add GHC.HetMet.{hetmet_kappa,hetmet_kappa_app}

[ghc-base.git] / Data / Unique.hs

diff --git a/Data/Unique.hs b/Data/Unique.hs
index 502739f..c4c8827 100644 (file)
--- a/Data/Unique.hs
+++ b/Data/Unique.hs
@@ -1,3 +1,9 @@
+{-# LANGUAGE CPP #-}
+
+#ifdef __GLASGOW_HASKELL__
+{-# LANGUAGE MagicHash, DeriveDataTypeable #-}
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Unique
@@ -21,20 +27,25 @@ module Data.Unique (
 
 import Prelude
 
-import Control.Concurrent.MVar
 import System.IO.Unsafe (unsafePerformIO)
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.Base
-import GHC.Num  ( Integer(..) )
+import GHC.Num
+import GHC.Conc
+import Data.Typeable
 #endif
 
 -- | An abstract unique object.  Objects of type 'Unique' may be
 -- compared for equality and ordering and hashed into 'Int'.
-newtype Unique = Unique Integer deriving (Eq,Ord)
+newtype Unique = Unique Integer deriving (Eq,Ord
+#ifdef __GLASGOW_HASKELL__
+   ,Typeable
+#endif
+   )
 
-uniqSource :: MVar Integer
-uniqSource = unsafePerformIO (newMVar 0)
+uniqSource :: TVar Integer
+uniqSource = unsafePerformIO (newTVarIO 0)
 {-# NOINLINE uniqSource #-}
 
 -- | Creates a new object of type 'Unique'.  The value returned will
@@ -42,20 +53,25 @@ uniqSource = unsafePerformIO (newMVar 0)
 -- previous calls to 'newUnique'.  There is no limit on the number of
 -- times 'newUnique' may be called.
 newUnique :: IO Unique
-newUnique = do
-   val <- takeMVar uniqSource
-   let next = val+1
-   putMVar uniqSource next
-   return (Unique next)
+newUnique = atomically $ do
+  val <- readTVar uniqSource
+  let next = val+1
+  writeTVar uniqSource $! next
+  return (Unique next)
+
+-- SDM (18/3/2010): changed from MVar to STM.  This fixes
+--  1. there was no async exception protection
+--  2. there was a space leak (now new value is strict)
+--  3. using atomicModifyIORef would be slightly quicker, but can
+--     suffer from adverse scheduling issues (see #3838)
+--  4. also, the STM version is faster.
 
 -- | Hashes a 'Unique' into an 'Int'.  Two 'Unique's may hash to the
 -- same value, although in practice this is unlikely.  The 'Int'
 -- returned makes a good hash key.
 hashUnique :: Unique -> Int
-#ifdef __GLASGOW_HASKELL__ 
-hashUnique (Unique (S# i))   = I# i
-hashUnique (Unique (J# s d)) | s ==# 0#  = 0
-                             | otherwise = I# (indexIntArray# d 0#)
+#if defined(__GLASGOW_HASKELL__)
+hashUnique (Unique i) = I# (hashInteger i)
 #else
 hashUnique (Unique u) = fromInteger (u `mod` (toInteger (maxBound :: Int) + 1))
 #endif