qffmpegplaybackengineobject_p.h

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QFFMPEGPLAYBACKENGINEOBJECT_P_H
#define QFFMPEGPLAYBACKENGINEOBJECT_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#include <QtCore/qatomic.h>
#include <QtCore/qthread.h>
#include <QtCore/qcoreevent.h>
#include <QtCore/qcoreapplication.h>
#include <QtMultimedia/qmediaplayer.h>
#include <QtFFmpegMediaPluginImpl/private/qffmpegplaybackenginedefs_p.h>
#include <QtFFmpegMediaPluginImpl/private/qffmpegplaybackutils_p.h>
 
#include <chrono>
#include <optional>
 
QT_BEGIN_NAMESPACE
 
class QChronoTimer;
 
namespace QFFmpeg {
 
class PlaybackEngineObject : public QObject
{
    Q_OBJECT
 
    static constexpr QEvent::Type FuncEventType = QEvent::User;
    class FuncEvent : public QEvent
    {
    public:
        FuncEvent() : QEvent(FuncEventType) { }
        virtual void invoke() = 0;
    };
 
    template <typename F>
    class FuncEventImpl final : public FuncEvent
    {
    public:
        explicit FuncEventImpl(F &&f) : m_func(std::forward<F>(f)) { }
        void invoke() override { m_func(); }
 
    private:
        std::decay_t<F> m_func;
    };
 
public:
    using TimePoint = SteadyClock::time_point;
    using TimePointOpt = std::optional<TimePoint>;
 
    explicit PlaybackEngineObject(const PlaybackEngineObjectID &id);
 
    ~PlaybackEngineObject() override;
 
    bool isPaused() const;
 
    bool isAtEnd() const;
 
    void kill();
 
    void setPaused(bool isPaused);
 
    quint64 objectID() const { return m_id.objectID; }
 
Q_SIGNALS:
    void atEnd(PlaybackEngineObjectID id);
 
    void error(QMediaPlayer::Error, const QString &errorString);
 
protected:
    bool event(QEvent *e) override;
 
    bool checkSessionID(quint64 sessionID) const { return sessionID == m_id.sessionID; }
 
    bool checkID(const PlaybackEngineObjectID &id) const
    {
        return checkSessionID(id.sessionID) && id.objectID == objectID();
    }
 
    const PlaybackEngineObjectID &id() const
    {
        Q_ASSERT(thread()->isCurrentThread());
        return m_id;
    }
 
    template <typename F>
    void updateSession(quint64 newID, F &&f)
    {
        m_invalidateCounter.fetch_add(1, std::memory_order_relaxed);
        invokePriorityMethod([f = std::forward<F>(f), this, newID]() {
            const int count = m_invalidateCounter.fetch_sub(1, std::memory_order_relaxed) - 1;
            Q_ASSERT(count >= 0);
            if (count)
                return;
 
            m_id.sessionID = newID;
            setAtEnd(false);
            f();
        });
    }
 
    template <typename F>
    void invokePriorityMethod(F &&f)
    {
        Q_ASSERT(!thread()->isCurrentThread());
        // Note, that the event loop takes ownership of the event
        QCoreApplication::postEvent(this, new FuncEventImpl<F>(std::forward<F>(f)),
                                    Qt::HighEventPriority);
    }
 
    QChronoTimer &timer();
 
    void scheduleNextStep();
 
    virtual void onPauseChanged();
 
    virtual bool canDoNextStep() const;
 
    virtual TimePoint nextTimePoint() const;
 
    void setAtEnd(bool isAtEnd);
 
    virtual void doNextStep() { }
 
private Q_SLOTS:
    void onTimeout();
 
private:
    enum class StepType : uint8_t { None, Timeout, Immediate };
 
    void doNextStep(StepType type);
 
    bool isValid() const { return m_invalidateCounter.load(std::memory_order_relaxed) == 0; }
 
    std::unique_ptr<QChronoTimer> m_timer;
 
    QAtomicInteger<bool> m_paused = true;
    QAtomicInteger<bool> m_atEnd = false;
    std::atomic_int m_invalidateCounter = 0;
    PlaybackEngineObjectID m_id;
 
    TimePointOpt m_nextTimePoint;
    TimePointOpt m_timePoint;
    StepType m_stepType = StepType::None;
};
} // namespace QFFmpeg
 
QT_END_NAMESPACE
 
#endif // QFFMPEGPLAYBACKENGINEOBJECT_P_H