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|
{- Handles for lock pools.
-
- Copyright 2015 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE CPP #-}
module Utility.LockPool.LockHandle where
import qualified Utility.LockPool.STM as P
#ifndef mingw32_HOST_OS
import qualified Utility.LockFile.Posix as F
#else
import qualified Utility.LockFile.Windows as F
#endif
import Control.Concurrent.STM
import Control.Exception
data LockHandle = LockHandle P.LockHandle F.LockHandle
dropLock :: LockHandle -> IO ()
dropLock (LockHandle ph fh) = P.releaseLock ph (F.dropLock fh)
-- Take a lock, by first updating the lock pool, and then taking the file
-- lock. If taking the file lock fails for any reason, take care to
-- release the lock in the lock pool.
makeLockHandle :: STM P.LockHandle -> IO F.LockHandle -> IO LockHandle
makeLockHandle pa fa = bracketOnError setup cleanup go
where
setup = atomically pa
cleanup ph = P.releaseLock ph (return ())
go ph = do
fh <- fa
return $ LockHandle ph fh
tryMakeLockHandle :: STM (Maybe P.LockHandle) -> IO (Maybe F.LockHandle) -> IO (Maybe LockHandle)
tryMakeLockHandle pa fa = bracketOnError setup cleanup go
where
setup = atomically pa
cleanup Nothing = return ()
cleanup (Just ph) = P.releaseLock ph (return ())
go Nothing = return Nothing
go (Just ph) = do
mfh <- fa
case mfh of
Nothing -> do
cleanup (Just ph)
return Nothing
Just fh -> return $ Just $ LockHandle ph fh
|
