Protobuf c的使用范例

protobuffer (簡稱PB)　網上的文章一大堆，隨便看看，PB使用起來非常方便。這里主要講講Protobuf C(簡稱PC)的使用

1，代碼

https://github.com/protobuf-c/protobufc/releases/download/v1.3.2/protobuf-c-1.3.2.tar.gz

2，編譯

先決條件（PB也要安裝）

sudo apt-get install autoconf automake libtool curl make g++ unzip

PC的編譯

./autogen.sh && make &&make check之后sudo make install;sudo ldconfig

3，“編譯”proto文件

protoc-c -I=./proto --c_out=./proto ./proto/main.proto

4，proto文件定義

這部分和PB是完全一樣的，這里就不重復了

enum MessageType {
    MSG_REQUEST = 0;
    MSG_NOTIFICATION = 1;
}

message Message {
    MessageType type = 1;
    fixed32 seq = 2;
    fixed64 session_id = 3;
    string using_for_test = 4;
    Response response = 5;
}

message Response {
    enum ResponseType {
        RESPONSE_SYSTEM_STATE = 0;
        RESPONSE_HARDWARE_STATE = 1;

    }
    ResponseType response_type = 1;
}

5，代碼中對PC定義的數據的訪問方式

生成一個消息

    /* example of using protobuf message */

    Message msg = MESSAGE__INIT;
    Response res = RESPONSE__INIT;

    //response msg
    msg.response = &res;
    res.response_type = RESPONSE_HARDWARE_STATE;

    msg->using_for_test = (char *)malloc(PROTO_STRING_LEN);
    memset(msg->using_for_test, 0, PROTO_STRING_LEN);

序列化一個消息

    //pack
    int len = message__get_packed_size(&msg);
    uint8_t *buf = (uint8_t *)malloc(len);
    message__pack(&msg, buf);

反序列化一個消息

    Message*rev = message__unpack(NULL, len, buf);
    message__free_unpacked(rev, NULL);

不要忘了手動釋放申請的資源 (這點PC很麻煩，涉及到動態長度的元素，資源要手動申請釋放)

　　free(buf);
　　free(msg->using_for_test);