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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, 2}, {space, 1}])]).
[
  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">>

%% If you want to safely cast object keys to atoms, the `attempt_atom' option will help.
> jsone:decode(<<"{\"hello\": \"world\"}">>, [{keys, attempt_atom}]).
#{<<"hello">> => <<"world">>}  % There is no atom named "hello", so the key is decoded as binary.

> hello.  % Create "hello" atom.
hello

> jsone:decode(<<"{\"hello\": \"world\"}">>, [{keys, attempt_atom}]).
#{hello => <<"world">>} % Now, the key is decoded as atom.

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/README.md file for more information.

Encoding (Unit: IPS=inputs per second)

Input data \ Library Jason jiffy JSON* jsone JSX Poison Tiny
Blockchain 2.77 K 4.55 K 0.45 K 1.44 K (3) 0.60 K 1.30 K 0.99 K
Giphy 230.65 487.67 47.73 114.57 (4) 44.97 114.57 113.59
GitHub 880.03 1566.67 139.79 300.26 (5) 99.68 424.75 455.07
GovTrack 6.57 24.92 2.33 5.35 (5) 2.65 7.06 7.86
Issue 90 22.80 21.92 0.77 14.30 (3) 5.33 12.60 12.95
JSON Generateor 200.40 606.81 42.45 147.12 (4) 68.73 187.95 123.93
Pokedex 209.51 776.67 62.60 161.45 (4) 69.87 190.93 125.16
UTF-8 unescaped 626.25 6644.53 1167.89 582.41 (4) 273.48 401.44 220.14

* Only JSON didn't escape non-ASCII unicode characters on the encoding

Decoding (Unit: IPS=inputs per second)

Input data \ Library Jason jiffy JSON jsone JSX Poison Tiny
Blockchain 2.75 K 2.62 K 0.35 K 2.21 K (3) 0.89 K 1.32 K 1.49 K
Giphy 212.18 243.45 35.67 109.11 (5) 64.32 110.76 114.54
GitHub 973.41 1052.94 137.02 662.39 (3) 271.97 438.79 542.67
GovTrack 10.77 8.32 0.80 5.08 (3) 2.81 3.58 3.65
Issue 90 17.85 41.16 0.88 10.79 (5) 6.02 13.63 14.03
JSON Generateor 320.79 243.93 25.16 184.23 (3) 111.24 135.47 139.78
JSON Generateor (Pretty) 273.57 205.09 25.04 158.82 (3) 97.93 123.31 136.65
Pokedex 527.63 285.43 33.70 245.36 (3) 140.90 172.45 152.59
UTF-8 escaped 1224.48 7923.08 326.43 573.70 (4) 550.36 918.21 520.31
UTF-8 unescaped 5.56 K 12.54 K 1.35 K 5.09 K (3) 3.30 K 4.39 K 1.46 K

License

This library is released under the MIT License.

See the COPYING file for full license information.