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Revision 1.24 by root, Thu Mar 29 01:27:36 2007 UTC vs.
Revision 1.43 by root, Sat Jun 23 23:49:29 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 = '0.8'; 90our $VERSION = '1.3';
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 $scalar
130
131Returns true if the passed scalar represents either JSON::XS::true or
132JSON::XS::false, two constants that act like C<1> and C<0>, respectively
133and are used to represent JSON C<true> and C<false> values in Perl.
134
135See MAPPING, below, for more information on how JSON values are mapped to
136Perl.
131 137
132=back 138=back
133 139
134 140
135=head1 OBJECT-ORIENTED INTERFACE 141=head1 OBJECT-ORIENTED INTERFACE
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154 160
155If C<$enable> is true (or missing), then the C<encode> method will not 161If C<$enable> is true (or missing), then the C<encode> method will not
156generate characters outside the code range C<0..127> (which is ASCII). Any 162generate characters outside the code range C<0..127> (which is ASCII). Any
157unicode characters outside that range will be escaped using either a 163unicode characters outside that range will be escaped using either a
158single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 164single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159as per RFC4627. 165as per RFC4627. The resulting encoded JSON text can be treated as a native
166unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
167or any other superset of ASCII.
160 168
161If C<$enable> is false, then the C<encode> method will not escape Unicode 169If C<$enable> is false, then the C<encode> method will not escape Unicode
162characters unless required by the JSON syntax. This results in a faster 170characters unless required by the JSON syntax or other flags. This results
163and more compact format. 171in a faster and more compact format.
172
173The main use for this flag is to produce JSON texts that can be
174transmitted over a 7-bit channel, as the encoded JSON texts will not
175contain any 8 bit characters.
164 176
165 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 177 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
166 => ["\ud801\udc01"] 178 => ["\ud801\udc01"]
179
180=item $json = $json->latin1 ([$enable])
181
182If C<$enable> is true (or missing), then the C<encode> method will encode
183the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
184outside the code range C<0..255>. The resulting string can be treated as a
185latin1-encoded JSON text or a native unicode string. The C<decode> method
186will not be affected in any way by this flag, as C<decode> by default
187expects unicode, which is a strict superset of latin1.
188
189If C<$enable> is false, then the C<encode> method will not escape Unicode
190characters unless required by the JSON syntax or other flags.
191
192The main use for this flag is efficiently encoding binary data as JSON
193text, as most octets will not be escaped, resulting in a smaller encoded
194size. The disadvantage is that the resulting JSON text is encoded
195in latin1 (and must correctly be treated as such when storing and
196transfering), a rare encoding for JSON. It is therefore most useful when
197you want to store data structures known to contain binary data efficiently
198in files or databases, not when talking to other JSON encoders/decoders.
199
200 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
201 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
167 202
168=item $json = $json->utf8 ([$enable]) 203=item $json = $json->utf8 ([$enable])
169 204
170If C<$enable> is true (or missing), then the C<encode> method will encode 205If C<$enable> is true (or missing), then the C<encode> method will encode
171the JSON result into UTF-8, as required by many protocols, while the 206the JSON result into UTF-8, as required by many protocols, while the
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309strings that look like integers or floats into integers or floats 344strings that look like integers or floats into integers or floats
310internally (there is no difference on the Perl level), saving space. 345internally (there is no difference on the Perl level), saving space.
311 346
312=item $json = $json->max_depth ([$maximum_nesting_depth]) 347=item $json = $json->max_depth ([$maximum_nesting_depth])
313 348
314Sets the maximum nesting level (default C<8192>) accepted while encoding 349Sets the maximum nesting level (default C<512>) accepted while encoding
315or decoding. If the JSON text or Perl data structure has an equal or 350or decoding. If the JSON text or Perl data structure has an equal or
316higher nesting level then this limit, then the encoder and decoder will 351higher nesting level then this limit, then the encoder and decoder will
317stop and croak at that point. 352stop and croak at that point.
318 353
319Nesting level is defined by number of hash- or arrayrefs that the encoder 354Nesting level is defined by number of hash- or arrayrefs that the encoder
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345 380
346JSON numbers and strings become simple Perl scalars. JSON arrays become 381JSON numbers and strings become simple Perl scalars. JSON arrays become
347Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 382Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
348C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 383C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
349 384
385=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
386
387This works like the C<decode> method, but instead of raising an exception
388when there is trailing garbage after the first JSON object, it will
389silently stop parsing there and return the number of characters consumed
390so far.
391
392This is useful if your JSON texts are not delimited by an outer protocol
393(which is not the brightest thing to do in the first place) and you need
394to know where the JSON text ends.
395
396 JSON::XS->new->decode_prefix ("[1] the tail")
397 => ([], 3)
398
350=back 399=back
351 400
352 401
353=head1 MAPPING 402=head1 MAPPING
354 403
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358(what you put in comes out as something equivalent). 407(what you put in comes out as something equivalent).
359 408
360For the more enlightened: note that in the following descriptions, 409For the more enlightened: note that in the following descriptions,
361lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 410lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
362refers to the abstract Perl language itself. 411refers to the abstract Perl language itself.
412
363 413
364=head2 JSON -> PERL 414=head2 JSON -> PERL
365 415
366=over 4 416=over 4
367 417
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388conversion details, but an integer may take slightly less memory and might 438conversion details, but an integer may take slightly less memory and might
389represent more values exactly than (floating point) numbers. 439represent more values exactly than (floating point) numbers.
390 440
391=item true, false 441=item true, false
392 442
393These JSON atoms become C<0>, C<1>, respectively. Information is lost in 443These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
394this process. Future versions might represent those values differently, 444respectively. They are overloaded to act almost exactly like the numbers
395but they will be guarenteed to act like these integers would normally in 445C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
396Perl. 446the C<JSON::XS::is_bool> function.
397 447
398=item null 448=item null
399 449
400A JSON null atom becomes C<undef> in Perl. 450A JSON null atom becomes C<undef> in Perl.
401 451
402=back 452=back
453
403 454
404=head2 PERL -> JSON 455=head2 PERL -> JSON
405 456
406The mapping from Perl to JSON is slightly more difficult, as Perl is a 457The mapping from Perl to JSON is slightly more difficult, as Perl is a
407truly typeless language, so we can only guess which JSON type is meant by 458truly typeless language, so we can only guess which JSON type is meant by
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410=over 4 461=over 4
411 462
412=item hash references 463=item hash references
413 464
414Perl hash references become JSON objects. As there is no inherent ordering 465Perl hash references become JSON objects. As there is no inherent ordering
415in hash keys, they will usually be encoded in a pseudo-random order that 466in hash keys (or JSON objects), they will usually be encoded in a
416can change between runs of the same program but stays generally the same 467pseudo-random order that can change between runs of the same program but
417within a single run of a program. JSON::XS can optionally sort the hash 468stays generally the same within a single run of a program. JSON::XS can
418keys (determined by the I<canonical> flag), so the same datastructure 469optionally sort the hash keys (determined by the I<canonical> flag), so
419will serialise to the same JSON text (given same settings and version of 470the same datastructure will serialise to the same JSON text (given same
420JSON::XS), but this incurs a runtime overhead. 471settings and version of JSON::XS), but this incurs a runtime overhead
472and is only rarely useful, e.g. when you want to compare some JSON text
473against another for equality.
421 474
422=item array references 475=item array references
423 476
424Perl array references become JSON arrays. 477Perl array references become JSON arrays.
478
479=item other references
480
481Other unblessed references are generally not allowed and will cause an
482exception to be thrown, except for references to the integers C<0> and
483C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
484also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
485
486 to_json [\0,JSON::XS::true] # yields [false,true]
487
488=item JSON::XS::true, JSON::XS::false
489
490These special values become JSON true and JSON false values,
491respectively. You cna alos use C<\1> and C<\0> directly if you want.
425 492
426=item blessed objects 493=item blessed objects
427 494
428Blessed objects are not allowed. JSON::XS currently tries to encode their 495Blessed objects are not allowed. JSON::XS currently tries to encode their
429underlying representation (hash- or arrayref), but this behaviour might 496underlying representation (hash- or arrayref), but this behaviour might
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461 $x += 0; # numify it, ensuring it will be dumped as a number 528 $x += 0; # numify it, ensuring it will be dumped as a number
462 $x *= 1; # same thing, the choise is yours. 529 $x *= 1; # same thing, the choise is yours.
463 530
464You can not currently output JSON booleans or force the type in other, 531You can not currently output JSON booleans or force the type in other,
465less obscure, ways. Tell me if you need this capability. 532less obscure, ways. Tell me if you need this capability.
466
467=item circular data structures
468
469Those will be encoded until memory or stackspace runs out.
470 533
471=back 534=back
472 535
473 536
474=head1 COMPARISON 537=head1 COMPARISON
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555 618
556Does not check input for validity. 619Does not check input for validity.
557 620
558=back 621=back
559 622
623
624=head2 JSON and YAML
625
626You often hear that JSON is a subset (or a close subset) of YAML. This is,
627however, a mass hysteria and very far from the truth. In general, there is
628no way to configure JSON::XS to output a data structure as valid YAML.
629
630If you really must use JSON::XS to generate YAML, you should use this
631algorithm (subject to change in future versions):
632
633 my $to_yaml = JSON::XS->new->utf8->space_after (1);
634 my $yaml = $to_yaml->encode ($ref) . "\n";
635
636This will usually generate JSON texts that also parse as valid
637YAML. Please note that YAML has hardcoded limits on (simple) object key
638lengths that JSON doesn't have, so you should make sure that your hash
639keys are noticably shorter than the 1024 characters YAML allows.
640
641There might be other incompatibilities that I am not aware of. In general
642you should not try to generate YAML with a JSON generator or vice versa,
643or try to parse JSON with a YAML parser or vice versa: chances are high
644that you will run into severe interoperability problems.
645
646
560=head2 SPEED 647=head2 SPEED
561 648
562It seems that JSON::XS is surprisingly fast, as shown in the following 649It seems that JSON::XS is surprisingly fast, as shown in the following
563tables. They have been generated with the help of the C<eg/bench> program 650tables. They have been generated with the help of the C<eg/bench> program
564in the JSON::XS distribution, to make it easy to compare on your own 651in the JSON::XS distribution, to make it easy to compare on your own
565system. 652system.
566 653
567First comes a comparison between various modules using a very short JSON 654First comes a comparison between various modules using a very short
568string: 655single-line JSON string:
569 656
570 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 657 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
658 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
571 659
572It shows the number of encodes/decodes per second (JSON::XS uses the 660It shows the number of encodes/decodes per second (JSON::XS uses
573functional interface, while JSON::XS/2 uses the OO interface with 661the functional interface, while JSON::XS/2 uses the OO interface
574pretty-printing and hashkey sorting enabled). Higher is better: 662with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
663shrink). Higher is better:
575 664
576 module | encode | decode | 665 module | encode | decode |
577 -----------|------------|------------| 666 -----------|------------|------------|
578 JSON | 11488.516 | 7823.035 | 667 JSON | 7645.468 | 4208.613 |
579 JSON::DWIW | 94708.054 | 129094.260 | 668 JSON::DWIW | 40721.398 | 77101.176 |
580 JSON::PC | 63884.157 | 128528.212 | 669 JSON::PC | 65948.176 | 78251.940 |
581 JSON::Syck | 34898.677 | 42096.911 | 670 JSON::Syck | 22844.793 | 26479.192 |
582 JSON::XS | 654027.064 | 396423.669 | 671 JSON::XS | 388361.481 | 199728.762 |
583 JSON::XS/2 | 371564.190 | 371725.613 | 672 JSON::XS/2 | 218453.333 | 192399.266 |
673 JSON::XS/3 | 338250.323 | 192399.266 |
674 Storable | 15779.925 | 14169.946 |
584 -----------+------------+------------+ 675 -----------+------------+------------+
585 676
586That is, JSON::XS is more than six times faster than JSON::DWIW on 677That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
587encoding, more than three times faster on decoding, and about thirty times 678about three times faster on decoding, and over fourty times faster
588faster than JSON, even with pretty-printing and key sorting. 679than JSON, even with pretty-printing and key sorting. It also compares
680favourably to Storable for small amounts of data.
589 681
590Using a longer test string (roughly 18KB, generated from Yahoo! Locals 682Using a longer test string (roughly 18KB, generated from Yahoo! Locals
591search API (http://nanoref.com/yahooapis/mgPdGg): 683search API (http://nanoref.com/yahooapis/mgPdGg):
592 684
593 module | encode | decode | 685 module | encode | decode |
594 -----------|------------|------------| 686 -----------|------------|------------|
595 JSON | 273.023 | 44.674 | 687 JSON | 254.685 | 37.665 |
596 JSON::DWIW | 1089.383 | 1145.704 | 688 JSON::DWIW | 843.343 | 1049.731 |
597 JSON::PC | 3097.419 | 2393.921 | 689 JSON::PC | 3602.116 | 2307.352 |
598 JSON::Syck | 514.060 | 843.053 | 690 JSON::Syck | 505.107 | 787.899 |
599 JSON::XS | 6479.668 | 3636.364 | 691 JSON::XS | 5747.196 | 3690.220 |
600 JSON::XS/2 | 3774.221 | 3599.124 | 692 JSON::XS/2 | 3968.121 | 3676.634 |
693 JSON::XS/3 | 6105.246 | 3662.508 |
694 Storable | 4417.337 | 5285.161 |
601 -----------+------------+------------+ 695 -----------+------------+------------+
602 696
603Again, JSON::XS leads by far. 697Again, JSON::XS leads by far (except for Storable which non-surprisingly
698decodes faster).
604 699
605On large strings containing lots of high unicode characters, some modules 700On large strings containing lots of high unicode characters, some modules
606(such as JSON::PC) seem to decode faster than JSON::XS, but the result 701(such as JSON::PC) seem to decode faster than JSON::XS, but the result
607will be broken due to missing (or wrong) unicode handling. Others refuse 702will be broken due to missing (or wrong) unicode handling. Others refuse
608to decode or encode properly, so it was impossible to prepare a fair 703to decode or encode properly, so it was impossible to prepare a fair
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625usually a good indication of the size of the resources required to decode 720usually a good indication of the size of the resources required to decode
626it into a Perl structure. 721it into a Perl structure.
627 722
628Third, JSON::XS recurses using the C stack when decoding objects and 723Third, JSON::XS recurses using the C stack when decoding objects and
629arrays. The C stack is a limited resource: for instance, on my amd64 724arrays. The C stack is a limited resource: for instance, on my amd64
630machine with 8MB of stack size I can decode around 180k nested arrays 725machine with 8MB of stack size I can decode around 180k nested arrays but
631but only 14k nested JSON objects. If that is exceeded, the program 726only 14k nested JSON objects (due to perl itself recursing deeply on croak
727to free the temporary). If that is exceeded, the program crashes. to be
632crashes. Thats why the default nesting limit is set to 8192. If your 728conservative, the default nesting limit is set to 512. If your process
633process has a smaller stack, you should adjust this setting accordingly 729has a smaller stack, you should adjust this setting accordingly with the
634with the C<max_depth> method. 730C<max_depth> method.
635 731
636And last but least, something else could bomb you that I forgot to think 732And last but least, something else could bomb you that I forgot to think
637of. In that case, you get to keep the pieces. I am alway sopen for hints, 733of. In that case, you get to keep the pieces. I am always open for hints,
638though... 734though...
735
736If you are using JSON::XS to return packets to consumption
737by javascript scripts in a browser you should have a look at
738L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
739you are vulnerable to some common attack vectors (which really are browser
740design bugs, but it is still you who will have to deal with it, as major
741browser developers care only for features, not about doing security
742right).
639 743
640 744
641=head1 BUGS 745=head1 BUGS
642 746
643While the goal of this module is to be correct, that unfortunately does 747While the goal of this module is to be correct, that unfortunately does
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645still relatively early in its development. If you keep reporting bugs they 749still relatively early in its development. If you keep reporting bugs they
646will be fixed swiftly, though. 750will be fixed swiftly, though.
647 751
648=cut 752=cut
649 753
754our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
755our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
756
757sub true() { $true }
758sub false() { $false }
759
760sub is_bool($) {
761 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
762 or UNIVERSAL::isa $_[0], "JSON::Literal"
763}
764
765XSLoader::load "JSON::XS", $VERSION;
766
767package JSON::XS::Boolean;
768
769use overload
770 "0+" => sub { ${$_[0]} },
771 "++" => sub { $_[0] = ${$_[0]} + 1 },
772 "--" => sub { $_[0] = ${$_[0]} - 1 },
773 fallback => 1;
774
6501; 7751;
651 776
652=head1 AUTHOR 777=head1 AUTHOR
653 778
654 Marc Lehmann <schmorp@schmorp.de> 779 Marc Lehmann <schmorp@schmorp.de>

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