jsone (1.0.0)

An Erlang library for encoding, decoding JSON data.

Features

• Provides simple encode/decode function only
• RFC4627-compliant
• Supports UTF-8 encoded binary
• Pure Erlang
• Highly Efficient
  • Maybe one of the fastest JSON library (except those which are implemented in NIF)
    • See Benchmark
  • Decode function is written in continuation-passing style(CPS)
    • CPS facilitates application of 'creation of sub binary delayed' optimization
    • See also Erlang Efficiency Guide

QuickStart

# clone
$ git clone git://github.com/sile/jsone.git
$ cd jsone

# If you want to use HiPE enabled version, please execute following command.
# $ git checkout hipe

# compile
$ make compile

# run tests
$ make eunit

# dialyze
$ make dialyze

# Erlang shell
$ make start
1> jsone:decode(<<"[1,2,3]">>).
[1,2,3]

Usage Example

%% Decode
> jsone:decode(<<"[1,2,3]">>).
[1,2,3]

> jsone:decode(<<"{\"1\":2}">>).
#{<<"1">> => 2}

> jsone:decode(<<"{\"1\":2}">>, [{object_format, tuple}]). % tuple format
{[{<<"1">>, 2}]}

> jsone:decode(<<"{\"1\":2}">>, [{object_format, proplist}]). % proplist format
[{<<"1">>, 2}]

> jsone:try_decode(<<"[1,2,3] \"next value\"">>). % try_decode/1 returns remaining (unconsumed binary)
{ok,[1,2,3],<<" \"next value\"">>}

% error: raises exception
> jsone:decode(<<"1.x">>).
** exception error: bad argument
     in function  jsone_decode:number_fraction_part_rest/6
        called as jsone_decode:number_fraction_part_rest(<<"x">>,1,1,0,[],<<>>)
     in call from jsone:decode/1 (src/jsone.erl, line 71)

% error: returns {error, Reason}
> jsone:try_decode(<<"1.x">>).
{error,{badarg,[{jsone_decode,number_fraction_part_rest,
                              [<<"x">>,1,1,0,[],<<>>],
                              [{line,228}]}]}}


%% Encode
> jsone:encode([1,2,3]).
<<"[1,2,3]">>

> jsone:encode(#{<<"key">> => <<"value">>}).  % map format
> jsone:encode({[{<<"key">>, <<"value">>}]}). % tuple format
> jsone:encode([{<<"key">>, <<"value">>}]).  % proplist format
<<"{\"key\":\"value\"}">>

> jsone:encode(#{key => <<"value">>}). % atom key is allowed
<<"{\"key\":\"value\"}">>

% error: raises exception
> jsone:encode(#{123 => <<"value">>}). % non binary|atom key is not allowed
** exception error: bad argument
     in function  jsone_encode:object_members/3
        called as jsone_encode:object_members([{123,<<"value">>}],[],<<"{">>)
     in call from jsone:encode/1 (src/jsone.erl, line 97)

% error: returns {error, Reason}
> jsone:try_encode({[{123, <<"value">>}]}).
{error,{badarg,[{jsone_encode,object_members,
                              [[{123,<<"value">>}],[],<<"{">>],
                              [{line,138}]}]}}

% 'object_key_type' option allows non-string object key
> jsone:encode({[{123, <<"value">>}]}, [{object_key_type, scalar}]).
<<"{\"123\":\"value\"}">>

%% Pretty Print
> Data = [true, #{<<"1">> => 2, <<"array">> => [[[[1]]], #{<<"ab">> => <<"cd">>}, false]}, null].
> io:format("~s\n", [jsone:encode(Data, [{indent, 1}, {space, 2}])]).
[
  true,
  {
    "1": 2,
    "array": [
      [
        [
          [
            1
          ]
        ]
      ],
      {
        "ab": "cd"
      },
      false
    ]
  },
  null
]
ok

%% Number Format
> jsone:encode(1). % integer
<<"1">>

> jsone:encode(1.23). % float
<<"1.22999999999999998224e+00">> % default: scientific notation

> jsone:encode(1.23, [{float_format, [{decimals, 4}]}]). % decimal notation
<<"1.2300">>

> jsone:encode(1.23, [{float_format, [{decimals, 4}, compact]}]). % compact decimal notation
<<"1.23">>

Data Mapping (Erlang <=> JSON)

Erlang                  JSON             Erlang
=================================================================================================

null                 -> null          -> null
true                 -> true          -> true
false                -> false         -> false
<<"abc">>            -> "abc"         -> <<"abc">>
abc                  -> "abc"         -> <<"abc">> % non-special atom is regarded as a binary
123                  -> 123           -> 123
123.4                -> 123.4         -> 123.4
[1,2,3]              -> [1,2,3]       -> [1,2,3]
{[]}                 -> {}            -> {[]}                       % object_format=tuple
{[{key, <<"val">>}]} -> {"key":"val"} -> {[{<<"key">>, <<"val">>}]} % object_format=tuple
[{}]                 -> {}            -> [{}]                       % object_format=proplist
[{<<"key">>, val}]   -> {"key":"val"} -> [{<<"key">>, <<"val">>}]   % object_format=proplist
#{}                  -> {}            -> #{}                        % object_format=map
#{key => val}        -> {"key":"val"} -> #{<<"key">> => <<"val">>}  % object_format=map

API

See EDoc Document

Benchmark

Environment/Method

• OS: CentOS 6.5
• CPU: Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz (x8)
• Erlang/OTP: R17.1
• Benchmark Tool: erl_json_test
• CompileOption: [native, {hipe, [o3]}]

Target

• jiffy-0.11.3 (NIF)
• jsone-v0.2.3 (HiPE)
• jsonerl (HiPE)
• jsonx (NIF)
• jsx-v2.0.1 (HiPE)
• mochijson2 (HiPE)
• yawsjson2 (HiPE)

Decode Result

• column: module name
• row: data size (bytes)
• cell: elapsed time (micro seconds)

Encode Result

• column: module name
• row: data size (bytes)
• cell: elapsed time (micro seconds)