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Current version: 2.3.2

ZThreads

A platform-independent, multi-threading and synchronization library for C++

Semaphore Class Reference

#include <Semaphore.h>

Inheritance diagram for Semaphore:

List of all members.

Public Member Functions
	Semaphore (int count=1, unsigned int maxCount=1)
virtual	~Semaphore ()
	Destroy the Semaphore.
void	wait ()
bool	tryWait (unsigned long timeout)
void	post ()
virtual int	count ()
virtual bool	tryAcquire (unsigned long timeout)
virtual void	acquire ()
virtual void	release ()

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Detailed Description

Author:

Eric Crahen <http://www.code-foo.com>

Date:

<2003-07-16T15:28:01-0400>

Version:

2.2.1

A Semaphore is an owner-less Lockable object. Its probably best described as a set of 'permits'. A Semaphore is initialized with an initial count and a maximum count, these would correspond to the number of 'permits' currently available and the number of' permits' in total.

• Acquiring the Semaphore means taking a permit, but if there are none (the count is 0) the Semaphore will block the calling thread.

• Releasing the Semaphore means returning a permit, unblocking a thread waiting for one.

A Semaphore with an initial value of 1 and maximum value of 1 will act as a Mutex.

Threads blocked on a Semaphore are resumed in FIFO order.

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Constructor & Destructor Documentation

Semaphore (  int  count = 1, unsigned int  maxCount = 1 )

Create a new Semaphore. Parameters: count  initial count maxCount  maximum count

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Member Function Documentation

virtual void acquire (   )  [virtual]

Decrement the count, blocking that calling thread if the count becomes 0 or less than 0. The calling thread will remain blocked until the count is raised above 0 or if an exception is thrown. Exceptions: Interrupted_Exception  thrown when the calling thread is interrupted. A thread may be interrupted at any time, prematurely ending any wait. See also: Lockable::acquire() Implements Lockable.

virtual int count (   )  [virtual]

Get the current count of the semaphore. This value may change immediately after this function returns to the calling thread. Returns: int count

void post (   )

Provided to reflect the traditional Semaphore semantics See also: release()

virtual void release (   )  [virtual]

Increment the count, unblocking one thread if count is positive. Exceptions: InvalidOp_Exception  thrown if the maximum count would be exceeded. See also: Lockable::release() Implements Lockable.

virtual bool tryAcquire (  unsigned long  timeout  )  [virtual]

Decrement the count, blocking that calling thread if the count becomes 0 or less than 0. The calling thread will remain blocked until the count is raised above 0, an exception is thrown or the given amount of time expires. Parameters: timeout  maximum amount of time (milliseconds) this method could block Returns: true if the Semaphore was acquired before timeout milliseconds elapse. false otherwise. Exceptions: Interrupted_Exception  thrown when the calling thread is interrupted. A thread may be interrupted at any time, prematurely ending any wait. See also: Lockable::tryAcquire(unsigned long timeout) Implements Lockable.

bool tryWait (  unsigned long  timeout  )

Provided to reflect the traditional Semaphore semantics See also: tryAcquire(unsigned long timeout)

void wait (   )

Provided to reflect the traditional Semaphore semantics See also: acquire()

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The documentation for this class was generated from the following file:

• Semaphore.h

ZThreads is Copyright © 2000-2005 by Eric Crahen, see the license for details.