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Revision 1.36 by root, Wed May 23 22:07:43 2007 UTC vs.
Revision 1.80 by root, Sat Dec 29 17:22:39 2007 UTC

1=head1 NAME 1=head1 NAME
2 2
3JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
4
5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4 7
5=head1 SYNOPSIS 8=head1 SYNOPSIS
6 9
7 use JSON::XS; 10 use JSON::XS;
8 11
9 # exported functions, they croak on error 12 # exported functions, they croak on error
10 # and expect/generate UTF-8 13 # and expect/generate UTF-8
11 14
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15 # objToJson and jsonToObj aliases to to_json and from_json
16 # are exported for compatibility to the JSON module,
17 # but should not be used in new code.
18 17
19 # OO-interface 18 # OO-interface
20 19
21 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
22 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
23 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
24 23
24 # Note that JSON version 2.0 and above will automatically use JSON::XS
25 # if available, at virtually no speed overhead either, so you should
26 # be able to just:
27
28 use JSON;
29
30 # and do the same things, except that you have a pure-perl fallback now.
31
25=head1 DESCRIPTION 32=head1 DESCRIPTION
26 33
27This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
28primary goal is to be I<correct> and its secondary goal is to be 35primary goal is to be I<correct> and its secondary goal is to be
29I<fast>. To reach the latter goal it was written in C. 36I<fast>. To reach the latter goal it was written in C.
37
38Beginning with version 2.0 of the JSON module, when both JSON and
39JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40overriden) with no overhead due to emulation (by inheritign constructor
41and methods). If JSON::XS is not available, it will fall back to the
42compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43gives you a portable JSON API that can be fast when you need and doesn't
44require a C compiler when that is a problem.
30 45
31As this is the n-th-something JSON module on CPAN, what was the reason 46As this is the n-th-something JSON module on CPAN, what was the reason
32to write yet another JSON module? While it seems there are many JSON 47to write yet another JSON module? While it seems there are many JSON
33modules, none of them correctly handle all corner cases, and in most cases 48modules, none of them correctly handle all corner cases, and in most cases
34their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
… …
41 56
42=head2 FEATURES 57=head2 FEATURES
43 58
44=over 4 59=over 4
45 60
46=item * correct unicode handling 61=item * correct Unicode handling
47 62
48This module knows how to handle Unicode, and even documents how and when 63This module knows how to handle Unicode, and even documents how and when
49it does so. 64it does so.
50 65
51=item * round-trip integrity 66=item * round-trip integrity
… …
71This module has both a simple functional interface as well as an OO 86This module has both a simple functional interface as well as an OO
72interface. 87interface.
73 88
74=item * reasonably versatile output formats 89=item * reasonably versatile output formats
75 90
76You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
77possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
78(for when your transport is not 8-bit clean, still supports the whole 93(for when your transport is not 8-bit clean, still supports the whole
79unicode range), or a pretty-printed format (for when you want to read that 94Unicode range), or a pretty-printed format (for when you want to read that
80stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
81 96
82=back 97=back
83 98
84=cut 99=cut
85 100
86package JSON::XS; 101package JSON::XS;
87 102
88use strict; 103use strict;
89 104
90BEGIN {
91 our $VERSION = '1.22'; 105our $VERSION = '2.01';
92 our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
93 107
94 our @EXPORT = qw(to_json from_json objToJson jsonToObj); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
95 require Exporter;
96 109
110sub to_json($) {
97 require XSLoader; 111 require Carp;
98 XSLoader::load JSON::XS::, $VERSION; 112 Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
99} 113}
100 114
115sub from_json($) {
116 require Carp;
117 Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
118}
119
120use Exporter;
121use XSLoader;
122
101=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
102 124
103The following convinience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
104exported by default: 126exported by default:
105 127
106=over 4 128=over 4
107 129
108=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
109 131
110Converts the given Perl data structure (a simple scalar or a reference to 132Converts the given Perl data structure to a UTF-8 encoded, binary string
111a hash or array) to a UTF-8 encoded, binary string (that is, the string contains 133(that is, the string contains octets only). Croaks on error.
112octets only). Croaks on error.
113 134
114This function call is functionally identical to: 135This function call is functionally identical to:
115 136
116 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
117 138
118except being faster. 139except being faster.
119 140
120=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
121 142
122The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to 143The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
123parse that as an UTF-8 encoded JSON text, returning the resulting simple 144to parse that as an UTF-8 encoded JSON text, returning the resulting
124scalar or reference. Croaks on error. 145reference. Croaks on error.
125 146
126This function call is functionally identical to: 147This function call is functionally identical to:
127 148
128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 149 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129 150
130except being faster. 151except being faster.
131 152
153=item $is_boolean = JSON::XS::is_bool $scalar
154
155Returns true if the passed scalar represents either JSON::XS::true or
156JSON::XS::false, two constants that act like C<1> and C<0>, respectively
157and are used to represent JSON C<true> and C<false> values in Perl.
158
159See MAPPING, below, for more information on how JSON values are mapped to
160Perl.
161
132=back 162=back
163
164
165=head1 A FEW NOTES ON UNICODE AND PERL
166
167Since this often leads to confusion, here are a few very clear words on
168how Unicode works in Perl, modulo bugs.
169
170=over 4
171
172=item 1. Perl strings can store characters with ordinal values > 255.
173
174This enables you to store Unicode characters as single characters in a
175Perl string - very natural.
176
177=item 2. Perl does I<not> associate an encoding with your strings.
178
179Unless you force it to, e.g. when matching it against a regex, or printing
180the scalar to a file, in which case Perl either interprets your string as
181locale-encoded text, octets/binary, or as Unicode, depending on various
182settings. In no case is an encoding stored together with your data, it is
183I<use> that decides encoding, not any magical metadata.
184
185=item 3. The internal utf-8 flag has no meaning with regards to the
186encoding of your string.
187
188Just ignore that flag unless you debug a Perl bug, a module written in
189XS or want to dive into the internals of perl. Otherwise it will only
190confuse you, as, despite the name, it says nothing about how your string
191is encoded. You can have Unicode strings with that flag set, with that
192flag clear, and you can have binary data with that flag set and that flag
193clear. Other possibilities exist, too.
194
195If you didn't know about that flag, just the better, pretend it doesn't
196exist.
197
198=item 4. A "Unicode String" is simply a string where each character can be
199validly interpreted as a Unicode codepoint.
200
201If you have UTF-8 encoded data, it is no longer a Unicode string, but a
202Unicode string encoded in UTF-8, giving you a binary string.
203
204=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
205
206It's a fact. Learn to live with it.
207
208=back
209
210I hope this helps :)
133 211
134 212
135=head1 OBJECT-ORIENTED INTERFACE 213=head1 OBJECT-ORIENTED INTERFACE
136 214
137The object oriented interface lets you configure your own encoding or 215The object oriented interface lets you configure your own encoding or
… …
150 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 228 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
151 => {"a": [1, 2]} 229 => {"a": [1, 2]}
152 230
153=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
154 232
233=item $enabled = $json->get_ascii
234
155If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
156generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
157unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
158single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159as per RFC4627. The resulting encoded JSON text can be treated as a native 239as per RFC4627. The resulting encoded JSON text can be treated as a native
160unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 240Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
161or any other superset of ASCII. 241or any other superset of ASCII.
162 242
163If C<$enable> is false, then the C<encode> method will not escape Unicode 243If C<$enable> is false, then the C<encode> method will not escape Unicode
164characters unless required by the JSON syntax or other flags. This results 244characters unless required by the JSON syntax or other flags. This results
165in a faster and more compact format. 245in a faster and more compact format.
… …
171 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
172 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
173 253
174=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
175 255
256=item $enabled = $json->get_latin1
257
176If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
177the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
178outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
179latin1-encoded JSON text or a native unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
180will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
181expects unicode, which is a strict superset of latin1. 263expects Unicode, which is a strict superset of latin1.
182 264
183If C<$enable> is false, then the C<encode> method will not escape Unicode 265If C<$enable> is false, then the C<encode> method will not escape Unicode
184characters unless required by the JSON syntax or other flags. 266characters unless required by the JSON syntax or other flags.
185 267
186The main use for this flag is efficiently encoding binary data as JSON 268The main use for this flag is efficiently encoding binary data as JSON
187text, as most octets will not be escaped, resulting in a smaller encoded 269text, as most octets will not be escaped, resulting in a smaller encoded
188size. The disadvantage is that the resulting JSON text is encoded 270size. The disadvantage is that the resulting JSON text is encoded
189in latin1 (and must correctly be treated as such when storing and 271in latin1 (and must correctly be treated as such when storing and
190transfering), a rare encoding for JSON. It is therefore most useful when 272transferring), a rare encoding for JSON. It is therefore most useful when
191you want to store data structures known to contain binary data efficiently 273you want to store data structures known to contain binary data efficiently
192in files or databases, not when talking to other JSON encoders/decoders. 274in files or databases, not when talking to other JSON encoders/decoders.
193 275
194 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
195 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
196 278
197=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
198 282
199If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
200the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
201C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
202note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
203range C<0..255>, they are thus useful for bytewise/binary I/O. In future 287range C<0..255>, they are thus useful for bytewise/binary I/O. In future
204versions, enabling this option might enable autodetection of the UTF-16 288versions, enabling this option might enable autodetection of the UTF-16
205and UTF-32 encoding families, as described in RFC4627. 289and UTF-32 encoding families, as described in RFC4627.
206 290
207If C<$enable> is false, then the C<encode> method will return the JSON 291If C<$enable> is false, then the C<encode> method will return the JSON
208string as a (non-encoded) unicode string, while C<decode> expects thus a 292string as a (non-encoded) Unicode string, while C<decode> expects thus a
209unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 293Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
210to be done yourself, e.g. using the Encode module. 294to be done yourself, e.g. using the Encode module.
211 295
212Example, output UTF-16BE-encoded JSON: 296Example, output UTF-16BE-encoded JSON:
213 297
214 use Encode; 298 use Encode;
… …
236 ] 320 ]
237 } 321 }
238 322
239=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
240 324
325=item $enabled = $json->get_indent
326
241If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
242format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
243into its own line, identing them properly. 329into its own line, indenting them properly.
244 330
245If C<$enable> is false, no newlines or indenting will be produced, and the 331If C<$enable> is false, no newlines or indenting will be produced, and the
246resulting JSON text is guarenteed not to contain any C<newlines>. 332resulting JSON text is guaranteed not to contain any C<newlines>.
247 333
248This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
249 335
250=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
337
338=item $enabled = $json->get_space_before
251 339
252If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
253optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
254 342
255If C<$enable> is false, then the C<encode> method will not add any extra 343If C<$enable> is false, then the C<encode> method will not add any extra
… …
261Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
262 350
263 {"key" :"value"} 351 {"key" :"value"}
264 352
265=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
266 356
267If C<$enable> is true (or missing), then the C<encode> method will add an extra 357If C<$enable> is true (or missing), then the C<encode> method will add an extra
268optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
269and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
270members. 360members.
… …
276 366
277Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
278 368
279 {"key": "value"} 369 {"key": "value"}
280 370
371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
374
375If C<$enable> is true (or missing), then C<decode> will accept some
376extensions to normal JSON syntax (see below). C<encode> will not be
377affected in anyway. I<Be aware that this option makes you accept invalid
378JSON texts as if they were valid!>. I suggest only to use this option to
379parse application-specific files written by humans (configuration files,
380resource files etc.)
381
382If C<$enable> is false (the default), then C<decode> will only accept
383valid JSON texts.
384
385Currently accepted extensions are:
386
387=over 4
388
389=item * list items can have an end-comma
390
391JSON I<separates> array elements and key-value pairs with commas. This
392can be annoying if you write JSON texts manually and want to be able to
393quickly append elements, so this extension accepts comma at the end of
394such items not just between them:
395
396 [
397 1,
398 2, <- this comma not normally allowed
399 ]
400 {
401 "k1": "v1",
402 "k2": "v2", <- this comma not normally allowed
403 }
404
405=item * shell-style '#'-comments
406
407Whenever JSON allows whitespace, shell-style comments are additionally
408allowed. They are terminated by the first carriage-return or line-feed
409character, after which more white-space and comments are allowed.
410
411 [
412 1, # this comment not allowed in JSON
413 # neither this one...
414 ]
415
416=back
417
281=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
419
420=item $enabled = $json->get_canonical
282 421
283If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
285 424
286If C<$enable> is false, then the C<encode> method will output key-value 425If C<$enable> is false, then the C<encode> method will output key-value
287pairs in the order Perl stores them (which will likely change between runs 426pairs in the order Perl stores them (which will likely change between runs
288of the same script). 427of the same script).
289 428
290This option is useful if you want the same data structure to be encoded as 429This option is useful if you want the same data structure to be encoded as
291the same JSON text (given the same overall settings). If it is disabled, 430the same JSON text (given the same overall settings). If it is disabled,
292the same hash migh be encoded differently even if contains the same data, 431the same hash might be encoded differently even if contains the same data,
293as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
294 433
295This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
296 435
297=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
298 439
299If C<$enable> is true (or missing), then the C<encode> method can convert a 440If C<$enable> is true (or missing), then the C<encode> method can convert a
300non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
301which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 442which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
302values instead of croaking. 443values instead of croaking.
… …
310resulting in an invalid JSON text: 451resulting in an invalid JSON text:
311 452
312 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
313 => "Hello, World!" 454 => "Hello, World!"
314 455
456=item $json = $json->allow_blessed ([$enable])
457
458=item $enabled = $json->get_allow_blessed
459
460If C<$enable> is true (or missing), then the C<encode> method will not
461barf when it encounters a blessed reference. Instead, the value of the
462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
463disabled or no C<TO_JSON> method found) or a representation of the
464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
465encoded. Has no effect on C<decode>.
466
467If C<$enable> is false (the default), then C<encode> will throw an
468exception when it encounters a blessed object.
469
470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
473
474If C<$enable> is true (or missing), then C<encode>, upon encountering a
475blessed object, will check for the availability of the C<TO_JSON> method
476on the object's class. If found, it will be called in scalar context
477and the resulting scalar will be encoded instead of the object. If no
478C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
479to do.
480
481The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
482returns other blessed objects, those will be handled in the same
483way. C<TO_JSON> must take care of not causing an endless recursion cycle
484(== crash) in this case. The name of C<TO_JSON> was chosen because other
485methods called by the Perl core (== not by the user of the object) are
486usually in upper case letters and to avoid collisions with any C<to_json>
487function or method.
488
489This setting does not yet influence C<decode> in any way, but in the
490future, global hooks might get installed that influence C<decode> and are
491enabled by this setting.
492
493If C<$enable> is false, then the C<allow_blessed> setting will decide what
494to do when a blessed object is found.
495
496=item $json = $json->filter_json_object ([$coderef->($hashref)])
497
498When C<$coderef> is specified, it will be called from C<decode> each
499time it decodes a JSON object. The only argument is a reference to the
500newly-created hash. If the code references returns a single scalar (which
501need not be a reference), this value (i.e. a copy of that scalar to avoid
502aliasing) is inserted into the deserialised data structure. If it returns
503an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
504original deserialised hash will be inserted. This setting can slow down
505decoding considerably.
506
507When C<$coderef> is omitted or undefined, any existing callback will
508be removed and C<decode> will not change the deserialised hash in any
509way.
510
511Example, convert all JSON objects into the integer 5:
512
513 my $js = JSON::XS->new->filter_json_object (sub { 5 });
514 # returns [5]
515 $js->decode ('[{}]')
516 # throw an exception because allow_nonref is not enabled
517 # so a lone 5 is not allowed.
518 $js->decode ('{"a":1, "b":2}');
519
520=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
521
522Works remotely similar to C<filter_json_object>, but is only called for
523JSON objects having a single key named C<$key>.
524
525This C<$coderef> is called before the one specified via
526C<filter_json_object>, if any. It gets passed the single value in the JSON
527object. If it returns a single value, it will be inserted into the data
528structure. If it returns nothing (not even C<undef> but the empty list),
529the callback from C<filter_json_object> will be called next, as if no
530single-key callback were specified.
531
532If C<$coderef> is omitted or undefined, the corresponding callback will be
533disabled. There can only ever be one callback for a given key.
534
535As this callback gets called less often then the C<filter_json_object>
536one, decoding speed will not usually suffer as much. Therefore, single-key
537objects make excellent targets to serialise Perl objects into, especially
538as single-key JSON objects are as close to the type-tagged value concept
539as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
540support this in any way, so you need to make sure your data never looks
541like a serialised Perl hash.
542
543Typical names for the single object key are C<__class_whatever__>, or
544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
545things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
546with real hashes.
547
548Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
549into the corresponding C<< $WIDGET{<id>} >> object:
550
551 # return whatever is in $WIDGET{5}:
552 JSON::XS
553 ->new
554 ->filter_json_single_key_object (__widget__ => sub {
555 $WIDGET{ $_[0] }
556 })
557 ->decode ('{"__widget__": 5')
558
559 # this can be used with a TO_JSON method in some "widget" class
560 # for serialisation to json:
561 sub WidgetBase::TO_JSON {
562 my ($self) = @_;
563
564 unless ($self->{id}) {
565 $self->{id} = ..get..some..id..;
566 $WIDGET{$self->{id}} = $self;
567 }
568
569 { __widget__ => $self->{id} }
570 }
571
315=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
316 575
317Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
319C<encode> or C<decode> to their minimum size possible. This can save 578C<encode> or C<decode> to their minimum size possible. This can save
320memory when your JSON texts are either very very long or you have many 579memory when your JSON texts are either very very long or you have many
… …
338strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
339internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
340 599
341=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
342 601
602=item $max_depth = $json->get_max_depth
603
343Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
344or decoding. If the JSON text or Perl data structure has an equal or 605or decoding. If the JSON text or Perl data structure has an equal or
345higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
346stop and croak at that point. 607stop and croak at that point.
347 608
… …
351given character in a string. 612given character in a string.
352 613
353Setting the maximum depth to one disallows any nesting, so that ensures 614Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 615that the object is only a single hash/object or array.
355 616
356The argument to C<max_depth> will be rounded up to the next nearest power 617The argument to C<max_depth> will be rounded up to the next highest power
357of two. 618of two. If no argument is given, the highest possible setting will be
619used, which is rarely useful.
620
621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
622
623=item $json = $json->max_size ([$maximum_string_size])
624
625=item $max_size = $json->get_max_size
626
627Set the maximum length a JSON text may have (in bytes) where decoding is
628being attempted. The default is C<0>, meaning no limit. When C<decode>
629is called on a string longer then this number of characters it will not
630attempt to decode the string but throw an exception. This setting has no
631effect on C<encode> (yet).
632
633The argument to C<max_size> will be rounded up to the next B<highest>
634power of two (so may be more than requested). If no argument is given, the
635limit check will be deactivated (same as when C<0> is specified).
358 636
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 637See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 638
361=item $json_text = $json->encode ($perl_scalar) 639=item $json_text = $json->encode ($perl_scalar)
362 640
… …
399vice versa. These mappings are designed to "do the right thing" in most 677vice versa. These mappings are designed to "do the right thing" in most
400circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
401(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
402 680
403For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
404lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
405refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
406 684
685
407=head2 JSON -> PERL 686=head2 JSON -> PERL
408 687
409=over 4 688=over 4
410 689
411=item object 690=item object
412 691
413A JSON object becomes a reference to a hash in Perl. No ordering of object 692A JSON object becomes a reference to a hash in Perl. No ordering of object
414keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
415 694
416=item array 695=item array
417 696
418A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
419 698
… …
423are represented by the same codepoints in the Perl string, so no manual 702are represented by the same codepoints in the Perl string, so no manual
424decoding is necessary. 703decoding is necessary.
425 704
426=item number 705=item number
427 706
428A JSON number becomes either an integer or numeric (floating point) 707A JSON number becomes either an integer, numeric (floating point) or
429scalar in perl, depending on its range and any fractional parts. On the 708string scalar in perl, depending on its range and any fractional parts. On
430Perl level, there is no difference between those as Perl handles all the 709the Perl level, there is no difference between those as Perl handles all
431conversion details, but an integer may take slightly less memory and might 710the conversion details, but an integer may take slightly less memory and
432represent more values exactly than (floating point) numbers. 711might represent more values exactly than (floating point) numbers.
712
713If the number consists of digits only, JSON::XS will try to represent
714it as an integer value. If that fails, it will try to represent it as
715a numeric (floating point) value if that is possible without loss of
716precision. Otherwise it will preserve the number as a string value.
717
718Numbers containing a fractional or exponential part will always be
719represented as numeric (floating point) values, possibly at a loss of
720precision.
721
722This might create round-tripping problems as numbers might become strings,
723but as Perl is typeless there is no other way to do it.
433 724
434=item true, false 725=item true, false
435 726
436These JSON atoms become C<0>, C<1>, respectively. Information is lost in 727These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
437this process. Future versions might represent those values differently, 728respectively. They are overloaded to act almost exactly like the numbers
438but they will be guarenteed to act like these integers would normally in 729C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
439Perl. 730the C<JSON::XS::is_bool> function.
440 731
441=item null 732=item null
442 733
443A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
444 735
445=back 736=back
737
446 738
447=head2 PERL -> JSON 739=head2 PERL -> JSON
448 740
449The mapping from Perl to JSON is slightly more difficult, as Perl is a 741The mapping from Perl to JSON is slightly more difficult, as Perl is a
450truly typeless language, so we can only guess which JSON type is meant by 742truly typeless language, so we can only guess which JSON type is meant by
… …
473Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
474exception to be thrown, except for references to the integers C<0> and 766exception to be thrown, except for references to the integers C<0> and
475C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 767C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
476also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 768also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
477 769
478 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
771
772=item JSON::XS::true, JSON::XS::false
773
774These special values become JSON true and JSON false values,
775respectively. You can also use C<\1> and C<\0> directly if you want.
479 776
480=item blessed objects 777=item blessed objects
481 778
482Blessed objects are not allowed. JSON::XS currently tries to encode their 779Blessed objects are not allowed. JSON::XS currently tries to encode their
483underlying representation (hash- or arrayref), but this behaviour might 780underlying representation (hash- or arrayref), but this behaviour might
… …
489difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
490JSON null value, scalars that have last been used in a string context 787JSON null value, scalars that have last been used in a string context
491before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
492 789
493 # dump as number 790 # dump as number
494 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
495 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
496 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
497 794
498 # used as string, so dump as string 795 # used as string, so dump as string
499 print $value; 796 print $value;
500 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
501 798
502 # undef becomes null 799 # undef becomes null
503 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
504 801
505You can force the type to be a string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
506 803
507 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
508 "$x"; # stringified 805 "$x"; # stringified
509 $x .= ""; # another, more awkward way to stringify 806 $x .= ""; # another, more awkward way to stringify
510 print $x; # perl does it for you, too, quite often 807 print $x; # perl does it for you, too, quite often
511 808
512You can force the type to be a number by numifying it: 809You can force the type to be a JSON number by numifying it:
513 810
514 my $x = "3"; # some variable containing a string 811 my $x = "3"; # some variable containing a string
515 $x += 0; # numify it, ensuring it will be dumped as a number 812 $x += 0; # numify it, ensuring it will be dumped as a number
516 $x *= 1; # same thing, the choise is yours. 813 $x *= 1; # same thing, the choice is yours.
517 814
518You can not currently output JSON booleans or force the type in other, 815You can not currently force the type in other, less obscure, ways. Tell me
519less obscure, ways. Tell me if you need this capability. 816if you need this capability.
520 817
521=back 818=back
522 819
523 820
524=head1 COMPARISON 821=head1 COMPARISON
… …
533 830
534=item JSON 1.07 831=item JSON 1.07
535 832
536Slow (but very portable, as it is written in pure Perl). 833Slow (but very portable, as it is written in pure Perl).
537 834
538Undocumented/buggy Unicode handling (how JSON handles unicode values is 835Undocumented/buggy Unicode handling (how JSON handles Unicode values is
539undocumented. One can get far by feeding it unicode strings and doing 836undocumented. One can get far by feeding it Unicode strings and doing
540en-/decoding oneself, but unicode escapes are not working properly). 837en-/decoding oneself, but Unicode escapes are not working properly).
541 838
542No roundtripping (strings get clobbered if they look like numbers, e.g. 839No round-tripping (strings get clobbered if they look like numbers, e.g.
543the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 840the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
544decode into the number 2. 841decode into the number 2.
545 842
546=item JSON::PC 0.01 843=item JSON::PC 0.01
547 844
548Very fast. 845Very fast.
549 846
550Undocumented/buggy Unicode handling. 847Undocumented/buggy Unicode handling.
551 848
552No roundtripping. 849No round-tripping.
553 850
554Has problems handling many Perl values (e.g. regex results and other magic 851Has problems handling many Perl values (e.g. regex results and other magic
555values will make it croak). 852values will make it croak).
556 853
557Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 854Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
… …
567Very inflexible (no human-readable format supported, format pretty much 864Very inflexible (no human-readable format supported, format pretty much
568undocumented. I need at least a format for easy reading by humans and a 865undocumented. I need at least a format for easy reading by humans and a
569single-line compact format for use in a protocol, and preferably a way to 866single-line compact format for use in a protocol, and preferably a way to
570generate ASCII-only JSON texts). 867generate ASCII-only JSON texts).
571 868
572Completely broken (and confusingly documented) Unicode handling (unicode 869Completely broken (and confusingly documented) Unicode handling (Unicode
573escapes are not working properly, you need to set ImplicitUnicode to 870escapes are not working properly, you need to set ImplicitUnicode to
574I<different> values on en- and decoding to get symmetric behaviour). 871I<different> values on en- and decoding to get symmetric behaviour).
575 872
576No roundtripping (simple cases work, but this depends on wether the scalar 873No round-tripping (simple cases work, but this depends on whether the scalar
577value was used in a numeric context or not). 874value was used in a numeric context or not).
578 875
579Dumping hashes may skip hash values depending on iterator state. 876Dumping hashes may skip hash values depending on iterator state.
580 877
581Unmaintained (maintainer unresponsive for many months, bugs are not 878Unmaintained (maintainer unresponsive for many months, bugs are not
582getting fixed). 879getting fixed).
583 880
584Does not check input for validity (i.e. will accept non-JSON input and 881Does not check input for validity (i.e. will accept non-JSON input and
585return "something" instead of raising an exception. This is a security 882return "something" instead of raising an exception. This is a security
586issue: imagine two banks transfering money between each other using 883issue: imagine two banks transferring money between each other using
587JSON. One bank might parse a given non-JSON request and deduct money, 884JSON. One bank might parse a given non-JSON request and deduct money,
588while the other might reject the transaction with a syntax error. While a 885while the other might reject the transaction with a syntax error. While a
589good protocol will at least recover, that is extra unnecessary work and 886good protocol will at least recover, that is extra unnecessary work and
590the transaction will still not succeed). 887the transaction will still not succeed).
591 888
592=item JSON::DWIW 0.04 889=item JSON::DWIW 0.04
593 890
594Very fast. Very natural. Very nice. 891Very fast. Very natural. Very nice.
595 892
596Undocumented unicode handling (but the best of the pack. Unicode escapes 893Undocumented Unicode handling (but the best of the pack. Unicode escapes
597still don't get parsed properly). 894still don't get parsed properly).
598 895
599Very inflexible. 896Very inflexible.
600 897
601No roundtripping. 898No round-tripping.
602 899
603Does not generate valid JSON texts (key strings are often unquoted, empty keys 900Does not generate valid JSON texts (key strings are often unquoted, empty keys
604result in nothing being output) 901result in nothing being output)
605 902
606Does not check input for validity. 903Does not check input for validity.
607 904
608=back 905=back
906
907
908=head2 JSON and YAML
909
910You often hear that JSON is a subset of YAML. This is, however, a mass
911hysteria and very far from the truth. In general, there is no way to
912configure JSON::XS to output a data structure as valid YAML that works for
913all cases.
914
915If you really must use JSON::XS to generate YAML, you should use this
916algorithm (subject to change in future versions):
917
918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
919 my $yaml = $to_yaml->encode ($ref) . "\n";
920
921This will usually generate JSON texts that also parse as valid
922YAML. Please note that YAML has hardcoded limits on (simple) object key
923lengths that JSON doesn't have and also has different and incompatible
924unicode handling, so you should make sure that your hash keys are
925noticeably shorter than the 1024 "stream characters" YAML allows and that
926you do not have codepoints with values outside the Unicode BMP (basic
927multilingual page).
928
929There might be other incompatibilities that I am not aware of. In general
930you should not try to generate YAML with a JSON generator or vice versa,
931or try to parse JSON with a YAML parser or vice versa: chances are high
932that you will run into severe interoperability problems when you least
933expect it.
934
609 935
610=head2 SPEED 936=head2 SPEED
611 937
612It seems that JSON::XS is surprisingly fast, as shown in the following 938It seems that JSON::XS is surprisingly fast, as shown in the following
613tables. They have been generated with the help of the C<eg/bench> program 939tables. They have been generated with the help of the C<eg/bench> program
614in the JSON::XS distribution, to make it easy to compare on your own 940in the JSON::XS distribution, to make it easy to compare on your own
615system. 941system.
616 942
617First comes a comparison between various modules using a very short JSON 943First comes a comparison between various modules using a very short
618string: 944single-line JSON string:
619 945
620 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 946 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
947 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
621 948
622It shows the number of encodes/decodes per second (JSON::XS uses the 949It shows the number of encodes/decodes per second (JSON::XS uses
623functional interface, while JSON::XS/2 uses the OO interface with 950the functional interface, while JSON::XS/2 uses the OO interface
624pretty-printing and hashkey sorting enabled). Higher is better: 951with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
952shrink). Higher is better:
625 953
626 module | encode | decode | 954 module | encode | decode |
627 -----------|------------|------------| 955 -----------|------------|------------|
628 JSON | 11488.516 | 7823.035 | 956 JSON 1.x | 4990.842 | 4088.813 |
629 JSON::DWIW | 94708.054 | 129094.260 | 957 JSON::DWIW | 51653.990 | 71575.154 |
630 JSON::PC | 63884.157 | 128528.212 | 958 JSON::PC | 65948.176 | 74631.744 |
631 JSON::Syck | 34898.677 | 42096.911 | 959 JSON::PP | 8931.652 | 3817.168 |
632 JSON::XS | 654027.064 | 396423.669 | 960 JSON::Syck | 24877.248 | 27776.848 |
633 JSON::XS/2 | 371564.190 | 371725.613 | 961 JSON::XS | 388361.481 | 227951.304 |
962 JSON::XS/2 | 227951.304 | 218453.333 |
963 JSON::XS/3 | 338250.323 | 218453.333 |
964 Storable | 16500.016 | 135300.129 |
634 -----------+------------+------------+ 965 -----------+------------+------------+
635 966
636That is, JSON::XS is more than six times faster than JSON::DWIW on 967That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
637encoding, more than three times faster on decoding, and about thirty times 968about three times faster on decoding, and over forty times faster
638faster than JSON, even with pretty-printing and key sorting. 969than JSON, even with pretty-printing and key sorting. It also compares
970favourably to Storable for small amounts of data.
639 971
640Using a longer test string (roughly 18KB, generated from Yahoo! Locals 972Using a longer test string (roughly 18KB, generated from Yahoo! Locals
641search API (http://nanoref.com/yahooapis/mgPdGg): 973search API (http://nanoref.com/yahooapis/mgPdGg):
642 974
643 module | encode | decode | 975 module | encode | decode |
644 -----------|------------|------------| 976 -----------|------------|------------|
645 JSON | 273.023 | 44.674 | 977 JSON 1.x | 55.260 | 34.971 |
646 JSON::DWIW | 1089.383 | 1145.704 | 978 JSON::DWIW | 825.228 | 1082.513 |
647 JSON::PC | 3097.419 | 2393.921 | 979 JSON::PC | 3571.444 | 2394.829 |
648 JSON::Syck | 514.060 | 843.053 | 980 JSON::PP | 210.987 | 32.574 |
649 JSON::XS | 6479.668 | 3636.364 | 981 JSON::Syck | 552.551 | 787.544 |
650 JSON::XS/2 | 3774.221 | 3599.124 | 982 JSON::XS | 5780.463 | 4854.519 |
983 JSON::XS/2 | 3869.998 | 4798.975 |
984 JSON::XS/3 | 5862.880 | 4798.975 |
985 Storable | 4445.002 | 5235.027 |
651 -----------+------------+------------+ 986 -----------+------------+------------+
652 987
653Again, JSON::XS leads by far. 988Again, JSON::XS leads by far (except for Storable which non-surprisingly
989decodes faster).
654 990
655On large strings containing lots of high unicode characters, some modules 991On large strings containing lots of high Unicode characters, some modules
656(such as JSON::PC) seem to decode faster than JSON::XS, but the result 992(such as JSON::PC) seem to decode faster than JSON::XS, but the result
657will be broken due to missing (or wrong) unicode handling. Others refuse 993will be broken due to missing (or wrong) Unicode handling. Others refuse
658to decode or encode properly, so it was impossible to prepare a fair 994to decode or encode properly, so it was impossible to prepare a fair
659comparison table for that case. 995comparison table for that case.
660 996
661 997
662=head1 SECURITY CONSIDERATIONS 998=head1 SECURITY CONSIDERATIONS
… …
668any buffer overflows. Obviously, this module should ensure that and I am 1004any buffer overflows. Obviously, this module should ensure that and I am
669trying hard on making that true, but you never know. 1005trying hard on making that true, but you never know.
670 1006
671Second, you need to avoid resource-starving attacks. That means you should 1007Second, you need to avoid resource-starving attacks. That means you should
672limit the size of JSON texts you accept, or make sure then when your 1008limit the size of JSON texts you accept, or make sure then when your
673resources run out, thats just fine (e.g. by using a separate process that 1009resources run out, that's just fine (e.g. by using a separate process that
674can crash safely). The size of a JSON text in octets or characters is 1010can crash safely). The size of a JSON text in octets or characters is
675usually a good indication of the size of the resources required to decode 1011usually a good indication of the size of the resources required to decode
676it into a Perl structure. 1012it into a Perl structure. While JSON::XS can check the size of the JSON
1013text, it might be too late when you already have it in memory, so you
1014might want to check the size before you accept the string.
677 1015
678Third, JSON::XS recurses using the C stack when decoding objects and 1016Third, JSON::XS recurses using the C stack when decoding objects and
679arrays. The C stack is a limited resource: for instance, on my amd64 1017arrays. The C stack is a limited resource: for instance, on my amd64
680machine with 8MB of stack size I can decode around 180k nested arrays but 1018machine with 8MB of stack size I can decode around 180k nested arrays but
681only 14k nested JSON objects (due to perl itself recursing deeply on croak 1019only 14k nested JSON objects (due to perl itself recursing deeply on croak
682to free the temporary). If that is exceeded, the program crashes. to be 1020to free the temporary). If that is exceeded, the program crashes. To be
683conservative, the default nesting limit is set to 512. If your process 1021conservative, the default nesting limit is set to 512. If your process
684has a smaller stack, you should adjust this setting accordingly with the 1022has a smaller stack, you should adjust this setting accordingly with the
685C<max_depth> method. 1023C<max_depth> method.
686 1024
687And last but least, something else could bomb you that I forgot to think 1025And last but least, something else could bomb you that I forgot to think
688of. In that case, you get to keep the pieces. I am always open for hints, 1026of. In that case, you get to keep the pieces. I am always open for hints,
689though... 1027though...
1028
1029If you are using JSON::XS to return packets to consumption
1030by JavaScript scripts in a browser you should have a look at
1031L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1032you are vulnerable to some common attack vectors (which really are browser
1033design bugs, but it is still you who will have to deal with it, as major
1034browser developers care only for features, not about getting security
1035right).
1036
1037
1038=head1 THREADS
1039
1040This module is I<not> guaranteed to be thread safe and there are no
1041plans to change this until Perl gets thread support (as opposed to the
1042horribly slow so-called "threads" which are simply slow and bloated
1043process simulations - use fork, its I<much> faster, cheaper, better).
1044
1045(It might actually work, but you have been warned).
690 1046
691 1047
692=head1 BUGS 1048=head1 BUGS
693 1049
694While the goal of this module is to be correct, that unfortunately does 1050While the goal of this module is to be correct, that unfortunately does
695not mean its bug-free, only that I think its design is bug-free. It is 1051not mean its bug-free, only that I think its design is bug-free. It is
696still relatively early in its development. If you keep reporting bugs they 1052still relatively early in its development. If you keep reporting bugs they
697will be fixed swiftly, though. 1053will be fixed swiftly, though.
698 1054
1055Please refrain from using rt.cpan.org or any other bug reporting
1056service. I put the contact address into my modules for a reason.
1057
699=cut 1058=cut
700 1059
1060our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
1061our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
1062
701sub true() { \1 } 1063sub true() { $true }
702sub false() { \0 } 1064sub false() { $false }
1065
1066sub is_bool($) {
1067 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1068# or UNIVERSAL::isa $_[0], "JSON::Literal"
1069}
1070
1071XSLoader::load "JSON::XS", $VERSION;
1072
1073package JSON::XS::Boolean;
1074
1075use overload
1076 "0+" => sub { ${$_[0]} },
1077 "++" => sub { $_[0] = ${$_[0]} + 1 },
1078 "--" => sub { $_[0] = ${$_[0]} - 1 },
1079 fallback => 1;
703 1080
7041; 10811;
705 1082
706=head1 AUTHOR 1083=head1 AUTHOR
707 1084

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