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Revision 1.27 by root, Thu Nov 28 15:43:24 2013 UTC vs.
Revision 1.57 by root, Mon Apr 25 21:57:57 2016 UTC

26 substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string 26 substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string
27 } 27 }
28 28
29=head1 DESCRIPTION 29=head1 DESCRIPTION
30 30
31WARNING! This module is very new, and not very well tested (that's up
32to you to do). Furthermore, details of the implementation might change
33freely before version 1.0. And lastly, most extensions depend on an IANA
34assignment, and until that assignment is official, this implementation is
35not interoperable with other implementations (even future versions of this
36module) until the assignment is done.
37
38You are still invited to try out CBOR, and this module.
39
40This module converts Perl data structures to the Concise Binary Object 31This module converts Perl data structures to the Concise Binary Object
41Representation (CBOR) and vice versa. CBOR is a fast binary serialisation 32Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
42format that aims to use a superset of the JSON data model, i.e. when you 33format that aims to use an (almost) superset of the JSON data model, i.e.
43can represent something in JSON, you should be able to represent it in 34when you can represent something useful in JSON, you should be able to
44CBOR. 35represent it in CBOR.
45 36
46In short, CBOR is a faster and very compact binary alternative to JSON, 37In short, CBOR is a faster and quite compact binary alternative to JSON,
47with the added ability of supporting serialisation of Perl objects. (JSON 38with the added ability of supporting serialisation of Perl objects. (JSON
48often compresses better than CBOR though, so if you plan to compress the 39often compresses better than CBOR though, so if you plan to compress the
49data later you might want to compare both formats first). 40data later and speed is less important you might want to compare both
41formats first).
50 42
51To give you a general idea about speed, with texts in the megabyte range, 43To give you a general idea about speed, with texts in the megabyte range,
52C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or 44C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or
53L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the 45L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
54data, the worse L<Storable> performs in comparison. 46data, the worse L<Storable> performs in comparison.
55 47
56As for compactness, C<CBOR::XS> encoded data structures are usually about 48Regarding compactness, C<CBOR::XS>-encoded data structures are usually
5720% smaller than the same data encoded as (compact) JSON or L<Storable>. 49about 20% smaller than the same data encoded as (compact) JSON or
50L<Storable>.
58 51
59In addition to the core CBOR data format, this module implements a number 52In addition to the core CBOR data format, this module implements a
60of extensions, to support cyclic and self-referencing data structures 53number of extensions, to support cyclic and shared data structures
61(see C<allow_sharing>), string deduplication (see C<pack_strings>) and 54(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
62scalar references (always enabled). 55C<pack_strings>) and scalar references (always enabled).
63 56
64The primary goal of this module is to be I<correct> and the secondary goal 57The primary goal of this module is to be I<correct> and the secondary goal
65is to be I<fast>. To reach the latter goal it was written in C. 58is to be I<fast>. To reach the latter goal it was written in C.
66 59
67See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and 60See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
71 64
72package CBOR::XS; 65package CBOR::XS;
73 66
74use common::sense; 67use common::sense;
75 68
76our $VERSION = 0.09; 69our $VERSION = 1.5;
77our @ISA = qw(Exporter); 70our @ISA = qw(Exporter);
78 71
79our @EXPORT = qw(encode_cbor decode_cbor); 72our @EXPORT = qw(encode_cbor decode_cbor);
80 73
81use Exporter; 74use Exporter;
187reference to the earlier value. 180reference to the earlier value.
188 181
189This means that such values will only be encoded once, and will not result 182This means that such values will only be encoded once, and will not result
190in a deep cloning of the value on decode, in decoders supporting the value 183in a deep cloning of the value on decode, in decoders supporting the value
191sharing extension. This also makes it possible to encode cyclic data 184sharing extension. This also makes it possible to encode cyclic data
192structures. 185structures (which need C<allow_cycles> to ne enabled to be decoded by this
186module).
193 187
194It is recommended to leave it off unless you know your 188It is recommended to leave it off unless you know your
195communication partner supports the value sharing extensions to CBOR 189communication partner supports the value sharing extensions to CBOR
196(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the 190(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
197resulting data structure might be unusable. 191resulting data structure might be unusable.
198 192
199Detecting shared values incurs a runtime overhead when values are encoded 193Detecting shared values incurs a runtime overhead when values are encoded
200that have a reference counter large than one, and might unnecessarily 194that have a reference counter large than one, and might unnecessarily
201increase the encoded size, as potentially shared values are encode as 195increase the encoded size, as potentially shared values are encode as
202sharable whether or not they are actually shared. 196shareable whether or not they are actually shared.
203 197
204At the moment, only targets of references can be shared (e.g. scalars, 198At the moment, only targets of references can be shared (e.g. scalars,
205arrays or hashes pointed to by a reference). Weirder constructs, such as 199arrays or hashes pointed to by a reference). Weirder constructs, such as
206an array with multiple "copies" of the I<same> string, which are hard but 200an array with multiple "copies" of the I<same> string, which are hard but
207not impossible to create in Perl, are not supported (this is the same as 201not impossible to create in Perl, are not supported (this is the same as
212structures cannot be encoded in this mode. 206structures cannot be encoded in this mode.
213 207
214This option does not affect C<decode> in any way - shared values and 208This option does not affect C<decode> in any way - shared values and
215references will always be decoded properly if present. 209references will always be decoded properly if present.
216 210
211=item $cbor = $cbor->allow_cycles ([$enable])
212
213=item $enabled = $cbor->get_allow_cycles
214
215If C<$enable> is true (or missing), then C<decode> will happily decode
216self-referential (cyclic) data structures. By default these will not be
217decoded, as they need manual cleanup to avoid memory leaks, so code that
218isn't prepared for this will not leak memory.
219
220If C<$enable> is false (the default), then C<decode> will throw an error
221when it encounters a self-referential/cyclic data structure.
222
223FUTURE DIRECTION: the motivation behind this option is to avoid I<real>
224cycles - future versions of this module might chose to decode cyclic data
225structures using weak references when this option is off, instead of
226throwing an error.
227
228This option does not affect C<encode> in any way - shared values and
229references will always be encoded properly if present.
230
217=item $cbor = $cbor->pack_strings ([$enable]) 231=item $cbor = $cbor->pack_strings ([$enable])
218 232
219=item $enabled = $cbor->get_pack_strings 233=item $enabled = $cbor->get_pack_strings
220 234
221If C<$enable> is true (or missing), then C<encode> will try not to encode 235If C<$enable> is true (or missing), then C<encode> will try not to encode
233the standard CBOR way. 247the standard CBOR way.
234 248
235This option does not affect C<decode> in any way - string references will 249This option does not affect C<decode> in any way - string references will
236always be decoded properly if present. 250always be decoded properly if present.
237 251
252=item $cbor = $cbor->text_keys ([$enable])
253
254=item $enabled = $cbor->get_text_keys
255
256If C<$enabled> is true (or missing), then C<encode> will encode all
257perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed.
258
259If C<$enable> is false (the default), then C<encode> will encode hash keys
260normally - upgraded perl strings (strings internally encoded as UTF-8) as
261CBOR text strings, and downgraded perl strings as CBOR byte strings.
262
263This option does not affect C<decode> in any way.
264
265This option is useful for interoperability with CBOR decoders that don't
266treat byte strings as a form of text. It is especially useful as Perl
267gives very little control over hash keys.
268
269Enabling this option can be slow, as all downgraded hash keys that are
270encoded need to be scanned and converted to UTF-8.
271
272=item $cbor = $cbor->text_strings ([$enable])
273
274=item $enabled = $cbor->get_text_strings
275
276This option works similar to C<text_keys>, above, but works on all strings
277(including hash keys), so C<text_keys> has no further effect after
278enabling C<text_strings>.
279
280If C<$enabled> is true (or missing), then C<encode> will encode all perl
281strings as CBOR text strings/UTF-8 strings, upgrading them as needed.
282
283If C<$enable> is false (the default), then C<encode> will encode strings
284normally (but see C<text_keys>) - upgraded perl strings (strings
285internally encoded as UTF-8) as CBOR text strings, and downgraded perl
286strings as CBOR byte strings.
287
288This option does not affect C<decode> in any way.
289
290This option has similar advantages and disadvantages as C<text_keys>. In
291addition, this option effectively removes the ability to encode byte
292strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely
293on this, such as bignum encoding, so this option is mainly useful for very
294simple data.
295
296=item $cbor = $cbor->validate_utf8 ([$enable])
297
298=item $enabled = $cbor->get_validate_utf8
299
300If C<$enable> is true (or missing), then C<decode> will validate that
301elements (text strings) containing UTF-8 data in fact contain valid UTF-8
302data (instead of blindly accepting it). This validation obviously takes
303extra time during decoding.
304
305The concept of "valid UTF-8" used is perl's concept, which is a superset
306of the official UTF-8.
307
308If C<$enable> is false (the default), then C<decode> will blindly accept
309UTF-8 data, marking them as valid UTF-8 in the resulting data structure
310regardless of whether that's true or not.
311
312Perl isn't too happy about corrupted UTF-8 in strings, but should
313generally not crash or do similarly evil things. Extensions might be not
314so forgiving, so it's recommended to turn on this setting if you receive
315untrusted CBOR.
316
317This option does not affect C<encode> in any way - strings that are
318supposedly valid UTF-8 will simply be dumped into the resulting CBOR
319string without checking whether that is, in fact, true or not.
320
238=item $cbor = $cbor->filter ([$cb->($tag, $value)]) 321=item $cbor = $cbor->filter ([$cb->($tag, $value)])
239 322
240=item $cb_or_undef = $cbor->get_filter 323=item $cb_or_undef = $cbor->get_filter
241 324
242Sets or replaces the tagged value decoding filter (when C<$cb> is 325Sets or replaces the tagged value decoding filter (when C<$cb> is
259function, C<CBOR::XS::default_filter>, is used. This function simply looks 342function, C<CBOR::XS::default_filter>, is used. This function simply looks
260up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be 343up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be
261a code reference that is called with tag and value, and is responsible for 344a code reference that is called with tag and value, and is responsible for
262decoding the value. If no entry exists, it returns no values. 345decoding the value. If no entry exists, it returns no values.
263 346
264Example: decode all tags not handled internally into CBOR::XS::Tagged 347Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
265objects, with no other special handling (useful when working with 348objects, with no other special handling (useful when working with
266potentially "unsafe" CBOR data). 349potentially "unsafe" CBOR data).
267 350
268 CBOR::XS->new->filter (sub { })->decode ($cbor_data); 351 CBOR::XS->new->filter (sub { })->decode ($cbor_data);
269 352
296and you need to know where the first CBOR string ends amd the next one 379and you need to know where the first CBOR string ends amd the next one
297starts. 380starts.
298 381
299 CBOR::XS->new->decode_prefix ("......") 382 CBOR::XS->new->decode_prefix ("......")
300 => ("...", 3) 383 => ("...", 3)
384
385=back
386
387=head2 INCREMENTAL PARSING
388
389In some cases, there is the need for incremental parsing of JSON
390texts. While this module always has to keep both CBOR text and resulting
391Perl data structure in memory at one time, it does allow you to parse a
392CBOR stream incrementally, using a similar to using "decode_prefix" to see
393if a full CBOR object is available, but is much more efficient.
394
395It basically works by parsing as much of a CBOR string as possible - if
396the CBOR data is not complete yet, the pasrer will remember where it was,
397to be able to restart when more data has been accumulated. Once enough
398data is available to either decode a complete CBOR value or raise an
399error, a real decode will be attempted.
400
401A typical use case would be a network protocol that consists of sending
402and receiving CBOR-encoded messages. The solution that works with CBOR and
403about anything else is by prepending a length to every CBOR value, so the
404receiver knows how many octets to read. More compact (and slightly slower)
405would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
406a CBOR value ends, and doesn't need an explicit length.
407
408The following methods help with this:
409
410=over 4
411
412=item @decoded = $cbor->incr_parse ($buffer)
413
414This method attempts to decode exactly one CBOR value from the beginning
415of the given C<$buffer>. The value is removed from the C<$buffer> on
416success. When C<$buffer> doesn't contain a complete value yet, it returns
417nothing. Finally, when the C<$buffer> doesn't start with something
418that could ever be a valid CBOR value, it raises an exception, just as
419C<decode> would. In the latter case the decoder state is undefined and
420must be reset before being able to parse further.
421
422This method modifies the C<$buffer> in place. When no CBOR value can be
423decoded, the decoder stores the current string offset. On the next call,
424continues decoding at the place where it stopped before. For this to make
425sense, the C<$buffer> must begin with the same octets as on previous
426unsuccessful calls.
427
428You can call this method in scalar context, in which case it either
429returns a decoded value or C<undef>. This makes it impossible to
430distinguish between CBOR null values (which decode to C<undef>) and an
431unsuccessful decode, which is often acceptable.
432
433=item @decoded = $cbor->incr_parse_multiple ($buffer)
434
435Same as C<incr_parse>, but attempts to decode as many CBOR values as
436possible in one go, instead of at most one. Calls to C<incr_parse> and
437C<incr_parse_multiple> can be interleaved.
438
439=item $cbor->incr_reset
440
441Resets the incremental decoder. This throws away any saved state, so that
442subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
443a new CBOR value from the beginning of the C<$buffer> again.
444
445This method can be caled at any time, but it I<must> be called if you want
446to change your C<$buffer> or there was a decoding error and you want to
447reuse the C<$cbor> object for future incremental parsings.
301 448
302=back 449=back
303 450
304 451
305=head1 MAPPING 452=head1 MAPPING
356=item tagged values 503=item tagged values
357 504
358Tagged items consists of a numeric tag and another CBOR value. 505Tagged items consists of a numeric tag and another CBOR value.
359 506
360See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> 507See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
361for details. 508for details on which tags are handled how.
362 509
363=item anything else 510=item anything else
364 511
365Anything else (e.g. unsupported simple values) will raise a decoding 512Anything else (e.g. unsupported simple values) will raise a decoding
366error. 513error.
369 516
370 517
371=head2 PERL -> CBOR 518=head2 PERL -> CBOR
372 519
373The mapping from Perl to CBOR is slightly more difficult, as Perl is a 520The mapping from Perl to CBOR is slightly more difficult, as Perl is a
374truly typeless language, so we can only guess which CBOR type is meant by 521typeless language. That means this module can only guess which CBOR type
375a Perl value. 522is meant by a perl value.
376 523
377=over 4 524=over 4
378 525
379=item hash references 526=item hash references
380 527
381Perl hash references become CBOR maps. As there is no inherent ordering in 528Perl hash references become CBOR maps. As there is no inherent ordering in
382hash keys (or CBOR maps), they will usually be encoded in a pseudo-random 529hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
383order. 530order. This order can be different each time a hash is encoded.
384 531
385Currently, tied hashes will use the indefinite-length format, while normal 532Currently, tied hashes will use the indefinite-length format, while normal
386hashes will use the fixed-length format. 533hashes will use the fixed-length format.
387 534
388=item array references 535=item array references
389 536
390Perl array references become fixed-length CBOR arrays. 537Perl array references become fixed-length CBOR arrays.
391 538
392=item other references 539=item other references
393 540
394Other unblessed references are generally not allowed and will cause an 541Other unblessed references will be represented using
395exception to be thrown, except for references to the integers C<0> and 542the indirection tag extension (tag value C<22098>,
396C<1>, which get turned into false and true in CBOR. 543L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
544to be able to decode these values somehow, by either "doing the right
545thing", decoding into a generic tagged object, simply ignoring the tag, or
546something else.
397 547
398=item CBOR::XS::Tagged objects 548=item CBOR::XS::Tagged objects
399 549
400Objects of this type must be arrays consisting of a single C<[tag, value]> 550Objects of this type must be arrays consisting of a single C<[tag, value]>
401pair. The (numerical) tag will be encoded as a CBOR tag, the value will 551pair. The (numerical) tag will be encoded as a CBOR tag, the value will
402be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to 552be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
403create such objects. 553create such objects.
404 554
405=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error 555=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
406 556
407These special values become CBOR true, CBOR false and CBOR undefined 557These special values become CBOR true, CBOR false and CBOR undefined
438 my $x = 3.1; # some variable containing a number 588 my $x = 3.1; # some variable containing a number
439 "$x"; # stringified 589 "$x"; # stringified
440 $x .= ""; # another, more awkward way to stringify 590 $x .= ""; # another, more awkward way to stringify
441 print $x; # perl does it for you, too, quite often 591 print $x; # perl does it for you, too, quite often
442 592
443You can force whether a string ie encoded as byte or text string by using 593You can force whether a string is encoded as byte or text string by using
444C<utf8::upgrade> and C<utf8::downgrade>): 594C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):
445 595
446 utf8::upgrade $x; # encode $x as text string 596 utf8::upgrade $x; # encode $x as text string
447 utf8::downgrade $x; # encode $x as byte string 597 utf8::downgrade $x; # encode $x as byte string
448 598
449Perl doesn't define what operations up- and downgrade strings, so if the 599Perl doesn't define what operations up- and downgrade strings, so if the
450difference between byte and text is important, you should up- or downgrade 600difference between byte and text is important, you should up- or downgrade
451your string as late as possible before encoding. 601your string as late as possible before encoding. You can also force the
602use of CBOR text strings by using C<text_keys> or C<text_strings>.
452 603
453You can force the type to be a CBOR number by numifying it: 604You can force the type to be a CBOR number by numifying it:
454 605
455 my $x = "3"; # some variable containing a string 606 my $x = "3"; # some variable containing a string
456 $x += 0; # numify it, ensuring it will be dumped as a number 607 $x += 0; # numify it, ensuring it will be dumped as a number
469 620
470=back 621=back
471 622
472=head2 OBJECT SERIALISATION 623=head2 OBJECT SERIALISATION
473 624
625This module implements both a CBOR-specific and the generic
626L<Types::Serialier> object serialisation protocol. The following
627subsections explain both methods.
628
629=head3 ENCODING
630
474This module knows two way to serialise a Perl object: The CBOR-specific 631This module knows two way to serialise a Perl object: The CBOR-specific
475way, and the generic way. 632way, and the generic way.
476 633
477Whenever the encoder encounters a Perl object that it cnanot serialise 634Whenever the encoder encounters a Perl object that it cannot serialise
478directly (most of them), it will first look up the C<TO_CBOR> method on 635directly (most of them), it will first look up the C<TO_CBOR> method on
479it. 636it.
480 637
481If it has a C<TO_CBOR> method, it will call it with the object as only 638If it has a C<TO_CBOR> method, it will call it with the object as only
482argument, and expects exactly one return value, which it will then 639argument, and expects exactly one return value, which it will then
488 645
489The C<FREEZE> method can return any number of values (i.e. zero or 646The C<FREEZE> method can return any number of values (i.e. zero or
490more). These will be encoded as CBOR perl object, together with the 647more). These will be encoded as CBOR perl object, together with the
491classname. 648classname.
492 649
650These methods I<MUST NOT> change the data structure that is being
651serialised. Failure to comply to this can result in memory corruption -
652and worse.
653
493If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail 654If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
494with an error. 655with an error.
495 656
657=head3 DECODING
658
496Objects encoded via C<TO_CBOR> cannot be automatically decoded, but 659Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
497objects encoded via C<FREEZE> can be decoded using the following protocol: 660but objects encoded via C<FREEZE> can be decoded using the following
661protocol:
498 662
499When an encoded CBOR perl object is encountered by the decoder, it will 663When an encoded CBOR perl object is encountered by the decoder, it will
500look up the C<THAW> method, by using the stored classname, and will fail 664look up the C<THAW> method, by using the stored classname, and will fail
501if the method cannot be found. 665if the method cannot be found.
502 666
503After the lookup it will call the C<THAW> method with the stored classname 667After the lookup it will call the C<THAW> method with the stored classname
504as first argument, the constant string C<CBOR> as second argument, and all 668as first argument, the constant string C<CBOR> as second argument, and all
505values returned by C<FREEZE> as remaining arguments. 669values returned by C<FREEZE> as remaining arguments.
506 670
507=head4 EXAMPLES 671=head3 EXAMPLES
508 672
509Here is an example C<TO_CBOR> method: 673Here is an example C<TO_CBOR> method:
510 674
511 sub My::Object::TO_CBOR { 675 sub My::Object::TO_CBOR {
512 my ($obj) = @_; 676 my ($obj) = @_;
523 687
524 sub URI::TO_CBOR { 688 sub URI::TO_CBOR {
525 my ($self) = @_; 689 my ($self) = @_;
526 my $uri = "$self"; # stringify uri 690 my $uri = "$self"; # stringify uri
527 utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string 691 utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
528 CBOR::XS::tagged 32, "$_[0]" 692 CBOR::XS::tag 32, "$_[0]"
529 } 693 }
530 694
531This will encode URIs as a UTF-8 string with tag 32, which indicates an 695This will encode URIs as a UTF-8 string with tag 32, which indicates an
532URI. 696URI.
533 697
544 "$self" # encode url string 708 "$self" # encode url string
545 } 709 }
546 710
547 sub URI::THAW { 711 sub URI::THAW {
548 my ($class, $serialiser, $uri) = @_; 712 my ($class, $serialiser, $uri) = @_;
549
550 $class->new ($uri) 713 $class->new ($uri)
551 } 714 }
552 715
553Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For 716Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
554example, a C<FREEZE> method that returns "type", "id" and "variant" values 717example, a C<FREEZE> method that returns "type", "id" and "variant" values
685additional tags (such as base64url). 848additional tags (such as base64url).
686 849
687=head2 ENFORCED TAGS 850=head2 ENFORCED TAGS
688 851
689These tags are always handled when decoding, and their handling cannot be 852These tags are always handled when decoding, and their handling cannot be
690overriden by the user. 853overridden by the user.
691 854
692=over 4 855=over 4
693 856
694=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>) 857=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
695 858
696These tags are automatically created (and decoded) for serialisable 859These tags are automatically created (and decoded) for serialisable
697objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object 860objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
698serialisation protocol). See L<OBJECT SERIALISATION> for details. 861serialisation protocol). See L<OBJECT SERIALISATION> for details.
699 862
700=item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) 863=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
701 864
702These tags are automatically decoded when encountered, resulting in 865These tags are automatically decoded when encountered (and they do not
866result in a cyclic data structure, see C<allow_cycles>), resulting in
703shared values in the decoded object. They are only encoded, however, when 867shared values in the decoded object. They are only encoded, however, when
704C<allow_sharable> is enabled. 868C<allow_sharing> is enabled.
705 869
870Not all shared values can be successfully decoded: values that reference
871themselves will I<currently> decode as C<undef> (this is not the same
872as a reference pointing to itself, which will be represented as a value
873that contains an indirect reference to itself - these will be decoded
874properly).
875
876Note that considerably more shared value data structures can be decoded
877than will be encoded - currently, only values pointed to by references
878will be shared, others will not. While non-reference shared values can be
879generated in Perl with some effort, they were considered too unimportant
880to be supported in the encoder. The decoder, however, will decode these
881values as shared values.
882
706=item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) 883=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
707 884
708These tags are automatically decoded when encountered. They are only 885These tags are automatically decoded when encountered. They are only
709encoded, however, when C<pack_strings> is enabled. 886encoded, however, when C<pack_strings> is enabled.
710 887
711=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) 888=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
712 889
713This tag is automatically generated when a reference are encountered (with 890This tag is automatically generated when a reference are encountered (with
714the exception of hash and array refernces). It is converted to a reference 891the exception of hash and array references). It is converted to a reference
715when decoding. 892when decoding.
716 893
717=item 55799 (self-describe CBOR, RFC 7049) 894=item 55799 (self-describe CBOR, RFC 7049)
718 895
719This value is not generated on encoding (unless explicitly requested by 896This value is not generated on encoding (unless explicitly requested by
722=back 899=back
723 900
724=head2 NON-ENFORCED TAGS 901=head2 NON-ENFORCED TAGS
725 902
726These tags have default filters provided when decoding. Their handling can 903These tags have default filters provided when decoding. Their handling can
727be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by 904be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
728providing a custom C<filter> callback when decoding. 905providing a custom C<filter> callback when decoding.
729 906
730When they result in decoding into a specific Perl class, the module 907When they result in decoding into a specific Perl class, the module
731usually provides a corresponding C<TO_CBOR> method as well. 908usually provides a corresponding C<TO_CBOR> method as well.
732 909
735provide these modules. The decoding usually fails with an exception if the 912provide these modules. The decoding usually fails with an exception if the
736required module cannot be loaded. 913required module cannot be loaded.
737 914
738=over 4 915=over 4
739 916
917=item 0, 1 (date/time string, seconds since the epoch)
918
919These tags are decoded into L<Time::Piece> objects. The corresponding
920C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
921
922The L<Time::Piece> API is generally surprisingly bad, and fractional
923seconds are only accidentally kept intact, so watch out. On the plus side,
924the module comes with perl since 5.10, which has to count for something.
925
740=item 2, 3 (positive/negative bignum) 926=item 2, 3 (positive/negative bignum)
741 927
742These tags are decoded into L<Math::BigInt> objects. The corresponding 928These tags are decoded into L<Math::BigInt> objects. The corresponding
743C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR 929C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
744integers, and others into positive/negative CBOR bignums. 930integers, and others into positive/negative CBOR bignums.
745 931
746=item 4, 5 (decimal fraction/bigfloat) 932=item 4, 5, 264, 265 (decimal fraction/bigfloat)
747 933
748Both decimal fractions and bigfloats are decoded into L<Math::BigFloat> 934Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
749objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always> 935objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
750encodes into a decimal fraction. 936encodes into a decimal fraction (either tag 4 or 264).
751 937
752CBOR cannot represent bigfloats with I<very> large exponents - conversion 938NaN and infinities are not encoded properly, as they cannot be represented
753of such big float objects is undefined. 939in CBOR.
754 940
755Also, NaN and infinities are not encoded properly. 941See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
756 942
757=item 21, 22, 23 (expected later JSON conversion) 943=item 21, 22, 23 (expected later JSON conversion)
758 944
759CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these 945CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
760tags. 946tags.
765C<URI::TO_CBOR> method again results in a CBOR URI value. 951C<URI::TO_CBOR> method again results in a CBOR URI value.
766 952
767=back 953=back
768 954
769=cut 955=cut
770
771our %FILTER = (
772 # 0 # rfc4287 datetime, utf-8
773 # 1 # unix timestamp, any
774
775 2 => sub { # pos bigint
776 require Math::BigInt;
777 Math::BigInt->new ("0x" . unpack "H*", pop)
778 },
779
780 3 => sub { # neg bigint
781 require Math::BigInt;
782 -Math::BigInt->new ("0x" . unpack "H*", pop)
783 },
784
785 4 => sub { # decimal fraction, array
786 require Math::BigFloat;
787 Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
788 },
789
790 5 => sub { # bigfloat, array
791 require Math::BigFloat;
792 scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
793 },
794
795 21 => sub { pop }, # expected conversion to base64url encoding
796 22 => sub { pop }, # expected conversion to base64 encoding
797 23 => sub { pop }, # expected conversion to base16 encoding
798
799 # 24 # embedded cbor, byte string
800
801 32 => sub {
802 require URI;
803 URI->new (pop)
804 },
805
806 # 33 # base64url rfc4648, utf-8
807 # 34 # base64 rfc46484, utf-8
808 # 35 # regex pcre/ecma262, utf-8
809 # 36 # mime message rfc2045, utf-8
810);
811
812 956
813=head1 CBOR and JSON 957=head1 CBOR and JSON
814 958
815CBOR is supposed to implement a superset of the JSON data model, and is, 959CBOR is supposed to implement a superset of the JSON data model, and is,
816with some coercion, able to represent all JSON texts (something that other 960with some coercion, able to represent all JSON texts (something that other
858Also keep in mind that CBOR::XS might leak contents of your Perl data 1002Also keep in mind that CBOR::XS might leak contents of your Perl data
859structures in its error messages, so when you serialise sensitive 1003structures in its error messages, so when you serialise sensitive
860information you might want to make sure that exceptions thrown by CBOR::XS 1004information you might want to make sure that exceptions thrown by CBOR::XS
861will not end up in front of untrusted eyes. 1005will not end up in front of untrusted eyes.
862 1006
1007
1008=head1 BIGNUM SECURITY CONSIDERATIONS
1009
1010CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
1011L<Math::BigFloat> that tries to encode the number in the simplest possible
1012way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
10134) or an arbitrary-exponent decimal fraction (tag 264).
1014
1015It will also understand base-2 bigfloat or arbitrary-exponent bigfloats
1016(tags 5 and 265), but it will never generate these on its own.
1017
1018Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
1019decimal fractions is generally fast. Decoding bigints can be slow for very
1020big numbers, and decoding bigfloats or arbitrary-exponent bigfloats can be
1021extremely slow (minutes, decades) for large exponents.
1022
1023Additionally, L<Math::BigInt> can take advantage of other bignum
1024libraries, such as L<Math::GMP>, which cannot handle big
1025floats with large exponents, and might simply abort or crash your program,
1026due to their code quality.
1027
1028This can be a concern if you want to parse untrusted CBOR. If it is, you
1029need to disable decoding of tag 2 (bigint) and 3 (negative bigint) types,
1030which will also disable bigfloat support (to be sure, you can also disable
1031types 4, 5, 264 and 265).
1032
1033
863=head1 CBOR IMPLEMENTATION NOTES 1034=head1 CBOR IMPLEMENTATION NOTES
864 1035
865This section contains some random implementation notes. They do not 1036This section contains some random implementation notes. They do not
866describe guaranteed behaviour, but merely behaviour as-is implemented 1037describe guaranteed behaviour, but merely behaviour as-is implemented
867right now. 1038right now.
875Only the double data type is supported for NV data types - when Perl uses 1046Only the double data type is supported for NV data types - when Perl uses
876long double to represent floating point values, they might not be encoded 1047long double to represent floating point values, they might not be encoded
877properly. Half precision types are accepted, but not encoded. 1048properly. Half precision types are accepted, but not encoded.
878 1049
879Strict mode and canonical mode are not implemented. 1050Strict mode and canonical mode are not implemented.
1051
1052
1053=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
1054
1055On perls that were built without 64 bit integer support (these are rare
1056nowadays, even on 32 bit architectures, as all major Perl distributions
1057are built with 64 bit integer support), support for any kind of 64 bit
1058integer in CBOR is very limited - most likely, these 64 bit values will
1059be truncated, corrupted, or otherwise not decoded correctly. This also
1060includes string, array and map sizes that are stored as 64 bit integers.
880 1061
881 1062
882=head1 THREADS 1063=head1 THREADS
883 1064
884This module is I<not> guaranteed to be thread safe and there are no 1065This module is I<not> guaranteed to be thread safe and there are no
899service. I put the contact address into my modules for a reason. 1080service. I put the contact address into my modules for a reason.
900 1081
901=cut 1082=cut
902 1083
903our %FILTER = ( 1084our %FILTER = (
904 # 0 # rfc4287 datetime, utf-8 1085 0 => sub { # rfc4287 datetime, utf-8
905 # 1 # unix timestamp, any 1086 require Time::Piece;
1087 # Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
1088 # from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
1089 # else either. Whats incredibe over standard strptime totally escapes me.
1090 # doesn't do fractional times, either. sigh.
1091 # In fact, it's all a lie, it uses whatever strptime it wants, and of course,
1092 # they are all incompatible. The openbsd one simply ignores %z (but according to the
1093 # docs, it would be much more incredibly flexible indeed. If it worked, that is.).
1094 scalar eval {
1095 my $s = $_[1];
1096
1097 $s =~ s/Z$/+00:00/;
1098 $s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
1099 or die;
1100
1101 my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
1102 my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
1103
1104 Time::Piece::gmtime ($d->epoch + $b)
1105 } || die "corrupted CBOR date/time string ($_[0])";
1106 },
1107
1108 1 => sub { # seconds since the epoch, possibly fractional
1109 require Time::Piece;
1110 scalar Time::Piece::gmtime (pop)
1111 },
906 1112
907 2 => sub { # pos bigint 1113 2 => sub { # pos bigint
908 require Math::BigInt; 1114 require Math::BigInt;
909 Math::BigInt->new ("0x" . unpack "H*", pop) 1115 Math::BigInt->new ("0x" . unpack "H*", pop)
910 }, 1116 },
919 Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) 1125 Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
920 }, 1126 },
921 1127
922 5 => sub { # bigfloat, array 1128 5 => sub { # bigfloat, array
923 require Math::BigFloat; 1129 require Math::BigFloat;
924 scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2) 1130 scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
925 }, 1131 },
926 1132
927 21 => sub { pop }, # expected conversion to base64url encoding 1133 21 => sub { pop }, # expected conversion to base64url encoding
928 22 => sub { pop }, # expected conversion to base64 encoding 1134 22 => sub { pop }, # expected conversion to base64 encoding
929 23 => sub { pop }, # expected conversion to base16 encoding 1135 23 => sub { pop }, # expected conversion to base16 encoding
937 1143
938 # 33 # base64url rfc4648, utf-8 1144 # 33 # base64url rfc4648, utf-8
939 # 34 # base64 rfc46484, utf-8 1145 # 34 # base64 rfc46484, utf-8
940 # 35 # regex pcre/ecma262, utf-8 1146 # 35 # regex pcre/ecma262, utf-8
941 # 36 # mime message rfc2045, utf-8 1147 # 36 # mime message rfc2045, utf-8
1148
1149 264 => sub { # decimal fraction with arbitrary exponent
1150 require Math::BigFloat;
1151 Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
1152 },
1153
1154 265 => sub { # bigfloat with arbitrary exponent
1155 require Math::BigFloat;
1156 scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
1157 },
942); 1158);
943 1159
944sub CBOR::XS::default_filter { 1160sub CBOR::XS::default_filter {
945 &{ $FILTER{$_[0]} or return } 1161 &{ $FILTER{$_[0]} or return }
946} 1162}
947 1163
948sub URI::TO_CBOR { 1164sub URI::TO_CBOR {
949 my $uri = $_[0]->as_string; 1165 my $uri = $_[0]->as_string;
950 utf8::upgrade $uri; 1166 utf8::upgrade $uri;
951 CBOR::XS::tag 32, $uri 1167 tag 32, $uri
952} 1168}
953 1169
954sub Math::BigInt::TO_CBOR { 1170sub Math::BigInt::TO_CBOR {
955 if ($_[0] >= -2147483648 && $_[0] <= 2147483647) { 1171 if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
956 $_[0]->numify 1172 $_[0]->numify
957 } else { 1173 } else {
958 my $hex = substr $_[0]->as_hex, 2; 1174 my $hex = substr $_[0]->as_hex, 2;
959 $hex = "0$hex" if 1 & length $hex; # sigh 1175 $hex = "0$hex" if 1 & length $hex; # sigh
960 CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex 1176 tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
961 } 1177 }
962} 1178}
963 1179
964sub Math::BigFloat::TO_CBOR { 1180sub Math::BigFloat::TO_CBOR {
965 my ($m, $e) = $_[0]->parts; 1181 my ($m, $e) = $_[0]->parts;
1182
1183 -9223372036854775808 <= $e && $e <= 18446744073709551615
966 CBOR::XS::tag 4, [$e->numify, $m] 1184 ? tag 4, [$e->numify, $m]
1185 : tag 264, [$e, $m]
1186}
1187
1188sub Time::Piece::TO_CBOR {
1189 tag 1, 0 + $_[0]->epoch
967} 1190}
968 1191
969XSLoader::load "CBOR::XS", $VERSION; 1192XSLoader::load "CBOR::XS", $VERSION;
970 1193
971=head1 SEE ALSO 1194=head1 SEE ALSO

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