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(自用)交互协议设计——protobuf序列化

news 来源：原创 2024/9/17 2:59:43

protobuf是一种比json和xml等序列化工具更加轻量和高效的结构化数据存储格式，性能比json和xml真的强很多，毕竟google出品。

protobuf原理

protobuf如何使用

创建xxx.proto文件

开头写上

syntax="proto2"package tutorial;

表明使用的proto版本和导入tutorial包

以充值查询响应为例，对应proto文件中代码如下

message list_account_records_response
{required int32   code   = 1;    // 响应代号optional string  desc   = 2;    // 验证码message account_record{required int32  type      = 1; // 0 : 骑行消费,  1 : 充值, 2 : 退款required int32  limit     = 2; // 消费或者充值金额required uint64 timestamp = 3; // 记录发生时的时间戳}repeated account_record records = 3;
}

PS:

可在message中自定义message类型，如上图中的account_record

编译message文件

编译语法：

protoc -I=$SRC_DIR --cpp_out=$DST_DIR  bike.proto

SRC_DIR 表示proto文件所在的目录，cpp_out指定了生成的代码的路径， bike.proto指proto文件名。

protoc -I=./ --cpp_out=./ bike.proto

这样在当前目录生成了bike.pb.cc和bike.pb.h两个文件。

编译生成的c++文件

g++  -std=c++11   example.cc bike.pb.cc -lprotobuf

std=c++11表示使用c++11的标准

protobuf使用示例代码

example.cc

#include"bike.pb.h"
#include<string>
#include<iostream>using namespace std;
using namespace tutorial;int main(void)
{std::string data;//存储序列化的消息//客户端发送请求{mobile_request mr;mr.set_mobile("18106050285");mr.SerializeToString(&data);//格式化，变成序列化的消息//客户端发送data  send(sockfd,data.c_str(),data.length())}//服务器端接收请求{//receive(sockfd,data,....);mobile_request mr;mr.ParseFromString(data);cout << "客户端手机号码:" << mr.mobile() << endl;}return 0;
}

进行编译


g++  -std=c++11   example.cc bike.pb.cc -lprotobuf

生成a.out

执行a.out:

复杂一些的使用示例:

list_account_records_response对象中的records对象为可重复的，如何在一个list_account_records_response中添加多个records呢？

example1.cc

#include"bike.pb.h"
#include<string>
#include<iostream>using namespace std;
using namespace tutorial;int main(void)
{std::string data;//存储序列化的消息//客户端发送请求{list_account_records_response larr;larr.set_code(200);larr.set_desc("ok");for (size_t i = 0; i < 5; i++){list_account_records_response_account_record* ar = larr.add_records();ar->set_type(0);ar->set_limit(i*100);ar->set_timestamp(NULL);}cout << "records size :" << larr.records_size() << endl;larr.SerializeToString(&data);//客户端发送data  send(sockfd,data.c_str(),data.length())}//服务器端接收请求{//receive(sockfd,data,....);list_account_records_response larr;larr.ParseFromString(data);cout << "records size :" << larr.records_size() << endl;printf("code : %d \n",larr.code());for (int i = 0; i < larr.records_size(); i++){const list_account_records_response_account_record& ar = larr.records(i);printf("limit: %d \n",ar.limit());}}return 0;
}

Libevent与Protobuf一起协作

客户端代码

client.cc

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>#include<stdio.h>
#include<string.h>
#include<stdlib.h>#include<event.h>
#include<event2/bufferevent.h>
#include<event2/buffer.h>
#include<event2/util.h>#include"bike.pb.h"using namespace std;
using namespace tutorial;int tcp_connect_server(const char* server_ip, int port);void cmd_msg_cb(int fd,short events,void* arg);
void server_msg_cb(int fd, short events, void* arg);
void event_cb(struct bufferevent *bev,short event,void *arg);int main(int argc, char** argv)
{if( argc < 3 ){printf("please input 2 parameters\n");return -1;}//两个参数依次是服务器端的IP地址、端口号int sockfd = tcp_connect_server(argv[1], atoi(argv[2]));if( sockfd == -1){perror("tcp_connect error ");return -1;}printf("connect to server successfully\n");struct event_base* base = event_base_new();struct bufferevent* bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE);bufferevent_enable(bev, EV_READ | EV_PERSIST);struct event *ev_sockfd = event_new(base, sockfd,EV_READ | EV_PERSIST,server_msg_cb, NULL);event_add(ev_sockfd, NULL);//监听终端输入事件struct event* ev_cmd = event_new(base, STDIN_FILENO,EV_READ | EV_PERSIST, cmd_msg_cb,(void*)bev);event_add(ev_cmd, NULL);event_base_dispatch(base);printf("finished \n");return 0;
}void cmd_msg_cb(int fd, short events, void* arg)
{char msg[1024];string proto_msg;int ret = read(fd, msg, sizeof(msg));if( ret <= 0 ){perror("read fail ");exit(1);}cout <<"终端输入:" << msg << endl;struct bufferevent* bev = (struct bufferevent*)arg;list_account_records_request larr;larr.set_mobile("18106050285");larr.SerializeToString(&proto_msg);cout << "proto_msg 内容:"<<proto_msg.c_str() << endl;cout << "proto_msg长度为:"<<proto_msg.length() << endl;if (bev==NULL)cout << "bev为空" << endl;bufferevent_write(bev,proto_msg.c_str(),proto_msg.length());
}void server_msg_cb(int fd, short events, void* arg)
{char msg[1024];//为了简单起见，不考虑读一半数据的情况int len = read(fd, msg, sizeof(msg)-1);msg[len] = '\0';if( len == 0 ){printf("connection close. exit~\n");exit(1);}else if(len < 0){perror("read fail ");return ;}msg[len] = '\0';printf("recv from server<<<<< [%s] \n", msg);
}typedef struct sockaddr SA;
int tcp_connect_server(const char* server_ip, int port)
{int sockfd, status, save_errno;struct sockaddr_in server_addr;memset(&server_addr, 0, sizeof(server_addr) );server_addr.sin_family = AF_INET;server_addr.sin_port = htons(port);status = inet_aton(server_ip, &server_addr.sin_addr);if( status == 0 ) //the server_ip is not valid value{errno = EINVAL;return -1;}sockfd = socket(PF_INET, SOCK_STREAM, 0);if( sockfd == -1 )return sockfd;status = connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );if( status == -1 ){save_errno = errno;close(sockfd);errno = save_errno; //the close may be errorreturn -1;}//evutil_make_socket_nonblocking(sockfd);return sockfd;
}

编译

g++ -std=c++11 client.cc bike.pb.cc -lprotobuf -levent -o client.exe

要加上-lprotobuf -levent 和 C++11标准

服务端代码

server.cc

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>#include <unistd.h>
#include <event.h>
#include <event2/event.h>
#include<event2/listener.h>
#include <assert.h>
#include<string>#include"bike.pb.h"#define BUFLEN  1024using namespace std;
using namespace tutorial;typedef struct _ConnectStat {//struct event*  ev;struct bufferevent* bev;char buf[BUFLEN];
}ConnectStat;//echo 服务实现相关代码
ConnectStat * stat_init(int fd, struct bufferevent *bev);void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,  struct sockaddr *sock, int socklen, void *arg); //accept_connection(int fd, short events, void* arg);
void do_echo_request(struct bufferevent* bev, void* arg);
void event_cb(struct bufferevent *bev, short event, void *arg);
//void do_echo_response(int fd, short events, void *arg);int tcp_server_init(int port, int listen_num);struct event_base* base;int main(int argc, char** argv)
{struct sockaddr_in sin;  memset(&sin, 0, sizeof(struct sockaddr_in));  sin.sin_family = AF_INET;  sin.sin_port = htons(9999);  base = event_base_new();  struct evconnlistener *listener  = evconnlistener_new_bind(base, listener_cb, base,  LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE,  10, (struct sockaddr*)&sin,  sizeof(struct sockaddr_in));  event_base_dispatch(base);  evconnlistener_free(listener);event_base_free(base);return 0;  
}ConnectStat * stat_init(int fd, struct bufferevent *bev) {ConnectStat * temp = NULL;temp = (ConnectStat *)malloc(sizeof(ConnectStat));if (!temp) {fprintf(stderr, "malloc failed. reason: %m\n");return NULL;}memset(temp, '\0', sizeof(ConnectStat));temp->bev = bev;}/*
一个新客户端连接上服务器此函数就会被调用,当此函数被调用时，libevent已经帮我们accept了这个客户端。
该客户端的文件描述符为fd
*/
void listener_cb(struct evconnlistener *listener, evutil_socket_t fd,  struct sockaddr *sock, int socklen, void *arg)  
{  printf("accept a client %d\n", fd);  struct event_base *base = (struct event_base*)arg;  //为这个客户端分配一个bufferevent  struct bufferevent *bev =  bufferevent_socket_new(base, fd,  BEV_OPT_CLOSE_ON_FREE);ConnectStat *stat = stat_init(fd, bev);											   bufferevent_setcb(bev, do_echo_request, NULL, event_cb, stat);  bufferevent_enable(bev, EV_READ | EV_PERSIST);  
}  void do_echo_request(struct bufferevent* bev, void* arg)
{string request;ConnectStat *stat = (ConnectStat *)arg;char *msg = stat->buf;printf("do echo request ...\n");size_t len = bufferevent_read(bev, msg, BUFLEN);msg[len] = '\0';//解析protobuf 请求{list_account_records_request larr;request = msg;larr.ParseFromString(request);//反序列化printf("recv from client<<<< %s\n", larr.mobile().c_str());bufferevent_write(bev, larr.mobile().c_str(), larr.mobile().length());}}void event_cb(struct bufferevent *bev, short event, void *arg)
{ConnectStat *stat = (ConnectStat *)arg;if (event & BEV_EVENT_EOF)printf("connection closed\n");else if (event & BEV_EVENT_ERROR)printf("some other error\n");//这将自动close套接字和free读写缓冲区bufferevent_free(bev);free(stat);
}