[ViewVC] Diff of: cvs/CBOR-XS/XS.pm

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.6 by root, Sun Oct 27 20:40:25 2013 UTC vs.
Revision 1.20 by root, Wed Nov 20 02:03:08 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
31	WARNING! THIS IS A PRE-ALPHA RELEASE! IT WILL CRASH, CORRUPT YOUR DATA	31	WARNING! This module is very new, and not very well tested (that's up to
32	AND EAT YOUR CHILDREN! (Actually, apart from being untested and a bit	32	you to do). Furthermore, details of the implementation might change freely
33	feature-limited, it might already be useful).	33	before version 1.0. And lastly, the object serialisation protocol depends
		34	on a pending IANA assignment, and until that assignment is official, this
		35	implementation is not interoperable with other implementations (even
		36	future versions of this module) until the assignment is done.
		37
		38	You are still invited to try out CBOR, and this module.
34		39
35	This module converts Perl data structures to the Concise Binary Object	40	This module converts Perl data structures to the Concise Binary Object
36	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation	41	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
37	format that aims to use a superset of the JSON data model, i.e. when you	42	format that aims to use a superset of the JSON data model, i.e. when you
38	can represent something in JSON, you should be able to represent it in	43	can represent something in JSON, you should be able to represent it in
39	CBOR.	44	CBOR.
40		45
41	This makes it a faster and more compact binary alternative to JSON, with	46	In short, CBOR is a faster and very compact binary alternative to JSON,
42	the added ability of supporting serialising of perl objects.	47	with the added ability of supporting serialisation of Perl objects. (JSON
		48	often compresses better than CBOR though, so if you plan to compress the
		49	data later you might want to compare both formats first).
		50
		51	To give you a general idea about speed, with texts in the megabyte range,
		52	C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or
		53	L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
		54	data, the worse L<Storable> performs in comparison.
		55
		56	As for compactness, C<CBOR::XS> encoded data structures are usually about
		57	20% smaller than the same data encoded as (compact) JSON or L<Storable>.
43		58
44	The primary goal of this module is to be I<correct> and the secondary goal	59	The primary goal of this module is to be I<correct> and the secondary goal
45	is to be I<fast>. To reach the latter goal it was written in C.	60	is to be I<fast>. To reach the latter goal it was written in C.
46		61
47	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and	62	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
…		…
51		66
52	package CBOR::XS;	67	package CBOR::XS;
53		68
54	use common::sense;	69	use common::sense;
55		70
56	our $VERSION = 0.03;	71	our $VERSION = 0.08;
57	our @ISA = qw(Exporter);	72	our @ISA = qw(Exporter);
58		73
59	our @EXPORT = qw(encode_cbor decode_cbor);	74	our @EXPORT = qw(encode_cbor decode_cbor);
60		75
61	use Exporter;	76	use Exporter;
…		…
142	If no argument is given, the limit check will be deactivated (same as when	157	If no argument is given, the limit check will be deactivated (same as when
143	C<0> is specified).	158	C<0> is specified).
144		159
145	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	160	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
146		161
		162	=item $cbor = $cbor->allow_unknown ([$enable])
		163
		164	=item $enabled = $cbor->get_allow_unknown
		165
		166	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		167	exception when it encounters values it cannot represent in CBOR (for
		168	example, filehandles) but instead will encode a CBOR C<error> value.
		169
		170	If C<$enable> is false (the default), then C<encode> will throw an
		171	exception when it encounters anything it cannot encode as CBOR.
		172
		173	This option does not affect C<decode> in any way, and it is recommended to
		174	leave it off unless you know your communications partner.
		175
		176	=item $cbor = $cbor->allow_sharing ([$enable])
		177
		178	=item $enabled = $cbor->get_allow_sharing
		179
		180	If C<$enable> is true (or missing), then C<encode> will not double-encode
		181	values that have been referenced before (e.g. when the same object, such
		182	as an array, is referenced multiple times), but instead will emit a
		183	reference to the earlier value.
		184
		185	This means that such values will only be encoded once, and will not result
		186	in a deep cloning of the value on decode, in decoders supporting the value
		187	sharing extension.
		188
		189	Detecting shared values incurs a runtime overhead when values are encoded
		190	that have a reference counter large than one, and might unnecessarily
		191	increase the encoded size, as potentially shared values are encode as
		192	sharable whether or not they are actually shared.
		193
		194	At the moment, only targets of references can be shared (e.g. scalars,
		195	arrays or hashes pointed to by a reference). Weirder constructs, such as
		196	an array with multiple "copies" of the I<same> string, which are hard but
		197	not impossible to create in Perl, are not supported (this is the same as
		198	for L<Storable>).
		199
		200	If C<$enable> is false (the default), then C<encode> will encode
		201	exception when it encounters anything it cannot encode as CBOR.
		202
		203	This option does not affect C<decode> in any way - shared values and
		204	references will always be decoded properly if present. It is recommended
		205	to leave it off unless you know your communications partner supports the
		206	value sharing extensions to CBOR (http://cbor.schmorp.de/value-sharing).
		207
147	=item $cbor_data = $cbor->encode ($perl_scalar)	208	=item $cbor_data = $cbor->encode ($perl_scalar)
148		209
149	Converts the given Perl data structure (a scalar value) to its CBOR	210	Converts the given Perl data structure (a scalar value) to its CBOR
150	representation.	211	representation.
151		212
…		…
221	C<1> and C<0> (for true and false) or to throw an exception on access (for	282	C<1> and C<0> (for true and false) or to throw an exception on access (for
222	error). See the L<Types::Serialiser> manpage for details.	283	error). See the L<Types::Serialiser> manpage for details.
223		284
224	=item CBOR tag 256 (perl object)	285	=item CBOR tag 256 (perl object)
225		286
226	The tag value C<256> (TODO: pending iana registration) will be used to	287	The tag value C<256> (TODO: pending iana registration) will be used
227	deserialise a Perl object.	288	to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
228		289	SERIALISATION>, below, for details.
229	TODO For this to work, the class must be loaded and must have a
230	C<FROM_CBOR> method. The decoder will then call the C<FROM_CBOR> method
231	with the constructor arguments provided by the C<TO_CBOR> method (see
232	below).
233
234	The C<FROM_CBOR> method must return a single value that will then be used
235	as the deserialised value.
236		290
237	=item CBOR tag 55799 (magic header)	291	=item CBOR tag 55799 (magic header)
238		292
239	The tag 55799 is ignored (this tag implements the magic header).	293	The tag 55799 is ignored (this tag implements the magic header).
240		294
…		…
283	C<1>, which get turned into false and true in CBOR.	337	C<1>, which get turned into false and true in CBOR.
284		338
285	=item CBOR::XS::Tagged objects	339	=item CBOR::XS::Tagged objects
286		340
287	Objects of this type must be arrays consisting of a single C<[tag, value]>	341	Objects of this type must be arrays consisting of a single C<[tag, value]>
288	pair. The (numerical) tag will be encoded as a CBOR tag, the value will be	342	pair. The (numerical) tag will be encoded as a CBOR tag, the value will
289	encoded as appropriate for the value.	343	be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to
		344	create such objects.
290		345
291	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error	346	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
292		347
293	These special values become CBOR true, CBOR false and CBOR undefined	348	These special values become CBOR true, CBOR false and CBOR undefined
294	values, respectively. You can also use C<\1>, C<\0> and C<\undef> directly	349	values, respectively. You can also use C<\1>, C<\0> and C<\undef> directly
295	if you want.	350	if you want.
296		351
297	=item blessed objects	352	=item other blessed objects
298		353
299	Other blessed objects currently need to have a C<TO_CBOR> method. It	354	Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See
300	will be called on every object that is being serialised, and must return	355	L<OBJECT SERIALISATION>, below, for details.
301	something that can be encoded in CBOR.
302		356
303	=item simple scalars	357	=item simple scalars
304		358
305	TODO	359	TODO
306	Simple Perl scalars (any scalar that is not a reference) are the most	360	Simple Perl scalars (any scalar that is not a reference) are the most
…		…
344	represent numerical values are supported, but might suffer loss of	398	represent numerical values are supported, but might suffer loss of
345	precision.	399	precision.
346		400
347	=back	401	=back
348		402
		403	=head2 OBJECT SERIALISATION
349		404
		405	This module knows two way to serialise a Perl object: The CBOR-specific
		406	way, and the generic way.
		407
		408	Whenever the encoder encounters a Perl object that it cnanot serialise
		409	directly (most of them), it will first look up the C<TO_CBOR> method on
		410	it.
		411
		412	If it has a C<TO_CBOR> method, it will call it with the object as only
		413	argument, and expects exactly one return value, which it will then
		414	substitute and encode it in the place of the object.
		415
		416	Otherwise, it will look up the C<FREEZE> method. If it exists, it will
		417	call it with the object as first argument, and the constant string C<CBOR>
		418	as the second argument, to distinguish it from other serialisers.
		419
		420	The C<FREEZE> method can return any number of values (i.e. zero or
		421	more). These will be encoded as CBOR perl object, together with the
		422	classname.
		423
		424	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
		425	with an error.
		426
		427	Objects encoded via C<TO_CBOR> cannot be automatically decoded, but
		428	objects encoded via C<FREEZE> can be decoded using the following protocol:
		429
		430	When an encoded CBOR perl object is encountered by the decoder, it will
		431	look up the C<THAW> method, by using the stored classname, and will fail
		432	if the method cannot be found.
		433
		434	After the lookup it will call the C<THAW> method with the stored classname
		435	as first argument, the constant string C<CBOR> as second argument, and all
		436	values returned by C<FREEZE> as remaining arguments.
		437
		438	=head4 EXAMPLES
		439
		440	Here is an example C<TO_CBOR> method:
		441
		442	sub My::Object::TO_CBOR {
		443	my ($obj) = @_;
		444
		445	["this is a serialised My::Object object", $obj->{id}]
		446	}
		447
		448	When a C<My::Object> is encoded to CBOR, it will instead encode a simple
		449	array with two members: a string, and the "object id". Decoding this CBOR
		450	string will yield a normal perl array reference in place of the object.
		451
		452	A more useful and practical example would be a serialisation method for
		453	the URI module. CBOR has a custom tag value for URIs, namely 32:
		454
		455	sub URI::TO_CBOR {
		456	my ($self) = @_;
		457	my $uri = "$self"; # stringify uri
		458	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
		459	CBOR::XS::tagged 32, "$_[0]"
		460	}
		461
		462	This will encode URIs as a UTF-8 string with tag 32, which indicates an
		463	URI.
		464
		465	Decoding such an URI will not (currently) give you an URI object, but
		466	instead a CBOR::XS::Tagged object with tag number 32 and the string -
		467	exactly what was returned by C<TO_CBOR>.
		468
		469	To serialise an object so it can automatically be deserialised, you need
		470	to use C<FREEZE> and C<THAW>. To take the URI module as example, this
		471	would be a possible implementation:
		472
		473	sub URI::FREEZE {
		474	my ($self, $serialiser) = @_;
		475	"$self" # encode url string
		476	}
		477
		478	sub URI::THAW {
		479	my ($class, $serialiser, $uri) = @_;
		480
		481	$class->new ($uri)
		482	}
		483
		484	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
		485	example, a C<FREEZE> method that returns "type", "id" and "variant" values
		486	would cause an invocation of C<THAW> with 5 arguments:
		487
		488	sub My::Object::FREEZE {
		489	my ($self, $serialiser) = @_;
		490
		491	($self->{type}, $self->{id}, $self->{variant})
		492	}
		493
		494	sub My::Object::THAW {
		495	my ($class, $serialiser, $type, $id, $variant) = @_;
		496
		497	$class-<new (type => $type, id => $id, variant => $variant)
		498	}
		499
		500
350	=head2 MAGIC HEADER	501	=head1 MAGIC HEADER
351		502
352	There is no way to distinguish CBOR from other formats	503	There is no way to distinguish CBOR from other formats
353	programmatically. To make it easier to distinguish CBOR from other	504	programmatically. To make it easier to distinguish CBOR from other
354	formats, the CBOR specification has a special "magic string" that can be	505	formats, the CBOR specification has a special "magic string" that can be
355	prepended to any CBOR string without changing it's meaning.	506	prepended to any CBOR string without changing its meaning.
356		507
357	This string is available as C<$CBOR::XS::MAGIC>. This module does not	508	This string is available as C<$CBOR::XS::MAGIC>. This module does not
358	prepend this string tot he CBOR data it generates, but it will ignroe it	509	prepend this string to the CBOR data it generates, but it will ignore it
359	if present, so users can prepend this string as a "file type" indicator as	510	if present, so users can prepend this string as a "file type" indicator as
360	required.	511	required.
361		512
362		513
		514	=head1 THE CBOR::XS::Tagged CLASS
		515
		516	CBOR has the concept of tagged values - any CBOR value can be tagged with
		517	a numeric 64 bit number, which are centrally administered.
		518
		519	C<CBOR::XS> handles a few tags internally when en- or decoding. You can
		520	also create tags yourself by encoding C<CBOR::XS::Tagged> objects, and the
		521	decoder will create C<CBOR::XS::Tagged> objects itself when it hits an
		522	unknown tag.
		523
		524	These objects are simply blessed array references - the first member of
		525	the array being the numerical tag, the second being the value.
		526
		527	You can interact with C<CBOR::XS::Tagged> objects in the following ways:
		528
		529	=over 4
		530
		531	=item $tagged = CBOR::XS::tag $tag, $value
		532
		533	This function(!) creates a new C<CBOR::XS::Tagged> object using the given
		534	C<$tag> (0..2**64-1) to tag the given C<$value> (which can be any Perl
		535	value that can be encoded in CBOR, including serialisable Perl objects and
		536	C<CBOR::XS::Tagged> objects).
		537
		538	=item $tagged->[0]
		539
		540	=item $tagged->[0] = $new_tag
		541
		542	=item $tag = $tagged->tag
		543
		544	=item $new_tag = $tagged->tag ($new_tag)
		545
		546	Access/mutate the tag.
		547
		548	=item $tagged->[1]
		549
		550	=item $tagged->[1] = $new_value
		551
		552	=item $value = $tagged->value
		553
		554	=item $new_value = $tagged->value ($new_value)
		555
		556	Access/mutate the tagged value.
		557
		558	=back
		559
		560	=cut
		561
		562	sub tag($$) {
		563	bless [@_], CBOR::XS::Tagged::;
		564	}
		565
		566	sub CBOR::XS::Tagged::tag {
		567	$_[0][0] = $_[1] if $#_;
		568	$_[0][0]
		569	}
		570
		571	sub CBOR::XS::Tagged::value {
		572	$_[0][1] = $_[1] if $#_;
		573	$_[0][1]
		574	}
		575
		576	=head2 EXAMPLES
		577
		578	Here are some examples of C<CBOR::XS::Tagged> uses to tag objects.
		579
		580	You can look up CBOR tag value and emanings in the IANA registry at
		581	L<http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml>.
		582
		583	Prepend a magic header (C<$CBOR::XS::MAGIC>):
		584
		585	my $cbor = encode_cbor CBOR::XS::tag 55799, $value;
		586	# same as:
		587	my $cbor = $CBOR::XS::MAGIC . encode_cbor $value;
		588
		589	Serialise some URIs and a regex in an array:
		590
		591	my $cbor = encode_cbor [
		592	(CBOR::XS::tag 32, "http://www.nethype.de/"),
		593	(CBOR::XS::tag 32, "http://software.schmorp.de/"),
		594	(CBOR::XS::tag 35, "^[Pp][Ee][Rr][lL]\$"),
		595	];
		596
		597	Wrap CBOR data in CBOR:
		598
		599	my $cbor_cbor = encode_cbor
		600	CBOR::XS::tag 24,
		601	encode_cbor [1, 2, 3];
		602
		603	=head1 TAG HANDLING AND EXTENSIONS
		604
		605	This section describes how this module handles specific tagged values and
		606	extensions. If a tag is not mentioned here, then the default handling
		607	applies (creating a CBOR::XS::Tagged object on decoding, and only encoding
		608	the tag when explicitly requested).
		609
		610	Future versions of this module reserve the right to special case
		611	additional tags (such as bigfloat or base64url).
		612
		613	=over 4
		614
		615	=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)
		616
		617	These tags are automatically created for serialisable objects using the
		618	C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation
		619	protocol).
		620
		621	=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
		622
		623	These tags are automatically decoded when encountered, resulting in
		624	shared values in the decoded object. They are only encoded, however, when
		625	C<allow_sharable> is enabled.
		626
		627	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
		628
		629	This tag is automatically generated when a reference are encountered (with
		630	the exception of hash and array refernces). It is converted to a reference
		631	when decoding.
		632
		633	=item 55799 (self-describe CBOR, RFC 7049)
		634
		635	This value is not generated on encoding (unless explicitly requested by
		636	the user), and is simply ignored when decoding.
		637
		638	=back
		639
		640
363	=head2 CBOR and JSON	641	=head1 CBOR and JSON
364		642
365	CBOR is supposed to implement a superset of the JSON data model, and is,	643	CBOR is supposed to implement a superset of the JSON data model, and is,
366	with some coercion, able to represent all JSON texts (something that other	644	with some coercion, able to represent all JSON texts (something that other
367	"binary JSON" formats such as BSON generally do not support).	645	"binary JSON" formats such as BSON generally do not support).
368		646

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing CBOR-XS/XS.pm (file contents): Revision 1.6 by root, Sun Oct 27 20:40:25 2013 UTC vs. Revision 1.20 by root, Wed Nov 20 02:03:08 2013 UTC

Diff Legend

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.6 by root, Sun Oct 27 20:40:25 2013 UTC vs.
Revision 1.20 by root, Wed Nov 20 02:03:08 2013 UTC