Erlang JSON library
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README.md

jsone

hex.pm version Build Status Code Coverage License: MIT

An Erlang library for encoding, decoding JSON data.

Features

  • Provides simple encode/decode function only
  • RFC7159-compliant
  • Supports UTF-8 encoded binary
  • Pure Erlang
  • Highly Efficient
    • Maybe one of the fastest JSON library (except those which are implemented in NIF)
    • Decode function is written in continuation-passing style(CPS)

QuickStart

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

# compile
$ make compile

# run tests
$ make eunit

# dialyze
$ make dialyze

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

Enable HiPE

If you want to use HiPE compiled version, please add following code to your rebar.config.

{overrides,
  [
    {override, jsone, [{erl_opts, [{d, 'ENABLE_HIPE'}, inline]}]}
  ]}.

or use native profile. The make command supports profile as well. For example:

$ make start profile=native

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\"}">>

% 'undefined_as_null' option allows encoding atom undefined as null
> jsone:encode(undefined,[undefined_as_null]).
<<"null">>

%% 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
undefined              -> null                       -> undefined                  % undefined_as_null
true                   -> true                       -> true
false                  -> false                      -> false
<<"abc">>              -> "abc"                      -> <<"abc">>
abc                    -> "abc"                      -> <<"abc">> % non-special atom is regarded as a binary
{{2010,1,1},{0,0,0}}   -> "2010-01-01T00:00:00Z"     -> <<"2010-01-01T00:00:00Z">>     % datetime*
{{2010,1,1},{0,0,0.0}} -> "2010-01-01T00:00:00.000Z" -> <<"2010-01-01T00:00:00.000Z">> % datetime*
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
{{json, IOList}}       -> Value                      -> ~~~                        % UTF-8 encoded term**
{{json_utf8, Chars}}   -> Value                      -> ~~~                        % Unicode code points**

* see jsone:datetime_encode_format()

** {json, IOList} and {json_utf8, Chars} allows inline already encoded JSON values. For example, you obtain JSON encoded data from database so you don't have to decode it first and encode again. See jsone:json_term().

API

See EDoc Document

Benchmark

The results of poison benchmarking.

See the BENCHMARK.md file for more information.

EncoderBench Result

Non HiPE:

jiffy jsone poison jazz jsx
maps 7.23 μs/op 10.64 μs/op (2) 13.58 μs/op 19.30 μs/op 29.28 μs/op
lists 210.40 μs/op 157.39 μs/op (3) 109.30 μs/op 201.82 μs/op 357.25 μs/op
strings* 98.80 μs/op 595.63 μs/op (5) 416.78 μs/op 399.89 μs/op 262.18 μs/op
string escaping* 144.01 μs/op 732.44 μs/op (2) 1318.82 μs/op 1197.06 μs/op 1324.04 μs/op
large value** 408.03 μs/op 1556.85 μs/op (3) 1447.71 μs/op 1824.05 μs/op 2184.59 μs/op
pretty print** 420.94 μs/op 1686.55 μs/op (3) 1534.74 μs/op 2041.22 μs/op 5533.04 μs/op

HiPE:

jiffy jsone poison jazz jsx
maps 7.69 μs/op 6.12 μs/op (1) 12.32 μs/op 22.90 μs/op 27.03 μs/op
lists 207.75 μs/op 69.93 μs/op (1) 79.04 μs/op 229.95 μs/op 278.01 μs/op
strings* 96.67 μs/op 321.69 μs/op (5) 142.43 μs/op 310.10 μs/op 179.96 μs/op
string escaping* 146.85 μs/op 317.10 μs/op (2) 1277.54 μs/op 1311.85 μs/op 767.67 μs/op
large value** 409.73 μs/op 664.34 μs/op (2) 806.24 μs/op 1630.21 μs/op 1777.62 μs/op
pretty print** 419.55 μs/op 724.28 μs/op (2) 844.76 μs/op 1888.71 μs/op 4872.34 μs/op

* binary representation of UTF-8-demo.txt
** generated.json

ParserBench Result

Non HiPE:

jiffy jsone poison jsx
json value* 544.84 μs/op 1364.38 μs/op (2) 1401.35 μs/op 1844.55 μs/op
UTF-8 unescaping** 63.01 μs/op 399.38 μs/op (4) 249.70 μs/op 281.84 μs/op

HiPE:

jiffy jsone poison jsx
json value* 542.77 μs/op 561.15 μs/op (2) 751.36 μs/op 1435.10 μs/op
UTF-8 unescaping** 62.42 μs/op 92.63 μs/op (2) 118.97 μs/op 172.07 μs/op

* generated.json
** UTF-8-demo.txt

License

This library is released under the MIT License.

See the COPYING file for full license information.