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Revision 1.13 by root, Tue Oct 29 15:56:31 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
46In short, CBOR is a faster and very compact binary alternative to JSON, 46In short, CBOR is a faster and very compact binary alternative to JSON,
47with the added ability of supporting serialisation of Perl objects. (JSON 47with the added ability of supporting serialisation of Perl objects. (JSON
48often compresses better than CBOR though, so if you plan to compress the 48often compresses better than CBOR though, so if you plan to compress the
49data later you might want to compare both formats first). 49data later you might want to compare both formats first).
50 50
51To 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
53L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
54data, the worse L<Storable> performs in comparison.
55
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>.
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
51The 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
52is 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.
53 66
54See 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
55vice versa. 68vice versa.
58 71
59package CBOR::XS; 72package CBOR::XS;
60 73
61use common::sense; 74use common::sense;
62 75
63our $VERSION = 0.06; 76our $VERSION = 0.09;
64our @ISA = qw(Exporter); 77our @ISA = qw(Exporter);
65 78
66our @EXPORT = qw(encode_cbor decode_cbor); 79our @EXPORT = qw(encode_cbor decode_cbor);
67 80
68use Exporter; 81use Exporter;
105strings. All boolean flags described below are by default I<disabled>. 118strings. All boolean flags described below are by default I<disabled>.
106 119
107The 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
108be chained: 121be chained:
109 122
110#TODO
111 my $cbor = CBOR::XS->new->encode ({a => [1,2]}); 123 my $cbor = CBOR::XS->new->encode ({a => [1,2]});
112 124
113=item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) 125=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
114 126
115=item $max_depth = $cbor->get_max_depth 127=item $max_depth = $cbor->get_max_depth
149If no argument is given, the limit check will be deactivated (same as when 161If no argument is given, the limit check will be deactivated (same as when
150C<0> is specified). 162C<0> is specified).
151 163
152See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 164See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
153 165
166=item $cbor = $cbor->allow_unknown ([$enable])
167
168=item $enabled = $cbor->get_allow_unknown
169
170If C<$enable> is true (or missing), then C<encode> will I<not> throw an
171exception when it encounters values it cannot represent in CBOR (for
172example, filehandles) but instead will encode a CBOR C<error> value.
173
174If C<$enable> is false (the default), then C<encode> will throw an
175exception when it encounters anything it cannot encode as CBOR.
176
177This option does not affect C<decode> in any way, and it is recommended to
178leave it off unless you know your communications partner.
179
180=item $cbor = $cbor->allow_sharing ([$enable])
181
182=item $enabled = $cbor->get_allow_sharing
183
184If C<$enable> is true (or missing), then C<encode> will not double-encode
185values that have been referenced before (e.g. when the same object, such
186as an array, is referenced multiple times), but instead will emit a
187reference to the earlier value.
188
189This means that such values will only be encoded once, and will not result
190in a deep cloning of the value on decode, in decoders supporting the value
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.
198
199Detecting shared values incurs a runtime overhead when values are encoded
200that have a reference counter large than one, and might unnecessarily
201increase the encoded size, as potentially shared values are encode as
202sharable whether or not they are actually shared.
203
204At the moment, only targets of references can be shared (e.g. scalars,
205arrays or hashes pointed to by a reference). Weirder constructs, such as
206an array with multiple "copies" of the I<same> string, which are hard but
207not impossible to create in Perl, are not supported (this is the same as
208with L<Storable>).
209
210If C<$enable> is false (the default), then C<encode> will encode shared
211data structures repeatedly, unsharing them in the process. Cyclic data
212structures cannot be encoded in this mode.
213
214This option does not affect C<decode> in any way - shared values and
215references will always be decoded properly if present.
216
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 };
278
154=item $cbor_data = $cbor->encode ($perl_scalar) 279=item $cbor_data = $cbor->encode ($perl_scalar)
155 280
156Converts the given Perl data structure (a scalar value) to its CBOR 281Converts the given Perl data structure (a scalar value) to its CBOR
157representation. 282representation.
158 283
198CBOR integers become (numeric) perl scalars. On perls without 64 bit 323CBOR integers become (numeric) perl scalars. On perls without 64 bit
199support, 64 bit integers will be truncated or otherwise corrupted. 324support, 64 bit integers will be truncated or otherwise corrupted.
200 325
201=item byte strings 326=item byte strings
202 327
203Byte 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
204will simply become characters of the same value in Perl). 329will simply become characters of the same value in Perl).
205 330
206=item UTF-8 strings 331=item UTF-8 strings
207 332
208UTF-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
226C<Types:Serialiser::false> and C<Types::Serialiser::error>, 351C<Types:Serialiser::false> and C<Types::Serialiser::error>,
227respectively. They are overloaded to act almost exactly like the numbers 352respectively. They are overloaded to act almost exactly like the numbers
228C<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
229error). See the L<Types::Serialiser> manpage for details. 354error). See the L<Types::Serialiser> manpage for details.
230 355
231=item CBOR tag 256 (perl object) 356=item tagged values
232 357
233The tag value C<256> (TODO: pending iana registration) will be used
234to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
235SERIALISATION>, below, for details.
236
237=item CBOR tag 55799 (magic header)
238
239The tag 55799 is ignored (this tag implements the magic header).
240
241=item other CBOR tags
242
243Tagged items consists of a numeric tag and another CBOR value. Tags not 358Tagged items consists of a numeric tag and another CBOR value.
244handled internally are currently converted into a L<CBOR::XS::Tagged>
245object, which is simply a blessed array reference consisting of the
246numeric tag value followed by the (decoded) CBOR value.
247 359
248In the future, support for user-supplied conversions might get added. 360See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
361for details.
249 362
250=item anything else 363=item anything else
251 364
252Anything else (e.g. unsupported simple values) will raise a decoding 365Anything else (e.g. unsupported simple values) will raise a decoding
253error. 366error.
296if you want. 409if you want.
297 410
298=item other blessed objects 411=item other blessed objects
299 412
300Other 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
301L<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.
302 416
303=item simple scalars 417=item simple scalars
304 418
305TODO
306Simple 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
307difficult objects to encode: CBOR::XS will encode undefined scalars as 420difficult objects to encode: CBOR::XS will encode undefined scalars as
308CBOR 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
309before encoding as CBOR strings, and anything else as number value: 422before encoding as CBOR strings, and anything else as number value:
310 423
311 # dump as number 424 # dump as number
312 encode_cbor [2] # yields [2] 425 encode_cbor [2] # yields [2]
313 encode_cbor [-3.0e17] # yields [-3e+17] 426 encode_cbor [-3.0e17] # yields [-3e+17]
314 my $value = 5; encode_cbor [$value] # yields [5] 427 my $value = 5; encode_cbor [$value] # yields [5]
315 428
316 # used as string, so dump as string 429 # used as string, so dump as string (either byte or text)
317 print $value; 430 print $value;
318 encode_cbor [$value] # yields ["5"] 431 encode_cbor [$value] # yields ["5"]
319 432
320 # undef becomes null 433 # undef becomes null
321 encode_cbor [undef] # yields [null] 434 encode_cbor [undef] # yields [null]
324 437
325 my $x = 3.1; # some variable containing a number 438 my $x = 3.1; # some variable containing a number
326 "$x"; # stringified 439 "$x"; # stringified
327 $x .= ""; # another, more awkward way to stringify 440 $x .= ""; # another, more awkward way to stringify
328 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.
329 452
330You 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:
331 454
332 my $x = "3"; # some variable containing a string 455 my $x = "3"; # some variable containing a string
333 $x += 0; # numify it, ensuring it will be dumped as a number 456 $x += 0; # numify it, ensuring it will be dumped as a number
447=head1 MAGIC HEADER 570=head1 MAGIC HEADER
448 571
449There is no way to distinguish CBOR from other formats 572There is no way to distinguish CBOR from other formats
450programmatically. To make it easier to distinguish CBOR from other 573programmatically. To make it easier to distinguish CBOR from other
451formats, the CBOR specification has a special "magic string" that can be 574formats, the CBOR specification has a special "magic string" that can be
452prepended to any CBOR string without changing it's meaning. 575prepended to any CBOR string without changing its meaning.
453 576
454This string is available as C<$CBOR::XS::MAGIC>. This module does not 577This string is available as C<$CBOR::XS::MAGIC>. This module does not
455prepend this string tot he CBOR data it generates, but it will ignroe it 578prepend this string to the CBOR data it generates, but it will ignore it
456if present, so users can prepend this string as a "file type" indicator as 579if present, so users can prepend this string as a "file type" indicator as
457required. 580required.
458 581
459 582
460=head1 THE CBOR::XS::Tagged CLASS 583=head1 THE CBOR::XS::Tagged CLASS
543Wrap CBOR data in CBOR: 666Wrap CBOR data in CBOR:
544 667
545 my $cbor_cbor = encode_cbor 668 my $cbor_cbor = encode_cbor
546 CBOR::XS::tag 24, 669 CBOR::XS::tag 24,
547 encode_cbor [1, 2, 3]; 670 encode_cbor [1, 2, 3];
671
672=head1 TAG HANDLING AND EXTENSIONS
673
674This section describes how this module handles specific tagged values
675and extensions. If a tag is not mentioned here and no additional filters
676are provided for it, then the default handling applies (creating a
677CBOR::XS::Tagged object on decoding, and only encoding the tag when
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.
683
684Future versions of this module reserve the right to special case
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.
691
692=over 4
693
694=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
695
696These tags are automatically created (and decoded) for serialisable
697objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
698serialisation protocol). See L<OBJECT SERIALISATION> for details.
699
700=item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
701
702These tags are automatically decoded when encountered, resulting in
703shared values in the decoded object. They are only encoded, however, when
704C<allow_sharable> is enabled.
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
711=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
712
713This tag is automatically generated when a reference are encountered (with
714the exception of hash and array refernces). It is converted to a reference
715when decoding.
716
717=item 55799 (self-describe CBOR, RFC 7049)
718
719This value is not generated on encoding (unless explicitly requested by
720the user), and is simply ignored when decoding.
721
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 ($_[1][0], 2)
793 },
794
795 21 => sub { pop }, # expected conversion to base64url encoding
796 22 => sub { pop }, # expected conversion to base64 encoding
797 23 => sub { pop }, # expected conversion to base16 encoding
798
799 # 24 # embedded cbor, byte string
800
801 32 => sub {
802 require URI;
803 URI->new (pop)
804 },
805
806 # 33 # base64url rfc4648, utf-8
807 # 34 # base64 rfc46484, utf-8
808 # 35 # regex pcre/ecma262, utf-8
809 # 36 # mime message rfc2045, utf-8
810);
811
548 812
549=head1 CBOR and JSON 813=head1 CBOR and JSON
550 814
551CBOR is supposed to implement a superset of the JSON data model, and is, 815CBOR is supposed to implement a superset of the JSON data model, and is,
552with some coercion, able to represent all JSON texts (something that other 816with some coercion, able to represent all JSON texts (something that other
634Please refrain from using rt.cpan.org or any other bug reporting 898Please refrain from using rt.cpan.org or any other bug reporting
635service. I put the contact address into my modules for a reason. 899service. I put the contact address into my modules for a reason.
636 900
637=cut 901=cut
638 902
903our %FILTER = (
904 # 0 # rfc4287 datetime, utf-8
905 # 1 # unix timestamp, any
906
907 2 => sub { # pos bigint
908 require Math::BigInt;
909 Math::BigInt->new ("0x" . unpack "H*", pop)
910 },
911
912 3 => sub { # neg bigint
913 require Math::BigInt;
914 -Math::BigInt->new ("0x" . unpack "H*", pop)
915 },
916
917 4 => sub { # decimal fraction, array
918 require Math::BigFloat;
919 Math::BigFloat->new ($_[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
639XSLoader::load "CBOR::XS", $VERSION; 969XSLoader::load "CBOR::XS", $VERSION;
640 970
641=head1 SEE ALSO 971=head1 SEE ALSO
642 972
643The 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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