gecko-dev/dom/media/MediaQueue.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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/. */
#if !defined(MediaQueue_h_)
#  define MediaQueue_h_

#  include <type_traits>

#  include "mozilla/RecursiveMutex.h"
#  include "mozilla/TaskQueue.h"

#  include "nsDeque.h"
#  include "MediaEventSource.h"
#  include "TimeUnits.h"

namespace mozilla {

class AudioData;

template <class T>
class MediaQueue : private nsRefPtrDeque<T> {
 public:
  MediaQueue()
      : nsRefPtrDeque<T>(),
        mRecursiveMutex("mediaqueue"),
        mEndOfStream(false) {}

  ~MediaQueue() { Reset(); }

  inline size_t GetSize() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return nsRefPtrDeque<T>::GetSize();
  }

  inline void PushFront(T* aItem) {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    nsRefPtrDeque<T>::PushFront(aItem);
  }

  inline void Push(T* aItem) {
    MOZ_DIAGNOSTIC_ASSERT(aItem);
    Push(do_AddRef(aItem));
  }

  inline void Push(already_AddRefed<T> aItem) {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    T* item = aItem.take();

    MOZ_DIAGNOSTIC_ASSERT(item);
    MOZ_DIAGNOSTIC_ASSERT(item->GetEndTime() >= item->mTime);
    nsRefPtrDeque<T>::Push(dont_AddRef(item));
    mPushEvent.Notify(RefPtr<T>(item));

    // Pushing new data after queue has ended means that the stream is active
    // again, so we should not mark it as ended.
    if (mEndOfStream) {
      mEndOfStream = false;
    }
  }

  inline already_AddRefed<T> PopFront() {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    RefPtr<T> rv = nsRefPtrDeque<T>::PopFront();
    if (rv) {
      MOZ_DIAGNOSTIC_ASSERT(rv->GetEndTime() >= rv->mTime);
      mPopFrontEvent.Notify(RefPtr<T>(rv));
    }
    return rv.forget();
  }

  inline already_AddRefed<T> PopBack() {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return nsRefPtrDeque<T>::Pop();
  }

  inline RefPtr<T> PeekFront() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return nsRefPtrDeque<T>::PeekFront();
  }

  inline RefPtr<T> PeekBack() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return nsRefPtrDeque<T>::Peek();
  }

  void Reset() {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    nsRefPtrDeque<T>::Erase();
    mEndOfStream = false;
  }

  bool AtEndOfStream() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return GetSize() == 0 && mEndOfStream;
  }

  // Returns true if the media queue has had its last item added to it.
  // This happens when the media stream has been completely decoded. Note this
  // does not mean that the corresponding stream has finished playback.
  bool IsFinished() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    return mEndOfStream;
  }

  // Informs the media queue that it won't be receiving any more items.
  void Finish() {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    if (!mEndOfStream) {
      mEndOfStream = true;
      mFinishEvent.Notify();
    }
  }

  // Returns the approximate number of microseconds of items in the queue.
  int64_t Duration() const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    if (GetSize() == 0) {
      return 0;
    }
    T* last = nsRefPtrDeque<T>::Peek();
    T* first = nsRefPtrDeque<T>::PeekFront();
    return (last->GetEndTime() - first->mTime).ToMicroseconds();
  }

  void LockedForEach(nsDequeFunctor<T>& aFunctor) const {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    nsRefPtrDeque<T>::ForEach(aFunctor);
  }

  // Fill aResult with the elements which end later than the given time aTime.
  void GetElementsAfter(const media::TimeUnit& aTime,
                        nsTArray<RefPtr<T>>* aResult) {
    GetElementsAfterStrict(aTime.ToMicroseconds(), aResult);
  }

  void GetFirstElements(uint32_t aMaxElements, nsTArray<RefPtr<T>>* aResult) {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    for (size_t i = 0; i < aMaxElements && i < GetSize(); ++i) {
      *aResult->AppendElement() = nsRefPtrDeque<T>::ObjectAt(i);
    }
  }

  uint32_t AudioFramesCount() {
    static_assert(std::is_same_v<T, AudioData>,
                  "Only usable with MediaQueue<AudioData>");
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    uint32_t frames = 0;
    for (size_t i = 0; i < GetSize(); ++i) {
      T* v = nsRefPtrDeque<T>::ObjectAt(i);
      frames += v->Frames();
    }
    return frames;
  }

  MediaEventSource<RefPtr<T>>& PopFrontEvent() { return mPopFrontEvent; }

  MediaEventSource<RefPtr<T>>& PushEvent() { return mPushEvent; }

  MediaEventSource<void>& FinishEvent() { return mFinishEvent; }

 private:
  // Extracts elements from the queue into aResult, in order.
  // Elements whose end time is before or equal to aTime are ignored.
  void GetElementsAfterStrict(int64_t aTime, nsTArray<RefPtr<T>>* aResult) {
    RecursiveMutexAutoLock lock(mRecursiveMutex);
    if (GetSize() == 0) return;
    size_t i;
    for (i = GetSize() - 1; i > 0; --i) {
      T* v = nsRefPtrDeque<T>::ObjectAt(i);
      if (v->GetEndTime().ToMicroseconds() < aTime) break;
    }
    for (; i < GetSize(); ++i) {
      RefPtr<T> elem = nsRefPtrDeque<T>::ObjectAt(i);
      if (elem->GetEndTime().ToMicroseconds() > aTime) {
        aResult->AppendElement(elem);
      }
    }
  }

  mutable RecursiveMutex mRecursiveMutex;
  MediaEventProducer<RefPtr<T>> mPopFrontEvent;
  MediaEventProducer<RefPtr<T>> mPushEvent;
  MediaEventProducer<void> mFinishEvent;
  // True when we've decoded the last frame of data in the
  // bitstream for which we're queueing frame data.
  bool mEndOfStream;
};

}  // namespace mozilla

#endif