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Revision 1.47 by root, Mon Jun 25 06:57:42 2007 UTC vs.
Revision 1.75 by root, Thu Nov 29 13:35:35 2007 UTC

1=head1 NAME 1=head1 NAME
2 2
3JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
4
5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4 7
5=head1 SYNOPSIS 8=head1 SYNOPSIS
6 9
7 use JSON::XS; 10 use JSON::XS;
8 11
9 # exported functions, they croak on error 12 # exported functions, they croak on error
10 # and expect/generate UTF-8 13 # and expect/generate UTF-8
11 14
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
14
15 # objToJson and jsonToObj aliases to to_json and from_json
16 # are exported for compatibility to the JSON module,
17 # but should not be used in new code.
18 17
19 # OO-interface 18 # OO-interface
20 19
21 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
22 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
41 40
42=head2 FEATURES 41=head2 FEATURES
43 42
44=over 4 43=over 4
45 44
46=item * correct unicode handling 45=item * correct Unicode handling
47 46
48This 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
49it does so. 48it does so.
50 49
51=item * round-trip integrity 50=item * round-trip integrity
71This 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
72interface. 71interface.
73 72
74=item * reasonably versatile output formats 73=item * reasonably versatile output formats
75 74
76You can choose between the most compact guarenteed single-line format 75You can choose between the most compact guaranteed single-line format
77possible (nice for simple line-based protocols), a pure-ascii format 76possible (nice for simple line-based protocols), a pure-ascii format
78(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
79unicode 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
80stuff). Or you can combine those features in whatever way you like. 79stuff). Or you can combine those features in whatever way you like.
81 80
82=back 81=back
83 82
84=cut 83=cut
85 84
86package JSON::XS; 85package JSON::XS;
87 86
88use strict; 87use strict;
89 88
90our $VERSION = '1.4'; 89our $VERSION = '2.0';
91our @ISA = qw(Exporter); 90our @ISA = qw(Exporter);
92 91
93our @EXPORT = qw(to_json from_json objToJson jsonToObj); 92our @EXPORT = qw(to_json from_json);
94 93
95use Exporter; 94use Exporter;
96use XSLoader; 95use XSLoader;
97 96
98=head1 FUNCTIONAL INTERFACE 97=head1 FUNCTIONAL INTERFACE
99 98
100The following convinience methods are provided by this module. They are 99The following convenience methods are provided by this module. They are
101exported by default: 100exported by default:
102 101
103=over 4 102=over 4
104 103
105=item $json_text = to_json $perl_scalar 104=item $json_text = to_json $perl_scalar
106 105
107Converts 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
108a 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.
109octets only). Croaks on error.
110 108
111This function call is functionally identical to: 109This function call is functionally identical to:
112 110
113 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114 112
115except being faster. 113except being faster.
116 114
117=item $perl_scalar = from_json $json_text 115=item $perl_scalar = from_json $json_text
118 116
119The 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
120parse 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
121scalar or reference. Croaks on error. 119reference. Croaks on error.
122 120
123This function call is functionally identical to: 121This function call is functionally identical to:
124 122
125 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 123 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
126 124
136Perl. 134Perl.
137 135
138=back 136=back
139 137
140 138
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
141=head1 OBJECT-ORIENTED INTERFACE 187=head1 OBJECT-ORIENTED INTERFACE
142 188
143The object oriented interface lets you configure your own encoding or 189The object oriented interface lets you configure your own encoding or
144decoding style, within the limits of supported formats. 190decoding style, within the limits of supported formats.
145 191
156 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]})
157 => {"a": [1, 2]} 203 => {"a": [1, 2]}
158 204
159=item $json = $json->ascii ([$enable]) 205=item $json = $json->ascii ([$enable])
160 206
207=item $enabled = $json->get_ascii
208
161If C<$enable> is true (or missing), then the C<encode> method will not 209If C<$enable> is true (or missing), then the C<encode> method will not
162generate characters outside the code range C<0..127> (which is ASCII). Any 210generate characters outside the code range C<0..127> (which is ASCII). Any
163unicode characters outside that range will be escaped using either a 211Unicode characters outside that range will be escaped using either a
164single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
165as per RFC4627. The resulting encoded JSON text can be treated as a native 213as per RFC4627. The resulting encoded JSON text can be treated as a native
166unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 214Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
167or any other superset of ASCII. 215or any other superset of ASCII.
168 216
169If C<$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
170characters unless required by the JSON syntax or other flags. This results 218characters unless required by the JSON syntax or other flags. This results
171in a faster and more compact format. 219in a faster and more compact format.
177 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 225 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178 => ["\ud801\udc01"] 226 => ["\ud801\udc01"]
179 227
180=item $json = $json->latin1 ([$enable]) 228=item $json = $json->latin1 ([$enable])
181 229
230=item $enabled = $json->get_latin1
231
182If C<$enable> is true (or missing), then the C<encode> method will encode 232If C<$enable> is true (or missing), then the C<encode> method will encode
183the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 233the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
184outside the code range C<0..255>. The resulting string can be treated as a 234outside the code range C<0..255>. The resulting string can be treated as a
185latin1-encoded JSON text or a native unicode string. The C<decode> method 235latin1-encoded JSON text or a native Unicode string. The C<decode> method
186will not be affected in any way by this flag, as C<decode> by default 236will not be affected in any way by this flag, as C<decode> by default
187expects unicode, which is a strict superset of latin1. 237expects Unicode, which is a strict superset of latin1.
188 238
189If C<$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
190characters unless required by the JSON syntax or other flags. 240characters unless required by the JSON syntax or other flags.
191 241
192The 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
193text, 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
194size. The disadvantage is that the resulting JSON text is encoded 244size. The disadvantage is that the resulting JSON text is encoded
195in latin1 (and must correctly be treated as such when storing and 245in latin1 (and must correctly be treated as such when storing and
196transfering), a rare encoding for JSON. It is therefore most useful when 246transferring), a rare encoding for JSON. It is therefore most useful when
197you want to store data structures known to contain binary data efficiently 247you want to store data structures known to contain binary data efficiently
198in files or databases, not when talking to other JSON encoders/decoders. 248in files or databases, not when talking to other JSON encoders/decoders.
199 249
200 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 250 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
201 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 251 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
202 252
203=item $json = $json->utf8 ([$enable]) 253=item $json = $json->utf8 ([$enable])
254
255=item $enabled = $json->get_utf8
204 256
205If C<$enable> is true (or missing), then the C<encode> method will encode 257If C<$enable> is true (or missing), then the C<encode> method will encode
206the JSON result into UTF-8, as required by many protocols, while the 258the JSON result into UTF-8, as required by many protocols, while the
207C<decode> method expects to be handled an UTF-8-encoded string. Please 259C<decode> method expects to be handled an UTF-8-encoded string. Please
208note that UTF-8-encoded strings do not contain any characters outside the 260note that UTF-8-encoded strings do not contain any characters outside the
209range C<0..255>, they are thus useful for bytewise/binary I/O. In future 261range C<0..255>, they are thus useful for bytewise/binary I/O. In future
210versions, enabling this option might enable autodetection of the UTF-16 262versions, enabling this option might enable autodetection of the UTF-16
211and UTF-32 encoding families, as described in RFC4627. 263and UTF-32 encoding families, as described in RFC4627.
212 264
213If C<$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
214string 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
215unicode 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
216to be done yourself, e.g. using the Encode module. 268to be done yourself, e.g. using the Encode module.
217 269
218Example, output UTF-16BE-encoded JSON: 270Example, output UTF-16BE-encoded JSON:
219 271
220 use Encode; 272 use Encode;
242 ] 294 ]
243 } 295 }
244 296
245=item $json = $json->indent ([$enable]) 297=item $json = $json->indent ([$enable])
246 298
299=item $enabled = $json->get_indent
300
247If C<$enable> is true (or missing), then the C<encode> method will use a multiline 301If C<$enable> is true (or missing), then the C<encode> method will use a multiline
248format as output, putting every array member or object/hash key-value pair 302format as output, putting every array member or object/hash key-value pair
249into its own line, identing them properly. 303into its own line, indenting them properly.
250 304
251If C<$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
252resulting JSON text is guarenteed not to contain any C<newlines>. 306resulting JSON text is guaranteed not to contain any C<newlines>.
253 307
254This setting has no effect when decoding JSON texts. 308This setting has no effect when decoding JSON texts.
255 309
256=item $json = $json->space_before ([$enable]) 310=item $json = $json->space_before ([$enable])
311
312=item $enabled = $json->get_space_before
257 313
258If C<$enable> is true (or missing), then the C<encode> method will add an extra 314If C<$enable> is true (or missing), then the C<encode> method will add an extra
259optional space before the C<:> separating keys from values in JSON objects. 315optional space before the C<:> separating keys from values in JSON objects.
260 316
261If C<$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
267Example, space_before enabled, space_after and indent disabled: 323Example, space_before enabled, space_after and indent disabled:
268 324
269 {"key" :"value"} 325 {"key" :"value"}
270 326
271=item $json = $json->space_after ([$enable]) 327=item $json = $json->space_after ([$enable])
328
329=item $enabled = $json->get_space_after
272 330
273If C<$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
274optional space after the C<:> separating keys from values in JSON objects 332optional space after the C<:> separating keys from values in JSON objects
275and extra whitespace after the C<,> separating key-value pairs and array 333and extra whitespace after the C<,> separating key-value pairs and array
276members. 334members.
282 340
283Example, space_before and indent disabled, space_after enabled: 341Example, space_before and indent disabled, space_after enabled:
284 342
285 {"key": "value"} 343 {"key": "value"}
286 344
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
287=item $json = $json->canonical ([$enable]) 392=item $json = $json->canonical ([$enable])
393
394=item $enabled = $json->get_canonical
288 395
289If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 396If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
290by sorting their keys. This is adding a comparatively high overhead. 397by sorting their keys. This is adding a comparatively high overhead.
291 398
292If C<$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
293pairs 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
294of the same script). 401of the same script).
295 402
296This 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
297the 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,
298the 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,
299as key-value pairs have no inherent ordering in Perl. 406as key-value pairs have no inherent ordering in Perl.
300 407
301This setting has no effect when decoding JSON texts. 408This setting has no effect when decoding JSON texts.
302 409
303=item $json = $json->allow_nonref ([$enable]) 410=item $json = $json->allow_nonref ([$enable])
411
412=item $enabled = $json->get_allow_nonref
304 413
305If C<$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
306non-reference into its corresponding string, number or null JSON value, 415non-reference into its corresponding string, number or null JSON value,
307which 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
308values instead of croaking. 417values instead of croaking.
318 JSON::XS->new->allow_nonref->encode ("Hello, World!") 427 JSON::XS->new->allow_nonref->encode ("Hello, World!")
319 => "Hello, World!" 428 => "Hello, World!"
320 429
321=item $json = $json->allow_blessed ([$enable]) 430=item $json = $json->allow_blessed ([$enable])
322 431
432=item $enabled = $json->get_allow_blessed
433
323If C<$enable> is true (or missing), then the C<encode> method will not 434If C<$enable> is true (or missing), then the C<encode> method will not
324barf when it encounters a blessed reference. Instead, the value of the 435barf when it encounters a blessed reference. Instead, the value of the
325B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 436B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
326disabled or no C<to_json> method found) or a representation of the 437disabled or no C<to_json> method found) or a representation of the
327object (C<convert_blessed> enabled and C<to_json> method found) is being 438object (C<convert_blessed> enabled and C<to_json> method found) is being
328encoded. Has no effect on C<decode>. 439encoded. Has no effect on C<decode>.
329 440
330If C<$enable> is false (the default), then C<encode> will throw an 441If C<$enable> is false (the default), then C<encode> will throw an
331exception when it encounters a blessed object. 442exception when it encounters a blessed object.
332 443
333=item $json = $json->convert_blessed ([$enable]) 444=item $json = $json->convert_blessed ([$enable])
445
446=item $enabled = $json->get_convert_blessed
334 447
335If C<$enable> is true (or missing), then C<encode>, upon encountering a 448If C<$enable> is true (or missing), then C<encode>, upon encountering a
336blessed object, will check for the availability of the C<TO_JSON> method 449blessed object, will check for the availability of the C<TO_JSON> method
337on the object's class. If found, it will be called in scalar context 450on the object's class. If found, it will be called in scalar context
338and the resulting scalar will be encoded instead of the object. If no 451and the resulting scalar will be encoded instead of the object. If no
352enabled by this setting. 465enabled by this setting.
353 466
354If C<$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
355to do when a blessed object is found. 468to do when a blessed object is found.
356 469
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
357=item $json = $json->shrink ([$enable]) 546=item $json = $json->shrink ([$enable])
547
548=item $enabled = $json->get_shrink
358 549
359Perl usually over-allocates memory a bit when allocating space for 550Perl usually over-allocates memory a bit when allocating space for
360strings. This flag optionally resizes strings generated by either 551strings. This flag optionally resizes strings generated by either
361C<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
362memory 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
380strings that look like integers or floats into integers or floats 571strings that look like integers or floats into integers or floats
381internally (there is no difference on the Perl level), saving space. 572internally (there is no difference on the Perl level), saving space.
382 573
383=item $json = $json->max_depth ([$maximum_nesting_depth]) 574=item $json = $json->max_depth ([$maximum_nesting_depth])
384 575
576=item $max_depth = $json->get_max_depth
577
385Sets the maximum nesting level (default C<512>) accepted while encoding 578Sets the maximum nesting level (default C<512>) accepted while encoding
386or 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
387higher nesting level then this limit, then the encoder and decoder will 580higher nesting level then this limit, then the encoder and decoder will
388stop and croak at that point. 581stop and croak at that point.
389 582
400used, which is rarely useful. 593used, which is rarely useful.
401 594
402See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 595See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
403 596
404=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
405 600
406Set 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
407being 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>
408is 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
409attempt 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
456vice 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
457circumstances automatically, preserving round-tripping characteristics 652circumstances automatically, preserving round-tripping characteristics
458(what you put in comes out as something equivalent). 653(what you put in comes out as something equivalent).
459 654
460For the more enlightened: note that in the following descriptions, 655For the more enlightened: note that in the following descriptions,
461lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 656lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
462refers to the abstract Perl language itself. 657refers to the abstract Perl language itself.
463 658
464 659
465=head2 JSON -> PERL 660=head2 JSON -> PERL
466 661
467=over 4 662=over 4
468 663
469=item object 664=item object
470 665
471A 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
472keys is preserved (JSON does not preserver object key ordering itself). 667keys is preserved (JSON does not preserve object key ordering itself).
473 668
474=item array 669=item array
475 670
476A JSON array becomes a reference to an array in Perl. 671A JSON array becomes a reference to an array in Perl.
477 672
481are 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
482decoding is necessary. 677decoding is necessary.
483 678
484=item number 679=item number
485 680
486A JSON number becomes either an integer or numeric (floating point) 681A JSON number becomes either an integer, numeric (floating point) or
487scalar 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
488Perl 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
489conversion details, but an integer may take slightly less memory and might 684the conversion details, but an integer may take slightly less memory and
490represent 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.
491 698
492=item true, false 699=item true, false
493 700
494These 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>,
495respectively. They are overloaded to act almost exactly like the numbers 702respectively. They are overloaded to act almost exactly like the numbers
496C<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
497the C<JSON::XS::is_bool> function. 704the C<JSON::XS::is_bool> function.
498 705
499=item null 706=item null
500 707
501A JSON null atom becomes C<undef> in Perl. 708A JSON null atom becomes C<undef> in Perl.
537 to_json [\0,JSON::XS::true] # yields [false,true] 744 to_json [\0,JSON::XS::true] # yields [false,true]
538 745
539=item JSON::XS::true, JSON::XS::false 746=item JSON::XS::true, JSON::XS::false
540 747
541These special values become JSON true and JSON false values, 748These special values become JSON true and JSON false values,
542respectively. 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.
543 750
544=item blessed objects 751=item blessed objects
545 752
546Blessed objects are not allowed. JSON::XS currently tries to encode their 753Blessed objects are not allowed. JSON::XS currently tries to encode their
547underlying representation (hash- or arrayref), but this behaviour might 754underlying representation (hash- or arrayref), but this behaviour might
564 to_json [$value] # yields ["5"] 771 to_json [$value] # yields ["5"]
565 772
566 # undef becomes null 773 # undef becomes null
567 to_json [undef] # yields [null] 774 to_json [undef] # yields [null]
568 775
569You can force the type to be a string by stringifying it: 776You can force the type to be a JSON string by stringifying it:
570 777
571 my $x = 3.1; # some variable containing a number 778 my $x = 3.1; # some variable containing a number
572 "$x"; # stringified 779 "$x"; # stringified
573 $x .= ""; # another, more awkward way to stringify 780 $x .= ""; # another, more awkward way to stringify
574 print $x; # perl does it for you, too, quite often 781 print $x; # perl does it for you, too, quite often
575 782
576You can force the type to be a number by numifying it: 783You can force the type to be a JSON number by numifying it:
577 784
578 my $x = "3"; # some variable containing a string 785 my $x = "3"; # some variable containing a string
579 $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
580 $x *= 1; # same thing, the choise is yours. 787 $x *= 1; # same thing, the choice is yours.
581 788
582You 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
583less obscure, ways. Tell me if you need this capability. 790if you need this capability.
584 791
585=back 792=back
586 793
587 794
588=head1 COMPARISON 795=head1 COMPARISON
597 804
598=item JSON 1.07 805=item JSON 1.07
599 806
600Slow (but very portable, as it is written in pure Perl). 807Slow (but very portable, as it is written in pure Perl).
601 808
602Undocumented/buggy Unicode handling (how JSON handles unicode values is 809Undocumented/buggy Unicode handling (how JSON handles Unicode values is
603undocumented. One can get far by feeding it unicode strings and doing 810undocumented. One can get far by feeding it Unicode strings and doing
604en-/decoding oneself, but unicode escapes are not working properly). 811en-/decoding oneself, but Unicode escapes are not working properly).
605 812
606No roundtripping (strings get clobbered if they look like numbers, e.g. 813No round-tripping (strings get clobbered if they look like numbers, e.g.
607the 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
608decode into the number 2. 815decode into the number 2.
609 816
610=item JSON::PC 0.01 817=item JSON::PC 0.01
611 818
612Very fast. 819Very fast.
613 820
614Undocumented/buggy Unicode handling. 821Undocumented/buggy Unicode handling.
615 822
616No roundtripping. 823No round-tripping.
617 824
618Has 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
619values will make it croak). 826values will make it croak).
620 827
621Does 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}>
631Very inflexible (no human-readable format supported, format pretty much 838Very inflexible (no human-readable format supported, format pretty much
632undocumented. 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
633single-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
634generate ASCII-only JSON texts). 841generate ASCII-only JSON texts).
635 842
636Completely broken (and confusingly documented) Unicode handling (unicode 843Completely broken (and confusingly documented) Unicode handling (Unicode
637escapes are not working properly, you need to set ImplicitUnicode to 844escapes are not working properly, you need to set ImplicitUnicode to
638I<different> values on en- and decoding to get symmetric behaviour). 845I<different> values on en- and decoding to get symmetric behaviour).
639 846
640No roundtripping (simple cases work, but this depends on wether the scalar 847No round-tripping (simple cases work, but this depends on whether the scalar
641value was used in a numeric context or not). 848value was used in a numeric context or not).
642 849
643Dumping hashes may skip hash values depending on iterator state. 850Dumping hashes may skip hash values depending on iterator state.
644 851
645Unmaintained (maintainer unresponsive for many months, bugs are not 852Unmaintained (maintainer unresponsive for many months, bugs are not
646getting fixed). 853getting fixed).
647 854
648Does 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
649return "something" instead of raising an exception. This is a security 856return "something" instead of raising an exception. This is a security
650issue: imagine two banks transfering money between each other using 857issue: imagine two banks transferring money between each other using
651JSON. 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,
652while 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
653good protocol will at least recover, that is extra unnecessary work and 860good protocol will at least recover, that is extra unnecessary work and
654the transaction will still not succeed). 861the transaction will still not succeed).
655 862
656=item JSON::DWIW 0.04 863=item JSON::DWIW 0.04
657 864
658Very fast. Very natural. Very nice. 865Very fast. Very natural. Very nice.
659 866
660Undocumented unicode handling (but the best of the pack. Unicode escapes 867Undocumented Unicode handling (but the best of the pack. Unicode escapes
661still don't get parsed properly). 868still don't get parsed properly).
662 869
663Very inflexible. 870Very inflexible.
664 871
665No roundtripping. 872No round-tripping.
666 873
667Does 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
668result in nothing being output) 875result in nothing being output)
669 876
670Does not check input for validity. 877Does not check input for validity.
685 my $yaml = $to_yaml->encode ($ref) . "\n"; 892 my $yaml = $to_yaml->encode ($ref) . "\n";
686 893
687This will usually generate JSON texts that also parse as valid 894This will usually generate JSON texts that also parse as valid
688YAML. Please note that YAML has hardcoded limits on (simple) object key 895YAML. Please note that YAML has hardcoded limits on (simple) object key
689lengths 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
690keys are noticably shorter than the 1024 characters YAML allows. 897keys are noticeably shorter than the 1024 characters YAML allows.
691 898
692There 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
693you 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,
694or 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
695that you will run into severe interoperability problems. 902that you will run into severe interoperability problems.
713with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 920with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
714shrink). Higher is better: 921shrink). Higher is better:
715 922
716 module | encode | decode | 923 module | encode | decode |
717 -----------|------------|------------| 924 -----------|------------|------------|
718 JSON | 7645.468 | 4208.613 | 925 JSON 1.x | 4990.842 | 4088.813 |
719 JSON::DWIW | 40721.398 | 77101.176 | 926 JSON::DWIW | 51653.990 | 71575.154 |
720 JSON::PC | 65948.176 | 78251.940 | 927 JSON::PC | 65948.176 | 74631.744 |
721 JSON::Syck | 22844.793 | 26479.192 | 928 JSON::PP | 8931.652 | 3817.168 |
929 JSON::Syck | 24877.248 | 27776.848 |
722 JSON::XS | 388361.481 | 199728.762 | 930 JSON::XS | 388361.481 | 227951.304 |
723 JSON::XS/2 | 218453.333 | 192399.266 | 931 JSON::XS/2 | 227951.304 | 218453.333 |
724 JSON::XS/3 | 338250.323 | 192399.266 | 932 JSON::XS/3 | 338250.323 | 218453.333 |
725 Storable | 15779.925 | 14169.946 | 933 Storable | 16500.016 | 135300.129 |
726 -----------+------------+------------+ 934 -----------+------------+------------+
727 935
728That 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,
729about three times faster on decoding, and over fourty times faster 937about three times faster on decoding, and over forty times faster
730than JSON, even with pretty-printing and key sorting. It also compares 938than JSON, even with pretty-printing and key sorting. It also compares
731favourably to Storable for small amounts of data. 939favourably to Storable for small amounts of data.
732 940
733Using a longer test string (roughly 18KB, generated from Yahoo! Locals 941Using a longer test string (roughly 18KB, generated from Yahoo! Locals
734search API (http://nanoref.com/yahooapis/mgPdGg): 942search API (http://nanoref.com/yahooapis/mgPdGg):
735 943
736 module | encode | decode | 944 module | encode | decode |
737 -----------|------------|------------| 945 -----------|------------|------------|
738 JSON | 254.685 | 37.665 | 946 JSON 1.x | 55.260 | 34.971 |
739 JSON::DWIW | 843.343 | 1049.731 | 947 JSON::DWIW | 825.228 | 1082.513 |
740 JSON::PC | 3602.116 | 2307.352 | 948 JSON::PC | 3571.444 | 2394.829 |
949 JSON::PP | 210.987 | 32.574 |
741 JSON::Syck | 505.107 | 787.899 | 950 JSON::Syck | 552.551 | 787.544 |
742 JSON::XS | 5747.196 | 3690.220 | 951 JSON::XS | 5780.463 | 4854.519 |
743 JSON::XS/2 | 3968.121 | 3676.634 | 952 JSON::XS/2 | 3869.998 | 4798.975 |
744 JSON::XS/3 | 6105.246 | 3662.508 | 953 JSON::XS/3 | 5862.880 | 4798.975 |
745 Storable | 4417.337 | 5285.161 | 954 Storable | 4445.002 | 5235.027 |
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.
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.
804 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" };

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