COVERING_INDEX_SCAN] compile-time option, or is "on"
-** if that compile-time option is omitted.
-** The ability to disable the use of covering indices for full table scans
-** is because some incorrectly coded legacy applications might malfunction
-** when the optimization is enabled.  Providing the ability to
-** disable the optimization allows the older, buggy application code to work
-** without change even with newer versions of SQLite.
-**
-** [[SQLITE_CONFIG_PCACHE]] [[SQLITE_CONFIG_GETPCACHE]]
-** <dt>SQLITE_CONFIG_PCACHE and SQLITE_CONFIG_GETPCACHE
-** <dd> These options are obsolete and should not be used by new code.
-** They are retained for backwards compatibility but are now no-ops.
-** </dd>
-**
-** [[SQLITE_CONFIG_MMAP_SIZE]]
-** <dt>SQLITE_CONFIG_MMAP_SIZE
-** <dd>^SQLITE_CONFIG_MMAP_SIZE takes two 64-bit integer (sqlite3_int64) values
-** that are the default mmap size limit (the default setting for
-** [PRAGMA mmap_size]) and the maximum allowed mmap size limit.
-** ^The default setting can be overridden by each database connection using
-** either the [PRAGMA mmap_size] command, or by using the
-** [SQLITE_FCNTL_MMAP_SIZE] file control.  ^(The maximum allowed mmap size
-** will be silently truncated if necessary so that it does not exceed the
-** compile-time maximum mmap size set by the
-** [SQLITE_MAX_MMAP_SIZE] compile-time option.)^
-** ^If either argument to this option is negative, then that argument is
-** changed to its compile-time default.
-**
-** [[SQLITE_CONFIG_WIN32_HEAPSIZE]]
-** <dt>SQLITE_CONFIG_WIN32_HEAPSIZE
-** <dd>^The SQLITE_CONFIG_WIN32_HEAPSIZE option is only available if SQLite is
-** compiled for Windows with the [SQLITE_WIN32_MALLOC] pre-processor macro
-** defined. ^SQLITE_CONFIG_WIN32_HEAPSIZE takes a 32-bit unsigned integer value
-** that specifies the maximum size of the created heap.
-**
-** [[SQLITE_CONFIG_PCACHE_HDRSZ]]
-** <dt>SQLITE_CONFIG_PCACHE_HDRSZ
-** <dd>^The SQLITE_CONFIG_PCACHE_HDRSZ option takes a single parameter which
-** is a pointer to an integer and writes into that integer the number of extra
-** bytes per page required for each page in [SQLITE_CONFIG_PAGECACHE].
-** The amount of extra space required can change depending on the compiler,
-** target platform, and SQLite version.
-**
-** [[SQLITE_CONFIG_PMASZ]]
-** <dt>SQLITE_CONFIG_PMASZ
-** <dd>^The SQLITE_CONFIG_PMASZ option takes a single parameter which
-** is an unsigned integer and sets the "Minimum PMA Size" for the multithreaded
-** sorter to that integer.  The default minimum PMA Size is set by the
-** [SQLITE_SORTER_PMASZ] compile-time option.  New threads are launched
-** to help with sort operations when multithreaded sorting
-** is enabled (using the [PRAGMA threads] command) and the amount of content
-** to be sorted exceeds the page size times the minimum of the
-** [PRAGMA cache_size] setting and this value.
-** </dl>
-*/
-#define SQLITE_CONFIG_SINGLETHREAD  1  /* nil */
-#define SQLITE_CONFIG_MULTITHREAD   2  /* nil */
-#define SQLITE_CONFIG_SERIALIZED    3  /* nil */
-#define SQLITE_CONFIG_MALLOC        4  /* sqlite3_mem_methods* */
-#define SQLITE_CONFIG_GETMALLOC     5  /* sqlite3_mem_methods* */
-#define SQLITE_CONFIG_SCRATCH       6  /* void*, int sz, int N */
-#define SQLITE_CONFIG_PAGECACHE     7  /* void*, int sz, int N */
-#define SQLITE_CONFIG_HEAP          8  /* void*, int nByte, int min */
-#define SQLITE_CONFIG_MEMSTATUS     9  /* boolean */
-#define SQLITE_CONFIG_MUTEX        10  /* sqlite3_mutex_methods* */
-#define SQLITE_CONFIG_GETMUTEX     11  /* sqlite3_mutex_methods* */
-/* previously SQLITE_CONFIG_CHUNKALLOC 12 which is now unused. */ 
-#define SQLITE_CONFIG_LOOKASIDE    13  /* int int */
-#define SQLITE_CONFIG_PCACHE       14  /* no-op */
-#define SQLITE_CONFIG_GETPCACHE    15  /* no-op */
-#define SQLITE_CONFIG_LOG          16  /* xFunc, void* */
-#define SQLITE_CONFIG_URI          17  /* int */
-#define SQLITE_CONFIG_PCACHE2      18  /* sqlite3_pcache_methods2* */
-#define SQLITE_CONFIG_GETPCACHE2   19  /* sqlite3_pcache_methods2* */
-#define SQLITE_CONFIG_COVERING_INDEX_SCAN 20  /* int */
-#define SQLITE_CONFIG_SQLLOG       21  /* xSqllog, void* */
-#define SQLITE_CONFIG_MMAP_SIZE    22  /* sqlite3_int64, sqlite3_int64 */
-#define SQLITE_CONFIG_WIN32_HEAPSIZE      23  /* int nByte */
-#define SQLITE_CONFIG_PCACHE_HDRSZ        24  /* int *psz */
-#define SQLITE_CONFIG_PMASZ               25  /* unsigned int szPma */
-
-/*
-** CAPI3REF: Formatted String Printing Functions
-**
-** These routines are work-alikes of the "printf()" family of functions
-** from the standard C library.
-** These routines understand most of the common K&R formatting options,
-** plus some additional non-standard formats, detailed below.
-** Note that some of the more obscure formatting options from recent
-** C-library standards are omitted from this implementation.
-**
-** ^The sqlite3_mprintf() and sqlite3_vmprintf() routines write their
-** results into memory obtained from [sqlite3_malloc()].
-** The strings returned by these two routines should be
-** released by [sqlite3_free()].  ^Both routines return a
-** NULL pointer if [sqlite3_malloc()] is unable to allocate enough
-** memory to hold the resulting string.
-**
-** ^(The sqlite3_snprintf() routine is similar to "snprintf()" from
-** the standard C library.  The result is written into the
-** buffer supplied as the second parameter whose size is given by
-** the first parameter. Note that the order of the
-** first two parameters is reversed from snprintf().)^  This is an
-** historical accident that cannot be fixed without breaking
-** backwards compatibility.  ^(Note also that sqlite3_snprintf()
-** returns a pointer to its buffer instead of the number of
-** characters actually written into the buffer.)^  We admit that
-** the number of characters written would be a more useful return
-** value but we cannot change the implementation of sqlite3_snprintf()
-** now without breaking compatibility.
-**
-** ^As long as the buffer size is greater than zero, sqlite3_snprintf()
-** guarantees that the buffer is always zero-terminated.  ^The first
-** parameter "n" is the total size of the buffer, including space for
-** the zero terminator.  So the longest string that can be completely
-** written will be n-1 characters.
-**
-** ^The sqlite3_vsnprintf() routine is a varargs version of sqlite3_snprintf().
-**
-** These routines all implement some additional formatting
-** options that are useful for constructing SQL statements.
-** All of the usual printf() formatting options apply.  In addition, there
-** is are "%q", "%Q", "%w" and "%z" options.
-**
-** ^(The %q option works like %s in that it substitutes a nul-terminated
-** string from the argument list.  But %q also doubles every '\'' character.
-** %q is designed for use inside a string literal.)^  By doubling each '\''
-** character it escapes that character and allows it to be inserted into
-** the string.
-**
-** For example, assume the string variable zText contains text as follows:
-**
-** <blockquote><pre>
-**  char *zText = "It's a happy day!";
-** </pre></blockquote>
-**
-** One can use this text in an SQL statement as follows:
-**
-** <blockquote><pre>
-**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES('%q')", zText);
-**  sqlite3_exec(db, zSQL, 0, 0, 0);
-**  sqlite3_free(zSQL);
-** </pre></blockquote>
-**
-** Because the %q format string is used, the '\'' character in zText
-** is escaped and the SQL generated is as follows:
-**
-** <blockquote><pre>
-**  INSERT INTO table1 VALUES('It''s a happy day!')
-** </pre></blockquote>
-**
-** This is correct.  Had we used %s instead of %q, the generated SQL
-** would have looked like this:
-**
-** <blockquote><pre>
-**  INSERT INTO table1 VALUES('It's a happy day!');
-** </pre></blockquote>
-**
-** This second example is an SQL syntax error.  As a general rule you should
-** always use %q instead of %s when inserting text into a string literal.
-**
-** ^(The %Q option works like %q except it also adds single quotes around
-** the outside of the total string.  Additionally, if the parameter in the
-** argument list is a NULL pointer, %Q substitutes the text "NULL" (without
-** single quotes).)^  So, for example, one could say:
-**
-** <blockquote><pre>
-**  char *zSQL = sqlite3_mprintf("INSERT INTO table VALUES(%Q)", zText);
-**  sqlite3_exec(db, zSQL, 0, 0, 0);
-**  sqlite3_free(zSQL);
-** </pre></blockquote>
-**
-** The code above will render a correct SQL statement in the zSQL
-** variable even if the zText variable is a NULL pointer.
-**
-** ^(The "%w" formatting option is like "%q" except that it expects to
-** be contained within double-quotes instead of single quotes, and it
-** escapes the double-quote character instead of the single-quote
-** character.)^  The "%w" formatting option is intended for safely inserting
-** table and column names into a constructed SQL statement.
-**
-** ^(The "%z" formatting option works like "%s" but with the
-** addition that after the string has been read and copied into
-** the result, [sqlite3_free()] is called on the input string.)^
-*/
-SQLITE_PRIVATE char *sqlite3_mprintf(const char*,...);
-SQLITE_PRIVATE char *sqlite3_vmprintf(const char*, va_list);
-SQLITE_PRIVATE char *sqlite3_snprintf(int,char*,const char*, ...);
-SQLITE_PRIVATE char *sqlite3_vsnprintf(int,char*,const char*, va_list);
-
-/*
-** CAPI3REF: Memory Allocation Subsystem
-**
-** The SQLite core uses these three routines for all of its own
-** internal memory allocation needs. "Core" in the previous sentence
-** does not include operating-system specific VFS implementation.  The
-** Windows VFS uses native malloc() and free() for some operations.
-**
-** ^The sqlite3_malloc() routine returns a pointer to a block
-** of memory at least N bytes in length, where N is the parameter.
-** ^If sqlite3_malloc() is unable to obtain sufficient free
-** memory, it returns a NULL pointer.  ^If the parameter N to
-** sqlite3_malloc() is zero or negative then sqlite3_malloc() returns
-** a NULL pointer.
-**
-** ^The sqlite3_malloc64(N) routine works just like
-** sqlite3_malloc(N) except that N is an unsigned 64-bit integer instead
-** of a signed 32-bit integer.
-**
-** ^Calling sqlite3_free() with a pointer previously returned
-** by sqlite3_malloc() or sqlite3_realloc() releases that memory so
-** that it might be reused.  ^The sqlite3_free() routine is
-** a no-op if is called with a NULL pointer.  Passing a NULL pointer
-** to sqlite3_free() is harmless.  After being freed, memory
-** should neither be read nor written.  Even reading previously freed
-** memory might result in a segmentation fault or other severe error.
-** Memory corruption, a segmentation fault, or other severe error
-** might result if sqlite3_free() is called with a non-NULL pointer that
-** was not obtained from sqlite3_malloc() or sqlite3_realloc().
-**
-** ^The sqlite3_realloc(X,N) interface attempts to resize a
-** prior memory allocation X to be at least N bytes.
-** ^If the X parameter to sqlite3_realloc(X,N)
-** is a NULL pointer then its behavior is identical to calling
-** sqlite3_malloc(N).
-** ^If the N parameter to sqlite3_realloc(X,N) is zero or
-** negative then the behavior is exactly the same as calling
-** sqlite3_free(X).
-** ^sqlite3_realloc(X,N) returns a pointer to a memory allocation
-** of at least N bytes in size or NULL if insufficient memory is available.
-** ^If M is the size of the prior allocation, then min(N,M) bytes
-** of the prior allocation are copied into the beginning of buffer returned
-** by sqlite3_realloc(X,N) and the prior allocation is freed.
-** ^If sqlite3_realloc(X,N) returns NULL and N is positive, then the
-** prior allocation is not freed.
-**
-** ^The sqlite3_realloc64(X,N) interfaces works the same as
-** sqlite3_realloc(X,N) except that N is a 64-bit unsigned integer instead
-** of a 32-bit signed integer.
-**
-** ^The memory returned by sqlite3_malloc(), sqlite3_realloc(),
-** sqlite3_malloc64(), and sqlite3_realloc64()
-** is always aligned to at least an 8 byte boundary, or to a
-** 4 byte boundary if the [SQLITE_4_BYTE_ALIGNED_MALLOC] compile-time
-** option is used.
-**
-** In SQLite version 3.5.0 and 3.5.1, it was possible to define
-** the SQLITE_OMIT_MEMORY_ALLOCATION which would cause the built-in
-** implementation of these routines to be omitted.  That capability
-** is no longer provided.  Only built-in memory allocators can be used.
-**
-** Prior to SQLite version 3.7.10, the Windows OS interface layer called
-** the system malloc() and free() directly when converting
-** filenames between the UTF-8 encoding used by SQLite
-** and whatever filename encoding is used by the particular Windows
-** installation.  Memory allocation errors were detected, but
-** they were reported back as [SQLITE_CANTOPEN] or
-** [SQLITE_IOERR] rather than [SQLITE_NOMEM].
-**
-** The pointer arguments to [sqlite3_free()] and [sqlite3_realloc()]
-** must be either NULL or else pointers obtained from a prior
-** invocation of [sqlite3_malloc()] or [sqlite3_realloc()] that have
-** not yet been released.
-**
-** The application must not read or write any part of
-** a block of memory after it has been released using
-** [sqlite3_free()] or [sqlite3_realloc()].
-*/
-SQLITE_PRIVATE void *sqlite3_malloc(int);
-SQLITE_PRIVATE void *sqlite3_malloc64(sqlite3_uint64);
-SQLITE_PRIVATE void *sqlite3_realloc(void*, int);
-SQLITE_PRIVATE void *sqlite3_realloc64(void*, sqlite3_uint64);
-SQLITE_PRIVATE void sqlite3_free(void*);
-
-/*
-** CAPI3REF: Run-Time Limit Categories
-** KEYWORDS: {limit category} {*limit categories}
-**
-** These constants define various performance limits
-** that can be lowered at run-time using [sqlite3_limit()].
-** The synopsis of the meanings of the various limits is shown below.
-** Additional information is available at [limits | Limits in SQLite].
-**
-** <dl>
-** [[SQLITE_LIMIT_LENGTH]] ^(<dt>SQLITE_LIMIT_LENGTH</dt>
-** <dd>The maximum size of any string or BLOB or table row, in bytes.<dd>)^
-**
-** [[SQLITE_LIMIT_SQL_LENGTH]] ^(<dt>SQLITE_LIMIT_SQL_LENGTH</dt>
-** <dd>The maximum length of an SQL statement, in bytes.</dd>)^
-**
-** [[SQLITE_LIMIT_COLUMN]] ^(<dt>SQLITE_LIMIT_COLUMN</dt>
-** <dd>The maximum number of columns in a table definition or in the
-** result set of a [SELECT] or the maximum number of columns in an index
-** or in an ORDER BY or GROUP BY clause.</dd>)^
-**
-** [[SQLITE_LIMIT_EXPR_DEPTH]] ^(<dt>SQLITE_LIMIT_EXPR_DEPTH</dt>
-** <dd>The maximum depth of the parse tree on any expression.</dd>)^
-**
-** [[SQLITE_LIMIT_COMPOUND_SELECT]] ^(<dt>SQLITE_LIMIT_COMPOUND_SELECT</dt>
-** <dd>The maximum number of terms in a compound SELECT statement.</dd>)^
-**
-** [[SQLITE_LIMIT_VDBE_OP]] ^(<dt>SQLITE_LIMIT_VDBE_OP</dt>
-** <dd>The maximum number of instructions in a virtual machine program
-** used to implement an SQL statement.  This limit is not currently
-** enforced, though that might be added in some future release of
-** SQLite.</dd>)^
-**
-** [[SQLITE_LIMIT_FUNCTION_ARG]] ^(<dt>SQLITE_LIMIT_FUNCTION_ARG</dt>
-** <dd>The maximum number of arguments on a function.</dd>)^
-**
-** [[SQLITE_LIMIT_ATTACHED]] ^(<dt>SQLITE_LIMIT_ATTACHED</dt>
-** <dd>The maximum number of [ATTACH | attached databases].)^</dd>
-**
-** [[SQLITE_LIMIT_LIKE_PATTERN_LENGTH]]
-** ^(<dt>SQLITE_LIMIT_LIKE_PATTERN_LENGTH</dt>
-** <dd>The maximum length of the pattern argument to the [LIKE] or
-** [GLOB] operators.</dd>)^
-**
-** [[SQLITE_LIMIT_VARIABLE_NUMBER]]
-** ^(<dt>SQLITE_LIMIT_VARIABLE_NUMBER</dt>
-** <dd>The maximum index number of any [parameter] in an SQL statement.)^
-**
-** [[SQLITE_LIMIT_TRIGGER_DEPTH]] ^(<dt>SQLITE_LIMIT_TRIGGER_DEPTH</dt>
-** <dd>The maximum depth of recursion for triggers.</dd>)^
-**
-** [[SQLITE_LIMIT_WORKER_THREADS]] ^(<dt>SQLITE_LIMIT_WORKER_THREADS</dt>
-** <dd>The maximum number of auxiliary worker threads that a single
-** [prepared statement] may start.</dd>)^
-** </dl>
-*/
-#define SQLITE_LIMIT_LENGTH                    0
-#define SQLITE_LIMIT_SQL_LENGTH                1
-#define SQLITE_LIMIT_COLUMN                    2
-#define SQLITE_LIMIT_EXPR_DEPTH                3
-#define SQLITE_LIMIT_COMPOUND_SELECT           4
-#define SQLITE_LIMIT_VDBE_OP                   5
-#define SQLITE_LIMIT_FUNCTION_ARG              6
-#define SQLITE_LIMIT_ATTACHED                  7
-#define SQLITE_LIMIT_LIKE_PATTERN_LENGTH       8
-#define SQLITE_LIMIT_VARIABLE_NUMBER           9
-#define SQLITE_LIMIT_TRIGGER_DEPTH            10
-#define SQLITE_LIMIT_WORKER_THREADS           11
-
-/*
-** CAPI3REF: Name Of The Folder Holding Temporary Files
-**
-** ^(If this global variable is made to point to a string which is
-** the name of a folder (a.k.a. directory), then all temporary files
-** created by SQLite when using a built-in [sqlite3_vfs | VFS]
-** will be placed in that directory.)^  ^If this variable
-** is a NULL pointer, then SQLite performs a search for an appropriate
-** temporary file directory.
-**
-** Applications are strongly discouraged from using this global variable.
-** It is required to set a temporary folder on Windows Runtime (WinRT).
-** But for all other platforms, it is highly recommended that applications
-** neither read nor write this variable.  This global variable is a relic
-** that exists for backwards compatibility of legacy applications and should
-** be avoided in new projects.
-**
-** It is not safe to read or modify this variable in more than one
-** thread at a time.  It is not safe to read or modify this variable
-** if a [database connection] is being used at the same time in a separate
-** thread.
-** It is intended that this variable be set once
-** as part of process initialization and before any SQLite interface
-** routines have been called and that this variable remain unchanged
-** thereafter.
-**
-** ^The [temp_store_directory pragma] may modify this variable and cause
-** it to point to memory obtained from [sqlite3_malloc].  ^Furthermore,
-** the [temp_store_directory pragma] always assumes that any string
-** that this variable points to is held in memory obtained from 
-** [sqlite3_malloc] and the pragma may attempt to free that memory
-** using [sqlite3_free].
-** Hence, if this variable is modified directly, either it should be
-** made NULL or made to point to memory obtained from [sqlite3_malloc]
-** or else the use of the [temp_store_directory pragma] should be avoided.
-** Except when requested by the [temp_store_directory pragma], SQLite
-** does not free the memory that sqlite3_temp_directory points to.  If
-** the application wants that memory to be freed, it must do
-** so itself, taking care to only do so after all [database connection]
-** objects have been destroyed.
-**
-** <b>Note to Windows Runtime users:</b>  The temporary directory must be set
-** prior to calling [sqlite3_open] or [sqlite3_open_v2].  Otherwise, various
-** features that require the use of temporary files may fail.  Here is an
-** example of how to do this using C++ with the Windows Runtime:
-**
-** <blockquote><pre>
-** LPCWSTR zPath = Windows::Storage::ApplicationData::Current->
-** &nbsp;     TemporaryFolder->Path->Data();
-** char zPathBuf&#91;MAX_PATH + 1&#93;;
-** memset(zPathBuf, 0, sizeof(zPathBuf));
-** WideCharToMultiByte(CP_UTF8, 0, zPath, -1, zPathBuf, sizeof(zPathBuf),
-** &nbsp;     NULL, NULL);
-** sqlite3_temp_directory = sqlite3_mprintf("%s", zPathBuf);
-** </pre></blockquote>
-*/
-SQLITE_PRIVATE char *sqlite3_temp_directory;
-
-/*
-** CAPI3REF: Virtual File System Objects
-**
-** A virtual filesystem (VFS) is an [sqlite3_vfs] object
-** that SQLite uses to interact
-** with the underlying operating system.  Most SQLite builds come with a
-** single default VFS that is appropriate for the host computer.
-** New VFSes can be registered and existing VFSes can be unregistered.
-** The following interfaces are provided.
-**
-** ^The sqlite3_vfs_find() interface returns a pointer to a VFS given its name.
-** ^Names are case sensitive.
-** ^Names are zero-terminated UTF-8 strings.
-** ^If there is no match, a NULL pointer is returned.
-** ^If zVfsName is NULL then the default VFS is returned.
-**
-** ^New VFSes are registered with sqlite3_vfs_register().
-** ^Each new VFS becomes the default VFS if the makeDflt flag is set.
-** ^The same VFS can be registered multiple times without injury.
-** ^To make an existing VFS into the default VFS, register it again
-** with the makeDflt flag set.  If two different VFSes with the
-** same name are registered, the behavior is undefined.  If a
-** VFS is registered with a name that is NULL or an empty string,
-** then the behavior is undefined.
-**
-*/
-SQLITE_PRIVATE sqlite3_vfs *sqlite3_vfs_find(const char *zVfsName);
-SQLITE_PRIVATE int sqlite3_vfs_register(sqlite3_vfs*, int makeDflt);
-
-/*
-** CAPI3REF: Mutexes
-**
-** The SQLite core uses these routines for thread
-** synchronization. Though they are intended for internal
-** use by SQLite, code that links against SQLite is
-** permitted to use any of these routines.
-**
-** The SQLite source code contains multiple implementations
-** of these mutex routines.  An appropriate implementation
-** is selected automatically at compile-time.  The following
-** implementations are available in the SQLite core:
-**
-** <ul>
-** <li>   SQLITE_MUTEX_PTHREADS
-** <li>   SQLITE_MUTEX_W32
-** <li>   SQLITE_MUTEX_NOOP
-** </ul>
-**
-** The SQLITE_MUTEX_NOOP implementation is a set of routines
-** that does no real locking and is appropriate for use in
-** a single-threaded application.  The SQLITE_MUTEX_PTHREADS and
-** SQLITE_MUTEX_W32 implementations are appropriate for use on Unix
-** and Windows.
-**
-** If SQLite is compiled with the SQLITE_MUTEX_APPDEF preprocessor
-** macro defined (with "-DSQLITE_MUTEX_APPDEF=1"), then no mutex
-** implementation is included with the library. In this case the
-** application must supply a custom mutex implementation using the
-** [SQLITE_CONFIG_MUTEX] option of the sqlite3_config() function
-** before calling sqlite3BtreeInitialize() or any other public sqlite3_
-** function that calls sqlite3BtreeInitialize().
-**
-** ^The sqlite3_mutex_alloc() routine allocates a new
-** mutex and returns a pointer to it. ^The sqlite3_mutex_alloc()
-** routine returns NULL if it is unable to allocate the requested
-** mutex.  The argument to sqlite3_mutex_alloc() must one of these
-** integer constants:
-**
-** <ul>
-** <li>  SQLITE_MUTEX_FAST
-** <li>  SQLITE_MUTEX_RECURSIVE
-** <li>  SQLITE_MUTEX_STATIC_MASTER
-** <li>  SQLITE_MUTEX_STATIC_MEM
-** <li>  SQLITE_MUTEX_STATIC_OPEN
-** <li>  SQLITE_MUTEX_STATIC_PRNG
-** <li>  SQLITE_MUTEX_STATIC_LRU
-** <li>  SQLITE_MUTEX_STATIC_PMEM
-** <li>  SQLITE_MUTEX_STATIC_APP1
-** <li>  SQLITE_MUTEX_STATIC_APP2
-** <li>  SQLITE_MUTEX_STATIC_APP3
-** <li>  SQLITE_MUTEX_STATIC_VFS1
-** <li>  SQLITE_MUTEX_STATIC_VFS2
-** <li>  SQLITE_MUTEX_STATIC_VFS3
-** </ul>
-**
-** ^The first two constants (SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE)
-** cause sqlite3_mutex_alloc() to create
-** a new mutex.  ^The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
-** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
-** The mutex implementation does not need to make a distinction
-** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
-** not want to.  SQLite will only request a recursive mutex in
-** cases where it really needs one.  If a faster non-recursive mutex
-** implementation is available on the host platform, the mutex subsystem
-** might return such a mutex in response to SQLITE_MUTEX_FAST.
-**
-** ^The other allowed parameters to sqlite3_mutex_alloc() (anything other
-** than SQLITE_MUTEX_FAST and SQLITE_MUTEX_RECURSIVE) each return
-** a pointer to a static preexisting mutex.  ^Nine static mutexes are
-** used by the current version of SQLite.  Future versions of SQLite
-** may add additional static mutexes.  Static mutexes are for internal
-** use by SQLite only.  Applications that use SQLite mutexes should
-** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
-** SQLITE_MUTEX_RECURSIVE.
-**
-** ^Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
-** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
-** returns a different mutex on every call.  ^For the static
-** mutex types, the same mutex is returned on every call that has
-** the same type number.
-**
-** ^The sqlite3_mutex_free() routine deallocates a previously
-** allocated dynamic mutex.  Attempting to deallocate a static
-** mutex results in undefined behavior.
-**
-** ^The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
-** to enter a mutex.  ^If another thread is already within the mutex,
-** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
-** SQLITE_BUSY.  ^The sqlite3_mutex_try() interface returns [SQLITE_OK]
-** upon successful entry.  ^(Mutexes created using
-** SQLITE_MUTEX_RECURSIVE can be entered multiple times by the same thread.
-** In such cases, the
-** mutex must be exited an equal number of times before another thread
-** can enter.)^  If the same thread tries to enter any mutex other
-** than an SQLITE_MUTEX_RECURSIVE more than once, the behavior is undefined.
-**
-** ^(Some systems (for example, Windows 95) do not support the operation
-** implemented by sqlite3_mutex_try().  On those systems, sqlite3_mutex_try()
-** will always return SQLITE_BUSY. The SQLite core only ever uses
-** sqlite3_mutex_try() as an optimization so this is acceptable 
-** behavior.)^
-**
-** ^The sqlite3_mutex_leave() routine exits a mutex that was
-** previously entered by the same thread.   The behavior
-** is undefined if the mutex is not currently entered by the
-** calling thread or is not currently allocated.
-**
-** ^If the argument to sqlite3_mutex_enter(), sqlite3_mutex_try(), or
-** sqlite3_mutex_leave() is a NULL pointer, then all three routines
-** behave as no-ops.
-**
-** See also: [sqlite3_mutex_held()] and [sqlite3_mutex_notheld()].
-*/
-SQLITE_PRIVATE sqlite3_mutex *sqlite3_mutex_alloc(int);
-SQLITE_PRIVATE void sqlite3_mutex_free(sqlite3_mutex*);
-SQLITE_PRIVATE void sqlite3_mutex_enter(sqlite3_mutex*);
-SQLITE_PRIVATE int sqlite3_mutex_try(sqlite3_mutex*);
-SQLITE_PRIVATE void sqlite3_mutex_leave(sqlite3_mutex*);
-
-/*
-** CAPI3REF: Mutex Methods Object
-**
-** An instance of this structure defines the low-level routines
-** used to allocate and use mutexes.
-**
-** Usually, the default mutex implementations provided by SQLite are
-** sufficient, however the application has the option of substituting a custom
-** implementation for specialized deployments or systems for which SQLite
-** does not provide a suitable implementation. In this case, the application
-** creates and populates an instance of this structure to pass
-** to sqlite3_config() along with the [SQLITE_CONFIG_MUTEX] option.
-** Additionally, an instance of this structure can be used as an
-** output variable when querying the system for the current mutex
-** implementation, using the [SQLITE_CONFIG_GETMUTEX] option.
-**
-** ^The xMutexInit method defined by this structure is invoked as
-** part of system initialization by the sqlite3BtreeInitialize() function.
-** ^The xMutexInit routine is called by SQLite exactly once for each
-** effective call to [sqlite3BtreeInitialize()].
-**
-** ^The xMutexEnd method defined by this structure is invoked as
-** part of system shutdown by the sqlite3BtreeShutdown() function. The
-** implementation of this method is expected to release all outstanding
-** resources obtained by the mutex methods implementation, especially
-** those obtained by the xMutexInit method.  ^The xMutexEnd()
-** interface is invoked exactly once for each call to [sqlite3BtreeShutdown()].
-**
-** ^(The remaining seven methods defined by this structure (xMutexAlloc,
-** xMutexFree, xMutexEnter, xMutexTry, xMutexLeave, xMutexHeld and
-** xMutexNotheld) implement the following interfaces (respectively):
-**
-** <ul>
-**   <li>  [sqlite3_mutex_alloc()] </li>
-**   <li>  [sqlite3_mutex_free()] </li>
-**   <li>  [sqlite3_mutex_enter()] </li>
-**   <li>  [sqlite3_mutex_try()] </li>
-**   <li>  [sqlite3_mutex_leave()] </li>
-**   <li>  [sqlite3_mutex_held()] </li>
-**   <li>  [sqlite3_mutex_notheld()] </li>
-** </ul>)^
-**
-** The only difference is that the public sqlite3_XXX functions enumerated
-** above silently ignore any invocations that pass a NULL pointer instead
-** of a valid mutex handle. The implementations of the methods defined
-** by this structure are not required to handle this case, the results
-** of passing a NULL pointer instead of a valid mutex handle are undefined
-** (i.e. it is acceptable to provide an implementation that segfaults if
-** it is passed a NULL pointer).
-**
-** The xMutexInit() method must be threadsafe.  It must be harmless to
-** invoke xMutexInit() multiple times within the same process and without
-** intervening calls to xMutexEnd().  Second and subsequent calls to
-** xMutexInit() must be no-ops.
-**
-** xMutexInit() must not use SQLite memory allocation ([sqlite3_malloc()]
-** and its associates).  Similarly, xMutexAlloc() must not use SQLite memory
-** allocation for a static mutex.  ^However xMutexAlloc() may use SQLite
-** memory allocation for a fast or recursive mutex.
-**
-** ^SQLite will invoke the xMutexEnd() method when [sqlite3BtreeShutdown()] is
-** called, but only if the prior call to xMutexInit returned SQLITE_OK.
-** If xMutexInit fails in any way, it is expected to clean up after itself
-** prior to returning.
-*/
-typedef struct sqlite3_mutex_methods sqlite3_mutex_methods;
-struct sqlite3_mutex_methods {
-  int (*xMutexInit)(void);
-  int (*xMutexEnd)(void);
-  sqlite3_mutex *(*xMutexAlloc)(int);
-  void (*xMutexFree)(sqlite3_mutex *);
-  void (*xMutexEnter)(sqlite3_mutex *);
-  int (*xMutexTry)(sqlite3_mutex *);
-  void (*xMutexLeave)(sqlite3_mutex *);
-  int (*xMutexHeld)(sqlite3_mutex *);
-  int (*xMutexNotheld)(sqlite3_mutex *);
-};
-
-/*
-** CAPI3REF: Mutex Types
-**
-** The [sqlite3_mutex_alloc()] interface takes a single argument
-** which is one of these integer constants.
-**
-** The set of static mutexes may change from one SQLite release to the
-** next.  Applications that override the built-in mutex logic must be
-** prepared to accommodate additional static mutexes.
-*/
-#define SQLITE_MUTEX_FAST             0
-#define SQLITE_MUTEX_RECURSIVE        1
-#define SQLITE_MUTEX_STATIC_MASTER    2
-#define SQLITE_MUTEX_STATIC_MEM       3  /* sqlite3_malloc() */
-#define SQLITE_MUTEX_STATIC_MEM2      4  /* NOT USED */
-#define SQLITE_MUTEX_STATIC_OPEN      4  /* sqlite3BtreeOpen() */
-#define SQLITE_MUTEX_STATIC_PRNG      5  /* sqlite3_random() */
-#define SQLITE_MUTEX_STATIC_LRU       6  /* lru page list */
-#define SQLITE_MUTEX_STATIC_LRU2      7  /* NOT USED */
-#define SQLITE_MUTEX_STATIC_PMEM      7  /* sqlite3PageMalloc() */
-#define SQLITE_MUTEX_STATIC_APP1      8  /* For use by application */
-#define SQLITE_MUTEX_STATIC_APP2      9  /* For use by application */
-#define SQLITE_MUTEX_STATIC_APP3     10  /* For use by application */
-#define SQLITE_MUTEX_STATIC_VFS1     11  /* For use by built-in VFS */
-#define SQLITE_MUTEX_STATIC_VFS2     12  /* For use by extension VFS */
-#define SQLITE_MUTEX_STATIC_VFS3     13  /* For use by application VFS */
-
-/*
-** CAPI3REF: Status Parameters
-** KEYWORDS: {status parameters}
-**
-** These integer constants designate various run-time status parameters
-** that can be returned by [sqlite3_status()].
-**
-** <dl>
-** [[SQLITE_STATUS_MEMORY_USED]] ^(<dt>SQLITE_STATUS_MEMORY_USED</dt>
-** <dd>This parameter is the current amount of memory checked out
-** using [sqlite3_malloc()], either directly or indirectly.  The
-** figure includes calls made to [sqlite3_malloc()] by the application
-** and internal memory usage by the SQLite library.  Scratch memory
-** controlled by [SQLITE_CONFIG_SCRATCH] and auxiliary page-cache
-** memory controlled by [SQLITE_CONFIG_PAGECACHE] is not included in
-** this parameter.  The amount returned is the sum of the allocation
-** sizes as reported by the xSize method in [sqlite3_mem_methods].</dd>)^
-**
-** [[SQLITE_STATUS_MALLOC_SIZE]] ^(<dt>SQLITE_STATUS_MALLOC_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [sqlite3_malloc()] or [sqlite3_realloc()] (or their
-** internal equivalents).  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** [[SQLITE_STATUS_MALLOC_COUNT]] ^(<dt>SQLITE_STATUS_MALLOC_COUNT</dt>
-** <dd>This parameter records the number of separate memory allocations
-** currently checked out.</dd>)^
-**
-** [[SQLITE_STATUS_PAGECACHE_USED]] ^(<dt>SQLITE_STATUS_PAGECACHE_USED</dt>
-** <dd>This parameter returns the number of pages used out of the
-** [pagecache memory allocator] that was configured using 
-** [SQLITE_CONFIG_PAGECACHE].  The
-** value returned is in pages, not in bytes.</dd>)^
-**
-** [[SQLITE_STATUS_PAGECACHE_OVERFLOW]] 
-** ^(<dt>SQLITE_STATUS_PAGECACHE_OVERFLOW</dt>
-** <dd>This parameter returns the number of bytes of page cache
-** allocation which could not be satisfied by the [SQLITE_CONFIG_PAGECACHE]
-** buffer and where forced to overflow to [sqlite3_malloc()].  The
-** returned value includes allocations that overflowed because they
-** where too large (they were larger than the "sz" parameter to
-** [SQLITE_CONFIG_PAGECACHE]) and allocations that overflowed because
-** no space was left in the page cache.</dd>)^
-**
-** [[SQLITE_STATUS_PAGECACHE_SIZE]] ^(<dt>SQLITE_STATUS_PAGECACHE_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [pagecache memory allocator].  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** [[SQLITE_STATUS_SCRATCH_USED]] ^(<dt>SQLITE_STATUS_SCRATCH_USED</dt>
-** <dd>This parameter returns the number of allocations used out of the
-** [scratch memory allocator] configured using
-** [SQLITE_CONFIG_SCRATCH].  The value returned is in allocations, not
-** in bytes.  Since a single thread may only have one scratch allocation
-** outstanding at time, this parameter also reports the number of threads
-** using scratch memory at the same time.</dd>)^
-**
-** [[SQLITE_STATUS_SCRATCH_OVERFLOW]] ^(<dt>SQLITE_STATUS_SCRATCH_OVERFLOW</dt>
-** <dd>This parameter returns the number of bytes of scratch memory
-** allocation which could not be satisfied by the [SQLITE_CONFIG_SCRATCH]
-** buffer and where forced to overflow to [sqlite3_malloc()].  The values
-** returned include overflows because the requested allocation was too
-** larger (that is, because the requested allocation was larger than the
-** "sz" parameter to [SQLITE_CONFIG_SCRATCH]) and because no scratch buffer
-** slots were available.
-** </dd>)^
-**
-** [[SQLITE_STATUS_SCRATCH_SIZE]] ^(<dt>SQLITE_STATUS_SCRATCH_SIZE</dt>
-** <dd>This parameter records the largest memory allocation request
-** handed to [scratch memory allocator].  Only the value returned in the
-** *pHighwater parameter to [sqlite3_status()] is of interest.  
-** The value written into the *pCurrent parameter is undefined.</dd>)^
-**
-** [[SQLITE_STATUS_PARSER_STACK]] ^(<dt>SQLITE_STATUS_PARSER_STACK</dt>
-** <dd>This parameter records the deepest parser stack.  It is only
-** meaningful if SQLite is compiled with [YYTRACKMAXSTACKDEPTH].</dd>)^
-** </dl>
-**
-** New status parameters may be added from time to time.
-*/
-#define SQLITE_STATUS_MEMORY_USED          0
-#define SQLITE_STATUS_PAGECACHE_USED       1
-#define SQLITE_STATUS_PAGECACHE_OVERFLOW   2
-#define SQLITE_STATUS_SCRATCH_USED         3
-#define SQLITE_STATUS_SCRATCH_OVERFLOW     4
-#define SQLITE_STATUS_MALLOC_SIZE          5
-#define SQLITE_STATUS_PARSER_STACK         6
-#define SQLITE_STATUS_PAGECACHE_SIZE       7
-#define SQLITE_STATUS_SCRATCH_SIZE         8
-#define SQLITE_STATUS_MALLOC_COUNT         9
-
-/*
-** CAPI3REF: Status Parameters for database connections
-** KEYWORDS: {SQLITE_DBSTATUS options}
-**
-** These constants are the available integer "verbs" that can be passed as
-** the second argument to the [sqlite3_db_status()] interface.
-**
-** New verbs may be added in future releases of SQLite. Existing verbs
-** might be discontinued. Applications should check the return code from
-** [sqlite3_db_status()] to make sure that the call worked.
-** The [sqlite3_db_status()] interface will return a non-zero error code
-** if a discontinued or unsupported verb is invoked.
-**
-** <dl>
-** [[SQLITE_DBSTATUS_LOOKASIDE_USED]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_USED</dt>
-** <dd>This parameter returns the number of lookaside memory slots currently
-** checked out.</dd>)^
-**
-** [[SQLITE_DBSTATUS_LOOKASIDE_HIT]] ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_HIT</dt>
-** <dd>This parameter returns the number malloc attempts that were 
-** satisfied using lookaside memory. Only the high-water value is meaningful;
-** the current value is always zero.)^
-**
-** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE]]
-** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE</dt>
-** <dd>This parameter returns the number malloc attempts that might have
-** been satisfied using lookaside memory but failed due to the amount of
-** memory requested being larger than the lookaside slot size.
-** Only the high-water value is meaningful;
-** the current value is always zero.)^
-**
-** [[SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL]]
-** ^(<dt>SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL</dt>
-** <dd>This parameter returns the number malloc attempts that might have
-** been satisfied using lookaside memory but failed due to all lookaside
-** memory already being in use.
-** Only the high-water value is meaningful;
-** the current value is always zero.)^
-**
-** [[SQLITE_DBSTATUS_CACHE_USED]] ^(<dt>SQLITE_DBSTATUS_CACHE_USED</dt>
-** <dd>This parameter returns the approximate number of bytes of heap
-** memory used by all pager caches associated with the database connection.)^
-** ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_USED is always 0.
-**
-** [[SQLITE_DBSTATUS_SCHEMA_USED]] ^(<dt>SQLITE_DBSTATUS_SCHEMA_USED</dt>
-** <dd>This parameter returns the approximate number of bytes of heap
-** memory used to store the schema for all databases associated
-** with the connection - main, temp, and any [ATTACH]-ed databases.)^ 
-** ^The full amount of memory used by the schemas is reported, even if the
-** schema memory is shared with other database connections due to
-** [shared cache mode] being enabled.
-** ^The highwater mark associated with SQLITE_DBSTATUS_SCHEMA_USED is always 0.
-**
-** [[SQLITE_DBSTATUS_STMT_USED]] ^(<dt>SQLITE_DBSTATUS_STMT_USED</dt>
-** <dd>This parameter returns the approximate number of bytes of heap
-** and lookaside memory used by all prepared statements associated with
-** the database connection.)^
-** ^The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always 0.
-** </dd>
-**
-** [[SQLITE_DBSTATUS_CACHE_HIT]] ^(<dt>SQLITE_DBSTATUS_CACHE_HIT</dt>
-** <dd>This parameter returns the number of pager cache hits that have
-** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_HIT 
-** is always 0.
-** </dd>
-**
-** [[SQLITE_DBSTATUS_CACHE_MISS]] ^(<dt>SQLITE_DBSTATUS_CACHE_MISS</dt>
-** <dd>This parameter returns the number of pager cache misses that have
-** occurred.)^ ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_MISS 
-** is always 0.
-** </dd>
-**
-** [[SQLITE_DBSTATUS_CACHE_WRITE]] ^(<dt>SQLITE_DBSTATUS_CACHE_WRITE</dt>
-** <dd>This parameter returns the number of dirty cache entries that have
-** been written to disk. Specifically, the number of pages written to the
-** wal file in wal mode databases, or the number of pages written to the
-** database file in rollback mode databases. Any pages written as part of
-** transaction rollback or database recovery operations are not included.
-** If an IO or other error occurs while writing a page to disk, the effect
-** on subsequent SQLITE_DBSTATUS_CACHE_WRITE requests is undefined.)^ ^The
-** highwater mark associated with SQLITE_DBSTATUS_CACHE_WRITE is always 0.
-** </dd>
-**
-** [[SQLITE_DBSTATUS_DEFERRED_FKS]] ^(<dt>SQLITE_DBSTATUS_DEFERRED_FKS</dt>
-** <dd>This parameter returns zero for the current value if and only if
-** all foreign key constraints (deferred or immediate) have been
-** resolved.)^  ^The highwater mark is always 0.
-** </dd>
-** </dl>
-*/
-#define SQLITE_DBSTATUS_LOOKASIDE_USED       0
-#define SQLITE_DBSTATUS_CACHE_USED           1
-#define SQLITE_DBSTATUS_SCHEMA_USED          2
-#define SQLITE_DBSTATUS_STMT_USED            3
-#define SQLITE_DBSTATUS_LOOKASIDE_HIT        4
-#define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE  5
-#define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL  6
-#define SQLITE_DBSTATUS_CACHE_HIT            7
-#define SQLITE_DBSTATUS_CACHE_MISS           8
-#define SQLITE_DBSTATUS_CACHE_WRITE          9
-#define SQLITE_DBSTATUS_DEFERRED_FKS        10
-#define SQLITE_DBSTATUS_MAX                 10   /* Largest defined DBSTATUS */
-
-/*
-** CAPI3REF: Checkpoint Mode Values
-** KEYWORDS: {checkpoint mode}
-**
-** These constants define all valid values for the "checkpoint mode" passed
-** as the third parameter to the [sqlite3_wal_checkpoint_v2()] interface.
-** See the [sqlite3_wal_checkpoint_v2()] documentation for details on the
-** meaning of each of these checkpoint modes.
-*/
-#define SQLITE_CHECKPOINT_PASSIVE  0  /* Do as much as possible w/o blocking */
-#define SQLITE_CHECKPOINT_FULL     1  /* Wait for writers, then checkpoint */
-#define SQLITE_CHECKPOINT_RESTART  2  /* Like FULL but wait for for readers */
-#define SQLITE_CHECKPOINT_TRUNCATE 3  /* Like RESTART but also truncate WAL */
-
-/*
-** CAPI3REF: Custom Page Cache Object
-**
-** The sqlite3_pcache type is opaque.  It is implemented by
-** the pluggable module.  The SQLite core has no knowledge of
-** its size or internal structure and never deals with the
-** sqlite3_pcache object except by holding and passing pointers
-** to the object.
-**
-** See [sqlite3_pcache_methods2] for additional information.
-*/
-typedef struct sqlite3_pcache sqlite3_pcache;
-
-/*
-** CAPI3REF: Custom Page Cache Object
-**
-** The sqlite3_pcache_page object represents a single page in the
-** page cache.  The page cache will allocate instances of this
-** object.  Various methods of the page cache use pointers to instances
-** of this object as parameters or as their return value.
-**
-** See [sqlite3_pcache_methods2] for additional information.
-*/
-typedef struct sqlite3_pcache_page sqlite3_pcache_page;
-struct sqlite3_pcache_page {
-  void *pBuf;        /* The content of the page */
-  void *pExtra;      /* Extra information associated with the page */
-};
-
-/*
-** CAPI3REF: Application Defined Page Cache.
-** KEYWORDS: {page cache}
-**
-** ^(The [sqlite3_config]([SQLITE_CONFIG_PCACHE2], ...) interface can
-** register an alternative page cache implementation by passing in an 
-** instance of the sqlite3_pcache_methods2 structure.)^
-** In many applications, most of the heap memory allocated by 
-** SQLite is used for the page cache.
-** By implementing a 
-** custom page cache using this API, an application can better control
-** the amount of memory consumed by SQLite, the way in which 
-** that memory is allocated and released, and the policies used to 
-** determine exactly which parts of a database file are cached and for 
-** how long.
-**
-** The alternative page cache mechanism is an
-** extreme measure that is only needed by the most demanding applications.
-** The built-in page cache is recommended for most uses.
-**
-** ^(The contents of the sqlite3_pcache_methods2 structure are copied to an
-** internal buffer by SQLite within the call to [sqlite3_config].  Hence
-** the application may discard the parameter after the call to
-** [sqlite3_config()] returns.)^
-**
-** [[the xInit() page cache method]]
-** ^(The xInit() method is called once for each effective 
-** call to [sqlite3BtreeInitialize()])^
-** (usually only once during the lifetime of the process). ^(The xInit()
-** method is passed a copy of the sqlite3_pcache_methods2.pArg value.)^
-** The intent of the xInit() method is to set up global data structures 
-** required by the custom page cache implementation. 
-** ^(If the xInit() method is NULL, then the 
-** built-in default page cache is used instead of the application defined
-** page cache.)^
-**
-** [[the xShutdown() page cache method]]
-** ^The xShutdown() method is called by [sqlite3BtreeShutdown()].
-** It can be used to clean up 
-** any outstanding resources before process shutdown, if required.
-** ^The xShutdown() method may be NULL.
-**
-** ^SQLite automatically serializes calls to the xInit method,
-** so the xInit method need not be threadsafe.  ^The
-** xShutdown method is only called from [sqlite3BtreeShutdown()] so it does
-** not need to be threadsafe either.  All other methods must be threadsafe
-** in multithreaded applications.
-**
-** ^SQLite will never invoke xInit() more than once without an intervening
-** call to xShutdown().
-**
-** [[the xCreate() page cache methods]]
-** ^SQLite invokes the xCreate() method to construct a new cache instance.
-** SQLite will typically create one cache instance for each open database file,
-** though this is not guaranteed. ^The
-** first parameter, szPage, is the size in bytes of the pages that must
-** be allocated by the cache.  ^szPage will always a power of two.  ^The
-** second parameter szExtra is a number of bytes of extra storage 
-** associated with each page cache entry.  ^The szExtra parameter will
-** a number less than 250.  SQLite will use the
-** extra szExtra bytes on each page to store metadata about the underlying
-** database page on disk.  The value passed into szExtra depends
-** on the SQLite version, the target platform, and how SQLite was compiled.
-** ^The third argument to xCreate(), bPurgeable, is true if the cache being
-** created will be used to cache database pages of a file stored on disk, or
-** false if it is used for an in-memory database. The cache implementation
-** does not have to do anything special based with the value of bPurgeable;
-** it is purely advisory.  ^On a cache where bPurgeable is false, SQLite will
-** never invoke xUnpin() except to deliberately delete a page.
-** ^In other words, calls to xUnpin() on a cache with bPurgeable set to
-** false will always have the "discard" flag set to true.  
-** ^Hence, a cache created with bPurgeable false will
-** never contain any unpinned pages.
-**
-** [[the xCachesize() page cache method]]
-** ^(The xCachesize() method may be called at any time by SQLite to set the
-** suggested maximum cache-size (number of pages stored by) the cache
-** instance passed as the first argument. This is the value configured using
-** the SQLite "[PRAGMA cache_size]" command.)^  As with the bPurgeable
-** parameter, the implementation is not required to do anything with this
-** value; it is advisory only.
-**
-** [[the xPagecount() page cache methods]]
-** The xPagecount() method must return the number of pages currently
-** stored in the cache, both pinned and unpinned.
-** 
-** [[the xFetch() page cache methods]]
-** The xFetch() method locates a page in the cache and returns a pointer to 
-** an sqlite3_pcache_page object associated with that page, or a NULL pointer.
-** The pBuf element of the returned sqlite3_pcache_page object will be a
-** pointer to a buffer of szPage bytes used to store the content of a 
-** single database page.  The pExtra element of sqlite3_pcache_page will be
-** a pointer to the szExtra bytes of extra storage that SQLite has requested
-** for each entry in the page cache.
-**
-** The page to be fetched is determined by the key. ^The minimum key value
-** is 1.  After it has been retrieved using xFetch, the page is considered
-** to be "pinned".
-**
-** If the requested page is already in the page cache, then the page cache
-** implementation must return a pointer to the page buffer with its content
-** intact.  If the requested page is not already in the cache, then the
-** cache implementation should use the value of the createFlag
-** parameter to help it determined what action to take:
-**
-** <table border=1 width=85% align=center>
-** <tr><th> createFlag <th> Behavior when page is not already in cache
-** <tr><td> 0 <td> Do not allocate a new page.  Return NULL.
-** <tr><td> 1 <td> Allocate a new page if it easy and convenient to do so.
-**                 Otherwise return NULL.
-** <tr><td> 2 <td> Make every effort to allocate a new page.  Only return
-**                 NULL if allocating a new page is effectively impossible.
-** </table>
-**
-** ^(SQLite will normally invoke xFetch() with a createFlag of 0 or 1.  SQLite
-** will only use a createFlag of 2 after a prior call with a createFlag of 1
-** failed.)^  In between the to xFetch() calls, SQLite may
-** attempt to unpin one or more cache pages by spilling the content of
-** pinned pages to disk and synching the operating system disk cache.
-**
-** [[the xUnpin() page cache method]]
-** ^xUnpin() is called by SQLite with a pointer to a currently pinned page
-** as its second argument.  If the third parameter, discard, is non-zero,
-** then the page must be evicted from the cache.
-** ^If the discard parameter is
-** zero, then the page may be discarded or retained at the discretion of
-** page cache implementation. ^The page cache implementation
-** may choose to evict unpinned pages at any time.
-**
-** The cache must not perform any reference counting. A single 
-** call to xUnpin() unpins the page regardless of the number of prior calls 
-** to xFetch().
-**
-** [[the xRekey() page cache methods]]
-** The xRekey() method is used to change the key value associated with the
-** page passed as the second argument. If the cache
-** previously contains an entry associated with newKey, it must be
-** discarded. ^Any prior cache entry associated with newKey is guaranteed not
-** to be pinned.
-**
-** When SQLite calls the xTruncate() method, the cache must discard all
-** existing cache entries with page numbers (keys) greater than or equal
-** to the value of the iLimit parameter passed to xTruncate(). If any
-** of these pages are pinned, they are implicitly unpinned, meaning that
-** they can be safely discarded.
-**
-** [[the xDestroy() page cache method]]
-** ^The xDestroy() method is used to delete a cache allocated by xCreate().
-** All resources associated with the specified cache should be freed. ^After
-** calling the xDestroy() method, SQLite considers the [sqlite3_pcache*]
-** handle invalid, and will not use it with any other sqlite3_pcache_methods2
-** functions.
-**
-** [[the xShrink() page cache method]]
-** ^SQLite invokes the xShrink() method when it wants the page cache to
-** free up as much of heap memory as possible.  The page cache implementation
-** is not obligated to free any memory, but well-behaved implementations should
-** do their best.
-*/
-typedef struct sqlite3_pcache_methods2 sqlite3_pcache_methods2;
-struct sqlite3_pcache_methods2 {
-  int iVersion;
-  void *pArg;
-  int (*xInit)(void*);
-  void (*xShutdown)(void*);
-  sqlite3_pcache *(*xCreate)(int szPage, int szExtra, int bPurgeable);
-  void (*xCachesize)(sqlite3_pcache*, int nCachesize);
-  int (*xPagecount)(sqlite3_pcache*);
-  sqlite3_pcache_page *(*xFetch)(sqlite3_pcache*, unsigned key, int createFlag);
-  void (*xUnpin)(sqlite3_pcache*, sqlite3_pcache_page*, int discard);
-  void (*xRekey)(sqlite3_pcache*, sqlite3_pcache_page*, 
-      unsigned oldKey, unsigned newKey);
-  void (*xTruncate)(sqlite3_pcache*, unsigned iLimit);
-  void (*xDestroy)(sqlite3_pcache*);
-  void (*xShrink)(sqlite3_pcache*);
-};
-
-/*
-** CAPI3REF: Online Backup Object
-**
-** The sqlite3_backup object records state information about an ongoing
-** online backup operation.  ^The sqlite3_backup object is created by
-** a call to [sqlite3_backup_init()] and is destroyed by a call to
-** [sqlite3_backup_finish()].
-**
-** See Also: [Using the SQLite Online Backup API]
-*/
-typedef struct sqlite3_backup sqlite3_backup;
-
-/*
-** CAPI3REF: Error Logging Interface
-**
-** ^The [sqlite3_log()] interface writes a message into the [error log]
-** established by the [SQLITE_CONFIG_LOG] option to [sqlite3_config()].
-** ^If logging is enabled, the zFormat string and subsequent arguments are
-** used with [sqlite3_snprintf()] to generate the final output string.
-**
-** The sqlite3_log() interface is intended for use by extensions such as
-** virtual tables, collating functions, and SQL functions.  While there is
-** nothing to prevent an application from calling sqlite3_log(), doing so
-** is considered bad form.
-**
-** The zFormat string must not be NULL.
-**
-** To avoid deadlocks and other threading problems, the sqlite3_log() routine
-** will not use dynamically allocated memory.  The log message is stored in
-** a fixed-length buffer on the stack.  If the log message is longer than
-** a few hundred characters, it will be truncated to the length of the
-** buffer.
-*/
-SQLITE_PRIVATE void sqlite3_log(int iErrCode, const char *zFormat, ...);
-
-/*
-** CAPI3REF: Text Encodings
-**
-** These constant define integer codes that represent the various
-** text encodings supported by SQLite.
-*/
-#define SQLITE_UTF8           1    /* IMP: R-37514-35566 */
-#define SQLITE_UTF16LE        2    /* IMP: R-03371-37637 */
-#define SQLITE_UTF16BE        3    /* IMP: R-51971-34154 */
-#define SQLITE_UTF16          4    /* Use native byte order */
-#define SQLITE_ANY            5    /* Deprecated */
-#define SQLITE_UTF16_ALIGNED  8    /* sqlite3_create_collation only */
-
-/*
-** Include the configuration header output by 'configure' if we're using the
-** autoconf-based build
-*/
-#ifdef _HAVE_SQLITE_CONFIG_H
-#include "config.h"
-#endif
-
-/************** Include sqliteLimit.h in the middle of sqliteInt.h ***********/
-/************** Begin file sqliteLimit.h *************************************/
-/*
-** 2007 May 7
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** 
-** This file defines various limits of what SQLite can process.
-*/
-
-/*
-** The maximum length of a TEXT or BLOB in bytes.   This also
-** limits the size of a row in a table or index.
-**
-** The hard limit is the ability of a 32-bit signed integer
-** to count the size: 2^31-1 or 2147483647.
-*/
-#ifndef SQLITE_MAX_LENGTH
-# define SQLITE_MAX_LENGTH 1000000000
-#endif
-
-/*
-** This is the maximum number of
-**
-**    * Columns in a table
-**    * Columns in an index
-**    * Columns in a view
-**    * Terms in the SET clause of an UPDATE statement
-**    * Terms in the result set of a SELECT statement
-**    * Terms in the GROUP BY or ORDER BY clauses of a SELECT statement.
-**    * Terms in the VALUES clause of an INSERT statement
-**
-** The hard upper limit here is 32676.  Most database people will
-** tell you that in a well-normalized database, you usually should
-** not have more than a dozen or so columns in any table.  And if
-** that is the case, there is no point in having more than a few
-** dozen values in any of the other situations described above.
-*/
-#ifndef SQLITE_MAX_COLUMN
-# define SQLITE_MAX_COLUMN 2000
-#endif
-
-/*
-** The maximum length of a single SQL statement in bytes.
-**
-** It used to be the case that setting this value to zero would
-** turn the limit off.  That is no longer true.  It is not possible
-** to turn this limit off.
-*/
-#ifndef SQLITE_MAX_SQL_LENGTH
-# define SQLITE_MAX_SQL_LENGTH 1000000000
-#endif
-
-/*
-** The maximum depth of an expression tree. This is limited to 
-** some extent by SQLITE_MAX_SQL_LENGTH. But sometime you might 
-** want to place more severe limits on the complexity of an 
-** expression.
-**
-** A value of 0 used to mean that the limit was not enforced.
-** But that is no longer true.  The limit is now strictly enforced
-** at all times.
-*/
-#ifndef SQLITE_MAX_EXPR_DEPTH
-# define SQLITE_MAX_EXPR_DEPTH 1000
-#endif
-
-/*
-** The maximum number of terms in a compound SELECT statement.
-** The code generator for compound SELECT statements does one
-** level of recursion for each term.  A stack overflow can result
-** if the number of terms is too large.  In practice, most SQL
-** never has more than 3 or 4 terms.  Use a value of 0 to disable
-** any limit on the number of terms in a compount SELECT.
-*/
-#ifndef SQLITE_MAX_COMPOUND_SELECT
-# define SQLITE_MAX_COMPOUND_SELECT 500
-#endif
-
-/*
-** The maximum number of opcodes in a VDBE program.
-** Not currently enforced.
-*/
-#ifndef SQLITE_MAX_VDBE_OP
-# define SQLITE_MAX_VDBE_OP 25000
-#endif
-
-/*
-** The maximum number of arguments to an SQL function.
-*/
-#ifndef SQLITE_MAX_FUNCTION_ARG
-# define SQLITE_MAX_FUNCTION_ARG 127
-#endif
-
-/*
-** The suggested maximum number of in-memory pages to use for
-** the main database table and for temporary tables.
-**
-** IMPLEMENTATION-OF: R-31093-59126 The default suggested cache size
-** is 2000 pages.
-** IMPLEMENTATION-OF: R-48205-43578 The default suggested cache size can be
-** altered using the SQLITE_DEFAULT_CACHE_SIZE compile-time options.
-*/
-#ifndef SQLITE_DEFAULT_CACHE_SIZE
-# define SQLITE_DEFAULT_CACHE_SIZE  2000
-#endif
-
-/*
-** The default number of frames to accumulate in the log file before
-** checkpointing the database in WAL mode.
-*/
-#ifndef SQLITE_DEFAULT_WAL_AUTOCHECKPOINT
-# define SQLITE_DEFAULT_WAL_AUTOCHECKPOINT  1000
-#endif
-
-/*
-** The maximum number of attached databases.  This must be between 0
-** and 62.  The upper bound on 62 is because a 64-bit integer bitmap
-** is used internally to track attached databases.
-*/
-#ifndef SQLITE_MAX_ATTACHED
-# define SQLITE_MAX_ATTACHED 10
-#endif
-
-
-/*
-** The maximum value of a ?nnn wildcard that the parser will accept.
-*/
-#ifndef SQLITE_MAX_VARIABLE_NUMBER
-# define SQLITE_MAX_VARIABLE_NUMBER 999
-#endif
-
-/* Maximum page size.  The upper bound on this value is 65536.  This a limit
-** imposed by the use of 16-bit offsets within each page.
-**
-** Earlier versions of SQLite allowed the user to change this value at
-** compile time. This is no longer permitted, on the grounds that it creates
-** a library that is technically incompatible with an SQLite library 
-** compiled with a different limit. If a process operating on a database 
-** with a page-size of 65536 bytes crashes, then an instance of SQLite 
-** compiled with the default page-size limit will not be able to rollback 
-** the aborted transaction. This could lead to database corruption.
-*/
-#ifdef SQLITE_MAX_PAGE_SIZE
-# undef SQLITE_MAX_PAGE_SIZE
-#endif
-#define SQLITE_MAX_PAGE_SIZE 65536
-
-
-/*
-** The default size of a database page.
-*/
-#ifndef SQLITE_DEFAULT_PAGE_SIZE
-# define SQLITE_DEFAULT_PAGE_SIZE 1024
-#endif
-#if SQLITE_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
-# undef SQLITE_DEFAULT_PAGE_SIZE
-# define SQLITE_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
-#endif
-
-/*
-** Ordinarily, if no value is explicitly provided, SQLite creates databases
-** with page size SQLITE_DEFAULT_PAGE_SIZE. However, based on certain
-** device characteristics (sector-size and atomic write() support),
-** SQLite may choose a larger value. This constant is the maximum value
-** SQLite will choose on its own.
-*/
-#ifndef SQLITE_MAX_DEFAULT_PAGE_SIZE
-# define SQLITE_MAX_DEFAULT_PAGE_SIZE 8192
-#endif
-#if SQLITE_MAX_DEFAULT_PAGE_SIZE>SQLITE_MAX_PAGE_SIZE
-# undef SQLITE_MAX_DEFAULT_PAGE_SIZE
-# define SQLITE_MAX_DEFAULT_PAGE_SIZE SQLITE_MAX_PAGE_SIZE
-#endif
-
-
-/*
-** Maximum number of pages in one database file.
-**
-** This is really just the default value for the max_page_count pragma.
-** This value can be lowered (or raised) at run-time using that the
-** max_page_count macro.
-*/
-#ifndef SQLITE_MAX_PAGE_COUNT
-# define SQLITE_MAX_PAGE_COUNT 1073741823
-#endif
-
-/*
-** Maximum length (in bytes) of the pattern in a LIKE or GLOB
-** operator.
-*/
-#ifndef SQLITE_MAX_LIKE_PATTERN_LENGTH
-# define SQLITE_MAX_LIKE_PATTERN_LENGTH 50000
-#endif
-
-/*
-** Maximum depth of recursion for triggers.
-**
-** A value of 1 means that a trigger program will not be able to itself
-** fire any triggers. A value of 0 means that no trigger programs at all 
-** may be executed.
-*/
-#ifndef SQLITE_MAX_TRIGGER_DEPTH
-# define SQLITE_MAX_TRIGGER_DEPTH 1000
-#endif
-
-/************** End of sqliteLimit.h *****************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/* Disable nuisance warnings on Borland compilers */
-#if defined(__BORLANDC__)
-#pragma warn -rch /* unreachable code */
-#pragma warn -ccc /* Condition is always true or false */
-#pragma warn -aus /* Assigned value is never used */
-#pragma warn -csu /* Comparing signed and unsigned */
-#pragma warn -spa /* Suspicious pointer arithmetic */
-#endif
-
-/*
-** Include standard header files as necessary
-*/
-#ifdef HAVE_STDINT_H
-#include <stdint.h>
-#endif
-#ifdef HAVE_INTTYPES_H
-#include <inttypes.h>
-#endif
-
-/*
-** The following macros are used to cast pointers to integers and
-** integers to pointers.  The way you do this varies from one compiler
-** to the next, so we have developed the following set of #if statements
-** to generate appropriate macros for a wide range of compilers.
-**
-** The correct "ANSI" way to do this is to use the intptr_t type. 
-** Unfortunately, that typedef is not available on all compilers, or
-** if it is available, it requires an #include of specific headers
-** that vary from one machine to the next.
-**
-** Ticket #3860:  The llvm-gcc-4.2 compiler from Apple chokes on
-** the ((void*)&((char*)0)[X]) construct.  But MSVC chokes on ((void*)(X)).
-** So we have to define the macros in different ways depending on the
-** compiler.
-*/
-#if defined(__PTRDIFF_TYPE__)  /* This case should work for GCC */
-# define SQLITE_INT_TO_PTR(X)  ((void*)(__PTRDIFF_TYPE__)(X))
-# define SQLITE_PTR_TO_INT(X)  ((int)(__PTRDIFF_TYPE__)(X))
-#elif !defined(__GNUC__)       /* Works for compilers other than LLVM */
-# define SQLITE_INT_TO_PTR(X)  ((void*)&((char*)0)[X])
-# define SQLITE_PTR_TO_INT(X)  ((int)(((char*)X)-(char*)0))
-#elif defined(HAVE_STDINT_H)   /* Use this case if we have ANSI headers */
-# define SQLITE_INT_TO_PTR(X)  ((void*)(intptr_t)(X))
-# define SQLITE_PTR_TO_INT(X)  ((int)(intptr_t)(X))
-#else                          /* Generates a warning - but it always works */
-# define SQLITE_INT_TO_PTR(X)  ((void*)(X))
-# define SQLITE_PTR_TO_INT(X)  ((int)(X))
-#endif
-
-/*
-** A macro to hint to the compiler that a function should not be
-** inlined.
-*/
-#if defined(__GNUC__)
-#  define SQLITE_NOINLINE  __attribute__((noinline))
-#elif defined(_MSC_VER) && _MSC_VER>=1310
-#  define SQLITE_NOINLINE  __declspec(noinline)
-#else
-#  define SQLITE_NOINLINE
-#endif
-
-/*
-** Make sure that the compiler intrinsics we desire are enabled when
-** compiling with an appropriate version of MSVC unless prevented by
-** the SQLITE_DISABLE_INTRINSIC define.
-*/
-#if !defined(SQLITE_DISABLE_INTRINSIC)
-#  if defined(_MSC_VER) && _MSC_VER>=1300
-#    if !defined(_WIN32_WCE)
-#      include <intrin.h>
-#      pragma intrinsic(_byteswap_ushort)
-#      pragma intrinsic(_byteswap_ulong)
-#      pragma intrinsic(_ReadWriteBarrier)
-#    else
-#      include <cmnintrin.h>
-#    endif
-#  endif
-#endif
-
-/*
-** Powersafe overwrite is on by default.  But can be turned off using
-** the -DSQLITE_POWERSAFE_OVERWRITE=0 command-line option.
-*/
-#ifndef SQLITE_POWERSAFE_OVERWRITE
-# define SQLITE_POWERSAFE_OVERWRITE 1
-#endif
-
-/*
-** EVIDENCE-OF: R-25715-37072 Memory allocation statistics are enabled by
-** default unless SQLite is compiled with SQLITE_DEFAULT_MEMSTATUS=0 in
-** which case memory allocation statistics are disabled by default.
-*/
-#if !defined(SQLITE_DEFAULT_MEMSTATUS)
-# define SQLITE_DEFAULT_MEMSTATUS 1
-#endif
-
-/*
-** Exactly one of the following macros must be defined in order to
-** specify which memory allocation subsystem to use.
-**
-**     SQLITE_SYSTEM_MALLOC          // Use normal system malloc()
-**     SQLITE_WIN32_MALLOC           // Use Win32 native heap API
-**     SQLITE_ZERO_MALLOC            // Use a stub allocator that always fails
-**     SQLITE_MEMDEBUG               // Debugging version of system malloc()
-**
-** On Windows, if the SQLITE_WIN32_MALLOC_VALIDATE macro is defined and the
-** assert() macro is enabled, each call into the Win32 native heap subsystem
-** will cause HeapValidate to be called.  If heap validation should fail, an
-** assertion will be triggered.
-**
-** If none of the above are defined, then set SQLITE_SYSTEM_MALLOC as
-** the default.
-*/
-#if defined(SQLITE_SYSTEM_MALLOC) \
-  + defined(SQLITE_WIN32_MALLOC) \
-  + defined(SQLITE_ZERO_MALLOC) \
-  + defined(SQLITE_MEMDEBUG)>1
-# error "Two or more of the following compile-time configuration options\
- are defined but at most one is allowed:\
- SQLITE_SYSTEM_MALLOC, SQLITE_WIN32_MALLOC, SQLITE_MEMDEBUG,\
- SQLITE_ZERO_MALLOC"
-#endif
-#if defined(SQLITE_SYSTEM_MALLOC) \
-  + defined(SQLITE_WIN32_MALLOC) \
-  + defined(SQLITE_ZERO_MALLOC) \
-  + defined(SQLITE_MEMDEBUG)==0
-# define SQLITE_SYSTEM_MALLOC 1
-#endif
-
-/*
-** We need to define _XOPEN_SOURCE as follows in order to enable
-** recursive mutexes on most Unix systems and fchmod() on OpenBSD.
-** But _XOPEN_SOURCE define causes problems for Mac OS X, so omit
-** it.
-*/
-#if !defined(_XOPEN_SOURCE) && !defined(__DARWIN__) && !defined(__APPLE__)
-#  define _XOPEN_SOURCE 600
-#endif
-
-/*
-** NDEBUG and SQLITE_DEBUG are opposites.  It should always be true that
-** defined(NDEBUG)==!defined(SQLITE_DEBUG).  If this is not currently true,
-** make it true by defining or undefining NDEBUG.
-**
-** Setting NDEBUG makes the code smaller and faster by disabling the
-** assert() statements in the code.  So we want the default action
-** to be for NDEBUG to be set and NDEBUG to be undefined only if SQLITE_DEBUG
-** is set.  Thus NDEBUG becomes an opt-in rather than an opt-out
-** feature.
-*/
-#if !defined(NDEBUG) && !defined(SQLITE_DEBUG) 
-# define NDEBUG 1
-#endif
-#if defined(NDEBUG) && defined(SQLITE_DEBUG)
-# undef NDEBUG
-#endif
-
-/*
-** The testcase() macro is used to aid in coverage testing.  When 
-** doing coverage testing, the condition inside the argument to
-** testcase() must be evaluated both true and false in order to
-** get full branch coverage.  The testcase() macro is inserted
-** to help ensure adequate test coverage in places where simple
-** condition/decision coverage is inadequate.  For example, testcase()
-** can be used to make sure boundary values are tested.  For
-** bitmask tests, testcase() can be used to make sure each bit
-** is significant and used at least once.  On switch statements
-** where multiple cases go to the same block of code, testcase()
-** can insure that all cases are evaluated.
-**
-*/
-#ifdef SQLITE_COVERAGE_TEST
-SQLITE_PRIVATE   void sqlite3Coverage(int);
-# define testcase(X)  if( X ){ sqlite3Coverage(__LINE__); }
-#else
-# define testcase(X)
-#endif
-
-/*
-** The TESTONLY macro is used to enclose variable declarations or
-** other bits of code that are needed to support the arguments
-** within testcase() and assert() macros.
-*/
-#if !defined(NDEBUG) || defined(SQLITE_COVERAGE_TEST)
-# define TESTONLY(X)  X
-#else
-# define TESTONLY(X)
-#endif
-
-/*
-** Sometimes we need a small amount of code such as a variable initialization
-** to setup for a later assert() statement.  We do not want this code to
-** appear when assert() is disabled.  The following macro is therefore
-** used to contain that setup code.  The "VVA" acronym stands for
-** "Verification, Validation, and Accreditation".  In other words, the
-** code within VVA_ONLY() will only run during verification processes.
-*/
-#ifndef NDEBUG
-# define VVA_ONLY(X)  X
-#else
-# define VVA_ONLY(X)
-#endif
-
-/*
-** The ALWAYS and NEVER macros surround boolean expressions which 
-** are intended to always be true or false, respectively.  Such
-** expressions could be omitted from the code completely.  But they
-** are included in a few cases in order to enhance the resilience
-** of SQLite to unexpected behavior - to make the code "self-healing"
-** or "ductile" rather than being "brittle" and crashing at the first
-** hint of unplanned behavior.
-**
-** In other words, ALWAYS and NEVER are added for defensive code.
-**
-** When doing coverage testing ALWAYS and NEVER are hard-coded to
-** be true and false so that the unreachable code they specify will
-** not be counted as untested code.
-*/
-#if defined(SQLITE_COVERAGE_TEST)
-# define ALWAYS(X)      (1)
-# define NEVER(X)       (0)
-#elif !defined(NDEBUG)
-# define ALWAYS(X)      ((X)?1:(assert(0),0))
-# define NEVER(X)       ((X)?(assert(0),1):0)
-#else
-# define ALWAYS(X)      (X)
-# define NEVER(X)       (X)
-#endif
-
-/*
-** Declarations used for tracing the operating system interfaces.
-*/
-#if defined(SQLITE_FORCE_OS_TRACE) || defined(SQLITE_TEST) || \
-    (defined(SQLITE_DEBUG) && SQLITE_OS_WIN)
-  extern int sqlite3OSTrace;
-# define OSTRACE(X)          if( sqlite3OSTrace ) sqlite3DebugPrintf X
-# define SQLITE_HAVE_OS_TRACE
-#else
-# define OSTRACE(X)
-# undef  SQLITE_HAVE_OS_TRACE
-#endif
-
-/*
-** Is the sqlite3ErrName() function needed in the build?  Currently,
-** it is needed by "mutex_w32.c" (when debugging), "os_win.c" (when
-** OSTRACE is enabled), and by several "test*.c" files (which are
-** compiled using SQLITE_TEST).
-*/
-#if defined(SQLITE_HAVE_OS_TRACE) || defined(SQLITE_TEST) || \
-    (defined(SQLITE_DEBUG) && SQLITE_OS_WIN)
-# define SQLITE_NEED_ERR_NAME
-#else
-# undef  SQLITE_NEED_ERR_NAME
-#endif
-
-/*
-** The macro unlikely() is a hint that surrounds a boolean
-** expression that is usually false.  Macro likely() surrounds
-** a boolean expression that is usually true.  These hints could,
-** in theory, be used by the compiler to generate better code, but
-** currently they are just comments for human readers.
-*/
-#define likely(X)    (X)
-#define unlikely(X)  (X)
-
-#include <stdlib.h>
-#include <string.h>
-#include <assert.h>
-#include <stddef.h>
-
-/*
-** The "file format" number is an integer that is incremented whenever
-** the VDBE-level file format changes.  The following macros define the
-** the default file format for new databases and the maximum file format
-** that the library can read.
-*/
-#define SQLITE_MAX_FILE_FORMAT 4
-#ifndef SQLITE_DEFAULT_FILE_FORMAT
-# define SQLITE_DEFAULT_FILE_FORMAT 4
-#endif
-
-/*
-** The default initial allocation for the pagecache when using separate
-** pagecaches for each database connection.  A positive number is the
-** number of pages.  A negative number N translations means that a buffer
-** of -1024*N bytes is allocated and used for as many pages as it will hold.
-*/
-#ifndef SQLITE_DEFAULT_PCACHE_INITSZ
-# define SQLITE_DEFAULT_PCACHE_INITSZ 100
-#endif
-
-/*
-** GCC does not define the offsetof() macro so we'll have to do it
-** ourselves.
-*/
-#ifndef offsetof
-#define offsetof(STRUCTURE,FIELD) ((int)((char*)&((STRUCTURE*)0)->FIELD))
-#endif
-
-/*
-** Macros to compute minimum and maximum of two numbers.
-*/
-#define MIN(A,B) ((A)<(B)?(A):(B))
-#define MAX(A,B) ((A)>(B)?(A):(B))
-
-/*
-** Swap two objects of type TYPE.
-*/
-#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
-
-/*
-** SQLITE_MAX_U32 is a u64 constant that is the maximum u64 value
-** that can be stored in a u32 without loss of data.  The value
-** is 0x00000000ffffffff.  But because of quirks of some compilers, we
-** have to specify the value in the less intuitive manner shown:
-*/
-#define SQLITE_MAX_U32  ((((u64)1)<<32)-1)
-
-/*
-** Set the SQLITE_PTRSIZE macro to the number of bytes in a pointer
-*/
-#ifndef SQLITE_PTRSIZE
-# if defined(__SIZEOF_POINTER__)
-#   define SQLITE_PTRSIZE __SIZEOF_POINTER__
-# elif defined(i386)     || defined(__i386__)   || defined(_M_IX86) ||    \
-       defined(_M_ARM)   || defined(__arm__)    || defined(__x86)
-#   define SQLITE_PTRSIZE 4
-# else
-#   define SQLITE_PTRSIZE 8
-# endif
-#endif
-
-/*
-** Constants for the largest and smallest possible 64-bit signed integers.
-** These macros are designed to work correctly on both 32-bit and 64-bit
-** compilers.
-*/
-#define LARGEST_INT64  (0xffffffff|(((i64)0x7fffffff)<<32))
-#define SMALLEST_INT64 (((i64)-1) - LARGEST_INT64)
-
-/* 
-** Round up a number to the next larger multiple of 8.  This is used
-** to force 8-byte alignment on 64-bit architectures.
-*/
-#define ROUND8(x)     (((x)+7)&~7)
-
-/*
-** Round down to the nearest multiple of 8
-*/
-#define ROUNDDOWN8(x) ((x)&~7)
-
-/*
-** Disable MMAP on platforms where it is known to not work
-*/
-#if defined(__OpenBSD__) || defined(__QNXNTO__)
-# undef SQLITE_MAX_MMAP_SIZE
-# define SQLITE_MAX_MMAP_SIZE 0
-#endif
-
-/*
-** Default maximum size of memory used by memory-mapped I/O in the VFS
-*/
-#ifdef __APPLE__
-# include <TargetConditionals.h>
-# if TARGET_OS_IPHONE
-#   undef SQLITE_MAX_MMAP_SIZE
-#   define SQLITE_MAX_MMAP_SIZE 0
-# endif
-#endif
-#ifndef SQLITE_MAX_MMAP_SIZE
-# if defined(__linux__) \
-  || defined(_WIN32) \
-  || (defined(__APPLE__) && defined(__MACH__)) \
-  || defined(__sun) \
-  || defined(__FreeBSD__) \
-  || defined(__DragonFly__)
-#   define SQLITE_MAX_MMAP_SIZE 0x7fff0000  /* 2147418112 */
-# else
-#   define SQLITE_MAX_MMAP_SIZE 0
-# endif
-# define SQLITE_MAX_MMAP_SIZE_xc 1 /* exclude from ctime.c */
-#endif
-
-/*
-** The default MMAP_SIZE is zero on all platforms.  Or, even if a larger
-** default MMAP_SIZE is specified at compile-time, make sure that it does
-** not exceed the maximum mmap size.
-*/
-#ifndef SQLITE_DEFAULT_MMAP_SIZE
-# define SQLITE_DEFAULT_MMAP_SIZE 0
-# define SQLITE_DEFAULT_MMAP_SIZE_xc 1  /* Exclude from ctime.c */
-#endif
-#if SQLITE_DEFAULT_MMAP_SIZE>SQLITE_MAX_MMAP_SIZE
-# undef SQLITE_DEFAULT_MMAP_SIZE
-# define SQLITE_DEFAULT_MMAP_SIZE SQLITE_MAX_MMAP_SIZE
-#endif
-
-/*
-** An instance of the following structure is used to store the busy-handler
-** callback for a given sqlite handle. 
-**
-** The sqlite.busyHandler member of the sqlite struct contains the busy
-** callback for the database handle. Each pager opened via the sqlite
-** handle is passed a pointer to sqlite.busyHandler. The busy-handler
-** callback is currently invoked only from within pager.c.
-*/
-typedef struct BusyHandler BusyHandler;
-struct BusyHandler {
-  int (*xFunc)(void *,int);  /* The busy callback */
-  void *pArg;                /* First arg to busy callback */
-  int nBusy;                 /* Incremented with each busy call */
-};
-
-/*
-** The root-page of the master database table.
-*/
-#define MASTER_ROOT       1
-
-/*
-** A convenience macro that returns the number of elements in
-** an array.
-*/
-#define ArraySize(X)    ((int)(sizeof(X)/sizeof(X[0])))
-
-/*
-** When SQLITE_OMIT_WSD is defined, it means that the target platform does
-** not support Writable Static Data (WSD) such as global and static variables.
-** All variables must either be on the stack or dynamically allocated from
-** the heap.  When WSD is unsupported, the variable declarations scattered
-** throughout the SQLite code must become constants instead.  The SQLITE_WSD
-** macro is used for this purpose.  And instead of referencing the variable
-** directly, we use its constant as a key to lookup the run-time allocated
-** buffer that holds real variable.  The constant is also the initializer
-** for the run-time allocated buffer.
-**
-** In the usual case where WSD is supported, the SQLITE_WSD and GLOBAL
-** macros become no-ops and have zero performance impact.
-*/
-#ifdef SQLITE_OMIT_WSD
-  #define SQLITE_WSD const
-  #define GLOBAL(t,v) (*(t*)sqlite3_wsd_find((void*)&(v), sizeof(v)))
-  #define sqlite3GlobalConfig GLOBAL(struct Sqlite3Config, sqlite3Config)
-SQLITE_PRIVATE   int sqlite3_wsd_init(int N, int J);
-SQLITE_PRIVATE   void *sqlite3_wsd_find(void *K, int L);
-#else
-  #define SQLITE_WSD 
-  #define GLOBAL(t,v) v
-  #define sqlite3GlobalConfig sqlite3Config
-#endif
-
-/*
-** The following macros are used to suppress compiler warnings and to
-** make it clear to human readers when a function parameter is deliberately 
-** left unused within the body of a function. This usually happens when
-** a function is called via a function pointer. For example the 
-** implementation of an SQL aggregate step callback may not use the
-** parameter indicating the number of arguments passed to the aggregate,
-** if it knows that this is enforced elsewhere.
-**
-** When a function parameter is not used at all within the body of a function,
-** it is generally named "NotUsed" or "NotUsed2" to make things even clearer.
-** However, these macros may also be used to suppress warnings related to
-** parameters that may or may not be used depending on compilation options.
-** For example those parameters only used in assert() statements. In these
-** cases the parameters are named as per the usual conventions.
-*/
-#define UNUSED_PARAMETER(x) (void)(x)
-#define UNUSED_PARAMETER2(x,y) UNUSED_PARAMETER(x),UNUSED_PARAMETER(y)
-
-typedef struct Bitvec Bitvec;
-typedef struct CollSeq CollSeq;
-typedef struct PrintfArguments PrintfArguments;
-typedef struct Savepoint Savepoint;
-typedef struct StrAccum StrAccum;
-
-/************** Include pager.h in the middle of sqliteInt.h *****************/
-/************** Begin file pager.h *******************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This header file defines the interface that the sqlite page cache
-** subsystem.  The page cache subsystem reads and writes a file a page
-** at a time and provides a journal for rollback.
-*/
-
-#ifndef _PAGER_H_
-#define _PAGER_H_
-
-/*
-** Default maximum size for persistent journal files. A negative 
-** value means no limit. This value may be overridden using the 
-** sqlite3PagerJournalSizeLimit() API. See also "PRAGMA journal_size_limit".
-*/
-#ifndef SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT
-  #define SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT -1
-#endif
-
-/*
-** The type used to represent a page number.  The first page in a file
-** is called page 1.  0 is used to represent "not a page".
-*/
-typedef u32 Pgno;
-
-/*
-** Each open file is managed by a separate instance of the "Pager" structure.
-*/
-typedef struct Pager Pager;
-
-/*
-** Handle type for pages.
-*/
-typedef struct PgHdr DbPage;
-
-/*
-** Page number PAGER_MJ_PGNO is never used in an SQLite database (it is
-** reserved for working around a windows/posix incompatibility). It is
-** used in the journal to signify that the remainder of the journal file 
-** is devoted to storing a master journal name - there are no more pages to
-** roll back. See comments for function writeMasterJournal() in pager.c 
-** for details.
-*/
-#define PAGER_MJ_PGNO(x) ((Pgno)((PENDING_BYTE/((x)->pageSize))+1))
-
-/*
-** Allowed values for the flags parameter to sqlite3PagerOpen().
-**
-** NOTE: These values must match the corresponding BTREE_ values in btree.h.
-*/
-#define PAGER_OMIT_JOURNAL  0x0001    /* Do not use a rollback journal */
-#define PAGER_MEMORY        0x0002    /* In-memory database */
-
-/*
-** Valid values for the second argument to sqlite3PagerLockingMode().
-*/
-#define PAGER_LOCKINGMODE_QUERY      -1
-#define PAGER_LOCKINGMODE_NORMAL      0
-#define PAGER_LOCKINGMODE_EXCLUSIVE   1
-
-/*
-** Numeric constants that encode the journalmode.  
-*/
-#define PAGER_JOURNALMODE_QUERY     (-1)  /* Query the value of journalmode */
-#define PAGER_JOURNALMODE_DELETE      0   /* Commit by deleting journal file */
-#define PAGER_JOURNALMODE_PERSIST     1   /* Commit by zeroing journal header */
-#define PAGER_JOURNALMODE_OFF         2   /* Journal omitted.  */
-#define PAGER_JOURNALMODE_TRUNCATE    3   /* Commit by truncating journal */
-#define PAGER_JOURNALMODE_MEMORY      4   /* In-memory journal file */
-#define PAGER_JOURNALMODE_WAL         5   /* Use write-ahead logging */
-
-/*
-** Flags that make up the mask passed to sqlite3PagerAcquire().
-*/
-#define PAGER_GET_NOCONTENT     0x01  /* Do not load data from disk */
-#define PAGER_GET_READONLY      0x02  /* Read-only page is acceptable */
-
-/*
-** Flags for sqlite3PagerSetFlags()
-*/
-#define PAGER_SYNCHRONOUS_OFF       0x01  /* PRAGMA synchronous=OFF */
-#define PAGER_SYNCHRONOUS_NORMAL    0x02  /* PRAGMA synchronous=NORMAL */
-#define PAGER_SYNCHRONOUS_FULL      0x03  /* PRAGMA synchronous=FULL */
-#define PAGER_SYNCHRONOUS_MASK      0x03  /* Mask for three values above */
-#define PAGER_FULLFSYNC             0x04  /* PRAGMA fullfsync=ON */
-#define PAGER_CKPT_FULLFSYNC        0x08  /* PRAGMA checkpoint_fullfsync=ON */
-#define PAGER_CACHESPILL            0x10  /* PRAGMA cache_spill=ON */
-#define PAGER_FLAGS_MASK            0x1c  /* All above except SYNCHRONOUS */
-
-/*
-** The remainder of this file contains the declarations of the functions
-** that make up the Pager sub-system API. See source code comments for 
-** a detailed description of each routine.
-*/
-
-/* Open and close a Pager connection. */ 
-SQLITE_PRIVATE int sqlite3PagerOpen(
-  sqlite3_vfs*,
-  Pager **ppPager,
-  const char*,
-  int,
-  int,
-  int,
-  void(*)(DbPage*)
-);
-SQLITE_PRIVATE int sqlite3PagerClose(Pager *pPager);
-SQLITE_PRIVATE int sqlite3PagerReadFileheader(Pager*, int, unsigned char*);
-
-/* Functions used to configure a Pager object. */
-SQLITE_PRIVATE void sqlite3PagerSetBusyhandler(Pager*, int(*)(void *), void *);
-SQLITE_PRIVATE int sqlite3PagerSetPagesize(Pager*, u32*, int);
-#ifdef SQLITE_HAS_CODEC
-SQLITE_PRIVATE void sqlite3PagerAlignReserve(Pager*,Pager*);
-#endif
-SQLITE_PRIVATE int sqlite3PagerMaxPageCount(Pager*, int);
-SQLITE_PRIVATE void sqlite3PagerSetCachesize(Pager*, int);
-SQLITE_PRIVATE void sqlite3PagerSetMmapLimit(Pager *, sqlite3_int64);
-SQLITE_PRIVATE void sqlite3PagerSetFlags(Pager*,unsigned);
-#if 0
-SQLITE_PRIVATE int sqlite3PagerLockingMode(Pager *, int);
-SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *, int);
-SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager*);
-SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager*);
-SQLITE_PRIVATE i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
-#endif
-
-/* Functions used to obtain and release page references. */ 
-SQLITE_PRIVATE int sqlite3PagerAcquire(Pager *pPager, Pgno pgno, DbPage **ppPage, int clrFlag);
-#define sqlite3PagerGet(A,B,C) sqlite3PagerAcquire(A,B,C,0)
-SQLITE_PRIVATE DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno);
-SQLITE_PRIVATE void sqlite3PagerRef(DbPage*);
-SQLITE_PRIVATE void sqlite3PagerUnref(DbPage*);
-SQLITE_PRIVATE void sqlite3PagerUnrefNotNull(DbPage*);
-
-/* Operations on page references. */
-SQLITE_PRIVATE int sqlite3PagerWrite(DbPage*);
-SQLITE_PRIVATE void sqlite3PagerDontWrite(DbPage*);
-SQLITE_PRIVATE int sqlite3PagerMovepage(Pager*,DbPage*,Pgno,int);
-SQLITE_PRIVATE int sqlite3PagerPageRefcount(DbPage*);
-SQLITE_PRIVATE void *sqlite3PagerGetData(DbPage *); 
-SQLITE_PRIVATE void *sqlite3PagerGetExtra(DbPage *); 
-
-/* Functions used to manage pager transactions and savepoints. */
-SQLITE_PRIVATE void sqlite3PagerPagecount(Pager*, int*);
-SQLITE_PRIVATE int sqlite3PagerBegin(Pager*, int exFlag, int);
-SQLITE_PRIVATE int sqlite3PagerCommitPhaseOne(Pager*,const char *zMaster, int);
-SQLITE_PRIVATE int sqlite3PagerExclusiveLock(Pager*);
-SQLITE_PRIVATE int sqlite3PagerSync(Pager *pPager, const char *zMaster);
-SQLITE_PRIVATE int sqlite3PagerCommitPhaseTwo(Pager*);
-SQLITE_PRIVATE int sqlite3PagerRollback(Pager*);
-SQLITE_PRIVATE int sqlite3PagerOpenSavepoint(Pager *pPager, int n);
-SQLITE_PRIVATE int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint);
-SQLITE_PRIVATE int sqlite3PagerSharedLock(Pager *pPager);
-
-#ifndef SQLITE_OMIT_WAL
-SQLITE_PRIVATE   int sqlite3PagerCheckpoint(Pager *pPager, int, int*, int*);
-SQLITE_PRIVATE   int sqlite3PagerWalSupported(Pager *pPager);
-#if 0
-SQLITE_PRIVATE   int sqlite3PagerWalCallback(Pager *pPager);
-#endif
-SQLITE_PRIVATE   int sqlite3PagerOpenWal(Pager *pPager, int *pisOpen);
-#if 0
-SQLITE_PRIVATE   int sqlite3PagerCloseWal(Pager *pPager);
-#endif
-#endif
-
-#ifdef SQLITE_ENABLE_ZIPVFS
-SQLITE_PRIVATE   int sqlite3PagerWalFramesize(Pager *pPager);
-#endif
-
-/* Functions used to query pager state and configuration. */
-SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager*);
-SQLITE_PRIVATE u32 sqlite3PagerDataVersion(Pager*);
-#ifdef SQLITE_DEBUG
-SQLITE_PRIVATE   int sqlite3PagerRefcount(Pager*);
-#endif
-#if 0
-SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager*);
-#endif
-SQLITE_PRIVATE const char *sqlite3PagerFilename(Pager*, int);
-SQLITE_PRIVATE const sqlite3_vfs *sqlite3PagerVfs(Pager*);
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-SQLITE_PRIVATE sqlite3_file *sqlite3PagerFile(Pager*);
-#endif
-SQLITE_PRIVATE const char *sqlite3PagerJournalname(Pager*);
-SQLITE_PRIVATE int sqlite3PagerNosync(Pager*);
-SQLITE_PRIVATE void *sqlite3PagerTempSpace(Pager*);
-#if 0
-SQLITE_PRIVATE void sqlite3PagerCacheStat(Pager *, int, int, int *);
-SQLITE_PRIVATE void sqlite3PagerClearCache(Pager *);
-#endif
-SQLITE_PRIVATE int sqlite3SectorSize(sqlite3_file *);
-
-/* Functions used to truncate the database file. */
-SQLITE_PRIVATE void sqlite3PagerTruncateImage(Pager*,Pgno);
-
-SQLITE_PRIVATE void sqlite3PagerRekey(DbPage*, Pgno, u16);
-
-#if defined(SQLITE_HAS_CODEC) && !defined(SQLITE_OMIT_WAL)
-SQLITE_PRIVATE void *sqlite3PagerCodec(DbPage *);
-#endif
-
-/* Functions to support testing and debugging. */
-#if !defined(NDEBUG) || defined(SQLITE_TEST)
-SQLITE_PRIVATE   Pgno sqlite3PagerPagenumber(DbPage*);
-SQLITE_PRIVATE   int sqlite3PagerIswriteable(DbPage*);
-#endif
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE   int *sqlite3PagerStats(Pager*);
-SQLITE_PRIVATE   void sqlite3PagerRefdump(Pager*);
-  void disable_simulated_io_errors(void);
-  void enable_simulated_io_errors(void);
-#else
-# define disable_simulated_io_errors()
-# define enable_simulated_io_errors()
-#endif
-
-#endif /* _PAGER_H_ */
-
-/************** End of pager.h ***********************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-/************** Include pcache.h in the middle of sqliteInt.h ****************/
-/************** Begin file pcache.h ******************************************/
-/*
-** 2008 August 05
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This header file defines the interface that the sqlite page cache
-** subsystem. 
-*/
-
-#ifndef _PCACHE_H_
-
-typedef struct PgHdr PgHdr;
-typedef struct PCache PCache;
-
-/*
-** Every page in the cache is controlled by an instance of the following
-** structure.
-*/
-struct PgHdr {
-  sqlite3_pcache_page *pPage;    /* Pcache object page handle */
-  void *pData;                   /* Page data */
-  void *pExtra;                  /* Extra content */
-  PgHdr *pDirty;                 /* Transient list of dirty pages */
-  Pager *pPager;                 /* The pager this page is part of */
-  Pgno pgno;                     /* Page number for this page */
-#ifdef SQLITE_CHECK_PAGES
-  u32 pageHash;                  /* Hash of page content */
-#endif
-  u16 flags;                     /* PGHDR flags defined below */
-
-  /**********************************************************************
-  ** Elements above are public.  All that follows is private to pcache.c
-  ** and should not be accessed by other modules.
-  */
-  i16 nRef;                      /* Number of users of this page */
-  PCache *pCache;                /* Cache that owns this page */
-
-  PgHdr *pDirtyNext;             /* Next element in list of dirty pages */
-  PgHdr *pDirtyPrev;             /* Previous element in list of dirty pages */
-};
-
-/* Bit values for PgHdr.flags */
-#define PGHDR_CLEAN           0x001  /* Page not on the PCache.pDirty list */
-#define PGHDR_DIRTY           0x002  /* Page is on the PCache.pDirty list */
-#define PGHDR_WRITEABLE       0x004  /* Journaled and ready to modify */
-#define PGHDR_NEED_SYNC       0x008  /* Fsync the rollback journal before
-                                     ** writing this page to the database */
-#define PGHDR_NEED_READ       0x010  /* Content is unread */
-#define PGHDR_DONT_WRITE      0x020  /* Do not write content to disk */
-#define PGHDR_MMAP            0x040  /* This is an mmap page object */
-
-/* Initialize and shutdown the page cache subsystem */
-SQLITE_PRIVATE int sqlite3PcacheInitialize(void);
-SQLITE_PRIVATE void sqlite3PcacheShutdown(void);
-
-/* Page cache buffer management:
-** These routines implement SQLITE_CONFIG_PAGECACHE.
-*/
-SQLITE_PRIVATE void sqlite3PCacheBufferSetup(void *, int sz, int n);
-
-/* Create a new pager cache.
-** Under memory stress, invoke xStress to try to make pages clean.
-** Only clean and unpinned pages can be reclaimed.
-*/
-SQLITE_PRIVATE int sqlite3PcacheOpen(
-  int szPage,                    /* Size of every page */
-  int szExtra,                   /* Extra space associated with each page */
-  int bPurgeable,                /* True if pages are on backing store */
-  int (*xStress)(void*, PgHdr*), /* Call to try to make pages clean */
-  void *pStress,                 /* Argument to xStress */
-  PCache *pToInit                /* Preallocated space for the PCache */
-);
-
-/* Modify the page-size after the cache has been created. */
-SQLITE_PRIVATE int sqlite3PcacheSetPageSize(PCache *, int);
-
-/* Return the size in bytes of a PCache object.  Used to preallocate
-** storage space.
-*/
-SQLITE_PRIVATE int sqlite3PcacheSize(void);
-
-/* One release per successful fetch.  Page is pinned until released.
-** Reference counted. 
-*/
-SQLITE_PRIVATE sqlite3_pcache_page *sqlite3PcacheFetch(PCache*, Pgno, int createFlag);
-SQLITE_PRIVATE int sqlite3PcacheFetchStress(PCache*, Pgno, sqlite3_pcache_page**);
-SQLITE_PRIVATE PgHdr *sqlite3PcacheFetchFinish(PCache*, Pgno, sqlite3_pcache_page *pPage);
-SQLITE_PRIVATE void sqlite3PcacheRelease(PgHdr*);
-
-SQLITE_PRIVATE void sqlite3PcacheDrop(PgHdr*);         /* Remove page from cache */
-SQLITE_PRIVATE void sqlite3PcacheMakeDirty(PgHdr*);    /* Make sure page is marked dirty */
-SQLITE_PRIVATE void sqlite3PcacheMakeClean(PgHdr*);    /* Mark a single page as clean */
-SQLITE_PRIVATE void sqlite3PcacheCleanAll(PCache*);    /* Mark all dirty list pages as clean */
-
-/* Change a page number.  Used by incr-vacuum. */
-SQLITE_PRIVATE void sqlite3PcacheMove(PgHdr*, Pgno);
-
-/* Remove all pages with pgno>x.  Reset the cache if x==0 */
-SQLITE_PRIVATE void sqlite3PcacheTruncate(PCache*, Pgno x);
-
-/* Get a list of all dirty pages in the cache, sorted by page number */
-SQLITE_PRIVATE PgHdr *sqlite3PcacheDirtyList(PCache*);
-
-/* Reset and close the cache object */
-SQLITE_PRIVATE void sqlite3PcacheClose(PCache*);
-
-/* Clear flags from pages of the page cache */
-SQLITE_PRIVATE void sqlite3PcacheClearSyncFlags(PCache *);
-
-/* Discard the contents of the cache */
-SQLITE_PRIVATE void sqlite3PcacheClear(PCache*);
-
-/* Return the total number of outstanding page references */
-SQLITE_PRIVATE int sqlite3PcacheRefCount(PCache*);
-
-/* Increment the reference count of an existing page */
-SQLITE_PRIVATE void sqlite3PcacheRef(PgHdr*);
-
-SQLITE_PRIVATE int sqlite3PcachePageRefcount(PgHdr*);
-
-#ifdef SQLITE_TEST
-/* Return the total number of pages stored in the cache */
-SQLITE_PRIVATE int sqlite3PcachePagecount(PCache*);
-#endif
-
-#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
-/* Iterate through all dirty pages currently stored in the cache. This
-** interface is only available if SQLITE_CHECK_PAGES is defined when the 
-** library is built.
-*/
-SQLITE_PRIVATE void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *));
-#endif
-
-/* Set and get the suggested cache-size for the specified pager-cache.
-**
-** If no global maximum is configured, then the system attempts to limit
-** the total number of pages cached by purgeable pager-caches to the sum
-** of the suggested cache-sizes.
-*/
-SQLITE_PRIVATE void sqlite3PcacheSetCachesize(PCache *, int);
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3PcacheGetCachesize(PCache *);
-#endif
-
-#if 0
-/* Free up as much memory as possible from the page cache */
-SQLITE_PRIVATE void sqlite3PcacheShrink(PCache*);
-#endif
-
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-/* Try to return memory used by the pcache module to the main memory heap */
-SQLITE_PRIVATE int sqlite3PcacheReleaseMemory(int);
-#endif
-
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE void sqlite3PcacheStats(int*,int*,int*,int*);
-#endif
-
-SQLITE_PRIVATE void sqlite3PCacheSetDefault(void);
-
-/* Return the header size */
-SQLITE_PRIVATE int sqlite3HeaderSizePcache(void);
-SQLITE_PRIVATE int sqlite3HeaderSizePcache1(void);
-
-#endif /* _PCACHE_H_ */
-
-/************** End of pcache.h **********************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/************** Include os.h in the middle of sqliteInt.h ********************/
-/************** Begin file os.h **********************************************/
-/*
-** 2001 September 16
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This header file (together with is companion C source-code file
-** "os.c") attempt to abstract the underlying operating system so that
-** the SQLite library will work on both POSIX and windows systems.
-**
-** This header file is #include-ed by sqliteInt.h and thus ends up
-** being included by every source file.
-*/
-#ifndef _SQLITE_OS_H_
-#define _SQLITE_OS_H_
-
-/*
-** Attempt to automatically detect the operating system and setup the
-** necessary pre-processor macros for it.
-*/
-/************** Include os_setup.h in the middle of os.h *********************/
-/************** Begin file os_setup.h ****************************************/
-/*
-** 2013 November 25
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains pre-processor directives related to operating system
-** detection and/or setup.
-*/
-#ifndef _OS_SETUP_H_
-#define _OS_SETUP_H_
-
-/*
-** Figure out if we are dealing with Unix, Windows, or some other operating
-** system.
-**
-** After the following block of preprocess macros, all of SQLITE_OS_UNIX,
-** SQLITE_OS_WIN, and SQLITE_OS_OTHER will defined to either 1 or 0.  One of
-** the three will be 1.  The other two will be 0.
-*/
-#if defined(SQLITE_OS_OTHER)
-#  if SQLITE_OS_OTHER==1
-#    undef SQLITE_OS_UNIX
-#    define SQLITE_OS_UNIX 0
-#    undef SQLITE_OS_WIN
-#    define SQLITE_OS_WIN 0
-#  else
-#    undef SQLITE_OS_OTHER
-#  endif
-#endif
-#if !defined(SQLITE_OS_UNIX) && !defined(SQLITE_OS_OTHER)
-#  define SQLITE_OS_OTHER 0
-#  ifndef SQLITE_OS_WIN
-#    if defined(_WIN32) || defined(WIN32) || defined(__CYGWIN__) || \
-        defined(__MINGW32__) || defined(__BORLANDC__)
-#      define SQLITE_OS_WIN 1
-#      define SQLITE_OS_UNIX 0
-#    else
-#      define SQLITE_OS_WIN 0
-#      define SQLITE_OS_UNIX 1
-#    endif
-#  else
-#    define SQLITE_OS_UNIX 0
-#  endif
-#else
-#  ifndef SQLITE_OS_WIN
-#    define SQLITE_OS_WIN 0
-#  endif
-#endif
-
-#endif /* _OS_SETUP_H_ */
-
-/************** End of os_setup.h ********************************************/
-/************** Continuing where we left off in os.h *************************/
-
-/* If the SET_FULLSYNC macro is not defined above, then make it
-** a no-op
-*/
-#ifndef SET_FULLSYNC
-# define SET_FULLSYNC(x,y)
-#endif
-
-/*
-** The default size of a disk sector
-*/
-#ifndef SQLITE_DEFAULT_SECTOR_SIZE
-# define SQLITE_DEFAULT_SECTOR_SIZE 4096
-#endif
-
-/*
-** Temporary files are named starting with this prefix followed by 16 random
-** alphanumeric characters, and no file extension. They are stored in the
-** OS's standard temporary file directory, and are deleted prior to exit.
-** If sqlite is being embedded in another program, you may wish to change the
-** prefix to reflect your program's name, so that if your program exits
-** prematurely, old temporary files can be easily identified. This can be done
-** using -DSQLITE_TEMP_FILE_PREFIX=myprefix_ on the compiler command line.
-**
-** 2006-10-31:  The default prefix used to be "sqlite_".  But then
-** Mcafee started using SQLite in their anti-virus product and it
-** started putting files with the "sqlite" name in the c:/temp folder.
-** This annoyed many windows users.  Those users would then do a 
-** Google search for "sqlite", find the telephone numbers of the
-** developers and call to wake them up at night and complain.
-** For this reason, the default name prefix is changed to be "sqlite" 
-** spelled backwards.  So the temp files are still identified, but
-** anybody smart enough to figure out the code is also likely smart
-** enough to know that calling the developer will not help get rid
-** of the file.
-*/
-#ifndef SQLITE_TEMP_FILE_PREFIX
-# define SQLITE_TEMP_FILE_PREFIX "etilqs_"
-#endif
-
-/*
-** The following values may be passed as the second argument to
-** sqlite3OsLock(). The various locks exhibit the following semantics:
-**
-** SHARED:    Any number of processes may hold a SHARED lock simultaneously.
-** RESERVED:  A single process may hold a RESERVED lock on a file at
-**            any time. Other processes may hold and obtain new SHARED locks.
-** PENDING:   A single process may hold a PENDING lock on a file at
-**            any one time. Existing SHARED locks may persist, but no new
-**            SHARED locks may be obtained by other processes.
-** EXCLUSIVE: An EXCLUSIVE lock precludes all other locks.
-**
-** PENDING_LOCK may not be passed directly to sqlite3OsLock(). Instead, a
-** process that requests an EXCLUSIVE lock may actually obtain a PENDING
-** lock. This can be upgraded to an EXCLUSIVE lock by a subsequent call to
-** sqlite3OsLock().
-*/
-#define NO_LOCK         0
-#define SHARED_LOCK     1
-#define RESERVED_LOCK   2
-#define PENDING_LOCK    3
-#define EXCLUSIVE_LOCK  4
-
-/*
-** File Locking Notes:  (Mostly about windows but also some info for Unix)
-**
-** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
-** those functions are not available.  So we use only LockFile() and
-** UnlockFile().
-**
-** LockFile() prevents not just writing but also reading by other processes.
-** A SHARED_LOCK is obtained by locking a single randomly-chosen 
-** byte out of a specific range of bytes. The lock byte is obtained at 
-** random so two separate readers can probably access the file at the 
-** same time, unless they are unlucky and choose the same lock byte.
-** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
-** There can only be one writer.  A RESERVED_LOCK is obtained by locking
-** a single byte of the file that is designated as the reserved lock byte.
-** A PENDING_LOCK is obtained by locking a designated byte different from
-** the RESERVED_LOCK byte.
-**
-** On WinNT/2K/XP systems, LockFileEx() and UnlockFileEx() are available,
-** which means we can use reader/writer locks.  When reader/writer locks
-** are used, the lock is placed on the same range of bytes that is used
-** for probabilistic locking in Win95/98/ME.  Hence, the locking scheme
-** will support two or more Win95 readers or two or more WinNT readers.
-** But a single Win95 reader will lock out all WinNT readers and a single
-** WinNT reader will lock out all other Win95 readers.
-**
-** The following #defines specify the range of bytes used for locking.
-** SHARED_SIZE is the number of bytes available in the pool from which
-** a random byte is selected for a shared lock.  The pool of bytes for
-** shared locks begins at SHARED_FIRST. 
-**
-** The same locking strategy and
-** byte ranges are used for Unix.  This leaves open the possibility of having
-** clients on win95, winNT, and unix all talking to the same shared file
-** and all locking correctly.  To do so would require that samba (or whatever
-** tool is being used for file sharing) implements locks correctly between
-** windows and unix.  I'm guessing that isn't likely to happen, but by
-** using the same locking range we are at least open to the possibility.
-**
-** Locking in windows is manditory.  For this reason, we cannot store
-** actual data in the bytes used for locking.  The pager never allocates
-** the pages involved in locking therefore.  SHARED_SIZE is selected so
-** that all locks will fit on a single page even at the minimum page size.
-** PENDING_BYTE defines the beginning of the locks.  By default PENDING_BYTE
-** is set high so that we don't have to allocate an unused page except
-** for very large databases.  But one should test the page skipping logic 
-** by setting PENDING_BYTE low and running the entire regression suite.
-**
-** Changing the value of PENDING_BYTE results in a subtly incompatible
-** file format.  Depending on how it is changed, you might not notice
-** the incompatibility right away, even running a full regression test.
-** The default location of PENDING_BYTE is the first byte past the
-** 1GB boundary.
-**
-*/
-#ifdef SQLITE_OMIT_WSD
-# define PENDING_BYTE     (0x40000000)
-#else
-# define PENDING_BYTE      sqlite3PendingByte
-#endif
-#define RESERVED_BYTE     (PENDING_BYTE+1)
-#define SHARED_FIRST      (PENDING_BYTE+2)
-#define SHARED_SIZE       510
-
-/*
-** Wrapper around OS specific sqlite3_os_init() function.
-*/
-SQLITE_PRIVATE int sqlite3OsInit(void);
-
-/* 
-** Functions for accessing sqlite3_file methods 
-*/
-SQLITE_PRIVATE int sqlite3OsClose(sqlite3_file*);
-SQLITE_PRIVATE int sqlite3OsRead(sqlite3_file*, void*, int amt, i64 offset);
-SQLITE_PRIVATE int sqlite3OsWrite(sqlite3_file*, const void*, int amt, i64 offset);
-SQLITE_PRIVATE int sqlite3OsTruncate(sqlite3_file*, i64 size);
-SQLITE_PRIVATE int sqlite3OsSync(sqlite3_file*, int);
-SQLITE_PRIVATE int sqlite3OsFileSize(sqlite3_file*, i64 *pSize);
-SQLITE_PRIVATE int sqlite3OsLock(sqlite3_file*, int);
-SQLITE_PRIVATE int sqlite3OsUnlock(sqlite3_file*, int);
-SQLITE_PRIVATE int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut);
-SQLITE_PRIVATE int sqlite3OsFileControl(sqlite3_file*,int,void*);
-SQLITE_PRIVATE void sqlite3OsFileControlHint(sqlite3_file*,int,void*);
-#define SQLITE_FCNTL_DB_UNCHANGED 0xca093fa0
-SQLITE_PRIVATE int sqlite3OsSectorSize(sqlite3_file *id);
-SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id);
-SQLITE_PRIVATE int sqlite3OsShmMap(sqlite3_file *,int,int,int,void volatile **);
-SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int, int, int);
-SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id);
-SQLITE_PRIVATE int sqlite3OsShmUnmap(sqlite3_file *id, int);
-SQLITE_PRIVATE int sqlite3OsFetch(sqlite3_file *id, i64, int, void **);
-SQLITE_PRIVATE int sqlite3OsUnfetch(sqlite3_file *, i64, void *);
-
-
-/* 
-** Functions for accessing sqlite3_vfs methods 
-*/
-SQLITE_PRIVATE int sqlite3OsOpen(sqlite3_vfs *, const char *, sqlite3_file*, int, int *);
-SQLITE_PRIVATE int sqlite3OsDelete(sqlite3_vfs *, const char *, int);
-SQLITE_PRIVATE int sqlite3OsAccess(sqlite3_vfs *, const char *, int, int *pResOut);
-SQLITE_PRIVATE int sqlite3OsFullPathname(sqlite3_vfs *, const char *, int, char *);
-SQLITE_PRIVATE int sqlite3OsRandomness(sqlite3_vfs *, int, char *);
-SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *, int);
-
-#endif /* _SQLITE_OS_H_ */
-
-/************** End of os.h **************************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-/************** Include mutex.h in the middle of sqliteInt.h *****************/
-/************** Begin file mutex.h *******************************************/
-/*
-** 2007 August 28
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains the common header for all mutex implementations.
-** The sqliteInt.h header #includes this file so that it is available
-** to all source files.  We break it out in an effort to keep the code
-** better organized.
-**
-** NOTE:  source files should *not* #include this header file directly.
-** Source files should #include the sqliteInt.h file and let that file
-** include this one indirectly.
-*/
-
-
-/*
-** Figure out what version of the code to use.  The choices are
-**
-**   SQLITE_MUTEX_OMIT         No mutex logic.  Not even stubs.  The
-**                             mutexes implementation cannot be overridden
-**                             at start-time.
-**
-**   SQLITE_MUTEX_NOOP         For single-threaded applications.  No
-**                             mutual exclusion is provided.  But this
-**                             implementation can be overridden at
-**                             start-time.
-**
-**   SQLITE_MUTEX_PTHREADS     For multi-threaded applications on Unix.
-**
-**   SQLITE_MUTEX_W32          For multi-threaded applications on Win32.
-*/
-#if !SQLITE_THREADSAFE
-# define SQLITE_MUTEX_OMIT
-#endif
-#if SQLITE_THREADSAFE && !defined(SQLITE_MUTEX_NOOP)
-#  if SQLITE_OS_UNIX
-#    define SQLITE_MUTEX_PTHREADS
-#  elif SQLITE_OS_WIN
-#    define SQLITE_MUTEX_W32
-#  else
-#    define SQLITE_MUTEX_NOOP
-#  endif
-#endif
-
-#ifdef SQLITE_MUTEX_OMIT
-/*
-** If this is a no-op implementation, implement everything as macros.
-*/
-#define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)
-#define sqlite3_mutex_free(X)
-#define sqlite3_mutex_enter(X)    
-#define sqlite3_mutex_try(X)      SQLITE_OK
-#define sqlite3_mutex_leave(X)    
-#define sqlite3_mutex_held(X)     ((void)(X),1)
-#define sqlite3_mutex_notheld(X)  ((void)(X),1)
-#define sqlite3MutexAlloc(X)      ((sqlite3_mutex*)8)
-#define sqlite3MutexInit()        SQLITE_OK
-#define sqlite3MutexEnd()
-#define MUTEX_LOGIC(X)
-#else
-#define MUTEX_LOGIC(X)            X
-#endif /* defined(SQLITE_MUTEX_OMIT) */
-
-/************** End of mutex.h ***********************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/*
-** The number of different kinds of things that can be limited
-** using the sqlite3_limit() interface.
-*/
-#define SQLITE_N_LIMIT (SQLITE_LIMIT_WORKER_THREADS+1)
-
-/*
-** Possible values for the sqlite.magic field.
-** The numbers are obtained at random and have no special meaning, other
-** than being distinct from one another.
-*/
-#define SQLITE_MAGIC_OPEN     0xa029a697  /* Database is open */
-#define SQLITE_MAGIC_CLOSED   0x9f3c2d33  /* Database is closed */
-#define SQLITE_MAGIC_SICK     0x4b771290  /* Error and awaiting close */
-#define SQLITE_MAGIC_BUSY     0xf03b7906  /* Database currently in use */
-#define SQLITE_MAGIC_ERROR    0xb5357930  /* An SQLITE_MISUSE error occurred */
-#define SQLITE_MAGIC_ZOMBIE   0x64cffc7f  /* Close with last statement close */
-
-/*
-** The SQLITE_*_BKPT macros are substitutes for the error codes with
-** the same name but without the _BKPT suffix.  These macros invoke
-** routines that report the line-number on which the error originated
-** using sqlite3_log().  The routines also provide a convenient place
-** to set a debugger breakpoint.
-*/
-SQLITE_PRIVATE int sqlite3CorruptError(int);
-SQLITE_PRIVATE int sqlite3MisuseError(int);
-SQLITE_PRIVATE int sqlite3CantopenError(int);
-#define SQLITE_CORRUPT_BKPT sqlite3CorruptError(__LINE__)
-#define SQLITE_MISUSE_BKPT sqlite3MisuseError(__LINE__)
-#define SQLITE_CANTOPEN_BKPT sqlite3CantopenError(__LINE__)
-
-#include <ctype.h>
-
-# define sqlite3Toupper(x)   toupper((unsigned char)(x))
-# define sqlite3Isspace(x)   isspace((unsigned char)(x))
-# define sqlite3Isalnum(x)   isalnum((unsigned char)(x))
-# define sqlite3Isalpha(x)   isalpha((unsigned char)(x))
-# define sqlite3Isdigit(x)   isdigit((unsigned char)(x))
-# define sqlite3Isxdigit(x)  isxdigit((unsigned char)(x))
-# define sqlite3Tolower(x)   tolower((unsigned char)(x))
-
-/*
-** Internal function prototypes
-*/
-SQLITE_PRIVATE int sqlite3Strlen30(const char*);
-
-SQLITE_PRIVATE int sqlite3MallocInit(void);
-SQLITE_PRIVATE void sqlite3MallocEnd(void);
-SQLITE_PRIVATE void *sqlite3Malloc(u64);
-SQLITE_PRIVATE void *sqlite3MallocZero(u64);
-SQLITE_PRIVATE void *sqlite3DbMallocZero(Btree*, u64);
-SQLITE_PRIVATE void *sqlite3DbMallocRaw(Btree*, u64);
-SQLITE_PRIVATE void *sqlite3Realloc(void*, u64);
-SQLITE_PRIVATE void *sqlite3DbReallocOrFree(Btree*, void *, u64);
-SQLITE_PRIVATE void *sqlite3DbRealloc(Btree*, void *, u64);
-SQLITE_PRIVATE void sqlite3DbFree(Btree*, void*);
-SQLITE_PRIVATE int sqlite3MallocSize(void*);
-SQLITE_PRIVATE int sqlite3DbMallocSize(Btree*, void*);
-SQLITE_PRIVATE void *sqlite3ScratchMalloc(int);
-SQLITE_PRIVATE void sqlite3ScratchFree(void*);
-SQLITE_PRIVATE void *sqlite3PageMalloc(int);
-SQLITE_PRIVATE void sqlite3PageFree(void*);
-SQLITE_PRIVATE void sqlite3MemSetDefault(void);
-SQLITE_PRIVATE int sqlite3HeapNearlyFull(void);
-
-/*
-** On systems with ample stack space and that support alloca(), make
-** use of alloca() to obtain space for large automatic objects.  By default,
-** obtain space from malloc().
-**
-** The alloca() routine never returns NULL.  This will cause code paths
-** that deal with sqlite3StackAlloc() failures to be unreachable.
-*/
-#ifdef SQLITE_USE_ALLOCA
-# define sqlite3StackAllocRaw(D,N)   alloca(N)
-# define sqlite3StackAllocZero(D,N)  memset(alloca(N), 0, N)
-# define sqlite3StackFree(D,P)       
-#else
-# define sqlite3StackAllocRaw(D,N)   sqlite3DbMallocRaw(D,N)
-# define sqlite3StackAllocZero(D,N)  sqlite3DbMallocZero(D,N)
-# define sqlite3StackFree(D,P)       sqlite3DbFree(D,P)
-#endif
-
-#ifndef SQLITE_MUTEX_OMIT
-SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3DefaultMutex(void);
-SQLITE_PRIVATE   sqlite3_mutex_methods const *sqlite3NoopMutex(void);
-SQLITE_PRIVATE   sqlite3_mutex *sqlite3MutexAlloc(int);
-SQLITE_PRIVATE   int sqlite3MutexInit(void);
-SQLITE_PRIVATE   int sqlite3MutexEnd(void);
-#endif
-#if !defined(SQLITE_MUTEX_OMIT) && !defined(SQLITE_MUTEX_NOOP)
-SQLITE_PRIVATE   void sqlite3MemoryBarrier(void);
-#else
-# define sqlite3MemoryBarrier()
-#endif
-
-#ifndef SQLITE_OMIT_FLOATING_POINT
-SQLITE_PRIVATE   int sqlite3IsNaN(double);
-#else
-# define sqlite3IsNaN(X)  0
-#endif
-
-/*
-** An instance of the following structure holds information about SQL
-** functions arguments that are the parameters to the printf() function.
-*/
-struct PrintfArguments {
-  int nArg;                /* Total number of arguments */
-  int nUsed;               /* Number of arguments used so far */
-  Mem **apArg;   /* The argument values */
-};
-
-#define SQLITE_PRINTF_INTERNAL 0x01
-#define SQLITE_PRINTF_SQLFUNC  0x02
-
-SQLITE_PRIVATE void sqlite3StrAccumInit(StrAccum*, Btree* pBtree, char*, int, int);
-SQLITE_PRIVATE void sqlite3StrAccumAppend(StrAccum*,const char*,int);
-SQLITE_PRIVATE void sqlite3AppendChar(StrAccum*,int,char);
-SQLITE_PRIVATE char *sqlite3StrAccumFinish(StrAccum*);
-SQLITE_PRIVATE void sqlite3StrAccumReset(StrAccum*);
-
-SQLITE_PRIVATE int sqlite3SafetyCheckSickOrOk(Btree*);
-
-SQLITE_PRIVATE int sqlite3InvokeBusyHandler(BusyHandler*);
-
-SQLITE_PRIVATE void sqlite3BackupRestart(sqlite3_backup *);
-SQLITE_PRIVATE void sqlite3BackupUpdate(sqlite3_backup *, Pgno, const u8 *);
-
-typedef int (*RecordCompare)(int,const void*,UnpackedRecord*);
-
-#define SQLITE_RecoveryMode   0x00010000  /* Ignore schema errors */
-#define SQLITE_CellSizeCk     0x10000000  /* Check btree cell sizes on load */
-
-/*
-** The following are used as the second parameter to sqlite3Savepoint(),
-** and as the P1 argument to the OP_Savepoint instruction.
-*/
-#define SAVEPOINT_BEGIN      0
-#define SAVEPOINT_RELEASE    1
-#define SAVEPOINT_ROLLBACK   2
-
-/*
-** A "Collating Sequence" is defined by an instance of the following
-** structure. Conceptually, a collating sequence consists of a name and
-** a comparison routine that defines the order of that sequence.
-**
-** If CollSeq.xCmp is NULL, it means that the
-** collating sequence is undefined.  Indices built on an undefined
-** collating sequence may not be read or written.
-*/
-struct CollSeq {
-  char *zName;          /* Name of the collating sequence, UTF-8 encoded */
-  u8 enc;               /* Text encoding handled by xCmp() */
-  void *pUser;          /* First argument to xCmp() */
-  int (*xCmp)(void*,int, const void*, int, const void*);
-  void (*xDel)(void*);  /* Destructor for pUser */
-};
-
-/*
-** An instance of the following structure is passed as the first
-** argument to sqlite3VdbeKeyCompare and is used to control the 
-** comparison of the two index keys.
-**
-** Note that aSortOrder[] and aColl[] have nField+1 slots.  There
-** are nField slots for the columns of an index then one extra slot
-** for the rowid at the end.
-*/
-struct KeyInfo {
-  u32 nRef;           /* Number of references to this KeyInfo object */
-  u8 enc;             /* Text encoding - one of the SQLITE_UTF* values */
-  u16 nField;         /* Number of key columns in the index */
-  u16 nXField;        /* Number of columns beyond the key columns */
-  Btree *pBtree;      /* The database connection */
-  u8 *aSortOrder;     /* Sort order for each column. */
-  CollSeq *aColl[1];  /* Collating sequence for each term of the key */
-};
-
-/*
-** An objected used to accumulate the text of a string where we
-** do not necessarily know how big the string will be in the end.
-*/
-struct StrAccum {
-  Btree *pBtree;       /* Optional database for lookaside.  Can be NULL */
-  char *zBase;         /* A base allocation.  Not from malloc. */
-  char *zText;         /* The string collected so far */
-  int  nChar;          /* Length of the string so far */
-  int  nAlloc;         /* Amount of space allocated in zText */
-  int  mxAlloc;        /* Maximum allowed allocation.  0 for no malloc usage */
-  u8   accError;       /* STRACCUM_NOMEM or STRACCUM_TOOBIG */
-};
-#define STRACCUM_NOMEM   1
-#define STRACCUM_TOOBIG  2
-
-/************** Include btreeInt.h in the middle of sqliteInt.h **************/
-/************** Begin file btreeInt.h ****************************************/
-/*
-** 2004 April 6
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file implements an external (disk-based) database using BTrees.
-** For a detailed discussion of BTrees, refer to
-**
-**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
-**     "Sorting And Searching", pages 473-480. Addison-Wesley
-**     Publishing Company, Reading, Massachusetts.
-**
-** The basic idea is that each page of the file contains N database
-** entries and N+1 pointers to subpages.
-**
-**   ----------------------------------------------------------------
-**   |  Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N-1) | Ptr(N) |
-**   ----------------------------------------------------------------
-**
-** All of the keys on the page that Ptr(0) points to have values less
-** than Key(0).  All of the keys on page Ptr(1) and its subpages have
-** values greater than Key(0) and less than Key(1).  All of the keys
-** on Ptr(N) and its subpages have values greater than Key(N-1).  And
-** so forth.
-**
-** Finding a particular key requires reading O(log(M)) pages from the 
-** disk where M is the number of entries in the tree.
-**
-** In this implementation, a single file can hold one or more separate 
-** BTrees.  Each BTree is identified by the index of its root page.  The
-** key and data for any entry are combined to form the "payload".  A
-** fixed amount of payload can be carried directly on the database
-** page.  If the payload is larger than the preset amount then surplus
-** bytes are stored on overflow pages.  The payload for an entry
-** and the preceding pointer are combined to form a "Cell".  Each 
-** page has a small header which contains the Ptr(N) pointer and other
-** information such as the size of key and data.
-**
-** FORMAT DETAILS
-**
-** The file is divided into pages.  The first page is called page 1,
-** the second is page 2, and so forth.  A page number of zero indicates
-** "no such page".  The page size can be any power of 2 between 512 and 65536.
-** Each page can be either a btree page, a freelist page, an overflow
-** page, or a pointer-map page.
-**
-** The first page is always a btree page.  The first 100 bytes of the first
-** page contain a special header (the "file header") that describes the file.
-** The format of the file header is as follows:
-**
-**   OFFSET   SIZE    DESCRIPTION
-**      0      16     Header string: "SQLite format 3\000"
-**     16       2     Page size in bytes.  (1 means 65536)
-**     18       1     File format write version
-**     19       1     File format read version
-**     20       1     Bytes of unused space at the end of each page
-**     21       1     Max embedded payload fraction (must be 64)
-**     22       1     Min embedded payload fraction (must be 32)
-**     23       1     Min leaf payload fraction (must be 32)
-**     24       4     File change counter
-**     28       4     Reserved for future use
-**     32       4     First freelist page
-**     36       4     Number of freelist pages in the file
-**     40      60     15 4-byte meta values passed to higher layers
-**
-**     40       4     Schema cookie
-**     44       4     File format of schema layer
-**     48       4     Size of page cache
-**     52       4     Largest root-page (auto/incr_vacuum)
-**     56       4     1=UTF-8 2=UTF16le 3=UTF16be
-**     60       4     User version
-**     64       4     Incremental vacuum mode
-**     68       4     Application-ID
-**     72      20     unused
-**     92       4     The version-valid-for number
-**     96       4     SQLITE_VERSION_NUMBER
-**
-** All of the integer values are big-endian (most significant byte first).
-**
-** The file change counter is incremented when the database is changed
-** This counter allows other processes to know when the file has changed
-** and thus when they need to flush their cache.
-**
-** The max embedded payload fraction is the amount of the total usable
-** space in a page that can be consumed by a single cell for standard
-** B-tree (non-LEAFDATA) tables.  A value of 255 means 100%.  The default
-** is to limit the maximum cell size so that at least 4 cells will fit
-** on one page.  Thus the default max embedded payload fraction is 64.
-**
-** If the payload for a cell is larger than the max payload, then extra
-** payload is spilled to overflow pages.  Once an overflow page is allocated,
-** as many bytes as possible are moved into the overflow pages without letting
-** the cell size drop below the min embedded payload fraction.
-**
-** The min leaf payload fraction is like the min embedded payload fraction
-** except that it applies to leaf nodes in a LEAFDATA tree.  The maximum
-** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
-** not specified in the header.
-**
-** Each btree pages is divided into three sections:  The header, the
-** cell pointer array, and the cell content area.  Page 1 also has a 100-byte
-** file header that occurs before the page header.
-**
-**      |----------------|
-**      | file header    |   100 bytes.  Page 1 only.
-**      |----------------|
-**      | page header    |   8 bytes for leaves.  12 bytes for interior nodes
-**      |----------------|
-**      | cell pointer   |   |  2 bytes per cell.  Sorted order.
-**      | array          |   |  Grows downward
-**      |                |   v
-**      |----------------|
-**      | unallocated    |
-**      | space          |
-**      |----------------|   ^  Grows upwards
-**      | cell content   |   |  Arbitrary order interspersed with freeblocks.
-**      | area           |   |  and free space fragments.
-**      |----------------|
-**
-** The page headers looks like this:
-**
-**   OFFSET   SIZE     DESCRIPTION
-**      0       1      Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
-**      1       2      byte offset to the first freeblock
-**      3       2      number of cells on this page
-**      5       2      first byte of the cell content area
-**      7       1      number of fragmented free bytes
-**      8       4      Right child (the Ptr(N) value).  Omitted on leaves.
-**
-** The flags define the format of this btree page.  The leaf flag means that
-** this page has no children.  The zerodata flag means that this page carries
-** only keys and no data.  The intkey flag means that the key is an integer
-** which is stored in the key size entry of the cell header rather than in
-** the payload area.
-**
-** The cell pointer array begins on the first byte after the page header.
-** The cell pointer array contains zero or more 2-byte numbers which are
-** offsets from the beginning of the page to the cell content in the cell
-** content area.  The cell pointers occur in sorted order.  The system strives
-** to keep free space after the last cell pointer so that new cells can
-** be easily added without having to defragment the page.
-**
-** Cell content is stored at the very end of the page and grows toward the
-** beginning of the page.
-**
-** Unused space within the cell content area is collected into a linked list of
-** freeblocks.  Each freeblock is at least 4 bytes in size.  The byte offset
-** to the first freeblock is given in the header.  Freeblocks occur in
-** increasing order.  Because a freeblock must be at least 4 bytes in size,
-** any group of 3 or fewer unused bytes in the cell content area cannot
-** exist on the freeblock chain.  A group of 3 or fewer free bytes is called
-** a fragment.  The total number of bytes in all fragments is recorded.
-** in the page header at offset 7.
-**
-**    SIZE    DESCRIPTION
-**      2     Byte offset of the next freeblock
-**      2     Bytes in this freeblock
-**
-** Cells are of variable length.  Cells are stored in the cell content area at
-** the end of the page.  Pointers to the cells are in the cell pointer array
-** that immediately follows the page header.  Cells is not necessarily
-** contiguous or in order, but cell pointers are contiguous and in order.
-**
-** Cell content makes use of variable length integers.  A variable
-** length integer is 1 to 9 bytes where the lower 7 bits of each 
-** byte are used.  The integer consists of all bytes that have bit 8 set and
-** the first byte with bit 8 clear.  The most significant byte of the integer
-** appears first.  A variable-length integer may not be more than 9 bytes long.
-** As a special case, all 8 bytes of the 9th byte are used as data.  This
-** allows a 64-bit integer to be encoded in 9 bytes.
-**
-**    0x00                      becomes  0x00000000
-**    0x7f                      becomes  0x0000007f
-**    0x81 0x00                 becomes  0x00000080
-**    0x82 0x00                 becomes  0x00000100
-**    0x80 0x7f                 becomes  0x0000007f
-**    0x8a 0x91 0xd1 0xac 0x78  becomes  0x12345678
-**    0x81 0x81 0x81 0x81 0x01  becomes  0x10204081
-**
-** Variable length integers are used for rowids and to hold the number of
-** bytes of key and data in a btree cell.
-**
-** The content of a cell looks like this:
-**
-**    SIZE    DESCRIPTION
-**      4     Page number of the left child. Omitted if leaf flag is set.
-**     var    Number of bytes of data. Omitted if the zerodata flag is set.
-**     var    Number of bytes of key. Or the key itself if intkey flag is set.
-**      *     Payload
-**      4     First page of the overflow chain.  Omitted if no overflow
-**
-** Overflow pages form a linked list.  Each page except the last is completely
-** filled with data (pagesize - 4 bytes).  The last page can have as little
-** as 1 byte of data.
-**
-**    SIZE    DESCRIPTION
-**      4     Page number of next overflow page
-**      *     Data
-**
-** Freelist pages come in two subtypes: trunk pages and leaf pages.  The
-** file header points to the first in a linked list of trunk page.  Each trunk
-** page points to multiple leaf pages.  The content of a leaf page is
-** unspecified.  A trunk page looks like this:
-**
-**    SIZE    DESCRIPTION
-**      4     Page number of next trunk page
-**      4     Number of leaf pointers on this page
-**      *     zero or more pages numbers of leaves
-*/
-/* #include "sqliteInt.h" */
-
-
-/* The following value is the maximum cell size assuming a maximum page
-** size give above.
-*/
-#define MX_CELL_SIZE(pBt)  ((int)(pBt->pageSize-8))
-
-/* The maximum number of cells on a single page of the database.  This
-** assumes a minimum cell size of 6 bytes  (4 bytes for the cell itself
-** plus 2 bytes for the index to the cell in the page header).  Such
-** small cells will be rare, but they are possible.
-*/
-#define MX_CELL(pBt) ((pBt->pageSize-8)/6)
-
-/* Forward declarations */
-typedef struct MemPage MemPage;
-typedef struct BtLock BtLock;
-typedef struct CellInfo CellInfo;
-
-/*
-** This is a magic string that appears at the beginning of every
-** SQLite database in order to identify the file as a real database.
-**
-** You can change this value at compile-time by specifying a
-** -DSQLITE_FILE_HEADER="..." on the compiler command-line.  The
-** header must be exactly 16 bytes including the zero-terminator so
-** the string itself should be 15 characters long.  If you change
-** the header, then your custom library will not be able to read 
-** databases generated by the standard tools and the standard tools
-** will not be able to read databases created by your custom library.
-*/
-#ifndef SQLITE_FILE_HEADER /* 123456789 123456 */
-#  define SQLITE_FILE_HEADER "SQLite Btree v3"
-                             
-#endif
-
-/*
-** Page type flags.  An ORed combination of these flags appear as the
-** first byte of on-disk image of every BTree page.
-*/
-#define PTF_INTKEY    0x01
-#define PTF_ZERODATA  0x02
-#define PTF_LEAFDATA  0x04
-#define PTF_LEAF      0x08
-
-/*
-** As each page of the file is loaded into memory, an instance of the following
-** structure is appended and initialized to zero.  This structure stores
-** information about the page that is decoded from the raw file page.
-**
-** The pParent field points back to the parent page.  This allows us to
-** walk up the BTree from any leaf to the root.  Care must be taken to
-** unref() the parent page pointer when this page is no longer referenced.
-** The pageDestructor() routine handles that chore.
-**
-** Access to all fields of this structure is controlled by the mutex
-** stored in MemPage.pBt->mutex.
-*/
-struct MemPage {
-  u8 isInit;           /* True if previously initialized. MUST BE FIRST! */
-  u8 nOverflow;        /* Number of overflow cell bodies in aCell[] */
-  u8 intKey;           /* True if table b-trees.  False for index b-trees */
-  u8 intKeyLeaf;       /* True if the leaf of an intKey table */
-  u8 noPayload;        /* True if internal intKey page (thus w/o data) */
-  u8 leaf;             /* True if a leaf page */
-  u8 hdrOffset;        /* 100 for page 1.  0 otherwise */
-  u8 childPtrSize;     /* 0 if leaf==1.  4 if leaf==0 */
-  u8 max1bytePayload;  /* min(maxLocal,127) */
-  u8 bBusy;            /* Prevent endless loops on corrupt database files */
-  u16 maxLocal;        /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
-  u16 minLocal;        /* Copy of BtShared.minLocal or BtShared.minLeaf */
-  u16 cellOffset;      /* Index in aData of first cell pointer */
-  u16 nFree;           /* Number of free bytes on the page */
-  u16 nCell;           /* Number of cells on this page, local and ovfl */
-  u16 maskPage;        /* Mask for page offset */
-  u16 aiOvfl[5];       /* Insert the i-th overflow cell before the aiOvfl-th
-                       ** non-overflow cell */
-  u8 *apOvfl[5];       /* Pointers to the body of overflow cells */
-  BtShared *pBt;       /* Pointer to BtShared that this page is part of */
-  u8 *aData;           /* Pointer to disk image of the page data */
-  u8 *aDataEnd;        /* One byte past the end of usable data */
-  u8 *aCellIdx;        /* The cell index area */
-  u8 *aDataOfst;       /* Same as aData for leaves.  aData+4 for interior */
-  DbPage *pDbPage;     /* Pager page handle */
-  u16 (*xCellSize)(MemPage*,u8*);             /* cellSizePtr method */
-  void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
-  Pgno pgno;           /* Page number for this page */
-};
-
-/*
-** The in-memory image of a disk page has the auxiliary information appended
-** to the end.  EXTRA_SIZE is the number of bytes of space needed to hold
-** that extra information.
-*/
-#define EXTRA_SIZE sizeof(MemPage)
-
-/*
-** A linked list of the following structures is stored at BtShared.pLock.
-** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor 
-** is opened on the table with root page BtShared.iTable. Locks are removed
-** from this list when a transaction is committed or rolled back, or when
-** a btree handle is closed.
-*/
-struct BtLock {
-  Btree *pBtree;        /* Btree handle holding this lock */
-  Pgno iTable;          /* Root page of table */
-  u8 eLock;             /* READ_LOCK or WRITE_LOCK */
-  BtLock *pNext;        /* Next in BtShared.pLock list */
-};
-
-/* Candidate values for BtLock.eLock */
-#define READ_LOCK     1
-#define WRITE_LOCK    2
-
-/* A Btree handle
-**
-** A database connection contains a pointer to an instance of
-** this object for every database file that it has open.  This structure
-** is opaque to the database connection.  The database connection cannot
-** see the internals of this structure and only deals with pointers to
-** this structure.
-**
-** For some database files, the same underlying database cache might be 
-** shared between multiple connections.  In that case, each connection
-** has it own instance of this object.  But each instance of this object
-** points to the same BtShared object.  The database cache and the
-** schema associated with the database file are all contained within
-** the BtShared object.
-**
-** All fields in this structure are accessed under sqlite3.mutex.
-** The pBt pointer itself may not be changed while there exists cursors 
-** in the referenced BtShared that point back to this Btree since those
-** cursors have to go through this Btree to find their BtShared and
-** they often do so without holding sqlite3.mutex.
-*/
-struct Btree {
-  sqlite3_mutex *mutex;         /* Connection mutex */
-  int flags;                    /* Miscellaneous flags */
-  i64 szMmap;                   /* Default mmap_size setting */
-  u8 enc;                       /* Text encoding */
-  u8 mallocFailed;              /* True if we have seen a malloc failure */
-  u32 magic;                    /* Magic number for detect library misuse */
-  int nVdbeRead;                /* Number of active VDBEs that read or write */
-  BusyHandler busyHandler;      /* Busy callback */
-  int nSavepoint;               /* Number of non-transaction savepoints */
-  int *pnBytesFreed;            /* If not NULL, increment this in DbFree() */
-  BtShared *pBt;     /* Sharable content of this btree */
-  u8 inTrans;        /* TRANS_NONE, TRANS_READ or TRANS_WRITE */
-  u8 sharable;       /* True if we can share pBt with another db */
-  u8 locked;         /* True if db currently has pBt locked */
-  u8 hasIncrblobCur; /* True if there are one or more Incrblob cursors */
-  int wantToLock;    /* Number of nested calls to sqlite3BtreeEnter() */
-  int nBackup;       /* Number of backup operations reading this btree */
-  u32 iDataVersion;  /* Combines with pBt->pPager->iDataVersion */
-  Btree *pNext;      /* List of other sharable Btrees from the same db */
-  Btree *pPrev;      /* Back pointer of the same list */
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  BtLock lock;       /* Object used to lock page 1 */
-#endif
-};
-
-/*
-** Btree.inTrans may take one of the following values.
-**
-** If the shared-data extension is enabled, there may be multiple users
-** of the Btree structure. At most one of these may open a write transaction,
-** but any number may have active read transactions.
-*/
-#define TRANS_NONE  0
-#define TRANS_READ  1
-#define TRANS_WRITE 2
-
-/*
-** An instance of this object represents a single database file.
-** 
-** A single database file can be in use at the same time by two
-** or more database connections.  When two or more connections are
-** sharing the same database file, each connection has it own
-** private Btree object for the file and each of those Btrees points
-** to this one BtShared object.  BtShared.nRef is the number of
-** connections currently sharing this database file.
-**
-** Fields in this structure are accessed under the BtShared.mutex
-** mutex, except for nRef and pNext which are accessed under the
-** global SQLITE_MUTEX_STATIC_MASTER mutex.  The pPager field
-** may not be modified once it is initially set as long as nRef>0.
-** The pSchema field may be set once under BtShared.mutex and
-** thereafter is unchanged as long as nRef>0.
-**
-** isPending:
-**
-**   If a BtShared client fails to obtain a write-lock on a database
-**   table (because there exists one or more read-locks on the table),
-**   the shared-cache enters 'pending-lock' state and isPending is
-**   set to true.
-**
-**   The shared-cache leaves the 'pending lock' state when either of
-**   the following occur:
-**
-**     1) The current writer (BtShared.pWriter) concludes its transaction, OR
-**     2) The number of locks held by other connections drops to zero.
-**
-**   while in the 'pending-lock' state, no connection may start a new
-**   transaction.
-**
-**   This feature is included to help prevent writer-starvation.
-*/
-struct BtShared {
-  Pager *pPager;        /* The page cache */
-  Btree *pBt;          /* Database connection currently using this Btree */
-  BtCursor *pCursor;    /* A list of all open cursors */
-  MemPage *pPage1;      /* First page of the database */
-  u8 openFlags;         /* Flags to sqlite3BtreeOpen() */
-#ifndef SQLITE_OMIT_AUTOVACUUM
-  u8 autoVacuum;        /* True if auto-vacuum is enabled */
-  u8 incrVacuum;        /* True if incr-vacuum is enabled */
-  u8 bDoTruncate;       /* True to truncate db on commit */
-#endif
-  u8 inTransaction;     /* Transaction state */
-  u8 max1bytePayload;   /* Maximum first byte of cell for a 1-byte payload */
-#ifdef SQLITE_HAS_CODEC
-  u8 optimalReserve;    /* Desired amount of reserved space per page */
-#endif
-  u16 btsFlags;         /* Boolean parameters.  See BTS_* macros below */
-  u16 maxLocal;         /* Maximum local payload in non-LEAFDATA tables */
-  u16 minLocal;         /* Minimum local payload in non-LEAFDATA tables */
-  u16 maxLeaf;          /* Maximum local payload in a LEAFDATA table */
-  u16 minLeaf;          /* Minimum local payload in a LEAFDATA table */
-  u32 pageSize;         /* Total number of bytes on a page */
-  u32 file_format;      /* File Format */
-  u32 usableSize;       /* Number of usable bytes on each page */
-  int nTransaction;     /* Number of open transactions (read + write) */
-  u32 nPage;            /* Number of pages in the database */
-  void *pSchema;        /* Pointer to space allocated by sqlite3BtreeSchema() */
-  void (*xFreeSchema)(void*);  /* Destructor for BtShared.pSchema */
-  sqlite3_mutex *mutex; /* Non-recursive mutex required to access this object */
-  Bitvec *pHasContent;  /* Set of pages moved to free-list this transaction */
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  int nRef;             /* Number of references to this structure */
-  BtShared *pNext;      /* Next on a list of sharable BtShared structs */
-  BtLock *pLock;        /* List of locks held on this shared-btree struct */
-  Btree *pWriter;       /* Btree with currently open write transaction */
-#endif
-  u8 *pTmpSpace;        /* Temp space sufficient to hold a single cell */
-};
-
-/*
-** Allowed values for BtShared.btsFlags
-*/
-#define BTS_READ_ONLY        0x0001   /* Underlying file is readonly */
-#define BTS_PAGESIZE_FIXED   0x0002   /* Page size can no longer be changed */
-#define BTS_SECURE_DELETE    0x0004   /* PRAGMA secure_delete is enabled */
-#define BTS_INITIALLY_EMPTY  0x0008   /* Database was empty at trans start */
-#define BTS_NO_WAL           0x0010   /* Do not open write-ahead-log files */
-#define BTS_EXCLUSIVE        0x0020   /* pWriter has an exclusive lock */
-#define BTS_PENDING          0x0040   /* Waiting for read-locks to clear */
-
-/*
-** An instance of the following structure is used to hold information
-** about a cell.  The parseCellPtr() function fills in this structure
-** based on information extract from the raw disk page.
-*/
-struct CellInfo {
-  i64 nKey;      /* The key for INTKEY tables, or nPayload otherwise */
-  u8 *pPayload;  /* Pointer to the start of payload */
-  u32 nPayload;  /* Bytes of payload */
-  u16 nLocal;    /* Amount of payload held locally, not on overflow */
-  u16 iOverflow; /* Offset to overflow page number.  Zero if no overflow */
-  u16 nSize;     /* Size of the cell content on the main b-tree page */
-};
-
-/*
-** Maximum depth of an SQLite B-Tree structure. Any B-Tree deeper than
-** this will be declared corrupt. This value is calculated based on a
-** maximum database size of 2^31 pages a minimum fanout of 2 for a
-** root-node and 3 for all other internal nodes.
-**
-** If a tree that appears to be taller than this is encountered, it is
-** assumed that the database is corrupt.
-*/
-#define BTCURSOR_MAX_DEPTH 20
-
-/*
-** A cursor is a pointer to a particular entry within a particular
-** b-tree within a database file.
-**
-** The entry is identified by its MemPage and the index in
-** MemPage.aCell[] of the entry.
-**
-** A single database file can be shared by two more database connections,
-** but cursors cannot be shared.  Each cursor is associated with a
-** particular database connection identified BtCursor.pBtree.db.
-**
-** Fields in this structure are accessed under the BtShared.mutex
-** found at self->pBt->mutex. 
-**
-** skipNext meaning:
-**    eState==SKIPNEXT && skipNext>0:  Next sqlite3BtreeNext() is no-op.
-**    eState==SKIPNEXT && skipNext<0:  Next sqlite3BtreePrevious() is no-op.
-**    eState==FAULT:                   Cursor fault with skipNext as error code.
-*/
-struct BtCursor {
-  Btree *pBtree;            /* The Btree to which this cursor belongs */
-  BtShared *pBt;            /* The BtShared this cursor points to */
-  BtCursor *pNext;          /* Forms a linked list of all cursors */
-  Pgno *aOverflow;          /* Cache of overflow page locations */
-  CellInfo info;            /* A parse of the cell we are pointing at */
-  i64 nKey;                 /* Size of pKey, or last integer key */
-  void *pKey;               /* Saved key that was cursor last known position */
-  Pgno pgnoRoot;            /* The root page of this tree */
-  int nOvflAlloc;           /* Allocated size of aOverflow[] array */
-  int skipNext;    /* Prev() is noop if negative. Next() is noop if positive.
-                   ** Error code if eState==CURSOR_FAULT */
-  u8 curFlags;              /* zero or more BTCF_* flags defined below */
-  u8 curPagerFlags;         /* Flags to send to sqlite3PagerAcquire() */
-  u8 eState;                /* One of the CURSOR_XXX constants (see below) */
-  u8 hints;                 /* As configured by CursorSetHints() */
-  i8 iPage;                 /* Index of current page in apPage */
-  u8 curIntKey;             /* Value of apPage[0]->intKey */
-  struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */
-  void *padding1;           /* Make object size a multiple of 16 */
-  u16 aiIdx[BTCURSOR_MAX_DEPTH];        /* Current index in apPage[i] */
-  MemPage *apPage[BTCURSOR_MAX_DEPTH];  /* Pages from root to current page */
-};
-
-/*
-** Legal values for BtCursor.curFlags
-*/
-#define BTCF_WriteFlag    0x01   /* True if a write cursor */
-#define BTCF_ValidNKey    0x02   /* True if info.nKey is valid */
-#define BTCF_ValidOvfl    0x04   /* True if aOverflow is valid */
-#define BTCF_AtLast       0x08   /* Cursor is pointing ot the last entry */
-#define BTCF_Incrblob     0x10   /* True if an incremental I/O handle */
-#define BTCF_Multiple     0x20   /* Maybe another cursor on the same btree */
-
-/*
-** Potential values for BtCursor.eState.
-**
-** CURSOR_INVALID:
-**   Cursor does not point to a valid entry. This can happen (for example) 
-**   because the table is empty or because BtreeCursorFirst() has not been
-**   called.
-**
-** CURSOR_VALID:
-**   Cursor points to a valid entry. getPayload() etc. may be called.
-**
-** CURSOR_SKIPNEXT:
-**   Cursor is valid except that the Cursor.skipNext field is non-zero
-**   indicating that the next sqlite3BtreeNext() or sqlite3BtreePrevious()
-**   operation should be a no-op.
-**
-** CURSOR_REQUIRESEEK:
-**   The table that this cursor was opened on still exists, but has been 
-**   modified since the cursor was last used. The cursor position is saved
-**   in variables BtCursor.pKey and BtCursor.nKey. When a cursor is in 
-**   this state, restoreCursorPosition() can be called to attempt to
-**   seek the cursor to the saved position.
-**
-** CURSOR_FAULT:
-**   An unrecoverable error (an I/O error or a malloc failure) has occurred
-**   on a different connection that shares the BtShared cache with this
-**   cursor.  The error has left the cache in an inconsistent state.
-**   Do nothing else with this cursor.  Any attempt to use the cursor
-**   should return the error code stored in BtCursor.skipNext
-*/
-#define CURSOR_INVALID           0
-#define CURSOR_VALID             1
-#define CURSOR_SKIPNEXT          2
-#define CURSOR_REQUIRESEEK       3
-#define CURSOR_FAULT             4
-
-/* 
-** The database page the PENDING_BYTE occupies. This page is never used.
-*/
-# define PENDING_BYTE_PAGE(pBt) PAGER_MJ_PGNO(pBt)
-
-/*
-** These macros define the location of the pointer-map entry for a 
-** database page. The first argument to each is the number of usable
-** bytes on each page of the database (often 1024). The second is the
-** page number to look up in the pointer map.
-**
-** PTRMAP_PAGENO returns the database page number of the pointer-map
-** page that stores the required pointer. PTRMAP_PTROFFSET returns
-** the offset of the requested map entry.
-**
-** If the pgno argument passed to PTRMAP_PAGENO is a pointer-map page,
-** then pgno is returned. So (pgno==PTRMAP_PAGENO(pgsz, pgno)) can be
-** used to test if pgno is a pointer-map page. PTRMAP_ISPAGE implements
-** this test.
-*/
-#define PTRMAP_PAGENO(pBt, pgno) ptrmapPageno(pBt, pgno)
-#define PTRMAP_PTROFFSET(pgptrmap, pgno) (5*(pgno-pgptrmap-1))
-#define PTRMAP_ISPAGE(pBt, pgno) (PTRMAP_PAGENO((pBt),(pgno))==(pgno))
-
-/*
-** The pointer map is a lookup table that identifies the parent page for
-** each child page in the database file.  The parent page is the page that
-** contains a pointer to the child.  Every page in the database contains
-** 0 or 1 parent pages.  (In this context 'database page' refers
-** to any page that is not part of the pointer map itself.)  Each pointer map
-** entry consists of a single byte 'type' and a 4 byte parent page number.
-** The PTRMAP_XXX identifiers below are the valid types.
-**
-** The purpose of the pointer map is to facility moving pages from one
-** position in the file to another as part of autovacuum.  When a page
-** is moved, the pointer in its parent must be updated to point to the
-** new location.  The pointer map is used to locate the parent page quickly.
-**
-** PTRMAP_ROOTPAGE: The database page is a root-page. The page-number is not
-**                  used in this case.
-**
-** PTRMAP_FREEPAGE: The database page is an unused (free) page. The page-number 
-**                  is not used in this case.
-**
-** PTRMAP_OVERFLOW1: The database page is the first page in a list of 
-**                   overflow pages. The page number identifies the page that
-**                   contains the cell with a pointer to this overflow page.
-**
-** PTRMAP_OVERFLOW2: The database page is the second or later page in a list of
-**                   overflow pages. The page-number identifies the previous
-**                   page in the overflow page list.
-**
-** PTRMAP_BTREE: The database page is a non-root btree page. The page number
-**               identifies the parent page in the btree.
-*/
-#define PTRMAP_ROOTPAGE 1
-#define PTRMAP_FREEPAGE 2
-#define PTRMAP_OVERFLOW1 3
-#define PTRMAP_OVERFLOW2 4
-#define PTRMAP_BTREE 5
-
-/* A bunch of assert() statements to check the transaction state variables
-** of handle p (type Btree*) are internally consistent.
-*/
-#define btreeIntegrity(p) \
-  assert( p->pBt->inTransaction!=TRANS_NONE || p->pBt->nTransaction==0 ); \
-  assert( p->pBt->inTransaction>=p->inTrans ); 
-
-
-/*
-** The ISAUTOVACUUM macro is used within balance_nonroot() to determine
-** if the database supports auto-vacuum or not. Because it is used
-** within an expression that is an argument to another macro 
-** (sqliteMallocRaw), it is not possible to use conditional compilation.
-** So, this macro is defined instead.
-*/
-#ifndef SQLITE_OMIT_AUTOVACUUM
-#define ISAUTOVACUUM (pBt->autoVacuum)
-#else
-#define ISAUTOVACUUM 0
-#endif
-
-
-/*
-** This structure is passed around through all the sanity checking routines
-** in order to keep track of some global state information.
-**
-** The aRef[] array is allocated so that there is 1 bit for each page in
-** the database. As the integrity-check proceeds, for each page used in
-** the database the corresponding bit is set. This allows integrity-check to 
-** detect pages that are used twice and orphaned pages (both of which 
-** indicate corruption).
-*/
-typedef struct IntegrityCk IntegrityCk;
-struct IntegrityCk {
-  BtShared *pBt;    /* The tree being checked out */
-  Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
-  u8 *aPgRef;       /* 1 bit per page in the db (see above) */
-  Pgno nPage;       /* Number of pages in the database */
-  int mxErr;        /* Stop accumulating errors when this reaches zero */
-  int nErr;         /* Number of messages written to zErrMsg so far */
-  int mallocFailed; /* A memory allocation error has occurred */
-  const char *zPfx; /* Error message prefix */
-  int v1, v2;       /* Values for up to two %d fields in zPfx */
-  StrAccum errMsg;  /* Accumulate the error message text here */
-  u32 *heap;        /* Min-heap used for analyzing cell coverage */
-};
-
-/*
-** Routines to read or write a two- and four-byte big-endian integer values.
-*/
-#define get2byte(x)   ((x)[0]<<8 | (x)[1])
-#define put2byte(p,v) ((p)[0] = (u8)((v)>>8), (p)[1] = (u8)(v))
-#define get4byte sqlite3Get4byte
-#define put4byte sqlite3Put4byte
-
-/*
-** get2byteAligned(), unlike get2byte(), requires that its argument point to a
-** two-byte aligned address.  get2bytea() is only used for accessing the
-** cell addresses in a btree header.
-*/
-#if SQLITE_BYTEORDER==4321
-# define get2byteAligned(x)  (*(u16*)(x))
-#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && GCC_VERSION>=4008000
-# define get2byteAligned(x)  __builtin_bswap16(*(u16*)(x))
-#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(_MSC_VER) && _MSC_VER>=1300
-# define get2byteAligned(x)  _byteswap_ushort(*(u16*)(x))
-#else
-# define get2byteAligned(x)  ((x)[0]<<8 | (x)[1])
-#endif
-
-#ifndef SQLITE_OMIT_INCRBLOB
-SQLITE_PRIVATE   int sqlite3VdbeMemExpandBlob(Mem *);
-  #define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
-#else
-  #define sqlite3VdbeMemExpandBlob(x) SQLITE_OK
-  #define ExpandBlob(P) SQLITE_OK
-#endif
-
-SQLITE_PRIVATE int sqlite3HeaderSizeBtree(void);
-
-SQLITE_PRIVATE void sqlite3VdbeRecordUnpack(KeyInfo*,int,const void*,UnpackedRecord*);
-SQLITE_PRIVATE UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(KeyInfo *, char *, int, char **);
-
-SQLITE_PRIVATE RecordCompare sqlite3VdbeFindCompare(UnpackedRecord*);
-
-/************** End of btreeInt.h ********************************************/
-/************** Continuing where we left off in sqliteInt.h ******************/
-
-/*
-** Structure containing global configuration data for the SQLite library.
-**
-** This structure also contains some state information.
-*/
-struct Sqlite3Config {
-  int bMemstat;                     /* True to enable memory status */
-  int bCoreMutex;                   /* True to enable core mutexing */
-  int bFullMutex;                   /* True to enable full mutexing */
-  int bOpenUri;                     /* True to interpret filenames as URIs */
-  int bUseCis;                      /* Use covering indices for full-scans */
-  int mxStrlen;                     /* Maximum string length */
-  int neverCorrupt;                 /* Database is always well-formed */
-  int szLookaside;                  /* Default lookaside buffer size */
-  int nLookaside;                   /* Default lookaside buffer count */
-  sqlite3_mem_methods m;            /* Low-level memory allocation interface */
-  sqlite3_mutex_methods mutex;      /* Low-level mutex interface */
-  sqlite3_pcache_methods2 pcache2;  /* Low-level page-cache interface */
-  void *pHeap;                      /* Heap storage space */
-  int nHeap;                        /* Size of pHeap[] */
-  int mnReq, mxReq;                 /* Min and max heap requests sizes */
-  sqlite3_int64 szMmap;             /* mmap() space per open file */
-  sqlite3_int64 mxMmap;             /* Maximum value for szMmap */
-  void *pScratch;                   /* Scratch memory */
-  int szScratch;                    /* Size of each scratch buffer */
-  int nScratch;                     /* Number of scratch buffers */
-  void *pPage;                      /* Page cache memory */
-  int szPage;                       /* Size of each page in pPage[] */
-  int nPage;                        /* Number of pages in pPage[] */
-  int mxParserStack;                /* maximum depth of the parser stack */
-  int sharedCacheEnabled;           /* true if shared-cache mode enabled */
-  u32 szPma;                        /* Maximum Sorter PMA size */
-  /* The above might be initialized to non-zero.  The following need to always
-  ** initially be zero, however. */
-  int isInit;                       /* True after initialization has finished */
-  int inProgress;                   /* True while initialization in progress */
-  int isMutexInit;                  /* True after mutexes are initialized */
-  int isMallocInit;                 /* True after malloc is initialized */
-  int isPCacheInit;                 /* True after malloc is initialized */
-  int nRefInitMutex;                /* Number of users of pInitMutex */
-  sqlite3_mutex *pInitMutex;        /* Mutex used by sqlite3BtreeInitialize() */
-  void (*xLog)(void*,int,const char*); /* Function for logging */
-  void *pLogArg;                       /* First argument to xLog() */
-#ifdef SQLITE_VDBE_COVERAGE
-  /* The following callback (if not NULL) is invoked on every VDBE branch
-  ** operation.  Set the callback using SQLITE_TESTCTRL_VDBE_COVERAGE.
-  */
-  void (*xVdbeBranch)(void*,int iSrcLine,u8 eThis,u8 eMx);  /* Callback */
-  void *pVdbeBranchArg;                                     /* 1st argument */
-#endif
-  int bLocaltimeFault;              /* True to fail localtime() calls */
-};
-
-#ifndef SQLITE_AMALGAMATION
-SQLITE_PRIVATE SQLITE_WSD struct Sqlite3Config sqlite3Config;
-#ifndef SQLITE_OMIT_WSD
-SQLITE_PRIVATE int sqlite3PendingByte;
-#endif
-#endif
-
-#if (defined(i386)     || defined(__i386__)   || defined(_M_IX86) ||    \
-     defined(__x86_64) || defined(__x86_64__) || defined(_M_X64)  ||    \
-     defined(_M_AMD64) || defined(_M_ARM)     || defined(__x86)   ||    \
-     defined(__arm__)) && !defined(SQLITE_RUNTIME_BYTEORDER)
-# define SQLITE_BYTEORDER    1234
-# define SQLITE_BIGENDIAN    0
-# define SQLITE_LITTLEENDIAN 1
-# define SQLITE_UTF16NATIVE  SQLITE_UTF16LE
-#endif
-#if (defined(sparc)    || defined(__ppc__))  \
-    && !defined(SQLITE_RUNTIME_BYTEORDER)
-# define SQLITE_BYTEORDER    4321
-# define SQLITE_BIGENDIAN    1
-# define SQLITE_LITTLEENDIAN 0
-# define SQLITE_UTF16NATIVE  SQLITE_UTF16BE
-#endif
-#if !defined(SQLITE_BYTEORDER)
-const int sqlite3one = 1;
-# define SQLITE_BYTEORDER    0     /* 0 means "unknown at compile-time" */
-# define SQLITE_BIGENDIAN    (*(char *)(&sqlite3one)==0)
-# define SQLITE_LITTLEENDIAN (*(char *)(&sqlite3one)==1)
-# define SQLITE_UTF16NATIVE  (SQLITE_BIGENDIAN?SQLITE_UTF16BE:SQLITE_UTF16LE)
-#endif
-
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-SQLITE_PRIVATE   int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
-SQLITE_PRIVATE   int sqlite3JournalSize(sqlite3_vfs *);
-SQLITE_PRIVATE   int sqlite3JournalCreate(sqlite3_file *);
-SQLITE_PRIVATE   int sqlite3JournalExists(sqlite3_file *p);
-#else
-  #define sqlite3JournalSize(pVfs) ((pVfs)->szOsFile)
-  #define sqlite3JournalExists(p) 1
-#endif
-
-SQLITE_PRIVATE void sqlite3MemJournalOpen(sqlite3_file *);
-SQLITE_PRIVATE int sqlite3MemJournalSize(void);
-SQLITE_PRIVATE int sqlite3IsMemJournal(sqlite3_file *);
-
-#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
-SQLITE_PRIVATE   void sqlite3ConnectionBlocked(Btree*, Btree*);
-SQLITE_PRIVATE   void sqlite3ConnectionUnlocked(Btree *db);
-SQLITE_PRIVATE   void sqlite3ConnectionClosed(Btree *db);
-#else
-  #define sqlite3ConnectionBlocked(x,y)
-  #define sqlite3ConnectionUnlocked(x)
-  #define sqlite3ConnectionClosed(x)
-#endif
-
-/*
-** If the SQLITE_ENABLE IOTRACE exists then the global variable
-** sqlite3IoTrace is a pointer to a printf-like routine used to
-** print I/O tracing messages. 
-*/
-#ifdef SQLITE_ENABLE_IOTRACE
-# define IOTRACE(A)  if( sqlite3IoTrace ){ sqlite3IoTrace A; }
-SQLITE_PRIVATE   void sqlite3VdbeIOTraceSql(Vdbe*);
-SQLITE_API SQLITE_EXTERN void (SQLITE_CDECL *sqlite3IoTrace)(const char*,...);
-#else
-# define IOTRACE(A)
-# define sqlite3VdbeIOTraceSql(X)
-#endif
-
-SQLITE_PRIVATE Bitvec *sqlite3BitvecCreate(u32);
-SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec*, u32);
-SQLITE_PRIVATE int sqlite3BitvecTestNotNull(Bitvec*, u32);
-SQLITE_PRIVATE int sqlite3BitvecSet(Bitvec*, u32);
-SQLITE_PRIVATE void sqlite3BitvecClear(Bitvec*, u32, void*);
-SQLITE_PRIVATE void sqlite3BitvecDestroy(Bitvec*);
-SQLITE_PRIVATE u32 sqlite3BitvecSize(Bitvec*);
-
-SQLITE_PRIVATE const void *sqlite3ValueText(Mem*, u8);
-
-/*
-** These routines are available for the mem2.c debugging memory allocator
-** only.  They are used to verify that different "types" of memory
-** allocations are properly tracked by the system.
-**
-** sqlite3MemdebugSetType() sets the "type" of an allocation to one of
-** the MEMTYPE_* macros defined below.  The type must be a bitmask with
-** a single bit set.
-**
-** sqlite3MemdebugHasType() returns true if any of the bits in its second
-** argument match the type set by the previous sqlite3MemdebugSetType().
-** sqlite3MemdebugHasType() is intended for use inside assert() statements.
-**
-** sqlite3MemdebugNoType() returns true if none of the bits in its second
-** argument match the type set by the previous sqlite3MemdebugSetType().
-**
-** Perhaps the most important point is the difference between MEMTYPE_HEAP
-** and MEMTYPE_LOOKASIDE.  If an allocation is MEMTYPE_LOOKASIDE, that means
-** it might have been allocated by lookaside, except the allocation was
-** too large or lookaside was already full.  It is important to verify
-** that allocations that might have been satisfied by lookaside are not
-** passed back to non-lookaside free() routines.  Asserts such as the
-** example above are placed on the non-lookaside free() routines to verify
-** this constraint. 
-**
-** All of this is no-op for a production build.  It only comes into
-** play when the SQLITE_MEMDEBUG compile-time option is used.
-*/
-#ifdef SQLITE_MEMDEBUG
-SQLITE_PRIVATE   void sqlite3MemdebugSetType(void*,u8);
-SQLITE_PRIVATE   int sqlite3MemdebugHasType(void*,u8);
-SQLITE_PRIVATE   int sqlite3MemdebugNoType(void*,u8);
-#else
-# define sqlite3MemdebugSetType(X,Y)  /* no-op */
-# define sqlite3MemdebugHasType(X,Y)  1
-# define sqlite3MemdebugNoType(X,Y)   1
-#endif
-#define MEMTYPE_HEAP       0x01  /* General heap allocations */
-#define MEMTYPE_LOOKASIDE  0x02  /* Heap that might have been lookaside */
-#define MEMTYPE_SCRATCH    0x04  /* Scratch allocations */
-#define MEMTYPE_PCACHE     0x08  /* Page cache allocations */
-
-
-SQLITE_PRIVATE i64 sqlite3VdbeIntValue(Mem*);
-SQLITE_PRIVATE double sqlite3VdbeRealValue(Mem*);
-
-SQLITE_PRIVATE int sqlite3VdbeRecordCompareWithSkip(int, const void *, UnpackedRecord *, int);
-
-#endif /* _SQLITEINT_H_ */
-
-/************** End of sqliteInt.h *******************************************/
-/************** Begin file global.c ******************************************/
-/*
-** 2008 June 13
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains definitions of global variables and constants.
-*/
-/* #include "sqliteInt.h" */
-
-/* An array to map all upper-case characters into their corresponding
-** lower-case character. 
-**
-** SQLite only considers US-ASCII (or EBCDIC) characters.  We do not
-** handle case conversions for the UTF character set since the tables
-** involved are nearly as big or bigger than SQLite itself.
-*/
-const unsigned char sqlite3UpperToLower[] = {
-      0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17,
-     18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
-     36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
-     54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 97, 98, 99,100,101,102,103,
-    104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,
-    122, 91, 92, 93, 94, 95, 96, 97, 98, 99,100,101,102,103,104,105,106,107,
-    108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,
-    126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
-    144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,
-    162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,
-    180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,
-    198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,
-    216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,
-    234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,
-    252,253,254,255
-};
-/* EVIDENCE-OF: R-02982-34736 In order to maintain full backwards
-** compatibility for legacy applications, the URI filename capability is
-** disabled by default.
-**
-** EVIDENCE-OF: R-38799-08373 URI filenames can be enabled or disabled
-** using the SQLITE_USE_URI=1 or SQLITE_USE_URI=0 compile-time options.
-**
-** EVIDENCE-OF: R-43642-56306 By default, URI handling is globally
-** disabled. The default value may be changed by compiling with the
-** SQLITE_USE_URI symbol defined.
-*/
-#ifndef SQLITE_USE_URI
-# define  SQLITE_USE_URI 0
-#endif
-
-/* EVIDENCE-OF: R-38720-18127 The default setting is determined by the
-** SQLITE_ALLOW_COVERING_INDEX_SCAN compile-time option, or is "on" if
-** that compile-time option is omitted.
-*/
-#ifndef SQLITE_ALLOW_COVERING_INDEX_SCAN
-# define SQLITE_ALLOW_COVERING_INDEX_SCAN 1
-#endif
-
-/* The minimum PMA size is set to this value multiplied by the database
-** page size in bytes.
-*/
-#ifndef SQLITE_SORTER_PMASZ
-# define SQLITE_SORTER_PMASZ 250
-#endif
-
-/*
-** The following singleton contains the global configuration for
-** the SQLite library.
-*/
-SQLITE_PRIVATE SQLITE_WSD struct Sqlite3Config sqlite3Config = {
-   SQLITE_DEFAULT_MEMSTATUS,  /* bMemstat */
-   1,                         /* bCoreMutex */
-   SQLITE_THREADSAFE==1,      /* bFullMutex */
-   SQLITE_USE_URI,            /* bOpenUri */
-   SQLITE_ALLOW_COVERING_INDEX_SCAN,   /* bUseCis */
-   0x7ffffffe,                /* mxStrlen */
-   0,                         /* neverCorrupt */
-   128,                       /* szLookaside */
-   500,                       /* nLookaside */
-   {0,0,0,0,0,0,0,0},         /* m */
-   {0,0,0,0,0,0,0,0,0},       /* mutex */
-   {0,0,0,0,0,0,0,0,0,0,0,0,0},/* pcache2 */
-   (void*)0,                  /* pHeap */
-   0,                         /* nHeap */
-   0, 0,                      /* mnHeap, mxHeap */
-   SQLITE_DEFAULT_MMAP_SIZE,  /* szMmap */
-   SQLITE_MAX_MMAP_SIZE,      /* mxMmap */
-   (void*)0,                  /* pScratch */
-   0,                         /* szScratch */
-   0,                         /* nScratch */
-   (void*)0,                  /* pPage */
-   0,                         /* szPage */
-   SQLITE_DEFAULT_PCACHE_INITSZ, /* nPage */
-   0,                         /* mxParserStack */
-   0,                         /* sharedCacheEnabled */
-   SQLITE_SORTER_PMASZ,       /* szPma */
-   /* All the rest should always be initialized to zero */
-   0,                         /* isInit */
-   0,                         /* inProgress */
-   0,                         /* isMutexInit */
-   0,                         /* isMallocInit */
-   0,                         /* isPCacheInit */
-   0,                         /* nRefInitMutex */
-   0,                         /* pInitMutex */
-   0,                         /* xLog */
-   0,                         /* pLogArg */
-#ifdef SQLITE_VDBE_COVERAGE
-   0,                         /* xVdbeBranch */
-   0,                         /* pVbeBranchArg */
-#endif
-   0                          /* bLocaltimeFault */
-};
-
-/*
-** The value of the "pending" byte must be 0x40000000 (1 byte past the
-** 1-gibabyte boundary) in a compatible database.  SQLite never uses
-** the database page that contains the pending byte.  It never attempts
-** to read or write that page.  The pending byte page is set assign
-** for use by the VFS layers as space for managing file locks.
-**
-** During testing, it is often desirable to move the pending byte to
-** a different position in the file.  This allows code that has to
-** deal with the pending byte to run on files that are much smaller
-** than 1 GiB.  The sqlite3_test_control() interface can be used to
-** move the pending byte.
-**
-** IMPORTANT:  Changing the pending byte to any value other than
-** 0x40000000 results in an incompatible database file format!
-** Changing the pending byte during operation will result in undefined
-** and incorrect behavior.
-*/
-#ifndef SQLITE_OMIT_WSD
-SQLITE_PRIVATE int sqlite3PendingByte = 0x40000000;
-#endif
-
-/************** End of global.c **********************************************/
-/************** Begin file status.c ******************************************/
-/*
-** 2008 June 18
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This module implements the sqlite3_status() interface and related
-** functionality.
-*/
-/* #include "sqliteInt.h" */
-
-/*
-** Variables in which to record status information.
-*/
-typedef struct sqlite3StatType sqlite3StatType;
-static SQLITE_WSD struct sqlite3StatType {
-#if SQLITE_PTRSIZE>4
-  sqlite3_int64 nowValue[10];         /* Current value */
-  sqlite3_int64 mxValue[10];          /* Maximum value */
-#else
-  u32 nowValue[10];                   /* Current value */
-  u32 mxValue[10];                    /* Maximum value */
-#endif
-} sqlite3Stat = { {0,}, {0,} };
-
-#ifndef NDEBUG
-/*
-** Elements of sqlite3Stat[] are protected by either the memory allocator
-** mutex, or by the pcache1 mutex.  The following array determines which.
-*/
-static const char statMutex[] = {
-  0,  /* SQLITE_STATUS_MEMORY_USED */
-  1,  /* SQLITE_STATUS_PAGECACHE_USED */
-  1,  /* SQLITE_STATUS_PAGECACHE_OVERFLOW */
-  0,  /* SQLITE_STATUS_SCRATCH_USED */
-  0,  /* SQLITE_STATUS_SCRATCH_OVERFLOW */
-  0,  /* SQLITE_STATUS_MALLOC_SIZE */
-  0,  /* SQLITE_STATUS_PARSER_STACK */
-  1,  /* SQLITE_STATUS_PAGECACHE_SIZE */
-  0,  /* SQLITE_STATUS_SCRATCH_SIZE */
-  0,  /* SQLITE_STATUS_MALLOC_COUNT */
-};
-#endif
-
-/* The "wsdStat" macro will resolve to the status information
-** state vector.  If writable static data is unsupported on the target,
-** we have to locate the state vector at run-time.  In the more common
-** case where writable static data is supported, wsdStat can refer directly
-** to the "sqlite3Stat" state vector declared above.
-*/
-#ifdef SQLITE_OMIT_WSD
-# define wsdStatInit  sqlite3StatType *x = &GLOBAL(sqlite3StatType,sqlite3Stat)
-# define wsdStat x[0]
-#else
-# define wsdStatInit
-# define wsdStat sqlite3Stat
-#endif
-
-/*
-** Return the current value of a status parameter.  The caller must
-** be holding the appropriate mutex.
-*/
-SQLITE_PRIVATE sqlite3_int64 sqlite3StatusValue(int op){
-  wsdStatInit;
-  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
-  assert( op>=0 && op<ArraySize(statMutex) );
-  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
-                                           : sqlite3MallocMutex()) );
-  return wsdStat.nowValue[op];
-}
-
-
-/*
-** Add N to the value of a status record.  The caller must hold the
-** appropriate mutex.  (Locking is checked by assert()).
-**
-** The StatusUp() routine can accept positive or negative values for N.
-** The value of N is added to the current status value and the high-water
-** mark is adjusted if necessary.
-**
-** The StatusDown() routine lowers the current value by N.  The highwater
-** mark is unchanged.  N must be non-negative for StatusDown().
-*/
-SQLITE_PRIVATE void sqlite3StatusUp(int op, int N){
-  wsdStatInit;
-  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
-  assert( op>=0 && op<ArraySize(statMutex) );
-  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
-                                           : sqlite3MallocMutex()) );
-  wsdStat.nowValue[op] += N;
-  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
-    wsdStat.mxValue[op] = wsdStat.nowValue[op];
-  }
-}
-SQLITE_PRIVATE void sqlite3StatusDown(int op, int N){
-  wsdStatInit;
-  assert( N>=0 );
-  assert( op>=0 && op<ArraySize(statMutex) );
-  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
-                                           : sqlite3MallocMutex()) );
-  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
-  wsdStat.nowValue[op] -= N;
-}
-
-/*
-** Set the value of a status to X.  The highwater mark is adjusted if
-** necessary.  The caller must hold the appropriate mutex.
-*/
-SQLITE_PRIVATE void sqlite3StatusSet(int op, int X){
-  wsdStatInit;
-  assert( op>=0 && op<ArraySize(wsdStat.nowValue) );
-  assert( op>=0 && op<ArraySize(statMutex) );
-  assert( sqlite3_mutex_held(statMutex[op] ? sqlite3Pcache1Mutex()
-                                           : sqlite3MallocMutex()) );
-  wsdStat.nowValue[op] = X;
-  if( wsdStat.nowValue[op]>wsdStat.mxValue[op] ){
-    wsdStat.mxValue[op] = wsdStat.nowValue[op];
-  }
-}
-
-/************** End of status.c **********************************************/
-/************** Begin file os.c **********************************************/
-/*
-** 2005 November 29
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains OS interface code that is common to all
-** architectures.
-*/
-#define _SQLITE_OS_C_ 1
-/* #include "sqliteInt.h" */
-#undef _SQLITE_OS_C_
-
-/*
-** The default SQLite sqlite3_vfs implementations do not allocate
-** memory (actually, os_unix.c allocates a small amount of memory
-** from within OsOpen()), but some third-party implementations may.
-** So we test the effects of a malloc() failing and the sqlite3OsXXX()
-** function returning SQLITE_IOERR_NOMEM using the DO_OS_MALLOC_TEST macro.
-**
-** The following functions are instrumented for malloc() failure 
-** testing:
-**
-**     sqlite3OsRead()
-**     sqlite3OsWrite()
-**     sqlite3OsSync()
-**     sqlite3OsFileSize()
-**     sqlite3OsLock()
-**     sqlite3OsCheckReservedLock()
-**     sqlite3OsFileControl()
-**     sqlite3OsShmMap()
-**     sqlite3OsOpen()
-**     sqlite3OsDelete()
-**     sqlite3OsAccess()
-**     sqlite3OsFullPathname()
-**
-*/
-#if defined(SQLITE_TEST)
-SQLITE_PRIVATE int sqlite3_memdebug_vfs_oom_test = 1;
-  #define DO_OS_MALLOC_TEST(x)                                       \
-  if (sqlite3_memdebug_vfs_oom_test && (!x || !sqlite3IsMemJournal(x))) {  \
-    void *pTstAlloc = sqlite3Malloc(10);                             \
-    if (!pTstAlloc) return SQLITE_IOERR_NOMEM;                       \
-    sqlite3_free(pTstAlloc);                                         \
-  }
-#else
-  #define DO_OS_MALLOC_TEST(x)
-#endif
-
-/*
-** The following routines are convenience wrappers around methods
-** of the sqlite3_file object.  This is mostly just syntactic sugar. All
-** of this would be completely automatic if SQLite were coded using
-** C++ instead of plain old C.
-*/
-SQLITE_PRIVATE int sqlite3OsClose(sqlite3_file *pId){
-  int rc = SQLITE_OK;
-  if( pId->pMethods ){
-    rc = pId->pMethods->xClose(pId);
-    pId->pMethods = 0;
-  }
-  return rc;
-}
-SQLITE_PRIVATE int sqlite3OsRead(sqlite3_file *id, void *pBuf, int amt, i64 offset){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xRead(id, pBuf, amt, offset);
-}
-SQLITE_PRIVATE int sqlite3OsWrite(sqlite3_file *id, const void *pBuf, int amt, i64 offset){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xWrite(id, pBuf, amt, offset);
-}
-SQLITE_PRIVATE int sqlite3OsTruncate(sqlite3_file *id, i64 size){
-  return id->pMethods->xTruncate(id, size);
-}
-SQLITE_PRIVATE int sqlite3OsSync(sqlite3_file *id, int flags){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xSync(id, flags);
-}
-SQLITE_PRIVATE int sqlite3OsFileSize(sqlite3_file *id, i64 *pSize){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xFileSize(id, pSize);
-}
-SQLITE_PRIVATE int sqlite3OsLock(sqlite3_file *id, int lockType){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xLock(id, lockType);
-}
-SQLITE_PRIVATE int sqlite3OsUnlock(sqlite3_file *id, int lockType){
-  return id->pMethods->xUnlock(id, lockType);
-}
-SQLITE_PRIVATE int sqlite3OsCheckReservedLock(sqlite3_file *id, int *pResOut){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xCheckReservedLock(id, pResOut);
-}
-
-/*
-** Use sqlite3OsFileControl() when we are doing something that might fail
-** and we need to know about the failures.  Use sqlite3OsFileControlHint()
-** when simply tossing information over the wall to the VFS and we do not
-** really care if the VFS receives and understands the information since it
-** is only a hint and can be safely ignored.  The sqlite3OsFileControlHint()
-** routine has no return value since the return value would be meaningless.
-*/
-SQLITE_PRIVATE int sqlite3OsFileControl(sqlite3_file *id, int op, void *pArg){
-#ifdef SQLITE_TEST
-  if( op!=SQLITE_FCNTL_COMMIT_PHASETWO ){
-    /* Faults are not injected into COMMIT_PHASETWO because, assuming SQLite
-    ** is using a regular VFS, it is called after the corresponding 
-    ** transaction has been committed. Injecting a fault at this point 
-    ** confuses the test scripts - the COMMIT comand returns SQLITE_NOMEM
-    ** but the transaction is committed anyway.
-    **
-    ** The core must call OsFileControl() though, not OsFileControlHint(),
-    ** as if a custom VFS (e.g. zipvfs) returns an error here, it probably
-    ** means the commit really has failed and an error should be returned
-    ** to the user.  */
-    DO_OS_MALLOC_TEST(id);
-  }
-#endif
-  return id->pMethods->xFileControl(id, op, pArg);
-}
-SQLITE_PRIVATE void sqlite3OsFileControlHint(sqlite3_file *id, int op, void *pArg){
-  (void)id->pMethods->xFileControl(id, op, pArg);
-}
-
-SQLITE_PRIVATE int sqlite3OsSectorSize(sqlite3_file *id){
-  int (*xSectorSize)(sqlite3_file*) = id->pMethods->xSectorSize;
-  return (xSectorSize ? xSectorSize(id) : SQLITE_DEFAULT_SECTOR_SIZE);
-}
-SQLITE_PRIVATE int sqlite3OsDeviceCharacteristics(sqlite3_file *id){
-  return id->pMethods->xDeviceCharacteristics(id);
-}
-SQLITE_PRIVATE int sqlite3OsShmLock(sqlite3_file *id, int offset, int n, int flags){
-  return id->pMethods->xShmLock(id, offset, n, flags);
-}
-SQLITE_PRIVATE void sqlite3OsShmBarrier(sqlite3_file *id){
-  id->pMethods->xShmBarrier(id);
-}
-SQLITE_PRIVATE int sqlite3OsShmUnmap(sqlite3_file *id, int deleteFlag){
-  return id->pMethods->xShmUnmap(id, deleteFlag);
-}
-SQLITE_PRIVATE int sqlite3OsShmMap(
-  sqlite3_file *id,               /* Database file handle */
-  int iPage,
-  int pgsz,
-  int bExtend,                    /* True to extend file if necessary */
-  void volatile **pp              /* OUT: Pointer to mapping */
-){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xShmMap(id, iPage, pgsz, bExtend, pp);
-}
-
-#if SQLITE_MAX_MMAP_SIZE>0
-/* The real implementation of xFetch and xUnfetch */
-SQLITE_PRIVATE int sqlite3OsFetch(sqlite3_file *id, i64 iOff, int iAmt, void **pp){
-  DO_OS_MALLOC_TEST(id);
-  return id->pMethods->xFetch(id, iOff, iAmt, pp);
-}
-SQLITE_PRIVATE int sqlite3OsUnfetch(sqlite3_file *id, i64 iOff, void *p){
-  return id->pMethods->xUnfetch(id, iOff, p);
-}
-#else
-/* No-op stubs to use when memory-mapped I/O is disabled */
-SQLITE_PRIVATE int sqlite3OsFetch(sqlite3_file *id, i64 iOff, int iAmt, void **pp){
-  *pp = 0;
-  return SQLITE_OK;
-}
-SQLITE_PRIVATE int sqlite3OsUnfetch(sqlite3_file *id, i64 iOff, void *p){
-  return SQLITE_OK;
-}
-#endif
-
-/*
-** The next group of routines are convenience wrappers around the
-** VFS methods.
-*/
-SQLITE_PRIVATE int sqlite3OsOpen(
-  sqlite3_vfs *pVfs, 
-  const char *zPath, 
-  sqlite3_file *pFile, 
-  int flags, 
-  int *pFlagsOut
-){
-  int rc;
-  DO_OS_MALLOC_TEST(0);
-  /* 0x87f7f is a mask of SQLITE_OPEN_ flags that are valid to be passed
-  ** down into the VFS layer.  Some SQLITE_OPEN_ flags (for example,
-  ** SQLITE_OPEN_FULLMUTEX or SQLITE_OPEN_SHAREDCACHE) are blocked before
-  ** reaching the VFS. */
-  rc = pVfs->xOpen(pVfs, zPath, pFile, flags & 0x87f7f, pFlagsOut);
-  assert( rc==SQLITE_OK || pFile->pMethods==0 );
-  return rc;
-}
-SQLITE_PRIVATE int sqlite3OsDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
-  DO_OS_MALLOC_TEST(0);
-  assert( dirSync==0 || dirSync==1 );
-  return pVfs->xDelete(pVfs, zPath, dirSync);
-}
-SQLITE_PRIVATE int sqlite3OsAccess(
-  sqlite3_vfs *pVfs, 
-  const char *zPath, 
-  int flags, 
-  int *pResOut
-){
-  DO_OS_MALLOC_TEST(0);
-  return pVfs->xAccess(pVfs, zPath, flags, pResOut);
-}
-SQLITE_PRIVATE int sqlite3OsFullPathname(
-  sqlite3_vfs *pVfs, 
-  const char *zPath, 
-  int nPathOut, 
-  char *zPathOut
-){
-  DO_OS_MALLOC_TEST(0);
-  zPathOut[0] = 0;
-  return pVfs->xFullPathname(pVfs, zPath, nPathOut, zPathOut);
-}
-SQLITE_PRIVATE int sqlite3OsRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
-  return pVfs->xRandomness(pVfs, nByte, zBufOut);
-}
-SQLITE_PRIVATE int sqlite3OsSleep(sqlite3_vfs *pVfs, int nMicro){
-  return pVfs->xSleep(pVfs, nMicro);
-}
-
-/*
-** This function is a wrapper around the OS specific implementation of
-** sqlite3_os_init(). The purpose of the wrapper is to provide the
-** ability to simulate a malloc failure, so that the handling of an
-** error in sqlite3_os_init() by the upper layers can be tested.
-*/
-SQLITE_PRIVATE int sqlite3OsInit(void){
-  void *p = sqlite3_malloc(10);
-  if( p==0 ) return SQLITE_NOMEM;
-  sqlite3_free(p);
-  return sqlite3_os_init();
-}
-
-/*
-** The list of all registered VFS implementations.
-*/
-static sqlite3_vfs * SQLITE_WSD vfsList = 0;
-#define vfsList GLOBAL(sqlite3_vfs *, vfsList)
-
-/*
-** Locate a VFS by name.  If no name is given, simply return the
-** first VFS on the list.
-*/
-SQLITE_PRIVATE sqlite3_vfs *sqlite3_vfs_find(const char *zVfs){
-  sqlite3_vfs *pVfs = 0;
-#if SQLITE_THREADSAFE
-  sqlite3_mutex *mutex;
-#endif
-#ifndef SQLITE_OMIT_AUTOINIT
-  int rc = sqlite3BtreeInitialize();
-  if( rc ) return 0;
-#endif
-#if SQLITE_THREADSAFE
-  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
-#endif
-  sqlite3_mutex_enter(mutex);
-  for(pVfs = vfsList; pVfs; pVfs=pVfs->pNext){
-    if( zVfs==0 ) break;
-    if( strcmp(zVfs, pVfs->zName)==0 ) break;
-  }
-  sqlite3_mutex_leave(mutex);
-  return pVfs;
-}
-
-/*
-** Unlink a VFS from the linked list
-*/
-static void vfsUnlink(sqlite3_vfs *pVfs){
-  assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)) );
-  if( pVfs==0 ){
-    /* No-op */
-  }else if( vfsList==pVfs ){
-    vfsList = pVfs->pNext;
-  }else if( vfsList ){
-    sqlite3_vfs *p = vfsList;
-    while( p->pNext && p->pNext!=pVfs ){
-      p = p->pNext;
-    }
-    if( p->pNext==pVfs ){
-      p->pNext = pVfs->pNext;
-    }
-  }
-}
-
-/*
-** Register a VFS with the system.  It is harmless to register the same
-** VFS multiple times.  The new VFS becomes the default if makeDflt is
-** true.
-*/
-SQLITE_PRIVATE int sqlite3_vfs_register(sqlite3_vfs *pVfs, int makeDflt){
-  MUTEX_LOGIC(sqlite3_mutex *mutex;)
-#ifndef SQLITE_OMIT_AUTOINIT
-  int rc = sqlite3BtreeInitialize();
-  if( rc ) return rc;
-#endif
-#ifdef SQLITE_ENABLE_API_ARMOR
-  if( pVfs==0 ) return SQLITE_MISUSE_BKPT;
-#endif
-
-  MUTEX_LOGIC( mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
-  sqlite3_mutex_enter(mutex);
-  vfsUnlink(pVfs);
-  if( makeDflt || vfsList==0 ){
-    pVfs->pNext = vfsList;
-    vfsList = pVfs;
-  }else{
-    pVfs->pNext = vfsList->pNext;
-    vfsList->pNext = pVfs;
-  }
-  assert(vfsList);
-  sqlite3_mutex_leave(mutex);
-  return SQLITE_OK;
-}
-
-/************** End of os.c **************************************************/
-/************** Begin file mem1.c ********************************************/
-/*
-** 2007 August 14
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains low-level memory allocation drivers for when
-** SQLite will use the standard C-library malloc/realloc/free interface
-** to obtain the memory it needs.
-**
-** This file contains implementations of the low-level memory allocation
-** routines specified in the sqlite3_mem_methods object.  The content of
-** this file is only used if SQLITE_SYSTEM_MALLOC is defined.  The
-** SQLITE_SYSTEM_MALLOC macro is defined automatically if neither the
-** SQLITE_MEMDEBUG nor the SQLITE_WIN32_MALLOC macros are defined.  The
-** default configuration is to use memory allocation routines in this
-** file.
-**
-** C-preprocessor macro summary:
-**
-**    HAVE_MALLOC_USABLE_SIZE     The configure script sets this symbol if
-**                                the malloc_usable_size() interface exists
-**                                on the target platform.  Or, this symbol
-**                                can be set manually, if desired.
-**                                If an equivalent interface exists by
-**                                a different name, using a separate -D
-**                                option to rename it.
-**
-**    SQLITE_WITHOUT_ZONEMALLOC   Some older macs lack support for the zone
-**                                memory allocator.  Set this symbol to enable
-**                                building on older macs.
-**
-**    SQLITE_WITHOUT_MSIZE        Set this symbol to disable the use of
-**                                _msize() on windows systems.  This might
-**                                be necessary when compiling for Delphi,
-**                                for example.
-*/
-/* #include "sqliteInt.h" */
-
-/*
-** This version of the memory allocator is the default.  It is
-** used when no other memory allocator is specified using compile-time
-** macros.
-*/
-#ifdef SQLITE_SYSTEM_MALLOC
-#if defined(__APPLE__) && !defined(SQLITE_WITHOUT_ZONEMALLOC)
-
-/*
-** Use the zone allocator available on apple products unless the
-** SQLITE_WITHOUT_ZONEMALLOC symbol is defined.
-*/
-#include <sys/sysctl.h>
-#include <malloc/malloc.h>
-#include <libkern/OSAtomic.h>
-static malloc_zone_t* _sqliteZone_;
-#define SQLITE_MALLOC(x) malloc_zone_malloc(_sqliteZone_, (x))
-#define SQLITE_FREE(x) malloc_zone_free(_sqliteZone_, (x));
-#define SQLITE_REALLOC(x,y) malloc_zone_realloc(_sqliteZone_, (x), (y))
-#define SQLITE_MALLOCSIZE(x) \
-        (_sqliteZone_ ? _sqliteZone_->size(_sqliteZone_,x) : malloc_size(x))
-
-#else /* if not __APPLE__ */
-
-/*
-** Use standard C library malloc and free on non-Apple systems.  
-** Also used by Apple systems if SQLITE_WITHOUT_ZONEMALLOC is defined.
-*/
-#define SQLITE_MALLOC(x)             malloc(x)
-#define SQLITE_FREE(x)               free(x)
-#define SQLITE_REALLOC(x,y)          realloc((x),(y))
-
-/*
-** The malloc.h header file is needed for malloc_usable_size() function
-** on some systems (e.g. Linux).
-*/
-#if HAVE_MALLOC_H && HAVE_MALLOC_USABLE_SIZE
-#  define SQLITE_USE_MALLOC_H 1
-#  define SQLITE_USE_MALLOC_USABLE_SIZE 1
-/*
-** The MSVCRT has malloc_usable_size(), but it is called _msize().  The
-** use of _msize() is automatic, but can be disabled by compiling with
-** -DSQLITE_WITHOUT_MSIZE.  Using the _msize() function also requires
-** the malloc.h header file.
-*/
-#elif defined(_MSC_VER) && !defined(SQLITE_WITHOUT_MSIZE)
-#  define SQLITE_USE_MALLOC_H
-#  define SQLITE_USE_MSIZE
-#endif
-
-/*
-** Include the malloc.h header file, if necessary.  Also set define macro
-** SQLITE_MALLOCSIZE to the appropriate function name, which is _msize()
-** for MSVC and malloc_usable_size() for most other systems (e.g. Linux).
-** The memory size function can always be overridden manually by defining
-** the macro SQLITE_MALLOCSIZE to the desired function name.
-*/
-#if defined(SQLITE_USE_MALLOC_H)
-#  include <malloc.h>
-#  if defined(SQLITE_USE_MALLOC_USABLE_SIZE)
-#    if !defined(SQLITE_MALLOCSIZE)
-#      define SQLITE_MALLOCSIZE(x)   malloc_usable_size(x)
-#    endif
-#  elif defined(SQLITE_USE_MSIZE)
-#    if !defined(SQLITE_MALLOCSIZE)
-#      define SQLITE_MALLOCSIZE      _msize
-#    endif
-#  endif
-#endif /* defined(SQLITE_USE_MALLOC_H) */
-
-#endif /* __APPLE__ or not __APPLE__ */
-
-/*
-** Like malloc(), but remember the size of the allocation
-** so that we can find it later using sqlite3MemSize().
-**
-** For this low-level routine, we are guaranteed that nByte>0 because
-** cases of nByte<=0 will be intercepted and dealt with by higher level
-** routines.
-*/
-static void *sqlite3MemMalloc(int nByte){
-#ifdef SQLITE_MALLOCSIZE
-  void *p = SQLITE_MALLOC( nByte );
-  if( p==0 ){
-    testcase( sqlite3GlobalConfig.xLog!=0 );
-    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes of memory", nByte);
-  }
-  return p;
-#else
-  sqlite3_int64 *p;
-  assert( nByte>0 );
-  nByte = ROUND8(nByte);
-  p = SQLITE_MALLOC( nByte+8 );
-  if( p ){
-    p[0] = nByte;
-    p++;
-  }else{
-    testcase( sqlite3GlobalConfig.xLog!=0 );
-    sqlite3_log(SQLITE_NOMEM, "failed to allocate %u bytes of memory", nByte);
-  }
-  return (void *)p;
-#endif
-}
-
-/*
-** Like free() but works for allocations obtained from sqlite3MemMalloc()
-** or sqlite3MemRealloc().
-**
-** For this low-level routine, we already know that pPrior!=0 since
-** cases where pPrior==0 will have been intecepted and dealt with
-** by higher-level routines.
-*/
-static void sqlite3MemFree(void *pPrior){
-#ifdef SQLITE_MALLOCSIZE
-  SQLITE_FREE(pPrior);
-#else
-  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
-  assert( pPrior!=0 );
-  p--;
-  SQLITE_FREE(p);
-#endif
-}
-
-/*
-** Report the allocated size of a prior return from xMalloc()
-** or xRealloc().
-*/
-static int sqlite3MemSize(void *pPrior){
-#ifdef SQLITE_MALLOCSIZE
-  return pPrior ? (int)SQLITE_MALLOCSIZE(pPrior) : 0;
-#else
-  sqlite3_int64 *p;
-  if( pPrior==0 ) return 0;
-  p = (sqlite3_int64*)pPrior;
-  p--;
-  return (int)p[0];
-#endif
-}
-
-/*
-** Like realloc().  Resize an allocation previously obtained from
-** sqlite3MemMalloc().
-**
-** For this low-level interface, we know that pPrior!=0.  Cases where
-** pPrior==0 while have been intercepted by higher-level routine and
-** redirected to xMalloc.  Similarly, we know that nByte>0 because
-** cases where nByte<=0 will have been intercepted by higher-level
-** routines and redirected to xFree.
-*/
-static void *sqlite3MemRealloc(void *pPrior, int nByte){
-#ifdef SQLITE_MALLOCSIZE
-  void *p = SQLITE_REALLOC(pPrior, nByte);
-  if( p==0 ){
-    testcase( sqlite3GlobalConfig.xLog!=0 );
-    sqlite3_log(SQLITE_NOMEM,
-      "failed memory resize %u to %u bytes",
-      SQLITE_MALLOCSIZE(pPrior), nByte);
-  }
-  return p;
-#else
-  sqlite3_int64 *p = (sqlite3_int64*)pPrior;
-  assert( pPrior!=0 && nByte>0 );
-  assert( nByte==ROUND8(nByte) ); /* EV: R-46199-30249 */
-  p--;
-  p = SQLITE_REALLOC(p, nByte+8 );
-  if( p ){
-    p[0] = nByte;
-    p++;
-  }else{
-    testcase( sqlite3GlobalConfig.xLog!=0 );
-    sqlite3_log(SQLITE_NOMEM,
-      "failed memory resize %u to %u bytes",
-      sqlite3MemSize(pPrior), nByte);
-  }
-  return (void*)p;
-#endif
-}
-
-/*
-** Round up a request size to the next valid allocation size.
-*/
-static int sqlite3MemRoundup(int n){
-  return ROUND8(n);
-}
-
-/*
-** Initialize this module.
-*/
-static int sqlite3MemInit(void *NotUsed){
-#if defined(__APPLE__) && !defined(SQLITE_WITHOUT_ZONEMALLOC)
-  int cpuCount;
-  size_t len;
-  if( _sqliteZone_ ){
-    return SQLITE_OK;
-  }
-  len = sizeof(cpuCount);
-  /* One usually wants to use hw.acctivecpu for MT decisions, but not here */
-  sysctlbyname("hw.ncpu", &cpuCount, &len, NULL, 0);
-  if( cpuCount>1 ){
-    /* defer MT decisions to system malloc */
-    _sqliteZone_ = malloc_default_zone();
-  }else{
-    /* only 1 core, use our own zone to contention over global locks, 
-    ** e.g. we have our own dedicated locks */
-    bool success;
-    malloc_zone_t* newzone = malloc_create_zone(4096, 0);
-    malloc_set_zone_name(newzone, "Sqlite_Heap");
-    do{
-      success = OSAtomicCompareAndSwapPtrBarrier(NULL, newzone, 
-                                 (void * volatile *)&_sqliteZone_);
-    }while(!_sqliteZone_);
-    if( !success ){
-      /* somebody registered a zone first */
-      malloc_destroy_zone(newzone);
-    }
-  }
-#endif
-  UNUSED_PARAMETER(NotUsed);
-  return SQLITE_OK;
-}
-
-/*
-** Deinitialize this module.
-*/
-static void sqlite3MemShutdown(void *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  return;
-}
-
-/*
-** This routine is the only routine in this file with external linkage.
-**
-** Populate the low-level memory allocation function pointers in
-** sqlite3GlobalConfig.m with pointers to the routines in this file.
-*/
-SQLITE_PRIVATE void sqlite3MemSetDefault(void){
-  static const sqlite3_mem_methods defaultMethods = {
-     sqlite3MemMalloc,
-     sqlite3MemFree,
-     sqlite3MemRealloc,
-     sqlite3MemSize,
-     sqlite3MemRoundup,
-     sqlite3MemInit,
-     sqlite3MemShutdown,
-     0
-  };
-  sqlite3_config(SQLITE_CONFIG_MALLOC, &defaultMethods);
-}
-
-#endif /* SQLITE_SYSTEM_MALLOC */
-
-/************** End of mem1.c ************************************************/
-/************** Begin file mutex.c *******************************************/
-/*
-** 2007 August 14
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains the C functions that implement mutexes.
-**
-** This file contains code that is common across all mutex implementations.
-*/
-/* #include "sqliteInt.h" */
-
-#if defined(SQLITE_DEBUG) && !defined(SQLITE_MUTEX_OMIT)
-/*
-** For debugging purposes, record when the mutex subsystem is initialized
-** and uninitialized so that we can assert() if there is an attempt to
-** allocate a mutex while the system is uninitialized.
-*/
-static SQLITE_WSD int mutexIsInit = 0;
-#endif /* SQLITE_DEBUG && !defined(SQLITE_MUTEX_OMIT) */
-
-
-#ifndef SQLITE_MUTEX_OMIT
-/*
-** Initialize the mutex system.
-*/
-SQLITE_PRIVATE int sqlite3MutexInit(void){ 
-  int rc = SQLITE_OK;
-  if( !sqlite3GlobalConfig.mutex.xMutexAlloc ){
-    /* If the xMutexAlloc method has not been set, then the user did not
-    ** install a mutex implementation via sqlite3_config() prior to 
-    ** sqlite3BtreeInitialize() being called. This block copies pointers to
-    ** the default implementation into the sqlite3GlobalConfig structure.
-    */
-    sqlite3_mutex_methods const *pFrom;
-    sqlite3_mutex_methods *pTo = &sqlite3GlobalConfig.mutex;
-
-    if( sqlite3GlobalConfig.bCoreMutex ){
-      pFrom = sqlite3DefaultMutex();
-    }else{
-      pFrom = sqlite3NoopMutex();
-    }
-    pTo->xMutexInit = pFrom->xMutexInit;
-    pTo->xMutexEnd = pFrom->xMutexEnd;
-    pTo->xMutexFree = pFrom->xMutexFree;
-    pTo->xMutexEnter = pFrom->xMutexEnter;
-    pTo->xMutexTry = pFrom->xMutexTry;
-    pTo->xMutexLeave = pFrom->xMutexLeave;
-    pTo->xMutexHeld = pFrom->xMutexHeld;
-    pTo->xMutexNotheld = pFrom->xMutexNotheld;
-    sqlite3MemoryBarrier();
-    pTo->xMutexAlloc = pFrom->xMutexAlloc;
-  }
-  assert( sqlite3GlobalConfig.mutex.xMutexInit );
-  rc = sqlite3GlobalConfig.mutex.xMutexInit();
-
-#ifdef SQLITE_DEBUG
-  GLOBAL(int, mutexIsInit) = 1;
-#endif
-
-  return rc;
-}
-
-/*
-** Shutdown the mutex system. This call frees resources allocated by
-** sqlite3MutexInit().
-*/
-SQLITE_PRIVATE int sqlite3MutexEnd(void){
-  int rc = SQLITE_OK;
-  if( sqlite3GlobalConfig.mutex.xMutexEnd ){
-    rc = sqlite3GlobalConfig.mutex.xMutexEnd();
-  }
-
-#ifdef SQLITE_DEBUG
-  GLOBAL(int, mutexIsInit) = 0;
-#endif
-
-  return rc;
-}
-
-/*
-** Retrieve a pointer to a static mutex or allocate a new dynamic one.
-*/
-SQLITE_PRIVATE sqlite3_mutex *sqlite3_mutex_alloc(int id){
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( id<=SQLITE_MUTEX_RECURSIVE && sqlite3BtreeInitialize() ) return 0;
-  if( id>SQLITE_MUTEX_RECURSIVE && sqlite3MutexInit() ) return 0;
-#endif
-  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
-  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
-}
-
-SQLITE_PRIVATE sqlite3_mutex *sqlite3MutexAlloc(int id){
-  if( !sqlite3GlobalConfig.bCoreMutex ){
-    return 0;
-  }
-  assert( GLOBAL(int, mutexIsInit) );
-  assert( sqlite3GlobalConfig.mutex.xMutexAlloc );
-  return sqlite3GlobalConfig.mutex.xMutexAlloc(id);
-}
-
-/*
-** Free a dynamic mutex.
-*/
-SQLITE_PRIVATE void sqlite3_mutex_free(sqlite3_mutex *p){
-  if( p ){
-    assert( sqlite3GlobalConfig.mutex.xMutexFree );
-    sqlite3GlobalConfig.mutex.xMutexFree(p);
-  }
-}
-
-/*
-** Obtain the mutex p. If some other thread already has the mutex, block
-** until it can be obtained.
-*/
-SQLITE_PRIVATE void sqlite3_mutex_enter(sqlite3_mutex *p){
-  if( p ){
-    assert( sqlite3GlobalConfig.mutex.xMutexEnter );
-    sqlite3GlobalConfig.mutex.xMutexEnter(p);
-  }
-}
-
-/*
-** Obtain the mutex p. If successful, return SQLITE_OK. Otherwise, if another
-** thread holds the mutex and it cannot be obtained, return SQLITE_BUSY.
-*/
-SQLITE_PRIVATE int sqlite3_mutex_try(sqlite3_mutex *p){
-  int rc = SQLITE_OK;
-  if( p ){
-    assert( sqlite3GlobalConfig.mutex.xMutexTry );
-    return sqlite3GlobalConfig.mutex.xMutexTry(p);
-  }
-  return rc;
-}
-
-/*
-** The sqlite3_mutex_leave() routine exits a mutex that was previously
-** entered by the same thread.  The behavior is undefined if the mutex 
-** is not currently entered. If a NULL pointer is passed as an argument
-** this function is a no-op.
-*/
-SQLITE_PRIVATE void sqlite3_mutex_leave(sqlite3_mutex *p){
-  if( p ){
-    assert( sqlite3GlobalConfig.mutex.xMutexLeave );
-    sqlite3GlobalConfig.mutex.xMutexLeave(p);
-  }
-}
-
-#ifndef NDEBUG
-/*
-** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
-** intended for use inside assert() statements.
-*/
-SQLITE_PRIVATE int sqlite3_mutex_held(sqlite3_mutex *p){
-  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexHeld );
-  return p==0 || sqlite3GlobalConfig.mutex.xMutexHeld(p);
-}
-SQLITE_PRIVATE int sqlite3_mutex_notheld(sqlite3_mutex *p){
-  assert( p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld );
-  return p==0 || sqlite3GlobalConfig.mutex.xMutexNotheld(p);
-}
-#endif
-
-#endif /* !defined(SQLITE_MUTEX_OMIT) */
-
-/************** End of mutex.c ***********************************************/
-/************** Begin file mutex_noop.c **************************************/
-/*
-** 2008 October 07
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains the C functions that implement mutexes.
-**
-** This implementation in this file does not provide any mutual
-** exclusion and is thus suitable for use only in applications
-** that use SQLite in a single thread.  The routines defined
-** here are place-holders.  Applications can substitute working
-** mutex routines at start-time using the
-**
-**     sqlite3_config(SQLITE_CONFIG_MUTEX,...)
-**
-** interface.
-**
-** If compiled with SQLITE_DEBUG, then additional logic is inserted
-** that does error checking on mutexes to make sure they are being
-** called correctly.
-*/
-/* #include "sqliteInt.h" */
-
-#ifndef SQLITE_MUTEX_OMIT
-
-#ifndef SQLITE_DEBUG
-/*
-** Stub routines for all mutex methods.
-**
-** This routines provide no mutual exclusion or error checking.
-*/
-static int noopMutexInit(void){ return SQLITE_OK; }
-static int noopMutexEnd(void){ return SQLITE_OK; }
-static sqlite3_mutex *noopMutexAlloc(int id){ 
-  UNUSED_PARAMETER(id);
-  return (sqlite3_mutex*)8; 
-}
-static void noopMutexFree(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
-static void noopMutexEnter(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
-static int noopMutexTry(sqlite3_mutex *p){
-  UNUSED_PARAMETER(p);
-  return SQLITE_OK;
-}
-static void noopMutexLeave(sqlite3_mutex *p){ UNUSED_PARAMETER(p); return; }
-
-SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
-  static const sqlite3_mutex_methods sMutex = {
-    noopMutexInit,
-    noopMutexEnd,
-    noopMutexAlloc,
-    noopMutexFree,
-    noopMutexEnter,
-    noopMutexTry,
-    noopMutexLeave,
-
-    0,
-    0,
-  };
-
-  return &sMutex;
-}
-#endif /* !SQLITE_DEBUG */
-
-#ifdef SQLITE_DEBUG
-/*
-** In this implementation, error checking is provided for testing
-** and debugging purposes.  The mutexes still do not provide any
-** mutual exclusion.
-*/
-
-/*
-** The mutex object
-*/
-typedef struct sqlite3_debug_mutex {
-  int id;     /* The mutex type */
-  int cnt;    /* Number of entries without a matching leave */
-} sqlite3_debug_mutex;
-
-/*
-** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
-** intended for use inside assert() statements.
-*/
-static int debugMutexHeld(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  return p==0 || p->cnt>0;
-}
-static int debugMutexNotheld(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  return p==0 || p->cnt==0;
-}
-
-/*
-** Initialize and deinitialize the mutex subsystem.
-*/
-static int debugMutexInit(void){ return SQLITE_OK; }
-static int debugMutexEnd(void){ return SQLITE_OK; }
-
-/*
-** The sqlite3_mutex_alloc() routine allocates a new
-** mutex and returns a pointer to it.  If it returns NULL
-** that means that a mutex could not be allocated. 
-*/
-static sqlite3_mutex *debugMutexAlloc(int id){
-  static sqlite3_debug_mutex aStatic[SQLITE_MUTEX_STATIC_VFS3 - 1];
-  sqlite3_debug_mutex *pNew = 0;
-  switch( id ){
-    case SQLITE_MUTEX_FAST:
-    case SQLITE_MUTEX_RECURSIVE: {
-      pNew = sqlite3Malloc(sizeof(*pNew));
-      if( pNew ){
-        pNew->id = id;
-        pNew->cnt = 0;
-      }
-      break;
-    }
-    default: {
-#ifdef SQLITE_ENABLE_API_ARMOR
-      if( id-2<0 || id-2>=ArraySize(aStatic) ){
-        (void)SQLITE_MISUSE_BKPT;
-        return 0;
-      }
-#endif
-      pNew = &aStatic[id-2];
-      pNew->id = id;
-      break;
-    }
-  }
-  return (sqlite3_mutex*)pNew;
-}
-
-/*
-** This routine deallocates a previously allocated mutex.
-*/
-static void debugMutexFree(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  assert( p->cnt==0 );
-  if( p->id==SQLITE_MUTEX_RECURSIVE || p->id==SQLITE_MUTEX_FAST ){
-    sqlite3_free(p);
-  }else{
-#ifdef SQLITE_ENABLE_API_ARMOR
-    (void)SQLITE_MISUSE_BKPT;
-#endif
-  }
-}
-
-/*
-** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
-** to enter a mutex.  If another thread is already within the mutex,
-** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
-** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
-** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
-** be entered multiple times by the same thread.  In such cases the,
-** mutex must be exited an equal number of times before another thread
-** can enter.  If the same thread tries to enter any other kind of mutex
-** more than once, the behavior is undefined.
-*/
-static void debugMutexEnter(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
-  p->cnt++;
-}
-static int debugMutexTry(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
-  p->cnt++;
-  return SQLITE_OK;
-}
-
-/*
-** The sqlite3_mutex_leave() routine exits a mutex that was
-** previously entered by the same thread.  The behavior
-** is undefined if the mutex is not currently entered or
-** is not currently allocated.  SQLite will never do either.
-*/
-static void debugMutexLeave(sqlite3_mutex *pX){
-  sqlite3_debug_mutex *p = (sqlite3_debug_mutex*)pX;
-  assert( debugMutexHeld(pX) );
-  p->cnt--;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || debugMutexNotheld(pX) );
-}
-
-SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3NoopMutex(void){
-  static const sqlite3_mutex_methods sMutex = {
-    debugMutexInit,
-    debugMutexEnd,
-    debugMutexAlloc,
-    debugMutexFree,
-    debugMutexEnter,
-    debugMutexTry,
-    debugMutexLeave,
-
-    debugMutexHeld,
-    debugMutexNotheld
-  };
-
-  return &sMutex;
-}
-#endif /* SQLITE_DEBUG */
-
-/*
-** If compiled with SQLITE_MUTEX_NOOP, then the no-op mutex implementation
-** is used regardless of the run-time threadsafety setting.
-*/
-#ifdef SQLITE_MUTEX_NOOP
-SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
-  return sqlite3NoopMutex();
-}
-#endif /* defined(SQLITE_MUTEX_NOOP) */
-#endif /* !defined(SQLITE_MUTEX_OMIT) */
-
-/************** End of mutex_noop.c ******************************************/
-/************** Begin file mutex_unix.c **************************************/
-/*
-** 2007 August 28
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains the C functions that implement mutexes for pthreads
-*/
-/* #include "sqliteInt.h" */
-
-/*
-** The code in this file is only used if we are compiling threadsafe
-** under unix with pthreads.
-**
-** Note that this implementation requires a version of pthreads that
-** supports recursive mutexes.
-*/
-#ifdef SQLITE_MUTEX_PTHREADS
-
-#include <pthread.h>
-
-/*
-** The sqlite3_mutex.id, sqlite3_mutex.nRef, and sqlite3_mutex.owner fields
-** are necessary under two condidtions:  (1) Debug builds and (2) using
-** home-grown mutexes.  Encapsulate these conditions into a single #define.
-*/
-#if defined(SQLITE_DEBUG) || defined(SQLITE_HOMEGROWN_RECURSIVE_MUTEX)
-# define SQLITE_MUTEX_NREF 1
-#else
-# define SQLITE_MUTEX_NREF 0
-#endif
-
-/*
-** Each recursive mutex is an instance of the following structure.
-*/
-struct sqlite3_mutex {
-  pthread_mutex_t mutex;     /* Mutex controlling the lock */
-#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
-  int id;                    /* Mutex type */
-#endif
-#if SQLITE_MUTEX_NREF
-  volatile int nRef;         /* Number of entrances */
-  volatile pthread_t owner;  /* Thread that is within this mutex */
-  int trace;                 /* True to trace changes */
-#endif
-};
-#if SQLITE_MUTEX_NREF
-#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, 0, 0, (pthread_t)0, 0 }
-#else
-#define SQLITE3_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
-#endif
-
-/*
-** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
-** intended for use only inside assert() statements.  On some platforms,
-** there might be race conditions that can cause these routines to
-** deliver incorrect results.  In particular, if pthread_equal() is
-** not an atomic operation, then these routines might delivery
-** incorrect results.  On most platforms, pthread_equal() is a 
-** comparison of two integers and is therefore atomic.  But we are
-** told that HPUX is not such a platform.  If so, then these routines
-** will not always work correctly on HPUX.
-**
-** On those platforms where pthread_equal() is not atomic, SQLite
-** should be compiled without -DSQLITE_DEBUG and with -DNDEBUG to
-** make sure no assert() statements are evaluated and hence these
-** routines are never called.
-*/
-#if !defined(NDEBUG) || defined(SQLITE_DEBUG)
-static int pthreadMutexHeld(sqlite3_mutex *p){
-  return (p->nRef!=0 && pthread_equal(p->owner, pthread_self()));
-}
-static int pthreadMutexNotheld(sqlite3_mutex *p){
-  return p->nRef==0 || pthread_equal(p->owner, pthread_self())==0;
-}
-#endif
-
-/*
-** Try to provide a memory barrier operation, needed for initialization
-** and also for the implementation of xShmBarrier in the VFS in cases
-** where SQLite is compiled without mutexes.
-*/
-SQLITE_PRIVATE void sqlite3MemoryBarrier(void){
-#if defined(SQLITE_MEMORY_BARRIER)
-  SQLITE_MEMORY_BARRIER;
-#elif defined(__GNUC__) && GCC_VERSION>=4001000
-  __sync_synchronize();
-#endif
-}
-
-/*
-** Initialize and deinitialize the mutex subsystem.
-*/
-static int pthreadMutexInit(void){ return SQLITE_OK; }
-static int pthreadMutexEnd(void){ return SQLITE_OK; }
-
-/*
-** The sqlite3_mutex_alloc() routine allocates a new
-** mutex and returns a pointer to it.  If it returns NULL
-** that means that a mutex could not be allocated.  SQLite
-** will unwind its stack and return an error.  The argument
-** to sqlite3_mutex_alloc() is one of these integer constants:
-**
-** <ul>
-** <li>  SQLITE_MUTEX_FAST
-** <li>  SQLITE_MUTEX_RECURSIVE
-** <li>  SQLITE_MUTEX_STATIC_MASTER
-** <li>  SQLITE_MUTEX_STATIC_MEM
-** <li>  SQLITE_MUTEX_STATIC_OPEN
-** <li>  SQLITE_MUTEX_STATIC_PRNG
-** <li>  SQLITE_MUTEX_STATIC_LRU
-** <li>  SQLITE_MUTEX_STATIC_PMEM
-** <li>  SQLITE_MUTEX_STATIC_APP1
-** <li>  SQLITE_MUTEX_STATIC_APP2
-** <li>  SQLITE_MUTEX_STATIC_APP3
-** <li>  SQLITE_MUTEX_STATIC_VFS1
-** <li>  SQLITE_MUTEX_STATIC_VFS2
-** <li>  SQLITE_MUTEX_STATIC_VFS3
-** </ul>
-**
-** The first two constants cause sqlite3_mutex_alloc() to create
-** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
-** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
-** The mutex implementation does not need to make a distinction
-** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
-** not want to.  But SQLite will only request a recursive mutex in
-** cases where it really needs one.  If a faster non-recursive mutex
-** implementation is available on the host platform, the mutex subsystem
-** might return such a mutex in response to SQLITE_MUTEX_FAST.
-**
-** The other allowed parameters to sqlite3_mutex_alloc() each return
-** a pointer to a static preexisting mutex.  Six static mutexes are
-** used by the current version of SQLite.  Future versions of SQLite
-** may add additional static mutexes.  Static mutexes are for internal
-** use by SQLite only.  Applications that use SQLite mutexes should
-** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
-** SQLITE_MUTEX_RECURSIVE.
-**
-** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
-** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
-** returns a different mutex on every call.  But for the static 
-** mutex types, the same mutex is returned on every call that has
-** the same type number.
-*/
-static sqlite3_mutex *pthreadMutexAlloc(int iType){
-  static sqlite3_mutex staticMutexes[] = {
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER,
-    SQLITE3_MUTEX_INITIALIZER
-  };
-  sqlite3_mutex *p;
-  switch( iType ){
-    case SQLITE_MUTEX_RECURSIVE: {
-      p = sqlite3MallocZero( sizeof(*p) );
-      if( p ){
-#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
-        /* If recursive mutexes are not available, we will have to
-        ** build our own.  See below. */
-        pthread_mutex_init(&p->mutex, 0);
-#else
-        /* Use a recursive mutex if it is available */
-        pthread_mutexattr_t recursiveAttr;
-        pthread_mutexattr_init(&recursiveAttr);
-        pthread_mutexattr_settype(&recursiveAttr, PTHREAD_MUTEX_RECURSIVE);
-        pthread_mutex_init(&p->mutex, &recursiveAttr);
-        pthread_mutexattr_destroy(&recursiveAttr);
-#endif
-      }
-      break;
-    }
-    case SQLITE_MUTEX_FAST: {
-      p = sqlite3MallocZero( sizeof(*p) );
-      if( p ){
-        pthread_mutex_init(&p->mutex, 0);
-      }
-      break;
-    }
-    default: {
-#ifdef SQLITE_ENABLE_API_ARMOR
-      if( iType-2<0 || iType-2>=ArraySize(staticMutexes) ){
-        (void)SQLITE_MISUSE_BKPT;
-        return 0;
-      }
-#endif
-      p = &staticMutexes[iType-2];
-      break;
-    }
-  }
-#if SQLITE_MUTEX_NREF || defined(SQLITE_ENABLE_API_ARMOR)
-  if( p ) p->id = iType;
-#endif
-  return p;
-}
-
-
-/*
-** This routine deallocates a previously
-** allocated mutex.  SQLite is careful to deallocate every
-** mutex that it allocates.
-*/
-static void pthreadMutexFree(sqlite3_mutex *p){
-  assert( p->nRef==0 );
-#if SQLITE_ENABLE_API_ARMOR
-  if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE )
-#endif
-  {
-    pthread_mutex_destroy(&p->mutex);
-    sqlite3_free(p);
-  }
-#ifdef SQLITE_ENABLE_API_ARMOR
-  else{
-    (void)SQLITE_MISUSE_BKPT;
-  }
-#endif
-}
-
-/*
-** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
-** to enter a mutex.  If another thread is already within the mutex,
-** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
-** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
-** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
-** be entered multiple times by the same thread.  In such cases the,
-** mutex must be exited an equal number of times before another thread
-** can enter.  If the same thread tries to enter any other kind of mutex
-** more than once, the behavior is undefined.
-*/
-static void pthreadMutexEnter(sqlite3_mutex *p){
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
-
-#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
-  /* If recursive mutexes are not available, then we have to grow
-  ** our own.  This implementation assumes that pthread_equal()
-  ** is atomic - that it cannot be deceived into thinking self
-  ** and p->owner are equal if p->owner changes between two values
-  ** that are not equal to self while the comparison is taking place.
-  ** This implementation also assumes a coherent cache - that 
-  ** separate processes cannot read different values from the same
-  ** address at the same time.  If either of these two conditions
-  ** are not met, then the mutexes will fail and problems will result.
-  */
-  {
-    pthread_t self = pthread_self();
-    if( p->nRef>0 && pthread_equal(p->owner, self) ){
-      p->nRef++;
-    }else{
-      pthread_mutex_lock(&p->mutex);
-      assert( p->nRef==0 );
-      p->owner = self;
-      p->nRef = 1;
-    }
-  }
-#else
-  /* Use the built-in recursive mutexes if they are available.
-  */
-  pthread_mutex_lock(&p->mutex);
-#if SQLITE_MUTEX_NREF
-  assert( p->nRef>0 || p->owner==0 );
-  p->owner = pthread_self();
-  p->nRef++;
-#endif
-#endif
-
-#ifdef SQLITE_DEBUG
-  if( p->trace ){
-    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
-  }
-#endif
-}
-static int pthreadMutexTry(sqlite3_mutex *p){
-  int rc;
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || pthreadMutexNotheld(p) );
-
-#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
-  /* If recursive mutexes are not available, then we have to grow
-  ** our own.  This implementation assumes that pthread_equal()
-  ** is atomic - that it cannot be deceived into thinking self
-  ** and p->owner are equal if p->owner changes between two values
-  ** that are not equal to self while the comparison is taking place.
-  ** This implementation also assumes a coherent cache - that 
-  ** separate processes cannot read different values from the same
-  ** address at the same time.  If either of these two conditions
-  ** are not met, then the mutexes will fail and problems will result.
-  */
-  {
-    pthread_t self = pthread_self();
-    if( p->nRef>0 && pthread_equal(p->owner, self) ){
-      p->nRef++;
-      rc = SQLITE_OK;
-    }else if( pthread_mutex_trylock(&p->mutex)==0 ){
-      assert( p->nRef==0 );
-      p->owner = self;
-      p->nRef = 1;
-      rc = SQLITE_OK;
-    }else{
-      rc = SQLITE_BUSY;
-    }
-  }
-#else
-  /* Use the built-in recursive mutexes if they are available.
-  */
-  if( pthread_mutex_trylock(&p->mutex)==0 ){
-#if SQLITE_MUTEX_NREF
-    p->owner = pthread_self();
-    p->nRef++;
-#endif
-    rc = SQLITE_OK;
-  }else{
-    rc = SQLITE_BUSY;
-  }
-#endif
-
-#ifdef SQLITE_DEBUG
-  if( rc==SQLITE_OK && p->trace ){
-    printf("enter mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
-  }
-#endif
-  return rc;
-}
-
-/*
-** The sqlite3_mutex_leave() routine exits a mutex that was
-** previously entered by the same thread.  The behavior
-** is undefined if the mutex is not currently entered or
-** is not currently allocated.  SQLite will never do either.
-*/
-static void pthreadMutexLeave(sqlite3_mutex *p){
-  assert( pthreadMutexHeld(p) );
-#if SQLITE_MUTEX_NREF
-  p->nRef--;
-  if( p->nRef==0 ) p->owner = 0;
-#endif
-  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
-
-#ifdef SQLITE_HOMEGROWN_RECURSIVE_MUTEX
-  if( p->nRef==0 ){
-    pthread_mutex_unlock(&p->mutex);
-  }
-#else
-  pthread_mutex_unlock(&p->mutex);
-#endif
-
-#ifdef SQLITE_DEBUG
-  if( p->trace ){
-    printf("leave mutex %p (%d) with nRef=%d\n", p, p->trace, p->nRef);
-  }
-#endif
-}
-
-SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
-  static const sqlite3_mutex_methods sMutex = {
-    pthreadMutexInit,
-    pthreadMutexEnd,
-    pthreadMutexAlloc,
-    pthreadMutexFree,
-    pthreadMutexEnter,
-    pthreadMutexTry,
-    pthreadMutexLeave,
-#ifdef SQLITE_DEBUG
-    pthreadMutexHeld,
-    pthreadMutexNotheld
-#else
-    0,
-    0
-#endif
-  };
-
-  return &sMutex;
-}
-
-#endif /* SQLITE_MUTEX_PTHREADS */
-
-/************** End of mutex_unix.c ******************************************/
-/************** Begin file mutex_w32.c ***************************************/
-/*
-** 2007 August 14
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains the C functions that implement mutexes for Win32.
-*/
-/* #include "sqliteInt.h" */
-
-#if SQLITE_OS_WIN
-/*
-** Include code that is common to all os_*.c files
-*/
-/************** Include os_common.h in the middle of mutex_w32.c *************/
-/************** Begin file os_common.h ***************************************/
-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains macros and a little bit of code that is common to
-** all of the platform-specific files (os_*.c) and is #included into those
-** files.
-**
-** This file should be #included by the os_*.c files only.  It is not a
-** general purpose header file.
-*/
-#ifndef _OS_COMMON_H_
-#define _OS_COMMON_H_
-
-/*
-** At least two bugs have slipped in because we changed the MEMORY_DEBUG
-** macro to SQLITE_DEBUG and some older makefiles have not yet made the
-** switch.  The following code should catch this problem at compile-time.
-*/
-#ifdef MEMORY_DEBUG
-# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
-#endif
-
-/*
-** Macros for performance tracing.  Normally turned off.  Only works
-** on i486 hardware.
-*/
-#ifdef SQLITE_PERFORMANCE_TRACE
-
-/* 
-** hwtime.h contains inline assembler code for implementing 
-** high-performance timing routines.
-*/
-#include "hwtime.h"
-
-static sqlite_uint64 g_start;
-static sqlite_uint64 g_elapsed;
-#define TIMER_START       g_start=sqlite3Hwtime()
-#define TIMER_END         g_elapsed=sqlite3Hwtime()-g_start
-#define TIMER_ELAPSED     g_elapsed
-#else
-#define TIMER_START
-#define TIMER_END
-#define TIMER_ELAPSED     ((sqlite_uint64)0)
-#endif
-
-/*
-** If we compile with the SQLITE_TEST macro set, then the following block
-** of code will give us the ability to simulate a disk I/O error.  This
-** is used for testing the I/O recovery logic.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_io_error_hit = 0;            /* Total number of I/O Errors */
-SQLITE_PRIVATE int sqlite3_io_error_hardhit = 0;        /* Number of non-benign errors */
-SQLITE_PRIVATE int sqlite3_io_error_pending = 0;        /* Count down to first I/O error */
-SQLITE_PRIVATE int sqlite3_io_error_persist = 0;        /* True if I/O errors persist */
-SQLITE_PRIVATE int sqlite3_io_error_benign = 0;         /* True if errors are benign */
-SQLITE_PRIVATE int sqlite3_diskfull_pending = 0;
-SQLITE_PRIVATE int sqlite3_diskfull = 0;
-#define SimulateIOErrorBenign(X) sqlite3_io_error_benign=(X)
-#define SimulateIOError(CODE)  \
-  if( (sqlite3_io_error_persist && sqlite3_io_error_hit) \
-       || sqlite3_io_error_pending-- == 1 )  \
-              { local_ioerr(); CODE; }
-static void local_ioerr(){
-  IOTRACE(("IOERR\n"));
-  sqlite3_io_error_hit++;
-  if( !sqlite3_io_error_benign ) sqlite3_io_error_hardhit++;
-}
-#define SimulateDiskfullError(CODE) \
-   if( sqlite3_diskfull_pending ){ \
-     if( sqlite3_diskfull_pending == 1 ){ \
-       local_ioerr(); \
-       sqlite3_diskfull = 1; \
-       sqlite3_io_error_hit = 1; \
-       CODE; \
-     }else{ \
-       sqlite3_diskfull_pending--; \
-     } \
-   }
-#else
-#define SimulateIOErrorBenign(X)
-#define SimulateIOError(A)
-#define SimulateDiskfullError(A)
-#endif
-
-/*
-** When testing, keep a count of the number of open files.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_open_file_count = 0;
-#define OpenCounter(X)  sqlite3_open_file_count+=(X)
-#else
-#define OpenCounter(X)
-#endif
-
-#endif /* !defined(_OS_COMMON_H_) */
-
-/************** End of os_common.h *******************************************/
-/************** Continuing where we left off in mutex_w32.c ******************/
-
-/*
-** Include the header file for the Windows VFS.
-*/
-/************** Include os_win.h in the middle of mutex_w32.c ****************/
-/************** Begin file os_win.h ******************************************/
-/*
-** 2013 November 25
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains code that is specific to Windows.
-*/
-#ifndef _OS_WIN_H_
-#define _OS_WIN_H_
-
-/*
-** Include the primary Windows SDK header file.
-*/
-#include "windows.h"
-
-#ifdef __CYGWIN__
-# include <sys/cygwin.h>
-# include <errno.h> /* amalgamator: dontcache */
-#endif
-
-/*
-** Determine if we are dealing with Windows NT.
-**
-** We ought to be able to determine if we are compiling for Windows 9x or
-** Windows NT using the _WIN32_WINNT macro as follows:
-**
-** #if defined(_WIN32_WINNT)
-** # define SQLITE_OS_WINNT 1
-** #else
-** # define SQLITE_OS_WINNT 0
-** #endif
-**
-** However, Visual Studio 2005 does not set _WIN32_WINNT by default, as
-** it ought to, so the above test does not work.  We'll just assume that
-** everything is Windows NT unless the programmer explicitly says otherwise
-** by setting SQLITE_OS_WINNT to 0.
-*/
-#if SQLITE_OS_WIN && !defined(SQLITE_OS_WINNT)
-# define SQLITE_OS_WINNT 1
-#endif
-
-/*
-** Determine if we are dealing with Windows CE - which has a much reduced
-** API.
-*/
-#if defined(_WIN32_WCE)
-# define SQLITE_OS_WINCE 1
-#else
-# define SQLITE_OS_WINCE 0
-#endif
-
-/*
-** Determine if we are dealing with WinRT, which provides only a subset of
-** the full Win32 API.
-*/
-#if !defined(SQLITE_OS_WINRT)
-# define SQLITE_OS_WINRT 0
-#endif
-
-/*
-** For WinCE, some API function parameters do not appear to be declared as
-** volatile.
-*/
-#if SQLITE_OS_WINCE
-# define SQLITE_WIN32_VOLATILE
-#else
-# define SQLITE_WIN32_VOLATILE volatile
-#endif
-
-/*
-** For some Windows sub-platforms, the _beginthreadex() / _endthreadex()
-** functions are not available (e.g. those not using MSVC, Cygwin, etc).
-*/
-#if SQLITE_OS_WIN && !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && \
-    SQLITE_THREADSAFE>0 && !defined(__CYGWIN__)
-# define SQLITE_OS_WIN_THREADS 1
-#else
-# define SQLITE_OS_WIN_THREADS 0
-#endif
-
-#endif /* _OS_WIN_H_ */
-
-/************** End of os_win.h **********************************************/
-/************** Continuing where we left off in mutex_w32.c ******************/
-#endif
-
-/*
-** The code in this file is only used if we are compiling multithreaded
-** on a Win32 system.
-*/
-#ifdef SQLITE_MUTEX_W32
-
-/*
-** Each recursive mutex is an instance of the following structure.
-*/
-struct sqlite3_mutex {
-  CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
-  int id;                    /* Mutex type */
-#ifdef SQLITE_DEBUG
-  volatile int nRef;         /* Number of enterances */
-  volatile DWORD owner;      /* Thread holding this mutex */
-  volatile int trace;        /* True to trace changes */
-#endif
-};
-
-/*
-** These are the initializer values used when declaring a "static" mutex
-** on Win32.  It should be noted that all mutexes require initialization
-** on the Win32 platform.
-*/
-#define SQLITE_W32_MUTEX_INITIALIZER { 0 }
-
-#ifdef SQLITE_DEBUG
-#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0, \
-                                    0L, (DWORD)0, 0 }
-#else
-#define SQLITE3_MUTEX_INITIALIZER { SQLITE_W32_MUTEX_INITIALIZER, 0 }
-#endif
-
-#ifdef SQLITE_DEBUG
-/*
-** The sqlite3_mutex_held() and sqlite3_mutex_notheld() routine are
-** intended for use only inside assert() statements.
-*/
-static int winMutexHeld(sqlite3_mutex *p){
-  return p->nRef!=0 && p->owner==GetCurrentThreadId();
-}
-
-static int winMutexNotheld2(sqlite3_mutex *p, DWORD tid){
-  return p->nRef==0 || p->owner!=tid;
-}
-
-static int winMutexNotheld(sqlite3_mutex *p){
-  DWORD tid = GetCurrentThreadId();
-  return winMutexNotheld2(p, tid);
-}
-#endif
-
-/*
-** Try to provide a memory barrier operation, needed for initialization
-** and also for the xShmBarrier method of the VFS in cases when SQLite is
-** compiled without mutexes (SQLITE_THREADSAFE=0).
-*/
-SQLITE_PRIVATE void sqlite3MemoryBarrier(void){
-#if defined(SQLITE_MEMORY_BARRIER)
-  SQLITE_MEMORY_BARRIER;
-#elif defined(__GNUC__)
-  __sync_synchronize();
-#elif !defined(SQLITE_DISABLE_INTRINSIC) && \
-      defined(_MSC_VER) && _MSC_VER>=1300
-  _ReadWriteBarrier();
-#elif defined(MemoryBarrier)
-  MemoryBarrier();
-#endif
-}
-
-/*
-** Initialize and deinitialize the mutex subsystem.
-*/
-static sqlite3_mutex winMutex_staticMutexes[] = {
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER,
-  SQLITE3_MUTEX_INITIALIZER
-};
-
-static int winMutex_isInit = 0;
-static int winMutex_isNt = -1; /* <0 means "need to query" */
-
-/* As the winMutexInit() and winMutexEnd() functions are called as part
-** of the sqlite3BtreeInitialize() and sqlite3BtreeShutdown() processing, the
-** "interlocked" magic used here is probably not strictly necessary.
-*/
-static LONG SQLITE_WIN32_VOLATILE winMutex_lock = 0;
-
-SQLITE_PRIVATE int sqlite3_win32_is_nt(void); /* os_win.c */
-SQLITE_PRIVATE void sqlite3_win32_sleep(DWORD milliseconds); /* os_win.c */
-
-static int winMutexInit(void){
-  /* The first to increment to 1 does actual initialization */
-  if( InterlockedCompareExchange(&winMutex_lock, 1, 0)==0 ){
-    int i;
-    for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
-#if SQLITE_OS_WINRT
-      InitializeCriticalSectionEx(&winMutex_staticMutexes[i].mutex, 0, 0);
-#else
-      InitializeCriticalSection(&winMutex_staticMutexes[i].mutex);
-#endif
-    }
-    winMutex_isInit = 1;
-  }else{
-    /* Another thread is (in the process of) initializing the static
-    ** mutexes */
-    while( !winMutex_isInit ){
-      sqlite3_win32_sleep(1);
-    }
-  }
-  return SQLITE_OK;
-}
-
-static int winMutexEnd(void){
-  /* The first to decrement to 0 does actual shutdown
-  ** (which should be the last to shutdown.) */
-  if( InterlockedCompareExchange(&winMutex_lock, 0, 1)==1 ){
-    if( winMutex_isInit==1 ){
-      int i;
-      for(i=0; i<ArraySize(winMutex_staticMutexes); i++){
-        DeleteCriticalSection(&winMutex_staticMutexes[i].mutex);
-      }
-      winMutex_isInit = 0;
-    }
-  }
-  return SQLITE_OK;
-}
-
-/*
-** The sqlite3_mutex_alloc() routine allocates a new
-** mutex and returns a pointer to it.  If it returns NULL
-** that means that a mutex could not be allocated.  SQLite
-** will unwind its stack and return an error.  The argument
-** to sqlite3_mutex_alloc() is one of these integer constants:
-**
-** <ul>
-** <li>  SQLITE_MUTEX_FAST
-** <li>  SQLITE_MUTEX_RECURSIVE
-** <li>  SQLITE_MUTEX_STATIC_MASTER
-** <li>  SQLITE_MUTEX_STATIC_MEM
-** <li>  SQLITE_MUTEX_STATIC_OPEN
-** <li>  SQLITE_MUTEX_STATIC_PRNG
-** <li>  SQLITE_MUTEX_STATIC_LRU
-** <li>  SQLITE_MUTEX_STATIC_PMEM
-** <li>  SQLITE_MUTEX_STATIC_APP1
-** <li>  SQLITE_MUTEX_STATIC_APP2
-** <li>  SQLITE_MUTEX_STATIC_APP3
-** <li>  SQLITE_MUTEX_STATIC_VFS1
-** <li>  SQLITE_MUTEX_STATIC_VFS2
-** <li>  SQLITE_MUTEX_STATIC_VFS3
-** </ul>
-**
-** The first two constants cause sqlite3_mutex_alloc() to create
-** a new mutex.  The new mutex is recursive when SQLITE_MUTEX_RECURSIVE
-** is used but not necessarily so when SQLITE_MUTEX_FAST is used.
-** The mutex implementation does not need to make a distinction
-** between SQLITE_MUTEX_RECURSIVE and SQLITE_MUTEX_FAST if it does
-** not want to.  But SQLite will only request a recursive mutex in
-** cases where it really needs one.  If a faster non-recursive mutex
-** implementation is available on the host platform, the mutex subsystem
-** might return such a mutex in response to SQLITE_MUTEX_FAST.
-**
-** The other allowed parameters to sqlite3_mutex_alloc() each return
-** a pointer to a static preexisting mutex.  Six static mutexes are
-** used by the current version of SQLite.  Future versions of SQLite
-** may add additional static mutexes.  Static mutexes are for internal
-** use by SQLite only.  Applications that use SQLite mutexes should
-** use only the dynamic mutexes returned by SQLITE_MUTEX_FAST or
-** SQLITE_MUTEX_RECURSIVE.
-**
-** Note that if one of the dynamic mutex parameters (SQLITE_MUTEX_FAST
-** or SQLITE_MUTEX_RECURSIVE) is used then sqlite3_mutex_alloc()
-** returns a different mutex on every call.  But for the static
-** mutex types, the same mutex is returned on every call that has
-** the same type number.
-*/
-static sqlite3_mutex *winMutexAlloc(int iType){
-  sqlite3_mutex *p;
-
-  switch( iType ){
-    case SQLITE_MUTEX_FAST:
-    case SQLITE_MUTEX_RECURSIVE: {
-      p = sqlite3MallocZero( sizeof(*p) );
-      if( p ){
-        p->id = iType;
-#ifdef SQLITE_DEBUG
-#ifdef SQLITE_WIN32_MUTEX_TRACE_DYNAMIC
-        p->trace = 1;
-#endif
-#endif
-#if SQLITE_OS_WINRT
-        InitializeCriticalSectionEx(&p->mutex, 0, 0);
-#else
-        InitializeCriticalSection(&p->mutex);
-#endif
-      }
-      break;
-    }
-    default: {
-#ifdef SQLITE_ENABLE_API_ARMOR
-      if( iType-2<0 || iType-2>=ArraySize(winMutex_staticMutexes) ){
-        (void)SQLITE_MISUSE_BKPT;
-        return 0;
-      }
-#endif
-      p = &winMutex_staticMutexes[iType-2];
-      p->id = iType;
-#ifdef SQLITE_DEBUG
-#ifdef SQLITE_WIN32_MUTEX_TRACE_STATIC
-      p->trace = 1;
-#endif
-#endif
-      break;
-    }
-  }
-  return p;
-}
-
-
-/*
-** This routine deallocates a previously
-** allocated mutex.  SQLite is careful to deallocate every
-** mutex that it allocates.
-*/
-static void winMutexFree(sqlite3_mutex *p){
-  assert( p );
-  assert( p->nRef==0 && p->owner==0 );
-  if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ){
-    DeleteCriticalSection(&p->mutex);
-    sqlite3_free(p);
-  }else{
-#ifdef SQLITE_ENABLE_API_ARMOR
-    (void)SQLITE_MISUSE_BKPT;
-#endif
-  }
-}
-
-/*
-** The sqlite3_mutex_enter() and sqlite3_mutex_try() routines attempt
-** to enter a mutex.  If another thread is already within the mutex,
-** sqlite3_mutex_enter() will block and sqlite3_mutex_try() will return
-** SQLITE_BUSY.  The sqlite3_mutex_try() interface returns SQLITE_OK
-** upon successful entry.  Mutexes created using SQLITE_MUTEX_RECURSIVE can
-** be entered multiple times by the same thread.  In such cases the,
-** mutex must be exited an equal number of times before another thread
-** can enter.  If the same thread tries to enter any other kind of mutex
-** more than once, the behavior is undefined.
-*/
-static void winMutexEnter(sqlite3_mutex *p){
-#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
-  DWORD tid = GetCurrentThreadId();
-#endif
-#ifdef SQLITE_DEBUG
-  assert( p );
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
-#else
-  assert( p );
-#endif
-  assert( winMutex_isInit==1 );
-  EnterCriticalSection(&p->mutex);
-#ifdef SQLITE_DEBUG
-  assert( p->nRef>0 || p->owner==0 );
-  p->owner = tid;
-  p->nRef++;
-  if( p->trace ){
-    OSTRACE(("ENTER-MUTEX tid=%lu, mutex=%p (%d), nRef=%d\n",
-             tid, p, p->trace, p->nRef));
-  }
-#endif
-}
-
-static int winMutexTry(sqlite3_mutex *p){
-#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
-  DWORD tid = GetCurrentThreadId();
-#endif
-  int rc = SQLITE_BUSY;
-  assert( p );
-  assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
-  /*
-  ** The sqlite3_mutex_try() routine is very rarely used, and when it
-  ** is used it is merely an optimization.  So it is OK for it to always
-  ** fail.
-  **
-  ** The TryEnterCriticalSection() interface is only available on WinNT.
-  ** And some windows compilers complain if you try to use it without
-  ** first doing some #defines that prevent SQLite from building on Win98.
-  ** For that reason, we will omit this optimization for now.  See
-  ** ticket #2685.
-  */
-#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x0400
-  assert( winMutex_isInit==1 );
-  assert( winMutex_isNt>=-1 && winMutex_isNt<=1 );
-  if( winMutex_isNt<0 ){
-    winMutex_isNt = sqlite3_win32_is_nt();
-  }
-  assert( winMutex_isNt==0 || winMutex_isNt==1 );
-  if( winMutex_isNt && TryEnterCriticalSection(&p->mutex) ){
-#ifdef SQLITE_DEBUG
-    p->owner = tid;
-    p->nRef++;
-#endif
-    rc = SQLITE_OK;
-  }
-#else
-  UNUSED_PARAMETER(p);
-#endif
-#ifdef SQLITE_DEBUG
-  if( p->trace ){
-    OSTRACE(("TRY-MUTEX tid=%lu, mutex=%p (%d), owner=%lu, nRef=%d, rc=%s\n",
-             tid, p, p->trace, p->owner, p->nRef, sqlite3ErrName(rc)));
-  }
-#endif
-  return rc;
-}
-
-/*
-** The sqlite3_mutex_leave() routine exits a mutex that was
-** previously entered by the same thread.  The behavior
-** is undefined if the mutex is not currently entered or
-** is not currently allocated.  SQLite will never do either.
-*/
-static void winMutexLeave(sqlite3_mutex *p){
-#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
-  DWORD tid = GetCurrentThreadId();
-#endif
-  assert( p );
-#ifdef SQLITE_DEBUG
-  assert( p->nRef>0 );
-  assert( p->owner==tid );
-  p->nRef--;
-  if( p->nRef==0 ) p->owner = 0;
-  assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
-#endif
-  assert( winMutex_isInit==1 );
-  LeaveCriticalSection(&p->mutex);
-#ifdef SQLITE_DEBUG
-  if( p->trace ){
-    OSTRACE(("LEAVE-MUTEX tid=%lu, mutex=%p (%d), nRef=%d\n",
-             tid, p, p->trace, p->nRef));
-  }
-#endif
-}
-
-SQLITE_PRIVATE sqlite3_mutex_methods const *sqlite3DefaultMutex(void){
-  static const sqlite3_mutex_methods sMutex = {
-    winMutexInit,
-    winMutexEnd,
-    winMutexAlloc,
-    winMutexFree,
-    winMutexEnter,
-    winMutexTry,
-    winMutexLeave,
-#ifdef SQLITE_DEBUG
-    winMutexHeld,
-    winMutexNotheld
-#else
-    0,
-    0
-#endif
-  };
-  return &sMutex;
-}
-
-#endif /* SQLITE_MUTEX_W32 */
-
-/************** End of mutex_w32.c *******************************************/
-/************** Begin file malloc.c ******************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** Memory allocation functions used throughout sqlite.
-*/
-/* #include "sqliteInt.h" */
-/* #include <stdarg.h> */
-
-/*
-** Attempt to release up to n bytes of non-essential memory currently
-** held by SQLite. An example of non-essential memory is memory used to
-** cache database pages that are not currently in use.
-*/
-SQLITE_PRIVATE int sqlite3_release_memory(int n){
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-  return sqlite3PcacheReleaseMemory(n);
-#else
-  /* IMPLEMENTATION-OF: R-34391-24921 The sqlite3_release_memory() routine
-  ** is a no-op returning zero if SQLite is not compiled with
-  ** SQLITE_ENABLE_MEMORY_MANAGEMENT. */
-  UNUSED_PARAMETER(n);
-  return 0;
-#endif
-}
-
-/*
-** An instance of the following object records the location of
-** each unused scratch buffer.
-*/
-typedef struct ScratchFreeslot {
-  struct ScratchFreeslot *pNext;   /* Next unused scratch buffer */
-} ScratchFreeslot;
-
-/*
-** State information local to the memory allocation subsystem.
-*/
-static SQLITE_WSD struct Mem0Global {
-  sqlite3_mutex *mutex;         /* Mutex to serialize access */
-  sqlite3_int64 alarmThreshold; /* The soft heap limit */
-
-  /*
-  ** Pointers to the end of sqlite3GlobalConfig.pScratch memory
-  ** (so that a range test can be used to determine if an allocation
-  ** being freed came from pScratch) and a pointer to the list of
-  ** unused scratch allocations.
-  */
-  void *pScratchEnd;
-  ScratchFreeslot *pScratchFree;
-  u32 nScratchFree;
-
-  /*
-  ** True if heap is nearly "full" where "full" is defined by the
-  ** sqlite3_soft_heap_limit() setting.
-  */
-  int nearlyFull;
-} mem0 = { 0, 0, 0, 0, 0, 0 };
-
-#define mem0 GLOBAL(struct Mem0Global, mem0)
-
-#ifndef NDEBUG
-/*
-** Return the memory allocator mutex. sqlite3_status() needs it.
-*/
-SQLITE_PRIVATE sqlite3_mutex *sqlite3MallocMutex(void){
-  return mem0.mutex;
-}
-#endif
-
-/*
-** Initialize the memory allocation subsystem.
-*/
-SQLITE_PRIVATE int sqlite3MallocInit(void){
-  int rc;
-  if( sqlite3GlobalConfig.m.xMalloc==0 ){
-    sqlite3MemSetDefault();
-  }
-  memset(&mem0, 0, sizeof(mem0));
-  if( sqlite3GlobalConfig.bCoreMutex ){
-    mem0.mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MEM);
-  }
-  if( sqlite3GlobalConfig.pScratch && sqlite3GlobalConfig.szScratch>=100
-      && sqlite3GlobalConfig.nScratch>0 ){
-    int i, n, sz;
-    ScratchFreeslot *pSlot;
-    sz = ROUNDDOWN8(sqlite3GlobalConfig.szScratch);
-    sqlite3GlobalConfig.szScratch = sz;
-    pSlot = (ScratchFreeslot*)sqlite3GlobalConfig.pScratch;
-    n = sqlite3GlobalConfig.nScratch;
-    mem0.pScratchFree = pSlot;
-    mem0.nScratchFree = n;
-    for(i=0; i<n-1; i++){
-      pSlot->pNext = (ScratchFreeslot*)(sz+(char*)pSlot);
-      pSlot = pSlot->pNext;
-    }
-    pSlot->pNext = 0;
-    mem0.pScratchEnd = (void*)&pSlot[1];
-  }else{
-    mem0.pScratchEnd = 0;
-    sqlite3GlobalConfig.pScratch = 0;
-    sqlite3GlobalConfig.szScratch = 0;
-    sqlite3GlobalConfig.nScratch = 0;
-  }
-  if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
-      || sqlite3GlobalConfig.nPage<=0 ){
-    sqlite3GlobalConfig.pPage = 0;
-    sqlite3GlobalConfig.szPage = 0;
-  }
-  rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
-  if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));
-  return rc;
-}
-
-/*
-** Return true if the heap is currently under memory pressure - in other
-** words if the amount of heap used is close to the limit set by
-** sqlite3_soft_heap_limit().
-*/
-SQLITE_PRIVATE int sqlite3HeapNearlyFull(void){
-  return mem0.nearlyFull;
-}
-
-/*
-** Deinitialize the memory allocation subsystem.
-*/
-SQLITE_PRIVATE void sqlite3MallocEnd(void){
-  if( sqlite3GlobalConfig.m.xShutdown ){
-    sqlite3GlobalConfig.m.xShutdown(sqlite3GlobalConfig.m.pAppData);
-  }
-  memset(&mem0, 0, sizeof(mem0));
-}
-
-/*
-** Trigger the alarm 
-*/
-static void sqlite3MallocAlarm(int nByte){
-  if( mem0.alarmThreshold<=0 ) return;
-  sqlite3_mutex_leave(mem0.mutex);
-  sqlite3_release_memory(nByte);
-  sqlite3_mutex_enter(mem0.mutex);
-}
-
-/*
-** Do a memory allocation with statistics and alarms.  Assume the
-** lock is already held.
-*/
-static int mallocWithAlarm(int n, void **pp){
-  int nFull;
-  void *p;
-  assert( sqlite3_mutex_held(mem0.mutex) );
-  nFull = sqlite3GlobalConfig.m.xRoundup(n);
-  sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, n);
-  if( mem0.alarmThreshold>0 ){
-    sqlite3_int64 nUsed = sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED);
-    if( nUsed >= mem0.alarmThreshold - nFull ){
-      mem0.nearlyFull = 1;
-      sqlite3MallocAlarm(nFull);
-    }else{
-      mem0.nearlyFull = 0;
-    }
-  }
-  p = sqlite3GlobalConfig.m.xMalloc(nFull);
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-  if( p==0 && mem0.alarmThreshold>0 ){
-    sqlite3MallocAlarm(nFull);
-    p = sqlite3GlobalConfig.m.xMalloc(nFull);
-  }
-#endif
-  if( p ){
-    nFull = sqlite3MallocSize(p);
-    sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nFull);
-    sqlite3StatusUp(SQLITE_STATUS_MALLOC_COUNT, 1);
-  }
-  *pp = p;
-  return nFull;
-}
-
-/*
-** Allocate memory.  This routine is like sqlite3_malloc() except that it
-** assumes the memory subsystem has already been initialized.
-*/
-SQLITE_PRIVATE void *sqlite3Malloc(u64 n){
-  void *p;
-  if( n==0 || n>=0x7fffff00 ){
-    /* A memory allocation of a number of bytes which is near the maximum
-    ** signed integer value might cause an integer overflow inside of the
-    ** xMalloc().  Hence we limit the maximum size to 0x7fffff00, giving
-    ** 255 bytes of overhead.  SQLite itself will never use anything near
-    ** this amount.  The only way to reach the limit is with sqlite3_malloc() */
-    p = 0;
-  }else if( sqlite3GlobalConfig.bMemstat ){
-    sqlite3_mutex_enter(mem0.mutex);
-    mallocWithAlarm((int)n, &p);
-    sqlite3_mutex_leave(mem0.mutex);
-  }else{
-    p = sqlite3GlobalConfig.m.xMalloc((int)n);
-  }
-  assert( EIGHT_BYTE_ALIGNMENT(p) );  /* IMP: R-11148-40995 */
-  return p;
-}
-
-/*
-** This version of the memory allocation is for use by the application.
-** First make sure the memory subsystem is initialized, then do the
-** allocation.
-*/
-SQLITE_PRIVATE void *sqlite3_malloc(int n){
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  return n<=0 ? 0 : sqlite3Malloc(n);
-}
-SQLITE_PRIVATE void *sqlite3_malloc64(sqlite3_uint64 n){
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  return sqlite3Malloc(n);
-}
-
-/*
-** Each thread may only have a single outstanding allocation from
-** xScratchMalloc().  We verify this constraint in the single-threaded
-** case by setting scratchAllocOut to 1 when an allocation
-** is outstanding clearing it when the allocation is freed.
-*/
-#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
-static int scratchAllocOut = 0;
-#endif
-
-
-/*
-** Allocate memory that is to be used and released right away.
-** This routine is similar to alloca() in that it is not intended
-** for situations where the memory might be held long-term.  This
-** routine is intended to get memory to old large transient data
-** structures that would not normally fit on the stack of an
-** embedded processor.
-*/
-SQLITE_PRIVATE void *sqlite3ScratchMalloc(int n){
-  void *p;
-  assert( n>0 );
-
-  sqlite3_mutex_enter(mem0.mutex);
-  sqlite3StatusSet(SQLITE_STATUS_SCRATCH_SIZE, n);
-  if( mem0.nScratchFree && sqlite3GlobalConfig.szScratch>=n ){
-    p = mem0.pScratchFree;
-    mem0.pScratchFree = mem0.pScratchFree->pNext;
-    mem0.nScratchFree--;
-    sqlite3StatusUp(SQLITE_STATUS_SCRATCH_USED, 1);
-    sqlite3_mutex_leave(mem0.mutex);
-  }else{
-    sqlite3_mutex_leave(mem0.mutex);
-    p = sqlite3Malloc(n);
-    if( sqlite3GlobalConfig.bMemstat && p ){
-      sqlite3_mutex_enter(mem0.mutex);
-      sqlite3StatusUp(SQLITE_STATUS_SCRATCH_OVERFLOW, sqlite3MallocSize(p));
-      sqlite3_mutex_leave(mem0.mutex);
-    }
-    sqlite3MemdebugSetType(p, MEMTYPE_SCRATCH);
-  }
-  assert( sqlite3_mutex_notheld(mem0.mutex) );
-
-
-#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
-  /* EVIDENCE-OF: R-12970-05880 SQLite will not use more than one scratch
-  ** buffers per thread.
-  **
-  ** This can only be checked in single-threaded mode.
-  */
-  assert( scratchAllocOut==0 );
-  if( p ) scratchAllocOut++;
-#endif
-
-  return p;
-}
-SQLITE_PRIVATE void sqlite3ScratchFree(void *p){
-  if( p ){
-
-#if SQLITE_THREADSAFE==0 && !defined(NDEBUG)
-    /* Verify that no more than two scratch allocation per thread
-    ** is outstanding at one time.  (This is only checked in the
-    ** single-threaded case since checking in the multi-threaded case
-    ** would be much more complicated.) */
-    assert( scratchAllocOut>=1 && scratchAllocOut<=2 );
-    scratchAllocOut--;
-#endif
-
-    if( p>=sqlite3GlobalConfig.pScratch && p<mem0.pScratchEnd ){
-      /* Release memory from the SQLITE_CONFIG_SCRATCH allocation */
-      ScratchFreeslot *pSlot;
-      pSlot = (ScratchFreeslot*)p;
-      sqlite3_mutex_enter(mem0.mutex);
-      pSlot->pNext = mem0.pScratchFree;
-      mem0.pScratchFree = pSlot;
-      mem0.nScratchFree++;
-      assert( mem0.nScratchFree <= (u32)sqlite3GlobalConfig.nScratch );
-      sqlite3StatusDown(SQLITE_STATUS_SCRATCH_USED, 1);
-      sqlite3_mutex_leave(mem0.mutex);
-    }else{
-      /* Release memory back to the heap */
-      assert( sqlite3MemdebugHasType(p, MEMTYPE_SCRATCH) );
-      assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_SCRATCH) );
-      sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-      if( sqlite3GlobalConfig.bMemstat ){
-        int iSize = sqlite3MallocSize(p);
-        sqlite3_mutex_enter(mem0.mutex);
-        sqlite3StatusDown(SQLITE_STATUS_SCRATCH_OVERFLOW, iSize);
-        sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, iSize);
-        sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
-        sqlite3GlobalConfig.m.xFree(p);
-        sqlite3_mutex_leave(mem0.mutex);
-      }else{
-        sqlite3GlobalConfig.m.xFree(p);
-      }
-    }
-  }
-}
-
-/*
-** Return the size of a memory allocation previously obtained from
-** sqlite3Malloc() or sqlite3_malloc().
-*/
-SQLITE_PRIVATE int sqlite3MallocSize(void *p){
-  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
-  return sqlite3GlobalConfig.m.xSize(p);
-}
-SQLITE_PRIVATE int sqlite3DbMallocSize(Btree *pBtree, void *p){
-  if( pBtree==0 ){
-#if SQLITE_DEBUG
-    assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
-    assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
-#endif
-    return sqlite3GlobalConfig.m.xSize(p);
-  }else{
-    assert( sqlite3_mutex_held(pBtree->mutex) );
-    return 0;
-  }
-}
-
-/*
-** Free memory previously obtained from sqlite3Malloc().
-*/
-SQLITE_PRIVATE void sqlite3_free(void *p){
-  if( p==0 ) return;  /* IMP: R-49053-54554 */
-  assert( sqlite3MemdebugHasType(p, MEMTYPE_HEAP) );
-  assert( sqlite3MemdebugNoType(p, (u8)~MEMTYPE_HEAP) );
-  if( sqlite3GlobalConfig.bMemstat ){
-    sqlite3_mutex_enter(mem0.mutex);
-    sqlite3StatusDown(SQLITE_STATUS_MEMORY_USED, sqlite3MallocSize(p));
-    sqlite3StatusDown(SQLITE_STATUS_MALLOC_COUNT, 1);
-    sqlite3GlobalConfig.m.xFree(p);
-    sqlite3_mutex_leave(mem0.mutex);
-  }else{
-    sqlite3GlobalConfig.m.xFree(p);
-  }
-}
-
-/*
-** Add the size of memory allocation "p" to the count in
-** *db->pnBytesFreed.
-*/
-static SQLITE_NOINLINE void measureAllocationSize(Btree *pBtree, void *p){
-  *pBtree->pnBytesFreed += sqlite3DbMallocSize(pBtree,p);
-}
-
-/*
-** Free memory that might be associated with a particular database
-** connection.
-*/
-SQLITE_PRIVATE void sqlite3DbFree(Btree *pBtree, void *p){
-  assert( pBTree==0 || sqlite3_mutex_held(pTree->mutex) );
-  if( p==0 ) return;
-  if( pBtree ){
-    if( pBtree->pnBytesFreed ){
-      measureAllocationSize(pBtree, p);
-      return;
-    }
-  }
-  assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
-  assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
-  assert( pBtree!=0 || sqlite3MemdebugNoType(p, MEMTYPE_LOOKASIDE) );
-  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-  sqlite3_free(p);
-}
-
-/*
-** Change the size of an existing memory allocation
-*/
-SQLITE_PRIVATE void *sqlite3Realloc(void *pOld, u64 nBytes){
-  int nOld, nNew, nDiff;
-  void *pNew;
-  assert( sqlite3MemdebugHasType(pOld, MEMTYPE_HEAP) );
-  assert( sqlite3MemdebugNoType(pOld, (u8)~MEMTYPE_HEAP) );
-  if( pOld==0 ){
-    return sqlite3Malloc(nBytes); /* IMP: R-04300-56712 */
-  }
-  if( nBytes==0 ){
-    sqlite3_free(pOld); /* IMP: R-26507-47431 */
-    return 0;
-  }
-  if( nBytes>=0x7fffff00 ){
-    /* The 0x7ffff00 limit term is explained in comments on sqlite3Malloc() */
-    return 0;
-  }
-  nOld = sqlite3MallocSize(pOld);
-  /* IMPLEMENTATION-OF: R-46199-30249 SQLite guarantees that the second
-  ** argument to xRealloc is always a value returned by a prior call to
-  ** xRoundup. */
-  nNew = sqlite3GlobalConfig.m.xRoundup((int)nBytes);
-  if( nOld==nNew ){
-    pNew = pOld;
-  }else if( sqlite3GlobalConfig.bMemstat ){
-    sqlite3_mutex_enter(mem0.mutex);
-    sqlite3StatusSet(SQLITE_STATUS_MALLOC_SIZE, (int)nBytes);
-    nDiff = nNew - nOld;
-    if( sqlite3StatusValue(SQLITE_STATUS_MEMORY_USED) >= 
-          mem0.alarmThreshold-nDiff ){
-      sqlite3MallocAlarm(nDiff);
-    }
-    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
-    if( pNew==0 && mem0.alarmThreshold>0 ){
-      sqlite3MallocAlarm((int)nBytes);
-      pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
-    }
-    if( pNew ){
-      nNew = sqlite3MallocSize(pNew);
-      sqlite3StatusUp(SQLITE_STATUS_MEMORY_USED, nNew-nOld);
-    }
-    sqlite3_mutex_leave(mem0.mutex);
-  }else{
-    pNew = sqlite3GlobalConfig.m.xRealloc(pOld, nNew);
-  }
-  assert( EIGHT_BYTE_ALIGNMENT(pNew) ); /* IMP: R-11148-40995 */
-  return pNew;
-}
-
-/*
-** The public interface to sqlite3Realloc.  Make sure that the memory
-** subsystem is initialized prior to invoking sqliteRealloc.
-*/
-SQLITE_PRIVATE void *sqlite3_realloc(void *pOld, int n){
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  if( n<0 ) n = 0;  /* IMP: R-26507-47431 */
-  return sqlite3Realloc(pOld, n);
-}
-SQLITE_PRIVATE void *sqlite3_realloc64(void *pOld, sqlite3_uint64 n){
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  return sqlite3Realloc(pOld, n);
-}
-
-
-/*
-** Allocate and zero memory.
-*/ 
-SQLITE_PRIVATE void *sqlite3MallocZero(u64 n){
-  void *p = sqlite3Malloc(n);
-  if( p ){
-    memset(p, 0, (size_t)n);
-  }
-  return p;
-}
-
-/*
-** Allocate and zero memory.  If the allocation fails, make
-** the mallocFailed flag in the connection pointer.
-*/
-SQLITE_PRIVATE void *sqlite3DbMallocZero(Btree *pBtree, u64 n){
-  void *p = sqlite3DbMallocRaw(pBtree, n);
-  if( p ){
-    memset(p, 0, (size_t)n);
-  }
-  return p;
-}
-
-/*
-** Allocate and zero memory.  If the allocation fails, make
-** the mallocFailed flag in the connection pointer.
-**
-** If pBtree!=0 and pBtree->mallocFailed is true (indicating a prior malloc
-** failure on the same database connection) then always return 0.
-** Hence for a particular database connection, once malloc starts
-** failing, it fails consistently until mallocFailed is reset.
-** This is an important assumption.  There are many places in the
-** code that do things like this:
-**
-**         int *a = (int*)sqlite3DbMallocRaw(pBtree, 100);
-**         int *b = (int*)sqlite3DbMallocRaw(pBtree, 200);
-**         if( b ) a[10] = 9;
-**
-** In other words, if a subsequent malloc (ex: "b") worked, it is assumed
-** that all prior mallocs (ex: "a") worked too.
-*/
-SQLITE_PRIVATE void *sqlite3DbMallocRaw(Btree *pBtree, u64 n){
-  void *p;
-  assert( pBtree==0 || sqlite3_mutex_held(pBtree->mutex) );
-  assert( pBtree==0 || pBtree->pnBytesFreed==0 );
-  if( pBtree && pBtree->mallocFailed ){
-    return 0;
-  }
-  p = sqlite3Malloc(n);
-  if( !p && pBtree ){
-    pBtree->mallocFailed = 1;
-  }
-  sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-  return p;
-}
-
-/*
-** Resize the block of memory pointed to by p to n bytes. If the
-** resize fails, set the mallocFailed flag in the connection object.
-*/
-SQLITE_PRIVATE void *sqlite3DbRealloc(Btree *pBtree, void *p, u64 n){
-  void *pNew = 0;
-  assert( pBtree!=0 );
-  assert( sqlite3_mutex_held(pBtree->mutex) );
-  if( pBtree->mallocFailed==0 ){
-    if( p==0 ){
-      return sqlite3DbMallocRaw(pBtree, n);
-    }
-    assert( sqlite3MemdebugHasType(p, (MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
-    assert( sqlite3MemdebugNoType(p, (u8)~(MEMTYPE_LOOKASIDE|MEMTYPE_HEAP)) );
-    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-    pNew = sqlite3_realloc64(p, n);
-    if( !pNew ){
-      pBtree->mallocFailed = 1;
-    }
-    sqlite3MemdebugSetType(pNew, MEMTYPE_HEAP);
-  }
-  return pNew;
-}
-
-/*
-** Attempt to reallocate p.  If the reallocation fails, then free p
-** and set the mallocFailed flag in the database connection.
-*/
-SQLITE_PRIVATE void *sqlite3DbReallocOrFree(Btree *pBtree, void *p, u64 n){
-  void *pNew;
-  pNew = sqlite3DbRealloc(pBtree, p, n);
-  if( !pNew ){
-    sqlite3DbFree(pBtree, p);
-  }
-  return pNew;
-}
-
-/*
-** Make a copy of a string in memory obtained from sqliteMalloc(). These 
-** functions call sqlite3MallocRaw() directly instead of sqliteMalloc(). This
-** is because when memory debugging is turned on, these two functions are 
-** called via macros that record the current file and line number in the
-** ThreadData structure.
-*/
-char *sqlite3DbStrDup(Btree *pBtree, const char *z){
-  char *zNew;
-  size_t n;
-  if( z==0 ){
-    return 0;
-  }
-  n = sqlite3Strlen30(z) + 1;
-  assert( (n&0x7fffffff)==n );
-  zNew = sqlite3DbMallocRaw(pBtree, (int)n);
-  if( zNew ){
-    memcpy(zNew, z, n);
-  }
-  return zNew;
-}
-
-/************** End of malloc.c **********************************************/
-/************** Begin file printf.c ******************************************/
-/*
-** The "printf" code that follows dates from the 1980's.  It is in
-** the public domain. 
-**
-**************************************************************************
-**
-** This file contains code for a set of "printf"-like routines.  These
-** routines format strings much like the printf() from the standard C
-** library, though the implementation here has enhancements to support
-** SQLite.
-*/
-/* #include "sqliteInt.h" */
-
-/*
-** Conversion types fall into various categories as defined by the
-** following enumeration.
-*/
-#define etRADIX       1 /* Integer types.  %d, %x, %o, and so forth */
-#define etFLOAT       2 /* Floating point.  %f */
-#define etEXP         3 /* Exponentional notation. %e and %E */
-#define etGENERIC     4 /* Floating or exponential, depending on exponent. %g */
-#define etSIZE        5 /* Return number of characters processed so far. %n */
-#define etSTRING      6 /* Strings. %s */
-#define etDYNSTRING   7 /* Dynamically allocated strings. %z */
-#define etPERCENT     8 /* Percent symbol. %% */
-#define etCHARX       9 /* Characters. %c */
-/* The rest are extensions, not normally found in printf() */
-#define etSQLESCAPE  10 /* Strings with '\'' doubled.  %q */
-#define etSQLESCAPE2 11 /* Strings with '\'' doubled and enclosed in '',
-                          NULL pointers replaced by SQL NULL.  %Q */
-#define etPOINTER    14 /* The %p conversion */
-#define etSQLESCAPE3 15 /* %w -> Strings with '\"' doubled */
-#define etORDINAL    16 /* %r -> 1st, 2nd, 3rd, 4th, etc.  English only */
-
-#define etINVALID     0 /* Any unrecognized conversion type */
-
-
-/*
-** An "etByte" is an 8-bit unsigned value.
-*/
-typedef unsigned char etByte;
-
-/*
-** Each builtin conversion character (ex: the 'd' in "%d") is described
-** by an instance of the following structure
-*/
-typedef struct et_info {   /* Information about each format field */
-  char fmttype;            /* The format field code letter */
-  etByte base;             /* The base for radix conversion */
-  etByte flags;            /* One or more of FLAG_ constants below */
-  etByte type;             /* Conversion paradigm */
-  etByte charset;          /* Offset into aDigits[] of the digits string */
-  etByte prefix;           /* Offset into aPrefix[] of the prefix string */
-} et_info;
-
-/*
-** Allowed values for et_info.flags
-*/
-#define FLAG_SIGNED  1     /* True if the value to convert is signed */
-#define FLAG_INTERN  2     /* True if for internal use only */
-#define FLAG_STRING  4     /* Allow infinity precision */
-
-
-/*
-** The following table is searched linearly, so it is good to put the
-** most frequently used conversion types first.
-*/
-static const char aDigits[] = "0123456789ABCDEF0123456789abcdef";
-static const char aPrefix[] = "-x0\000X0";
-static const et_info fmtinfo[] = {
-  {  'd', 10, 1, etRADIX,      0,  0 },
-  {  's',  0, 4, etSTRING,     0,  0 },
-  {  'g',  0, 1, etGENERIC,    30, 0 },
-  {  'z',  0, 4, etDYNSTRING,  0,  0 },
-  {  'q',  0, 4, etSQLESCAPE,  0,  0 },
-  {  'Q',  0, 4, etSQLESCAPE2, 0,  0 },
-  {  'w',  0, 4, etSQLESCAPE3, 0,  0 },
-  {  'c',  0, 0, etCHARX,      0,  0 },
-  {  'o',  8, 0, etRADIX,      0,  2 },
-  {  'u', 10, 0, etRADIX,      0,  0 },
-  {  'x', 16, 0, etRADIX,      16, 1 },
-  {  'X', 16, 0, etRADIX,      0,  4 },
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  {  'f',  0, 1, etFLOAT,      0,  0 },
-  {  'e',  0, 1, etEXP,        30, 0 },
-  {  'E',  0, 1, etEXP,        14, 0 },
-  {  'G',  0, 1, etGENERIC,    14, 0 },
-#endif
-  {  'i', 10, 1, etRADIX,      0,  0 },
-  {  'n',  0, 0, etSIZE,       0,  0 },
-  {  '%',  0, 0, etPERCENT,    0,  0 },
-  {  'p', 16, 0, etPOINTER,    0,  1 },
-
-/* All the rest have the FLAG_INTERN bit set and are thus for internal
-** use only */
-  {  'r', 10, 3, etORDINAL,    0,  0 },
-};
-
-/*
-** If SQLITE_OMIT_FLOATING_POINT is defined, then none of the floating point
-** conversions will work.
-*/
-#ifndef SQLITE_OMIT_FLOATING_POINT
-/*
-** "*val" is a double such that 0.1 <= *val < 10.0
-** Return the ascii code for the leading digit of *val, then
-** multiply "*val" by 10.0 to renormalize.
-**
-** Example:
-**     input:     *val = 3.14159
-**     output:    *val = 1.4159    function return = '3'
-**
-** The counter *cnt is incremented each time.  After counter exceeds
-** 16 (the number of significant digits in a 64-bit float) '0' is
-** always returned.
-*/
-static char et_getdigit(LONGDOUBLE_TYPE *val, int *cnt){
-  int digit;
-  LONGDOUBLE_TYPE d;
-  if( (*cnt)<=0 ) return '0';
-  (*cnt)--;
-  digit = (int)*val;
-  d = digit;
-  digit += '0';
-  *val = (*val - d)*10.0;
-  return (char)digit;
-}
-#endif /* SQLITE_OMIT_FLOATING_POINT */
-
-/*
-** Set the StrAccum object to an error mode.
-*/
-static void setStrAccumError(StrAccum *p, u8 eError){
-  assert( eError==STRACCUM_NOMEM || eError==STRACCUM_TOOBIG );
-  p->accError = eError;
-  p->nAlloc = 0;
-}
-
-/*
-** Extra argument values from a PrintfArguments object
-*/
-static sqlite3_int64 getIntArg(PrintfArguments *p){
-  if( p->nArg<=p->nUsed ) return 0;
-  return sqlite3VdbeIntValue((Mem*)p->apArg[p->nUsed++]);
-}
-static double getDoubleArg(PrintfArguments *p){
-  if( p->nArg<=p->nUsed ) return 0.0;
-  return sqlite3VdbeRealValue((Mem*)p->apArg[p->nUsed++]);
-}
-static char *getTextArg(PrintfArguments *p){
-  if( p->nArg<=p->nUsed ) return 0;
-  return (char*)sqlite3ValueText(p->apArg[p->nUsed++], SQLITE_UTF8);
-}
-
-
-/*
-** On machines with a small stack size, you can redefine the
-** SQLITE_PRINT_BUF_SIZE to be something smaller, if desired.
-*/
-#ifndef SQLITE_PRINT_BUF_SIZE
-# define SQLITE_PRINT_BUF_SIZE 70
-#endif
-#define etBUFSIZE SQLITE_PRINT_BUF_SIZE  /* Size of the output buffer */
-
-/*
-** Render a string given by "fmt" into the StrAccum object.
-*/
-SQLITE_PRIVATE void sqlite3VXPrintf(
-  StrAccum *pAccum,          /* Accumulate results here */
-  u32 bFlags,                /* SQLITE_PRINTF_* flags */
-  const char *fmt,           /* Format string */
-  va_list ap                 /* arguments */
-){
-  int c;                     /* Next character in the format string */
-  char *bufpt;               /* Pointer to the conversion buffer */
-  int precision;             /* Precision of the current field */
-  int length;                /* Length of the field */
-  int idx;                   /* A general purpose loop counter */
-  int width;                 /* Width of the current field */
-  etByte flag_leftjustify;   /* True if "-" flag is present */
-  etByte flag_plussign;      /* True if "+" flag is present */
-  etByte flag_blanksign;     /* True if " " flag is present */
-  etByte flag_alternateform; /* True if "#" flag is present */
-  etByte flag_altform2;      /* True if "!" flag is present */
-  etByte flag_zeropad;       /* True if field width constant starts with zero */
-  etByte flag_long;          /* True if "l" flag is present */
-  etByte flag_longlong;      /* True if the "ll" flag is present */
-  etByte done;               /* Loop termination flag */
-  etByte xtype = 0;          /* Conversion paradigm */
-  u8 bArgList;               /* True for SQLITE_PRINTF_SQLFUNC */
-  u8 useIntern;              /* Ok to use internal conversions (ex: %T) */
-  char prefix;               /* Prefix character.  "+" or "-" or " " or '\0'. */
-  sqlite_uint64 longvalue;   /* Value for integer types */
-  LONGDOUBLE_TYPE realvalue; /* Value for real types */
-  const et_info *infop;      /* Pointer to the appropriate info structure */
-  char *zOut;                /* Rendering buffer */
-  int nOut;                  /* Size of the rendering buffer */
-  char *zExtra = 0;          /* Malloced memory used by some conversion */
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  int  exp, e2;              /* exponent of real numbers */
-  int nsd;                   /* Number of significant digits returned */
-  double rounder;            /* Used for rounding floating point values */
-  etByte flag_dp;            /* True if decimal point should be shown */
-  etByte flag_rtz;           /* True if trailing zeros should be removed */
-#endif
-  PrintfArguments *pArgList = 0; /* Arguments for SQLITE_PRINTF_SQLFUNC */
-  char buf[etBUFSIZE];       /* Conversion buffer */
-
-  bufpt = 0;
-  if( bFlags ){
-    if( (bArgList = (bFlags & SQLITE_PRINTF_SQLFUNC))!=0 ){
-      pArgList = va_arg(ap, PrintfArguments*);
-    }
-    useIntern = bFlags & SQLITE_PRINTF_INTERNAL;
-  }else{
-    bArgList = useIntern = 0;
-  }
-  for(; (c=(*fmt))!=0; ++fmt){
-    if( c!='%' ){
-      bufpt = (char *)fmt;
-#if HAVE_STRCHRNUL
-      fmt = strchrnul(fmt, '%');
-#else
-      do{ fmt++; }while( *fmt && *fmt != '%' );
-#endif
-      sqlite3StrAccumAppend(pAccum, bufpt, (int)(fmt - bufpt));
-      if( *fmt==0 ) break;
-    }
-    if( (c=(*++fmt))==0 ){
-      sqlite3StrAccumAppend(pAccum, "%", 1);
-      break;
-    }
-    /* Find out what flags are present */
-    flag_leftjustify = flag_plussign = flag_blanksign = 
-     flag_alternateform = flag_altform2 = flag_zeropad = 0;
-    done = 0;
-    do{
-      switch( c ){
-        case '-':   flag_leftjustify = 1;     break;
-        case '+':   flag_plussign = 1;        break;
-        case ' ':   flag_blanksign = 1;       break;
-        case '#':   flag_alternateform = 1;   break;
-        case '!':   flag_altform2 = 1;        break;
-        case '0':   flag_zeropad = 1;         break;
-        default:    done = 1;                 break;
-      }
-    }while( !done && (c=(*++fmt))!=0 );
-    /* Get the field width */
-    if( c=='*' ){
-      if( bArgList ){
-        width = (int)getIntArg(pArgList);
-      }else{
-        width = va_arg(ap,int);
-      }
-      if( width<0 ){
-        flag_leftjustify = 1;
-        width = width >= -2147483647 ? -width : 0;
-      }
-      c = *++fmt;
-    }else{
-      unsigned wx = 0;
-      while( c>='0' && c<='9' ){
-        wx = wx*10 + c - '0';
-        c = *++fmt;
-      }
-      testcase( wx>0x7fffffff );
-      width = wx & 0x7fffffff;
-    }
-
-    /* Get the precision */
-    if( c=='.' ){
-      c = *++fmt;
-      if( c=='*' ){
-        if( bArgList ){
-          precision = (int)getIntArg(pArgList);
-        }else{
-          precision = va_arg(ap,int);
-        }
-        c = *++fmt;
-        if( precision<0 ){
-          precision = precision >= -2147483647 ? -precision : -1;
-        }
-      }else{
-        unsigned px = 0;
-        while( c>='0' && c<='9' ){
-          px = px*10 + c - '0';
-          c = *++fmt;
-        }
-        testcase( px>0x7fffffff );
-        precision = px & 0x7fffffff;
-      }
-    }else{
-      precision = -1;
-    }
-    /* Get the conversion type modifier */
-    if( c=='l' ){
-      flag_long = 1;
-      c = *++fmt;
-      if( c=='l' ){
-        flag_longlong = 1;
-        c = *++fmt;
-      }else{
-        flag_longlong = 0;
-      }
-    }else{
-      flag_long = flag_longlong = 0;
-    }
-    /* Fetch the info entry for the field */
-    infop = &fmtinfo[0];
-    xtype = etINVALID;
-    for(idx=0; idx<ArraySize(fmtinfo); idx++){
-      if( c==fmtinfo[idx].fmttype ){
-        infop = &fmtinfo[idx];
-        if( useIntern || (infop->flags & FLAG_INTERN)==0 ){
-          xtype = infop->type;
-        }else{
-          return;
-        }
-        break;
-      }
-    }
-
-    /*
-    ** At this point, variables are initialized as follows:
-    **
-    **   flag_alternateform          TRUE if a '#' is present.
-    **   flag_altform2               TRUE if a '!' is present.
-    **   flag_plussign               TRUE if a '+' is present.
-    **   flag_leftjustify            TRUE if a '-' is present or if the
-    **                               field width was negative.
-    **   flag_zeropad                TRUE if the width began with 0.
-    **   flag_long                   TRUE if the letter 'l' (ell) prefixed
-    **                               the conversion character.
-    **   flag_longlong               TRUE if the letter 'll' (ell ell) prefixed
-    **                               the conversion character.
-    **   flag_blanksign              TRUE if a ' ' is present.
-    **   width                       The specified field width.  This is
-    **                               always non-negative.  Zero is the default.
-    **   precision                   The specified precision.  The default
-    **                               is -1.
-    **   xtype                       The class of the conversion.
-    **   infop                       Pointer to the appropriate info struct.
-    */
-    switch( xtype ){
-      case etPOINTER:
-        flag_longlong = sizeof(char*)==sizeof(i64);
-        flag_long = sizeof(char*)==sizeof(long int);
-        /* Fall through into the next case */
-      case etORDINAL:
-      case etRADIX:
-        if( infop->flags & FLAG_SIGNED ){
-          i64 v;
-          if( bArgList ){
-            v = getIntArg(pArgList);
-          }else if( flag_longlong ){
-            v = va_arg(ap,i64);
-          }else if( flag_long ){
-            v = va_arg(ap,long int);
-          }else{
-            v = va_arg(ap,int);
-          }
-          if( v<0 ){
-            if( v==SMALLEST_INT64 ){
-              longvalue = ((u64)1)<<63;
-            }else{
-              longvalue = -v;
-            }
-            prefix = '-';
-          }else{
-            longvalue = v;
-            if( flag_plussign )        prefix = '+';
-            else if( flag_blanksign )  prefix = ' ';
-            else                       prefix = 0;
-          }
-        }else{
-          if( bArgList ){
-            longvalue = (u64)getIntArg(pArgList);
-          }else if( flag_longlong ){
-            longvalue = va_arg(ap,u64);
-          }else if( flag_long ){
-            longvalue = va_arg(ap,unsigned long int);
-          }else{
-            longvalue = va_arg(ap,unsigned int);
-          }
-          prefix = 0;
-        }
-        if( longvalue==0 ) flag_alternateform = 0;
-        if( flag_zeropad && precision<width-(prefix!=0) ){
-          precision = width-(prefix!=0);
-        }
-        if( precision<etBUFSIZE-10 ){
-          nOut = etBUFSIZE;
-          zOut = buf;
-        }else{
-          nOut = precision + 10;
-          zOut = zExtra = sqlite3Malloc( nOut );
-          if( zOut==0 ){
-            setStrAccumError(pAccum, STRACCUM_NOMEM);
-            return;
-          }
-        }
-        bufpt = &zOut[nOut-1];
-        if( xtype==etORDINAL ){
-          static const char zOrd[] = "thstndrd";
-          int x = (int)(longvalue % 10);
-          if( x>=4 || (longvalue/10)%10==1 ){
-            x = 0;
-          }
-          *(--bufpt) = zOrd[x*2+1];
-          *(--bufpt) = zOrd[x*2];
-        }
-        {
-          const char *cset = &aDigits[infop->charset];
-          u8 base = infop->base;
-          do{                                           /* Convert to ascii */
-            *(--bufpt) = cset[longvalue%base];
-            longvalue = longvalue/base;
-          }while( longvalue>0 );
-        }
-        length = (int)(&zOut[nOut-1]-bufpt);
-        for(idx=precision-length; idx>0; idx--){
-          *(--bufpt) = '0';                             /* Zero pad */
-        }
-        if( prefix ) *(--bufpt) = prefix;               /* Add sign */
-        if( flag_alternateform && infop->prefix ){      /* Add "0" or "0x" */
-          const char *pre;
-          char x;
-          pre = &aPrefix[infop->prefix];
-          for(; (x=(*pre))!=0; pre++) *(--bufpt) = x;
-        }
-        length = (int)(&zOut[nOut-1]-bufpt);
-        break;
-      case etFLOAT:
-      case etEXP:
-      case etGENERIC:
-        if( bArgList ){
-          realvalue = getDoubleArg(pArgList);
-        }else{
-          realvalue = va_arg(ap,double);
-        }
-#ifdef SQLITE_OMIT_FLOATING_POINT
-        length = 0;
-#else
-        if( precision<0 ) precision = 6;         /* Set default precision */
-        if( realvalue<0.0 ){
-          realvalue = -realvalue;
-          prefix = '-';
-        }else{
-          if( flag_plussign )          prefix = '+';
-          else if( flag_blanksign )    prefix = ' ';
-          else                         prefix = 0;
-        }
-        if( xtype==etGENERIC && precision>0 ) precision--;
-        testcase( precision>0xfff );
-        for(idx=precision&0xfff, rounder=0.5; idx>0; idx--, rounder*=0.1){}
-        if( xtype==etFLOAT ) realvalue += rounder;
-        /* Normalize realvalue to within 10.0 > realvalue >= 1.0 */
-        exp = 0;
-        if( sqlite3IsNaN((double)realvalue) ){
-          bufpt = "NaN";
-          length = 3;
-          break;
-        }
-        if( realvalue>0.0 ){
-          LONGDOUBLE_TYPE scale = 1.0;
-          while( realvalue>=1e100*scale && exp<=350 ){ scale *= 1e100;exp+=100;}
-          while( realvalue>=1e10*scale && exp<=350 ){ scale *= 1e10; exp+=10; }
-          while( realvalue>=10.0*scale && exp<=350 ){ scale *= 10.0; exp++; }
-          realvalue /= scale;
-          while( realvalue<1e-8 ){ realvalue *= 1e8; exp-=8; }
-          while( realvalue<1.0 ){ realvalue *= 10.0; exp--; }
-          if( exp>350 ){
-            bufpt = buf;
-            buf[0] = prefix;
-            memcpy(buf+(prefix!=0),"Inf",4);
-            length = 3+(prefix!=0);
-            break;
-          }
-        }
-        bufpt = buf;
-        /*
-        ** If the field type is etGENERIC, then convert to either etEXP
-        ** or etFLOAT, as appropriate.
-        */
-        if( xtype!=etFLOAT ){
-          realvalue += rounder;
-          if( realvalue>=10.0 ){ realvalue *= 0.1; exp++; }
-        }
-        if( xtype==etGENERIC ){
-          flag_rtz = !flag_alternateform;
-          if( exp<-4 || exp>precision ){
-            xtype = etEXP;
-          }else{
-            precision = precision - exp;
-            xtype = etFLOAT;
-          }
-        }else{
-          flag_rtz = flag_altform2;
-        }
-        if( xtype==etEXP ){
-          e2 = 0;
-        }else{
-          e2 = exp;
-        }
-        if( MAX(e2,0)+(i64)precision+(i64)width > etBUFSIZE - 15 ){
-          bufpt = zExtra 
-              = sqlite3Malloc( MAX(e2,0)+(i64)precision+(i64)width+15 );
-          if( bufpt==0 ){
-            setStrAccumError(pAccum, STRACCUM_NOMEM);
-            return;
-          }
-        }
-        zOut = bufpt;
-        nsd = 16 + flag_altform2*10;
-        flag_dp = (precision>0 ?1:0) | flag_alternateform | flag_altform2;
-        /* The sign in front of the number */
-        if( prefix ){
-          *(bufpt++) = prefix;
-        }
-        /* Digits prior to the decimal point */
-        if( e2<0 ){
-          *(bufpt++) = '0';
-        }else{
-          for(; e2>=0; e2--){
-            *(bufpt++) = et_getdigit(&realvalue,&nsd);
-          }
-        }
-        /* The decimal point */
-        if( flag_dp ){
-          *(bufpt++) = '.';
-        }
-        /* "0" digits after the decimal point but before the first
-        ** significant digit of the number */
-        for(e2++; e2<0; precision--, e2++){
-          assert( precision>0 );
-          *(bufpt++) = '0';
-        }
-        /* Significant digits after the decimal point */
-        while( (precision--)>0 ){
-          *(bufpt++) = et_getdigit(&realvalue,&nsd);
-        }
-        /* Remove trailing zeros and the "." if no digits follow the "." */
-        if( flag_rtz && flag_dp ){
-          while( bufpt[-1]=='0' ) *(--bufpt) = 0;
-          assert( bufpt>zOut );
-          if( bufpt[-1]=='.' ){
-            if( flag_altform2 ){
-              *(bufpt++) = '0';
-            }else{
-              *(--bufpt) = 0;
-            }
-          }
-        }
-        /* Add the "eNNN" suffix */
-        if( xtype==etEXP ){
-          *(bufpt++) = aDigits[infop->charset];
-          if( exp<0 ){
-            *(bufpt++) = '-'; exp = -exp;
-          }else{
-            *(bufpt++) = '+';
-          }
-          if( exp>=100 ){
-            *(bufpt++) = (char)((exp/100)+'0');        /* 100's digit */
-            exp %= 100;
-          }
-          *(bufpt++) = (char)(exp/10+'0');             /* 10's digit */
-          *(bufpt++) = (char)(exp%10+'0');             /* 1's digit */
-        }
-        *bufpt = 0;
-
-        /* The converted number is in buf[] and zero terminated. Output it.
-        ** Note that the number is in the usual order, not reversed as with
-        ** integer conversions. */
-        length = (int)(bufpt-zOut);
-        bufpt = zOut;
-
-        /* Special case:  Add leading zeros if the flag_zeropad flag is
-        ** set and we are not left justified */
-        if( flag_zeropad && !flag_leftjustify && length < width){
-          int i;
-          int nPad = width - length;
-          for(i=width; i>=nPad; i--){
-            bufpt[i] = bufpt[i-nPad];
-          }
-          i = prefix!=0;
-          while( nPad-- ) bufpt[i++] = '0';
-          length = width;
-        }
-#endif /* !defined(SQLITE_OMIT_FLOATING_POINT) */
-        break;
-      case etSIZE:
-        if( !bArgList ){
-          *(va_arg(ap,int*)) = pAccum->nChar;
-        }
-        length = width = 0;
-        break;
-      case etPERCENT:
-        buf[0] = '%';
-        bufpt = buf;
-        length = 1;
-        break;
-      case etCHARX:
-        if( bArgList ){
-          bufpt = getTextArg(pArgList);
-          c = bufpt ? bufpt[0] : 0;
-        }else{
-          c = va_arg(ap,int);
-        }
-        if( precision>1 ){
-          width -= precision-1;
-          if( width>1 && !flag_leftjustify ){
-            sqlite3AppendChar(pAccum, width-1, ' ');
-            width = 0;
-          }
-          sqlite3AppendChar(pAccum, precision-1, c);
-        }
-        length = 1;
-        buf[0] = c;
-        bufpt = buf;
-        break;
-      case etSTRING:
-      case etDYNSTRING:
-        if( bArgList ){
-          bufpt = getTextArg(pArgList);
-          xtype = etSTRING;
-        }else{
-          bufpt = va_arg(ap,char*);
-        }
-        if( bufpt==0 ){
-          bufpt = "";
-        }else if( xtype==etDYNSTRING ){
-          zExtra = bufpt;
-        }
-        if( precision>=0 ){
-          for(length=0; length<precision && bufpt[length]; length++){}
-        }else{
-          length = sqlite3Strlen30(bufpt);
-        }
-        break;
-      case etSQLESCAPE:           /* Escape ' characters */
-      case etSQLESCAPE2:          /* Escape ' and enclose in '...' */
-      case etSQLESCAPE3: {        /* Escape " characters */
-        int i, j, k, n, isnull;
-        int needQuote;
-        char ch;
-        char q = ((xtype==etSQLESCAPE3)?'"':'\'');   /* Quote character */
-        char *escarg;
-
-        if( bArgList ){
-          escarg = getTextArg(pArgList);
-        }else{
-          escarg = va_arg(ap,char*);
-        }
-        isnull = escarg==0;
-        if( isnull ) escarg = (xtype==etSQLESCAPE2 ? "NULL" : "(NULL)");
-        k = precision;
-        for(i=n=0; k!=0 && (ch=escarg[i])!=0; i++, k--){
-          if( ch==q )  n++;
-        }
-        needQuote = !isnull && xtype==etSQLESCAPE2;
-        n += i + 3;
-        if( n>etBUFSIZE ){
-          bufpt = zExtra = sqlite3Malloc( n );
-          if( bufpt==0 ){
-            setStrAccumError(pAccum, STRACCUM_NOMEM);
-            return;
-          }
-        }else{
-          bufpt = buf;
-        }
-        j = 0;
-        if( needQuote ) bufpt[j++] = q;
-        k = i;
-        for(i=0; i<k; i++){
-          bufpt[j++] = ch = escarg[i];
-          if( ch==q ) bufpt[j++] = ch;
-        }
-        if( needQuote ) bufpt[j++] = q;
-        bufpt[j] = 0;
-        length = j;
-        /* The precision in %q and %Q means how many input characters to
-        ** consume, not the length of the output...
-        ** if( precision>=0 && precision<length ) length = precision; */
-        break;
-      }
-      default: {
-        assert( xtype==etINVALID );
-        return;
-      }
-    }/* End switch over the format type */
-    /*
-    ** The text of the conversion is pointed to by "bufpt" and is
-    ** "length" characters long.  The field width is "width".  Do
-    ** the output.
-    */
-    width -= length;
-    if( width>0 && !flag_leftjustify ) sqlite3AppendChar(pAccum, width, ' ');
-    sqlite3StrAccumAppend(pAccum, bufpt, length);
-    if( width>0 && flag_leftjustify ) sqlite3AppendChar(pAccum, width, ' ');
-
-    if( zExtra ){
-      sqlite3_free(zExtra);
-      zExtra = 0;
-    }
-  }/* End for loop over the format string */
-} /* End of function */
-
-/*
-** Enlarge the memory allocation on a StrAccum object so that it is
-** able to accept at least N more bytes of text.
-**
-** Return the number of bytes of text that StrAccum is able to accept
-** after the attempted enlargement.  The value returned might be zero.
-*/
-static int sqlite3StrAccumEnlarge(StrAccum *p, int N){
-  char *zNew;
-  assert( p->nChar+(i64)N >= p->nAlloc ); /* Only called if really needed */
-  if( p->accError ){
-    testcase(p->accError==STRACCUM_TOOBIG);
-    testcase(p->accError==STRACCUM_NOMEM);
-    return 0;
-  }
-  if( p->mxAlloc==0 ){
-    N = p->nAlloc - p->nChar - 1;
-    setStrAccumError(p, STRACCUM_TOOBIG);
-    return N;
-  }else{
-    char *zOld = (p->zText==p->zBase ? 0 : p->zText);
-    i64 szNew = p->nChar;
-    szNew += N + 1;
-    if( szNew+p->nChar<=p->mxAlloc ){
-      /* Force exponential buffer size growth as long as it does not overflow,
-      ** to avoid having to call this routine too often */
-      szNew += p->nChar;
-    }
-    if( szNew > p->mxAlloc ){
-      sqlite3StrAccumReset(p);
-      setStrAccumError(p, STRACCUM_TOOBIG);
-      return 0;
-    }else{
-      p->nAlloc = (int)szNew;
-    }
-    if( p->pBtree ){
-      zNew = sqlite3DbRealloc(p->pBtree, zOld, p->nAlloc);
-    }else{
-      zNew = sqlite3_realloc64(zOld, p->nAlloc);
-    }
-    if( zNew ){
-      assert( p->zText!=0 || p->nChar==0 );
-      if( zOld==0 && p->nChar>0 ) memcpy(zNew, p->zText, p->nChar);
-      p->zText = zNew;
-      p->nAlloc = sqlite3DbMallocSize(p->pBtree, zNew);
-    }else{
-      sqlite3StrAccumReset(p);
-      setStrAccumError(p, STRACCUM_NOMEM);
-      return 0;
-    }
-  }
-  return N;
-}
-
-/*
-** Append N copies of character c to the given string buffer.
-*/
-SQLITE_PRIVATE void sqlite3AppendChar(StrAccum *p, int N, char c){
-  testcase( p->nChar + (i64)N > 0x7fffffff );
-  if( p->nChar+(i64)N >= p->nAlloc && (N = sqlite3StrAccumEnlarge(p, N))<=0 ){
-    return;
-  }
-  while( (N--)>0 ) p->zText[p->nChar++] = c;
-}
-
-/*
-** The StrAccum "p" is not large enough to accept N new bytes of z[].
-** So enlarge if first, then do the append.
-**
-** This is a helper routine to sqlite3StrAccumAppend() that does special-case
-** work (enlarging the buffer) using tail recursion, so that the
-** sqlite3StrAccumAppend() routine can use fast calling semantics.
-*/
-static void SQLITE_NOINLINE enlargeAndAppend(StrAccum *p, const char *z, int N){
-  N = sqlite3StrAccumEnlarge(p, N);
-  if( N>0 ){
-    memcpy(&p->zText[p->nChar], z, N);
-    p->nChar += N;
-  }
-}
-
-/*
-** Append N bytes of text from z to the StrAccum object.  Increase the
-** size of the memory allocation for StrAccum if necessary.
-*/
-SQLITE_PRIVATE void sqlite3StrAccumAppend(StrAccum *p, const char *z, int N){
-  assert( z!=0 || N==0 );
-  assert( p->zText!=0 || p->nChar==0 || p->accError );
-  assert( N>=0 );
-  assert( p->accError==0 || p->nAlloc==0 );
-  if( p->nChar+N >= p->nAlloc ){
-    enlargeAndAppend(p,z,N);
-  }else{
-    assert( p->zText );
-    p->nChar += N;
-    memcpy(&p->zText[p->nChar-N], z, N);
-  }
-}
-
-/*
-** Finish off a string by making sure it is zero-terminated.
-** Return a pointer to the resulting string.  Return a NULL
-** pointer if any kind of error was encountered.
-*/
-SQLITE_PRIVATE char *sqlite3StrAccumFinish(StrAccum *p){
-  if( p->zText ){
-    p->zText[p->nChar] = 0;
-    if( p->mxAlloc>0 && p->zText==p->zBase ){
-      p->zText = sqlite3DbMallocRaw(p->pBtree, p->nChar+1 );
-      if( p->zText ){
-        memcpy(p->zText, p->zBase, p->nChar+1);
-      }else{
-        setStrAccumError(p, STRACCUM_NOMEM);
-      }
-    }
-  }
-  return p->zText;
-}
-
-/*
-** Reset an StrAccum string.  Reclaim all malloced memory.
-*/
-SQLITE_PRIVATE void sqlite3StrAccumReset(StrAccum *p){
-  if( p->zText!=p->zBase ){
-    sqlite3DbFree(p->pBtree, p->zText);
-  }
-  p->zText = 0;
-}
-
-/*
-** Initialize a string accumulator.
-**
-** p:     The accumulator to be initialized.
-** db:    Pointer to a database connection.  May be NULL.  Lookaside
-**        memory is used if not NULL. db->mallocFailed is set appropriately
-**        when not NULL.
-** zBase: An initial buffer.  May be NULL in which case the initial buffer
-**        is malloced.
-** n:     Size of zBase in bytes.  If total space requirements never exceed
-**        n then no memory allocations ever occur.
-** mx:    Maximum number of bytes to accumulate.  If mx==0 then no memory
-**        allocations will ever occur.
-*/
-SQLITE_PRIVATE void sqlite3StrAccumInit(StrAccum *p, Btree* pBtree, char *zBase, int n, int mx){
-  p->zText = p->zBase = zBase;
-  p->pBtree = pBtree;
-  p->nChar = 0;
-  p->nAlloc = n;
-  p->mxAlloc = mx;
-  p->accError = 0;
-}
-
-/*
-** Print into memory obtained from sqlite3_malloc().  Omit the internal
-** %-conversion extensions.
-*/
-SQLITE_PRIVATE char *sqlite3_vmprintf(const char *zFormat, va_list ap){
-  char *z;
-  char zBase[SQLITE_PRINT_BUF_SIZE];
-  StrAccum acc;
-
-#ifdef SQLITE_ENABLE_API_ARMOR  
-  if( zFormat==0 ){
-    (void)SQLITE_MISUSE_BKPT;
-    return 0;
-  }
-#endif
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  sqlite3StrAccumInit(&acc, 0, zBase, sizeof(zBase), SQLITE_MAX_LENGTH);
-  sqlite3VXPrintf(&acc, 0, zFormat, ap);
-  z = sqlite3StrAccumFinish(&acc);
-  return z;
-}
-
-/*
-** Print into memory obtained from sqlite3_malloc()().  Omit the internal
-** %-conversion extensions.
-*/
-SQLITE_PRIVATE char *sqlite3_mprintf(const char *zFormat, ...){
-  va_list ap;
-  char *z;
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return 0;
-#endif
-  va_start(ap, zFormat);
-  z = sqlite3_vmprintf(zFormat, ap);
-  va_end(ap);
-  return z;
-}
-
-/*
-** sqlite3_snprintf() works like snprintf() except that it ignores the
-** current locale settings.  This is important for SQLite because we
-** are not able to use a "," as the decimal point in place of "." as
-** specified by some locales.
-**
-** Oops:  The first two arguments of sqlite3_snprintf() are backwards
-** from the snprintf() standard.  Unfortunately, it is too late to change
-** this without breaking compatibility, so we just have to live with the
-** mistake.
-**
-** sqlite3_vsnprintf() is the varargs version.
-*/
-SQLITE_PRIVATE char *sqlite3_vsnprintf(int n, char *zBuf, const char *zFormat, va_list ap){
-  StrAccum acc;
-  if( n<=0 ) return zBuf;
-#ifdef SQLITE_ENABLE_API_ARMOR
-  if( zBuf==0 || zFormat==0 ) {
-    (void)SQLITE_MISUSE_BKPT;
-    if( zBuf ) zBuf[0] = 0;
-    return zBuf;
-  }
-#endif
-  sqlite3StrAccumInit(&acc, 0, zBuf, n, 0);
-  sqlite3VXPrintf(&acc, 0, zFormat, ap);
-  return sqlite3StrAccumFinish(&acc);
-}
-SQLITE_PRIVATE char *sqlite3_snprintf(int n, char *zBuf, const char *zFormat, ...){
-  char *z;
-  va_list ap;
-  va_start(ap,zFormat);
-  z = sqlite3_vsnprintf(n, zBuf, zFormat, ap);
-  va_end(ap);
-  return z;
-}
-
-/*
-** This is the routine that actually formats the sqlite3_log() message.
-** We house it in a separate routine from sqlite3_log() to avoid using
-** stack space on small-stack systems when logging is disabled.
-**
-** sqlite3_log() must render into a static buffer.  It cannot dynamically
-** allocate memory because it might be called while the memory allocator
-** mutex is held.
-**
-** sqlite3VXPrintf() might ask for *temporary* memory allocations for
-** certain format characters (%q) or for very large precisions or widths.
-** Care must be taken that any sqlite3_log() calls that occur while the
-** memory mutex is held do not use these mechanisms.
-*/
-static void renderLogMsg(int iErrCode, const char *zFormat, va_list ap){
-  StrAccum acc;                          /* String accumulator */
-  char zMsg[SQLITE_PRINT_BUF_SIZE*3];    /* Complete log message */
-
-  sqlite3StrAccumInit(&acc, 0, zMsg, sizeof(zMsg), 0);
-  sqlite3VXPrintf(&acc, 0, zFormat, ap);
-  sqlite3GlobalConfig.xLog(sqlite3GlobalConfig.pLogArg, iErrCode,
-                           sqlite3StrAccumFinish(&acc));
-}
-
-/*
-** Format and write a message to the log if logging is enabled.
-*/
-SQLITE_PRIVATE void sqlite3_log(int iErrCode, const char *zFormat, ...){
-  va_list ap;                             /* Vararg list */
-  if( sqlite3GlobalConfig.xLog ){
-    va_start(ap, zFormat);
-    renderLogMsg(iErrCode, zFormat, ap);
-    va_end(ap);
-  }
-}
-
-#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
-/*
-** A version of printf() that understands %lld.  Used for debugging.
-** The printf() built into some versions of windows does not understand %lld
-** and segfaults if you give it a long long int.
-*/
-SQLITE_PRIVATE void sqlite3DebugPrintf(const char *zFormat, ...){
-  va_list ap;
-  StrAccum acc;
-  char zBuf[500];
-  sqlite3StrAccumInit(&acc, 0, zBuf, sizeof(zBuf), 0);
-  va_start(ap,zFormat);
-  sqlite3VXPrintf(&acc, 0, zFormat, ap);
-  va_end(ap);
-  sqlite3StrAccumFinish(&acc);
-  fprintf(stdout,"%s", zBuf);
-  fflush(stdout);
-}
-#endif
-
-
-/*
-** variable-argument wrapper around sqlite3VXPrintf().  The bFlags argument
-** can contain the bit SQLITE_PRINTF_INTERNAL enable internal formats.
-*/
-SQLITE_PRIVATE void sqlite3XPrintf(StrAccum *p, u32 bFlags, const char *zFormat, ...){
-  va_list ap;
-  va_start(ap,zFormat);
-  sqlite3VXPrintf(p, bFlags, zFormat, ap);
-  va_end(ap);
-}
-
-/************** End of printf.c **********************************************/
-/************** Begin file random.c ******************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains code to implement a pseudo-random number
-** generator (PRNG) for SQLite.
-**
-** Random numbers are used by some of the database backends in order
-** to generate random integer keys for tables or random filenames.
-*/
-/* #include "sqliteInt.h" */
-
-
-/* All threads share a single random number generator.
-** This structure is the current state of the generator.
-*/
-static SQLITE_WSD struct sqlite3PrngType {
-  unsigned char isInit;          /* True if initialized */
-  unsigned char i, j;            /* State variables */
-  unsigned char s[256];          /* State variables */
-} sqlite3Prng;
-
-/*
-** Return N random bytes.
-*/
-SQLITE_PRIVATE void sqlite3_randomness(int N, void *pBuf){
-  unsigned char t;
-  unsigned char *zBuf = pBuf;
-
-  /* The "wsdPrng" macro will resolve to the pseudo-random number generator
-  ** state vector.  If writable static data is unsupported on the target,
-  ** we have to locate the state vector at run-time.  In the more common
-  ** case where writable static data is supported, wsdPrng can refer directly
-  ** to the "sqlite3Prng" state vector declared above.
-  */
-#ifdef SQLITE_OMIT_WSD
-  struct sqlite3PrngType *p = &GLOBAL(struct sqlite3PrngType, sqlite3Prng);
-# define wsdPrng p[0]
-#else
-# define wsdPrng sqlite3Prng
-#endif
-
-#if SQLITE_THREADSAFE
-  sqlite3_mutex *mutex;
-#endif
-
-#ifndef SQLITE_OMIT_AUTOINIT
-  if( sqlite3BtreeInitialize() ) return;
-#endif
-
-#if SQLITE_THREADSAFE
-  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
-#endif
-
-  sqlite3_mutex_enter(mutex);
-  if( N<=0 || pBuf==0 ){
-    wsdPrng.isInit = 0;
-    sqlite3_mutex_leave(mutex);
-    return;
-  }
-
-  /* Initialize the state of the random number generator once,
-  ** the first time this routine is called.  The seed value does
-  ** not need to contain a lot of randomness since we are not
-  ** trying to do secure encryption or anything like that...
-  **
-  ** Nothing in this file or anywhere else in SQLite does any kind of
-  ** encryption.  The RC4 algorithm is being used as a PRNG (pseudo-random
-  ** number generator) not as an encryption device.
-  */
-  if( !wsdPrng.isInit ){
-    int i;
-    char k[256];
-    wsdPrng.j = 0;
-    wsdPrng.i = 0;
-    sqlite3OsRandomness(sqlite3_vfs_find(0), 256, k);
-    for(i=0; i<256; i++){
-      wsdPrng.s[i] = (u8)i;
-    }
-    for(i=0; i<256; i++){
-      wsdPrng.j += wsdPrng.s[i] + k[i];
-      t = wsdPrng.s[wsdPrng.j];
-      wsdPrng.s[wsdPrng.j] = wsdPrng.s[i];
-      wsdPrng.s[i] = t;
-    }
-    wsdPrng.isInit = 1;
-  }
-
-  assert( N>0 );
-  do{
-    wsdPrng.i++;
-    t = wsdPrng.s[wsdPrng.i];
-    wsdPrng.j += t;
-    wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j];
-    wsdPrng.s[wsdPrng.j] = t;
-    t += wsdPrng.s[wsdPrng.i];
-    *(zBuf++) = wsdPrng.s[t];
-  }while( --N );
-  sqlite3_mutex_leave(mutex);
-}
-
-/************** End of random.c **********************************************/
-/************** Begin file util.c ********************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** Utility functions used throughout sqlite.
-**
-** This file contains functions for allocating memory, comparing
-** strings, and stuff like that.
-**
-*/
-/* #include "sqliteInt.h" */
-/* #include <stdarg.h> */
-#if HAVE_ISNAN || SQLITE_HAVE_ISNAN
-# include <math.h>
-#endif
-
-/*
-** Routine needed to support the testcase() macro.
-*/
-#ifdef SQLITE_COVERAGE_TEST
-SQLITE_PRIVATE void sqlite3Coverage(int x){
-  static unsigned dummy = 0;
-  dummy += (unsigned)x;
-}
-#endif
-
-#ifndef SQLITE_OMIT_FLOATING_POINT
-/*
-** Return true if the floating point value is Not a Number (NaN).
-**
-** Use the math library isnan() function if compiled with SQLITE_HAVE_ISNAN.
-** Otherwise, we have our own implementation that works on most systems.
-*/
-SQLITE_PRIVATE int sqlite3IsNaN(double x){
-  int rc;   /* The value return */
-#if !SQLITE_HAVE_ISNAN && !HAVE_ISNAN
-  /*
-  ** Systems that support the isnan() library function should probably
-  ** make use of it by compiling with -DSQLITE_HAVE_ISNAN.  But we have
-  ** found that many systems do not have a working isnan() function so
-  ** this implementation is provided as an alternative.
-  **
-  ** This NaN test sometimes fails if compiled on GCC with -ffast-math.
-  ** On the other hand, the use of -ffast-math comes with the following
-  ** warning:
-  **
-  **      This option [-ffast-math] should never be turned on by any
-  **      -O option since it can result in incorrect output for programs
-  **      which depend on an exact implementation of IEEE or ISO 
-  **      rules/specifications for math functions.
-  **
-  ** Under MSVC, this NaN test may fail if compiled with a floating-
-  ** point precision mode other than /fp:precise.  From the MSDN 
-  ** documentation:
-  **
-  **      The compiler [with /fp:precise] will properly handle comparisons 
-  **      involving NaN. For example, x != x evaluates to true if x is NaN 
-  **      ...
-  */
-#ifdef __FAST_MATH__
-# error SQLite will not work correctly with the -ffast-math option of GCC.
-#endif
-  volatile double y = x;
-  volatile double z = y;
-  rc = (y!=z);
-#else  /* if HAVE_ISNAN */
-  rc = isnan(x);
-#endif /* HAVE_ISNAN */
-  testcase( rc );
-  return rc;
-}
-#endif /* SQLITE_OMIT_FLOATING_POINT */
-
-/*
-** Compute a string length that is limited to what can be stored in
-** lower 30 bits of a 32-bit signed integer.
-**
-** The value returned will never be negative.  Nor will it ever be greater
-** than the actual length of the string.  For very long strings (greater
-** than 1GiB) the value returned might be less than the true string length.
-*/
-SQLITE_PRIVATE int sqlite3Strlen30(const char *z){
-  if( z==0 ) return 0;
-  return 0x3fffffff & (int)strlen(z);
-}
-
-/* Convenient short-hand */
-#define UpperToLower sqlite3UpperToLower
-
-int sqlite3StrICmp(const char *zLeft, const char *zRight){
-  unsigned char *a, *b;
-  int c;
-  a = (unsigned char *)zLeft;
-  b = (unsigned char *)zRight;
-  for(;;){
-    c = (int)UpperToLower[*a] - (int)UpperToLower[*b];
-    if( c || *a==0 ) break;
-    a++;
-    b++;
-  }
-  return c;
-}
-/*
-** The string z[] is an text representation of a real number.
-** Convert this string to a double and write it into *pResult.
-**
-** The string z[] is length bytes in length (bytes, not characters) and
-** uses the encoding enc.  The string is not necessarily zero-terminated.
-**
-** Return TRUE if the result is a valid real number (or integer) and FALSE
-** if the string is empty or contains extraneous text.  Valid numbers
-** are in one of these formats:
-**
-**    [+-]digits[E[+-]digits]
-**    [+-]digits.[digits][E[+-]digits]
-**    [+-].digits[E[+-]digits]
-**
-** Leading and trailing whitespace is ignored for the purpose of determining
-** validity.
-**
-** If some prefix of the input string is a valid number, this routine
-** returns FALSE but it still converts the prefix and writes the result
-** into *pResult.
-*/
-SQLITE_PRIVATE int sqlite3AtoF(const char *z, double *pResult, int length, u8 enc){
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  int incr;
-  const char *zEnd = z + length;
-  /* sign * significand * (10 ^ (esign * exponent)) */
-  int sign = 1;    /* sign of significand */
-  i64 s = 0;       /* significand */
-  int d = 0;       /* adjust exponent for shifting decimal point */
-  int esign = 1;   /* sign of exponent */
-  int e = 0;       /* exponent */
-  int eValid = 1;  /* True exponent is either not used or is well-formed */
-  double result;
-  int nDigits = 0;
-  int nonNum = 0;
-
-  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
-  *pResult = 0.0;   /* Default return value, in case of an error */
-
-  if( enc==SQLITE_UTF8 ){
-    incr = 1;
-  }else{
-    int i;
-    incr = 2;
-    assert( SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
-    for(i=3-enc; i<length && z[i]==0; i+=2){}
-    nonNum = i<length;
-    zEnd = z+i+enc-3;
-    z += (enc&1);
-  }
-
-  /* skip leading spaces */
-  while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
-  if( z>=zEnd ) return 0;
-
-  /* get sign of significand */
-  if( *z=='-' ){
-    sign = -1;
-    z+=incr;
-  }else if( *z=='+' ){
-    z+=incr;
-  }
-
-  /* skip leading zeroes */
-  while( z<zEnd && z[0]=='0' ) z+=incr, nDigits++;
-
-  /* copy max significant digits to significand */
-  while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
-    s = s*10 + (*z - '0');
-    z+=incr, nDigits++;
-  }
-
-  /* skip non-significant significand digits
-  ** (increase exponent by d to shift decimal left) */
-  while( z<zEnd && sqlite3Isdigit(*z) ) z+=incr, nDigits++, d++;
-  if( z>=zEnd ) goto do_atof_calc;
-
-  /* if decimal point is present */
-  if( *z=='.' ){
-    z+=incr;
-    /* copy digits from after decimal to significand
-    ** (decrease exponent by d to shift decimal right) */
-    while( z<zEnd && sqlite3Isdigit(*z) && s<((LARGEST_INT64-9)/10) ){
-      s = s*10 + (*z - '0');
-      z+=incr, nDigits++, d--;
-    }
-    /* skip non-significant digits */
-    while( z<zEnd && sqlite3Isdigit(*z) ) z+=incr, nDigits++;
-  }
-  if( z>=zEnd ) goto do_atof_calc;
-
-  /* if exponent is present */
-  if( *z=='e' || *z=='E' ){
-    z+=incr;
-    eValid = 0;
-    if( z>=zEnd ) goto do_atof_calc;
-    /* get sign of exponent */
-    if( *z=='-' ){
-      esign = -1;
-      z+=incr;
-    }else if( *z=='+' ){
-      z+=incr;
-    }
-    /* copy digits to exponent */
-    while( z<zEnd && sqlite3Isdigit(*z) ){
-      e = e<10000 ? (e*10 + (*z - '0')) : 10000;
-      z+=incr;
-      eValid = 1;
-    }
-  }
-
-  /* skip trailing spaces */
-  if( nDigits && eValid ){
-    while( z<zEnd && sqlite3Isspace(*z) ) z+=incr;
-  }
-
-do_atof_calc:
-  /* adjust exponent by d, and update sign */
-  e = (e*esign) + d;
-  if( e<0 ) {
-    esign = -1;
-    e *= -1;
-  } else {
-    esign = 1;
-  }
-
-  /* if 0 significand */
-  if( !s ) {
-    /* In the IEEE 754 standard, zero is signed.
-    ** Add the sign if we've seen at least one digit */
-    result = (sign<0 && nDigits) ? -(double)0 : (double)0;
-  } else {
-    /* attempt to reduce exponent */
-    if( esign>0 ){
-      while( s<(LARGEST_INT64/10) && e>0 ) e--,s*=10;
-    }else{
-      while( !(s%10) && e>0 ) e--,s/=10;
-    }
-
-    /* adjust the sign of significand */
-    s = sign<0 ? -s : s;
-
-    /* if exponent, scale significand as appropriate
-    ** and store in result. */
-    if( e ){
-      LONGDOUBLE_TYPE scale = 1.0;
-      /* attempt to handle extremely small/large numbers better */
-      if( e>307 && e<342 ){
-        while( e%308 ) { scale *= 1.0e+1; e -= 1; }
-        if( esign<0 ){
-          result = s / scale;
-          result /= 1.0e+308;
-        }else{
-          result = s * scale;
-          result *= 1.0e+308;
-        }
-      }else if( e>=342 ){
-        if( esign<0 ){
-          result = 0.0*s;
-        }else{
-          result = 1e308*1e308*s;  /* Infinity */
-        }
-      }else{
-        /* 1.0e+22 is the largest power of 10 than can be 
-        ** represented exactly. */
-        while( e%22 ) { scale *= 1.0e+1; e -= 1; }
-        while( e>0 ) { scale *= 1.0e+22; e -= 22; }
-        if( esign<0 ){
-          result = s / scale;
-        }else{
-          result = s * scale;
-        }
-      }
-    } else {
-      result = (double)s;
-    }
-  }
-
-  /* store the result */
-  *pResult = result;
-
-  /* return true if number and no extra non-whitespace chracters after */
-  return z>=zEnd && nDigits>0 && eValid && nonNum==0;
-#else
-  return !sqlite3Atoi64(z, pResult, length, enc);
-#endif /* SQLITE_OMIT_FLOATING_POINT */
-}
-
-/*
-** Compare the 19-character string zNum against the text representation
-** value 2^63:  9223372036854775808.  Return negative, zero, or positive
-** if zNum is less than, equal to, or greater than the string.
-** Note that zNum must contain exactly 19 characters.
-**
-** Unlike memcmp() this routine is guaranteed to return the difference
-** in the values of the last digit if the only difference is in the
-** last digit.  So, for example,
-**
-**      compare2pow63("9223372036854775800", 1)
-**
-** will return -8.
-*/
-static int compare2pow63(const char *zNum, int incr){
-  int c = 0;
-  int i;
-                    /* 012345678901234567 */
-  const char *pow63 = "922337203685477580";
-  for(i=0; c==0 && i<18; i++){
-    c = (zNum[i*incr]-pow63[i])*10;
-  }
-  if( c==0 ){
-    c = zNum[18*incr] - '8';
-    testcase( c==(-1) );
-    testcase( c==0 );
-    testcase( c==(+1) );
-  }
-  return c;
-}
-
-/*
-** Convert zNum to a 64-bit signed integer.  zNum must be decimal. This
-** routine does *not* accept hexadecimal notation.
-**
-** If the zNum value is representable as a 64-bit twos-complement 
-** integer, then write that value into *pNum and return 0.
-**
-** If zNum is exactly 9223372036854775808, return 2.  This special
-** case is broken out because while 9223372036854775808 cannot be a 
-** signed 64-bit integer, its negative -9223372036854775808 can be.
-**
-** If zNum is too big for a 64-bit integer and is not
-** 9223372036854775808  or if zNum contains any non-numeric text,
-** then return 1.
-**
-** length is the number of bytes in the string (bytes, not characters).
-** The string is not necessarily zero-terminated.  The encoding is
-** given by enc.
-*/
-SQLITE_PRIVATE int sqlite3Atoi64(const char *zNum, i64 *pNum, int length, u8 enc){
-  int incr;
-  u64 u = 0;
-  int neg = 0; /* assume positive */
-  int i;
-  int c = 0;
-  int nonNum = 0;
-  const char *zStart;
-  const char *zEnd = zNum + length;
-  assert( enc==SQLITE_UTF8 || enc==SQLITE_UTF16LE || enc==SQLITE_UTF16BE );
-  if( enc==SQLITE_UTF8 ){
-    incr = 1;
-  }else{
-    incr = 2;
-    assert( SQLITE_UTF16LE==2 && SQLITE_UTF16BE==3 );
-    for(i=3-enc; i<length && zNum[i]==0; i+=2){}
-    nonNum = i<length;
-    zEnd = zNum+i+enc-3;
-    zNum += (enc&1);
-  }
-  while( zNum<zEnd && sqlite3Isspace(*zNum) ) zNum+=incr;
-  if( zNum<zEnd ){
-    if( *zNum=='-' ){
-      neg = 1;
-      zNum+=incr;
-    }else if( *zNum=='+' ){
-      zNum+=incr;
-    }
-  }
-  zStart = zNum;
-  while( zNum<zEnd && zNum[0]=='0' ){ zNum+=incr; } /* Skip leading zeros. */
-  for(i=0; &zNum[i]<zEnd && (c=zNum[i])>='0' && c<='9'; i+=incr){
-    u = u*10 + c - '0';
-  }
-  if( u>LARGEST_INT64 ){
-    *pNum = neg ? SMALLEST_INT64 : LARGEST_INT64;
-  }else if( neg ){
-    *pNum = -(i64)u;
-  }else{
-    *pNum = (i64)u;
-  }
-  testcase( i==18 );
-  testcase( i==19 );
-  testcase( i==20 );
-  if( (c!=0 && &zNum[i]<zEnd) || (i==0 && zStart==zNum) || i>19*incr || nonNum ){
-    /* zNum is empty or contains non-numeric text or is longer
-    ** than 19 digits (thus guaranteeing that it is too large) */
-    return 1;
-  }else if( i<19*incr ){
-    /* Less than 19 digits, so we know that it fits in 64 bits */
-    assert( u<=LARGEST_INT64 );
-    return 0;
-  }else{
-    /* zNum is a 19-digit numbers.  Compare it against 9223372036854775808. */
-    c = compare2pow63(zNum, incr);
-    if( c<0 ){
-      /* zNum is less than 9223372036854775808 so it fits */
-      assert( u<=LARGEST_INT64 );
-      return 0;
-    }else if( c>0 ){
-      /* zNum is greater than 9223372036854775808 so it overflows */
-      return 1;
-    }else{
-      /* zNum is exactly 9223372036854775808.  Fits if negative.  The
-      ** special case 2 overflow if positive */
-      assert( u-1==LARGEST_INT64 );
-      return neg ? 0 : 2;
-    }
-  }
-}
-
-/*
-** The variable-length integer encoding is as follows:
-**
-** KEY:
-**         A = 0xxxxxxx    7 bits of data and one flag bit
-**         B = 1xxxxxxx    7 bits of data and one flag bit
-**         C = xxxxxxxx    8 bits of data
-**
-**  7 bits - A
-** 14 bits - BA
-** 21 bits - BBA
-** 28 bits - BBBA
-** 35 bits - BBBBA
-** 42 bits - BBBBBA
-** 49 bits - BBBBBBA
-** 56 bits - BBBBBBBA
-** 64 bits - BBBBBBBBC
-*/
-
-/*
-** Write a 64-bit variable-length integer to memory starting at p[0].
-** The length of data write will be between 1 and 9 bytes.  The number
-** of bytes written is returned.
-**
-** A variable-length integer consists of the lower 7 bits of each byte
-** for all bytes that have the 8th bit set and one byte with the 8th
-** bit clear.  Except, if we get to the 9th byte, it stores the full
-** 8 bits and is the last byte.
-*/
-static int SQLITE_NOINLINE putVarint64(unsigned char *p, u64 v){
-  int i, j, n;
-  u8 buf[10];
-  if( v & (((u64)0xff000000)<<32) ){
-    p[8] = (u8)v;
-    v >>= 8;
-    for(i=7; i>=0; i--){
-      p[i] = (u8)((v & 0x7f) | 0x80);
-      v >>= 7;
-    }
-    return 9;
-  }    
-  n = 0;
-  do{
-    buf[n++] = (u8)((v & 0x7f) | 0x80);
-    v >>= 7;
-  }while( v!=0 );
-  buf[0] &= 0x7f;
-  assert( n<=9 );
-  for(i=0, j=n-1; j>=0; j--, i++){
-    p[i] = buf[j];
-  }
-  return n;
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreePutVarint(unsigned char *p, u64 v){
-  if( v<=0x7f ){
-    p[0] = v&0x7f;
-    return 1;
-  }
-  if( v<=0x3fff ){
-    p[0] = ((v>>7)&0x7f)|0x80;
-    p[1] = v&0x7f;
-    return 2;
-  }
-  return putVarint64(p,v);
-}
-
-/*
-** Bitmasks used by sqlite3GetVarint().  These precomputed constants
-** are defined here rather than simply putting the constant expressions
-** inline in order to work around bugs in the RVT compiler.
-**
-** SLOT_2_0     A mask for  (0x7f<<14) | 0x7f
-**
-** SLOT_4_2_0   A mask for  (0x7f<<28) | SLOT_2_0
-*/
-#define SLOT_2_0     0x001fc07f
-#define SLOT_4_2_0   0xf01fc07f
-
-
-/*
-** Read a 64-bit variable-length integer from memory starting at p[0].
-** Return the number of bytes read.  The value is stored in *v.
-*/
-SQLITE_API u8 SQLITE_STDCALL sqlite3BtreeGetVarint(const unsigned char *p, u64 *v){
-  u32 a,b,s;
-
-  a = *p;
-  /* a: p0 (unmasked) */
-  if (!(a&0x80))
-  {
-    *v = a;
-    return 1;
-  }
-
-  p++;
-  b = *p;
-  /* b: p1 (unmasked) */
-  if (!(b&0x80))
-  {
-    a &= 0x7f;
-    a = a<<7;
-    a |= b;
-    *v = a;
-    return 2;
-  }
-
-  /* Verify that constants are precomputed correctly */
-  assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );
-  assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );
-
-  p++;
-  a = a<<14;
-  a |= *p;
-  /* a: p0<<14 | p2 (unmasked) */
-  if (!(a&0x80))
-  {
-    a &= SLOT_2_0;
-    b &= 0x7f;
-    b = b<<7;
-    a |= b;
-    *v = a;
-    return 3;
-  }
-
-  /* CSE1 from below */
-  a &= SLOT_2_0;
-  p++;
-  b = b<<14;
-  b |= *p;
-  /* b: p1<<14 | p3 (unmasked) */
-  if (!(b&0x80))
-  {
-    b &= SLOT_2_0;
-    /* moved CSE1 up */
-    /* a &= (0x7f<<14)|(0x7f); */
-    a = a<<7;
-    a |= b;
-    *v = a;
-    return 4;
-  }
-
-  /* a: p0<<14 | p2 (masked) */
-  /* b: p1<<14 | p3 (unmasked) */
-  /* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
-  /* moved CSE1 up */
-  /* a &= (0x7f<<14)|(0x7f); */
-  b &= SLOT_2_0;
-  s = a;
-  /* s: p0<<14 | p2 (masked) */
-
-  p++;
-  a = a<<14;
-  a |= *p;
-  /* a: p0<<28 | p2<<14 | p4 (unmasked) */
-  if (!(a&0x80))
-  {
-    /* we can skip these cause they were (effectively) done above in calc'ing s */
-    /* a &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
-    /* b &= (0x7f<<14)|(0x7f); */
-    b = b<<7;
-    a |= b;
-    s = s>>18;
-    *v = ((u64)s)<<32 | a;
-    return 5;
-  }
-
-  /* 2:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
-  s = s<<7;
-  s |= b;
-  /* s: p0<<21 | p1<<14 | p2<<7 | p3 (masked) */
-
-  p++;
-  b = b<<14;
-  b |= *p;
-  /* b: p1<<28 | p3<<14 | p5 (unmasked) */
-  if (!(b&0x80))
-  {
-    /* we can skip this cause it was (effectively) done above in calc'ing s */
-    /* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */
-    a &= SLOT_2_0;
-    a = a<<7;
-    a |= b;
-    s = s>>18;
-    *v = ((u64)s)<<32 | a;
-    return 6;
-  }
-
-  p++;
-  a = a<<14;
-  a |= *p;
-  /* a: p2<<28 | p4<<14 | p6 (unmasked) */
-  if (!(a&0x80))
-  {
-    a &= SLOT_4_2_0;
-    b &= SLOT_2_0;
-    b = b<<7;
-    a |= b;
-    s = s>>11;
-    *v = ((u64)s)<<32 | a;
-    return 7;
-  }
-
-  /* CSE2 from below */
-  a &= SLOT_2_0;
-  p++;
-  b = b<<14;
-  b |= *p;
-  /* b: p3<<28 | p5<<14 | p7 (unmasked) */
-  if (!(b&0x80))
-  {
-    b &= SLOT_4_2_0;
-    /* moved CSE2 up */
-    /* a &= (0x7f<<14)|(0x7f); */
-    a = a<<7;
-    a |= b;
-    s = s>>4;
-    *v = ((u64)s)<<32 | a;
-    return 8;
-  }
-
-  p++;
-  a = a<<15;
-  a |= *p;
-  /* a: p4<<29 | p6<<15 | p8 (unmasked) */
-
-  /* moved CSE2 up */
-  /* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */
-  b &= SLOT_2_0;
-  b = b<<8;
-  a |= b;
-
-  s = s<<4;
-  b = p[-4];
-  b &= 0x7f;
-  b = b>>3;
-  s |= b;
-
-  *v = ((u64)s)<<32 | a;
-
-  return 9;
-}
-
-/*
-** Read a 32-bit variable-length integer from memory starting at p[0].
-** Return the number of bytes read.  The value is stored in *v.
-**
-** If the varint stored in p[0] is larger than can fit in a 32-bit unsigned
-** integer, then set *v to 0xffffffff.
-**
-** A MACRO version, getVarint32, is provided which inlines the 
-** single-byte case.  All code should use the MACRO version as 
-** this function assumes the single-byte case has already been handled.
-*/
-SQLITE_API u8 SQLITE_STDCALL sqlite3BtreeGetVarint32(const unsigned char *p, u32 *v){
-  u32 a,b;
-
-  /* The 1-byte case.  Overwhelmingly the most common.  Handled inline
-  ** by the getVarin32() macro */
-  a = *p;
-  /* a: p0 (unmasked) */
-#ifndef getVarint32
-  if (!(a&0x80))
-  {
-    /* Values between 0 and 127 */
-    *v = a;
-    return 1;
-  }
-#endif
-
-  /* The 2-byte case */
-  p++;
-  b = *p;
-  /* b: p1 (unmasked) */
-  if (!(b&0x80))
-  {
-    /* Values between 128 and 16383 */
-    a &= 0x7f;
-    a = a<<7;
-    *v = a | b;
-    return 2;
-  }
-
-  /* The 3-byte case */
-  p++;
-  a = a<<14;
-  a |= *p;
-  /* a: p0<<14 | p2 (unmasked) */
-  if (!(a&0x80))
-  {
-    /* Values between 16384 and 2097151 */
-    a &= (0x7f<<14)|(0x7f);
-    b &= 0x7f;
-    b = b<<7;
-    *v = a | b;
-    return 3;
-  }
-
-  /* A 32-bit varint is used to store size information in btrees.
-  ** Objects are rarely larger than 2MiB limit of a 3-byte varint.
-  ** A 3-byte varint is sufficient, for example, to record the size
-  ** of a 1048569-byte BLOB or string.
-  **
-  ** We only unroll the first 1-, 2-, and 3- byte cases.  The very
-  ** rare larger cases can be handled by the slower 64-bit varint
-  ** routine.
-  */
-#if 1
-  {
-    u64 v64;
-    u8 n;
-
-    p -= 2;
-    n = sqlite3BtreeGetVarint(p, &v64);
-    assert( n>3 && n<=9 );
-    if( (v64 & SQLITE_MAX_U32)!=v64 ){
-      *v = 0xffffffff;
-    }else{
-      *v = (u32)v64;
-    }
-    return n;
-  }
-
-#else
-  /* For following code (kept for historical record only) shows an
-  ** unrolling for the 3- and 4-byte varint cases.  This code is
-  ** slightly faster, but it is also larger and much harder to test.
-  */
-  p++;
-  b = b<<14;
-  b |= *p;
-  /* b: p1<<14 | p3 (unmasked) */
-  if (!(b&0x80))
-  {
-    /* Values between 2097152 and 268435455 */
-    b &= (0x7f<<14)|(0x7f);
-    a &= (0x7f<<14)|(0x7f);
-    a = a<<7;
-    *v = a | b;
-    return 4;
-  }
-
-  p++;
-  a = a<<14;
-  a |= *p;
-  /* a: p0<<28 | p2<<14 | p4 (unmasked) */
-  if (!(a&0x80))
-  {
-    /* Values  between 268435456 and 34359738367 */
-    a &= SLOT_4_2_0;
-    b &= SLOT_4_2_0;
-    b = b<<7;
-    *v = a | b;
-    return 5;
-  }
-
-  /* We can only reach this point when reading a corrupt database
-  ** file.  In that case we are not in any hurry.  Use the (relatively
-  ** slow) general-purpose sqlite3BtreeGetVarint() routine to extract the
-  ** value. */
-  {
-    u64 v64;
-    u8 n;
-
-    p -= 4;
-    n = sqlite3BtreeGetVarint(p, &v64);
-    assert( n>5 && n<=9 );
-    *v = (u32)v64;
-    return n;
-  }
-#endif
-}
-
-/*
-** Return the number of bytes that will be needed to store the given
-** 64-bit integer.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeVarintLen(u64 v){
-  int i;
-  for(i=1; (v >>= 7)!=0; i++){ assert( i<9 ); }
-  return i;
-}
-
-
-/*
-** Read or write a four-byte big-endian integer value.
-*/
-SQLITE_PRIVATE u32 sqlite3Get4byte(const u8 *p){
-#if SQLITE_BYTEORDER==4321
-  u32 x;
-  memcpy(&x,p,4);
-  return x;
-#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(__GNUC__) && GCC_VERSION>=4003000
-  u32 x;
-  memcpy(&x,p,4);
-  return __builtin_bswap32(x);
-#elif SQLITE_BYTEORDER==1234 && !defined(SQLITE_DISABLE_INTRINSIC) \
-    && defined(_MSC_VER) && _MSC_VER>=1300
-  u32 x;
-  memcpy(&x,p,4);
-  return _byteswap_ulong(x);
-#else
-  testcase( p[0]&0x80 );
-  return ((unsigned)p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
-#endif
-}
-SQLITE_PRIVATE void sqlite3Put4byte(unsigned char *p, u32 v){
-#if SQLITE_BYTEORDER==4321
-  memcpy(p,&v,4);
-#elif SQLITE_BYTEORDER==1234 && defined(__GNUC__) && GCC_VERSION>=4003000
-  u32 x = __builtin_bswap32(v);
-  memcpy(p,&x,4);
-#elif SQLITE_BYTEORDER==1234 && defined(_MSC_VER) && _MSC_VER>=1300
-  u32 x = _byteswap_ulong(v);
-  memcpy(p,&x,4);
-#else
-  p[0] = (u8)(v>>24);
-  p[1] = (u8)(v>>16);
-  p[2] = (u8)(v>>8);
-  p[3] = (u8)v;
-#endif
-}
-
-/*
-** Log an error that is an API call on a connection pointer that should
-** not have been used.  The "type" of connection pointer is given as the
-** argument.  The zType is a word like "NULL" or "closed" or "invalid".
-*/
-static void logBadConnection(const char *zType){
-  sqlite3_log(SQLITE_MISUSE, 
-     "API call with %s database connection pointer",
-     zType
-  );
-}
-
-SQLITE_PRIVATE int sqlite3SafetyCheckSickOrOk(Btree *pBtree){
-  u32 magic;
-  magic = pBtree->magic;
-  if( magic!=SQLITE_MAGIC_SICK &&
-      magic!=SQLITE_MAGIC_OPEN &&
-      magic!=SQLITE_MAGIC_BUSY ){
-    testcase( sqlite3GlobalConfig.xLog!=0 );
-    logBadConnection("invalid");
-    return 0;
-  }else{
-    return 1;
-  }
-}
-
-/*
-** Compute the absolute value of a 32-bit signed integer, of possible.  Or 
-** if the integer has a value of -2147483648, return +2147483647
-*/
-SQLITE_PRIVATE int sqlite3AbsInt32(int x){
-  if( x>=0 ) return x;
-  if( x==(int)0x80000000 ) return 0x7fffffff;
-  return -x;
-}
-
-/************** End of util.c ************************************************/
-/************** Begin file os_unix.c *****************************************/
-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains the VFS implementation for unix-like operating systems
-** include Linux, MacOSX, *BSD, QNX, VxWorks, AIX, HPUX, and others.
-**
-** There are actually several different VFS implementations in this file.
-** The differences are in the way that file locking is done.  The default
-** implementation uses Posix Advisory Locks.  Alternative implementations
-** use flock(), dot-files, various proprietary locking schemas, or simply
-** skip locking all together.
-**
-** This source file is organized into divisions where the logic for various
-** subfunctions is contained within the appropriate division.  PLEASE
-** KEEP THE STRUCTURE OF THIS FILE INTACT.  New code should be placed
-** in the correct division and should be clearly labeled.
-**
-** The layout of divisions is as follows:
-**
-**   *  General-purpose declarations and utility functions.
-**   *  Unique file ID logic used by VxWorks.
-**   *  Various locking primitive implementations (all except proxy locking):
-**      + for Posix Advisory Locks
-**      + for no-op locks
-**      + for dot-file locks
-**      + for flock() locking
-**      + for named semaphore locks (VxWorks only)
-**      + for AFP filesystem locks (MacOSX only)
-**   *  sqlite3_file methods not associated with locking.
-**   *  Definitions of sqlite3_io_methods objects for all locking
-**      methods plus "finder" functions for each locking method.
-**   *  sqlite3_vfs method implementations.
-**   *  Locking primitives for the proxy uber-locking-method. (MacOSX only)
-**   *  Definitions of sqlite3_vfs objects for all locking methods
-**      plus implementations of sqlite3_os_init() and sqlite3_os_end().
-*/
-/* #include "sqliteInt.h" */
-#if SQLITE_OS_UNIX              /* This file is used on unix only */
-
-/*
-** There are various methods for file locking used for concurrency
-** control:
-**
-**   1. POSIX locking (the default),
-**   2. No locking,
-**   3. Dot-file locking,
-**   4. flock() locking,
-**   5. AFP locking (OSX only),
-**   6. Named POSIX semaphores (VXWorks only),
-**   7. proxy locking. (OSX only)
-**
-** Styles 4, 5, and 7 are only available of SQLITE_ENABLE_LOCKING_STYLE
-** is defined to 1.  The SQLITE_ENABLE_LOCKING_STYLE also enables automatic
-** selection of the appropriate locking style based on the filesystem
-** where the database is located.  
-*/
-#if !defined(SQLITE_ENABLE_LOCKING_STYLE)
-#  if defined(__APPLE__)
-#    define SQLITE_ENABLE_LOCKING_STYLE 1
-#  else
-#    define SQLITE_ENABLE_LOCKING_STYLE 0
-#  endif
-#endif
-
-/*
-** standard include files.
-*/
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <time.h>
-#include <sys/time.h>
-#include <errno.h>
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-# include <sys/mman.h>
-#endif
-
-#if SQLITE_ENABLE_LOCKING_STYLE
-# include <sys/ioctl.h>
-# include <sys/file.h>
-# include <sys/param.h>
-#endif /* SQLITE_ENABLE_LOCKING_STYLE */
-
-#if defined(__APPLE__) && ((__MAC_OS_X_VERSION_MIN_REQUIRED > 1050) || \
-                           (__IPHONE_OS_VERSION_MIN_REQUIRED > 2000))
-#  if (!defined(TARGET_OS_EMBEDDED) || (TARGET_OS_EMBEDDED==0)) \
-       && (!defined(TARGET_IPHONE_SIMULATOR) || (TARGET_IPHONE_SIMULATOR==0))
-#    define HAVE_GETHOSTUUID 1
-#  else
-#    warning "gethostuuid() is disabled."
-#  endif
-#endif
-
-
-#if OS_VXWORKS
-/* # include <sys/ioctl.h> */
-# include <semaphore.h>
-# include <limits.h>
-#endif /* OS_VXWORKS */
-
-#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
-# include <sys/mount.h>
-#endif
-
-#ifdef HAVE_UTIME
-# include <utime.h>
-#endif
-
-/*
-** Allowed values of unixFile.fsFlags
-*/
-#define SQLITE_FSFLAGS_IS_MSDOS     0x1
-
-/*
-** If we are to be thread-safe, include the pthreads header and define
-** the SQLITE_UNIX_THREADS macro.
-*/
-#if SQLITE_THREADSAFE
-/* # include <pthread.h> */
-# define SQLITE_UNIX_THREADS 1
-#endif
-
-/*
-** Default permissions when creating a new file
-*/
-#ifndef SQLITE_DEFAULT_FILE_PERMISSIONS
-# define SQLITE_DEFAULT_FILE_PERMISSIONS 0644
-#endif
-
-/*
-** Default permissions when creating auto proxy dir
-*/
-#ifndef SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
-# define SQLITE_DEFAULT_PROXYDIR_PERMISSIONS 0755
-#endif
-
-/*
-** Maximum supported path-length.
-*/
-#define MAX_PATHNAME 512
-
-/* Always cast the getpid() return type for compatibility with
-** kernel modules in VxWorks. */
-#define osGetpid(X) (pid_t)getpid()
-
-/*
-** Only set the lastErrno if the error code is a real error and not 
-** a normal expected return code of SQLITE_BUSY or SQLITE_OK
-*/
-#define IS_LOCK_ERROR(x)  ((x != SQLITE_OK) && (x != SQLITE_BUSY))
-
-/* Forward references */
-typedef struct unixShm unixShm;               /* Connection shared memory */
-typedef struct unixShmNode unixShmNode;       /* Shared memory instance */
-typedef struct unixInodeInfo unixInodeInfo;   /* An i-node */
-typedef struct UnixUnusedFd UnixUnusedFd;     /* An unused file descriptor */
-
-/*
-** Sometimes, after a file handle is closed by SQLite, the file descriptor
-** cannot be closed immediately. In these cases, instances of the following
-** structure are used to store the file descriptor while waiting for an
-** opportunity to either close or reuse it.
-*/
-struct UnixUnusedFd {
-  int fd;                   /* File descriptor to close */
-  int flags;                /* Flags this file descriptor was opened with */
-  UnixUnusedFd *pNext;      /* Next unused file descriptor on same file */
-};
-
-/*
-** The unixFile structure is subclass of sqlite3_file specific to the unix
-** VFS implementations.
-*/
-typedef struct unixFile unixFile;
-struct unixFile {
-  sqlite3_io_methods const *pMethod;  /* Always the first entry */
-  sqlite3_vfs *pVfs;                  /* The VFS that created this unixFile */
-  unixInodeInfo *pInode;              /* Info about locks on this inode */
-  int h;                              /* The file descriptor */
-  unsigned char eFileLock;            /* The type of lock held on this fd */
-  unsigned short int ctrlFlags;       /* Behavioral bits.  UNIXFILE_* flags */
-  int lastErrno;                      /* The unix errno from last I/O error */
-  void *lockingContext;               /* Locking style specific state */
-  UnixUnusedFd *pUnused;              /* Pre-allocated UnixUnusedFd */
-  const char *zPath;                  /* Name of the file */
-  unixShm *pShm;                      /* Shared memory segment information */
-  int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
-#if SQLITE_MAX_MMAP_SIZE>0
-  int nFetchOut;                      /* Number of outstanding xFetch refs */
-  sqlite3_int64 mmapSize;             /* Usable size of mapping at pMapRegion */
-  sqlite3_int64 mmapSizeActual;       /* Actual size of mapping at pMapRegion */
-  sqlite3_int64 mmapSizeMax;          /* Configured FCNTL_MMAP_SIZE value */
-  void *pMapRegion;                   /* Memory mapped region */
-#endif
-#ifdef __QNXNTO__
-  int sectorSize;                     /* Device sector size */
-  int deviceCharacteristics;          /* Precomputed device characteristics */
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE
-  int openFlags;                      /* The flags specified at open() */
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
-  unsigned fsFlags;                   /* cached details from statfs() */
-#endif
-#if OS_VXWORKS
-  struct vxworksFileId *pId;          /* Unique file ID */
-#endif
-#ifdef SQLITE_DEBUG
-  /* The next group of variables are used to track whether or not the
-  ** transaction counter in bytes 24-27 of database files are updated
-  ** whenever any part of the database changes.  An assertion fault will
-  ** occur if a file is updated without also updating the transaction
-  ** counter.  This test is made to avoid new problems similar to the
-  ** one described by ticket #3584. 
-  */
-  unsigned char transCntrChng;   /* True if the transaction counter changed */
-  unsigned char dbUpdate;        /* True if any part of database file changed */
-  unsigned char inNormalWrite;   /* True if in a normal write operation */
-
-#endif
-
-#ifdef SQLITE_TEST
-  /* In test mode, increase the size of this structure a bit so that 
-  ** it is larger than the struct CrashFile defined in test6.c.
-  */
-  char aPadding[32];
-#endif
-};
-
-/* This variable holds the process id (pid) from when the xRandomness()
-** method was called.  If xOpen() is called from a different process id,
-** indicating that a fork() has occurred, the PRNG will be reset.
-*/
-static pid_t randomnessPid = 0;
-
-/*
-** Allowed values for the unixFile.ctrlFlags bitmask:
-*/
-#define UNIXFILE_EXCL        0x01     /* Connections from one process only */
-#define UNIXFILE_RDONLY      0x02     /* Connection is read only */
-#define UNIXFILE_PERSIST_WAL 0x04     /* Persistent WAL mode */
-#ifndef SQLITE_DISABLE_DIRSYNC
-# define UNIXFILE_DIRSYNC    0x08     /* Directory sync needed */
-#else
-# define UNIXFILE_DIRSYNC    0x00
-#endif
-#define UNIXFILE_PSOW        0x10     /* SQLITE_IOCAP_POWERSAFE_OVERWRITE */
-#define UNIXFILE_DELETE      0x20     /* Delete on close */
-#define UNIXFILE_URI         0x40     /* Filename might have query parameters */
-#define UNIXFILE_NOLOCK      0x80     /* Do no file locking */
-#define UNIXFILE_WARNED    0x0100     /* verifyDbFile() warnings issued */
-#define UNIXFILE_BLOCK     0x0200     /* Next SHM lock might block */
-
-/*
-** Include code that is common to all os_*.c files
-*/
-/************** Include os_common.h in the middle of os_unix.c ***************/
-/************** Begin file os_common.h ***************************************/
-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains macros and a little bit of code that is common to
-** all of the platform-specific files (os_*.c) and is #included into those
-** files.
-**
-** This file should be #included by the os_*.c files only.  It is not a
-** general purpose header file.
-*/
-#ifndef _OS_COMMON_H_
-#define _OS_COMMON_H_
-
-/*
-** At least two bugs have slipped in because we changed the MEMORY_DEBUG
-** macro to SQLITE_DEBUG and some older makefiles have not yet made the
-** switch.  The following code should catch this problem at compile-time.
-*/
-#ifdef MEMORY_DEBUG
-# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
-#endif
-
-/*
-** Macros for performance tracing.  Normally turned off.  Only works
-** on i486 hardware.
-*/
-#ifdef SQLITE_PERFORMANCE_TRACE
-
-/* 
-** hwtime.h contains inline assembler code for implementing 
-** high-performance timing routines.
-*/
-/* #include "hwtime.h" */
-
-static sqlite_uint64 g_start;
-static sqlite_uint64 g_elapsed;
-#define TIMER_START       g_start=sqlite3Hwtime()
-#define TIMER_END         g_elapsed=sqlite3Hwtime()-g_start
-#define TIMER_ELAPSED     g_elapsed
-#else
-#define TIMER_START
-#define TIMER_END
-#define TIMER_ELAPSED     ((sqlite_uint64)0)
-#endif
-
-/*
-** If we compile with the SQLITE_TEST macro set, then the following block
-** of code will give us the ability to simulate a disk I/O error.  This
-** is used for testing the I/O recovery logic.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_io_error_hit = 0;            /* Total number of I/O Errors */
-SQLITE_PRIVATE int sqlite3_io_error_hardhit = 0;        /* Number of non-benign errors */
-SQLITE_PRIVATE int sqlite3_io_error_pending = 0;        /* Count down to first I/O error */
-SQLITE_PRIVATE int sqlite3_io_error_persist = 0;        /* True if I/O errors persist */
-SQLITE_PRIVATE int sqlite3_io_error_benign = 0;         /* True if errors are benign */
-SQLITE_PRIVATE int sqlite3_diskfull_pending = 0;
-SQLITE_PRIVATE int sqlite3_diskfull = 0;
-#define SimulateIOErrorBenign(X) sqlite3_io_error_benign=(X)
-#define SimulateIOError(CODE)  \
-  if( (sqlite3_io_error_persist && sqlite3_io_error_hit) \
-       || sqlite3_io_error_pending-- == 1 )  \
-              { local_ioerr(); CODE; }
-static void local_ioerr(){
-  IOTRACE(("IOERR\n"));
-  sqlite3_io_error_hit++;
-  if( !sqlite3_io_error_benign ) sqlite3_io_error_hardhit++;
-}
-#define SimulateDiskfullError(CODE) \
-   if( sqlite3_diskfull_pending ){ \
-     if( sqlite3_diskfull_pending == 1 ){ \
-       local_ioerr(); \
-       sqlite3_diskfull = 1; \
-       sqlite3_io_error_hit = 1; \
-       CODE; \
-     }else{ \
-       sqlite3_diskfull_pending--; \
-     } \
-   }
-#else
-#define SimulateIOErrorBenign(X)
-#define SimulateIOError(A)
-#define SimulateDiskfullError(A)
-#endif
-
-/*
-** When testing, keep a count of the number of open files.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_open_file_count = 0;
-#define OpenCounter(X)  sqlite3_open_file_count+=(X)
-#else
-#define OpenCounter(X)
-#endif
-
-#endif /* !defined(_OS_COMMON_H_) */
-
-/************** End of os_common.h *******************************************/
-/************** Continuing where we left off in os_unix.c ********************/
-
-/*
-** Define various macros that are missing from some systems.
-*/
-#ifndef O_LARGEFILE
-# define O_LARGEFILE 0
-#endif
-#ifdef SQLITE_DISABLE_LFS
-# undef O_LARGEFILE
-# define O_LARGEFILE 0
-#endif
-#ifndef O_NOFOLLOW
-# define O_NOFOLLOW 0
-#endif
-#ifndef O_BINARY
-# define O_BINARY 0
-#endif
-
-/*
-** The threadid macro resolves to the thread-id or to 0.  Used for
-** testing and debugging only.
-*/
-#if SQLITE_THREADSAFE
-#define threadid pthread_self()
-#else
-#define threadid 0
-#endif
-
-/*
-** HAVE_MREMAP defaults to true on Linux and false everywhere else.
-*/
-#if !defined(HAVE_MREMAP)
-# if defined(__linux__) && defined(_GNU_SOURCE)
-#  define HAVE_MREMAP 1
-# else
-#  define HAVE_MREMAP 0
-# endif
-#endif
-
-/*
-** Explicitly call the 64-bit version of lseek() on Android. Otherwise, lseek()
-** is the 32-bit version, even if _FILE_OFFSET_BITS=64 is defined.
-*/
-#ifdef __ANDROID__
-# define lseek lseek64
-#endif
-
-/*
-** Different Unix systems declare open() in different ways.  Same use
-** open(const char*,int,mode_t).  Others use open(const char*,int,...).
-** The difference is important when using a pointer to the function.
-**
-** The safest way to deal with the problem is to always use this wrapper
-** which always has the same well-defined interface.
-*/
-static int posixOpen(const char *zFile, int flags, int mode){
-  return open(zFile, flags, mode);
-}
-
-/*
-** On some systems, calls to fchown() will trigger a message in a security
-** log if they come from non-root processes.  So avoid calling fchown() if
-** we are not running as root.
-*/
-static int posixFchown(int fd, uid_t uid, gid_t gid){
-#if OS_VXWORKS
-  return 0;
-#else
-  return geteuid() ? 0 : fchown(fd,uid,gid);
-#endif
-}
-
-/* Forward reference */
-static int openDirectory(const char*, int*);
-static int unixGetpagesize(void);
-
-/*
-** Many system calls are accessed through pointer-to-functions so that
-** they may be overridden at runtime to facilitate fault injection during
-** testing and sandboxing.  The following array holds the names and pointers
-** to all overrideable system calls.
-*/
-static struct unix_syscall {
-  const char *zName;            /* Name of the system call */
-  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
-  sqlite3_syscall_ptr pDefault; /* Default value */
-} aSyscall[] = {
-  { "open",         (sqlite3_syscall_ptr)posixOpen,  0  },
-#define osOpen      ((int(*)(const char*,int,int))aSyscall[0].pCurrent)
-
-  { "close",        (sqlite3_syscall_ptr)close,      0  },
-#define osClose     ((int(*)(int))aSyscall[1].pCurrent)
-
-  { "access",       (sqlite3_syscall_ptr)access,     0  },
-#define osAccess    ((int(*)(const char*,int))aSyscall[2].pCurrent)
-
-  { "getcwd",       (sqlite3_syscall_ptr)getcwd,     0  },
-#define osGetcwd    ((char*(*)(char*,size_t))aSyscall[3].pCurrent)
-
-  { "stat",         (sqlite3_syscall_ptr)stat,       0  },
-#define osStat      ((int(*)(const char*,struct stat*))aSyscall[4].pCurrent)
-
-/*
-** The DJGPP compiler environment looks mostly like Unix, but it
-** lacks the fcntl() system call.  So redefine fcntl() to be something
-** that always succeeds.  This means that locking does not occur under
-** DJGPP.  But it is DOS - what did you expect?
-*/
-#ifdef __DJGPP__
-  { "fstat",        0,                 0  },
-#define osFstat(a,b,c)    0
-#else     
-  { "fstat",        (sqlite3_syscall_ptr)fstat,      0  },
-#define osFstat     ((int(*)(int,struct stat*))aSyscall[5].pCurrent)
-#endif
-
-  { "ftruncate",    (sqlite3_syscall_ptr)ftruncate,  0  },
-#define osFtruncate ((int(*)(int,off_t))aSyscall[6].pCurrent)
-
-  { "fcntl",        (sqlite3_syscall_ptr)fcntl,      0  },
-#define osFcntl     ((int(*)(int,int,...))aSyscall[7].pCurrent)
-
-  { "read",         (sqlite3_syscall_ptr)read,       0  },
-#define osRead      ((ssize_t(*)(int,void*,size_t))aSyscall[8].pCurrent)
-
-#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
-  { "pread",        (sqlite3_syscall_ptr)pread,      0  },
-#else
-  { "pread",        (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPread     ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[9].pCurrent)
-
-#if defined(USE_PREAD64)
-  { "pread64",      (sqlite3_syscall_ptr)pread64,    0  },
-#else
-  { "pread64",      (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPread64   ((ssize_t(*)(int,void*,size_t,off_t))aSyscall[10].pCurrent)
-
-  { "write",        (sqlite3_syscall_ptr)write,      0  },
-#define osWrite     ((ssize_t(*)(int,const void*,size_t))aSyscall[11].pCurrent)
-
-#if defined(USE_PREAD) || SQLITE_ENABLE_LOCKING_STYLE
-  { "pwrite",       (sqlite3_syscall_ptr)pwrite,     0  },
-#else
-  { "pwrite",       (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPwrite    ((ssize_t(*)(int,const void*,size_t,off_t))\
-                    aSyscall[12].pCurrent)
-
-#if defined(USE_PREAD64)
-  { "pwrite64",     (sqlite3_syscall_ptr)pwrite64,   0  },
-#else
-  { "pwrite64",     (sqlite3_syscall_ptr)0,          0  },
-#endif
-#define osPwrite64  ((ssize_t(*)(int,const void*,size_t,off_t))\
-                    aSyscall[13].pCurrent)
-
-  { "fchmod",       (sqlite3_syscall_ptr)fchmod,     0  },
-#define osFchmod    ((int(*)(int,mode_t))aSyscall[14].pCurrent)
-
-#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
-  { "fallocate",    (sqlite3_syscall_ptr)posix_fallocate,  0 },
-#else
-  { "fallocate",    (sqlite3_syscall_ptr)0,                0 },
-#endif
-#define osFallocate ((int(*)(int,off_t,off_t))aSyscall[15].pCurrent)
-
-  { "unlink",       (sqlite3_syscall_ptr)unlink,           0 },
-#define osUnlink    ((int(*)(const char*))aSyscall[16].pCurrent)
-
-  { "openDirectory",    (sqlite3_syscall_ptr)openDirectory,      0 },
-#define osOpenDirectory ((int(*)(const char*,int*))aSyscall[17].pCurrent)
-
-  { "mkdir",        (sqlite3_syscall_ptr)mkdir,           0 },
-#define osMkdir     ((int(*)(const char*,mode_t))aSyscall[18].pCurrent)
-
-  { "rmdir",        (sqlite3_syscall_ptr)rmdir,           0 },
-#define osRmdir     ((int(*)(const char*))aSyscall[19].pCurrent)
-
-  { "fchown",       (sqlite3_syscall_ptr)posixFchown,     0 },
-#define osFchown    ((int(*)(int,uid_t,gid_t))aSyscall[20].pCurrent)
-
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-  { "mmap",       (sqlite3_syscall_ptr)mmap,     0 },
-#define osMmap ((void*(*)(void*,size_t,int,int,int,off_t))aSyscall[21].pCurrent)
-
-  { "munmap",       (sqlite3_syscall_ptr)munmap,          0 },
-#define osMunmap ((void*(*)(void*,size_t))aSyscall[22].pCurrent)
-
-#if HAVE_MREMAP
-  { "mremap",       (sqlite3_syscall_ptr)mremap,          0 },
-#else
-  { "mremap",       (sqlite3_syscall_ptr)0,               0 },
-#endif
-#define osMremap ((void*(*)(void*,size_t,size_t,int,...))aSyscall[23].pCurrent)
-  { "getpagesize",  (sqlite3_syscall_ptr)unixGetpagesize, 0 },
-#define osGetpagesize ((int(*)(void))aSyscall[24].pCurrent)
-
-#endif
-
-}; /* End of the overrideable system calls */
-
-/*
-** This is the xSetSystemCall() method of sqlite3_vfs for all of the
-** "unix" VFSes.  Return SQLITE_OK opon successfully updating the
-** system call pointer, or SQLITE_NOTFOUND if there is no configurable
-** system call named zName.
-*/
-static int unixSetSystemCall(
-  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
-  const char *zName,            /* Name of system call to override */
-  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
-){
-  unsigned int i;
-  int rc = SQLITE_NOTFOUND;
-
-  UNUSED_PARAMETER(pNotUsed);
-  if( zName==0 ){
-    /* If no zName is given, restore all system calls to their default
-    ** settings and return NULL
-    */
-    rc = SQLITE_OK;
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( aSyscall[i].pDefault ){
-        aSyscall[i].pCurrent = aSyscall[i].pDefault;
-      }
-    }
-  }else{
-    /* If zName is specified, operate on only the one system call
-    ** specified.
-    */
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ){
-        if( aSyscall[i].pDefault==0 ){
-          aSyscall[i].pDefault = aSyscall[i].pCurrent;
-        }
-        rc = SQLITE_OK;
-        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
-        aSyscall[i].pCurrent = pNewFunc;
-        break;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Return the value of a system call.  Return NULL if zName is not a
-** recognized system call name.  NULL is also returned if the system call
-** is currently undefined.
-*/
-static sqlite3_syscall_ptr unixGetSystemCall(
-  sqlite3_vfs *pNotUsed,
-  const char *zName
-){
-  unsigned int i;
-
-  UNUSED_PARAMETER(pNotUsed);
-  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
-  }
-  return 0;
-}
-
-/*
-** Return the name of the first system call after zName.  If zName==NULL
-** then return the name of the first system call.  Return NULL if zName
-** is the last system call or if zName is not the name of a valid
-** system call.
-*/
-static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
-  int i = -1;
-
-  UNUSED_PARAMETER(p);
-  if( zName ){
-    for(i=0; i<ArraySize(aSyscall)-1; i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
-    }
-  }
-  for(i++; i<ArraySize(aSyscall); i++){
-    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
-  }
-  return 0;
-}
-
-/*
-** Do not accept any file descriptor less than this value, in order to avoid
-** opening database file using file descriptors that are commonly used for 
-** standard input, output, and error.
-*/
-#ifndef SQLITE_MINIMUM_FILE_DESCRIPTOR
-# define SQLITE_MINIMUM_FILE_DESCRIPTOR 3
-#endif
-
-/*
-** Invoke open().  Do so multiple times, until it either succeeds or
-** fails for some reason other than EINTR.
-**
-** If the file creation mode "m" is 0 then set it to the default for
-** SQLite.  The default is SQLITE_DEFAULT_FILE_PERMISSIONS (normally
-** 0644) as modified by the system umask.  If m is not 0, then
-** make the file creation mode be exactly m ignoring the umask.
-**
-** The m parameter will be non-zero only when creating -wal, -journal,
-** and -shm files.  We want those files to have *exactly* the same
-** permissions as their original database, unadulterated by the umask.
-** In that way, if a database file is -rw-rw-rw or -rw-rw-r-, and a
-** transaction crashes and leaves behind hot journals, then any
-** process that is able to write to the database will also be able to
-** recover the hot journals.
-*/
-static int robust_open(const char *z, int f, mode_t m){
-  int fd;
-  mode_t m2 = m ? m : SQLITE_DEFAULT_FILE_PERMISSIONS;
-  while(1){
-#if defined(O_CLOEXEC)
-    fd = osOpen(z,f|O_CLOEXEC,m2);
-#else
-    fd = osOpen(z,f,m2);
-#endif
-    if( fd<0 ){
-      if( errno==EINTR ) continue;
-      break;
-    }
-    if( fd>=SQLITE_MINIMUM_FILE_DESCRIPTOR ) break;
-    osClose(fd);
-//    sqlite3_log(SQLITE_WARNING, 
-//                "attempt to open \"%s\" as file descriptor %d", z, fd);
-    fd = -1;
-    if( osOpen("/dev/null", f, m)<0 ) break;
-  }
-  if( fd>=0 ){
-    if( m!=0 ){
-      struct stat statbuf;
-      if( osFstat(fd, &statbuf)==0 
-       && statbuf.st_size==0
-       && (statbuf.st_mode&0777)!=m 
-      ){
-        osFchmod(fd, m);
-      }
-    }
-#if defined(FD_CLOEXEC) && (!defined(O_CLOEXEC) || O_CLOEXEC==0)
-    osFcntl(fd, F_SETFD, osFcntl(fd, F_GETFD, 0) | FD_CLOEXEC);
-#endif
-  }
-  return fd;
-}
-
-/*
-** Helper functions to obtain and relinquish the global mutex. The
-** global mutex is used to protect the unixInodeInfo and
-** vxworksFileId objects used by this file, all of which may be 
-** shared by multiple threads.
-**
-** Function unixMutexHeld() is used to assert() that the global mutex 
-** is held when required. This function is only used as part of assert() 
-** statements. e.g.
-**
-**   unixEnterMutex()
-**     assert( unixMutexHeld() );
-**   unixEnterLeave()
-*/
-static void unixEnterMutex(void){
-  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-static void unixLeaveMutex(void){
-  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-
-#ifndef NDEBUG
-static int unixMutexHeld(void) {
-  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-#endif
-
-
-
-#ifdef SQLITE_HAVE_OS_TRACE
-/*
-** Helper function for printing out trace information from debugging
-** binaries. This returns the string representation of the supplied
-** integer lock-type.
-*/
-static const char *azFileLock(int eFileLock){
-  switch( eFileLock ){
-    case NO_LOCK: return "NONE";
-    case SHARED_LOCK: return "SHARED";
-    case RESERVED_LOCK: return "RESERVED";
-    case PENDING_LOCK: return "PENDING";
-    case EXCLUSIVE_LOCK: return "EXCLUSIVE";
-  }
-  return "ERROR";
-}
-#endif
-
-#ifdef SQLITE_LOCK_TRACE
-/*
-** Print out information about all locking operations.
-**
-** This routine is used for troubleshooting locks on multithreaded
-** platforms.  Enable by compiling with the -DSQLITE_LOCK_TRACE
-** command-line option on the compiler.  This code is normally
-** turned off.
-*/
-static int lockTrace(int fd, int op, struct flock *p){
-  char *zOpName, *zType;
-  int s;
-  int savedErrno;
-  if( op==F_GETLK ){
-    zOpName = "GETLK";
-  }else if( op==F_SETLK ){
-    zOpName = "SETLK";
-  }else{
-    s = osFcntl(fd, op, p);
-    sqlite3DebugPrintf("fcntl unknown %d %d %d\n", fd, op, s);
-    return s;
-  }
-  if( p->l_type==F_RDLCK ){
-    zType = "RDLCK";
-  }else if( p->l_type==F_WRLCK ){
-    zType = "WRLCK";
-  }else if( p->l_type==F_UNLCK ){
-    zType = "UNLCK";
-  }else{
-    assert( 0 );
-  }
-  assert( p->l_whence==SEEK_SET );
-  s = osFcntl(fd, op, p);
-  savedErrno = errno;
-  sqlite3DebugPrintf("fcntl %d %d %s %s %d %d %d %d\n",
-     threadid, fd, zOpName, zType, (int)p->l_start, (int)p->l_len,
-     (int)p->l_pid, s);
-  if( s==(-1) && op==F_SETLK && (p->l_type==F_RDLCK || p->l_type==F_WRLCK) ){
-    struct flock l2;
-    l2 = *p;
-    osFcntl(fd, F_GETLK, &l2);
-    if( l2.l_type==F_RDLCK ){
-      zType = "RDLCK";
-    }else if( l2.l_type==F_WRLCK ){
-      zType = "WRLCK";
-    }else if( l2.l_type==F_UNLCK ){
-      zType = "UNLCK";
-    }else{
-      assert( 0 );
-    }
-    sqlite3DebugPrintf("fcntl-failure-reason: %s %d %d %d\n",
-       zType, (int)l2.l_start, (int)l2.l_len, (int)l2.l_pid);
-  }
-  errno = savedErrno;
-  return s;
-}
-#undef osFcntl
-#define osFcntl lockTrace
-#endif /* SQLITE_LOCK_TRACE */
-
-/*
-** Retry ftruncate() calls that fail due to EINTR
-**
-** All calls to ftruncate() within this file should be made through
-** this wrapper.  On the Android platform, bypassing the logic below
-** could lead to a corrupt database.
-*/
-static int robust_ftruncate(int h, sqlite3_int64 sz){
-  int rc;
-#ifdef __ANDROID__
-  /* On Android, ftruncate() always uses 32-bit offsets, even if 
-  ** _FILE_OFFSET_BITS=64 is defined. This means it is unsafe to attempt to
-  ** truncate a file to any size larger than 2GiB. Silently ignore any
-  ** such attempts.  */
-  if( sz>(sqlite3_int64)0x7FFFFFFF ){
-    rc = SQLITE_OK;
-  }else
-#endif
-  do{ rc = osFtruncate(h,sz); }while( rc<0 && errno==EINTR );
-  return rc;
-}
-
-/*
-** This routine translates a standard POSIX errno code into something
-** useful to the clients of the sqlite3 functions.  Specifically, it is
-** intended to translate a variety of "try again" errors into SQLITE_BUSY
-** and a variety of "please close the file descriptor NOW" errors into 
-** SQLITE_IOERR
-** 
-** Errors during initialization of locks, or file system support for locks,
-** should handle ENOLCK, ENOTSUP, EOPNOTSUPP separately.
-*/
-static int sqliteErrorFromPosixError(int posixError, int sqliteIOErr) {
-  switch (posixError) {
-#if 0
-  /* At one point this code was not commented out. In theory, this branch
-  ** should never be hit, as this function should only be called after
-  ** a locking-related function (i.e. fcntl()) has returned non-zero with
-  ** the value of errno as the first argument. Since a system call has failed,
-  ** errno should be non-zero.
-  **
-  ** Despite this, if errno really is zero, we still don't want to return
-  ** SQLITE_OK. The system call failed, and *some* SQLite error should be
-  ** propagated back to the caller. Commenting this branch out means errno==0
-  ** will be handled by the "default:" case below.
-  */
-  case 0: 
-    return SQLITE_OK;
-#endif
-
-  case EAGAIN:
-  case ETIMEDOUT:
-  case EBUSY:
-  case EINTR:
-  case ENOLCK:  
-    /* random NFS retry error, unless during file system support 
-     * introspection, in which it actually means what it says */
-    return SQLITE_BUSY;
-    
-  case EACCES: 
-    /* EACCES is like EAGAIN during locking operations, but not any other time*/
-    if( (sqliteIOErr == SQLITE_IOERR_LOCK) || 
-        (sqliteIOErr == SQLITE_IOERR_UNLOCK) || 
-        (sqliteIOErr == SQLITE_IOERR_RDLOCK) ||
-        (sqliteIOErr == SQLITE_IOERR_CHECKRESERVEDLOCK) ){
-      return SQLITE_BUSY;
-    }
-    /* else fall through */
-  case EPERM: 
-    return SQLITE_PERM;
-    
-#if EOPNOTSUPP!=ENOTSUP
-  case EOPNOTSUPP: 
-    /* something went terribly awry, unless during file system support 
-     * introspection, in which it actually means what it says */
-#endif
-#ifdef ENOTSUP
-  case ENOTSUP: 
-    /* invalid fd, unless during file system support introspection, in which 
-     * it actually means what it says */
-#endif
-  case EIO:
-  case EBADF:
-  case EINVAL:
-  case ENOTCONN:
-  case ENODEV:
-  case ENXIO:
-  case ENOENT:
-#ifdef ESTALE                     /* ESTALE is not defined on Interix systems */
-  case ESTALE:
-#endif
-  case ENOSYS:
-    /* these should force the client to close the file and reconnect */
-    
-  default: 
-    return sqliteIOErr;
-  }
-}
-
-
-/******************************************************************************
-****************** Begin Unique File ID Utility Used By VxWorks ***************
-**
-** On most versions of unix, we can get a unique ID for a file by concatenating
-** the device number and the inode number.  But this does not work on VxWorks.
-** On VxWorks, a unique file id must be based on the canonical filename.
-**
-** A pointer to an instance of the following structure can be used as a
-** unique file ID in VxWorks.  Each instance of this structure contains
-** a copy of the canonical filename.  There is also a reference count.  
-** The structure is reclaimed when the number of pointers to it drops to
-** zero.
-**
-** There are never very many files open at one time and lookups are not
-** a performance-critical path, so it is sufficient to put these
-** structures on a linked list.
-*/
-struct vxworksFileId {
-  struct vxworksFileId *pNext;  /* Next in a list of them all */
-  int nRef;                     /* Number of references to this one */
-  int nName;                    /* Length of the zCanonicalName[] string */
-  char *zCanonicalName;         /* Canonical filename */
-};
-
-#if OS_VXWORKS
-/* 
-** All unique filenames are held on a linked list headed by this
-** variable:
-*/
-static struct vxworksFileId *vxworksFileList = 0;
-
-/*
-** Simplify a filename into its canonical form
-** by making the following changes:
-**
-**  * removing any trailing and duplicate /
-**  * convert /./ into just /
-**  * convert /A/../ where A is any simple name into just /
-**
-** Changes are made in-place.  Return the new name length.
-**
-** The original filename is in z[0..n-1].  Return the number of
-** characters in the simplified name.
-*/
-static int vxworksSimplifyName(char *z, int n){
-  int i, j;
-  while( n>1 && z[n-1]=='/' ){ n--; }
-  for(i=j=0; i<n; i++){
-    if( z[i]=='/' ){
-      if( z[i+1]=='/' ) continue;
-      if( z[i+1]=='.' && i+2<n && z[i+2]=='/' ){
-        i += 1;
-        continue;
-      }
-      if( z[i+1]=='.' && i+3<n && z[i+2]=='.' && z[i+3]=='/' ){
-        while( j>0 && z[j-1]!='/' ){ j--; }
-        if( j>0 ){ j--; }
-        i += 2;
-        continue;
-      }
-    }
-    z[j++] = z[i];
-  }
-  z[j] = 0;
-  return j;
-}
-
-/*
-** Find a unique file ID for the given absolute pathname.  Return
-** a pointer to the vxworksFileId object.  This pointer is the unique
-** file ID.
-**
-** The nRef field of the vxworksFileId object is incremented before
-** the object is returned.  A new vxworksFileId object is created
-** and added to the global list if necessary.
-**
-** If a memory allocation error occurs, return NULL.
-*/
-static struct vxworksFileId *vxworksFindFileId(const char *zAbsoluteName){
-  struct vxworksFileId *pNew;         /* search key and new file ID */
-  struct vxworksFileId *pCandidate;   /* For looping over existing file IDs */
-  int n;                              /* Length of zAbsoluteName string */
-
-  assert( zAbsoluteName[0]=='/' );
-  n = (int)strlen(zAbsoluteName);
-  pNew = sqlite3_malloc64( sizeof(*pNew) + (n+1) );
-  if( pNew==0 ) return 0;
-  pNew->zCanonicalName = (char*)&pNew[1];
-  memcpy(pNew->zCanonicalName, zAbsoluteName, n+1);
-  n = vxworksSimplifyName(pNew->zCanonicalName, n);
-
-  /* Search for an existing entry that matching the canonical name.
-  ** If found, increment the reference count and return a pointer to
-  ** the existing file ID.
-  */
-  unixEnterMutex();
-  for(pCandidate=vxworksFileList; pCandidate; pCandidate=pCandidate->pNext){
-    if( pCandidate->nName==n 
-     && memcmp(pCandidate->zCanonicalName, pNew->zCanonicalName, n)==0
-    ){
-       sqlite3_free(pNew);
-       pCandidate->nRef++;
-       unixLeaveMutex();
-       return pCandidate;
-    }
-  }
-
-  /* No match was found.  We will make a new file ID */
-  pNew->nRef = 1;
-  pNew->nName = n;
-  pNew->pNext = vxworksFileList;
-  vxworksFileList = pNew;
-  unixLeaveMutex();
-  return pNew;
-}
-
-/*
-** Decrement the reference count on a vxworksFileId object.  Free
-** the object when the reference count reaches zero.
-*/
-static void vxworksReleaseFileId(struct vxworksFileId *pId){
-  unixEnterMutex();
-  assert( pId->nRef>0 );
-  pId->nRef--;
-  if( pId->nRef==0 ){
-    struct vxworksFileId **pp;
-    for(pp=&vxworksFileList; *pp && *pp!=pId; pp = &((*pp)->pNext)){}
-    assert( *pp==pId );
-    *pp = pId->pNext;
-    sqlite3_free(pId);
-  }
-  unixLeaveMutex();
-}
-#endif /* OS_VXWORKS */
-/*************** End of Unique File ID Utility Used By VxWorks ****************
-******************************************************************************/
-
-
-/******************************************************************************
-*************************** Posix Advisory Locking ****************************
-**
-** POSIX advisory locks are broken by design.  ANSI STD 1003.1 (1996)
-** section 6.5.2.2 lines 483 through 490 specify that when a process
-** sets or clears a lock, that operation overrides any prior locks set
-** by the same process.  It does not explicitly say so, but this implies
-** that it overrides locks set by the same process using a different
-** file descriptor.  Consider this test case:
-**
-**       int fd1 = open("./file1", O_RDWR|O_CREAT, 0644);
-**       int fd2 = open("./file2", O_RDWR|O_CREAT, 0644);
-**
-** Suppose ./file1 and ./file2 are really the same file (because
-** one is a hard or symbolic link to the other) then if you set
-** an exclusive lock on fd1, then try to get an exclusive lock
-** on fd2, it works.  I would have expected the second lock to
-** fail since there was already a lock on the file due to fd1.
-** But not so.  Since both locks came from the same process, the
-** second overrides the first, even though they were on different
-** file descriptors opened on different file names.
-**
-** This means that we cannot use POSIX locks to synchronize file access
-** among competing threads of the same process.  POSIX locks will work fine
-** to synchronize access for threads in separate processes, but not
-** threads within the same process.
-**
-** To work around the problem, SQLite has to manage file locks internally
-** on its own.  Whenever a new database is opened, we have to find the
-** specific inode of the database file (the inode is determined by the
-** st_dev and st_ino fields of the stat structure that fstat() fills in)
-** and check for locks already existing on that inode.  When locks are
-** created or removed, we have to look at our own internal record of the
-** locks to see if another thread has previously set a lock on that same
-** inode.
-**
-** (Aside: The use of inode numbers as unique IDs does not work on VxWorks.
-** For VxWorks, we have to use the alternative unique ID system based on
-** canonical filename and implemented in the previous division.)
-**
-** The sqlite3_file structure for POSIX is no longer just an integer file
-** descriptor.  It is now a structure that holds the integer file
-** descriptor and a pointer to a structure that describes the internal
-** locks on the corresponding inode.  There is one locking structure
-** per inode, so if the same inode is opened twice, both unixFile structures
-** point to the same locking structure.  The locking structure keeps
-** a reference count (so we will know when to delete it) and a "cnt"
-** field that tells us its internal lock status.  cnt==0 means the
-** file is unlocked.  cnt==-1 means the file has an exclusive lock.
-** cnt>0 means there are cnt shared locks on the file.
-**
-** Any attempt to lock or unlock a file first checks the locking
-** structure.  The fcntl() system call is only invoked to set a 
-** POSIX lock if the internal lock structure transitions between
-** a locked and an unlocked state.
-**
-** But wait:  there are yet more problems with POSIX advisory locks.
-**
-** If you close a file descriptor that points to a file that has locks,
-** all locks on that file that are owned by the current process are
-** released.  To work around this problem, each unixInodeInfo object
-** maintains a count of the number of pending locks on tha inode.
-** When an attempt is made to close an unixFile, if there are
-** other unixFile open on the same inode that are holding locks, the call
-** to close() the file descriptor is deferred until all of the locks clear.
-** The unixInodeInfo structure keeps a list of file descriptors that need to
-** be closed and that list is walked (and cleared) when the last lock
-** clears.
-**
-** Yet another problem:  LinuxThreads do not play well with posix locks.
-**
-** Many older versions of linux use the LinuxThreads library which is
-** not posix compliant.  Under LinuxThreads, a lock created by thread
-** A cannot be modified or overridden by a different thread B.
-** Only thread A can modify the lock.  Locking behavior is correct
-** if the appliation uses the newer Native Posix Thread Library (NPTL)
-** on linux - with NPTL a lock created by thread A can override locks
-** in thread B.  But there is no way to know at compile-time which
-** threading library is being used.  So there is no way to know at
-** compile-time whether or not thread A can override locks on thread B.
-** One has to do a run-time check to discover the behavior of the
-** current process.
-**
-** SQLite used to support LinuxThreads.  But support for LinuxThreads
-** was dropped beginning with version 3.7.0.  SQLite will still work with
-** LinuxThreads provided that (1) there is no more than one connection 
-** per database file in the same process and (2) database connections
-** do not move across threads.
-*/
-
-/*
-** An instance of the following structure serves as the key used
-** to locate a particular unixInodeInfo object.
-*/
-struct unixFileId {
-  dev_t dev;                  /* Device number */
-#if OS_VXWORKS
-  struct vxworksFileId *pId;  /* Unique file ID for vxworks. */
-#else
-  ino_t ino;                  /* Inode number */
-#endif
-};
-
-/*
-** An instance of the following structure is allocated for each open
-** inode.  Or, on LinuxThreads, there is one of these structures for
-** each inode opened by each thread.
-**
-** A single inode can have multiple file descriptors, so each unixFile
-** structure contains a pointer to an instance of this object and this
-** object keeps a count of the number of unixFile pointing to it.
-*/
-struct unixInodeInfo {
-  struct unixFileId fileId;       /* The lookup key */
-  int nShared;                    /* Number of SHARED locks held */
-  unsigned char eFileLock;        /* One of SHARED_LOCK, RESERVED_LOCK etc. */
-  unsigned char bProcessLock;     /* An exclusive process lock is held */
-  int nRef;                       /* Number of pointers to this structure */
-  unixShmNode *pShmNode;          /* Shared memory associated with this inode */
-  int nLock;                      /* Number of outstanding file locks */
-  UnixUnusedFd *pUnused;          /* Unused file descriptors to close */
-  unixInodeInfo *pNext;           /* List of all unixInodeInfo objects */
-  unixInodeInfo *pPrev;           /*    .... doubly linked */
-#if SQLITE_ENABLE_LOCKING_STYLE
-  unsigned long long sharedByte;  /* for AFP simulated shared lock */
-#endif
-#if OS_VXWORKS
-  sem_t *pSem;                    /* Named POSIX semaphore */
-  char aSemName[MAX_PATHNAME+2];  /* Name of that semaphore */
-#endif
-};
-
-/*
-** A lists of all unixInodeInfo objects.
-*/
-static unixInodeInfo *inodeList = 0;
-
-/*
-**
-** This function - unixLogError_x(), is only ever called via the macro
-** unixLogError().
-**
-** It is invoked after an error occurs in an OS function and errno has been
-** set. It logs a message using sqlite3_log() containing the current value of
-** errno and, if possible, the human-readable equivalent from strerror() or
-** strerror_r().
-**
-** The first argument passed to the macro should be the error code that
-** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN). 
-** The two subsequent arguments should be the name of the OS function that
-** failed (e.g. "unlink", "open") and the associated file-system path,
-** if any.
-*/
-#define unixLogError(a,b,c)     unixLogErrorAtLine(a,b,c,__LINE__)
-static int unixLogErrorAtLine(
-  int errcode,                    /* SQLite error code */
-  const char *zFunc,              /* Name of OS function that failed */
-  const char *zPath,              /* File path associated with error */
-  int iLine                       /* Source line number where error occurred */
-){
-  char *zErr;                     /* Message from strerror() or equivalent */
-  int iErrno = errno;             /* Saved syscall error number */
-
-  /* If this is not a threadsafe build (SQLITE_THREADSAFE==0), then use
-  ** the strerror() function to obtain the human-readable error message
-  ** equivalent to errno. Otherwise, use strerror_r().
-  */ 
-#if SQLITE_THREADSAFE && defined(HAVE_STRERROR_R)
-  char aErr[80];
-  memset(aErr, 0, sizeof(aErr));
-  zErr = aErr;
-
-  /* If STRERROR_R_CHAR_P (set by autoconf scripts) or __USE_GNU is defined,
-  ** assume that the system provides the GNU version of strerror_r() that
-  ** returns a pointer to a buffer containing the error message. That pointer 
-  ** may point to aErr[], or it may point to some static storage somewhere. 
-  ** Otherwise, assume that the system provides the POSIX version of 
-  ** strerror_r(), which always writes an error message into aErr[].
-  **
-  ** If the code incorrectly assumes that it is the POSIX version that is
-  ** available, the error message will often be an empty string. Not a
-  ** huge problem. Incorrectly concluding that the GNU version is available 
-  ** could lead to a segfault though.
-  */
-#if defined(STRERROR_R_CHAR_P) || defined(__USE_GNU)
-  zErr = 
-# endif
-  strerror_r(iErrno, aErr, sizeof(aErr)-1);
-
-#elif SQLITE_THREADSAFE
-  /* This is a threadsafe build, but strerror_r() is not available. */
-  zErr = "";
-#else
-  /* Non-threadsafe build, use strerror(). */
-  zErr = strerror(iErrno);
-#endif
-
-  if( zPath==0 ) zPath = "";
-  sqlite3_log(errcode,
-      "os_unix.c:%d: (%d) %s(%s) - %s",
-      iLine, iErrno, zFunc, zPath, zErr
-  );
-
-  return errcode;
-}
-
-/*
-** Close a file descriptor.
-**
-** We assume that close() almost always works, since it is only in a
-** very sick application or on a very sick platform that it might fail.
-** If it does fail, simply leak the file descriptor, but do log the
-** error.
-**
-** Note that it is not safe to retry close() after EINTR since the
-** file descriptor might have already been reused by another thread.
-** So we don't even try to recover from an EINTR.  Just log the error
-** and move on.
-*/
-static void robust_close(unixFile *pFile, int h, int lineno){
-  if( osClose(h) ){
-    unixLogErrorAtLine(SQLITE_IOERR_CLOSE, "close",
-                       pFile ? pFile->zPath : 0, lineno);
-  }
-}
-
-/*
-** Set the pFile->lastErrno.  Do this in a subroutine as that provides
-** a convenient place to set a breakpoint.
-*/
-static void storeLastErrno(unixFile *pFile, int error){
-  pFile->lastErrno = error;
-}
-
-/*
-** Close all file descriptors accumuated in the unixInodeInfo->pUnused list.
-*/ 
-static void closePendingFds(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  UnixUnusedFd *p;
-  UnixUnusedFd *pNext;
-  for(p=pInode->pUnused; p; p=pNext){
-    pNext = p->pNext;
-    robust_close(pFile, p->fd, __LINE__);
-    sqlite3_free(p);
-  }
-  pInode->pUnused = 0;
-}
-
-/*
-** Release a unixInodeInfo structure previously allocated by findInodeInfo().
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-*/
-static void releaseInodeInfo(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  assert( unixMutexHeld() );
-  if( ALWAYS(pInode) ){
-    pInode->nRef--;
-    if( pInode->nRef==0 ){
-      assert( pInode->pShmNode==0 );
-      closePendingFds(pFile);
-      if( pInode->pPrev ){
-        assert( pInode->pPrev->pNext==pInode );
-        pInode->pPrev->pNext = pInode->pNext;
-      }else{
-        assert( inodeList==pInode );
-        inodeList = pInode->pNext;
-      }
-      if( pInode->pNext ){
-        assert( pInode->pNext->pPrev==pInode );
-        pInode->pNext->pPrev = pInode->pPrev;
-      }
-      sqlite3_free(pInode);
-    }
-  }
-}
-
-/*
-** Given a file descriptor, locate the unixInodeInfo object that
-** describes that file descriptor.  Create a new one if necessary.  The
-** return value might be uninitialized if an error occurs.
-**
-** The mutex entered using the unixEnterMutex() function must be held
-** when this function is called.
-**
-** Return an appropriate error code.
-*/
-static int findInodeInfo(
-  unixFile *pFile,               /* Unix file with file desc used in the key */
-  unixInodeInfo **ppInode        /* Return the unixInodeInfo object here */
-){
-  int rc;                        /* System call return code */
-  int fd;                        /* The file descriptor for pFile */
-  struct unixFileId fileId;      /* Lookup key for the unixInodeInfo */
-  struct stat statbuf;           /* Low-level file information */
-  unixInodeInfo *pInode = 0;     /* Candidate unixInodeInfo object */
-
-  assert( unixMutexHeld() );
-
-  /* Get low-level information about the file that we can used to
-  ** create a unique name for the file.
-  */
-  fd = pFile->h;
-  rc = osFstat(fd, &statbuf);
-  if( rc!=0 ){
-    storeLastErrno(pFile, errno);
-#ifdef EOVERFLOW
-    if( pFile->lastErrno==EOVERFLOW ) return SQLITE_NOLFS;
-#endif
-    return SQLITE_IOERR;
-  }
-
-#ifdef __APPLE__
-  /* On OS X on an msdos filesystem, the inode number is reported
-  ** incorrectly for zero-size files.  See ticket #3260.  To work
-  ** around this problem (we consider it a bug in OS X, not SQLite)
-  ** we always increase the file size to 1 by writing a single byte
-  ** prior to accessing the inode number.  The one byte written is
-  ** an ASCII 'S' character which also happens to be the first byte
-  ** in the header of every SQLite database.  In this way, if there
-  ** is a race condition such that another thread has already populated
-  ** the first page of the database, no damage is done.
-  */
-  if( statbuf.st_size==0 && (pFile->fsFlags & SQLITE_FSFLAGS_IS_MSDOS)!=0 ){
-    do{ rc = osWrite(fd, "S", 1); }while( rc<0 && errno==EINTR );
-    if( rc!=1 ){
-      storeLastErrno(pFile, errno);
-      return SQLITE_IOERR;
-    }
-    rc = osFstat(fd, &statbuf);
-    if( rc!=0 ){
-      storeLastErrno(pFile, errno);
-      return SQLITE_IOERR;
-    }
-  }
-#endif
-
-  memset(&fileId, 0, sizeof(fileId));
-  fileId.dev = statbuf.st_dev;
-#if OS_VXWORKS
-  fileId.pId = pFile->pId;
-#else
-  fileId.ino = statbuf.st_ino;
-#endif
-  pInode = inodeList;
-  while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){
-    pInode = pInode->pNext;
-  }
-  if( pInode==0 ){
-    pInode = sqlite3_malloc64( sizeof(*pInode) );
-    if( pInode==0 ){
-      return SQLITE_NOMEM;
-    }
-    memset(pInode, 0, sizeof(*pInode));
-    memcpy(&pInode->fileId, &fileId, sizeof(fileId));
-    pInode->nRef = 1;
-    pInode->pNext = inodeList;
-    pInode->pPrev = 0;
-    if( inodeList ) inodeList->pPrev = pInode;
-    inodeList = pInode;
-  }else{
-    pInode->nRef++;
-  }
-  *ppInode = pInode;
-  return SQLITE_OK;
-}
-
-/*
-** Return TRUE if pFile has been renamed or unlinked since it was first opened.
-*/
-static int fileHasMoved(unixFile *pFile){
-#if OS_VXWORKS
-  return pFile->pInode!=0 && pFile->pId!=pFile->pInode->fileId.pId;
-#else
-  struct stat buf;
-  return pFile->pInode!=0 &&
-      (osStat(pFile->zPath, &buf)!=0 || buf.st_ino!=pFile->pInode->fileId.ino);
-#endif
-}
-
-
-/*
-** Check a unixFile that is a database.  Verify the following:
-**
-** (1) There is exactly one hard link on the file
-** (2) The file is not a symbolic link
-** (3) The file has not been renamed or unlinked
-**
-** Issue sqlite3_log(SQLITE_WARNING,...) messages if anything is not right.
-*/
-static void verifyDbFile(unixFile *pFile){
-  struct stat buf;
-  int rc;
-  if( pFile->ctrlFlags & UNIXFILE_WARNED ){
-    /* One or more of the following warnings have already been issued.  Do not
-    ** repeat them so as not to clutter the error log */
-    return;
-  }
-  rc = osFstat(pFile->h, &buf);
-  if( rc!=0 ){
-//    sqlite3_log(SQLITE_WARNING, "cannot fstat db file %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( buf.st_nlink==0 && (pFile->ctrlFlags & UNIXFILE_DELETE)==0 ){
-//    sqlite3_log(SQLITE_WARNING, "file unlinked while open: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( buf.st_nlink>1 ){
-//    sqlite3_log(SQLITE_WARNING, "multiple links to file: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-  if( fileHasMoved(pFile) ){
-//    sqlite3_log(SQLITE_WARNING, "file renamed while open: %s", pFile->zPath);
-    pFile->ctrlFlags |= UNIXFILE_WARNED;
-    return;
-  }
-}
-
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-
-  assert( pFile );
-  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->pInode->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-
-  /* Otherwise see if some other process holds it.
-  */
-#ifndef __DJGPP__
-  if( !reserved && !pFile->pInode->bProcessLock ){
-    struct flock lock;
-    lock.l_whence = SEEK_SET;
-    lock.l_start = RESERVED_BYTE;
-    lock.l_len = 1;
-    lock.l_type = F_WRLCK;
-    if( osFcntl(pFile->h, F_GETLK, &lock) ){
-      rc = SQLITE_IOERR_CHECKRESERVEDLOCK;
-      storeLastErrno(pFile, errno);
-    } else if( lock.l_type!=F_UNLCK ){
-      reserved = 1;
-    }
-  }
-#endif
-  
-  unixLeaveMutex();
-  OSTRACE(("TEST WR-LOCK %d %d %d (unix)\n", pFile->h, rc, reserved));
-
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Attempt to set a system-lock on the file pFile.  The lock is 
-** described by pLock.
-**
-** If the pFile was opened read/write from unix-excl, then the only lock
-** ever obtained is an exclusive lock, and it is obtained exactly once
-** the first time any lock is attempted.  All subsequent system locking
-** operations become no-ops.  Locking operations still happen internally,
-** in order to coordinate access between separate database connections
-** within this process, but all of that is handled in memory and the
-** operating system does not participate.
-**
-** This function is a pass-through to fcntl(F_SETLK) if pFile is using
-** any VFS other than "unix-excl" or if pFile is opened on "unix-excl"
-** and is read-only.
-**
-** Zero is returned if the call completes successfully, or -1 if a call
-** to fcntl() fails. In this case, errno is set appropriately (by fcntl()).
-*/
-static int unixFileLock(unixFile *pFile, struct flock *pLock){
-  int rc;
-  unixInodeInfo *pInode = pFile->pInode;
-  assert( unixMutexHeld() );
-  assert( pInode!=0 );
-  if( ((pFile->ctrlFlags & UNIXFILE_EXCL)!=0 || pInode->bProcessLock)
-   && ((pFile->ctrlFlags & UNIXFILE_RDONLY)==0)
-  ){
-    if( pInode->bProcessLock==0 ){
-      struct flock lock;
-      assert( pInode->nLock==0 );
-      lock.l_whence = SEEK_SET;
-      lock.l_start = SHARED_FIRST;
-      lock.l_len = SHARED_SIZE;
-      lock.l_type = F_WRLCK;
-      rc = osFcntl(pFile->h, F_SETLK, &lock);
-      if( rc<0 ) return rc;
-      pInode->bProcessLock = 1;
-      pInode->nLock++;
-    }else{
-      rc = 0;
-    }
-  }else{
-    rc = osFcntl(pFile->h, F_SETLK, pLock);
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int unixLock(sqlite3_file *id, int eFileLock){
-  /* The following describes the implementation of the various locks and
-  ** lock transitions in terms of the POSIX advisory shared and exclusive
-  ** lock primitives (called read-locks and write-locks below, to avoid
-  ** confusion with SQLite lock names). The algorithms are complicated
-  ** slightly in order to be compatible with windows systems simultaneously
-  ** accessing the same database file, in case that is ever required.
-  **
-  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
-  ** byte', each single bytes at well known offsets, and the 'shared byte
-  ** range', a range of 510 bytes at a well known offset.
-  **
-  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
-  ** byte'.  If this is successful, a random byte from the 'shared byte
-  ** range' is read-locked and the lock on the 'pending byte' released.
-  **
-  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
-  ** A RESERVED lock is implemented by grabbing a write-lock on the
-  ** 'reserved byte'. 
-  **
-  ** A process may only obtain a PENDING lock after it has obtained a
-  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
-  ** on the 'pending byte'. This ensures that no new SHARED locks can be
-  ** obtained, but existing SHARED locks are allowed to persist. A process
-  ** does not have to obtain a RESERVED lock on the way to a PENDING lock.
-  ** This property is used by the algorithm for rolling back a journal file
-  ** after a crash.
-  **
-  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
-  ** implemented by obtaining a write-lock on the entire 'shared byte
-  ** range'. Since all other locks require a read-lock on one of the bytes
-  ** within this range, this ensures that no other locks are held on the
-  ** database. 
-  **
-  ** The reason a single byte cannot be used instead of the 'shared byte
-  ** range' is that some versions of windows do not support read-locks. By
-  ** locking a random byte from a range, concurrent SHARED locks may exist
-  ** even if the locking primitive used is always a write-lock.
-  */
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  struct flock lock;
-  int tErrno = 0;
-
-  assert( pFile );
-  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (unix)\n", pFile->h,
-      azFileLock(eFileLock), azFileLock(pFile->eFileLock),
-      azFileLock(pFile->pInode->eFileLock), pFile->pInode->nShared,
-      osGetpid(0)));
-
-  /* If there is already a lock of this type or more restrictive on the
-  ** unixFile, do nothing. Don't use the end_lock: exit path, as
-  ** unixEnterMutex() hasn't been called yet.
-  */
-  if( pFile->eFileLock>=eFileLock ){
-    OSTRACE(("LOCK    %d %s ok (already held) (unix)\n", pFile->h,
-            azFileLock(eFileLock)));
-    return SQLITE_OK;
-  }
-
-  /* Make sure the locking sequence is correct.
-  **  (1) We never move from unlocked to anything higher than shared lock.
-  **  (2) SQLite never explicitly requests a pendig lock.
-  **  (3) A shared lock is always held when a reserve lock is requested.
-  */
-  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
-  assert( eFileLock!=PENDING_LOCK );
-  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
-
-  /* This mutex is needed because pFile->pInode is shared across threads
-  */
-  unixEnterMutex();
-  pInode = pFile->pInode;
-
-  /* If some thread using this PID has a lock via a different unixFile*
-  ** handle that precludes the requested lock, return BUSY.
-  */
-  if( (pFile->eFileLock!=pInode->eFileLock && 
-          (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
-  ){
-    rc = SQLITE_BUSY;
-    goto end_lock;
-  }
-
-  /* If a SHARED lock is requested, and some thread using this PID already
-  ** has a SHARED or RESERVED lock, then increment reference counts and
-  ** return SQLITE_OK.
-  */
-  if( eFileLock==SHARED_LOCK && 
-      (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
-    assert( eFileLock==SHARED_LOCK );
-    assert( pFile->eFileLock==0 );
-    assert( pInode->nShared>0 );
-    pFile->eFileLock = SHARED_LOCK;
-    pInode->nShared++;
-    pInode->nLock++;
-    goto end_lock;
-  }
-
-
-  /* A PENDING lock is needed before acquiring a SHARED lock and before
-  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
-  ** be released.
-  */
-  lock.l_len = 1L;
-  lock.l_whence = SEEK_SET;
-  if( eFileLock==SHARED_LOCK 
-      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
-  ){
-    lock.l_type = (eFileLock==SHARED_LOCK?F_RDLCK:F_WRLCK);
-    lock.l_start = PENDING_BYTE;
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( rc!=SQLITE_BUSY ){
-        storeLastErrno(pFile, tErrno);
-      }
-      goto end_lock;
-    }
-  }
-
-
-  /* If control gets to this point, then actually go ahead and make
-  ** operating system calls for the specified lock.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    assert( pInode->nShared==0 );
-    assert( pInode->eFileLock==0 );
-    assert( rc==SQLITE_OK );
-
-    /* Now get the read-lock */
-    lock.l_start = SHARED_FIRST;
-    lock.l_len = SHARED_SIZE;
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-    }
-
-    /* Drop the temporary PENDING lock */
-    lock.l_start = PENDING_BYTE;
-    lock.l_len = 1L;
-    lock.l_type = F_UNLCK;
-    if( unixFileLock(pFile, &lock) && rc==SQLITE_OK ){
-      /* This could happen with a network mount */
-      tErrno = errno;
-      rc = SQLITE_IOERR_UNLOCK; 
-    }
-
-    if( rc ){
-      if( rc!=SQLITE_BUSY ){
-        storeLastErrno(pFile, tErrno);
-      }
-      goto end_lock;
-    }else{
-      pFile->eFileLock = SHARED_LOCK;
-      pInode->nLock++;
-      pInode->nShared = 1;
-    }
-  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
-    /* We are trying for an exclusive lock but another thread in this
-    ** same process is still holding a shared lock. */
-    rc = SQLITE_BUSY;
-  }else{
-    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
-    ** assumed that there is a SHARED or greater lock on the file
-    ** already.
-    */
-    assert( 0!=pFile->eFileLock );
-    lock.l_type = F_WRLCK;
-
-    assert( eFileLock==RESERVED_LOCK || eFileLock==EXCLUSIVE_LOCK );
-    if( eFileLock==RESERVED_LOCK ){
-      lock.l_start = RESERVED_BYTE;
-      lock.l_len = 1L;
-    }else{
-      lock.l_start = SHARED_FIRST;
-      lock.l_len = SHARED_SIZE;
-    }
-
-    if( unixFileLock(pFile, &lock) ){
-      tErrno = errno;
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( rc!=SQLITE_BUSY ){
-        storeLastErrno(pFile, tErrno);
-      }
-    }
-  }
-  
-
-#ifdef SQLITE_DEBUG
-  /* Set up the transaction-counter change checking flags when
-  ** transitioning from a SHARED to a RESERVED lock.  The change
-  ** from SHARED to RESERVED marks the beginning of a normal
-  ** write operation (not a hot journal rollback).
-  */
-  if( rc==SQLITE_OK
-   && pFile->eFileLock<=SHARED_LOCK
-   && eFileLock==RESERVED_LOCK
-  ){
-    pFile->transCntrChng = 0;
-    pFile->dbUpdate = 0;
-    pFile->inNormalWrite = 1;
-  }
-#endif
-
-
-  if( rc==SQLITE_OK ){
-    pFile->eFileLock = eFileLock;
-    pInode->eFileLock = eFileLock;
-  }else if( eFileLock==EXCLUSIVE_LOCK ){
-    pFile->eFileLock = PENDING_LOCK;
-    pInode->eFileLock = PENDING_LOCK;
-  }
-
-end_lock:
-  unixLeaveMutex();
-  OSTRACE(("LOCK    %d %s %s (unix)\n", pFile->h, azFileLock(eFileLock), 
-      rc==SQLITE_OK ? "ok" : "failed"));
-  return rc;
-}
-
-/*
-** Add the file descriptor used by file handle pFile to the corresponding
-** pUnused list.
-*/
-static void setPendingFd(unixFile *pFile){
-  unixInodeInfo *pInode = pFile->pInode;
-  UnixUnusedFd *p = pFile->pUnused;
-  p->pNext = pInode->pUnused;
-  pInode->pUnused = p;
-  pFile->h = -1;
-  pFile->pUnused = 0;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-** 
-** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED
-** the byte range is divided into 2 parts and the first part is unlocked then
-** set to a read lock, then the other part is simply unlocked.  This works 
-** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to 
-** remove the write lock on a region when a read lock is set.
-*/
-static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  struct flock lock;
-  int rc = SQLITE_OK;
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock,
-      pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
-      osGetpid(0)));
-
-  assert( eFileLock<=SHARED_LOCK );
-  if( pFile->eFileLock<=eFileLock ){
-    return SQLITE_OK;
-  }
-  unixEnterMutex();
-  pInode = pFile->pInode;
-  assert( pInode->nShared!=0 );
-  if( pFile->eFileLock>SHARED_LOCK ){
-    assert( pInode->eFileLock==pFile->eFileLock );
-
-#ifdef SQLITE_DEBUG
-    /* When reducing a lock such that other processes can start
-    ** reading the database file again, make sure that the
-    ** transaction counter was updated if any part of the database
-    ** file changed.  If the transaction counter is not updated,
-    ** other connections to the same file might not realize that
-    ** the file has changed and hence might not know to flush their
-    ** cache.  The use of a stale cache can lead to database corruption.
-    */
-    pFile->inNormalWrite = 0;
-#endif
-
-    /* downgrading to a shared lock on NFS involves clearing the write lock
-    ** before establishing the readlock - to avoid a race condition we downgrade
-    ** the lock in 2 blocks, so that part of the range will be covered by a 
-    ** write lock until the rest is covered by a read lock:
-    **  1:   [WWWWW]
-    **  2:   [....W]
-    **  3:   [RRRRW]
-    **  4:   [RRRR.]
-    */
-    if( eFileLock==SHARED_LOCK ){
-#if !defined(__APPLE__) || !SQLITE_ENABLE_LOCKING_STYLE
-      (void)handleNFSUnlock;
-      assert( handleNFSUnlock==0 );
-#endif
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-      if( handleNFSUnlock ){
-        int tErrno;               /* Error code from system call errors */
-        off_t divSize = SHARED_SIZE - 1;
-        
-        lock.l_type = F_UNLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            storeLastErrno(pFile, tErrno);
-          }
-          goto end_unlock;
-        }
-        lock.l_type = F_RDLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_RDLOCK);
-          if( IS_LOCK_ERROR(rc) ){
-            storeLastErrno(pFile, tErrno);
-          }
-          goto end_unlock;
-        }
-        lock.l_type = F_UNLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST+divSize;
-        lock.l_len = SHARED_SIZE-divSize;
-        if( unixFileLock(pFile, &lock)==(-1) ){
-          tErrno = errno;
-          rc = SQLITE_IOERR_UNLOCK;
-          if( IS_LOCK_ERROR(rc) ){
-            storeLastErrno(pFile, tErrno);
-          }
-          goto end_unlock;
-        }
-      }else
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-      {
-        lock.l_type = F_RDLCK;
-        lock.l_whence = SEEK_SET;
-        lock.l_start = SHARED_FIRST;
-        lock.l_len = SHARED_SIZE;
-        if( unixFileLock(pFile, &lock) ){
-          /* In theory, the call to unixFileLock() cannot fail because another
-          ** process is holding an incompatible lock. If it does, this 
-          ** indicates that the other process is not following the locking
-          ** protocol. If this happens, return SQLITE_IOERR_RDLOCK. Returning
-          ** SQLITE_BUSY would confuse the upper layer (in practice it causes 
-          ** an assert to fail). */ 
-          rc = SQLITE_IOERR_RDLOCK;
-          storeLastErrno(pFile, errno);
-          goto end_unlock;
-        }
-      }
-    }
-    lock.l_type = F_UNLCK;
-    lock.l_whence = SEEK_SET;
-    lock.l_start = PENDING_BYTE;
-    lock.l_len = 2L;  assert( PENDING_BYTE+1==RESERVED_BYTE );
-    if( unixFileLock(pFile, &lock)==0 ){
-      pInode->eFileLock = SHARED_LOCK;
-    }else{
-      rc = SQLITE_IOERR_UNLOCK;
-      storeLastErrno(pFile, errno);
-      goto end_unlock;
-    }
-  }
-  if( eFileLock==NO_LOCK ){
-    /* Decrement the shared lock counter.  Release the lock using an
-    ** OS call only when all threads in this same process have released
-    ** the lock.
-    */
-    pInode->nShared--;
-    if( pInode->nShared==0 ){
-      lock.l_type = F_UNLCK;
-      lock.l_whence = SEEK_SET;
-      lock.l_start = lock.l_len = 0L;
-      if( unixFileLock(pFile, &lock)==0 ){
-        pInode->eFileLock = NO_LOCK;
-      }else{
-        rc = SQLITE_IOERR_UNLOCK;
-        storeLastErrno(pFile, errno);
-        pInode->eFileLock = NO_LOCK;
-        pFile->eFileLock = NO_LOCK;
-      }
-    }
-
-    /* Decrement the count of locks against this same file.  When the
-    ** count reaches zero, close any other file descriptors whose close
-    ** was deferred because of outstanding locks.
-    */
-    pInode->nLock--;
-    assert( pInode->nLock>=0 );
-    if( pInode->nLock==0 ){
-      closePendingFds(pFile);
-    }
-  }
-
-end_unlock:
-  unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int unixUnlock(sqlite3_file *id, int eFileLock){
-#if SQLITE_MAX_MMAP_SIZE>0
-  assert( eFileLock==SHARED_LOCK || ((unixFile *)id)->nFetchOut==0 );
-#endif
-  return posixUnlock(id, eFileLock, 0);
-}
-
-#if SQLITE_MAX_MMAP_SIZE>0
-static int unixMapfile(unixFile *pFd, i64 nByte);
-static void unixUnmapfile(unixFile *pFd);
-#endif
-
-/*
-** This function performs the parts of the "close file" operation 
-** common to all locking schemes. It closes the directory and file
-** handles, if they are valid, and sets all fields of the unixFile
-** structure to 0.
-**
-** It is *not* necessary to hold the mutex when this routine is called,
-** even on VxWorks.  A mutex will be acquired on VxWorks by the
-** vxworksReleaseFileId() routine.
-*/
-static int closeUnixFile(sqlite3_file *id){
-  unixFile *pFile = (unixFile*)id;
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixUnmapfile(pFile);
-#endif
-  if( pFile->h>=0 ){
-    robust_close(pFile, pFile->h, __LINE__);
-    pFile->h = -1;
-  }
-#if OS_VXWORKS
-  if( pFile->pId ){
-    if( pFile->ctrlFlags & UNIXFILE_DELETE ){
-      osUnlink(pFile->pId->zCanonicalName);
-    }
-    vxworksReleaseFileId(pFile->pId);
-    pFile->pId = 0;
-  }
-#endif
-#ifdef SQLITE_UNLINK_AFTER_CLOSE
-  if( pFile->ctrlFlags & UNIXFILE_DELETE ){
-    osUnlink(pFile->zPath);
-    sqlite3_free(*(char**)&pFile->zPath);
-    pFile->zPath = 0;
-  }
-#endif
-  OSTRACE(("CLOSE   %-3d\n", pFile->h));
-  OpenCounter(-1);
-  sqlite3_free(pFile->pUnused);
-  memset(pFile, 0, sizeof(unixFile));
-  return SQLITE_OK;
-}
-
-/*
-** Close a file.
-*/
-static int unixClose(sqlite3_file *id){
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile *)id;
-  verifyDbFile(pFile);
-  unixUnlock(id, NO_LOCK);
-  unixEnterMutex();
-
-  /* unixFile.pInode is always valid here. Otherwise, a different close
-  ** routine (e.g. nolockClose()) would be called instead.
-  */
-  assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 );
-  if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){
-    /* If there are outstanding locks, do not actually close the file just
-    ** yet because that would clear those locks.  Instead, add the file
-    ** descriptor to pInode->pUnused list.  It will be automatically closed 
-    ** when the last lock is cleared.
-    */
-    setPendingFd(pFile);
-  }
-  releaseInodeInfo(pFile);
-  rc = closeUnixFile(id);
-  unixLeaveMutex();
-  return rc;
-}
-
-/************** End of the posix advisory lock implementation *****************
-******************************************************************************/
-
-/******************************************************************************
-****************************** No-op Locking **********************************
-**
-** Of the various locking implementations available, this is by far the
-** simplest:  locking is ignored.  No attempt is made to lock the database
-** file for reading or writing.
-**
-** This locking mode is appropriate for use on read-only databases
-** (ex: databases that are burned into CD-ROM, for example.)  It can
-** also be used if the application employs some external mechanism to
-** prevent simultaneous access of the same database by two or more
-** database connections.  But there is a serious risk of database
-** corruption if this locking mode is used in situations where multiple
-** database connections are accessing the same database file at the same
-** time and one or more of those connections are writing.
-*/
-
-static int nolockCheckReservedLock(sqlite3_file *NotUsed, int *pResOut){
-  UNUSED_PARAMETER(NotUsed);
-  *pResOut = 0;
-  return SQLITE_OK;
-}
-static int nolockLock(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  return SQLITE_OK;
-}
-static int nolockUnlock(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  return SQLITE_OK;
-}
-
-/*
-** Close the file.
-*/
-static int nolockClose(sqlite3_file *id) {
-  return closeUnixFile(id);
-}
-
-/******************* End of the no-op lock implementation *********************
-******************************************************************************/
-
-/******************************************************************************
-************************* Begin dot-file Locking ******************************
-**
-** The dotfile locking implementation uses the existence of separate lock
-** files (really a directory) to control access to the database.  This works
-** on just about every filesystem imaginable.  But there are serious downsides:
-**
-**    (1)  There is zero concurrency.  A single reader blocks all other
-**         connections from reading or writing the database.
-**
-**    (2)  An application crash or power loss can leave stale lock files
-**         sitting around that need to be cleared manually.
-**
-** Nevertheless, a dotlock is an appropriate locking mode for use if no
-** other locking strategy is available.
-**
-** Dotfile locking works by creating a subdirectory in the same directory as
-** the database and with the same name but with a ".lock" extension added.
-** The existence of a lock directory implies an EXCLUSIVE lock.  All other
-** lock types (SHARED, RESERVED, PENDING) are mapped into EXCLUSIVE.
-*/
-
-/*
-** The file suffix added to the data base filename in order to create the
-** lock directory.
-*/
-#define DOTLOCK_SUFFIX ".lock"
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-**
-** In dotfile locking, either a lock exists or it does not.  So in this
-** variation of CheckReservedLock(), *pResOut is set to true if any lock
-** is held on the file and false if the file is unlocked.
-*/
-static int dotlockCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    /* Either this connection or some other connection in the same process
-    ** holds a lock on the file.  No need to check further. */
-    reserved = 1;
-  }else{
-    /* The lock is held if and only if the lockfile exists */
-    const char *zLockFile = (const char*)pFile->lockingContext;
-    reserved = osAccess(zLockFile, 0)==0;
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (dotlock)\n", pFile->h, rc, reserved));
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-**
-** With dotfile locking, we really only support state (4): EXCLUSIVE.
-** But we track the other locking levels internally.
-*/
-static int dotlockLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  char *zLockFile = (char *)pFile->lockingContext;
-  int rc = SQLITE_OK;
-
-
-  /* If we have any lock, then the lock file already exists.  All we have
-  ** to do is adjust our internal record of the lock level.
-  */
-  if( pFile->eFileLock > NO_LOCK ){
-    pFile->eFileLock = eFileLock;
-    /* Always update the timestamp on the old file */
-#ifdef HAVE_UTIME
-    utime(zLockFile, NULL);
-#else
-    utimes(zLockFile, NULL);
-#endif
-    return SQLITE_OK;
-  }
-  
-  /* grab an exclusive lock */
-  rc = osMkdir(zLockFile, 0777);
-  if( rc<0 ){
-    /* failed to open/create the lock directory */
-    int tErrno = errno;
-    if( EEXIST == tErrno ){
-      rc = SQLITE_BUSY;
-    } else {
-      rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-      if( IS_LOCK_ERROR(rc) ){
-        storeLastErrno(pFile, tErrno);
-      }
-    }
-    return rc;
-  } 
-  
-  /* got it, set the type and return ok */
-  pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-**
-** When the locking level reaches NO_LOCK, delete the lock file.
-*/
-static int dotlockUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  char *zLockFile = (char *)pFile->lockingContext;
-  int rc;
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (dotlock)\n", pFile->h, eFileLock,
-           pFile->eFileLock, osGetpid(0)));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-
-  /* To downgrade to shared, simply update our internal notion of the
-  ** lock state.  No need to mess with the file on disk.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    pFile->eFileLock = SHARED_LOCK;
-    return SQLITE_OK;
-  }
-  
-  /* To fully unlock the database, delete the lock file */
-  assert( eFileLock==NO_LOCK );
-  rc = osRmdir(zLockFile);
-  if( rc<0 && errno==ENOTDIR ) rc = osUnlink(zLockFile);
-  if( rc<0 ){
-    int tErrno = errno;
-    rc = 0;
-    if( ENOENT != tErrno ){
-      rc = SQLITE_IOERR_UNLOCK;
-    }
-    if( IS_LOCK_ERROR(rc) ){
-      storeLastErrno(pFile, tErrno);
-    }
-    return rc; 
-  }
-  pFile->eFileLock = NO_LOCK;
-  return SQLITE_OK;
-}
-
-/*
-** Close a file.  Make sure the lock has been released before closing.
-*/
-static int dotlockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    dotlockUnlock(id, NO_LOCK);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-  }
-  return rc;
-}
-/****************** End of the dot-file lock implementation *******************
-******************************************************************************/
-
-/******************************************************************************
-************************** Begin flock Locking ********************************
-**
-** Use the flock() system call to do file locking.
-**
-** flock() locking is like dot-file locking in that the various
-** fine-grain locking levels supported by SQLite are collapsed into
-** a single exclusive lock.  In other words, SHARED, RESERVED, and
-** PENDING locks are the same thing as an EXCLUSIVE lock.  SQLite
-** still works when you do this, but concurrency is reduced since
-** only a single process can be reading the database at a time.
-**
-** Omit this section if SQLITE_ENABLE_LOCKING_STYLE is turned off
-*/
-#if SQLITE_ENABLE_LOCKING_STYLE
-
-/*
-** Retry flock() calls that fail with EINTR
-*/
-#ifdef EINTR
-static int robust_flock(int fd, int op){
-  int rc;
-  do{ rc = flock(fd,op); }while( rc<0 && errno==EINTR );
-  return rc;
-}
-#else
-# define robust_flock(a,b) flock(a,b)
-#endif
-     
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int flockCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-  
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-  
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it. */
-  if( !reserved ){
-    /* attempt to get the lock */
-    int lrc = robust_flock(pFile->h, LOCK_EX | LOCK_NB);
-    if( !lrc ){
-      /* got the lock, unlock it */
-      lrc = robust_flock(pFile->h, LOCK_UN);
-      if ( lrc ) {
-        int tErrno = errno;
-        /* unlock failed with an error */
-        lrc = SQLITE_IOERR_UNLOCK; 
-        if( IS_LOCK_ERROR(lrc) ){
-          storeLastErrno(pFile, tErrno);
-          rc = lrc;
-        }
-      }
-    } else {
-      int tErrno = errno;
-      reserved = 1;
-      /* someone else might have it reserved */
-      lrc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK); 
-      if( IS_LOCK_ERROR(lrc) ){
-        storeLastErrno(pFile, tErrno);
-        rc = lrc;
-      }
-    }
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (flock)\n", pFile->h, rc, reserved));
-
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
-    rc = SQLITE_OK;
-    reserved=1;
-  }
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** flock() only really support EXCLUSIVE locks.  We track intermediate
-** lock states in the sqlite3_file structure, but all locks SHARED or
-** above are really EXCLUSIVE locks and exclude all other processes from
-** access the file.
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int flockLock(sqlite3_file *id, int eFileLock) {
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-
-  assert( pFile );
-
-  /* if we already have a lock, it is exclusive.  
-  ** Just adjust level and punt on outta here. */
-  if (pFile->eFileLock > NO_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* grab an exclusive lock */
-  
-  if (robust_flock(pFile->h, LOCK_EX | LOCK_NB)) {
-    int tErrno = errno;
-    /* didn't get, must be busy */
-    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_LOCK);
-    if( IS_LOCK_ERROR(rc) ){
-      storeLastErrno(pFile, tErrno);
-    }
-  } else {
-    /* got it, set the type and return ok */
-    pFile->eFileLock = eFileLock;
-  }
-  OSTRACE(("LOCK    %d %s %s (flock)\n", pFile->h, azFileLock(eFileLock), 
-           rc==SQLITE_OK ? "ok" : "failed"));
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-  if( (rc & SQLITE_IOERR) == SQLITE_IOERR ){
-    rc = SQLITE_BUSY;
-  }
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-  return rc;
-}
-
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int flockUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (flock)\n", pFile->h, eFileLock,
-           pFile->eFileLock, osGetpid(0)));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-  
-  /* shared can just be set because we always have an exclusive */
-  if (eFileLock==SHARED_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* no, really, unlock. */
-  if( robust_flock(pFile->h, LOCK_UN) ){
-#ifdef SQLITE_IGNORE_FLOCK_LOCK_ERRORS
-    return SQLITE_OK;
-#endif /* SQLITE_IGNORE_FLOCK_LOCK_ERRORS */
-    return SQLITE_IOERR_UNLOCK;
-  }else{
-    pFile->eFileLock = NO_LOCK;
-    return SQLITE_OK;
-  }
-}
-
-/*
-** Close a file.
-*/
-static int flockClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    flockUnlock(id, NO_LOCK);
-    rc = closeUnixFile(id);
-  }
-  return rc;
-}
-
-#endif /* SQLITE_ENABLE_LOCKING_STYLE && !OS_VXWORK */
-
-/******************* End of the flock lock implementation *********************
-******************************************************************************/
-
-/******************************************************************************
-************************ Begin Named Semaphore Locking ************************
-**
-** Named semaphore locking is only supported on VxWorks.
-**
-** Semaphore locking is like dot-lock and flock in that it really only
-** supports EXCLUSIVE locking.  Only a single process can read or write
-** the database file at a time.  This reduces potential concurrency, but
-** makes the lock implementation much easier.
-*/
-#if OS_VXWORKS
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int semXCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it. */
-  if( !reserved ){
-    sem_t *pSem = pFile->pInode->pSem;
-
-    if( sem_trywait(pSem)==-1 ){
-      int tErrno = errno;
-      if( EAGAIN != tErrno ){
-        rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_CHECKRESERVEDLOCK);
-        storeLastErrno(pFile, tErrno);
-      } else {
-        /* someone else has the lock when we are in NO_LOCK */
-        reserved = (pFile->eFileLock < SHARED_LOCK);
-      }
-    }else{
-      /* we could have it if we want it */
-      sem_post(pSem);
-    }
-  }
-  OSTRACE(("TEST WR-LOCK %d %d %d (sem)\n", pFile->h, rc, reserved));
-
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** Semaphore locks only really support EXCLUSIVE locks.  We track intermediate
-** lock states in the sqlite3_file structure, but all locks SHARED or
-** above are really EXCLUSIVE locks and exclude all other processes from
-** access the file.
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int semXLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pInode->pSem;
-  int rc = SQLITE_OK;
-
-  /* if we already have a lock, it is exclusive.  
-  ** Just adjust level and punt on outta here. */
-  if (pFile->eFileLock > NO_LOCK) {
-    pFile->eFileLock = eFileLock;
-    rc = SQLITE_OK;
-    goto sem_end_lock;
-  }
-  
-  /* lock semaphore now but bail out when already locked. */
-  if( sem_trywait(pSem)==-1 ){
-    rc = SQLITE_BUSY;
-    goto sem_end_lock;
-  }
-
-  /* got it, set the type and return ok */
-  pFile->eFileLock = eFileLock;
-
- sem_end_lock:
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int semXUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  sem_t *pSem = pFile->pInode->pSem;
-
-  assert( pFile );
-  assert( pSem );
-  OSTRACE(("UNLOCK  %d %d was %d pid=%d (sem)\n", pFile->h, eFileLock,
-           pFile->eFileLock, osGetpid(0)));
-  assert( eFileLock<=SHARED_LOCK );
-  
-  /* no-op if possible */
-  if( pFile->eFileLock==eFileLock ){
-    return SQLITE_OK;
-  }
-  
-  /* shared can just be set because we always have an exclusive */
-  if (eFileLock==SHARED_LOCK) {
-    pFile->eFileLock = eFileLock;
-    return SQLITE_OK;
-  }
-  
-  /* no, really unlock. */
-  if ( sem_post(pSem)==-1 ) {
-    int rc, tErrno = errno;
-    rc = sqliteErrorFromPosixError(tErrno, SQLITE_IOERR_UNLOCK);
-    if( IS_LOCK_ERROR(rc) ){
-      storeLastErrno(pFile, tErrno);
-    }
-    return rc; 
-  }
-  pFile->eFileLock = NO_LOCK;
-  return SQLITE_OK;
-}
-
-/*
- ** Close a file.
- */
-static int semXClose(sqlite3_file *id) {
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    semXUnlock(id, NO_LOCK);
-    assert( pFile );
-    unixEnterMutex();
-    releaseInodeInfo(pFile);
-    unixLeaveMutex();
-    closeUnixFile(id);
-  }
-  return SQLITE_OK;
-}
-
-#endif /* OS_VXWORKS */
-/*
-** Named semaphore locking is only available on VxWorks.
-**
-*************** End of the named semaphore lock implementation ****************
-******************************************************************************/
-
-
-/******************************************************************************
-*************************** Begin AFP Locking *********************************
-**
-** AFP is the Apple Filing Protocol.  AFP is a network filesystem found
-** on Apple Macintosh computers - both OS9 and OSX.
-**
-** Third-party implementations of AFP are available.  But this code here
-** only works on OSX.
-*/
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/*
-** The afpLockingContext structure contains all afp lock specific state
-*/
-typedef struct afpLockingContext afpLockingContext;
-struct afpLockingContext {
-  int reserved;
-  const char *dbPath;             /* Name of the open file */
-};
-
-struct ByteRangeLockPB2
-{
-  unsigned long long offset;        /* offset to first byte to lock */
-  unsigned long long length;        /* nbr of bytes to lock */
-  unsigned long long retRangeStart; /* nbr of 1st byte locked if successful */
-  unsigned char unLockFlag;         /* 1 = unlock, 0 = lock */
-  unsigned char startEndFlag;       /* 1=rel to end of fork, 0=rel to start */
-  int fd;                           /* file desc to assoc this lock with */
-};
-
-#define afpfsByteRangeLock2FSCTL        _IOWR('z', 23, struct ByteRangeLockPB2)
-
-/*
-** This is a utility for setting or clearing a bit-range lock on an
-** AFP filesystem.
-** 
-** Return SQLITE_OK on success, SQLITE_BUSY on failure.
-*/
-static int afpSetLock(
-  const char *path,              /* Name of the file to be locked or unlocked */
-  unixFile *pFile,               /* Open file descriptor on path */
-  unsigned long long offset,     /* First byte to be locked */
-  unsigned long long length,     /* Number of bytes to lock */
-  int setLockFlag                /* True to set lock.  False to clear lock */
-){
-  struct ByteRangeLockPB2 pb;
-  int err;
-  
-  pb.unLockFlag = setLockFlag ? 0 : 1;
-  pb.startEndFlag = 0;
-  pb.offset = offset;
-  pb.length = length; 
-  pb.fd = pFile->h;
-  
-  OSTRACE(("AFPSETLOCK [%s] for %d%s in range %llx:%llx\n", 
-    (setLockFlag?"ON":"OFF"), pFile->h, (pb.fd==-1?"[testval-1]":""),
-    offset, length));
-  err = fsctl(path, afpfsByteRangeLock2FSCTL, &pb, 0);
-  if ( err==-1 ) {
-    int rc;
-    int tErrno = errno;
-    OSTRACE(("AFPSETLOCK failed to fsctl() '%s' %d %s\n",
-             path, tErrno, strerror(tErrno)));
-#ifdef SQLITE_IGNORE_AFP_LOCK_ERRORS
-    rc = SQLITE_BUSY;
-#else
-    rc = sqliteErrorFromPosixError(tErrno,
-                    setLockFlag ? SQLITE_IOERR_LOCK : SQLITE_IOERR_UNLOCK);
-#endif /* SQLITE_IGNORE_AFP_LOCK_ERRORS */
-    if( IS_LOCK_ERROR(rc) ){
-      storeLastErrno(pFile, tErrno);
-    }
-    return rc;
-  } else {
-    return SQLITE_OK;
-  }
-}
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int afpCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int rc = SQLITE_OK;
-  int reserved = 0;
-  unixFile *pFile = (unixFile*)id;
-  afpLockingContext *context;
-  
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  
-  assert( pFile );
-  context = (afpLockingContext *) pFile->lockingContext;
-  if( context->reserved ){
-    *pResOut = 1;
-    return SQLITE_OK;
-  }
-  unixEnterMutex(); /* Because pFile->pInode is shared across threads */
-  
-  /* Check if a thread in this process holds such a lock */
-  if( pFile->pInode->eFileLock>SHARED_LOCK ){
-    reserved = 1;
-  }
-  
-  /* Otherwise see if some other process holds it.
-   */
-  if( !reserved ){
-    /* lock the RESERVED byte */
-    int lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);  
-    if( SQLITE_OK==lrc ){
-      /* if we succeeded in taking the reserved lock, unlock it to restore
-      ** the original state */
-      lrc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
-    } else {
-      /* if we failed to get the lock then someone else must have it */
-      reserved = 1;
-    }
-    if( IS_LOCK_ERROR(lrc) ){
-      rc=lrc;
-    }
-  }
-  
-  unixLeaveMutex();
-  OSTRACE(("TEST WR-LOCK %d %d %d (afp)\n", pFile->h, rc, reserved));
-  
-  *pResOut = reserved;
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int afpLock(sqlite3_file *id, int eFileLock){
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode = pFile->pInode;
-  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
-  
-  assert( pFile );
-  OSTRACE(("LOCK    %d %s was %s(%s,%d) pid=%d (afp)\n", pFile->h,
-           azFileLock(eFileLock), azFileLock(pFile->eFileLock),
-           azFileLock(pInode->eFileLock), pInode->nShared , osGetpid(0)));
-
-  /* If there is already a lock of this type or more restrictive on the
-  ** unixFile, do nothing. Don't use the afp_end_lock: exit path, as
-  ** unixEnterMutex() hasn't been called yet.
-  */
-  if( pFile->eFileLock>=eFileLock ){
-    OSTRACE(("LOCK    %d %s ok (already held) (afp)\n", pFile->h,
-           azFileLock(eFileLock)));
-    return SQLITE_OK;
-  }
-
-  /* Make sure the locking sequence is correct
-  **  (1) We never move from unlocked to anything higher than shared lock.
-  **  (2) SQLite never explicitly requests a pendig lock.
-  **  (3) A shared lock is always held when a reserve lock is requested.
-  */
-  assert( pFile->eFileLock!=NO_LOCK || eFileLock==SHARED_LOCK );
-  assert( eFileLock!=PENDING_LOCK );
-  assert( eFileLock!=RESERVED_LOCK || pFile->eFileLock==SHARED_LOCK );
-  
-  /* This mutex is needed because pFile->pInode is shared across threads
-  */
-  unixEnterMutex();
-  pInode = pFile->pInode;
-
-  /* If some thread using this PID has a lock via a different unixFile*
-  ** handle that precludes the requested lock, return BUSY.
-  */
-  if( (pFile->eFileLock!=pInode->eFileLock && 
-       (pInode->eFileLock>=PENDING_LOCK || eFileLock>SHARED_LOCK))
-     ){
-    rc = SQLITE_BUSY;
-    goto afp_end_lock;
-  }
-  
-  /* If a SHARED lock is requested, and some thread using this PID already
-  ** has a SHARED or RESERVED lock, then increment reference counts and
-  ** return SQLITE_OK.
-  */
-  if( eFileLock==SHARED_LOCK && 
-     (pInode->eFileLock==SHARED_LOCK || pInode->eFileLock==RESERVED_LOCK) ){
-    assert( eFileLock==SHARED_LOCK );
-    assert( pFile->eFileLock==0 );
-    assert( pInode->nShared>0 );
-    pFile->eFileLock = SHARED_LOCK;
-    pInode->nShared++;
-    pInode->nLock++;
-    goto afp_end_lock;
-  }
-    
-  /* A PENDING lock is needed before acquiring a SHARED lock and before
-  ** acquiring an EXCLUSIVE lock.  For the SHARED lock, the PENDING will
-  ** be released.
-  */
-  if( eFileLock==SHARED_LOCK 
-      || (eFileLock==EXCLUSIVE_LOCK && pFile->eFileLock<PENDING_LOCK)
-  ){
-    int failed;
-    failed = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 1);
-    if (failed) {
-      rc = failed;
-      goto afp_end_lock;
-    }
-  }
-  
-  /* If control gets to this point, then actually go ahead and make
-  ** operating system calls for the specified lock.
-  */
-  if( eFileLock==SHARED_LOCK ){
-    int lrc1, lrc2, lrc1Errno = 0;
-    long lk, mask;
-    
-    assert( pInode->nShared==0 );
-    assert( pInode->eFileLock==0 );
-        
-    mask = (sizeof(long)==8) ? LARGEST_INT64 : 0x7fffffff;
-    /* Now get the read-lock SHARED_LOCK */
-    /* note that the quality of the randomness doesn't matter that much */
-    lk = random(); 
-    pInode->sharedByte = (lk & mask)%(SHARED_SIZE - 1);
-    lrc1 = afpSetLock(context->dbPath, pFile, 
-          SHARED_FIRST+pInode->sharedByte, 1, 1);
-    if( IS_LOCK_ERROR(lrc1) ){
-      lrc1Errno = pFile->lastErrno;
-    }
-    /* Drop the temporary PENDING lock */
-    lrc2 = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
-    
-    if( IS_LOCK_ERROR(lrc1) ) {
-      storeLastErrno(pFile, lrc1Errno);
-      rc = lrc1;
-      goto afp_end_lock;
-    } else if( IS_LOCK_ERROR(lrc2) ){
-      rc = lrc2;
-      goto afp_end_lock;
-    } else if( lrc1 != SQLITE_OK ) {
-      rc = lrc1;
-    } else {
-      pFile->eFileLock = SHARED_LOCK;
-      pInode->nLock++;
-      pInode->nShared = 1;
-    }
-  }else if( eFileLock==EXCLUSIVE_LOCK && pInode->nShared>1 ){
-    /* We are trying for an exclusive lock but another thread in this
-     ** same process is still holding a shared lock. */
-    rc = SQLITE_BUSY;
-  }else{
-    /* The request was for a RESERVED or EXCLUSIVE lock.  It is
-    ** assumed that there is a SHARED or greater lock on the file
-    ** already.
-    */
-    int failed = 0;
-    assert( 0!=pFile->eFileLock );
-    if (eFileLock >= RESERVED_LOCK && pFile->eFileLock < RESERVED_LOCK) {
-        /* Acquire a RESERVED lock */
-        failed = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1,1);
-      if( !failed ){
-        context->reserved = 1;
-      }
-    }
-    if (!failed && eFileLock == EXCLUSIVE_LOCK) {
-      /* Acquire an EXCLUSIVE lock */
-        
-      /* Remove the shared lock before trying the range.  we'll need to 
-      ** reestablish the shared lock if we can't get the  afpUnlock
-      */
-      if( !(failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST +
-                         pInode->sharedByte, 1, 0)) ){
-        int failed2 = SQLITE_OK;
-        /* now attemmpt to get the exclusive lock range */
-        failed = afpSetLock(context->dbPath, pFile, SHARED_FIRST, 
-                               SHARED_SIZE, 1);
-        if( failed && (failed2 = afpSetLock(context->dbPath, pFile, 
-                       SHARED_FIRST + pInode->sharedByte, 1, 1)) ){
-          /* Can't reestablish the shared lock.  Sqlite can't deal, this is
-          ** a critical I/O error
-          */
-          rc = ((failed & SQLITE_IOERR) == SQLITE_IOERR) ? failed2 : 
-               SQLITE_IOERR_LOCK;
-          goto afp_end_lock;
-        } 
-      }else{
-        rc = failed; 
-      }
-    }
-    if( failed ){
-      rc = failed;
-    }
-  }
-  
-  if( rc==SQLITE_OK ){
-    pFile->eFileLock = eFileLock;
-    pInode->eFileLock = eFileLock;
-  }else if( eFileLock==EXCLUSIVE_LOCK ){
-    pFile->eFileLock = PENDING_LOCK;
-    pInode->eFileLock = PENDING_LOCK;
-  }
-  
-afp_end_lock:
-  unixLeaveMutex();
-  OSTRACE(("LOCK    %d %s %s (afp)\n", pFile->h, azFileLock(eFileLock), 
-         rc==SQLITE_OK ? "ok" : "failed"));
-  return rc;
-}
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int afpUnlock(sqlite3_file *id, int eFileLock) {
-  int rc = SQLITE_OK;
-  unixFile *pFile = (unixFile*)id;
-  unixInodeInfo *pInode;
-  afpLockingContext *context = (afpLockingContext *) pFile->lockingContext;
-  int skipShared = 0;
-#ifdef SQLITE_TEST
-  int h = pFile->h;
-#endif
-
-  assert( pFile );
-  OSTRACE(("UNLOCK  %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock,
-           pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared,
-           osGetpid(0)));
-
-  assert( eFileLock<=SHARED_LOCK );
-  if( pFile->eFileLock<=eFileLock ){
-    return SQLITE_OK;
-  }
-  unixEnterMutex();
-  pInode = pFile->pInode;
-  assert( pInode->nShared!=0 );
-  if( pFile->eFileLock>SHARED_LOCK ){
-    assert( pInode->eFileLock==pFile->eFileLock );
-    SimulateIOErrorBenign(1);
-    SimulateIOError( h=(-1) )
-    SimulateIOErrorBenign(0);
-    
-#ifdef SQLITE_DEBUG
-    /* When reducing a lock such that other processes can start
-    ** reading the database file again, make sure that the
-    ** transaction counter was updated if any part of the database
-    ** file changed.  If the transaction counter is not updated,
-    ** other connections to the same file might not realize that
-    ** the file has changed and hence might not know to flush their
-    ** cache.  The use of a stale cache can lead to database corruption.
-    */
-    assert( pFile->inNormalWrite==0
-           || pFile->dbUpdate==0
-           || pFile->transCntrChng==1 );
-    pFile->inNormalWrite = 0;
-#endif
-    
-    if( pFile->eFileLock==EXCLUSIVE_LOCK ){
-      rc = afpSetLock(context->dbPath, pFile, SHARED_FIRST, SHARED_SIZE, 0);
-      if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1) ){
-        /* only re-establish the shared lock if necessary */
-        int sharedLockByte = SHARED_FIRST+pInode->sharedByte;
-        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 1);
-      } else {
-        skipShared = 1;
-      }
-    }
-    if( rc==SQLITE_OK && pFile->eFileLock>=PENDING_LOCK ){
-      rc = afpSetLock(context->dbPath, pFile, PENDING_BYTE, 1, 0);
-    } 
-    if( rc==SQLITE_OK && pFile->eFileLock>=RESERVED_LOCK && context->reserved ){
-      rc = afpSetLock(context->dbPath, pFile, RESERVED_BYTE, 1, 0);
-      if( !rc ){ 
-        context->reserved = 0; 
-      }
-    }
-    if( rc==SQLITE_OK && (eFileLock==SHARED_LOCK || pInode->nShared>1)){
-      pInode->eFileLock = SHARED_LOCK;
-    }
-  }
-  if( rc==SQLITE_OK && eFileLock==NO_LOCK ){
-
-    /* Decrement the shared lock counter.  Release the lock using an
-    ** OS call only when all threads in this same process have released
-    ** the lock.
-    */
-    unsigned long long sharedLockByte = SHARED_FIRST+pInode->sharedByte;
-    pInode->nShared--;
-    if( pInode->nShared==0 ){
-      SimulateIOErrorBenign(1);
-      SimulateIOError( h=(-1) )
-      SimulateIOErrorBenign(0);
-      if( !skipShared ){
-        rc = afpSetLock(context->dbPath, pFile, sharedLockByte, 1, 0);
-      }
-      if( !rc ){
-        pInode->eFileLock = NO_LOCK;
-        pFile->eFileLock = NO_LOCK;
-      }
-    }
-    if( rc==SQLITE_OK ){
-      pInode->nLock--;
-      assert( pInode->nLock>=0 );
-      if( pInode->nLock==0 ){
-        closePendingFds(pFile);
-      }
-    }
-  }
-  
-  unixLeaveMutex();
-  if( rc==SQLITE_OK ) pFile->eFileLock = eFileLock;
-  return rc;
-}
-
-/*
-** Close a file & cleanup AFP specific locking context 
-*/
-static int afpClose(sqlite3_file *id) {
-  int rc = SQLITE_OK;
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    afpUnlock(id, NO_LOCK);
-    unixEnterMutex();
-    if( pFile->pInode && pFile->pInode->nLock ){
-      /* If there are outstanding locks, do not actually close the file just
-      ** yet because that would clear those locks.  Instead, add the file
-      ** descriptor to pInode->aPending.  It will be automatically closed when
-      ** the last lock is cleared.
-      */
-      setPendingFd(pFile);
-    }
-    releaseInodeInfo(pFile);
-    sqlite3_free(pFile->lockingContext);
-    rc = closeUnixFile(id);
-    unixLeaveMutex();
-  }
-  return rc;
-}
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The code above is the AFP lock implementation.  The code is specific
-** to MacOSX and does not work on other unix platforms.  No alternative
-** is available.  If you don't compile for a mac, then the "unix-afp"
-** VFS is not available.
-**
-********************* End of the AFP lock implementation **********************
-******************************************************************************/
-
-/******************************************************************************
-*************************** Begin NFS Locking ********************************/
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/*
- ** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
- ** must be either NO_LOCK or SHARED_LOCK.
- **
- ** If the locking level of the file descriptor is already at or below
- ** the requested locking level, this routine is a no-op.
- */
-static int nfsUnlock(sqlite3_file *id, int eFileLock){
-  return posixUnlock(id, eFileLock, 1);
-}
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The code above is the NFS lock implementation.  The code is specific
-** to MacOSX and does not work on other unix platforms.  No alternative
-** is available.  
-**
-********************* End of the NFS lock implementation **********************
-******************************************************************************/
-
-/******************************************************************************
-**************** Non-locking sqlite3_file methods *****************************
-**
-** The next division contains implementations for all methods of the 
-** sqlite3_file object other than the locking methods.  The locking
-** methods were defined in divisions above (one locking method per
-** division).  Those methods that are common to all locking modes
-** are gather together into this division.
-*/
-
-/*
-** Seek to the offset passed as the second argument, then read cnt 
-** bytes into pBuf. Return the number of bytes actually read.
-**
-** NB:  If you define USE_PREAD or USE_PREAD64, then it might also
-** be necessary to define _XOPEN_SOURCE to be 500.  This varies from
-** one system to another.  Since SQLite does not define USE_PREAD
-** in any form by default, we will not attempt to define _XOPEN_SOURCE.
-** See tickets #2741 and #2681.
-**
-** To avoid stomping the errno value on a failed read the lastErrno value
-** is set before returning.
-*/
-static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
-  int got;
-  int prior = 0;
-#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
-  i64 newOffset;
-#endif
-  TIMER_START;
-  assert( cnt==(cnt&0x1ffff) );
-  assert( id->h>2 );
-  do{
-#if defined(USE_PREAD)
-    got = osPread(id->h, pBuf, cnt, offset);
-    SimulateIOError( got = -1 );
-#elif defined(USE_PREAD64)
-    got = osPread64(id->h, pBuf, cnt, offset);
-    SimulateIOError( got = -1 );
-#else
-    newOffset = lseek(id->h, offset, SEEK_SET);
-    SimulateIOError( newOffset-- );
-    if( newOffset!=offset ){
-      if( newOffset == -1 ){
-        storeLastErrno((unixFile*)id, errno);
-      }else{
-        storeLastErrno((unixFile*)id, 0);
-      }
-      return -1;
-    }
-    got = osRead(id->h, pBuf, cnt);
-#endif
-    if( got==cnt ) break;
-    if( got<0 ){
-      if( errno==EINTR ){ got = 1; continue; }
-      prior = 0;
-      storeLastErrno((unixFile*)id,  errno);
-      break;
-    }else if( got>0 ){
-      cnt -= got;
-      offset += got;
-      prior += got;
-      pBuf = (void*)(got + (char*)pBuf);
-    }
-  }while( got>0 );
-  TIMER_END;
-  OSTRACE(("READ    %-3d %5d %7lld %llu\n",
-            id->h, got+prior, offset-prior, TIMER_ELAPSED));
-  return got+prior;
-}
-
-/*
-** Read data from a file into a buffer.  Return SQLITE_OK if all
-** bytes were read successfully and SQLITE_IOERR if anything goes
-** wrong.
-*/
-static int unixRead(
-  sqlite3_file *id, 
-  void *pBuf, 
-  int amt,
-  sqlite3_int64 offset
-){
-  unixFile *pFile = (unixFile *)id;
-  int got;
-  assert( id );
-  assert( offset>=0 );
-  assert( amt>0 );
-
-  /* If this is a database file (not a journal, master-journal or temp
-  ** file), the bytes in the locking range should never be read or written. */
-#if 0
-  assert( pFile->pUnused==0
-       || offset>=PENDING_BYTE+512
-       || offset+amt<=PENDING_BYTE 
-  );
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this read request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], amt);
-      return SQLITE_OK;
-    }else{
-      int nCopy = pFile->mmapSize - offset;
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
-
-  got = seekAndRead(pFile, offset, pBuf, amt);
-  if( got==amt ){
-    return SQLITE_OK;
-  }else if( got<0 ){
-    /* lastErrno set by seekAndRead */
-    return SQLITE_IOERR_READ;
-  }else{
-    storeLastErrno(pFile, 0);   /* not a system error */
-    /* Unread parts of the buffer must be zero-filled */
-    memset(&((char*)pBuf)[got], 0, amt-got);
-    return SQLITE_IOERR_SHORT_READ;
-  }
-}
-
-/*
-** Attempt to seek the file-descriptor passed as the first argument to
-** absolute offset iOff, then attempt to write nBuf bytes of data from
-** pBuf to it. If an error occurs, return -1 and set *piErrno. Otherwise, 
-** return the actual number of bytes written (which may be less than
-** nBuf).
-*/
-static int seekAndWriteFd(
-  int fd,                         /* File descriptor to write to */
-  i64 iOff,                       /* File offset to begin writing at */
-  const void *pBuf,               /* Copy data from this buffer to the file */
-  int nBuf,                       /* Size of buffer pBuf in bytes */
-  int *piErrno                    /* OUT: Error number if error occurs */
-){
-  int rc = 0;                     /* Value returned by system call */
-
-  assert( nBuf==(nBuf&0x1ffff) );
-  assert( fd>2 );
-  nBuf &= 0x1ffff;
-  TIMER_START;
-
-#if defined(USE_PREAD)
-  do{ rc = (int)osPwrite(fd, pBuf, nBuf, iOff); }while( rc<0 && errno==EINTR );
-#elif defined(USE_PREAD64)
-  do{ rc = (int)osPwrite64(fd, pBuf, nBuf, iOff);}while( rc<0 && errno==EINTR);
-#else
-  do{
-    i64 iSeek = lseek(fd, iOff, SEEK_SET);
-    SimulateIOError( iSeek-- );
-
-    if( iSeek!=iOff ){
-      if( piErrno ) *piErrno = (iSeek==-1 ? errno : 0);
-      return -1;
-    }
-    rc = osWrite(fd, pBuf, nBuf);
-  }while( rc<0 && errno==EINTR );
-#endif
-
-  TIMER_END;
-  OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", fd, rc, iOff, TIMER_ELAPSED));
-
-  if( rc<0 && piErrno ) *piErrno = errno;
-  return rc;
-}
-
-
-/*
-** Seek to the offset in id->offset then read cnt bytes into pBuf.
-** Return the number of bytes actually read.  Update the offset.
-**
-** To avoid stomping the errno value on a failed write the lastErrno value
-** is set before returning.
-*/
-static int seekAndWrite(unixFile *id, i64 offset, const void *pBuf, int cnt){
-  return seekAndWriteFd(id->h, offset, pBuf, cnt, &id->lastErrno);
-}
-
-
-/*
-** Write data from a buffer into a file.  Return SQLITE_OK on success
-** or some other error code on failure.
-*/
-static int unixWrite(
-  sqlite3_file *id, 
-  const void *pBuf, 
-  int amt,
-  sqlite3_int64 offset 
-){
-  unixFile *pFile = (unixFile*)id;
-  int wrote = 0;
-  assert( id );
-  assert( amt>0 );
-
-  /* If this is a database file (not a journal, master-journal or temp
-  ** file), the bytes in the locking range should never be read or written. */
-#if 0
-  assert( pFile->pUnused==0
-       || offset>=PENDING_BYTE+512
-       || offset+amt<=PENDING_BYTE 
-  );
-#endif
-
-#ifdef SQLITE_DEBUG
-  /* If we are doing a normal write to a database file (as opposed to
-  ** doing a hot-journal rollback or a write to some file other than a
-  ** normal database file) then record the fact that the database
-  ** has changed.  If the transaction counter is modified, record that
-  ** fact too.
-  */
-  if( pFile->inNormalWrite ){
-    pFile->dbUpdate = 1;  /* The database has been modified */
-    if( offset<=24 && offset+amt>=27 ){
-      int rc;
-      char oldCntr[4];
-      SimulateIOErrorBenign(1);
-      rc = seekAndRead(pFile, 24, oldCntr, 4);
-      SimulateIOErrorBenign(0);
-      if( rc!=4 || memcmp(oldCntr, &((char*)pBuf)[24-offset], 4)!=0 ){
-        pFile->transCntrChng = 1;  /* The transaction counter has changed */
-      }
-    }
-  }
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this write request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, amt);
-      return SQLITE_OK;
-    }else{
-      int nCopy = pFile->mmapSize - offset;
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
- 
-  while( (wrote = seekAndWrite(pFile, offset, pBuf, amt))<amt && wrote>0 ){
-    amt -= wrote;
-    offset += wrote;
-    pBuf = &((char*)pBuf)[wrote];
-  }
-  SimulateIOError(( wrote=(-1), amt=1 ));
-  SimulateDiskfullError(( wrote=0, amt=1 ));
-
-  if( amt>wrote ){
-    if( wrote<0 && pFile->lastErrno!=ENOSPC ){
-      /* lastErrno set by seekAndWrite */
-      return SQLITE_IOERR_WRITE;
-    }else{
-      storeLastErrno(pFile, 0); /* not a system error */
-      return SQLITE_FULL;
-    }
-  }
-
-  return SQLITE_OK;
-}
-
-#ifdef SQLITE_TEST
-/*
-** Count the number of fullsyncs and normal syncs.  This is used to test
-** that syncs and fullsyncs are occurring at the right times.
-*/
-SQLITE_PRIVATE int sqlite3_sync_count = 0;
-SQLITE_PRIVATE int sqlite3_fullsync_count = 0;
-#endif
-
-/*
-** We do not trust systems to provide a working fdatasync().  Some do.
-** Others do no.  To be safe, we will stick with the (slightly slower)
-** fsync(). If you know that your system does support fdatasync() correctly,
-** then simply compile with -Dfdatasync=fdatasync or -DHAVE_FDATASYNC
-*/
-#if !defined(fdatasync) && !HAVE_FDATASYNC
-# define fdatasync fsync
-#endif
-
-/*
-** Define HAVE_FULLFSYNC to 0 or 1 depending on whether or not
-** the F_FULLFSYNC macro is defined.  F_FULLFSYNC is currently
-** only available on Mac OS X.  But that could change.
-*/
-#ifdef F_FULLFSYNC
-# define HAVE_FULLFSYNC 1
-#else
-# define HAVE_FULLFSYNC 0
-#endif
-
-
-/*
-** The fsync() system call does not work as advertised on many
-** unix systems.  The following procedure is an attempt to make
-** it work better.
-**
-** The SQLITE_NO_SYNC macro disables all fsync()s.  This is useful
-** for testing when we want to run through the test suite quickly.
-** You are strongly advised *not* to deploy with SQLITE_NO_SYNC
-** enabled, however, since with SQLITE_NO_SYNC enabled, an OS crash
-** or power failure will likely corrupt the database file.
-**
-** SQLite sets the dataOnly flag if the size of the file is unchanged.
-** The idea behind dataOnly is that it should only write the file content
-** to disk, not the inode.  We only set dataOnly if the file size is 
-** unchanged since the file size is part of the inode.  However, 
-** Ted Ts'o tells us that fdatasync() will also write the inode if the
-** file size has changed.  The only real difference between fdatasync()
-** and fsync(), Ted tells us, is that fdatasync() will not flush the
-** inode if the mtime or owner or other inode attributes have changed.
-** We only care about the file size, not the other file attributes, so
-** as far as SQLite is concerned, an fdatasync() is always adequate.
-** So, we always use fdatasync() if it is available, regardless of
-** the value of the dataOnly flag.
-*/
-static int full_fsync(int fd, int fullSync, int dataOnly){
-  int rc;
-
-  /* The following "ifdef/elif/else/" block has the same structure as
-  ** the one below. It is replicated here solely to avoid cluttering 
-  ** up the real code with the UNUSED_PARAMETER() macros.
-  */
-#ifdef SQLITE_NO_SYNC
-  UNUSED_PARAMETER(fd);
-  UNUSED_PARAMETER(fullSync);
-  UNUSED_PARAMETER(dataOnly);
-#elif HAVE_FULLFSYNC
-  UNUSED_PARAMETER(dataOnly);
-#else
-  UNUSED_PARAMETER(fullSync);
-  UNUSED_PARAMETER(dataOnly);
-#endif
-
-  /* Record the number of times that we do a normal fsync() and 
-  ** FULLSYNC.  This is used during testing to verify that this procedure
-  ** gets called with the correct arguments.
-  */
-#ifdef SQLITE_TEST
-  if( fullSync ) sqlite3_fullsync_count++;
-  sqlite3_sync_count++;
-#endif
-
-  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
-  ** no-op
-  */
-#ifdef SQLITE_NO_SYNC
-  rc = SQLITE_OK;
-#elif HAVE_FULLFSYNC
-  if( fullSync ){
-    rc = osFcntl(fd, F_FULLFSYNC, 0);
-  }else{
-    rc = 1;
-  }
-  /* If the FULLFSYNC failed, fall back to attempting an fsync().
-  ** It shouldn't be possible for fullfsync to fail on the local 
-  ** file system (on OSX), so failure indicates that FULLFSYNC
-  ** isn't supported for this file system. So, attempt an fsync 
-  ** and (for now) ignore the overhead of a superfluous fcntl call.  
-  ** It'd be better to detect fullfsync support once and avoid 
-  ** the fcntl call every time sync is called.
-  */
-  if( rc ) rc = fsync(fd);
-
-#elif defined(__APPLE__)
-  /* fdatasync() on HFS+ doesn't yet flush the file size if it changed correctly
-  ** so currently we default to the macro that redefines fdatasync to fsync
-  */
-  rc = fsync(fd);
-#else 
-  rc = fdatasync(fd);
-#if OS_VXWORKS
-  if( rc==-1 && errno==ENOTSUP ){
-    rc = fsync(fd);
-  }
-#endif /* OS_VXWORKS */
-#endif /* ifdef SQLITE_NO_SYNC elif HAVE_FULLFSYNC */
-
-  if( OS_VXWORKS && rc!= -1 ){
-    rc = 0;
-  }
-  return rc;
-}
-
-/*
-** Open a file descriptor to the directory containing file zFilename.
-** If successful, *pFd is set to the opened file descriptor and
-** SQLITE_OK is returned. If an error occurs, either SQLITE_NOMEM
-** or SQLITE_CANTOPEN is returned and *pFd is set to an undefined
-** value.
-**
-** The directory file descriptor is used for only one thing - to
-** fsync() a directory to make sure file creation and deletion events
-** are flushed to disk.  Such fsyncs are not needed on newer
-** journaling filesystems, but are required on older filesystems.
-**
-** This routine can be overridden using the xSetSysCall interface.
-** The ability to override this routine was added in support of the
-** chromium sandbox.  Opening a directory is a security risk (we are
-** told) so making it overrideable allows the chromium sandbox to
-** replace this routine with a harmless no-op.  To make this routine
-** a no-op, replace it with a stub that returns SQLITE_OK but leaves
-** *pFd set to a negative number.
-**
-** If SQLITE_OK is returned, the caller is responsible for closing
-** the file descriptor *pFd using close().
-*/
-static int openDirectory(const char *zFilename, int *pFd){
-  int ii;
-  int fd = -1;
-  char zDirname[MAX_PATHNAME+1];
-
-  sqlite3_snprintf(MAX_PATHNAME, zDirname, "%s", zFilename);
-  for(ii=(int)strlen(zDirname); ii>1 && zDirname[ii]!='/'; ii--);
-  if( ii>0 ){
-    zDirname[ii] = '\0';
-    fd = robust_open(zDirname, O_RDONLY|O_BINARY, 0);
-    if( fd>=0 ){
-      OSTRACE(("OPENDIR %-3d %s\n", fd, zDirname));
-    }
-  }
-  *pFd = fd;
-  return (fd>=0?SQLITE_OK:unixLogError(SQLITE_CANTOPEN_BKPT, "open", zDirname));
-}
-
-/*
-** Make sure all writes to a particular file are committed to disk.
-**
-** If dataOnly==0 then both the file itself and its metadata (file
-** size, access time, etc) are synced.  If dataOnly!=0 then only the
-** file data is synced.
-**
-** Under Unix, also make sure that the directory entry for the file
-** has been created by fsync-ing the directory that contains the file.
-** If we do not do this and we encounter a power failure, the directory
-** entry for the journal might not exist after we reboot.  The next
-** SQLite to access the file will not know that the journal exists (because
-** the directory entry for the journal was never created) and the transaction
-** will not roll back - possibly leading to database corruption.
-*/
-static int unixSync(sqlite3_file *id, int flags){
-  int rc;
-  unixFile *pFile = (unixFile*)id;
-
-  int isDataOnly = (flags&SQLITE_SYNC_DATAONLY);
-  int isFullsync = (flags&0x0F)==SQLITE_SYNC_FULL;
-
-  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
-  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
-      || (flags&0x0F)==SQLITE_SYNC_FULL
-  );
-
-  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
-  ** line is to test that doing so does not cause any problems.
-  */
-  SimulateDiskfullError( return SQLITE_FULL );
-
-  assert( pFile );
-  OSTRACE(("SYNC    %-3d\n", pFile->h));
-  rc = full_fsync(pFile->h, isFullsync, isDataOnly);
-  SimulateIOError( rc=1 );
-  if( rc ){
-    storeLastErrno(pFile, errno);
-    return unixLogError(SQLITE_IOERR_FSYNC, "full_fsync", pFile->zPath);
-  }
-
-  /* Also fsync the directory containing the file if the DIRSYNC flag
-  ** is set.  This is a one-time occurrence.  Many systems (examples: AIX)
-  ** are unable to fsync a directory, so ignore errors on the fsync.
-  */
-  if( pFile->ctrlFlags & UNIXFILE_DIRSYNC ){
-    int dirfd;
-    OSTRACE(("DIRSYNC %s (have_fullfsync=%d fullsync=%d)\n", pFile->zPath,
-            HAVE_FULLFSYNC, isFullsync));
-    rc = osOpenDirectory(pFile->zPath, &dirfd);
-    if( rc==SQLITE_OK && dirfd>=0 ){
-      full_fsync(dirfd, 0, 0);
-      robust_close(pFile, dirfd, __LINE__);
-    }else if( rc==SQLITE_CANTOPEN ){
-      rc = SQLITE_OK;
-    }
-    pFile->ctrlFlags &= ~UNIXFILE_DIRSYNC;
-  }
-  return rc;
-}
-
-/*
-** Truncate an open file to a specified size
-*/
-static int unixTruncate(sqlite3_file *id, i64 nByte){
-  unixFile *pFile = (unixFile *)id;
-  int rc;
-  assert( pFile );
-  SimulateIOError( return SQLITE_IOERR_TRUNCATE );
-
-  /* If the user has configured a chunk-size for this file, truncate the
-  ** file so that it consists of an integer number of chunks (i.e. the
-  ** actual file size after the operation may be larger than the requested
-  ** size).
-  */
-  if( pFile->szChunk>0 ){
-    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
-  }
-
-  rc = robust_ftruncate(pFile->h, nByte);
-  if( rc ){
-    storeLastErrno(pFile, errno);
-    return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
-  }else{
-#ifdef SQLITE_DEBUG
-    /* If we are doing a normal write to a database file (as opposed to
-    ** doing a hot-journal rollback or a write to some file other than a
-    ** normal database file) and we truncate the file to zero length,
-    ** that effectively updates the change counter.  This might happen
-    ** when restoring a database using the backup API from a zero-length
-    ** source.
-    */
-    if( pFile->inNormalWrite && nByte==0 ){
-      pFile->transCntrChng = 1;
-    }
-#endif
-
-#if SQLITE_MAX_MMAP_SIZE>0
-    /* If the file was just truncated to a size smaller than the currently
-    ** mapped region, reduce the effective mapping size as well. SQLite will
-    ** use read() and write() to access data beyond this point from now on.  
-    */
-    if( nByte<pFile->mmapSize ){
-      pFile->mmapSize = nByte;
-    }
-#endif
-
-    return SQLITE_OK;
-  }
-}
-
-/*
-** Determine the current size of a file in bytes
-*/
-static int unixFileSize(sqlite3_file *id, i64 *pSize){
-  int rc;
-  struct stat buf;
-  assert( id );
-  rc = osFstat(((unixFile*)id)->h, &buf);
-  SimulateIOError( rc=1 );
-  if( rc!=0 ){
-    storeLastErrno((unixFile*)id, errno);
-    return SQLITE_IOERR_FSTAT;
-  }
-  *pSize = buf.st_size;
-
-  /* When opening a zero-size database, the findInodeInfo() procedure
-  ** writes a single byte into that file in order to work around a bug
-  ** in the OS-X msdos filesystem.  In order to avoid problems with upper
-  ** layers, we need to report this file size as zero even though it is
-  ** really 1.   Ticket #3260.
-  */
-  if( *pSize==1 ) *pSize = 0;
-
-
-  return SQLITE_OK;
-}
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-/*
-** Handler for proxy-locking file-control verbs.  Defined below in the
-** proxying locking division.
-*/
-static int proxyFileControl(sqlite3_file*,int,void*);
-#endif
-
-/* 
-** This function is called to handle the SQLITE_FCNTL_SIZE_HINT 
-** file-control operation.  Enlarge the database to nBytes in size
-** (rounded up to the next chunk-size).  If the database is already
-** nBytes or larger, this routine is a no-op.
-*/
-static int fcntlSizeHint(unixFile *pFile, i64 nByte){
-  if( pFile->szChunk>0 ){
-    i64 nSize;                    /* Required file size */
-    struct stat buf;              /* Used to hold return values of fstat() */
-   
-    if( osFstat(pFile->h, &buf) ){
-      return SQLITE_IOERR_FSTAT;
-    }
-
-    nSize = ((nByte+pFile->szChunk-1) / pFile->szChunk) * pFile->szChunk;
-    if( nSize>(i64)buf.st_size ){
-
-#if defined(HAVE_POSIX_FALLOCATE) && HAVE_POSIX_FALLOCATE
-      /* The code below is handling the return value of osFallocate() 
-      ** correctly. posix_fallocate() is defined to "returns zero on success, 
-      ** or an error number on  failure". See the manpage for details. */
-      int err;
-      do{
-        err = osFallocate(pFile->h, buf.st_size, nSize-buf.st_size);
-      }while( err==EINTR );
-      if( err ) return SQLITE_IOERR_WRITE;
-#else
-      /* If the OS does not have posix_fallocate(), fake it. Write a 
-      ** single byte to the last byte in each block that falls entirely
-      ** within the extended region. Then, if required, a single byte
-      ** at offset (nSize-1), to set the size of the file correctly.
-      ** This is a similar technique to that used by glibc on systems
-      ** that do not have a real fallocate() call.
-      */
-      int nBlk = buf.st_blksize;  /* File-system block size */
-      int nWrite = 0;             /* Number of bytes written by seekAndWrite */
-      i64 iWrite;                 /* Next offset to write to */
-
-      iWrite = ((buf.st_size + 2*nBlk - 1)/nBlk)*nBlk-1;
-      assert( iWrite>=buf.st_size );
-      assert( (iWrite/nBlk)==((buf.st_size+nBlk-1)/nBlk) );
-      assert( ((iWrite+1)%nBlk)==0 );
-      for(/*no-op*/; iWrite<nSize; iWrite+=nBlk ){
-        nWrite = seekAndWrite(pFile, iWrite, "", 1);
-        if( nWrite!=1 ) return SQLITE_IOERR_WRITE;
-      }
-      if( nWrite==0 || (nSize%nBlk) ){
-        nWrite = seekAndWrite(pFile, nSize-1, "", 1);
-        if( nWrite!=1 ) return SQLITE_IOERR_WRITE;
-      }
-#endif
-    }
-  }
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFile->mmapSizeMax>0 && nByte>pFile->mmapSize ){
-    int rc;
-    if( pFile->szChunk<=0 ){
-      if( robust_ftruncate(pFile->h, nByte) ){
-        storeLastErrno(pFile, errno);
-        return unixLogError(SQLITE_IOERR_TRUNCATE, "ftruncate", pFile->zPath);
-      }
-    }
-
-    rc = unixMapfile(pFile, nByte);
-    return rc;
-  }
-#endif
-
-  return SQLITE_OK;
-}
-
-/*
-** If *pArg is initially negative then this is a query.  Set *pArg to
-** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
-**
-** If *pArg is 0 or 1, then clear or set the mask bit of pFile->ctrlFlags.
-*/
-static void unixModeBit(unixFile *pFile, unsigned char mask, int *pArg){
-  if( *pArg<0 ){
-    *pArg = (pFile->ctrlFlags & mask)!=0;
-  }else if( (*pArg)==0 ){
-    pFile->ctrlFlags &= ~mask;
-  }else{
-    pFile->ctrlFlags |= mask;
-  }
-}
-
-/* Forward declaration */
-static int unixGetTempname(int nBuf, char *zBuf);
-
-/*
-** Information and control of an open file handle.
-*/
-static int unixFileControl(sqlite3_file *id, int op, void *pArg){
-  unixFile *pFile = (unixFile*)id;
-  switch( op ){
-    case SQLITE_FCNTL_WAL_BLOCK: {
-      /* pFile->ctrlFlags |= UNIXFILE_BLOCK; // Deferred feature */
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_LOCKSTATE: {
-      *(int*)pArg = pFile->eFileLock;
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_LAST_ERRNO: {
-      *(int*)pArg = pFile->lastErrno;
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_CHUNK_SIZE: {
-      pFile->szChunk = *(int *)pArg;
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_SIZE_HINT: {
-      int rc;
-      SimulateIOErrorBenign(1);
-      rc = fcntlSizeHint(pFile, *(i64 *)pArg);
-      SimulateIOErrorBenign(0);
-      return rc;
-    }
-    case SQLITE_FCNTL_PERSIST_WAL: {
-      unixModeBit(pFile, UNIXFILE_PERSIST_WAL, (int*)pArg);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
-      unixModeBit(pFile, UNIXFILE_PSOW, (int*)pArg);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_VFSNAME: {
-      *(char**)pArg = sqlite3_mprintf("%s", pFile->pVfs->zName);
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_TEMPFILENAME: {
-      char *zTFile = sqlite3_malloc64( pFile->pVfs->mxPathname );
-      if( zTFile ){
-        unixGetTempname(pFile->pVfs->mxPathname, zTFile);
-        *(char**)pArg = zTFile;
-      }
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_HAS_MOVED: {
-      *(int*)pArg = fileHasMoved(pFile);
-      return SQLITE_OK;
-    }
-#if SQLITE_MAX_MMAP_SIZE>0
-    case SQLITE_FCNTL_MMAP_SIZE: {
-      i64 newLimit = *(i64*)pArg;
-      int rc = SQLITE_OK;
-      if( newLimit>sqlite3GlobalConfig.mxMmap ){
-        newLimit = sqlite3GlobalConfig.mxMmap;
-      }
-      *(i64*)pArg = pFile->mmapSizeMax;
-      if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
-        pFile->mmapSizeMax = newLimit;
-        if( pFile->mmapSize>0 ){
-          unixUnmapfile(pFile);
-          rc = unixMapfile(pFile, -1);
-        }
-      }
-      return rc;
-    }
-#endif
-#ifdef SQLITE_DEBUG
-    /* The pager calls this method to signal that it has done
-    ** a rollback and that the database is therefore unchanged and
-    ** it hence it is OK for the transaction change counter to be
-    ** unchanged.
-    */
-    case SQLITE_FCNTL_DB_UNCHANGED: {
-      ((unixFile*)id)->dbUpdate = 0;
-      return SQLITE_OK;
-    }
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-    case SQLITE_FCNTL_SET_LOCKPROXYFILE:
-    case SQLITE_FCNTL_GET_LOCKPROXYFILE: {
-      return proxyFileControl(id,op,pArg);
-    }
-#endif /* SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__) */
-  }
-  return SQLITE_NOTFOUND;
-}
-
-/*
-** Return the sector size in bytes of the underlying block device for
-** the specified file. This is almost always 512 bytes, but may be
-** larger for some devices.
-**
-** SQLite code assumes this function cannot fail. It also assumes that
-** if two files are created in the same file-system directory (i.e.
-** a database and its journal file) that the sector size will be the
-** same for both.
-*/
-#ifndef __QNXNTO__ 
-static int unixSectorSize(sqlite3_file *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  return SQLITE_DEFAULT_SECTOR_SIZE;
-}
-#endif
-
-/*
-** The following version of unixSectorSize() is optimized for QNX.
-*/
-#ifdef __QNXNTO__
-#include <sys/dcmd_blk.h>
-#include <sys/statvfs.h>
-static int unixSectorSize(sqlite3_file *id){
-  unixFile *pFile = (unixFile*)id;
-  if( pFile->sectorSize == 0 ){
-    struct statvfs fsInfo;
-       
-    /* Set defaults for non-supported filesystems */
-    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
-    pFile->deviceCharacteristics = 0;
-    if( fstatvfs(pFile->h, &fsInfo) == -1 ) {
-      return pFile->sectorSize;
-    }
-
-    if( !strcmp(fsInfo.f_basetype, "tmp") ) {
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC4K |       /* All ram filesystem writes are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( strstr(fsInfo.f_basetype, "etfs") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* etfs cluster size writes are atomic */
-        (pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) |
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( !strcmp(fsInfo.f_basetype, "qnx6") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC |         /* All filesystem writes are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( !strcmp(fsInfo.f_basetype, "qnx4") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* full bitset of atomics from max sector size and smaller */
-        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else if( strstr(fsInfo.f_basetype, "dos") ){
-      pFile->sectorSize = fsInfo.f_bsize;
-      pFile->deviceCharacteristics =
-        /* full bitset of atomics from max sector size and smaller */
-        ((pFile->sectorSize / 512 * SQLITE_IOCAP_ATOMIC512) << 1) - 2 |
-        SQLITE_IOCAP_SEQUENTIAL |     /* The ram filesystem has no write behind
-                                      ** so it is ordered */
-        0;
-    }else{
-      pFile->deviceCharacteristics =
-        SQLITE_IOCAP_ATOMIC512 |      /* blocks are atomic */
-        SQLITE_IOCAP_SAFE_APPEND |    /* growing the file does not occur until
-                                      ** the write succeeds */
-        0;
-    }
-  }
-  /* Last chance verification.  If the sector size isn't a multiple of 512
-  ** then it isn't valid.*/
-  if( pFile->sectorSize % 512 != 0 ){
-    pFile->deviceCharacteristics = 0;
-    pFile->sectorSize = SQLITE_DEFAULT_SECTOR_SIZE;
-  }
-  return pFile->sectorSize;
-}
-#endif /* __QNXNTO__ */
-
-/*
-** Return the device characteristics for the file.
-**
-** This VFS is set up to return SQLITE_IOCAP_POWERSAFE_OVERWRITE by default.
-** However, that choice is controversial since technically the underlying
-** file system does not always provide powersafe overwrites.  (In other
-** words, after a power-loss event, parts of the file that were never
-** written might end up being altered.)  However, non-PSOW behavior is very,
-** very rare.  And asserting PSOW makes a large reduction in the amount
-** of required I/O for journaling, since a lot of padding is eliminated.
-**  Hence, while POWERSAFE_OVERWRITE is on by default, there is a file-control
-** available to turn it off and URI query parameter available to turn it off.
-*/
-static int unixDeviceCharacteristics(sqlite3_file *id){
-  unixFile *p = (unixFile*)id;
-  int rc = 0;
-#ifdef __QNXNTO__
-  if( p->sectorSize==0 ) unixSectorSize(id);
-  rc = p->deviceCharacteristics;
-#endif
-  if( p->ctrlFlags & UNIXFILE_PSOW ){
-    rc |= SQLITE_IOCAP_POWERSAFE_OVERWRITE;
-  }
-  return rc;
-}
-
-#if !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-
-/*
-** Return the system page size.
-**
-** This function should not be called directly by other code in this file. 
-** Instead, it should be called via macro osGetpagesize().
-*/
-static int unixGetpagesize(void){
-#if OS_VXWORKS
-  return 1024;
-#elif defined(_BSD_SOURCE)
-  return getpagesize();
-#else
-  return (int)sysconf(_SC_PAGESIZE);
-#endif
-}
-
-#endif /* !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0 */
-
-#ifndef SQLITE_OMIT_WAL
-
-/*
-** Object used to represent an shared memory buffer.  
-**
-** When multiple threads all reference the same wal-index, each thread
-** has its own unixShm object, but they all point to a single instance
-** of this unixShmNode object.  In other words, each wal-index is opened
-** only once per process.
-**
-** Each unixShmNode object is connected to a single unixInodeInfo object.
-** We could coalesce this object into unixInodeInfo, but that would mean
-** every open file that does not use shared memory (in other words, most
-** open files) would have to carry around this extra information.  So
-** the unixInodeInfo object contains a pointer to this unixShmNode object
-** and the unixShmNode object is created only when needed.
-**
-** unixMutexHeld() must be true when creating or destroying
-** this object or while reading or writing the following fields:
-**
-**      nRef
-**
-** The following fields are read-only after the object is created:
-** 
-**      fid
-**      zFilename
-**
-** Either unixShmNode.mutex must be held or unixShmNode.nRef==0 and
-** unixMutexHeld() is true when reading or writing any other field
-** in this structure.
-*/
-struct unixShmNode {
-  unixInodeInfo *pInode;     /* unixInodeInfo that owns this SHM node */
-  sqlite3_mutex *mutex;      /* Mutex to access this object */
-  char *zFilename;           /* Name of the mmapped file */
-  int h;                     /* Open file descriptor */
-  int szRegion;              /* Size of shared-memory regions */
-  u16 nRegion;               /* Size of array apRegion */
-  u8 isReadonly;             /* True if read-only */
-  char **apRegion;           /* Array of mapped shared-memory regions */
-  int nRef;                  /* Number of unixShm objects pointing to this */
-  unixShm *pFirst;           /* All unixShm objects pointing to this */
-#ifdef SQLITE_DEBUG
-  u8 exclMask;               /* Mask of exclusive locks held */
-  u8 sharedMask;             /* Mask of shared locks held */
-  u8 nextShmId;              /* Next available unixShm.id value */
-#endif
-};
-
-/*
-** Structure used internally by this VFS to record the state of an
-** open shared memory connection.
-**
-** The following fields are initialized when this object is created and
-** are read-only thereafter:
-**
-**    unixShm.pFile
-**    unixShm.id
-**
-** All other fields are read/write.  The unixShm.pFile->mutex must be held
-** while accessing any read/write fields.
-*/
-struct unixShm {
-  unixShmNode *pShmNode;     /* The underlying unixShmNode object */
-  unixShm *pNext;            /* Next unixShm with the same unixShmNode */
-  u8 hasMutex;               /* True if holding the unixShmNode mutex */
-  u8 id;                     /* Id of this connection within its unixShmNode */
-  u16 sharedMask;            /* Mask of shared locks held */
-  u16 exclMask;              /* Mask of exclusive locks held */
-};
-
-/*
-** Constants used for locking
-*/
-#define UNIX_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)         /* first lock byte */
-#define UNIX_SHM_DMS    (UNIX_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
-
-/*
-** Apply posix advisory locks for all bytes from ofst through ofst+n-1.
-**
-** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
-** otherwise.
-*/
-static int unixShmSystemLock(
-  unixFile *pFile,       /* Open connection to the WAL file */
-  int lockType,          /* F_UNLCK, F_RDLCK, or F_WRLCK */
-  int ofst,              /* First byte of the locking range */
-  int n                  /* Number of bytes to lock */
-){
-  unixShmNode *pShmNode; /* Apply locks to this open shared-memory segment */
-  struct flock f;        /* The posix advisory locking structure */
-  int rc = SQLITE_OK;    /* Result code form fcntl() */
-
-  /* Access to the unixShmNode object is serialized by the caller */
-  pShmNode = pFile->pInode->pShmNode;
-  assert( sqlite3_mutex_held(pShmNode->mutex) || pShmNode->nRef==0 );
-
-  /* Shared locks never span more than one byte */
-  assert( n==1 || lockType!=F_RDLCK );
-
-  /* Locks are within range */
-  assert( n>=1 && n<SQLITE_SHM_NLOCK );
-
-  if( pShmNode->h>=0 ){
-    int lkType;
-    /* Initialize the locking parameters */
-    memset(&f, 0, sizeof(f));
-    f.l_type = lockType;
-    f.l_whence = SEEK_SET;
-    f.l_start = ofst;
-    f.l_len = n;
-
-    lkType = (pFile->ctrlFlags & UNIXFILE_BLOCK)!=0 ? F_SETLKW : F_SETLK;
-    rc = osFcntl(pShmNode->h, lkType, &f);
-    rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
-    pFile->ctrlFlags &= ~UNIXFILE_BLOCK;
-  }
-
-  /* Update the global lock state and do debug tracing */
-#ifdef SQLITE_DEBUG
-  { u16 mask;
-  OSTRACE(("SHM-LOCK "));
-  mask = ofst>31 ? 0xffff : (1<<(ofst+n)) - (1<<ofst);
-  if( rc==SQLITE_OK ){
-    if( lockType==F_UNLCK ){
-      OSTRACE(("unlock %d ok", ofst));
-      pShmNode->exclMask &= ~mask;
-      pShmNode->sharedMask &= ~mask;
-    }else if( lockType==F_RDLCK ){
-      OSTRACE(("read-lock %d ok", ofst));
-      pShmNode->exclMask &= ~mask;
-      pShmNode->sharedMask |= mask;
-    }else{
-      assert( lockType==F_WRLCK );
-      OSTRACE(("write-lock %d ok", ofst));
-      pShmNode->exclMask |= mask;
-      pShmNode->sharedMask &= ~mask;
-    }
-  }else{
-    if( lockType==F_UNLCK ){
-      OSTRACE(("unlock %d failed", ofst));
-    }else if( lockType==F_RDLCK ){
-      OSTRACE(("read-lock failed"));
-    }else{
-      assert( lockType==F_WRLCK );
-      OSTRACE(("write-lock %d failed", ofst));
-    }
-  }
-  OSTRACE((" - afterwards %03x,%03x\n",
-           pShmNode->sharedMask, pShmNode->exclMask));
-  }
-#endif
-
-  return rc;        
-}
-
-/*
-** Return the minimum number of 32KB shm regions that should be mapped at
-** a time, assuming that each mapping must be an integer multiple of the
-** current system page-size.
-**
-** Usually, this is 1. The exception seems to be systems that are configured
-** to use 64KB pages - in this case each mapping must cover at least two
-** shm regions.
-*/
-static int unixShmRegionPerMap(void){
-  int shmsz = 32*1024;            /* SHM region size */
-  int pgsz = osGetpagesize();   /* System page size */
-  assert( ((pgsz-1)&pgsz)==0 );   /* Page size must be a power of 2 */
-  if( pgsz<shmsz ) return 1;
-  return pgsz/shmsz;
-}
-
-/*
-** Purge the unixShmNodeList list of all entries with unixShmNode.nRef==0.
-**
-** This is not a VFS shared-memory method; it is a utility function called
-** by VFS shared-memory methods.
-*/
-static void unixShmPurge(unixFile *pFd){
-  unixShmNode *p = pFd->pInode->pShmNode;
-  assert( unixMutexHeld() );
-  if( p && p->nRef==0 ){
-    int nShmPerMap = unixShmRegionPerMap();
-    int i;
-    assert( p->pInode==pFd->pInode );
-    sqlite3_mutex_free(p->mutex);
-    for(i=0; i<p->nRegion; i+=nShmPerMap){
-      if( p->h>=0 ){
-        osMunmap(p->apRegion[i], p->szRegion);
-      }else{
-        sqlite3_free(p->apRegion[i]);
-      }
-    }
-    sqlite3_free(p->apRegion);
-    if( p->h>=0 ){
-      robust_close(pFd, p->h, __LINE__);
-      p->h = -1;
-    }
-    p->pInode->pShmNode = 0;
-    sqlite3_free(p);
-  }
-}
-
-/*
-** Open a shared-memory area associated with open database file pDbFd.  
-** This particular implementation uses mmapped files.
-**
-** The file used to implement shared-memory is in the same directory
-** as the open database file and has the same name as the open database
-** file with the "-shm" suffix added.  For example, if the database file
-** is "/home/user1/config.db" then the file that is created and mmapped
-** for shared memory will be called "/home/user1/config.db-shm".  
-**
-** Another approach to is to use files in /dev/shm or /dev/tmp or an
-** some other tmpfs mount. But if a file in a different directory
-** from the database file is used, then differing access permissions
-** or a chroot() might cause two different processes on the same
-** database to end up using different files for shared memory - 
-** meaning that their memory would not really be shared - resulting
-** in database corruption.  Nevertheless, this tmpfs file usage
-** can be enabled at compile-time using -DSQLITE_SHM_DIRECTORY="/dev/shm"
-** or the equivalent.  The use of the SQLITE_SHM_DIRECTORY compile-time
-** option results in an incompatible build of SQLite;  builds of SQLite
-** that with differing SQLITE_SHM_DIRECTORY settings attempt to use the
-** same database file at the same time, database corruption will likely
-** result. The SQLITE_SHM_DIRECTORY compile-time option is considered
-** "unsupported" and may go away in a future SQLite release.
-**
-** When opening a new shared-memory file, if no other instances of that
-** file are currently open, in this process or in other processes, then
-** the file must be truncated to zero length or have its header cleared.
-**
-** If the original database file (pDbFd) is using the "unix-excl" VFS
-** that means that an exclusive lock is held on the database file and
-** that no other processes are able to read or write the database.  In
-** that case, we do not really need shared memory.  No shared memory
-** file is created.  The shared memory will be simulated with heap memory.
-*/
-static int unixOpenSharedMemory(unixFile *pDbFd){
-  struct unixShm *p = 0;          /* The connection to be opened */
-  struct unixShmNode *pShmNode;   /* The underlying mmapped file */
-  int rc;                         /* Result code */
-  unixInodeInfo *pInode;          /* The inode of fd */
-  char *zShmFilename;             /* Name of the file used for SHM */
-  int nShmFilename;               /* Size of the SHM filename in bytes */
-
-  /* Allocate space for the new unixShm object. */
-  p = sqlite3_malloc64( sizeof(*p) );
-  if( p==0 ) return SQLITE_NOMEM;
-  memset(p, 0, sizeof(*p));
-  assert( pDbFd->pShm==0 );
-
-  /* Check to see if a unixShmNode object already exists. Reuse an existing
-  ** one if present. Create a new one if necessary.
-  */
-  unixEnterMutex();
-  pInode = pDbFd->pInode;
-  pShmNode = pInode->pShmNode;
-  if( pShmNode==0 ){
-    struct stat sStat;                 /* fstat() info for database file */
-#ifndef SQLITE_SHM_DIRECTORY
-    const char *zBasePath = pDbFd->zPath;
-#endif
-
-    /* Call fstat() to figure out the permissions on the database file. If
-    ** a new *-shm file is created, an attempt will be made to create it
-    ** with the same permissions.
-    */
-    if( osFstat(pDbFd->h, &sStat) && pInode->bProcessLock==0 ){
-      rc = SQLITE_IOERR_FSTAT;
-      goto shm_open_err;
-    }
-
-#ifdef SQLITE_SHM_DIRECTORY
-    nShmFilename = sizeof(SQLITE_SHM_DIRECTORY) + 31;
-#else
-    nShmFilename = 6 + (int)strlen(zBasePath);
-#endif
-    pShmNode = sqlite3_malloc64( sizeof(*pShmNode) + nShmFilename );
-    if( pShmNode==0 ){
-      rc = SQLITE_NOMEM;
-      goto shm_open_err;
-    }
-    memset(pShmNode, 0, sizeof(*pShmNode)+nShmFilename);
-    zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
-#ifdef SQLITE_SHM_DIRECTORY
-    sqlite3_snprintf(nShmFilename, zShmFilename, 
-                     SQLITE_SHM_DIRECTORY "/sqlite-shm-%x-%x",
-                     (u32)sStat.st_ino, (u32)sStat.st_dev);
-#else
-    sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", zBasePath);
-#endif
-    pShmNode->h = -1;
-    pDbFd->pInode->pShmNode = pShmNode;
-    pShmNode->pInode = pDbFd->pInode;
-    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
-    if( pShmNode->mutex==0 ){
-      rc = SQLITE_NOMEM;
-      goto shm_open_err;
-    }
-
-    if( pInode->bProcessLock==0 ){
-      int openFlags = O_RDWR | O_CREAT;
-      pShmNode->h = robust_open(zShmFilename, openFlags, (sStat.st_mode&0777));
-      if( pShmNode->h<0 ){
-        rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zShmFilename);
-        goto shm_open_err;
-      }
-
-      /* If this process is running as root, make sure that the SHM file
-      ** is owned by the same user that owns the original database.  Otherwise,
-      ** the original owner will not be able to connect.
-      */
-      osFchown(pShmNode->h, sStat.st_uid, sStat.st_gid);
-  
-      /* Check to see if another process is holding the dead-man switch.
-      ** If not, truncate the file to zero length. 
-      */
-      rc = SQLITE_OK;
-      if( unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1)==SQLITE_OK ){
-        if( robust_ftruncate(pShmNode->h, 0) ){
-          rc = unixLogError(SQLITE_IOERR_SHMOPEN, "ftruncate", zShmFilename);
-        }
-      }
-      if( rc==SQLITE_OK ){
-        rc = unixShmSystemLock(pDbFd, F_RDLCK, UNIX_SHM_DMS, 1);
-      }
-      if( rc ) goto shm_open_err;
-    }
-  }
-
-  /* Make the new connection a child of the unixShmNode */
-  p->pShmNode = pShmNode;
-#ifdef SQLITE_DEBUG
-  p->id = pShmNode->nextShmId++;
-#endif
-  pShmNode->nRef++;
-  pDbFd->pShm = p;
-  unixLeaveMutex();
-
-  /* The reference count on pShmNode has already been incremented under
-  ** the cover of the unixEnterMutex() mutex and the pointer from the
-  ** new (struct unixShm) object to the pShmNode has been set. All that is
-  ** left to do is to link the new object into the linked list starting
-  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex 
-  ** mutex.
-  */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  p->pNext = pShmNode->pFirst;
-  pShmNode->pFirst = p;
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return SQLITE_OK;
-
-  /* Jump here on any error */
-shm_open_err:
-  unixShmPurge(pDbFd);       /* This call frees pShmNode if required */
-  sqlite3_free(p);
-  unixLeaveMutex();
-  return rc;
-}
-
-/*
-** This function is called to obtain a pointer to region iRegion of the 
-** shared-memory associated with the database file fd. Shared-memory regions 
-** are numbered starting from zero. Each shared-memory region is szRegion 
-** bytes in size.
-**
-** If an error occurs, an error code is returned and *pp is set to NULL.
-**
-** Otherwise, if the bExtend parameter is 0 and the requested shared-memory
-** region has not been allocated (by any client, including one running in a
-** separate process), then *pp is set to NULL and SQLITE_OK returned. If 
-** bExtend is non-zero and the requested shared-memory region has not yet 
-** been allocated, it is allocated by this function.
-**
-** If the shared-memory region has already been allocated or is allocated by
-** this call as described above, then it is mapped into this processes 
-** address space (if it is not already), *pp is set to point to the mapped 
-** memory and SQLITE_OK returned.
-*/
-static int unixShmMap(
-  sqlite3_file *fd,               /* Handle open on database file */
-  int iRegion,                    /* Region to retrieve */
-  int szRegion,                   /* Size of regions */
-  int bExtend,                    /* True to extend file if necessary */
-  void volatile **pp              /* OUT: Mapped memory */
-){
-  unixFile *pDbFd = (unixFile*)fd;
-  unixShm *p;
-  unixShmNode *pShmNode;
-  int rc = SQLITE_OK;
-  int nShmPerMap = unixShmRegionPerMap();
-  int nReqRegion;
-
-  /* If the shared-memory file has not yet been opened, open it now. */
-  if( pDbFd->pShm==0 ){
-    rc = unixOpenSharedMemory(pDbFd);
-    if( rc!=SQLITE_OK ) return rc;
-  }
-
-  p = pDbFd->pShm;
-  pShmNode = p->pShmNode;
-  sqlite3_mutex_enter(pShmNode->mutex);
-  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
-  assert( pShmNode->pInode==pDbFd->pInode );
-  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
-  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
-
-  /* Minimum number of regions required to be mapped. */
-  nReqRegion = ((iRegion+nShmPerMap) / nShmPerMap) * nShmPerMap;
-
-  if( pShmNode->nRegion<nReqRegion ){
-    char **apNew;                      /* New apRegion[] array */
-    int nByte = nReqRegion*szRegion;   /* Minimum required file size */
-    struct stat sStat;                 /* Used by fstat() */
-
-    pShmNode->szRegion = szRegion;
-
-    if( pShmNode->h>=0 ){
-      /* The requested region is not mapped into this processes address space.
-      ** Check to see if it has been allocated (i.e. if the wal-index file is
-      ** large enough to contain the requested region).
-      */
-      if( osFstat(pShmNode->h, &sStat) ){
-        rc = SQLITE_IOERR_SHMSIZE;
-        goto shmpage_out;
-      }
-  
-      if( sStat.st_size<nByte ){
-        /* The requested memory region does not exist. If bExtend is set to
-        ** false, exit early. *pp will be set to NULL and SQLITE_OK returned.
-        */
-        if( !bExtend ){
-          goto shmpage_out;
-        }
-
-        /* Alternatively, if bExtend is true, extend the file. Do this by
-        ** writing a single byte to the end of each (OS) page being
-        ** allocated or extended. Technically, we need only write to the
-        ** last page in order to extend the file. But writing to all new
-        ** pages forces the OS to allocate them immediately, which reduces
-        ** the chances of SIGBUS while accessing the mapped region later on.
-        */
-        else{
-          static const int pgsz = 4096;
-          int iPg;
-
-          /* Write to the last byte of each newly allocated or extended page */
-          assert( (nByte % pgsz)==0 );
-          for(iPg=(sStat.st_size/pgsz); iPg<(nByte/pgsz); iPg++){
-            if( seekAndWriteFd(pShmNode->h, iPg*pgsz + pgsz-1, "", 1, 0)!=1 ){
-              const char *zFile = pShmNode->zFilename;
-              rc = unixLogError(SQLITE_IOERR_SHMSIZE, "write", zFile);
-              goto shmpage_out;
-            }
-          }
-        }
-      }
-    }
-
-    /* Map the requested memory region into this processes address space. */
-    apNew = (char **)sqlite3_realloc(
-        pShmNode->apRegion, nReqRegion*sizeof(char *)
-    );
-    if( !apNew ){
-      rc = SQLITE_IOERR_NOMEM;
-      goto shmpage_out;
-    }
-    pShmNode->apRegion = apNew;
-    while( pShmNode->nRegion<nReqRegion ){
-      int nMap = szRegion*nShmPerMap;
-      int i;
-      void *pMem;
-      if( pShmNode->h>=0 ){
-        pMem = osMmap(0, nMap,
-            pShmNode->isReadonly ? PROT_READ : PROT_READ|PROT_WRITE, 
-            MAP_SHARED, pShmNode->h, szRegion*(i64)pShmNode->nRegion
-        );
-        if( pMem==MAP_FAILED ){
-          rc = unixLogError(SQLITE_IOERR_SHMMAP, "mmap", pShmNode->zFilename);
-          goto shmpage_out;
-        }
-      }else{
-        pMem = sqlite3_malloc64(szRegion);
-        if( pMem==0 ){
-          rc = SQLITE_NOMEM;
-          goto shmpage_out;
-        }
-        memset(pMem, 0, szRegion);
-      }
-
-      for(i=0; i<nShmPerMap; i++){
-        pShmNode->apRegion[pShmNode->nRegion+i] = &((char*)pMem)[szRegion*i];
-      }
-      pShmNode->nRegion += nShmPerMap;
-    }
-  }
-
-shmpage_out:
-  if( pShmNode->nRegion>iRegion ){
-    *pp = pShmNode->apRegion[iRegion];
-  }else{
-    *pp = 0;
-  }
-  if( pShmNode->isReadonly && rc==SQLITE_OK ) rc = SQLITE_READONLY;
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return rc;
-}
-
-/*
-** Change the lock state for a shared-memory segment.
-**
-** Note that the relationship between SHAREd and EXCLUSIVE locks is a little
-** different here than in posix.  In xShmLock(), one can go from unlocked
-** to shared and back or from unlocked to exclusive and back.  But one may
-** not go from shared to exclusive or from exclusive to shared.
-*/
-static int unixShmLock(
-  sqlite3_file *fd,          /* Database file holding the shared memory */
-  int ofst,                  /* First lock to acquire or release */
-  int n,                     /* Number of locks to acquire or release */
-  int flags                  /* What to do with the lock */
-){
-  unixFile *pDbFd = (unixFile*)fd;      /* Connection holding shared memory */
-  unixShm *p = pDbFd->pShm;             /* The shared memory being locked */
-  unixShm *pX;                          /* For looping over all siblings */
-  unixShmNode *pShmNode = p->pShmNode;  /* The underlying file iNode */
-  int rc = SQLITE_OK;                   /* Result code */
-  u16 mask;                             /* Mask of locks to take or release */
-
-  assert( pShmNode==pDbFd->pInode->pShmNode );
-  assert( pShmNode->pInode==pDbFd->pInode );
-  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
-  assert( n>=1 );
-  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
-  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
-  assert( pShmNode->h>=0 || pDbFd->pInode->bProcessLock==1 );
-  assert( pShmNode->h<0 || pDbFd->pInode->bProcessLock==0 );
-
-  mask = (1<<(ofst+n)) - (1<<ofst);
-  assert( n>1 || mask==(1<<ofst) );
-  sqlite3_mutex_enter(pShmNode->mutex);
-  if( flags & SQLITE_SHM_UNLOCK ){
-    u16 allMask = 0; /* Mask of locks held by siblings */
-
-    /* See if any siblings hold this same lock */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( pX==p ) continue;
-      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
-      allMask |= pX->sharedMask;
-    }
-
-    /* Unlock the system-level locks */
-    if( (mask & allMask)==0 ){
-      rc = unixShmSystemLock(pDbFd, F_UNLCK, ofst+UNIX_SHM_BASE, n);
-    }else{
-      rc = SQLITE_OK;
-    }
-
-    /* Undo the local locks */
-    if( rc==SQLITE_OK ){
-      p->exclMask &= ~mask;
-      p->sharedMask &= ~mask;
-    } 
-  }else if( flags & SQLITE_SHM_SHARED ){
-    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
-
-    /* Find out which shared locks are already held by sibling connections.
-    ** If any sibling already holds an exclusive lock, go ahead and return
-    ** SQLITE_BUSY.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-      allShared |= pX->sharedMask;
-    }
-
-    /* Get shared locks at the system level, if necessary */
-    if( rc==SQLITE_OK ){
-      if( (allShared & mask)==0 ){
-        rc = unixShmSystemLock(pDbFd, F_RDLCK, ofst+UNIX_SHM_BASE, n);
-      }else{
-        rc = SQLITE_OK;
-      }
-    }
-
-    /* Get the local shared locks */
-    if( rc==SQLITE_OK ){
-      p->sharedMask |= mask;
-    }
-  }else{
-    /* Make sure no sibling connections hold locks that will block this
-    ** lock.  If any do, return SQLITE_BUSY right away.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-    }
-  
-    /* Get the exclusive locks at the system level.  Then if successful
-    ** also mark the local connection as being locked.
-    */
-    if( rc==SQLITE_OK ){
-      rc = unixShmSystemLock(pDbFd, F_WRLCK, ofst+UNIX_SHM_BASE, n);
-      if( rc==SQLITE_OK ){
-        assert( (p->sharedMask & mask)==0 );
-        p->exclMask |= mask;
-      }
-    }
-  }
-  sqlite3_mutex_leave(pShmNode->mutex);
-  OSTRACE(("SHM-LOCK shmid-%d, pid-%d got %03x,%03x\n",
-           p->id, osGetpid(0), p->sharedMask, p->exclMask));
-  return rc;
-}
-
-/*
-** Implement a memory barrier or memory fence on shared memory.  
-**
-** All loads and stores begun before the barrier must complete before
-** any load or store begun after the barrier.
-*/
-static void unixShmBarrier(
-  sqlite3_file *fd                /* Database file holding the shared memory */
-){
-  UNUSED_PARAMETER(fd);
-  sqlite3MemoryBarrier();         /* compiler-defined memory barrier */
-  unixEnterMutex();               /* Also mutex, for redundancy */
-  unixLeaveMutex();
-}
-
-/*
-** Close a connection to shared-memory.  Delete the underlying 
-** storage if deleteFlag is true.
-**
-** If there is no shared memory associated with the connection then this
-** routine is a harmless no-op.
-*/
-static int unixShmUnmap(
-  sqlite3_file *fd,               /* The underlying database file */
-  int deleteFlag                  /* Delete shared-memory if true */
-){
-  unixShm *p;                     /* The connection to be closed */
-  unixShmNode *pShmNode;          /* The underlying shared-memory file */
-  unixShm **pp;                   /* For looping over sibling connections */
-  unixFile *pDbFd;                /* The underlying database file */
-
-  pDbFd = (unixFile*)fd;
-  p = pDbFd->pShm;
-  if( p==0 ) return SQLITE_OK;
-  pShmNode = p->pShmNode;
-
-  assert( pShmNode==pDbFd->pInode->pShmNode );
-  assert( pShmNode->pInode==pDbFd->pInode );
-
-  /* Remove connection p from the set of connections associated
-  ** with pShmNode */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
-  *pp = p->pNext;
-
-  /* Free the connection p */
-  sqlite3_free(p);
-  pDbFd->pShm = 0;
-  sqlite3_mutex_leave(pShmNode->mutex);
-
-  /* If pShmNode->nRef has reached 0, then close the underlying
-  ** shared-memory file, too */
-  unixEnterMutex();
-  assert( pShmNode->nRef>0 );
-  pShmNode->nRef--;
-  if( pShmNode->nRef==0 ){
-    if( deleteFlag && pShmNode->h>=0 ){
-      osUnlink(pShmNode->zFilename);
-    }
-    unixShmPurge(pDbFd);
-  }
-  unixLeaveMutex();
-
-  return SQLITE_OK;
-}
-
-
-#else
-# define unixShmMap     0
-# define unixShmLock    0
-# define unixShmBarrier 0
-# define unixShmUnmap   0
-#endif /* #ifndef SQLITE_OMIT_WAL */
-
-#if SQLITE_MAX_MMAP_SIZE>0
-/*
-** If it is currently memory mapped, unmap file pFd.
-*/
-static void unixUnmapfile(unixFile *pFd){
-  assert( pFd->nFetchOut==0 );
-  if( pFd->pMapRegion ){
-    osMunmap(pFd->pMapRegion, pFd->mmapSizeActual);
-    pFd->pMapRegion = 0;
-    pFd->mmapSize = 0;
-    pFd->mmapSizeActual = 0;
-  }
-}
-
-/*
-** Attempt to set the size of the memory mapping maintained by file 
-** descriptor pFd to nNew bytes. Any existing mapping is discarded.
-**
-** If successful, this function sets the following variables:
-**
-**       unixFile.pMapRegion
-**       unixFile.mmapSize
-**       unixFile.mmapSizeActual
-**
-** If unsuccessful, an error message is logged via sqlite3_log() and
-** the three variables above are zeroed. In this case SQLite should
-** continue accessing the database using the xRead() and xWrite()
-** methods.
-*/
-static void unixRemapfile(
-  unixFile *pFd,                  /* File descriptor object */
-  i64 nNew                        /* Required mapping size */
-){
-  const char *zErr = "mmap";
-  int h = pFd->h;                      /* File descriptor open on db file */
-  u8 *pOrig = (u8 *)pFd->pMapRegion;   /* Pointer to current file mapping */
-  i64 nOrig = pFd->mmapSizeActual;     /* Size of pOrig region in bytes */
-  u8 *pNew = 0;                        /* Location of new mapping */
-  int flags = PROT_READ;               /* Flags to pass to mmap() */
-
-  assert( pFd->nFetchOut==0 );
-  assert( nNew>pFd->mmapSize );
-  assert( nNew<=pFd->mmapSizeMax );
-  assert( nNew>0 );
-  assert( pFd->mmapSizeActual>=pFd->mmapSize );
-  assert( MAP_FAILED!=0 );
-
-  if( (pFd->ctrlFlags & UNIXFILE_RDONLY)==0 ) flags |= PROT_WRITE;
-
-  if( pOrig ){
-#if HAVE_MREMAP
-    i64 nReuse = pFd->mmapSize;
-#else
-    const int szSyspage = osGetpagesize();
-    i64 nReuse = (pFd->mmapSize & ~(szSyspage-1));
-#endif
-    u8 *pReq = &pOrig[nReuse];
-
-    /* Unmap any pages of the existing mapping that cannot be reused. */
-    if( nReuse!=nOrig ){
-      osMunmap(pReq, nOrig-nReuse);
-    }
-
-#if HAVE_MREMAP
-    pNew = osMremap(pOrig, nReuse, nNew, MREMAP_MAYMOVE);
-    zErr = "mremap";
-#else
-    pNew = osMmap(pReq, nNew-nReuse, flags, MAP_SHARED, h, nReuse);
-    if( pNew!=MAP_FAILED ){
-      if( pNew!=pReq ){
-        osMunmap(pNew, nNew - nReuse);
-        pNew = 0;
-      }else{
-        pNew = pOrig;
-      }
-    }
-#endif
-
-    /* The attempt to extend the existing mapping failed. Free it. */
-    if( pNew==MAP_FAILED || pNew==0 ){
-      osMunmap(pOrig, nReuse);
-    }
-  }
-
-  /* If pNew is still NULL, try to create an entirely new mapping. */
-  if( pNew==0 ){
-    pNew = osMmap(0, nNew, flags, MAP_SHARED, h, 0);
-  }
-
-  if( pNew==MAP_FAILED ){
-    pNew = 0;
-    nNew = 0;
-    unixLogError(SQLITE_OK, zErr, pFd->zPath);
-
-    /* If the mmap() above failed, assume that all subsequent mmap() calls
-    ** will probably fail too. Fall back to using xRead/xWrite exclusively
-    ** in this case.  */
-    pFd->mmapSizeMax = 0;
-  }
-  pFd->pMapRegion = (void *)pNew;
-  pFd->mmapSize = pFd->mmapSizeActual = nNew;
-}
-
-/*
-** Memory map or remap the file opened by file-descriptor pFd (if the file
-** is already mapped, the existing mapping is replaced by the new). Or, if 
-** there already exists a mapping for this file, and there are still 
-** outstanding xFetch() references to it, this function is a no-op.
-**
-** If parameter nByte is non-negative, then it is the requested size of 
-** the mapping to create. Otherwise, if nByte is less than zero, then the 
-** requested size is the size of the file on disk. The actual size of the
-** created mapping is either the requested size or the value configured 
-** using SQLITE_FCNTL_MMAP_LIMIT, whichever is smaller.
-**
-** SQLITE_OK is returned if no error occurs (even if the mapping is not
-** recreated as a result of outstanding references) or an SQLite error
-** code otherwise.
-*/
-static int unixMapfile(unixFile *pFd, i64 nByte){
-  i64 nMap = nByte;
-  int rc;
-
-  assert( nMap>=0 || pFd->nFetchOut==0 );
-  if( pFd->nFetchOut>0 ) return SQLITE_OK;
-
-  if( nMap<0 ){
-    struct stat statbuf;          /* Low-level file information */
-    rc = osFstat(pFd->h, &statbuf);
-    if( rc!=SQLITE_OK ){
-      return SQLITE_IOERR_FSTAT;
-    }
-    nMap = statbuf.st_size;
-  }
-  if( nMap>pFd->mmapSizeMax ){
-    nMap = pFd->mmapSizeMax;
-  }
-
-  if( nMap!=pFd->mmapSize ){
-    if( nMap>0 ){
-      unixRemapfile(pFd, nMap);
-    }else{
-      unixUnmapfile(pFd);
-    }
-  }
-
-  return SQLITE_OK;
-}
-#endif /* SQLITE_MAX_MMAP_SIZE>0 */
-
-/*
-** If possible, return a pointer to a mapping of file fd starting at offset
-** iOff. The mapping must be valid for at least nAmt bytes.
-**
-** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
-** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
-** Finally, if an error does occur, return an SQLite error code. The final
-** value of *pp is undefined in this case.
-**
-** If this function does return a pointer, the caller must eventually 
-** release the reference by calling unixUnfetch().
-*/
-static int unixFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
-#endif
-  *pp = 0;
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFd->mmapSizeMax>0 ){
-    if( pFd->pMapRegion==0 ){
-      int rc = unixMapfile(pFd, -1);
-      if( rc!=SQLITE_OK ) return rc;
-    }
-    if( pFd->mmapSize >= iOff+nAmt ){
-      *pp = &((u8 *)pFd->pMapRegion)[iOff];
-      pFd->nFetchOut++;
-    }
-  }
-#endif
-  return SQLITE_OK;
-}
-
-/*
-** If the third argument is non-NULL, then this function releases a 
-** reference obtained by an earlier call to unixFetch(). The second
-** argument passed to this function must be the same as the corresponding
-** argument that was passed to the unixFetch() invocation. 
-**
-** Or, if the third argument is NULL, then this function is being called 
-** to inform the VFS layer that, according to POSIX, any existing mapping 
-** may now be invalid and should be unmapped.
-*/
-static int unixUnfetch(sqlite3_file *fd, i64 iOff, void *p){
-#if SQLITE_MAX_MMAP_SIZE>0
-  unixFile *pFd = (unixFile *)fd;   /* The underlying database file */
-  UNUSED_PARAMETER(iOff);
-
-  /* If p==0 (unmap the entire file) then there must be no outstanding 
-  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
-  ** then there must be at least one outstanding.  */
-  assert( (p==0)==(pFd->nFetchOut==0) );
-
-  /* If p!=0, it must match the iOff value. */
-  assert( p==0 || p==&((u8 *)pFd->pMapRegion)[iOff] );
-
-  if( p ){
-    pFd->nFetchOut--;
-  }else{
-    unixUnmapfile(pFd);
-  }
-
-  assert( pFd->nFetchOut>=0 );
-#else
-  UNUSED_PARAMETER(fd);
-  UNUSED_PARAMETER(p);
-  UNUSED_PARAMETER(iOff);
-#endif
-  return SQLITE_OK;
-}
-
-/*
-** Here ends the implementation of all sqlite3_file methods.
-**
-********************** End sqlite3_file Methods *******************************
-******************************************************************************/
-
-/*
-** This division contains definitions of sqlite3_io_methods objects that
-** implement various file locking strategies.  It also contains definitions
-** of "finder" functions.  A finder-function is used to locate the appropriate
-** sqlite3_io_methods object for a particular database file.  The pAppData
-** field of the sqlite3_vfs VFS objects are initialized to be pointers to
-** the correct finder-function for that VFS.
-**
-** Most finder functions return a pointer to a fixed sqlite3_io_methods
-** object.  The only interesting finder-function is autolockIoFinder, which
-** looks at the filesystem type and tries to guess the best locking
-** strategy from that.
-**
-** For finder-function F, two objects are created:
-**
-**    (1) The real finder-function named "FImpt()".
-**
-**    (2) A constant pointer to this function named just "F".
-**
-**
-** A pointer to the F pointer is used as the pAppData value for VFS
-** objects.  We have to do this instead of letting pAppData point
-** directly at the finder-function since C90 rules prevent a void*
-** from be cast into a function pointer.
-**
-**
-** Each instance of this macro generates two objects:
-**
-**   *  A constant sqlite3_io_methods object call METHOD that has locking
-**      methods CLOSE, LOCK, UNLOCK, CKRESLOCK.
-**
-**   *  An I/O method finder function called FINDER that returns a pointer
-**      to the METHOD object in the previous bullet.
-*/
-#define IOMETHODS(FINDER,METHOD,VERSION,CLOSE,LOCK,UNLOCK,CKLOCK,SHMMAP)     \
-static const sqlite3_io_methods METHOD = {                                   \
-   VERSION,                    /* iVersion */                                \
-   CLOSE,                      /* xClose */                                  \
-   unixRead,                   /* xRead */                                   \
-   unixWrite,                  /* xWrite */                                  \
-   unixTruncate,               /* xTruncate */                               \
-   unixSync,                   /* xSync */                                   \
-   unixFileSize,               /* xFileSize */                               \
-   LOCK,                       /* xLock */                                   \
-   UNLOCK,                     /* xUnlock */                                 \
-   CKLOCK,                     /* xCheckReservedLock */                      \
-   unixFileControl,            /* xFileControl */                            \
-   unixSectorSize,             /* xSectorSize */                             \
-   unixDeviceCharacteristics,  /* xDeviceCapabilities */                     \
-   SHMMAP,                     /* xShmMap */                                 \
-   unixShmLock,                /* xShmLock */                                \
-   unixShmBarrier,             /* xShmBarrier */                             \
-   unixShmUnmap,               /* xShmUnmap */                               \
-   unixFetch,                  /* xFetch */                                  \
-   unixUnfetch,                /* xUnfetch */                                \
-};                                                                           \
-static const sqlite3_io_methods *FINDER##Impl(const char *z, unixFile *p){   \
-  UNUSED_PARAMETER(z); UNUSED_PARAMETER(p);                                  \
-  return &METHOD;                                                            \
-}                                                                            \
-static const sqlite3_io_methods *(*const FINDER)(const char*,unixFile *p)    \
-    = FINDER##Impl;
-
-/*
-** Here are all of the sqlite3_io_methods objects for each of the
-** locking strategies.  Functions that return pointers to these methods
-** are also created.
-*/
-IOMETHODS(
-  posixIoFinder,            /* Finder function name */
-  posixIoMethods,           /* sqlite3_io_methods object name */
-  3,                        /* shared memory and mmap are enabled */
-  unixClose,                /* xClose method */
-  unixLock,                 /* xLock method */
-  unixUnlock,               /* xUnlock method */
-  unixCheckReservedLock,    /* xCheckReservedLock method */
-  unixShmMap                /* xShmMap method */
-)
-IOMETHODS(
-  nolockIoFinder,           /* Finder function name */
-  nolockIoMethods,          /* sqlite3_io_methods object name */
-  3,                        /* shared memory is disabled */
-  nolockClose,              /* xClose method */
-  nolockLock,               /* xLock method */
-  nolockUnlock,             /* xUnlock method */
-  nolockCheckReservedLock,  /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-IOMETHODS(
-  dotlockIoFinder,          /* Finder function name */
-  dotlockIoMethods,         /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  dotlockClose,             /* xClose method */
-  dotlockLock,              /* xLock method */
-  dotlockUnlock,            /* xUnlock method */
-  dotlockCheckReservedLock, /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-
-#if SQLITE_ENABLE_LOCKING_STYLE
-IOMETHODS(
-  flockIoFinder,            /* Finder function name */
-  flockIoMethods,           /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  flockClose,               /* xClose method */
-  flockLock,                /* xLock method */
-  flockUnlock,              /* xUnlock method */
-  flockCheckReservedLock,   /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-#if OS_VXWORKS
-IOMETHODS(
-  semIoFinder,              /* Finder function name */
-  semIoMethods,             /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  semXClose,                /* xClose method */
-  semXLock,                 /* xLock method */
-  semXUnlock,               /* xUnlock method */
-  semXCheckReservedLock,    /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-IOMETHODS(
-  afpIoFinder,              /* Finder function name */
-  afpIoMethods,             /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  afpClose,                 /* xClose method */
-  afpLock,                  /* xLock method */
-  afpUnlock,                /* xUnlock method */
-  afpCheckReservedLock,     /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-/*
-** The proxy locking method is a "super-method" in the sense that it
-** opens secondary file descriptors for the conch and lock files and
-** it uses proxy, dot-file, AFP, and flock() locking methods on those
-** secondary files.  For this reason, the division that implements
-** proxy locking is located much further down in the file.  But we need
-** to go ahead and define the sqlite3_io_methods and finder function
-** for proxy locking here.  So we forward declare the I/O methods.
-*/
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-static int proxyClose(sqlite3_file*);
-static int proxyLock(sqlite3_file*, int);
-static int proxyUnlock(sqlite3_file*, int);
-static int proxyCheckReservedLock(sqlite3_file*, int*);
-IOMETHODS(
-  proxyIoFinder,            /* Finder function name */
-  proxyIoMethods,           /* sqlite3_io_methods object name */
-  1,                        /* shared memory is disabled */
-  proxyClose,               /* xClose method */
-  proxyLock,                /* xLock method */
-  proxyUnlock,              /* xUnlock method */
-  proxyCheckReservedLock,   /* xCheckReservedLock method */
-  0                         /* xShmMap method */
-)
-#endif
-
-/* nfs lockd on OSX 10.3+ doesn't clear write locks when a read lock is set */
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-IOMETHODS(
-  nfsIoFinder,               /* Finder function name */
-  nfsIoMethods,              /* sqlite3_io_methods object name */
-  1,                         /* shared memory is disabled */
-  unixClose,                 /* xClose method */
-  unixLock,                  /* xLock method */
-  nfsUnlock,                 /* xUnlock method */
-  unixCheckReservedLock,     /* xCheckReservedLock method */
-  0                          /* xShmMap method */
-)
-#endif
-
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-/* 
-** This "finder" function attempts to determine the best locking strategy 
-** for the database file "filePath".  It then returns the sqlite3_io_methods
-** object that implements that strategy.
-**
-** This is for MacOSX only.
-*/
-static const sqlite3_io_methods *autolockIoFinderImpl(
-  const char *filePath,    /* name of the database file */
-  unixFile *pNew           /* open file object for the database file */
-){
-  static const struct Mapping {
-    const char *zFilesystem;              /* Filesystem type name */
-    const sqlite3_io_methods *pMethods;   /* Appropriate locking method */
-  } aMap[] = {
-    { "hfs",    &posixIoMethods },
-    { "ufs",    &posixIoMethods },
-    { "afpfs",  &afpIoMethods },
-    { "smbfs",  &afpIoMethods },
-    { "webdav", &nolockIoMethods },
-    { 0, 0 }
-  };
-  int i;
-  struct statfs fsInfo;
-  struct flock lockInfo;
-
-  if( !filePath ){
-    /* If filePath==NULL that means we are dealing with a transient file
-    ** that does not need to be locked. */
-    return &nolockIoMethods;
-  }
-  if( statfs(filePath, &fsInfo) != -1 ){
-    if( fsInfo.f_flags & MNT_RDONLY ){
-      return &nolockIoMethods;
-    }
-    for(i=0; aMap[i].zFilesystem; i++){
-      if( strcmp(fsInfo.f_fstypename, aMap[i].zFilesystem)==0 ){
-        return aMap[i].pMethods;
-      }
-    }
-  }
-
-  /* Default case. Handles, amongst others, "nfs".
-  ** Test byte-range lock using fcntl(). If the call succeeds, 
-  ** assume that the file-system supports POSIX style locks. 
-  */
-  lockInfo.l_len = 1;
-  lockInfo.l_start = 0;
-  lockInfo.l_whence = SEEK_SET;
-  lockInfo.l_type = F_RDLCK;
-  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    if( strcmp(fsInfo.f_fstypename, "nfs")==0 ){
-      return &nfsIoMethods;
-    } else {
-      return &posixIoMethods;
-    }
-  }else{
-    return &dotlockIoMethods;
-  }
-}
-static const sqlite3_io_methods 
-  *(*const autolockIoFinder)(const char*,unixFile*) = autolockIoFinderImpl;
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-
-#if OS_VXWORKS
-/*
-** This "finder" function for VxWorks checks to see if posix advisory
-** locking works.  If it does, then that is what is used.  If it does not
-** work, then fallback to named semaphore locking.
-*/
-static const sqlite3_io_methods *vxworksIoFinderImpl(
-  const char *filePath,    /* name of the database file */
-  unixFile *pNew           /* the open file object */
-){
-  struct flock lockInfo;
-
-  if( !filePath ){
-    /* If filePath==NULL that means we are dealing with a transient file
-    ** that does not need to be locked. */
-    return &nolockIoMethods;
-  }
-
-  /* Test if fcntl() is supported and use POSIX style locks.
-  ** Otherwise fall back to the named semaphore method.
-  */
-  lockInfo.l_len = 1;
-  lockInfo.l_start = 0;
-  lockInfo.l_whence = SEEK_SET;
-  lockInfo.l_type = F_RDLCK;
-  if( osFcntl(pNew->h, F_GETLK, &lockInfo)!=-1 ) {
-    return &posixIoMethods;
-  }else{
-    return &semIoMethods;
-  }
-}
-static const sqlite3_io_methods 
-  *(*const vxworksIoFinder)(const char*,unixFile*) = vxworksIoFinderImpl;
-
-#endif /* OS_VXWORKS */
-
-/*
-** An abstract type for a pointer to an IO method finder function:
-*/
-typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*);
-
-
-/****************************************************************************
-**************************** sqlite3_vfs methods ****************************
-**
-** This division contains the implementation of methods on the
-** sqlite3_vfs object.
-*/
-
-/*
-** Initialize the contents of the unixFile structure pointed to by pId.
-*/
-static int fillInUnixFile(
-  sqlite3_vfs *pVfs,      /* Pointer to vfs object */
-  int h,                  /* Open file descriptor of file being opened */
-  sqlite3_file *pId,      /* Write to the unixFile structure here */
-  const char *zFilename,  /* Name of the file being opened */
-  int ctrlFlags           /* Zero or more UNIXFILE_* values */
-){
-  const sqlite3_io_methods *pLockingStyle;
-  unixFile *pNew = (unixFile *)pId;
-  int rc = SQLITE_OK;
-
-  assert( pNew->pInode==NULL );
-
-  /* Usually the path zFilename should not be a relative pathname. The
-  ** exception is when opening the proxy "conch" file in builds that
-  ** include the special Apple locking styles.
-  */
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-  assert( zFilename==0 || zFilename[0]=='/' 
-    || pVfs->pAppData==(void*)&autolockIoFinder );
-#else
-  assert( zFilename==0 || zFilename[0]=='/' );
-#endif
-
-  /* No locking occurs in temporary files */
-  assert( zFilename!=0 || (ctrlFlags & UNIXFILE_NOLOCK)!=0 );
-
-  OSTRACE(("OPEN    %-3d %s\n", h, zFilename));
-  pNew->h = h;
-  pNew->pVfs = pVfs;
-  pNew->zPath = zFilename;
-  pNew->ctrlFlags = (u8)ctrlFlags;
-#if SQLITE_MAX_MMAP_SIZE>0
-  pNew->mmapSizeMax = sqlite3GlobalConfig.szMmap;
-#endif
-  if( SQLITE_POWERSAFE_OVERWRITE ){
-    pNew->ctrlFlags |= UNIXFILE_PSOW;
-  }
-  if( strcmp(pVfs->zName,"unix-excl")==0 ){
-    pNew->ctrlFlags |= UNIXFILE_EXCL;
-  }
-
-#if OS_VXWORKS
-  pNew->pId = vxworksFindFileId(zFilename);
-  if( pNew->pId==0 ){
-    ctrlFlags |= UNIXFILE_NOLOCK;
-    rc = SQLITE_NOMEM;
-  }
-#endif
-
-  if( ctrlFlags & UNIXFILE_NOLOCK ){
-    pLockingStyle = &nolockIoMethods;
-  }else{
-    pLockingStyle = (**(finder_type*)pVfs->pAppData)(zFilename, pNew);
-#if SQLITE_ENABLE_LOCKING_STYLE
-    /* Cache zFilename in the locking context (AFP and dotlock override) for
-    ** proxyLock activation is possible (remote proxy is based on db name)
-    ** zFilename remains valid until file is closed, to support */
-    pNew->lockingContext = (void*)zFilename;
-#endif
-  }
-
-  if( pLockingStyle == &posixIoMethods
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-    || pLockingStyle == &nfsIoMethods
-#endif
-  ){
-    unixEnterMutex();
-    rc = findInodeInfo(pNew, &pNew->pInode);
-    if( rc!=SQLITE_OK ){
-      /* If an error occurred in findInodeInfo(), close the file descriptor
-      ** immediately, before releasing the mutex. findInodeInfo() may fail
-      ** in two scenarios:
-      **
-      **   (a) A call to fstat() failed.
-      **   (b) A malloc failed.
-      **
-      ** Scenario (b) may only occur if the process is holding no other
-      ** file descriptors open on the same file. If there were other file
-      ** descriptors on this file, then no malloc would be required by
-      ** findInodeInfo(). If this is the case, it is quite safe to close
-      ** handle h - as it is guaranteed that no posix locks will be released
-      ** by doing so.
-      **
-      ** If scenario (a) caused the error then things are not so safe. The
-      ** implicit assumption here is that if fstat() fails, things are in
-      ** such bad shape that dropping a lock or two doesn't matter much.
-      */
-      robust_close(pNew, h, __LINE__);
-      h = -1;
-    }
-    unixLeaveMutex();
-  }
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-  else if( pLockingStyle == &afpIoMethods ){
-    /* AFP locking uses the file path so it needs to be included in
-    ** the afpLockingContext.
-    */
-    afpLockingContext *pCtx;
-    pNew->lockingContext = pCtx = sqlite3_malloc64( sizeof(*pCtx) );
-    if( pCtx==0 ){
-      rc = SQLITE_NOMEM;
-    }else{
-      /* NB: zFilename exists and remains valid until the file is closed
-      ** according to requirement F11141.  So we do not need to make a
-      ** copy of the filename. */
-      pCtx->dbPath = zFilename;
-      pCtx->reserved = 0;
-      srandomdev();
-      unixEnterMutex();
-      rc = findInodeInfo(pNew, &pNew->pInode);
-      if( rc!=SQLITE_OK ){
-        sqlite3_free(pNew->lockingContext);
-        robust_close(pNew, h, __LINE__);
-        h = -1;
-      }
-      unixLeaveMutex();        
-    }
-  }
-#endif
-
-  else if( pLockingStyle == &dotlockIoMethods ){
-    /* Dotfile locking uses the file path so it needs to be included in
-    ** the dotlockLockingContext 
-    */
-    char *zLockFile;
-    int nFilename;
-    assert( zFilename!=0 );
-    nFilename = (int)strlen(zFilename) + 6;
-    zLockFile = (char *)sqlite3_malloc64(nFilename);
-    if( zLockFile==0 ){
-      rc = SQLITE_NOMEM;
-    }else{
-      sqlite3_snprintf(nFilename, zLockFile, "%s" DOTLOCK_SUFFIX, zFilename);
-    }
-    pNew->lockingContext = zLockFile;
-  }
-
-#if OS_VXWORKS
-  else if( pLockingStyle == &semIoMethods ){
-    /* Named semaphore locking uses the file path so it needs to be
-    ** included in the semLockingContext
-    */
-    unixEnterMutex();
-    rc = findInodeInfo(pNew, &pNew->pInode);
-    if( (rc==SQLITE_OK) && (pNew->pInode->pSem==NULL) ){
-      char *zSemName = pNew->pInode->aSemName;
-      int n;
-      sqlite3_snprintf(MAX_PATHNAME, zSemName, "/%s.sem",
-                       pNew->pId->zCanonicalName);
-      for( n=1; zSemName[n]; n++ )
-        if( zSemName[n]=='/' ) zSemName[n] = '_';
-      pNew->pInode->pSem = sem_open(zSemName, O_CREAT, 0666, 1);
-      if( pNew->pInode->pSem == SEM_FAILED ){
-        rc = SQLITE_NOMEM;
-        pNew->pInode->aSemName[0] = '\0';
-      }
-    }
-    unixLeaveMutex();
-  }
-#endif
-  
-  storeLastErrno(pNew, 0);
-#if OS_VXWORKS
-  if( rc!=SQLITE_OK ){
-    if( h>=0 ) robust_close(pNew, h, __LINE__);
-    h = -1;
-    osUnlink(zFilename);
-    pNew->ctrlFlags |= UNIXFILE_DELETE;
-  }
-#endif
-  if( rc!=SQLITE_OK ){
-    if( h>=0 ) robust_close(pNew, h, __LINE__);
-  }else{
-    pNew->pMethod = pLockingStyle;
-    OpenCounter(+1);
-    verifyDbFile(pNew);
-  }
-  return rc;
-}
-
-/*
-** Return the name of a directory in which to put temporary files.
-** If no suitable temporary file directory can be found, return NULL.
-*/
-static const char *unixTempFileDir(void){
-  static const char *azDirs[] = {
-     0,
-     0,
-     0,
-     "/var/tmp",
-     "/usr/tmp",
-     "/tmp",
-     0        /* List terminator */
-  };
-  unsigned int i;
-  struct stat buf;
-  const char *zDir = 0;
-
-  azDirs[0] = sqlite3_temp_directory;
-  if( !azDirs[1] ) azDirs[1] = getenv("SQLITE_TMPDIR");
-  if( !azDirs[2] ) azDirs[2] = getenv("TMPDIR");
-  for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
-    if( zDir==0 ) continue;
-    if( osStat(zDir, &buf) ) continue;
-    if( !S_ISDIR(buf.st_mode) ) continue;
-    if( osAccess(zDir, 07) ) continue;
-    break;
-  }
-  return zDir;
-}
-
-/*
-** Create a temporary file name in zBuf.  zBuf must be allocated
-** by the calling process and must be big enough to hold at least
-** pVfs->mxPathname bytes.
-*/
-static int unixGetTempname(int nBuf, char *zBuf){
-  static const unsigned char zChars[] =
-    "abcdefghijklmnopqrstuvwxyz"
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-    "0123456789";
-  unsigned int i, j;
-  const char *zDir;
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing. 
-  */
-  SimulateIOError( return SQLITE_IOERR );
-
-  zDir = unixTempFileDir();
-  if( zDir==0 ) zDir = ".";
-
-  /* Check that the output buffer is large enough for the temporary file 
-  ** name. If it is not, return SQLITE_ERROR.
-  */
-  if( (strlen(zDir) + strlen(SQLITE_TEMP_FILE_PREFIX) + 18) >= (size_t)nBuf ){
-    return SQLITE_ERROR;
-  }
-
-  do{
-    sqlite3_snprintf(nBuf-18, zBuf, "%s/"SQLITE_TEMP_FILE_PREFIX, zDir);
-    j = (int)strlen(zBuf);
-    sqlite3_randomness(15, &zBuf[j]);
-    for(i=0; i<15; i++, j++){
-      zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
-    }
-    zBuf[j] = 0;
-    zBuf[j+1] = 0;
-  }while( osAccess(zBuf,0)==0 );
-  return SQLITE_OK;
-}
-
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-/*
-** Routine to transform a unixFile into a proxy-locking unixFile.
-** Implementation in the proxy-lock division, but used by unixOpen()
-** if SQLITE_PREFER_PROXY_LOCKING is defined.
-*/
-static int proxyTransformUnixFile(unixFile*, const char*);
-#endif
-
-/*
-** Search for an unused file descriptor that was opened on the database 
-** file (not a journal or master-journal file) identified by pathname
-** zPath with SQLITE_OPEN_XXX flags matching those passed as the second
-** argument to this function.
-**
-** Such a file descriptor may exist if a database connection was closed
-** but the associated file descriptor could not be closed because some
-** other file descriptor open on the same file is holding a file-lock.
-** Refer to comments in the unixClose() function and the lengthy comment
-** describing "Posix Advisory Locking" at the start of this file for 
-** further details. Also, ticket #4018.
-**
-** If a suitable file descriptor is found, then it is returned. If no
-** such file descriptor is located, -1 is returned.
-*/
-static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
-  UnixUnusedFd *pUnused = 0;
-
-  /* Do not search for an unused file descriptor on vxworks. Not because
-  ** vxworks would not benefit from the change (it might, we're not sure),
-  ** but because no way to test it is currently available. It is better 
-  ** not to risk breaking vxworks support for the sake of such an obscure 
-  ** feature.  */
-#if !OS_VXWORKS
-  struct stat sStat;                   /* Results of stat() call */
-
-  /* A stat() call may fail for various reasons. If this happens, it is
-  ** almost certain that an open() call on the same path will also fail.
-  ** For this reason, if an error occurs in the stat() call here, it is
-  ** ignored and -1 is returned. The caller will try to open a new file
-  ** descriptor on the same path, fail, and return an error to SQLite.
-  **
-  ** Even if a subsequent open() call does succeed, the consequences of
-  ** not searching for a reusable file descriptor are not dire.  */
-  if( 0==osStat(zPath, &sStat) ){
-    unixInodeInfo *pInode;
-
-    unixEnterMutex();
-    pInode = inodeList;
-    while( pInode && (pInode->fileId.dev!=sStat.st_dev
-                     || pInode->fileId.ino!=sStat.st_ino) ){
-       pInode = pInode->pNext;
-    }
-    if( pInode ){
-      UnixUnusedFd **pp;
-      for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext));
-      pUnused = *pp;
-      if( pUnused ){
-        *pp = pUnused->pNext;
-      }
-    }
-    unixLeaveMutex();
-  }
-#endif    /* if !OS_VXWORKS */
-  return pUnused;
-}
-
-/*
-** This function is called by unixOpen() to determine the unix permissions
-** to create new files with. If no error occurs, then SQLITE_OK is returned
-** and a value suitable for passing as the third argument to open(2) is
-** written to *pMode. If an IO error occurs, an SQLite error code is 
-** returned and the value of *pMode is not modified.
-**
-** In most cases, this routine sets *pMode to 0, which will become
-** an indication to robust_open() to create the file using
-** SQLITE_DEFAULT_FILE_PERMISSIONS adjusted by the umask.
-** But if the file being opened is a WAL or regular journal file, then 
-** this function queries the file-system for the permissions on the 
-** corresponding database file and sets *pMode to this value. Whenever 
-** possible, WAL and journal files are created using the same permissions 
-** as the associated database file.
-*/
-static int findCreateFileMode(
-  const char *zPath,              /* Path of file (possibly) being created */
-  int flags,                      /* Flags passed as 4th argument to xOpen() */
-  mode_t *pMode,                  /* OUT: Permissions to open file with */
-  uid_t *pUid,                    /* OUT: uid to set on the file */
-  gid_t *pGid                     /* OUT: gid to set on the file */
-){
-  int rc = SQLITE_OK;             /* Return Code */
-  *pMode = 0;
-  *pUid = 0;
-  *pGid = 0;
-  if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
-    char zDb[MAX_PATHNAME+1];     /* Database file path */
-    int nDb;                      /* Number of valid bytes in zDb */
-    struct stat sStat;            /* Output of stat() on database file */
-
-    /* zPath is a path to a WAL or journal file. The following block derives
-    ** the path to the associated database file from zPath. This block handles
-    ** the following naming conventions:
-    **
-    **   "<path to db>-journal"
-    **   "<path to db>-wal"
-    **   "<path to db>-journalNN"
-    **   "<path to db>-walNN"
-    **
-    ** where NN is a decimal number. The NN naming schemes are 
-    ** used by the test_multiplex.c module.
-    */
-    nDb = sqlite3Strlen30(zPath) - 1; 
-    while( zPath[nDb]!='-' ){
-      assert( nDb>0 );
-      assert( zPath[nDb]!='\n' );
-      nDb--;
-    }
-    memcpy(zDb, zPath, nDb);
-    zDb[nDb] = '\0';
-
-    if( 0==osStat(zDb, &sStat) ){
-      *pMode = sStat.st_mode & 0777;
-      *pUid = sStat.st_uid;
-      *pGid = sStat.st_gid;
-    }else{
-      rc = SQLITE_IOERR_FSTAT;
-    }
-  }else if( flags & SQLITE_OPEN_DELETEONCLOSE ){
-    *pMode = 0600;
-  }
-  return rc;
-}
-
-/*
-** Open the file zPath.
-** 
-** Previously, the SQLite OS layer used three functions in place of this
-** one:
-**
-**     sqlite3OsOpenReadWrite();
-**     sqlite3OsOpenReadOnly();
-**     sqlite3OsOpenExclusive();
-**
-** These calls correspond to the following combinations of flags:
-**
-**     ReadWrite() ->     (READWRITE | CREATE)
-**     ReadOnly()  ->     (READONLY) 
-**     OpenExclusive() -> (READWRITE | CREATE | EXCLUSIVE)
-**
-** The old OpenExclusive() accepted a boolean argument - "delFlag". If
-** true, the file was configured to be automatically deleted when the
-** file handle closed. To achieve the same effect using this new 
-** interface, add the DELETEONCLOSE flag to those specified above for 
-** OpenExclusive().
-*/
-static int unixOpen(
-  sqlite3_vfs *pVfs,           /* The VFS for which this is the xOpen method */
-  const char *zPath,           /* Pathname of file to be opened */
-  sqlite3_file *pFile,         /* The file descriptor to be filled in */
-  int flags,                   /* Input flags to control the opening */
-  int *pOutFlags               /* Output flags returned to SQLite core */
-){
-  unixFile *p = (unixFile *)pFile;
-  int fd = -1;                   /* File descriptor returned by open() */
-  int openFlags = 0;             /* Flags to pass to open() */
-  int eType = flags&0xFFFFFF00;  /* Type of file to open */
-  int noLock;                    /* True to omit locking primitives */
-  int rc = SQLITE_OK;            /* Function Return Code */
-  int ctrlFlags = 0;             /* UNIXFILE_* flags */
-
-  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
-  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
-  int isCreate     = (flags & SQLITE_OPEN_CREATE);
-  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
-  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
-#if SQLITE_ENABLE_LOCKING_STYLE
-  int isAutoProxy  = (flags & SQLITE_OPEN_AUTOPROXY);
-#endif
-#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
-  struct statfs fsInfo;
-#endif
-
-  /* If creating a master or main-file journal, this function will open
-  ** a file-descriptor on the directory too. The first time unixSync()
-  ** is called the directory file descriptor will be fsync()ed and close()d.
-  */
-  int syncDir = (isCreate && (
-        eType==SQLITE_OPEN_MASTER_JOURNAL 
-     || eType==SQLITE_OPEN_MAIN_JOURNAL 
-     || eType==SQLITE_OPEN_WAL
-  ));
-
-  /* If argument zPath is a NULL pointer, this function is required to open
-  ** a temporary file. Use this buffer to store the file name in.
-  */
-  char zTmpname[MAX_PATHNAME+2];
-  const char *zName = zPath;
-
-  /* Check the following statements are true: 
-  **
-  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and 
-  **   (b) if CREATE is set, then READWRITE must also be set, and
-  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
-  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
-  */
-  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
-  assert(isCreate==0 || isReadWrite);
-  assert(isExclusive==0 || isCreate);
-  assert(isDelete==0 || isCreate);
-
-  /* The main DB, main journal, WAL file and master journal are never 
-  ** automatically deleted. Nor are they ever temporary files.  */
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
-
-  /* Assert that the upper layer has set one of the "file-type" flags. */
-  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB 
-       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL 
-       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL 
-       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
-  );
-
-  /* Detect a pid change and reset the PRNG.  There is a race condition
-  ** here such that two or more threads all trying to open databases at
-  ** the same instant might all reset the PRNG.  But multiple resets
-  ** are harmless.
-  */
-  if( randomnessPid!=osGetpid(0) ){
-    randomnessPid = osGetpid(0);
-    sqlite3_randomness(0,0);
-  }
-
-  memset(p, 0, sizeof(unixFile));
-
-  if( eType==SQLITE_OPEN_MAIN_DB ){
-    UnixUnusedFd *pUnused;
-    pUnused = findReusableFd(zName, flags);
-    if( pUnused ){
-      fd = pUnused->fd;
-    }else{
-      pUnused = sqlite3_malloc64(sizeof(*pUnused));
-      if( !pUnused ){
-        return SQLITE_NOMEM;
-      }
-    }
-    p->pUnused = pUnused;
-
-    /* Database filenames are double-zero terminated if they are not
-    ** URIs with parameters.  Hence, they can always be passed into
-    ** sqlite3_uri_parameter(). */
-    assert( (flags & SQLITE_OPEN_URI) || zName[strlen(zName)+1]==0 );
-
-  }else if( !zName ){
-    /* If zName is NULL, the upper layer is requesting a temp file. */
-    assert(isDelete && !syncDir);
-    rc = unixGetTempname(MAX_PATHNAME+2, zTmpname);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    zName = zTmpname;
-
-    /* Generated temporary filenames are always double-zero terminated
-    ** for use by sqlite3_uri_parameter(). */
-    assert( zName[strlen(zName)+1]==0 );
-  }
-
-  /* Determine the value of the flags parameter passed to POSIX function
-  ** open(). These must be calculated even if open() is not called, as
-  ** they may be stored as part of the file handle and used by the 
-  ** 'conch file' locking functions later on.  */
-  if( isReadonly )  openFlags |= O_RDONLY;
-  if( isReadWrite ) openFlags |= O_RDWR;
-  if( isCreate )    openFlags |= O_CREAT;
-  if( isExclusive ) openFlags |= (O_EXCL|O_NOFOLLOW);
-  openFlags |= (O_LARGEFILE|O_BINARY);
-
-  if( fd<0 ){
-    mode_t openMode;              /* Permissions to create file with */
-    uid_t uid;                    /* Userid for the file */
-    gid_t gid;                    /* Groupid for the file */
-    rc = findCreateFileMode(zName, flags, &openMode, &uid, &gid);
-    if( rc!=SQLITE_OK ){
-      assert( !p->pUnused );
-      assert( eType==SQLITE_OPEN_WAL || eType==SQLITE_OPEN_MAIN_JOURNAL );
-      return rc;
-    }
-    fd = robust_open(zName, openFlags, openMode);
-    OSTRACE(("OPENX   %-3d %s 0%o\n", fd, zName, openFlags));
-    if( fd<0 && errno!=EISDIR && isReadWrite && !isExclusive ){
-      /* Failed to open the file for read/write access. Try read-only. */
-      flags &= ~(SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE);
-      openFlags &= ~(O_RDWR|O_CREAT);
-      flags |= SQLITE_OPEN_READONLY;
-      openFlags |= O_RDONLY;
-      isReadonly = 1;
-      fd = robust_open(zName, openFlags, openMode);
-    }
-    if( fd<0 ){
-      rc = unixLogError(SQLITE_CANTOPEN_BKPT, "open", zName);
-      goto open_finished;
-    }
-
-    /* If this process is running as root and if creating a new rollback
-    ** journal or WAL file, set the ownership of the journal or WAL to be
-    ** the same as the original database.
-    */
-    if( flags & (SQLITE_OPEN_WAL|SQLITE_OPEN_MAIN_JOURNAL) ){
-      osFchown(fd, uid, gid);
-    }
-  }
-  assert( fd>=0 );
-  if( pOutFlags ){
-    *pOutFlags = flags;
-  }
-
-  if( p->pUnused ){
-    p->pUnused->fd = fd;
-    p->pUnused->flags = flags;
-  }
-
-  if( isDelete ){
-#if OS_VXWORKS
-    zPath = zName;
-#elif defined(SQLITE_UNLINK_AFTER_CLOSE)
-    zPath = sqlite3_mprintf("%s", zName);
-    if( zPath==0 ){
-      robust_close(p, fd, __LINE__);
-      return SQLITE_NOMEM;
-    }
-#else
-    osUnlink(zName);
-#endif
-  }
-#if SQLITE_ENABLE_LOCKING_STYLE
-  else{
-    p->openFlags = openFlags;
-  }
-#endif
-
-  noLock = eType!=SQLITE_OPEN_MAIN_DB;
-
-  
-#if defined(__APPLE__) || SQLITE_ENABLE_LOCKING_STYLE
-  if( fstatfs(fd, &fsInfo) == -1 ){
-    storeLastErrno(p, errno);
-    robust_close(p, fd, __LINE__);
-    return SQLITE_IOERR_ACCESS;
-  }
-  if (0 == strncmp("msdos", fsInfo.f_fstypename, 5)) {
-    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
-  }
-  if (0 == strncmp("exfat", fsInfo.f_fstypename, 5)) {
-    ((unixFile*)pFile)->fsFlags |= SQLITE_FSFLAGS_IS_MSDOS;
-  }
-#endif
-
-  /* Set up appropriate ctrlFlags */
-  if( isDelete )                ctrlFlags |= UNIXFILE_DELETE;
-  if( isReadonly )              ctrlFlags |= UNIXFILE_RDONLY;
-  if( noLock )                  ctrlFlags |= UNIXFILE_NOLOCK;
-  if( syncDir )                 ctrlFlags |= UNIXFILE_DIRSYNC;
-  if( flags & SQLITE_OPEN_URI ) ctrlFlags |= UNIXFILE_URI;
-
-#if SQLITE_ENABLE_LOCKING_STYLE
-#if SQLITE_PREFER_PROXY_LOCKING
-  isAutoProxy = 1;
-#endif
-  if( isAutoProxy && (zPath!=NULL) && (!noLock) && pVfs->xOpen ){
-    char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
-    int useProxy = 0;
-
-    /* SQLITE_FORCE_PROXY_LOCKING==1 means force always use proxy, 0 means 
-    ** never use proxy, NULL means use proxy for non-local files only.  */
-    if( envforce!=NULL ){
-      useProxy = atoi(envforce)>0;
-    }else{
-      useProxy = !(fsInfo.f_flags&MNT_LOCAL);
-    }
-    if( useProxy ){
-      rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
-      if( rc==SQLITE_OK ){
-        rc = proxyTransformUnixFile((unixFile*)pFile, ":auto:");
-        if( rc!=SQLITE_OK ){
-          /* Use unixClose to clean up the resources added in fillInUnixFile 
-          ** and clear all the structure's references.  Specifically, 
-          ** pFile->pMethods will be NULL so sqlite3OsClose will be a no-op 
-          */
-          unixClose(pFile);
-          return rc;
-        }
-      }
-      goto open_finished;
-    }
-  }
-#endif
-  
-  rc = fillInUnixFile(pVfs, fd, pFile, zPath, ctrlFlags);
-
-open_finished:
-  if( rc!=SQLITE_OK ){
-    sqlite3_free(p->pUnused);
-  }
-  return rc;
-}
-
-
-/*
-** Delete the file at zPath. If the dirSync argument is true, fsync()
-** the directory after deleting the file.
-*/
-static int unixDelete(
-  sqlite3_vfs *NotUsed,     /* VFS containing this as the xDelete method */
-  const char *zPath,        /* Name of file to be deleted */
-  int dirSync               /* If true, fsync() directory after deleting file */
-){
-  int rc = SQLITE_OK;
-  UNUSED_PARAMETER(NotUsed);
-  SimulateIOError(return SQLITE_IOERR_DELETE);
-  if( osUnlink(zPath)==(-1) ){
-    if( errno==ENOENT
-#if OS_VXWORKS
-        || osAccess(zPath,0)!=0
-#endif
-    ){
-      rc = SQLITE_IOERR_DELETE_NOENT;
-    }else{
-      rc = unixLogError(SQLITE_IOERR_DELETE, "unlink", zPath);
-    }
-    return rc;
-  }
-#ifndef SQLITE_DISABLE_DIRSYNC
-  if( (dirSync & 1)!=0 ){
-    int fd;
-    rc = osOpenDirectory(zPath, &fd);
-    if( rc==SQLITE_OK ){
-#if OS_VXWORKS
-      if( fsync(fd)==-1 )
-#else
-      if( fsync(fd) )
-#endif
-      {
-        rc = unixLogError(SQLITE_IOERR_DIR_FSYNC, "fsync", zPath);
-      }
-      robust_close(0, fd, __LINE__);
-    }else if( rc==SQLITE_CANTOPEN ){
-      rc = SQLITE_OK;
-    }
-  }
-#endif
-  return rc;
-}
-
-/*
-** Test the existence of or access permissions of file zPath. The
-** test performed depends on the value of flags:
-**
-**     SQLITE_ACCESS_EXISTS: Return 1 if the file exists
-**     SQLITE_ACCESS_READWRITE: Return 1 if the file is read and writable.
-**     SQLITE_ACCESS_READONLY: Return 1 if the file is readable.
-**
-** Otherwise return 0.
-*/
-static int unixAccess(
-  sqlite3_vfs *NotUsed,   /* The VFS containing this xAccess method */
-  const char *zPath,      /* Path of the file to examine */
-  int flags,              /* What do we want to learn about the zPath file? */
-  int *pResOut            /* Write result boolean here */
-){
-  int amode = 0;
-  UNUSED_PARAMETER(NotUsed);
-  SimulateIOError( return SQLITE_IOERR_ACCESS; );
-  switch( flags ){
-    case SQLITE_ACCESS_EXISTS:
-      amode = F_OK;
-      break;
-    case SQLITE_ACCESS_READWRITE:
-      amode = W_OK|R_OK;
-      break;
-    case SQLITE_ACCESS_READ:
-      amode = R_OK;
-      break;
-
-    default:
-      assert(!"Invalid flags argument");
-  }
-  *pResOut = (osAccess(zPath, amode)==0);
-  if( flags==SQLITE_ACCESS_EXISTS && *pResOut ){
-    struct stat buf;
-    if( 0==osStat(zPath, &buf) && buf.st_size==0 ){
-      *pResOut = 0;
-    }
-  }
-  return SQLITE_OK;
-}
-
-
-/*
-** Turn a relative pathname into a full pathname. The relative path
-** is stored as a nul-terminated string in the buffer pointed to by
-** zPath. 
-**
-** zOut points to a buffer of at least sqlite3_vfs.mxPathname bytes 
-** (in this case, MAX_PATHNAME bytes). The full-path is written to
-** this buffer before returning.
-*/
-static int unixFullPathname(
-  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
-  const char *zPath,            /* Possibly relative input path */
-  int nOut,                     /* Size of output buffer in bytes */
-  char *zOut                    /* Output buffer */
-){
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing. This function could fail if, for example, the
-  ** current working directory has been unlinked.
-  */
-  SimulateIOError( return SQLITE_ERROR );
-
-  assert( pVfs->mxPathname==MAX_PATHNAME );
-  UNUSED_PARAMETER(pVfs);
-
-  zOut[nOut-1] = '\0';
-  if( zPath[0]=='/' ){
-    sqlite3_snprintf(nOut, zOut, "%s", zPath);
-  }else{
-    int nCwd;
-    if( osGetcwd(zOut, nOut-1)==0 ){
-      return unixLogError(SQLITE_CANTOPEN_BKPT, "getcwd", zPath);
-    }
-    nCwd = (int)strlen(zOut);
-    sqlite3_snprintf(nOut-nCwd, &zOut[nCwd], "/%s", zPath);
-  }
-  return SQLITE_OK;
-}
-
-  #define unixDlOpen  0
-  #define unixDlError 0
-  #define unixDlSym   0
-  #define unixDlClose 0
-
-/*
-** Write nBuf bytes of random data to the supplied buffer zBuf.
-*/
-static int unixRandomness(sqlite3_vfs *NotUsed, int nBuf, char *zBuf){
-  UNUSED_PARAMETER(NotUsed);
-  assert((size_t)nBuf>=(sizeof(time_t)+sizeof(int)));
-
-  /* We have to initialize zBuf to prevent valgrind from reporting
-  ** errors.  The reports issued by valgrind are incorrect - we would
-  ** prefer that the randomness be increased by making use of the
-  ** uninitialized space in zBuf - but valgrind errors tend to worry
-  ** some users.  Rather than argue, it seems easier just to initialize
-  ** the whole array and silence valgrind, even if that means less randomness
-  ** in the random seed.
-  **
-  ** When testing, initializing zBuf[] to zero is all we do.  That means
-  ** that we always use the same random number sequence.  This makes the
-  ** tests repeatable.
-  */
-  memset(zBuf, 0, nBuf);
-  randomnessPid = osGetpid(0);  
-#if !defined(SQLITE_TEST) && !defined(SQLITE_OMIT_RANDOMNESS)
-  {
-    int fd, got;
-    fd = robust_open("/dev/urandom", O_RDONLY, 0);
-    if( fd<0 ){
-      time_t t;
-      time(&t);
-      memcpy(zBuf, &t, sizeof(t));
-      memcpy(&zBuf[sizeof(t)], &randomnessPid, sizeof(randomnessPid));
-      assert( sizeof(t)+sizeof(randomnessPid)<=(size_t)nBuf );
-      nBuf = sizeof(t) + sizeof(randomnessPid);
-    }else{
-      do{ got = osRead(fd, zBuf, nBuf); }while( got<0 && errno==EINTR );
-      robust_close(0, fd, __LINE__);
-    }
-  }
-#endif
-  return nBuf;
-}
-
-
-/*
-** Sleep for a little while.  Return the amount of time slept.
-** The argument is the number of microseconds we want to sleep.
-** The return value is the number of microseconds of sleep actually
-** requested from the underlying operating system, a number which
-** might be greater than or equal to the argument, but not less
-** than the argument.
-*/
-static int unixSleep(sqlite3_vfs *NotUsed, int microseconds){
-#if OS_VXWORKS
-  struct timespec sp;
-
-  sp.tv_sec = microseconds / 1000000;
-  sp.tv_nsec = (microseconds % 1000000) * 1000;
-  nanosleep(&sp, NULL);
-  UNUSED_PARAMETER(NotUsed);
-  return microseconds;
-#elif defined(HAVE_USLEEP) && HAVE_USLEEP
-  usleep(microseconds);
-  UNUSED_PARAMETER(NotUsed);
-  return microseconds;
-#else
-  int seconds = (microseconds+999999)/1000000;
-  sleep(seconds);
-  UNUSED_PARAMETER(NotUsed);
-  return seconds*1000000;
-#endif
-}
-
-/*
-** The following variable, if set to a non-zero value, is interpreted as
-** the number of seconds since 1970 and is used to set the result of
-** sqlite3OsCurrentTime() during testing.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
-#endif
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write into *piNow
-** the current time and date as a Julian Day number times 86_400_000.  In
-** other words, write into *piNow the number of milliseconds since the Julian
-** epoch of noon in Greenwich on November 24, 4714 B.C according to the
-** proleptic Gregorian calendar.
-**
-** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date 
-** cannot be found.
-*/
-static int unixCurrentTimeInt64(sqlite3_vfs *NotUsed, sqlite3_int64 *piNow){
-  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
-  int rc = SQLITE_OK;
-#if defined(NO_GETTOD)
-  time_t t;
-  time(&t);
-  *piNow = ((sqlite3_int64)t)*1000 + unixEpoch;
-#elif OS_VXWORKS
-  struct timespec sNow;
-  clock_gettime(CLOCK_REALTIME, &sNow);
-  *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_nsec/1000000;
-#else
-  struct timeval sNow;
-  if( gettimeofday(&sNow, 0)==0 ){
-    *piNow = unixEpoch + 1000*(sqlite3_int64)sNow.tv_sec + sNow.tv_usec/1000;
-  }else{
-    rc = SQLITE_ERROR;
-  }
-#endif
-
-#ifdef SQLITE_TEST
-  if( sqlite3_current_time ){
-    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
-  }
-#endif
-  UNUSED_PARAMETER(NotUsed);
-  return rc;
-}
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write the
-** current time and date as a Julian Day number into *prNow and
-** return 0.  Return 1 if the time and date cannot be found.
-*/
-static int unixCurrentTime(sqlite3_vfs *NotUsed, double *prNow){
-  sqlite3_int64 i = 0;
-  int rc;
-  UNUSED_PARAMETER(NotUsed);
-  rc = unixCurrentTimeInt64(0, &i);
-  *prNow = i/86400000.0;
-  return rc;
-}
-
-/*
-** We added the xGetLastError() method with the intention of providing
-** better low-level error messages when operating-system problems come up
-** during SQLite operation.  But so far, none of that has been implemented
-** in the core.  So this routine is never called.  For now, it is merely
-** a place-holder.
-*/
-static int unixGetLastError(sqlite3_vfs *NotUsed, int NotUsed2, char *NotUsed3){
-  UNUSED_PARAMETER(NotUsed);
-  UNUSED_PARAMETER(NotUsed2);
-  UNUSED_PARAMETER(NotUsed3);
-  return 0;
-}
-
-
-/*
-************************ End of sqlite3_vfs methods ***************************
-******************************************************************************/
-
-/******************************************************************************
-************************** Begin Proxy Locking ********************************
-**
-** Proxy locking is a "uber-locking-method" in this sense:  It uses the
-** other locking methods on secondary lock files.  Proxy locking is a
-** meta-layer over top of the primitive locking implemented above.  For
-** this reason, the division that implements of proxy locking is deferred
-** until late in the file (here) after all of the other I/O methods have
-** been defined - so that the primitive locking methods are available
-** as services to help with the implementation of proxy locking.
-**
-****
-**
-** The default locking schemes in SQLite use byte-range locks on the
-** database file to coordinate safe, concurrent access by multiple readers
-** and writers [http://sqlite.org/lockingv3.html].  The five file locking
-** states (UNLOCKED, PENDING, SHARED, RESERVED, EXCLUSIVE) are implemented
-** as POSIX read & write locks over fixed set of locations (via fsctl),
-** on AFP and SMB only exclusive byte-range locks are available via fsctl
-** with _IOWR('z', 23, struct ByteRangeLockPB2) to track the same 5 states.
-** To simulate a F_RDLCK on the shared range, on AFP a randomly selected
-** address in the shared range is taken for a SHARED lock, the entire
-** shared range is taken for an EXCLUSIVE lock):
-**
-**      PENDING_BYTE        0x40000000
-**      RESERVED_BYTE       0x40000001
-**      SHARED_RANGE        0x40000002 -> 0x40000200
-**
-** This works well on the local file system, but shows a nearly 100x
-** slowdown in read performance on AFP because the AFP client disables
-** the read cache when byte-range locks are present.  Enabling the read
-** cache exposes a cache coherency problem that is present on all OS X
-** supported network file systems.  NFS and AFP both observe the
-** close-to-open semantics for ensuring cache coherency
-** [http://nfs.sourceforge.net/#faq_a8], which does not effectively
-** address the requirements for concurrent database access by multiple
-** readers and writers
-** [http://www.nabble.com/SQLite-on-NFS-cache-coherency-td15655701.html].
-**
-** To address the performance and cache coherency issues, proxy file locking
-** changes the way database access is controlled by limiting access to a
-** single host at a time and moving file locks off of the database file
-** and onto a proxy file on the local file system.  
-**
-**
-** Using proxy locks
-** -----------------
-**
-** C APIs
-**
-**  sqlite3_file_control(db, dbname, SQLITE_FCNTL_SET_LOCKPROXYFILE,
-**                       <proxy_path> | ":auto:");
-**  sqlite3_file_control(db, dbname, SQLITE_FCNTL_GET_LOCKPROXYFILE,
-**                       &<proxy_path>);
-**
-**
-** SQL pragmas
-**
-**  PRAGMA [database.]lock_proxy_file=<proxy_path> | :auto:
-**  PRAGMA [database.]lock_proxy_file
-**
-** Specifying ":auto:" means that if there is a conch file with a matching
-** host ID in it, the proxy path in the conch file will be used, otherwise
-** a proxy path based on the user's temp dir
-** (via confstr(_CS_DARWIN_USER_TEMP_DIR,...)) will be used and the
-** actual proxy file name is generated from the name and path of the
-** database file.  For example:
-**
-**       For database path "/Users/me/foo.db" 
-**       The lock path will be "<tmpdir>/sqliteplocks/_Users_me_foo.db:auto:")
-**
-** Once a lock proxy is configured for a database connection, it can not
-** be removed, however it may be switched to a different proxy path via
-** the above APIs (assuming the conch file is not being held by another
-** connection or process). 
-**
-**
-** How proxy locking works
-** -----------------------
-**
-** Proxy file locking relies primarily on two new supporting files: 
-**
-**   *  conch file to limit access to the database file to a single host
-**      at a time
-**
-**   *  proxy file to act as a proxy for the advisory locks normally
-**      taken on the database
-**
-** The conch file - to use a proxy file, sqlite must first "hold the conch"
-** by taking an sqlite-style shared lock on the conch file, reading the
-** contents and comparing the host's unique host ID (see below) and lock
-** proxy path against the values stored in the conch.  The conch file is
-** stored in the same directory as the database file and the file name
-** is patterned after the database file name as ".<databasename>-conch".
-** If the conch file does not exist, or its contents do not match the
-** host ID and/or proxy path, then the lock is escalated to an exclusive
-** lock and the conch file contents is updated with the host ID and proxy
-** path and the lock is downgraded to a shared lock again.  If the conch
-** is held by another process (with a shared lock), the exclusive lock
-** will fail and SQLITE_BUSY is returned.
-**
-** The proxy file - a single-byte file used for all advisory file locks
-** normally taken on the database file.   This allows for safe sharing
-** of the database file for multiple readers and writers on the same
-** host (the conch ensures that they all use the same local lock file).
-**
-** Requesting the lock proxy does not immediately take the conch, it is
-** only taken when the first request to lock database file is made.  
-** This matches the semantics of the traditional locking behavior, where
-** opening a connection to a database file does not take a lock on it.
-** The shared lock and an open file descriptor are maintained until 
-** the connection to the database is closed. 
-**
-** The proxy file and the lock file are never deleted so they only need
-** to be created the first time they are used.
-**
-** Configuration options
-** ---------------------
-**
-**  SQLITE_PREFER_PROXY_LOCKING
-**
-**       Database files accessed on non-local file systems are
-**       automatically configured for proxy locking, lock files are
-**       named automatically using the same logic as
-**       PRAGMA lock_proxy_file=":auto:"
-**    
-**  SQLITE_PROXY_DEBUG
-**
-**       Enables the logging of error messages during host id file
-**       retrieval and creation
-**
-**  LOCKPROXYDIR
-**
-**       Overrides the default directory used for lock proxy files that
-**       are named automatically via the ":auto:" setting
-**
-**  SQLITE_DEFAULT_PROXYDIR_PERMISSIONS
-**
-**       Permissions to use when creating a directory for storing the
-**       lock proxy files, only used when LOCKPROXYDIR is not set.
-**    
-**    
-** As mentioned above, when compiled with SQLITE_PREFER_PROXY_LOCKING,
-** setting the environment variable SQLITE_FORCE_PROXY_LOCKING to 1 will
-** force proxy locking to be used for every database file opened, and 0
-** will force automatic proxy locking to be disabled for all database
-** files (explicitly calling the SQLITE_FCNTL_SET_LOCKPROXYFILE pragma or
-** sqlite_file_control API is not affected by SQLITE_FORCE_PROXY_LOCKING).
-*/
-
-/*
-** Proxy locking is only available on MacOSX 
-*/
-#if defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE
-
-/*
-** The proxyLockingContext has the path and file structures for the remote 
-** and local proxy files in it
-*/
-typedef struct proxyLockingContext proxyLockingContext;
-struct proxyLockingContext {
-  unixFile *conchFile;         /* Open conch file */
-  char *conchFilePath;         /* Name of the conch file */
-  unixFile *lockProxy;         /* Open proxy lock file */
-  char *lockProxyPath;         /* Name of the proxy lock file */
-  char *dbPath;                /* Name of the open file */
-  int conchHeld;               /* 1 if the conch is held, -1 if lockless */
-  int nFails;                  /* Number of conch taking failures */
-  void *oldLockingContext;     /* Original lockingcontext to restore on close */
-  sqlite3_io_methods const *pOldMethod;     /* Original I/O methods for close */
-};
-
-/* 
-** The proxy lock file path for the database at dbPath is written into lPath, 
-** which must point to valid, writable memory large enough for a maxLen length
-** file path. 
-*/
-static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
-  int len;
-  int dbLen;
-  int i;
-
-#ifdef LOCKPROXYDIR
-  len = strlcpy(lPath, LOCKPROXYDIR, maxLen);
-#else
-# ifdef _CS_DARWIN_USER_TEMP_DIR
-  {
-    if( !confstr(_CS_DARWIN_USER_TEMP_DIR, lPath, maxLen) ){
-      OSTRACE(("GETLOCKPATH  failed %s errno=%d pid=%d\n",
-               lPath, errno, osGetpid(0)));
-      return SQLITE_IOERR_LOCK;
-    }
-    len = strlcat(lPath, "sqliteplocks", maxLen);    
-  }
-# else
-  len = strlcpy(lPath, "/tmp/", maxLen);
-# endif
-#endif
-
-  if( lPath[len-1]!='/' ){
-    len = strlcat(lPath, "/", maxLen);
-  }
-  
-  /* transform the db path to a unique cache name */
-  dbLen = (int)strlen(dbPath);
-  for( i=0; i<dbLen && (i+len+7)<(int)maxLen; i++){
-    char c = dbPath[i];
-    lPath[i+len] = (c=='/')?'_':c;
-  }
-  lPath[i+len]='\0';
-  strlcat(lPath, ":auto:", maxLen);
-  OSTRACE(("GETLOCKPATH  proxy lock path=%s pid=%d\n", lPath, osGetpid(0)));
-  return SQLITE_OK;
-}
-
-/* 
- ** Creates the lock file and any missing directories in lockPath
- */
-static int proxyCreateLockPath(const char *lockPath){
-  int i, len;
-  char buf[MAXPATHLEN];
-  int start = 0;
-  
-  assert(lockPath!=NULL);
-  /* try to create all the intermediate directories */
-  len = (int)strlen(lockPath);
-  buf[0] = lockPath[0];
-  for( i=1; i<len; i++ ){
-    if( lockPath[i] == '/' && (i - start > 0) ){
-      /* only mkdir if leaf dir != "." or "/" or ".." */
-      if( i-start>2 || (i-start==1 && buf[start] != '.' && buf[start] != '/') 
-         || (i-start==2 && buf[start] != '.' && buf[start+1] != '.') ){
-        buf[i]='\0';
-        if( osMkdir(buf, SQLITE_DEFAULT_PROXYDIR_PERMISSIONS) ){
-          int err=errno;
-          if( err!=EEXIST ) {
-            OSTRACE(("CREATELOCKPATH  FAILED creating %s, "
-                     "'%s' proxy lock path=%s pid=%d\n",
-                     buf, strerror(err), lockPath, osGetpid(0)));
-            return err;
-          }
-        }
-      }
-      start=i+1;
-    }
-    buf[i] = lockPath[i];
-  }
-  OSTRACE(("CREATELOCKPATH  proxy lock path=%s pid=%d\n", lockPath, osGetpid(0)));
-  return 0;
-}
-
-/*
-** Create a new VFS file descriptor (stored in memory obtained from
-** sqlite3_malloc) and open the file named "path" in the file descriptor.
-**
-** The caller is responsible not only for closing the file descriptor
-** but also for freeing the memory associated with the file descriptor.
-*/
-static int proxyCreateUnixFile(
-    const char *path,        /* path for the new unixFile */
-    unixFile **ppFile,       /* unixFile created and returned by ref */
-    int islockfile           /* if non zero missing dirs will be created */
-) {
-  int fd = -1;
-  unixFile *pNew;
-  int rc = SQLITE_OK;
-  int openFlags = O_RDWR | O_CREAT;
-  sqlite3_vfs dummyVfs;
-  int terrno = 0;
-  UnixUnusedFd *pUnused = NULL;
-
-  /* 1. first try to open/create the file
-  ** 2. if that fails, and this is a lock file (not-conch), try creating
-  ** the parent directories and then try again.
-  ** 3. if that fails, try to open the file read-only
-  ** otherwise return BUSY (if lock file) or CANTOPEN for the conch file
-  */
-  pUnused = findReusableFd(path, openFlags);
-  if( pUnused ){
-    fd = pUnused->fd;
-  }else{
-    pUnused = sqlite3_malloc64(sizeof(*pUnused));
-    if( !pUnused ){
-      return SQLITE_NOMEM;
-    }
-  }
-  if( fd<0 ){
-    fd = robust_open(path, openFlags, 0);
-    terrno = errno;
-    if( fd<0 && errno==ENOENT && islockfile ){
-      if( proxyCreateLockPath(path) == SQLITE_OK ){
-        fd = robust_open(path, openFlags, 0);
-      }
-    }
-  }
-  if( fd<0 ){
-    openFlags = O_RDONLY;
-    fd = robust_open(path, openFlags, 0);
-    terrno = errno;
-  }
-  if( fd<0 ){
-    if( islockfile ){
-      return SQLITE_BUSY;
-    }
-    switch (terrno) {
-      case EACCES:
-        return SQLITE_PERM;
-      case EIO: 
-        return SQLITE_IOERR_LOCK; /* even though it is the conch */
-      default:
-        return SQLITE_CANTOPEN_BKPT;
-    }
-  }
-  
-  pNew = (unixFile *)sqlite3_malloc64(sizeof(*pNew));
-  if( pNew==NULL ){
-    rc = SQLITE_NOMEM;
-    goto end_create_proxy;
-  }
-  memset(pNew, 0, sizeof(unixFile));
-  pNew->openFlags = openFlags;
-  memset(&dummyVfs, 0, sizeof(dummyVfs));
-  dummyVfs.pAppData = (void*)&autolockIoFinder;
-  dummyVfs.zName = "dummy";
-  pUnused->fd = fd;
-  pUnused->flags = openFlags;
-  pNew->pUnused = pUnused;
-  
-  rc = fillInUnixFile(&dummyVfs, fd, (sqlite3_file*)pNew, path, 0);
-  if( rc==SQLITE_OK ){
-    *ppFile = pNew;
-    return SQLITE_OK;
-  }
-end_create_proxy:    
-  robust_close(pNew, fd, __LINE__);
-  sqlite3_free(pNew);
-  sqlite3_free(pUnused);
-  return rc;
-}
-
-#ifdef SQLITE_TEST
-/* simulate multiple hosts by creating unique hostid file paths */
-SQLITE_PRIVATE int sqlite3_hostid_num = 0;
-#endif
-
-#define PROXY_HOSTIDLEN    16  /* conch file host id length */
-
-#ifdef HAVE_GETHOSTUUID
-/* Not always defined in the headers as it ought to be */
-extern int gethostuuid(uuid_t id, const struct timespec *wait);
-#endif
-
-/* get the host ID via gethostuuid(), pHostID must point to PROXY_HOSTIDLEN 
-** bytes of writable memory.
-*/
-static int proxyGetHostID(unsigned char *pHostID, int *pError){
-  assert(PROXY_HOSTIDLEN == sizeof(uuid_t));
-  memset(pHostID, 0, PROXY_HOSTIDLEN);
-#ifdef HAVE_GETHOSTUUID
-  {
-    struct timespec timeout = {1, 0}; /* 1 sec timeout */
-    if( gethostuuid(pHostID, &timeout) ){
-      int err = errno;
-      if( pError ){
-        *pError = err;
-      }
-      return SQLITE_IOERR;
-    }
-  }
-#else
-  UNUSED_PARAMETER(pError);
-#endif
-#ifdef SQLITE_TEST
-  /* simulate multiple hosts by creating unique hostid file paths */
-  if( sqlite3_hostid_num != 0){
-    pHostID[0] = (char)(pHostID[0] + (char)(sqlite3_hostid_num & 0xFF));
-  }
-#endif
-  
-  return SQLITE_OK;
-}
-
-/* The conch file contains the header, host id and lock file path
- */
-#define PROXY_CONCHVERSION 2   /* 1-byte header, 16-byte host id, path */
-#define PROXY_HEADERLEN    1   /* conch file header length */
-#define PROXY_PATHINDEX    (PROXY_HEADERLEN+PROXY_HOSTIDLEN)
-#define PROXY_MAXCONCHLEN  (PROXY_HEADERLEN+PROXY_HOSTIDLEN+MAXPATHLEN)
-
-/* 
-** Takes an open conch file, copies the contents to a new path and then moves 
-** it back.  The newly created file's file descriptor is assigned to the
-** conch file structure and finally the original conch file descriptor is 
-** closed.  Returns zero if successful.
-*/
-static int proxyBreakConchLock(unixFile *pFile, uuid_t myHostID){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  unixFile *conchFile = pCtx->conchFile;
-  char tPath[MAXPATHLEN];
-  char buf[PROXY_MAXCONCHLEN];
-  char *cPath = pCtx->conchFilePath;
-  size_t readLen = 0;
-  size_t pathLen = 0;
-  char errmsg[64] = "";
-  int fd = -1;
-  int rc = -1;
-  UNUSED_PARAMETER(myHostID);
-
-  /* create a new path by replace the trailing '-conch' with '-break' */
-  pathLen = strlcpy(tPath, cPath, MAXPATHLEN);
-  if( pathLen>MAXPATHLEN || pathLen<6 || 
-     (strlcpy(&tPath[pathLen-5], "break", 6) != 5) ){
-    sqlite3_snprintf(sizeof(errmsg),errmsg,"path error (len %d)",(int)pathLen);
-    goto end_breaklock;
-  }
-  /* read the conch content */
-  readLen = osPread(conchFile->h, buf, PROXY_MAXCONCHLEN, 0);
-  if( readLen<PROXY_PATHINDEX ){
-    sqlite3_snprintf(sizeof(errmsg),errmsg,"read error (len %d)",(int)readLen);
-    goto end_breaklock;
-  }
-  /* write it out to the temporary break file */
-  fd = robust_open(tPath, (O_RDWR|O_CREAT|O_EXCL), 0);
-  if( fd<0 ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "create failed (%d)", errno);
-    goto end_breaklock;
-  }
-  if( osPwrite(fd, buf, readLen, 0) != (ssize_t)readLen ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "write failed (%d)", errno);
-    goto end_breaklock;
-  }
-  if( rename(tPath, cPath) ){
-    sqlite3_snprintf(sizeof(errmsg), errmsg, "rename failed (%d)", errno);
-    goto end_breaklock;
-  }
-  rc = 0;
-  fprintf(stderr, "broke stale lock on %s\n", cPath);
-  robust_close(pFile, conchFile->h, __LINE__);
-  conchFile->h = fd;
-  conchFile->openFlags = O_RDWR | O_CREAT;
-
-end_breaklock:
-  if( rc ){
-    if( fd>=0 ){
-      osUnlink(tPath);
-      robust_close(pFile, fd, __LINE__);
-    }
-    fprintf(stderr, "failed to break stale lock on %s, %s\n", cPath, errmsg);
-  }
-  return rc;
-}
-
-/* Take the requested lock on the conch file and break a stale lock if the 
-** host id matches.
-*/
-static int proxyConchLock(unixFile *pFile, uuid_t myHostID, int lockType){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  unixFile *conchFile = pCtx->conchFile;
-  int rc = SQLITE_OK;
-  int nTries = 0;
-  struct timespec conchModTime;
-  
-  memset(&conchModTime, 0, sizeof(conchModTime));
-  do {
-    rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
-    nTries ++;
-    if( rc==SQLITE_BUSY ){
-      /* If the lock failed (busy):
-       * 1st try: get the mod time of the conch, wait 0.5s and try again. 
-       * 2nd try: fail if the mod time changed or host id is different, wait 
-       *           10 sec and try again
-       * 3rd try: break the lock unless the mod time has changed.
-       */
-      struct stat buf;
-      if( osFstat(conchFile->h, &buf) ){
-        storeLastErrno(pFile, errno);
-        return SQLITE_IOERR_LOCK;
-      }
-      
-      if( nTries==1 ){
-        conchModTime = buf.st_mtimespec;
-        usleep(500000); /* wait 0.5 sec and try the lock again*/
-        continue;  
-      }
-
-      assert( nTries>1 );
-      if( conchModTime.tv_sec != buf.st_mtimespec.tv_sec || 
-         conchModTime.tv_nsec != buf.st_mtimespec.tv_nsec ){
-        return SQLITE_BUSY;
-      }
-      
-      if( nTries==2 ){  
-        char tBuf[PROXY_MAXCONCHLEN];
-        int len = osPread(conchFile->h, tBuf, PROXY_MAXCONCHLEN, 0);
-        if( len<0 ){
-          storeLastErrno(pFile, errno);
-          return SQLITE_IOERR_LOCK;
-        }
-        if( len>PROXY_PATHINDEX && tBuf[0]==(char)PROXY_CONCHVERSION){
-          /* don't break the lock if the host id doesn't match */
-          if( 0!=memcmp(&tBuf[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN) ){
-            return SQLITE_BUSY;
-          }
-        }else{
-          /* don't break the lock on short read or a version mismatch */
-          return SQLITE_BUSY;
-        }
-        usleep(10000000); /* wait 10 sec and try the lock again */
-        continue; 
-      }
-      
-      assert( nTries==3 );
-      if( 0==proxyBreakConchLock(pFile, myHostID) ){
-        rc = SQLITE_OK;
-        if( lockType==EXCLUSIVE_LOCK ){
-          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, SHARED_LOCK);
-        }
-        if( !rc ){
-          rc = conchFile->pMethod->xLock((sqlite3_file*)conchFile, lockType);
-        }
-      }
-    }
-  } while( rc==SQLITE_BUSY && nTries<3 );
-  
-  return rc;
-}
-
-/* Takes the conch by taking a shared lock and read the contents conch, if 
-** lockPath is non-NULL, the host ID and lock file path must match.  A NULL 
-** lockPath means that the lockPath in the conch file will be used if the 
-** host IDs match, or a new lock path will be generated automatically 
-** and written to the conch file.
-*/
-static int proxyTakeConch(unixFile *pFile){
-  proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext; 
-  
-  if( pCtx->conchHeld!=0 ){
-    return SQLITE_OK;
-  }else{
-    unixFile *conchFile = pCtx->conchFile;
-    uuid_t myHostID;
-    int pError = 0;
-    char readBuf[PROXY_MAXCONCHLEN];
-    char lockPath[MAXPATHLEN];
-    char *tempLockPath = NULL;
-    int rc = SQLITE_OK;
-    int createConch = 0;
-    int hostIdMatch = 0;
-    int readLen = 0;
-    int tryOldLockPath = 0;
-    int forceNewLockPath = 0;
-    
-    OSTRACE(("TAKECONCH  %d for %s pid=%d\n", conchFile->h,
-             (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"),
-             osGetpid(0)));
-
-    rc = proxyGetHostID(myHostID, &pError);
-    if( (rc&0xff)==SQLITE_IOERR ){
-      storeLastErrno(pFile, pError);
-      goto end_takeconch;
-    }
-    rc = proxyConchLock(pFile, myHostID, SHARED_LOCK);
-    if( rc!=SQLITE_OK ){
-      goto end_takeconch;
-    }
-    /* read the existing conch file */
-    readLen = seekAndRead((unixFile*)conchFile, 0, readBuf, PROXY_MAXCONCHLEN);
-    if( readLen<0 ){
-      /* I/O error: lastErrno set by seekAndRead */
-      storeLastErrno(pFile, conchFile->lastErrno);
-      rc = SQLITE_IOERR_READ;
-      goto end_takeconch;
-    }else if( readLen<=(PROXY_HEADERLEN+PROXY_HOSTIDLEN) || 
-             readBuf[0]!=(char)PROXY_CONCHVERSION ){
-      /* a short read or version format mismatch means we need to create a new 
-      ** conch file. 
-      */
-      createConch = 1;
-    }
-    /* if the host id matches and the lock path already exists in the conch
-    ** we'll try to use the path there, if we can't open that path, we'll 
-    ** retry with a new auto-generated path 
-    */
-    do { /* in case we need to try again for an :auto: named lock file */
-
-      if( !createConch && !forceNewLockPath ){
-        hostIdMatch = !memcmp(&readBuf[PROXY_HEADERLEN], myHostID, 
-                                  PROXY_HOSTIDLEN);
-        /* if the conch has data compare the contents */
-        if( !pCtx->lockProxyPath ){
-          /* for auto-named local lock file, just check the host ID and we'll
-           ** use the local lock file path that's already in there
-           */
-          if( hostIdMatch ){
-            size_t pathLen = (readLen - PROXY_PATHINDEX);
-            
-            if( pathLen>=MAXPATHLEN ){
-              pathLen=MAXPATHLEN-1;
-            }
-            memcpy(lockPath, &readBuf[PROXY_PATHINDEX], pathLen);
-            lockPath[pathLen] = 0;
-            tempLockPath = lockPath;
-            tryOldLockPath = 1;
-            /* create a copy of the lock path if the conch is taken */
-            goto end_takeconch;
-          }
-        }else if( hostIdMatch
-               && !strncmp(pCtx->lockProxyPath, &readBuf[PROXY_PATHINDEX],
-                           readLen-PROXY_PATHINDEX)
-        ){
-          /* conch host and lock path match */
-          goto end_takeconch; 
-        }
-      }
-      
-      /* if the conch isn't writable and doesn't match, we can't take it */
-      if( (conchFile->openFlags&O_RDWR) == 0 ){
-        rc = SQLITE_BUSY;
-        goto end_takeconch;
-      }
-      
-      /* either the conch didn't match or we need to create a new one */
-      if( !pCtx->lockProxyPath ){
-        proxyGetLockPath(pCtx->dbPath, lockPath, MAXPATHLEN);
-        tempLockPath = lockPath;
-        /* create a copy of the lock path _only_ if the conch is taken */
-      }
-      
-      /* update conch with host and path (this will fail if other process
-      ** has a shared lock already), if the host id matches, use the big
-      ** stick.
-      */
-      futimes(conchFile->h, NULL);
-      if( hostIdMatch && !createConch ){
-        if( conchFile->pInode && conchFile->pInode->nShared>1 ){
-          /* We are trying for an exclusive lock but another thread in this
-           ** same process is still holding a shared lock. */
-          rc = SQLITE_BUSY;
-        } else {          
-          rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
-        }
-      }else{
-        rc = proxyConchLock(pFile, myHostID, EXCLUSIVE_LOCK);
-      }
-      if( rc==SQLITE_OK ){
-        char writeBuffer[PROXY_MAXCONCHLEN];
-        int writeSize = 0;
-        
-        writeBuffer[0] = (char)PROXY_CONCHVERSION;
-        memcpy(&writeBuffer[PROXY_HEADERLEN], myHostID, PROXY_HOSTIDLEN);
-        if( pCtx->lockProxyPath!=NULL ){
-          strlcpy(&writeBuffer[PROXY_PATHINDEX], pCtx->lockProxyPath,
-                  MAXPATHLEN);
-        }else{
-          strlcpy(&writeBuffer[PROXY_PATHINDEX], tempLockPath, MAXPATHLEN);
-        }
-        writeSize = PROXY_PATHINDEX + strlen(&writeBuffer[PROXY_PATHINDEX]);
-        robust_ftruncate(conchFile->h, writeSize);
-        rc = unixWrite((sqlite3_file *)conchFile, writeBuffer, writeSize, 0);
-        fsync(conchFile->h);
-        /* If we created a new conch file (not just updated the contents of a 
-         ** valid conch file), try to match the permissions of the database 
-         */
-        if( rc==SQLITE_OK && createConch ){
-          struct stat buf;
-          int err = osFstat(pFile->h, &buf);
-          if( err==0 ){
-            mode_t cmode = buf.st_mode&(S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP |
-                                        S_IROTH|S_IWOTH);
-            /* try to match the database file R/W permissions, ignore failure */
-#ifndef SQLITE_PROXY_DEBUG
-            osFchmod(conchFile->h, cmode);
-#else
-            do{
-              rc = osFchmod(conchFile->h, cmode);
-            }while( rc==(-1) && errno==EINTR );
-            if( rc!=0 ){
-              int code = errno;
-              fprintf(stderr, "fchmod %o FAILED with %d %s\n",
-                      cmode, code, strerror(code));
-            } else {
-              fprintf(stderr, "fchmod %o SUCCEDED\n",cmode);
-            }
-          }else{
-            int code = errno;
-            fprintf(stderr, "STAT FAILED[%d] with %d %s\n", 
-                    err, code, strerror(code));
-#endif
-          }
-        }
-      }
-      conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, SHARED_LOCK);
-      
-    end_takeconch:
-      OSTRACE(("TRANSPROXY: CLOSE  %d\n", pFile->h));
-      if( rc==SQLITE_OK && pFile->openFlags ){
-        int fd;
-        if( pFile->h>=0 ){
-          robust_close(pFile, pFile->h, __LINE__);
-        }
-        pFile->h = -1;
-        fd = robust_open(pCtx->dbPath, pFile->openFlags, 0);
-        OSTRACE(("TRANSPROXY: OPEN  %d\n", fd));
-        if( fd>=0 ){
-          pFile->h = fd;
-        }else{
-          rc=SQLITE_CANTOPEN_BKPT; /* SQLITE_BUSY? proxyTakeConch called
-           during locking */
-        }
-      }
-      if( rc==SQLITE_OK && !pCtx->lockProxy ){
-        char *path = tempLockPath ? tempLockPath : pCtx->lockProxyPath;
-        rc = proxyCreateUnixFile(path, &pCtx->lockProxy, 1);
-        if( rc!=SQLITE_OK && rc!=SQLITE_NOMEM && tryOldLockPath ){
-          /* we couldn't create the proxy lock file with the old lock file path
-           ** so try again via auto-naming 
-           */
-          forceNewLockPath = 1;
-          tryOldLockPath = 0;
-          continue; /* go back to the do {} while start point, try again */
-        }
-      }
-      if( rc==SQLITE_OK ){
-        /* Need to make a copy of path if we extracted the value
-         ** from the conch file or the path was allocated on the stack
-         */
-        if( tempLockPath ){
-          pCtx->lockProxyPath = sqlite3DbStrDup(0, tempLockPath);
-          if( !pCtx->lockProxyPath ){
-            rc = SQLITE_NOMEM;
-          }
-        }
-      }
-      if( rc==SQLITE_OK ){
-        pCtx->conchHeld = 1;
-        
-        if( pCtx->lockProxy->pMethod == &afpIoMethods ){
-          afpLockingContext *afpCtx;
-          afpCtx = (afpLockingContext *)pCtx->lockProxy->lockingContext;
-          afpCtx->dbPath = pCtx->lockProxyPath;
-        }
-      } else {
-        conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-      }
-      OSTRACE(("TAKECONCH  %d %s\n", conchFile->h,
-               rc==SQLITE_OK?"ok":"failed"));
-      return rc;
-    } while (1); /* in case we need to retry the :auto: lock file - 
-                 ** we should never get here except via the 'continue' call. */
-  }
-}
-
-/*
-** If pFile holds a lock on a conch file, then release that lock.
-*/
-static int proxyReleaseConch(unixFile *pFile){
-  int rc = SQLITE_OK;         /* Subroutine return code */
-  proxyLockingContext *pCtx;  /* The locking context for the proxy lock */
-  unixFile *conchFile;        /* Name of the conch file */
-
-  pCtx = (proxyLockingContext *)pFile->lockingContext;
-  conchFile = pCtx->conchFile;
-  OSTRACE(("RELEASECONCH  %d for %s pid=%d\n", conchFile->h,
-           (pCtx->lockProxyPath ? pCtx->lockProxyPath : ":auto:"), 
-           osGetpid(0)));
-  if( pCtx->conchHeld>0 ){
-    rc = conchFile->pMethod->xUnlock((sqlite3_file*)conchFile, NO_LOCK);
-  }
-  pCtx->conchHeld = 0;
-  OSTRACE(("RELEASECONCH  %d %s\n", conchFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed")));
-  return rc;
-}
-
-/*
-** Given the name of a database file, compute the name of its conch file.
-** Store the conch filename in memory obtained from sqlite3_malloc64().
-** Make *pConchPath point to the new name.  Return SQLITE_OK on success
-** or SQLITE_NOMEM if unable to obtain memory.
-**
-** The caller is responsible for ensuring that the allocated memory
-** space is eventually freed.
-**
-** *pConchPath is set to NULL if a memory allocation error occurs.
-*/
-static int proxyCreateConchPathname(char *dbPath, char **pConchPath){
-  int i;                        /* Loop counter */
-  int len = (int)strlen(dbPath); /* Length of database filename - dbPath */
-  char *conchPath;              /* buffer in which to construct conch name */
-
-  /* Allocate space for the conch filename and initialize the name to
-  ** the name of the original database file. */  
-  *pConchPath = conchPath = (char *)sqlite3_malloc64(len + 8);
-  if( conchPath==0 ){
-    return SQLITE_NOMEM;
-  }
-  memcpy(conchPath, dbPath, len+1);
-  
-  /* now insert a "." before the last / character */
-  for( i=(len-1); i>=0; i-- ){
-    if( conchPath[i]=='/' ){
-      i++;
-      break;
-    }
-  }
-  conchPath[i]='.';
-  while ( i<len ){
-    conchPath[i+1]=dbPath[i];
-    i++;
-  }
-
-  /* append the "-conch" suffix to the file */
-  memcpy(&conchPath[i+1], "-conch", 7);
-  assert( (int)strlen(conchPath) == len+7 );
-
-  return SQLITE_OK;
-}
-
-
-/* Takes a fully configured proxy locking-style unix file and switches
-** the local lock file path 
-*/
-static int switchLockProxyPath(unixFile *pFile, const char *path) {
-  proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
-  char *oldPath = pCtx->lockProxyPath;
-  int rc = SQLITE_OK;
-
-  if( pFile->eFileLock!=NO_LOCK ){
-    return SQLITE_BUSY;
-  }  
-
-  /* nothing to do if the path is NULL, :auto: or matches the existing path */
-  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ||
-    (oldPath && !strncmp(oldPath, path, MAXPATHLEN)) ){
-    return SQLITE_OK;
-  }else{
-    unixFile *lockProxy = pCtx->lockProxy;
-    pCtx->lockProxy=NULL;
-    pCtx->conchHeld = 0;
-    if( lockProxy!=NULL ){
-      rc=lockProxy->pMethod->xClose((sqlite3_file *)lockProxy);
-      if( rc ) return rc;
-      sqlite3_free(lockProxy);
-    }
-    sqlite3_free(oldPath);
-    pCtx->lockProxyPath = sqlite3DbStrDup(0, path);
-  }
-  
-  return rc;
-}
-
-/*
-** pFile is a file that has been opened by a prior xOpen call.  dbPath
-** is a string buffer at least MAXPATHLEN+1 characters in size.
-**
-** This routine find the filename associated with pFile and writes it
-** int dbPath.
-*/
-static int proxyGetDbPathForUnixFile(unixFile *pFile, char *dbPath){
-#if defined(__APPLE__)
-  if( pFile->pMethod == &afpIoMethods ){
-    /* afp style keeps a reference to the db path in the filePath field 
-    ** of the struct */
-    assert( (int)strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strlcpy(dbPath, ((afpLockingContext *)pFile->lockingContext)->dbPath,
-            MAXPATHLEN);
-  } else
-#endif
-  if( pFile->pMethod == &dotlockIoMethods ){
-    /* dot lock style uses the locking context to store the dot lock
-    ** file path */
-    int len = strlen((char *)pFile->lockingContext) - strlen(DOTLOCK_SUFFIX);
-    memcpy(dbPath, (char *)pFile->lockingContext, len + 1);
-  }else{
-    /* all other styles use the locking context to store the db file path */
-    assert( strlen((char*)pFile->lockingContext)<=MAXPATHLEN );
-    strlcpy(dbPath, (char *)pFile->lockingContext, MAXPATHLEN);
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Takes an already filled in unix file and alters it so all file locking 
-** will be performed on the local proxy lock file.  The following fields
-** are preserved in the locking context so that they can be restored and 
-** the unix structure properly cleaned up at close time:
-**  ->lockingContext
-**  ->pMethod
-*/
-static int proxyTransformUnixFile(unixFile *pFile, const char *path) {
-  proxyLockingContext *pCtx;
-  char dbPath[MAXPATHLEN+1];       /* Name of the database file */
-  char *lockPath=NULL;
-  int rc = SQLITE_OK;
-  
-  if( pFile->eFileLock!=NO_LOCK ){
-    return SQLITE_BUSY;
-  }
-  proxyGetDbPathForUnixFile(pFile, dbPath);
-  if( !path || path[0]=='\0' || !strcmp(path, ":auto:") ){
-    lockPath=NULL;
-  }else{
-    lockPath=(char *)path;
-  }
-  
-  OSTRACE(("TRANSPROXY  %d for %s pid=%d\n", pFile->h,
-           (lockPath ? lockPath : ":auto:"), osGetpid(0)));
-
-  pCtx = sqlite3_malloc64( sizeof(*pCtx) );
-  if( pCtx==0 ){
-    return SQLITE_NOMEM;
-  }
-  memset(pCtx, 0, sizeof(*pCtx));
-
-  rc = proxyCreateConchPathname(dbPath, &pCtx->conchFilePath);
-  if( rc==SQLITE_OK ){
-    rc = proxyCreateUnixFile(pCtx->conchFilePath, &pCtx->conchFile, 0);
-    if( rc==SQLITE_CANTOPEN && ((pFile->openFlags&O_RDWR) == 0) ){
-      /* if (a) the open flags are not O_RDWR, (b) the conch isn't there, and
-      ** (c) the file system is read-only, then enable no-locking access.
-      ** Ugh, since O_RDONLY==0x0000 we test for !O_RDWR since unixOpen asserts
-      ** that openFlags will have only one of O_RDONLY or O_RDWR.
-      */
-      struct statfs fsInfo;
-      struct stat conchInfo;
-      int goLockless = 0;
-
-      if( osStat(pCtx->conchFilePath, &conchInfo) == -1 ) {
-        int err = errno;
-        if( (err==ENOENT) && (statfs(dbPath, &fsInfo) != -1) ){
-          goLockless = (fsInfo.f_flags&MNT_RDONLY) == MNT_RDONLY;
-        }
-      }
-      if( goLockless ){
-        pCtx->conchHeld = -1; /* read only FS/ lockless */
-        rc = SQLITE_OK;
-      }
-    }
-  }  
-  if( rc==SQLITE_OK && lockPath ){
-    pCtx->lockProxyPath = sqlite3DbStrDup(0, lockPath);
-  }
-
-  if( rc==SQLITE_OK ){
-    pCtx->dbPath = sqlite3DbStrDup(0, dbPath);
-    if( pCtx->dbPath==NULL ){
-      rc = SQLITE_NOMEM;
-    }
-  }
-  if( rc==SQLITE_OK ){
-    /* all memory is allocated, proxys are created and assigned, 
-    ** switch the locking context and pMethod then return.
-    */
-    pCtx->oldLockingContext = pFile->lockingContext;
-    pFile->lockingContext = pCtx;
-    pCtx->pOldMethod = pFile->pMethod;
-    pFile->pMethod = &proxyIoMethods;
-  }else{
-    if( pCtx->conchFile ){ 
-      pCtx->conchFile->pMethod->xClose((sqlite3_file *)pCtx->conchFile);
-      sqlite3_free(pCtx->conchFile);
-    }
-    sqlite3DbFree(0, pCtx->lockProxyPath);
-    sqlite3_free(pCtx->conchFilePath); 
-    sqlite3_free(pCtx);
-  }
-  OSTRACE(("TRANSPROXY  %d %s\n", pFile->h,
-           (rc==SQLITE_OK ? "ok" : "failed")));
-  return rc;
-}
-
-
-/*
-** This routine handles sqlite3_file_control() calls that are specific
-** to proxy locking.
-*/
-static int proxyFileControl(sqlite3_file *id, int op, void *pArg){
-  switch( op ){
-    case SQLITE_FCNTL_GET_LOCKPROXYFILE: {
-      unixFile *pFile = (unixFile*)id;
-      if( pFile->pMethod == &proxyIoMethods ){
-        proxyLockingContext *pCtx = (proxyLockingContext*)pFile->lockingContext;
-        proxyTakeConch(pFile);
-        if( pCtx->lockProxyPath ){
-          *(const char **)pArg = pCtx->lockProxyPath;
-        }else{
-          *(const char **)pArg = ":auto: (not held)";
-        }
-      } else {
-        *(const char **)pArg = NULL;
-      }
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_SET_LOCKPROXYFILE: {
-      unixFile *pFile = (unixFile*)id;
-      int rc = SQLITE_OK;
-      int isProxyStyle = (pFile->pMethod == &proxyIoMethods);
-      if( pArg==NULL || (const char *)pArg==0 ){
-        if( isProxyStyle ){
-          /* turn off proxy locking - not supported.  If support is added for
-          ** switching proxy locking mode off then it will need to fail if
-          ** the journal mode is WAL mode. 
-          */
-          rc = SQLITE_ERROR /*SQLITE_PROTOCOL? SQLITE_MISUSE?*/;
-        }else{
-          /* turn off proxy locking - already off - NOOP */
-          rc = SQLITE_OK;
-        }
-      }else{
-        const char *proxyPath = (const char *)pArg;
-        if( isProxyStyle ){
-          proxyLockingContext *pCtx = 
-            (proxyLockingContext*)pFile->lockingContext;
-          if( !strcmp(pArg, ":auto:") 
-           || (pCtx->lockProxyPath &&
-               !strncmp(pCtx->lockProxyPath, proxyPath, MAXPATHLEN))
-          ){
-            rc = SQLITE_OK;
-          }else{
-            rc = switchLockProxyPath(pFile, proxyPath);
-          }
-        }else{
-          /* turn on proxy file locking */
-          rc = proxyTransformUnixFile(pFile, proxyPath);
-        }
-      }
-      return rc;
-    }
-    default: {
-      assert( 0 );  /* The call assures that only valid opcodes are sent */
-    }
-  }
-  /*NOTREACHED*/
-  return SQLITE_ERROR;
-}
-
-/*
-** Within this division (the proxying locking implementation) the procedures
-** above this point are all utilities.  The lock-related methods of the
-** proxy-locking sqlite3_io_method object follow.
-*/
-
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, set *pResOut
-** to a non-zero value otherwise *pResOut is set to zero.  The return value
-** is set to SQLITE_OK unless an I/O error occurs during lock checking.
-*/
-static int proxyCheckReservedLock(sqlite3_file *id, int *pResOut) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      return proxy->pMethod->xCheckReservedLock((sqlite3_file*)proxy, pResOut);
-    }else{ /* conchHeld < 0 is lockless */
-      pResOut=0;
-    }
-  }
-  return rc;
-}
-
-/*
-** Lock the file with the lock specified by parameter eFileLock - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  Use the sqlite3OsUnlock()
-** routine to lower a locking level.
-*/
-static int proxyLock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      rc = proxy->pMethod->xLock((sqlite3_file*)proxy, eFileLock);
-      pFile->eFileLock = proxy->eFileLock;
-    }else{
-      /* conchHeld < 0 is lockless */
-    }
-  }
-  return rc;
-}
-
-
-/*
-** Lower the locking level on file descriptor pFile to eFileLock.  eFileLock
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-*/
-static int proxyUnlock(sqlite3_file *id, int eFileLock) {
-  unixFile *pFile = (unixFile*)id;
-  int rc = proxyTakeConch(pFile);
-  if( rc==SQLITE_OK ){
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    if( pCtx->conchHeld>0 ){
-      unixFile *proxy = pCtx->lockProxy;
-      rc = proxy->pMethod->xUnlock((sqlite3_file*)proxy, eFileLock);
-      pFile->eFileLock = proxy->eFileLock;
-    }else{
-      /* conchHeld < 0 is lockless */
-    }
-  }
-  return rc;
-}
-
-/*
-** Close a file that uses proxy locks.
-*/
-static int proxyClose(sqlite3_file *id) {
-  if( id ){
-    unixFile *pFile = (unixFile*)id;
-    proxyLockingContext *pCtx = (proxyLockingContext *)pFile->lockingContext;
-    unixFile *lockProxy = pCtx->lockProxy;
-    unixFile *conchFile = pCtx->conchFile;
-    int rc = SQLITE_OK;
-    
-    if( lockProxy ){
-      rc = lockProxy->pMethod->xUnlock((sqlite3_file*)lockProxy, NO_LOCK);
-      if( rc ) return rc;
-      rc = lockProxy->pMethod->xClose((sqlite3_file*)lockProxy);
-      if( rc ) return rc;
-      sqlite3_free(lockProxy);
-      pCtx->lockProxy = 0;
-    }
-    if( conchFile ){
-      if( pCtx->conchHeld ){
-        rc = proxyReleaseConch(pFile);
-        if( rc ) return rc;
-      }
-      rc = conchFile->pMethod->xClose((sqlite3_file*)conchFile);
-      if( rc ) return rc;
-      sqlite3_free(conchFile);
-    }
-    sqlite3DbFree(0, pCtx->lockProxyPath);
-    sqlite3_free(pCtx->conchFilePath);
-    sqlite3DbFree(0, pCtx->dbPath);
-    /* restore the original locking context and pMethod then close it */
-    pFile->lockingContext = pCtx->oldLockingContext;
-    pFile->pMethod = pCtx->pOldMethod;
-    sqlite3_free(pCtx);
-    return pFile->pMethod->xClose(id);
-  }
-  return SQLITE_OK;
-}
-
-
-
-#endif /* defined(__APPLE__) && SQLITE_ENABLE_LOCKING_STYLE */
-/*
-** The proxy locking style is intended for use with AFP filesystems.
-** And since AFP is only supported on MacOSX, the proxy locking is also
-** restricted to MacOSX.
-** 
-**
-******************* End of the proxy lock implementation **********************
-******************************************************************************/
-
-/*
-** Initialize the operating system interface.
-**
-** This routine registers all VFS implementations for unix-like operating
-** systems.  This routine, and the sqlite3_os_end() routine that follows,
-** should be the only routines in this file that are visible from other
-** files.
-**
-** This routine is called once during SQLite initialization and by a
-** single thread.  The memory allocation and mutex subsystems have not
-** necessarily been initialized when this routine is called, and so they
-** should not be used.
-*/
-SQLITE_PRIVATE int sqlite3_os_init(void){ 
-  /* 
-  ** The following macro defines an initializer for an sqlite3_vfs object.
-  ** The name of the VFS is NAME.  The pAppData is a pointer to a pointer
-  ** to the "finder" function.  (pAppData is a pointer to a pointer because
-  ** silly C90 rules prohibit a void* from being cast to a function pointer
-  ** and so we have to go through the intermediate pointer to avoid problems
-  ** when compiling with -pedantic-errors on GCC.)
-  **
-  ** The FINDER parameter to this macro is the name of the pointer to the
-  ** finder-function.  The finder-function returns a pointer to the
-  ** sqlite_io_methods object that implements the desired locking
-  ** behaviors.  See the division above that contains the IOMETHODS
-  ** macro for addition information on finder-functions.
-  **
-  ** Most finders simply return a pointer to a fixed sqlite3_io_methods
-  ** object.  But the "autolockIoFinder" available on MacOSX does a little
-  ** more than that; it looks at the filesystem type that hosts the 
-  ** database file and tries to choose an locking method appropriate for
-  ** that filesystem time.
-  */
-  #define UNIXVFS(VFSNAME, FINDER) {                        \
-    3,                    /* iVersion */                    \
-    sizeof(unixFile),     /* szOsFile */                    \
-    MAX_PATHNAME,         /* mxPathname */                  \
-    0,                    /* pNext */                       \
-    VFSNAME,              /* zName */                       \
-    (void*)&FINDER,       /* pAppData */                    \
-    unixOpen,             /* xOpen */                       \
-    unixDelete,           /* xDelete */                     \
-    unixAccess,           /* xAccess */                     \
-    unixFullPathname,     /* xFullPathname */               \
-    unixDlOpen,           /* xDlOpen */                     \
-    unixDlError,          /* xDlError */                    \
-    unixDlSym,            /* xDlSym */                      \
-    unixDlClose,          /* xDlClose */                    \
-    unixRandomness,       /* xRandomness */                 \
-    unixSleep,            /* xSleep */                      \
-    unixCurrentTime,      /* xCurrentTime */                \
-    unixGetLastError,     /* xGetLastError */               \
-    unixCurrentTimeInt64, /* xCurrentTimeInt64 */           \
-    unixSetSystemCall,    /* xSetSystemCall */              \
-    unixGetSystemCall,    /* xGetSystemCall */              \
-    unixNextSystemCall,   /* xNextSystemCall */             \
-  }
-
-  /*
-  ** All default VFSes for unix are contained in the following array.
-  **
-  ** Note that the sqlite3_vfs.pNext field of the VFS object is modified
-  ** by the SQLite core when the VFS is registered.  So the following
-  ** array cannot be const.
-  */
-  static sqlite3_vfs aVfs[] = {
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-    UNIXVFS("unix",          autolockIoFinder ),
-#elif OS_VXWORKS
-    UNIXVFS("unix",          vxworksIoFinder ),
-#else
-    UNIXVFS("unix",          posixIoFinder ),
-#endif
-    UNIXVFS("unix-none",     nolockIoFinder ),
-    UNIXVFS("unix-dotfile",  dotlockIoFinder ),
-    UNIXVFS("unix-excl",     posixIoFinder ),
-#if OS_VXWORKS
-    UNIXVFS("unix-namedsem", semIoFinder ),
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE || OS_VXWORKS
-    UNIXVFS("unix-posix",    posixIoFinder ),
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE
-    UNIXVFS("unix-flock",    flockIoFinder ),
-#endif
-#if SQLITE_ENABLE_LOCKING_STYLE && defined(__APPLE__)
-    UNIXVFS("unix-afp",      afpIoFinder ),
-    UNIXVFS("unix-nfs",      nfsIoFinder ),
-    UNIXVFS("unix-proxy",    proxyIoFinder ),
-#endif
-  };
-  unsigned int i;          /* Loop counter */
-
-  /* Double-check that the aSyscall[] array has been constructed
-  ** correctly.  See ticket [bb3a86e890c8e96ab] */
-  assert( ArraySize(aSyscall)==25 );
-
-  /* Register all VFSes defined in the aVfs[] array */
-  for(i=0; i<(sizeof(aVfs)/sizeof(sqlite3_vfs)); i++){
-    sqlite3_vfs_register(&aVfs[i], i==0);
-  }
-  return SQLITE_OK; 
-}
-
-/*
-** Shutdown the operating system interface.
-**
-** Some operating systems might need to do some cleanup in this routine,
-** to release dynamically allocated objects.  But not on unix.
-** This routine is a no-op for unix.
-*/
-SQLITE_PRIVATE int sqlite3_os_end(void){ 
-  return SQLITE_OK; 
-}
- 
-#endif /* SQLITE_OS_UNIX */
-
-/************** End of os_unix.c *********************************************/
-/************** Begin file os_win.c ******************************************/
-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains code that is specific to Windows.
-*/
-/* #include "sqliteInt.h" */
-#if SQLITE_OS_WIN               /* This file is used for Windows only */
-
-/*
-** Include code that is common to all os_*.c files
-*/
-/************** Include os_common.h in the middle of os_win.c ****************/
-/************** Begin file os_common.h ***************************************/
-/*
-** 2004 May 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-******************************************************************************
-**
-** This file contains macros and a little bit of code that is common to
-** all of the platform-specific files (os_*.c) and is #included into those
-** files.
-**
-** This file should be #included by the os_*.c files only.  It is not a
-** general purpose header file.
-*/
-#ifndef _OS_COMMON_H_
-#define _OS_COMMON_H_
-
-/*
-** At least two bugs have slipped in because we changed the MEMORY_DEBUG
-** macro to SQLITE_DEBUG and some older makefiles have not yet made the
-** switch.  The following code should catch this problem at compile-time.
-*/
-#ifdef MEMORY_DEBUG
-# error "The MEMORY_DEBUG macro is obsolete.  Use SQLITE_DEBUG instead."
-#endif
-
-/*
-** Macros for performance tracing.  Normally turned off.  Only works
-** on i486 hardware.
-*/
-#ifdef SQLITE_PERFORMANCE_TRACE
-
-/* 
-** hwtime.h contains inline assembler code for implementing 
-** high-performance timing routines.
-*/
-/* #include "hwtime.h" */
-
-static sqlite_uint64 g_start;
-static sqlite_uint64 g_elapsed;
-#define TIMER_START       g_start=sqlite3Hwtime()
-#define TIMER_END         g_elapsed=sqlite3Hwtime()-g_start
-#define TIMER_ELAPSED     g_elapsed
-#else
-#define TIMER_START
-#define TIMER_END
-#define TIMER_ELAPSED     ((sqlite_uint64)0)
-#endif
-
-/*
-** If we compile with the SQLITE_TEST macro set, then the following block
-** of code will give us the ability to simulate a disk I/O error.  This
-** is used for testing the I/O recovery logic.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_io_error_hit = 0;            /* Total number of I/O Errors */
-SQLITE_PRIVATE int sqlite3_io_error_hardhit = 0;        /* Number of non-benign errors */
-SQLITE_PRIVATE int sqlite3_io_error_pending = 0;        /* Count down to first I/O error */
-SQLITE_PRIVATE int sqlite3_io_error_persist = 0;        /* True if I/O errors persist */
-SQLITE_PRIVATE int sqlite3_io_error_benign = 0;         /* True if errors are benign */
-SQLITE_PRIVATE int sqlite3_diskfull_pending = 0;
-SQLITE_PRIVATE int sqlite3_diskfull = 0;
-#define SimulateIOErrorBenign(X) sqlite3_io_error_benign=(X)
-#define SimulateIOError(CODE)  \
-  if( (sqlite3_io_error_persist && sqlite3_io_error_hit) \
-       || sqlite3_io_error_pending-- == 1 )  \
-              { local_ioerr(); CODE; }
-static void local_ioerr(){
-  IOTRACE(("IOERR\n"));
-  sqlite3_io_error_hit++;
-  if( !sqlite3_io_error_benign ) sqlite3_io_error_hardhit++;
-}
-#define SimulateDiskfullError(CODE) \
-   if( sqlite3_diskfull_pending ){ \
-     if( sqlite3_diskfull_pending == 1 ){ \
-       local_ioerr(); \
-       sqlite3_diskfull = 1; \
-       sqlite3_io_error_hit = 1; \
-       CODE; \
-     }else{ \
-       sqlite3_diskfull_pending--; \
-     } \
-   }
-#else
-#define SimulateIOErrorBenign(X)
-#define SimulateIOError(A)
-#define SimulateDiskfullError(A)
-#endif
-
-/*
-** When testing, keep a count of the number of open files.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_open_file_count = 0;
-#define OpenCounter(X)  sqlite3_open_file_count+=(X)
-#else
-#define OpenCounter(X)
-#endif
-
-#endif /* !defined(_OS_COMMON_H_) */
-
-/************** End of os_common.h *******************************************/
-/************** Continuing where we left off in os_win.c *********************/
-
-/*
-** Include the header file for the Windows VFS.
-*/
-/* #include "os_win.h" */
-
-/*
-** Compiling and using WAL mode requires several APIs that are only
-** available in Windows platforms based on the NT kernel.
-*/
-#if !SQLITE_OS_WINNT && !defined(SQLITE_OMIT_WAL)
-#  error "WAL mode requires support from the Windows NT kernel, compile\
- with SQLITE_OMIT_WAL."
-#endif
-
-#if !SQLITE_OS_WINNT && SQLITE_MAX_MMAP_SIZE>0
-#  error "Memory mapped files require support from the Windows NT kernel,\
- compile with SQLITE_MAX_MMAP_SIZE=0."
-#endif
-
-/*
-** Are most of the Win32 ANSI APIs available (i.e. with certain exceptions
-** based on the sub-platform)?
-*/
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && !defined(SQLITE_WIN32_NO_ANSI)
-#  define SQLITE_WIN32_HAS_ANSI
-#endif
-
-/*
-** Are most of the Win32 Unicode APIs available (i.e. with certain exceptions
-** based on the sub-platform)?
-*/
-#if (SQLITE_OS_WINCE || SQLITE_OS_WINNT || SQLITE_OS_WINRT) && \
-    !defined(SQLITE_WIN32_NO_WIDE)
-#  define SQLITE_WIN32_HAS_WIDE
-#endif
-
-/*
-** Make sure at least one set of Win32 APIs is available.
-*/
-#if !defined(SQLITE_WIN32_HAS_ANSI) && !defined(SQLITE_WIN32_HAS_WIDE)
-#  error "At least one of SQLITE_WIN32_HAS_ANSI and SQLITE_WIN32_HAS_WIDE\
- must be defined."
-#endif
-
-/*
-** Define the required Windows SDK version constants if they are not
-** already available.
-*/
-#ifndef NTDDI_WIN8
-#  define NTDDI_WIN8                        0x06020000
-#endif
-
-#ifndef NTDDI_WINBLUE
-#  define NTDDI_WINBLUE                     0x06030000
-#endif
-
-/*
-** Check to see if the GetVersionEx[AW] functions are deprecated on the
-** target system.  GetVersionEx was first deprecated in Win8.1.
-*/
-#ifndef SQLITE_WIN32_GETVERSIONEX
-#  if defined(NTDDI_VERSION) && NTDDI_VERSION >= NTDDI_WINBLUE
-#    define SQLITE_WIN32_GETVERSIONEX   0   /* GetVersionEx() is deprecated */
-#  else
-#    define SQLITE_WIN32_GETVERSIONEX   1   /* GetVersionEx() is current */
-#  endif
-#endif
-
-/*
-** This constant should already be defined (in the "WinDef.h" SDK file).
-*/
-#ifndef MAX_PATH
-#  define MAX_PATH                      (260)
-#endif
-
-/*
-** Maximum pathname length (in chars) for Win32.  This should normally be
-** MAX_PATH.
-*/
-#ifndef SQLITE_WIN32_MAX_PATH_CHARS
-#  define SQLITE_WIN32_MAX_PATH_CHARS   (MAX_PATH)
-#endif
-
-/*
-** This constant should already be defined (in the "WinNT.h" SDK file).
-*/
-#ifndef UNICODE_STRING_MAX_CHARS
-#  define UNICODE_STRING_MAX_CHARS      (32767)
-#endif
-
-/*
-** Maximum pathname length (in chars) for WinNT.  This should normally be
-** UNICODE_STRING_MAX_CHARS.
-*/
-#ifndef SQLITE_WINNT_MAX_PATH_CHARS
-#  define SQLITE_WINNT_MAX_PATH_CHARS   (UNICODE_STRING_MAX_CHARS)
-#endif
-
-/*
-** Maximum pathname length (in bytes) for Win32.  The MAX_PATH macro is in
-** characters, so we allocate 4 bytes per character assuming worst-case of
-** 4-bytes-per-character for UTF8.
-*/
-#ifndef SQLITE_WIN32_MAX_PATH_BYTES
-#  define SQLITE_WIN32_MAX_PATH_BYTES   (SQLITE_WIN32_MAX_PATH_CHARS*4)
-#endif
-
-/*
-** Maximum pathname length (in bytes) for WinNT.  This should normally be
-** UNICODE_STRING_MAX_CHARS * sizeof(WCHAR).
-*/
-#ifndef SQLITE_WINNT_MAX_PATH_BYTES
-#  define SQLITE_WINNT_MAX_PATH_BYTES   \
-                            (sizeof(WCHAR) * SQLITE_WINNT_MAX_PATH_CHARS)
-#endif
-
-/*
-** Maximum error message length (in chars) for WinRT.
-*/
-#ifndef SQLITE_WIN32_MAX_ERRMSG_CHARS
-#  define SQLITE_WIN32_MAX_ERRMSG_CHARS (1024)
-#endif
-
-/*
-** Returns non-zero if the character should be treated as a directory
-** separator.
-*/
-#ifndef winIsDirSep
-#  define winIsDirSep(a)                (((a) == '/') || ((a) == '\\'))
-#endif
-
-/*
-** This macro is used when a local variable is set to a value that is
-** [sometimes] not used by the code (e.g. via conditional compilation).
-*/
-#ifndef UNUSED_VARIABLE_VALUE
-#  define UNUSED_VARIABLE_VALUE(x)      (void)(x)
-#endif
-
-/*
-** Returns the character that should be used as the directory separator.
-*/
-#ifndef winGetDirSep
-#  define winGetDirSep()                '\\'
-#endif
-
-/*
-** Do we need to manually define the Win32 file mapping APIs for use with WAL
-** mode or memory mapped files (e.g. these APIs are available in the Windows
-** CE SDK; however, they are not present in the header file)?
-*/
-#if SQLITE_WIN32_FILEMAPPING_API && \
-        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
-/*
-** Two of the file mapping APIs are different under WinRT.  Figure out which
-** set we need.
-*/
-#if SQLITE_OS_WINRT
-WINBASEAPI HANDLE WINAPI CreateFileMappingFromApp(HANDLE, \
-        LPSECURITY_ATTRIBUTES, ULONG, ULONG64, LPCWSTR);
-
-WINBASEAPI LPVOID WINAPI MapViewOfFileFromApp(HANDLE, ULONG, ULONG64, SIZE_T);
-#else
-#if defined(SQLITE_WIN32_HAS_ANSI)
-WINBASEAPI HANDLE WINAPI CreateFileMappingA(HANDLE, LPSECURITY_ATTRIBUTES, \
-        DWORD, DWORD, DWORD, LPCSTR);
-#endif /* defined(SQLITE_WIN32_HAS_ANSI) */
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-WINBASEAPI HANDLE WINAPI CreateFileMappingW(HANDLE, LPSECURITY_ATTRIBUTES, \
-        DWORD, DWORD, DWORD, LPCWSTR);
-#endif /* defined(SQLITE_WIN32_HAS_WIDE) */
-
-WINBASEAPI LPVOID WINAPI MapViewOfFile(HANDLE, DWORD, DWORD, DWORD, SIZE_T);
-#endif /* SQLITE_OS_WINRT */
-
-/*
-** These file mapping APIs are common to both Win32 and WinRT.
-*/
-
-WINBASEAPI BOOL WINAPI FlushViewOfFile(LPCVOID, SIZE_T);
-WINBASEAPI BOOL WINAPI UnmapViewOfFile(LPCVOID);
-#endif /* SQLITE_WIN32_FILEMAPPING_API */
-
-/*
-** Some Microsoft compilers lack this definition.
-*/
-#ifndef INVALID_FILE_ATTRIBUTES
-# define INVALID_FILE_ATTRIBUTES ((DWORD)-1)
-#endif
-
-#ifndef FILE_FLAG_MASK
-# define FILE_FLAG_MASK          (0xFF3C0000)
-#endif
-
-#ifndef FILE_ATTRIBUTE_MASK
-# define FILE_ATTRIBUTE_MASK     (0x0003FFF7)
-#endif
-
-#ifndef SQLITE_OMIT_WAL
-/* Forward references to structures used for WAL */
-typedef struct winShm winShm;           /* A connection to shared-memory */
-typedef struct winShmNode winShmNode;   /* A region of shared-memory */
-#endif
-
-/*
-** WinCE lacks native support for file locking so we have to fake it
-** with some code of our own.
-*/
-#if SQLITE_OS_WINCE
-typedef struct winceLock {
-  int nReaders;       /* Number of reader locks obtained */
-  BOOL bPending;      /* Indicates a pending lock has been obtained */
-  BOOL bReserved;     /* Indicates a reserved lock has been obtained */
-  BOOL bExclusive;    /* Indicates an exclusive lock has been obtained */
-} winceLock;
-#endif
-
-/*
-** The winFile structure is a subclass of sqlite3_file* specific to the win32
-** portability layer.
-*/
-typedef struct winFile winFile;
-struct winFile {
-  const sqlite3_io_methods *pMethod; /*** Must be first ***/
-  sqlite3_vfs *pVfs;      /* The VFS used to open this file */
-  HANDLE h;               /* Handle for accessing the file */
-  u8 locktype;            /* Type of lock currently held on this file */
-  short sharedLockByte;   /* Randomly chosen byte used as a shared lock */
-  u8 ctrlFlags;           /* Flags.  See WINFILE_* below */
-  DWORD lastErrno;        /* The Windows errno from the last I/O error */
-#ifndef SQLITE_OMIT_WAL
-  winShm *pShm;           /* Instance of shared memory on this file */
-#endif
-  const char *zPath;      /* Full pathname of this file */
-  int szChunk;            /* Chunk size configured by FCNTL_CHUNK_SIZE */
-#if SQLITE_OS_WINCE
-  LPWSTR zDeleteOnClose;  /* Name of file to delete when closing */
-  HANDLE hMutex;          /* Mutex used to control access to shared lock */
-  HANDLE hShared;         /* Shared memory segment used for locking */
-  winceLock local;        /* Locks obtained by this instance of winFile */
-  winceLock *shared;      /* Global shared lock memory for the file  */
-#endif
-#if SQLITE_MAX_MMAP_SIZE>0
-  int nFetchOut;                /* Number of outstanding xFetch references */
-  HANDLE hMap;                  /* Handle for accessing memory mapping */
-  void *pMapRegion;             /* Area memory mapped */
-  sqlite3_int64 mmapSize;       /* Usable size of mapped region */
-  sqlite3_int64 mmapSizeActual; /* Actual size of mapped region */
-  sqlite3_int64 mmapSizeMax;    /* Configured FCNTL_MMAP_SIZE value */
-#endif
-};
-
-/*
-** Allowed values for winFile.ctrlFlags
-*/
-#define WINFILE_RDONLY          0x02   /* Connection is read only */
-#define WINFILE_PERSIST_WAL     0x04   /* Persistent WAL mode */
-#define WINFILE_PSOW            0x10   /* SQLITE_IOCAP_POWERSAFE_OVERWRITE */
-
-/*
- * The value used with sqlite3_win32_set_directory() to specify that
- * the temporary directory should be changed.
- */
-#ifndef SQLITE_WIN32_TEMP_DIRECTORY_TYPE
-#  define SQLITE_WIN32_TEMP_DIRECTORY_TYPE (2)
-#endif
-
-/*
- * If compiled with SQLITE_WIN32_MALLOC on Windows, we will use the
- * various Win32 API heap functions instead of our own.
- */
-#ifdef SQLITE_WIN32_MALLOC
-
-/*
- * If this is non-zero, an isolated heap will be created by the native Win32
- * allocator subsystem; otherwise, the default process heap will be used.  This
- * setting has no effect when compiling for WinRT.  By default, this is enabled
- * and an isolated heap will be created to store all allocated data.
- *
- ******************************************************************************
- * WARNING: It is important to note that when this setting is non-zero and the
- *          winMemShutdown function is called (e.g. by the sqlite3BtreeShutdown
- *          function), all data that was allocated using the isolated heap will
- *          be freed immediately and any attempt to access any of that freed
- *          data will almost certainly result in an immediate access violation.
- ******************************************************************************
- */
-#ifndef SQLITE_WIN32_HEAP_CREATE
-#  define SQLITE_WIN32_HEAP_CREATE    (TRUE)
-#endif
-
-/*
- * The initial size of the Win32-specific heap.  This value may be zero.
- */
-#ifndef SQLITE_WIN32_HEAP_INIT_SIZE
-#  define SQLITE_WIN32_HEAP_INIT_SIZE ((SQLITE_DEFAULT_CACHE_SIZE) * \
-                                       (SQLITE_DEFAULT_PAGE_SIZE) + 4194304)
-#endif
-
-/*
- * The maximum size of the Win32-specific heap.  This value may be zero.
- */
-#ifndef SQLITE_WIN32_HEAP_MAX_SIZE
-#  define SQLITE_WIN32_HEAP_MAX_SIZE  (0)
-#endif
-
-/*
- * The extra flags to use in calls to the Win32 heap APIs.  This value may be
- * zero for the default behavior.
- */
-#ifndef SQLITE_WIN32_HEAP_FLAGS
-#  define SQLITE_WIN32_HEAP_FLAGS     (0)
-#endif
-
-
-/*
-** The winMemData structure stores information required by the Win32-specific
-** sqlite3_mem_methods implementation.
-*/
-typedef struct winMemData winMemData;
-struct winMemData {
-#ifndef NDEBUG
-  u32 magic1;   /* Magic number to detect structure corruption. */
-#endif
-  HANDLE hHeap; /* The handle to our heap. */
-  BOOL bOwned;  /* Do we own the heap (i.e. destroy it on shutdown)? */
-#ifndef NDEBUG
-  u32 magic2;   /* Magic number to detect structure corruption. */
-#endif
-};
-
-#ifndef NDEBUG
-#define WINMEM_MAGIC1     0x42b2830b
-#define WINMEM_MAGIC2     0xbd4d7cf4
-#endif
-
-static struct winMemData win_mem_data = {
-#ifndef NDEBUG
-  WINMEM_MAGIC1,
-#endif
-  NULL, FALSE
-#ifndef NDEBUG
-  ,WINMEM_MAGIC2
-#endif
-};
-
-#ifndef NDEBUG
-#define winMemAssertMagic1() assert( win_mem_data.magic1==WINMEM_MAGIC1 )
-#define winMemAssertMagic2() assert( win_mem_data.magic2==WINMEM_MAGIC2 )
-#define winMemAssertMagic()  winMemAssertMagic1(); winMemAssertMagic2();
-#else
-#define winMemAssertMagic()
-#endif
-
-#define winMemGetDataPtr()  &win_mem_data
-#define winMemGetHeap()     win_mem_data.hHeap
-#define winMemGetOwned()    win_mem_data.bOwned
-
-static void *winMemMalloc(int nBytes);
-static void winMemFree(void *pPrior);
-static void *winMemRealloc(void *pPrior, int nBytes);
-static int winMemSize(void *p);
-static int winMemRoundup(int n);
-static int winMemInit(void *pAppData);
-static void winMemShutdown(void *pAppData);
-
-SQLITE_PRIVATE const sqlite3_mem_methods *sqlite3MemGetWin32(void);
-#endif /* SQLITE_WIN32_MALLOC */
-
-/*
-** The following variable is (normally) set once and never changes
-** thereafter.  It records whether the operating system is Win9x
-** or WinNT.
-**
-** 0:   Operating system unknown.
-** 1:   Operating system is Win9x.
-** 2:   Operating system is WinNT.
-**
-** In order to facilitate testing on a WinNT system, the test fixture
-** can manually set this value to 1 to emulate Win98 behavior.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE LONG SQLITE_WIN32_VOLATILE sqlite3_os_type = 0;
-#else
-static LONG SQLITE_WIN32_VOLATILE sqlite3_os_type = 0;
-#endif
-
-#ifndef SYSCALL
-#  define SYSCALL sqlite3_syscall_ptr
-#endif
-
-/*
-** This function is not available on Windows CE or WinRT.
- */
-
-#if SQLITE_OS_WINCE || SQLITE_OS_WINRT
-#  define osAreFileApisANSI()       1
-#endif
-
-/*
-** Many system calls are accessed through pointer-to-functions so that
-** they may be overridden at runtime to facilitate fault injection during
-** testing and sandboxing.  The following array holds the names and pointers
-** to all overrideable system calls.
-*/
-static struct win_syscall {
-  const char *zName;            /* Name of the system call */
-  sqlite3_syscall_ptr pCurrent; /* Current value of the system call */
-  sqlite3_syscall_ptr pDefault; /* Default value */
-} aSyscall[] = {
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
-  { "AreFileApisANSI",         (SYSCALL)AreFileApisANSI,         0 },
-#else
-  { "AreFileApisANSI",         (SYSCALL)0,                       0 },
-#endif
-
-#ifndef osAreFileApisANSI
-#define osAreFileApisANSI ((BOOL(WINAPI*)(VOID))aSyscall[0].pCurrent)
-#endif
-
-#if SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_WIDE)
-  { "CharLowerW",              (SYSCALL)CharLowerW,              0 },
-#else
-  { "CharLowerW",              (SYSCALL)0,                       0 },
-#endif
-
-#define osCharLowerW ((LPWSTR(WINAPI*)(LPWSTR))aSyscall[1].pCurrent)
-
-#if SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_WIDE)
-  { "CharUpperW",              (SYSCALL)CharUpperW,              0 },
-#else
-  { "CharUpperW",              (SYSCALL)0,                       0 },
-#endif
-
-#define osCharUpperW ((LPWSTR(WINAPI*)(LPWSTR))aSyscall[2].pCurrent)
-
-  { "CloseHandle",             (SYSCALL)CloseHandle,             0 },
-
-#define osCloseHandle ((BOOL(WINAPI*)(HANDLE))aSyscall[3].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "CreateFileA",             (SYSCALL)CreateFileA,             0 },
-#else
-  { "CreateFileA",             (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateFileA ((HANDLE(WINAPI*)(LPCSTR,DWORD,DWORD, \
-        LPSECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE))aSyscall[4].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "CreateFileW",             (SYSCALL)CreateFileW,             0 },
-#else
-  { "CreateFileW",             (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateFileW ((HANDLE(WINAPI*)(LPCWSTR,DWORD,DWORD, \
-        LPSECURITY_ATTRIBUTES,DWORD,DWORD,HANDLE))aSyscall[5].pCurrent)
-
-#if (!SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_ANSI) && \
-        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0))
-  { "CreateFileMappingA",      (SYSCALL)CreateFileMappingA,      0 },
-#else
-  { "CreateFileMappingA",      (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateFileMappingA ((HANDLE(WINAPI*)(HANDLE,LPSECURITY_ATTRIBUTES, \
-        DWORD,DWORD,DWORD,LPCSTR))aSyscall[6].pCurrent)
-
-#if SQLITE_OS_WINCE || (!SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE) && \
-        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0))
-  { "CreateFileMappingW",      (SYSCALL)CreateFileMappingW,      0 },
-#else
-  { "CreateFileMappingW",      (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateFileMappingW ((HANDLE(WINAPI*)(HANDLE,LPSECURITY_ATTRIBUTES, \
-        DWORD,DWORD,DWORD,LPCWSTR))aSyscall[7].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "CreateMutexW",            (SYSCALL)CreateMutexW,            0 },
-#else
-  { "CreateMutexW",            (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateMutexW ((HANDLE(WINAPI*)(LPSECURITY_ATTRIBUTES,BOOL, \
-        LPCWSTR))aSyscall[8].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "DeleteFileA",             (SYSCALL)DeleteFileA,             0 },
-#else
-  { "DeleteFileA",             (SYSCALL)0,                       0 },
-#endif
-
-#define osDeleteFileA ((BOOL(WINAPI*)(LPCSTR))aSyscall[9].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  { "DeleteFileW",             (SYSCALL)DeleteFileW,             0 },
-#else
-  { "DeleteFileW",             (SYSCALL)0,                       0 },
-#endif
-
-#define osDeleteFileW ((BOOL(WINAPI*)(LPCWSTR))aSyscall[10].pCurrent)
-
-#if SQLITE_OS_WINCE
-  { "FileTimeToLocalFileTime", (SYSCALL)FileTimeToLocalFileTime, 0 },
-#else
-  { "FileTimeToLocalFileTime", (SYSCALL)0,                       0 },
-#endif
-
-#define osFileTimeToLocalFileTime ((BOOL(WINAPI*)(CONST FILETIME*, \
-        LPFILETIME))aSyscall[11].pCurrent)
-
-#if SQLITE_OS_WINCE
-  { "FileTimeToSystemTime",    (SYSCALL)FileTimeToSystemTime,    0 },
-#else
-  { "FileTimeToSystemTime",    (SYSCALL)0,                       0 },
-#endif
-
-#define osFileTimeToSystemTime ((BOOL(WINAPI*)(CONST FILETIME*, \
-        LPSYSTEMTIME))aSyscall[12].pCurrent)
-
-  { "FlushFileBuffers",        (SYSCALL)FlushFileBuffers,        0 },
-
-#define osFlushFileBuffers ((BOOL(WINAPI*)(HANDLE))aSyscall[13].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "FormatMessageA",          (SYSCALL)FormatMessageA,          0 },
-#else
-  { "FormatMessageA",          (SYSCALL)0,                       0 },
-#endif
-
-#define osFormatMessageA ((DWORD(WINAPI*)(DWORD,LPCVOID,DWORD,DWORD,LPSTR, \
-        DWORD,va_list*))aSyscall[14].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  { "FormatMessageW",          (SYSCALL)FormatMessageW,          0 },
-#else
-  { "FormatMessageW",          (SYSCALL)0,                       0 },
-#endif
-
-#define osFormatMessageW ((DWORD(WINAPI*)(DWORD,LPCVOID,DWORD,DWORD,LPWSTR, \
-        DWORD,va_list*))aSyscall[15].pCurrent)
-
-  { "FreeLibrary",             (SYSCALL)0,                       0 },
-
-#define osFreeLibrary ((BOOL(WINAPI*)(HMODULE))aSyscall[16].pCurrent)
-
-  { "GetCurrentProcessId",     (SYSCALL)GetCurrentProcessId,     0 },
-
-#define osGetCurrentProcessId ((DWORD(WINAPI*)(VOID))aSyscall[17].pCurrent)
-
-#if !SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_ANSI)
-  { "GetDiskFreeSpaceA",       (SYSCALL)GetDiskFreeSpaceA,       0 },
-#else
-  { "GetDiskFreeSpaceA",       (SYSCALL)0,                       0 },
-#endif
-
-#define osGetDiskFreeSpaceA ((BOOL(WINAPI*)(LPCSTR,LPDWORD,LPDWORD,LPDWORD, \
-        LPDWORD))aSyscall[18].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "GetDiskFreeSpaceW",       (SYSCALL)GetDiskFreeSpaceW,       0 },
-#else
-  { "GetDiskFreeSpaceW",       (SYSCALL)0,                       0 },
-#endif
-
-#define osGetDiskFreeSpaceW ((BOOL(WINAPI*)(LPCWSTR,LPDWORD,LPDWORD,LPDWORD, \
-        LPDWORD))aSyscall[19].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "GetFileAttributesA",      (SYSCALL)GetFileAttributesA,      0 },
-#else
-  { "GetFileAttributesA",      (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFileAttributesA ((DWORD(WINAPI*)(LPCSTR))aSyscall[20].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "GetFileAttributesW",      (SYSCALL)GetFileAttributesW,      0 },
-#else
-  { "GetFileAttributesW",      (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFileAttributesW ((DWORD(WINAPI*)(LPCWSTR))aSyscall[21].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  { "GetFileAttributesExW",    (SYSCALL)GetFileAttributesExW,    0 },
-#else
-  { "GetFileAttributesExW",    (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFileAttributesExW ((BOOL(WINAPI*)(LPCWSTR,GET_FILEEX_INFO_LEVELS, \
-        LPVOID))aSyscall[22].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "GetFileSize",             (SYSCALL)GetFileSize,             0 },
-#else
-  { "GetFileSize",             (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFileSize ((DWORD(WINAPI*)(HANDLE,LPDWORD))aSyscall[23].pCurrent)
-
-#if !SQLITE_OS_WINCE && defined(SQLITE_WIN32_HAS_ANSI)
-  { "GetFullPathNameA",        (SYSCALL)GetFullPathNameA,        0 },
-#else
-  { "GetFullPathNameA",        (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFullPathNameA ((DWORD(WINAPI*)(LPCSTR,DWORD,LPSTR, \
-        LPSTR*))aSyscall[24].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "GetFullPathNameW",        (SYSCALL)GetFullPathNameW,        0 },
-#else
-  { "GetFullPathNameW",        (SYSCALL)0,                       0 },
-#endif
-
-#define osGetFullPathNameW ((DWORD(WINAPI*)(LPCWSTR,DWORD,LPWSTR, \
-        LPWSTR*))aSyscall[25].pCurrent)
-
-  { "GetLastError",            (SYSCALL)GetLastError,            0 },
-
-#define osGetLastError ((DWORD(WINAPI*)(VOID))aSyscall[26].pCurrent)
-
-  { "GetProcAddressA",         (SYSCALL)0,                       0 },
-
-#define osGetProcAddressA ((FARPROC(WINAPI*)(HMODULE, \
-        LPCSTR))aSyscall[27].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "GetSystemInfo",           (SYSCALL)GetSystemInfo,           0 },
-#else
-  { "GetSystemInfo",           (SYSCALL)0,                       0 },
-#endif
-
-#define osGetSystemInfo ((VOID(WINAPI*)(LPSYSTEM_INFO))aSyscall[28].pCurrent)
-
-  { "GetSystemTime",           (SYSCALL)GetSystemTime,           0 },
-
-#define osGetSystemTime ((VOID(WINAPI*)(LPSYSTEMTIME))aSyscall[29].pCurrent)
-
-#if !SQLITE_OS_WINCE
-  { "GetSystemTimeAsFileTime", (SYSCALL)GetSystemTimeAsFileTime, 0 },
-#else
-  { "GetSystemTimeAsFileTime", (SYSCALL)0,                       0 },
-#endif
-
-#define osGetSystemTimeAsFileTime ((VOID(WINAPI*)( \
-        LPFILETIME))aSyscall[30].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "GetTempPathA",            (SYSCALL)GetTempPathA,            0 },
-#else
-  { "GetTempPathA",            (SYSCALL)0,                       0 },
-#endif
-
-#define osGetTempPathA ((DWORD(WINAPI*)(DWORD,LPSTR))aSyscall[31].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "GetTempPathW",            (SYSCALL)GetTempPathW,            0 },
-#else
-  { "GetTempPathW",            (SYSCALL)0,                       0 },
-#endif
-
-#define osGetTempPathW ((DWORD(WINAPI*)(DWORD,LPWSTR))aSyscall[32].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "GetTickCount",            (SYSCALL)GetTickCount,            0 },
-#else
-  { "GetTickCount",            (SYSCALL)0,                       0 },
-#endif
-
-#define osGetTickCount ((DWORD(WINAPI*)(VOID))aSyscall[33].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI) && defined(SQLITE_WIN32_GETVERSIONEX) && \
-        SQLITE_WIN32_GETVERSIONEX
-  { "GetVersionExA",           (SYSCALL)GetVersionExA,           0 },
-#else
-  { "GetVersionExA",           (SYSCALL)0,                       0 },
-#endif
-
-#define osGetVersionExA ((BOOL(WINAPI*)( \
-        LPOSVERSIONINFOA))aSyscall[34].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE) && \
-        defined(SQLITE_WIN32_GETVERSIONEX) && SQLITE_WIN32_GETVERSIONEX
-  { "GetVersionExW",           (SYSCALL)GetVersionExW,           0 },
-#else
-  { "GetVersionExW",           (SYSCALL)0,                       0 },
-#endif
-
-#define osGetVersionExW ((BOOL(WINAPI*)( \
-        LPOSVERSIONINFOW))aSyscall[35].pCurrent)
-
-  { "HeapAlloc",               (SYSCALL)HeapAlloc,               0 },
-
-#define osHeapAlloc ((LPVOID(WINAPI*)(HANDLE,DWORD, \
-        SIZE_T))aSyscall[36].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "HeapCreate",              (SYSCALL)HeapCreate,              0 },
-#else
-  { "HeapCreate",              (SYSCALL)0,                       0 },
-#endif
-
-#define osHeapCreate ((HANDLE(WINAPI*)(DWORD,SIZE_T, \
-        SIZE_T))aSyscall[37].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "HeapDestroy",             (SYSCALL)HeapDestroy,             0 },
-#else
-  { "HeapDestroy",             (SYSCALL)0,                       0 },
-#endif
-
-#define osHeapDestroy ((BOOL(WINAPI*)(HANDLE))aSyscall[38].pCurrent)
-
-  { "HeapFree",                (SYSCALL)HeapFree,                0 },
-
-#define osHeapFree ((BOOL(WINAPI*)(HANDLE,DWORD,LPVOID))aSyscall[39].pCurrent)
-
-  { "HeapReAlloc",             (SYSCALL)HeapReAlloc,             0 },
-
-#define osHeapReAlloc ((LPVOID(WINAPI*)(HANDLE,DWORD,LPVOID, \
-        SIZE_T))aSyscall[40].pCurrent)
-
-  { "HeapSize",                (SYSCALL)HeapSize,                0 },
-
-#define osHeapSize ((SIZE_T(WINAPI*)(HANDLE,DWORD, \
-        LPCVOID))aSyscall[41].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "HeapValidate",            (SYSCALL)HeapValidate,            0 },
-#else
-  { "HeapValidate",            (SYSCALL)0,                       0 },
-#endif
-
-#define osHeapValidate ((BOOL(WINAPI*)(HANDLE,DWORD, \
-        LPCVOID))aSyscall[42].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
-  { "HeapCompact",             (SYSCALL)HeapCompact,             0 },
-#else
-  { "HeapCompact",             (SYSCALL)0,                       0 },
-#endif
-
-#define osHeapCompact ((UINT(WINAPI*)(HANDLE,DWORD))aSyscall[43].pCurrent)
-
-  { "LoadLibraryA",            (SYSCALL)0,                       0 },
-
-#define osLoadLibraryA ((HMODULE(WINAPI*)(LPCSTR))aSyscall[44].pCurrent)
-
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_HAS_WIDE)
-  { "LoadLibraryW",            (SYSCALL)LoadLibraryW,            0 },
-#else
-  { "LoadLibraryW",            (SYSCALL)0,                       0 },
-#endif
-
-#define osLoadLibraryW ((HMODULE(WINAPI*)(LPCWSTR))aSyscall[45].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "LocalFree",               (SYSCALL)LocalFree,               0 },
-#else
-  { "LocalFree",               (SYSCALL)0,                       0 },
-#endif
-
-#define osLocalFree ((HLOCAL(WINAPI*)(HLOCAL))aSyscall[46].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
-  { "LockFile",                (SYSCALL)LockFile,                0 },
-#else
-  { "LockFile",                (SYSCALL)0,                       0 },
-#endif
-
-#ifndef osLockFile
-#define osLockFile ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
-        DWORD))aSyscall[47].pCurrent)
-#endif
-
-#if !SQLITE_OS_WINCE
-  { "LockFileEx",              (SYSCALL)LockFileEx,              0 },
-#else
-  { "LockFileEx",              (SYSCALL)0,                       0 },
-#endif
-
-#ifndef osLockFileEx
-#define osLockFileEx ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD,DWORD, \
-        LPOVERLAPPED))aSyscall[48].pCurrent)
-#endif
-
-#if SQLITE_OS_WINCE || (!SQLITE_OS_WINRT && \
-        (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0))
-  { "MapViewOfFile",           (SYSCALL)MapViewOfFile,           0 },
-#else
-  { "MapViewOfFile",           (SYSCALL)0,                       0 },
-#endif
-
-#define osMapViewOfFile ((LPVOID(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
-        SIZE_T))aSyscall[49].pCurrent)
-
-  { "MultiByteToWideChar",     (SYSCALL)MultiByteToWideChar,     0 },
-
-#define osMultiByteToWideChar ((int(WINAPI*)(UINT,DWORD,LPCSTR,int,LPWSTR, \
-        int))aSyscall[50].pCurrent)
-
-  { "QueryPerformanceCounter", (SYSCALL)QueryPerformanceCounter, 0 },
-
-#define osQueryPerformanceCounter ((BOOL(WINAPI*)( \
-        LARGE_INTEGER*))aSyscall[51].pCurrent)
-
-  { "ReadFile",                (SYSCALL)ReadFile,                0 },
-
-#define osReadFile ((BOOL(WINAPI*)(HANDLE,LPVOID,DWORD,LPDWORD, \
-        LPOVERLAPPED))aSyscall[52].pCurrent)
-
-  { "SetEndOfFile",            (SYSCALL)SetEndOfFile,            0 },
-
-#define osSetEndOfFile ((BOOL(WINAPI*)(HANDLE))aSyscall[53].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "SetFilePointer",          (SYSCALL)SetFilePointer,          0 },
-#else
-  { "SetFilePointer",          (SYSCALL)0,                       0 },
-#endif
-
-#define osSetFilePointer ((DWORD(WINAPI*)(HANDLE,LONG,PLONG, \
-        DWORD))aSyscall[54].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "Sleep",                   (SYSCALL)Sleep,                   0 },
-#else
-  { "Sleep",                   (SYSCALL)0,                       0 },
-#endif
-
-#define osSleep ((VOID(WINAPI*)(DWORD))aSyscall[55].pCurrent)
-
-  { "SystemTimeToFileTime",    (SYSCALL)SystemTimeToFileTime,    0 },
-
-#define osSystemTimeToFileTime ((BOOL(WINAPI*)(CONST SYSTEMTIME*, \
-        LPFILETIME))aSyscall[56].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
-  { "UnlockFile",              (SYSCALL)UnlockFile,              0 },
-#else
-  { "UnlockFile",              (SYSCALL)0,                       0 },
-#endif
-
-#ifndef osUnlockFile
-#define osUnlockFile ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
-        DWORD))aSyscall[57].pCurrent)
-#endif
-
-#if !SQLITE_OS_WINCE
-  { "UnlockFileEx",            (SYSCALL)UnlockFileEx,            0 },
-#else
-  { "UnlockFileEx",            (SYSCALL)0,                       0 },
-#endif
-
-#define osUnlockFileEx ((BOOL(WINAPI*)(HANDLE,DWORD,DWORD,DWORD, \
-        LPOVERLAPPED))aSyscall[58].pCurrent)
-
-#if SQLITE_OS_WINCE || !defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0
-  { "UnmapViewOfFile",         (SYSCALL)UnmapViewOfFile,         0 },
-#else
-  { "UnmapViewOfFile",         (SYSCALL)0,                       0 },
-#endif
-
-#define osUnmapViewOfFile ((BOOL(WINAPI*)(LPCVOID))aSyscall[59].pCurrent)
-
-  { "WideCharToMultiByte",     (SYSCALL)WideCharToMultiByte,     0 },
-
-#define osWideCharToMultiByte ((int(WINAPI*)(UINT,DWORD,LPCWSTR,int,LPSTR,int, \
-        LPCSTR,LPBOOL))aSyscall[60].pCurrent)
-
-  { "WriteFile",               (SYSCALL)WriteFile,               0 },
-
-#define osWriteFile ((BOOL(WINAPI*)(HANDLE,LPCVOID,DWORD,LPDWORD, \
-        LPOVERLAPPED))aSyscall[61].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "CreateEventExW",          (SYSCALL)CreateEventExW,          0 },
-#else
-  { "CreateEventExW",          (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateEventExW ((HANDLE(WINAPI*)(LPSECURITY_ATTRIBUTES,LPCWSTR, \
-        DWORD,DWORD))aSyscall[62].pCurrent)
-
-#if !SQLITE_OS_WINRT
-  { "WaitForSingleObject",     (SYSCALL)WaitForSingleObject,     0 },
-#else
-  { "WaitForSingleObject",     (SYSCALL)0,                       0 },
-#endif
-
-#define osWaitForSingleObject ((DWORD(WINAPI*)(HANDLE, \
-        DWORD))aSyscall[63].pCurrent)
-
-#if !SQLITE_OS_WINCE
-  { "WaitForSingleObjectEx",   (SYSCALL)WaitForSingleObjectEx,   0 },
-#else
-  { "WaitForSingleObjectEx",   (SYSCALL)0,                       0 },
-#endif
-
-#define osWaitForSingleObjectEx ((DWORD(WINAPI*)(HANDLE,DWORD, \
-        BOOL))aSyscall[64].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "SetFilePointerEx",        (SYSCALL)SetFilePointerEx,        0 },
-#else
-  { "SetFilePointerEx",        (SYSCALL)0,                       0 },
-#endif
-
-#define osSetFilePointerEx ((BOOL(WINAPI*)(HANDLE,LARGE_INTEGER, \
-        PLARGE_INTEGER,DWORD))aSyscall[65].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "GetFileInformationByHandleEx", (SYSCALL)GetFileInformationByHandleEx, 0 },
-#else
-  { "GetFileInformationByHandleEx", (SYSCALL)0,                  0 },
-#endif
-
-#define osGetFileInformationByHandleEx ((BOOL(WINAPI*)(HANDLE, \
-        FILE_INFO_BY_HANDLE_CLASS,LPVOID,DWORD))aSyscall[66].pCurrent)
-
-#if SQLITE_OS_WINRT && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
-  { "MapViewOfFileFromApp",    (SYSCALL)MapViewOfFileFromApp,    0 },
-#else
-  { "MapViewOfFileFromApp",    (SYSCALL)0,                       0 },
-#endif
-
-#define osMapViewOfFileFromApp ((LPVOID(WINAPI*)(HANDLE,ULONG,ULONG64, \
-        SIZE_T))aSyscall[67].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "CreateFile2",             (SYSCALL)CreateFile2,             0 },
-#else
-  { "CreateFile2",             (SYSCALL)0,                       0 },
-#endif
-
-#define osCreateFile2 ((HANDLE(WINAPI*)(LPCWSTR,DWORD,DWORD,DWORD, \
-        LPCREATEFILE2_EXTENDED_PARAMETERS))aSyscall[68].pCurrent)
-
-  { "LoadPackagedLibrary",     (SYSCALL)0,                       0 },
-
-#define osLoadPackagedLibrary ((HMODULE(WINAPI*)(LPCWSTR, \
-        DWORD))aSyscall[69].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "GetTickCount64",          (SYSCALL)GetTickCount64,          0 },
-#else
-  { "GetTickCount64",          (SYSCALL)0,                       0 },
-#endif
-
-#define osGetTickCount64 ((ULONGLONG(WINAPI*)(VOID))aSyscall[70].pCurrent)
-
-#if SQLITE_OS_WINRT
-  { "GetNativeSystemInfo",     (SYSCALL)GetNativeSystemInfo,     0 },
-#else
-  { "GetNativeSystemInfo",     (SYSCALL)0,                       0 },
-#endif
-
-#define osGetNativeSystemInfo ((VOID(WINAPI*)( \
-        LPSYSTEM_INFO))aSyscall[71].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_ANSI)
-  { "OutputDebugStringA",      (SYSCALL)OutputDebugStringA,      0 },
-#else
-  { "OutputDebugStringA",      (SYSCALL)0,                       0 },
-#endif
-
-#define osOutputDebugStringA ((VOID(WINAPI*)(LPCSTR))aSyscall[72].pCurrent)
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  { "OutputDebugStringW",      (SYSCALL)OutputDebugStringW,      0 },
-#else
-  { "OutputDebugStringW",      (SYSCALL)0,                       0 },
-#endif
-
-#define osOutputDebugStringW ((VOID(WINAPI*)(LPCWSTR))aSyscall[73].pCurrent)
-
-  { "GetProcessHeap",          (SYSCALL)GetProcessHeap,          0 },
-
-#define osGetProcessHeap ((HANDLE(WINAPI*)(VOID))aSyscall[74].pCurrent)
-
-#if SQLITE_OS_WINRT && (!defined(SQLITE_OMIT_WAL) || SQLITE_MAX_MMAP_SIZE>0)
-  { "CreateFileMappingFromApp", (SYSCALL)CreateFileMappingFromApp, 0 },
-#else
-  { "CreateFileMappingFromApp", (SYSCALL)0,                      0 },
-#endif
-
-#define osCreateFileMappingFromApp ((HANDLE(WINAPI*)(HANDLE, \
-        LPSECURITY_ATTRIBUTES,ULONG,ULONG64,LPCWSTR))aSyscall[75].pCurrent)
-
-/*
-** NOTE: On some sub-platforms, the InterlockedCompareExchange "function"
-**       is really just a macro that uses a compiler intrinsic (e.g. x64).
-**       So do not try to make this is into a redefinable interface.
-*/
-#if defined(InterlockedCompareExchange)
-  { "InterlockedCompareExchange", (SYSCALL)0,                    0 },
-
-#define osInterlockedCompareExchange InterlockedCompareExchange
-#else
-  { "InterlockedCompareExchange", (SYSCALL)InterlockedCompareExchange, 0 },
-
-#define osInterlockedCompareExchange ((LONG(WINAPI*)(LONG \
-        SQLITE_WIN32_VOLATILE*, LONG,LONG))aSyscall[76].pCurrent)
-#endif /* defined(InterlockedCompareExchange) */
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
-  { "UuidCreate",               (SYSCALL)UuidCreate,             0 },
-#else
-  { "UuidCreate",               (SYSCALL)0,                      0 },
-#endif
-
-#define osUuidCreate ((RPC_STATUS(RPC_ENTRY*)(UUID*))aSyscall[77].pCurrent)
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
-  { "UuidCreateSequential",     (SYSCALL)UuidCreateSequential,   0 },
-#else
-  { "UuidCreateSequential",     (SYSCALL)0,                      0 },
-#endif
-
-#define osUuidCreateSequential \
-        ((RPC_STATUS(RPC_ENTRY*)(UUID*))aSyscall[78].pCurrent)
-
-#if !defined(SQLITE_NO_SYNC) && SQLITE_MAX_MMAP_SIZE>0
-  { "FlushViewOfFile",          (SYSCALL)FlushViewOfFile,        0 },
-#else
-  { "FlushViewOfFile",          (SYSCALL)0,                      0 },
-#endif
-
-#define osFlushViewOfFile \
-        ((BOOL(WINAPI*)(LPCVOID,SIZE_T))aSyscall[79].pCurrent)
-
-}; /* End of the overrideable system calls */
-
-/*
-** This is the xSetSystemCall() method of sqlite3_vfs for all of the
-** "win32" VFSes.  Return SQLITE_OK opon successfully updating the
-** system call pointer, or SQLITE_NOTFOUND if there is no configurable
-** system call named zName.
-*/
-static int winSetSystemCall(
-  sqlite3_vfs *pNotUsed,        /* The VFS pointer.  Not used */
-  const char *zName,            /* Name of system call to override */
-  sqlite3_syscall_ptr pNewFunc  /* Pointer to new system call value */
-){
-  unsigned int i;
-  int rc = SQLITE_NOTFOUND;
-
-  UNUSED_PARAMETER(pNotUsed);
-  if( zName==0 ){
-    /* If no zName is given, restore all system calls to their default
-    ** settings and return NULL
-    */
-    rc = SQLITE_OK;
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( aSyscall[i].pDefault ){
-        aSyscall[i].pCurrent = aSyscall[i].pDefault;
-      }
-    }
-  }else{
-    /* If zName is specified, operate on only the one system call
-    ** specified.
-    */
-    for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ){
-        if( aSyscall[i].pDefault==0 ){
-          aSyscall[i].pDefault = aSyscall[i].pCurrent;
-        }
-        rc = SQLITE_OK;
-        if( pNewFunc==0 ) pNewFunc = aSyscall[i].pDefault;
-        aSyscall[i].pCurrent = pNewFunc;
-        break;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Return the value of a system call.  Return NULL if zName is not a
-** recognized system call name.  NULL is also returned if the system call
-** is currently undefined.
-*/
-static sqlite3_syscall_ptr winGetSystemCall(
-  sqlite3_vfs *pNotUsed,
-  const char *zName
-){
-  unsigned int i;
-
-  UNUSED_PARAMETER(pNotUsed);
-  for(i=0; i<sizeof(aSyscall)/sizeof(aSyscall[0]); i++){
-    if( strcmp(zName, aSyscall[i].zName)==0 ) return aSyscall[i].pCurrent;
-  }
-  return 0;
-}
-
-/*
-** Return the name of the first system call after zName.  If zName==NULL
-** then return the name of the first system call.  Return NULL if zName
-** is the last system call or if zName is not the name of a valid
-** system call.
-*/
-static const char *winNextSystemCall(sqlite3_vfs *p, const char *zName){
-  int i = -1;
-
-  UNUSED_PARAMETER(p);
-  if( zName ){
-    for(i=0; i<ArraySize(aSyscall)-1; i++){
-      if( strcmp(zName, aSyscall[i].zName)==0 ) break;
-    }
-  }
-  for(i++; i<ArraySize(aSyscall); i++){
-    if( aSyscall[i].pCurrent!=0 ) return aSyscall[i].zName;
-  }
-  return 0;
-}
-
-#ifdef SQLITE_WIN32_MALLOC
-/*
-** If a Win32 native heap has been configured, this function will attempt to
-** compact it.  Upon success, SQLITE_OK will be returned.  Upon failure, one
-** of SQLITE_NOMEM, SQLITE_ERROR, or SQLITE_NOTFOUND will be returned.  The
-** "pnLargest" argument, if non-zero, will be used to return the size of the
-** largest committed free block in the heap, in bytes.
-*/
-SQLITE_PRIVATE int sqlite3_win32_compact_heap(LPUINT pnLargest){
-  int rc = SQLITE_OK;
-  UINT nLargest = 0;
-  HANDLE hHeap;
-
-  winMemAssertMagic();
-  hHeap = winMemGetHeap();
-  assert( hHeap!=0 );
-  assert( hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
-#endif
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT
-  if( (nLargest=osHeapCompact(hHeap, SQLITE_WIN32_HEAP_FLAGS))==0 ){
-    DWORD lastErrno = osGetLastError();
-    if( lastErrno==NO_ERROR ){
-      sqlite3_log(SQLITE_NOMEM, "failed to HeapCompact (no space), heap=%p",
-                  (void*)hHeap);
-      rc = SQLITE_NOMEM;
-    }else{
-      sqlite3_log(SQLITE_ERROR, "failed to HeapCompact (%lu), heap=%p",
-                  osGetLastError(), (void*)hHeap);
-      rc = SQLITE_ERROR;
-    }
-  }
-#else
-  sqlite3_log(SQLITE_NOTFOUND, "failed to HeapCompact, heap=%p",
-              (void*)hHeap);
-  rc = SQLITE_NOTFOUND;
-#endif
-  if( pnLargest ) *pnLargest = nLargest;
-  return rc;
-}
-
-/*
-** If a Win32 native heap has been configured, this function will attempt to
-** destroy and recreate it.  If the Win32 native heap is not isolated and/or
-** the sqlite3_memory_used() function does not return zero, SQLITE_BUSY will
-** be returned and no changes will be made to the Win32 native heap.
-*/
-SQLITE_PRIVATE int sqlite3_win32_reset_heap(){
-  int rc;
-  MUTEX_LOGIC( sqlite3_mutex *pMaster; ) /* The main static mutex */
-  MUTEX_LOGIC( sqlite3_mutex *pMem; )    /* The memsys static mutex */
-  MUTEX_LOGIC( pMaster = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER); )
-  MUTEX_LOGIC( pMem = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MEM); )
-  sqlite3_mutex_enter(pMaster);
-  sqlite3_mutex_enter(pMem);
-  winMemAssertMagic();
-  if( winMemGetHeap()!=NULL && winMemGetOwned() && sqlite3_memory_used()==0 ){
-    /*
-    ** At this point, there should be no outstanding memory allocations on
-    ** the heap.  Also, since both the master and memsys locks are currently
-    ** being held by us, no other function (i.e. from another thread) should
-    ** be able to even access the heap.  Attempt to destroy and recreate our
-    ** isolated Win32 native heap now.
-    */
-    assert( winMemGetHeap()!=NULL );
-    assert( winMemGetOwned() );
-    assert( sqlite3_memory_used()==0 );
-    winMemShutdown(winMemGetDataPtr());
-    assert( winMemGetHeap()==NULL );
-    assert( !winMemGetOwned() );
-    assert( sqlite3_memory_used()==0 );
-    rc = winMemInit(winMemGetDataPtr());
-    assert( rc!=SQLITE_OK || winMemGetHeap()!=NULL );
-    assert( rc!=SQLITE_OK || winMemGetOwned() );
-    assert( rc!=SQLITE_OK || sqlite3_memory_used()==0 );
-  }else{
-    /*
-    ** The Win32 native heap cannot be modified because it may be in use.
-    */
-    rc = SQLITE_BUSY;
-  }
-  sqlite3_mutex_leave(pMem);
-  sqlite3_mutex_leave(pMaster);
-  return rc;
-}
-#endif /* SQLITE_WIN32_MALLOC */
-
-/*
-** The following routine suspends the current thread for at least ms
-** milliseconds.  This is equivalent to the Win32 Sleep() interface.
-*/
-#if SQLITE_OS_WINRT
-static HANDLE sleepObj = NULL;
-#endif
-
-SQLITE_PRIVATE void sqlite3_win32_sleep(DWORD milliseconds){
-#if SQLITE_OS_WINRT
-  if ( sleepObj==NULL ){
-    sleepObj = osCreateEventExW(NULL, NULL, CREATE_EVENT_MANUAL_RESET,
-                                SYNCHRONIZE);
-  }
-  assert( sleepObj!=NULL );
-  osWaitForSingleObjectEx(sleepObj, milliseconds, FALSE);
-#else
-  osSleep(milliseconds);
-#endif
-}
-
-#if SQLITE_MAX_WORKER_THREADS>0 && !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && \
-        SQLITE_THREADSAFE>0
-SQLITE_PRIVATE DWORD sqlite3Win32Wait(HANDLE hObject){
-  DWORD rc;
-  while( (rc = osWaitForSingleObjectEx(hObject, INFINITE,
-                                       TRUE))==WAIT_IO_COMPLETION ){}
-  return rc;
-}
-#endif
-
-/*
-** Return true (non-zero) if we are running under WinNT, Win2K, WinXP,
-** or WinCE.  Return false (zero) for Win95, Win98, or WinME.
-**
-** Here is an interesting observation:  Win95, Win98, and WinME lack
-** the LockFileEx() API.  But we can still statically link against that
-** API as long as we don't call it when running Win95/98/ME.  A call to
-** this routine is used to determine if the host is Win95/98/ME or
-** WinNT/2K/XP so that we will know whether or not we can safely call
-** the LockFileEx() API.
-*/
-
-#if !defined(SQLITE_WIN32_GETVERSIONEX) || !SQLITE_WIN32_GETVERSIONEX
-# define osIsNT()  (1)
-#elif SQLITE_OS_WINCE || SQLITE_OS_WINRT || !defined(SQLITE_WIN32_HAS_ANSI)
-# define osIsNT()  (1)
-#elif !defined(SQLITE_WIN32_HAS_WIDE)
-# define osIsNT()  (0)
-#else
-# define osIsNT()  ((sqlite3_os_type==2) || sqlite3_win32_is_nt())
-#endif
-
-/*
-** This function determines if the machine is running a version of Windows
-** based on the NT kernel.
-*/
-SQLITE_PRIVATE int sqlite3_win32_is_nt(void){
-#if SQLITE_OS_WINRT
-  /*
-  ** NOTE: The WinRT sub-platform is always assumed to be based on the NT
-  **       kernel.
-  */
-  return 1;
-#elif defined(SQLITE_WIN32_GETVERSIONEX) && SQLITE_WIN32_GETVERSIONEX
-  if( osInterlockedCompareExchange(&sqlite3_os_type, 0, 0)==0 ){
-#if defined(SQLITE_WIN32_HAS_ANSI)
-    OSVERSIONINFOA sInfo;
-    sInfo.dwOSVersionInfoSize = sizeof(sInfo);
-    osGetVersionExA(&sInfo);
-    osInterlockedCompareExchange(&sqlite3_os_type,
-        (sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
-#elif defined(SQLITE_WIN32_HAS_WIDE)
-    OSVERSIONINFOW sInfo;
-    sInfo.dwOSVersionInfoSize = sizeof(sInfo);
-    osGetVersionExW(&sInfo);
-    osInterlockedCompareExchange(&sqlite3_os_type,
-        (sInfo.dwPlatformId == VER_PLATFORM_WIN32_NT) ? 2 : 1, 0);
-#endif
-  }
-  return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
-#elif SQLITE_TEST
-  return osInterlockedCompareExchange(&sqlite3_os_type, 2, 2)==2;
-#else
-  /*
-  ** NOTE: All sub-platforms where the GetVersionEx[AW] functions are
-  **       deprecated are always assumed to be based on the NT kernel.
-  */
-  return 1;
-#endif
-}
-
-#ifdef SQLITE_WIN32_MALLOC
-/*
-** Allocate nBytes of memory.
-*/
-static void *winMemMalloc(int nBytes){
-  HANDLE hHeap;
-  void *p;
-
-  winMemAssertMagic();
-  hHeap = winMemGetHeap();
-  assert( hHeap!=0 );
-  assert( hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
-#endif
-  assert( nBytes>=0 );
-  p = osHeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
-  if( !p ){
-    sqlite3_log(SQLITE_NOMEM, "failed to HeapAlloc %u bytes (%lu), heap=%p",
-                nBytes, osGetLastError(), (void*)hHeap);
-  }
-  return p;
-}
-
-/*
-** Free memory.
-*/
-static void winMemFree(void *pPrior){
-  HANDLE hHeap;
-
-  winMemAssertMagic();
-  hHeap = winMemGetHeap();
-  assert( hHeap!=0 );
-  assert( hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
-#endif
-  if( !pPrior ) return; /* Passing NULL to HeapFree is undefined. */
-  if( !osHeapFree(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) ){
-    sqlite3_log(SQLITE_NOMEM, "failed to HeapFree block %p (%lu), heap=%p",
-                pPrior, osGetLastError(), (void*)hHeap);
-  }
-}
-
-/*
-** Change the size of an existing memory allocation
-*/
-static void *winMemRealloc(void *pPrior, int nBytes){
-  HANDLE hHeap;
-  void *p;
-
-  winMemAssertMagic();
-  hHeap = winMemGetHeap();
-  assert( hHeap!=0 );
-  assert( hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior) );
-#endif
-  assert( nBytes>=0 );
-  if( !pPrior ){
-    p = osHeapAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, (SIZE_T)nBytes);
-  }else{
-    p = osHeapReAlloc(hHeap, SQLITE_WIN32_HEAP_FLAGS, pPrior, (SIZE_T)nBytes);
-  }
-  if( !p ){
-    sqlite3_log(SQLITE_NOMEM, "failed to %s %u bytes (%lu), heap=%p",
-                pPrior ? "HeapReAlloc" : "HeapAlloc", nBytes, osGetLastError(),
-                (void*)hHeap);
-  }
-  return p;
-}
-
-/*
-** Return the size of an outstanding allocation, in bytes.
-*/
-static int winMemSize(void *p){
-  HANDLE hHeap;
-  SIZE_T n;
-
-  winMemAssertMagic();
-  hHeap = winMemGetHeap();
-  assert( hHeap!=0 );
-  assert( hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(hHeap, SQLITE_WIN32_HEAP_FLAGS, p) );
-#endif
-  if( !p ) return 0;
-  n = osHeapSize(hHeap, SQLITE_WIN32_HEAP_FLAGS, p);
-  if( n==(SIZE_T)-1 ){
-    sqlite3_log(SQLITE_NOMEM, "failed to HeapSize block %p (%lu), heap=%p",
-                p, osGetLastError(), (void*)hHeap);
-    return 0;
-  }
-  return (int)n;
-}
-
-/*
-** Round up a request size to the next valid allocation size.
-*/
-static int winMemRoundup(int n){
-  return n;
-}
-
-/*
-** Initialize this module.
-*/
-static int winMemInit(void *pAppData){
-  winMemData *pWinMemData = (winMemData *)pAppData;
-
-  if( !pWinMemData ) return SQLITE_ERROR;
-  assert( pWinMemData->magic1==WINMEM_MAGIC1 );
-  assert( pWinMemData->magic2==WINMEM_MAGIC2 );
-
-#if !SQLITE_OS_WINRT && SQLITE_WIN32_HEAP_CREATE
-  if( !pWinMemData->hHeap ){
-    DWORD dwInitialSize = SQLITE_WIN32_HEAP_INIT_SIZE;
-    DWORD dwMaximumSize = (DWORD)sqlite3GlobalConfig.nHeap;
-    if( dwMaximumSize==0 ){
-      dwMaximumSize = SQLITE_WIN32_HEAP_MAX_SIZE;
-    }else if( dwInitialSize>dwMaximumSize ){
-      dwInitialSize = dwMaximumSize;
-    }
-    pWinMemData->hHeap = osHeapCreate(SQLITE_WIN32_HEAP_FLAGS,
-                                      dwInitialSize, dwMaximumSize);
-    if( !pWinMemData->hHeap ){
-      sqlite3_log(SQLITE_NOMEM,
-          "failed to HeapCreate (%lu), flags=%u, initSize=%lu, maxSize=%lu",
-          osGetLastError(), SQLITE_WIN32_HEAP_FLAGS, dwInitialSize,
-          dwMaximumSize);
-      return SQLITE_NOMEM;
-    }
-    pWinMemData->bOwned = TRUE;
-    assert( pWinMemData->bOwned );
-  }
-#else
-  pWinMemData->hHeap = osGetProcessHeap();
-  if( !pWinMemData->hHeap ){
-    sqlite3_log(SQLITE_NOMEM,
-        "failed to GetProcessHeap (%lu)", osGetLastError());
-    return SQLITE_NOMEM;
-  }
-  pWinMemData->bOwned = FALSE;
-  assert( !pWinMemData->bOwned );
-#endif
-  assert( pWinMemData->hHeap!=0 );
-  assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-  assert( osHeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
-#endif
-  return SQLITE_OK;
-}
-
-/*
-** Deinitialize this module.
-*/
-static void winMemShutdown(void *pAppData){
-  winMemData *pWinMemData = (winMemData *)pAppData;
-
-  if( !pWinMemData ) return;
-  assert( pWinMemData->magic1==WINMEM_MAGIC1 );
-  assert( pWinMemData->magic2==WINMEM_MAGIC2 );
-
-  if( pWinMemData->hHeap ){
-    assert( pWinMemData->hHeap!=INVALID_HANDLE_VALUE );
-#if !SQLITE_OS_WINRT && defined(SQLITE_WIN32_MALLOC_VALIDATE)
-    assert( osHeapValidate(pWinMemData->hHeap, SQLITE_WIN32_HEAP_FLAGS, NULL) );
-#endif
-    if( pWinMemData->bOwned ){
-      if( !osHeapDestroy(pWinMemData->hHeap) ){
-        sqlite3_log(SQLITE_NOMEM, "failed to HeapDestroy (%lu), heap=%p",
-                    osGetLastError(), (void*)pWinMemData->hHeap);
-      }
-      pWinMemData->bOwned = FALSE;
-    }
-    pWinMemData->hHeap = NULL;
-  }
-}
-
-/*
-** Populate the low-level memory allocation function pointers in
-** sqlite3GlobalConfig.m with pointers to the routines in this file. The
-** arguments specify the block of memory to manage.
-**
-** This routine is only called by sqlite3_config(), and therefore
-** is not required to be threadsafe (it is not).
-*/
-SQLITE_PRIVATE const sqlite3_mem_methods *sqlite3MemGetWin32(void){
-  static const sqlite3_mem_methods winMemMethods = {
-    winMemMalloc,
-    winMemFree,
-    winMemRealloc,
-    winMemSize,
-    winMemRoundup,
-    winMemInit,
-    winMemShutdown,
-    &win_mem_data
-  };
-  return &winMemMethods;
-}
-
-SQLITE_PRIVATE void sqlite3MemSetDefault(void){
-  sqlite3_config(SQLITE_CONFIG_MALLOC, sqlite3MemGetWin32());
-}
-#endif /* SQLITE_WIN32_MALLOC */
-
-/*
-** Convert a UTF-8 string to Microsoft Unicode (UTF-16?).
-**
-** Space to hold the returned string is obtained from malloc.
-*/
-static LPWSTR winUtf8ToUnicode(const char *zFilename){
-  int nChar;
-  LPWSTR zWideFilename;
-
-  nChar = osMultiByteToWideChar(CP_UTF8, 0, zFilename, -1, NULL, 0);
-  if( nChar==0 ){
-    return 0;
-  }
-  zWideFilename = sqlite3MallocZero( nChar*sizeof(zWideFilename[0]) );
-  if( zWideFilename==0 ){
-    return 0;
-  }
-  nChar = osMultiByteToWideChar(CP_UTF8, 0, zFilename, -1, zWideFilename,
-                                nChar);
-  if( nChar==0 ){
-    sqlite3_free(zWideFilename);
-    zWideFilename = 0;
-  }
-  return zWideFilename;
-}
-
-/*
-** Convert Microsoft Unicode to UTF-8.  Space to hold the returned string is
-** obtained from sqlite3_malloc().
-*/
-static char *winUnicodeToUtf8(LPCWSTR zWideFilename){
-  int nByte;
-  char *zFilename;
-
-  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, 0, 0, 0, 0);
-  if( nByte == 0 ){
-    return 0;
-  }
-  zFilename = sqlite3MallocZero( nByte );
-  if( zFilename==0 ){
-    return 0;
-  }
-  nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideFilename, -1, zFilename, nByte,
-                                0, 0);
-  if( nByte == 0 ){
-    sqlite3_free(zFilename);
-    zFilename = 0;
-  }
-  return zFilename;
-}
-
-/*
-** Convert an ANSI string to Microsoft Unicode, based on the
-** current codepage settings for file apis.
-**
-** Space to hold the returned string is obtained
-** from sqlite3_malloc.
-*/
-static LPWSTR winMbcsToUnicode(const char *zFilename){
-  int nByte;
-  LPWSTR zMbcsFilename;
-  int codepage = osAreFileApisANSI() ? CP_ACP : CP_OEMCP;
-
-  nByte = osMultiByteToWideChar(codepage, 0, zFilename, -1, NULL,
-                                0)*sizeof(WCHAR);
-  if( nByte==0 ){
-    return 0;
-  }
-  zMbcsFilename = sqlite3MallocZero( nByte*sizeof(zMbcsFilename[0]) );
-  if( zMbcsFilename==0 ){
-    return 0;
-  }
-  nByte = osMultiByteToWideChar(codepage, 0, zFilename, -1, zMbcsFilename,
-                                nByte);
-  if( nByte==0 ){
-    sqlite3_free(zMbcsFilename);
-    zMbcsFilename = 0;
-  }
-  return zMbcsFilename;
-}
-
-/*
-** Convert Microsoft Unicode to multi-byte character string, based on the
-** user's ANSI codepage.
-**
-** Space to hold the returned string is obtained from
-** sqlite3_malloc().
-*/
-static char *winUnicodeToMbcs(LPCWSTR zWideFilename){
-  int nByte;
-  char *zFilename;
-  int codepage = osAreFileApisANSI() ? CP_ACP : CP_OEMCP;
-
-  nByte = osWideCharToMultiByte(codepage, 0, zWideFilename, -1, 0, 0, 0, 0);
-  if( nByte == 0 ){
-    return 0;
-  }
-  zFilename = sqlite3MallocZero( nByte );
-  if( zFilename==0 ){
-    return 0;
-  }
-  nByte = osWideCharToMultiByte(codepage, 0, zWideFilename, -1, zFilename,
-                                nByte, 0, 0);
-  if( nByte == 0 ){
-    sqlite3_free(zFilename);
-    zFilename = 0;
-  }
-  return zFilename;
-}
-
-/*
-** Convert multibyte character string to UTF-8.  Space to hold the
-** returned string is obtained from sqlite3_malloc().
-*/
-SQLITE_PRIVATE char *sqlite3_win32_mbcs_to_utf8(const char *zFilename){
-  char *zFilenameUtf8;
-  LPWSTR zTmpWide;
-
-  zTmpWide = winMbcsToUnicode(zFilename);
-  if( zTmpWide==0 ){
-    return 0;
-  }
-  zFilenameUtf8 = winUnicodeToUtf8(zTmpWide);
-  sqlite3_free(zTmpWide);
-  return zFilenameUtf8;
-}
-
-/*
-** Convert UTF-8 to multibyte character string.  Space to hold the
-** returned string is obtained from sqlite3_malloc().
-*/
-SQLITE_PRIVATE char *sqlite3_win32_utf8_to_mbcs(const char *zFilename){
-  char *zFilenameMbcs;
-  LPWSTR zTmpWide;
-
-  zTmpWide = winUtf8ToUnicode(zFilename);
-  if( zTmpWide==0 ){
-    return 0;
-  }
-  zFilenameMbcs = winUnicodeToMbcs(zTmpWide);
-  sqlite3_free(zTmpWide);
-  return zFilenameMbcs;
-}
-
-/*
-** The return value of winGetLastErrorMsg
-** is zero if the error message fits in the buffer, or non-zero
-** otherwise (if the message was truncated).
-*/
-static int winGetLastErrorMsg(DWORD lastErrno, int nBuf, char *zBuf){
-  /* FormatMessage returns 0 on failure.  Otherwise it
-  ** returns the number of TCHARs written to the output
-  ** buffer, excluding the terminating null char.
-  */
-  DWORD dwLen = 0;
-  char *zOut = 0;
-
-  if( osIsNT() ){
-#if SQLITE_OS_WINRT
-    WCHAR zTempWide[SQLITE_WIN32_MAX_ERRMSG_CHARS+1];
-    dwLen = osFormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM |
-                             FORMAT_MESSAGE_IGNORE_INSERTS,
-                             NULL,
-                             lastErrno,
-                             0,
-                             zTempWide,
-                             SQLITE_WIN32_MAX_ERRMSG_CHARS,
-                             0);
-#else
-    LPWSTR zTempWide = NULL;
-    dwLen = osFormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
-                             FORMAT_MESSAGE_FROM_SYSTEM |
-                             FORMAT_MESSAGE_IGNORE_INSERTS,
-                             NULL,
-                             lastErrno,
-                             0,
-                             (LPWSTR) &zTempWide,
-                             0,
-                             0);
-#endif
-    if( dwLen > 0 ){
-      /* allocate a buffer and convert to UTF8 */
-      zOut = winUnicodeToUtf8(zTempWide);
-#if !SQLITE_OS_WINRT
-      /* free the system buffer allocated by FormatMessage */
-      osLocalFree(zTempWide);
-#endif
-    }
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    char *zTemp = NULL;
-    dwLen = osFormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
-                             FORMAT_MESSAGE_FROM_SYSTEM |
-                             FORMAT_MESSAGE_IGNORE_INSERTS,
-                             NULL,
-                             lastErrno,
-                             0,
-                             (LPSTR) &zTemp,
-                             0,
-                             0);
-    if( dwLen > 0 ){
-      /* allocate a buffer and convert to UTF8 */
-      zOut = sqlite3_win32_mbcs_to_utf8(zTemp);
-      /* free the system buffer allocated by FormatMessage */
-      osLocalFree(zTemp);
-    }
-  }
-#endif
-  if( 0 == dwLen ){
-    sqlite3_snprintf(nBuf, zBuf, "OsError 0x%lx (%lu)", lastErrno, lastErrno);
-  }else{
-    /* copy a maximum of nBuf chars to output buffer */
-    sqlite3_snprintf(nBuf, zBuf, "%s", zOut);
-    /* free the UTF8 buffer */
-    sqlite3_free(zOut);
-  }
-  return 0;
-}
-
-/*
-**
-** This function - winLogErrorAtLine() - is only ever called via the macro
-** winLogError().
-**
-** This routine is invoked after an error occurs in an OS function.
-** It logs a message using sqlite3_log() containing the current value of
-** error code and, if possible, the human-readable equivalent from
-** FormatMessage.
-**
-** The first argument passed to the macro should be the error code that
-** will be returned to SQLite (e.g. SQLITE_IOERR_DELETE, SQLITE_CANTOPEN).
-** The two subsequent arguments should be the name of the OS function that
-** failed and the associated file-system path, if any.
-*/
-#define winLogError(a,b,c,d)   winLogErrorAtLine(a,b,c,d,__LINE__)
-static int winLogErrorAtLine(
-  int errcode,                    /* SQLite error code */
-  DWORD lastErrno,                /* Win32 last error */
-  const char *zFunc,              /* Name of OS function that failed */
-  const char *zPath,              /* File path associated with error */
-  int iLine                       /* Source line number where error occurred */
-){
-  char zMsg[500];                 /* Human readable error text */
-  int i;                          /* Loop counter */
-
-  zMsg[0] = 0;
-  winGetLastErrorMsg(lastErrno, sizeof(zMsg), zMsg);
-  assert( errcode!=SQLITE_OK );
-  if( zPath==0 ) zPath = "";
-  for(i=0; zMsg[i] && zMsg[i]!='\r' && zMsg[i]!='\n'; i++){}
-  zMsg[i] = 0;
-  sqlite3_log(errcode,
-      "os_win.c:%d: (%lu) %s(%s) - %s",
-      iLine, lastErrno, zFunc, zPath, zMsg
-  );
-
-  return errcode;
-}
-
-/*
-** The number of times that a ReadFile(), WriteFile(), and DeleteFile()
-** will be retried following a locking error - probably caused by
-** antivirus software.  Also the initial delay before the first retry.
-** The delay increases linearly with each retry.
-*/
-#ifndef SQLITE_WIN32_IOERR_RETRY
-# define SQLITE_WIN32_IOERR_RETRY 10
-#endif
-#ifndef SQLITE_WIN32_IOERR_RETRY_DELAY
-# define SQLITE_WIN32_IOERR_RETRY_DELAY 25
-#endif
-static int winIoerrRetry = SQLITE_WIN32_IOERR_RETRY;
-static int winIoerrRetryDelay = SQLITE_WIN32_IOERR_RETRY_DELAY;
-
-/*
-** The "winIoerrCanRetry1" macro is used to determine if a particular I/O
-** error code obtained via GetLastError() is eligible to be retried.  It
-** must accept the error code DWORD as its only argument and should return
-** non-zero if the error code is transient in nature and the operation
-** responsible for generating the original error might succeed upon being
-** retried.  The argument to this macro should be a variable.
-**
-** Additionally, a macro named "winIoerrCanRetry2" may be defined.  If it
-** is defined, it will be consulted only when the macro "winIoerrCanRetry1"
-** returns zero.  The "winIoerrCanRetry2" macro is completely optional and
-** may be used to include additional error codes in the set that should
-** result in the failing I/O operation being retried by the caller.  If
-** defined, the "winIoerrCanRetry2" macro must exhibit external semantics
-** identical to those of the "winIoerrCanRetry1" macro.
-*/
-#if !defined(winIoerrCanRetry1)
-#define winIoerrCanRetry1(a) (((a)==ERROR_ACCESS_DENIED)        || \
-                              ((a)==ERROR_SHARING_VIOLATION)    || \
-                              ((a)==ERROR_LOCK_VIOLATION)       || \
-                              ((a)==ERROR_DEV_NOT_EXIST)        || \
-                              ((a)==ERROR_NETNAME_DELETED)      || \
-                              ((a)==ERROR_SEM_TIMEOUT)          || \
-                              ((a)==ERROR_NETWORK_UNREACHABLE))
-#endif
-
-/*
-** If a ReadFile() or WriteFile() error occurs, invoke this routine
-** to see if it should be retried.  Return TRUE to retry.  Return FALSE
-** to give up with an error.
-*/
-static int winRetryIoerr(int *pnRetry, DWORD *pError){
-  DWORD e = osGetLastError();
-  if( *pnRetry>=winIoerrRetry ){
-    if( pError ){
-      *pError = e;
-    }
-    return 0;
-  }
-  if( winIoerrCanRetry1(e) ){
-    sqlite3_win32_sleep(winIoerrRetryDelay*(1+*pnRetry));
-    ++*pnRetry;
-    return 1;
-  }
-#if defined(winIoerrCanRetry2)
-  else if( winIoerrCanRetry2(e) ){
-    sqlite3_win32_sleep(winIoerrRetryDelay*(1+*pnRetry));
-    ++*pnRetry;
-    return 1;
-  }
-#endif
-  if( pError ){
-    *pError = e;
-  }
-  return 0;
-}
-
-/*
-** Log a I/O error retry episode.
-*/
-static void winLogIoerr(int nRetry, int lineno){
-  if( nRetry ){
-    sqlite3_log(SQLITE_NOTICE,
-      "delayed %dms for lock/sharing conflict at line %d",
-      winIoerrRetryDelay*nRetry*(nRetry+1)/2, lineno
-    );
-  }
-}
-
-#if SQLITE_OS_WINCE
-/*************************************************************************
-** This section contains code for WinCE only.
-*/
-#if !defined(SQLITE_MSVC_LOCALTIME_API) || !SQLITE_MSVC_LOCALTIME_API
-/*
-** The MSVC CRT on Windows CE may not have a localtime() function.  So
-** create a substitute.
-*/
-/* #include <time.h> */
-struct tm *__cdecl localtime(const time_t *t)
-{
-  static struct tm y;
-  FILETIME uTm, lTm;
-  SYSTEMTIME pTm;
-  sqlite3_int64 t64;
-  t64 = *t;
-  t64 = (t64 + 11644473600)*10000000;
-  uTm.dwLowDateTime = (DWORD)(t64 & 0xFFFFFFFF);
-  uTm.dwHighDateTime= (DWORD)(t64 >> 32);
-  osFileTimeToLocalFileTime(&uTm,&lTm);
-  osFileTimeToSystemTime(&lTm,&pTm);
-  y.tm_year = pTm.wYear - 1900;
-  y.tm_mon = pTm.wMonth - 1;
-  y.tm_wday = pTm.wDayOfWeek;
-  y.tm_mday = pTm.wDay;
-  y.tm_hour = pTm.wHour;
-  y.tm_min = pTm.wMinute;
-  y.tm_sec = pTm.wSecond;
-  return &y;
-}
-#endif
-
-#define HANDLE_TO_WINFILE(a) (winFile*)&((char*)a)[-(int)offsetof(winFile,h)]
-
-/*
-** Acquire a lock on the handle h
-*/
-static void winceMutexAcquire(HANDLE h){
-   DWORD dwErr;
-   do {
-     dwErr = osWaitForSingleObject(h, INFINITE);
-   } while (dwErr != WAIT_OBJECT_0 && dwErr != WAIT_ABANDONED);
-}
-/*
-** Release a lock acquired by winceMutexAcquire()
-*/
-#define winceMutexRelease(h) ReleaseMutex(h)
-
-/*
-** Create the mutex and shared memory used for locking in the file
-** descriptor pFile
-*/
-static int winceCreateLock(const char *zFilename, winFile *pFile){
-  LPWSTR zTok;
-  LPWSTR zName;
-  DWORD lastErrno;
-  BOOL bLogged = FALSE;
-  BOOL bInit = TRUE;
-
-  zName = winUtf8ToUnicode(zFilename);
-  if( zName==0 ){
-    /* out of memory */
-    return SQLITE_IOERR_NOMEM;
-  }
-
-  /* Initialize the local lockdata */
-  memset(&pFile->local, 0, sizeof(pFile->local));
-
-  /* Replace the backslashes from the filename and lowercase it
-  ** to derive a mutex name. */
-  zTok = osCharLowerW(zName);
-  for (;*zTok;zTok++){
-    if (*zTok == '\\') *zTok = '_';
-  }
-
-  /* Create/open the named mutex */
-  pFile->hMutex = osCreateMutexW(NULL, FALSE, zName);
-  if (!pFile->hMutex){
-    pFile->lastErrno = osGetLastError();
-    sqlite3_free(zName);
-    return winLogError(SQLITE_IOERR, pFile->lastErrno,
-                       "winceCreateLock1", zFilename);
-  }
-
-  /* Acquire the mutex before continuing */
-  winceMutexAcquire(pFile->hMutex);
-
-  /* Since the names of named mutexes, semaphores, file mappings etc are
-  ** case-sensitive, take advantage of that by uppercasing the mutex name
-  ** and using that as the shared filemapping name.
-  */
-  osCharUpperW(zName);
-  pFile->hShared = osCreateFileMappingW(INVALID_HANDLE_VALUE, NULL,
-                                        PAGE_READWRITE, 0, sizeof(winceLock),
-                                        zName);
-
-  /* Set a flag that indicates we're the first to create the memory so it
-  ** must be zero-initialized */
-  lastErrno = osGetLastError();
-  if (lastErrno == ERROR_ALREADY_EXISTS){
-    bInit = FALSE;
-  }
-
-  sqlite3_free(zName);
-
-  /* If we succeeded in making the shared memory handle, map it. */
-  if( pFile->hShared ){
-    pFile->shared = (winceLock*)osMapViewOfFile(pFile->hShared,
-             FILE_MAP_READ|FILE_MAP_WRITE, 0, 0, sizeof(winceLock));
-    /* If mapping failed, close the shared memory handle and erase it */
-    if( !pFile->shared ){
-      pFile->lastErrno = osGetLastError();
-      winLogError(SQLITE_IOERR, pFile->lastErrno,
-                  "winceCreateLock2", zFilename);
-      bLogged = TRUE;
-      osCloseHandle(pFile->hShared);
-      pFile->hShared = NULL;
-    }
-  }
-
-  /* If shared memory could not be created, then close the mutex and fail */
-  if( pFile->hShared==NULL ){
-    if( !bLogged ){
-      pFile->lastErrno = lastErrno;
-      winLogError(SQLITE_IOERR, pFile->lastErrno,
-                  "winceCreateLock3", zFilename);
-      bLogged = TRUE;
-    }
-    winceMutexRelease(pFile->hMutex);
-    osCloseHandle(pFile->hMutex);
-    pFile->hMutex = NULL;
-    return SQLITE_IOERR;
-  }
-
-  /* Initialize the shared memory if we're supposed to */
-  if( bInit ){
-    memset(pFile->shared, 0, sizeof(winceLock));
-  }
-
-  winceMutexRelease(pFile->hMutex);
-  return SQLITE_OK;
-}
-
-/*
-** Destroy the part of winFile that deals with wince locks
-*/
-static void winceDestroyLock(winFile *pFile){
-  if (pFile->hMutex){
-    /* Acquire the mutex */
-    winceMutexAcquire(pFile->hMutex);
-
-    /* The following blocks should probably assert in debug mode, but they
-       are to cleanup in case any locks remained open */
-    if (pFile->local.nReaders){
-      pFile->shared->nReaders --;
-    }
-    if (pFile->local.bReserved){
-      pFile->shared->bReserved = FALSE;
-    }
-    if (pFile->local.bPending){
-      pFile->shared->bPending = FALSE;
-    }
-    if (pFile->local.bExclusive){
-      pFile->shared->bExclusive = FALSE;
-    }
-
-    /* De-reference and close our copy of the shared memory handle */
-    osUnmapViewOfFile(pFile->shared);
-    osCloseHandle(pFile->hShared);
-
-    /* Done with the mutex */
-    winceMutexRelease(pFile->hMutex);
-    osCloseHandle(pFile->hMutex);
-    pFile->hMutex = NULL;
-  }
-}
-
-/*
-** An implementation of the LockFile() API of Windows for CE
-*/
-static BOOL winceLockFile(
-  LPHANDLE phFile,
-  DWORD dwFileOffsetLow,
-  DWORD dwFileOffsetHigh,
-  DWORD nNumberOfBytesToLockLow,
-  DWORD nNumberOfBytesToLockHigh
-){
-  winFile *pFile = HANDLE_TO_WINFILE(phFile);
-  BOOL bReturn = FALSE;
-
-  UNUSED_PARAMETER(dwFileOffsetHigh);
-  UNUSED_PARAMETER(nNumberOfBytesToLockHigh);
-
-  if (!pFile->hMutex) return TRUE;
-  winceMutexAcquire(pFile->hMutex);
-
-  /* Wanting an exclusive lock? */
-  if (dwFileOffsetLow == (DWORD)SHARED_FIRST
-       && nNumberOfBytesToLockLow == (DWORD)SHARED_SIZE){
-    if (pFile->shared->nReaders == 0 && pFile->shared->bExclusive == 0){
-       pFile->shared->bExclusive = TRUE;
-       pFile->local.bExclusive = TRUE;
-       bReturn = TRUE;
-    }
-  }
-
-  /* Want a read-only lock? */
-  else if (dwFileOffsetLow == (DWORD)SHARED_FIRST &&
-           nNumberOfBytesToLockLow == 1){
-    if (pFile->shared->bExclusive == 0){
-      pFile->local.nReaders ++;
-      if (pFile->local.nReaders == 1){
-        pFile->shared->nReaders ++;
-      }
-      bReturn = TRUE;
-    }
-  }
-
-  /* Want a pending lock? */
-  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE
-           && nNumberOfBytesToLockLow == 1){
-    /* If no pending lock has been acquired, then acquire it */
-    if (pFile->shared->bPending == 0) {
-      pFile->shared->bPending = TRUE;
-      pFile->local.bPending = TRUE;
-      bReturn = TRUE;
-    }
-  }
-
-  /* Want a reserved lock? */
-  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE
-           && nNumberOfBytesToLockLow == 1){
-    if (pFile->shared->bReserved == 0) {
-      pFile->shared->bReserved = TRUE;
-      pFile->local.bReserved = TRUE;
-      bReturn = TRUE;
-    }
-  }
-
-  winceMutexRelease(pFile->hMutex);
-  return bReturn;
-}
-
-/*
-** An implementation of the UnlockFile API of Windows for CE
-*/
-static BOOL winceUnlockFile(
-  LPHANDLE phFile,
-  DWORD dwFileOffsetLow,
-  DWORD dwFileOffsetHigh,
-  DWORD nNumberOfBytesToUnlockLow,
-  DWORD nNumberOfBytesToUnlockHigh
-){
-  winFile *pFile = HANDLE_TO_WINFILE(phFile);
-  BOOL bReturn = FALSE;
-
-  UNUSED_PARAMETER(dwFileOffsetHigh);
-  UNUSED_PARAMETER(nNumberOfBytesToUnlockHigh);
-
-  if (!pFile->hMutex) return TRUE;
-  winceMutexAcquire(pFile->hMutex);
-
-  /* Releasing a reader lock or an exclusive lock */
-  if (dwFileOffsetLow == (DWORD)SHARED_FIRST){
-    /* Did we have an exclusive lock? */
-    if (pFile->local.bExclusive){
-      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE);
-      pFile->local.bExclusive = FALSE;
-      pFile->shared->bExclusive = FALSE;
-      bReturn = TRUE;
-    }
-
-    /* Did we just have a reader lock? */
-    else if (pFile->local.nReaders){
-      assert(nNumberOfBytesToUnlockLow == (DWORD)SHARED_SIZE
-             || nNumberOfBytesToUnlockLow == 1);
-      pFile->local.nReaders --;
-      if (pFile->local.nReaders == 0)
-      {
-        pFile->shared->nReaders --;
-      }
-      bReturn = TRUE;
-    }
-  }
-
-  /* Releasing a pending lock */
-  else if (dwFileOffsetLow == (DWORD)PENDING_BYTE
-           && nNumberOfBytesToUnlockLow == 1){
-    if (pFile->local.bPending){
-      pFile->local.bPending = FALSE;
-      pFile->shared->bPending = FALSE;
-      bReturn = TRUE;
-    }
-  }
-  /* Releasing a reserved lock */
-  else if (dwFileOffsetLow == (DWORD)RESERVED_BYTE
-           && nNumberOfBytesToUnlockLow == 1){
-    if (pFile->local.bReserved) {
-      pFile->local.bReserved = FALSE;
-      pFile->shared->bReserved = FALSE;
-      bReturn = TRUE;
-    }
-  }
-
-  winceMutexRelease(pFile->hMutex);
-  return bReturn;
-}
-/*
-** End of the special code for wince
-*****************************************************************************/
-#endif /* SQLITE_OS_WINCE */
-
-/*
-** Lock a file region.
-*/
-static BOOL winLockFile(
-  LPHANDLE phFile,
-  DWORD flags,
-  DWORD offsetLow,
-  DWORD offsetHigh,
-  DWORD numBytesLow,
-  DWORD numBytesHigh
-){
-#if SQLITE_OS_WINCE
-  /*
-  ** NOTE: Windows CE is handled differently here due its lack of the Win32
-  **       API LockFile.
-  */
-  return winceLockFile(phFile, offsetLow, offsetHigh,
-                       numBytesLow, numBytesHigh);
-#else
-  if( osIsNT() ){
-    OVERLAPPED ovlp;
-    memset(&ovlp, 0, sizeof(OVERLAPPED));
-    ovlp.Offset = offsetLow;
-    ovlp.OffsetHigh = offsetHigh;
-    return osLockFileEx(*phFile, flags, 0, numBytesLow, numBytesHigh, &ovlp);
-  }else{
-    return osLockFile(*phFile, offsetLow, offsetHigh, numBytesLow,
-                      numBytesHigh);
-  }
-#endif
-}
-
-/*
-** Unlock a file region.
- */
-static BOOL winUnlockFile(
-  LPHANDLE phFile,
-  DWORD offsetLow,
-  DWORD offsetHigh,
-  DWORD numBytesLow,
-  DWORD numBytesHigh
-){
-#if SQLITE_OS_WINCE
-  /*
-  ** NOTE: Windows CE is handled differently here due its lack of the Win32
-  **       API UnlockFile.
-  */
-  return winceUnlockFile(phFile, offsetLow, offsetHigh,
-                         numBytesLow, numBytesHigh);
-#else
-  if( osIsNT() ){
-    OVERLAPPED ovlp;
-    memset(&ovlp, 0, sizeof(OVERLAPPED));
-    ovlp.Offset = offsetLow;
-    ovlp.OffsetHigh = offsetHigh;
-    return osUnlockFileEx(*phFile, 0, numBytesLow, numBytesHigh, &ovlp);
-  }else{
-    return osUnlockFile(*phFile, offsetLow, offsetHigh, numBytesLow,
-                        numBytesHigh);
-  }
-#endif
-}
-
-/*****************************************************************************
-** The next group of routines implement the I/O methods specified
-** by the sqlite3_io_methods object.
-******************************************************************************/
-
-/*
-** Some Microsoft compilers lack this definition.
-*/
-#ifndef INVALID_SET_FILE_POINTER
-# define INVALID_SET_FILE_POINTER ((DWORD)-1)
-#endif
-
-/*
-** Move the current position of the file handle passed as the first
-** argument to offset iOffset within the file. If successful, return 0.
-** Otherwise, set pFile->lastErrno and return non-zero.
-*/
-static int winSeekFile(winFile *pFile, sqlite3_int64 iOffset){
-#if !SQLITE_OS_WINRT
-  LONG upperBits;                 /* Most sig. 32 bits of new offset */
-  LONG lowerBits;                 /* Least sig. 32 bits of new offset */
-  DWORD dwRet;                    /* Value returned by SetFilePointer() */
-  DWORD lastErrno;                /* Value returned by GetLastError() */
-
-  OSTRACE(("SEEK file=%p, offset=%lld\n", pFile->h, iOffset));
-
-  upperBits = (LONG)((iOffset>>32) & 0x7fffffff);
-  lowerBits = (LONG)(iOffset & 0xffffffff);
-
-  /* API oddity: If successful, SetFilePointer() returns a dword
-  ** containing the lower 32-bits of the new file-offset. Or, if it fails,
-  ** it returns INVALID_SET_FILE_POINTER. However according to MSDN,
-  ** INVALID_SET_FILE_POINTER may also be a valid new offset. So to determine
-  ** whether an error has actually occurred, it is also necessary to call
-  ** GetLastError().
-  */
-  dwRet = osSetFilePointer(pFile->h, lowerBits, &upperBits, FILE_BEGIN);
-
-  if( (dwRet==INVALID_SET_FILE_POINTER
-      && ((lastErrno = osGetLastError())!=NO_ERROR)) ){
-    pFile->lastErrno = lastErrno;
-    winLogError(SQLITE_IOERR_SEEK, pFile->lastErrno,
-                "winSeekFile", pFile->zPath);
-    OSTRACE(("SEEK file=%p, rc=SQLITE_IOERR_SEEK\n", pFile->h));
-    return 1;
-  }
-
-  OSTRACE(("SEEK file=%p, rc=SQLITE_OK\n", pFile->h));
-  return 0;
-#else
-  /*
-  ** Same as above, except that this implementation works for WinRT.
-  */
-
-  LARGE_INTEGER x;                /* The new offset */
-  BOOL bRet;                      /* Value returned by SetFilePointerEx() */
-
-  x.QuadPart = iOffset;
-  bRet = osSetFilePointerEx(pFile->h, x, 0, FILE_BEGIN);
-
-  if(!bRet){
-    pFile->lastErrno = osGetLastError();
-    winLogError(SQLITE_IOERR_SEEK, pFile->lastErrno,
-                "winSeekFile", pFile->zPath);
-    OSTRACE(("SEEK file=%p, rc=SQLITE_IOERR_SEEK\n", pFile->h));
-    return 1;
-  }
-
-  OSTRACE(("SEEK file=%p, rc=SQLITE_OK\n", pFile->h));
-  return 0;
-#endif
-}
-
-#if SQLITE_MAX_MMAP_SIZE>0
-/* Forward references to VFS helper methods used for memory mapped files */
-static int winMapfile(winFile*, sqlite3_int64);
-static int winUnmapfile(winFile*);
-#endif
-
-/*
-** Close a file.
-**
-** It is reported that an attempt to close a handle might sometimes
-** fail.  This is a very unreasonable result, but Windows is notorious
-** for being unreasonable so I do not doubt that it might happen.  If
-** the close fails, we pause for 100 milliseconds and try again.  As
-** many as MX_CLOSE_ATTEMPT attempts to close the handle are made before
-** giving up and returning an error.
-*/
-#define MX_CLOSE_ATTEMPT 3
-static int winClose(sqlite3_file *id){
-  int rc, cnt = 0;
-  winFile *pFile = (winFile*)id;
-
-  assert( id!=0 );
-#ifndef SQLITE_OMIT_WAL
-  assert( pFile->pShm==0 );
-#endif
-  assert( pFile->h!=NULL && pFile->h!=INVALID_HANDLE_VALUE );
-  OSTRACE(("CLOSE pid=%lu, pFile=%p, file=%p\n",
-           osGetCurrentProcessId(), pFile, pFile->h));
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  winUnmapfile(pFile);
-#endif
-
-  do{
-    rc = osCloseHandle(pFile->h);
-    /* SimulateIOError( rc=0; cnt=MX_CLOSE_ATTEMPT; ); */
-  }while( rc==0 && ++cnt < MX_CLOSE_ATTEMPT && (sqlite3_win32_sleep(100), 1) );
-#if SQLITE_OS_WINCE
-#define WINCE_DELETION_ATTEMPTS 3
-  winceDestroyLock(pFile);
-  if( pFile->zDeleteOnClose ){
-    int cnt = 0;
-    while(
-           osDeleteFileW(pFile->zDeleteOnClose)==0
-        && osGetFileAttributesW(pFile->zDeleteOnClose)!=0xffffffff
-        && cnt++ < WINCE_DELETION_ATTEMPTS
-    ){
-       sqlite3_win32_sleep(100);  /* Wait a little before trying again */
-    }
-    sqlite3_free(pFile->zDeleteOnClose);
-  }
-#endif
-  if( rc ){
-    pFile->h = NULL;
-  }
-  OpenCounter(-1);
-  OSTRACE(("CLOSE pid=%lu, pFile=%p, file=%p, rc=%s\n",
-           osGetCurrentProcessId(), pFile, pFile->h, rc ? "ok" : "failed"));
-  return rc ? SQLITE_OK
-            : winLogError(SQLITE_IOERR_CLOSE, osGetLastError(),
-                          "winClose", pFile->zPath);
-}
-
-/*
-** Read data from a file into a buffer.  Return SQLITE_OK if all
-** bytes were read successfully and SQLITE_IOERR if anything goes
-** wrong.
-*/
-static int winRead(
-  sqlite3_file *id,          /* File to read from */
-  void *pBuf,                /* Write content into this buffer */
-  int amt,                   /* Number of bytes to read */
-  sqlite3_int64 offset       /* Begin reading at this offset */
-){
-#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
-  OVERLAPPED overlapped;          /* The offset for ReadFile. */
-#endif
-  winFile *pFile = (winFile*)id;  /* file handle */
-  DWORD nRead;                    /* Number of bytes actually read from file */
-  int nRetry = 0;                 /* Number of retrys */
-
-  assert( id!=0 );
-  assert( amt>0 );
-  assert( offset>=0 );
-  SimulateIOError(return SQLITE_IOERR_READ);
-  OSTRACE(("READ pid=%lu, pFile=%p, file=%p, buffer=%p, amount=%d, "
-           "offset=%lld, lock=%d\n", osGetCurrentProcessId(), pFile,
-           pFile->h, pBuf, amt, offset, pFile->locktype));
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this read request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], amt);
-      OSTRACE(("READ-MMAP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-               osGetCurrentProcessId(), pFile, pFile->h));
-      return SQLITE_OK;
-    }else{
-      int nCopy = (int)(pFile->mmapSize - offset);
-      memcpy(pBuf, &((u8 *)(pFile->pMapRegion))[offset], nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
-
-#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
-  if( winSeekFile(pFile, offset) ){
-    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_FULL\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return SQLITE_FULL;
-  }
-  while( !osReadFile(pFile->h, pBuf, amt, &nRead, 0) ){
-#else
-  memset(&overlapped, 0, sizeof(OVERLAPPED));
-  overlapped.Offset = (LONG)(offset & 0xffffffff);
-  overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
-  while( !osReadFile(pFile->h, pBuf, amt, &nRead, &overlapped) &&
-         osGetLastError()!=ERROR_HANDLE_EOF ){
-#endif
-    DWORD lastErrno;
-    if( winRetryIoerr(&nRetry, &lastErrno) ) continue;
-    pFile->lastErrno = lastErrno;
-    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_READ\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return winLogError(SQLITE_IOERR_READ, pFile->lastErrno,
-                       "winRead", pFile->zPath);
-  }
-  winLogIoerr(nRetry, __LINE__);
-  if( nRead<(DWORD)amt ){
-    /* Unread parts of the buffer must be zero-filled */
-    memset(&((char*)pBuf)[nRead], 0, amt-nRead);
-    OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_SHORT_READ\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return SQLITE_IOERR_SHORT_READ;
-  }
-
-  OSTRACE(("READ pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), pFile, pFile->h));
-  return SQLITE_OK;
-}
-
-/*
-** Write data from a buffer into a file.  Return SQLITE_OK on success
-** or some other error code on failure.
-*/
-static int winWrite(
-  sqlite3_file *id,               /* File to write into */
-  const void *pBuf,               /* The bytes to be written */
-  int amt,                        /* Number of bytes to write */
-  sqlite3_int64 offset            /* Offset into the file to begin writing at */
-){
-  int rc = 0;                     /* True if error has occurred, else false */
-  winFile *pFile = (winFile*)id;  /* File handle */
-  int nRetry = 0;                 /* Number of retries */
-
-  assert( amt>0 );
-  assert( pFile );
-  SimulateIOError(return SQLITE_IOERR_WRITE);
-  SimulateDiskfullError(return SQLITE_FULL);
-
-  OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, buffer=%p, amount=%d, "
-           "offset=%lld, lock=%d\n", osGetCurrentProcessId(), pFile,
-           pFile->h, pBuf, amt, offset, pFile->locktype));
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* Deal with as much of this write request as possible by transfering
-  ** data from the memory mapping using memcpy().  */
-  if( offset<pFile->mmapSize ){
-    if( offset+amt <= pFile->mmapSize ){
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, amt);
-      OSTRACE(("WRITE-MMAP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-               osGetCurrentProcessId(), pFile, pFile->h));
-      return SQLITE_OK;
-    }else{
-      int nCopy = (int)(pFile->mmapSize - offset);
-      memcpy(&((u8 *)(pFile->pMapRegion))[offset], pBuf, nCopy);
-      pBuf = &((u8 *)pBuf)[nCopy];
-      amt -= nCopy;
-      offset += nCopy;
-    }
-  }
-#endif
-
-#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
-  rc = winSeekFile(pFile, offset);
-  if( rc==0 ){
-#else
-  {
-#endif
-#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
-    OVERLAPPED overlapped;        /* The offset for WriteFile. */
-#endif
-    u8 *aRem = (u8 *)pBuf;        /* Data yet to be written */
-    int nRem = amt;               /* Number of bytes yet to be written */
-    DWORD nWrite;                 /* Bytes written by each WriteFile() call */
-    DWORD lastErrno = NO_ERROR;   /* Value returned by GetLastError() */
-
-#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
-    memset(&overlapped, 0, sizeof(OVERLAPPED));
-    overlapped.Offset = (LONG)(offset & 0xffffffff);
-    overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
-#endif
-
-    while( nRem>0 ){
-#if SQLITE_OS_WINCE || defined(SQLITE_WIN32_NO_OVERLAPPED)
-      if( !osWriteFile(pFile->h, aRem, nRem, &nWrite, 0) ){
-#else
-      if( !osWriteFile(pFile->h, aRem, nRem, &nWrite, &overlapped) ){
-#endif
-        if( winRetryIoerr(&nRetry, &lastErrno) ) continue;
-        break;
-      }
-      assert( nWrite==0 || nWrite<=(DWORD)nRem );
-      if( nWrite==0 || nWrite>(DWORD)nRem ){
-        lastErrno = osGetLastError();
-        break;
-      }
-#if !SQLITE_OS_WINCE && !defined(SQLITE_WIN32_NO_OVERLAPPED)
-      offset += nWrite;
-      overlapped.Offset = (LONG)(offset & 0xffffffff);
-      overlapped.OffsetHigh = (LONG)((offset>>32) & 0x7fffffff);
-#endif
-      aRem += nWrite;
-      nRem -= nWrite;
-    }
-    if( nRem>0 ){
-      pFile->lastErrno = lastErrno;
-      rc = 1;
-    }
-  }
-
-  if( rc ){
-    if(   ( pFile->lastErrno==ERROR_HANDLE_DISK_FULL )
-       || ( pFile->lastErrno==ERROR_DISK_FULL )){
-      OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_FULL\n",
-               osGetCurrentProcessId(), pFile, pFile->h));
-      return winLogError(SQLITE_FULL, pFile->lastErrno,
-                         "winWrite1", pFile->zPath);
-    }
-    OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_WRITE\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return winLogError(SQLITE_IOERR_WRITE, pFile->lastErrno,
-                       "winWrite2", pFile->zPath);
-  }else{
-    winLogIoerr(nRetry, __LINE__);
-  }
-  OSTRACE(("WRITE pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), pFile, pFile->h));
-  return SQLITE_OK;
-}
-
-/*
-** Truncate an open file to a specified size
-*/
-static int winTruncate(sqlite3_file *id, sqlite3_int64 nByte){
-  winFile *pFile = (winFile*)id;  /* File handle object */
-  int rc = SQLITE_OK;             /* Return code for this function */
-  DWORD lastErrno;
-
-  assert( pFile );
-  SimulateIOError(return SQLITE_IOERR_TRUNCATE);
-  OSTRACE(("TRUNCATE pid=%lu, pFile=%p, file=%p, size=%lld, lock=%d\n",
-           osGetCurrentProcessId(), pFile, pFile->h, nByte, pFile->locktype));
-
-  /* If the user has configured a chunk-size for this file, truncate the
-  ** file so that it consists of an integer number of chunks (i.e. the
-  ** actual file size after the operation may be larger than the requested
-  ** size).
-  */
-  if( pFile->szChunk>0 ){
-    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
-  }
-
-  /* SetEndOfFile() returns non-zero when successful, or zero when it fails. */
-  if( winSeekFile(pFile, nByte) ){
-    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
-                     "winTruncate1", pFile->zPath);
-  }else if( 0==osSetEndOfFile(pFile->h) &&
-            ((lastErrno = osGetLastError())!=ERROR_USER_MAPPED_FILE) ){
-    pFile->lastErrno = lastErrno;
-    rc = winLogError(SQLITE_IOERR_TRUNCATE, pFile->lastErrno,
-                     "winTruncate2", pFile->zPath);
-  }
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  /* If the file was truncated to a size smaller than the currently
-  ** mapped region, reduce the effective mapping size as well. SQLite will
-  ** use read() and write() to access data beyond this point from now on.
-  */
-  if( pFile->pMapRegion && nByte<pFile->mmapSize ){
-    pFile->mmapSize = nByte;
-  }
-#endif
-
-  OSTRACE(("TRUNCATE pid=%lu, pFile=%p, file=%p, rc=%s\n",
-           osGetCurrentProcessId(), pFile, pFile->h, sqlite3ErrName(rc)));
-  return rc;
-}
-
-#ifdef SQLITE_TEST
-/*
-** Count the number of fullsyncs and normal syncs.  This is used to test
-** that syncs and fullsyncs are occuring at the right times.
-*/
-SQLITE_PRIVATE int sqlite3_sync_count = 0;
-SQLITE_PRIVATE int sqlite3_fullsync_count = 0;
-#endif
-
-/*
-** Make sure all writes to a particular file are committed to disk.
-*/
-static int winSync(sqlite3_file *id, int flags){
-#ifndef SQLITE_NO_SYNC
-  /*
-  ** Used only when SQLITE_NO_SYNC is not defined.
-   */
-  BOOL rc;
-#endif
-#if !defined(NDEBUG) || !defined(SQLITE_NO_SYNC) || \
-    defined(SQLITE_HAVE_OS_TRACE)
-  /*
-  ** Used when SQLITE_NO_SYNC is not defined and by the assert() and/or
-  ** OSTRACE() macros.
-   */
-  winFile *pFile = (winFile*)id;
-#else
-  UNUSED_PARAMETER(id);
-#endif
-
-  assert( pFile );
-  /* Check that one of SQLITE_SYNC_NORMAL or FULL was passed */
-  assert((flags&0x0F)==SQLITE_SYNC_NORMAL
-      || (flags&0x0F)==SQLITE_SYNC_FULL
-  );
-
-  /* Unix cannot, but some systems may return SQLITE_FULL from here. This
-  ** line is to test that doing so does not cause any problems.
-  */
-  SimulateDiskfullError( return SQLITE_FULL );
-
-  OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, flags=%x, lock=%d\n",
-           osGetCurrentProcessId(), pFile, pFile->h, flags,
-           pFile->locktype));
-
-#ifndef SQLITE_TEST
-  UNUSED_PARAMETER(flags);
-#else
-  if( (flags&0x0F)==SQLITE_SYNC_FULL ){
-    sqlite3_fullsync_count++;
-  }
-  sqlite3_sync_count++;
-#endif
-
-  /* If we compiled with the SQLITE_NO_SYNC flag, then syncing is a
-  ** no-op
-  */
-#ifdef SQLITE_NO_SYNC
-  OSTRACE(("SYNC-NOP pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), pFile, pFile->h));
-  return SQLITE_OK;
-#else
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFile->pMapRegion ){
-    if( osFlushViewOfFile(pFile->pMapRegion, 0) ){
-      OSTRACE(("SYNC-MMAP pid=%lu, pFile=%p, pMapRegion=%p, "
-               "rc=SQLITE_OK\n", osGetCurrentProcessId(),
-               pFile, pFile->pMapRegion));
-    }else{
-      pFile->lastErrno = osGetLastError();
-      OSTRACE(("SYNC-MMAP pid=%lu, pFile=%p, pMapRegion=%p, "
-               "rc=SQLITE_IOERR_MMAP\n", osGetCurrentProcessId(),
-               pFile, pFile->pMapRegion));
-      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
-                         "winSync1", pFile->zPath);
-    }
-  }
-#endif
-  rc = osFlushFileBuffers(pFile->h);
-  SimulateIOError( rc=FALSE );
-  if( rc ){
-    OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, rc=SQLITE_OK\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return SQLITE_OK;
-  }else{
-    pFile->lastErrno = osGetLastError();
-    OSTRACE(("SYNC pid=%lu, pFile=%p, file=%p, rc=SQLITE_IOERR_FSYNC\n",
-             osGetCurrentProcessId(), pFile, pFile->h));
-    return winLogError(SQLITE_IOERR_FSYNC, pFile->lastErrno,
-                       "winSync2", pFile->zPath);
-  }
-#endif
-}
-
-/*
-** Determine the current size of a file in bytes
-*/
-static int winFileSize(sqlite3_file *id, sqlite3_int64 *pSize){
-  winFile *pFile = (winFile*)id;
-  int rc = SQLITE_OK;
-
-  assert( id!=0 );
-  assert( pSize!=0 );
-  SimulateIOError(return SQLITE_IOERR_FSTAT);
-  OSTRACE(("SIZE file=%p, pSize=%p\n", pFile->h, pSize));
-
-#if SQLITE_OS_WINRT
-  {
-    FILE_STANDARD_INFO info;
-    if( osGetFileInformationByHandleEx(pFile->h, FileStandardInfo,
-                                     &info, sizeof(info)) ){
-      *pSize = info.EndOfFile.QuadPart;
-    }else{
-      pFile->lastErrno = osGetLastError();
-      rc = winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
-                       "winFileSize", pFile->zPath);
-    }
-  }
-#else
-  {
-    DWORD upperBits;
-    DWORD lowerBits;
-    DWORD lastErrno;
-
-    lowerBits = osGetFileSize(pFile->h, &upperBits);
-    *pSize = (((sqlite3_int64)upperBits)<<32) + lowerBits;
-    if(   (lowerBits == INVALID_FILE_SIZE)
-       && ((lastErrno = osGetLastError())!=NO_ERROR) ){
-      pFile->lastErrno = lastErrno;
-      rc = winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
-                       "winFileSize", pFile->zPath);
-    }
-  }
-#endif
-  OSTRACE(("SIZE file=%p, pSize=%p, *pSize=%lld, rc=%s\n",
-           pFile->h, pSize, *pSize, sqlite3ErrName(rc)));
-  return rc;
-}
-
-/*
-** LOCKFILE_FAIL_IMMEDIATELY is undefined on some Windows systems.
-*/
-#ifndef LOCKFILE_FAIL_IMMEDIATELY
-# define LOCKFILE_FAIL_IMMEDIATELY 1
-#endif
-
-#ifndef LOCKFILE_EXCLUSIVE_LOCK
-# define LOCKFILE_EXCLUSIVE_LOCK 2
-#endif
-
-/*
-** Historically, SQLite has used both the LockFile and LockFileEx functions.
-** When the LockFile function was used, it was always expected to fail
-** immediately if the lock could not be obtained.  Also, it always expected to
-** obtain an exclusive lock.  These flags are used with the LockFileEx function
-** and reflect those expectations; therefore, they should not be changed.
-*/
-#ifndef SQLITE_LOCKFILE_FLAGS
-# define SQLITE_LOCKFILE_FLAGS   (LOCKFILE_FAIL_IMMEDIATELY | \
-                                  LOCKFILE_EXCLUSIVE_LOCK)
-#endif
-
-/*
-** Currently, SQLite never calls the LockFileEx function without wanting the
-** call to fail immediately if the lock cannot be obtained.
-*/
-#ifndef SQLITE_LOCKFILEEX_FLAGS
-# define SQLITE_LOCKFILEEX_FLAGS (LOCKFILE_FAIL_IMMEDIATELY)
-#endif
-
-/*
-** Acquire a reader lock.
-** Different API routines are called depending on whether or not this
-** is Win9x or WinNT.
-*/
-static int winGetReadLock(winFile *pFile){
-  int res;
-  OSTRACE(("READ-LOCK file=%p, lock=%d\n", pFile->h, pFile->locktype));
-  if( osIsNT() ){
-#if SQLITE_OS_WINCE
-    /*
-    ** NOTE: Windows CE is handled differently here due its lack of the Win32
-    **       API LockFileEx.
-    */
-    res = winceLockFile(&pFile->h, SHARED_FIRST, 0, 1, 0);
-#else
-    res = winLockFile(&pFile->h, SQLITE_LOCKFILEEX_FLAGS, SHARED_FIRST, 0,
-                      SHARED_SIZE, 0);
-#endif
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    int lk;
-    sqlite3_randomness(sizeof(lk), &lk);
-    pFile->sharedLockByte = (short)((lk & 0x7fffffff)%(SHARED_SIZE - 1));
-    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS,
-                      SHARED_FIRST+pFile->sharedLockByte, 0, 1, 0);
-  }
-#endif
-  if( res == 0 ){
-    pFile->lastErrno = osGetLastError();
-    /* No need to log a failure to lock */
-  }
-  OSTRACE(("READ-LOCK file=%p, result=%d\n", pFile->h, res));
-  return res;
-}
-
-/*
-** Undo a readlock
-*/
-static int winUnlockReadLock(winFile *pFile){
-  int res;
-  DWORD lastErrno;
-  OSTRACE(("READ-UNLOCK file=%p, lock=%d\n", pFile->h, pFile->locktype));
-  if( osIsNT() ){
-    res = winUnlockFile(&pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    res = winUnlockFile(&pFile->h, SHARED_FIRST+pFile->sharedLockByte, 0, 1, 0);
-  }
-#endif
-  if( res==0 && ((lastErrno = osGetLastError())!=ERROR_NOT_LOCKED) ){
-    pFile->lastErrno = lastErrno;
-    winLogError(SQLITE_IOERR_UNLOCK, pFile->lastErrno,
-                "winUnlockReadLock", pFile->zPath);
-  }
-  OSTRACE(("READ-UNLOCK file=%p, result=%d\n", pFile->h, res));
-  return res;
-}
-
-/*
-** Lock the file with the lock specified by parameter locktype - one
-** of the following:
-**
-**     (1) SHARED_LOCK
-**     (2) RESERVED_LOCK
-**     (3) PENDING_LOCK
-**     (4) EXCLUSIVE_LOCK
-**
-** Sometimes when requesting one lock state, additional lock states
-** are inserted in between.  The locking might fail on one of the later
-** transitions leaving the lock state different from what it started but
-** still short of its goal.  The following chart shows the allowed
-** transitions and the inserted intermediate states:
-**
-**    UNLOCKED -> SHARED
-**    SHARED -> RESERVED
-**    SHARED -> (PENDING) -> EXCLUSIVE
-**    RESERVED -> (PENDING) -> EXCLUSIVE
-**    PENDING -> EXCLUSIVE
-**
-** This routine will only increase a lock.  The winUnlock() routine
-** erases all locks at once and returns us immediately to locking level 0.
-** It is not possible to lower the locking level one step at a time.  You
-** must go straight to locking level 0.
-*/
-static int winLock(sqlite3_file *id, int locktype){
-  int rc = SQLITE_OK;    /* Return code from subroutines */
-  int res = 1;           /* Result of a Windows lock call */
-  int newLocktype;       /* Set pFile->locktype to this value before exiting */
-  int gotPendingLock = 0;/* True if we acquired a PENDING lock this time */
-  winFile *pFile = (winFile*)id;
-  DWORD lastErrno = NO_ERROR;
-
-  assert( id!=0 );
-  OSTRACE(("LOCK file=%p, oldLock=%d(%d), newLock=%d\n",
-           pFile->h, pFile->locktype, pFile->sharedLockByte, locktype));
-
-  /* If there is already a lock of this type or more restrictive on the
-  ** OsFile, do nothing. Don't use the end_lock: exit path, as
-  ** sqlite3OsEnterMutex() hasn't been called yet.
-  */
-  if( pFile->locktype>=locktype ){
-    OSTRACE(("LOCK-HELD file=%p, rc=SQLITE_OK\n", pFile->h));
-    return SQLITE_OK;
-  }
-
-  /* Do not allow any kind of write-lock on a read-only database
-  */
-  if( (pFile->ctrlFlags & WINFILE_RDONLY)!=0 && locktype>=RESERVED_LOCK ){
-    return SQLITE_IOERR_LOCK;
-  }
-
-  /* Make sure the locking sequence is correct
-  */
-  assert( pFile->locktype!=NO_LOCK || locktype==SHARED_LOCK );
-  assert( locktype!=PENDING_LOCK );
-  assert( locktype!=RESERVED_LOCK || pFile->locktype==SHARED_LOCK );
-
-  /* Lock the PENDING_LOCK byte if we need to acquire a PENDING lock or
-  ** a SHARED lock.  If we are acquiring a SHARED lock, the acquisition of
-  ** the PENDING_LOCK byte is temporary.
-  */
-  newLocktype = pFile->locktype;
-  if(   (pFile->locktype==NO_LOCK)
-     || (   (locktype==EXCLUSIVE_LOCK)
-         && (pFile->locktype==RESERVED_LOCK))
-  ){
-    int cnt = 3;
-    while( cnt-->0 && (res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS,
-                                         PENDING_BYTE, 0, 1, 0))==0 ){
-      /* Try 3 times to get the pending lock.  This is needed to work
-      ** around problems caused by indexing and/or anti-virus software on
-      ** Windows systems.
-      ** If you are using this code as a model for alternative VFSes, do not
-      ** copy this retry logic.  It is a hack intended for Windows only.
-      */
-      lastErrno = osGetLastError();
-      OSTRACE(("LOCK-PENDING-FAIL file=%p, count=%d, result=%d\n",
-               pFile->h, cnt, res));
-      if( lastErrno==ERROR_INVALID_HANDLE ){
-        pFile->lastErrno = lastErrno;
-        rc = SQLITE_IOERR_LOCK;
-        OSTRACE(("LOCK-FAIL file=%p, count=%d, rc=%s\n",
-                 pFile->h, cnt, sqlite3ErrName(rc)));
-        return rc;
-      }
-      if( cnt ) sqlite3_win32_sleep(1);
-    }
-    gotPendingLock = res;
-    if( !res ){
-      lastErrno = osGetLastError();
-    }
-  }
-
-  /* Acquire a shared lock
-  */
-  if( locktype==SHARED_LOCK && res ){
-    assert( pFile->locktype==NO_LOCK );
-    res = winGetReadLock(pFile);
-    if( res ){
-      newLocktype = SHARED_LOCK;
-    }else{
-      lastErrno = osGetLastError();
-    }
-  }
-
-  /* Acquire a RESERVED lock
-  */
-  if( locktype==RESERVED_LOCK && res ){
-    assert( pFile->locktype==SHARED_LOCK );
-    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS, RESERVED_BYTE, 0, 1, 0);
-    if( res ){
-      newLocktype = RESERVED_LOCK;
-    }else{
-      lastErrno = osGetLastError();
-    }
-  }
-
-  /* Acquire a PENDING lock
-  */
-  if( locktype==EXCLUSIVE_LOCK && res ){
-    newLocktype = PENDING_LOCK;
-    gotPendingLock = 0;
-  }
-
-  /* Acquire an EXCLUSIVE lock
-  */
-  if( locktype==EXCLUSIVE_LOCK && res ){
-    assert( pFile->locktype>=SHARED_LOCK );
-    res = winUnlockReadLock(pFile);
-    res = winLockFile(&pFile->h, SQLITE_LOCKFILE_FLAGS, SHARED_FIRST, 0,
-                      SHARED_SIZE, 0);
-    if( res ){
-      newLocktype = EXCLUSIVE_LOCK;
-    }else{
-      lastErrno = osGetLastError();
-      winGetReadLock(pFile);
-    }
-  }
-
-  /* If we are holding a PENDING lock that ought to be released, then
-  ** release it now.
-  */
-  if( gotPendingLock && locktype==SHARED_LOCK ){
-    winUnlockFile(&pFile->h, PENDING_BYTE, 0, 1, 0);
-  }
-
-  /* Update the state of the lock has held in the file descriptor then
-  ** return the appropriate result code.
-  */
-  if( res ){
-    rc = SQLITE_OK;
-  }else{
-    pFile->lastErrno = lastErrno;
-    rc = SQLITE_BUSY;
-    OSTRACE(("LOCK-FAIL file=%p, wanted=%d, got=%d\n",
-             pFile->h, locktype, newLocktype));
-  }
-  pFile->locktype = (u8)newLocktype;
-  OSTRACE(("LOCK file=%p, lock=%d, rc=%s\n",
-           pFile->h, pFile->locktype, sqlite3ErrName(rc)));
-  return rc;
-}
-
-/*
-** This routine checks if there is a RESERVED lock held on the specified
-** file by this or any other process. If such a lock is held, return
-** non-zero, otherwise zero.
-*/
-static int winCheckReservedLock(sqlite3_file *id, int *pResOut){
-  int res;
-  winFile *pFile = (winFile*)id;
-
-  SimulateIOError( return SQLITE_IOERR_CHECKRESERVEDLOCK; );
-  OSTRACE(("TEST-WR-LOCK file=%p, pResOut=%p\n", pFile->h, pResOut));
-
-  assert( id!=0 );
-  if( pFile->locktype>=RESERVED_LOCK ){
-    res = 1;
-    OSTRACE(("TEST-WR-LOCK file=%p, result=%d (local)\n", pFile->h, res));
-  }else{
-    res = winLockFile(&pFile->h, SQLITE_LOCKFILEEX_FLAGS,RESERVED_BYTE, 0, 1, 0);
-    if( res ){
-      winUnlockFile(&pFile->h, RESERVED_BYTE, 0, 1, 0);
-    }
-    res = !res;
-    OSTRACE(("TEST-WR-LOCK file=%p, result=%d (remote)\n", pFile->h, res));
-  }
-  *pResOut = res;
-  OSTRACE(("TEST-WR-LOCK file=%p, pResOut=%p, *pResOut=%d, rc=SQLITE_OK\n",
-           pFile->h, pResOut, *pResOut));
-  return SQLITE_OK;
-}
-
-/*
-** Lower the locking level on file descriptor id to locktype.  locktype
-** must be either NO_LOCK or SHARED_LOCK.
-**
-** If the locking level of the file descriptor is already at or below
-** the requested locking level, this routine is a no-op.
-**
-** It is not possible for this routine to fail if the second argument
-** is NO_LOCK.  If the second argument is SHARED_LOCK then this routine
-** might return SQLITE_IOERR;
-*/
-static int winUnlock(sqlite3_file *id, int locktype){
-  int type;
-  winFile *pFile = (winFile*)id;
-  int rc = SQLITE_OK;
-  assert( pFile!=0 );
-  assert( locktype<=SHARED_LOCK );
-  OSTRACE(("UNLOCK file=%p, oldLock=%d(%d), newLock=%d\n",
-           pFile->h, pFile->locktype, pFile->sharedLockByte, locktype));
-  type = pFile->locktype;
-  if( type>=EXCLUSIVE_LOCK ){
-    winUnlockFile(&pFile->h, SHARED_FIRST, 0, SHARED_SIZE, 0);
-    if( locktype==SHARED_LOCK && !winGetReadLock(pFile) ){
-      /* This should never happen.  We should always be able to
-      ** reacquire the read lock */
-      rc = winLogError(SQLITE_IOERR_UNLOCK, osGetLastError(),
-                       "winUnlock", pFile->zPath);
-    }
-  }
-  if( type>=RESERVED_LOCK ){
-    winUnlockFile(&pFile->h, RESERVED_BYTE, 0, 1, 0);
-  }
-  if( locktype==NO_LOCK && type>=SHARED_LOCK ){
-    winUnlockReadLock(pFile);
-  }
-  if( type>=PENDING_LOCK ){
-    winUnlockFile(&pFile->h, PENDING_BYTE, 0, 1, 0);
-  }
-  pFile->locktype = (u8)locktype;
-  OSTRACE(("UNLOCK file=%p, lock=%d, rc=%s\n",
-           pFile->h, pFile->locktype, sqlite3ErrName(rc)));
-  return rc;
-}
-
-/*
-** If *pArg is initially negative then this is a query.  Set *pArg to
-** 1 or 0 depending on whether or not bit mask of pFile->ctrlFlags is set.
-**
-** If *pArg is 0 or 1, then clear or set the mask bit of pFile->ctrlFlags.
-*/
-static void winModeBit(winFile *pFile, unsigned char mask, int *pArg){
-  if( *pArg<0 ){
-    *pArg = (pFile->ctrlFlags & mask)!=0;
-  }else if( (*pArg)==0 ){
-    pFile->ctrlFlags &= ~mask;
-  }else{
-    pFile->ctrlFlags |= mask;
-  }
-}
-
-/* Forward references to VFS helper methods used for temporary files */
-static int winGetTempname(sqlite3_vfs *, char **);
-static int winIsDir(const void *);
-static BOOL winIsDriveLetterAndColon(const char *);
-
-/*
-** Control and query of the open file handle.
-*/
-static int winFileControl(sqlite3_file *id, int op, void *pArg){
-  winFile *pFile = (winFile*)id;
-  OSTRACE(("FCNTL file=%p, op=%d, pArg=%p\n", pFile->h, op, pArg));
-  switch( op ){
-    case SQLITE_FCNTL_LOCKSTATE: {
-      *(int*)pArg = pFile->locktype;
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_LAST_ERRNO: {
-      *(int*)pArg = (int)pFile->lastErrno;
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_CHUNK_SIZE: {
-      pFile->szChunk = *(int *)pArg;
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_SIZE_HINT: {
-      if( pFile->szChunk>0 ){
-        sqlite3_int64 oldSz;
-        int rc = winFileSize(id, &oldSz);
-        if( rc==SQLITE_OK ){
-          sqlite3_int64 newSz = *(sqlite3_int64*)pArg;
-          if( newSz>oldSz ){
-            SimulateIOErrorBenign(1);
-            rc = winTruncate(id, newSz);
-            SimulateIOErrorBenign(0);
-          }
-        }
-        OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
-        return rc;
-      }
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_PERSIST_WAL: {
-      winModeBit(pFile, WINFILE_PERSIST_WAL, (int*)pArg);
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_POWERSAFE_OVERWRITE: {
-      winModeBit(pFile, WINFILE_PSOW, (int*)pArg);
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_VFSNAME: {
-      *(char**)pArg = sqlite3_mprintf("%s", pFile->pVfs->zName);
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-    case SQLITE_FCNTL_WIN32_AV_RETRY: {
-      int *a = (int*)pArg;
-      if( a[0]>0 ){
-        winIoerrRetry = a[0];
-      }else{
-        a[0] = winIoerrRetry;
-      }
-      if( a[1]>0 ){
-        winIoerrRetryDelay = a[1];
-      }else{
-        a[1] = winIoerrRetryDelay;
-      }
-      OSTRACE(("FCNTL file=%p, rc=SQLITE_OK\n", pFile->h));
-      return SQLITE_OK;
-    }
-#ifdef SQLITE_TEST
-    case SQLITE_FCNTL_WIN32_SET_HANDLE: {
-      LPHANDLE phFile = (LPHANDLE)pArg;
-      HANDLE hOldFile = pFile->h;
-      pFile->h = *phFile;
-      *phFile = hOldFile;
-      OSTRACE(("FCNTL oldFile=%p, newFile=%p, rc=SQLITE_OK\n",
-               hOldFile, pFile->h));
-      return SQLITE_OK;
-    }
-#endif
-    case SQLITE_FCNTL_TEMPFILENAME: {
-      char *zTFile = 0;
-      int rc = winGetTempname(pFile->pVfs, &zTFile);
-      if( rc==SQLITE_OK ){
-        *(char**)pArg = zTFile;
-      }
-      OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
-      return rc;
-    }
-#if SQLITE_MAX_MMAP_SIZE>0
-    case SQLITE_FCNTL_MMAP_SIZE: {
-      i64 newLimit = *(i64*)pArg;
-      int rc = SQLITE_OK;
-      if( newLimit>sqlite3GlobalConfig.mxMmap ){
-        newLimit = sqlite3GlobalConfig.mxMmap;
-      }
-      *(i64*)pArg = pFile->mmapSizeMax;
-      if( newLimit>=0 && newLimit!=pFile->mmapSizeMax && pFile->nFetchOut==0 ){
-        pFile->mmapSizeMax = newLimit;
-        if( pFile->mmapSize>0 ){
-          winUnmapfile(pFile);
-          rc = winMapfile(pFile, -1);
-        }
-      }
-      OSTRACE(("FCNTL file=%p, rc=%s\n", pFile->h, sqlite3ErrName(rc)));
-      return rc;
-    }
-#endif
-  }
-  OSTRACE(("FCNTL file=%p, rc=SQLITE_NOTFOUND\n", pFile->h));
-  return SQLITE_NOTFOUND;
-}
-
-/*
-** Return the sector size in bytes of the underlying block device for
-** the specified file. This is almost always 512 bytes, but may be
-** larger for some devices.
-**
-** SQLite code assumes this function cannot fail. It also assumes that
-** if two files are created in the same file-system directory (i.e.
-** a database and its journal file) that the sector size will be the
-** same for both.
-*/
-static int winSectorSize(sqlite3_file *id){
-  (void)id;
-  return SQLITE_DEFAULT_SECTOR_SIZE;
-}
-
-/*
-** Return a vector of device characteristics.
-*/
-static int winDeviceCharacteristics(sqlite3_file *id){
-  winFile *p = (winFile*)id;
-  return SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN |
-         ((p->ctrlFlags & WINFILE_PSOW)?SQLITE_IOCAP_POWERSAFE_OVERWRITE:0);
-}
-
-/*
-** Windows will only let you create file view mappings
-** on allocation size granularity boundaries.
-** During sqlite3_os_init() we do a GetSystemInfo()
-** to get the granularity size.
-*/
-static SYSTEM_INFO winSysInfo;
-
-#ifndef SQLITE_OMIT_WAL
-
-/*
-** Helper functions to obtain and relinquish the global mutex. The
-** global mutex is used to protect the winLockInfo objects used by
-** this file, all of which may be shared by multiple threads.
-**
-** Function winShmMutexHeld() is used to assert() that the global mutex
-** is held when required. This function is only used as part of assert()
-** statements. e.g.
-**
-**   winShmEnterMutex()
-**     assert( winShmMutexHeld() );
-**   winShmLeaveMutex()
-*/
-static void winShmEnterMutex(void){
-  sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-static void winShmLeaveMutex(void){
-  sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-#ifndef NDEBUG
-static int winShmMutexHeld(void) {
-  return sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_VFS1));
-}
-#endif
-
-/*
-** Object used to represent a single file opened and mmapped to provide
-** shared memory.  When multiple threads all reference the same
-** log-summary, each thread has its own winFile object, but they all
-** point to a single instance of this object.  In other words, each
-** log-summary is opened only once per process.
-**
-** winShmMutexHeld() must be true when creating or destroying
-** this object or while reading or writing the following fields:
-**
-**      nRef
-**      pNext
-**
-** The following fields are read-only after the object is created:
-**
-**      fid
-**      zFilename
-**
-** Either winShmNode.mutex must be held or winShmNode.nRef==0 and
-** winShmMutexHeld() is true when reading or writing any other field
-** in this structure.
-**
-*/
-struct winShmNode {
-  sqlite3_mutex *mutex;      /* Mutex to access this object */
-  char *zFilename;           /* Name of the file */
-  winFile hFile;             /* File handle from winOpen */
-
-  int szRegion;              /* Size of shared-memory regions */
-  int nRegion;               /* Size of array apRegion */
-  struct ShmRegion {
-    HANDLE hMap;             /* File handle from CreateFileMapping */
-    void *pMap;
-  } *aRegion;
-  DWORD lastErrno;           /* The Windows errno from the last I/O error */
-
-  int nRef;                  /* Number of winShm objects pointing to this */
-  winShm *pFirst;            /* All winShm objects pointing to this */
-  winShmNode *pNext;         /* Next in list of all winShmNode objects */
-#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
-  u8 nextShmId;              /* Next available winShm.id value */
-#endif
-};
-
-/*
-** A global array of all winShmNode objects.
-**
-** The winShmMutexHeld() must be true while reading or writing this list.
-*/
-static winShmNode *winShmNodeList = 0;
-
-/*
-** Structure used internally by this VFS to record the state of an
-** open shared memory connection.
-**
-** The following fields are initialized when this object is created and
-** are read-only thereafter:
-**
-**    winShm.pShmNode
-**    winShm.id
-**
-** All other fields are read/write.  The winShm.pShmNode->mutex must be held
-** while accessing any read/write fields.
-*/
-struct winShm {
-  winShmNode *pShmNode;      /* The underlying winShmNode object */
-  winShm *pNext;             /* Next winShm with the same winShmNode */
-  u8 hasMutex;               /* True if holding the winShmNode mutex */
-  u16 sharedMask;            /* Mask of shared locks held */
-  u16 exclMask;              /* Mask of exclusive locks held */
-#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
-  u8 id;                     /* Id of this connection with its winShmNode */
-#endif
-};
-
-/*
-** Constants used for locking
-*/
-#define WIN_SHM_BASE   ((22+SQLITE_SHM_NLOCK)*4)        /* first lock byte */
-#define WIN_SHM_DMS    (WIN_SHM_BASE+SQLITE_SHM_NLOCK)  /* deadman switch */
-
-/*
-** Apply advisory locks for all n bytes beginning at ofst.
-*/
-#define _SHM_UNLCK  1
-#define _SHM_RDLCK  2
-#define _SHM_WRLCK  3
-static int winShmSystemLock(
-  winShmNode *pFile,    /* Apply locks to this open shared-memory segment */
-  int lockType,         /* _SHM_UNLCK, _SHM_RDLCK, or _SHM_WRLCK */
-  int ofst,             /* Offset to first byte to be locked/unlocked */
-  int nByte             /* Number of bytes to lock or unlock */
-){
-  int rc = 0;           /* Result code form Lock/UnlockFileEx() */
-
-  /* Access to the winShmNode object is serialized by the caller */
-  assert( sqlite3_mutex_held(pFile->mutex) || pFile->nRef==0 );
-
-  OSTRACE(("SHM-LOCK file=%p, lock=%d, offset=%d, size=%d\n",
-           pFile->hFile.h, lockType, ofst, nByte));
-
-  /* Release/Acquire the system-level lock */
-  if( lockType==_SHM_UNLCK ){
-    rc = winUnlockFile(&pFile->hFile.h, ofst, 0, nByte, 0);
-  }else{
-    /* Initialize the locking parameters */
-    DWORD dwFlags = LOCKFILE_FAIL_IMMEDIATELY;
-    if( lockType == _SHM_WRLCK ) dwFlags |= LOCKFILE_EXCLUSIVE_LOCK;
-    rc = winLockFile(&pFile->hFile.h, dwFlags, ofst, 0, nByte, 0);
-  }
-
-  if( rc!= 0 ){
-    rc = SQLITE_OK;
-  }else{
-    pFile->lastErrno =  osGetLastError();
-    rc = SQLITE_BUSY;
-  }
-
-  OSTRACE(("SHM-LOCK file=%p, func=%s, errno=%lu, rc=%s\n",
-           pFile->hFile.h, (lockType == _SHM_UNLCK) ? "winUnlockFile" :
-           "winLockFile", pFile->lastErrno, sqlite3ErrName(rc)));
-
-  return rc;
-}
-
-/* Forward references to VFS methods */
-static int winOpen(sqlite3_vfs*,const char*,sqlite3_file*,int,int*);
-static int winDelete(sqlite3_vfs *,const char*,int);
-
-/*
-** Purge the winShmNodeList list of all entries with winShmNode.nRef==0.
-**
-** This is not a VFS shared-memory method; it is a utility function called
-** by VFS shared-memory methods.
-*/
-static void winShmPurge(sqlite3_vfs *pVfs, int deleteFlag){
-  winShmNode **pp;
-  winShmNode *p;
-  assert( winShmMutexHeld() );
-  OSTRACE(("SHM-PURGE pid=%lu, deleteFlag=%d\n",
-           osGetCurrentProcessId(), deleteFlag));
-  pp = &winShmNodeList;
-  while( (p = *pp)!=0 ){
-    if( p->nRef==0 ){
-      int i;
-      if( p->mutex ){ sqlite3_mutex_free(p->mutex); }
-      for(i=0; i<p->nRegion; i++){
-        BOOL bRc = osUnmapViewOfFile(p->aRegion[i].pMap);
-        OSTRACE(("SHM-PURGE-UNMAP pid=%lu, region=%d, rc=%s\n",
-                 osGetCurrentProcessId(), i, bRc ? "ok" : "failed"));
-        UNUSED_VARIABLE_VALUE(bRc);
-        bRc = osCloseHandle(p->aRegion[i].hMap);
-        OSTRACE(("SHM-PURGE-CLOSE pid=%lu, region=%d, rc=%s\n",
-                 osGetCurrentProcessId(), i, bRc ? "ok" : "failed"));
-        UNUSED_VARIABLE_VALUE(bRc);
-      }
-      if( p->hFile.h!=NULL && p->hFile.h!=INVALID_HANDLE_VALUE ){
-        SimulateIOErrorBenign(1);
-        winClose((sqlite3_file *)&p->hFile);
-        SimulateIOErrorBenign(0);
-      }
-      if( deleteFlag ){
-        SimulateIOErrorBenign(1);
-        winDelete(pVfs, p->zFilename, 0);
-        SimulateIOErrorBenign(0);
-      }
-      *pp = p->pNext;
-      sqlite3_free(p->aRegion);
-      sqlite3_free(p);
-    }else{
-      pp = &p->pNext;
-    }
-  }
-}
-
-/*
-** Open the shared-memory area associated with database file pDbFd.
-**
-** When opening a new shared-memory file, if no other instances of that
-** file are currently open, in this process or in other processes, then
-** the file must be truncated to zero length or have its header cleared.
-*/
-static int winOpenSharedMemory(winFile *pDbFd){
-  struct winShm *p;                  /* The connection to be opened */
-  struct winShmNode *pShmNode = 0;   /* The underlying mmapped file */
-  int rc;                            /* Result code */
-  struct winShmNode *pNew;           /* Newly allocated winShmNode */
-  int nName;                         /* Size of zName in bytes */
-
-  assert( pDbFd->pShm==0 );    /* Not previously opened */
-
-  /* Allocate space for the new sqlite3_shm object.  Also speculatively
-  ** allocate space for a new winShmNode and filename.
-  */
-  p = sqlite3MallocZero( sizeof(*p) );
-  if( p==0 ) return SQLITE_IOERR_NOMEM;
-  nName = sqlite3Strlen30(pDbFd->zPath);
-  pNew = sqlite3MallocZero( sizeof(*pShmNode) + nName + 17 );
-  if( pNew==0 ){
-    sqlite3_free(p);
-    return SQLITE_IOERR_NOMEM;
-  }
-  pNew->zFilename = (char*)&pNew[1];
-  sqlite3_snprintf(nName+15, pNew->zFilename, "%s-shm", pDbFd->zPath);
-
-  /* Look to see if there is an existing winShmNode that can be used.
-  ** If no matching winShmNode currently exists, create a new one.
-  */
-  winShmEnterMutex();
-  for(pShmNode = winShmNodeList; pShmNode; pShmNode=pShmNode->pNext){
-    /* TBD need to come up with better match here.  Perhaps
-    ** use FILE_ID_BOTH_DIR_INFO Structure.
-    */
-    if( sqlite3StrICmp(pShmNode->zFilename, pNew->zFilename)==0 ) break;
-  }
-  if( pShmNode ){
-    sqlite3_free(pNew);
-  }else{
-    pShmNode = pNew;
-    pNew = 0;
-    ((winFile*)(&pShmNode->hFile))->h = INVALID_HANDLE_VALUE;
-    pShmNode->pNext = winShmNodeList;
-    winShmNodeList = pShmNode;
-
-    pShmNode->mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
-    if( pShmNode->mutex==0 ){
-      rc = SQLITE_IOERR_NOMEM;
-      goto shm_open_err;
-    }
-
-    rc = winOpen(pDbFd->pVfs,
-                 pShmNode->zFilename,             /* Name of the file (UTF-8) */
-                 (sqlite3_file*)&pShmNode->hFile,  /* File handle here */
-                 SQLITE_OPEN_WAL | SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE,
-                 0);
-    if( SQLITE_OK!=rc ){
-      goto shm_open_err;
-    }
-
-    /* Check to see if another process is holding the dead-man switch.
-    ** If not, truncate the file to zero length.
-    */
-    if( winShmSystemLock(pShmNode, _SHM_WRLCK, WIN_SHM_DMS, 1)==SQLITE_OK ){
-      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, 0);
-      if( rc!=SQLITE_OK ){
-        rc = winLogError(SQLITE_IOERR_SHMOPEN, osGetLastError(),
-                         "winOpenShm", pDbFd->zPath);
-      }
-    }
-    if( rc==SQLITE_OK ){
-      winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
-      rc = winShmSystemLock(pShmNode, _SHM_RDLCK, WIN_SHM_DMS, 1);
-    }
-    if( rc ) goto shm_open_err;
-  }
-
-  /* Make the new connection a child of the winShmNode */
-  p->pShmNode = pShmNode;
-#if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)
-  p->id = pShmNode->nextShmId++;
-#endif
-  pShmNode->nRef++;
-  pDbFd->pShm = p;
-  winShmLeaveMutex();
-
-  /* The reference count on pShmNode has already been incremented under
-  ** the cover of the winShmEnterMutex() mutex and the pointer from the
-  ** new (struct winShm) object to the pShmNode has been set. All that is
-  ** left to do is to link the new object into the linked list starting
-  ** at pShmNode->pFirst. This must be done while holding the pShmNode->mutex
-  ** mutex.
-  */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  p->pNext = pShmNode->pFirst;
-  pShmNode->pFirst = p;
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return SQLITE_OK;
-
-  /* Jump here on any error */
-shm_open_err:
-  winShmSystemLock(pShmNode, _SHM_UNLCK, WIN_SHM_DMS, 1);
-  winShmPurge(pDbFd->pVfs, 0);      /* This call frees pShmNode if required */
-  sqlite3_free(p);
-  sqlite3_free(pNew);
-  winShmLeaveMutex();
-  return rc;
-}
-
-/*
-** Close a connection to shared-memory.  Delete the underlying
-** storage if deleteFlag is true.
-*/
-static int winShmUnmap(
-  sqlite3_file *fd,          /* Database holding shared memory */
-  int deleteFlag             /* Delete after closing if true */
-){
-  winFile *pDbFd;       /* Database holding shared-memory */
-  winShm *p;            /* The connection to be closed */
-  winShmNode *pShmNode; /* The underlying shared-memory file */
-  winShm **pp;          /* For looping over sibling connections */
-
-  pDbFd = (winFile*)fd;
-  p = pDbFd->pShm;
-  if( p==0 ) return SQLITE_OK;
-  pShmNode = p->pShmNode;
-
-  /* Remove connection p from the set of connections associated
-  ** with pShmNode */
-  sqlite3_mutex_enter(pShmNode->mutex);
-  for(pp=&pShmNode->pFirst; (*pp)!=p; pp = &(*pp)->pNext){}
-  *pp = p->pNext;
-
-  /* Free the connection p */
-  sqlite3_free(p);
-  pDbFd->pShm = 0;
-  sqlite3_mutex_leave(pShmNode->mutex);
-
-  /* If pShmNode->nRef has reached 0, then close the underlying
-  ** shared-memory file, too */
-  winShmEnterMutex();
-  assert( pShmNode->nRef>0 );
-  pShmNode->nRef--;
-  if( pShmNode->nRef==0 ){
-    winShmPurge(pDbFd->pVfs, deleteFlag);
-  }
-  winShmLeaveMutex();
-
-  return SQLITE_OK;
-}
-
-/*
-** Change the lock state for a shared-memory segment.
-*/
-static int winShmLock(
-  sqlite3_file *fd,          /* Database file holding the shared memory */
-  int ofst,                  /* First lock to acquire or release */
-  int n,                     /* Number of locks to acquire or release */
-  int flags                  /* What to do with the lock */
-){
-  winFile *pDbFd = (winFile*)fd;        /* Connection holding shared memory */
-  winShm *p = pDbFd->pShm;              /* The shared memory being locked */
-  winShm *pX;                           /* For looping over all siblings */
-  winShmNode *pShmNode = p->pShmNode;
-  int rc = SQLITE_OK;                   /* Result code */
-  u16 mask;                             /* Mask of locks to take or release */
-
-  assert( ofst>=0 && ofst+n<=SQLITE_SHM_NLOCK );
-  assert( n>=1 );
-  assert( flags==(SQLITE_SHM_LOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED)
-       || flags==(SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE) );
-  assert( n==1 || (flags & SQLITE_SHM_EXCLUSIVE)!=0 );
-
-  mask = (u16)((1U<<(ofst+n)) - (1U<<ofst));
-  assert( n>1 || mask==(1<<ofst) );
-  sqlite3_mutex_enter(pShmNode->mutex);
-  if( flags & SQLITE_SHM_UNLOCK ){
-    u16 allMask = 0; /* Mask of locks held by siblings */
-
-    /* See if any siblings hold this same lock */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( pX==p ) continue;
-      assert( (pX->exclMask & (p->exclMask|p->sharedMask))==0 );
-      allMask |= pX->sharedMask;
-    }
-
-    /* Unlock the system-level locks */
-    if( (mask & allMask)==0 ){
-      rc = winShmSystemLock(pShmNode, _SHM_UNLCK, ofst+WIN_SHM_BASE, n);
-    }else{
-      rc = SQLITE_OK;
-    }
-
-    /* Undo the local locks */
-    if( rc==SQLITE_OK ){
-      p->exclMask &= ~mask;
-      p->sharedMask &= ~mask;
-    }
-  }else if( flags & SQLITE_SHM_SHARED ){
-    u16 allShared = 0;  /* Union of locks held by connections other than "p" */
-
-    /* Find out which shared locks are already held by sibling connections.
-    ** If any sibling already holds an exclusive lock, go ahead and return
-    ** SQLITE_BUSY.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-      allShared |= pX->sharedMask;
-    }
-
-    /* Get shared locks at the system level, if necessary */
-    if( rc==SQLITE_OK ){
-      if( (allShared & mask)==0 ){
-        rc = winShmSystemLock(pShmNode, _SHM_RDLCK, ofst+WIN_SHM_BASE, n);
-      }else{
-        rc = SQLITE_OK;
-      }
-    }
-
-    /* Get the local shared locks */
-    if( rc==SQLITE_OK ){
-      p->sharedMask |= mask;
-    }
-  }else{
-    /* Make sure no sibling connections hold locks that will block this
-    ** lock.  If any do, return SQLITE_BUSY right away.
-    */
-    for(pX=pShmNode->pFirst; pX; pX=pX->pNext){
-      if( (pX->exclMask & mask)!=0 || (pX->sharedMask & mask)!=0 ){
-        rc = SQLITE_BUSY;
-        break;
-      }
-    }
-
-    /* Get the exclusive locks at the system level.  Then if successful
-    ** also mark the local connection as being locked.
-    */
-    if( rc==SQLITE_OK ){
-      rc = winShmSystemLock(pShmNode, _SHM_WRLCK, ofst+WIN_SHM_BASE, n);
-      if( rc==SQLITE_OK ){
-        assert( (p->sharedMask & mask)==0 );
-        p->exclMask |= mask;
-      }
-    }
-  }
-  sqlite3_mutex_leave(pShmNode->mutex);
-  OSTRACE(("SHM-LOCK pid=%lu, id=%d, sharedMask=%03x, exclMask=%03x, rc=%s\n",
-           osGetCurrentProcessId(), p->id, p->sharedMask, p->exclMask,
-           sqlite3ErrName(rc)));
-  return rc;
-}
-
-/*
-** Implement a memory barrier or memory fence on shared memory.
-**
-** All loads and stores begun before the barrier must complete before
-** any load or store begun after the barrier.
-*/
-static void winShmBarrier(
-  sqlite3_file *fd          /* Database holding the shared memory */
-){
-  UNUSED_PARAMETER(fd);
-  sqlite3MemoryBarrier();   /* compiler-defined memory barrier */
-  winShmEnterMutex();       /* Also mutex, for redundancy */
-  winShmLeaveMutex();
-}
-
-/*
-** This function is called to obtain a pointer to region iRegion of the
-** shared-memory associated with the database file fd. Shared-memory regions
-** are numbered starting from zero. Each shared-memory region is szRegion
-** bytes in size.
-**
-** If an error occurs, an error code is returned and *pp is set to NULL.
-**
-** Otherwise, if the isWrite parameter is 0 and the requested shared-memory
-** region has not been allocated (by any client, including one running in a
-** separate process), then *pp is set to NULL and SQLITE_OK returned. If
-** isWrite is non-zero and the requested shared-memory region has not yet
-** been allocated, it is allocated by this function.
-**
-** If the shared-memory region has already been allocated or is allocated by
-** this call as described above, then it is mapped into this processes
-** address space (if it is not already), *pp is set to point to the mapped
-** memory and SQLITE_OK returned.
-*/
-static int winShmMap(
-  sqlite3_file *fd,               /* Handle open on database file */
-  int iRegion,                    /* Region to retrieve */
-  int szRegion,                   /* Size of regions */
-  int isWrite,                    /* True to extend file if necessary */
-  void volatile **pp              /* OUT: Mapped memory */
-){
-  winFile *pDbFd = (winFile*)fd;
-  winShm *pShm = pDbFd->pShm;
-  winShmNode *pShmNode;
-  int rc = SQLITE_OK;
-
-  if( !pShm ){
-    rc = winOpenSharedMemory(pDbFd);
-    if( rc!=SQLITE_OK ) return rc;
-    pShm = pDbFd->pShm;
-  }
-  pShmNode = pShm->pShmNode;
-
-  sqlite3_mutex_enter(pShmNode->mutex);
-  assert( szRegion==pShmNode->szRegion || pShmNode->nRegion==0 );
-
-  if( pShmNode->nRegion<=iRegion ){
-    struct ShmRegion *apNew;           /* New aRegion[] array */
-    int nByte = (iRegion+1)*szRegion;  /* Minimum required file size */
-    sqlite3_int64 sz;                  /* Current size of wal-index file */
-
-    pShmNode->szRegion = szRegion;
-
-    /* The requested region is not mapped into this processes address space.
-    ** Check to see if it has been allocated (i.e. if the wal-index file is
-    ** large enough to contain the requested region).
-    */
-    rc = winFileSize((sqlite3_file *)&pShmNode->hFile, &sz);
-    if( rc!=SQLITE_OK ){
-      rc = winLogError(SQLITE_IOERR_SHMSIZE, osGetLastError(),
-                       "winShmMap1", pDbFd->zPath);
-      goto shmpage_out;
-    }
-
-    if( sz<nByte ){
-      /* The requested memory region does not exist. If isWrite is set to
-      ** zero, exit early. *pp will be set to NULL and SQLITE_OK returned.
-      **
-      ** Alternatively, if isWrite is non-zero, use ftruncate() to allocate
-      ** the requested memory region.
-      */
-      if( !isWrite ) goto shmpage_out;
-      rc = winTruncate((sqlite3_file *)&pShmNode->hFile, nByte);
-      if( rc!=SQLITE_OK ){
-        rc = winLogError(SQLITE_IOERR_SHMSIZE, osGetLastError(),
-                         "winShmMap2", pDbFd->zPath);
-        goto shmpage_out;
-      }
-    }
-
-    /* Map the requested memory region into this processes address space. */
-    apNew = (struct ShmRegion *)sqlite3_realloc64(
-        pShmNode->aRegion, (iRegion+1)*sizeof(apNew[0])
-    );
-    if( !apNew ){
-      rc = SQLITE_IOERR_NOMEM;
-      goto shmpage_out;
-    }
-    pShmNode->aRegion = apNew;
-
-    while( pShmNode->nRegion<=iRegion ){
-      HANDLE hMap = NULL;         /* file-mapping handle */
-      void *pMap = 0;             /* Mapped memory region */
-
-#if SQLITE_OS_WINRT
-      hMap = osCreateFileMappingFromApp(pShmNode->hFile.h,
-          NULL, PAGE_READWRITE, nByte, NULL
-      );
-#elif defined(SQLITE_WIN32_HAS_WIDE)
-      hMap = osCreateFileMappingW(pShmNode->hFile.h,
-          NULL, PAGE_READWRITE, 0, nByte, NULL
-      );
-#elif defined(SQLITE_WIN32_HAS_ANSI)
-      hMap = osCreateFileMappingA(pShmNode->hFile.h,
-          NULL, PAGE_READWRITE, 0, nByte, NULL
-      );
-#endif
-      OSTRACE(("SHM-MAP-CREATE pid=%lu, region=%d, size=%d, rc=%s\n",
-               osGetCurrentProcessId(), pShmNode->nRegion, nByte,
-               hMap ? "ok" : "failed"));
-      if( hMap ){
-        int iOffset = pShmNode->nRegion*szRegion;
-        int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
-#if SQLITE_OS_WINRT
-        pMap = osMapViewOfFileFromApp(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
-            iOffset - iOffsetShift, szRegion + iOffsetShift
-        );
-#else
-        pMap = osMapViewOfFile(hMap, FILE_MAP_WRITE | FILE_MAP_READ,
-            0, iOffset - iOffsetShift, szRegion + iOffsetShift
-        );
-#endif
-        OSTRACE(("SHM-MAP-MAP pid=%lu, region=%d, offset=%d, size=%d, rc=%s\n",
-                 osGetCurrentProcessId(), pShmNode->nRegion, iOffset,
-                 szRegion, pMap ? "ok" : "failed"));
-      }
-      if( !pMap ){
-        pShmNode->lastErrno = osGetLastError();
-        rc = winLogError(SQLITE_IOERR_SHMMAP, pShmNode->lastErrno,
-                         "winShmMap3", pDbFd->zPath);
-        if( hMap ) osCloseHandle(hMap);
-        goto shmpage_out;
-      }
-
-      pShmNode->aRegion[pShmNode->nRegion].pMap = pMap;
-      pShmNode->aRegion[pShmNode->nRegion].hMap = hMap;
-      pShmNode->nRegion++;
-    }
-  }
-
-shmpage_out:
-  if( pShmNode->nRegion>iRegion ){
-    int iOffset = iRegion*szRegion;
-    int iOffsetShift = iOffset % winSysInfo.dwAllocationGranularity;
-    char *p = (char *)pShmNode->aRegion[iRegion].pMap;
-    *pp = (void *)&p[iOffsetShift];
-  }else{
-    *pp = 0;
-  }
-  sqlite3_mutex_leave(pShmNode->mutex);
-  return rc;
-}
-
-#else
-# define winShmMap     0
-# define winShmLock    0
-# define winShmBarrier 0
-# define winShmUnmap   0
-#endif /* #ifndef SQLITE_OMIT_WAL */
-
-/*
-** Cleans up the mapped region of the specified file, if any.
-*/
-#if SQLITE_MAX_MMAP_SIZE>0
-static int winUnmapfile(winFile *pFile){
-  assert( pFile!=0 );
-  OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, hMap=%p, pMapRegion=%p, "
-           "mmapSize=%lld, mmapSizeActual=%lld, mmapSizeMax=%lld\n",
-           osGetCurrentProcessId(), pFile, pFile->hMap, pFile->pMapRegion,
-           pFile->mmapSize, pFile->mmapSizeActual, pFile->mmapSizeMax));
-  if( pFile->pMapRegion ){
-    if( !osUnmapViewOfFile(pFile->pMapRegion) ){
-      pFile->lastErrno = osGetLastError();
-      OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, pMapRegion=%p, "
-               "rc=SQLITE_IOERR_MMAP\n", osGetCurrentProcessId(), pFile,
-               pFile->pMapRegion));
-      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
-                         "winUnmapfile1", pFile->zPath);
-    }
-    pFile->pMapRegion = 0;
-    pFile->mmapSize = 0;
-    pFile->mmapSizeActual = 0;
-  }
-  if( pFile->hMap!=NULL ){
-    if( !osCloseHandle(pFile->hMap) ){
-      pFile->lastErrno = osGetLastError();
-      OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, hMap=%p, rc=SQLITE_IOERR_MMAP\n",
-               osGetCurrentProcessId(), pFile, pFile->hMap));
-      return winLogError(SQLITE_IOERR_MMAP, pFile->lastErrno,
-                         "winUnmapfile2", pFile->zPath);
-    }
-    pFile->hMap = NULL;
-  }
-  OSTRACE(("UNMAP-FILE pid=%lu, pFile=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), pFile));
-  return SQLITE_OK;
-}
-
-/*
-** Memory map or remap the file opened by file-descriptor pFd (if the file
-** is already mapped, the existing mapping is replaced by the new). Or, if
-** there already exists a mapping for this file, and there are still
-** outstanding xFetch() references to it, this function is a no-op.
-**
-** If parameter nByte is non-negative, then it is the requested size of
-** the mapping to create. Otherwise, if nByte is less than zero, then the
-** requested size is the size of the file on disk. The actual size of the
-** created mapping is either the requested size or the value configured
-** using SQLITE_FCNTL_MMAP_SIZE, whichever is smaller.
-**
-** SQLITE_OK is returned if no error occurs (even if the mapping is not
-** recreated as a result of outstanding references) or an SQLite error
-** code otherwise.
-*/
-static int winMapfile(winFile *pFd, sqlite3_int64 nByte){
-  sqlite3_int64 nMap = nByte;
-  int rc;
-
-  assert( nMap>=0 || pFd->nFetchOut==0 );
-  OSTRACE(("MAP-FILE pid=%lu, pFile=%p, size=%lld\n",
-           osGetCurrentProcessId(), pFd, nByte));
-
-  if( pFd->nFetchOut>0 ) return SQLITE_OK;
-
-  if( nMap<0 ){
-    rc = winFileSize((sqlite3_file*)pFd, &nMap);
-    if( rc ){
-      OSTRACE(("MAP-FILE pid=%lu, pFile=%p, rc=SQLITE_IOERR_FSTAT\n",
-               osGetCurrentProcessId(), pFd));
-      return SQLITE_IOERR_FSTAT;
-    }
-  }
-  if( nMap>pFd->mmapSizeMax ){
-    nMap = pFd->mmapSizeMax;
-  }
-  nMap &= ~(sqlite3_int64)(winSysInfo.dwPageSize - 1);
-
-  if( nMap==0 && pFd->mmapSize>0 ){
-    winUnmapfile(pFd);
-  }
-  if( nMap!=pFd->mmapSize ){
-    void *pNew = 0;
-    DWORD protect = PAGE_READONLY;
-    DWORD flags = FILE_MAP_READ;
-
-    winUnmapfile(pFd);
-    if( (pFd->ctrlFlags & WINFILE_RDONLY)==0 ){
-      protect = PAGE_READWRITE;
-      flags |= FILE_MAP_WRITE;
-    }
-#if SQLITE_OS_WINRT
-    pFd->hMap = osCreateFileMappingFromApp(pFd->h, NULL, protect, nMap, NULL);
-#elif defined(SQLITE_WIN32_HAS_WIDE)
-    pFd->hMap = osCreateFileMappingW(pFd->h, NULL, protect,
-                                (DWORD)((nMap>>32) & 0xffffffff),
-                                (DWORD)(nMap & 0xffffffff), NULL);
-#elif defined(SQLITE_WIN32_HAS_ANSI)
-    pFd->hMap = osCreateFileMappingA(pFd->h, NULL, protect,
-                                (DWORD)((nMap>>32) & 0xffffffff),
-                                (DWORD)(nMap & 0xffffffff), NULL);
-#endif
-    if( pFd->hMap==NULL ){
-      pFd->lastErrno = osGetLastError();
-      rc = winLogError(SQLITE_IOERR_MMAP, pFd->lastErrno,
-                       "winMapfile1", pFd->zPath);
-      /* Log the error, but continue normal operation using xRead/xWrite */
-      OSTRACE(("MAP-FILE-CREATE pid=%lu, pFile=%p, rc=%s\n",
-               osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
-      return SQLITE_OK;
-    }
-    assert( (nMap % winSysInfo.dwPageSize)==0 );
-    assert( sizeof(SIZE_T)==sizeof(sqlite3_int64) || nMap<=0xffffffff );
-#if SQLITE_OS_WINRT
-    pNew = osMapViewOfFileFromApp(pFd->hMap, flags, 0, (SIZE_T)nMap);
-#else
-    pNew = osMapViewOfFile(pFd->hMap, flags, 0, 0, (SIZE_T)nMap);
-#endif
-    if( pNew==NULL ){
-      osCloseHandle(pFd->hMap);
-      pFd->hMap = NULL;
-      pFd->lastErrno = osGetLastError();
-      rc = winLogError(SQLITE_IOERR_MMAP, pFd->lastErrno,
-                       "winMapfile2", pFd->zPath);
-      /* Log the error, but continue normal operation using xRead/xWrite */
-      OSTRACE(("MAP-FILE-MAP pid=%lu, pFile=%p, rc=%s\n",
-               osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
-      return SQLITE_OK;
-    }
-    pFd->pMapRegion = pNew;
-    pFd->mmapSize = nMap;
-    pFd->mmapSizeActual = nMap;
-  }
-
-  OSTRACE(("MAP-FILE pid=%lu, pFile=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), pFd));
-  return SQLITE_OK;
-}
-#endif /* SQLITE_MAX_MMAP_SIZE>0 */
-
-/*
-** If possible, return a pointer to a mapping of file fd starting at offset
-** iOff. The mapping must be valid for at least nAmt bytes.
-**
-** If such a pointer can be obtained, store it in *pp and return SQLITE_OK.
-** Or, if one cannot but no error occurs, set *pp to 0 and return SQLITE_OK.
-** Finally, if an error does occur, return an SQLite error code. The final
-** value of *pp is undefined in this case.
-**
-** If this function does return a pointer, the caller must eventually
-** release the reference by calling winUnfetch().
-*/
-static int winFetch(sqlite3_file *fd, i64 iOff, int nAmt, void **pp){
-#if SQLITE_MAX_MMAP_SIZE>0
-  winFile *pFd = (winFile*)fd;   /* The underlying database file */
-#endif
-  *pp = 0;
-
-  OSTRACE(("FETCH pid=%lu, pFile=%p, offset=%lld, amount=%d, pp=%p\n",
-           osGetCurrentProcessId(), fd, iOff, nAmt, pp));
-
-#if SQLITE_MAX_MMAP_SIZE>0
-  if( pFd->mmapSizeMax>0 ){
-    if( pFd->pMapRegion==0 ){
-      int rc = winMapfile(pFd, -1);
-      if( rc!=SQLITE_OK ){
-        OSTRACE(("FETCH pid=%lu, pFile=%p, rc=%s\n",
-                 osGetCurrentProcessId(), pFd, sqlite3ErrName(rc)));
-        return rc;
-      }
-    }
-    if( pFd->mmapSize >= iOff+nAmt ){
-      *pp = &((u8 *)pFd->pMapRegion)[iOff];
-      pFd->nFetchOut++;
-    }
-  }
-#endif
-
-  OSTRACE(("FETCH pid=%lu, pFile=%p, pp=%p, *pp=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), fd, pp, *pp));
-  return SQLITE_OK;
-}
-
-/*
-** If the third argument is non-NULL, then this function releases a
-** reference obtained by an earlier call to winFetch(). The second
-** argument passed to this function must be the same as the corresponding
-** argument that was passed to the winFetch() invocation.
-**
-** Or, if the third argument is NULL, then this function is being called
-** to inform the VFS layer that, according to POSIX, any existing mapping
-** may now be invalid and should be unmapped.
-*/
-static int winUnfetch(sqlite3_file *fd, i64 iOff, void *p){
-#if SQLITE_MAX_MMAP_SIZE>0
-  winFile *pFd = (winFile*)fd;   /* The underlying database file */
-
-  /* If p==0 (unmap the entire file) then there must be no outstanding
-  ** xFetch references. Or, if p!=0 (meaning it is an xFetch reference),
-  ** then there must be at least one outstanding.  */
-  assert( (p==0)==(pFd->nFetchOut==0) );
-
-  /* If p!=0, it must match the iOff value. */
-  assert( p==0 || p==&((u8 *)pFd->pMapRegion)[iOff] );
-
-  OSTRACE(("UNFETCH pid=%lu, pFile=%p, offset=%lld, p=%p\n",
-           osGetCurrentProcessId(), pFd, iOff, p));
-
-  if( p ){
-    pFd->nFetchOut--;
-  }else{
-    /* FIXME:  If Windows truly always prevents truncating or deleting a
-    ** file while a mapping is held, then the following winUnmapfile() call
-    ** is unnecessary can be omitted - potentially improving
-    ** performance.  */
-    winUnmapfile(pFd);
-  }
-
-  assert( pFd->nFetchOut>=0 );
-#endif
-
-  OSTRACE(("UNFETCH pid=%lu, pFile=%p, rc=SQLITE_OK\n",
-           osGetCurrentProcessId(), fd));
-  return SQLITE_OK;
-}
-
-/*
-** Here ends the implementation of all sqlite3_file methods.
-**
-********************** End sqlite3_file Methods *******************************
-******************************************************************************/
-
-/*
-** This vector defines all the methods that can operate on an
-** sqlite3_file for win32.
-*/
-static const sqlite3_io_methods winIoMethod = {
-  3,                              /* iVersion */
-  winClose,                       /* xClose */
-  winRead,                        /* xRead */
-  winWrite,                       /* xWrite */
-  winTruncate,                    /* xTruncate */
-  winSync,                        /* xSync */
-  winFileSize,                    /* xFileSize */
-  winLock,                        /* xLock */
-  winUnlock,                      /* xUnlock */
-  winCheckReservedLock,           /* xCheckReservedLock */
-  winFileControl,                 /* xFileControl */
-  winSectorSize,                  /* xSectorSize */
-  winDeviceCharacteristics,       /* xDeviceCharacteristics */
-  winShmMap,                      /* xShmMap */
-  winShmLock,                     /* xShmLock */
-  winShmBarrier,                  /* xShmBarrier */
-  winShmUnmap,                    /* xShmUnmap */
-  winFetch,                       /* xFetch */
-  winUnfetch                      /* xUnfetch */
-};
-
-/****************************************************************************
-**************************** sqlite3_vfs methods ****************************
-**
-** This division contains the implementation of methods on the
-** sqlite3_vfs object.
-*/
-
-#if defined(__CYGWIN__)
-/*
-** Convert a filename from whatever the underlying operating system
-** supports for filenames into UTF-8.  Space to hold the result is
-** obtained from malloc and must be freed by the calling function.
-*/
-static char *winConvertToUtf8Filename(const void *zFilename){
-  char *zConverted = 0;
-  if( osIsNT() ){
-    zConverted = winUnicodeToUtf8(zFilename);
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    zConverted = sqlite3_win32_mbcs_to_utf8(zFilename);
-  }
-#endif
-  /* caller will handle out of memory */
-  return zConverted;
-}
-#endif
-
-/*
-** Convert a UTF-8 filename into whatever form the underlying
-** operating system wants filenames in.  Space to hold the result
-** is obtained from malloc and must be freed by the calling
-** function.
-*/
-static void *winConvertFromUtf8Filename(const char *zFilename){
-  void *zConverted = 0;
-  if( osIsNT() ){
-    zConverted = winUtf8ToUnicode(zFilename);
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    zConverted = sqlite3_win32_utf8_to_mbcs(zFilename);
-  }
-#endif
-  /* caller will handle out of memory */
-  return zConverted;
-}
-
-/*
-** This function returns non-zero if the specified UTF-8 string buffer
-** ends with a directory separator character or one was successfully
-** added to it.
-*/
-static int winMakeEndInDirSep(int nBuf, char *zBuf){
-  if( zBuf ){
-    int nLen = sqlite3Strlen30(zBuf);
-    if( nLen>0 ){
-      if( winIsDirSep(zBuf[nLen-1]) ){
-        return 1;
-      }else if( nLen+1<nBuf ){
-        zBuf[nLen] = winGetDirSep();
-        zBuf[nLen+1] = '\0';
-        return 1;
-      }
-    }
-  }
-  return 0;
-}
-
-/*
-** Create a temporary file name and store the resulting pointer into pzBuf.
-** The pointer returned in pzBuf must be freed via sqlite3_free().
-*/
-static int winGetTempname(sqlite3_vfs *pVfs, char **pzBuf){
-  static char zChars[] =
-    "abcdefghijklmnopqrstuvwxyz"
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-    "0123456789";
-  size_t i, j;
-  int nPre = sqlite3Strlen30(SQLITE_TEMP_FILE_PREFIX);
-  int nMax, nBuf, nDir, nLen;
-  char *zBuf;
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing.
-  */
-  SimulateIOError( return SQLITE_IOERR );
-
-  /* Allocate a temporary buffer to store the fully qualified file
-  ** name for the temporary file.  If this fails, we cannot continue.
-  */
-  nMax = pVfs->mxPathname; nBuf = nMax + 2;
-  zBuf = sqlite3MallocZero( nBuf );
-  if( !zBuf ){
-    OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-    return SQLITE_IOERR_NOMEM;
-  }
-
-  /* Figure out the effective temporary directory.  First, check if one
-  ** has been explicitly set by the application; otherwise, use the one
-  ** configured by the operating system.
-  */
-  nDir = nMax - (nPre + 15);
-  assert( nDir>0 );
-  if( sqlite3_temp_directory ){
-    int nDirLen = sqlite3Strlen30(sqlite3_temp_directory);
-    if( nDirLen>0 ){
-      if( !winIsDirSep(sqlite3_temp_directory[nDirLen-1]) ){
-        nDirLen++;
-      }
-      if( nDirLen>nDir ){
-        sqlite3_free(zBuf);
-        OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
-        return winLogError(SQLITE_ERROR, 0, "winGetTempname1", 0);
-      }
-      sqlite3_snprintf(nMax, zBuf, "%s", sqlite3_temp_directory);
-    }
-  }
-#if defined(__CYGWIN__)
-  else{
-    static const char *azDirs[] = {
-       0, /* getenv("SQLITE_TMPDIR") */
-       0, /* getenv("TMPDIR") */
-       0, /* getenv("TMP") */
-       0, /* getenv("TEMP") */
-       0, /* getenv("USERPROFILE") */
-       "/var/tmp",
-       "/usr/tmp",
-       "/tmp",
-       ".",
-       0        /* List terminator */
-    };
-    unsigned int i;
-    const char *zDir = 0;
-
-    if( !azDirs[0] ) azDirs[0] = getenv("SQLITE_TMPDIR");
-    if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
-    if( !azDirs[2] ) azDirs[2] = getenv("TMP");
-    if( !azDirs[3] ) azDirs[3] = getenv("TEMP");
-    if( !azDirs[4] ) azDirs[4] = getenv("USERPROFILE");
-    for(i=0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
-      void *zConverted;
-      if( zDir==0 ) continue;
-      /* If the path starts with a drive letter followed by the colon
-      ** character, assume it is already a native Win32 path; otherwise,
-      ** it must be converted to a native Win32 path via the Cygwin API
-      ** prior to using it.
-      */
-      if( winIsDriveLetterAndColon(zDir) ){
-        zConverted = winConvertFromUtf8Filename(zDir);
-        if( !zConverted ){
-          sqlite3_free(zBuf);
-          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-          return SQLITE_IOERR_NOMEM;
-        }
-        if( winIsDir(zConverted) ){
-          sqlite3_snprintf(nMax, zBuf, "%s", zDir);
-          sqlite3_free(zConverted);
-          break;
-        }
-        sqlite3_free(zConverted);
-      }else{
-        zConverted = sqlite3MallocZero( nMax+1 );
-        if( !zConverted ){
-          sqlite3_free(zBuf);
-          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-          return SQLITE_IOERR_NOMEM;
-        }
-        if( cygwin_conv_path(
-                osIsNT() ? CCP_POSIX_TO_WIN_W : CCP_POSIX_TO_WIN_A, zDir,
-                zConverted, nMax+1)<0 ){
-          sqlite3_free(zConverted);
-          sqlite3_free(zBuf);
-          OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_CONVPATH\n"));
-          return winLogError(SQLITE_IOERR_CONVPATH, (DWORD)errno,
-                             "winGetTempname2", zDir);
-        }
-        if( winIsDir(zConverted) ){
-          /* At this point, we know the candidate directory exists and should
-          ** be used.  However, we may need to convert the string containing
-          ** its name into UTF-8 (i.e. if it is UTF-16 right now).
-          */
-          char *zUtf8 = winConvertToUtf8Filename(zConverted);
-          if( !zUtf8 ){
-            sqlite3_free(zConverted);
-            sqlite3_free(zBuf);
-            OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-            return SQLITE_IOERR_NOMEM;
-          }
-          sqlite3_snprintf(nMax, zBuf, "%s", zUtf8);
-          sqlite3_free(zUtf8);
-          sqlite3_free(zConverted);
-          break;
-        }
-        sqlite3_free(zConverted);
-      }
-    }
-  }
-#elif !SQLITE_OS_WINRT && !defined(__CYGWIN__)
-  else if( osIsNT() ){
-    char *zMulti;
-    LPWSTR zWidePath = sqlite3MallocZero( nMax*sizeof(WCHAR) );
-    if( !zWidePath ){
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-      return SQLITE_IOERR_NOMEM;
-    }
-    if( osGetTempPathW(nMax, zWidePath)==0 ){
-      sqlite3_free(zWidePath);
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_GETTEMPPATH\n"));
-      return winLogError(SQLITE_IOERR_GETTEMPPATH, osGetLastError(),
-                         "winGetTempname2", 0);
-    }
-    zMulti = winUnicodeToUtf8(zWidePath);
-    if( zMulti ){
-      sqlite3_snprintf(nMax, zBuf, "%s", zMulti);
-      sqlite3_free(zMulti);
-      sqlite3_free(zWidePath);
-    }else{
-      sqlite3_free(zWidePath);
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-      return SQLITE_IOERR_NOMEM;
-    }
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    char *zUtf8;
-    char *zMbcsPath = sqlite3MallocZero( nMax );
-    if( !zMbcsPath ){
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-      return SQLITE_IOERR_NOMEM;
-    }
-    if( osGetTempPathA(nMax, zMbcsPath)==0 ){
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_GETTEMPPATH\n"));
-      return winLogError(SQLITE_IOERR_GETTEMPPATH, osGetLastError(),
-                         "winGetTempname3", 0);
-    }
-    zUtf8 = sqlite3_win32_mbcs_to_utf8(zMbcsPath);
-    if( zUtf8 ){
-      sqlite3_snprintf(nMax, zBuf, "%s", zUtf8);
-      sqlite3_free(zUtf8);
-    }else{
-      sqlite3_free(zBuf);
-      OSTRACE(("TEMP-FILENAME rc=SQLITE_IOERR_NOMEM\n"));
-      return SQLITE_IOERR_NOMEM;
-    }
-  }
-#endif /* SQLITE_WIN32_HAS_ANSI */
-#endif /* !SQLITE_OS_WINRT */
-
-  /*
-  ** Check to make sure the temporary directory ends with an appropriate
-  ** separator.  If it does not and there is not enough space left to add
-  ** one, fail.
-  */
-  if( !winMakeEndInDirSep(nDir+1, zBuf) ){
-    sqlite3_free(zBuf);
-    OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
-    return winLogError(SQLITE_ERROR, 0, "winGetTempname4", 0);
-  }
-
-  /*
-  ** Check that the output buffer is large enough for the temporary file
-  ** name in the following format:
-  **
-  **   "<temporary_directory>/etilqs_XXXXXXXXXXXXXXX\0\0"
-  **
-  ** If not, return SQLITE_ERROR.  The number 17 is used here in order to
-  ** account for the space used by the 15 character random suffix and the
-  ** two trailing NUL characters.  The final directory separator character
-  ** has already added if it was not already present.
-  */
-  nLen = sqlite3Strlen30(zBuf);
-  if( (nLen + nPre + 17) > nBuf ){
-    sqlite3_free(zBuf);
-    OSTRACE(("TEMP-FILENAME rc=SQLITE_ERROR\n"));
-    return winLogError(SQLITE_ERROR, 0, "winGetTempname5", 0);
-  }
-
-  sqlite3_snprintf(nBuf-16-nLen, zBuf+nLen, SQLITE_TEMP_FILE_PREFIX);
-
-  j = sqlite3Strlen30(zBuf);
-  sqlite3_randomness(15, &zBuf[j]);
-  for(i=0; i<15; i++, j++){
-    zBuf[j] = (char)zChars[ ((unsigned char)zBuf[j])%(sizeof(zChars)-1) ];
-  }
-  zBuf[j] = 0;
-  zBuf[j+1] = 0;
-  *pzBuf = zBuf;
-
-  OSTRACE(("TEMP-FILENAME name=%s, rc=SQLITE_OK\n", zBuf));
-  return SQLITE_OK;
-}
-
-/*
-** Return TRUE if the named file is really a directory.  Return false if
-** it is something other than a directory, or if there is any kind of memory
-** allocation failure.
-*/
-static int winIsDir(const void *zConverted){
-  DWORD attr;
-  int rc = 0;
-  DWORD lastErrno;
-
-  if( osIsNT() ){
-    int cnt = 0;
-    WIN32_FILE_ATTRIBUTE_DATA sAttrData;
-    memset(&sAttrData, 0, sizeof(sAttrData));
-    while( !(rc = osGetFileAttributesExW((LPCWSTR)zConverted,
-                             GetFileExInfoStandard,
-                             &sAttrData)) && winRetryIoerr(&cnt, &lastErrno) ){}
-    if( !rc ){
-      return 0; /* Invalid name? */
-    }
-    attr = sAttrData.dwFileAttributes;
-#if SQLITE_OS_WINCE==0
-  }else{
-    attr = osGetFileAttributesA((char*)zConverted);
-#endif
-  }
-  return (attr!=INVALID_FILE_ATTRIBUTES) && (attr&FILE_ATTRIBUTE_DIRECTORY);
-}
-
-/*
-** Open a file.
-*/
-static int winOpen(
-  sqlite3_vfs *pVfs,        /* Used to get maximum path name length */
-  const char *zName,        /* Name of the file (UTF-8) */
-  sqlite3_file *id,         /* Write the SQLite file handle here */
-  int flags,                /* Open mode flags */
-  int *pOutFlags            /* Status return flags */
-){
-  HANDLE h;
-  DWORD lastErrno = 0;
-  DWORD dwDesiredAccess;
-  DWORD dwShareMode;
-  DWORD dwCreationDisposition;
-  DWORD dwFlagsAndAttributes = 0;
-#if SQLITE_OS_WINCE
-  int isTemp = 0;
-#endif
-  winFile *pFile = (winFile*)id;
-  void *zConverted;              /* Filename in OS encoding */
-  const char *zUtf8Name = zName; /* Filename in UTF-8 encoding */
-  int cnt = 0;
-
-  /* If argument zPath is a NULL pointer, this function is required to open
-  ** a temporary file. Use this buffer to store the file name in.
-  */
-  char *zTmpname = 0; /* For temporary filename, if necessary. */
-
-  int rc = SQLITE_OK;            /* Function Return Code */
-#if !defined(NDEBUG) || SQLITE_OS_WINCE
-  int eType = flags&0xFFFFFF00;  /* Type of file to open */
-#endif
-
-  int isExclusive  = (flags & SQLITE_OPEN_EXCLUSIVE);
-  int isDelete     = (flags & SQLITE_OPEN_DELETEONCLOSE);
-  int isCreate     = (flags & SQLITE_OPEN_CREATE);
-  int isReadonly   = (flags & SQLITE_OPEN_READONLY);
-  int isReadWrite  = (flags & SQLITE_OPEN_READWRITE);
-
-#ifndef NDEBUG
-  int isOpenJournal = (isCreate && (
-        eType==SQLITE_OPEN_MASTER_JOURNAL
-     || eType==SQLITE_OPEN_MAIN_JOURNAL
-     || eType==SQLITE_OPEN_WAL
-  ));
-#endif
-
-  OSTRACE(("OPEN name=%s, pFile=%p, flags=%x, pOutFlags=%p\n",
-           zUtf8Name, id, flags, pOutFlags));
-
-  /* Check the following statements are true:
-  **
-  **   (a) Exactly one of the READWRITE and READONLY flags must be set, and
-  **   (b) if CREATE is set, then READWRITE must also be set, and
-  **   (c) if EXCLUSIVE is set, then CREATE must also be set.
-  **   (d) if DELETEONCLOSE is set, then CREATE must also be set.
-  */
-  assert((isReadonly==0 || isReadWrite==0) && (isReadWrite || isReadonly));
-  assert(isCreate==0 || isReadWrite);
-  assert(isExclusive==0 || isCreate);
-  assert(isDelete==0 || isCreate);
-
-  /* The main DB, main journal, WAL file and master journal are never
-  ** automatically deleted. Nor are they ever temporary files.  */
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_DB );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MAIN_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_MASTER_JOURNAL );
-  assert( (!isDelete && zName) || eType!=SQLITE_OPEN_WAL );
-
-  /* Assert that the upper layer has set one of the "file-type" flags. */
-  assert( eType==SQLITE_OPEN_MAIN_DB      || eType==SQLITE_OPEN_TEMP_DB
-       || eType==SQLITE_OPEN_MAIN_JOURNAL || eType==SQLITE_OPEN_TEMP_JOURNAL
-       || eType==SQLITE_OPEN_SUBJOURNAL   || eType==SQLITE_OPEN_MASTER_JOURNAL
-       || eType==SQLITE_OPEN_TRANSIENT_DB || eType==SQLITE_OPEN_WAL
-  );
-
-  assert( pFile!=0 );
-  memset(pFile, 0, sizeof(winFile));
-  pFile->h = INVALID_HANDLE_VALUE;
-
-#if SQLITE_OS_WINRT
-  if( !zUtf8Name && !sqlite3_temp_directory ){
-    sqlite3_log(SQLITE_ERROR,
-        "sqlite3_temp_directory variable should be set for WinRT");
-  }
-#endif
-
-  /* If the second argument to this function is NULL, generate a
-  ** temporary file name to use
-  */
-  if( !zUtf8Name ){
-    assert( isDelete && !isOpenJournal );
-    rc = winGetTempname(pVfs, &zTmpname);
-    if( rc!=SQLITE_OK ){
-      OSTRACE(("OPEN name=%s, rc=%s", zUtf8Name, sqlite3ErrName(rc)));
-      return rc;
-    }
-    zUtf8Name = zTmpname;
-  }
-
-  /* Database filenames are double-zero terminated if they are not
-  ** URIs with parameters.  Hence, they can always be passed into
-  ** sqlite3_uri_parameter().
-  */
-  assert( (eType!=SQLITE_OPEN_MAIN_DB) || (flags & SQLITE_OPEN_URI) ||
-       zUtf8Name[sqlite3Strlen30(zUtf8Name)+1]==0 );
-
-  /* Convert the filename to the system encoding. */
-  zConverted = winConvertFromUtf8Filename(zUtf8Name);
-  if( zConverted==0 ){
-    sqlite3_free(zTmpname);
-    OSTRACE(("OPEN name=%s, rc=SQLITE_IOERR_NOMEM", zUtf8Name));
-    return SQLITE_IOERR_NOMEM;
-  }
-
-  if( winIsDir(zConverted) ){
-    sqlite3_free(zConverted);
-    sqlite3_free(zTmpname);
-    OSTRACE(("OPEN name=%s, rc=SQLITE_CANTOPEN_ISDIR", zUtf8Name));
-    return SQLITE_CANTOPEN_ISDIR;
-  }
-
-  if( isReadWrite ){
-    dwDesiredAccess = GENERIC_READ | GENERIC_WRITE;
-  }else{
-    dwDesiredAccess = GENERIC_READ;
-  }
-
-  /* SQLITE_OPEN_EXCLUSIVE is used to make sure that a new file is
-  ** created. SQLite doesn't use it to indicate "exclusive access"
-  ** as it is usually understood.
-  */
-  if( isExclusive ){
-    /* Creates a new file, only if it does not already exist. */
-    /* If the file exists, it fails. */
-    dwCreationDisposition = CREATE_NEW;
-  }else if( isCreate ){
-    /* Open existing file, or create if it doesn't exist */
-    dwCreationDisposition = OPEN_ALWAYS;
-  }else{
-    /* Opens a file, only if it exists. */
-    dwCreationDisposition = OPEN_EXISTING;
-  }
-
-  dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
-
-  if( isDelete ){
-#if SQLITE_OS_WINCE
-    dwFlagsAndAttributes = FILE_ATTRIBUTE_HIDDEN;
-    isTemp = 1;
-#else
-    dwFlagsAndAttributes = FILE_ATTRIBUTE_TEMPORARY
-                               | FILE_ATTRIBUTE_HIDDEN
-                               | FILE_FLAG_DELETE_ON_CLOSE;
-#endif
-  }else{
-    dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
-  }
-  /* Reports from the internet are that performance is always
-  ** better if FILE_FLAG_RANDOM_ACCESS is used.  Ticket #2699. */
-#if SQLITE_OS_WINCE
-  dwFlagsAndAttributes |= FILE_FLAG_RANDOM_ACCESS;
-#endif
-
-  if( osIsNT() ){
-#if SQLITE_OS_WINRT
-    CREATEFILE2_EXTENDED_PARAMETERS extendedParameters;
-    extendedParameters.dwSize = sizeof(CREATEFILE2_EXTENDED_PARAMETERS);
-    extendedParameters.dwFileAttributes =
-            dwFlagsAndAttributes & FILE_ATTRIBUTE_MASK;
-    extendedParameters.dwFileFlags = dwFlagsAndAttributes & FILE_FLAG_MASK;
-    extendedParameters.dwSecurityQosFlags = SECURITY_ANONYMOUS;
-    extendedParameters.lpSecurityAttributes = NULL;
-    extendedParameters.hTemplateFile = NULL;
-    while( (h = osCreateFile2((LPCWSTR)zConverted,
-                              dwDesiredAccess,
-                              dwShareMode,
-                              dwCreationDisposition,
-                              &extendedParameters))==INVALID_HANDLE_VALUE &&
-                              winRetryIoerr(&cnt, &lastErrno) ){
-               /* Noop */
-    }
-#else
-    while( (h = osCreateFileW((LPCWSTR)zConverted,
-                              dwDesiredAccess,
-                              dwShareMode, NULL,
-                              dwCreationDisposition,
-                              dwFlagsAndAttributes,
-                              NULL))==INVALID_HANDLE_VALUE &&
-                              winRetryIoerr(&cnt, &lastErrno) ){
-               /* Noop */
-    }
-#endif
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    while( (h = osCreateFileA((LPCSTR)zConverted,
-                              dwDesiredAccess,
-                              dwShareMode, NULL,
-                              dwCreationDisposition,
-                              dwFlagsAndAttributes,
-                              NULL))==INVALID_HANDLE_VALUE &&
-                              winRetryIoerr(&cnt, &lastErrno) ){
-               /* Noop */
-    }
-  }
-#endif
-  winLogIoerr(cnt, __LINE__);
-
-  OSTRACE(("OPEN file=%p, name=%s, access=%lx, rc=%s\n", h, zUtf8Name,
-           dwDesiredAccess, (h==INVALID_HANDLE_VALUE) ? "failed" : "ok"));
-
-  if( h==INVALID_HANDLE_VALUE ){
-    pFile->lastErrno = lastErrno;
-    winLogError(SQLITE_CANTOPEN, pFile->lastErrno, "winOpen", zUtf8Name);
-    sqlite3_free(zConverted);
-    sqlite3_free(zTmpname);
-    if( isReadWrite && !isExclusive ){
-      return winOpen(pVfs, zName, id,
-         ((flags|SQLITE_OPEN_READONLY) &
-                     ~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE)),
-         pOutFlags);
-    }else{
-      return SQLITE_CANTOPEN_BKPT;
-    }
-  }
-
-  if( pOutFlags ){
-    if( isReadWrite ){
-      *pOutFlags = SQLITE_OPEN_READWRITE;
-    }else{
-      *pOutFlags = SQLITE_OPEN_READONLY;
-    }
-  }
-
-  OSTRACE(("OPEN file=%p, name=%s, access=%lx, pOutFlags=%p, *pOutFlags=%d, "
-           "rc=%s\n", h, zUtf8Name, dwDesiredAccess, pOutFlags, pOutFlags ?
-           *pOutFlags : 0, (h==INVALID_HANDLE_VALUE) ? "failed" : "ok"));
-
-#if SQLITE_OS_WINCE
-  if( isReadWrite && eType==SQLITE_OPEN_MAIN_DB
-       && (rc = winceCreateLock(zName, pFile))!=SQLITE_OK
-  ){
-    osCloseHandle(h);
-    sqlite3_free(zConverted);
-    sqlite3_free(zTmpname);
-    OSTRACE(("OPEN-CE-LOCK name=%s, rc=%s\n", zName, sqlite3ErrName(rc)));
-    return rc;
-  }
-  if( isTemp ){
-    pFile->zDeleteOnClose = zConverted;
-  }else
-#endif
-  {
-    sqlite3_free(zConverted);
-  }
-
-  sqlite3_free(zTmpname);
-  pFile->pMethod = &winIoMethod;
-  pFile->pVfs = pVfs;
-  pFile->h = h;
-  if( isReadonly ){
-    pFile->ctrlFlags |= WINFILE_RDONLY;
-  }
-  pFile->lastErrno = NO_ERROR;
-  pFile->zPath = zName;
-#if SQLITE_MAX_MMAP_SIZE>0
-  pFile->hMap = NULL;
-  pFile->pMapRegion = 0;
-  pFile->mmapSize = 0;
-  pFile->mmapSizeActual = 0;
-  pFile->mmapSizeMax = sqlite3GlobalConfig.szMmap;
-#endif
-
-  OpenCounter(+1);
-  return rc;
-}
-
-/*
-** Delete the named file.
-**
-** Note that Windows does not allow a file to be deleted if some other
-** process has it open.  Sometimes a virus scanner or indexing program
-** will open a journal file shortly after it is created in order to do
-** whatever it does.  While this other process is holding the
-** file open, we will be unable to delete it.  To work around this
-** problem, we delay 100 milliseconds and try to delete again.  Up
-** to MX_DELETION_ATTEMPTs deletion attempts are run before giving
-** up and returning an error.
-*/
-static int winDelete(
-  sqlite3_vfs *pVfs,          /* Not used on win32 */
-  const char *zFilename,      /* Name of file to delete */
-  int syncDir                 /* Not used on win32 */
-){
-  int cnt = 0;
-  int rc;
-  DWORD attr;
-  DWORD lastErrno = 0;
-  void *zConverted;
-  UNUSED_PARAMETER(pVfs);
-  UNUSED_PARAMETER(syncDir);
-
-  SimulateIOError(return SQLITE_IOERR_DELETE);
-  OSTRACE(("DELETE name=%s, syncDir=%d\n", zFilename, syncDir));
-
-  zConverted = winConvertFromUtf8Filename(zFilename);
-  if( zConverted==0 ){
-    OSTRACE(("DELETE name=%s, rc=SQLITE_IOERR_NOMEM\n", zFilename));
-    return SQLITE_IOERR_NOMEM;
-  }
-  if( osIsNT() ){
-    do {
-#if SQLITE_OS_WINRT
-      WIN32_FILE_ATTRIBUTE_DATA sAttrData;
-      memset(&sAttrData, 0, sizeof(sAttrData));
-      if ( osGetFileAttributesExW(zConverted, GetFileExInfoStandard,
-                                  &sAttrData) ){
-        attr = sAttrData.dwFileAttributes;
-      }else{
-        lastErrno = osGetLastError();
-        if( lastErrno==ERROR_FILE_NOT_FOUND
-         || lastErrno==ERROR_PATH_NOT_FOUND ){
-          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
-        }else{
-          rc = SQLITE_ERROR;
-        }
-        break;
-      }
-#else
-      attr = osGetFileAttributesW(zConverted);
-#endif
-      if ( attr==INVALID_FILE_ATTRIBUTES ){
-        lastErrno = osGetLastError();
-        if( lastErrno==ERROR_FILE_NOT_FOUND
-         || lastErrno==ERROR_PATH_NOT_FOUND ){
-          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
-        }else{
-          rc = SQLITE_ERROR;
-        }
-        break;
-      }
-      if ( attr&FILE_ATTRIBUTE_DIRECTORY ){
-        rc = SQLITE_ERROR; /* Files only. */
-        break;
-      }
-      if ( osDeleteFileW(zConverted) ){
-        rc = SQLITE_OK; /* Deleted OK. */
-        break;
-      }
-      if ( !winRetryIoerr(&cnt, &lastErrno) ){
-        rc = SQLITE_ERROR; /* No more retries. */
-        break;
-      }
-    } while(1);
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    do {
-      attr = osGetFileAttributesA(zConverted);
-      if ( attr==INVALID_FILE_ATTRIBUTES ){
-        lastErrno = osGetLastError();
-        if( lastErrno==ERROR_FILE_NOT_FOUND
-         || lastErrno==ERROR_PATH_NOT_FOUND ){
-          rc = SQLITE_IOERR_DELETE_NOENT; /* Already gone? */
-        }else{
-          rc = SQLITE_ERROR;
-        }
-        break;
-      }
-      if ( attr&FILE_ATTRIBUTE_DIRECTORY ){
-        rc = SQLITE_ERROR; /* Files only. */
-        break;
-      }
-      if ( osDeleteFileA(zConverted) ){
-        rc = SQLITE_OK; /* Deleted OK. */
-        break;
-      }
-      if ( !winRetryIoerr(&cnt, &lastErrno) ){
-        rc = SQLITE_ERROR; /* No more retries. */
-        break;
-      }
-    } while(1);
-  }
-#endif
-  if( rc && rc!=SQLITE_IOERR_DELETE_NOENT ){
-    rc = winLogError(SQLITE_IOERR_DELETE, lastErrno, "winDelete", zFilename);
-  }else{
-    winLogIoerr(cnt, __LINE__);
-  }
-  sqlite3_free(zConverted);
-  OSTRACE(("DELETE name=%s, rc=%s\n", zFilename, sqlite3ErrName(rc)));
-  return rc;
-}
-
-/*
-** Check the existence and status of a file.
-*/
-static int winAccess(
-  sqlite3_vfs *pVfs,         /* Not used on win32 */
-  const char *zFilename,     /* Name of file to check */
-  int flags,                 /* Type of test to make on this file */
-  int *pResOut               /* OUT: Result */
-){
-  DWORD attr;
-  int rc = 0;
-  DWORD lastErrno = 0;
-  void *zConverted;
-  UNUSED_PARAMETER(pVfs);
-
-  SimulateIOError( return SQLITE_IOERR_ACCESS; );
-  OSTRACE(("ACCESS name=%s, flags=%x, pResOut=%p\n",
-           zFilename, flags, pResOut));
-
-  zConverted = winConvertFromUtf8Filename(zFilename);
-  if( zConverted==0 ){
-    OSTRACE(("ACCESS name=%s, rc=SQLITE_IOERR_NOMEM\n", zFilename));
-    return SQLITE_IOERR_NOMEM;
-  }
-  if( osIsNT() ){
-    int cnt = 0;
-    WIN32_FILE_ATTRIBUTE_DATA sAttrData;
-    memset(&sAttrData, 0, sizeof(sAttrData));
-    while( !(rc = osGetFileAttributesExW((LPCWSTR)zConverted,
-                             GetFileExInfoStandard,
-                             &sAttrData)) && winRetryIoerr(&cnt, &lastErrno) ){}
-    if( rc ){
-      /* For an SQLITE_ACCESS_EXISTS query, treat a zero-length file
-      ** as if it does not exist.
-      */
-      if(    flags==SQLITE_ACCESS_EXISTS
-          && sAttrData.nFileSizeHigh==0
-          && sAttrData.nFileSizeLow==0 ){
-        attr = INVALID_FILE_ATTRIBUTES;
-      }else{
-        attr = sAttrData.dwFileAttributes;
-      }
-    }else{
-      winLogIoerr(cnt, __LINE__);
-      if( lastErrno!=ERROR_FILE_NOT_FOUND && lastErrno!=ERROR_PATH_NOT_FOUND ){
-        sqlite3_free(zConverted);
-        return winLogError(SQLITE_IOERR_ACCESS, lastErrno, "winAccess",
-                           zFilename);
-      }else{
-        attr = INVALID_FILE_ATTRIBUTES;
-      }
-    }
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    attr = osGetFileAttributesA((char*)zConverted);
-  }
-#endif
-  sqlite3_free(zConverted);
-  switch( flags ){
-    case SQLITE_ACCESS_READ:
-    case SQLITE_ACCESS_EXISTS:
-      rc = attr!=INVALID_FILE_ATTRIBUTES;
-      break;
-    case SQLITE_ACCESS_READWRITE:
-      rc = attr!=INVALID_FILE_ATTRIBUTES &&
-             (attr & FILE_ATTRIBUTE_READONLY)==0;
-      break;
-    default:
-      assert(!"Invalid flags argument");
-  }
-  *pResOut = rc;
-  OSTRACE(("ACCESS name=%s, pResOut=%p, *pResOut=%d, rc=SQLITE_OK\n",
-           zFilename, pResOut, *pResOut));
-  return SQLITE_OK;
-}
-
-/*
-** Returns non-zero if the specified path name starts with a drive letter
-** followed by a colon character.
-*/
-static BOOL winIsDriveLetterAndColon(
-  const char *zPathname
-){
-  return ( sqlite3Isalpha(zPathname[0]) && zPathname[1]==':' );
-}
-
-/*
-** Turn a relative pathname into a full pathname.  Write the full
-** pathname into zOut[].  zOut[] will be at least pVfs->mxPathname
-** bytes in size.
-*/
-static int winFullPathname(
-  sqlite3_vfs *pVfs,            /* Pointer to vfs object */
-  const char *zRelative,        /* Possibly relative input path */
-  int nFull,                    /* Size of output buffer in bytes */
-  char *zFull                   /* Output buffer */
-){
-
-#if defined(__CYGWIN__)
-  SimulateIOError( return SQLITE_ERROR );
-  UNUSED_PARAMETER(nFull);
-  assert( nFull>=pVfs->mxPathname );
-  char *zOut = sqlite3MallocZero( pVfs->mxPathname+1 );
-  if( !zOut ){
-    return SQLITE_IOERR_NOMEM;
-  }
-  if( cygwin_conv_path(
-          (osIsNT() ? CCP_POSIX_TO_WIN_W : CCP_POSIX_TO_WIN_A),
-          zRelative, zOut, pVfs->mxPathname+1)<0 ){
-    sqlite3_free(zOut);
-    return winLogError(SQLITE_CANTOPEN_CONVPATH, (DWORD)errno,
-                       "winFullPathname2", zRelative);
-  }else{
-    char *zUtf8 = winConvertToUtf8Filename(zOut);
-    if( !zUtf8 ){
-      sqlite3_free(zOut);
-      return SQLITE_IOERR_NOMEM;
-    }
-    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zUtf8);
-    sqlite3_free(zUtf8);
-    sqlite3_free(zOut);
-  }
-  return SQLITE_OK;
-#endif
-
-#if (SQLITE_OS_WINCE || SQLITE_OS_WINRT) && !defined(__CYGWIN__)
-  SimulateIOError( return SQLITE_ERROR );
-  /* WinCE has no concept of a relative pathname, or so I am told. */
-  /* WinRT has no way to convert a relative path to an absolute one. */
-  sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zRelative);
-  return SQLITE_OK;
-#endif
-
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && !defined(__CYGWIN__)
-  DWORD nByte;
-  void *zConverted;
-  char *zOut;
-
-  /* If this path name begins with "/X:", where "X" is any alphabetic
-  ** character, discard the initial "/" from the pathname.
-  */
-  if( zRelative[0]=='/' && winIsDriveLetterAndColon(zRelative+1) ){
-    zRelative++;
-  }
-
-  /* It's odd to simulate an io-error here, but really this is just
-  ** using the io-error infrastructure to test that SQLite handles this
-  ** function failing. This function could fail if, for example, the
-  ** current working directory has been unlinked.
-  */
-  SimulateIOError( return SQLITE_ERROR );
-  zConverted = winConvertFromUtf8Filename(zRelative);
-  if( zConverted==0 ){
-    return SQLITE_IOERR_NOMEM;
-  }
-  if( osIsNT() ){
-    LPWSTR zTemp;
-    nByte = osGetFullPathNameW((LPCWSTR)zConverted, 0, 0, 0);
-    if( nByte==0 ){
-      sqlite3_free(zConverted);
-      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
-                         "winFullPathname1", zRelative);
-    }
-    nByte += 3;
-    zTemp = sqlite3MallocZero( nByte*sizeof(zTemp[0]) );
-    if( zTemp==0 ){
-      sqlite3_free(zConverted);
-      return SQLITE_IOERR_NOMEM;
-    }
-    nByte = osGetFullPathNameW((LPCWSTR)zConverted, nByte, zTemp, 0);
-    if( nByte==0 ){
-      sqlite3_free(zConverted);
-      sqlite3_free(zTemp);
-      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
-                         "winFullPathname2", zRelative);
-    }
-    sqlite3_free(zConverted);
-    zOut = winUnicodeToUtf8(zTemp);
-    sqlite3_free(zTemp);
-  }
-#ifdef SQLITE_WIN32_HAS_ANSI
-  else{
-    char *zTemp;
-    nByte = osGetFullPathNameA((char*)zConverted, 0, 0, 0);
-    if( nByte==0 ){
-      sqlite3_free(zConverted);
-      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
-                         "winFullPathname3", zRelative);
-    }
-    nByte += 3;
-    zTemp = sqlite3MallocZero( nByte*sizeof(zTemp[0]) );
-    if( zTemp==0 ){
-      sqlite3_free(zConverted);
-      return SQLITE_IOERR_NOMEM;
-    }
-    nByte = osGetFullPathNameA((char*)zConverted, nByte, zTemp, 0);
-    if( nByte==0 ){
-      sqlite3_free(zConverted);
-      sqlite3_free(zTemp);
-      return winLogError(SQLITE_CANTOPEN_FULLPATH, osGetLastError(),
-                         "winFullPathname4", zRelative);
-    }
-    sqlite3_free(zConverted);
-    zOut = sqlite3_win32_mbcs_to_utf8(zTemp);
-    sqlite3_free(zTemp);
-  }
-#endif
-  if( zOut ){
-    sqlite3_snprintf(MIN(nFull, pVfs->mxPathname), zFull, "%s", zOut);
-    sqlite3_free(zOut);
-    return SQLITE_OK;
-  }else{
-    return SQLITE_IOERR_NOMEM;
-  }
-#endif
-}
-
-  #define winDlOpen  0
-  #define winDlError 0
-  #define winDlSym   0
-  #define winDlClose 0
-
-
-/*
-** Write up to nBuf bytes of randomness into zBuf.
-*/
-static int winRandomness(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
-  int n = 0;
-  UNUSED_PARAMETER(pVfs);
-#if defined(SQLITE_TEST) || defined(SQLITE_OMIT_RANDOMNESS)
-  n = nBuf;
-  memset(zBuf, 0, nBuf);
-#else
-  if( sizeof(SYSTEMTIME)<=nBuf-n ){
-    SYSTEMTIME x;
-    osGetSystemTime(&x);
-    memcpy(&zBuf[n], &x, sizeof(x));
-    n += sizeof(x);
-  }
-  if( sizeof(DWORD)<=nBuf-n ){
-    DWORD pid = osGetCurrentProcessId();
-    memcpy(&zBuf[n], &pid, sizeof(pid));
-    n += sizeof(pid);
-  }
-#if SQLITE_OS_WINRT
-  if( sizeof(ULONGLONG)<=nBuf-n ){
-    ULONGLONG cnt = osGetTickCount64();
-    memcpy(&zBuf[n], &cnt, sizeof(cnt));
-    n += sizeof(cnt);
-  }
-#else
-  if( sizeof(DWORD)<=nBuf-n ){
-    DWORD cnt = osGetTickCount();
-    memcpy(&zBuf[n], &cnt, sizeof(cnt));
-    n += sizeof(cnt);
-  }
-#endif
-  if( sizeof(LARGE_INTEGER)<=nBuf-n ){
-    LARGE_INTEGER i;
-    osQueryPerformanceCounter(&i);
-    memcpy(&zBuf[n], &i, sizeof(i));
-    n += sizeof(i);
-  }
-#if !SQLITE_OS_WINCE && !SQLITE_OS_WINRT && SQLITE_WIN32_USE_UUID
-  if( sizeof(UUID)<=nBuf-n ){
-    UUID id;
-    memset(&id, 0, sizeof(UUID));
-    osUuidCreate(&id);
-    memcpy(&zBuf[n], &id, sizeof(UUID));
-    n += sizeof(UUID);
-  }
-  if( sizeof(UUID)<=nBuf-n ){
-    UUID id;
-    memset(&id, 0, sizeof(UUID));
-    osUuidCreateSequential(&id);
-    memcpy(&zBuf[n], &id, sizeof(UUID));
-    n += sizeof(UUID);
-  }
-#endif
-#endif /* defined(SQLITE_TEST) || defined(SQLITE_ZERO_PRNG_SEED) */
-  return n;
-}
-
-
-/*
-** Sleep for a little while.  Return the amount of time slept.
-*/
-static int winSleep(sqlite3_vfs *pVfs, int microsec){
-  sqlite3_win32_sleep((microsec+999)/1000);
-  UNUSED_PARAMETER(pVfs);
-  return ((microsec+999)/1000)*1000;
-}
-
-/*
-** The following variable, if set to a non-zero value, is interpreted as
-** the number of seconds since 1970 and is used to set the result of
-** sqlite3OsCurrentTime() during testing.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_current_time = 0;  /* Fake system time in seconds since 1970. */
-#endif
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write into *piNow
-** the current time and date as a Julian Day number times 86_400_000.  In
-** other words, write into *piNow the number of milliseconds since the Julian
-** epoch of noon in Greenwich on November 24, 4714 B.C according to the
-** proleptic Gregorian calendar.
-**
-** On success, return SQLITE_OK.  Return SQLITE_ERROR if the time and date
-** cannot be found.
-*/
-static int winCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *piNow){
-  /* FILETIME structure is a 64-bit value representing the number of
-     100-nanosecond intervals since January 1, 1601 (= JD 2305813.5).
-  */
-  FILETIME ft;
-  static const sqlite3_int64 winFiletimeEpoch = 23058135*(sqlite3_int64)8640000;
-#ifdef SQLITE_TEST
-  static const sqlite3_int64 unixEpoch = 24405875*(sqlite3_int64)8640000;
-#endif
-  /* 2^32 - to avoid use of LL and warnings in gcc */
-  static const sqlite3_int64 max32BitValue =
-      (sqlite3_int64)2000000000 + (sqlite3_int64)2000000000 +
-      (sqlite3_int64)294967296;
-
-#if SQLITE_OS_WINCE
-  SYSTEMTIME time;
-  osGetSystemTime(&time);
-  /* if SystemTimeToFileTime() fails, it returns zero. */
-  if (!osSystemTimeToFileTime(&time,&ft)){
-    return SQLITE_ERROR;
-  }
-#else
-  osGetSystemTimeAsFileTime( &ft );
-#endif
-
-  *piNow = winFiletimeEpoch +
-            ((((sqlite3_int64)ft.dwHighDateTime)*max32BitValue) +
-               (sqlite3_int64)ft.dwLowDateTime)/(sqlite3_int64)10000;
-
-#ifdef SQLITE_TEST
-  if( sqlite3_current_time ){
-    *piNow = 1000*(sqlite3_int64)sqlite3_current_time + unixEpoch;
-  }
-#endif
-  UNUSED_PARAMETER(pVfs);
-  return SQLITE_OK;
-}
-
-/*
-** Find the current time (in Universal Coordinated Time).  Write the
-** current time and date as a Julian Day number into *prNow and
-** return 0.  Return 1 if the time and date cannot be found.
-*/
-static int winCurrentTime(sqlite3_vfs *pVfs, double *prNow){
-  int rc;
-  sqlite3_int64 i;
-  rc = winCurrentTimeInt64(pVfs, &i);
-  if( !rc ){
-    *prNow = i/86400000.0;
-  }
-  return rc;
-}
-
-/*
-** The idea is that this function works like a combination of
-** GetLastError() and FormatMessage() on Windows (or errno and
-** strerror_r() on Unix). After an error is returned by an OS
-** function, SQLite calls this function with zBuf pointing to
-** a buffer of nBuf bytes. The OS layer should populate the
-** buffer with a nul-terminated UTF-8 encoded error message
-** describing the last IO error to have occurred within the calling
-** thread.
-**
-** If the error message is too large for the supplied buffer,
-** it should be truncated. The return value of xGetLastError
-** is zero if the error message fits in the buffer, or non-zero
-** otherwise (if the message was truncated). If non-zero is returned,
-** then it is not necessary to include the nul-terminator character
-** in the output buffer.
-**
-** Not supplying an error message will have no adverse effect
-** on SQLite. It is fine to have an implementation that never
-** returns an error message:
-**
-**   int xGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
-**     assert(zBuf[0]=='\0');
-**     return 0;
-**   }
-**
-** However if an error message is supplied, it will be incorporated
-** by sqlite into the error message available to the user using
-** sqlite3_errmsg(), possibly making IO errors easier to debug.
-*/
-static int winGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
-  UNUSED_PARAMETER(pVfs);
-  return winGetLastErrorMsg(osGetLastError(), nBuf, zBuf);
-}
-
-/*
-** Initialize and deinitialize the operating system interface.
-*/
-SQLITE_PRIVATE int sqlite3_os_init(void){
-  static sqlite3_vfs winVfs = {
-    3,                   /* iVersion */
-    sizeof(winFile),     /* szOsFile */
-    SQLITE_WIN32_MAX_PATH_BYTES, /* mxPathname */
-    0,                   /* pNext */
-    "win32",             /* zName */
-    0,                   /* pAppData */
-    winOpen,             /* xOpen */
-    winDelete,           /* xDelete */
-    winAccess,           /* xAccess */
-    winFullPathname,     /* xFullPathname */
-    winDlOpen,           /* xDlOpen */
-    winDlError,          /* xDlError */
-    winDlSym,            /* xDlSym */
-    winDlClose,          /* xDlClose */
-    winRandomness,       /* xRandomness */
-    winSleep,            /* xSleep */
-    winCurrentTime,      /* xCurrentTime */
-    winGetLastError,     /* xGetLastError */
-    winCurrentTimeInt64, /* xCurrentTimeInt64 */
-    winSetSystemCall,    /* xSetSystemCall */
-    winGetSystemCall,    /* xGetSystemCall */
-    winNextSystemCall,   /* xNextSystemCall */
-  };
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  static sqlite3_vfs winLongPathVfs = {
-    3,                   /* iVersion */
-    sizeof(winFile),     /* szOsFile */
-    SQLITE_WINNT_MAX_PATH_BYTES, /* mxPathname */
-    0,                   /* pNext */
-    "win32-longpath",    /* zName */
-    0,                   /* pAppData */
-    winOpen,             /* xOpen */
-    winDelete,           /* xDelete */
-    winAccess,           /* xAccess */
-    winFullPathname,     /* xFullPathname */
-    winDlOpen,           /* xDlOpen */
-    winDlError,          /* xDlError */
-    winDlSym,            /* xDlSym */
-    winDlClose,          /* xDlClose */
-    winRandomness,       /* xRandomness */
-    winSleep,            /* xSleep */
-    winCurrentTime,      /* xCurrentTime */
-    winGetLastError,     /* xGetLastError */
-    winCurrentTimeInt64, /* xCurrentTimeInt64 */
-    winSetSystemCall,    /* xSetSystemCall */
-    winGetSystemCall,    /* xGetSystemCall */
-    winNextSystemCall,   /* xNextSystemCall */
-  };
-#endif
-
-  /* Double-check that the aSyscall[] array has been constructed
-  ** correctly.  See ticket [bb3a86e890c8e96ab] */
-  assert( ArraySize(aSyscall)==80 );
-
-  /* get memory map allocation granularity */
-  memset(&winSysInfo, 0, sizeof(SYSTEM_INFO));
-#if SQLITE_OS_WINRT
-  osGetNativeSystemInfo(&winSysInfo);
-#else
-  osGetSystemInfo(&winSysInfo);
-#endif
-  assert( winSysInfo.dwAllocationGranularity>0 );
-  assert( winSysInfo.dwPageSize>0 );
-
-  sqlite3_vfs_register(&winVfs, 1);
-
-#if defined(SQLITE_WIN32_HAS_WIDE)
-  sqlite3_vfs_register(&winLongPathVfs, 0);
-#endif
-
-  return SQLITE_OK;
-}
-
-SQLITE_PRIVATE int sqlite3_os_end(void){
-#if SQLITE_OS_WINRT
-  if( sleepObj!=NULL ){
-    osCloseHandle(sleepObj);
-    sleepObj = NULL;
-  }
-#endif
-  return SQLITE_OK;
-}
-
-#endif /* SQLITE_OS_WIN */
-
-/************** End of os_win.c **********************************************/
-/************** Begin file bitvec.c ******************************************/
-/*
-** 2008 February 16
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file implements an object that represents a fixed-length
-** bitmap.  Bits are numbered starting with 1.
-**
-** A bitmap is used to record which pages of a database file have been
-** journalled during a transaction, or which pages have the "dont-write"
-** property.  Usually only a few pages are meet either condition.
-** So the bitmap is usually sparse and has low cardinality.
-** But sometimes (for example when during a DROP of a large table) most
-** or all of the pages in a database can get journalled.  In those cases, 
-** the bitmap becomes dense with high cardinality.  The algorithm needs 
-** to handle both cases well.
-**
-** The size of the bitmap is fixed when the object is created.
-**
-** All bits are clear when the bitmap is created.  Individual bits
-** may be set or cleared one at a time.
-**
-** Test operations are about 100 times more common that set operations.
-** Clear operations are exceedingly rare.  There are usually between
-** 5 and 500 set operations per Bitvec object, though the number of sets can
-** sometimes grow into tens of thousands or larger.  The size of the
-** Bitvec object is the number of pages in the database file at the
-** start of a transaction, and is thus usually less than a few thousand,
-** but can be as large as 2 billion for a really big database.
-*/
-/* #include "sqliteInt.h" */
-
-/* Size of the Bitvec structure in bytes. */
-#define BITVEC_SZ        512
-
-/* Round the union size down to the nearest pointer boundary, since that's how 
-** it will be aligned within the Bitvec struct. */
-#define BITVEC_USIZE     (((BITVEC_SZ-(3*sizeof(u32)))/sizeof(Bitvec*))*sizeof(Bitvec*))
-
-/* Type of the array "element" for the bitmap representation. 
-** Should be a power of 2, and ideally, evenly divide into BITVEC_USIZE. 
-** Setting this to the "natural word" size of your CPU may improve
-** performance. */
-#define BITVEC_TELEM     u8
-/* Size, in bits, of the bitmap element. */
-#define BITVEC_SZELEM    8
-/* Number of elements in a bitmap array. */
-#define BITVEC_NELEM     (BITVEC_USIZE/sizeof(BITVEC_TELEM))
-/* Number of bits in the bitmap array. */
-#define BITVEC_NBIT      (BITVEC_NELEM*BITVEC_SZELEM)
-
-/* Number of u32 values in hash table. */
-#define BITVEC_NINT      (BITVEC_USIZE/sizeof(u32))
-/* Maximum number of entries in hash table before 
-** sub-dividing and re-hashing. */
-#define BITVEC_MXHASH    (BITVEC_NINT/2)
-/* Hashing function for the aHash representation.
-** Empirical testing showed that the *37 multiplier 
-** (an arbitrary prime)in the hash function provided 
-** no fewer collisions than the no-op *1. */
-#define BITVEC_HASH(X)   (((X)*1)%BITVEC_NINT)
-
-#define BITVEC_NPTR      (BITVEC_USIZE/sizeof(Bitvec *))
-
-
-/*
-** A bitmap is an instance of the following structure.
-**
-** This bitmap records the existence of zero or more bits
-** with values between 1 and iSize, inclusive.
-**
-** There are three possible representations of the bitmap.
-** If iSize<=BITVEC_NBIT, then Bitvec.u.aBitmap[] is a straight
-** bitmap.  The least significant bit is bit 1.
-**
-** If iSize>BITVEC_NBIT and iDivisor==0 then Bitvec.u.aHash[] is
-** a hash table that will hold up to BITVEC_MXHASH distinct values.
-**
-** Otherwise, the value i is redirected into one of BITVEC_NPTR
-** sub-bitmaps pointed to by Bitvec.u.apSub[].  Each subbitmap
-** handles up to iDivisor separate values of i.  apSub[0] holds
-** values between 1 and iDivisor.  apSub[1] holds values between
-** iDivisor+1 and 2*iDivisor.  apSub[N] holds values between
-** N*iDivisor+1 and (N+1)*iDivisor.  Each subbitmap is normalized
-** to hold deal with values between 1 and iDivisor.
-*/
-struct Bitvec {
-  u32 iSize;      /* Maximum bit index.  Max iSize is 4,294,967,296. */
-  u32 nSet;       /* Number of bits that are set - only valid for aHash
-                  ** element.  Max is BITVEC_NINT.  For BITVEC_SZ of 512,
-                  ** this would be 125. */
-  u32 iDivisor;   /* Number of bits handled by each apSub[] entry. */
-                  /* Should >=0 for apSub element. */
-                  /* Max iDivisor is max(u32) / BITVEC_NPTR + 1.  */
-                  /* For a BITVEC_SZ of 512, this would be 34,359,739. */
-  union {
-    BITVEC_TELEM aBitmap[BITVEC_NELEM];    /* Bitmap representation */
-    u32 aHash[BITVEC_NINT];      /* Hash table representation */
-    Bitvec *apSub[BITVEC_NPTR];  /* Recursive representation */
-  } u;
-};
-
-/*
-** Create a new bitmap object able to handle bits between 0 and iSize,
-** inclusive.  Return a pointer to the new object.  Return NULL if 
-** malloc fails.
-*/
-SQLITE_PRIVATE Bitvec *sqlite3BitvecCreate(u32 iSize){
-  Bitvec *p;
-  assert( sizeof(*p)==BITVEC_SZ );
-  p = sqlite3MallocZero( sizeof(*p) );
-  if( p ){
-    p->iSize = iSize;
-  }
-  return p;
-}
-
-/*
-** Check to see if the i-th bit is set.  Return true or false.
-** If p is NULL (if the bitmap has not been created) or if
-** i is out of range, then return false.
-*/
-SQLITE_PRIVATE int sqlite3BitvecTestNotNull(Bitvec *p, u32 i){
-  assert( p!=0 );
-  i--;
-  if( i>=p->iSize ) return 0;
-  while( p->iDivisor ){
-    u32 bin = i/p->iDivisor;
-    i = i%p->iDivisor;
-    p = p->u.apSub[bin];
-    if (!p) {
-      return 0;
-    }
-  }
-  if( p->iSize<=BITVEC_NBIT ){
-    return (p->u.aBitmap[i/BITVEC_SZELEM] & (1<<(i&(BITVEC_SZELEM-1))))!=0;
-  } else{
-    u32 h = BITVEC_HASH(i++);
-    while( p->u.aHash[h] ){
-      if( p->u.aHash[h]==i ) return 1;
-      h = (h+1) % BITVEC_NINT;
-    }
-    return 0;
-  }
-}
-SQLITE_PRIVATE int sqlite3BitvecTest(Bitvec *p, u32 i){
-  return p!=0 && sqlite3BitvecTestNotNull(p,i);
-}
-
-/*
-** Set the i-th bit.  Return 0 on success and an error code if
-** anything goes wrong.
-**
-** This routine might cause sub-bitmaps to be allocated.  Failing
-** to get the memory needed to hold the sub-bitmap is the only
-** that can go wrong with an insert, assuming p and i are valid.
-**
-** The calling function must ensure that p is a valid Bitvec object
-** and that the value for "i" is within range of the Bitvec object.
-** Otherwise the behavior is undefined.
-*/
-SQLITE_PRIVATE int sqlite3BitvecSet(Bitvec *p, u32 i){
-  u32 h;
-  if( p==0 ) return SQLITE_OK;
-  assert( i>0 );
-  assert( i<=p->iSize );
-  i--;
-  while((p->iSize > BITVEC_NBIT) && p->iDivisor) {
-    u32 bin = i/p->iDivisor;
-    i = i%p->iDivisor;
-    if( p->u.apSub[bin]==0 ){
-      p->u.apSub[bin] = sqlite3BitvecCreate( p->iDivisor );
-      if( p->u.apSub[bin]==0 ) return SQLITE_NOMEM;
-    }
-    p = p->u.apSub[bin];
-  }
-  if( p->iSize<=BITVEC_NBIT ){
-    p->u.aBitmap[i/BITVEC_SZELEM] |= 1 << (i&(BITVEC_SZELEM-1));
-    return SQLITE_OK;
-  }
-  h = BITVEC_HASH(i++);
-  /* if there wasn't a hash collision, and this doesn't */
-  /* completely fill the hash, then just add it without */
-  /* worring about sub-dividing and re-hashing. */
-  if( !p->u.aHash[h] ){
-    if (p->nSet<(BITVEC_NINT-1)) {
-      goto bitvec_set_end;
-    } else {
-      goto bitvec_set_rehash;
-    }
-  }
-  /* there was a collision, check to see if it's already */
-  /* in hash, if not, try to find a spot for it */
-  do {
-    if( p->u.aHash[h]==i ) return SQLITE_OK;
-    h++;
-    if( h>=BITVEC_NINT ) h = 0;
-  } while( p->u.aHash[h] );
-  /* we didn't find it in the hash.  h points to the first */
-  /* available free spot. check to see if this is going to */
-  /* make our hash too "full".  */
-bitvec_set_rehash:
-  if( p->nSet>=BITVEC_MXHASH ){
-    unsigned int j;
-    int rc;
-    u32 *aiValues = sqlite3StackAllocRaw(0, sizeof(p->u.aHash));
-    if( aiValues==0 ){
-      return SQLITE_NOMEM;
-    }else{
-      memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
-      memset(p->u.apSub, 0, sizeof(p->u.apSub));
-      p->iDivisor = (p->iSize + BITVEC_NPTR - 1)/BITVEC_NPTR;
-      rc = sqlite3BitvecSet(p, i);
-      for(j=0; j<BITVEC_NINT; j++){
-        if( aiValues[j] ) rc |= sqlite3BitvecSet(p, aiValues[j]);
-      }
-      sqlite3StackFree(0, aiValues);
-      return rc;
-    }
-  }
-bitvec_set_end:
-  p->nSet++;
-  p->u.aHash[h] = i;
-  return SQLITE_OK;
-}
-
-/*
-** Clear the i-th bit.
-**
-** pBuf must be a pointer to at least BITVEC_SZ bytes of temporary storage
-** that BitvecClear can use to rebuilt its hash table.
-*/
-SQLITE_PRIVATE void sqlite3BitvecClear(Bitvec *p, u32 i, void *pBuf){
-  if( p==0 ) return;
-  assert( i>0 );
-  i--;
-  while( p->iDivisor ){
-    u32 bin = i/p->iDivisor;
-    i = i%p->iDivisor;
-    p = p->u.apSub[bin];
-    if (!p) {
-      return;
-    }
-  }
-  if( p->iSize<=BITVEC_NBIT ){
-    p->u.aBitmap[i/BITVEC_SZELEM] &= ~(1 << (i&(BITVEC_SZELEM-1)));
-  }else{
-    unsigned int j;
-    u32 *aiValues = pBuf;
-    memcpy(aiValues, p->u.aHash, sizeof(p->u.aHash));
-    memset(p->u.aHash, 0, sizeof(p->u.aHash));
-    p->nSet = 0;
-    for(j=0; j<BITVEC_NINT; j++){
-      if( aiValues[j] && aiValues[j]!=(i+1) ){
-        u32 h = BITVEC_HASH(aiValues[j]-1);
-        p->nSet++;
-        while( p->u.aHash[h] ){
-          h++;
-          if( h>=BITVEC_NINT ) h = 0;
-        }
-        p->u.aHash[h] = aiValues[j];
-      }
-    }
-  }
-}
-
-/*
-** Destroy a bitmap object.  Reclaim all memory used.
-*/
-SQLITE_PRIVATE void sqlite3BitvecDestroy(Bitvec *p){
-  if( p==0 ) return;
-  if( p->iDivisor ){
-    unsigned int i;
-    for(i=0; i<BITVEC_NPTR; i++){
-      sqlite3BitvecDestroy(p->u.apSub[i]);
-    }
-  }
-  sqlite3_free(p);
-}
-
-/*
-** Return the value of the iSize parameter specified when Bitvec *p
-** was created.
-*/
-SQLITE_PRIVATE u32 sqlite3BitvecSize(Bitvec *p){
-  return p->iSize;
-}
-
-/************** End of bitvec.c **********************************************/
-/************** Begin file pcache.c ******************************************/
-/*
-** 2008 August 05
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file implements that page cache.
-*/
-/* #include "sqliteInt.h" */
-
-/*
-** A complete page cache is an instance of this structure.
-*/
-struct PCache {
-  PgHdr *pDirty, *pDirtyTail;         /* List of dirty pages in LRU order */
-  PgHdr *pSynced;                     /* Last synced page in dirty page list */
-  int nRefSum;                        /* Sum of ref counts over all pages */
-  int szCache;                        /* Configured cache size */
-  int szPage;                         /* Size of every page in this cache */
-  int szExtra;                        /* Size of extra space for each page */
-  u8 bPurgeable;                      /* True if pages are on backing store */
-  u8 eCreate;                         /* eCreate value for for xFetch() */
-  int (*xStress)(void*,PgHdr*);       /* Call to try make a page clean */
-  void *pStress;                      /* Argument to xStress */
-  sqlite3_pcache *pCache;             /* Pluggable cache module */
-};
-
-/********************************** Linked List Management ********************/
-
-/* Allowed values for second argument to pcacheManageDirtyList() */
-#define PCACHE_DIRTYLIST_REMOVE   1    /* Remove pPage from dirty list */
-#define PCACHE_DIRTYLIST_ADD      2    /* Add pPage to the dirty list */
-#define PCACHE_DIRTYLIST_FRONT    3    /* Move pPage to the front of the list */
-
-/*
-** Manage pPage's participation on the dirty list.  Bits of the addRemove
-** argument determines what operation to do.  The 0x01 bit means first
-** remove pPage from the dirty list.  The 0x02 means add pPage back to
-** the dirty list.  Doing both moves pPage to the front of the dirty list.
-*/
-static void pcacheManageDirtyList(PgHdr *pPage, u8 addRemove){
-  PCache *p = pPage->pCache;
-
-  if( addRemove & PCACHE_DIRTYLIST_REMOVE ){
-    assert( pPage->pDirtyNext || pPage==p->pDirtyTail );
-    assert( pPage->pDirtyPrev || pPage==p->pDirty );
-  
-    /* Update the PCache1.pSynced variable if necessary. */
-    if( p->pSynced==pPage ){
-      PgHdr *pSynced = pPage->pDirtyPrev;
-      while( pSynced && (pSynced->flags&PGHDR_NEED_SYNC) ){
-        pSynced = pSynced->pDirtyPrev;
-      }
-      p->pSynced = pSynced;
-    }
-  
-    if( pPage->pDirtyNext ){
-      pPage->pDirtyNext->pDirtyPrev = pPage->pDirtyPrev;
-    }else{
-      assert( pPage==p->pDirtyTail );
-      p->pDirtyTail = pPage->pDirtyPrev;
-    }
-    if( pPage->pDirtyPrev ){
-      pPage->pDirtyPrev->pDirtyNext = pPage->pDirtyNext;
-    }else{
-      assert( pPage==p->pDirty );
-      p->pDirty = pPage->pDirtyNext;
-      if( p->pDirty==0 && p->bPurgeable ){
-        assert( p->eCreate==1 );
-        p->eCreate = 2;
-      }
-    }
-    pPage->pDirtyNext = 0;
-    pPage->pDirtyPrev = 0;
-  }
-  if( addRemove & PCACHE_DIRTYLIST_ADD ){
-    assert( pPage->pDirtyNext==0 && pPage->pDirtyPrev==0 && p->pDirty!=pPage );
-  
-    pPage->pDirtyNext = p->pDirty;
-    if( pPage->pDirtyNext ){
-      assert( pPage->pDirtyNext->pDirtyPrev==0 );
-      pPage->pDirtyNext->pDirtyPrev = pPage;
-    }else{
-      p->pDirtyTail = pPage;
-      if( p->bPurgeable ){
-        assert( p->eCreate==2 );
-        p->eCreate = 1;
-      }
-    }
-    p->pDirty = pPage;
-    if( !p->pSynced && 0==(pPage->flags&PGHDR_NEED_SYNC) ){
-      p->pSynced = pPage;
-    }
-  }
-}
-
-/*
-** Wrapper around the pluggable caches xUnpin method. If the cache is
-** being used for an in-memory database, this function is a no-op.
-*/
-static void pcacheUnpin(PgHdr *p){
-  if( p->pCache->bPurgeable ){
-    sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 0);
-  }
-}
-
-/*
-** Compute the number of pages of cache requested.  p->szCache is the
-** cache size requested by the "PRAGMA cache_size" statement.
-**
-**
-*/
-static int numberOfCachePages(PCache *p){
-  if( p->szCache>=0 ){
-    /* IMPLEMENTATION-OF: R-42059-47211 If the argument N is positive then the
-    ** suggested cache size is set to N. */
-    return p->szCache;
-  }else{
-    /* IMPLEMENTATION-OF: R-61436-13639 If the argument N is negative, then
-    ** the number of cache pages is adjusted to use approximately abs(N*1024)
-    ** bytes of memory. */
-    return (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));
-  }
-}
-
-/*************************************************** General Interfaces ******
-**
-** Initialize and shutdown the page cache subsystem. Neither of these 
-** functions are threadsafe.
-*/
-SQLITE_PRIVATE int sqlite3PcacheInitialize(void){
-  if( sqlite3GlobalConfig.pcache2.xInit==0 ){
-    /* IMPLEMENTATION-OF: R-26801-64137 If the xInit() method is NULL, then the
-    ** built-in default page cache is used instead of the application defined
-    ** page cache. */
-    sqlite3PCacheSetDefault();
-  }
-  return sqlite3GlobalConfig.pcache2.xInit(sqlite3GlobalConfig.pcache2.pArg);
-}
-SQLITE_PRIVATE void sqlite3PcacheShutdown(void){
-  if( sqlite3GlobalConfig.pcache2.xShutdown ){
-    /* IMPLEMENTATION-OF: R-26000-56589 The xShutdown() method may be NULL. */
-    sqlite3GlobalConfig.pcache2.xShutdown(sqlite3GlobalConfig.pcache2.pArg);
-  }
-}
-
-/*
-** Return the size in bytes of a PCache object.
-*/
-SQLITE_PRIVATE int sqlite3PcacheSize(void){ return sizeof(PCache); }
-
-/*
-** Create a new PCache object. Storage space to hold the object
-** has already been allocated and is passed in as the p pointer. 
-** The caller discovers how much space needs to be allocated by 
-** calling sqlite3PcacheSize().
-*/
-SQLITE_PRIVATE int sqlite3PcacheOpen(
-  int szPage,                  /* Size of every page */
-  int szExtra,                 /* Extra space associated with each page */
-  int bPurgeable,              /* True if pages are on backing store */
-  int (*xStress)(void*,PgHdr*),/* Call to try to make pages clean */
-  void *pStress,               /* Argument to xStress */
-  PCache *p                    /* Preallocated space for the PCache */
-){
-  memset(p, 0, sizeof(PCache));
-  p->szPage = 1;
-  p->szExtra = szExtra;
-  p->bPurgeable = bPurgeable;
-  p->eCreate = 2;
-  p->xStress = xStress;
-  p->pStress = pStress;
-  p->szCache = 100;
-  return sqlite3PcacheSetPageSize(p, szPage);
-}
-
-/*
-** Change the page size for PCache object. The caller must ensure that there
-** are no outstanding page references when this function is called.
-*/
-SQLITE_PRIVATE int sqlite3PcacheSetPageSize(PCache *pCache, int szPage){
-  assert( pCache->nRefSum==0 && pCache->pDirty==0 );
-  if( pCache->szPage ){
-    sqlite3_pcache *pNew;
-    pNew = sqlite3GlobalConfig.pcache2.xCreate(
-                szPage, pCache->szExtra + ROUND8(sizeof(PgHdr)),
-                pCache->bPurgeable
-    );
-    if( pNew==0 ) return SQLITE_NOMEM;
-    sqlite3GlobalConfig.pcache2.xCachesize(pNew, numberOfCachePages(pCache));
-    if( pCache->pCache ){
-      sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
-    }
-    pCache->pCache = pNew;
-    pCache->szPage = szPage;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Try to obtain a page from the cache.
-**
-** This routine returns a pointer to an sqlite3_pcache_page object if
-** such an object is already in cache, or if a new one is created.
-** This routine returns a NULL pointer if the object was not in cache
-** and could not be created.
-**
-** The createFlags should be 0 to check for existing pages and should
-** be 3 (not 1, but 3) to try to create a new page.
-**
-** If the createFlag is 0, then NULL is always returned if the page
-** is not already in the cache.  If createFlag is 1, then a new page
-** is created only if that can be done without spilling dirty pages
-** and without exceeding the cache size limit.
-**
-** The caller needs to invoke sqlite3PcacheFetchFinish() to properly
-** initialize the sqlite3_pcache_page object and convert it into a
-** PgHdr object.  The sqlite3PcacheFetch() and sqlite3PcacheFetchFinish()
-** routines are split this way for performance reasons. When separated
-** they can both (usually) operate without having to push values to
-** the stack on entry and pop them back off on exit, which saves a
-** lot of pushing and popping.
-*/
-SQLITE_PRIVATE sqlite3_pcache_page *sqlite3PcacheFetch(
-  PCache *pCache,       /* Obtain the page from this cache */
-  Pgno pgno,            /* Page number to obtain */
-  int createFlag        /* If true, create page if it does not exist already */
-){
-  int eCreate;
-
-  assert( pCache!=0 );
-  assert( pCache->pCache!=0 );
-  assert( createFlag==3 || createFlag==0 );
-  assert( pgno>0 );
-
-  /* eCreate defines what to do if the page does not exist.
-  **    0     Do not allocate a new page.  (createFlag==0)
-  **    1     Allocate a new page if doing so is inexpensive.
-  **          (createFlag==1 AND bPurgeable AND pDirty)
-  **    2     Allocate a new page even it doing so is difficult.
-  **          (createFlag==1 AND !(bPurgeable AND pDirty)
-  */
-  eCreate = createFlag & pCache->eCreate;
-  assert( eCreate==0 || eCreate==1 || eCreate==2 );
-  assert( createFlag==0 || pCache->eCreate==eCreate );
-  assert( createFlag==0 || eCreate==1+(!pCache->bPurgeable||!pCache->pDirty) );
-  return sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, eCreate);
-}
-
-/*
-** If the sqlite3PcacheFetch() routine is unable to allocate a new
-** page because new clean pages are available for reuse and the cache
-** size limit has been reached, then this routine can be invoked to 
-** try harder to allocate a page.  This routine might invoke the stress
-** callback to spill dirty pages to the journal.  It will then try to
-** allocate the new page and will only fail to allocate a new page on
-** an OOM error.
-**
-** This routine should be invoked only after sqlite3PcacheFetch() fails.
-*/
-SQLITE_PRIVATE int sqlite3PcacheFetchStress(
-  PCache *pCache,                 /* Obtain the page from this cache */
-  Pgno pgno,                      /* Page number to obtain */
-  sqlite3_pcache_page **ppPage    /* Write result here */
-){
-  PgHdr *pPg;
-  if( pCache->eCreate==2 ) return 0;
-
-
-  /* Find a dirty page to write-out and recycle. First try to find a 
-  ** page that does not require a journal-sync (one with PGHDR_NEED_SYNC
-  ** cleared), but if that is not possible settle for any other 
-  ** unreferenced dirty page.
-  */
-  for(pPg=pCache->pSynced; 
-      pPg && (pPg->nRef || (pPg->flags&PGHDR_NEED_SYNC)); 
-      pPg=pPg->pDirtyPrev
-  );
-  pCache->pSynced = pPg;
-  if( !pPg ){
-    for(pPg=pCache->pDirtyTail; pPg && pPg->nRef; pPg=pPg->pDirtyPrev);
-  }
-  if( pPg ){
-    int rc;
-#ifdef SQLITE_LOG_CACHE_SPILL
-    sqlite3_log(SQLITE_FULL, 
-                "spill page %d making room for %d - cache used: %d/%d",
-                pPg->pgno, pgno,
-                sqlite3GlobalConfig.pcache.xPagecount(pCache->pCache),
-                numberOfCachePages(pCache));
-#endif
-    rc = pCache->xStress(pCache->pStress, pPg);
-    if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
-      return rc;
-    }
-  }
-  *ppPage = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache, pgno, 2);
-  return *ppPage==0 ? SQLITE_NOMEM : SQLITE_OK;
-}
-
-/*
-** This is a helper routine for sqlite3PcacheFetchFinish()
-**
-** In the uncommon case where the page being fetched has not been
-** initialized, this routine is invoked to do the initialization.
-** This routine is broken out into a separate function since it
-** requires extra stack manipulation that can be avoided in the common
-** case.
-*/
-static SQLITE_NOINLINE PgHdr *pcacheFetchFinishWithInit(
-  PCache *pCache,             /* Obtain the page from this cache */
-  Pgno pgno,                  /* Page number obtained */
-  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
-){
-  PgHdr *pPgHdr;
-  assert( pPage!=0 );
-  pPgHdr = (PgHdr*)pPage->pExtra;
-  assert( pPgHdr->pPage==0 );
-  memset(pPgHdr, 0, sizeof(PgHdr));
-  pPgHdr->pPage = pPage;
-  pPgHdr->pData = pPage->pBuf;
-  pPgHdr->pExtra = (void *)&pPgHdr[1];
-  memset(pPgHdr->pExtra, 0, pCache->szExtra);
-  pPgHdr->pCache = pCache;
-  pPgHdr->pgno = pgno;
-  pPgHdr->flags = PGHDR_CLEAN;
-  return sqlite3PcacheFetchFinish(pCache,pgno,pPage);
-}
-
-/*
-** This routine converts the sqlite3_pcache_page object returned by
-** sqlite3PcacheFetch() into an initialized PgHdr object.  This routine
-** must be called after sqlite3PcacheFetch() in order to get a usable
-** result.
-*/
-SQLITE_PRIVATE PgHdr *sqlite3PcacheFetchFinish(
-  PCache *pCache,             /* Obtain the page from this cache */
-  Pgno pgno,                  /* Page number obtained */
-  sqlite3_pcache_page *pPage  /* Page obtained by prior PcacheFetch() call */
-){
-  PgHdr *pPgHdr;
-
-  assert( pPage!=0 );
-  pPgHdr = (PgHdr *)pPage->pExtra;
-
-  if( !pPgHdr->pPage ){
-    return pcacheFetchFinishWithInit(pCache, pgno, pPage);
-  }
-  pCache->nRefSum++;
-  pPgHdr->nRef++;
-  return pPgHdr;
-}
-
-/*
-** Decrement the reference count on a page. If the page is clean and the
-** reference count drops to 0, then it is made eligible for recycling.
-*/
-SQLITE_PRIVATE void SQLITE_NOINLINE sqlite3PcacheRelease(PgHdr *p){
-  assert( p->nRef>0 );
-  p->pCache->nRefSum--;
-  if( (--p->nRef)==0 ){
-    if( p->flags&PGHDR_CLEAN ){
-      pcacheUnpin(p);
-    }else if( p->pDirtyPrev!=0 ){
-      /* Move the page to the head of the dirty list. */
-      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
-    }
-  }
-}
-
-/*
-** Increase the reference count of a supplied page by 1.
-*/
-SQLITE_PRIVATE void sqlite3PcacheRef(PgHdr *p){
-  assert(p->nRef>0);
-  p->nRef++;
-  p->pCache->nRefSum++;
-}
-
-/*
-** Drop a page from the cache. There must be exactly one reference to the
-** page. This function deletes that reference, so after it returns the
-** page pointed to by p is invalid.
-*/
-SQLITE_PRIVATE void sqlite3PcacheDrop(PgHdr *p){
-  assert( p->nRef==1 );
-  if( p->flags&PGHDR_DIRTY ){
-    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
-  }
-  p->pCache->nRefSum--;
-  sqlite3GlobalConfig.pcache2.xUnpin(p->pCache->pCache, p->pPage, 1);
-}
-
-/*
-** Make sure the page is marked as dirty. If it isn't dirty already,
-** make it so.
-*/
-SQLITE_PRIVATE void sqlite3PcacheMakeDirty(PgHdr *p){
-  assert( p->nRef>0 );
-  if( p->flags & (PGHDR_CLEAN|PGHDR_DONT_WRITE) ){
-    p->flags &= ~PGHDR_DONT_WRITE;
-    if( p->flags & PGHDR_CLEAN ){
-      p->flags ^= (PGHDR_DIRTY|PGHDR_CLEAN);
-      assert( (p->flags & (PGHDR_DIRTY|PGHDR_CLEAN))==PGHDR_DIRTY );
-      pcacheManageDirtyList(p, PCACHE_DIRTYLIST_ADD);
-    }
-  }
-}
-
-/*
-** Make sure the page is marked as clean. If it isn't clean already,
-** make it so.
-*/
-SQLITE_PRIVATE void sqlite3PcacheMakeClean(PgHdr *p){
-  if( (p->flags & PGHDR_DIRTY) ){
-    assert( (p->flags & PGHDR_CLEAN)==0 );
-    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_REMOVE);
-    p->flags &= ~(PGHDR_DIRTY|PGHDR_NEED_SYNC|PGHDR_WRITEABLE);
-    p->flags |= PGHDR_CLEAN;
-    if( p->nRef==0 ){
-      pcacheUnpin(p);
-    }
-  }
-}
-
-/*
-** Make every page in the cache clean.
-*/
-SQLITE_PRIVATE void sqlite3PcacheCleanAll(PCache *pCache){
-  PgHdr *p;
-  while( (p = pCache->pDirty)!=0 ){
-    sqlite3PcacheMakeClean(p);
-  }
-}
-
-/*
-** Clear the PGHDR_NEED_SYNC flag from all dirty pages.
-*/
-SQLITE_PRIVATE void sqlite3PcacheClearSyncFlags(PCache *pCache){
-  PgHdr *p;
-  for(p=pCache->pDirty; p; p=p->pDirtyNext){
-    p->flags &= ~PGHDR_NEED_SYNC;
-  }
-  pCache->pSynced = pCache->pDirtyTail;
-}
-
-/*
-** Change the page number of page p to newPgno. 
-*/
-SQLITE_PRIVATE void sqlite3PcacheMove(PgHdr *p, Pgno newPgno){
-  PCache *pCache = p->pCache;
-  assert( p->nRef>0 );
-  assert( newPgno>0 );
-  sqlite3GlobalConfig.pcache2.xRekey(pCache->pCache, p->pPage, p->pgno,newPgno);
-  p->pgno = newPgno;
-  if( (p->flags&PGHDR_DIRTY) && (p->flags&PGHDR_NEED_SYNC) ){
-    pcacheManageDirtyList(p, PCACHE_DIRTYLIST_FRONT);
-  }
-}
-
-/*
-** Drop every cache entry whose page number is greater than "pgno". The
-** caller must ensure that there are no outstanding references to any pages
-** other than page 1 with a page number greater than pgno.
-**
-** If there is a reference to page 1 and the pgno parameter passed to this
-** function is 0, then the data area associated with page 1 is zeroed, but
-** the page object is not dropped.
-*/
-SQLITE_PRIVATE void sqlite3PcacheTruncate(PCache *pCache, Pgno pgno){
-  if( pCache->pCache ){
-    PgHdr *p;
-    PgHdr *pNext;
-    for(p=pCache->pDirty; p; p=pNext){
-      pNext = p->pDirtyNext;
-      /* This routine never gets call with a positive pgno except right
-      ** after sqlite3PcacheCleanAll().  So if there are dirty pages,
-      ** it must be that pgno==0.
-      */
-      assert( p->pgno>0 );
-      if( ALWAYS(p->pgno>pgno) ){
-        assert( p->flags&PGHDR_DIRTY );
-        sqlite3PcacheMakeClean(p);
-      }
-    }
-    if( pgno==0 && pCache->nRefSum ){
-      sqlite3_pcache_page *pPage1;
-      pPage1 = sqlite3GlobalConfig.pcache2.xFetch(pCache->pCache,1,0);
-      if( ALWAYS(pPage1) ){  /* Page 1 is always available in cache, because
-                             ** pCache->nRefSum>0 */
-        memset(pPage1->pBuf, 0, pCache->szPage);
-        pgno = 1;
-      }
-    }
-    sqlite3GlobalConfig.pcache2.xTruncate(pCache->pCache, pgno+1);
-  }
-}
-
-/*
-** Close a cache.
-*/
-SQLITE_PRIVATE void sqlite3PcacheClose(PCache *pCache){
-  assert( pCache->pCache!=0 );
-  sqlite3GlobalConfig.pcache2.xDestroy(pCache->pCache);
-}
-
-/* 
-** Discard the contents of the cache.
-*/
-SQLITE_PRIVATE void sqlite3PcacheClear(PCache *pCache){
-  sqlite3PcacheTruncate(pCache, 0);
-}
-
-/*
-** Merge two lists of pages connected by pDirty and in pgno order.
-** Do not both fixing the pDirtyPrev pointers.
-*/
-static PgHdr *pcacheMergeDirtyList(PgHdr *pA, PgHdr *pB){
-  PgHdr result, *pTail;
-  pTail = &result;
-  while( pA && pB ){
-    if( pA->pgno<pB->pgno ){
-      pTail->pDirty = pA;
-      pTail = pA;
-      pA = pA->pDirty;
-    }else{
-      pTail->pDirty = pB;
-      pTail = pB;
-      pB = pB->pDirty;
-    }
-  }
-  if( pA ){
-    pTail->pDirty = pA;
-  }else if( pB ){
-    pTail->pDirty = pB;
-  }else{
-    pTail->pDirty = 0;
-  }
-  return result.pDirty;
-}
-
-/*
-** Sort the list of pages in accending order by pgno.  Pages are
-** connected by pDirty pointers.  The pDirtyPrev pointers are
-** corrupted by this sort.
-**
-** Since there cannot be more than 2^31 distinct pages in a database,
-** there cannot be more than 31 buckets required by the merge sorter.
-** One extra bucket is added to catch overflow in case something
-** ever changes to make the previous sentence incorrect.
-*/
-#define N_SORT_BUCKET  32
-static PgHdr *pcacheSortDirtyList(PgHdr *pIn){
-  PgHdr *a[N_SORT_BUCKET], *p;
-  int i;
-  memset(a, 0, sizeof(a));
-  while( pIn ){
-    p = pIn;
-    pIn = p->pDirty;
-    p->pDirty = 0;
-    for(i=0; ALWAYS(i<N_SORT_BUCKET-1); i++){
-      if( a[i]==0 ){
-        a[i] = p;
-        break;
-      }else{
-        p = pcacheMergeDirtyList(a[i], p);
-        a[i] = 0;
-      }
-    }
-    if( NEVER(i==N_SORT_BUCKET-1) ){
-      /* To get here, there need to be 2^(N_SORT_BUCKET) elements in
-      ** the input list.  But that is impossible.
-      */
-      a[i] = pcacheMergeDirtyList(a[i], p);
-    }
-  }
-  p = a[0];
-  for(i=1; i<N_SORT_BUCKET; i++){
-    p = pcacheMergeDirtyList(p, a[i]);
-  }
-  return p;
-}
-
-/*
-** Return a list of all dirty pages in the cache, sorted by page number.
-*/
-SQLITE_PRIVATE PgHdr *sqlite3PcacheDirtyList(PCache *pCache){
-  PgHdr *p;
-  for(p=pCache->pDirty; p; p=p->pDirtyNext){
-    p->pDirty = p->pDirtyNext;
-  }
-  return pcacheSortDirtyList(pCache->pDirty);
-}
-
-/* 
-** Return the total number of references to all pages held by the cache.
-**
-** This is not the total number of pages referenced, but the sum of the
-** reference count for all pages.
-*/
-SQLITE_PRIVATE int sqlite3PcacheRefCount(PCache *pCache){
-  return pCache->nRefSum;
-}
-
-/*
-** Return the number of references to the page supplied as an argument.
-*/
-SQLITE_PRIVATE int sqlite3PcachePageRefcount(PgHdr *p){
-  return p->nRef;
-}
-
-#ifdef SQLITE_TEST
-/* 
-** Return the total number of pages in the cache.
-*/
-SQLITE_PRIVATE int sqlite3PcachePagecount(PCache *pCache){
-  assert( pCache->pCache!=0 );
-  return sqlite3GlobalConfig.pcache2.xPagecount(pCache->pCache);
-}
-
-/*
-** Get the suggested cache-size value.
-*/
-SQLITE_PRIVATE int sqlite3PcacheGetCachesize(PCache *pCache){
-  return numberOfCachePages(pCache);
-}
-#endif
-
-/*
-** Set the suggested cache-size value.
-*/
-SQLITE_PRIVATE void sqlite3PcacheSetCachesize(PCache *pCache, int mxPage){
-  assert( pCache->pCache!=0 );
-  pCache->szCache = mxPage;
-  sqlite3GlobalConfig.pcache2.xCachesize(pCache->pCache,
-                                         numberOfCachePages(pCache));
-}
-
-#if 0
-/*
-** Free up as much memory as possible from the page cache.
-*/
-SQLITE_PRIVATE void sqlite3PcacheShrink(PCache *pCache){
-  assert( pCache->pCache!=0 );
-  sqlite3GlobalConfig.pcache2.xShrink(pCache->pCache);
-}
-#endif
-
-/*
-** Return the size of the header added by this middleware layer
-** in the page-cache hierarchy.
-*/
-SQLITE_PRIVATE int sqlite3HeaderSizePcache(void){ return ROUND8(sizeof(PgHdr)); }
-
-
-#if defined(SQLITE_CHECK_PAGES) || defined(SQLITE_DEBUG)
-/*
-** For all dirty pages currently in the cache, invoke the specified
-** callback. This is only used if the SQLITE_CHECK_PAGES macro is
-** defined.
-*/
-SQLITE_PRIVATE void sqlite3PcacheIterateDirty(PCache *pCache, void (*xIter)(PgHdr *)){
-  PgHdr *pDirty;
-  for(pDirty=pCache->pDirty; pDirty; pDirty=pDirty->pDirtyNext){
-    xIter(pDirty);
-  }
-}
-#endif
-
-/************** End of pcache.c **********************************************/
-/************** Begin file pcache1.c *****************************************/
-/*
-** 2008 November 05
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file implements the default page cache implementation (the
-** sqlite3_pcache interface). It also contains part of the implementation
-** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
-** If the default page cache implementation is overridden, then neither of
-** these two features are available.
-**
-** A Page cache line looks like this:
-**
-**  -------------------------------------------------------------
-**  |  database page content   |  PgHdr1  |  MemPage  |  PgHdr  |
-**  -------------------------------------------------------------
-**
-** The database page content is up front (so that buffer overreads tend to
-** flow harmlessly into the PgHdr1, MemPage, and PgHdr extensions).   MemPage
-** is the extension added by the btree.c module containing information such
-** as the database page number and how that database page is used.  PgHdr
-** is added by the pcache.c layer and contains information used to keep track
-** of which pages are "dirty".  PgHdr1 is an extension added by this
-** module (pcache1.c).  The PgHdr1 header is a subclass of sqlite3_pcache_page.
-** PgHdr1 contains information needed to look up a page by its page number.
-** The superclass sqlite3_pcache_page.pBuf points to the start of the
-** database page content and sqlite3_pcache_page.pExtra points to PgHdr.
-**
-** The size of the extension (MemPage+PgHdr+PgHdr1) can be determined at
-** runtime using sqlite3_config(SQLITE_CONFIG_PCACHE_HDRSZ, &size).  The
-** sizes of the extensions sum to 272 bytes on x64 for 3.8.10, but this
-** size can vary according to architecture, compile-time options, and
-** SQLite library version number.
-**
-** If SQLITE_PCACHE_SEPARATE_HEADER is defined, then the extension is obtained
-** using a separate memory allocation from the database page content.  This
-** seeks to overcome the "clownshoe" problem (also called "internal
-** fragmentation" in academic literature) of allocating a few bytes more
-** than a power of two with the memory allocator rounding up to the next
-** power of two, and leaving the rounded-up space unused.
-**
-** This module tracks pointers to PgHdr1 objects.  Only pcache.c communicates
-** with this module.  Information is passed back and forth as PgHdr1 pointers.
-**
-** The pcache.c and pager.c modules deal pointers to PgHdr objects.
-** The btree.c module deals with pointers to MemPage objects.
-**
-** SOURCE OF PAGE CACHE MEMORY:
-**
-** Memory for a page might come from any of three sources:
-**
-**    (1)  The general-purpose memory allocator - sqlite3Malloc()
-**    (2)  Global page-cache memory provided using sqlite3_config() with
-**         SQLITE_CONFIG_PAGECACHE.
-**    (3)  PCache-local bulk allocation.
-**
-** The third case is a chunk of heap memory (defaulting to 100 pages worth)
-** that is allocated when the page cache is created.  The size of the local
-** bulk allocation can be adjusted using 
-**
-**     sqlite3_config(SQLITE_CONFIG_PAGECACHE, 0, 0, N).
-**
-** If N is positive, then N pages worth of memory are allocated using a single
-** sqlite3Malloc() call and that memory is used for the first N pages allocated.
-** Or if N is negative, then -1024*N bytes of memory are allocated and used
-** for as many pages as can be accomodated.
-**
-** Only one of (2) or (3) can be used.  Once the memory available to (2) or
-** (3) is exhausted, subsequent allocations fail over to the general-purpose
-** memory allocator (1).
-**
-** Earlier versions of SQLite used only methods (1) and (2).  But experiments
-** show that method (3) with N==100 provides about a 5% performance boost for
-** common workloads.
-*/
-/* #include "sqliteInt.h" */
-
-typedef struct PCache1 PCache1;
-typedef struct PgHdr1 PgHdr1;
-typedef struct PgFreeslot PgFreeslot;
-typedef struct PGroup PGroup;
-
-/*
-** Each cache entry is represented by an instance of the following 
-** structure. Unless SQLITE_PCACHE_SEPARATE_HEADER is defined, a buffer of
-** PgHdr1.pCache->szPage bytes is allocated directly before this structure 
-** in memory.
-*/
-struct PgHdr1 {
-  sqlite3_pcache_page page;      /* Base class. Must be first. pBuf & pExtra */
-  unsigned int iKey;             /* Key value (page number) */
-  u8 isPinned;                   /* Page in use, not on the LRU list */
-  u8 isBulkLocal;                /* This page from bulk local storage */
-  u8 isAnchor;                   /* This is the PGroup.lru element */
-  PgHdr1 *pNext;                 /* Next in hash table chain */
-  PCache1 *pCache;               /* Cache that currently owns this page */
-  PgHdr1 *pLruNext;              /* Next in LRU list of unpinned pages */
-  PgHdr1 *pLruPrev;              /* Previous in LRU list of unpinned pages */
-};
-
-/* Each page cache (or PCache) belongs to a PGroup.  A PGroup is a set 
-** of one or more PCaches that are able to recycle each other's unpinned
-** pages when they are under memory pressure.  A PGroup is an instance of
-** the following object.
-**
-** This page cache implementation works in one of two modes:
-**
-**   (1)  Every PCache is the sole member of its own PGroup.  There is
-**        one PGroup per PCache.
-**
-**   (2)  There is a single global PGroup that all PCaches are a member
-**        of.
-**
-** Mode 1 uses more memory (since PCache instances are not able to rob
-** unused pages from other PCaches) but it also operates without a mutex,
-** and is therefore often faster.  Mode 2 requires a mutex in order to be
-** threadsafe, but recycles pages more efficiently.
-**
-** For mode (1), PGroup.mutex is NULL.  For mode (2) there is only a single
-** PGroup which is the pcache1.grp global variable and its mutex is
-** SQLITE_MUTEX_STATIC_LRU.
-*/
-struct PGroup {
-  sqlite3_mutex *mutex;          /* MUTEX_STATIC_LRU or NULL */
-  unsigned int nMaxPage;         /* Sum of nMax for purgeable caches */
-  unsigned int nMinPage;         /* Sum of nMin for purgeable caches */
-  unsigned int mxPinned;         /* nMaxpage + 10 - nMinPage */
-  unsigned int nCurrentPage;     /* Number of purgeable pages allocated */
-  PgHdr1 lru;                    /* The beginning and end of the LRU list */
-};
-
-/* Each page cache is an instance of the following object.  Every
-** open database file (including each in-memory database and each
-** temporary or transient database) has a single page cache which
-** is an instance of this object.
-**
-** Pointers to structures of this type are cast and returned as 
-** opaque sqlite3_pcache* handles.
-*/
-struct PCache1 {
-  /* Cache configuration parameters. Page size (szPage) and the purgeable
-  ** flag (bPurgeable) are set when the cache is created. nMax may be 
-  ** modified at any time by a call to the pcache1Cachesize() method.
-  ** The PGroup mutex must be held when accessing nMax.
-  */
-  PGroup *pGroup;                     /* PGroup this cache belongs to */
-  int szPage;                         /* Size of database content section */
-  int szExtra;                        /* sizeof(MemPage)+sizeof(PgHdr) */
-  int szAlloc;                        /* Total size of one pcache line */
-  int bPurgeable;                     /* True if cache is purgeable */
-  unsigned int nMin;                  /* Minimum number of pages reserved */
-  unsigned int nMax;                  /* Configured "cache_size" value */
-  unsigned int n90pct;                /* nMax*9/10 */
-  unsigned int iMaxKey;               /* Largest key seen since xTruncate() */
-
-  /* Hash table of all pages. The following variables may only be accessed
-  ** when the accessor is holding the PGroup mutex.
-  */
-  unsigned int nRecyclable;           /* Number of pages in the LRU list */
-  unsigned int nPage;                 /* Total number of pages in apHash */
-  unsigned int nHash;                 /* Number of slots in apHash[] */
-  PgHdr1 **apHash;                    /* Hash table for fast lookup by key */
-  PgHdr1 *pFree;                      /* List of unused pcache-local pages */
-  void *pBulk;                        /* Bulk memory used by pcache-local */
-};
-
-/*
-** Free slots in the allocator used to divide up the global page cache
-** buffer provided using the SQLITE_CONFIG_PAGECACHE mechanism.
-*/
-struct PgFreeslot {
-  PgFreeslot *pNext;  /* Next free slot */
-};
-
-/*
-** Global data used by this cache.
-*/
-static SQLITE_WSD struct PCacheGlobal {
-  PGroup grp;                    /* The global PGroup for mode (2) */
-
-  /* Variables related to SQLITE_CONFIG_PAGECACHE settings.  The
-  ** szSlot, nSlot, pStart, pEnd, nReserve, and isInit values are all
-  ** fixed at sqlite3BtreeInitialize() time and do not require mutex protection.
-  ** The nFreeSlot and pFree values do require mutex protection.
-  */
-  int isInit;                    /* True if initialized */
-  int separateCache;             /* Use a new PGroup for each PCache */
-  int nInitPage;                 /* Initial bulk allocation size */   
-  int szSlot;                    /* Size of each free slot */
-  int nSlot;                     /* The number of pcache slots */
-  int nReserve;                  /* Try to keep nFreeSlot above this */
-  void *pStart, *pEnd;           /* Bounds of global page cache memory */
-  /* Above requires no mutex.  Use mutex below for variable that follow. */
-  sqlite3_mutex *mutex;          /* Mutex for accessing the following: */
-  PgFreeslot *pFree;             /* Free page blocks */
-  int nFreeSlot;                 /* Number of unused pcache slots */
-  /* The following value requires a mutex to change.  We skip the mutex on
-  ** reading because (1) most platforms read a 32-bit integer atomically and
-  ** (2) even if an incorrect value is read, no great harm is done since this
-  ** is really just an optimization. */
-  int bUnderPressure;            /* True if low on PAGECACHE memory */
-} pcache1_g;
-
-/*
-** All code in this file should access the global structure above via the
-** alias "pcache1". This ensures that the WSD emulation is used when
-** compiling for systems that do not support real WSD.
-*/
-#define pcache1 (GLOBAL(struct PCacheGlobal, pcache1_g))
-
-/*
-** Macros to enter and leave the PCache LRU mutex.
-*/
-#if !defined(SQLITE_ENABLE_MEMORY_MANAGEMENT) || SQLITE_THREADSAFE==0
-# define pcache1EnterMutex(X)  assert((X)->mutex==0)
-# define pcache1LeaveMutex(X)  assert((X)->mutex==0)
-# define PCACHE1_MIGHT_USE_GROUP_MUTEX 0
-#else
-# define pcache1EnterMutex(X) sqlite3_mutex_enter((X)->mutex)
-# define pcache1LeaveMutex(X) sqlite3_mutex_leave((X)->mutex)
-# define PCACHE1_MIGHT_USE_GROUP_MUTEX 1
-#endif
-
-/******************************************************************************/
-/******** Page Allocation/SQLITE_CONFIG_PCACHE Related Functions **************/
-
-
-/*
-** This function is called during initialization if a static buffer is 
-** supplied to use for the page-cache by passing the SQLITE_CONFIG_PAGECACHE
-** verb to sqlite3_config(). Parameter pBuf points to an allocation large
-** enough to contain 'n' buffers of 'sz' bytes each.
-**
-** This routine is called from sqlite3_initialize() and so it is guaranteed
-** to be serialized already.  There is no need for further mutexing.
-*/
-SQLITE_PRIVATE void sqlite3PCacheBufferSetup(void *pBuf, int sz, int n){
-  if( pcache1.isInit ){
-    PgFreeslot *p;
-    if( pBuf==0 ) sz = n = 0;
-    sz = ROUNDDOWN8(sz);
-    pcache1.szSlot = sz;
-    pcache1.nSlot = pcache1.nFreeSlot = n;
-    pcache1.nReserve = n>90 ? 10 : (n/10 + 1);
-    pcache1.pStart = pBuf;
-    pcache1.pFree = 0;
-    pcache1.bUnderPressure = 0;
-    while( n-- ){
-      p = (PgFreeslot*)pBuf;
-      p->pNext = pcache1.pFree;
-      pcache1.pFree = p;
-      pBuf = (void*)&((char*)pBuf)[sz];
-    }
-    pcache1.pEnd = pBuf;
-  }
-}
-
-/*
-** Try to initialize the pCache->pFree and pCache->pBulk fields.  Return
-** true if pCache->pFree ends up containing one or more free pages.
-*/
-static int pcache1InitBulk(PCache1 *pCache){
-  i64 szBulk;
-  char *zBulk;
-  if( pcache1.nInitPage==0 ) return 0;
-  /* Do not bother with a bulk allocation if the cache size very small */
-  if( pCache->nMax<3 ) return 0;
-  if( pcache1.nInitPage>0 ){
-    szBulk = pCache->szAlloc * (i64)pcache1.nInitPage;
-  }else{
-    szBulk = -1024 * (i64)pcache1.nInitPage;
-  }
-  if( szBulk > pCache->szAlloc*(i64)pCache->nMax ){
-    szBulk = pCache->szAlloc*pCache->nMax;
-  }
-  zBulk = pCache->pBulk = sqlite3Malloc( szBulk );
-  if( zBulk ){
-    int nBulk = sqlite3MallocSize(zBulk)/pCache->szAlloc;
-    int i;
-    for(i=0; i<nBulk; i++){
-      PgHdr1 *pX = (PgHdr1*)&zBulk[pCache->szPage];
-      pX->page.pBuf = zBulk;
-      pX->page.pExtra = &pX[1];
-      pX->isBulkLocal = 1;
-      pX->isAnchor = 0;
-      pX->pNext = pCache->pFree;
-      pCache->pFree = pX;
-      zBulk += pCache->szAlloc;
-    }
-  }
-  return pCache->pFree!=0;
-}
-
-/*
-** Malloc function used within this file to allocate space from the buffer
-** configured using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no 
-** such buffer exists or there is no space left in it, this function falls 
-** back to sqlite3Malloc().
-**
-** Multiple threads can run this routine at the same time.  Global variables
-** in pcache1 need to be protected via mutex.
-*/
-static void *pcache1Alloc(int nByte){
-  void *p = 0;
-  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
-  if( nByte<=pcache1.szSlot ){
-    sqlite3_mutex_enter(pcache1.mutex);
-    p = (PgHdr1 *)pcache1.pFree;
-    if( p ){
-      pcache1.pFree = pcache1.pFree->pNext;
-      pcache1.nFreeSlot--;
-      pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
-      assert( pcache1.nFreeSlot>=0 );
-      sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
-      sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_USED, 1);
-    }
-    sqlite3_mutex_leave(pcache1.mutex);
-  }
-  if( p==0 ){
-    /* Memory is not available in the SQLITE_CONFIG_PAGECACHE pool.  Get
-    ** it from sqlite3Malloc instead.
-    */
-    p = sqlite3Malloc(nByte);
-#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
-    if( p ){
-      int sz = sqlite3MallocSize(p);
-      sqlite3_mutex_enter(pcache1.mutex);
-      sqlite3StatusSet(SQLITE_STATUS_PAGECACHE_SIZE, nByte);
-      sqlite3StatusUp(SQLITE_STATUS_PAGECACHE_OVERFLOW, sz);
-      sqlite3_mutex_leave(pcache1.mutex);
-    }
-#endif
-    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
-  }
-  return p;
-}
-
-/*
-** Free an allocated buffer obtained from pcache1Alloc().
-*/
-static void pcache1Free(void *p){
-  int nFreed = 0;
-  if( p==0 ) return;
-  if( p>=pcache1.pStart && p<pcache1.pEnd ){
-    PgFreeslot *pSlot;
-    sqlite3_mutex_enter(pcache1.mutex);
-    sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_USED, 1);
-    pSlot = (PgFreeslot*)p;
-    pSlot->pNext = pcache1.pFree;
-    pcache1.pFree = pSlot;
-    pcache1.nFreeSlot++;
-    pcache1.bUnderPressure = pcache1.nFreeSlot<pcache1.nReserve;
-    assert( pcache1.nFreeSlot<=pcache1.nSlot );
-    sqlite3_mutex_leave(pcache1.mutex);
-  }else{
-    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
-    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-#ifndef SQLITE_DISABLE_PAGECACHE_OVERFLOW_STATS
-    nFreed = sqlite3MallocSize(p);
-    sqlite3_mutex_enter(pcache1.mutex);
-    sqlite3StatusDown(SQLITE_STATUS_PAGECACHE_OVERFLOW, nFreed);
-    sqlite3_mutex_leave(pcache1.mutex);
-#endif
-    sqlite3_free(p);
-  }
-}
-
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-/*
-** Return the size of a pcache allocation
-*/
-static int pcache1MemSize(void *p){
-  if( p>=pcache1.pStart && p<pcache1.pEnd ){
-    return pcache1.szSlot;
-  }else{
-    int iSize;
-    assert( sqlite3MemdebugHasType(p, MEMTYPE_PCACHE) );
-    sqlite3MemdebugSetType(p, MEMTYPE_HEAP);
-    iSize = sqlite3MallocSize(p);
-    sqlite3MemdebugSetType(p, MEMTYPE_PCACHE);
-    return iSize;
-  }
-}
-#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
-
-/*
-** Allocate a new page object initially associated with cache pCache.
-*/
-static PgHdr1 *pcache1AllocPage(PCache1 *pCache, int benignMalloc){
-  PgHdr1 *p = 0;
-  void *pPg;
-
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  if( pCache->pFree || (pCache->nPage==0 && pcache1InitBulk(pCache)) ){
-    p = pCache->pFree;
-    pCache->pFree = p->pNext;
-    p->pNext = 0;
-  }else{
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-    /* The group mutex must be released before pcache1Alloc() is called. This
-    ** is because it might call sqlite3_release_memory(), which assumes that 
-    ** this mutex is not held. */
-    assert( pcache1.separateCache==0 );
-    assert( pCache->pGroup==&pcache1.grp );
-    pcache1LeaveMutex(pCache->pGroup);
-#endif
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-    pPg = pcache1Alloc(pCache->szPage);
-    p = sqlite3Malloc(sizeof(PgHdr1) + pCache->szExtra);
-    if( !pPg || !p ){
-      pcache1Free(pPg);
-      sqlite3_free(p);
-      pPg = 0;
-    }
-#else
-    pPg = pcache1Alloc(pCache->szAlloc);
-    p = (PgHdr1 *)&((u8 *)pPg)[pCache->szPage];
-#endif
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-    pcache1EnterMutex(pCache->pGroup);
-#endif
-    if( pPg==0 ) return 0;
-    p->page.pBuf = pPg;
-    p->page.pExtra = &p[1];
-    p->isBulkLocal = 0;
-    p->isAnchor = 0;
-  }
-  if( pCache->bPurgeable ){
-    pCache->pGroup->nCurrentPage++;
-  }
-  return p;
-}
-
-/*
-** Free a page object allocated by pcache1AllocPage().
-*/
-static void pcache1FreePage(PgHdr1 *p){
-  PCache1 *pCache;
-  assert( p!=0 );
-  pCache = p->pCache;
-  assert( sqlite3_mutex_held(p->pCache->pGroup->mutex) );
-  if( p->isBulkLocal ){
-    p->pNext = pCache->pFree;
-    pCache->pFree = p;
-  }else{
-    pcache1Free(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-    sqlite3_free(p);
-#endif
-  }
-  if( pCache->bPurgeable ){
-    pCache->pGroup->nCurrentPage--;
-  }
-}
-
-/*
-** Malloc function used by SQLite to obtain space from the buffer configured
-** using sqlite3_config(SQLITE_CONFIG_PAGECACHE) option. If no such buffer
-** exists, this function falls back to sqlite3Malloc().
-*/
-SQLITE_PRIVATE void *sqlite3PageMalloc(int sz){
-  return pcache1Alloc(sz);
-}
-
-/*
-** Free an allocated buffer obtained from sqlite3PageMalloc().
-*/
-SQLITE_PRIVATE void sqlite3PageFree(void *p){
-  pcache1Free(p);
-}
-
-
-/*
-** Return true if it desirable to avoid allocating a new page cache
-** entry.
-**
-** If memory was allocated specifically to the page cache using
-** SQLITE_CONFIG_PAGECACHE but that memory has all been used, then
-** it is desirable to avoid allocating a new page cache entry because
-** presumably SQLITE_CONFIG_PAGECACHE was suppose to be sufficient
-** for all page cache needs and we should not need to spill the
-** allocation onto the heap.
-**
-** Or, the heap is used for all page cache memory but the heap is
-** under memory pressure, then again it is desirable to avoid
-** allocating a new page cache entry in order to avoid stressing
-** the heap even further.
-*/
-static int pcache1UnderMemoryPressure(PCache1 *pCache){
-  if( pcache1.nSlot && (pCache->szPage+pCache->szExtra)<=pcache1.szSlot ){
-    return pcache1.bUnderPressure;
-  }else{
-    return sqlite3HeapNearlyFull();
-  }
-}
-
-/******************************************************************************/
-/******** General Implementation Functions ************************************/
-
-/*
-** This function is used to resize the hash table used by the cache passed
-** as the first argument.
-**
-** The PCache mutex must be held when this function is called.
-*/
-static void pcache1ResizeHash(PCache1 *p){
-  PgHdr1 **apNew;
-  unsigned int nNew;
-  unsigned int i;
-
-  assert( sqlite3_mutex_held(p->pGroup->mutex) );
-
-  nNew = p->nHash*2;
-  if( nNew<256 ){
-    nNew = 256;
-  }
-
-  pcache1LeaveMutex(p->pGroup);
-  apNew = (PgHdr1 **)sqlite3MallocZero(sizeof(PgHdr1 *)*nNew);
-  pcache1EnterMutex(p->pGroup);
-  if( apNew ){
-    for(i=0; i<p->nHash; i++){
-      PgHdr1 *pPage;
-      PgHdr1 *pNext = p->apHash[i];
-      while( (pPage = pNext)!=0 ){
-        unsigned int h = pPage->iKey % nNew;
-        pNext = pPage->pNext;
-        pPage->pNext = apNew[h];
-        apNew[h] = pPage;
-      }
-    }
-    sqlite3_free(p->apHash);
-    p->apHash = apNew;
-    p->nHash = nNew;
-  }
-}
-
-/*
-** This function is used internally to remove the page pPage from the 
-** PGroup LRU list, if is part of it. If pPage is not part of the PGroup
-** LRU list, then this function is a no-op.
-**
-** The PGroup mutex must be held when this function is called.
-*/
-static PgHdr1 *pcache1PinPage(PgHdr1 *pPage){
-  PCache1 *pCache;
-
-  assert( pPage!=0 );
-  assert( pPage->isPinned==0 );
-  pCache = pPage->pCache;
-  assert( pPage->pLruNext );
-  assert( pPage->pLruPrev );
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  pPage->pLruPrev->pLruNext = pPage->pLruNext;
-  pPage->pLruNext->pLruPrev = pPage->pLruPrev;
-  pPage->pLruNext = 0;
-  pPage->pLruPrev = 0;
-  pPage->isPinned = 1;
-  assert( pPage->isAnchor==0 );
-  assert( pCache->pGroup->lru.isAnchor==1 );
-  pCache->nRecyclable--;
-  return pPage;
-}
-
-
-/*
-** Remove the page supplied as an argument from the hash table 
-** (PCache1.apHash structure) that it is currently stored in.
-** Also free the page if freePage is true.
-**
-** The PGroup mutex must be held when this function is called.
-*/
-static void pcache1RemoveFromHash(PgHdr1 *pPage, int freeFlag){
-  unsigned int h;
-  PCache1 *pCache = pPage->pCache;
-  PgHdr1 **pp;
-
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  h = pPage->iKey % pCache->nHash;
-  for(pp=&pCache->apHash[h]; (*pp)!=pPage; pp=&(*pp)->pNext);
-  *pp = (*pp)->pNext;
-
-  pCache->nPage--;
-  if( freeFlag ) pcache1FreePage(pPage);
-}
-
-/*
-** If there are currently more than nMaxPage pages allocated, try
-** to recycle pages to reduce the number allocated to nMaxPage.
-*/
-static void pcache1EnforceMaxPage(PCache1 *pCache){
-  PGroup *pGroup = pCache->pGroup;
-  PgHdr1 *p;
-  assert( sqlite3_mutex_held(pGroup->mutex) );
-  while( pGroup->nCurrentPage>pGroup->nMaxPage
-      && (p=pGroup->lru.pLruPrev)->isAnchor==0
-  ){
-    assert( p->pCache->pGroup==pGroup );
-    assert( p->isPinned==0 );
-    pcache1PinPage(p);
-    pcache1RemoveFromHash(p, 1);
-  }
-  if( pCache->nPage==0 && pCache->pBulk ){
-    sqlite3_free(pCache->pBulk);
-    pCache->pBulk = pCache->pFree = 0;
-  }
-}
-
-/*
-** Discard all pages from cache pCache with a page number (key value) 
-** greater than or equal to iLimit. Any pinned pages that meet this 
-** criteria are unpinned before they are discarded.
-**
-** The PCache mutex must be held when this function is called.
-*/
-static void pcache1TruncateUnsafe(
-  PCache1 *pCache,             /* The cache to truncate */
-  unsigned int iLimit          /* Drop pages with this pgno or larger */
-){
-  TESTONLY( unsigned int nPage = 0; )  /* To assert pCache->nPage is correct */
-  unsigned int h;
-  assert( sqlite3_mutex_held(pCache->pGroup->mutex) );
-  for(h=0; h<pCache->nHash; h++){
-    PgHdr1 **pp = &pCache->apHash[h]; 
-    PgHdr1 *pPage;
-    while( (pPage = *pp)!=0 ){
-      if( pPage->iKey>=iLimit ){
-        pCache->nPage--;
-        *pp = pPage->pNext;
-        if( !pPage->isPinned ) pcache1PinPage(pPage);
-        pcache1FreePage(pPage);
-      }else{
-        pp = &pPage->pNext;
-        TESTONLY( nPage++; )
-      }
-    }
-  }
-  assert( pCache->nPage==nPage );
-}
-
-/******************************************************************************/
-/******** sqlite3_pcache Methods **********************************************/
-
-/*
-** Implementation of the sqlite3_pcache.xInit method.
-*/
-static int pcache1Init(void *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  assert( pcache1.isInit==0 );
-  memset(&pcache1, 0, sizeof(pcache1));
-
-
-  /*
-  ** The pcache1.separateCache variable is true if each PCache has its own
-  ** private PGroup (mode-1).  pcache1.separateCache is false if the single
-  ** PGroup in pcache1.grp is used for all page caches (mode-2).
-  **
-  **   *  Always use a unified cache (mode-2) if ENABLE_MEMORY_MANAGEMENT
-  **
-  **   *  Use a unified cache in single-threaded applications that have
-  **      configured a start-time buffer for use as page-cache memory using
-  **      sqlite3_config(SQLITE_CONFIG_PAGECACHE, pBuf, sz, N) with non-NULL 
-  **      pBuf argument.
-  **
-  **   *  Otherwise use separate caches (mode-1)
-  */
-#if defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
-  pcache1.separateCache = 0;
-#elif SQLITE_THREADSAFE
-  pcache1.separateCache = sqlite3GlobalConfig.pPage==0
-                          || sqlite3GlobalConfig.bCoreMutex>0;
-#else
-  pcache1.separateCache = sqlite3GlobalConfig.pPage==0;
-#endif
-
-#if SQLITE_THREADSAFE
-  if( sqlite3GlobalConfig.bCoreMutex ){
-    pcache1.grp.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_LRU);
-    pcache1.mutex = sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_PMEM);
-  }
-#endif
-  if( pcache1.separateCache
-   && sqlite3GlobalConfig.nPage!=0
-   && sqlite3GlobalConfig.pPage==0
-  ){
-    pcache1.nInitPage = sqlite3GlobalConfig.nPage;
-  }else{
-    pcache1.nInitPage = 0;
-  }
-  pcache1.grp.mxPinned = 10;
-  pcache1.isInit = 1;
-  return SQLITE_OK;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xShutdown method.
-** Note that the static mutex allocated in xInit does 
-** not need to be freed.
-*/
-static void pcache1Shutdown(void *NotUsed){
-  UNUSED_PARAMETER(NotUsed);
-  assert( pcache1.isInit!=0 );
-  memset(&pcache1, 0, sizeof(pcache1));
-}
-
-/* forward declaration */
-static void pcache1Destroy(sqlite3_pcache *p);
-
-/*
-** Implementation of the sqlite3_pcache.xCreate method.
-**
-** Allocate a new cache.
-*/
-static sqlite3_pcache *pcache1Create(int szPage, int szExtra, int bPurgeable){
-  PCache1 *pCache;      /* The newly created page cache */
-  PGroup *pGroup;       /* The group the new page cache will belong to */
-  int sz;               /* Bytes of memory required to allocate the new cache */
-
-  assert( (szPage & (szPage-1))==0 && szPage>=512 && szPage<=65536 );
-  assert( szExtra < 300 );
-
-  sz = sizeof(PCache1) + sizeof(PGroup)*pcache1.separateCache;
-  pCache = (PCache1 *)sqlite3MallocZero(sz);
-  if( pCache ){
-    if( pcache1.separateCache ){
-      pGroup = (PGroup*)&pCache[1];
-      pGroup->mxPinned = 10;
-    }else{
-      pGroup = &pcache1.grp;
-    }
-    if( pGroup->lru.isAnchor==0 ){
-      pGroup->lru.isAnchor = 1;
-      pGroup->lru.pLruPrev = pGroup->lru.pLruNext = &pGroup->lru;
-    }
-    pCache->pGroup = pGroup;
-    pCache->szPage = szPage;
-    pCache->szExtra = szExtra;
-    pCache->szAlloc = szPage + szExtra + ROUND8(sizeof(PgHdr1));
-    pCache->bPurgeable = (bPurgeable ? 1 : 0);
-    pcache1EnterMutex(pGroup);
-    pcache1ResizeHash(pCache);
-    if( bPurgeable ){
-      pCache->nMin = 10;
-      pGroup->nMinPage += pCache->nMin;
-      pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-    }
-    pcache1LeaveMutex(pGroup);
-    if( pCache->nHash==0 ){
-      pcache1Destroy((sqlite3_pcache*)pCache);
-      pCache = 0;
-    }
-  }
-  return (sqlite3_pcache *)pCache;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xCachesize method. 
-**
-** Configure the cache_size limit for a cache.
-*/
-static void pcache1Cachesize(sqlite3_pcache *p, int nMax){
-  PCache1 *pCache = (PCache1 *)p;
-  if( pCache->bPurgeable ){
-    PGroup *pGroup = pCache->pGroup;
-    pcache1EnterMutex(pGroup);
-    pGroup->nMaxPage += (nMax - pCache->nMax);
-    pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-    pCache->nMax = nMax;
-    pCache->n90pct = pCache->nMax*9/10;
-    pcache1EnforceMaxPage(pCache);
-    pcache1LeaveMutex(pGroup);
-  }
-}
-
-/*
-** Implementation of the sqlite3_pcache.xShrink method. 
-**
-** Free up as much memory as possible.
-*/
-static void pcache1Shrink(sqlite3_pcache *p){
-  PCache1 *pCache = (PCache1*)p;
-  if( pCache->bPurgeable ){
-    PGroup *pGroup = pCache->pGroup;
-    int savedMaxPage;
-    pcache1EnterMutex(pGroup);
-    savedMaxPage = pGroup->nMaxPage;
-    pGroup->nMaxPage = 0;
-    pcache1EnforceMaxPage(pCache);
-    pGroup->nMaxPage = savedMaxPage;
-    pcache1LeaveMutex(pGroup);
-  }
-}
-
-/*
-** Implementation of the sqlite3_pcache.xPagecount method. 
-*/
-static int pcache1Pagecount(sqlite3_pcache *p){
-  int n;
-  PCache1 *pCache = (PCache1*)p;
-  pcache1EnterMutex(pCache->pGroup);
-  n = pCache->nPage;
-  pcache1LeaveMutex(pCache->pGroup);
-  return n;
-}
-
-
-/*
-** Implement steps 3, 4, and 5 of the pcache1Fetch() algorithm described
-** in the header of the pcache1Fetch() procedure.
-**
-** This steps are broken out into a separate procedure because they are
-** usually not needed, and by avoiding the stack initialization required
-** for these steps, the main pcache1Fetch() procedure can run faster.
-*/
-static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
-  PCache1 *pCache, 
-  unsigned int iKey, 
-  int createFlag
-){
-  unsigned int nPinned;
-  PGroup *pGroup = pCache->pGroup;
-  PgHdr1 *pPage = 0;
-
-  /* Step 3: Abort if createFlag is 1 but the cache is nearly full */
-  assert( pCache->nPage >= pCache->nRecyclable );
-  nPinned = pCache->nPage - pCache->nRecyclable;
-  assert( pGroup->mxPinned == pGroup->nMaxPage + 10 - pGroup->nMinPage );
-  assert( pCache->n90pct == pCache->nMax*9/10 );
-  if( createFlag==1 && (
-        nPinned>=pGroup->mxPinned
-     || nPinned>=pCache->n90pct
-     || (pcache1UnderMemoryPressure(pCache) && pCache->nRecyclable<nPinned)
-  )){
-    return 0;
-  }
-
-  if( pCache->nPage>=pCache->nHash ) pcache1ResizeHash(pCache);
-  assert( pCache->nHash>0 && pCache->apHash );
-
-  /* Step 4. Try to recycle a page. */
-  if( pCache->bPurgeable
-   && !pGroup->lru.pLruPrev->isAnchor
-   && ((pCache->nPage+1>=pCache->nMax) || pcache1UnderMemoryPressure(pCache))
-  ){
-    PCache1 *pOther;
-    pPage = pGroup->lru.pLruPrev;
-    assert( pPage->isPinned==0 );
-    pcache1RemoveFromHash(pPage, 0);
-    pcache1PinPage(pPage);
-    pOther = pPage->pCache;
-    if( pOther->szAlloc != pCache->szAlloc ){
-      pcache1FreePage(pPage);
-      pPage = 0;
-    }else{
-      pGroup->nCurrentPage -= (pOther->bPurgeable - pCache->bPurgeable);
-    }
-  }
-
-  /* Step 5. If a usable page buffer has still not been found, 
-  ** attempt to allocate a new one. 
-  */
-  if( !pPage ){
-    pPage = pcache1AllocPage(pCache, createFlag==1);
-  }
-
-  if( pPage ){
-    unsigned int h = iKey % pCache->nHash;
-    pCache->nPage++;
-    pPage->iKey = iKey;
-    pPage->pNext = pCache->apHash[h];
-    pPage->pCache = pCache;
-    pPage->pLruPrev = 0;
-    pPage->pLruNext = 0;
-    pPage->isPinned = 1;
-    *(void **)pPage->page.pExtra = 0;
-    pCache->apHash[h] = pPage;
-    if( iKey>pCache->iMaxKey ){
-      pCache->iMaxKey = iKey;
-    }
-  }
-  return pPage;
-}
-
-/*
-** Implementation of the sqlite3_pcache.xFetch method. 
-**
-** Fetch a page by key value.
-**
-** Whether or not a new page may be allocated by this function depends on
-** the value of the createFlag argument.  0 means do not allocate a new
-** page.  1 means allocate a new page if space is easily available.  2 
-** means to try really hard to allocate a new page.
-**
-** For a non-purgeable cache (a cache used as the storage for an in-memory
-** database) there is really no difference between createFlag 1 and 2.  So
-** the calling function (pcache.c) will never have a createFlag of 1 on
-** a non-purgeable cache.
-**
-** There are three different approaches to obtaining space for a page,
-** depending on the value of parameter createFlag (which may be 0, 1 or 2).
-**
-**   1. Regardless of the value of createFlag, the cache is searched for a 
-**      copy of the requested page. If one is found, it is returned.
-**
-**   2. If createFlag==0 and the page is not already in the cache, NULL is
-**      returned.
-**
-**   3. If createFlag is 1, and the page is not already in the cache, then
-**      return NULL (do not allocate a new page) if any of the following
-**      conditions are true:
-**
-**       (a) the number of pages pinned by the cache is greater than
-**           PCache1.nMax, or
-**
-**       (b) the number of pages pinned by the cache is greater than
-**           the sum of nMax for all purgeable caches, less the sum of 
-**           nMin for all other purgeable caches, or
-**
-**   4. If none of the first three conditions apply and the cache is marked
-**      as purgeable, and if one of the following is true:
-**
-**       (a) The number of pages allocated for the cache is already 
-**           PCache1.nMax, or
-**
-**       (b) The number of pages allocated for all purgeable caches is
-**           already equal to or greater than the sum of nMax for all
-**           purgeable caches,
-**
-**       (c) The system is under memory pressure and wants to avoid
-**           unnecessary pages cache entry allocations
-**
-**      then attempt to recycle a page from the LRU list. If it is the right
-**      size, return the recycled buffer. Otherwise, free the buffer and
-**      proceed to step 5. 
-**
-**   5. Otherwise, allocate and return a new page buffer.
-**
-** There are two versions of this routine.  pcache1FetchWithMutex() is
-** the general case.  pcache1FetchNoMutex() is a faster implementation for
-** the common case where pGroup->mutex is NULL.  The pcache1Fetch() wrapper
-** invokes the appropriate routine.
-*/
-static PgHdr1 *pcache1FetchNoMutex(
-  sqlite3_pcache *p, 
-  unsigned int iKey, 
-  int createFlag
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = 0;
-
-  /* Step 1: Search the hash table for an existing entry. */
-  pPage = pCache->apHash[iKey % pCache->nHash];
-  while( pPage && pPage->iKey!=iKey ){ pPage = pPage->pNext; }
-
-  /* Step 2: If the page was found in the hash table, then return it.
-  ** If the page was not in the hash table and createFlag is 0, abort.
-  ** Otherwise (page not in hash and createFlag!=0) continue with
-  ** subsequent steps to try to create the page. */
-  if( pPage ){
-    if( !pPage->isPinned ){
-      return pcache1PinPage(pPage);
-    }else{
-      return pPage;
-    }
-  }else if( createFlag ){
-    /* Steps 3, 4, and 5 implemented by this subroutine */
-    return pcache1FetchStage2(pCache, iKey, createFlag);
-  }else{
-    return 0;
-  }
-}
-#if PCACHE1_MIGHT_USE_GROUP_MUTEX
-static PgHdr1 *pcache1FetchWithMutex(
-  sqlite3_pcache *p, 
-  unsigned int iKey, 
-  int createFlag
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage;
-
-  pcache1EnterMutex(pCache->pGroup);
-  pPage = pcache1FetchNoMutex(p, iKey, createFlag);
-  assert( pPage==0 || pCache->iMaxKey>=iKey );
-  pcache1LeaveMutex(pCache->pGroup);
-  return pPage;
-}
-#endif
-static sqlite3_pcache_page *pcache1Fetch(
-  sqlite3_pcache *p, 
-  unsigned int iKey, 
-  int createFlag
-){
-#if PCACHE1_MIGHT_USE_GROUP_MUTEX || defined(SQLITE_DEBUG)
-  PCache1 *pCache = (PCache1 *)p;
-#endif
-
-  assert( offsetof(PgHdr1,page)==0 );
-  assert( pCache->bPurgeable || createFlag!=1 );
-  assert( pCache->bPurgeable || pCache->nMin==0 );
-  assert( pCache->bPurgeable==0 || pCache->nMin==10 );
-  assert( pCache->nMin==0 || pCache->bPurgeable );
-  assert( pCache->nHash>0 );
-#if PCACHE1_MIGHT_USE_GROUP_MUTEX
-  if( pCache->pGroup->mutex ){
-    return (sqlite3_pcache_page*)pcache1FetchWithMutex(p, iKey, createFlag);
-  }else
-#endif
-  {
-    return (sqlite3_pcache_page*)pcache1FetchNoMutex(p, iKey, createFlag);
-  }
-}
-
-
-/*
-** Implementation of the sqlite3_pcache.xUnpin method.
-**
-** Mark a page as unpinned (eligible for asynchronous recycling).
-*/
-static void pcache1Unpin(
-  sqlite3_pcache *p, 
-  sqlite3_pcache_page *pPg, 
-  int reuseUnlikely
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = (PgHdr1 *)pPg;
-  PGroup *pGroup = pCache->pGroup;
- 
-  assert( pPage->pCache==pCache );
-  pcache1EnterMutex(pGroup);
-
-  /* It is an error to call this function if the page is already 
-  ** part of the PGroup LRU list.
-  */
-  assert( pPage->pLruPrev==0 && pPage->pLruNext==0 );
-  assert( pPage->isPinned==1 );
-
-  if( reuseUnlikely || pGroup->nCurrentPage>pGroup->nMaxPage ){
-    pcache1RemoveFromHash(pPage, 1);
-  }else{
-    /* Add the page to the PGroup LRU list. */
-    PgHdr1 **ppFirst = &pGroup->lru.pLruNext;
-    pPage->pLruPrev = &pGroup->lru;
-    (pPage->pLruNext = *ppFirst)->pLruPrev = pPage;
-    *ppFirst = pPage;
-    pCache->nRecyclable++;
-    pPage->isPinned = 0;
-  }
-
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** Implementation of the sqlite3_pcache.xRekey method. 
-*/
-static void pcache1Rekey(
-  sqlite3_pcache *p,
-  sqlite3_pcache_page *pPg,
-  unsigned int iOld,
-  unsigned int iNew
-){
-  PCache1 *pCache = (PCache1 *)p;
-  PgHdr1 *pPage = (PgHdr1 *)pPg;
-  PgHdr1 **pp;
-  unsigned int h; 
-  assert( pPage->iKey==iOld );
-  assert( pPage->pCache==pCache );
-
-  pcache1EnterMutex(pCache->pGroup);
-
-  h = iOld%pCache->nHash;
-  pp = &pCache->apHash[h];
-  while( (*pp)!=pPage ){
-    pp = &(*pp)->pNext;
-  }
-  *pp = pPage->pNext;
-
-  h = iNew%pCache->nHash;
-  pPage->iKey = iNew;
-  pPage->pNext = pCache->apHash[h];
-  pCache->apHash[h] = pPage;
-  if( iNew>pCache->iMaxKey ){
-    pCache->iMaxKey = iNew;
-  }
-
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** Implementation of the sqlite3_pcache.xTruncate method. 
-**
-** Discard all unpinned pages in the cache with a page number equal to
-** or greater than parameter iLimit. Any pinned pages with a page number
-** equal to or greater than iLimit are implicitly unpinned.
-*/
-static void pcache1Truncate(sqlite3_pcache *p, unsigned int iLimit){
-  PCache1 *pCache = (PCache1 *)p;
-  pcache1EnterMutex(pCache->pGroup);
-  if( iLimit<=pCache->iMaxKey ){
-    pcache1TruncateUnsafe(pCache, iLimit);
-    pCache->iMaxKey = iLimit-1;
-  }
-  pcache1LeaveMutex(pCache->pGroup);
-}
-
-/*
-** Implementation of the sqlite3_pcache.xDestroy method. 
-**
-** Destroy a cache allocated using pcache1Create().
-*/
-static void pcache1Destroy(sqlite3_pcache *p){
-  PCache1 *pCache = (PCache1 *)p;
-  PGroup *pGroup = pCache->pGroup;
-  assert( pCache->bPurgeable || (pCache->nMax==0 && pCache->nMin==0) );
-  pcache1EnterMutex(pGroup);
-  pcache1TruncateUnsafe(pCache, 0);
-  assert( pGroup->nMaxPage >= pCache->nMax );
-  pGroup->nMaxPage -= pCache->nMax;
-  assert( pGroup->nMinPage >= pCache->nMin );
-  pGroup->nMinPage -= pCache->nMin;
-  pGroup->mxPinned = pGroup->nMaxPage + 10 - pGroup->nMinPage;
-  pcache1EnforceMaxPage(pCache);
-  pcache1LeaveMutex(pGroup);
-  sqlite3_free(pCache->pBulk);
-  sqlite3_free(pCache->apHash);
-  sqlite3_free(pCache);
-}
-
-/*
-** This function is called during initialization (sqlite3BtreeInitialize()) to
-** install the default pluggable cache module, assuming the user has not
-** already provided an alternative.
-*/
-SQLITE_PRIVATE void sqlite3PCacheSetDefault(void){
-  static const sqlite3_pcache_methods2 defaultMethods = {
-    1,                       /* iVersion */
-    0,                       /* pArg */
-    pcache1Init,             /* xInit */
-    pcache1Shutdown,         /* xShutdown */
-    pcache1Create,           /* xCreate */
-    pcache1Cachesize,        /* xCachesize */
-    pcache1Pagecount,        /* xPagecount */
-    pcache1Fetch,            /* xFetch */
-    pcache1Unpin,            /* xUnpin */
-    pcache1Rekey,            /* xRekey */
-    pcache1Truncate,         /* xTruncate */
-    pcache1Destroy,          /* xDestroy */
-    pcache1Shrink            /* xShrink */
-  };
-  sqlite3_config(SQLITE_CONFIG_PCACHE2, &defaultMethods);
-}
-
-/*
-** Return the size of the header on each page of this PCACHE implementation.
-*/
-SQLITE_PRIVATE int sqlite3HeaderSizePcache1(void){ return ROUND8(sizeof(PgHdr1)); }
-
-/*
-** Return the global mutex used by this PCACHE implementation.  The
-** sqlite3_status() routine needs access to this mutex.
-*/
-#ifndef NDEBUG
-SQLITE_PRIVATE sqlite3_mutex *sqlite3Pcache1Mutex(void){
-  return pcache1.mutex;
-}
-#endif
-
-#ifdef SQLITE_ENABLE_MEMORY_MANAGEMENT
-/*
-** This function is called to free superfluous dynamically allocated memory
-** held by the pager system. Memory in use by any SQLite pager allocated
-** by the current thread may be sqlite3_free()ed.
-**
-** nReq is the number of bytes of memory required. Once this much has
-** been released, the function returns. The return value is the total number 
-** of bytes of memory released.
-*/
-SQLITE_PRIVATE int sqlite3PcacheReleaseMemory(int nReq){
-  int nFree = 0;
-  assert( sqlite3_mutex_notheld(pcache1.grp.mutex) );
-  assert( sqlite3_mutex_notheld(pcache1.mutex) );
-  if( sqlite3GlobalConfig.nPage==0 ){
-    PgHdr1 *p;
-    pcache1EnterMutex(&pcache1.grp);
-    while( (nReq<0 || nFree<nReq)
-       &&  (p=pcache1.grp.lru.pLruPrev)!=0
-       &&  p->isAnchor==0
-    ){
-      nFree += pcache1MemSize(p->page.pBuf);
-#ifdef SQLITE_PCACHE_SEPARATE_HEADER
-      nFree += sqlite3MemSize(p);
-#endif
-      assert( p->isPinned==0 );
-      pcache1PinPage(p);
-      pcache1RemoveFromHash(p, 1);
-    }
-    pcache1LeaveMutex(&pcache1.grp);
-  }
-  return nFree;
-}
-#endif /* SQLITE_ENABLE_MEMORY_MANAGEMENT */
-
-#ifdef SQLITE_TEST
-/*
-** This function is used by test procedures to inspect the internal state
-** of the global cache.
-*/
-SQLITE_PRIVATE void sqlite3PcacheStats(
-  int *pnCurrent,      /* OUT: Total number of pages cached */
-  int *pnMax,          /* OUT: Global maximum cache size */
-  int *pnMin,          /* OUT: Sum of PCache1.nMin for purgeable caches */
-  int *pnRecyclable    /* OUT: Total number of pages available for recycling */
-){
-  PgHdr1 *p;
-  int nRecyclable = 0;
-  for(p=pcache1.grp.lru.pLruNext; p && !p->isAnchor; p=p->pLruNext){
-    assert( p->isPinned==0 );
-    nRecyclable++;
-  }
-  *pnCurrent = pcache1.grp.nCurrentPage;
-  *pnMax = (int)pcache1.grp.nMaxPage;
-  *pnMin = (int)pcache1.grp.nMinPage;
-  *pnRecyclable = nRecyclable;
-}
-#endif
-
-/************** End of pcache1.c *********************************************/
-/************** Begin file pager.c *******************************************/
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This is the implementation of the page cache subsystem or "pager".
-** 
-** The pager is used to access a database disk file.  It implements
-** atomic commit and rollback through the use of a journal file that
-** is separate from the database file.  The pager also implements file
-** locking to prevent two processes from writing the same database
-** file simultaneously, or one process from reading the database while
-** another is writing.
-*/
-#ifndef SQLITE_OMIT_DISKIO
-/* #include "sqliteInt.h" */
-/************** Include wal.h in the middle of pager.c ***********************/
-/************** Begin file wal.h *********************************************/
-/*
-** 2010 February 1
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This header file defines the interface to the write-ahead logging 
-** system. Refer to the comments below and the header comment attached to 
-** the implementation of each function in log.c for further details.
-*/
-
-#ifndef _WAL_H_
-#define _WAL_H_
-
-/* #include "sqliteInt.h" */
-
-/* Additional values that can be added to the sync_flags argument of
-** sqlite3WalFrames():
-*/
-#define WAL_SYNC_TRANSACTIONS  0x20   /* Sync at the end of each transaction */
-#define SQLITE_SYNC_MASK       0x13   /* Mask off the SQLITE_SYNC_* values */
-
-#ifdef SQLITE_OMIT_WAL
-# define sqlite3WalOpen(x,y,z)                   0
-#if 0
-# define sqlite3WalLimit(x,y)
-#endif
-# define sqlite3WalClose(w,x,y,z)                0
-# define sqlite3WalBeginReadTransaction(y,z)     0
-# define sqlite3WalEndReadTransaction(z)
-# define sqlite3WalDbsize(y)                     0
-# define sqlite3WalBeginWriteTransaction(y)      0
-# define sqlite3WalEndWriteTransaction(x)        0
-# define sqlite3WalUndo(x,y,z)                   0
-# define sqlite3WalSavepoint(y,z)
-# define sqlite3WalSavepointUndo(y,z)            0
-# define sqlite3WalFrames(u,v,w,x,y,z)           0
-# define sqlite3WalCheckpoint(r,s,t,u,v,w,x,y,z) 0
-#if 0
-# define sqlite3WalCallback(z)                   0
-#endif
-# define sqlite3WalExclusiveMode(y,z)            0
-#if 0
-# define sqlite3WalHeapMemory(z)                 0
-#endif
-# define sqlite3WalFramesize(z)                  0
-# define sqlite3WalFindFrame(x,y,z)              0
-#else
-
-#define WAL_SAVEPOINT_NDATA 4
-
-/* Connection to a write-ahead log (WAL) file. 
-** There is one object of this type for each pager. 
-*/
-typedef struct Wal Wal;
-
-/* Open and close a connection to a write-ahead log. */
-SQLITE_PRIVATE int sqlite3WalOpen(sqlite3_vfs*, sqlite3_file*, const char *, int, i64, Wal**);
-SQLITE_PRIVATE int sqlite3WalClose(Wal *pWal, int sync_flags, int, u8 *);
-
-#if 0
-/* Set the limiting size of a WAL file. */
-SQLITE_PRIVATE void sqlite3WalLimit(Wal*, i64);
-#endif
-
-/* Used by readers to open (lock) and close (unlock) a snapshot.  A 
-** snapshot is like a read-transaction.  It is the state of the database
-** at an instant in time.  sqlite3WalOpenSnapshot gets a read lock and
-** preserves the current state even if the other threads or processes
-** write to or checkpoint the WAL.  sqlite3WalCloseSnapshot() closes the
-** transaction and releases the lock.
-*/
-SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *);
-SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal);
-
-/* Read a page from the write-ahead log, if it is present. */
-SQLITE_PRIVATE int sqlite3WalFindFrame(Wal *, Pgno, u32 *);
-SQLITE_PRIVATE int sqlite3WalReadFrame(Wal *, u32, int, u8 *);
-
-/* If the WAL is not empty, return the size of the database. */
-SQLITE_PRIVATE Pgno sqlite3WalDbsize(Wal *pWal);
-
-/* Obtain or release the WRITER lock. */
-SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal);
-SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal);
-
-/* Undo any frames written (but not committed) to the log */
-SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx);
-
-/* Return an integer that records the current (uncommitted) write
-** position in the WAL */
-SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData);
-
-/* Move the write position of the WAL back to iFrame.  Called in
-** response to a ROLLBACK TO command. */
-SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData);
-
-/* Write a frame or frames to the log. */
-SQLITE_PRIVATE int sqlite3WalFrames(Wal *pWal, int, PgHdr *, Pgno, int, int);
-
-/* Copy pages from the log to the database file */ 
-SQLITE_PRIVATE int sqlite3WalCheckpoint(
-  Wal *pWal,                      /* Write-ahead log connection */
-  int eMode,                      /* One of PASSIVE, FULL and RESTART */
-  int (*xBusy)(void*),            /* Function to call when busy */
-  void *pBusyArg,                 /* Context argument for xBusyHandler */
-  int sync_flags,                 /* Flags to sync db file with (or 0) */
-  int nBuf,                       /* Size of buffer nBuf */
-  u8 *zBuf,                       /* Temporary buffer to use */
-  int *pnLog,                     /* OUT: Number of frames in WAL */
-  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
-);
-
-#if 0
-/* Return the value to pass to a sqlite3_wal_hook callback, the
-** number of frames in the WAL at the point of the last commit since
-** sqlite3WalCallback() was called.  If no commits have occurred since
-** the last call, then return 0.
-*/
-SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal);
-#endif
-
-/* Tell the wal layer that an EXCLUSIVE lock has been obtained (or released)
-** by the pager layer on the database file.
-*/
-SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op);
-
-#if 0
-/* Return true if the argument is non-NULL and the WAL module is using
-** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
-** WAL module is using shared-memory, return false. 
-*/
-SQLITE_PRIVATE int sqlite3WalHeapMemory(Wal *pWal);
-#endif
-
-#ifdef SQLITE_ENABLE_ZIPVFS
-/* If the WAL file is not empty, return the number of bytes of content
-** stored in each frame (i.e. the db page-size when the WAL was created).
-*/
-SQLITE_PRIVATE int sqlite3WalFramesize(Wal *pWal);
-#endif
-
-#endif /* ifndef SQLITE_OMIT_WAL */
-#endif /* _WAL_H_ */
-
-/************** End of wal.h *************************************************/
-/************** Continuing where we left off in pager.c **********************/
-
-
-/******************* NOTES ON THE DESIGN OF THE PAGER ************************
-**
-** This comment block describes invariants that hold when using a rollback
-** journal.  These invariants do not apply for journal_mode=WAL,
-** journal_mode=MEMORY, or journal_mode=OFF.
-**
-** Within this comment block, a page is deemed to have been synced
-** automatically as soon as it is written when PRAGMA synchronous=OFF.
-** Otherwise, the page is not synced until the xSync method of the VFS
-** is called successfully on the file containing the page.
-**
-** Definition:  A page of the database file is said to be "overwriteable" if
-** one or more of the following are true about the page:
-** 
-**     (a)  The original content of the page as it was at the beginning of
-**          the transaction has been written into the rollback journal and
-**          synced.
-** 
-**     (b)  The page was a freelist leaf page at the start of the transaction.
-** 
-**     (c)  The page number is greater than the largest page that existed in
-**          the database file at the start of the transaction.
-** 
-** (1) A page of the database file is never overwritten unless one of the
-**     following are true:
-** 
-**     (a) The page and all other pages on the same sector are overwriteable.
-** 
-**     (b) The atomic page write optimization is enabled, and the entire
-**         transaction other than the update of the transaction sequence
-**         number consists of a single page change.
-** 
-** (2) The content of a page written into the rollback journal exactly matches
-**     both the content in the database when the rollback journal was written
-**     and the content in the database at the beginning of the current
-**     transaction.
-** 
-** (3) Writes to the database file are an integer multiple of the page size
-**     in length and are aligned on a page boundary.
-** 
-** (4) Reads from the database file are either aligned on a page boundary and
-**     an integer multiple of the page size in length or are taken from the
-**     first 100 bytes of the database file.
-** 
-** (5) All writes to the database file are synced prior to the rollback journal
-**     being deleted, truncated, or zeroed.
-** 
-** (6) If a master journal file is used, then all writes to the database file
-**     are synced prior to the master journal being deleted.
-** 
-** Definition: Two databases (or the same database at two points it time)
-** are said to be "logically equivalent" if they give the same answer to
-** all queries.  Note in particular the content of freelist leaf
-** pages can be changed arbitrarily without affecting the logical equivalence
-** of the database.
-** 
-** (7) At any time, if any subset, including the empty set and the total set,
-**     of the unsynced changes to a rollback journal are removed and the 
-**     journal is rolled back, the resulting database file will be logically
-**     equivalent to the database file at the beginning of the transaction.
-** 
-** (8) When a transaction is rolled back, the xTruncate method of the VFS
-**     is called to restore the database file to the same size it was at
-**     the beginning of the transaction.  (In some VFSes, the xTruncate
-**     method is a no-op, but that does not change the fact the SQLite will
-**     invoke it.)
-** 
-** (9) Whenever the database file is modified, at least one bit in the range
-**     of bytes from 24 through 39 inclusive will be changed prior to releasing
-**     the EXCLUSIVE lock, thus signaling other connections on the same
-**     database to flush their caches.
-**
-** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less
-**      than one billion transactions.
-**
-** (11) A database file is well-formed at the beginning and at the conclusion
-**      of every transaction.
-**
-** (12) An EXCLUSIVE lock is held on the database file when writing to
-**      the database file.
-**
-** (13) A SHARED lock is held on the database file while reading any
-**      content out of the database file.
-**
-******************************************************************************/
-
-/*
-** Macros for troubleshooting.  Normally turned off
-*/
-#if 0
-int sqlite3PagerTrace=1;  /* True to enable tracing */
-#define sqlite3DebugPrintf printf
-#define PAGERTRACE(X)     if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; }
-#else
-#define PAGERTRACE(X)
-#endif
-
-/*
-** The following two macros are used within the PAGERTRACE() macros above
-** to print out file-descriptors. 
-**
-** PAGERID() takes a pointer to a Pager struct as its argument. The
-** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file
-** struct as its argument.
-*/
-#define PAGERID(p) ((int)(p->fd))
-#define FILEHANDLEID(fd) ((int)fd)
-
-/*
-** The Pager.eState variable stores the current 'state' of a pager. A
-** pager may be in any one of the seven states shown in the following
-** state diagram.
-**
-**                            OPEN <------+------+
-**                              |         |      |
-**                              V         |      |
-**               +---------> READER-------+      |
-**               |              |                |
-**               |              V                |
-**               |<-------WRITER_LOCKED------> ERROR
-**               |              |                ^  
-**               |              V                |
-**               |<------WRITER_CACHEMOD-------->|
-**               |              |                |
-**               |              V                |
-**               |<-------WRITER_DBMOD---------->|
-**               |              |                |
-**               |              V                |
-**               +<------WRITER_FINISHED-------->+
-**
-**
-** List of state transitions and the C [function] that performs each:
-** 
-**   OPEN              -> READER              [sqlite3PagerSharedLock]
-**   READER            -> OPEN                [pager_unlock]
-**
-**   READER            -> WRITER_LOCKED       [sqlite3PagerBegin]
-**   WRITER_LOCKED     -> WRITER_CACHEMOD     [pager_open_journal]
-**   WRITER_CACHEMOD   -> WRITER_DBMOD        [syncJournal]
-**   WRITER_DBMOD      -> WRITER_FINISHED     [sqlite3PagerCommitPhaseOne]
-**   WRITER_***        -> READER              [pager_end_transaction]
-**
-**   WRITER_***        -> ERROR               [pager_error]
-**   ERROR             -> OPEN                [pager_unlock]
-** 
-**
-**  OPEN:
-**
-**    The pager starts up in this state. Nothing is guaranteed in this
-**    state - the file may or may not be locked and the database size is
-**    unknown. The database may not be read or written.
-**
-**    * No read or write transaction is active.
-**    * Any lock, or no lock at all, may be held on the database file.
-**    * The dbSize, dbOrigSize and dbFileSize variables may not be trusted.
-**
-**  READER:
-**
-**    In this state all the requirements for reading the database in 
-**    rollback (non-WAL) mode are met. Unless the pager is (or recently
-**    was) in exclusive-locking mode, a user-level read transaction is 
-**    open. The database size is known in this state.
-**
-**    A connection running with locking_mode=normal enters this state when
-**    it opens a read-transaction on the database and returns to state
-**    OPEN after the read-transaction is completed. However a connection
-**    running in locking_mode=exclusive (including temp databases) remains in
-**    this state even after the read-transaction is closed. The only way
-**    a locking_mode=exclusive connection can transition from READER to OPEN
-**    is via the ERROR state (see below).
-** 
-**    * A read transaction may be active (but a write-transaction cannot).
-**    * A SHARED or greater lock is held on the database file.
-**    * The dbSize variable may be trusted (even if a user-level read 
-**      transaction is not active). The dbOrigSize and dbFileSize variables
-**      may not be trusted at this point.
-**    * If the database is a WAL database, then the WAL connection is open.
-**    * Even if a read-transaction is not open, it is guaranteed that 
-**      there is no hot-journal in the file-system.
-**
-**  WRITER_LOCKED:
-**
-**    The pager moves to this state from READER when a write-transaction
-**    is first opened on the database. In WRITER_LOCKED state, all locks 
-**    required to start a write-transaction are held, but no actual 
-**    modifications to the cache or database have taken place.
-**
-**    In rollback mode, a RESERVED or (if the transaction was opened with 
-**    BEGIN EXCLUSIVE) EXCLUSIVE lock is obtained on the database file when
-**    moving to this state, but the journal file is not written to or opened 
-**    to in this state. If the transaction is committed or rolled back while 
-**    in WRITER_LOCKED state, all that is required is to unlock the database 
-**    file.
-**
-**    IN WAL mode, WalBeginWriteTransaction() is called to lock the log file.
-**    If the connection is running with locking_mode=exclusive, an attempt
-**    is made to obtain an EXCLUSIVE lock on the database file.
-**
-**    * A write transaction is active.
-**    * If the connection is open in rollback-mode, a RESERVED or greater 
-**      lock is held on the database file.
-**    * If the connection is open in WAL-mode, a WAL write transaction
-**      is open (i.e. sqlite3WalBeginWriteTransaction() has been successfully
-**      called).
-**    * The dbSize, dbOrigSize and dbFileSize variables are all valid.
-**    * The contents of the pager cache have not been modified.
-**    * The journal file may or may not be open.
-**    * Nothing (not even the first header) has been written to the journal.
-**
-**  WRITER_CACHEMOD:
-**
-**    A pager moves from WRITER_LOCKED state to this state when a page is
-**    first modified by the upper layer. In rollback mode the journal file
-**    is opened (if it is not already open) and a header written to the
-**    start of it. The database file on disk has not been modified.
-**
-**    * A write transaction is active.
-**    * A RESERVED or greater lock is held on the database file.
-**    * The journal file is open and the first header has been written 
-**      to it, but the header has not been synced to disk.
-**    * The contents of the page cache have been modified.
-**
-**  WRITER_DBMOD:
-**
-**    The pager transitions from WRITER_CACHEMOD into WRITER_DBMOD state
-**    when it modifies the contents of the database file. WAL connections
-**    never enter this state (since they do not modify the database file,
-**    just the log file).
-**
-**    * A write transaction is active.
-**    * An EXCLUSIVE or greater lock is held on the database file.
-**    * The journal file is open and the first header has been written 
-**      and synced to disk.
-**    * The contents of the page cache have been modified (and possibly
-**      written to disk).
-**
-**  WRITER_FINISHED:
-**
-**    It is not possible for a WAL connection to enter this state.
-**
-**    A rollback-mode pager changes to WRITER_FINISHED state from WRITER_DBMOD
-**    state after the entire transaction has been successfully written into the
-**    database file. In this state the transaction may be committed simply
-**    by finalizing the journal file. Once in WRITER_FINISHED state, it is 
-**    not possible to modify the database further. At this point, the upper 
-**    layer must either commit or rollback the transaction.
-**
-**    * A write transaction is active.
-**    * An EXCLUSIVE or greater lock is held on the database file.
-**    * All writing and syncing of journal and database data has finished.
-**      If no error occurred, all that remains is to finalize the journal to
-**      commit the transaction. If an error did occur, the caller will need
-**      to rollback the transaction. 
-**
-**  ERROR:
-**
-**    The ERROR state is entered when an IO or disk-full error (including
-**    SQLITE_IOERR_NOMEM) occurs at a point in the code that makes it 
-**    difficult to be sure that the in-memory pager state (cache contents, 
-**    db size etc.) are consistent with the contents of the file-system.
-**
-**    Temporary pager files may enter the ERROR state, but in-memory pagers
-**    cannot.
-**
-**    For example, if an IO error occurs while performing a rollback, 
-**    the contents of the page-cache may be left in an inconsistent state.
-**    At this point it would be dangerous to change back to READER state
-**    (as usually happens after a rollback). Any subsequent readers might
-**    report database corruption (due to the inconsistent cache), and if
-**    they upgrade to writers, they may inadvertently corrupt the database
-**    file. To avoid this hazard, the pager switches into the ERROR state
-**    instead of READER following such an error.
-**
-**    Once it has entered the ERROR state, any attempt to use the pager
-**    to read or write data returns an error. Eventually, once all 
-**    outstanding transactions have been abandoned, the pager is able to
-**    transition back to OPEN state, discarding the contents of the 
-**    page-cache and any other in-memory state at the same time. Everything
-**    is reloaded from disk (and, if necessary, hot-journal rollback peformed)
-**    when a read-transaction is next opened on the pager (transitioning
-**    the pager into READER state). At that point the system has recovered 
-**    from the error.
-**
-**    Specifically, the pager jumps into the ERROR state if:
-**
-**      1. An error occurs while attempting a rollback. This happens in
-**         function sqlite3PagerRollback().
-**
-**      2. An error occurs while attempting to finalize a journal file
-**         following a commit in function sqlite3PagerCommitPhaseTwo().
-**
-**      3. An error occurs while attempting to write to the journal or
-**         database file in function pagerStress() in order to free up
-**         memory.
-**
-**    In other cases, the error is returned to the b-tree layer. The b-tree
-**    layer then attempts a rollback operation. If the error condition 
-**    persists, the pager enters the ERROR state via condition (1) above.
-**
-**    Condition (3) is necessary because it can be triggered by a read-only
-**    statement executed within a transaction. In this case, if the error
-**    code were simply returned to the user, the b-tree layer would not
-**    automatically attempt a rollback, as it assumes that an error in a
-**    read-only statement cannot leave the pager in an internally inconsistent 
-**    state.
-**
-**    * The Pager.errCode variable is set to something other than SQLITE_OK.
-**    * There are one or more outstanding references to pages (after the
-**      last reference is dropped the pager should move back to OPEN state).
-**    * The pager is not an in-memory pager.
-**    
-**
-** Notes:
-**
-**   * A pager is never in WRITER_DBMOD or WRITER_FINISHED state if the
-**     connection is open in WAL mode. A WAL connection is always in one
-**     of the first four states.
-**
-**   * Normally, a connection open in exclusive mode is never in PAGER_OPEN
-**     state. There are two exceptions: immediately after exclusive-mode has
-**     been turned on (and before any read or write transactions are 
-**     executed), and when the pager is leaving the "error state".
-**
-**   * See also: assert_pager_state().
-*/
-#define PAGER_OPEN                  0
-#define PAGER_READER                1
-#define PAGER_WRITER_LOCKED         2
-#define PAGER_WRITER_CACHEMOD       3
-#define PAGER_WRITER_DBMOD          4
-#define PAGER_WRITER_FINISHED       5
-#define PAGER_ERROR                 6
-
-/*
-** The Pager.eLock variable is almost always set to one of the 
-** following locking-states, according to the lock currently held on
-** the database file: NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
-** This variable is kept up to date as locks are taken and released by
-** the pagerLockDb() and pagerUnlockDb() wrappers.
-**
-** If the VFS xLock() or xUnlock() returns an error other than SQLITE_BUSY
-** (i.e. one of the SQLITE_IOERR subtypes), it is not clear whether or not
-** the operation was successful. In these circumstances pagerLockDb() and
-** pagerUnlockDb() take a conservative approach - eLock is always updated
-** when unlocking the file, and only updated when locking the file if the
-** VFS call is successful. This way, the Pager.eLock variable may be set
-** to a less exclusive (lower) value than the lock that is actually held
-** at the system level, but it is never set to a more exclusive value.
-**
-** This is usually safe. If an xUnlock fails or appears to fail, there may 
-** be a few redundant xLock() calls or a lock may be held for longer than
-** required, but nothing really goes wrong.
-**
-** The exception is when the database file is unlocked as the pager moves
-** from ERROR to OPEN state. At this point there may be a hot-journal file 
-** in the file-system that needs to be rolled back (as part of an OPEN->SHARED
-** transition, by the same pager or any other). If the call to xUnlock()
-** fails at this point and the pager is left holding an EXCLUSIVE lock, this
-** can confuse the call to xCheckReservedLock() call made later as part
-** of hot-journal detection.
-**
-** xCheckReservedLock() is defined as returning true "if there is a RESERVED 
-** lock held by this process or any others". So xCheckReservedLock may 
-** return true because the caller itself is holding an EXCLUSIVE lock (but
-** doesn't know it because of a previous error in xUnlock). If this happens
-** a hot-journal may be mistaken for a journal being created by an active
-** transaction in another process, causing SQLite to read from the database
-** without rolling it back.
-**
-** To work around this, if a call to xUnlock() fails when unlocking the
-** database in the ERROR state, Pager.eLock is set to UNKNOWN_LOCK. It
-** is only changed back to a real locking state after a successful call
-** to xLock(EXCLUSIVE). Also, the code to do the OPEN->SHARED state transition
-** omits the check for a hot-journal if Pager.eLock is set to UNKNOWN_LOCK 
-** lock. Instead, it assumes a hot-journal exists and obtains an EXCLUSIVE
-** lock on the database file before attempting to roll it back. See function
-** PagerSharedLock() for more detail.
-**
-** Pager.eLock may only be set to UNKNOWN_LOCK when the pager is in 
-** PAGER_OPEN state.
-*/
-#define UNKNOWN_LOCK                (EXCLUSIVE_LOCK+1)
-
-/*
-** A macro used for invoking the codec if there is one
-*/
-#ifdef SQLITE_HAS_CODEC
-# define CODEC1(P,D,N,X,E) \
-    if( P->xCodec && P->xCodec(P->pCodec,D,N,X)==0 ){ E; }
-# define CODEC2(P,D,N,X,E,O) \
-    if( P->xCodec==0 ){ O=(char*)D; }else \
-    if( (O=(char*)(P->xCodec(P->pCodec,D,N,X)))==0 ){ E; }
-#else
-# define CODEC1(P,D,N,X,E)   /* NO-OP */
-# define CODEC2(P,D,N,X,E,O) O=(char*)D
-#endif
-
-/*
-** The maximum allowed sector size. 64KiB. If the xSectorsize() method 
-** returns a value larger than this, then MAX_SECTOR_SIZE is used instead.
-** This could conceivably cause corruption following a power failure on
-** such a system. This is currently an undocumented limit.
-*/
-#define MAX_SECTOR_SIZE 0x10000
-
-/*
-** An instance of the following structure is allocated for each active
-** savepoint and statement transaction in the system. All such structures
-** are stored in the Pager.aSavepoint[] array, which is allocated and
-** resized using sqlite3Realloc().
-**
-** When a savepoint is created, the PagerSavepoint.iHdrOffset field is
-** set to 0. If a journal-header is written into the main journal while
-** the savepoint is active, then iHdrOffset is set to the byte offset 
-** immediately following the last journal record written into the main
-** journal before the journal-header. This is required during savepoint
-** rollback (see pagerPlaybackSavepoint()).
-*/
-typedef struct PagerSavepoint PagerSavepoint;
-struct PagerSavepoint {
-  i64 iOffset;                 /* Starting offset in main journal */
-  i64 iHdrOffset;              /* See above */
-  Bitvec *pInSavepoint;        /* Set of pages in this savepoint */
-  Pgno nOrig;                  /* Original number of pages in file */
-  Pgno iSubRec;                /* Index of first record in sub-journal */
-#ifndef SQLITE_OMIT_WAL
-  u32 aWalData[WAL_SAVEPOINT_NDATA];        /* WAL savepoint context */
-#endif
-};
-
-/*
-** Bits of the Pager.doNotSpill flag.  See further description below.
-*/
-#define SPILLFLAG_OFF         0x01 /* Never spill cache.  Set via pragma */
-#define SPILLFLAG_ROLLBACK    0x02 /* Current rolling back, so do not spill */
-#define SPILLFLAG_NOSYNC      0x04 /* Spill is ok, but do not sync */
-
-/*
-** An open page cache is an instance of struct Pager. A description of
-** some of the more important member variables follows:
-**
-** eState
-**
-**   The current 'state' of the pager object. See the comment and state
-**   diagram above for a description of the pager state.
-**
-** eLock
-**
-**   For a real on-disk database, the current lock held on the database file -
-**   NO_LOCK, SHARED_LOCK, RESERVED_LOCK or EXCLUSIVE_LOCK.
-**
-**   For a temporary or in-memory database (neither of which require any
-**   locks), this variable is always set to EXCLUSIVE_LOCK. Since such
-**   databases always have Pager.exclusiveMode==1, this tricks the pager
-**   logic into thinking that it already has all the locks it will ever
-**   need (and no reason to release them).
-**
-**   In some (obscure) circumstances, this variable may also be set to
-**   UNKNOWN_LOCK. See the comment above the #define of UNKNOWN_LOCK for
-**   details.
-**
-** changeCountDone
-**
-**   This boolean variable is used to make sure that the change-counter 
-**   (the 4-byte header field at byte offset 24 of the database file) is 
-**   not updated more often than necessary. 
-**
-**   It is set to true when the change-counter field is updated, which 
-**   can only happen if an exclusive lock is held on the database file.
-**   It is cleared (set to false) whenever an exclusive lock is 
-**   relinquished on the database file. Each time a transaction is committed,
-**   The changeCountDone flag is inspected. If it is true, the work of
-**   updating the change-counter is omitted for the current transaction.
-**
-**   This mechanism means that when running in exclusive mode, a connection 
-**   need only update the change-counter once, for the first transaction
-**   committed.
-**
-** setMaster
-**
-**   When PagerCommitPhaseOne() is called to commit a transaction, it may
-**   (or may not) specify a master-journal name to be written into the 
-**   journal file before it is synced to disk.
-**
-**   Whether or not a journal file contains a master-journal pointer affects 
-**   the way in which the journal file is finalized after the transaction is 
-**   committed or rolled back when running in "journal_mode=PERSIST" mode.
-**   If a journal file does not contain a master-journal pointer, it is
-**   finalized by overwriting the first journal header with zeroes. If
-**   it does contain a master-journal pointer the journal file is finalized 
-**   by truncating it to zero bytes, just as if the connection were 
-**   running in "journal_mode=truncate" mode.
-**
-**   Journal files that contain master journal pointers cannot be finalized
-**   simply by overwriting the first journal-header with zeroes, as the
-**   master journal pointer could interfere with hot-journal rollback of any
-**   subsequently interrupted transaction that reuses the journal file.
-**
-**   The flag is cleared as soon as the journal file is finalized (either
-**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
-**   journal file from being successfully finalized, the setMaster flag
-**   is cleared anyway (and the pager will move to ERROR state).
-**
-** doNotSpill
-**
-**   This variables control the behavior of cache-spills  (calls made by
-**   the pcache module to the pagerStress() routine to write cached data
-**   to the file-system in order to free up memory).
-**
-**   When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
-**   writing to the database from pagerStress() is disabled altogether.
-**   The SPILLFLAG_ROLLBACK case is done in a very obscure case that
-**   comes up during savepoint rollback that requires the pcache module
-**   to allocate a new page to prevent the journal file from being written
-**   while it is being traversed by code in pager_playback().  The SPILLFLAG_OFF
-**   case is a user preference.
-** 
-**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from
-**   pagerStress() is permitted, but syncing the journal file is not.
-**   This flag is set by sqlite3PagerWrite() when the file-system sector-size
-**   is larger than the database page-size in order to prevent a journal sync
-**   from happening in between the journalling of two pages on the same sector. 
-**
-** subjInMemory
-**
-**   This is a boolean variable. If true, then any required sub-journal
-**   is opened as an in-memory journal file. If false, then in-memory
-**   sub-journals are only used for in-memory pager files.
-**
-**   This variable is updated by the upper layer each time a new 
-**   write-transaction is opened.
-**
-** dbSize, dbOrigSize, dbFileSize
-**
-**   Variable dbSize is set to the number of pages in the database file.
-**   It is valid in PAGER_READER and higher states (all states except for
-**   OPEN and ERROR). 
-**
-**   dbSize is set based on the size of the database file, which may be 
-**   larger than the size of the database (the value stored at offset
-**   28 of the database header by the btree). If the size of the file
-**   is not an integer multiple of the page-size, the value stored in
-**   dbSize is rounded down (i.e. a 5KB file with 2K page-size has dbSize==2).
-**   Except, any file that is greater than 0 bytes in size is considered
-**   to have at least one page. (i.e. a 1KB file with 2K page-size leads
-**   to dbSize==1).
-**
-**   During a write-transaction, if pages with page-numbers greater than
-**   dbSize are modified in the cache, dbSize is updated accordingly.
-**   Similarly, if the database is truncated using PagerTruncateImage(), 
-**   dbSize is updated.
-**
-**   Variables dbOrigSize and dbFileSize are valid in states 
-**   PAGER_WRITER_LOCKED and higher. dbOrigSize is a copy of the dbSize
-**   variable at the start of the transaction. It is used during rollback,
-**   and to determine whether or not pages need to be journalled before
-**   being modified.
-**
-**   Throughout a write-transaction, dbFileSize contains the size of
-**   the file on disk in pages. It is set to a copy of dbSize when the
-**   write-transaction is first opened, and updated when VFS calls are made
-**   to write or truncate the database file on disk. 
-**
-**   The only reason the dbFileSize variable is required is to suppress 
-**   unnecessary calls to xTruncate() after committing a transaction. If, 
-**   when a transaction is committed, the dbFileSize variable indicates 
-**   that the database file is larger than the database image (Pager.dbSize), 
-**   pager_truncate() is called. The pager_truncate() call uses xFilesize()
-**   to measure the database file on disk, and then truncates it if required.
-**   dbFileSize is not used when rolling back a transaction. In this case
-**   pager_truncate() is called unconditionally (which means there may be
-**   a call to xFilesize() that is not strictly required). In either case,
-**   pager_truncate() may cause the file to become smaller or larger.
-**
-** dbHintSize
-**
-**   The dbHintSize variable is used to limit the number of calls made to
-**   the VFS xFileControl(FCNTL_SIZE_HINT) method. 
-**
-**   dbHintSize is set to a copy of the dbSize variable when a
-**   write-transaction is opened (at the same time as dbFileSize and
-**   dbOrigSize). If the xFileControl(FCNTL_SIZE_HINT) method is called,
-**   dbHintSize is increased to the number of pages that correspond to the
-**   size-hint passed to the method call. See pager_write_pagelist() for 
-**   details.
-**
-** errCode
-**
-**   The Pager.errCode variable is only ever used in PAGER_ERROR state. It
-**   is set to zero in all other states. In PAGER_ERROR state, Pager.errCode 
-**   is always set to SQLITE_FULL, SQLITE_IOERR or one of the SQLITE_IOERR_XXX 
-**   sub-codes.
-*/
-struct Pager {
-  sqlite3_vfs *pVfs;          /* OS functions to use for IO */
-  u8 exclusiveMode;           /* Boolean. True if locking_mode==EXCLUSIVE */
-  u8 journalMode;             /* One of the PAGER_JOURNALMODE_* values */
-  u8 useJournal;              /* Use a rollback journal on this file */
-  u8 noSync;                  /* Do not sync the journal if true */
-  u8 fullSync;                /* Do extra syncs of the journal for robustness */
-  u8 ckptSyncFlags;           /* SYNC_NORMAL or SYNC_FULL for checkpoint */
-  u8 walSyncFlags;            /* SYNC_NORMAL or SYNC_FULL for wal writes */
-  u8 syncFlags;               /* SYNC_NORMAL or SYNC_FULL otherwise */
-  u8 tempFile;                /* zFilename is a temporary or immutable file */
-  u8 noLock;                  /* Do not lock (except in WAL mode) */
-  u8 readOnly;                /* True for a read-only database */
-  u8 memDb;                   /* True to inhibit all file I/O */
-
-  /**************************************************************************
-  ** The following block contains those class members that change during
-  ** routine operation.  Class members not in this block are either fixed
-  ** when the pager is first created or else only change when there is a
-  ** significant mode change (such as changing the page_size, locking_mode,
-  ** or the journal_mode).  From another view, these class members describe
-  ** the "state" of the pager, while other class members describe the
-  ** "configuration" of the pager.
-  */
-  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
-  u8 eLock;                   /* Current lock held on database file */
-  u8 changeCountDone;         /* Set after incrementing the change-counter */
-  u8 setMaster;               /* True if a m-j name has been written to jrnl */
-  u8 doNotSpill;              /* Do not spill the cache when non-zero */
-  u8 subjInMemory;            /* True to use in-memory sub-journals */
-  u8 bUseFetch;               /* True to use xFetch() */
-  u8 hasHeldSharedLock;       /* True if a shared lock has ever been held */
-  Pgno dbSize;                /* Number of pages in the database */
-  Pgno dbOrigSize;            /* dbSize before the current transaction */
-  Pgno dbFileSize;            /* Number of pages in the database file */
-  Pgno dbHintSize;            /* Value passed to FCNTL_SIZE_HINT call */
-  int errCode;                /* One of several kinds of errors */
-  int nRec;                   /* Pages journalled since last j-header written */
-  u32 cksumInit;              /* Quasi-random value added to every checksum */
-  u32 nSubRec;                /* Number of records written to sub-journal */
-  Bitvec *pInJournal;         /* One bit for each page in the database file */
-  sqlite3_file *fd;           /* File descriptor for database */
-  sqlite3_file *jfd;          /* File descriptor for main journal */
-  sqlite3_file *sjfd;         /* File descriptor for sub-journal */
-  i64 journalOff;             /* Current write offset in the journal file */
-  i64 journalHdr;             /* Byte offset to previous journal header */
-  sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
-  PagerSavepoint *aSavepoint; /* Array of active savepoints */
-  int nSavepoint;             /* Number of elements in aSavepoint[] */
-  u32 iDataVersion;           /* Changes whenever database content changes */
-  char dbFileVers[16];        /* Changes whenever database file changes */
-
-  int nMmapOut;               /* Number of mmap pages currently outstanding */
-  sqlite3_int64 szMmap;       /* Desired maximum mmap size */
-  PgHdr *pMmapFreelist;       /* List of free mmap page headers (pDirty) */
-  /*
-  ** End of the routinely-changing class members
-  ***************************************************************************/
-
-  u16 nExtra;                 /* Add this many bytes to each in-memory page */
-  i16 nReserve;               /* Number of unused bytes at end of each page */
-  u32 vfsFlags;               /* Flags for sqlite3_vfs.xOpen() */
-  u32 sectorSize;             /* Assumed sector size during rollback */
-  int pageSize;               /* Number of bytes in a page */
-  Pgno mxPgno;                /* Maximum allowed size of the database */
-  i64 journalSizeLimit;       /* Size limit for persistent journal files */
-  char *zFilename;            /* Name of the database file */
-  char *zJournal;             /* Name of the journal file */
-  int (*xBusyHandler)(void*); /* Function to call when busy */
-  void *pBusyHandlerArg;      /* Context argument for xBusyHandler */
-  int aStat[3];               /* Total cache hits, misses and writes */
-#ifdef SQLITE_TEST
-  int nRead;                  /* Database pages read */
-#endif
-  void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
-#ifdef SQLITE_HAS_CODEC
-  void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */
-  void (*xCodecSizeChng)(void*,int,int); /* Notify of page size changes */
-  void (*xCodecFree)(void*);             /* Destructor for the codec */
-  void *pCodec;               /* First argument to xCodec... methods */
-#endif
-  char *pTmpSpace;            /* Pager.pageSize bytes of space for tmp use */
-  PCache *pPCache;            /* Pointer to page cache object */
-#ifndef SQLITE_OMIT_WAL
-  Wal *pWal;                  /* Write-ahead log used by "journal_mode=wal" */
-  char *zWal;                 /* File name for write-ahead log */
-#endif
-};
-
-/*
-** Indexes for use with Pager.aStat[]. The Pager.aStat[] array contains
-** the values accessed by passing SQLITE_DBSTATUS_CACHE_HIT, CACHE_MISS 
-** or CACHE_WRITE to sqlite3_db_status().
-*/
-#define PAGER_STAT_HIT   0
-#define PAGER_STAT_MISS  1
-#define PAGER_STAT_WRITE 2
-
-/*
-** The following global variables hold counters used for
-** testing purposes only.  These variables do not exist in
-** a non-testing build.  These variables are not thread-safe.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_pager_readdb_count = 0;    /* Number of full pages read from DB */
-SQLITE_PRIVATE int sqlite3_pager_writedb_count = 0;   /* Number of full pages written to DB */
-SQLITE_PRIVATE int sqlite3_pager_writej_count = 0;    /* Number of pages written to journal */
-# define PAGER_INCR(v)  v++
-#else
-# define PAGER_INCR(v)
-#endif
-
-
-
-/*
-** Journal files begin with the following magic string.  The data
-** was obtained from /dev/random.  It is used only as a sanity check.
-**
-** Since version 2.8.0, the journal format contains additional sanity
-** checking information.  If the power fails while the journal is being
-** written, semi-random garbage data might appear in the journal
-** file after power is restored.  If an attempt is then made
-** to roll the journal back, the database could be corrupted.  The additional
-** sanity checking data is an attempt to discover the garbage in the
-** journal and ignore it.
-**
-** The sanity checking information for the new journal format consists
-** of a 32-bit checksum on each page of data.  The checksum covers both
-** the page number and the pPager->pageSize bytes of data for the page.
-** This cksum is initialized to a 32-bit random value that appears in the
-** journal file right after the header.  The random initializer is important,
-** because garbage data that appears at the end of a journal is likely
-** data that was once in other files that have now been deleted.  If the
-** garbage data came from an obsolete journal file, the checksums might
-** be correct.  But by initializing the checksum to random value which
-** is different for every journal, we minimize that risk.
-*/
-static const unsigned char aJournalMagic[] = {
-  0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7,
-};
-
-/*
-** The size of the of each page record in the journal is given by
-** the following macro.
-*/
-#define JOURNAL_PG_SZ(pPager)  ((pPager->pageSize) + 8)
-
-/*
-** The journal header size for this pager. This is usually the same 
-** size as a single disk sector. See also setSectorSize().
-*/
-#define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize)
-
-/*
-** The macro USEFETCH is true if we are allowed to use the xFetch and xUnfetch
-** interfaces to access the database using memory-mapped I/O.
-*/
-#if SQLITE_MAX_MMAP_SIZE>0
-# define USEFETCH(x) ((x)->bUseFetch)
-#else
-# define USEFETCH(x) 0
-#endif
-
-/*
-** The maximum legal page number is (2^31 - 1).
-*/
-#define PAGER_MAX_PGNO 2147483647
-
-/*
-** The argument to this macro is a file descriptor (type sqlite3_file*).
-** Return 0 if it is not open, or non-zero (but not 1) if it is.
-**
-** This is so that expressions can be written as:
-**
-**   if( isOpen(pPager->jfd) ){ ...
-**
-** instead of
-**
-**   if( pPager->jfd->pMethods ){ ...
-*/
-#define isOpen(pFd) ((pFd)->pMethods!=0)
-
-/*
-** Return true if this pager uses a write-ahead log instead of the usual
-** rollback journal. Otherwise false.
-*/
-#ifndef SQLITE_OMIT_WAL
-static int pagerUseWal(Pager *pPager){
-  return (pPager->pWal!=0);
-}
-#else
-# define pagerUseWal(x) 0
-# define pagerRollbackWal(x) 0
-# define pagerWalFrames(v,w,x,y) 0
-# define pagerOpenWalIfPresent(z) SQLITE_OK
-# define pagerBeginReadTransaction(z) SQLITE_OK
-#endif
-
-#ifndef NDEBUG 
-/*
-** Usage:
-**
-**   assert( assert_pager_state(pPager) );
-**
-** This function runs many asserts to try to find inconsistencies in
-** the internal state of the Pager object.
-*/
-static int assert_pager_state(Pager *p){
-  Pager *pPager = p;
-
-  /* State must be valid. */
-  assert( p->eState==PAGER_OPEN
-       || p->eState==PAGER_READER
-       || p->eState==PAGER_WRITER_LOCKED
-       || p->eState==PAGER_WRITER_CACHEMOD
-       || p->eState==PAGER_WRITER_DBMOD
-       || p->eState==PAGER_WRITER_FINISHED
-       || p->eState==PAGER_ERROR
-  );
-
-  /* Regardless of the current state, a temp-file connection always behaves
-  ** as if it has an exclusive lock on the database file. It never updates
-  ** the change-counter field, so the changeCountDone flag is always set.
-  */
-  assert( p->tempFile==0 || p->eLock==EXCLUSIVE_LOCK );
-  assert( p->tempFile==0 || pPager->changeCountDone );
-
-  /* If the useJournal flag is clear, the journal-mode must be "OFF". 
-  ** And if the journal-mode is "OFF", the journal file must not be open.
-  */
-  assert( p->journalMode==PAGER_JOURNALMODE_OFF || p->useJournal );
-  assert( p->journalMode!=PAGER_JOURNALMODE_OFF || !isOpen(p->jfd) );
-
-  /* If changeCountDone is set, a RESERVED lock or greater must be held
-  ** on the file.
-  */
-  assert( pPager->changeCountDone==0 || pPager->eLock>=RESERVED_LOCK );
-  assert( p->eLock!=PENDING_LOCK );
-
-  switch( p->eState ){
-    case PAGER_OPEN:
-      assert( pPager->errCode==SQLITE_OK );
-      assert( sqlite3PcacheRefCount(pPager->pPCache)==0 || pPager->tempFile );
-      break;
-
-    case PAGER_READER:
-      assert( pPager->errCode==SQLITE_OK );
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( p->eLock>=SHARED_LOCK );
-      break;
-
-    case PAGER_WRITER_LOCKED:
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      if( !pagerUseWal(pPager) ){
-        assert( p->eLock>=RESERVED_LOCK );
-      }
-      assert( pPager->dbSize==pPager->dbOrigSize );
-      assert( pPager->dbOrigSize==pPager->dbFileSize );
-      assert( pPager->dbOrigSize==pPager->dbHintSize );
-      assert( pPager->setMaster==0 );
-      break;
-
-    case PAGER_WRITER_CACHEMOD:
-      assert( p->eLock!=UNKNOWN_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      if( !pagerUseWal(pPager) ){
-        /* It is possible that if journal_mode=wal here that neither the
-        ** journal file nor the WAL file are open. This happens during
-        ** a rollback transaction that switches from journal_mode=off
-        ** to journal_mode=wal.
-        */
-        assert( p->eLock>=RESERVED_LOCK );
-        assert( isOpen(p->jfd) 
-             || p->journalMode==PAGER_JOURNALMODE_OFF 
-             || p->journalMode==PAGER_JOURNALMODE_WAL 
-        );
-      }
-      assert( pPager->dbOrigSize==pPager->dbFileSize );
-      assert( pPager->dbOrigSize==pPager->dbHintSize );
-      break;
-
-    case PAGER_WRITER_DBMOD:
-      assert( p->eLock==EXCLUSIVE_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      assert( !pagerUseWal(pPager) );
-      assert( p->eLock>=EXCLUSIVE_LOCK );
-      assert( isOpen(p->jfd) 
-           || p->journalMode==PAGER_JOURNALMODE_OFF 
-           || p->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      assert( pPager->dbOrigSize<=pPager->dbHintSize );
-      break;
-
-    case PAGER_WRITER_FINISHED:
-      assert( p->eLock==EXCLUSIVE_LOCK );
-      assert( pPager->errCode==SQLITE_OK );
-      assert( !pagerUseWal(pPager) );
-      assert( isOpen(p->jfd) 
-           || p->journalMode==PAGER_JOURNALMODE_OFF 
-           || p->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      break;
-
-    case PAGER_ERROR:
-      /* There must be at least one outstanding reference to the pager if
-      ** in ERROR state. Otherwise the pager should have already dropped
-      ** back to OPEN state.
-      */
-      assert( pPager->errCode!=SQLITE_OK );
-      assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
-      break;
-  }
-
-  return 1;
-}
-#endif /* ifndef NDEBUG */
-
-#ifdef SQLITE_DEBUG 
-/*
-** Return a pointer to a human readable string in a static buffer
-** containing the state of the Pager object passed as an argument. This
-** is intended to be used within debuggers. For example, as an alternative
-** to "print *pPager" in gdb:
-**
-** (gdb) printf "%s", print_pager_state(pPager)
-*/
-static char *print_pager_state(Pager *p){
-  static char zRet[1024];
-
-  sqlite3_snprintf(1024, zRet,
-      "Filename:      %s\n"
-      "State:         %s errCode=%d\n"
-      "Lock:          %s\n"
-      "Locking mode:  locking_mode=%s\n"
-      "Journal mode:  journal_mode=%s\n"
-      "Backing store: tempFile=%d memDb=%d useJournal=%d\n"
-      "Journal:       journalOff=%lld journalHdr=%lld\n"
-      "Size:          dbsize=%d dbOrigSize=%d dbFileSize=%d\n"
-      , p->zFilename
-      , p->eState==PAGER_OPEN            ? "OPEN" :
-        p->eState==PAGER_READER          ? "READER" :
-        p->eState==PAGER_WRITER_LOCKED   ? "WRITER_LOCKED" :
-        p->eState==PAGER_WRITER_CACHEMOD ? "WRITER_CACHEMOD" :
-        p->eState==PAGER_WRITER_DBMOD    ? "WRITER_DBMOD" :
-        p->eState==PAGER_WRITER_FINISHED ? "WRITER_FINISHED" :
-        p->eState==PAGER_ERROR           ? "ERROR" : "?error?"
-      , (int)p->errCode
-      , p->eLock==NO_LOCK         ? "NO_LOCK" :
-        p->eLock==RESERVED_LOCK   ? "RESERVED" :
-        p->eLock==EXCLUSIVE_LOCK  ? "EXCLUSIVE" :
-        p->eLock==SHARED_LOCK     ? "SHARED" :
-        p->eLock==UNKNOWN_LOCK    ? "UNKNOWN" : "?error?"
-      , p->exclusiveMode ? "exclusive" : "normal"
-      , p->journalMode==PAGER_JOURNALMODE_MEMORY   ? "memory" :
-        p->journalMode==PAGER_JOURNALMODE_OFF      ? "off" :
-        p->journalMode==PAGER_JOURNALMODE_DELETE   ? "delete" :
-        p->journalMode==PAGER_JOURNALMODE_PERSIST  ? "persist" :
-        p->journalMode==PAGER_JOURNALMODE_TRUNCATE ? "truncate" :
-        p->journalMode==PAGER_JOURNALMODE_WAL      ? "wal" : "?error?"
-      , (int)p->tempFile, (int)p->memDb, (int)p->useJournal
-      , p->journalOff, p->journalHdr
-      , (int)p->dbSize, (int)p->dbOrigSize, (int)p->dbFileSize
-  );
-
-  return zRet;
-}
-#endif
-
-/*
-** Return true if it is necessary to write page *pPg into the sub-journal.
-** A page needs to be written into the sub-journal if there exists one
-** or more open savepoints for which:
-**
-**   * The page-number is less than or equal to PagerSavepoint.nOrig, and
-**   * The bit corresponding to the page-number is not set in
-**     PagerSavepoint.pInSavepoint.
-*/
-static int subjRequiresPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  PagerSavepoint *p;
-  Pgno pgno = pPg->pgno;
-  int i;
-  for(i=0; i<pPager->nSavepoint; i++){
-    p = &pPager->aSavepoint[i];
-    if( p->nOrig>=pgno && 0==sqlite3BitvecTestNotNull(p->pInSavepoint, pgno) ){
-      return 1;
-    }
-  }
-  return 0;
-}
-
-#ifdef SQLITE_DEBUG
-/*
-** Return true if the page is already in the journal file.
-*/
-static int pageInJournal(Pager *pPager, PgHdr *pPg){
-  return sqlite3BitvecTest(pPager->pInJournal, pPg->pgno);
-}
-#endif
-
-/*
-** Read a 32-bit integer from the given file descriptor.  Store the integer
-** that is read in *pRes.  Return SQLITE_OK if everything worked, or an
-** error code is something goes wrong.
-**
-** All values are stored on disk as big-endian.
-*/
-static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){
-  unsigned char ac[4];
-  int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset);
-  if( rc==SQLITE_OK ){
-    *pRes = sqlite3Get4byte(ac);
-  }
-  return rc;
-}
-
-/*
-** Write a 32-bit integer into a string buffer in big-endian byte order.
-*/
-#define put32bits(A,B)  sqlite3Put4byte((u8*)A,B)
-
-
-/*
-** Write a 32-bit integer into the given file descriptor.  Return SQLITE_OK
-** on success or an error code is something goes wrong.
-*/
-static int write32bits(sqlite3_file *fd, i64 offset, u32 val){
-  char ac[4];
-  put32bits(ac, val);
-  return sqlite3OsWrite(fd, ac, 4, offset);
-}
-
-/*
-** Unlock the database file to level eLock, which must be either NO_LOCK
-** or SHARED_LOCK. Regardless of whether or not the call to xUnlock()
-** succeeds, set the Pager.eLock variable to match the (attempted) new lock.
-**
-** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is
-** called, do not modify it. See the comment above the #define of 
-** UNKNOWN_LOCK for an explanation of this.
-*/
-static int pagerUnlockDb(Pager *pPager, int eLock){
-  int rc = SQLITE_OK;
-
-  assert( !pPager->exclusiveMode || pPager->eLock==eLock );
-  assert( eLock==NO_LOCK || eLock==SHARED_LOCK );
-  assert( eLock!=NO_LOCK || pagerUseWal(pPager)==0 );
-  if( isOpen(pPager->fd) ){
-    assert( pPager->eLock>=eLock );
-    rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
-    if( pPager->eLock!=UNKNOWN_LOCK ){
-      pPager->eLock = (u8)eLock;
-    }
-    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
-  }
-  return rc;
-}
-
-/*
-** Lock the database file to level eLock, which must be either SHARED_LOCK,
-** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
-** Pager.eLock variable to the new locking state. 
-**
-** Except, if Pager.eLock is set to UNKNOWN_LOCK when this function is 
-** called, do not modify it unless the new locking state is EXCLUSIVE_LOCK. 
-** See the comment above the #define of UNKNOWN_LOCK for an explanation 
-** of this.
-*/
-static int pagerLockDb(Pager *pPager, int eLock){
-  int rc = SQLITE_OK;
-
-  assert( eLock==SHARED_LOCK || eLock==RESERVED_LOCK || eLock==EXCLUSIVE_LOCK );
-  if( pPager->eLock<eLock || pPager->eLock==UNKNOWN_LOCK ){
-    rc = pPager->noLock ? SQLITE_OK : sqlite3OsLock(pPager->fd, eLock);
-    if( rc==SQLITE_OK && (pPager->eLock!=UNKNOWN_LOCK||eLock==EXCLUSIVE_LOCK) ){
-      pPager->eLock = (u8)eLock;
-      IOTRACE(("LOCK %p %d\n", pPager, eLock))
-    }
-  }
-  return rc;
-}
-
-/*
-** This function determines whether or not the atomic-write optimization
-** can be used with this pager. The optimization can be used if:
-**
-**  (a) the value returned by OsDeviceCharacteristics() indicates that
-**      a database page may be written atomically, and
-**  (b) the value returned by OsSectorSize() is less than or equal
-**      to the page size.
-**
-** The optimization is also always enabled for temporary files. It is
-** an error to call this function if pPager is opened on an in-memory
-** database.
-**
-** If the optimization cannot be used, 0 is returned. If it can be used,
-** then the value returned is the size of the journal file when it
-** contains rollback data for exactly one page.
-*/
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-static int jrnlBufferSize(Pager *pPager){
-  if( !pPager->tempFile ){
-    int dc;                           /* Device characteristics */
-    int nSector;                      /* Sector size */
-    int szPage;                       /* Page size */
-
-    assert( isOpen(pPager->fd) );
-    dc = sqlite3OsDeviceCharacteristics(pPager->fd);
-    nSector = pPager->sectorSize;
-    szPage = pPager->pageSize;
-
-    assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
-    assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
-    if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){
-      return 0;
-    }
-  }
-
-  return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager);
-}
-#endif
-
-/*
-** If SQLITE_CHECK_PAGES is defined then we do some sanity checking
-** on the cache using a hash function.  This is used for testing
-** and debugging only.
-*/
-#ifdef SQLITE_CHECK_PAGES
-/*
-** Return a 32-bit hash of the page data for pPage.
-*/
-static u32 pager_datahash(int nByte, unsigned char *pData){
-  u32 hash = 0;
-  int i;
-  for(i=0; i<nByte; i++){
-    hash = (hash*1039) + pData[i];
-  }
-  return hash;
-}
-static u32 pager_pagehash(PgHdr *pPage){
-  return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData);
-}
-static void pager_set_pagehash(PgHdr *pPage){
-  pPage->pageHash = pager_pagehash(pPage);
-}
-
-/*
-** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES
-** is defined, and NDEBUG is not defined, an assert() statement checks
-** that the page is either dirty or still matches the calculated page-hash.
-*/
-#define CHECK_PAGE(x) checkPage(x)
-static void checkPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) );
-}
-
-#else
-#define pager_datahash(X,Y)  0
-#define pager_pagehash(X)  0
-#define pager_set_pagehash(X)
-#define CHECK_PAGE(x)
-#endif  /* SQLITE_CHECK_PAGES */
-
-/*
-** When this is called the journal file for pager pPager must be open.
-** This function attempts to read a master journal file name from the 
-** end of the file and, if successful, copies it into memory supplied 
-** by the caller. See comments above writeMasterJournal() for the format
-** used to store a master journal file name at the end of a journal file.
-**
-** zMaster must point to a buffer of at least nMaster bytes allocated by
-** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is
-** enough space to write the master journal name). If the master journal
-** name in the journal is longer than nMaster bytes (including a
-** nul-terminator), then this is handled as if no master journal name
-** were present in the journal.
-**
-** If a master journal file name is present at the end of the journal
-** file, then it is copied into the buffer pointed to by zMaster. A
-** nul-terminator byte is appended to the buffer following the master
-** journal file name.
-**
-** If it is determined that no master journal file name is present 
-** zMaster[0] is set to 0 and SQLITE_OK returned.
-**
-** If an error occurs while reading from the journal file, an SQLite
-** error code is returned.
-*/
-static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){
-  int rc;                    /* Return code */
-  u32 len;                   /* Length in bytes of master journal name */
-  i64 szJ;                   /* Total size in bytes of journal file pJrnl */
-  u32 cksum;                 /* MJ checksum value read from journal */
-  u32 u;                     /* Unsigned loop counter */
-  unsigned char aMagic[8];   /* A buffer to hold the magic header */
-  zMaster[0] = '\0';
-
-  if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ))
-   || szJ<16
-   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len))
-   || len>=nMaster 
-   || len==0 
-   || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum))
-   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8))
-   || memcmp(aMagic, aJournalMagic, 8)
-   || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len))
-  ){
-    return rc;
-  }
-
-  /* See if the checksum matches the master journal name */
-  for(u=0; u<len; u++){
-    cksum -= zMaster[u];
-  }
-  if( cksum ){
-    /* If the checksum doesn't add up, then one or more of the disk sectors
-    ** containing the master journal filename is corrupted. This means
-    ** definitely roll back, so just return SQLITE_OK and report a (nul)
-    ** master-journal filename.
-    */
-    len = 0;
-  }
-  zMaster[len] = '\0';
-   
-  return SQLITE_OK;
-}
-
-/*
-** Return the offset of the sector boundary at or immediately 
-** following the value in pPager->journalOff, assuming a sector 
-** size of pPager->sectorSize bytes.
-**
-** i.e for a sector size of 512:
-**
-**   Pager.journalOff          Return value
-**   ---------------------------------------
-**   0                         0
-**   512                       512
-**   100                       512
-**   2000                      2048
-** 
-*/
-static i64 journalHdrOffset(Pager *pPager){
-  i64 offset = 0;
-  i64 c = pPager->journalOff;
-  if( c ){
-    offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager);
-  }
-  assert( offset%JOURNAL_HDR_SZ(pPager)==0 );
-  assert( offset>=c );
-  assert( (offset-c)<JOURNAL_HDR_SZ(pPager) );
-  return offset;
-}
-
-/*
-** The journal file must be open when this function is called.
-**
-** This function is a no-op if the journal file has not been written to
-** within the current transaction (i.e. if Pager.journalOff==0).
-**
-** If doTruncate is non-zero or the Pager.journalSizeLimit variable is
-** set to 0, then truncate the journal file to zero bytes in size. Otherwise,
-** zero the 28-byte header at the start of the journal file. In either case, 
-** if the pager is not in no-sync mode, sync the journal file immediately 
-** after writing or truncating it.
-**
-** If Pager.journalSizeLimit is set to a positive, non-zero value, and
-** following the truncation or zeroing described above the size of the 
-** journal file in bytes is larger than this value, then truncate the
-** journal file to Pager.journalSizeLimit bytes. The journal file does
-** not need to be synced following this operation.
-**
-** If an IO error occurs, abandon processing and return the IO error code.
-** Otherwise, return SQLITE_OK.
-*/
-static int zeroJournalHdr(Pager *pPager, int doTruncate){
-  int rc = SQLITE_OK;                               /* Return code */
-  assert( isOpen(pPager->jfd) );
-  if( pPager->journalOff ){
-    const i64 iLimit = pPager->journalSizeLimit;    /* Local cache of jsl */
-
-    IOTRACE(("JZEROHDR %p\n", pPager))
-    if( doTruncate || iLimit==0 ){
-      rc = sqlite3OsTruncate(pPager->jfd, 0);
-    }else{
-      static const char zeroHdr[28] = {0};
-      rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0);
-    }
-    if( rc==SQLITE_OK && !pPager->noSync ){
-      rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->syncFlags);
-    }
-
-    /* At this point the transaction is committed but the write lock 
-    ** is still held on the file. If there is a size limit configured for 
-    ** the persistent journal and the journal file currently consumes more
-    ** space than that limit allows for, truncate it now. There is no need
-    ** to sync the file following this operation.
-    */
-    if( rc==SQLITE_OK && iLimit>0 ){
-      i64 sz;
-      rc = sqlite3OsFileSize(pPager->jfd, &sz);
-      if( rc==SQLITE_OK && sz>iLimit ){
-        rc = sqlite3OsTruncate(pPager->jfd, iLimit);
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** The journal file must be open when this routine is called. A journal
-** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the
-** current location.
-**
-** The format for the journal header is as follows:
-** - 8 bytes: Magic identifying journal format.
-** - 4 bytes: Number of records in journal, or -1 no-sync mode is on.
-** - 4 bytes: Random number used for page hash.
-** - 4 bytes: Initial database page count.
-** - 4 bytes: Sector size used by the process that wrote this journal.
-** - 4 bytes: Database page size.
-** 
-** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space.
-*/
-static int writeJournalHdr(Pager *pPager){
-  int rc = SQLITE_OK;                 /* Return code */
-  char *zHeader = pPager->pTmpSpace;  /* Temporary space used to build header */
-  u32 nHeader = (u32)pPager->pageSize;/* Size of buffer pointed to by zHeader */
-  u32 nWrite;                         /* Bytes of header sector written */
-  int ii;                             /* Loop counter */
-
-  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
-
-  if( nHeader>JOURNAL_HDR_SZ(pPager) ){
-    nHeader = JOURNAL_HDR_SZ(pPager);
-  }
-
-  /* If there are active savepoints and any of them were created 
-  ** since the most recent journal header was written, update the 
-  ** PagerSavepoint.iHdrOffset fields now.
-  */
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    if( pPager->aSavepoint[ii].iHdrOffset==0 ){
-      pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff;
-    }
-  }
-
-  pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager);
-
-  /* 
-  ** Write the nRec Field - the number of page records that follow this
-  ** journal header. Normally, zero is written to this value at this time.
-  ** After the records are added to the journal (and the journal synced, 
-  ** if in full-sync mode), the zero is overwritten with the true number
-  ** of records (see syncJournal()).
-  **
-  ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When
-  ** reading the journal this value tells SQLite to assume that the
-  ** rest of the journal file contains valid page records. This assumption
-  ** is dangerous, as if a failure occurred whilst writing to the journal
-  ** file it may contain some garbage data. There are two scenarios
-  ** where this risk can be ignored:
-  **
-  **   * When the pager is in no-sync mode. Corruption can follow a
-  **     power failure in this case anyway.
-  **
-  **   * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees
-  **     that garbage data is never appended to the journal file.
-  */
-  assert( isOpen(pPager->fd) || pPager->noSync );
-  if( pPager->noSync || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY)
-   || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) 
-  ){
-    memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-    put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff);
-  }else{
-    memset(zHeader, 0, sizeof(aJournalMagic)+4);
-  }
-
-  /* The random check-hash initializer */ 
-  sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit);
-  put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit);
-  /* The initial database size */
-  put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize);
-  /* The assumed sector size for this process */
-  put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize);
-
-  /* The page size */
-  put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize);
-
-  /* Initializing the tail of the buffer is not necessary.  Everything
-  ** works find if the following memset() is omitted.  But initializing
-  ** the memory prevents valgrind from complaining, so we are willing to
-  ** take the performance hit.
-  */
-  memset(&zHeader[sizeof(aJournalMagic)+20], 0,
-         nHeader-(sizeof(aJournalMagic)+20));
-
-  /* In theory, it is only necessary to write the 28 bytes that the 
-  ** journal header consumes to the journal file here. Then increment the 
-  ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next 
-  ** record is written to the following sector (leaving a gap in the file
-  ** that will be implicitly filled in by the OS).
-  **
-  ** However it has been discovered that on some systems this pattern can 
-  ** be significantly slower than contiguously writing data to the file,
-  ** even if that means explicitly writing data to the block of 
-  ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what
-  ** is done. 
-  **
-  ** The loop is required here in case the sector-size is larger than the 
-  ** database page size. Since the zHeader buffer is only Pager.pageSize
-  ** bytes in size, more than one call to sqlite3OsWrite() may be required
-  ** to populate the entire journal header sector.
-  */ 
-  for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){
-    IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader))
-    rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff);
-    assert( pPager->journalHdr <= pPager->journalOff );
-    pPager->journalOff += nHeader;
-  }
-
-  return rc;
-}
-
-/*
-** The journal file must be open when this is called. A journal header file
-** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal
-** file. The current location in the journal file is given by
-** pPager->journalOff. See comments above function writeJournalHdr() for
-** a description of the journal header format.
-**
-** If the header is read successfully, *pNRec is set to the number of
-** page records following this header and *pDbSize is set to the size of the
-** database before the transaction began, in pages. Also, pPager->cksumInit
-** is set to the value read from the journal header. SQLITE_OK is returned
-** in this case.
-**
-** If the journal header file appears to be corrupted, SQLITE_DONE is
-** returned and *pNRec and *PDbSize are undefined.  If JOURNAL_HDR_SZ bytes
-** cannot be read from the journal file an error code is returned.
-*/
-static int readJournalHdr(
-  Pager *pPager,               /* Pager object */
-  int isHot,
-  i64 journalSize,             /* Size of the open journal file in bytes */
-  u32 *pNRec,                  /* OUT: Value read from the nRec field */
-  u32 *pDbSize                 /* OUT: Value of original database size field */
-){
-  int rc;                      /* Return code */
-  unsigned char aMagic[8];     /* A buffer to hold the magic header */
-  i64 iHdrOff;                 /* Offset of journal header being read */
-
-  assert( isOpen(pPager->jfd) );      /* Journal file must be open. */
-
-  /* Advance Pager.journalOff to the start of the next sector. If the
-  ** journal file is too small for there to be a header stored at this
-  ** point, return SQLITE_DONE.
-  */
-  pPager->journalOff = journalHdrOffset(pPager);
-  if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){
-    return SQLITE_DONE;
-  }
-  iHdrOff = pPager->journalOff;
-
-  /* Read in the first 8 bytes of the journal header. If they do not match
-  ** the  magic string found at the start of each journal header, return
-  ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise,
-  ** proceed.
-  */
-  if( isHot || iHdrOff!=pPager->journalHdr ){
-    rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff);
-    if( rc ){
-      return rc;
-    }
-    if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){
-      return SQLITE_DONE;
-    }
-  }
-
-  /* Read the first three 32-bit fields of the journal header: The nRec
-  ** field, the checksum-initializer and the database size at the start
-  ** of the transaction. Return an error code if anything goes wrong.
-  */
-  if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec))
-   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit))
-   || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize))
-  ){
-    return rc;
-  }
-
-  if( pPager->journalOff==0 ){
-    u32 iPageSize;               /* Page-size field of journal header */
-    u32 iSectorSize;             /* Sector-size field of journal header */
-
-    /* Read the page-size and sector-size journal header fields. */
-    if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize))
-     || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize))
-    ){
-      return rc;
-    }
-
-    /* Versions of SQLite prior to 3.5.8 set the page-size field of the
-    ** journal header to zero. In this case, assume that the Pager.pageSize
-    ** variable is already set to the correct page size.
-    */
-    if( iPageSize==0 ){
-      iPageSize = pPager->pageSize;
-    }
-
-    /* Check that the values read from the page-size and sector-size fields
-    ** are within range. To be 'in range', both values need to be a power
-    ** of two greater than or equal to 512 or 32, and not greater than their 
-    ** respective compile time maximum limits.
-    */
-    if( iPageSize<512                  || iSectorSize<32
-     || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE
-     || ((iPageSize-1)&iPageSize)!=0   || ((iSectorSize-1)&iSectorSize)!=0 
-    ){
-      /* If the either the page-size or sector-size in the journal-header is 
-      ** invalid, then the process that wrote the journal-header must have 
-      ** crashed before the header was synced. In this case stop reading 
-      ** the journal file here.
-      */
-      return SQLITE_DONE;
-    }
-
-    /* Update the page-size to match the value read from the journal. 
-    ** Use a testcase() macro to make sure that malloc failure within 
-    ** PagerSetPagesize() is tested.
-    */
-    rc = sqlite3PagerSetPagesize(pPager, &iPageSize, -1);
-    testcase( rc!=SQLITE_OK );
-
-    /* Update the assumed sector-size to match the value used by 
-    ** the process that created this journal. If this journal was
-    ** created by a process other than this one, then this routine
-    ** is being called from within pager_playback(). The local value
-    ** of Pager.sectorSize is restored at the end of that routine.
-    */
-    pPager->sectorSize = iSectorSize;
-  }
-
-  pPager->journalOff += JOURNAL_HDR_SZ(pPager);
-  return rc;
-}
-
-
-/*
-** Write the supplied master journal name into the journal file for pager
-** pPager at the current location. The master journal name must be the last
-** thing written to a journal file. If the pager is in full-sync mode, the
-** journal file descriptor is advanced to the next sector boundary before
-** anything is written. The format is:
-**
-**   + 4 bytes: PAGER_MJ_PGNO.
-**   + N bytes: Master journal filename in utf-8.
-**   + 4 bytes: N (length of master journal name in bytes, no nul-terminator).
-**   + 4 bytes: Master journal name checksum.
-**   + 8 bytes: aJournalMagic[].
-**
-** The master journal page checksum is the sum of the bytes in the master
-** journal name, where each byte is interpreted as a signed 8-bit integer.
-**
-** If zMaster is a NULL pointer (occurs for a single database transaction), 
-** this call is a no-op.
-*/
-static int writeMasterJournal(Pager *pPager, const char *zMaster){
-  int rc;                          /* Return code */
-  int nMaster;                     /* Length of string zMaster */
-  i64 iHdrOff;                     /* Offset of header in journal file */
-  i64 jrnlSize;                    /* Size of journal file on disk */
-  u32 cksum = 0;                   /* Checksum of string zMaster */
-
-  assert( pPager->setMaster==0 );
-  assert( !pagerUseWal(pPager) );
-
-  if( !zMaster 
-   || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
-   || !isOpen(pPager->jfd)
-  ){
-    return SQLITE_OK;
-  }
-  pPager->setMaster = 1;
-  assert( pPager->journalHdr <= pPager->journalOff );
-
-  /* Calculate the length in bytes and the checksum of zMaster */
-  for(nMaster=0; zMaster[nMaster]; nMaster++){
-    cksum += zMaster[nMaster];
-  }
-
-  /* If in full-sync mode, advance to the next disk sector before writing
-  ** the master journal name. This is in case the previous page written to
-  ** the journal has already been synced.
-  */
-  if( pPager->fullSync ){
-    pPager->journalOff = journalHdrOffset(pPager);
-  }
-  iHdrOff = pPager->journalOff;
-
-  /* Write the master journal data to the end of the journal file. If
-  ** an error occurs, return the error code to the caller.
-  */
-  if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager))))
-   || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4)))
-   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster)))
-   || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum)))
-   || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8,
-                                 iHdrOff+4+nMaster+8)))
-  ){
-    return rc;
-  }
-  pPager->journalOff += (nMaster+20);
-
-  /* If the pager is in peristent-journal mode, then the physical 
-  ** journal-file may extend past the end of the master-journal name
-  ** and 8 bytes of magic data just written to the file. This is 
-  ** dangerous because the code to rollback a hot-journal file
-  ** will not be able to find the master-journal name to determine 
-  ** whether or not the journal is hot. 
-  **
-  ** Easiest thing to do in this scenario is to truncate the journal 
-  ** file to the required size.
-  */ 
-  if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize))
-   && jrnlSize>pPager->journalOff
-  ){
-    rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff);
-  }
-  return rc;
-}
-
-/*
-** Discard the entire contents of the in-memory page-cache.
-*/
-static void pager_reset(Pager *pPager){
-  pPager->iDataVersion++;
-  sqlite3BackupRestart(pPager->pBackup);
-  sqlite3PcacheClear(pPager->pPCache);
-}
-
-/*
-** Return the pPager->iDataVersion value
-*/
-SQLITE_PRIVATE u32 sqlite3PagerDataVersion(Pager *pPager){
-  assert( pPager->eState>PAGER_OPEN );
-  return pPager->iDataVersion;
-}
-
-/*
-** Free all structures in the Pager.aSavepoint[] array and set both
-** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal
-** if it is open and the pager is not in exclusive mode.
-*/
-static void releaseAllSavepoints(Pager *pPager){
-  int ii;               /* Iterator for looping through Pager.aSavepoint */
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
-  }
-  if( !pPager->exclusiveMode || sqlite3IsMemJournal(pPager->sjfd) ){
-    sqlite3OsClose(pPager->sjfd);
-  }
-  sqlite3_free(pPager->aSavepoint);
-  pPager->aSavepoint = 0;
-  pPager->nSavepoint = 0;
-  pPager->nSubRec = 0;
-}
-
-/*
-** Set the bit number pgno in the PagerSavepoint.pInSavepoint 
-** bitvecs of all open savepoints. Return SQLITE_OK if successful
-** or SQLITE_NOMEM if a malloc failure occurs.
-*/
-static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){
-  int ii;                   /* Loop counter */
-  int rc = SQLITE_OK;       /* Result code */
-
-  for(ii=0; ii<pPager->nSavepoint; ii++){
-    PagerSavepoint *p = &pPager->aSavepoint[ii];
-    if( pgno<=p->nOrig ){
-      rc |= sqlite3BitvecSet(p->pInSavepoint, pgno);
-      testcase( rc==SQLITE_NOMEM );
-      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-    }
-  }
-  return rc;
-}
-
-/*
-** This function is a no-op if the pager is in exclusive mode and not
-** in the ERROR state. Otherwise, it switches the pager to PAGER_OPEN
-** state.
-**
-** If the pager is not in exclusive-access mode, the database file is
-** completely unlocked. If the file is unlocked and the file-system does
-** not exhibit the UNDELETABLE_WHEN_OPEN property, the journal file is
-** closed (if it is open).
-**
-** If the pager is in ERROR state when this function is called, the 
-** contents of the pager cache are discarded before switching back to 
-** the OPEN state. Regardless of whether the pager is in exclusive-mode
-** or not, any journal file left in the file-system will be treated
-** as a hot-journal and rolled back the next time a read-transaction
-** is opened (by this or by any other connection).
-*/
-static void pager_unlock(Pager *pPager){
-
-  assert( pPager->eState==PAGER_READER 
-       || pPager->eState==PAGER_OPEN 
-       || pPager->eState==PAGER_ERROR 
-  );
-
-  sqlite3BitvecDestroy(pPager->pInJournal);
-  pPager->pInJournal = 0;
-  releaseAllSavepoints(pPager);
-
-  if( pagerUseWal(pPager) ){
-    assert( !isOpen(pPager->jfd) );
-    sqlite3WalEndReadTransaction(pPager->pWal);
-    pPager->eState = PAGER_OPEN;
-  }else if( !pPager->exclusiveMode ){
-    int rc;                       /* Error code returned by pagerUnlockDb() */
-    int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0;
-
-    /* If the operating system support deletion of open files, then
-    ** close the journal file when dropping the database lock.  Otherwise
-    ** another connection with journal_mode=delete might delete the file
-    ** out from under us.
-    */
-    assert( (PAGER_JOURNALMODE_MEMORY   & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_OFF      & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_WAL      & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_DELETE   & 5)!=1 );
-    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
-    assert( (PAGER_JOURNALMODE_PERSIST  & 5)==1 );
-    if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN)
-     || 1!=(pPager->journalMode & 5)
-    ){
-      sqlite3OsClose(pPager->jfd);
-    }
-
-    /* If the pager is in the ERROR state and the call to unlock the database
-    ** file fails, set the current lock to UNKNOWN_LOCK. See the comment
-    ** above the #define for UNKNOWN_LOCK for an explanation of why this
-    ** is necessary.
-    */
-    rc = pagerUnlockDb(pPager, NO_LOCK);
-    if( rc!=SQLITE_OK && pPager->eState==PAGER_ERROR ){
-      pPager->eLock = UNKNOWN_LOCK;
-    }
-
-    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
-    ** without clearing the error code. This is intentional - the error
-    ** code is cleared and the cache reset in the block below.
-    */
-    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
-    pPager->changeCountDone = 0;
-    pPager->eState = PAGER_OPEN;
-  }
-
-  /* If Pager.errCode is set, the contents of the pager cache cannot be
-  ** trusted. Now that there are no outstanding references to the pager,
-  ** it can safely move back to PAGER_OPEN state. This happens in both
-  ** normal and exclusive-locking mode.
-  */
-  if( pPager->errCode ){
-    pager_reset(pPager);
-    pPager->changeCountDone = pPager->tempFile;
-    pPager->eState = PAGER_OPEN;
-    pPager->errCode = SQLITE_OK;
-    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
-  }
-
-  pPager->journalOff = 0;
-  pPager->journalHdr = 0;
-  pPager->setMaster = 0;
-}
-
-/*
-** This function is called whenever an IOERR or FULL error that requires
-** the pager to transition into the ERROR state may ahve occurred.
-** The first argument is a pointer to the pager structure, the second 
-** the error-code about to be returned by a pager API function. The 
-** value returned is a copy of the second argument to this function. 
-**
-** If the second argument is SQLITE_FULL, SQLITE_IOERR or one of the
-** IOERR sub-codes, the pager enters the ERROR state and the error code
-** is stored in Pager.errCode. While the pager remains in the ERROR state,
-** all major API calls on the Pager will immediately return Pager.errCode.
-**
-** The ERROR state indicates that the contents of the pager-cache 
-** cannot be trusted. This state can be cleared by completely discarding 
-** the contents of the pager-cache. If a transaction was active when
-** the persistent error occurred, then the rollback journal may need
-** to be replayed to restore the contents of the database file (as if
-** it were a hot-journal).
-*/
-static int pager_error(Pager *pPager, int rc){
-  int rc2 = rc & 0xff;
-  assert( rc==SQLITE_OK );
-  assert(
-       pPager->errCode==SQLITE_FULL ||
-       pPager->errCode==SQLITE_OK ||
-       (pPager->errCode & 0xff)==SQLITE_IOERR
-  );
-  if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){
-    pPager->errCode = rc;
-    pPager->eState = PAGER_ERROR;
-  }
-  return rc;
-}
-
-static int pager_truncate(Pager *pPager, Pgno nPage);
-
-/*
-** This routine ends a transaction. A transaction is usually ended by 
-** either a COMMIT or a ROLLBACK operation. This routine may be called 
-** after rollback of a hot-journal, or if an error occurs while opening
-** the journal file or writing the very first journal-header of a
-** database transaction.
-** 
-** This routine is never called in PAGER_ERROR state. If it is called
-** in PAGER_NONE or PAGER_SHARED state and the lock held is less
-** exclusive than a RESERVED lock, it is a no-op.
-**
-** Otherwise, any active savepoints are released.
-**
-** If the journal file is open, then it is "finalized". Once a journal 
-** file has been finalized it is not possible to use it to roll back a 
-** transaction. Nor will it be considered to be a hot-journal by this
-** or any other database connection. Exactly how a journal is finalized
-** depends on whether or not the pager is running in exclusive mode and
-** the current journal-mode (Pager.journalMode value), as follows:
-**
-**   journalMode==MEMORY
-**     Journal file descriptor is simply closed. This destroys an 
-**     in-memory journal.
-**
-**   journalMode==TRUNCATE
-**     Journal file is truncated to zero bytes in size.
-**
-**   journalMode==PERSIST
-**     The first 28 bytes of the journal file are zeroed. This invalidates
-**     the first journal header in the file, and hence the entire journal
-**     file. An invalid journal file cannot be rolled back.
-**
-**   journalMode==DELETE
-**     The journal file is closed and deleted using sqlite3OsDelete().
-**
-**     If the pager is running in exclusive mode, this method of finalizing
-**     the journal file is never used. Instead, if the journalMode is
-**     DELETE and the pager is in exclusive mode, the method described under
-**     journalMode==PERSIST is used instead.
-**
-** After the journal is finalized, the pager moves to PAGER_READER state.
-** If running in non-exclusive rollback mode, the lock on the file is 
-** downgraded to a SHARED_LOCK.
-**
-** SQLITE_OK is returned if no error occurs. If an error occurs during
-** any of the IO operations to finalize the journal file or unlock the
-** database then the IO error code is returned to the user. If the 
-** operation to finalize the journal file fails, then the code still
-** tries to unlock the database file if not in exclusive mode. If the
-** unlock operation fails as well, then the first error code related
-** to the first error encountered (the journal finalization one) is
-** returned.
-*/
-static int pager_end_transaction(Pager *pPager, int hasMaster, int bCommit){
-  int rc = SQLITE_OK;      /* Error code from journal finalization operation */
-  int rc2 = SQLITE_OK;     /* Error code from db file unlock operation */
-
-  /* Do nothing if the pager does not have an open write transaction
-  ** or at least a RESERVED lock. This function may be called when there
-  ** is no write-transaction active but a RESERVED or greater lock is
-  ** held under two circumstances:
-  **
-  **   1. After a successful hot-journal rollback, it is called with
-  **      eState==PAGER_NONE and eLock==EXCLUSIVE_LOCK.
-  **
-  **   2. If a connection with locking_mode=exclusive holding an EXCLUSIVE 
-  **      lock switches back to locking_mode=normal and then executes a
-  **      read-transaction, this function is called with eState==PAGER_READER 
-  **      and eLock==EXCLUSIVE_LOCK when the read-transaction is closed.
-  */
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState!=PAGER_ERROR );
-  if( pPager->eState<PAGER_WRITER_LOCKED && pPager->eLock<RESERVED_LOCK ){
-    return SQLITE_OK;
-  }
-
-  releaseAllSavepoints(pPager);
-  assert( isOpen(pPager->jfd) || pPager->pInJournal==0 );
-  if( isOpen(pPager->jfd) ){
-    assert( !pagerUseWal(pPager) );
-
-    /* Finalize the journal file. */
-    if( sqlite3IsMemJournal(pPager->jfd) ){
-      assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY );
-      sqlite3OsClose(pPager->jfd);
-    }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){
-      if( pPager->journalOff==0 ){
-        rc = SQLITE_OK;
-      }else{
-        rc = sqlite3OsTruncate(pPager->jfd, 0);
-        if( rc==SQLITE_OK && pPager->fullSync ){
-          /* Make sure the new file size is written into the inode right away.
-          ** Otherwise the journal might resurrect following a power loss and
-          ** cause the last transaction to roll back.  See
-          ** https://bugzilla.mozilla.org/show_bug.cgi?id=1072773
-          */
-          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
-        }
-      }
-      pPager->journalOff = 0;
-    }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST
-      || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL)
-    ){
-      rc = zeroJournalHdr(pPager, hasMaster);
-      pPager->journalOff = 0;
-    }else{
-      /* This branch may be executed with Pager.journalMode==MEMORY if
-      ** a hot-journal was just rolled back. In this case the journal
-      ** file should be closed and deleted. If this connection writes to
-      ** the database file, it will do so using an in-memory journal. 
-      */
-      int bDelete = (!pPager->tempFile && sqlite3JournalExists(pPager->jfd));
-      assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE 
-           || pPager->journalMode==PAGER_JOURNALMODE_MEMORY 
-           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      sqlite3OsClose(pPager->jfd);
-      if( bDelete ){
-        rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-      }
-    }
-  }
-
-#ifdef SQLITE_CHECK_PAGES
-  sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash);
-  if( pPager->dbSize==0 && sqlite3PcacheRefCount(pPager->pPCache)>0 ){
-    PgHdr *p = sqlite3PagerLookup(pPager, 1);
-    if( p ){
-      p->pageHash = 0;
-      sqlite3PagerUnrefNotNull(p);
-    }
-  }
-#endif
-
-  sqlite3BitvecDestroy(pPager->pInJournal);
-  pPager->pInJournal = 0;
-  pPager->nRec = 0;
-  sqlite3PcacheCleanAll(pPager->pPCache);
-  sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize);
-
-  if( pagerUseWal(pPager) ){
-    /* Drop the WAL write-lock, if any. Also, if the connection was in 
-    ** locking_mode=exclusive mode but is no longer, drop the EXCLUSIVE 
-    ** lock held on the database file.
-    */
-    rc2 = sqlite3WalEndWriteTransaction(pPager->pWal);
-    assert( rc2==SQLITE_OK );
-  }else if( rc==SQLITE_OK && bCommit && pPager->dbFileSize>pPager->dbSize ){
-    /* This branch is taken when committing a transaction in rollback-journal
-    ** mode if the database file on disk is larger than the database image.
-    ** At this point the journal has been finalized and the transaction 
-    ** successfully committed, but the EXCLUSIVE lock is still held on the
-    ** file. So it is safe to truncate the database file to its minimum
-    ** required size.  */
-    assert( pPager->eLock==EXCLUSIVE_LOCK );
-    rc = pager_truncate(pPager, pPager->dbSize);
-  }
-
-  if( rc==SQLITE_OK && bCommit && isOpen(pPager->fd) ){
-    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_COMMIT_PHASETWO, 0);
-    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
-  }
-
-  if( !pPager->exclusiveMode 
-   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
-  ){
-    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
-    pPager->changeCountDone = 0;
-  }
-  pPager->eState = PAGER_READER;
-  pPager->setMaster = 0;
-
-  return (rc==SQLITE_OK?rc2:rc);
-}
-
-/*
-** Execute a rollback if a transaction is active and unlock the 
-** database file. 
-**
-** If the pager has already entered the ERROR state, do not attempt 
-** the rollback at this time. Instead, pager_unlock() is called. The
-** call to pager_unlock() will discard all in-memory pages, unlock
-** the database file and move the pager back to OPEN state. If this 
-** means that there is a hot-journal left in the file-system, the next 
-** connection to obtain a shared lock on the pager (which may be this one) 
-** will roll it back.
-**
-** If the pager has not already entered the ERROR state, but an IO or
-** malloc error occurs during a rollback, then this will itself cause 
-** the pager to enter the ERROR state. Which will be cleared by the
-** call to pager_unlock(), as described above.
-*/
-static void pagerUnlockAndRollback(Pager *pPager){
-  if( pPager->eState!=PAGER_ERROR && pPager->eState!=PAGER_OPEN ){
-    assert( assert_pager_state(pPager) );
-    if( pPager->eState>=PAGER_WRITER_LOCKED ){
-      sqlite3PagerRollback(pPager);
-    }else if( !pPager->exclusiveMode ){
-      assert( pPager->eState==PAGER_READER );
-      pager_end_transaction(pPager, 0, 0);
-    }
-  }
-  pager_unlock(pPager);
-}
-
-/*
-** Parameter aData must point to a buffer of pPager->pageSize bytes
-** of data. Compute and return a checksum based ont the contents of the 
-** page of data and the current value of pPager->cksumInit.
-**
-** This is not a real checksum. It is really just the sum of the 
-** random initial value (pPager->cksumInit) and every 200th byte
-** of the page data, starting with byte offset (pPager->pageSize%200).
-** Each byte is interpreted as an 8-bit unsigned integer.
-**
-** Changing the formula used to compute this checksum results in an
-** incompatible journal file format.
-**
-** If journal corruption occurs due to a power failure, the most likely 
-** scenario is that one end or the other of the record will be changed. 
-** It is much less likely that the two ends of the journal record will be
-** correct and the middle be corrupt.  Thus, this "checksum" scheme,
-** though fast and simple, catches the mostly likely kind of corruption.
-*/
-static u32 pager_cksum(Pager *pPager, const u8 *aData){
-  u32 cksum = pPager->cksumInit;         /* Checksum value to return */
-  int i = pPager->pageSize-200;          /* Loop counter */
-  while( i>0 ){
-    cksum += aData[i];
-    i -= 200;
-  }
-  return cksum;
-}
-
-/*
-** Report the current page size and number of reserved bytes back
-** to the codec.
-*/
-#ifdef SQLITE_HAS_CODEC
-static void pagerReportSize(Pager *pPager){
-  if( pPager->xCodecSizeChng ){
-    pPager->xCodecSizeChng(pPager->pCodec, pPager->pageSize,
-                           (int)pPager->nReserve);
-  }
-}
-#else
-# define pagerReportSize(X)     /* No-op if we do not support a codec */
-#endif
-
-#ifdef SQLITE_HAS_CODEC
-/*
-** Make sure the number of reserved bits is the same in the destination
-** pager as it is in the source.  This comes up when a VACUUM changes the
-** number of reserved bits to the "optimal" amount.
-*/
-SQLITE_PRIVATE void sqlite3PagerAlignReserve(Pager *pDest, Pager *pSrc){
-  if( pDest->nReserve!=pSrc->nReserve ){
-    pDest->nReserve = pSrc->nReserve;
-    pagerReportSize(pDest);
-  }
-}
-#endif
-
-/*
-** Read a single page from either the journal file (if isMainJrnl==1) or
-** from the sub-journal (if isMainJrnl==0) and playback that page.
-** The page begins at offset *pOffset into the file. The *pOffset
-** value is increased to the start of the next page in the journal.
-**
-** The main rollback journal uses checksums - the statement journal does 
-** not.
-**
-** If the page number of the page record read from the (sub-)journal file
-** is greater than the current value of Pager.dbSize, then playback is
-** skipped and SQLITE_OK is returned.
-**
-** If pDone is not NULL, then it is a record of pages that have already
-** been played back.  If the page at *pOffset has already been played back
-** (if the corresponding pDone bit is set) then skip the playback.
-** Make sure the pDone bit corresponding to the *pOffset page is set
-** prior to returning.
-**
-** If the page record is successfully read from the (sub-)journal file
-** and played back, then SQLITE_OK is returned. If an IO error occurs
-** while reading the record from the (sub-)journal file or while writing
-** to the database file, then the IO error code is returned. If data
-** is successfully read from the (sub-)journal file but appears to be
-** corrupted, SQLITE_DONE is returned. Data is considered corrupted in
-** two circumstances:
-** 
-**   * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or
-**   * If the record is being rolled back from the main journal file
-**     and the checksum field does not match the record content.
-**
-** Neither of these two scenarios are possible during a savepoint rollback.
-**
-** If this is a savepoint rollback, then memory may have to be dynamically
-** allocated by this function. If this is the case and an allocation fails,
-** SQLITE_NOMEM is returned.
-*/
-static int pager_playback_one_page(
-  Pager *pPager,                /* The pager being played back */
-  i64 *pOffset,                 /* Offset of record to playback */
-  Bitvec *pDone,                /* Bitvec of pages already played back */
-  int isMainJrnl,               /* 1 -> main journal. 0 -> sub-journal. */
-  int isSavepnt                 /* True for a savepoint rollback */
-){
-  int rc;
-  PgHdr *pPg;                   /* An existing page in the cache */
-  Pgno pgno;                    /* The page number of a page in journal */
-  u32 cksum;                    /* Checksum used for sanity checking */
-  char *aData;                  /* Temporary storage for the page */
-  sqlite3_file *jfd;            /* The file descriptor for the journal file */
-  int isSynced;                 /* True if journal page is synced */
-
-  assert( (isMainJrnl&~1)==0 );      /* isMainJrnl is 0 or 1 */
-  assert( (isSavepnt&~1)==0 );       /* isSavepnt is 0 or 1 */
-  assert( isMainJrnl || pDone );     /* pDone always used on sub-journals */
-  assert( isSavepnt || pDone==0 );   /* pDone never used on non-savepoint */
-
-  aData = pPager->pTmpSpace;
-  assert( aData );         /* Temp storage must have already been allocated */
-  assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) );
-
-  /* Either the state is greater than PAGER_WRITER_CACHEMOD (a transaction 
-  ** or savepoint rollback done at the request of the caller) or this is
-  ** a hot-journal rollback. If it is a hot-journal rollback, the pager
-  ** is in state OPEN and holds an EXCLUSIVE lock. Hot-journal rollback
-  ** only reads from the main journal, not the sub-journal.
-  */
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD
-       || (pPager->eState==PAGER_OPEN && pPager->eLock==EXCLUSIVE_LOCK)
-  );
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD || isMainJrnl );
-
-  /* Read the page number and page data from the journal or sub-journal
-  ** file. Return an error code to the caller if an IO error occurs.
-  */
-  jfd = isMainJrnl ? pPager->jfd : pPager->sjfd;
-  rc = read32bits(jfd, *pOffset, &pgno);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4);
-  if( rc!=SQLITE_OK ) return rc;
-  *pOffset += pPager->pageSize + 4 + isMainJrnl*4;
-
-  /* Sanity checking on the page.  This is more important that I originally
-  ** thought.  If a power failure occurs while the journal is being written,
-  ** it could cause invalid data to be written into the journal.  We need to
-  ** detect this invalid data (with high probability) and ignore it.
-  */
-  if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){
-    assert( !isSavepnt );
-    return SQLITE_DONE;
-  }
-  if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){
-    return SQLITE_OK;
-  }
-  if( isMainJrnl ){
-    rc = read32bits(jfd, (*pOffset)-4, &cksum);
-    if( rc ) return rc;
-    if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){
-      return SQLITE_DONE;
-    }
-  }
-
-  /* If this page has already been played back before during the current
-  ** rollback, then don't bother to play it back again.
-  */
-  if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){
-    return rc;
-  }
-
-  /* When playing back page 1, restore the nReserve setting
-  */
-  if( pgno==1 && pPager->nReserve!=((u8*)aData)[20] ){
-    pPager->nReserve = ((u8*)aData)[20];
-    pagerReportSize(pPager);
-  }
-
-  /* If the pager is in CACHEMOD state, then there must be a copy of this
-  ** page in the pager cache. In this case just update the pager cache,
-  ** not the database file. The page is left marked dirty in this case.
-  **
-  ** An exception to the above rule: If the database is in no-sync mode
-  ** and a page is moved during an incremental vacuum then the page may
-  ** not be in the pager cache. Later: if a malloc() or IO error occurs
-  ** during a Movepage() call, then the page may not be in the cache
-  ** either. So the condition described in the above paragraph is not
-  ** assert()able.
-  **
-  ** If in WRITER_DBMOD, WRITER_FINISHED or OPEN state, then we update the
-  ** pager cache if it exists and the main file. The page is then marked 
-  ** not dirty. Since this code is only executed in PAGER_OPEN state for
-  ** a hot-journal rollback, it is guaranteed that the page-cache is empty
-  ** if the pager is in OPEN state.
-  **
-  ** Ticket #1171:  The statement journal might contain page content that is
-  ** different from the page content at the start of the transaction.
-  ** This occurs when a page is changed prior to the start of a statement
-  ** then changed again within the statement.  When rolling back such a
-  ** statement we must not write to the original database unless we know
-  ** for certain that original page contents are synced into the main rollback
-  ** journal.  Otherwise, a power loss might leave modified data in the
-  ** database file without an entry in the rollback journal that can
-  ** restore the database to its original form.  Two conditions must be
-  ** met before writing to the database files. (1) the database must be
-  ** locked.  (2) we know that the original page content is fully synced
-  ** in the main journal either because the page is not in cache or else
-  ** the page is marked as needSync==0.
-  **
-  ** 2008-04-14:  When attempting to vacuum a corrupt database file, it
-  ** is possible to fail a statement on a database that does not yet exist.
-  ** Do not attempt to write if database file has never been opened.
-  */
-  if( pagerUseWal(pPager) ){
-    pPg = 0;
-  }else{
-    pPg = sqlite3PagerLookup(pPager, pgno);
-  }
-  assert( pPg );
-  assert( pPager->eState!=PAGER_OPEN || pPg==0 );
-  PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n",
-           PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData),
-           (isMainJrnl?"main-journal":"sub-journal")
-  ));
-  if( isMainJrnl ){
-    isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr);
-  }else{
-    isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC));
-  }
-  if( isOpen(pPager->fd)
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
-   && isSynced
-  ){
-    i64 ofst = (pgno-1)*(i64)pPager->pageSize;
-    testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 );
-    assert( !pagerUseWal(pPager) );
-    rc = sqlite3OsWrite(pPager->fd, (u8 *)aData, pPager->pageSize, ofst);
-    if( pgno>pPager->dbFileSize ){
-      pPager->dbFileSize = pgno;
-    }
-    if( pPager->pBackup ){
-      CODEC1(pPager, aData, pgno, 3, rc=SQLITE_NOMEM);
-      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData);
-      CODEC2(pPager, aData, pgno, 7, rc=SQLITE_NOMEM, aData);
-    }
-  }else if( !isMainJrnl && pPg==0 ){
-    /* If this is a rollback of a savepoint and data was not written to
-    ** the database and the page is not in-memory, there is a potential
-    ** problem. When the page is next fetched by the b-tree layer, it 
-    ** will be read from the database file, which may or may not be 
-    ** current. 
-    **
-    ** There are a couple of different ways this can happen. All are quite
-    ** obscure. When running in synchronous mode, this can only happen 
-    ** if the page is on the free-list at the start of the transaction, then
-    ** populated, then moved using sqlite3PagerMovepage().
-    **
-    ** The solution is to add an in-memory page to the cache containing
-    ** the data just read from the sub-journal. Mark the page as dirty 
-    ** and if the pager requires a journal-sync, then mark the page as 
-    ** requiring a journal-sync before it is written.
-    */
-    assert( isSavepnt );
-    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)==0 );
-    pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
-    rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1);
-    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
-    pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
-    if( rc!=SQLITE_OK ) return rc;
-    pPg->flags &= ~PGHDR_NEED_READ;
-    sqlite3PcacheMakeDirty(pPg);
-  }
-  if( pPg ){
-    /* No page should ever be explicitly rolled back that is in use, except
-    ** for page 1 which is held in use in order to keep the lock on the
-    ** database active. However such a page may be rolled back as a result
-    ** of an internal error resulting in an automatic call to
-    ** sqlite3PagerRollback().
-    */
-    void *pData;
-    pData = pPg->pData;
-    memcpy(pData, (u8*)aData, pPager->pageSize);
-    pPager->xReiniter(pPg);
-    if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){
-      /* If the contents of this page were just restored from the main 
-      ** journal file, then its content must be as they were when the 
-      ** transaction was first opened. In this case we can mark the page
-      ** as clean, since there will be no need to write it out to the
-      ** database.
-      **
-      ** There is one exception to this rule. If the page is being rolled
-      ** back as part of a savepoint (or statement) rollback from an 
-      ** unsynced portion of the main journal file, then it is not safe
-      ** to mark the page as clean. This is because marking the page as
-      ** clean will clear the PGHDR_NEED_SYNC flag. Since the page is
-      ** already in the journal file (recorded in Pager.pInJournal) and
-      ** the PGHDR_NEED_SYNC flag is cleared, if the page is written to
-      ** again within this transaction, it will be marked as dirty but
-      ** the PGHDR_NEED_SYNC flag will not be set. It could then potentially
-      ** be written out into the database file before its journal file
-      ** segment is synced. If a crash occurs during or following this,
-      ** database corruption may ensue.
-      */
-      assert( !pagerUseWal(pPager) );
-      sqlite3PcacheMakeClean(pPg);
-    }
-    pager_set_pagehash(pPg);
-
-    /* If this was page 1, then restore the value of Pager.dbFileVers.
-    ** Do this before any decoding. */
-    if( pgno==1 ){
-      memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers));
-    }
-
-    /* Decode the page just read from disk */
-    CODEC1(pPager, pData, pPg->pgno, 3, rc=SQLITE_NOMEM);
-    sqlite3PcacheRelease(pPg);
-  }
-  return rc;
-}
-
-/*
-** Parameter zMaster is the name of a master journal file. A single journal
-** file that referred to the master journal file has just been rolled back.
-** This routine checks if it is possible to delete the master journal file,
-** and does so if it is.
-**
-** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not 
-** available for use within this function.
-**
-** When a master journal file is created, it is populated with the names 
-** of all of its child journals, one after another, formatted as utf-8 
-** encoded text. The end of each child journal file is marked with a 
-** nul-terminator byte (0x00). i.e. the entire contents of a master journal
-** file for a transaction involving two databases might be:
-**
-**   "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00"
-**
-** A master journal file may only be deleted once all of its child 
-** journals have been rolled back.
-**
-** This function reads the contents of the master-journal file into 
-** memory and loops through each of the child journal names. For
-** each child journal, it checks if:
-**
-**   * if the child journal exists, and if so
-**   * if the child journal contains a reference to master journal 
-**     file zMaster
-**
-** If a child journal can be found that matches both of the criteria
-** above, this function returns without doing anything. Otherwise, if
-** no such child journal can be found, file zMaster is deleted from
-** the file-system using sqlite3OsDelete().
-**
-** If an IO error within this function, an error code is returned. This
-** function allocates memory by calling sqlite3Malloc(). If an allocation
-** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors 
-** occur, SQLITE_OK is returned.
-**
-** TODO: This function allocates a single block of memory to load
-** the entire contents of the master journal file. This could be
-** a couple of kilobytes or so - potentially larger than the page 
-** size.
-*/
-static int pager_delmaster(Pager *pPager, const char *zMaster){
-  sqlite3_vfs *pVfs = pPager->pVfs;
-  int rc;                   /* Return code */
-  sqlite3_file *pMaster;    /* Malloc'd master-journal file descriptor */
-  sqlite3_file *pJournal;   /* Malloc'd child-journal file descriptor */
-  char *zMasterJournal = 0; /* Contents of master journal file */
-  i64 nMasterJournal;       /* Size of master journal file */
-  char *zJournal;           /* Pointer to one journal within MJ file */
-  char *zMasterPtr;         /* Space to hold MJ filename from a journal file */
-  int nMasterPtr;           /* Amount of space allocated to zMasterPtr[] */
-
-  /* Allocate space for both the pJournal and pMaster file descriptors.
-  ** If successful, open the master journal file for reading.
-  */
-  pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2);
-  pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile);
-  if( !pMaster ){
-    rc = SQLITE_NOMEM;
-  }else{
-    const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL);
-    rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0);
-  }
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-
-  /* Load the entire master journal file into space obtained from
-  ** sqlite3_malloc() and pointed to by zMasterJournal.   Also obtain
-  ** sufficient space (in zMasterPtr) to hold the names of master
-  ** journal files extracted from regular rollback-journals.
-  */
-  rc = sqlite3OsFileSize(pMaster, &nMasterJournal);
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-  nMasterPtr = pVfs->mxPathname+1;
-  zMasterJournal = sqlite3Malloc(nMasterJournal + nMasterPtr + 1);
-  if( !zMasterJournal ){
-    rc = SQLITE_NOMEM;
-    goto delmaster_out;
-  }
-  zMasterPtr = &zMasterJournal[nMasterJournal+1];
-  rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0);
-  if( rc!=SQLITE_OK ) goto delmaster_out;
-  zMasterJournal[nMasterJournal] = 0;
-
-  zJournal = zMasterJournal;
-  while( (zJournal-zMasterJournal)<nMasterJournal ){
-    int exists;
-    rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists);
-    if( rc!=SQLITE_OK ){
-      goto delmaster_out;
-    }
-    if( exists ){
-      /* One of the journals pointed to by the master journal exists.
-      ** Open it and check if it points at the master journal. If
-      ** so, return without deleting the master journal file.
-      */
-      int c;
-      int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL);
-      rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0);
-      if( rc!=SQLITE_OK ){
-        goto delmaster_out;
-      }
-
-      rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr);
-      sqlite3OsClose(pJournal);
-      if( rc!=SQLITE_OK ){
-        goto delmaster_out;
-      }
-
-      c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0;
-      if( c ){
-        /* We have a match. Do not delete the master journal file. */
-        goto delmaster_out;
-      }
-    }
-    zJournal += (sqlite3Strlen30(zJournal)+1);
-  }
- 
-  sqlite3OsClose(pMaster);
-  rc = sqlite3OsDelete(pVfs, zMaster, 0);
-
-delmaster_out:
-  sqlite3_free(zMasterJournal);
-  if( pMaster ){
-    sqlite3OsClose(pMaster);
-    assert( !isOpen(pJournal) );
-    sqlite3_free(pMaster);
-  }
-  return rc;
-}
-
-
-/*
-** This function is used to change the actual size of the database 
-** file in the file-system. This only happens when committing a transaction,
-** or rolling back a transaction (including rolling back a hot-journal).
-**
-** If the main database file is not open, or the pager is not in either
-** DBMOD or OPEN state, this function is a no-op. Otherwise, the size 
-** of the file is changed to nPage pages (nPage*pPager->pageSize bytes). 
-** If the file on disk is currently larger than nPage pages, then use the VFS
-** xTruncate() method to truncate it.
-**
-** Or, it might be the case that the file on disk is smaller than 
-** nPage pages. Some operating system implementations can get confused if 
-** you try to truncate a file to some size that is larger than it 
-** currently is, so detect this case and write a single zero byte to 
-** the end of the new file instead.
-**
-** If successful, return SQLITE_OK. If an IO error occurs while modifying
-** the database file, return the error code to the caller.
-*/
-static int pager_truncate(Pager *pPager, Pgno nPage){
-  int rc = SQLITE_OK;
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( pPager->eState!=PAGER_READER );
-  
-  if( isOpen(pPager->fd) 
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN) 
-  ){
-    i64 currentSize, newSize;
-    int szPage = pPager->pageSize;
-    assert( pPager->eLock==EXCLUSIVE_LOCK );
-    /* TODO: Is it safe to use Pager.dbFileSize here? */
-    rc = sqlite3OsFileSize(pPager->fd, &currentSize);
-    newSize = szPage*(i64)nPage;
-    if( rc==SQLITE_OK && currentSize!=newSize ){
-      if( currentSize>newSize ){
-        rc = sqlite3OsTruncate(pPager->fd, newSize);
-      }else if( (currentSize+szPage)<=newSize ){
-        char *pTmp = pPager->pTmpSpace;
-        memset(pTmp, 0, szPage);
-        testcase( (newSize-szPage) == currentSize );
-        testcase( (newSize-szPage) >  currentSize );
-        rc = sqlite3OsWrite(pPager->fd, pTmp, szPage, newSize-szPage);
-      }
-      if( rc==SQLITE_OK ){
-        pPager->dbFileSize = nPage;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Return a sanitized version of the sector-size of OS file pFile. The
-** return value is guaranteed to lie between 32 and MAX_SECTOR_SIZE.
-*/
-SQLITE_PRIVATE int sqlite3SectorSize(sqlite3_file *pFile){
-  int iRet = sqlite3OsSectorSize(pFile);
-  if( iRet<32 ){
-    iRet = 512;
-  }else if( iRet>MAX_SECTOR_SIZE ){
-    assert( MAX_SECTOR_SIZE>=512 );
-    iRet = MAX_SECTOR_SIZE;
-  }
-  return iRet;
-}
-
-/*
-** Set the value of the Pager.sectorSize variable for the given
-** pager based on the value returned by the xSectorSize method
-** of the open database file. The sector size will be used 
-** to determine the size and alignment of journal header and 
-** master journal pointers within created journal files.
-**
-** For temporary files the effective sector size is always 512 bytes.
-**
-** Otherwise, for non-temporary files, the effective sector size is
-** the value returned by the xSectorSize() method rounded up to 32 if
-** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it
-** is greater than MAX_SECTOR_SIZE.
-**
-** If the file has the SQLITE_IOCAP_POWERSAFE_OVERWRITE property, then set
-** the effective sector size to its minimum value (512).  The purpose of
-** pPager->sectorSize is to define the "blast radius" of bytes that
-** might change if a crash occurs while writing to a single byte in
-** that range.  But with POWERSAFE_OVERWRITE, the blast radius is zero
-** (that is what POWERSAFE_OVERWRITE means), so we minimize the sector
-** size.  For backwards compatibility of the rollback journal file format,
-** we cannot reduce the effective sector size below 512.
-*/
-static void setSectorSize(Pager *pPager){
-  assert( isOpen(pPager->fd) || pPager->tempFile );
-
-  if( pPager->tempFile
-   || (sqlite3OsDeviceCharacteristics(pPager->fd) & 
-              SQLITE_IOCAP_POWERSAFE_OVERWRITE)!=0
-  ){
-    /* Sector size doesn't matter for temporary files. Also, the file
-    ** may not have been opened yet, in which case the OsSectorSize()
-    ** call will segfault. */
-    pPager->sectorSize = 512;
-  }else{
-    pPager->sectorSize = sqlite3SectorSize(pPager->fd);
-  }
-}
-
-/*
-** Playback the journal and thus restore the database file to
-** the state it was in before we started making changes.  
-**
-** The journal file format is as follows: 
-**
-**  (1)  8 byte prefix.  A copy of aJournalMagic[].
-**  (2)  4 byte big-endian integer which is the number of valid page records
-**       in the journal.  If this value is 0xffffffff, then compute the
-**       number of page records from the journal size.
-**  (3)  4 byte big-endian integer which is the initial value for the 
-**       sanity checksum.
-**  (4)  4 byte integer which is the number of pages to truncate the
-**       database to during a rollback.
-**  (5)  4 byte big-endian integer which is the sector size.  The header
-**       is this many bytes in size.
-**  (6)  4 byte big-endian integer which is the page size.
-**  (7)  zero padding out to the next sector size.
-**  (8)  Zero or more pages instances, each as follows:
-**        +  4 byte page number.
-**        +  pPager->pageSize bytes of data.
-**        +  4 byte checksum
-**
-** When we speak of the journal header, we mean the first 7 items above.
-** Each entry in the journal is an instance of the 8th item.
-**
-** Call the value from the second bullet "nRec".  nRec is the number of
-** valid page entries in the journal.  In most cases, you can compute the
-** value of nRec from the size of the journal file.  But if a power
-** failure occurred while the journal was being written, it could be the
-** case that the size of the journal file had already been increased but
-** the extra entries had not yet made it safely to disk.  In such a case,
-** the value of nRec computed from the file size would be too large.  For
-** that reason, we always use the nRec value in the header.
-**
-** If the nRec value is 0xffffffff it means that nRec should be computed
-** from the file size.  This value is used when the user selects the
-** no-sync option for the journal.  A power failure could lead to corruption
-** in this case.  But for things like temporary table (which will be
-** deleted when the power is restored) we don't care.  
-**
-** If the file opened as the journal file is not a well-formed
-** journal file then all pages up to the first corrupted page are rolled
-** back (or no pages if the journal header is corrupted). The journal file
-** is then deleted and SQLITE_OK returned, just as if no corruption had
-** been encountered.
-**
-** If an I/O or malloc() error occurs, the journal-file is not deleted
-** and an error code is returned.
-**
-** The isHot parameter indicates that we are trying to rollback a journal
-** that might be a hot journal.  Or, it could be that the journal is 
-** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE.
-** If the journal really is hot, reset the pager cache prior rolling
-** back any content.  If the journal is merely persistent, no reset is
-** needed.
-*/
-static int pager_playback(Pager *pPager, int isHot){
-  sqlite3_vfs *pVfs = pPager->pVfs;
-  i64 szJ;                 /* Size of the journal file in bytes */
-  u32 nRec;                /* Number of Records in the journal */
-  u32 u;                   /* Unsigned loop counter */
-  Pgno mxPg = 0;           /* Size of the original file in pages */
-  int rc;                  /* Result code of a subroutine */
-  int res = 1;             /* Value returned by sqlite3OsAccess() */
-  char *zMaster = 0;       /* Name of master journal file if any */
-  int needPagerReset;      /* True to reset page prior to first page rollback */
-  int nPlayback = 0;       /* Total number of pages restored from journal */
-
-  /* Figure out how many records are in the journal.  Abort early if
-  ** the journal is empty.
-  */
-  assert( isOpen(pPager->jfd) );
-  rc = sqlite3OsFileSize(pPager->jfd, &szJ);
-  if( rc!=SQLITE_OK ){
-    goto end_playback;
-  }
-
-  /* Read the master journal name from the journal, if it is present.
-  ** If a master journal file name is specified, but the file is not
-  ** present on disk, then the journal is not hot and does not need to be
-  ** played back.
-  **
-  ** TODO: Technically the following is an error because it assumes that
-  ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that
-  ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c,
-  **  mxPathname is 512, which is the same as the minimum allowable value
-  ** for pageSize.
-  */
-  zMaster = pPager->pTmpSpace;
-  rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
-  if( rc==SQLITE_OK && zMaster[0] ){
-    rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res);
-  }
-  zMaster = 0;
-  if( rc!=SQLITE_OK || !res ){
-    goto end_playback;
-  }
-  pPager->journalOff = 0;
-  needPagerReset = isHot;
-
-  /* This loop terminates either when a readJournalHdr() or 
-  ** pager_playback_one_page() call returns SQLITE_DONE or an IO error 
-  ** occurs. 
-  */
-  while( 1 ){
-    /* Read the next journal header from the journal file.  If there are
-    ** not enough bytes left in the journal file for a complete header, or
-    ** it is corrupted, then a process must have failed while writing it.
-    ** This indicates nothing more needs to be rolled back.
-    */
-    rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg);
-    if( rc!=SQLITE_OK ){ 
-      if( rc==SQLITE_DONE ){
-        rc = SQLITE_OK;
-      }
-      goto end_playback;
-    }
-
-    /* If nRec is 0xffffffff, then this journal was created by a process
-    ** working in no-sync mode. This means that the rest of the journal
-    ** file consists of pages, there are no more journal headers. Compute
-    ** the value of nRec based on this assumption.
-    */
-    if( nRec==0xffffffff ){
-      assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) );
-      nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager));
-    }
-
-    /* If nRec is 0 and this rollback is of a transaction created by this
-    ** process and if this is the final header in the journal, then it means
-    ** that this part of the journal was being filled but has not yet been
-    ** synced to disk.  Compute the number of pages based on the remaining
-    ** size of the file.
-    **
-    ** The third term of the test was added to fix ticket #2565.
-    ** When rolling back a hot journal, nRec==0 always means that the next
-    ** chunk of the journal contains zero pages to be rolled back.  But
-    ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in
-    ** the journal, it means that the journal might contain additional
-    ** pages that need to be rolled back and that the number of pages 
-    ** should be computed based on the journal file size.
-    */
-    if( nRec==0 && !isHot &&
-        pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){
-      nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager));
-    }
-
-    /* If this is the first header read from the journal, truncate the
-    ** database file back to its original size.
-    */
-    if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){
-      rc = pager_truncate(pPager, mxPg);
-      if( rc!=SQLITE_OK ){
-        goto end_playback;
-      }
-      pPager->dbSize = mxPg;
-    }
-
-    /* Copy original pages out of the journal and back into the 
-    ** database file and/or page cache.
-    */
-    for(u=0; u<nRec; u++){
-      if( needPagerReset ){
-        pager_reset(pPager);
-        needPagerReset = 0;
-      }
-      rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0);
-      if( rc==SQLITE_OK ){
-        nPlayback++;
-      }else{
-        if( rc==SQLITE_DONE ){
-          pPager->journalOff = szJ;
-          break;
-        }else if( rc==SQLITE_IOERR_SHORT_READ ){
-          /* If the journal has been truncated, simply stop reading and
-          ** processing the journal. This might happen if the journal was
-          ** not completely written and synced prior to a crash.  In that
-          ** case, the database should have never been written in the
-          ** first place so it is OK to simply abandon the rollback. */
-          rc = SQLITE_OK;
-          goto end_playback;
-        }else{
-          /* If we are unable to rollback, quit and return the error
-          ** code.  This will cause the pager to enter the error state
-          ** so that no further harm will be done.  Perhaps the next
-          ** process to come along will be able to rollback the database.
-          */
-          goto end_playback;
-        }
-      }
-    }
-  }
-  /*NOTREACHED*/
-  assert( 0 );
-
-end_playback:
-  /* Following a rollback, the database file should be back in its original
-  ** state prior to the start of the transaction, so invoke the
-  ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the
-  ** assertion that the transaction counter was modified.
-  */
-#ifdef SQLITE_DEBUG
-  if( pPager->fd->pMethods ){
-    sqlite3OsFileControlHint(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0);
-  }
-#endif
-
-  /* If this playback is happening automatically as a result of an IO or 
-  ** malloc error that occurred after the change-counter was updated but 
-  ** before the transaction was committed, then the change-counter 
-  ** modification may just have been reverted. If this happens in exclusive 
-  ** mode, then subsequent transactions performed by the connection will not
-  ** update the change-counter at all. This may lead to cache inconsistency
-  ** problems for other processes at some point in the future. So, just
-  ** in case this has happened, clear the changeCountDone flag now.
-  */
-  pPager->changeCountDone = pPager->tempFile;
-
-  if( rc==SQLITE_OK ){
-    zMaster = pPager->pTmpSpace;
-    rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( rc==SQLITE_OK
-   && (pPager->eState>=PAGER_WRITER_DBMOD || pPager->eState==PAGER_OPEN)
-  ){
-    rc = sqlite3PagerSync(pPager, 0);
-  }
-  if( rc==SQLITE_OK ){
-    rc = pager_end_transaction(pPager, zMaster[0]!='\0', 0);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( rc==SQLITE_OK && zMaster[0] && res ){
-    /* If there was a master journal and this routine will return success,
-    ** see if it is possible to delete the master journal.
-    */
-    rc = pager_delmaster(pPager, zMaster);
-    testcase( rc!=SQLITE_OK );
-  }
-  if( isHot && nPlayback ){
-    sqlite3_log(SQLITE_NOTICE_RECOVER_ROLLBACK, "recovered %d pages from %s",
-                nPlayback, pPager->zJournal);
-  }
-
-  /* The Pager.sectorSize variable may have been updated while rolling
-  ** back a journal created by a process with a different sector size
-  ** value. Reset it to the correct value for this process.
-  */
-  setSectorSize(pPager);
-  return rc;
-}
-
-
-/*
-** Read the content for page pPg out of the database file and into 
-** pPg->pData. A shared lock or greater must be held on the database
-** file before this function is called.
-**
-** If page 1 is read, then the value of Pager.dbFileVers[] is set to
-** the value read from the database file.
-**
-** If an IO error occurs, then the IO error is returned to the caller.
-** Otherwise, SQLITE_OK is returned.
-*/
-static int readDbPage(PgHdr *pPg, u32 iFrame){
-  Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */
-  Pgno pgno = pPg->pgno;       /* Page number to read */
-  int rc = SQLITE_OK;          /* Return code */
-  int pgsz = pPager->pageSize; /* Number of bytes to read */
-
-  assert( pPager->eState>=PAGER_READER );
-  assert( isOpen(pPager->fd) );
-
-#ifndef SQLITE_OMIT_WAL
-  if( iFrame ){
-    /* Try to pull the page from the write-ahead log. */
-    rc = sqlite3WalReadFrame(pPager->pWal, iFrame, pgsz, pPg->pData);
-  }else
-#endif
-  {
-    i64 iOffset = (pgno-1)*(i64)pPager->pageSize;
-    rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset);
-    if( rc==SQLITE_IOERR_SHORT_READ ){
-      rc = SQLITE_OK;
-    }
-  }
-
-  if( pgno==1 ){
-    if( rc ){
-      /* If the read is unsuccessful, set the dbFileVers[] to something
-      ** that will never be a valid file version.  dbFileVers[] is a copy
-      ** of bytes 24..39 of the database.  Bytes 28..31 should always be
-      ** zero or the size of the database in page. Bytes 32..35 and 35..39
-      ** should be page numbers which are never 0xffffffff.  So filling
-      ** pPager->dbFileVers[] with all 0xff bytes should suffice.
-      **
-      ** For an encrypted database, the situation is more complex:  bytes
-      ** 24..39 of the database are white noise.  But the probability of
-      ** white noise equaling 16 bytes of 0xff is vanishingly small so
-      ** we should still be ok.
-      */
-      memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
-    }else{
-      u8 *dbFileVers = &((u8*)pPg->pData)[24];
-      memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers));
-    }
-  }
-  CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM);
-
-  PAGER_INCR(sqlite3_pager_readdb_count);
-  PAGER_INCR(pPager->nRead);
-  IOTRACE(("PGIN %p %d\n", pPager, pgno));
-  PAGERTRACE(("FETCH %d page %d hash(%08x)\n",
-               PAGERID(pPager), pgno, pager_pagehash(pPg)));
-
-  return rc;
-}
-
-/*
-** Update the value of the change-counter at offsets 24 and 92 in
-** the header and the sqlite version number at offset 96.
-**
-** This is an unconditional update.  See also the pager_incr_changecounter()
-** routine which only updates the change-counter if the update is actually
-** needed, as determined by the pPager->changeCountDone state variable.
-*/
-static void pager_write_changecounter(PgHdr *pPg){
-  u32 change_counter;
-
-  /* Increment the value just read and write it back to byte 24. */
-  change_counter = sqlite3Get4byte((u8*)pPg->pPager->dbFileVers)+1;
-  put32bits(((char*)pPg->pData)+24, change_counter);
-
-  /* Also store the SQLite version number in bytes 96..99 and in
-  ** bytes 92..95 store the change counter for which the version number
-  ** is valid. */
-  put32bits(((char*)pPg->pData)+92, change_counter);
-  put32bits(((char*)pPg->pData)+96, SQLITE_VERSION_NUMBER);
-}
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** This function is invoked once for each page that has already been 
-** written into the log file when a WAL transaction is rolled back.
-** Parameter iPg is the page number of said page. The pCtx argument 
-** is actually a pointer to the Pager structure.
-**
-** If page iPg is present in the cache, and has no outstanding references,
-** it is discarded. Otherwise, if there are one or more outstanding
-** references, the page content is reloaded from the database. If the
-** attempt to reload content from the database is required and fails, 
-** return an SQLite error code. Otherwise, SQLITE_OK.
-*/
-static int pagerUndoCallback(void *pCtx, Pgno iPg){
-  int rc = SQLITE_OK;
-  Pager *pPager = (Pager *)pCtx;
-  PgHdr *pPg;
-
-  assert( pagerUseWal(pPager) );
-  pPg = sqlite3PagerLookup(pPager, iPg);
-  if( pPg ){
-    if( sqlite3PcachePageRefcount(pPg)==1 ){
-      sqlite3PcacheDrop(pPg);
-    }else{
-      u32 iFrame = 0;
-      rc = sqlite3WalFindFrame(pPager->pWal, pPg->pgno, &iFrame);
-      if( rc==SQLITE_OK ){
-        rc = readDbPage(pPg, iFrame);
-      }
-      if( rc==SQLITE_OK ){
-        pPager->xReiniter(pPg);
-      }
-      sqlite3PagerUnrefNotNull(pPg);
-    }
-  }
-
-  /* Normally, if a transaction is rolled back, any backup processes are
-  ** updated as data is copied out of the rollback journal and into the
-  ** database. This is not generally possible with a WAL database, as
-  ** rollback involves simply truncating the log file. Therefore, if one
-  ** or more frames have already been written to the log (and therefore 
-  ** also copied into the backup databases) as part of this transaction,
-  ** the backups must be restarted.
-  */
-  sqlite3BackupRestart(pPager->pBackup);
-
-  return rc;
-}
-
-/*
-** This function is called to rollback a transaction on a WAL database.
-*/
-static int pagerRollbackWal(Pager *pPager){
-  int rc;                         /* Return Code */
-  PgHdr *pList;                   /* List of dirty pages to revert */
-
-  /* For all pages in the cache that are currently dirty or have already
-  ** been written (but not committed) to the log file, do one of the 
-  ** following:
-  **
-  **   + Discard the cached page (if refcount==0), or
-  **   + Reload page content from the database (if refcount>0).
-  */
-  pPager->dbSize = pPager->dbOrigSize;
-  rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager);
-  pList = sqlite3PcacheDirtyList(pPager->pPCache);
-  while( pList && rc==SQLITE_OK ){
-    PgHdr *pNext = pList->pDirty;
-    rc = pagerUndoCallback((void *)pPager, pList->pgno);
-    pList = pNext;
-  }
-
-  return rc;
-}
-
-/*
-** This function is a wrapper around sqlite3WalFrames(). As well as logging
-** the contents of the list of pages headed by pList (connected by pDirty),
-** this function notifies any active backup processes that the pages have
-** changed. 
-**
-** The list of pages passed into this routine is always sorted by page number.
-** Hence, if page 1 appears anywhere on the list, it will be the first page.
-*/ 
-static int pagerWalFrames(
-  Pager *pPager,                  /* Pager object */
-  PgHdr *pList,                   /* List of frames to log */
-  Pgno nTruncate,                 /* Database size after this commit */
-  int isCommit                    /* True if this is a commit */
-){
-  int rc;                         /* Return code */
-  int nList;                      /* Number of pages in pList */
-  PgHdr *p;                       /* For looping over pages */
-
-  assert( pPager->pWal );
-  assert( pList );
-#ifdef SQLITE_DEBUG
-  /* Verify that the page list is in accending order */
-  for(p=pList; p && p->pDirty; p=p->pDirty){
-    assert( p->pgno < p->pDirty->pgno );
-  }
-#endif
-
-  assert( pList->pDirty==0 || isCommit );
-  if( isCommit ){
-    /* If a WAL transaction is being committed, there is no point in writing
-    ** any pages with page numbers greater than nTruncate into the WAL file.
-    ** They will never be read by any client. So remove them from the pDirty
-    ** list here. */
-    PgHdr **ppNext = &pList;
-    nList = 0;
-    for(p=pList; (*ppNext = p)!=0; p=p->pDirty){
-      if( p->pgno<=nTruncate ){
-        ppNext = &p->pDirty;
-        nList++;
-      }
-    }
-    assert( pList );
-  }else{
-    nList = 1;
-  }
-  pPager->aStat[PAGER_STAT_WRITE] += nList;
-
-  if( pList->pgno==1 ) pager_write_changecounter(pList);
-  rc = sqlite3WalFrames(pPager->pWal, 
-      pPager->pageSize, pList, nTruncate, isCommit, pPager->walSyncFlags
-  );
-  if( rc==SQLITE_OK && pPager->pBackup ){
-    for(p=pList; p; p=p->pDirty){
-      sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData);
-    }
-  }
-
-#ifdef SQLITE_CHECK_PAGES
-  pList = sqlite3PcacheDirtyList(pPager->pPCache);
-  for(p=pList; p; p=p->pDirty){
-    pager_set_pagehash(p);
-  }
-#endif
-
-  return rc;
-}
-
-/*
-** Begin a read transaction on the WAL.
-**
-** This routine used to be called "pagerOpenSnapshot()" because it essentially
-** makes a snapshot of the database at the current point in time and preserves
-** that snapshot for use by the reader in spite of concurrently changes by
-** other writers or checkpointers.
-*/
-static int pagerBeginReadTransaction(Pager *pPager){
-  int rc;                         /* Return code */
-  int changed = 0;                /* True if cache must be reset */
-
-  assert( pagerUseWal(pPager) );
-  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
-
-  /* sqlite3WalEndReadTransaction() was not called for the previous
-  ** transaction in locking_mode=EXCLUSIVE.  So call it now.  If we
-  ** are in locking_mode=NORMAL and EndRead() was previously called,
-  ** the duplicate call is harmless.
-  */
-  sqlite3WalEndReadTransaction(pPager->pWal);
-
-  rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed);
-  if( rc!=SQLITE_OK || changed ){
-    pager_reset(pPager);
-    if( USEFETCH(pPager) ) sqlite3OsUnfetch(pPager->fd, 0, 0);
-  }
-
-  return rc;
-}
-#endif
-
-/*
-** This function is called as part of the transition from PAGER_OPEN
-** to PAGER_READER state to determine the size of the database file
-** in pages (assuming the page size currently stored in Pager.pageSize).
-**
-** If no error occurs, SQLITE_OK is returned and the size of the database
-** in pages is stored in *pnPage. Otherwise, an error code (perhaps
-** SQLITE_IOERR_FSTAT) is returned and *pnPage is left unmodified.
-*/
-static int pagerPagecount(Pager *pPager, Pgno *pnPage){
-  Pgno nPage;                     /* Value to return via *pnPage */
-
-  /* Query the WAL sub-system for the database size. The WalDbsize()
-  ** function returns zero if the WAL is not open (i.e. Pager.pWal==0), or
-  ** if the database size is not available. The database size is not
-  ** available from the WAL sub-system if the log file is empty or
-  ** contains no valid committed transactions.
-  */
-  assert( pPager->eState==PAGER_OPEN );
-  assert( pPager->eLock>=SHARED_LOCK );
-  nPage = sqlite3WalDbsize(pPager->pWal);
-
-  /* If the number of pages in the database is not available from the
-  ** WAL sub-system, determine the page counte based on the size of
-  ** the database file.  If the size of the database file is not an
-  ** integer multiple of the page-size, round up the result.
-  */
-  if( nPage==0 ){
-    i64 n = 0;                    /* Size of db file in bytes */
-    assert( isOpen(pPager->fd) || pPager->tempFile );
-    if( isOpen(pPager->fd) ){
-      int rc = sqlite3OsFileSize(pPager->fd, &n);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }
-    nPage = (Pgno)((n+pPager->pageSize-1) / pPager->pageSize);
-  }
-
-  /* If the current number of pages in the file is greater than the
-  ** configured maximum pager number, increase the allowed limit so
-  ** that the file can be read.
-  */
-  if( nPage>pPager->mxPgno ){
-    pPager->mxPgno = (Pgno)nPage;
-  }
-
-  *pnPage = nPage;
-  return SQLITE_OK;
-}
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** Check if the *-wal file that corresponds to the database opened by pPager
-** exists if the database is not empy, or verify that the *-wal file does
-** not exist (by deleting it) if the database file is empty.
-**
-** If the database is not empty and the *-wal file exists, open the pager
-** in WAL mode.  If the database is empty or if no *-wal file exists and
-** if no error occurs, make sure Pager.journalMode is not set to
-** PAGER_JOURNALMODE_WAL.
-**
-** Return SQLITE_OK or an error code.
-**
-** The caller must hold a SHARED lock on the database file to call this
-** function. Because an EXCLUSIVE lock on the db file is required to delete 
-** a WAL on a none-empty database, this ensures there is no race condition 
-** between the xAccess() below and an xDelete() being executed by some 
-** other connection.
-*/
-static int pagerOpenWalIfPresent(Pager *pPager){
-  int rc = SQLITE_OK;
-  assert( pPager->eState==PAGER_OPEN );
-  assert( pPager->eLock>=SHARED_LOCK );
-
-  if( !pPager->tempFile ){
-    int isWal;                    /* True if WAL file exists */
-    Pgno nPage;                   /* Size of the database file */
-
-    rc = pagerPagecount(pPager, &nPage);
-    if( rc ) return rc;
-    if( nPage==0 ){
-      rc = sqlite3OsDelete(pPager->pVfs, pPager->zWal, 0);
-      if( rc==SQLITE_IOERR_DELETE_NOENT ) rc = SQLITE_OK;
-      isWal = 0;
-    }else{
-      rc = sqlite3OsAccess(
-          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &isWal
-      );
-    }
-    if( rc==SQLITE_OK ){
-      if( isWal ){
-        testcase( sqlite3PcachePagecount(pPager->pPCache)==0 );
-        rc = sqlite3PagerOpenWal(pPager, 0);
-      }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){
-        pPager->journalMode = PAGER_JOURNALMODE_DELETE;
-      }
-    }
-  }
-  return rc;
-}
-#endif
-
-/*
-** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback
-** the entire master journal file. The case pSavepoint==NULL occurs when 
-** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction 
-** savepoint.
-**
-** When pSavepoint is not NULL (meaning a non-transaction savepoint is 
-** being rolled back), then the rollback consists of up to three stages,
-** performed in the order specified:
-**
-**   * Pages are played back from the main journal starting at byte
-**     offset PagerSavepoint.iOffset and continuing to 
-**     PagerSavepoint.iHdrOffset, or to the end of the main journal
-**     file if PagerSavepoint.iHdrOffset is zero.
-**
-**   * If PagerSavepoint.iHdrOffset is not zero, then pages are played
-**     back starting from the journal header immediately following 
-**     PagerSavepoint.iHdrOffset to the end of the main journal file.
-**
-**   * Pages are then played back from the sub-journal file, starting
-**     with the PagerSavepoint.iSubRec and continuing to the end of
-**     the journal file.
-**
-** Throughout the rollback process, each time a page is rolled back, the
-** corresponding bit is set in a bitvec structure (variable pDone in the
-** implementation below). This is used to ensure that a page is only
-** rolled back the first time it is encountered in either journal.
-**
-** If pSavepoint is NULL, then pages are only played back from the main
-** journal file. There is no need for a bitvec in this case.
-**
-** In either case, before playback commences the Pager.dbSize variable
-** is reset to the value that it held at the start of the savepoint 
-** (or transaction). No page with a page-number greater than this value
-** is played back. If one is encountered it is simply skipped.
-*/
-static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){
-  i64 szJ;                 /* Effective size of the main journal */
-  i64 iHdrOff;             /* End of first segment of main-journal records */
-  int rc = SQLITE_OK;      /* Return code */
-  Bitvec *pDone = 0;       /* Bitvec to ensure pages played back only once */
-
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-
-  /* Allocate a bitvec to use to store the set of pages rolled back */
-  if( pSavepoint ){
-    pDone = sqlite3BitvecCreate(pSavepoint->nOrig);
-    if( !pDone ){
-      return SQLITE_NOMEM;
-    }
-  }
-
-  /* Set the database size back to the value it was before the savepoint 
-  ** being reverted was opened.
-  */
-  pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize;
-  pPager->changeCountDone = pPager->tempFile;
-
-  if( !pSavepoint && pagerUseWal(pPager) ){
-    return pagerRollbackWal(pPager);
-  }
-
-  /* Use pPager->journalOff as the effective size of the main rollback
-  ** journal.  The actual file might be larger than this in
-  ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST.  But anything
-  ** past pPager->journalOff is off-limits to us.
-  */
-  szJ = pPager->journalOff;
-  assert( pagerUseWal(pPager)==0 || szJ==0 );
-
-  /* Begin by rolling back records from the main journal starting at
-  ** PagerSavepoint.iOffset and continuing to the next journal header.
-  ** There might be records in the main journal that have a page number
-  ** greater than the current database size (pPager->dbSize) but those
-  ** will be skipped automatically.  Pages are added to pDone as they
-  ** are played back.
-  */
-  if( pSavepoint && !pagerUseWal(pPager) ){
-    iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ;
-    pPager->journalOff = pSavepoint->iOffset;
-    while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){
-      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }else{
-    pPager->journalOff = 0;
-  }
-
-  /* Continue rolling back records out of the main journal starting at
-  ** the first journal header seen and continuing until the effective end
-  ** of the main journal file.  Continue to skip out-of-range pages and
-  ** continue adding pages rolled back to pDone.
-  */
-  while( rc==SQLITE_OK && pPager->journalOff<szJ ){
-    u32 ii;            /* Loop counter */
-    u32 nJRec = 0;     /* Number of Journal Records */
-    u32 dummy;
-    rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy);
-    assert( rc!=SQLITE_DONE );
-
-    /*
-    ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff"
-    ** test is related to ticket #2565.  See the discussion in the
-    ** pager_playback() function for additional information.
-    */
-    if( nJRec==0 
-     && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff
-    ){
-      nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager));
-    }
-    for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){
-      rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }
-  assert( rc!=SQLITE_OK || pPager->journalOff>=szJ );
-
-  /* Finally,  rollback pages from the sub-journal.  Page that were
-  ** previously rolled back out of the main journal (and are hence in pDone)
-  ** will be skipped.  Out-of-range pages are also skipped.
-  */
-  if( pSavepoint ){
-    u32 ii;            /* Loop counter */
-    i64 offset = (i64)pSavepoint->iSubRec*(4+pPager->pageSize);
-
-    if( pagerUseWal(pPager) ){
-      rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData);
-    }
-    for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){
-      assert( offset==(i64)ii*(4+pPager->pageSize) );
-      rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1);
-    }
-    assert( rc!=SQLITE_DONE );
-  }
-
-  sqlite3BitvecDestroy(pDone);
-  if( rc==SQLITE_OK ){
-    pPager->journalOff = szJ;
-  }
-
-  return rc;
-}
-
-/*
-** Change the maximum number of in-memory pages that are allowed.
-*/
-SQLITE_PRIVATE void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){
-  sqlite3PcacheSetCachesize(pPager->pPCache, mxPage);
-}
-
-/*
-** Invoke SQLITE_FCNTL_MMAP_SIZE based on the current value of szMmap.
-*/
-static void pagerFixMaplimit(Pager *pPager){
-#if SQLITE_MAX_MMAP_SIZE>0
-  sqlite3_file *fd = pPager->fd;
-  if( isOpen(fd) && fd->pMethods->iVersion>=3 ){
-    sqlite3_int64 sz;
-    sz = pPager->szMmap;
-    pPager->bUseFetch = (sz>0);
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_MMAP_SIZE, &sz);
-  }
-#endif
-}
-
-/*
-** Change the maximum size of any memory mapping made of the database file.
-*/
-SQLITE_PRIVATE void sqlite3PagerSetMmapLimit(Pager *pPager, sqlite3_int64 szMmap){
-  pPager->szMmap = szMmap;
-  pagerFixMaplimit(pPager);
-}
-
-/*
-** Adjust settings of the pager to those specified in the pgFlags parameter.
-**
-** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
-** of the database to damage due to OS crashes or power failures by
-** changing the number of syncs()s when writing the journals.
-** There are three levels:
-**
-**    OFF       sqlite3OsSync() is never called.  This is the default
-**              for temporary and transient files.
-**
-**    NORMAL    The journal is synced once before writes begin on the
-**              database.  This is normally adequate protection, but
-**              it is theoretically possible, though very unlikely,
-**              that an inopertune power failure could leave the journal
-**              in a state which would cause damage to the database
-**              when it is rolled back.
-**
-**    FULL      The journal is synced twice before writes begin on the
-**              database (with some additional information - the nRec field
-**              of the journal header - being written in between the two
-**              syncs).  If we assume that writing a
-**              single disk sector is atomic, then this mode provides
-**              assurance that the journal will not be corrupted to the
-**              point of causing damage to the database during rollback.
-**
-** The above is for a rollback-journal mode.  For WAL mode, OFF continues
-** to mean that no syncs ever occur.  NORMAL means that the WAL is synced
-** prior to the start of checkpoint and that the database file is synced
-** at the conclusion of the checkpoint if the entire content of the WAL
-** was written back into the database.  But no sync operations occur for
-** an ordinary commit in NORMAL mode with WAL.  FULL means that the WAL
-** file is synced following each commit operation, in addition to the
-** syncs associated with NORMAL.
-**
-** Do not confuse synchronous=FULL with SQLITE_SYNC_FULL.  The
-** SQLITE_SYNC_FULL macro means to use the MacOSX-style full-fsync
-** using fcntl(F_FULLFSYNC).  SQLITE_SYNC_NORMAL means to do an
-** ordinary fsync() call.  There is no difference between SQLITE_SYNC_FULL
-** and SQLITE_SYNC_NORMAL on platforms other than MacOSX.  But the
-** synchronous=FULL versus synchronous=NORMAL setting determines when
-** the xSync primitive is called and is relevant to all platforms.
-**
-** Numeric values associated with these states are OFF==1, NORMAL=2,
-** and FULL=3.
-*/
-#ifndef SQLITE_OMIT_PAGER_PRAGMAS
-SQLITE_PRIVATE void sqlite3PagerSetFlags(
-  Pager *pPager,        /* The pager to set safety level for */
-  unsigned pgFlags      /* Various flags */
-){
-  unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
-  assert( level>=1 && level<=3 );
-  pPager->noSync =  (level==1 || pPager->tempFile) ?1:0;
-  pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0;
-  if( pPager->noSync ){
-    pPager->syncFlags = 0;
-    pPager->ckptSyncFlags = 0;
-  }else if( pgFlags & PAGER_FULLFSYNC ){
-    pPager->syncFlags = SQLITE_SYNC_FULL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
-  }else if( pgFlags & PAGER_CKPT_FULLFSYNC ){
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
-  }else{
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
-  }
-  pPager->walSyncFlags = pPager->syncFlags;
-  if( pPager->fullSync ){
-    pPager->walSyncFlags |= WAL_SYNC_TRANSACTIONS;
-  }
-  if( pgFlags & PAGER_CACHESPILL ){
-    pPager->doNotSpill &= ~SPILLFLAG_OFF;
-  }else{
-    pPager->doNotSpill |= SPILLFLAG_OFF;
-  }
-}
-#endif
-
-/*
-** The following global variable is incremented whenever the library
-** attempts to open a temporary file.  This information is used for
-** testing and analysis only.  
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_opentemp_count = 0;
-#endif
-
-/*
-** Open a temporary file.
-**
-** Write the file descriptor into *pFile. Return SQLITE_OK on success 
-** or some other error code if we fail. The OS will automatically 
-** delete the temporary file when it is closed.
-**
-** The flags passed to the VFS layer xOpen() call are those specified
-** by parameter vfsFlags ORed with the following:
-**
-**     SQLITE_OPEN_READWRITE
-**     SQLITE_OPEN_CREATE
-**     SQLITE_OPEN_EXCLUSIVE
-**     SQLITE_OPEN_DELETEONCLOSE
-*/
-static int pagerOpentemp(
-  Pager *pPager,        /* The pager object */
-  sqlite3_file *pFile,  /* Write the file descriptor here */
-  int vfsFlags          /* Flags passed through to the VFS */
-){
-  int rc;               /* Return code */
-
-#ifdef SQLITE_TEST
-  sqlite3_opentemp_count++;  /* Used for testing and analysis only */
-#endif
-
-  vfsFlags |=  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE |
-            SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE;
-  rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0);
-  assert( rc!=SQLITE_OK || isOpen(pFile) );
-  return rc;
-}
-
-/*
-** Set the busy handler function.
-**
-** The pager invokes the busy-handler if sqlite3OsLock() returns 
-** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock,
-** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE 
-** lock. It does *not* invoke the busy handler when upgrading from
-** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE
-** (which occurs during hot-journal rollback). Summary:
-**
-**   Transition                        | Invokes xBusyHandler
-**   --------------------------------------------------------
-**   NO_LOCK       -> SHARED_LOCK      | Yes
-**   SHARED_LOCK   -> RESERVED_LOCK    | No
-**   SHARED_LOCK   -> EXCLUSIVE_LOCK   | No
-**   RESERVED_LOCK -> EXCLUSIVE_LOCK   | Yes
-**
-** If the busy-handler callback returns non-zero, the lock is 
-** retried. If it returns zero, then the SQLITE_BUSY error is
-** returned to the caller of the pager API function.
-*/
-SQLITE_PRIVATE void sqlite3PagerSetBusyhandler(
-  Pager *pPager,                       /* Pager object */
-  int (*xBusyHandler)(void *),         /* Pointer to busy-handler function */
-  void *pBusyHandlerArg                /* Argument to pass to xBusyHandler */
-){
-  pPager->xBusyHandler = xBusyHandler;
-  pPager->pBusyHandlerArg = pBusyHandlerArg;
-
-  if( isOpen(pPager->fd) ){
-    void **ap = (void **)&pPager->xBusyHandler;
-    assert( ((int(*)(void *))(ap[0]))==xBusyHandler );
-    assert( ap[1]==pBusyHandlerArg );
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_BUSYHANDLER, (void *)ap);
-  }
-}
-
-/*
-** Change the page size used by the Pager object. The new page size 
-** is passed in *pPageSize.
-**
-** If the pager is in the error state when this function is called, it
-** is a no-op. The value returned is the error state error code (i.e. 
-** one of SQLITE_IOERR, an SQLITE_IOERR_xxx sub-code or SQLITE_FULL).
-**
-** Otherwise, if all of the following are true:
-**
-**   * the new page size (value of *pPageSize) is valid (a power 
-**     of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and
-**
-**   * there are no outstanding page references, and
-**
-**   * the database is either not an in-memory database or it is
-**     an in-memory database that currently consists of zero pages.
-**
-** then the pager object page size is set to *pPageSize.
-**
-** If the page size is changed, then this function uses sqlite3PagerMalloc() 
-** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt 
-** fails, SQLITE_NOMEM is returned and the page size remains unchanged. 
-** In all other cases, SQLITE_OK is returned.
-**
-** If the page size is not changed, either because one of the enumerated
-** conditions above is not true, the pager was in error state when this
-** function was called, or because the memory allocation attempt failed, 
-** then *pPageSize is set to the old, retained page size before returning.
-*/
-SQLITE_PRIVATE int sqlite3PagerSetPagesize(Pager *pPager, u32 *pPageSize, int nReserve){
-  int rc = SQLITE_OK;
-
-  /* It is not possible to do a full assert_pager_state() here, as this
-  ** function may be called from within PagerOpen(), before the state
-  ** of the Pager object is internally consistent.
-  **
-  ** At one point this function returned an error if the pager was in 
-  ** PAGER_ERROR state. But since PAGER_ERROR state guarantees that
-  ** there is at least one outstanding page reference, this function
-  ** is a no-op for that case anyhow.
-  */
-
-  u32 pageSize = *pPageSize;
-  assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) );
-  if( (pPager->memDb==0 || pPager->dbSize==0)
-   && sqlite3PcacheRefCount(pPager->pPCache)==0 
-   && pageSize && pageSize!=(u32)pPager->pageSize 
-  ){
-    char *pNew = NULL;             /* New temp space */
-    i64 nByte = 0;
-
-    if( pPager->eState>PAGER_OPEN && isOpen(pPager->fd) ){
-      rc = sqlite3OsFileSize(pPager->fd, &nByte);
-    }
-    if( rc==SQLITE_OK ){
-      pNew = (char *)sqlite3PageMalloc(pageSize);
-      if( !pNew ) rc = SQLITE_NOMEM;
-    }
-
-    if( rc==SQLITE_OK ){
-      pager_reset(pPager);
-      rc = sqlite3PcacheSetPageSize(pPager->pPCache, pageSize);
-    }
-    if( rc==SQLITE_OK ){
-      sqlite3PageFree(pPager->pTmpSpace);
-      pPager->pTmpSpace = pNew;
-      pPager->dbSize = (Pgno)((nByte+pageSize-1)/pageSize);
-      pPager->pageSize = pageSize;
-    }else{
-      sqlite3PageFree(pNew);
-    }
-  }
-
-  *pPageSize = pPager->pageSize;
-  if( rc==SQLITE_OK ){
-    if( nReserve<0 ) nReserve = pPager->nReserve;
-    assert( nReserve>=0 && nReserve<1000 );
-    pPager->nReserve = (i16)nReserve;
-    pagerReportSize(pPager);
-    pagerFixMaplimit(pPager);
-  }
-  return rc;
-}
-
-/*
-** Return a pointer to the "temporary page" buffer held internally
-** by the pager.  This is a buffer that is big enough to hold the
-** entire content of a database page.  This buffer is used internally
-** during rollback and will be overwritten whenever a rollback
-** occurs.  But other modules are free to use it too, as long as
-** no rollbacks are happening.
-*/
-SQLITE_PRIVATE void *sqlite3PagerTempSpace(Pager *pPager){
-  return pPager->pTmpSpace;
-}
-
-/*
-** Attempt to set the maximum database page count if mxPage is positive. 
-** Make no changes if mxPage is zero or negative.  And never reduce the
-** maximum page count below the current size of the database.
-**
-** Regardless of mxPage, return the current maximum page count.
-*/
-SQLITE_PRIVATE int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){
-  if( mxPage>0 ){
-    pPager->mxPgno = mxPage;
-  }
-  assert( pPager->eState!=PAGER_OPEN );      /* Called only by OP_MaxPgcnt */
-  assert( pPager->mxPgno>=pPager->dbSize );  /* OP_MaxPgcnt enforces this */
-  return pPager->mxPgno;
-}
-
-/*
-** The following set of routines are used to disable the simulated
-** I/O error mechanism.  These routines are used to avoid simulated
-** errors in places where we do not care about errors.
-**
-** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops
-** and generate no code.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE int sqlite3_io_error_pending;
-SQLITE_PRIVATE int sqlite3_io_error_hit;
-static int saved_cnt;
-void disable_simulated_io_errors(void){
-  saved_cnt = sqlite3_io_error_pending;
-  sqlite3_io_error_pending = -1;
-}
-void enable_simulated_io_errors(void){
-  sqlite3_io_error_pending = saved_cnt;
-}
-#else
-# define disable_simulated_io_errors()
-# define enable_simulated_io_errors()
-#endif
-
-/*
-** Read the first N bytes from the beginning of the file into memory
-** that pDest points to. 
-**
-** If the pager was opened on a transient file (zFilename==""), or
-** opened on a file less than N bytes in size, the output buffer is
-** zeroed and SQLITE_OK returned. The rationale for this is that this 
-** function is used to read database headers, and a new transient or
-** zero sized database has a header than consists entirely of zeroes.
-**
-** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered,
-** the error code is returned to the caller and the contents of the
-** output buffer undefined.
-*/
-SQLITE_PRIVATE int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){
-  int rc = SQLITE_OK;
-  memset(pDest, 0, N);
-  assert( isOpen(pPager->fd) || pPager->tempFile );
-
-  /* This routine is only called by btree immediately after creating
-  ** the Pager object.  There has not been an opportunity to transition
-  ** to WAL mode yet.
-  */
-  assert( !pagerUseWal(pPager) );
-
-  if( isOpen(pPager->fd) ){
-    IOTRACE(("DBHDR %p 0 %d\n", pPager, N))
-    rc = sqlite3OsRead(pPager->fd, pDest, N, 0);
-    if( rc==SQLITE_IOERR_SHORT_READ ){
-      rc = SQLITE_OK;
-    }
-  }
-  return rc;
-}
-
-/*
-** This function may only be called when a read-transaction is open on
-** the pager. It returns the total number of pages in the database.
-**
-** However, if the file is between 1 and <page-size> bytes in size, then 
-** this is considered a 1 page file.
-*/
-SQLITE_PRIVATE void sqlite3PagerPagecount(Pager *pPager, int *pnPage){
-  assert( pPager->eState>=PAGER_READER );
-  assert( pPager->eState!=PAGER_WRITER_FINISHED );
-  *pnPage = (int)pPager->dbSize;
-}
-
-
-/*
-** Try to obtain a lock of type locktype on the database file. If
-** a similar or greater lock is already held, this function is a no-op
-** (returning SQLITE_OK immediately).
-**
-** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke 
-** the busy callback if the lock is currently not available. Repeat 
-** until the busy callback returns false or until the attempt to 
-** obtain the lock succeeds.
-**
-** Return SQLITE_OK on success and an error code if we cannot obtain
-** the lock. If the lock is obtained successfully, set the Pager.state 
-** variable to locktype before returning.
-*/
-static int pager_wait_on_lock(Pager *pPager, int locktype){
-  int rc;                              /* Return code */
-
-  /* Check that this is either a no-op (because the requested lock is 
-  ** already held), or one of the transitions that the busy-handler
-  ** may be invoked during, according to the comment above
-  ** sqlite3PagerSetBusyhandler().
-  */
-  assert( (pPager->eLock>=locktype)
-       || (pPager->eLock==NO_LOCK && locktype==SHARED_LOCK)
-       || (pPager->eLock==RESERVED_LOCK && locktype==EXCLUSIVE_LOCK)
-  );
-
-  do {
-    rc = pagerLockDb(pPager, locktype);
-  }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) );
-  return rc;
-}
-
-/*
-** Function assertTruncateConstraint(pPager) checks that one of the 
-** following is true for all dirty pages currently in the page-cache:
-**
-**   a) The page number is less than or equal to the size of the 
-**      current database image, in pages, OR
-**
-**   b) if the page content were written at this time, it would not
-**      be necessary to write the current content out to the sub-journal
-**      (as determined by function subjRequiresPage()).
-**
-** If the condition asserted by this function were not true, and the
-** dirty page were to be discarded from the cache via the pagerStress()
-** routine, pagerStress() would not write the current page content to
-** the database file. If a savepoint transaction were rolled back after
-** this happened, the correct behavior would be to restore the current
-** content of the page. However, since this content is not present in either
-** the database file or the portion of the rollback journal and 
-** sub-journal rolled back the content could not be restored and the
-** database image would become corrupt. It is therefore fortunate that 
-** this circumstance cannot arise.
-*/
-#if defined(SQLITE_DEBUG)
-static void assertTruncateConstraintCb(PgHdr *pPg){
-  assert( pPg->flags&PGHDR_DIRTY );
-  assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize );
-}
-static void assertTruncateConstraint(Pager *pPager){
-  sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb);
-}
-#else
-# define assertTruncateConstraint(pPager)
-#endif
-
-/*
-** Truncate the in-memory database file image to nPage pages. This 
-** function does not actually modify the database file on disk. It 
-** just sets the internal state of the pager object so that the 
-** truncation will be done when the current transaction is committed.
-**
-** This function is only called right before committing a transaction.
-** Once this function has been called, the transaction must either be
-** rolled back or committed. It is not safe to call this function and
-** then continue writing to the database.
-*/
-SQLITE_PRIVATE void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){
-  assert( pPager->dbSize>=nPage );
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
-  pPager->dbSize = nPage;
-
-  /* At one point the code here called assertTruncateConstraint() to
-  ** ensure that all pages being truncated away by this operation are,
-  ** if one or more savepoints are open, present in the savepoint 
-  ** journal so that they can be restored if the savepoint is rolled
-  ** back. This is no longer necessary as this function is now only
-  ** called right before committing a transaction. So although the 
-  ** Pager object may still have open savepoints (Pager.nSavepoint!=0), 
-  ** they cannot be rolled back. So the assertTruncateConstraint() call
-  ** is no longer correct. */
-}
-
-
-/*
-** This function is called before attempting a hot-journal rollback. It
-** syncs the journal file to disk, then sets pPager->journalHdr to the
-** size of the journal file so that the pager_playback() routine knows
-** that the entire journal file has been synced.
-**
-** Syncing a hot-journal to disk before attempting to roll it back ensures 
-** that if a power-failure occurs during the rollback, the process that
-** attempts rollback following system recovery sees the same journal
-** content as this process.
-**
-** If everything goes as planned, SQLITE_OK is returned. Otherwise, 
-** an SQLite error code.
-*/
-static int pagerSyncHotJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( !pPager->noSync ){
-    rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL);
-  }
-  if( rc==SQLITE_OK ){
-    rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr);
-  }
-  return rc;
-}
-
-/*
-** Obtain a reference to a memory mapped page object for page number pgno. 
-** The new object will use the pointer pData, obtained from xFetch().
-** If successful, set *ppPage to point to the new page reference
-** and return SQLITE_OK. Otherwise, return an SQLite error code and set
-** *ppPage to zero.
-**
-** Page references obtained by calling this function should be released
-** by calling pagerReleaseMapPage().
-*/
-static int pagerAcquireMapPage(
-  Pager *pPager,                  /* Pager object */
-  Pgno pgno,                      /* Page number */
-  void *pData,                    /* xFetch()'d data for this page */
-  PgHdr **ppPage                  /* OUT: Acquired page object */
-){
-  PgHdr *p;                       /* Memory mapped page to return */
-  
-  if( pPager->pMmapFreelist ){
-    *ppPage = p = pPager->pMmapFreelist;
-    pPager->pMmapFreelist = p->pDirty;
-    p->pDirty = 0;
-    memset(p->pExtra, 0, pPager->nExtra);
-  }else{
-    *ppPage = p = (PgHdr *)sqlite3MallocZero(sizeof(PgHdr) + pPager->nExtra);
-    if( p==0 ){
-      sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1) * pPager->pageSize, pData);
-      return SQLITE_NOMEM;
-    }
-    p->pExtra = (void *)&p[1];
-    p->flags = PGHDR_MMAP;
-    p->nRef = 1;
-    p->pPager = pPager;
-  }
-
-  assert( p->pExtra==(void *)&p[1] );
-  assert( p->pPage==0 );
-  assert( p->flags==PGHDR_MMAP );
-  assert( p->pPager==pPager );
-  assert( p->nRef==1 );
-
-  p->pgno = pgno;
-  p->pData = pData;
-  pPager->nMmapOut++;
-
-  return SQLITE_OK;
-}
-
-/*
-** Release a reference to page pPg. pPg must have been returned by an 
-** earlier call to pagerAcquireMapPage().
-*/
-static void pagerReleaseMapPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  pPager->nMmapOut--;
-  pPg->pDirty = pPager->pMmapFreelist;
-  pPager->pMmapFreelist = pPg;
-
-  assert( pPager->fd->pMethods->iVersion>=3 );
-  sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
-}
-
-/*
-** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
-*/
-static void pagerFreeMapHdrs(Pager *pPager){
-  PgHdr *p;
-  PgHdr *pNext;
-  for(p=pPager->pMmapFreelist; p; p=pNext){
-    pNext = p->pDirty;
-    sqlite3_free(p);
-  }
-}
-
-
-/*
-** Shutdown the page cache.  Free all memory and close all files.
-**
-** If a transaction was in progress when this routine is called, that
-** transaction is rolled back.  All outstanding pages are invalidated
-** and their memory is freed.  Any attempt to use a page associated
-** with this page cache after this function returns will likely
-** result in a coredump.
-**
-** This function always succeeds. If a transaction is active an attempt
-** is made to roll it back. If an error occurs during the rollback 
-** a hot journal may be left in the filesystem but no error is returned
-** to the caller.
-*/
-SQLITE_PRIVATE int sqlite3PagerClose(Pager *pPager){
-  u8 *pTmp = (u8 *)pPager->pTmpSpace;
-
-  assert( assert_pager_state(pPager) );
-  disable_simulated_io_errors();
-  pagerFreeMapHdrs(pPager);
-  /* pPager->errCode = 0; */
-  pPager->exclusiveMode = 0;
-#ifndef SQLITE_OMIT_WAL
-  sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags, pPager->pageSize, pTmp);
-  pPager->pWal = 0;
-#endif
-  pager_reset(pPager);
-
-  /* If it is open, sync the journal file before calling UnlockAndRollback.
-   ** If this is not done, then an unsynced portion of the open journal 
-   ** file may be played back into the database. If a power failure occurs 
-   ** while this is happening, the database could become corrupt.
-   **
-   ** If an error occurs while trying to sync the journal, shift the pager
-   ** into the ERROR state. This causes UnlockAndRollback to unlock the
-   ** database and close the journal file without attempting to roll it
-   ** back or finalize it. The next database user will have to do hot-journal
-   ** rollback before accessing the database file.
-   */
-  if( isOpen(pPager->jfd) ){
-    pager_error(pPager, pagerSyncHotJournal(pPager));
-  }
-  pagerUnlockAndRollback(pPager);
-
-  enable_simulated_io_errors();
-  PAGERTRACE(("CLOSE %d\n", PAGERID(pPager)));
-  IOTRACE(("CLOSE %p\n", pPager))
-  sqlite3OsClose(pPager->jfd);
-  sqlite3OsClose(pPager->fd);
-  sqlite3PageFree(pTmp);
-  sqlite3PcacheClose(pPager->pPCache);
-
-#ifdef SQLITE_HAS_CODEC
-  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
-#endif
-
-  assert( !pPager->aSavepoint && !pPager->pInJournal );
-  assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) );
-
-  sqlite3_free(pPager);
-  return SQLITE_OK;
-}
-
-#if !defined(NDEBUG) || defined(SQLITE_TEST)
-/*
-** Return the page number for page pPg.
-*/
-SQLITE_PRIVATE Pgno sqlite3PagerPagenumber(DbPage *pPg){
-  return pPg->pgno;
-}
-#endif
-
-/*
-** Increment the reference count for page pPg.
-*/
-SQLITE_PRIVATE void sqlite3PagerRef(DbPage *pPg){
-  sqlite3PcacheRef(pPg);
-}
-
-/*
-** Sync the journal. In other words, make sure all the pages that have
-** been written to the journal have actually reached the surface of the
-** disk and can be restored in the event of a hot-journal rollback.
-**
-** If the Pager.noSync flag is set, then this function is a no-op.
-** Otherwise, the actions required depend on the journal-mode and the 
-** device characteristics of the file-system, as follows:
-**
-**   * If the journal file is an in-memory journal file, no action need
-**     be taken.
-**
-**   * Otherwise, if the device does not support the SAFE_APPEND property,
-**     then the nRec field of the most recently written journal header
-**     is updated to contain the number of journal records that have
-**     been written following it. If the pager is operating in full-sync
-**     mode, then the journal file is synced before this field is updated.
-**
-**   * If the device does not support the SEQUENTIAL property, then 
-**     journal file is synced.
-**
-** Or, in pseudo-code:
-**
-**   if( NOT <in-memory journal> ){
-**     if( NOT SAFE_APPEND ){
-**       if( <full-sync mode> ) xSync(<journal file>);
-**       <update nRec field>
-**     } 
-**     if( NOT SEQUENTIAL ) xSync(<journal file>);
-**   }
-**
-** If successful, this routine clears the PGHDR_NEED_SYNC flag of every 
-** page currently held in memory before returning SQLITE_OK. If an IO
-** error is encountered, then the IO error code is returned to the caller.
-*/
-static int syncJournal(Pager *pPager, int newHdr){
-  int rc;                         /* Return code */
-
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-  assert( !pagerUseWal(pPager) );
-
-  rc = sqlite3PagerExclusiveLock(pPager);
-  if( rc!=SQLITE_OK ) return rc;
-
-  if( !pPager->noSync ){
-    assert( !pPager->tempFile );
-    if( isOpen(pPager->jfd) && pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){
-      const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
-      assert( isOpen(pPager->jfd) );
-
-      if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
-        /* This block deals with an obscure problem. If the last connection
-        ** that wrote to this database was operating in persistent-journal
-        ** mode, then the journal file may at this point actually be larger
-        ** than Pager.journalOff bytes. If the next thing in the journal
-        ** file happens to be a journal-header (written as part of the
-        ** previous connection's transaction), and a crash or power-failure 
-        ** occurs after nRec is updated but before this connection writes 
-        ** anything else to the journal file (or commits/rolls back its 
-        ** transaction), then SQLite may become confused when doing the 
-        ** hot-journal rollback following recovery. It may roll back all
-        ** of this connections data, then proceed to rolling back the old,
-        ** out-of-date data that follows it. Database corruption.
-        **
-        ** To work around this, if the journal file does appear to contain
-        ** a valid header following Pager.journalOff, then write a 0x00
-        ** byte to the start of it to prevent it from being recognized.
-        **
-        ** Variable iNextHdrOffset is set to the offset at which this
-        ** problematic header will occur, if it exists. aMagic is used 
-        ** as a temporary buffer to inspect the first couple of bytes of
-        ** the potential journal header.
-        */
-        i64 iNextHdrOffset;
-        u8 aMagic[8];
-        u8 zHeader[sizeof(aJournalMagic)+4];
-
-        memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic));
-        put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec);
-
-        iNextHdrOffset = journalHdrOffset(pPager);
-        rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset);
-        if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){
-          static const u8 zerobyte = 0;
-          rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset);
-        }
-        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
-          return rc;
-        }
-
-        /* Write the nRec value into the journal file header. If in
-        ** full-synchronous mode, sync the journal first. This ensures that
-        ** all data has really hit the disk before nRec is updated to mark
-        ** it as a candidate for rollback.
-        **
-        ** This is not required if the persistent media supports the
-        ** SAFE_APPEND property. Because in this case it is not possible 
-        ** for garbage data to be appended to the file, the nRec field
-        ** is populated with 0xFFFFFFFF when the journal header is written
-        ** and never needs to be updated.
-        */
-        if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
-          PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
-          IOTRACE(("JSYNC %p\n", pPager))
-          rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags);
-          if( rc!=SQLITE_OK ) return rc;
-        }
-        IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr));
-        rc = sqlite3OsWrite(
-            pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr
-        );
-        if( rc!=SQLITE_OK ) return rc;
-      }
-      if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){
-        PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager)));
-        IOTRACE(("JSYNC %p\n", pPager))
-        rc = sqlite3OsSync(pPager->jfd, pPager->syncFlags| 
-          (pPager->syncFlags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0)
-        );
-        if( rc!=SQLITE_OK ) return rc;
-      }
-
-      pPager->journalHdr = pPager->journalOff;
-      if( newHdr && 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){
-        pPager->nRec = 0;
-        rc = writeJournalHdr(pPager);
-        if( rc!=SQLITE_OK ) return rc;
-      }
-    }else{
-      pPager->journalHdr = pPager->journalOff;
-    }
-  }
-
-  /* Unless the pager is in noSync mode, the journal file was just 
-  ** successfully synced. Either way, clear the PGHDR_NEED_SYNC flag on 
-  ** all pages.
-  */
-  sqlite3PcacheClearSyncFlags(pPager->pPCache);
-  pPager->eState = PAGER_WRITER_DBMOD;
-  assert( assert_pager_state(pPager) );
-  return SQLITE_OK;
-}
-
-/*
-** The argument is the first in a linked list of dirty pages connected
-** by the PgHdr.pDirty pointer. This function writes each one of the
-** in-memory pages in the list to the database file. The argument may
-** be NULL, representing an empty list. In this case this function is
-** a no-op.
-**
-** The pager must hold at least a RESERVED lock when this function
-** is called. Before writing anything to the database file, this lock
-** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained,
-** SQLITE_BUSY is returned and no data is written to the database file.
-** 
-** If the pager is a temp-file pager and the actual file-system file
-** is not yet open, it is created and opened before any data is 
-** written out.
-**
-** Once the lock has been upgraded and, if necessary, the file opened,
-** the pages are written out to the database file in list order. Writing
-** a page is skipped if it meets either of the following criteria:
-**
-**   * The page number is greater than Pager.dbSize, or
-**   * The PGHDR_DONT_WRITE flag is set on the page.
-**
-** If writing out a page causes the database file to grow, Pager.dbFileSize
-** is updated accordingly. If page 1 is written out, then the value cached
-** in Pager.dbFileVers[] is updated to match the new value stored in
-** the database file.
-**
-** If everything is successful, SQLITE_OK is returned. If an IO error 
-** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot
-** be obtained, SQLITE_BUSY is returned.
-*/
-static int pager_write_pagelist(Pager *pPager, PgHdr *pList){
-  int rc = SQLITE_OK;                  /* Return code */
-
-  /* This function is only called for rollback pagers in WRITER_DBMOD state. */
-  assert( !pagerUseWal(pPager) );
-  assert( pPager->eState==PAGER_WRITER_DBMOD );
-  assert( pPager->eLock==EXCLUSIVE_LOCK );
-
-  /* If the file is a temp-file has not yet been opened, open it now. It
-  ** is not possible for rc to be other than SQLITE_OK if this branch
-  ** is taken, as pager_wait_on_lock() is a no-op for temp-files.
-  */
-  if( !isOpen(pPager->fd) ){
-    assert( pPager->tempFile && rc==SQLITE_OK );
-    rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags);
-  }
-
-  /* Before the first write, give the VFS a hint of what the final
-  ** file size will be.
-  */
-  assert( rc!=SQLITE_OK || isOpen(pPager->fd) );
-  if( rc==SQLITE_OK 
-   && pPager->dbHintSize<pPager->dbSize
-   && (pList->pDirty || pList->pgno>pPager->dbHintSize)
-  ){
-    sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize;
-    sqlite3OsFileControlHint(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile);
-    pPager->dbHintSize = pPager->dbSize;
-  }
-
-  while( rc==SQLITE_OK && pList ){
-    Pgno pgno = pList->pgno;
-
-    /* If there are dirty pages in the page cache with page numbers greater
-    ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to
-    ** make the file smaller (presumably by auto-vacuum code). Do not write
-    ** any such pages to the file.
-    **
-    ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag
-    ** set (set by sqlite3PagerDontWrite()).
-    */
-    if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){
-      i64 offset = (pgno-1)*(i64)pPager->pageSize;   /* Offset to write */
-      char *pData;                                   /* Data to write */    
-
-      assert( (pList->flags&PGHDR_NEED_SYNC)==0 );
-      if( pList->pgno==1 ) pager_write_changecounter(pList);
-
-      /* Encode the database */
-      CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData);
-
-      /* Write out the page data. */
-      rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset);
-
-      /* If page 1 was just written, update Pager.dbFileVers to match
-      ** the value now stored in the database file. If writing this 
-      ** page caused the database file to grow, update dbFileSize. 
-      */
-      if( pgno==1 ){
-        memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers));
-      }
-      if( pgno>pPager->dbFileSize ){
-        pPager->dbFileSize = pgno;
-      }
-      pPager->aStat[PAGER_STAT_WRITE]++;
-
-      /* Update any backup objects copying the contents of this pager. */
-      sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData);
-
-      PAGERTRACE(("STORE %d page %d hash(%08x)\n",
-                   PAGERID(pPager), pgno, pager_pagehash(pList)));
-      IOTRACE(("PGOUT %p %d\n", pPager, pgno));
-      PAGER_INCR(sqlite3_pager_writedb_count);
-    }else{
-      PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno));
-    }
-    pager_set_pagehash(pList);
-    pList = pList->pDirty;
-  }
-
-  return rc;
-}
-
-/*
-** Ensure that the sub-journal file is open. If it is already open, this 
-** function is a no-op.
-**
-** SQLITE_OK is returned if everything goes according to plan. An 
-** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() 
-** fails.
-*/
-static int openSubJournal(Pager *pPager){
-  int rc = SQLITE_OK;
-  if( !isOpen(pPager->sjfd) ){
-    if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){
-      sqlite3MemJournalOpen(pPager->sjfd);
-    }else{
-      rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL);
-    }
-  }
-  return rc;
-}
-
-/*
-** Append a record of the current state of page pPg to the sub-journal. 
-**
-** If successful, set the bit corresponding to pPg->pgno in the bitvecs
-** for all open savepoints before returning.
-**
-** This function returns SQLITE_OK if everything is successful, an IO
-** error code if the attempt to write to the sub-journal fails, or 
-** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint
-** bitvec.
-*/
-static int subjournalPage(PgHdr *pPg){
-  int rc = SQLITE_OK;
-  Pager *pPager = pPg->pPager;
-  if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-
-    /* Open the sub-journal, if it has not already been opened */
-    assert( pPager->useJournal );
-    assert( isOpen(pPager->jfd) || pagerUseWal(pPager) );
-    assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 );
-    assert( pagerUseWal(pPager) 
-         || pageInJournal(pPager, pPg) 
-         || pPg->pgno>pPager->dbOrigSize 
-    );
-    rc = openSubJournal(pPager);
-
-    /* If the sub-journal was opened successfully (or was already open),
-    ** write the journal record into the file.  */
-    if( rc==SQLITE_OK ){
-      void *pData = pPg->pData;
-      i64 offset = (i64)pPager->nSubRec*(4+pPager->pageSize);
-      char *pData2;
-  
-      CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-      PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno));
-      rc = write32bits(pPager->sjfd, offset, pPg->pgno);
-      if( rc==SQLITE_OK ){
-        rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4);
-      }
-    }
-  }
-  if( rc==SQLITE_OK ){
-    pPager->nSubRec++;
-    assert( pPager->nSavepoint>0 );
-    rc = addToSavepointBitvecs(pPager, pPg->pgno);
-  }
-  return rc;
-}
-static int subjournalPageIfRequired(PgHdr *pPg){
-  if( subjRequiresPage(pPg) ){
-    return subjournalPage(pPg);
-  }else{
-    return SQLITE_OK;
-  }
-}
-
-/*
-** This function is called by the pcache layer when it has reached some
-** soft memory limit. The first argument is a pointer to a Pager object
-** (cast as a void*). The pager is always 'purgeable' (not an in-memory
-** database). The second argument is a reference to a page that is 
-** currently dirty but has no outstanding references. The page
-** is always associated with the Pager object passed as the first 
-** argument.
-**
-** The job of this function is to make pPg clean by writing its contents
-** out to the database file, if possible. This may involve syncing the
-** journal file. 
-**
-** If successful, sqlite3PcacheMakeClean() is called on the page and
-** SQLITE_OK returned. If an IO error occurs while trying to make the
-** page clean, the IO error code is returned. If the page cannot be
-** made clean for some other reason, but no error occurs, then SQLITE_OK
-** is returned by sqlite3PcacheMakeClean() is not called.
-*/
-static int pagerStress(void *p, PgHdr *pPg){
-  Pager *pPager = (Pager *)p;
-  int rc = SQLITE_OK;
-
-  assert( pPg->pPager==pPager );
-  assert( pPg->flags&PGHDR_DIRTY );
-
-  /* The doNotSpill NOSYNC bit is set during times when doing a sync of
-  ** journal (and adding a new header) is not allowed.  This occurs
-  ** during calls to sqlite3PagerWrite() while trying to journal multiple
-  ** pages belonging to the same sector.
-  **
-  ** The doNotSpill ROLLBACK and OFF bits inhibits all cache spilling
-  ** regardless of whether or not a sync is required.  This is set during
-  ** a rollback or by user request, respectively.
-  **
-  ** Spilling is also prohibited when in an error state since that could
-  ** lead to database corruption.   In the current implementation it 
-  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==3
-  ** while in the error state, hence it is impossible for this routine to
-  ** be called in the error state.  Nevertheless, we include a NEVER()
-  ** test for the error state as a safeguard against future changes.
-  */
-  if( NEVER(pPager->errCode) ) return SQLITE_OK;
-  testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
-  testcase( pPager->doNotSpill & SPILLFLAG_OFF );
-  testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
-  if( pPager->doNotSpill
-   && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
-      || (pPg->flags & PGHDR_NEED_SYNC)!=0)
-  ){
-    return SQLITE_OK;
-  }
-
-  pPg->pDirty = 0;
-  if( pagerUseWal(pPager) ){
-    /* Write a single frame for this page to the log. */
-    rc = subjournalPageIfRequired(pPg); 
-    if( rc==SQLITE_OK ){
-      rc = pagerWalFrames(pPager, pPg, 0, 0);
-    }
-  }else{
-  
-    /* Sync the journal file if required. */
-    if( pPg->flags&PGHDR_NEED_SYNC 
-     || pPager->eState==PAGER_WRITER_CACHEMOD
-    ){
-      rc = syncJournal(pPager, 1);
-    }
-  
-    /* Write the contents of the page out to the database file. */
-    if( rc==SQLITE_OK ){
-      assert( (pPg->flags&PGHDR_NEED_SYNC)==0 );
-      rc = pager_write_pagelist(pPager, pPg);
-    }
-  }
-
-  /* Mark the page as clean. */
-  if( rc==SQLITE_OK ){
-    PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno));
-    sqlite3PcacheMakeClean(pPg);
-  }
-
-  return pager_error(pPager, rc); 
-}
-
-
-/*
-** Allocate and initialize a new Pager object and put a pointer to it
-** in *ppPager. The pager should eventually be freed by passing it
-** to sqlite3PagerClose().
-**
-** The zFilename argument is the path to the database file to open.
-** If zFilename is NULL then a randomly-named temporary file is created
-** and used as the file to be cached. Temporary files are be deleted
-** automatically when they are closed. If zFilename is ":memory:" then 
-** all information is held in cache. It is never written to disk. 
-** This can be used to implement an in-memory database.
-**
-** The nExtra parameter specifies the number of bytes of space allocated
-** along with each page reference. This space is available to the user
-** via the sqlite3PagerGetExtra() API.
-**
-** The flags argument is used to specify properties that affect the
-** operation of the pager. It should be passed some bitwise combination
-** of the PAGER_* flags.
-**
-** The vfsFlags parameter is a bitmask to pass to the flags parameter
-** of the xOpen() method of the supplied VFS when opening files. 
-**
-** If the pager object is allocated and the specified file opened 
-** successfully, SQLITE_OK is returned and *ppPager set to point to
-** the new pager object. If an error occurs, *ppPager is set to NULL
-** and error code returned. This function may return SQLITE_NOMEM
-** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or 
-** various SQLITE_IO_XXX errors.
-*/
-SQLITE_PRIVATE int sqlite3PagerOpen(
-  sqlite3_vfs *pVfs,       /* The virtual file system to use */
-  Pager **ppPager,         /* OUT: Return the Pager structure here */
-  const char *zFilename,   /* Name of the database file to open */
-  int nExtra,              /* Extra bytes append to each in-memory page */
-  int flags,               /* flags controlling this file */
-  int vfsFlags,            /* flags passed through to sqlite3_vfs.xOpen() */
-  void (*xReinit)(DbPage*) /* Function to reinitialize pages */
-){
-  u8 *pPtr;
-  Pager *pPager = 0;       /* Pager object to allocate and return */
-  int rc = SQLITE_OK;      /* Return code */
-  int tempFile = 0;        /* True for temp files (incl. in-memory files) */
-  int memDb = 0;           /* True if this is an in-memory file */
-  int readOnly = 0;        /* True if this is a read-only file */
-  int journalFileSize;     /* Bytes to allocate for each journal fd */
-  char *zPathname = 0;     /* Full path to database file */
-  int nPathname = 0;       /* Number of bytes in zPathname */
-  int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */
-  int pcacheSize = sqlite3PcacheSize();       /* Bytes to allocate for PCache */
-  u32 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE;  /* Default page size */
-  const char *zUri = 0;    /* URI args to copy */
-  int nUri = 0;            /* Number of bytes of URI args at *zUri */
-
-  /* Figure out how much space is required for each journal file-handle
-  ** (there are two of them, the main journal and the sub-journal). This
-  ** is the maximum space required for an in-memory journal file handle 
-  ** and a regular journal file-handle. Note that a "regular journal-handle"
-  ** may be a wrapper capable of caching the first portion of the journal
-  ** file in memory to implement the atomic-write optimization (see 
-  ** source file journal.c).
-  */
-  if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){
-    journalFileSize = ROUND8(sqlite3JournalSize(pVfs));
-  }else{
-    journalFileSize = ROUND8(sqlite3MemJournalSize());
-  }
-
-  /* Set the output variable to NULL in case an error occurs. */
-  *ppPager = 0;
-
-  /* Compute and store the full pathname in an allocated buffer pointed
-  ** to by zPathname, length nPathname. Or, if this is a temporary file,
-  ** leave both nPathname and zPathname set to 0.
-  */
-  if( zFilename && zFilename[0] ){
-    const char *z;
-    nPathname = pVfs->mxPathname+1;
-    zPathname = sqlite3DbMallocRaw(0, nPathname*2);
-    if( zPathname==0 ){
-      return SQLITE_NOMEM;
-    }
-    zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */
-    rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname);
-    nPathname = sqlite3Strlen30(zPathname);
-    z = zUri = &zFilename[sqlite3Strlen30(zFilename)+1];
-    while( *z ){
-      z += sqlite3Strlen30(z)+1;
-      z += sqlite3Strlen30(z)+1;
-    }
-    nUri = (int)(&z[1] - zUri);
-    assert( nUri>=0 );
-    if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){
-      /* This branch is taken when the journal path required by
-      ** the database being opened will be more than pVfs->mxPathname
-      ** bytes in length. This means the database cannot be opened,
-      ** as it will not be possible to open the journal file or even
-      ** check for a hot-journal before reading.
-      */
-      rc = SQLITE_CANTOPEN_BKPT;
-    }
-    if( rc!=SQLITE_OK ){
-      sqlite3DbFree(0, zPathname);
-      return rc;
-    }
-  }
-
-  /* Allocate memory for the Pager structure, PCache object, the
-  ** three file descriptors, the database file name and the journal 
-  ** file name. The layout in memory is as follows:
-  **
-  **     Pager object                    (sizeof(Pager) bytes)
-  **     PCache object                   (sqlite3PcacheSize() bytes)
-  **     Database file handle            (pVfs->szOsFile bytes)
-  **     Sub-journal file handle         (journalFileSize bytes)
-  **     Main journal file handle        (journalFileSize bytes)
-  **     Database file name              (nPathname+1 bytes)
-  **     Journal file name               (nPathname+8+1 bytes)
-  */
-  pPtr = (u8 *)sqlite3MallocZero(
-    ROUND8(sizeof(*pPager)) +      /* Pager structure */
-    ROUND8(pcacheSize) +           /* PCache object */
-    ROUND8(pVfs->szOsFile) +       /* The main db file */
-    journalFileSize * 2 +          /* The two journal files */ 
-    nPathname + 1 + nUri +         /* zFilename */
-    nPathname + 8 + 2              /* zJournal */
-#ifndef SQLITE_OMIT_WAL
-    + nPathname + 4 + 2            /* zWal */
-#endif
-  );
-  assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) );
-  if( !pPtr ){
-    sqlite3DbFree(0, zPathname);
-    return SQLITE_NOMEM;
-  }
-  pPager =              (Pager*)(pPtr);
-  pPager->pPCache =    (PCache*)(pPtr += ROUND8(sizeof(*pPager)));
-  pPager->fd =   (sqlite3_file*)(pPtr += ROUND8(pcacheSize));
-  pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile));
-  pPager->jfd =  (sqlite3_file*)(pPtr += journalFileSize);
-  pPager->zFilename =    (char*)(pPtr += journalFileSize);
-  assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) );
-
-  /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */
-  if( zPathname ){
-    assert( nPathname>0 );
-    pPager->zJournal =   (char*)(pPtr += nPathname + 1 + nUri);
-    memcpy(pPager->zFilename, zPathname, nPathname);
-    if( nUri ) memcpy(&pPager->zFilename[nPathname+1], zUri, nUri);
-    memcpy(pPager->zJournal, zPathname, nPathname);
-    memcpy(&pPager->zJournal[nPathname], "-journal\000", 8+2);
-#ifndef SQLITE_OMIT_WAL
-    pPager->zWal = &pPager->zJournal[nPathname+8+1];
-    memcpy(pPager->zWal, zPathname, nPathname);
-    memcpy(&pPager->zWal[nPathname], "-wal\000", 4+1);
-#endif
-    sqlite3DbFree(0, zPathname);
-  }
-  pPager->pVfs = pVfs;
-  pPager->vfsFlags = vfsFlags;
-
-  /* Open the pager file.
-  */
-  if( zFilename && zFilename[0] ){
-    int fout = 0;                    /* VFS flags returned by xOpen() */
-    rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout);
-    assert( !memDb );
-    readOnly = (fout&SQLITE_OPEN_READONLY);
-
-    /* If the file was successfully opened for read/write access,
-    ** choose a default page size in case we have to create the
-    ** database file. The default page size is the maximum of:
-    **
-    **    + SQLITE_DEFAULT_PAGE_SIZE,
-    **    + The value returned by sqlite3OsSectorSize()
-    **    + The largest page size that can be written atomically.
-    */
-    if( rc==SQLITE_OK ){
-      int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
-      if( !readOnly ){
-        setSectorSize(pPager);
-        assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE);
-        if( szPageDflt<pPager->sectorSize ){
-          if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){
-            szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE;
-          }else{
-            szPageDflt = (u32)pPager->sectorSize;
-          }
-        }
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-        {
-          int ii;
-          assert(SQLITE_IOCAP_ATOMIC512==(512>>8));
-          assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8));
-          assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536);
-          for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){
-            if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){
-              szPageDflt = ii;
-            }
-          }
-        }
-#endif
-      }
-      pPager->noLock = 0;
-      if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0 ){
-          vfsFlags |= SQLITE_OPEN_READONLY;
-          goto act_like_temp_file;
-      }
-    }
-  }else{
-    /* If a temporary file is requested, it is not opened immediately.
-    ** In this case we accept the default page size and delay actually
-    ** opening the file until the first call to OsWrite().
-    **
-    ** This branch is also run for an in-memory database. An in-memory
-    ** database is the same as a temp-file that is never written out to
-    ** disk and uses an in-memory rollback journal.
-    **
-    ** This branch also runs for files marked as immutable.
-    */ 
-act_like_temp_file:
-    tempFile = 1;
-    pPager->eState = PAGER_READER;     /* Pretend we already have a lock */
-    pPager->eLock = EXCLUSIVE_LOCK;    /* Pretend we are in EXCLUSIVE mode */
-    pPager->noLock = 1;                /* Do no locking */
-    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
-  }
-
-  /* The following call to PagerSetPagesize() serves to set the value of 
-  ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer.
-  */
-  if( rc==SQLITE_OK ){
-    assert( pPager->memDb==0 );
-    rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1);
-    testcase( rc!=SQLITE_OK );
-  }
-
-  /* Initialize the PCache object. */
-  if( rc==SQLITE_OK ){
-    assert( nExtra<1000 );
-    nExtra = ROUND8(nExtra);
-    rc = sqlite3PcacheOpen(szPageDflt, nExtra, !memDb,
-                       !memDb?pagerStress:0, (void *)pPager, pPager->pPCache);
-  }
-
-  /* If an error occurred above, free the  Pager structure and close the file.
-  */
-  if( rc!=SQLITE_OK ){
-    sqlite3OsClose(pPager->fd);
-    sqlite3PageFree(pPager->pTmpSpace);
-    sqlite3_free(pPager);
-    return rc;
-  }
-
-  PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename));
-  IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename))
-
-  pPager->useJournal = (u8)useJournal;
-  /* pPager->stmtOpen = 0; */
-  /* pPager->stmtInUse = 0; */
-  /* pPager->nRef = 0; */
-  /* pPager->stmtSize = 0; */
-  /* pPager->stmtJSize = 0; */
-  /* pPager->nPage = 0; */
-  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
-  /* pPager->state = PAGER_UNLOCK; */
-  /* pPager->errMask = 0; */
-  pPager->tempFile = (u8)tempFile;
-  assert( tempFile==PAGER_LOCKINGMODE_NORMAL 
-          || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
-  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
-  pPager->exclusiveMode = (u8)tempFile; 
-  pPager->changeCountDone = pPager->tempFile;
-  pPager->memDb = (u8)memDb;
-  pPager->readOnly = (u8)readOnly;
-  assert( useJournal || pPager->tempFile );
-  pPager->noSync = pPager->tempFile;
-  if( pPager->noSync ){
-    assert( pPager->fullSync==0 );
-    assert( pPager->syncFlags==0 );
-    assert( pPager->walSyncFlags==0 );
-    assert( pPager->ckptSyncFlags==0 );
-  }else{
-    pPager->fullSync = 1;
-    pPager->syncFlags = SQLITE_SYNC_NORMAL;
-    pPager->walSyncFlags = SQLITE_SYNC_NORMAL | WAL_SYNC_TRANSACTIONS;
-    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
-  }
-  /* pPager->pFirst = 0; */
-  /* pPager->pFirstSynced = 0; */
-  /* pPager->pLast = 0; */
-  pPager->nExtra = (u16)nExtra;
-  pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT;
-  assert( isOpen(pPager->fd) || tempFile );
-  setSectorSize(pPager);
-  if( !useJournal ){
-    pPager->journalMode = PAGER_JOURNALMODE_OFF;
-  }else if( memDb ){
-    pPager->journalMode = PAGER_JOURNALMODE_MEMORY;
-  }
-  /* pPager->xBusyHandler = 0; */
-  /* pPager->pBusyHandlerArg = 0; */
-  pPager->xReiniter = xReinit;
-  /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */
-  /* pPager->szMmap = SQLITE_DEFAULT_MMAP_SIZE // will be set by btree.c */
-
-  *ppPager = pPager;
-  return SQLITE_OK;
-}
-
-
-/* Verify that the database file has not be deleted or renamed out from
-** under the pager.  Return SQLITE_OK if the database is still were it ought
-** to be on disk.  Return non-zero (SQLITE_READONLY_DBMOVED or some other error
-** code from sqlite3OsAccess()) if the database has gone missing.
-*/
-static int databaseIsUnmoved(Pager *pPager){
-  int bHasMoved = 0;
-  int rc;
-
-  if( pPager->tempFile ) return SQLITE_OK;
-  if( pPager->dbSize==0 ) return SQLITE_OK;
-  assert( pPager->zFilename && pPager->zFilename[0] );
-  rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_HAS_MOVED, &bHasMoved);
-  if( rc==SQLITE_NOTFOUND ){
-    /* If the HAS_MOVED file-control is unimplemented, assume that the file
-    ** has not been moved.  That is the historical behavior of SQLite: prior to
-    ** version 3.8.3, it never checked */
-    rc = SQLITE_OK;
-  }else if( rc==SQLITE_OK && bHasMoved ){
-    rc = SQLITE_READONLY_DBMOVED;
-  }
-  return rc;
-}
-
-
-/*
-** This function is called after transitioning from PAGER_UNLOCK to
-** PAGER_SHARED state. It tests if there is a hot journal present in
-** the file-system for the given pager. A hot journal is one that 
-** needs to be played back. According to this function, a hot-journal
-** file exists if the following criteria are met:
-**
-**   * The journal file exists in the file system, and
-**   * No process holds a RESERVED or greater lock on the database file, and
-**   * The database file itself is greater than 0 bytes in size, and
-**   * The first byte of the journal file exists and is not 0x00.
-**
-** If the current size of the database file is 0 but a journal file
-** exists, that is probably an old journal left over from a prior
-** database with the same name. In this case the journal file is
-** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK
-** is returned.
-**
-** This routine does not check if there is a master journal filename
-** at the end of the file. If there is, and that master journal file
-** does not exist, then the journal file is not really hot. In this
-** case this routine will return a false-positive. The pager_playback()
-** routine will discover that the journal file is not really hot and 
-** will not roll it back. 
-**
-** If a hot-journal file is found to exist, *pExists is set to 1 and 
-** SQLITE_OK returned. If no hot-journal file is present, *pExists is
-** set to 0 and SQLITE_OK returned. If an IO error occurs while trying
-** to determine whether or not a hot-journal file exists, the IO error
-** code is returned and the value of *pExists is undefined.
-*/
-static int hasHotJournal(Pager *pPager, int *pExists){
-  sqlite3_vfs * const pVfs = pPager->pVfs;
-  int rc = SQLITE_OK;           /* Return code */
-  int exists = 1;               /* True if a journal file is present */
-  int jrnlOpen = !!isOpen(pPager->jfd);
-
-  assert( pPager->useJournal );
-  assert( isOpen(pPager->fd) );
-  assert( pPager->eState==PAGER_OPEN );
-
-  assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) &
-    SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
-  ));
-
-  *pExists = 0;
-  if( !jrnlOpen ){
-    rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists);
-  }
-  if( rc==SQLITE_OK && exists ){
-    int locked = 0;             /* True if some process holds a RESERVED lock */
-
-    /* Race condition here:  Another process might have been holding the
-    ** the RESERVED lock and have a journal open at the sqlite3OsAccess() 
-    ** call above, but then delete the journal and drop the lock before
-    ** we get to the following sqlite3OsCheckReservedLock() call.  If that
-    ** is the case, this routine might think there is a hot journal when
-    ** in fact there is none.  This results in a false-positive which will
-    ** be dealt with by the playback routine.  Ticket #3883.
-    */
-    rc = sqlite3OsCheckReservedLock(pPager->fd, &locked);
-    if( rc==SQLITE_OK && !locked ){
-      Pgno nPage;                 /* Number of pages in database file */
-
-      rc = pagerPagecount(pPager, &nPage);
-      if( rc==SQLITE_OK ){
-        /* If the database is zero pages in size, that means that either (1) the
-        ** journal is a remnant from a prior database with the same name where
-        ** the database file but not the journal was deleted, or (2) the initial
-        ** transaction that populates a new database is being rolled back.
-        ** In either case, the journal file can be deleted.  However, take care
-        ** not to delete the journal file if it is already open due to
-        ** journal_mode=PERSIST.
-        */
-        if( nPage==0 && !jrnlOpen ){
-          if( pagerLockDb(pPager, RESERVED_LOCK)==SQLITE_OK ){
-            sqlite3OsDelete(pVfs, pPager->zJournal, 0);
-            if( !pPager->exclusiveMode ) pagerUnlockDb(pPager, SHARED_LOCK);
-          }
-        }else{
-          /* The journal file exists and no other connection has a reserved
-          ** or greater lock on the database file. Now check that there is
-          ** at least one non-zero bytes at the start of the journal file.
-          ** If there is, then we consider this journal to be hot. If not, 
-          ** it can be ignored.
-          */
-          if( !jrnlOpen ){
-            int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL;
-            rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f);
-          }
-          if( rc==SQLITE_OK ){
-            u8 first = 0;
-            rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0);
-            if( rc==SQLITE_IOERR_SHORT_READ ){
-              rc = SQLITE_OK;
-            }
-            if( !jrnlOpen ){
-              sqlite3OsClose(pPager->jfd);
-            }
-            *pExists = (first!=0);
-          }else if( rc==SQLITE_CANTOPEN ){
-            /* If we cannot open the rollback journal file in order to see if
-            ** it has a zero header, that might be due to an I/O error, or
-            ** it might be due to the race condition described above and in
-            ** ticket #3883.  Either way, assume that the journal is hot.
-            ** This might be a false positive.  But if it is, then the
-            ** automatic journal playback and recovery mechanism will deal
-            ** with it under an EXCLUSIVE lock where we do not need to
-            ** worry so much with race conditions.
-            */
-            *pExists = 1;
-            rc = SQLITE_OK;
-          }
-        }
-      }
-    }
-  }
-
-  return rc;
-}
-
-/*
-** This function is called to obtain a shared lock on the database file.
-** It is illegal to call sqlite3PagerAcquire() until after this function
-** has been successfully called. If a shared-lock is already held when
-** this function is called, it is a no-op.
-**
-** The following operations are also performed by this function.
-**
-**   1) If the pager is currently in PAGER_OPEN state (no lock held
-**      on the database file), then an attempt is made to obtain a
-**      SHARED lock on the database file. Immediately after obtaining
-**      the SHARED lock, the file-system is checked for a hot-journal,
-**      which is played back if present. Following any hot-journal 
-**      rollback, the contents of the cache are validated by checking
-**      the 'change-counter' field of the database file header and
-**      discarded if they are found to be invalid.
-**
-**   2) If the pager is running in exclusive-mode, and there are currently
-**      no outstanding references to any pages, and is in the error state,
-**      then an attempt is made to clear the error state by discarding
-**      the contents of the page cache and rolling back any open journal
-**      file.
-**
-** If everything is successful, SQLITE_OK is returned. If an IO error 
-** occurs while locking the database, checking for a hot-journal file or 
-** rolling back a journal file, the IO error code is returned.
-*/
-SQLITE_PRIVATE int sqlite3PagerSharedLock(Pager *pPager){
-  int rc = SQLITE_OK;                /* Return code */
-
-  /* This routine is only called from b-tree and only when there are no
-  ** outstanding pages. This implies that the pager state should either
-  ** be OPEN or READER. READER is only possible if the pager is or was in 
-  ** exclusive access mode.
-  */
-  assert( sqlite3PcacheRefCount(pPager->pPCache)==0 );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState==PAGER_OPEN || pPager->eState==PAGER_READER );
-
-  if( !pagerUseWal(pPager) && pPager->eState==PAGER_OPEN ){
-    int bHotJournal = 1;          /* True if there exists a hot journal-file */
-
-    rc = pager_wait_on_lock(pPager, SHARED_LOCK);
-    if( rc!=SQLITE_OK ){
-      assert( pPager->eLock==NO_LOCK || pPager->eLock==UNKNOWN_LOCK );
-      goto failed;
-    }
-
-    /* If a journal file exists, and there is no RESERVED lock on the
-    ** database file, then it either needs to be played back or deleted.
-    */
-    if( pPager->eLock<=SHARED_LOCK ){
-      rc = hasHotJournal(pPager, &bHotJournal);
-    }
-    if( rc!=SQLITE_OK ){
-      goto failed;
-    }
-    if( bHotJournal ){
-      if( pPager->readOnly ){
-        rc = SQLITE_READONLY_ROLLBACK;
-        goto failed;
-      }
-
-      /* Get an EXCLUSIVE lock on the database file. At this point it is
-      ** important that a RESERVED lock is not obtained on the way to the
-      ** EXCLUSIVE lock. If it were, another process might open the
-      ** database file, detect the RESERVED lock, and conclude that the
-      ** database is safe to read while this process is still rolling the 
-      ** hot-journal back.
-      ** 
-      ** Because the intermediate RESERVED lock is not requested, any
-      ** other process attempting to access the database file will get to 
-      ** this point in the code and fail to obtain its own EXCLUSIVE lock 
-      ** on the database file.
-      **
-      ** Unless the pager is in locking_mode=exclusive mode, the lock is
-      ** downgraded to SHARED_LOCK before this function returns.
-      */
-      rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-      if( rc!=SQLITE_OK ){
-        goto failed;
-      }
- 
-      /* If it is not already open and the file exists on disk, open the 
-      ** journal for read/write access. Write access is required because 
-      ** in exclusive-access mode the file descriptor will be kept open 
-      ** and possibly used for a transaction later on. Also, write-access 
-      ** is usually required to finalize the journal in journal_mode=persist 
-      ** mode (and also for journal_mode=truncate on some systems).
-      **
-      ** If the journal does not exist, it usually means that some 
-      ** other connection managed to get in and roll it back before 
-      ** this connection obtained the exclusive lock above. Or, it 
-      ** may mean that the pager was in the error-state when this
-      ** function was called and the journal file does not exist.
-      */
-      if( !isOpen(pPager->jfd) ){
-        sqlite3_vfs * const pVfs = pPager->pVfs;
-        int bExists;              /* True if journal file exists */
-        rc = sqlite3OsAccess(
-            pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &bExists);
-        if( rc==SQLITE_OK && bExists ){
-          int fout = 0;
-          int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL;
-          assert( !pPager->tempFile );
-          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout);
-          assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
-          if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){
-            rc = SQLITE_CANTOPEN_BKPT;
-            sqlite3OsClose(pPager->jfd);
-          }
-        }
-      }
- 
-      /* Playback and delete the journal.  Drop the database write
-      ** lock and reacquire the read lock. Purge the cache before
-      ** playing back the hot-journal so that we don't end up with
-      ** an inconsistent cache.  Sync the hot journal before playing
-      ** it back since the process that crashed and left the hot journal
-      ** probably did not sync it and we are required to always sync
-      ** the journal before playing it back.
-      */
-      if( isOpen(pPager->jfd) ){
-        assert( rc==SQLITE_OK );
-        rc = pagerSyncHotJournal(pPager);
-        if( rc==SQLITE_OK ){
-          rc = pager_playback(pPager, 1);
-          pPager->eState = PAGER_OPEN;
-        }
-      }else if( !pPager->exclusiveMode ){
-        pagerUnlockDb(pPager, SHARED_LOCK);
-      }
-
-      if( rc!=SQLITE_OK ){
-        /* This branch is taken if an error occurs while trying to open
-        ** or roll back a hot-journal while holding an EXCLUSIVE lock. The
-        ** pager_unlock() routine will be called before returning to unlock
-        ** the file. If the unlock attempt fails, then Pager.eLock must be
-        ** set to UNKNOWN_LOCK (see the comment above the #define for 
-        ** UNKNOWN_LOCK above for an explanation). 
-        **
-        ** In order to get pager_unlock() to do this, set Pager.eState to
-        ** PAGER_ERROR now. This is not actually counted as a transition
-        ** to ERROR state in the state diagram at the top of this file,
-        ** since we know that the same call to pager_unlock() will very
-        ** shortly transition the pager object to the OPEN state. Calling
-        ** assert_pager_state() would fail now, as it should not be possible
-        ** to be in ERROR state when there are zero outstanding page 
-        ** references.
-        */
-        pager_error(pPager, rc);
-        goto failed;
-      }
-
-      assert( pPager->eState==PAGER_OPEN );
-      assert( (pPager->eLock==SHARED_LOCK)
-           || (pPager->exclusiveMode && pPager->eLock>SHARED_LOCK)
-      );
-    }
-
-    if( !pPager->tempFile && pPager->hasHeldSharedLock ){
-      /* The shared-lock has just been acquired then check to
-      ** see if the database has been modified.  If the database has changed,
-      ** flush the cache.  The hasHeldSharedLock flag prevents this from
-      ** occurring on the very first access to a file, in order to save a
-      ** single unnecessary sqlite3OsRead() call at the start-up.
-      **
-      ** Database changes are detected by looking at 15 bytes beginning
-      ** at offset 24 into the file.  The first 4 of these 16 bytes are
-      ** a 32-bit counter that is incremented with each change.  The
-      ** other bytes change randomly with each file change when
-      ** a codec is in use.
-      ** 
-      ** There is a vanishingly small chance that a change will not be 
-      ** detected.  The chance of an undetected change is so small that
-      ** it can be neglected.
-      */
-      Pgno nPage = 0;
-      char dbFileVers[sizeof(pPager->dbFileVers)];
-
-      rc = pagerPagecount(pPager, &nPage);
-      if( rc ) goto failed;
-
-      if( nPage>0 ){
-        IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers)));
-        rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24);
-        if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){
-          goto failed;
-        }
-      }else{
-        memset(dbFileVers, 0, sizeof(dbFileVers));
-      }
-
-      if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){
-        pager_reset(pPager);
-
-        /* Unmap the database file. It is possible that external processes
-        ** may have truncated the database file and then extended it back
-        ** to its original size while this process was not holding a lock.
-        ** In this case there may exist a Pager.pMap mapping that appears
-        ** to be the right size but is not actually valid. Avoid this
-        ** possibility by unmapping the db here. */
-        if( USEFETCH(pPager) ){
-          sqlite3OsUnfetch(pPager->fd, 0, 0);
-        }
-      }
-    }
-
-    /* If there is a WAL file in the file-system, open this database in WAL
-    ** mode. Otherwise, the following function call is a no-op.
-    */
-    rc = pagerOpenWalIfPresent(pPager);
-#ifndef SQLITE_OMIT_WAL
-    assert( pPager->pWal==0 || rc==SQLITE_OK );
-#endif
-  }
-
-  if( pagerUseWal(pPager) ){
-    assert( rc==SQLITE_OK );
-    rc = pagerBeginReadTransaction(pPager);
-  }
-
-  if( pPager->eState==PAGER_OPEN && rc==SQLITE_OK ){
-    rc = pagerPagecount(pPager, &pPager->dbSize);
-  }
-
- failed:
-  if( rc!=SQLITE_OK ){
-    pager_unlock(pPager);
-    assert( pPager->eState==PAGER_OPEN );
-  }else{
-    pPager->eState = PAGER_READER;
-    pPager->hasHeldSharedLock = 1;
-  }
-  return rc;
-}
-
-/*
-** If the reference count has reached zero, rollback any active
-** transaction and unlock the pager.
-**
-** Except, in locking_mode=EXCLUSIVE when there is nothing to in
-** the rollback journal, the unlock is not performed and there is
-** nothing to rollback, so this routine is a no-op.
-*/ 
-static void pagerUnlockIfUnused(Pager *pPager){
-  if( pPager->nMmapOut==0 && (sqlite3PcacheRefCount(pPager->pPCache)==0) ){
-    pagerUnlockAndRollback(pPager);
-  }
-}
-
-/*
-** Acquire a reference to page number pgno in pager pPager (a page
-** reference has type DbPage*). If the requested reference is 
-** successfully obtained, it is copied to *ppPage and SQLITE_OK returned.
-**
-** If the requested page is already in the cache, it is returned. 
-** Otherwise, a new page object is allocated and populated with data
-** read from the database file. In some cases, the pcache module may
-** choose not to allocate a new page object and may reuse an existing
-** object with no outstanding references.
-**
-** The extra data appended to a page is always initialized to zeros the 
-** first time a page is loaded into memory. If the page requested is 
-** already in the cache when this function is called, then the extra
-** data is left as it was when the page object was last used.
-**
-** If the database image is smaller than the requested page or if a 
-** non-zero value is passed as the noContent parameter and the 
-** requested page is not already stored in the cache, then no 
-** actual disk read occurs. In this case the memory image of the 
-** page is initialized to all zeros. 
-**
-** If noContent is true, it means that we do not care about the contents
-** of the page. This occurs in two scenarios:
-**
-**   a) When reading a free-list leaf page from the database, and
-**
-**   b) When a savepoint is being rolled back and we need to load
-**      a new page into the cache to be filled with the data read
-**      from the savepoint journal.
-**
-** If noContent is true, then the data returned is zeroed instead of
-** being read from the database. Additionally, the bits corresponding
-** to pgno in Pager.pInJournal (bitvec of pages already written to the
-** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open
-** savepoints are set. This means if the page is made writable at any
-** point in the future, using a call to sqlite3PagerWrite(), its contents
-** will not be journaled. This saves IO.
-**
-** The acquisition might fail for several reasons.  In all cases,
-** an appropriate error code is returned and *ppPage is set to NULL.
-**
-** See also sqlite3PagerLookup().  Both this routine and Lookup() attempt
-** to find a page in the in-memory cache first.  If the page is not already
-** in memory, this routine goes to disk to read it in whereas Lookup()
-** just returns 0.  This routine acquires a read-lock the first time it
-** has to go to disk, and could also playback an old journal if necessary.
-** Since Lookup() never goes to disk, it never has to deal with locks
-** or journal files.
-*/
-SQLITE_PRIVATE int sqlite3PagerAcquire(
-  Pager *pPager,      /* The pager open on the database file */
-  Pgno pgno,          /* Page number to fetch */
-  DbPage **ppPage,    /* Write a pointer to the page here */
-  int flags           /* PAGER_GET_XXX flags */
-){
-  int rc = SQLITE_OK;
-  PgHdr *pPg = 0;
-  u32 iFrame = 0;                 /* Frame to read from WAL file */
-  const int noContent = (flags & PAGER_GET_NOCONTENT);
-
-  /* It is acceptable to use a read-only (mmap) page for any page except
-  ** page 1 if there is no write-transaction open or the ACQUIRE_READONLY
-  ** flag was specified by the caller. And so long as the db is not a 
-  ** temporary or in-memory database.  */
-  const int bMmapOk = (pgno>1 && USEFETCH(pPager)
-   && (pPager->eState==PAGER_READER || (flags & PAGER_GET_READONLY))
-#ifdef SQLITE_HAS_CODEC
-   && pPager->xCodec==0
-#endif
-  );
-
-  /* Optimization note:  Adding the "pgno<=1" term before "pgno==0" here
-  ** allows the compiler optimizer to reuse the results of the "pgno>1"
-  ** test in the previous statement, and avoid testing pgno==0 in the
-  ** common case where pgno is large. */
-  if( pgno<=1 && pgno==0 ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  assert( pPager->eState>=PAGER_READER );
-  assert( assert_pager_state(pPager) );
-  assert( noContent==0 || bMmapOk==0 );
-
-  assert( pPager->hasHeldSharedLock==1 );
-
-  /* If the pager is in the error state, return an error immediately. 
-  ** Otherwise, request the page from the PCache layer. */
-  if( pPager->errCode!=SQLITE_OK ){
-    rc = pPager->errCode;
-  }else{
-    if( bMmapOk && pagerUseWal(pPager) ){
-      rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-      if( rc!=SQLITE_OK ) goto pager_acquire_err;
-    }
-
-    if( bMmapOk && iFrame==0 ){
-      void *pData = 0;
-
-      rc = sqlite3OsFetch(pPager->fd, 
-          (i64)(pgno-1) * pPager->pageSize, pPager->pageSize, &pData
-      );
-
-      if( rc==SQLITE_OK && pData ){
-        if( pPager->eState>PAGER_READER ){
-          pPg = sqlite3PagerLookup(pPager, pgno);
-        }
-        if( pPg==0 ){
-          rc = pagerAcquireMapPage(pPager, pgno, pData, &pPg);
-        }else{
-          sqlite3OsUnfetch(pPager->fd, (i64)(pgno-1)*pPager->pageSize, pData);
-        }
-        if( pPg ){
-          assert( rc==SQLITE_OK );
-          *ppPage = pPg;
-          return SQLITE_OK;
-        }
-      }
-      if( rc!=SQLITE_OK ){
-        goto pager_acquire_err;
-      }
-    }
-
-    {
-      sqlite3_pcache_page *pBase;
-      pBase = sqlite3PcacheFetch(pPager->pPCache, pgno, 3);
-      if( pBase==0 ){
-        rc = sqlite3PcacheFetchStress(pPager->pPCache, pgno, &pBase);
-        if( rc!=SQLITE_OK ) goto pager_acquire_err;
-        if( pBase==0 ){
-          pPg = *ppPage = 0;
-          rc = SQLITE_NOMEM;
-          goto pager_acquire_err;
-        }
-      }
-      pPg = *ppPage = sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pBase);
-      assert( pPg!=0 );
-    }
-  }
-
-  if( rc!=SQLITE_OK ){
-    /* Either the call to sqlite3PcacheFetch() returned an error or the
-    ** pager was already in the error-state when this function was called.
-    ** Set pPg to 0 and jump to the exception handler.  */
-    pPg = 0;
-    goto pager_acquire_err;
-  }
-  assert( pPg==(*ppPage) );
-  assert( pPg->pgno==pgno );
-  assert( pPg->pPager==pPager || pPg->pPager==0 );
-
-  if( pPg->pPager && !noContent ){
-    /* In this case the pcache already contains an initialized copy of
-    ** the page. Return without further ado.  */
-    assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
-    pPager->aStat[PAGER_STAT_HIT]++;
-    return SQLITE_OK;
-
-  }else{
-    /* The pager cache has created a new page. Its content needs to 
-    ** be initialized.  */
-
-    pPg->pPager = pPager;
-
-    /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page
-    ** number greater than this, or the unused locking-page, is requested. */
-    if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto pager_acquire_err;
-    }
-
-    if( pPager->dbSize<pgno || noContent || !isOpen(pPager->fd) ){
-      if( pgno>pPager->mxPgno ){
-        rc = SQLITE_FULL;
-        goto pager_acquire_err;
-      }
-      if( noContent ){
-        /* Failure to set the bits in the InJournal bit-vectors is benign.
-        ** It merely means that we might do some extra work to journal a 
-        ** page that does not need to be journaled.  Nevertheless, be sure 
-        ** to test the case where a malloc error occurs while trying to set 
-        ** a bit in a bit vector.
-        */
-        if( pgno<=pPager->dbOrigSize ){
-          TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno);
-          testcase( rc==SQLITE_NOMEM );
-        }
-        TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno);
-        testcase( rc==SQLITE_NOMEM );
-      }
-      memset(pPg->pData, 0, pPager->pageSize);
-      IOTRACE(("ZERO %p %d\n", pPager, pgno));
-    }else{
-      if( pagerUseWal(pPager) && bMmapOk==0 ){
-        rc = sqlite3WalFindFrame(pPager->pWal, pgno, &iFrame);
-        if( rc!=SQLITE_OK ) goto pager_acquire_err;
-      }
-      assert( pPg->pPager==pPager );
-      pPager->aStat[PAGER_STAT_MISS]++;
-      rc = readDbPage(pPg, iFrame);
-      if( rc!=SQLITE_OK ){
-        goto pager_acquire_err;
-      }
-    }
-    pager_set_pagehash(pPg);
-  }
-
-  return SQLITE_OK;
-
-pager_acquire_err:
-  assert( rc!=SQLITE_OK );
-  if( pPg ){
-    sqlite3PcacheDrop(pPg);
-  }
-  pagerUnlockIfUnused(pPager);
-
-  *ppPage = 0;
-  return rc;
-}
-
-/*
-** Acquire a page if it is already in the in-memory cache.  Do
-** not read the page from disk.  Return a pointer to the page,
-** or 0 if the page is not in cache. 
-**
-** See also sqlite3PagerGet().  The difference between this routine
-** and sqlite3PagerGet() is that _get() will go to the disk and read
-** in the page if the page is not already in cache.  This routine
-** returns NULL if the page is not in cache or if a disk I/O error 
-** has ever happened.
-*/
-SQLITE_PRIVATE DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
-  sqlite3_pcache_page *pPage;
-  assert( pPager!=0 );
-  assert( pgno!=0 );
-  assert( pPager->pPCache!=0 );
-  pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
-  assert( pPage==0 || pPager->hasHeldSharedLock );
-  if( pPage==0 ) return 0;
-  return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
-}
-
-/*
-** Release a page reference.
-**
-** If the number of references to the page drop to zero, then the
-** page is added to the LRU list.  When all references to all pages
-** are released, a rollback occurs and the lock on the database is
-** removed.
-*/
-SQLITE_PRIVATE void sqlite3PagerUnrefNotNull(DbPage *pPg){
-  Pager *pPager;
-  assert( pPg!=0 );
-  pPager = pPg->pPager;
-  if( pPg->flags & PGHDR_MMAP ){
-    pagerReleaseMapPage(pPg);
-  }else{
-    sqlite3PcacheRelease(pPg);
-  }
-  pagerUnlockIfUnused(pPager);
-}
-SQLITE_PRIVATE void sqlite3PagerUnref(DbPage *pPg){
-  if( pPg ) sqlite3PagerUnrefNotNull(pPg);
-}
-
-/*
-** This function is called at the start of every write transaction.
-** There must already be a RESERVED or EXCLUSIVE lock on the database 
-** file when this routine is called.
-**
-** Open the journal file for pager pPager and write a journal header
-** to the start of it. If there are active savepoints, open the sub-journal
-** as well. This function is only used when the journal file is being 
-** opened to write a rollback log for a transaction. It is not used 
-** when opening a hot journal file to roll it back.
-**
-** If the journal file is already open (as it may be in exclusive mode),
-** then this function just writes a journal header to the start of the
-** already open file. 
-**
-** Whether or not the journal file is opened by this function, the
-** Pager.pInJournal bitvec structure is allocated.
-**
-** Return SQLITE_OK if everything is successful. Otherwise, return 
-** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or 
-** an IO error code if opening or writing the journal file fails.
-*/
-static int pager_open_journal(Pager *pPager){
-  int rc = SQLITE_OK;                        /* Return code */
-  sqlite3_vfs * const pVfs = pPager->pVfs;   /* Local cache of vfs pointer */
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->pInJournal==0 );
-  
-  /* If already in the error state, this function is a no-op.  But on
-  ** the other hand, this routine is never called if we are already in
-  ** an error state. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  if( !pagerUseWal(pPager) && pPager->journalMode!=PAGER_JOURNALMODE_OFF ){
-    pPager->pInJournal = sqlite3BitvecCreate(pPager->dbSize);
-    if( pPager->pInJournal==0 ){
-      return SQLITE_NOMEM;
-    }
-  
-    /* Open the journal file if it is not already open. */
-    if( !isOpen(pPager->jfd) ){
-      if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){
-        sqlite3MemJournalOpen(pPager->jfd);
-      }else{
-        const int flags =                   /* VFS flags to open journal file */
-          SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|
-          (pPager->tempFile ? 
-            (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL):
-            (SQLITE_OPEN_MAIN_JOURNAL)
-          );
-
-        /* Verify that the database still has the same name as it did when
-        ** it was originally opened. */
-        rc = databaseIsUnmoved(pPager);
-        if( rc==SQLITE_OK ){
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-          rc = sqlite3JournalOpen(
-              pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager)
-          );
-#else
-          rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0);
-#endif
-        }
-      }
-      assert( rc!=SQLITE_OK || isOpen(pPager->jfd) );
-    }
-  
-  
-    /* Write the first journal header to the journal file and open 
-    ** the sub-journal if necessary.
-    */
-    if( rc==SQLITE_OK ){
-      /* TODO: Check if all of these are really required. */
-      pPager->nRec = 0;
-      pPager->journalOff = 0;
-      pPager->setMaster = 0;
-      pPager->journalHdr = 0;
-      rc = writeJournalHdr(pPager);
-    }
-  }
-
-  if( rc!=SQLITE_OK ){
-    sqlite3BitvecDestroy(pPager->pInJournal);
-    pPager->pInJournal = 0;
-  }else{
-    assert( pPager->eState==PAGER_WRITER_LOCKED );
-    pPager->eState = PAGER_WRITER_CACHEMOD;
-  }
-
-  return rc;
-}
-
-/*
-** Begin a write-transaction on the specified pager object. If a 
-** write-transaction has already been opened, this function is a no-op.
-**
-** If the exFlag argument is false, then acquire at least a RESERVED
-** lock on the database file. If exFlag is true, then acquire at least
-** an EXCLUSIVE lock. If such a lock is already held, no locking 
-** functions need be called.
-**
-** If the subjInMemory argument is non-zero, then any sub-journal opened
-** within this transaction will be opened as an in-memory file. This
-** has no effect if the sub-journal is already opened (as it may be when
-** running in exclusive mode) or if the transaction does not require a
-** sub-journal. If the subjInMemory argument is zero, then any required
-** sub-journal is implemented in-memory if pPager is an in-memory database, 
-** or using a temporary file otherwise.
-*/
-SQLITE_PRIVATE int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){
-  int rc = SQLITE_OK;
-
-  if( pPager->errCode ) return pPager->errCode;
-  assert( pPager->eState>=PAGER_READER && pPager->eState<PAGER_ERROR );
-  pPager->subjInMemory = (u8)subjInMemory;
-
-  if( ALWAYS(pPager->eState==PAGER_READER) ){
-    assert( pPager->pInJournal==0 );
-
-    if( pagerUseWal(pPager) ){
-      /* If the pager is configured to use locking_mode=exclusive, and an
-      ** exclusive lock on the database is not already held, obtain it now.
-      */
-      if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){
-        rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        sqlite3WalExclusiveMode(pPager->pWal, 1);
-      }
-
-      /* Grab the write lock on the log file. If successful, upgrade to
-      ** PAGER_RESERVED state. Otherwise, return an error code to the caller.
-      ** The busy-handler is not invoked if another connection already
-      ** holds the write-lock. If possible, the upper layer will call it.
-      */
-      rc = sqlite3WalBeginWriteTransaction(pPager->pWal);
-    }else{
-      /* Obtain a RESERVED lock on the database file. If the exFlag parameter
-      ** is true, then immediately upgrade this to an EXCLUSIVE lock. The
-      ** busy-handler callback can be used when upgrading to the EXCLUSIVE
-      ** lock, but not when obtaining the RESERVED lock.
-      */
-      rc = pagerLockDb(pPager, RESERVED_LOCK);
-      if( rc==SQLITE_OK && exFlag ){
-        rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
-      }
-    }
-
-    if( rc==SQLITE_OK ){
-      /* Change to WRITER_LOCKED state.
-      **
-      ** WAL mode sets Pager.eState to PAGER_WRITER_LOCKED or CACHEMOD
-      ** when it has an open transaction, but never to DBMOD or FINISHED.
-      ** This is because in those states the code to roll back savepoint 
-      ** transactions may copy data from the sub-journal into the database 
-      ** file as well as into the page cache. Which would be incorrect in 
-      ** WAL mode.
-      */
-      pPager->eState = PAGER_WRITER_LOCKED;
-      pPager->dbHintSize = pPager->dbSize;
-      pPager->dbFileSize = pPager->dbSize;
-      pPager->dbOrigSize = pPager->dbSize;
-      pPager->journalOff = 0;
-    }
-
-    assert( rc==SQLITE_OK || pPager->eState==PAGER_READER );
-    assert( rc!=SQLITE_OK || pPager->eState==PAGER_WRITER_LOCKED );
-    assert( assert_pager_state(pPager) );
-  }
-
-  PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager)));
-  return rc;
-}
-
-/*
-** Write page pPg onto the end of the rollback journal.
-*/
-static SQLITE_NOINLINE int pagerAddPageToRollbackJournal(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  int rc;
-  u32 cksum;
-  char *pData2;
-  i64 iOff = pPager->journalOff;
-
-  /* We should never write to the journal file the page that
-  ** contains the database locks.  The following assert verifies
-  ** that we do not. */
-  assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) );
-
-  assert( pPager->journalHdr<=pPager->journalOff );
-  CODEC2(pPager, pPg->pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2);
-  cksum = pager_cksum(pPager, (u8*)pData2);
-
-  /* Even if an IO or diskfull error occurs while journalling the
-  ** page in the block above, set the need-sync flag for the page.
-  ** Otherwise, when the transaction is rolled back, the logic in
-  ** playback_one_page() will think that the page needs to be restored
-  ** in the database file. And if an IO error occurs while doing so,
-  ** then corruption may follow.
-  */
-  pPg->flags |= PGHDR_NEED_SYNC;
-
-  rc = write32bits(pPager->jfd, iOff, pPg->pgno);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, iOff+4);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = write32bits(pPager->jfd, iOff+pPager->pageSize+4, cksum);
-  if( rc!=SQLITE_OK ) return rc;
-
-  IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, 
-           pPager->journalOff, pPager->pageSize));
-  PAGER_INCR(sqlite3_pager_writej_count);
-  PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n",
-       PAGERID(pPager), pPg->pgno, 
-       ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg)));
-
-  pPager->journalOff += 8 + pPager->pageSize;
-  pPager->nRec++;
-  assert( pPager->pInJournal!=0 );
-  rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno);
-  testcase( rc==SQLITE_NOMEM );
-  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-  rc |= addToSavepointBitvecs(pPager, pPg->pgno);
-  assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
-  return rc;
-}
-
-/*
-** Mark a single data page as writeable. The page is written into the 
-** main journal or sub-journal as required. If the page is written into
-** one of the journals, the corresponding bit is set in the 
-** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs
-** of any open savepoints as appropriate.
-*/
-static int pager_write(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  int rc = SQLITE_OK;
-
-  /* This routine is not called unless a write-transaction has already 
-  ** been started. The journal file may or may not be open at this point.
-  ** It is never called in the ERROR state.
-  */
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-  assert( pPager->errCode==0 );
-  assert( pPager->readOnly==0 );
-  CHECK_PAGE(pPg);
-
-  /* The journal file needs to be opened. Higher level routines have already
-  ** obtained the necessary locks to begin the write-transaction, but the
-  ** rollback journal might not yet be open. Open it now if this is the case.
-  **
-  ** This is done before calling sqlite3PcacheMakeDirty() on the page. 
-  ** Otherwise, if it were done after calling sqlite3PcacheMakeDirty(), then
-  ** an error might occur and the pager would end up in WRITER_LOCKED state
-  ** with pages marked as dirty in the cache.
-  */
-  if( pPager->eState==PAGER_WRITER_LOCKED ){
-    rc = pager_open_journal(pPager);
-    if( rc!=SQLITE_OK ) return rc;
-  }
-  assert( pPager->eState>=PAGER_WRITER_CACHEMOD );
-  assert( assert_pager_state(pPager) );
-
-  /* Mark the page that is about to be modified as dirty. */
-  sqlite3PcacheMakeDirty(pPg);
-
-  /* If a rollback journal is in use, them make sure the page that is about
-  ** to change is in the rollback journal, or if the page is a new page off
-  ** then end of the file, make sure it is marked as PGHDR_NEED_SYNC.
-  */
-  assert( (pPager->pInJournal!=0) == isOpen(pPager->jfd) );
-  if( pPager->pInJournal!=0
-   && sqlite3BitvecTestNotNull(pPager->pInJournal, pPg->pgno)==0
-  ){
-    assert( pagerUseWal(pPager)==0 );
-    if( pPg->pgno<=pPager->dbOrigSize ){
-      rc = pagerAddPageToRollbackJournal(pPg);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }else{
-      if( pPager->eState!=PAGER_WRITER_DBMOD ){
-        pPg->flags |= PGHDR_NEED_SYNC;
-      }
-      PAGERTRACE(("APPEND %d page %d needSync=%d\n",
-              PAGERID(pPager), pPg->pgno,
-             ((pPg->flags&PGHDR_NEED_SYNC)?1:0)));
-    }
-  }
-
-  /* The PGHDR_DIRTY bit is set above when the page was added to the dirty-list
-  ** and before writing the page into the rollback journal.  Wait until now,
-  ** after the page has been successfully journalled, before setting the
-  ** PGHDR_WRITEABLE bit that indicates that the page can be safely modified.
-  */
-  pPg->flags |= PGHDR_WRITEABLE;
-  
-  /* If the statement journal is open and the page is not in it,
-  ** then write the page into the statement journal.
-  */
-  if( pPager->nSavepoint>0 ){
-    rc = subjournalPageIfRequired(pPg);
-  }
-
-  /* Update the database size and return. */
-  if( pPager->dbSize<pPg->pgno ){
-    pPager->dbSize = pPg->pgno;
-  }
-  return rc;
-}
-
-/*
-** This is a variant of sqlite3PagerWrite() that runs when the sector size
-** is larger than the page size.  SQLite makes the (reasonable) assumption that
-** all bytes of a sector are written together by hardware.  Hence, all bytes of
-** a sector need to be journalled in case of a power loss in the middle of
-** a write.
-**
-** Usually, the sector size is less than or equal to the page size, in which
-** case pages can be individually written.  This routine only runs in the
-** exceptional case where the page size is smaller than the sector size.
-*/
-static SQLITE_NOINLINE int pagerWriteLargeSector(PgHdr *pPg){
-  int rc = SQLITE_OK;          /* Return code */
-  Pgno nPageCount;             /* Total number of pages in database file */
-  Pgno pg1;                    /* First page of the sector pPg is located on. */
-  int nPage = 0;               /* Number of pages starting at pg1 to journal */
-  int ii;                      /* Loop counter */
-  int needSync = 0;            /* True if any page has PGHDR_NEED_SYNC */
-  Pager *pPager = pPg->pPager; /* The pager that owns pPg */
-  Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize);
-
-  /* Set the doNotSpill NOSYNC bit to 1. This is because we cannot allow
-  ** a journal header to be written between the pages journaled by
-  ** this function.
-  */
-  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)==0 );
-  pPager->doNotSpill |= SPILLFLAG_NOSYNC;
-
-  /* This trick assumes that both the page-size and sector-size are
-  ** an integer power of 2. It sets variable pg1 to the identifier
-  ** of the first page of the sector pPg is located on.
-  */
-  pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1;
-
-  nPageCount = pPager->dbSize;
-  if( pPg->pgno>nPageCount ){
-    nPage = (pPg->pgno - pg1)+1;
-  }else if( (pg1+nPagePerSector-1)>nPageCount ){
-    nPage = nPageCount+1-pg1;
-  }else{
-    nPage = nPagePerSector;
-  }
-  assert(nPage>0);
-  assert(pg1<=pPg->pgno);
-  assert((pg1+nPage)>pPg->pgno);
-
-  for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){
-    Pgno pg = pg1+ii;
-    PgHdr *pPage;
-    if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){
-      if( pg!=PAGER_MJ_PGNO(pPager) ){
-        rc = sqlite3PagerGet(pPager, pg, &pPage);
-        if( rc==SQLITE_OK ){
-          rc = pager_write(pPage);
-          if( pPage->flags&PGHDR_NEED_SYNC ){
-            needSync = 1;
-          }
-          sqlite3PagerUnrefNotNull(pPage);
-        }
-      }
-    }else if( (pPage = sqlite3PagerLookup(pPager, pg))!=0 ){
-      if( pPage->flags&PGHDR_NEED_SYNC ){
-        needSync = 1;
-      }
-      sqlite3PagerUnrefNotNull(pPage);
-    }
-  }
-
-  /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages 
-  ** starting at pg1, then it needs to be set for all of them. Because
-  ** writing to any of these nPage pages may damage the others, the
-  ** journal file must contain sync()ed copies of all of them
-  ** before any of them can be written out to the database file.
-  */
-  if( rc==SQLITE_OK && needSync ){
-    for(ii=0; ii<nPage; ii++){
-      PgHdr *pPage = sqlite3PagerLookup(pPager, pg1+ii);
-      if( pPage ){
-        pPage->flags |= PGHDR_NEED_SYNC;
-        sqlite3PagerUnrefNotNull(pPage);
-      }
-    }
-  }
-
-  assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
-  pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
-  return rc;
-}
-
-/*
-** Mark a data page as writeable. This routine must be called before 
-** making changes to a page. The caller must check the return value 
-** of this function and be careful not to change any page data unless 
-** this routine returns SQLITE_OK.
-**
-** The difference between this function and pager_write() is that this
-** function also deals with the special case where 2 or more pages
-** fit on a single disk sector. In this case all co-resident pages
-** must have been written to the journal file before returning.
-**
-** If an error occurs, SQLITE_NOMEM or an IO error code is returned
-** as appropriate. Otherwise, SQLITE_OK.
-*/
-SQLITE_PRIVATE int sqlite3PagerWrite(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  assert( (pPg->flags & PGHDR_MMAP)==0 );
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( pPager->eState!=PAGER_ERROR );
-  assert( assert_pager_state(pPager) );
-  if( (pPg->flags & PGHDR_WRITEABLE)!=0 && pPager->dbSize>=pPg->pgno ){
-    if( pPager->nSavepoint ) return subjournalPageIfRequired(pPg);
-    return SQLITE_OK;
-  }else if( pPager->sectorSize > (u32)pPager->pageSize ){
-    return pagerWriteLargeSector(pPg);
-  }else{
-    return pager_write(pPg);
-  }
-}
-
-/*
-** Return TRUE if the page given in the argument was previously passed
-** to sqlite3PagerWrite().  In other words, return TRUE if it is ok
-** to change the content of the page.
-*/
-#ifndef NDEBUG
-SQLITE_PRIVATE int sqlite3PagerIswriteable(DbPage *pPg){
-  return pPg->flags & PGHDR_WRITEABLE;
-}
-#endif
-
-/*
-** A call to this routine tells the pager that it is not necessary to
-** write the information on page pPg back to the disk, even though
-** that page might be marked as dirty.  This happens, for example, when
-** the page has been added as a leaf of the freelist and so its
-** content no longer matters.
-**
-** The overlying software layer calls this routine when all of the data
-** on the given page is unused. The pager marks the page as clean so
-** that it does not get written to disk.
-**
-** Tests show that this optimization can quadruple the speed of large 
-** DELETE operations.
-*/
-SQLITE_PRIVATE void sqlite3PagerDontWrite(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){
-    PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager)));
-    IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno))
-    pPg->flags |= PGHDR_DONT_WRITE;
-    pPg->flags &= ~PGHDR_WRITEABLE;
-    pager_set_pagehash(pPg);
-  }
-}
-
-/*
-** This routine is called to increment the value of the database file 
-** change-counter, stored as a 4-byte big-endian integer starting at 
-** byte offset 24 of the pager file.  The secondary change counter at
-** 92 is also updated, as is the SQLite version number at offset 96.
-**
-** But this only happens if the pPager->changeCountDone flag is false.
-** To avoid excess churning of page 1, the update only happens once.
-** See also the pager_write_changecounter() routine that does an 
-** unconditional update of the change counters.
-**
-** If the isDirectMode flag is zero, then this is done by calling 
-** sqlite3PagerWrite() on page 1, then modifying the contents of the
-** page data. In this case the file will be updated when the current
-** transaction is committed.
-**
-** The isDirectMode flag may only be non-zero if the library was compiled
-** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case,
-** if isDirect is non-zero, then the database file is updated directly
-** by writing an updated version of page 1 using a call to the 
-** sqlite3OsWrite() function.
-*/
-static int pager_incr_changecounter(Pager *pPager, int isDirectMode){
-  int rc = SQLITE_OK;
-
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* Declare and initialize constant integer 'isDirect'. If the
-  ** atomic-write optimization is enabled in this build, then isDirect
-  ** is initialized to the value passed as the isDirectMode parameter
-  ** to this function. Otherwise, it is always set to zero.
-  **
-  ** The idea is that if the atomic-write optimization is not
-  ** enabled at compile time, the compiler can omit the tests of
-  ** 'isDirect' below, as well as the block enclosed in the
-  ** "if( isDirect )" condition.
-  */
-#ifndef SQLITE_ENABLE_ATOMIC_WRITE
-# define DIRECT_MODE 0
-  assert( isDirectMode==0 );
-  UNUSED_PARAMETER(isDirectMode);
-#else
-# define DIRECT_MODE isDirectMode
-#endif
-
-  if( !pPager->changeCountDone && ALWAYS(pPager->dbSize>0) ){
-    PgHdr *pPgHdr;                /* Reference to page 1 */
-
-    assert( !pPager->tempFile && isOpen(pPager->fd) );
-
-    /* Open page 1 of the file for writing. */
-    rc = sqlite3PagerGet(pPager, 1, &pPgHdr);
-    assert( pPgHdr==0 || rc==SQLITE_OK );
-
-    /* If page one was fetched successfully, and this function is not
-    ** operating in direct-mode, make page 1 writable.  When not in 
-    ** direct mode, page 1 is always held in cache and hence the PagerGet()
-    ** above is always successful - hence the ALWAYS on rc==SQLITE_OK.
-    */
-    if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){
-      rc = sqlite3PagerWrite(pPgHdr);
-    }
-
-    if( rc==SQLITE_OK ){
-      /* Actually do the update of the change counter */
-      pager_write_changecounter(pPgHdr);
-
-      /* If running in direct mode, write the contents of page 1 to the file. */
-      if( DIRECT_MODE ){
-        const void *zBuf;
-        assert( pPager->dbFileSize>0 );
-        CODEC2(pPager, pPgHdr->pData, 1, 6, rc=SQLITE_NOMEM, zBuf);
-        if( rc==SQLITE_OK ){
-          rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0);
-          pPager->aStat[PAGER_STAT_WRITE]++;
-        }
-        if( rc==SQLITE_OK ){
-          /* Update the pager's copy of the change-counter. Otherwise, the
-          ** next time a read transaction is opened the cache will be
-          ** flushed (as the change-counter values will not match).  */
-          const void *pCopy = (const void *)&((const char *)zBuf)[24];
-          memcpy(&pPager->dbFileVers, pCopy, sizeof(pPager->dbFileVers));
-          pPager->changeCountDone = 1;
-        }
-      }else{
-        pPager->changeCountDone = 1;
-      }
-    }
-
-    /* Release the page reference. */
-    sqlite3PagerUnref(pPgHdr);
-  }
-  return rc;
-}
-
-/*
-** Sync the database file to disk. This is a no-op for in-memory databases
-** or pages with the Pager.noSync flag set.
-**
-** If successful, or if called on a pager for which it is a no-op, this
-** function returns SQLITE_OK. Otherwise, an IO error code is returned.
-*/
-SQLITE_PRIVATE int sqlite3PagerSync(Pager *pPager, const char *zMaster){
-  int rc = SQLITE_OK;
-
-  if( isOpen(pPager->fd) ){
-    void *pArg = (void*)zMaster;
-    rc = sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SYNC, pArg);
-    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
-  }
-  if( rc==SQLITE_OK && !pPager->noSync ){
-    rc = sqlite3OsSync(pPager->fd, pPager->syncFlags);
-  }
-  return rc;
-}
-
-/*
-** This function may only be called while a write-transaction is active in
-** rollback. If the connection is in WAL mode, this call is a no-op. 
-** Otherwise, if the connection does not already have an EXCLUSIVE lock on 
-** the database file, an attempt is made to obtain one.
-**
-** If the EXCLUSIVE lock is already held or the attempt to obtain it is
-** successful, or the connection is in WAL mode, SQLITE_OK is returned.
-** Otherwise, either SQLITE_BUSY or an SQLITE_IOERR_XXX error code is 
-** returned.
-*/
-SQLITE_PRIVATE int sqlite3PagerExclusiveLock(Pager *pPager){
-  int rc = SQLITE_OK;
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD 
-       || pPager->eState==PAGER_WRITER_DBMOD 
-       || pPager->eState==PAGER_WRITER_LOCKED 
-  );
-  assert( assert_pager_state(pPager) );
-  if( 0==pagerUseWal(pPager) ){
-    rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK);
-  }
-  return rc;
-}
-
-/*
-** Sync the database file for the pager pPager. zMaster points to the name
-** of a master journal file that should be written into the individual
-** journal file. zMaster may be NULL, which is interpreted as no master
-** journal (a single database transaction).
-**
-** This routine ensures that:
-**
-**   * The database file change-counter is updated,
-**   * the journal is synced (unless the atomic-write optimization is used),
-**   * all dirty pages are written to the database file, 
-**   * the database file is truncated (if required), and
-**   * the database file synced. 
-**
-** The only thing that remains to commit the transaction is to finalize 
-** (delete, truncate or zero the first part of) the journal file (or 
-** delete the master journal file if specified).
-**
-** Note that if zMaster==NULL, this does not overwrite a previous value
-** passed to an sqlite3PagerCommitPhaseOne() call.
-**
-** If the final parameter - noSync - is true, then the database file itself
-** is not synced. The caller must call sqlite3PagerSync() directly to
-** sync the database file before calling CommitPhaseTwo() to delete the
-** journal file in this case.
-*/
-SQLITE_PRIVATE int sqlite3PagerCommitPhaseOne(
-  Pager *pPager,                  /* Pager object */
-  const char *zMaster,            /* If not NULL, the master journal name */
-  int noSync                      /* True to omit the xSync on the db file */
-){
-  int rc = SQLITE_OK;             /* Return code */
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-       || pPager->eState==PAGER_ERROR
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* If a prior error occurred, report that error again. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", 
-      pPager->zFilename, zMaster, pPager->dbSize));
-
-  /* If no database changes have been made, return early. */
-  if( pPager->eState<PAGER_WRITER_CACHEMOD ) return SQLITE_OK;
-
-  {
-    if( pagerUseWal(pPager) ){
-      PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache);
-      PgHdr *pPageOne = 0;
-      if( pList==0 ){
-        /* Must have at least one page for the WAL commit flag.
-        ** Ticket [2d1a5c67dfc2363e44f29d9bbd57f] 2011-05-18 */
-        rc = sqlite3PagerGet(pPager, 1, &pPageOne);
-        pList = pPageOne;
-        pList->pDirty = 0;
-      }
-      assert( rc==SQLITE_OK );
-      if( ALWAYS(pList) ){
-        rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1);
-      }
-      sqlite3PagerUnref(pPageOne);
-      if( rc==SQLITE_OK ){
-        sqlite3PcacheCleanAll(pPager->pPCache);
-      }
-    }else{
-      /* The following block updates the change-counter. Exactly how it
-      ** does this depends on whether or not the atomic-update optimization
-      ** was enabled at compile time, and if this transaction meets the 
-      ** runtime criteria to use the operation: 
-      **
-      **    * The file-system supports the atomic-write property for
-      **      blocks of size page-size, and 
-      **    * This commit is not part of a multi-file transaction, and
-      **    * Exactly one page has been modified and store in the journal file.
-      **
-      ** If the optimization was not enabled at compile time, then the
-      ** pager_incr_changecounter() function is called to update the change
-      ** counter in 'indirect-mode'. If the optimization is compiled in but
-      ** is not applicable to this transaction, call sqlite3JournalCreate()
-      ** to make sure the journal file has actually been created, then call
-      ** pager_incr_changecounter() to update the change-counter in indirect
-      ** mode. 
-      **
-      ** Otherwise, if the optimization is both enabled and applicable,
-      ** then call pager_incr_changecounter() to update the change-counter
-      ** in 'direct' mode. In this case the journal file will never be
-      ** created for this transaction.
-      */
-  #ifdef SQLITE_ENABLE_ATOMIC_WRITE
-      PgHdr *pPg;
-      assert( isOpen(pPager->jfd) 
-           || pPager->journalMode==PAGER_JOURNALMODE_OFF 
-           || pPager->journalMode==PAGER_JOURNALMODE_WAL 
-      );
-      if( !zMaster && isOpen(pPager->jfd) 
-       && pPager->journalOff==jrnlBufferSize(pPager) 
-       && pPager->dbSize>=pPager->dbOrigSize
-       && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty)
-      ){
-        /* Update the db file change counter via the direct-write method. The 
-        ** following call will modify the in-memory representation of page 1 
-        ** to include the updated change counter and then write page 1 
-        ** directly to the database file. Because of the atomic-write 
-        ** property of the host file-system, this is safe.
-        */
-        rc = pager_incr_changecounter(pPager, 1);
-      }else{
-        rc = sqlite3JournalCreate(pPager->jfd);
-        if( rc==SQLITE_OK ){
-          rc = pager_incr_changecounter(pPager, 0);
-        }
-      }
-  #else
-      rc = pager_incr_changecounter(pPager, 0);
-  #endif
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      /* Write the master journal name into the journal file. If a master 
-      ** journal file name has already been written to the journal file, 
-      ** or if zMaster is NULL (no master journal), then this call is a no-op.
-      */
-      rc = writeMasterJournal(pPager, zMaster);
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      /* Sync the journal file and write all dirty pages to the database.
-      ** If the atomic-update optimization is being used, this sync will not 
-      ** create the journal file or perform any real IO.
-      **
-      ** Because the change-counter page was just modified, unless the
-      ** atomic-update optimization is used it is almost certain that the
-      ** journal requires a sync here. However, in locking_mode=exclusive
-      ** on a system under memory pressure it is just possible that this is 
-      ** not the case. In this case it is likely enough that the redundant
-      ** xSync() call will be changed to a no-op by the OS anyhow. 
-      */
-      rc = syncJournal(pPager, 0);
-      if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-  
-      rc = pager_write_pagelist(pPager,sqlite3PcacheDirtyList(pPager->pPCache));
-      if( rc!=SQLITE_OK ){
-        assert( rc!=SQLITE_IOERR_BLOCKED );
-        goto commit_phase_one_exit;
-      }
-      sqlite3PcacheCleanAll(pPager->pPCache);
-
-      /* If the file on disk is smaller than the database image, use 
-      ** pager_truncate to grow the file here. This can happen if the database
-      ** image was extended as part of the current transaction and then the
-      ** last page in the db image moved to the free-list. In this case the
-      ** last page is never written out to disk, leaving the database file
-      ** undersized. Fix this now if it is the case.  */
-      if( pPager->dbSize>pPager->dbFileSize ){
-        Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager));
-        assert( pPager->eState==PAGER_WRITER_DBMOD );
-        rc = pager_truncate(pPager, nNew);
-        if( rc!=SQLITE_OK ) goto commit_phase_one_exit;
-      }
-  
-      /* Finally, sync the database file. */
-      if( !noSync ){
-        rc = sqlite3PagerSync(pPager, zMaster);
-      }
-      IOTRACE(("DBSYNC %p\n", pPager))
-    }
-  }
-
-commit_phase_one_exit:
-  if( rc==SQLITE_OK && !pagerUseWal(pPager) ){
-    pPager->eState = PAGER_WRITER_FINISHED;
-  }
-  return rc;
-}
-
-
-/*
-** When this function is called, the database file has been completely
-** updated to reflect the changes made by the current transaction and
-** synced to disk. The journal file still exists in the file-system 
-** though, and if a failure occurs at this point it will eventually
-** be used as a hot-journal and the current transaction rolled back.
-**
-** This function finalizes the journal file, either by deleting, 
-** truncating or partially zeroing it, so that it cannot be used 
-** for hot-journal rollback. Once this is done the transaction is
-** irrevocably committed.
-**
-** If an error occurs, an IO error code is returned and the pager
-** moves into the error state. Otherwise, SQLITE_OK is returned.
-*/
-SQLITE_PRIVATE int sqlite3PagerCommitPhaseTwo(Pager *pPager){
-  int rc = SQLITE_OK;                  /* Return code */
-
-  /* This routine should not be called if a prior error has occurred.
-  ** But if (due to a coding error elsewhere in the system) it does get
-  ** called, just return the same error code without doing anything. */
-  if( NEVER(pPager->errCode) ) return pPager->errCode;
-
-  assert( pPager->eState==PAGER_WRITER_LOCKED
-       || pPager->eState==PAGER_WRITER_FINISHED
-       || (pagerUseWal(pPager) && pPager->eState==PAGER_WRITER_CACHEMOD)
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* An optimization. If the database was not actually modified during
-  ** this transaction, the pager is running in exclusive-mode and is
-  ** using persistent journals, then this function is a no-op.
-  **
-  ** The start of the journal file currently contains a single journal 
-  ** header with the nRec field set to 0. If such a journal is used as
-  ** a hot-journal during hot-journal rollback, 0 changes will be made
-  ** to the database file. So there is no need to zero the journal 
-  ** header. Since the pager is in exclusive mode, there is no need
-  ** to drop any locks either.
-  */
-  if( pPager->eState==PAGER_WRITER_LOCKED 
-   && pPager->exclusiveMode 
-   && pPager->journalMode==PAGER_JOURNALMODE_PERSIST
-  ){
-    assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff );
-    pPager->eState = PAGER_READER;
-    return SQLITE_OK;
-  }
-
-  PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
-  pPager->iDataVersion++;
-  rc = pager_end_transaction(pPager, pPager->setMaster, 1);
-  return pager_error(pPager, rc);
-}
-
-/*
-** If a write transaction is open, then all changes made within the 
-** transaction are reverted and the current write-transaction is closed.
-** The pager falls back to PAGER_READER state if successful, or PAGER_ERROR
-** state if an error occurs.
-**
-** If the pager is already in PAGER_ERROR state when this function is called,
-** it returns Pager.errCode immediately. No work is performed in this case.
-**
-** Otherwise, in rollback mode, this function performs two functions:
-**
-**   1) It rolls back the journal file, restoring all database file and 
-**      in-memory cache pages to the state they were in when the transaction
-**      was opened, and
-**
-**   2) It finalizes the journal file, so that it is not used for hot
-**      rollback at any point in the future.
-**
-** Finalization of the journal file (task 2) is only performed if the 
-** rollback is successful.
-**
-** In WAL mode, all cache-entries containing data modified within the
-** current transaction are either expelled from the cache or reverted to
-** their pre-transaction state by re-reading data from the database or
-** WAL files. The WAL transaction is then closed.
-*/
-SQLITE_PRIVATE int sqlite3PagerRollback(Pager *pPager){
-  int rc = SQLITE_OK;                  /* Return code */
-  PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager)));
-
-  /* PagerRollback() is a no-op if called in READER or OPEN state. If
-  ** the pager is already in the ERROR state, the rollback is not 
-  ** attempted here. Instead, the error code is returned to the caller.
-  */
-  assert( assert_pager_state(pPager) );
-  if( pPager->eState==PAGER_ERROR ) return pPager->errCode;
-  if( pPager->eState<=PAGER_READER ) return SQLITE_OK;
-
-  if( pagerUseWal(pPager) ){
-    int rc2;
-    rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1);
-    rc2 = pager_end_transaction(pPager, pPager->setMaster, 0);
-    if( rc==SQLITE_OK ) rc = rc2;
-  }else if( !isOpen(pPager->jfd) || pPager->eState==PAGER_WRITER_LOCKED ){
-    int eState = pPager->eState;
-    rc = pager_end_transaction(pPager, 0, 0);
-    if( eState>PAGER_WRITER_LOCKED ){
-      /* This can happen using journal_mode=off. Move the pager to the error 
-      ** state to indicate that the contents of the cache may not be trusted.
-      ** Any active readers will get SQLITE_ABORT.
-      */
-      pPager->errCode = SQLITE_ABORT;
-      pPager->eState = PAGER_ERROR;
-      return rc;
-    }
-  }else{
-    rc = pager_playback(pPager, 0);
-  }
-
-  assert( pPager->eState==PAGER_READER || rc!=SQLITE_OK );
-  assert( rc==SQLITE_OK || rc==SQLITE_FULL || rc==SQLITE_CORRUPT
-          || rc==SQLITE_NOMEM || (rc&0xFF)==SQLITE_IOERR 
-          || rc==SQLITE_CANTOPEN
-  );
-
-  /* If an error occurs during a ROLLBACK, we can no longer trust the pager
-  ** cache. So call pager_error() on the way out to make any error persistent.
-  */
-  return pager_error(pPager, rc);
-}
-
-/*
-** Return TRUE if the database file is opened read-only.  Return FALSE
-** if the database is (in theory) writable.
-*/
-SQLITE_PRIVATE u8 sqlite3PagerIsreadonly(Pager *pPager){
-  return pPager->readOnly;
-}
-
-#ifdef SQLITE_DEBUG
-/*
-** Return the sum of the reference counts for all pages held by pPager.
-*/
-SQLITE_PRIVATE int sqlite3PagerRefcount(Pager *pPager){
-  return sqlite3PcacheRefCount(pPager->pPCache);
-}
-#endif
-
-#if 0
-/*
-** Return the approximate number of bytes of memory currently
-** used by the pager and its associated cache.
-*/
-SQLITE_PRIVATE int sqlite3PagerMemUsed(Pager *pPager){
-  int perPageSize = pPager->pageSize + pPager->nExtra + sizeof(PgHdr)
-                                     + 5*sizeof(void*);
-  return perPageSize*sqlite3PcachePagecount(pPager->pPCache)
-           + sqlite3MallocSize(pPager)
-           + pPager->pageSize;
-}
-#endif
-
-/*
-** Return the number of references to the specified page.
-*/
-SQLITE_PRIVATE int sqlite3PagerPageRefcount(DbPage *pPage){
-  return sqlite3PcachePageRefcount(pPage);
-}
-
-#ifdef SQLITE_TEST
-/*
-** This routine is used for testing and analysis only.
-*/
-SQLITE_PRIVATE int *sqlite3PagerStats(Pager *pPager){
-  static int a[11];
-  a[0] = sqlite3PcacheRefCount(pPager->pPCache);
-  a[1] = sqlite3PcachePagecount(pPager->pPCache);
-  a[2] = sqlite3PcacheGetCachesize(pPager->pPCache);
-  a[3] = pPager->eState==PAGER_OPEN ? -1 : (int) pPager->dbSize;
-  a[4] = pPager->eState;
-  a[5] = pPager->errCode;
-  a[6] = pPager->aStat[PAGER_STAT_HIT];
-  a[7] = pPager->aStat[PAGER_STAT_MISS];
-  a[8] = 0;  /* Used to be pPager->nOvfl */
-  a[9] = pPager->nRead;
-  a[10] = pPager->aStat[PAGER_STAT_WRITE];
-  return a;
-}
-#endif
-
-#if 0
-/*
-** Parameter eStat must be either SQLITE_DBSTATUS_CACHE_HIT or
-** SQLITE_DBSTATUS_CACHE_MISS. Before returning, *pnVal is incremented by the
-** current cache hit or miss count, according to the value of eStat. If the 
-** reset parameter is non-zero, the cache hit or miss count is zeroed before 
-** returning.
-*/
-SQLITE_PRIVATE void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, int *pnVal){
-
-  assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
-       || eStat==SQLITE_DBSTATUS_CACHE_MISS
-       || eStat==SQLITE_DBSTATUS_CACHE_WRITE
-  );
-
-  assert( SQLITE_DBSTATUS_CACHE_HIT+1==SQLITE_DBSTATUS_CACHE_MISS );
-  assert( SQLITE_DBSTATUS_CACHE_HIT+2==SQLITE_DBSTATUS_CACHE_WRITE );
-  assert( PAGER_STAT_HIT==0 && PAGER_STAT_MISS==1 && PAGER_STAT_WRITE==2 );
-
-  *pnVal += pPager->aStat[eStat - SQLITE_DBSTATUS_CACHE_HIT];
-  if( reset ){
-    pPager->aStat[eStat - SQLITE_DBSTATUS_CACHE_HIT] = 0;
-  }
-}
-#endif
-
-/*
-** Check that there are at least nSavepoint savepoints open. If there are
-** currently less than nSavepoints open, then open one or more savepoints
-** to make up the difference. If the number of savepoints is already
-** equal to nSavepoint, then this function is a no-op.
-**
-** If a memory allocation fails, SQLITE_NOMEM is returned. If an error 
-** occurs while opening the sub-journal file, then an IO error code is
-** returned. Otherwise, SQLITE_OK.
-*/
-static SQLITE_NOINLINE int pagerOpenSavepoint(Pager *pPager, int nSavepoint){
-  int rc = SQLITE_OK;                       /* Return code */
-  int nCurrent = pPager->nSavepoint;        /* Current number of savepoints */
-  int ii;                                   /* Iterator variable */
-  PagerSavepoint *aNew;                     /* New Pager.aSavepoint array */
-
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-  assert( nSavepoint>nCurrent && pPager->useJournal );
-
-  /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM
-  ** if the allocation fails. Otherwise, zero the new portion in case a 
-  ** malloc failure occurs while populating it in the for(...) loop below.
-  */
-  aNew = (PagerSavepoint *)sqlite3Realloc(
-      pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint
-  );
-  if( !aNew ){
-    return SQLITE_NOMEM;
-  }
-  memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint));
-  pPager->aSavepoint = aNew;
-
-  /* Populate the PagerSavepoint structures just allocated. */
-  for(ii=nCurrent; ii<nSavepoint; ii++){
-    aNew[ii].nOrig = pPager->dbSize;
-    if( isOpen(pPager->jfd) && pPager->journalOff>0 ){
-      aNew[ii].iOffset = pPager->journalOff;
-    }else{
-      aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager);
-    }
-    aNew[ii].iSubRec = pPager->nSubRec;
-    aNew[ii].pInSavepoint = sqlite3BitvecCreate(pPager->dbSize);
-    if( !aNew[ii].pInSavepoint ){
-      return SQLITE_NOMEM;
-    }
-    if( pagerUseWal(pPager) ){
-      sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData);
-    }
-    pPager->nSavepoint = ii+1;
-  }
-  assert( pPager->nSavepoint==nSavepoint );
-  assertTruncateConstraint(pPager);
-  return rc;
-}
-SQLITE_PRIVATE int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){
-  assert( pPager->eState>=PAGER_WRITER_LOCKED );
-  assert( assert_pager_state(pPager) );
-
-  if( nSavepoint>pPager->nSavepoint && pPager->useJournal ){
-    return pagerOpenSavepoint(pPager, nSavepoint);
-  }else{
-    return SQLITE_OK;
-  }
-}
-
-
-/*
-** This function is called to rollback or release (commit) a savepoint.
-** The savepoint to release or rollback need not be the most recently 
-** created savepoint.
-**
-** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE.
-** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with
-** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes
-** that have occurred since the specified savepoint was created.
-**
-** The savepoint to rollback or release is identified by parameter 
-** iSavepoint. A value of 0 means to operate on the outermost savepoint
-** (the first created). A value of (Pager.nSavepoint-1) means operate
-** on the most recently created savepoint. If iSavepoint is greater than
-** (Pager.nSavepoint-1), then this function is a no-op.
-**
-** If a negative value is passed to this function, then the current
-** transaction is rolled back. This is different to calling 
-** sqlite3PagerRollback() because this function does not terminate
-** the transaction or unlock the database, it just restores the 
-** contents of the database to its original state. 
-**
-** In any case, all savepoints with an index greater than iSavepoint 
-** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE),
-** then savepoint iSavepoint is also destroyed.
-**
-** This function may return SQLITE_NOMEM if a memory allocation fails,
-** or an IO error code if an IO error occurs while rolling back a 
-** savepoint. If no errors occur, SQLITE_OK is returned.
-*/ 
-SQLITE_PRIVATE int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){
-  int rc = pPager->errCode;       /* Return code */
-
-  assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
-  assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK );
-
-  if( rc==SQLITE_OK && iSavepoint<pPager->nSavepoint ){
-    int ii;            /* Iterator variable */
-    int nNew;          /* Number of remaining savepoints after this op. */
-
-    /* Figure out how many savepoints will still be active after this
-    ** operation. Store this value in nNew. Then free resources associated 
-    ** with any savepoints that are destroyed by this operation.
-    */
-    nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1);
-    for(ii=nNew; ii<pPager->nSavepoint; ii++){
-      sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint);
-    }
-    pPager->nSavepoint = nNew;
-
-    /* If this is a release of the outermost savepoint, truncate 
-    ** the sub-journal to zero bytes in size. */
-    if( op==SAVEPOINT_RELEASE ){
-      if( nNew==0 && isOpen(pPager->sjfd) ){
-        /* Only truncate if it is an in-memory sub-journal. */
-        if( sqlite3IsMemJournal(pPager->sjfd) ){
-          rc = sqlite3OsTruncate(pPager->sjfd, 0);
-          assert( rc==SQLITE_OK );
-        }
-        pPager->nSubRec = 0;
-      }
-    }
-    /* Else this is a rollback operation, playback the specified savepoint.
-    ** If this is a temp-file, it is possible that the journal file has
-    ** not yet been opened. In this case there have been no changes to
-    ** the database file, so the playback operation can be skipped.
-    */
-    else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){
-      PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1];
-      rc = pagerPlaybackSavepoint(pPager, pSavepoint);
-      assert(rc!=SQLITE_DONE);
-    }
-  }
-
-  return rc;
-}
-
-/*
-** Return the full pathname of the database file.
-**
-** Except, if the pager is in-memory only, then return an empty string if
-** nullIfMemDb is true.  This routine is called with nullIfMemDb==1 when
-** used to report the filename to the user, for compatibility with legacy
-** behavior.  But when the Btree needs to know the filename for matching to
-** shared cache, it uses nullIfMemDb==0 so that in-memory databases can
-** participate in shared-cache.
-*/
-SQLITE_PRIVATE const char *sqlite3PagerFilename(Pager *pPager, int nullIfMemDb){
-  return (nullIfMemDb && pPager->memDb) ? "" : pPager->zFilename;
-}
-
-/*
-** Return the VFS structure for the pager.
-*/
-SQLITE_PRIVATE const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){
-  return pPager->pVfs;
-}
-
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-/*
-** Return the file handle for the database file associated
-** with the pager.  This might return NULL if the file has
-** not yet been opened.
-*/
-SQLITE_PRIVATE sqlite3_file *sqlite3PagerFile(Pager *pPager){
-  return pPager->fd;
-}
-#endif
-
-/*
-** Return the full pathname of the journal file.
-*/
-SQLITE_PRIVATE const char *sqlite3PagerJournalname(Pager *pPager){
-  return pPager->zJournal;
-}
-
-/*
-** Return true if fsync() calls are disabled for this pager.  Return FALSE
-** if fsync()s are executed normally.
-*/
-SQLITE_PRIVATE int sqlite3PagerNosync(Pager *pPager){
-  return pPager->noSync;
-}
-
-#ifdef SQLITE_HAS_CODEC
-/*
-** Set or retrieve the codec for this pager
-*/
-SQLITE_PRIVATE void sqlite3PagerSetCodec(
-  Pager *pPager,
-  void *(*xCodec)(void*,void*,Pgno,int),
-  void (*xCodecSizeChng)(void*,int,int),
-  void (*xCodecFree)(void*),
-  void *pCodec
-){
-  if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec);
-  pPager->xCodec = pPager->memDb ? 0 : xCodec;
-  pPager->xCodecSizeChng = xCodecSizeChng;
-  pPager->xCodecFree = xCodecFree;
-  pPager->pCodec = pCodec;
-  pagerReportSize(pPager);
-}
-SQLITE_PRIVATE void *sqlite3PagerGetCodec(Pager *pPager){
-  return pPager->pCodec;
-}
-
-/*
-** This function is called by the wal module when writing page content
-** into the log file.
-**
-** This function returns a pointer to a buffer containing the encrypted
-** page content. If a malloc fails, this function may return NULL.
-*/
-SQLITE_PRIVATE void *sqlite3PagerCodec(PgHdr *pPg){
-  void *aData = 0;
-  CODEC2(pPg->pPager, pPg->pData, pPg->pgno, 6, return 0, aData);
-  return aData;
-}
-
-/*
-** Return the current pager state
-*/
-SQLITE_PRIVATE int sqlite3PagerState(Pager *pPager){
-  return pPager->eState;
-}
-#endif /* SQLITE_HAS_CODEC */
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-/*
-** Move the page pPg to location pgno in the file.
-**
-** There must be no references to the page previously located at
-** pgno (which we call pPgOld) though that page is allowed to be
-** in cache.  If the page previously located at pgno is not already
-** in the rollback journal, it is not put there by by this routine.
-**
-** References to the page pPg remain valid. Updating any
-** meta-data associated with pPg (i.e. data stored in the nExtra bytes
-** allocated along with the page) is the responsibility of the caller.
-**
-** A transaction must be active when this routine is called. It used to be
-** required that a statement transaction was not active, but this restriction
-** has been removed (CREATE INDEX needs to move a page when a statement
-** transaction is active).
-**
-** If the fourth argument, isCommit, is non-zero, then this page is being
-** moved as part of a database reorganization just before the transaction 
-** is being committed. In this case, it is guaranteed that the database page 
-** pPg refers to will not be written to again within this transaction.
-**
-** This function may return SQLITE_NOMEM or an IO error code if an error
-** occurs. Otherwise, it returns SQLITE_OK.
-*/
-SQLITE_PRIVATE int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
-  PgHdr *pPgOld;               /* The page being overwritten. */
-  Pgno needSyncPgno = 0;       /* Old value of pPg->pgno, if sync is required */
-  int rc;                      /* Return code */
-
-  assert( pPg->nRef>0 );
-  assert( pPager->eState==PAGER_WRITER_CACHEMOD
-       || pPager->eState==PAGER_WRITER_DBMOD
-  );
-  assert( assert_pager_state(pPager) );
-
-  /* If the page being moved is dirty and has not been saved by the latest
-  ** savepoint, then save the current contents of the page into the 
-  ** sub-journal now. This is required to handle the following scenario:
-  **
-  **   BEGIN;
-  **     <journal page X, then modify it in memory>
-  **     SAVEPOINT one;
-  **       <Move page X to location Y>
-  **     ROLLBACK TO one;
-  **
-  ** If page X were not written to the sub-journal here, it would not
-  ** be possible to restore its contents when the "ROLLBACK TO one"
-  ** statement were is processed.
-  **
-  ** subjournalPage() may need to allocate space to store pPg->pgno into
-  ** one or more savepoint bitvecs. This is the reason this function
-  ** may return SQLITE_NOMEM.
-  */
-  if( (pPg->flags & PGHDR_DIRTY)!=0
-   && SQLITE_OK!=(rc = subjournalPageIfRequired(pPg))
-  ){
-    return rc;
-  }
-
-  PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", 
-      PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno));
-  IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno))
-
-  /* If the journal needs to be sync()ed before page pPg->pgno can
-  ** be written to, store pPg->pgno in local variable needSyncPgno.
-  **
-  ** If the isCommit flag is set, there is no need to remember that
-  ** the journal needs to be sync()ed before database page pPg->pgno 
-  ** can be written to. The caller has already promised not to write to it.
-  */
-  if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){
-    needSyncPgno = pPg->pgno;
-    assert( pPager->journalMode==PAGER_JOURNALMODE_OFF ||
-            pageInJournal(pPager, pPg) || pPg->pgno>pPager->dbOrigSize );
-    assert( pPg->flags&PGHDR_DIRTY );
-  }
-
-  /* If the cache contains a page with page-number pgno, remove it
-  ** from its hash chain. Also, if the PGHDR_NEED_SYNC flag was set for 
-  ** page pgno before the 'move' operation, it needs to be retained 
-  ** for the page moved there.
-  */
-  pPg->flags &= ~PGHDR_NEED_SYNC;
-  pPgOld = sqlite3PagerLookup(pPager, pgno);
-  assert( !pPgOld || pPgOld->nRef==1 );
-  if( pPgOld ){
-    pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC);
-    sqlite3PcacheDrop(pPgOld);
-  }
-
-  sqlite3PcacheMove(pPg, pgno);
-  sqlite3PcacheMakeDirty(pPg);
-
-  if( needSyncPgno ){
-    /* If needSyncPgno is non-zero, then the journal file needs to be 
-    ** sync()ed before any data is written to database file page needSyncPgno.
-    ** Currently, no such page exists in the page-cache and the 
-    ** "is journaled" bitvec flag has been set. This needs to be remedied by
-    ** loading the page into the pager-cache and setting the PGHDR_NEED_SYNC
-    ** flag.
-    **
-    ** If the attempt to load the page into the page-cache fails, (due
-    ** to a malloc() or IO failure), clear the bit in the pInJournal[]
-    ** array. Otherwise, if the page is loaded and written again in
-    ** this transaction, it may be written to the database file before
-    ** it is synced into the journal file. This way, it may end up in
-    ** the journal file twice, but that is not a problem.
-    */
-    PgHdr *pPgHdr;
-    rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr);
-    if( rc!=SQLITE_OK ){
-      if( needSyncPgno<=pPager->dbOrigSize ){
-        assert( pPager->pTmpSpace!=0 );
-        sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace);
-      }
-      return rc;
-    }
-    pPgHdr->flags |= PGHDR_NEED_SYNC;
-    sqlite3PcacheMakeDirty(pPgHdr);
-    sqlite3PagerUnrefNotNull(pPgHdr);
-  }
-
-  return SQLITE_OK;
-}
-#endif
-
-/*
-** The page handle passed as the first argument refers to a dirty page 
-** with a page number other than iNew. This function changes the page's 
-** page number to iNew and sets the value of the PgHdr.flags field to 
-** the value passed as the third parameter.
-*/
-SQLITE_PRIVATE void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
-  assert( pPg->pgno!=iNew );
-  pPg->flags = flags;
-  sqlite3PcacheMove(pPg, iNew);
-}
-
-/*
-** Return a pointer to the data for the specified page.
-*/
-SQLITE_PRIVATE void *sqlite3PagerGetData(DbPage *pPg){
-  assert( pPg->nRef>0 || pPg->pPager->memDb );
-  return pPg->pData;
-}
-
-/*
-** Return a pointer to the Pager.nExtra bytes of "extra" space 
-** allocated along with the specified page.
-*/
-SQLITE_PRIVATE void *sqlite3PagerGetExtra(DbPage *pPg){
-  return pPg->pExtra;
-}
-
-#if 0
-/*
-** Get/set the locking-mode for this pager. Parameter eMode must be one
-** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or 
-** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then
-** the locking-mode is set to the value specified.
-**
-** The returned value is either PAGER_LOCKINGMODE_NORMAL or
-** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
-** locking-mode.
-*/
-SQLITE_PRIVATE int sqlite3PagerLockingMode(Pager *pPager, int eMode){
-  assert( eMode==PAGER_LOCKINGMODE_QUERY
-            || eMode==PAGER_LOCKINGMODE_NORMAL
-            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
-  assert( PAGER_LOCKINGMODE_QUERY<0 );
-  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
-  assert( pPager->exclusiveMode || 0==sqlite3WalHeapMemory(pPager->pWal) );
-  if( eMode>=0 && !pPager->tempFile && !sqlite3WalHeapMemory(pPager->pWal) ){
-    pPager->exclusiveMode = (u8)eMode;
-  }
-  return (int)pPager->exclusiveMode;
-}
-
-/*
-** Set the journal-mode for this pager. Parameter eMode must be one of:
-**
-**    PAGER_JOURNALMODE_DELETE
-**    PAGER_JOURNALMODE_TRUNCATE
-**    PAGER_JOURNALMODE_PERSIST
-**    PAGER_JOURNALMODE_OFF
-**    PAGER_JOURNALMODE_MEMORY
-**    PAGER_JOURNALMODE_WAL
-**
-** The journalmode is set to the value specified if the change is allowed.
-** The change may be disallowed for the following reasons:
-**
-**   *  An in-memory database can only have its journal_mode set to _OFF
-**      or _MEMORY.
-**
-**   *  Temporary databases cannot have _WAL journalmode.
-**
-** The returned indicate the current (possibly updated) journal-mode.
-*/
-SQLITE_PRIVATE int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){
-  u8 eOld = pPager->journalMode;    /* Prior journalmode */
-
-#ifdef SQLITE_DEBUG
-  /* The print_pager_state() routine is intended to be used by the debugger
-  ** only.  We invoke it once here to suppress a compiler warning. */
-  print_pager_state(pPager);
-#endif
-
-
-  /* The eMode parameter is always valid */
-  assert(      eMode==PAGER_JOURNALMODE_DELETE
-            || eMode==PAGER_JOURNALMODE_TRUNCATE
-            || eMode==PAGER_JOURNALMODE_PERSIST
-            || eMode==PAGER_JOURNALMODE_OFF 
-            || eMode==PAGER_JOURNALMODE_WAL 
-            || eMode==PAGER_JOURNALMODE_MEMORY );
-
-  /* This routine is only called from the OP_JournalMode opcode, and
-  ** the logic there will never allow a temporary file to be changed
-  ** to WAL mode.
-  */
-  assert( pPager->tempFile==0 || eMode!=PAGER_JOURNALMODE_WAL );
-
-  if( eMode!=eOld ){
-
-    /* Change the journal mode. */
-    assert( pPager->eState!=PAGER_ERROR );
-    pPager->journalMode = (u8)eMode;
-
-    /* When transistioning from TRUNCATE or PERSIST to any other journal
-    ** mode except WAL, unless the pager is in locking_mode=exclusive mode,
-    ** delete the journal file.
-    */
-    assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 );
-    assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 );
-    assert( (PAGER_JOURNALMODE_DELETE & 5)==0 );
-    assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 );
-    assert( (PAGER_JOURNALMODE_OFF & 5)==0 );
-    assert( (PAGER_JOURNALMODE_WAL & 5)==5 );
-
-    assert( isOpen(pPager->fd) || pPager->exclusiveMode );
-    if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){
-
-      /* In this case we would like to delete the journal file. If it is
-      ** not possible, then that is not a problem. Deleting the journal file
-      ** here is an optimization only.
-      **
-      ** Before deleting the journal file, obtain a RESERVED lock on the
-      ** database file. This ensures that the journal file is not deleted
-      ** while it is in use by some other client.
-      */
-      sqlite3OsClose(pPager->jfd);
-      if( pPager->eLock>=RESERVED_LOCK ){
-        sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-      }else{
-        int rc = SQLITE_OK;
-        int state = pPager->eState;
-        assert( state==PAGER_OPEN || state==PAGER_READER );
-        if( state==PAGER_OPEN ){
-          rc = sqlite3PagerSharedLock(pPager);
-        }
-        if( pPager->eState==PAGER_READER ){
-          assert( rc==SQLITE_OK );
-          rc = pagerLockDb(pPager, RESERVED_LOCK);
-        }
-        if( rc==SQLITE_OK ){
-          sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0);
-        }
-        if( rc==SQLITE_OK && state==PAGER_READER ){
-          pagerUnlockDb(pPager, SHARED_LOCK);
-        }else if( state==PAGER_OPEN ){
-          pager_unlock(pPager);
-        }
-        assert( state==pPager->eState );
-      }
-    }else if( eMode==PAGER_JOURNALMODE_OFF ){
-      sqlite3OsClose(pPager->jfd);
-    }
-  }
-
-  /* Return the new journal mode */
-  return (int)pPager->journalMode;
-}
-
-/*
-** Return the current journal mode.
-*/
-SQLITE_PRIVATE int sqlite3PagerGetJournalMode(Pager *pPager){
-  return (int)pPager->journalMode;
-}
-
-/*
-** Return TRUE if the pager is in a state where it is OK to change the
-** journalmode.  Journalmode changes can only happen when the database
-** is unmodified.
-*/
-SQLITE_PRIVATE int sqlite3PagerOkToChangeJournalMode(Pager *pPager){
-  assert( assert_pager_state(pPager) );
-  if( pPager->eState>=PAGER_WRITER_CACHEMOD ) return 0;
-  if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0;
-  return 1;
-}
-
-/*
-** Get/set the size-limit used for persistent journal files.
-**
-** Setting the size limit to -1 means no limit is enforced.
-** An attempt to set a limit smaller than -1 is a no-op.
-*/
-SQLITE_PRIVATE i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){
-  if( iLimit>=-1 ){
-    pPager->journalSizeLimit = iLimit;
-    sqlite3WalLimit(pPager->pWal, iLimit);
-  }
-  return pPager->journalSizeLimit;
-}
-#endif
-
-#ifndef SQLITE_OMIT_VACUUM
-#if 0
-/*
-** Clear the pager cache.
-*/
-SQLITE_PRIVATE void sqlite3PagerClearCache(Pager *pPager){
-  if( pPager->tempFile==0 ) pager_reset(pPager);
-}
-#endif
-#endif
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** This function is called when the user invokes "PRAGMA wal_checkpoint",
-** "PRAGMA wal_blocking_checkpoint" or calls the sqlite3_wal_checkpoint()
-** or wal_blocking_checkpoint() API functions.
-**
-** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
-*/
-SQLITE_PRIVATE int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
-  int rc = SQLITE_OK;
-  if( pPager->pWal ){
-    rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
-        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
-        pPager->pBusyHandlerArg,
-        pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
-        pnLog, pnCkpt
-    );
-  }
-  return rc;
-}
-
-#if 0
-SQLITE_PRIVATE int sqlite3PagerWalCallback(Pager *pPager){
-  return sqlite3WalCallback(pPager->pWal);
-}
-#endif
-
-/*
-** Return true if the underlying VFS for the given pager supports the
-** primitives necessary for write-ahead logging.
-*/
-SQLITE_PRIVATE int sqlite3PagerWalSupported(Pager *pPager){
-  const sqlite3_io_methods *pMethods = pPager->fd->pMethods;
-  return pPager->exclusiveMode || (pMethods->iVersion>=2 && pMethods->xShmMap);
-}
-
-/*
-** Attempt to take an exclusive lock on the database file. If a PENDING lock
-** is obtained instead, immediately release it.
-*/
-static int pagerExclusiveLock(Pager *pPager){
-  int rc;                         /* Return code */
-
-  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
-  rc = pagerLockDb(pPager, EXCLUSIVE_LOCK);
-  if( rc!=SQLITE_OK ){
-    /* If the attempt to grab the exclusive lock failed, release the 
-    ** pending lock that may have been obtained instead.  */
-    pagerUnlockDb(pPager, SHARED_LOCK);
-  }
-
-  return rc;
-}
-
-/*
-** Call sqlite3WalOpen() to open the WAL handle. If the pager is in 
-** exclusive-locking mode when this function is called, take an EXCLUSIVE
-** lock on the database file and use heap-memory to store the wal-index
-** in. Otherwise, use the normal shared-memory.
-*/
-static int pagerOpenWal(Pager *pPager){
-  int rc = SQLITE_OK;
-
-  assert( pPager->pWal==0 && pPager->tempFile==0 );
-  assert( pPager->eLock==SHARED_LOCK || pPager->eLock==EXCLUSIVE_LOCK );
-
-  /* If the pager is already in exclusive-mode, the WAL module will use 
-  ** heap-memory for the wal-index instead of the VFS shared-memory 
-  ** implementation. Take the exclusive lock now, before opening the WAL
-  ** file, to make sure this is safe.
-  */
-  if( pPager->exclusiveMode ){
-    rc = pagerExclusiveLock(pPager);
-  }
-
-  /* Open the connection to the log file. If this operation fails, 
-  ** (e.g. due to malloc() failure), return an error code.
-  */
-  if( rc==SQLITE_OK ){
-    rc = sqlite3WalOpen(pPager->pVfs,
-        pPager->fd, pPager->zWal, pPager->exclusiveMode,
-        pPager->journalSizeLimit, &pPager->pWal
-    );
-  }
-  pagerFixMaplimit(pPager);
-
-  return rc;
-}
-
-
-/*
-** The caller must be holding a SHARED lock on the database file to call
-** this function.
-**
-** If the pager passed as the first argument is open on a real database
-** file (not a temp file or an in-memory database), and the WAL file
-** is not already open, make an attempt to open it now. If successful,
-** return SQLITE_OK. If an error occurs or the VFS used by the pager does 
-** not support the xShmXXX() methods, return an error code. *pbOpen is
-** not modified in either case.
-**
-** If the pager is open on a temp-file (or in-memory database), or if
-** the WAL file is already open, set *pbOpen to 1 and return SQLITE_OK
-** without doing anything.
-*/
-SQLITE_PRIVATE int sqlite3PagerOpenWal(
-  Pager *pPager,                  /* Pager object */
-  int *pbOpen                     /* OUT: Set to true if call is a no-op */
-){
-  int rc = SQLITE_OK;             /* Return code */
-
-  assert( assert_pager_state(pPager) );
-  assert( pPager->eState==PAGER_OPEN   || pbOpen );
-  assert( pPager->eState==PAGER_READER || !pbOpen );
-  assert( pbOpen==0 || *pbOpen==0 );
-  assert( pbOpen!=0 || (!pPager->tempFile && !pPager->pWal) );
-
-  if( !pPager->tempFile && !pPager->pWal ){
-    if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN;
-
-    /* Close any rollback journal previously open */
-    sqlite3OsClose(pPager->jfd);
-
-    rc = pagerOpenWal(pPager);
-    if( rc==SQLITE_OK ){
-      pPager->journalMode = PAGER_JOURNALMODE_WAL;
-      pPager->eState = PAGER_OPEN;
-    }
-  }else{
-    *pbOpen = 1;
-  }
-
-  return rc;
-}
-
-/*
-** This function is called to close the connection to the log file prior
-** to switching from WAL to rollback mode.
-**
-** Before closing the log file, this function attempts to take an 
-** EXCLUSIVE lock on the database file. If this cannot be obtained, an
-** error (SQLITE_BUSY) is returned and the log connection is not closed.
-** If successful, the EXCLUSIVE lock is not released before returning.
-*/
-#if 0
-SQLITE_PRIVATE int sqlite3PagerCloseWal(Pager *pPager){
-  int rc = SQLITE_OK;
-
-  assert( pPager->journalMode==PAGER_JOURNALMODE_WAL );
-
-  /* If the log file is not already open, but does exist in the file-system,
-  ** it may need to be checkpointed before the connection can switch to
-  ** rollback mode. Open it now so this can happen.
-  */
-  if( !pPager->pWal ){
-    int logexists = 0;
-    rc = pagerLockDb(pPager, SHARED_LOCK);
-    if( rc==SQLITE_OK ){
-      rc = sqlite3OsAccess(
-          pPager->pVfs, pPager->zWal, SQLITE_ACCESS_EXISTS, &logexists
-      );
-    }
-    if( rc==SQLITE_OK && logexists ){
-      rc = pagerOpenWal(pPager);
-    }
-  }
-    
-  /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on
-  ** the database file, the log and log-summary files will be deleted.
-  */
-  if( rc==SQLITE_OK && pPager->pWal ){
-    rc = pagerExclusiveLock(pPager);
-    if( rc==SQLITE_OK ){
-      rc = sqlite3WalClose(pPager->pWal, pPager->ckptSyncFlags,
-                           pPager->pageSize, (u8*)pPager->pTmpSpace);
-      pPager->pWal = 0;
-      pagerFixMaplimit(pPager);
-    }
-  }
-  return rc;
-}
-#endif
-#endif /* !SQLITE_OMIT_WAL */
-
-#ifdef SQLITE_ENABLE_ZIPVFS
-/*
-** A read-lock must be held on the pager when this function is called. If
-** the pager is in WAL mode and the WAL file currently contains one or more
-** frames, return the size in bytes of the page images stored within the
-** WAL frames. Otherwise, if this is not a WAL database or the WAL file
-** is empty, return 0.
-*/
-SQLITE_PRIVATE int sqlite3PagerWalFramesize(Pager *pPager){
-  assert( pPager->eState>=PAGER_READER );
-  return sqlite3WalFramesize(pPager->pWal);
-}
-#endif
-
-
-#endif /* SQLITE_OMIT_DISKIO */
-
-/************** End of pager.c ***********************************************/
-/************** Begin file wal.c *********************************************/
-/*
-** 2010 February 1
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains the implementation of a write-ahead log (WAL) used in 
-** "journal_mode=WAL" mode.
-**
-** WRITE-AHEAD LOG (WAL) FILE FORMAT
-**
-** A WAL file consists of a header followed by zero or more "frames".
-** Each frame records the revised content of a single page from the
-** database file.  All changes to the database are recorded by writing
-** frames into the WAL.  Transactions commit when a frame is written that
-** contains a commit marker.  A single WAL can and usually does record 
-** multiple transactions.  Periodically, the content of the WAL is
-** transferred back into the database file in an operation called a
-** "checkpoint".
-**
-** A single WAL file can be used multiple times.  In other words, the
-** WAL can fill up with frames and then be checkpointed and then new
-** frames can overwrite the old ones.  A WAL always grows from beginning
-** toward the end.  Checksums and counters attached to each frame are
-** used to determine which frames within the WAL are valid and which
-** are leftovers from prior checkpoints.
-**
-** The WAL header is 32 bytes in size and consists of the following eight
-** big-endian 32-bit unsigned integer values:
-**
-**     0: Magic number.  0x377f0682 or 0x377f0683
-**     4: File format version.  Currently 3007000
-**     8: Database page size.  Example: 1024
-**    12: Checkpoint sequence number
-**    16: Salt-1, random integer incremented with each checkpoint
-**    20: Salt-2, a different random integer changing with each ckpt
-**    24: Checksum-1 (first part of checksum for first 24 bytes of header).
-**    28: Checksum-2 (second part of checksum for first 24 bytes of header).
-**
-** Immediately following the wal-header are zero or more frames. Each
-** frame consists of a 24-byte frame-header followed by a <page-size> bytes
-** of page data. The frame-header is six big-endian 32-bit unsigned 
-** integer values, as follows:
-**
-**     0: Page number.
-**     4: For commit records, the size of the database image in pages 
-**        after the commit. For all other records, zero.
-**     8: Salt-1 (copied from the header)
-**    12: Salt-2 (copied from the header)
-**    16: Checksum-1.
-**    20: Checksum-2.
-**
-** A frame is considered valid if and only if the following conditions are
-** true:
-**
-**    (1) The salt-1 and salt-2 values in the frame-header match
-**        salt values in the wal-header
-**
-**    (2) The checksum values in the final 8 bytes of the frame-header
-**        exactly match the checksum computed consecutively on the
-**        WAL header and the first 8 bytes and the content of all frames
-**        up to and including the current frame.
-**
-** The checksum is computed using 32-bit big-endian integers if the
-** magic number in the first 4 bytes of the WAL is 0x377f0683 and it
-** is computed using little-endian if the magic number is 0x377f0682.
-** The checksum values are always stored in the frame header in a
-** big-endian format regardless of which byte order is used to compute
-** the checksum.  The checksum is computed by interpreting the input as
-** an even number of unsigned 32-bit integers: x[0] through x[N].  The
-** algorithm used for the checksum is as follows:
-** 
-**   for i from 0 to n-1 step 2:
-**     s0 += x[i] + s1;
-**     s1 += x[i+1] + s0;
-**   endfor
-**
-** Note that s0 and s1 are both weighted checksums using fibonacci weights
-** in reverse order (the largest fibonacci weight occurs on the first element
-** of the sequence being summed.)  The s1 value spans all 32-bit 
-** terms of the sequence whereas s0 omits the final term.
-**
-** On a checkpoint, the WAL is first VFS.xSync-ed, then valid content of the
-** WAL is transferred into the database, then the database is VFS.xSync-ed.
-** The VFS.xSync operations serve as write barriers - all writes launched
-** before the xSync must complete before any write that launches after the
-** xSync begins.
-**
-** After each checkpoint, the salt-1 value is incremented and the salt-2
-** value is randomized.  This prevents old and new frames in the WAL from
-** being considered valid at the same time and being checkpointing together
-** following a crash.
-**
-** READER ALGORITHM
-**
-** To read a page from the database (call it page number P), a reader
-** first checks the WAL to see if it contains page P.  If so, then the
-** last valid instance of page P that is a followed by a commit frame
-** or is a commit frame itself becomes the value read.  If the WAL
-** contains no copies of page P that are valid and which are a commit
-** frame or are followed by a commit frame, then page P is read from
-** the database file.
-**
-** To start a read transaction, the reader records the index of the last
-** valid frame in the WAL.  The reader uses this recorded "mxFrame" value
-** for all subsequent read operations.  New transactions can be appended
-** to the WAL, but as long as the reader uses its original mxFrame value
-** and ignores the newly appended content, it will see a consistent snapshot
-** of the database from a single point in time.  This technique allows
-** multiple concurrent readers to view different versions of the database
-** content simultaneously.
-**
-** The reader algorithm in the previous paragraphs works correctly, but 
-** because frames for page P can appear anywhere within the WAL, the
-** reader has to scan the entire WAL looking for page P frames.  If the
-** WAL is large (multiple megabytes is typical) that scan can be slow,
-** and read performance suffers.  To overcome this problem, a separate
-** data structure called the wal-index is maintained to expedite the
-** search for frames of a particular page.
-** 
-** WAL-INDEX FORMAT
-**
-** Conceptually, the wal-index is shared memory, though VFS implementations
-** might choose to implement the wal-index using a mmapped file.  Because
-** the wal-index is shared memory, SQLite does not support journal_mode=WAL 
-** on a network filesystem.  All users of the database must be able to
-** share memory.
-**
-** The wal-index is transient.  After a crash, the wal-index can (and should
-** be) reconstructed from the original WAL file.  In fact, the VFS is required
-** to either truncate or zero the header of the wal-index when the last
-** connection to it closes.  Because the wal-index is transient, it can
-** use an architecture-specific format; it does not have to be cross-platform.
-** Hence, unlike the database and WAL file formats which store all values
-** as big endian, the wal-index can store multi-byte values in the native
-** byte order of the host computer.
-**
-** The purpose of the wal-index is to answer this question quickly:  Given
-** a page number P and a maximum frame index M, return the index of the 
-** last frame in the wal before frame M for page P in the WAL, or return
-** NULL if there are no frames for page P in the WAL prior to M.
-**
-** The wal-index consists of a header region, followed by an one or
-** more index blocks.  
-**
-** The wal-index header contains the total number of frames within the WAL
-** in the mxFrame field.
-**
-** Each index block except for the first contains information on 
-** HASHTABLE_NPAGE frames. The first index block contains information on
-** HASHTABLE_NPAGE_ONE frames. The values of HASHTABLE_NPAGE_ONE and 
-** HASHTABLE_NPAGE are selected so that together the wal-index header and
-** first index block are the same size as all other index blocks in the
-** wal-index.
-**
-** Each index block contains two sections, a page-mapping that contains the
-** database page number associated with each wal frame, and a hash-table 
-** that allows readers to query an index block for a specific page number.
-** The page-mapping is an array of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE
-** for the first index block) 32-bit page numbers. The first entry in the 
-** first index-block contains the database page number corresponding to the
-** first frame in the WAL file. The first entry in the second index block
-** in the WAL file corresponds to the (HASHTABLE_NPAGE_ONE+1)th frame in
-** the log, and so on.
-**
-** The last index block in a wal-index usually contains less than the full
-** complement of HASHTABLE_NPAGE (or HASHTABLE_NPAGE_ONE) page-numbers,
-** depending on the contents of the WAL file. This does not change the
-** allocated size of the page-mapping array - the page-mapping array merely
-** contains unused entries.
-**
-** Even without using the hash table, the last frame for page P
-** can be found by scanning the page-mapping sections of each index block
-** starting with the last index block and moving toward the first, and
-** within each index block, starting at the end and moving toward the
-** beginning.  The first entry that equals P corresponds to the frame
-** holding the content for that page.
-**
-** The hash table consists of HASHTABLE_NSLOT 16-bit unsigned integers.
-** HASHTABLE_NSLOT = 2*HASHTABLE_NPAGE, and there is one entry in the
-** hash table for each page number in the mapping section, so the hash 
-** table is never more than half full.  The expected number of collisions 
-** prior to finding a match is 1.  Each entry of the hash table is an
-** 1-based index of an entry in the mapping section of the same
-** index block.   Let K be the 1-based index of the largest entry in
-** the mapping section.  (For index blocks other than the last, K will
-** always be exactly HASHTABLE_NPAGE (4096) and for the last index block
-** K will be (mxFrame%HASHTABLE_NPAGE).)  Unused slots of the hash table
-** contain a value of 0.
-**
-** To look for page P in the hash table, first compute a hash iKey on
-** P as follows:
-**
-**      iKey = (P * 383) % HASHTABLE_NSLOT
-**
-** Then start scanning entries of the hash table, starting with iKey
-** (wrapping around to the beginning when the end of the hash table is
-** reached) until an unused hash slot is found. Let the first unused slot
-** be at index iUnused.  (iUnused might be less than iKey if there was
-** wrap-around.) Because the hash table is never more than half full,
-** the search is guaranteed to eventually hit an unused entry.  Let 
-** iMax be the value between iKey and iUnused, closest to iUnused,
-** where aHash[iMax]==P.  If there is no iMax entry (if there exists
-** no hash slot such that aHash[i]==p) then page P is not in the
-** current index block.  Otherwise the iMax-th mapping entry of the
-** current index block corresponds to the last entry that references 
-** page P.
-**
-** A hash search begins with the last index block and moves toward the
-** first index block, looking for entries corresponding to page P.  On
-** average, only two or three slots in each index block need to be
-** examined in order to either find the last entry for page P, or to
-** establish that no such entry exists in the block.  Each index block
-** holds over 4000 entries.  So two or three index blocks are sufficient
-** to cover a typical 10 megabyte WAL file, assuming 1K pages.  8 or 10
-** comparisons (on average) suffice to either locate a frame in the
-** WAL or to establish that the frame does not exist in the WAL.  This
-** is much faster than scanning the entire 10MB WAL.
-**
-** Note that entries are added in order of increasing K.  Hence, one
-** reader might be using some value K0 and a second reader that started
-** at a later time (after additional transactions were added to the WAL
-** and to the wal-index) might be using a different value K1, where K1>K0.
-** Both readers can use the same hash table and mapping section to get
-** the correct result.  There may be entries in the hash table with
-** K>K0 but to the first reader, those entries will appear to be unused
-** slots in the hash table and so the first reader will get an answer as
-** if no values greater than K0 had ever been inserted into the hash table
-** in the first place - which is what reader one wants.  Meanwhile, the
-** second reader using K1 will see additional values that were inserted
-** later, which is exactly what reader two wants.  
-**
-** When a rollback occurs, the value of K is decreased. Hash table entries
-** that correspond to frames greater than the new K value are removed
-** from the hash table at this point.
-*/
-#ifndef SQLITE_OMIT_WAL
-
-/* #include "wal.h" */
-
-/*
-** Trace output macros
-*/
-#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
-SQLITE_PRIVATE int sqlite3WalTrace = 0;
-# define WALTRACE(X)  if(sqlite3WalTrace) sqlite3DebugPrintf X
-#else
-# define WALTRACE(X)
-#endif
-
-/*
-** The maximum (and only) versions of the wal and wal-index formats
-** that may be interpreted by this version of SQLite.
-**
-** If a client begins recovering a WAL file and finds that (a) the checksum
-** values in the wal-header are correct and (b) the version field is not
-** WAL_MAX_VERSION, recovery fails and SQLite returns SQLITE_CANTOPEN.
-**
-** Similarly, if a client successfully reads a wal-index header (i.e. the 
-** checksum test is successful) and finds that the version field is not
-** WALINDEX_MAX_VERSION, then no read-transaction is opened and SQLite
-** returns SQLITE_CANTOPEN.
-*/
-#define WAL_MAX_VERSION      3007000
-#define WALINDEX_MAX_VERSION 3007000
-
-/*
-** Indices of various locking bytes.   WAL_NREADER is the number
-** of available reader locks and should be at least 3.
-*/
-#define WAL_WRITE_LOCK         0
-#define WAL_ALL_BUT_WRITE      1
-#define WAL_CKPT_LOCK          1
-#define WAL_RECOVER_LOCK       2
-#define WAL_READ_LOCK(I)       (3+(I))
-#define WAL_NREADER            (SQLITE_SHM_NLOCK-3)
-
-
-/* Object declarations */
-typedef struct WalIndexHdr WalIndexHdr;
-typedef struct WalIterator WalIterator;
-typedef struct WalCkptInfo WalCkptInfo;
-
-
-/*
-** The following object holds a copy of the wal-index header content.
-**
-** The actual header in the wal-index consists of two copies of this
-** object.
-**
-** The szPage value can be any power of 2 between 512 and 32768, inclusive.
-** Or it can be 1 to represent a 65536-byte page.  The latter case was
-** added in 3.7.1 when support for 64K pages was added.  
-*/
-struct WalIndexHdr {
-  u32 iVersion;                   /* Wal-index version */
-  u32 unused;                     /* Unused (padding) field */
-  u32 iChange;                    /* Counter incremented each transaction */
-  u8 isInit;                      /* 1 when initialized */
-  u8 bigEndCksum;                 /* True if checksums in WAL are big-endian */
-  u16 szPage;                     /* Database page size in bytes. 1==64K */
-  u32 mxFrame;                    /* Index of last valid frame in the WAL */
-  u32 nPage;                      /* Size of database in pages */
-  u32 aFrameCksum[2];             /* Checksum of last frame in log */
-  u32 aSalt[2];                   /* Two salt values copied from WAL header */
-  u32 aCksum[2];                  /* Checksum over all prior fields */
-};
-
-/*
-** A copy of the following object occurs in the wal-index immediately
-** following the second copy of the WalIndexHdr.  This object stores
-** information used by checkpoint.
-**
-** nBackfill is the number of frames in the WAL that have been written
-** back into the database. (We call the act of moving content from WAL to
-** database "backfilling".)  The nBackfill number is never greater than
-** WalIndexHdr.mxFrame.  nBackfill can only be increased by threads
-** holding the WAL_CKPT_LOCK lock (which includes a recovery thread).
-** However, a WAL_WRITE_LOCK thread can move the value of nBackfill from
-** mxFrame back to zero when the WAL is reset.
-**
-** There is one entry in aReadMark[] for each reader lock.  If a reader
-** holds read-lock K, then the value in aReadMark[K] is no greater than
-** the mxFrame for that reader.  The value READMARK_NOT_USED (0xffffffff)
-** for any aReadMark[] means that entry is unused.  aReadMark[0] is 
-** a special case; its value is never used and it exists as a place-holder
-** to avoid having to offset aReadMark[] indexs by one.  Readers holding
-** WAL_READ_LOCK(0) always ignore the entire WAL and read all content
-** directly from the database.
-**
-** The value of aReadMark[K] may only be changed by a thread that
-** is holding an exclusive lock on WAL_READ_LOCK(K).  Thus, the value of
-** aReadMark[K] cannot changed while there is a reader is using that mark
-** since the reader will be holding a shared lock on WAL_READ_LOCK(K).
-**
-** The checkpointer may only transfer frames from WAL to database where
-** the frame numbers are less than or equal to every aReadMark[] that is
-** in use (that is, every aReadMark[j] for which there is a corresponding
-** WAL_READ_LOCK(j)).  New readers (usually) pick the aReadMark[] with the
-** largest value and will increase an unused aReadMark[] to mxFrame if there
-** is not already an aReadMark[] equal to mxFrame.  The exception to the
-** previous sentence is when nBackfill equals mxFrame (meaning that everything
-** in the WAL has been backfilled into the database) then new readers
-** will choose aReadMark[0] which has value 0 and hence such reader will
-** get all their all content directly from the database file and ignore 
-** the WAL.
-**
-** Writers normally append new frames to the end of the WAL.  However,
-** if nBackfill equals mxFrame (meaning that all WAL content has been
-** written back into the database) and if no readers are using the WAL
-** (in other words, if there are no WAL_READ_LOCK(i) where i>0) then
-** the writer will first "reset" the WAL back to the beginning and start
-** writing new content beginning at frame 1.
-**
-** We assume that 32-bit loads are atomic and so no locks are needed in
-** order to read from any aReadMark[] entries.
-*/
-struct WalCkptInfo {
-  u32 nBackfill;                  /* Number of WAL frames backfilled into DB */
-  u32 aReadMark[WAL_NREADER];     /* Reader marks */
-};
-#define READMARK_NOT_USED  0xffffffff
-
-
-/* A block of WALINDEX_LOCK_RESERVED bytes beginning at
-** WALINDEX_LOCK_OFFSET is reserved for locks. Since some systems
-** only support mandatory file-locks, we do not read or write data
-** from the region of the file on which locks are applied.
-*/
-#define WALINDEX_LOCK_OFFSET   (sizeof(WalIndexHdr)*2 + sizeof(WalCkptInfo))
-#define WALINDEX_LOCK_RESERVED 16
-#define WALINDEX_HDR_SIZE      (WALINDEX_LOCK_OFFSET+WALINDEX_LOCK_RESERVED)
-
-/* Size of header before each frame in wal */
-#define WAL_FRAME_HDRSIZE 24
-
-/* Size of write ahead log header, including checksum. */
-/* #define WAL_HDRSIZE 24 */
-#define WAL_HDRSIZE 32
-
-/* WAL magic value. Either this value, or the same value with the least
-** significant bit also set (WAL_MAGIC | 0x00000001) is stored in 32-bit
-** big-endian format in the first 4 bytes of a WAL file.
-**
-** If the LSB is set, then the checksums for each frame within the WAL
-** file are calculated by treating all data as an array of 32-bit 
-** big-endian words. Otherwise, they are calculated by interpreting 
-** all data as 32-bit little-endian words.
-*/
-#define WAL_MAGIC 0x377f0682
-
-/*
-** Return the offset of frame iFrame in the write-ahead log file, 
-** assuming a database page size of szPage bytes. The offset returned
-** is to the start of the write-ahead log frame-header.
-*/
-#define walFrameOffset(iFrame, szPage) (                               \
-  WAL_HDRSIZE + ((iFrame)-1)*(i64)((szPage)+WAL_FRAME_HDRSIZE)         \
-)
-
-/*
-** An open write-ahead log file is represented by an instance of the
-** following object.
-*/
-struct Wal {
-  sqlite3_vfs *pVfs;         /* The VFS used to create pDbFd */
-  sqlite3_file *pDbFd;       /* File handle for the database file */
-  sqlite3_file *pWalFd;      /* File handle for WAL file */
-  u32 iCallback;             /* Value to pass to log callback (or 0) */
-  i64 mxWalSize;             /* Truncate WAL to this size upon reset */
-  int nWiData;               /* Size of array apWiData */
-  int szFirstBlock;          /* Size of first block written to WAL file */
-  volatile u32 **apWiData;   /* Pointer to wal-index content in memory */
-  u32 szPage;                /* Database page size */
-  i16 readLock;              /* Which read lock is being held.  -1 for none */
-  u8 syncFlags;              /* Flags to use to sync header writes */
-  u8 exclusiveMode;          /* Non-zero if connection is in exclusive mode */
-  u8 writeLock;              /* True if in a write transaction */
-  u8 ckptLock;               /* True if holding a checkpoint lock */
-  u8 readOnly;               /* WAL_RDWR, WAL_RDONLY, or WAL_SHM_RDONLY */
-  u8 truncateOnCommit;       /* True to truncate WAL file on commit */
-  u8 syncHeader;             /* Fsync the WAL header if true */
-  u8 padToSectorBoundary;    /* Pad transactions out to the next sector */
-  WalIndexHdr hdr;           /* Wal-index header for current transaction */
-  u32 minFrame;              /* Ignore wal frames before this one */
-  const char *zWalName;      /* Name of WAL file */
-  u32 nCkpt;                 /* Checkpoint sequence counter in the wal-header */
-#ifdef SQLITE_DEBUG
-  u8 lockError;              /* True if a locking error has occurred */
-#endif
-};
-
-/*
-** Candidate values for Wal.exclusiveMode.
-*/
-#define WAL_NORMAL_MODE     0
-#define WAL_EXCLUSIVE_MODE  1     
-#define WAL_HEAPMEMORY_MODE 2
-
-/*
-** Possible values for WAL.readOnly
-*/
-#define WAL_RDWR        0    /* Normal read/write connection */
-#define WAL_RDONLY      1    /* The WAL file is readonly */
-#define WAL_SHM_RDONLY  2    /* The SHM file is readonly */
-
-/*
-** Each page of the wal-index mapping contains a hash-table made up of
-** an array of HASHTABLE_NSLOT elements of the following type.
-*/
-typedef u16 ht_slot;
-
-/*
-** This structure is used to implement an iterator that loops through
-** all frames in the WAL in database page order. Where two or more frames
-** correspond to the same database page, the iterator visits only the 
-** frame most recently written to the WAL (in other words, the frame with
-** the largest index).
-**
-** The internals of this structure are only accessed by:
-**
-**   walIteratorInit() - Create a new iterator,
-**   walIteratorNext() - Step an iterator,
-**   walIteratorFree() - Free an iterator.
-**
-** This functionality is used by the checkpoint code (see walCheckpoint()).
-*/
-struct WalIterator {
-  int iPrior;                     /* Last result returned from the iterator */
-  int nSegment;                   /* Number of entries in aSegment[] */
-  struct WalSegment {
-    int iNext;                    /* Next slot in aIndex[] not yet returned */
-    ht_slot *aIndex;              /* i0, i1, i2... such that aPgno[iN] ascend */
-    u32 *aPgno;                   /* Array of page numbers. */
-    int nEntry;                   /* Nr. of entries in aPgno[] and aIndex[] */
-    int iZero;                    /* Frame number associated with aPgno[0] */
-  } aSegment[1];                  /* One for every 32KB page in the wal-index */
-};
-
-/*
-** Define the parameters of the hash tables in the wal-index file. There
-** is a hash-table following every HASHTABLE_NPAGE page numbers in the
-** wal-index.
-**
-** Changing any of these constants will alter the wal-index format and
-** create incompatibilities.
-*/
-#define HASHTABLE_NPAGE      4096                 /* Must be power of 2 */
-#define HASHTABLE_HASH_1     383                  /* Should be prime */
-#define HASHTABLE_NSLOT      (HASHTABLE_NPAGE*2)  /* Must be a power of 2 */
-
-/* 
-** The block of page numbers associated with the first hash-table in a
-** wal-index is smaller than usual. This is so that there is a complete
-** hash-table on each aligned 32KB page of the wal-index.
-*/
-#define HASHTABLE_NPAGE_ONE  (HASHTABLE_NPAGE - (WALINDEX_HDR_SIZE/sizeof(u32)))
-
-/* The wal-index is divided into pages of WALINDEX_PGSZ bytes each. */
-#define WALINDEX_PGSZ   (                                         \
-    sizeof(ht_slot)*HASHTABLE_NSLOT + HASHTABLE_NPAGE*sizeof(u32) \
-)
-
-/*
-** Obtain a pointer to the iPage'th page of the wal-index. The wal-index
-** is broken into pages of WALINDEX_PGSZ bytes. Wal-index pages are
-** numbered from zero.
-**
-** If this call is successful, *ppPage is set to point to the wal-index
-** page and SQLITE_OK is returned. If an error (an OOM or VFS error) occurs,
-** then an SQLite error code is returned and *ppPage is set to 0.
-*/
-static int walIndexPage(Wal *pWal, int iPage, volatile u32 **ppPage){
-  int rc = SQLITE_OK;
-
-  /* Enlarge the pWal->apWiData[] array if required */
-  if( pWal->nWiData<=iPage ){
-    int nByte = sizeof(u32*)*(iPage+1);
-    volatile u32 **apNew;
-    apNew = (volatile u32 **)sqlite3_realloc64((void *)pWal->apWiData, nByte);
-    if( !apNew ){
-      *ppPage = 0;
-      return SQLITE_NOMEM;
-    }
-    memset((void*)&apNew[pWal->nWiData], 0,
-           sizeof(u32*)*(iPage+1-pWal->nWiData));
-    pWal->apWiData = apNew;
-    pWal->nWiData = iPage+1;
-  }
-
-  /* Request a pointer to the required page from the VFS */
-  if( pWal->apWiData[iPage]==0 ){
-    if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
-      pWal->apWiData[iPage] = (u32 volatile *)sqlite3MallocZero(WALINDEX_PGSZ);
-      if( !pWal->apWiData[iPage] ) rc = SQLITE_NOMEM;
-    }else{
-      rc = sqlite3OsShmMap(pWal->pDbFd, iPage, WALINDEX_PGSZ, 
-          pWal->writeLock, (void volatile **)&pWal->apWiData[iPage]
-      );
-      if( rc==SQLITE_READONLY ){
-        pWal->readOnly |= WAL_SHM_RDONLY;
-        rc = SQLITE_OK;
-      }
-    }
-  }
-
-  *ppPage = pWal->apWiData[iPage];
-  assert( iPage==0 || *ppPage || rc!=SQLITE_OK );
-  return rc;
-}
-
-/*
-** Return a pointer to the WalCkptInfo structure in the wal-index.
-*/
-static volatile WalCkptInfo *walCkptInfo(Wal *pWal){
-  assert( pWal->nWiData>0 && pWal->apWiData[0] );
-  return (volatile WalCkptInfo*)&(pWal->apWiData[0][sizeof(WalIndexHdr)/2]);
-}
-
-/*
-** Return a pointer to the WalIndexHdr structure in the wal-index.
-*/
-static volatile WalIndexHdr *walIndexHdr(Wal *pWal){
-  assert( pWal->nWiData>0 && pWal->apWiData[0] );
-  return (volatile WalIndexHdr*)pWal->apWiData[0];
-}
-
-/*
-** The argument to this macro must be of type u32. On a little-endian
-** architecture, it returns the u32 value that results from interpreting
-** the 4 bytes as a big-endian value. On a big-endian architecture, it
-** returns the value that would be produced by interpreting the 4 bytes
-** of the input value as a little-endian integer.
-*/
-#define BYTESWAP32(x) ( \
-    (((x)&0x000000FF)<<24) + (((x)&0x0000FF00)<<8)  \
-  + (((x)&0x00FF0000)>>8)  + (((x)&0xFF000000)>>24) \
-)
-
-/*
-** Generate or extend an 8 byte checksum based on the data in 
-** array aByte[] and the initial values of aIn[0] and aIn[1] (or
-** initial values of 0 and 0 if aIn==NULL).
-**
-** The checksum is written back into aOut[] before returning.
-**
-** nByte must be a positive multiple of 8.
-*/
-static void walChecksumBytes(
-  int nativeCksum, /* True for native byte-order, false for non-native */
-  u8 *a,           /* Content to be checksummed */
-  int nByte,       /* Bytes of content in a[].  Must be a multiple of 8. */
-  const u32 *aIn,  /* Initial checksum value input */
-  u32 *aOut        /* OUT: Final checksum value output */
-){
-  u32 s1, s2;
-  u32 *aData = (u32 *)a;
-  u32 *aEnd = (u32 *)&a[nByte];
-
-  if( aIn ){
-    s1 = aIn[0];
-    s2 = aIn[1];
-  }else{
-    s1 = s2 = 0;
-  }
-
-  assert( nByte>=8 );
-  assert( (nByte&0x00000007)==0 );
-
-  if( nativeCksum ){
-    do {
-      s1 += *aData++ + s2;
-      s2 += *aData++ + s1;
-    }while( aData<aEnd );
-  }else{
-    do {
-      s1 += BYTESWAP32(aData[0]) + s2;
-      s2 += BYTESWAP32(aData[1]) + s1;
-      aData += 2;
-    }while( aData<aEnd );
-  }
-
-  aOut[0] = s1;
-  aOut[1] = s2;
-}
-
-static void walShmBarrier(Wal *pWal){
-  if( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE ){
-    sqlite3OsShmBarrier(pWal->pDbFd);
-  }
-}
-
-/*
-** Write the header information in pWal->hdr into the wal-index.
-**
-** The checksum on pWal->hdr is updated before it is written.
-*/
-static void walIndexWriteHdr(Wal *pWal){
-  volatile WalIndexHdr *aHdr = walIndexHdr(pWal);
-  const int nCksum = offsetof(WalIndexHdr, aCksum);
-
-  assert( pWal->writeLock );
-  pWal->hdr.isInit = 1;
-  pWal->hdr.iVersion = WALINDEX_MAX_VERSION;
-  walChecksumBytes(1, (u8*)&pWal->hdr, nCksum, 0, pWal->hdr.aCksum);
-  memcpy((void*)&aHdr[1], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
-  walShmBarrier(pWal);
-  memcpy((void*)&aHdr[0], (const void*)&pWal->hdr, sizeof(WalIndexHdr));
-}
-
-/*
-** This function encodes a single frame header and writes it to a buffer
-** supplied by the caller. A frame-header is made up of a series of 
-** 4-byte big-endian integers, as follows:
-**
-**     0: Page number.
-**     4: For commit records, the size of the database image in pages 
-**        after the commit. For all other records, zero.
-**     8: Salt-1 (copied from the wal-header)
-**    12: Salt-2 (copied from the wal-header)
-**    16: Checksum-1.
-**    20: Checksum-2.
-*/
-static void walEncodeFrame(
-  Wal *pWal,                      /* The write-ahead log */
-  u32 iPage,                      /* Database page number for frame */
-  u32 nTruncate,                  /* New db size (or 0 for non-commit frames) */
-  u8 *aData,                      /* Pointer to page data */
-  u8 *aFrame                      /* OUT: Write encoded frame here */
-){
-  int nativeCksum;                /* True for native byte-order checksums */
-  u32 *aCksum = pWal->hdr.aFrameCksum;
-  assert( WAL_FRAME_HDRSIZE==24 );
-  sqlite3Put4byte(&aFrame[0], iPage);
-  sqlite3Put4byte(&aFrame[4], nTruncate);
-  memcpy(&aFrame[8], pWal->hdr.aSalt, 8);
-
-  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
-  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
-  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
-
-  sqlite3Put4byte(&aFrame[16], aCksum[0]);
-  sqlite3Put4byte(&aFrame[20], aCksum[1]);
-}
-
-/*
-** Check to see if the frame with header in aFrame[] and content
-** in aData[] is valid.  If it is a valid frame, fill *piPage and
-** *pnTruncate and return true.  Return if the frame is not valid.
-*/
-static int walDecodeFrame(
-  Wal *pWal,                      /* The write-ahead log */
-  u32 *piPage,                    /* OUT: Database page number for frame */
-  u32 *pnTruncate,                /* OUT: New db size (or 0 if not commit) */
-  u8 *aData,                      /* Pointer to page data (for checksum) */
-  u8 *aFrame                      /* Frame data */
-){
-  int nativeCksum;                /* True for native byte-order checksums */
-  u32 *aCksum = pWal->hdr.aFrameCksum;
-  u32 pgno;                       /* Page number of the frame */
-  assert( WAL_FRAME_HDRSIZE==24 );
-
-  /* A frame is only valid if the salt values in the frame-header
-  ** match the salt values in the wal-header. 
-  */
-  if( memcmp(&pWal->hdr.aSalt, &aFrame[8], 8)!=0 ){
-    return 0;
-  }
-
-  /* A frame is only valid if the page number is creater than zero.
-  */
-  pgno = sqlite3Get4byte(&aFrame[0]);
-  if( pgno==0 ){
-    return 0;
-  }
-
-  /* A frame is only valid if a checksum of the WAL header,
-  ** all prior frams, the first 16 bytes of this frame-header, 
-  ** and the frame-data matches the checksum in the last 8 
-  ** bytes of this frame-header.
-  */
-  nativeCksum = (pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN);
-  walChecksumBytes(nativeCksum, aFrame, 8, aCksum, aCksum);
-  walChecksumBytes(nativeCksum, aData, pWal->szPage, aCksum, aCksum);
-  if( aCksum[0]!=sqlite3Get4byte(&aFrame[16]) 
-   || aCksum[1]!=sqlite3Get4byte(&aFrame[20]) 
-  ){
-    /* Checksum failed. */
-    return 0;
-  }
-
-  /* If we reach this point, the frame is valid.  Return the page number
-  ** and the new database size.
-  */
-  *piPage = pgno;
-  *pnTruncate = sqlite3Get4byte(&aFrame[4]);
-  return 1;
-}
-
-
-#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
-/*
-** Names of locks.  This routine is used to provide debugging output and is not
-** a part of an ordinary build.
-*/
-static const char *walLockName(int lockIdx){
-  if( lockIdx==WAL_WRITE_LOCK ){
-    return "WRITE-LOCK";
-  }else if( lockIdx==WAL_CKPT_LOCK ){
-    return "CKPT-LOCK";
-  }else if( lockIdx==WAL_RECOVER_LOCK ){
-    return "RECOVER-LOCK";
-  }else{
-    static char zName[15];
-    sqlite3_snprintf(sizeof(zName), zName, "READ-LOCK[%d]",
-                     lockIdx-WAL_READ_LOCK(0));
-    return zName;
-  }
-}
-#endif /*defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
-    
-
-/*
-** Set or release locks on the WAL.  Locks are either shared or exclusive.
-** A lock cannot be moved directly between shared and exclusive - it must go
-** through the unlocked state first.
-**
-** In locking_mode=EXCLUSIVE, all of these routines become no-ops.
-*/
-static int walLockShared(Wal *pWal, int lockIdx){
-  int rc;
-  if( pWal->exclusiveMode ) return SQLITE_OK;
-  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
-                        SQLITE_SHM_LOCK | SQLITE_SHM_SHARED);
-  WALTRACE(("WAL%p: acquire SHARED-%s %s\n", pWal,
-            walLockName(lockIdx), rc ? "failed" : "ok"));
-  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
-  return rc;
-}
-static void walUnlockShared(Wal *pWal, int lockIdx){
-  if( pWal->exclusiveMode ) return;
-  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, 1,
-                         SQLITE_SHM_UNLOCK | SQLITE_SHM_SHARED);
-  WALTRACE(("WAL%p: release SHARED-%s\n", pWal, walLockName(lockIdx)));
-}
-static int walLockExclusive(Wal *pWal, int lockIdx, int n, int fBlock){
-  int rc;
-  if( pWal->exclusiveMode ) return SQLITE_OK;
-  if( fBlock ) sqlite3OsFileControl(pWal->pDbFd, SQLITE_FCNTL_WAL_BLOCK, 0);
-  rc = sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
-                        SQLITE_SHM_LOCK | SQLITE_SHM_EXCLUSIVE);
-  WALTRACE(("WAL%p: acquire EXCLUSIVE-%s cnt=%d %s\n", pWal,
-            walLockName(lockIdx), n, rc ? "failed" : "ok"));
-  VVA_ONLY( pWal->lockError = (u8)(rc!=SQLITE_OK && rc!=SQLITE_BUSY); )
-  return rc;
-}
-static void walUnlockExclusive(Wal *pWal, int lockIdx, int n){
-  if( pWal->exclusiveMode ) return;
-  (void)sqlite3OsShmLock(pWal->pDbFd, lockIdx, n,
-                         SQLITE_SHM_UNLOCK | SQLITE_SHM_EXCLUSIVE);
-  WALTRACE(("WAL%p: release EXCLUSIVE-%s cnt=%d\n", pWal,
-             walLockName(lockIdx), n));
-}
-
-/*
-** Compute a hash on a page number.  The resulting hash value must land
-** between 0 and (HASHTABLE_NSLOT-1).  The walHashNext() function advances
-** the hash to the next value in the event of a collision.
-*/
-static int walHash(u32 iPage){
-  assert( iPage>0 );
-  assert( (HASHTABLE_NSLOT & (HASHTABLE_NSLOT-1))==0 );
-  return (iPage*HASHTABLE_HASH_1) & (HASHTABLE_NSLOT-1);
-}
-static int walNextHash(int iPriorHash){
-  return (iPriorHash+1)&(HASHTABLE_NSLOT-1);
-}
-
-/* 
-** Return pointers to the hash table and page number array stored on
-** page iHash of the wal-index. The wal-index is broken into 32KB pages
-** numbered starting from 0.
-**
-** Set output variable *paHash to point to the start of the hash table
-** in the wal-index file. Set *piZero to one less than the frame 
-** number of the first frame indexed by this hash table. If a
-** slot in the hash table is set to N, it refers to frame number 
-** (*piZero+N) in the log.
-**
-** Finally, set *paPgno so that *paPgno[1] is the page number of the
-** first frame indexed by the hash table, frame (*piZero+1).
-*/
-static int walHashGet(
-  Wal *pWal,                      /* WAL handle */
-  int iHash,                      /* Find the iHash'th table */
-  volatile ht_slot **paHash,      /* OUT: Pointer to hash index */
-  volatile u32 **paPgno,          /* OUT: Pointer to page number array */
-  u32 *piZero                     /* OUT: Frame associated with *paPgno[0] */
-){
-  int rc;                         /* Return code */
-  volatile u32 *aPgno;
-
-  rc = walIndexPage(pWal, iHash, &aPgno);
-  assert( rc==SQLITE_OK || iHash>0 );
-
-  if( rc==SQLITE_OK ){
-    u32 iZero;
-    volatile ht_slot *aHash;
-
-    aHash = (volatile ht_slot *)&aPgno[HASHTABLE_NPAGE];
-    if( iHash==0 ){
-      aPgno = &aPgno[WALINDEX_HDR_SIZE/sizeof(u32)];
-      iZero = 0;
-    }else{
-      iZero = HASHTABLE_NPAGE_ONE + (iHash-1)*HASHTABLE_NPAGE;
-    }
-  
-    *paPgno = &aPgno[-1];
-    *paHash = aHash;
-    *piZero = iZero;
-  }
-  return rc;
-}
-
-/*
-** Return the number of the wal-index page that contains the hash-table
-** and page-number array that contain entries corresponding to WAL frame
-** iFrame. The wal-index is broken up into 32KB pages. Wal-index pages 
-** are numbered starting from 0.
-*/
-static int walFramePage(u32 iFrame){
-  int iHash = (iFrame+HASHTABLE_NPAGE-HASHTABLE_NPAGE_ONE-1) / HASHTABLE_NPAGE;
-  assert( (iHash==0 || iFrame>HASHTABLE_NPAGE_ONE)
-       && (iHash>=1 || iFrame<=HASHTABLE_NPAGE_ONE)
-       && (iHash<=1 || iFrame>(HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE))
-       && (iHash>=2 || iFrame<=HASHTABLE_NPAGE_ONE+HASHTABLE_NPAGE)
-       && (iHash<=2 || iFrame>(HASHTABLE_NPAGE_ONE+2*HASHTABLE_NPAGE))
-  );
-  return iHash;
-}
-
-/*
-** Return the page number associated with frame iFrame in this WAL.
-*/
-static u32 walFramePgno(Wal *pWal, u32 iFrame){
-  int iHash = walFramePage(iFrame);
-  if( iHash==0 ){
-    return pWal->apWiData[0][WALINDEX_HDR_SIZE/sizeof(u32) + iFrame - 1];
-  }
-  return pWal->apWiData[iHash][(iFrame-1-HASHTABLE_NPAGE_ONE)%HASHTABLE_NPAGE];
-}
-
-/*
-** Remove entries from the hash table that point to WAL slots greater
-** than pWal->hdr.mxFrame.
-**
-** This function is called whenever pWal->hdr.mxFrame is decreased due
-** to a rollback or savepoint.
-**
-** At most only the hash table containing pWal->hdr.mxFrame needs to be
-** updated.  Any later hash tables will be automatically cleared when
-** pWal->hdr.mxFrame advances to the point where those hash tables are
-** actually needed.
-*/
-static void walCleanupHash(Wal *pWal){
-  volatile ht_slot *aHash = 0;    /* Pointer to hash table to clear */
-  volatile u32 *aPgno = 0;        /* Page number array for hash table */
-  u32 iZero = 0;                  /* frame == (aHash[x]+iZero) */
-  int iLimit = 0;                 /* Zero values greater than this */
-  int nByte;                      /* Number of bytes to zero in aPgno[] */
-  int i;                          /* Used to iterate through aHash[] */
-
-  assert( pWal->writeLock );
-  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE-1 );
-  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE );
-  testcase( pWal->hdr.mxFrame==HASHTABLE_NPAGE_ONE+1 );
-
-  if( pWal->hdr.mxFrame==0 ) return;
-
-  /* Obtain pointers to the hash-table and page-number array containing 
-  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
-  ** that the page said hash-table and array reside on is already mapped.
-  */
-  assert( pWal->nWiData>walFramePage(pWal->hdr.mxFrame) );
-  assert( pWal->apWiData[walFramePage(pWal->hdr.mxFrame)] );
-  walHashGet(pWal, walFramePage(pWal->hdr.mxFrame), &aHash, &aPgno, &iZero);
-
-  /* Zero all hash-table entries that correspond to frame numbers greater
-  ** than pWal->hdr.mxFrame.
-  */
-  iLimit = pWal->hdr.mxFrame - iZero;
-  assert( iLimit>0 );
-  for(i=0; i<HASHTABLE_NSLOT; i++){
-    if( aHash[i]>iLimit ){
-      aHash[i] = 0;
-    }
-  }
-  
-  /* Zero the entries in the aPgno array that correspond to frames with
-  ** frame numbers greater than pWal->hdr.mxFrame. 
-  */
-  nByte = (int)((char *)aHash - (char *)&aPgno[iLimit+1]);
-  memset((void *)&aPgno[iLimit+1], 0, nByte);
-
-#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
-  /* Verify that the every entry in the mapping region is still reachable
-  ** via the hash table even after the cleanup.
-  */
-  if( iLimit ){
-    int j;           /* Loop counter */
-    int iKey;        /* Hash key */
-    for(j=1; j<=iLimit; j++){
-      for(iKey=walHash(aPgno[j]); aHash[iKey]; iKey=walNextHash(iKey)){
-        if( aHash[iKey]==j ) break;
-      }
-      assert( aHash[iKey]==j );
-    }
-  }
-#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
-}
-
-
-/*
-** Set an entry in the wal-index that will map database page number
-** pPage into WAL frame iFrame.
-*/
-static int walIndexAppend(Wal *pWal, u32 iFrame, u32 iPage){
-  int rc;                         /* Return code */
-  u32 iZero = 0;                  /* One less than frame number of aPgno[1] */
-  volatile u32 *aPgno = 0;        /* Page number array */
-  volatile ht_slot *aHash = 0;    /* Hash table */
-
-  rc = walHashGet(pWal, walFramePage(iFrame), &aHash, &aPgno, &iZero);
-
-  /* Assuming the wal-index file was successfully mapped, populate the
-  ** page number array and hash table entry.
-  */
-  if( rc==SQLITE_OK ){
-    int iKey;                     /* Hash table key */
-    int idx;                      /* Value to write to hash-table slot */
-    int nCollide;                 /* Number of hash collisions */
-
-    idx = iFrame - iZero;
-    assert( idx <= HASHTABLE_NSLOT/2 + 1 );
-    
-    /* If this is the first entry to be added to this hash-table, zero the
-    ** entire hash table and aPgno[] array before proceeding. 
-    */
-    if( idx==1 ){
-      int nByte = (int)((u8 *)&aHash[HASHTABLE_NSLOT] - (u8 *)&aPgno[1]);
-      memset((void*)&aPgno[1], 0, nByte);
-    }
-
-    /* If the entry in aPgno[] is already set, then the previous writer
-    ** must have exited unexpectedly in the middle of a transaction (after
-    ** writing one or more dirty pages to the WAL to free up memory). 
-    ** Remove the remnants of that writers uncommitted transaction from 
-    ** the hash-table before writing any new entries.
-    */
-    if( aPgno[idx] ){
-      walCleanupHash(pWal);
-      assert( !aPgno[idx] );
-    }
-
-    /* Write the aPgno[] array entry and the hash-table slot. */
-    nCollide = idx;
-    for(iKey=walHash(iPage); aHash[iKey]; iKey=walNextHash(iKey)){
-      if( (nCollide--)==0 ) return SQLITE_CORRUPT_BKPT;
-    }
-    aPgno[idx] = iPage;
-    aHash[iKey] = (ht_slot)idx;
-
-#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
-    /* Verify that the number of entries in the hash table exactly equals
-    ** the number of entries in the mapping region.
-    */
-    {
-      int i;           /* Loop counter */
-      int nEntry = 0;  /* Number of entries in the hash table */
-      for(i=0; i<HASHTABLE_NSLOT; i++){ if( aHash[i] ) nEntry++; }
-      assert( nEntry==idx );
-    }
-
-    /* Verify that the every entry in the mapping region is reachable
-    ** via the hash table.  This turns out to be a really, really expensive
-    ** thing to check, so only do this occasionally - not on every
-    ** iteration.
-    */
-    if( (idx&0x3ff)==0 ){
-      int i;           /* Loop counter */
-      for(i=1; i<=idx; i++){
-        for(iKey=walHash(aPgno[i]); aHash[iKey]; iKey=walNextHash(iKey)){
-          if( aHash[iKey]==i ) break;
-        }
-        assert( aHash[iKey]==i );
-      }
-    }
-#endif /* SQLITE_ENABLE_EXPENSIVE_ASSERT */
-  }
-
-
-  return rc;
-}
-
-
-/*
-** Recover the wal-index by reading the write-ahead log file. 
-**
-** This routine first tries to establish an exclusive lock on the
-** wal-index to prevent other threads/processes from doing anything
-** with the WAL or wal-index while recovery is running.  The
-** WAL_RECOVER_LOCK is also held so that other threads will know
-** that this thread is running recovery.  If unable to establish
-** the necessary locks, this routine returns SQLITE_BUSY.
-*/
-static int walIndexRecover(Wal *pWal){
-  int rc;                         /* Return Code */
-  i64 nSize;                      /* Size of log file */
-  u32 aFrameCksum[2] = {0, 0};
-  int iLock;                      /* Lock offset to lock for checkpoint */
-  int nLock;                      /* Number of locks to hold */
-
-  /* Obtain an exclusive lock on all byte in the locking range not already
-  ** locked by the caller. The caller is guaranteed to have locked the
-  ** WAL_WRITE_LOCK byte, and may have also locked the WAL_CKPT_LOCK byte.
-  ** If successful, the same bytes that are locked here are unlocked before
-  ** this function returns.
-  */
-  assert( pWal->ckptLock==1 || pWal->ckptLock==0 );
-  assert( WAL_ALL_BUT_WRITE==WAL_WRITE_LOCK+1 );
-  assert( WAL_CKPT_LOCK==WAL_ALL_BUT_WRITE );
-  assert( pWal->writeLock );
-  iLock = WAL_ALL_BUT_WRITE + pWal->ckptLock;
-  nLock = SQLITE_SHM_NLOCK - iLock;
-  rc = walLockExclusive(pWal, iLock, nLock, 0);
-  if( rc ){
-    return rc;
-  }
-  WALTRACE(("WAL%p: recovery begin...\n", pWal));
-
-  memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
-
-  rc = sqlite3OsFileSize(pWal->pWalFd, &nSize);
-  if( rc!=SQLITE_OK ){
-    goto recovery_error;
-  }
-
-  if( nSize>WAL_HDRSIZE ){
-    u8 aBuf[WAL_HDRSIZE];         /* Buffer to load WAL header into */
-    u8 *aFrame = 0;               /* Malloc'd buffer to load entire frame */
-    int szFrame;                  /* Number of bytes in buffer aFrame[] */
-    u8 *aData;                    /* Pointer to data part of aFrame buffer */
-    int iFrame;                   /* Index of last frame read */
-    i64 iOffset;                  /* Next offset to read from log file */
-    int szPage;                   /* Page size according to the log */
-    u32 magic;                    /* Magic value read from WAL header */
-    u32 version;                  /* Magic value read from WAL header */
-    int isValid;                  /* True if this frame is valid */
-
-    /* Read in the WAL header. */
-    rc = sqlite3OsRead(pWal->pWalFd, aBuf, WAL_HDRSIZE, 0);
-    if( rc!=SQLITE_OK ){
-      goto recovery_error;
-    }
-
-    /* If the database page size is not a power of two, or is greater than
-    ** SQLITE_MAX_PAGE_SIZE, conclude that the WAL file contains no valid 
-    ** data. Similarly, if the 'magic' value is invalid, ignore the whole
-    ** WAL file.
-    */
-    magic = sqlite3Get4byte(&aBuf[0]);
-    szPage = sqlite3Get4byte(&aBuf[8]);
-    if( (magic&0xFFFFFFFE)!=WAL_MAGIC 
-     || szPage&(szPage-1) 
-     || szPage>SQLITE_MAX_PAGE_SIZE 
-     || szPage<512 
-    ){
-      goto finished;
-    }
-    pWal->hdr.bigEndCksum = (u8)(magic&0x00000001);
-    pWal->szPage = szPage;
-    pWal->nCkpt = sqlite3Get4byte(&aBuf[12]);
-    memcpy(&pWal->hdr.aSalt, &aBuf[16], 8);
-
-    /* Verify that the WAL header checksum is correct */
-    walChecksumBytes(pWal->hdr.bigEndCksum==SQLITE_BIGENDIAN, 
-        aBuf, WAL_HDRSIZE-2*4, 0, pWal->hdr.aFrameCksum
-    );
-    if( pWal->hdr.aFrameCksum[0]!=sqlite3Get4byte(&aBuf[24])
-     || pWal->hdr.aFrameCksum[1]!=sqlite3Get4byte(&aBuf[28])
-    ){
-      goto finished;
-    }
-
-    /* Verify that the version number on the WAL format is one that
-    ** are able to understand */
-    version = sqlite3Get4byte(&aBuf[4]);
-    if( version!=WAL_MAX_VERSION ){
-      rc = SQLITE_CANTOPEN_BKPT;
-      goto finished;
-    }
-
-    /* Malloc a buffer to read frames into. */
-    szFrame = szPage + WAL_FRAME_HDRSIZE;
-    aFrame = (u8 *)sqlite3_malloc64(szFrame);
-    if( !aFrame ){
-      rc = SQLITE_NOMEM;
-      goto recovery_error;
-    }
-    aData = &aFrame[WAL_FRAME_HDRSIZE];
-
-    /* Read all frames from the log file. */
-    iFrame = 0;
-    for(iOffset=WAL_HDRSIZE; (iOffset+szFrame)<=nSize; iOffset+=szFrame){
-      u32 pgno;                   /* Database page number for frame */
-      u32 nTruncate;              /* dbsize field from frame header */
-
-      /* Read and decode the next log frame. */
-      iFrame++;
-      rc = sqlite3OsRead(pWal->pWalFd, aFrame, szFrame, iOffset);
-      if( rc!=SQLITE_OK ) break;
-      isValid = walDecodeFrame(pWal, &pgno, &nTruncate, aData, aFrame);
-      if( !isValid ) break;
-      rc = walIndexAppend(pWal, iFrame, pgno);
-      if( rc!=SQLITE_OK ) break;
-
-      /* If nTruncate is non-zero, this is a commit record. */
-      if( nTruncate ){
-        pWal->hdr.mxFrame = iFrame;
-        pWal->hdr.nPage = nTruncate;
-        pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
-        testcase( szPage<=32768 );
-        testcase( szPage>=65536 );
-        aFrameCksum[0] = pWal->hdr.aFrameCksum[0];
-        aFrameCksum[1] = pWal->hdr.aFrameCksum[1];
-      }
-    }
-
-    sqlite3_free(aFrame);
-  }
-
-finished:
-  if( rc==SQLITE_OK ){
-    volatile WalCkptInfo *pInfo;
-    int i;
-    pWal->hdr.aFrameCksum[0] = aFrameCksum[0];
-    pWal->hdr.aFrameCksum[1] = aFrameCksum[1];
-    walIndexWriteHdr(pWal);
-
-    /* Reset the checkpoint-header. This is safe because this thread is 
-    ** currently holding locks that exclude all other readers, writers and
-    ** checkpointers.
-    */
-    pInfo = walCkptInfo(pWal);
-    pInfo->nBackfill = 0;
-    pInfo->aReadMark[0] = 0;
-    for(i=1; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
-    if( pWal->hdr.mxFrame ) pInfo->aReadMark[1] = pWal->hdr.mxFrame;
-
-    /* If more than one frame was recovered from the log file, report an
-    ** event via sqlite3_log(). This is to help with identifying performance
-    ** problems caused by applications routinely shutting down without
-    ** checkpointing the log file.
-    */
-    if( pWal->hdr.nPage ){
-      sqlite3_log(SQLITE_NOTICE_RECOVER_WAL,
-          "recovered %d frames from WAL file %s",
-          pWal->hdr.mxFrame, pWal->zWalName
-      );
-    }
-  }
-
-recovery_error:
-  WALTRACE(("WAL%p: recovery %s\n", pWal, rc ? "failed" : "ok"));
-  walUnlockExclusive(pWal, iLock, nLock);
-  return rc;
-}
-
-/*
-** Close an open wal-index.
-*/
-static void walIndexClose(Wal *pWal, int isDelete){
-  if( pWal->exclusiveMode==WAL_HEAPMEMORY_MODE ){
-    int i;
-    for(i=0; i<pWal->nWiData; i++){
-      sqlite3_free((void *)pWal->apWiData[i]);
-      pWal->apWiData[i] = 0;
-    }
-  }else{
-    sqlite3OsShmUnmap(pWal->pDbFd, isDelete);
-  }
-}
-
-/* 
-** Open a connection to the WAL file zWalName. The database file must 
-** already be opened on connection pDbFd. The buffer that zWalName points
-** to must remain valid for the lifetime of the returned Wal* handle.
-**
-** A SHARED lock should be held on the database file when this function
-** is called. The purpose of this SHARED lock is to prevent any other
-** client from unlinking the WAL or wal-index file. If another process
-** were to do this just after this client opened one of these files, the
-** system would be badly broken.
-**
-** If the log file is successfully opened, SQLITE_OK is returned and 
-** *ppWal is set to point to a new WAL handle. If an error occurs,
-** an SQLite error code is returned and *ppWal is left unmodified.
-*/
-SQLITE_PRIVATE int sqlite3WalOpen(
-  sqlite3_vfs *pVfs,              /* vfs module to open wal and wal-index */
-  sqlite3_file *pDbFd,            /* The open database file */
-  const char *zWalName,           /* Name of the WAL file */
-  int bNoShm,                     /* True to run in heap-memory mode */
-  i64 mxWalSize,                  /* Truncate WAL to this size on reset */
-  Wal **ppWal                     /* OUT: Allocated Wal handle */
-){
-  int rc;                         /* Return Code */
-  Wal *pRet;                      /* Object to allocate and return */
-  int flags;                      /* Flags passed to OsOpen() */
-
-  assert( zWalName && zWalName[0] );
-  assert( pDbFd );
-
-  /* In the amalgamation, the os_unix.c and os_win.c source files come before
-  ** this source file.  Verify that the #defines of the locking byte offsets
-  ** in os_unix.c and os_win.c agree with the WALINDEX_LOCK_OFFSET value.
-  */
-#ifdef WIN_SHM_BASE
-  assert( WIN_SHM_BASE==WALINDEX_LOCK_OFFSET );
-#endif
-#ifdef UNIX_SHM_BASE
-  assert( UNIX_SHM_BASE==WALINDEX_LOCK_OFFSET );
-#endif
-
-
-  /* Allocate an instance of struct Wal to return. */
-  *ppWal = 0;
-  pRet = (Wal*)sqlite3MallocZero(sizeof(Wal) + pVfs->szOsFile);
-  if( !pRet ){
-    return SQLITE_NOMEM;
-  }
-
-  pRet->pVfs = pVfs;
-  pRet->pWalFd = (sqlite3_file *)&pRet[1];
-  pRet->pDbFd = pDbFd;
-  pRet->readLock = -1;
-  pRet->mxWalSize = mxWalSize;
-  pRet->zWalName = zWalName;
-  pRet->syncHeader = 1;
-  pRet->padToSectorBoundary = 1;
-  pRet->exclusiveMode = (bNoShm ? WAL_HEAPMEMORY_MODE: WAL_NORMAL_MODE);
-
-  /* Open file handle on the write-ahead log file. */
-  flags = (SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE|SQLITE_OPEN_WAL);
-  rc = sqlite3OsOpen(pVfs, zWalName, pRet->pWalFd, flags, &flags);
-  if( rc==SQLITE_OK && flags&SQLITE_OPEN_READONLY ){
-    pRet->readOnly = WAL_RDONLY;
-  }
-
-  if( rc!=SQLITE_OK ){
-    walIndexClose(pRet, 0);
-    sqlite3OsClose(pRet->pWalFd);
-    sqlite3_free(pRet);
-  }else{
-    int iDC = sqlite3OsDeviceCharacteristics(pDbFd);
-    if( iDC & SQLITE_IOCAP_SEQUENTIAL ){ pRet->syncHeader = 0; }
-    if( iDC & SQLITE_IOCAP_POWERSAFE_OVERWRITE ){
-      pRet->padToSectorBoundary = 0;
-    }
-    *ppWal = pRet;
-    WALTRACE(("WAL%d: opened\n", pRet));
-  }
-  return rc;
-}
-
-#if 0
-/*
-** Change the size to which the WAL file is trucated on each reset.
-*/
-SQLITE_PRIVATE void sqlite3WalLimit(Wal *pWal, i64 iLimit){
-  if( pWal ) pWal->mxWalSize = iLimit;
-}
-#endif
-
-/*
-** Find the smallest page number out of all pages held in the WAL that
-** has not been returned by any prior invocation of this method on the
-** same WalIterator object.   Write into *piFrame the frame index where
-** that page was last written into the WAL.  Write into *piPage the page
-** number.
-**
-** Return 0 on success.  If there are no pages in the WAL with a page
-** number larger than *piPage, then return 1.
-*/
-static int walIteratorNext(
-  WalIterator *p,               /* Iterator */
-  u32 *piPage,                  /* OUT: The page number of the next page */
-  u32 *piFrame                  /* OUT: Wal frame index of next page */
-){
-  u32 iMin;                     /* Result pgno must be greater than iMin */
-  u32 iRet = 0xFFFFFFFF;        /* 0xffffffff is never a valid page number */
-  int i;                        /* For looping through segments */
-
-  iMin = p->iPrior;
-  assert( iMin<0xffffffff );
-  for(i=p->nSegment-1; i>=0; i--){
-    struct WalSegment *pSegment = &p->aSegment[i];
-    while( pSegment->iNext<pSegment->nEntry ){
-      u32 iPg = pSegment->aPgno[pSegment->aIndex[pSegment->iNext]];
-      if( iPg>iMin ){
-        if( iPg<iRet ){
-          iRet = iPg;
-          *piFrame = pSegment->iZero + pSegment->aIndex[pSegment->iNext];
-        }
-        break;
-      }
-      pSegment->iNext++;
-    }
-  }
-
-  *piPage = p->iPrior = iRet;
-  return (iRet==0xFFFFFFFF);
-}
-
-/*
-** This function merges two sorted lists into a single sorted list.
-**
-** aLeft[] and aRight[] are arrays of indices.  The sort key is
-** aContent[aLeft[]] and aContent[aRight[]].  Upon entry, the following
-** is guaranteed for all J<K:
-**
-**        aContent[aLeft[J]] < aContent[aLeft[K]]
-**        aContent[aRight[J]] < aContent[aRight[K]]
-**
-** This routine overwrites aRight[] with a new (probably longer) sequence
-** of indices such that the aRight[] contains every index that appears in
-** either aLeft[] or the old aRight[] and such that the second condition
-** above is still met.
-**
-** The aContent[aLeft[X]] values will be unique for all X.  And the
-** aContent[aRight[X]] values will be unique too.  But there might be
-** one or more combinations of X and Y such that
-**
-**      aLeft[X]!=aRight[Y]  &&  aContent[aLeft[X]] == aContent[aRight[Y]]
-**
-** When that happens, omit the aLeft[X] and use the aRight[Y] index.
-*/
-static void walMerge(
-  const u32 *aContent,            /* Pages in wal - keys for the sort */
-  ht_slot *aLeft,                 /* IN: Left hand input list */
-  int nLeft,                      /* IN: Elements in array *paLeft */
-  ht_slot **paRight,              /* IN/OUT: Right hand input list */
-  int *pnRight,                   /* IN/OUT: Elements in *paRight */
-  ht_slot *aTmp                   /* Temporary buffer */
-){
-  int iLeft = 0;                  /* Current index in aLeft */
-  int iRight = 0;                 /* Current index in aRight */
-  int iOut = 0;                   /* Current index in output buffer */
-  int nRight = *pnRight;
-  ht_slot *aRight = *paRight;
-
-  assert( nLeft>0 && nRight>0 );
-  while( iRight<nRight || iLeft<nLeft ){
-    ht_slot logpage;
-    Pgno dbpage;
-
-    if( (iLeft<nLeft) 
-     && (iRight>=nRight || aContent[aLeft[iLeft]]<aContent[aRight[iRight]])
-    ){
-      logpage = aLeft[iLeft++];
-    }else{
-      logpage = aRight[iRight++];
-    }
-    dbpage = aContent[logpage];
-
-    aTmp[iOut++] = logpage;
-    if( iLeft<nLeft && aContent[aLeft[iLeft]]==dbpage ) iLeft++;
-
-    assert( iLeft>=nLeft || aContent[aLeft[iLeft]]>dbpage );
-    assert( iRight>=nRight || aContent[aRight[iRight]]>dbpage );
-  }
-
-  *paRight = aLeft;
-  *pnRight = iOut;
-  memcpy(aLeft, aTmp, sizeof(aTmp[0])*iOut);
-}
-
-/*
-** Sort the elements in list aList using aContent[] as the sort key.
-** Remove elements with duplicate keys, preferring to keep the
-** larger aList[] values.
-**
-** The aList[] entries are indices into aContent[].  The values in
-** aList[] are to be sorted so that for all J<K:
-**
-**      aContent[aList[J]] < aContent[aList[K]]
-**
-** For any X and Y such that
-**
-**      aContent[aList[X]] == aContent[aList[Y]]
-**
-** Keep the larger of the two values aList[X] and aList[Y] and discard
-** the smaller.
-*/
-static void walMergesort(
-  const u32 *aContent,            /* Pages in wal */
-  ht_slot *aBuffer,               /* Buffer of at least *pnList items to use */
-  ht_slot *aList,                 /* IN/OUT: List to sort */
-  int *pnList                     /* IN/OUT: Number of elements in aList[] */
-){
-  struct Sublist {
-    int nList;                    /* Number of elements in aList */
-    ht_slot *aList;               /* Pointer to sub-list content */
-  };
-
-  const int nList = *pnList;      /* Size of input list */
-  int nMerge = 0;                 /* Number of elements in list aMerge */
-  ht_slot *aMerge = 0;            /* List to be merged */
-  int iList;                      /* Index into input list */
-  u32 iSub = 0;                   /* Index into aSub array */
-  struct Sublist aSub[13];        /* Array of sub-lists */
-
-  memset(aSub, 0, sizeof(aSub));
-  assert( nList<=HASHTABLE_NPAGE && nList>0 );
-  assert( HASHTABLE_NPAGE==(1<<(ArraySize(aSub)-1)) );
-
-  for(iList=0; iList<nList; iList++){
-    nMerge = 1;
-    aMerge = &aList[iList];
-    for(iSub=0; iList & (1<<iSub); iSub++){
-      struct Sublist *p;
-      assert( iSub<ArraySize(aSub) );
-      p = &aSub[iSub];
-      assert( p->aList && p->nList<=(1<<iSub) );
-      assert( p->aList==&aList[iList&~((2<<iSub)-1)] );
-      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
-    }
-    aSub[iSub].aList = aMerge;
-    aSub[iSub].nList = nMerge;
-  }
-
-  for(iSub++; iSub<ArraySize(aSub); iSub++){
-    if( nList & (1<<iSub) ){
-      struct Sublist *p;
-      assert( iSub<ArraySize(aSub) );
-      p = &aSub[iSub];
-      assert( p->nList<=(1<<iSub) );
-      assert( p->aList==&aList[nList&~((2<<iSub)-1)] );
-      walMerge(aContent, p->aList, p->nList, &aMerge, &nMerge, aBuffer);
-    }
-  }
-  assert( aMerge==aList );
-  *pnList = nMerge;
-
-#ifdef SQLITE_DEBUG
-  {
-    int i;
-    for(i=1; i<*pnList; i++){
-      assert( aContent[aList[i]] > aContent[aList[i-1]] );
-    }
-  }
-#endif
-}
-
-/* 
-** Free an iterator allocated by walIteratorInit().
-*/
-static void walIteratorFree(WalIterator *p){
-  sqlite3_free(p);
-}
-
-/*
-** Construct a WalInterator object that can be used to loop over all 
-** pages in the WAL in ascending order. The caller must hold the checkpoint
-** lock.
-**
-** On success, make *pp point to the newly allocated WalInterator object
-** return SQLITE_OK. Otherwise, return an error code. If this routine
-** returns an error, the value of *pp is undefined.
-**
-** The calling routine should invoke walIteratorFree() to destroy the
-** WalIterator object when it has finished with it.
-*/
-static int walIteratorInit(Wal *pWal, WalIterator **pp){
-  WalIterator *p;                 /* Return value */
-  int nSegment;                   /* Number of segments to merge */
-  u32 iLast;                      /* Last frame in log */
-  int nByte;                      /* Number of bytes to allocate */
-  int i;                          /* Iterator variable */
-  ht_slot *aTmp;                  /* Temp space used by merge-sort */
-  int rc = SQLITE_OK;             /* Return Code */
-
-  /* This routine only runs while holding the checkpoint lock. And
-  ** it only runs if there is actually content in the log (mxFrame>0).
-  */
-  assert( pWal->ckptLock && pWal->hdr.mxFrame>0 );
-  iLast = pWal->hdr.mxFrame;
-
-  /* Allocate space for the WalIterator object. */
-  nSegment = walFramePage(iLast) + 1;
-  nByte = sizeof(WalIterator) 
-        + (nSegment-1)*sizeof(struct WalSegment)
-        + iLast*sizeof(ht_slot);
-  p = (WalIterator *)sqlite3_malloc64(nByte);
-  if( !p ){
-    return SQLITE_NOMEM;
-  }
-  memset(p, 0, nByte);
-  p->nSegment = nSegment;
-
-  /* Allocate temporary space used by the merge-sort routine. This block
-  ** of memory will be freed before this function returns.
-  */
-  aTmp = (ht_slot *)sqlite3_malloc64(
-      sizeof(ht_slot) * (iLast>HASHTABLE_NPAGE?HASHTABLE_NPAGE:iLast)
-  );
-  if( !aTmp ){
-    rc = SQLITE_NOMEM;
-  }
-
-  for(i=0; rc==SQLITE_OK && i<nSegment; i++){
-    volatile ht_slot *aHash;
-    u32 iZero;
-    volatile u32 *aPgno;
-
-    rc = walHashGet(pWal, i, &aHash, &aPgno, &iZero);
-    if( rc==SQLITE_OK ){
-      int j;                      /* Counter variable */
-      int nEntry;                 /* Number of entries in this segment */
-      ht_slot *aIndex;            /* Sorted index for this segment */
-
-      aPgno++;
-      if( (i+1)==nSegment ){
-        nEntry = (int)(iLast - iZero);
-      }else{
-        nEntry = (int)((u32*)aHash - (u32*)aPgno);
-      }
-      aIndex = &((ht_slot *)&p->aSegment[p->nSegment])[iZero];
-      iZero++;
-  
-      for(j=0; j<nEntry; j++){
-        aIndex[j] = (ht_slot)j;
-      }
-      walMergesort((u32 *)aPgno, aTmp, aIndex, &nEntry);
-      p->aSegment[i].iZero = iZero;
-      p->aSegment[i].nEntry = nEntry;
-      p->aSegment[i].aIndex = aIndex;
-      p->aSegment[i].aPgno = (u32 *)aPgno;
-    }
-  }
-  sqlite3_free(aTmp);
-
-  if( rc!=SQLITE_OK ){
-    walIteratorFree(p);
-  }
-  *pp = p;
-  return rc;
-}
-
-/*
-** Attempt to obtain the exclusive WAL lock defined by parameters lockIdx and
-** n. If the attempt fails and parameter xBusy is not NULL, then it is a
-** busy-handler function. Invoke it and retry the lock until either the
-** lock is successfully obtained or the busy-handler returns 0.
-*/
-static int walBusyLock(
-  Wal *pWal,                      /* WAL connection */
-  int (*xBusy)(void*),            /* Function to call when busy */
-  void *pBusyArg,                 /* Context argument for xBusyHandler */
-  int lockIdx,                    /* Offset of first byte to lock */
-  int n                           /* Number of bytes to lock */
-){
-  int rc;
-  do {
-    rc = walLockExclusive(pWal, lockIdx, n, 0);
-  }while( xBusy && rc==SQLITE_BUSY && xBusy(pBusyArg) );
-  return rc;
-}
-
-/*
-** The cache of the wal-index header must be valid to call this function.
-** Return the page-size in bytes used by the database.
-*/
-static int walPagesize(Wal *pWal){
-  return (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
-}
-
-/*
-** The following is guaranteed when this function is called:
-**
-**   a) the WRITER lock is held,
-**   b) the entire log file has been checkpointed, and
-**   c) any existing readers are reading exclusively from the database
-**      file - there are no readers that may attempt to read a frame from
-**      the log file.
-**
-** This function updates the shared-memory structures so that the next
-** client to write to the database (which may be this one) does so by
-** writing frames into the start of the log file.
-**
-** The value of parameter salt1 is used as the aSalt[1] value in the 
-** new wal-index header. It should be passed a pseudo-random value (i.e. 
-** one obtained from sqlite3_randomness()).
-*/
-static void walRestartHdr(Wal *pWal, u32 salt1){
-  volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
-  int i;                          /* Loop counter */
-  u32 *aSalt = pWal->hdr.aSalt;   /* Big-endian salt values */
-  pWal->nCkpt++;
-  pWal->hdr.mxFrame = 0;
-  sqlite3Put4byte((u8*)&aSalt[0], 1 + sqlite3Get4byte((u8*)&aSalt[0]));
-  memcpy(&pWal->hdr.aSalt[1], &salt1, 4);
-  walIndexWriteHdr(pWal);
-  pInfo->nBackfill = 0;
-  pInfo->aReadMark[1] = 0;
-  for(i=2; i<WAL_NREADER; i++) pInfo->aReadMark[i] = READMARK_NOT_USED;
-  assert( pInfo->aReadMark[0]==0 );
-}
-
-/*
-** Copy as much content as we can from the WAL back into the database file
-** in response to an sqlite3_wal_checkpoint() request or the equivalent.
-**
-** The amount of information copies from WAL to database might be limited
-** by active readers.  This routine will never overwrite a database page
-** that a concurrent reader might be using.
-**
-** All I/O barrier operations (a.k.a fsyncs) occur in this routine when
-** SQLite is in WAL-mode in synchronous=NORMAL.  That means that if 
-** checkpoints are always run by a background thread or background 
-** process, foreground threads will never block on a lengthy fsync call.
-**
-** Fsync is called on the WAL before writing content out of the WAL and
-** into the database.  This ensures that if the new content is persistent
-** in the WAL and can be recovered following a power-loss or hard reset.
-**
-** Fsync is also called on the database file if (and only if) the entire
-** WAL content is copied into the database file.  This second fsync makes
-** it safe to delete the WAL since the new content will persist in the
-** database file.
-**
-** This routine uses and updates the nBackfill field of the wal-index header.
-** This is the only routine that will increase the value of nBackfill.  
-** (A WAL reset or recovery will revert nBackfill to zero, but not increase
-** its value.)
-**
-** The caller must be holding sufficient locks to ensure that no other
-** checkpoint is running (in any other thread or process) at the same
-** time.
-*/
-static int walCheckpoint(
-  Wal *pWal,                      /* Wal connection */
-  int eMode,                      /* One of PASSIVE, FULL or RESTART */
-  int (*xBusy)(void*),            /* Function to call when busy */
-  void *pBusyArg,                 /* Context argument for xBusyHandler */
-  int sync_flags,                 /* Flags for OsSync() (or 0) */
-  u8 *zBuf                        /* Temporary buffer to use */
-){
-  int rc = SQLITE_OK;             /* Return code */
-  int szPage;                     /* Database page-size */
-  WalIterator *pIter = 0;         /* Wal iterator context */
-  u32 iDbpage = 0;                /* Next database page to write */
-  u32 iFrame = 0;                 /* Wal frame containing data for iDbpage */
-  u32 mxSafeFrame;                /* Max frame that can be backfilled */
-  u32 mxPage;                     /* Max database page to write */
-  int i;                          /* Loop counter */
-  volatile WalCkptInfo *pInfo;    /* The checkpoint status information */
-
-  szPage = walPagesize(pWal);
-  testcase( szPage<=32768 );
-  testcase( szPage>=65536 );
-  pInfo = walCkptInfo(pWal);
-  if( pInfo->nBackfill<pWal->hdr.mxFrame ){
-
-    /* Allocate the iterator */
-    rc = walIteratorInit(pWal, &pIter);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    assert( pIter );
-
-    /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
-    ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
-    assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
-
-    /* Compute in mxSafeFrame the index of the last frame of the WAL that is
-    ** safe to write into the database.  Frames beyond mxSafeFrame might
-    ** overwrite database pages that are in use by active readers and thus
-    ** cannot be backfilled from the WAL.
-    */
-    mxSafeFrame = pWal->hdr.mxFrame;
-    mxPage = pWal->hdr.nPage;
-    for(i=1; i<WAL_NREADER; i++){
-      /* Thread-sanitizer reports that the following is an unsafe read,
-      ** as some other thread may be in the process of updating the value
-      ** of the aReadMark[] slot. The assumption here is that if that is
-      ** happening, the other client may only be increasing the value,
-      ** not decreasing it. So assuming either that either the "old" or
-      ** "new" version of the value is read, and not some arbitrary value
-      ** that would never be written by a real client, things are still 
-      ** safe.  */
-      u32 y = pInfo->aReadMark[i];
-      if( mxSafeFrame>y ){
-        assert( y<=pWal->hdr.mxFrame );
-        rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(i), 1);
-        if( rc==SQLITE_OK ){
-          pInfo->aReadMark[i] = (i==1 ? mxSafeFrame : READMARK_NOT_USED);
-          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
-        }else if( rc==SQLITE_BUSY ){
-          mxSafeFrame = y;
-          xBusy = 0;
-        }else{
-          goto walcheckpoint_out;
-        }
-      }
-    }
-
-    if( pInfo->nBackfill<mxSafeFrame
-     && (rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(0),1))==SQLITE_OK
-    ){
-      i64 nSize;                    /* Current size of database file */
-      u32 nBackfill = pInfo->nBackfill;
-
-      /* Sync the WAL to disk */
-      if( sync_flags ){
-        rc = sqlite3OsSync(pWal->pWalFd, sync_flags);
-      }
-
-      /* If the database may grow as a result of this checkpoint, hint
-      ** about the eventual size of the db file to the VFS layer.
-      */
-      if( rc==SQLITE_OK ){
-        i64 nReq = ((i64)mxPage * szPage);
-        rc = sqlite3OsFileSize(pWal->pDbFd, &nSize);
-        if( rc==SQLITE_OK && nSize<nReq ){
-          sqlite3OsFileControlHint(pWal->pDbFd, SQLITE_FCNTL_SIZE_HINT, &nReq);
-        }
-      }
-
-
-      /* Iterate through the contents of the WAL, copying data to the db file */
-      while( rc==SQLITE_OK && 0==walIteratorNext(pIter, &iDbpage, &iFrame) ){
-        i64 iOffset;
-        assert( walFramePgno(pWal, iFrame)==iDbpage );
-        if( iFrame<=nBackfill || iFrame>mxSafeFrame || iDbpage>mxPage ){
-          continue;
-        }
-        iOffset = walFrameOffset(iFrame, szPage) + WAL_FRAME_HDRSIZE;
-        /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL file */
-        rc = sqlite3OsRead(pWal->pWalFd, zBuf, szPage, iOffset);
-        if( rc!=SQLITE_OK ) break;
-        iOffset = (iDbpage-1)*(i64)szPage;
-        testcase( IS_BIG_INT(iOffset) );
-        rc = sqlite3OsWrite(pWal->pDbFd, zBuf, szPage, iOffset);
-        if( rc!=SQLITE_OK ) break;
-      }
-
-      /* If work was actually accomplished... */
-      if( rc==SQLITE_OK ){
-        if( mxSafeFrame==walIndexHdr(pWal)->mxFrame ){
-          i64 szDb = pWal->hdr.nPage*(i64)szPage;
-          testcase( IS_BIG_INT(szDb) );
-          rc = sqlite3OsTruncate(pWal->pDbFd, szDb);
-          if( rc==SQLITE_OK && sync_flags ){
-            rc = sqlite3OsSync(pWal->pDbFd, sync_flags);
-          }
-        }
-        if( rc==SQLITE_OK ){
-          pInfo->nBackfill = mxSafeFrame;
-        }
-      }
-
-      /* Release the reader lock held while backfilling */
-      walUnlockExclusive(pWal, WAL_READ_LOCK(0), 1);
-    }
-
-    if( rc==SQLITE_BUSY ){
-      /* Reset the return code so as not to report a checkpoint failure
-      ** just because there are active readers.  */
-      rc = SQLITE_OK;
-    }
-  }
-
-  /* If this is an SQLITE_CHECKPOINT_RESTART or TRUNCATE operation, and the
-  ** entire wal file has been copied into the database file, then block 
-  ** until all readers have finished using the wal file. This ensures that 
-  ** the next process to write to the database restarts the wal file.
-  */
-  if( rc==SQLITE_OK && eMode!=SQLITE_CHECKPOINT_PASSIVE ){
-    assert( pWal->writeLock );
-    if( pInfo->nBackfill<pWal->hdr.mxFrame ){
-      rc = SQLITE_BUSY;
-    }else if( eMode>=SQLITE_CHECKPOINT_RESTART ){
-      u32 salt1;
-      sqlite3_randomness(4, &salt1);
-      assert( pInfo->nBackfill==pWal->hdr.mxFrame );
-      rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_READ_LOCK(1), WAL_NREADER-1);
-      if( rc==SQLITE_OK ){
-        if( eMode==SQLITE_CHECKPOINT_TRUNCATE ){
-          /* IMPLEMENTATION-OF: R-44699-57140 This mode works the same way as
-          ** SQLITE_CHECKPOINT_RESTART with the addition that it also
-          ** truncates the log file to zero bytes just prior to a
-          ** successful return.
-          **
-          ** In theory, it might be safe to do this without updating the
-          ** wal-index header in shared memory, as all subsequent reader or
-          ** writer clients should see that the entire log file has been
-          ** checkpointed and behave accordingly. This seems unsafe though,
-          ** as it would leave the system in a state where the contents of
-          ** the wal-index header do not match the contents of the 
-          ** file-system. To avoid this, update the wal-index header to
-          ** indicate that the log file contains zero valid frames.  */
-          walRestartHdr(pWal, salt1);
-          rc = sqlite3OsTruncate(pWal->pWalFd, 0);
-        }
-        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
-      }
-    }
-  }
-
- walcheckpoint_out:
-  walIteratorFree(pIter);
-  return rc;
-}
-
-/*
-** If the WAL file is currently larger than nMax bytes in size, truncate
-** it to exactly nMax bytes. If an error occurs while doing so, ignore it.
-*/
-static void walLimitSize(Wal *pWal, i64 nMax){
-  i64 sz;
-  int rx;
-  rx = sqlite3OsFileSize(pWal->pWalFd, &sz);
-  if( rx==SQLITE_OK && (sz > nMax ) ){
-    rx = sqlite3OsTruncate(pWal->pWalFd, nMax);
-  }
-  if( rx ){
-    sqlite3_log(rx, "cannot limit WAL size: %s", pWal->zWalName);
-  }
-}
-
-/*
-** Close a connection to a log file.
-*/
-SQLITE_PRIVATE int sqlite3WalClose(
-  Wal *pWal,                      /* Wal to close */
-  int sync_flags,                 /* Flags to pass to OsSync() (or 0) */
-  int nBuf,
-  u8 *zBuf                        /* Buffer of at least nBuf bytes */
-){
-  int rc = SQLITE_OK;
-  if( pWal ){
-    int isDelete = 0;             /* True to unlink wal and wal-index files */
-
-    /* If an EXCLUSIVE lock can be obtained on the database file (using the
-    ** ordinary, rollback-mode locking methods, this guarantees that the
-    ** connection associated with this log file is the only connection to
-    ** the database. In this case checkpoint the database and unlink both
-    ** the wal and wal-index files.
-    **
-    ** The EXCLUSIVE lock is not released before returning.
-    */
-    rc = sqlite3OsLock(pWal->pDbFd, SQLITE_LOCK_EXCLUSIVE);
-    if( rc==SQLITE_OK ){
-      if( pWal->exclusiveMode==WAL_NORMAL_MODE ){
-        pWal->exclusiveMode = WAL_EXCLUSIVE_MODE;
-      }
-      rc = sqlite3WalCheckpoint(
-          pWal, SQLITE_CHECKPOINT_PASSIVE, 0, 0, sync_flags, nBuf, zBuf, 0, 0
-      );
-      if( rc==SQLITE_OK ){
-        int bPersist = -1;
-        sqlite3OsFileControlHint(
-            pWal->pDbFd, SQLITE_FCNTL_PERSIST_WAL, &bPersist
-        );
-        if( bPersist!=1 ){
-          /* Try to delete the WAL file if the checkpoint completed and
-          ** fsyned (rc==SQLITE_OK) and if we are not in persistent-wal
-          ** mode (!bPersist) */
-          isDelete = 1;
-        }else if( pWal->mxWalSize>=0 ){
-          /* Try to truncate the WAL file to zero bytes if the checkpoint
-          ** completed and fsynced (rc==SQLITE_OK) and we are in persistent
-          ** WAL mode (bPersist) and if the PRAGMA journal_size_limit is a
-          ** non-negative value (pWal->mxWalSize>=0).  Note that we truncate
-          ** to zero bytes as truncating to the journal_size_limit might
-          ** leave a corrupt WAL file on disk. */
-          walLimitSize(pWal, 0);
-        }
-      }
-    }
-
-    walIndexClose(pWal, isDelete);
-    sqlite3OsClose(pWal->pWalFd);
-    if( isDelete ){
-      sqlite3OsDelete(pWal->pVfs, pWal->zWalName, 0);
-    }
-    WALTRACE(("WAL%p: closed\n", pWal));
-    sqlite3_free((void *)pWal->apWiData);
-    sqlite3_free(pWal);
-  }
-  return rc;
-}
-
-/*
-** Try to read the wal-index header.  Return 0 on success and 1 if
-** there is a problem.
-**
-** The wal-index is in shared memory.  Another thread or process might
-** be writing the header at the same time this procedure is trying to
-** read it, which might result in inconsistency.  A dirty read is detected
-** by verifying that both copies of the header are the same and also by
-** a checksum on the header.
-**
-** If and only if the read is consistent and the header is different from
-** pWal->hdr, then pWal->hdr is updated to the content of the new header
-** and *pChanged is set to 1.
-**
-** If the checksum cannot be verified return non-zero. If the header
-** is read successfully and the checksum verified, return zero.
-*/
-static int walIndexTryHdr(Wal *pWal, int *pChanged){
-  u32 aCksum[2];                  /* Checksum on the header content */
-  WalIndexHdr h1, h2;             /* Two copies of the header content */
-  WalIndexHdr volatile *aHdr;     /* Header in shared memory */
-
-  /* The first page of the wal-index must be mapped at this point. */
-  assert( pWal->nWiData>0 && pWal->apWiData[0] );
-
-  /* Read the header. This might happen concurrently with a write to the
-  ** same area of shared memory on a different CPU in a SMP,
-  ** meaning it is possible that an inconsistent snapshot is read
-  ** from the file. If this happens, return non-zero.
-  **
-  ** There are two copies of the header at the beginning of the wal-index.
-  ** When reading, read [0] first then [1].  Writes are in the reverse order.
-  ** Memory barriers are used to prevent the compiler or the hardware from
-  ** reordering the reads and writes.
-  */
-  aHdr = walIndexHdr(pWal);
-  memcpy(&h1, (void *)&aHdr[0], sizeof(h1));
-  walShmBarrier(pWal);
-  memcpy(&h2, (void *)&aHdr[1], sizeof(h2));
-
-  if( memcmp(&h1, &h2, sizeof(h1))!=0 ){
-    return 1;   /* Dirty read */
-  }  
-  if( h1.isInit==0 ){
-    return 1;   /* Malformed header - probably all zeros */
-  }
-  walChecksumBytes(1, (u8*)&h1, sizeof(h1)-sizeof(h1.aCksum), 0, aCksum);
-  if( aCksum[0]!=h1.aCksum[0] || aCksum[1]!=h1.aCksum[1] ){
-    return 1;   /* Checksum does not match */
-  }
-
-  if( memcmp(&pWal->hdr, &h1, sizeof(WalIndexHdr)) ){
-    *pChanged = 1;
-    memcpy(&pWal->hdr, &h1, sizeof(WalIndexHdr));
-    pWal->szPage = (pWal->hdr.szPage&0xfe00) + ((pWal->hdr.szPage&0x0001)<<16);
-    testcase( pWal->szPage<=32768 );
-    testcase( pWal->szPage>=65536 );
-  }
-
-  /* The header was successfully read. Return zero. */
-  return 0;
-}
-
-/*
-** Read the wal-index header from the wal-index and into pWal->hdr.
-** If the wal-header appears to be corrupt, try to reconstruct the
-** wal-index from the WAL before returning.
-**
-** Set *pChanged to 1 if the wal-index header value in pWal->hdr is
-** changed by this operation.  If pWal->hdr is unchanged, set *pChanged
-** to 0.
-**
-** If the wal-index header is successfully read, return SQLITE_OK. 
-** Otherwise an SQLite error code.
-*/
-static int walIndexReadHdr(Wal *pWal, int *pChanged){
-  int rc;                         /* Return code */
-  int badHdr;                     /* True if a header read failed */
-  volatile u32 *page0;            /* Chunk of wal-index containing header */
-
-  /* Ensure that page 0 of the wal-index (the page that contains the 
-  ** wal-index header) is mapped. Return early if an error occurs here.
-  */
-  assert( pChanged );
-  rc = walIndexPage(pWal, 0, &page0);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  };
-  assert( page0 || pWal->writeLock==0 );
-
-  /* If the first page of the wal-index has been mapped, try to read the
-  ** wal-index header immediately, without holding any lock. This usually
-  ** works, but may fail if the wal-index header is corrupt or currently 
-  ** being modified by another thread or process.
-  */
-  badHdr = (page0 ? walIndexTryHdr(pWal, pChanged) : 1);
-
-  /* If the first attempt failed, it might have been due to a race
-  ** with a writer.  So get a WRITE lock and try again.
-  */
-  assert( badHdr==0 || pWal->writeLock==0 );
-  if( badHdr ){
-    if( pWal->readOnly & WAL_SHM_RDONLY ){
-      if( SQLITE_OK==(rc = walLockShared(pWal, WAL_WRITE_LOCK)) ){
-        walUnlockShared(pWal, WAL_WRITE_LOCK);
-        rc = SQLITE_READONLY_RECOVERY;
-      }
-    }else if( SQLITE_OK==(rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1, 1)) ){
-      pWal->writeLock = 1;
-      if( SQLITE_OK==(rc = walIndexPage(pWal, 0, &page0)) ){
-        badHdr = walIndexTryHdr(pWal, pChanged);
-        if( badHdr ){
-          /* If the wal-index header is still malformed even while holding
-          ** a WRITE lock, it can only mean that the header is corrupted and
-          ** needs to be reconstructed.  So run recovery to do exactly that.
-          */
-          rc = walIndexRecover(pWal);
-          *pChanged = 1;
-        }
-      }
-      pWal->writeLock = 0;
-      walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
-    }
-  }
-
-  /* If the header is read successfully, check the version number to make
-  ** sure the wal-index was not constructed with some future format that
-  ** this version of SQLite cannot understand.
-  */
-  if( badHdr==0 && pWal->hdr.iVersion!=WALINDEX_MAX_VERSION ){
-    rc = SQLITE_CANTOPEN_BKPT;
-  }
-
-  return rc;
-}
-
-/*
-** This is the value that walTryBeginRead returns when it needs to
-** be retried.
-*/
-#define WAL_RETRY  (-1)
-
-/*
-** Attempt to start a read transaction.  This might fail due to a race or
-** other transient condition.  When that happens, it returns WAL_RETRY to
-** indicate to the caller that it is safe to retry immediately.
-**
-** On success return SQLITE_OK.  On a permanent failure (such an
-** I/O error or an SQLITE_BUSY because another process is running
-** recovery) return a positive error code.
-**
-** The useWal parameter is true to force the use of the WAL and disable
-** the case where the WAL is bypassed because it has been completely
-** checkpointed.  If useWal==0 then this routine calls walIndexReadHdr() 
-** to make a copy of the wal-index header into pWal->hdr.  If the 
-** wal-index header has changed, *pChanged is set to 1 (as an indication 
-** to the caller that the local paget cache is obsolete and needs to be 
-** flushed.)  When useWal==1, the wal-index header is assumed to already
-** be loaded and the pChanged parameter is unused.
-**
-** The caller must set the cnt parameter to the number of prior calls to
-** this routine during the current read attempt that returned WAL_RETRY.
-** This routine will start taking more aggressive measures to clear the
-** race conditions after multiple WAL_RETRY returns, and after an excessive
-** number of errors will ultimately return SQLITE_PROTOCOL.  The
-** SQLITE_PROTOCOL return indicates that some other process has gone rogue
-** and is not honoring the locking protocol.  There is a vanishingly small
-** chance that SQLITE_PROTOCOL could be returned because of a run of really
-** bad luck when there is lots of contention for the wal-index, but that
-** possibility is so small that it can be safely neglected, we believe.
-**
-** On success, this routine obtains a read lock on 
-** WAL_READ_LOCK(pWal->readLock).  The pWal->readLock integer is
-** in the range 0 <= pWal->readLock < WAL_NREADER.  If pWal->readLock==(-1)
-** that means the Wal does not hold any read lock.  The reader must not
-** access any database page that is modified by a WAL frame up to and
-** including frame number aReadMark[pWal->readLock].  The reader will
-** use WAL frames up to and including pWal->hdr.mxFrame if pWal->readLock>0
-** Or if pWal->readLock==0, then the reader will ignore the WAL
-** completely and get all content directly from the database file.
-** If the useWal parameter is 1 then the WAL will never be ignored and
-** this routine will always set pWal->readLock>0 on success.
-** When the read transaction is completed, the caller must release the
-** lock on WAL_READ_LOCK(pWal->readLock) and set pWal->readLock to -1.
-**
-** This routine uses the nBackfill and aReadMark[] fields of the header
-** to select a particular WAL_READ_LOCK() that strives to let the
-** checkpoint process do as much work as possible.  This routine might
-** update values of the aReadMark[] array in the header, but if it does
-** so it takes care to hold an exclusive lock on the corresponding
-** WAL_READ_LOCK() while changing values.
-*/
-static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
-  volatile WalCkptInfo *pInfo;    /* Checkpoint information in wal-index */
-  u32 mxReadMark;                 /* Largest aReadMark[] value */
-  int mxI;                        /* Index of largest aReadMark[] value */
-  int i;                          /* Loop counter */
-  int rc = SQLITE_OK;             /* Return code  */
-
-  assert( pWal->readLock<0 );     /* Not currently locked */
-
-  /* Take steps to avoid spinning forever if there is a protocol error.
-  **
-  ** Circumstances that cause a RETRY should only last for the briefest
-  ** instances of time.  No I/O or other system calls are done while the
-  ** locks are held, so the locks should not be held for very long. But 
-  ** if we are unlucky, another process that is holding a lock might get
-  ** paged out or take a page-fault that is time-consuming to resolve, 
-  ** during the few nanoseconds that it is holding the lock.  In that case,
-  ** it might take longer than normal for the lock to free.
-  **
-  ** After 5 RETRYs, we begin calling sqlite3OsSleep().  The first few
-  ** calls to sqlite3OsSleep() have a delay of 1 microsecond.  Really this
-  ** is more of a scheduler yield than an actual delay.  But on the 10th
-  ** an subsequent retries, the delays start becoming longer and longer, 
-  ** so that on the 100th (and last) RETRY we delay for 323 milliseconds.
-  ** The total delay time before giving up is less than 10 seconds.
-  */
-  if( cnt>5 ){
-    int nDelay = 1;                      /* Pause time in microseconds */
-    if( cnt>100 ){
-      VVA_ONLY( pWal->lockError = 1; )
-      return SQLITE_PROTOCOL;
-    }
-    if( cnt>=10 ) nDelay = (cnt-9)*(cnt-9)*39;
-    sqlite3OsSleep(pWal->pVfs, nDelay);
-  }
-
-  if( !useWal ){
-    rc = walIndexReadHdr(pWal, pChanged);
-    if( rc==SQLITE_BUSY ){
-      /* If there is not a recovery running in another thread or process
-      ** then convert BUSY errors to WAL_RETRY.  If recovery is known to
-      ** be running, convert BUSY to BUSY_RECOVERY.  There is a race here
-      ** which might cause WAL_RETRY to be returned even if BUSY_RECOVERY
-      ** would be technically correct.  But the race is benign since with
-      ** WAL_RETRY this routine will be called again and will probably be
-      ** right on the second iteration.
-      */
-      if( pWal->apWiData[0]==0 ){
-        /* This branch is taken when the xShmMap() method returns SQLITE_BUSY.
-        ** We assume this is a transient condition, so return WAL_RETRY. The
-        ** xShmMap() implementation used by the default unix and win32 VFS 
-        ** modules may return SQLITE_BUSY due to a race condition in the 
-        ** code that determines whether or not the shared-memory region 
-        ** must be zeroed before the requested page is returned.
-        */
-        rc = WAL_RETRY;
-      }else if( SQLITE_OK==(rc = walLockShared(pWal, WAL_RECOVER_LOCK)) ){
-        walUnlockShared(pWal, WAL_RECOVER_LOCK);
-        rc = WAL_RETRY;
-      }else if( rc==SQLITE_BUSY ){
-        rc = SQLITE_BUSY_RECOVERY;
-      }
-    }
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-  }
-
-  pInfo = walCkptInfo(pWal);
-  if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame ){
-    /* The WAL has been completely backfilled (or it is empty).
-    ** and can be safely ignored.
-    */
-    rc = walLockShared(pWal, WAL_READ_LOCK(0));
-    walShmBarrier(pWal);
-    if( rc==SQLITE_OK ){
-      if( memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr)) ){
-        /* It is not safe to allow the reader to continue here if frames
-        ** may have been appended to the log before READ_LOCK(0) was obtained.
-        ** When holding READ_LOCK(0), the reader ignores the entire log file,
-        ** which implies that the database file contains a trustworthy
-        ** snapshot. Since holding READ_LOCK(0) prevents a checkpoint from
-        ** happening, this is usually correct.
-        **
-        ** However, if frames have been appended to the log (or if the log 
-        ** is wrapped and written for that matter) before the READ_LOCK(0)
-        ** is obtained, that is not necessarily true. A checkpointer may
-        ** have started to backfill the appended frames but crashed before
-        ** it finished. Leaving a corrupt image in the database file.
-        */
-        walUnlockShared(pWal, WAL_READ_LOCK(0));
-        return WAL_RETRY;
-      }
-      pWal->readLock = 0;
-      return SQLITE_OK;
-    }else if( rc!=SQLITE_BUSY ){
-      return rc;
-    }
-  }
-
-  /* If we get this far, it means that the reader will want to use
-  ** the WAL to get at content from recent commits.  The job now is
-  ** to select one of the aReadMark[] entries that is closest to
-  ** but not exceeding pWal->hdr.mxFrame and lock that entry.
-  */
-  mxReadMark = 0;
-  mxI = 0;
-  for(i=1; i<WAL_NREADER; i++){
-    u32 thisMark = pInfo->aReadMark[i];
-    if( mxReadMark<=thisMark && thisMark<=pWal->hdr.mxFrame ){
-      assert( thisMark!=READMARK_NOT_USED );
-      mxReadMark = thisMark;
-      mxI = i;
-    }
-  }
-  /* There was once an "if" here. The extra "{" is to preserve indentation. */
-  {
-    if( (pWal->readOnly & WAL_SHM_RDONLY)==0
-     && (mxReadMark<pWal->hdr.mxFrame || mxI==0)
-    ){
-      for(i=1; i<WAL_NREADER; i++){
-        rc = walLockExclusive(pWal, WAL_READ_LOCK(i), 1, 0);
-        if( rc==SQLITE_OK ){
-          mxReadMark = pInfo->aReadMark[i] = pWal->hdr.mxFrame;
-          mxI = i;
-          walUnlockExclusive(pWal, WAL_READ_LOCK(i), 1);
-          break;
-        }else if( rc!=SQLITE_BUSY ){
-          return rc;
-        }
-      }
-    }
-    if( mxI==0 ){
-      assert( rc==SQLITE_BUSY || (pWal->readOnly & WAL_SHM_RDONLY)!=0 );
-      return rc==SQLITE_BUSY ? WAL_RETRY : SQLITE_READONLY_CANTLOCK;
-    }
-
-    rc = walLockShared(pWal, WAL_READ_LOCK(mxI));
-    if( rc ){
-      return rc==SQLITE_BUSY ? WAL_RETRY : rc;
-    }
-    /* Now that the read-lock has been obtained, check that neither the
-    ** value in the aReadMark[] array or the contents of the wal-index
-    ** header have changed.
-    **
-    ** It is necessary to check that the wal-index header did not change
-    ** between the time it was read and when the shared-lock was obtained
-    ** on WAL_READ_LOCK(mxI) was obtained to account for the possibility
-    ** that the log file may have been wrapped by a writer, or that frames
-    ** that occur later in the log than pWal->hdr.mxFrame may have been
-    ** copied into the database by a checkpointer. If either of these things
-    ** happened, then reading the database with the current value of
-    ** pWal->hdr.mxFrame risks reading a corrupted snapshot. So, retry
-    ** instead.
-    **
-    ** Before checking that the live wal-index header has not changed
-    ** since it was read, set Wal.minFrame to the first frame in the wal
-    ** file that has not yet been checkpointed. This client will not need
-    ** to read any frames earlier than minFrame from the wal file - they
-    ** can be safely read directly from the database file.
-    **
-    ** Because a ShmBarrier() call is made between taking the copy of 
-    ** nBackfill and checking that the wal-header in shared-memory still
-    ** matches the one cached in pWal->hdr, it is guaranteed that the 
-    ** checkpointer that set nBackfill was not working with a wal-index
-    ** header newer than that cached in pWal->hdr. If it were, that could
-    ** cause a problem. The checkpointer could omit to checkpoint
-    ** a version of page X that lies before pWal->minFrame (call that version
-    ** A) on the basis that there is a newer version (version B) of the same
-    ** page later in the wal file. But if version B happens to like past
-    ** frame pWal->hdr.mxFrame - then the client would incorrectly assume
-    ** that it can read version A from the database file. However, since
-    ** we can guarantee that the checkpointer that set nBackfill could not
-    ** see any pages past pWal->hdr.mxFrame, this problem does not come up.
-    */
-    pWal->minFrame = pInfo->nBackfill+1;
-    walShmBarrier(pWal);
-    if( pInfo->aReadMark[mxI]!=mxReadMark
-     || memcmp((void *)walIndexHdr(pWal), &pWal->hdr, sizeof(WalIndexHdr))
-    ){
-      walUnlockShared(pWal, WAL_READ_LOCK(mxI));
-      return WAL_RETRY;
-    }else{
-      assert( mxReadMark<=pWal->hdr.mxFrame );
-      pWal->readLock = (i16)mxI;
-    }
-  }
-  return rc;
-}
-
-/*
-** Begin a read transaction on the database.
-**
-** This routine used to be called sqlite3OpenSnapshot() and with good reason:
-** it takes a snapshot of the state of the WAL and wal-index for the current
-** instant in time.  The current thread will continue to use this snapshot.
-** Other threads might append new content to the WAL and wal-index but
-** that extra content is ignored by the current thread.
-**
-** If the database contents have changes since the previous read
-** transaction, then *pChanged is set to 1 before returning.  The
-** Pager layer will use this to know that is cache is stale and
-** needs to be flushed.
-*/
-SQLITE_PRIVATE int sqlite3WalBeginReadTransaction(Wal *pWal, int *pChanged){
-  int rc;                         /* Return code */
-  int cnt = 0;                    /* Number of TryBeginRead attempts */
-
-  do{
-    rc = walTryBeginRead(pWal, pChanged, 0, ++cnt);
-  }while( rc==WAL_RETRY );
-  testcase( (rc&0xff)==SQLITE_BUSY );
-  testcase( (rc&0xff)==SQLITE_IOERR );
-  testcase( rc==SQLITE_PROTOCOL );
-  testcase( rc==SQLITE_OK );
-  return rc;
-}
-
-/*
-** Finish with a read transaction.  All this does is release the
-** read-lock.
-*/
-SQLITE_PRIVATE void sqlite3WalEndReadTransaction(Wal *pWal){
-  sqlite3WalEndWriteTransaction(pWal);
-  if( pWal->readLock>=0 ){
-    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
-    pWal->readLock = -1;
-  }
-}
-
-/*
-** Search the wal file for page pgno. If found, set *piRead to the frame that
-** contains the page. Otherwise, if pgno is not in the wal file, set *piRead
-** to zero.
-**
-** Return SQLITE_OK if successful, or an error code if an error occurs. If an
-** error does occur, the final value of *piRead is undefined.
-*/
-SQLITE_PRIVATE int sqlite3WalFindFrame(
-  Wal *pWal,                      /* WAL handle */
-  Pgno pgno,                      /* Database page number to read data for */
-  u32 *piRead                     /* OUT: Frame number (or zero) */
-){
-  u32 iRead = 0;                  /* If !=0, WAL frame to return data from */
-  u32 iLast = pWal->hdr.mxFrame;  /* Last page in WAL for this reader */
-  int iHash;                      /* Used to loop through N hash tables */
-  int iMinHash;
-
-  /* This routine is only be called from within a read transaction. */
-  assert( pWal->readLock>=0 || pWal->lockError );
-
-  /* If the "last page" field of the wal-index header snapshot is 0, then
-  ** no data will be read from the wal under any circumstances. Return early
-  ** in this case as an optimization.  Likewise, if pWal->readLock==0, 
-  ** then the WAL is ignored by the reader so return early, as if the 
-  ** WAL were empty.
-  */
-  if( iLast==0 || pWal->readLock==0 ){
-    *piRead = 0;
-    return SQLITE_OK;
-  }
-
-  /* Search the hash table or tables for an entry matching page number
-  ** pgno. Each iteration of the following for() loop searches one
-  ** hash table (each hash table indexes up to HASHTABLE_NPAGE frames).
-  **
-  ** This code might run concurrently to the code in walIndexAppend()
-  ** that adds entries to the wal-index (and possibly to this hash 
-  ** table). This means the value just read from the hash 
-  ** slot (aHash[iKey]) may have been added before or after the 
-  ** current read transaction was opened. Values added after the
-  ** read transaction was opened may have been written incorrectly -
-  ** i.e. these slots may contain garbage data. However, we assume
-  ** that any slots written before the current read transaction was
-  ** opened remain unmodified.
-  **
-  ** For the reasons above, the if(...) condition featured in the inner
-  ** loop of the following block is more stringent that would be required 
-  ** if we had exclusive access to the hash-table:
-  **
-  **   (aPgno[iFrame]==pgno): 
-  **     This condition filters out normal hash-table collisions.
-  **
-  **   (iFrame<=iLast): 
-  **     This condition filters out entries that were added to the hash
-  **     table after the current read-transaction had started.
-  */
-  iMinHash = walFramePage(pWal->minFrame);
-  for(iHash=walFramePage(iLast); iHash>=iMinHash && iRead==0; iHash--){
-    volatile ht_slot *aHash;      /* Pointer to hash table */
-    volatile u32 *aPgno;          /* Pointer to array of page numbers */
-    u32 iZero;                    /* Frame number corresponding to aPgno[0] */
-    int iKey;                     /* Hash slot index */
-    int nCollide;                 /* Number of hash collisions remaining */
-    int rc;                       /* Error code */
-
-    rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    nCollide = HASHTABLE_NSLOT;
-    for(iKey=walHash(pgno); aHash[iKey]; iKey=walNextHash(iKey)){
-      u32 iFrame = aHash[iKey] + iZero;
-      if( iFrame<=iLast && iFrame>=pWal->minFrame && aPgno[aHash[iKey]]==pgno ){
-        assert( iFrame>iRead || CORRUPT_DB );
-        iRead = iFrame;
-      }
-      if( (nCollide--)==0 ){
-        return SQLITE_CORRUPT_BKPT;
-      }
-    }
-  }
-
-#ifdef SQLITE_ENABLE_EXPENSIVE_ASSERT
-  /* If expensive assert() statements are available, do a linear search
-  ** of the wal-index file content. Make sure the results agree with the
-  ** result obtained using the hash indexes above.  */
-  {
-    u32 iRead2 = 0;
-    u32 iTest;
-    assert( pWal->minFrame>0 );
-    for(iTest=iLast; iTest>=pWal->minFrame; iTest--){
-      if( walFramePgno(pWal, iTest)==pgno ){
-        iRead2 = iTest;
-        break;
-      }
-    }
-    assert( iRead==iRead2 );
-  }
-#endif
-
-  *piRead = iRead;
-  return SQLITE_OK;
-}
-
-/*
-** Read the contents of frame iRead from the wal file into buffer pOut
-** (which is nOut bytes in size). Return SQLITE_OK if successful, or an
-** error code otherwise.
-*/
-SQLITE_PRIVATE int sqlite3WalReadFrame(
-  Wal *pWal,                      /* WAL handle */
-  u32 iRead,                      /* Frame to read */
-  int nOut,                       /* Size of buffer pOut in bytes */
-  u8 *pOut                        /* Buffer to write page data to */
-){
-  int sz;
-  i64 iOffset;
-  sz = pWal->hdr.szPage;
-  sz = (sz&0xfe00) + ((sz&0x0001)<<16);
-  testcase( sz<=32768 );
-  testcase( sz>=65536 );
-  iOffset = walFrameOffset(iRead, sz) + WAL_FRAME_HDRSIZE;
-  /* testcase( IS_BIG_INT(iOffset) ); // requires a 4GiB WAL */
-  return sqlite3OsRead(pWal->pWalFd, pOut, (nOut>sz ? sz : nOut), iOffset);
-}
-
-/* 
-** Return the size of the database in pages (or zero, if unknown).
-*/
-SQLITE_PRIVATE Pgno sqlite3WalDbsize(Wal *pWal){
-  if( pWal && ALWAYS(pWal->readLock>=0) ){
-    return pWal->hdr.nPage;
-  }
-  return 0;
-}
-
-
-/* 
-** This function starts a write transaction on the WAL.
-**
-** A read transaction must have already been started by a prior call
-** to sqlite3WalBeginReadTransaction().
-**
-** If another thread or process has written into the database since
-** the read transaction was started, then it is not possible for this
-** thread to write as doing so would cause a fork.  So this routine
-** returns SQLITE_BUSY in that case and no write transaction is started.
-**
-** There can only be a single writer active at a time.
-*/
-SQLITE_PRIVATE int sqlite3WalBeginWriteTransaction(Wal *pWal){
-  int rc;
-
-  /* Cannot start a write transaction without first holding a read
-  ** transaction. */
-  assert( pWal->readLock>=0 );
-
-  if( pWal->readOnly ){
-    return SQLITE_READONLY;
-  }
-
-  /* Only one writer allowed at a time.  Get the write lock.  Return
-  ** SQLITE_BUSY if unable.
-  */
-  rc = walLockExclusive(pWal, WAL_WRITE_LOCK, 1, 0);
-  if( rc ){
-    return rc;
-  }
-  pWal->writeLock = 1;
-
-  /* If another connection has written to the database file since the
-  ** time the read transaction on this connection was started, then
-  ** the write is disallowed.
-  */
-  if( memcmp(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr))!=0 ){
-    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
-    pWal->writeLock = 0;
-    rc = SQLITE_BUSY_SNAPSHOT;
-  }
-
-  return rc;
-}
-
-/*
-** End a write transaction.  The commit has already been done.  This
-** routine merely releases the lock.
-*/
-SQLITE_PRIVATE int sqlite3WalEndWriteTransaction(Wal *pWal){
-  if( pWal->writeLock ){
-    walUnlockExclusive(pWal, WAL_WRITE_LOCK, 1);
-    pWal->writeLock = 0;
-    pWal->truncateOnCommit = 0;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** If any data has been written (but not committed) to the log file, this
-** function moves the write-pointer back to the start of the transaction.
-**
-** Additionally, the callback function is invoked for each frame written
-** to the WAL since the start of the transaction. If the callback returns
-** other than SQLITE_OK, it is not invoked again and the error code is
-** returned to the caller.
-**
-** Otherwise, if the callback function does not return an error, this
-** function returns SQLITE_OK.
-*/
-SQLITE_PRIVATE int sqlite3WalUndo(Wal *pWal, int (*xUndo)(void *, Pgno), void *pUndoCtx){
-  int rc = SQLITE_OK;
-  if( ALWAYS(pWal->writeLock) ){
-    Pgno iMax = pWal->hdr.mxFrame;
-    Pgno iFrame;
-  
-    /* Restore the clients cache of the wal-index header to the state it
-    ** was in before the client began writing to the database. 
-    */
-    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
-
-    for(iFrame=pWal->hdr.mxFrame+1; 
-        ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; 
-        iFrame++
-    ){
-      /* This call cannot fail. Unless the page for which the page number
-      ** is passed as the second argument is (a) in the cache and 
-      ** (b) has an outstanding reference, then xUndo is either a no-op
-      ** (if (a) is false) or simply expels the page from the cache (if (b)
-      ** is false).
-      **
-      ** If the upper layer is doing a rollback, it is guaranteed that there
-      ** are no outstanding references to any page other than page 1. And
-      ** page 1 is never written to the log until the transaction is
-      ** committed. As a result, the call to xUndo may not fail.
-      */
-      assert( walFramePgno(pWal, iFrame)!=1 );
-      rc = xUndo(pUndoCtx, walFramePgno(pWal, iFrame));
-    }
-    if( iMax!=pWal->hdr.mxFrame ) walCleanupHash(pWal);
-  }
-  return rc;
-}
-
-/* 
-** Argument aWalData must point to an array of WAL_SAVEPOINT_NDATA u32 
-** values. This function populates the array with values required to 
-** "rollback" the write position of the WAL handle back to the current 
-** point in the event of a savepoint rollback (via WalSavepointUndo()).
-*/
-SQLITE_PRIVATE void sqlite3WalSavepoint(Wal *pWal, u32 *aWalData){
-  assert( pWal->writeLock );
-  aWalData[0] = pWal->hdr.mxFrame;
-  aWalData[1] = pWal->hdr.aFrameCksum[0];
-  aWalData[2] = pWal->hdr.aFrameCksum[1];
-  aWalData[3] = pWal->nCkpt;
-}
-
-/* 
-** Move the write position of the WAL back to the point identified by
-** the values in the aWalData[] array. aWalData must point to an array
-** of WAL_SAVEPOINT_NDATA u32 values that has been previously populated
-** by a call to WalSavepoint().
-*/
-SQLITE_PRIVATE int sqlite3WalSavepointUndo(Wal *pWal, u32 *aWalData){
-  int rc = SQLITE_OK;
-
-  assert( pWal->writeLock );
-  assert( aWalData[3]!=pWal->nCkpt || aWalData[0]<=pWal->hdr.mxFrame );
-
-  if( aWalData[3]!=pWal->nCkpt ){
-    /* This savepoint was opened immediately after the write-transaction
-    ** was started. Right after that, the writer decided to wrap around
-    ** to the start of the log. Update the savepoint values to match.
-    */
-    aWalData[0] = 0;
-    aWalData[3] = pWal->nCkpt;
-  }
-
-  if( aWalData[0]<pWal->hdr.mxFrame ){
-    pWal->hdr.mxFrame = aWalData[0];
-    pWal->hdr.aFrameCksum[0] = aWalData[1];
-    pWal->hdr.aFrameCksum[1] = aWalData[2];
-    walCleanupHash(pWal);
-  }
-
-  return rc;
-}
-
-/*
-** This function is called just before writing a set of frames to the log
-** file (see sqlite3WalFrames()). It checks to see if, instead of appending
-** to the current log file, it is possible to overwrite the start of the
-** existing log file with the new frames (i.e. "reset" the log). If so,
-** it sets pWal->hdr.mxFrame to 0. Otherwise, pWal->hdr.mxFrame is left
-** unchanged.
-**
-** SQLITE_OK is returned if no error is encountered (regardless of whether
-** or not pWal->hdr.mxFrame is modified). An SQLite error code is returned
-** if an error occurs.
-*/
-static int walRestartLog(Wal *pWal){
-  int rc = SQLITE_OK;
-  int cnt;
-
-  if( pWal->readLock==0 ){
-    volatile WalCkptInfo *pInfo = walCkptInfo(pWal);
-    assert( pInfo->nBackfill==pWal->hdr.mxFrame );
-    if( pInfo->nBackfill>0 ){
-      u32 salt1;
-      sqlite3_randomness(4, &salt1);
-      rc = walLockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1, 0);
-      if( rc==SQLITE_OK ){
-        /* If all readers are using WAL_READ_LOCK(0) (in other words if no
-        ** readers are currently using the WAL), then the transactions
-        ** frames will overwrite the start of the existing log. Update the
-        ** wal-index header to reflect this.
-        **
-        ** In theory it would be Ok to update the cache of the header only
-        ** at this point. But updating the actual wal-index header is also
-        ** safe and means there is no special case for sqlite3WalUndo()
-        ** to handle if this transaction is rolled back.  */
-        walRestartHdr(pWal, salt1);
-        walUnlockExclusive(pWal, WAL_READ_LOCK(1), WAL_NREADER-1);
-      }else if( rc!=SQLITE_BUSY ){
-        return rc;
-      }
-    }
-    walUnlockShared(pWal, WAL_READ_LOCK(0));
-    pWal->readLock = -1;
-    cnt = 0;
-    do{
-      int notUsed;
-      rc = walTryBeginRead(pWal, &notUsed, 1, ++cnt);
-    }while( rc==WAL_RETRY );
-    assert( (rc&0xff)!=SQLITE_BUSY ); /* BUSY not possible when useWal==1 */
-    testcase( (rc&0xff)==SQLITE_IOERR );
-    testcase( rc==SQLITE_PROTOCOL );
-    testcase( rc==SQLITE_OK );
-  }
-  return rc;
-}
-
-/*
-** Information about the current state of the WAL file and where
-** the next fsync should occur - passed from sqlite3WalFrames() into
-** walWriteToLog().
-*/
-typedef struct WalWriter {
-  Wal *pWal;                   /* The complete WAL information */
-  sqlite3_file *pFd;           /* The WAL file to which we write */
-  sqlite3_int64 iSyncPoint;    /* Fsync at this offset */
-  int syncFlags;               /* Flags for the fsync */
-  int szPage;                  /* Size of one page */
-} WalWriter;
-
-/*
-** Write iAmt bytes of content into the WAL file beginning at iOffset.
-** Do a sync when crossing the p->iSyncPoint boundary.
-**
-** In other words, if iSyncPoint is in between iOffset and iOffset+iAmt,
-** first write the part before iSyncPoint, then sync, then write the
-** rest.
-*/
-static int walWriteToLog(
-  WalWriter *p,              /* WAL to write to */
-  void *pContent,            /* Content to be written */
-  int iAmt,                  /* Number of bytes to write */
-  sqlite3_int64 iOffset      /* Start writing at this offset */
-){
-  int rc;
-  if( iOffset<p->iSyncPoint && iOffset+iAmt>=p->iSyncPoint ){
-    int iFirstAmt = (int)(p->iSyncPoint - iOffset);
-    rc = sqlite3OsWrite(p->pFd, pContent, iFirstAmt, iOffset);
-    if( rc ) return rc;
-    iOffset += iFirstAmt;
-    iAmt -= iFirstAmt;
-    pContent = (void*)(iFirstAmt + (char*)pContent);
-    assert( p->syncFlags & (SQLITE_SYNC_NORMAL|SQLITE_SYNC_FULL) );
-    rc = sqlite3OsSync(p->pFd, p->syncFlags & SQLITE_SYNC_MASK);
-    if( iAmt==0 || rc ) return rc;
-  }
-  rc = sqlite3OsWrite(p->pFd, pContent, iAmt, iOffset);
-  return rc;
-}
-
-/*
-** Write out a single frame of the WAL
-*/
-static int walWriteOneFrame(
-  WalWriter *p,               /* Where to write the frame */
-  PgHdr *pPage,               /* The page of the frame to be written */
-  int nTruncate,              /* The commit flag.  Usually 0.  >0 for commit */
-  sqlite3_int64 iOffset       /* Byte offset at which to write */
-){
-  int rc;                         /* Result code from subfunctions */
-  void *pData;                    /* Data actually written */
-  u8 aFrame[WAL_FRAME_HDRSIZE];   /* Buffer to assemble frame-header in */
-#if defined(SQLITE_HAS_CODEC)
-  if( (pData = sqlite3PagerCodec(pPage))==0 ) return SQLITE_NOMEM;
-#else
-  pData = pPage->pData;
-#endif
-  walEncodeFrame(p->pWal, pPage->pgno, nTruncate, pData, aFrame);
-  rc = walWriteToLog(p, aFrame, sizeof(aFrame), iOffset);
-  if( rc ) return rc;
-  /* Write the page data */
-  rc = walWriteToLog(p, pData, p->szPage, iOffset+sizeof(aFrame));
-  return rc;
-}
-
-/* 
-** Write a set of frames to the log. The caller must hold the write-lock
-** on the log file (obtained using sqlite3WalBeginWriteTransaction()).
-*/
-SQLITE_PRIVATE int sqlite3WalFrames(
-  Wal *pWal,                      /* Wal handle to write to */
-  int szPage,                     /* Database page-size in bytes */
-  PgHdr *pList,                   /* List of dirty pages to write */
-  Pgno nTruncate,                 /* Database size after this commit */
-  int isCommit,                   /* True if this is a commit */
-  int sync_flags                  /* Flags to pass to OsSync() (or 0) */
-){
-  int rc;                         /* Used to catch return codes */
-  u32 iFrame;                     /* Next frame address */
-  PgHdr *p;                       /* Iterator to run through pList with. */
-  PgHdr *pLast = 0;               /* Last frame in list */
-  int nExtra = 0;                 /* Number of extra copies of last page */
-  int szFrame;                    /* The size of a single frame */
-  i64 iOffset;                    /* Next byte to write in WAL file */
-  WalWriter w;                    /* The writer */
-
-  assert( pList );
-  assert( pWal->writeLock );
-
-  /* If this frame set completes a transaction, then nTruncate>0.  If
-  ** nTruncate==0 then this frame set does not complete the transaction. */
-  assert( (isCommit!=0)==(nTruncate!=0) );
-
-#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
-  { int cnt; for(cnt=0, p=pList; p; p=p->pDirty, cnt++){}
-    WALTRACE(("WAL%p: frame write begin. %d frames. mxFrame=%d. %s\n",
-              pWal, cnt, pWal->hdr.mxFrame, isCommit ? "Commit" : "Spill"));
-  }
-#endif
-
-  /* See if it is possible to write these frames into the start of the
-  ** log file, instead of appending to it at pWal->hdr.mxFrame.
-  */
-  if( SQLITE_OK!=(rc = walRestartLog(pWal)) ){
-    return rc;
-  }
-
-  /* If this is the first frame written into the log, write the WAL
-  ** header to the start of the WAL file. See comments at the top of
-  ** this source file for a description of the WAL header format.
-  */
-  iFrame = pWal->hdr.mxFrame;
-  if( iFrame==0 ){
-    u8 aWalHdr[WAL_HDRSIZE];      /* Buffer to assemble wal-header in */
-    u32 aCksum[2];                /* Checksum for wal-header */
-
-    sqlite3Put4byte(&aWalHdr[0], (WAL_MAGIC | SQLITE_BIGENDIAN));
-    sqlite3Put4byte(&aWalHdr[4], WAL_MAX_VERSION);
-    sqlite3Put4byte(&aWalHdr[8], szPage);
-    sqlite3Put4byte(&aWalHdr[12], pWal->nCkpt);
-    if( pWal->nCkpt==0 ) sqlite3_randomness(8, pWal->hdr.aSalt);
-    memcpy(&aWalHdr[16], pWal->hdr.aSalt, 8);
-    walChecksumBytes(1, aWalHdr, WAL_HDRSIZE-2*4, 0, aCksum);
-    sqlite3Put4byte(&aWalHdr[24], aCksum[0]);
-    sqlite3Put4byte(&aWalHdr[28], aCksum[1]);
-    
-    pWal->szPage = szPage;
-    pWal->hdr.bigEndCksum = SQLITE_BIGENDIAN;
-    pWal->hdr.aFrameCksum[0] = aCksum[0];
-    pWal->hdr.aFrameCksum[1] = aCksum[1];
-    pWal->truncateOnCommit = 1;
-
-    rc = sqlite3OsWrite(pWal->pWalFd, aWalHdr, sizeof(aWalHdr), 0);
-    WALTRACE(("WAL%p: wal-header write %s\n", pWal, rc ? "failed" : "ok"));
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-
-    /* Sync the header (unless SQLITE_IOCAP_SEQUENTIAL is true or unless
-    ** all syncing is turned off by PRAGMA synchronous=OFF).  Otherwise
-    ** an out-of-order write following a WAL restart could result in
-    ** database corruption.  See the ticket:
-    **
-    **     http://localhost:591/sqlite/info/ff5be73dee
-    */
-    if( pWal->syncHeader && sync_flags ){
-      rc = sqlite3OsSync(pWal->pWalFd, sync_flags & SQLITE_SYNC_MASK);
-      if( rc ) return rc;
-    }
-  }
-  assert( (int)pWal->szPage==szPage );
-
-  /* Setup information needed to write frames into the WAL */
-  w.pWal = pWal;
-  w.pFd = pWal->pWalFd;
-  w.iSyncPoint = 0;
-  w.syncFlags = sync_flags;
-  w.szPage = szPage;
-  iOffset = walFrameOffset(iFrame+1, szPage);
-  szFrame = szPage + WAL_FRAME_HDRSIZE;
-
-  /* Write all frames into the log file exactly once */
-  for(p=pList; p; p=p->pDirty){
-    int nDbSize;   /* 0 normally.  Positive == commit flag */
-    iFrame++;
-    assert( iOffset==walFrameOffset(iFrame, szPage) );
-    nDbSize = (isCommit && p->pDirty==0) ? nTruncate : 0;
-    rc = walWriteOneFrame(&w, p, nDbSize, iOffset);
-    if( rc ) return rc;
-    pLast = p;
-    iOffset += szFrame;
-  }
-
-  /* If this is the end of a transaction, then we might need to pad
-  ** the transaction and/or sync the WAL file.
-  **
-  ** Padding and syncing only occur if this set of frames complete a
-  ** transaction and if PRAGMA synchronous=FULL.  If synchronous==NORMAL
-  ** or synchronous==OFF, then no padding or syncing are needed.
-  **
-  ** If SQLITE_IOCAP_POWERSAFE_OVERWRITE is defined, then padding is not
-  ** needed and only the sync is done.  If padding is needed, then the
-  ** final frame is repeated (with its commit mark) until the next sector
-  ** boundary is crossed.  Only the part of the WAL prior to the last
-  ** sector boundary is synced; the part of the last frame that extends
-  ** past the sector boundary is written after the sync.
-  */
-  if( isCommit && (sync_flags & WAL_SYNC_TRANSACTIONS)!=0 ){
-    if( pWal->padToSectorBoundary ){
-      int sectorSize = sqlite3SectorSize(pWal->pWalFd);
-      w.iSyncPoint = ((iOffset+sectorSize-1)/sectorSize)*sectorSize;
-      while( iOffset<w.iSyncPoint ){
-        rc = walWriteOneFrame(&w, pLast, nTruncate, iOffset);
-        if( rc ) return rc;
-        iOffset += szFrame;
-        nExtra++;
-      }
-    }else{
-      rc = sqlite3OsSync(w.pFd, sync_flags & SQLITE_SYNC_MASK);
-    }
-  }
-
-  /* If this frame set completes the first transaction in the WAL and
-  ** if PRAGMA journal_size_limit is set, then truncate the WAL to the
-  ** journal size limit, if possible.
-  */
-  if( isCommit && pWal->truncateOnCommit && pWal->mxWalSize>=0 ){
-    i64 sz = pWal->mxWalSize;
-    if( walFrameOffset(iFrame+nExtra+1, szPage)>pWal->mxWalSize ){
-      sz = walFrameOffset(iFrame+nExtra+1, szPage);
-    }
-    walLimitSize(pWal, sz);
-    pWal->truncateOnCommit = 0;
-  }
-
-  /* Append data to the wal-index. It is not necessary to lock the 
-  ** wal-index to do this as the SQLITE_SHM_WRITE lock held on the wal-index
-  ** guarantees that there are no other writers, and no data that may
-  ** be in use by existing readers is being overwritten.
-  */
-  iFrame = pWal->hdr.mxFrame;
-  for(p=pList; p && rc==SQLITE_OK; p=p->pDirty){
-    iFrame++;
-    rc = walIndexAppend(pWal, iFrame, p->pgno);
-  }
-  while( rc==SQLITE_OK && nExtra>0 ){
-    iFrame++;
-    nExtra--;
-    rc = walIndexAppend(pWal, iFrame, pLast->pgno);
-  }
-
-  if( rc==SQLITE_OK ){
-    /* Update the private copy of the header. */
-    pWal->hdr.szPage = (u16)((szPage&0xff00) | (szPage>>16));
-    testcase( szPage<=32768 );
-    testcase( szPage>=65536 );
-    pWal->hdr.mxFrame = iFrame;
-    if( isCommit ){
-      pWal->hdr.iChange++;
-      pWal->hdr.nPage = nTruncate;
-    }
-    /* If this is a commit, update the wal-index header too. */
-    if( isCommit ){
-      walIndexWriteHdr(pWal);
-      pWal->iCallback = iFrame;
-    }
-  }
-
-  WALTRACE(("WAL%p: frame write %s\n", pWal, rc ? "failed" : "ok"));
-  return rc;
-}
-
-/* 
-** This routine is called to implement sqlite3_wal_checkpoint() and
-** related interfaces.
-**
-** Obtain a CHECKPOINT lock and then backfill as much information as
-** we can from WAL into the database.
-**
-** If parameter xBusy is not NULL, it is a pointer to a busy-handler
-** callback. In this case this function runs a blocking checkpoint.
-*/
-SQLITE_PRIVATE int sqlite3WalCheckpoint(
-  Wal *pWal,                      /* Wal connection */
-  int eMode,                      /* PASSIVE, FULL, RESTART, or TRUNCATE */
-  int (*xBusy)(void*),            /* Function to call when busy */
-  void *pBusyArg,                 /* Context argument for xBusyHandler */
-  int sync_flags,                 /* Flags to sync db file with (or 0) */
-  int nBuf,                       /* Size of temporary buffer */
-  u8 *zBuf,                       /* Temporary buffer to use */
-  int *pnLog,                     /* OUT: Number of frames in WAL */
-  int *pnCkpt                     /* OUT: Number of backfilled frames in WAL */
-){
-  int rc;                         /* Return code */
-  int isChanged = 0;              /* True if a new wal-index header is loaded */
-  int eMode2 = eMode;             /* Mode to pass to walCheckpoint() */
-  int (*xBusy2)(void*) = xBusy;   /* Busy handler for eMode2 */
-
-  assert( pWal->ckptLock==0 );
-  assert( pWal->writeLock==0 );
-
-  /* EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
-  ** in the SQLITE_CHECKPOINT_PASSIVE mode. */
-  assert( eMode!=SQLITE_CHECKPOINT_PASSIVE || xBusy==0 );
-
-  if( pWal->readOnly ) return SQLITE_READONLY;
-  WALTRACE(("WAL%p: checkpoint begins\n", pWal));
-
-  /* IMPLEMENTATION-OF: R-62028-47212 All calls obtain an exclusive 
-  ** "checkpoint" lock on the database file. */
-  rc = walLockExclusive(pWal, WAL_CKPT_LOCK, 1, 0);
-  if( rc ){
-    /* EVIDENCE-OF: R-10421-19736 If any other process is running a
-    ** checkpoint operation at the same time, the lock cannot be obtained and
-    ** SQLITE_BUSY is returned.
-    ** EVIDENCE-OF: R-53820-33897 Even if there is a busy-handler configured,
-    ** it will not be invoked in this case.
-    */
-    testcase( rc==SQLITE_BUSY );
-    testcase( xBusy!=0 );
-    return rc;
-  }
-  pWal->ckptLock = 1;
-
-  /* IMPLEMENTATION-OF: R-59782-36818 The SQLITE_CHECKPOINT_FULL, RESTART and
-  ** TRUNCATE modes also obtain the exclusive "writer" lock on the database
-  ** file.
-  **
-  ** EVIDENCE-OF: R-60642-04082 If the writer lock cannot be obtained
-  ** immediately, and a busy-handler is configured, it is invoked and the
-  ** writer lock retried until either the busy-handler returns 0 or the
-  ** lock is successfully obtained.
-  */
-  if( eMode!=SQLITE_CHECKPOINT_PASSIVE ){
-    rc = walBusyLock(pWal, xBusy, pBusyArg, WAL_WRITE_LOCK, 1);
-    if( rc==SQLITE_OK ){
-      pWal->writeLock = 1;
-    }else if( rc==SQLITE_BUSY ){
-      eMode2 = SQLITE_CHECKPOINT_PASSIVE;
-      xBusy2 = 0;
-      rc = SQLITE_OK;
-    }
-  }
-
-  /* Read the wal-index header. */
-  if( rc==SQLITE_OK ){
-    rc = walIndexReadHdr(pWal, &isChanged);
-    if( isChanged && pWal->pDbFd->pMethods->iVersion>=3 ){
-      sqlite3OsUnfetch(pWal->pDbFd, 0, 0);
-    }
-  }
-
-  /* Copy data from the log to the database file. */
-  if( rc==SQLITE_OK ){
-    if( pWal->hdr.mxFrame && walPagesize(pWal)!=nBuf ){
-      rc = SQLITE_CORRUPT_BKPT;
-    }else{
-      rc = walCheckpoint(pWal, eMode2, xBusy2, pBusyArg, sync_flags, zBuf);
-    }
-
-    /* If no error occurred, set the output variables. */
-    if( rc==SQLITE_OK || rc==SQLITE_BUSY ){
-      if( pnLog ) *pnLog = (int)pWal->hdr.mxFrame;
-      if( pnCkpt ) *pnCkpt = (int)(walCkptInfo(pWal)->nBackfill);
-    }
-  }
-
-  if( isChanged ){
-    /* If a new wal-index header was loaded before the checkpoint was 
-    ** performed, then the pager-cache associated with pWal is now
-    ** out of date. So zero the cached wal-index header to ensure that
-    ** next time the pager opens a snapshot on this database it knows that
-    ** the cache needs to be reset.
-    */
-    memset(&pWal->hdr, 0, sizeof(WalIndexHdr));
-  }
-
-  /* Release the locks. */
-  sqlite3WalEndWriteTransaction(pWal);
-  walUnlockExclusive(pWal, WAL_CKPT_LOCK, 1);
-  pWal->ckptLock = 0;
-  WALTRACE(("WAL%p: checkpoint %s\n", pWal, rc ? "failed" : "ok"));
-  return (rc==SQLITE_OK && eMode!=eMode2 ? SQLITE_BUSY : rc);
-}
-
-#if 0
-/* Return the value to pass to a sqlite3_wal_hook callback, the
-** number of frames in the WAL at the point of the last commit since
-** sqlite3WalCallback() was called.  If no commits have occurred since
-** the last call, then return 0.
-*/
-SQLITE_PRIVATE int sqlite3WalCallback(Wal *pWal){
-  u32 ret = 0;
-  if( pWal ){
-    ret = pWal->iCallback;
-    pWal->iCallback = 0;
-  }
-  return (int)ret;
-}
-#endif
-
-/*
-** This function is called to change the WAL subsystem into or out
-** of locking_mode=EXCLUSIVE.
-**
-** If op is zero, then attempt to change from locking_mode=EXCLUSIVE
-** into locking_mode=NORMAL.  This means that we must acquire a lock
-** on the pWal->readLock byte.  If the WAL is already in locking_mode=NORMAL
-** or if the acquisition of the lock fails, then return 0.  If the
-** transition out of exclusive-mode is successful, return 1.  This
-** operation must occur while the pager is still holding the exclusive
-** lock on the main database file.
-**
-** If op is one, then change from locking_mode=NORMAL into 
-** locking_mode=EXCLUSIVE.  This means that the pWal->readLock must
-** be released.  Return 1 if the transition is made and 0 if the
-** WAL is already in exclusive-locking mode - meaning that this
-** routine is a no-op.  The pager must already hold the exclusive lock
-** on the main database file before invoking this operation.
-**
-** If op is negative, then do a dry-run of the op==1 case but do
-** not actually change anything. The pager uses this to see if it
-** should acquire the database exclusive lock prior to invoking
-** the op==1 case.
-*/
-SQLITE_PRIVATE int sqlite3WalExclusiveMode(Wal *pWal, int op){
-  int rc;
-  assert( pWal->writeLock==0 );
-  assert( pWal->exclusiveMode!=WAL_HEAPMEMORY_MODE || op==-1 );
-
-  /* pWal->readLock is usually set, but might be -1 if there was a 
-  ** prior error while attempting to acquire are read-lock. This cannot 
-  ** happen if the connection is actually in exclusive mode (as no xShmLock
-  ** locks are taken in this case). Nor should the pager attempt to
-  ** upgrade to exclusive-mode following such an error.
-  */
-  assert( pWal->readLock>=0 || pWal->lockError );
-  assert( pWal->readLock>=0 || (op<=0 && pWal->exclusiveMode==0) );
-
-  if( op==0 ){
-    if( pWal->exclusiveMode ){
-      pWal->exclusiveMode = 0;
-      if( walLockShared(pWal, WAL_READ_LOCK(pWal->readLock))!=SQLITE_OK ){
-        pWal->exclusiveMode = 1;
-      }
-      rc = pWal->exclusiveMode==0;
-    }else{
-      /* Already in locking_mode=NORMAL */
-      rc = 0;
-    }
-  }else if( op>0 ){
-    assert( pWal->exclusiveMode==0 );
-    assert( pWal->readLock>=0 );
-    walUnlockShared(pWal, WAL_READ_LOCK(pWal->readLock));
-    pWal->exclusiveMode = 1;
-    rc = 1;
-  }else{
-    rc = pWal->exclusiveMode==0;
-  }
-  return rc;
-}
-
-#if 0
-/* 
-** Return true if the argument is non-NULL and the WAL module is using
-** heap-memory for the wal-index. Otherwise, if the argument is NULL or the
-** WAL module is using shared-memory, return false. 
-*/
-SQLITE_PRIVATE int sqlite3WalHeapMemory(Wal *pWal){
-  return (pWal && pWal->exclusiveMode==WAL_HEAPMEMORY_MODE );
-}
-#endif
-
-#ifdef SQLITE_ENABLE_ZIPVFS
-/*
-** If the argument is not NULL, it points to a Wal object that holds a
-** read-lock. This function returns the database page-size if it is known,
-** or zero if it is not (or if pWal is NULL).
-*/
-SQLITE_PRIVATE int sqlite3WalFramesize(Wal *pWal){
-  assert( pWal==0 || pWal->readLock>=0 );
-  return (pWal ? pWal->szPage : 0);
-}
-#endif
-
-#endif /* #ifndef SQLITE_OMIT_WAL */
-
-/************** End of wal.c *************************************************/
-/************** Begin file btmutex.c *****************************************/
-/*
-** 2007 August 27
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains code used to implement mutexes on Btree objects.
-** This code really belongs in btree.c.  But btree.c is getting too
-** big and we want to break it down some.  This packaged seemed like
-** a good breakout.
-*/
-/* #include "btreeInt.h" */
-#ifndef SQLITE_OMIT_SHARED_CACHE
-#if SQLITE_THREADSAFE
-
-/*
-** Obtain the BtShared mutex associated with B-Tree handle p. Also,
-** set BtShared.db to the database handle associated with p and the
-** p->locked boolean to true.
-*/
-static void lockBtreeMutex(Btree *p){
-  assert( p->locked==0 );
-  assert( sqlite3_mutex_notheld(p->pBt->mutex) );
-  assert( sqlite3_mutex_held(p->mutex) );
-
-  sqlite3_mutex_enter(p->pBt->mutex);
-  p->pBt->pBt = p;
-  p->locked = 1;
-}
-
-/*
-** Release the BtShared mutex associated with B-Tree handle p and
-** clear the p->locked boolean.
-*/
-static void SQLITE_NOINLINE unlockBtreeMutex(Btree *p){
-  BtShared *pBt = p->pBt;
-  assert( p->locked==1 );
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  assert( p->db==pBt->db );
-
-  sqlite3_mutex_leave(pBt->mutex);
-  p->locked = 0;
-}
-
-/* Forward reference */
-static void SQLITE_NOINLINE btreeLockCarefully(Btree *p);
-
-/*
-** Enter a mutex on the given BTree object.
-**
-** If the object is not sharable, then no mutex is ever required
-** and this routine is a no-op.  The underlying mutex is non-recursive.
-** But we keep a reference count in Btree.wantToLock so the behavior
-** of this interface is recursive.
-**
-** To avoid deadlocks, multiple Btrees are locked in the same order
-** by all database connections.  The p->pNext is a list of other
-** Btrees belonging to the same database connection as the p Btree
-** which need to be locked after p.  If we cannot get a lock on
-** p, then first unlock all of the others on p->pNext, then wait
-** for the lock to become available on p, then relock all of the
-** subsequent Btrees that desire a lock.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeEnter(Btree *p){
-  /* Some basic sanity checking on the Btree.  The list of Btrees
-  ** connected by pNext and pPrev should be in sorted order by
-  ** Btree.pBt value. All elements of the list should belong to
-  ** the same connection. Only shared Btrees are on the list. */
-  assert( p->pNext==0 || p->pNext->pBt>p->pBt );
-  assert( p->pPrev==0 || p->pPrev->pBt<p->pBt );
-  assert( p->pNext==0 || p->pNext->db==p->db );
-  assert( p->pPrev==0 || p->pPrev->db==p->db );
-  assert( p->sharable || (p->pNext==0 && p->pPrev==0) );
-
-  /* Check for locking consistency */
-  assert( !p->locked || p->wantToLock>0 );
-  assert( p->sharable || p->wantToLock==0 );
-
-  /* We should already hold a lock on the database connection */
-  assert( sqlite3_mutex_held(p->db->mutex) );
-
-  /* Unless the database is sharable and unlocked, then BtShared.db
-  ** should already be set correctly. */
-  assert( (p->locked==0 && p->sharable) || p->pBt->db==p->db );
-
-  if( !p->sharable ) return;
-  p->wantToLock++;
-  if( p->locked ) return;
-  btreeLockCarefully(p);
-}
-
-/* This is a helper function for sqlite3BtreeLock(). By moving
-** complex, but seldom used logic, out of sqlite3BtreeLock() and
-** into this routine, we avoid unnecessary stack pointer changes
-** and thus help the sqlite3BtreeLock() routine to run much faster
-** in the common case.
-*/
-static void SQLITE_NOINLINE btreeLockCarefully(Btree *p){
-  Btree *pLater;
-
-  /* In most cases, we should be able to acquire the lock we
-  ** want without having to go through the ascending lock
-  ** procedure that follows.  Just be sure not to block.
-  */
-  if( sqlite3_mutex_try(p->pBt->mutex)==SQLITE_OK ){
-    p->pBt->pBt = p;
-    p->locked = 1;
-    return;
-  }
-
-  /* To avoid deadlock, first release all locks with a larger
-  ** BtShared address.  Then acquire our lock.  Then reacquire
-  ** the other BtShared locks that we used to hold in ascending
-  ** order.
-  */
-  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
-    assert( pLater->sharable );
-    assert( pLater->pNext==0 || pLater->pNext->pBt>pLater->pBt );
-    assert( !pLater->locked || pLater->wantToLock>0 );
-    if( pLater->locked ){
-      unlockBtreeMutex(pLater);
-    }
-  }
-  lockBtreeMutex(p);
-  for(pLater=p->pNext; pLater; pLater=pLater->pNext){
-    if( pLater->wantToLock ){
-      lockBtreeMutex(pLater);
-    }
-  }
-}
-
-
-/*
-** Exit the recursive mutex on a Btree.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeLeave(Btree *p){
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  if( p->sharable ){
-    assert( p->wantToLock>0 );
-    p->wantToLock--;
-    if( p->wantToLock==0 ){
-      unlockBtreeMutex(p);
-    }
-  }
-}
-
-#ifndef NDEBUG
-/*
-** Return true if the BtShared mutex is held on the btree, or if the
-** B-Tree is not marked as sharable.
-**
-** This routine is used only from within assert() statements.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeHoldsMutex(Btree *p){
-  assert( p->sharable==0 || p->locked==0 || p->wantToLock>0 );
-  assert( p->sharable==0 || p->locked==0 || p->db==p->pBt->db );
-  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->pBt->mutex) );
-  assert( p->sharable==0 || p->locked==0 || sqlite3_mutex_held(p->db->mutex) );
-
-  return (p->sharable==0 || p->locked);
-}
-#endif
-
-
-#ifndef SQLITE_OMIT_INCRBLOB
-/*
-** Enter and leave a mutex on a Btree given a cursor owned by that
-** Btree.  These entry points are used by incremental I/O and can be
-** omitted if that module is not used.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeEnterCursor(BtCursor *pCur){
-  sqlite3BtreeEnter(pCur->pBtree);
-}
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeLeaveCursor(BtCursor *pCur){
-  sqlite3BtreeLeave(pCur->pBtree);
-}
-#endif /* SQLITE_OMIT_INCRBLOB */
-
-/*
-** Return true if a particular Btree requires a lock.  Return FALSE if
-** no lock is ever required since it is not sharable.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSharable(Btree *p){
-  return p->sharable;
-}
-
-#else /* SQLITE_THREADSAFE>0 above.  SQLITE_THREADSAFE==0 below */
-/*
-** The following are special cases for mutex enter routines for use
-** in single threaded applications that use shared cache.  Except for
-** these two routines, all mutex operations are no-ops in that case and
-** are null #defines in btree.h.
-**
-** If shared cache is disabled, then all btree mutex routines, including
-** the ones below, are no-ops and are null #defines in btree.h.
-*/
-
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeEnter(Btree *p){
-  p->pBt->db = p->db;
-}
-#endif /* if SQLITE_THREADSAFE */
-#endif /* ifndef SQLITE_OMIT_SHARED_CACHE */
-
-/************** End of btmutex.c *********************************************/
-/************** Begin file btree.c *******************************************/
-/*
-** 2004 April 6
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file implements an external (disk-based) database using BTrees.
-** See the header comment on "btreeInt.h" for additional information.
-** Including a description of file format and an overview of operation.
-*/
-/* #include "btreeInt.h" */
-
-/*
-** The header string that appears at the beginning of every
-** SQLite database.
-*/
-static const char zMagicHeader[] = SQLITE_FILE_HEADER;
-
-/*
-** Set this global variable to 1 to enable tracing using the TRACE
-** macro.
-*/
-#if 0
-int sqlite3BtreeTrace=1;  /* True to enable tracing */
-# define TRACE(X)  if(sqlite3BtreeTrace){printf X;fflush(stdout);}
-#else
-# define TRACE(X)
-#endif
-
-/*
-** Extract a 2-byte big-endian integer from an array of unsigned bytes.
-** But if the value is zero, make it 65536.
-**
-** This routine is used to extract the "offset to cell content area" value
-** from the header of a btree page.  If the page size is 65536 and the page
-** is empty, the offset should be 65536, but the 2-byte value stores zero.
-** This routine makes the necessary adjustment to 65536.
-*/
-#define get2byteNotZero(X)  (((((int)get2byte(X))-1)&0xffff)+1)
-
-/*
-** Values passed as the 5th argument to allocateBtreePage()
-*/
-#define BTALLOC_ANY   0           /* Allocate any page */
-#define BTALLOC_EXACT 1           /* Allocate exact page if possible */
-#define BTALLOC_LE    2           /* Allocate any page <= the parameter */
-
-/*
-** Macro IfNotOmitAV(x) returns (x) if SQLITE_OMIT_AUTOVACUUM is not 
-** defined, or 0 if it is. For example:
-**
-**   bIncrVacuum = IfNotOmitAV(pBtShared->incrVacuum);
-*/
-#ifndef SQLITE_OMIT_AUTOVACUUM
-#define IfNotOmitAV(expr) (expr)
-#else
-#define IfNotOmitAV(expr) 0
-#endif
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-/*
-** A list of BtShared objects that are eligible for participation
-** in shared cache.  This variable has file scope during normal builds,
-** but the test harness needs to access it so we make it global for 
-** test builds.
-**
-** Access to this variable is protected by SQLITE_MUTEX_STATIC_MASTER.
-*/
-#ifdef SQLITE_TEST
-SQLITE_PRIVATE BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
-#else
-static BtShared *SQLITE_WSD sqlite3SharedCacheList = 0;
-#endif
-#endif /* SQLITE_OMIT_SHARED_CACHE */
-
-#ifdef SQLITE_OMIT_SHARED_CACHE
-  /*
-  ** The functions querySharedCacheTableLock(), setSharedCacheTableLock(),
-  ** and clearAllSharedCacheTableLocks()
-  ** manipulate entries in the BtShared.pLock linked list used to store
-  ** shared-cache table level locks. If the library is compiled with the
-  ** shared-cache feature disabled, then there is only ever one user
-  ** of each BtShared structure and so this locking is not necessary. 
-  ** So define the lock related functions as no-ops.
-  */
-  #define querySharedCacheTableLock(a,b,c) SQLITE_OK
-  #define setSharedCacheTableLock(a,b,c) SQLITE_OK
-  #define clearAllSharedCacheTableLocks(a)
-  #define downgradeAllSharedCacheTableLocks(a)
-  #define hasSharedCacheTableLock(a,b,c,d) 1
-  #define hasReadConflicts(a, b) 0
-#endif
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-
-#ifdef SQLITE_DEBUG
-/*
-**** This function is only used as part of an assert() statement. ***
-**
-** Check to see if pBtree holds the required locks to read or write to the 
-** table with root page iRoot.   Return 1 if it does and 0 if not.
-**
-** For example, when writing to a table with root-page iRoot via 
-** Btree connection pBtree:
-**
-**    assert( hasSharedCacheTableLock(pBtree, iRoot, 0, WRITE_LOCK) );
-**
-** When writing to an index that resides in a sharable database, the 
-** caller should have first obtained a lock specifying the root page of
-** the corresponding table. This makes things a bit more complicated,
-** as this module treats each table as a separate structure. To determine
-** the table corresponding to the index being written, this
-** function has to search through the database schema.
-**
-** Instead of a lock on the table/index rooted at page iRoot, the caller may
-** hold a write-lock on the schema table (root page 1). This is also
-** acceptable.
-*/
-static int hasSharedCacheTableLock(
-  Btree *pBtree,         /* Handle that must hold lock */
-  Pgno iRoot,            /* Root page of b-tree */
-  int isIndex,           /* True if iRoot is the root of an index b-tree */
-  int eLockType          /* Required lock type (READ_LOCK or WRITE_LOCK) */
-){
-  Schema *pSchema = (Schema *)pBtree->pBt->pSchema;
-  Pgno iTab = 0;
-  BtLock *pLock;
-
-  /* If this database is not shareable, or if the client is reading
-  ** and has the read-uncommitted flag set, then no lock is required. 
-  ** Return true immediately.
-  */
-  if( (pBtree->sharable==0)
-   || (eLockType==READ_LOCK && (pBtree->flags & SQLITE_ReadUncommitted))
-  ){
-    return 1;
-  }
-
-  /* If the client is reading  or writing an index and the schema is
-  ** not loaded, then it is too difficult to actually check to see if
-  ** the correct locks are held.  So do not bother - just return true.
-  ** This case does not come up very often anyhow.
-  */
-  if( isIndex && (!pSchema || (pSchema->schemaFlags&DB_SchemaLoaded)==0) ){
-    return 1;
-  }
-
-  /* Figure out the root-page that the lock should be held on. For table
-  ** b-trees, this is just the root page of the b-tree being read or
-  ** written. For index b-trees, it is the root page of the associated
-  ** table.  */
-  if( isIndex ){
-    HashElem *p;
-    for(p=sqliteHashFirst(&pSchema->idxHash); p; p=sqliteHashNext(p)){
-      Index *pIdx = (Index *)sqliteHashData(p);
-      if( pIdx->tnum==(int)iRoot ){
-        if( iTab ){
-          /* Two or more indexes share the same root page.  There must
-          ** be imposter tables.  So just return true.  The assert is not
-          ** useful in that case. */
-          return 1;
-        }
-        iTab = pIdx->pTable->tnum;
-      }
-    }
-  }else{
-    iTab = iRoot;
-  }
-
-  /* Search for the required lock. Either a write-lock on root-page iTab, a 
-  ** write-lock on the schema table, or (if the client is reading) a
-  ** read-lock on iTab will suffice. Return 1 if any of these are found.  */
-  for(pLock=pBtree->pBt->pLock; pLock; pLock=pLock->pNext){
-    if( pLock->pBtree==pBtree 
-     && (pLock->iTable==iTab || (pLock->eLock==WRITE_LOCK && pLock->iTable==1))
-     && pLock->eLock>=eLockType 
-    ){
-      return 1;
-    }
-  }
-
-  /* Failed to find the required lock. */
-  return 0;
-}
-#endif /* SQLITE_DEBUG */
-
-#ifdef SQLITE_DEBUG
-/*
-**** This function may be used as part of assert() statements only. ****
-**
-** Return true if it would be illegal for pBtree to write into the
-** table or index rooted at iRoot because other shared connections are
-** simultaneously reading that same table or index.
-**
-** It is illegal for pBtree to write if some other Btree object that
-** shares the same BtShared object is currently reading or writing
-** the iRoot table.  Except, if the other Btree object has the
-** read-uncommitted flag set, then it is OK for the other object to
-** have a read cursor.
-**
-** For example, before writing to any part of the table or index
-** rooted at page iRoot, one should call:
-**
-**    assert( !hasReadConflicts(pBtree, iRoot) );
-*/
-static int hasReadConflicts(Btree *pBtree, Pgno iRoot){
-  BtCursor *p;
-  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
-    if( p->pgnoRoot==iRoot 
-     && p->pBtree!=pBtree
-     && 0==(p->pBtree->flags & SQLITE_ReadUncommitted)
-    ){
-      return 1;
-    }
-  }
-  return 0;
-}
-#endif    /* #ifdef SQLITE_DEBUG */
-
-/*
-** Query to see if Btree handle p may obtain a lock of type eLock 
-** (READ_LOCK or WRITE_LOCK) on the table with root-page iTab. Return
-** SQLITE_OK if the lock may be obtained (by calling
-** setSharedCacheTableLock()), or SQLITE_LOCKED if not.
-*/
-static int querySharedCacheTableLock(Btree *p, Pgno iTab, u8 eLock){
-  BtShared *pBt = p->pBt;
-  BtLock *pIter;
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
-  assert( !(p->flags&SQLITE_ReadUncommitted)||eLock==WRITE_LOCK||iTab==1 );
-  
-  /* If requesting a write-lock, then the Btree must have an open write
-  ** transaction on this file. And, obviously, for this to be so there 
-  ** must be an open write transaction on the file itself.
-  */
-  assert( eLock==READ_LOCK || (p==pBt->pWriter && p->inTrans==TRANS_WRITE) );
-  assert( eLock==READ_LOCK || pBt->inTransaction==TRANS_WRITE );
-  
-  /* This routine is a no-op if the shared-cache is not enabled */
-  if( !p->sharable ){
-    return SQLITE_OK;
-  }
-
-  /* If some other connection is holding an exclusive lock, the
-  ** requested lock may not be obtained.
-  */
-  if( pBt->pWriter!=p && (pBt->btsFlags & BTS_EXCLUSIVE)!=0 ){
-    sqlite3ConnectionBlocked(p->db, pBt->pWriter->db);
-    return SQLITE_LOCKED_SHAREDCACHE;
-  }
-
-  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
-    /* The condition (pIter->eLock!=eLock) in the following if(...) 
-    ** statement is a simplification of:
-    **
-    **   (eLock==WRITE_LOCK || pIter->eLock==WRITE_LOCK)
-    **
-    ** since we know that if eLock==WRITE_LOCK, then no other connection
-    ** may hold a WRITE_LOCK on any table in this file (since there can
-    ** only be a single writer).
-    */
-    assert( pIter->eLock==READ_LOCK || pIter->eLock==WRITE_LOCK );
-    assert( eLock==READ_LOCK || pIter->pBtree==p || pIter->eLock==READ_LOCK);
-    if( pIter->pBtree!=p && pIter->iTable==iTab && pIter->eLock!=eLock ){
-      sqlite3ConnectionBlocked(p->db, pIter->pBtree->db);
-      if( eLock==WRITE_LOCK ){
-        assert( p==pBt->pWriter );
-        pBt->btsFlags |= BTS_PENDING;
-      }
-      return SQLITE_LOCKED_SHAREDCACHE;
-    }
-  }
-  return SQLITE_OK;
-}
-#endif /* !SQLITE_OMIT_SHARED_CACHE */
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-/*
-** Add a lock on the table with root-page iTable to the shared-btree used
-** by Btree handle p. Parameter eLock must be either READ_LOCK or 
-** WRITE_LOCK.
-**
-** This function assumes the following:
-**
-**   (a) The specified Btree object p is connected to a sharable
-**       database (one with the BtShared.sharable flag set), and
-**
-**   (b) No other Btree objects hold a lock that conflicts
-**       with the requested lock (i.e. querySharedCacheTableLock() has
-**       already been called and returned SQLITE_OK).
-**
-** SQLITE_OK is returned if the lock is added successfully. SQLITE_NOMEM 
-** is returned if a malloc attempt fails.
-*/
-static int setSharedCacheTableLock(Btree *p, Pgno iTable, u8 eLock){
-  BtShared *pBt = p->pBt;
-  BtLock *pLock = 0;
-  BtLock *pIter;
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( eLock==READ_LOCK || eLock==WRITE_LOCK );
-  assert( p->db!=0 );
-
-  /* A connection with the read-uncommitted flag set will never try to
-  ** obtain a read-lock using this function. The only read-lock obtained
-  ** by a connection in read-uncommitted mode is on the sqlite_master 
-  ** table, and that lock is obtained in BtreeBeginTrans().  */
-  assert( 0==(p->db->flags&SQLITE_ReadUncommitted) || eLock==WRITE_LOCK );
-
-  /* This function should only be called on a sharable b-tree after it 
-  ** has been determined that no other b-tree holds a conflicting lock.  */
-  assert( p->sharable );
-  assert( SQLITE_OK==querySharedCacheTableLock(p, iTable, eLock) );
-
-  /* First search the list for an existing lock on this table. */
-  for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
-    if( pIter->iTable==iTable && pIter->pBtree==p ){
-      pLock = pIter;
-      break;
-    }
-  }
-
-  /* If the above search did not find a BtLock struct associating Btree p
-  ** with table iTable, allocate one and link it into the list.
-  */
-  if( !pLock ){
-    pLock = (BtLock *)sqlite3MallocZero(sizeof(BtLock));
-    if( !pLock ){
-      return SQLITE_NOMEM;
-    }
-    pLock->iTable = iTable;
-    pLock->pBtree = p;
-    pLock->pNext = pBt->pLock;
-    pBt->pLock = pLock;
-  }
-
-  /* Set the BtLock.eLock variable to the maximum of the current lock
-  ** and the requested lock. This means if a write-lock was already held
-  ** and a read-lock requested, we don't incorrectly downgrade the lock.
-  */
-  assert( WRITE_LOCK>READ_LOCK );
-  if( eLock>pLock->eLock ){
-    pLock->eLock = eLock;
-  }
-
-  return SQLITE_OK;
-}
-#endif /* !SQLITE_OMIT_SHARED_CACHE */
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-/*
-** Release all the table locks (locks obtained via calls to
-** the setSharedCacheTableLock() procedure) held by Btree object p.
-**
-** This function assumes that Btree p has an open read or write 
-** transaction. If it does not, then the BTS_PENDING flag
-** may be incorrectly cleared.
-*/
-static void clearAllSharedCacheTableLocks(Btree *p){
-  BtShared *pBt = p->pBt;
-  BtLock **ppIter = &pBt->pLock;
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( p->sharable || 0==*ppIter );
-  assert( p->inTrans>0 );
-
-  while( *ppIter ){
-    BtLock *pLock = *ppIter;
-    assert( (pBt->btsFlags & BTS_EXCLUSIVE)==0 || pBt->pWriter==pLock->pBtree );
-    assert( pLock->pBtree->inTrans>=pLock->eLock );
-    if( pLock->pBtree==p ){
-      *ppIter = pLock->pNext;
-      assert( pLock->iTable!=1 || pLock==&p->lock );
-      if( pLock->iTable!=1 ){
-        sqlite3_free(pLock);
-      }
-    }else{
-      ppIter = &pLock->pNext;
-    }
-  }
-
-  assert( (pBt->btsFlags & BTS_PENDING)==0 || pBt->pWriter );
-  if( pBt->pWriter==p ){
-    pBt->pWriter = 0;
-    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
-  }else if( pBt->nTransaction==2 ){
-    /* This function is called when Btree p is concluding its 
-    ** transaction. If there currently exists a writer, and p is not
-    ** that writer, then the number of locks held by connections other
-    ** than the writer must be about to drop to zero. In this case
-    ** set the BTS_PENDING flag to 0.
-    **
-    ** If there is not currently a writer, then BTS_PENDING must
-    ** be zero already. So this next line is harmless in that case.
-    */
-    pBt->btsFlags &= ~BTS_PENDING;
-  }
-}
-
-/*
-** This function changes all write-locks held by Btree p into read-locks.
-*/
-static void downgradeAllSharedCacheTableLocks(Btree *p){
-  BtShared *pBt = p->pBt;
-  if( pBt->pWriter==p ){
-    BtLock *pLock;
-    pBt->pWriter = 0;
-    pBt->btsFlags &= ~(BTS_EXCLUSIVE|BTS_PENDING);
-    for(pLock=pBt->pLock; pLock; pLock=pLock->pNext){
-      assert( pLock->eLock==READ_LOCK || pLock->pBtree==p );
-      pLock->eLock = READ_LOCK;
-    }
-  }
-}
-
-#endif /* SQLITE_OMIT_SHARED_CACHE */
-
-static void releasePage(MemPage *pPage);  /* Forward reference */
-
-/*
-***** This routine is used inside of assert() only ****
-**
-** Verify that the cursor holds the mutex on its BtShared
-*/
-#ifdef SQLITE_DEBUG
-static int cursorHoldsMutex(BtCursor *p){
-  return sqlite3_mutex_held(p->pBt->mutex);
-}
-#endif
-
-/*
-** Invalidate the overflow cache of the cursor passed as the first argument.
-** on the shared btree structure pBt.
-*/
-#define invalidateOverflowCache(pCur) (pCur->curFlags &= ~BTCF_ValidOvfl)
-
-/*
-** Invalidate the overflow page-list cache for all cursors opened
-** on the shared btree structure pBt.
-*/
-static void invalidateAllOverflowCache(BtShared *pBt){
-  BtCursor *p;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  for(p=pBt->pCursor; p; p=p->pNext){
-    invalidateOverflowCache(p);
-  }
-}
-
-#ifndef SQLITE_OMIT_INCRBLOB
-/*
-** This function is called before modifying the contents of a table
-** to invalidate any incrblob cursors that are open on the
-** row or one of the rows being modified.
-**
-** If argument isClearTable is true, then the entire contents of the
-** table is about to be deleted. In this case invalidate all incrblob
-** cursors open on any row within the table with root-page pgnoRoot.
-**
-** Otherwise, if argument isClearTable is false, then the row with
-** rowid iRow is being replaced or deleted. In this case invalidate
-** only those incrblob cursors open on that specific row.
-*/
-static void invalidateIncrblobCursors(
-  Btree *pBtree,          /* The database file to check */
-  i64 iRow,               /* The rowid that might be changing */
-  int isClearTable        /* True if all rows are being deleted */
-){
-  BtCursor *p;
-  if( pBtree->hasIncrblobCur==0 ) return;
-  assert( sqlite3BtreeHoldsMutex(pBtree) );
-  pBtree->hasIncrblobCur = 0;
-  for(p=pBtree->pBt->pCursor; p; p=p->pNext){
-    if( (p->curFlags & BTCF_Incrblob)!=0 ){
-      pBtree->hasIncrblobCur = 1;
-      if( isClearTable || p->info.nKey==iRow ){
-        p->eState = CURSOR_INVALID;
-      }
-    }
-  }
-}
-
-#else
-  /* Stub function when INCRBLOB is omitted */
-  #define invalidateIncrblobCursors(x,y,z)
-#endif /* SQLITE_OMIT_INCRBLOB */
-
-/*
-** Set bit pgno of the BtShared.pHasContent bitvec. This is called 
-** when a page that previously contained data becomes a free-list leaf 
-** page.
-**
-** The BtShared.pHasContent bitvec exists to work around an obscure
-** bug caused by the interaction of two useful IO optimizations surrounding
-** free-list leaf pages:
-**
-**   1) When all data is deleted from a page and the page becomes
-**      a free-list leaf page, the page is not written to the database
-**      (as free-list leaf pages contain no meaningful data). Sometimes
-**      such a page is not even journalled (as it will not be modified,
-**      why bother journalling it?).
-**
-**   2) When a free-list leaf page is reused, its content is not read
-**      from the database or written to the journal file (why should it
-**      be, if it is not at all meaningful?).
-**
-** By themselves, these optimizations work fine and provide a handy
-** performance boost to bulk delete or insert operations. However, if
-** a page is moved to the free-list and then reused within the same
-** transaction, a problem comes up. If the page is not journalled when
-** it is moved to the free-list and it is also not journalled when it
-** is extracted from the free-list and reused, then the original data
-** may be lost. In the event of a rollback, it may not be possible
-** to restore the database to its original configuration.
-**
-** The solution is the BtShared.pHasContent bitvec. Whenever a page is 
-** moved to become a free-list leaf page, the corresponding bit is
-** set in the bitvec. Whenever a leaf page is extracted from the free-list,
-** optimization 2 above is omitted if the corresponding bit is already
-** set in BtShared.pHasContent. The contents of the bitvec are cleared
-** at the end of every transaction.
-*/
-static int btreeSetHasContent(BtShared *pBt, Pgno pgno){
-  int rc = SQLITE_OK;
-  if( !pBt->pHasContent ){
-    assert( pgno<=pBt->nPage );
-    pBt->pHasContent = sqlite3BitvecCreate(pBt->nPage);
-    if( !pBt->pHasContent ){
-      rc = SQLITE_NOMEM;
-    }
-  }
-  if( rc==SQLITE_OK && pgno<=sqlite3BitvecSize(pBt->pHasContent) ){
-    rc = sqlite3BitvecSet(pBt->pHasContent, pgno);
-  }
-  return rc;
-}
-
-/*
-** Query the BtShared.pHasContent vector.
-**
-** This function is called when a free-list leaf page is removed from the
-** free-list for reuse. It returns false if it is safe to retrieve the
-** page from the pager layer with the 'no-content' flag set. True otherwise.
-*/
-static int btreeGetHasContent(BtShared *pBt, Pgno pgno){
-  Bitvec *p = pBt->pHasContent;
-  return (p && (pgno>sqlite3BitvecSize(p) || sqlite3BitvecTest(p, pgno)));
-}
-
-/*
-** Clear (destroy) the BtShared.pHasContent bitvec. This should be
-** invoked at the conclusion of each write-transaction.
-*/
-static void btreeClearHasContent(BtShared *pBt){
-  sqlite3BitvecDestroy(pBt->pHasContent);
-  pBt->pHasContent = 0;
-}
-
-/*
-** Release all of the apPage[] pages for a cursor.
-*/
-static void btreeReleaseAllCursorPages(BtCursor *pCur){
-  int i;
-  for(i=0; i<=pCur->iPage; i++){
-    releasePage(pCur->apPage[i]);
-    pCur->apPage[i] = 0;
-  }
-  pCur->iPage = -1;
-}
-
-/*
-** The cursor passed as the only argument must point to a valid entry
-** when this function is called (i.e. have eState==CURSOR_VALID). This
-** function saves the current cursor key in variables pCur->nKey and
-** pCur->pKey. SQLITE_OK is returned if successful or an SQLite error 
-** code otherwise.
-**
-** If the cursor is open on an intkey table, then the integer key
-** (the rowid) is stored in pCur->nKey and pCur->pKey is left set to
-** NULL. If the cursor is open on a non-intkey table, then pCur->pKey is 
-** set to point to a malloced buffer pCur->nKey bytes in size containing 
-** the key.
-*/
-static int saveCursorKey(BtCursor *pCur){
-  int rc;
-  assert( CURSOR_VALID==pCur->eState );
-  assert( 0==pCur->pKey );
-  assert( cursorHoldsMutex(pCur) );
-
-  rc = sqlite3BtreeKeySize(pCur, &pCur->nKey);
-  assert( rc==SQLITE_OK );  /* KeySize() cannot fail */
-
-  /* If this is an intKey table, then the above call to BtreeKeySize()
-  ** stores the integer key in pCur->nKey. In this case this value is
-  ** all that is required. Otherwise, if pCur is not open on an intKey
-  ** table, then malloc space for and store the pCur->nKey bytes of key 
-  ** data.  */
-  if( 0==pCur->curIntKey ){
-    void *pKey = sqlite3Malloc( pCur->nKey );
-    if( pKey ){
-      rc = sqlite3BtreeKey(pCur, 0, (int)pCur->nKey, pKey);
-      if( rc==SQLITE_OK ){
-        pCur->pKey = pKey;
-      }else{
-        sqlite3_free(pKey);
-      }
-    }else{
-      rc = SQLITE_NOMEM;
-    }
-  }
-  assert( !pCur->curIntKey || !pCur->pKey );
-  return rc;
-}
-
-/*
-** Save the current cursor position in the variables BtCursor.nKey 
-** and BtCursor.pKey. The cursor's state is set to CURSOR_REQUIRESEEK.
-**
-** The caller must ensure that the cursor is valid (has eState==CURSOR_VALID)
-** prior to calling this routine.  
-*/
-static int saveCursorPosition(BtCursor *pCur){
-  int rc;
-
-  assert( CURSOR_VALID==pCur->eState || CURSOR_SKIPNEXT==pCur->eState );
-  assert( 0==pCur->pKey );
-  assert( cursorHoldsMutex(pCur) );
-
-  if( pCur->eState==CURSOR_SKIPNEXT ){
-    pCur->eState = CURSOR_VALID;
-  }else{
-    pCur->skipNext = 0;
-  }
-
-  rc = saveCursorKey(pCur);
-  if( rc==SQLITE_OK ){
-    btreeReleaseAllCursorPages(pCur);
-    pCur->eState = CURSOR_REQUIRESEEK;
-  }
-
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl|BTCF_AtLast);
-  return rc;
-}
-
-/* Forward reference */
-static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
-
-/*
-** Save the positions of all cursors (except pExcept) that are open on
-** the table with root-page iRoot.  "Saving the cursor position" means that
-** the location in the btree is remembered in such a way that it can be
-** moved back to the same spot after the btree has been modified.  This
-** routine is called just before cursor pExcept is used to modify the
-** table, for example in BtreeDelete() or BtreeInsert().
-**
-** If there are two or more cursors on the same btree, then all such 
-** cursors should have their BTCF_Multiple flag set.  The btreeCursor()
-** routine enforces that rule.  This routine only needs to be called in
-** the uncommon case when pExpect has the BTCF_Multiple flag set.
-**
-** If pExpect!=NULL and if no other cursors are found on the same root-page,
-** then the BTCF_Multiple flag on pExpect is cleared, to avoid another
-** pointless call to this routine.
-**
-** Implementation note:  This routine merely checks to see if any cursors
-** need to be saved.  It calls out to saveCursorsOnList() in the (unusual)
-** event that cursors are in need to being saved.
-*/
-static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
-  BtCursor *p;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( pExcept==0 || pExcept->pBt==pBt );
-  for(p=pBt->pCursor; p; p=p->pNext){
-    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
-  }
-  if( p ) return saveCursorsOnList(p, iRoot, pExcept);
-  if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple;
-  return SQLITE_OK;
-}
-
-/* This helper routine to saveAllCursors does the actual work of saving
-** the cursors if and when a cursor is found that actually requires saving.
-** The common case is that no cursors need to be saved, so this routine is
-** broken out from its caller to avoid unnecessary stack pointer movement.
-*/
-static int SQLITE_NOINLINE saveCursorsOnList(
-  BtCursor *p,         /* The first cursor that needs saving */
-  Pgno iRoot,          /* Only save cursor with this iRoot. Save all if zero */
-  BtCursor *pExcept    /* Do not save this cursor */
-){
-  do{
-    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
-      if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
-        int rc = saveCursorPosition(p);
-        if( SQLITE_OK!=rc ){
-          return rc;
-        }
-      }else{
-        testcase( p->iPage>0 );
-        btreeReleaseAllCursorPages(p);
-      }
-    }
-    p = p->pNext;
-  }while( p );
-  return SQLITE_OK;
-}
-
-/*
-** Clear the current cursor position.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeClearCursor(BtCursor *pCur){
-  assert( cursorHoldsMutex(pCur) );
-  sqlite3_free(pCur->pKey);
-  pCur->pKey = 0;
-  pCur->eState = CURSOR_INVALID;
-}
-
-/*
-** In this version of BtreeMoveto, pKey is a packed index record
-** such as is generated by the OP_MakeRecord opcode.  Unpack the
-** record and then call BtreeMovetoUnpacked() to do the work.
-*/
-static int btreeMoveto(
-  BtCursor *pCur,     /* Cursor open on the btree to be searched */
-  const void *pKey,   /* Packed key if the btree is an index */
-  i64 nKey,           /* Integer key for tables.  Size of pKey for indices */
-  int bias,           /* Bias search to the high end */
-  int *pRes           /* Write search results here */
-){
-  int rc;                    /* Status code */
-  UnpackedRecord *pIdxKey;   /* Unpacked index key */
-  char aSpace[200];          /* Temp space for pIdxKey - to avoid a malloc */
-  char *pFree = 0;
-
-  if( pKey ){
-    assert( nKey==(i64)(int)nKey );
-    pIdxKey = sqlite3VdbeAllocUnpackedRecord(
-        pCur->pKeyInfo, aSpace, sizeof(aSpace), &pFree
-    );
-    if( pIdxKey==0 ) return SQLITE_NOMEM;
-    sqlite3VdbeRecordUnpack(pCur->pKeyInfo, (int)nKey, pKey, pIdxKey);
-    if( pIdxKey->nField==0 ){
-      sqlite3DbFree(pCur->pKeyInfo->pBtree, pFree);
-      return SQLITE_CORRUPT_BKPT;
-    }
-  }else{
-    pIdxKey = 0;
-  }
-  rc = sqlite3BtreeMovetoUnpacked(pCur, pIdxKey, nKey, bias, pRes);
-  if( pFree ){
-    sqlite3DbFree(pCur->pKeyInfo->pBtree, pFree);
-  }
-  return rc;
-}
-
-/*
-** Restore the cursor to the position it was in (or as close to as possible)
-** when saveCursorPosition() was called. Note that this call deletes the 
-** saved position info stored by saveCursorPosition(), so there can be
-** at most one effective restoreCursorPosition() call after each 
-** saveCursorPosition().
-*/
-static int btreeRestoreCursorPosition(BtCursor *pCur){
-  int rc;
-  int skipNext;
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState>=CURSOR_REQUIRESEEK );
-  if( pCur->eState==CURSOR_FAULT ){
-    return pCur->skipNext;
-  }
-  pCur->eState = CURSOR_INVALID;
-  rc = btreeMoveto(pCur, pCur->pKey, pCur->nKey, 0, &skipNext);
-  if( rc==SQLITE_OK ){
-    sqlite3_free(pCur->pKey);
-    pCur->pKey = 0;
-    assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_INVALID );
-    pCur->skipNext |= skipNext;
-    if( pCur->skipNext && pCur->eState==CURSOR_VALID ){
-      pCur->eState = CURSOR_SKIPNEXT;
-    }
-  }
-  return rc;
-}
-
-#define restoreCursorPosition(p) \
-  (p->eState>=CURSOR_REQUIRESEEK ? \
-         btreeRestoreCursorPosition(p) : \
-         SQLITE_OK)
-
-/*
-** Determine whether or not a cursor has moved from the position where
-** it was last placed, or has been invalidated for any other reason.
-** Cursors can move when the row they are pointing at is deleted out
-** from under them, for example.  Cursor might also move if a btree
-** is rebalanced.
-**
-** Calling this routine with a NULL cursor pointer returns false.
-**
-** Use the separate sqlite3BtreeCursorRestore() routine to restore a cursor
-** back to where it ought to be if this routine returns true.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursorHasMoved(BtCursor *pCur){
-  return pCur->eState!=CURSOR_VALID;
-}
-
-/*
-** This routine restores a cursor back to its original position after it
-** has been moved by some outside activity (such as a btree rebalance or
-** a row having been deleted out from under the cursor).  
-**
-** On success, the *pDifferentRow parameter is false if the cursor is left
-** pointing at exactly the same row.  *pDifferntRow is the row the cursor
-** was pointing to has been deleted, forcing the cursor to point to some
-** nearby row.
-**
-** This routine should only be called for a cursor that just returned
-** TRUE from sqlite3BtreeCursorHasMoved().
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursorRestore(BtCursor *pCur, int *pDifferentRow){
-  int rc;
-
-  assert( pCur!=0 );
-  assert( pCur->eState!=CURSOR_VALID );
-  rc = restoreCursorPosition(pCur);
-  if( rc ){
-    *pDifferentRow = 1;
-    return rc;
-  }
-  if( pCur->eState!=CURSOR_VALID ){
-    *pDifferentRow = 1;
-  }else{
-    assert( pCur->skipNext==0 );
-    *pDifferentRow = 0;
-  }
-  return SQLITE_OK;
-}
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-/*
-** Given a page number of a regular database page, return the page
-** number for the pointer-map page that contains the entry for the
-** input page number.
-**
-** Return 0 (not a valid page) for pgno==1 since there is
-** no pointer map associated with page 1.  The integrity_check logic
-** requires that ptrmapPageno(*,1)!=1.
-*/
-static Pgno ptrmapPageno(BtShared *pBt, Pgno pgno){
-  int nPagesPerMapPage;
-  Pgno iPtrMap, ret;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pgno<2 ) return 0;
-  nPagesPerMapPage = (pBt->usableSize/5)+1;
-  iPtrMap = (pgno-2)/nPagesPerMapPage;
-  ret = (iPtrMap*nPagesPerMapPage) + 2; 
-  if( ret==PENDING_BYTE_PAGE(pBt) ){
-    ret++;
-  }
-  return ret;
-}
-
-/*
-** Write an entry into the pointer map.
-**
-** This routine updates the pointer map entry for page number 'key'
-** so that it maps to type 'eType' and parent page number 'pgno'.
-**
-** If *pRC is initially non-zero (non-SQLITE_OK) then this routine is
-** a no-op.  If an error occurs, the appropriate error code is written
-** into *pRC.
-*/
-static void ptrmapPut(BtShared *pBt, Pgno key, u8 eType, Pgno parent, int *pRC){
-  DbPage *pDbPage;  /* The pointer map page */
-  u8 *pPtrmap;      /* The pointer map data */
-  Pgno iPtrmap;     /* The pointer map page number */
-  int offset;       /* Offset in pointer map page */
-  int rc;           /* Return code from subfunctions */
-
-  if( *pRC ) return;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  /* The master-journal page number must never be used as a pointer map page */
-  assert( 0==PTRMAP_ISPAGE(pBt, PENDING_BYTE_PAGE(pBt)) );
-
-  assert( pBt->autoVacuum );
-  if( key==0 ){
-    *pRC = SQLITE_CORRUPT_BKPT;
-    return;
-  }
-  iPtrmap = PTRMAP_PAGENO(pBt, key);
-  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
-  if( rc!=SQLITE_OK ){
-    *pRC = rc;
-    return;
-  }
-  offset = PTRMAP_PTROFFSET(iPtrmap, key);
-  if( offset<0 ){
-    *pRC = SQLITE_CORRUPT_BKPT;
-    goto ptrmap_exit;
-  }
-  assert( offset <= (int)pBt->usableSize-5 );
-  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
-
-  if( eType!=pPtrmap[offset] || get4byte(&pPtrmap[offset+1])!=parent ){
-    TRACE(("PTRMAP_UPDATE: %d->(%d,%d)\n", key, eType, parent));
-    *pRC= rc = sqlite3PagerWrite(pDbPage);
-    if( rc==SQLITE_OK ){
-      pPtrmap[offset] = eType;
-      put4byte(&pPtrmap[offset+1], parent);
-    }
-  }
-
-ptrmap_exit:
-  sqlite3PagerUnref(pDbPage);
-}
-
-/*
-** Read an entry from the pointer map.
-**
-** This routine retrieves the pointer map entry for page 'key', writing
-** the type and parent page number to *pEType and *pPgno respectively.
-** An error code is returned if something goes wrong, otherwise SQLITE_OK.
-*/
-static int ptrmapGet(BtShared *pBt, Pgno key, u8 *pEType, Pgno *pPgno){
-  DbPage *pDbPage;   /* The pointer map page */
-  int iPtrmap;       /* Pointer map page index */
-  u8 *pPtrmap;       /* Pointer map page data */
-  int offset;        /* Offset of entry in pointer map */
-  int rc;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-
-  iPtrmap = PTRMAP_PAGENO(pBt, key);
-  rc = sqlite3PagerGet(pBt->pPager, iPtrmap, &pDbPage);
-  if( rc!=0 ){
-    return rc;
-  }
-  pPtrmap = (u8 *)sqlite3PagerGetData(pDbPage);
-
-  offset = PTRMAP_PTROFFSET(iPtrmap, key);
-  if( offset<0 ){
-    sqlite3PagerUnref(pDbPage);
-    return SQLITE_CORRUPT_BKPT;
-  }
-  assert( offset <= (int)pBt->usableSize-5 );
-  assert( pEType!=0 );
-  *pEType = pPtrmap[offset];
-  if( pPgno ) *pPgno = get4byte(&pPtrmap[offset+1]);
-
-  sqlite3PagerUnref(pDbPage);
-  if( *pEType<1 || *pEType>5 ) return SQLITE_CORRUPT_BKPT;
-  return SQLITE_OK;
-}
-
-#else /* if defined SQLITE_OMIT_AUTOVACUUM */
-  #define ptrmapPut(w,x,y,z,rc)
-  #define ptrmapGet(w,x,y,z) SQLITE_OK
-  #define ptrmapPutOvflPtr(x, y, rc)
-#endif
-
-/*
-** Given a btree page and a cell index (0 means the first cell on
-** the page, 1 means the second cell, and so forth) return a pointer
-** to the cell content.
-**
-** findCellPastPtr() does the same except it skips past the initial
-** 4-byte child pointer found on interior pages, if there is one.
-**
-** This routine works only for pages that do not contain overflow cells.
-*/
-#define findCell(P,I) \
-  ((P)->aData + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
-#define findCellPastPtr(P,I) \
-  ((P)->aDataOfst + ((P)->maskPage & get2byteAligned(&(P)->aCellIdx[2*(I)])))
-
-
-/*
-** This is common tail processing for btreeParseCellPtr() and
-** btreeParseCellPtrIndex() for the case when the cell does not fit entirely
-** on a single B-tree page.  Make necessary adjustments to the CellInfo
-** structure.
-*/
-static SQLITE_NOINLINE void btreeParseCellAdjustSizeForOverflow(
-  MemPage *pPage,         /* Page containing the cell */
-  u8 *pCell,              /* Pointer to the cell text. */
-  CellInfo *pInfo         /* Fill in this structure */
-){
-  /* If the payload will not fit completely on the local page, we have
-  ** to decide how much to store locally and how much to spill onto
-  ** overflow pages.  The strategy is to minimize the amount of unused
-  ** space on overflow pages while keeping the amount of local storage
-  ** in between minLocal and maxLocal.
-  **
-  ** Warning:  changing the way overflow payload is distributed in any
-  ** way will result in an incompatible file format.
-  */
-  int minLocal;  /* Minimum amount of payload held locally */
-  int maxLocal;  /* Maximum amount of payload held locally */
-  int surplus;   /* Overflow payload available for local storage */
-
-  minLocal = pPage->minLocal;
-  maxLocal = pPage->maxLocal;
-  surplus = minLocal + (pInfo->nPayload - minLocal)%(pPage->pBt->usableSize-4);
-  testcase( surplus==maxLocal );
-  testcase( surplus==maxLocal+1 );
-  if( surplus <= maxLocal ){
-    pInfo->nLocal = (u16)surplus;
-  }else{
-    pInfo->nLocal = (u16)minLocal;
-  }
-  pInfo->iOverflow = (u16)(&pInfo->pPayload[pInfo->nLocal] - pCell);
-  pInfo->nSize = pInfo->iOverflow + 4;
-}
-
-/*
-** The following routines are implementations of the MemPage.xParseCell()
-** method.
-**
-** Parse a cell content block and fill in the CellInfo structure.
-**
-** btreeParseCellPtr()        =>   table btree leaf nodes
-** btreeParseCellNoPayload()  =>   table btree internal nodes
-** btreeParseCellPtrIndex()   =>   index btree nodes
-**
-** There is also a wrapper function btreeParseCell() that works for
-** all MemPage types and that references the cell by index rather than
-** by pointer.
-*/
-static void btreeParseCellPtrNoPayload(
-  MemPage *pPage,         /* Page containing the cell */
-  u8 *pCell,              /* Pointer to the cell text. */
-  CellInfo *pInfo         /* Fill in this structure */
-){
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( pPage->leaf==0 );
-  assert( pPage->noPayload );
-  assert( pPage->childPtrSize==4 );
-#ifndef SQLITE_DEBUG
-  UNUSED_PARAMETER(pPage);
-#endif
-  pInfo->nSize = 4 + getVarint(&pCell[4], (u64*)&pInfo->nKey);
-  pInfo->nPayload = 0;
-  pInfo->nLocal = 0;
-  pInfo->iOverflow = 0;
-  pInfo->pPayload = 0;
-  return;
-}
-static void btreeParseCellPtr(
-  MemPage *pPage,         /* Page containing the cell */
-  u8 *pCell,              /* Pointer to the cell text. */
-  CellInfo *pInfo         /* Fill in this structure */
-){
-  u8 *pIter;              /* For scanning through pCell */
-  u32 nPayload;           /* Number of bytes of cell payload */
-  u64 iKey;               /* Extracted Key value */
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( pPage->leaf==0 || pPage->leaf==1 );
-  assert( pPage->intKeyLeaf || pPage->noPayload );
-  assert( pPage->noPayload==0 );
-  assert( pPage->intKeyLeaf );
-  assert( pPage->childPtrSize==0 );
-  pIter = pCell;
-
-  /* The next block of code is equivalent to:
-  **
-  **     pIter += getVarint32(pIter, nPayload);
-  **
-  ** The code is inlined to avoid a function call.
-  */
-  nPayload = *pIter;
-  if( nPayload>=0x80 ){
-    u8 *pEnd = &pIter[8];
-    nPayload &= 0x7f;
-    do{
-      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
-    }while( (*pIter)>=0x80 && pIter<pEnd );
-  }
-  pIter++;
-
-  /* The next block of code is equivalent to:
-  **
-  **     pIter += getVarint(pIter, (u64*)&pInfo->nKey);
-  **
-  ** The code is inlined to avoid a function call.
-  */
-  iKey = *pIter;
-  if( iKey>=0x80 ){
-    u8 *pEnd = &pIter[7];
-    iKey &= 0x7f;
-    while(1){
-      iKey = (iKey<<7) | (*++pIter & 0x7f);
-      if( (*pIter)<0x80 ) break;
-      if( pIter>=pEnd ){
-        iKey = (iKey<<8) | *++pIter;
-        break;
-      }
-    }
-  }
-  pIter++;
-
-  pInfo->nKey = *(i64*)&iKey;
-  pInfo->nPayload = nPayload;
-  pInfo->pPayload = pIter;
-  testcase( nPayload==pPage->maxLocal );
-  testcase( nPayload==pPage->maxLocal+1 );
-  if( nPayload<=pPage->maxLocal ){
-    /* This is the (easy) common case where the entire payload fits
-    ** on the local page.  No overflow is required.
-    */
-    pInfo->nSize = nPayload + (u16)(pIter - pCell);
-    if( pInfo->nSize<4 ) pInfo->nSize = 4;
-    pInfo->nLocal = (u16)nPayload;
-    pInfo->iOverflow = 0;
-  }else{
-    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
-  }
-}
-static void btreeParseCellPtrIndex(
-  MemPage *pPage,         /* Page containing the cell */
-  u8 *pCell,              /* Pointer to the cell text. */
-  CellInfo *pInfo         /* Fill in this structure */
-){
-  u8 *pIter;              /* For scanning through pCell */
-  u32 nPayload;           /* Number of bytes of cell payload */
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( pPage->leaf==0 || pPage->leaf==1 );
-  assert( pPage->intKeyLeaf==0 );
-  assert( pPage->noPayload==0 );
-  pIter = pCell + pPage->childPtrSize;
-  nPayload = *pIter;
-  if( nPayload>=0x80 ){
-    u8 *pEnd = &pIter[8];
-    nPayload &= 0x7f;
-    do{
-      nPayload = (nPayload<<7) | (*++pIter & 0x7f);
-    }while( *(pIter)>=0x80 && pIter<pEnd );
-  }
-  pIter++;
-  pInfo->nKey = nPayload;
-  pInfo->nPayload = nPayload;
-  pInfo->pPayload = pIter;
-  testcase( nPayload==pPage->maxLocal );
-  testcase( nPayload==pPage->maxLocal+1 );
-  if( nPayload<=pPage->maxLocal ){
-    /* This is the (easy) common case where the entire payload fits
-    ** on the local page.  No overflow is required.
-    */
-    pInfo->nSize = nPayload + (u16)(pIter - pCell);
-    if( pInfo->nSize<4 ) pInfo->nSize = 4;
-    pInfo->nLocal = (u16)nPayload;
-    pInfo->iOverflow = 0;
-  }else{
-    btreeParseCellAdjustSizeForOverflow(pPage, pCell, pInfo);
-  }
-}
-static void btreeParseCell(
-  MemPage *pPage,         /* Page containing the cell */
-  int iCell,              /* The cell index.  First cell is 0 */
-  CellInfo *pInfo         /* Fill in this structure */
-){
-  pPage->xParseCell(pPage, findCell(pPage, iCell), pInfo);
-}
-
-/*
-** The following routines are implementations of the MemPage.xCellSize
-** method.
-**
-** Compute the total number of bytes that a Cell needs in the cell
-** data area of the btree-page.  The return number includes the cell
-** data header and the local payload, but not any overflow page or
-** the space used by the cell pointer.
-**
-** cellSizePtrNoPayload()    =>   table internal nodes
-** cellSizePtr()             =>   all index nodes & table leaf nodes
-*/
-static u16 cellSizePtr(MemPage *pPage, u8 *pCell){
-  u8 *pIter = pCell + pPage->childPtrSize; /* For looping over bytes of pCell */
-  u8 *pEnd;                                /* End mark for a varint */
-  u32 nSize;                               /* Size value to return */
-
-#ifdef SQLITE_DEBUG
-  /* The value returned by this function should always be the same as
-  ** the (CellInfo.nSize) value found by doing a full parse of the
-  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
-  ** this function verifies that this invariant is not violated. */
-  CellInfo debuginfo;
-  pPage->xParseCell(pPage, pCell, &debuginfo);
-#endif
-
-  assert( pPage->noPayload==0 );
-  nSize = *pIter;
-  if( nSize>=0x80 ){
-    pEnd = &pIter[8];
-    nSize &= 0x7f;
-    do{
-      nSize = (nSize<<7) | (*++pIter & 0x7f);
-    }while( *(pIter)>=0x80 && pIter<pEnd );
-  }
-  pIter++;
-  if( pPage->intKey ){
-    /* pIter now points at the 64-bit integer key value, a variable length 
-    ** integer. The following block moves pIter to point at the first byte
-    ** past the end of the key value. */
-    pEnd = &pIter[9];
-    while( (*pIter++)&0x80 && pIter<pEnd );
-  }
-  testcase( nSize==pPage->maxLocal );
-  testcase( nSize==pPage->maxLocal+1 );
-  if( nSize<=pPage->maxLocal ){
-    nSize += (u32)(pIter - pCell);
-    if( nSize<4 ) nSize = 4;
-  }else{
-    int minLocal = pPage->minLocal;
-    nSize = minLocal + (nSize - minLocal) % (pPage->pBt->usableSize - 4);
-    testcase( nSize==pPage->maxLocal );
-    testcase( nSize==pPage->maxLocal+1 );
-    if( nSize>pPage->maxLocal ){
-      nSize = minLocal;
-    }
-    nSize += 4 + (u16)(pIter - pCell);
-  }
-  assert( nSize==debuginfo.nSize || CORRUPT_DB );
-  return (u16)nSize;
-}
-static u16 cellSizePtrNoPayload(MemPage *pPage, u8 *pCell){
-  u8 *pIter = pCell + 4; /* For looping over bytes of pCell */
-  u8 *pEnd;              /* End mark for a varint */
-
-#ifdef SQLITE_DEBUG
-  /* The value returned by this function should always be the same as
-  ** the (CellInfo.nSize) value found by doing a full parse of the
-  ** cell. If SQLITE_DEBUG is defined, an assert() at the bottom of
-  ** this function verifies that this invariant is not violated. */
-  CellInfo debuginfo;
-  pPage->xParseCell(pPage, pCell, &debuginfo);
-#else
-  UNUSED_PARAMETER(pPage);
-#endif
-
-  assert( pPage->childPtrSize==4 );
-  pEnd = pIter + 9;
-  while( (*pIter++)&0x80 && pIter<pEnd );
-  assert( debuginfo.nSize==(u16)(pIter - pCell) || CORRUPT_DB );
-  return (u16)(pIter - pCell);
-}
-
-
-#ifdef SQLITE_DEBUG
-/* This variation on cellSizePtr() is used inside of assert() statements
-** only. */
-static u16 cellSize(MemPage *pPage, int iCell){
-  return pPage->xCellSize(pPage, findCell(pPage, iCell));
-}
-#endif
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-/*
-** If the cell pCell, part of page pPage contains a pointer
-** to an overflow page, insert an entry into the pointer-map
-** for the overflow page.
-*/
-static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
-  CellInfo info;
-  if( *pRC ) return;
-  assert( pCell!=0 );
-  pPage->xParseCell(pPage, pCell, &info);
-  if( info.iOverflow ){
-    Pgno ovfl = get4byte(&pCell[info.iOverflow]);
-    ptrmapPut(pPage->pBt, ovfl, PTRMAP_OVERFLOW1, pPage->pgno, pRC);
-  }
-}
-#endif
-
-
-/*
-** Defragment the page given.  All Cells are moved to the
-** end of the page and all free space is collected into one
-** big FreeBlk that occurs in between the header and cell
-** pointer array and the cell content area.
-**
-** EVIDENCE-OF: R-44582-60138 SQLite may from time to time reorganize a
-** b-tree page so that there are no freeblocks or fragment bytes, all
-** unused bytes are contained in the unallocated space region, and all
-** cells are packed tightly at the end of the page.
-*/
-static int defragmentPage(MemPage *pPage){
-  int i;                     /* Loop counter */
-  int pc;                    /* Address of the i-th cell */
-  int hdr;                   /* Offset to the page header */
-  int size;                  /* Size of a cell */
-  int usableSize;            /* Number of usable bytes on a page */
-  int cellOffset;            /* Offset to the cell pointer array */
-  int cbrk;                  /* Offset to the cell content area */
-  int nCell;                 /* Number of cells on the page */
-  unsigned char *data;       /* The page data */
-  unsigned char *temp;       /* Temp area for cell content */
-  unsigned char *src;        /* Source of content */
-  int iCellFirst;            /* First allowable cell index */
-  int iCellLast;             /* Last possible cell index */
-
-
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( pPage->pBt!=0 );
-  assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
-  assert( pPage->nOverflow==0 );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  temp = 0;
-  src = data = pPage->aData;
-  hdr = pPage->hdrOffset;
-  cellOffset = pPage->cellOffset;
-  nCell = pPage->nCell;
-  assert( nCell==get2byte(&data[hdr+3]) );
-  usableSize = pPage->pBt->usableSize;
-  cbrk = usableSize;
-  iCellFirst = cellOffset + 2*nCell;
-  iCellLast = usableSize - 4;
-  for(i=0; i<nCell; i++){
-    u8 *pAddr;     /* The i-th cell pointer */
-    pAddr = &data[cellOffset + i*2];
-    pc = get2byte(pAddr);
-    testcase( pc==iCellFirst );
-    testcase( pc==iCellLast );
-    /* These conditions have already been verified in btreeInitPage()
-    ** if PRAGMA cell_size_check=ON.
-    */
-    if( pc<iCellFirst || pc>iCellLast ){
-      return SQLITE_CORRUPT_BKPT;
-    }
-    assert( pc>=iCellFirst && pc<=iCellLast );
-    size = pPage->xCellSize(pPage, &src[pc]);
-    cbrk -= size;
-    if( cbrk<iCellFirst || pc+size>usableSize ){
-      return SQLITE_CORRUPT_BKPT;
-    }
-    assert( cbrk+size<=usableSize && cbrk>=iCellFirst );
-    testcase( cbrk+size==usableSize );
-    testcase( pc+size==usableSize );
-    put2byte(pAddr, cbrk);
-    if( temp==0 ){
-      int x;
-      if( cbrk==pc ) continue;
-      temp = sqlite3PagerTempSpace(pPage->pBt->pPager);
-      x = get2byte(&data[hdr+5]);
-      memcpy(&temp[x], &data[x], (cbrk+size) - x);
-      src = temp;
-    }
-    memcpy(&data[cbrk], &src[pc], size);
-  }
-  assert( cbrk>=iCellFirst );
-  put2byte(&data[hdr+5], cbrk);
-  data[hdr+1] = 0;
-  data[hdr+2] = 0;
-  data[hdr+7] = 0;
-  memset(&data[iCellFirst], 0, cbrk-iCellFirst);
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  if( cbrk-iCellFirst!=pPage->nFree ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Search the free-list on page pPg for space to store a cell nByte bytes in
-** size. If one can be found, return a pointer to the space and remove it
-** from the free-list.
-**
-** If no suitable space can be found on the free-list, return NULL.
-**
-** This function may detect corruption within pPg.  If corruption is
-** detected then *pRc is set to SQLITE_CORRUPT and NULL is returned.
-**
-** Slots on the free list that are between 1 and 3 bytes larger than nByte
-** will be ignored if adding the extra space to the fragmentation count
-** causes the fragmentation count to exceed 60.
-*/
-static u8 *pageFindSlot(MemPage *pPg, int nByte, int *pRc){
-  const int hdr = pPg->hdrOffset;
-  u8 * const aData = pPg->aData;
-  int iAddr = hdr + 1;
-  int pc = get2byte(&aData[iAddr]);
-  int x;
-  int usableSize = pPg->pBt->usableSize;
-
-  assert( pc>0 );
-  do{
-    int size;            /* Size of the free slot */
-    /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
-    ** increasing offset. */
-    if( pc>usableSize-4 || pc<iAddr+4 ){
-      *pRc = SQLITE_CORRUPT_BKPT;
-      return 0;
-    }
-    /* EVIDENCE-OF: R-22710-53328 The third and fourth bytes of each
-    ** freeblock form a big-endian integer which is the size of the freeblock
-    ** in bytes, including the 4-byte header. */
-    size = get2byte(&aData[pc+2]);
-    if( (x = size - nByte)>=0 ){
-      testcase( x==4 );
-      testcase( x==3 );
-      if( pc < pPg->cellOffset+2*pPg->nCell || size+pc > usableSize ){
-        *pRc = SQLITE_CORRUPT_BKPT;
-        return 0;
-      }else if( x<4 ){
-        /* EVIDENCE-OF: R-11498-58022 In a well-formed b-tree page, the total
-        ** number of bytes in fragments may not exceed 60. */
-        if( aData[hdr+7]>57 ) return 0;
-
-        /* Remove the slot from the free-list. Update the number of
-        ** fragmented bytes within the page. */
-        memcpy(&aData[iAddr], &aData[pc], 2);
-        aData[hdr+7] += (u8)x;
-      }else{
-        /* The slot remains on the free-list. Reduce its size to account
-         ** for the portion used by the new allocation. */
-        put2byte(&aData[pc+2], x);
-      }
-      return &aData[pc + x];
-    }
-    iAddr = pc;
-    pc = get2byte(&aData[pc]);
-  }while( pc );
-
-  return 0;
-}
-
-/*
-** Allocate nByte bytes of space from within the B-Tree page passed
-** as the first argument. Write into *pIdx the index into pPage->aData[]
-** of the first byte of allocated space. Return either SQLITE_OK or
-** an error code (usually SQLITE_CORRUPT).
-**
-** The caller guarantees that there is sufficient space to make the
-** allocation.  This routine might need to defragment in order to bring
-** all the space together, however.  This routine will avoid using
-** the first two bytes past the cell pointer area since presumably this
-** allocation is being made in order to insert a new cell, so we will
-** also end up needing a new cell pointer.
-*/
-static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
-  const int hdr = pPage->hdrOffset;    /* Local cache of pPage->hdrOffset */
-  u8 * const data = pPage->aData;      /* Local cache of pPage->aData */
-  int top;                             /* First byte of cell content area */
-  int rc = SQLITE_OK;                  /* Integer return code */
-  int gap;        /* First byte of gap between cell pointers and cell content */
-  
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( pPage->pBt );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( nByte>=0 );  /* Minimum cell size is 4 */
-  assert( pPage->nFree>=nByte );
-  assert( pPage->nOverflow==0 );
-  assert( nByte < (int)(pPage->pBt->usableSize-8) );
-
-  assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
-  gap = pPage->cellOffset + 2*pPage->nCell;
-  assert( gap<=65536 );
-  /* EVIDENCE-OF: R-29356-02391 If the database uses a 65536-byte page size
-  ** and the reserved space is zero (the usual value for reserved space)
-  ** then the cell content offset of an empty page wants to be 65536.
-  ** However, that integer is too large to be stored in a 2-byte unsigned
-  ** integer, so a value of 0 is used in its place. */
-  top = get2byte(&data[hdr+5]);
-  assert( top<=(int)pPage->pBt->usableSize ); /* Prevent by getAndInitPage() */
-  if( gap>top ){
-    if( top==0 && pPage->pBt->usableSize==65536 ){
-      top = 65536;
-    }else{
-      return SQLITE_CORRUPT_BKPT;
-    }
-  }
-
-  /* If there is enough space between gap and top for one more cell pointer
-  ** array entry offset, and if the freelist is not empty, then search the
-  ** freelist looking for a free slot big enough to satisfy the request.
-  */
-  testcase( gap+2==top );
-  testcase( gap+1==top );
-  testcase( gap==top );
-  if( (data[hdr+2] || data[hdr+1]) && gap+2<=top ){
-    u8 *pSpace = pageFindSlot(pPage, nByte, &rc);
-    if( pSpace ){
-      assert( pSpace>=data && (pSpace - data)<65536 );
-      *pIdx = (int)(pSpace - data);
-      return SQLITE_OK;
-    }else if( rc ){
-      return rc;
-    }
-  }
-
-  /* The request could not be fulfilled using a freelist slot.  Check
-  ** to see if defragmentation is necessary.
-  */
-  testcase( gap+2+nByte==top );
-  if( gap+2+nByte>top ){
-    assert( pPage->nCell>0 || CORRUPT_DB );
-    rc = defragmentPage(pPage);
-    if( rc ) return rc;
-    top = get2byteNotZero(&data[hdr+5]);
-    assert( gap+nByte<=top );
-  }
-
-
-  /* Allocate memory from the gap in between the cell pointer array
-  ** and the cell content area.  The btreeInitPage() call has already
-  ** validated the freelist.  Given that the freelist is valid, there
-  ** is no way that the allocation can extend off the end of the page.
-  ** The assert() below verifies the previous sentence.
-  */
-  top -= nByte;
-  put2byte(&data[hdr+5], top);
-  assert( top+nByte <= (int)pPage->pBt->usableSize );
-  *pIdx = top;
-  return SQLITE_OK;
-}
-
-/*
-** Return a section of the pPage->aData to the freelist.
-** The first byte of the new free block is pPage->aData[iStart]
-** and the size of the block is iSize bytes.
-**
-** Adjacent freeblocks are coalesced.
-**
-** Note that even though the freeblock list was checked by btreeInitPage(),
-** that routine will not detect overlap between cells or freeblocks.  Nor
-** does it detect cells or freeblocks that encrouch into the reserved bytes
-** at the end of the page.  So do additional corruption checks inside this
-** routine and return SQLITE_CORRUPT if any problems are found.
-*/
-static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
-  u16 iPtr;                             /* Address of ptr to next freeblock */
-  u16 iFreeBlk;                         /* Address of the next freeblock */
-  u8 hdr;                               /* Page header size.  0 or 100 */
-  u8 nFrag = 0;                         /* Reduction in fragmentation */
-  u16 iOrigSize = iSize;                /* Original value of iSize */
-  u32 iLast = pPage->pBt->usableSize-4; /* Largest possible freeblock offset */
-  u32 iEnd = iStart + iSize;            /* First byte past the iStart buffer */
-  unsigned char *data = pPage->aData;   /* Page content */
-
-  assert( pPage->pBt!=0 );
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( CORRUPT_DB || iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
-  assert( CORRUPT_DB || iEnd <= pPage->pBt->usableSize );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( iSize>=4 );   /* Minimum cell size is 4 */
-  assert( iStart<=iLast );
-
-  /* Overwrite deleted information with zeros when the secure_delete
-  ** option is enabled */
-  if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
-    memset(&data[iStart], 0, iSize);
-  }
-
-  /* The list of freeblocks must be in ascending order.  Find the 
-  ** spot on the list where iStart should be inserted.
-  */
-  hdr = pPage->hdrOffset;
-  iPtr = hdr + 1;
-  if( data[iPtr+1]==0 && data[iPtr]==0 ){
-    iFreeBlk = 0;  /* Shortcut for the case when the freelist is empty */
-  }else{
-    while( (iFreeBlk = get2byte(&data[iPtr]))>0 && iFreeBlk<iStart ){
-      if( iFreeBlk<iPtr+4 ) return SQLITE_CORRUPT_BKPT;
-      iPtr = iFreeBlk;
-    }
-    if( iFreeBlk>iLast ) return SQLITE_CORRUPT_BKPT;
-    assert( iFreeBlk>iPtr || iFreeBlk==0 );
-  
-    /* At this point:
-    **    iFreeBlk:   First freeblock after iStart, or zero if none
-    **    iPtr:       The address of a pointer to iFreeBlk
-    **
-    ** Check to see if iFreeBlk should be coalesced onto the end of iStart.
-    */
-    if( iFreeBlk && iEnd+3>=iFreeBlk ){
-      nFrag = iFreeBlk - iEnd;
-      if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_BKPT;
-      iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
-      if( iEnd > pPage->pBt->usableSize ) return SQLITE_CORRUPT_BKPT;
-      iSize = iEnd - iStart;
-      iFreeBlk = get2byte(&data[iFreeBlk]);
-    }
-  
-    /* If iPtr is another freeblock (that is, if iPtr is not the freelist
-    ** pointer in the page header) then check to see if iStart should be
-    ** coalesced onto the end of iPtr.
-    */
-    if( iPtr>hdr+1 ){
-      int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
-      if( iPtrEnd+3>=iStart ){
-        if( iPtrEnd>iStart ) return SQLITE_CORRUPT_BKPT;
-        nFrag += iStart - iPtrEnd;
-        iSize = iEnd - iPtr;
-        iStart = iPtr;
-      }
-    }
-    if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_BKPT;
-    data[hdr+7] -= nFrag;
-  }
-  if( iStart==get2byte(&data[hdr+5]) ){
-    /* The new freeblock is at the beginning of the cell content area,
-    ** so just extend the cell content area rather than create another
-    ** freelist entry */
-    if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_BKPT;
-    put2byte(&data[hdr+1], iFreeBlk);
-    put2byte(&data[hdr+5], iEnd);
-  }else{
-    /* Insert the new freeblock into the freelist */
-    put2byte(&data[iPtr], iStart);
-    put2byte(&data[iStart], iFreeBlk);
-    put2byte(&data[iStart+2], iSize);
-  }
-  pPage->nFree += iOrigSize;
-  return SQLITE_OK;
-}
-
-/*
-** Decode the flags byte (the first byte of the header) for a page
-** and initialize fields of the MemPage structure accordingly.
-**
-** Only the following combinations are supported.  Anything different
-** indicates a corrupt database files:
-**
-**         PTF_ZERODATA
-**         PTF_ZERODATA | PTF_LEAF
-**         PTF_LEAFDATA | PTF_INTKEY
-**         PTF_LEAFDATA | PTF_INTKEY | PTF_LEAF
-*/
-static int decodeFlags(MemPage *pPage, int flagByte){
-  BtShared *pBt;     /* A copy of pPage->pBt */
-
-  assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  pPage->leaf = (u8)(flagByte>>3);  assert( PTF_LEAF == 1<<3 );
-  flagByte &= ~PTF_LEAF;
-  pPage->childPtrSize = 4-4*pPage->leaf;
-  pPage->xCellSize = cellSizePtr;
-  pBt = pPage->pBt;
-  if( flagByte==(PTF_LEAFDATA | PTF_INTKEY) ){
-    /* EVIDENCE-OF: R-03640-13415 A value of 5 means the page is an interior
-    ** table b-tree page. */
-    assert( (PTF_LEAFDATA|PTF_INTKEY)==5 );
-    /* EVIDENCE-OF: R-20501-61796 A value of 13 means the page is a leaf
-    ** table b-tree page. */
-    assert( (PTF_LEAFDATA|PTF_INTKEY|PTF_LEAF)==13 );
-    pPage->intKey = 1;
-    if( pPage->leaf ){
-      pPage->intKeyLeaf = 1;
-      pPage->noPayload = 0;
-      pPage->xParseCell = btreeParseCellPtr;
-    }else{
-      pPage->intKeyLeaf = 0;
-      pPage->noPayload = 1;
-      pPage->xCellSize = cellSizePtrNoPayload;
-      pPage->xParseCell = btreeParseCellPtrNoPayload;
-    }
-    pPage->maxLocal = pBt->maxLeaf;
-    pPage->minLocal = pBt->minLeaf;
-  }else if( flagByte==PTF_ZERODATA ){
-    /* EVIDENCE-OF: R-27225-53936 A value of 2 means the page is an interior
-    ** index b-tree page. */
-    assert( (PTF_ZERODATA)==2 );
-    /* EVIDENCE-OF: R-16571-11615 A value of 10 means the page is a leaf
-    ** index b-tree page. */
-    assert( (PTF_ZERODATA|PTF_LEAF)==10 );
-    pPage->intKey = 0;
-    pPage->intKeyLeaf = 0;
-    pPage->noPayload = 0;
-    pPage->xParseCell = btreeParseCellPtrIndex;
-    pPage->maxLocal = pBt->maxLocal;
-    pPage->minLocal = pBt->minLocal;
-  }else{
-    /* EVIDENCE-OF: R-47608-56469 Any other value for the b-tree page type is
-    ** an error. */
-    return SQLITE_CORRUPT_BKPT;
-  }
-  pPage->max1bytePayload = pBt->max1bytePayload;
-  return SQLITE_OK;
-}
-
-/*
-** Initialize the auxiliary information for a disk block.
-**
-** Return SQLITE_OK on success.  If we see that the page does
-** not contain a well-formed database page, then return 
-** SQLITE_CORRUPT.  Note that a return of SQLITE_OK does not
-** guarantee that the page is well-formed.  It only shows that
-** we failed to detect any corruption.
-*/
-static int btreeInitPage(MemPage *pPage){
-
-  assert( pPage->pBt!=0 );
-  assert( pPage->pBt->db!=0 );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) );
-  assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) );
-  assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) );
-
-  if( !pPage->isInit ){
-    u16 pc;            /* Address of a freeblock within pPage->aData[] */
-    u8 hdr;            /* Offset to beginning of page header */
-    u8 *data;          /* Equal to pPage->aData */
-    BtShared *pBt;        /* The main btree structure */
-    int usableSize;    /* Amount of usable space on each page */
-    u16 cellOffset;    /* Offset from start of page to first cell pointer */
-    int nFree;         /* Number of unused bytes on the page */
-    int top;           /* First byte of the cell content area */
-    int iCellFirst;    /* First allowable cell or freeblock offset */
-    int iCellLast;     /* Last possible cell or freeblock offset */
-
-    pBt = pPage->pBt;
-
-    hdr = pPage->hdrOffset;
-    data = pPage->aData;
-    /* EVIDENCE-OF: R-28594-02890 The one-byte flag at offset 0 indicating
-    ** the b-tree page type. */
-    if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT;
-    assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
-    pPage->maskPage = (u16)(pBt->pageSize - 1);
-    pPage->nOverflow = 0;
-    usableSize = pBt->usableSize;
-    pPage->cellOffset = cellOffset = hdr + 8 + pPage->childPtrSize;
-    pPage->aDataEnd = &data[usableSize];
-    pPage->aCellIdx = &data[cellOffset];
-    pPage->aDataOfst = &data[pPage->childPtrSize];
-    /* EVIDENCE-OF: R-58015-48175 The two-byte integer at offset 5 designates
-    ** the start of the cell content area. A zero value for this integer is
-    ** interpreted as 65536. */
-    top = get2byteNotZero(&data[hdr+5]);
-    /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
-    ** number of cells on the page. */
-    pPage->nCell = get2byte(&data[hdr+3]);
-    if( pPage->nCell>MX_CELL(pBt) ){
-      /* To many cells for a single page.  The page must be corrupt */
-      return SQLITE_CORRUPT_BKPT;
-    }
-    testcase( pPage->nCell==MX_CELL(pBt) );
-    /* EVIDENCE-OF: R-24089-57979 If a page contains no cells (which is only
-    ** possible for a root page of a table that contains no rows) then the
-    ** offset to the cell content area will equal the page size minus the
-    ** bytes of reserved space. */
-    assert( pPage->nCell>0 || top==usableSize || CORRUPT_DB );
-
-    /* A malformed database page might cause us to read past the end
-    ** of page when parsing a cell.  
-    **
-    ** The following block of code checks early to see if a cell extends
-    ** past the end of a page boundary and causes SQLITE_CORRUPT to be 
-    ** returned if it does.
-    */
-    iCellFirst = cellOffset + 2*pPage->nCell;
-    iCellLast = usableSize - 4;
-    if( pBt->pBt->flags & SQLITE_CellSizeCk ){
-      int i;            /* Index into the cell pointer array */
-      int sz;           /* Size of a cell */
-
-      if( !pPage->leaf ) iCellLast--;
-      for(i=0; i<pPage->nCell; i++){
-        pc = get2byteAligned(&data[cellOffset+i*2]);
-        testcase( pc==iCellFirst );
-        testcase( pc==iCellLast );
-        if( pc<iCellFirst || pc>iCellLast ){
-          return SQLITE_CORRUPT_BKPT;
-        }
-        sz = pPage->xCellSize(pPage, &data[pc]);
-        testcase( pc+sz==usableSize );
-        if( pc+sz>usableSize ){
-          return SQLITE_CORRUPT_BKPT;
-        }
-      }
-      if( !pPage->leaf ) iCellLast++;
-    }  
-
-    /* Compute the total free space on the page
-    ** EVIDENCE-OF: R-23588-34450 The two-byte integer at offset 1 gives the
-    ** start of the first freeblock on the page, or is zero if there are no
-    ** freeblocks. */
-    pc = get2byte(&data[hdr+1]);
-    nFree = data[hdr+7] + top;  /* Init nFree to non-freeblock free space */
-    while( pc>0 ){
-      u16 next, size;
-      if( pc<iCellFirst || pc>iCellLast ){
-        /* EVIDENCE-OF: R-55530-52930 In a well-formed b-tree page, there will
-        ** always be at least one cell before the first freeblock.
-        **
-        ** Or, the freeblock is off the end of the page
-        */
-        return SQLITE_CORRUPT_BKPT; 
-      }
-      next = get2byte(&data[pc]);
-      size = get2byte(&data[pc+2]);
-      if( (next>0 && next<=pc+size+3) || pc+size>usableSize ){
-        /* Free blocks must be in ascending order. And the last byte of
-        ** the free-block must lie on the database page.  */
-        return SQLITE_CORRUPT_BKPT; 
-      }
-      nFree = nFree + size;
-      pc = next;
-    }
-
-    /* At this point, nFree contains the sum of the offset to the start
-    ** of the cell-content area plus the number of free bytes within
-    ** the cell-content area. If this is greater than the usable-size
-    ** of the page, then the page must be corrupted. This check also
-    ** serves to verify that the offset to the start of the cell-content
-    ** area, according to the page header, lies within the page.
-    */
-    if( nFree>usableSize ){
-      return SQLITE_CORRUPT_BKPT; 
-    }
-    pPage->nFree = (u16)(nFree - iCellFirst);
-    pPage->isInit = 1;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Set up a raw page so that it looks like a database page holding
-** no entries.
-*/
-static void zeroPage(MemPage *pPage, int flags){
-  unsigned char *data = pPage->aData;
-  BtShared *pBt = pPage->pBt;
-  u8 hdr = pPage->hdrOffset;
-  u16 first;
-
-  assert( sqlite3PagerPagenumber(pPage->pDbPage)==pPage->pgno );
-  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
-  assert( sqlite3PagerGetData(pPage->pDbPage) == data );
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pBt->btsFlags & BTS_SECURE_DELETE ){
-    memset(&data[hdr], 0, pBt->usableSize - hdr);
-  }
-  data[hdr] = (char)flags;
-  first = hdr + ((flags&PTF_LEAF)==0 ? 12 : 8);
-  memset(&data[hdr+1], 0, 4);
-  data[hdr+7] = 0;
-  put2byte(&data[hdr+5], pBt->usableSize);
-  pPage->nFree = (u16)(pBt->usableSize - first);
-  decodeFlags(pPage, flags);
-  pPage->cellOffset = first;
-  pPage->aDataEnd = &data[pBt->usableSize];
-  pPage->aCellIdx = &data[first];
-  pPage->aDataOfst = &data[pPage->childPtrSize];
-  pPage->nOverflow = 0;
-  assert( pBt->pageSize>=512 && pBt->pageSize<=65536 );
-  pPage->maskPage = (u16)(pBt->pageSize - 1);
-  pPage->nCell = 0;
-  pPage->isInit = 1;
-}
-
-
-/*
-** Convert a DbPage obtained from the pager into a MemPage used by
-** the btree layer.
-*/
-static MemPage *btreePageFromDbPage(DbPage *pDbPage, Pgno pgno, BtShared *pBt){
-  MemPage *pPage = (MemPage*)sqlite3PagerGetExtra(pDbPage);
-  pPage->aData = sqlite3PagerGetData(pDbPage);
-  pPage->pDbPage = pDbPage;
-  pPage->pBt = pBt;
-  pPage->pgno = pgno;
-  pPage->hdrOffset = pgno==1 ? 100 : 0;
-  return pPage; 
-}
-
-/*
-** Get a page from the pager.  Initialize the MemPage.pBt and
-** MemPage.aData elements if needed.  See also: btreeGetUnusedPage().
-**
-** If the PAGER_GET_NOCONTENT flag is set, it means that we do not care
-** about the content of the page at this time.  So do not go to the disk
-** to fetch the content.  Just fill in the content with zeros for now.
-** If in the future we call sqlite3PagerWrite() on this page, that
-** means we have started to be concerned about content and the disk
-** read should occur at that point.
-*/
-static int btreeGetPage(
-  BtShared *pBt,       /* The btree */
-  Pgno pgno,           /* Number of the page to fetch */
-  MemPage **ppPage,    /* Return the page in this parameter */
-  int flags            /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
-){
-  int rc;
-  DbPage *pDbPage;
-
-  assert( flags==0 || flags==PAGER_GET_NOCONTENT || flags==PAGER_GET_READONLY );
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, flags);
-  if( rc ) return rc;
-  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
-  return SQLITE_OK;
-}
-
-/*
-** Retrieve a page from the pager cache. If the requested page is not
-** already in the pager cache return NULL. Initialize the MemPage.pBt and
-** MemPage.aData elements if needed.
-*/
-static MemPage *btreePageLookup(BtShared *pBt, Pgno pgno){
-  DbPage *pDbPage;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  pDbPage = sqlite3PagerLookup(pBt->pPager, pgno);
-  if( pDbPage ){
-    return btreePageFromDbPage(pDbPage, pgno, pBt);
-  }
-  return 0;
-}
-
-/*
-** Return the size of the database file in pages. If there is any kind of
-** error, return ((unsigned int)-1).
-*/
-static Pgno btreePagecount(BtShared *pBt){
-  return pBt->nPage;
-}
-SQLITE_API u32 SQLITE_STDCALL sqlite3BtreeLastPage(Btree *p){
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( ((p->pBt->nPage)&0x8000000)==0 );
-  return btreePagecount(p->pBt);
-}
-
-/*
-** Get a page from the pager and initialize it.
-**
-** If pCur!=0 then the page is being fetched as part of a moveToChild()
-** call.  Do additional sanity checking on the page in this case.
-** And if the fetch fails, this routine must decrement pCur->iPage.
-**
-** The page is fetched as read-write unless pCur is not NULL and is
-** a read-only cursor.
-**
-** If an error occurs, then *ppPage is undefined. It
-** may remain unchanged, or it may be set to an invalid value.
-*/
-static int getAndInitPage(
-  BtShared *pBt,                  /* The database file */
-  Pgno pgno,                      /* Number of the page to get */
-  MemPage **ppPage,               /* Write the page pointer here */
-  BtCursor *pCur,                 /* Cursor to receive the page, or NULL */
-  int bReadOnly                   /* True for a read-only page */
-){
-  int rc;
-  DbPage *pDbPage;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( pCur==0 || ppPage==&pCur->apPage[pCur->iPage] );
-  assert( pCur==0 || bReadOnly==pCur->curPagerFlags );
-  assert( pCur==0 || pCur->iPage>0 );
-
-  if( pgno>btreePagecount(pBt) ){
-    rc = SQLITE_CORRUPT_BKPT;
-    goto getAndInitPage_error;
-  }
-  rc = sqlite3PagerAcquire(pBt->pPager, pgno, (DbPage**)&pDbPage, bReadOnly);
-  if( rc ){
-    goto getAndInitPage_error;
-  }
-  *ppPage = btreePageFromDbPage(pDbPage, pgno, pBt);
-  if( (*ppPage)->isInit==0 ){
-    rc = btreeInitPage(*ppPage);
-    if( rc!=SQLITE_OK ){
-      releasePage(*ppPage);
-      goto getAndInitPage_error;
-    }
-  }
-
-  /* If obtaining a child page for a cursor, we must verify that the page is
-  ** compatible with the root page. */
-  if( pCur
-   && ((*ppPage)->nCell<1 || (*ppPage)->intKey!=pCur->curIntKey)
-  ){
-    rc = SQLITE_CORRUPT_BKPT;
-    releasePage(*ppPage);
-    goto getAndInitPage_error;
-  }
-  return SQLITE_OK;
-
-getAndInitPage_error:
-  if( pCur ) pCur->iPage--;
-  testcase( pgno==0 );
-  assert( pgno!=0 || rc==SQLITE_CORRUPT );
-  return rc;
-}
-
-/*
-** Release a MemPage.  This should be called once for each prior
-** call to btreeGetPage.
-*/
-static void releasePageNotNull(MemPage *pPage){
-  assert( pPage->aData );
-  assert( pPage->pBt );
-  assert( pPage->pDbPage!=0 );
-  assert( sqlite3PagerGetExtra(pPage->pDbPage) == (void*)pPage );
-  assert( sqlite3PagerGetData(pPage->pDbPage)==pPage->aData );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  sqlite3PagerUnrefNotNull(pPage->pDbPage);
-}
-static void releasePage(MemPage *pPage){
-  if( pPage ) releasePageNotNull(pPage);
-}
-
-/*
-** Get an unused page.
-**
-** This works just like btreeGetPage() with the addition:
-**
-**   *  If the page is already in use for some other purpose, immediately
-**      release it and return an SQLITE_CURRUPT error.
-**   *  Make sure the isInit flag is clear
-*/
-static int btreeGetUnusedPage(
-  BtShared *pBt,       /* The btree */
-  Pgno pgno,           /* Number of the page to fetch */
-  MemPage **ppPage,    /* Return the page in this parameter */
-  int flags            /* PAGER_GET_NOCONTENT or PAGER_GET_READONLY */
-){
-  int rc = btreeGetPage(pBt, pgno, ppPage, flags);
-  if( rc==SQLITE_OK ){
-    if( sqlite3PagerPageRefcount((*ppPage)->pDbPage)>1 ){
-      releasePage(*ppPage);
-      *ppPage = 0;
-      return SQLITE_CORRUPT_BKPT;
-    }
-    (*ppPage)->isInit = 0;
-  }else{
-    *ppPage = 0;
-  }
-  return rc;
-}
-
-
-/*
-** During a rollback, when the pager reloads information into the cache
-** so that the cache is restored to its original state at the start of
-** the transaction, for each page restored this routine is called.
-**
-** This routine needs to reset the extra data section at the end of the
-** page to agree with the restored data.
-*/
-static void pageReinit(DbPage *pData){
-  MemPage *pPage;
-  pPage = (MemPage *)sqlite3PagerGetExtra(pData);
-  assert( sqlite3PagerPageRefcount(pData)>0 );
-  if( pPage->isInit ){
-    assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-    pPage->isInit = 0;
-    if( sqlite3PagerPageRefcount(pData)>1 ){
-      /* pPage might not be a btree page;  it might be an overflow page
-      ** or ptrmap page or a free page.  In those cases, the following
-      ** call to btreeInitPage() will likely return SQLITE_CORRUPT.
-      ** But no harm is done by this.  And it is very important that
-      ** btreeInitPage() be called on every btree page so we make
-      ** the call for every page that comes in for re-initing. */
-      btreeInitPage(pPage);
-    }
-  }
-}
-
-/*
-** Invoke the busy handler for a btree.
-*/
-static int btreeInvokeBusyHandler(void *pArg){
-  BtShared *pBt = (BtShared*)pArg;
-  assert( pBt->pBt );
-  assert( sqlite3_mutex_held(pBt->pBt->mutex) );
-  return sqlite3InvokeBusyHandler(&pBt->pBt->busyHandler);
-}
-
-/*
-** Open a database file.
-** 
-** zFilename is the name of the database file.  If zFilename is NULL
-** then an ephemeral database is created.  The ephemeral database might
-** be exclusively in memory, or it might use a disk-based memory cache.
-** Either way, the ephemeral database will be automatically deleted 
-** when sqlite3BtreeClose() is called.
-**
-** If zFilename is ":memory:" then an in-memory database is created
-** that is automatically destroyed when it is closed.
-**
-** The "flags" parameter is a bitmask that might contain bits like
-** BTREE_OMIT_JOURNAL and/or BTREE_MEMORY.
-**
-** If the database is already opened in the same database connection
-** and we are in shared cache mode, then the open will fail with an
-** SQLITE_CONSTRAINT error.  We cannot allow two or more BtShared
-** objects in the same database connection since doing so will lead
-** to problems with locking.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeOpen(
-  const char *zVfs,       /* VFS to use for this b-tree */
-  const char *zFilename,  /* Name of the file containing the BTree database */
-  Btree **ppBtree,        /* Pointer to new Btree object written here */
-  int flags,              /* Options */
-  int vfsFlags            /* Flags passed through to sqlite3_vfs.xOpen() */
-){
-  BtShared *pBt = 0;             /* Shared part of btree structure */
-  Btree *p;                      /* Handle to return */
-  sqlite3_mutex *mutexOpen = 0;  /* Prevents a race condition. Ticket #3537 */
-  int rc = SQLITE_OK;            /* Result code from this function */
-  u8 nReserve;                   /* Byte of unused space on each page */
-  unsigned char zDbHeader[100];  /* Database header content */
-  int isThreadsafe;              /* True for threadsafe connections */
-
-#ifdef SQLITE_ENABLE_API_ARMOR
-  if( ppBtree==0 ) return SQLITE_MISUSE_BKPT;
-#endif
-  *ppBtree = 0;
-#ifndef SQLITE_OMIT_AUTOINIT
-  rc = sqlite3BtreeInitialize();
-  if( rc ) return rc;
-#endif
-
-  /* Only allow sensible combinations of bits in the vfsFlags argument.  
-  ** Throw an error if any non-sense combination is used.  If we
-  ** do not block illegal combinations here, it could trigger
-  ** assert() statements in deeper layers.  Sensible combinations
-  ** are:
-  **
-  **  1:  SQLITE_OPEN_READONLY
-  **  2:  SQLITE_OPEN_READWRITE
-  **  6:  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
-  */
-  assert( SQLITE_OPEN_READONLY  == 0x01 );
-  assert( SQLITE_OPEN_READWRITE == 0x02 );
-  assert( SQLITE_OPEN_CREATE    == 0x04 );
-  testcase( (1<<(vfsFlags&7))==0x02 ); /* READONLY */
-  testcase( (1<<(vfsFlags&7))==0x04 ); /* READWRITE */
-  testcase( (1<<(vfsFlags&7))==0x40 ); /* READWRITE | CREATE */
-  if( ((1<<(vfsFlags&7)) & 0x46)==0 ){
-    return SQLITE_MISUSE_BKPT;  /* IMP: R-65497-44594 */
-  }
-
-  if( sqlite3GlobalConfig.bCoreMutex==0 ){
-    isThreadsafe = 0;
-  }else if( vfsFlags & SQLITE_OPEN_NOMUTEX ){
-    isThreadsafe = 0;
-  }else if( vfsFlags & SQLITE_OPEN_FULLMUTEX ){
-    isThreadsafe = 1;
-  }else{
-    isThreadsafe = sqlite3GlobalConfig.bFullMutex;
-  }
-  if( vfsFlags & SQLITE_OPEN_PRIVATECACHE ){
-    vfsFlags &= ~SQLITE_OPEN_SHAREDCACHE;
-  }else if( sqlite3GlobalConfig.sharedCacheEnabled ){
-    vfsFlags |= SQLITE_OPEN_SHAREDCACHE;
-  }
-
-  /* Remove harmful bits from the vfsFlags parameter
-  **
-  ** The SQLITE_OPEN_NOMUTEX and SQLITE_OPEN_FULLMUTEX vfsFlags were
-  ** dealt with in the previous code block.  Besides these, the only
-  ** valid input vfsFlags for sqlite3_open_v2() are SQLITE_OPEN_READONLY,
-  ** SQLITE_OPEN_READWRITE, SQLITE_OPEN_CREATE, SQLITE_OPEN_SHAREDCACHE,
-  ** SQLITE_OPEN_PRIVATECACHE, and some reserved bits.  Silently mask
-  ** off all other vfsFlags.
-  */
-  vfsFlags &=  ~( SQLITE_OPEN_DELETEONCLOSE |
-                  SQLITE_OPEN_EXCLUSIVE |
-                  SQLITE_OPEN_MAIN_DB |
-                  SQLITE_OPEN_TEMP_DB | 
-                  SQLITE_OPEN_TRANSIENT_DB | 
-                  SQLITE_OPEN_MAIN_JOURNAL | 
-                  SQLITE_OPEN_TEMP_JOURNAL | 
-                  SQLITE_OPEN_SUBJOURNAL | 
-                  SQLITE_OPEN_MASTER_JOURNAL |
-                  SQLITE_OPEN_NOMUTEX |
-                  SQLITE_OPEN_FULLMUTEX |
-                  SQLITE_OPEN_WAL
-                );
-
-  assert( (vfsFlags&0xff)==vfsFlags );   /* flags fit in 8 bits */
-
-  /* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
-  assert( (vfsFlags & BTREE_UNORDERED)==0 || (vfsFlags & BTREE_SINGLE)!=0 );
-
-  sqlite3_vfs *pVfs =
-    sqlite3_vfs_find(zVfs);
-  if( pVfs==0 ){
-    return SQLITE_ERROR;
-  }
-
-  p = sqlite3MallocZero(sizeof(Btree));
-  if( !p ){
-    return SQLITE_NOMEM;
-  }
-  p->inTrans = TRANS_NONE;
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  p->lock.pBtree = p;
-  p->lock.iTable = 1;
-#endif
-  p->magic = SQLITE_MAGIC_BUSY;
-
-  if( isThreadsafe ){
-    p->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
-    if( p->mutex==0 ){
-      sqlite3_free(p);
-      p = 0;
-      goto btree_open_out;
-    }
-  }
-  sqlite3_mutex_enter(p->mutex);
-
-  p->enc    = SQLITE_UTF8;
-  p->szMmap = sqlite3GlobalConfig.szMmap;
-  p->flags |= 0
-#if SQLITE_DEFAULT_CKPTFULLFSYNC
-                 | SQLITE_CkptFullFSync
-#endif
-#if defined(SQLITE_ENABLE_OVERSIZE_CELL_CHECK)
-                 | SQLITE_CellSizeCk
-#endif
-;
-
-#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
-  /*
-  ** If this Btree is a candidate for shared cache, try to find an
-  ** existing BtShared object that we can share with
-  */
-  if( (vfsFlags&SQLITE_OPEN_URI)!=0 ){
-    if( vfsFlags & SQLITE_OPEN_SHAREDCACHE ){
-      int nFilename = sqlite3Strlen30(zFilename)+1;
-      int nFullPathname = pVfs->mxPathname+1;
-      char *zFullPathname = sqlite3Malloc(MAX(nFullPathname,nFilename));
-      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
-
-      p->sharable = 1;
-      if( !zFullPathname ){
-        sqlite3_free(p);
-        return SQLITE_NOMEM;
-      }
-      rc = sqlite3OsFullPathname(pVfs, zFilename,
-                                 nFullPathname, zFullPathname);
-      if( rc ){
-        sqlite3_free(zFullPathname);
-        sqlite3_free(p);
-        return rc;
-      }
-#if SQLITE_THREADSAFE
-      mutexOpen = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_OPEN);
-      sqlite3_mutex_enter(mutexOpen);
-      mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);
-      sqlite3_mutex_enter(mutexShared);
-#endif
-      for(pBt=GLOBAL(BtShared*,sqlite3SharedCacheList); pBt; pBt=pBt->pNext){
-        assert( pBt->nRef>0 );
-        if( 0==strcmp(zFullPathname, sqlite3PagerFilename(pBt->pPager, 0))
-                 && sqlite3PagerVfs(pBt->pPager)==pVfs ){
-          p->pBt = pBt;
-          pBt->nRef++;
-          break;
-        }
-      }
-      sqlite3_mutex_leave(mutexShared);
-      sqlite3_free(zFullPathname);
-    }
-#ifdef SQLITE_DEBUG
-    else{
-      /* In debug mode, we mark all persistent databases as sharable
-      ** even when they are not.  This exercises the locking code and
-      ** gives more opportunity for asserts(sqlite3_mutex_held())
-      ** statements to find locking problems.
-      */
-      p->sharable = 1;
-    }
-#endif
-  }
-#endif
-  if( pBt==0 ){
-    /*
-    ** The following asserts make sure that structures used by the btree are
-    ** the right size.  This is to guard against size changes that result
-    ** when compiling on a different architecture.
-    */
-    assert( sizeof(i64)==8 );
-    assert( sizeof(u64)==8 );
-    assert( sizeof(u32)==4 );
-    assert( sizeof(u16)==2 );
-    assert( sizeof(Pgno)==4 );
-  
-    pBt = sqlite3MallocZero( sizeof(*pBt) );
-    if( pBt==0 ){
-      rc = SQLITE_NOMEM;
-      goto btree_open_out;
-    }
-    rc = sqlite3PagerOpen(pVfs, &pBt->pPager, zFilename,
-                          EXTRA_SIZE, flags, vfsFlags, pageReinit);
-    if( rc==SQLITE_OK ){
-      sqlite3PagerSetMmapLimit(pBt->pPager, p->szMmap);
-      rc = sqlite3PagerReadFileheader(pBt->pPager,sizeof(zDbHeader),zDbHeader);
-    }
-    if( rc!=SQLITE_OK ){
-      goto btree_open_out;
-    }
-    pBt->openFlags = (u8)flags;
-    pBt->pBt = p;
-    sqlite3PagerSetBusyhandler(pBt->pPager, btreeInvokeBusyHandler, pBt);
-    p->pBt = pBt;
-
-    pBt->pCursor = 0;
-    pBt->pPage1 = 0;
-    if( sqlite3PagerIsreadonly(pBt->pPager) ) pBt->btsFlags |= BTS_READ_ONLY;
-#ifdef SQLITE_SECURE_DELETE
-    pBt->btsFlags |= BTS_SECURE_DELETE;
-#endif
-    /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
-    ** determined by the 2-byte integer located at an offset of 16 bytes from
-    ** the beginning of the database file. */
-    pBt->pageSize = (zDbHeader[16]<<8) | (zDbHeader[17]<<16);
-    if( pBt->pageSize<512 || pBt->pageSize>SQLITE_MAX_PAGE_SIZE
-         || ((pBt->pageSize-1)&pBt->pageSize)!=0 ){
-      pBt->pageSize = 0;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      /* If the magic name ":memory:" will create an in-memory database, then
-      ** leave the autoVacuum mode at 0 (do not auto-vacuum), even if
-      ** SQLITE_DEFAULT_AUTOVACUUM is true.
-      */
-      if( zFilename ){
-        pBt->autoVacuum = (SQLITE_DEFAULT_AUTOVACUUM ? 1 : 0);
-        pBt->incrVacuum = (SQLITE_DEFAULT_AUTOVACUUM==2 ? 1 : 0);
-      }
-#endif
-      nReserve = 0;
-    }else{
-      /* EVIDENCE-OF: R-37497-42412 The size of the reserved region is
-      ** determined by the one-byte unsigned integer found at an offset of 20
-      ** into the database file header. */
-      nReserve = zDbHeader[20];
-      pBt->btsFlags |= BTS_PAGESIZE_FIXED;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      pBt->autoVacuum = (get4byte(&zDbHeader[36 + 4*4])?1:0);
-      pBt->incrVacuum = (get4byte(&zDbHeader[36 + 7*4])?1:0);
-#endif
-    }
-    rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
-    if( rc ) goto btree_open_out;
-    pBt->usableSize = pBt->pageSize - nReserve;
-    assert( (pBt->pageSize & 7)==0 );  /* 8-byte alignment of pageSize */
-
-    /*
-    ** file_format==1    Version 3.0.0.
-    ** file_format==2    Version 3.1.3.  // ALTER TABLE ADD COLUMN
-    ** file_format==3    Version 3.1.4.  // ditto but with non-NULL defaults
-    ** file_format==4    Version 3.3.0.  // DESC indices.  Boolean constants
-    */
-    pBt->file_format = zDbHeader[18];
-    if( pBt->file_format==0 ){
-      pBt->file_format = 1;
-    }
-    if( pBt->file_format>SQLITE_MAX_FILE_FORMAT ){
-      rc = SQLITE_ERROR;
-      goto btree_open_out;
-    }
-   
-#if !defined(SQLITE_OMIT_SHARED_CACHE) && !defined(SQLITE_OMIT_DISKIO)
-    /* Add the new BtShared object to the linked list sharable BtShareds.
-    */
-    if( p->sharable ){
-      MUTEX_LOGIC( sqlite3_mutex *mutexShared; )
-      pBt->nRef = 1;
-      MUTEX_LOGIC( mutexShared = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER);)
-      if( SQLITE_THREADSAFE && sqlite3GlobalConfig.bCoreMutex ){
-        pBt->mutex = sqlite3MutexAlloc(SQLITE_MUTEX_FAST);
-        if( pBt->mutex==0 ){
-          rc = SQLITE_NOMEM;
-          p->mallocFailed = 0;
-          goto btree_open_out;
-        }
-      }
-      sqlite3_mutex_enter(mutexShared);
-      pBt->pNext = GLOBAL(BtShared*,sqlite3SharedCacheList);
-      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt;
-      sqlite3_mutex_leave(mutexShared);
-    }
-#endif
-  }
-
-  sqlite3PagerSetCachesize(pBt->pPager, SQLITE_DEFAULT_CACHE_SIZE);
-
-  p->magic = SQLITE_MAGIC_OPEN;
-
-  /* -DSQLITE_DEFAULT_LOCKING_MODE=1 makes EXCLUSIVE the default locking
-  ** mode.  -DSQLITE_DEFAULT_LOCKING_MODE=0 make NORMAL the default locking
-  ** mode.  Doing nothing at all also makes NORMAL the default.
-  */
-#ifdef SQLITE_DEFAULT_LOCKING_MODE
-  sqlite3PagerLockingMode(sqlite3BtreePager(db->aDb[0].pBt),
-                          SQLITE_DEFAULT_LOCKING_MODE);
-#endif
-
-  *ppBtree = p;
-
-btree_open_out:
-  if( rc!=SQLITE_OK ){
-    if( pBt && pBt->pPager ){
-      sqlite3PagerClose(pBt->pPager);
-    }
-    sqlite3_free(pBt);
-    sqlite3_free(p);
-    *ppBtree = 0;
-  }else{
-    if (p) {
-      assert( p->mutex!=0 || isThreadsafe==0
-             || sqlite3GlobalConfig.bFullMutex==0 );
-      sqlite3_mutex_leave(p->mutex);
-    }
-
-    /* If the B-Tree was successfully opened, set the pager-cache size to the
-    ** default value. Except, when opening on an existing shared pager-cache,
-    ** do not change the pager-cache size.
-    */
-    if( sqlite3BtreeSchema(p, 0, 0)==0 ){
-      sqlite3PagerSetCachesize(pBt->pPager, SQLITE_DEFAULT_CACHE_SIZE);
-    }
-  }
-  if( mutexOpen ){
-    assert( sqlite3_mutex_held(mutexOpen) );
-    sqlite3_mutex_leave(mutexOpen);
-  }
-  return rc;
-}
-
-/*
-** Decrement the BtShared.nRef counter.  When it reaches zero,
-** remove the BtShared structure from the sharing list.  Return
-** true if the BtShared.nRef counter reaches zero and return
-** false if it is still positive.
-*/
-static int removeFromSharingList(BtShared *pBt){
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  MUTEX_LOGIC( sqlite3_mutex *pMaster; )
-  BtShared *pList;
-  int removed = 0;
-
-  assert( sqlite3_mutex_notheld(pBt->mutex) );
-  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
-  sqlite3_mutex_enter(pMaster);
-  pBt->nRef--;
-  if( pBt->nRef<=0 ){
-    if( GLOBAL(BtShared*,sqlite3SharedCacheList)==pBt ){
-      GLOBAL(BtShared*,sqlite3SharedCacheList) = pBt->pNext;
-    }else{
-      pList = GLOBAL(BtShared*,sqlite3SharedCacheList);
-      while( ALWAYS(pList) && pList->pNext!=pBt ){
-        pList=pList->pNext;
-      }
-      if( ALWAYS(pList) ){
-        pList->pNext = pBt->pNext;
-      }
-    }
-    if( SQLITE_THREADSAFE ){
-      sqlite3_mutex_free(pBt->mutex);
-    }
-    removed = 1;
-  }
-  sqlite3_mutex_leave(pMaster);
-  return removed;
-#else
-  return 1;
-#endif
-}
-
-/*
-** Make sure pBt->pTmpSpace points to an allocation of 
-** MX_CELL_SIZE(pBt) bytes with a 4-byte prefix for a left-child
-** pointer.
-*/
-static void allocateTempSpace(BtShared *pBt){
-  if( !pBt->pTmpSpace ){
-    pBt->pTmpSpace = sqlite3PageMalloc( pBt->pageSize );
-
-    /* One of the uses of pBt->pTmpSpace is to format cells before
-    ** inserting them into a leaf page (function fillInCell()). If
-    ** a cell is less than 4 bytes in size, it is rounded up to 4 bytes
-    ** by the various routines that manipulate binary cells. Which
-    ** can mean that fillInCell() only initializes the first 2 or 3
-    ** bytes of pTmpSpace, but that the first 4 bytes are copied from
-    ** it into a database page. This is not actually a problem, but it
-    ** does cause a valgrind error when the 1 or 2 bytes of unitialized 
-    ** data is passed to system call write(). So to avoid this error,
-    ** zero the first 4 bytes of temp space here.
-    **
-    ** Also:  Provide four bytes of initialized space before the
-    ** beginning of pTmpSpace as an area available to prepend the
-    ** left-child pointer to the beginning of a cell.
-    */
-    if( pBt->pTmpSpace ){
-      memset(pBt->pTmpSpace, 0, 8);
-      pBt->pTmpSpace += 4;
-    }
-  }
-}
-
-/*
-** Free the pBt->pTmpSpace allocation
-*/
-static void freeTempSpace(BtShared *pBt){
-  if( pBt->pTmpSpace ){
-    pBt->pTmpSpace -= 4;
-    sqlite3PageFree(pBt->pTmpSpace);
-    pBt->pTmpSpace = 0;
-  }
-}
-
-/*
-** Close an open database and invalidate all cursors.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeClose(Btree *p){
-  if( !p ){
-    /* EVIDENCE-OF: R-63257-11740 Calling sqlite3BtreeClose()
-    ** with a NULL pointer argument is a harmless no-op. */
-    return SQLITE_OK;
-  }
-
-  if( !sqlite3SafetyCheckSickOrOk(p) ){
-    return SQLITE_MISUSE_BKPT;
-  }
-
-  sqlite3_mutex_enter(p->mutex);
-
-  p->magic = SQLITE_MAGIC_ZOMBIE;
-
-  BtShared *pBt = p->pBt;
-  BtCursor *pCur;
-
-  /* Close all cursors opened via this handle.  */
-  sqlite3BtreeEnter(p);
-  pCur = pBt->pCursor;
-  while( pCur ){
-    BtCursor *pTmp = pCur;
-    pCur = pCur->pNext;
-    if( pTmp->pBtree==p ){
-      sqlite3BtreeCloseCursor(pTmp);
-    }
-  }
-
-  /* Rollback any active transaction and free the handle structure.
-  ** The call to sqlite3BtreeRollback() drops any table-locks held by
-  ** this handle.
-  */
-  sqlite3BtreeRollback(p, SQLITE_OK, 0);
-  sqlite3BtreeLeave(p);
-
-  /* If there are still other outstanding references to the shared-btree
-  ** structure, return now. The remainder of this procedure cleans 
-  ** up the shared-btree.
-  */
-  assert( p->wantToLock==0 && p->locked==0 );
-  if( !p->sharable || removeFromSharingList(pBt) ){
-    /* The pBt is no longer on the sharing list, so we can access
-    ** it without having to hold the mutex.
-    **
-    ** Clean out and delete the BtShared object.
-    */
-    assert( !pBt->pCursor );
-    sqlite3PagerClose(pBt->pPager);
-    if( pBt->xFreeSchema && pBt->pSchema ){
-      pBt->xFreeSchema(pBt->pSchema);
-    }
-    sqlite3DbFree(0, pBt->pSchema);
-    freeTempSpace(pBt);
-    sqlite3_free(pBt);
-  }
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  assert( p->wantToLock==0 );
-  assert( p->locked==0 );
-  if( p->pPrev ) p->pPrev->pNext = p->pNext;
-  if( p->pNext ) p->pNext->pPrev = p->pPrev;
-#endif
-
-  sqlite3_mutex_leave(p->mutex);
-  sqlite3_mutex_free(p->mutex);
-
-  p->magic = SQLITE_MAGIC_CLOSED;
-
-  sqlite3_free(p);
-  return SQLITE_OK;
-}
-
-/*
-** Change the limit on the number of pages allowed in the cache.
-**
-** The maximum number of cache pages is set to the absolute
-** value of mxPage.  If mxPage is negative, the pager will
-** operate asynchronously - it will not stop to do fsync()s
-** to insure data is written to the disk surface before
-** continuing.  Transactions still work if synchronous is off,
-** and the database cannot be corrupted if this program
-** crashes.  But if the operating system crashes or there is
-** an abrupt power failure when synchronous is off, the database
-** could be left in an inconsistent and unrecoverable state.
-** Synchronous is on by default so database corruption is not
-** normally a worry.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetCacheSize(Btree *p, int mxPage){
-  BtShared *pBt = p->pBt;
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  sqlite3BtreeEnter(p);
-  sqlite3PagerSetCachesize(pBt->pPager, mxPage);
-  sqlite3BtreeLeave(p);
-  return SQLITE_OK;
-}
-
-#if SQLITE_MAX_MMAP_SIZE>0
-/*
-** Change the limit on the amount of the database file that may be
-** memory mapped.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetMmapLimit(Btree *p, sqlite3_int64 szMmap){
-  BtShared *pBt = p->pBt;
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  sqlite3BtreeEnter(p);
-  sqlite3PagerSetMmapLimit(pBt->pPager, szMmap);
-  sqlite3BtreeLeave(p);
-  return SQLITE_OK;
-}
-#endif /* SQLITE_MAX_MMAP_SIZE>0 */
-
-/*
-** Change the way data is synced to disk in order to increase or decrease
-** how well the database resists damage due to OS crashes and power
-** failures.  Level 1 is the same as asynchronous (no syncs() occur and
-** there is a high probability of damage)  Level 2 is the default.  There
-** is a very low but non-zero probability of damage.  Level 3 reduces the
-** probability of damage to near zero but with a write performance reduction.
-*/
-#ifndef SQLITE_OMIT_PAGER_PRAGMAS
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetPagerFlags(
-  Btree *p,              /* The btree to set the safety level on */
-  unsigned pgFlags       /* Various PAGER_* flags */
-){
-  BtShared *pBt = p->pBt;
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  sqlite3BtreeEnter(p);
-  sqlite3PagerSetFlags(pBt->pPager, pgFlags);
-  sqlite3BtreeLeave(p);
-  return SQLITE_OK;
-}
-#endif
-
-/*
-** Return TRUE if the given btree is set to safety level 1.  In other
-** words, return TRUE if no sync() occurs on the disk files.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSyncDisabled(Btree *p){
-  BtShared *pBt = p->pBt;
-  int rc;
-  assert( sqlite3_mutex_held(p->db->mutex) );  
-  sqlite3BtreeEnter(p);
-  assert( pBt && pBt->pPager );
-  rc = sqlite3PagerNosync(pBt->pPager);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Change the default pages size and the number of reserved bytes per page.
-** Or, if the page size has already been fixed, return SQLITE_READONLY 
-** without changing anything.
-**
-** The page size must be a power of 2 between 512 and 65536.  If the page
-** size supplied does not meet this constraint then the page size is not
-** changed.
-**
-** Page sizes are constrained to be a power of two so that the region
-** of the database file used for locking (beginning at PENDING_BYTE,
-** the first byte past the 1GB boundary, 0x40000000) needs to occur
-** at the beginning of a page.
-**
-** If parameter nReserve is less than zero, then the number of reserved
-** bytes per page is left unchanged.
-**
-** If the iFix!=0 then the BTS_PAGESIZE_FIXED flag is set so that the page size
-** and autovacuum mode can no longer be changed.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetPageSize(Btree *p, int pageSize, int nReserve, int iFix){
-  int rc = SQLITE_OK;
-  BtShared *pBt = p->pBt;
-  assert( nReserve>=-1 && nReserve<=255 );
-  sqlite3BtreeEnter(p);
-#if SQLITE_HAS_CODEC
-  if( nReserve>pBt->optimalReserve ) pBt->optimalReserve = (u8)nReserve;
-#endif
-  if( pBt->btsFlags & BTS_PAGESIZE_FIXED ){
-    sqlite3BtreeLeave(p);
-    return SQLITE_READONLY;
-  }
-  if( nReserve<0 ){
-    nReserve = pBt->pageSize - pBt->usableSize;
-  }
-  assert( nReserve>=0 && nReserve<=255 );
-  if( pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE &&
-        ((pageSize-1)&pageSize)==0 ){
-    assert( (pageSize & 7)==0 );
-    assert( !pBt->pCursor );
-    pBt->pageSize = (u32)pageSize;
-    freeTempSpace(pBt);
-  }
-  rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize, nReserve);
-  pBt->usableSize = pBt->pageSize - (u16)nReserve;
-  if( iFix ) pBt->btsFlags |= BTS_PAGESIZE_FIXED;
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Return the currently defined page size
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeGetPageSize(Btree *p){
-  return p->pBt->pageSize;
-}
-
-/*
-** This function is similar to sqlite3BtreeGetReserve(), except that it
-** may only be called if it is guaranteed that the b-tree mutex is already
-** held.
-**
-** This is useful in one special case in the backup API code where it is
-** known that the shared b-tree mutex is held, but the mutex on the 
-** database handle that owns *p is not. In this case if sqlite3BtreeEnter()
-** were to be called, it might collide with some other operation on the
-** database handle that owns *p, causing undefined behavior.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeGetReserveNoMutex(Btree *p){
-  int n;
-  assert( sqlite3_mutex_held(p->pBt->mutex) );
-  n = p->pBt->pageSize - p->pBt->usableSize;
-  return n;
-}
-
-/*
-** Return the number of bytes of space at the end of every page that
-** are intentually left unused.  This is the "reserved" space that is
-** sometimes used by extensions.
-**
-** If SQLITE_HAS_MUTEX is defined then the number returned is the
-** greater of the current reserved space and the maximum requested
-** reserve space.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeGetOptimalReserve(Btree *p){
-  int n;
-  sqlite3BtreeEnter(p);
-  n = sqlite3BtreeGetReserveNoMutex(p);
-#ifdef SQLITE_HAS_CODEC
-  if( n<p->pBt->optimalReserve ) n = p->pBt->optimalReserve;
-#endif
-  sqlite3BtreeLeave(p);
-  return n;
-}
-
-
-/*
-** Set the maximum page count for a database if mxPage is positive.
-** No changes are made if mxPage is 0 or negative.
-** Regardless of the value of mxPage, return the maximum page count.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeMaxPageCount(Btree *p, int mxPage){
-  int n;
-  sqlite3BtreeEnter(p);
-  n = sqlite3PagerMaxPageCount(p->pBt->pPager, mxPage);
-  sqlite3BtreeLeave(p);
-  return n;
-}
-
-/*
-** Set the BTS_SECURE_DELETE flag if newFlag is 0 or 1.  If newFlag is -1,
-** then make no changes.  Always return the value of the BTS_SECURE_DELETE
-** setting after the change.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSecureDelete(Btree *p, int newFlag){
-  int b;
-  if( p==0 ) return 0;
-  sqlite3BtreeEnter(p);
-  if( newFlag>=0 ){
-    p->pBt->btsFlags &= ~BTS_SECURE_DELETE;
-    if( newFlag ) p->pBt->btsFlags |= BTS_SECURE_DELETE;
-  } 
-  b = (p->pBt->btsFlags & BTS_SECURE_DELETE)!=0;
-  sqlite3BtreeLeave(p);
-  return b;
-}
-
-/*
-** Change the 'auto-vacuum' property of the database. If the 'autoVacuum'
-** parameter is non-zero, then auto-vacuum mode is enabled. If zero, it
-** is disabled. The default value for the auto-vacuum property is 
-** determined by the SQLITE_DEFAULT_AUTOVACUUM macro.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetAutoVacuum(Btree *p, int autoVacuum){
-#ifdef SQLITE_OMIT_AUTOVACUUM
-  return SQLITE_READONLY;
-#else
-  BtShared *pBt = p->pBt;
-  int rc = SQLITE_OK;
-  u8 av = (u8)autoVacuum;
-
-  sqlite3BtreeEnter(p);
-  if( (pBt->btsFlags & BTS_PAGESIZE_FIXED)!=0 && (av ?1:0)!=pBt->autoVacuum ){
-    rc = SQLITE_READONLY;
-  }else{
-    pBt->autoVacuum = av ?1:0;
-    pBt->incrVacuum = av==2 ?1:0;
-  }
-  sqlite3BtreeLeave(p);
-  return rc;
-#endif
-}
-
-/*
-** Return the value of the 'auto-vacuum' property. If auto-vacuum is 
-** enabled 1 is returned. Otherwise 0.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeGetAutoVacuum(Btree *p){
-#ifdef SQLITE_OMIT_AUTOVACUUM
-  return BTREE_AUTOVACUUM_NONE;
-#else
-  int rc;
-  sqlite3BtreeEnter(p);
-  rc = (
-    (!p->pBt->autoVacuum)?BTREE_AUTOVACUUM_NONE:
-    (!p->pBt->incrVacuum)?BTREE_AUTOVACUUM_FULL:
-    BTREE_AUTOVACUUM_INCR
-  );
-  sqlite3BtreeLeave(p);
-  return rc;
-#endif
-}
-
-
-/*
-** Get a reference to pPage1 of the database file.  This will
-** also acquire a readlock on that file.
-**
-** SQLITE_OK is returned on success.  If the file is not a
-** well-formed database file, then SQLITE_CORRUPT is returned.
-** SQLITE_BUSY is returned if the database is locked.  SQLITE_NOMEM
-** is returned if we run out of memory. 
-*/
-static int lockBtree(BtShared *pBt){
-  int rc;              /* Result code from subfunctions */
-  MemPage *pPage1;     /* Page 1 of the database file */
-  int nPage;           /* Number of pages in the database */
-  int nPageFile = 0;   /* Number of pages in the database file */
-  int nPageHeader;     /* Number of pages in the database according to hdr */
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( pBt->pPage1==0 );
-  rc = sqlite3PagerSharedLock(pBt->pPager);
-  if( rc!=SQLITE_OK ) return rc;
-  rc = btreeGetPage(pBt, 1, &pPage1, 0);
-  if( rc!=SQLITE_OK ) return rc;
-
-  /* Do some checking to help insure the file we opened really is
-  ** a valid database file. 
-  */
-  nPage = nPageHeader = get4byte(28+(u8*)pPage1->aData);
-  sqlite3PagerPagecount(pBt->pPager, &nPageFile);
-  if( nPage==0 || memcmp(24+(u8*)pPage1->aData, 92+(u8*)pPage1->aData,4)!=0 ){
-    nPage = nPageFile;
-  }
-  if( nPage>0 ){
-    u32 pageSize;
-    u32 usableSize;
-    u8 *page1 = pPage1->aData;
-    rc = SQLITE_NOTADB;
-    /* EVIDENCE-OF: R-43737-39999 Every valid SQLite database file begins
-    ** with the following 16 bytes (in hex): 53 51 4c 69 74 65 20 66 6f 72 6d
-    ** 61 74 20 33 00. */
-    if( memcmp(page1, zMagicHeader, 16)!=0 ){
-      goto page1_init_failed;
-    }
-
-#ifdef SQLITE_OMIT_WAL
-    if( page1[18]>1 ){
-      pBt->btsFlags |= BTS_READ_ONLY;
-    }
-    if( page1[19]>1 ){
-      goto page1_init_failed;
-    }
-#else
-    if( page1[18]>2 ){
-      pBt->btsFlags |= BTS_READ_ONLY;
-    }
-    if( page1[19]>2 ){
-      goto page1_init_failed;
-    }
-
-    /* If the write version is set to 2, this database should be accessed
-    ** in WAL mode. If the log is not already open, open it now. Then 
-    ** return SQLITE_OK and return without populating BtShared.pPage1.
-    ** The caller detects this and calls this function again. This is
-    ** required as the version of page 1 currently in the page1 buffer
-    ** may not be the latest version - there may be a newer one in the log
-    ** file.
-    */
-    if( page1[19]==2 && (pBt->btsFlags & BTS_NO_WAL)==0 ){
-      int isOpen = 0;
-      rc = sqlite3PagerOpenWal(pBt->pPager, &isOpen);
-      if( rc!=SQLITE_OK ){
-        goto page1_init_failed;
-      }else if( isOpen==0 ){
-        releasePage(pPage1);
-        return SQLITE_OK;
-      }
-      rc = SQLITE_NOTADB;
-    }
-#endif
-
-    /* EVIDENCE-OF: R-15465-20813 The maximum and minimum embedded payload
-    ** fractions and the leaf payload fraction values must be 64, 32, and 32.
-    **
-    ** The original design allowed these amounts to vary, but as of
-    ** version 3.6.0, we require them to be fixed.
-    */
-    if( memcmp(&page1[21], "\100\040\040",3)!=0 ){
-      goto page1_init_failed;
-    }
-    /* EVIDENCE-OF: R-51873-39618 The page size for a database file is
-    ** determined by the 2-byte integer located at an offset of 16 bytes from
-    ** the beginning of the database file. */
-    pageSize = (page1[16]<<8) | (page1[17]<<16);
-    /* EVIDENCE-OF: R-25008-21688 The size of a page is a power of two
-    ** between 512 and 65536 inclusive. */
-    if( ((pageSize-1)&pageSize)!=0
-     || pageSize>SQLITE_MAX_PAGE_SIZE 
-     || pageSize<=256 
-    ){
-      goto page1_init_failed;
-    }
-    assert( (pageSize & 7)==0 );
-    /* EVIDENCE-OF: R-59310-51205 The "reserved space" size in the 1-byte
-    ** integer at offset 20 is the number of bytes of space at the end of
-    ** each page to reserve for extensions. 
-    **
-    ** EVIDENCE-OF: R-37497-42412 The size of the reserved region is
-    ** determined by the one-byte unsigned integer found at an offset of 20
-    ** into the database file header. */
-    usableSize = pageSize - page1[20];
-    if( (u32)pageSize!=pBt->pageSize ){
-      /* After reading the first page of the database assuming a page size
-      ** of BtShared.pageSize, we have discovered that the page-size is
-      ** actually pageSize. Unlock the database, leave pBt->pPage1 at
-      ** zero and return SQLITE_OK. The caller will call this function
-      ** again with the correct page-size.
-      */
-      releasePage(pPage1);
-      pBt->usableSize = usableSize;
-      pBt->pageSize = pageSize;
-      freeTempSpace(pBt);
-      rc = sqlite3PagerSetPagesize(pBt->pPager, &pBt->pageSize,
-                                   pageSize-usableSize);
-      return rc;
-    }
-    if( (pBt->pBt->flags & SQLITE_RecoveryMode)==0 && nPage>nPageFile ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto page1_init_failed;
-    }
-    /* EVIDENCE-OF: R-28312-64704 However, the usable size is not allowed to
-    ** be less than 480. In other words, if the page size is 512, then the
-    ** reserved space size cannot exceed 32. */
-    if( usableSize<480 ){
-      goto page1_init_failed;
-    }
-    pBt->pageSize = pageSize;
-    pBt->usableSize = usableSize;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    pBt->autoVacuum = (get4byte(&page1[36 + 4*4])?1:0);
-    pBt->incrVacuum = (get4byte(&page1[36 + 7*4])?1:0);
-#endif
-  }
-
-  /* maxLocal is the maximum amount of payload to store locally for
-  ** a cell.  Make sure it is small enough so that at least minFanout
-  ** cells can will fit on one page.  We assume a 10-byte page header.
-  ** Besides the payload, the cell must store:
-  **     2-byte pointer to the cell
-  **     4-byte child pointer
-  **     9-byte nKey value
-  **     4-byte nData value
-  **     4-byte overflow page pointer
-  ** So a cell consists of a 2-byte pointer, a header which is as much as
-  ** 17 bytes long, 0 to N bytes of payload, and an optional 4 byte overflow
-  ** page pointer.
-  */
-  pBt->maxLocal = (u16)((pBt->usableSize-12)*64/255 - 23);
-  pBt->minLocal = (u16)((pBt->usableSize-12)*32/255 - 23);
-  pBt->maxLeaf = (u16)(pBt->usableSize - 35);
-  pBt->minLeaf = (u16)((pBt->usableSize-12)*32/255 - 23);
-  if( pBt->maxLocal>127 ){
-    pBt->max1bytePayload = 127;
-  }else{
-    pBt->max1bytePayload = (u8)pBt->maxLocal;
-  }
-  assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE(pBt) );
-  pBt->pPage1 = pPage1;
-  pBt->nPage = nPage;
-  return SQLITE_OK;
-
-page1_init_failed:
-  releasePage(pPage1);
-  pBt->pPage1 = 0;
-  return rc;
-}
-
-#ifndef NDEBUG
-/*
-** Return the number of cursors open on pBt. This is for use
-** in assert() expressions, so it is only compiled if NDEBUG is not
-** defined.
-**
-** Only write cursors are counted if wrOnly is true.  If wrOnly is
-** false then all cursors are counted.
-**
-** For the purposes of this routine, a cursor is any cursor that
-** is capable of reading or writing to the database.  Cursors that
-** have been tripped into the CURSOR_FAULT state are not counted.
-*/
-static int countValidCursors(BtShared *pBt, int wrOnly){
-  BtCursor *pCur;
-  int r = 0;
-  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
-    if( (wrOnly==0 || (pCur->curFlags & BTCF_WriteFlag)!=0)
-     && pCur->eState!=CURSOR_FAULT ) r++; 
-  }
-  return r;
-}
-#endif
-
-/*
-** If there are no outstanding cursors and we are not in the middle
-** of a transaction but there is a read lock on the database, then
-** this routine unrefs the first page of the database file which 
-** has the effect of releasing the read lock.
-**
-** If there is a transaction in progress, this routine is a no-op.
-*/
-static void unlockBtreeIfUnused(BtShared *pBt){
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( countValidCursors(pBt,0)==0 || pBt->inTransaction>TRANS_NONE );
-  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
-    MemPage *pPage1 = pBt->pPage1;
-    assert( pPage1->aData );
-    assert( sqlite3PagerRefcount(pBt->pPager)==1 );
-    pBt->pPage1 = 0;
-    releasePageNotNull(pPage1);
-  }
-}
-
-/*
-** If pBt points to an empty file then convert that empty file
-** into a new empty database by initializing the first page of
-** the database.
-*/
-static int newDatabase(BtShared *pBt){
-  MemPage *pP1;
-  unsigned char *data;
-  int rc;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pBt->nPage>0 ){
-    return SQLITE_OK;
-  }
-  pP1 = pBt->pPage1;
-  assert( pP1!=0 );
-  data = pP1->aData;
-  rc = sqlite3PagerWrite(pP1->pDbPage);
-  if( rc ) return rc;
-  memcpy(data, zMagicHeader, sizeof(zMagicHeader));
-  assert( sizeof(zMagicHeader)==16 );
-  data[16] = (u8)((pBt->pageSize>>8)&0xff);
-  data[17] = (u8)((pBt->pageSize>>16)&0xff);
-  data[18] = 1;
-  data[19] = 1;
-  assert( pBt->usableSize<=pBt->pageSize && pBt->usableSize+255>=pBt->pageSize);
-  data[20] = (u8)(pBt->pageSize - pBt->usableSize);
-  data[21] = 64;
-  data[22] = 32;
-  data[23] = 32;
-  memset(&data[24], 0, 100-24);
-  zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
-  pBt->btsFlags |= BTS_PAGESIZE_FIXED;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-  assert( pBt->autoVacuum==1 || pBt->autoVacuum==0 );
-  assert( pBt->incrVacuum==1 || pBt->incrVacuum==0 );
-  put4byte(&data[36 + 4*4], pBt->autoVacuum);
-  put4byte(&data[36 + 7*4], pBt->incrVacuum);
-#endif
-  pBt->nPage = 1;
-  data[31] = 1;
-  return SQLITE_OK;
-}
-
-/*
-** Initialize the first page of the database file (creating a database
-** consisting of a single page and no schema objects). Return SQLITE_OK
-** if successful, or an SQLite error code otherwise.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeNewDb(Btree *p){
-  int rc;
-  sqlite3BtreeEnter(p);
-  p->pBt->nPage = 0;
-  rc = newDatabase(p->pBt);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Attempt to start a new transaction. A write-transaction
-** is started if the second argument is nonzero, otherwise a read-
-** transaction.  If the second argument is 2 or more and exclusive
-** transaction is started, meaning that no other process is allowed
-** to access the database.  A preexisting transaction may not be
-** upgraded to exclusive by calling this routine a second time - the
-** exclusivity flag only works for a new transaction.
-**
-** A write-transaction must be started before attempting any 
-** changes to the database.  None of the following routines 
-** will work unless a transaction is started first:
-**
-**      sqlite3BtreeCreateTable()
-**      sqlite3BtreeCreateIndex()
-**      sqlite3BtreeClearTable()
-**      sqlite3BtreeDropTable()
-**      sqlite3BtreeInsert()
-**      sqlite3BtreeDelete()
-**      sqlite3BtreeUpdateMeta()
-**
-** If an initial attempt to acquire the lock fails because of lock contention
-** and the database was previously unlocked, then invoke the busy handler
-** if there is one.  But if there was previously a read-lock, do not
-** invoke the busy handler - just return SQLITE_BUSY.  SQLITE_BUSY is 
-** returned when there is already a read-lock in order to avoid a deadlock.
-**
-** Suppose there are two processes A and B.  A has a read lock and B has
-** a reserved lock.  B tries to promote to exclusive but is blocked because
-** of A's read lock.  A tries to promote to reserved but is blocked by B.
-** One or the other of the two processes must give way or there can be
-** no progress.  By returning SQLITE_BUSY and not invoking the busy callback
-** when A already has a read lock, we encourage A to give up and let B
-** proceed.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeBeginTrans(Btree *p, int wrflag){
-  Btree *pBlock = 0;
-  BtShared *pBt = p->pBt;
-  int rc = SQLITE_OK;
-
-  sqlite3BtreeEnter(p);
-  btreeIntegrity(p);
-
-  /* If the btree is already in a write-transaction, or it
-  ** is already in a read-transaction and a read-transaction
-  ** is requested, this is a no-op.
-  */
-  if( p->inTrans==TRANS_WRITE || (p->inTrans==TRANS_READ && !wrflag) ){
-    goto trans_begun;
-  }
-  assert( pBt->inTransaction==TRANS_WRITE || IfNotOmitAV(pBt->bDoTruncate)==0 );
-
-  /* Write transactions are not possible on a read-only database */
-  if( (pBt->btsFlags & BTS_READ_ONLY)!=0 && wrflag ){
-    rc = SQLITE_READONLY;
-    goto trans_begun;
-  }
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  /* If another database handle has already opened a write transaction 
-  ** on this shared-btree structure and a second write transaction is
-  ** requested, return SQLITE_LOCKED.
-  */
-  if( (wrflag && pBt->inTransaction==TRANS_WRITE)
-   || (pBt->btsFlags & BTS_PENDING)!=0
-  ){
-    pBlock = pBt->pWriter;
-  }else if( wrflag>1 ){
-    BtLock *pIter;
-    for(pIter=pBt->pLock; pIter; pIter=pIter->pNext){
-      if( pIter->pBtree!=p ){
-        pBlock = pIter->pBtree;
-        break;
-      }
-    }
-  }
-  if( pBlock ){
-    sqlite3ConnectionBlocked(p, pBlock);
-    rc = SQLITE_LOCKED_SHAREDCACHE;
-    goto trans_begun;
-  }
-#endif
-
-  /* Any read-only or read-write transaction implies a read-lock on 
-  ** page 1. So if some other shared-cache client already has a write-lock 
-  ** on page 1, the transaction cannot be opened. */
-  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
-  if( SQLITE_OK!=rc ) goto trans_begun;
-
-  pBt->btsFlags &= ~BTS_INITIALLY_EMPTY;
-  if( pBt->nPage==0 ) pBt->btsFlags |= BTS_INITIALLY_EMPTY;
-  do {
-    /* Call lockBtree() until either pBt->pPage1 is populated or
-    ** lockBtree() returns something other than SQLITE_OK. lockBtree()
-    ** may return SQLITE_OK but leave pBt->pPage1 set to 0 if after
-    ** reading page 1 it discovers that the page-size of the database 
-    ** file is not pBt->pageSize. In this case lockBtree() will update
-    ** pBt->pageSize to the page-size of the file on disk.
-    */
-    while( pBt->pPage1==0 && SQLITE_OK==(rc = lockBtree(pBt)) );
-
-    if( rc==SQLITE_OK && wrflag ){
-      if( (pBt->btsFlags & BTS_READ_ONLY)!=0 ){
-        rc = SQLITE_READONLY;
-      }else{
-        rc = sqlite3PagerBegin(pBt->pPager,wrflag>1,0);
-        if( rc==SQLITE_OK ){
-          rc = newDatabase(pBt);
-        }
-      }
-    }
-  
-    if( rc!=SQLITE_OK ){
-      unlockBtreeIfUnused(pBt);
-    }
-  }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
-          btreeInvokeBusyHandler(pBt) );
-
-  if( rc==SQLITE_OK ){
-    if( p->inTrans==TRANS_NONE ){
-      pBt->nTransaction++;
-#ifndef SQLITE_OMIT_SHARED_CACHE
-      if( p->sharable ){
-        assert( p->lock.pBtree==p && p->lock.iTable==1 );
-        p->lock.eLock = READ_LOCK;
-        p->lock.pNext = pBt->pLock;
-        pBt->pLock = &p->lock;
-      }
-#endif
-    }
-    p->inTrans = (wrflag?TRANS_WRITE:TRANS_READ);
-    if( p->inTrans>pBt->inTransaction ){
-      pBt->inTransaction = p->inTrans;
-    }
-    if( wrflag ){
-      MemPage *pPage1 = pBt->pPage1;
-#ifndef SQLITE_OMIT_SHARED_CACHE
-      assert( !pBt->pWriter );
-      pBt->pWriter = p;
-      pBt->btsFlags &= ~BTS_EXCLUSIVE;
-      if( wrflag>1 ) pBt->btsFlags |= BTS_EXCLUSIVE;
-#endif
-
-      /* If the db-size header field is incorrect (as it may be if an old
-      ** client has been writing the database file), update it now. Doing
-      ** this sooner rather than later means the database size can safely 
-      ** re-read the database size from page 1 if a savepoint or transaction
-      ** rollback occurs within the transaction.
-      */
-      if( pBt->nPage!=get4byte(&pPage1->aData[28]) ){
-        rc = sqlite3PagerWrite(pPage1->pDbPage);
-        if( rc==SQLITE_OK ){
-          put4byte(&pPage1->aData[28], pBt->nPage);
-        }
-      }
-    }
-  }
-
-
-trans_begun:
-  if( rc==SQLITE_OK && wrflag ){
-    /* This call makes sure that the pager has the correct number of
-    ** open savepoints. If the second parameter is greater than 0 and
-    ** the sub-journal is not already open, then it will be opened here.
-    */
-    rc = sqlite3PagerOpenSavepoint(pBt->pPager, p->nSavepoint);
-  }
-
-  btreeIntegrity(p);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-
-/*
-** Set the pointer-map entries for all children of page pPage. Also, if
-** pPage contains cells that point to overflow pages, set the pointer
-** map entries for the overflow pages as well.
-*/
-static int setChildPtrmaps(MemPage *pPage){
-  int i;                             /* Counter variable */
-  int nCell;                         /* Number of cells in page pPage */
-  int rc;                            /* Return code */
-  BtShared *pBt = pPage->pBt;
-  u8 isInitOrig = pPage->isInit;
-  Pgno pgno = pPage->pgno;
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  rc = btreeInitPage(pPage);
-  if( rc!=SQLITE_OK ){
-    goto set_child_ptrmaps_out;
-  }
-  nCell = pPage->nCell;
-
-  for(i=0; i<nCell; i++){
-    u8 *pCell = findCell(pPage, i);
-
-    ptrmapPutOvflPtr(pPage, pCell, &rc);
-
-    if( !pPage->leaf ){
-      Pgno childPgno = get4byte(pCell);
-      ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
-    }
-  }
-
-  if( !pPage->leaf ){
-    Pgno childPgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
-    ptrmapPut(pBt, childPgno, PTRMAP_BTREE, pgno, &rc);
-  }
-
-set_child_ptrmaps_out:
-  pPage->isInit = isInitOrig;
-  return rc;
-}
-
-/*
-** Somewhere on pPage is a pointer to page iFrom.  Modify this pointer so
-** that it points to iTo. Parameter eType describes the type of pointer to
-** be modified, as  follows:
-**
-** PTRMAP_BTREE:     pPage is a btree-page. The pointer points at a child 
-**                   page of pPage.
-**
-** PTRMAP_OVERFLOW1: pPage is a btree-page. The pointer points at an overflow
-**                   page pointed to by one of the cells on pPage.
-**
-** PTRMAP_OVERFLOW2: pPage is an overflow-page. The pointer points at the next
-**                   overflow page in the list.
-*/
-static int modifyPagePointer(MemPage *pPage, Pgno iFrom, Pgno iTo, u8 eType){
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  if( eType==PTRMAP_OVERFLOW2 ){
-    /* The pointer is always the first 4 bytes of the page in this case.  */
-    if( get4byte(pPage->aData)!=iFrom ){
-      return SQLITE_CORRUPT_BKPT;
-    }
-    put4byte(pPage->aData, iTo);
-  }else{
-    u8 isInitOrig = pPage->isInit;
-    int i;
-    int nCell;
-    int rc;
-
-    rc = btreeInitPage(pPage);
-    if( rc ) return rc;
-    nCell = pPage->nCell;
-
-    for(i=0; i<nCell; i++){
-      u8 *pCell = findCell(pPage, i);
-      if( eType==PTRMAP_OVERFLOW1 ){
-        CellInfo info;
-        pPage->xParseCell(pPage, pCell, &info);
-        if( info.iOverflow
-         && pCell+info.iOverflow+3<=pPage->aData+pPage->maskPage
-         && iFrom==get4byte(&pCell[info.iOverflow])
-        ){
-          put4byte(&pCell[info.iOverflow], iTo);
-          break;
-        }
-      }else{
-        if( get4byte(pCell)==iFrom ){
-          put4byte(pCell, iTo);
-          break;
-        }
-      }
-    }
-  
-    if( i==nCell ){
-      if( eType!=PTRMAP_BTREE || 
-          get4byte(&pPage->aData[pPage->hdrOffset+8])!=iFrom ){
-        return SQLITE_CORRUPT_BKPT;
-      }
-      put4byte(&pPage->aData[pPage->hdrOffset+8], iTo);
-    }
-
-    pPage->isInit = isInitOrig;
-  }
-  return SQLITE_OK;
-}
-
-
-/*
-** Move the open database page pDbPage to location iFreePage in the 
-** database. The pDbPage reference remains valid.
-**
-** The isCommit flag indicates that there is no need to remember that
-** the journal needs to be sync()ed before database page pDbPage->pgno 
-** can be written to. The caller has already promised not to write to that
-** page.
-*/
-static int relocatePage(
-  BtShared *pBt,           /* Btree */
-  MemPage *pDbPage,        /* Open page to move */
-  u8 eType,                /* Pointer map 'type' entry for pDbPage */
-  Pgno iPtrPage,           /* Pointer map 'page-no' entry for pDbPage */
-  Pgno iFreePage,          /* The location to move pDbPage to */
-  int isCommit             /* isCommit flag passed to sqlite3PagerMovepage */
-){
-  MemPage *pPtrPage;   /* The page that contains a pointer to pDbPage */
-  Pgno iDbPage = pDbPage->pgno;
-  Pager *pPager = pBt->pPager;
-  int rc;
-
-  assert( eType==PTRMAP_OVERFLOW2 || eType==PTRMAP_OVERFLOW1 || 
-      eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE );
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( pDbPage->pBt==pBt );
-
-  /* Move page iDbPage from its current location to page number iFreePage */
-  TRACE(("AUTOVACUUM: Moving %d to free page %d (ptr page %d type %d)\n", 
-      iDbPage, iFreePage, iPtrPage, eType));
-  rc = sqlite3PagerMovepage(pPager, pDbPage->pDbPage, iFreePage, isCommit);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-  pDbPage->pgno = iFreePage;
-
-  /* If pDbPage was a btree-page, then it may have child pages and/or cells
-  ** that point to overflow pages. The pointer map entries for all these
-  ** pages need to be changed.
-  **
-  ** If pDbPage is an overflow page, then the first 4 bytes may store a
-  ** pointer to a subsequent overflow page. If this is the case, then
-  ** the pointer map needs to be updated for the subsequent overflow page.
-  */
-  if( eType==PTRMAP_BTREE || eType==PTRMAP_ROOTPAGE ){
-    rc = setChildPtrmaps(pDbPage);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-  }else{
-    Pgno nextOvfl = get4byte(pDbPage->aData);
-    if( nextOvfl!=0 ){
-      ptrmapPut(pBt, nextOvfl, PTRMAP_OVERFLOW2, iFreePage, &rc);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }
-  }
-
-  /* Fix the database pointer on page iPtrPage that pointed at iDbPage so
-  ** that it points at iFreePage. Also fix the pointer map entry for
-  ** iPtrPage.
-  */
-  if( eType!=PTRMAP_ROOTPAGE ){
-    rc = btreeGetPage(pBt, iPtrPage, &pPtrPage, 0);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    rc = sqlite3PagerWrite(pPtrPage->pDbPage);
-    if( rc!=SQLITE_OK ){
-      releasePage(pPtrPage);
-      return rc;
-    }
-    rc = modifyPagePointer(pPtrPage, iDbPage, iFreePage, eType);
-    releasePage(pPtrPage);
-    if( rc==SQLITE_OK ){
-      ptrmapPut(pBt, iFreePage, eType, iPtrPage, &rc);
-    }
-  }
-  return rc;
-}
-
-/* Forward declaration required by incrVacuumStep(). */
-static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
-
-/*
-** Perform a single step of an incremental-vacuum. If successful, return
-** SQLITE_OK. If there is no work to do (and therefore no point in 
-** calling this function again), return SQLITE_DONE. Or, if an error 
-** occurs, return some other error code.
-**
-** More specifically, this function attempts to re-organize the database so 
-** that the last page of the file currently in use is no longer in use.
-**
-** Parameter nFin is the number of pages that this database would contain
-** were this function called until it returns SQLITE_DONE.
-**
-** If the bCommit parameter is non-zero, this function assumes that the 
-** caller will keep calling incrVacuumStep() until it returns SQLITE_DONE 
-** or an error. bCommit is passed true for an auto-vacuum-on-commit 
-** operation, or false for an incremental vacuum.
-*/
-static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
-  Pgno nFreeList;           /* Number of pages still on the free-list */
-  int rc;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( iLastPg>nFin );
-
-  if( !PTRMAP_ISPAGE(pBt, iLastPg) && iLastPg!=PENDING_BYTE_PAGE(pBt) ){
-    u8 eType;
-    Pgno iPtrPage;
-
-    nFreeList = get4byte(&pBt->pPage1->aData[36]);
-    if( nFreeList==0 ){
-      return SQLITE_DONE;
-    }
-
-    rc = ptrmapGet(pBt, iLastPg, &eType, &iPtrPage);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    if( eType==PTRMAP_ROOTPAGE ){
-      return SQLITE_CORRUPT_BKPT;
-    }
-
-    if( eType==PTRMAP_FREEPAGE ){
-      if( bCommit==0 ){
-        /* Remove the page from the files free-list. This is not required
-        ** if bCommit is non-zero. In that case, the free-list will be
-        ** truncated to zero after this function returns, so it doesn't 
-        ** matter if it still contains some garbage entries.
-        */
-        Pgno iFreePg;
-        MemPage *pFreePg;
-        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, BTALLOC_EXACT);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        assert( iFreePg==iLastPg );
-        releasePage(pFreePg);
-      }
-    } else {
-      Pgno iFreePg;             /* Index of free page to move pLastPg to */
-      MemPage *pLastPg;
-      u8 eMode = BTALLOC_ANY;   /* Mode parameter for allocateBtreePage() */
-      Pgno iNear = 0;           /* nearby parameter for allocateBtreePage() */
-
-      rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-
-      /* If bCommit is zero, this loop runs exactly once and page pLastPg
-      ** is swapped with the first free page pulled off the free list.
-      **
-      ** On the other hand, if bCommit is greater than zero, then keep
-      ** looping until a free-page located within the first nFin pages
-      ** of the file is found.
-      */
-      if( bCommit==0 ){
-        eMode = BTALLOC_LE;
-        iNear = nFin;
-      }
-      do {
-        MemPage *pFreePg;
-        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iNear, eMode);
-        if( rc!=SQLITE_OK ){
-          releasePage(pLastPg);
-          return rc;
-        }
-        releasePage(pFreePg);
-      }while( bCommit && iFreePg>nFin );
-      assert( iFreePg<iLastPg );
-      
-      rc = relocatePage(pBt, pLastPg, eType, iPtrPage, iFreePg, bCommit);
-      releasePage(pLastPg);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-    }
-  }
-
-  if( bCommit==0 ){
-    do {
-      iLastPg--;
-    }while( iLastPg==PENDING_BYTE_PAGE(pBt) || PTRMAP_ISPAGE(pBt, iLastPg) );
-    pBt->bDoTruncate = 1;
-    pBt->nPage = iLastPg;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** The database opened by the first argument is an auto-vacuum database
-** nOrig pages in size containing nFree free pages. Return the expected 
-** size of the database in pages following an auto-vacuum operation.
-*/
-static Pgno finalDbSize(BtShared *pBt, Pgno nOrig, Pgno nFree){
-  int nEntry;                     /* Number of entries on one ptrmap page */
-  Pgno nPtrmap;                   /* Number of PtrMap pages to be freed */
-  Pgno nFin;                      /* Return value */
-
-  nEntry = pBt->usableSize/5;
-  nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
-  nFin = nOrig - nFree - nPtrmap;
-  if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
-    nFin--;
-  }
-  while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
-    nFin--;
-  }
-
-  return nFin;
-}
-
-/*
-** A write-transaction must be opened before calling this function.
-** It performs a single unit of work towards an incremental vacuum.
-**
-** If the incremental vacuum is finished after this function has run,
-** SQLITE_DONE is returned. If it is not finished, but no error occurred,
-** SQLITE_OK is returned. Otherwise an SQLite error code. 
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIncrVacuum(Btree *p){
-  int rc;
-  BtShared *pBt = p->pBt;
-
-  sqlite3BtreeEnter(p);
-  assert( pBt->inTransaction==TRANS_WRITE && p->inTrans==TRANS_WRITE );
-  if( !pBt->autoVacuum ){
-    rc = SQLITE_DONE;
-  }else{
-    Pgno nOrig = btreePagecount(pBt);
-    Pgno nFree = get4byte(&pBt->pPage1->aData[36]);
-    Pgno nFin = finalDbSize(pBt, nOrig, nFree);
-
-    if( nOrig<nFin ){
-      rc = SQLITE_CORRUPT_BKPT;
-    }else if( nFree>0 ){
-      rc = saveAllCursors(pBt, 0, 0);
-      if( rc==SQLITE_OK ){
-        invalidateAllOverflowCache(pBt);
-        rc = incrVacuumStep(pBt, nFin, nOrig, 0);
-      }
-      if( rc==SQLITE_OK ){
-        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-        put4byte(&pBt->pPage1->aData[28], pBt->nPage);
-      }
-    }else{
-      rc = SQLITE_DONE;
-    }
-  }
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** This routine is called prior to sqlite3PagerCommit when a transaction
-** is committed for an auto-vacuum database.
-**
-** If SQLITE_OK is returned, then *pnTrunc is set to the number of pages
-** the database file should be truncated to during the commit process. 
-** i.e. the database has been reorganized so that only the first *pnTrunc
-** pages are in use.
-*/
-static int autoVacuumCommit(BtShared *pBt){
-  int rc = SQLITE_OK;
-  Pager *pPager = pBt->pPager;
-  VVA_ONLY( int nRef = sqlite3PagerRefcount(pPager); )
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  invalidateAllOverflowCache(pBt);
-  assert(pBt->autoVacuum);
-  if( !pBt->incrVacuum ){
-    Pgno nFin;         /* Number of pages in database after autovacuuming */
-    Pgno nFree;        /* Number of pages on the freelist initially */
-    Pgno iFree;        /* The next page to be freed */
-    Pgno nOrig;        /* Database size before freeing */
-
-    nOrig = btreePagecount(pBt);
-    if( PTRMAP_ISPAGE(pBt, nOrig) || nOrig==PENDING_BYTE_PAGE(pBt) ){
-      /* It is not possible to create a database for which the final page
-      ** is either a pointer-map page or the pending-byte page. If one
-      ** is encountered, this indicates corruption.
-      */
-      return SQLITE_CORRUPT_BKPT;
-    }
-
-    nFree = get4byte(&pBt->pPage1->aData[36]);
-    nFin = finalDbSize(pBt, nOrig, nFree);
-    if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
-    if( nFin<nOrig ){
-      rc = saveAllCursors(pBt, 0, 0);
-    }
-    for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
-      rc = incrVacuumStep(pBt, nFin, iFree, 1);
-    }
-    if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
-      rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-      put4byte(&pBt->pPage1->aData[32], 0);
-      put4byte(&pBt->pPage1->aData[36], 0);
-      put4byte(&pBt->pPage1->aData[28], nFin);
-      pBt->bDoTruncate = 1;
-      pBt->nPage = nFin;
-    }
-    if( rc!=SQLITE_OK ){
-      sqlite3PagerRollback(pPager);
-    }
-  }
-
-  assert( nRef>=sqlite3PagerRefcount(pPager) );
-  return rc;
-}
-
-#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
-# define setChildPtrmaps(x) SQLITE_OK
-#endif
-
-/*
-** This routine does the first phase of a two-phase commit.  This routine
-** causes a rollback journal to be created (if it does not already exist)
-** and populated with enough information so that if a power loss occurs
-** the database can be restored to its original state by playing back
-** the journal.  Then the contents of the journal are flushed out to
-** the disk.  After the journal is safely on oxide, the changes to the
-** database are written into the database file and flushed to oxide.
-** At the end of this call, the rollback journal still exists on the
-** disk and we are still holding all locks, so the transaction has not
-** committed.  See sqlite3BtreeCommitPhaseTwo() for the second phase of the
-** commit process.
-**
-** This call is a no-op if no write-transaction is currently active on pBt.
-**
-** Otherwise, sync the database file for the btree pBt. zMaster points to
-** the name of a master journal file that should be written into the
-** individual journal file, or is NULL, indicating no master journal file 
-** (single database transaction).
-**
-** When this is called, the master journal should already have been
-** created, populated with this journal pointer and synced to disk.
-**
-** Once this is routine has returned, the only thing required to commit
-** the write-transaction for this database file is to delete the journal.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCommitPhaseOne(Btree *p, const char *zMaster){
-  int rc = SQLITE_OK;
-  if( p->inTrans==TRANS_WRITE ){
-    BtShared *pBt = p->pBt;
-    sqlite3BtreeEnter(p);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum ){
-      rc = autoVacuumCommit(pBt);
-      if( rc!=SQLITE_OK ){
-        sqlite3BtreeLeave(p);
-        return rc;
-      }
-    }
-    if( pBt->bDoTruncate ){
-      sqlite3PagerTruncateImage(pBt->pPager, pBt->nPage);
-    }
-#endif
-    rc = sqlite3PagerCommitPhaseOne(pBt->pPager, zMaster, 0);
-    sqlite3BtreeLeave(p);
-  }
-  return rc;
-}
-
-/*
-** This function is called from both BtreeCommitPhaseTwo() and BtreeRollback()
-** at the conclusion of a transaction.
-*/
-static void btreeEndTransaction(Btree *p){
-  BtShared *pBt = p->pBt;
-  assert( sqlite3BtreeHoldsMutex(p) );
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-  pBt->bDoTruncate = 0;
-#endif
-  if( p->inTrans>TRANS_NONE && p->nVdbeRead>1 ){
-    /* If there are other active statements that belong to this database
-    ** handle, downgrade to a read-only transaction. The other statements
-    ** may still be reading from the database.  */
-    downgradeAllSharedCacheTableLocks(p);
-    p->inTrans = TRANS_READ;
-  }else{
-    /* If the handle had any kind of transaction open, decrement the 
-    ** transaction count of the shared btree. If the transaction count 
-    ** reaches 0, set the shared state to TRANS_NONE. The unlockBtreeIfUnused()
-    ** call below will unlock the pager.  */
-    if( p->inTrans!=TRANS_NONE ){
-      clearAllSharedCacheTableLocks(p);
-      pBt->nTransaction--;
-      if( 0==pBt->nTransaction ){
-        pBt->inTransaction = TRANS_NONE;
-      }
-    }
-
-    /* Set the current transaction state to TRANS_NONE and unlock the 
-    ** pager if this call closed the only read or write transaction.  */
-    p->inTrans = TRANS_NONE;
-    unlockBtreeIfUnused(pBt);
-  }
-
-  btreeIntegrity(p);
-}
-
-/*
-** Commit the transaction currently in progress.
-**
-** This routine implements the second phase of a 2-phase commit.  The
-** sqlite3BtreeCommitPhaseOne() routine does the first phase and should
-** be invoked prior to calling this routine.  The sqlite3BtreeCommitPhaseOne()
-** routine did all the work of writing information out to disk and flushing the
-** contents so that they are written onto the disk platter.  All this
-** routine has to do is delete or truncate or zero the header in the
-** the rollback journal (which causes the transaction to commit) and
-** drop locks.
-**
-** Normally, if an error occurs while the pager layer is attempting to 
-** finalize the underlying journal file, this function returns an error and
-** the upper layer will attempt a rollback. However, if the second argument
-** is non-zero then this b-tree transaction is part of a multi-file 
-** transaction. In this case, the transaction has already been committed 
-** (by deleting a master journal file) and the caller will ignore this 
-** functions return code. So, even if an error occurs in the pager layer,
-** reset the b-tree objects internal state to indicate that the write
-** transaction has been closed. This is quite safe, as the pager will have
-** transitioned to the error state.
-**
-** This will release the write lock on the database file.  If there
-** are no active cursors, it also releases the read lock.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCommitPhaseTwo(Btree *p, int bCleanup){
-
-  if( p->inTrans==TRANS_NONE ) return SQLITE_OK;
-  sqlite3BtreeEnter(p);
-  btreeIntegrity(p);
-
-  /* If the handle has a write-transaction open, commit the shared-btrees 
-  ** transaction and set the shared state to TRANS_READ.
-  */
-  if( p->inTrans==TRANS_WRITE ){
-    int rc;
-    BtShared *pBt = p->pBt;
-    assert( pBt->inTransaction==TRANS_WRITE );
-    assert( pBt->nTransaction>0 );
-    rc = sqlite3PagerCommitPhaseTwo(pBt->pPager);
-    if( rc!=SQLITE_OK && bCleanup==0 ){
-      sqlite3BtreeLeave(p);
-      return rc;
-    }
-    p->iDataVersion--;  /* Compensate for pPager->iDataVersion++; */
-    pBt->inTransaction = TRANS_READ;
-    btreeClearHasContent(pBt);
-  }
-
-  btreeEndTransaction(p);
-  sqlite3BtreeLeave(p);
-  return SQLITE_OK;
-}
-
-/*
-** Do both phases of a commit.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCommit(Btree *p){
-  int rc;
-  sqlite3BtreeEnter(p);
-  rc = sqlite3BtreeCommitPhaseOne(p, 0);
-  if( rc==SQLITE_OK ){
-    rc = sqlite3BtreeCommitPhaseTwo(p, 0);
-  }
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** This routine sets the state to CURSOR_FAULT and the error
-** code to errCode for every cursor on any BtShared that pBtree
-** references.  Or if the writeOnly flag is set to 1, then only
-** trip write cursors and leave read cursors unchanged.
-**
-** Every cursor is a candidate to be tripped, including cursors
-** that belong to other database connections that happen to be
-** sharing the cache with pBtree.
-**
-** This routine gets called when a rollback occurs. If the writeOnly
-** flag is true, then only write-cursors need be tripped - read-only
-** cursors save their current positions so that they may continue 
-** following the rollback. Or, if writeOnly is false, all cursors are 
-** tripped. In general, writeOnly is false if the transaction being
-** rolled back modified the database schema. In this case b-tree root
-** pages may be moved or deleted from the database altogether, making
-** it unsafe for read cursors to continue.
-**
-** If the writeOnly flag is true and an error is encountered while 
-** saving the current position of a read-only cursor, all cursors, 
-** including all read-cursors are tripped.
-**
-** SQLITE_OK is returned if successful, or if an error occurs while
-** saving a cursor position, an SQLite error code.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeTripAllCursors(Btree *pBtree, int errCode, int writeOnly){
-  BtCursor *p;
-  int rc = SQLITE_OK;
-
-  assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
-  if( pBtree ){
-    sqlite3BtreeEnter(pBtree);
-    for(p=pBtree->pBt->pCursor; p; p=p->pNext){
-      int i;
-      if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
-        if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
-          rc = saveCursorPosition(p);
-          if( rc!=SQLITE_OK ){
-            (void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
-            break;
-          }
-        }
-      }else{
-        sqlite3BtreeClearCursor(p);
-        p->eState = CURSOR_FAULT;
-        p->skipNext = errCode;
-      }
-      for(i=0; i<=p->iPage; i++){
-        releasePage(p->apPage[i]);
-        p->apPage[i] = 0;
-      }
-    }
-    sqlite3BtreeLeave(pBtree);
-  }
-  return rc;
-}
-
-/*
-** Rollback the transaction in progress.
-**
-** If tripCode is not SQLITE_OK then cursors will be invalidated (tripped).
-** Only write cursors are tripped if writeOnly is true but all cursors are
-** tripped if writeOnly is false.  Any attempt to use
-** a tripped cursor will result in an error.
-**
-** This will release the write lock on the database file.  If there
-** are no active cursors, it also releases the read lock.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeRollback(Btree *p, int tripCode, int writeOnly){
-  int rc;
-  BtShared *pBt = p->pBt;
-  MemPage *pPage1;
-
-  assert( writeOnly==1 || writeOnly==0 );
-  assert( tripCode==SQLITE_ABORT_ROLLBACK || tripCode==SQLITE_OK );
-  sqlite3BtreeEnter(p);
-  if( tripCode==SQLITE_OK ){
-    rc = tripCode = saveAllCursors(pBt, 0, 0);
-    if( rc ) writeOnly = 0;
-  }else{
-    rc = SQLITE_OK;
-  }
-  if( tripCode ){
-    int rc2 = sqlite3BtreeTripAllCursors(p, tripCode, writeOnly);
-    assert( rc==SQLITE_OK || (writeOnly==0 && rc2==SQLITE_OK) );
-    if( rc2!=SQLITE_OK ) rc = rc2;
-  }
-  btreeIntegrity(p);
-
-  if( p->inTrans==TRANS_WRITE ){
-    int rc2;
-
-    assert( TRANS_WRITE==pBt->inTransaction );
-    rc2 = sqlite3PagerRollback(pBt->pPager);
-    if( rc2!=SQLITE_OK ){
-      rc = rc2;
-    }
-
-    /* The rollback may have destroyed the pPage1->aData value.  So
-    ** call btreeGetPage() on page 1 again to make
-    ** sure pPage1->aData is set correctly. */
-    if( btreeGetPage(pBt, 1, &pPage1, 0)==SQLITE_OK ){
-      int nPage = get4byte(28+(u8*)pPage1->aData);
-      testcase( nPage==0 );
-      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
-      testcase( pBt->nPage!=nPage );
-      pBt->nPage = nPage;
-      releasePage(pPage1);
-    }
-    assert( countValidCursors(pBt, 1)==0 );
-    pBt->inTransaction = TRANS_READ;
-    btreeClearHasContent(pBt);
-  }
-
-  btreeEndTransaction(p);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Start a statement subtransaction. The subtransaction can be rolled
-** back independently of the main transaction. You must start a transaction 
-** before starting a subtransaction. The subtransaction is ended automatically 
-** if the main transaction commits or rolls back.
-**
-** Statement subtransactions are used around individual SQL statements
-** that are contained within a BEGIN...COMMIT block.  If a constraint
-** error occurs within the statement, the effect of that one statement
-** can be rolled back without having to rollback the entire transaction.
-**
-** A statement sub-transaction is implemented as an anonymous savepoint. The
-** value passed as the second parameter is the total number of savepoints,
-** including the new anonymous savepoint, open on the B-Tree. i.e. if there
-** are no active savepoints and no other statement-transactions open,
-** iStatement is 1. This anonymous savepoint can be released or rolled back
-** using the sqlite3BtreeSavepoint() function.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeBeginStmt(Btree *p, int iStatement){
-  int rc;
-  BtShared *pBt = p->pBt;
-  sqlite3BtreeEnter(p);
-  assert( p->inTrans==TRANS_WRITE );
-  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
-  assert( iStatement>0 );
-  assert( iStatement>p->nSavepoint );
-  assert( pBt->inTransaction==TRANS_WRITE );
-  /* At the pager level, a statement transaction is a savepoint with
-  ** an index greater than all savepoints created explicitly using
-  ** SQL statements. It is illegal to open, release or rollback any
-  ** such savepoints while the statement transaction savepoint is active.
-  */
-  rc = sqlite3PagerOpenSavepoint(pBt->pPager, iStatement);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** The second argument to this function, op, is always SAVEPOINT_ROLLBACK
-** or SAVEPOINT_RELEASE. This function either releases or rolls back the
-** savepoint identified by parameter iSavepoint, depending on the value 
-** of op.
-**
-** Normally, iSavepoint is greater than or equal to zero. However, if op is
-** SAVEPOINT_ROLLBACK, then iSavepoint may also be -1. In this case the 
-** contents of the entire transaction are rolled back. This is different
-** from a normal transaction rollback, as no locks are released and the
-** transaction remains open.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSavepoint(Btree *p, int op, int iSavepoint){
-  int rc = SQLITE_OK;
-  if( p && p->inTrans==TRANS_WRITE ){
-    BtShared *pBt = p->pBt;
-    assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK );
-    assert( iSavepoint>=0 || (iSavepoint==-1 && op==SAVEPOINT_ROLLBACK) );
-    sqlite3BtreeEnter(p);
-    rc = sqlite3PagerSavepoint(pBt->pPager, op, iSavepoint);
-    if( rc==SQLITE_OK ){
-      if( iSavepoint<0 && (pBt->btsFlags & BTS_INITIALLY_EMPTY)!=0 ){
-        pBt->nPage = 0;
-      }
-      rc = newDatabase(pBt);
-      pBt->nPage = get4byte(28 + pBt->pPage1->aData);
-
-      /* The database size was written into the offset 28 of the header
-      ** when the transaction started, so we know that the value at offset
-      ** 28 is nonzero. */
-      assert( pBt->nPage>0 );
-    }
-    sqlite3BtreeLeave(p);
-  }
-  return rc;
-}
-
-/*
-** Create a new cursor for the BTree whose root is on the page
-** iTable. If a read-only cursor is requested, it is assumed that
-** the caller already has at least a read-only transaction open
-** on the database already. If a write-cursor is requested, then
-** the caller is assumed to have an open write transaction.
-**
-** If wrFlag==0, then the cursor can only be used for reading.
-** If wrFlag==1, then the cursor can be used for reading or for
-** writing if other conditions for writing are also met.  These
-** are the conditions that must be met in order for writing to
-** be allowed:
-**
-** 1:  The cursor must have been opened with wrFlag==1
-**
-** 2:  Other database connections that share the same pager cache
-**     but which are not in the READ_UNCOMMITTED state may not have
-**     cursors open with wrFlag==0 on the same table.  Otherwise
-**     the changes made by this write cursor would be visible to
-**     the read cursors in the other database connection.
-**
-** 3:  The database must be writable (not on read-only media)
-**
-** 4:  There must be an active transaction.
-**
-** No checking is done to make sure that page iTable really is the
-** root page of a b-tree.  If it is not, then the cursor acquired
-** will not work correctly.
-*/
-static int btreeCursor(
-  Btree *p,                              /* The btree */
-  int iTable,                            /* Root page of table to open */
-  int wrFlag,                            /* 1 to write. 0 read-only */
-  struct KeyInfo *pKeyInfo,              /* First arg to comparison function */
-  BtCursor *pCur                         /* Space for new cursor */
-){
-  BtShared *pBt = p->pBt;                /* Shared b-tree handle */
-  BtCursor *pX;                          /* Looping over other all cursors */
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( wrFlag==0 || wrFlag==1 );
-
-  /* The following assert statements verify that if this is a sharable 
-  ** b-tree database, the connection is holding the required table locks, 
-  ** and that no other connection has any open cursor that conflicts with 
-  ** this lock.  */
-  assert( hasSharedCacheTableLock(p, iTable, pKeyInfo!=0, wrFlag+1) );
-  assert( wrFlag==0 || !hasReadConflicts(p, iTable) );
-
-  /* Assert that the caller has opened the required transaction. */
-  assert( p->inTrans>TRANS_NONE );
-  assert( wrFlag==0 || p->inTrans==TRANS_WRITE );
-  assert( pBt->pPage1 && pBt->pPage1->aData );
-  assert( wrFlag==0 || (pBt->btsFlags & BTS_READ_ONLY)==0 );
-
-  if( wrFlag ){
-    allocateTempSpace(pBt);
-    if( pBt->pTmpSpace==0 ) return SQLITE_NOMEM;
-  }
-  if( iTable==1 && btreePagecount(pBt)==0 ){
-    assert( wrFlag==0 );
-    iTable = 0;
-  }
-
-  /* Now that no other errors can occur, finish filling in the BtCursor
-  ** variables and link the cursor into the BtShared list.  */
-  pCur->pgnoRoot = (Pgno)iTable;
-  pCur->iPage = -1;
-  pCur->pKeyInfo = pKeyInfo;
-  pCur->pBtree = p;
-  pCur->pBt = pBt;
-  assert( wrFlag==0 || wrFlag==BTCF_WriteFlag );
-  pCur->curFlags = wrFlag;
-  pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY;
-  /* If there are two or more cursors on the same btree, then all such
-  ** cursors *must* have the BTCF_Multiple flag set. */
-  for(pX=pBt->pCursor; pX; pX=pX->pNext){
-    if( pX->pgnoRoot==(Pgno)iTable ){
-      pX->curFlags |= BTCF_Multiple;
-      pCur->curFlags |= BTCF_Multiple;
-    }
-  }
-  pCur->pNext = pBt->pCursor;
-  pBt->pCursor = pCur;
-  pCur->eState = CURSOR_INVALID;
-  return SQLITE_OK;
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursor(
-  Btree *p,                                   /* The btree */
-  int iTable,                                 /* Root page of table to open */
-  int wrFlag,                                 /* 1 to write. 0 read-only */
-  int N, int X,                               /* index of N key columns and X extra columns */
-  BtCursor **ppCur                            /* Write new cursor here */
-){
-  int rc;
-  
-  *ppCur = 0;
-  if( iTable<1 ){
-    rc = SQLITE_CORRUPT_BKPT;
-  }else{
-    KeyInfo *pKeyInfo = NULL;
-    if (N > 0 || X > 0) {
-      pKeyInfo = sqlite3DbMallocZero(0, 
-          	                   sizeof(KeyInfo) + (N+X)*(sizeof(CollSeq*)+1));
-      if( pKeyInfo ){
-        pKeyInfo->aSortOrder = (u8*)&pKeyInfo->aColl[N+X];
-        pKeyInfo->nField = (u16)N;
-        pKeyInfo->nXField = (u16)X;
-        pKeyInfo->enc = p->enc;
-        pKeyInfo->pBtree = p;
-        pKeyInfo->nRef = 1;
-      }else{
-        p->mallocFailed = 1;
-        return SQLITE_NOMEM;
-      }
-    }
-
-	BtCursor *pCur = sqlite3MallocZero(sizeof(BtCursor));
-	if (!pCur) {
-	  p->mallocFailed = 1;
-	  sqlite3_free(pKeyInfo);
-	  return SQLITE_NOMEM;
-	}
-
-    sqlite3BtreeEnter(p);
-    rc = btreeCursor(p, iTable, wrFlag, pKeyInfo, pCur);
-    sqlite3BtreeLeave(p);
-    
-    if (rc != SQLITE_OK) {
-		sqlite3_free(pKeyInfo);
-		sqlite3_free(pCur);
-		return rc;
-	}
-
-	*ppCur = pCur;
-  }
-  return rc;
-}
-
-/*
-** Return the size of a BtCursor object in bytes.
-**
-** This interfaces is needed so that users of cursors can preallocate
-** sufficient storage to hold a cursor.  The BtCursor object is opaque
-** to users so they cannot do the sizeof() themselves - they must call
-** this routine.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursorSize(void){
-  return ROUND8(sizeof(BtCursor));
-}
-
-/*
-** Close a cursor.  The read lock on the database file is released
-** when the last cursor is closed.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCloseCursor(BtCursor *pCur){
-  Btree *pBtree = pCur->pBtree;
-  if( pBtree ){
-    int i;
-    BtShared *pBt = pCur->pBt;
-    sqlite3BtreeEnter(pBtree);
-    sqlite3BtreeClearCursor(pCur);
-    assert( pBt->pCursor!=0 );
-    if( pBt->pCursor==pCur ){
-      pBt->pCursor = pCur->pNext;
-    }else{
-      BtCursor *pPrev = pBt->pCursor;
-      do{
-        if( pPrev->pNext==pCur ){
-          pPrev->pNext = pCur->pNext;
-          break;
-        }
-        pPrev = pPrev->pNext;
-      }while( ALWAYS(pPrev) );
-    }
-    for(i=0; i<=pCur->iPage; i++){
-      releasePage(pCur->apPage[i]);
-    }
-    unlockBtreeIfUnused(pBt);
-    sqlite3_free(pCur->aOverflow);
-    /* sqlite3_free(pCur); */
-    sqlite3BtreeLeave(pBtree);
-  }
-  
-  if( pCur->pKeyInfo ) {
-    assert( pCur->pKeyInfo->nRef>0 );
-    pCur->pKeyInfo->nRef--;
-    if( pCur->pKeyInfo->nRef==0 ) sqlite3DbFree(0, pCur->pKeyInfo);
-  }
-
-  sqlite3_free(pCur);
-  return SQLITE_OK;
-}
-
-/*
-** Make sure the BtCursor* given in the argument has a valid
-** BtCursor.info structure.  If it is not already valid, call
-** btreeParseCell() to fill it in.
-**
-** BtCursor.info is a cache of the information in the current cell.
-** Using this cache reduces the number of calls to btreeParseCell().
-*/
-#ifndef NDEBUG
-  static void assertCellInfo(BtCursor *pCur){
-    CellInfo info;
-    int iPage = pCur->iPage;
-    memset(&info, 0, sizeof(info));
-    btreeParseCell(pCur->apPage[iPage], pCur->aiIdx[iPage], &info);
-    assert( CORRUPT_DB || memcmp(&info, &pCur->info, sizeof(info))==0 );
-  }
-#else
-  #define assertCellInfo(x)
-#endif
-static SQLITE_NOINLINE void getCellInfo(BtCursor *pCur){
-  if( pCur->info.nSize==0 ){
-    int iPage = pCur->iPage;
-    pCur->curFlags |= BTCF_ValidNKey;
-    btreeParseCell(pCur->apPage[iPage],pCur->aiIdx[iPage],&pCur->info);
-  }else{
-    assertCellInfo(pCur);
-  }
-}
-
-#ifndef NDEBUG  /* The next routine used only within assert() statements */
-/*
-** Return true if the given BtCursor is valid.  A valid cursor is one
-** that is currently pointing to a row in a (non-empty) table.
-** This is a verification routine is used only within assert() statements.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursorIsValid(BtCursor *pCur){
-  return pCur && pCur->eState==CURSOR_VALID;
-}
-#endif /* NDEBUG */
-
-/*
-** Set *pSize to the size of the buffer needed to hold the value of
-** the key for the current entry.  If the cursor is not pointing
-** to a valid entry, *pSize is set to 0. 
-**
-** For a table with the INTKEY flag set, this routine returns the key
-** itself, not the number of bytes in the key.
-**
-** The caller must position the cursor prior to invoking this routine.
-** 
-** This routine cannot fail.  It always returns SQLITE_OK.  
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  getCellInfo(pCur);
-  *pSize = pCur->info.nKey;
-  return SQLITE_OK;
-}
-
-/*
-** Set *pSize to the number of bytes of data in the entry the
-** cursor currently points to.
-**
-** The caller must guarantee that the cursor is pointing to a non-NULL
-** valid entry.  In other words, the calling procedure must guarantee
-** that the cursor has Cursor.eState==CURSOR_VALID.
-**
-** Failure is not possible.  This function always returns SQLITE_OK.
-** It might just as well be a procedure (returning void) but we continue
-** to return an integer result code for historical reasons.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  assert( pCur->iPage>=0 );
-  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
-  assert( pCur->apPage[pCur->iPage]->intKeyLeaf==1 );
-  getCellInfo(pCur);
-  *pSize = pCur->info.nPayload;
-  return SQLITE_OK;
-}
-
-/*
-** Given the page number of an overflow page in the database (parameter
-** ovfl), this function finds the page number of the next page in the 
-** linked list of overflow pages. If possible, it uses the auto-vacuum
-** pointer-map data instead of reading the content of page ovfl to do so. 
-**
-** If an error occurs an SQLite error code is returned. Otherwise:
-**
-** The page number of the next overflow page in the linked list is 
-** written to *pPgnoNext. If page ovfl is the last page in its linked 
-** list, *pPgnoNext is set to zero. 
-**
-** If ppPage is not NULL, and a reference to the MemPage object corresponding
-** to page number pOvfl was obtained, then *ppPage is set to point to that
-** reference. It is the responsibility of the caller to call releasePage()
-** on *ppPage to free the reference. In no reference was obtained (because
-** the pointer-map was used to obtain the value for *pPgnoNext), then
-** *ppPage is set to zero.
-*/
-static int getOverflowPage(
-  BtShared *pBt,               /* The database file */
-  Pgno ovfl,                   /* Current overflow page number */
-  MemPage **ppPage,            /* OUT: MemPage handle (may be NULL) */
-  Pgno *pPgnoNext              /* OUT: Next overflow page number */
-){
-  Pgno next = 0;
-  MemPage *pPage = 0;
-  int rc = SQLITE_OK;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert(pPgnoNext);
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-  /* Try to find the next page in the overflow list using the
-  ** autovacuum pointer-map pages. Guess that the next page in 
-  ** the overflow list is page number (ovfl+1). If that guess turns 
-  ** out to be wrong, fall back to loading the data of page 
-  ** number ovfl to determine the next page number.
-  */
-  if( pBt->autoVacuum ){
-    Pgno pgno;
-    Pgno iGuess = ovfl+1;
-    u8 eType;
-
-    while( PTRMAP_ISPAGE(pBt, iGuess) || iGuess==PENDING_BYTE_PAGE(pBt) ){
-      iGuess++;
-    }
-
-    if( iGuess<=btreePagecount(pBt) ){
-      rc = ptrmapGet(pBt, iGuess, &eType, &pgno);
-      if( rc==SQLITE_OK && eType==PTRMAP_OVERFLOW2 && pgno==ovfl ){
-        next = iGuess;
-        rc = SQLITE_DONE;
-      }
-    }
-  }
-#endif
-
-  assert( next==0 || rc==SQLITE_DONE );
-  if( rc==SQLITE_OK ){
-    rc = btreeGetPage(pBt, ovfl, &pPage, (ppPage==0) ? PAGER_GET_READONLY : 0);
-    assert( rc==SQLITE_OK || pPage==0 );
-    if( rc==SQLITE_OK ){
-      next = get4byte(pPage->aData);
-    }
-  }
-
-  *pPgnoNext = next;
-  if( ppPage ){
-    *ppPage = pPage;
-  }else{
-    releasePage(pPage);
-  }
-  return (rc==SQLITE_DONE ? SQLITE_OK : rc);
-}
-
-/*
-** Copy data from a buffer to a page, or from a page to a buffer.
-**
-** pPayload is a pointer to data stored on database page pDbPage.
-** If argument eOp is false, then nByte bytes of data are copied
-** from pPayload to the buffer pointed at by pBuf. If eOp is true,
-** then sqlite3PagerWrite() is called on pDbPage and nByte bytes
-** of data are copied from the buffer pBuf to pPayload.
-**
-** SQLITE_OK is returned on success, otherwise an error code.
-*/
-static int copyPayload(
-  void *pPayload,           /* Pointer to page data */
-  void *pBuf,               /* Pointer to buffer */
-  int nByte,                /* Number of bytes to copy */
-  int eOp,                  /* 0 -> copy from page, 1 -> copy to page */
-  DbPage *pDbPage           /* Page containing pPayload */
-){
-  if( eOp ){
-    /* Copy data from buffer to page (a write operation) */
-    int rc = sqlite3PagerWrite(pDbPage);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    memcpy(pPayload, pBuf, nByte);
-  }else{
-    /* Copy data from page to buffer (a read operation) */
-    memcpy(pBuf, pPayload, nByte);
-  }
-  return SQLITE_OK;
-}
-
-/*
-** This function is used to read or overwrite payload information
-** for the entry that the pCur cursor is pointing to. The eOp
-** argument is interpreted as follows:
-**
-**   0: The operation is a read. Populate the overflow cache.
-**   1: The operation is a write. Populate the overflow cache.
-**   2: The operation is a read. Do not populate the overflow cache.
-**
-** A total of "amt" bytes are read or written beginning at "offset".
-** Data is read to or from the buffer pBuf.
-**
-** The content being read or written might appear on the main page
-** or be scattered out on multiple overflow pages.
-**
-** If the current cursor entry uses one or more overflow pages and the
-** eOp argument is not 2, this function may allocate space for and lazily 
-** populates the overflow page-list cache array (BtCursor.aOverflow). 
-** Subsequent calls use this cache to make seeking to the supplied offset 
-** more efficient.
-**
-** Once an overflow page-list cache has been allocated, it may be
-** invalidated if some other cursor writes to the same table, or if
-** the cursor is moved to a different row. Additionally, in auto-vacuum
-** mode, the following events may invalidate an overflow page-list cache.
-**
-**   * An incremental vacuum,
-**   * A commit in auto_vacuum="full" mode,
-**   * Creating a table (may require moving an overflow page).
-*/
-static int accessPayload(
-  BtCursor *pCur,      /* Cursor pointing to entry to read from */
-  u32 offset,          /* Begin reading this far into payload */
-  u32 amt,             /* Read this many bytes */
-  unsigned char *pBuf, /* Write the bytes into this buffer */ 
-  int eOp              /* zero to read. non-zero to write. */
-){
-  unsigned char *aPayload;
-  int rc = SQLITE_OK;
-  int iIdx = 0;
-  MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
-  BtShared *pBt = pCur->pBt;                  /* Btree this cursor belongs to */
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-  unsigned char * const pBufStart = pBuf;
-  int bEnd;                                 /* True if reading to end of data */
-#endif
-
-  assert( pPage );
-  assert( pCur->eState==CURSOR_VALID );
-  assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
-  assert( cursorHoldsMutex(pCur) );
-  assert( eOp!=2 || offset==0 );    /* Always start from beginning for eOp==2 */
-
-  getCellInfo(pCur);
-  aPayload = pCur->info.pPayload;
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-  bEnd = offset+amt==pCur->info.nPayload;
-#endif
-  assert( offset+amt <= pCur->info.nPayload );
-
-  if( &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize] ){
-    /* Trying to read or write past the end of the data is an error */
-    return SQLITE_CORRUPT_BKPT;
-  }
-
-  /* Check if data must be read/written to/from the btree page itself. */
-  if( offset<pCur->info.nLocal ){
-    int a = amt;
-    if( a+offset>pCur->info.nLocal ){
-      a = pCur->info.nLocal - offset;
-    }
-    rc = copyPayload(&aPayload[offset], pBuf, a, (eOp & 0x01), pPage->pDbPage);
-    offset = 0;
-    pBuf += a;
-    amt -= a;
-  }else{
-    offset -= pCur->info.nLocal;
-  }
-
-
-  if( rc==SQLITE_OK && amt>0 ){
-    const u32 ovflSize = pBt->usableSize - 4;  /* Bytes content per ovfl page */
-    Pgno nextPage;
-
-    nextPage = get4byte(&aPayload[pCur->info.nLocal]);
-
-    /* If the BtCursor.aOverflow[] has not been allocated, allocate it now.
-    ** Except, do not allocate aOverflow[] for eOp==2.
-    **
-    ** The aOverflow[] array is sized at one entry for each overflow page
-    ** in the overflow chain. The page number of the first overflow page is
-    ** stored in aOverflow[0], etc. A value of 0 in the aOverflow[] array
-    ** means "not yet known" (the cache is lazily populated).
-    */
-    if( eOp!=2 && (pCur->curFlags & BTCF_ValidOvfl)==0 ){
-      int nOvfl = (pCur->info.nPayload-pCur->info.nLocal+ovflSize-1)/ovflSize;
-      if( nOvfl>pCur->nOvflAlloc ){
-        Pgno *aNew = (Pgno*)sqlite3Realloc(
-            pCur->aOverflow, nOvfl*2*sizeof(Pgno)
-        );
-        if( aNew==0 ){
-          rc = SQLITE_NOMEM;
-        }else{
-          pCur->nOvflAlloc = nOvfl*2;
-          pCur->aOverflow = aNew;
-        }
-      }
-      if( rc==SQLITE_OK ){
-        memset(pCur->aOverflow, 0, nOvfl*sizeof(Pgno));
-        pCur->curFlags |= BTCF_ValidOvfl;
-      }
-    }
-
-    /* If the overflow page-list cache has been allocated and the
-    ** entry for the first required overflow page is valid, skip
-    ** directly to it.
-    */
-    if( (pCur->curFlags & BTCF_ValidOvfl)!=0
-     && pCur->aOverflow[offset/ovflSize]
-    ){
-      iIdx = (offset/ovflSize);
-      nextPage = pCur->aOverflow[iIdx];
-      offset = (offset%ovflSize);
-    }
-
-    for( ; rc==SQLITE_OK && amt>0 && nextPage; iIdx++){
-
-      /* If required, populate the overflow page-list cache. */
-      if( (pCur->curFlags & BTCF_ValidOvfl)!=0 ){
-        assert(!pCur->aOverflow[iIdx] || pCur->aOverflow[iIdx]==nextPage);
-        pCur->aOverflow[iIdx] = nextPage;
-      }
-
-      if( offset>=ovflSize ){
-        /* The only reason to read this page is to obtain the page
-        ** number for the next page in the overflow chain. The page
-        ** data is not required. So first try to lookup the overflow
-        ** page-list cache, if any, then fall back to the getOverflowPage()
-        ** function.
-        **
-        ** Note that the aOverflow[] array must be allocated because eOp!=2
-        ** here.  If eOp==2, then offset==0 and this branch is never taken.
-        */
-        assert( eOp!=2 );
-        assert( pCur->curFlags & BTCF_ValidOvfl );
-        assert( pCur->pBtree->db==pBt->db );
-        if( pCur->aOverflow[iIdx+1] ){
-          nextPage = pCur->aOverflow[iIdx+1];
-        }else{
-          rc = getOverflowPage(pBt, nextPage, 0, &nextPage);
-        }
-        offset -= ovflSize;
-      }else{
-        /* Need to read this page properly. It contains some of the
-        ** range of data that is being read (eOp==0) or written (eOp!=0).
-        */
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-        sqlite3_file *fd;
-#endif
-        int a = amt;
-        if( a + offset > ovflSize ){
-          a = ovflSize - offset;
-        }
-
-#ifdef SQLITE_DIRECT_OVERFLOW_READ
-        /* If all the following are true:
-        **
-        **   1) this is a read operation, and 
-        **   2) data is required from the start of this overflow page, and
-        **   3) the database is file-backed, and
-        **   4) there is no open write-transaction, and
-        **   5) the database is not a WAL database,
-        **   6) all data from the page is being read.
-        **   7) at least 4 bytes have already been read into the output buffer 
-        **
-        ** then data can be read directly from the database file into the
-        ** output buffer, bypassing the page-cache altogether. This speeds
-        ** up loading large records that span many overflow pages.
-        */
-        if( (eOp&0x01)==0                                      /* (1) */
-         && offset==0                                          /* (2) */
-         && (bEnd || a==ovflSize)                              /* (6) */
-         && pBt->inTransaction==TRANS_READ                     /* (4) */
-         && (fd = sqlite3PagerFile(pBt->pPager))->pMethods     /* (3) */
-         && pBt->pPage1->aData[19]==0x01                       /* (5) */
-         && &pBuf[-4]>=pBufStart                               /* (7) */
-        ){
-          u8 aSave[4];
-          u8 *aWrite = &pBuf[-4];
-          assert( aWrite>=pBufStart );                         /* hence (7) */
-          memcpy(aSave, aWrite, 4);
-          rc = sqlite3OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
-          nextPage = get4byte(aWrite);
-          memcpy(aWrite, aSave, 4);
-        }else
-#endif
-
-        {
-          DbPage *pDbPage;
-          rc = sqlite3PagerAcquire(pBt->pPager, nextPage, &pDbPage,
-              ((eOp&0x01)==0 ? PAGER_GET_READONLY : 0)
-          );
-          if( rc==SQLITE_OK ){
-            aPayload = sqlite3PagerGetData(pDbPage);
-            nextPage = get4byte(aPayload);
-            rc = copyPayload(&aPayload[offset+4], pBuf, a, (eOp&0x01), pDbPage);
-            sqlite3PagerUnref(pDbPage);
-            offset = 0;
-          }
-        }
-        amt -= a;
-        pBuf += a;
-      }
-    }
-  }
-
-  if( rc==SQLITE_OK && amt>0 ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  return rc;
-}
-
-/*
-** Read part of the key associated with cursor pCur.  Exactly
-** "amt" bytes will be transferred into pBuf[].  The transfer
-** begins at "offset".
-**
-** The caller must ensure that pCur is pointing to a valid row
-** in the table.
-**
-** Return SQLITE_OK on success or an error code if anything goes
-** wrong.  An error is returned if "offset+amt" is larger than
-** the available payload.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
-  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
-  return accessPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
-}
-
-/*
-** Read part of the data associated with cursor pCur.  Exactly
-** "amt" bytes will be transfered into pBuf[].  The transfer
-** begins at "offset".
-**
-** Return SQLITE_OK on success or an error code if anything goes
-** wrong.  An error is returned if "offset+amt" is larger than
-** the available payload.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
-  int rc;
-
-#ifndef SQLITE_OMIT_INCRBLOB
-  if ( pCur->eState==CURSOR_INVALID ){
-    return SQLITE_ABORT;
-  }
-#endif
-
-  assert( cursorHoldsMutex(pCur) );
-  rc = restoreCursorPosition(pCur);
-  if( rc==SQLITE_OK ){
-    assert( pCur->eState==CURSOR_VALID );
-    assert( pCur->iPage>=0 && pCur->apPage[pCur->iPage] );
-    assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
-    rc = accessPayload(pCur, offset, amt, pBuf, 0);
-  }
-  return rc;
-}
-
-/*
-** Return a pointer to payload information from the entry that the 
-** pCur cursor is pointing to.  The pointer is to the beginning of
-** the key if index btrees (pPage->intKey==0) and is the data for
-** table btrees (pPage->intKey==1). The number of bytes of available
-** key/data is written into *pAmt.  If *pAmt==0, then the value
-** returned will not be a valid pointer.
-**
-** This routine is an optimization.  It is common for the entire key
-** and data to fit on the local page and for there to be no overflow
-** pages.  When that is so, this routine can be used to access the
-** key and data without making a copy.  If the key and/or data spills
-** onto overflow pages, then accessPayload() must be used to reassemble
-** the key/data and copy it into a preallocated buffer.
-**
-** The pointer returned by this routine looks directly into the cached
-** page of the database.  The data might change or move the next time
-** any btree routine is called.
-*/
-static const void *fetchPayload(
-  BtCursor *pCur,      /* Cursor pointing to entry to read from */
-  u32 *pAmt            /* Write the number of available bytes here */
-){
-  u32 amt;
-  assert( pCur!=0 && pCur->iPage>=0 && pCur->apPage[pCur->iPage]);
-  assert( pCur->eState==CURSOR_VALID );
-  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
-  assert( pCur->info.nSize>0 );
-  assert( pCur->info.pPayload>pCur->apPage[pCur->iPage]->aData || CORRUPT_DB );
-  assert( pCur->info.pPayload<pCur->apPage[pCur->iPage]->aDataEnd ||CORRUPT_DB);
-  amt = (int)(pCur->apPage[pCur->iPage]->aDataEnd - pCur->info.pPayload);
-  if( pCur->info.nLocal<amt ) amt = pCur->info.nLocal;
-  *pAmt = amt;
-  return (void*)pCur->info.pPayload;
-}
-
-
-/*
-** For the entry that cursor pCur is point to, return as
-** many bytes of the key or data as are available on the local
-** b-tree page.  Write the number of available bytes into *pAmt.
-**
-** The pointer returned is ephemeral.  The key/data may move
-** or be destroyed on the next call to any Btree routine,
-** including calls from other threads against the same cache.
-** Hence, a mutex on the BtShared should be held prior to calling
-** this routine.
-**
-** These routines is used to get quick access to key and data
-** in the common case where no overflow pages are used.
-*/
-SQLITE_API const void *SQLITE_STDCALL sqlite3BtreeKeyFetch(BtCursor *pCur, u32 *pAmt){
-  return fetchPayload(pCur, pAmt);
-}
-SQLITE_API const void *SQLITE_STDCALL sqlite3BtreeDataFetch(BtCursor *pCur, u32 *pAmt){
-  return fetchPayload(pCur, pAmt);
-}
-
-
-/*
-** Move the cursor down to a new child page.  The newPgno argument is the
-** page number of the child page to move to.
-**
-** This function returns SQLITE_CORRUPT if the page-header flags field of
-** the new child page does not match the flags field of the parent (i.e.
-** if an intkey page appears to be the parent of a non-intkey page, or
-** vice-versa).
-*/
-static int moveToChild(BtCursor *pCur, u32 newPgno){
-  BtShared *pBt = pCur->pBt;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  assert( pCur->iPage<BTCURSOR_MAX_DEPTH );
-  assert( pCur->iPage>=0 );
-  if( pCur->iPage>=(BTCURSOR_MAX_DEPTH-1) ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  pCur->iPage++;
-  pCur->aiIdx[pCur->iPage] = 0;
-  return getAndInitPage(pBt, newPgno, &pCur->apPage[pCur->iPage],
-                        pCur, pCur->curPagerFlags);
-}
-
-#if SQLITE_DEBUG
-/*
-** Page pParent is an internal (non-leaf) tree page. This function 
-** asserts that page number iChild is the left-child if the iIdx'th
-** cell in page pParent. Or, if iIdx is equal to the total number of
-** cells in pParent, that page number iChild is the right-child of
-** the page.
-*/
-static void assertParentIndex(MemPage *pParent, int iIdx, Pgno iChild){
-  if( CORRUPT_DB ) return;  /* The conditions tested below might not be true
-                            ** in a corrupt database */
-  assert( iIdx<=pParent->nCell );
-  if( iIdx==pParent->nCell ){
-    assert( get4byte(&pParent->aData[pParent->hdrOffset+8])==iChild );
-  }else{
-    assert( get4byte(findCell(pParent, iIdx))==iChild );
-  }
-}
-#else
-#  define assertParentIndex(x,y,z) 
-#endif
-
-/*
-** Move the cursor up to the parent page.
-**
-** pCur->idx is set to the cell index that contains the pointer
-** to the page we are coming from.  If we are coming from the
-** right-most child page then pCur->idx is set to one more than
-** the largest cell index.
-*/
-static void moveToParent(BtCursor *pCur){
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  assert( pCur->iPage>0 );
-  assert( pCur->apPage[pCur->iPage] );
-  assertParentIndex(
-    pCur->apPage[pCur->iPage-1], 
-    pCur->aiIdx[pCur->iPage-1], 
-    pCur->apPage[pCur->iPage]->pgno
-  );
-  testcase( pCur->aiIdx[pCur->iPage-1] > pCur->apPage[pCur->iPage-1]->nCell );
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  releasePageNotNull(pCur->apPage[pCur->iPage--]);
-}
-
-/*
-** Move the cursor to point to the root page of its b-tree structure.
-**
-** If the table has a virtual root page, then the cursor is moved to point
-** to the virtual root page instead of the actual root page. A table has a
-** virtual root page when the actual root page contains no cells and a 
-** single child page. This can only happen with the table rooted at page 1.
-**
-** If the b-tree structure is empty, the cursor state is set to 
-** CURSOR_INVALID. Otherwise, the cursor is set to point to the first
-** cell located on the root (or virtual root) page and the cursor state
-** is set to CURSOR_VALID.
-**
-** If this function returns successfully, it may be assumed that the
-** page-header flags indicate that the [virtual] root-page is the expected 
-** kind of b-tree page (i.e. if when opening the cursor the caller did not
-** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D,
-** indicating a table b-tree, or if the caller did specify a KeyInfo 
-** structure the flags byte is set to 0x02 or 0x0A, indicating an index
-** b-tree).
-*/
-static int moveToRoot(BtCursor *pCur){
-  MemPage *pRoot;
-  int rc = SQLITE_OK;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
-  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
-  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
-  if( pCur->eState>=CURSOR_REQUIRESEEK ){
-    if( pCur->eState==CURSOR_FAULT ){
-      assert( pCur->skipNext!=SQLITE_OK );
-      return pCur->skipNext;
-    }
-    sqlite3BtreeClearCursor(pCur);
-  }
-
-  if( pCur->iPage>=0 ){
-    while( pCur->iPage ){
-      assert( pCur->apPage[pCur->iPage]!=0 );
-      releasePageNotNull(pCur->apPage[pCur->iPage--]);
-    }
-  }else if( pCur->pgnoRoot==0 ){
-    pCur->eState = CURSOR_INVALID;
-    return SQLITE_OK;
-  }else{
-    assert( pCur->iPage==(-1) );
-    rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
-                        0, pCur->curPagerFlags);
-    if( rc!=SQLITE_OK ){
-      pCur->eState = CURSOR_INVALID;
-      return rc;
-    }
-    pCur->iPage = 0;
-    pCur->curIntKey = pCur->apPage[0]->intKey;
-  }
-  pRoot = pCur->apPage[0];
-  assert( pRoot->pgno==pCur->pgnoRoot );
-
-  /* If pCur->pKeyInfo is not NULL, then the caller that opened this cursor
-  ** expected to open it on an index b-tree. Otherwise, if pKeyInfo is
-  ** NULL, the caller expects a table b-tree. If this is not the case,
-  ** return an SQLITE_CORRUPT error. 
-  **
-  ** Earlier versions of SQLite assumed that this test could not fail
-  ** if the root page was already loaded when this function was called (i.e.
-  ** if pCur->iPage>=0). But this is not so if the database is corrupted 
-  ** in such a way that page pRoot is linked into a second b-tree table 
-  ** (or the freelist).  */
-  assert( pRoot->intKey==1 || pRoot->intKey==0 );
-  if( pRoot->isInit==0 || (pCur->pKeyInfo==0)!=pRoot->intKey ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-
-  pCur->aiIdx[0] = 0;
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidNKey|BTCF_ValidOvfl);
-
-  if( pRoot->nCell>0 ){
-    pCur->eState = CURSOR_VALID;
-  }else if( !pRoot->leaf ){
-    Pgno subpage;
-    if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT;
-    subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
-    pCur->eState = CURSOR_VALID;
-    rc = moveToChild(pCur, subpage);
-  }else{
-    pCur->eState = CURSOR_INVALID;
-  }
-  return rc;
-}
-
-/*
-** Move the cursor down to the left-most leaf entry beneath the
-** entry to which it is currently pointing.
-**
-** The left-most leaf is the one with the smallest key - the first
-** in ascending order.
-*/
-static int moveToLeftmost(BtCursor *pCur){
-  Pgno pgno;
-  int rc = SQLITE_OK;
-  MemPage *pPage;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  while( rc==SQLITE_OK && !(pPage = pCur->apPage[pCur->iPage])->leaf ){
-    assert( pCur->aiIdx[pCur->iPage]<pPage->nCell );
-    pgno = get4byte(findCell(pPage, pCur->aiIdx[pCur->iPage]));
-    rc = moveToChild(pCur, pgno);
-  }
-  return rc;
-}
-
-/*
-** Move the cursor down to the right-most leaf entry beneath the
-** page to which it is currently pointing.  Notice the difference
-** between moveToLeftmost() and moveToRightmost().  moveToLeftmost()
-** finds the left-most entry beneath the *entry* whereas moveToRightmost()
-** finds the right-most entry beneath the *page*.
-**
-** The right-most entry is the one with the largest key - the last
-** key in ascending order.
-*/
-static int moveToRightmost(BtCursor *pCur){
-  Pgno pgno;
-  int rc = SQLITE_OK;
-  MemPage *pPage = 0;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->eState==CURSOR_VALID );
-  while( !(pPage = pCur->apPage[pCur->iPage])->leaf ){
-    pgno = get4byte(&pPage->aData[pPage->hdrOffset+8]);
-    pCur->aiIdx[pCur->iPage] = pPage->nCell;
-    rc = moveToChild(pCur, pgno);
-    if( rc ) return rc;
-  }
-  pCur->aiIdx[pCur->iPage] = pPage->nCell-1;
-  assert( pCur->info.nSize==0 );
-  assert( (pCur->curFlags & BTCF_ValidNKey)==0 );
-  return SQLITE_OK;
-}
-
-/* Move the cursor to the first entry in the table.  Return SQLITE_OK
-** on success.  Set *pRes to 0 if the cursor actually points to something
-** or set *pRes to 1 if the table is empty.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
-  int rc;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
-  rc = moveToRoot(pCur);
-  if( rc==SQLITE_OK ){
-    if( pCur->eState==CURSOR_INVALID ){
-      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-      *pRes = 1;
-    }else{
-      assert( pCur->apPage[pCur->iPage]->nCell>0 );
-      *pRes = 0;
-      rc = moveToLeftmost(pCur);
-    }
-  }
-  return rc;
-}
-
-/* Move the cursor to the last entry in the table.  Return SQLITE_OK
-** on success.  Set *pRes to 0 if the cursor actually points to something
-** or set *pRes to 1 if the table is empty.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeLast(BtCursor *pCur, int *pRes){
-  int rc;
- 
-  assert( cursorHoldsMutex(pCur) );
-  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
-
-  /* If the cursor already points to the last entry, this is a no-op. */
-  if( CURSOR_VALID==pCur->eState && (pCur->curFlags & BTCF_AtLast)!=0 ){
-#ifdef SQLITE_DEBUG
-    /* This block serves to assert() that the cursor really does point 
-    ** to the last entry in the b-tree. */
-    int ii;
-    for(ii=0; ii<pCur->iPage; ii++){
-      assert( pCur->aiIdx[ii]==pCur->apPage[ii]->nCell );
-    }
-    assert( pCur->aiIdx[pCur->iPage]==pCur->apPage[pCur->iPage]->nCell-1 );
-    assert( pCur->apPage[pCur->iPage]->leaf );
-#endif
-    return SQLITE_OK;
-  }
-
-  rc = moveToRoot(pCur);
-  if( rc==SQLITE_OK ){
-    if( CURSOR_INVALID==pCur->eState ){
-      assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-      *pRes = 1;
-    }else{
-      assert( pCur->eState==CURSOR_VALID );
-      *pRes = 0;
-      rc = moveToRightmost(pCur);
-      if( rc==SQLITE_OK ){
-        pCur->curFlags |= BTCF_AtLast;
-      }else{
-        pCur->curFlags &= ~BTCF_AtLast;
-      }
-   
-    }
-  }
-  return rc;
-}
-
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeInitUnpackedRecord(
-  UnpackedRecord *pUnKey,
-  BtCursor* pCur,
-  int nField,
-  int default_rc,
-  Mem* pMem)
-{
-	pUnKey->pKeyInfo = pCur->pKeyInfo;
-	pUnKey->nField = nField;
-	pUnKey->default_rc = default_rc;
-	pUnKey->aMem = pMem;
-}
-
-/* Move the cursor so that it points to an entry near the key 
-** specified by pIdxKey or intKey.   Return a success code.
-**
-** For INTKEY tables, the intKey parameter is used.  pIdxKey 
-** must be NULL.  For index tables, pIdxKey is used and intKey
-** is ignored.
-**
-** If an exact match is not found, then the cursor is always
-** left pointing at a leaf page which would hold the entry if it
-** were present.  The cursor might point to an entry that comes
-** before or after the key.
-**
-** An integer is written into *pRes which is the result of
-** comparing the key with the entry to which the cursor is 
-** pointing.  The meaning of the integer written into
-** *pRes is as follows:
-**
-**     *pRes<0      The cursor is left pointing at an entry that
-**                  is smaller than intKey/pIdxKey or if the table is empty
-**                  and the cursor is therefore left point to nothing.
-**
-**     *pRes==0     The cursor is left pointing at an entry that
-**                  exactly matches intKey/pIdxKey.
-**
-**     *pRes>0      The cursor is left pointing at an entry that
-**                  is larger than intKey/pIdxKey.
-**
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeMovetoUnpacked(
-  BtCursor *pCur,          /* The cursor to be moved */
-  UnpackedRecord *pIdxKey, /* Unpacked index key */
-  i64 intKey,              /* The table key */
-  int biasRight,           /* If true, bias the search to the high end */
-  int *pRes                /* Write search results here */
-){
-  int rc;
-  RecordCompare xRecordCompare;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
-  assert( pRes );
-  assert( (pIdxKey==0)==(pCur->pKeyInfo==0) );
-
-  /* If the cursor is already positioned at the point we are trying
-  ** to move to, then just return without doing any work */
-  if( pCur->eState==CURSOR_VALID && (pCur->curFlags & BTCF_ValidNKey)!=0
-   && pCur->curIntKey 
-  ){
-    if( pCur->info.nKey==intKey ){
-      *pRes = 0;
-      return SQLITE_OK;
-    }
-    if( (pCur->curFlags & BTCF_AtLast)!=0 && pCur->info.nKey<intKey ){
-      *pRes = -1;
-      return SQLITE_OK;
-    }
-  }
-
-  if( pIdxKey ){
-    xRecordCompare = sqlite3VdbeFindCompare(pIdxKey);
-    pIdxKey->errCode = 0;
-    assert( pIdxKey->default_rc==1 
-         || pIdxKey->default_rc==0 
-         || pIdxKey->default_rc==-1
-    );
-  }else{
-    xRecordCompare = 0; /* All keys are integers */
-  }
-
-  rc = moveToRoot(pCur);
-  if( rc ){
-    return rc;
-  }
-  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage] );
-  assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->isInit );
-  assert( pCur->eState==CURSOR_INVALID || pCur->apPage[pCur->iPage]->nCell>0 );
-  if( pCur->eState==CURSOR_INVALID ){
-    *pRes = -1;
-    assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 );
-    return SQLITE_OK;
-  }
-  assert( pCur->apPage[0]->intKey==pCur->curIntKey );
-  assert( pCur->curIntKey || pIdxKey );
-  for(;;){
-    int lwr, upr, idx, c;
-    Pgno chldPg;
-    MemPage *pPage = pCur->apPage[pCur->iPage];
-    u8 *pCell;                          /* Pointer to current cell in pPage */
-
-    /* pPage->nCell must be greater than zero. If this is the root-page
-    ** the cursor would have been INVALID above and this for(;;) loop
-    ** not run. If this is not the root-page, then the moveToChild() routine
-    ** would have already detected db corruption. Similarly, pPage must
-    ** be the right kind (index or table) of b-tree page. Otherwise
-    ** a moveToChild() or moveToRoot() call would have detected corruption.  */
-    assert( pPage->nCell>0 );
-    assert( pPage->intKey==(pIdxKey==0) );
-    lwr = 0;
-    upr = pPage->nCell-1;
-    assert( biasRight==0 || biasRight==1 );
-    idx = upr>>(1-biasRight); /* idx = biasRight ? upr : (lwr+upr)/2; */
-    pCur->aiIdx[pCur->iPage] = (u16)idx;
-    if( xRecordCompare==0 ){
-      for(;;){
-        i64 nCellKey;
-        pCell = findCellPastPtr(pPage, idx);
-        if( pPage->intKeyLeaf ){
-          while( 0x80 <= *(pCell++) ){
-            if( pCell>=pPage->aDataEnd ) return SQLITE_CORRUPT_BKPT;
-          }
-        }
-        getVarint(pCell, (u64*)&nCellKey);
-        if( nCellKey<intKey ){
-          lwr = idx+1;
-          if( lwr>upr ){ c = -1; break; }
-        }else if( nCellKey>intKey ){
-          upr = idx-1;
-          if( lwr>upr ){ c = +1; break; }
-        }else{
-          assert( nCellKey==intKey );
-          pCur->curFlags |= BTCF_ValidNKey;
-          pCur->info.nKey = nCellKey;
-          pCur->aiIdx[pCur->iPage] = (u16)idx;
-          if( !pPage->leaf ){
-            lwr = idx;
-            goto moveto_next_layer;
-          }else{
-            *pRes = 0;
-            rc = SQLITE_OK;
-            goto moveto_finish;
-          }
-        }
-        assert( lwr+upr>=0 );
-        idx = (lwr+upr)>>1;  /* idx = (lwr+upr)/2; */
-      }
-    }else{
-      for(;;){
-        int nCell;  /* Size of the pCell cell in bytes */
-        pCell = findCellPastPtr(pPage, idx);
-
-        /* The maximum supported page-size is 65536 bytes. This means that
-        ** the maximum number of record bytes stored on an index B-Tree
-        ** page is less than 16384 bytes and may be stored as a 2-byte
-        ** varint. This information is used to attempt to avoid parsing 
-        ** the entire cell by checking for the cases where the record is 
-        ** stored entirely within the b-tree page by inspecting the first 
-        ** 2 bytes of the cell.
-        */
-        nCell = pCell[0];
-        if( nCell<=pPage->max1bytePayload ){
-          /* This branch runs if the record-size field of the cell is a
-          ** single byte varint and the record fits entirely on the main
-          ** b-tree page.  */
-          testcase( pCell+nCell+1==pPage->aDataEnd );
-          c = xRecordCompare(nCell, (void*)&pCell[1], pIdxKey);
-        }else if( !(pCell[1] & 0x80) 
-          && (nCell = ((nCell&0x7f)<<7) + pCell[1])<=pPage->maxLocal
-        ){
-          /* The record-size field is a 2 byte varint and the record 
-          ** fits entirely on the main b-tree page.  */
-          testcase( pCell+nCell+2==pPage->aDataEnd );
-          c = xRecordCompare(nCell, (void*)&pCell[2], pIdxKey);
-        }else{
-          /* The record flows over onto one or more overflow pages. In
-          ** this case the whole cell needs to be parsed, a buffer allocated
-          ** and accessPayload() used to retrieve the record into the
-          ** buffer before VdbeRecordCompare() can be called. 
-          **
-          ** If the record is corrupt, the xRecordCompare routine may read
-          ** up to two varints past the end of the buffer. An extra 18 
-          ** bytes of padding is allocated at the end of the buffer in
-          ** case this happens.  */
-          void *pCellKey;
-          u8 * const pCellBody = pCell - pPage->childPtrSize;
-          pPage->xParseCell(pPage, pCellBody, &pCur->info);
-          nCell = (int)pCur->info.nKey;
-          testcase( nCell<0 );   /* True if key size is 2^32 or more */
-          testcase( nCell==0 );  /* Invalid key size:  0x80 0x80 0x00 */
-          testcase( nCell==1 );  /* Invalid key size:  0x80 0x80 0x01 */
-          testcase( nCell==2 );  /* Minimum legal index key size */
-          if( nCell<2 ){
-            rc = SQLITE_CORRUPT_BKPT;
-            goto moveto_finish;
-          }
-          pCellKey = sqlite3Malloc( nCell+18 );
-          if( pCellKey==0 ){
-            rc = SQLITE_NOMEM;
-            goto moveto_finish;
-          }
-          pCur->aiIdx[pCur->iPage] = (u16)idx;
-          rc = accessPayload(pCur, 0, nCell, (unsigned char*)pCellKey, 2);
-          if( rc ){
-            sqlite3_free(pCellKey);
-            goto moveto_finish;
-          }
-          c = xRecordCompare(nCell, pCellKey, pIdxKey);
-          sqlite3_free(pCellKey);
-        }
-        assert( 
-            (pIdxKey->errCode!=SQLITE_CORRUPT || c==0)
-         && (pIdxKey->errCode!=SQLITE_NOMEM || pCur->pBtree->mallocFailed)
-        );
-        if( c<0 ){
-          lwr = idx+1;
-        }else if( c>0 ){
-          upr = idx-1;
-        }else{
-          assert( c==0 );
-          *pRes = 0;
-          rc = SQLITE_OK;
-          pCur->aiIdx[pCur->iPage] = (u16)idx;
-          if( pIdxKey->errCode ) rc = SQLITE_CORRUPT;
-          goto moveto_finish;
-        }
-        if( lwr>upr ) break;
-        assert( lwr+upr>=0 );
-        idx = (lwr+upr)>>1;  /* idx = (lwr+upr)/2 */
-      }
-    }
-    assert( lwr==upr+1 || (pPage->intKey && !pPage->leaf) );
-    assert( pPage->isInit );
-    if( pPage->leaf ){
-      assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
-      pCur->aiIdx[pCur->iPage] = (u16)idx;
-      *pRes = c;
-      rc = SQLITE_OK;
-      goto moveto_finish;
-    }
-moveto_next_layer:
-    if( lwr>=pPage->nCell ){
-      chldPg = get4byte(&pPage->aData[pPage->hdrOffset+8]);
-    }else{
-      chldPg = get4byte(findCell(pPage, lwr));
-    }
-    pCur->aiIdx[pCur->iPage] = (u16)lwr;
-    rc = moveToChild(pCur, chldPg);
-    if( rc ) break;
-  }
-moveto_finish:
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  return rc;
-}
-
-
-/*
-** Return TRUE if the cursor is not pointing at an entry of the table.
-**
-** TRUE will be returned after a call to sqlite3BtreeNext() moves
-** past the last entry in the table or sqlite3BtreePrev() moves past
-** the first entry.  TRUE is also returned if the table is empty.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeEof(BtCursor *pCur){
-  /* TODO: What if the cursor is in CURSOR_REQUIRESEEK but all table entries
-  ** have been deleted? This API will need to change to return an error code
-  ** as well as the boolean result value.
-  */
-  return (CURSOR_VALID!=pCur->eState);
-}
-
-/*
-** Advance the cursor to the next entry in the database.  If
-** successful then set *pRes=0.  If the cursor
-** was already pointing to the last entry in the database before
-** this routine was called, then set *pRes=1.
-**
-** The main entry point is sqlite3BtreeNext().  That routine is optimized
-** for the common case of merely incrementing the cell counter BtCursor.aiIdx
-** to the next cell on the current page.  The (slower) btreeNext() helper
-** routine is called when it is necessary to move to a different page or
-** to restore the cursor.
-**
-** The calling function will set *pRes to 0 or 1.  The initial *pRes value
-** will be 1 if the cursor being stepped corresponds to an SQL index and
-** if this routine could have been skipped if that SQL index had been
-** a unique index.  Otherwise the caller will have set *pRes to zero.
-** Zero is the common case. The btree implementation is free to use the
-** initial *pRes value as a hint to improve performance, but the current
-** SQLite btree implementation does not. (Note that the comdb2 btree
-** implementation does use this hint, however.)
-*/
-static SQLITE_NOINLINE int btreeNext(BtCursor *pCur, int *pRes){
-  int rc;
-  int idx;
-  MemPage *pPage;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
-  assert( *pRes==0 );
-  if( pCur->eState!=CURSOR_VALID ){
-    assert( (pCur->curFlags & BTCF_ValidOvfl)==0 );
-    rc = restoreCursorPosition(pCur);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    if( CURSOR_INVALID==pCur->eState ){
-      *pRes = 1;
-      return SQLITE_OK;
-    }
-    if( pCur->skipNext ){
-      assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
-      pCur->eState = CURSOR_VALID;
-      if( pCur->skipNext>0 ){
-        pCur->skipNext = 0;
-        return SQLITE_OK;
-      }
-      pCur->skipNext = 0;
-    }
-  }
-
-  pPage = pCur->apPage[pCur->iPage];
-  idx = ++pCur->aiIdx[pCur->iPage];
-  assert( pPage->isInit );
-
-  /* If the database file is corrupt, it is possible for the value of idx 
-  ** to be invalid here. This can only occur if a second cursor modifies
-  ** the page while cursor pCur is holding a reference to it. Which can
-  ** only happen if the database is corrupt in such a way as to link the
-  ** page into more than one b-tree structure. */
-  testcase( idx>pPage->nCell );
-
-  if( idx>=pPage->nCell ){
-    if( !pPage->leaf ){
-      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
-      if( rc ) return rc;
-      return moveToLeftmost(pCur);
-    }
-    do{
-      if( pCur->iPage==0 ){
-        *pRes = 1;
-        pCur->eState = CURSOR_INVALID;
-        return SQLITE_OK;
-      }
-      moveToParent(pCur);
-      pPage = pCur->apPage[pCur->iPage];
-    }while( pCur->aiIdx[pCur->iPage]>=pPage->nCell );
-    if( pPage->intKey ){
-      return sqlite3BtreeNext(pCur, pRes);
-    }else{
-      return SQLITE_OK;
-    }
-  }
-  if( pPage->leaf ){
-    return SQLITE_OK;
-  }else{
-    return moveToLeftmost(pCur);
-  }
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeNext(BtCursor *pCur, int *pRes){
-  MemPage *pPage;
-  assert( cursorHoldsMutex(pCur) );
-  assert( pRes!=0 );
-  assert( *pRes==0 || *pRes==1 );
-  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
-  pCur->info.nSize = 0;
-  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl);
-  *pRes = 0;
-  if( pCur->eState!=CURSOR_VALID ) return btreeNext(pCur, pRes);
-  pPage = pCur->apPage[pCur->iPage];
-  if( (++pCur->aiIdx[pCur->iPage])>=pPage->nCell ){
-    pCur->aiIdx[pCur->iPage]--;
-    return btreeNext(pCur, pRes);
-  }
-  if( pPage->leaf ){
-    return SQLITE_OK;
-  }else{
-    return moveToLeftmost(pCur);
-  }
-}
-
-/*
-** Step the cursor to the back to the previous entry in the database.  If
-** successful then set *pRes=0.  If the cursor
-** was already pointing to the first entry in the database before
-** this routine was called, then set *pRes=1.
-**
-** The main entry point is sqlite3BtreePrevious().  That routine is optimized
-** for the common case of merely decrementing the cell counter BtCursor.aiIdx
-** to the previous cell on the current page.  The (slower) btreePrevious()
-** helper routine is called when it is necessary to move to a different page
-** or to restore the cursor.
-**
-** The calling function will set *pRes to 0 or 1.  The initial *pRes value
-** will be 1 if the cursor being stepped corresponds to an SQL index and
-** if this routine could have been skipped if that SQL index had been
-** a unique index.  Otherwise the caller will have set *pRes to zero.
-** Zero is the common case. The btree implementation is free to use the
-** initial *pRes value as a hint to improve performance, but the current
-** SQLite btree implementation does not. (Note that the comdb2 btree
-** implementation does use this hint, however.)
-*/
-static SQLITE_NOINLINE int btreePrevious(BtCursor *pCur, int *pRes){
-  int rc;
-  MemPage *pPage;
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pRes!=0 );
-  assert( *pRes==0 );
-  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
-  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
-  assert( pCur->info.nSize==0 );
-  if( pCur->eState!=CURSOR_VALID ){
-    rc = restoreCursorPosition(pCur);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-    if( CURSOR_INVALID==pCur->eState ){
-      *pRes = 1;
-      return SQLITE_OK;
-    }
-    if( pCur->skipNext ){
-      assert( pCur->eState==CURSOR_VALID || pCur->eState==CURSOR_SKIPNEXT );
-      pCur->eState = CURSOR_VALID;
-      if( pCur->skipNext<0 ){
-        pCur->skipNext = 0;
-        return SQLITE_OK;
-      }
-      pCur->skipNext = 0;
-    }
-  }
-
-  pPage = pCur->apPage[pCur->iPage];
-  assert( pPage->isInit );
-  if( !pPage->leaf ){
-    int idx = pCur->aiIdx[pCur->iPage];
-    rc = moveToChild(pCur, get4byte(findCell(pPage, idx)));
-    if( rc ) return rc;
-    rc = moveToRightmost(pCur);
-  }else{
-    while( pCur->aiIdx[pCur->iPage]==0 ){
-      if( pCur->iPage==0 ){
-        pCur->eState = CURSOR_INVALID;
-        *pRes = 1;
-        return SQLITE_OK;
-      }
-      moveToParent(pCur);
-    }
-    assert( pCur->info.nSize==0 );
-    assert( (pCur->curFlags & (BTCF_ValidNKey|BTCF_ValidOvfl))==0 );
-
-    pCur->aiIdx[pCur->iPage]--;
-    pPage = pCur->apPage[pCur->iPage];
-    if( pPage->intKey && !pPage->leaf ){
-      rc = sqlite3BtreePrevious(pCur, pRes);
-    }else{
-      rc = SQLITE_OK;
-    }
-  }
-  return rc;
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
-  assert( cursorHoldsMutex(pCur) );
-  assert( pRes!=0 );
-  assert( *pRes==0 || *pRes==1 );
-  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
-  *pRes = 0;
-  pCur->curFlags &= ~(BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey);
-  pCur->info.nSize = 0;
-  if( pCur->eState!=CURSOR_VALID
-   || pCur->aiIdx[pCur->iPage]==0
-   || pCur->apPage[pCur->iPage]->leaf==0
-  ){
-    return btreePrevious(pCur, pRes);
-  }
-  pCur->aiIdx[pCur->iPage]--;
-  return SQLITE_OK;
-}
-
-/*
-** Allocate a new page from the database file.
-**
-** The new page is marked as dirty.  (In other words, sqlite3PagerWrite()
-** has already been called on the new page.)  The new page has also
-** been referenced and the calling routine is responsible for calling
-** sqlite3PagerUnref() on the new page when it is done.
-**
-** SQLITE_OK is returned on success.  Any other return value indicates
-** an error.  *ppPage is set to NULL in the event of an error.
-**
-** If the "nearby" parameter is not 0, then an effort is made to 
-** locate a page close to the page number "nearby".  This can be used in an
-** attempt to keep related pages close to each other in the database file,
-** which in turn can make database access faster.
-**
-** If the eMode parameter is BTALLOC_EXACT and the nearby page exists
-** anywhere on the free-list, then it is guaranteed to be returned.  If
-** eMode is BTALLOC_LT then the page returned will be less than or equal
-** to nearby if any such page exists.  If eMode is BTALLOC_ANY then there
-** are no restrictions on which page is returned.
-*/
-static int allocateBtreePage(
-  BtShared *pBt,         /* The btree */
-  MemPage **ppPage,      /* Store pointer to the allocated page here */
-  Pgno *pPgno,           /* Store the page number here */
-  Pgno nearby,           /* Search for a page near this one */
-  u8 eMode               /* BTALLOC_EXACT, BTALLOC_LT, or BTALLOC_ANY */
-){
-  MemPage *pPage1;
-  int rc;
-  u32 n;     /* Number of pages on the freelist */
-  u32 k;     /* Number of leaves on the trunk of the freelist */
-  MemPage *pTrunk = 0;
-  MemPage *pPrevTrunk = 0;
-  Pgno mxPage;     /* Total size of the database file */
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( eMode==BTALLOC_ANY || (nearby>0 && IfNotOmitAV(pBt->autoVacuum)) );
-  pPage1 = pBt->pPage1;
-  mxPage = btreePagecount(pBt);
-  /* EVIDENCE-OF: R-05119-02637 The 4-byte big-endian integer at offset 36
-  ** stores stores the total number of pages on the freelist. */
-  n = get4byte(&pPage1->aData[36]);
-  testcase( n==mxPage-1 );
-  if( n>=mxPage ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  if( n>0 ){
-    /* There are pages on the freelist.  Reuse one of those pages. */
-    Pgno iTrunk;
-    u8 searchList = 0; /* If the free-list must be searched for 'nearby' */
-    u32 nSearch = 0;   /* Count of the number of search attempts */
-    
-    /* If eMode==BTALLOC_EXACT and a query of the pointer-map
-    ** shows that the page 'nearby' is somewhere on the free-list, then
-    ** the entire-list will be searched for that page.
-    */
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( eMode==BTALLOC_EXACT ){
-      if( nearby<=mxPage ){
-        u8 eType;
-        assert( nearby>0 );
-        assert( pBt->autoVacuum );
-        rc = ptrmapGet(pBt, nearby, &eType, 0);
-        if( rc ) return rc;
-        if( eType==PTRMAP_FREEPAGE ){
-          searchList = 1;
-        }
-      }
-    }else if( eMode==BTALLOC_LE ){
-      searchList = 1;
-    }
-#endif
-
-    /* Decrement the free-list count by 1. Set iTrunk to the index of the
-    ** first free-list trunk page. iPrevTrunk is initially 1.
-    */
-    rc = sqlite3PagerWrite(pPage1->pDbPage);
-    if( rc ) return rc;
-    put4byte(&pPage1->aData[36], n-1);
-
-    /* The code within this loop is run only once if the 'searchList' variable
-    ** is not true. Otherwise, it runs once for each trunk-page on the
-    ** free-list until the page 'nearby' is located (eMode==BTALLOC_EXACT)
-    ** or until a page less than 'nearby' is located (eMode==BTALLOC_LT)
-    */
-    do {
-      pPrevTrunk = pTrunk;
-      if( pPrevTrunk ){
-        /* EVIDENCE-OF: R-01506-11053 The first integer on a freelist trunk page
-        ** is the page number of the next freelist trunk page in the list or
-        ** zero if this is the last freelist trunk page. */
-        iTrunk = get4byte(&pPrevTrunk->aData[0]);
-      }else{
-        /* EVIDENCE-OF: R-59841-13798 The 4-byte big-endian integer at offset 32
-        ** stores the page number of the first page of the freelist, or zero if
-        ** the freelist is empty. */
-        iTrunk = get4byte(&pPage1->aData[32]);
-      }
-      testcase( iTrunk==mxPage );
-      if( iTrunk>mxPage || nSearch++ > n ){
-        rc = SQLITE_CORRUPT_BKPT;
-      }else{
-        rc = btreeGetUnusedPage(pBt, iTrunk, &pTrunk, 0);
-      }
-      if( rc ){
-        pTrunk = 0;
-        goto end_allocate_page;
-      }
-      assert( pTrunk!=0 );
-      assert( pTrunk->aData!=0 );
-      /* EVIDENCE-OF: R-13523-04394 The second integer on a freelist trunk page
-      ** is the number of leaf page pointers to follow. */
-      k = get4byte(&pTrunk->aData[4]);
-      if( k==0 && !searchList ){
-        /* The trunk has no leaves and the list is not being searched. 
-        ** So extract the trunk page itself and use it as the newly 
-        ** allocated page */
-        assert( pPrevTrunk==0 );
-        rc = sqlite3PagerWrite(pTrunk->pDbPage);
-        if( rc ){
-          goto end_allocate_page;
-        }
-        *pPgno = iTrunk;
-        memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
-        *ppPage = pTrunk;
-        pTrunk = 0;
-        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
-      }else if( k>(u32)(pBt->usableSize/4 - 2) ){
-        /* Value of k is out of range.  Database corruption */
-        rc = SQLITE_CORRUPT_BKPT;
-        goto end_allocate_page;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      }else if( searchList 
-            && (nearby==iTrunk || (iTrunk<nearby && eMode==BTALLOC_LE)) 
-      ){
-        /* The list is being searched and this trunk page is the page
-        ** to allocate, regardless of whether it has leaves.
-        */
-        *pPgno = iTrunk;
-        *ppPage = pTrunk;
-        searchList = 0;
-        rc = sqlite3PagerWrite(pTrunk->pDbPage);
-        if( rc ){
-          goto end_allocate_page;
-        }
-        if( k==0 ){
-          if( !pPrevTrunk ){
-            memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
-          }else{
-            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
-            if( rc!=SQLITE_OK ){
-              goto end_allocate_page;
-            }
-            memcpy(&pPrevTrunk->aData[0], &pTrunk->aData[0], 4);
-          }
-        }else{
-          /* The trunk page is required by the caller but it contains 
-          ** pointers to free-list leaves. The first leaf becomes a trunk
-          ** page in this case.
-          */
-          MemPage *pNewTrunk;
-          Pgno iNewTrunk = get4byte(&pTrunk->aData[8]);
-          if( iNewTrunk>mxPage ){ 
-            rc = SQLITE_CORRUPT_BKPT;
-            goto end_allocate_page;
-          }
-          testcase( iNewTrunk==mxPage );
-          rc = btreeGetUnusedPage(pBt, iNewTrunk, &pNewTrunk, 0);
-          if( rc!=SQLITE_OK ){
-            goto end_allocate_page;
-          }
-          rc = sqlite3PagerWrite(pNewTrunk->pDbPage);
-          if( rc!=SQLITE_OK ){
-            releasePage(pNewTrunk);
-            goto end_allocate_page;
-          }
-          memcpy(&pNewTrunk->aData[0], &pTrunk->aData[0], 4);
-          put4byte(&pNewTrunk->aData[4], k-1);
-          memcpy(&pNewTrunk->aData[8], &pTrunk->aData[12], (k-1)*4);
-          releasePage(pNewTrunk);
-          if( !pPrevTrunk ){
-            assert( sqlite3PagerIswriteable(pPage1->pDbPage) );
-            put4byte(&pPage1->aData[32], iNewTrunk);
-          }else{
-            rc = sqlite3PagerWrite(pPrevTrunk->pDbPage);
-            if( rc ){
-              goto end_allocate_page;
-            }
-            put4byte(&pPrevTrunk->aData[0], iNewTrunk);
-          }
-        }
-        pTrunk = 0;
-        TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
-#endif
-      }else if( k>0 ){
-        /* Extract a leaf from the trunk */
-        u32 closest;
-        Pgno iPage;
-        unsigned char *aData = pTrunk->aData;
-        if( nearby>0 ){
-          u32 i;
-          closest = 0;
-          if( eMode==BTALLOC_LE ){
-            for(i=0; i<k; i++){
-              iPage = get4byte(&aData[8+i*4]);
-              if( iPage<=nearby ){
-                closest = i;
-                break;
-              }
-            }
-          }else{
-            int dist;
-            dist = sqlite3AbsInt32(get4byte(&aData[8]) - nearby);
-            for(i=1; i<k; i++){
-              int d2 = sqlite3AbsInt32(get4byte(&aData[8+i*4]) - nearby);
-              if( d2<dist ){
-                closest = i;
-                dist = d2;
-              }
-            }
-          }
-        }else{
-          closest = 0;
-        }
-
-        iPage = get4byte(&aData[8+closest*4]);
-        testcase( iPage==mxPage );
-        if( iPage>mxPage ){
-          rc = SQLITE_CORRUPT_BKPT;
-          goto end_allocate_page;
-        }
-        testcase( iPage==mxPage );
-        if( !searchList 
-         || (iPage==nearby || (iPage<nearby && eMode==BTALLOC_LE)) 
-        ){
-          int noContent;
-          *pPgno = iPage;
-          TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
-                 ": %d more free pages\n",
-                 *pPgno, closest+1, k, pTrunk->pgno, n-1));
-          rc = sqlite3PagerWrite(pTrunk->pDbPage);
-          if( rc ) goto end_allocate_page;
-          if( closest<k-1 ){
-            memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
-          }
-          put4byte(&aData[4], k-1);
-          noContent = !btreeGetHasContent(pBt, *pPgno)? PAGER_GET_NOCONTENT : 0;
-          rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, noContent);
-          if( rc==SQLITE_OK ){
-            rc = sqlite3PagerWrite((*ppPage)->pDbPage);
-            if( rc!=SQLITE_OK ){
-              releasePage(*ppPage);
-              *ppPage = 0;
-            }
-          }
-          searchList = 0;
-        }
-      }
-      releasePage(pPrevTrunk);
-      pPrevTrunk = 0;
-    }while( searchList );
-  }else{
-    /* There are no pages on the freelist, so append a new page to the
-    ** database image.
-    **
-    ** Normally, new pages allocated by this block can be requested from the
-    ** pager layer with the 'no-content' flag set. This prevents the pager
-    ** from trying to read the pages content from disk. However, if the
-    ** current transaction has already run one or more incremental-vacuum
-    ** steps, then the page we are about to allocate may contain content
-    ** that is required in the event of a rollback. In this case, do
-    ** not set the no-content flag. This causes the pager to load and journal
-    ** the current page content before overwriting it.
-    **
-    ** Note that the pager will not actually attempt to load or journal 
-    ** content for any page that really does lie past the end of the database
-    ** file on disk. So the effects of disabling the no-content optimization
-    ** here are confined to those pages that lie between the end of the
-    ** database image and the end of the database file.
-    */
-    int bNoContent = (0==IfNotOmitAV(pBt->bDoTruncate))? PAGER_GET_NOCONTENT:0;
-
-    rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-    if( rc ) return rc;
-    pBt->nPage++;
-    if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ) pBt->nPage++;
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum && PTRMAP_ISPAGE(pBt, pBt->nPage) ){
-      /* If *pPgno refers to a pointer-map page, allocate two new pages
-      ** at the end of the file instead of one. The first allocated page
-      ** becomes a new pointer-map page, the second is used by the caller.
-      */
-      MemPage *pPg = 0;
-      TRACE(("ALLOCATE: %d from end of file (pointer-map page)\n", pBt->nPage));
-      assert( pBt->nPage!=PENDING_BYTE_PAGE(pBt) );
-      rc = btreeGetUnusedPage(pBt, pBt->nPage, &pPg, bNoContent);
-      if( rc==SQLITE_OK ){
-        rc = sqlite3PagerWrite(pPg->pDbPage);
-        releasePage(pPg);
-      }
-      if( rc ) return rc;
-      pBt->nPage++;
-      if( pBt->nPage==PENDING_BYTE_PAGE(pBt) ){ pBt->nPage++; }
-    }
-#endif
-    put4byte(28 + (u8*)pBt->pPage1->aData, pBt->nPage);
-    *pPgno = pBt->nPage;
-
-    assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-    rc = btreeGetUnusedPage(pBt, *pPgno, ppPage, bNoContent);
-    if( rc ) return rc;
-    rc = sqlite3PagerWrite((*ppPage)->pDbPage);
-    if( rc!=SQLITE_OK ){
-      releasePage(*ppPage);
-      *ppPage = 0;
-    }
-    TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
-  }
-
-  assert( *pPgno!=PENDING_BYTE_PAGE(pBt) );
-
-end_allocate_page:
-  releasePage(pTrunk);
-  releasePage(pPrevTrunk);
-  assert( rc!=SQLITE_OK || sqlite3PagerPageRefcount((*ppPage)->pDbPage)<=1 );
-  assert( rc!=SQLITE_OK || (*ppPage)->isInit==0 );
-  return rc;
-}
-
-/*
-** This function is used to add page iPage to the database file free-list. 
-** It is assumed that the page is not already a part of the free-list.
-**
-** The value passed as the second argument to this function is optional.
-** If the caller happens to have a pointer to the MemPage object 
-** corresponding to page iPage handy, it may pass it as the second value. 
-** Otherwise, it may pass NULL.
-**
-** If a pointer to a MemPage object is passed as the second argument,
-** its reference count is not altered by this function.
-*/
-static int freePage2(BtShared *pBt, MemPage *pMemPage, Pgno iPage){
-  MemPage *pTrunk = 0;                /* Free-list trunk page */
-  Pgno iTrunk = 0;                    /* Page number of free-list trunk page */ 
-  MemPage *pPage1 = pBt->pPage1;      /* Local reference to page 1 */
-  MemPage *pPage;                     /* Page being freed. May be NULL. */
-  int rc;                             /* Return Code */
-  int nFree;                          /* Initial number of pages on free-list */
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( CORRUPT_DB || iPage>1 );
-  assert( !pMemPage || pMemPage->pgno==iPage );
-
-  if( iPage<2 ) return SQLITE_CORRUPT_BKPT;
-  if( pMemPage ){
-    pPage = pMemPage;
-    sqlite3PagerRef(pPage->pDbPage);
-  }else{
-    pPage = btreePageLookup(pBt, iPage);
-  }
-
-  /* Increment the free page count on pPage1 */
-  rc = sqlite3PagerWrite(pPage1->pDbPage);
-  if( rc ) goto freepage_out;
-  nFree = get4byte(&pPage1->aData[36]);
-  put4byte(&pPage1->aData[36], nFree+1);
-
-  if( pBt->btsFlags & BTS_SECURE_DELETE ){
-    /* If the secure_delete option is enabled, then
-    ** always fully overwrite deleted information with zeros.
-    */
-    if( (!pPage && ((rc = btreeGetPage(pBt, iPage, &pPage, 0))!=0) )
-     ||            ((rc = sqlite3PagerWrite(pPage->pDbPage))!=0)
-    ){
-      goto freepage_out;
-    }
-    memset(pPage->aData, 0, pPage->pBt->pageSize);
-  }
-
-  /* If the database supports auto-vacuum, write an entry in the pointer-map
-  ** to indicate that the page is free.
-  */
-  if( ISAUTOVACUUM ){
-    ptrmapPut(pBt, iPage, PTRMAP_FREEPAGE, 0, &rc);
-    if( rc ) goto freepage_out;
-  }
-
-  /* Now manipulate the actual database free-list structure. There are two
-  ** possibilities. If the free-list is currently empty, or if the first
-  ** trunk page in the free-list is full, then this page will become a
-  ** new free-list trunk page. Otherwise, it will become a leaf of the
-  ** first trunk page in the current free-list. This block tests if it
-  ** is possible to add the page as a new free-list leaf.
-  */
-  if( nFree!=0 ){
-    u32 nLeaf;                /* Initial number of leaf cells on trunk page */
-
-    iTrunk = get4byte(&pPage1->aData[32]);
-    rc = btreeGetPage(pBt, iTrunk, &pTrunk, 0);
-    if( rc!=SQLITE_OK ){
-      goto freepage_out;
-    }
-
-    nLeaf = get4byte(&pTrunk->aData[4]);
-    assert( pBt->usableSize>32 );
-    if( nLeaf > (u32)pBt->usableSize/4 - 2 ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto freepage_out;
-    }
-    if( nLeaf < (u32)pBt->usableSize/4 - 8 ){
-      /* In this case there is room on the trunk page to insert the page
-      ** being freed as a new leaf.
-      **
-      ** Note that the trunk page is not really full until it contains
-      ** usableSize/4 - 2 entries, not usableSize/4 - 8 entries as we have
-      ** coded.  But due to a coding error in versions of SQLite prior to
-      ** 3.6.0, databases with freelist trunk pages holding more than
-      ** usableSize/4 - 8 entries will be reported as corrupt.  In order
-      ** to maintain backwards compatibility with older versions of SQLite,
-      ** we will continue to restrict the number of entries to usableSize/4 - 8
-      ** for now.  At some point in the future (once everyone has upgraded
-      ** to 3.6.0 or later) we should consider fixing the conditional above
-      ** to read "usableSize/4-2" instead of "usableSize/4-8".
-      **
-      ** EVIDENCE-OF: R-19920-11576 However, newer versions of SQLite still
-      ** avoid using the last six entries in the freelist trunk page array in
-      ** order that database files created by newer versions of SQLite can be
-      ** read by older versions of SQLite.
-      */
-      rc = sqlite3PagerWrite(pTrunk->pDbPage);
-      if( rc==SQLITE_OK ){
-        put4byte(&pTrunk->aData[4], nLeaf+1);
-        put4byte(&pTrunk->aData[8+nLeaf*4], iPage);
-        if( pPage && (pBt->btsFlags & BTS_SECURE_DELETE)==0 ){
-          sqlite3PagerDontWrite(pPage->pDbPage);
-        }
-        rc = btreeSetHasContent(pBt, iPage);
-      }
-      TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
-      goto freepage_out;
-    }
-  }
-
-  /* If control flows to this point, then it was not possible to add the
-  ** the page being freed as a leaf page of the first trunk in the free-list.
-  ** Possibly because the free-list is empty, or possibly because the 
-  ** first trunk in the free-list is full. Either way, the page being freed
-  ** will become the new first trunk page in the free-list.
-  */
-  if( pPage==0 && SQLITE_OK!=(rc = btreeGetPage(pBt, iPage, &pPage, 0)) ){
-    goto freepage_out;
-  }
-  rc = sqlite3PagerWrite(pPage->pDbPage);
-  if( rc!=SQLITE_OK ){
-    goto freepage_out;
-  }
-  put4byte(pPage->aData, iTrunk);
-  put4byte(&pPage->aData[4], 0);
-  put4byte(&pPage1->aData[32], iPage);
-  TRACE(("FREE-PAGE: %d new trunk page replacing %d\n", pPage->pgno, iTrunk));
-
-freepage_out:
-  if( pPage ){
-    pPage->isInit = 0;
-  }
-  releasePage(pPage);
-  releasePage(pTrunk);
-  return rc;
-}
-static void freePage(MemPage *pPage, int *pRC){
-  if( (*pRC)==SQLITE_OK ){
-    *pRC = freePage2(pPage->pBt, pPage, pPage->pgno);
-  }
-}
-
-/*
-** Free any overflow pages associated with the given Cell.  Write the
-** local Cell size (the number of bytes on the original page, omitting
-** overflow) into *pnSize.
-*/
-static int clearCell(
-  MemPage *pPage,          /* The page that contains the Cell */
-  unsigned char *pCell,    /* First byte of the Cell */
-  u16 *pnSize              /* Write the size of the Cell here */
-){
-  BtShared *pBt = pPage->pBt;
-  CellInfo info;
-  Pgno ovflPgno;
-  int rc;
-  int nOvfl;
-  u32 ovflPageSize;
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  pPage->xParseCell(pPage, pCell, &info);
-  *pnSize = info.nSize;
-  if( info.iOverflow==0 ){
-    return SQLITE_OK;  /* No overflow pages. Return without doing anything */
-  }
-  if( pCell+info.iOverflow+3 > pPage->aData+pPage->maskPage ){
-    return SQLITE_CORRUPT_BKPT;  /* Cell extends past end of page */
-  }
-  ovflPgno = get4byte(&pCell[info.iOverflow]);
-  assert( pBt->usableSize > 4 );
-  ovflPageSize = pBt->usableSize - 4;
-  nOvfl = (info.nPayload - info.nLocal + ovflPageSize - 1)/ovflPageSize;
-  assert( nOvfl>0 || 
-    (CORRUPT_DB && (info.nPayload + ovflPageSize)<ovflPageSize)
-  );
-  while( nOvfl-- ){
-    Pgno iNext = 0;
-    MemPage *pOvfl = 0;
-    if( ovflPgno<2 || ovflPgno>btreePagecount(pBt) ){
-      /* 0 is not a legal page number and page 1 cannot be an 
-      ** overflow page. Therefore if ovflPgno<2 or past the end of the 
-      ** file the database must be corrupt. */
-      return SQLITE_CORRUPT_BKPT;
-    }
-    if( nOvfl ){
-      rc = getOverflowPage(pBt, ovflPgno, &pOvfl, &iNext);
-      if( rc ) return rc;
-    }
-
-    if( ( pOvfl || ((pOvfl = btreePageLookup(pBt, ovflPgno))!=0) )
-     && sqlite3PagerPageRefcount(pOvfl->pDbPage)!=1
-    ){
-      /* There is no reason any cursor should have an outstanding reference 
-      ** to an overflow page belonging to a cell that is being deleted/updated.
-      ** So if there exists more than one reference to this page, then it 
-      ** must not really be an overflow page and the database must be corrupt. 
-      ** It is helpful to detect this before calling freePage2(), as 
-      ** freePage2() may zero the page contents if secure-delete mode is
-      ** enabled. If this 'overflow' page happens to be a page that the
-      ** caller is iterating through or using in some other way, this
-      ** can be problematic.
-      */
-      rc = SQLITE_CORRUPT_BKPT;
-    }else{
-      rc = freePage2(pBt, pOvfl, ovflPgno);
-    }
-
-    if( pOvfl ){
-      sqlite3PagerUnref(pOvfl->pDbPage);
-    }
-    if( rc ) return rc;
-    ovflPgno = iNext;
-  }
-  return SQLITE_OK;
-}
-
-/*
-** Create the byte sequence used to represent a cell on page pPage
-** and write that byte sequence into pCell[].  Overflow pages are
-** allocated and filled in as necessary.  The calling procedure
-** is responsible for making sure sufficient space has been allocated
-** for pCell[].
-**
-** Note that pCell does not necessary need to point to the pPage->aData
-** area.  pCell might point to some temporary storage.  The cell will
-** be constructed in this temporary area then copied into pPage->aData
-** later.
-*/
-static int fillInCell(
-  MemPage *pPage,                /* The page that contains the cell */
-  unsigned char *pCell,          /* Complete text of the cell */
-  const void *pKey, i64 nKey,    /* The key */
-  const void *pData,int nData,   /* The data */
-  int nZero,                     /* Extra zero bytes to append to pData */
-  int *pnSize                    /* Write cell size here */
-){
-  int nPayload;
-  const u8 *pSrc;
-  int nSrc, n, rc;
-  int spaceLeft;
-  MemPage *pOvfl = 0;
-  MemPage *pToRelease = 0;
-  unsigned char *pPrior;
-  unsigned char *pPayload;
-  BtShared *pBt = pPage->pBt;
-  Pgno pgnoOvfl = 0;
-  int nHeader;
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-
-  /* pPage is not necessarily writeable since pCell might be auxiliary
-  ** buffer space that is separate from the pPage buffer area */
-  assert( pCell<pPage->aData || pCell>=&pPage->aData[pBt->pageSize]
-            || sqlite3PagerIswriteable(pPage->pDbPage) );
-
-  /* Fill in the header. */
-  nHeader = pPage->childPtrSize;
-  nPayload = nData + nZero;
-  if( pPage->intKeyLeaf ){
-    nHeader += putVarint32(&pCell[nHeader], nPayload);
-  }else{
-    assert( nData==0 );
-    assert( nZero==0 );
-  }
-  nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
-  
-  /* Fill in the payload size */
-  if( pPage->intKey ){
-    pSrc = pData;
-    nSrc = nData;
-    nData = 0;
-  }else{ 
-    assert( nKey<=0x7fffffff && pKey!=0 );
-    nPayload = (int)nKey;
-    pSrc = pKey;
-    nSrc = (int)nKey;
-  }
-  if( nPayload<=pPage->maxLocal ){
-    n = nHeader + nPayload;
-    testcase( n==3 );
-    testcase( n==4 );
-    if( n<4 ) n = 4;
-    *pnSize = n;
-    spaceLeft = nPayload;
-    pPrior = pCell;
-  }else{
-    int mn = pPage->minLocal;
-    n = mn + (nPayload - mn) % (pPage->pBt->usableSize - 4);
-    testcase( n==pPage->maxLocal );
-    testcase( n==pPage->maxLocal+1 );
-    if( n > pPage->maxLocal ) n = mn;
-    spaceLeft = n;
-    *pnSize = n + nHeader + 4;
-    pPrior = &pCell[nHeader+n];
-  }
-  pPayload = &pCell[nHeader];
-
-  /* At this point variables should be set as follows:
-  **
-  **   nPayload           Total payload size in bytes
-  **   pPayload           Begin writing payload here
-  **   spaceLeft          Space available at pPayload.  If nPayload>spaceLeft,
-  **                      that means content must spill into overflow pages.
-  **   *pnSize            Size of the local cell (not counting overflow pages)
-  **   pPrior             Where to write the pgno of the first overflow page
-  **
-  ** Use a call to btreeParseCellPtr() to verify that the values above
-  ** were computed correctly.
-  */
-#if SQLITE_DEBUG
-  {
-    CellInfo info;
-    pPage->xParseCell(pPage, pCell, &info);
-    assert( nHeader=(int)(info.pPayload - pCell) );
-    assert( info.nKey==nKey );
-    assert( *pnSize == info.nSize );
-    assert( spaceLeft == info.nLocal );
-    assert( pPrior == &pCell[info.iOverflow] );
-  }
-#endif
-
-  /* Write the payload into the local Cell and any extra into overflow pages */
-  while( nPayload>0 ){
-    if( spaceLeft==0 ){
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      Pgno pgnoPtrmap = pgnoOvfl; /* Overflow page pointer-map entry page */
-      if( pBt->autoVacuum ){
-        do{
-          pgnoOvfl++;
-        } while( 
-          PTRMAP_ISPAGE(pBt, pgnoOvfl) || pgnoOvfl==PENDING_BYTE_PAGE(pBt) 
-        );
-      }
-#endif
-      rc = allocateBtreePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl, 0);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      /* If the database supports auto-vacuum, and the second or subsequent
-      ** overflow page is being allocated, add an entry to the pointer-map
-      ** for that page now. 
-      **
-      ** If this is the first overflow page, then write a partial entry 
-      ** to the pointer-map. If we write nothing to this pointer-map slot,
-      ** then the optimistic overflow chain processing in clearCell()
-      ** may misinterpret the uninitialized values and delete the
-      ** wrong pages from the database.
-      */
-      if( pBt->autoVacuum && rc==SQLITE_OK ){
-        u8 eType = (pgnoPtrmap?PTRMAP_OVERFLOW2:PTRMAP_OVERFLOW1);
-        ptrmapPut(pBt, pgnoOvfl, eType, pgnoPtrmap, &rc);
-        if( rc ){
-          releasePage(pOvfl);
-        }
-      }
-#endif
-      if( rc ){
-        releasePage(pToRelease);
-        return rc;
-      }
-
-      /* If pToRelease is not zero than pPrior points into the data area
-      ** of pToRelease.  Make sure pToRelease is still writeable. */
-      assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
-
-      /* If pPrior is part of the data area of pPage, then make sure pPage
-      ** is still writeable */
-      assert( pPrior<pPage->aData || pPrior>=&pPage->aData[pBt->pageSize]
-            || sqlite3PagerIswriteable(pPage->pDbPage) );
-
-      put4byte(pPrior, pgnoOvfl);
-      releasePage(pToRelease);
-      pToRelease = pOvfl;
-      pPrior = pOvfl->aData;
-      put4byte(pPrior, 0);
-      pPayload = &pOvfl->aData[4];
-      spaceLeft = pBt->usableSize - 4;
-    }
-    n = nPayload;
-    if( n>spaceLeft ) n = spaceLeft;
-
-    /* If pToRelease is not zero than pPayload points into the data area
-    ** of pToRelease.  Make sure pToRelease is still writeable. */
-    assert( pToRelease==0 || sqlite3PagerIswriteable(pToRelease->pDbPage) );
-
-    /* If pPayload is part of the data area of pPage, then make sure pPage
-    ** is still writeable */
-    assert( pPayload<pPage->aData || pPayload>=&pPage->aData[pBt->pageSize]
-            || sqlite3PagerIswriteable(pPage->pDbPage) );
-
-    if( nSrc>0 ){
-      if( n>nSrc ) n = nSrc;
-      assert( pSrc );
-      memcpy(pPayload, pSrc, n);
-    }else{
-      memset(pPayload, 0, n);
-    }
-    nPayload -= n;
-    pPayload += n;
-    pSrc += n;
-    nSrc -= n;
-    spaceLeft -= n;
-    if( nSrc==0 ){
-      nSrc = nData;
-      pSrc = pData;
-    }
-  }
-  releasePage(pToRelease);
-  return SQLITE_OK;
-}
-
-/*
-** Remove the i-th cell from pPage.  This routine effects pPage only.
-** The cell content is not freed or deallocated.  It is assumed that
-** the cell content has been copied someplace else.  This routine just
-** removes the reference to the cell from pPage.
-**
-** "sz" must be the number of bytes in the cell.
-*/
-static void dropCell(MemPage *pPage, int idx, int sz, int *pRC){
-  u32 pc;         /* Offset to cell content of cell being deleted */
-  u8 *data;       /* pPage->aData */
-  u8 *ptr;        /* Used to move bytes around within data[] */
-  int rc;         /* The return code */
-  int hdr;        /* Beginning of the header.  0 most pages.  100 page 1 */
-
-  if( *pRC ) return;
-
-  assert( idx>=0 && idx<pPage->nCell );
-  assert( CORRUPT_DB || sz==cellSize(pPage, idx) );
-  assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  data = pPage->aData;
-  ptr = &pPage->aCellIdx[2*idx];
-  pc = get2byte(ptr);
-  hdr = pPage->hdrOffset;
-  testcase( pc==get2byte(&data[hdr+5]) );
-  testcase( pc+sz==pPage->pBt->usableSize );
-  if( pc < (u32)get2byte(&data[hdr+5]) || pc+sz > pPage->pBt->usableSize ){
-    *pRC = SQLITE_CORRUPT_BKPT;
-    return;
-  }
-  rc = freeSpace(pPage, pc, sz);
-  if( rc ){
-    *pRC = rc;
-    return;
-  }
-  pPage->nCell--;
-  if( pPage->nCell==0 ){
-    memset(&data[hdr+1], 0, 4);
-    data[hdr+7] = 0;
-    put2byte(&data[hdr+5], pPage->pBt->usableSize);
-    pPage->nFree = pPage->pBt->usableSize - pPage->hdrOffset
-                       - pPage->childPtrSize - 8;
-  }else{
-    memmove(ptr, ptr+2, 2*(pPage->nCell - idx));
-    put2byte(&data[hdr+3], pPage->nCell);
-    pPage->nFree += 2;
-  }
-}
-
-/*
-** Insert a new cell on pPage at cell index "i".  pCell points to the
-** content of the cell.
-**
-** If the cell content will fit on the page, then put it there.  If it
-** will not fit, then make a copy of the cell content into pTemp if
-** pTemp is not null.  Regardless of pTemp, allocate a new entry
-** in pPage->apOvfl[] and make it point to the cell content (either
-** in pTemp or the original pCell) and also record its index. 
-** Allocating a new entry in pPage->aCell[] implies that 
-** pPage->nOverflow is incremented.
-*/
-static void insertCell(
-  MemPage *pPage,   /* Page into which we are copying */
-  int i,            /* New cell becomes the i-th cell of the page */
-  u8 *pCell,        /* Content of the new cell */
-  int sz,           /* Bytes of content in pCell */
-  u8 *pTemp,        /* Temp storage space for pCell, if needed */
-  Pgno iChild,      /* If non-zero, replace first 4 bytes with this value */
-  int *pRC          /* Read and write return code from here */
-){
-  int idx = 0;      /* Where to write new cell content in data[] */
-  int j;            /* Loop counter */
-  u8 *data;         /* The content of the whole page */
-  u8 *pIns;         /* The point in pPage->aCellIdx[] where no cell inserted */
-
-  if( *pRC ) return;
-
-  assert( i>=0 && i<=pPage->nCell+pPage->nOverflow );
-  assert( MX_CELL(pPage->pBt)<=10921 );
-  assert( pPage->nCell<=MX_CELL(pPage->pBt) || CORRUPT_DB );
-  assert( pPage->nOverflow<=ArraySize(pPage->apOvfl) );
-  assert( ArraySize(pPage->apOvfl)==ArraySize(pPage->aiOvfl) );
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  /* The cell should normally be sized correctly.  However, when moving a
-  ** malformed cell from a leaf page to an interior page, if the cell size
-  ** wanted to be less than 4 but got rounded up to 4 on the leaf, then size
-  ** might be less than 8 (leaf-size + pointer) on the interior node.  Hence
-  ** the term after the || in the following assert(). */
-  assert( sz==pPage->xCellSize(pPage, pCell) || (sz==8 && iChild>0) );
-  if( pPage->nOverflow || sz+2>pPage->nFree ){
-    if( pTemp ){
-      memcpy(pTemp, pCell, sz);
-      pCell = pTemp;
-    }
-    if( iChild ){
-      put4byte(pCell, iChild);
-    }
-    j = pPage->nOverflow++;
-    assert( j<(int)(sizeof(pPage->apOvfl)/sizeof(pPage->apOvfl[0])) );
-    pPage->apOvfl[j] = pCell;
-    pPage->aiOvfl[j] = (u16)i;
-
-    /* When multiple overflows occur, they are always sequential and in
-    ** sorted order.  This invariants arise because multiple overflows can
-    ** only occur when inserting divider cells into the parent page during
-    ** balancing, and the dividers are adjacent and sorted.
-    */
-    assert( j==0 || pPage->aiOvfl[j-1]<(u16)i ); /* Overflows in sorted order */
-    assert( j==0 || i==pPage->aiOvfl[j-1]+1 );   /* Overflows are sequential */
-  }else{
-    int rc = sqlite3PagerWrite(pPage->pDbPage);
-    if( rc!=SQLITE_OK ){
-      *pRC = rc;
-      return;
-    }
-    assert( sqlite3PagerIswriteable(pPage->pDbPage) );
-    data = pPage->aData;
-    assert( &data[pPage->cellOffset]==pPage->aCellIdx );
-    rc = allocateSpace(pPage, sz, &idx);
-    if( rc ){ *pRC = rc; return; }
-    /* The allocateSpace() routine guarantees the following properties
-    ** if it returns successfully */
-    assert( idx >= 0 );
-    assert( idx >= pPage->cellOffset+2*pPage->nCell+2 || CORRUPT_DB );
-    assert( idx+sz <= (int)pPage->pBt->usableSize );
-    pPage->nFree -= (u16)(2 + sz);
-    memcpy(&data[idx], pCell, sz);
-    if( iChild ){
-      put4byte(&data[idx], iChild);
-    }
-    pIns = pPage->aCellIdx + i*2;
-    memmove(pIns+2, pIns, 2*(pPage->nCell - i));
-    put2byte(pIns, idx);
-    pPage->nCell++;
-    /* increment the cell count */
-    if( (++data[pPage->hdrOffset+4])==0 ) data[pPage->hdrOffset+3]++;
-    assert( get2byte(&data[pPage->hdrOffset+3])==pPage->nCell );
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pPage->pBt->autoVacuum ){
-      /* The cell may contain a pointer to an overflow page. If so, write
-      ** the entry for the overflow page into the pointer map.
-      */
-      ptrmapPutOvflPtr(pPage, pCell, pRC);
-    }
-#endif
-  }
-}
-
-/*
-** A CellArray object contains a cache of pointers and sizes for a
-** consecutive sequence of cells that might be held multiple pages.
-*/
-typedef struct CellArray CellArray;
-struct CellArray {
-  int nCell;              /* Number of cells in apCell[] */
-  MemPage *pRef;          /* Reference page */
-  u8 **apCell;            /* All cells begin balanced */
-  u16 *szCell;            /* Local size of all cells in apCell[] */
-};
-
-/*
-** Make sure the cell sizes at idx, idx+1, ..., idx+N-1 have been
-** computed.
-*/
-static void populateCellCache(CellArray *p, int idx, int N){
-  assert( idx>=0 && idx+N<=p->nCell );
-  while( N>0 ){
-    assert( p->apCell[idx]!=0 );
-    if( p->szCell[idx]==0 ){
-      p->szCell[idx] = p->pRef->xCellSize(p->pRef, p->apCell[idx]);
-    }else{
-      assert( CORRUPT_DB ||
-              p->szCell[idx]==p->pRef->xCellSize(p->pRef, p->apCell[idx]) );
-    }
-    idx++;
-    N--;
-  }
-}
-
-/*
-** Return the size of the Nth element of the cell array
-*/
-static SQLITE_NOINLINE u16 computeCellSize(CellArray *p, int N){
-  assert( N>=0 && N<p->nCell );
-  assert( p->szCell[N]==0 );
-  p->szCell[N] = p->pRef->xCellSize(p->pRef, p->apCell[N]);
-  return p->szCell[N];
-}
-static u16 cachedCellSize(CellArray *p, int N){
-  assert( N>=0 && N<p->nCell );
-  if( p->szCell[N] ) return p->szCell[N];
-  return computeCellSize(p, N);
-}
-
-/*
-** Array apCell[] contains pointers to nCell b-tree page cells. The 
-** szCell[] array contains the size in bytes of each cell. This function
-** replaces the current contents of page pPg with the contents of the cell
-** array.
-**
-** Some of the cells in apCell[] may currently be stored in pPg. This
-** function works around problems caused by this by making a copy of any 
-** such cells before overwriting the page data.
-**
-** The MemPage.nFree field is invalidated by this function. It is the 
-** responsibility of the caller to set it correctly.
-*/
-static int rebuildPage(
-  MemPage *pPg,                   /* Edit this page */
-  int nCell,                      /* Final number of cells on page */
-  u8 **apCell,                    /* Array of cells */
-  u16 *szCell                     /* Array of cell sizes */
-){
-  const int hdr = pPg->hdrOffset;          /* Offset of header on pPg */
-  u8 * const aData = pPg->aData;           /* Pointer to data for pPg */
-  const int usableSize = pPg->pBt->usableSize;
-  u8 * const pEnd = &aData[usableSize];
-  int i;
-  u8 *pCellptr = pPg->aCellIdx;
-  u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
-  u8 *pData;
-
-  i = get2byte(&aData[hdr+5]);
-  memcpy(&pTmp[i], &aData[i], usableSize - i);
-
-  pData = pEnd;
-  for(i=0; i<nCell; i++){
-    u8 *pCell = apCell[i];
-    if( pCell>aData && pCell<pEnd ){
-      pCell = &pTmp[pCell - aData];
-    }
-    pData -= szCell[i];
-    put2byte(pCellptr, (pData - aData));
-    pCellptr += 2;
-    if( pData < pCellptr ) return SQLITE_CORRUPT_BKPT;
-    memcpy(pData, pCell, szCell[i]);
-    assert( szCell[i]==pPg->xCellSize(pPg, pCell) || CORRUPT_DB );
-    testcase( szCell[i]!=pPg->xCellSize(pPg,pCell) );
-  }
-
-  /* The pPg->nFree field is now set incorrectly. The caller will fix it. */
-  pPg->nCell = nCell;
-  pPg->nOverflow = 0;
-
-  put2byte(&aData[hdr+1], 0);
-  put2byte(&aData[hdr+3], pPg->nCell);
-  put2byte(&aData[hdr+5], pData - aData);
-  aData[hdr+7] = 0x00;
-  return SQLITE_OK;
-}
-
-/*
-** Array apCell[] contains nCell pointers to b-tree cells. Array szCell
-** contains the size in bytes of each such cell. This function attempts to 
-** add the cells stored in the array to page pPg. If it cannot (because 
-** the page needs to be defragmented before the cells will fit), non-zero
-** is returned. Otherwise, if the cells are added successfully, zero is
-** returned.
-**
-** Argument pCellptr points to the first entry in the cell-pointer array
-** (part of page pPg) to populate. After cell apCell[0] is written to the
-** page body, a 16-bit offset is written to pCellptr. And so on, for each
-** cell in the array. It is the responsibility of the caller to ensure
-** that it is safe to overwrite this part of the cell-pointer array.
-**
-** When this function is called, *ppData points to the start of the 
-** content area on page pPg. If the size of the content area is extended,
-** *ppData is updated to point to the new start of the content area
-** before returning.
-**
-** Finally, argument pBegin points to the byte immediately following the
-** end of the space required by this page for the cell-pointer area (for
-** all cells - not just those inserted by the current call). If the content
-** area must be extended to before this point in order to accomodate all
-** cells in apCell[], then the cells do not fit and non-zero is returned.
-*/
-static int pageInsertArray(
-  MemPage *pPg,                   /* Page to add cells to */
-  u8 *pBegin,                     /* End of cell-pointer array */
-  u8 **ppData,                    /* IN/OUT: Page content -area pointer */
-  u8 *pCellptr,                   /* Pointer to cell-pointer area */
-  int iFirst,                     /* Index of first cell to add */
-  int nCell,                      /* Number of cells to add to pPg */
-  CellArray *pCArray              /* Array of cells */
-){
-  int i;
-  u8 *aData = pPg->aData;
-  u8 *pData = *ppData;
-  int iEnd = iFirst + nCell;
-  assert( CORRUPT_DB || pPg->hdrOffset==0 );    /* Never called on page 1 */
-  for(i=iFirst; i<iEnd; i++){
-    int sz, rc;
-    u8 *pSlot;
-    sz = cachedCellSize(pCArray, i);
-    if( (aData[1]==0 && aData[2]==0) || (pSlot = pageFindSlot(pPg,sz,&rc))==0 ){
-      pData -= sz;
-      if( pData<pBegin ) return 1;
-      pSlot = pData;
-    }
-    /* pSlot and pCArray->apCell[i] will never overlap on a well-formed
-    ** database.  But they might for a corrupt database.  Hence use memmove()
-    ** since memcpy() sends SIGABORT with overlapping buffers on OpenBSD */
-    assert( (pSlot+sz)<=pCArray->apCell[i]
-         || pSlot>=(pCArray->apCell[i]+sz)
-         || CORRUPT_DB );
-    memmove(pSlot, pCArray->apCell[i], sz);
-    put2byte(pCellptr, (pSlot - aData));
-    pCellptr += 2;
-  }
-  *ppData = pData;
-  return 0;
-}
-
-/*
-** Array apCell[] contains nCell pointers to b-tree cells. Array szCell 
-** contains the size in bytes of each such cell. This function adds the
-** space associated with each cell in the array that is currently stored 
-** within the body of pPg to the pPg free-list. The cell-pointers and other
-** fields of the page are not updated.
-**
-** This function returns the total number of cells added to the free-list.
-*/
-static int pageFreeArray(
-  MemPage *pPg,                   /* Page to edit */
-  int iFirst,                     /* First cell to delete */
-  int nCell,                      /* Cells to delete */
-  CellArray *pCArray              /* Array of cells */
-){
-  u8 * const aData = pPg->aData;
-  u8 * const pEnd = &aData[pPg->pBt->usableSize];
-  u8 * const pStart = &aData[pPg->hdrOffset + 8 + pPg->childPtrSize];
-  int nRet = 0;
-  int i;
-  int iEnd = iFirst + nCell;
-  u8 *pFree = 0;
-  int szFree = 0;
-
-  for(i=iFirst; i<iEnd; i++){
-    u8 *pCell = pCArray->apCell[i];
-    if( pCell>=pStart && pCell<pEnd ){
-      int sz;
-      /* No need to use cachedCellSize() here.  The sizes of all cells that
-      ** are to be freed have already been computing while deciding which
-      ** cells need freeing */
-      sz = pCArray->szCell[i];  assert( sz>0 );
-      if( pFree!=(pCell + sz) ){
-        if( pFree ){
-          assert( pFree>aData && (pFree - aData)<65536 );
-          freeSpace(pPg, (u16)(pFree - aData), szFree);
-        }
-        pFree = pCell;
-        szFree = sz;
-        if( pFree+sz>pEnd ) return 0;
-      }else{
-        pFree = pCell;
-        szFree += sz;
-      }
-      nRet++;
-    }
-  }
-  if( pFree ){
-    assert( pFree>aData && (pFree - aData)<65536 );
-    freeSpace(pPg, (u16)(pFree - aData), szFree);
-  }
-  return nRet;
-}
-
-/*
-** apCell[] and szCell[] contains pointers to and sizes of all cells in the
-** pages being balanced.  The current page, pPg, has pPg->nCell cells starting
-** with apCell[iOld].  After balancing, this page should hold nNew cells
-** starting at apCell[iNew].
-**
-** This routine makes the necessary adjustments to pPg so that it contains
-** the correct cells after being balanced.
-**
-** The pPg->nFree field is invalid when this function returns. It is the
-** responsibility of the caller to set it correctly.
-*/
-static int editPage(
-  MemPage *pPg,                   /* Edit this page */
-  int iOld,                       /* Index of first cell currently on page */
-  int iNew,                       /* Index of new first cell on page */
-  int nNew,                       /* Final number of cells on page */
-  CellArray *pCArray              /* Array of cells and sizes */
-){
-  u8 * const aData = pPg->aData;
-  const int hdr = pPg->hdrOffset;
-  u8 *pBegin = &pPg->aCellIdx[nNew * 2];
-  int nCell = pPg->nCell;       /* Cells stored on pPg */
-  u8 *pData;
-  u8 *pCellptr;
-  int i;
-  int iOldEnd = iOld + pPg->nCell + pPg->nOverflow;
-  int iNewEnd = iNew + nNew;
-
-#ifdef SQLITE_DEBUG
-  u8 *pTmp = sqlite3PagerTempSpace(pPg->pBt->pPager);
-  memcpy(pTmp, aData, pPg->pBt->usableSize);
-#endif
-
-  /* Remove cells from the start and end of the page */
-  if( iOld<iNew ){
-    int nShift = pageFreeArray(pPg, iOld, iNew-iOld, pCArray);
-    memmove(pPg->aCellIdx, &pPg->aCellIdx[nShift*2], nCell*2);
-    nCell -= nShift;
-  }
-  if( iNewEnd < iOldEnd ){
-    nCell -= pageFreeArray(pPg, iNewEnd, iOldEnd - iNewEnd, pCArray);
-  }
-
-  pData = &aData[get2byteNotZero(&aData[hdr+5])];
-  if( pData<pBegin ) goto editpage_fail;
-
-  /* Add cells to the start of the page */
-  if( iNew<iOld ){
-    int nAdd = MIN(nNew,iOld-iNew);
-    assert( (iOld-iNew)<nNew || nCell==0 || CORRUPT_DB );
-    pCellptr = pPg->aCellIdx;
-    memmove(&pCellptr[nAdd*2], pCellptr, nCell*2);
-    if( pageInsertArray(
-          pPg, pBegin, &pData, pCellptr,
-          iNew, nAdd, pCArray
-    ) ) goto editpage_fail;
-    nCell += nAdd;
-  }
-
-  /* Add any overflow cells */
-  for(i=0; i<pPg->nOverflow; i++){
-    int iCell = (iOld + pPg->aiOvfl[i]) - iNew;
-    if( iCell>=0 && iCell<nNew ){
-      pCellptr = &pPg->aCellIdx[iCell * 2];
-      memmove(&pCellptr[2], pCellptr, (nCell - iCell) * 2);
-      nCell++;
-      if( pageInsertArray(
-            pPg, pBegin, &pData, pCellptr,
-            iCell+iNew, 1, pCArray
-      ) ) goto editpage_fail;
-    }
-  }
-
-  /* Append cells to the end of the page */
-  pCellptr = &pPg->aCellIdx[nCell*2];
-  if( pageInsertArray(
-        pPg, pBegin, &pData, pCellptr,
-        iNew+nCell, nNew-nCell, pCArray
-  ) ) goto editpage_fail;
-
-  pPg->nCell = nNew;
-  pPg->nOverflow = 0;
-
-  put2byte(&aData[hdr+3], pPg->nCell);
-  put2byte(&aData[hdr+5], pData - aData);
-
-#ifdef SQLITE_DEBUG
-  for(i=0; i<nNew && !CORRUPT_DB; i++){
-    u8 *pCell = pCArray->apCell[i+iNew];
-    int iOff = get2byteAligned(&pPg->aCellIdx[i*2]);
-    if( pCell>=aData && pCell<&aData[pPg->pBt->usableSize] ){
-      pCell = &pTmp[pCell - aData];
-    }
-    assert( 0==memcmp(pCell, &aData[iOff],
-            pCArray->pRef->xCellSize(pCArray->pRef, pCArray->apCell[i+iNew])) );
-  }
-#endif
-
-  return SQLITE_OK;
- editpage_fail:
-  /* Unable to edit this page. Rebuild it from scratch instead. */
-  populateCellCache(pCArray, iNew, nNew);
-  return rebuildPage(pPg, nNew, &pCArray->apCell[iNew], &pCArray->szCell[iNew]);
-}
-
-/*
-** The following parameters determine how many adjacent pages get involved
-** in a balancing operation.  NN is the number of neighbors on either side
-** of the page that participate in the balancing operation.  NB is the
-** total number of pages that participate, including the target page and
-** NN neighbors on either side.
-**
-** The minimum value of NN is 1 (of course).  Increasing NN above 1
-** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
-** in exchange for a larger degradation in INSERT and UPDATE performance.
-** The value of NN appears to give the best results overall.
-*/
-#define NN 1             /* Number of neighbors on either side of pPage */
-#define NB (NN*2+1)      /* Total pages involved in the balance */
-
-
-#ifndef SQLITE_OMIT_QUICKBALANCE
-/*
-** This version of balance() handles the common special case where
-** a new entry is being inserted on the extreme right-end of the
-** tree, in other words, when the new entry will become the largest
-** entry in the tree.
-**
-** Instead of trying to balance the 3 right-most leaf pages, just add
-** a new page to the right-hand side and put the one new entry in
-** that page.  This leaves the right side of the tree somewhat
-** unbalanced.  But odds are that we will be inserting new entries
-** at the end soon afterwards so the nearly empty page will quickly
-** fill up.  On average.
-**
-** pPage is the leaf page which is the right-most page in the tree.
-** pParent is its parent.  pPage must have a single overflow entry
-** which is also the right-most entry on the page.
-**
-** The pSpace buffer is used to store a temporary copy of the divider
-** cell that will be inserted into pParent. Such a cell consists of a 4
-** byte page number followed by a variable length integer. In other
-** words, at most 13 bytes. Hence the pSpace buffer must be at
-** least 13 bytes in size.
-*/
-static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
-  BtShared *const pBt = pPage->pBt;    /* B-Tree Database */
-  MemPage *pNew;                       /* Newly allocated page */
-  int rc;                              /* Return Code */
-  Pgno pgnoNew;                        /* Page number of pNew */
-
-  assert( sqlite3_mutex_held(pPage->pBt->mutex) );
-  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
-  assert( pPage->nOverflow==1 );
-
-  /* This error condition is now caught prior to reaching this function */
-  if( NEVER(pPage->nCell==0) ) return SQLITE_CORRUPT_BKPT;
-
-  /* Allocate a new page. This page will become the right-sibling of 
-  ** pPage. Make the parent page writable, so that the new divider cell
-  ** may be inserted. If both these operations are successful, proceed.
-  */
-  rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
-
-  if( rc==SQLITE_OK ){
-
-    u8 *pOut = &pSpace[4];
-    u8 *pCell = pPage->apOvfl[0];
-    u16 szCell = pPage->xCellSize(pPage, pCell);
-    u8 *pStop;
-
-    assert( sqlite3PagerIswriteable(pNew->pDbPage) );
-    assert( pPage->aData[0]==(PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF) );
-    zeroPage(pNew, PTF_INTKEY|PTF_LEAFDATA|PTF_LEAF);
-    rc = rebuildPage(pNew, 1, &pCell, &szCell);
-    if( NEVER(rc) ) return rc;
-    pNew->nFree = pBt->usableSize - pNew->cellOffset - 2 - szCell;
-
-    /* If this is an auto-vacuum database, update the pointer map
-    ** with entries for the new page, and any pointer from the 
-    ** cell on the page to an overflow page. If either of these
-    ** operations fails, the return code is set, but the contents
-    ** of the parent page are still manipulated by thh code below.
-    ** That is Ok, at this point the parent page is guaranteed to
-    ** be marked as dirty. Returning an error code will cause a
-    ** rollback, undoing any changes made to the parent page.
-    */
-    if( ISAUTOVACUUM ){
-      ptrmapPut(pBt, pgnoNew, PTRMAP_BTREE, pParent->pgno, &rc);
-      if( szCell>pNew->minLocal ){
-        ptrmapPutOvflPtr(pNew, pCell, &rc);
-      }
-    }
-  
-    /* Create a divider cell to insert into pParent. The divider cell
-    ** consists of a 4-byte page number (the page number of pPage) and
-    ** a variable length key value (which must be the same value as the
-    ** largest key on pPage).
-    **
-    ** To find the largest key value on pPage, first find the right-most 
-    ** cell on pPage. The first two fields of this cell are the 
-    ** record-length (a variable length integer at most 32-bits in size)
-    ** and the key value (a variable length integer, may have any value).
-    ** The first of the while(...) loops below skips over the record-length
-    ** field. The second while(...) loop copies the key value from the
-    ** cell on pPage into the pSpace buffer.
-    */
-    pCell = findCell(pPage, pPage->nCell-1);
-    pStop = &pCell[9];
-    while( (*(pCell++)&0x80) && pCell<pStop );
-    pStop = &pCell[9];
-    while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
-
-    /* Insert the new divider cell into pParent. */
-    insertCell(pParent, pParent->nCell, pSpace, (int)(pOut-pSpace),
-               0, pPage->pgno, &rc);
-
-    /* Set the right-child pointer of pParent to point to the new page. */
-    put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
-  
-    /* Release the reference to the new page. */
-    releasePage(pNew);
-  }
-
-  return rc;
-}
-#endif /* SQLITE_OMIT_QUICKBALANCE */
-
-#if 0
-/*
-** This function does not contribute anything to the operation of SQLite.
-** it is sometimes activated temporarily while debugging code responsible 
-** for setting pointer-map entries.
-*/
-static int ptrmapCheckPages(MemPage **apPage, int nPage){
-  int i, j;
-  for(i=0; i<nPage; i++){
-    Pgno n;
-    u8 e;
-    MemPage *pPage = apPage[i];
-    BtShared *pBt = pPage->pBt;
-    assert( pPage->isInit );
-
-    for(j=0; j<pPage->nCell; j++){
-      CellInfo info;
-      u8 *z;
-     
-      z = findCell(pPage, j);
-      pPage->xParseCell(pPage, z, &info);
-      if( info.iOverflow ){
-        Pgno ovfl = get4byte(&z[info.iOverflow]);
-        ptrmapGet(pBt, ovfl, &e, &n);
-        assert( n==pPage->pgno && e==PTRMAP_OVERFLOW1 );
-      }
-      if( !pPage->leaf ){
-        Pgno child = get4byte(z);
-        ptrmapGet(pBt, child, &e, &n);
-        assert( n==pPage->pgno && e==PTRMAP_BTREE );
-      }
-    }
-    if( !pPage->leaf ){
-      Pgno child = get4byte(&pPage->aData[pPage->hdrOffset+8]);
-      ptrmapGet(pBt, child, &e, &n);
-      assert( n==pPage->pgno && e==PTRMAP_BTREE );
-    }
-  }
-  return 1;
-}
-#endif
-
-/*
-** This function is used to copy the contents of the b-tree node stored 
-** on page pFrom to page pTo. If page pFrom was not a leaf page, then
-** the pointer-map entries for each child page are updated so that the
-** parent page stored in the pointer map is page pTo. If pFrom contained
-** any cells with overflow page pointers, then the corresponding pointer
-** map entries are also updated so that the parent page is page pTo.
-**
-** If pFrom is currently carrying any overflow cells (entries in the
-** MemPage.apOvfl[] array), they are not copied to pTo. 
-**
-** Before returning, page pTo is reinitialized using btreeInitPage().
-**
-** The performance of this function is not critical. It is only used by 
-** the balance_shallower() and balance_deeper() procedures, neither of
-** which are called often under normal circumstances.
-*/
-static void copyNodeContent(MemPage *pFrom, MemPage *pTo, int *pRC){
-  if( (*pRC)==SQLITE_OK ){
-    BtShared * const pBt = pFrom->pBt;
-    u8 * const aFrom = pFrom->aData;
-    u8 * const aTo = pTo->aData;
-    int const iFromHdr = pFrom->hdrOffset;
-    int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
-    int rc;
-    int iData;
-  
-  
-    assert( pFrom->isInit );
-    assert( pFrom->nFree>=iToHdr );
-    assert( get2byte(&aFrom[iFromHdr+5]) <= (int)pBt->usableSize );
-  
-    /* Copy the b-tree node content from page pFrom to page pTo. */
-    iData = get2byte(&aFrom[iFromHdr+5]);
-    memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
-    memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
-  
-    /* Reinitialize page pTo so that the contents of the MemPage structure
-    ** match the new data. The initialization of pTo can actually fail under
-    ** fairly obscure circumstances, even though it is a copy of initialized 
-    ** page pFrom.
-    */
-    pTo->isInit = 0;
-    rc = btreeInitPage(pTo);
-    if( rc!=SQLITE_OK ){
-      *pRC = rc;
-      return;
-    }
-  
-    /* If this is an auto-vacuum database, update the pointer-map entries
-    ** for any b-tree or overflow pages that pTo now contains the pointers to.
-    */
-    if( ISAUTOVACUUM ){
-      *pRC = setChildPtrmaps(pTo);
-    }
-  }
-}
-
-/*
-** This routine redistributes cells on the iParentIdx'th child of pParent
-** (hereafter "the page") and up to 2 siblings so that all pages have about the
-** same amount of free space. Usually a single sibling on either side of the
-** page are used in the balancing, though both siblings might come from one
-** side if the page is the first or last child of its parent. If the page 
-** has fewer than 2 siblings (something which can only happen if the page
-** is a root page or a child of a root page) then all available siblings
-** participate in the balancing.
-**
-** The number of siblings of the page might be increased or decreased by 
-** one or two in an effort to keep pages nearly full but not over full. 
-**
-** Note that when this routine is called, some of the cells on the page
-** might not actually be stored in MemPage.aData[]. This can happen
-** if the page is overfull. This routine ensures that all cells allocated
-** to the page and its siblings fit into MemPage.aData[] before returning.
-**
-** In the course of balancing the page and its siblings, cells may be
-** inserted into or removed from the parent page (pParent). Doing so
-** may cause the parent page to become overfull or underfull. If this
-** happens, it is the responsibility of the caller to invoke the correct
-** balancing routine to fix this problem (see the balance() routine). 
-**
-** If this routine fails for any reason, it might leave the database
-** in a corrupted state. So if this routine fails, the database should
-** be rolled back.
-**
-** The third argument to this function, aOvflSpace, is a pointer to a
-** buffer big enough to hold one page. If while inserting cells into the parent
-** page (pParent) the parent page becomes overfull, this buffer is
-** used to store the parent's overflow cells. Because this function inserts
-** a maximum of four divider cells into the parent page, and the maximum
-** size of a cell stored within an internal node is always less than 1/4
-** of the page-size, the aOvflSpace[] buffer is guaranteed to be large
-** enough for all overflow cells.
-**
-** If aOvflSpace is set to a null pointer, this function returns 
-** SQLITE_NOMEM.
-*/
-#if defined(_MSC_VER) && _MSC_VER >= 1700 && defined(_M_ARM)
-#pragma optimize("", off)
-#endif
-static int balance_nonroot(
-  MemPage *pParent,               /* Parent page of siblings being balanced */
-  int iParentIdx,                 /* Index of "the page" in pParent */
-  u8 *aOvflSpace,                 /* page-size bytes of space for parent ovfl */
-  int isRoot,                     /* True if pParent is a root-page */
-  int bBulk                       /* True if this call is part of a bulk load */
-){
-  BtShared *pBt;               /* The whole database */
-  int nMaxCells = 0;           /* Allocated size of apCell, szCell, aFrom. */
-  int nNew = 0;                /* Number of pages in apNew[] */
-  int nOld;                    /* Number of pages in apOld[] */
-  int i, j, k;                 /* Loop counters */
-  int nxDiv;                   /* Next divider slot in pParent->aCell[] */
-  int rc = SQLITE_OK;          /* The return code */
-  u16 leafCorrection;          /* 4 if pPage is a leaf.  0 if not */
-  int leafData;                /* True if pPage is a leaf of a LEAFDATA tree */
-  int usableSpace;             /* Bytes in pPage beyond the header */
-  int pageFlags;               /* Value of pPage->aData[0] */
-  int iSpace1 = 0;             /* First unused byte of aSpace1[] */
-  int iOvflSpace = 0;          /* First unused byte of aOvflSpace[] */
-  int szScratch;               /* Size of scratch memory requested */
-  MemPage *apOld[NB];          /* pPage and up to two siblings */
-  MemPage *apNew[NB+2];        /* pPage and up to NB siblings after balancing */
-  u8 *pRight;                  /* Location in parent of right-sibling pointer */
-  u8 *apDiv[NB-1];             /* Divider cells in pParent */
-  int cntNew[NB+2];            /* Index in b.paCell[] of cell after i-th page */
-  int cntOld[NB+2];            /* Old index in b.apCell[] */
-  int szNew[NB+2];             /* Combined size of cells placed on i-th page */
-  u8 *aSpace1;                 /* Space for copies of dividers cells */
-  Pgno pgno;                   /* Temp var to store a page number in */
-  u8 abDone[NB+2];             /* True after i'th new page is populated */
-  Pgno aPgno[NB+2];            /* Page numbers of new pages before shuffling */
-  Pgno aPgOrder[NB+2];         /* Copy of aPgno[] used for sorting pages */
-  u16 aPgFlags[NB+2];          /* flags field of new pages before shuffling */
-  CellArray b;                  /* Parsed information on cells being balanced */
-
-  memset(abDone, 0, sizeof(abDone));
-  b.nCell = 0;
-  b.apCell = 0;
-  pBt = pParent->pBt;
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
-
-#if 0
-  TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
-#endif
-
-  /* At this point pParent may have at most one overflow cell. And if
-  ** this overflow cell is present, it must be the cell with 
-  ** index iParentIdx. This scenario comes about when this function
-  ** is called (indirectly) from sqlite3BtreeDelete().
-  */
-  assert( pParent->nOverflow==0 || pParent->nOverflow==1 );
-  assert( pParent->nOverflow==0 || pParent->aiOvfl[0]==iParentIdx );
-
-  if( !aOvflSpace ){
-    return SQLITE_NOMEM;
-  }
-
-  /* Find the sibling pages to balance. Also locate the cells in pParent 
-  ** that divide the siblings. An attempt is made to find NN siblings on 
-  ** either side of pPage. More siblings are taken from one side, however, 
-  ** if there are fewer than NN siblings on the other side. If pParent
-  ** has NB or fewer children then all children of pParent are taken.  
-  **
-  ** This loop also drops the divider cells from the parent page. This
-  ** way, the remainder of the function does not have to deal with any
-  ** overflow cells in the parent page, since if any existed they will
-  ** have already been removed.
-  */
-  i = pParent->nOverflow + pParent->nCell;
-  if( i<2 ){
-    nxDiv = 0;
-  }else{
-    assert( bBulk==0 || bBulk==1 );
-    if( iParentIdx==0 ){                 
-      nxDiv = 0;
-    }else if( iParentIdx==i ){
-      nxDiv = i-2+bBulk;
-    }else{
-      nxDiv = iParentIdx-1;
-    }
-    i = 2-bBulk;
-  }
-  nOld = i+1;
-  if( (i+nxDiv-pParent->nOverflow)==pParent->nCell ){
-    pRight = &pParent->aData[pParent->hdrOffset+8];
-  }else{
-    pRight = findCell(pParent, i+nxDiv-pParent->nOverflow);
-  }
-  pgno = get4byte(pRight);
-  while( 1 ){
-    rc = getAndInitPage(pBt, pgno, &apOld[i], 0, 0);
-    if( rc ){
-      memset(apOld, 0, (i+1)*sizeof(MemPage*));
-      goto balance_cleanup;
-    }
-    nMaxCells += 1+apOld[i]->nCell+apOld[i]->nOverflow;
-    if( (i--)==0 ) break;
-
-    if( i+nxDiv==pParent->aiOvfl[0] && pParent->nOverflow ){
-      apDiv[i] = pParent->apOvfl[0];
-      pgno = get4byte(apDiv[i]);
-      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
-      pParent->nOverflow = 0;
-    }else{
-      apDiv[i] = findCell(pParent, i+nxDiv-pParent->nOverflow);
-      pgno = get4byte(apDiv[i]);
-      szNew[i] = pParent->xCellSize(pParent, apDiv[i]);
-
-      /* Drop the cell from the parent page. apDiv[i] still points to
-      ** the cell within the parent, even though it has been dropped.
-      ** This is safe because dropping a cell only overwrites the first
-      ** four bytes of it, and this function does not need the first
-      ** four bytes of the divider cell. So the pointer is safe to use
-      ** later on.  
-      **
-      ** But not if we are in secure-delete mode. In secure-delete mode,
-      ** the dropCell() routine will overwrite the entire cell with zeroes.
-      ** In this case, temporarily copy the cell into the aOvflSpace[]
-      ** buffer. It will be copied out again as soon as the aSpace[] buffer
-      ** is allocated.  */
-      if( pBt->btsFlags & BTS_SECURE_DELETE ){
-        int iOff;
-
-        iOff = SQLITE_PTR_TO_INT(apDiv[i]) - SQLITE_PTR_TO_INT(pParent->aData);
-        if( (iOff+szNew[i])>(int)pBt->usableSize ){
-          rc = SQLITE_CORRUPT_BKPT;
-          memset(apOld, 0, (i+1)*sizeof(MemPage*));
-          goto balance_cleanup;
-        }else{
-          memcpy(&aOvflSpace[iOff], apDiv[i], szNew[i]);
-          apDiv[i] = &aOvflSpace[apDiv[i]-pParent->aData];
-        }
-      }
-      dropCell(pParent, i+nxDiv-pParent->nOverflow, szNew[i], &rc);
-    }
-  }
-
-  /* Make nMaxCells a multiple of 4 in order to preserve 8-byte
-  ** alignment */
-  nMaxCells = (nMaxCells + 3)&~3;
-
-  /*
-  ** Allocate space for memory structures
-  */
-  szScratch =
-       nMaxCells*sizeof(u8*)                       /* b.apCell */
-     + nMaxCells*sizeof(u16)                       /* b.szCell */
-     + pBt->pageSize;                              /* aSpace1 */
-
-  /* EVIDENCE-OF: R-28375-38319 SQLite will never request a scratch buffer
-  ** that is more than 6 times the database page size. */
-  assert( szScratch<=6*(int)pBt->pageSize );
-  b.apCell = sqlite3ScratchMalloc( szScratch ); 
-  if( b.apCell==0 ){
-    rc = SQLITE_NOMEM;
-    goto balance_cleanup;
-  }
-  b.szCell = (u16*)&b.apCell[nMaxCells];
-  aSpace1 = (u8*)&b.szCell[nMaxCells];
-  assert( EIGHT_BYTE_ALIGNMENT(aSpace1) );
-
-  /*
-  ** Load pointers to all cells on sibling pages and the divider cells
-  ** into the local b.apCell[] array.  Make copies of the divider cells
-  ** into space obtained from aSpace1[]. The divider cells have already
-  ** been removed from pParent.
-  **
-  ** If the siblings are on leaf pages, then the child pointers of the
-  ** divider cells are stripped from the cells before they are copied
-  ** into aSpace1[].  In this way, all cells in b.apCell[] are without
-  ** child pointers.  If siblings are not leaves, then all cell in
-  ** b.apCell[] include child pointers.  Either way, all cells in b.apCell[]
-  ** are alike.
-  **
-  ** leafCorrection:  4 if pPage is a leaf.  0 if pPage is not a leaf.
-  **       leafData:  1 if pPage holds key+data and pParent holds only keys.
-  */
-  b.pRef = apOld[0];
-  leafCorrection = b.pRef->leaf*4;
-  leafData = b.pRef->intKeyLeaf;
-  for(i=0; i<nOld; i++){
-    MemPage *pOld = apOld[i];
-    int limit = pOld->nCell;
-    u8 *aData = pOld->aData;
-    u16 maskPage = pOld->maskPage;
-    u8 *piCell = aData + pOld->cellOffset;
-    u8 *piEnd;
-
-    /* Verify that all sibling pages are of the same "type" (table-leaf,
-    ** table-interior, index-leaf, or index-interior).
-    */
-    if( pOld->aData[0]!=apOld[0]->aData[0] ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto balance_cleanup;
-    }
-
-    /* Load b.apCell[] with pointers to all cells in pOld.  If pOld
-    ** constains overflow cells, include them in the b.apCell[] array
-    ** in the correct spot.
-    **
-    ** Note that when there are multiple overflow cells, it is always the
-    ** case that they are sequential and adjacent.  This invariant arises
-    ** because multiple overflows can only occurs when inserting divider
-    ** cells into a parent on a prior balance, and divider cells are always
-    ** adjacent and are inserted in order.  There is an assert() tagged
-    ** with "NOTE 1" in the overflow cell insertion loop to prove this
-    ** invariant.
-    **
-    ** This must be done in advance.  Once the balance starts, the cell
-    ** offset section of the btree page will be overwritten and we will no
-    ** long be able to find the cells if a pointer to each cell is not saved
-    ** first.
-    */
-    memset(&b.szCell[b.nCell], 0, sizeof(b.szCell[0])*limit);
-    if( pOld->nOverflow>0 ){
-      memset(&b.szCell[b.nCell+limit], 0, sizeof(b.szCell[0])*pOld->nOverflow);
-      limit = pOld->aiOvfl[0];
-      for(j=0; j<limit; j++){
-        b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
-        piCell += 2;
-        b.nCell++;
-      }
-      for(k=0; k<pOld->nOverflow; k++){
-        assert( k==0 || pOld->aiOvfl[k-1]+1==pOld->aiOvfl[k] );/* NOTE 1 */
-        b.apCell[b.nCell] = pOld->apOvfl[k];
-        b.nCell++;
-      }
-    }
-    piEnd = aData + pOld->cellOffset + 2*pOld->nCell;
-    while( piCell<piEnd ){
-      assert( b.nCell<nMaxCells );
-      b.apCell[b.nCell] = aData + (maskPage & get2byteAligned(piCell));
-      piCell += 2;
-      b.nCell++;
-    }
-
-    cntOld[i] = b.nCell;
-    if( i<nOld-1 && !leafData){
-      u16 sz = (u16)szNew[i];
-      u8 *pTemp;
-      assert( b.nCell<nMaxCells );
-      b.szCell[b.nCell] = sz;
-      pTemp = &aSpace1[iSpace1];
-      iSpace1 += sz;
-      assert( sz<=pBt->maxLocal+23 );
-      assert( iSpace1 <= (int)pBt->pageSize );
-      memcpy(pTemp, apDiv[i], sz);
-      b.apCell[b.nCell] = pTemp+leafCorrection;
-      assert( leafCorrection==0 || leafCorrection==4 );
-      b.szCell[b.nCell] = b.szCell[b.nCell] - leafCorrection;
-      if( !pOld->leaf ){
-        assert( leafCorrection==0 );
-        assert( pOld->hdrOffset==0 );
-        /* The right pointer of the child page pOld becomes the left
-        ** pointer of the divider cell */
-        memcpy(b.apCell[b.nCell], &pOld->aData[8], 4);
-      }else{
-        assert( leafCorrection==4 );
-        while( b.szCell[b.nCell]<4 ){
-          /* Do not allow any cells smaller than 4 bytes. If a smaller cell
-          ** does exist, pad it with 0x00 bytes. */
-          assert( b.szCell[b.nCell]==3 || CORRUPT_DB );
-          assert( b.apCell[b.nCell]==&aSpace1[iSpace1-3] || CORRUPT_DB );
-          aSpace1[iSpace1++] = 0x00;
-          b.szCell[b.nCell]++;
-        }
-      }
-      b.nCell++;
-    }
-  }
-
-  /*
-  ** Figure out the number of pages needed to hold all b.nCell cells.
-  ** Store this number in "k".  Also compute szNew[] which is the total
-  ** size of all cells on the i-th page and cntNew[] which is the index
-  ** in b.apCell[] of the cell that divides page i from page i+1.  
-  ** cntNew[k] should equal b.nCell.
-  **
-  ** Values computed by this block:
-  **
-  **           k: The total number of sibling pages
-  **    szNew[i]: Spaced used on the i-th sibling page.
-  **   cntNew[i]: Index in b.apCell[] and b.szCell[] for the first cell to
-  **              the right of the i-th sibling page.
-  ** usableSpace: Number of bytes of space available on each sibling.
-  ** 
-  */
-  usableSpace = pBt->usableSize - 12 + leafCorrection;
-  for(i=0; i<nOld; i++){
-    MemPage *p = apOld[i];
-    szNew[i] = usableSpace - p->nFree;
-    if( szNew[i]<0 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
-    for(j=0; j<p->nOverflow; j++){
-      szNew[i] += 2 + p->xCellSize(p, p->apOvfl[j]);
-    }
-    cntNew[i] = cntOld[i];
-  }
-  k = nOld;
-  for(i=0; i<k; i++){
-    int sz;
-    while( szNew[i]>usableSpace ){
-      if( i+1>=k ){
-        k = i+2;
-        if( k>NB+2 ){ rc = SQLITE_CORRUPT_BKPT; goto balance_cleanup; }
-        szNew[k-1] = 0;
-        cntNew[k-1] = b.nCell;
-      }
-      sz = 2 + cachedCellSize(&b, cntNew[i]-1);
-      szNew[i] -= sz;
-      if( !leafData ){
-        if( cntNew[i]<b.nCell ){
-          sz = 2 + cachedCellSize(&b, cntNew[i]);
-        }else{
-          sz = 0;
-        }
-      }
-      szNew[i+1] += sz;
-      cntNew[i]--;
-    }
-    while( cntNew[i]<b.nCell ){
-      sz = 2 + cachedCellSize(&b, cntNew[i]);
-      if( szNew[i]+sz>usableSpace ) break;
-      szNew[i] += sz;
-      cntNew[i]++;
-      if( !leafData ){
-        if( cntNew[i]<b.nCell ){
-          sz = 2 + cachedCellSize(&b, cntNew[i]);
-        }else{
-          sz = 0;
-        }
-      }
-      szNew[i+1] -= sz;
-    }
-    if( cntNew[i]>=b.nCell ){
-      k = i+1;
-    }else if( cntNew[i] <= (i>0 ? cntNew[i-1] : 0) ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto balance_cleanup;
-    }
-  }
-
-  /*
-  ** The packing computed by the previous block is biased toward the siblings
-  ** on the left side (siblings with smaller keys). The left siblings are
-  ** always nearly full, while the right-most sibling might be nearly empty.
-  ** The next block of code attempts to adjust the packing of siblings to
-  ** get a better balance.
-  **
-  ** This adjustment is more than an optimization.  The packing above might
-  ** be so out of balance as to be illegal.  For example, the right-most
-  ** sibling might be completely empty.  This adjustment is not optional.
-  */
-  for(i=k-1; i>0; i--){
-    int szRight = szNew[i];  /* Size of sibling on the right */
-    int szLeft = szNew[i-1]; /* Size of sibling on the left */
-    int r;              /* Index of right-most cell in left sibling */
-    int d;              /* Index of first cell to the left of right sibling */
-
-    r = cntNew[i-1] - 1;
-    d = r + 1 - leafData;
-    (void)cachedCellSize(&b, d);
-    do{
-      assert( d<nMaxCells );
-      assert( r<nMaxCells );
-      (void)cachedCellSize(&b, r);
-      if( szRight!=0
-       && (bBulk || szRight+b.szCell[d]+2 > szLeft-(b.szCell[r]+2)) ){
-        break;
-      }
-      szRight += b.szCell[d] + 2;
-      szLeft -= b.szCell[r] + 2;
-      cntNew[i-1] = r;
-      r--;
-      d--;
-    }while( r>=0 );
-    szNew[i] = szRight;
-    szNew[i-1] = szLeft;
-    if( cntNew[i-1] <= (i>1 ? cntNew[i-2] : 0) ){
-      rc = SQLITE_CORRUPT_BKPT;
-      goto balance_cleanup;
-    }
-  }
-
-  /* Sanity check:  For a non-corrupt database file one of the follwing
-  ** must be true:
-  **    (1) We found one or more cells (cntNew[0])>0), or
-  **    (2) pPage is a virtual root page.  A virtual root page is when
-  **        the real root page is page 1 and we are the only child of
-  **        that page.
-  */
-  assert( cntNew[0]>0 || (pParent->pgno==1 && pParent->nCell==0) || CORRUPT_DB);
-  TRACE(("BALANCE: old: %d(nc=%d) %d(nc=%d) %d(nc=%d)\n",
-    apOld[0]->pgno, apOld[0]->nCell,
-    nOld>=2 ? apOld[1]->pgno : 0, nOld>=2 ? apOld[1]->nCell : 0,
-    nOld>=3 ? apOld[2]->pgno : 0, nOld>=3 ? apOld[2]->nCell : 0
-  ));
-
-  /*
-  ** Allocate k new pages.  Reuse old pages where possible.
-  */
-  pageFlags = apOld[0]->aData[0];
-  for(i=0; i<k; i++){
-    MemPage *pNew;
-    if( i<nOld ){
-      pNew = apNew[i] = apOld[i];
-      apOld[i] = 0;
-      rc = sqlite3PagerWrite(pNew->pDbPage);
-      nNew++;
-      if( rc ) goto balance_cleanup;
-    }else{
-      assert( i>0 );
-      rc = allocateBtreePage(pBt, &pNew, &pgno, (bBulk ? 1 : pgno), 0);
-      if( rc ) goto balance_cleanup;
-      zeroPage(pNew, pageFlags);
-      apNew[i] = pNew;
-      nNew++;
-      cntOld[i] = b.nCell;
-
-      /* Set the pointer-map entry for the new sibling page. */
-      if( ISAUTOVACUUM ){
-        ptrmapPut(pBt, pNew->pgno, PTRMAP_BTREE, pParent->pgno, &rc);
-        if( rc!=SQLITE_OK ){
-          goto balance_cleanup;
-        }
-      }
-    }
-  }
-
-  /*
-  ** Reassign page numbers so that the new pages are in ascending order. 
-  ** This helps to keep entries in the disk file in order so that a scan
-  ** of the table is closer to a linear scan through the file. That in turn 
-  ** helps the operating system to deliver pages from the disk more rapidly.
-  **
-  ** An O(n^2) insertion sort algorithm is used, but since n is never more 
-  ** than (NB+2) (a small constant), that should not be a problem.
-  **
-  ** When NB==3, this one optimization makes the database about 25% faster 
-  ** for large insertions and deletions.
-  */
-  for(i=0; i<nNew; i++){
-    aPgOrder[i] = aPgno[i] = apNew[i]->pgno;
-    aPgFlags[i] = apNew[i]->pDbPage->flags;
-    for(j=0; j<i; j++){
-      if( aPgno[j]==aPgno[i] ){
-        /* This branch is taken if the set of sibling pages somehow contains
-        ** duplicate entries. This can happen if the database is corrupt. 
-        ** It would be simpler to detect this as part of the loop below, but
-        ** we do the detection here in order to avoid populating the pager
-        ** cache with two separate objects associated with the same
-        ** page number.  */
-        assert( CORRUPT_DB );
-        rc = SQLITE_CORRUPT_BKPT;
-        goto balance_cleanup;
-      }
-    }
-  }
-  for(i=0; i<nNew; i++){
-    int iBest = 0;                /* aPgno[] index of page number to use */
-    for(j=1; j<nNew; j++){
-      if( aPgOrder[j]<aPgOrder[iBest] ) iBest = j;
-    }
-    pgno = aPgOrder[iBest];
-    aPgOrder[iBest] = 0xffffffff;
-    if( iBest!=i ){
-      if( iBest>i ){
-        sqlite3PagerRekey(apNew[iBest]->pDbPage, pBt->nPage+iBest+1, 0);
-      }
-      sqlite3PagerRekey(apNew[i]->pDbPage, pgno, aPgFlags[iBest]);
-      apNew[i]->pgno = pgno;
-    }
-  }
-
-  TRACE(("BALANCE: new: %d(%d nc=%d) %d(%d nc=%d) %d(%d nc=%d) "
-         "%d(%d nc=%d) %d(%d nc=%d)\n",
-    apNew[0]->pgno, szNew[0], cntNew[0],
-    nNew>=2 ? apNew[1]->pgno : 0, nNew>=2 ? szNew[1] : 0,
-    nNew>=2 ? cntNew[1] - cntNew[0] - !leafData : 0,
-    nNew>=3 ? apNew[2]->pgno : 0, nNew>=3 ? szNew[2] : 0,
-    nNew>=3 ? cntNew[2] - cntNew[1] - !leafData : 0,
-    nNew>=4 ? apNew[3]->pgno : 0, nNew>=4 ? szNew[3] : 0,
-    nNew>=4 ? cntNew[3] - cntNew[2] - !leafData : 0,
-    nNew>=5 ? apNew[4]->pgno : 0, nNew>=5 ? szNew[4] : 0,
-    nNew>=5 ? cntNew[4] - cntNew[3] - !leafData : 0
-  ));
-
-  assert( sqlite3PagerIswriteable(pParent->pDbPage) );
-  put4byte(pRight, apNew[nNew-1]->pgno);
-
-  /* If the sibling pages are not leaves, ensure that the right-child pointer
-  ** of the right-most new sibling page is set to the value that was 
-  ** originally in the same field of the right-most old sibling page. */
-  if( (pageFlags & PTF_LEAF)==0 && nOld!=nNew ){
-    MemPage *pOld = (nNew>nOld ? apNew : apOld)[nOld-1];
-    memcpy(&apNew[nNew-1]->aData[8], &pOld->aData[8], 4);
-  }
-
-  /* Make any required updates to pointer map entries associated with 
-  ** cells stored on sibling pages following the balance operation. Pointer
-  ** map entries associated with divider cells are set by the insertCell()
-  ** routine. The associated pointer map entries are:
-  **
-  **   a) if the cell contains a reference to an overflow chain, the
-  **      entry associated with the first page in the overflow chain, and
-  **
-  **   b) if the sibling pages are not leaves, the child page associated
-  **      with the cell.
-  **
-  ** If the sibling pages are not leaves, then the pointer map entry 
-  ** associated with the right-child of each sibling may also need to be 
-  ** updated. This happens below, after the sibling pages have been 
-  ** populated, not here.
-  */
-  if( ISAUTOVACUUM ){
-    MemPage *pNew = apNew[0];
-    u8 *aOld = pNew->aData;
-    int cntOldNext = pNew->nCell + pNew->nOverflow;
-    int usableSize = pBt->usableSize;
-    int iNew = 0;
-    int iOld = 0;
-
-    for(i=0; i<b.nCell; i++){
-      u8 *pCell = b.apCell[i];
-      if( i==cntOldNext ){
-        MemPage *pOld = (++iOld)<nNew ? apNew[iOld] : apOld[iOld];
-        cntOldNext += pOld->nCell + pOld->nOverflow + !leafData;
-        aOld = pOld->aData;
-      }
-      if( i==cntNew[iNew] ){
-        pNew = apNew[++iNew];
-        if( !leafData ) continue;
-      }
-
-      /* Cell pCell is destined for new sibling page pNew. Originally, it
-      ** was either part of sibling page iOld (possibly an overflow cell), 
-      ** or else the divider cell to the left of sibling page iOld. So,
-      ** if sibling page iOld had the same page number as pNew, and if
-      ** pCell really was a part of sibling page iOld (not a divider or
-      ** overflow cell), we can skip updating the pointer map entries.  */
-      if( iOld>=nNew
-       || pNew->pgno!=aPgno[iOld]
-       || pCell<aOld
-       || pCell>=&aOld[usableSize]
-      ){
-        if( !leafCorrection ){
-          ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
-        }
-        if( cachedCellSize(&b,i)>pNew->minLocal ){
-          ptrmapPutOvflPtr(pNew, pCell, &rc);
-        }
-        if( rc ) goto balance_cleanup;
-      }
-    }
-  }
-
-  /* Insert new divider cells into pParent. */
-  for(i=0; i<nNew-1; i++){
-    u8 *pCell;
-    u8 *pTemp;
-    int sz;
-    MemPage *pNew = apNew[i];
-    j = cntNew[i];
-
-    assert( j<nMaxCells );
-    assert( b.apCell[j]!=0 );
-    pCell = b.apCell[j];
-    sz = b.szCell[j] + leafCorrection;
-    pTemp = &aOvflSpace[iOvflSpace];
-    if( !pNew->leaf ){
-      memcpy(&pNew->aData[8], pCell, 4);
-    }else if( leafData ){
-      /* If the tree is a leaf-data tree, and the siblings are leaves, 
-      ** then there is no divider cell in b.apCell[]. Instead, the divider 
-      ** cell consists of the integer key for the right-most cell of 
-      ** the sibling-page assembled above only.
-      */
-      CellInfo info;
-      j--;
-      pNew->xParseCell(pNew, b.apCell[j], &info);
-      pCell = pTemp;
-      sz = 4 + putVarint(&pCell[4], info.nKey);
-      pTemp = 0;
-    }else{
-      pCell -= 4;
-      /* Obscure case for non-leaf-data trees: If the cell at pCell was
-      ** previously stored on a leaf node, and its reported size was 4
-      ** bytes, then it may actually be smaller than this 
-      ** (see btreeParseCellPtr(), 4 bytes is the minimum size of
-      ** any cell). But it is important to pass the correct size to 
-      ** insertCell(), so reparse the cell now.
-      **
-      ** Note that this can never happen in an SQLite data file, as all
-      ** cells are at least 4 bytes. It only happens in b-trees used
-      ** to evaluate "IN (SELECT ...)" and similar clauses.
-      */
-      if( b.szCell[j]==4 ){
-        assert(leafCorrection==4);
-        sz = pParent->xCellSize(pParent, pCell);
-      }
-    }
-    iOvflSpace += sz;
-    assert( sz<=pBt->maxLocal+23 );
-    assert( iOvflSpace <= (int)pBt->pageSize );
-    insertCell(pParent, nxDiv+i, pCell, sz, pTemp, pNew->pgno, &rc);
-    if( rc!=SQLITE_OK ) goto balance_cleanup;
-    assert( sqlite3PagerIswriteable(pParent->pDbPage) );
-  }
-
-  /* Now update the actual sibling pages. The order in which they are updated
-  ** is important, as this code needs to avoid disrupting any page from which
-  ** cells may still to be read. In practice, this means:
-  **
-  **  (1) If cells are moving left (from apNew[iPg] to apNew[iPg-1])
-  **      then it is not safe to update page apNew[iPg] until after
-  **      the left-hand sibling apNew[iPg-1] has been updated.
-  **
-  **  (2) If cells are moving right (from apNew[iPg] to apNew[iPg+1])
-  **      then it is not safe to update page apNew[iPg] until after
-  **      the right-hand sibling apNew[iPg+1] has been updated.
-  **
-  ** If neither of the above apply, the page is safe to update.
-  **
-  ** The iPg value in the following loop starts at nNew-1 goes down
-  ** to 0, then back up to nNew-1 again, thus making two passes over
-  ** the pages.  On the initial downward pass, only condition (1) above
-  ** needs to be tested because (2) will always be true from the previous
-  ** step.  On the upward pass, both conditions are always true, so the
-  ** upwards pass simply processes pages that were missed on the downward
-  ** pass.
-  */
-  for(i=1-nNew; i<nNew; i++){
-    int iPg = i<0 ? -i : i;
-    assert( iPg>=0 && iPg<nNew );
-    if( abDone[iPg] ) continue;         /* Skip pages already processed */
-    if( i>=0                            /* On the upwards pass, or... */
-     || cntOld[iPg-1]>=cntNew[iPg-1]    /* Condition (1) is true */
-    ){
-      int iNew;
-      int iOld;
-      int nNewCell;
-
-      /* Verify condition (1):  If cells are moving left, update iPg
-      ** only after iPg-1 has already been updated. */
-      assert( iPg==0 || cntOld[iPg-1]>=cntNew[iPg-1] || abDone[iPg-1] );
-
-      /* Verify condition (2):  If cells are moving right, update iPg
-      ** only after iPg+1 has already been updated. */
-      assert( cntNew[iPg]>=cntOld[iPg] || abDone[iPg+1] );
-
-      if( iPg==0 ){
-        iNew = iOld = 0;
-        nNewCell = cntNew[0];
-      }else{
-        iOld = iPg<nOld ? (cntOld[iPg-1] + !leafData) : b.nCell;
-        iNew = cntNew[iPg-1] + !leafData;
-        nNewCell = cntNew[iPg] - iNew;
-      }
-
-      rc = editPage(apNew[iPg], iOld, iNew, nNewCell, &b);
-      if( rc ) goto balance_cleanup;
-      abDone[iPg]++;
-      apNew[iPg]->nFree = usableSpace-szNew[iPg];
-      assert( apNew[iPg]->nOverflow==0 );
-      assert( apNew[iPg]->nCell==nNewCell );
-    }
-  }
-
-  /* All pages have been processed exactly once */
-  assert( memcmp(abDone, "\01\01\01\01\01", nNew)==0 );
-
-  assert( nOld>0 );
-  assert( nNew>0 );
-
-  if( isRoot && pParent->nCell==0 && pParent->hdrOffset<=apNew[0]->nFree ){
-    /* The root page of the b-tree now contains no cells. The only sibling
-    ** page is the right-child of the parent. Copy the contents of the
-    ** child page into the parent, decreasing the overall height of the
-    ** b-tree structure by one. This is described as the "balance-shallower"
-    ** sub-algorithm in some documentation.
-    **
-    ** If this is an auto-vacuum database, the call to copyNodeContent() 
-    ** sets all pointer-map entries corresponding to database image pages 
-    ** for which the pointer is stored within the content being copied.
-    **
-    ** It is critical that the child page be defragmented before being
-    ** copied into the parent, because if the parent is page 1 then it will
-    ** by smaller than the child due to the database header, and so all the
-    ** free space needs to be up front.
-    */
-    assert( nNew==1 || CORRUPT_DB );
-    rc = defragmentPage(apNew[0]);
-    testcase( rc!=SQLITE_OK );
-    assert( apNew[0]->nFree == 
-        (get2byte(&apNew[0]->aData[5])-apNew[0]->cellOffset-apNew[0]->nCell*2)
-      || rc!=SQLITE_OK
-    );
-    copyNodeContent(apNew[0], pParent, &rc);
-    freePage(apNew[0], &rc);
-  }else if( ISAUTOVACUUM && !leafCorrection ){
-    /* Fix the pointer map entries associated with the right-child of each
-    ** sibling page. All other pointer map entries have already been taken
-    ** care of.  */
-    for(i=0; i<nNew; i++){
-      u32 key = get4byte(&apNew[i]->aData[8]);
-      ptrmapPut(pBt, key, PTRMAP_BTREE, apNew[i]->pgno, &rc);
-    }
-  }
-
-  assert( pParent->isInit );
-  TRACE(("BALANCE: finished: old=%d new=%d cells=%d\n",
-          nOld, nNew, b.nCell));
-
-  /* Free any old pages that were not reused as new pages.
-  */
-  for(i=nNew; i<nOld; i++){
-    freePage(apOld[i], &rc);
-  }
-
-#if 0
-  if( ISAUTOVACUUM && rc==SQLITE_OK && apNew[0]->isInit ){
-    /* The ptrmapCheckPages() contains assert() statements that verify that
-    ** all pointer map pages are set correctly. This is helpful while 
-    ** debugging. This is usually disabled because a corrupt database may
-    ** cause an assert() statement to fail.  */
-    ptrmapCheckPages(apNew, nNew);
-    ptrmapCheckPages(&pParent, 1);
-  }
-#endif
-
-  /*
-  ** Cleanup before returning.
-  */
-balance_cleanup:
-  sqlite3ScratchFree(b.apCell);
-  for(i=0; i<nOld; i++){
-    releasePage(apOld[i]);
-  }
-  for(i=0; i<nNew; i++){
-    releasePage(apNew[i]);
-  }
-
-  return rc;
-}
-#if defined(_MSC_VER) && _MSC_VER >= 1700 && defined(_M_ARM)
-#pragma optimize("", on)
-#endif
-
-
-/*
-** This function is called when the root page of a b-tree structure is
-** overfull (has one or more overflow pages).
-**
-** A new child page is allocated and the contents of the current root
-** page, including overflow cells, are copied into the child. The root
-** page is then overwritten to make it an empty page with the right-child 
-** pointer pointing to the new page.
-**
-** Before returning, all pointer-map entries corresponding to pages 
-** that the new child-page now contains pointers to are updated. The
-** entry corresponding to the new right-child pointer of the root
-** page is also updated.
-**
-** If successful, *ppChild is set to contain a reference to the child 
-** page and SQLITE_OK is returned. In this case the caller is required
-** to call releasePage() on *ppChild exactly once. If an error occurs,
-** an error code is returned and *ppChild is set to 0.
-*/
-static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
-  int rc;                        /* Return value from subprocedures */
-  MemPage *pChild = 0;           /* Pointer to a new child page */
-  Pgno pgnoChild = 0;            /* Page number of the new child page */
-  BtShared *pBt = pRoot->pBt;    /* The BTree */
-
-  assert( pRoot->nOverflow>0 );
-  assert( sqlite3_mutex_held(pBt->mutex) );
-
-  /* Make pRoot, the root page of the b-tree, writable. Allocate a new 
-  ** page that will become the new right-child of pPage. Copy the contents
-  ** of the node stored on pRoot into the new child page.
-  */
-  rc = sqlite3PagerWrite(pRoot->pDbPage);
-  if( rc==SQLITE_OK ){
-    rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0);
-    copyNodeContent(pRoot, pChild, &rc);
-    if( ISAUTOVACUUM ){
-      ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno, &rc);
-    }
-  }
-  if( rc ){
-    *ppChild = 0;
-    releasePage(pChild);
-    return rc;
-  }
-  assert( sqlite3PagerIswriteable(pChild->pDbPage) );
-  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
-  assert( pChild->nCell==pRoot->nCell );
-
-  TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));
-
-  /* Copy the overflow cells from pRoot to pChild */
-  memcpy(pChild->aiOvfl, pRoot->aiOvfl,
-         pRoot->nOverflow*sizeof(pRoot->aiOvfl[0]));
-  memcpy(pChild->apOvfl, pRoot->apOvfl,
-         pRoot->nOverflow*sizeof(pRoot->apOvfl[0]));
-  pChild->nOverflow = pRoot->nOverflow;
-
-  /* Zero the contents of pRoot. Then install pChild as the right-child. */
-  zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
-  put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
-
-  *ppChild = pChild;
-  return SQLITE_OK;
-}
-
-/*
-** The page that pCur currently points to has just been modified in
-** some way. This function figures out if this modification means the
-** tree needs to be balanced, and if so calls the appropriate balancing 
-** routine. Balancing routines are:
-**
-**   balance_quick()
-**   balance_deeper()
-**   balance_nonroot()
-*/
-static int balance(BtCursor *pCur){
-  int rc = SQLITE_OK;
-  const int nMin = pCur->pBt->usableSize * 2 / 3;
-  u8 aBalanceQuickSpace[13];
-  u8 *pFree = 0;
-
-  TESTONLY( int balance_quick_called = 0 );
-  TESTONLY( int balance_deeper_called = 0 );
-
-  do {
-    int iPage = pCur->iPage;
-    MemPage *pPage = pCur->apPage[iPage];
-
-    if( iPage==0 ){
-      if( pPage->nOverflow ){
-        /* The root page of the b-tree is overfull. In this case call the
-        ** balance_deeper() function to create a new child for the root-page
-        ** and copy the current contents of the root-page to it. The
-        ** next iteration of the do-loop will balance the child page.
-        */ 
-        assert( (balance_deeper_called++)==0 );
-        rc = balance_deeper(pPage, &pCur->apPage[1]);
-        if( rc==SQLITE_OK ){
-          pCur->iPage = 1;
-          pCur->aiIdx[0] = 0;
-          pCur->aiIdx[1] = 0;
-          assert( pCur->apPage[1]->nOverflow );
-        }
-      }else{
-        break;
-      }
-    }else if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
-      break;
-    }else{
-      MemPage * const pParent = pCur->apPage[iPage-1];
-      int const iIdx = pCur->aiIdx[iPage-1];
-
-      rc = sqlite3PagerWrite(pParent->pDbPage);
-      if( rc==SQLITE_OK ){
-#ifndef SQLITE_OMIT_QUICKBALANCE
-        if( pPage->intKeyLeaf
-         && pPage->nOverflow==1
-         && pPage->aiOvfl[0]==pPage->nCell
-         && pParent->pgno!=1
-         && pParent->nCell==iIdx
-        ){
-          /* Call balance_quick() to create a new sibling of pPage on which
-          ** to store the overflow cell. balance_quick() inserts a new cell
-          ** into pParent, which may cause pParent overflow. If this
-          ** happens, the next iteration of the do-loop will balance pParent 
-          ** use either balance_nonroot() or balance_deeper(). Until this
-          ** happens, the overflow cell is stored in the aBalanceQuickSpace[]
-          ** buffer. 
-          **
-          ** The purpose of the following assert() is to check that only a
-          ** single call to balance_quick() is made for each call to this
-          ** function. If this were not verified, a subtle bug involving reuse
-          ** of the aBalanceQuickSpace[] might sneak in.
-          */
-          assert( (balance_quick_called++)==0 );
-          rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
-        }else
-#endif
-        {
-          /* In this case, call balance_nonroot() to redistribute cells
-          ** between pPage and up to 2 of its sibling pages. This involves
-          ** modifying the contents of pParent, which may cause pParent to
-          ** become overfull or underfull. The next iteration of the do-loop
-          ** will balance the parent page to correct this.
-          ** 
-          ** If the parent page becomes overfull, the overflow cell or cells
-          ** are stored in the pSpace buffer allocated immediately below. 
-          ** A subsequent iteration of the do-loop will deal with this by
-          ** calling balance_nonroot() (balance_deeper() may be called first,
-          ** but it doesn't deal with overflow cells - just moves them to a
-          ** different page). Once this subsequent call to balance_nonroot() 
-          ** has completed, it is safe to release the pSpace buffer used by
-          ** the previous call, as the overflow cell data will have been 
-          ** copied either into the body of a database page or into the new
-          ** pSpace buffer passed to the latter call to balance_nonroot().
-          */
-          u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
-          rc = balance_nonroot(pParent, iIdx, pSpace, iPage==1,
-                               pCur->hints&BTREE_BULKLOAD);
-          if( pFree ){
-            /* If pFree is not NULL, it points to the pSpace buffer used 
-            ** by a previous call to balance_nonroot(). Its contents are
-            ** now stored either on real database pages or within the 
-            ** new pSpace buffer, so it may be safely freed here. */
-            sqlite3PageFree(pFree);
-          }
-
-          /* The pSpace buffer will be freed after the next call to
-          ** balance_nonroot(), or just before this function returns, whichever
-          ** comes first. */
-          pFree = pSpace;
-        }
-      }
-
-      pPage->nOverflow = 0;
-
-      /* The next iteration of the do-loop balances the parent page. */
-      releasePage(pPage);
-      pCur->iPage--;
-      assert( pCur->iPage>=0 );
-    }
-  }while( rc==SQLITE_OK );
-
-  if( pFree ){
-    sqlite3PageFree(pFree);
-  }
-  return rc;
-}
-
-
-/*
-** Insert a new record into the BTree.  The key is given by (pKey,nKey)
-** and the data is given by (pData,nData).  The cursor is used only to
-** define what table the record should be inserted into.  The cursor
-** is left pointing at a random location.
-**
-** For an INTKEY table, only the nKey value of the key is used.  pKey is
-** ignored.  For a ZERODATA table, the pData and nData are both ignored.
-**
-** If the seekResult parameter is non-zero, then a successful call to
-** MovetoUnpacked() to seek cursor pCur to (pKey, nKey) has already
-** been performed. seekResult is the search result returned (a negative
-** number if pCur points at an entry that is smaller than (pKey, nKey), or
-** a positive value if pCur points at an entry that is larger than 
-** (pKey, nKey)). 
-**
-** If the seekResult parameter is non-zero, then the caller guarantees that
-** cursor pCur is pointing at the existing copy of a row that is to be
-** overwritten.  If the seekResult parameter is 0, then cursor pCur may
-** point to any entry or to no entry at all and so this function has to seek
-** the cursor before the new key can be inserted.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeInsert(
-  BtCursor *pCur,                /* Insert data into the table of this cursor */
-  const void *pKey, i64 nKey,    /* The key of the new record */
-  const void *pData, int nData,  /* The data of the new record */
-  int nZero,                     /* Number of extra 0 bytes to append to data */
-  int appendBias,                /* True if this is likely an append */
-  int seekResult                 /* Result of prior MovetoUnpacked() call */
-){
-  int rc;
-  int loc = seekResult;          /* -1: before desired location  +1: after */
-  int szNew = 0;
-  int idx;
-  MemPage *pPage;
-  Btree *p = pCur->pBtree;
-  BtShared *pBt = p->pBt;
-  unsigned char *oldCell;
-  unsigned char *newCell = 0;
-
-  if( pCur->eState==CURSOR_FAULT ){
-    assert( pCur->skipNext!=SQLITE_OK );
-    return pCur->skipNext;
-  }
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( (pCur->curFlags & BTCF_WriteFlag)!=0
-              && pBt->inTransaction==TRANS_WRITE
-              && (pBt->btsFlags & BTS_READ_ONLY)==0 );
-  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
-
-  /* Assert that the caller has been consistent. If this cursor was opened
-  ** expecting an index b-tree, then the caller should be inserting blob
-  ** keys with no associated data. If the cursor was opened expecting an
-  ** intkey table, the caller should be inserting integer keys with a
-  ** blob of associated data.  */
-  assert( (pKey==0)==(pCur->pKeyInfo==0) );
-
-  /* Save the positions of any other cursors open on this table.
-  **
-  ** In some cases, the call to btreeMoveto() below is a no-op. For
-  ** example, when inserting data into a table with auto-generated integer
-  ** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the 
-  ** integer key to use. It then calls this function to actually insert the 
-  ** data into the intkey B-Tree. In this case btreeMoveto() recognizes
-  ** that the cursor is already where it needs to be and returns without
-  ** doing any work. To avoid thwarting these optimizations, it is important
-  ** not to clear the cursor here.
-  */
-  if( pCur->curFlags & BTCF_Multiple ){
-    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
-    if( rc ) return rc;
-  }
-
-  if( pCur->pKeyInfo==0 ){
-    assert( pKey==0 );
-    /* If this is an insert into a table b-tree, invalidate any incrblob 
-    ** cursors open on the row being replaced */
-    invalidateIncrblobCursors(p, nKey, 0);
-
-    /* If the cursor is currently on the last row and we are appending a
-    ** new row onto the end, set the "loc" to avoid an unnecessary
-    ** btreeMoveto() call */
-    if( (pCur->curFlags&BTCF_ValidNKey)!=0 && nKey>0
-      && pCur->info.nKey==nKey-1 ){
-       loc = -1;
-    }else if( loc==0 ){
-      rc = sqlite3BtreeMovetoUnpacked(pCur, 0, nKey, appendBias, &loc);
-      if( rc ) return rc;
-    }
-  }else if( loc==0 ){
-    rc = btreeMoveto(pCur, pKey, nKey, appendBias, &loc);
-    if( rc ) return rc;
-  }
-  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );
-
-  pPage = pCur->apPage[pCur->iPage];
-  assert( pPage->intKey || nKey>=0 );
-  assert( pPage->leaf || !pPage->intKey );
-
-  TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
-          pCur->pgnoRoot, nKey, nData, pPage->pgno,
-          loc==0 ? "overwrite" : "new entry"));
-  assert( pPage->isInit );
-  newCell = pBt->pTmpSpace;
-  assert( newCell!=0 );
-  rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, nZero, &szNew);
-  if( rc ) goto end_insert;
-  assert( szNew==pPage->xCellSize(pPage, newCell) );
-  assert( szNew <= MX_CELL_SIZE(pBt) );
-  idx = pCur->aiIdx[pCur->iPage];
-  if( loc==0 ){
-    u16 szOld;
-    assert( idx<pPage->nCell );
-    rc = sqlite3PagerWrite(pPage->pDbPage);
-    if( rc ){
-      goto end_insert;
-    }
-    oldCell = findCell(pPage, idx);
-    if( !pPage->leaf ){
-      memcpy(newCell, oldCell, 4);
-    }
-    rc = clearCell(pPage, oldCell, &szOld);
-    dropCell(pPage, idx, szOld, &rc);
-    if( rc ) goto end_insert;
-  }else if( loc<0 && pPage->nCell>0 ){
-    assert( pPage->leaf );
-    idx = ++pCur->aiIdx[pCur->iPage];
-  }else{
-    assert( pPage->leaf );
-  }
-  insertCell(pPage, idx, newCell, szNew, 0, 0, &rc);
-  assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
-
-  /* If no error has occurred and pPage has an overflow cell, call balance() 
-  ** to redistribute the cells within the tree. Since balance() may move
-  ** the cursor, zero the BtCursor.info.nSize and BTCF_ValidNKey
-  ** variables.
-  **
-  ** Previous versions of SQLite called moveToRoot() to move the cursor
-  ** back to the root page as balance() used to invalidate the contents
-  ** of BtCursor.apPage[] and BtCursor.aiIdx[]. Instead of doing that,
-  ** set the cursor state to "invalid". This makes common insert operations
-  ** slightly faster.
-  **
-  ** There is a subtle but important optimization here too. When inserting
-  ** multiple records into an intkey b-tree using a single cursor (as can
-  ** happen while processing an "INSERT INTO ... SELECT" statement), it
-  ** is advantageous to leave the cursor pointing to the last entry in
-  ** the b-tree if possible. If the cursor is left pointing to the last
-  ** entry in the table, and the next row inserted has an integer key
-  ** larger than the largest existing key, it is possible to insert the
-  ** row without seeking the cursor. This can be a big performance boost.
-  */
-  pCur->info.nSize = 0;
-  if( rc==SQLITE_OK && pPage->nOverflow ){
-    pCur->curFlags &= ~(BTCF_ValidNKey);
-    rc = balance(pCur);
-
-    /* Must make sure nOverflow is reset to zero even if the balance()
-    ** fails. Internal data structure corruption will result otherwise. 
-    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
-    ** from trying to save the current position of the cursor.  */
-    pCur->apPage[pCur->iPage]->nOverflow = 0;
-    pCur->eState = CURSOR_INVALID;
-  }
-  assert( pCur->apPage[pCur->iPage]->nOverflow==0 );
-
-end_insert:
-  return rc;
-}
-
-/*
-** Delete the entry that the cursor is pointing to. 
-**
-** If the second parameter is zero, then the cursor is left pointing at an
-** arbitrary location after the delete. If it is non-zero, then the cursor 
-** is left in a state such that the next call to BtreeNext() or BtreePrev()
-** moves it to the same row as it would if the call to BtreeDelete() had
-** been omitted.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeDelete(BtCursor *pCur, int bPreserve){
-  Btree *p = pCur->pBtree;
-  BtShared *pBt = p->pBt;              
-  int rc;                              /* Return code */
-  MemPage *pPage;                      /* Page to delete cell from */
-  unsigned char *pCell;                /* Pointer to cell to delete */
-  int iCellIdx;                        /* Index of cell to delete */
-  int iCellDepth;                      /* Depth of node containing pCell */ 
-  u16 szCell;                          /* Size of the cell being deleted */
-  int bSkipnext = 0;                   /* Leaf cursor in SKIPNEXT state */
-
-  assert( cursorHoldsMutex(pCur) );
-  assert( pBt->inTransaction==TRANS_WRITE );
-  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
-  assert( pCur->curFlags & BTCF_WriteFlag );
-  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
-  assert( !hasReadConflicts(p, pCur->pgnoRoot) );
-  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
-  assert( pCur->eState==CURSOR_VALID );
-
-  iCellDepth = pCur->iPage;
-  iCellIdx = pCur->aiIdx[iCellDepth];
-  pPage = pCur->apPage[iCellDepth];
-  pCell = findCell(pPage, iCellIdx);
-
-  /* If the page containing the entry to delete is not a leaf page, move
-  ** the cursor to the largest entry in the tree that is smaller than
-  ** the entry being deleted. This cell will replace the cell being deleted
-  ** from the internal node. The 'previous' entry is used for this instead
-  ** of the 'next' entry, as the previous entry is always a part of the
-  ** sub-tree headed by the child page of the cell being deleted. This makes
-  ** balancing the tree following the delete operation easier.  */
-  if( !pPage->leaf ){
-    int notUsed = 0;
-    rc = sqlite3BtreePrevious(pCur, &notUsed);
-    if( rc ) return rc;
-  }
-
-  /* Save the positions of any other cursors open on this table before
-  ** making any modifications.  */
-  if( pCur->curFlags & BTCF_Multiple ){
-    rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur);
-    if( rc ) return rc;
-  }
-
-  /* If this is a delete operation to remove a row from a table b-tree,
-  ** invalidate any incrblob cursors open on the row being deleted.  */
-  if( pCur->pKeyInfo==0 ){
-    invalidateIncrblobCursors(p, pCur->info.nKey, 0);
-  }
-
-  /* If the bPreserve flag is set to true, then the cursor position must
-  ** be preserved following this delete operation. If the current delete
-  ** will cause a b-tree rebalance, then this is done by saving the cursor
-  ** key and leaving the cursor in CURSOR_REQUIRESEEK state before 
-  ** returning. 
-  **
-  ** Or, if the current delete will not cause a rebalance, then the cursor
-  ** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
-  ** before or after the deleted entry. In this case set bSkipnext to true.  */
-  if( bPreserve ){
-    if( !pPage->leaf 
-     || (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
-    ){
-      /* A b-tree rebalance will be required after deleting this entry.
-      ** Save the cursor key.  */
-      rc = saveCursorKey(pCur);
-      if( rc ) return rc;
-    }else{
-      bSkipnext = 1;
-    }
-  }
-
-  /* Make the page containing the entry to be deleted writable. Then free any
-  ** overflow pages associated with the entry and finally remove the cell
-  ** itself from within the page.  */
-  rc = sqlite3PagerWrite(pPage->pDbPage);
-  if( rc ) return rc;
-  rc = clearCell(pPage, pCell, &szCell);
-  dropCell(pPage, iCellIdx, szCell, &rc);
-  if( rc ) return rc;
-
-  /* If the cell deleted was not located on a leaf page, then the cursor
-  ** is currently pointing to the largest entry in the sub-tree headed
-  ** by the child-page of the cell that was just deleted from an internal
-  ** node. The cell from the leaf node needs to be moved to the internal
-  ** node to replace the deleted cell.  */
-  if( !pPage->leaf ){
-    MemPage *pLeaf = pCur->apPage[pCur->iPage];
-    int nCell;
-    Pgno n = pCur->apPage[iCellDepth+1]->pgno;
-    unsigned char *pTmp;
-
-    pCell = findCell(pLeaf, pLeaf->nCell-1);
-    if( pCell<&pLeaf->aData[4] ) return SQLITE_CORRUPT_BKPT;
-    nCell = pLeaf->xCellSize(pLeaf, pCell);
-    assert( MX_CELL_SIZE(pBt) >= nCell );
-    pTmp = pBt->pTmpSpace;
-    assert( pTmp!=0 );
-    rc = sqlite3PagerWrite(pLeaf->pDbPage);
-    insertCell(pPage, iCellIdx, pCell-4, nCell+4, pTmp, n, &rc);
-    dropCell(pLeaf, pLeaf->nCell-1, nCell, &rc);
-    if( rc ) return rc;
-  }
-
-  /* Balance the tree. If the entry deleted was located on a leaf page,
-  ** then the cursor still points to that page. In this case the first
-  ** call to balance() repairs the tree, and the if(...) condition is
-  ** never true.
-  **
-  ** Otherwise, if the entry deleted was on an internal node page, then
-  ** pCur is pointing to the leaf page from which a cell was removed to
-  ** replace the cell deleted from the internal node. This is slightly
-  ** tricky as the leaf node may be underfull, and the internal node may
-  ** be either under or overfull. In this case run the balancing algorithm
-  ** on the leaf node first. If the balance proceeds far enough up the
-  ** tree that we can be sure that any problem in the internal node has
-  ** been corrected, so be it. Otherwise, after balancing the leaf node,
-  ** walk the cursor up the tree to the internal node and balance it as 
-  ** well.  */
-  rc = balance(pCur);
-  if( rc==SQLITE_OK && pCur->iPage>iCellDepth ){
-    while( pCur->iPage>iCellDepth ){
-      releasePage(pCur->apPage[pCur->iPage--]);
-    }
-    rc = balance(pCur);
-  }
-
-  if( rc==SQLITE_OK ){
-    if( bSkipnext ){
-      assert( bPreserve && pCur->iPage==iCellDepth );
-      assert( pPage==pCur->apPage[pCur->iPage] );
-      assert( (pPage->nCell>0 || CORRUPT_DB) && iCellIdx<=pPage->nCell );
-      pCur->eState = CURSOR_SKIPNEXT;
-      if( iCellIdx>=pPage->nCell ){
-        pCur->skipNext = -1;
-        pCur->aiIdx[iCellDepth] = pPage->nCell-1;
-      }else{
-        pCur->skipNext = 1;
-      }
-    }else{
-      rc = moveToRoot(pCur);
-      if( bPreserve ){
-        pCur->eState = CURSOR_REQUIRESEEK;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Create a new BTree table.  Write into *piTable the page
-** number for the root page of the new table.
-**
-** The type of type is determined by the flags parameter.  Only the
-** following values of flags are currently in use.  Other values for
-** flags might not work:
-**
-**     BTREE_INTKEY|BTREE_LEAFDATA     Used for SQL tables with rowid keys
-**     BTREE_ZERODATA                  Used for SQL indices
-*/
-static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
-  BtShared *pBt = p->pBt;
-  MemPage *pRoot;
-  Pgno pgnoRoot;
-  int rc;
-  int ptfFlags;          /* Page-type flage for the root page of new table */
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( pBt->inTransaction==TRANS_WRITE );
-  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
-
-#ifdef SQLITE_OMIT_AUTOVACUUM
-  rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
-  if( rc ){
-    return rc;
-  }
-#else
-  if( pBt->autoVacuum ){
-    Pgno pgnoMove;      /* Move a page here to make room for the root-page */
-    MemPage *pPageMove; /* The page to move to. */
-
-    /* Creating a new table may probably require moving an existing database
-    ** to make room for the new tables root page. In case this page turns
-    ** out to be an overflow page, delete all overflow page-map caches
-    ** held by open cursors.
-    */
-    invalidateAllOverflowCache(pBt);
-
-    /* Read the value of meta[3] from the database to determine where the
-    ** root page of the new table should go. meta[3] is the largest root-page
-    ** created so far, so the new root-page is (meta[3]+1).
-    */
-    sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &pgnoRoot);
-    pgnoRoot++;
-
-    /* The new root-page may not be allocated on a pointer-map page, or the
-    ** PENDING_BYTE page.
-    */
-    while( pgnoRoot==PTRMAP_PAGENO(pBt, pgnoRoot) ||
-        pgnoRoot==PENDING_BYTE_PAGE(pBt) ){
-      pgnoRoot++;
-    }
-    assert( pgnoRoot>=3 || CORRUPT_DB );
-    testcase( pgnoRoot<3 );
-
-    /* Allocate a page. The page that currently resides at pgnoRoot will
-    ** be moved to the allocated page (unless the allocated page happens
-    ** to reside at pgnoRoot).
-    */
-    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, BTALLOC_EXACT);
-    if( rc!=SQLITE_OK ){
-      return rc;
-    }
-
-    if( pgnoMove!=pgnoRoot ){
-      /* pgnoRoot is the page that will be used for the root-page of
-      ** the new table (assuming an error did not occur). But we were
-      ** allocated pgnoMove. If required (i.e. if it was not allocated
-      ** by extending the file), the current page at position pgnoMove
-      ** is already journaled.
-      */
-      u8 eType = 0;
-      Pgno iPtrPage = 0;
-
-      /* Save the positions of any open cursors. This is required in
-      ** case they are holding a reference to an xFetch reference
-      ** corresponding to page pgnoRoot.  */
-      rc = saveAllCursors(pBt, 0, 0);
-      releasePage(pPageMove);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-
-      /* Move the page currently at pgnoRoot to pgnoMove. */
-      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-      rc = ptrmapGet(pBt, pgnoRoot, &eType, &iPtrPage);
-      if( eType==PTRMAP_ROOTPAGE || eType==PTRMAP_FREEPAGE ){
-        rc = SQLITE_CORRUPT_BKPT;
-      }
-      if( rc!=SQLITE_OK ){
-        releasePage(pRoot);
-        return rc;
-      }
-      assert( eType!=PTRMAP_ROOTPAGE );
-      assert( eType!=PTRMAP_FREEPAGE );
-      rc = relocatePage(pBt, pRoot, eType, iPtrPage, pgnoMove, 0);
-      releasePage(pRoot);
-
-      /* Obtain the page at pgnoRoot */
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-      rc = btreeGetPage(pBt, pgnoRoot, &pRoot, 0);
-      if( rc!=SQLITE_OK ){
-        return rc;
-      }
-      rc = sqlite3PagerWrite(pRoot->pDbPage);
-      if( rc!=SQLITE_OK ){
-        releasePage(pRoot);
-        return rc;
-      }
-    }else{
-      pRoot = pPageMove;
-    } 
-
-    /* Update the pointer-map and meta-data with the new root-page number. */
-    ptrmapPut(pBt, pgnoRoot, PTRMAP_ROOTPAGE, 0, &rc);
-    if( rc ){
-      releasePage(pRoot);
-      return rc;
-    }
-
-    /* When the new root page was allocated, page 1 was made writable in
-    ** order either to increase the database filesize, or to decrement the
-    ** freelist count.  Hence, the sqlite3BtreeUpdateMeta() call cannot fail.
-    */
-    assert( sqlite3PagerIswriteable(pBt->pPage1->pDbPage) );
-    rc = sqlite3BtreeUpdateMeta(p, 4, pgnoRoot);
-    if( NEVER(rc) ){
-      releasePage(pRoot);
-      return rc;
-    }
-
-  }else{
-    rc = allocateBtreePage(pBt, &pRoot, &pgnoRoot, 1, 0);
-    if( rc ) return rc;
-  }
-#endif
-  assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
-  if( createTabFlags & BTREE_INTKEY ){
-    ptfFlags = PTF_INTKEY | PTF_LEAFDATA | PTF_LEAF;
-  }else{
-    ptfFlags = PTF_ZERODATA | PTF_LEAF;
-  }
-  zeroPage(pRoot, ptfFlags);
-  sqlite3PagerUnref(pRoot->pDbPage);
-  assert( (pBt->openFlags & BTREE_SINGLE)==0 || pgnoRoot==2 );
-  *piTable = (int)pgnoRoot;
-  return SQLITE_OK;
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCreateTable(Btree *p, int *piTable, int flags){
-  int rc;
-  sqlite3BtreeEnter(p);
-  rc = btreeCreateTable(p, piTable, flags);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Erase the given database page and all its children.  Return
-** the page to the freelist.
-*/
-static int clearDatabasePage(
-  BtShared *pBt,           /* The BTree that contains the table */
-  Pgno pgno,               /* Page number to clear */
-  int freePageFlag,        /* Deallocate page if true */
-  int *pnChange            /* Add number of Cells freed to this counter */
-){
-  MemPage *pPage;
-  int rc;
-  unsigned char *pCell;
-  int i;
-  int hdr;
-  u16 szCell;
-
-  assert( sqlite3_mutex_held(pBt->mutex) );
-  if( pgno>btreePagecount(pBt) ){
-    return SQLITE_CORRUPT_BKPT;
-  }
-  rc = getAndInitPage(pBt, pgno, &pPage, 0, 0);
-  if( rc ) return rc;
-  if( pPage->bBusy ){
-    rc = SQLITE_CORRUPT_BKPT;
-    goto cleardatabasepage_out;
-  }
-  pPage->bBusy = 1;
-  hdr = pPage->hdrOffset;
-  for(i=0; i<pPage->nCell; i++){
-    pCell = findCell(pPage, i);
-    if( !pPage->leaf ){
-      rc = clearDatabasePage(pBt, get4byte(pCell), 1, pnChange);
-      if( rc ) goto cleardatabasepage_out;
-    }
-    rc = clearCell(pPage, pCell, &szCell);
-    if( rc ) goto cleardatabasepage_out;
-  }
-  if( !pPage->leaf ){
-    rc = clearDatabasePage(pBt, get4byte(&pPage->aData[hdr+8]), 1, pnChange);
-    if( rc ) goto cleardatabasepage_out;
-  }else if( pnChange ){
-    assert( pPage->intKey || CORRUPT_DB );
-    testcase( !pPage->intKey );
-    *pnChange += pPage->nCell;
-  }
-  if( freePageFlag ){
-    freePage(pPage, &rc);
-  }else if( (rc = sqlite3PagerWrite(pPage->pDbPage))==0 ){
-    zeroPage(pPage, pPage->aData[hdr] | PTF_LEAF);
-  }
-
-cleardatabasepage_out:
-  pPage->bBusy = 0;
-  releasePage(pPage);
-  return rc;
-}
-
-/*
-** Delete all information from a single table in the database.  iTable is
-** the page number of the root of the table.  After this routine returns,
-** the root page is empty, but still exists.
-**
-** This routine will fail with SQLITE_LOCKED if there are any open
-** read cursors on the table.  Open write cursors are moved to the
-** root of the table.
-**
-** If pnChange is not NULL, then table iTable must be an intkey table. The
-** integer value pointed to by pnChange is incremented by the number of
-** entries in the table.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeClearTable(Btree *p, int iTable, int *pnChange){
-  int rc;
-  BtShared *pBt = p->pBt;
-  sqlite3BtreeEnter(p);
-  assert( p->inTrans==TRANS_WRITE );
-
-  rc = saveAllCursors(pBt, (Pgno)iTable, 0);
-
-  if( SQLITE_OK==rc ){
-    /* Invalidate all incrblob cursors open on table iTable (assuming iTable
-    ** is the root of a table b-tree - if it is not, the following call is
-    ** a no-op).  */
-    invalidateIncrblobCursors(p, 0, 1);
-    rc = clearDatabasePage(pBt, (Pgno)iTable, 0, pnChange);
-  }
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-/*
-** Delete all information from the single table that pCur is open on.
-**
-** This routine only work for pCur on an ephemeral table.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeClearTableOfCursor(BtCursor *pCur){
-  return sqlite3BtreeClearTable(pCur->pBtree, pCur->pgnoRoot, 0);
-}
-
-/*
-** Erase all information in a table and add the root of the table to
-** the freelist.  Except, the root of the principle table (the one on
-** page 1) is never added to the freelist.
-**
-** This routine will fail with SQLITE_LOCKED if there are any open
-** cursors on the table.
-**
-** If AUTOVACUUM is enabled and the page at iTable is not the last
-** root page in the database file, then the last root page 
-** in the database file is moved into the slot formerly occupied by
-** iTable and that last slot formerly occupied by the last root page
-** is added to the freelist instead of iTable.  In this say, all
-** root pages are kept at the beginning of the database file, which
-** is necessary for AUTOVACUUM to work right.  *piMoved is set to the 
-** page number that used to be the last root page in the file before
-** the move.  If no page gets moved, *piMoved is set to 0.
-** The last root page is recorded in meta[3] and the value of
-** meta[3] is updated by this procedure.
-*/
-static int btreeDropTable(Btree *p, Pgno iTable, int *piMoved){
-  int rc;
-  MemPage *pPage = 0;
-  BtShared *pBt = p->pBt;
-
-  assert( sqlite3BtreeHoldsMutex(p) );
-  assert( p->inTrans==TRANS_WRITE );
-
-  /* It is illegal to drop a table if any cursors are open on the
-  ** database. This is because in auto-vacuum mode the backend may
-  ** need to move another root-page to fill a gap left by the deleted
-  ** root page. If an open cursor was using this page a problem would 
-  ** occur.
-  **
-  ** This error is caught long before control reaches this point.
-  */
-  if( NEVER(pBt->pCursor) ){
-    sqlite3ConnectionBlocked(p->db, pBt->pCursor->pBtree->db);
-    return SQLITE_LOCKED_SHAREDCACHE;
-  }
-
-  rc = btreeGetPage(pBt, (Pgno)iTable, &pPage, 0);
-  if( rc ) return rc;
-  rc = sqlite3BtreeClearTable(p, iTable, 0);
-  if( rc ){
-    releasePage(pPage);
-    return rc;
-  }
-
-  *piMoved = 0;
-
-  if( iTable>1 ){
-#ifdef SQLITE_OMIT_AUTOVACUUM
-    freePage(pPage, &rc);
-    releasePage(pPage);
-#else
-    if( pBt->autoVacuum ){
-      Pgno maxRootPgno;
-      sqlite3BtreeGetMeta(p, BTREE_LARGEST_ROOT_PAGE, &maxRootPgno);
-
-      if( iTable==maxRootPgno ){
-        /* If the table being dropped is the table with the largest root-page
-        ** number in the database, put the root page on the free list. 
-        */
-        freePage(pPage, &rc);
-        releasePage(pPage);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-      }else{
-        /* The table being dropped does not have the largest root-page
-        ** number in the database. So move the page that does into the 
-        ** gap left by the deleted root-page.
-        */
-        MemPage *pMove;
-        releasePage(pPage);
-        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        rc = relocatePage(pBt, pMove, PTRMAP_ROOTPAGE, 0, iTable, 0);
-        releasePage(pMove);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        pMove = 0;
-        rc = btreeGetPage(pBt, maxRootPgno, &pMove, 0);
-        freePage(pMove, &rc);
-        releasePage(pMove);
-        if( rc!=SQLITE_OK ){
-          return rc;
-        }
-        *piMoved = maxRootPgno;
-      }
-
-      /* Set the new 'max-root-page' value in the database header. This
-      ** is the old value less one, less one more if that happens to
-      ** be a root-page number, less one again if that is the
-      ** PENDING_BYTE_PAGE.
-      */
-      maxRootPgno--;
-      while( maxRootPgno==PENDING_BYTE_PAGE(pBt)
-             || PTRMAP_ISPAGE(pBt, maxRootPgno) ){
-        maxRootPgno--;
-      }
-      assert( maxRootPgno!=PENDING_BYTE_PAGE(pBt) );
-
-      rc = sqlite3BtreeUpdateMeta(p, 4, maxRootPgno);
-    }else{
-      freePage(pPage, &rc);
-      releasePage(pPage);
-    }
-#endif
-  }else{
-    /* If sqlite3BtreeDropTable was called on page 1.
-    ** This really never should happen except in a corrupt
-    ** database. 
-    */
-    zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
-    releasePage(pPage);
-  }
-  return rc;  
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeDropTable(Btree *p, int iTable, int *piMoved){
-  int rc;
-  sqlite3BtreeEnter(p);
-  rc = btreeDropTable(p, iTable, piMoved);
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-
-/*
-** This function may only be called if the b-tree connection already
-** has a read or write transaction open on the database.
-**
-** Read the meta-information out of a database file.  Meta[0]
-** is the number of free pages currently in the database.  Meta[1]
-** through meta[15] are available for use by higher layers.  Meta[0]
-** is read-only, the others are read/write.
-** 
-** The schema layer numbers meta values differently.  At the schema
-** layer (and the SetCookie and ReadCookie opcodes) the number of
-** free pages is not visible.  So Cookie[0] is the same as Meta[1].
-**
-** This routine treats Meta[BTREE_DATA_VERSION] as a special case.  Instead
-** of reading the value out of the header, it instead loads the "DataVersion"
-** from the pager.  The BTREE_DATA_VERSION value is not actually stored in the
-** database file.  It is a number computed by the pager.  But its access
-** pattern is the same as header meta values, and so it is convenient to
-** read it from this routine.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeGetMeta(Btree *p, int idx, u32 *pMeta){
-  BtShared *pBt = p->pBt;
-
-  sqlite3BtreeEnter(p);
-  assert( p->inTrans>TRANS_NONE );
-  assert( SQLITE_OK==querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK) );
-  assert( pBt->pPage1 );
-  assert( idx>=0 && idx<=15 );
-
-  if( idx==BTREE_DATA_VERSION ){
-    *pMeta = sqlite3PagerDataVersion(pBt->pPager) + p->iDataVersion;
-  }else{
-    *pMeta = get4byte(&pBt->pPage1->aData[36 + idx*4]);
-  }
-
-  /* If auto-vacuum is disabled in this build and this is an auto-vacuum
-  ** database, mark the database as read-only.  */
-#ifdef SQLITE_OMIT_AUTOVACUUM
-  if( idx==BTREE_LARGEST_ROOT_PAGE && *pMeta>0 ){
-    pBt->btsFlags |= BTS_READ_ONLY;
-  }
-#endif
-
-  sqlite3BtreeLeave(p);
-}
-
-/*
-** Write meta-information back into the database.  Meta[0] is
-** read-only and may not be written.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeUpdateMeta(Btree *p, int idx, u32 iMeta){
-  BtShared *pBt = p->pBt;
-  unsigned char *pP1;
-  int rc;
-  assert( idx>=1 && idx<=15 );
-  sqlite3BtreeEnter(p);
-  assert( p->inTrans==TRANS_WRITE );
-  assert( pBt->pPage1!=0 );
-  pP1 = pBt->pPage1->aData;
-  rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-  if( rc==SQLITE_OK ){
-    put4byte(&pP1[36 + idx*4], iMeta);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( idx==BTREE_INCR_VACUUM ){
-      assert( pBt->autoVacuum || iMeta==0 );
-      assert( iMeta==0 || iMeta==1 );
-      pBt->incrVacuum = (u8)iMeta;
-    }
-#endif
-  }
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-#ifndef SQLITE_OMIT_BTREECOUNT
-/*
-** The first argument, pCur, is a cursor opened on some b-tree. Count the
-** number of entries in the b-tree and write the result to *pnEntry.
-**
-** SQLITE_OK is returned if the operation is successfully executed. 
-** Otherwise, if an error is encountered (i.e. an IO error or database
-** corruption) an SQLite error code is returned.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){
-  i64 nEntry = 0;                      /* Value to return in *pnEntry */
-  int rc;                              /* Return code */
-
-  if( pCur->pgnoRoot==0 ){
-    *pnEntry = 0;
-    return SQLITE_OK;
-  }
-  rc = moveToRoot(pCur);
-
-  /* Unless an error occurs, the following loop runs one iteration for each
-  ** page in the B-Tree structure (not including overflow pages). 
-  */
-  while( rc==SQLITE_OK ){
-    int iIdx;                          /* Index of child node in parent */
-    MemPage *pPage;                    /* Current page of the b-tree */
-
-    /* If this is a leaf page or the tree is not an int-key tree, then 
-    ** this page contains countable entries. Increment the entry counter
-    ** accordingly.
-    */
-    pPage = pCur->apPage[pCur->iPage];
-    if( pPage->leaf || !pPage->intKey ){
-      nEntry += pPage->nCell;
-    }
-
-    /* pPage is a leaf node. This loop navigates the cursor so that it 
-    ** points to the first interior cell that it points to the parent of
-    ** the next page in the tree that has not yet been visited. The
-    ** pCur->aiIdx[pCur->iPage] value is set to the index of the parent cell
-    ** of the page, or to the number of cells in the page if the next page
-    ** to visit is the right-child of its parent.
-    **
-    ** If all pages in the tree have been visited, return SQLITE_OK to the
-    ** caller.
-    */
-    if( pPage->leaf ){
-      do {
-        if( pCur->iPage==0 ){
-          /* All pages of the b-tree have been visited. Return successfully. */
-          *pnEntry = nEntry;
-          return moveToRoot(pCur);
-        }
-        moveToParent(pCur);
-      }while ( pCur->aiIdx[pCur->iPage]>=pCur->apPage[pCur->iPage]->nCell );
-
-      pCur->aiIdx[pCur->iPage]++;
-      pPage = pCur->apPage[pCur->iPage];
-    }
-
-    /* Descend to the child node of the cell that the cursor currently 
-    ** points at. This is the right-child if (iIdx==pPage->nCell).
-    */
-    iIdx = pCur->aiIdx[pCur->iPage];
-    if( iIdx==pPage->nCell ){
-      rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+8]));
-    }else{
-      rc = moveToChild(pCur, get4byte(findCell(pPage, iIdx)));
-    }
-  }
-
-  /* An error has occurred. Return an error code. */
-  return rc;
-}
-#endif
-
-/*
-** Return the pager associated with a BTree.  This routine is used for
-** testing and debugging only.
-*/
-SQLITE_API Pager *SQLITE_STDCALL sqlite3BtreePager(Btree *p){
-  return p->pBt->pPager;
-}
-
-#ifndef SQLITE_OMIT_INTEGRITY_CHECK
-/*
-** Append a message to the error message string.
-*/
-static void checkAppendMsg(
-  IntegrityCk *pCheck,
-  const char *zFormat,
-  ...
-){
-  va_list ap;
-  if( !pCheck->mxErr ) return;
-  pCheck->mxErr--;
-  pCheck->nErr++;
-  va_start(ap, zFormat);
-  if( pCheck->errMsg.nChar ){
-    sqlite3StrAccumAppend(&pCheck->errMsg, "\n", 1);
-  }
-  if( pCheck->zPfx ){
-    sqlite3XPrintf(&pCheck->errMsg, 0, pCheck->zPfx, pCheck->v1, pCheck->v2);
-  }
-  sqlite3VXPrintf(&pCheck->errMsg, 1, zFormat, ap);
-  va_end(ap);
-  if( pCheck->errMsg.accError==STRACCUM_NOMEM ){
-    pCheck->mallocFailed = 1;
-  }
-}
-#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
-
-#ifndef SQLITE_OMIT_INTEGRITY_CHECK
-
-/*
-** Return non-zero if the bit in the IntegrityCk.aPgRef[] array that
-** corresponds to page iPg is already set.
-*/
-static int getPageReferenced(IntegrityCk *pCheck, Pgno iPg){
-  assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
-  return (pCheck->aPgRef[iPg/8] & (1 << (iPg & 0x07)));
-}
-
-/*
-** Set the bit in the IntegrityCk.aPgRef[] array that corresponds to page iPg.
-*/
-static void setPageReferenced(IntegrityCk *pCheck, Pgno iPg){
-  assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
-  pCheck->aPgRef[iPg/8] |= (1 << (iPg & 0x07));
-}
-
-
-/*
-** Add 1 to the reference count for page iPage.  If this is the second
-** reference to the page, add an error message to pCheck->zErrMsg.
-** Return 1 if there are 2 or more references to the page and 0 if
-** if this is the first reference to the page.
-**
-** Also check that the page number is in bounds.
-*/
-static int checkRef(IntegrityCk *pCheck, Pgno iPage){
-  if( iPage==0 ) return 1;
-  if( iPage>pCheck->nPage ){
-    checkAppendMsg(pCheck, "invalid page number %d", iPage);
-    return 1;
-  }
-  if( getPageReferenced(pCheck, iPage) ){
-    checkAppendMsg(pCheck, "2nd reference to page %d", iPage);
-    return 1;
-  }
-  setPageReferenced(pCheck, iPage);
-  return 0;
-}
-
-#ifndef SQLITE_OMIT_AUTOVACUUM
-/*
-** Check that the entry in the pointer-map for page iChild maps to 
-** page iParent, pointer type ptrType. If not, append an error message
-** to pCheck.
-*/
-static void checkPtrmap(
-  IntegrityCk *pCheck,   /* Integrity check context */
-  Pgno iChild,           /* Child page number */
-  u8 eType,              /* Expected pointer map type */
-  Pgno iParent           /* Expected pointer map parent page number */
-){
-  int rc;
-  u8 ePtrmapType;
-  Pgno iPtrmapParent;
-
-  rc = ptrmapGet(pCheck->pBt, iChild, &ePtrmapType, &iPtrmapParent);
-  if( rc!=SQLITE_OK ){
-    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ) pCheck->mallocFailed = 1;
-    checkAppendMsg(pCheck, "Failed to read ptrmap key=%d", iChild);
-    return;
-  }
-
-  if( ePtrmapType!=eType || iPtrmapParent!=iParent ){
-    checkAppendMsg(pCheck,
-      "Bad ptr map entry key=%d expected=(%d,%d) got=(%d,%d)", 
-      iChild, eType, iParent, ePtrmapType, iPtrmapParent);
-  }
-}
-#endif
-
-/*
-** Check the integrity of the freelist or of an overflow page list.
-** Verify that the number of pages on the list is N.
-*/
-static void checkList(
-  IntegrityCk *pCheck,  /* Integrity checking context */
-  int isFreeList,       /* True for a freelist.  False for overflow page list */
-  int iPage,            /* Page number for first page in the list */
-  int N                 /* Expected number of pages in the list */
-){
-  int i;
-  int expected = N;
-  int iFirst = iPage;
-  while( N-- > 0 && pCheck->mxErr ){
-    DbPage *pOvflPage;
-    unsigned char *pOvflData;
-    if( iPage<1 ){
-      checkAppendMsg(pCheck,
-         "%d of %d pages missing from overflow list starting at %d",
-          N+1, expected, iFirst);
-      break;
-    }
-    if( checkRef(pCheck, iPage) ) break;
-    if( sqlite3PagerGet(pCheck->pPager, (Pgno)iPage, &pOvflPage) ){
-      checkAppendMsg(pCheck, "failed to get page %d", iPage);
-      break;
-    }
-    pOvflData = (unsigned char *)sqlite3PagerGetData(pOvflPage);
-    if( isFreeList ){
-      int n = get4byte(&pOvflData[4]);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      if( pCheck->pBt->autoVacuum ){
-        checkPtrmap(pCheck, iPage, PTRMAP_FREEPAGE, 0);
-      }
-#endif
-      if( n>(int)pCheck->pBt->usableSize/4-2 ){
-        checkAppendMsg(pCheck,
-           "freelist leaf count too big on page %d", iPage);
-        N--;
-      }else{
-        for(i=0; i<n; i++){
-          Pgno iFreePage = get4byte(&pOvflData[8+i*4]);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-          if( pCheck->pBt->autoVacuum ){
-            checkPtrmap(pCheck, iFreePage, PTRMAP_FREEPAGE, 0);
-          }
-#endif
-          checkRef(pCheck, iFreePage);
-        }
-        N -= n;
-      }
-    }
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    else{
-      /* If this database supports auto-vacuum and iPage is not the last
-      ** page in this overflow list, check that the pointer-map entry for
-      ** the following page matches iPage.
-      */
-      if( pCheck->pBt->autoVacuum && N>0 ){
-        i = get4byte(pOvflData);
-        checkPtrmap(pCheck, i, PTRMAP_OVERFLOW2, iPage);
-      }
-    }
-#endif
-    iPage = get4byte(pOvflData);
-    sqlite3PagerUnref(pOvflPage);
-
-    if( isFreeList && N<(iPage!=0) ){
-      checkAppendMsg(pCheck, "free-page count in header is too small");
-    }
-  }
-}
-#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
-
-/*
-** An implementation of a min-heap.
-**
-** aHeap[0] is the number of elements on the heap.  aHeap[1] is the
-** root element.  The daughter nodes of aHeap[N] are aHeap[N*2]
-** and aHeap[N*2+1].
-**
-** The heap property is this:  Every node is less than or equal to both
-** of its daughter nodes.  A consequence of the heap property is that the
-** root node aHeap[1] is always the minimum value currently in the heap.
-**
-** The btreeHeapInsert() routine inserts an unsigned 32-bit number onto
-** the heap, preserving the heap property.  The btreeHeapPull() routine
-** removes the root element from the heap (the minimum value in the heap)
-** and then moves other nodes around as necessary to preserve the heap
-** property.
-**
-** This heap is used for cell overlap and coverage testing.  Each u32
-** entry represents the span of a cell or freeblock on a btree page.  
-** The upper 16 bits are the index of the first byte of a range and the
-** lower 16 bits are the index of the last byte of that range.
-*/
-static void btreeHeapInsert(u32 *aHeap, u32 x){
-  u32 j, i = ++aHeap[0];
-  aHeap[i] = x;
-  while( (j = i/2)>0 && aHeap[j]>aHeap[i] ){
-    x = aHeap[j];
-    aHeap[j] = aHeap[i];
-    aHeap[i] = x;
-    i = j;
-  }
-}
-static int btreeHeapPull(u32 *aHeap, u32 *pOut){
-  u32 j, i, x;
-  if( (x = aHeap[0])==0 ) return 0;
-  *pOut = aHeap[1];
-  aHeap[1] = aHeap[x];
-  aHeap[x] = 0xffffffff;
-  aHeap[0]--;
-  i = 1;
-  while( (j = i*2)<=aHeap[0] ){
-    if( aHeap[j]>aHeap[j+1] ) j++;
-    if( aHeap[i]<aHeap[j] ) break;
-    x = aHeap[i];
-    aHeap[i] = aHeap[j];
-    aHeap[j] = x;
-    i = j;
-  }
-  return 1;  
-}
-
-#ifndef SQLITE_OMIT_INTEGRITY_CHECK
-/*
-** Do various sanity checks on a single page of a tree.  Return
-** the tree depth.  Root pages return 0.  Parents of root pages
-** return 1, and so forth.
-** 
-** These checks are done:
-**
-**      1.  Make sure that cells and freeblocks do not overlap
-**          but combine to completely cover the page.
-**      2.  Make sure integer cell keys are in order.
-**      3.  Check the integrity of overflow pages.
-**      4.  Recursively call checkTreePage on all children.
-**      5.  Verify that the depth of all children is the same.
-*/
-static int checkTreePage(
-  IntegrityCk *pCheck,  /* Context for the sanity check */
-  int iPage,            /* Page number of the page to check */
-  i64 *piMinKey,        /* Write minimum integer primary key here */
-  i64 maxKey            /* Error if integer primary key greater than this */
-){
-  MemPage *pPage = 0;      /* The page being analyzed */
-  int i;                   /* Loop counter */
-  int rc;                  /* Result code from subroutine call */
-  int depth = -1, d2;      /* Depth of a subtree */
-  int pgno;                /* Page number */
-  int nFrag;               /* Number of fragmented bytes on the page */
-  int hdr;                 /* Offset to the page header */
-  int cellStart;           /* Offset to the start of the cell pointer array */
-  int nCell;               /* Number of cells */
-  int doCoverageCheck = 1; /* True if cell coverage checking should be done */
-  int keyCanBeEqual = 1;   /* True if IPK can be equal to maxKey
-                           ** False if IPK must be strictly less than maxKey */
-  u8 *data;                /* Page content */
-  u8 *pCell;               /* Cell content */
-  u8 *pCellIdx;            /* Next element of the cell pointer array */
-  BtShared *pBt;           /* The BtShared object that owns pPage */
-  u32 pc;                  /* Address of a cell */
-  u32 usableSize;          /* Usable size of the page */
-  u32 contentOffset;       /* Offset to the start of the cell content area */
-  u32 *heap = 0;           /* Min-heap used for checking cell coverage */
-  u32 x, prev = 0;         /* Next and previous entry on the min-heap */
-  const char *saved_zPfx = pCheck->zPfx;
-  int saved_v1 = pCheck->v1;
-  int saved_v2 = pCheck->v2;
-  u8 savedIsInit = 0;
-
-  /* Check that the page exists
-  */
-  pBt = pCheck->pBt;
-  usableSize = pBt->usableSize;
-  if( iPage==0 ) return 0;
-  if( checkRef(pCheck, iPage) ) return 0;
-  pCheck->zPfx = "Page %d: ";
-  pCheck->v1 = iPage;
-  if( (rc = btreeGetPage(pBt, (Pgno)iPage, &pPage, 0))!=0 ){
-    checkAppendMsg(pCheck,
-       "unable to get the page. error code=%d", rc);
-    goto end_of_check;
-  }
-
-  /* Clear MemPage.isInit to make sure the corruption detection code in
-  ** btreeInitPage() is executed.  */
-  savedIsInit = pPage->isInit;
-  pPage->isInit = 0;
-  if( (rc = btreeInitPage(pPage))!=0 ){
-    assert( rc==SQLITE_CORRUPT );  /* The only possible error from InitPage */
-    checkAppendMsg(pCheck,
-                   "btreeInitPage() returns error code %d", rc);
-    goto end_of_check;
-  }
-  data = pPage->aData;
-  hdr = pPage->hdrOffset;
-
-  /* Set up for cell analysis */
-  pCheck->zPfx = "On tree page %d cell %d: ";
-  contentOffset = get2byteNotZero(&data[hdr+5]);
-  assert( contentOffset<=usableSize );  /* Enforced by btreeInitPage() */
-
-  /* EVIDENCE-OF: R-37002-32774 The two-byte integer at offset 3 gives the
-  ** number of cells on the page. */
-  nCell = get2byte(&data[hdr+3]);
-  assert( pPage->nCell==nCell );
-
-  /* EVIDENCE-OF: R-23882-45353 The cell pointer array of a b-tree page
-  ** immediately follows the b-tree page header. */
-  cellStart = hdr + 12 - 4*pPage->leaf;
-  assert( pPage->aCellIdx==&data[cellStart] );
-  pCellIdx = &data[cellStart + 2*(nCell-1)];
-
-  if( !pPage->leaf ){
-    /* Analyze the right-child page of internal pages */
-    pgno = get4byte(&data[hdr+8]);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum ){
-      pCheck->zPfx = "On page %d at right child: ";
-      checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
-    }
-#endif
-    depth = checkTreePage(pCheck, pgno, &maxKey, maxKey);
-    keyCanBeEqual = 0;
-  }else{
-    /* For leaf pages, the coverage check will occur in the same loop
-    ** as the other cell checks, so initialize the heap.  */
-    heap = pCheck->heap;
-    heap[0] = 0;
-  }
-
-  /* EVIDENCE-OF: R-02776-14802 The cell pointer array consists of K 2-byte
-  ** integer offsets to the cell contents. */
-  for(i=nCell-1; i>=0 && pCheck->mxErr; i--){
-    CellInfo info;
-
-    /* Check cell size */
-    pCheck->v2 = i;
-    assert( pCellIdx==&data[cellStart + i*2] );
-    pc = get2byteAligned(pCellIdx);
-    pCellIdx -= 2;
-    if( pc<contentOffset || pc>usableSize-4 ){
-      checkAppendMsg(pCheck, "Offset %d out of range %d..%d",
-                             pc, contentOffset, usableSize-4);
-      doCoverageCheck = 0;
-      continue;
-    }
-    pCell = &data[pc];
-    pPage->xParseCell(pPage, pCell, &info);
-    if( pc+info.nSize>usableSize ){
-      checkAppendMsg(pCheck, "Extends off end of page");
-      doCoverageCheck = 0;
-      continue;
-    }
-
-    /* Check for integer primary key out of range */
-    if( pPage->intKey ){
-      if( keyCanBeEqual ? (info.nKey > maxKey) : (info.nKey >= maxKey) ){
-        checkAppendMsg(pCheck, "Rowid %lld out of order", info.nKey);
-      }
-      maxKey = info.nKey;
-    }
-
-    /* Check the content overflow list */
-    if( info.nPayload>info.nLocal ){
-      int nPage;       /* Number of pages on the overflow chain */
-      Pgno pgnoOvfl;   /* First page of the overflow chain */
-      assert( pc + info.iOverflow <= usableSize );
-      nPage = (info.nPayload - info.nLocal + usableSize - 5)/(usableSize - 4);
-      pgnoOvfl = get4byte(&pCell[info.iOverflow]);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      if( pBt->autoVacuum ){
-        checkPtrmap(pCheck, pgnoOvfl, PTRMAP_OVERFLOW1, iPage);
-      }
-#endif
-      checkList(pCheck, 0, pgnoOvfl, nPage);
-    }
-
-    if( !pPage->leaf ){
-      /* Check sanity of left child page for internal pages */
-      pgno = get4byte(pCell);
-#ifndef SQLITE_OMIT_AUTOVACUUM
-      if( pBt->autoVacuum ){
-        checkPtrmap(pCheck, pgno, PTRMAP_BTREE, iPage);
-      }
-#endif
-      d2 = checkTreePage(pCheck, pgno, &maxKey, maxKey);
-      keyCanBeEqual = 0;
-      if( d2!=depth ){
-        checkAppendMsg(pCheck, "Child page depth differs");
-        depth = d2;
-      }
-    }else{
-      /* Populate the coverage-checking heap for leaf pages */
-      btreeHeapInsert(heap, (pc<<16)|(pc+info.nSize-1));
-    }
-  }
-  *piMinKey = maxKey;
-
-  /* Check for complete coverage of the page
-  */
-  pCheck->zPfx = 0;
-  if( doCoverageCheck && pCheck->mxErr>0 ){
-    /* For leaf pages, the min-heap has already been initialized and the
-    ** cells have already been inserted.  But for internal pages, that has
-    ** not yet been done, so do it now */
-    if( !pPage->leaf ){
-      heap = pCheck->heap;
-      heap[0] = 0;
-      for(i=nCell-1; i>=0; i--){
-        u32 size;
-        pc = get2byteAligned(&data[cellStart+i*2]);
-        size = pPage->xCellSize(pPage, &data[pc]);
-        btreeHeapInsert(heap, (pc<<16)|(pc+size-1));
-      }
-    }
-    /* Add the freeblocks to the min-heap
-    **
-    ** EVIDENCE-OF: R-20690-50594 The second field of the b-tree page header
-    ** is the offset of the first freeblock, or zero if there are no
-    ** freeblocks on the page. 
-    */
-    i = get2byte(&data[hdr+1]);
-    while( i>0 ){
-      int size, j;
-      assert( (u32)i<=usableSize-4 );     /* Enforced by btreeInitPage() */
-      size = get2byte(&data[i+2]);
-      assert( (u32)(i+size)<=usableSize );  /* Enforced by btreeInitPage() */
-      btreeHeapInsert(heap, (((u32)i)<<16)|(i+size-1));
-      /* EVIDENCE-OF: R-58208-19414 The first 2 bytes of a freeblock are a
-      ** big-endian integer which is the offset in the b-tree page of the next
-      ** freeblock in the chain, or zero if the freeblock is the last on the
-      ** chain. */
-      j = get2byte(&data[i]);
-      /* EVIDENCE-OF: R-06866-39125 Freeblocks are always connected in order of
-      ** increasing offset. */
-      assert( j==0 || j>i+size );  /* Enforced by btreeInitPage() */
-      assert( (u32)j<=usableSize-4 );   /* Enforced by btreeInitPage() */
-      i = j;
-    }
-    /* Analyze the min-heap looking for overlap between cells and/or 
-    ** freeblocks, and counting the number of untracked bytes in nFrag.
-    ** 
-    ** Each min-heap entry is of the form:    (start_address<<16)|end_address.
-    ** There is an implied first entry the covers the page header, the cell
-    ** pointer index, and the gap between the cell pointer index and the start
-    ** of cell content.  
-    **
-    ** The loop below pulls entries from the min-heap in order and compares
-    ** the start_address against the previous end_address.  If there is an
-    ** overlap, that means bytes are used multiple times.  If there is a gap,
-    ** that gap is added to the fragmentation count.
-    */
-    nFrag = 0;
-    prev = contentOffset - 1;   /* Implied first min-heap entry */
-    while( btreeHeapPull(heap,&x) ){
-      if( (prev&0xffff)>=(x>>16) ){
-        checkAppendMsg(pCheck,
-          "Multiple uses for byte %u of page %d", x>>16, iPage);
-        break;
-      }else{
-        nFrag += (x>>16) - (prev&0xffff) - 1;
-        prev = x;
-      }
-    }
-    nFrag += usableSize - (prev&0xffff) - 1;
-    /* EVIDENCE-OF: R-43263-13491 The total number of bytes in all fragments
-    ** is stored in the fifth field of the b-tree page header.
-    ** EVIDENCE-OF: R-07161-27322 The one-byte integer at offset 7 gives the
-    ** number of fragmented free bytes within the cell content area.
-    */
-    if( heap[0]==0 && nFrag!=data[hdr+7] ){
-      checkAppendMsg(pCheck,
-          "Fragmentation of %d bytes reported as %d on page %d",
-          nFrag, data[hdr+7], iPage);
-    }
-  }
-
-end_of_check:
-  if( !doCoverageCheck ) pPage->isInit = savedIsInit;
-  releasePage(pPage);
-  pCheck->zPfx = saved_zPfx;
-  pCheck->v1 = saved_v1;
-  pCheck->v2 = saved_v2;
-  return depth+1;
-}
-#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
-
-#ifndef SQLITE_OMIT_INTEGRITY_CHECK
-/*
-** This routine does a complete check of the given BTree file.  aRoot[] is
-** an array of pages numbers were each page number is the root page of
-** a table.  nRoot is the number of entries in aRoot.
-**
-** A read-only or read-write transaction must be opened before calling
-** this function.
-**
-** Write the number of error seen in *pnErr.  Except for some memory
-** allocation errors,  an error message held in memory obtained from
-** malloc is returned if *pnErr is non-zero.  If *pnErr==0 then NULL is
-** returned.  If a memory allocation error occurs, NULL is returned.
-*/
-SQLITE_API char *SQLITE_STDCALL sqlite3BtreeIntegrityCheck(
-  Btree *p,     /* The btree to be checked */
-  int *aRoot,   /* An array of root pages numbers for individual trees */
-  int nRoot,    /* Number of entries in aRoot[] */
-  int mxErr,    /* Stop reporting errors after this many */
-  int *pnErr    /* Write number of errors seen to this variable */
-){
-  Pgno i;
-  IntegrityCk sCheck;
-  BtShared *pBt = p->pBt;
-  int savedDbFlags = pBt->pBt->flags;
-  char zErr[100];
-  VVA_ONLY( int nRef );
-
-  sqlite3BtreeEnter(p);
-  assert( p->inTrans>TRANS_NONE && pBt->inTransaction>TRANS_NONE );
-  assert( (nRef = sqlite3PagerRefcount(pBt->pPager))>=0 );
-  sCheck.pBt = pBt;
-  sCheck.pPager = pBt->pPager;
-  sCheck.nPage = btreePagecount(sCheck.pBt);
-  sCheck.mxErr = mxErr;
-  sCheck.nErr = 0;
-  sCheck.mallocFailed = 0;
-  sCheck.zPfx = 0;
-  sCheck.v1 = 0;
-  sCheck.v2 = 0;
-  sCheck.aPgRef = 0;
-  sCheck.heap = 0;
-  sqlite3StrAccumInit(&sCheck.errMsg, 0, zErr, sizeof(zErr), SQLITE_MAX_LENGTH);
-  if( sCheck.nPage==0 ){
-    goto integrity_ck_cleanup;
-  }
-
-  sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
-  if( !sCheck.aPgRef ){
-    sCheck.mallocFailed = 1;
-    goto integrity_ck_cleanup;
-  }
-  sCheck.heap = (u32*)sqlite3PageMalloc( pBt->pageSize );
-  if( sCheck.heap==0 ){
-    sCheck.mallocFailed = 1;
-    goto integrity_ck_cleanup;
-  }
-
-  i = PENDING_BYTE_PAGE(pBt);
-  if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
-
-  /* Check the integrity of the freelist
-  */
-  sCheck.zPfx = "Main freelist: ";
-  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
-            get4byte(&pBt->pPage1->aData[36]));
-  sCheck.zPfx = 0;
-
-  /* Check all the tables.
-  */
-  testcase( pBt->pBt->flags & SQLITE_CellSizeCk );
-  pBt->pBt->flags &= ~SQLITE_CellSizeCk;
-  for(i=0; (int)i<nRoot && sCheck.mxErr; i++){
-    i64 notUsed;
-    if( aRoot[i]==0 ) continue;
-#ifndef SQLITE_OMIT_AUTOVACUUM
-    if( pBt->autoVacuum && aRoot[i]>1 ){
-      checkPtrmap(&sCheck, aRoot[i], PTRMAP_ROOTPAGE, 0);
-    }
-#endif
-    checkTreePage(&sCheck, aRoot[i], &notUsed, LARGEST_INT64);
-  }
-  pBt->pBt->flags = savedDbFlags;
-
-  /* Make sure every page in the file is referenced
-  */
-  for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
-#ifdef SQLITE_OMIT_AUTOVACUUM
-    if( getPageReferenced(&sCheck, i)==0 ){
-      checkAppendMsg(&sCheck, "Page %d is never used", i);
-    }
-#else
-    /* If the database supports auto-vacuum, make sure no tables contain
-    ** references to pointer-map pages.
-    */
-    if( getPageReferenced(&sCheck, i)==0 && 
-       (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
-      checkAppendMsg(&sCheck, "Page %d is never used", i);
-    }
-    if( getPageReferenced(&sCheck, i)!=0 && 
-       (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
-      checkAppendMsg(&sCheck, "Pointer map page %d is referenced", i);
-    }
-#endif
-  }
-
-  /* Clean  up and report errors.
-  */
-integrity_ck_cleanup:
-  sqlite3PageFree(sCheck.heap);
-  sqlite3_free(sCheck.aPgRef);
-  if( sCheck.mallocFailed ){
-    sqlite3StrAccumReset(&sCheck.errMsg);
-    sCheck.nErr++;
-  }
-  *pnErr = sCheck.nErr;
-  if( sCheck.nErr==0 ) sqlite3StrAccumReset(&sCheck.errMsg);
-  /* Make sure this analysis did not leave any unref() pages. */
-  assert( nRef==sqlite3PagerRefcount(pBt->pPager) );
-  sqlite3BtreeLeave(p);
-  return sqlite3StrAccumFinish(&sCheck.errMsg);
-}
-#endif /* SQLITE_OMIT_INTEGRITY_CHECK */
-
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeFileFormat(Btree *p){
-	return p->pBt->file_format;
-}
-
-/*
-** Return the full pathname of the underlying database file.  Return
-** an empty string if the database is in-memory or a TEMP database.
-**
-** The pager filename is invariant as long as the pager is
-** open so it is safe to access without the BtShared mutex.
-*/
-SQLITE_API const char *SQLITE_STDCALL sqlite3BtreeGetFilename(Btree *p){
-  assert( p->pBt->pPager!=0 );
-  return sqlite3PagerFilename(p->pBt->pPager, 1);
-}
-
-/*
-** Return the pathname of the journal file for this database. The return
-** value of this routine is the same regardless of whether the journal file
-** has been created or not.
-**
-** The pager journal filename is invariant as long as the pager is
-** open so it is safe to access without the BtShared mutex.
-*/
-SQLITE_API const char *SQLITE_STDCALL sqlite3BtreeGetJournalname(Btree *p){
-  assert( p->pBt->pPager!=0 );
-  return sqlite3PagerJournalname(p->pBt->pPager);
-}
-
-/*
-** Return non-zero if a transaction is active.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIsInTrans(Btree *p){
-  assert( p==0 || sqlite3_mutex_held(p->db->mutex) );
-  return (p && (p->inTrans==TRANS_WRITE));
-}
-
-#ifndef SQLITE_OMIT_WAL
-/*
-** Run a checkpoint on the Btree passed as the first argument.
-**
-** Return SQLITE_LOCKED if this or any other connection has an open 
-** transaction on the shared-cache the argument Btree is connected to.
-**
-** Parameter eMode is one of SQLITE_CHECKPOINT_PASSIVE, FULL or RESTART.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCheckpoint(Btree *p, int eMode, int *pnLog, int *pnCkpt){
-  int rc = SQLITE_OK;
-  if( p ){
-    BtShared *pBt = p->pBt;
-    sqlite3BtreeEnter(p);
-    if( pBt->inTransaction!=TRANS_NONE ){
-      rc = SQLITE_LOCKED;
-    }else{
-      rc = sqlite3PagerCheckpoint(pBt->pPager, eMode, pnLog, pnCkpt);
-    }
-    sqlite3BtreeLeave(p);
-  }
-  return rc;
-}
-#endif
-
-/*
-** Return non-zero if a read (or write) transaction is active.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIsInReadTrans(Btree *p){
-  assert( p );
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  return p->inTrans!=TRANS_NONE;
-}
-
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIsInBackup(Btree *p){
-  assert( p );
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  return p->nBackup!=0;
-}
-
-/*
-** This function returns a pointer to a blob of memory associated with
-** a single shared-btree. The memory is used by client code for its own
-** purposes (for example, to store a high-level schema associated with 
-** the shared-btree). The btree layer manages reference counting issues.
-**
-** The first time this is called on a shared-btree, nBytes bytes of memory
-** are allocated, zeroed, and returned to the caller. For each subsequent 
-** call the nBytes parameter is ignored and a pointer to the same blob
-** of memory returned. 
-**
-** If the nBytes parameter is 0 and the blob of memory has not yet been
-** allocated, a null pointer is returned. If the blob has already been
-** allocated, it is returned as normal.
-**
-** Just before the shared-btree is closed, the function passed as the 
-** xFree argument when the memory allocation was made is invoked on the 
-** blob of allocated memory. The xFree function should not call sqlite3_free()
-** on the memory, the btree layer does that.
-*/
-SQLITE_API void *SQLITE_STDCALL sqlite3BtreeSchema(Btree *p, int nBytes, void(*xFree)(void *)){
-  BtShared *pBt = p->pBt;
-  sqlite3BtreeEnter(p);
-  if( !pBt->pSchema && nBytes ){
-    pBt->pSchema = sqlite3DbMallocZero(0, nBytes);
-    pBt->xFreeSchema = xFree;
-  }
-  sqlite3BtreeLeave(p);
-  return pBt->pSchema;
-}
-
-/*
-** Return SQLITE_LOCKED_SHAREDCACHE if another user of the same shared 
-** btree as the argument handle holds an exclusive lock on the 
-** sqlite_master table. Otherwise SQLITE_OK.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSchemaLocked(Btree *p){
-  int rc;
-  assert( sqlite3_mutex_held(p->db->mutex) );
-  sqlite3BtreeEnter(p);
-  rc = querySharedCacheTableLock(p, MASTER_ROOT, READ_LOCK);
-  assert( rc==SQLITE_OK || rc==SQLITE_LOCKED_SHAREDCACHE );
-  sqlite3BtreeLeave(p);
-  return rc;
-}
-
-
-#ifndef SQLITE_OMIT_SHARED_CACHE
-/*
-** Obtain a lock on the table whose root page is iTab.  The
-** lock is a write lock if isWritelock is true or a read lock
-** if it is false.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeLockTable(Btree *p, int iTab, u8 isWriteLock){
-  int rc = SQLITE_OK;
-  assert( p->inTrans!=TRANS_NONE );
-  if( p->sharable ){
-    u8 lockType = READ_LOCK + isWriteLock;
-    assert( READ_LOCK+1==WRITE_LOCK );
-    assert( isWriteLock==0 || isWriteLock==1 );
-
-    sqlite3BtreeEnter(p);
-    rc = querySharedCacheTableLock(p, iTab, lockType);
-    if( rc==SQLITE_OK ){
-      rc = setSharedCacheTableLock(p, iTab, lockType);
-    }
-    sqlite3BtreeLeave(p);
-  }
-  return rc;
-}
-#endif
-
-#ifndef SQLITE_OMIT_INCRBLOB
-/*
-** Argument pCsr must be a cursor opened for writing on an 
-** INTKEY table currently pointing at a valid table entry. 
-** This function modifies the data stored as part of that entry.
-**
-** Only the data content may only be modified, it is not possible to 
-** change the length of the data stored. If this function is called with
-** parameters that attempt to write past the end of the existing data,
-** no modifications are made and SQLITE_CORRUPT is returned.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreePutData(BtCursor *pCsr, u32 offset, u32 amt, void *z){
-  int rc;
-  assert( cursorHoldsMutex(pCsr) );
-  assert( sqlite3_mutex_held(pCsr->pBtree->db->mutex) );
-  assert( pCsr->curFlags & BTCF_Incrblob );
-
-  rc = restoreCursorPosition(pCsr);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-  assert( pCsr->eState!=CURSOR_REQUIRESEEK );
-  if( pCsr->eState!=CURSOR_VALID ){
-    return SQLITE_ABORT;
-  }
-
-  /* Save the positions of all other cursors open on this table. This is
-  ** required in case any of them are holding references to an xFetch
-  ** version of the b-tree page modified by the accessPayload call below.
-  **
-  ** Note that pCsr must be open on a INTKEY table and saveCursorPosition()
-  ** and hence saveAllCursors() cannot fail on a BTREE_INTKEY table, hence
-  ** saveAllCursors can only return SQLITE_OK.
-  */
-  VVA_ONLY(rc =) saveAllCursors(pCsr->pBt, pCsr->pgnoRoot, pCsr);
-  assert( rc==SQLITE_OK );
-
-  /* Check some assumptions: 
-  **   (a) the cursor is open for writing,
-  **   (b) there is a read/write transaction open,
-  **   (c) the connection holds a write-lock on the table (if required),
-  **   (d) there are no conflicting read-locks, and
-  **   (e) the cursor points at a valid row of an intKey table.
-  */
-  if( (pCsr->curFlags & BTCF_WriteFlag)==0 ){
-    return SQLITE_READONLY;
-  }
-  assert( (pCsr->pBt->btsFlags & BTS_READ_ONLY)==0
-              && pCsr->pBt->inTransaction==TRANS_WRITE );
-  assert( hasSharedCacheTableLock(pCsr->pBtree, pCsr->pgnoRoot, 0, 2) );
-  assert( !hasReadConflicts(pCsr->pBtree, pCsr->pgnoRoot) );
-  assert( pCsr->apPage[pCsr->iPage]->intKey );
-
-  return accessPayload(pCsr, offset, amt, (unsigned char *)z, 1);
-}
-
-/* 
-** Mark this cursor as an incremental blob cursor.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeIncrblobCursor(BtCursor *pCur){
-  pCur->curFlags |= BTCF_Incrblob;
-  pCur->pBtree->hasIncrblobCur = 1;
-}
-#endif
-
-/*
-** Set both the "read version" (single byte at byte offset 18) and 
-** "write version" (single byte at byte offset 19) fields in the database
-** header to iVersion.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeSetVersion(Btree *pBtree, int iVersion){
-  BtShared *pBt = pBtree->pBt;
-  int rc;                         /* Return code */
- 
-  assert( iVersion==1 || iVersion==2 );
-
-  /* If setting the version fields to 1, do not automatically open the
-  ** WAL connection, even if the version fields are currently set to 2.
-  */
-  pBt->btsFlags &= ~BTS_NO_WAL;
-  if( iVersion==1 ) pBt->btsFlags |= BTS_NO_WAL;
-
-  rc = sqlite3BtreeBeginTrans(pBtree, 0);
-  if( rc==SQLITE_OK ){
-    u8 *aData = pBt->pPage1->aData;
-    if( aData[18]!=(u8)iVersion || aData[19]!=(u8)iVersion ){
-      rc = sqlite3BtreeBeginTrans(pBtree, 2);
-      if( rc==SQLITE_OK ){
-        rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
-        if( rc==SQLITE_OK ){
-          aData[18] = (u8)iVersion;
-          aData[19] = (u8)iVersion;
-        }
-      }
-    }
-  }
-
-  pBt->btsFlags &= ~BTS_NO_WAL;
-  return rc;
-}
-
-/*
-** set the mask of hint flags for cursor pCsr.
-*/
-SQLITE_API void SQLITE_STDCALL sqlite3BtreeCursorHints(BtCursor *pCsr, unsigned int mask){
-  assert( mask==BTREE_BULKLOAD || mask==BTREE_SEEK_EQ || mask==0 );
-  pCsr->hints = mask;
-}
-
-#ifdef SQLITE_DEBUG
-/*
-** Return true if the cursor has a hint specified.  This routine is
-** only used from within assert() statements
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeCursorHasHint(BtCursor *pCsr, unsigned int mask){
-  return (pCsr->hints & mask)!=0;
-}
-#endif
-
-/*
-** Return true if the given Btree is read-only.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIsReadonly(Btree *p){
-  return (p->pBt->btsFlags & BTS_READ_ONLY)!=0;
-}
-
-/*
-** Return the size of the header added to each page by this module.
-*/
-SQLITE_PRIVATE int sqlite3HeaderSizeBtree(void){ return ROUND8(sizeof(MemPage)); }
-
-SQLITE_API const char *SQLITE_STDCALL sqlite3BtreeErrName(int rc){
-  const char *zName = 0;
-  int i, origRc = rc;
-  for(i=0; i<2 && zName==0; i++, rc &= 0xff){
-    switch( rc ){
-      case SQLITE_OK:                 zName = "SQLITE_OK";                break;
-      case SQLITE_ERROR:              zName = "SQLITE_ERROR";             break;
-      case SQLITE_INTERNAL:           zName = "SQLITE_INTERNAL";          break;
-      case SQLITE_PERM:               zName = "SQLITE_PERM";              break;
-      case SQLITE_ABORT:              zName = "SQLITE_ABORT";             break;
-      case SQLITE_ABORT_ROLLBACK:     zName = "SQLITE_ABORT_ROLLBACK";    break;
-      case SQLITE_BUSY:               zName = "SQLITE_BUSY";              break;
-      case SQLITE_BUSY_RECOVERY:      zName = "SQLITE_BUSY_RECOVERY";     break;
-      case SQLITE_BUSY_SNAPSHOT:      zName = "SQLITE_BUSY_SNAPSHOT";     break;
-      case SQLITE_LOCKED:             zName = "SQLITE_LOCKED";            break;
-      case SQLITE_LOCKED_SHAREDCACHE: zName = "SQLITE_LOCKED_SHAREDCACHE";break;
-      case SQLITE_NOMEM:              zName = "SQLITE_NOMEM";             break;
-      case SQLITE_READONLY:           zName = "SQLITE_READONLY";          break;
-      case SQLITE_READONLY_RECOVERY:  zName = "SQLITE_READONLY_RECOVERY"; break;
-      case SQLITE_READONLY_CANTLOCK:  zName = "SQLITE_READONLY_CANTLOCK"; break;
-      case SQLITE_READONLY_ROLLBACK:  zName = "SQLITE_READONLY_ROLLBACK"; break;
-      case SQLITE_READONLY_DBMOVED:   zName = "SQLITE_READONLY_DBMOVED";  break;
-      case SQLITE_INTERRUPT:          zName = "SQLITE_INTERRUPT";         break;
-      case SQLITE_IOERR:              zName = "SQLITE_IOERR";             break;
-      case SQLITE_IOERR_READ:         zName = "SQLITE_IOERR_READ";        break;
-      case SQLITE_IOERR_SHORT_READ:   zName = "SQLITE_IOERR_SHORT_READ";  break;
-      case SQLITE_IOERR_WRITE:        zName = "SQLITE_IOERR_WRITE";       break;
-      case SQLITE_IOERR_FSYNC:        zName = "SQLITE_IOERR_FSYNC";       break;
-      case SQLITE_IOERR_DIR_FSYNC:    zName = "SQLITE_IOERR_DIR_FSYNC";   break;
-      case SQLITE_IOERR_TRUNCATE:     zName = "SQLITE_IOERR_TRUNCATE";    break;
-      case SQLITE_IOERR_FSTAT:        zName = "SQLITE_IOERR_FSTAT";       break;
-      case SQLITE_IOERR_UNLOCK:       zName = "SQLITE_IOERR_UNLOCK";      break;
-      case SQLITE_IOERR_RDLOCK:       zName = "SQLITE_IOERR_RDLOCK";      break;
-      case SQLITE_IOERR_DELETE:       zName = "SQLITE_IOERR_DELETE";      break;
-      case SQLITE_IOERR_NOMEM:        zName = "SQLITE_IOERR_NOMEM";       break;
-      case SQLITE_IOERR_ACCESS:       zName = "SQLITE_IOERR_ACCESS";      break;
-      case SQLITE_IOERR_CHECKRESERVEDLOCK:
-                                zName = "SQLITE_IOERR_CHECKRESERVEDLOCK"; break;
-      case SQLITE_IOERR_LOCK:         zName = "SQLITE_IOERR_LOCK";        break;
-      case SQLITE_IOERR_CLOSE:        zName = "SQLITE_IOERR_CLOSE";       break;
-      case SQLITE_IOERR_DIR_CLOSE:    zName = "SQLITE_IOERR_DIR_CLOSE";   break;
-      case SQLITE_IOERR_SHMOPEN:      zName = "SQLITE_IOERR_SHMOPEN";     break;
-      case SQLITE_IOERR_SHMSIZE:      zName = "SQLITE_IOERR_SHMSIZE";     break;
-      case SQLITE_IOERR_SHMLOCK:      zName = "SQLITE_IOERR_SHMLOCK";     break;
-      case SQLITE_IOERR_SHMMAP:       zName = "SQLITE_IOERR_SHMMAP";      break;
-      case SQLITE_IOERR_SEEK:         zName = "SQLITE_IOERR_SEEK";        break;
-      case SQLITE_IOERR_DELETE_NOENT: zName = "SQLITE_IOERR_DELETE_NOENT";break;
-      case SQLITE_IOERR_MMAP:         zName = "SQLITE_IOERR_MMAP";        break;
-      case SQLITE_IOERR_GETTEMPPATH:  zName = "SQLITE_IOERR_GETTEMPPATH"; break;
-      case SQLITE_IOERR_CONVPATH:     zName = "SQLITE_IOERR_CONVPATH";    break;
-      case SQLITE_CORRUPT:            zName = "SQLITE_CORRUPT";           break;
-      case SQLITE_CORRUPT_VTAB:       zName = "SQLITE_CORRUPT_VTAB";      break;
-      case SQLITE_NOTFOUND:           zName = "SQLITE_NOTFOUND";          break;
-      case SQLITE_FULL:               zName = "SQLITE_FULL";              break;
-      case SQLITE_CANTOPEN:           zName = "SQLITE_CANTOPEN";          break;
-      case SQLITE_CANTOPEN_NOTEMPDIR: zName = "SQLITE_CANTOPEN_NOTEMPDIR";break;
-      case SQLITE_CANTOPEN_ISDIR:     zName = "SQLITE_CANTOPEN_ISDIR";    break;
-      case SQLITE_CANTOPEN_FULLPATH:  zName = "SQLITE_CANTOPEN_FULLPATH"; break;
-      case SQLITE_CANTOPEN_CONVPATH:  zName = "SQLITE_CANTOPEN_CONVPATH"; break;
-      case SQLITE_PROTOCOL:           zName = "SQLITE_PROTOCOL";          break;
-      case SQLITE_EMPTY:              zName = "SQLITE_EMPTY";             break;
-      case SQLITE_SCHEMA:             zName = "SQLITE_SCHEMA";            break;
-      case SQLITE_TOOBIG:             zName = "SQLITE_TOOBIG";            break;
-      case SQLITE_CONSTRAINT:         zName = "SQLITE_CONSTRAINT";        break;
-      case SQLITE_CONSTRAINT_UNIQUE:  zName = "SQLITE_CONSTRAINT_UNIQUE"; break;
-      case SQLITE_CONSTRAINT_TRIGGER: zName = "SQLITE_CONSTRAINT_TRIGGER";break;
-      case SQLITE_CONSTRAINT_FOREIGNKEY:
-                                  zName = "SQLITE_CONSTRAINT_FOREIGNKEY"; break;
-      case SQLITE_CONSTRAINT_CHECK:   zName = "SQLITE_CONSTRAINT_CHECK";  break;
-      case SQLITE_CONSTRAINT_PRIMARYKEY:
-                                   zName = "SQLITE_CONSTRAINT_PRIMARYKEY";break;
-      case SQLITE_CONSTRAINT_NOTNULL: zName = "SQLITE_CONSTRAINT_NOTNULL";break;
-      case SQLITE_CONSTRAINT_COMMITHOOK:
-                                   zName = "SQLITE_CONSTRAINT_COMMITHOOK";break;
-      case SQLITE_CONSTRAINT_VTAB:    zName = "SQLITE_CONSTRAINT_VTAB";   break;
-      case SQLITE_CONSTRAINT_FUNCTION:
-                                     zName = "SQLITE_CONSTRAINT_FUNCTION";break;
-      case SQLITE_CONSTRAINT_ROWID:   zName = "SQLITE_CONSTRAINT_ROWID";  break;
-      case SQLITE_MISMATCH:           zName = "SQLITE_MISMATCH";          break;
-      case SQLITE_MISUSE:             zName = "SQLITE_MISUSE";            break;
-      case SQLITE_NOLFS:              zName = "SQLITE_NOLFS";             break;
-      case SQLITE_AUTH:               zName = "SQLITE_AUTH";              break;
-      case SQLITE_FORMAT:             zName = "SQLITE_FORMAT";            break;
-      case SQLITE_RANGE:              zName = "SQLITE_RANGE";             break;
-      case SQLITE_NOTADB:             zName = "SQLITE_NOTADB";            break;
-      case SQLITE_ROW:                zName = "SQLITE_ROW";               break;
-      case SQLITE_NOTICE:             zName = "SQLITE_NOTICE";            break;
-      case SQLITE_NOTICE_RECOVER_WAL: zName = "SQLITE_NOTICE_RECOVER_WAL";break;
-      case SQLITE_NOTICE_RECOVER_ROLLBACK:
-                                zName = "SQLITE_NOTICE_RECOVER_ROLLBACK"; break;
-      case SQLITE_WARNING:            zName = "SQLITE_WARNING";           break;
-      case SQLITE_WARNING_AUTOINDEX:  zName = "SQLITE_WARNING_AUTOINDEX"; break;
-      case SQLITE_DONE:               zName = "SQLITE_DONE";              break;
-    }
-  }
-  if( zName==0 ){
-    static char zBuf[50];
-    sqlite3_snprintf(sizeof(zBuf), zBuf, "SQLITE_UNKNOWN(%d)", origRc);
-    zName = zBuf;
-  }
-  return zName;
-}
-
-/*
-** The following functions:
-**
-** sqlite3BtreeSerialType()
-** sqlite3BtreeSerialTypeLen()
-** sqlite3BtreeSerialLen()
-** sqlite3BtreeSerialPut()
-** sqlite3BtreeSerialGet()
-**
-** encapsulate the code that serializes values for storage in SQLite
-** data and index records. Each serialized value consists of a
-** 'serial-type' and a blob of data. The serial type is an 8-byte unsigned
-** integer, stored as a varint.
-**
-** In an SQLite index record, the serial type is stored directly before
-** the blob of data that it corresponds to. In a table record, all serial
-** types are stored at the start of the record, and the blobs of data at
-** the end. Hence these functions allow the caller to handle the
-** serial-type and data blob separately.
-**
-** The following table describes the various storage classes for data:
-**
-**   serial type        bytes of data      type
-**   --------------     ---------------    ---------------
-**      0                     0            NULL
-**      1                     1            signed integer
-**      2                     2            signed integer
-**      3                     3            signed integer
-**      4                     4            signed integer
-**      5                     6            signed integer
-**      6                     8            signed integer
-**      7                     8            IEEE float
-**      8                     0            Integer constant 0
-**      9                     0            Integer constant 1
-**     10,11                               reserved for expansion
-**    N>=12 and even       (N-12)/2        BLOB
-**    N>=13 and odd        (N-13)/2        text
-**
-** The 8 and 9 types were added in 3.3.0, file format 4.  Prior versions
-** of SQLite will not understand those serial types.
-*/
-
-/*
-** Return the serial-type for the value stored in pMem.
-*/
-SQLITE_API u32 SQLITE_STDCALL sqlite3BtreeSerialType(Mem *pMem, int file_format){
-  int flags = pMem->flags;
-  u32 n;
-
-  if( flags&MEM_Null ){
-    return 0;
-  }
-  if( flags&MEM_Int ){
-    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
-#   define MAX_6BYTE ((((i64)0x00008000)<<32)-1)
-    i64 i = pMem->u.i;
-    u64 u;
-    if( i<0 ){
-      u = ~i;
-    }else{
-      u = i;
-    }
-    if( u<=127 ){
-      return ((i&1)==i && file_format>=4) ? 8+(u32)u : 1;
-    }
-    if( u<=32767 ) return 2;
-    if( u<=8388607 ) return 3;
-    if( u<=2147483647 ) return 4;
-    if( u<=MAX_6BYTE ) return 5;
-    return 6;
-  }
-  if( flags&MEM_Real ){
-    return 7;
-  }
-  assert( pMem->pBtree->mallocFailed || flags&(MEM_Str|MEM_Blob) );
-  assert( pMem->n>=0 );
-  n = (u32)pMem->n;
-  if( flags & MEM_Zero ){
-    n += pMem->u.nZero;
-  }
-  return ((n*2) + 12 + ((flags&MEM_Str)!=0));
-}
-
-/*
-** The sizes for serial types less than 12
-*/
-static const u8 sqlite3SmallTypeSizes[] = {
-  0, 1, 2, 3, 4, 6, 8, 8, 0, 0, 0, 0
-};
-
-/*
-** Return the length of the data corresponding to the supplied serial-type.
-*/
-SQLITE_API u32 SQLITE_STDCALL sqlite3BtreeSerialTypeLen(u32 serial_type){
-  if( serial_type>=12 ){
-    return (serial_type-12)/2;
-  }else{
-    return sqlite3SmallTypeSizes[serial_type];
-  }
-}
-
-/*
-** If we are on an architecture with mixed-endian floating 
-** points (ex: ARM7) then swap the lower 4 bytes with the 
-** upper 4 bytes.  Return the result.
-**
-** For most architectures, this is a no-op.
-**
-** (later):  It is reported to me that the mixed-endian problem
-** on ARM7 is an issue with GCC, not with the ARM7 chip.  It seems
-** that early versions of GCC stored the two words of a 64-bit
-** float in the wrong order.  And that error has been propagated
-** ever since.  The blame is not necessarily with GCC, though.
-** GCC might have just copying the problem from a prior compiler.
-** I am also told that newer versions of GCC that follow a different
-** ABI get the byte order right.
-**
-** Developers using SQLite on an ARM7 should compile and run their
-** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
-** enabled, some asserts below will ensure that the byte order of
-** floating point values is correct.
-**
-** (2007-08-30)  Frank van Vugt has studied this problem closely
-** and has send his findings to the SQLite developers.  Frank
-** writes that some Linux kernels offer floating point hardware
-** emulation that uses only 32-bit mantissas instead of a full 
-** 48-bits as required by the IEEE standard.  (This is the
-** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
-** byte swapping becomes very complicated.  To avoid problems,
-** the necessary byte swapping is carried out using a 64-bit integer
-** rather than a 64-bit float.  Frank assures us that the code here
-** works for him.  We, the developers, have no way to independently
-** verify this, but Frank seems to know what he is talking about
-** so we trust him.
-*/
-#ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
-static u64 floatSwap(u64 in){
-  union {
-    u64 r;
-    u32 i[2];
-  } u;
-  u32 t;
-
-  u.r = in;
-  t = u.i[0];
-  u.i[0] = u.i[1];
-  u.i[1] = t;
-  return u.r;
-}
-# define swapMixedEndianFloat(X)  X = floatSwap(X)
-#else
-# define swapMixedEndianFloat(X)
-#endif
-
-/*
-** Write the serialized data blob for the value stored in pMem into 
-** buf. It is assumed that the caller has allocated sufficient space.
-** Return the number of bytes written.
-**
-** nBuf is the amount of space left in buf[].  The caller is responsible
-** for allocating enough space to buf[] to hold the entire field, exclusive
-** of the pMem->u.nZero bytes for a MEM_Zero value.
-**
-** Return the number of bytes actually written into buf[].  The number
-** of bytes in the zero-filled tail is included in the return value only
-** if those bytes were zeroed in buf[].
-*/ 
-SQLITE_API u32 SQLITE_STDCALL sqlite3BtreeSerialPut(u8 *buf, Mem *pMem, u32 serial_type){
-  u32 len;
-
-  /* Integer and Real */
-  if( serial_type<=7 && serial_type>0 ){
-    u64 v;
-    u32 i;
-    if( serial_type==7 ){
-      assert( sizeof(v)==sizeof(pMem->u.r) );
-      memcpy(&v, &pMem->u.r, sizeof(v));
-      swapMixedEndianFloat(v);
-    }else{
-      v = pMem->u.i;
-    }
-    len = i = sqlite3SmallTypeSizes[serial_type];
-    assert( i>0 );
-    do{
-      buf[--i] = (u8)(v&0xFF);
-      v >>= 8;
-    }while( i );
-    return len;
-  }
-
-  /* String or blob */
-  if( serial_type>=12 ){
-    assert( pMem->n + ((pMem->flags & MEM_Zero)?pMem->u.nZero:0)
-             == (int)sqlite3BtreeSerialTypeLen(serial_type) );
-    len = pMem->n;
-    memcpy(buf, pMem->z, len);
-    return len;
-  }
-
-  /* NULL or constants 0 or 1 */
-  return 0;
-}
-
-/* Input "x" is a sequence of unsigned characters that represent a
-** big-endian integer.  Return the equivalent native integer
-*/
-#define ONE_BYTE_INT(x)    ((i8)(x)[0])
-#define TWO_BYTE_INT(x)    (256*(i8)((x)[0])|(x)[1])
-#define THREE_BYTE_INT(x)  (65536*(i8)((x)[0])|((x)[1]<<8)|(x)[2])
-#define FOUR_BYTE_UINT(x)  (((u32)(x)[0]<<24)|((x)[1]<<16)|((x)[2]<<8)|(x)[3])
-#define FOUR_BYTE_INT(x) (16777216*(i8)((x)[0])|((x)[1]<<16)|((x)[2]<<8)|(x)[3])
-
-/*
-** Size of struct Mem not including the Mem.zMalloc member or anything that
-** follows.
-*/
-#define MEMCELLSIZE offsetof(Mem,zMalloc)
-
-#define VdbeMemDynamic(X)  \
-  (((X)->flags&MEM_Dyn)!=0)
-
-/*
-** Initialize bulk memory to be a consistent Mem object.
-**
-** The minimum amount of initialization feasible is performed.
-*/
-SQLITE_PRIVATE void sqlite3VdbeMemInit(Mem *pMem, Btree *pBtree, u16 flags){
-  assert( (flags & ~MEM_TypeMask)==0 );
-  pMem->flags = flags;
-  pMem->pBtree = pBtree;
-  pMem->szMalloc = 0;
-}
-
-/*
-** If pMem is an object with a valid string representation, this routine
-** ensures the internal encoding for the string representation is
-** 'desiredEnc', one of SQLITE_UTF8, SQLITE_UTF16LE or SQLITE_UTF16BE.
-**
-** If pMem is not a string object, or the encoding of the string
-** representation is already stored using the requested encoding, then this
-** routine is a no-op.
-**
-** SQLITE_OK is returned if the conversion is successful (or not required).
-** SQLITE_NOMEM may be returned if a malloc() fails during conversion
-** between formats.
-*/
-SQLITE_PRIVATE int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
-  assert( (pMem->flags&MEM_RowSet)==0 );
-  assert( desiredEnc==SQLITE_UTF8 || desiredEnc==SQLITE_UTF16LE
-           || desiredEnc==SQLITE_UTF16BE );
-  if( !(pMem->flags&MEM_Str) || pMem->enc==desiredEnc ){
-    return SQLITE_OK;
-  }
-  assert( pMem->db==0 || sqlite3_mutex_held(pMem->db->mutex) );
-  return SQLITE_ERROR;
-}
-
-/*
-** If the memory cell contains a value that must be freed by
-** invoking the external callback in Mem.xDel, then this routine
-** will free that value.  It also sets Mem.flags to MEM_Null.
-**
-** This is a helper routine for sqlite3VdbeMemSetNull() and
-** for sqlite3VdbeMemRelease().  Use those other routines as the
-** entry point for releasing Mem resources.
-*/
-static SQLITE_NOINLINE void vdbeMemClearExternAndSetNull(Mem *p){
-  assert( p->db==0 || sqlite3_mutex_held(p->db->mutex) );
-  assert( VdbeMemDynamic(p) );
-  if( p->flags&MEM_Dyn ){
-    assert( p->xDel!=SQLITE_DYNAMIC && p->xDel!=0 );
-    p->xDel((void *)p->z);
-  }
-  p->flags = MEM_Null;
-}
-
-/*
-** Delete any previous value and set the value stored in *pMem to NULL.
-**
-** This routine calls the Mem.xDel destructor to dispose of values that
-** require the destructor.  But it preserves the Mem.zMalloc memory allocation.
-** To free all resources, use sqlite3VdbeMemRelease(), which both calls this
-** routine to invoke the destructor and deallocates Mem.zMalloc.
-**
-** Use this routine to reset the Mem prior to insert a new value.
-**
-** Use sqlite3VdbeMemRelease() to complete erase the Mem prior to abandoning it.
-*/
-SQLITE_PRIVATE void sqlite3VdbeMemSetNull(Mem *pMem){
-  if( VdbeMemDynamic(pMem) ){
-    vdbeMemClearExternAndSetNull(pMem);
-  }else{
-    pMem->flags = MEM_Null;
-  }
-}
-
-/*
-** Make sure pMem->z points to a writable allocation of at least 
-** min(n,32) bytes.
-**
-** If the bPreserve argument is true, then copy of the content of
-** pMem->z into the new allocation.  pMem must be either a string or
-** blob if bPreserve is true.  If bPreserve is false, any prior content
-** in pMem->z is discarded.
-*/
-SQLITE_PRIVATE SQLITE_NOINLINE int sqlite3VdbeMemGrow(Mem *pMem, int n, int bPreserve){
-  assert( sqlite3VdbeCheckMemInvariants(pMem) );
-  assert( (pMem->flags&MEM_RowSet)==0 );
-
-  /* If the bPreserve flag is set to true, then the memory cell must already
-  ** contain a valid string or blob value.  */
-  assert( bPreserve==0 || pMem->flags&(MEM_Blob|MEM_Str) );
-  testcase( bPreserve && pMem->z==0 );
-
-  assert( pMem->szMalloc==0
-       || pMem->szMalloc==sqlite3DbMallocSize(pMem->pBtree, pMem->zMalloc) );
-  if( pMem->szMalloc<n ){
-    if( n<32 ) n = 32;
-    if( bPreserve && pMem->szMalloc>0 && pMem->z==pMem->zMalloc ){
-      pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->pBtree, pMem->z, n);
-      bPreserve = 0;
-    }else{
-      if( pMem->szMalloc>0 ) sqlite3DbFree(pMem->pBtree, pMem->zMalloc);
-      pMem->zMalloc = sqlite3DbMallocRaw(pMem->pBtree, n);
-    }
-    if( pMem->zMalloc==0 ){
-      sqlite3VdbeMemSetNull(pMem);
-      pMem->z = 0;
-      pMem->szMalloc = 0;
-      return SQLITE_NOMEM;
-    }else{
-      pMem->szMalloc = sqlite3DbMallocSize(pMem->pBtree, pMem->zMalloc);
-    }
-  }
-
-  if( bPreserve && pMem->z && pMem->z!=pMem->zMalloc ){
-    memcpy(pMem->zMalloc, pMem->z, pMem->n);
-  }
-  if( (pMem->flags&MEM_Dyn)!=0 ){
-    assert( pMem->xDel!=0 && pMem->xDel!=SQLITE_DYNAMIC );
-    pMem->xDel((void *)(pMem->z));
-  }
-
-  pMem->z = pMem->zMalloc;
-  pMem->flags &= ~(MEM_Dyn|MEM_Ephem|MEM_Static);
-  return SQLITE_OK;
-}
-
-/*
-** Change the pMem->zMalloc allocation to be at least szNew bytes.
-** If pMem->zMalloc already meets or exceeds the requested size, this
-** routine is a no-op.
-**
-** Any prior string or blob content in the pMem object may be discarded.
-** The pMem->xDel destructor is called, if it exists.  Though MEM_Str
-** and MEM_Blob values may be discarded, MEM_Int, MEM_Real, and MEM_Null
-** values are preserved.
-**
-** Return SQLITE_OK on success or an error code (probably SQLITE_NOMEM)
-** if unable to complete the resizing.
-*/
-SQLITE_PRIVATE int sqlite3VdbeMemClearAndResize(Mem *pMem, int szNew){
-  assert( szNew>0 );
-  assert( (pMem->flags & MEM_Dyn)==0 || pMem->szMalloc==0 );
-  if( pMem->szMalloc<szNew ){
-    return sqlite3VdbeMemGrow(pMem, szNew, 0);
-  }
-  assert( (pMem->flags & MEM_Dyn)==0 );
-  pMem->z = pMem->zMalloc;
-  pMem->flags &= (MEM_Null|MEM_Int|MEM_Real);
-  return SQLITE_OK;
-}
-
-#ifndef SQLITE_OMIT_INCRBLOB
-  int sqlite3VdbeMemExpandBlob(Mem *);
-  #define ExpandBlob(P) (((P)->flags&MEM_Zero)?sqlite3VdbeMemExpandBlob(P):0)
-#else
-  #define sqlite3VdbeMemExpandBlob(x) SQLITE_OK
-  #define ExpandBlob(P) SQLITE_OK
-#endif
-
-/*
-** Change pMem so that its MEM_Str or MEM_Blob value is stored in
-** MEM.zMalloc, where it can be safely written.
-**
-** Return SQLITE_OK on success or SQLITE_NOMEM if malloc fails.
-*/
-SQLITE_PRIVATE int sqlite3VdbeMemMakeWriteable(Mem *pMem){
-  int f;
-  assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-  assert( (pMem->flags&MEM_RowSet)==0 );
-  ExpandBlob(pMem);
-  f = pMem->flags;
-  if( (f&(MEM_Str|MEM_Blob)) && (pMem->szMalloc==0 || pMem->z!=pMem->zMalloc) ){
-    if( sqlite3VdbeMemGrow(pMem, pMem->n + 2, 1) ){
-      return SQLITE_NOMEM;
-    }
-    pMem->z[pMem->n] = 0;
-    pMem->z[pMem->n+1] = 0;
-    pMem->flags |= MEM_Term;
-  }
-  pMem->flags &= ~MEM_Ephem;
-#ifdef SQLITE_DEBUG
-  pMem->pScopyFrom = 0;
-#endif
-
-  return SQLITE_OK;
-}
-
-/*
-** It is already known that pMem contains an unterminated string.
-** Add the zero terminator.
-*/
-static SQLITE_NOINLINE int vdbeMemAddTerminator(Mem *pMem){
-  if( sqlite3VdbeMemGrow(pMem, pMem->n+2, 1) ){
-    return SQLITE_NOMEM;
-  }
-  pMem->z[pMem->n] = 0;
-  pMem->z[pMem->n+1] = 0;
-  pMem->flags |= MEM_Term;
-  return SQLITE_OK;
-}
-
-/*
-** Make sure the given Mem is \u0000 terminated.
-*/
-SQLITE_PRIVATE int sqlite3VdbeMemNulTerminate(Mem *pMem){
-  assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-  testcase( (pMem->flags & (MEM_Term|MEM_Str))==(MEM_Term|MEM_Str) );
-  testcase( (pMem->flags & (MEM_Term|MEM_Str))==0 );
-  if( (pMem->flags & (MEM_Term|MEM_Str))!=MEM_Str ){
-    return SQLITE_OK;   /* Nothing to do */
-  }else{
-    return vdbeMemAddTerminator(pMem);
-  }
-}
-
-/*
-** Add MEM_Str to the set of representations for the given Mem.  Numbers
-** are converted using sqlite3_snprintf().  Converting a BLOB to a string
-** is a no-op.
-**
-** Existing representations MEM_Int and MEM_Real are invalidated if
-** bForce is true but are retained if bForce is false.
-**
-** A MEM_Null value will never be passed to this function. This function is
-** used for converting values to text for returning to the user (i.e. via
-** sqlite3_value_text()), or for ensuring that values to be used as btree
-** keys are strings. In the former case a NULL pointer is returned the
-** user and the latter is an internal programming error.
-*/
-SQLITE_PRIVATE int sqlite3VdbeMemStringify(Mem *pMem, u8 enc, u8 bForce){
-  int fg = pMem->flags;
-  const int nByte = 32;
-
-  assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-  assert( !(fg&MEM_Zero) );
-  assert( !(fg&(MEM_Str|MEM_Blob)) );
-  assert( fg&(MEM_Int|MEM_Real) );
-  assert( (pMem->flags&MEM_RowSet)==0 );
-  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
-
-
-  if( sqlite3VdbeMemClearAndResize(pMem, nByte) ){
-    return SQLITE_NOMEM;
-  }
-
-  /* For a Real or Integer, use sqlite3_snprintf() to produce the UTF-8
-  ** string representation of the value. Then, if the required encoding
-  ** is UTF-16le or UTF-16be do a translation.
-  ** 
-  ** FIX ME: It would be better if sqlite3_snprintf() could do UTF-16.
-  */
-  if( fg & MEM_Int ){
-    sqlite3_snprintf(nByte, pMem->z, "%lld", pMem->u.i);
-  }else{
-    assert( fg & MEM_Real );
-    sqlite3_snprintf(nByte, pMem->z, "%!.15g", pMem->u.r);
-  }
-  pMem->n = sqlite3Strlen30(pMem->z);
-  pMem->enc = SQLITE_UTF8;
-  pMem->flags |= MEM_Str|MEM_Term;
-  if( bForce ) pMem->flags &= ~(MEM_Int|MEM_Real);
-  sqlite3VdbeChangeEncoding(pMem, enc);
-  return SQLITE_OK;
-}
-
-/*
-** Release memory held by the Mem p, both external memory cleared
-** by p->xDel and memory in p->zMalloc.
-**
-** This is a helper routine invoked by sqlite3VdbeMemRelease() in
-** the unusual case where there really is memory in p that needs
-** to be freed.
-*/
-static SQLITE_NOINLINE void vdbeMemClear(Mem *p){
-  if( VdbeMemDynamic(p) ){
-    vdbeMemClearExternAndSetNull(p);
-  }
-  if( p->szMalloc ){
-    sqlite3DbFree(p->pBtree, p->zMalloc);
-    p->szMalloc = 0;
-  }
-  p->z = 0;
-}
-
-/*
-** Release any memory resources held by the Mem.  Both the memory that is
-** free by Mem.xDel and the Mem.zMalloc allocation are freed.
-**
-** Use this routine prior to clean up prior to abandoning a Mem, or to
-** reset a Mem back to its minimum memory utilization.
-**
-** Use sqlite3VdbeMemSetNull() to release just the Mem.xDel space
-** prior to inserting new content into the Mem.
-*/
-SQLITE_PRIVATE void sqlite3VdbeMemRelease(Mem *p){
-  assert( sqlite3VdbeCheckMemInvariants(p) );
-  if( VdbeMemDynamic(p) || p->szMalloc ){
-    vdbeMemClear(p);
-  }
-}
-
-/*
-** Make an shallow copy of pFrom into pTo.  Prior contents of
-** pTo are freed.  The pFrom->z field is not duplicated.  If
-** pFrom->z is used, then pTo->z points to the same thing as pFrom->z
-** and flags gets srcType (either MEM_Ephem or MEM_Static).
-*/
-static void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType);
-static SQLITE_NOINLINE void vdbeClrCopy(Mem *pTo, const Mem *pFrom, int eType){
-  vdbeMemClearExternAndSetNull(pTo);
-  assert( !VdbeMemDynamic(pTo) );
-  sqlite3VdbeMemShallowCopy(pTo, pFrom, eType);
-}
-static void sqlite3VdbeMemShallowCopy(Mem *pTo, const Mem *pFrom, int srcType){
-  assert( (pFrom->flags & MEM_RowSet)==0 );
-  assert( pTo->pBtree==pFrom->pBtree );
-  if( VdbeMemDynamic(pTo) ){ vdbeClrCopy(pTo,pFrom,srcType); return; }
-  memcpy(pTo, pFrom, MEMCELLSIZE);
-  if( (pFrom->flags&MEM_Static)==0 ){
-    pTo->flags &= ~(MEM_Dyn|MEM_Static|MEM_Ephem);
-    assert( srcType==MEM_Ephem || srcType==MEM_Static );
-    pTo->flags |= srcType;
-  }
-}
-
-/*
-** Deserialize the data blob pointed to by buf as serial type serial_type
-** and store the result in pMem.  Return the number of bytes read.
-**
-** This function is implemented as two separate routines for performance.
-** The few cases that require local variables are broken out into a separate
-** routine so that in most cases the overhead of moving the stack pointer
-** is avoided.
-*/ 
-static u32 SQLITE_NOINLINE serialGet(
-  const unsigned char *buf,     /* Buffer to deserialize from */
-  u32 serial_type,              /* Serial type to deserialize */
-  Mem *pMem                     /* Memory cell to write value into */
-){
-  u64 x = FOUR_BYTE_UINT(buf);
-  u32 y = FOUR_BYTE_UINT(buf+4);
-  x = (x<<32) + y;
-  if( serial_type==6 ){
-    /* EVIDENCE-OF: R-29851-52272 Value is a big-endian 64-bit
-    ** twos-complement integer. */
-    pMem->u.i = *(i64*)&x;
-    pMem->flags = MEM_Int;
-    testcase( pMem->u.i<0 );
-  }else{
-    /* EVIDENCE-OF: R-57343-49114 Value is a big-endian IEEE 754-2008 64-bit
-    ** floating point number. */
-#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
-    /* Verify that integers and floating point values use the same
-    ** byte order.  Or, that if SQLITE_MIXED_ENDIAN_64BIT_FLOAT is
-    ** defined that 64-bit floating point values really are mixed
-    ** endian.
-    */
-    static const u64 t1 = ((u64)0x3ff00000)<<32;
-    static const double r1 = 1.0;
-    u64 t2 = t1;
-    swapMixedEndianFloat(t2);
-    assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
-#endif
-    assert( sizeof(x)==8 && sizeof(pMem->u.r)==8 );
-    swapMixedEndianFloat(x);
-    memcpy(&pMem->u.r, &x, sizeof(x));
-    pMem->flags = sqlite3IsNaN(pMem->u.r) ? MEM_Null : MEM_Real;
-  }
-  return 8;
-}
-SQLITE_API u32 SQLITE_STDCALL sqlite3BtreeSerialGet(
-  const unsigned char *buf,     /* Buffer to deserialize from */
-  u32 serial_type,              /* Serial type to deserialize */
-  Mem *pMem                     /* Memory cell to write value into */
-){
-  switch( serial_type ){
-    case 10:   /* Reserved for future use */
-    case 11:   /* Reserved for future use */
-    case 0: {  /* Null */
-      /* EVIDENCE-OF: R-24078-09375 Value is a NULL. */
-      pMem->flags = MEM_Null;
-      break;
-    }
-    case 1: {
-      /* EVIDENCE-OF: R-44885-25196 Value is an 8-bit twos-complement
-      ** integer. */
-      pMem->u.i = ONE_BYTE_INT(buf);
-      pMem->flags = MEM_Int;
-      testcase( pMem->u.i<0 );
-      return 1;
-    }
-    case 2: { /* 2-byte signed integer */
-      /* EVIDENCE-OF: R-49794-35026 Value is a big-endian 16-bit
-      ** twos-complement integer. */
-      pMem->u.i = TWO_BYTE_INT(buf);
-      pMem->flags = MEM_Int;
-      testcase( pMem->u.i<0 );
-      return 2;
-    }
-    case 3: { /* 3-byte signed integer */
-      /* EVIDENCE-OF: R-37839-54301 Value is a big-endian 24-bit
-      ** twos-complement integer. */
-      pMem->u.i = THREE_BYTE_INT(buf);
-      pMem->flags = MEM_Int;
-      testcase( pMem->u.i<0 );
-      return 3;
-    }
-    case 4: { /* 4-byte signed integer */
-      /* EVIDENCE-OF: R-01849-26079 Value is a big-endian 32-bit
-      ** twos-complement integer. */
-      pMem->u.i = FOUR_BYTE_INT(buf);
-      pMem->flags = MEM_Int;
-      testcase( pMem->u.i<0 );
-      return 4;
-    }
-    case 5: { /* 6-byte signed integer */
-      /* EVIDENCE-OF: R-50385-09674 Value is a big-endian 48-bit
-      ** twos-complement integer. */
-      pMem->u.i = FOUR_BYTE_UINT(buf+2) + (((i64)1)<<32)*TWO_BYTE_INT(buf);
-      pMem->flags = MEM_Int;
-      testcase( pMem->u.i<0 );
-      return 6;
-    }
-    case 6:   /* 8-byte signed integer */
-    case 7: { /* IEEE floating point */
-      /* These use local variables, so do them in a separate routine
-      ** to avoid having to move the frame pointer in the common case */
-      return serialGet(buf,serial_type,pMem);
-    }
-    case 8:    /* Integer 0 */
-    case 9: {  /* Integer 1 */
-      /* EVIDENCE-OF: R-12976-22893 Value is the integer 0. */
-      /* EVIDENCE-OF: R-18143-12121 Value is the integer 1. */
-      pMem->u.i = serial_type-8;
-      pMem->flags = MEM_Int;
-      return 0;
-    }
-    default: {
-      /* EVIDENCE-OF: R-14606-31564 Value is a BLOB that is (N-12)/2 bytes in
-      ** length.
-      ** EVIDENCE-OF: R-28401-00140 Value is a string in the text encoding and
-      ** (N-13)/2 bytes in length. */
-      static const u16 aFlag[] = { MEM_Blob|MEM_Ephem, MEM_Str|MEM_Ephem };
-      pMem->z = (char *)buf;
-      pMem->n = (serial_type-12)/2;
-      pMem->flags = aFlag[serial_type&1];
-      return pMem->n;
-    }
-  }
-  return 0;
-}
-
-/*
-** This routine is used to allocate sufficient space for an UnpackedRecord
-** structure large enough to be used with sqlite3VdbeRecordUnpack() if
-** the first argument is a pointer to KeyInfo structure pKeyInfo.
-**
-** The space is either allocated using sqlite3DbMallocRaw() or from within
-** the unaligned buffer passed via the second and third arguments (presumably
-** stack space). If the former, then *ppFree is set to a pointer that should
-** be eventually freed by the caller using sqlite3DbFree(). Or, if the 
-** allocation comes from the pSpace/szSpace buffer, *ppFree is set to NULL
-** before returning.
-**
-** If an OOM error occurs, NULL is returned.
-*/
-SQLITE_PRIVATE UnpackedRecord *sqlite3VdbeAllocUnpackedRecord(
-  KeyInfo *pKeyInfo,              /* Description of the record */
-  char *pSpace,                   /* Unaligned space available */
-  int szSpace,                    /* Size of pSpace[] in bytes */
-  char **ppFree                   /* OUT: Caller should free this pointer */
-){
-  UnpackedRecord *p;              /* Unpacked record to return */
-  int nOff;                       /* Increment pSpace by nOff to align it */
-  int nByte;                      /* Number of bytes required for *p */
-
-  /* We want to shift the pointer pSpace up such that it is 8-byte aligned.
-  ** Thus, we need to calculate a value, nOff, between 0 and 7, to shift 
-  ** it by.  If pSpace is already 8-byte aligned, nOff should be zero.
-  */
-  nOff = (8 - (SQLITE_PTR_TO_INT(pSpace) & 7)) & 7;
-  nByte = ROUND8(sizeof(UnpackedRecord)) + sizeof(Mem)*(pKeyInfo->nField+1);
-  if( nByte>szSpace+nOff ){
-    p = (UnpackedRecord *)sqlite3DbMallocRaw(pKeyInfo->pBtree, nByte);
-    *ppFree = (char *)p;
-    if( !p ) return 0;
-  }else{
-    p = (UnpackedRecord*)&pSpace[nOff];
-    *ppFree = 0;
-  }
-
-  p->aMem = (Mem*)&((char*)p)[ROUND8(sizeof(UnpackedRecord))];
-  assert( pKeyInfo->aSortOrder!=0 );
-  p->pKeyInfo = pKeyInfo;
-  p->nField = pKeyInfo->nField + 1;
-  return p;
-}
-
-/*
-** Given the nKey-byte encoding of a record in pKey[], populate the 
-** UnpackedRecord structure indicated by the fourth argument with the
-** contents of the decoded record.
-*/ 
-SQLITE_PRIVATE void sqlite3VdbeRecordUnpack(
-  KeyInfo *pKeyInfo,     /* Information about the record format */
-  int nKey,              /* Size of the binary record */
-  const void *pKey,      /* The binary record */
-  UnpackedRecord *p      /* Populate this structure before returning. */
-){
-  const unsigned char *aKey = (const unsigned char *)pKey;
-  int d; 
-  u32 idx;                        /* Offset in aKey[] to read from */
-  u16 u;                          /* Unsigned loop counter */
-  u32 szHdr;
-  Mem *pMem = p->aMem;
-
-  p->default_rc = 0;
-  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
-  idx = getVarint32(aKey, szHdr);
-  d = szHdr;
-  u = 0;
-  while( idx<szHdr && d<=nKey ){
-    u32 serial_type;
-
-    idx += getVarint32(&aKey[idx], serial_type);
-    pMem->enc = pKeyInfo->enc;
-    pMem->pBtree = pKeyInfo->pBtree;
-    /* pMem->flags = 0; // sqlite3BtreeSerialGet() will set this for us */
-    pMem->szMalloc = 0;
-    d += sqlite3BtreeSerialGet(&aKey[d], serial_type, pMem);
-    pMem++;
-    if( (++u)>=p->nField ) break;
-  }
-  assert( u<=pKeyInfo->nField + 1 );
-  p->nField = u;
-}
-
-#if SQLITE_DEBUG
-/*
-** Count the number of fields (a.k.a. columns) in the record given by
-** pKey,nKey.  The verify that this count is less than or equal to the
-** limit given by pKeyInfo->nField + pKeyInfo->nXField.
-**
-** If this constraint is not satisfied, it means that the high-speed
-** vdbeRecordCompareInt() and vdbeRecordCompareString() routines will
-** not work correctly.  If this assert() ever fires, it probably means
-** that the KeyInfo.nField or KeyInfo.nXField values were computed
-** incorrectly.
-*/
-static void vdbeAssertFieldCountWithinLimits(
-  int nKey, const void *pKey,   /* The record to verify */ 
-  const KeyInfo *pKeyInfo       /* Compare size with this KeyInfo */
-){
-  int nField = 0;
-  u32 szHdr;
-  u32 idx;
-  u32 notUsed;
-  const unsigned char *aKey = (const unsigned char*)pKey;
-
-  if( CORRUPT_DB ) return;
-  idx = getVarint32(aKey, szHdr);
-  assert( nKey>=0 );
-  assert( szHdr<=(u32)nKey );
-  while( idx<szHdr ){
-    idx += getVarint32(aKey+idx, notUsed);
-    nField++;
-  }
-  assert( nField <= pKeyInfo->nField+pKeyInfo->nXField );
-}
-#else
-# define vdbeAssertFieldCountWithinLimits(A,B,C)
-#endif
-
-/*
-** This function is an optimized version of sqlite3BtreeRecordCompare() 
-** that (a) the first field of pPKey2 is an integer, and (b) the 
-** size-of-header varint at the start of (pKey1/nKey1) fits in a single
-** byte (i.e. is less than 128).
-**
-** To avoid concerns about buffer overreads, this routine is only used
-** on schemas where the maximum valid header size is 63 bytes or less.
-*/
-static int vdbeRecordCompareInt(
-  int nKey1, const void *pKey1, /* Left key */
-  UnpackedRecord *pPKey2        /* Right key */
-){
-  const u8 *aKey = &((const u8*)pKey1)[*(const u8*)pKey1 & 0x3F];
-  int serial_type = ((const u8*)pKey1)[1];
-  int res;
-  u32 y;
-  u64 x;
-  i64 v = pPKey2->aMem[0].u.i;
-  i64 lhs;
-
-  vdbeAssertFieldCountWithinLimits(nKey1, pKey1, pPKey2->pKeyInfo);
-  assert( (*(u8*)pKey1)<=0x3F || CORRUPT_DB );
-  switch( serial_type ){
-    case 1: { /* 1-byte signed integer */
-      lhs = ONE_BYTE_INT(aKey);
-      testcase( lhs<0 );
-      break;
-    }
-    case 2: { /* 2-byte signed integer */
-      lhs = TWO_BYTE_INT(aKey);
-      testcase( lhs<0 );
-      break;
-    }
-    case 3: { /* 3-byte signed integer */
-      lhs = THREE_BYTE_INT(aKey);
-      testcase( lhs<0 );
-      break;
-    }
-    case 4: { /* 4-byte signed integer */
-      y = FOUR_BYTE_UINT(aKey);
-      lhs = (i64)*(int*)&y;
-      testcase( lhs<0 );
-      break;
-    }
-    case 5: { /* 6-byte signed integer */
-      lhs = FOUR_BYTE_UINT(aKey+2) + (((i64)1)<<32)*TWO_BYTE_INT(aKey);
-      testcase( lhs<0 );
-      break;
-    }
-    case 6: { /* 8-byte signed integer */
-      x = FOUR_BYTE_UINT(aKey);
-      x = (x<<32) | FOUR_BYTE_UINT(aKey+4);
-      lhs = *(i64*)&x;
-      testcase( lhs<0 );
-      break;
-    }
-    case 8: 
-      lhs = 0;
-      break;
-    case 9:
-      lhs = 1;
-      break;
-
-    /* This case could be removed without changing the results of running
-    ** this code. Including it causes gcc to generate a faster switch 
-    ** statement (since the range of switch targets now starts at zero and
-    ** is contiguous) but does not cause any duplicate code to be generated
-    ** (as gcc is clever enough to combine the two like cases). Other 
-    ** compilers might be similar.  */ 
-    case 0: case 7:
-      return sqlite3BtreeRecordCompare(nKey1, pKey1, pPKey2);
-
-    default:
-      return sqlite3BtreeRecordCompare(nKey1, pKey1, pPKey2);
-  }
-
-  if( v>lhs ){
-    res = pPKey2->r1;
-  }else if( v<lhs ){
-    res = pPKey2->r2;
-  }else if( pPKey2->nField>1 ){
-    /* The first fields of the two keys are equal. Compare the trailing 
-    ** fields.  */
-    res = sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 1);
-  }else{
-    /* The first fields of the two keys are equal and there are no trailing
-    ** fields. Return pPKey2->default_rc in this case. */
-    res = pPKey2->default_rc;
-  }
-
-  assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, res) );
-  return res;
-}
-
-/*
-** This function is an optimized version of sqlite3BtreeRecordCompare() 
-** that (a) the first field of pPKey2 is a string, that (b) the first field
-** uses the collation sequence BINARY and (c) that the size-of-header varint 
-** at the start of (pKey1/nKey1) fits in a single byte.
-*/
-static int vdbeRecordCompareString(
-  int nKey1, const void *pKey1, /* Left key */
-  UnpackedRecord *pPKey2        /* Right key */
-){
-  const u8 *aKey1 = (const u8*)pKey1;
-  int serial_type;
-  int res;
-
-  vdbeAssertFieldCountWithinLimits(nKey1, pKey1, pPKey2->pKeyInfo);
-  getVarint32(&aKey1[1], serial_type);
-  if( serial_type<12 ){
-    res = pPKey2->r1;      /* (pKey1/nKey1) is a number or a null */
-  }else if( !(serial_type & 0x01) ){ 
-    res = pPKey2->r2;      /* (pKey1/nKey1) is a blob */
-  }else{
-    int nCmp;
-    int nStr;
-    int szHdr = aKey1[0];
-
-    nStr = (serial_type-12) / 2;
-    if( (szHdr + nStr) > nKey1 ){
-      pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
-      return 0;    /* Corruption */
-    }
-    nCmp = MIN( pPKey2->aMem[0].n, nStr );
-    res = memcmp(&aKey1[szHdr], pPKey2->aMem[0].z, nCmp);
-
-    if( res==0 ){
-      res = nStr - pPKey2->aMem[0].n;
-      if( res==0 ){
-        if( pPKey2->nField>1 ){
-          res = sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 1);
-        }else{
-          res = pPKey2->default_rc;
-        }
-      }else if( res>0 ){
-        res = pPKey2->r2;
-      }else{
-        res = pPKey2->r1;
-      }
-    }else if( res>0 ){
-      res = pPKey2->r2;
-    }else{
-      res = pPKey2->r1;
-    }
-  }
-
-  assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, res)
-       || CORRUPT_DB
-       || pPKey2->pKeyInfo->pBtree->mallocFailed
-  );
-  return res;
-}
-
-/*
-** If the given Mem* has a zero-filled tail, turn it into an ordinary
-** blob stored in dynamically allocated space.
-*/
-#ifndef SQLITE_OMIT_INCRBLOB
-SQLITE_PRIVATE int sqlite3VdbeMemExpandBlob(Mem *pMem){
-  if( pMem->flags & MEM_Zero ){
-    int nByte;
-    assert( pMem->flags&MEM_Blob );
-    assert( (pMem->flags&MEM_RowSet)==0 );
-    assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-
-    /* Set nByte to the number of bytes required to store the expanded blob. */
-    nByte = pMem->n + pMem->u.nZero;
-    if( nByte<=0 ){
-      nByte = 1;
-    }
-    if( sqlite3VdbeMemGrow(pMem, nByte, 1) ){
-      return SQLITE_NOMEM;
-    }
-
-    memset(&pMem->z[pMem->n], 0, pMem->u.nZero);
-    pMem->n += pMem->u.nZero;
-    pMem->flags &= ~MEM_Zero;
-  }
-  return SQLITE_OK;
-}
-#endif
-
-/*
-** Convert a 64-bit IEEE double into a 64-bit signed integer.
-** If the double is out of range of a 64-bit signed integer then
-** return the closest available 64-bit signed integer.
-*/
-static i64 doubleToInt64(double r){
-#ifdef SQLITE_OMIT_FLOATING_POINT
-  /* When floating-point is omitted, double and int64 are the same thing */
-  return r;
-#else
-  /*
-  ** Many compilers we encounter do not define constants for the
-  ** minimum and maximum 64-bit integers, or they define them
-  ** inconsistently.  And many do not understand the "LL" notation.
-  ** So we define our own static constants here using nothing
-  ** larger than a 32-bit integer constant.
-  */
-  static const i64 maxInt = LARGEST_INT64;
-  static const i64 minInt = SMALLEST_INT64;
-
-  if( r<=(double)minInt ){
-    return minInt;
-  }else if( r>=(double)maxInt ){
-    return maxInt;
-  }else{
-    return (i64)r;
-  }
-#endif
-}
-
-/*
-** Return some kind of integer value which is the best we can do
-** at representing the value that *pMem describes as an integer.
-** If pMem is an integer, then the value is exact.  If pMem is
-** a floating-point then the value returned is the integer part.
-** If pMem is a string or blob, then we make an attempt to convert
-** it into an integer and return that.  If pMem represents an
-** an SQL-NULL value, return 0.
-**
-** If pMem represents a string value, its encoding might be changed.
-*/
-SQLITE_PRIVATE i64 sqlite3VdbeIntValue(Mem *pMem){
-  int flags;
-  assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
-  flags = pMem->flags;
-  if( flags & MEM_Int ){
-    return pMem->u.i;
-  }else if( flags & MEM_Real ){
-    return doubleToInt64(pMem->u.r);
-  }else if( flags & (MEM_Str|MEM_Blob) ){
-    i64 value = 0;
-    assert( pMem->z || pMem->n==0 );
-    sqlite3Atoi64(pMem->z, &value, pMem->n, pMem->enc);
-    return value;
-  }else{
-    return 0;
-  }
-}
-
-/*
-** Return the best representation of pMem that we can get into a
-** double.  If pMem is already a double or an integer, return its
-** value.  If it is a string or blob, try to convert it to a double.
-** If it is a NULL, return 0.0.
-*/
-SQLITE_PRIVATE double sqlite3VdbeRealValue(Mem *pMem){
-  assert( pMem->pBtree==0 || sqlite3_mutex_held(pMem->pBtree->mutex) );
-  assert( EIGHT_BYTE_ALIGNMENT(pMem) );
-  if( pMem->flags & MEM_Real ){
-    return pMem->u.r;
-  }else if( pMem->flags & MEM_Int ){
-    return (double)pMem->u.i;
-  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
-    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
-    double val = (double)0;
-    sqlite3AtoF(pMem->z, &val, pMem->n, pMem->enc);
-    return val;
-  }else{
-    /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
-    return (double)0;
-  }
-}
-
-/*
-** The pVal argument is known to be a value other than NULL.
-** Convert it into a string with encoding enc and return a pointer
-** to a zero-terminated version of that string.
-*/
-static SQLITE_NOINLINE const void *valueToText(Mem* pVal, u8 enc){
-  assert( pVal!=0 );
-  assert( pVal->pBtree==0 || sqlite3_mutex_held(pVal->pBtree->mutex) );
-  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
-  assert( (pVal->flags & MEM_RowSet)==0 );
-  assert( (pVal->flags & (MEM_Null))==0 );
-  if( pVal->flags & (MEM_Blob|MEM_Str) ){
-    pVal->flags |= MEM_Str;
-    if( pVal->flags & MEM_Zero ){
-      sqlite3VdbeMemExpandBlob(pVal);
-    }
-    if( pVal->enc != (enc & ~SQLITE_UTF16_ALIGNED) ){
-      sqlite3VdbeChangeEncoding(pVal, enc & ~SQLITE_UTF16_ALIGNED);
-    }
-    if( (enc & SQLITE_UTF16_ALIGNED)!=0 && 1==(1&SQLITE_PTR_TO_INT(pVal->z)) ){
-      assert( (pVal->flags & (MEM_Ephem|MEM_Static))!=0 );
-      if( sqlite3VdbeMemMakeWriteable(pVal)!=SQLITE_OK ){
-        return 0;
-      }
-    }
-    sqlite3VdbeMemNulTerminate(pVal); /* IMP: R-31275-44060 */
-  }else{
-    sqlite3VdbeMemStringify(pVal, enc, 0);
-    assert( 0==(1&SQLITE_PTR_TO_INT(pVal->z)) );
-  }
-  assert(pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) || pVal->pBtree==0
-              || pVal->pBtree->mallocFailed );
-  if( pVal->enc==(enc & ~SQLITE_UTF16_ALIGNED) ){
-    return pVal->z;
-  }else{
-    return 0;
-  }
-}
-
-/* This function is only available internally, it is not part of the
-** external API. It works in a similar way to sqlite3_value_text(),
-** except the data returned is in the encoding specified by the second
-** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or
-** SQLITE_UTF8.
-**
-** (2006-02-16:)  The enc value can be or-ed with SQLITE_UTF16_ALIGNED.
-** If that is the case, then the result must be aligned on an even byte
-** boundary.
-*/
-SQLITE_PRIVATE const void *sqlite3ValueText(Mem* pVal, u8 enc){
-  if( !pVal ) return 0;
-  assert( pVal->pBtree==0 || sqlite3_mutex_held(pVal->pBtree->mutex) );
-  assert( (enc&3)==(enc&~SQLITE_UTF16_ALIGNED) );
-  assert( (pVal->flags & MEM_RowSet)==0 );
-  if( (pVal->flags&MEM_Str)==MEM_Str && pVal->enc==enc ){
-    return pVal->z;
-  }
-  if( pVal->flags&MEM_Null ){
-    return 0;
-  }
-  return valueToText(pVal, enc);
-}
-
-/*
-** Both *pMem1 and *pMem2 contain string values. Compare the two values
-** using the collation sequence pColl. As usual, return a negative , zero
-** or positive value if *pMem1 is less than, equal to or greater than 
-** *pMem2, respectively. Similar in spirit to "rc = (*pMem1) - (*pMem2);".
-*/
-static int vdbeCompareMemString(
-  const Mem *pMem1,
-  const Mem *pMem2,
-  const CollSeq *pColl,
-  u8 *prcErr                      /* If an OOM occurs, set to SQLITE_NOMEM */
-){
-  if( pMem1->enc==pColl->enc ){
-    /* The strings are already in the correct encoding.  Call the
-     ** comparison function directly */
-    return pColl->xCmp(pColl->pUser,pMem1->n,pMem1->z,pMem2->n,pMem2->z);
-  }else{
-    int rc;
-    const void *v1, *v2;
-    int n1, n2;
-    Mem c1;
-    Mem c2;
-    sqlite3VdbeMemInit(&c1, pMem1->pBtree, MEM_Null);
-    sqlite3VdbeMemInit(&c2, pMem1->pBtree, MEM_Null);
-    sqlite3VdbeMemShallowCopy(&c1, pMem1, MEM_Ephem);
-    sqlite3VdbeMemShallowCopy(&c2, pMem2, MEM_Ephem);
-    v1 = sqlite3ValueText(&c1, pColl->enc);
-    n1 = v1==0 ? 0 : c1.n;
-    v2 = sqlite3ValueText(&c2, pColl->enc);
-    n2 = v2==0 ? 0 : c2.n;
-    rc = pColl->xCmp(pColl->pUser, n1, v1, n2, v2);
-    sqlite3VdbeMemRelease(&c1);
-    sqlite3VdbeMemRelease(&c2);
-    if( (v1==0 || v2==0) && prcErr ) *prcErr = SQLITE_NOMEM;
-    return rc;
-  }
-}
-
-/*
-** The first argument passed to this function is a serial-type that
-** corresponds to an integer - all values between 1 and 9 inclusive 
-** except 7. The second points to a buffer containing an integer value
-** serialized according to serial_type. This function deserializes
-** and returns the value.
-*/
-static i64 vdbeRecordDecodeInt(u32 serial_type, const u8 *aKey){
-  u32 y;
-  assert( CORRUPT_DB || (serial_type>=1 && serial_type<=9 && serial_type!=7) );
-  switch( serial_type ){
-    case 0:
-    case 1:
-      testcase( aKey[0]&0x80 );
-      return ONE_BYTE_INT(aKey);
-    case 2:
-      testcase( aKey[0]&0x80 );
-      return TWO_BYTE_INT(aKey);
-    case 3:
-      testcase( aKey[0]&0x80 );
-      return THREE_BYTE_INT(aKey);
-    case 4: {
-      testcase( aKey[0]&0x80 );
-      y = FOUR_BYTE_UINT(aKey);
-      return (i64)*(int*)&y;
-    }
-    case 5: {
-      testcase( aKey[0]&0x80 );
-      return FOUR_BYTE_UINT(aKey+2) + (((i64)1)<<32)*TWO_BYTE_INT(aKey);
-    }
-    case 6: {
-      u64 x = FOUR_BYTE_UINT(aKey);
-      testcase( aKey[0]&0x80 );
-      x = (x<<32) | FOUR_BYTE_UINT(aKey+4);
-      return (i64)*(i64*)&x;
-    }
-  }
-
-  return (serial_type - 8);
-}
-
-/*
-** This function compares the two table rows or index records
-** specified by {nKey1, pKey1} and pPKey2.  It returns a negative, zero
-** or positive integer if key1 is less than, equal to or 
-** greater than key2.  The {nKey1, pKey1} key must be a blob
-** created by the OP_MakeRecord opcode of the VDBE.  The pPKey2
-** key must be a parsed key such as obtained from
-** sqlite3VdbeParseRecord.
-**
-** If argument bSkip is non-zero, it is assumed that the caller has already
-** determined that the first fields of the keys are equal.
-**
-** Key1 and Key2 do not have to contain the same number of fields. If all 
-** fields that appear in both keys are equal, then pPKey2->default_rc is 
-** returned.
-**
-** If database corruption is discovered, set pPKey2->errCode to 
-** SQLITE_CORRUPT and return 0. If an OOM error is encountered, 
-** pPKey2->errCode is set to SQLITE_NOMEM and, if it is not NULL, the
-** malloc-failed flag set on database handle (pPKey2->pKeyInfo->pBtree).
-*/
-SQLITE_PRIVATE int sqlite3VdbeRecordCompareWithSkip(
-  int nKey1, const void *pKey1,   /* Left key */
-  UnpackedRecord *pPKey2,         /* Right key */
-  int bSkip                       /* If true, skip the first field */
-){
-  u32 d1;                         /* Offset into aKey[] of next data element */
-  int i;                          /* Index of next field to compare */
-  u32 szHdr1;                     /* Size of record header in bytes */
-  u32 idx1;                       /* Offset of first type in header */
-  int rc = 0;                     /* Return value */
-  Mem *pRhs = pPKey2->aMem;       /* Next field of pPKey2 to compare */
-  KeyInfo *pKeyInfo = pPKey2->pKeyInfo;
-  const unsigned char *aKey1 = (const unsigned char *)pKey1;
-  Mem mem1;
-
-  /* If bSkip is true, then the caller has already determined that the first
-  ** two elements in the keys are equal. Fix the various stack variables so
-  ** that this routine begins comparing at the second field. */
-  if( bSkip ){
-    u32 s1;
-    idx1 = 1 + getVarint32(&aKey1[1], s1);
-    szHdr1 = aKey1[0];
-    d1 = szHdr1 + sqlite3BtreeSerialTypeLen(s1);
-    i = 1;
-    pRhs++;
-  }else{
-    idx1 = getVarint32(aKey1, szHdr1);
-    d1 = szHdr1;
-    if( d1>(unsigned)nKey1 ){ 
-      pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
-      return 0;  /* Corruption */
-    }
-    i = 0;
-  }
-
-  VVA_ONLY( mem1.szMalloc = 0; ) /* Only needed by assert() statements */
-  assert( pPKey2->pKeyInfo->nField+pPKey2->pKeyInfo->nXField>=pPKey2->nField 
-       || CORRUPT_DB );
-  assert( pPKey2->pKeyInfo->aSortOrder!=0 );
-  assert( pPKey2->pKeyInfo->nField>0 );
-  assert( idx1<=szHdr1 || CORRUPT_DB );
-  do{
-    u32 serial_type;
-
-    /* RHS is an integer */
-    if( pRhs->flags & MEM_Int ){
-      serial_type = aKey1[idx1];
-      testcase( serial_type==12 );
-      if( serial_type>=10 ){
-        rc = +1;
-      }else if( serial_type==0 ){
-        rc = -1;
-      }else if( serial_type==7 ){
-        double rhs = (double)pRhs->u.i;
-        sqlite3BtreeSerialGet(&aKey1[d1], serial_type, &mem1);
-        if( mem1.u.r<rhs ){
-          rc = -1;
-        }else if( mem1.u.r>rhs ){
-          rc = +1;
-        }
-      }else{
-        i64 lhs = vdbeRecordDecodeInt(serial_type, &aKey1[d1]);
-        i64 rhs = pRhs->u.i;
-        if( lhs<rhs ){
-          rc = -1;
-        }else if( lhs>rhs ){
-          rc = +1;
-        }
-      }
-    }
-
-    /* RHS is real */
-    else if( pRhs->flags & MEM_Real ){
-      serial_type = aKey1[idx1];
-      if( serial_type>=10 ){
-        /* Serial types 12 or greater are strings and blobs (greater than
-        ** numbers). Types 10 and 11 are currently "reserved for future 
-        ** use", so it doesn't really matter what the results of comparing
-        ** them to numberic values are.  */
-        rc = +1;
-      }else if( serial_type==0 ){
-        rc = -1;
-      }else{
-        double rhs = pRhs->u.r;
-        double lhs;
-        sqlite3BtreeSerialGet(&aKey1[d1], serial_type, &mem1);
-        if( serial_type==7 ){
-          lhs = mem1.u.r;
-        }else{
-          lhs = (double)mem1.u.i;
-        }
-        if( lhs<rhs ){
-          rc = -1;
-        }else if( lhs>rhs ){
-          rc = +1;
-        }
-      }
-    }
-
-    /* RHS is a string */
-    else if( pRhs->flags & MEM_Str ){
-      getVarint32(&aKey1[idx1], serial_type);
-      testcase( serial_type==12 );
-      if( serial_type<12 ){
-        rc = -1;
-      }else if( !(serial_type & 0x01) ){
-        rc = +1;
-      }else{
-        mem1.n = (serial_type - 12) / 2;
-        testcase( (d1+mem1.n)==(unsigned)nKey1 );
-        testcase( (d1+mem1.n+1)==(unsigned)nKey1 );
-        if( (d1+mem1.n) > (unsigned)nKey1 ){
-          pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
-          return 0;                /* Corruption */
-        }else if( pKeyInfo->aColl[i] ){
-          mem1.enc = pKeyInfo->enc;
-          mem1.pBtree = pKeyInfo->pBtree;
-          mem1.flags = MEM_Str;
-          mem1.z = (char*)&aKey1[d1];
-          rc = vdbeCompareMemString(
-              &mem1, pRhs, pKeyInfo->aColl[i], &pPKey2->errCode
-          );
-        }else{
-          int nCmp = MIN(mem1.n, pRhs->n);
-          rc = memcmp(&aKey1[d1], pRhs->z, nCmp);
-          if( rc==0 ) rc = mem1.n - pRhs->n; 
-        }
-      }
-    }
-
-    /* RHS is a blob */
-    else if( pRhs->flags & MEM_Blob ){
-      getVarint32(&aKey1[idx1], serial_type);
-      testcase( serial_type==12 );
-      if( serial_type<12 || (serial_type & 0x01) ){
-        rc = -1;
-      }else{
-        int nStr = (serial_type - 12) / 2;
-        testcase( (d1+nStr)==(unsigned)nKey1 );
-        testcase( (d1+nStr+1)==(unsigned)nKey1 );
-        if( (d1+nStr) > (unsigned)nKey1 ){
-          pPKey2->errCode = (u8)SQLITE_CORRUPT_BKPT;
-          return 0;                /* Corruption */
-        }else{
-          int nCmp = MIN(nStr, pRhs->n);
-          rc = memcmp(&aKey1[d1], pRhs->z, nCmp);
-          if( rc==0 ) rc = nStr - pRhs->n;
-        }
-      }
-    }
-
-    /* RHS is null */
-    else{
-      serial_type = aKey1[idx1];
-      rc = (serial_type!=0);
-    }
-
-    if( rc!=0 ){
-      if( pKeyInfo->aSortOrder[i] ){
-        rc = -rc;
-      }
-      assert( vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, rc) );
-      assert( mem1.szMalloc==0 );  /* See comment below */
-      return rc;
-    }
-
-    i++;
-    pRhs++;
-    d1 += sqlite3BtreeSerialTypeLen(serial_type);
-    idx1 += sqlite3BtreeVarintLen(serial_type);
-  }while( idx1<(unsigned)szHdr1 && i<pPKey2->nField && d1<=(unsigned)nKey1 );
-
-  /* No memory allocation is ever used on mem1.  Prove this using
-  ** the following assert().  If the assert() fails, it indicates a
-  ** memory leak and a need to call sqlite3VdbeMemRelease(&mem1).  */
-  assert( mem1.szMalloc==0 );
-
-  /* rc==0 here means that one or both of the keys ran out of fields and
-  ** all the fields up to that point were equal. Return the default_rc
-  ** value.  */
-  assert( CORRUPT_DB 
-       || vdbeRecordCompareDebug(nKey1, pKey1, pPKey2, pPKey2->default_rc) 
-       || pKeyInfo->pBtree->mallocFailed
-  );
-  return pPKey2->default_rc;
-}
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeRecordCompare(
-  int nKey1, const void *pKey1,   /* Left key */
-  UnpackedRecord *pPKey2          /* Right key */
-){
-  return sqlite3VdbeRecordCompareWithSkip(nKey1, pKey1, pPKey2, 0);
-}
-
-/*
-** Return a pointer to an sqlite3BtreeRecordCompare() compatible function
-** suitable for comparing serialized records to the unpacked record passed
-** as the only argument.
-*/
-SQLITE_PRIVATE RecordCompare sqlite3VdbeFindCompare(UnpackedRecord *p){
-  /* varintRecordCompareInt() and varintRecordCompareString() both assume
-  ** that the size-of-header varint that occurs at the start of each record
-  ** fits in a single byte (i.e. is 127 or less). varintRecordCompareInt()
-  ** also assumes that it is safe to overread a buffer by at least the 
-  ** maximum possible legal header size plus 8 bytes. Because there is
-  ** guaranteed to be at least 74 (but not 136) bytes of padding following each
-  ** buffer passed to varintRecordCompareInt() this makes it convenient to
-  ** limit the size of the header to 64 bytes in cases where the first field
-  ** is an integer.
-  **
-  ** The easiest way to enforce this limit is to consider only records with
-  ** 13 fields or less. If the first field is an integer, the maximum legal
-  ** header size is (12*5 + 1 + 1) bytes.  */
-  if( (p->pKeyInfo->nField + p->pKeyInfo->nXField)<=13 ){
-    int flags = p->aMem[0].flags;
-    if( p->pKeyInfo->aSortOrder[0] ){
-      p->r1 = 1;
-      p->r2 = -1;
-    }else{
-      p->r1 = -1;
-      p->r2 = 1;
-    }
-    if( (flags & MEM_Int) ){
-      return vdbeRecordCompareInt;
-    }
-    testcase( flags & MEM_Real );
-    testcase( flags & MEM_Null );
-    testcase( flags & MEM_Blob );
-    if( (flags & (MEM_Real|MEM_Null|MEM_Blob))==0 && p->pKeyInfo->aColl[0]==0 ){
-      assert( flags & MEM_Str );
-      return vdbeRecordCompareString;
-    }
-  }
-
-  return sqlite3BtreeRecordCompare;
-}
-
-/*
-** Move data out of a btree key or data field and into a Mem structure.
-** The data or key is taken from the entry that pCur is currently pointing
-** to.  offset and amt determine what portion of the data or key to retrieve.
-** key is true to get the key or false to get data.  The result is written
-** into the pMem element.
-**
-** The pMem object must have been initialized.  This routine will use
-** pMem->zMalloc to hold the content from the btree, if possible.  New
-** pMem->zMalloc space will be allocated if necessary.  The calling routine
-** is responsible for making sure that the pMem object is eventually
-** destroyed.
-**
-** If this routine fails for any reason (malloc returns NULL or unable
-** to read from the disk) then the pMem is left in an inconsistent state.
-*/
-static SQLITE_NOINLINE int vdbeMemFromBtreeResize(
-  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
-  u32 offset,       /* Offset from the start of data to return bytes from. */
-  u32 amt,          /* Number of bytes to return. */
-  int key,          /* If true, retrieve from the btree key, not data. */
-  Mem *pMem         /* OUT: Return data in this Mem structure. */
-){
-  int rc;
-  pMem->flags = MEM_Null;
-  if( SQLITE_OK==(rc = sqlite3VdbeMemClearAndResize(pMem, amt+2)) ){
-    if( key ){
-      rc = sqlite3BtreeKey(pCur, offset, amt, pMem->z);
-    }else{
-      rc = sqlite3BtreeData(pCur, offset, amt, pMem->z);
-    }
-    if( rc==SQLITE_OK ){
-      pMem->z[amt] = 0;
-      pMem->z[amt+1] = 0;
-      pMem->flags = MEM_Blob|MEM_Term;
-      pMem->n = (int)amt;
-    }else{
-      sqlite3VdbeMemRelease(pMem);
-    }
-  }
-  return rc;
-}
-
-SQLITE_PRIVATE int sqlite3VdbeMemFromBtree(
-  BtCursor *pCur,   /* Cursor pointing at record to retrieve. */
-  u32 offset,       /* Offset from the start of data to return bytes from. */
-  u32 amt,          /* Number of bytes to return. */
-  int key,          /* If true, retrieve from the btree key, not data. */
-  Mem *pMem         /* OUT: Return data in this Mem structure. */
-){
-  char *zData;        /* Data from the btree layer */
-  u32 available = 0;  /* Number of bytes available on the local btree page */
-  int rc = SQLITE_OK; /* Return code */
-
-  assert( sqlite3BtreeCursorIsValid(pCur) );
-  assert( !VdbeMemDynamic(pMem) );
-
-  /* Note: the calls to BtreeKeyFetch() and DataFetch() below assert() 
-  ** that both the BtShared and database handle mutexes are held. */
-  assert( (pMem->flags & MEM_RowSet)==0 );
-  if( key ){
-    zData = (char *)sqlite3BtreeKeyFetch(pCur, &available);
-  }else{
-    zData = (char *)sqlite3BtreeDataFetch(pCur, &available);
-  }
-  assert( zData!=0 );
-
-  if( offset+amt<=available ){
-    pMem->z = &zData[offset];
-    pMem->flags = MEM_Blob|MEM_Ephem;
-    pMem->n = (int)amt;
-  }else{
-    rc = vdbeMemFromBtreeResize(pCur, offset, amt, key, pMem);
-  }
-
-  return rc;
-}
-
-/*
-** pCur points at an index entry created using the OP_MakeRecord opcode.
-** Read the rowid (the last field in the record) and store it in *rowid.
-** Return SQLITE_OK if everything works, or an error code otherwise.
-**
-** pCur might be pointing to text obtained from a corrupt database file.
-** So the content cannot be trusted.  Do appropriate checks on the content.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeIdxRowid(Btree* pBtree, BtCursor *pCur, i64 *rowid){
-  i64 nCellKey = 0;
-  int rc;
-  u32 szHdr;        /* Size of the header */
-  u32 typeRowid;    /* Serial type of the rowid */
-  u32 lenRowid;     /* Size of the rowid */
-  Mem m, v;
-
-  /* Get the size of the index entry.  Only indices entries of less
-  ** than 2GiB are support - anything large must be database corruption.
-  ** Any corruption is detected in sqlite3BtreeParseCellPtr(), though, so
-  ** this code can safely assume that nCellKey is 32-bits  
-  */
-  assert( sqlite3BtreeCursorIsValid(pCur) );
-  VVA_ONLY(rc =) sqlite3BtreeKeySize(pCur, &nCellKey);
-  assert( rc==SQLITE_OK );     /* pCur is always valid so KeySize cannot fail */
-  assert( (nCellKey & SQLITE_MAX_U32)==(u64)nCellKey );
-
-  /* Read in the complete content of the index entry */
-  sqlite3VdbeMemInit(&m, pBtree, 0);
-  rc = sqlite3VdbeMemFromBtree(pCur, 0, (u32)nCellKey, 1, &m);
-  if( rc ){
-    return rc;
-  }
-
-  /* The index entry must begin with a header size */
-  (void)getVarint32((u8*)m.z, szHdr);
-  testcase( szHdr==3 );
-  testcase( szHdr==m.n );
-  if( unlikely(szHdr<3 || (int)szHdr>m.n) ){
-    goto idx_rowid_corruption;
-  }
-
-  /* The last field of the index should be an integer - the ROWID.
-  ** Verify that the last entry really is an integer. */
-  (void)getVarint32((u8*)&m.z[szHdr-1], typeRowid);
-  testcase( typeRowid==1 );
-  testcase( typeRowid==2 );
-  testcase( typeRowid==3 );
-  testcase( typeRowid==4 );
-  testcase( typeRowid==5 );
-  testcase( typeRowid==6 );
-  testcase( typeRowid==8 );
-  testcase( typeRowid==9 );
-  if( unlikely(typeRowid<1 || typeRowid>9 || typeRowid==7) ){
-    goto idx_rowid_corruption;
-  }
-  lenRowid = sqlite3SmallTypeSizes[typeRowid];
-  testcase( (u32)m.n==szHdr+lenRowid );
-  if( unlikely((u32)m.n<szHdr+lenRowid) ){
-    goto idx_rowid_corruption;
-  }
-
-  /* Fetch the integer off the end of the index record */
-  sqlite3BtreeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
-  *rowid = v.u.i;
-  sqlite3VdbeMemRelease(&m);
-  return SQLITE_OK;
-
-  /* Jump here if database corruption is detected after m has been
-  ** allocated.  Free the m object and return SQLITE_CORRUPT. */
-idx_rowid_corruption:
-  testcase( m.szMalloc!=0 );
-  sqlite3VdbeMemRelease(&m);
-  return SQLITE_CORRUPT_BKPT;
-}
-
-/************** End of btree.c ***********************************************/
-/************** Begin file backup.c ******************************************/
-/*
-** 2009 January 28
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This file contains the implementation of the sqlite3_backup_XXX() 
-** API functions and the related features.
-*/
-/* #include "sqliteInt.h" */
-/* #include "btreeInt.h" */
-
-/*
-** Structure allocated for each backup operation.
-*/
-struct sqlite3_backup {
-  Btree *pDest;            /* Destination b-tree file */
-  u32 iDestSchema;         /* Original schema cookie in destination */
-  int bDestLocked;         /* True once a write-transaction is open on pDest */
-
-  Pgno iNext;              /* Page number of the next source page to copy */
-  Btree *pSrc;             /* Source b-tree file */
-
-  int rc;                  /* Backup process error code */
-
-  /* These two variables are set by every call to backup_step(). They are
-  ** read by calls to backup_remaining() and backup_pagecount().
-  */
-  Pgno nRemaining;         /* Number of pages left to copy */
-  Pgno nPagecount;         /* Total number of pages to copy */
-
-  int isAttached;          /* True once backup has been registered with pager */
-  sqlite3_backup *pNext;   /* Next backup associated with source pager */
-};
-
-/*
-** Argument rc is an SQLite error code. Return true if this error is 
-** considered fatal if encountered during a backup operation. All errors
-** are considered fatal except for SQLITE_BUSY and SQLITE_LOCKED.
-*/
-static int isFatalError(int rc){
-  return (rc!=SQLITE_OK && rc!=SQLITE_BUSY && ALWAYS(rc!=SQLITE_LOCKED));
-}
-
-/*
-** Parameter zSrcData points to a buffer containing the data for 
-** page iSrcPg from the source database. Copy this data into the 
-** destination database.
-*/
-static int backupOnePage(
-  sqlite3_backup *p,              /* Backup handle */
-  Pgno iSrcPg,                    /* Source database page to backup */
-  const u8 *zSrcData,             /* Source database page data */
-  int bUpdate                     /* True for an update, false otherwise */
-){
-  Pager * const pDestPager = sqlite3BtreePager(p->pDest);
-  const int nSrcPgsz = sqlite3BtreeGetPageSize(p->pSrc);
-  int nDestPgsz = sqlite3BtreeGetPageSize(p->pDest);
-  const int nCopy = MIN(nSrcPgsz, nDestPgsz);
-  const i64 iEnd = (i64)iSrcPg*(i64)nSrcPgsz;
-#ifdef SQLITE_HAS_CODEC
-  /* Use BtreeGetReserveNoMutex() for the source b-tree, as although it is
-  ** guaranteed that the shared-mutex is held by this thread, handle
-  ** p->pSrc may not actually be the owner.  */
-  int nSrcReserve = sqlite3BtreeGetReserveNoMutex(p->pSrc);
-  int nDestReserve = sqlite3BtreeGetOptimalReserve(p->pDest);
-#endif
-  int rc = SQLITE_OK;
-  i64 iOff;
-
-  assert( sqlite3BtreeGetReserveNoMutex(p->pSrc)>=0 );
-  assert( p->bDestLocked );
-  assert( !isFatalError(p->rc) );
-  assert( iSrcPg!=PENDING_BYTE_PAGE(p->pSrc->pBt) );
-  assert( zSrcData );
-
-#ifdef SQLITE_HAS_CODEC
-  /* Backup is not possible if the page size of the destination is changing
-  ** and a codec is in use.
-  */
-  if( nSrcPgsz!=nDestPgsz && sqlite3PagerGetCodec(pDestPager)!=0 ){
-    rc = SQLITE_READONLY;
-  }
-
-  /* Backup is not possible if the number of bytes of reserve space differ
-  ** between source and destination.  If there is a difference, try to
-  ** fix the destination to agree with the source.  If that is not possible,
-  ** then the backup cannot proceed.
-  */
-  if( nSrcReserve!=nDestReserve ){
-    u32 newPgsz = nSrcPgsz;
-    rc = sqlite3PagerSetPagesize(pDestPager, &newPgsz, nSrcReserve);
-    if( rc==SQLITE_OK && newPgsz!=nSrcPgsz ) rc = SQLITE_READONLY;
-  }
-#endif
-
-  /* This loop runs once for each destination page spanned by the source 
-  ** page. For each iteration, variable iOff is set to the byte offset
-  ** of the destination page.
-  */
-  for(iOff=iEnd-(i64)nSrcPgsz; rc==SQLITE_OK && iOff<iEnd; iOff+=nDestPgsz){
-    DbPage *pDestPg = 0;
-    Pgno iDest = (Pgno)(iOff/nDestPgsz)+1;
-    if( iDest==PENDING_BYTE_PAGE(p->pDest->pBt) ) continue;
-    if( SQLITE_OK==(rc = sqlite3PagerGet(pDestPager, iDest, &pDestPg))
-     && SQLITE_OK==(rc = sqlite3PagerWrite(pDestPg))
-    ){
-      const u8 *zIn = &zSrcData[iOff%nSrcPgsz];
-      u8 *zDestData = sqlite3PagerGetData(pDestPg);
-      u8 *zOut = &zDestData[iOff%nDestPgsz];
-
-      /* Copy the data from the source page into the destination page.
-      ** Then clear the Btree layer MemPage.isInit flag. Both this module
-      ** and the pager code use this trick (clearing the first byte
-      ** of the page 'extra' space to invalidate the Btree layers
-      ** cached parse of the page). MemPage.isInit is marked 
-      ** "MUST BE FIRST" for this purpose.
-      */
-      memcpy(zOut, zIn, nCopy);
-      ((u8 *)sqlite3PagerGetExtra(pDestPg))[0] = 0;
-      if( iOff==0 && bUpdate==0 ){
-        sqlite3Put4byte(&zOut[28], sqlite3BtreeLastPage(p->pSrc));
-      }
-    }
-    sqlite3PagerUnref(pDestPg);
-  }
-
-  return rc;
-}
-
-/*
-** This function is called after the contents of page iPage of the
-** source database have been modified. If page iPage has already been 
-** copied into the destination database, then the data written to the
-** destination is now invalidated. The destination copy of iPage needs
-** to be updated with the new data before the backup operation is
-** complete.
-**
-** It is assumed that the mutex associated with the BtShared object
-** corresponding to the source database is held when this function is
-** called.
-*/
-static SQLITE_NOINLINE void backupUpdate(
-  sqlite3_backup *p,
-  Pgno iPage,
-  const u8 *aData
-){
-  assert( p!=0 );
-  do{
-    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
-    if( !isFatalError(p->rc) && iPage<p->iNext ){
-      /* The backup process p has already copied page iPage. But now it
-      ** has been modified by a transaction on the source pager. Copy
-      ** the new data into the backup.
-      */
-      int rc;
-      assert( p->pDest );
-      sqlite3_mutex_enter(p->pDest->mutex);
-      rc = backupOnePage(p, iPage, aData, 1);
-      sqlite3_mutex_leave(p->pDest->mutex);
-      assert( rc!=SQLITE_BUSY && rc!=SQLITE_LOCKED );
-      if( rc!=SQLITE_OK ){
-        p->rc = rc;
-      }
-    }
-  }while( (p = p->pNext)!=0 );
-}
-SQLITE_PRIVATE void sqlite3BackupUpdate(sqlite3_backup *pBackup, Pgno iPage, const u8 *aData){
-  if( pBackup ) backupUpdate(pBackup, iPage, aData);
-}
-
-/*
-** Restart the backup process. This is called when the pager layer
-** detects that the database has been modified by an external database
-** connection. In this case there is no way of knowing which of the
-** pages that have been copied into the destination database are still 
-** valid and which are not, so the entire process needs to be restarted.
-**
-** It is assumed that the mutex associated with the BtShared object
-** corresponding to the source database is held when this function is
-** called.
-*/
-SQLITE_PRIVATE void sqlite3BackupRestart(sqlite3_backup *pBackup){
-  sqlite3_backup *p;                   /* Iterator variable */
-  for(p=pBackup; p; p=p->pNext){
-    assert( sqlite3_mutex_held(p->pSrc->pBt->mutex) );
-    p->iNext = 1;
-  }
-}
-
-/************** End of backup.c **********************************************/
-/************** Begin file journal.c *****************************************/
-/*
-** 2007 August 22
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file implements a special kind of sqlite3_file object used
-** by SQLite to create journal files if the atomic-write optimization
-** is enabled.
-**
-** The distinctive characteristic of this sqlite3_file is that the
-** actual on disk file is created lazily. When the file is created,
-** the caller specifies a buffer size for an in-memory buffer to
-** be used to service read() and write() requests. The actual file
-** on disk is not created or populated until either:
-**
-**   1) The in-memory representation grows too large for the allocated 
-**      buffer, or
-**   2) The sqlite3JournalCreate() function is called.
-*/
-#ifdef SQLITE_ENABLE_ATOMIC_WRITE
-/* #include "sqliteInt.h" */
-
-
-/*
-** A JournalFile object is a subclass of sqlite3_file used by
-** as an open file handle for journal files.
-*/
-struct JournalFile {
-  sqlite3_io_methods *pMethod;    /* I/O methods on journal files */
-  int nBuf;                       /* Size of zBuf[] in bytes */
-  char *zBuf;                     /* Space to buffer journal writes */
-  int iSize;                      /* Amount of zBuf[] currently used */
-  int flags;                      /* xOpen flags */
-  sqlite3_vfs *pVfs;              /* The "real" underlying VFS */
-  sqlite3_file *pReal;            /* The "real" underlying file descriptor */
-  const char *zJournal;           /* Name of the journal file */
-};
-typedef struct JournalFile JournalFile;
-
-/*
-** If it does not already exists, create and populate the on-disk file 
-** for JournalFile p.
-*/
-static int createFile(JournalFile *p){
-  int rc = SQLITE_OK;
-  if( !p->pReal ){
-    sqlite3_file *pReal = (sqlite3_file *)&p[1];
-    rc = sqlite3OsOpen(p->pVfs, p->zJournal, pReal, p->flags, 0);
-    if( rc==SQLITE_OK ){
-      p->pReal = pReal;
-      if( p->iSize>0 ){
-        assert(p->iSize<=p->nBuf);
-        rc = sqlite3OsWrite(p->pReal, p->zBuf, p->iSize, 0);
-      }
-      if( rc!=SQLITE_OK ){
-        /* If an error occurred while writing to the file, close it before
-        ** returning. This way, SQLite uses the in-memory journal data to 
-        ** roll back changes made to the internal page-cache before this
-        ** function was called.  */
-        sqlite3OsClose(pReal);
-        p->pReal = 0;
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Close the file.
-*/
-static int jrnlClose(sqlite3_file *pJfd){
-  JournalFile *p = (JournalFile *)pJfd;
-  if( p->pReal ){
-    sqlite3OsClose(p->pReal);
-  }
-  sqlite3_free(p->zBuf);
-  return SQLITE_OK;
-}
-
-/*
-** Read data from the file.
-*/
-static int jrnlRead(
-  sqlite3_file *pJfd,    /* The journal file from which to read */
-  void *zBuf,            /* Put the results here */
-  int iAmt,              /* Number of bytes to read */
-  sqlite_int64 iOfst     /* Begin reading at this offset */
-){
-  int rc = SQLITE_OK;
-  JournalFile *p = (JournalFile *)pJfd;
-  if( p->pReal ){
-    rc = sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
-  }else if( (iAmt+iOfst)>p->iSize ){
-    rc = SQLITE_IOERR_SHORT_READ;
-  }else{
-    memcpy(zBuf, &p->zBuf[iOfst], iAmt);
-  }
-  return rc;
-}
-
-/*
-** Write data to the file.
-*/
-static int jrnlWrite(
-  sqlite3_file *pJfd,    /* The journal file into which to write */
-  const void *zBuf,      /* Take data to be written from here */
-  int iAmt,              /* Number of bytes to write */
-  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
-){
-  int rc = SQLITE_OK;
-  JournalFile *p = (JournalFile *)pJfd;
-  if( !p->pReal && (iOfst+iAmt)>p->nBuf ){
-    rc = createFile(p);
-  }
-  if( rc==SQLITE_OK ){
-    if( p->pReal ){
-      rc = sqlite3OsWrite(p->pReal, zBuf, iAmt, iOfst);
-    }else{
-      memcpy(&p->zBuf[iOfst], zBuf, iAmt);
-      if( p->iSize<(iOfst+iAmt) ){
-        p->iSize = (iOfst+iAmt);
-      }
-    }
-  }
-  return rc;
-}
-
-/*
-** Truncate the file.
-*/
-static int jrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
-  int rc = SQLITE_OK;
-  JournalFile *p = (JournalFile *)pJfd;
-  if( p->pReal ){
-    rc = sqlite3OsTruncate(p->pReal, size);
-  }else if( size<p->iSize ){
-    p->iSize = size;
-  }
-  return rc;
-}
-
-/*
-** Sync the file.
-*/
-static int jrnlSync(sqlite3_file *pJfd, int flags){
-  int rc;
-  JournalFile *p = (JournalFile *)pJfd;
-  if( p->pReal ){
-    rc = sqlite3OsSync(p->pReal, flags);
-  }else{
-    rc = SQLITE_OK;
-  }
-  return rc;
-}
-
-/*
-** Query the size of the file in bytes.
-*/
-static int jrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
-  int rc = SQLITE_OK;
-  JournalFile *p = (JournalFile *)pJfd;
-  if( p->pReal ){
-    rc = sqlite3OsFileSize(p->pReal, pSize);
-  }else{
-    *pSize = (sqlite_int64) p->iSize;
-  }
-  return rc;
-}
-
-/*
-** Table of methods for JournalFile sqlite3_file object.
-*/
-static struct sqlite3_io_methods JournalFileMethods = {
-  1,             /* iVersion */
-  jrnlClose,     /* xClose */
-  jrnlRead,      /* xRead */
-  jrnlWrite,     /* xWrite */
-  jrnlTruncate,  /* xTruncate */
-  jrnlSync,      /* xSync */
-  jrnlFileSize,  /* xFileSize */
-  0,             /* xLock */
-  0,             /* xUnlock */
-  0,             /* xCheckReservedLock */
-  0,             /* xFileControl */
-  0,             /* xSectorSize */
-  0,             /* xDeviceCharacteristics */
-  0,             /* xShmMap */
-  0,             /* xShmLock */
-  0,             /* xShmBarrier */
-  0              /* xShmUnmap */
-};
-
-/* 
-** Open a journal file.
-*/
-SQLITE_PRIVATE int sqlite3JournalOpen(
-  sqlite3_vfs *pVfs,         /* The VFS to use for actual file I/O */
-  const char *zName,         /* Name of the journal file */
-  sqlite3_file *pJfd,        /* Preallocated, blank file handle */
-  int flags,                 /* Opening flags */
-  int nBuf                   /* Bytes buffered before opening the file */
-){
-  JournalFile *p = (JournalFile *)pJfd;
-  memset(p, 0, sqlite3JournalSize(pVfs));
-  if( nBuf>0 ){
-    p->zBuf = sqlite3MallocZero(nBuf);
-    if( !p->zBuf ){
-      return SQLITE_NOMEM;
-    }
-  }else{
-    return sqlite3OsOpen(pVfs, zName, pJfd, flags, 0);
-  }
-  p->pMethod = &JournalFileMethods;
-  p->nBuf = nBuf;
-  p->flags = flags;
-  p->zJournal = zName;
-  p->pVfs = pVfs;
-  return SQLITE_OK;
-}
-
-/*
-** If the argument p points to a JournalFile structure, and the underlying
-** file has not yet been created, create it now.
-*/
-SQLITE_PRIVATE int sqlite3JournalCreate(sqlite3_file *p){
-  if( p->pMethods!=&JournalFileMethods ){
-    return SQLITE_OK;
-  }
-  return createFile((JournalFile *)p);
-}
-
-/*
-** The file-handle passed as the only argument is guaranteed to be an open
-** file. It may or may not be of class JournalFile. If the file is a
-** JournalFile, and the underlying file on disk has not yet been opened,
-** return 0. Otherwise, return 1.
-*/
-SQLITE_PRIVATE int sqlite3JournalExists(sqlite3_file *p){
-  return (p->pMethods!=&JournalFileMethods || ((JournalFile *)p)->pReal!=0);
-}
-
-/* 
-** Return the number of bytes required to store a JournalFile that uses vfs
-** pVfs to create the underlying on-disk files.
-*/
-SQLITE_PRIVATE int sqlite3JournalSize(sqlite3_vfs *pVfs){
-  return (pVfs->szOsFile+sizeof(JournalFile));
-}
-#endif
-
-/************** End of journal.c *********************************************/
-/************** Begin file memjournal.c **************************************/
-/*
-** 2008 October 7
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-**
-** This file contains code use to implement an in-memory rollback journal.
-** The in-memory rollback journal is used to journal transactions for
-** ":memory:" databases and when the journal_mode=MEMORY pragma is used.
-*/
-/* #include "sqliteInt.h" */
-
-/* Forward references to internal structures */
-typedef struct MemJournal MemJournal;
-typedef struct FilePoint FilePoint;
-typedef struct FileChunk FileChunk;
-
-/* Space to hold the rollback journal is allocated in increments of
-** this many bytes.
-**
-** The size chosen is a little less than a power of two.  That way,
-** the FileChunk object will have a size that almost exactly fills
-** a power-of-two allocation.  This minimizes wasted space in power-of-two
-** memory allocators.
-*/
-#define JOURNAL_CHUNKSIZE ((int)(1024-sizeof(FileChunk*)))
-
-/*
-** The rollback journal is composed of a linked list of these structures.
-*/
-struct FileChunk {
-  FileChunk *pNext;               /* Next chunk in the journal */
-  u8 zChunk[JOURNAL_CHUNKSIZE];   /* Content of this chunk */
-};
-
-/*
-** An instance of this object serves as a cursor into the rollback journal.
-** The cursor can be either for reading or writing.
-*/
-struct FilePoint {
-  sqlite3_int64 iOffset;          /* Offset from the beginning of the file */
-  FileChunk *pChunk;              /* Specific chunk into which cursor points */
-};
-
-/*
-** This subclass is a subclass of sqlite3_file.  Each open memory-journal
-** is an instance of this class.
-*/
-struct MemJournal {
-  sqlite3_io_methods *pMethod;    /* Parent class. MUST BE FIRST */
-  FileChunk *pFirst;              /* Head of in-memory chunk-list */
-  FilePoint endpoint;             /* Pointer to the end of the file */
-  FilePoint readpoint;            /* Pointer to the end of the last xRead() */
-};
-
-/*
-** Read data from the in-memory journal file.  This is the implementation
-** of the sqlite3_vfs.xRead method.
-*/
-static int memjrnlRead(
-  sqlite3_file *pJfd,    /* The journal file from which to read */
-  void *zBuf,            /* Put the results here */
-  int iAmt,              /* Number of bytes to read */
-  sqlite_int64 iOfst     /* Begin reading at this offset */
-){
-  MemJournal *p = (MemJournal *)pJfd;
-  u8 *zOut = zBuf;
-  int nRead = iAmt;
-  int iChunkOffset;
-  FileChunk *pChunk;
-
-  /* SQLite never tries to read past the end of a rollback journal file */
-  assert( iOfst+iAmt<=p->endpoint.iOffset );
-
-  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
-    sqlite3_int64 iOff = 0;
-    for(pChunk=p->pFirst; 
-        ALWAYS(pChunk) && (iOff+JOURNAL_CHUNKSIZE)<=iOfst;
-        pChunk=pChunk->pNext
-    ){
-      iOff += JOURNAL_CHUNKSIZE;
-    }
-  }else{
-    pChunk = p->readpoint.pChunk;
-  }
-
-  iChunkOffset = (int)(iOfst%JOURNAL_CHUNKSIZE);
-  do {
-    int iSpace = JOURNAL_CHUNKSIZE - iChunkOffset;
-    int nCopy = MIN(nRead, (JOURNAL_CHUNKSIZE - iChunkOffset));
-    memcpy(zOut, &pChunk->zChunk[iChunkOffset], nCopy);
-    zOut += nCopy;
-    nRead -= iSpace;
-    iChunkOffset = 0;
-  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
-  p->readpoint.iOffset = iOfst+iAmt;
-  p->readpoint.pChunk = pChunk;
-
-  return SQLITE_OK;
-}
-
-/*
-** Write data to the file.
-*/
-static int memjrnlWrite(
-  sqlite3_file *pJfd,    /* The journal file into which to write */
-  const void *zBuf,      /* Take data to be written from here */
-  int iAmt,              /* Number of bytes to write */
-  sqlite_int64 iOfst     /* Begin writing at this offset into the file */
-){
-  MemJournal *p = (MemJournal *)pJfd;
-  int nWrite = iAmt;
-  u8 *zWrite = (u8 *)zBuf;
-
-  /* An in-memory journal file should only ever be appended to. Random
-  ** access writes are not required by sqlite.
-  */
-  assert( iOfst==p->endpoint.iOffset );
-  UNUSED_PARAMETER(iOfst);
-
-  while( nWrite>0 ){
-    FileChunk *pChunk = p->endpoint.pChunk;
-    int iChunkOffset = (int)(p->endpoint.iOffset%JOURNAL_CHUNKSIZE);
-    int iSpace = MIN(nWrite, JOURNAL_CHUNKSIZE - iChunkOffset);
-
-    if( iChunkOffset==0 ){
-      /* New chunk is required to extend the file. */
-      FileChunk *pNew = sqlite3_malloc(sizeof(FileChunk));
-      if( !pNew ){
-        return SQLITE_IOERR_NOMEM;
-      }
-      pNew->pNext = 0;
-      if( pChunk ){
-        assert( p->pFirst );
-        pChunk->pNext = pNew;
-      }else{
-        assert( !p->pFirst );
-        p->pFirst = pNew;
-      }
-      p->endpoint.pChunk = pNew;
-    }
-
-    memcpy(&p->endpoint.pChunk->zChunk[iChunkOffset], zWrite, iSpace);
-    zWrite += iSpace;
-    nWrite -= iSpace;
-    p->endpoint.iOffset += iSpace;
-  }
-
-  return SQLITE_OK;
-}
-
-/*
-** Truncate the file.
-*/
-static int memjrnlTruncate(sqlite3_file *pJfd, sqlite_int64 size){
-  MemJournal *p = (MemJournal *)pJfd;
-  FileChunk *pChunk;
-  assert(size==0);
-  UNUSED_PARAMETER(size);
-  pChunk = p->pFirst;
-  while( pChunk ){
-    FileChunk *pTmp = pChunk;
-    pChunk = pChunk->pNext;
-    sqlite3_free(pTmp);
-  }
-  sqlite3MemJournalOpen(pJfd);
-  return SQLITE_OK;
-}
-
-/*
-** Close the file.
-*/
-static int memjrnlClose(sqlite3_file *pJfd){
-  memjrnlTruncate(pJfd, 0);
-  return SQLITE_OK;
-}
-
-
-/*
-** Sync the file.
-**
-** Syncing an in-memory journal is a no-op.  And, in fact, this routine
-** is never called in a working implementation.  This implementation
-** exists purely as a contingency, in case some malfunction in some other
-** part of SQLite causes Sync to be called by mistake.
-*/
-static int memjrnlSync(sqlite3_file *NotUsed, int NotUsed2){
-  UNUSED_PARAMETER2(NotUsed, NotUsed2);
-  return SQLITE_OK;
-}
-
-/*
-** Query the size of the file in bytes.
-*/
-static int memjrnlFileSize(sqlite3_file *pJfd, sqlite_int64 *pSize){
-  MemJournal *p = (MemJournal *)pJfd;
-  *pSize = (sqlite_int64) p->endpoint.iOffset;
-  return SQLITE_OK;
-}
-
-/*
-** Table of methods for MemJournal sqlite3_file object.
-*/
-static const struct sqlite3_io_methods MemJournalMethods = {
-  1,                /* iVersion */
-  memjrnlClose,     /* xClose */
-  memjrnlRead,      /* xRead */
-  memjrnlWrite,     /* xWrite */
-  memjrnlTruncate,  /* xTruncate */
-  memjrnlSync,      /* xSync */
-  memjrnlFileSize,  /* xFileSize */
-  0,                /* xLock */
-  0,                /* xUnlock */
-  0,                /* xCheckReservedLock */
-  0,                /* xFileControl */
-  0,                /* xSectorSize */
-  0,                /* xDeviceCharacteristics */
-  0,                /* xShmMap */
-  0,                /* xShmLock */
-  0,                /* xShmBarrier */
-  0,                /* xShmUnmap */
-  0,                /* xFetch */
-  0                 /* xUnfetch */
-};
-
-/* 
-** Open a journal file.
-*/
-SQLITE_PRIVATE void sqlite3MemJournalOpen(sqlite3_file *pJfd){
-  MemJournal *p = (MemJournal *)pJfd;
-  assert( EIGHT_BYTE_ALIGNMENT(p) );
-  memset(p, 0, sqlite3MemJournalSize());
-  p->pMethod = (sqlite3_io_methods*)&MemJournalMethods;
-}
-
-/*
-** Return true if the file-handle passed as an argument is 
-** an in-memory journal 
-*/
-SQLITE_PRIVATE int sqlite3IsMemJournal(sqlite3_file *pJfd){
-  return pJfd->pMethods==&MemJournalMethods;
-}
-
-/* 
-** Return the number of bytes required to store a MemJournal file descriptor.
-*/
-SQLITE_PRIVATE int sqlite3MemJournalSize(void){
-  return sizeof(MemJournal);
-}
-
-/************** End of memjournal.c ******************************************/
-/************** Begin file main.c ********************************************/
-/* #include "sqliteInt.h" */
-
-/* IMPLEMENTATION-OF: R-63124-39300 The sqlite3_sourceid() function returns a
-** pointer to a string constant whose value is the same as the
-** SQLITE_SOURCE_ID C preprocessor macro. 
-*/
-SQLITE_PRIVATE const char *sqlite3_sourceid(void){ return SQLITE_SOURCE_ID; }
-
-/*
-** If the following global variable points to a string which is the
-** name of a directory, then that directory will be used to store
-** temporary files.
-**
-** See also the "PRAGMA temp_store_directory" SQL command.
-*/
-SQLITE_PRIVATE char *sqlite3_temp_directory = 0;
-
-/*
-** Initialize SQLite.  
-**
-** This routine must be called to initialize the memory allocation,
-** VFS, and mutex subsystems prior to doing any serious work with
-** SQLite.  But as long as you do not compile with SQLITE_OMIT_AUTOINIT
-** this routine will be called automatically by key routines such as
-** sqlite3_open().  
-**
-** This routine is a no-op except on its very first call for the process,
-** or for the first call after a call to sqlite3BtreeShutdown.
-**
-** The first thread to call this routine runs the initialization to
-** completion.  If subsequent threads call this routine before the first
-** thread has finished the initialization process, then the subsequent
-** threads must block until the first thread finishes with the initialization.
-**
-** The first thread might call this routine recursively.  Recursive
-** calls to this routine should not block, of course.  Otherwise the
-** initialization process would never complete.
-**
-** Let X be the first thread to enter this routine.  Let Y be some other
-** thread.  Then while the initial invocation of this routine by X is
-** incomplete, it is required that:
-**
-**    *  Calls to this routine from Y must block until the outer-most
-**       call by X completes.
-**
-**    *  Recursive calls to this routine from thread X return immediately
-**       without blocking.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeInitialize(void){
-  MUTEX_LOGIC( sqlite3_mutex *pMaster; )       /* The main static mutex */
-  int rc;                                      /* Result code */
-#ifdef SQLITE_EXTRA_INIT
-  int bRunExtraInit = 0;                       /* Extra initialization needed */
-#endif
-
-#ifdef SQLITE_OMIT_WSD
-  rc = sqlite3_wsd_init(4096, 24);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-#endif
-
-  /* If the following assert() fails on some obscure processor/compiler
-  ** combination, the work-around is to set the correct pointer
-  ** size at compile-time using -DSQLITE_PTRSIZE=n compile-time option */
-  assert( SQLITE_PTRSIZE==sizeof(char*) );
-
-  /* If SQLite is already completely initialized, then this call
-  ** to sqlite3BtreeInitialize() should be a no-op.  But the initialization
-  ** must be complete.  So isInit must not be set until the very end
-  ** of this routine.
-  */
-  if( sqlite3GlobalConfig.isInit ) return SQLITE_OK;
-
-  /* Make sure the mutex subsystem is initialized.  If unable to 
-  ** initialize the mutex subsystem, return early with the error.
-  ** If the system is so sick that we are unable to allocate a mutex,
-  ** there is not much SQLite is going to be able to do.
-  **
-  ** The mutex subsystem must take care of serializing its own
-  ** initialization.
-  */
-  rc = sqlite3MutexInit();
-  if( rc ) return rc;
-
-  /* Initialize the malloc() system and the recursive pInitMutex mutex.
-  ** This operation is protected by the STATIC_MASTER mutex.  Note that
-  ** MutexAlloc() is called for a static mutex prior to initializing the
-  ** malloc subsystem - this implies that the allocation of a static
-  ** mutex must not require support from the malloc subsystem.
-  */
-  MUTEX_LOGIC( pMaster = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER); )
-  sqlite3_mutex_enter(pMaster);
-  sqlite3GlobalConfig.isMutexInit = 1;
-  if( !sqlite3GlobalConfig.isMallocInit ){
-    rc = sqlite3MallocInit();
-  }
-  if( rc==SQLITE_OK ){
-    sqlite3GlobalConfig.isMallocInit = 1;
-    if( !sqlite3GlobalConfig.pInitMutex ){
-      sqlite3GlobalConfig.pInitMutex =
-           sqlite3MutexAlloc(SQLITE_MUTEX_RECURSIVE);
-      if( sqlite3GlobalConfig.bCoreMutex && !sqlite3GlobalConfig.pInitMutex ){
-        rc = SQLITE_NOMEM;
-      }
-    }
-  }
-  if( rc==SQLITE_OK ){
-    sqlite3GlobalConfig.nRefInitMutex++;
-  }
-  sqlite3_mutex_leave(pMaster);
-
-  /* If rc is not SQLITE_OK at this point, then either the malloc
-  ** subsystem could not be initialized or the system failed to allocate
-  ** the pInitMutex mutex. Return an error in either case.  */
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-
-  /* Do the rest of the initialization under the recursive mutex so
-  ** that we will be able to handle recursive calls into
-  ** sqlite3BtreeInitialize().  The recursive calls normally come through
-  ** sqlite3_os_init() when it invokes sqlite3_vfs_register(), but other
-  ** recursive calls might also be possible.
-  **
-  ** IMPLEMENTATION-OF: R-00140-37445 SQLite automatically serializes calls
-  ** to the xInit method, so the xInit method need not be threadsafe.
-  **
-  ** The following mutex is what serializes access to the appdef pcache xInit
-  ** methods.  The sqlite3_pcache_methods.xInit() all is embedded in the
-  ** call to sqlite3PcacheInitialize().
-  */
-  sqlite3_mutex_enter(sqlite3GlobalConfig.pInitMutex);
-  if( sqlite3GlobalConfig.isInit==0 && sqlite3GlobalConfig.inProgress==0 ){
-    sqlite3GlobalConfig.inProgress = 1;
-    if( sqlite3GlobalConfig.isPCacheInit==0 ){
-      rc = sqlite3PcacheInitialize();
-    }
-    if( rc==SQLITE_OK ){
-      sqlite3GlobalConfig.isPCacheInit = 1;
-      rc = sqlite3OsInit();
-    }
-    if( rc==SQLITE_OK ){
-      sqlite3PCacheBufferSetup( sqlite3GlobalConfig.pPage, 
-          sqlite3GlobalConfig.szPage, sqlite3GlobalConfig.nPage);
-      sqlite3GlobalConfig.isInit = 1;
-#ifdef SQLITE_EXTRA_INIT
-      bRunExtraInit = 1;
-#endif
-    }
-    sqlite3GlobalConfig.inProgress = 0;
-  }
-  sqlite3_mutex_leave(sqlite3GlobalConfig.pInitMutex);
-
-  /* Go back under the static mutex and clean up the recursive
-  ** mutex to prevent a resource leak.
-  */
-  sqlite3_mutex_enter(pMaster);
-  sqlite3GlobalConfig.nRefInitMutex--;
-  if( sqlite3GlobalConfig.nRefInitMutex<=0 ){
-    assert( sqlite3GlobalConfig.nRefInitMutex==0 );
-    sqlite3_mutex_free(sqlite3GlobalConfig.pInitMutex);
-    sqlite3GlobalConfig.pInitMutex = 0;
-  }
-  sqlite3_mutex_leave(pMaster);
-
-  /* The following is just a sanity check to make sure SQLite has
-  ** been compiled correctly.  It is important to run this code, but
-  ** we don't want to run it too often and soak up CPU cycles for no
-  ** reason.  So we run it once during initialization.
-  */
-#ifndef NDEBUG
-#ifndef SQLITE_OMIT_FLOATING_POINT
-  /* This section of code's only "output" is via assert() statements. */
-  if ( rc==SQLITE_OK ){
-    u64 x = (((u64)1)<<63)-1;
-    double y;
-    assert(sizeof(x)==8);
-    assert(sizeof(x)==sizeof(y));
-    memcpy(&y, &x, 8);
-    assert( sqlite3IsNaN(y) );
-  }
-#endif
-#endif
-
-  /* Do extra initialization steps requested by the SQLITE_EXTRA_INIT
-  ** compile-time option.
-  */
-#ifdef SQLITE_EXTRA_INIT
-  if( bRunExtraInit ){
-    int SQLITE_EXTRA_INIT(const char*);
-    rc = SQLITE_EXTRA_INIT(0);
-  }
-#endif
-
-  return rc;
-}
-
-/*
-** Undo the effects of sqlite3BtreeInitialize().  Must not be called while
-** there are outstanding database connections or memory allocations or
-** while any part of SQLite is otherwise in use in any thread.  This
-** routine is not threadsafe.  But it is safe to invoke this routine
-** on when SQLite is already shut down.  If SQLite is already shut down
-** when this routine is invoked, then this routine is a harmless no-op.
-*/
-SQLITE_API int SQLITE_STDCALL sqlite3BtreeShutdown(void){
-#ifdef SQLITE_OMIT_WSD
-  int rc = sqlite3_wsd_init(4096, 24);
-  if( rc!=SQLITE_OK ){
-    return rc;
-  }
-#endif
-
-  if( sqlite3GlobalConfig.isInit ){
-#ifdef SQLITE_EXTRA_SHUTDOWN
-    void SQLITE_EXTRA_SHUTDOWN(void);
-    SQLITE_EXTRA_SHUTDOWN();
-#endif
-    sqlite3_os_end();
-    sqlite3GlobalConfig.isInit = 0;
-  }
-  if( sqlite3GlobalConfig.isPCacheInit ){
-    sqlite3PcacheShutdown();
-    sqlite3GlobalConfig.isPCacheInit = 0;
-  }
-  if( sqlite3GlobalConfig.isMallocInit ){
-    sqlite3MallocEnd();
-    sqlite3GlobalConfig.isMallocInit = 0;
-  }
-  if( sqlite3GlobalConfig.isMutexInit ){
-    sqlite3MutexEnd();
-    sqlite3GlobalConfig.isMutexInit = 0;
-  }
-
-  return SQLITE_OK;
-}
-
-/*
-** The following routines are substitutes for constants SQLITE_CORRUPT,
-** SQLITE_MISUSE, SQLITE_CANTOPEN, SQLITE_IOERR and possibly other error
-** constants.  They serve two purposes:
-**
-**   1.  Serve as a convenient place to set a breakpoint in a debugger
-**       to detect when version error conditions occurs.
-**
-**   2.  Invoke sqlite3_log() to provide the source code location where
-**       a low-level error is first detected.
-*/
-SQLITE_PRIVATE int sqlite3CorruptError(int lineno){
-  testcase( sqlite3GlobalConfig.xLog!=0 );
-  sqlite3_log(SQLITE_CORRUPT,
-              "database corruption at line %d of [%.10s]",
-              lineno, 20+sqlite3_sourceid());
-  return SQLITE_CORRUPT;
-}
-SQLITE_PRIVATE int sqlite3MisuseError(int lineno){
-  testcase( sqlite3GlobalConfig.xLog!=0 );
-  sqlite3_log(SQLITE_MISUSE, 
-              "misuse at line %d of [%.10s]",
-              lineno, 20+sqlite3_sourceid());
-  return SQLITE_MISUSE;
-}
-SQLITE_PRIVATE int sqlite3CantopenError(int lineno){
-  testcase( sqlite3GlobalConfig.xLog!=0 );
-  sqlite3_log(SQLITE_CANTOPEN, 
-              "cannot open file at line %d of [%.10s]",
-              lineno, 20+sqlite3_sourceid());
-  return SQLITE_CANTOPEN;
-}
-
-/*
-** Invoke the given busy handler.
-**
-** This routine is called when an operation failed with a lock.
-** If this routine returns non-zero, the lock is retried.  If it
-** returns 0, the operation aborts with an SQLITE_BUSY error.
-*/
-SQLITE_PRIVATE int sqlite3InvokeBusyHandler(BusyHandler *p){
-  int rc;
-  if( NEVER(p==0) || p->xFunc==0 || p->nBusy<0 ) return 0;
-  rc = p->xFunc(p->pArg, p->nBusy);
-  if( rc==0 ){
-    p->nBusy = -1;
-  }else{
-    p->nBusy++;
-  }
-  return rc; 
-}
-
-/*
-** This API allows applications to modify the global configuration of
-** the SQLite library at run-time.
-**
-** This routine should only be called when there are no outstanding
-** database connections or memory allocations.  This routine is not
-** threadsafe.  Failure to heed these warnings can lead to unpredictable
-** behavior.
-*/
-SQLITE_PRIVATE int sqlite3_config(int op, ...){
-  va_list ap;
-  int rc = SQLITE_OK;
-
-  /* sqlite3_config() shall return SQLITE_MISUSE if it is invoked while
-  ** the SQLite library is in use. */
-  if( sqlite3GlobalConfig.isInit ) return SQLITE_MISUSE_BKPT;
-
-  va_start(ap, op);
-  switch( op ){
-
-    /* Mutex configuration options are only available in a threadsafe
-    ** compile.
-    */
-#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0  /* IMP: R-54466-46756 */
-    case SQLITE_CONFIG_SINGLETHREAD: {
-      /* EVIDENCE-OF: R-02748-19096 This option sets the threading mode to
-      ** Single-thread. */
-      sqlite3GlobalConfig.bCoreMutex = 0;  /* Disable mutex on core */
-      sqlite3GlobalConfig.bFullMutex = 0;  /* Disable mutex on connections */
-      break;
-    }
-#endif
-#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-20520-54086 */
-    case SQLITE_CONFIG_MULTITHREAD: {
-      /* EVIDENCE-OF: R-14374-42468 This option sets the threading mode to
-      ** Multi-thread. */
-      sqlite3GlobalConfig.bCoreMutex = 1;  /* Enable mutex on core */
-      sqlite3GlobalConfig.bFullMutex = 0;  /* Disable mutex on connections */
-      break;
-    }
-#endif
-#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-59593-21810 */
-    case SQLITE_CONFIG_SERIALIZED: {
-      /* EVIDENCE-OF: R-41220-51800 This option sets the threading mode to
-      ** Serialized. */
-      sqlite3GlobalConfig.bCoreMutex = 1;  /* Enable mutex on core */
-      sqlite3GlobalConfig.bFullMutex = 1;  /* Enable mutex on connections */
-      break;
-    }
-#endif
-#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-63666-48755 */
-    case SQLITE_CONFIG_MUTEX: {
-      /* Specify an alternative mutex implementation */
-      sqlite3GlobalConfig.mutex = *va_arg(ap, sqlite3_mutex_methods*);
-      break;
-    }
-#endif
-#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE>0 /* IMP: R-14450-37597 */
-    case SQLITE_CONFIG_GETMUTEX: {
-      /* Retrieve the current mutex implementation */
-      *va_arg(ap, sqlite3_mutex_methods*) = sqlite3GlobalConfig.mutex;
-      break;
-    }
-#endif
-
-    case SQLITE_CONFIG_MALLOC: {
-      /* EVIDENCE-OF: R-55594-21030 The SQLITE_CONFIG_MALLOC option takes a
-      ** single argument which is a pointer to an instance of the
-      ** sqlite3_mem_methods structure. The argument specifies alternative
-      ** low-level memory allocation routines to be used in place of the memory
-      ** allocation routines built into SQLite. */
-      sqlite3GlobalConfig.m = *va_arg(ap, sqlite3_mem_methods*);
-      break;
-    }
-    case SQLITE_CONFIG_GETMALLOC: {
-      /* EVIDENCE-OF: R-51213-46414 The SQLITE_CONFIG_GETMALLOC option takes a
-      ** single argument which is a pointer to an instance of the
-      ** sqlite3_mem_methods structure. The sqlite3_mem_methods structure is
-      ** filled with the currently defined memory allocation routines. */
-      if( sqlite3GlobalConfig.m.xMalloc==0 ) sqlite3MemSetDefault();
-      *va_arg(ap, sqlite3_mem_methods*) = sqlite3GlobalConfig.m;
-      break;
-    }
-    case SQLITE_CONFIG_MEMSTATUS: {
-      /* EVIDENCE-OF: R-61275-35157 The SQLITE_CONFIG_MEMSTATUS option takes
-      ** single argument of type int, interpreted as a boolean, which enables
-      ** or disables the collection of memory allocation statistics. */
-      sqlite3GlobalConfig.bMemstat = va_arg(ap, int);
-      break;
-    }
-    case SQLITE_CONFIG_SCRATCH: {
-      /* EVIDENCE-OF: R-08404-60887 There are three arguments to
-      ** SQLITE_CONFIG_SCRATCH: A pointer an 8-byte aligned memory buffer from
-      ** which the scratch allocations will be drawn, the size of each scratch
-      ** allocation (sz), and the maximum number of scratch allocations (N). */
-      sqlite3GlobalConfig.pScratch = va_arg(ap, void*);
-      sqlite3GlobalConfig.szScratch = va_arg(ap, int);
-      sqlite3GlobalConfig.nScratch = va_arg(ap, int);
-      break;
-    }
-    case SQLITE_CONFIG_PAGECACHE: {
-      /* EVIDENCE-OF: R-31408-40510 There are three arguments to
-      ** SQLITE_CONFIG_PAGECACHE: A pointer to 8-byte aligned memory, the size
-      ** of each page buffer (sz), and the number of pages (N). */
-      sqlite3GlobalConfig.pPage = va_arg(ap, void*);
-      sqlite3GlobalConfig.szPage = va_arg(ap, int);
-      sqlite3GlobalConfig.nPage = va_arg(ap, int);
-      break;
-    }
-    case SQLITE_CONFIG_PCACHE_HDRSZ: {
-      /* EVIDENCE-OF: R-39100-27317 The SQLITE_CONFIG_PCACHE_HDRSZ option takes
-      ** a single parameter which is a pointer to an integer and writes into
-      ** that integer the number of extra bytes per page required for each page
-      ** in SQLITE_CONFIG_PAGECACHE. */
-      *va_arg(ap, int*) = 
-          sqlite3HeaderSizeBtree() +
-          sqlite3HeaderSizePcache() +
-          sqlite3HeaderSizePcache1();
-      break;
-    }
-
-    case SQLITE_CONFIG_PCACHE: {
-      /* no-op */
-      break;
-    }
-    case SQLITE_CONFIG_GETPCACHE: {
-      /* now an error */
-      rc = SQLITE_ERROR;
-      break;
-    }
-
-    case SQLITE_CONFIG_PCACHE2: {
-      /* EVIDENCE-OF: R-63325-48378 The SQLITE_CONFIG_PCACHE2 option takes a
-      ** single argument which is a pointer to an sqlite3_pcache_methods2
-      ** object. This object specifies the interface to a custom page cache
-      ** implementation. */
-      sqlite3GlobalConfig.pcache2 = *va_arg(ap, sqlite3_pcache_methods2*);
-      break;
-    }
-    case SQLITE_CONFIG_GETPCACHE2: {
-      /* EVIDENCE-OF: R-22035-46182 The SQLITE_CONFIG_GETPCACHE2 option takes a
-      ** single argument which is a pointer to an sqlite3_pcache_methods2
-      ** object. SQLite copies of the current page cache implementation into
-      ** that object. */
-      if( sqlite3GlobalConfig.pcache2.xInit==0 ){
-        sqlite3PCacheSetDefault();
-      }
-      *va_arg(ap, sqlite3_pcache_methods2*) = sqlite3GlobalConfig.pcache2;
-      break;
-    }
-
-/* EVIDENCE-OF: R-06626-12911 The SQLITE_CONFIG_HEAP option is only
-** available if SQLite is compiled with either SQLITE_ENABLE_MEMSYS3 or
-** SQLITE_ENABLE_MEMSYS5 and returns SQLITE_ERROR if invoked otherwise. */
-#if defined(SQLITE_ENABLE_MEMSYS3) || defined(SQLITE_ENABLE_MEMSYS5)
-    case SQLITE_CONFIG_HEAP: {
-      /* EVIDENCE-OF: R-19854-42126 There are three arguments to
-      ** SQLITE_CONFIG_HEAP: An 8-byte aligned pointer to the memory, the
-      ** number of bytes in the memory buffer, and the minimum allocation size.
-      */
-      sqlite3GlobalConfig.pHeap = va_arg(ap, void*);
-      sqlite3GlobalConfig.nHeap = va_arg(ap, int);
-      sqlite3GlobalConfig.mnReq = va_arg(ap, int);
-
-      if( sqlite3GlobalConfig.mnReq<1 ){
-        sqlite3GlobalConfig.mnReq = 1;
-      }else if( sqlite3GlobalConfig.mnReq>(1<<12) ){
-        /* cap min request size at 2^12 */
-        sqlite3GlobalConfig.mnReq = (1<<12);
-      }
-
-      if( sqlite3GlobalConfig.pHeap==0 ){
-        /* EVIDENCE-OF: R-49920-60189 If the first pointer (the memory pointer)
-        ** is NULL, then SQLite reverts to using its default memory allocator
-        ** (the system malloc() implementation), undoing any prior invocation of
-        ** SQLITE_CONFIG_MALLOC.
-        **
-        ** Setting sqlite3GlobalConfig.m to all zeros will cause malloc to
-        ** revert to its default implementation when sqlite3BtreeInitialize() is run
-        */
-        memset(&sqlite3GlobalConfig.m, 0, sizeof(sqlite3GlobalConfig.m));
-      }else{
-        /* EVIDENCE-OF: R-61006-08918 If the memory pointer is not NULL then the
-        ** alternative memory allocator is engaged to handle all of SQLites
-        ** memory allocation needs. */
-#ifdef SQLITE_ENABLE_MEMSYS3
-        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys3();
-#endif
-#ifdef SQLITE_ENABLE_MEMSYS5
-        sqlite3GlobalConfig.m = *sqlite3MemGetMemsys5();
-#endif
-      }
-      break;
-    }
-#endif
-
-    case SQLITE_CONFIG_LOOKASIDE: {
-      sqlite3GlobalConfig.szLookaside = va_arg(ap, int);
-      sqlite3GlobalConfig.nLookaside = va_arg(ap, int);
-      break;
-    }
-    
-    /* Record a pointer to the logger function and its first argument.
-    ** The default is NULL.  Logging is disabled if the function pointer is
-    ** NULL.
-    */
-    case SQLITE_CONFIG_LOG: {
-      /* MSVC is picky about pulling func ptrs from va lists.
-      ** http://support.microsoft.com/kb/47961
-      ** sqlite3GlobalConfig.xLog = va_arg(ap, void(*)(void*,int,const char*));
-      */
-      typedef void(*LOGFUNC_t)(void*,int,const char*);
-      sqlite3GlobalConfig.xLog = va_arg(ap, LOGFUNC_t);
-      sqlite3GlobalConfig.pLogArg = va_arg(ap, void*);
-      break;
-    }
-
-    /* EVIDENCE-OF: R-55548-33817 The compile-time setting for URI filenames
-    ** can be changed at start-time using the
-    ** sqlite3_config(SQLITE_CONFIG_URI,1) or
-    ** sqlite3_config(SQLITE_CONFIG_URI,0) configuration calls.
-    */
-    case SQLITE_CONFIG_URI: {
-      /* EVIDENCE-OF: R-25451-61125 The SQLITE_CONFIG_URI option takes a single
-      ** argument of type int. If non-zero, then URI handling is globally
-      ** enabled. If the parameter is zero, then URI handling is globally
-      ** disabled. */
-      sqlite3GlobalConfig.bOpenUri = va_arg(ap, int);
-      break;
-    }
-
-    case SQLITE_CONFIG_COVERING_INDEX_SCAN: {
-      /* EVIDENCE-OF: R-36592-02772 The SQLITE_CONFIG_COVERING_INDEX_SCAN
-      ** option takes a single integer argument which is interpreted as a
-      ** boolean in order to enable or disable the use of covering indices for
-      ** full table scans in the query optimizer. */
-      sqlite3GlobalConfig.bUseCis = va_arg(ap, int);
-      break;
-    }
-
-    case SQLITE_CONFIG_MMAP_SIZE: {
-      /* EVIDENCE-OF: R-58063-38258 SQLITE_CONFIG_MMAP_SIZE takes two 64-bit
-      ** integer (sqlite3_int64) values that are the default mmap size limit
-      ** (the default setting for PRAGMA mmap_size) and the maximum allowed
-      ** mmap size limit. */
-      sqlite3_int64 szMmap = va_arg(ap, sqlite3_int64);
-      sqlite3_int64 mxMmap = va_arg(ap, sqlite3_int64);
-      /* EVIDENCE-OF: R-53367-43190 If either argument to this option is
-      ** negative, then that argument is changed to its compile-time default.
-      **
-      ** EVIDENCE-OF: R-34993-45031 The maximum allowed mmap size will be
-      ** silently truncated if necessary so that it does not exceed the
-      ** compile-time maximum mmap size set by the SQLITE_MAX_MMAP_SIZE
-      ** compile-time option.
-      */
-      if( mxMmap<0 || mxMmap>SQLITE_MAX_MMAP_SIZE ){
-        mxMmap = SQLITE_MAX_MMAP_SIZE;
-      }
-      if( szMmap<0 ) szMmap = SQLITE_DEFAULT_MMAP_SIZE;
-      if( szMmap>mxMmap) szMmap = mxMmap;
-      sqlite3GlobalConfig.mxMmap = mxMmap;
-      sqlite3GlobalConfig.szMmap = szMmap;
-      break;
-    }
-
-#if SQLITE_OS_WIN && defined(SQLITE_WIN32_MALLOC) /* IMP: R-04780-55815 */
-    case SQLITE_CONFIG_WIN32_HEAPSIZE: {
-      /* EVIDENCE-OF: R-34926-03360 SQLITE_CONFIG_WIN32_HEAPSIZE takes a 32-bit
-      ** unsigned integer value that specifies the maximum size of the created
-      ** heap. */
-      sqlite3GlobalConfig.nHeap = va_arg(ap, int);
-      break;
-    }
-#endif
-
-    case SQLITE_CONFIG_PMASZ: {
-      sqlite3GlobalConfig.szPma = va_arg(ap, unsigned int);
-      break;
-    }
-
-    default: {
-      rc = SQLITE_ERROR;
-      break;
-    }
-  }
-  va_end(ap);
-  return rc;
-}
-
-/************** End of main.c ************************************************/
diff --git a/src/runtime/c/sg/sqlite3Btree.h b/src/runtime/c/sg/sqlite3Btree.h
deleted file mode 100644
index b66b53c7e..000000000
--- a/src/runtime/c/sg/sqlite3Btree.h
+++ /dev/null
@@ -1,705 +0,0 @@
-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code.  In place of
-** a legal notice, here is a blessing:
-**
-**    May you do good and not evil.
-**    May you find forgiveness for yourself and forgive others.
-**    May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This header file defines the interface that the sqlite B-Tree file
-** subsystem.  See comments in the source code for a detailed description
-** of what each interface routine does.
-*/
-#ifndef _BTREE_H_
-#define _BTREE_H_
-
-/*
-** The SQLITE_THREADSAFE macro must be defined as 0, 1, or 2.
-** 0 means mutexes are permanently disable and the library is never
-** threadsafe.  1 means the library is serialized which is the highest
-** level of threadsafety.  2 means the library is multithreaded - multiple
-** threads can use SQLite as long as no two threads try to use the same
-** database connection at the same time.
-**
-** Older versions of SQLite used an optional THREADSAFE macro.
-** We support that for legacy.
-*/
-#if !defined(SQLITE_THREADSAFE)
-# if defined(THREADSAFE)
-#   define SQLITE_THREADSAFE THREADSAFE
-# else
-#   define SQLITE_THREADSAFE 1 /* IMP: R-07272-22309 */
-# endif
-#endif
-
-/*
-** CAPI3REF: 64-Bit Integer Types
-** KEYWORDS: sqlite_int64 sqlite_uint64
-**
-** Because there is no cross-platform way to specify 64-bit integer types
-** SQLite includes typedefs for 64-bit signed and unsigned integers.
-**
-** The sqlite3_int64 and sqlite3_uint64 are the preferred type definitions.
-** The sqlite_int64 and sqlite_uint64 types are supported for backwards
-** compatibility only.
-**
-** ^The sqlite3_int64 and sqlite_int64 types can store integer values
-** between -9223372036854775808 and +9223372036854775807 inclusive.  ^The
-** sqlite3_uint64 and sqlite_uint64 types can store integer values 
-** between 0 and +18446744073709551615 inclusive.
-*/
-#ifdef SQLITE_INT64_TYPE
-  typedef SQLITE_INT64_TYPE sqlite_int64;
-  typedef unsigned SQLITE_INT64_TYPE sqlite_uint64;
-#elif defined(_MSC_VER) || defined(__BORLANDC__)
-  typedef __int64 sqlite_int64;
-  typedef unsigned __int64 sqlite_uint64;
-#else
-  typedef long long int sqlite_int64;
-  typedef unsigned long long int sqlite_uint64;
-#endif
-typedef sqlite_int64 sqlite3_int64;
-typedef sqlite_uint64 sqlite3_uint64;
-
-/*
-** Integers of known sizes.  These typedefs might change for architectures
-** where the sizes very.  Preprocessor macros are available so that the
-** types can be conveniently redefined at compile-type.  Like this:
-**
-**         cc '-DUINTPTR_TYPE=long long int' ...
-*/
-#ifndef UINT32_TYPE
-# ifdef HAVE_UINT32_T
-#  define UINT32_TYPE uint32_t
-# else
-#  define UINT32_TYPE unsigned int
-# endif
-#endif
-#ifndef UINT16_TYPE
-# ifdef HAVE_UINT16_T
-#  define UINT16_TYPE uint16_t
-# else
-#  define UINT16_TYPE unsigned short int
-# endif
-#endif
-#ifndef INT16_TYPE
-# ifdef HAVE_INT16_T
-#  define INT16_TYPE int16_t
-# else
-#  define INT16_TYPE short int
-# endif
-#endif
-#ifndef UINT8_TYPE
-# ifdef HAVE_UINT8_T
-#  define UINT8_TYPE uint8_t
-# else
-#  define UINT8_TYPE unsigned char
-# endif
-#endif
-#ifndef INT8_TYPE
-# ifdef HAVE_INT8_T
-#  define INT8_TYPE int8_t
-# else
-#  define INT8_TYPE signed char
-# endif
-#endif
-#ifndef LONGDOUBLE_TYPE
-# define LONGDOUBLE_TYPE long double
-#endif
-typedef sqlite_int64 i64;          /* 8-byte signed integer */
-typedef sqlite_uint64 u64;         /* 8-byte unsigned integer */
-typedef UINT32_TYPE u32;           /* 4-byte unsigned integer */
-typedef UINT16_TYPE u16;           /* 2-byte unsigned integer */
-typedef INT16_TYPE i16;            /* 2-byte signed integer */
-typedef UINT8_TYPE u8;             /* 1-byte unsigned integer */
-typedef INT8_TYPE i8;              /* 1-byte signed integer */
-
-/* TODO: This definition is just included so other modules compile. It
-** needs to be revisited.
-*/
-#define SQLITE_N_BTREE_META 16
-
-/*
-** If defined as non-zero, auto-vacuum is enabled by default. Otherwise
-** it must be turned on for each database using "PRAGMA auto_vacuum = 1".
-*/
-#ifndef SQLITE_DEFAULT_AUTOVACUUM
-  #define SQLITE_DEFAULT_AUTOVACUUM 0
-#endif
-
-#define BTREE_AUTOVACUUM_NONE 0        /* Do not do auto-vacuum */
-#define BTREE_AUTOVACUUM_FULL 1        /* Do full auto-vacuum */
-#define BTREE_AUTOVACUUM_INCR 2        /* Incremental vacuum */
-
-/*
-** CAPI3REF: Initialize The SQLite Library
-**
-** ^The sqlite3BtreeInitialize() routine initializes the
-** SQLite library.  ^The sqlite3BtreeShutdown() routine
-** deallocates any resources that were allocated by sqlite3BtreeInitialize().
-** These routines are designed to aid in process initialization and
-** shutdown on embedded systems.  Workstation applications using
-** SQLite normally do not need to invoke either of these routines.
-**
-** A call to sqlite3BtreeInitialize() is an "effective" call if it is
-** the first time sqlite3BtreeInitialize() is invoked during the lifetime of
-** the process, or if it is the first time sqlite3BtreeInitialize() is invoked
-** following a call to sqlite3BtreeShutdown().  ^(Only an effective call
-** of sqlite3BtreeInitialize() does any initialization.  All other calls
-** are harmless no-ops.)^
-**
-** A call to sqlite3BtreeShutdown() is an "effective" call if it is the first
-** call to sqlite3BtreeShutdown() since the last sqlite3BtreeInitialize().  ^(Only
-** an effective call to sqlite3BtreeShutdown() does any deinitialization.
-** All other valid calls to sqlite3BtreeShutdown() are harmless no-ops.)^
-**
-** The sqlite3BtreeInitialize() interface is threadsafe, but sqlite3BtreeShutdown()
-** is not.  The sqlite3BtreeShutdown() interface must only be called from a
-** single thread.  All open [database connections] must be closed and all
-** other SQLite resources must be deallocated prior to invoking
-** sqlite3BtreeShutdown().
-**
-** Among other things, ^sqlite3BtreeInitialize() will invoke
-** sqlite3_os_init().  Similarly, ^sqlite3BtreeShutdown()
-** will invoke sqlite3_os_end().
-**
-** ^The sqlite3BtreeInitialize() routine returns [SQLITE_OK] on success.
-** ^If for some reason, sqlite3BtreeInitialize() is unable to initialize
-** the library (perhaps it is unable to allocate a needed resource such
-** as a mutex) it returns an [error code] other than [SQLITE_OK].
-**
-** ^The sqlite3BtreeInitialize() routine is called internally by many other
-** SQLite interfaces so that an application usually does not need to
-** invoke sqlite3BtreeInitialize() directly.  For example, [sqlite3_open()]
-** calls sqlite3BtreeInitialize() so the SQLite library will be automatically
-** initialized when [sqlite3_open()] is called if it has not be initialized
-** already.  ^However, if SQLite is compiled with the [SQLITE_OMIT_AUTOINIT]
-** compile-time option, then the automatic calls to sqlite3BtreeInitialize()
-** are omitted and the application must call sqlite3BtreeInitialize() directly
-** prior to using any other SQLite interface.  For maximum portability,
-** it is recommended that applications always invoke sqlite3BtreeInitialize()
-** directly prior to using any other SQLite interface.  Future releases
-** of SQLite may require this.  In other words, the behavior exhibited
-** when SQLite is compiled with [SQLITE_OMIT_AUTOINIT] might become the
-** default behavior in some future release of SQLite.
-**
-** The sqlite3_os_init() routine does operating-system specific
-** initialization of the SQLite library.  The sqlite3_os_end()
-** routine undoes the effect of sqlite3_os_init().  Typical tasks
-** performed by these routines include allocation or deallocation
-** of static resources, initialization of global variables,
-** setting up a default [sqlite3_vfs] module, or setting up
-** a default configuration using [sqlite3_config()].
-**
-** The application should never invoke either sqlite3_os_init()
-** or sqlite3_os_end() directly.  The application should only invoke
-** sqlite3BtreeInitialize() and sqlite3BtreeShutdown().  The sqlite3_os_init()
-** interface is called automatically by sqlite3BtreeInitialize() and
-** sqlite3_os_end() is called by sqlite3BtreeShutdown().  Appropriate
-** implementations for sqlite3_os_init() and sqlite3_os_end()
-** are built into SQLite when it is compiled for Unix, Windows, or OS/2.
-** When [custom builds | built for other platforms]
-** (using the [SQLITE_OS_OTHER=1] compile-time
-** option) the application must supply a suitable implementation for
-** sqlite3_os_init() and sqlite3_os_end().  An application-supplied
-** implementation of sqlite3_os_init() or sqlite3_os_end()
-** must return [SQLITE_OK] on success and some other [error code] upon
-** failure.
-*/
-int sqlite3BtreeInitialize(void);
-int sqlite3BtreeShutdown(void);
-
-/*
-** CAPI3REF: Result Codes
-** KEYWORDS: {result code definitions}
-**
-** Many SQLite functions return an integer result code from the set shown
-** here in order to indicate success or failure.
-**
-** New error codes may be added in future versions of SQLite.
-**
-** See also: [extended result code definitions]
-*/
-#define SQLITE_OK           0   /* Successful result */
-/* beginning-of-error-codes */
-#define SQLITE_ERROR        1   /* SQL error or missing database */
-#define SQLITE_INTERNAL     2   /* Internal logic error in SQLite */
-#define SQLITE_PERM         3   /* Access permission denied */
-#define SQLITE_ABORT        4   /* Callback routine requested an abort */
-#define SQLITE_BUSY         5   /* The database file is locked */
-#define SQLITE_LOCKED       6   /* A table in the database is locked */
-#define SQLITE_NOMEM        7   /* A malloc() failed */
-#define SQLITE_READONLY     8   /* Attempt to write a readonly database */
-#define SQLITE_INTERRUPT    9   /* Operation terminated by sqlite3_interrupt()*/
-#define SQLITE_IOERR       10   /* Some kind of disk I/O error occurred */
-#define SQLITE_CORRUPT     11   /* The database disk image is malformed */
-#define SQLITE_NOTFOUND    12   /* Unknown opcode in sqlite3_file_control() */
-#define SQLITE_FULL        13   /* Insertion failed because database is full */
-#define SQLITE_CANTOPEN    14   /* Unable to open the database file */
-#define SQLITE_PROTOCOL    15   /* Database lock protocol error */
-#define SQLITE_EMPTY       16   /* Database is empty */
-#define SQLITE_SCHEMA      17   /* The database schema changed */
-#define SQLITE_TOOBIG      18   /* String or BLOB exceeds size limit */
-#define SQLITE_CONSTRAINT  19   /* Abort due to constraint violation */
-#define SQLITE_MISMATCH    20   /* Data type mismatch */
-#define SQLITE_MISUSE      21   /* Library used incorrectly */
-#define SQLITE_NOLFS       22   /* Uses OS features not supported on host */
-#define SQLITE_AUTH        23   /* Authorization denied */
-#define SQLITE_FORMAT      24   /* Auxiliary database format error */
-#define SQLITE_RANGE       25   /* 2nd parameter to sqlite3_bind out of range */
-#define SQLITE_NOTADB      26   /* File opened that is not a database file */
-#define SQLITE_NOTICE      27   /* Notifications from sqlite3_log() */
-#define SQLITE_WARNING     28   /* Warnings from sqlite3_log() */
-#define SQLITE_ROW         100  /* sqlite3_step() has another row ready */
-#define SQLITE_DONE        101  /* sqlite3_step() has finished executing */
-/* end-of-error-codes */
-
-/*
-** CAPI3REF: Extended Result Codes
-** KEYWORDS: {extended result code definitions}
-**
-** In its default configuration, SQLite API routines return one of 30 integer
-** [result codes].  However, experience has shown that many of
-** these result codes are too coarse-grained.  They do not provide as
-** much information about problems as programmers might like.  In an effort to
-** address this, newer versions of SQLite (version 3.3.8 and later) include
-** support for additional result codes that provide more detailed information
-** about errors. These [extended result codes] are enabled or disabled
-** on a per database connection basis using the
-** [sqlite3_extended_result_codes()] API.  Or, the extended code for
-** the most recent error can be obtained using
-** [sqlite3_extended_errcode()].
-*/
-#define SQLITE_IOERR_READ              (SQLITE_IOERR | (1<<8))
-#define SQLITE_IOERR_SHORT_READ        (SQLITE_IOERR | (2<<8))
-#define SQLITE_IOERR_WRITE             (SQLITE_IOERR | (3<<8))
-#define SQLITE_IOERR_FSYNC             (SQLITE_IOERR | (4<<8))
-#define SQLITE_IOERR_DIR_FSYNC         (SQLITE_IOERR | (5<<8))
-#define SQLITE_IOERR_TRUNCATE          (SQLITE_IOERR | (6<<8))
-#define SQLITE_IOERR_FSTAT             (SQLITE_IOERR | (7<<8))
-#define SQLITE_IOERR_UNLOCK            (SQLITE_IOERR | (8<<8))
-#define SQLITE_IOERR_RDLOCK            (SQLITE_IOERR | (9<<8))
-#define SQLITE_IOERR_DELETE            (SQLITE_IOERR | (10<<8))
-#define SQLITE_IOERR_BLOCKED           (SQLITE_IOERR | (11<<8))
-#define SQLITE_IOERR_NOMEM             (SQLITE_IOERR | (12<<8))
-#define SQLITE_IOERR_ACCESS            (SQLITE_IOERR | (13<<8))
-#define SQLITE_IOERR_CHECKRESERVEDLOCK (SQLITE_IOERR | (14<<8))
-#define SQLITE_IOERR_LOCK              (SQLITE_IOERR | (15<<8))
-#define SQLITE_IOERR_CLOSE             (SQLITE_IOERR | (16<<8))
-#define SQLITE_IOERR_DIR_CLOSE         (SQLITE_IOERR | (17<<8))
-#define SQLITE_IOERR_SHMOPEN           (SQLITE_IOERR | (18<<8))
-#define SQLITE_IOERR_SHMSIZE           (SQLITE_IOERR | (19<<8))
-#define SQLITE_IOERR_SHMLOCK           (SQLITE_IOERR | (20<<8))
-#define SQLITE_IOERR_SHMMAP            (SQLITE_IOERR | (21<<8))
-#define SQLITE_IOERR_SEEK              (SQLITE_IOERR | (22<<8))
-#define SQLITE_IOERR_DELETE_NOENT      (SQLITE_IOERR | (23<<8))
-#define SQLITE_IOERR_MMAP              (SQLITE_IOERR | (24<<8))
-#define SQLITE_IOERR_GETTEMPPATH       (SQLITE_IOERR | (25<<8))
-#define SQLITE_IOERR_CONVPATH          (SQLITE_IOERR | (26<<8))
-#define SQLITE_IOERR_VNODE             (SQLITE_IOERR | (27<<8))
-#define SQLITE_LOCKED_SHAREDCACHE      (SQLITE_LOCKED |  (1<<8))
-#define SQLITE_BUSY_RECOVERY           (SQLITE_BUSY   |  (1<<8))
-#define SQLITE_BUSY_SNAPSHOT           (SQLITE_BUSY   |  (2<<8))
-#define SQLITE_CANTOPEN_NOTEMPDIR      (SQLITE_CANTOPEN | (1<<8))
-#define SQLITE_CANTOPEN_ISDIR          (SQLITE_CANTOPEN | (2<<8))
-#define SQLITE_CANTOPEN_FULLPATH       (SQLITE_CANTOPEN | (3<<8))
-#define SQLITE_CANTOPEN_CONVPATH       (SQLITE_CANTOPEN | (4<<8))
-#define SQLITE_CORRUPT_VTAB            (SQLITE_CORRUPT | (1<<8))
-#define SQLITE_READONLY_RECOVERY       (SQLITE_READONLY | (1<<8))
-#define SQLITE_READONLY_CANTLOCK       (SQLITE_READONLY | (2<<8))
-#define SQLITE_READONLY_ROLLBACK       (SQLITE_READONLY | (3<<8))
-#define SQLITE_READONLY_DBMOVED        (SQLITE_READONLY | (4<<8))
-#define SQLITE_ABORT_ROLLBACK          (SQLITE_ABORT | (2<<8))
-#define SQLITE_CONSTRAINT_CHECK        (SQLITE_CONSTRAINT | (1<<8))
-#define SQLITE_CONSTRAINT_COMMITHOOK   (SQLITE_CONSTRAINT | (2<<8))
-#define SQLITE_CONSTRAINT_FOREIGNKEY   (SQLITE_CONSTRAINT | (3<<8))
-#define SQLITE_CONSTRAINT_FUNCTION     (SQLITE_CONSTRAINT | (4<<8))
-#define SQLITE_CONSTRAINT_NOTNULL      (SQLITE_CONSTRAINT | (5<<8))
-#define SQLITE_CONSTRAINT_PRIMARYKEY   (SQLITE_CONSTRAINT | (6<<8))
-#define SQLITE_CONSTRAINT_TRIGGER      (SQLITE_CONSTRAINT | (7<<8))
-#define SQLITE_CONSTRAINT_UNIQUE       (SQLITE_CONSTRAINT | (8<<8))
-#define SQLITE_CONSTRAINT_VTAB         (SQLITE_CONSTRAINT | (9<<8))
-#define SQLITE_CONSTRAINT_ROWID        (SQLITE_CONSTRAINT |(10<<8))
-#define SQLITE_NOTICE_RECOVER_WAL      (SQLITE_NOTICE | (1<<8))
-#define SQLITE_NOTICE_RECOVER_ROLLBACK (SQLITE_NOTICE | (2<<8))
-#define SQLITE_WARNING_AUTOINDEX       (SQLITE_WARNING | (1<<8))
-#define SQLITE_AUTH_USER               (SQLITE_AUTH | (1<<8))
-
-/* Reserved:                         0x00F00000 */
-
-/*
-** Forward declarations of structure
-*/
-typedef struct Btree Btree;
-typedef struct BtCursor BtCursor;
-typedef struct BtShared BtShared;
-typedef struct Mem Mem;
-typedef struct KeyInfo KeyInfo;
-typedef struct UnpackedRecord UnpackedRecord;
-
-
-int sqlite3BtreeOpen(
-  const char *zVfs,        /* VFS to use with this b-tree */
-  const char *zFilename,   /* Name of database file to open */
-  Btree **ppBtree,         /* Return open Btree* here */
-  int flags,               /* Flags */
-  int vfsFlags             /* Flags passed through to VFS open */
-);
-
-/* The flags parameter to sqlite3BtreeOpen can be the bitwise or of the
-** following values.
-**
-** NOTE:  These values must match the corresponding PAGER_ values in
-** pager.h.
-*/
-#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
-#define BTREE_MEMORY        2  /* This is an in-memory DB */
-#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
-#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */
-
-/*
-** CAPI3REF: Flags For File Open Operations
-**
-** These bit values are intended for use in the
-** 3rd parameter to the [sqlite3_open_v2()] interface and
-** in the 4th parameter to the [sqlite3_vfs.xOpen] method.
-*/
-#define SQLITE_OPEN_READONLY         0x00000001  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_READWRITE        0x00000002  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_CREATE           0x00000004  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_DELETEONCLOSE    0x00000008  /* VFS only */
-#define SQLITE_OPEN_EXCLUSIVE        0x00000010  /* VFS only */
-#define SQLITE_OPEN_AUTOPROXY        0x00000020  /* VFS only */
-#define SQLITE_OPEN_URI              0x00000040  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_MEMORY           0x00000080  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_MAIN_DB          0x00000100  /* VFS only */
-#define SQLITE_OPEN_TEMP_DB          0x00000200  /* VFS only */
-#define SQLITE_OPEN_TRANSIENT_DB     0x00000400  /* VFS only */
-#define SQLITE_OPEN_MAIN_JOURNAL     0x00000800  /* VFS only */
-#define SQLITE_OPEN_TEMP_JOURNAL     0x00001000  /* VFS only */
-#define SQLITE_OPEN_SUBJOURNAL       0x00002000  /* VFS only */
-#define SQLITE_OPEN_MASTER_JOURNAL   0x00004000  /* VFS only */
-#define SQLITE_OPEN_NOMUTEX          0x00008000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_FULLMUTEX        0x00010000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_SHAREDCACHE      0x00020000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_PRIVATECACHE     0x00040000  /* Ok for sqlite3_open_v2() */
-#define SQLITE_OPEN_WAL              0x00080000  /* VFS only */
-
-int sqlite3BtreeClose(Btree*);
-int sqlite3BtreeSetCacheSize(Btree*,int);
-#if SQLITE_MAX_MMAP_SIZE>0
-  int sqlite3BtreeSetMmapLimit(Btree*,sqlite3_int64);
-#endif
-int sqlite3BtreeSetPagerFlags(Btree*,unsigned);
-int sqlite3BtreeSyncDisabled(Btree*);
-int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
-int sqlite3BtreeGetPageSize(Btree*);
-int sqlite3BtreeMaxPageCount(Btree*,int);
-u32 sqlite3BtreeLastPage(Btree*);
-int sqlite3BtreeSecureDelete(Btree*,int);
-int sqlite3BtreeGetOptimalReserve(Btree*);
-int sqlite3BtreeGetReserveNoMutex(Btree *p);
-int sqlite3BtreeSetAutoVacuum(Btree *, int);
-int sqlite3BtreeGetAutoVacuum(Btree *);
-int sqlite3BtreeBeginTrans(Btree*,int);
-int sqlite3BtreeCommitPhaseOne(Btree*, const char *zMaster);
-int sqlite3BtreeCommitPhaseTwo(Btree*, int);
-int sqlite3BtreeCommit(Btree*);
-int sqlite3BtreeRollback(Btree*,int,int);
-int sqlite3BtreeBeginStmt(Btree*,int);
-int sqlite3BtreeCreateTable(Btree*, int*, int flags);
-int sqlite3BtreeIsInTrans(Btree*);
-int sqlite3BtreeIsInReadTrans(Btree*);
-int sqlite3BtreeIsInBackup(Btree*);
-void *sqlite3BtreeSchema(Btree *, int, void(*)(void *));
-int sqlite3BtreeSchemaLocked(Btree *pBtree);
-int sqlite3BtreeLockTable(Btree *pBtree, int iTab, u8 isWriteLock);
-int sqlite3BtreeSavepoint(Btree *, int, int);
-
-int sqlite3BtreeFileFormat(Btree *);
-const char *sqlite3BtreeGetFilename(Btree *);
-const char *sqlite3BtreeGetJournalname(Btree *);
-int sqlite3BtreeCopyFile(Btree *, Btree *);
-
-int sqlite3BtreeIncrVacuum(Btree *);
-
-/* The flags parameter to sqlite3BtreeCreateTable can be the bitwise OR
-** of the flags shown below.
-**
-** Every SQLite table must have either BTREE_INTKEY or BTREE_BLOBKEY set.
-** With BTREE_INTKEY, the table key is a 64-bit integer and arbitrary data
-** is stored in the leaves.  (BTREE_INTKEY is used for SQL tables.)  With
-** BTREE_BLOBKEY, the key is an arbitrary BLOB and no content is stored
-** anywhere - the key is the content.  (BTREE_BLOBKEY is used for SQL
-** indices.)
-*/
-#define BTREE_INTKEY     1    /* Table has only 64-bit signed integer keys */
-#define BTREE_BLOBKEY    2    /* Table has keys only - no data */
-
-int sqlite3BtreeDropTable(Btree*, int, int*);
-int sqlite3BtreeClearTable(Btree*, int, int*);
-int sqlite3BtreeClearTableOfCursor(BtCursor*);
-int sqlite3BtreeTripAllCursors(Btree*, int, int);
-
-void sqlite3BtreeGetMeta(Btree *pBtree, int idx, u32 *pValue);
-int sqlite3BtreeUpdateMeta(Btree*, int idx, u32 value);
-
-int sqlite3BtreeNewDb(Btree *p);
-
-/*
-** The second parameter to sqlite3BtreeGetMeta or sqlite3BtreeUpdateMeta
-** should be one of the following values. The integer values are assigned 
-** to constants so that the offset of the corresponding field in an
-** SQLite database header may be found using the following formula:
-**
-**   offset = 36 + (idx * 4)
-**
-** For example, the free-page-count field is located at byte offset 36 of
-** the database file header. The incr-vacuum-flag field is located at
-** byte offset 64 (== 36+4*7).
-**
-** The BTREE_DATA_VERSION value is not really a value stored in the header.
-** It is a read-only number computed by the pager.  But we merge it with
-** the header value access routines since its access pattern is the same.
-** Call it a "virtual meta value".
-*/
-#define BTREE_FREE_PAGE_COUNT     0
-#define BTREE_SCHEMA_VERSION      1
-#define BTREE_FILE_FORMAT         2
-#define BTREE_DEFAULT_CACHE_SIZE  3
-#define BTREE_LARGEST_ROOT_PAGE   4
-#define BTREE_TEXT_ENCODING       5
-#define BTREE_USER_VERSION        6
-#define BTREE_INCR_VACUUM         7
-#define BTREE_APPLICATION_ID      8
-#define BTREE_DATA_VERSION        15  /* A virtual meta-value */
-
-/*
-** An instance of the following structure holds information about a
-** single index record that has already been parsed out into individual
-** values.
-**
-** A record is an object that contains one or more fields of data.
-** Records are used to store the content of a table row and to store
-** the key of an index.  A blob encoding of a record is created by
-** the OP_MakeRecord opcode of the VDBE and is disassembled by the
-** OP_Column opcode.
-**
-** This structure holds a record that has already been disassembled
-** into its constituent fields.
-**
-** The r1 and r2 member variables are only used by the optimized comparison
-** functions vdbeRecordCompareInt() and vdbeRecordCompareString().
-*/
-struct UnpackedRecord {
-  KeyInfo *pKeyInfo;  /* Collation and sort-order information */
-  u16 nField;         /* Number of entries in apMem[] */
-  i8 default_rc;      /* Comparison result if keys are equal */
-  u8 errCode;         /* Error detected by xRecordCompare (CORRUPT or NOMEM) */
-  Mem *aMem;          /* Values */
-  int r1;             /* Value to return if (lhs > rhs) */
-  int r2;             /* Value to return if (rhs < lhs) */
-};
-
-/* One or more of the following flags are set to indicate the validOK
-** representations of the value stored in the Mem struct.
-**
-** If the MEM_Null flag is set, then the value is an SQL NULL value.
-** No other flags may be set in this case.
-**
-** If the MEM_Str flag is set then Mem.z points at a string representation.
-** Usually this is encoded in the same unicode encoding as the main
-** database (see below for exceptions). If the MEM_Term flag is also
-** set, then the string is nul terminated. The MEM_Int and MEM_Real 
-** flags may coexist with the MEM_Str flag.
-*/
-#define MEM_Null      0x0001   /* Value is NULL */
-#define MEM_Str       0x0002   /* Value is a string */
-#define MEM_Int       0x0004   /* Value is an integer */
-#define MEM_Real      0x0008   /* Value is a real number */
-#define MEM_Blob      0x0010   /* Value is a BLOB */
-
-#define MEM_Term      0x0200   /* String rep is nul terminated */
-#define MEM_Dyn       0x0400   /* Need to call Mem.xDel() on Mem.z */
-#define MEM_Static    0x0800   /* Mem.z points to a static string */
-#define MEM_Ephem     0x1000   /* Mem.z points to an ephemeral string */
-#define MEM_Zero      0x4000   /* Mem.i contains count of 0s appended to blob */
-
-/*
-** Internally, the vdbe manipulates nearly all SQL values as Mem
-** structures. Each Mem struct may cache multiple representations (string,
-** integer etc.) of the same value.
-*/
-struct Mem {
-  union MemValue {
-    double r;           /* Real value used when MEM_Real is set in flags */
-    i64 i;              /* Integer value used when MEM_Int is set in flags */
-    int nZero;          /* Used when bit MEM_Zero is set in flags */
-  } u;
-  u16 flags;          /* Some combination of MEM_Null, MEM_Str, MEM_Dyn, etc. */
-  u8  enc;            /* SQLITE_UTF8, SQLITE_UTF16BE, SQLITE_UTF16LE */
-  u8  eSubtype;       /* Subtype for this value */
-  int n;              /* Number of characters in string value, excluding '\0' */
-  char *z;            /* String or BLOB value */
-  /* ShallowCopy only needs to copy the information above */
-  char *zMalloc;      /* Space to hold MEM_Str or MEM_Blob if szMalloc>0 */
-  int szMalloc;       /* Size of the zMalloc allocation */
-  u32 uTemp;          /* Transient storage for serial_type in OP_MakeRecord */
-  Btree *pBtree;      /* The associated database connection */
-  void (*xDel)(void*);/* Destructor for Mem.z - only valid if MEM_Dyn */
-#ifdef SQLITE_DEBUG
-  Mem *pScopyFrom;    /* This Mem is a shallow copy of pScopyFrom */
-  void *pFiller;      /* So that sizeof(Mem) is a multiple of 8 */
-#endif
-};
-
-/*
-** Values that may be OR'd together to form the second argument of an
-** sqlite3BtreeCursorHints() call.
-**
-** The BTREE_BULKLOAD flag is set on index cursors when the index is going
-** to be filled with content that is already in sorted order.
-**
-** The BTREE_SEEK_EQ flag is set on cursors that will get OP_SeekGE or
-** OP_SeekLE opcodes for a range search, but where the range of entries
-** selected will all have the same key.  In other words, the cursor will
-** be used only for equality key searches.
-**
-*/
-#define BTREE_BULKLOAD 0x00000001  /* Used to full index in sorted order */
-#define BTREE_SEEK_EQ  0x00000002  /* EQ seeks only - no range seeks */
-
-int sqlite3BtreeCursor(
-  Btree*,                              /* BTree containing table to open */
-  int iTable,                          /* Index of root page */
-  int wrFlag,                          /* 1 for writing.  0 for read-only */
-  int N, int X,                        /* index of N key columns and X extra columns */
-  BtCursor **ppCursor                  /* Space to write cursor pointer */
-);
-int sqlite3BtreeCursorSize(void);
-
-int sqlite3BtreeCloseCursor(BtCursor*);
-void sqlite3BtreeInitUnpackedRecord(
-  UnpackedRecord *pUnKey,
-  BtCursor* pCur,
-  int nField,
-  int default_rc,
-  Mem* pMem);
-int sqlite3BtreeMovetoUnpacked(
-  BtCursor*,
-  UnpackedRecord *pUnKey,
-  i64 intKey,
-  int bias,
-  int *pRes
-);
-int sqlite3BtreeCursorHasMoved(BtCursor*);
-int sqlite3BtreeCursorRestore(BtCursor*, int*);
-int sqlite3BtreeDelete(BtCursor*, int);
-int sqlite3BtreeInsert(BtCursor*, const void *pKey, i64 nKey,
-                                  const void *pData, int nData,
-                                  int nZero, int bias, int seekResult);
-int sqlite3BtreeFirst(BtCursor*, int *pRes);
-int sqlite3BtreeLast(BtCursor*, int *pRes);
-int sqlite3BtreeNext(BtCursor*, int *pRes);
-int sqlite3BtreeEof(BtCursor*);
-int sqlite3BtreePrevious(BtCursor*, int *pRes);
-int sqlite3BtreeKeySize(BtCursor*, i64 *pSize);
-int sqlite3BtreeKey(BtCursor*, u32 offset, u32 amt, void*);
-const void *sqlite3BtreeKeyFetch(BtCursor*, u32 *pAmt);
-const void *sqlite3BtreeDataFetch(BtCursor*, u32 *pAmt);
-int sqlite3BtreeDataSize(BtCursor*, u32 *pSize);
-int sqlite3BtreeData(BtCursor*, u32 offset, u32 amt, void*);
-
-char *sqlite3BtreeIntegrityCheck(Btree*, int *aRoot, int nRoot, int, int*);
-struct Pager *sqlite3BtreePager(Btree*);
-
-int sqlite3BtreePutData(BtCursor*, u32 offset, u32 amt, void*);
-void sqlite3BtreeIncrblobCursor(BtCursor *);
-void sqlite3BtreeClearCursor(BtCursor *);
-int sqlite3BtreeSetVersion(Btree *pBt, int iVersion);
-void sqlite3BtreeCursorHints(BtCursor *, unsigned int mask);
-#ifdef SQLITE_DEBUG
-int sqlite3BtreeCursorHasHint(BtCursor*, unsigned int mask);
-#endif
-int sqlite3BtreeIsReadonly(Btree *pBt);
-
-#ifndef NDEBUG
-int sqlite3BtreeCursorIsValid(BtCursor*);
-#endif
-
-#ifndef SQLITE_OMIT_BTREECOUNT
-int sqlite3BtreeCount(BtCursor *, i64 *);
-#endif
-
-#ifdef SQLITE_TEST
-int sqlite3BtreeCursorInfo(BtCursor*, int*, int);
-void sqlite3BtreeCursorList(Btree*);
-#endif
-
-#ifndef SQLITE_OMIT_WAL
-  int sqlite3BtreeCheckpoint(Btree*, int, int *, int *);
-#endif
-
-/*
-** If we are not using shared cache, then there is no need to
-** use mutexes to access the BtShared structures.  So make the
-** Enter and Leave procedures no-ops.
-*/
-#ifndef SQLITE_OMIT_SHARED_CACHE
-  void sqlite3BtreeEnter(Btree*);
-#else
-# define sqlite3BtreeEnter(X) 
-#endif
-
-#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE
-  int sqlite3BtreeSharable(Btree*);
-  void sqlite3BtreeLeave(Btree*);
-  void sqlite3BtreeEnterCursor(BtCursor*);
-  void sqlite3BtreeLeaveCursor(BtCursor*);
-#else
-
-# define sqlite3BtreeSharable(X) 0
-# define sqlite3BtreeLeave(X)
-# define sqlite3BtreeEnterCursor(X)
-# define sqlite3BtreeLeaveCursor(X)
-#endif
-
-u32 sqlite3BtreeSerialType(Mem *pMem, int file_format);
-u32 sqlite3BtreeSerialTypeLen(u32);
-u32 sqlite3BtreeSerialGet(const unsigned char*, u32, Mem *);
-u32 sqlite3BtreeSerialPut(u8*, Mem*, u32);
-
-/*
-** Routines to read and write variable-length integers.  These used to
-** be defined locally, but now we use the varint routines in the util.c
-** file.
-*/
-int sqlite3BtreePutVarint(unsigned char*, u64);
-u8 sqlite3BtreeGetVarint(const unsigned char *, u64 *);
-u8 sqlite3BtreeGetVarint32(const unsigned char *, u32 *);
-int sqlite3BtreeVarintLen(u64 v);
-
-/*
-** The common case is for a varint to be a single byte.  They following
-** macros handle the common case without a procedure call, but then call
-** the procedure for larger varints.
-*/
-#define getVarint32(A,B)  \
-  (u8)((*(A)<(u8)0x80)?((B)=(u32)*(A)),1:sqlite3BtreeGetVarint32((A),(u32 *)&(B)))
-#define putVarint32(A,B)  \
-  (u8)(((u32)(B)<(u32)0x80)?(*(A)=(unsigned char)(B)),1:\
-  sqlite3BtreePutVarint((A),(B)))
-#define getVarint    sqlite3BtreeGetVarint
-#define putVarint    sqlite3BtreePutVarint
-
-
-int sqlite3BtreeIdxRowid(Btree*, BtCursor*, i64*);
-
-int sqlite3BtreeRecordCompare(int,const void*,UnpackedRecord*);
-
-const char *sqlite3BtreeErrName(int rc);
-
-#endif /* _BTREE_H_ */