Safe Haskell	Trustworthy
Language	Haskell2010

Lukko

Contents

File descriptors
Handles

Description

Open Handle based locking

Synopsis

data FileLockingNotSupported = FileLockingNotSupported
fileLockingSupported :: Bool
type FileLockingSupported = True
data FileLockingMethod
- = MethodOFD
- | MethodFLock
- | MethodWindows
- | MethodNoOp
fileLockingMethod :: FileLockingMethod
data LockMode
- = SharedLock
- | ExclusiveLock
type FD = FD
fdOpen :: FilePath -> IO FD
fdClose :: FD -> IO ()
fdLock :: FD -> LockMode -> IO ()
fdTryLock :: FD -> LockMode -> IO Bool
fdUnlock :: FD -> IO ()
handleToFd :: Handle -> IO FD
hLock :: Handle -> LockMode -> IO ()
hTryLock :: Handle -> LockMode -> IO Bool
hUnlock :: Handle -> IO ()

Documentation

data FileLockingNotSupported Source #

Exception thrown by hLock on non-Windows platforms that don't support flock.

Constructors

FileLockingNotSupported

Instances

Show FileLockingNotSupported Source #
Instance details Defined in Lukko.Internal.Types Methods showsPrec :: Int -> FileLockingNotSupported -> ShowS # show :: FileLockingNotSupported -> String # showList :: [FileLockingNotSupported] -> ShowS #
Exception FileLockingNotSupported Source #
Instance details Defined in Lukko.Internal.Types Methods toException :: FileLockingNotSupported -> SomeException # fromException :: SomeException -> Maybe FileLockingNotSupported # displayException :: FileLockingNotSupported -> String #

fileLockingSupported :: Bool Source #

A constants specifying whether file locking is supported.

type FileLockingSupported = True Source #

A type level fileLockingSupported.

data FileLockingMethod Source #

Potentially availble lock methods.

Constructors

MethodOFD	open file descriptor locking
MethodFLock	BSD `flock`
MethodWindows	Windows locking
MethodNoOp	No-Op (throws `FileLockingNotSupported`)

Instances

Bounded FileLockingMethod Source #
Instance details Defined in Lukko.Internal.Types Methods minBound :: FileLockingMethod # maxBound :: FileLockingMethod #
Enum FileLockingMethod Source #
Instance details Defined in Lukko.Internal.Types Methods succ :: FileLockingMethod -> FileLockingMethod # pred :: FileLockingMethod -> FileLockingMethod # toEnum :: Int -> FileLockingMethod # fromEnum :: FileLockingMethod -> Int # enumFrom :: FileLockingMethod -> [FileLockingMethod] # enumFromThen :: FileLockingMethod -> FileLockingMethod -> [FileLockingMethod] # enumFromTo :: FileLockingMethod -> FileLockingMethod -> [FileLockingMethod] # enumFromThenTo :: FileLockingMethod -> FileLockingMethod -> FileLockingMethod -> [FileLockingMethod] #
Eq FileLockingMethod Source #
Instance details Defined in Lukko.Internal.Types Methods (==) :: FileLockingMethod -> FileLockingMethod -> Bool # (/=) :: FileLockingMethod -> FileLockingMethod -> Bool #
Ord FileLockingMethod Source #
Instance details Defined in Lukko.Internal.Types Methods compare :: FileLockingMethod -> FileLockingMethod -> Ordering # (<) :: FileLockingMethod -> FileLockingMethod -> Bool # (<=) :: FileLockingMethod -> FileLockingMethod -> Bool # (>) :: FileLockingMethod -> FileLockingMethod -> Bool # (>=) :: FileLockingMethod -> FileLockingMethod -> Bool # max :: FileLockingMethod -> FileLockingMethod -> FileLockingMethod # min :: FileLockingMethod -> FileLockingMethod -> FileLockingMethod #
Show FileLockingMethod Source #
Instance details Defined in Lukko.Internal.Types Methods showsPrec :: Int -> FileLockingMethod -> ShowS # show :: FileLockingMethod -> String # showList :: [FileLockingMethod] -> ShowS #

fileLockingMethod :: FileLockingMethod Source #

A constant specifying this method

data LockMode Source #

Indicates a mode in which a file should be locked.

Constructors

SharedLock
ExclusiveLock

File descriptors

type FD = FD Source #

Opaque file descriptor

An int / CInt on unix systems, and HANDLE on windows.

fdOpen :: FilePath -> IO FD Source #

Open file to be used for locking.

fdClose :: FD -> IO () Source #

Close lock file.

fdLock :: FD -> LockMode -> IO () Source #

Like hLock, but work on "raw" file descriptor, as handled by fdOpen and fdClose.

fdTryLock :: FD -> LockMode -> IO Bool Source #

Non-blocking version of fdLock.

fdUnlock :: FD -> IO () Source #

Release a lock taken with fdLock or fdTryLock.

Handles

handleToFd :: Handle -> IO FD Source #

Convert GHC Handle to lukko FD.

hLock :: Handle -> LockMode -> IO () Source #

If a Handle references a file descriptor, attempt to lock contents of the underlying file in appropriate mode. If the file is already locked in incompatible mode, this function blocks until the lock is established. The lock is automatically released upon closing a Handle.

Things to be aware of:

1) This function may block inside a C call. If it does, in order to be able to interrupt it with asynchronous exceptions and/or for other threads to continue working, you MUST use threaded version of the runtime system.

2) The implementation uses LockFileEx on Windows, open file descriptor locks on Linux, and flock otherwise, hence all of their caveats also apply here.

3) On non-Windows plaftorms that don't support flock (e.g. Solaris) this function throws FileLockingNotImplemented. We deliberately choose to not provide fcntl based locking instead because of its broken semantics.

hTryLock :: Handle -> LockMode -> IO Bool Source #

Non-blocking version of hLock.

hUnlock :: Handle -> IO () Source #

Release a lock taken with hLock or hTryLock.