protoc - C++ Codes

Overview

这一节给出C++代码调用protoc的例子。

Compiling dependent packages

对于C++代码，需要确定protobuf对应的include或lib查找路径，以及依赖库名称。对应的命令：

$ pkg-config --cflags --libs protobuf
-D_THREAD_SAFE -I/usr/local/include -L/usr/local/lib -lprotobuf -D_THREAD_SAFE
$ 

或

$ pkg-config --cflags --libs protobuf
-pthread
$ 

Write / Serialize

代码中给出生成命令、生成文件的内容。

/*
g++ writer.cpp helloworld.pb.cc -I/usr/local/include -L/usr/local/lib -lprotobuf -pthread -lpthread

$ hexdump -C log 
00000000  08 65 12 05 68 65 6c 6c  6f                       |.e..hello|
00000009
$ 
*/
#include <iostream>
#include <fstream>

#include "helloworld.pb.h"

int main(void) 
{ 
    helloworld msg1; 
    msg1.set_id(101); 
    msg1.set_str("hello"); 

    // Write the new address book back to disk. 
    std::fstream output("./log", std::ios::out | std::ios::trunc | std::ios::binary); 

    if (!msg1.SerializeToOstream(&output)) { 
        std::cerr << "Failed to write msg." << std::endl; 
        return -1; 
    }

    return 0; 
}

Read / Deserialize

/*
g++ reader.cpp helloworld.pb.cc -I/usr/local/include -L/usr/local/lib -lprotobuf -pthread -lpthread

$ g++ reader.cpp helloworld.pb.cc -I/usr/local/include -L/usr/local/lib -lprotobuf -pthread -lpthread
$ ./a.out 
101
hello
$ 
*/

#include <iostream>
#include <fstream>

#include "helloworld.pb.h" 

void ListMsg(const helloworld & msg) 
{ 
    std::cout << msg.id() << std::endl; 
    std::cout << msg.str() << std::endl; 
} 

int main(int argc, char* argv[]) 
{ 
    helloworld msg; 

    std::fstream input("./log", std::ios::in | std::ios::binary); 
    if (!msg.ParseFromIstream(&input)) { 
        std::cerr << "Failed to parse address book." << std::endl; 
        return -1; 
    } 

    ListMsg(msg); 

    return 0;
}