ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/CBOR-XS/XS.pm
(Generate patch)

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.14 by root, Tue Oct 29 20:59:16 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, with texts in the megabyte range, C<CBOR::XS> 51To give you a general idea about speed, with texts in the megabyte range,
52usually encodes roughly twice as fast as L<Storable> or L<JSON::XS> and 52C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or
53decodes about 15%-30% faster than those. The shorter the data, the worse 53L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
54L<Storable> performs in comparison. 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).
55 63
56The 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
57is 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.
58 66
59See 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
63 71
64package CBOR::XS; 72package CBOR::XS;
65 73
66use common::sense; 74use common::sense;
67 75
68our $VERSION = 0.06; 76our $VERSION = 0.09;
69our @ISA = qw(Exporter); 77our @ISA = qw(Exporter);
70 78
71our @EXPORT = qw(encode_cbor decode_cbor); 79our @EXPORT = qw(encode_cbor decode_cbor);
72 80
73use Exporter; 81use Exporter;
110strings. All boolean flags described below are by default I<disabled>. 118strings. All boolean flags described below are by default I<disabled>.
111 119
112The 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
113be chained: 121be chained:
114 122
115#TODO
116 my $cbor = CBOR::XS->new->encode ({a => [1,2]}); 123 my $cbor = CBOR::XS->new->encode ({a => [1,2]});
117 124
118=item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) 125=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
119 126
120=item $max_depth = $cbor->get_max_depth 127=item $max_depth = $cbor->get_max_depth
154If 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
155C<0> is specified). 162C<0> is specified).
156 163
157See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 164See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
158 165
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
159=item $cbor_data = $cbor->encode ($perl_scalar) 279=item $cbor_data = $cbor->encode ($perl_scalar)
160 280
161Converts the given Perl data structure (a scalar value) to its CBOR 281Converts the given Perl data structure (a scalar value) to its CBOR
162representation. 282representation.
163 283
203CBOR integers become (numeric) perl scalars. On perls without 64 bit 323CBOR integers become (numeric) perl scalars. On perls without 64 bit
204support, 64 bit integers will be truncated or otherwise corrupted. 324support, 64 bit integers will be truncated or otherwise corrupted.
205 325
206=item byte strings 326=item byte strings
207 327
208Byte 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
209will simply become characters of the same value in Perl). 329will simply become characters of the same value in Perl).
210 330
211=item UTF-8 strings 331=item UTF-8 strings
212 332
213UTF-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
231C<Types:Serialiser::false> and C<Types::Serialiser::error>, 351C<Types:Serialiser::false> and C<Types::Serialiser::error>,
232respectively. They are overloaded to act almost exactly like the numbers 352respectively. They are overloaded to act almost exactly like the numbers
233C<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
234error). See the L<Types::Serialiser> manpage for details. 354error). See the L<Types::Serialiser> manpage for details.
235 355
236=item CBOR tag 256 (perl object) 356=item tagged values
237 357
238The tag value C<256> (TODO: pending iana registration) will be used
239to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
240SERIALISATION>, below, for details.
241
242=item CBOR tag 55799 (magic header)
243
244The tag 55799 is ignored (this tag implements the magic header).
245
246=item other CBOR tags
247
248Tagged items consists of a numeric tag and another CBOR value. Tags not 358Tagged items consists of a numeric tag and another CBOR value.
249handled internally are currently converted into a L<CBOR::XS::Tagged>
250object, which is simply a blessed array reference consisting of the
251numeric tag value followed by the (decoded) CBOR value.
252 359
253In the future, support for user-supplied conversions might get added. 360See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
361for details.
254 362
255=item anything else 363=item anything else
256 364
257Anything else (e.g. unsupported simple values) will raise a decoding 365Anything else (e.g. unsupported simple values) will raise a decoding
258error. 366error.
301if you want. 409if you want.
302 410
303=item other blessed objects 411=item other blessed objects
304 412
305Other 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
306L<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.
307 416
308=item simple scalars 417=item simple scalars
309 418
310TODO
311Simple 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
312difficult objects to encode: CBOR::XS will encode undefined scalars as 420difficult objects to encode: CBOR::XS will encode undefined scalars as
313CBOR 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
314before encoding as CBOR strings, and anything else as number value: 422before encoding as CBOR strings, and anything else as number value:
315 423
316 # dump as number 424 # dump as number
317 encode_cbor [2] # yields [2] 425 encode_cbor [2] # yields [2]
318 encode_cbor [-3.0e17] # yields [-3e+17] 426 encode_cbor [-3.0e17] # yields [-3e+17]
319 my $value = 5; encode_cbor [$value] # yields [5] 427 my $value = 5; encode_cbor [$value] # yields [5]
320 428
321 # used as string, so dump as string 429 # used as string, so dump as string (either byte or text)
322 print $value; 430 print $value;
323 encode_cbor [$value] # yields ["5"] 431 encode_cbor [$value] # yields ["5"]
324 432
325 # undef becomes null 433 # undef becomes null
326 encode_cbor [undef] # yields [null] 434 encode_cbor [undef] # yields [null]
329 437
330 my $x = 3.1; # some variable containing a number 438 my $x = 3.1; # some variable containing a number
331 "$x"; # stringified 439 "$x"; # stringified
332 $x .= ""; # another, more awkward way to stringify 440 $x .= ""; # another, more awkward way to stringify
333 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.
334 452
335You 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:
336 454
337 my $x = "3"; # some variable containing a string 455 my $x = "3"; # some variable containing a string
338 $x += 0; # numify it, ensuring it will be dumped as a number 456 $x += 0; # numify it, ensuring it will be dumped as a number
452=head1 MAGIC HEADER 570=head1 MAGIC HEADER
453 571
454There is no way to distinguish CBOR from other formats 572There is no way to distinguish CBOR from other formats
455programmatically. To make it easier to distinguish CBOR from other 573programmatically. To make it easier to distinguish CBOR from other
456formats, the CBOR specification has a special "magic string" that can be 574formats, the CBOR specification has a special "magic string" that can be
457prepended to any CBOR string without changing it's meaning. 575prepended to any CBOR string without changing its meaning.
458 576
459This string is available as C<$CBOR::XS::MAGIC>. This module does not 577This string is available as C<$CBOR::XS::MAGIC>. This module does not
460prepend 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
461if 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
462required. 580required.
463 581
464 582
465=head1 THE CBOR::XS::Tagged CLASS 583=head1 THE CBOR::XS::Tagged CLASS
548Wrap CBOR data in CBOR: 666Wrap CBOR data in CBOR:
549 667
550 my $cbor_cbor = encode_cbor 668 my $cbor_cbor = encode_cbor
551 CBOR::XS::tag 24, 669 CBOR::XS::tag 24,
552 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 ($_[1][0], 2)
793 },
794
795 21 => sub { pop }, # expected conversion to base64url encoding
796 22 => sub { pop }, # expected conversion to base64 encoding
797 23 => sub { pop }, # expected conversion to base16 encoding
798
799 # 24 # embedded cbor, byte string
800
801 32 => sub {
802 require URI;
803 URI->new (pop)
804 },
805
806 # 33 # base64url rfc4648, utf-8
807 # 34 # base64 rfc46484, utf-8
808 # 35 # regex pcre/ecma262, utf-8
809 # 36 # mime message rfc2045, utf-8
810);
811
553 812
554=head1 CBOR and JSON 813=head1 CBOR and JSON
555 814
556CBOR is supposed to implement a superset of the JSON data model, and is, 815CBOR is supposed to implement a superset of the JSON data model, and is,
557with some coercion, able to represent all JSON texts (something that other 816with some coercion, able to represent all JSON texts (something that other
639Please refrain from using rt.cpan.org or any other bug reporting 898Please refrain from using rt.cpan.org or any other bug reporting
640service. I put the contact address into my modules for a reason. 899service. I put the contact address into my modules for a reason.
641 900
642=cut 901=cut
643 902
903our %FILTER = (
904 # 0 # rfc4287 datetime, utf-8
905 # 1 # unix timestamp, any
906
907 2 => sub { # pos bigint
908 require Math::BigInt;
909 Math::BigInt->new ("0x" . unpack "H*", pop)
910 },
911
912 3 => sub { # neg bigint
913 require Math::BigInt;
914 -Math::BigInt->new ("0x" . unpack "H*", pop)
915 },
916
917 4 => sub { # decimal fraction, array
918 require Math::BigFloat;
919 Math::BigFloat->new ($_[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
644XSLoader::load "CBOR::XS", $VERSION; 969XSLoader::load "CBOR::XS", $VERSION;
645 970
646=head1 SEE ALSO 971=head1 SEE ALSO
647 972
648The 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,

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines