WebRTC 分析一下peer connection的初始化过程吧

• 初始化代码

    _peerConnection = [_factory peerConnectionWithConfiguration:config
                                                    constraints:constraints
                                                       delegate:self];

• 文件sdk/objc/api/peerconnection/RTCPeerConnectionFactory.mm

- (RTCPeerConnection *)peerConnectionWithConfiguration:
    (RTCConfiguration *)configuration
                                           constraints:
    (RTCMediaConstraints *)constraints
                                              delegate:
    (nullable id<RTCPeerConnectionDelegate>)delegate {
  return [[RTCPeerConnection alloc] initWithFactory:self
                                      configuration:configuration
                                        constraints:constraints
                                           delegate:delegate];
}

调用

- (instancetype)initWithFactory:(RTCPeerConnectionFactory *)factory
                  configuration:(RTCConfiguration *)configuration
                    constraints:(RTCMediaConstraints *)constraints
                       delegate:(id<RTCPeerConnectionDelegate>)delegate {

    _peerConnection =
        factory.nativeFactory->CreatePeerConnection(*config,
                                                    nullptr,
                                                    nullptr,
                                                    _observer.get());

}

调用
api/peer_connection_factory_proxy.h

PROXY_METHOD4(rtc::scoped_refptr<PeerConnectionInterface>,
              CreatePeerConnection,
              const PeerConnectionInterface::RTCConfiguration&,
              std::unique_ptr<cricket::PortAllocator>,
              std::unique_ptr<rtc::RTCCertificateGeneratorInterface>,
              PeerConnectionObserver*);

调用
pc/peer_connection_factory.cc

rtc::scoped_refptr<PeerConnectionInterface>
PeerConnectionFactory::CreatePeerConnection(
    const PeerConnectionInterface::RTCConfiguration& configuration,
    std::unique_ptr<cricket::PortAllocator> allocator,
    std::unique_ptr<rtc::RTCCertificateGeneratorInterface> cert_generator,
    PeerConnectionObserver* observer) {
  // Convert the legacy API into the new depnedency structure.
  PeerConnectionDependencies dependencies(observer);
  dependencies.allocator = std::move(allocator);
  dependencies.cert_generator = std::move(cert_generator);
  // Pass that into the new API.
  return CreatePeerConnection(configuration, std::move(dependencies));
}

把参数传给新的接口

rtc::scoped_refptr<PeerConnectionInterface>
PeerConnectionFactory::CreatePeerConnection(
    const PeerConnectionInterface::RTCConfiguration& configuration,
    PeerConnectionDependencies dependencies) {
//就是在这里new 的peer connection
  rtc::scoped_refptr<PeerConnection> pc(
      new rtc::RefCountedObject<PeerConnection>(this, std::move(event_log),
                                                std::move(call)));
}

构造函数

PeerConnection::PeerConnection(PeerConnectionFactory* factory,
                               std::unique_ptr<RtcEventLog> event_log,
                               std::unique_ptr<Call> call)
    : factory_(factory),
      event_log_(std::move(event_log)),
      rtcp_cname_(GenerateRtcpCname()),
      local_streams_(StreamCollection::Create()),
      remote_streams_(StreamCollection::Create()),
      call_(std::move(call)) {}