add GF.Source.SharedString

1 files changed, 20 insertions, 0 deletions

diff --git a/src-3.0/GF/Source/SharedString.hs b/src-3.0/GF/Source/SharedString.hs
new file mode 100644
index 000000000..732873fe6
--- /dev/null
+++ b/src-3.0/GF/Source/SharedString.hs
@@ -0,0 +1,20 @@
+module GF.Source.SharedString (shareString) where

+

+import Data.Map as M

+import Data.IORef

+import qualified Data.ByteString.Char8 as BS

+import System.IO.Unsafe (unsafePerformIO)

+

+{-# NOINLINE stringPoolRef #-}

+stringPoolRef :: IORef (M.Map BS.ByteString BS.ByteString)

+stringPoolRef = unsafePerformIO $ newIORef M.empty

+

+{-# NOINLINE shareString #-}

+shareString :: BS.ByteString -> BS.ByteString

+shareString s = unsafePerformIO $ do

+  stringPool <- readIORef stringPoolRef

+  case M.lookup s stringPool of

+    Just s' -> return s'

+    Nothing -> do let s' = BS.copy s

+                  writeIORef stringPoolRef $! M.insert s' s' stringPool

+                  return s'