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Revision 1.63 by root, Thu Oct 11 23:07:43 2007 UTC vs.
Revision 1.77 by root, Tue Dec 4 10:37:42 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
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 = '2.0';
92our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
93 107
94our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(to_json from_json);
95 109
96use Exporter; 110use Exporter;
97use XSLoader; 111use XSLoader;
98 112
99=head1 FUNCTIONAL INTERFACE 113=head1 FUNCTIONAL INTERFACE
100 114
101The following convinience methods are provided by this module. They are 115The following convenience methods are provided by this module. They are
102exported by default: 116exported by default:
103 117
104=over 4 118=over 4
105 119
106=item $json_text = to_json $perl_scalar 120=item $json_text = to_json $perl_scalar
145 159
146=over 4 160=over 4
147 161
148=item 1. Perl strings can store characters with ordinal values > 255. 162=item 1. Perl strings can store characters with ordinal values > 255.
149 163
150This enables you to store unicode characters as single characters in a 164This enables you to store Unicode characters as single characters in a
151Perl string - very natural. 165Perl string - very natural.
152 166
153=item 2. Perl does I<not> associate an encoding with your strings. 167=item 2. Perl does I<not> associate an encoding with your strings.
154 168
155Unless you force it to, e.g. when matching it against a regex, or printing 169Unless you force it to, e.g. when matching it against a regex, or printing
162encoding of your string. 176encoding of your string.
163 177
164Just ignore that flag unless you debug a Perl bug, a module written in 178Just 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 179XS 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 180confuse 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 181is 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 182flag clear, and you can have binary data with that flag set and that flag
169clear. Other possibilities exist, too. 183clear. Other possibilities exist, too.
170 184
171If you didn't know about that flag, just the better, pretend it doesn't 185If you didn't know about that flag, just the better, pretend it doesn't
172exist. 186exist.
177If you have UTF-8 encoded data, it is no longer a Unicode string, but a 191If 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. 192Unicode string encoded in UTF-8, giving you a binary string.
179 193
180=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. 194=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
181 195
182Its a fact. Learn to live with it. 196It's a fact. Learn to live with it.
183 197
184=back 198=back
185 199
186I hope this helps :) 200I hope this helps :)
187 201
204 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 218 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
205 => {"a": [1, 2]} 219 => {"a": [1, 2]}
206 220
207=item $json = $json->ascii ([$enable]) 221=item $json = $json->ascii ([$enable])
208 222
223=item $enabled = $json->get_ascii
224
209If C<$enable> is true (or missing), then the C<encode> method will not 225If C<$enable> is true (or missing), then the C<encode> method will not
210generate characters outside the code range C<0..127> (which is ASCII). Any 226generate characters outside the code range C<0..127> (which is ASCII). Any
211unicode characters outside that range will be escaped using either a 227Unicode characters outside that range will be escaped using either a
212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 228single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
213as per RFC4627. The resulting encoded JSON text can be treated as a native 229as per RFC4627. The resulting encoded JSON text can be treated as a native
214unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 230Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
215or any other superset of ASCII. 231or any other superset of ASCII.
216 232
217If C<$enable> is false, then the C<encode> method will not escape Unicode 233If 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 234characters unless required by the JSON syntax or other flags. This results
219in a faster and more compact format. 235in a faster and more compact format.
225 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 241 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
226 => ["\ud801\udc01"] 242 => ["\ud801\udc01"]
227 243
228=item $json = $json->latin1 ([$enable]) 244=item $json = $json->latin1 ([$enable])
229 245
246=item $enabled = $json->get_latin1
247
230If C<$enable> is true (or missing), then the C<encode> method will encode 248If C<$enable> is true (or missing), then the C<encode> method will encode
231the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 249the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
232outside the code range C<0..255>. The resulting string can be treated as a 250outside the code range C<0..255>. The resulting string can be treated as a
233latin1-encoded JSON text or a native unicode string. The C<decode> method 251latin1-encoded JSON text or a native Unicode string. The C<decode> method
234will not be affected in any way by this flag, as C<decode> by default 252will not be affected in any way by this flag, as C<decode> by default
235expects unicode, which is a strict superset of latin1. 253expects Unicode, which is a strict superset of latin1.
236 254
237If C<$enable> is false, then the C<encode> method will not escape Unicode 255If C<$enable> is false, then the C<encode> method will not escape Unicode
238characters unless required by the JSON syntax or other flags. 256characters unless required by the JSON syntax or other flags.
239 257
240The main use for this flag is efficiently encoding binary data as JSON 258The 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 259text, as most octets will not be escaped, resulting in a smaller encoded
242size. The disadvantage is that the resulting JSON text is encoded 260size. The disadvantage is that the resulting JSON text is encoded
243in latin1 (and must correctly be treated as such when storing and 261in latin1 (and must correctly be treated as such when storing and
244transfering), a rare encoding for JSON. It is therefore most useful when 262transferring), a rare encoding for JSON. It is therefore most useful when
245you want to store data structures known to contain binary data efficiently 263you want to store data structures known to contain binary data efficiently
246in files or databases, not when talking to other JSON encoders/decoders. 264in files or databases, not when talking to other JSON encoders/decoders.
247 265
248 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 266 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
249 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 267 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
250 268
251=item $json = $json->utf8 ([$enable]) 269=item $json = $json->utf8 ([$enable])
270
271=item $enabled = $json->get_utf8
252 272
253If C<$enable> is true (or missing), then the C<encode> method will encode 273If C<$enable> is true (or missing), then the C<encode> method will encode
254the JSON result into UTF-8, as required by many protocols, while the 274the JSON result into UTF-8, as required by many protocols, while the
255C<decode> method expects to be handled an UTF-8-encoded string. Please 275C<decode> method expects to be handled an UTF-8-encoded string. Please
256note that UTF-8-encoded strings do not contain any characters outside the 276note that UTF-8-encoded strings do not contain any characters outside the
257range C<0..255>, they are thus useful for bytewise/binary I/O. In future 277range C<0..255>, they are thus useful for bytewise/binary I/O. In future
258versions, enabling this option might enable autodetection of the UTF-16 278versions, enabling this option might enable autodetection of the UTF-16
259and UTF-32 encoding families, as described in RFC4627. 279and UTF-32 encoding families, as described in RFC4627.
260 280
261If C<$enable> is false, then the C<encode> method will return the JSON 281If 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 282string 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 283Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
264to be done yourself, e.g. using the Encode module. 284to be done yourself, e.g. using the Encode module.
265 285
266Example, output UTF-16BE-encoded JSON: 286Example, output UTF-16BE-encoded JSON:
267 287
268 use Encode; 288 use Encode;
290 ] 310 ]
291 } 311 }
292 312
293=item $json = $json->indent ([$enable]) 313=item $json = $json->indent ([$enable])
294 314
315=item $enabled = $json->get_indent
316
295If C<$enable> is true (or missing), then the C<encode> method will use a multiline 317If C<$enable> is true (or missing), then the C<encode> method will use a multiline
296format as output, putting every array member or object/hash key-value pair 318format as output, putting every array member or object/hash key-value pair
297into its own line, identing them properly. 319into its own line, indenting them properly.
298 320
299If C<$enable> is false, no newlines or indenting will be produced, and the 321If C<$enable> is false, no newlines or indenting will be produced, and the
300resulting JSON text is guarenteed not to contain any C<newlines>. 322resulting JSON text is guaranteed not to contain any C<newlines>.
301 323
302This setting has no effect when decoding JSON texts. 324This setting has no effect when decoding JSON texts.
303 325
304=item $json = $json->space_before ([$enable]) 326=item $json = $json->space_before ([$enable])
327
328=item $enabled = $json->get_space_before
305 329
306If C<$enable> is true (or missing), then the C<encode> method will add an extra 330If C<$enable> is true (or missing), then the C<encode> method will add an extra
307optional space before the C<:> separating keys from values in JSON objects. 331optional space before the C<:> separating keys from values in JSON objects.
308 332
309If C<$enable> is false, then the C<encode> method will not add any extra 333If C<$enable> is false, then the C<encode> method will not add any extra
315Example, space_before enabled, space_after and indent disabled: 339Example, space_before enabled, space_after and indent disabled:
316 340
317 {"key" :"value"} 341 {"key" :"value"}
318 342
319=item $json = $json->space_after ([$enable]) 343=item $json = $json->space_after ([$enable])
344
345=item $enabled = $json->get_space_after
320 346
321If C<$enable> is true (or missing), then the C<encode> method will add an extra 347If 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 348optional space after the C<:> separating keys from values in JSON objects
323and extra whitespace after the C<,> separating key-value pairs and array 349and extra whitespace after the C<,> separating key-value pairs and array
324members. 350members.
331Example, space_before and indent disabled, space_after enabled: 357Example, space_before and indent disabled, space_after enabled:
332 358
333 {"key": "value"} 359 {"key": "value"}
334 360
335=item $json = $json->relaxed ([$enable]) 361=item $json = $json->relaxed ([$enable])
362
363=item $enabled = $json->get_relaxed
336 364
337If C<$enable> is true (or missing), then C<decode> will accept some 365If C<$enable> is true (or missing), then C<decode> will accept some
338extensions to normal JSON syntax (see below). C<encode> will not be 366extensions to normal JSON syntax (see below). C<encode> will not be
339affected in anyway. I<Be aware that this option makes you accept invalid 367affected 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 368JSON texts as if they were valid!>. I suggest only to use this option to
377 405
378=back 406=back
379 407
380=item $json = $json->canonical ([$enable]) 408=item $json = $json->canonical ([$enable])
381 409
410=item $enabled = $json->get_canonical
411
382If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 412If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
383by sorting their keys. This is adding a comparatively high overhead. 413by sorting their keys. This is adding a comparatively high overhead.
384 414
385If C<$enable> is false, then the C<encode> method will output key-value 415If 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 416pairs in the order Perl stores them (which will likely change between runs
387of the same script). 417of the same script).
388 418
389This option is useful if you want the same data structure to be encoded as 419This 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, 420the 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, 421the same hash might be encoded differently even if contains the same data,
392as key-value pairs have no inherent ordering in Perl. 422as key-value pairs have no inherent ordering in Perl.
393 423
394This setting has no effect when decoding JSON texts. 424This setting has no effect when decoding JSON texts.
395 425
396=item $json = $json->allow_nonref ([$enable]) 426=item $json = $json->allow_nonref ([$enable])
427
428=item $enabled = $json->get_allow_nonref
397 429
398If C<$enable> is true (or missing), then the C<encode> method can convert a 430If 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, 431non-reference into its corresponding string, number or null JSON value,
400which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 432which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
401values instead of croaking. 433values instead of croaking.
411 JSON::XS->new->allow_nonref->encode ("Hello, World!") 443 JSON::XS->new->allow_nonref->encode ("Hello, World!")
412 => "Hello, World!" 444 => "Hello, World!"
413 445
414=item $json = $json->allow_blessed ([$enable]) 446=item $json = $json->allow_blessed ([$enable])
415 447
448=item $enabled = $json->get_allow_blessed
449
416If C<$enable> is true (or missing), then the C<encode> method will not 450If C<$enable> is true (or missing), then the C<encode> method will not
417barf when it encounters a blessed reference. Instead, the value of the 451barf when it encounters a blessed reference. Instead, the value of the
418B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 452B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
419disabled or no C<to_json> method found) or a representation of the 453disabled or no C<TO_JSON> method found) or a representation of the
420object (C<convert_blessed> enabled and C<to_json> method found) is being 454object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
421encoded. Has no effect on C<decode>. 455encoded. Has no effect on C<decode>.
422 456
423If C<$enable> is false (the default), then C<encode> will throw an 457If C<$enable> is false (the default), then C<encode> will throw an
424exception when it encounters a blessed object. 458exception when it encounters a blessed object.
425 459
426=item $json = $json->convert_blessed ([$enable]) 460=item $json = $json->convert_blessed ([$enable])
461
462=item $enabled = $json->get_convert_blessed
427 463
428If C<$enable> is true (or missing), then C<encode>, upon encountering a 464If C<$enable> is true (or missing), then C<encode>, upon encountering a
429blessed object, will check for the availability of the C<TO_JSON> method 465blessed object, will check for the availability of the C<TO_JSON> method
430on the object's class. If found, it will be called in scalar context 466on the object's class. If found, it will be called in scalar context
431and the resulting scalar will be encoded instead of the object. If no 467and the resulting scalar will be encoded instead of the object. If no
488 524
489As this callback gets called less often then the C<filter_json_object> 525As this callback gets called less often then the C<filter_json_object>
490one, decoding speed will not usually suffer as much. Therefore, single-key 526one, decoding speed will not usually suffer as much. Therefore, single-key
491objects make excellent targets to serialise Perl objects into, especially 527objects make excellent targets to serialise Perl objects into, especially
492as single-key JSON objects are as close to the type-tagged value concept 528as single-key JSON objects are as close to the type-tagged value concept
493as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not 529as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
494support this in any way, so you need to make sure your data never looks 530support this in any way, so you need to make sure your data never looks
495like a serialised Perl hash. 531like a serialised Perl hash.
496 532
497Typical names for the single object key are C<__class_whatever__>, or 533Typical names for the single object key are C<__class_whatever__>, or
498C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 534C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
522 558
523 { __widget__ => $self->{id} } 559 { __widget__ => $self->{id} }
524 } 560 }
525 561
526=item $json = $json->shrink ([$enable]) 562=item $json = $json->shrink ([$enable])
563
564=item $enabled = $json->get_shrink
527 565
528Perl usually over-allocates memory a bit when allocating space for 566Perl usually over-allocates memory a bit when allocating space for
529strings. This flag optionally resizes strings generated by either 567strings. This flag optionally resizes strings generated by either
530C<encode> or C<decode> to their minimum size possible. This can save 568C<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 569memory when your JSON texts are either very very long or you have many
549strings that look like integers or floats into integers or floats 587strings that look like integers or floats into integers or floats
550internally (there is no difference on the Perl level), saving space. 588internally (there is no difference on the Perl level), saving space.
551 589
552=item $json = $json->max_depth ([$maximum_nesting_depth]) 590=item $json = $json->max_depth ([$maximum_nesting_depth])
553 591
592=item $max_depth = $json->get_max_depth
593
554Sets the maximum nesting level (default C<512>) accepted while encoding 594Sets the maximum nesting level (default C<512>) accepted while encoding
555or decoding. If the JSON text or Perl data structure has an equal or 595or 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 596higher nesting level then this limit, then the encoder and decoder will
557stop and croak at that point. 597stop and croak at that point.
558 598
569used, which is rarely useful. 609used, which is rarely useful.
570 610
571See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 611See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
572 612
573=item $json = $json->max_size ([$maximum_string_size]) 613=item $json = $json->max_size ([$maximum_string_size])
614
615=item $max_size = $json->get_max_size
574 616
575Set the maximum length a JSON text may have (in bytes) where decoding is 617Set 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> 618being 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 619is 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 620attempt 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 667vice versa. These mappings are designed to "do the right thing" in most
626circumstances automatically, preserving round-tripping characteristics 668circumstances automatically, preserving round-tripping characteristics
627(what you put in comes out as something equivalent). 669(what you put in comes out as something equivalent).
628 670
629For the more enlightened: note that in the following descriptions, 671For the more enlightened: note that in the following descriptions,
630lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 672lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
631refers to the abstract Perl language itself. 673refers to the abstract Perl language itself.
632 674
633 675
634=head2 JSON -> PERL 676=head2 JSON -> PERL
635 677
636=over 4 678=over 4
637 679
638=item object 680=item object
639 681
640A JSON object becomes a reference to a hash in Perl. No ordering of object 682A 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). 683keys is preserved (JSON does not preserve object key ordering itself).
642 684
643=item array 685=item array
644 686
645A JSON array becomes a reference to an array in Perl. 687A JSON array becomes a reference to an array in Perl.
646 688
672 714
673=item true, false 715=item true, false
674 716
675These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 717These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
676respectively. They are overloaded to act almost exactly like the numbers 718respectively. 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 719C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
678the C<JSON::XS::is_bool> function. 720the C<JSON::XS::is_bool> function.
679 721
680=item null 722=item null
681 723
682A JSON null atom becomes C<undef> in Perl. 724A JSON null atom becomes C<undef> in Perl.
745 to_json [$value] # yields ["5"] 787 to_json [$value] # yields ["5"]
746 788
747 # undef becomes null 789 # undef becomes null
748 to_json [undef] # yields [null] 790 to_json [undef] # yields [null]
749 791
750You can force the type to be a string by stringifying it: 792You can force the type to be a JSON string by stringifying it:
751 793
752 my $x = 3.1; # some variable containing a number 794 my $x = 3.1; # some variable containing a number
753 "$x"; # stringified 795 "$x"; # stringified
754 $x .= ""; # another, more awkward way to stringify 796 $x .= ""; # another, more awkward way to stringify
755 print $x; # perl does it for you, too, quite often 797 print $x; # perl does it for you, too, quite often
756 798
757You can force the type to be a number by numifying it: 799You can force the type to be a JSON number by numifying it:
758 800
759 my $x = "3"; # some variable containing a string 801 my $x = "3"; # some variable containing a string
760 $x += 0; # numify it, ensuring it will be dumped as a number 802 $x += 0; # numify it, ensuring it will be dumped as a number
761 $x *= 1; # same thing, the choise is yours. 803 $x *= 1; # same thing, the choice is yours.
762 804
763You can not currently output JSON booleans or force the type in other, 805You can not currently force the type in other, less obscure, ways. Tell me
764less obscure, ways. Tell me if you need this capability. 806if you need this capability.
765 807
766=back 808=back
767 809
768 810
769=head1 COMPARISON 811=head1 COMPARISON
778 820
779=item JSON 1.07 821=item JSON 1.07
780 822
781Slow (but very portable, as it is written in pure Perl). 823Slow (but very portable, as it is written in pure Perl).
782 824
783Undocumented/buggy Unicode handling (how JSON handles unicode values is 825Undocumented/buggy Unicode handling (how JSON handles Unicode values is
784undocumented. One can get far by feeding it unicode strings and doing 826undocumented. One can get far by feeding it Unicode strings and doing
785en-/decoding oneself, but unicode escapes are not working properly). 827en-/decoding oneself, but Unicode escapes are not working properly).
786 828
787No roundtripping (strings get clobbered if they look like numbers, e.g. 829No 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 830the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
789decode into the number 2. 831decode into the number 2.
790 832
791=item JSON::PC 0.01 833=item JSON::PC 0.01
792 834
793Very fast. 835Very fast.
794 836
795Undocumented/buggy Unicode handling. 837Undocumented/buggy Unicode handling.
796 838
797No roundtripping. 839No round-tripping.
798 840
799Has problems handling many Perl values (e.g. regex results and other magic 841Has problems handling many Perl values (e.g. regex results and other magic
800values will make it croak). 842values will make it croak).
801 843
802Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 844Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
812Very inflexible (no human-readable format supported, format pretty much 854Very inflexible (no human-readable format supported, format pretty much
813undocumented. I need at least a format for easy reading by humans and a 855undocumented. 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 856single-line compact format for use in a protocol, and preferably a way to
815generate ASCII-only JSON texts). 857generate ASCII-only JSON texts).
816 858
817Completely broken (and confusingly documented) Unicode handling (unicode 859Completely broken (and confusingly documented) Unicode handling (Unicode
818escapes are not working properly, you need to set ImplicitUnicode to 860escapes are not working properly, you need to set ImplicitUnicode to
819I<different> values on en- and decoding to get symmetric behaviour). 861I<different> values on en- and decoding to get symmetric behaviour).
820 862
821No roundtripping (simple cases work, but this depends on wether the scalar 863No round-tripping (simple cases work, but this depends on whether the scalar
822value was used in a numeric context or not). 864value was used in a numeric context or not).
823 865
824Dumping hashes may skip hash values depending on iterator state. 866Dumping hashes may skip hash values depending on iterator state.
825 867
826Unmaintained (maintainer unresponsive for many months, bugs are not 868Unmaintained (maintainer unresponsive for many months, bugs are not
827getting fixed). 869getting fixed).
828 870
829Does not check input for validity (i.e. will accept non-JSON input and 871Does not check input for validity (i.e. will accept non-JSON input and
830return "something" instead of raising an exception. This is a security 872return "something" instead of raising an exception. This is a security
831issue: imagine two banks transfering money between each other using 873issue: imagine two banks transferring money between each other using
832JSON. One bank might parse a given non-JSON request and deduct money, 874JSON. 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 875while the other might reject the transaction with a syntax error. While a
834good protocol will at least recover, that is extra unnecessary work and 876good protocol will at least recover, that is extra unnecessary work and
835the transaction will still not succeed). 877the transaction will still not succeed).
836 878
837=item JSON::DWIW 0.04 879=item JSON::DWIW 0.04
838 880
839Very fast. Very natural. Very nice. 881Very fast. Very natural. Very nice.
840 882
841Undocumented unicode handling (but the best of the pack. Unicode escapes 883Undocumented Unicode handling (but the best of the pack. Unicode escapes
842still don't get parsed properly). 884still don't get parsed properly).
843 885
844Very inflexible. 886Very inflexible.
845 887
846No roundtripping. 888No round-tripping.
847 889
848Does not generate valid JSON texts (key strings are often unquoted, empty keys 890Does not generate valid JSON texts (key strings are often unquoted, empty keys
849result in nothing being output) 891result in nothing being output)
850 892
851Does not check input for validity. 893Does not check input for validity.
866 my $yaml = $to_yaml->encode ($ref) . "\n"; 908 my $yaml = $to_yaml->encode ($ref) . "\n";
867 909
868This will usually generate JSON texts that also parse as valid 910This will usually generate JSON texts that also parse as valid
869YAML. Please note that YAML has hardcoded limits on (simple) object key 911YAML. 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 912lengths that JSON doesn't have, so you should make sure that your hash
871keys are noticably shorter than the 1024 characters YAML allows. 913keys are noticeably shorter than the 1024 characters YAML allows.
872 914
873There might be other incompatibilities that I am not aware of. In general 915There 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, 916you 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 917or try to parse JSON with a YAML parser or vice versa: chances are high
876that you will run into severe interoperability problems. 918that you will run into severe interoperability problems.
892It shows the number of encodes/decodes per second (JSON::XS uses 934It shows the number of encodes/decodes per second (JSON::XS uses
893the functional interface, while JSON::XS/2 uses the OO interface 935the functional interface, while JSON::XS/2 uses the OO interface
894with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 936with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
895shrink). Higher is better: 937shrink). Higher is better:
896 938
897 Storable | 15779.925 | 14169.946 |
898 -----------+------------+------------+
899 module | encode | decode | 939 module | encode | decode |
900 -----------|------------|------------| 940 -----------|------------|------------|
901 JSON | 4990.842 | 4088.813 | 941 JSON 1.x | 4990.842 | 4088.813 |
902 JSON::DWIW | 51653.990 | 71575.154 | 942 JSON::DWIW | 51653.990 | 71575.154 |
903 JSON::PC | 65948.176 | 74631.744 | 943 JSON::PC | 65948.176 | 74631.744 |
904 JSON::PP | 8931.652 | 3817.168 | 944 JSON::PP | 8931.652 | 3817.168 |
905 JSON::Syck | 24877.248 | 27776.848 | 945 JSON::Syck | 24877.248 | 27776.848 |
906 JSON::XS | 388361.481 | 227951.304 | 946 JSON::XS | 388361.481 | 227951.304 |
908 JSON::XS/3 | 338250.323 | 218453.333 | 948 JSON::XS/3 | 338250.323 | 218453.333 |
909 Storable | 16500.016 | 135300.129 | 949 Storable | 16500.016 | 135300.129 |
910 -----------+------------+------------+ 950 -----------+------------+------------+
911 951
912That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 952That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
913about three times faster on decoding, and over fourty times faster 953about three times faster on decoding, and over forty times faster
914than JSON, even with pretty-printing and key sorting. It also compares 954than JSON, even with pretty-printing and key sorting. It also compares
915favourably to Storable for small amounts of data. 955favourably to Storable for small amounts of data.
916 956
917Using a longer test string (roughly 18KB, generated from Yahoo! Locals 957Using a longer test string (roughly 18KB, generated from Yahoo! Locals
918search API (http://nanoref.com/yahooapis/mgPdGg): 958search API (http://nanoref.com/yahooapis/mgPdGg):
919 959
920 module | encode | decode | 960 module | encode | decode |
921 -----------|------------|------------| 961 -----------|------------|------------|
922 JSON | 55.260 | 34.971 | 962 JSON 1.x | 55.260 | 34.971 |
923 JSON::DWIW | 825.228 | 1082.513 | 963 JSON::DWIW | 825.228 | 1082.513 |
924 JSON::PC | 3571.444 | 2394.829 | 964 JSON::PC | 3571.444 | 2394.829 |
925 JSON::PP | 210.987 | 32.574 | 965 JSON::PP | 210.987 | 32.574 |
926 JSON::Syck | 552.551 | 787.544 | 966 JSON::Syck | 552.551 | 787.544 |
927 JSON::XS | 5780.463 | 4854.519 | 967 JSON::XS | 5780.463 | 4854.519 |
931 -----------+------------+------------+ 971 -----------+------------+------------+
932 972
933Again, JSON::XS leads by far (except for Storable which non-surprisingly 973Again, JSON::XS leads by far (except for Storable which non-surprisingly
934decodes faster). 974decodes faster).
935 975
936On large strings containing lots of high unicode characters, some modules 976On 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 977(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 978will be broken due to missing (or wrong) Unicode handling. Others refuse
939to decode or encode properly, so it was impossible to prepare a fair 979to decode or encode properly, so it was impossible to prepare a fair
940comparison table for that case. 980comparison table for that case.
941 981
942 982
943=head1 SECURITY CONSIDERATIONS 983=head1 SECURITY CONSIDERATIONS
949any buffer overflows. Obviously, this module should ensure that and I am 989any buffer overflows. Obviously, this module should ensure that and I am
950trying hard on making that true, but you never know. 990trying hard on making that true, but you never know.
951 991
952Second, you need to avoid resource-starving attacks. That means you should 992Second, 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 993limit 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 994resources 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 995can 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 996usually 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 997it 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 998text, 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. 999might want to check the size before you accept the string.
970And last but least, something else could bomb you that I forgot to think 1010And 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, 1011of. In that case, you get to keep the pieces. I am always open for hints,
972though... 1012though...
973 1013
974If you are using JSON::XS to return packets to consumption 1014If you are using JSON::XS to return packets to consumption
975by javascript scripts in a browser you should have a look at 1015by JavaScript scripts in a browser you should have a look at
976L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1016L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
977you are vulnerable to some common attack vectors (which really are browser 1017you 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 1018design 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 1019browser developers care only for features, not about doing security
980right). 1020right).
981 1021
982 1022
1023=head1 THREADS
1024
1025This module is I<not> guaranteed to be thread safe and there are no
1026plans to change this until Perl gets thread support (as opposed to the
1027horribly slow so-called "threads" which are simply slow and bloated
1028process simulations - use fork, its I<much> faster, cheaper, better).
1029
1030(It might actually work, but you have been warned).
1031
1032
983=head1 BUGS 1033=head1 BUGS
984 1034
985While the goal of this module is to be correct, that unfortunately does 1035While 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 1036not 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 1037still relatively early in its development. If you keep reporting bugs they
988will be fixed swiftly, though. 1038will be fixed swiftly, though.
1039
1040Please refrain from using rt.cpan.org or any other bug reporting
1041service. I put the contact address into my modules for a reason.
989 1042
990=cut 1043=cut
991 1044
992our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1045our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
993our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1046our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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