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#include "qplatformdefs.h"
#include "qapplication.h"
#include "qeventdispatcher_qpa_p.h"
#include "private/qeventdispatcher_unix_p.h"
#include "qapplication_p.h"
#include "qplatformeventloopintegration_qpa.h"

#include <QWindowSystemInterface>
#include <QtCore/QElapsedTimer>
#include <QtCore/QAtomicInt>
#include <QtCore/QSemaphore>

#include <errno.h>

QT_BEGIN_NAMESPACE

QT_USE_NAMESPACE

class Rendezvous
{
public:
    void checkpoint()
    {
        if (state.testAndSetOrdered(0,1)) {
            semaphore.acquire();
        } else if (state.testAndSetAcquire(1,0)) {
            semaphore.release();
        } else {
            qWarning("Barrier internal error");
        }
    }
private:
    QSemaphore semaphore;
    QAtomicInt state;
};

class SelectWorker : public QThread
{
public:
    SelectWorker(QEventDispatcherQPAPrivate *eventDispatcherPrivate)
        : QThread(),
          m_edPrivate(eventDispatcherPrivate),
          m_retVal(0)
    {
    }

    void setSelectValues(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds)
    {
        m_nfds = nfds;
        m_readfds = readfds;
        m_writefds = writefds;
        m_exceptfds = exceptfds;


    }

    int retVal() const {
        return m_retVal;
    }

protected:
    void run();

private:
    QEventDispatcherQPAPrivate *m_edPrivate;
    int m_retVal;

    int m_nfds;
    fd_set *m_readfds, *m_writefds, *m_exceptfds;
};

class QEventDispatcherQPAPrivate : public QEventDispatcherUNIXPrivate
{
    Q_DECLARE_PUBLIC(QEventDispatcherQPA)
public:
    QEventDispatcherQPAPrivate()
        :  eventLoopIntegration(0),
           barrierBeforeBlocking(0),
           barrierReturnValue(0),
           selectReturnMutex(0),
           selectWorkerNeedsSync(true),
           selectWorkerHasResult(false),
           m_integrationInitialised(false),
           m_hasIntegration(false)
    {

    }

    ~QEventDispatcherQPAPrivate()
    {
        delete selectWorker;
        delete eventLoopIntegration;
        delete barrierBeforeBlocking;
        delete barrierReturnValue;
        delete selectReturnMutex;
    }

    bool hasIntegration() const
    {
        if (!m_integrationInitialised) {
            QEventDispatcherQPAPrivate *that = const_cast<QEventDispatcherQPAPrivate *>(this);
            if (qApp && (qApp->thread() == QThread::currentThread())) { // guiThread
                if (QApplicationPrivate::platformIntegration()) {
                    that->eventLoopIntegration = QApplicationPrivate::platformIntegration()->createEventLoopIntegration();
                    if (that->eventLoopIntegration) {
                        that->selectWorker = new SelectWorker(that);
                        that->barrierBeforeBlocking = new Rendezvous;
                        that->barrierReturnValue = new Rendezvous;
                        that->selectReturnMutex = new QMutex;
                        that->selectWorker->start();
                        that->m_hasIntegration = true;
                        if (!QElapsedTimer::isMonotonic())
                            qWarning("Having eventloop integration without monotonic timers can lead to undefined behaviour");
                    }
                }
            }
            that->m_integrationInitialised = true;
        }
        return m_hasIntegration;
    }

    QPlatformEventLoopIntegration *eventLoopIntegration;
    Rendezvous *barrierBeforeBlocking;
    Rendezvous *barrierReturnValue;

    QMutex *selectReturnMutex;
    bool selectWorkerNeedsSync;
    bool selectWorkerHasResult;

    SelectWorker *selectWorker;
private:
    bool m_integrationInitialised;
    bool m_hasIntegration;
};

QEventDispatcherQPA::QEventDispatcherQPA(QObject *parent)
    : QEventDispatcherUNIX(*new QEventDispatcherQPAPrivate, parent)
{ }

QEventDispatcherQPA::~QEventDispatcherQPA()
{ }

bool QEventDispatcherQPA::processEvents(QEventLoop::ProcessEventsFlags flags)
{
    Q_D(QEventDispatcherQPA);
    int nevents = 0;

    // handle gui and posted events
    d->interrupt = false;
    QApplication::sendPostedEvents();

    while (!d->interrupt) {        // also flushes output buffer ###can be optimized
        QWindowSystemInterfacePrivate::WindowSystemEvent *event;
        if (!(flags & QEventLoop::ExcludeUserInputEvents)
            && QWindowSystemInterfacePrivate::windowSystemEventsQueued() > 0) {
            // process a pending user input event
            event = QWindowSystemInterfacePrivate::getWindowSystemEvent();
            if (!event)
                break;
        } else {
            break;
        }

        if (filterEvent(event)) {
            delete event;
            continue;
        }
        nevents++;

        QApplicationPrivate::processWindowSystemEvent(event);
        delete event;
    }

    if (!d->interrupt) {
        if (QEventDispatcherUNIX::processEvents(flags))
            return true;
    }
    return (nevents > 0);
}

bool QEventDispatcherQPA::hasPendingEvents()
{
    extern uint qGlobalPostedEventsCount(); // from qapplication.cpp
    return qGlobalPostedEventsCount() || QWindowSystemInterfacePrivate::windowSystemEventsQueued();
}

void QEventDispatcherQPA::registerSocketNotifier(QSocketNotifier *notifier)
{
    Q_D(QEventDispatcherQPA);
    QEventDispatcherUNIX::registerSocketNotifier(notifier);
    if (d->hasIntegration())
        wakeUp();

}

void QEventDispatcherQPA::unregisterSocketNotifier(QSocketNotifier *notifier)
{
    Q_D(QEventDispatcherQPA);
    QEventDispatcherUNIX::unregisterSocketNotifier(notifier);
    if (d->hasIntegration())
        wakeUp();
}

void QEventDispatcherQPA::flush()
{
    if(qApp)
        qApp->sendPostedEvents();
}


int QEventDispatcherQPA::select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
                                timeval *timeout)
{
    Q_D(QEventDispatcherQPA);
    int retVal = 0;
    if (d->hasIntegration()) {
        qint64 timeoutmsec = timeout->tv_sec * 1000 + (timeout->tv_usec/1000);
        d->selectReturnMutex->lock();
        if (d->selectWorkerNeedsSync) {
            if (d->selectWorkerHasResult) {
                retVal = d->selectWorker->retVal();
                d->selectWorkerHasResult = false;

                d->selectReturnMutex->unlock();
                d->barrierReturnValue->checkpoint();
                return retVal;
            } else {
                d->selectWorkerNeedsSync = false;
                d->selectWorker->setSelectValues(nfds,readfds, writefds, exceptfds);
                d->barrierBeforeBlocking->checkpoint();
            }
        }
        d->selectReturnMutex->unlock();
        d->eventLoopIntegration->processEvents(timeoutmsec);
        retVal = 0; //is 0 if select has not returned
    } else {
        retVal = QEventDispatcherUNIX::select(nfds, readfds, writefds, exceptfds, timeout);
    }
    return retVal;
}

void SelectWorker::run()
{
    while(true) {
        m_retVal = 0;
        m_edPrivate->barrierBeforeBlocking->checkpoint(); // wait for mainthread
        int tmpRet = qt_safe_select(m_nfds,m_readfds,m_writefds,m_exceptfds,0);
        m_edPrivate->selectReturnMutex->lock();
        m_edPrivate->eventLoopIntegration->wakeup();

        m_edPrivate->selectWorkerNeedsSync = true;
        m_edPrivate->selectWorkerHasResult = true;
        m_retVal = tmpRet;

        m_edPrivate->selectReturnMutex->unlock();
        m_edPrivate->barrierReturnValue->checkpoint();
    }
}
QT_END_NAMESPACE