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Revision 1.50 by root, Mon Jul 2 00:29:38 2007 UTC vs.
Revision 1.72 by root, Sun Nov 25 19:11:07 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 = '1.53';
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;
220 276
221 use Encode; 277 use Encode;
222 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); 278 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
223 279
224=item $json = $json->pretty ([$enable]) 280=item $json = $json->pretty ([$enable])
281
282=item $enabled = $json->get_pretty
225 283
226This enables (or disables) all of the C<indent>, C<space_before> and 284This enables (or disables) all of the C<indent>, C<space_before> and
227C<space_after> (and in the future possibly more) flags in one call to 285C<space_after> (and in the future possibly more) flags in one call to
228generate the most readable (or most compact) form possible. 286generate the most readable (or most compact) form possible.
229 287
238 ] 296 ]
239 } 297 }
240 298
241=item $json = $json->indent ([$enable]) 299=item $json = $json->indent ([$enable])
242 300
301=item $enabled = $json->get_indent
302
243If C<$enable> is true (or missing), then the C<encode> method will use a multiline 303If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244format as output, putting every array member or object/hash key-value pair 304format as output, putting every array member or object/hash key-value pair
245into its own line, identing them properly. 305into its own line, indenting them properly.
246 306
247If C<$enable> is false, no newlines or indenting will be produced, and the 307If C<$enable> is false, no newlines or indenting will be produced, and the
248resulting JSON text is guarenteed not to contain any C<newlines>. 308resulting JSON text is guaranteed not to contain any C<newlines>.
249 309
250This setting has no effect when decoding JSON texts. 310This setting has no effect when decoding JSON texts.
251 311
252=item $json = $json->space_before ([$enable]) 312=item $json = $json->space_before ([$enable])
313
314=item $enabled = $json->get_space_before
253 315
254If C<$enable> is true (or missing), then the C<encode> method will add an extra 316If C<$enable> is true (or missing), then the C<encode> method will add an extra
255optional space before the C<:> separating keys from values in JSON objects. 317optional space before the C<:> separating keys from values in JSON objects.
256 318
257If C<$enable> is false, then the C<encode> method will not add any extra 319If C<$enable> is false, then the C<encode> method will not add any extra
263Example, space_before enabled, space_after and indent disabled: 325Example, space_before enabled, space_after and indent disabled:
264 326
265 {"key" :"value"} 327 {"key" :"value"}
266 328
267=item $json = $json->space_after ([$enable]) 329=item $json = $json->space_after ([$enable])
330
331=item $enabled = $json->get_space_after
268 332
269If C<$enable> is true (or missing), then the C<encode> method will add an extra 333If 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 334optional space after the C<:> separating keys from values in JSON objects
271and extra whitespace after the C<,> separating key-value pairs and array 335and extra whitespace after the C<,> separating key-value pairs and array
272members. 336members.
278 342
279Example, space_before and indent disabled, space_after enabled: 343Example, space_before and indent disabled, space_after enabled:
280 344
281 {"key": "value"} 345 {"key": "value"}
282 346
347=item $json = $json->relaxed ([$enable])
348
349=item $enabled = $json->get_relaxed
350
351If C<$enable> is true (or missing), then C<decode> will accept some
352extensions to normal JSON syntax (see below). C<encode> will not be
353affected in anyway. I<Be aware that this option makes you accept invalid
354JSON texts as if they were valid!>. I suggest only to use this option to
355parse application-specific files written by humans (configuration files,
356resource files etc.)
357
358If C<$enable> is false (the default), then C<decode> will only accept
359valid JSON texts.
360
361Currently accepted extensions are:
362
363=over 4
364
365=item * list items can have an end-comma
366
367JSON I<separates> array elements and key-value pairs with commas. This
368can be annoying if you write JSON texts manually and want to be able to
369quickly append elements, so this extension accepts comma at the end of
370such items not just between them:
371
372 [
373 1,
374 2, <- this comma not normally allowed
375 ]
376 {
377 "k1": "v1",
378 "k2": "v2", <- this comma not normally allowed
379 }
380
381=item * shell-style '#'-comments
382
383Whenever JSON allows whitespace, shell-style comments are additionally
384allowed. They are terminated by the first carriage-return or line-feed
385character, after which more white-space and comments are allowed.
386
387 [
388 1, # this comment not allowed in JSON
389 # neither this one...
390 ]
391
392=back
393
283=item $json = $json->canonical ([$enable]) 394=item $json = $json->canonical ([$enable])
395
396=item $enabled = $json->get_canonical
284 397
285If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 398If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286by sorting their keys. This is adding a comparatively high overhead. 399by sorting their keys. This is adding a comparatively high overhead.
287 400
288If C<$enable> is false, then the C<encode> method will output key-value 401If 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 402pairs in the order Perl stores them (which will likely change between runs
290of the same script). 403of the same script).
291 404
292This option is useful if you want the same data structure to be encoded as 405This 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, 406the 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, 407the same hash might be encoded differently even if contains the same data,
295as key-value pairs have no inherent ordering in Perl. 408as key-value pairs have no inherent ordering in Perl.
296 409
297This setting has no effect when decoding JSON texts. 410This setting has no effect when decoding JSON texts.
298 411
299=item $json = $json->allow_nonref ([$enable]) 412=item $json = $json->allow_nonref ([$enable])
413
414=item $enabled = $json->get_allow_nonref
300 415
301If C<$enable> is true (or missing), then the C<encode> method can convert a 416If 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, 417non-reference into its corresponding string, number or null JSON value,
303which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 418which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304values instead of croaking. 419values instead of croaking.
314 JSON::XS->new->allow_nonref->encode ("Hello, World!") 429 JSON::XS->new->allow_nonref->encode ("Hello, World!")
315 => "Hello, World!" 430 => "Hello, World!"
316 431
317=item $json = $json->allow_blessed ([$enable]) 432=item $json = $json->allow_blessed ([$enable])
318 433
434=item $enabled = $json->get_allow_bless
435
319If C<$enable> is true (or missing), then the C<encode> method will not 436If C<$enable> is true (or missing), then the C<encode> method will not
320barf when it encounters a blessed reference. Instead, the value of the 437barf when it encounters a blessed reference. Instead, the value of the
321B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 438B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322disabled or no C<to_json> method found) or a representation of the 439disabled or no C<to_json> method found) or a representation of the
323object (C<convert_blessed> enabled and C<to_json> method found) is being 440object (C<convert_blessed> enabled and C<to_json> method found) is being
324encoded. Has no effect on C<decode>. 441encoded. Has no effect on C<decode>.
325 442
326If C<$enable> is false (the default), then C<encode> will throw an 443If C<$enable> is false (the default), then C<encode> will throw an
327exception when it encounters a blessed object. 444exception when it encounters a blessed object.
328 445
329=item $json = $json->convert_blessed ([$enable]) 446=item $json = $json->convert_blessed ([$enable])
447
448=item $enabled = $json->get_convert_blessed
330 449
331If C<$enable> is true (or missing), then C<encode>, upon encountering a 450If C<$enable> is true (or missing), then C<encode>, upon encountering a
332blessed object, will check for the availability of the C<TO_JSON> method 451blessed object, will check for the availability of the C<TO_JSON> method
333on the object's class. If found, it will be called in scalar context 452on the object's class. If found, it will be called in scalar context
334and the resulting scalar will be encoded instead of the object. If no 453and the resulting scalar will be encoded instead of the object. If no
348enabled by this setting. 467enabled by this setting.
349 468
350If C<$enable> is false, then the C<allow_blessed> setting will decide what 469If C<$enable> is false, then the C<allow_blessed> setting will decide what
351to do when a blessed object is found. 470to do when a blessed object is found.
352 471
472=item $json = $json->filter_json_object ([$coderef->($hashref)])
473
474When C<$coderef> is specified, it will be called from C<decode> each
475time it decodes a JSON object. The only argument is a reference to the
476newly-created hash. If the code references returns a single scalar (which
477need not be a reference), this value (i.e. a copy of that scalar to avoid
478aliasing) is inserted into the deserialised data structure. If it returns
479an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
480original deserialised hash will be inserted. This setting can slow down
481decoding considerably.
482
483When C<$coderef> is omitted or undefined, any existing callback will
484be removed and C<decode> will not change the deserialised hash in any
485way.
486
487Example, convert all JSON objects into the integer 5:
488
489 my $js = JSON::XS->new->filter_json_object (sub { 5 });
490 # returns [5]
491 $js->decode ('[{}]')
492 # throw an exception because allow_nonref is not enabled
493 # so a lone 5 is not allowed.
494 $js->decode ('{"a":1, "b":2}');
495
496=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
497
498Works remotely similar to C<filter_json_object>, but is only called for
499JSON objects having a single key named C<$key>.
500
501This C<$coderef> is called before the one specified via
502C<filter_json_object>, if any. It gets passed the single value in the JSON
503object. If it returns a single value, it will be inserted into the data
504structure. If it returns nothing (not even C<undef> but the empty list),
505the callback from C<filter_json_object> will be called next, as if no
506single-key callback were specified.
507
508If C<$coderef> is omitted or undefined, the corresponding callback will be
509disabled. There can only ever be one callback for a given key.
510
511As this callback gets called less often then the C<filter_json_object>
512one, decoding speed will not usually suffer as much. Therefore, single-key
513objects make excellent targets to serialise Perl objects into, especially
514as single-key JSON objects are as close to the type-tagged value concept
515as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
516support this in any way, so you need to make sure your data never looks
517like a serialised Perl hash.
518
519Typical names for the single object key are C<__class_whatever__>, or
520C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
521things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
522with real hashes.
523
524Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
525into the corresponding C<< $WIDGET{<id>} >> object:
526
527 # return whatever is in $WIDGET{5}:
528 JSON::XS
529 ->new
530 ->filter_json_single_key_object (__widget__ => sub {
531 $WIDGET{ $_[0] }
532 })
533 ->decode ('{"__widget__": 5')
534
535 # this can be used with a TO_JSON method in some "widget" class
536 # for serialisation to json:
537 sub WidgetBase::TO_JSON {
538 my ($self) = @_;
539
540 unless ($self->{id}) {
541 $self->{id} = ..get..some..id..;
542 $WIDGET{$self->{id}} = $self;
543 }
544
545 { __widget__ => $self->{id} }
546 }
547
353=item $json = $json->shrink ([$enable]) 548=item $json = $json->shrink ([$enable])
549
550=item $enabled = $json->get_shrink
354 551
355Perl usually over-allocates memory a bit when allocating space for 552Perl usually over-allocates memory a bit when allocating space for
356strings. This flag optionally resizes strings generated by either 553strings. This flag optionally resizes strings generated by either
357C<encode> or C<decode> to their minimum size possible. This can save 554C<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 555memory when your JSON texts are either very very long or you have many
376strings that look like integers or floats into integers or floats 573strings that look like integers or floats into integers or floats
377internally (there is no difference on the Perl level), saving space. 574internally (there is no difference on the Perl level), saving space.
378 575
379=item $json = $json->max_depth ([$maximum_nesting_depth]) 576=item $json = $json->max_depth ([$maximum_nesting_depth])
380 577
578=item $max_depth = $json->get_max_depth
579
381Sets the maximum nesting level (default C<512>) accepted while encoding 580Sets the maximum nesting level (default C<512>) accepted while encoding
382or decoding. If the JSON text or Perl data structure has an equal or 581or 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 582higher nesting level then this limit, then the encoder and decoder will
384stop and croak at that point. 583stop and croak at that point.
385 584
396used, which is rarely useful. 595used, which is rarely useful.
397 596
398See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 597See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
399 598
400=item $json = $json->max_size ([$maximum_string_size]) 599=item $json = $json->max_size ([$maximum_string_size])
600
601=item $max_size = $json->get_max_size
401 602
402Set the maximum length a JSON text may have (in bytes) where decoding is 603Set 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> 604being 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 605is 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 606attempt 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 653vice versa. These mappings are designed to "do the right thing" in most
453circumstances automatically, preserving round-tripping characteristics 654circumstances automatically, preserving round-tripping characteristics
454(what you put in comes out as something equivalent). 655(what you put in comes out as something equivalent).
455 656
456For the more enlightened: note that in the following descriptions, 657For the more enlightened: note that in the following descriptions,
457lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 658lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
458refers to the abstract Perl language itself. 659refers to the abstract Perl language itself.
459 660
460 661
461=head2 JSON -> PERL 662=head2 JSON -> PERL
462 663
463=over 4 664=over 4
464 665
465=item object 666=item object
466 667
467A JSON object becomes a reference to a hash in Perl. No ordering of object 668A 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). 669keys is preserved (JSON does not preserve object key ordering itself).
469 670
470=item array 671=item array
471 672
472A JSON array becomes a reference to an array in Perl. 673A JSON array becomes a reference to an array in Perl.
473 674
477are represented by the same codepoints in the Perl string, so no manual 678are represented by the same codepoints in the Perl string, so no manual
478decoding is necessary. 679decoding is necessary.
479 680
480=item number 681=item number
481 682
482A JSON number becomes either an integer or numeric (floating point) 683A JSON number becomes either an integer, numeric (floating point) or
483scalar in perl, depending on its range and any fractional parts. On the 684string 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 685the Perl level, there is no difference between those as Perl handles all
485conversion details, but an integer may take slightly less memory and might 686the conversion details, but an integer may take slightly less memory and
486represent more values exactly than (floating point) numbers. 687might represent more values exactly than (floating point) numbers.
688
689If the number consists of digits only, JSON::XS will try to represent
690it as an integer value. If that fails, it will try to represent it as
691a numeric (floating point) value if that is possible without loss of
692precision. Otherwise it will preserve the number as a string value.
693
694Numbers containing a fractional or exponential part will always be
695represented as numeric (floating point) values, possibly at a loss of
696precision.
697
698This might create round-tripping problems as numbers might become strings,
699but as Perl is typeless there is no other way to do it.
487 700
488=item true, false 701=item true, false
489 702
490These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 703These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
491respectively. They are overloaded to act almost exactly like the numbers 704respectively. 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 705C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
493the C<JSON::XS::is_bool> function. 706the C<JSON::XS::is_bool> function.
494 707
495=item null 708=item null
496 709
497A JSON null atom becomes C<undef> in Perl. 710A JSON null atom becomes C<undef> in Perl.
533 to_json [\0,JSON::XS::true] # yields [false,true] 746 to_json [\0,JSON::XS::true] # yields [false,true]
534 747
535=item JSON::XS::true, JSON::XS::false 748=item JSON::XS::true, JSON::XS::false
536 749
537These special values become JSON true and JSON false values, 750These special values become JSON true and JSON false values,
538respectively. You cna alos use C<\1> and C<\0> directly if you want. 751respectively. You can also use C<\1> and C<\0> directly if you want.
539 752
540=item blessed objects 753=item blessed objects
541 754
542Blessed objects are not allowed. JSON::XS currently tries to encode their 755Blessed objects are not allowed. JSON::XS currently tries to encode their
543underlying representation (hash- or arrayref), but this behaviour might 756underlying representation (hash- or arrayref), but this behaviour might
560 to_json [$value] # yields ["5"] 773 to_json [$value] # yields ["5"]
561 774
562 # undef becomes null 775 # undef becomes null
563 to_json [undef] # yields [null] 776 to_json [undef] # yields [null]
564 777
565You can force the type to be a string by stringifying it: 778You can force the type to be a JSON string by stringifying it:
566 779
567 my $x = 3.1; # some variable containing a number 780 my $x = 3.1; # some variable containing a number
568 "$x"; # stringified 781 "$x"; # stringified
569 $x .= ""; # another, more awkward way to stringify 782 $x .= ""; # another, more awkward way to stringify
570 print $x; # perl does it for you, too, quite often 783 print $x; # perl does it for you, too, quite often
571 784
572You can force the type to be a number by numifying it: 785You can force the type to be a JSON number by numifying it:
573 786
574 my $x = "3"; # some variable containing a string 787 my $x = "3"; # some variable containing a string
575 $x += 0; # numify it, ensuring it will be dumped as a number 788 $x += 0; # numify it, ensuring it will be dumped as a number
576 $x *= 1; # same thing, the choise is yours. 789 $x *= 1; # same thing, the choice is yours.
577 790
578You can not currently output JSON booleans or force the type in other, 791You can not currently force the type in other, less obscure, ways. Tell me
579less obscure, ways. Tell me if you need this capability. 792if you need this capability.
580 793
581=back 794=back
582 795
583 796
584=head1 COMPARISON 797=head1 COMPARISON
593 806
594=item JSON 1.07 807=item JSON 1.07
595 808
596Slow (but very portable, as it is written in pure Perl). 809Slow (but very portable, as it is written in pure Perl).
597 810
598Undocumented/buggy Unicode handling (how JSON handles unicode values is 811Undocumented/buggy Unicode handling (how JSON handles Unicode values is
599undocumented. One can get far by feeding it unicode strings and doing 812undocumented. One can get far by feeding it Unicode strings and doing
600en-/decoding oneself, but unicode escapes are not working properly). 813en-/decoding oneself, but Unicode escapes are not working properly).
601 814
602No roundtripping (strings get clobbered if they look like numbers, e.g. 815No 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 816the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
604decode into the number 2. 817decode into the number 2.
605 818
606=item JSON::PC 0.01 819=item JSON::PC 0.01
607 820
608Very fast. 821Very fast.
609 822
610Undocumented/buggy Unicode handling. 823Undocumented/buggy Unicode handling.
611 824
612No roundtripping. 825No round-tripping.
613 826
614Has problems handling many Perl values (e.g. regex results and other magic 827Has problems handling many Perl values (e.g. regex results and other magic
615values will make it croak). 828values will make it croak).
616 829
617Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 830Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
627Very inflexible (no human-readable format supported, format pretty much 840Very inflexible (no human-readable format supported, format pretty much
628undocumented. I need at least a format for easy reading by humans and a 841undocumented. 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 842single-line compact format for use in a protocol, and preferably a way to
630generate ASCII-only JSON texts). 843generate ASCII-only JSON texts).
631 844
632Completely broken (and confusingly documented) Unicode handling (unicode 845Completely broken (and confusingly documented) Unicode handling (Unicode
633escapes are not working properly, you need to set ImplicitUnicode to 846escapes are not working properly, you need to set ImplicitUnicode to
634I<different> values on en- and decoding to get symmetric behaviour). 847I<different> values on en- and decoding to get symmetric behaviour).
635 848
636No roundtripping (simple cases work, but this depends on wether the scalar 849No round-tripping (simple cases work, but this depends on whether the scalar
637value was used in a numeric context or not). 850value was used in a numeric context or not).
638 851
639Dumping hashes may skip hash values depending on iterator state. 852Dumping hashes may skip hash values depending on iterator state.
640 853
641Unmaintained (maintainer unresponsive for many months, bugs are not 854Unmaintained (maintainer unresponsive for many months, bugs are not
642getting fixed). 855getting fixed).
643 856
644Does not check input for validity (i.e. will accept non-JSON input and 857Does not check input for validity (i.e. will accept non-JSON input and
645return "something" instead of raising an exception. This is a security 858return "something" instead of raising an exception. This is a security
646issue: imagine two banks transfering money between each other using 859issue: imagine two banks transferring money between each other using
647JSON. One bank might parse a given non-JSON request and deduct money, 860JSON. 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 861while the other might reject the transaction with a syntax error. While a
649good protocol will at least recover, that is extra unnecessary work and 862good protocol will at least recover, that is extra unnecessary work and
650the transaction will still not succeed). 863the transaction will still not succeed).
651 864
652=item JSON::DWIW 0.04 865=item JSON::DWIW 0.04
653 866
654Very fast. Very natural. Very nice. 867Very fast. Very natural. Very nice.
655 868
656Undocumented unicode handling (but the best of the pack. Unicode escapes 869Undocumented Unicode handling (but the best of the pack. Unicode escapes
657still don't get parsed properly). 870still don't get parsed properly).
658 871
659Very inflexible. 872Very inflexible.
660 873
661No roundtripping. 874No round-tripping.
662 875
663Does not generate valid JSON texts (key strings are often unquoted, empty keys 876Does not generate valid JSON texts (key strings are often unquoted, empty keys
664result in nothing being output) 877result in nothing being output)
665 878
666Does not check input for validity. 879Does not check input for validity.
681 my $yaml = $to_yaml->encode ($ref) . "\n"; 894 my $yaml = $to_yaml->encode ($ref) . "\n";
682 895
683This will usually generate JSON texts that also parse as valid 896This will usually generate JSON texts that also parse as valid
684YAML. Please note that YAML has hardcoded limits on (simple) object key 897YAML. 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 898lengths that JSON doesn't have, so you should make sure that your hash
686keys are noticably shorter than the 1024 characters YAML allows. 899keys are noticeably shorter than the 1024 characters YAML allows.
687 900
688There might be other incompatibilities that I am not aware of. In general 901There 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, 902you 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 903or try to parse JSON with a YAML parser or vice versa: chances are high
691that you will run into severe interoperability problems. 904that you will run into severe interoperability problems.
707It shows the number of encodes/decodes per second (JSON::XS uses 920It shows the number of encodes/decodes per second (JSON::XS uses
708the functional interface, while JSON::XS/2 uses the OO interface 921the functional interface, while JSON::XS/2 uses the OO interface
709with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 922with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
710shrink). Higher is better: 923shrink). Higher is better:
711 924
712 Storable | 15779.925 | 14169.946 |
713 -----------+------------+------------+
714 module | encode | decode | 925 module | encode | decode |
715 -----------|------------|------------| 926 -----------|------------|------------|
716 JSON | 4990.842 | 4088.813 | 927 JSON 1.x | 4990.842 | 4088.813 |
717 JSON::DWIW | 51653.990 | 71575.154 | 928 JSON::DWIW | 51653.990 | 71575.154 |
718 JSON::PC | 65948.176 | 74631.744 | 929 JSON::PC | 65948.176 | 74631.744 |
719 JSON::PP | 8931.652 | 3817.168 | 930 JSON::PP | 8931.652 | 3817.168 |
720 JSON::Syck | 24877.248 | 27776.848 | 931 JSON::Syck | 24877.248 | 27776.848 |
721 JSON::XS | 388361.481 | 227951.304 | 932 JSON::XS | 388361.481 | 227951.304 |
723 JSON::XS/3 | 338250.323 | 218453.333 | 934 JSON::XS/3 | 338250.323 | 218453.333 |
724 Storable | 16500.016 | 135300.129 | 935 Storable | 16500.016 | 135300.129 |
725 -----------+------------+------------+ 936 -----------+------------+------------+
726 937
727That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 938That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
728about three times faster on decoding, and over fourty times faster 939about three times faster on decoding, and over forty times faster
729than JSON, even with pretty-printing and key sorting. It also compares 940than JSON, even with pretty-printing and key sorting. It also compares
730favourably to Storable for small amounts of data. 941favourably to Storable for small amounts of data.
731 942
732Using a longer test string (roughly 18KB, generated from Yahoo! Locals 943Using a longer test string (roughly 18KB, generated from Yahoo! Locals
733search API (http://nanoref.com/yahooapis/mgPdGg): 944search API (http://nanoref.com/yahooapis/mgPdGg):
734 945
735 module | encode | decode | 946 module | encode | decode |
736 -----------|------------|------------| 947 -----------|------------|------------|
737 JSON | 55.260 | 34.971 | 948 JSON 1.x | 55.260 | 34.971 |
738 JSON::DWIW | 825.228 | 1082.513 | 949 JSON::DWIW | 825.228 | 1082.513 |
739 JSON::PC | 3571.444 | 2394.829 | 950 JSON::PC | 3571.444 | 2394.829 |
740 JSON::PP | 210.987 | 32.574 | 951 JSON::PP | 210.987 | 32.574 |
741 JSON::Syck | 552.551 | 787.544 | 952 JSON::Syck | 552.551 | 787.544 |
742 JSON::XS | 5780.463 | 4854.519 | 953 JSON::XS | 5780.463 | 4854.519 |
746 -----------+------------+------------+ 957 -----------+------------+------------+
747 958
748Again, JSON::XS leads by far (except for Storable which non-surprisingly 959Again, JSON::XS leads by far (except for Storable which non-surprisingly
749decodes faster). 960decodes faster).
750 961
751On large strings containing lots of high unicode characters, some modules 962On 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 963(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 964will be broken due to missing (or wrong) Unicode handling. Others refuse
754to decode or encode properly, so it was impossible to prepare a fair 965to decode or encode properly, so it was impossible to prepare a fair
755comparison table for that case. 966comparison table for that case.
756 967
757 968
758=head1 SECURITY CONSIDERATIONS 969=head1 SECURITY CONSIDERATIONS
764any buffer overflows. Obviously, this module should ensure that and I am 975any buffer overflows. Obviously, this module should ensure that and I am
765trying hard on making that true, but you never know. 976trying hard on making that true, but you never know.
766 977
767Second, you need to avoid resource-starving attacks. That means you should 978Second, 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 979limit 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 980resources 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 981can 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 982usually 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 983it 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 984text, 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. 985might want to check the size before you accept the string.
785And last but least, something else could bomb you that I forgot to think 996And 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, 997of. In that case, you get to keep the pieces. I am always open for hints,
787though... 998though...
788 999
789If you are using JSON::XS to return packets to consumption 1000If you are using JSON::XS to return packets to consumption
790by javascript scripts in a browser you should have a look at 1001by JavaScript scripts in a browser you should have a look at
791L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1002L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792you are vulnerable to some common attack vectors (which really are browser 1003you 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 1004design 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 1005browser developers care only for features, not about doing security
795right). 1006right).
796 1007
797 1008
1009=head1 THREADS
1010
1011This module is I<not> guaranteed to be thread safe and there are no
1012plans to change this until Perl gets thread support (as opposed to the
1013horribly slow so-called "threads" which are simply slow and bloated
1014process simulations - use fork, its I<much> faster, cheaper, better).
1015
1016(It might actually work, but you have been warned).
1017
1018
798=head1 BUGS 1019=head1 BUGS
799 1020
800While the goal of this module is to be correct, that unfortunately does 1021While 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 1022not 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 1023still relatively early in its development. If you keep reporting bugs they
803will be fixed swiftly, though. 1024will be fixed swiftly, though.
804 1025
1026Please refrain from using rt.cpan.org or any other bug reporting
1027service. I put the contact address into my modules for a reason.
1028
805=cut 1029=cut
806 1030
807our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" }; 1031our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" }; 1032our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
809 1033
810sub true() { $true } 1034sub true() { $true }
811sub false() { $false } 1035sub false() { $false }
812 1036
813sub is_bool($) { 1037sub is_bool($) {

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