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Revision 1.33 by root, Wed May 9 16:10:37 2007 UTC vs.
Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC

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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 = '1.12'; 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
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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.
314 352
315=item $json = $json->shrink ([$enable]) 353=item $json = $json->shrink ([$enable])
316 354
317Perl usually over-allocates memory a bit when allocating space for 355Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 356strings. This flag optionally resizes strings generated by either
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351given character in a string. 389given character in a string.
352 390
353Setting the maximum depth to one disallows any nesting, so that ensures 391Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 392that the object is only a single hash/object or array.
355 393
356The argument to C<max_depth> will be rounded up to the next nearest power 394The argument to C<max_depth> will be rounded up to the next highest power
357of two. 395of two. If no argument is given, the highest possible setting will be
396used, which is rarely useful.
397
398See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
399
400=item $json = $json->max_size ([$maximum_string_size])
401
402Set the maximum length a JSON text may have (in bytes) where decoding is
403being attempted. The default is C<0>, meaning no limit. When C<decode>
404is called on a string longer then this number of characters it will not
405attempt to decode the string but throw an exception. This setting has no
406effect on C<encode> (yet).
407
408The argument to C<max_size> will be rounded up to the next B<highest>
409power of two (so may be more than requested). If no argument is given, the
410limit check will be deactivated (same as when C<0> is specified).
358 411
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 412See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 413
361=item $json_text = $json->encode ($perl_scalar) 414=item $json_text = $json->encode ($perl_scalar)
362 415
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374 427
375JSON numbers and strings become simple Perl scalars. JSON arrays become 428JSON numbers and strings become simple Perl scalars. JSON arrays become
376Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 429Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
377C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 430C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
378 431
432=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
433
434This works like the C<decode> method, but instead of raising an exception
435when there is trailing garbage after the first JSON object, it will
436silently stop parsing there and return the number of characters consumed
437so far.
438
439This is useful if your JSON texts are not delimited by an outer protocol
440(which is not the brightest thing to do in the first place) and you need
441to know where the JSON text ends.
442
443 JSON::XS->new->decode_prefix ("[1] the tail")
444 => ([], 3)
445
379=back 446=back
380 447
381 448
382=head1 MAPPING 449=head1 MAPPING
383 450
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387(what you put in comes out as something equivalent). 454(what you put in comes out as something equivalent).
388 455
389For the more enlightened: note that in the following descriptions, 456For the more enlightened: note that in the following descriptions,
390lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 457lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
391refers to the abstract Perl language itself. 458refers to the abstract Perl language itself.
459
392 460
393=head2 JSON -> PERL 461=head2 JSON -> PERL
394 462
395=over 4 463=over 4
396 464
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417conversion details, but an integer may take slightly less memory and might 485conversion details, but an integer may take slightly less memory and might
418represent more values exactly than (floating point) numbers. 486represent more values exactly than (floating point) numbers.
419 487
420=item true, false 488=item true, false
421 489
422These JSON atoms become C<0>, C<1>, respectively. Information is lost in 490These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
423this process. Future versions might represent those values differently, 491respectively. They are overloaded to act almost exactly like the numbers
424but they will be guarenteed to act like these integers would normally in 492C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
425Perl. 493the C<JSON::XS::is_bool> function.
426 494
427=item null 495=item null
428 496
429A JSON null atom becomes C<undef> in Perl. 497A JSON null atom becomes C<undef> in Perl.
430 498
431=back 499=back
500
432 501
433=head2 PERL -> JSON 502=head2 PERL -> JSON
434 503
435The mapping from Perl to JSON is slightly more difficult, as Perl is a 504The mapping from Perl to JSON is slightly more difficult, as Perl is a
436truly typeless language, so we can only guess which JSON type is meant by 505truly typeless language, so we can only guess which JSON type is meant by
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461C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 530C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
462also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 531also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
463 532
464 to_json [\0,JSON::XS::true] # yields [false,true] 533 to_json [\0,JSON::XS::true] # yields [false,true]
465 534
535=item JSON::XS::true, JSON::XS::false
536
537These special values become JSON true and JSON false values,
538respectively. You cna alos use C<\1> and C<\0> directly if you want.
539
466=item blessed objects 540=item blessed objects
467 541
468Blessed objects are not allowed. JSON::XS currently tries to encode their 542Blessed objects are not allowed. JSON::XS currently tries to encode their
469underlying representation (hash- or arrayref), but this behaviour might 543underlying representation (hash- or arrayref), but this behaviour might
470change in future versions. 544change in future versions.
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591 665
592Does not check input for validity. 666Does not check input for validity.
593 667
594=back 668=back
595 669
670
671=head2 JSON and YAML
672
673You often hear that JSON is a subset (or a close subset) of YAML. This is,
674however, a mass hysteria and very far from the truth. In general, there is
675no way to configure JSON::XS to output a data structure as valid YAML.
676
677If you really must use JSON::XS to generate YAML, you should use this
678algorithm (subject to change in future versions):
679
680 my $to_yaml = JSON::XS->new->utf8->space_after (1);
681 my $yaml = $to_yaml->encode ($ref) . "\n";
682
683This will usually generate JSON texts that also parse as valid
684YAML. Please note that YAML has hardcoded limits on (simple) object key
685lengths that JSON doesn't have, so you should make sure that your hash
686keys are noticably shorter than the 1024 characters YAML allows.
687
688There might be other incompatibilities that I am not aware of. In general
689you should not try to generate YAML with a JSON generator or vice versa,
690or try to parse JSON with a YAML parser or vice versa: chances are high
691that you will run into severe interoperability problems.
692
693
596=head2 SPEED 694=head2 SPEED
597 695
598It seems that JSON::XS is surprisingly fast, as shown in the following 696It seems that JSON::XS is surprisingly fast, as shown in the following
599tables. They have been generated with the help of the C<eg/bench> program 697tables. They have been generated with the help of the C<eg/bench> program
600in the JSON::XS distribution, to make it easy to compare on your own 698in the JSON::XS distribution, to make it easy to compare on your own
601system. 699system.
602 700
603First comes a comparison between various modules using a very short JSON 701First comes a comparison between various modules using a very short
604string: 702single-line JSON string:
605 703
606 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 704 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
705 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
607 706
608It shows the number of encodes/decodes per second (JSON::XS uses the 707It shows the number of encodes/decodes per second (JSON::XS uses
609functional interface, while JSON::XS/2 uses the OO interface with 708the functional interface, while JSON::XS/2 uses the OO interface
610pretty-printing and hashkey sorting enabled). Higher is better: 709with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
710shrink). Higher is better:
611 711
712 Storable | 15779.925 | 14169.946 |
713 -----------+------------+------------+
612 module | encode | decode | 714 module | encode | decode |
613 -----------|------------|------------| 715 -----------|------------|------------|
614 JSON | 11488.516 | 7823.035 | 716 JSON | 4990.842 | 4088.813 |
615 JSON::DWIW | 94708.054 | 129094.260 | 717 JSON::DWIW | 51653.990 | 71575.154 |
616 JSON::PC | 63884.157 | 128528.212 | 718 JSON::PC | 65948.176 | 74631.744 |
617 JSON::Syck | 34898.677 | 42096.911 | 719 JSON::PP | 8931.652 | 3817.168 |
618 JSON::XS | 654027.064 | 396423.669 | 720 JSON::Syck | 24877.248 | 27776.848 |
619 JSON::XS/2 | 371564.190 | 371725.613 | 721 JSON::XS | 388361.481 | 227951.304 |
722 JSON::XS/2 | 227951.304 | 218453.333 |
723 JSON::XS/3 | 338250.323 | 218453.333 |
724 Storable | 16500.016 | 135300.129 |
620 -----------+------------+------------+ 725 -----------+------------+------------+
621 726
622That is, JSON::XS is more than six times faster than JSON::DWIW on 727That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
623encoding, more than three times faster on decoding, and about thirty times 728about three times faster on decoding, and over fourty times faster
624faster than JSON, even with pretty-printing and key sorting. 729than JSON, even with pretty-printing and key sorting. It also compares
730favourably to Storable for small amounts of data.
625 731
626Using a longer test string (roughly 18KB, generated from Yahoo! Locals 732Using a longer test string (roughly 18KB, generated from Yahoo! Locals
627search API (http://nanoref.com/yahooapis/mgPdGg): 733search API (http://nanoref.com/yahooapis/mgPdGg):
628 734
629 module | encode | decode | 735 module | encode | decode |
630 -----------|------------|------------| 736 -----------|------------|------------|
631 JSON | 273.023 | 44.674 | 737 JSON | 55.260 | 34.971 |
632 JSON::DWIW | 1089.383 | 1145.704 | 738 JSON::DWIW | 825.228 | 1082.513 |
633 JSON::PC | 3097.419 | 2393.921 | 739 JSON::PC | 3571.444 | 2394.829 |
634 JSON::Syck | 514.060 | 843.053 | 740 JSON::PP | 210.987 | 32.574 |
635 JSON::XS | 6479.668 | 3636.364 | 741 JSON::Syck | 552.551 | 787.544 |
636 JSON::XS/2 | 3774.221 | 3599.124 | 742 JSON::XS | 5780.463 | 4854.519 |
743 JSON::XS/2 | 3869.998 | 4798.975 |
744 JSON::XS/3 | 5862.880 | 4798.975 |
745 Storable | 4445.002 | 5235.027 |
637 -----------+------------+------------+ 746 -----------+------------+------------+
638 747
639Again, JSON::XS leads by far. 748Again, JSON::XS leads by far (except for Storable which non-surprisingly
749decodes faster).
640 750
641On large strings containing lots of high unicode characters, some modules 751On large strings containing lots of high unicode characters, some modules
642(such as JSON::PC) seem to decode faster than JSON::XS, but the result 752(such as JSON::PC) seem to decode faster than JSON::XS, but the result
643will be broken due to missing (or wrong) unicode handling. Others refuse 753will be broken due to missing (or wrong) unicode handling. Others refuse
644to decode or encode properly, so it was impossible to prepare a fair 754to decode or encode properly, so it was impossible to prepare a fair
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657Second, you need to avoid resource-starving attacks. That means you should 767Second, you need to avoid resource-starving attacks. That means you should
658limit the size of JSON texts you accept, or make sure then when your 768limit the size of JSON texts you accept, or make sure then when your
659resources run out, thats just fine (e.g. by using a separate process that 769resources run out, thats just fine (e.g. by using a separate process that
660can crash safely). The size of a JSON text in octets or characters is 770can crash safely). The size of a JSON text in octets or characters is
661usually a good indication of the size of the resources required to decode 771usually a good indication of the size of the resources required to decode
662it into a Perl structure. 772it into a Perl structure. While JSON::XS can check the size of the JSON
773text, it might be too late when you already have it in memory, so you
774might want to check the size before you accept the string.
663 775
664Third, JSON::XS recurses using the C stack when decoding objects and 776Third, JSON::XS recurses using the C stack when decoding objects and
665arrays. The C stack is a limited resource: for instance, on my amd64 777arrays. The C stack is a limited resource: for instance, on my amd64
666machine with 8MB of stack size I can decode around 180k nested arrays but 778machine with 8MB of stack size I can decode around 180k nested arrays but
667only 14k nested JSON objects (due to perl itself recursing deeply on croak 779only 14k nested JSON objects (due to perl itself recursing deeply on croak
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672 784
673And last but least, something else could bomb you that I forgot to think 785And last but least, something else could bomb you that I forgot to think
674of. In that case, you get to keep the pieces. I am always open for hints, 786of. In that case, you get to keep the pieces. I am always open for hints,
675though... 787though...
676 788
789If you are using JSON::XS to return packets to consumption
790by javascript scripts in a browser you should have a look at
791L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
792you are vulnerable to some common attack vectors (which really are browser
793design bugs, but it is still you who will have to deal with it, as major
794browser developers care only for features, not about doing security
795right).
796
677 797
678=head1 BUGS 798=head1 BUGS
679 799
680While the goal of this module is to be correct, that unfortunately does 800While the goal of this module is to be correct, that unfortunately does
681not mean its bug-free, only that I think its design is bug-free. It is 801not mean its bug-free, only that I think its design is bug-free. It is
682still relatively early in its development. If you keep reporting bugs they 802still relatively early in its development. If you keep reporting bugs they
683will be fixed swiftly, though. 803will be fixed swiftly, though.
684 804
685=cut 805=cut
686 806
807our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
809
687sub true() { \1 } 810sub true() { $true }
688sub false() { \0 } 811sub false() { $false }
812
813sub is_bool($) {
814 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
815# or UNIVERSAL::isa $_[0], "JSON::Literal"
816}
817
818XSLoader::load "JSON::XS", $VERSION;
819
820package JSON::XS::Boolean;
821
822use overload
823 "0+" => sub { ${$_[0]} },
824 "++" => sub { $_[0] = ${$_[0]} + 1 },
825 "--" => sub { $_[0] = ${$_[0]} - 1 },
826 fallback => 1;
689 827
6901; 8281;
691 829
692=head1 AUTHOR 830=head1 AUTHOR
693 831

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