third_party/WebKit/Source/modules/webaudio/AudioContext.cpp

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "modules/webaudio/AudioContext.h"

#include "bindings/core/v8/ExceptionMessages.h"
#include "bindings/core/v8/ExceptionState.h"
#include "bindings/core/v8/ScriptPromiseResolver.h"
#include "core/dom/DOMException.h"
#include "core/dom/ExceptionCode.h"
#include "core/frame/UseCounter.h"
#include "modules/webaudio/AudioBufferCallback.h"
#include "platform/Histogram.h"
#include "platform/audio/AudioUtilities.h"

#if DEBUG_AUDIONODE_REFERENCES
#include <stdio.h>
#endif

namespace blink {

// Don't allow more than this number of simultaneous AudioContexts
// talking to hardware.
const unsigned MaxHardwareContexts = 6;
static unsigned s_hardwareContextCount = 0;
static unsigned s_contextId = 0;

AudioContext* AudioContext::create(Document& document,
                                   ExceptionState& exceptionState) {
  DCHECK(isMainThread());

  UseCounter::countCrossOriginIframe(document,
                                     UseCounter::AudioContextCrossOriginIframe);

  if (s_hardwareContextCount >= MaxHardwareContexts) {
    exceptionState.throwDOMException(
        NotSupportedError, ExceptionMessages::indexExceedsMaximumBound(
                               "number of hardware contexts",
                               s_hardwareContextCount, MaxHardwareContexts));
    return nullptr;
  }

  AudioContext* audioContext = new AudioContext(document);
  audioContext->suspendIfNeeded();

  if (!AudioUtilities::isValidAudioBufferSampleRate(
          audioContext->sampleRate())) {
    exceptionState.throwDOMException(
        NotSupportedError,
        ExceptionMessages::indexOutsideRange(
            "hardware sample rate", audioContext->sampleRate(),
            AudioUtilities::minAudioBufferSampleRate(),
            ExceptionMessages::InclusiveBound,
            AudioUtilities::maxAudioBufferSampleRate(),
            ExceptionMessages::InclusiveBound));
    return audioContext;
  }
  // This starts the audio thread. The destination node's
  // provideInput() method will now be called repeatedly to render
  // audio.  Each time provideInput() is called, a portion of the
  // audio stream is rendered. Let's call this time period a "render
  // quantum". NOTE: for now AudioContext does not need an explicit
  // startRendering() call from JavaScript.  We may want to consider
  // requiring it for symmetry with OfflineAudioContext.
  audioContext->maybeUnlockUserGesture();
  if (audioContext->isAllowedToStart())
    audioContext->startRendering();
  ++s_hardwareContextCount;
#if DEBUG_AUDIONODE_REFERENCES
  fprintf(stderr, "[%16p]: AudioContext::AudioContext(): %u #%u\n",
          audioContext, audioContext->m_contextId, s_hardwareContextCount);
#endif

  DEFINE_STATIC_LOCAL(SparseHistogram, maxChannelCountHistogram,
                      ("WebAudio.AudioContext.MaxChannelsAvailable"));
  DEFINE_STATIC_LOCAL(SparseHistogram, sampleRateHistogram,
                      ("WebAudio.AudioContext.HardwareSampleRate"));
  maxChannelCountHistogram.sample(
      audioContext->destination()->maxChannelCount());
  sampleRateHistogram.sample(audioContext->sampleRate());

  return audioContext;
}

AudioContext::AudioContext(Document& document)
    : BaseAudioContext(&document), m_contextId(s_contextId++) {}

AudioContext::~AudioContext() {
#if DEBUG_AUDIONODE_REFERENCES
  fprintf(stderr, "[%16p]: AudioContext::~AudioContext(): %u\n", this,
          m_contextId);
#endif
}

DEFINE_TRACE(AudioContext) {
  visitor->trace(m_closeResolver);
  BaseAudioContext::trace(visitor);
}

ScriptPromise AudioContext::suspendContext(ScriptState* scriptState) {
  DCHECK(isMainThread());
  AutoLocker locker(this);

  ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
  ScriptPromise promise = resolver->promise();

  if (contextState() == Closed) {
    resolver->reject(DOMException::create(
        InvalidStateError, "Cannot suspend a context that has been closed"));
  } else {
    // Stop rendering now.
    if (destination())
      stopRendering();

    // Since we don't have any way of knowing when the hardware actually stops,
    // we'll just resolve the promise now.
    resolver->resolve();
  }

  return promise;
}

ScriptPromise AudioContext::resumeContext(ScriptState* scriptState) {
  DCHECK(isMainThread());

  if (isContextClosed()) {
    return ScriptPromise::rejectWithDOMException(
        scriptState,
        DOMException::create(InvalidAccessError,
                             "cannot resume a closed AudioContext"));
  }

  ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
  ScriptPromise promise = resolver->promise();

  // Restart the destination node to pull on the audio graph.
  if (destination()) {
    maybeUnlockUserGesture();
    if (isAllowedToStart())
      startRendering();
  }

  // Save the resolver which will get resolved when the destination node starts
  // pulling on the graph again.
  {
    AutoLocker locker(this);
    m_resumeResolvers.append(resolver);
  }

  return promise;
}

ScriptPromise AudioContext::closeContext(ScriptState* scriptState) {
  if (isContextClosed()) {
    // We've already closed the context previously, but it hasn't yet been
    // resolved, so just create a new promise and reject it.
    return ScriptPromise::rejectWithDOMException(
        scriptState,
        DOMException::create(InvalidStateError,
                             "Cannot close a context that is being closed or "
                             "has already been closed."));
  }

  // Save the current sample rate for any subsequent decodeAudioData calls.
  setClosedContextSampleRate(sampleRate());

  m_closeResolver = ScriptPromiseResolver::create(scriptState);
  ScriptPromise promise = m_closeResolver->promise();

  // Stop the audio context. This will stop the destination node from pulling
  // audio anymore. And since we have disconnected the destination from the
  // audio graph, and thus has no references, the destination node can GCed if
  // JS has no references. uninitialize() will also resolve the Promise created
  // here.
  uninitialize();

  return promise;
}

void AudioContext::didClose() {
  // This is specific to AudioContexts. OfflineAudioContexts
  // are closed in their completion event.
  setContextState(Closed);

  DCHECK(s_hardwareContextCount);
  --s_hardwareContextCount;

  if (m_closeResolver)
    m_closeResolver->resolve();
}

bool AudioContext::isContextClosed() const {
  return m_closeResolver || BaseAudioContext::isContextClosed();
}

void AudioContext::stopRendering() {
  DCHECK(isMainThread());
  DCHECK(destination());

  if (contextState() == Running) {
    destination()->audioDestinationHandler().stopRendering();
    setContextState(Suspended);
    deferredTaskHandler().clearHandlersToBeDeleted();
  }
}

}  // namespace blink