katie/src/core/concurrent/qfuturewatcher.cpp

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** Copyright (C) 2016-2019 Ivailo Monev
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#include "qfuturewatcher.h"

#ifndef QT_NO_QFUTURE

#include <QtCore/qcoreevent.h>
#include <QtCore/qcoreapplication.h>
#include <QtCore/qthread.h>

#include "qfuturewatcher_p.h"

QT_BEGIN_NAMESPACE

/*! \class QFutureWatcher
    \reentrant
    \since 4.4

    \ingroup thread

    \brief The QFutureWatcher class allows monitoring a QFuture using signals
    and slots.

    QFutureWatcher provides information and notifications about a QFuture. Use
    the setFuture() function to start watching a particular QFuture. The
    future() function returns the future set with setFuture().

    For convenience, several of QFuture's functions are also available in
    QFutureWatcher: progressValue(), progressMinimum(), progressMaximum(),
    progressText(), isStarted(), isFinished(), isRunning(), isCanceled(),
    isPaused(), waitForFinished(), result(), and resultAt(). The cancel(),
    setPaused(), pause(), resume(), and togglePaused() functions are slots in
    QFutureWatcher.

    Status changes are reported via the started(), finished(), canceled(),
    paused(), resumed(), resultReadyAt(), and resultsReadyAt() signals.
    Progress information is provided from the progressRangeChanged(),
    void progressValueChanged(), and progressTextChanged() signals.

    Throttling control is provided by the setPendingResultsLimit() function.
    When the number of pending resultReadyAt() or resultsReadyAt() signals
    exceeds the limit, the computation represented by the future will be
    throttled automatically. The computation will resume once the number of
    pending signals drops below the limit.

    Example: Starting a computation and getting a slot callback when it's
    finished:

    \snippet doc/src/snippets/code/src_corelib_concurrent_qfuturewatcher.cpp 0

    Be aware that not all asynchronous computations can be canceled or paused.
    For example, the future returned by QtConcurrent::run() cannot be
    canceled; but the future returned by QtConcurrent::mappedReduced() can.

    QFutureWatcher<void> is specialized to not contain any of the result
    fetching functions. Any QFuture<T> can be watched by a
    QFutureWatcher<void> as well. This is useful if only status or progress
    information is needed; not the actual result data.

    \sa QFuture, {Concurrent Programming}{Qt Concurrent}
*/

/*! \fn QFutureWatcher::QFutureWatcher(QObject *parent)

    Constructs a new QFutureWatcher with the given \a parent.
*/
QFutureWatcherBase::QFutureWatcherBase(QObject *parent)
    :QObject(*new QFutureWatcherBasePrivate, parent)
{ }

/*! \fn QFutureWatcher::~QFutureWatcher()

    Destroys the QFutureWatcher.
*/

/*! \fn void QFutureWatcher::cancel()

    Cancels the asynchronous computation represented by the future(). Note that
    the cancelation is asynchronous. Use waitForFinished() after calling
    cancel() when you need synchronous cancelation.

    Currently available results may still be accessed on a canceled QFuture,
    but new results will \e not become available after calling this function.
    Also, this QFutureWatcher will not deliver progress and result ready
    signals once canceled. This includes the progressValueChanged(),
    progressRangeChanged(), progressTextChanged(), resultReadyAt(), and
    resultsReadyAt() signals.

    Be aware that not all asynchronous computations can be canceled. For
    example, the QFuture returned by QtConcurrent::run() cannot be canceled;
    but the QFuture returned by QtConcurrent::mappedReduced() can.
*/
void QFutureWatcherBase::cancel()
{
    futureInterface().cancel();
}

/*! \fn void QFutureWatcher::setPaused(bool paused)

    If \a paused is true, this function pauses the asynchronous computation
    represented by the future(). If the computation is already paused, this
    function does nothing. This QFutureWatcher will stop delivering progress
    and result ready signals while the future is paused. Signal delivery will
    continue once the computation is resumed.

    If \a paused is false, this function resumes the asynchronous computation.
    If the computation was not previously paused, this function does nothing.

    Be aware that not all computations can be paused. For example, the
    QFuture returned by QtConcurrent::run() cannot be paused; but the QFuture
    returned by QtConcurrent::mappedReduced() can.

    \sa pause(), resume(), togglePaused()
*/
void QFutureWatcherBase::setPaused(bool paused)
{
    futureInterface().setPaused(paused);
}

/*! \fn void QFutureWatcher::pause()

    Pauses the asynchronous computation represented by the future(). This is a
    convenience method that simply calls setPaused(true).

    \sa resume()
*/
void QFutureWatcherBase::pause()
{
    futureInterface().setPaused(true);
}

/*! \fn void QFutureWatcher::resume()

    Resumes the asynchronous computation represented by the future(). This is
    a convenience method that simply calls setPaused(false).

    \sa pause()
*/
void QFutureWatcherBase::resume()
{
    futureInterface().setPaused(false);
}

/*! \fn void QFutureWatcher::togglePaused()

    Toggles the paused state of the asynchronous computation. In other words,
    if the computation is currently paused, calling this function resumes it;
    if the computation is running, it becomes paused. This is a convenience
    method for calling setPaused(!isPaused()).

    \sa setPaused(), pause(), resume()
*/
void QFutureWatcherBase::togglePaused()
{
    futureInterface().togglePaused();
}

/*! \fn int QFutureWatcher::progressValue() const

    Returns the current progress value, which is between the progressMinimum()
    and progressMaximum().

    \sa progressMinimum(), progressMaximum()
*/
int QFutureWatcherBase::progressValue() const
{
    return futureInterface().progressValue();
}

/*! \fn int QFutureWatcher::progressMinimum() const

    Returns the minimum progressValue().

    \sa progressValue(), progressMaximum()
*/
int QFutureWatcherBase::progressMinimum() const
{
    return futureInterface().progressMinimum();
}

/*! \fn int QFutureWatcher::progressMaximum() const

    Returns the maximum progressValue().

    \sa progressValue(), progressMinimum()
*/
int QFutureWatcherBase::progressMaximum() const
{
    return futureInterface().progressMaximum();
}

/*! \fn QString QFutureWatcher::progressText() const

    Returns the (optional) textual representation of the progress as reported
    by the asynchronous computation.

    Be aware that not all computations provide a textual representation of the
    progress, and as such, this function may return an empty string.
*/
QString QFutureWatcherBase::progressText() const
{
    return futureInterface().progressText();
}

/*! \fn bool QFutureWatcher::isStarted() const

    Returns true if the asynchronous computation represented by the future()
    has been started; otherwise returns false.
*/
bool QFutureWatcherBase::isStarted() const
{
    return futureInterface().queryState(QFutureInterfaceBase::Started);
}

/*! \fn bool QFutureWatcher::isFinished() const

    Returns true if the asynchronous computation represented by the future()
    has finished; otherwise returns false.
*/
bool QFutureWatcherBase::isFinished() const
{
    Q_D(const QFutureWatcherBase);
    return d->finished;
}

/*! \fn bool QFutureWatcher::isRunning() const

    Returns true if the asynchronous computation represented by the future()
    is currently running; otherwise returns false.
*/
bool QFutureWatcherBase::isRunning() const
{
    return futureInterface().queryState(QFutureInterfaceBase::Running);
}

/*! \fn bool QFutureWatcher::isCanceled() const

    Returns true if the asynchronous computation has been canceled with the
    cancel() function; otherwise returns false.

    Be aware that the computation may still be running even though this
    function returns true. See cancel() for more details.
*/
bool QFutureWatcherBase::isCanceled() const
{
    return futureInterface().queryState(QFutureInterfaceBase::Canceled);
}

/*! \fn bool QFutureWatcher::isPaused() const

    Returns true if the asynchronous computation has been paused with the
    pause() function; otherwise returns false.

    Be aware that the computation may still be running even though this
    function returns true. See setPaused() for more details.

    \sa setPaused(), togglePaused()
*/
bool QFutureWatcherBase::isPaused() const
{
    return futureInterface().queryState(QFutureInterfaceBase::Paused);
}

/*! \fn void QFutureWatcher::waitForFinished()

    Waits for the asynchronous computation to finish (including cancel()ed
    computations).
*/
void QFutureWatcherBase::waitForFinished()
{
    futureInterface().waitForFinished();
}

/*! \fn void QFutureWatcher::setPendingResultsLimit(int limit)

    The setPendingResultsLimit() provides throttling control. When the number
    of pending resultReadyAt() or resultsReadyAt() signals exceeds the
    \a limit, the computation represented by the future will be throttled
    automatically. The computation will resume once the number of pending
    signals drops below the \a limit.
*/

bool QFutureWatcherBase::event(QEvent *event)
{
    Q_D(QFutureWatcherBase);
    if (event->type() == QEvent::FutureCallOut) {
        QFutureCallOutEvent *callOutEvent = static_cast<QFutureCallOutEvent *>(event);

        if (futureInterface().isPaused()) {
            d->pendingCallOutEvents.append(callOutEvent->clone());
            return true;
        }

        if (callOutEvent->callOutType == QFutureCallOutEvent::Resumed
            && !d->pendingCallOutEvents.isEmpty()) {
            // send the resume
            d->sendCallOutEvent(callOutEvent);

            // next send all pending call outs
            for (int i = 0; i < d->pendingCallOutEvents.count(); ++i)
                d->sendCallOutEvent(d->pendingCallOutEvents.at(i));
            qDeleteAll(d->pendingCallOutEvents);
            d->pendingCallOutEvents.clear();
        } else {
            d->sendCallOutEvent(callOutEvent);
        }
        return true;
    }
    return QObject::event(event);
}

void QFutureWatcherBase::setPendingResultsLimit(int limit)
{
    Q_D(QFutureWatcherBase);
    d->maximumPendingResultsReady = limit;
}

void QFutureWatcherBase::connectNotify(const char * signal)
{
    Q_D(QFutureWatcherBase);
    if (qstrcmp(signal, SIGNAL(resultReadyAt(int))) == 0)
        d->resultAtConnected.ref();
#ifndef QT_NO_DEBUG
    if (qstrcmp(signal, SIGNAL(finished())) == 0) {
        if (futureInterface().isRunning()) {
            //connections should be established before calling stFuture to avoid race.
            // (The future could finish before the connection is made.)
            qWarning("QFutureWatcher::connect: connecting after calling setFuture() is likely to produce race");
        }
    }
#endif
}

void QFutureWatcherBase::disconnectNotify(const char * signal)
{
    Q_D(QFutureWatcherBase);
    if (qstrcmp(signal, SIGNAL(resultReadyAt(int))) == 0)
        d->resultAtConnected.deref();
}

/*!
    \internal
*/
QFutureWatcherBasePrivate::QFutureWatcherBasePrivate()
    : maximumPendingResultsReady(QThread::idealThreadCount() * 2),
      resultAtConnected(0)
{ }

/*!
    \internal
*/
void QFutureWatcherBase::connectOutputInterface()
{
    futureInterface().d->connectOutputInterface(d_func());
}

/*!
    \internal
*/
void QFutureWatcherBase::disconnectOutputInterface(bool pendingAssignment)
{
    if (pendingAssignment) {
        Q_D(QFutureWatcherBase);
        d->pendingResultsReady = 0;
        qDeleteAll(d->pendingCallOutEvents);
        d->pendingCallOutEvents.clear();
        d->finished = false;
    }

    futureInterface().d->disconnectOutputInterface(d_func());
}

void QFutureWatcherBasePrivate::postCallOutEvent(const QFutureCallOutEvent &callOutEvent)
{
    Q_Q(QFutureWatcherBase);

    if (callOutEvent.callOutType == QFutureCallOutEvent::ResultsReady) {
        if (pendingResultsReady.fetchAndAddRelaxed(1) >= maximumPendingResultsReady)
            q->futureInterface().d->internal_setThrottled(true);
    }

    QCoreApplication::postEvent(q, callOutEvent.clone());
}

void QFutureWatcherBasePrivate::callOutInterfaceDisconnected()
{
    QCoreApplication::removePostedEvents(q_func(), QEvent::FutureCallOut);
}

void QFutureWatcherBasePrivate::sendCallOutEvent(QFutureCallOutEvent *event)
{
    Q_Q(QFutureWatcherBase);

    switch (event->callOutType) {
        case QFutureCallOutEvent::Started:
            emit q->started();
        break;
        case QFutureCallOutEvent::Finished:
            finished = true;
            emit q->finished();
        break;
        case QFutureCallOutEvent::Canceled:
            pendingResultsReady = 0;
            emit q->canceled();
        break;
        case QFutureCallOutEvent::Paused:
            if (q->futureInterface().isCanceled())
                break;
            emit q->paused();
        break;
        case QFutureCallOutEvent::Resumed:
            if (q->futureInterface().isCanceled())
                break;
            emit q->resumed();
        break;
        case QFutureCallOutEvent::ResultsReady: {
            if (q->futureInterface().isCanceled())
                break;

            if (pendingResultsReady.fetchAndAddRelaxed(-1) <= maximumPendingResultsReady)
                q->futureInterface().setThrottled(false);

            const int beginIndex = event->index1;
            const int endIndex = event->index2;

            emit q->resultsReadyAt(beginIndex, endIndex);

            if (int(resultAtConnected) <= 0)
                break;

            for (int i = beginIndex; i < endIndex; ++i)
                emit q->resultReadyAt(i);

        } break;
        case QFutureCallOutEvent::Progress:
            if (q->futureInterface().isCanceled())
                break;

            emit q->progressValueChanged(event->index1);
            if (!event->text.isNull()) // ###
                q->progressTextChanged(event->text);
        break;
        case QFutureCallOutEvent::ProgressRange:
            emit q->progressRangeChanged(event->index1, event->index2);
        break;
        default: break;
    }
}


/*! \fn const T &QFutureWatcher::result() const

    Returns the first result in the future(). If the result is not immediately
    available, this function will block and wait for the result to become
    available. This is a convenience method for calling resultAt(0).

    \sa resultAt()
*/

/*! \fn const T &QFutureWatcher::resultAt(int index) const

    Returns the result at \a index in the future(). If the result is not
    immediately available, this function will block and wait for the result to
    become available.

    \sa result()
*/

/*! \fn void QFutureWatcher::setFuture(const QFuture<T> &future)

    Starts watching the given \a future.

    One of the signals might be emitted for the current state of the
    \a future. For example, if the future is already stopped, the
    finished signal will be emitted.

    To avoid a race condition, it is important to call this function
    \e after doing the connections.
*/

/*! \fn QFuture<T> QFutureWatcher::future() const

    Returns the watched future.
*/

/*! \fn void QFutureWatcher::started()

    This signal is emitted when this QFutureWatcher starts watching the future
    set with setFuture().
*/

/*!
    \fn void QFutureWatcher::finished()
    This signal is emitted when the watched future finishes.
*/

/*!
    \fn void QFutureWatcher::canceled()
    This signal is emitted if the watched future is canceled.
*/

/*! \fn void QFutureWatcher::paused()
    This signal is emitted when the watched future is paused.
*/

/*! \fn void QFutureWatcher::resumed()
    This signal is emitted when the watched future is resumed.
*/

/*!
    \fn void QFutureWatcher::progressRangeChanged(int minimum, int maximum)

    The progress range for the watched future has changed to \a minimum and
    \a maximum
*/

/*!
    \fn void QFutureWatcher::progressValueChanged(int progressValue)

    This signal is emitted when the watched future reports progress,
    \a progressValue gives the current progress. In order to avoid overloading
    the GUI event loop, QFutureWatcher limits the progress signal emission
    rate. This means that listeners connected to this slot might not get all
    progress reports the future makes. The last progress update (where
    \a progressValue equals the maximum value) will always be delivered.
*/

/*! \fn void QFutureWatcher::progressTextChanged(const QString &progressText)

    This signal is emitted when the watched future reports textual progress
    information, \a progressText.
*/

/*!
    \fn void QFutureWatcher::resultReadyAt(int index)

    This signal is emitted when the watched future reports a ready result at
    \a index. If the future reports multiple results, the index will indicate
    which one it is. Results can be reported out-of-order. To get the result,
    call future().result(index);
*/

/*!
    \fn void QFutureWatcher::resultsReadyAt(int beginIndex, int endIndex);

    This signal is emitted when the watched future reports ready results.
    The results are indexed from \a beginIndex to \a endIndex.

*/

QT_END_NAMESPACE

#else

// On Symbian winscw target QT_NO_QFUTURE and QT_NO_CONCURRENT are both defined.
// However moc will be run without having them set, so provide a dummy stub at
// least for the slots to prevent linker errors.

void QFutureWatcherBase::cancel() { }
void QFutureWatcherBase::setPaused(bool) { }
void QFutureWatcherBase::pause() { }
void QFutureWatcherBase::resume() { }
void QFutureWatcherBase::togglePaused() { }
bool QFutureWatcherBase::event(QEvent *) { return false; }
void QFutureWatcherBase::connectNotify(const char *) { }
void QFutureWatcherBase::disconnectNotify(const char *) { }

#endif // QT_NO_QFUTURE

#include "moc_qfuturewatcher.h"