Mutex.hs

-- Communicating Haskell Processes.
-- Copyright (c) 2008, University of Kent.
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module Control.Concurrent.CHP.Mutex where

import Control.Concurrent
import Control.Monad.Trans

type Mutex = MVar ()

claimMutex :: MonadIO m => Mutex -> m ()
claimMutex = liftIO . takeMVar

newMutex :: MonadIO m => m Mutex
newMutex = liftIO $ newMVar ()

releaseMutex :: MonadIO m => Mutex -> m ()
releaseMutex m = liftIO $ putMVar m ()

-- | A wrapper (usually around a channel-end) indicating that the inner item
-- is shared.  Use the 'claim' function to use this type.
data Shared c a = Shared (Mutex, c a)