qsemaphore.cpp

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#include "qsemaphore.h"

#ifndef QT_NO_THREAD
#include "qmutex.h"
#include "qwaitcondition.h"
#include "qelapsedtimer.h"
#include "qdatetime.h"

QT_BEGIN_NAMESPACE

class QSemaphorePrivate {
public:
    inline QSemaphorePrivate(int n) : avail(n) { }

    QMutex mutex;
    QWaitCondition cond;

    int avail;
};

QSemaphore::QSemaphore(int n)
{
    Q_ASSERT_X(n >= 0, "QSemaphore", "parameter 'n' must be non-negative");
    d = new QSemaphorePrivate(n);
}

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

void QSemaphore::acquire(int n)
{
    Q_ASSERT_X(n >= 0, "QSemaphore::acquire", "parameter 'n' must be non-negative");
    QMutexLocker locker(&d->mutex);
    while (n > d->avail)
        d->cond.wait(locker.mutex());
    d->avail -= n;
}

void QSemaphore::release(int n)
{
    Q_ASSERT_X(n >= 0, "QSemaphore::release", "parameter 'n' must be non-negative");
    QMutexLocker locker(&d->mutex);
    d->avail += n;
    d->cond.wakeAll();
}

int QSemaphore::available() const
{
    QMutexLocker locker(&d->mutex);
    return d->avail;
}

bool QSemaphore::tryAcquire(int n)
{
    Q_ASSERT_X(n >= 0, "QSemaphore::tryAcquire", "parameter 'n' must be non-negative");
    QMutexLocker locker(&d->mutex);
    if (n > d->avail)
        return false;
    d->avail -= n;
    return true;
}

bool QSemaphore::tryAcquire(int n, int timeout)
{
    Q_ASSERT_X(n >= 0, "QSemaphore::tryAcquire", "parameter 'n' must be non-negative");
    QMutexLocker locker(&d->mutex);
    if (timeout < 0) {
        while (n > d->avail)
            d->cond.wait(locker.mutex());
    } else {
        QElapsedTimer timer;
        timer.start();
        while (n > d->avail) {
            const qint64 elapsed = timer.elapsed();
            if (timeout - elapsed <= 0
                || !d->cond.wait(locker.mutex(), timeout - elapsed))
                return false;
        }
    }
    d->avail -= n;
    return true;


}

QT_END_NAMESPACE

#endif // QT_NO_THREAD