+%%% Copyright (c) 2005-2006, A2Z Development USA, Inc. All Rights Reserved.
+%%%
+%%% The contents of this file are subject to the Erlang Public License,
+%%% Version 1.1, (the "License"); you may not use this file except in
+%%% compliance with the License. You should have received a copy of the
+%%% Erlang Public License along with this software. If not, it can be
+%%% retrieved via the world wide web at http://www.erlang.org/.
+%%%
+%%% Software distributed under the License is distributed on an "AS IS"
+%%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%%% the License for the specific language governing rights and limitations
+%%% under the License.
+%%%
+%%% The Initial Developer of the Original Code is A2Z Development USA, Inc.
+%%% All Rights Reserved.
+
+-module(json).
+-export([encode/1, decode_string/1, decode/2]).
+-export([is_obj/1, obj_new/0, obj_fetch/2, obj_find/2, obj_is_key/2]).
+-export([obj_store/3, obj_from_list/1, obj_fold/3]).
+-export([test/0]).
+-author("Jim Larson <jalarson@amazon.com>, Robert Wai-Chi Chu <robchu@amazon.com>").
+-vsn("1").
+
+%%% JavaScript Object Notation ("JSON", http://www.json.org) is a simple
+%%% data syntax meant as a lightweight alternative to other representations,
+%%% such as XML. JSON is natively supported by JavaScript, but many
+%%% other languages have conversion libraries available.
+%%%
+%%% This module translates JSON types into the following Erlang types:
+%%%
+%%% JSON Erlang
+%%% ---- ------
+%%% number number
+%%% string string
+%%% array tuple
+%%% object tagged proplist with string (or atom) keys
+%%% true, false, null atoms 'true', 'false', and 'null'
+%%%
+%%% Character Sets: the external representation, and the internal
+%%% representation of strings, are lists of UTF-16 code units.
+%%% The encoding of supplementary characters, as well as
+%%% transcoding to other schemes, such as UTF-8, can be provided
+%%% by other modules. (See discussion at
+%%% http://groups.yahoo.com/group/json/message/52)
+%%%
+%%% Numbers: Thanks to Erlang's bignums, JSON-encoded integers of any
+%%% size can be parsed. Conversely, extremely large integers may
+%%% be JSON-encoded. This may cause problems for interoperability
+%%% with JSON parsers which can't handle arbitrary-sized integers.
+%%% Erlang's floats are of fixed precision and limited range, so
+%%% syntactically valid JSON floating-point numbers could silently
+%%% lose precision or noisily cause an overflow. However, most
+%%% other JSON libraries are likely to behave in the same way.
+%%% The encoding precision defaults to 6 digits.
+%%%
+%%% Strings: If we represented JSON string data as Erlang binaries,
+%%% we would have to choose a particular unicode format. Instead,
+%%% we use lists of UTF-16 code units, which applications may then
+%%% change to binaries in their application-preferred manner.
+%%%
+%%% Arrays: Because of the string decision above, and Erlang's
+%%% lack of a distinguished string datatype, JSON arrays map
+%%% to Erlang tuples. Consider utilities like tuple_fold/3
+%%% to deal with tuples in their native form.
+%%%
+%%% Objects: Though not explicitly stated in the JSON "spec",
+%%% JSON's JavaScript heritage mandates that member names must
+%%% be unique within an object. The object/tuple ambiguity is
+%%% not a problem, since the atom 'json_object' is not an
+%%% allowable value. Object keys may be atoms or strings on
+%%% encoding but are always decoded as strings.
+
+%%% ENCODING
+
+%% Encode an erlang number, string, tuple, or object to JSON syntax, as a
+%% possibly deep list of UTF-16 code units, throwing a runtime error in the
+%% case of un-convertible input.
+%% Note: object keys may be either strings or atoms.
+
+encode(true) -> "true";
+encode(false) -> "false";
+encode(null) -> "null";
+encode(I) when is_integer(I) -> integer_to_list(I);
+encode(F) when is_float(F) -> io_lib:format("~g", [F]);
+encode(L) when is_list(L) -> encode_string(L);
+encode({}) -> "[]";
+encode({json_object, Props} = T) when is_list(Props) -> encode_object(T);
+encode(T) when is_tuple(T) -> encode_array(T);
+encode(Bad) -> exit({json_encode, {bad_term, Bad}}).
+
+%% Encode an Erlang string to JSON.
+%% Accumulate strings in reverse.
+
+encode_string(S) -> encode_string(S, [$"]).
+
+encode_string([], Acc) -> lists:reverse([$" | Acc]);
+encode_string([C | Cs], Acc) ->
+ case C of
+ $" -> encode_string(Cs, [$", $\\ | Acc]);
+ % (don't escape solidus on encode)
+ $\\ -> encode_string(Cs, [$\\, $\\ | Acc]);
+ $\b -> encode_string(Cs, [$b, $\\ | Acc]); % note missing \
+ $\f -> encode_string(Cs, [$f, $\\ | Acc]);
+ $\n -> encode_string(Cs, [$n, $\\ | Acc]);
+ $\r -> encode_string(Cs, [$r, $\\ | Acc]);
+ $\t -> encode_string(Cs, [$t, $\\ | Acc]);
+ C when C >= 0, C < $\s ->
+ % Control characters must be unicode-encoded.
+ Hex = lists:flatten(io_lib:format("~4.16.0b", [C])),
+ encode_string(Cs, lists:reverse(Hex) ++ "u\\" ++ Acc);
+ C when C =< 16#FFFF -> encode_string(Cs, [C | Acc]);
+ _ -> exit({json_encode, {bad_char, C}})
+ end.
+
+%% Encode an Erlang object as a JSON object, allowing string or atom keys.
+%% Note that order is irrelevant in both internal and external object
+%% representations. Nevertheless, the output will respect the order
+%% of the input.
+
+encode_object({json_object, _Props} = Obj) ->
+ M = obj_fold(fun({Key, Value}, Acc) ->
+ S = case Key of
+ L when is_list(L) -> encode_string(L);
+ A when is_atom(A) -> encode_string(atom_to_list(A));
+ _ -> exit({json_encode, {bad_key, Key}})
+ end,
+ V = encode(Value),
+ case Acc of
+ [] -> [S, $:, V];
+ _ -> [Acc, $,, S, $:, V]
+ end
+ end, [], Obj),
+ [${, M, $}].
+
+%% Encode an Erlang tuple as a JSON array.
+%% Order *is* significant in a JSON array!
+
+encode_array(T) ->
+ M = tuple_fold(fun(E, Acc) ->
+ V = encode(E),
+ case Acc of
+ [] -> V;
+ _ -> [Acc, $,, V]
+ end
+ end, [], T),
+ [$[, M, $]].
+
+%% A fold function for tuples (left-to-right).
+%% Folded function takes arguments (Element, Accumulator).
+
+tuple_fold(F, A, T) when is_tuple(T) ->
+ tuple_fold(F, A, T, 1, size(T)).
+
+tuple_fold(_F, A, _T, I, N) when I > N ->
+ A;
+tuple_fold(F, A, T, I, N) ->
+ A2 = F(element(I, T), A),
+ tuple_fold(F, A2, T, I + 1, N).
+
+%%% SCANNING
+%%%
+%%% Scanning funs return either:
+%%% {done, Result, LeftOverChars}
+%%% if a complete token is recognized, or
+%%% {more, Continuation}
+%%% if more input is needed.
+%%% Result is {ok, Term}, 'eof', or {error, Reason}.
+%%% Here, the Continuation is a simple Erlang string.
+%%%
+%%% Currently, error handling is rather crude - errors are recognized
+%%% by match failures. EOF is handled only by number scanning, where
+%%% it can delimit a number, and otherwise causes a match failure.
+%%%
+%%% Tokens are one of the following
+%%% JSON string -> erlang string
+%%% JSON number -> erlang number
+%%% true, false, null -> erlang atoms
+%%% { } [ ] : , -> lcbrace rcbrace lsbrace rsbrace colon comma
+
+token([]) -> {more, []};
+token(eof) -> {done, eof, []};
+
+token("true" ++ Rest) -> {done, {ok, true}, Rest};
+token("tru") -> {more, "tru"};
+token("tr") -> {more, "tr"};
+token("t") -> {more, "t"};
+
+token("false" ++ Rest) -> {done, {ok, false}, Rest};
+token("fals") -> {more, "fals"};
+token("fal") -> {more, "fal"};
+token("fa") -> {more, "fa"};
+token("f") -> {more, "f"};
+
+token("null" ++ Rest) -> {done, {ok, null}, Rest};
+token("nul") -> {more, "nul"};
+token("nu") -> {more, "nu"};
+token("n") -> {more, "n"};
+
+token([C | Cs] = Input) ->
+ case C of
+ $\s -> token(Cs); % eat whitespace
+ $\t -> token(Cs); % eat whitespace
+ $\n -> token(Cs); % eat whitespace
+ $\r -> token(Cs); % eat whitespace
+ $" -> scan_string(Input);
+ $- -> scan_number(Input);
+ D when D >= $0, D =< $9-> scan_number(Input);
+ ${ -> {done, {ok, lcbrace}, Cs};
+ $} -> {done, {ok, rcbrace}, Cs};
+ $[ -> {done, {ok, lsbrace}, Cs};
+ $] -> {done, {ok, rsbrace}, Cs};
+ $: -> {done, {ok, colon}, Cs};
+ $, -> {done, {ok, comma}, Cs};
+ $/ -> case scan_comment(Cs) of
+ {more, X} -> {more, X};
+ {done, _, Chars} -> token(Chars)
+ end;
+ _ -> {done, {error, {bad_char, C}}, Cs}
+ end.
+
+scan_string([$" | Cs] = Input) ->
+ scan_string(Cs, [], Input).
+
+%% Accumulate in reverse order, save original start-of-string for continuation.
+
+scan_string([], _, X) -> {more, X};
+scan_string(eof, _, X) -> {done, {error, missing_close_quote}, X};
+scan_string([$" | Rest], A, _) -> {done, {ok, lists:reverse(A)}, Rest};
+scan_string([$\\], _, X) -> {more, X};
+scan_string([$\\, $u, U1, U2, U3, U4 | Rest], A, X) ->
+ scan_string(Rest, [uni_char([U1, U2, U3, U4]) | A], X);
+scan_string([$\\, $u | _], _, X) -> {more, X};
+scan_string([$\\, C | Rest], A, X) ->
+ scan_string(Rest, [esc_to_char(C) | A], X);
+scan_string([C | Rest], A, X) ->
+ scan_string(Rest, [C | A], X).
+
+%% Given a list of hex characters, convert to the corresponding integer.
+
+uni_char(HexList) ->
+ erlang:list_to_integer(HexList, 16).
+
+esc_to_char($") -> $";
+esc_to_char($/) -> $/;
+esc_to_char($\\) -> $\\;
+esc_to_char($b) -> $\b;
+esc_to_char($f) -> $\f;
+esc_to_char($n) -> $\n;
+esc_to_char($r) -> $\r;
+esc_to_char($t) -> $\t.
+
+scan_number([]) -> {more, []};
+scan_number(eof) -> {done, {error, incomplete_number}, []};
+scan_number([$- | Ds] = Input) ->
+ case scan_number(Ds) of
+ {more, _Cont} -> {more, Input};
+ {done, {ok, N}, CharList} -> {done, {ok, -1 * N}, CharList};
+ {done, Other, Chars} -> {done, Other, Chars}
+ end;
+scan_number([D | Ds] = Input) when D >= $0, D =< $9 ->
+ scan_number(Ds, D - $0, Input).
+
+%% Numbers don't have a terminator, so stop at the first non-digit,
+%% and ask for more if we run out.
+
+scan_number([], _A, X) -> {more, X};
+scan_number(eof, A, _X) -> {done, {ok, A}, eof};
+scan_number([$.], _A, X) -> {more, X};
+scan_number([$., D | Ds], A, X) when D >= $0, D =< $9 ->
+ scan_fraction([D | Ds], A, X);
+scan_number([D | Ds], A, X) when A > 0, D >= $0, D =< $9 ->
+ % Note that nonzero numbers can't start with "0".
+ scan_number(Ds, 10 * A + (D - $0), X);
+scan_number([D | Ds], A, X) when D == $E; D == $e ->
+ scan_exponent_begin(Ds, float(A), X);
+scan_number([D | _] = Ds, A, _X) when D < $0; D > $9 ->
+ {done, {ok, A}, Ds}.
+
+scan_fraction(Ds, I, X) -> scan_fraction(Ds, [], I, X).
+
+scan_fraction([], _Fs, _I, X) -> {more, X};
+scan_fraction(eof, Fs, I, _X) ->
+ R = I + list_to_float("0." ++ lists:reverse(Fs)),
+ {done, {ok, R}, eof};
+scan_fraction([D | Ds], Fs, I, X) when D >= $0, D =< $9 ->
+ scan_fraction(Ds, [D | Fs], I, X);
+scan_fraction([D | Ds], Fs, I, X) when D == $E; D == $e ->
+ R = I + list_to_float("0." ++ lists:reverse(Fs)),
+ scan_exponent_begin(Ds, R, X);
+scan_fraction(Rest, Fs, I, _X) ->
+ R = I + list_to_float("0." ++ lists:reverse(Fs)),
+ {done, {ok, R}, Rest}.
+
+scan_exponent_begin(Ds, R, X) ->
+ scan_exponent_begin(Ds, [], R, X).
+
+scan_exponent_begin([], _Es, _R, X) -> {more, X};
+scan_exponent_begin(eof, _Es, _R, X) -> {done, {error, missing_exponent}, X};
+scan_exponent_begin([D | Ds], Es, R, X) when D == $-;
+ D == $+;
+ D >= $0, D =< $9 ->
+ scan_exponent(Ds, [D | Es], R, X).
+
+scan_exponent([], _Es, _R, X) -> {more, X};
+scan_exponent(eof, Es, R, _X) ->
+ X = R * math:pow(10, list_to_integer(lists:reverse(Es))),
+ {done, {ok, X}, eof};
+scan_exponent([D | Ds], Es, R, X) when D >= $0, D =< $9 ->
+ scan_exponent(Ds, [D | Es], R, X);
+scan_exponent(Rest, Es, R, _X) ->
+ X = R * math:pow(10, list_to_integer(lists:reverse(Es))),
+ {done, {ok, X}, Rest}.
+
+scan_comment([]) -> {more, "/"};
+scan_comment(eof) -> {done, eof, []};
+scan_comment([$/ | Rest]) -> scan_cpp_comment(Rest);
+scan_comment([$* | Rest]) -> scan_c_comment(Rest).
+
+%% Ignore up to next CR or LF. If the line ends in CRLF,
+%% the LF will be treated as separate whitespace, which is
+%% okay since it will also be ignored.
+
+scan_cpp_comment([]) -> {more, "//"};
+scan_cpp_comment(eof) -> {done, eof, []};
+scan_cpp_comment([$\r | Rest]) -> {done, [], Rest};
+scan_cpp_comment([$\n | Rest]) -> {done, [], Rest};
+scan_cpp_comment([_ | Rest]) -> scan_cpp_comment(Rest).
+
+scan_c_comment([]) -> {more, "/*"};
+scan_c_comment(eof) -> {done, eof, []};
+scan_c_comment([$*]) -> {more, "/**"};
+scan_c_comment([$*, $/ | Rest]) -> {done, [], Rest};
+scan_c_comment([_ | Rest]) -> scan_c_comment(Rest).
+
+%%% PARSING
+%%%
+%%% The decode function takes a char list as input, but
+%%% interprets the end of the list as only an end to the available
+%%% input, and returns a "continuation" requesting more input.
+%%% When additional characters are available, they, and the
+%%% continuation, are fed into decode/2. You can use the atom 'eof'
+%%% as a character to signal a true end to the input stream, and
+%%% possibly flush out an unfinished number. The decode_string/1
+%%% function appends 'eof' to its input and calls decode/1.
+%%%
+%%% Parsing and scanning errors are handled only by match failures.
+%%% The external caller must take care to wrap the call in a "catch"
+%%% or "try" if better error-handling is desired. Eventually parse
+%%% or scan errors will be returned explicitly with a description,
+%%% and someday with line numbers too.
+%%%
+%%% The parsing code uses a continuation-passing style to allow
+%%% for the parsing to suspend at any point and be resumed when
+%%% more input is available.
+%%% See http://en.wikipedia.org/wiki/Continuation_passing_style
+
+%% Return the first JSON value decoded from the input string.
+%% The string must contain at least one complete JSON value.
+
+decode_string(CharList) ->
+ {done, V, _} = decode([], CharList ++ eof),
+ V.
+
+%% Attempt to decode a JSON value from the input string
+%% and continuation, using empty list for the initial continuation.
+%% Return {done, Result, LeftoverChars} if a value is recognized,
+%% or {more, Continuation} if more input characters are needed.
+%% The Result can be {ok, Value}, eof, or {error, Reason}.
+%% The Continuation is then fed as an argument to decode/2 when
+%% more input is available.
+%% Use the atom 'eof' instead of a char list to signal
+%% a true end to the input, and may flush a final number.
+
+decode([], CharList) ->
+ decode(first_continuation(), CharList);
+
+decode(Continuation, CharList) ->
+ {OldChars, Kt} = Continuation,
+ get_token(OldChars ++ CharList, Kt).
+
+first_continuation() ->
+ {[], fun
+ (eof, Cs) ->
+ {done, eof, Cs};
+ (T, Cs) ->
+ parse_value(T, Cs, fun(V, C2) ->
+ {done, {ok, V}, C2}
+ end)
+ end}.
+
+%% Continuation Kt must accept (TokenOrEof, Chars)
+
+get_token(Chars, Kt) ->
+ case token(Chars) of
+ {done, {ok, T}, Rest} -> Kt(T, Rest);
+ {done, eof, Rest} -> Kt(eof, Rest);
+ {done, {error, Reason}, Rest} -> {done, {error, Reason}, Rest};
+ {more, X} -> {more, {X, Kt}}
+ end.
+
+%% Continuation Kv must accept (Value, Chars)
+
+parse_value(eof, C, _Kv) -> {done, {error, premature_eof}, C};
+parse_value(true, C, Kv) -> Kv(true, C);
+parse_value(false, C, Kv) -> Kv(false, C);
+parse_value(null, C, Kv) -> Kv(null, C);
+parse_value(S, C, Kv) when is_list(S) -> Kv(S, C);
+parse_value(N, C, Kv) when is_number(N) -> Kv(N, C);
+parse_value(lcbrace, C, Kv) -> parse_object(C, Kv);
+parse_value(lsbrace, C, Kv) -> parse_array(C, Kv);
+parse_value(_, C, _Kv) -> {done, {error, syntax_error}, C}.
+
+%% Continuation Kv must accept (Value, Chars)
+
+parse_object(Chars, Kv) ->
+ get_token(Chars, fun(T, C2) ->
+ Obj = obj_new(),
+ case T of
+ rcbrace -> Kv(Obj, C2); % empty object
+ _ -> parse_object(Obj, T, C2, Kv) % token must be string
+ end
+ end).
+
+parse_object(_Obj, eof, C, _Kv) ->
+ {done, {error, premature_eof}, C};
+
+parse_object(Obj, S, C, Kv) when is_list(S) -> % S is member name
+ get_token(C, fun
+ (colon, C2) ->
+ parse_object2(Obj, S, C2, Kv);
+ (T, C2) ->
+ {done, {error, {expecting_colon, T}}, C2}
+ end);
+
+parse_object(_Obj, M, C, _Kv) ->
+ {done, {error, {member_name_not_string, M}}, C}.
+
+parse_object2(Obj, S, C, Kv) ->
+ get_token(C, fun
+ (eof, C2) ->
+ {done, {error, premature_eof}, C2};
+ (T, C2) ->
+ parse_value(T, C2, fun(V, C3) -> % V is member value
+ Obj2 = obj_store(S, V, Obj),
+ get_token(C3, fun
+ (rcbrace, C4) ->
+ Kv(Obj2, C4); % "}" end of object
+ (comma, C4) -> % "," another member follows
+ get_token(C4, fun(T3, C5) ->
+ parse_object(Obj2, T3, C5, Kv)
+ end);
+ (eof, C4) ->
+ {done, {error, premature_eof}, C4};
+ (T2, C4) ->
+ {done, {error, {expecting_comma_or_curly, T2}}, C4}
+ end)
+ end)
+ end).
+
+%% Continuation Kv must accept (Value, Chars)
+
+parse_array(C, Kv) ->
+ get_token(C, fun
+ (eof, C2) -> {done, {error, premature_eof}, C2};
+ (rsbrace, C2) -> Kv({}, C2); % empty array
+ (T, C2) -> parse_array([], T, C2, Kv)
+ end).
+
+parse_array(E, T, C, Kv) ->
+ parse_value(T, C, fun(V, C2) ->
+ E2 = [V | E],
+ get_token(C2, fun
+ (rsbrace, C3) -> % "]" end of array
+ Kv(list_to_tuple(lists:reverse(E2)), C3);
+ (comma, C3) -> % "," another value follows
+ get_token(C3, fun(T3, C4) ->
+ parse_array(E2, T3, C4, Kv)
+ end);
+ (eof, C3) ->
+ {done, {error, premature_eof}, C3};
+ (T2, C3) ->
+ {done, {error, {expecting_comma_or_close_array, T2}}, C3}
+ end)
+ end).
+
+%%% OBJECTS
+%%%
+%%% We'll use tagged property lists as the internal representation
+%%% of JSON objects. Unordered lists perform worse than trees for
+%%% lookup and modification of members, but we expect objects to be
+%%% have only a few members. Lists also print better.
+
+%% Is this a proper JSON object representation?
+
+is_obj({json_object, Props}) when is_list(Props) ->
+ lists:all(fun
+ ({Member, _Value}) when is_atom(Member); is_list(Member) -> true;
+ (_) -> false
+ end, Props);
+
+is_obj(_) ->
+ false.
+
+%% Create a new, empty object.
+
+obj_new() ->
+ {json_object, []}.
+
+%% Fetch an object member's value, expecting it to be in the object.
+%% Return value, runtime error if no member found with that name.
+
+obj_fetch(Key, {json_object, Props}) when is_list(Props) ->
+ case proplists:get_value(Key, Props) of
+ undefined ->
+ exit({json_object_no_key, Key});
+ Value ->
+ Value
+ end.
+
+%% Fetch an object member's value, or indicate that there is no such member.
+%% Return {ok, Value} or 'error'.
+
+obj_find(Key, {json_object, Props}) when is_list(Props) ->
+ case proplists:get_value(Key, Props) of
+ undefined ->
+ error;
+ Value ->
+ {ok, Value}
+ end.
+
+obj_is_key(Key, {json_object, Props}) ->
+ proplists:is_defined(Key, Props).
+
+%% Store a new member in an object. Returns a new object.
+
+obj_store(Key, Value, {json_object, Props}) when is_list(Props) ->
+ {json_object, [{Key, Value} | proplists:delete(Key, Props)]}.
+
+%% Create an object from a list of Key/Value pairs.
+
+obj_from_list(Props) ->
+ Obj = {json_object, Props},
+ case is_obj(Obj) of
+ true -> Obj;
+ false -> exit(json_bad_object)
+ end.
+
+%% Fold Fun across object, with initial accumulator Acc.
+%% Fun should take (Value, Acc) as arguments and return Acc.
+
+obj_fold(Fun, Acc, {json_object, Props}) ->
+ lists:foldl(Fun, Acc, Props).
+
+%%% TESTING
+%%%
+%%% We can't expect to round-trip from JSON -> Erlang -> JSON,
+%%% due to the degrees of freedom in the JSON syntax: whitespace,
+%%% and ordering of object members. We can, however, expect to
+%%% round-trip from Erlang -> JSON -> Erlang, so the JSON parsing
+%%% tests will in fact test the Erlang equivalence of the
+%%% JSON -> Erlang -> JSON -> Erlang coding chain.
+
+%% Test driver. Return 'ok' or {failed, Failures}.
+
+test() ->
+ E2Js = e2j_test_vec(),
+ Failures = lists:foldl(fun({E, J}, Fs) ->
+ case (catch test_e2j(E, J)) of
+ ok ->
+ case (catch round_trip(E)) of
+ ok ->
+ case (catch round_trip_one_char(E)) of
+ ok -> Fs;
+ Reason -> [{round_trip_one_char, E, Reason} | Fs]
+ end;
+ Reason ->
+ [{round_trip, E, Reason} | Fs]
+ end;
+ Reason ->
+ [{erlang_to_json, E, J, Reason} | Fs]
+ end;
+ (end_of_tests, Fs) -> Fs end, [], E2Js),
+ case Failures of
+ [] -> ok;
+ _ -> {failed, Failures}
+ end.
+
+%% Test for conversion from Erlang to JSON. Note that unequal strings
+%% may represent equal JSON data, due to discretionary whitespace,
+%% object member order, trailing zeroes in floating point, etc.
+%% Legitimate changes to the encoding routines may require tweaks to
+%% the reference JSON strings in e2j_test_vec().
+
+test_e2j(E, J) ->
+ J2 = lists:flatten(encode(E)),
+ J = J2, % raises error if unequal
+ ok.
+
+%% Test that Erlang -> JSON -> Erlang round-trip yields equivalent term.
+
+round_trip(E) ->
+ J2 = lists:flatten(encode(E)),
+ {ok, E2} = decode_string(J2),
+ true = equiv(E, E2), % raises error if false
+ ok.
+
+%% Round-trip with one character at a time to test all continuations.
+
+round_trip_one_char(E) ->
+ J = lists:flatten(encode(E)),
+ {done, {ok, E2}, _} = lists:foldl(fun(C, Ret) ->
+ case Ret of
+ {done, _, _} -> Ret;
+ {more, Cont} -> decode(Cont, [C])
+ end
+ end, {more, first_continuation()}, J ++ [eof]),
+ true = equiv(E, E2), % raises error if false
+ ok.
+
+%% 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({json_object, Props1}, {json_object, Props2}) ->
+ equiv_object(Props1, Props2);
+equiv(T1, T2) when is_tuple(T1), is_tuple(T2) ->
+ equiv_tuple(T1, T2);
+equiv(N1, N2) when is_number(N1), is_number(N2) -> N1 == N2;
+equiv(S1, S2) when is_list(S1), is_list(S2) -> S1 == S2;
+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_tuple({}, {}) ->
+ true;
+equiv_tuple(T1, T2) when size(T1) == size(T2) ->
+ S = size(T1),
+ lists:all(fun(I) ->
+ equiv(element(I, T1), element(I, T2))
+ end, lists:seq(1, S)).
+
+e2j_test_vec() -> [
+ {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"},
+ {"foo", "\"foo\""},
+ {"foo" ++ [500] ++ "bar", [$", $f, $o, $o, 500, $b, $a, $r, $"]},
+ {"foo" ++ [5] ++ "bar", "\"foo\\u0005bar\""},
+ {"", "\"\""},
+ {[], "\"\""},
+ {"\n\n\n", "\"\\n\\n\\n\""},
+ {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]"},
+
+ end_of_tests
+].
+
+%%% TODO:
+%%%
+%%% Measure the overhead of the CPS-based parser by writing a conventional
+%%% scanner-parser that expects all input to be available.
+%%%
+%%% JSON has dropped comments - disable their parsing.
+%%%
+%%% Allow a compile-time option to decode object member names as atoms,
+%%% to reduce the internal representation overheads when communicating
+%%% with trusted peers.
projects / euphorik.git / commitdiff