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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.13 by root, Tue Oct 29 15:56:31 2013 UTC vs.
Revision 1.20 by root, Wed Nov 20 02:03:08 2013 UTC

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
51The primary goal of this module is to be I<correct> and the secondary goal 59The 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. 60is to be I<fast>. To reach the latter goal it was written in C.
53 61
54See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and 62See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
55vice versa. 63vice versa.
58 66
59package CBOR::XS; 67package CBOR::XS;
60 68
61use common::sense; 69use common::sense;
62 70
63our $VERSION = 0.06; 71our $VERSION = 0.08;
64our @ISA = qw(Exporter); 72our @ISA = qw(Exporter);
65 73
66our @EXPORT = qw(encode_cbor decode_cbor); 74our @EXPORT = qw(encode_cbor decode_cbor);
67 75
68use Exporter; 76use Exporter;
148 156
149If no argument is given, the limit check will be deactivated (same as when 157If no argument is given, the limit check will be deactivated (same as when
150C<0> is specified). 158C<0> is specified).
151 159
152See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 160See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
161
162=item $cbor = $cbor->allow_unknown ([$enable])
163
164=item $enabled = $cbor->get_allow_unknown
165
166If C<$enable> is true (or missing), then C<encode> will I<not> throw an
167exception when it encounters values it cannot represent in CBOR (for
168example, filehandles) but instead will encode a CBOR C<error> value.
169
170If C<$enable> is false (the default), then C<encode> will throw an
171exception when it encounters anything it cannot encode as CBOR.
172
173This option does not affect C<decode> in any way, and it is recommended to
174leave it off unless you know your communications partner.
175
176=item $cbor = $cbor->allow_sharing ([$enable])
177
178=item $enabled = $cbor->get_allow_sharing
179
180If C<$enable> is true (or missing), then C<encode> will not double-encode
181values that have been referenced before (e.g. when the same object, such
182as an array, is referenced multiple times), but instead will emit a
183reference to the earlier value.
184
185This 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
187sharing extension.
188
189Detecting shared values incurs a runtime overhead when values are encoded
190that have a reference counter large than one, and might unnecessarily
191increase the encoded size, as potentially shared values are encode as
192sharable whether or not they are actually shared.
193
194At the moment, only targets of references can be shared (e.g. scalars,
195arrays 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
197not impossible to create in Perl, are not supported (this is the same as
198for L<Storable>).
199
200If C<$enable> is false (the default), then C<encode> will encode
201exception when it encounters anything it cannot encode as CBOR.
202
203This option does not affect C<decode> in any way - shared values and
204references will always be decoded properly if present. It is recommended
205to leave it off unless you know your communications partner supports the
206value sharing extensions to CBOR (http://cbor.schmorp.de/value-sharing).
153 207
154=item $cbor_data = $cbor->encode ($perl_scalar) 208=item $cbor_data = $cbor->encode ($perl_scalar)
155 209
156Converts the given Perl data structure (a scalar value) to its CBOR 210Converts the given Perl data structure (a scalar value) to its CBOR
157representation. 211representation.
447=head1 MAGIC HEADER 501=head1 MAGIC HEADER
448 502
449There is no way to distinguish CBOR from other formats 503There is no way to distinguish CBOR from other formats
450programmatically. To make it easier to distinguish CBOR from other 504programmatically. To make it easier to distinguish CBOR from other
451formats, the CBOR specification has a special "magic string" that can be 505formats, the CBOR specification has a special "magic string" that can be
452prepended to any CBOR string without changing it's meaning. 506prepended to any CBOR string without changing its meaning.
453 507
454This string is available as C<$CBOR::XS::MAGIC>. This module does not 508This string is available as C<$CBOR::XS::MAGIC>. This module does not
455prepend this string tot he CBOR data it generates, but it will ignroe it 509prepend 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 510if present, so users can prepend this string as a "file type" indicator as
457required. 511required.
458 512
459 513
460=head1 THE CBOR::XS::Tagged CLASS 514=head1 THE CBOR::XS::Tagged CLASS
543Wrap CBOR data in CBOR: 597Wrap CBOR data in CBOR:
544 598
545 my $cbor_cbor = encode_cbor 599 my $cbor_cbor = encode_cbor
546 CBOR::XS::tag 24, 600 CBOR::XS::tag 24,
547 encode_cbor [1, 2, 3]; 601 encode_cbor [1, 2, 3];
602
603=head1 TAG HANDLING AND EXTENSIONS
604
605This section describes how this module handles specific tagged values and
606extensions. If a tag is not mentioned here, then the default handling
607applies (creating a CBOR::XS::Tagged object on decoding, and only encoding
608the tag when explicitly requested).
609
610Future versions of this module reserve the right to special case
611additional tags (such as bigfloat or base64url).
612
613=over 4
614
615=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)
616
617These tags are automatically created for serialisable objects using the
618C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation
619protocol).
620
621=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
622
623These tags are automatically decoded when encountered, resulting in
624shared values in the decoded object. They are only encoded, however, when
625C<allow_sharable> is enabled.
626
627=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
628
629This tag is automatically generated when a reference are encountered (with
630the exception of hash and array refernces). It is converted to a reference
631when decoding.
632
633=item 55799 (self-describe CBOR, RFC 7049)
634
635This value is not generated on encoding (unless explicitly requested by
636the user), and is simply ignored when decoding.
637
638=back
639
548 640
549=head1 CBOR and JSON 641=head1 CBOR and JSON
550 642
551CBOR is supposed to implement a superset of the JSON data model, and is, 643CBOR 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 644with some coercion, able to represent all JSON texts (something that other

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