115 lines
No EOL
4.2 KiB
Erlang
115 lines
No EOL
4.2 KiB
Erlang
%% The MIT License
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%% Copyright (c) 2010 Alisdair Sullivan <alisdairsullivan@yahoo.ca>
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%% Permission is hereby granted, free of charge, to any person obtaining a copy
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%% of this software and associated documentation files (the "Software"), to deal
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%% in the Software without restriction, including without limitation the rights
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%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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%% copies of the Software, and to permit persons to whom the Software is
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%% furnished to do so, subject to the following conditions:
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%% The above copyright notice and this permission notice shall be included in
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%% all copies or substantial portions of the Software.
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%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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%% THE SOFTWARE.
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%% this module is an example of how to use the raw parser api
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-module(jsx_parser).
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-author("alisdairsullivan@yahoo.ca").
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-export([decode/1, event/2]).
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%% export to allow the dirty hack below
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-export([literal/1, string/1, float/1, integer/1]).
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%% this is a strict parser, no comments, no naked values and only one key per object. it
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%% also is not streaming, though it could be modified to parse partial objects/lists.
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%% event takes two arguments, the result of calling the parser on a json argument (or the
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%% generator returned by the parser) and a term that holds the erlang representation of
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%% the json.
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decode(JSON) ->
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F = jsx:parser(),
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try event(F(JSON), [])
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catch error:badjson -> {error, badjson}
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end.
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%% erlang representation is dicts for objects and lists for arrays.
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event({start_object, Next}, Stack) ->
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event(Next(), [dict:new()] ++ Stack);
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event({start_array, Next}, Stack) ->
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event(Next(), [[]] ++ Stack);
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event({end_object, Next}, [Object, {key, Key}, Parent|Stack]) when is_tuple(Parent) ->
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event(Next(), [insert(Key, Object, Parent)] ++ Stack);
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event({end_array, Next}, [Array, {key, Key}, Parent|Stack]) when is_tuple(Parent) ->
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event(Next(), [insert(Key, lists:reverse(Array), Parent)] ++ Stack);
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event({end_object, Next}, [Object, Parent|Stack]) when is_list(Parent) ->
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event(Next(), [[Object] ++ Parent] ++ Stack);
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event({end_array, Next}, [Array, Parent|Stack]) when is_list(Parent) ->
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event(Next(), [[lists:reverse(Array)] ++ Parent] ++ Stack);
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%% special cases for closing the root objects
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event({end_object, Next}, [Object]) ->
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event(Next(), [Object]);
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event({end_array, Next}, [Array]) ->
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event(Next(), [lists:reverse(Array)]);
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%% keys are just pushed onto the stack until their corresponding value is
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%% encountered
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event({{key, Key}, Next}, [Stack]) ->
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event(Next(), [{key, Key}] ++ Stack);
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%% reject values that aren't wrapped by an array or object
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event({{_Type, _Value}, _Next}, []) ->
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{error, badjson};
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%% this is kind of a dirty hack, but erlang will interpret atoms when applied to (Args)
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%% as a function. so naming our formatting functions string, integer, float and literal will
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%% allow the following shortcut
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event({{Type, Value}, Next}, [{key, Key}, Object|Stack]) ->
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event(Next(), [insert(Key, ?MODULE:Type(Value), Object)] ++ Stack);
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event({{Type, Value}, Next}, [Array|Stack]) when is_list(Array) ->
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event(Next(), [[?MODULE:Type(Value)] ++ Array] ++ Stack);
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event({end_json, _}, [Stack]) ->
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Stack.
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%% we're restricting keys to one occurence per object, as the spec implies.
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insert(Key, Val, Dict) ->
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case dict:is_key(Key, Dict) of
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false -> dict:store(Key, Val, Dict)
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; true -> erlang:error(badjson)
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end.
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%% strings and literals we just return with no post-processing, numbers we convert
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%% from strings to integers/floats as appropriate
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string(String) ->
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String.
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integer(Number) ->
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list_to_integer(Number).
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float(Number) ->
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list_to_float(Number).
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literal(Literal) ->
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Literal. |