qaudiosystem_platform_stream_support_p.h

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// Copyright (C) 2025 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 QAUDIOSYSTEM_PLATFORM_STREAM_SUPPORT_P_H
#define QAUDIOSYSTEM_PLATFORM_STREAM_SUPPORT_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 <QtMultimedia/private/qaudio_qiodevice_support_p.h>
#include <QtMultimedia/private/qaudiohelpers_p.h>
#include <QtMultimedia/private/qaudioringbuffer_p.h>
#include <QtMultimedia/private/qaudiosystem_p.h>
#include <QtMultimedia/private/qautoresetevent_p.h>
#include <QtMultimedia/qaudiodevice.h>
#include <QtMultimedia/qaudioformat.h>
#include <QtMultimedia/qtmultimediaglobal.h>
#include <QtCore/qscopedvaluerollback.h>
#include <QtCore/qthread.h>
 
#include <optional>
#include <variant>
 
QT_BEGIN_NAMESPACE
 
namespace QtPrivate {
class QIODeviceRingBufferWriterBase;
}
 
namespace QtMultimediaPrivate {
 
class QPlatformAudioIOStream
{
    template <typename T>
    using QAudioRingBuffer = QtPrivate::QAudioRingBuffer<T>;
 
    using Ringbuffer = std::variant<QAudioRingBuffer<float>, QAudioRingBuffer<int32_t>,
                                    QAudioRingBuffer<int16_t>, QAudioRingBuffer<uint8_t>>;
 
public:
    static qsizetype inferRingbufferFrames(const std::optional<int> &ringbufferSize,
                                           const std::optional<NativePeriodFrames> &nativePeriodFrames,
                                           const QAudioFormat &);
    static qsizetype inferRingbufferBytes(const std::optional<int> &ringbufferSize,
                                          const std::optional<NativePeriodFrames> &nativePeriodFrames,
                                          const QAudioFormat &);
 
protected:
    using NativeSampleFormat = QAudioHelperInternal::NativeSampleFormat;
    using QAutoResetEvent = QtPrivate::QAutoResetEvent;
 
    QPlatformAudioIOStream(QAudioDevice m_audioDevice, QAudioFormat m_format,
                           std::optional<int> ringbufferSize,
                           std::optional<NativePeriodFrames> nativePeriodFrames, float volume);
    ~QPlatformAudioIOStream();
    Q_DISABLE_COPY_MOVE(QPlatformAudioIOStream)
 
    void setVolume(float);
    float volume() const { return m_volume.load(std::memory_order_relaxed); }
 
    template <typename Functor>
    auto visitRingbuffer(Functor &&f)
    {
        return std::visit(f, m_ringbuffer);
    }
 
    template <typename Functor>
    auto visitRingbuffer(Functor &&f) const
    {
        return std::visit(f, m_ringbuffer);
    }
 
    void prepareRingbuffer(std::optional<int> ringbufferSize);
    int ringbufferSizeInBytes();
 
    // stop requests
    void requestStop();
    bool isStopRequested(std::memory_order memory_order = std::memory_order_relaxed) const
    {
        return m_stopRequested.load(memory_order);
    }
 
    // members
    const QAudioDevice m_audioDevice;
    const QAudioFormat m_format;
    const std::optional<NativePeriodFrames> m_nativePeriodFrames;
 
private:
    std::atomic<float> m_volume{
        1.f,
    };
 
    Ringbuffer m_ringbuffer{
        std::in_place_type_t<QAudioRingBuffer<float>>{},
        0,
    };
 
    // stop requests
    std::atomic<bool> m_stopRequested = false;
 
public:
    enum class ShutdownPolicy : uint8_t
    {
        DrainRingbuffer,
        DiscardRingbuffer,
    };
};
 
////////////////////////////////////////////////////////////////////////////////////////////////////
 
class QPlatformAudioSinkStream : protected QPlatformAudioIOStream
{
public:
    using QPlatformAudioIOStream::ShutdownPolicy;
    using AudioCallback = QPlatformAudioSink::AudioCallback;
 
    using QPlatformAudioIOStream::requestStop;
 
protected:
    QPlatformAudioSinkStream(QAudioDevice, const QAudioFormat &, std::optional<int> ringbufferSize,
                             std::optional<NativePeriodFrames> nativePeriodFrames, float volume);
    ~QPlatformAudioSinkStream();
    Q_DISABLE_COPY_MOVE(QPlatformAudioSinkStream)
 
    uint64_t process(QSpan<std::byte> hostBuffer, qsizetype totalNumberOfFrames,
                     std::optional<NativeSampleFormat> = {}) noexcept Q_DECL_NONBLOCKING_FUNCTION;
 
    // ringbuffer / stats
    quint64 bytesFree() const;
    std::chrono::microseconds processedDuration() const;
 
    // downstream delegates
    virtual void updateStreamIdle(bool) = 0;
 
    // iodevice
    QIODevice *createRingbufferWriterDevice();
    void setQIODevice(QIODevice *device);
    void createQIODeviceConnections(QIODevice *device);
    void disconnectQIODeviceConnections();
    void pullFromQIODevice();
 
    // LATER: do we want to relax notifying the app thread?
    static constexpr int notificationThresholdBytes = 0;
 
    // idle detection
    void setIdleState(bool);
    bool isIdle(std::memory_order order = std::memory_order_relaxed) const
    {
        return m_streamIsIdle.load(order);
    }
    void stopIdleDetection();
 
    template <typename Functor>
    auto connectIdleHandler(Functor &&f)
    {
        return m_streamIdleDetectionNotifier.callOnActivated(std::forward<Functor>(f));
    }
 
    template <typename ParentType>
    void handleIOError(ParentType *parent)
    {
        if (parent) {
            Q_ASSERT(thread()->isCurrentThread());
            parent->m_stream = {};
            parent->setError(QAudio::IOError);
            parent->updateStreamState(QtAudio::State::StoppedState);
        }
    }
 
    QThread *thread() const;
 
    template <typename Functor>
    void invokeOnAppThread(Functor &&f)
    {
        // note: this is not a QObject, so we use the first QObject member of the stream as context
        QMetaObject::invokeMethod(&m_streamIdleDetectionNotifier, std::forward<Functor>(f));
    }
 
private:
    // qiodevice
    QIODevice *m_device = nullptr;
 
    // idle detection
    std::atomic<bool> m_streamIsIdle = false;
    QAutoResetEvent m_streamIdleDetectionNotifier;
    QMetaObject::Connection m_streamIdleDetectionConnection;
 
    // ringbuffer events
    QAutoResetEvent m_ringbufferHasSpace;
    QMetaObject::Connection m_ringbufferHasSpaceConnection;
    QMetaObject::Connection m_iodeviceHasNewDataConnection;
 
    std::unique_ptr<QtPrivate::QIODeviceRingBufferWriterBase> m_ringbufferWriterDevice;
 
    // stats
    std::atomic_int64_t m_totalFrameCount{};
    std::atomic_int64_t m_processedFrameCount{};
 
    void convertToNative(QSpan<const std::byte> internal, QSpan<std::byte> native, float volume,
                         NativeSampleFormat) noexcept Q_DECL_NONBLOCKING_FUNCTION;
 
    // pullFromQIODeviceToRingbuffer is not reentrant. however we might end up in situations where a
    // QIODevice emits readReady from within QIODevice::readData. We protect against this using a
    // reentrancy guard and queue invocations if we detect a reentrant call
    template <typename Functor>
    void withPullIODeviceReentrancyGuard(Functor f)
    {
        if (!m_pullIODeviceReentrancyGuard) {
            QScopedValueRollback<bool> guard{
                m_pullIODeviceReentrancyGuard,
                true,
            };
            f();
        } else {
            QMetaObject::invokeMethod(&m_streamIdleDetectionNotifier,
                                      [this, f = std::move(f)]() mutable {
                withPullIODeviceReentrancyGuard(std::move(f));
            }, Qt::QueuedConnection);
        }
    }
    bool m_pullIODeviceReentrancyGuard = false;
 
    void pullFromQIODeviceImpl();
};
 
////////////////////////////////////////////////////////////////////////////////////////////////////
 
class QPlatformAudioSourceStream : protected QPlatformAudioIOStream
{
public:
    using QPlatformAudioIOStream::ShutdownPolicy;
    using AudioCallback = QPlatformAudioSource::AudioCallback;
 
    using QPlatformAudioIOStream::requestStop;
 
protected:
    QPlatformAudioSourceStream(QAudioDevice, const QAudioFormat &,
                               std::optional<int> ringbufferSize,
                               std::optional<NativePeriodFrames> nativePeriodFrames, float volume);
    ~QPlatformAudioSourceStream();
 
    Q_DISABLE_COPY_MOVE(QPlatformAudioSourceStream)
 
    uint64_t process(QSpan<const std::byte> hostBuffer, qsizetype numberOfFrames,
                     std::optional<NativeSampleFormat> = {}) noexcept Q_DECL_NONBLOCKING_FUNCTION;
 
    // ringbuffer / stats
    qsizetype bytesReady() const;
    std::chrono::microseconds processedDuration() const;
 
    // iodevice
    void setQIODevice(QIODevice *device);
    void createQIODeviceConnections(QIODevice *device);
    void disconnectQIODeviceConnections();
    QIODevice *createRingbufferReaderDevice();
    void pushToIODevice();
    bool deviceIsRingbufferReader() const;
    void finalizeQIODevice(ShutdownPolicy);
    void emptyRingbuffer();
 
    // downstream delegates
    virtual void updateStreamIdle(bool) = 0;
 
    template <typename ParentType>
    void handleIOError(ParentType *parent)
    {
        if (parent) {
            Q_ASSERT(thread()->isCurrentThread());
 
            if (deviceIsRingbufferReader())
                // we own the qiodevice, so let's keep it alive to allow users to drain the
                // ringbuffer
                parent->m_retiredStream = std::move(parent->m_stream);
            else
                parent->m_stream = {};
 
            parent->setError(QAudio::IOError);
            parent->updateStreamState(QtAudio::State::StoppedState);
        }
    }
 
    QThread *thread() const;
 
    template <typename Functor>
    void invokeOnAppThread(Functor &&f)
    {
        // note: this is not a QObject, so we use the first QObject member of the stream as context
        QMetaObject::invokeMethod(&m_ringbufferHasData, std::forward<Functor>(f));
    }
 
private:
    // qiodevice
    QIODevice *m_device = nullptr;
    std::unique_ptr<QIODevice> m_ringbufferReaderDevice;
 
    // ringbuffer events
    QAutoResetEvent m_ringbufferHasData;
    QAutoResetEvent m_ringbufferIsFull;
 
    QMetaObject::Connection m_ringbufferHasDataConnection;
    QMetaObject::Connection m_ringbufferIsFullConnection;
 
    // stats
    std::atomic_uint64_t m_totalNumberOfFramesPushedToRingbuffer{};
 
    void convertFromNative(QSpan<const std::byte> native, QSpan<std::byte> internal, float volume,
                           NativeSampleFormat) noexcept Q_DECL_NONBLOCKING_FUNCTION;
};
 
} // namespace QtMultimediaPrivate
 
QT_END_NAMESPACE
 
#endif // QAUDIOSYSTEM_PLATFORM_STREAM_SUPPORT_P_H