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/****************************************************************************
**
** Copyright (C) 2020 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** 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
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef QPROMISE_H
#define QPROMISE_H
#include <QtCore/qglobal.h>
#include <QtCore/qfuture.h>
QT_REQUIRE_CONFIG(future);
QT_BEGIN_NAMESPACE
template<typename T>
class QPromise
{
static_assert (std::is_copy_constructible_v<T>
|| std::is_move_constructible_v<T>
|| std::is_same_v<T, void>,
"Type with copy or move constructors or type void is required");
public:
QPromise() = default;
Q_DISABLE_COPY(QPromise)
QPromise(QPromise<T> &&other) : d(other.d)
{
// In constructor, there's no need to perform swap(). Assign new
// QFutureInterface to other.d instead which is slightly cheaper.
other.d = QFutureInterface<T>();
}
QPromise& operator=(QPromise<T> &&other)
{
swap(other);
return *this;
}
~QPromise()
{
const int state = d.loadState();
// If QFutureInterface has no state, there is nothing to be done
if (state == static_cast<int>(QFutureInterfaceBase::State::NoState))
return;
// Otherwise, if computation is not finished at this point, cancel
// potential waits
if (!(state & QFutureInterfaceBase::State::Finished)) {
d.cancel();
reportFinished(); // required to finalize the state
}
}
// Core QPromise APIs
QFuture<T> future() const { return d.future(); }
template<typename U = T,
typename = QtPrivate::EnableForNonVoid<std::decay_t<U>>,
typename = QtPrivate::EnableIfSameOrConvertible<std::decay_t<U>, std::decay_t<T>>>
void addResult(U &&result, int index = -1)
{
d.reportResult(std::forward<U>(result), index);
}
#ifndef QT_NO_EXCEPTIONS
void setException(const QException &e) { d.reportException(e); }
void setException(std::exception_ptr e) { d.reportException(e); }
#endif
void reportStarted() { d.reportStarted(); }
void reportFinished() { d.reportFinished(); }
void suspendIfRequested() { d.suspendIfRequested(); }
bool isCanceled() const { return d.isCanceled(); }
// Progress methods
void setProgressRange(int minimum, int maximum) { d.setProgressRange(minimum, maximum); }
void setProgressValue(int progressValue) { d.setProgressValue(progressValue); }
void setProgressValueAndText(int progressValue, const QString &progressText)
{
d.setProgressValueAndText(progressValue, progressText);
}
private:
mutable QFutureInterface<T> d = QFutureInterface<T>();
void swap(QPromise<T> &other)
{
// Note: copy operations are expensive! They trigger several atomic
// reference counts
auto tmp = this->d;
this->d = other.d;
other.d = tmp;
}
};
QT_END_NAMESPACE
#endif // QPROMISE_H
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