base- Basic libraries

Copyright(c) The University of Glasgow 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Portabilitynon-portable (concurrency)
Safe HaskellSafe




Quantity semaphores in which each thread may wait for an arbitrary "amount".


General Quantity Semaphores

data QSemN Source #

QSemN is a quantity semaphore in which the resource is aqcuired and released in units of one. It provides guaranteed FIFO ordering for satisfying blocked waitQSemN calls.

The pattern

  bracket_ (waitQSemN n) (signalQSemN n) (...)

is safe; it never loses any of the resource.

newQSemN :: Int -> IO QSemN Source #

Build a new QSemN with a supplied initial quantity. The initial quantity must be at least 0.

waitQSemN :: QSemN -> Int -> IO () Source #

Wait for the specified quantity to become available

signalQSemN :: QSemN -> Int -> IO () Source #

Signal that a given quantity is now available from the QSemN.