dom/media/MediaStreamGraphImpl.h
author Andreas Pehrson <apehrson@mozilla.com>
Mon, 02 Sep 2019 14:57:47 +0000
changeset 554859 8773fdb19225d595eb2f27ced37d50777a743a48
parent 554365 77e0581c780d8498501de568ac966d2c80d1fa76
child 554861 02bc71fde278c94227ad2f05503e72a96abb62b5
child 555858 66ac27810a9468232f174f0a298a03c6f7ac08d4
permissions -rw-r--r--
Bug 1577537 - Catch AppendMessage calls that could be too late. r=karlt a=lizzard If all streams and all ports have been destroyed, there's no guarantee that the graph is still alive. By forbidding AppendMessage calls after this point, we can catch bugs with the offending callsite still being in the stack. Differential Revision: https://phabricator.services.mozilla.com/D44223

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef MOZILLA_MEDIASTREAMGRAPHIMPL_H_
#define MOZILLA_MEDIASTREAMGRAPHIMPL_H_

#include "MediaStreamGraph.h"

#include "AudioMixer.h"
#include "GraphDriver.h"
#include "mozilla/Atomics.h"
#include "mozilla/Monitor.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/WeakPtr.h"
#include "nsClassHashtable.h"
#include "nsIMemoryReporter.h"
#include "nsINamed.h"
#include "nsIRunnable.h"
#include "nsIThread.h"
#include "nsITimer.h"
#include "AsyncLogger.h"

namespace mozilla {

namespace media {
class ShutdownTicket;
}

template <typename T>
class LinkedList;
class GraphRunner;

/**
 * A per-stream update message passed from the media graph thread to the
 * main thread.
 */
struct StreamUpdate {
  RefPtr<MediaStream> mStream;
  StreamTime mNextMainThreadCurrentTime;
  bool mNextMainThreadFinished;
};

/**
 * This represents a message run on the graph thread to modify stream or graph
 * state.  These are passed from main thread to graph thread through
 * AppendMessage(), or scheduled on the graph thread with
 * RunMessageAfterProcessing().  A ControlMessage
 * always has a weak reference to a particular affected stream.
 */
class ControlMessage {
 public:
  explicit ControlMessage(MediaStream* aStream) : mStream(aStream) {
    MOZ_COUNT_CTOR(ControlMessage);
  }
  // All these run on the graph thread
  virtual ~ControlMessage() { MOZ_COUNT_DTOR(ControlMessage); }
  // Do the action of this message on the MediaStreamGraph thread. Any actions
  // affecting graph processing should take effect at mProcessedTime.
  // All stream data for times < mProcessedTime has already been
  // computed.
  virtual void Run() = 0;
  // RunDuringShutdown() is only relevant to messages generated on the main
  // thread (for AppendMessage()).
  // When we're shutting down the application, most messages are ignored but
  // some cleanup messages should still be processed (on the main thread).
  // This must not add new control messages to the graph.
  virtual void RunDuringShutdown() {}
  MediaStream* GetStream() { return mStream; }

 protected:
  // We do not hold a reference to mStream. The graph will be holding
  // a reference to the stream until the Destroy message is processed. The
  // last message referencing a stream is the Destroy message for that stream.
  MediaStream* mStream;
};

class MessageBlock {
 public:
  nsTArray<UniquePtr<ControlMessage>> mMessages;
};

/**
 * The implementation of a media stream graph. This class is private to this
 * file. It's not in the anonymous namespace because MediaStream needs to
 * be able to friend it.
 *
 * There can be multiple MediaStreamGraph per process: one per document.
 * Additionaly, each OfflineAudioContext object creates its own MediaStreamGraph
 * object too.
 */
class MediaStreamGraphImpl : public MediaStreamGraph,
                             public nsIMemoryReporter,
                             public nsITimerCallback,
                             public nsINamed {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIMEMORYREPORTER
  NS_DECL_NSITIMERCALLBACK
  NS_DECL_NSINAMED

  /**
   * Use aGraphDriverRequested with SYSTEM_THREAD_DRIVER or AUDIO_THREAD_DRIVER
   * to create a MediaStreamGraph which provides support for real-time audio
   * and/or video.  Set it to OFFLINE_THREAD_DRIVER in order to create a
   * non-realtime instance which just churns through its inputs and produces
   * output.  Those objects currently only support audio, and are used to
   * implement OfflineAudioContext.  They do not support MediaStream inputs.
   */
  explicit MediaStreamGraphImpl(GraphDriverType aGraphDriverRequested,
                                GraphRunType aRunTypeRequested,
                                TrackRate aSampleRate, uint32_t aChannelCount,
                                AbstractThread* aWindow);

  // Intended only for assertions, either on graph thread or not running (in
  // which case we must be on the main thread).
  bool OnGraphThreadOrNotRunning() const override;
  bool OnGraphThread() const override;

  bool Destroyed() const override;

#ifdef DEBUG
  /**
   * True if we're on aDriver's thread, or if we're on mGraphRunner's thread
   * and mGraphRunner is currently run by aDriver.
   */
  bool RunByGraphDriver(GraphDriver* aDriver);
#endif

  /**
   * Unregisters memory reporting and deletes this instance. This should be
   * called instead of calling the destructor directly.
   */
  void Destroy();

  // Main thread only.
  /**
   * This runs every time we need to sync state from the media graph thread
   * to the main thread while the main thread is not in the middle
   * of a script. It runs during a "stable state" (per HTML5) or during
   * an event posted to the main thread.
   * The boolean affects which boolean controlling runnable dispatch is cleared
   */
  void RunInStableState(bool aSourceIsMSG);
  /**
   * Ensure a runnable to run RunInStableState is posted to the appshell to
   * run at the next stable state (per HTML5).
   * See EnsureStableStateEventPosted.
   */
  void EnsureRunInStableState();
  /**
   * Called to apply a StreamUpdate to its stream.
   */
  void ApplyStreamUpdate(StreamUpdate* aUpdate);
  /**
   * Append a ControlMessage to the message queue. This queue is drained
   * during RunInStableState; the messages will run on the graph thread.
   */
  void AppendMessage(UniquePtr<ControlMessage> aMessage);

  /**
   * Dispatches a runnable from any thread to the correct main thread for this
   * MediaStreamGraph.
   */
  void Dispatch(already_AddRefed<nsIRunnable>&& aRunnable);

  /**
   * Make this MediaStreamGraph enter forced-shutdown state. This state
   * will be noticed by the media graph thread, which will shut down all streams
   * and other state controlled by the media graph thread.
   * This is called during application shutdown.
   */
  void ForceShutDown(media::ShutdownTicket* aShutdownTicket);

  /**
   * Called before the thread runs.
   */
  void Init();

  /**
   * Respond to CollectReports with sizes collected on the graph thread.
   */
  static void FinishCollectReports(
      nsIHandleReportCallback* aHandleReport, nsISupports* aData,
      const nsTArray<AudioNodeSizes>& aAudioStreamSizes);

  // The following methods run on the graph thread (or possibly the main thread
  // if mLifecycleState > LIFECYCLE_RUNNING)
  void CollectSizesForMemoryReport(
      already_AddRefed<nsIHandleReportCallback> aHandleReport,
      already_AddRefed<nsISupports> aHandlerData);

  /**
   * Returns true if this MediaStreamGraph should keep running
   */
  bool UpdateMainThreadState();

  /**
   * Proxy method called by GraphDriver to iterate the graph.
   * If this graph was created with GraphRunType SINGLE_THREAD, mGraphRunner
   * will take care of calling OneIterationImpl from its thread. Otherwise,
   * OneIterationImpl is called directly.
   */
  bool OneIteration(GraphTime aStateEnd);

  /**
   * Returns true if this MediaStreamGraph should keep running
   */
  bool OneIterationImpl(GraphTime aStateEnd);

  /**
   * Called from the driver, when the graph thread is about to stop, to tell
   * the main thread to attempt to begin cleanup.  The main thread may either
   * shutdown or revive the graph depending on whether it receives new
   * messages.
   */
  void SignalMainThreadCleanup();

  /* This is the end of the current iteration, that is, the current time of the
   * graph. */
  GraphTime IterationEnd() const;

  /**
   * Ensure there is an event posted to the main thread to run RunInStableState.
   * mMonitor must be held.
   * See EnsureRunInStableState
   */
  void EnsureStableStateEventPosted();
  /**
   * Generate messages to the main thread to update it for all state changes.
   * mMonitor must be held.
   */
  void PrepareUpdatesToMainThreadState(bool aFinalUpdate);
  /**
   * If we are rendering in non-realtime mode, we don't want to send messages to
   * the main thread at each iteration for performance reasons. We instead
   * notify the main thread at the same rate
   */
  bool ShouldUpdateMainThread();
  // The following methods are the various stages of RunThread processing.
  /**
   * Advance all stream state to mStateComputedTime.
   */
  void UpdateCurrentTimeForStreams(GraphTime aPrevCurrentTime);
  /**
   * Process chunks for all streams and raise events for properties that have
   * changed, such as principalId.
   */
  void ProcessChunkMetadata(GraphTime aPrevCurrentTime);
  /**
   * Process chunks for the given stream and interval, and raise events for
   * properties that have changed, such as principalId.
   */
  template <typename C, typename Chunk>
  void ProcessChunkMetadataForInterval(MediaStream* aStream, TrackID aTrackID,
                                       C& aSegment, StreamTime aStart,
                                       StreamTime aEnd);
  /**
   * Process graph messages in mFrontMessageQueue.
   */
  void RunMessagesInQueue();
  /**
   * Update stream processing order and recompute stream blocking until
   * aEndBlockingDecisions.
   */
  void UpdateGraph(GraphTime aEndBlockingDecisions);

  void SwapMessageQueues() {
    MOZ_ASSERT(OnGraphThread());
    MOZ_ASSERT(mFrontMessageQueue.IsEmpty());
    mMonitor.AssertCurrentThreadOwns();
    mFrontMessageQueue.SwapElements(mBackMessageQueue);
  }
  /**
   * Do all the processing and play the audio and video, from
   * mProcessedTime to mStateComputedTime.
   */
  void Process();

  /**
   * For use during ProcessedMediaStream::ProcessInput() or
   * MediaStreamTrackListener callbacks, when graph state cannot be changed.
   * Schedules |aMessage| to run after processing, at a time when graph state
   * can be changed.  Graph thread.
   */
  void RunMessageAfterProcessing(UniquePtr<ControlMessage> aMessage);

  /**
   * Called when a suspend/resume/close operation has been completed, on the
   * graph thread.
   */
  void AudioContextOperationCompleted(MediaStream* aStream, void* aPromise,
                                      dom::AudioContextOperation aOperation,
                                      dom::AudioContextOperationFlags aFlags);

  /**
   * Apply and AudioContext operation (suspend/resume/closed), on the graph
   * thread.
   */
  void ApplyAudioContextOperationImpl(MediaStream* aDestinationStream,
                                      const nsTArray<MediaStream*>& aStreams,
                                      dom::AudioContextOperation aOperation,
                                      void* aPromise,
                                      dom::AudioContextOperationFlags aSource);

  /**
   * Increment suspend count on aStream and move it to mSuspendedStreams if
   * necessary.
   */
  void IncrementSuspendCount(MediaStream* aStream);
  /**
   * Increment suspend count on aStream and move it to mStreams if
   * necessary.
   */
  void DecrementSuspendCount(MediaStream* aStream);

  /*
   * Move streams from the mStreams to mSuspendedStream if suspending/closing an
   * AudioContext, or the inverse when resuming an AudioContext.
   */
  void SuspendOrResumeStreams(dom::AudioContextOperation aAudioContextOperation,
                              const nsTArray<MediaStream*>& aStreamSet);

  /**
   * Determine if we have any audio tracks, or are about to add any audiotracks.
   */
  bool AudioTrackPresent();

  /**
   * Sort mStreams so that every stream not in a cycle is after any streams
   * it depends on, and every stream in a cycle is marked as being in a cycle.
   * Also sets mIsConsumed on every stream.
   */
  void UpdateStreamOrder();

  /**
   * Returns smallest value of t such that t is a multiple of
   * WEBAUDIO_BLOCK_SIZE and t >= aTime.
   */
  static GraphTime RoundUpToEndOfAudioBlock(GraphTime aTime);
  /**
   * Returns smallest value of t such that t is a multiple of
   * WEBAUDIO_BLOCK_SIZE and t > aTime.
   */
  static GraphTime RoundUpToNextAudioBlock(GraphTime aTime);
  /**
   * Produce data for all streams >= aStreamIndex for the current time interval.
   * Advances block by block, each iteration producing data for all streams
   * for a single block.
   * This is called whenever we have an AudioNodeStream in the graph.
   */
  void ProduceDataForStreamsBlockByBlock(uint32_t aStreamIndex,
                                         TrackRate aSampleRate);
  /**
   * If aStream will underrun between aTime, and aEndBlockingDecisions, returns
   * the time at which the underrun will start. Otherwise return
   * aEndBlockingDecisions.
   */
  GraphTime WillUnderrun(MediaStream* aStream, GraphTime aEndBlockingDecisions);

  /**
   * Given a graph time aTime, convert it to a stream time taking into
   * account the time during which aStream is scheduled to be blocked.
   */
  StreamTime GraphTimeToStreamTimeWithBlocking(const MediaStream* aStream,
                                               GraphTime aTime) const;

  /**
   * If aStream needs an audio stream but doesn't have one, create it.
   * If aStream doesn't need an audio stream but has one, destroy it.
   */
  void CreateOrDestroyAudioStreams(MediaStream* aStream);
  /**
   * Queue audio (mix of stream audio and silence for blocked intervals)
   * to the audio output stream. Returns the number of frames played.
   */
  StreamTime PlayAudio(MediaStream* aStream);
  /* Runs off a message on the graph thread when something requests audio from
   * an input audio device of ID aID, and delivers the input audio frames to
   * aListener. */
  void OpenAudioInputImpl(CubebUtils::AudioDeviceID aID,
                          AudioDataListener* aListener);
  /* Called on the main thread when something requests audio from an input
   * audio device aID. */
  virtual nsresult OpenAudioInput(CubebUtils::AudioDeviceID aID,
                                  AudioDataListener* aListener) override;
  /* Runs off a message on the graph when input audio from aID is not needed
   * anymore, for a particular stream. It can be that other streams still need
   * audio from this audio input device. */
  void CloseAudioInputImpl(Maybe<CubebUtils::AudioDeviceID>& aID,
                           AudioDataListener* aListener);
  /* Called on the main thread when input audio from aID is not needed
   * anymore, for a particular stream. It can be that other streams still need
   * audio from this audio input device. */
  virtual void CloseAudioInput(Maybe<CubebUtils::AudioDeviceID>& aID,
                               AudioDataListener* aListener) override;
  /* Called on the graph thread when the input device settings should be
   * reevaluated, for example, if the channel count of the input stream should
   * be changed. */
  void ReevaluateInputDevice();

  /* Called on the graph thread when there is new output data for listeners.
   * This is the mixed audio output of this MediaStreamGraph. */
  void NotifyOutputData(AudioDataValue* aBuffer, size_t aFrames,
                        TrackRate aRate, uint32_t aChannels);
  /* Called on the graph thread when there is new input data for listeners. This
   * is the raw audio input for this MediaStreamGraph. */
  void NotifyInputData(const AudioDataValue* aBuffer, size_t aFrames,
                       TrackRate aRate, uint32_t aChannels);
  /* Called every time there are changes to input/output audio devices like
   * plug/unplug etc. This can be called on any thread, and posts a message to
   * the main thread so that it can post a message to the graph thread. */
  void DeviceChanged();
  /* Called every time there are changes to input/output audio devices. This is
   * called on the graph thread. */
  void DeviceChangedImpl();

  /**
   * Compute how much stream data we would like to buffer for aStream.
   */
  StreamTime GetDesiredBufferEnd(MediaStream* aStream);
  /**
   * Returns true when there are no active streams.
   */
  bool IsEmpty() const {
    MOZ_ASSERT(
        OnGraphThreadOrNotRunning() ||
        (NS_IsMainThread() &&
         LifecycleStateRef() >= LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP));
    return mStreams.IsEmpty() && mSuspendedStreams.IsEmpty() && mPortCount == 0;
  }

  /**
   * Add aStream to the graph and initializes its graph-specific state.
   */
  void AddStreamGraphThread(MediaStream* aStream);
  /**
   * Remove aStream from the graph. Ensures that pending messages about the
   * stream back to the main thread are flushed.
   */
  void RemoveStreamGraphThread(MediaStream* aStream);
  /**
   * Remove a stream from the graph. Main thread.
   */
  void RemoveStream(MediaStream* aStream);
  /**
   * Remove aPort from the graph and release it.
   */
  void DestroyPort(MediaInputPort* aPort);
  /**
   * Mark the media stream order as dirty.
   */
  void SetStreamOrderDirty() {
    MOZ_ASSERT(OnGraphThreadOrNotRunning());
    mStreamOrderDirty = true;
  }

  uint32_t AudioOutputChannelCount() const { return mOutputChannels; }

  double AudioOutputLatency();

  /**
   * The audio input channel count for a MediaStreamGraph is the max of all the
   * channel counts requested by the listeners. The max channel count is
   * delivered to the listeners themselves, and they take care of downmixing.
   */
  uint32_t AudioInputChannelCount() {
    MOZ_ASSERT(OnGraphThreadOrNotRunning());

#ifdef ANDROID
    if (!mInputDeviceUsers.GetValue(mInputDeviceID)) {
      return 0;
    }
#else
    if (!mInputDeviceID) {
      MOZ_ASSERT(mInputDeviceUsers.Count() == 0,
                 "If running on a platform other than android,"
                 "an explicit device id should be present");
      return 0;
    }
#endif
    uint32_t maxInputChannels = 0;
    // When/if we decide to support multiple input device per graph, this needs
    // loop over them.
    nsTArray<RefPtr<AudioDataListener>>* listeners =
        mInputDeviceUsers.GetValue(mInputDeviceID);
    MOZ_ASSERT(listeners);
    for (const auto& listener : *listeners) {
      maxInputChannels = std::max(maxInputChannels,
                                  listener->RequestedInputChannelCount(this));
    }
    return maxInputChannels;
  }

  AudioInputType AudioInputDevicePreference() {
    MOZ_ASSERT(OnGraphThreadOrNotRunning());

    if (!mInputDeviceUsers.GetValue(mInputDeviceID)) {
      return AudioInputType::Unknown;
    }
    bool voiceInput = false;
    // When/if we decide to support multiple input device per graph, this needs
    // loop over them.
    nsTArray<RefPtr<AudioDataListener>>* listeners =
        mInputDeviceUsers.GetValue(mInputDeviceID);
    MOZ_ASSERT(listeners);

    // If at least one stream is considered to be voice,
    for (const auto& listener : *listeners) {
      voiceInput |= listener->IsVoiceInput(this);
    }
    if (voiceInput) {
      return AudioInputType::Voice;
    }
    return AudioInputType::Unknown;
  }

  CubebUtils::AudioDeviceID InputDeviceID() { return mInputDeviceID; }

  double MediaTimeToSeconds(GraphTime aTime) const {
    NS_ASSERTION(aTime > -STREAM_TIME_MAX && aTime <= STREAM_TIME_MAX,
                 "Bad time");
    return static_cast<double>(aTime) / GraphRate();
  }

  GraphTime SecondsToMediaTime(double aS) const {
    NS_ASSERTION(0 <= aS && aS <= TRACK_TICKS_MAX / TRACK_RATE_MAX,
                 "Bad seconds");
    return GraphRate() * aS;
  }

  GraphTime MillisecondsToMediaTime(int32_t aMS) const {
    return RateConvertTicksRoundDown(GraphRate(), 1000, aMS);
  }

  /**
   * Signal to the graph that the thread has paused indefinitly,
   * or resumed.
   */
  void PausedIndefinitly();
  void ResumedFromPaused();

  /**
   * Not safe to call off the MediaStreamGraph thread unless monitor is held!
   */
  GraphDriver* CurrentDriver() const {
#ifdef DEBUG
    if (!OnGraphThreadOrNotRunning()) {
      mMonitor.AssertCurrentThreadOwns();
    }
#endif
    return mDriver;
  }

  /**
   * Effectively set the new driver, while we are switching.
   * It is only safe to call this at the very end of an iteration, when there
   * has been a SwitchAtNextIteration call during the iteration. The driver
   * should return and pass the control to the new driver shortly after.
   * We can also switch from Revive() (on MainThread). Monitor must be held.
   */
  void SetCurrentDriver(GraphDriver* aDriver) {
    MOZ_ASSERT(RunByGraphDriver(mDriver) || !mDriver->ThreadRunning());
#ifdef DEBUG
    mMonitor.AssertCurrentThreadOwns();
#endif
    mDriver = aDriver;
  }

  Monitor& GetMonitor() { return mMonitor; }

  void EnsureNextIteration() {
    mNeedAnotherIteration = true;  // atomic
    // Note: GraphDriver must ensure that there's no race on setting
    // mNeedAnotherIteration and mGraphDriverAsleep -- see
    // WaitForNextIteration()
    if (mGraphDriverAsleep) {  // atomic
      MonitorAutoLock mon(mMonitor);
      CurrentDriver()
          ->WakeUp();  // Might not be the same driver; might have woken already
    }
  }

  void EnsureNextIterationLocked() {
    mNeedAnotherIteration = true;  // atomic
    if (mGraphDriverAsleep) {      // atomic
      CurrentDriver()
          ->WakeUp();  // Might not be the same driver; might have woken already
    }
  }

  // Capture Stream API. This allows to get a mixed-down output for a window.
  void RegisterCaptureStreamForWindow(uint64_t aWindowId,
                                      ProcessedMediaStream* aCaptureStream);
  void UnregisterCaptureStreamForWindow(uint64_t aWindowId);
  already_AddRefed<MediaInputPort> ConnectToCaptureStream(
      uint64_t aWindowId, MediaStream* aMediaStream);

  Watchable<GraphTime>& CurrentTime() override;

  class StreamSet {
   public:
    class iterator {
     public:
      explicit iterator(MediaStreamGraphImpl& aGraph)
          : mGraph(&aGraph), mArrayNum(-1), mArrayIndex(0) {
        ++(*this);
      }
      iterator() : mGraph(nullptr), mArrayNum(2), mArrayIndex(0) {}
      MediaStream* operator*() { return Array()->ElementAt(mArrayIndex); }
      iterator operator++() {
        ++mArrayIndex;
        while (mArrayNum < 2 &&
               (mArrayNum < 0 || mArrayIndex >= Array()->Length())) {
          ++mArrayNum;
          mArrayIndex = 0;
        }
        return *this;
      }
      bool operator==(const iterator& aOther) const {
        return mArrayNum == aOther.mArrayNum &&
               mArrayIndex == aOther.mArrayIndex;
      }
      bool operator!=(const iterator& aOther) const {
        return !(*this == aOther);
      }

     private:
      nsTArray<MediaStream*>* Array() {
        return mArrayNum == 0 ? &mGraph->mStreams : &mGraph->mSuspendedStreams;
      }
      MediaStreamGraphImpl* mGraph;
      int mArrayNum;
      uint32_t mArrayIndex;
    };

    explicit StreamSet(MediaStreamGraphImpl& aGraph) : mGraph(aGraph) {}
    iterator begin() { return iterator(mGraph); }
    iterator end() { return iterator(); }

   private:
    MediaStreamGraphImpl& mGraph;
  };
  StreamSet AllStreams() { return StreamSet(*this); }

  // Data members

  /*
   * If set, the GraphRunner class handles handing over data from audio
   * callbacks to a common single thread, shared across GraphDrivers.
   */
  const UniquePtr<GraphRunner> mGraphRunner;

  /**
   * Main-thread view of the number of streams in this graph, for lifetime
   * management.
   *
   * When this becomes zero, the graph is marked as forbidden to add more
   * streams to. It will be shut down shortly after.
   */
  size_t mMainThreadStreamCount = 0;

  /**
   * Main-thread view of the number of ports in this graph, to catch bugs.
   *
   * When this becomes zero, and mMainThreadStreamCount is 0, the graph is
   * marked as forbidden to add more ControlMessages to. It will be shut down
   * shortly after.
   */
  size_t mMainThreadPortCount = 0;

  /**
   * Graphs own owning references to their driver, until shutdown. When a driver
   * switch occur, previous driver is either deleted, or it's ownership is
   * passed to a event that will take care of the asynchronous cleanup, as
   * audio stream can take some time to shut down.
   * Accessed on both the main thread and the graph thread; both read and write.
   * Must hold monitor to access it.
   */
  RefPtr<GraphDriver> mDriver;

  // The following state is managed on the graph thread only, unless
  // mLifecycleState > LIFECYCLE_RUNNING in which case the graph thread
  // is not running and this state can be used from the main thread.

  /**
   * The graph keeps a reference to each stream.
   * References are maintained manually to simplify reordering without
   * unnecessary thread-safe refcount changes.
   * Must satisfy OnGraphThreadOrNotRunning().
   */
  nsTArray<MediaStream*> mStreams;
  /**
   * This stores MediaStreams that are part of suspended AudioContexts.
   * mStreams and mSuspendStream are disjoint sets: a stream is either suspended
   * or not suspended. Suspended streams are not ordered in UpdateStreamOrder,
   * and are therefore not doing any processing.
   * Must satisfy OnGraphThreadOrNotRunning().
   */
  nsTArray<MediaStream*> mSuspendedStreams;
  /**
   * Streams from mFirstCycleBreaker to the end of mStreams produce output
   * before they receive input.  They correspond to DelayNodes that are in
   * cycles.
   */
  uint32_t mFirstCycleBreaker;
  /**
   * Blocking decisions have been computed up to this time.
   * Between each iteration, this is the same as mProcessedTime.
   */
  GraphTime mStateComputedTime = 0;
  /**
   * All stream contents have been computed up to this time.
   * The next batch of updates from the main thread will be processed
   * at this time.  This is behind mStateComputedTime during processing.
   */
  GraphTime mProcessedTime = 0;
  /**
   * The graph should stop processing at this time.
   */
  GraphTime mEndTime;
  /**
   * Date of the last time we updated the main thread with the graph state.
   */
  TimeStamp mLastMainThreadUpdate;
  /**
   * Number of active MediaInputPorts
   */
  int32_t mPortCount;
  /**
   * Runnables to run after the next update to main thread state, but that are
   * still waiting for the next iteration to finish.
   */
  nsTArray<nsCOMPtr<nsIRunnable>> mPendingUpdateRunnables;

  /**
   * Devices to use for cubeb input & output, or nullptr for default device.
   * A MediaStreamGraph always has an output (even if silent).
   * If `mInputDeviceUsers.Count() != 0`, this MediaStreamGraph wants audio
   * input.
   *
   * In any case, the number of channels to use can be queried (on the graph
   * thread) by AudioInputChannelCount() and AudioOutputChannelCount().
   */
  CubebUtils::AudioDeviceID mInputDeviceID;
  CubebUtils::AudioDeviceID mOutputDeviceID;
  // Maps AudioDeviceID to an array of their users (that are listeners). This is
  // used to deliver audio input frames and to notify the listeners that the
  // audio device that delivers the audio frames has changed.
  // This is only touched on the graph thread.
  nsDataHashtable<nsVoidPtrHashKey, nsTArray<RefPtr<AudioDataListener>>>
      mInputDeviceUsers;

  // True if the graph needs another iteration after the current iteration.
  Atomic<bool> mNeedAnotherIteration;
  // GraphDriver may need a WakeUp() if something changes
  Atomic<bool> mGraphDriverAsleep;

  // mMonitor guards the data below.
  // MediaStreamGraph normally does its work without holding mMonitor, so it is
  // not safe to just grab mMonitor from some thread and start monkeying with
  // the graph. Instead, communicate with the graph thread using provided
  // mechanisms such as the ControlMessage queue.
  Monitor mMonitor;

  // Data guarded by mMonitor (must always be accessed with mMonitor held,
  // regardless of the value of mLifecycleState).

  /**
   * State to copy to main thread
   */
  nsTArray<StreamUpdate> mStreamUpdates;
  /**
   * Runnables to run after the next update to main thread state.
   */
  nsTArray<nsCOMPtr<nsIRunnable>> mUpdateRunnables;
  /**
   * A list of batches of messages to process. Each batch is processed
   * as an atomic unit.
   */
  /*
   * Message queue processed by the MSG thread during an iteration.
   * Accessed on graph thread only.
   */
  nsTArray<MessageBlock> mFrontMessageQueue;
  /*
   * Message queue in which the main thread appends messages.
   * Access guarded by mMonitor.
   */
  nsTArray<MessageBlock> mBackMessageQueue;

  /* True if there will messages to process if we swap the message queues. */
  bool MessagesQueued() const {
    mMonitor.AssertCurrentThreadOwns();
    return !mBackMessageQueue.IsEmpty();
  }
  /**
   * This enum specifies where this graph is in its lifecycle. This is used
   * to control shutdown.
   * Shutdown is tricky because it can happen in two different ways:
   * 1) Shutdown due to inactivity. RunThread() detects that it has no
   * pending messages and no streams, and exits. The next RunInStableState()
   * checks if there are new pending messages from the main thread (true only
   * if new stream creation raced with shutdown); if there are, it revives
   * RunThread(), otherwise it commits to shutting down the graph. New stream
   * creation after this point will create a new graph. An async event is
   * dispatched to Shutdown() the graph's threads and then delete the graph
   * object.
   * 2) Forced shutdown at application shutdown, or completion of a
   * non-realtime graph. A flag is set, RunThread() detects the flag and
   * exits, the next RunInStableState() detects the flag, and dispatches the
   * async event to Shutdown() the graph's threads. However the graph object
   * is not deleted. New messages for the graph are processed synchronously on
   * the main thread if necessary. When the last stream is destroyed, the
   * graph object is deleted.
   *
   * This should be kept in sync with the LifecycleState_str array in
   * MediaStreamGraph.cpp
   */
  enum LifecycleState {
    // The graph thread hasn't started yet.
    LIFECYCLE_THREAD_NOT_STARTED,
    // RunThread() is running normally.
    LIFECYCLE_RUNNING,
    // In the following states, the graph thread is not running so
    // all "graph thread only" state in this class can be used safely
    // on the main thread.
    // RunThread() has exited and we're waiting for the next
    // RunInStableState(), at which point we can clean up the main-thread
    // side of the graph.
    LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP,
    // RunInStableState() posted a ShutdownRunnable, and we're waiting for it
    // to shut down the graph thread(s).
    LIFECYCLE_WAITING_FOR_THREAD_SHUTDOWN,
    // Graph threads have shut down but we're waiting for remaining streams
    // to be destroyed. Only happens during application shutdown and on
    // completed non-realtime graphs, since normally we'd only shut down a
    // realtime graph when it has no streams.
    LIFECYCLE_WAITING_FOR_STREAM_DESTRUCTION
  };

  /**
   * Modified only in mMonitor.  Transitions to
   * LIFECYCLE_WAITING_FOR_MAIN_THREAD_CLEANUP occur on the graph thread at
   * the end of an iteration.  All other transitions occur on the main thread.
   */
  LifecycleState mLifecycleState;
  LifecycleState& LifecycleStateRef() {
#if DEBUG
    if (!mDetectedNotRunning) {
      mMonitor.AssertCurrentThreadOwns();
    }
#endif
    return mLifecycleState;
  }
  const LifecycleState& LifecycleStateRef() const {
#if DEBUG
    if (!mDetectedNotRunning) {
      mMonitor.AssertCurrentThreadOwns();
    }
#endif
    return mLifecycleState;
  }

  /**
   * True when we need to do a forced shutdown, during application shutdown or
   * when shutting down a non-realtime graph.
   * Only set on the graph thread.
   * Can be read safely on the thread currently owning the graph, as indicated
   * by mLifecycleState.
   */
  bool mForceShutDown;

  /**
   * Drop this reference during shutdown to unblock shutdown.
   * Only accessed on the main thread.
   **/
  RefPtr<media::ShutdownTicket> mForceShutdownTicket;

  /**
   * True when we have posted an event to the main thread to run
   * RunInStableState() and the event hasn't run yet.
   * Accessed on both main and MSG thread, mMonitor must be held.
   */
  bool mPostedRunInStableStateEvent;

  // Main thread only

  /**
   * Messages posted by the current event loop task. These are forwarded to
   * the media graph thread during RunInStableState. We can't forward them
   * immediately because we want all messages between stable states to be
   * processed as an atomic batch.
   */
  nsTArray<UniquePtr<ControlMessage>> mCurrentTaskMessageQueue;
  /**
   * True when RunInStableState has determined that mLifecycleState is >
   * LIFECYCLE_RUNNING. Since only the main thread can reset mLifecycleState to
   * LIFECYCLE_RUNNING, this can be relied on to not change unexpectedly.
   */
  Atomic<bool> mDetectedNotRunning;
  /**
   * True when a stable state runner has been posted to the appshell to run
   * RunInStableState at the next stable state.
   * Only accessed on the main thread.
   */
  bool mPostedRunInStableState;
  /**
   * True when processing real-time audio/video.  False when processing
   * non-realtime audio.
   */
  const bool mRealtime;
  /**
   * True when a change has happened which requires us to recompute the stream
   * blocking order.
   */
  bool mStreamOrderDirty;
  AudioMixer mMixer;
  const RefPtr<AbstractThread> mAbstractMainThread;

  // used to limit graph shutdown time
  // Only accessed on the main thread.
  nsCOMPtr<nsITimer> mShutdownTimer;

 private:
  virtual ~MediaStreamGraphImpl();

  MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)

  /**
   * This class uses manual memory management, and all pointers to it are raw
   * pointers. However, in order for it to implement nsIMemoryReporter, it needs
   * to implement nsISupports and so be ref-counted. So it maintains a single
   * nsRefPtr to itself, giving it a ref-count of 1 during its entire lifetime,
   * and Destroy() nulls this self-reference in order to trigger self-deletion.
   */
  RefPtr<MediaStreamGraphImpl> mSelfRef;

  struct WindowAndStream {
    uint64_t mWindowId;
    RefPtr<ProcessedMediaStream> mCaptureStreamSink;
  };
  /**
   * Stream for window audio capture.
   */
  nsTArray<WindowAndStream> mWindowCaptureStreams;

  /**
   * Number of channels on output.
   */
  const uint32_t mOutputChannels;

  /**
   * Global volume scale. Used when running tests so that the output is not too
   * loud.
   */
  const float mGlobalVolume;

#ifdef DEBUG
  /**
   * Used to assert when AppendMessage() runs ControlMessages synchronously.
   */
  bool mCanRunMessagesSynchronously;
#endif

  /**
   * The graph's main-thread observable graph time.
   * Updated by the stable state runnable after each iteration.
   */
  Watchable<GraphTime> mMainThreadGraphTime;

  /**
   * Set based on mProcessedTime at end of iteration.
   * Read by stable state runnable on main thread. Protected by mMonitor.
   */
  GraphTime mNextMainThreadGraphTime = 0;

  /**
   * Cached audio output latency, in seconds. Main thread only. This is reset
   * whenever the audio device running this MediaStreamGraph changes.
   */
  double mAudioOutputLatency;
};

}  // namespace mozilla

#endif /* MEDIASTREAMGRAPHIMPL_H_ */