protocol buffers c语言的使用

以下源码示例来源于https://github.com/protobuf-c/protobuf-c/wiki/Examples

定义消息

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

安装protobuf-c

我们需要把proto文件编译成c源码，才能在代码中使用，所以需要用到官方的编译工具

sudo apt-get install protobuf-c-compiler

编译

protoc-c --c_out=. amessage.proto //将会产生amessage.pb-c.c  amessage.pb-c.h两个文件

代码中使用

序列化：

//serialize_main.c#include <stdio.h>#include <stdlib.h>#include "amessage.pb-c.h"int main (int argc, const char * argv[]) {  AMessage msg = AMESSAGE__INIT; // AMessage  void *buf;                     // Buffer to store serialized data  unsigned len;                  // Length of serialized data  if (argc != 2 && argc != 3)  {   // Allow one or two integers    fprintf(stderr,"usage: amessage a [b]\n");    return 1;  }  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 %d serialized bytes\n",len); // See the length of message  fwrite(buf,len,1,stdout); // Write to stdout to allow direct command line piping  free(buf); // Free the allocated serialized buffer  return 0;}

反序列化：

//unserialize_main.c#include <stdio.h>#include <stdlib.h>#include "amessage.pb-c.h"#define MAX_MSG_SIZE 1024static size_tread_buffer (unsigned max_length, uint8_t *out){  size_t cur_len = 0;  size_t nread;  while ((nread=fread(out + cur_len, 1, max_length - cur_len, stdin)) != 0)  {    cur_len += nread;    if (cur_len == max_length)    {      fprintf(stderr, "max message length exceeded\n");      exit(1);    }  }  return cur_len;}int main (int argc, const char * 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, "error unpacking incoming message\n");    exit(1);  }  // display the message's fields.  printf("Received: a=%d",msg->a);  // required field  if (msg->has_b)                   // handle optional field    printf("  b=%d",msg->b);  printf("\n");  // Free the unpacked message  amessage__free_unpacked(msg, NULL);  return 0;}

编译可执行程序

gcc -o serialize_main serialize_main.c amessage.pb-c.c -lprotobuf-cgcc -o unserialize_main unserialize_main.c amessage.pb-c.c -lprotobuf-c

运行

./serialize_main 10086 -123 | ./unserialize_main