Protobuf是一种可以实现内存与外存交换的协议接口。这是由谷歌开发的开源工具，目前研究Caffe源码时用到。
一个软件项目 = 数据结构 + 算法 + 参数，对于数据结构和算法我们都已经有较多研究，但不同开发者对参数管理却各有千秋。有人喜欢TXT格式化的参数文件，有人喜欢BIN简单高效，也有人喜欢图形化界面的直观。不一致的参数管理带来很多问题，例如一个项目组内不同成员必须约定一套统一的参数方案，或者称为通信协议，这样便于模块集成。而Protobuf工具就完美解决了这个问题，关键部分代码自动生成，节省了大量的开发、调试时间。
首先下载protobuf，地址（打不开？……不解释）
这里用Linux版本2.5.0
解压：
tar zxvf protobuf-2.5.0.tar.gz
切到主目录：
cdprotobuf-2.5.0
编译：
./configure
make
sudo make install
添加环境变量：
export PKG_CONFIG_PATH=$(pwd)
编译examples:
cd examples/
make cpp
这里我们只编译C++代码。
编译完成，生成了以下可执行文件：
add_person_cpp
list_people_cpp
这是个通讯录的例子。我们首先运行add_person_cpp：
./add_person_cpp zykzyk: File not found. Creating a new file.Enter person ID number: 123Enter name: zhaoyongkeEnter email address (blank for none): zhaoyongke@yeah.netEnter a phone number (or leave blank to finish): 188188188Is this a mobile, home, or work phone?（回车）Unknown phone type. Using default.Enter a phone number (or leave blank to finish):（回车）然后运行list_people_cpp：./list_people_cpp zykPerson ID: 123 Name: zhaoyongke E-mail address: zhaoyongke@yeah.net Home phone #: 188188188可见我们生成了新的通讯录zyk，里面保存了相应的信息。
例子运行结束了，我们看下代码是如何生成的。
protobuf使用前，先编写proto文件，这是描述我们需要配置参数的数据结构。这个例子里面的proto如下：
// See README.txt for information and build instructions.package tutorial;option java_package = "com.example.tutorial";option java_outer_classname = "AddressBookProtos";message Person { required string name = 1; required int32 id = 2;// Unique ID number for this person. 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;}// Our address book file is just one of these.message AddressBook { repeated Person person = 1;}前几行是定义包的，可以忽略。
message Person{…}定义了一个需要传输的参数结构体，可见包括这么几个单元：name（string类型）、id（int32类型）、email（string类型）、phone（PhoneNumber类型，嵌套在Person内的类）。前面标记为“required”是必须有值的，而“optional“则为可选项，”repeated“表示后面单元为相同类型的一组向量。
有了如上定义，我们可以用protobuf工具生成接口代码，命令如下：
protoc –cpp_out=. addressbook.proto运行后生成了两个文件：addressbook.pb.cc 和addressbook.pb.h，代码比较长就不贴了。我们的应用程序可以通过自动生成的接口实现参数的序列化/反序列化，代码如下：//add_person.c#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;}把自己当傻瓜，不懂就问，你会学的更多
