protobuf入门教程(五)：枚举(enum)、包（package）

枚举(enum)

消息格式

当需要定义一个消息类型的时候，可能想为一个字段指定某“预定义值序列”中的一个值，这时候可以通过枚举实现。

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

    enum PhoneType //枚举消息类型
    {
        MOBILE = 0; //proto3版本中，首成员必须为0，成员不应有相同的值
        HOME = 1;
        WORK = 2;
    }

    message PhoneNumber
    {
        string number = 1;
        PhoneType type = 2;
    }

    repeated PhoneNumber phones = 4; //phones为数组
}

message AddressBook
{
    repeated Person people = 1;
}

测试程序

void set_addressbook()
{
    AddressBook obj;

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

    Person::PhoneNumber *phone1 = p1->add_phones(); //增加一个phone
    phone1->set_number("110");
    phone1->set_type(Person::MOBILE);

    Person::PhoneNumber *phone2 = p1->add_phones(); //增加一个phone
    phone2->set_number("120");
    phone2->set_type(Person::HOME);

    fstream output("pb.xxx", 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.xxx", 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;

        for (int j = 0; j < person.phones_size(); j++)
        {
            const Person::PhoneNumber& phone_number = person.phones(j);

            switch (phone_number.type())
            {
            case Person::MOBILE:
                cout << "  Mobile phone #: ";
                break;
            case Person::HOME:
                cout << "  Home phone #: ";
                break;
            case Person::WORK:
                cout << "  Work phone #: ";
                break;
            }

            cout << phone_number.number() << endl;
        }
        cout <<

包（package）

消息格式

.proto文件新增一个可选的package声明符，用来防止不同的消息类型有命名冲突。包的声明符会根据使用语言的不同影响生成的代码。对于C++，产生的类会被包装在C++的命名空间中。

syntax = "proto3";//指定版本信息，不指定会报错

package tutorial; //package声明符

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

    enum PhoneType //枚举消息类型
    {
        MOBILE = 0; //proto3版本中，首成员必须为0，成员不应有相同的值
        HOME = 1;
        WORK = 2;
    }

    message PhoneNumber
    {
        string number = 1;
        PhoneType type = 2;
    }

    repeated PhoneNumber phones = 4; //phones为数组
}

message AddressBook
{
    repeated Person people = 1;
}

测试程序

void set_addressbook()
{
    tutorial::AddressBook obj;

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

    tutorial::Person::PhoneNumber *phone1 = p1->add_phones(); //增加一个phone
    phone1->set_number("110");
    phone1->set_type(tutorial::Person::MOBILE);

    tutorial::Person::PhoneNumber *phone2 = p1->add_phones(); //增加一个phone
    phone2->set_number("120");
    phone2->set_type(tutorial::Person::HOME);

    fstream output("pb.xxx", 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()
{
    tutorial::AddressBook obj;
    fstream input("./pb.xxx", 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 tutorial::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;

        for (int j = 0; j < person.phones_size(); j++)
        {
            const tutorial::Person::PhoneNumber& phone_number = person.phones(j);

            switch (phone_number.type())
            {
            case tutorial::Person::MOBILE:
                cout << "  Mobile phone #: ";
                break;
            case tutorial::Person::HOME:
                cout << "  Home phone #: ";
                break;
            case tutorial::Person::WORK:
                cout << "  Work phone #: ";
                break;
            }

            cout << phone_number.number() << endl;
        }
        cout <<