google-protobuf使用指南
Oct 12, 2015
首先是安装必备的包
环境:fedora 22 64位
sudo dnf install gcc-g++
安装protoc
首先阅读protobuf介绍官网的What are protocol buffers?部分 清晰明了的介绍 就是类似于XML方式的格式化数据序列化 然后去protobuf-download下载最新的protobuf 安装过程以2.6.1为例:
$ tar -xzvf protobuf-2.6.1.tar.gz
$ cd protobuf-2.6.1
$ ./configure
$ make
$ make check
$ sudo make install
C++ demo实践
这里主要是跟着C++ toturial来进行 首先编写.proto
文件 emacs addressbook.proto
package tutorial;
message Person {
required string name = 1;
required int32 id = 2;
optional string email = 3;
enum PhoneType {
MOBILE = 0;
HOME = 1;
WORK = 2;
}
message PhoneNumber {
required string number = 1;
optional PhoneType type = 2 [default = HOME];
}
repeated PhoneNumber phone = 4;
}
message AddressBook {
repeated Person person = 1;
}
然后在当前目录下执行:
protoc -I=./ --cpp_out=./ addressbook.proto
会生成2个文件 addressbook.pb.cc addressbook.pb.h
序列化到文件中 emacs message_writer.cc
:
#include <iostream>
#include <fstream>
#include <string>
#include "addressbook.pb.h"
using namespace std;
// This function fills in a Person message based on user input.
void PromptForAddress(tutorial::Person* person) {
cout << "Enter person ID number: ";
int id;
cin >> id;
person->set_id(id);
cin.ignore(256, '\n');
cout << "Enter name: ";
getline(cin, *person->mutable_name());
cout << "Enter email address (blank for none): ";
string email;
getline(cin, email);
if (!email.empty()) {
person->set_email(email);
}
while (true) {
cout << "Enter a phone number (or leave blank to finish): ";
string number;
getline(cin, number);
if (number.empty()) {
break;
}
tutorial::Person::PhoneNumber* phone_number = person->add_phone();
phone_number->set_number(number);
cout << "Is this a mobile, home, or work phone? ";
string type;
getline(cin, type);
if (type == "mobile") {
phone_number->set_type(tutorial::Person::MOBILE);
} else if (type == "home") {
phone_number->set_type(tutorial::Person::HOME);
} else if (type == "work") {
phone_number->set_type(tutorial::Person::WORK);
} else {
cout << "Unknown phone type. Using default." << endl;
}
}
}
// Main function: Reads the entire address book from a file,
// adds one person based on user input, then writes it back out to the same
// file.
int main(int argc, char* argv[]) {
// 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;
if (argc != 2) {
cerr << "Usage: " << argv[0] << " ADDRESS_BOOK_FILE" << endl;
return -1;
}
tutorial::AddressBook address_book;
{
// Read the existing address book.
fstream input(argv[1], ios::in | ios::binary);
if (!input) {
cout << argv[1] << ": File not found. Creating a new file." << endl;
} else if (!address_book.ParseFromIstream(&input)) {
cerr << "Failed to parse address book." << endl;
return -1;
}
}
// Add an address.
PromptForAddress(address_book.add_person());
{
// Write the new address book back to disk.
fstream output(argv[1], ios::out | ios::trunc | ios::binary);
if (!address_book.SerializeToOstream(&output)) {
cerr << "Failed to write address book." << endl;
return -1;
}
}
// Optional: Delete all global objects allocated by libprotobuf.
google::protobuf::ShutdownProtobufLibrary();
return 0;
}
编译执行:
$ g++ -l protobuf addressbook.pb.cc message_writer.cc -o message_w
$ ./message_w book
./message_w: error while loading shared libraries: libprotobuf.so.9: cannot open shared object file: No such file or directory
这里一定注意的是 使用 g++ 并且要使用-l protobuf
选项!
此时执行一般会报上面的错误:
$ export LD_LIBRARY_PATH=/usr/local/lib
$ ./message_w book
编写序列化文件读取 emacs message_reader.cc
#include <iostream>
#include <fstream>
#include <string>
#include "addressbook.pb.h"
using namespace std;
// Iterates though all people in the AddressBook and prints info about them.
void ListPeople(const tutorial::AddressBook& address_book) {
for (int i = 0; i < address_book.person_size(); i++) {
const tutorial::Person& person = address_book.person(i);
cout << "Person ID: " << person.id() << endl;
cout << " Name: " << person.name() << endl;
if (person.has_email()) {
cout << " E-mail address: " << person.email() << endl;
}
for (int j = 0; j < person.phone_size(); j++) {
const tutorial::Person::PhoneNumber& phone_number = person.phone(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;
}
}
}
// Main function: Reads the entire address book from a file and prints all
// the information inside.
int main(int argc, char* argv[]) {
// 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;
if (argc != 2) {
cerr << "Usage: " << argv[0] << " ADDRESS_BOOK_FILE" << endl;
return -1;
}
tutorial::AddressBook address_book;
{
// Read the existing address book.
fstream input(argv[1], ios::in | ios::binary);
if (!address_book.ParseFromIstream(&input)) {
cerr << "Failed to parse address book." << endl;
return -1;
}
}
ListPeople(address_book);
// Optional: Delete all global objects allocated by libprotobuf.
google::protobuf::ShutdownProtobufLibrary();
return 0;
}
之后:
$ g++ -l protobuf addressbook.pb.cc message_reader.cc -o message_r
[hercules@diana cpp]$ ./message_r book
Person ID: 7
Name: will
E-mail address: xz.will.shek@gmail.com
Mobile phone #: 13355667788
Person ID: 4
Name: will
E-mail address: will@gmai.com
Person ID: 6
Name: Jack
E-mail address: Jack.ma@alibaba.com
Home phone #: 13370614984
Home phone #: 88887777
Person ID: 8
Name: Tom
E-mail address: tom@126.com
Mobile phone #: 13344445555
Mobile phone #: 14433332222
Work phone #: 88896754