… | |
… | |
48 | Regarding compactness, C<CBOR::XS>-encoded data structures are usually |
48 | Regarding compactness, C<CBOR::XS>-encoded data structures are usually |
49 | about 20% smaller than the same data encoded as (compact) JSON or |
49 | about 20% smaller than the same data encoded as (compact) JSON or |
50 | L<Storable>. |
50 | L<Storable>. |
51 | |
51 | |
52 | In addition to the core CBOR data format, this module implements a |
52 | In addition to the core CBOR data format, this module implements a |
53 | number of extensions, to support cyclic and shared data structures (see |
53 | number of extensions, to support cyclic and shared data structures |
54 | C<allow_sharing>), string deduplication (see C<pack_strings>) and scalar |
54 | (see C<allow_sharing> and C<allow_cycles>), string deduplication (see |
55 | references (always enabled). |
55 | C<pack_strings>) and scalar references (always enabled). |
56 | |
56 | |
57 | 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 |
58 | 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. |
59 | |
59 | |
60 | 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 |
… | |
… | |
64 | |
64 | |
65 | package CBOR::XS; |
65 | package CBOR::XS; |
66 | |
66 | |
67 | use common::sense; |
67 | use common::sense; |
68 | |
68 | |
69 | our $VERSION = '1.0'; |
69 | our $VERSION = 1.11; |
70 | our @ISA = qw(Exporter); |
70 | our @ISA = qw(Exporter); |
71 | |
71 | |
72 | our @EXPORT = qw(encode_cbor decode_cbor); |
72 | our @EXPORT = qw(encode_cbor decode_cbor); |
73 | |
73 | |
74 | use Exporter; |
74 | use Exporter; |
… | |
… | |
180 | reference to the earlier value. |
180 | reference to the earlier value. |
181 | |
181 | |
182 | 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 |
183 | 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 |
184 | sharing extension. This also makes it possible to encode cyclic data |
184 | sharing extension. This also makes it possible to encode cyclic data |
185 | structures. |
185 | structures (which need C<allow_cycles> to ne enabled to be decoded by this |
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186 | module). |
186 | |
187 | |
187 | It is recommended to leave it off unless you know your |
188 | It is recommended to leave it off unless you know your |
188 | communication partner supports the value sharing extensions to CBOR |
189 | communication partner supports the value sharing extensions to CBOR |
189 | (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 |
190 | resulting data structure might be unusable. |
191 | resulting data structure might be unusable. |
191 | |
192 | |
192 | Detecting shared values incurs a runtime overhead when values are encoded |
193 | Detecting shared values incurs a runtime overhead when values are encoded |
193 | that have a reference counter large than one, and might unnecessarily |
194 | that have a reference counter large than one, and might unnecessarily |
194 | increase the encoded size, as potentially shared values are encode as |
195 | increase the encoded size, as potentially shared values are encode as |
195 | sharable whether or not they are actually shared. |
196 | shareable whether or not they are actually shared. |
196 | |
197 | |
197 | 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, |
198 | 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 |
199 | 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 |
200 | 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 |
… | |
… | |
205 | structures cannot be encoded in this mode. |
206 | structures cannot be encoded in this mode. |
206 | |
207 | |
207 | 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 |
208 | references will always be decoded properly if present. |
209 | references will always be decoded properly if present. |
209 | |
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. |
|
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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. |
|
|
225 | |
210 | =item $cbor = $cbor->pack_strings ([$enable]) |
226 | =item $cbor = $cbor->pack_strings ([$enable]) |
211 | |
227 | |
212 | =item $enabled = $cbor->get_pack_strings |
228 | =item $enabled = $cbor->get_pack_strings |
213 | |
229 | |
214 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
230 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
… | |
… | |
225 | If C<$enable> is false (the default), then C<encode> will encode strings |
241 | If C<$enable> is false (the default), then C<encode> will encode strings |
226 | the standard CBOR way. |
242 | the standard CBOR way. |
227 | |
243 | |
228 | This option does not affect C<decode> in any way - string references will |
244 | This option does not affect C<decode> in any way - string references will |
229 | always be decoded properly if present. |
245 | always be decoded properly if present. |
|
|
246 | |
|
|
247 | =item $cbor = $cbor->validate_utf8 ([$enable]) |
|
|
248 | |
|
|
249 | =item $enabled = $cbor->get_validate_utf8 |
|
|
250 | |
|
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251 | If C<$enable> is true (or missing), then C<decode> will validate that |
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|
252 | elements (text strings) containing UTF-8 data in fact contain valid UTF-8 |
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253 | data (instead of blindly accepting it). This validation obviously takes |
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254 | extra time during decoding. |
|
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255 | |
|
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256 | The concept of "valid UTF-8" used is perl's concept, which is a superset |
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257 | of the official UTF-8. |
|
|
258 | |
|
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259 | If C<$enable> is false (the default), then C<decode> will blindly accept |
|
|
260 | UTF-8 data, marking them as valid UTF-8 in the resulting data structure |
|
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261 | regardless of whether thats true or not. |
|
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262 | |
|
|
263 | Perl isn't too happy about corrupted UTF-8 in strings, but should |
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|
264 | generally not crash or do similarly evil things. Extensions might be not |
|
|
265 | so forgiving, so it's recommended to turn on this setting if you receive |
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266 | untrusted CBOR. |
|
|
267 | |
|
|
268 | This option does not affect C<encode> in any way - strings that are |
|
|
269 | supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
|
|
270 | string without checking whether that is, in fact, true or not. |
230 | |
271 | |
231 | =item $cbor = $cbor->filter ([$cb->($tag, $value)]) |
272 | =item $cbor = $cbor->filter ([$cb->($tag, $value)]) |
232 | |
273 | |
233 | =item $cb_or_undef = $cbor->get_filter |
274 | =item $cb_or_undef = $cbor->get_filter |
234 | |
275 | |
… | |
… | |
465 | |
506 | |
466 | =back |
507 | =back |
467 | |
508 | |
468 | =head2 OBJECT SERIALISATION |
509 | =head2 OBJECT SERIALISATION |
469 | |
510 | |
|
|
511 | This module implements both a CBOR-specific and the generic |
|
|
512 | L<Types::Serialier> object serialisation protocol. The following |
|
|
513 | subsections explain both methods. |
|
|
514 | |
|
|
515 | =head3 ENCODING |
|
|
516 | |
470 | This module knows two way to serialise a Perl object: The CBOR-specific |
517 | This module knows two way to serialise a Perl object: The CBOR-specific |
471 | way, and the generic way. |
518 | way, and the generic way. |
472 | |
519 | |
473 | Whenever the encoder encounters a Perl object that it cnanot serialise |
520 | Whenever the encoder encounters a Perl object that it cannot serialise |
474 | directly (most of them), it will first look up the C<TO_CBOR> method on |
521 | directly (most of them), it will first look up the C<TO_CBOR> method on |
475 | it. |
522 | it. |
476 | |
523 | |
477 | If it has a C<TO_CBOR> method, it will call it with the object as only |
524 | If it has a C<TO_CBOR> method, it will call it with the object as only |
478 | argument, and expects exactly one return value, which it will then |
525 | argument, and expects exactly one return value, which it will then |
… | |
… | |
484 | |
531 | |
485 | The C<FREEZE> method can return any number of values (i.e. zero or |
532 | The C<FREEZE> method can return any number of values (i.e. zero or |
486 | more). These will be encoded as CBOR perl object, together with the |
533 | more). These will be encoded as CBOR perl object, together with the |
487 | classname. |
534 | classname. |
488 | |
535 | |
|
|
536 | These methods I<MUST NOT> change the data structure that is being |
|
|
537 | serialised. Failure to comply to this can result in memory corruption - |
|
|
538 | and worse. |
|
|
539 | |
489 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
540 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
490 | with an error. |
541 | with an error. |
491 | |
542 | |
|
|
543 | =head3 DECODING |
|
|
544 | |
492 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
545 | Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded, |
493 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
546 | but objects encoded via C<FREEZE> can be decoded using the following |
|
|
547 | protocol: |
494 | |
548 | |
495 | When an encoded CBOR perl object is encountered by the decoder, it will |
549 | When an encoded CBOR perl object is encountered by the decoder, it will |
496 | look up the C<THAW> method, by using the stored classname, and will fail |
550 | look up the C<THAW> method, by using the stored classname, and will fail |
497 | if the method cannot be found. |
551 | if the method cannot be found. |
498 | |
552 | |
499 | After the lookup it will call the C<THAW> method with the stored classname |
553 | After the lookup it will call the C<THAW> method with the stored classname |
500 | as first argument, the constant string C<CBOR> as second argument, and all |
554 | as first argument, the constant string C<CBOR> as second argument, and all |
501 | values returned by C<FREEZE> as remaining arguments. |
555 | values returned by C<FREEZE> as remaining arguments. |
502 | |
556 | |
503 | =head4 EXAMPLES |
557 | =head3 EXAMPLES |
504 | |
558 | |
505 | Here is an example C<TO_CBOR> method: |
559 | Here is an example C<TO_CBOR> method: |
506 | |
560 | |
507 | sub My::Object::TO_CBOR { |
561 | sub My::Object::TO_CBOR { |
508 | my ($obj) = @_; |
562 | my ($obj) = @_; |
… | |
… | |
691 | |
745 | |
692 | These tags are automatically created (and decoded) for serialisable |
746 | These tags are automatically created (and decoded) for serialisable |
693 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
747 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
694 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
748 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
695 | |
749 | |
696 | =item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
750 | =item 28, 29 (shareable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
697 | |
751 | |
698 | These tags are automatically decoded when encountered, resulting in |
752 | These tags are automatically decoded when encountered (and they do not |
|
|
753 | result in a cyclic data structure, see C<allow_cycles>), resulting in |
699 | shared values in the decoded object. They are only encoded, however, when |
754 | shared values in the decoded object. They are only encoded, however, when |
700 | C<allow_sharable> is enabled. |
755 | C<allow_sharing> is enabled. |
|
|
756 | |
|
|
757 | Not all shared values can be successfully decoded: values that reference |
|
|
758 | themselves will I<currently> decode as C<undef> (this is not the same |
|
|
759 | as a reference pointing to itself, which will be represented as a value |
|
|
760 | that contains an indirect reference to itself - these will be decoded |
|
|
761 | properly). |
|
|
762 | |
|
|
763 | Note that considerably more shared value data structures can be decoded |
|
|
764 | than will be encoded - currently, only values pointed to by references |
|
|
765 | will be shared, others will not. While non-reference shared values can be |
|
|
766 | generated in Perl with some effort, they were considered too unimportant |
|
|
767 | to be supported in the encoder. The decoder, however, will decode these |
|
|
768 | values as shared values. |
701 | |
769 | |
702 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
770 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
703 | |
771 | |
704 | These tags are automatically decoded when encountered. They are only |
772 | These tags are automatically decoded when encountered. They are only |
705 | encoded, however, when C<pack_strings> is enabled. |
773 | encoded, however, when C<pack_strings> is enabled. |
… | |
… | |
871 | Only the double data type is supported for NV data types - when Perl uses |
939 | Only the double data type is supported for NV data types - when Perl uses |
872 | long double to represent floating point values, they might not be encoded |
940 | long double to represent floating point values, they might not be encoded |
873 | properly. Half precision types are accepted, but not encoded. |
941 | properly. Half precision types are accepted, but not encoded. |
874 | |
942 | |
875 | Strict mode and canonical mode are not implemented. |
943 | Strict mode and canonical mode are not implemented. |
|
|
944 | |
|
|
945 | |
|
|
946 | =head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
947 | |
|
|
948 | On perls that were built without 64 bit integer support (these are rare |
|
|
949 | nowadays, even on 32 bit architectures), support for any kind of 64 bit |
|
|
950 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
951 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
952 | includes string, array and map sizes that are stored as 64 bit integers. |
876 | |
953 | |
877 | |
954 | |
878 | =head1 THREADS |
955 | =head1 THREADS |
879 | |
956 | |
880 | This module is I<not> guaranteed to be thread safe and there are no |
957 | This module is I<not> guaranteed to be thread safe and there are no |