Source/modules/webaudio/ScriptProcessorNode.h

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef ScriptProcessorNode_h
#define ScriptProcessorNode_h

#include "platform/audio/AudioBus.h"
#include "modules/webaudio/AudioNode.h"
#include "wtf/Forward.h"
#include "wtf/PassRefPtr.h"
#include "wtf/RefPtr.h"
#include "wtf/Vector.h"

namespace blink {

class AudioBuffer;
class AudioContext;

// ScriptProcessorNode is an AudioNode which allows for arbitrary synthesis or processing directly using JavaScript.
// The API allows for a variable number of inputs and outputs, although it must have at least one input or output.
// This basic implementation supports no more than one input and output.
// The "onaudioprocess" attribute is an event listener which will get called periodically with an AudioProcessingEvent which has
// AudioBuffers for each input and output.

class ScriptProcessorNode final : public AudioNode {
    DEFINE_WRAPPERTYPEINFO();
public:
    // bufferSize must be one of the following values: 256, 512, 1024, 2048, 4096, 8192, 16384.
    // This value controls how frequently the onaudioprocess event handler is called and how many sample-frames need to be processed each call.
    // Lower numbers for bufferSize will result in a lower (better) latency. Higher numbers will be necessary to avoid audio breakup and glitches.
    // The value chosen must carefully balance between latency and audio quality.
    static ScriptProcessorNode* create(AudioContext*, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels);

    virtual ~ScriptProcessorNode();

    // AudioNode
    virtual void dispose() override;
    virtual void process(size_t framesToProcess) override;
    virtual void initialize() override;
    virtual void uninitialize() override;

    size_t bufferSize() const { return m_bufferSize; }

    virtual void setChannelCount(unsigned long, ExceptionState&) override;
    virtual void setChannelCountMode(const String&, ExceptionState&) override;

    DEFINE_ATTRIBUTE_EVENT_LISTENER(audioprocess);

    void trace(Visitor*);

private:
    virtual double tailTime() const override;
    virtual double latencyTime() const override;

    ScriptProcessorNode(AudioContext*, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels);

    void fireProcessEvent();

    // Double buffering
    unsigned doubleBufferIndex() const { return m_doubleBufferIndex; }
    void swapBuffers() { m_doubleBufferIndex = 1 - m_doubleBufferIndex; }
    unsigned m_doubleBufferIndex;
    unsigned m_doubleBufferIndexForEvent;
    HeapVector<Member<AudioBuffer> > m_inputBuffers;
    HeapVector<Member<AudioBuffer> > m_outputBuffers;

    size_t m_bufferSize;
    unsigned m_bufferReadWriteIndex;

    unsigned m_numberOfInputChannels;
    unsigned m_numberOfOutputChannels;

    RefPtr<AudioBus> m_internalInputBus;
    // Synchronize process() with fireProcessEvent().
    mutable Mutex m_processEventLock;
};

} // namespace blink

#endif // ScriptProcessorNode_h