Jiffy - JSON NIFs for Erlang
============================
A JSON parser as a NIF. This is a complete rewrite of the work I did
in EEP0018 that was based on Yajl. This new version is a hand crafted
state machine that does its best to be as quick and efficient as
possible while not placing any constraints on the parsed JSON.
[![Build Status](https://travis-ci.org/davisp/jiffy.svg?branch=master)](https://travis-ci.org/davisp/jiffy)
Usage
-----
Jiffy is a simple API. The only thing that might catch you off guard
is that the return type of `jiffy:encode/1` is an iolist even though
it returns a binary most of the time.
A quick note on unicode. Jiffy only understands UTF-8 in binaries. End
of story.
Errors are raised as error exceptions.
Eshell V5.8.2 (abort with ^G)
1> jiffy:decode(<<"{\"foo\": \"bar\"}">>).
{[{<<"foo">>,<<"bar">>}]}
2> Doc = {[{foo, [<<"bing">>, 2.3, true]}]}.
{[{foo,[<<"bing">>,2.3,true]}]}
3> jiffy:encode(Doc).
<<"{\"foo\":[\"bing\",2.3,true]}">>
`jiffy:decode/1,2`
------------------
* `jiffy:decode(IoData)`
* `jiffy:decode(IoData, Options)`
The options for decode are:
* `return_maps` - Tell Jiffy to return objects using the maps data type
on VMs that support it. This raises an error on VMs that don't support
maps.
* `{null_term, Term}` - Returns the specified `Term` instead of `null`
when decoding JSON. This is for people that wish to use `undefined`
instead of `null`.
* `use_nil` - Returns the atom `nil` instead of `null` when decoding
JSON. This is a short hand for `{null_term, nil}`.
* `return_trailer` - If any non-whitespace is found after the first
JSON term is decoded the return value of decode/2 becomes
`{has_trailer, FirstTerm, RestData::iodata()}`. This is useful to
decode multiple terms in a single binary.
* `dedupe_keys` - If a key is repeated in a JSON object this flag
will ensure that the parsed object only contains a single entry
containing the last value seen. This mirrors the parsing beahvior
of virtually every other JSON parser.
* `copy_strings` - Normally, when strings are decoded, they are
created as sub-binaries of the input data. With some workloads, this
leads to an undesirable bloating of memory: Strings in the decode
result keep a reference to the full JSON document alive. Setting
this option will instead allocate new binaries for each string, so
the original JSON document can be garbage collected even though
the decode result is still in use.
* `{bytes_per_red, N}` where N >= 0 - This controls the number of
bytes that Jiffy will process as an equivalent to a reduction. Each
20 reductions we consume 1% of our allocated time slice for the current
process. When the Erlang VM indicates we need to return from the NIF.
* `{bytes_per_iter, N}` where N >= 0 - Backwards compatible option
that is converted into the `bytes_per_red` value.
`jiffy:encode/1,2`
------------------
* `jiffy:encode(EJSON)`
* `jiffy:encode(EJSON, Options)`
where EJSON is a valid representation of JSON in Erlang according to
the table below.
The options for encode are:
* `uescape` - Escapes UTF-8 sequences to produce a 7-bit clean output
* `pretty` - Produce JSON using two-space indentation
* `force_utf8` - Force strings to encode as UTF-8 by fixing broken
surrogate pairs and/or using the replacement character to remove
broken UTF-8 sequences in data.
* `use_nil` - Encode's the atom `nil` as `null`.
* `escape_forward_slashes` - Escapes the `/` character which can be
useful when encoding URLs in some cases.
* `{bytes_per_red, N}` - Refer to the decode options
* `{bytes_per_iter, N}` - Refer to the decode options
Data Format
-----------
Erlang JSON Erlang
==========================================================================
null -> null -> null
true -> true -> true
false -> false -> false
"hi" -> [104, 105] -> [104, 105]
<<"hi">> -> "hi" -> <<"hi">>
hi -> "hi" -> <<"hi">>
1 -> 1 -> 1
1.25 -> 1.25 -> 1.25
[] -> [] -> []
[true, 1.0] -> [true, 1.0] -> [true, 1.0]
{[]} -> {} -> {[]}
{[{foo, bar}]} -> {"foo": "bar"} -> {[{<<"foo">>, <<"bar">>}]}
{[{<<"foo">>, <<"bar">>}]} -> {"foo": "bar"} -> {[{<<"foo">>, <<"bar">>}]}
#{<<"foo">> => <<"bar">>} -> {"foo": "bar"} -> #{<<"foo">> => <<"bar">>}
N.B. The last entry in this table is only valid for VM's that support
the `maps` data type (i.e., 17.0 and newer) and client code must pass
the `return_maps` option to `jiffy:decode/2`.
Improvements over EEP0018
-------------------------
Jiffy should be in all ways an improvement over EEP0018. It no longer
imposes limits on the nesting depth. It is capable of encoding and
decoding large numbers and it does quite a bit more validation of UTF-8 in strings.