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Comparing JSON-XS/XS.pm (file contents):
Revision 1.46 by root, Mon Jun 25 04:21:14 2007 UTC vs.
Revision 1.57 by root, Mon Aug 13 16:05:42 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 = '1.4'; 86our $VERSION = '1.44';
91our @ISA = qw(Exporter); 87our @ISA = qw(Exporter);
92 88
93our @EXPORT = qw(to_json from_json objToJson jsonToObj); 89our @EXPORT = qw(to_json from_json);
94 90
95use Exporter; 91use Exporter;
96use XSLoader; 92use XSLoader;
97 93
98=head1 FUNCTIONAL INTERFACE 94=head1 FUNCTIONAL INTERFACE
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351future, global hooks might get installed that influence C<decode> and are 347future, global hooks might get installed that influence C<decode> and are
352enabled by this setting. 348enabled by this setting.
353 349
354If C<$enable> is false, then the C<allow_blessed> setting will decide what 350If C<$enable> is false, then the C<allow_blessed> setting will decide what
355to do when a blessed object is found. 351to do when a blessed object is found.
352
353=item $json = $json->filter_json_object ([$coderef->($hashref)])
354
355When C<$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, any existing callback will
365be removed and C<decode> will not change the deserialised hash in any
366way.
367
368Example, convert all JSON objects into the integer 5:
369
370 my $js = JSON::XS->new->filter_json_object (sub { 5 });
371 # returns [5]
372 $js->decode ('[{}]')
373 # throw an exception because allow_nonref is not enabled
374 # so a lone 5 is not allowed.
375 $js->decode ('{"a":1, "b":2}');
376
377=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
378
379Works remotely similar to C<filter_json_object>, but is only called for
380JSON objects having a single key named C<$key>.
381
382This C<$coderef> is called before the one specified via
383C<filter_json_object>, if any. It gets passed the single value in the JSON
384object. If it returns a single value, it will be inserted into the data
385structure. If it returns nothing (not even C<undef> but the empty list),
386the callback from C<filter_json_object> will be called next, as if no
387single-key callback were specified.
388
389If C<$coderef> is omitted or undefined, the corresponding callback will be
390disabled. There can only ever be one callback for a given key.
391
392As this callback gets called less often then the C<filter_json_object>
393one, decoding speed will not usually suffer as much. Therefore, single-key
394objects make excellent targets to serialise Perl objects into, especially
395as single-key JSON objects are as close to the type-tagged value concept
396as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
397support this in any way, so you need to make sure your data never looks
398like a serialised Perl hash.
399
400Typical names for the single object key are C<__class_whatever__>, or
401C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
402things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
403with real hashes.
404
405Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
406into the corresponding C<< $WIDGET{<id>} >> object:
407
408 # return whatever is in $WIDGET{5}:
409 JSON::XS
410 ->new
411 ->filter_json_single_key_object (__widget__ => sub {
412 $WIDGET{ $_[0] }
413 })
414 ->decode ('{"__widget__": 5')
415
416 # this can be used with a TO_JSON method in some "widget" class
417 # for serialisation to json:
418 sub WidgetBase::TO_JSON {
419 my ($self) = @_;
420
421 unless ($self->{id}) {
422 $self->{id} = ..get..some..id..;
423 $WIDGET{$self->{id}} = $self;
424 }
425
426 { __widget__ => $self->{id} }
427 }
356 428
357=item $json = $json->shrink ([$enable]) 429=item $json = $json->shrink ([$enable])
358 430
359Perl usually over-allocates memory a bit when allocating space for 431Perl usually over-allocates memory a bit when allocating space for
360strings. This flag optionally resizes strings generated by either 432strings. This flag optionally resizes strings generated by either
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393given character in a string. 465given character in a string.
394 466
395Setting the maximum depth to one disallows any nesting, so that ensures 467Setting the maximum depth to one disallows any nesting, so that ensures
396that the object is only a single hash/object or array. 468that the object is only a single hash/object or array.
397 469
398The argument to C<max_depth> will be rounded up to the next nearest power 470The argument to C<max_depth> will be rounded up to the next highest power
399of two. 471of two. If no argument is given, the highest possible setting will be
472used, which is rarely useful.
473
474See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
475
476=item $json = $json->max_size ([$maximum_string_size])
477
478Set the maximum length a JSON text may have (in bytes) where decoding is
479being attempted. The default is C<0>, meaning no limit. When C<decode>
480is called on a string longer then this number of characters it will not
481attempt to decode the string but throw an exception. This setting has no
482effect on C<encode> (yet).
483
484The argument to C<max_size> will be rounded up to the next B<highest>
485power of two (so may be more than requested). If no argument is given, the
486limit check will be deactivated (same as when C<0> is specified).
400 487
401See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 488See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
402 489
403=item $json_text = $json->encode ($perl_scalar) 490=item $json_text = $json->encode ($perl_scalar)
404 491
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466are represented by the same codepoints in the Perl string, so no manual 553are represented by the same codepoints in the Perl string, so no manual
467decoding is necessary. 554decoding is necessary.
468 555
469=item number 556=item number
470 557
471A JSON number becomes either an integer or numeric (floating point) 558A JSON number becomes either an integer, numeric (floating point) or
472scalar in perl, depending on its range and any fractional parts. On the 559string scalar in perl, depending on its range and any fractional parts. On
473Perl level, there is no difference between those as Perl handles all the 560the Perl level, there is no difference between those as Perl handles all
474conversion details, but an integer may take slightly less memory and might 561the conversion details, but an integer may take slightly less memory and
475represent more values exactly than (floating point) numbers. 562might represent more values exactly than (floating point) numbers.
563
564If the number consists of digits only, JSON::XS will try to represent
565it as an integer value. If that fails, it will try to represent it as
566a numeric (floating point) value if that is possible without loss of
567precision. Otherwise it will preserve the number as a string value.
568
569Numbers containing a fractional or exponential part will always be
570represented as numeric (floating point) values, possibly at a loss of
571precision.
572
573This might create round-tripping problems as numbers might become strings,
574but as Perl is typeless there is no other way to do it.
476 575
477=item true, false 576=item true, false
478 577
479These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 578These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
480respectively. They are overloaded to act almost exactly like the numbers 579respectively. They are overloaded to act almost exactly like the numbers
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696It shows the number of encodes/decodes per second (JSON::XS uses 795It shows the number of encodes/decodes per second (JSON::XS uses
697the functional interface, while JSON::XS/2 uses the OO interface 796the functional interface, while JSON::XS/2 uses the OO interface
698with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 797with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
699shrink). Higher is better: 798shrink). Higher is better:
700 799
800 Storable | 15779.925 | 14169.946 |
801 -----------+------------+------------+
701 module | encode | decode | 802 module | encode | decode |
702 -----------|------------|------------| 803 -----------|------------|------------|
703 JSON | 7645.468 | 4208.613 | 804 JSON | 4990.842 | 4088.813 |
704 JSON::DWIW | 40721.398 | 77101.176 | 805 JSON::DWIW | 51653.990 | 71575.154 |
705 JSON::PC | 65948.176 | 78251.940 | 806 JSON::PC | 65948.176 | 74631.744 |
706 JSON::Syck | 22844.793 | 26479.192 | 807 JSON::PP | 8931.652 | 3817.168 |
808 JSON::Syck | 24877.248 | 27776.848 |
707 JSON::XS | 388361.481 | 199728.762 | 809 JSON::XS | 388361.481 | 227951.304 |
708 JSON::XS/2 | 218453.333 | 192399.266 | 810 JSON::XS/2 | 227951.304 | 218453.333 |
709 JSON::XS/3 | 338250.323 | 192399.266 | 811 JSON::XS/3 | 338250.323 | 218453.333 |
710 Storable | 15779.925 | 14169.946 | 812 Storable | 16500.016 | 135300.129 |
711 -----------+------------+------------+ 813 -----------+------------+------------+
712 814
713That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 815That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
714about three times faster on decoding, and over fourty times faster 816about three times faster on decoding, and over fourty times faster
715than JSON, even with pretty-printing and key sorting. It also compares 817than JSON, even with pretty-printing and key sorting. It also compares
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718Using a longer test string (roughly 18KB, generated from Yahoo! Locals 820Using a longer test string (roughly 18KB, generated from Yahoo! Locals
719search API (http://nanoref.com/yahooapis/mgPdGg): 821search API (http://nanoref.com/yahooapis/mgPdGg):
720 822
721 module | encode | decode | 823 module | encode | decode |
722 -----------|------------|------------| 824 -----------|------------|------------|
723 JSON | 254.685 | 37.665 | 825 JSON | 55.260 | 34.971 |
724 JSON::DWIW | 843.343 | 1049.731 | 826 JSON::DWIW | 825.228 | 1082.513 |
725 JSON::PC | 3602.116 | 2307.352 | 827 JSON::PC | 3571.444 | 2394.829 |
828 JSON::PP | 210.987 | 32.574 |
726 JSON::Syck | 505.107 | 787.899 | 829 JSON::Syck | 552.551 | 787.544 |
727 JSON::XS | 5747.196 | 3690.220 | 830 JSON::XS | 5780.463 | 4854.519 |
728 JSON::XS/2 | 3968.121 | 3676.634 | 831 JSON::XS/2 | 3869.998 | 4798.975 |
729 JSON::XS/3 | 6105.246 | 3662.508 | 832 JSON::XS/3 | 5862.880 | 4798.975 |
730 Storable | 4417.337 | 5285.161 | 833 Storable | 4445.002 | 5235.027 |
731 -----------+------------+------------+ 834 -----------+------------+------------+
732 835
733Again, JSON::XS leads by far (except for Storable which non-surprisingly 836Again, JSON::XS leads by far (except for Storable which non-surprisingly
734decodes faster). 837decodes faster).
735 838
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752Second, you need to avoid resource-starving attacks. That means you should 855Second, you need to avoid resource-starving attacks. That means you should
753limit the size of JSON texts you accept, or make sure then when your 856limit the size of JSON texts you accept, or make sure then when your
754resources run out, thats just fine (e.g. by using a separate process that 857resources run out, thats just fine (e.g. by using a separate process that
755can crash safely). The size of a JSON text in octets or characters is 858can crash safely). The size of a JSON text in octets or characters is
756usually a good indication of the size of the resources required to decode 859usually a good indication of the size of the resources required to decode
757it into a Perl structure. 860it into a Perl structure. While JSON::XS can check the size of the JSON
861text, it might be too late when you already have it in memory, so you
862might want to check the size before you accept the string.
758 863
759Third, JSON::XS recurses using the C stack when decoding objects and 864Third, JSON::XS recurses using the C stack when decoding objects and
760arrays. The C stack is a limited resource: for instance, on my amd64 865arrays. The C stack is a limited resource: for instance, on my amd64
761machine with 8MB of stack size I can decode around 180k nested arrays but 866machine with 8MB of stack size I can decode around 180k nested arrays but
762only 14k nested JSON objects (due to perl itself recursing deeply on croak 867only 14k nested JSON objects (due to perl itself recursing deeply on croak

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