在erlang项目中使用protobuf

在erlang项目中使用protobuf

http://blog.csdn.net/mycwq/article/details/21864191

protobuf是google的一个序列化框架，类似XML，JSON，其特点是基于二进制，比XML表示同样一段内容要短小得多，还可以定义一些可选字段，广泛用于服务端与客户端通信。文章将着重介绍在erlang中如何使用protobuf。

首先google没有提供对erlang语言的直接支持，所以这里使用到的第三方的protobuf库（erlang_protobuffs）

https://github.com/basho/erlang_protobuffs

定义一个protobuf结构，保存为test.proto，如下：

enum PhoneType {
 　　PhoneType_Home = 1;
       PhoneType_Company = 2;
}

message Person {
  required int32 age = 1;
  required string name = 2;
}

message Other {
  required PhoneType type = 1;
  required string phone = 2;
}

message Family {
  required int32 mainid = 1;
  optional Other other = 2;
  repeated Person person = 3;
}

编译这个protobuf结构，生成相应的erlang代码：

% 生成相应的erl和hrl文件
protobuffs_compile:generate_source("test.proto").

% 生成相应的beam和hrl文件
protobuffs_compile:scan_file("test.proto").

下面我们以例子简单说明如何使用：

-module(test).

-compile([export_all]).

-include("test_pb.hrl").

encode() ->
    Person = #person{age=25, name="John"},
    test_pb:encode_person(Person).

decode() ->
    Data = erlang:iolist_to_binary(encode()),
    io:format("Data is ~p~n", [Data]),
    test_pb:decode_person(Data).

encode_repeat() ->
    OtherData = #other{type='PhoneType_Company', phone="028-12345678"},
    RepeatData =
    [
        #person{age=25, name="John"},
        #person{age=23, name="Lucy"},
        #person{age=2, name="Tony"}
    ],
    Family = #family{mainid=111, other=OtherData, person=RepeatData},
    test_pb:encode_family(Family).

decode_repeat() ->
    Data = erlang:iolist_to_binary(encode_repeat()),
    io:format("Data is ~p~n", [Data]),
    %test_pb:decode_family(Data).
    FamilyData = test_pb:decode_family(Data),
    {family, _, _, PersonData} = FamilyData,
    io:format("~p~n", [FamilyData]),
    io:format("Per Len is ~w~n~n", [length(PersonData)]),
    parse_repeat(PersonData).


parse_repeat([]) ->
    ok;
parse_repeat([H|T]) ->
    if is_record(H, person) ->
     　　　　   io:format("age[~p],name[~p]~n", [H#person.age, H#person.name])
    end,
    parse_repeat(T).

运行代码，如下：

5> c(test_pb).
{ok,test_pb}
6> c(test).
{ok,test}

7> test:encode().
[[["",[25]],[[18],[4],<<"John">>]]]

8> test:decode().
Data is <<8,25,18,4,74,111,104,110>>{person,25,"John"}

9> test:encode_repeat().
[[["","o"],  [[18],[16],[[["",[2]],[[18],"f",<<"028-12345678">>]]]],  [[[26],"",[[["",[25]],[[18],[4],<<"John">>]]]],   [[26],"",[[["",[23]],[[18],[4],<<"Lucy">>]]]],   [[26],"",[[["",[2]],[[18],[4],<<"Tony">>]]]]]]]

10> test:decode_repeat().
Data is <<8,111,18,16,8,2,18,12,48,50,56,45,49,50,51,52,53,54,55,56,26,8,8,25,          18,4,74,111,104,110,26,8,8,23,18,4,76,117,99,121,26,8,8,2,18,4,84,          111,110,121>>{family,111,        {other,'PhoneType_Company',"028-12345678"},        [{person,25,"John"},{person,23,"Lucy"},{person,2,"Tony"}]}Per Len is 3
age[25],name["John"]age[23],name["Lucy"]age[2],name["Tony"]ok

文章完整例子下载：http://download.csdn.net/detail/cwqcwk1/7087293