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Comparing JSON-XS/XS.pm (file contents):
Revision 1.28 by root, Tue Apr 3 23:59:04 2007 UTC vs.
Revision 1.53 by root, Mon Jul 2 07:39:31 2007 UTC

9 # exported functions, they croak on error 9 # exported functions, they croak on error
10 # and expect/generate UTF-8 10 # and expect/generate UTF-8
11 11
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
14
15 # objToJson and jsonToObj aliases to to_json and from_json
16 # are exported for compatibility to the JSON module,
17 # but should not be used in new code.
18 14
19 # OO-interface 15 # OO-interface
20 16
21 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 17 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
22 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 18 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
85 81
86package JSON::XS; 82package JSON::XS;
87 83
88use strict; 84use strict;
89 85
90BEGIN {
91 our $VERSION = '1.1'; 86our $VERSION = '1.4';
92 our @ISA = qw(Exporter); 87our @ISA = qw(Exporter);
93 88
94 our @EXPORT = qw(to_json from_json objToJson jsonToObj); 89our @EXPORT = qw(to_json from_json);
95 require Exporter;
96 90
97 require XSLoader; 91use Exporter;
98 XSLoader::load JSON::XS::, $VERSION; 92use XSLoader;
99}
100 93
101=head1 FUNCTIONAL INTERFACE 94=head1 FUNCTIONAL INTERFACE
102 95
103The following convinience methods are provided by this module. They are 96The following convinience methods are provided by this module. They are
104exported by default: 97exported by default:
126This function call is functionally identical to: 119This function call is functionally identical to:
127 120
128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129 122
130except being faster. 123except being faster.
124
125=item $is_boolean = JSON::XS::is_bool $scalar
126
127Returns true if the passed scalar represents either JSON::XS::true or
128JSON::XS::false, two constants that act like C<1> and C<0>, respectively
129and are used to represent JSON C<true> and C<false> values in Perl.
130
131See MAPPING, below, for more information on how JSON values are mapped to
132Perl.
131 133
132=back 134=back
133 135
134 136
135=head1 OBJECT-ORIENTED INTERFACE 137=head1 OBJECT-ORIENTED INTERFACE
154 156
155If C<$enable> is true (or missing), then the C<encode> method will not 157If C<$enable> is true (or missing), then the C<encode> method will not
156generate characters outside the code range C<0..127> (which is ASCII). Any 158generate characters outside the code range C<0..127> (which is ASCII). Any
157unicode characters outside that range will be escaped using either a 159unicode characters outside that range will be escaped using either a
158single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 160single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159as per RFC4627. 161as per RFC4627. The resulting encoded JSON text can be treated as a native
162unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163or any other superset of ASCII.
160 164
161If C<$enable> is false, then the C<encode> method will not escape Unicode 165If C<$enable> is false, then the C<encode> method will not escape Unicode
162characters unless required by the JSON syntax. This results in a faster 166characters unless required by the JSON syntax or other flags. This results
163and more compact format. 167in a faster and more compact format.
168
169The main use for this flag is to produce JSON texts that can be
170transmitted over a 7-bit channel, as the encoded JSON texts will not
171contain any 8 bit characters.
164 172
165 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 173 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
166 => ["\ud801\udc01"] 174 => ["\ud801\udc01"]
175
176=item $json = $json->latin1 ([$enable])
177
178If C<$enable> is true (or missing), then the C<encode> method will encode
179the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180outside the code range C<0..255>. The resulting string can be treated as a
181latin1-encoded JSON text or a native unicode string. The C<decode> method
182will not be affected in any way by this flag, as C<decode> by default
183expects unicode, which is a strict superset of latin1.
184
185If C<$enable> is false, then the C<encode> method will not escape Unicode
186characters unless required by the JSON syntax or other flags.
187
188The main use for this flag is efficiently encoding binary data as JSON
189text, as most octets will not be escaped, resulting in a smaller encoded
190size. The disadvantage is that the resulting JSON text is encoded
191in latin1 (and must correctly be treated as such when storing and
192transfering), a rare encoding for JSON. It is therefore most useful when
193you want to store data structures known to contain binary data efficiently
194in files or databases, not when talking to other JSON encoders/decoders.
195
196 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
167 198
168=item $json = $json->utf8 ([$enable]) 199=item $json = $json->utf8 ([$enable])
169 200
170If C<$enable> is true (or missing), then the C<encode> method will encode 201If C<$enable> is true (or missing), then the C<encode> method will encode
171the JSON result into UTF-8, as required by many protocols, while the 202the JSON result into UTF-8, as required by many protocols, while the
280Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, 311Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
281resulting in an invalid JSON text: 312resulting in an invalid JSON text:
282 313
283 JSON::XS->new->allow_nonref->encode ("Hello, World!") 314 JSON::XS->new->allow_nonref->encode ("Hello, World!")
284 => "Hello, World!" 315 => "Hello, World!"
316
317=item $json = $json->allow_blessed ([$enable])
318
319If C<$enable> is true (or missing), then the C<encode> method will not
320barf when it encounters a blessed reference. Instead, the value of the
321B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
322disabled or no C<to_json> method found) or a representation of the
323object (C<convert_blessed> enabled and C<to_json> method found) is being
324encoded. Has no effect on C<decode>.
325
326If C<$enable> is false (the default), then C<encode> will throw an
327exception when it encounters a blessed object.
328
329=item $json = $json->convert_blessed ([$enable])
330
331If C<$enable> is true (or missing), then C<encode>, upon encountering a
332blessed object, will check for the availability of the C<TO_JSON> method
333on the object's class. If found, it will be called in scalar context
334and the resulting scalar will be encoded instead of the object. If no
335C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
336to do.
337
338The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
339returns other blessed objects, those will be handled in the same
340way. C<TO_JSON> must take care of not causing an endless recursion cycle
341(== crash) in this case. The name of C<TO_JSON> was chosen because other
342methods called by the Perl core (== not by the user of the object) are
343usually in upper case letters and to avoid collisions with the C<to_json>
344function.
345
346This setting does not yet influence C<decode> in any way, but in the
347future, global hooks might get installed that influence C<decode> and are
348enabled by this setting.
349
350If C<$enable> is false, then the C<allow_blessed> setting will decide what
351to do when a blessed object is found.
352
353=item $json = $json->filter_json_object ([$coderef->($hashref)])
354
355When C<$coderef> is specified, it will be called from C<decode> each
356time it decodes a JSON object. The only argument is a reference to the
357newly-created hash. If the code references returns a single scalar (which
358need not be a reference), this value (i.e. a copy of that scalar to avoid
359aliasing) is inserted into the deserialised data structure. If it returns
360an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
361original deserialised hash will be inserted. This setting can slow down
362decoding considerably.
363
364When C<$coderef> is omitted or undefined, any existing callback will
365be removed and C<decode> will not change the deserialised hash in any
366way.
367
368Example, convert all JSON objects into the integer 5:
369
370 my $js = JSON::XS->new->filter_json_object (sub { 5 });
371 # returns [5]
372 $js->decode ('[{}]')
373 # throw an exception because allow_nonref is not enabled
374 # so a lone 5 is not allowed.
375 $js->decode ('{"a":1, "b":2}');
376
377=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
378
379Works remotely similar to C<filter_json_object>, but is only called for
380JSON objects having a single key named C<$key>.
381
382This C<$coderef> is called before the one specified via
383C<filter_json_object>, if any. It gets passed the single value in the JSON
384object. If it returns a single value, it will be inserted into the data
385structure. If it returns nothing (not even C<undef> but the empty list),
386the callback from C<filter_json_object> will be called next, as if no
387single-key callback were specified.
388
389If C<$coderef> is omitted or undefined, the corresponding callback will be
390disabled. There can only ever be one callback for a given key.
391
392As this callback gets called less often then the C<filter_json_object>
393one, decoding speed will not usually suffer as much. Therefore, single-key
394objects make excellent targets to serialise Perl objects into, especially
395as single-key JSON objects are as close to the type-tagged value concept
396as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
397support this in any way, so you need to make sure your data never looks
398like a serialised Perl hash.
399
400Typical names for the single object key are C<__class_whatever__>, or
401C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
402things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
403with real hashes.
404
405Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
406into the corresponding C<< $WIDGET{<id>} >> object:
407
408 # return whatever is in $WIDGET{5}:
409 JSON::XS
410 ->new
411 ->filter_json_single_key_object (__widget__ => sub {
412 $WIDGET{ $_[0] }
413 })
414 ->decode ('{"__widget__": 5')
415
416 # this can be used with a TO_JSON method in some "widget" class
417 # for serialisation to json:
418 sub WidgetBase::TO_JSON {
419 my ($self) = @_;
420
421 unless ($self->{id}) {
422 $self->{id} = ..get..some..id..;
423 $WIDGET{$self->{id}} = $self;
424 }
425
426 { __widget__ => $self->{id} }
427 }
285 428
286=item $json = $json->shrink ([$enable]) 429=item $json = $json->shrink ([$enable])
287 430
288Perl usually over-allocates memory a bit when allocating space for 431Perl usually over-allocates memory a bit when allocating space for
289strings. This flag optionally resizes strings generated by either 432strings. This flag optionally resizes strings generated by either
322given character in a string. 465given character in a string.
323 466
324Setting the maximum depth to one disallows any nesting, so that ensures 467Setting the maximum depth to one disallows any nesting, so that ensures
325that the object is only a single hash/object or array. 468that the object is only a single hash/object or array.
326 469
327The argument to C<max_depth> will be rounded up to the next nearest power 470The argument to C<max_depth> will be rounded up to the next highest power
328of two. 471of two. If no argument is given, the highest possible setting will be
472used, which is rarely useful.
473
474See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
475
476=item $json = $json->max_size ([$maximum_string_size])
477
478Set the maximum length a JSON text may have (in bytes) where decoding is
479being attempted. The default is C<0>, meaning no limit. When C<decode>
480is called on a string longer then this number of characters it will not
481attempt to decode the string but throw an exception. This setting has no
482effect on C<encode> (yet).
483
484The argument to C<max_size> will be rounded up to the next B<highest>
485power of two (so may be more than requested). If no argument is given, the
486limit check will be deactivated (same as when C<0> is specified).
329 487
330See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 488See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
331 489
332=item $json_text = $json->encode ($perl_scalar) 490=item $json_text = $json->encode ($perl_scalar)
333 491
345 503
346JSON numbers and strings become simple Perl scalars. JSON arrays become 504JSON numbers and strings become simple Perl scalars. JSON arrays become
347Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 505Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
348C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 506C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
349 507
508=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
509
510This works like the C<decode> method, but instead of raising an exception
511when there is trailing garbage after the first JSON object, it will
512silently stop parsing there and return the number of characters consumed
513so far.
514
515This is useful if your JSON texts are not delimited by an outer protocol
516(which is not the brightest thing to do in the first place) and you need
517to know where the JSON text ends.
518
519 JSON::XS->new->decode_prefix ("[1] the tail")
520 => ([], 3)
521
350=back 522=back
351 523
352 524
353=head1 MAPPING 525=head1 MAPPING
354 526
358(what you put in comes out as something equivalent). 530(what you put in comes out as something equivalent).
359 531
360For the more enlightened: note that in the following descriptions, 532For the more enlightened: note that in the following descriptions,
361lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 533lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
362refers to the abstract Perl language itself. 534refers to the abstract Perl language itself.
535
363 536
364=head2 JSON -> PERL 537=head2 JSON -> PERL
365 538
366=over 4 539=over 4
367 540
388conversion details, but an integer may take slightly less memory and might 561conversion details, but an integer may take slightly less memory and might
389represent more values exactly than (floating point) numbers. 562represent more values exactly than (floating point) numbers.
390 563
391=item true, false 564=item true, false
392 565
393These JSON atoms become C<0>, C<1>, respectively. Information is lost in 566These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
394this process. Future versions might represent those values differently, 567respectively. They are overloaded to act almost exactly like the numbers
395but they will be guarenteed to act like these integers would normally in 568C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
396Perl. 569the C<JSON::XS::is_bool> function.
397 570
398=item null 571=item null
399 572
400A JSON null atom becomes C<undef> in Perl. 573A JSON null atom becomes C<undef> in Perl.
401 574
402=back 575=back
576
403 577
404=head2 PERL -> JSON 578=head2 PERL -> JSON
405 579
406The mapping from Perl to JSON is slightly more difficult, as Perl is a 580The mapping from Perl to JSON is slightly more difficult, as Perl is a
407truly typeless language, so we can only guess which JSON type is meant by 581truly typeless language, so we can only guess which JSON type is meant by
432C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 606C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
433also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 607also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
434 608
435 to_json [\0,JSON::XS::true] # yields [false,true] 609 to_json [\0,JSON::XS::true] # yields [false,true]
436 610
611=item JSON::XS::true, JSON::XS::false
612
613These special values become JSON true and JSON false values,
614respectively. You cna alos use C<\1> and C<\0> directly if you want.
615
437=item blessed objects 616=item blessed objects
438 617
439Blessed objects are not allowed. JSON::XS currently tries to encode their 618Blessed objects are not allowed. JSON::XS currently tries to encode their
440underlying representation (hash- or arrayref), but this behaviour might 619underlying representation (hash- or arrayref), but this behaviour might
441change in future versions. 620change in future versions.
562 741
563Does not check input for validity. 742Does not check input for validity.
564 743
565=back 744=back
566 745
746
747=head2 JSON and YAML
748
749You often hear that JSON is a subset (or a close subset) of YAML. This is,
750however, a mass hysteria and very far from the truth. In general, there is
751no way to configure JSON::XS to output a data structure as valid YAML.
752
753If you really must use JSON::XS to generate YAML, you should use this
754algorithm (subject to change in future versions):
755
756 my $to_yaml = JSON::XS->new->utf8->space_after (1);
757 my $yaml = $to_yaml->encode ($ref) . "\n";
758
759This will usually generate JSON texts that also parse as valid
760YAML. Please note that YAML has hardcoded limits on (simple) object key
761lengths that JSON doesn't have, so you should make sure that your hash
762keys are noticably shorter than the 1024 characters YAML allows.
763
764There might be other incompatibilities that I am not aware of. In general
765you should not try to generate YAML with a JSON generator or vice versa,
766or try to parse JSON with a YAML parser or vice versa: chances are high
767that you will run into severe interoperability problems.
768
769
567=head2 SPEED 770=head2 SPEED
568 771
569It seems that JSON::XS is surprisingly fast, as shown in the following 772It seems that JSON::XS is surprisingly fast, as shown in the following
570tables. They have been generated with the help of the C<eg/bench> program 773tables. They have been generated with the help of the C<eg/bench> program
571in the JSON::XS distribution, to make it easy to compare on your own 774in the JSON::XS distribution, to make it easy to compare on your own
572system. 775system.
573 776
574First comes a comparison between various modules using a very short JSON 777First comes a comparison between various modules using a very short
575string: 778single-line JSON string:
576 779
577 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 780 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
781 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
578 782
579It shows the number of encodes/decodes per second (JSON::XS uses the 783It shows the number of encodes/decodes per second (JSON::XS uses
580functional interface, while JSON::XS/2 uses the OO interface with 784the functional interface, while JSON::XS/2 uses the OO interface
581pretty-printing and hashkey sorting enabled). Higher is better: 785with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
786shrink). Higher is better:
582 787
788 Storable | 15779.925 | 14169.946 |
789 -----------+------------+------------+
583 module | encode | decode | 790 module | encode | decode |
584 -----------|------------|------------| 791 -----------|------------|------------|
585 JSON | 11488.516 | 7823.035 | 792 JSON | 4990.842 | 4088.813 |
586 JSON::DWIW | 94708.054 | 129094.260 | 793 JSON::DWIW | 51653.990 | 71575.154 |
587 JSON::PC | 63884.157 | 128528.212 | 794 JSON::PC | 65948.176 | 74631.744 |
588 JSON::Syck | 34898.677 | 42096.911 | 795 JSON::PP | 8931.652 | 3817.168 |
589 JSON::XS | 654027.064 | 396423.669 | 796 JSON::Syck | 24877.248 | 27776.848 |
590 JSON::XS/2 | 371564.190 | 371725.613 | 797 JSON::XS | 388361.481 | 227951.304 |
798 JSON::XS/2 | 227951.304 | 218453.333 |
799 JSON::XS/3 | 338250.323 | 218453.333 |
800 Storable | 16500.016 | 135300.129 |
591 -----------+------------+------------+ 801 -----------+------------+------------+
592 802
593That is, JSON::XS is more than six times faster than JSON::DWIW on 803That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
594encoding, more than three times faster on decoding, and about thirty times 804about three times faster on decoding, and over fourty times faster
595faster than JSON, even with pretty-printing and key sorting. 805than JSON, even with pretty-printing and key sorting. It also compares
806favourably to Storable for small amounts of data.
596 807
597Using a longer test string (roughly 18KB, generated from Yahoo! Locals 808Using a longer test string (roughly 18KB, generated from Yahoo! Locals
598search API (http://nanoref.com/yahooapis/mgPdGg): 809search API (http://nanoref.com/yahooapis/mgPdGg):
599 810
600 module | encode | decode | 811 module | encode | decode |
601 -----------|------------|------------| 812 -----------|------------|------------|
602 JSON | 273.023 | 44.674 | 813 JSON | 55.260 | 34.971 |
603 JSON::DWIW | 1089.383 | 1145.704 | 814 JSON::DWIW | 825.228 | 1082.513 |
604 JSON::PC | 3097.419 | 2393.921 | 815 JSON::PC | 3571.444 | 2394.829 |
605 JSON::Syck | 514.060 | 843.053 | 816 JSON::PP | 210.987 | 32.574 |
606 JSON::XS | 6479.668 | 3636.364 | 817 JSON::Syck | 552.551 | 787.544 |
607 JSON::XS/2 | 3774.221 | 3599.124 | 818 JSON::XS | 5780.463 | 4854.519 |
819 JSON::XS/2 | 3869.998 | 4798.975 |
820 JSON::XS/3 | 5862.880 | 4798.975 |
821 Storable | 4445.002 | 5235.027 |
608 -----------+------------+------------+ 822 -----------+------------+------------+
609 823
610Again, JSON::XS leads by far. 824Again, JSON::XS leads by far (except for Storable which non-surprisingly
825decodes faster).
611 826
612On large strings containing lots of high unicode characters, some modules 827On large strings containing lots of high unicode characters, some modules
613(such as JSON::PC) seem to decode faster than JSON::XS, but the result 828(such as JSON::PC) seem to decode faster than JSON::XS, but the result
614will be broken due to missing (or wrong) unicode handling. Others refuse 829will be broken due to missing (or wrong) unicode handling. Others refuse
615to decode or encode properly, so it was impossible to prepare a fair 830to decode or encode properly, so it was impossible to prepare a fair
628Second, you need to avoid resource-starving attacks. That means you should 843Second, you need to avoid resource-starving attacks. That means you should
629limit the size of JSON texts you accept, or make sure then when your 844limit the size of JSON texts you accept, or make sure then when your
630resources run out, thats just fine (e.g. by using a separate process that 845resources run out, thats just fine (e.g. by using a separate process that
631can crash safely). The size of a JSON text in octets or characters is 846can crash safely). The size of a JSON text in octets or characters is
632usually a good indication of the size of the resources required to decode 847usually a good indication of the size of the resources required to decode
633it into a Perl structure. 848it into a Perl structure. While JSON::XS can check the size of the JSON
849text, it might be too late when you already have it in memory, so you
850might want to check the size before you accept the string.
634 851
635Third, JSON::XS recurses using the C stack when decoding objects and 852Third, JSON::XS recurses using the C stack when decoding objects and
636arrays. The C stack is a limited resource: for instance, on my amd64 853arrays. The C stack is a limited resource: for instance, on my amd64
637machine with 8MB of stack size I can decode around 180k nested arrays but 854machine with 8MB of stack size I can decode around 180k nested arrays but
638only 14k nested JSON objects (due to perl itself recursing deeply on croak 855only 14k nested JSON objects (due to perl itself recursing deeply on croak
640conservative, the default nesting limit is set to 512. If your process 857conservative, the default nesting limit is set to 512. If your process
641has a smaller stack, you should adjust this setting accordingly with the 858has a smaller stack, you should adjust this setting accordingly with the
642C<max_depth> method. 859C<max_depth> method.
643 860
644And last but least, something else could bomb you that I forgot to think 861And last but least, something else could bomb you that I forgot to think
645of. In that case, you get to keep the pieces. I am alway sopen for hints, 862of. In that case, you get to keep the pieces. I am always open for hints,
646though... 863though...
864
865If you are using JSON::XS to return packets to consumption
866by javascript scripts in a browser you should have a look at
867L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
868you are vulnerable to some common attack vectors (which really are browser
869design bugs, but it is still you who will have to deal with it, as major
870browser developers care only for features, not about doing security
871right).
647 872
648 873
649=head1 BUGS 874=head1 BUGS
650 875
651While the goal of this module is to be correct, that unfortunately does 876While the goal of this module is to be correct, that unfortunately does
653still relatively early in its development. If you keep reporting bugs they 878still relatively early in its development. If you keep reporting bugs they
654will be fixed swiftly, though. 879will be fixed swiftly, though.
655 880
656=cut 881=cut
657 882
883our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
884our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
885
658sub true() { \1 } 886sub true() { $true }
659sub false() { \0 } 887sub false() { $false }
888
889sub is_bool($) {
890 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
891# or UNIVERSAL::isa $_[0], "JSON::Literal"
892}
893
894XSLoader::load "JSON::XS", $VERSION;
895
896package JSON::XS::Boolean;
897
898use overload
899 "0+" => sub { ${$_[0]} },
900 "++" => sub { $_[0] = ${$_[0]} + 1 },
901 "--" => sub { $_[0] = ${$_[0]} - 1 },
902 fallback => 1;
660 903
6611; 9041;
662 905
663=head1 AUTHOR 906=head1 AUTHOR
664 907

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