GoLang-Protocol Buffer

Protocol Buffer

Protocol Buffer is like json、xml, but smaller, faster, simplifier.
Only have to define data structure once, and it will generate the file which is match to your programming language automatically, let you use directly.

Structure is Document

Define data structure.

File should be .proto as suffix.

// Format is Proto v3
syntax = "proto3";

// User
message User {
    string username = 2;
    string password = 3;
}

// Post
message Post {
    int64 id       = 1;
    string content = 2;
}

What is the number after each field?

In fact, these are protocol buffer’s id when using decode and encode.
These will make you remove one of the field without messing up entire data structure encoding or decoding.

Pros and Cons with Json

• More lightweight
• Confusion: being encoded
• Performance high
• Much more convenient: structure is your data model, don’t have to create object to mapping these data
• Clear, no need document: .proto is your document

Installation

1. Install protocol buffer generator

• First, install protoc, which is the tool for transforming .proto to program.
• https://github.com/protocolbuffers/protobuf/releases install the protocol compiler
• After unzip, put the bin/protoc file to $PATH, this make us to use in terminal.

2. Install Golang plugin

• go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
• Do touch .bash_profile, and export PATH=$PATH:/Users/pingjing/go/bin to execute in terminal.

3. Transform proto document

• Create a example.proto file

// Format is Proto v3
syntax = "proto3";

// 生成的程式在 Golang 中將會是屬於 protobuf 套件
package protobuf;

// User
message User {
    int64 id        = 1;
    string username = 2;
    string password = 3;
}

• protoc --go_out=. *.proto transform to golang
• And we will get a file example.pb.go which is belongs to protobuf plugin.
• Then we can use this structure in golang.

4. Decode and Encode

• Create a folder /protobuf, and put example.pb.go in it.
• Create main.go

package main

import (
	"fmt"

	"./protobuf"
	"github.com/golang/protobuf/proto"
)

func main() {
	// Create a User format, and put data into it.
	data := protobuf.User{
		Id:       12345,
		Username: "Yu Wang",
		Password: "Hello",
	}

	// Make data encode to Protocol buffer format (Be aware of using Pointer)
	dataBuffer, _ := proto.Marshal(&data)

	// Make the data which is already encoded, decode to protobuf.User format
	var user protobuf.User
	proto.Unmarshal(dataBuffer, &user)

	// Output the result
	fmt.Println(user.Id, " ", user.Username, " ", user.Password)
}

• go run main.go
• Output 12345 Yu Wang Hello