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**
** Copyright (C) 2020 The Qt Company Ltd.
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**
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**
** $QT_BEGIN_LICENSE:LGPL$
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** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
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** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
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** included in the packaging of this file. Please review the following
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****************************************************************************/

// qfutureinterface.h included from qfuture.h
#include "qfuture.h"
#include "qfutureinterface_p.h"

#include <QtCore/qatomic.h>
#include <QtCore/qthread.h>
#include <private/qthreadpool_p.h>

#ifdef interface
#  undef interface
#endif

QT_BEGIN_NAMESPACE

enum {
    MaxProgressEmitsPerSecond = 25
};

namespace {
class ThreadPoolThreadReleaser {
    QThreadPool *m_pool;
public:
    explicit ThreadPoolThreadReleaser(QThreadPool *pool)
        : m_pool(pool)
    { if (pool) pool->releaseThread(); }
    ~ThreadPoolThreadReleaser()
    { if (m_pool) m_pool->reserveThread(); }
};

const auto suspendingOrSuspended =
        QFutureInterfaceBase::Suspending | QFutureInterfaceBase::Suspended;

} // unnamed namespace

QFutureCallOutInterface::~QFutureCallOutInterface()
    = default;

QFutureInterfaceBase::QFutureInterfaceBase(State initialState)
    : d(new QFutureInterfaceBasePrivate(initialState))
{ }

QFutureInterfaceBase::QFutureInterfaceBase(const QFutureInterfaceBase &other)
    : d(other.d)
{
    d->refCount.ref();
}

QFutureInterfaceBase::~QFutureInterfaceBase()
{
    if (d && !d->refCount.deref())
        delete d;
}

static inline int switch_on(QAtomicInt &a, int which)
{
    return a.fetchAndOrRelaxed(which) | which;
}

static inline int switch_off(QAtomicInt &a, int which)
{
    return a.fetchAndAndRelaxed(~which) & ~which;
}

static inline int switch_from_to(QAtomicInt &a, int from, int to)
{
    int newValue;
    int expected = a.loadRelaxed();
    do {
        newValue = (expected & ~from) | to;
    } while (!a.testAndSetRelaxed(expected, newValue, expected));
    return newValue;
}

void QFutureInterfaceBase::cancel()
{
    cancel(CancelMode::CancelOnly);
}

void QFutureInterfaceBase::cancel(QFutureInterfaceBase::CancelMode mode)
{
    QMutexLocker locker(&d->m_mutex);

    const auto oldState = d->state.loadRelaxed();

    switch (mode) {
    case CancelMode::CancelAndFinish:
        if ((oldState & Finished) && (oldState & Canceled))
            return;
        switch_from_to(d->state, suspendingOrSuspended | Running, Canceled | Finished);
        break;
    case CancelMode::CancelOnly:
        if (oldState & Canceled)
            return;
        switch_from_to(d->state, suspendingOrSuspended, Canceled);
        break;
    }

    d->waitCondition.wakeAll();
    d->pausedWaitCondition.wakeAll();

    if (!(oldState & Canceled))
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Canceled));
    if (mode == CancelMode::CancelAndFinish && !(oldState & Finished))
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Finished));

    d->isValid = false;
}

void QFutureInterfaceBase::setSuspended(bool suspend)
{
    QMutexLocker locker(&d->m_mutex);
    if (suspend) {
        switch_on(d->state, Suspending);
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Suspending));
    } else {
        switch_off(d->state, suspendingOrSuspended);
        d->pausedWaitCondition.wakeAll();
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Resumed));
    }
}

void QFutureInterfaceBase::toggleSuspended()
{
    QMutexLocker locker(&d->m_mutex);
    if (d->state.loadRelaxed() & suspendingOrSuspended) {
        switch_off(d->state, suspendingOrSuspended);
        d->pausedWaitCondition.wakeAll();
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Resumed));
    } else {
        switch_on(d->state, Suspending);
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Suspending));
    }
}

void QFutureInterfaceBase::reportSuspended() const
{
    // Needs to be called when pause is in effect,
    // i.e. no more events will be reported.

    QMutexLocker locker(&d->m_mutex);
    const int state = d->state;
    if (!(state & Suspending) || (state & Suspended))
        return;

    switch_from_to(d->state, Suspending, Suspended);
    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Suspended));
}

void QFutureInterfaceBase::setThrottled(bool enable)
{
    QMutexLocker lock(&d->m_mutex);
    if (enable) {
        switch_on(d->state, Throttled);
    } else {
        switch_off(d->state, Throttled);
        if (!(d->state.loadRelaxed() & suspendingOrSuspended))
            d->pausedWaitCondition.wakeAll();
    }
}


bool QFutureInterfaceBase::isRunning() const
{
    return queryState(Running);
}

bool QFutureInterfaceBase::isStarted() const
{
    return queryState(Started);
}

bool QFutureInterfaceBase::isCanceled() const
{
    return queryState(Canceled);
}

bool QFutureInterfaceBase::isFinished() const
{
    return queryState(Finished);
}

bool QFutureInterfaceBase::isSuspending() const
{
    return queryState(Suspending);
}

#if QT_DEPRECATED_SINCE(6, 0)
bool QFutureInterfaceBase::isPaused() const
{
    return queryState(static_cast<State>(suspendingOrSuspended));
}
#endif

bool QFutureInterfaceBase::isSuspended() const
{
    return queryState(Suspended);
}

bool QFutureInterfaceBase::isThrottled() const
{
    return queryState(Throttled);
}

bool QFutureInterfaceBase::isResultReadyAt(int index) const
{
    QMutexLocker lock(&d->m_mutex);
    return d->internal_isResultReadyAt(index);
}

bool QFutureInterfaceBase::isValid() const
{
    const QMutexLocker lock(&d->m_mutex);
    return d->isValid;
}

bool QFutureInterfaceBase::isRunningOrPending() const
{
    return queryState(static_cast<State>(Running | Pending));
}

bool QFutureInterfaceBase::waitForNextResult()
{
    QMutexLocker lock(&d->m_mutex);
    return d->internal_waitForNextResult();
}

void QFutureInterfaceBase::waitForResume()
{
    // return early if possible to avoid taking the mutex lock.
    {
        const int state = d->state.loadRelaxed();
        if (!(state & suspendingOrSuspended) || (state & Canceled))
            return;
    }

    QMutexLocker lock(&d->m_mutex);
    const int state = d->state.loadRelaxed();
    if (!(state & suspendingOrSuspended) || (state & Canceled))
        return;

    // decrease active thread count since this thread will wait.
    const ThreadPoolThreadReleaser releaser(d->pool());

    d->pausedWaitCondition.wait(&d->m_mutex);
}

void QFutureInterfaceBase::suspendIfRequested()
{
    const auto canSuspend = [] (int state) {
        // can suspend only if 1) in any suspend-related state; 2) not canceled
        return (state & suspendingOrSuspended) && !(state & Canceled);
    };

    // return early if possible to avoid taking the mutex lock.
    {
        const int state = d->state.loadRelaxed();
        if (!canSuspend(state))
            return;
    }

    QMutexLocker lock(&d->m_mutex);
    const int state = d->state.loadRelaxed();
    if (!canSuspend(state))
        return;

    // Note: expecting that Suspending and Suspended are mutually exclusive
    if (!(state & Suspended)) {
        // switch state in case this is the first invocation
        switch_from_to(d->state, Suspending, Suspended);
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Suspended));
    }

    // decrease active thread count since this thread will wait.
    const ThreadPoolThreadReleaser releaser(d->pool());
    d->pausedWaitCondition.wait(&d->m_mutex);
}

int QFutureInterfaceBase::progressValue() const
{
    const QMutexLocker lock(&d->m_mutex);
    return d->m_progressValue;
}

int QFutureInterfaceBase::progressMinimum() const
{
    const QMutexLocker lock(&d->m_mutex);
    return d->m_progress ? d->m_progress->minimum : 0;
}

int QFutureInterfaceBase::progressMaximum() const
{
    const QMutexLocker lock(&d->m_mutex);
    return d->m_progress ? d->m_progress->maximum : 0;
}

int QFutureInterfaceBase::resultCount() const
{
    QMutexLocker lock(&d->m_mutex);
    return d->internal_resultCount();
}

QString QFutureInterfaceBase::progressText() const
{
    QMutexLocker locker(&d->m_mutex);
    return d->m_progress ? d->m_progress->text : QString();
}

bool QFutureInterfaceBase::isProgressUpdateNeeded() const
{
    QMutexLocker locker(&d->m_mutex);
    return !d->progressTime.isValid() || (d->progressTime.elapsed() > (1000 / MaxProgressEmitsPerSecond));
}

void QFutureInterfaceBase::reportStarted()
{
    QMutexLocker locker(&d->m_mutex);
    if (d->state.loadRelaxed() & (Started|Canceled|Finished))
        return;
    d->setState(State(Started | Running));
    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Started));
    d->isValid = true;
}

void QFutureInterfaceBase::reportCanceled()
{
    cancel();
}

#ifndef QT_NO_EXCEPTIONS
void QFutureInterfaceBase::reportException(const QException &exception)
{
    try {
        exception.raise();
    } catch (...) {
        reportException(std::current_exception());
    }
}

#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
void QFutureInterfaceBase::reportException(std::exception_ptr exception)
#else
void QFutureInterfaceBase::reportException(const std::exception_ptr &exception)
#endif
{
    QMutexLocker locker(&d->m_mutex);
    if (d->state.loadRelaxed() & (Canceled|Finished))
        return;

    d->hasException = true;
    d->data.setException(exception);
    switch_on(d->state, Canceled);
    d->waitCondition.wakeAll();
    d->pausedWaitCondition.wakeAll();
    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Canceled));
}
#endif

void QFutureInterfaceBase::reportFinished()
{
    QMutexLocker locker(&d->m_mutex);
    if (!isFinished()) {
        switch_from_to(d->state, Running, Finished);
        d->waitCondition.wakeAll();
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Finished));
    }
}

void QFutureInterfaceBase::setExpectedResultCount(int resultCount)
{
    if (d->m_progress)
        setProgressRange(0, resultCount);
    d->m_expectedResultCount = resultCount;
}

int QFutureInterfaceBase::expectedResultCount()
{
    return d->m_expectedResultCount;
}

bool QFutureInterfaceBase::queryState(State state) const
{
    return d->state.loadRelaxed() & state;
}

int QFutureInterfaceBase::loadState() const
{
    // Used from ~QPromise, so this check is needed
    if (!d)
        return QFutureInterfaceBase::State::NoState;
    return d->state.loadRelaxed();
}

void QFutureInterfaceBase::waitForResult(int resultIndex)
{
    if (d->hasException)
        d->data.m_exceptionStore.rethrowException();

    QMutexLocker lock(&d->m_mutex);
    if (!isRunningOrPending())
        return;
    lock.unlock();

    // To avoid deadlocks and reduce the number of threads used, try to
    // run the runnable in the current thread.
    d->pool()->d_func()->stealAndRunRunnable(d->runnable);

    lock.relock();

    const int waitIndex = (resultIndex == -1) ? INT_MAX : resultIndex;
    while (isRunningOrPending() && !d->internal_isResultReadyAt(waitIndex))
        d->waitCondition.wait(&d->m_mutex);

    if (d->hasException)
        d->data.m_exceptionStore.rethrowException();
}

void QFutureInterfaceBase::waitForFinished()
{
    QMutexLocker lock(&d->m_mutex);
    const bool alreadyFinished = isFinished();
    lock.unlock();

    if (!alreadyFinished) {
        d->pool()->d_func()->stealAndRunRunnable(d->runnable);

        lock.relock();

        while (!isFinished())
            d->waitCondition.wait(&d->m_mutex);
    }

    if (d->hasException)
        d->data.m_exceptionStore.rethrowException();
}

void QFutureInterfaceBase::reportResultsReady(int beginIndex, int endIndex)
{
    if (beginIndex == endIndex || (d->state.loadRelaxed() & (Canceled|Finished)))
        return;

    d->waitCondition.wakeAll();

    if (!d->m_progress) {
        if (d->internal_updateProgressValue(d->m_progressValue + endIndex - beginIndex) == false) {
            d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::ResultsReady,
                                               beginIndex,
                                               endIndex));
            return;
        }

        d->sendCallOuts(QFutureCallOutEvent(QFutureCallOutEvent::Progress,
                                            d->m_progressValue,
                                            QString()),
                        QFutureCallOutEvent(QFutureCallOutEvent::ResultsReady,
                                            beginIndex,
                                            endIndex));
        return;
    }
    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::ResultsReady, beginIndex, endIndex));
}

void QFutureInterfaceBase::setRunnable(QRunnable *runnable)
{
    d->runnable = runnable;
}

void QFutureInterfaceBase::setThreadPool(QThreadPool *pool)
{
    d->m_pool = pool;
}

QThreadPool *QFutureInterfaceBase::threadPool() const
{
    return d->m_pool;
}

void QFutureInterfaceBase::setFilterMode(bool enable)
{
    QMutexLocker locker(&d->m_mutex);
    if (!hasException())
        resultStoreBase().setFilterMode(enable);
}

/*!
    \internal
    Sets the progress range's minimum and maximum values to \a minimum and
    \a maximum respectively.

    If \a maximum is smaller than \a minimum, \a minimum becomes the only
    legal value.

    The progress value is reset to be \a minimum.

    The progress range usage can be disabled by using setProgressRange(0, 0).
    In this case progress value is also reset to 0.

    The behavior of this method is mostly inspired by
    \l QProgressBar::setRange.
*/
void QFutureInterfaceBase::setProgressRange(int minimum, int maximum)
{
    QMutexLocker locker(&d->m_mutex);
    if (!d->m_progress)
        d->m_progress.reset(new QFutureInterfaceBasePrivate::ProgressData());
    d->m_progress->minimum = minimum;
    d->m_progress->maximum = qMax(minimum, maximum);
    d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::ProgressRange, minimum, maximum));
    d->m_progressValue = minimum;
}

void QFutureInterfaceBase::setProgressValue(int progressValue)
{
    setProgressValueAndText(progressValue, QString());
}

/*!
    \internal
    In case of the \a progressValue falling out of the progress range,
    this method has no effect.
    Such behavior is inspired by \l QProgressBar::setValue.
*/
void QFutureInterfaceBase::setProgressValueAndText(int progressValue,
                                                   const QString &progressText)
{
    QMutexLocker locker(&d->m_mutex);
    if (!d->m_progress)
        d->m_progress.reset(new QFutureInterfaceBasePrivate::ProgressData());

    const bool useProgressRange = (d->m_progress->maximum != 0) || (d->m_progress->minimum != 0);
    if (useProgressRange
        && ((progressValue < d->m_progress->minimum) || (progressValue > d->m_progress->maximum))) {
        return;
    }

    if (d->m_progressValue >= progressValue)
        return;

    if (d->state.loadRelaxed() & (Canceled|Finished))
        return;

    if (d->internal_updateProgress(progressValue, progressText)) {
        d->sendCallOut(QFutureCallOutEvent(QFutureCallOutEvent::Progress,
                                           d->m_progressValue,
                                           d->m_progress->text));
    }
}

QMutex &QFutureInterfaceBase::mutex() const
{
    return d->m_mutex;
}

bool QFutureInterfaceBase::hasException() const
{
    return d->hasException;
}

QtPrivate::ExceptionStore &QFutureInterfaceBase::exceptionStore()
{
    Q_ASSERT(d->hasException);
    return d->data.m_exceptionStore;
}

QtPrivate::ResultStoreBase &QFutureInterfaceBase::resultStoreBase()
{
    Q_ASSERT(!d->hasException);
    return d->data.m_results;
}

const QtPrivate::ResultStoreBase &QFutureInterfaceBase::resultStoreBase() const
{
    Q_ASSERT(!d->hasException);
    return d->data.m_results;
}

QFutureInterfaceBase &QFutureInterfaceBase::operator=(const QFutureInterfaceBase &other)
{
    QFutureInterfaceBase copy(other);
    swap(copy);
    return *this;
}

// ### Qt 7: inline
void QFutureInterfaceBase::swap(QFutureInterfaceBase &other) noexcept
{
    qSwap(d, other.d);
}

bool QFutureInterfaceBase::refT() const noexcept
{
    return d->refCount.refT();
}

bool QFutureInterfaceBase::derefT() const noexcept
{
    // Called from ~QFutureInterface
    return !d || d->refCount.derefT();
}

void QFutureInterfaceBase::reset()
{
    d->m_progressValue = 0;
    d->m_progress.reset();
    d->setState(QFutureInterfaceBase::NoState);
    d->progressTime.invalidate();
    d->isValid = false;
}

void QFutureInterfaceBase::rethrowPossibleException()
{
    if (hasException())
        exceptionStore().rethrowException();
}

QFutureInterfaceBasePrivate::QFutureInterfaceBasePrivate(QFutureInterfaceBase::State initialState)
    : state(initialState)
{
    progressTime.invalidate();
}

QFutureInterfaceBasePrivate::~QFutureInterfaceBasePrivate()
{
    if (hasException)
        data.m_exceptionStore.~ExceptionStore();
    else
        data.m_results.~ResultStoreBase();
}

int QFutureInterfaceBasePrivate::internal_resultCount() const
{
    return hasException ? 0 : data.m_results.count(); // ### subtract canceled results.
}

bool QFutureInterfaceBasePrivate::internal_isResultReadyAt(int index) const
{
    return hasException ? false : (data.m_results.contains(index));
}

bool QFutureInterfaceBasePrivate::internal_waitForNextResult()
{
    if (hasException)
        return false;

    if (data.m_results.hasNextResult())
        return true;

    while ((state.loadRelaxed() & QFutureInterfaceBase::Running)
           && data.m_results.hasNextResult() == false)
        waitCondition.wait(&m_mutex);

    return !(state.loadRelaxed() & QFutureInterfaceBase::Canceled)
            && data.m_results.hasNextResult();
}

bool QFutureInterfaceBasePrivate::internal_updateProgressValue(int progress)
{
    if (m_progressValue >= progress)
        return false;

    m_progressValue = progress;

    if (progressTime.isValid() && m_progressValue != 0) // make sure the first and last steps are emitted.
        if (progressTime.elapsed() < (1000 / MaxProgressEmitsPerSecond))
            return false;

    progressTime.start();
    return true;

}

bool QFutureInterfaceBasePrivate::internal_updateProgress(int progress,
                                                          const QString &progressText)
{
    if (m_progressValue >= progress)
        return false;

    Q_ASSERT(m_progress);

    m_progressValue = progress;
    m_progress->text = progressText;

    if (progressTime.isValid() && m_progressValue != m_progress->maximum) // make sure the first and last steps are emitted.
        if (progressTime.elapsed() < (1000 / MaxProgressEmitsPerSecond))
            return false;

    progressTime.start();
    return true;
}

void QFutureInterfaceBasePrivate::internal_setThrottled(bool enable)
{
    // bail out if we are not changing the state
    if ((enable && (state.loadRelaxed() & QFutureInterfaceBase::Throttled))
        || (!enable && !(state.loadRelaxed() & QFutureInterfaceBase::Throttled)))
        return;

    // change the state
    if (enable) {
        switch_on(state, QFutureInterfaceBase::Throttled);
    } else {
        switch_off(state, QFutureInterfaceBase::Throttled);
        if (!(state.loadRelaxed() & suspendingOrSuspended))
            pausedWaitCondition.wakeAll();
    }
}

void QFutureInterfaceBasePrivate::sendCallOut(const QFutureCallOutEvent &callOutEvent)
{
    if (outputConnections.isEmpty())
        return;

    for (int i = 0; i < outputConnections.count(); ++i)
        outputConnections.at(i)->postCallOutEvent(callOutEvent);
}

void QFutureInterfaceBasePrivate::sendCallOuts(const QFutureCallOutEvent &callOutEvent1,
                                     const QFutureCallOutEvent &callOutEvent2)
{
    if (outputConnections.isEmpty())
        return;

    for (int i = 0; i < outputConnections.count(); ++i) {
        QFutureCallOutInterface *interface = outputConnections.at(i);
        interface->postCallOutEvent(callOutEvent1);
        interface->postCallOutEvent(callOutEvent2);
    }
}

// This function connects an output interface (for example a QFutureWatcher)
// to this future. While holding the lock we check the state and ready results
// and add the appropriate callouts to the queue. In order to avoid deadlocks,
// the actual callouts are made at the end while not holding the lock.
void QFutureInterfaceBasePrivate::connectOutputInterface(QFutureCallOutInterface *interface)
{
    QMutexLocker locker(&m_mutex);

    const auto currentState = state.loadRelaxed();
    if (currentState & QFutureInterfaceBase::Started) {
        interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Started));
        if (m_progress) {
            interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::ProgressRange,
                                                            m_progress->minimum,
                                                            m_progress->maximum));
            interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Progress,
                                                            m_progressValue,
                                                            m_progress->text));
        } else {
            interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::ProgressRange,
                                                            0,
                                                            0));
            interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Progress,
                                                            m_progressValue,
                                                            QString()));
        }
    }

    if (!hasException) {
        QtPrivate::ResultIteratorBase it = data.m_results.begin();
        while (it != data.m_results.end()) {
            const int begin = it.resultIndex();
            const int end = begin + it.batchSize();
            interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::ResultsReady,
                                                            begin,
                                                            end));
            it.batchedAdvance();
        }
    }

    if (currentState & QFutureInterfaceBase::Suspended)
        interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Suspended));
    else if (currentState & QFutureInterfaceBase::Suspending)
        interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Suspending));

    if (currentState & QFutureInterfaceBase::Canceled)
        interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Canceled));

    if (currentState & QFutureInterfaceBase::Finished)
        interface->postCallOutEvent(QFutureCallOutEvent(QFutureCallOutEvent::Finished));

    outputConnections.append(interface);
}

void QFutureInterfaceBasePrivate::disconnectOutputInterface(QFutureCallOutInterface *interface)
{
    QMutexLocker lock(&m_mutex);
    const int index = outputConnections.indexOf(interface);
    if (index == -1)
        return;
    outputConnections.removeAt(index);

    interface->callOutInterfaceDisconnected();
}

void QFutureInterfaceBasePrivate::setState(QFutureInterfaceBase::State newState)
{
    state.storeRelaxed(newState);
}

void QFutureInterfaceBase::setContinuation(std::function<void(const QFutureInterfaceBase &)> func)
{
    setContinuation(std::move(func), nullptr);
}

void QFutureInterfaceBase::setContinuation(std::function<void(const QFutureInterfaceBase &)> func,
                                           QFutureInterfaceBasePrivate *continuationFutureData)
{
    QMutexLocker lock(&d->continuationMutex);

    if (continuationFutureData)
        continuationFutureData->parentData = d;

    // If the state is ready, run continuation immediately,
    // otherwise save it for later.
    if (isFinished()) {
        lock.unlock();
        func(*this);
    } else {
        d->continuation = std::move(func);
    }
}

void QFutureInterfaceBase::cleanContinuation()
{
    if (!d)
        return;

    // This is called when the associated QPromise is being destroyed.
    // Clear the continuation, to make sure it doesn't keep any ref-counted
    // copies of this, so that the allocated memory can be freed.
    QMutexLocker lock(&d->continuationMutex);
    d->continuation = nullptr;
}

void QFutureInterfaceBase::runContinuation() const
{
    QMutexLocker lock(&d->continuationMutex);
    if (d->continuation) {
        auto fn = std::exchange(d->continuation, nullptr);
        lock.unlock();
        fn(*this);
    }
}

bool QFutureInterfaceBase::isChainCanceled() const
{
    if (isCanceled())
        return true;

    auto parent = d->parentData;
    while (parent) {
        // If the future is in Canceled state because it had an exception, we want to
        // continue checking the chain of parents for cancellation, otherwise if the exception
        // is handeled inside the chain, it won't be interrupted even though cancellation has
        // been requested.
        if ((parent->state.loadRelaxed() & Canceled) && !parent->hasException)
            return true;
        parent = parent->parentData;
    }
    return false;
}

void QFutureInterfaceBase::setLaunchAsync(bool value)
{
    d->launchAsync = value;
}

bool QFutureInterfaceBase::launchAsync() const
{
    return d->launchAsync;
}

QT_END_NAMESPACE