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add tryLockShared

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This commit is contained in:
Joey Hess 2015-10-08 13:40:23 -04:00
parent 9461019e9a
commit c8fad345f2
Failed to extract signature
2 changed files with 26 additions and 8 deletions
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25
Utility/LockFile/Posix.hs
View file

@ -9,6 +9,7 @@ module Utility.LockFile.Posix (
LockHandle,
lockShared,
lockExclusive,
tryLockShared,
tryLockExclusive,
checkLocked,
getLockStatus,
@ -36,16 +37,13 @@ lockShared = lock ReadLock
lockExclusive :: Maybe FileMode -> LockFile -> IO LockHandle
lockExclusive = lock WriteLock
-- Tries to take a shared lock, but does not block.
tryLockShared :: Maybe FileMode -> LockFile -> IO (Maybe LockHandle)
tryLockShared = tryLock ReadLock
-- Tries to take an exclusive lock, but does not block.
tryLockExclusive :: Maybe FileMode -> LockFile -> IO (Maybe LockHandle)
tryLockExclusive mode lockfile = do
l <- openLockFile WriteLock mode lockfile
v <- tryIO $ setLock l (WriteLock, AbsoluteSeek, 0, 0)
case v of
Left _ -> do
closeFd l
return Nothing
Right _ -> return $ Just $ LockHandle l
tryLockExclusive = tryLock WriteLock
-- Setting the FileMode allows creation of a new lock file.
-- If it's Nothing then this only succeeds when the lock file already exists.
@ -55,6 +53,17 @@ lock lockreq mode lockfile = do
waitToSetLock l (lockreq, AbsoluteSeek, 0, 0)
return (LockHandle l)
-- Tries to take an lock, but does not block.
tryLock :: LockRequest -> Maybe FileMode -> LockFile -> IO (Maybe LockHandle)
tryLock lockreq mode lockfile = do
l <- openLockFile lockreq mode lockfile
v <- tryIO $ setLock l (lockreq, AbsoluteSeek, 0, 0)
case v of
Left _ -> do
closeFd l
return Nothing
Right _ -> return $ Just $ LockHandle l
-- Close on exec flag is set so child processes do not inherit the lock.
openLockFile :: LockRequest -> Maybe FileMode -> LockFile -> IO Fd
openLockFile lockreq filemode lockfile = do

9
Utility/LockPool/Posix.hs
View file

@ -9,6 +9,7 @@ module Utility.LockPool.Posix (
LockHandle,
lockShared,
lockExclusive,
tryLockShared,
tryLockExclusive,
checkLocked,
getLockStatus,
@ -35,11 +36,19 @@ lockShared mode file = makeLockHandle
(P.waitTakeLock P.lockPool file LockShared)
(F.lockShared mode file)
-- Takes an exclusive lock, blocking until the lock is available.
lockExclusive :: Maybe FileMode -> LockFile -> IO LockHandle
lockExclusive mode file = makeLockHandle
(P.waitTakeLock P.lockPool file LockExclusive)
(F.lockExclusive mode file)
-- Tries to take a shared lock, but does not block.
tryLockShared :: Maybe FileMode -> LockFile -> IO (Maybe LockHandle)
tryLockShared mode file = tryMakeLockHandle
(P.tryTakeLock P.lockPool file LockShared)
(F.tryLockShared mode file)
-- Tries to take an exclusive lock, but does not block.
tryLockExclusive :: Maybe FileMode -> LockFile -> IO (Maybe LockHandle)
tryLockExclusive mode file = tryMakeLockHandle
(P.tryTakeLock P.lockPool file LockExclusive)