+{-# LANGUAGE CPP #-}
+
-----------------------------------------------------------------------------
-- |
-- Module : Control.Concurrent.QSemN
import Prelude
import Control.Concurrent.MVar
-import Control.Exception ( block )
+import Control.Exception ( mask_ )
import Data.Typeable
#include "Typeable.h"
-- |A 'QSemN' is a quantity semaphore, in which the available
-- \"quantity\" may be signalled or waited for in arbitrary amounts.
-newtype QSemN = QSemN (MVar (Int,[(Int,MVar ())]))
+newtype QSemN = QSemN (MVar (Int,[(Int,MVar ())])) deriving Eq
INSTANCE_TYPEABLE0(QSemN,qSemNTc,"QSemN")
-- |Wait for the specified quantity to become available
waitQSemN :: QSemN -> Int -> IO ()
-waitQSemN (QSemN sem) sz = block $ do
+waitQSemN (QSemN sem) sz = mask_ $ do
(avail,blocked) <- takeMVar sem -- gain ex. access
let remaining = avail - sz
if remaining >= 0 then
-- |Signal that a given quantity is now available from the 'QSemN'.
signalQSemN :: QSemN -> Int -> IO ()
-signalQSemN (QSemN sem) n = block $ do
+signalQSemN (QSemN sem) n = mask_ $ do
(avail,blocked) <- takeMVar sem
(avail',blocked') <- free (avail+n) blocked
avail' `seq` putMVar sem (avail',blocked')