mochijson2.erl - mochiweb

‹r86

r102

Source path: svn/ trunk/ src/ mochijson2.erl

%% @author Bob Ippolito <bob@mochimedia.com>
%% @copyright 2007 Mochi Media, Inc.

%% @doc Yet another JSON (RFC 4627) library for Erlang. mochijson2 works
%%      with binaries as strings, arrays as lists (without an {array, _})
%%      wrapper and it only knows how to decode UTF-8 (and ASCII).

-module(mochijson2).
-author('bob@mochimedia.com').
-export([encoder/1, encode/1]).
-export([decoder/1, decode/1]).
-export([test/0]).

% This is a macro to placate syntax highlighters..
-define(Q, $\").
-define(ADV_COL(S, N), S#decoder{offset=N+S#decoder.offset,
                                 column=N+S#decoder.column}).
-define(INC_COL(S), S#decoder{offset=1+S#decoder.offset,
                              column=1+S#decoder.column}).
-define(INC_LINE(S), S#decoder{offset=1+S#decoder.offset,
                               column=1,
                               line=1+S#decoder.line}).
-define(INC_CHAR(S, C),
        case C of
            $\n ->
                S#decoder{column=1,
                          line=1+S#decoder.line,
                          offset=1+S#decoder.offset};
            _ ->
                S#decoder{column=1+S#decoder.column,
                          offset=1+S#decoder.offset}
        end).
-define(IS_WHITESPACE(C),
        (C =:= $\s orelse C =:= $\t orelse C =:= $\r orelse C =:= $\n)).

%% @type iolist() = [char() | binary() | iolist()]
%% @type iodata() = iolist() | binary()
%% @type json_string() = atom | binary()
%% @type json_number() = integer() | float()
%% @type json_array() = [json_term()]
%% @type json_object() = {struct, [{json_string(), json_term()}]}
%% @type json_term() = json_string() | json_number() | json_array() |
%%                     json_object()

-record(encoder, {handler=null,
                  utf8=false}).

-record(decoder, {object_hook=null,
                  offset=0,
                  line=1,
                  column=1,
                  state=null}).

%% @spec encoder([encoder_option()]) -> function()
%% @doc Create an encoder/1 with the given options.
%% @type encoder_option() = handler_option() | utf8_option()
%% @type utf8_option() = boolean(). Emit unicode as utf8 (default - false)
encoder(Options) ->
    State = parse_encoder_options(Options, #encoder{}),
    fun (O) -> json_encode(O, State) end.

%% @spec encode(json_term()) -> iolist()
%% @doc Encode the given as JSON to an iolist.
encode(Any) ->
    json_encode(Any, #encoder{}).

%% @spec decoder([decoder_option()]) -> function()
%% @doc Create a decoder/1 with the given options.
decoder(Options) ->
    State = parse_decoder_options(Options, #decoder{}),
    fun (O) -> json_decode(O, State) end.

%% @spec decode(iolist()) -> json_term()
%% @doc Decode the given iolist to Erlang terms.
decode(S) ->
    json_decode(S, #decoder{}).

test() ->
    test_all().

%% Internal API

parse_encoder_options([], State) ->
    State;
parse_encoder_options([{handler, Handler} | Rest], State) ->
    parse_encoder_options(Rest, State#encoder{handler=Handler});
parse_encoder_options([{utf8, Switch} | Rest], State) ->
    parse_encoder_options(Rest, State#encoder{utf8=Switch}).

parse_decoder_options([], State) ->
    State;
parse_decoder_options([{object_hook, Hook} | Rest], State) ->
    parse_decoder_options(Rest, State#decoder{object_hook=Hook}).

json_encode(true, _State) ->
    <<"true">>;
json_encode(false, _State) ->
    <<"false">>;
json_encode(null, _State) ->
    <<"null">>;
json_encode(I, _State) when is_integer(I) andalso I >= -2147483648 andalso I =< 2147483647 ->
    %% Anything outside of 32-bit integers should be encoded as a float
    integer_to_list(I);
json_encode(I, _State) when is_integer(I) ->
    mochinum:digits(float(I));
json_encode(F, _State) when is_float(F) ->
    mochinum:digits(F);
json_encode(S, State) when is_binary(S); is_atom(S) ->
    json_encode_string(S, State);
json_encode(Array, State) when is_list(Array) ->
    json_encode_array(Array, State);
json_encode({struct, Props}, State) when is_list(Props) ->
    json_encode_proplist(Props, State);
json_encode(Bad, #encoder{handler=null}) ->
    exit({json_encode, {bad_term, Bad}});
json_encode(Bad, State=#encoder{handler=Handler}) ->
    json_encode(Handler(Bad), State).

json_encode_array([], _State) ->
    <<"[]">>;
json_encode_array(L, State) ->
    F = fun (O, Acc) ->
                [$,, json_encode(O, State) | Acc]
        end,
    [$, | Acc1] = lists:foldl(F, "[", L),
    lists:reverse([$\] | Acc1]).

json_encode_proplist([], _State) ->
    <<"{}">>;
json_encode_proplist(Props, State) ->
    F = fun ({K, V}, Acc) ->
                KS = json_encode_string(K, State),
                VS = json_encode(V, State),
                [$,, VS, $:, KS | Acc]
        end,
    [$, | Acc1] = lists:foldl(F, "{", Props),
    lists:reverse([$\} | Acc1]).

json_encode_string(A, State) when is_atom(A) ->
    L = atom_to_list(A),
    case json_string_is_safe(L) of
        true ->
            [?Q, L, ?Q];
        false ->
            json_encode_string_unicode(xmerl_ucs:from_utf8(L), State, [?Q])
    end;
json_encode_string(B, State) when is_binary(B) ->
    case json_bin_is_safe(B) of
        true ->
            [?Q, B, ?Q];
        false ->
            json_encode_string_unicode(xmerl_ucs:from_utf8(B), State, [?Q])
    end;
json_encode_string(I, _State) when is_integer(I) ->
    [?Q, integer_to_list(I), ?Q];
json_encode_string(L, State) when is_list(L) ->
    case json_string_is_safe(L) of
        true ->
            [?Q, L, ?Q];
        false ->
            json_encode_string_unicode(L, State, [?Q])
    end.

json_string_is_safe([]) ->
    true;
json_string_is_safe([C | Rest]) ->
    case C of
        ?Q ->
            false;
        $\\ ->
            false;
        $\b ->
            false;
        $\f ->
            false;
        $\n ->
            false;
        $\r ->
            false;
        $\t ->
            false;
        C when C >= 0, C < $\s; C >= 16#7f, C =< 16#10FFFF ->
            false;
        C when C < 16#7f ->
            json_string_is_safe(Rest);
        _ ->
            false
    end.

json_bin_is_safe(<<>>) ->
    true;
json_bin_is_safe(<<C, Rest/binary>>) ->
    case C of
        ?Q ->
            false;
        $\\ ->
            false;
        $\b ->
            false;
        $\f ->
            false;
        $\n ->
            false;
        $\r ->
            false;
        $\t ->
            false;
        C when C >= 0, C < $\s; C >= 16#7f, C =< 16#10FFFF ->
            false;
        C when C < 16#7f ->
            json_bin_is_safe(Rest);
        _ ->
            false
    end.


json_encode_string_unicode([], _State, Acc) ->
    lists:reverse([$\" | Acc]);
json_encode_string_unicode([C | Cs], State, Acc) ->
    Acc1 = case C of
               ?Q ->
                   [?Q, $\\ | Acc];
               %% Escaping solidus is only useful when trying to protect
               %% against "</script>" injection attacks which are only
               %% possible when JSON is inserted into a HTML document
               %% in-line. mochijson2 does not protect you from this, so
               %% if you do insert directly into HTML then you need to
               %% uncomment the following case or escape the output of encode.
               %%
               %% $/ ->
               %%    [$/, $\\ | Acc];
               %%
               $\\ ->
                   [$\\, $\\ | Acc];
               $\b ->
                   [$b, $\\ | Acc];
               $\f ->
                   [$f, $\\ | Acc];
               $\n ->
                   [$n, $\\ | Acc];
               $\r ->
                   [$r, $\\ | Acc];
               $\t ->
                   [$t, $\\ | Acc];
               C when C >= 0, C < $\s ->
                   [unihex(C) | Acc];
               C when C >= 16#7f, C =< 16#10FFFF, State#encoder.utf8 ->
                   [xmerl_ucs:to_utf8(C) | Acc];
               C when  C >= 16#7f, C =< 16#10FFFF, not State#encoder.utf8 ->
                   [unihex(C) | Acc];
               C when C < 16#7f ->
                   [C | Acc];
               _ ->
                   exit({json_encode, {bad_char, C}})
           end,
    json_encode_string_unicode(Cs, State, Acc1).

hexdigit(C) when C >= 0, C =< 9 ->
    C + $0;
hexdigit(C) when C =< 15 ->
    C + $a - 10.

unihex(C) when C < 16#10000 ->
    <<D3:4, D2:4, D1:4, D0:4>> = <<C:16>>,
    Digits = [hexdigit(D) || D <- [D3, D2, D1, D0]],
    [$\\, $u | Digits];
unihex(C) when C =< 16#10FFFF ->
    N = C - 16#10000,
    S1 = 16#d800 bor ((N bsr 10) band 16#3ff),
    S2 = 16#dc00 bor (N band 16#3ff),
    [unihex(S1), unihex(S2)].

json_decode(L, S) when is_list(L) ->
    json_decode(iolist_to_binary(L), S);
json_decode(B, S) ->
    {Res, S1} = decode1(B, S),
    {eof, _} = tokenize(B, S1#decoder{state=trim}),
    Res.

decode1(B, S=#decoder{state=null}) ->
    case tokenize(B, S#decoder{state=any}) of
        {{const, C}, S1} ->
            {C, S1};
        {start_array, S1} ->
            decode_array(B, S1);
        {start_object, S1} ->
            decode_object(B, S1)
    end.

make_object(V, #decoder{object_hook=null}) ->
    V;
make_object(V, #decoder{object_hook=Hook}) ->
    Hook(V).

decode_object(B, S) ->
    decode_object(B, S#decoder{state=key}, []).

decode_object(B, S=#decoder{state=key}, Acc) ->
    case tokenize(B, S) of
        {end_object, S1} ->
            V = make_object({struct, lists:reverse(Acc)}, S1),
            {V, S1#decoder{state=null}};
        {{const, K}, S1} ->
            {colon, S2} = tokenize(B, S1),
            {V, S3} = decode1(B, S2#decoder{state=null}),
            decode_object(B, S3#decoder{state=comma}, [{K, V} | Acc])
    end;
decode_object(B, S=#decoder{state=comma}, Acc) ->
    case tokenize(B, S) of
        {end_object, S1} ->
            V = make_object({struct, lists:reverse(Acc)}, S1),
            {V, S1#decoder{state=null}};
        {comma, S1} ->
            decode_object(B, S1#decoder{state=key}, Acc)
    end.

decode_array(B, S) ->
    decode_array(B, S#decoder{state=any}, []).

decode_array(B, S=#decoder{state=any}, Acc) ->
    case tokenize(B, S) of
        {end_array, S1} ->
            {lists:reverse(Acc), S1#decoder{state=null}};
        {start_array, S1} ->
            {Array, S2} = decode_array(B, S1),
            decode_array(B, S2#decoder{state=comma}, [Array | Acc]);
        {start_object, S1} ->
            {Array, S2} = decode_object(B, S1),
            decode_array(B, S2#decoder{state=comma}, [Array | Acc]);
        {{const, Const}, S1} ->
            decode_array(B, S1#decoder{state=comma}, [Const | Acc])
    end;
decode_array(B, S=#decoder{state=comma}, Acc) ->
    case tokenize(B, S) of
        {end_array, S1} ->
            {lists:reverse(Acc), S1#decoder{state=null}};
        {comma, S1} ->
            decode_array(B, S1#decoder{state=any}, Acc)
    end.

tokenize_string(B, S=#decoder{offset=O}) ->
    case tokenize_string_fast(B, O) of
        {escape, O1} ->
            Length = O1 - O,
            S1 = ?ADV_COL(S, Length),
            <<_:O/binary, Head:Length/binary, _/binary>> = B,
            tokenize_string(B, S1, lists:reverse(binary_to_list(Head)));
        O1 ->
            Length = O1 - O,
            <<_:O/binary, String:Length/binary, ?Q, _/binary>> = B,
            {{const, String}, ?ADV_COL(S, Length + 1)}
    end.

tokenize_string_fast(B, O) ->
    case B of
        <<_:O/binary, ?Q, _/binary>> ->
            O;
        <<_:O/binary, C, _/binary>> when C =/= $\\ ->
            tokenize_string_fast(B, 1 + O);
        _ ->
            {escape, O}
    end.

tokenize_string(B, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, ?Q, _/binary>> ->
            {{const, iolist_to_binary(lists:reverse(Acc))}, ?INC_COL(S)};
        <<_:O/binary, "\\\"", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\" | Acc]);
        <<_:O/binary, "\\\\", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\\ | Acc]);
        <<_:O/binary, "\\/", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$/ | Acc]);
        <<_:O/binary, "\\b", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\b | Acc]);
        <<_:O/binary, "\\f", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\f | Acc]);
        <<_:O/binary, "\\n", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\n | Acc]);
        <<_:O/binary, "\\r", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\r | Acc]);
        <<_:O/binary, "\\t", _/binary>> ->
            tokenize_string(B, ?ADV_COL(S, 2), [$\t | Acc]);
        <<_:O/binary, "\\u", C3, C2, C1, C0, _/binary>> ->
            %% coalesce UTF-16 surrogate pair?
            C = erlang:list_to_integer([C3, C2, C1, C0], 16),
            Acc1 = lists:reverse(xmerl_ucs:to_utf8(C), Acc),
            tokenize_string(B, ?ADV_COL(S, 6), Acc1);
        <<_:O/binary, C, _/binary>> ->
            tokenize_string(B, ?INC_CHAR(S, C), [C | Acc])
    end.

tokenize_number(B, S) ->
    case tokenize_number(B, sign, S, []) of
        {{int, Int}, S1} ->
            {{const, list_to_integer(Int)}, S1};
        {{float, Float}, S1} ->
            {{const, list_to_float(Float)}, S1}
    end.

tokenize_number(B, sign, S=#decoder{offset=O}, []) ->
    case B of
        <<_:O/binary, $-, _/binary>> ->
            tokenize_number(B, int, ?INC_COL(S), [$-]);
        _ ->
            tokenize_number(B, int, S, [])
    end;
tokenize_number(B, int, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, $0, _/binary>> ->
            tokenize_number(B, frac, ?INC_COL(S), [$0 | Acc]);
        <<_:O/binary, C, _/binary>> when C >= $1 andalso C =< $9 ->
            tokenize_number(B, int1, ?INC_COL(S), [C | Acc])
    end;
tokenize_number(B, int1, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
            tokenize_number(B, int1, ?INC_COL(S), [C | Acc]);
        _ ->
            tokenize_number(B, frac, S, Acc)
    end;
tokenize_number(B, frac, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, $., C, _/binary>> when C >= $0, C =< $9 ->
            tokenize_number(B, frac1, ?ADV_COL(S, 2), [C, $. | Acc]);
        <<_:O/binary, E, _/binary>> when E =:= $e orelse E =:= $E ->
            tokenize_number(B, esign, ?INC_COL(S), [$e, $0, $. | Acc]);
        _ ->
            {{int, lists:reverse(Acc)}, S}
    end;
tokenize_number(B, frac1, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
            tokenize_number(B, frac1, ?INC_COL(S), [C | Acc]);
        <<_:O/binary, E, _/binary>> when E =:= $e orelse E =:= $E ->
            tokenize_number(B, esign, ?INC_COL(S), [$e | Acc]);
        _ ->
            {{float, lists:reverse(Acc)}, S}
    end;
tokenize_number(B, esign, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, C, _/binary>> when C =:= $- orelse C=:= $+ ->
            tokenize_number(B, eint, ?INC_COL(S), [C | Acc]);
        _ ->
            tokenize_number(B, eint, S, Acc)
    end;
tokenize_number(B, eint, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
            tokenize_number(B, eint1, ?INC_COL(S), [C | Acc])
    end;
tokenize_number(B, eint1, S=#decoder{offset=O}, Acc) ->
    case B of
        <<_:O/binary, C, _/binary>> when C >= $0 andalso C =< $9 ->
            tokenize_number(B, eint1, ?INC_COL(S), [C | Acc]);
        _ ->
            {{float, lists:reverse(Acc)}, S}
    end.


tokenize(B, S=#decoder{offset=O}) ->
    case B of
        <<_:O/binary, C, _/binary>> when ?IS_WHITESPACE(C) ->
            tokenize(B, ?INC_CHAR(S, C));
        <<_:O/binary, "{", _/binary>> ->
            {start_object, ?INC_COL(S)};
        <<_:O/binary, "}", _/binary>> ->
            {end_object, ?INC_COL(S)};
        <<_:O/binary, "[", _/binary>> ->
            {start_array, ?INC_COL(S)};
        <<_:O/binary, "]", _/binary>> ->
            {end_array, ?INC_COL(S)};
        <<_:O/binary, ",", _/binary>> ->
            {comma, ?INC_COL(S)};
        <<_:O/binary, ":", _/binary>> ->
            {colon, ?INC_COL(S)};
        <<_:O/binary, "null", _/binary>> ->
            {{const, null}, ?ADV_COL(S, 4)};
        <<_:O/binary, "true", _/binary>> ->
            {{const, true}, ?ADV_COL(S, 4)};
        <<_:O/binary, "false", _/binary>> ->
            {{const, false}, ?ADV_COL(S, 5)};
        <<_:O/binary, "\"", _/binary>> ->
            tokenize_string(B, ?INC_COL(S));
        <<_:O/binary, C, _/binary>> when (C >= $0 andalso C =< $9)
                                         orelse C =:= $- ->
            tokenize_number(B, S);
        <<_:O/binary>> ->
            trim = S#decoder.state,
            {eof, S}
    end.

%% testing constructs borrowed from the Yaws JSON implementation.

%% Create an object from a list of Key/Value pairs.

obj_new() ->
    {struct, []}.

is_obj({struct, Props}) ->
    F = fun ({K, _}) when is_binary(K) ->
                true;
            (_) ->
                false
        end,    
    lists:all(F, Props).

obj_from_list(Props) ->
    Obj = {struct, Props},
    case is_obj(Obj) of
        true -> Obj;
        false -> exit({json_bad_object, Obj})
    end.

%% Test for equivalence of Erlang terms.
%% Due to arbitrary order of construction, equivalent objects might
%% compare unequal as erlang terms, so we need to carefully recurse
%% through aggregates (tuples and objects).

equiv({struct, Props1}, {struct, Props2}) ->
    equiv_object(Props1, Props2);
equiv(L1, L2) when is_list(L1), is_list(L2) ->
    equiv_list(L1, L2);
equiv(N1, N2) when is_number(N1), is_number(N2) -> N1 == N2;
equiv(B1, B2) when is_binary(B1), is_binary(B2) -> B1 == B2;
equiv(true, true) -> true;
equiv(false, false) -> true;
equiv(null, null) -> true.

%% Object representation and traversal order is unknown.
%% Use the sledgehammer and sort property lists.

equiv_object(Props1, Props2) ->
    L1 = lists:keysort(1, Props1),
    L2 = lists:keysort(1, Props2),
    Pairs = lists:zip(L1, L2),
    true = lists:all(fun({{K1, V1}, {K2, V2}}) ->
                             equiv(K1, K2) and equiv(V1, V2)
                     end, Pairs).

%% Recursively compare tuple elements for equivalence.

equiv_list([], []) ->
    true;
equiv_list([V1 | L1], [V2 | L2]) ->
    case equiv(V1, V2) of
        true ->
            equiv_list(L1, L2);
        false ->
            false
    end.

test_all() ->
    [1199344435545.0, 1] = decode(<<"[1199344435545.0,1]">>),
    test_encoder_utf8(),
    test_one(e2j_test_vec(utf8), 1).

test_one([], _N) ->
    %% io:format("~p tests passed~n", [N-1]),
    ok;
test_one([{E, J} | Rest], N) ->
    %% io:format("[~p] ~p ~p~n", [N, E, J]),
    true = equiv(E, decode(J)),
    true = equiv(E, decode(encode(E))),
    test_one(Rest, 1+N).

e2j_test_vec(utf8) ->
    [
     {1, "1"},
     {3.1416, "3.14160"}, %% text representation may truncate, trail zeroes
     {-1, "-1"},
     {-3.1416, "-3.14160"},
     {12.0e10, "1.20000e+11"},
     {1.234E+10, "1.23400e+10"},
     {-1.234E-10, "-1.23400e-10"},
     {10.0, "1.0e+01"},
     {123.456, "1.23456E+2"},
     {10.0, "1e1"},
     {<<"foo">>, "\"foo\""},
     {<<"foo", 5, "bar">>, "\"foo\\u0005bar\""},
     {<<"">>, "\"\""},
     {<<"\n\n\n">>, "\"\\n\\n\\n\""},
     {<<"\" \b\f\r\n\t\"">>, "\"\\\" \\b\\f\\r\\n\\t\\\"\""},
     {obj_new(), "{}"},
     {obj_from_list([{<<"foo">>, <<"bar">>}]), "{\"foo\":\"bar\"}"},
     {obj_from_list([{<<"foo">>, <<"bar">>}, {<<"baz">>, 123}]),
      "{\"foo\":\"bar\",\"baz\":123}"},
     {[], "[]"},
     {[[]], "[[]]"},
     {[1, <<"foo">>], "[1,\"foo\"]"},
     
     %% json array in a json object
     {obj_from_list([{<<"foo">>, [123]}]),
      "{\"foo\":[123]}"},
     
     %% json object in a json object
     {obj_from_list([{<<"foo">>, obj_from_list([{<<"bar">>, true}])}]),
      "{\"foo\":{\"bar\":true}}"},
     
     %% fold evaluation order
     {obj_from_list([{<<"foo">>, []},
                     {<<"bar">>, obj_from_list([{<<"baz">>, true}])},
                     {<<"alice">>, <<"bob">>}]),
      "{\"foo\":[],\"bar\":{\"baz\":true},\"alice\":\"bob\"}"},
     
     %% json object in a json array
     {[-123, <<"foo">>, obj_from_list([{<<"bar">>, []}]), null],
      "[-123,\"foo\",{\"bar\":[]},null]"}
    ].

%% test utf8 encoding
test_encoder_utf8() ->
    %% safe conversion case (default)
    [34,"\\u0001","\\u0442","\\u0435","\\u0441","\\u0442",34] = 
        encode(<<1,"\321\202\320\265\321\201\321\202">>),

    %% raw utf8 output (optional)
    Enc = mochijson2:encoder([{utf8, true}]),
    [34,"\\u0001",[209,130],[208,181],[209,129],[209,130],34] =
        Enc(<<1,"\321\202\320\265\321\201\321\202">>).

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Change log

r99 by bob.ippolito on Apr 04, 2009 Diff

http://code.google.com/p/mochiweb/issues/d
etail?id=32 utf-8 output option for
mochijson2:encoder

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Older revisions

r86 by bob.ippolito on Sep 23, 2008 Diff

another small optimization since we
can easily know the index at which the
string escape occurs

r85 by bob.ippolito on Sep 22, 2008 Diff

fast-path for mochijson2 string
tokenization

r84 by bob.ippolito on Jul 30, 2008 Diff

mochijson2 encoding optimization

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