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Revision 1.43 by root, Sat Jun 23 23:49:29 2007 UTC vs.
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC

… …
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
90our $VERSION = '1.3'; 86our $VERSION = '1.4';
91our @ISA = qw(Exporter); 87our @ISA = qw(Exporter);
92 88
93our @EXPORT = qw(to_json from_json objToJson jsonToObj); 89our @EXPORT = qw(to_json from_json);
94 90
95use Exporter; 91use Exporter;
96use XSLoader; 92use XSLoader;
97 93
98=head1 FUNCTIONAL INTERFACE 94=head1 FUNCTIONAL INTERFACE
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315Example, 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>,
316resulting in an invalid JSON text: 312resulting in an invalid JSON text:
317 313
318 JSON::XS->new->allow_nonref->encode ("Hello, World!") 314 JSON::XS->new->allow_nonref->encode ("Hello, World!")
319 => "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.
352
353=item $json = $json->filter_json_object ([$coderef])
354
355When C<$coderef> is specified, it will be called from C<decode> each
356time it decodes a JSON object. The only argument is a reference to the
357newly-created hash. If the code references returns a single scalar (which
358need not be a reference), this value (i.e. a copy of that scalar to avoid
359aliasing) is inserted into the deserialised data structure. If it returns
360an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
361original deserialised hash will be inserted. This setting can slow down
362decoding considerably.
363
364When C<$coderef> is omitted or undefined, C<decode> will not change the
365deserialised hash in any way. This is maximally fast.
366
367Example, convert all JSON objects into the integer 5:
368
369 my $js = JSON::XS->new->filter_json_object (sub { 5 });
370 # returns [5]
371 $js->decode ('[{}]')
372 # throw an exception because allow_nonref is not enabled:
373 $js->decode ('{"a":1, "b":2}');
374
375=item $json = $json->filter_json_single_key_object ([$coderef])
376
377Works like C<filter_json_object>, but is only called for JSON objects
378having only a single key.
379
380This C<$coderef> is called before the one specified via
381C<filter_json_object>, if any. If it returns something, that will be
382inserted into the data structure. If it returns nothing, the callback
383from C<filter_json_object> will be called next. If you want to force
384insertion of single-key objects even in the presence of a mutating
385C<filter_json_object> callback, simply return the passed hash.
386
387As this callback gets called less often then the C<filter_json_object>
388one, decoding speed will not usually suffer as much. Therefore, single-key
389objects make excellent targets to serialise Perl objects into, especially
390as single-key JSON objects are as close to the type-tagged value concept
391as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
392support this in any way, so you need to make sure your data never looks
393like a serialised Perl hash.
394
395Typical names for the single object key are C<__class_whatever__>, or
396C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
397things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
398with real hashes.
399
400Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
401into the corresponding C<< $WIDGET{<id>} >> object:
402
403 # return whatever is in $WIDGET{5}:
404 JSON::XS
405 ->new
406 ->filter_json_single_key_object (sub {
407 exists $_[0]{__widget__}
408 ? $WIDGET{ $_[0]{__widget__} }
409 : ()
410 })
411 ->decode ('{"__widget__": 5')
412
413 # this can be used with a TO_JSON method in some "widget" class
414 # for serialisation to json:
415 sub WidgetBase::TO_JSON {
416 my ($self) = @_;
417
418 unless ($self->{id}) {
419 $self->{id} = ..get..some..id..;
420 $WIDGET{$self->{id}} = $self;
421 }
422
423 { __widget__ => $self->{id} }
424 }
320 425
321=item $json = $json->shrink ([$enable]) 426=item $json = $json->shrink ([$enable])
322 427
323Perl usually over-allocates memory a bit when allocating space for 428Perl usually over-allocates memory a bit when allocating space for
324strings. This flag optionally resizes strings generated by either 429strings. This flag optionally resizes strings generated by either
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357given character in a string. 462given character in a string.
358 463
359Setting the maximum depth to one disallows any nesting, so that ensures 464Setting the maximum depth to one disallows any nesting, so that ensures
360that the object is only a single hash/object or array. 465that the object is only a single hash/object or array.
361 466
362The argument to C<max_depth> will be rounded up to the next nearest power 467The argument to C<max_depth> will be rounded up to the next highest power
363of two. 468of two. If no argument is given, the highest possible setting will be
469used, which is rarely useful.
470
471See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
472
473=item $json = $json->max_size ([$maximum_string_size])
474
475Set the maximum length a JSON text may have (in bytes) where decoding is
476being attempted. The default is C<0>, meaning no limit. When C<decode>
477is called on a string longer then this number of characters it will not
478attempt to decode the string but throw an exception. This setting has no
479effect on C<encode> (yet).
480
481The argument to C<max_size> will be rounded up to the next B<highest>
482power of two (so may be more than requested). If no argument is given, the
483limit check will be deactivated (same as when C<0> is specified).
364 484
365See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 485See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
366 486
367=item $json_text = $json->encode ($perl_scalar) 487=item $json_text = $json->encode ($perl_scalar)
368 488
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660It shows the number of encodes/decodes per second (JSON::XS uses 780It shows the number of encodes/decodes per second (JSON::XS uses
661the functional interface, while JSON::XS/2 uses the OO interface 781the functional interface, while JSON::XS/2 uses the OO interface
662with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 782with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
663shrink). Higher is better: 783shrink). Higher is better:
664 784
785 Storable | 15779.925 | 14169.946 |
786 -----------+------------+------------+
665 module | encode | decode | 787 module | encode | decode |
666 -----------|------------|------------| 788 -----------|------------|------------|
667 JSON | 7645.468 | 4208.613 | 789 JSON | 4990.842 | 4088.813 |
668 JSON::DWIW | 40721.398 | 77101.176 | 790 JSON::DWIW | 51653.990 | 71575.154 |
669 JSON::PC | 65948.176 | 78251.940 | 791 JSON::PC | 65948.176 | 74631.744 |
670 JSON::Syck | 22844.793 | 26479.192 | 792 JSON::PP | 8931.652 | 3817.168 |
793 JSON::Syck | 24877.248 | 27776.848 |
671 JSON::XS | 388361.481 | 199728.762 | 794 JSON::XS | 388361.481 | 227951.304 |
672 JSON::XS/2 | 218453.333 | 192399.266 | 795 JSON::XS/2 | 227951.304 | 218453.333 |
673 JSON::XS/3 | 338250.323 | 192399.266 | 796 JSON::XS/3 | 338250.323 | 218453.333 |
674 Storable | 15779.925 | 14169.946 | 797 Storable | 16500.016 | 135300.129 |
675 -----------+------------+------------+ 798 -----------+------------+------------+
676 799
677That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 800That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
678about three times faster on decoding, and over fourty times faster 801about three times faster on decoding, and over fourty times faster
679than JSON, even with pretty-printing and key sorting. It also compares 802than JSON, even with pretty-printing and key sorting. It also compares
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682Using a longer test string (roughly 18KB, generated from Yahoo! Locals 805Using a longer test string (roughly 18KB, generated from Yahoo! Locals
683search API (http://nanoref.com/yahooapis/mgPdGg): 806search API (http://nanoref.com/yahooapis/mgPdGg):
684 807
685 module | encode | decode | 808 module | encode | decode |
686 -----------|------------|------------| 809 -----------|------------|------------|
687 JSON | 254.685 | 37.665 | 810 JSON | 55.260 | 34.971 |
688 JSON::DWIW | 843.343 | 1049.731 | 811 JSON::DWIW | 825.228 | 1082.513 |
689 JSON::PC | 3602.116 | 2307.352 | 812 JSON::PC | 3571.444 | 2394.829 |
813 JSON::PP | 210.987 | 32.574 |
690 JSON::Syck | 505.107 | 787.899 | 814 JSON::Syck | 552.551 | 787.544 |
691 JSON::XS | 5747.196 | 3690.220 | 815 JSON::XS | 5780.463 | 4854.519 |
692 JSON::XS/2 | 3968.121 | 3676.634 | 816 JSON::XS/2 | 3869.998 | 4798.975 |
693 JSON::XS/3 | 6105.246 | 3662.508 | 817 JSON::XS/3 | 5862.880 | 4798.975 |
694 Storable | 4417.337 | 5285.161 | 818 Storable | 4445.002 | 5235.027 |
695 -----------+------------+------------+ 819 -----------+------------+------------+
696 820
697Again, JSON::XS leads by far (except for Storable which non-surprisingly 821Again, JSON::XS leads by far (except for Storable which non-surprisingly
698decodes faster). 822decodes faster).
699 823
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716Second, you need to avoid resource-starving attacks. That means you should 840Second, you need to avoid resource-starving attacks. That means you should
717limit the size of JSON texts you accept, or make sure then when your 841limit the size of JSON texts you accept, or make sure then when your
718resources run out, thats just fine (e.g. by using a separate process that 842resources run out, thats just fine (e.g. by using a separate process that
719can crash safely). The size of a JSON text in octets or characters is 843can crash safely). The size of a JSON text in octets or characters is
720usually a good indication of the size of the resources required to decode 844usually a good indication of the size of the resources required to decode
721it into a Perl structure. 845it into a Perl structure. While JSON::XS can check the size of the JSON
846text, it might be too late when you already have it in memory, so you
847might want to check the size before you accept the string.
722 848
723Third, JSON::XS recurses using the C stack when decoding objects and 849Third, JSON::XS recurses using the C stack when decoding objects and
724arrays. The C stack is a limited resource: for instance, on my amd64 850arrays. The C stack is a limited resource: for instance, on my amd64
725machine with 8MB of stack size I can decode around 180k nested arrays but 851machine with 8MB of stack size I can decode around 180k nested arrays but
726only 14k nested JSON objects (due to perl itself recursing deeply on croak 852only 14k nested JSON objects (due to perl itself recursing deeply on croak
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749still relatively early in its development. If you keep reporting bugs they 875still relatively early in its development. If you keep reporting bugs they
750will be fixed swiftly, though. 876will be fixed swiftly, though.
751 877
752=cut 878=cut
753 879
754our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 880our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };
755our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 881our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };
756 882
757sub true() { $true } 883sub true() { $true }
758sub false() { $false } 884sub false() { $false }
759 885
760sub is_bool($) { 886sub is_bool($) {
761 UNIVERSAL::isa $_[0], "JSON::XS::Boolean" 887 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
762 or UNIVERSAL::isa $_[0], "JSON::Literal" 888# or UNIVERSAL::isa $_[0], "JSON::Literal"
763} 889}
764 890
765XSLoader::load "JSON::XS", $VERSION; 891XSLoader::load "JSON::XS", $VERSION;
766 892
767package JSON::XS::Boolean; 893package JSON::XS::Boolean;

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