Source/modules/webaudio/AudioScheduledSourceNode.h

/*
 * Copyright (C) 2012 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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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
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 */

#ifndef AudioScheduledSourceNode_h
#define AudioScheduledSourceNode_h

#include "modules/webaudio/AudioSourceNode.h"

namespace blink {

class AbstractAudioContext;
class AudioBus;

class AudioScheduledSourceHandler : public AudioHandler {
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 (via start()), 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
    };

    AudioScheduledSourceHandler(NodeType, AudioNode&, float sampleRate);

    // Scheduling.
    void start(double when, ExceptionState&);
    void stop(double when, ExceptionState&);

    PlaybackState playbackState() const
    {
        return static_cast<PlaybackState>(acquireLoad(&m_playbackState));
    }

    void setPlaybackState(PlaybackState newState)
    {
        releaseStore(&m_playbackState, newState);
    }

    bool isPlayingOrScheduled() const
    {
        PlaybackState state = playbackState();
        return state == PLAYING_STATE || state == SCHEDULED_STATE;
    }

    bool hasFinished() const
    {
        return playbackState() == FINISHED_STATE;
    }

    void setHasEndedListener() { m_hasEndedListener = true; }

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 stop() time has been reached. No onEnded
    // event is called.
    virtual void finishWithoutOnEnded();

    // Like finishWithoutOnEnded(), but an onEnded (if specified) is called.
    virtual void finish();

    void notifyEnded();

    // This synchronizes with process() and any other method that needs to be synchronized like
    // setBuffer for AudioBufferSource.
    mutable Mutex m_processLock;

    // 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; // 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

    bool m_hasEndedListener;

    static const double UnknownTime;
private:
    // This is accessed by both the main thread and audio thread.  Use the setter and getter to
    // protect the access to this!
    int m_playbackState;
};

class AudioScheduledSourceNode : public AudioSourceNode {
public:
    void start(ExceptionState&);
    void start(double when, ExceptionState&);
    void stop(ExceptionState&);
    void stop(double when, ExceptionState&);

    EventListener* onended();
    void setOnended(PassRefPtrWillBeRawPtr<EventListener>);

protected:
    explicit AudioScheduledSourceNode(AbstractAudioContext&);
    AudioScheduledSourceHandler& audioScheduledSourceHandler() const;
};

} // namespace blink

#endif // AudioScheduledSourceNode_h