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Revision 1.17 by root, Sat Mar 24 19:42:14 2007 UTC vs.
Revision 1.42 by root, Thu Jun 14 23:58:57 2007 UTC

4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use JSON::XS; 7 use JSON::XS;
8 8
9 # exported functions, croak on error 9 # exported functions, they croak on error
10 # and expect/generate UTF-8
10 11
11 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
12 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
13 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 # oo-interface 19 # OO-interface
15 20
16 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 21 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
17 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 22 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
18 $perl_scalar = $coder->decode ($unicode_json_text); 23 $perl_scalar = $coder->decode ($unicode_json_text);
19 24
36 41
37=head2 FEATURES 42=head2 FEATURES
38 43
39=over 4 44=over 4
40 45
41=item * correct handling of unicode issues 46=item * correct unicode handling
42 47
43This module knows how to handle Unicode, and even documents how and when 48This module knows how to handle Unicode, and even documents how and when
44it does so. 49it does so.
45 50
46=item * round-trip integrity 51=item * round-trip integrity
47 52
48When you serialise a perl data structure using only datatypes supported 53When you serialise a perl data structure using only datatypes supported
49by JSON, the deserialised data structure is identical on the Perl level. 54by JSON, the deserialised data structure is identical on the Perl level.
50(e.g. the string "2.0" doesn't suddenly become "2"). 55(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
56like a number).
51 57
52=item * strict checking of JSON correctness 58=item * strict checking of JSON correctness
53 59
54There is no guessing, no generating of illegal JSON texts by default, 60There is no guessing, no generating of illegal JSON texts by default,
55and only JSON is accepted as input by default (the latter is a security 61and only JSON is accepted as input by default (the latter is a security
66interface. 72interface.
67 73
68=item * reasonably versatile output formats 74=item * reasonably versatile output formats
69 75
70You can choose between the most compact guarenteed single-line format 76You can choose between the most compact guarenteed single-line format
71possible (nice for simple line-based protocols), a pure-ascii format (for 77possible (nice for simple line-based protocols), a pure-ascii format
72when your transport is not 8-bit clean), or a pretty-printed format (for 78(for when your transport is not 8-bit clean, still supports the whole
73when you want to read that stuff). Or you can combine those features in 79unicode range), or a pretty-printed format (for when you want to read that
74whatever way you like. 80stuff). Or you can combine those features in whatever way you like.
75 81
76=back 82=back
77 83
78=cut 84=cut
79 85
80package JSON::XS; 86package JSON::XS;
81 87
88use strict;
89
82BEGIN { 90BEGIN {
83 $VERSION = '0.5'; 91 our $VERSION = '1.24';
84 @ISA = qw(Exporter); 92 our @ISA = qw(Exporter);
85 93
86 @EXPORT = qw(to_json from_json); 94 our @EXPORT = qw(to_json from_json objToJson jsonToObj);
87 require Exporter; 95 require Exporter;
88 96
89 require XSLoader; 97 require XSLoader;
90 XSLoader::load JSON::XS::, $VERSION; 98 XSLoader::load JSON::XS::, $VERSION;
91} 99}
120 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
121 129
122except being faster. 130except being faster.
123 131
124=back 132=back
133
125 134
126=head1 OBJECT-ORIENTED INTERFACE 135=head1 OBJECT-ORIENTED INTERFACE
127 136
128The object oriented interface lets you configure your own encoding or 137The object oriented interface lets you configure your own encoding or
129decoding style, within the limits of supported formats. 138decoding style, within the limits of supported formats.
145 154
146If C<$enable> is true (or missing), then the C<encode> method will not 155If C<$enable> is true (or missing), then the C<encode> method will not
147generate characters outside the code range C<0..127> (which is ASCII). Any 156generate characters outside the code range C<0..127> (which is ASCII). Any
148unicode characters outside that range will be escaped using either a 157unicode characters outside that range will be escaped using either a
149single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 158single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
150as per RFC4627. 159as per RFC4627. The resulting encoded JSON text can be treated as a native
160unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
161or any other superset of ASCII.
151 162
152If C<$enable> is false, then the C<encode> method will not escape Unicode 163If C<$enable> is false, then the C<encode> method will not escape Unicode
153characters unless required by the JSON syntax. This results in a faster 164characters unless required by the JSON syntax or other flags. This results
154and more compact format. 165in a faster and more compact format.
166
167The main use for this flag is to produce JSON texts that can be
168transmitted over a 7-bit channel, as the encoded JSON texts will not
169contain any 8 bit characters.
155 170
156 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 171 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
157 => ["\ud801\udc01"] 172 => ["\ud801\udc01"]
173
174=item $json = $json->latin1 ([$enable])
175
176If C<$enable> is true (or missing), then the C<encode> method will encode
177the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
178outside the code range C<0..255>. The resulting string can be treated as a
179latin1-encoded JSON text or a native unicode string. The C<decode> method
180will not be affected in any way by this flag, as C<decode> by default
181expects unicode, which is a strict superset of latin1.
182
183If C<$enable> is false, then the C<encode> method will not escape Unicode
184characters unless required by the JSON syntax or other flags.
185
186The main use for this flag is efficiently encoding binary data as JSON
187text, as most octets will not be escaped, resulting in a smaller encoded
188size. The disadvantage is that the resulting JSON text is encoded
189in latin1 (and must correctly be treated as such when storing and
190transfering), a rare encoding for JSON. It is therefore most useful when
191you want to store data structures known to contain binary data efficiently
192in files or databases, not when talking to other JSON encoders/decoders.
193
194 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
195 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
158 196
159=item $json = $json->utf8 ([$enable]) 197=item $json = $json->utf8 ([$enable])
160 198
161If C<$enable> is true (or missing), then the C<encode> method will encode 199If C<$enable> is true (or missing), then the C<encode> method will encode
162the JSON result into UTF-8, as required by many protocols, while the 200the JSON result into UTF-8, as required by many protocols, while the
275 => "Hello, World!" 313 => "Hello, World!"
276 314
277=item $json = $json->shrink ([$enable]) 315=item $json = $json->shrink ([$enable])
278 316
279Perl usually over-allocates memory a bit when allocating space for 317Perl usually over-allocates memory a bit when allocating space for
280strings. This flag optionally resizes strings generated by either 318strings. This flag optionally resizes strings generated by either
281C<encode> or C<decode> to their minimum size possible. This can save 319C<encode> or C<decode> to their minimum size possible. This can save
282memory when your JSON texts are either very very long or you have many 320memory when your JSON texts are either very very long or you have many
283short strings. It will also try to downgrade any strings to octet-form 321short strings. It will also try to downgrade any strings to octet-form
284if possible: perl stores strings internally either in an encoding called 322if possible: perl stores strings internally either in an encoding called
285UTF-X or in octet-form. The latter cannot store everything but uses less 323UTF-X or in octet-form. The latter cannot store everything but uses less
286space in general. 324space in general (and some buggy Perl or C code might even rely on that
325internal representation being used).
287 326
327The actual definition of what shrink does might change in future versions,
328but it will always try to save space at the expense of time.
329
288If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit, 330If C<$enable> is true (or missing), the string returned by C<encode> will
289while all strings generated by C<decode> will also be shrunk-to-fit. 331be shrunk-to-fit, while all strings generated by C<decode> will also be
332shrunk-to-fit.
290 333
291If C<$enable> is false, then the normal perl allocation algorithms are used. 334If C<$enable> is false, then the normal perl allocation algorithms are used.
292If you work with your data, then this is likely to be faster. 335If you work with your data, then this is likely to be faster.
293 336
294In the future, this setting might control other things, such as converting 337In the future, this setting might control other things, such as converting
295strings that look like integers or floats into integers or floats 338strings that look like integers or floats into integers or floats
296internally (there is no difference on the Perl level), saving space. 339internally (there is no difference on the Perl level), saving space.
340
341=item $json = $json->max_depth ([$maximum_nesting_depth])
342
343Sets the maximum nesting level (default C<512>) accepted while encoding
344or decoding. If the JSON text or Perl data structure has an equal or
345higher nesting level then this limit, then the encoder and decoder will
346stop and croak at that point.
347
348Nesting level is defined by number of hash- or arrayrefs that the encoder
349needs to traverse to reach a given point or the number of C<{> or C<[>
350characters without their matching closing parenthesis crossed to reach a
351given character in a string.
352
353Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array.
355
356The argument to C<max_depth> will be rounded up to the next nearest power
357of two.
358
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
297 360
298=item $json_text = $json->encode ($perl_scalar) 361=item $json_text = $json->encode ($perl_scalar)
299 362
300Converts the given Perl data structure (a simple scalar or a reference 363Converts the given Perl data structure (a simple scalar or a reference
301to a hash or array) to its JSON representation. Simple scalars will be 364to a hash or array) to its JSON representation. Simple scalars will be
311 374
312JSON numbers and strings become simple Perl scalars. JSON arrays become 375JSON numbers and strings become simple Perl scalars. JSON arrays become
313Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 376Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
314C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 377C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
315 378
379=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
380
381This works like the C<decode> method, but instead of raising an exception
382when there is trailing garbage after the first JSON object, it will
383silently stop parsing there and return the number of characters consumed
384so far.
385
386This is useful if your JSON texts are not delimited by an outer protocol
387(which is not the brightest thing to do in the first place) and you need
388to know where the JSON text ends.
389
390 JSON::XS->new->decode_prefix ("[1] the tail")
391 => ([], 3)
392
316=back 393=back
394
317 395
318=head1 MAPPING 396=head1 MAPPING
319 397
320This section describes how JSON::XS maps Perl values to JSON values and 398This section describes how JSON::XS maps Perl values to JSON values and
321vice versa. These mappings are designed to "do the right thing" in most 399vice versa. These mappings are designed to "do the right thing" in most
323(what you put in comes out as something equivalent). 401(what you put in comes out as something equivalent).
324 402
325For the more enlightened: note that in the following descriptions, 403For the more enlightened: note that in the following descriptions,
326lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 404lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
327refers to the abstract Perl language itself. 405refers to the abstract Perl language itself.
406
328 407
329=head2 JSON -> PERL 408=head2 JSON -> PERL
330 409
331=over 4 410=over 4
332 411
364 443
365A JSON null atom becomes C<undef> in Perl. 444A JSON null atom becomes C<undef> in Perl.
366 445
367=back 446=back
368 447
448
369=head2 PERL -> JSON 449=head2 PERL -> JSON
370 450
371The mapping from Perl to JSON is slightly more difficult, as Perl is a 451The mapping from Perl to JSON is slightly more difficult, as Perl is a
372truly typeless language, so we can only guess which JSON type is meant by 452truly typeless language, so we can only guess which JSON type is meant by
373a Perl value. 453a Perl value.
375=over 4 455=over 4
376 456
377=item hash references 457=item hash references
378 458
379Perl hash references become JSON objects. As there is no inherent ordering 459Perl hash references become JSON objects. As there is no inherent ordering
380in hash keys, they will usually be encoded in a pseudo-random order that 460in hash keys (or JSON objects), they will usually be encoded in a
381can change between runs of the same program but stays generally the same 461pseudo-random order that can change between runs of the same program but
382within a single run of a program. JSON::XS can optionally sort the hash 462stays generally the same within a single run of a program. JSON::XS can
383keys (determined by the I<canonical> flag), so the same datastructure 463optionally sort the hash keys (determined by the I<canonical> flag), so
384will serialise to the same JSON text (given same settings and version of 464the same datastructure will serialise to the same JSON text (given same
385JSON::XS), but this incurs a runtime overhead. 465settings and version of JSON::XS), but this incurs a runtime overhead
466and is only rarely useful, e.g. when you want to compare some JSON text
467against another for equality.
386 468
387=item array references 469=item array references
388 470
389Perl array references become JSON arrays. 471Perl array references become JSON arrays.
472
473=item other references
474
475Other unblessed references are generally not allowed and will cause an
476exception to be thrown, except for references to the integers C<0> and
477C<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.
479
480 to_json [\0,JSON::XS::true] # yields [false,true]
390 481
391=item blessed objects 482=item blessed objects
392 483
393Blessed objects are not allowed. JSON::XS currently tries to encode their 484Blessed objects are not allowed. JSON::XS currently tries to encode their
394underlying representation (hash- or arrayref), but this behaviour might 485underlying representation (hash- or arrayref), but this behaviour might
427 $x *= 1; # same thing, the choise is yours. 518 $x *= 1; # same thing, the choise is yours.
428 519
429You can not currently output JSON booleans or force the type in other, 520You can not currently output JSON booleans or force the type in other,
430less obscure, ways. Tell me if you need this capability. 521less obscure, ways. Tell me if you need this capability.
431 522
432=item circular data structures
433
434Those will be encoded until memory or stackspace runs out.
435
436=back 523=back
524
437 525
438=head1 COMPARISON 526=head1 COMPARISON
439 527
440As already mentioned, this module was created because none of the existing 528As already mentioned, this module was created because none of the existing
441JSON modules could be made to work correctly. First I will describe the 529JSON modules could be made to work correctly. First I will describe the
519 607
520Does not check input for validity. 608Does not check input for validity.
521 609
522=back 610=back
523 611
612
613=head2 JSON and YAML
614
615You 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
617no way to configure JSON::XS to output a data structure as valid YAML.
618
619If you really must use JSON::XS to generate YAML, you should use this
620algorithm (subject to change in future versions):
621
622 my $to_yaml = JSON::XS->new->utf8->space_after (1);
623 my $yaml = $to_yaml->encode ($ref) . "\n";
624
625This will usually generate JSON texts that also parse as valid
626YAML. Please note that YAML has hardcoded limits on (simple) object key
627lengths that JSON doesn't have, so you should make sure that your hash
628keys are noticably shorter than the 1024 characters YAML allows.
629
630There 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,
632or try to parse JSON with a YAML parser or vice versa: chances are high
633that you will run into severe interoperability problems.
634
635
524=head2 SPEED 636=head2 SPEED
525 637
526It seems that JSON::XS is surprisingly fast, as shown in the following 638It seems that JSON::XS is surprisingly fast, as shown in the following
527tables. They have been generated with the help of the C<eg/bench> program 639tables. They have been generated with the help of the C<eg/bench> program
528in the JSON::XS distribution, to make it easy to compare on your own 640in the JSON::XS distribution, to make it easy to compare on your own
529system. 641system.
530 642
531First comes a comparison between various modules using a very short JSON 643First comes a comparison between various modules using a very short
532string (83 bytes), showing the number of encodes/decodes per second 644single-line JSON string:
645
646 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
647 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
648
649It shows the number of encodes/decodes per second (JSON::XS uses
533(JSON::XS is the functional interface, while JSON::XS/2 is the OO 650the functional interface, while JSON::XS/2 uses the OO interface
534interface with pretty-printing and hashkey sorting enabled). Higher is 651with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
535better: 652shrink). Higher is better:
536 653
537 module | encode | decode | 654 module | encode | decode |
538 -----------|------------|------------| 655 -----------|------------|------------|
539 JSON | 14006 | 6820 | 656 JSON | 7645.468 | 4208.613 |
540 JSON::DWIW | 200937 | 120386 | 657 JSON::DWIW | 40721.398 | 77101.176 |
541 JSON::PC | 85065 | 129366 | 658 JSON::PC | 65948.176 | 78251.940 |
542 JSON::Syck | 59898 | 44232 | 659 JSON::Syck | 22844.793 | 26479.192 |
543 JSON::XS | 1171478 | 342435 | 660 JSON::XS | 388361.481 | 199728.762 |
544 JSON::XS/2 | 730760 | 328714 | 661 JSON::XS/2 | 218453.333 | 192399.266 |
662 JSON::XS/3 | 338250.323 | 192399.266 |
663 Storable | 15779.925 | 14169.946 |
545 -----------+------------+------------+ 664 -----------+------------+------------+
546 665
547That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80 666That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
667about three times faster on decoding, and over fourty times faster
548times faster than JSON, even with pretty-printing and key sorting. 668than JSON, even with pretty-printing and key sorting. It also compares
669favourably to Storable for small amounts of data.
549 670
550Using a longer test string (roughly 18KB, generated from Yahoo! Locals 671Using a longer test string (roughly 18KB, generated from Yahoo! Locals
551search API (http://nanoref.com/yahooapis/mgPdGg): 672search API (http://nanoref.com/yahooapis/mgPdGg):
552 673
553 module | encode | decode | 674 module | encode | decode |
554 -----------|------------|------------| 675 -----------|------------|------------|
555 JSON | 673 | 38 | 676 JSON | 254.685 | 37.665 |
556 JSON::DWIW | 5271 | 770 | 677 JSON::DWIW | 843.343 | 1049.731 |
557 JSON::PC | 9901 | 2491 | 678 JSON::PC | 3602.116 | 2307.352 |
558 JSON::Syck | 2360 | 786 | 679 JSON::Syck | 505.107 | 787.899 |
559 JSON::XS | 37398 | 3202 | 680 JSON::XS | 5747.196 | 3690.220 |
560 JSON::XS/2 | 13765 | 3153 | 681 JSON::XS/2 | 3968.121 | 3676.634 |
682 JSON::XS/3 | 6105.246 | 3662.508 |
683 Storable | 4417.337 | 5285.161 |
561 -----------+------------+------------+ 684 -----------+------------+------------+
562 685
563Again, JSON::XS leads by far in the encoding case, while still beating 686Again, JSON::XS leads by far (except for Storable which non-surprisingly
564every other module in the decoding case. 687decodes faster).
565 688
566On large strings containing lots of unicode characters, some modules 689On large strings containing lots of high unicode characters, some modules
567(such as JSON::PC) decode faster than JSON::XS, but the result will be 690(such as JSON::PC) seem to decode faster than JSON::XS, but the result
568broken due to missing unicode handling. Others refuse to decode or encode 691will be broken due to missing (or wrong) unicode handling. Others refuse
569properly, so it was impossible to prepare a fair comparison table for that 692to decode or encode properly, so it was impossible to prepare a fair
570case. 693comparison table for that case.
571 694
572=head1 RESOURCE LIMITS
573 695
574JSON::XS does not impose any limits on the size of JSON texts or Perl 696=head1 SECURITY CONSIDERATIONS
575values they represent - if your machine can handle it, JSON::XS will 697
576encode or decode it. Future versions might optionally impose structure 698When you are using JSON in a protocol, talking to untrusted potentially
577depth and memory use resource limits. 699hostile creatures requires relatively few measures.
700
701First of all, your JSON decoder should be secure, that is, should not have
702any buffer overflows. Obviously, this module should ensure that and I am
703trying hard on making that true, but you never know.
704
705Second, you need to avoid resource-starving attacks. That means you should
706limit the size of JSON texts you accept, or make sure then when your
707resources run out, thats just fine (e.g. by using a separate process that
708can crash safely). The size of a JSON text in octets or characters is
709usually a good indication of the size of the resources required to decode
710it into a Perl structure.
711
712Third, JSON::XS recurses using the C stack when decoding objects and
713arrays. The C stack is a limited resource: for instance, on my amd64
714machine with 8MB of stack size I can decode around 180k nested arrays but
715only 14k nested JSON objects (due to perl itself recursing deeply on croak
716to free the temporary). If that is exceeded, the program crashes. to be
717conservative, the default nesting limit is set to 512. If your process
718has a smaller stack, you should adjust this setting accordingly with the
719C<max_depth> method.
720
721And last but least, something else could bomb you that I forgot to think
722of. In that case, you get to keep the pieces. I am always open for hints,
723though...
724
725If you are using JSON::XS to return packets to consumption
726by javascript scripts in a browser you should have a look at
727L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
728you are vulnerable to some common attack vectors (which really are browser
729design bugs, but it is still you who will have to deal with it, as major
730browser developers care only for features, not about doing security
731right).
732
578 733
579=head1 BUGS 734=head1 BUGS
580 735
581While the goal of this module is to be correct, that unfortunately does 736While the goal of this module is to be correct, that unfortunately does
582not mean its bug-free, only that I think its design is bug-free. It is 737not mean its bug-free, only that I think its design is bug-free. It is
583still very young and not well-tested. If you keep reporting bugs they will 738still relatively early in its development. If you keep reporting bugs they
584be fixed swiftly, though. 739will be fixed swiftly, though.
585 740
586=cut 741=cut
742
743sub true() { \1 }
744sub false() { \0 }
587 745
5881; 7461;
589 747
590=head1 AUTHOR 748=head1 AUTHOR
591 749

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