Source/WebCore/Modules/webaudio/AudioScheduledSourceNode.h

/*
 * Copyright (C) 2012 Google Inc. All rights reserved.
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 *     notice, this list of conditions and the following disclaimer in the
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 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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#pragma once

#include "ActiveDOMObject.h"
#include "AudioNode.h"

namespace WebCore {

class AudioScheduledSourceNode : public AudioNode, public ActiveDOMObject {
    WTF_MAKE_ISO_ALLOCATED(AudioScheduledSourceNode);
public:
    // These are the possible states an AudioScheduledSourceNode can be in:
    //
    // UNSCHEDULED_STATE - Initial playback state. Created, but not yet scheduled.
    // SCHEDULED_STATE - Scheduled to play but not yet playing.
    // PLAYING_STATE - Generating sound.
    // FINISHED_STATE - Finished generating sound.
    //
    // The state can only transition to the next state, except for the FINISHED_STATE which can
    // never be changed.
    enum PlaybackState {
        // These must be defined with the same names and values as in the .idl file.
        UNSCHEDULED_STATE = 0,
        SCHEDULED_STATE = 1,
        PLAYING_STATE = 2,
        FINISHED_STATE = 3
    };
    
    AudioScheduledSourceNode(AudioContext&, float sampleRate);

    ExceptionOr<void> startLater(double when);
    ExceptionOr<void> stopLater(double when);

    void didBecomeMarkedForDeletion() override;

    unsigned short playbackState() const { return static_cast<unsigned short>(m_playbackState); }
    bool isPlayingOrScheduled() const { return m_playbackState == PLAYING_STATE || m_playbackState == SCHEDULED_STATE; }
    bool hasFinished() const { return m_playbackState == FINISHED_STATE; }

protected:
    // Get frame information for the current time quantum.
    // We handle the transition into PLAYING_STATE and FINISHED_STATE here,
    // zeroing out portions of the outputBus which are outside the range of startFrame and endFrame.
    // Each frame time is relative to the context's currentSampleFrame().
    // quantumFrameOffset: Offset frame in this time quantum to start rendering.
    // nonSilentFramesToProcess: Number of frames rendering non-silence (will be <= quantumFrameSize).
    void updateSchedulingInfo(size_t quantumFrameSize, AudioBus& outputBus, size_t& quantumFrameOffset, size_t& nonSilentFramesToProcess);

    // Called when we have no more sound to play or the noteOff() time has been reached.
    virtual void finish();

    PlaybackState m_playbackState { UNSCHEDULED_STATE };

    RefPtr<PendingActivity<AudioScheduledSourceNode>> m_pendingActivity;
    // m_startTime is the time to start playing based on the context's timeline (0 or a time less than the context's current time means "now").
    double m_startTime { 0 }; // in seconds

    // m_endTime is the time to stop playing based on the context's timeline (0 or a time less than the context's current time means "now").
    // If it hasn't been set explicitly, then the sound will not stop playing (if looping) or will stop when the end of the AudioBuffer
    // has been reached.
    double m_endTime; // in seconds

    static const double UnknownTime;
};

} // namespace WebCore