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Revision 1.22 by root, Fri Nov 22 15:28:38 2013 UTC vs.
Revision 1.49 by root, Thu Apr 21 16:24:03 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<allow_stringref>) 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 = 0.08; 69our $VERSION = 1.41;
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;
118strings. All boolean flags described below are by default I<disabled>. 111strings. All boolean flags described below are by default I<disabled>.
119 112
120The mutators for flags all return the CBOR object again and thus calls can 113The mutators for flags all return the CBOR object again and thus calls can
121be chained: 114be chained:
122 115
123#TODO
124 my $cbor = CBOR::XS->new->encode ({a => [1,2]}); 116 my $cbor = CBOR::XS->new->encode ({a => [1,2]});
125 117
126=item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) 118=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
127 119
128=item $max_depth = $cbor->get_max_depth 120=item $max_depth = $cbor->get_max_depth
187as an array, is referenced multiple times), but instead will emit a 179as an array, is referenced multiple times), but instead will emit a
188reference to the earlier value. 180reference to the earlier value.
189 181
190This 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
191in 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
192sharing extension. 184sharing extension. This also makes it possible to encode cyclic data
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(http://cbor.schmorp.de/value-sharing). 190(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
191resulting data structure might be unusable.
197 192
198Detecting shared values incurs a runtime overhead when values are encoded 193Detecting shared values incurs a runtime overhead when values are encoded
199that have a reference counter large than one, and might unnecessarily 194that have a reference counter large than one, and might unnecessarily
200increase the encoded size, as potentially shared values are encode as 195increase the encoded size, as potentially shared values are encode as
201sharable whether or not they are actually shared. 196shareable whether or not they are actually shared.
202 197
203At 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,
204arrays or hashes pointed to by a reference). Weirder constructs, such as 199arrays or hashes pointed to by a reference). Weirder constructs, such as
205an 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
206not 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
207for L<Storable>). 202with L<Storable>).
208 203
209If C<$enable> is false (the default), then C<encode> will encode 204If C<$enable> is false (the default), then C<encode> will encode shared
210exception when it encounters anything it cannot encode as CBOR. 205data structures repeatedly, unsharing them in the process. Cyclic data
206structures cannot be encoded in this mode.
211 207
212This 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
213references will always be decoded properly if present. 209references will always be decoded properly if present.
214 210
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
215=item $cbor = $cbor->allow_stringref ([$enable]) 231=item $cbor = $cbor->pack_strings ([$enable])
216 232
217=item $enabled = $cbor->get_allow_stringref 233=item $enabled = $cbor->get_pack_strings
218 234
219If C<$enable> is true (or missing), then C<encode> will try not to encode 235If C<$enable> is true (or missing), then C<encode> will try not to encode
220the same string twice, but will instead encode a reference to the string 236the same string twice, but will instead encode a reference to the string
221instead. Depending on your data format. this can save a lot of space, but 237instead. Depending on your data format, this can save a lot of space, but
222also results in a very large runtime overhead (expect encoding times to be 238also results in a very large runtime overhead (expect encoding times to be
2232-4 times as high as without). 2392-4 times as high as without).
224 240
225It is recommended to leave it off unless you know your 241It is recommended to leave it off unless you know your
226communications partner supports the stringref extension to CBOR 242communications partner supports the stringref extension to CBOR
227(http://cbor.schmorp.de/stringref). 243(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
244resulting data structure might not be usable.
228 245
229If C<$enable> is false (the default), then C<encode> will encode 246If C<$enable> is false (the default), then C<encode> will encode strings
230exception when it encounters anything it cannot encode as CBOR. 247the standard CBOR way.
231 248
232This 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
233always be decoded properly if present. 250always be decoded properly if present.
251
252=item $cbor = $cbor->validate_utf8 ([$enable])
253
254=item $enabled = $cbor->get_validate_utf8
255
256If C<$enable> is true (or missing), then C<decode> will validate that
257elements (text strings) containing UTF-8 data in fact contain valid UTF-8
258data (instead of blindly accepting it). This validation obviously takes
259extra time during decoding.
260
261The concept of "valid UTF-8" used is perl's concept, which is a superset
262of the official UTF-8.
263
264If C<$enable> is false (the default), then C<decode> will blindly accept
265UTF-8 data, marking them as valid UTF-8 in the resulting data structure
266regardless of whether thats true or not.
267
268Perl isn't too happy about corrupted UTF-8 in strings, but should
269generally not crash or do similarly evil things. Extensions might be not
270so forgiving, so it's recommended to turn on this setting if you receive
271untrusted CBOR.
272
273This option does not affect C<encode> in any way - strings that are
274supposedly valid UTF-8 will simply be dumped into the resulting CBOR
275string without checking whether that is, in fact, true or not.
276
277=item $cbor = $cbor->filter ([$cb->($tag, $value)])
278
279=item $cb_or_undef = $cbor->get_filter
280
281Sets or replaces the tagged value decoding filter (when C<$cb> is
282specified) or clears the filter (if no argument or C<undef> is provided).
283
284The filter callback is called only during decoding, when a non-enforced
285tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a
286list of enforced tags). For specific tags, it's often better to provide a
287default converter using the C<%CBOR::XS::FILTER> hash (see below).
288
289The first argument is the numerical tag, the second is the (decoded) value
290that has been tagged.
291
292The filter function should return either exactly one value, which will
293replace the tagged value in the decoded data structure, or no values,
294which will result in default handling, which currently means the decoder
295creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
296
297When the filter is cleared (the default state), the default filter
298function, C<CBOR::XS::default_filter>, is used. This function simply looks
299up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be
300a code reference that is called with tag and value, and is responsible for
301decoding the value. If no entry exists, it returns no values.
302
303Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
304objects, with no other special handling (useful when working with
305potentially "unsafe" CBOR data).
306
307 CBOR::XS->new->filter (sub { })->decode ($cbor_data);
308
309Example: provide a global filter for tag 1347375694, converting the value
310into some string form.
311
312 $CBOR::XS::FILTER{1347375694} = sub {
313 my ($tag, $value);
314
315 "tag 1347375694 value $value"
316 };
234 317
235=item $cbor_data = $cbor->encode ($perl_scalar) 318=item $cbor_data = $cbor->encode ($perl_scalar)
236 319
237Converts the given Perl data structure (a scalar value) to its CBOR 320Converts the given Perl data structure (a scalar value) to its CBOR
238representation. 321representation.
252and you need to know where the first CBOR string ends amd the next one 335and you need to know where the first CBOR string ends amd the next one
253starts. 336starts.
254 337
255 CBOR::XS->new->decode_prefix ("......") 338 CBOR::XS->new->decode_prefix ("......")
256 => ("...", 3) 339 => ("...", 3)
340
341=back
342
343=head2 INCREMENTAL PARSING
344
345In some cases, there is the need for incremental parsing of JSON
346texts. While this module always has to keep both CBOR text and resulting
347Perl data structure in memory at one time, it does allow you to parse a
348CBOR stream incrementally, using a similar to using "decode_prefix" to see
349if a full CBOR object is available, but is much more efficient.
350
351It basically works by parsing as much of a CBOR string as possible - if
352the CBOR data is not complete yet, the pasrer will remember where it was,
353to be able to restart when more data has been accumulated. Once enough
354data is available to either decode a complete CBOR value or raise an
355error, a real decode will be attempted.
356
357A typical use case would be a network protocol that consists of sending
358and receiving CBOR-encoded messages. The solution that works with CBOR and
359about anything else is by prepending a length to every CBOR value, so the
360receiver knows how many octets to read. More compact (and slightly slower)
361would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
362a CBOR value ends, and doesn't need an explicit length.
363
364The following methods help with this:
365
366=over 4
367
368=item @decoded = $cbor->incr_parse ($buffer)
369
370This method attempts to decode exactly one CBOR value from the beginning
371of the given C<$buffer>. The value is removed from the C<$buffer> on
372success. When C<$buffer> doesn't contain a complete value yet, it returns
373nothing. Finally, when the C<$buffer> doesn't start with something
374that could ever be a valid CBOR value, it raises an exception, just as
375C<decode> would. In the latter case the decoder state is undefined and
376must be reset before being able to parse further.
377
378This method modifies the C<$buffer> in place. When no CBOR value can be
379decoded, the decoder stores the current string offset. On the next call,
380continues decoding at the place where it stopped before. For this to make
381sense, the C<$buffer> must begin with the same octets as on previous
382unsuccessful calls.
383
384You can call this method in scalar context, in which case it either
385returns a decoded value or C<undef>. This makes it impossible to
386distinguish between CBOR null values (which decode to C<undef>) and an
387unsuccessful decode, which is often acceptable.
388
389=item @decoded = $cbor->incr_parse_multiple ($buffer)
390
391Same as C<incr_parse>, but attempts to decode as many CBOR values as
392possible in one go, instead of at most one. Calls to C<incr_parse> and
393C<incr_parse_multiple> can be interleaved.
394
395=item $cbor->incr_reset
396
397Resets the incremental decoder. This throws away any saved state, so that
398subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
399a new CBOR value from the beginning of the C<$buffer> again.
400
401This method can be caled at any time, but it I<must> be called if you want
402to change your C<$buffer> or there was a decoding error and you want to
403reuse the C<$cbor> object for future incremental parsings.
257 404
258=back 405=back
259 406
260 407
261=head1 MAPPING 408=head1 MAPPING
279CBOR integers become (numeric) perl scalars. On perls without 64 bit 426CBOR integers become (numeric) perl scalars. On perls without 64 bit
280support, 64 bit integers will be truncated or otherwise corrupted. 427support, 64 bit integers will be truncated or otherwise corrupted.
281 428
282=item byte strings 429=item byte strings
283 430
284Byte strings will become octet strings in Perl (the byte values 0..255 431Byte strings will become octet strings in Perl (the Byte values 0..255
285will simply become characters of the same value in Perl). 432will simply become characters of the same value in Perl).
286 433
287=item UTF-8 strings 434=item UTF-8 strings
288 435
289UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be 436UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
307C<Types:Serialiser::false> and C<Types::Serialiser::error>, 454C<Types:Serialiser::false> and C<Types::Serialiser::error>,
308respectively. They are overloaded to act almost exactly like the numbers 455respectively. They are overloaded to act almost exactly like the numbers
309C<1> and C<0> (for true and false) or to throw an exception on access (for 456C<1> and C<0> (for true and false) or to throw an exception on access (for
310error). See the L<Types::Serialiser> manpage for details. 457error). See the L<Types::Serialiser> manpage for details.
311 458
312=item CBOR tag 256 (perl object) 459=item tagged values
313 460
314The tag value C<256> (TODO: pending iana registration) will be used
315to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
316SERIALISATION>, below, for details.
317
318=item CBOR tag 55799 (magic header)
319
320The tag 55799 is ignored (this tag implements the magic header).
321
322=item other CBOR tags
323
324Tagged items consists of a numeric tag and another CBOR value. Tags not 461Tagged items consists of a numeric tag and another CBOR value.
325handled internally are currently converted into a L<CBOR::XS::Tagged>
326object, which is simply a blessed array reference consisting of the
327numeric tag value followed by the (decoded) CBOR value.
328 462
329In the future, support for user-supplied conversions might get added. 463See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
464for details on which tags are handled how.
330 465
331=item anything else 466=item anything else
332 467
333Anything else (e.g. unsupported simple values) will raise a decoding 468Anything else (e.g. unsupported simple values) will raise a decoding
334error. 469error.
337 472
338 473
339=head2 PERL -> CBOR 474=head2 PERL -> CBOR
340 475
341The mapping from Perl to CBOR is slightly more difficult, as Perl is a 476The mapping from Perl to CBOR is slightly more difficult, as Perl is a
342truly typeless language, so we can only guess which CBOR type is meant by 477typeless language. That means this module can only guess which CBOR type
343a Perl value. 478is meant by a perl value.
344 479
345=over 4 480=over 4
346 481
347=item hash references 482=item hash references
348 483
349Perl hash references become CBOR maps. As there is no inherent ordering in 484Perl hash references become CBOR maps. As there is no inherent ordering in
350hash keys (or CBOR maps), they will usually be encoded in a pseudo-random 485hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
351order. 486order. This order can be different each time a hash is encoded.
352 487
353Currently, tied hashes will use the indefinite-length format, while normal 488Currently, tied hashes will use the indefinite-length format, while normal
354hashes will use the fixed-length format. 489hashes will use the fixed-length format.
355 490
356=item array references 491=item array references
357 492
358Perl array references become fixed-length CBOR arrays. 493Perl array references become fixed-length CBOR arrays.
359 494
360=item other references 495=item other references
361 496
362Other unblessed references are generally not allowed and will cause an 497Other unblessed references will be represented using
363exception to be thrown, except for references to the integers C<0> and 498the indirection tag extension (tag value C<22098>,
364C<1>, which get turned into false and true in CBOR. 499L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
500to be able to decode these values somehow, by either "doing the right
501thing", decoding into a generic tagged object, simply ignoring the tag, or
502something else.
365 503
366=item CBOR::XS::Tagged objects 504=item CBOR::XS::Tagged objects
367 505
368Objects of this type must be arrays consisting of a single C<[tag, value]> 506Objects of this type must be arrays consisting of a single C<[tag, value]>
369pair. The (numerical) tag will be encoded as a CBOR tag, the value will 507pair. The (numerical) tag will be encoded as a CBOR tag, the value will
370be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to 508be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
371create such objects. 509create such objects.
372 510
373=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error 511=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
374 512
375These special values become CBOR true, CBOR false and CBOR undefined 513These special values become CBOR true, CBOR false and CBOR undefined
377if you want. 515if you want.
378 516
379=item other blessed objects 517=item other blessed objects
380 518
381Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See 519Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See
382L<OBJECT SERIALISATION>, below, for details. 520L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this
521module, and L<OBJECT SERIALISATION> for generic object serialisation.
383 522
384=item simple scalars 523=item simple scalars
385 524
386TODO
387Simple Perl scalars (any scalar that is not a reference) are the most 525Simple Perl scalars (any scalar that is not a reference) are the most
388difficult objects to encode: CBOR::XS will encode undefined scalars as 526difficult objects to encode: CBOR::XS will encode undefined scalars as
389CBOR null values, scalars that have last been used in a string context 527CBOR null values, scalars that have last been used in a string context
390before encoding as CBOR strings, and anything else as number value: 528before encoding as CBOR strings, and anything else as number value:
391 529
392 # dump as number 530 # dump as number
393 encode_cbor [2] # yields [2] 531 encode_cbor [2] # yields [2]
394 encode_cbor [-3.0e17] # yields [-3e+17] 532 encode_cbor [-3.0e17] # yields [-3e+17]
395 my $value = 5; encode_cbor [$value] # yields [5] 533 my $value = 5; encode_cbor [$value] # yields [5]
396 534
397 # used as string, so dump as string 535 # used as string, so dump as string (either byte or text)
398 print $value; 536 print $value;
399 encode_cbor [$value] # yields ["5"] 537 encode_cbor [$value] # yields ["5"]
400 538
401 # undef becomes null 539 # undef becomes null
402 encode_cbor [undef] # yields [null] 540 encode_cbor [undef] # yields [null]
405 543
406 my $x = 3.1; # some variable containing a number 544 my $x = 3.1; # some variable containing a number
407 "$x"; # stringified 545 "$x"; # stringified
408 $x .= ""; # another, more awkward way to stringify 546 $x .= ""; # another, more awkward way to stringify
409 print $x; # perl does it for you, too, quite often 547 print $x; # perl does it for you, too, quite often
548
549You can force whether a string ie encoded as byte or text string by using
550C<utf8::upgrade> and C<utf8::downgrade>):
551
552 utf8::upgrade $x; # encode $x as text string
553 utf8::downgrade $x; # encode $x as byte string
554
555Perl doesn't define what operations up- and downgrade strings, so if the
556difference between byte and text is important, you should up- or downgrade
557your string as late as possible before encoding.
410 558
411You can force the type to be a CBOR number by numifying it: 559You can force the type to be a CBOR number by numifying it:
412 560
413 my $x = "3"; # some variable containing a string 561 my $x = "3"; # some variable containing a string
414 $x += 0; # numify it, ensuring it will be dumped as a number 562 $x += 0; # numify it, ensuring it will be dumped as a number
427 575
428=back 576=back
429 577
430=head2 OBJECT SERIALISATION 578=head2 OBJECT SERIALISATION
431 579
580This module implements both a CBOR-specific and the generic
581L<Types::Serialier> object serialisation protocol. The following
582subsections explain both methods.
583
584=head3 ENCODING
585
432This module knows two way to serialise a Perl object: The CBOR-specific 586This module knows two way to serialise a Perl object: The CBOR-specific
433way, and the generic way. 587way, and the generic way.
434 588
435Whenever the encoder encounters a Perl object that it cnanot serialise 589Whenever the encoder encounters a Perl object that it cannot serialise
436directly (most of them), it will first look up the C<TO_CBOR> method on 590directly (most of them), it will first look up the C<TO_CBOR> method on
437it. 591it.
438 592
439If it has a C<TO_CBOR> method, it will call it with the object as only 593If it has a C<TO_CBOR> method, it will call it with the object as only
440argument, and expects exactly one return value, which it will then 594argument, and expects exactly one return value, which it will then
446 600
447The C<FREEZE> method can return any number of values (i.e. zero or 601The C<FREEZE> method can return any number of values (i.e. zero or
448more). These will be encoded as CBOR perl object, together with the 602more). These will be encoded as CBOR perl object, together with the
449classname. 603classname.
450 604
605These methods I<MUST NOT> change the data structure that is being
606serialised. Failure to comply to this can result in memory corruption -
607and worse.
608
451If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail 609If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
452with an error. 610with an error.
453 611
612=head3 DECODING
613
454Objects encoded via C<TO_CBOR> cannot be automatically decoded, but 614Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
455objects encoded via C<FREEZE> can be decoded using the following protocol: 615but objects encoded via C<FREEZE> can be decoded using the following
616protocol:
456 617
457When an encoded CBOR perl object is encountered by the decoder, it will 618When an encoded CBOR perl object is encountered by the decoder, it will
458look up the C<THAW> method, by using the stored classname, and will fail 619look up the C<THAW> method, by using the stored classname, and will fail
459if the method cannot be found. 620if the method cannot be found.
460 621
461After the lookup it will call the C<THAW> method with the stored classname 622After the lookup it will call the C<THAW> method with the stored classname
462as first argument, the constant string C<CBOR> as second argument, and all 623as first argument, the constant string C<CBOR> as second argument, and all
463values returned by C<FREEZE> as remaining arguments. 624values returned by C<FREEZE> as remaining arguments.
464 625
465=head4 EXAMPLES 626=head3 EXAMPLES
466 627
467Here is an example C<TO_CBOR> method: 628Here is an example C<TO_CBOR> method:
468 629
469 sub My::Object::TO_CBOR { 630 sub My::Object::TO_CBOR {
470 my ($obj) = @_; 631 my ($obj) = @_;
481 642
482 sub URI::TO_CBOR { 643 sub URI::TO_CBOR {
483 my ($self) = @_; 644 my ($self) = @_;
484 my $uri = "$self"; # stringify uri 645 my $uri = "$self"; # stringify uri
485 utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string 646 utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
486 CBOR::XS::tagged 32, "$_[0]" 647 CBOR::XS::tag 32, "$_[0]"
487 } 648 }
488 649
489This will encode URIs as a UTF-8 string with tag 32, which indicates an 650This will encode URIs as a UTF-8 string with tag 32, which indicates an
490URI. 651URI.
491 652
633and extensions. If a tag is not mentioned here and no additional filters 794and extensions. If a tag is not mentioned here and no additional filters
634are provided for it, then the default handling applies (creating a 795are provided for it, then the default handling applies (creating a
635CBOR::XS::Tagged object on decoding, and only encoding the tag when 796CBOR::XS::Tagged object on decoding, and only encoding the tag when
636explicitly requested). 797explicitly requested).
637 798
799Tags not handled specifically are currently converted into a
800L<CBOR::XS::Tagged> object, which is simply a blessed array reference
801consisting of the numeric tag value followed by the (decoded) CBOR value.
802
638Future versions of this module reserve the right to special case 803Future versions of this module reserve the right to special case
639additional tags (such as base64url). 804additional tags (such as base64url).
640 805
641=head2 ENFORCED TAGS 806=head2 ENFORCED TAGS
642 807
643These tags are always handled when decoding, and their handling cannot be 808These tags are always handled when decoding, and their handling cannot be
644overriden by the user. 809overriden by the user.
645 810
646=over 4 811=over 4
647 812
648=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>) 813=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
649 814
650These tags are automatically created for serialisable objects using the 815These tags are automatically created (and decoded) for serialisable
651C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation 816objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
652protocol). 817serialisation protocol). See L<OBJECT SERIALISATION> for details.
653 818
654=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) 819=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
655 820
656These tags are automatically decoded when encountered, resulting in 821These tags are automatically decoded when encountered (and they do not
822result in a cyclic data structure, see C<allow_cycles>), resulting in
657shared values in the decoded object. They are only encoded, however, when 823shared values in the decoded object. They are only encoded, however, when
658C<allow_sharable> is enabled. 824C<allow_sharing> is enabled.
659 825
826Not all shared values can be successfully decoded: values that reference
827themselves will I<currently> decode as C<undef> (this is not the same
828as a reference pointing to itself, which will be represented as a value
829that contains an indirect reference to itself - these will be decoded
830properly).
831
832Note that considerably more shared value data structures can be decoded
833than will be encoded - currently, only values pointed to by references
834will be shared, others will not. While non-reference shared values can be
835generated in Perl with some effort, they were considered too unimportant
836to be supported in the encoder. The decoder, however, will decode these
837values as shared values.
838
660=item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) 839=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
661 840
662These tags are automatically decoded when encountered. They are only 841These tags are automatically decoded when encountered. They are only
663encoded, however, when C<allow_stringref> is enabled. 842encoded, however, when C<pack_strings> is enabled.
664 843
665=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) 844=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
666 845
667This tag is automatically generated when a reference are encountered (with 846This tag is automatically generated when a reference are encountered (with
668the exception of hash and array refernces). It is converted to a reference 847the exception of hash and array refernces). It is converted to a reference
673This value is not generated on encoding (unless explicitly requested by 852This value is not generated on encoding (unless explicitly requested by
674the user), and is simply ignored when decoding. 853the user), and is simply ignored when decoding.
675 854
676=back 855=back
677 856
678=head2 OPTIONAL TAGS 857=head2 NON-ENFORCED TAGS
679 858
680These tags have default filters provided when decoding. Their handling can 859These tags have default filters provided when decoding. Their handling can
681be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by 860be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
682providing a custom C<filter> function when decoding. 861providing a custom C<filter> callback when decoding.
683 862
684When they result in decoding into a specific Perl class, the module 863When they result in decoding into a specific Perl class, the module
685usually provides a corresponding C<TO_CBOR> method as well. 864usually provides a corresponding C<TO_CBOR> method as well.
686 865
687When any of these need to load additional modules that are not part of the 866When any of these need to load additional modules that are not part of the
688perl core distribution (e.g. L<URI>), it is (currently) up to the user to 867perl core distribution (e.g. L<URI>), it is (currently) up to the user to
689provide these modules. The decoding usually fails with an exception if the 868provide these modules. The decoding usually fails with an exception if the
690required module cannot be loaded. 869required module cannot be loaded.
691 870
692=over 4 871=over 4
872
873=item 0, 1 (date/time string, seconds since the epoch)
874
875These tags are decoded into L<Time::Piece> objects. The corresponding
876C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
877
878The L<Time::Piece> API is generally surprisingly bad, and fractional
879seconds are only accidentally kept intact, so watch out. On the plus side,
880the module comes with perl since 5.10, which has to count for something.
693 881
694=item 2, 3 (positive/negative bignum) 882=item 2, 3 (positive/negative bignum)
695 883
696These tags are decoded into L<Math::BigInt> objects. The corresponding 884These tags are decoded into L<Math::BigInt> objects. The corresponding
697C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR 885C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
831properly. Half precision types are accepted, but not encoded. 1019properly. Half precision types are accepted, but not encoded.
832 1020
833Strict mode and canonical mode are not implemented. 1021Strict mode and canonical mode are not implemented.
834 1022
835 1023
1024=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
1025
1026On perls that were built without 64 bit integer support (these are rare
1027nowadays, even on 32 bit architectures, as all major Perl distributions
1028are built with 64 bit integer support), support for any kind of 64 bit
1029integer in CBOR is very limited - most likely, these 64 bit values will
1030be truncated, corrupted, or otherwise not decoded correctly. This also
1031includes string, array and map sizes that are stored as 64 bit integers.
1032
1033
836=head1 THREADS 1034=head1 THREADS
837 1035
838This module is I<not> guaranteed to be thread safe and there are no 1036This module is I<not> guaranteed to be thread safe and there are no
839plans to change this until Perl gets thread support (as opposed to the 1037plans to change this until Perl gets thread support (as opposed to the
840horribly slow so-called "threads" which are simply slow and bloated 1038horribly slow so-called "threads" which are simply slow and bloated
853service. I put the contact address into my modules for a reason. 1051service. I put the contact address into my modules for a reason.
854 1052
855=cut 1053=cut
856 1054
857our %FILTER = ( 1055our %FILTER = (
858 # 0 # rfc4287 datetime, utf-8 1056 0 => sub { # rfc4287 datetime, utf-8
859 # 1 # unix timestamp, any 1057 require Time::Piece;
1058 # Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
1059 # from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
1060 # else either. Whats incredibe over standard strptime totally escapes me.
1061 # doesn't do fractional times, either. sigh.
1062 # In fact, it's all a lie, it uses whatever strptime it wants, and of course,
1063 # they are all incompatible. The openbsd one simply ignores %z (but according to the
1064 # docs, it would be much more incredibly flexible indeed. If it worked, that is.).
1065 scalar eval {
1066 my $s = $_[1];
1067
1068 $s =~ s/Z$/+00:00/;
1069 $s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
1070 or die;
1071
1072 my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
1073 my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
1074
1075 Time::Piece::gmtime ($d->epoch + $b)
1076 } || die "corrupted CBOR date/time string ($_[0])";
1077 },
1078
1079 1 => sub { # seconds since the epoch, possibly fractional
1080 require Time::Piece;
1081 scalar Time::Piece::gmtime (pop)
1082 },
860 1083
861 2 => sub { # pos bigint 1084 2 => sub { # pos bigint
862 require Math::BigInt; 1085 require Math::BigInt;
863 Math::BigInt->new ("0x" . unpack "H*", pop) 1086 Math::BigInt->new ("0x" . unpack "H*", pop)
864 }, 1087 },
900} 1123}
901 1124
902sub URI::TO_CBOR { 1125sub URI::TO_CBOR {
903 my $uri = $_[0]->as_string; 1126 my $uri = $_[0]->as_string;
904 utf8::upgrade $uri; 1127 utf8::upgrade $uri;
905 CBOR::XS::tag 32, $uri 1128 tag 32, $uri
906} 1129}
907 1130
908sub Math::BigInt::TO_CBOR { 1131sub Math::BigInt::TO_CBOR {
909 if ($_[0] >= -2147483648 && $_[0] <= 2147483647) { 1132 if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {
910 $_[0]->numify 1133 $_[0]->numify
911 } else { 1134 } else {
912 my $hex = substr $_[0]->as_hex, 2; 1135 my $hex = substr $_[0]->as_hex, 2;
913 $hex = "0$hex" if 1 & length $hex; # sigh 1136 $hex = "0$hex" if 1 & length $hex; # sigh
914 CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex 1137 tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
915 } 1138 }
916} 1139}
917 1140
918sub Math::BigFloat::TO_CBOR { 1141sub Math::BigFloat::TO_CBOR {
919 my ($m, $e) = $_[0]->parts; 1142 my ($m, $e) = $_[0]->parts;
920 CBOR::XS::tag 4, [$e->numify, $m] 1143 tag 4, [$e->numify, $m]
1144}
1145
1146sub Time::Piece::TO_CBOR {
1147 tag 1, 0 + $_[0]->epoch
921} 1148}
922 1149
923XSLoader::load "CBOR::XS", $VERSION; 1150XSLoader::load "CBOR::XS", $VERSION;
924 1151
925=head1 SEE ALSO 1152=head1 SEE ALSO

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