utils/FastFunctions.hs

    {-
    Z%
    (c) The University of Glasgow, 2000-2006

    \section{Fast functions}
    -}

    {-# LANGUAGE CPP, MagicHash, UnboxedTuples #-}

    module FastFunctions (
        unsafeChr, inlinePerformIO, unsafeDupableInterleaveIO,
        indexWord8OffFastPtr,
        indexWord8OffFastPtrAsFastChar, indexWord8OffFastPtrAsFastInt,
        global, Global
      ) where

    #include "HsVersions.h"

    import FastTypes
    import Data.IORef
    import System.IO.Unsafe

    import GHC.Exts
    import GHC.Word
    import GHC.Base (unsafeChr)

    import GHC.IO   (IO(..), unsafeDupableInterleaveIO)

    -- Just like unsafePerformIO, but we inline it.
    {-# INLINE inlinePerformIO #-}
    inlinePerformIO :: IO a -> a
    inlinePerformIO (IO m) = case m realWorld# of (# _, r #)   -> r

    indexWord8OffFastPtr p i = W8# (indexWord8OffAddr# p i)
    indexWord8OffFastPtrAsFastChar p i = indexCharOffAddr# p i
    indexWord8OffFastPtrAsFastInt p i = word2Int# (indexWord8OffAddr# p i)
    -- or ord# (indexCharOffAddr# p i)

    --just so we can refer to the type clearly in a macro
    type Global a = IORef a
    global :: a -> Global a
    global a = unsafePerformIO (newIORef a)

    indexWord8OffFastPtr :: FastPtr Word8 -> FastInt -> Word8
    indexWord8OffFastPtrAsFastChar :: FastPtr Word8 -> FastInt -> FastChar
    indexWord8OffFastPtrAsFastInt :: FastPtr Word8 -> FastInt -> FastInt