53 lines
1.4 KiB
Haskell
53 lines
1.4 KiB
Haskell
|
{- 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
|