protocol buffers c语言的使用

定义消息

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

安装protobuf-c

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

//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;
}

//unserialize_main.c
#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;
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-c
gcc -o unserialize_main unserialize_main.c amessage.pb-c.c -lprotobuf-c

运行

./serialize_main 10086 -123 | ./unserialize_main