DSSemaphore.cpp   [plain text]

/*
 * Copyright (c) 2002 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

/*!
 * @header DSSemaphore
 * Implementation of the DSSemaphore (lock) base class.
 */

#include <sys/time.h>	// for struct timespec and gettimeofday()

#include "DSSemaphore.h"

/******************************************************************************
	==>  DSSemaphore class implementation  <==
******************************************************************************/

DSSemaphore::DSSemaphore (
	sInt32 initialCount)
	: mExcessSignals (initialCount), mDestroying (false)
{
	::pthread_mutex_init (&mConditionLock, NULL);
	::pthread_cond_init (&mSemaphore, NULL);
}

DSSemaphore::~DSSemaphore (void)
{
	::pthread_mutex_lock (&mConditionLock);
	mDestroying = true;
	::pthread_cond_broadcast (&mSemaphore);
	::pthread_mutex_unlock (&mConditionLock);

	::pthread_cond_destroy (&mSemaphore);
	::pthread_mutex_destroy (&mConditionLock);
}

void
DSSemaphore::Signal (void)
{
	::pthread_mutex_lock (&mConditionLock);
	mExcessSignals++;
	::pthread_cond_signal (&mSemaphore);
	::pthread_mutex_unlock (&mConditionLock);
}

sInt32 DSSemaphore::Wait (sInt32 milliSecs)
{
	::pthread_mutex_lock (&mConditionLock);
	if ((mExcessSignals <= 0) && (milliSecs == kNever)) {
		::pthread_mutex_unlock (&mConditionLock);
		return semTimedOutErr;
	}
	if (milliSecs == kForever) {
		while (!mDestroying && (mExcessSignals <= 0))
			::pthread_cond_wait (&mSemaphore, &mConditionLock);
	} else {
		struct timeval	tvNow;
		struct timespec	tsTimeout;

		// Timeout is passed as an absolute time!
		::gettimeofday (&tvNow, NULL);
		TIMEVAL_TO_TIMESPEC (&tvNow, &tsTimeout);
		tsTimeout.tv_sec += (milliSecs / 1000);
		tsTimeout.tv_nsec += ((milliSecs % 1000) * 1000000);
		while (!mDestroying && (mExcessSignals <= 0))
			if (ETIMEDOUT == ::pthread_cond_timedwait (&mSemaphore,
											&mConditionLock, &tsTimeout)) {
				::pthread_mutex_unlock (&mConditionLock);
				return semTimedOutErr;
			}
	}
	if (!mDestroying)
		mExcessSignals--;
	::pthread_mutex_unlock (&mConditionLock);
	return (mDestroying ? semDestroyedErr : semNoErr);
}