ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/JSON-XS/XS.pm
(Generate patch)

Comparing JSON-XS/XS.pm (file contents):
Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC vs.
Revision 1.134 by root, Mon Feb 21 15:38:06 2011 UTC

1=head1 NAME 1=head1 NAME
2 2
3JSON::XS - JSON serialising/deserialising, done correctly and fast
4
3=encoding utf-8 5=encoding utf-8
4
5JSON::XS - JSON serialising/deserialising, done correctly and fast
6 6
7JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ 7JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
8 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) 8 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9 9
10=head1 SYNOPSIS 10=head1 SYNOPSIS
37primary goal is to be I<correct> and its secondary goal is to be 37primary goal is to be I<correct> and its secondary goal is to be
38I<fast>. To reach the latter goal it was written in C. 38I<fast>. To reach the latter goal it was written in C.
39 39
40Beginning with version 2.0 of the JSON module, when both JSON and 40Beginning with version 2.0 of the JSON module, when both JSON and
41JSON::XS are installed, then JSON will fall back on JSON::XS (this can be 41JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
42overriden) with no overhead due to emulation (by inheritign constructor 42overridden) with no overhead due to emulation (by inheriting constructor
43and methods). If JSON::XS is not available, it will fall back to the 43and methods). If JSON::XS is not available, it will fall back to the
44compatible JSON::PP module as backend, so using JSON instead of JSON::XS 44compatible JSON::PP module as backend, so using JSON instead of JSON::XS
45gives you a portable JSON API that can be fast when you need and doesn't 45gives you a portable JSON API that can be fast when you need and doesn't
46require a C compiler when that is a problem. 46require a C compiler when that is a problem.
47 47
49to write yet another JSON module? While it seems there are many JSON 49to write yet another JSON module? While it seems there are many JSON
50modules, none of them correctly handle all corner cases, and in most cases 50modules, none of them correctly handle all corner cases, and in most cases
51their maintainers are unresponsive, gone missing, or not listening to bug 51their maintainers are unresponsive, gone missing, or not listening to bug
52reports for other reasons. 52reports for other reasons.
53 53
54See COMPARISON, below, for a comparison to some other JSON modules.
55
56See MAPPING, below, on how JSON::XS maps perl values to JSON values and 54See MAPPING, below, on how JSON::XS maps perl values to JSON values and
57vice versa. 55vice versa.
58 56
59=head2 FEATURES 57=head2 FEATURES
60 58
65This module knows how to handle Unicode, documents how and when it does 63This module knows how to handle Unicode, documents how and when it does
66so, and even documents what "correct" means. 64so, and even documents what "correct" means.
67 65
68=item * round-trip integrity 66=item * round-trip integrity
69 67
70When you serialise a perl data structure using only datatypes supported 68When you serialise a perl data structure using only data types supported
71by JSON, the deserialised data structure is identical on the Perl level. 69by JSON and Perl, the deserialised data structure is identical on the Perl
72(e.g. the string "2.0" doesn't suddenly become "2" just because it looks 70level. (e.g. the string "2.0" doesn't suddenly become "2" just because
73like a number). There minor I<are> exceptions to this, read the MAPPING 71it looks like a number). There I<are> minor exceptions to this, read the
74section below to learn about those. 72MAPPING section below to learn about those.
75 73
76=item * strict checking of JSON correctness 74=item * strict checking of JSON correctness
77 75
78There is no guessing, no generating of illegal JSON texts by default, 76There is no guessing, no generating of illegal JSON texts by default,
79and only JSON is accepted as input by default (the latter is a security 77and only JSON is accepted as input by default (the latter is a security
84Compared to other JSON modules and other serialisers such as Storable, 82Compared to other JSON modules and other serialisers such as Storable,
85this module usually compares favourably in terms of speed, too. 83this module usually compares favourably in terms of speed, too.
86 84
87=item * simple to use 85=item * simple to use
88 86
89This module has both a simple functional interface as well as an objetc 87This module has both a simple functional interface as well as an object
90oriented interface interface. 88oriented interface interface.
91 89
92=item * reasonably versatile output formats 90=item * reasonably versatile output formats
93 91
94You can choose between the most compact guaranteed-single-line format 92You can choose between the most compact guaranteed-single-line format
95possible (nice for simple line-based protocols), a pure-ascii format 93possible (nice for simple line-based protocols), a pure-ASCII format
96(for when your transport is not 8-bit clean, still supports the whole 94(for when your transport is not 8-bit clean, still supports the whole
97Unicode range), or a pretty-printed format (for when you want to read that 95Unicode range), or a pretty-printed format (for when you want to read that
98stuff). Or you can combine those features in whatever way you like. 96stuff). Or you can combine those features in whatever way you like.
99 97
100=back 98=back
101 99
102=cut 100=cut
103 101
104package JSON::XS; 102package JSON::XS;
105 103
106use strict; 104use common::sense;
107 105
108our $VERSION = '2.1'; 106our $VERSION = '2.3';
109our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
110 108
111our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json to_json from_json);
112 110
113sub to_json($) { 111sub to_json($) {
137 135
138This function call is functionally identical to: 136This function call is functionally identical to:
139 137
140 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 138 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141 139
142except being faster. 140Except being faster.
143 141
144=item $perl_scalar = decode_json $json_text 142=item $perl_scalar = decode_json $json_text
145 143
146The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries 144The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
147to parse that as an UTF-8 encoded JSON text, returning the resulting 145to parse that as an UTF-8 encoded JSON text, returning the resulting
149 147
150This function call is functionally identical to: 148This function call is functionally identical to:
151 149
152 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 150 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153 151
154except being faster. 152Except being faster.
155 153
156=item $is_boolean = JSON::XS::is_bool $scalar 154=item $is_boolean = JSON::XS::is_bool $scalar
157 155
158Returns true if the passed scalar represents either JSON::XS::true or 156Returns true if the passed scalar represents either JSON::XS::true or
159JSON::XS::false, two constants that act like C<1> and C<0>, respectively 157JSON::XS::false, two constants that act like C<1> and C<0>, respectively
197 195
198If you didn't know about that flag, just the better, pretend it doesn't 196If you didn't know about that flag, just the better, pretend it doesn't
199exist. 197exist.
200 198
201=item 4. A "Unicode String" is simply a string where each character can be 199=item 4. A "Unicode String" is simply a string where each character can be
202validly interpreted as a Unicode codepoint. 200validly interpreted as a Unicode code point.
203 201
204If you have UTF-8 encoded data, it is no longer a Unicode string, but a 202If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205Unicode string encoded in UTF-8, giving you a binary string. 203Unicode string encoded in UTF-8, giving you a binary string.
206 204
207=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. 205=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
443the same hash might be encoded differently even if contains the same data, 441the same hash might be encoded differently even if contains the same data,
444as key-value pairs have no inherent ordering in Perl. 442as key-value pairs have no inherent ordering in Perl.
445 443
446This setting has no effect when decoding JSON texts. 444This setting has no effect when decoding JSON texts.
447 445
446This setting has currently no effect on tied hashes.
447
448=item $json = $json->allow_nonref ([$enable]) 448=item $json = $json->allow_nonref ([$enable])
449 449
450=item $enabled = $json->get_allow_nonref 450=item $enabled = $json->get_allow_nonref
451 451
452If C<$enable> is true (or missing), then the C<encode> method can convert a 452If C<$enable> is true (or missing), then the C<encode> method can convert a
462Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, 462Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
463resulting in an invalid JSON text: 463resulting in an invalid JSON text:
464 464
465 JSON::XS->new->allow_nonref->encode ("Hello, World!") 465 JSON::XS->new->allow_nonref->encode ("Hello, World!")
466 => "Hello, World!" 466 => "Hello, World!"
467
468=item $json = $json->allow_unknown ([$enable])
469
470=item $enabled = $json->get_allow_unknown
471
472If C<$enable> is true (or missing), then C<encode> will I<not> throw an
473exception when it encounters values it cannot represent in JSON (for
474example, filehandles) but instead will encode a JSON C<null> value. Note
475that blessed objects are not included here and are handled separately by
476c<allow_nonref>.
477
478If C<$enable> is false (the default), then C<encode> will throw an
479exception when it encounters anything it cannot encode as JSON.
480
481This option does not affect C<decode> in any way, and it is recommended to
482leave it off unless you know your communications partner.
467 483
468=item $json = $json->allow_blessed ([$enable]) 484=item $json = $json->allow_blessed ([$enable])
469 485
470=item $enabled = $json->get_allow_blessed 486=item $enabled = $json->get_allow_blessed
471 487
612=item $json = $json->max_depth ([$maximum_nesting_depth]) 628=item $json = $json->max_depth ([$maximum_nesting_depth])
613 629
614=item $max_depth = $json->get_max_depth 630=item $max_depth = $json->get_max_depth
615 631
616Sets the maximum nesting level (default C<512>) accepted while encoding 632Sets the maximum nesting level (default C<512>) accepted while encoding
617or decoding. If the JSON text or Perl data structure has an equal or 633or decoding. If a higher nesting level is detected in JSON text or a Perl
618higher nesting level then this limit, then the encoder and decoder will 634data structure, then the encoder and decoder will stop and croak at that
619stop and croak at that point. 635point.
620 636
621Nesting level is defined by number of hash- or arrayrefs that the encoder 637Nesting level is defined by number of hash- or arrayrefs that the encoder
622needs to traverse to reach a given point or the number of C<{> or C<[> 638needs to traverse to reach a given point or the number of C<{> or C<[>
623characters without their matching closing parenthesis crossed to reach a 639characters without their matching closing parenthesis crossed to reach a
624given character in a string. 640given character in a string.
625 641
626Setting the maximum depth to one disallows any nesting, so that ensures 642Setting the maximum depth to one disallows any nesting, so that ensures
627that the object is only a single hash/object or array. 643that the object is only a single hash/object or array.
628 644
629The argument to C<max_depth> will be rounded up to the next highest power
630of two. If no argument is given, the highest possible setting will be 645If no argument is given, the highest possible setting will be used, which
631used, which is rarely useful. 646is rarely useful.
647
648Note that nesting is implemented by recursion in C. The default value has
649been chosen to be as large as typical operating systems allow without
650crashing.
632 651
633See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 652See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
634 653
635=item $json = $json->max_size ([$maximum_string_size]) 654=item $json = $json->max_size ([$maximum_string_size])
636 655
637=item $max_size = $json->get_max_size 656=item $max_size = $json->get_max_size
638 657
639Set the maximum length a JSON text may have (in bytes) where decoding is 658Set the maximum length a JSON text may have (in bytes) where decoding is
640being attempted. The default is C<0>, meaning no limit. When C<decode> 659being attempted. The default is C<0>, meaning no limit. When C<decode>
641is called on a string longer then this number of characters it will not 660is called on a string that is longer then this many bytes, it will not
642attempt to decode the string but throw an exception. This setting has no 661attempt to decode the string but throw an exception. This setting has no
643effect on C<encode> (yet). 662effect on C<encode> (yet).
644 663
645The argument to C<max_size> will be rounded up to the next B<highest> 664If no argument is given, the limit check will be deactivated (same as when
646power of two (so may be more than requested). If no argument is given, the 665C<0> is specified).
647limit check will be deactivated (same as when C<0> is specified).
648 666
649See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 667See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
650 668
651=item $json_text = $json->encode ($perl_scalar) 669=item $json_text = $json->encode ($perl_scalar)
652 670
683=back 701=back
684 702
685 703
686=head1 INCREMENTAL PARSING 704=head1 INCREMENTAL PARSING
687 705
688[This section is still EXPERIMENTAL]
689
690In some cases, there is the need for incremental parsing of JSON 706In some cases, there is the need for incremental parsing of JSON
691texts. While this module always has to keep both JSON text and resulting 707texts. While this module always has to keep both JSON text and resulting
692Perl data structure in memory at one time, it does allow you to parse a 708Perl data structure in memory at one time, it does allow you to parse a
693JSON stream incrementally. It does so by accumulating text until it has 709JSON stream incrementally. It does so by accumulating text until it has
694a full JSON object, which it then can decode. This process is similar to 710a full JSON object, which it then can decode. This process is similar to
695using C<decode_prefix> to see if a full JSON object is available, but is 711using C<decode_prefix> to see if a full JSON object is available, but
696much more efficient (JSON::XS will only attempt to parse the JSON text 712is much more efficient (and can be implemented with a minimum of method
713calls).
714
715JSON::XS will only attempt to parse the JSON text once it is sure it
697once it is sure it has enough text to get a decisive result, using a very 716has enough text to get a decisive result, using a very simple but
698simple but truly incremental parser). 717truly incremental parser. This means that it sometimes won't stop as
718early as the full parser, for example, it doesn't detect mismatched
719parentheses. The only thing it guarantees is that it starts decoding as
720soon as a syntactically valid JSON text has been seen. This means you need
721to set resource limits (e.g. C<max_size>) to ensure the parser will stop
722parsing in the presence if syntax errors.
699 723
700The following two methods deal with this. 724The following methods implement this incremental parser.
701 725
702=over 4 726=over 4
703 727
704=item [void, scalar or list context] = $json->incr_parse ([$string]) 728=item [void, scalar or list context] = $json->incr_parse ([$string])
705 729
714return without doing anything further. This can be used to add more text 738return without doing anything further. This can be used to add more text
715in as many chunks as you want. 739in as many chunks as you want.
716 740
717If the method is called in scalar context, then it will try to extract 741If the method is called in scalar context, then it will try to extract
718exactly I<one> JSON object. If that is successful, it will return this 742exactly I<one> JSON object. If that is successful, it will return this
719object, otherwise it will return C<undef>. This is the most common way of 743object, otherwise it will return C<undef>. If there is a parse error,
744this method will croak just as C<decode> would do (one can then use
745C<incr_skip> to skip the errornous part). This is the most common way of
720using the method. 746using the method.
721 747
722And finally, in list context, it will try to extract as many objects 748And finally, in list context, it will try to extract as many objects
723from the stream as it can find and return them, or the empty list 749from the stream as it can find and return them, or the empty list
724otherwise. For this to work, there must be no separators between the JSON 750otherwise. For this to work, there must be no separators between the JSON
725objects or arrays, instead they must be concatenated back-to-back. 751objects or arrays, instead they must be concatenated back-to-back. If
752an error occurs, an exception will be raised as in the scalar context
753case. Note that in this case, any previously-parsed JSON texts will be
754lost.
755
756Example: Parse some JSON arrays/objects in a given string and return
757them.
758
759 my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
726 760
727=item $lvalue_string = $json->incr_text 761=item $lvalue_string = $json->incr_text
728 762
729This method returns the currently stored JSON fragment as an lvalue, that 763This method returns the currently stored JSON fragment as an lvalue, that
730is, you can manipulate it. This I<only> works when a preceding call to 764is, you can manipulate it. This I<only> works when a preceding call to
735method before having parsed anything. 769method before having parsed anything.
736 770
737This function is useful in two cases: a) finding the trailing text after a 771This function is useful in two cases: a) finding the trailing text after a
738JSON object or b) parsing multiple JSON objects separated by non-JSON text 772JSON object or b) parsing multiple JSON objects separated by non-JSON text
739(such as commas). 773(such as commas).
774
775=item $json->incr_skip
776
777This will reset the state of the incremental parser and will remove
778the parsed text from the input buffer so far. This is useful after
779C<incr_parse> died, in which case the input buffer and incremental parser
780state is left unchanged, to skip the text parsed so far and to reset the
781parse state.
782
783The difference to C<incr_reset> is that only text until the parse error
784occured is removed.
785
786=item $json->incr_reset
787
788This completely resets the incremental parser, that is, after this call,
789it will be as if the parser had never parsed anything.
790
791This is useful if you want to repeatedly parse JSON objects and want to
792ignore any trailing data, which means you have to reset the parser after
793each successful decode.
740 794
741=back 795=back
742 796
743=head2 LIMITATIONS 797=head2 LIMITATIONS
744 798
940Numbers containing a fractional or exponential part will always be 994Numbers containing a fractional or exponential part will always be
941represented as numeric (floating point) values, possibly at a loss of 995represented as numeric (floating point) values, possibly at a loss of
942precision (in which case you might lose perfect roundtripping ability, but 996precision (in which case you might lose perfect roundtripping ability, but
943the JSON number will still be re-encoded as a JSON number). 997the JSON number will still be re-encoded as a JSON number).
944 998
999Note that precision is not accuracy - binary floating point values cannot
1000represent most decimal fractions exactly, and when converting from and to
1001floating point, JSON::XS only guarantees precision up to but not including
1002the leats significant bit.
1003
945=item true, false 1004=item true, false
946 1005
947These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 1006These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
948respectively. They are overloaded to act almost exactly like the numbers 1007respectively. They are overloaded to act almost exactly like the numbers
949C<1> and C<0>. You can check whether a scalar is a JSON boolean by using 1008C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
985Other unblessed references are generally not allowed and will cause an 1044Other unblessed references are generally not allowed and will cause an
986exception to be thrown, except for references to the integers C<0> and 1045exception to be thrown, except for references to the integers C<0> and
987C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 1046C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
988also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 1047also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
989 1048
990 encode_json [\0,JSON::XS::true] # yields [false,true] 1049 encode_json [\0, JSON::XS::true] # yields [false,true]
991 1050
992=item JSON::XS::true, JSON::XS::false 1051=item JSON::XS::true, JSON::XS::false
993 1052
994These special values become JSON true and JSON false values, 1053These special values become JSON true and JSON false values,
995respectively. You can also use C<\1> and C<\0> directly if you want. 1054respectively. You can also use C<\1> and C<\0> directly if you want.
1035 $x *= 1; # same thing, the choice is yours. 1094 $x *= 1; # same thing, the choice is yours.
1036 1095
1037You can not currently force the type in other, less obscure, ways. Tell me 1096You can not currently force the type in other, less obscure, ways. Tell me
1038if you need this capability (but don't forget to explain why it's needed 1097if you need this capability (but don't forget to explain why it's needed
1039:). 1098:).
1099
1100Note that numerical precision has the same meaning as under Perl (so
1101binary to decimal conversion follows the same rules as in Perl, which
1102can differ to other languages). Also, your perl interpreter might expose
1103extensions to the floating point numbers of your platform, such as
1104infinities or NaN's - these cannot be represented in JSON, and it is an
1105error to pass those in.
1040 1106
1041=back 1107=back
1042 1108
1043 1109
1044=head1 ENCODING/CODESET FLAG NOTES 1110=head1 ENCODING/CODESET FLAG NOTES
1137proper subset of most 8-bit and multibyte encodings in use in the world. 1203proper subset of most 8-bit and multibyte encodings in use in the world.
1138 1204
1139=back 1205=back
1140 1206
1141 1207
1142=head1 COMPARISON 1208=head2 JSON and ECMAscript
1143 1209
1144As already mentioned, this module was created because none of the existing 1210JSON syntax is based on how literals are represented in javascript (the
1145JSON modules could be made to work correctly. First I will describe the 1211not-standardised predecessor of ECMAscript) which is presumably why it is
1146problems (or pleasures) I encountered with various existing JSON modules, 1212called "JavaScript Object Notation".
1147followed by some benchmark values. JSON::XS was designed not to suffer
1148from any of these problems or limitations.
1149 1213
1150=over 4 1214However, JSON is not a subset (and also not a superset of course) of
1215ECMAscript (the standard) or javascript (whatever browsers actually
1216implement).
1151 1217
1152=item JSON 2.xx 1218If you want to use javascript's C<eval> function to "parse" JSON, you
1219might run into parse errors for valid JSON texts, or the resulting data
1220structure might not be queryable:
1153 1221
1154A marvellous piece of engineering, this module either uses JSON::XS 1222One of the problems is that U+2028 and U+2029 are valid characters inside
1155directly when available (so will be 100% compatible with it, including 1223JSON strings, but are not allowed in ECMAscript string literals, so the
1156speed), or it uses JSON::PP, which is basically JSON::XS translated to 1224following Perl fragment will not output something that can be guaranteed
1157Pure Perl, which should be 100% compatible with JSON::XS, just a bit 1225to be parsable by javascript's C<eval>:
1158slower.
1159 1226
1160You cannot really lose by using this module, especially as it tries very 1227 use JSON::XS;
1161hard to work even with ancient Perl versions, while JSON::XS does not.
1162 1228
1163=item JSON 1.07 1229 print encode_json [chr 0x2028];
1164 1230
1165Slow (but very portable, as it is written in pure Perl). 1231The right fix for this is to use a proper JSON parser in your javascript
1232programs, and not rely on C<eval> (see for example Douglas Crockford's
1233F<json2.js> parser).
1166 1234
1167Undocumented/buggy Unicode handling (how JSON handles Unicode values is 1235If this is not an option, you can, as a stop-gap measure, simply encode to
1168undocumented. One can get far by feeding it Unicode strings and doing 1236ASCII-only JSON:
1169en-/decoding oneself, but Unicode escapes are not working properly).
1170 1237
1171No round-tripping (strings get clobbered if they look like numbers, e.g. 1238 use JSON::XS;
1172the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
1173decode into the number 2.
1174 1239
1175=item JSON::PC 0.01 1240 print JSON::XS->new->ascii->encode ([chr 0x2028]);
1176 1241
1177Very fast. 1242Note that this will enlarge the resulting JSON text quite a bit if you
1243have many non-ASCII characters. You might be tempted to run some regexes
1244to only escape U+2028 and U+2029, e.g.:
1178 1245
1179Undocumented/buggy Unicode handling. 1246 # DO NOT USE THIS!
1247 my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
1248 $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
1249 $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
1250 print $json;
1180 1251
1181No round-tripping. 1252Note that I<this is a bad idea>: the above only works for U+2028 and
1253U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
1254javascript implementations, however, have issues with other characters as
1255well - using C<eval> naively simply I<will> cause problems.
1182 1256
1183Has problems handling many Perl values (e.g. regex results and other magic 1257Another problem is that some javascript implementations reserve
1184values will make it croak). 1258some property names for their own purposes (which probably makes
1259them non-ECMAscript-compliant). For example, Iceweasel reserves the
1260C<__proto__> property name for its own purposes.
1185 1261
1186Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 1262If that is a problem, you could parse try to filter the resulting JSON
1187which is not a valid JSON text. 1263output for these property strings, e.g.:
1188 1264
1189Unmaintained (maintainer unresponsive for many months, bugs are not 1265 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1190getting fixed).
1191 1266
1192=item JSON::Syck 0.21 1267This works because C<__proto__> is not valid outside of strings, so every
1268occurence of C<"__proto__"\s*:> must be a string used as property name.
1193 1269
1194Very buggy (often crashes). 1270If you know of other incompatibilities, please let me know.
1195
1196Very inflexible (no human-readable format supported, format pretty much
1197undocumented. I need at least a format for easy reading by humans and a
1198single-line compact format for use in a protocol, and preferably a way to
1199generate ASCII-only JSON texts).
1200
1201Completely broken (and confusingly documented) Unicode handling (Unicode
1202escapes are not working properly, you need to set ImplicitUnicode to
1203I<different> values on en- and decoding to get symmetric behaviour).
1204
1205No round-tripping (simple cases work, but this depends on whether the scalar
1206value was used in a numeric context or not).
1207
1208Dumping hashes may skip hash values depending on iterator state.
1209
1210Unmaintained (maintainer unresponsive for many months, bugs are not
1211getting fixed).
1212
1213Does not check input for validity (i.e. will accept non-JSON input and
1214return "something" instead of raising an exception. This is a security
1215issue: imagine two banks transferring money between each other using
1216JSON. One bank might parse a given non-JSON request and deduct money,
1217while the other might reject the transaction with a syntax error. While a
1218good protocol will at least recover, that is extra unnecessary work and
1219the transaction will still not succeed).
1220
1221=item JSON::DWIW 0.04
1222
1223Very fast. Very natural. Very nice.
1224
1225Undocumented Unicode handling (but the best of the pack. Unicode escapes
1226still don't get parsed properly).
1227
1228Very inflexible.
1229
1230No round-tripping.
1231
1232Does not generate valid JSON texts (key strings are often unquoted, empty keys
1233result in nothing being output)
1234
1235Does not check input for validity.
1236
1237=back
1238 1271
1239 1272
1240=head2 JSON and YAML 1273=head2 JSON and YAML
1241 1274
1242You often hear that JSON is a subset of YAML. This is, however, a mass 1275You often hear that JSON is a subset of YAML. This is, however, a mass
1252 my $yaml = $to_yaml->encode ($ref) . "\n"; 1285 my $yaml = $to_yaml->encode ($ref) . "\n";
1253 1286
1254This will I<usually> generate JSON texts that also parse as valid 1287This will I<usually> generate JSON texts that also parse as valid
1255YAML. Please note that YAML has hardcoded limits on (simple) object key 1288YAML. Please note that YAML has hardcoded limits on (simple) object key
1256lengths that JSON doesn't have and also has different and incompatible 1289lengths that JSON doesn't have and also has different and incompatible
1257unicode handling, so you should make sure that your hash keys are 1290unicode character escape syntax, so you should make sure that your hash
1258noticeably shorter than the 1024 "stream characters" YAML allows and that 1291keys are noticeably shorter than the 1024 "stream characters" YAML allows
1259you do not have characters with codepoint values outside the Unicode BMP 1292and that you do not have characters with codepoint values outside the
1260(basic multilingual page). YAML also does not allow C<\/> sequences in 1293Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1261strings (which JSON::XS does not I<currently> generate, but other JSON 1294sequences in strings (which JSON::XS does not I<currently> generate, but
1262generators might). 1295other JSON generators might).
1263 1296
1264There might be other incompatibilities that I am not aware of (or the YAML 1297There might be other incompatibilities that I am not aware of (or the YAML
1265specification has been changed yet again - it does so quite often). In 1298specification has been changed yet again - it does so quite often). In
1266general you should not try to generate YAML with a JSON generator or vice 1299general you should not try to generate YAML with a JSON generator or vice
1267versa, or try to parse JSON with a YAML parser or vice versa: chances are 1300versa, or try to parse JSON with a YAML parser or vice versa: chances are
1286that difficult or long) and finally make YAML compatible to it, and 1319that difficult or long) and finally make YAML compatible to it, and
1287educating users about the changes, instead of spreading lies about the 1320educating users about the changes, instead of spreading lies about the
1288real compatibility for many I<years> and trying to silence people who 1321real compatibility for many I<years> and trying to silence people who
1289point out that it isn't true. 1322point out that it isn't true.
1290 1323
1324Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
1325though the incompatibilities have been documented (and are known to
1326Brian) for many years and the spec makes explicit claims that YAML is a
1327superset of JSON. It would be so easy to fix, but apparently, bullying and
1328corrupting userdata is so much easier.
1329
1291=back 1330=back
1292 1331
1293 1332
1294=head2 SPEED 1333=head2 SPEED
1295 1334
1300 1339
1301First comes a comparison between various modules using 1340First comes a comparison between various modules using
1302a very short single-line JSON string (also available at 1341a very short single-line JSON string (also available at
1303L<http://dist.schmorp.de/misc/json/short.json>). 1342L<http://dist.schmorp.de/misc/json/short.json>).
1304 1343
1305 {"method": "handleMessage", "params": ["user1", "we were just talking"], \ 1344 {"method": "handleMessage", "params": ["user1",
1306 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} 1345 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1346 1, 0]}
1307 1347
1308It shows the number of encodes/decodes per second (JSON::XS uses 1348It shows the number of encodes/decodes per second (JSON::XS uses
1309the functional interface, while JSON::XS/2 uses the OO interface 1349the functional interface, while JSON::XS/2 uses the OO interface
1310with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 1350with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1311shrink). Higher is better: 1351shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
1352uses the from_json method). Higher is better:
1312 1353
1313 module | encode | decode | 1354 module | encode | decode |
1314 -----------|------------|------------| 1355 --------------|------------|------------|
1315 JSON 1.x | 4990.842 | 4088.813 | 1356 JSON::DWIW/DS | 86302.551 | 102300.098 |
1316 JSON::DWIW | 51653.990 | 71575.154 | 1357 JSON::DWIW/FJ | 86302.551 | 75983.768 |
1317 JSON::PC | 65948.176 | 74631.744 | 1358 JSON::PP | 15827.562 | 6638.658 |
1318 JSON::PP | 8931.652 | 3817.168 | 1359 JSON::Syck | 63358.066 | 47662.545 |
1319 JSON::Syck | 24877.248 | 27776.848 | 1360 JSON::XS | 511500.488 | 511500.488 |
1320 JSON::XS | 388361.481 | 227951.304 | 1361 JSON::XS/2 | 291271.111 | 388361.481 |
1321 JSON::XS/2 | 227951.304 | 218453.333 | 1362 JSON::XS/3 | 361577.931 | 361577.931 |
1322 JSON::XS/3 | 338250.323 | 218453.333 | 1363 Storable | 66788.280 | 265462.278 |
1323 Storable | 16500.016 | 135300.129 |
1324 -----------+------------+------------+ 1364 --------------+------------+------------+
1325 1365
1326That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 1366That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1327about three times faster on decoding, and over forty times faster 1367about five times faster on decoding, and over thirty to seventy times
1328than JSON, even with pretty-printing and key sorting. It also compares 1368faster than JSON's pure perl implementation. It also compares favourably
1329favourably to Storable for small amounts of data. 1369to Storable for small amounts of data.
1330 1370
1331Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1371Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1332search API (L<http://dist.schmorp.de/misc/json/long.json>). 1372search API (L<http://dist.schmorp.de/misc/json/long.json>).
1333 1373
1334 module | encode | decode | 1374 module | encode | decode |
1335 -----------|------------|------------| 1375 --------------|------------|------------|
1336 JSON 1.x | 55.260 | 34.971 | 1376 JSON::DWIW/DS | 1647.927 | 2673.916 |
1337 JSON::DWIW | 825.228 | 1082.513 | 1377 JSON::DWIW/FJ | 1630.249 | 2596.128 |
1338 JSON::PC | 3571.444 | 2394.829 |
1339 JSON::PP | 210.987 | 32.574 | 1378 JSON::PP | 400.640 | 62.311 |
1340 JSON::Syck | 552.551 | 787.544 | 1379 JSON::Syck | 1481.040 | 1524.869 |
1341 JSON::XS | 5780.463 | 4854.519 | 1380 JSON::XS | 20661.596 | 9541.183 |
1342 JSON::XS/2 | 3869.998 | 4798.975 | 1381 JSON::XS/2 | 10683.403 | 9416.938 |
1343 JSON::XS/3 | 5862.880 | 4798.975 | 1382 JSON::XS/3 | 20661.596 | 9400.054 |
1344 Storable | 4445.002 | 5235.027 | 1383 Storable | 19765.806 | 10000.725 |
1345 -----------+------------+------------+ 1384 --------------+------------+------------+
1346 1385
1347Again, JSON::XS leads by far (except for Storable which non-surprisingly 1386Again, JSON::XS leads by far (except for Storable which non-surprisingly
1348decodes faster). 1387decodes a bit faster).
1349 1388
1350On large strings containing lots of high Unicode characters, some modules 1389On large strings containing lots of high Unicode characters, some modules
1351(such as JSON::PC) seem to decode faster than JSON::XS, but the result 1390(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1352will be broken due to missing (or wrong) Unicode handling. Others refuse 1391will be broken due to missing (or wrong) Unicode handling. Others refuse
1353to decode or encode properly, so it was impossible to prepare a fair 1392to decode or encode properly, so it was impossible to prepare a fair
1389information you might want to make sure that exceptions thrown by JSON::XS 1428information you might want to make sure that exceptions thrown by JSON::XS
1390will not end up in front of untrusted eyes. 1429will not end up in front of untrusted eyes.
1391 1430
1392If you are using JSON::XS to return packets to consumption 1431If you are using JSON::XS to return packets to consumption
1393by JavaScript scripts in a browser you should have a look at 1432by JavaScript scripts in a browser you should have a look at
1394L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1433L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1395you are vulnerable to some common attack vectors (which really are browser 1434see whether you are vulnerable to some common attack vectors (which really
1396design bugs, but it is still you who will have to deal with it, as major 1435are browser design bugs, but it is still you who will have to deal with
1397browser developers care only for features, not about getting security 1436it, as major browser developers care only for features, not about getting
1398right). 1437security right).
1399 1438
1400 1439
1401=head1 THREADS 1440=head1 THREADS
1402 1441
1403This module is I<not> guaranteed to be thread safe and there are no 1442This module is I<not> guaranteed to be thread safe and there are no
1409 1448
1410 1449
1411=head1 BUGS 1450=head1 BUGS
1412 1451
1413While the goal of this module is to be correct, that unfortunately does 1452While the goal of this module is to be correct, that unfortunately does
1414not mean it's bug-free, only that I think its design is bug-free. It is 1453not mean it's bug-free, only that I think its design is bug-free. If you
1415still relatively early in its development. If you keep reporting bugs they 1454keep reporting bugs they will be fixed swiftly, though.
1416will be fixed swiftly, though.
1417 1455
1418Please refrain from using rt.cpan.org or any other bug reporting 1456Please refrain from using rt.cpan.org or any other bug reporting
1419service. I put the contact address into my modules for a reason. 1457service. I put the contact address into my modules for a reason.
1420 1458
1421=cut 1459=cut

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines