qsemaphore_unix.cpp

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/****************************************************************************
** $Id: qsemaphore_unix.cpp,v 1.2 2003/07/10 02:40:12 llornkcor Exp $
**
** QSemaphore class for Unix
**
** Created : 20010725
**
** Copyright (C) 1992-2002 Trolltech AS.  All rights reserved.
**
** This file is part of the tools module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
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**   information about Qt Commercial License Agreements.
** See http://www.trolltech.com/qpl/ for QPL licensing information.
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**********************************************************************/

#if defined(QT_THREAD_SUPPORT)

#include "qsemaphore.h"
#include "qmutex.h"
#include "qwaitcondition.h"


class QSemaphorePrivate {
public:
    QSemaphorePrivate(int);

    QMutex mutex;
    QWaitCondition cond;

    int value, max;
};


QSemaphorePrivate::QSemaphorePrivate(int m)
    : mutex(FALSE), value(0), max(m)
{
}


QSemaphore::QSemaphore(int maxcount)
{
    d = new QSemaphorePrivate(maxcount);
}


QSemaphore::~QSemaphore()
{
    delete d;
}


int QSemaphore::operator++(int)
{
    int ret;

    d->mutex.lock();

    while (d->value >= d->max)
        d->cond.wait(&(d->mutex));

    ++(d->value);
    if (d->value > d->max) d->value = d->max;
    ret = d->value;

    d->mutex.unlock();

    return ret;
}


int QSemaphore::operator--(int)
{
    int ret;

    d->mutex.lock();

    --(d->value);
    if (d->value < 0) d->value = 0;
    ret = d->value;

    d->cond.wakeAll();
    d->mutex.unlock();

    return ret;
}


int QSemaphore::operator+=(int n)
{
    int ret;

    d->mutex.lock();

    if ( n < 0 || n > d->max ) {
#ifdef QT_CHECK_RANGE
        qWarning( "QSemaphore::operator+=: paramter %d out of range", n );
#endif // QT_CHECK_RANGE
        n = n < 0 ? 0 : d->max;
    }

    while (d->value + n > d->max)
        d->cond.wait(&(d->mutex));

    d->value += n;
    ret = d->value;

    d->mutex.unlock();

    return ret;
}


int QSemaphore::operator-=(int n)
{
    int ret;

    d->mutex.lock();

    if ( n < 0 || n > d->value ) {
#ifdef QT_CHECK_RANGE
        qWarning( "QSemaphore::operator-=: paramter %d out of range", n );
#endif // QT_CHECK_RANGE
        n = n < 0 ? 0 : d->value;
    }

    d->value -= n;
    ret = d->value;

    d->cond.wakeOne();
    d->mutex.unlock();

    return ret;
}


int QSemaphore::available() const {
    int ret;

    d->mutex.lock();
    ret = d->max - d->value;
    d->mutex.unlock();

    return ret;
}


int QSemaphore::total() const {
    int ret;

    d->mutex.lock();
    ret = d->max;
    d->mutex.unlock();

    return ret;
}


bool QSemaphore::tryAccess(int n)
{
    if (! d->mutex.tryLock())
        return FALSE;

    if (d->value + n > d->max) {
        d->mutex.unlock();
        return FALSE;
    }

    d->value += n;

#ifdef QT_CHECK_RANGE
    if (d->value > d->max) {
        qWarning("QSemaphore::operator+=: attempt to allocate more resources than available");
        d->value = d->max;
    }
#endif

    d->mutex.unlock();

    return TRUE;
}

#endif // QT_THREAD_SUPPORT

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