Lukko.OFD

Linux open file descriptor locking.

https://www.gnu.org/software/libc/manual/html_node/Open-File-Description-Locks.html

We prefer this over BSD locking (e.g. flock) since the latter appears to break in some NFS configurations. Note that we intentionally do not try to use ordinary POSIX file locking due to its peculiar semantics under multi-threaded environments.

Types

data FileLockingNotSupported

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

Constructors

FileLockingNotSupported

Instances

Show FileLockingNotSupported

Defined in Lukko.Internal.Types

Methods

showsPrec :: Int -> FileLockingNotSupported -> ShowS

show :: FileLockingNotSupported -> String

showList :: [FileLockingNotSupported] -> ShowS

Exception FileLockingNotSupported

Defined in Lukko.Internal.Types

Methods

toException :: FileLockingNotSupported -> SomeException

fromException :: SomeException -> Maybe FileLockingNotSupported

displayException :: FileLockingNotSupported -> String

fileLockingSupported :: Bool

A constants specifying whether file locking is supported.

type FileLockingSupported = True

A type level fileLockingSupported.

data FileLockingMethod

Potentially availble lock methods.

Constructors

MethodOFD

open file descriptor locking

MethodFLock

BSD flock

MethodWindows

Windows locking

MethodNoOp

No-Op (throws FileLockingNotSupported)

Instances

Bounded FileLockingMethod

Defined in Lukko.Internal.Types

Methods

minBound :: FileLockingMethod

maxBound :: FileLockingMethod

Enum FileLockingMethod

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

Defined in Lukko.Internal.Types

Methods

(==) :: FileLockingMethod -> FileLockingMethod -> Bool

(/=) :: FileLockingMethod -> FileLockingMethod -> Bool

Ord FileLockingMethod

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

Defined in Lukko.Internal.Types

Methods

showsPrec :: Int -> FileLockingMethod -> ShowS

show :: FileLockingMethod -> String

showList :: [FileLockingMethod] -> ShowS

fileLockingMethod :: FileLockingMethod

A constant specifying this method

data LockMode

Indicates a mode in which a file should be locked.

Constructors

SharedLock

ExclusiveLock

File descriptors

data FD

Opaque file descriptor

This is a wrapper over CInt

fdOpen :: FilePath -> IO FD

Open file to be used for locking.

open(path, O_RDWR | O_CREAT);

fdClose :: FD -> IO ()

Close lock file.

close(fd);

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

Lock using OFD locks.

fdTryLock :: FD -> LockMode -> IO Bool

Try to lock using OFD locks.

fdUnlock :: FD -> IO ()

Unlock using OFD locks.

Handles

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

Lock using OFD locks.

hTryLock :: Handle -> LockMode -> IO Bool

Try to lock using OFD locks.

hUnlock :: Handle -> IO ()

Unlock using OFD locks.