codec.h

// Copyright 2011, Shuo Chen.  All rights reserved.
// http://code.google.com/p/muduo/
//
// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#ifndef MUDUO_EXAMPLES_PROTOBUF_CODEC_CODEC_H
#define MUDUO_EXAMPLES_PROTOBUF_CODEC_CODEC_H

#include <muduo/net/Buffer.h>
#include <muduo/net/TcpConnection.h>

#include <google/protobuf/message.h>

// struct ProtobufTransportFormat __attribute__ ((__packed__))
// {
//   int32_t  len;
//   int32_t  nameLen;
//   char     typeName[nameLen];
//   char     protobufData[len-nameLen-8];
//   int32_t  checkSum; // adler32 of nameLen, typeName and protobufData
// }

typedef std::shared_ptr<google::protobuf::Message> MessagePtr;

//
// FIXME: merge with RpcCodec
//
class ProtobufCodec : muduo::noncopyable
{
 public:

  enum ErrorCode
  {
    kNoError = 0,
    kInvalidLength,
    kCheckSumError,
    kInvalidNameLen,
    kUnknownMessageType,
    kParseError,
  };

  typedef std::function<void (const muduo::net::TcpConnectionPtr&,
                                const MessagePtr&,
                                muduo::Timestamp)> ProtobufMessageCallback;

  typedef std::function<void (const muduo::net::TcpConnectionPtr&,
                                muduo::net::Buffer*,
                                muduo::Timestamp,
                                ErrorCode)> ErrorCallback;

  explicit ProtobufCodec(const ProtobufMessageCallback& messageCb)
    : messageCallback_(messageCb),
      errorCallback_(defaultErrorCallback)
  {
  }

  ProtobufCodec(const ProtobufMessageCallback& messageCb, const ErrorCallback& errorCb)
    : messageCallback_(messageCb),
      errorCallback_(errorCb)
  {
  }

  void onMessage(const muduo::net::TcpConnectionPtr& conn,
                 muduo::net::Buffer* buf,
                 muduo::Timestamp receiveTime);

  void send(const muduo::net::TcpConnectionPtr& conn,
            const google::protobuf::Message& message)
  {
    // FIXME: serialize to TcpConnection::outputBuffer()
    muduo::net::Buffer buf;
    fillEmptyBuffer(&buf, message);
    conn->send(&buf);
  }

  static const muduo::string& errorCodeToString(ErrorCode errorCode);
  static void fillEmptyBuffer(muduo::net::Buffer* buf, const google::protobuf::Message& message);
  static google::protobuf::Message* createMessage(const std::string& type_name);
  static MessagePtr parse(const char* buf, int len, ErrorCode* errorCode);

 private:
  static void defaultErrorCallback(const muduo::net::TcpConnectionPtr&,
                                   muduo::net::Buffer*,
                                   muduo::Timestamp,
                                   ErrorCode);

  ProtobufMessageCallback messageCallback_;
  ErrorCallback errorCallback_;

  const static int kHeaderLen = sizeof(int32_t);
  const static int kMinMessageLen = 2*kHeaderLen + 2; // nameLen + typeName + checkSum
  const static int kMaxMessageLen = 64*1024*1024; // same as codec_stream.h kDefaultTotalBytesLimit
};

#endif  // MUDUO_EXAMPLES_PROTOBUF_CODEC_CODEC_H