First step in providing a UdpTransportChannel.

webrtc/p2p/base/udptransportchannel.h

Index: webrtc/p2p/base/udptransportchannel.h
diff --git a/webrtc/p2p/base/udptransportchannel.h b/webrtc/p2p/base/udptransportchannel.h
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+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_P2P_BASE_UDPTRANSPORTCHANNEL_H_
+#define WEBRTC_P2P_BASE_UDPTRANSPORTCHANNEL_H_
+
+#include <memory>
+#include <string>
+
+#include "webrtc/base/optional.h"
+#include "webrtc/base/thread_checker.h"
+#include "webrtc/p2p/base/packettransportinterface.h"
+
+namespace rtc {
+class AsyncPacketSocket;
+class PhysicalSocketServer;
+class SocketAddress;
+class SocketServer;
+class Thread;
+}
+
+namespace cricket {
+
+class UdpTransportChannel : public rtc::PacketTransportInterface {
+ public:
+  enum class State { INIT, CONNECTING, CONNECTED, FAILED };
+  explicit UdpTransportChannel(const std::string& transport_name);
+  UdpTransportChannel(const std::string& transport_name, rtc::SocketServer* ss);
+  ~UdpTransportChannel();
+
+  const std::string debug_name() const override { return transport_name_; }
+
+  bool receiving() const override {
+    // TODO(johan): Implement method and signal.
+    return true;
+  }
+
+  bool writable() const override;
+
+  int SendPacket(const char* data,
+                 size_t len,
+                 const rtc::PacketOptions& options,
+                 int flags) override;
+
+  int SetOption(rtc::Socket::Option opt, int value) override { return 0; }
+
+  int GetError() override { return send_error_; }
+
+  State state() const {
+    RTC_DCHECK_RUN_ON(&network_thread_checker_);
+    return state_;
+  }
+
+  // Start() makes UdpTransportChannel transition from state INIT to CONNECTING.
+  // It creates the local UDP socket and binds it to a port.
+  // Consider checking state() after calling Start().
+  void Start();
+
+  void SetRemoteParameters(const rtc::SocketAddress& remote);
+
+  // Returned optional does not have a value if in the INIT or FAILED state.
+  // Consider checking state() before calling local_parameters().
+  rtc::Optional<rtc::SocketAddress> local_parameters() const {
+    return local_parameters_;
+  }
+
+ private:
+  void OnSocketReadPacket(rtc::AsyncPacketSocket* socket,
+                          const char* data,
+                          size_t len,
+                          const rtc::SocketAddress& remote_addr,
+                          const rtc::PacketTime& packet_time);
+  void OnSocketSentPacket(rtc::AsyncPacketSocket* socket,
+                          const rtc::SentPacket& packet);
+  void SetState(State state);  // Set State and Signal.
+  bool IsLocalConsistent();
+  void UpdateState();
+  std::string transport_name_;
+  rtc::SocketServer* socket_server_;
+  State state_ = State::INIT;
+  int send_error_ = 0;
+  std::unique_ptr<rtc::AsyncPacketSocket> socket_;
+  rtc::Optional<rtc::SocketAddress> local_parameters_;
+  rtc::Optional<rtc::SocketAddress> remote_parameters_;
+  rtc::ThreadChecker network_thread_checker_;
+};
+}  // namespace cricket
+
+#endif  // WEBRTC_P2P_BASE_UDPTRANSPORTCHANNEL_H_