protobuf 打包 与 解包

// excerpts from 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 (giantchen at gmail dot com)   #ifndef PROTOBUF_CODEC_H #define PROTOBUF_CODEC_H   #include <google/protobuf/descriptor.h> #include <google/protobuf/message.h> #include <zlib.h>// adler32   #include <string>   #include <arpa/inet.h>// htonl, ntohl #include <stdint.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 // }   const int kHeaderLen = sizeof(int32_t); /// /// Encode protobuf Message to transport format defined above /// returns a std::string. /// /// returns a empty string if message.AppendToString() fails. /// inline std::string encode(const google::protobuf::Message& message) { std::string result;   result.resize(kHeaderLen);   const std::string& typeName = message.GetTypeName(); int32_t nameLen = static_cast<int32_t>(typeName.size()+1); int32_t be32 = ::htonl(nameLen); result.append(reinterpret_cast<char*>(&be32),sizeof be32); result.append(typeName.c_str(), nameLen); bool succeed = message.AppendToString(&result);   if (succeed) { const char* begin = result.c_str() +kHeaderLen; int32_t checkSum = adler32(1, reinterpret_cast<const Bytef*>(begin), result.size()-kHeaderLen); int32_t be32 = ::htonl(checkSum); result.append(reinterpret_cast<char*>(&be32),sizeof be32);   int32_t len = ::htonl(result.size() -kHeaderLen); std::copy(reinterpret_cast<char*>(&len), reinterpret_cast<char*>(&len) +sizeof len, result.begin()); } else { result.clear(); }   return result; }   inline google::protobuf::Message*createMessage(const std::string& type_name) { google::protobuf::Message* message = NULL; const google::protobuf::Descriptor* descriptor = google::protobuf::DescriptorPool::generated_pool()->FindMessageTypeByName(type_name); if (descriptor) { const google::protobuf::Message* prototype = google::protobuf::MessageFactory::generated_factory()->GetPrototype(descriptor); if (prototype) { message = prototype->New(); } } return message; }   inline int32_t asInt32(constchar* buf) { int32_t be32 = 0; ::memcpy(&be32, buf, sizeof(be32)); return ::ntohl(be32); }   /// /// Decode protobuf Message from transport format defined above. /// returns a Message* /// /// returns NULL if fails. /// inline google::protobuf::Message*decode(const std::string& buf) { google::protobuf::Message* result = NULL;   int32_t len = static_cast<int32_t>(buf.size()); if (len >= 10) { int32_t expectedCheckSum =asInt32(buf.c_str() + buf.size() -kHeaderLen); const char* begin = buf.c_str(); int32_t checkSum = adler32(1, reinterpret_cast<const Bytef*>(begin), len-kHeaderLen); if (checkSum == expectedCheckSum) { int32_t nameLen = asInt32(buf.c_str()); if (nameLen >= 2 && nameLen <= len - 2*kHeaderLen) { std::string typeName(buf.begin() +kHeaderLen, buf.begin() +kHeaderLen + nameLen - 1); google::protobuf::Message* message = createMessage(typeName); if (message) { const char* data = buf.c_str() +kHeaderLen + nameLen; int32_t dataLen = len - nameLen -2*kHeaderLen; if (message->ParseFromArray(data, dataLen)) { result = message; } else { // parse error delete message; } } else { // unknown message type } } else { // invalid name len } } else { // check sum error } }   return result; }   #endif // PROTOBUF_CODEC_H