base- Basic libraries

Copyright(c) The University of Glasgow 2001
License(c) The University of Glasgow 2001
Portabilitynon-portable (concurrency)
Safe HaskellTrustworthy




Simple quantity semaphores.


Simple Quantity Semaphores

data QSem Source

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

The pattern

   bracket_ waitQSem signalQSem (...)

is safe; it never loses a unit of the resource.

newQSem :: Int -> IO QSemSource

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

waitQSem :: QSem -> IO ()Source

Wait for a unit to become available

signalQSem :: QSem -> IO ()Source

Signal that a unit of the QSem is available