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Comparing JSON-XS/XS.pm (file contents):
Revision 1.33 by root, Wed May 9 16:10:37 2007 UTC vs.
Revision 1.47 by root, Mon Jun 25 06:57:42 2007 UTC

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85 85
86package JSON::XS; 86package JSON::XS;
87 87
88use strict; 88use strict;
89 89
90BEGIN {
91 our $VERSION = '1.12'; 90our $VERSION = '1.4';
92 our @ISA = qw(Exporter); 91our @ISA = qw(Exporter);
93 92
94 our @EXPORT = qw(to_json from_json objToJson jsonToObj); 93our @EXPORT = qw(to_json from_json objToJson jsonToObj);
95 require Exporter;
96 94
97 require XSLoader; 95use Exporter;
98 XSLoader::load JSON::XS::, $VERSION; 96use XSLoader;
99}
100 97
101=head1 FUNCTIONAL INTERFACE 98=head1 FUNCTIONAL INTERFACE
102 99
103The following convinience methods are provided by this module. They are 100The following convinience methods are provided by this module. They are
104exported by default: 101exported by default:
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126This function call is functionally identical to: 123This function call is functionally identical to:
127 124
128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 125 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129 126
130except being faster. 127except being faster.
128
129=item $is_boolean = JSON::XS::is_bool $scalar
130
131Returns true if the passed scalar represents either JSON::XS::true or
132JSON::XS::false, two constants that act like C<1> and C<0>, respectively
133and are used to represent JSON C<true> and C<false> values in Perl.
134
135See MAPPING, below, for more information on how JSON values are mapped to
136Perl.
131 137
132=back 138=back
133 139
134 140
135=head1 OBJECT-ORIENTED INTERFACE 141=head1 OBJECT-ORIENTED INTERFACE
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309Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, 315Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
310resulting in an invalid JSON text: 316resulting in an invalid JSON text:
311 317
312 JSON::XS->new->allow_nonref->encode ("Hello, World!") 318 JSON::XS->new->allow_nonref->encode ("Hello, World!")
313 => "Hello, World!" 319 => "Hello, World!"
320
321=item $json = $json->allow_blessed ([$enable])
322
323If C<$enable> is true (or missing), then the C<encode> method will not
324barf when it encounters a blessed reference. Instead, the value of the
325B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
326disabled or no C<to_json> method found) or a representation of the
327object (C<convert_blessed> enabled and C<to_json> method found) is being
328encoded. Has no effect on C<decode>.
329
330If C<$enable> is false (the default), then C<encode> will throw an
331exception when it encounters a blessed object.
332
333=item $json = $json->convert_blessed ([$enable])
334
335If C<$enable> is true (or missing), then C<encode>, upon encountering a
336blessed object, will check for the availability of the C<TO_JSON> method
337on the object's class. If found, it will be called in scalar context
338and the resulting scalar will be encoded instead of the object. If no
339C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
340to do.
341
342The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
343returns other blessed objects, those will be handled in the same
344way. C<TO_JSON> must take care of not causing an endless recursion cycle
345(== crash) in this case. The name of C<TO_JSON> was chosen because other
346methods called by the Perl core (== not by the user of the object) are
347usually in upper case letters and to avoid collisions with the C<to_json>
348function.
349
350This setting does not yet influence C<decode> in any way, but in the
351future, global hooks might get installed that influence C<decode> and are
352enabled by this setting.
353
354If C<$enable> is false, then the C<allow_blessed> setting will decide what
355to do when a blessed object is found.
314 356
315=item $json = $json->shrink ([$enable]) 357=item $json = $json->shrink ([$enable])
316 358
317Perl usually over-allocates memory a bit when allocating space for 359Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 360strings. This flag optionally resizes strings generated by either
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351given character in a string. 393given character in a string.
352 394
353Setting the maximum depth to one disallows any nesting, so that ensures 395Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 396that the object is only a single hash/object or array.
355 397
356The argument to C<max_depth> will be rounded up to the next nearest power 398The argument to C<max_depth> will be rounded up to the next highest power
357of two. 399of two. If no argument is given, the highest possible setting will be
400used, which is rarely useful.
401
402See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
403
404=item $json = $json->max_size ([$maximum_string_size])
405
406Set the maximum length a JSON text may have (in bytes) where decoding is
407being attempted. The default is C<0>, meaning no limit. When C<decode>
408is called on a string longer then this number of characters it will not
409attempt to decode the string but throw an exception. This setting has no
410effect on C<encode> (yet).
411
412The argument to C<max_size> will be rounded up to the next B<highest>
413power of two (so may be more than requested). If no argument is given, the
414limit check will be deactivated (same as when C<0> is specified).
358 415
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 416See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 417
361=item $json_text = $json->encode ($perl_scalar) 418=item $json_text = $json->encode ($perl_scalar)
362 419
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374 431
375JSON numbers and strings become simple Perl scalars. JSON arrays become 432JSON numbers and strings become simple Perl scalars. JSON arrays become
376Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 433Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
377C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 434C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
378 435
436=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
437
438This works like the C<decode> method, but instead of raising an exception
439when there is trailing garbage after the first JSON object, it will
440silently stop parsing there and return the number of characters consumed
441so far.
442
443This is useful if your JSON texts are not delimited by an outer protocol
444(which is not the brightest thing to do in the first place) and you need
445to know where the JSON text ends.
446
447 JSON::XS->new->decode_prefix ("[1] the tail")
448 => ([], 3)
449
379=back 450=back
380 451
381 452
382=head1 MAPPING 453=head1 MAPPING
383 454
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387(what you put in comes out as something equivalent). 458(what you put in comes out as something equivalent).
388 459
389For the more enlightened: note that in the following descriptions, 460For the more enlightened: note that in the following descriptions,
390lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 461lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
391refers to the abstract Perl language itself. 462refers to the abstract Perl language itself.
463
392 464
393=head2 JSON -> PERL 465=head2 JSON -> PERL
394 466
395=over 4 467=over 4
396 468
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417conversion details, but an integer may take slightly less memory and might 489conversion details, but an integer may take slightly less memory and might
418represent more values exactly than (floating point) numbers. 490represent more values exactly than (floating point) numbers.
419 491
420=item true, false 492=item true, false
421 493
422These JSON atoms become C<0>, C<1>, respectively. Information is lost in 494These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
423this process. Future versions might represent those values differently, 495respectively. They are overloaded to act almost exactly like the numbers
424but they will be guarenteed to act like these integers would normally in 496C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
425Perl. 497the C<JSON::XS::is_bool> function.
426 498
427=item null 499=item null
428 500
429A JSON null atom becomes C<undef> in Perl. 501A JSON null atom becomes C<undef> in Perl.
430 502
431=back 503=back
504
432 505
433=head2 PERL -> JSON 506=head2 PERL -> JSON
434 507
435The mapping from Perl to JSON is slightly more difficult, as Perl is a 508The 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 509truly 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 534C<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. 535also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
463 536
464 to_json [\0,JSON::XS::true] # yields [false,true] 537 to_json [\0,JSON::XS::true] # yields [false,true]
465 538
539=item JSON::XS::true, JSON::XS::false
540
541These special values become JSON true and JSON false values,
542respectively. You cna alos use C<\1> and C<\0> directly if you want.
543
466=item blessed objects 544=item blessed objects
467 545
468Blessed objects are not allowed. JSON::XS currently tries to encode their 546Blessed objects are not allowed. JSON::XS currently tries to encode their
469underlying representation (hash- or arrayref), but this behaviour might 547underlying representation (hash- or arrayref), but this behaviour might
470change in future versions. 548change in future versions.
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591 669
592Does not check input for validity. 670Does not check input for validity.
593 671
594=back 672=back
595 673
674
675=head2 JSON and YAML
676
677You often hear that JSON is a subset (or a close subset) of YAML. This is,
678however, a mass hysteria and very far from the truth. In general, there is
679no way to configure JSON::XS to output a data structure as valid YAML.
680
681If you really must use JSON::XS to generate YAML, you should use this
682algorithm (subject to change in future versions):
683
684 my $to_yaml = JSON::XS->new->utf8->space_after (1);
685 my $yaml = $to_yaml->encode ($ref) . "\n";
686
687This will usually generate JSON texts that also parse as valid
688YAML. Please note that YAML has hardcoded limits on (simple) object key
689lengths that JSON doesn't have, so you should make sure that your hash
690keys are noticably shorter than the 1024 characters YAML allows.
691
692There might be other incompatibilities that I am not aware of. In general
693you should not try to generate YAML with a JSON generator or vice versa,
694or try to parse JSON with a YAML parser or vice versa: chances are high
695that you will run into severe interoperability problems.
696
697
596=head2 SPEED 698=head2 SPEED
597 699
598It seems that JSON::XS is surprisingly fast, as shown in the following 700It 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 701tables. 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 702in the JSON::XS distribution, to make it easy to compare on your own
601system. 703system.
602 704
603First comes a comparison between various modules using a very short JSON 705First comes a comparison between various modules using a very short
604string: 706single-line JSON string:
605 707
606 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 708 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
709 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
607 710
608It shows the number of encodes/decodes per second (JSON::XS uses the 711It shows the number of encodes/decodes per second (JSON::XS uses
609functional interface, while JSON::XS/2 uses the OO interface with 712the functional interface, while JSON::XS/2 uses the OO interface
610pretty-printing and hashkey sorting enabled). Higher is better: 713with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
714shrink). Higher is better:
611 715
612 module | encode | decode | 716 module | encode | decode |
613 -----------|------------|------------| 717 -----------|------------|------------|
614 JSON | 11488.516 | 7823.035 | 718 JSON | 7645.468 | 4208.613 |
615 JSON::DWIW | 94708.054 | 129094.260 | 719 JSON::DWIW | 40721.398 | 77101.176 |
616 JSON::PC | 63884.157 | 128528.212 | 720 JSON::PC | 65948.176 | 78251.940 |
617 JSON::Syck | 34898.677 | 42096.911 | 721 JSON::Syck | 22844.793 | 26479.192 |
618 JSON::XS | 654027.064 | 396423.669 | 722 JSON::XS | 388361.481 | 199728.762 |
619 JSON::XS/2 | 371564.190 | 371725.613 | 723 JSON::XS/2 | 218453.333 | 192399.266 |
724 JSON::XS/3 | 338250.323 | 192399.266 |
725 Storable | 15779.925 | 14169.946 |
620 -----------+------------+------------+ 726 -----------+------------+------------+
621 727
622That is, JSON::XS is more than six times faster than JSON::DWIW on 728That 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 729about three times faster on decoding, and over fourty times faster
624faster than JSON, even with pretty-printing and key sorting. 730than JSON, even with pretty-printing and key sorting. It also compares
731favourably to Storable for small amounts of data.
625 732
626Using a longer test string (roughly 18KB, generated from Yahoo! Locals 733Using a longer test string (roughly 18KB, generated from Yahoo! Locals
627search API (http://nanoref.com/yahooapis/mgPdGg): 734search API (http://nanoref.com/yahooapis/mgPdGg):
628 735
629 module | encode | decode | 736 module | encode | decode |
630 -----------|------------|------------| 737 -----------|------------|------------|
631 JSON | 273.023 | 44.674 | 738 JSON | 254.685 | 37.665 |
632 JSON::DWIW | 1089.383 | 1145.704 | 739 JSON::DWIW | 843.343 | 1049.731 |
633 JSON::PC | 3097.419 | 2393.921 | 740 JSON::PC | 3602.116 | 2307.352 |
634 JSON::Syck | 514.060 | 843.053 | 741 JSON::Syck | 505.107 | 787.899 |
635 JSON::XS | 6479.668 | 3636.364 | 742 JSON::XS | 5747.196 | 3690.220 |
636 JSON::XS/2 | 3774.221 | 3599.124 | 743 JSON::XS/2 | 3968.121 | 3676.634 |
744 JSON::XS/3 | 6105.246 | 3662.508 |
745 Storable | 4417.337 | 5285.161 |
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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