/usr/include/zthread/Semaphore.h is in libzthread-dev 2.3.2-7ubuntu2.
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* Copyright (c) 2005, Eric Crahen
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is furnished
* to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#ifndef __ZTSEMAPHORE_H__
#define __ZTSEMAPHORE_H__
#include "zthread/Lockable.h"
#include "zthread/NonCopyable.h"
namespace ZThread {
class FifoSemaphoreImpl;
/**
* @class Semaphore
* @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.
*
*/
class ZTHREAD_API Semaphore : public Lockable, private NonCopyable {
FifoSemaphoreImpl* _impl;
public:
/**
* Create a new Semaphore.
*
* @param count initial count
* @param maxCount maximum count
*/
Semaphore(int count = 1, unsigned int maxCount = 1);
//! Destroy the Semaphore
virtual ~Semaphore();
/**
* <i>Provided to reflect the traditional Semaphore semantics</i>
*
* @see acquire()
*/
void wait();
/**
* <i>Provided to reflect the traditional Semaphore semantics</i>
*
* @see tryAcquire(unsigned long timeout)
*/
bool tryWait(unsigned long timeout);
/**
* <i>Provided to reflect the traditional Semaphore semantics</i>
*
* @see release()
*/
void post();
/**
* Get the current count of the semaphore.
*
* This value may change immediately after this function returns to the calling thread.
*
* @return <em>int</em> count
*/
virtual int count();
/**
* 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.
*
* @param timeout maximum amount of time (milliseconds) this method could block
*
* @return
* - <em>true</em> if the Semaphore was acquired before <i>timeout</i> milliseconds elapse.
* - <em>false</em> otherwise.
*
* @exception Interrupted_Exception thrown when the calling thread is interrupted.
* A thread may be interrupted at any time, prematurely ending any wait.
*
* @see Lockable::tryAcquire(unsigned long timeout)
*/
virtual bool tryAcquire(unsigned long timeout);
/**
* 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.
*
* @exception Interrupted_Exception thrown when the calling thread is interrupted.
* A thread may be interrupted at any time, prematurely ending any wait.
*
* @see Lockable::acquire()
*/
virtual void acquire();
/**
* Increment the count, unblocking one thread if count is positive.
*
* @exception InvalidOp_Exception thrown if the maximum count would be exceeded.
*
* @see Lockable::release()
*/
virtual void release();
};
} // namespace ZThread
#endif // __ZTSEMAPHORE_H__
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