… | |
… | |
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 | |
31 | WARNING! This module is very new, and not very well tested (that's up |
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32 | to you to do). Furthermore, details of the implementation might change |
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|
33 | freely before version 1.0. And lastly, most extensions depend on an IANA |
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34 | assignment, and until that assignment is official, this implementation is |
|
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35 | not interoperable with other implementations (even future versions of this |
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36 | module) until the assignment is done. |
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37 | |
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38 | You are still invited to try out CBOR, and this module. |
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39 | |
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40 | This module converts Perl data structures to the Concise Binary Object |
31 | This module converts Perl data structures to the Concise Binary Object |
41 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
32 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
42 | format that aims to use a superset of the JSON data model, i.e. when you |
33 | format that aims to use an (almost) superset of the JSON data model, i.e. |
43 | can represent something in JSON, you should be able to represent it in |
34 | when you can represent something useful in JSON, you should be able to |
44 | CBOR. |
35 | represent it in CBOR. |
45 | |
36 | |
46 | In short, CBOR is a faster and very compact binary alternative to JSON, |
37 | In short, CBOR is a faster and quite compact binary alternative to JSON, |
47 | with the added ability of supporting serialisation of Perl objects. (JSON |
38 | with the added ability of supporting serialisation of Perl objects. (JSON |
48 | often compresses better than CBOR though, so if you plan to compress the |
39 | often compresses better than CBOR though, so if you plan to compress the |
49 | data later you might want to compare both formats first). |
40 | data later and speed is less important you might want to compare both |
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41 | formats first). |
50 | |
42 | |
51 | To give you a general idea about speed, with texts in the megabyte range, |
43 | To give you a general idea about speed, with texts in the megabyte range, |
52 | C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or |
44 | C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or |
53 | L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the |
45 | L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the |
54 | data, the worse L<Storable> performs in comparison. |
46 | data, the worse L<Storable> performs in comparison. |
55 | |
47 | |
56 | As for compactness, C<CBOR::XS> encoded data structures are usually about |
48 | Regarding compactness, C<CBOR::XS>-encoded data structures are usually |
57 | 20% smaller than the same data encoded as (compact) JSON or L<Storable>. |
49 | about 20% smaller than the same data encoded as (compact) JSON or |
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50 | L<Storable>. |
58 | |
51 | |
59 | In addition to the core CBOR data format, this module implements a number |
52 | In addition to the core CBOR data format, this module implements a |
60 | of extensions, to support cyclic and self-referencing data structures |
53 | number 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 |
62 | scalar references (always enabled). |
55 | C<pack_strings>) and scalar references (always enabled). |
63 | |
56 | |
64 | The primary goal of this module is to be I<correct> and the secondary goal |
57 | The primary goal of this module is to be I<correct> and the secondary goal |
65 | is to be I<fast>. To reach the latter goal it was written in C. |
58 | is to be I<fast>. To reach the latter goal it was written in C. |
66 | |
59 | |
67 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
60 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
… | |
… | |
71 | |
64 | |
72 | package CBOR::XS; |
65 | package CBOR::XS; |
73 | |
66 | |
74 | use common::sense; |
67 | use common::sense; |
75 | |
68 | |
76 | our $VERSION = 0.09; |
69 | our $VERSION = 1.1; |
77 | our @ISA = qw(Exporter); |
70 | our @ISA = qw(Exporter); |
78 | |
71 | |
79 | our @EXPORT = qw(encode_cbor decode_cbor); |
72 | our @EXPORT = qw(encode_cbor decode_cbor); |
80 | |
73 | |
81 | use Exporter; |
74 | use Exporter; |
… | |
… | |
187 | reference to the earlier value. |
180 | reference to the earlier value. |
188 | |
181 | |
189 | This means that such values will only be encoded once, and will not result |
182 | This means that such values will only be encoded once, and will not result |
190 | in a deep cloning of the value on decode, in decoders supporting the value |
183 | in a deep cloning of the value on decode, in decoders supporting the value |
191 | sharing extension. This also makes it possible to encode cyclic data |
184 | sharing extension. This also makes it possible to encode cyclic data |
192 | structures. |
185 | structures (which need C<allow_cycles> to ne enabled to be decoded by this |
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186 | module). |
193 | |
187 | |
194 | It is recommended to leave it off unless you know your |
188 | It is recommended to leave it off unless you know your |
195 | communication partner supports the value sharing extensions to CBOR |
189 | communication 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 |
197 | resulting data structure might be unusable. |
191 | resulting data structure might be unusable. |
198 | |
192 | |
199 | Detecting shared values incurs a runtime overhead when values are encoded |
193 | Detecting shared values incurs a runtime overhead when values are encoded |
200 | that have a reference counter large than one, and might unnecessarily |
194 | that have a reference counter large than one, and might unnecessarily |
201 | increase the encoded size, as potentially shared values are encode as |
195 | increase the encoded size, as potentially shared values are encode as |
202 | sharable whether or not they are actually shared. |
196 | shareable whether or not they are actually shared. |
203 | |
197 | |
204 | At the moment, only targets of references can be shared (e.g. scalars, |
198 | At the moment, only targets of references can be shared (e.g. scalars, |
205 | arrays or hashes pointed to by a reference). Weirder constructs, such as |
199 | arrays or hashes pointed to by a reference). Weirder constructs, such as |
206 | an array with multiple "copies" of the I<same> string, which are hard but |
200 | an array with multiple "copies" of the I<same> string, which are hard but |
207 | not impossible to create in Perl, are not supported (this is the same as |
201 | not impossible to create in Perl, are not supported (this is the same as |
… | |
… | |
212 | structures cannot be encoded in this mode. |
206 | structures cannot be encoded in this mode. |
213 | |
207 | |
214 | This option does not affect C<decode> in any way - shared values and |
208 | This option does not affect C<decode> in any way - shared values and |
215 | references will always be decoded properly if present. |
209 | references will always be decoded properly if present. |
216 | |
210 | |
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211 | =item $cbor = $cbor->allow_cycles ([$enable]) |
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212 | |
|
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213 | =item $enabled = $cbor->get_allow_cycles |
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214 | |
|
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215 | If C<$enable> is true (or missing), then C<decode> will happily decode |
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216 | self-referential (cyclic) data structures. By default these will not be |
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217 | decoded, as they need manual cleanup to avoid memory leaks, so code that |
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218 | isn't prepared for this will not leak memory. |
|
|
219 | |
|
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220 | If C<$enable> is false (the default), then C<decode> will throw an error |
|
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221 | when it encounters a self-referential/cyclic data structure. |
|
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222 | |
|
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223 | This option does not affect C<encode> in any way - shared values and |
|
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224 | references will always be decoded properly if present. |
|
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225 | |
217 | =item $cbor = $cbor->pack_strings ([$enable]) |
226 | =item $cbor = $cbor->pack_strings ([$enable]) |
218 | |
227 | |
219 | =item $enabled = $cbor->get_pack_strings |
228 | =item $enabled = $cbor->get_pack_strings |
220 | |
229 | |
221 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
230 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
… | |
… | |
259 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
268 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
260 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
269 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
261 | a code reference that is called with tag and value, and is responsible for |
270 | a code reference that is called with tag and value, and is responsible for |
262 | decoding the value. If no entry exists, it returns no values. |
271 | decoding the value. If no entry exists, it returns no values. |
263 | |
272 | |
264 | Example: decode all tags not handled internally into CBOR::XS::Tagged |
273 | Example: decode all tags not handled internally into C<CBOR::XS::Tagged> |
265 | objects, with no other special handling (useful when working with |
274 | objects, with no other special handling (useful when working with |
266 | potentially "unsafe" CBOR data). |
275 | potentially "unsafe" CBOR data). |
267 | |
276 | |
268 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
277 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
269 | |
278 | |
… | |
… | |
356 | =item tagged values |
365 | =item tagged values |
357 | |
366 | |
358 | Tagged items consists of a numeric tag and another CBOR value. |
367 | Tagged items consists of a numeric tag and another CBOR value. |
359 | |
368 | |
360 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
369 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
361 | for details. |
370 | for details on which tags are handled how. |
362 | |
371 | |
363 | =item anything else |
372 | =item anything else |
364 | |
373 | |
365 | Anything else (e.g. unsupported simple values) will raise a decoding |
374 | Anything else (e.g. unsupported simple values) will raise a decoding |
366 | error. |
375 | error. |
… | |
… | |
369 | |
378 | |
370 | |
379 | |
371 | =head2 PERL -> CBOR |
380 | =head2 PERL -> CBOR |
372 | |
381 | |
373 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
382 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
374 | truly typeless language, so we can only guess which CBOR type is meant by |
383 | typeless language. That means this module can only guess which CBOR type |
375 | a Perl value. |
384 | is meant by a perl value. |
376 | |
385 | |
377 | =over 4 |
386 | =over 4 |
378 | |
387 | |
379 | =item hash references |
388 | =item hash references |
380 | |
389 | |
381 | Perl hash references become CBOR maps. As there is no inherent ordering in |
390 | Perl hash references become CBOR maps. As there is no inherent ordering in |
382 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
391 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
383 | order. |
392 | order. This order can be different each time a hahs is encoded. |
384 | |
393 | |
385 | Currently, tied hashes will use the indefinite-length format, while normal |
394 | Currently, tied hashes will use the indefinite-length format, while normal |
386 | hashes will use the fixed-length format. |
395 | hashes will use the fixed-length format. |
387 | |
396 | |
388 | =item array references |
397 | =item array references |
389 | |
398 | |
390 | Perl array references become fixed-length CBOR arrays. |
399 | Perl array references become fixed-length CBOR arrays. |
391 | |
400 | |
392 | =item other references |
401 | =item other references |
393 | |
402 | |
394 | Other unblessed references are generally not allowed and will cause an |
403 | Other unblessed references will be represented using |
395 | exception to be thrown, except for references to the integers C<0> and |
404 | the indirection tag extension (tag value C<22098>, |
396 | C<1>, which get turned into false and true in CBOR. |
405 | L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
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|
406 | to be able to decode these values somehow, by either "doing the right |
|
|
407 | thing", decoding into a generic tagged object, simply ignoring the tag, or |
|
|
408 | something else. |
397 | |
409 | |
398 | =item CBOR::XS::Tagged objects |
410 | =item CBOR::XS::Tagged objects |
399 | |
411 | |
400 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
412 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
401 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
413 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
402 | be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to |
414 | be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to |
403 | create such objects. |
415 | create such objects. |
404 | |
416 | |
405 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
417 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
406 | |
418 | |
407 | These special values become CBOR true, CBOR false and CBOR undefined |
419 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
… | |
469 | |
481 | |
470 | =back |
482 | =back |
471 | |
483 | |
472 | =head2 OBJECT SERIALISATION |
484 | =head2 OBJECT SERIALISATION |
473 | |
485 | |
|
|
486 | This module implements both a CBOR-specific and the generic |
|
|
487 | L<Types::Serialier> object serialisation protocol. The following |
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488 | subsections explain both methods. |
|
|
489 | |
|
|
490 | =head3 ENCODING |
|
|
491 | |
474 | This module knows two way to serialise a Perl object: The CBOR-specific |
492 | This module knows two way to serialise a Perl object: The CBOR-specific |
475 | way, and the generic way. |
493 | way, and the generic way. |
476 | |
494 | |
477 | Whenever the encoder encounters a Perl object that it cnanot serialise |
495 | Whenever the encoder encounters a Perl object that it cannot serialise |
478 | directly (most of them), it will first look up the C<TO_CBOR> method on |
496 | directly (most of them), it will first look up the C<TO_CBOR> method on |
479 | it. |
497 | it. |
480 | |
498 | |
481 | If it has a C<TO_CBOR> method, it will call it with the object as only |
499 | If it has a C<TO_CBOR> method, it will call it with the object as only |
482 | argument, and expects exactly one return value, which it will then |
500 | argument, and expects exactly one return value, which it will then |
… | |
… | |
488 | |
506 | |
489 | The C<FREEZE> method can return any number of values (i.e. zero or |
507 | The C<FREEZE> method can return any number of values (i.e. zero or |
490 | more). These will be encoded as CBOR perl object, together with the |
508 | more). These will be encoded as CBOR perl object, together with the |
491 | classname. |
509 | classname. |
492 | |
510 | |
|
|
511 | These methods I<MUST NOT> change the data structure that is being |
|
|
512 | serialised. Failure to comply to this can result in memory corruption - |
|
|
513 | and worse. |
|
|
514 | |
493 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
515 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
494 | with an error. |
516 | with an error. |
495 | |
517 | |
|
|
518 | =head3 DECODING |
|
|
519 | |
496 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
520 | Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded, |
497 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
521 | but objects encoded via C<FREEZE> can be decoded using the following |
|
|
522 | protocol: |
498 | |
523 | |
499 | When an encoded CBOR perl object is encountered by the decoder, it will |
524 | When an encoded CBOR perl object is encountered by the decoder, it will |
500 | look up the C<THAW> method, by using the stored classname, and will fail |
525 | look up the C<THAW> method, by using the stored classname, and will fail |
501 | if the method cannot be found. |
526 | if the method cannot be found. |
502 | |
527 | |
503 | After the lookup it will call the C<THAW> method with the stored classname |
528 | After the lookup it will call the C<THAW> method with the stored classname |
504 | as first argument, the constant string C<CBOR> as second argument, and all |
529 | as first argument, the constant string C<CBOR> as second argument, and all |
505 | values returned by C<FREEZE> as remaining arguments. |
530 | values returned by C<FREEZE> as remaining arguments. |
506 | |
531 | |
507 | =head4 EXAMPLES |
532 | =head3 EXAMPLES |
508 | |
533 | |
509 | Here is an example C<TO_CBOR> method: |
534 | Here is an example C<TO_CBOR> method: |
510 | |
535 | |
511 | sub My::Object::TO_CBOR { |
536 | sub My::Object::TO_CBOR { |
512 | my ($obj) = @_; |
537 | my ($obj) = @_; |
… | |
… | |
523 | |
548 | |
524 | sub URI::TO_CBOR { |
549 | sub URI::TO_CBOR { |
525 | my ($self) = @_; |
550 | my ($self) = @_; |
526 | my $uri = "$self"; # stringify uri |
551 | my $uri = "$self"; # stringify uri |
527 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
552 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
528 | CBOR::XS::tagged 32, "$_[0]" |
553 | CBOR::XS::tag 32, "$_[0]" |
529 | } |
554 | } |
530 | |
555 | |
531 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
556 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
532 | URI. |
557 | URI. |
533 | |
558 | |
… | |
… | |
695 | |
720 | |
696 | These tags are automatically created (and decoded) for serialisable |
721 | These tags are automatically created (and decoded) for serialisable |
697 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
722 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
698 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
723 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
699 | |
724 | |
700 | =item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
725 | =item 28, 29 (shareable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
701 | |
726 | |
702 | These tags are automatically decoded when encountered, resulting in |
727 | These tags are automatically decoded when encountered (and they do not |
|
|
728 | result in a cyclic data structure, see C<allow_cycles>), resulting in |
703 | shared values in the decoded object. They are only encoded, however, when |
729 | shared values in the decoded object. They are only encoded, however, when |
704 | C<allow_sharable> is enabled. |
730 | C<allow_sharing> is enabled. |
|
|
731 | |
|
|
732 | Not all shared values can be successfully decoded: values that reference |
|
|
733 | themselves will I<currently> decode as C<undef> (this is not the same |
|
|
734 | as a reference pointing to itself, which will be represented as a value |
|
|
735 | that contains an indirect reference to itself - these will be decoded |
|
|
736 | properly). |
|
|
737 | |
|
|
738 | Note that considerably more shared value data structures can be decoded |
|
|
739 | than will be encoded - currently, only values pointed to by references |
|
|
740 | will be shared, others will not. While non-reference shared values can be |
|
|
741 | generated in Perl with some effort, they were considered too unimportant |
|
|
742 | to be supported in the encoder. The decoder, however, will decode these |
|
|
743 | values as shared values. |
705 | |
744 | |
706 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
745 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
707 | |
746 | |
708 | These tags are automatically decoded when encountered. They are only |
747 | These tags are automatically decoded when encountered. They are only |
709 | encoded, however, when C<pack_strings> is enabled. |
748 | encoded, however, when C<pack_strings> is enabled. |
… | |
… | |
875 | Only the double data type is supported for NV data types - when Perl uses |
914 | Only the double data type is supported for NV data types - when Perl uses |
876 | long double to represent floating point values, they might not be encoded |
915 | long double to represent floating point values, they might not be encoded |
877 | properly. Half precision types are accepted, but not encoded. |
916 | properly. Half precision types are accepted, but not encoded. |
878 | |
917 | |
879 | Strict mode and canonical mode are not implemented. |
918 | Strict mode and canonical mode are not implemented. |
|
|
919 | |
|
|
920 | |
|
|
921 | =head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
922 | |
|
|
923 | On perls that were built without 64 bit integer support (these are rare |
|
|
924 | nowadays, even on 32 bit architectures), support for any kind of 64 bit |
|
|
925 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
926 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
927 | includes string, array and map sizes that are stored as 64 bit integers. |
880 | |
928 | |
881 | |
929 | |
882 | =head1 THREADS |
930 | =head1 THREADS |
883 | |
931 | |
884 | This module is I<not> guaranteed to be thread safe and there are no |
932 | This module is I<not> guaranteed to be thread safe and there are no |