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Comparing JSON-XS/XS.pm (file contents):
Revision 1.22 by root, Sun Mar 25 02:37:00 2007 UTC vs.
Revision 1.30 by root, Mon Apr 9 06:37:40 2007 UTC

… …
86package JSON::XS; 86package JSON::XS;
87 87
88use strict; 88use strict;
89 89
90BEGIN { 90BEGIN {
91 our $VERSION = '0.8'; 91 our $VERSION = '1.11';
92 our @ISA = qw(Exporter); 92 our @ISA = qw(Exporter);
93 93
94 our @EXPORT = qw(to_json from_json objToJson jsonToObj); 94 our @EXPORT = qw(to_json from_json objToJson jsonToObj);
95 require Exporter; 95 require Exporter;
96 96
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128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129 129
130except being faster. 130except being faster.
131 131
132=back 132=back
133
133 134
134=head1 OBJECT-ORIENTED INTERFACE 135=head1 OBJECT-ORIENTED INTERFACE
135 136
136The object oriented interface lets you configure your own encoding or 137The object oriented interface lets you configure your own encoding or
137decoding style, within the limits of supported formats. 138decoding style, within the limits of supported formats.
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283 => "Hello, World!" 284 => "Hello, World!"
284 285
285=item $json = $json->shrink ([$enable]) 286=item $json = $json->shrink ([$enable])
286 287
287Perl usually over-allocates memory a bit when allocating space for 288Perl usually over-allocates memory a bit when allocating space for
288strings. This flag optionally resizes strings generated by either 289strings. This flag optionally resizes strings generated by either
289C<encode> or C<decode> to their minimum size possible. This can save 290C<encode> or C<decode> to their minimum size possible. This can save
290memory when your JSON texts are either very very long or you have many 291memory when your JSON texts are either very very long or you have many
291short strings. It will also try to downgrade any strings to octet-form 292short strings. It will also try to downgrade any strings to octet-form
292if possible: perl stores strings internally either in an encoding called 293if possible: perl stores strings internally either in an encoding called
293UTF-X or in octet-form. The latter cannot store everything but uses less 294UTF-X or in octet-form. The latter cannot store everything but uses less
294space in general. 295space in general (and some buggy Perl or C code might even rely on that
296internal representation being used).
295 297
298The actual definition of what shrink does might change in future versions,
299but it will always try to save space at the expense of time.
300
296If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit, 301If C<$enable> is true (or missing), the string returned by C<encode> will
297while all strings generated by C<decode> will also be shrunk-to-fit. 302be shrunk-to-fit, while all strings generated by C<decode> will also be
303shrunk-to-fit.
298 304
299If C<$enable> is false, then the normal perl allocation algorithms are used. 305If C<$enable> is false, then the normal perl allocation algorithms are used.
300If you work with your data, then this is likely to be faster. 306If you work with your data, then this is likely to be faster.
301 307
302In the future, this setting might control other things, such as converting 308In the future, this setting might control other things, such as converting
303strings that look like integers or floats into integers or floats 309strings that look like integers or floats into integers or floats
304internally (there is no difference on the Perl level), saving space. 310internally (there is no difference on the Perl level), saving space.
311
312=item $json = $json->max_depth ([$maximum_nesting_depth])
313
314Sets the maximum nesting level (default C<512>) accepted while encoding
315or 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
317stop and croak at that point.
318
319Nesting level is defined by number of hash- or arrayrefs that the encoder
320needs to traverse to reach a given point or the number of C<{> or C<[>
321characters without their matching closing parenthesis crossed to reach a
322given character in a string.
323
324Setting the maximum depth to one disallows any nesting, so that ensures
325that the object is only a single hash/object or array.
326
327The argument to C<max_depth> will be rounded up to the next nearest power
328of two.
329
330See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
305 331
306=item $json_text = $json->encode ($perl_scalar) 332=item $json_text = $json->encode ($perl_scalar)
307 333
308Converts the given Perl data structure (a simple scalar or a reference 334Converts the given Perl data structure (a simple scalar or a reference
309to a hash or array) to its JSON representation. Simple scalars will be 335to a hash or array) to its JSON representation. Simple scalars will be
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321Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes 347Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
322C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. 348C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
323 349
324=back 350=back
325 351
352
326=head1 MAPPING 353=head1 MAPPING
327 354
328This section describes how JSON::XS maps Perl values to JSON values and 355This section describes how JSON::XS maps Perl values to JSON values and
329vice versa. These mappings are designed to "do the right thing" in most 356vice versa. These mappings are designed to "do the right thing" in most
330circumstances automatically, preserving round-tripping characteristics 357circumstances automatically, preserving round-tripping characteristics
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383=over 4 410=over 4
384 411
385=item hash references 412=item hash references
386 413
387Perl hash references become JSON objects. As there is no inherent ordering 414Perl hash references become JSON objects. As there is no inherent ordering
388in hash keys, they will usually be encoded in a pseudo-random order that 415in hash keys (or JSON objects), they will usually be encoded in a
389can change between runs of the same program but stays generally the same 416pseudo-random order that can change between runs of the same program but
390within a single run of a program. JSON::XS can optionally sort the hash 417stays generally the same within a single run of a program. JSON::XS can
391keys (determined by the I<canonical> flag), so the same datastructure 418optionally sort the hash keys (determined by the I<canonical> flag), so
392will serialise to the same JSON text (given same settings and version of 419the same datastructure will serialise to the same JSON text (given same
393JSON::XS), but this incurs a runtime overhead. 420settings and version of JSON::XS), but this incurs a runtime overhead
421and is only rarely useful, e.g. when you want to compare some JSON text
422against another for equality.
394 423
395=item array references 424=item array references
396 425
397Perl array references become JSON arrays. 426Perl array references become JSON arrays.
427
428=item other references
429
430Other unblessed references are generally not allowed and will cause an
431exception to be thrown, except for references to the integers C<0> and
432C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
433also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
434
435 to_json [\0,JSON::XS::true] # yields [false,true]
398 436
399=item blessed objects 437=item blessed objects
400 438
401Blessed objects are not allowed. JSON::XS currently tries to encode their 439Blessed objects are not allowed. JSON::XS currently tries to encode their
402underlying representation (hash- or arrayref), but this behaviour might 440underlying representation (hash- or arrayref), but this behaviour might
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435 $x *= 1; # same thing, the choise is yours. 473 $x *= 1; # same thing, the choise is yours.
436 474
437You can not currently output JSON booleans or force the type in other, 475You can not currently output JSON booleans or force the type in other,
438less obscure, ways. Tell me if you need this capability. 476less obscure, ways. Tell me if you need this capability.
439 477
440=item circular data structures
441
442Those will be encoded until memory or stackspace runs out.
443
444=back 478=back
479
445 480
446=head1 COMPARISON 481=head1 COMPARISON
447 482
448As already mentioned, this module was created because none of the existing 483As already mentioned, this module was created because none of the existing
449JSON modules could be made to work correctly. First I will describe the 484JSON modules could be made to work correctly. First I will describe the
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578(such as JSON::PC) seem to decode faster than JSON::XS, but the result 613(such as JSON::PC) seem to decode faster than JSON::XS, but the result
579will be broken due to missing (or wrong) unicode handling. Others refuse 614will be broken due to missing (or wrong) unicode handling. Others refuse
580to decode or encode properly, so it was impossible to prepare a fair 615to decode or encode properly, so it was impossible to prepare a fair
581comparison table for that case. 616comparison table for that case.
582 617
583=head1 RESOURCE LIMITS
584 618
585JSON::XS does not impose any limits on the size of JSON texts or Perl 619=head1 SECURITY CONSIDERATIONS
586values they represent - if your machine can handle it, JSON::XS will 620
587encode or decode it. Future versions might optionally impose structure 621When you are using JSON in a protocol, talking to untrusted potentially
588depth and memory use resource limits. 622hostile creatures requires relatively few measures.
623
624First of all, your JSON decoder should be secure, that is, should not have
625any buffer overflows. Obviously, this module should ensure that and I am
626trying hard on making that true, but you never know.
627
628Second, you need to avoid resource-starving attacks. That means you should
629limit the size of JSON texts you accept, or make sure then when your
630resources run out, thats just fine (e.g. by using a separate process that
631can crash safely). The size of a JSON text in octets or characters is
632usually a good indication of the size of the resources required to decode
633it into a Perl structure.
634
635Third, JSON::XS recurses using the C stack when decoding objects and
636arrays. The C stack is a limited resource: for instance, on my amd64
637machine with 8MB of stack size I can decode around 180k nested arrays but
638only 14k nested JSON objects (due to perl itself recursing deeply on croak
639to free the temporary). If that is exceeded, the program crashes. to be
640conservative, the default nesting limit is set to 512. If your process
641has a smaller stack, you should adjust this setting accordingly with the
642C<max_depth> method.
643
644And last but least, something else could bomb you that I forgot to think
645of. In that case, you get to keep the pieces. I am always open for hints,
646though...
647
589 648
590=head1 BUGS 649=head1 BUGS
591 650
592While the goal of this module is to be correct, that unfortunately does 651While the goal of this module is to be correct, that unfortunately does
593not mean its bug-free, only that I think its design is bug-free. It is 652not mean its bug-free, only that I think its design is bug-free. It is
594still very young and not well-tested. If you keep reporting bugs they will 653still relatively early in its development. If you keep reporting bugs they
595be fixed swiftly, though. 654will be fixed swiftly, though.
596 655
597=cut 656=cut
657
658sub true() { \1 }
659sub false() { \0 }
598 660
5991; 6611;
600 662
601=head1 AUTHOR 663=head1 AUTHOR
602 664

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