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Revision 1.20 by root, Wed Nov 20 02:03:08 2013 UTC vs.
Revision 1.27 by root, Thu Nov 28 15:43:24 2013 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 to 31WARNING! This module is very new, and not very well tested (that's up
32you to do). Furthermore, details of the implementation might change freely 32to you to do). Furthermore, details of the implementation might change
33before version 1.0. And lastly, the object serialisation protocol depends 33freely before version 1.0. And lastly, most extensions depend on an IANA
34on a pending IANA assignment, and until that assignment is official, this 34assignment, and until that assignment is official, this implementation is
35implementation is not interoperable with other implementations (even 35not interoperable with other implementations (even future versions of this
36future versions of this module) until the assignment is done. 36module) until the assignment is done.
37 37
38You are still invited to try out CBOR, and this module. 38You are still invited to try out CBOR, and this module.
39 39
40This module converts Perl data structures to the Concise Binary Object 40This module converts Perl data structures to the Concise Binary Object
41Representation (CBOR) and vice versa. CBOR is a fast binary serialisation 41Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
54data, the worse L<Storable> performs in comparison. 54data, the worse L<Storable> performs in comparison.
55 55
56As for compactness, C<CBOR::XS> encoded data structures are usually about 56As for compactness, C<CBOR::XS> encoded data structures are usually about
5720% smaller than the same data encoded as (compact) JSON or L<Storable>. 5720% smaller than the same data encoded as (compact) JSON or L<Storable>.
58 58
59In addition to the core CBOR data format, this module implements a number
60of extensions, to support cyclic and self-referencing data structures
61(see C<allow_sharing>), string deduplication (see C<pack_strings>) and
62scalar references (always enabled).
63
59The primary goal of this module is to be I<correct> and the secondary goal 64The primary goal of this module is to be I<correct> and the secondary goal
60is to be I<fast>. To reach the latter goal it was written in C. 65is to be I<fast>. To reach the latter goal it was written in C.
61 66
62See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and 67See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
63vice versa. 68vice versa.
66 71
67package CBOR::XS; 72package CBOR::XS;
68 73
69use common::sense; 74use common::sense;
70 75
71our $VERSION = 0.08; 76our $VERSION = 0.09;
72our @ISA = qw(Exporter); 77our @ISA = qw(Exporter);
73 78
74our @EXPORT = qw(encode_cbor decode_cbor); 79our @EXPORT = qw(encode_cbor decode_cbor);
75 80
76use Exporter; 81use Exporter;
113strings. All boolean flags described below are by default I<disabled>. 118strings. All boolean flags described below are by default I<disabled>.
114 119
115The mutators for flags all return the CBOR object again and thus calls can 120The mutators for flags all return the CBOR object again and thus calls can
116be chained: 121be chained:
117 122
118#TODO
119 my $cbor = CBOR::XS->new->encode ({a => [1,2]}); 123 my $cbor = CBOR::XS->new->encode ({a => [1,2]});
120 124
121=item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) 125=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
122 126
123=item $max_depth = $cbor->get_max_depth 127=item $max_depth = $cbor->get_max_depth
182as an array, is referenced multiple times), but instead will emit a 186as an array, is referenced multiple times), but instead will emit a
183reference to the earlier value. 187reference to the earlier value.
184 188
185This means that such values will only be encoded once, and will not result 189This means that such values will only be encoded once, and will not result
186in a deep cloning of the value on decode, in decoders supporting the value 190in a deep cloning of the value on decode, in decoders supporting the value
187sharing extension. 191sharing extension. This also makes it possible to encode cyclic data
192structures.
193
194It is recommended to leave it off unless you know your
195communication partner supports the value sharing extensions to CBOR
196(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
197resulting data structure might be unusable.
188 198
189Detecting shared values incurs a runtime overhead when values are encoded 199Detecting shared values incurs a runtime overhead when values are encoded
190that have a reference counter large than one, and might unnecessarily 200that have a reference counter large than one, and might unnecessarily
191increase the encoded size, as potentially shared values are encode as 201increase the encoded size, as potentially shared values are encode as
192sharable whether or not they are actually shared. 202sharable whether or not they are actually shared.
193 203
194At the moment, only targets of references can be shared (e.g. scalars, 204At the moment, only targets of references can be shared (e.g. scalars,
195arrays or hashes pointed to by a reference). Weirder constructs, such as 205arrays or hashes pointed to by a reference). Weirder constructs, such as
196an array with multiple "copies" of the I<same> string, which are hard but 206an array with multiple "copies" of the I<same> string, which are hard but
197not impossible to create in Perl, are not supported (this is the same as 207not impossible to create in Perl, are not supported (this is the same as
198for L<Storable>). 208with L<Storable>).
199 209
200If C<$enable> is false (the default), then C<encode> will encode 210If C<$enable> is false (the default), then C<encode> will encode shared
201exception when it encounters anything it cannot encode as CBOR. 211data structures repeatedly, unsharing them in the process. Cyclic data
212structures cannot be encoded in this mode.
202 213
203This option does not affect C<decode> in any way - shared values and 214This option does not affect C<decode> in any way - shared values and
204references will always be decoded properly if present. It is recommended 215references will always be decoded properly if present.
205to leave it off unless you know your communications partner supports the 216
206value sharing extensions to CBOR (http://cbor.schmorp.de/value-sharing). 217=item $cbor = $cbor->pack_strings ([$enable])
218
219=item $enabled = $cbor->get_pack_strings
220
221If C<$enable> is true (or missing), then C<encode> will try not to encode
222the same string twice, but will instead encode a reference to the string
223instead. Depending on your data format, this can save a lot of space, but
224also results in a very large runtime overhead (expect encoding times to be
2252-4 times as high as without).
226
227It is recommended to leave it off unless you know your
228communications partner supports the stringref extension to CBOR
229(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
230resulting data structure might not be usable.
231
232If C<$enable> is false (the default), then C<encode> will encode strings
233the standard CBOR way.
234
235This option does not affect C<decode> in any way - string references will
236always be decoded properly if present.
237
238=item $cbor = $cbor->filter ([$cb->($tag, $value)])
239
240=item $cb_or_undef = $cbor->get_filter
241
242Sets or replaces the tagged value decoding filter (when C<$cb> is
243specified) or clears the filter (if no argument or C<undef> is provided).
244
245The filter callback is called only during decoding, when a non-enforced
246tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a
247list of enforced tags). For specific tags, it's often better to provide a
248default converter using the C<%CBOR::XS::FILTER> hash (see below).
249
250The first argument is the numerical tag, the second is the (decoded) value
251that has been tagged.
252
253The filter function should return either exactly one value, which will
254replace the tagged value in the decoded data structure, or no values,
255which will result in default handling, which currently means the decoder
256creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
257
258When the filter is cleared (the default state), the default filter
259function, 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
261a code reference that is called with tag and value, and is responsible for
262decoding the value. If no entry exists, it returns no values.
263
264Example: decode all tags not handled internally into CBOR::XS::Tagged
265objects, with no other special handling (useful when working with
266potentially "unsafe" CBOR data).
267
268 CBOR::XS->new->filter (sub { })->decode ($cbor_data);
269
270Example: provide a global filter for tag 1347375694, converting the value
271into some string form.
272
273 $CBOR::XS::FILTER{1347375694} = sub {
274 my ($tag, $value);
275
276 "tag 1347375694 value $value"
277 };
207 278
208=item $cbor_data = $cbor->encode ($perl_scalar) 279=item $cbor_data = $cbor->encode ($perl_scalar)
209 280
210Converts the given Perl data structure (a scalar value) to its CBOR 281Converts the given Perl data structure (a scalar value) to its CBOR
211representation. 282representation.
252CBOR integers become (numeric) perl scalars. On perls without 64 bit 323CBOR integers become (numeric) perl scalars. On perls without 64 bit
253support, 64 bit integers will be truncated or otherwise corrupted. 324support, 64 bit integers will be truncated or otherwise corrupted.
254 325
255=item byte strings 326=item byte strings
256 327
257Byte strings will become octet strings in Perl (the byte values 0..255 328Byte strings will become octet strings in Perl (the Byte values 0..255
258will simply become characters of the same value in Perl). 329will simply become characters of the same value in Perl).
259 330
260=item UTF-8 strings 331=item UTF-8 strings
261 332
262UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be 333UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
280C<Types:Serialiser::false> and C<Types::Serialiser::error>, 351C<Types:Serialiser::false> and C<Types::Serialiser::error>,
281respectively. They are overloaded to act almost exactly like the numbers 352respectively. They are overloaded to act almost exactly like the numbers
282C<1> and C<0> (for true and false) or to throw an exception on access (for 353C<1> and C<0> (for true and false) or to throw an exception on access (for
283error). See the L<Types::Serialiser> manpage for details. 354error). See the L<Types::Serialiser> manpage for details.
284 355
285=item CBOR tag 256 (perl object) 356=item tagged values
286 357
287The tag value C<256> (TODO: pending iana registration) will be used
288to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
289SERIALISATION>, below, for details.
290
291=item CBOR tag 55799 (magic header)
292
293The tag 55799 is ignored (this tag implements the magic header).
294
295=item other CBOR tags
296
297Tagged items consists of a numeric tag and another CBOR value. Tags not 358Tagged items consists of a numeric tag and another CBOR value.
298handled internally are currently converted into a L<CBOR::XS::Tagged>
299object, which is simply a blessed array reference consisting of the
300numeric tag value followed by the (decoded) CBOR value.
301 359
302In the future, support for user-supplied conversions might get added. 360See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
361for details.
303 362
304=item anything else 363=item anything else
305 364
306Anything else (e.g. unsupported simple values) will raise a decoding 365Anything else (e.g. unsupported simple values) will raise a decoding
307error. 366error.
350if you want. 409if you want.
351 410
352=item other blessed objects 411=item other blessed objects
353 412
354Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See 413Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See
355L<OBJECT SERIALISATION>, below, for details. 414L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this
415module, and L<OBJECT SERIALISATION> for generic object serialisation.
356 416
357=item simple scalars 417=item simple scalars
358 418
359TODO
360Simple Perl scalars (any scalar that is not a reference) are the most 419Simple Perl scalars (any scalar that is not a reference) are the most
361difficult objects to encode: CBOR::XS will encode undefined scalars as 420difficult objects to encode: CBOR::XS will encode undefined scalars as
362CBOR null values, scalars that have last been used in a string context 421CBOR null values, scalars that have last been used in a string context
363before encoding as CBOR strings, and anything else as number value: 422before encoding as CBOR strings, and anything else as number value:
364 423
365 # dump as number 424 # dump as number
366 encode_cbor [2] # yields [2] 425 encode_cbor [2] # yields [2]
367 encode_cbor [-3.0e17] # yields [-3e+17] 426 encode_cbor [-3.0e17] # yields [-3e+17]
368 my $value = 5; encode_cbor [$value] # yields [5] 427 my $value = 5; encode_cbor [$value] # yields [5]
369 428
370 # used as string, so dump as string 429 # used as string, so dump as string (either byte or text)
371 print $value; 430 print $value;
372 encode_cbor [$value] # yields ["5"] 431 encode_cbor [$value] # yields ["5"]
373 432
374 # undef becomes null 433 # undef becomes null
375 encode_cbor [undef] # yields [null] 434 encode_cbor [undef] # yields [null]
378 437
379 my $x = 3.1; # some variable containing a number 438 my $x = 3.1; # some variable containing a number
380 "$x"; # stringified 439 "$x"; # stringified
381 $x .= ""; # another, more awkward way to stringify 440 $x .= ""; # another, more awkward way to stringify
382 print $x; # perl does it for you, too, quite often 441 print $x; # perl does it for you, too, quite often
442
443You can force whether a string ie encoded as byte or text string by using
444C<utf8::upgrade> and C<utf8::downgrade>):
445
446 utf8::upgrade $x; # encode $x as text string
447 utf8::downgrade $x; # encode $x as byte string
448
449Perl doesn't define what operations up- and downgrade strings, so if the
450difference between byte and text is important, you should up- or downgrade
451your string as late as possible before encoding.
383 452
384You can force the type to be a CBOR number by numifying it: 453You can force the type to be a CBOR number by numifying it:
385 454
386 my $x = "3"; # some variable containing a string 455 my $x = "3"; # some variable containing a string
387 $x += 0; # numify it, ensuring it will be dumped as a number 456 $x += 0; # numify it, ensuring it will be dumped as a number
600 CBOR::XS::tag 24, 669 CBOR::XS::tag 24,
601 encode_cbor [1, 2, 3]; 670 encode_cbor [1, 2, 3];
602 671
603=head1 TAG HANDLING AND EXTENSIONS 672=head1 TAG HANDLING AND EXTENSIONS
604 673
605This section describes how this module handles specific tagged values and 674This section describes how this module handles specific tagged values
606extensions. If a tag is not mentioned here, then the default handling 675and extensions. If a tag is not mentioned here and no additional filters
676are provided for it, then the default handling applies (creating a
607applies (creating a CBOR::XS::Tagged object on decoding, and only encoding 677CBOR::XS::Tagged object on decoding, and only encoding the tag when
608the tag when explicitly requested). 678explicitly requested).
679
680Tags not handled specifically are currently converted into a
681L<CBOR::XS::Tagged> object, which is simply a blessed array reference
682consisting of the numeric tag value followed by the (decoded) CBOR value.
609 683
610Future versions of this module reserve the right to special case 684Future versions of this module reserve the right to special case
611additional tags (such as bigfloat or base64url). 685additional tags (such as base64url).
686
687=head2 ENFORCED TAGS
688
689These tags are always handled when decoding, and their handling cannot be
690overriden by the user.
612 691
613=over 4 692=over 4
614 693
615=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>) 694=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
616 695
617These tags are automatically created for serialisable objects using the 696These tags are automatically created (and decoded) for serialisable
618C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation 697objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
619protocol). 698serialisation protocol). See L<OBJECT SERIALISATION> for details.
620 699
621=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) 700=item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
622 701
623These tags are automatically decoded when encountered, resulting in 702These tags are automatically decoded when encountered, resulting in
624shared values in the decoded object. They are only encoded, however, when 703shared values in the decoded object. They are only encoded, however, when
625C<allow_sharable> is enabled. 704C<allow_sharable> is enabled.
626 705
706=item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)
707
708These tags are automatically decoded when encountered. They are only
709encoded, however, when C<pack_strings> is enabled.
710
627=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) 711=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
628 712
629This tag is automatically generated when a reference are encountered (with 713This tag is automatically generated when a reference are encountered (with
630the exception of hash and array refernces). It is converted to a reference 714the exception of hash and array refernces). It is converted to a reference
631when decoding. 715when decoding.
634 718
635This value is not generated on encoding (unless explicitly requested by 719This value is not generated on encoding (unless explicitly requested by
636the user), and is simply ignored when decoding. 720the user), and is simply ignored when decoding.
637 721
638=back 722=back
723
724=head2 NON-ENFORCED TAGS
725
726These 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
728providing a custom C<filter> callback when decoding.
729
730When they result in decoding into a specific Perl class, the module
731usually provides a corresponding C<TO_CBOR> method as well.
732
733When any of these need to load additional modules that are not part of the
734perl core distribution (e.g. L<URI>), it is (currently) up to the user to
735provide these modules. The decoding usually fails with an exception if the
736required module cannot be loaded.
737
738=over 4
739
740=item 2, 3 (positive/negative bignum)
741
742These tags are decoded into L<Math::BigInt> objects. The corresponding
743C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
744integers, and others into positive/negative CBOR bignums.
745
746=item 4, 5 (decimal fraction/bigfloat)
747
748Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
749objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
750encodes into a decimal fraction.
751
752CBOR cannot represent bigfloats with I<very> large exponents - conversion
753of such big float objects is undefined.
754
755Also, NaN and infinities are not encoded properly.
756
757=item 21, 22, 23 (expected later JSON conversion)
758
759CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
760tags.
761
762=item 32 (URI)
763
764These objects decode into L<URI> objects. The corresponding
765C<URI::TO_CBOR> method again results in a CBOR URI value.
766
767=back
768
769=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 ($_[1][0], 2)
793 },
794
795 21 => sub { pop }, # expected conversion to base64url encoding
796 22 => sub { pop }, # expected conversion to base64 encoding
797 23 => sub { pop }, # expected conversion to base16 encoding
798
799 # 24 # embedded cbor, byte string
800
801 32 => sub {
802 require URI;
803 URI->new (pop)
804 },
805
806 # 33 # base64url rfc4648, utf-8
807 # 34 # base64 rfc46484, utf-8
808 # 35 # regex pcre/ecma262, utf-8
809 # 36 # mime message rfc2045, utf-8
810);
639 811
640 812
641=head1 CBOR and JSON 813=head1 CBOR and JSON
642 814
643CBOR is supposed to implement a superset of the JSON data model, and is, 815CBOR is supposed to implement a superset of the JSON data model, and is,
726Please refrain from using rt.cpan.org or any other bug reporting 898Please refrain from using rt.cpan.org or any other bug reporting
727service. I put the contact address into my modules for a reason. 899service. I put the contact address into my modules for a reason.
728 900
729=cut 901=cut
730 902
903our %FILTER = (
904 # 0 # rfc4287 datetime, utf-8
905 # 1 # unix timestamp, any
906
907 2 => sub { # pos bigint
908 require Math::BigInt;
909 Math::BigInt->new ("0x" . unpack "H*", pop)
910 },
911
912 3 => sub { # neg bigint
913 require Math::BigInt;
914 -Math::BigInt->new ("0x" . unpack "H*", pop)
915 },
916
917 4 => sub { # decimal fraction, array
918 require Math::BigFloat;
919 Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
920 },
921
922 5 => sub { # bigfloat, array
923 require Math::BigFloat;
924 scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
925 },
926
927 21 => sub { pop }, # expected conversion to base64url encoding
928 22 => sub { pop }, # expected conversion to base64 encoding
929 23 => sub { pop }, # expected conversion to base16 encoding
930
931 # 24 # embedded cbor, byte string
932
933 32 => sub {
934 require URI;
935 URI->new (pop)
936 },
937
938 # 33 # base64url rfc4648, utf-8
939 # 34 # base64 rfc46484, utf-8
940 # 35 # regex pcre/ecma262, utf-8
941 # 36 # mime message rfc2045, utf-8
942);
943
944sub CBOR::XS::default_filter {
945 &{ $FILTER{$_[0]} or return }
946}
947
948sub URI::TO_CBOR {
949 my $uri = $_[0]->as_string;
950 utf8::upgrade $uri;
951 CBOR::XS::tag 32, $uri
952}
953
954sub Math::BigInt::TO_CBOR {
955 if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {
956 $_[0]->numify
957 } else {
958 my $hex = substr $_[0]->as_hex, 2;
959 $hex = "0$hex" if 1 & length $hex; # sigh
960 CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
961 }
962}
963
964sub Math::BigFloat::TO_CBOR {
965 my ($m, $e) = $_[0]->parts;
966 CBOR::XS::tag 4, [$e->numify, $m]
967}
968
731XSLoader::load "CBOR::XS", $VERSION; 969XSLoader::load "CBOR::XS", $VERSION;
732 970
733=head1 SEE ALSO 971=head1 SEE ALSO
734 972
735The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, 973The L<JSON> and L<JSON::XS> modules that do similar, but human-readable,

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