protobuf的C简单的代码例子（一）

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三.开始一个最简单的项目好了，一切配置好了，该写代码了,我们做一个最简单的输入输出。新建一个main.cpp,然后把之前生成的person.pb.h和person.pb.cc复制到项目里面，并添加到项目里面。[cpp] view plaincopy在CODE上查看代码片派生到我的代码片#include <iostream> #include "person.pb.h" using namespace std; using namespace tutorial; int main() {    Person person;    person.set_name("flamingo");       person.set_age(18);       cout<<person.name()<<endl;    cout<<person.age()<<endl;    system("pause");    return 0; } 有些人说可以正常运行，但是我这边不行，主要是网上查找原因，终于发现，需要在代码里面加两行：[cpp] view plaincopy在CODE上查看代码片派生到我的代码片#pragma comment(lib,"libprotobuf.lib") #pragma comment(lib,"libprotoc.lib") 就能正常跑了：

根据语言指导手册创建一个简单的文件：amessage.proto ，内容如下

message AMessage
{
required int32 a=1;
optional int32 b=2;
}

t通过命令行产生相应的.h和.c源文件。 # protoc-c --c_out=.amessage.proto

C文件如下所示

#include<stdio.h>
#include<stdlib.h>
#include"amessage.pb-c.h"

int main (int argc,constchar* argv[])
{
  AMessage msg = AMESSAGE__INIT;// AMessage
  void*buf;        // Buffer to storeserialized data
  unsigned len;      // Length of serialized data

  if(argc !=2&& argc !=3)
  {   // Allow one or twointegers
fprintf(stderr,"usage:amessage a [b]\n");
  return1;
  }

msg.a = atoi(argv[1]);
  if(argc ==3){ msg.has_b =1; msg.b = atoi(argv[2]);}
len =amessage__get_packed_size(&msg);

buf = malloc(len);
amessage__pack(&msg,buf);

fprintf(stderr,"Writing %dserialized bytes\n",len);// See the lengthof message
fwrite(buf,len,1,stdout);// Write to stdoutto allow direct command line piping

free(buf);// Free theallocated serialized buffer
  return0;
}

注意以下几点:

使用A_MESSAGE__INIT宏创建信息的架构
参数b是可选的
amessage__get_packed_size返回数据包的长度。
a_message__pack 对你设计的信息进行打包。

下面给出对amessage解包的代码。

#include<stdio.h>
#include<stdlib.h>
#include"amessage.pb-c.h"
#define MAX_MSG_SIZE 1024

static size_t
read_buffer (unsigned max_length, uint8_t *out)
{
size_t cur_len =0;
uint8_t c;
  while((nread=fread(out+ cur_len,1, max_length - cur_len,stdin))!=0)
  {
cur_len += nread;
  if(cur_len == max_length)
  {
fprintf(stderr,"max messagelength exceeded\n");
  exit(1);
  }
  }
  return cur_len;
}

int main (int argc,constchar* argv[])
{
  AMessage*msg;

  // Read packed message from standard-input.
uint8_t buf[MAX_MSG_SIZE];
size_t msg_len = read_buffer (MAX_MSG_SIZE, buf);

  // Unpack the message using protobuf-c.
msg = amessage__unpack(NULL, msg_len, buf);
  if(msg == NULL)
  {
fprintf(stderr,"errorunpacking incoming message\n");
  exit(1);
  }

  // display the message's fields.
printf("Received: a=%d",msg->a);  // required field
  if(msg->has_b)        // handle optionalfield
printf(" b=%d",msg->b);
printf("\n");

  // Free the unpacked message
amessage__free_unpacked(msg, NULL);
  return0;
}

编译连接的时候要包含 '-lprotobuf-c'，否则编译不通过

Test by piping one program into the next atcommand line:

#./amessage_serialize 10 2 | ./amessage_deserialize ---->使用管道命令
Writing:4 serialized bytes
Received: a=10 b=2

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