Fast YAML

Fast YAML is an Erlang wrapper for libyaml "C" library.

It is designed to be fast and efficient.

Installation

Dependencies

Fast YAML depends on native LibYaml library. You need development headers for LibYaml library to build it.

The minimum required Erlang/OTP version is 18.0

Generic build

You can trigger build with:

./configure && make

OSX build example

You can install LibYaml and with Homebrew:

brew install libyaml

You can then export environment variable to use LibYaml as installed by Homebrew, before issuing compilation commands:

export LDFLAGS="-L/usr/local/lib"
export CFLAGS="-I/usr/local/include"
export CPPFLAGS="-I/usr/local/include"

./configure && make

Example usage

erl -pa ebin -pa deps/*/ebin
Erlang/OTP 18 [erts-7.1] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Eshell V7.1  (abort with ^G)

1> application:start(fast_yaml).
ok

2> fast_yaml:decode(<<"a: 1\nb: -3.0">>).
{ok,[[{<<"a">>,1},{<<"b">>,-3.0}]]}

Option `plain_as_atom`

Converts all unquoted YAML values to atoms

3> fast_yaml:decode(<<"a: 1\nb: -3.0">>, [{plain_as_atom, true}]).
{ok,[[{a,1},{b,-3.0}]]}

4> fast_yaml:decode(<<"a: b\nc">>).
{error,{scanner_error,<<"could not find expected ':'">>,2,
                      0}}.

5> fast_yaml:decode_from_file("test/test2.yml", [plain_as_atom]).
{ok,[[[{step,[{instrument,<<"Lasik 2000">>},
              {pulseEnergy,5.4},
              {pulseDuration,12},
              {repetition,1000},
              {spotSize,<<"1mm">>}]}],
      [{step,[{instrument,<<"Lasik 2000">>},
              {pulseEnergy,5.0},
              {pulseDuration,10},
              {repetition,500},
              {spotSize,<<"2mm">>}]}],
      [{step,<<"id001">>}],
      [{step,<<"id002">>}],
      [{step,<<"id001">>}],
      [{step,<<"id002">>}]]]}

Option `sane_scalars`

Converts the following scalar values to their Erlang-native data type:

"null" → undefined "true" → true "false" → false

Integer and float values also get converted. All other scalar values stay binaries. Key in mappings also stay binary and never get coerced into int / float / atom .

An unquoted mapping value that is an empty string gets converted into undefined. (e.g. the string "foo:" decodes as [{<<"foo">>, undefined}])

Option `maps`

Convert YAML mappings into Erlang maps.

7> fast_yaml:decode(<<"a: true\nb: -3.0\nc: string">>, [{maps, true}]).
{ok, [#{"a" => "true", "b" => -3.0, "c" => "string"}]}

For compatibility with the yamerl and YamlElixir libraries, use the [sane_scalars, maps] options.

Development

Test

Unit test

You can run eunit test with the command:

make test

processone/fast_yaml