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Revision 1.18 by root, Sun Nov 17 05:26:14 2013 UTC vs.
Revision 1.21 by root, Wed Nov 20 16:29:02 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<allow_stringref>) 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.
156 161
157If no argument is given, the limit check will be deactivated (same as when 162If no argument is given, the limit check will be deactivated (same as when
158C<0> is specified). 163C<0> is specified).
159 164
160See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 165See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
166
167=item $cbor = $cbor->allow_unknown ([$enable])
168
169=item $enabled = $cbor->get_allow_unknown
170
171If C<$enable> is true (or missing), then C<encode> will I<not> throw an
172exception when it encounters values it cannot represent in CBOR (for
173example, filehandles) but instead will encode a CBOR C<error> value.
174
175If C<$enable> is false (the default), then C<encode> will throw an
176exception when it encounters anything it cannot encode as CBOR.
177
178This option does not affect C<decode> in any way, and it is recommended to
179leave it off unless you know your communications partner.
180
181=item $cbor = $cbor->allow_sharing ([$enable])
182
183=item $enabled = $cbor->get_allow_sharing
184
185If C<$enable> is true (or missing), then C<encode> will not double-encode
186values that have been referenced before (e.g. when the same object, such
187as an array, is referenced multiple times), but instead will emit a
188reference to the earlier value.
189
190This means that such values will only be encoded once, and will not result
191in a deep cloning of the value on decode, in decoders supporting the value
192sharing extension.
193
194It is recommended to leave it off unless you know your
195communication partner supports the value sharing extensions to CBOR
196(http://cbor.schmorp.de/value-sharing).
197
198Detecting shared values incurs a runtime overhead when values are encoded
199that have a reference counter large than one, and might unnecessarily
200increase the encoded size, as potentially shared values are encode as
201sharable whether or not they are actually shared.
202
203At the moment, only targets of references can be shared (e.g. scalars,
204arrays or hashes pointed to by a reference). Weirder constructs, such as
205an array with multiple "copies" of the I<same> string, which are hard but
206not impossible to create in Perl, are not supported (this is the same as
207for L<Storable>).
208
209If C<$enable> is false (the default), then C<encode> will encode
210exception when it encounters anything it cannot encode as CBOR.
211
212This option does not affect C<decode> in any way - shared values and
213references will always be decoded properly if present.
214
215=item $cbor = $cbor->allow_stringref ([$enable])
216
217=item $enabled = $cbor->get_allow_stringref
218
219If C<$enable> is true (or missing), then C<encode> will try not to encode
220the same string twice, but will instead encode a reference to the string
221instead. Depending on your data format. this can save a lot of space, but
222also results in a very large runtime overhead (expect encoding times to be
2232-4 times as high as without).
224
225It is recommended to leave it off unless you know your
226communications partner supports the stringref extension to CBOR
227(http://cbor.schmorp.de/stringref).
228
229If C<$enable> is false (the default), then C<encode> will encode
230exception when it encounters anything it cannot encode as CBOR.
231
232This option does not affect C<decode> in any way - string references will
233always be decoded properly if present.
161 234
162=item $cbor_data = $cbor->encode ($perl_scalar) 235=item $cbor_data = $cbor->encode ($perl_scalar)
163 236
164Converts the given Perl data structure (a scalar value) to its CBOR 237Converts the given Perl data structure (a scalar value) to its CBOR
165representation. 238representation.
551Wrap CBOR data in CBOR: 624Wrap CBOR data in CBOR:
552 625
553 my $cbor_cbor = encode_cbor 626 my $cbor_cbor = encode_cbor
554 CBOR::XS::tag 24, 627 CBOR::XS::tag 24,
555 encode_cbor [1, 2, 3]; 628 encode_cbor [1, 2, 3];
629
630=head1 TAG HANDLING AND EXTENSIONS
631
632This section describes how this module handles specific tagged values and
633extensions. If a tag is not mentioned here, then the default handling
634applies (creating a CBOR::XS::Tagged object on decoding, and only encoding
635the tag when explicitly requested).
636
637Future versions of this module reserve the right to special case
638additional tags (such as bigfloat or base64url).
639
640=over 4
641
642=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)
643
644These tags are automatically created for serialisable objects using the
645C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation
646protocol).
647
648=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
649
650These tags are automatically decoded when encountered, resulting in
651shared values in the decoded object. They are only encoded, however, when
652C<allow_sharable> is enabled.
653
654=item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)
655
656These tags are automatically decoded when encountered. They are only
657encoded, however, when C<allow_stringref> is enabled.
658
659=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
660
661This tag is automatically generated when a reference are encountered (with
662the exception of hash and array refernces). It is converted to a reference
663when decoding.
664
665=item 55799 (self-describe CBOR, RFC 7049)
666
667This value is not generated on encoding (unless explicitly requested by
668the user), and is simply ignored when decoding.
669
670=back
671
556 672
557=head1 CBOR and JSON 673=head1 CBOR and JSON
558 674
559CBOR is supposed to implement a superset of the JSON data model, and is, 675CBOR is supposed to implement a superset of the JSON data model, and is,
560with some coercion, able to represent all JSON texts (something that other 676with some coercion, able to represent all JSON texts (something that other

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