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Revision 1.63 by root, Thu Oct 11 23:07:43 2007 UTC vs.
Revision 1.79 by root, Wed Dec 19 11:42:52 2007 UTC

1=encoding utf-8
2
3=head1 NAME 1=head1 NAME
4 2
5JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
6 4
7JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ 5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
12 use JSON::XS; 10 use JSON::XS;
13 11
14 # exported functions, they croak on error 12 # exported functions, they croak on error
15 # and expect/generate UTF-8 13 # and expect/generate UTF-8
16 14
17 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
18 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
19 17
20 # OO-interface 18 # OO-interface
21 19
22 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
23 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
24 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
25 23
24 # Note that JSON version 2.0 and above will automatically use JSON::XS
25 # if available, at virtually no speed overhead either, so you should
26 # be able to just:
27
28 use JSON;
29
30 # and do the same things, except that you have a pure-perl fallback now.
31
26=head1 DESCRIPTION 32=head1 DESCRIPTION
27 33
28This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
29primary goal is to be I<correct> and its secondary goal is to be 35primary goal is to be I<correct> and its secondary goal is to be
30I<fast>. To reach the latter goal it was written in C. 36I<fast>. To reach the latter goal it was written in C.
37
38Beginning with version 2.0 of the JSON module, when both JSON and
39JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40overriden) with no overhead due to emulation (by inheritign constructor
41and methods). If JSON::XS is not available, it will fall back to the
42compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43gives you a portable JSON API that can be fast when you need and doesn't
44require a C compiler when that is a problem.
31 45
32As this is the n-th-something JSON module on CPAN, what was the reason 46As this is the n-th-something JSON module on CPAN, what was the reason
33to write yet another JSON module? While it seems there are many JSON 47to write yet another JSON module? While it seems there are many JSON
34modules, none of them correctly handle all corner cases, and in most cases 48modules, none of them correctly handle all corner cases, and in most cases
35their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
42 56
43=head2 FEATURES 57=head2 FEATURES
44 58
45=over 4 59=over 4
46 60
47=item * correct unicode handling 61=item * correct Unicode handling
48 62
49This module knows how to handle Unicode, and even documents how and when 63This module knows how to handle Unicode, and even documents how and when
50it does so. 64it does so.
51 65
52=item * round-trip integrity 66=item * round-trip integrity
72This module has both a simple functional interface as well as an OO 86This module has both a simple functional interface as well as an OO
73interface. 87interface.
74 88
75=item * reasonably versatile output formats 89=item * reasonably versatile output formats
76 90
77You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
78possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
79(for when your transport is not 8-bit clean, still supports the whole 93(for when your transport is not 8-bit clean, still supports the whole
80unicode range), or a pretty-printed format (for when you want to read that 94Unicode range), or a pretty-printed format (for when you want to read that
81stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
82 96
83=back 97=back
84 98
85=cut 99=cut
86 100
87package JSON::XS; 101package JSON::XS;
88 102
89use strict; 103use strict;
90 104
91our $VERSION = '1.5'; 105our $VERSION = '2.01';
92our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
93 107
94our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
111 require Carp;
112 Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
113}
114
115sub from_json($) {
116 require Carp;
117 Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
118}
95 119
96use Exporter; 120use Exporter;
97use XSLoader; 121use XSLoader;
98 122
99=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
100 124
101The following convinience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
102exported by default: 126exported by default:
103 127
104=over 4 128=over 4
105 129
106=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
107 131
108Converts the given Perl data structure to a UTF-8 encoded, binary string 132Converts the given Perl data structure to a UTF-8 encoded, binary string
109(that is, the string contains octets only). Croaks on error. 133(that is, the string contains octets only). Croaks on error.
110 134
111This function call is functionally identical to: 135This function call is functionally identical to:
112 136
113 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114 138
115except being faster. 139except being faster.
116 140
117=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
118 142
119The opposite of C<to_json>: expects an UTF-8 (binary) string and tries 143The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
120to parse that as an UTF-8 encoded JSON text, returning the resulting 144to parse that as an UTF-8 encoded JSON text, returning the resulting
121reference. Croaks on error. 145reference. Croaks on error.
122 146
123This function call is functionally identical to: 147This function call is functionally identical to:
124 148
145 169
146=over 4 170=over 4
147 171
148=item 1. Perl strings can store characters with ordinal values > 255. 172=item 1. Perl strings can store characters with ordinal values > 255.
149 173
150This enables you to store unicode characters as single characters in a 174This enables you to store Unicode characters as single characters in a
151Perl string - very natural. 175Perl string - very natural.
152 176
153=item 2. Perl does I<not> associate an encoding with your strings. 177=item 2. Perl does I<not> associate an encoding with your strings.
154 178
155Unless you force it to, e.g. when matching it against a regex, or printing 179Unless you force it to, e.g. when matching it against a regex, or printing
162encoding of your string. 186encoding of your string.
163 187
164Just ignore that flag unless you debug a Perl bug, a module written in 188Just ignore that flag unless you debug a Perl bug, a module written in
165XS or want to dive into the internals of perl. Otherwise it will only 189XS or want to dive into the internals of perl. Otherwise it will only
166confuse you, as, despite the name, it says nothing about how your string 190confuse you, as, despite the name, it says nothing about how your string
167is encoded. You can have unicode strings with that flag set, with that 191is encoded. You can have Unicode strings with that flag set, with that
168flag clear, and you can have binary data with that flag set and that flag 192flag clear, and you can have binary data with that flag set and that flag
169clear. Other possibilities exist, too. 193clear. Other possibilities exist, too.
170 194
171If you didn't know about that flag, just the better, pretend it doesn't 195If you didn't know about that flag, just the better, pretend it doesn't
172exist. 196exist.
177If you have UTF-8 encoded data, it is no longer a Unicode string, but a 201If you have UTF-8 encoded data, it is no longer a Unicode string, but a
178Unicode string encoded in UTF-8, giving you a binary string. 202Unicode string encoded in UTF-8, giving you a binary string.
179 203
180=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. 204=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
181 205
182Its a fact. Learn to live with it. 206It's a fact. Learn to live with it.
183 207
184=back 208=back
185 209
186I hope this helps :) 210I hope this helps :)
187 211
204 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 228 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
205 => {"a": [1, 2]} 229 => {"a": [1, 2]}
206 230
207=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
208 232
233=item $enabled = $json->get_ascii
234
209If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
210generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
211unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
213as per RFC4627. The resulting encoded JSON text can be treated as a native 239as per RFC4627. The resulting encoded JSON text can be treated as a native
214unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 240Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
215or any other superset of ASCII. 241or any other superset of ASCII.
216 242
217If C<$enable> is false, then the C<encode> method will not escape Unicode 243If C<$enable> is false, then the C<encode> method will not escape Unicode
218characters unless required by the JSON syntax or other flags. This results 244characters unless required by the JSON syntax or other flags. This results
219in a faster and more compact format. 245in a faster and more compact format.
225 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
226 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
227 253
228=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
229 255
256=item $enabled = $json->get_latin1
257
230If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
231the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
232outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
233latin1-encoded JSON text or a native unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
234will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
235expects unicode, which is a strict superset of latin1. 263expects Unicode, which is a strict superset of latin1.
236 264
237If C<$enable> is false, then the C<encode> method will not escape Unicode 265If C<$enable> is false, then the C<encode> method will not escape Unicode
238characters unless required by the JSON syntax or other flags. 266characters unless required by the JSON syntax or other flags.
239 267
240The main use for this flag is efficiently encoding binary data as JSON 268The main use for this flag is efficiently encoding binary data as JSON
241text, as most octets will not be escaped, resulting in a smaller encoded 269text, as most octets will not be escaped, resulting in a smaller encoded
242size. The disadvantage is that the resulting JSON text is encoded 270size. The disadvantage is that the resulting JSON text is encoded
243in latin1 (and must correctly be treated as such when storing and 271in latin1 (and must correctly be treated as such when storing and
244transfering), a rare encoding for JSON. It is therefore most useful when 272transferring), a rare encoding for JSON. It is therefore most useful when
245you want to store data structures known to contain binary data efficiently 273you want to store data structures known to contain binary data efficiently
246in files or databases, not when talking to other JSON encoders/decoders. 274in files or databases, not when talking to other JSON encoders/decoders.
247 275
248 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
249 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
250 278
251=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
252 282
253If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
254the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
255C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
256note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
257range C<0..255>, they are thus useful for bytewise/binary I/O. In future 287range C<0..255>, they are thus useful for bytewise/binary I/O. In future
258versions, enabling this option might enable autodetection of the UTF-16 288versions, enabling this option might enable autodetection of the UTF-16
259and UTF-32 encoding families, as described in RFC4627. 289and UTF-32 encoding families, as described in RFC4627.
260 290
261If C<$enable> is false, then the C<encode> method will return the JSON 291If C<$enable> is false, then the C<encode> method will return the JSON
262string as a (non-encoded) unicode string, while C<decode> expects thus a 292string as a (non-encoded) Unicode string, while C<decode> expects thus a
263unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 293Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
264to be done yourself, e.g. using the Encode module. 294to be done yourself, e.g. using the Encode module.
265 295
266Example, output UTF-16BE-encoded JSON: 296Example, output UTF-16BE-encoded JSON:
267 297
268 use Encode; 298 use Encode;
290 ] 320 ]
291 } 321 }
292 322
293=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
294 324
325=item $enabled = $json->get_indent
326
295If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
296format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
297into its own line, identing them properly. 329into its own line, indenting them properly.
298 330
299If C<$enable> is false, no newlines or indenting will be produced, and the 331If C<$enable> is false, no newlines or indenting will be produced, and the
300resulting JSON text is guarenteed not to contain any C<newlines>. 332resulting JSON text is guaranteed not to contain any C<newlines>.
301 333
302This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
303 335
304=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
337
338=item $enabled = $json->get_space_before
305 339
306If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
307optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
308 342
309If C<$enable> is false, then the C<encode> method will not add any extra 343If C<$enable> is false, then the C<encode> method will not add any extra
315Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
316 350
317 {"key" :"value"} 351 {"key" :"value"}
318 352
319=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
320 356
321If C<$enable> is true (or missing), then the C<encode> method will add an extra 357If C<$enable> is true (or missing), then the C<encode> method will add an extra
322optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
323and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
324members. 360members.
331Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
332 368
333 {"key": "value"} 369 {"key": "value"}
334 370
335=item $json = $json->relaxed ([$enable]) 371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
336 374
337If C<$enable> is true (or missing), then C<decode> will accept some 375If C<$enable> is true (or missing), then C<decode> will accept some
338extensions to normal JSON syntax (see below). C<encode> will not be 376extensions to normal JSON syntax (see below). C<encode> will not be
339affected in anyway. I<Be aware that this option makes you accept invalid 377affected in anyway. I<Be aware that this option makes you accept invalid
340JSON texts as if they were valid!>. I suggest only to use this option to 378JSON texts as if they were valid!>. I suggest only to use this option to
377 415
378=back 416=back
379 417
380=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
381 419
420=item $enabled = $json->get_canonical
421
382If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
383by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
384 424
385If C<$enable> is false, then the C<encode> method will output key-value 425If C<$enable> is false, then the C<encode> method will output key-value
386pairs in the order Perl stores them (which will likely change between runs 426pairs in the order Perl stores them (which will likely change between runs
387of the same script). 427of the same script).
388 428
389This option is useful if you want the same data structure to be encoded as 429This option is useful if you want the same data structure to be encoded as
390the same JSON text (given the same overall settings). If it is disabled, 430the same JSON text (given the same overall settings). If it is disabled,
391the same hash migh be encoded differently even if contains the same data, 431the same hash might be encoded differently even if contains the same data,
392as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
393 433
394This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
395 435
396=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
397 439
398If C<$enable> is true (or missing), then the C<encode> method can convert a 440If C<$enable> is true (or missing), then the C<encode> method can convert a
399non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
400which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 442which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
401values instead of croaking. 443values instead of croaking.
411 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
412 => "Hello, World!" 454 => "Hello, World!"
413 455
414=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
415 457
458=item $enabled = $json->get_allow_blessed
459
416If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
417barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
418B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
419disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
420object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
421encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
422 466
423If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
424exception when it encounters a blessed object. 468exception when it encounters a blessed object.
425 469
426=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
427 473
428If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
429blessed object, will check for the availability of the C<TO_JSON> method 475blessed object, will check for the availability of the C<TO_JSON> method
430on the object's class. If found, it will be called in scalar context 476on the object's class. If found, it will be called in scalar context
431and the resulting scalar will be encoded instead of the object. If no 477and the resulting scalar will be encoded instead of the object. If no
435The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> 481The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
436returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
437way. C<TO_JSON> must take care of not causing an endless recursion cycle 483way. C<TO_JSON> must take care of not causing an endless recursion cycle
438(== crash) in this case. The name of C<TO_JSON> was chosen because other 484(== crash) in this case. The name of C<TO_JSON> was chosen because other
439methods called by the Perl core (== not by the user of the object) are 485methods called by the Perl core (== not by the user of the object) are
440usually in upper case letters and to avoid collisions with the C<to_json> 486usually in upper case letters and to avoid collisions with any C<to_json>
441function. 487function or method.
442 488
443This setting does not yet influence C<decode> in any way, but in the 489This setting does not yet influence C<decode> in any way, but in the
444future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
445enabled by this setting. 491enabled by this setting.
446 492
488 534
489As this callback gets called less often then the C<filter_json_object> 535As this callback gets called less often then the C<filter_json_object>
490one, decoding speed will not usually suffer as much. Therefore, single-key 536one, decoding speed will not usually suffer as much. Therefore, single-key
491objects make excellent targets to serialise Perl objects into, especially 537objects make excellent targets to serialise Perl objects into, especially
492as single-key JSON objects are as close to the type-tagged value concept 538as single-key JSON objects are as close to the type-tagged value concept
493as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not 539as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
494support this in any way, so you need to make sure your data never looks 540support this in any way, so you need to make sure your data never looks
495like a serialised Perl hash. 541like a serialised Perl hash.
496 542
497Typical names for the single object key are C<__class_whatever__>, or 543Typical names for the single object key are C<__class_whatever__>, or
498C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
522 568
523 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
524 } 570 }
525 571
526=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
527 575
528Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
529strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
530C<encode> or C<decode> to their minimum size possible. This can save 578C<encode> or C<decode> to their minimum size possible. This can save
531memory when your JSON texts are either very very long or you have many 579memory when your JSON texts are either very very long or you have many
549strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
550internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
551 599
552=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
553 601
602=item $max_depth = $json->get_max_depth
603
554Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
555or decoding. If the JSON text or Perl data structure has an equal or 605or decoding. If the JSON text or Perl data structure has an equal or
556higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
557stop and croak at that point. 607stop and croak at that point.
558 608
569used, which is rarely useful. 619used, which is rarely useful.
570 620
571See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
572 622
573=item $json = $json->max_size ([$maximum_string_size]) 623=item $json = $json->max_size ([$maximum_string_size])
624
625=item $max_size = $json->get_max_size
574 626
575Set the maximum length a JSON text may have (in bytes) where decoding is 627Set the maximum length a JSON text may have (in bytes) where decoding is
576being attempted. The default is C<0>, meaning no limit. When C<decode> 628being attempted. The default is C<0>, meaning no limit. When C<decode>
577is called on a string longer then this number of characters it will not 629is called on a string longer then this number of characters it will not
578attempt to decode the string but throw an exception. This setting has no 630attempt to decode the string but throw an exception. This setting has no
625vice versa. These mappings are designed to "do the right thing" in most 677vice versa. These mappings are designed to "do the right thing" in most
626circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
627(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
628 680
629For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
630lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
631refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
632 684
633 685
634=head2 JSON -> PERL 686=head2 JSON -> PERL
635 687
636=over 4 688=over 4
637 689
638=item object 690=item object
639 691
640A JSON object becomes a reference to a hash in Perl. No ordering of object 692A JSON object becomes a reference to a hash in Perl. No ordering of object
641keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
642 694
643=item array 695=item array
644 696
645A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
646 698
672 724
673=item true, false 725=item true, false
674 726
675These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 727These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
676respectively. They are overloaded to act almost exactly like the numbers 728respectively. They are overloaded to act almost exactly like the numbers
677C<1> and C<0>. You can check wether a scalar is a JSON boolean by using 729C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
678the C<JSON::XS::is_bool> function. 730the C<JSON::XS::is_bool> function.
679 731
680=item null 732=item null
681 733
682A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
713Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
714exception to be thrown, except for references to the integers C<0> and 766exception to be thrown, except for references to the integers C<0> and
715C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 767C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
716also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 768also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
717 769
718 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
719 771
720=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
721 773
722These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
723respectively. You can also use C<\1> and C<\0> directly if you want. 775respectively. You can also use C<\1> and C<\0> directly if you want.
734difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
735JSON null value, scalars that have last been used in a string context 787JSON null value, scalars that have last been used in a string context
736before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
737 789
738 # dump as number 790 # dump as number
739 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
740 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
741 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
742 794
743 # used as string, so dump as string 795 # used as string, so dump as string
744 print $value; 796 print $value;
745 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
746 798
747 # undef becomes null 799 # undef becomes null
748 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
749 801
750You can force the type to be a string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
751 803
752 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
753 "$x"; # stringified 805 "$x"; # stringified
754 $x .= ""; # another, more awkward way to stringify 806 $x .= ""; # another, more awkward way to stringify
755 print $x; # perl does it for you, too, quite often 807 print $x; # perl does it for you, too, quite often
756 808
757You can force the type to be a number by numifying it: 809You can force the type to be a JSON number by numifying it:
758 810
759 my $x = "3"; # some variable containing a string 811 my $x = "3"; # some variable containing a string
760 $x += 0; # numify it, ensuring it will be dumped as a number 812 $x += 0; # numify it, ensuring it will be dumped as a number
761 $x *= 1; # same thing, the choise is yours. 813 $x *= 1; # same thing, the choice is yours.
762 814
763You can not currently output JSON booleans or force the type in other, 815You can not currently force the type in other, less obscure, ways. Tell me
764less obscure, ways. Tell me if you need this capability. 816if you need this capability.
765 817
766=back 818=back
767 819
768 820
769=head1 COMPARISON 821=head1 COMPARISON
778 830
779=item JSON 1.07 831=item JSON 1.07
780 832
781Slow (but very portable, as it is written in pure Perl). 833Slow (but very portable, as it is written in pure Perl).
782 834
783Undocumented/buggy Unicode handling (how JSON handles unicode values is 835Undocumented/buggy Unicode handling (how JSON handles Unicode values is
784undocumented. One can get far by feeding it unicode strings and doing 836undocumented. One can get far by feeding it Unicode strings and doing
785en-/decoding oneself, but unicode escapes are not working properly). 837en-/decoding oneself, but Unicode escapes are not working properly).
786 838
787No roundtripping (strings get clobbered if they look like numbers, e.g. 839No round-tripping (strings get clobbered if they look like numbers, e.g.
788the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 840the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
789decode into the number 2. 841decode into the number 2.
790 842
791=item JSON::PC 0.01 843=item JSON::PC 0.01
792 844
793Very fast. 845Very fast.
794 846
795Undocumented/buggy Unicode handling. 847Undocumented/buggy Unicode handling.
796 848
797No roundtripping. 849No round-tripping.
798 850
799Has problems handling many Perl values (e.g. regex results and other magic 851Has problems handling many Perl values (e.g. regex results and other magic
800values will make it croak). 852values will make it croak).
801 853
802Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 854Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
812Very inflexible (no human-readable format supported, format pretty much 864Very inflexible (no human-readable format supported, format pretty much
813undocumented. I need at least a format for easy reading by humans and a 865undocumented. I need at least a format for easy reading by humans and a
814single-line compact format for use in a protocol, and preferably a way to 866single-line compact format for use in a protocol, and preferably a way to
815generate ASCII-only JSON texts). 867generate ASCII-only JSON texts).
816 868
817Completely broken (and confusingly documented) Unicode handling (unicode 869Completely broken (and confusingly documented) Unicode handling (Unicode
818escapes are not working properly, you need to set ImplicitUnicode to 870escapes are not working properly, you need to set ImplicitUnicode to
819I<different> values on en- and decoding to get symmetric behaviour). 871I<different> values on en- and decoding to get symmetric behaviour).
820 872
821No roundtripping (simple cases work, but this depends on wether the scalar 873No round-tripping (simple cases work, but this depends on whether the scalar
822value was used in a numeric context or not). 874value was used in a numeric context or not).
823 875
824Dumping hashes may skip hash values depending on iterator state. 876Dumping hashes may skip hash values depending on iterator state.
825 877
826Unmaintained (maintainer unresponsive for many months, bugs are not 878Unmaintained (maintainer unresponsive for many months, bugs are not
827getting fixed). 879getting fixed).
828 880
829Does not check input for validity (i.e. will accept non-JSON input and 881Does not check input for validity (i.e. will accept non-JSON input and
830return "something" instead of raising an exception. This is a security 882return "something" instead of raising an exception. This is a security
831issue: imagine two banks transfering money between each other using 883issue: imagine two banks transferring money between each other using
832JSON. One bank might parse a given non-JSON request and deduct money, 884JSON. One bank might parse a given non-JSON request and deduct money,
833while the other might reject the transaction with a syntax error. While a 885while the other might reject the transaction with a syntax error. While a
834good protocol will at least recover, that is extra unnecessary work and 886good protocol will at least recover, that is extra unnecessary work and
835the transaction will still not succeed). 887the transaction will still not succeed).
836 888
837=item JSON::DWIW 0.04 889=item JSON::DWIW 0.04
838 890
839Very fast. Very natural. Very nice. 891Very fast. Very natural. Very nice.
840 892
841Undocumented unicode handling (but the best of the pack. Unicode escapes 893Undocumented Unicode handling (but the best of the pack. Unicode escapes
842still don't get parsed properly). 894still don't get parsed properly).
843 895
844Very inflexible. 896Very inflexible.
845 897
846No roundtripping. 898No round-tripping.
847 899
848Does not generate valid JSON texts (key strings are often unquoted, empty keys 900Does not generate valid JSON texts (key strings are often unquoted, empty keys
849result in nothing being output) 901result in nothing being output)
850 902
851Does not check input for validity. 903Does not check input for validity.
866 my $yaml = $to_yaml->encode ($ref) . "\n"; 918 my $yaml = $to_yaml->encode ($ref) . "\n";
867 919
868This will usually generate JSON texts that also parse as valid 920This will usually generate JSON texts that also parse as valid
869YAML. Please note that YAML has hardcoded limits on (simple) object key 921YAML. Please note that YAML has hardcoded limits on (simple) object key
870lengths that JSON doesn't have, so you should make sure that your hash 922lengths that JSON doesn't have, so you should make sure that your hash
871keys are noticably shorter than the 1024 characters YAML allows. 923keys are noticeably shorter than the 1024 characters YAML allows.
872 924
873There might be other incompatibilities that I am not aware of. In general 925There might be other incompatibilities that I am not aware of. In general
874you should not try to generate YAML with a JSON generator or vice versa, 926you should not try to generate YAML with a JSON generator or vice versa,
875or try to parse JSON with a YAML parser or vice versa: chances are high 927or try to parse JSON with a YAML parser or vice versa: chances are high
876that you will run into severe interoperability problems. 928that you will run into severe interoperability problems.
892It shows the number of encodes/decodes per second (JSON::XS uses 944It shows the number of encodes/decodes per second (JSON::XS uses
893the functional interface, while JSON::XS/2 uses the OO interface 945the functional interface, while JSON::XS/2 uses the OO interface
894with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 946with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
895shrink). Higher is better: 947shrink). Higher is better:
896 948
897 Storable | 15779.925 | 14169.946 |
898 -----------+------------+------------+
899 module | encode | decode | 949 module | encode | decode |
900 -----------|------------|------------| 950 -----------|------------|------------|
901 JSON | 4990.842 | 4088.813 | 951 JSON 1.x | 4990.842 | 4088.813 |
902 JSON::DWIW | 51653.990 | 71575.154 | 952 JSON::DWIW | 51653.990 | 71575.154 |
903 JSON::PC | 65948.176 | 74631.744 | 953 JSON::PC | 65948.176 | 74631.744 |
904 JSON::PP | 8931.652 | 3817.168 | 954 JSON::PP | 8931.652 | 3817.168 |
905 JSON::Syck | 24877.248 | 27776.848 | 955 JSON::Syck | 24877.248 | 27776.848 |
906 JSON::XS | 388361.481 | 227951.304 | 956 JSON::XS | 388361.481 | 227951.304 |
908 JSON::XS/3 | 338250.323 | 218453.333 | 958 JSON::XS/3 | 338250.323 | 218453.333 |
909 Storable | 16500.016 | 135300.129 | 959 Storable | 16500.016 | 135300.129 |
910 -----------+------------+------------+ 960 -----------+------------+------------+
911 961
912That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 962That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
913about three times faster on decoding, and over fourty times faster 963about three times faster on decoding, and over forty times faster
914than JSON, even with pretty-printing and key sorting. It also compares 964than JSON, even with pretty-printing and key sorting. It also compares
915favourably to Storable for small amounts of data. 965favourably to Storable for small amounts of data.
916 966
917Using a longer test string (roughly 18KB, generated from Yahoo! Locals 967Using a longer test string (roughly 18KB, generated from Yahoo! Locals
918search API (http://nanoref.com/yahooapis/mgPdGg): 968search API (http://nanoref.com/yahooapis/mgPdGg):
919 969
920 module | encode | decode | 970 module | encode | decode |
921 -----------|------------|------------| 971 -----------|------------|------------|
922 JSON | 55.260 | 34.971 | 972 JSON 1.x | 55.260 | 34.971 |
923 JSON::DWIW | 825.228 | 1082.513 | 973 JSON::DWIW | 825.228 | 1082.513 |
924 JSON::PC | 3571.444 | 2394.829 | 974 JSON::PC | 3571.444 | 2394.829 |
925 JSON::PP | 210.987 | 32.574 | 975 JSON::PP | 210.987 | 32.574 |
926 JSON::Syck | 552.551 | 787.544 | 976 JSON::Syck | 552.551 | 787.544 |
927 JSON::XS | 5780.463 | 4854.519 | 977 JSON::XS | 5780.463 | 4854.519 |
931 -----------+------------+------------+ 981 -----------+------------+------------+
932 982
933Again, JSON::XS leads by far (except for Storable which non-surprisingly 983Again, JSON::XS leads by far (except for Storable which non-surprisingly
934decodes faster). 984decodes faster).
935 985
936On large strings containing lots of high unicode characters, some modules 986On large strings containing lots of high Unicode characters, some modules
937(such as JSON::PC) seem to decode faster than JSON::XS, but the result 987(such as JSON::PC) seem to decode faster than JSON::XS, but the result
938will be broken due to missing (or wrong) unicode handling. Others refuse 988will be broken due to missing (or wrong) Unicode handling. Others refuse
939to decode or encode properly, so it was impossible to prepare a fair 989to decode or encode properly, so it was impossible to prepare a fair
940comparison table for that case. 990comparison table for that case.
941 991
942 992
943=head1 SECURITY CONSIDERATIONS 993=head1 SECURITY CONSIDERATIONS
949any buffer overflows. Obviously, this module should ensure that and I am 999any buffer overflows. Obviously, this module should ensure that and I am
950trying hard on making that true, but you never know. 1000trying hard on making that true, but you never know.
951 1001
952Second, you need to avoid resource-starving attacks. That means you should 1002Second, you need to avoid resource-starving attacks. That means you should
953limit the size of JSON texts you accept, or make sure then when your 1003limit the size of JSON texts you accept, or make sure then when your
954resources run out, thats just fine (e.g. by using a separate process that 1004resources run out, that's just fine (e.g. by using a separate process that
955can crash safely). The size of a JSON text in octets or characters is 1005can crash safely). The size of a JSON text in octets or characters is
956usually a good indication of the size of the resources required to decode 1006usually a good indication of the size of the resources required to decode
957it into a Perl structure. While JSON::XS can check the size of the JSON 1007it into a Perl structure. While JSON::XS can check the size of the JSON
958text, it might be too late when you already have it in memory, so you 1008text, it might be too late when you already have it in memory, so you
959might want to check the size before you accept the string. 1009might want to check the size before you accept the string.
960 1010
961Third, JSON::XS recurses using the C stack when decoding objects and 1011Third, JSON::XS recurses using the C stack when decoding objects and
962arrays. The C stack is a limited resource: for instance, on my amd64 1012arrays. The C stack is a limited resource: for instance, on my amd64
963machine with 8MB of stack size I can decode around 180k nested arrays but 1013machine with 8MB of stack size I can decode around 180k nested arrays but
964only 14k nested JSON objects (due to perl itself recursing deeply on croak 1014only 14k nested JSON objects (due to perl itself recursing deeply on croak
965to free the temporary). If that is exceeded, the program crashes. to be 1015to free the temporary). If that is exceeded, the program crashes. To be
966conservative, the default nesting limit is set to 512. If your process 1016conservative, the default nesting limit is set to 512. If your process
967has a smaller stack, you should adjust this setting accordingly with the 1017has a smaller stack, you should adjust this setting accordingly with the
968C<max_depth> method. 1018C<max_depth> method.
969 1019
970And last but least, something else could bomb you that I forgot to think 1020And last but least, something else could bomb you that I forgot to think
971of. In that case, you get to keep the pieces. I am always open for hints, 1021of. In that case, you get to keep the pieces. I am always open for hints,
972though... 1022though...
973 1023
974If you are using JSON::XS to return packets to consumption 1024If you are using JSON::XS to return packets to consumption
975by javascript scripts in a browser you should have a look at 1025by JavaScript scripts in a browser you should have a look at
976L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1026L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
977you are vulnerable to some common attack vectors (which really are browser 1027you are vulnerable to some common attack vectors (which really are browser
978design bugs, but it is still you who will have to deal with it, as major 1028design bugs, but it is still you who will have to deal with it, as major
979browser developers care only for features, not about doing security 1029browser developers care only for features, not about getting security
980right). 1030right).
1031
1032
1033=head1 THREADS
1034
1035This module is I<not> guaranteed to be thread safe and there are no
1036plans to change this until Perl gets thread support (as opposed to the
1037horribly slow so-called "threads" which are simply slow and bloated
1038process simulations - use fork, its I<much> faster, cheaper, better).
1039
1040(It might actually work, but you have been warned).
981 1041
982 1042
983=head1 BUGS 1043=head1 BUGS
984 1044
985While the goal of this module is to be correct, that unfortunately does 1045While the goal of this module is to be correct, that unfortunately does
986not mean its bug-free, only that I think its design is bug-free. It is 1046not mean its bug-free, only that I think its design is bug-free. It is
987still relatively early in its development. If you keep reporting bugs they 1047still relatively early in its development. If you keep reporting bugs they
988will be fixed swiftly, though. 1048will be fixed swiftly, though.
1049
1050Please refrain from using rt.cpan.org or any other bug reporting
1051service. I put the contact address into my modules for a reason.
989 1052
990=cut 1053=cut
991 1054
992our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1055our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
993our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1056our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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