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Revision 1.39 by root, Mon Jun 11 02:58:10 2007 UTC vs.
Revision 1.52 by root, Mon Jul 2 02:57:11 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);
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85 81
86package JSON::XS; 82package JSON::XS;
87 83
88use strict; 84use strict;
89 85
90BEGIN {
91 our $VERSION = '1.23'; 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:
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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
… …
309Example, 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>,
310resulting in an invalid JSON text: 312resulting in an invalid JSON text:
311 313
312 JSON::XS->new->allow_nonref->encode ("Hello, World!") 314 JSON::XS->new->allow_nonref->encode ("Hello, World!")
313 => "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 }
314 428
315=item $json = $json->shrink ([$enable]) 429=item $json = $json->shrink ([$enable])
316 430
317Perl usually over-allocates memory a bit when allocating space for 431Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 432strings. This flag optionally resizes strings generated by either
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351given character in a string. 465given character in a string.
352 466
353Setting the maximum depth to one disallows any nesting, so that ensures 467Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 468that the object is only a single hash/object or array.
355 469
356The 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
357of 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).
358 487
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 488See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 489
361=item $json_text = $json->encode ($perl_scalar) 490=item $json_text = $json->encode ($perl_scalar)
362 491
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432conversion details, but an integer may take slightly less memory and might 561conversion details, but an integer may take slightly less memory and might
433represent more values exactly than (floating point) numbers. 562represent more values exactly than (floating point) numbers.
434 563
435=item true, false 564=item true, false
436 565
437These 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>,
438this process. Future versions might represent those values differently, 567respectively. They are overloaded to act almost exactly like the numbers
439but 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
440Perl. 569the C<JSON::XS::is_bool> function.
441 570
442=item null 571=item null
443 572
444A JSON null atom becomes C<undef> in Perl. 573A JSON null atom becomes C<undef> in Perl.
445 574
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477C<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
478also 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.
479 608
480 to_json [\0,JSON::XS::true] # yields [false,true] 609 to_json [\0,JSON::XS::true] # yields [false,true]
481 610
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
482=item blessed objects 616=item blessed objects
483 617
484Blessed objects are not allowed. JSON::XS currently tries to encode their 618Blessed objects are not allowed. JSON::XS currently tries to encode their
485underlying representation (hash- or arrayref), but this behaviour might 619underlying representation (hash- or arrayref), but this behaviour might
486change in future versions. 620change in future versions.
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614 748
615You often hear that JSON is a subset (or a close subset) of YAML. This is, 749You often hear that JSON is a subset (or a close subset) of YAML. This is,
616however, a mass hysteria and very far from the truth. In general, there is 750however, a mass hysteria and very far from the truth. In general, there is
617no way to configure JSON::XS to output a data structure as valid YAML. 751no way to configure JSON::XS to output a data structure as valid YAML.
618 752
619If you really must use JSON::XS to generate YAML, you should this 753If you really must use JSON::XS to generate YAML, you should use this
620algorithm (subject to change in future versions): 754algorithm (subject to change in future versions):
621 755
622 my $to_yaml = JSON::XS->new->utf8->space_after (1); 756 my $to_yaml = JSON::XS->new->utf8->space_after (1);
623 my $yaml = $to_yaml->encode ($ref) . "\n"; 757 my $yaml = $to_yaml->encode ($ref) . "\n";
624 758
625This will usually generate JSON texts that also parse as valid 759This will usually generate JSON texts that also parse as valid
626YAML. Please note that YAML has hardcoded limits on object key lengths 760YAML. Please note that YAML has hardcoded limits on (simple) object key
627that JSON doesn't have, so you should make sure that your hash keys are 761lengths that JSON doesn't have, so you should make sure that your hash
628noticably shorter than 1024 characters. 762keys are noticably shorter than the 1024 characters YAML allows.
629 763
630There might be other incompatibilities that I am not aware of. In general 764There might be other incompatibilities that I am not aware of. In general
631you should not try to generate YAML with a JSON generator or vice versa, 765you should not try to generate YAML with a JSON generator or vice versa,
632or try to parse JSON with a YAML parser 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.
633 768
634 769
635=head2 SPEED 770=head2 SPEED
636 771
637It 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
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648It shows the number of encodes/decodes per second (JSON::XS uses 783It shows the number of encodes/decodes per second (JSON::XS uses
649the functional interface, while JSON::XS/2 uses the OO interface 784the functional interface, while JSON::XS/2 uses the OO interface
650with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 785with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
651shrink). Higher is better: 786shrink). Higher is better:
652 787
788 Storable | 15779.925 | 14169.946 |
789 -----------+------------+------------+
653 module | encode | decode | 790 module | encode | decode |
654 -----------|------------|------------| 791 -----------|------------|------------|
655 JSON | 7645.468 | 4208.613 | 792 JSON | 4990.842 | 4088.813 |
656 JSON::DWIW | 68534.379 | 79437.576 | 793 JSON::DWIW | 51653.990 | 71575.154 |
657 JSON::PC | 65948.176 | 78251.940 | 794 JSON::PC | 65948.176 | 74631.744 |
658 JSON::Syck | 23379.621 | 28416.694 | 795 JSON::PP | 8931.652 | 3817.168 |
796 JSON::Syck | 24877.248 | 27776.848 |
659 JSON::XS | 388361.481 | 199728.762 | 797 JSON::XS | 388361.481 | 227951.304 |
660 JSON::XS/2 | 218453.333 | 192399.266 | 798 JSON::XS/2 | 227951.304 | 218453.333 |
661 JSON::XS/3 | 338250.323 | 192399.266 | 799 JSON::XS/3 | 338250.323 | 218453.333 |
662 Storable | 15732.573 | 28571.553 | 800 Storable | 16500.016 | 135300.129 |
663 -----------+------------+------------+ 801 -----------+------------+------------+
664 802
665That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 803That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
666about three times faster on decoding, and over fourty times faster 804about three times faster on decoding, and over fourty times faster
667than JSON, even with pretty-printing and key sorting. It also compares 805than JSON, even with pretty-printing and key sorting. It also compares
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670Using a longer test string (roughly 18KB, generated from Yahoo! Locals 808Using a longer test string (roughly 18KB, generated from Yahoo! Locals
671search API (http://nanoref.com/yahooapis/mgPdGg): 809search API (http://nanoref.com/yahooapis/mgPdGg):
672 810
673 module | encode | decode | 811 module | encode | decode |
674 -----------|------------|------------| 812 -----------|------------|------------|
675 JSON | 254.685 | 37.665 | 813 JSON | 55.260 | 34.971 |
676 JSON::DWIW | 1014.244 | 1087.678 | 814 JSON::DWIW | 825.228 | 1082.513 |
677 JSON::PC | 3602.116 | 2307.352 | 815 JSON::PC | 3571.444 | 2394.829 |
678 JSON::Syck | 558.035 | 776.263 | 816 JSON::PP | 210.987 | 32.574 |
679 JSON::XS | 5747.196 | 3543.684 | 817 JSON::Syck | 552.551 | 787.544 |
680 JSON::XS/2 | 3968.121 | 3589.170 | 818 JSON::XS | 5780.463 | 4854.519 |
681 JSON::XS/3 | 6105.246 | 3561.134 | 819 JSON::XS/2 | 3869.998 | 4798.975 |
682 Storable | 4456.337 | 5320.020 | 820 JSON::XS/3 | 5862.880 | 4798.975 |
821 Storable | 4445.002 | 5235.027 |
683 -----------+------------+------------+ 822 -----------+------------+------------+
684 823
685Again, JSON::XS leads by far. 824Again, JSON::XS leads by far (except for Storable which non-surprisingly
825decodes faster).
686 826
687On large strings containing lots of high unicode characters, some modules 827On large strings containing lots of high unicode characters, some modules
688(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
689will be broken due to missing (or wrong) unicode handling. Others refuse 829will be broken due to missing (or wrong) unicode handling. Others refuse
690to 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
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703Second, you need to avoid resource-starving attacks. That means you should 843Second, you need to avoid resource-starving attacks. That means you should
704limit 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
705resources 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
706can 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
707usually 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
708it 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.
709 851
710Third, JSON::XS recurses using the C stack when decoding objects and 852Third, JSON::XS recurses using the C stack when decoding objects and
711arrays. 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
712machine 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
713only 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
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718 860
719And 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
720of. In that case, you get to keep the pieces. I am always open for hints, 862of. In that case, you get to keep the pieces. I am always open for hints,
721though... 863though...
722 864
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).
872
723 873
724=head1 BUGS 874=head1 BUGS
725 875
726While 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
727not mean its bug-free, only that I think its design is bug-free. It is 877not mean its bug-free, only that I think its design is bug-free. It is
728still relatively early in its development. If you keep reporting bugs they 878still relatively early in its development. If you keep reporting bugs they
729will be fixed swiftly, though. 879will be fixed swiftly, though.
730 880
731=cut 881=cut
732 882
883our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };
884our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };
885
733sub true() { \1 } 886sub true() { $true }
734sub 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;
735 903
7361; 9041;
737 905
738=head1 AUTHOR 906=head1 AUTHOR
739 907

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