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Revision 1.65 by root, Sat Oct 13 01:55:31 2007 UTC vs.
Revision 1.72 by root, Sun Nov 25 19:11:07 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
42 40
43=head2 FEATURES 41=head2 FEATURES
44 42
45=over 4 43=over 4
46 44
47=item * correct unicode handling 45=item * correct Unicode handling
48 46
49This 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
50it does so. 48it does so.
51 49
52=item * round-trip integrity 50=item * round-trip integrity
72This 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
73interface. 71interface.
74 72
75=item * reasonably versatile output formats 73=item * reasonably versatile output formats
76 74
77You can choose between the most compact guarenteed single-line format 75You can choose between the most compact guaranteed single-line format
78possible (nice for simple line-based protocols), a pure-ascii format 76possible (nice for simple line-based protocols), a pure-ascii format
79(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
80unicode 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
81stuff). Or you can combine those features in whatever way you like. 79stuff). Or you can combine those features in whatever way you like.
82 80
83=back 81=back
84 82
85=cut 83=cut
86 84
87package JSON::XS; 85package JSON::XS;
88 86
89use strict; 87use strict;
90 88
91our $VERSION = '1.51'; 89our $VERSION = '1.53';
92our @ISA = qw(Exporter); 90our @ISA = qw(Exporter);
93 91
94our @EXPORT = qw(to_json from_json); 92our @EXPORT = qw(to_json from_json);
95 93
96use Exporter; 94use Exporter;
97use XSLoader; 95use XSLoader;
98 96
99=head1 FUNCTIONAL INTERFACE 97=head1 FUNCTIONAL INTERFACE
100 98
101The following convinience methods are provided by this module. They are 99The following convenience methods are provided by this module. They are
102exported by default: 100exported by default:
103 101
104=over 4 102=over 4
105 103
106=item $json_text = to_json $perl_scalar 104=item $json_text = to_json $perl_scalar
145 143
146=over 4 144=over 4
147 145
148=item 1. Perl strings can store characters with ordinal values > 255. 146=item 1. Perl strings can store characters with ordinal values > 255.
149 147
150This enables you to store unicode characters as single characters in a 148This enables you to store Unicode characters as single characters in a
151Perl string - very natural. 149Perl string - very natural.
152 150
153=item 2. Perl does I<not> associate an encoding with your strings. 151=item 2. Perl does I<not> associate an encoding with your strings.
154 152
155Unless you force it to, e.g. when matching it against a regex, or printing 153Unless you force it to, e.g. when matching it against a regex, or printing
162encoding of your string. 160encoding of your string.
163 161
164Just ignore that flag unless you debug a Perl bug, a module written in 162Just 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 163XS 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 164confuse 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 165is 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 166flag clear, and you can have binary data with that flag set and that flag
169clear. Other possibilities exist, too. 167clear. Other possibilities exist, too.
170 168
171If you didn't know about that flag, just the better, pretend it doesn't 169If you didn't know about that flag, just the better, pretend it doesn't
172exist. 170exist.
177If you have UTF-8 encoded data, it is no longer a Unicode string, but a 175If 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. 176Unicode string encoded in UTF-8, giving you a binary string.
179 177
180=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. 178=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
181 179
182Its a fact. Learn to live with it. 180It's a fact. Learn to live with it.
183 181
184=back 182=back
185 183
186I hope this helps :) 184I hope this helps :)
187 185
204 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]})
205 => {"a": [1, 2]} 203 => {"a": [1, 2]}
206 204
207=item $json = $json->ascii ([$enable]) 205=item $json = $json->ascii ([$enable])
208 206
207=item $enabled = $json->get_ascii
208
209If C<$enable> is true (or missing), then the C<encode> method will not 209If C<$enable> is true (or missing), then the C<encode> method will not
210generate characters outside the code range C<0..127> (which is ASCII). Any 210generate characters outside the code range C<0..127> (which is ASCII). Any
211unicode characters outside that range will be escaped using either a 211Unicode characters outside that range will be escaped using either a
212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
213as per RFC4627. The resulting encoded JSON text can be treated as a native 213as per RFC4627. The resulting encoded JSON text can be treated as a native
214unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 214Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
215or any other superset of ASCII. 215or any other superset of ASCII.
216 216
217If C<$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
218characters unless required by the JSON syntax or other flags. This results 218characters unless required by the JSON syntax or other flags. This results
219in a faster and more compact format. 219in a faster and more compact format.
225 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 225 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
226 => ["\ud801\udc01"] 226 => ["\ud801\udc01"]
227 227
228=item $json = $json->latin1 ([$enable]) 228=item $json = $json->latin1 ([$enable])
229 229
230=item $enabled = $json->get_latin1
231
230If C<$enable> is true (or missing), then the C<encode> method will encode 232If C<$enable> is true (or missing), then the C<encode> method will encode
231the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 233the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
232outside the code range C<0..255>. The resulting string can be treated as a 234outside the code range C<0..255>. The resulting string can be treated as a
233latin1-encoded JSON text or a native unicode string. The C<decode> method 235latin1-encoded JSON text or a native Unicode string. The C<decode> method
234will not be affected in any way by this flag, as C<decode> by default 236will not be affected in any way by this flag, as C<decode> by default
235expects unicode, which is a strict superset of latin1. 237expects Unicode, which is a strict superset of latin1.
236 238
237If C<$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
238characters unless required by the JSON syntax or other flags. 240characters unless required by the JSON syntax or other flags.
239 241
240The 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
241text, 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
242size. The disadvantage is that the resulting JSON text is encoded 244size. The disadvantage is that the resulting JSON text is encoded
243in latin1 (and must correctly be treated as such when storing and 245in latin1 (and must correctly be treated as such when storing and
244transfering), a rare encoding for JSON. It is therefore most useful when 246transferring), a rare encoding for JSON. It is therefore most useful when
245you want to store data structures known to contain binary data efficiently 247you want to store data structures known to contain binary data efficiently
246in files or databases, not when talking to other JSON encoders/decoders. 248in files or databases, not when talking to other JSON encoders/decoders.
247 249
248 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 250 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
249 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 251 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
250 252
251=item $json = $json->utf8 ([$enable]) 253=item $json = $json->utf8 ([$enable])
254
255=item $enabled = $json->get_utf8
252 256
253If C<$enable> is true (or missing), then the C<encode> method will encode 257If C<$enable> is true (or missing), then the C<encode> method will encode
254the JSON result into UTF-8, as required by many protocols, while the 258the JSON result into UTF-8, as required by many protocols, while the
255C<decode> method expects to be handled an UTF-8-encoded string. Please 259C<decode> method expects to be handled an UTF-8-encoded string. Please
256note that UTF-8-encoded strings do not contain any characters outside the 260note that UTF-8-encoded strings do not contain any characters outside the
257range C<0..255>, they are thus useful for bytewise/binary I/O. In future 261range C<0..255>, they are thus useful for bytewise/binary I/O. In future
258versions, enabling this option might enable autodetection of the UTF-16 262versions, enabling this option might enable autodetection of the UTF-16
259and UTF-32 encoding families, as described in RFC4627. 263and UTF-32 encoding families, as described in RFC4627.
260 264
261If C<$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
262string 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
263unicode 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
264to be done yourself, e.g. using the Encode module. 268to be done yourself, e.g. using the Encode module.
265 269
266Example, output UTF-16BE-encoded JSON: 270Example, output UTF-16BE-encoded JSON:
267 271
268 use Encode; 272 use Encode;
272 276
273 use Encode; 277 use Encode;
274 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); 278 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
275 279
276=item $json = $json->pretty ([$enable]) 280=item $json = $json->pretty ([$enable])
281
282=item $enabled = $json->get_pretty
277 283
278This enables (or disables) all of the C<indent>, C<space_before> and 284This enables (or disables) all of the C<indent>, C<space_before> and
279C<space_after> (and in the future possibly more) flags in one call to 285C<space_after> (and in the future possibly more) flags in one call to
280generate the most readable (or most compact) form possible. 286generate the most readable (or most compact) form possible.
281 287
290 ] 296 ]
291 } 297 }
292 298
293=item $json = $json->indent ([$enable]) 299=item $json = $json->indent ([$enable])
294 300
301=item $enabled = $json->get_indent
302
295If C<$enable> is true (or missing), then the C<encode> method will use a multiline 303If C<$enable> is true (or missing), then the C<encode> method will use a multiline
296format as output, putting every array member or object/hash key-value pair 304format as output, putting every array member or object/hash key-value pair
297into its own line, identing them properly. 305into its own line, indenting them properly.
298 306
299If C<$enable> is false, no newlines or indenting will be produced, and the 307If C<$enable> is false, no newlines or indenting will be produced, and the
300resulting JSON text is guarenteed not to contain any C<newlines>. 308resulting JSON text is guaranteed not to contain any C<newlines>.
301 309
302This setting has no effect when decoding JSON texts. 310This setting has no effect when decoding JSON texts.
303 311
304=item $json = $json->space_before ([$enable]) 312=item $json = $json->space_before ([$enable])
313
314=item $enabled = $json->get_space_before
305 315
306If C<$enable> is true (or missing), then the C<encode> method will add an extra 316If C<$enable> is true (or missing), then the C<encode> method will add an extra
307optional space before the C<:> separating keys from values in JSON objects. 317optional space before the C<:> separating keys from values in JSON objects.
308 318
309If C<$enable> is false, then the C<encode> method will not add any extra 319If C<$enable> is false, then the C<encode> method will not add any extra
315Example, space_before enabled, space_after and indent disabled: 325Example, space_before enabled, space_after and indent disabled:
316 326
317 {"key" :"value"} 327 {"key" :"value"}
318 328
319=item $json = $json->space_after ([$enable]) 329=item $json = $json->space_after ([$enable])
330
331=item $enabled = $json->get_space_after
320 332
321If C<$enable> is true (or missing), then the C<encode> method will add an extra 333If C<$enable> is true (or missing), then the C<encode> method will add an extra
322optional space after the C<:> separating keys from values in JSON objects 334optional space after the C<:> separating keys from values in JSON objects
323and extra whitespace after the C<,> separating key-value pairs and array 335and extra whitespace after the C<,> separating key-value pairs and array
324members. 336members.
331Example, space_before and indent disabled, space_after enabled: 343Example, space_before and indent disabled, space_after enabled:
332 344
333 {"key": "value"} 345 {"key": "value"}
334 346
335=item $json = $json->relaxed ([$enable]) 347=item $json = $json->relaxed ([$enable])
348
349=item $enabled = $json->get_relaxed
336 350
337If C<$enable> is true (or missing), then C<decode> will accept some 351If C<$enable> is true (or missing), then C<decode> will accept some
338extensions to normal JSON syntax (see below). C<encode> will not be 352extensions to normal JSON syntax (see below). C<encode> will not be
339affected in anyway. I<Be aware that this option makes you accept invalid 353affected 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 354JSON texts as if they were valid!>. I suggest only to use this option to
377 391
378=back 392=back
379 393
380=item $json = $json->canonical ([$enable]) 394=item $json = $json->canonical ([$enable])
381 395
396=item $enabled = $json->get_canonical
397
382If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 398If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
383by sorting their keys. This is adding a comparatively high overhead. 399by sorting their keys. This is adding a comparatively high overhead.
384 400
385If C<$enable> is false, then the C<encode> method will output key-value 401If C<$enable> is false, then the C<encode> method will output key-value
386pairs in the order Perl stores them (which will likely change between runs 402pairs in the order Perl stores them (which will likely change between runs
387of the same script). 403of the same script).
388 404
389This option is useful if you want the same data structure to be encoded as 405This option is useful if you want the same data structure to be encoded as
390the same JSON text (given the same overall settings). If it is disabled, 406the same JSON text (given the same overall settings). If it is disabled,
391the same hash migh be encoded differently even if contains the same data, 407the same hash might be encoded differently even if contains the same data,
392as key-value pairs have no inherent ordering in Perl. 408as key-value pairs have no inherent ordering in Perl.
393 409
394This setting has no effect when decoding JSON texts. 410This setting has no effect when decoding JSON texts.
395 411
396=item $json = $json->allow_nonref ([$enable]) 412=item $json = $json->allow_nonref ([$enable])
413
414=item $enabled = $json->get_allow_nonref
397 415
398If C<$enable> is true (or missing), then the C<encode> method can convert a 416If C<$enable> is true (or missing), then the C<encode> method can convert a
399non-reference into its corresponding string, number or null JSON value, 417non-reference into its corresponding string, number or null JSON value,
400which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 418which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
401values instead of croaking. 419values instead of croaking.
411 JSON::XS->new->allow_nonref->encode ("Hello, World!") 429 JSON::XS->new->allow_nonref->encode ("Hello, World!")
412 => "Hello, World!" 430 => "Hello, World!"
413 431
414=item $json = $json->allow_blessed ([$enable]) 432=item $json = $json->allow_blessed ([$enable])
415 433
434=item $enabled = $json->get_allow_bless
435
416If C<$enable> is true (or missing), then the C<encode> method will not 436If C<$enable> is true (or missing), then the C<encode> method will not
417barf when it encounters a blessed reference. Instead, the value of the 437barf when it encounters a blessed reference. Instead, the value of the
418B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 438B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
419disabled or no C<to_json> method found) or a representation of the 439disabled or no C<to_json> method found) or a representation of the
420object (C<convert_blessed> enabled and C<to_json> method found) is being 440object (C<convert_blessed> enabled and C<to_json> method found) is being
421encoded. Has no effect on C<decode>. 441encoded. Has no effect on C<decode>.
422 442
423If C<$enable> is false (the default), then C<encode> will throw an 443If C<$enable> is false (the default), then C<encode> will throw an
424exception when it encounters a blessed object. 444exception when it encounters a blessed object.
425 445
426=item $json = $json->convert_blessed ([$enable]) 446=item $json = $json->convert_blessed ([$enable])
447
448=item $enabled = $json->get_convert_blessed
427 449
428If C<$enable> is true (or missing), then C<encode>, upon encountering a 450If C<$enable> is true (or missing), then C<encode>, upon encountering a
429blessed object, will check for the availability of the C<TO_JSON> method 451blessed object, will check for the availability of the C<TO_JSON> method
430on the object's class. If found, it will be called in scalar context 452on the object's class. If found, it will be called in scalar context
431and the resulting scalar will be encoded instead of the object. If no 453and the resulting scalar will be encoded instead of the object. If no
488 510
489As this callback gets called less often then the C<filter_json_object> 511As this callback gets called less often then the C<filter_json_object>
490one, decoding speed will not usually suffer as much. Therefore, single-key 512one, decoding speed will not usually suffer as much. Therefore, single-key
491objects make excellent targets to serialise Perl objects into, especially 513objects make excellent targets to serialise Perl objects into, especially
492as single-key JSON objects are as close to the type-tagged value concept 514as single-key JSON objects are as close to the type-tagged value concept
493as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not 515as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
494support this in any way, so you need to make sure your data never looks 516support this in any way, so you need to make sure your data never looks
495like a serialised Perl hash. 517like a serialised Perl hash.
496 518
497Typical names for the single object key are C<__class_whatever__>, or 519Typical names for the single object key are C<__class_whatever__>, or
498C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 520C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
522 544
523 { __widget__ => $self->{id} } 545 { __widget__ => $self->{id} }
524 } 546 }
525 547
526=item $json = $json->shrink ([$enable]) 548=item $json = $json->shrink ([$enable])
549
550=item $enabled = $json->get_shrink
527 551
528Perl usually over-allocates memory a bit when allocating space for 552Perl usually over-allocates memory a bit when allocating space for
529strings. This flag optionally resizes strings generated by either 553strings. This flag optionally resizes strings generated by either
530C<encode> or C<decode> to their minimum size possible. This can save 554C<encode> or C<decode> to their minimum size possible. This can save
531memory when your JSON texts are either very very long or you have many 555memory when your JSON texts are either very very long or you have many
549strings that look like integers or floats into integers or floats 573strings that look like integers or floats into integers or floats
550internally (there is no difference on the Perl level), saving space. 574internally (there is no difference on the Perl level), saving space.
551 575
552=item $json = $json->max_depth ([$maximum_nesting_depth]) 576=item $json = $json->max_depth ([$maximum_nesting_depth])
553 577
578=item $max_depth = $json->get_max_depth
579
554Sets the maximum nesting level (default C<512>) accepted while encoding 580Sets the maximum nesting level (default C<512>) accepted while encoding
555or decoding. If the JSON text or Perl data structure has an equal or 581or decoding. If the JSON text or Perl data structure has an equal or
556higher nesting level then this limit, then the encoder and decoder will 582higher nesting level then this limit, then the encoder and decoder will
557stop and croak at that point. 583stop and croak at that point.
558 584
569used, which is rarely useful. 595used, which is rarely useful.
570 596
571See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 597See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
572 598
573=item $json = $json->max_size ([$maximum_string_size]) 599=item $json = $json->max_size ([$maximum_string_size])
600
601=item $max_size = $json->get_max_size
574 602
575Set the maximum length a JSON text may have (in bytes) where decoding is 603Set the maximum length a JSON text may have (in bytes) where decoding is
576being attempted. The default is C<0>, meaning no limit. When C<decode> 604being attempted. The default is C<0>, meaning no limit. When C<decode>
577is called on a string longer then this number of characters it will not 605is called on a string longer then this number of characters it will not
578attempt to decode the string but throw an exception. This setting has no 606attempt to decode the string but throw an exception. This setting has no
625vice versa. These mappings are designed to "do the right thing" in most 653vice versa. These mappings are designed to "do the right thing" in most
626circumstances automatically, preserving round-tripping characteristics 654circumstances automatically, preserving round-tripping characteristics
627(what you put in comes out as something equivalent). 655(what you put in comes out as something equivalent).
628 656
629For the more enlightened: note that in the following descriptions, 657For the more enlightened: note that in the following descriptions,
630lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 658lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
631refers to the abstract Perl language itself. 659refers to the abstract Perl language itself.
632 660
633 661
634=head2 JSON -> PERL 662=head2 JSON -> PERL
635 663
636=over 4 664=over 4
637 665
638=item object 666=item object
639 667
640A JSON object becomes a reference to a hash in Perl. No ordering of object 668A JSON object becomes a reference to a hash in Perl. No ordering of object
641keys is preserved (JSON does not preserver object key ordering itself). 669keys is preserved (JSON does not preserve object key ordering itself).
642 670
643=item array 671=item array
644 672
645A JSON array becomes a reference to an array in Perl. 673A JSON array becomes a reference to an array in Perl.
646 674
672 700
673=item true, false 701=item true, false
674 702
675These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 703These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
676respectively. They are overloaded to act almost exactly like the numbers 704respectively. 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 705C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
678the C<JSON::XS::is_bool> function. 706the C<JSON::XS::is_bool> function.
679 707
680=item null 708=item null
681 709
682A JSON null atom becomes C<undef> in Perl. 710A JSON null atom becomes C<undef> in Perl.
745 to_json [$value] # yields ["5"] 773 to_json [$value] # yields ["5"]
746 774
747 # undef becomes null 775 # undef becomes null
748 to_json [undef] # yields [null] 776 to_json [undef] # yields [null]
749 777
750You can force the type to be a string by stringifying it: 778You can force the type to be a JSON string by stringifying it:
751 779
752 my $x = 3.1; # some variable containing a number 780 my $x = 3.1; # some variable containing a number
753 "$x"; # stringified 781 "$x"; # stringified
754 $x .= ""; # another, more awkward way to stringify 782 $x .= ""; # another, more awkward way to stringify
755 print $x; # perl does it for you, too, quite often 783 print $x; # perl does it for you, too, quite often
756 784
757You can force the type to be a number by numifying it: 785You can force the type to be a JSON number by numifying it:
758 786
759 my $x = "3"; # some variable containing a string 787 my $x = "3"; # some variable containing a string
760 $x += 0; # numify it, ensuring it will be dumped as a number 788 $x += 0; # numify it, ensuring it will be dumped as a number
761 $x *= 1; # same thing, the choise is yours. 789 $x *= 1; # same thing, the choice is yours.
762 790
763You can not currently output JSON booleans or force the type in other, 791You can not currently force the type in other, less obscure, ways. Tell me
764less obscure, ways. Tell me if you need this capability. 792if you need this capability.
765 793
766=back 794=back
767 795
768 796
769=head1 COMPARISON 797=head1 COMPARISON
778 806
779=item JSON 1.07 807=item JSON 1.07
780 808
781Slow (but very portable, as it is written in pure Perl). 809Slow (but very portable, as it is written in pure Perl).
782 810
783Undocumented/buggy Unicode handling (how JSON handles unicode values is 811Undocumented/buggy Unicode handling (how JSON handles Unicode values is
784undocumented. One can get far by feeding it unicode strings and doing 812undocumented. One can get far by feeding it Unicode strings and doing
785en-/decoding oneself, but unicode escapes are not working properly). 813en-/decoding oneself, but Unicode escapes are not working properly).
786 814
787No roundtripping (strings get clobbered if they look like numbers, e.g. 815No 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 816the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
789decode into the number 2. 817decode into the number 2.
790 818
791=item JSON::PC 0.01 819=item JSON::PC 0.01
792 820
793Very fast. 821Very fast.
794 822
795Undocumented/buggy Unicode handling. 823Undocumented/buggy Unicode handling.
796 824
797No roundtripping. 825No round-tripping.
798 826
799Has problems handling many Perl values (e.g. regex results and other magic 827Has problems handling many Perl values (e.g. regex results and other magic
800values will make it croak). 828values will make it croak).
801 829
802Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 830Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
812Very inflexible (no human-readable format supported, format pretty much 840Very inflexible (no human-readable format supported, format pretty much
813undocumented. I need at least a format for easy reading by humans and a 841undocumented. I need at least a format for easy reading by humans and a
814single-line compact format for use in a protocol, and preferably a way to 842single-line compact format for use in a protocol, and preferably a way to
815generate ASCII-only JSON texts). 843generate ASCII-only JSON texts).
816 844
817Completely broken (and confusingly documented) Unicode handling (unicode 845Completely broken (and confusingly documented) Unicode handling (Unicode
818escapes are not working properly, you need to set ImplicitUnicode to 846escapes are not working properly, you need to set ImplicitUnicode to
819I<different> values on en- and decoding to get symmetric behaviour). 847I<different> values on en- and decoding to get symmetric behaviour).
820 848
821No roundtripping (simple cases work, but this depends on wether the scalar 849No round-tripping (simple cases work, but this depends on whether the scalar
822value was used in a numeric context or not). 850value was used in a numeric context or not).
823 851
824Dumping hashes may skip hash values depending on iterator state. 852Dumping hashes may skip hash values depending on iterator state.
825 853
826Unmaintained (maintainer unresponsive for many months, bugs are not 854Unmaintained (maintainer unresponsive for many months, bugs are not
827getting fixed). 855getting fixed).
828 856
829Does not check input for validity (i.e. will accept non-JSON input and 857Does not check input for validity (i.e. will accept non-JSON input and
830return "something" instead of raising an exception. This is a security 858return "something" instead of raising an exception. This is a security
831issue: imagine two banks transfering money between each other using 859issue: imagine two banks transferring money between each other using
832JSON. One bank might parse a given non-JSON request and deduct money, 860JSON. One bank might parse a given non-JSON request and deduct money,
833while the other might reject the transaction with a syntax error. While a 861while the other might reject the transaction with a syntax error. While a
834good protocol will at least recover, that is extra unnecessary work and 862good protocol will at least recover, that is extra unnecessary work and
835the transaction will still not succeed). 863the transaction will still not succeed).
836 864
837=item JSON::DWIW 0.04 865=item JSON::DWIW 0.04
838 866
839Very fast. Very natural. Very nice. 867Very fast. Very natural. Very nice.
840 868
841Undocumented unicode handling (but the best of the pack. Unicode escapes 869Undocumented Unicode handling (but the best of the pack. Unicode escapes
842still don't get parsed properly). 870still don't get parsed properly).
843 871
844Very inflexible. 872Very inflexible.
845 873
846No roundtripping. 874No round-tripping.
847 875
848Does not generate valid JSON texts (key strings are often unquoted, empty keys 876Does not generate valid JSON texts (key strings are often unquoted, empty keys
849result in nothing being output) 877result in nothing being output)
850 878
851Does not check input for validity. 879Does not check input for validity.
866 my $yaml = $to_yaml->encode ($ref) . "\n"; 894 my $yaml = $to_yaml->encode ($ref) . "\n";
867 895
868This will usually generate JSON texts that also parse as valid 896This will usually generate JSON texts that also parse as valid
869YAML. Please note that YAML has hardcoded limits on (simple) object key 897YAML. 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 898lengths that JSON doesn't have, so you should make sure that your hash
871keys are noticably shorter than the 1024 characters YAML allows. 899keys are noticeably shorter than the 1024 characters YAML allows.
872 900
873There might be other incompatibilities that I am not aware of. In general 901There might be other incompatibilities that I am not aware of. In general
874you should not try to generate YAML with a JSON generator or vice versa, 902you should not try to generate YAML with a JSON generator or vice versa,
875or try to parse JSON with a YAML parser or vice versa: chances are high 903or try to parse JSON with a YAML parser or vice versa: chances are high
876that you will run into severe interoperability problems. 904that you will run into severe interoperability problems.
892It shows the number of encodes/decodes per second (JSON::XS uses 920It shows the number of encodes/decodes per second (JSON::XS uses
893the functional interface, while JSON::XS/2 uses the OO interface 921the functional interface, while JSON::XS/2 uses the OO interface
894with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 922with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
895shrink). Higher is better: 923shrink). Higher is better:
896 924
897 Storable | 15779.925 | 14169.946 |
898 -----------+------------+------------+
899 module | encode | decode | 925 module | encode | decode |
900 -----------|------------|------------| 926 -----------|------------|------------|
901 JSON | 4990.842 | 4088.813 | 927 JSON 1.x | 4990.842 | 4088.813 |
902 JSON::DWIW | 51653.990 | 71575.154 | 928 JSON::DWIW | 51653.990 | 71575.154 |
903 JSON::PC | 65948.176 | 74631.744 | 929 JSON::PC | 65948.176 | 74631.744 |
904 JSON::PP | 8931.652 | 3817.168 | 930 JSON::PP | 8931.652 | 3817.168 |
905 JSON::Syck | 24877.248 | 27776.848 | 931 JSON::Syck | 24877.248 | 27776.848 |
906 JSON::XS | 388361.481 | 227951.304 | 932 JSON::XS | 388361.481 | 227951.304 |
908 JSON::XS/3 | 338250.323 | 218453.333 | 934 JSON::XS/3 | 338250.323 | 218453.333 |
909 Storable | 16500.016 | 135300.129 | 935 Storable | 16500.016 | 135300.129 |
910 -----------+------------+------------+ 936 -----------+------------+------------+
911 937
912That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 938That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
913about three times faster on decoding, and over fourty times faster 939about three times faster on decoding, and over forty times faster
914than JSON, even with pretty-printing and key sorting. It also compares 940than JSON, even with pretty-printing and key sorting. It also compares
915favourably to Storable for small amounts of data. 941favourably to Storable for small amounts of data.
916 942
917Using a longer test string (roughly 18KB, generated from Yahoo! Locals 943Using a longer test string (roughly 18KB, generated from Yahoo! Locals
918search API (http://nanoref.com/yahooapis/mgPdGg): 944search API (http://nanoref.com/yahooapis/mgPdGg):
919 945
920 module | encode | decode | 946 module | encode | decode |
921 -----------|------------|------------| 947 -----------|------------|------------|
922 JSON | 55.260 | 34.971 | 948 JSON 1.x | 55.260 | 34.971 |
923 JSON::DWIW | 825.228 | 1082.513 | 949 JSON::DWIW | 825.228 | 1082.513 |
924 JSON::PC | 3571.444 | 2394.829 | 950 JSON::PC | 3571.444 | 2394.829 |
925 JSON::PP | 210.987 | 32.574 | 951 JSON::PP | 210.987 | 32.574 |
926 JSON::Syck | 552.551 | 787.544 | 952 JSON::Syck | 552.551 | 787.544 |
927 JSON::XS | 5780.463 | 4854.519 | 953 JSON::XS | 5780.463 | 4854.519 |
931 -----------+------------+------------+ 957 -----------+------------+------------+
932 958
933Again, JSON::XS leads by far (except for Storable which non-surprisingly 959Again, JSON::XS leads by far (except for Storable which non-surprisingly
934decodes faster). 960decodes faster).
935 961
936On large strings containing lots of high unicode characters, some modules 962On 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 963(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 964will be broken due to missing (or wrong) Unicode handling. Others refuse
939to decode or encode properly, so it was impossible to prepare a fair 965to decode or encode properly, so it was impossible to prepare a fair
940comparison table for that case. 966comparison table for that case.
941 967
942 968
943=head1 SECURITY CONSIDERATIONS 969=head1 SECURITY CONSIDERATIONS
949any buffer overflows. Obviously, this module should ensure that and I am 975any buffer overflows. Obviously, this module should ensure that and I am
950trying hard on making that true, but you never know. 976trying hard on making that true, but you never know.
951 977
952Second, you need to avoid resource-starving attacks. That means you should 978Second, 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 979limit 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 980resources 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 981can 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 982usually 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 983it 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 984text, 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. 985might want to check the size before you accept the string.
970And last but least, something else could bomb you that I forgot to think 996And last but least, something else could bomb you that I forgot to think
971of. In that case, you get to keep the pieces. I am always open for hints, 997of. In that case, you get to keep the pieces. I am always open for hints,
972though... 998though...
973 999
974If you are using JSON::XS to return packets to consumption 1000If you are using JSON::XS to return packets to consumption
975by javascript scripts in a browser you should have a look at 1001by JavaScript scripts in a browser you should have a look at
976L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1002L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
977you are vulnerable to some common attack vectors (which really are browser 1003you 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 1004design 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 1005browser developers care only for features, not about doing security
980right). 1006right).
981 1007
982 1008
983=head1 THREADS 1009=head1 THREADS
984 1010
985This module is I<not> guarenteed to be thread safe and there are no 1011This module is I<not> guaranteed to be thread safe and there are no
986plans to change this until Perl gets thread support (as opposed to the 1012plans to change this until Perl gets thread support (as opposed to the
987horribly slow so-called "threads" which are simply slow and bloated 1013horribly slow so-called "threads" which are simply slow and bloated
988process simulations - use fork, its I<much> faster, cheaper, better). 1014process simulations - use fork, its I<much> faster, cheaper, better).
989 1015
990(It might actually work, but you ahve ben warned). 1016(It might actually work, but you have been warned).
991 1017
992 1018
993=head1 BUGS 1019=head1 BUGS
994 1020
995While the goal of this module is to be correct, that unfortunately does 1021While the goal of this module is to be correct, that unfortunately does

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