third_party/WebKit/Source/modules/webaudio/AudioNodeInput.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
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 */

#ifndef AudioNodeInput_h
#define AudioNodeInput_h

#include "modules/webaudio/AudioNode.h"
#include "modules/webaudio/AudioSummingJunction.h"
#include "platform/audio/AudioBus.h"
#include "wtf/Allocator.h"
#include "wtf/HashSet.h"
#include <memory>

namespace blink {

class AudioNodeOutput;

// An AudioNodeInput represents an input to an AudioNode and can be connected from one or more AudioNodeOutputs.
// In the case of multiple connections, the input will act as a unity-gain summing junction, mixing all the outputs.
// The number of channels of the input's bus is the maximum of the number of channels of all its connections.

class AudioNodeInput final : public AudioSummingJunction {
  USING_FAST_MALLOC(AudioNodeInput);

 public:
  static std::unique_ptr<AudioNodeInput> create(AudioHandler&);

  // AudioSummingJunction
  void didUpdate() override;

  // Can be called from any thread.
  AudioHandler& handler() const { return m_handler; }

  // Must be called with the context's graph lock.
  void connect(AudioNodeOutput&);
  void disconnect(AudioNodeOutput&);

  // disable() will take the output out of the active connections list and set aside in a disabled list.
  // enable() will put the output back into the active connections list.
  // Must be called with the context's graph lock.
  void enable(AudioNodeOutput&);
  void disable(AudioNodeOutput&);

  // pull() processes all of the AudioNodes connected to us.
  // In the case of multiple connections it sums the result into an internal summing bus.
  // In the single connection case, it allows in-place processing where possible using inPlaceBus.
  // It returns the bus which it rendered into, returning inPlaceBus if in-place processing was performed.
  // Called from context's audio thread.
  AudioBus* pull(AudioBus* inPlaceBus, size_t framesToProcess);

  // bus() contains the rendered audio after pull() has been called for each time quantum.
  // Called from context's audio thread.
  AudioBus* bus();

  // updateInternalBus() updates m_internalSummingBus appropriately for the number of channels.
  // This must be called when we own the context's graph lock in the audio thread at the very start or end of the render quantum.
  void updateInternalBus();

  // The number of channels of the connection with the largest number of channels.
  unsigned numberOfChannels() const;

 private:
  explicit AudioNodeInput(AudioHandler&);

  // This reference is safe because the AudioHandler owns this AudioNodeInput
  // object.
  AudioHandler& m_handler;

  // m_disabledOutputs contains the AudioNodeOutputs which are disabled (will
  // not be processed) by the audio graph rendering.  But, from JavaScript's
  // perspective, these outputs are still connected to us.
  // Generally, these represent disabled connections from "notes" which have
  // finished playing but are not yet garbage collected.
  // These raw pointers are safe. Owner AudioNodes of these AudioNodeOutputs
  // manage their lifetime, and AudioNode::dispose() disconnects all of
  // connections.
  HashSet<AudioNodeOutput*> m_disabledOutputs;

  // Called from context's audio thread.
  AudioBus* internalSummingBus();
  void sumAllConnections(AudioBus* summingBus, size_t framesToProcess);

  RefPtr<AudioBus> m_internalSummingBus;
};

}  // namespace blink

#endif  // AudioNodeInput_h