Add packet logger and server

webrtc/tools/network_tester/packet_logger.cc

+/*
+ *  Copyright 2017 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.
+ */
+#include "webrtc/tools/network_tester/packet_logger.h"
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+PacketLogger::PacketLogger(const std::string& log_file_path)
+    : packet_logger_stream_(log_file_path,
+                            std::ios_base::out | std::ios_base::binary) {
+  RTC_DCHECK(packet_logger_stream_.is_open());
+  RTC_DCHECK(packet_logger_stream_.good());
+}
+
+PacketLogger::~PacketLogger() = default;
+
+void PacketLogger::LogPacket(const NetworkTesterPacket& packet) {
+  std::string log_data;
+  packet.SerializeToString(&log_data);
+  char size = packet.ByteSize();
+  packet_logger_stream_.write(&size, sizeof(size));

[nisse-webrtc, 2017/04/06 12:46:29]

This looks confusing.

If the intention is to write a record with a length field followed by the data,
then I'd use log_data.length() rather than packet.ByteSize to get the
appropriate length.

If there's only a single byte length field in the file, add to CHECK or DCHECK
that length isn't too large.

If it's binary data rather than ascii, I'd also prefer uint8_t and
std::basic_string<uint8_t> over char and std::string. 

[michaelt, 2017/04/06 14:42:11]

  Done
  Done
Protobuffer don't accept std::basic_string<uint8_t> for serialization.

I tried to make this a bit less confusing by changing the names of the variables
a bit. :)

+  packet_logger_stream_.write(log_data.data(), log_data.length());
+}
+
+}  // namespace webrtc