Copyright	(c) Daniel Franke 2007
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	experimental
Portability	non-portable (requires POSIX)
Safe Haskell	Safe
Language	Haskell2010

System.Posix.Semaphore

Description

POSIX named semaphore support.

Synopsis

data OpenSemFlags = OpenSemFlags {
- semCreate :: Bool
- semExclusive :: Bool
}
data Semaphore
semOpen :: String -> OpenSemFlags -> FileMode -> Int -> IO Semaphore
semUnlink :: String -> IO ()
semWait :: Semaphore -> IO ()
semWaitInterruptible :: Semaphore -> IO Bool
semTryWait :: Semaphore -> IO Bool
semThreadWait :: Semaphore -> IO ()
semPost :: Semaphore -> IO ()
semGetValue :: Semaphore -> IO Int

Documentation

data OpenSemFlags Source #

Constructors

OpenSemFlags
Fields semCreate :: Bool If true, create the semaphore if it does not yet exist. semExclusive :: Bool If true, throw an exception if the semaphore already exists.

data Semaphore Source #

semOpen :: String -> OpenSemFlags -> FileMode -> Int -> IO Semaphore Source #

Open a named semaphore with the given name, flags, mode, and initial value.

semUnlink :: String -> IO () Source #

Delete the semaphore with the given name.

semWait :: Semaphore -> IO () Source #

Lock the semaphore, blocking until it becomes available. Since this is done through a system call, this will block the *entire runtime*, not just the current thread. If this is not the behaviour you want, use semThreadWait instead.

semWaitInterruptible :: Semaphore -> IO Bool Source #

Lock the semaphore, blocking until it becomes available.

Unlike semWait, this wait operation can be interrupted with an asynchronous exception (e.g. a call to throwTo from another thread).

semTryWait :: Semaphore -> IO Bool Source #

Attempt to lock the semaphore without blocking. Immediately return False if it is not available.

semThreadWait :: Semaphore -> IO () Source #

Poll the semaphore until it is available, then lock it. Unlike semWait, this will block only the current thread rather than the entire process.

semPost :: Semaphore -> IO () Source #

Unlock the semaphore.

semGetValue :: Semaphore -> IO Int Source #

Return the semaphore's current value.