X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Flib%2Fstd%2FPrelConc.lhs;h=0ffe3a9d5eab19d25631158f454789df86b3483c;hb=f1a7474164cebbb19da431a18da6ebcbbd37733f;hp=f096db1fd242e27460da983d73a9fcb4eeb5034e;hpb=a103a9dc0de992716e62c30d7ac81c0bc0dbcdc5;p=ghc-hetmet.git

diff --git a/ghc/lib/std/PrelConc.lhs b/ghc/lib/std/PrelConc.lhs
index f096db1..0ffe3a9 100644
--- a/ghc/lib/std/PrelConc.lhs
+++ b/ghc/lib/std/PrelConc.lhs
@@ -1,5 +1,7 @@
+% -----------------------------------------------------------------------------
+% $Id: PrelConc.lhs,v 1.24 2001/05/18 16:54:05 simonmar Exp $
 %
-% (c) The AQUA Project, Glasgow University, 1994-1996
+% (c) The University of Glasgow, 1994-2000
 %
 
 \section[PrelConc]{Module @PrelConc@}
@@ -7,7 +9,7 @@
 Basic concurrency stuff
 
 \begin{code}
-{-# OPTIONS -fcompiling-prelude -fno-implicit-prelude #-}
+{-# OPTIONS -fno-implicit-prelude #-}
 
 module PrelConc
 	( ThreadId(..)
@@ -15,7 +17,7 @@ module PrelConc
 	-- Forking and suchlike
 	, myThreadId 	-- :: IO ThreadId
 	, killThread	-- :: ThreadId -> IO ()
-	, raiseInThread -- :: ThreadId -> Exception -> IO ()
+	, throwTo       -- :: ThreadId -> Exception -> IO ()
 	, par  		-- :: a -> b -> b
 	, seq  		-- :: a -> b -> b
 	, yield         -- :: IO ()
@@ -31,16 +33,17 @@ module PrelConc
 	, newEmptyMVar  -- :: IO (MVar a)
 	, takeMVar 	-- :: MVar a -> IO a
 	, putMVar  	-- :: MVar a -> a -> IO ()
-	, readMVar 	-- :: MVar a -> IO a
-	, swapMVar 	-- :: MVar a -> a -> IO a
+	, tryTakeMVar   -- :: MVar a -> IO (Maybe a)
+	, tryPutMVar  	-- :: MVar a -> a -> IO Bool
 	, isEmptyMVar	-- :: MVar a -> IO Bool
+	, addMVarFinalizer -- :: MVar a -> IO () -> IO ()
 
     ) where
 
 import PrelBase
-import PrelErr ( parError, seqError )
-import PrelST	  	( liftST )
-import PrelIOBase	( IO(..), MVar(..), unsafePerformIO )
+import PrelMaybe
+import PrelErr		( parError, seqError )
+import PrelIOBase	( IO(..), MVar(..) )
 import PrelBase		( Int(..) )
 import PrelException    ( Exception(..), AsyncException(..) )
 
@@ -65,8 +68,8 @@ killThread :: ThreadId -> IO ()
 killThread (ThreadId id) = IO $ \ s ->
    case (killThread# id (AsyncException ThreadKilled) s) of s1 -> (# s1, () #)
 
-raiseInThread :: ThreadId -> Exception -> IO ()
-raiseInThread (ThreadId id) ex = IO $ \ s ->
+throwTo :: ThreadId -> Exception -> IO ()
+throwTo (ThreadId id) ex = IO $ \ s ->
    case (killThread# id ex s) of s1 -> (# s1, () #)
 
 myThreadId :: IO ThreadId
@@ -77,7 +80,7 @@ yield :: IO ()
 yield = IO $ \s -> 
    case (yield# s) of s1 -> (# s1, () #)
 
--- "seq" is defined a bit wierdly (see below)
+-- "seq" is defined a bit weirdly (see below)
 --
 -- The reason for the strange "0# -> parError" case is that
 -- it fools the compiler into thinking that seq is non-strict in
@@ -115,48 +118,45 @@ writes.
 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
 
 newEmptyMVar  :: IO (MVar a)
-
 newEmptyMVar = IO $ \ s# ->
     case newMVar# s# of
          (# s2#, svar# #) -> (# s2#, MVar svar# #)
 
 takeMVar :: MVar a -> IO a
-
 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
 
 putMVar  :: MVar a -> a -> IO ()
-
 putMVar (MVar mvar#) x = IO $ \ s# ->
     case putMVar# mvar# x s# of
         s2# -> (# s2#, () #)
 
-newMVar :: a -> IO (MVar a)
+tryPutMVar  :: MVar a -> a -> IO Bool
+tryPutMVar (MVar mvar#) x = IO $ \ s# ->
+    case tryPutMVar# mvar# x s# of
+        (# s, 0# #) -> (# s, False #)
+        (# s, _  #) -> (# s, True #)
 
+newMVar :: a -> IO (MVar a)
 newMVar value =
     newEmptyMVar	>>= \ mvar ->
     putMVar mvar value	>>
     return mvar
 
-readMVar :: MVar a -> IO a
-
-readMVar mvar =
-    takeMVar mvar	>>= \ value ->
-    putMVar mvar value	>>
-    return value
-
-swapMVar :: MVar a -> a -> IO a
-
-swapMVar mvar new =
-    takeMVar mvar	>>= \ old ->
-    putMVar mvar new	>>
-    return old
+-- tryTakeMVar is a non-blocking takeMVar
+tryTakeMVar :: MVar a -> IO (Maybe a)
+tryTakeMVar (MVar m) = IO $ \ s ->
+    case tryTakeMVar# m s of
+	(# s, 0#, _ #) -> (# s, Nothing #)	-- MVar is empty
+	(# s, _,  a #) -> (# s, Just a  #)	-- MVar is full
 
 {- 
  Low-level op. for checking whether an MVar is filled-in or not.
  Notice that the boolean value returned  is just a snapshot of
  the state of the MVar. By the time you get to react on its result,
  the MVar may have been filled (or emptied) - so be extremely
- careful when using this operation.
+ careful when using this operation.  
+
+ Use tryTakeMVar instead if possible.
 
  If you can re-work your abstractions to avoid having to
  depend on isEmptyMVar, then you're encouraged to do so,
@@ -167,6 +167,11 @@ isEmptyMVar :: MVar a -> IO Bool
 isEmptyMVar (MVar mv#) = IO $ \ s# -> 
     case isEmptyMVar# mv# s# of
         (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
+
+-- Like addForeignPtrFinalizer, but for MVars
+addMVarFinalizer :: MVar a -> IO () -> IO ()
+addMVarFinalizer (MVar m) finalizer = 
+  IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
 \end{code}