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Revision 1.50 by root, Mon Jul 2 00:29:38 2007 UTC vs.
Revision 1.76 by root, Sun Dec 2 15:34:13 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
37 40
38=head2 FEATURES 41=head2 FEATURES
39 42
40=over 4 43=over 4
41 44
42=item * correct unicode handling 45=item * correct Unicode handling
43 46
44This module knows how to handle Unicode, and even documents how and when 47This module knows how to handle Unicode, and even documents how and when
45it does so. 48it does so.
46 49
47=item * round-trip integrity 50=item * round-trip integrity
67This module has both a simple functional interface as well as an OO 70This module has both a simple functional interface as well as an OO
68interface. 71interface.
69 72
70=item * reasonably versatile output formats 73=item * reasonably versatile output formats
71 74
72You can choose between the most compact guarenteed single-line format 75You can choose between the most compact guaranteed single-line format
73possible (nice for simple line-based protocols), a pure-ascii format 76possible (nice for simple line-based protocols), a pure-ascii format
74(for when your transport is not 8-bit clean, still supports the whole 77(for when your transport is not 8-bit clean, still supports the whole
75unicode range), or a pretty-printed format (for when you want to read that 78Unicode range), or a pretty-printed format (for when you want to read that
76stuff). Or you can combine those features in whatever way you like. 79stuff). Or you can combine those features in whatever way you like.
77 80
78=back 81=back
79 82
80=cut 83=cut
81 84
82package JSON::XS; 85package JSON::XS;
83 86
84use strict; 87use strict;
85 88
86our $VERSION = '1.4'; 89our $VERSION = '2.0';
87our @ISA = qw(Exporter); 90our @ISA = qw(Exporter);
88 91
89our @EXPORT = qw(to_json from_json); 92our @EXPORT = qw(to_json from_json);
90 93
91use Exporter; 94use Exporter;
92use XSLoader; 95use XSLoader;
93 96
94=head1 FUNCTIONAL INTERFACE 97=head1 FUNCTIONAL INTERFACE
95 98
96The following convinience methods are provided by this module. They are 99The following convenience methods are provided by this module. They are
97exported by default: 100exported by default:
98 101
99=over 4 102=over 4
100 103
101=item $json_text = to_json $perl_scalar 104=item $json_text = to_json $perl_scalar
102 105
103Converts the given Perl data structure (a simple scalar or a reference to 106Converts the given Perl data structure to a UTF-8 encoded, binary string
104a hash or array) to a UTF-8 encoded, binary string (that is, the string contains 107(that is, the string contains octets only). Croaks on error.
105octets only). Croaks on error.
106 108
107This function call is functionally identical to: 109This function call is functionally identical to:
108 110
109 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110 112
111except being faster. 113except being faster.
112 114
113=item $perl_scalar = from_json $json_text 115=item $perl_scalar = from_json $json_text
114 116
115The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to 117The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
116parse that as an UTF-8 encoded JSON text, returning the resulting simple 118to parse that as an UTF-8 encoded JSON text, returning the resulting
117scalar or reference. Croaks on error. 119reference. Croaks on error.
118 120
119This function call is functionally identical to: 121This function call is functionally identical to:
120 122
121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 123 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122 124
132Perl. 134Perl.
133 135
134=back 136=back
135 137
136 138
139=head1 A FEW NOTES ON UNICODE AND PERL
140
141Since this often leads to confusion, here are a few very clear words on
142how Unicode works in Perl, modulo bugs.
143
144=over 4
145
146=item 1. Perl strings can store characters with ordinal values > 255.
147
148This enables you to store Unicode characters as single characters in a
149Perl string - very natural.
150
151=item 2. Perl does I<not> associate an encoding with your strings.
152
153Unless you force it to, e.g. when matching it against a regex, or printing
154the scalar to a file, in which case Perl either interprets your string as
155locale-encoded text, octets/binary, or as Unicode, depending on various
156settings. In no case is an encoding stored together with your data, it is
157I<use> that decides encoding, not any magical metadata.
158
159=item 3. The internal utf-8 flag has no meaning with regards to the
160encoding of your string.
161
162Just ignore that flag unless you debug a Perl bug, a module written in
163XS or want to dive into the internals of perl. Otherwise it will only
164confuse you, as, despite the name, it says nothing about how your string
165is encoded. You can have Unicode strings with that flag set, with that
166flag clear, and you can have binary data with that flag set and that flag
167clear. Other possibilities exist, too.
168
169If you didn't know about that flag, just the better, pretend it doesn't
170exist.
171
172=item 4. A "Unicode String" is simply a string where each character can be
173validly interpreted as a Unicode codepoint.
174
175If you have UTF-8 encoded data, it is no longer a Unicode string, but a
176Unicode string encoded in UTF-8, giving you a binary string.
177
178=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
179
180It's a fact. Learn to live with it.
181
182=back
183
184I hope this helps :)
185
186
137=head1 OBJECT-ORIENTED INTERFACE 187=head1 OBJECT-ORIENTED INTERFACE
138 188
139The object oriented interface lets you configure your own encoding or 189The object oriented interface lets you configure your own encoding or
140decoding style, within the limits of supported formats. 190decoding style, within the limits of supported formats.
141 191
152 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 202 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
153 => {"a": [1, 2]} 203 => {"a": [1, 2]}
154 204
155=item $json = $json->ascii ([$enable]) 205=item $json = $json->ascii ([$enable])
156 206
207=item $enabled = $json->get_ascii
208
157If C<$enable> is true (or missing), then the C<encode> method will not 209If C<$enable> is true (or missing), then the C<encode> method will not
158generate characters outside the code range C<0..127> (which is ASCII). Any 210generate characters outside the code range C<0..127> (which is ASCII). Any
159unicode characters outside that range will be escaped using either a 211Unicode characters outside that range will be escaped using either a
160single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161as per RFC4627. The resulting encoded JSON text can be treated as a native 213as per RFC4627. The resulting encoded JSON text can be treated as a native
162unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 214Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163or any other superset of ASCII. 215or any other superset of ASCII.
164 216
165If C<$enable> is false, then the C<encode> method will not escape Unicode 217If C<$enable> is false, then the C<encode> method will not escape Unicode
166characters unless required by the JSON syntax or other flags. This results 218characters unless required by the JSON syntax or other flags. This results
167in a faster and more compact format. 219in a faster and more compact format.
173 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 225 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174 => ["\ud801\udc01"] 226 => ["\ud801\udc01"]
175 227
176=item $json = $json->latin1 ([$enable]) 228=item $json = $json->latin1 ([$enable])
177 229
230=item $enabled = $json->get_latin1
231
178If C<$enable> is true (or missing), then the C<encode> method will encode 232If C<$enable> is true (or missing), then the C<encode> method will encode
179the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 233the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180outside the code range C<0..255>. The resulting string can be treated as a 234outside the code range C<0..255>. The resulting string can be treated as a
181latin1-encoded JSON text or a native unicode string. The C<decode> method 235latin1-encoded JSON text or a native Unicode string. The C<decode> method
182will not be affected in any way by this flag, as C<decode> by default 236will not be affected in any way by this flag, as C<decode> by default
183expects unicode, which is a strict superset of latin1. 237expects Unicode, which is a strict superset of latin1.
184 238
185If C<$enable> is false, then the C<encode> method will not escape Unicode 239If C<$enable> is false, then the C<encode> method will not escape Unicode
186characters unless required by the JSON syntax or other flags. 240characters unless required by the JSON syntax or other flags.
187 241
188The main use for this flag is efficiently encoding binary data as JSON 242The main use for this flag is efficiently encoding binary data as JSON
189text, as most octets will not be escaped, resulting in a smaller encoded 243text, as most octets will not be escaped, resulting in a smaller encoded
190size. The disadvantage is that the resulting JSON text is encoded 244size. The disadvantage is that the resulting JSON text is encoded
191in latin1 (and must correctly be treated as such when storing and 245in latin1 (and must correctly be treated as such when storing and
192transfering), a rare encoding for JSON. It is therefore most useful when 246transferring), a rare encoding for JSON. It is therefore most useful when
193you want to store data structures known to contain binary data efficiently 247you want to store data structures known to contain binary data efficiently
194in files or databases, not when talking to other JSON encoders/decoders. 248in files or databases, not when talking to other JSON encoders/decoders.
195 249
196 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 250 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 251 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198 252
199=item $json = $json->utf8 ([$enable]) 253=item $json = $json->utf8 ([$enable])
254
255=item $enabled = $json->get_utf8
200 256
201If C<$enable> is true (or missing), then the C<encode> method will encode 257If C<$enable> is true (or missing), then the C<encode> method will encode
202the JSON result into UTF-8, as required by many protocols, while the 258the JSON result into UTF-8, as required by many protocols, while the
203C<decode> method expects to be handled an UTF-8-encoded string. Please 259C<decode> method expects to be handled an UTF-8-encoded string. Please
204note that UTF-8-encoded strings do not contain any characters outside the 260note that UTF-8-encoded strings do not contain any characters outside the
205range C<0..255>, they are thus useful for bytewise/binary I/O. In future 261range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206versions, enabling this option might enable autodetection of the UTF-16 262versions, enabling this option might enable autodetection of the UTF-16
207and UTF-32 encoding families, as described in RFC4627. 263and UTF-32 encoding families, as described in RFC4627.
208 264
209If C<$enable> is false, then the C<encode> method will return the JSON 265If C<$enable> is false, then the C<encode> method will return the JSON
210string as a (non-encoded) unicode string, while C<decode> expects thus a 266string as a (non-encoded) Unicode string, while C<decode> expects thus a
211unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 267Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
212to be done yourself, e.g. using the Encode module. 268to be done yourself, e.g. using the Encode module.
213 269
214Example, output UTF-16BE-encoded JSON: 270Example, output UTF-16BE-encoded JSON:
215 271
216 use Encode; 272 use Encode;
238 ] 294 ]
239 } 295 }
240 296
241=item $json = $json->indent ([$enable]) 297=item $json = $json->indent ([$enable])
242 298
299=item $enabled = $json->get_indent
300
243If C<$enable> is true (or missing), then the C<encode> method will use a multiline 301If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244format as output, putting every array member or object/hash key-value pair 302format as output, putting every array member or object/hash key-value pair
245into its own line, identing them properly. 303into its own line, indenting them properly.
246 304
247If C<$enable> is false, no newlines or indenting will be produced, and the 305If C<$enable> is false, no newlines or indenting will be produced, and the
248resulting JSON text is guarenteed not to contain any C<newlines>. 306resulting JSON text is guaranteed not to contain any C<newlines>.
249 307
250This setting has no effect when decoding JSON texts. 308This setting has no effect when decoding JSON texts.
251 309
252=item $json = $json->space_before ([$enable]) 310=item $json = $json->space_before ([$enable])
311
312=item $enabled = $json->get_space_before
253 313
254If C<$enable> is true (or missing), then the C<encode> method will add an extra 314If C<$enable> is true (or missing), then the C<encode> method will add an extra
255optional space before the C<:> separating keys from values in JSON objects. 315optional space before the C<:> separating keys from values in JSON objects.
256 316
257If C<$enable> is false, then the C<encode> method will not add any extra 317If C<$enable> is false, then the C<encode> method will not add any extra
263Example, space_before enabled, space_after and indent disabled: 323Example, space_before enabled, space_after and indent disabled:
264 324
265 {"key" :"value"} 325 {"key" :"value"}
266 326
267=item $json = $json->space_after ([$enable]) 327=item $json = $json->space_after ([$enable])
328
329=item $enabled = $json->get_space_after
268 330
269If C<$enable> is true (or missing), then the C<encode> method will add an extra 331If C<$enable> is true (or missing), then the C<encode> method will add an extra
270optional space after the C<:> separating keys from values in JSON objects 332optional space after the C<:> separating keys from values in JSON objects
271and extra whitespace after the C<,> separating key-value pairs and array 333and extra whitespace after the C<,> separating key-value pairs and array
272members. 334members.
278 340
279Example, space_before and indent disabled, space_after enabled: 341Example, space_before and indent disabled, space_after enabled:
280 342
281 {"key": "value"} 343 {"key": "value"}
282 344
345=item $json = $json->relaxed ([$enable])
346
347=item $enabled = $json->get_relaxed
348
349If C<$enable> is true (or missing), then C<decode> will accept some
350extensions to normal JSON syntax (see below). C<encode> will not be
351affected in anyway. I<Be aware that this option makes you accept invalid
352JSON texts as if they were valid!>. I suggest only to use this option to
353parse application-specific files written by humans (configuration files,
354resource files etc.)
355
356If C<$enable> is false (the default), then C<decode> will only accept
357valid JSON texts.
358
359Currently accepted extensions are:
360
361=over 4
362
363=item * list items can have an end-comma
364
365JSON I<separates> array elements and key-value pairs with commas. This
366can be annoying if you write JSON texts manually and want to be able to
367quickly append elements, so this extension accepts comma at the end of
368such items not just between them:
369
370 [
371 1,
372 2, <- this comma not normally allowed
373 ]
374 {
375 "k1": "v1",
376 "k2": "v2", <- this comma not normally allowed
377 }
378
379=item * shell-style '#'-comments
380
381Whenever JSON allows whitespace, shell-style comments are additionally
382allowed. They are terminated by the first carriage-return or line-feed
383character, after which more white-space and comments are allowed.
384
385 [
386 1, # this comment not allowed in JSON
387 # neither this one...
388 ]
389
390=back
391
283=item $json = $json->canonical ([$enable]) 392=item $json = $json->canonical ([$enable])
393
394=item $enabled = $json->get_canonical
284 395
285If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 396If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286by sorting their keys. This is adding a comparatively high overhead. 397by sorting their keys. This is adding a comparatively high overhead.
287 398
288If C<$enable> is false, then the C<encode> method will output key-value 399If C<$enable> is false, then the C<encode> method will output key-value
289pairs in the order Perl stores them (which will likely change between runs 400pairs in the order Perl stores them (which will likely change between runs
290of the same script). 401of the same script).
291 402
292This option is useful if you want the same data structure to be encoded as 403This option is useful if you want the same data structure to be encoded as
293the same JSON text (given the same overall settings). If it is disabled, 404the same JSON text (given the same overall settings). If it is disabled,
294the same hash migh be encoded differently even if contains the same data, 405the same hash might be encoded differently even if contains the same data,
295as key-value pairs have no inherent ordering in Perl. 406as key-value pairs have no inherent ordering in Perl.
296 407
297This setting has no effect when decoding JSON texts. 408This setting has no effect when decoding JSON texts.
298 409
299=item $json = $json->allow_nonref ([$enable]) 410=item $json = $json->allow_nonref ([$enable])
411
412=item $enabled = $json->get_allow_nonref
300 413
301If C<$enable> is true (or missing), then the C<encode> method can convert a 414If C<$enable> is true (or missing), then the C<encode> method can convert a
302non-reference into its corresponding string, number or null JSON value, 415non-reference into its corresponding string, number or null JSON value,
303which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 416which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304values instead of croaking. 417values instead of croaking.
314 JSON::XS->new->allow_nonref->encode ("Hello, World!") 427 JSON::XS->new->allow_nonref->encode ("Hello, World!")
315 => "Hello, World!" 428 => "Hello, World!"
316 429
317=item $json = $json->allow_blessed ([$enable]) 430=item $json = $json->allow_blessed ([$enable])
318 431
432=item $enabled = $json->get_allow_blessed
433
319If C<$enable> is true (or missing), then the C<encode> method will not 434If C<$enable> is true (or missing), then the C<encode> method will not
320barf when it encounters a blessed reference. Instead, the value of the 435barf when it encounters a blessed reference. Instead, the value of the
321B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 436B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322disabled or no C<to_json> method found) or a representation of the 437disabled or no C<TO_JSON> method found) or a representation of the
323object (C<convert_blessed> enabled and C<to_json> method found) is being 438object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324encoded. Has no effect on C<decode>. 439encoded. Has no effect on C<decode>.
325 440
326If C<$enable> is false (the default), then C<encode> will throw an 441If C<$enable> is false (the default), then C<encode> will throw an
327exception when it encounters a blessed object. 442exception when it encounters a blessed object.
328 443
329=item $json = $json->convert_blessed ([$enable]) 444=item $json = $json->convert_blessed ([$enable])
445
446=item $enabled = $json->get_convert_blessed
330 447
331If C<$enable> is true (or missing), then C<encode>, upon encountering a 448If C<$enable> is true (or missing), then C<encode>, upon encountering a
332blessed object, will check for the availability of the C<TO_JSON> method 449blessed object, will check for the availability of the C<TO_JSON> method
333on the object's class. If found, it will be called in scalar context 450on the object's class. If found, it will be called in scalar context
334and the resulting scalar will be encoded instead of the object. If no 451and the resulting scalar will be encoded instead of the object. If no
348enabled by this setting. 465enabled by this setting.
349 466
350If C<$enable> is false, then the C<allow_blessed> setting will decide what 467If C<$enable> is false, then the C<allow_blessed> setting will decide what
351to do when a blessed object is found. 468to do when a blessed object is found.
352 469
470=item $json = $json->filter_json_object ([$coderef->($hashref)])
471
472When C<$coderef> is specified, it will be called from C<decode> each
473time it decodes a JSON object. The only argument is a reference to the
474newly-created hash. If the code references returns a single scalar (which
475need not be a reference), this value (i.e. a copy of that scalar to avoid
476aliasing) is inserted into the deserialised data structure. If it returns
477an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
478original deserialised hash will be inserted. This setting can slow down
479decoding considerably.
480
481When C<$coderef> is omitted or undefined, any existing callback will
482be removed and C<decode> will not change the deserialised hash in any
483way.
484
485Example, convert all JSON objects into the integer 5:
486
487 my $js = JSON::XS->new->filter_json_object (sub { 5 });
488 # returns [5]
489 $js->decode ('[{}]')
490 # throw an exception because allow_nonref is not enabled
491 # so a lone 5 is not allowed.
492 $js->decode ('{"a":1, "b":2}');
493
494=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
495
496Works remotely similar to C<filter_json_object>, but is only called for
497JSON objects having a single key named C<$key>.
498
499This C<$coderef> is called before the one specified via
500C<filter_json_object>, if any. It gets passed the single value in the JSON
501object. If it returns a single value, it will be inserted into the data
502structure. If it returns nothing (not even C<undef> but the empty list),
503the callback from C<filter_json_object> will be called next, as if no
504single-key callback were specified.
505
506If C<$coderef> is omitted or undefined, the corresponding callback will be
507disabled. There can only ever be one callback for a given key.
508
509As this callback gets called less often then the C<filter_json_object>
510one, decoding speed will not usually suffer as much. Therefore, single-key
511objects make excellent targets to serialise Perl objects into, especially
512as single-key JSON objects are as close to the type-tagged value concept
513as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
514support this in any way, so you need to make sure your data never looks
515like a serialised Perl hash.
516
517Typical names for the single object key are C<__class_whatever__>, or
518C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
519things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
520with real hashes.
521
522Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
523into the corresponding C<< $WIDGET{<id>} >> object:
524
525 # return whatever is in $WIDGET{5}:
526 JSON::XS
527 ->new
528 ->filter_json_single_key_object (__widget__ => sub {
529 $WIDGET{ $_[0] }
530 })
531 ->decode ('{"__widget__": 5')
532
533 # this can be used with a TO_JSON method in some "widget" class
534 # for serialisation to json:
535 sub WidgetBase::TO_JSON {
536 my ($self) = @_;
537
538 unless ($self->{id}) {
539 $self->{id} = ..get..some..id..;
540 $WIDGET{$self->{id}} = $self;
541 }
542
543 { __widget__ => $self->{id} }
544 }
545
353=item $json = $json->shrink ([$enable]) 546=item $json = $json->shrink ([$enable])
547
548=item $enabled = $json->get_shrink
354 549
355Perl usually over-allocates memory a bit when allocating space for 550Perl usually over-allocates memory a bit when allocating space for
356strings. This flag optionally resizes strings generated by either 551strings. This flag optionally resizes strings generated by either
357C<encode> or C<decode> to their minimum size possible. This can save 552C<encode> or C<decode> to their minimum size possible. This can save
358memory when your JSON texts are either very very long or you have many 553memory when your JSON texts are either very very long or you have many
376strings that look like integers or floats into integers or floats 571strings that look like integers or floats into integers or floats
377internally (there is no difference on the Perl level), saving space. 572internally (there is no difference on the Perl level), saving space.
378 573
379=item $json = $json->max_depth ([$maximum_nesting_depth]) 574=item $json = $json->max_depth ([$maximum_nesting_depth])
380 575
576=item $max_depth = $json->get_max_depth
577
381Sets the maximum nesting level (default C<512>) accepted while encoding 578Sets the maximum nesting level (default C<512>) accepted while encoding
382or decoding. If the JSON text or Perl data structure has an equal or 579or decoding. If the JSON text or Perl data structure has an equal or
383higher nesting level then this limit, then the encoder and decoder will 580higher nesting level then this limit, then the encoder and decoder will
384stop and croak at that point. 581stop and croak at that point.
385 582
396used, which is rarely useful. 593used, which is rarely useful.
397 594
398See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 595See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
399 596
400=item $json = $json->max_size ([$maximum_string_size]) 597=item $json = $json->max_size ([$maximum_string_size])
598
599=item $max_size = $json->get_max_size
401 600
402Set the maximum length a JSON text may have (in bytes) where decoding is 601Set the maximum length a JSON text may have (in bytes) where decoding is
403being attempted. The default is C<0>, meaning no limit. When C<decode> 602being attempted. The default is C<0>, meaning no limit. When C<decode>
404is called on a string longer then this number of characters it will not 603is called on a string longer then this number of characters it will not
405attempt to decode the string but throw an exception. This setting has no 604attempt to decode the string but throw an exception. This setting has no
452vice versa. These mappings are designed to "do the right thing" in most 651vice versa. These mappings are designed to "do the right thing" in most
453circumstances automatically, preserving round-tripping characteristics 652circumstances automatically, preserving round-tripping characteristics
454(what you put in comes out as something equivalent). 653(what you put in comes out as something equivalent).
455 654
456For the more enlightened: note that in the following descriptions, 655For the more enlightened: note that in the following descriptions,
457lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 656lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
458refers to the abstract Perl language itself. 657refers to the abstract Perl language itself.
459 658
460 659
461=head2 JSON -> PERL 660=head2 JSON -> PERL
462 661
463=over 4 662=over 4
464 663
465=item object 664=item object
466 665
467A JSON object becomes a reference to a hash in Perl. No ordering of object 666A JSON object becomes a reference to a hash in Perl. No ordering of object
468keys is preserved (JSON does not preserver object key ordering itself). 667keys is preserved (JSON does not preserve object key ordering itself).
469 668
470=item array 669=item array
471 670
472A JSON array becomes a reference to an array in Perl. 671A JSON array becomes a reference to an array in Perl.
473 672
477are represented by the same codepoints in the Perl string, so no manual 676are represented by the same codepoints in the Perl string, so no manual
478decoding is necessary. 677decoding is necessary.
479 678
480=item number 679=item number
481 680
482A JSON number becomes either an integer or numeric (floating point) 681A JSON number becomes either an integer, numeric (floating point) or
483scalar in perl, depending on its range and any fractional parts. On the 682string scalar in perl, depending on its range and any fractional parts. On
484Perl level, there is no difference between those as Perl handles all the 683the Perl level, there is no difference between those as Perl handles all
485conversion details, but an integer may take slightly less memory and might 684the conversion details, but an integer may take slightly less memory and
486represent more values exactly than (floating point) numbers. 685might represent more values exactly than (floating point) numbers.
686
687If the number consists of digits only, JSON::XS will try to represent
688it as an integer value. If that fails, it will try to represent it as
689a numeric (floating point) value if that is possible without loss of
690precision. Otherwise it will preserve the number as a string value.
691
692Numbers containing a fractional or exponential part will always be
693represented as numeric (floating point) values, possibly at a loss of
694precision.
695
696This might create round-tripping problems as numbers might become strings,
697but as Perl is typeless there is no other way to do it.
487 698
488=item true, false 699=item true, false
489 700
490These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 701These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
491respectively. They are overloaded to act almost exactly like the numbers 702respectively. They are overloaded to act almost exactly like the numbers
492C<1> and C<0>. You can check wether a scalar is a JSON boolean by using 703C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
493the C<JSON::XS::is_bool> function. 704the C<JSON::XS::is_bool> function.
494 705
495=item null 706=item null
496 707
497A JSON null atom becomes C<undef> in Perl. 708A JSON null atom becomes C<undef> in Perl.
533 to_json [\0,JSON::XS::true] # yields [false,true] 744 to_json [\0,JSON::XS::true] # yields [false,true]
534 745
535=item JSON::XS::true, JSON::XS::false 746=item JSON::XS::true, JSON::XS::false
536 747
537These special values become JSON true and JSON false values, 748These special values become JSON true and JSON false values,
538respectively. You cna alos use C<\1> and C<\0> directly if you want. 749respectively. You can also use C<\1> and C<\0> directly if you want.
539 750
540=item blessed objects 751=item blessed objects
541 752
542Blessed objects are not allowed. JSON::XS currently tries to encode their 753Blessed objects are not allowed. JSON::XS currently tries to encode their
543underlying representation (hash- or arrayref), but this behaviour might 754underlying representation (hash- or arrayref), but this behaviour might
560 to_json [$value] # yields ["5"] 771 to_json [$value] # yields ["5"]
561 772
562 # undef becomes null 773 # undef becomes null
563 to_json [undef] # yields [null] 774 to_json [undef] # yields [null]
564 775
565You can force the type to be a string by stringifying it: 776You can force the type to be a JSON string by stringifying it:
566 777
567 my $x = 3.1; # some variable containing a number 778 my $x = 3.1; # some variable containing a number
568 "$x"; # stringified 779 "$x"; # stringified
569 $x .= ""; # another, more awkward way to stringify 780 $x .= ""; # another, more awkward way to stringify
570 print $x; # perl does it for you, too, quite often 781 print $x; # perl does it for you, too, quite often
571 782
572You can force the type to be a number by numifying it: 783You can force the type to be a JSON number by numifying it:
573 784
574 my $x = "3"; # some variable containing a string 785 my $x = "3"; # some variable containing a string
575 $x += 0; # numify it, ensuring it will be dumped as a number 786 $x += 0; # numify it, ensuring it will be dumped as a number
576 $x *= 1; # same thing, the choise is yours. 787 $x *= 1; # same thing, the choice is yours.
577 788
578You can not currently output JSON booleans or force the type in other, 789You can not currently force the type in other, less obscure, ways. Tell me
579less obscure, ways. Tell me if you need this capability. 790if you need this capability.
580 791
581=back 792=back
582 793
583 794
584=head1 COMPARISON 795=head1 COMPARISON
593 804
594=item JSON 1.07 805=item JSON 1.07
595 806
596Slow (but very portable, as it is written in pure Perl). 807Slow (but very portable, as it is written in pure Perl).
597 808
598Undocumented/buggy Unicode handling (how JSON handles unicode values is 809Undocumented/buggy Unicode handling (how JSON handles Unicode values is
599undocumented. One can get far by feeding it unicode strings and doing 810undocumented. One can get far by feeding it Unicode strings and doing
600en-/decoding oneself, but unicode escapes are not working properly). 811en-/decoding oneself, but Unicode escapes are not working properly).
601 812
602No roundtripping (strings get clobbered if they look like numbers, e.g. 813No round-tripping (strings get clobbered if they look like numbers, e.g.
603the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 814the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
604decode into the number 2. 815decode into the number 2.
605 816
606=item JSON::PC 0.01 817=item JSON::PC 0.01
607 818
608Very fast. 819Very fast.
609 820
610Undocumented/buggy Unicode handling. 821Undocumented/buggy Unicode handling.
611 822
612No roundtripping. 823No round-tripping.
613 824
614Has problems handling many Perl values (e.g. regex results and other magic 825Has problems handling many Perl values (e.g. regex results and other magic
615values will make it croak). 826values will make it croak).
616 827
617Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 828Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
627Very inflexible (no human-readable format supported, format pretty much 838Very inflexible (no human-readable format supported, format pretty much
628undocumented. I need at least a format for easy reading by humans and a 839undocumented. I need at least a format for easy reading by humans and a
629single-line compact format for use in a protocol, and preferably a way to 840single-line compact format for use in a protocol, and preferably a way to
630generate ASCII-only JSON texts). 841generate ASCII-only JSON texts).
631 842
632Completely broken (and confusingly documented) Unicode handling (unicode 843Completely broken (and confusingly documented) Unicode handling (Unicode
633escapes are not working properly, you need to set ImplicitUnicode to 844escapes are not working properly, you need to set ImplicitUnicode to
634I<different> values on en- and decoding to get symmetric behaviour). 845I<different> values on en- and decoding to get symmetric behaviour).
635 846
636No roundtripping (simple cases work, but this depends on wether the scalar 847No round-tripping (simple cases work, but this depends on whether the scalar
637value was used in a numeric context or not). 848value was used in a numeric context or not).
638 849
639Dumping hashes may skip hash values depending on iterator state. 850Dumping hashes may skip hash values depending on iterator state.
640 851
641Unmaintained (maintainer unresponsive for many months, bugs are not 852Unmaintained (maintainer unresponsive for many months, bugs are not
642getting fixed). 853getting fixed).
643 854
644Does not check input for validity (i.e. will accept non-JSON input and 855Does not check input for validity (i.e. will accept non-JSON input and
645return "something" instead of raising an exception. This is a security 856return "something" instead of raising an exception. This is a security
646issue: imagine two banks transfering money between each other using 857issue: imagine two banks transferring money between each other using
647JSON. One bank might parse a given non-JSON request and deduct money, 858JSON. One bank might parse a given non-JSON request and deduct money,
648while the other might reject the transaction with a syntax error. While a 859while the other might reject the transaction with a syntax error. While a
649good protocol will at least recover, that is extra unnecessary work and 860good protocol will at least recover, that is extra unnecessary work and
650the transaction will still not succeed). 861the transaction will still not succeed).
651 862
652=item JSON::DWIW 0.04 863=item JSON::DWIW 0.04
653 864
654Very fast. Very natural. Very nice. 865Very fast. Very natural. Very nice.
655 866
656Undocumented unicode handling (but the best of the pack. Unicode escapes 867Undocumented Unicode handling (but the best of the pack. Unicode escapes
657still don't get parsed properly). 868still don't get parsed properly).
658 869
659Very inflexible. 870Very inflexible.
660 871
661No roundtripping. 872No round-tripping.
662 873
663Does not generate valid JSON texts (key strings are often unquoted, empty keys 874Does not generate valid JSON texts (key strings are often unquoted, empty keys
664result in nothing being output) 875result in nothing being output)
665 876
666Does not check input for validity. 877Does not check input for validity.
681 my $yaml = $to_yaml->encode ($ref) . "\n"; 892 my $yaml = $to_yaml->encode ($ref) . "\n";
682 893
683This will usually generate JSON texts that also parse as valid 894This will usually generate JSON texts that also parse as valid
684YAML. Please note that YAML has hardcoded limits on (simple) object key 895YAML. Please note that YAML has hardcoded limits on (simple) object key
685lengths that JSON doesn't have, so you should make sure that your hash 896lengths that JSON doesn't have, so you should make sure that your hash
686keys are noticably shorter than the 1024 characters YAML allows. 897keys are noticeably shorter than the 1024 characters YAML allows.
687 898
688There might be other incompatibilities that I am not aware of. In general 899There might be other incompatibilities that I am not aware of. In general
689you should not try to generate YAML with a JSON generator or vice versa, 900you should not try to generate YAML with a JSON generator or vice versa,
690or try to parse JSON with a YAML parser or vice versa: chances are high 901or try to parse JSON with a YAML parser or vice versa: chances are high
691that you will run into severe interoperability problems. 902that you will run into severe interoperability problems.
707It shows the number of encodes/decodes per second (JSON::XS uses 918It shows the number of encodes/decodes per second (JSON::XS uses
708the functional interface, while JSON::XS/2 uses the OO interface 919the functional interface, while JSON::XS/2 uses the OO interface
709with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 920with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
710shrink). Higher is better: 921shrink). Higher is better:
711 922
712 Storable | 15779.925 | 14169.946 |
713 -----------+------------+------------+
714 module | encode | decode | 923 module | encode | decode |
715 -----------|------------|------------| 924 -----------|------------|------------|
716 JSON | 4990.842 | 4088.813 | 925 JSON 1.x | 4990.842 | 4088.813 |
717 JSON::DWIW | 51653.990 | 71575.154 | 926 JSON::DWIW | 51653.990 | 71575.154 |
718 JSON::PC | 65948.176 | 74631.744 | 927 JSON::PC | 65948.176 | 74631.744 |
719 JSON::PP | 8931.652 | 3817.168 | 928 JSON::PP | 8931.652 | 3817.168 |
720 JSON::Syck | 24877.248 | 27776.848 | 929 JSON::Syck | 24877.248 | 27776.848 |
721 JSON::XS | 388361.481 | 227951.304 | 930 JSON::XS | 388361.481 | 227951.304 |
723 JSON::XS/3 | 338250.323 | 218453.333 | 932 JSON::XS/3 | 338250.323 | 218453.333 |
724 Storable | 16500.016 | 135300.129 | 933 Storable | 16500.016 | 135300.129 |
725 -----------+------------+------------+ 934 -----------+------------+------------+
726 935
727That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 936That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
728about three times faster on decoding, and over fourty times faster 937about three times faster on decoding, and over forty times faster
729than JSON, even with pretty-printing and key sorting. It also compares 938than JSON, even with pretty-printing and key sorting. It also compares
730favourably to Storable for small amounts of data. 939favourably to Storable for small amounts of data.
731 940
732Using a longer test string (roughly 18KB, generated from Yahoo! Locals 941Using a longer test string (roughly 18KB, generated from Yahoo! Locals
733search API (http://nanoref.com/yahooapis/mgPdGg): 942search API (http://nanoref.com/yahooapis/mgPdGg):
734 943
735 module | encode | decode | 944 module | encode | decode |
736 -----------|------------|------------| 945 -----------|------------|------------|
737 JSON | 55.260 | 34.971 | 946 JSON 1.x | 55.260 | 34.971 |
738 JSON::DWIW | 825.228 | 1082.513 | 947 JSON::DWIW | 825.228 | 1082.513 |
739 JSON::PC | 3571.444 | 2394.829 | 948 JSON::PC | 3571.444 | 2394.829 |
740 JSON::PP | 210.987 | 32.574 | 949 JSON::PP | 210.987 | 32.574 |
741 JSON::Syck | 552.551 | 787.544 | 950 JSON::Syck | 552.551 | 787.544 |
742 JSON::XS | 5780.463 | 4854.519 | 951 JSON::XS | 5780.463 | 4854.519 |
746 -----------+------------+------------+ 955 -----------+------------+------------+
747 956
748Again, JSON::XS leads by far (except for Storable which non-surprisingly 957Again, JSON::XS leads by far (except for Storable which non-surprisingly
749decodes faster). 958decodes faster).
750 959
751On large strings containing lots of high unicode characters, some modules 960On large strings containing lots of high Unicode characters, some modules
752(such as JSON::PC) seem to decode faster than JSON::XS, but the result 961(such as JSON::PC) seem to decode faster than JSON::XS, but the result
753will be broken due to missing (or wrong) unicode handling. Others refuse 962will be broken due to missing (or wrong) Unicode handling. Others refuse
754to decode or encode properly, so it was impossible to prepare a fair 963to decode or encode properly, so it was impossible to prepare a fair
755comparison table for that case. 964comparison table for that case.
756 965
757 966
758=head1 SECURITY CONSIDERATIONS 967=head1 SECURITY CONSIDERATIONS
764any buffer overflows. Obviously, this module should ensure that and I am 973any buffer overflows. Obviously, this module should ensure that and I am
765trying hard on making that true, but you never know. 974trying hard on making that true, but you never know.
766 975
767Second, you need to avoid resource-starving attacks. That means you should 976Second, you need to avoid resource-starving attacks. That means you should
768limit the size of JSON texts you accept, or make sure then when your 977limit the size of JSON texts you accept, or make sure then when your
769resources run out, thats just fine (e.g. by using a separate process that 978resources run out, that's just fine (e.g. by using a separate process that
770can crash safely). The size of a JSON text in octets or characters is 979can crash safely). The size of a JSON text in octets or characters is
771usually a good indication of the size of the resources required to decode 980usually a good indication of the size of the resources required to decode
772it into a Perl structure. While JSON::XS can check the size of the JSON 981it into a Perl structure. While JSON::XS can check the size of the JSON
773text, it might be too late when you already have it in memory, so you 982text, it might be too late when you already have it in memory, so you
774might want to check the size before you accept the string. 983might want to check the size before you accept the string.
785And last but least, something else could bomb you that I forgot to think 994And last but least, something else could bomb you that I forgot to think
786of. In that case, you get to keep the pieces. I am always open for hints, 995of. In that case, you get to keep the pieces. I am always open for hints,
787though... 996though...
788 997
789If you are using JSON::XS to return packets to consumption 998If you are using JSON::XS to return packets to consumption
790by javascript scripts in a browser you should have a look at 999by JavaScript scripts in a browser you should have a look at
791L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1000L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792you are vulnerable to some common attack vectors (which really are browser 1001you are vulnerable to some common attack vectors (which really are browser
793design bugs, but it is still you who will have to deal with it, as major 1002design bugs, but it is still you who will have to deal with it, as major
794browser developers care only for features, not about doing security 1003browser developers care only for features, not about doing security
795right). 1004right).
796 1005
797 1006
1007=head1 THREADS
1008
1009This module is I<not> guaranteed to be thread safe and there are no
1010plans to change this until Perl gets thread support (as opposed to the
1011horribly slow so-called "threads" which are simply slow and bloated
1012process simulations - use fork, its I<much> faster, cheaper, better).
1013
1014(It might actually work, but you have been warned).
1015
1016
798=head1 BUGS 1017=head1 BUGS
799 1018
800While the goal of this module is to be correct, that unfortunately does 1019While the goal of this module is to be correct, that unfortunately does
801not mean its bug-free, only that I think its design is bug-free. It is 1020not mean its bug-free, only that I think its design is bug-free. It is
802still relatively early in its development. If you keep reporting bugs they 1021still relatively early in its development. If you keep reporting bugs they
803will be fixed swiftly, though. 1022will be fixed swiftly, though.
804 1023
1024Please refrain from using rt.cpan.org or any other bug reporting
1025service. I put the contact address into my modules for a reason.
1026
805=cut 1027=cut
806 1028
807our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" }; 1029our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" }; 1030our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
809 1031
810sub true() { $true } 1032sub true() { $true }
811sub false() { $false } 1033sub false() { $false }
812 1034
813sub is_bool($) { 1035sub is_bool($) {

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