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Comparing JSON-XS/XS.pm (file contents):
Revision 1.34 by root, Wed May 9 16:33:53 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 = '1.2'; 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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402 459
403For the more enlightened: note that in the following descriptions, 460For the more enlightened: note that in the following descriptions,
404lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 461lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
405refers to the abstract Perl language itself. 462refers to the abstract Perl language itself.
406 463
464
407=head2 JSON -> PERL 465=head2 JSON -> PERL
408 466
409=over 4 467=over 4
410 468
411=item object 469=item object
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431conversion details, but an integer may take slightly less memory and might 489conversion details, but an integer may take slightly less memory and might
432represent more values exactly than (floating point) numbers. 490represent more values exactly than (floating point) numbers.
433 491
434=item true, false 492=item true, false
435 493
436These 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>,
437this process. Future versions might represent those values differently, 495respectively. They are overloaded to act almost exactly like the numbers
438but 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
439Perl. 497the C<JSON::XS::is_bool> function.
440 498
441=item null 499=item null
442 500
443A JSON null atom becomes C<undef> in Perl. 501A JSON null atom becomes C<undef> in Perl.
444 502
445=back 503=back
504
446 505
447=head2 PERL -> JSON 506=head2 PERL -> JSON
448 507
449The 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
450truly 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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475C<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
476also 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.
477 536
478 to_json [\0,JSON::XS::true] # yields [false,true] 537 to_json [\0,JSON::XS::true] # yields [false,true]
479 538
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
480=item blessed objects 544=item blessed objects
481 545
482Blessed objects are not allowed. JSON::XS currently tries to encode their 546Blessed objects are not allowed. JSON::XS currently tries to encode their
483underlying representation (hash- or arrayref), but this behaviour might 547underlying representation (hash- or arrayref), but this behaviour might
484change in future versions. 548change in future versions.
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605 669
606Does not check input for validity. 670Does not check input for validity.
607 671
608=back 672=back
609 673
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
610=head2 SPEED 698=head2 SPEED
611 699
612It 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
613tables. 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
614in 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
615system. 703system.
616 704
617First comes a comparison between various modules using a very short JSON 705First comes a comparison between various modules using a very short
618string: 706single-line JSON string:
619 707
620 {"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]}
621 710
622It shows the number of encodes/decodes per second (JSON::XS uses the 711It shows the number of encodes/decodes per second (JSON::XS uses
623functional interface, while JSON::XS/2 uses the OO interface with 712the functional interface, while JSON::XS/2 uses the OO interface
624pretty-printing and hashkey sorting enabled). Higher is better: 713with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
714shrink). Higher is better:
625 715
626 module | encode | decode | 716 module | encode | decode |
627 -----------|------------|------------| 717 -----------|------------|------------|
628 JSON | 11488.516 | 7823.035 | 718 JSON | 7645.468 | 4208.613 |
629 JSON::DWIW | 94708.054 | 129094.260 | 719 JSON::DWIW | 40721.398 | 77101.176 |
630 JSON::PC | 63884.157 | 128528.212 | 720 JSON::PC | 65948.176 | 78251.940 |
631 JSON::Syck | 34898.677 | 42096.911 | 721 JSON::Syck | 22844.793 | 26479.192 |
632 JSON::XS | 654027.064 | 396423.669 | 722 JSON::XS | 388361.481 | 199728.762 |
633 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 |
634 -----------+------------+------------+ 726 -----------+------------+------------+
635 727
636That 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,
637encoding, more than three times faster on decoding, and about thirty times 729about three times faster on decoding, and over fourty times faster
638faster 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.
639 732
640Using a longer test string (roughly 18KB, generated from Yahoo! Locals 733Using a longer test string (roughly 18KB, generated from Yahoo! Locals
641search API (http://nanoref.com/yahooapis/mgPdGg): 734search API (http://nanoref.com/yahooapis/mgPdGg):
642 735
643 module | encode | decode | 736 module | encode | decode |
644 -----------|------------|------------| 737 -----------|------------|------------|
645 JSON | 273.023 | 44.674 | 738 JSON | 254.685 | 37.665 |
646 JSON::DWIW | 1089.383 | 1145.704 | 739 JSON::DWIW | 843.343 | 1049.731 |
647 JSON::PC | 3097.419 | 2393.921 | 740 JSON::PC | 3602.116 | 2307.352 |
648 JSON::Syck | 514.060 | 843.053 | 741 JSON::Syck | 505.107 | 787.899 |
649 JSON::XS | 6479.668 | 3636.364 | 742 JSON::XS | 5747.196 | 3690.220 |
650 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 |
651 -----------+------------+------------+ 746 -----------+------------+------------+
652 747
653Again, JSON::XS leads by far. 748Again, JSON::XS leads by far (except for Storable which non-surprisingly
749decodes faster).
654 750
655On large strings containing lots of high unicode characters, some modules 751On 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 752(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 753will be broken due to missing (or wrong) unicode handling. Others refuse
658to 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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671Second, you need to avoid resource-starving attacks. That means you should 767Second, 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 768limit 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 769resources 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 770can 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 771usually a good indication of the size of the resources required to decode
676it 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.
677 775
678Third, JSON::XS recurses using the C stack when decoding objects and 776Third, JSON::XS recurses using the C stack when decoding objects and
679arrays. 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
680machine 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
681only 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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686 784
687And 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
688of. 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,
689though... 787though...
690 788
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
691 797
692=head1 BUGS 798=head1 BUGS
693 799
694While 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
695not 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
696still relatively early in its development. If you keep reporting bugs they 802still relatively early in its development. If you keep reporting bugs they
697will be fixed swiftly, though. 803will be fixed swiftly, though.
698 804
699=cut 805=cut
700 806
807our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
809
701sub true() { \1 } 810sub true() { $true }
702sub 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;
703 827
7041; 8281;
705 829
706=head1 AUTHOR 830=head1 AUTHOR
707 831

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