【Protocol Buffer】Protocol Buffer入门教程(五)：repeated限定修饰符

版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。

本文链接： https://blog.csdn.net/dengjin20104042056/article/details/102465638

00. 目录

01. 限定修饰符介绍

repeated 代表可重复，我们可以理解为数组

syntax = "proto3";//指定版本信息，不指定会报错

message Person //message为关键字，作用为定义一种消息类型
{
    string name = 1;    //姓名
    int32 id = 2;       //id
    string email = 3;   //邮件
}

message AddressBook
{
    repeated Person people = 1;
}

02. 字段API分析

deng@itcast:/mnt/hgfs/LinuxHome/day03$ protoc addressbook.proto --cpp_out=./
deng@itcast:/mnt/hgfs/LinuxHome/day03$ 

而对于字段修饰符为repeated的字段生成的函数，则稍微有一些不同，如people字段，则编译器会为其产生如下的代码：

  enum : int {
    kPeopleFieldNumber = 1,
  };  
  // repeated .Person people = 1;
  int people_size() const;
  private:
  int _internal_people_size() const;
  public:
  void clear_people();
  ::Person* mutable_people(int index);
  ::PROTOBUF_NAMESPACE_ID::RepeatedPtrField< ::Person >*
      mutable_people();
  private:
  const ::Person& _internal_people(int index) const;
  ::Person* _internal_add_people();
  public:
  const ::Person& people(int index) const;
  ::Person* add_people();
  const ::PROTOBUF_NAMESPACE_ID::RepeatedPtrField< ::Person >&
      people() const;

03. 测试代码

参考代码如下：

#include "addressbook.pb.h"
#include <iostream>
#include <fstream>


using namespace std;

void set_addressbook()
{
    AddressBook obj;

    Person *p1 = obj.add_people(); //新增加一个Person
    p1->set_name("tom");
    p1->set_id(1);
    p1->set_email("[email protected]");

    Person *p2 = obj.add_people(); //新增加一个Person
    p2->set_name("jim");
    p2->set_id(2);
    p2->set_email("[email protected]");

    Person *p3 = obj.add_people(); //新增加一个Person
    p3->set_name("abc");
    p3->set_id(3);
    p3->set_email("[email protected]");

    fstream output("pb.itcast", ios::out | ios::trunc | ios::binary);

    bool flag = obj.SerializeToOstream(&output);//序列化
    if (!flag)
    {
        cerr << "Failed to write file." << endl;
        return;
    }

    output.close();//关闭文件
}

void get_addressbook()
{
    AddressBook obj;
    fstream input("./pb.itcast", ios::in | ios::binary);
    obj.ParseFromIstream(&input);  //反序列化
    input.close(); //关闭文件

    for (int i = 0; i < obj.people_size(); i++)
    {
        const Person& person = obj.people(i);//取第i个people
        cout << "第" << i + 1 << "个信息\n";
        cout << "name = " << person.name() << endl;
        cout << "id = " << person.id() << endl;
        cout << "email = " << person.email() << endl << endl;
    }
}

int main()
{
    // Verify that the version of the library that we linked against is
    // compatible with the version of the headers we compiled against.
    GOOGLE_PROTOBUF_VERIFY_VERSION;

    set_addressbook(); //序列化
    get_addressbook(); //反序列化

    // Optional:  Delete all global objects allocated by libprotobuf.
    google::protobuf::ShutdownProtobufLibrary();

    return 0;
}

04. 编译和测试

编译和测试

deng@itcast:/mnt/hgfs/LinuxHome/day03$ g++  test.cpp addressbook.pb.cc `pkg-config --libs --cflags protobuf`
deng@itcast:/mnt/hgfs/LinuxHome/day03$ ./a.out 
第1个信息
name = tom
id = 1
email = [email protected]

第2个信息
name = jim
id = 2
email = [email protected]

第3个信息
name = abc
id = 3
email = [email protected]

deng@itcast:/mnt/hgfs/LinuxHome/day03$ 

05. 参考

官方参考文档:https://developers.google.cn/protocol-buffers/docs/reference/cpp-generated#repeatednumeric

测试代码下载：测试代码下载