chromium/third_party/blink/renderer/modules/peerconnection/rtc_rtp_receiver_impl.h

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_RTC_RTP_RECEIVER_IMPL_H_
#define THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_RTC_RTP_RECEIVER_IMPL_H_

#include <vector>

#include "base/memory/scoped_refptr.h"
#include "base/task/single_thread_task_runner.h"
#include "third_party/blink/renderer/modules/modules_export.h"
#include "third_party/blink/renderer/modules/peerconnection/webrtc_media_stream_track_adapter_map.h"
#include "third_party/blink/renderer/platform/allow_discouraged_type.h"
#include "third_party/blink/renderer/platform/peerconnection/rtc_rtp_receiver_platform.h"
#include "third_party/blink/renderer/platform/peerconnection/rtc_rtp_transceiver_platform.h"
#include "third_party/blink/renderer/platform/peerconnection/rtc_stats.h"
#include "third_party/webrtc/api/media_stream_interface.h"
#include "third_party/webrtc/api/peer_connection_interface.h"
#include "third_party/webrtc/api/rtp_receiver_interface.h"
#include "third_party/webrtc/api/stats/rtc_stats.h"

namespace blink {

class RTCEncodedAudioStreamTransformer;
class RTCEncodedVideoStreamTransformer;

// This class represents the state of a receiver; a snapshot of what a
// webrtc-layer receiver looked like when it was inspected on the signaling
// thread such that this information can be moved to the main thread in a single
// PostTask. It is used to surface state changes to make the blink-layer
// receiver up-to-date.
//
// Blink objects live on the main thread and webrtc objects live on the
// signaling thread. If multiple asynchronous operations begin execution on the
// main thread they are posted and executed in order on the signaling thread.
// For example, operation A and operation B are called in JavaScript. When A is
// done on the signaling thread, webrtc object states will be updated. A
// callback is posted to the main thread so that blink objects can be updated to
// match the result of operation A. But if callback A tries to inspect the
// webrtc objects from the main thread this requires posting back to the
// signaling thread and waiting, which also includes waiting for the previously
// posted task: operation B. Inspecting the webrtc object like this does not
// guarantee you to get the state of operation A.
//
// As such, all state changes associated with an operation have to be surfaced
// in the same callback. This includes copying any states into a separate object
// so that it can be inspected on the main thread without any additional thread
// hops.
//
// The RtpReceiverState is a snapshot of what the webrtc::RtpReceiverInterface
// looked like when the RtpReceiverState was created on the signaling thread. It
// also takes care of initializing track adapters, such that we have access to a
// blink track corresponding to the webrtc track of the receiver.
//
// Except for initialization logic and operator=(), the RtpReceiverState is
// immutable and only accessible on the main thread.
//
// TODO(crbug.com/787254): Consider merging RTCRtpReceiverImpl and
// RTCRtpReceiver, and removing RTCRtpReceiverPlatform when all its clients are
// Onion soup'ed. Also, move away from using std::vector.
class MODULES_EXPORT RtpReceiverState { … };

// Used to surface |webrtc::RtpReceiverInterface| to blink. Multiple
// |RTCRtpReceiverImpl|s could reference the same webrtc receiver; |id| is the
// value of the pointer to the webrtc receiver.
class MODULES_EXPORT RTCRtpReceiverImpl : public RTCRtpReceiverPlatform { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_MODULES_PEERCONNECTION_RTC_RTP_RECEIVER_IMPL_H_