75 lines
2.1 KiB
Haskell
75 lines
2.1 KiB
Haskell
{- Handles for lock pools.
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-
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- Copyright 2015 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE CPP #-}
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module Utility.LockPool.LockHandle (
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LockHandle,
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FileLockOps(..),
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dropLock,
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#ifndef mingw32_HOST_OS
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checkSaneLock,
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#endif
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makeLockHandle,
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tryMakeLockHandle,
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) where
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import qualified Utility.LockPool.STM as P
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import Utility.LockPool.STM (LockFile)
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import Control.Concurrent.STM
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import Control.Exception
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import Control.Applicative
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import Prelude
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data LockHandle = LockHandle P.LockHandle FileLockOps
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data FileLockOps = FileLockOps
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{ fDropLock :: IO ()
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#ifndef mingw32_HOST_OS
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, fCheckSaneLock :: LockFile -> IO Bool
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#endif
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}
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dropLock :: LockHandle -> IO ()
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dropLock (LockHandle ph _) = P.releaseLock ph
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#ifndef mingw32_HOST_OS
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checkSaneLock :: LockFile -> LockHandle -> IO Bool
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checkSaneLock lockfile (LockHandle _ flo) = fCheckSaneLock flo lockfile
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#endif
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-- Take a lock, by first updating the lock pool, and then taking the file
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-- lock. If taking the file lock fails for any reason, take care to
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-- release the lock in the lock pool.
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makeLockHandle :: P.LockPool -> LockFile -> (P.LockPool -> LockFile -> STM P.LockHandle) -> (LockFile -> IO FileLockOps) -> IO LockHandle
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makeLockHandle pool file pa fa = bracketOnError setup cleanup go
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where
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setup = atomically (pa pool file)
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cleanup ph = P.releaseLock ph
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go ph = mkLockHandle pool file ph =<< fa file
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tryMakeLockHandle :: P.LockPool -> LockFile -> (P.LockPool -> LockFile -> STM (Maybe P.LockHandle)) -> (LockFile -> IO (Maybe FileLockOps)) -> IO (Maybe LockHandle)
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tryMakeLockHandle pool file pa fa = bracketOnError setup cleanup go
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where
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setup = atomically (pa pool file)
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cleanup Nothing = return ()
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cleanup (Just ph) = P.releaseLock ph
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go Nothing = return Nothing
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go (Just ph) = do
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mfo <- fa file
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case mfo of
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Nothing -> do
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cleanup (Just ph)
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return Nothing
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Just fo -> Just <$> mkLockHandle pool file ph fo
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mkLockHandle :: P.LockPool -> LockFile -> P.LockHandle -> FileLockOps -> IO LockHandle
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mkLockHandle pool file ph fo = do
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atomically $ P.registerCloseLockFile pool file (fDropLock fo)
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return $ LockHandle ph fo
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