Cli to generate protocol buffers

This article is about generating binary from cli, and not about what protocol buffers are.

If you want to know, you should see official documentation: https://developers.google.com/protocol-buffers/docs/overview

Getting Started

Install a compiler for protocol buffer by homebrew first.

$ brew install protobuf
$ protoc --version
libprotoc 3.5.1

Prepare a proto file

$ cat protos/main.proto
syntax = "proto3";
message Html {
    enum Type {
        NO_TYPE = 0;
        HTML5 = 1;
        XHTML = 2;
    }
    Type type = 1;
    string head = 2;
    Body body = 3;
}
message Body {
    string header = 1;
    repeated string main = 2;
    string footer = 3;
}

Protoc cli usage

• Generate a code from a proto file

$ protoc --php_out=php protos/main.proto
$ ls php
Body.php GPBMetadata Html.php Html_Type.php

• Generate a binary by protoc with an encode option

$ cat proto.text
type: HTML5
head: "css"
body: {
    header: "header"
    main: "main"
    main: "main2"
    footer: "footer"
}
$ protoc --encode=Html protos/main.proto < proto.text  > binary.data
$ hexdump -C binary.data
00000000  08 01 12 03 63 73 73 1a  1d 0a 06 68 65 61 64 65  |....css....heade|
00000010  72 12 04 6d 61 69 6e 12  05 6d 61 69 6e 32 1a 06  |r..main..main2..|
00000020  66 6f 6f 74 65 72                                 |footer|
00000026$

• Unserialize from binary by protoc with decode option

$ protoc --decode Html protos/main.proto < binary.data
type: HTML5
head: "css"
body {
    header: "header"
    main: "main"
    main: "main2"
    footer: "footer"
}

Reference

• To use protocol buffers

jcayzac/play-protobuf

• The home brew repository for protocol buffers

Protobuf - BrewFormulas

• GitHub Issue: Use json format to decode by protoc

decode to json from command line · Issue #4024 · google/protobuf