1 files changed, 61 insertions, 0 deletions
diff --git a/compiler/GHC/Data/FastMutInt.hs b/compiler/GHC/Data/FastMutInt.hs
new file mode 100644
index 0000000000..cc81b88b01
--- /dev/null
+++ b/compiler/GHC/Data/FastMutInt.hs
@@ -0,0 +1,61 @@
+{-# LANGUAGE BangPatterns, MagicHash, UnboxedTuples #-}
+{-# OPTIONS_GHC -O2 #-}
+-- We always optimise this, otherwise performance of a non-optimised
+-- compiler is severely affected
+--
+-- (c) The University of Glasgow 2002-2006
+--
+-- Unboxed mutable Ints
+
+module GHC.Data.FastMutInt(
+        FastMutInt, newFastMutInt,
+        readFastMutInt, writeFastMutInt,
+
+        FastMutPtr, newFastMutPtr,
+        readFastMutPtr, writeFastMutPtr
+  ) where
+
+import GHC.Prelude
+
+import Data.Bits
+import GHC.Base
+import GHC.Ptr
+
+newFastMutInt :: IO FastMutInt
+readFastMutInt :: FastMutInt -> IO Int
+writeFastMutInt :: FastMutInt -> Int -> IO ()
+
+newFastMutPtr :: IO FastMutPtr
+readFastMutPtr :: FastMutPtr -> IO (Ptr a)
+writeFastMutPtr :: FastMutPtr -> Ptr a -> IO ()
+
+data FastMutInt = FastMutInt (MutableByteArray# RealWorld)
+
+newFastMutInt = IO $ \s ->
+  case newByteArray# size s of { (# s, arr #) ->
+  (# s, FastMutInt arr #) }
+  where !(I# size) = finiteBitSize (0 :: Int)
+
+readFastMutInt (FastMutInt arr) = IO $ \s ->
+  case readIntArray# arr 0# s of { (# s, i #) ->
+  (# s, I# i #) }
+
+writeFastMutInt (FastMutInt arr) (I# i) = IO $ \s ->
+  case writeIntArray# arr 0# i s of { s ->
+  (# s, () #) }
+
+data FastMutPtr = FastMutPtr (MutableByteArray# RealWorld)
+
+newFastMutPtr = IO $ \s ->
+  case newByteArray# size s of { (# s, arr #) ->
+  (# s, FastMutPtr arr #) }
+  -- GHC assumes 'sizeof (Int) == sizeof (Ptr a)'
+  where !(I# size) = finiteBitSize (0 :: Int)
+
+readFastMutPtr (FastMutPtr arr) = IO $ \s ->
+  case readAddrArray# arr 0# s of { (# s, i #) ->
+  (# s, Ptr i #) }
+
+writeFastMutPtr (FastMutPtr arr) (Ptr i) = IO $ \s ->
+  case writeAddrArray# arr 0# i s of { s ->
+  (# s, () #) }