From ac4ce06a21ddb9034855b3839176c83f0b9783f0 Mon Sep 17 00:00:00 2001
From: bringert <unknown>
Date: Fri, 11 Nov 2005 10:12:49 +0000
Subject: Allow disabling signal support in configure.

---
 src/GF/System/UseSignal.hs | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 src/GF/System/UseSignal.hs

(limited to 'src/GF/System/UseSignal.hs')

diff --git a/src/GF/System/UseSignal.hs b/src/GF/System/UseSignal.hs
new file mode 100644
index 000000000..8f3874711
--- /dev/null
+++ b/src/GF/System/UseSignal.hs
@@ -0,0 +1,50 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : GF.System.UseSignal
+-- Maintainer  : Bjorn Bringert
+-- Stability   : (stability)
+-- Portability : (portability)
+--
+-- > CVS $Date: 2005/11/11 11:12:50 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.1 $
+--
+-- Allows SIGINT (Ctrl-C) to interrupt computations.
+-----------------------------------------------------------------------------
+
+module GF.System.UseSignal where
+
+import Control.Concurrent (myThreadId, killThread)
+import Control.Exception (Exception,catch)
+import Prelude hiding (catch)
+import System.IO
+import System.Posix.Signals
+
+{-# NOINLINE runInterruptibly #-}
+
+-- | Run an IO action, and allow it to be interrupted
+--   by a SIGINT to the current process. Returns
+--   an exception if the process did not complete 
+--   normally.
+--   NOTES: 
+--   * This will replace any existing SIGINT
+--     handler during the action. After the computation 
+--     has completed the existing handler will be restored.
+--   * If the IO action is lazy (e.g. using readFile,
+--     unsafeInterleaveIO etc.) the lazy computation will
+--     not be interruptible, as it will be performed
+--     after the signal handler has been removed.
+runInterruptibly :: IO a -> IO (Either Exception a)
+runInterruptibly a = 
+    do t <- myThreadId
+       oldH <- installHandler sigINT (Catch (killThread t)) Nothing
+       x <- p `catch` h
+       installHandler sigINT oldH Nothing
+       return x
+  where p = a >>= \x -> return $! Right $! x
+        h e = return $ Left e
+
+-- | Like 'runInterruptibly', but always returns (), whether
+--   the computation fails or not.
+runInterruptibly_ :: IO () -> IO ()
+runInterruptibly_ = fmap (either (const ()) id) . runInterruptibly
-- 
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