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Revision 1.36 by root, Wed May 23 22:07:43 2007 UTC vs.
Revision 1.61 by root, Wed Sep 12 17:42:36 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 = '1.22'; 86our $VERSION = '1.5';
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
276 278
277Example, space_before and indent disabled, space_after enabled: 279Example, space_before and indent disabled, space_after enabled:
278 280
279 {"key": "value"} 281 {"key": "value"}
280 282
283=item $json = $json->relaxed ([$enable])
284
285If C<$enable> is true (or missing), then C<decode> will accept some
286extensions to normal JSON syntax (see below). C<encode> will not be
287affected in anyway. I<Be aware that this option makes you accept invalid
288JSON texts as if they were valid!>. I suggest only to use this option to
289parse application-specific files written by humans (configuration files,
290resource files etc.)
291
292If C<$enable> is false (the default), then C<decode> will only accept
293valid JSON texts.
294
295Currently accepted extensions are:
296
297=over 4
298
299=item * list items can have an end-comma
300
301JSON I<separates> array elements and key-value pairs with commas. This
302can be annoying if you write JSON texts manually and want to be able to
303quickly append elements, so this extension accepts comma at the end of
304such items not just between them:
305
306 [
307 1,
308 2, <- this comma not normally allowed
309 ]
310 {
311 "k1": "v1",
312 "k2": "v2", <- this comma not normally allowed
313 }
314
315=item * shell-style '#'-comments
316
317Whenever JSON allows whitespace, shell-style comments are additionally
318allowed. They are terminated by the first carriage-return or line-feed
319character, after which more white-space and comments are allowed.
320
321 [
322 1, # this comment not allowed in JSON
323 # neither this one...
324 ]
325
326=back
327
281=item $json = $json->canonical ([$enable]) 328=item $json = $json->canonical ([$enable])
282 329
283If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 330If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284by sorting their keys. This is adding a comparatively high overhead. 331by sorting their keys. This is adding a comparatively high overhead.
285 332
309Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, 356Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
310resulting in an invalid JSON text: 357resulting in an invalid JSON text:
311 358
312 JSON::XS->new->allow_nonref->encode ("Hello, World!") 359 JSON::XS->new->allow_nonref->encode ("Hello, World!")
313 => "Hello, World!" 360 => "Hello, World!"
361
362=item $json = $json->allow_blessed ([$enable])
363
364If C<$enable> is true (or missing), then the C<encode> method will not
365barf when it encounters a blessed reference. Instead, the value of the
366B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
367disabled or no C<to_json> method found) or a representation of the
368object (C<convert_blessed> enabled and C<to_json> method found) is being
369encoded. Has no effect on C<decode>.
370
371If C<$enable> is false (the default), then C<encode> will throw an
372exception when it encounters a blessed object.
373
374=item $json = $json->convert_blessed ([$enable])
375
376If C<$enable> is true (or missing), then C<encode>, upon encountering a
377blessed object, will check for the availability of the C<TO_JSON> method
378on the object's class. If found, it will be called in scalar context
379and the resulting scalar will be encoded instead of the object. If no
380C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
381to do.
382
383The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
384returns other blessed objects, those will be handled in the same
385way. C<TO_JSON> must take care of not causing an endless recursion cycle
386(== crash) in this case. The name of C<TO_JSON> was chosen because other
387methods called by the Perl core (== not by the user of the object) are
388usually in upper case letters and to avoid collisions with the C<to_json>
389function.
390
391This setting does not yet influence C<decode> in any way, but in the
392future, global hooks might get installed that influence C<decode> and are
393enabled by this setting.
394
395If C<$enable> is false, then the C<allow_blessed> setting will decide what
396to do when a blessed object is found.
397
398=item $json = $json->filter_json_object ([$coderef->($hashref)])
399
400When C<$coderef> is specified, it will be called from C<decode> each
401time it decodes a JSON object. The only argument is a reference to the
402newly-created hash. If the code references returns a single scalar (which
403need not be a reference), this value (i.e. a copy of that scalar to avoid
404aliasing) is inserted into the deserialised data structure. If it returns
405an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
406original deserialised hash will be inserted. This setting can slow down
407decoding considerably.
408
409When C<$coderef> is omitted or undefined, any existing callback will
410be removed and C<decode> will not change the deserialised hash in any
411way.
412
413Example, convert all JSON objects into the integer 5:
414
415 my $js = JSON::XS->new->filter_json_object (sub { 5 });
416 # returns [5]
417 $js->decode ('[{}]')
418 # throw an exception because allow_nonref is not enabled
419 # so a lone 5 is not allowed.
420 $js->decode ('{"a":1, "b":2}');
421
422=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
423
424Works remotely similar to C<filter_json_object>, but is only called for
425JSON objects having a single key named C<$key>.
426
427This C<$coderef> is called before the one specified via
428C<filter_json_object>, if any. It gets passed the single value in the JSON
429object. If it returns a single value, it will be inserted into the data
430structure. If it returns nothing (not even C<undef> but the empty list),
431the callback from C<filter_json_object> will be called next, as if no
432single-key callback were specified.
433
434If C<$coderef> is omitted or undefined, the corresponding callback will be
435disabled. There can only ever be one callback for a given key.
436
437As this callback gets called less often then the C<filter_json_object>
438one, decoding speed will not usually suffer as much. Therefore, single-key
439objects make excellent targets to serialise Perl objects into, especially
440as single-key JSON objects are as close to the type-tagged value concept
441as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
442support this in any way, so you need to make sure your data never looks
443like a serialised Perl hash.
444
445Typical names for the single object key are C<__class_whatever__>, or
446C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
447things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
448with real hashes.
449
450Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
451into the corresponding C<< $WIDGET{<id>} >> object:
452
453 # return whatever is in $WIDGET{5}:
454 JSON::XS
455 ->new
456 ->filter_json_single_key_object (__widget__ => sub {
457 $WIDGET{ $_[0] }
458 })
459 ->decode ('{"__widget__": 5')
460
461 # this can be used with a TO_JSON method in some "widget" class
462 # for serialisation to json:
463 sub WidgetBase::TO_JSON {
464 my ($self) = @_;
465
466 unless ($self->{id}) {
467 $self->{id} = ..get..some..id..;
468 $WIDGET{$self->{id}} = $self;
469 }
470
471 { __widget__ => $self->{id} }
472 }
314 473
315=item $json = $json->shrink ([$enable]) 474=item $json = $json->shrink ([$enable])
316 475
317Perl usually over-allocates memory a bit when allocating space for 476Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 477strings. This flag optionally resizes strings generated by either
351given character in a string. 510given character in a string.
352 511
353Setting the maximum depth to one disallows any nesting, so that ensures 512Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 513that the object is only a single hash/object or array.
355 514
356The argument to C<max_depth> will be rounded up to the next nearest power 515The argument to C<max_depth> will be rounded up to the next highest power
357of two. 516of two. If no argument is given, the highest possible setting will be
517used, which is rarely useful.
518
519See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
520
521=item $json = $json->max_size ([$maximum_string_size])
522
523Set the maximum length a JSON text may have (in bytes) where decoding is
524being attempted. The default is C<0>, meaning no limit. When C<decode>
525is called on a string longer then this number of characters it will not
526attempt to decode the string but throw an exception. This setting has no
527effect on C<encode> (yet).
528
529The argument to C<max_size> will be rounded up to the next B<highest>
530power of two (so may be more than requested). If no argument is given, the
531limit check will be deactivated (same as when C<0> is specified).
358 532
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 533See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 534
361=item $json_text = $json->encode ($perl_scalar) 535=item $json_text = $json->encode ($perl_scalar)
362 536
402 576
403For the more enlightened: note that in the following descriptions, 577For the more enlightened: note that in the following descriptions,
404lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 578lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
405refers to the abstract Perl language itself. 579refers to the abstract Perl language itself.
406 580
581
407=head2 JSON -> PERL 582=head2 JSON -> PERL
408 583
409=over 4 584=over 4
410 585
411=item object 586=item object
423are represented by the same codepoints in the Perl string, so no manual 598are represented by the same codepoints in the Perl string, so no manual
424decoding is necessary. 599decoding is necessary.
425 600
426=item number 601=item number
427 602
428A JSON number becomes either an integer or numeric (floating point) 603A JSON number becomes either an integer, numeric (floating point) or
429scalar in perl, depending on its range and any fractional parts. On the 604string scalar in perl, depending on its range and any fractional parts. On
430Perl level, there is no difference between those as Perl handles all the 605the Perl level, there is no difference between those as Perl handles all
431conversion details, but an integer may take slightly less memory and might 606the conversion details, but an integer may take slightly less memory and
432represent more values exactly than (floating point) numbers. 607might represent more values exactly than (floating point) numbers.
608
609If the number consists of digits only, JSON::XS will try to represent
610it as an integer value. If that fails, it will try to represent it as
611a numeric (floating point) value if that is possible without loss of
612precision. Otherwise it will preserve the number as a string value.
613
614Numbers containing a fractional or exponential part will always be
615represented as numeric (floating point) values, possibly at a loss of
616precision.
617
618This might create round-tripping problems as numbers might become strings,
619but as Perl is typeless there is no other way to do it.
433 620
434=item true, false 621=item true, false
435 622
436These JSON atoms become C<0>, C<1>, respectively. Information is lost in 623These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
437this process. Future versions might represent those values differently, 624respectively. They are overloaded to act almost exactly like the numbers
438but they will be guarenteed to act like these integers would normally in 625C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
439Perl. 626the C<JSON::XS::is_bool> function.
440 627
441=item null 628=item null
442 629
443A JSON null atom becomes C<undef> in Perl. 630A JSON null atom becomes C<undef> in Perl.
444 631
445=back 632=back
633
446 634
447=head2 PERL -> JSON 635=head2 PERL -> JSON
448 636
449The mapping from Perl to JSON is slightly more difficult, as Perl is a 637The mapping from Perl to JSON is slightly more difficult, as Perl is a
450truly typeless language, so we can only guess which JSON type is meant by 638truly typeless language, so we can only guess which JSON type is meant by
475C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 663C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
476also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 664also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
477 665
478 to_json [\0,JSON::XS::true] # yields [false,true] 666 to_json [\0,JSON::XS::true] # yields [false,true]
479 667
668=item JSON::XS::true, JSON::XS::false
669
670These special values become JSON true and JSON false values,
671respectively. You can also use C<\1> and C<\0> directly if you want.
672
480=item blessed objects 673=item blessed objects
481 674
482Blessed objects are not allowed. JSON::XS currently tries to encode their 675Blessed objects are not allowed. JSON::XS currently tries to encode their
483underlying representation (hash- or arrayref), but this behaviour might 676underlying representation (hash- or arrayref), but this behaviour might
484change in future versions. 677change in future versions.
605 798
606Does not check input for validity. 799Does not check input for validity.
607 800
608=back 801=back
609 802
803
804=head2 JSON and YAML
805
806You often hear that JSON is a subset (or a close subset) of YAML. This is,
807however, a mass hysteria and very far from the truth. In general, there is
808no way to configure JSON::XS to output a data structure as valid YAML.
809
810If you really must use JSON::XS to generate YAML, you should use this
811algorithm (subject to change in future versions):
812
813 my $to_yaml = JSON::XS->new->utf8->space_after (1);
814 my $yaml = $to_yaml->encode ($ref) . "\n";
815
816This will usually generate JSON texts that also parse as valid
817YAML. Please note that YAML has hardcoded limits on (simple) object key
818lengths that JSON doesn't have, so you should make sure that your hash
819keys are noticably shorter than the 1024 characters YAML allows.
820
821There might be other incompatibilities that I am not aware of. In general
822you should not try to generate YAML with a JSON generator or vice versa,
823or try to parse JSON with a YAML parser or vice versa: chances are high
824that you will run into severe interoperability problems.
825
826
610=head2 SPEED 827=head2 SPEED
611 828
612It seems that JSON::XS is surprisingly fast, as shown in the following 829It seems that JSON::XS is surprisingly fast, as shown in the following
613tables. They have been generated with the help of the C<eg/bench> program 830tables. They have been generated with the help of the C<eg/bench> program
614in the JSON::XS distribution, to make it easy to compare on your own 831in the JSON::XS distribution, to make it easy to compare on your own
615system. 832system.
616 833
617First comes a comparison between various modules using a very short JSON 834First comes a comparison between various modules using a very short
618string: 835single-line JSON string:
619 836
620 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 837 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
838 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
621 839
622It shows the number of encodes/decodes per second (JSON::XS uses the 840It shows the number of encodes/decodes per second (JSON::XS uses
623functional interface, while JSON::XS/2 uses the OO interface with 841the functional interface, while JSON::XS/2 uses the OO interface
624pretty-printing and hashkey sorting enabled). Higher is better: 842with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
843shrink). Higher is better:
625 844
845 Storable | 15779.925 | 14169.946 |
846 -----------+------------+------------+
626 module | encode | decode | 847 module | encode | decode |
627 -----------|------------|------------| 848 -----------|------------|------------|
628 JSON | 11488.516 | 7823.035 | 849 JSON | 4990.842 | 4088.813 |
629 JSON::DWIW | 94708.054 | 129094.260 | 850 JSON::DWIW | 51653.990 | 71575.154 |
630 JSON::PC | 63884.157 | 128528.212 | 851 JSON::PC | 65948.176 | 74631.744 |
631 JSON::Syck | 34898.677 | 42096.911 | 852 JSON::PP | 8931.652 | 3817.168 |
632 JSON::XS | 654027.064 | 396423.669 | 853 JSON::Syck | 24877.248 | 27776.848 |
633 JSON::XS/2 | 371564.190 | 371725.613 | 854 JSON::XS | 388361.481 | 227951.304 |
855 JSON::XS/2 | 227951.304 | 218453.333 |
856 JSON::XS/3 | 338250.323 | 218453.333 |
857 Storable | 16500.016 | 135300.129 |
634 -----------+------------+------------+ 858 -----------+------------+------------+
635 859
636That is, JSON::XS is more than six times faster than JSON::DWIW on 860That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
637encoding, more than three times faster on decoding, and about thirty times 861about three times faster on decoding, and over fourty times faster
638faster than JSON, even with pretty-printing and key sorting. 862than JSON, even with pretty-printing and key sorting. It also compares
863favourably to Storable for small amounts of data.
639 864
640Using a longer test string (roughly 18KB, generated from Yahoo! Locals 865Using a longer test string (roughly 18KB, generated from Yahoo! Locals
641search API (http://nanoref.com/yahooapis/mgPdGg): 866search API (http://nanoref.com/yahooapis/mgPdGg):
642 867
643 module | encode | decode | 868 module | encode | decode |
644 -----------|------------|------------| 869 -----------|------------|------------|
645 JSON | 273.023 | 44.674 | 870 JSON | 55.260 | 34.971 |
646 JSON::DWIW | 1089.383 | 1145.704 | 871 JSON::DWIW | 825.228 | 1082.513 |
647 JSON::PC | 3097.419 | 2393.921 | 872 JSON::PC | 3571.444 | 2394.829 |
648 JSON::Syck | 514.060 | 843.053 | 873 JSON::PP | 210.987 | 32.574 |
649 JSON::XS | 6479.668 | 3636.364 | 874 JSON::Syck | 552.551 | 787.544 |
650 JSON::XS/2 | 3774.221 | 3599.124 | 875 JSON::XS | 5780.463 | 4854.519 |
876 JSON::XS/2 | 3869.998 | 4798.975 |
877 JSON::XS/3 | 5862.880 | 4798.975 |
878 Storable | 4445.002 | 5235.027 |
651 -----------+------------+------------+ 879 -----------+------------+------------+
652 880
653Again, JSON::XS leads by far. 881Again, JSON::XS leads by far (except for Storable which non-surprisingly
882decodes faster).
654 883
655On large strings containing lots of high unicode characters, some modules 884On large strings containing lots of high unicode characters, some modules
656(such as JSON::PC) seem to decode faster than JSON::XS, but the result 885(such as JSON::PC) seem to decode faster than JSON::XS, but the result
657will be broken due to missing (or wrong) unicode handling. Others refuse 886will be broken due to missing (or wrong) unicode handling. Others refuse
658to decode or encode properly, so it was impossible to prepare a fair 887to decode or encode properly, so it was impossible to prepare a fair
671Second, you need to avoid resource-starving attacks. That means you should 900Second, you need to avoid resource-starving attacks. That means you should
672limit the size of JSON texts you accept, or make sure then when your 901limit the size of JSON texts you accept, or make sure then when your
673resources run out, thats just fine (e.g. by using a separate process that 902resources run out, thats just fine (e.g. by using a separate process that
674can crash safely). The size of a JSON text in octets or characters is 903can crash safely). The size of a JSON text in octets or characters is
675usually a good indication of the size of the resources required to decode 904usually a good indication of the size of the resources required to decode
676it into a Perl structure. 905it into a Perl structure. While JSON::XS can check the size of the JSON
906text, it might be too late when you already have it in memory, so you
907might want to check the size before you accept the string.
677 908
678Third, JSON::XS recurses using the C stack when decoding objects and 909Third, JSON::XS recurses using the C stack when decoding objects and
679arrays. The C stack is a limited resource: for instance, on my amd64 910arrays. The C stack is a limited resource: for instance, on my amd64
680machine with 8MB of stack size I can decode around 180k nested arrays but 911machine with 8MB of stack size I can decode around 180k nested arrays but
681only 14k nested JSON objects (due to perl itself recursing deeply on croak 912only 14k nested JSON objects (due to perl itself recursing deeply on croak
686 917
687And last but least, something else could bomb you that I forgot to think 918And last but least, something else could bomb you that I forgot to think
688of. In that case, you get to keep the pieces. I am always open for hints, 919of. In that case, you get to keep the pieces. I am always open for hints,
689though... 920though...
690 921
922If you are using JSON::XS to return packets to consumption
923by javascript scripts in a browser you should have a look at
924L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
925you are vulnerable to some common attack vectors (which really are browser
926design bugs, but it is still you who will have to deal with it, as major
927browser developers care only for features, not about doing security
928right).
929
691 930
692=head1 BUGS 931=head1 BUGS
693 932
694While the goal of this module is to be correct, that unfortunately does 933While the goal of this module is to be correct, that unfortunately does
695not mean its bug-free, only that I think its design is bug-free. It is 934not mean its bug-free, only that I think its design is bug-free. It is
696still relatively early in its development. If you keep reporting bugs they 935still relatively early in its development. If you keep reporting bugs they
697will be fixed swiftly, though. 936will be fixed swiftly, though.
698 937
699=cut 938=cut
700 939
940our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
941our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
942
701sub true() { \1 } 943sub true() { $true }
702sub false() { \0 } 944sub false() { $false }
945
946sub is_bool($) {
947 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
948# or UNIVERSAL::isa $_[0], "JSON::Literal"
949}
950
951XSLoader::load "JSON::XS", $VERSION;
952
953package JSON::XS::Boolean;
954
955use overload
956 "0+" => sub { ${$_[0]} },
957 "++" => sub { $_[0] = ${$_[0]} + 1 },
958 "--" => sub { $_[0] = ${$_[0]} - 1 },
959 fallback => 1;
703 960
7041; 9611;
705 962
706=head1 AUTHOR 963=head1 AUTHOR
707 964

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