Protocol buffers基本上我把他想成是一個資料庫應用的延伸, 這話該如何說呢? 基本上他就是透過名為proto的meta file, 用以描述資料形態與內容(做encode/decode).
How does the Protocol Buffers work?
先定義你的message結構, 如
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;
}
再用protoc將該檔案轉成code, 目前支援(C++, Java and Python), 如下例子, 將brook.proto轉成C++(brook.pb.cc與brook.pb.h).
brook@vista:~/protobuf/CPP$ protoc --cpp_out=. brook.proto
brook@vista:~/protobuf/CPP$ ls
brook.pb.cc brook.pb.h brook.proto
這些code會包含存取每一個欄位的API(如下由doxygen產生的圖), 如email()與set_email(), 用以serialize/parse資料,
接著我們就可以用這些API寫一段code, 做serialize/parse資料
#include <iostream>
#include <fstream>
#include "brook.pb.h"
using namespace std;
static void _Serialize(void)
{
Person person;
person.set_name("John Doe");
person.set_id(1234);
person.set_email("jdoe@example.com");
fstream output("myfile", ios::out | ios::binary);
person.SerializeToOstream(&output);
}
static void _Parse(void)
{
Person person;
fstream input("myfile", ios::in | ios::binary);
person.ParseFromIstream(&input);
cout << "Name: " << person.name() << endl;
cout << "E-mail: " << person.email() << endl;
}
int main(int argc, char *argv[])
{
_Serialize();
_Parse();
return 0;
}
brook@vista:~/protobuf/CPP$ g++ main.c brook.pb.cc -lprotobuf
brook@vista:~/protobuf/CPP$ ./a.out
Name: John Doe
E-mail: jdoe@example.com
參考資料:
- protocol buffer簡介, https://developers.google.com/protocol-buffers/docs/overview
brook@vista:~/qemu/busybox$ cd ../busybox-build brook@vista:~/qemu/busybox-build$ make -j8 brook@vista:~/qemu/busybox-build$ cp busybox ../initrd-arm/bin/busybox generate initrd-image brook@vista:~/qemu$ ./linux-arm/usr/gen_initramfs_list.sh -d initrd-arm > /tmp/brook_initramfs_list brook@vista:~/qemu$ ./linux-arm/usr/gen_init_cpio /tmp/brook_initramfs_list > initrd-arm.img 執行QEMU brook@vista:~/qemu$ /usr/local/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel ./linux-arm/arch/arm/boot/zImage -dtb ./linux-arm/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -initrd ./initrd-arm.img -nographic -append "console=ttyAMA0"
