[ViewVC] Diff of: cvs/CBOR-XS/README

Comparing CBOR-XS/README (file contents):
Revision 1.3 by root, Sat Oct 26 11:08:34 2013 UTC vs.
Revision 1.10 by root, Thu Nov 28 16:09:04 2013 UTC

…		…
8	$perl_value = decode_cbor $binary_cbor_data;	8	$perl_value = decode_cbor $binary_cbor_data;
9		9
10	# OO-interface	10	# OO-interface
11		11
12	$coder = CBOR::XS->new;	12	$coder = CBOR::XS->new;
13	#TODO	13	$binary_cbor_data = $coder->encode ($perl_value);
		14	$perl_value = $coder->decode ($binary_cbor_data);
		15
		16	# prefix decoding
		17
		18	my $many_cbor_strings = ...;
		19	while (length $many_cbor_strings) {
		20	my ($data, $length) = $cbor->decode_prefix ($many_cbor_strings);
		21	# data was decoded
		22	substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string
		23	}
14		24
15	DESCRIPTION	25	DESCRIPTION
16	WARNING! THIS IS A PRE-ALPHA RELEASE! IT WILL CRASH, CORRUPT YOUR DATA	26	This module converts Perl data structures to the Concise Binary Object
17	AND EAT YOUR CHILDREN!	27	Representation (CBOR) and vice versa. CBOR is a fast binary
		28	serialisation format that aims to use an (almost) superset of the JSON
		29	data model, i.e. when you can represent something useful in JSON, you
		30	should be able to represent it in CBOR.
18		31
19	This module converts Perl data structures to CBOR and vice versa. Its	32	In short, CBOR is a faster and quite compact binary alternative to JSON,
20	primary goal is to be correct and its secondary goal is to be fast.	33	with the added ability of supporting serialisation of Perl objects.
		34	(JSON often compresses better than CBOR though, so if you plan to
		35	compress the data later and speed is less important you might want to
		36	compare both formats first).
		37
		38	To give you a general idea about speed, with texts in the megabyte
		39	range, "CBOR::XS" usually encodes roughly twice as fast as Storable or
		40	JSON::XS and decodes about 15%-30% faster than those. The shorter the
		41	data, the worse Storable performs in comparison.
		42
		43	Regarding compactness, "CBOR::XS"-encoded data structures are usually
		44	about 20% smaller than the same data encoded as (compact) JSON or
		45	Storable.
		46
		47	In addition to the core CBOR data format, this module implements a
		48	number of extensions, to support cyclic and shared data structures (see
		49	"allow_sharing"), string deduplication (see "pack_strings") and scalar
		50	references (always enabled).
		51
		52	The primary goal of this module is to be correct and the secondary
21	To reach the latter goal it was written in C.	53	goal is to be fast. To reach the latter goal it was written in C.
22		54
23	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and	55	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
24	vice versa.	56	vice versa.
25		57
26	FUNCTIONAL INTERFACE	58	FUNCTIONAL INTERFACE
…		…
45	disabled.	77	disabled.
46		78
47	The mutators for flags all return the CBOR object again and thus	79	The mutators for flags all return the CBOR object again and thus
48	calls can be chained:	80	calls can be chained:
49		81
50	#TODO my $cbor = CBOR::XS->new->encode ({a => [1,2]});	82	my $cbor = CBOR::XS->new->encode ({a => [1,2]});
51		83
52	$cbor = $cbor->max_depth ([$maximum_nesting_depth])	84	$cbor = $cbor->max_depth ([$maximum_nesting_depth])
53	$max_depth = $cbor->get_max_depth	85	$max_depth = $cbor->get_max_depth
54	Sets the maximum nesting level (default 512) accepted while encoding	86	Sets the maximum nesting level (default 512) accepted while encoding
55	or decoding. If a higher nesting level is detected in CBOR data or a	87	or decoding. If a higher nesting level is detected in CBOR data or a
…		…
86	as when 0 is specified).	118	as when 0 is specified).
87		119
88	See SECURITY CONSIDERATIONS, below, for more info on why this is	120	See SECURITY CONSIDERATIONS, below, for more info on why this is
89	useful.	121	useful.
90		122
		123	$cbor = $cbor->allow_unknown ([$enable])
		124	$enabled = $cbor->get_allow_unknown
		125	If $enable is true (or missing), then "encode" will not throw an
		126	exception when it encounters values it cannot represent in CBOR (for
		127	example, filehandles) but instead will encode a CBOR "error" value.
		128
		129	If $enable is false (the default), then "encode" will throw an
		130	exception when it encounters anything it cannot encode as CBOR.
		131
		132	This option does not affect "decode" in any way, and it is
		133	recommended to leave it off unless you know your communications
		134	partner.
		135
		136	$cbor = $cbor->allow_sharing ([$enable])
		137	$enabled = $cbor->get_allow_sharing
		138	If $enable is true (or missing), then "encode" will not
		139	double-encode values that have been referenced before (e.g. when the
		140	same object, such as an array, is referenced multiple times), but
		141	instead will emit a reference to the earlier value.
		142
		143	This means that such values will only be encoded once, and will not
		144	result in a deep cloning of the value on decode, in decoders
		145	supporting the value sharing extension. This also makes it possible
		146	to encode cyclic data structures.
		147
		148	It is recommended to leave it off unless you know your communication
		149	partner supports the value sharing extensions to CBOR
		150	(<http://cbor.schmorp.de/value-sharing>), as without decoder
		151	support, the resulting data structure might be unusable.
		152
		153	Detecting shared values incurs a runtime overhead when values are
		154	encoded that have a reference counter large than one, and might
		155	unnecessarily increase the encoded size, as potentially shared
		156	values are encode as sharable whether or not they are actually
		157	shared.
		158
		159	At the moment, only targets of references can be shared (e.g.
		160	scalars, arrays or hashes pointed to by a reference). Weirder
		161	constructs, such as an array with multiple "copies" of the same
		162	string, which are hard but not impossible to create in Perl, are not
		163	supported (this is the same as with Storable).
		164
		165	If $enable is false (the default), then "encode" will encode shared
		166	data structures repeatedly, unsharing them in the process. Cyclic
		167	data structures cannot be encoded in this mode.
		168
		169	This option does not affect "decode" in any way - shared values and
		170	references will always be decoded properly if present.
		171
		172	$cbor = $cbor->pack_strings ([$enable])
		173	$enabled = $cbor->get_pack_strings
		174	If $enable is true (or missing), then "encode" will try not to
		175	encode the same string twice, but will instead encode a reference to
		176	the string instead. Depending on your data format, this can save a
		177	lot of space, but also results in a very large runtime overhead
		178	(expect encoding times to be 2-4 times as high as without).
		179
		180	It is recommended to leave it off unless you know your
		181	communications partner supports the stringref extension to CBOR
		182	(<http://cbor.schmorp.de/stringref>), as without decoder support,
		183	the resulting data structure might not be usable.
		184
		185	If $enable is false (the default), then "encode" will encode strings
		186	the standard CBOR way.
		187
		188	This option does not affect "decode" in any way - string references
		189	will always be decoded properly if present.
		190
		191	$cbor = $cbor->filter ([$cb->($tag, $value)])
		192	$cb_or_undef = $cbor->get_filter
		193	Sets or replaces the tagged value decoding filter (when $cb is
		194	specified) or clears the filter (if no argument or "undef" is
		195	provided).
		196
		197	The filter callback is called only during decoding, when a
		198	non-enforced tagged value has been decoded (see "TAG HANDLING AND
		199	EXTENSIONS" for a list of enforced tags). For specific tags, it's
		200	often better to provide a default converter using the
		201	%CBOR::XS::FILTER hash (see below).
		202
		203	The first argument is the numerical tag, the second is the (decoded)
		204	value that has been tagged.
		205
		206	The filter function should return either exactly one value, which
		207	will replace the tagged value in the decoded data structure, or no
		208	values, which will result in default handling, which currently means
		209	the decoder creates a "CBOR::XS::Tagged" object to hold the tag and
		210	the value.
		211
		212	When the filter is cleared (the default state), the default filter
		213	function, "CBOR::XS::default_filter", is used. This function simply
		214	looks up the tag in the %CBOR::XS::FILTER hash. If an entry exists
		215	it must be a code reference that is called with tag and value, and
		216	is responsible for decoding the value. If no entry exists, it
		217	returns no values.
		218
		219	Example: decode all tags not handled internally into
		220	"CBOR::XS::Tagged" objects, with no other special handling (useful
		221	when working with potentially "unsafe" CBOR data).
		222
		223	CBOR::XS->new->filter (sub { })->decode ($cbor_data);
		224
		225	Example: provide a global filter for tag 1347375694, converting the
		226	value into some string form.
		227
		228	$CBOR::XS::FILTER{1347375694} = sub {
		229	my ($tag, $value);
		230
		231	"tag 1347375694 value $value"
		232	};
		233
91	$cbor_data = $cbor->encode ($perl_scalar)	234	$cbor_data = $cbor->encode ($perl_scalar)
92	Converts the given Perl data structure (a scalar value) to its CBOR	235	Converts the given Perl data structure (a scalar value) to its CBOR
93	representation.	236	representation.
94		237
95	$perl_scalar = $cbor->decode ($cbor_data)	238	$perl_scalar = $cbor->decode ($cbor_data)
…		…
118	For the more enlightened: note that in the following descriptions,	261	For the more enlightened: note that in the following descriptions,
119	lowercase perl refers to the Perl interpreter, while uppercase Perl	262	lowercase perl refers to the Perl interpreter, while uppercase Perl
120	refers to the abstract Perl language itself.	263	refers to the abstract Perl language itself.
121		264
122	CBOR -> PERL	265	CBOR -> PERL
123	True, False	266	integers
124	These CBOR values become "CBOR::XS::true" and "CBOR::XS::false",	267	CBOR integers become (numeric) perl scalars. On perls without 64 bit
		268	support, 64 bit integers will be truncated or otherwise corrupted.
		269
		270	byte strings
		271	Byte strings will become octet strings in Perl (the Byte values
		272	0..255 will simply become characters of the same value in Perl).
		273
		274	UTF-8 strings
		275	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
		276	decoded into proper Unicode code points. At the moment, the validity
		277	of the UTF-8 octets will not be validated - corrupt input will
		278	result in corrupted Perl strings.
		279
		280	arrays, maps
		281	CBOR arrays and CBOR maps will be converted into references to a
		282	Perl array or hash, respectively. The keys of the map will be
		283	stringified during this process.
		284
		285	null
		286	CBOR null becomes "undef" in Perl.
		287
		288	true, false, undefined
		289	These CBOR values become "Types:Serialiser::true",
		290	"Types:Serialiser::false" and "Types::Serialiser::error",
125	respectively. They are overloaded to act almost exactly like the	291	respectively. They are overloaded to act almost exactly like the
126	numbers 1 and 0. You can check whether a scalar is a CBOR boolean by	292	numbers 1 and 0 (for true and false) or to throw an exception on
127	using the "CBOR::XS::is_bool" function.	293	access (for error). See the Types::Serialiser manpage for details.
128		294
129	Null, Undefined	295	tagged values
130	CBOR Null and Undefined values becomes "undef" in Perl (in the	296	Tagged items consists of a numeric tag and another CBOR value.
131	future, Undefined may raise an exception).	297
		298	See "TAG HANDLING AND EXTENSIONS" and the description of "->filter"
		299	for details on which tags are handled how.
		300
		301	anything else
		302	Anything else (e.g. unsupported simple values) will raise a decoding
		303	error.
132		304
133	PERL -> CBOR	305	PERL -> CBOR
134	The mapping from Perl to CBOR is slightly more difficult, as Perl is a	306	The mapping from Perl to CBOR is slightly more difficult, as Perl is a
135	truly typeless language, so we can only guess which CBOR type is meant	307	typeless language. That means this module can only guess which CBOR type
136	by a Perl value.	308	is meant by a perl value.
137		309
138	hash references	310	hash references
139	Perl hash references become CBOR maps. As there is no inherent	311	Perl hash references become CBOR maps. As there is no inherent
140	ordering in hash keys (or CBOR maps), they will usually be encoded	312	ordering in hash keys (or CBOR maps), they will usually be encoded
141	in a pseudo-random order.	313	in a pseudo-random order. This order can be different each time a
		314	hahs is encoded.
		315
		316	Currently, tied hashes will use the indefinite-length format, while
		317	normal hashes will use the fixed-length format.
142		318
143	array references	319	array references
144	Perl array references become CBOR arrays.	320	Perl array references become fixed-length CBOR arrays.
145		321
146	other references	322	other references
147	Other unblessed references are generally not allowed and will cause	323	Other unblessed references will be represented using the indirection
148	an exception to be thrown, except for references to the integers 0	324	tag extension (tag value 22098,
149	and 1, which get turned into "False" and "True" in CBOR.	325	<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
		326	to be able to decode these values somehow, by either "doing the
		327	right thing", decoding into a generic tagged object, simply ignoring
		328	the tag, or something else.
150		329
151	CBOR::XS::true, CBOR::XS::false	330	CBOR::XS::Tagged objects
		331	Objects of this type must be arrays consisting of a single "[tag,
		332	value]" pair. The (numerical) tag will be encoded as a CBOR tag, the
		333	value will be encoded as appropriate for the value. You must use
		334	"CBOR::XS::tag" to create such objects.
		335
		336	Types::Serialiser::true, Types::Serialiser::false,
		337	Types::Serialiser::error
152	These special values become CBOR True and CBOR False values,	338	These special values become CBOR true, CBOR false and CBOR undefined
153	respectively. You can also use "\1" and "\0" directly if you want.	339	values, respectively. You can also use "\1", "\0" and "\undef"
		340	directly if you want.
154		341
155	blessed objects	342	other blessed objects
156	Blessed objects are not directly representable in CBOR. TODO See the	343	Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See
157	"allow_blessed" and "convert_blessed" methods on various options on	344	"TAG HANDLING AND EXTENSIONS" for specific classes handled by this
158	how to deal with this: basically, you can choose between throwing an	345	module, and "OBJECT SERIALISATION" for generic object serialisation.
159	exception, encoding the reference as if it weren't blessed, or
160	provide your own serialiser method.
161		346
162	simple scalars	347	simple scalars
163	TODO Simple Perl scalars (any scalar that is not a reference) are	348	Simple Perl scalars (any scalar that is not a reference) are the
164	the most difficult objects to encode: CBOR::XS will encode undefined	349	most difficult objects to encode: CBOR::XS will encode undefined
165	scalars as CBOR "Null" values, scalars that have last been used in a	350	scalars as CBOR null values, scalars that have last been used in a
166	string context before encoding as CBOR strings, and anything else as	351	string context before encoding as CBOR strings, and anything else as
167	number value:	352	number value:
168		353
169	# dump as number	354	# dump as number
170	encode_cbor [2] # yields [2]	355	encode_cbor [2] # yields [2]
171	encode_cbor [-3.0e17] # yields [-3e+17]	356	encode_cbor [-3.0e17] # yields [-3e+17]
172	my $value = 5; encode_cbor [$value] # yields [5]	357	my $value = 5; encode_cbor [$value] # yields [5]
173		358
174	# used as string, so dump as string	359	# used as string, so dump as string (either byte or text)
175	print $value;	360	print $value;
176	encode_cbor [$value] # yields ["5"]	361	encode_cbor [$value] # yields ["5"]
177		362
178	# undef becomes null	363	# undef becomes null
179	encode_cbor [undef] # yields [null]	364	encode_cbor [undef] # yields [null]
…		…
183	my $x = 3.1; # some variable containing a number	368	my $x = 3.1; # some variable containing a number
184	"$x"; # stringified	369	"$x"; # stringified
185	$x .= ""; # another, more awkward way to stringify	370	$x .= ""; # another, more awkward way to stringify
186	print $x; # perl does it for you, too, quite often	371	print $x; # perl does it for you, too, quite often
187		372
		373	You can force whether a string ie encoded as byte or text string by
		374	using "utf8::upgrade" and "utf8::downgrade"):
		375
		376	utf8::upgrade $x; # encode $x as text string
		377	utf8::downgrade $x; # encode $x as byte string
		378
		379	Perl doesn't define what operations up- and downgrade strings, so if
		380	the difference between byte and text is important, you should up- or
		381	downgrade your string as late as possible before encoding.
		382
188	You can force the type to be a CBOR number by numifying it:	383	You can force the type to be a CBOR number by numifying it:
189		384
190	my $x = "3"; # some variable containing a string	385	my $x = "3"; # some variable containing a string
191	$x += 0; # numify it, ensuring it will be dumped as a number	386	$x += 0; # numify it, ensuring it will be dumped as a number
192	$x *= 1; # same thing, the choice is yours.	387	$x *= 1; # same thing, the choice is yours.
193		388
194	You can not currently force the type in other, less obscure, ways.	389	You can not currently force the type in other, less obscure, ways.
195	Tell me if you need this capability (but don't forget to explain why	390	Tell me if you need this capability (but don't forget to explain why
196	it's needed :).	391	it's needed :).
197		392
198	Note that numerical precision has the same meaning as under Perl (so	393	Perl values that seem to be integers generally use the shortest
199	binary to decimal conversion follows the same rules as in Perl,	394	possible representation. Floating-point values will use either the
200	which can differ to other languages). Also, your perl interpreter	395	IEEE single format if possible without loss of precision, otherwise
201	might expose extensions to the floating point numbers of your	396	the IEEE double format will be used. Perls that use formats other
202	platform, such as infinities or NaN's - these cannot be represented	397	than IEEE double to represent numerical values are supported, but
203	in CBOR, and it is an error to pass those in.	398	might suffer loss of precision.
204		399
		400	OBJECT SERIALISATION
		401	This module knows two way to serialise a Perl object: The CBOR-specific
		402	way, and the generic way.
		403
		404	Whenever the encoder encounters a Perl object that it cnanot serialise
		405	directly (most of them), it will first look up the "TO_CBOR" method on
		406	it.
		407
		408	If it has a "TO_CBOR" method, it will call it with the object as only
		409	argument, and expects exactly one return value, which it will then
		410	substitute and encode it in the place of the object.
		411
		412	Otherwise, it will look up the "FREEZE" method. If it exists, it will
		413	call it with the object as first argument, and the constant string
		414	"CBOR" as the second argument, to distinguish it from other serialisers.
		415
		416	The "FREEZE" method can return any number of values (i.e. zero or more).
		417	These will be encoded as CBOR perl object, together with the classname.
		418
		419	If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail
		420	with an error.
		421
		422	Objects encoded via "TO_CBOR" cannot be automatically decoded, but
		423	objects encoded via "FREEZE" can be decoded using the following
		424	protocol:
		425
		426	When an encoded CBOR perl object is encountered by the decoder, it will
		427	look up the "THAW" method, by using the stored classname, and will fail
		428	if the method cannot be found.
		429
		430	After the lookup it will call the "THAW" method with the stored
		431	classname as first argument, the constant string "CBOR" as second
		432	argument, and all values returned by "FREEZE" as remaining arguments.
		433
		434	EXAMPLES
		435	Here is an example "TO_CBOR" method:
		436
		437	sub My::Object::TO_CBOR {
		438	my ($obj) = @_;
		439
		440	["this is a serialised My::Object object", $obj->{id}]
		441	}
		442
		443	When a "My::Object" is encoded to CBOR, it will instead encode a simple
		444	array with two members: a string, and the "object id". Decoding this
		445	CBOR string will yield a normal perl array reference in place of the
		446	object.
		447
		448	A more useful and practical example would be a serialisation method for
		449	the URI module. CBOR has a custom tag value for URIs, namely 32:
		450
		451	sub URI::TO_CBOR {
		452	my ($self) = @_;
		453	my $uri = "$self"; # stringify uri
		454	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
		455	CBOR::XS::tag 32, "$_[0]"
		456	}
		457
		458	This will encode URIs as a UTF-8 string with tag 32, which indicates an
		459	URI.
		460
		461	Decoding such an URI will not (currently) give you an URI object, but
		462	instead a CBOR::XS::Tagged object with tag number 32 and the string -
		463	exactly what was returned by "TO_CBOR".
		464
		465	To serialise an object so it can automatically be deserialised, you need
		466	to use "FREEZE" and "THAW". To take the URI module as example, this
		467	would be a possible implementation:
		468
		469	sub URI::FREEZE {
		470	my ($self, $serialiser) = @_;
		471	"$self" # encode url string
		472	}
		473
		474	sub URI::THAW {
		475	my ($class, $serialiser, $uri) = @_;
		476
		477	$class->new ($uri)
		478	}
		479
		480	Unlike "TO_CBOR", multiple values can be returned by "FREEZE". For
		481	example, a "FREEZE" method that returns "type", "id" and "variant"
		482	values would cause an invocation of "THAW" with 5 arguments:
		483
		484	sub My::Object::FREEZE {
		485	my ($self, $serialiser) = @_;
		486
		487	($self->{type}, $self->{id}, $self->{variant})
		488	}
		489
		490	sub My::Object::THAW {
		491	my ($class, $serialiser, $type, $id, $variant) = @_;
		492
		493	$class-<new (type => $type, id => $id, variant => $variant)
		494	}
		495
205	MAGIC HEADER	496	MAGIC HEADER
206	There is no way to distinguish CBOR from other formats programmatically.	497	There is no way to distinguish CBOR from other formats programmatically.
207	To make it easier to distinguish CBOR from other formats, the CBOR	498	To make it easier to distinguish CBOR from other formats, the CBOR
208	specification has a special "magic string" that can be prepended to any	499	specification has a special "magic string" that can be prepended to any
209	CBOR string without changing it's meaning.	500	CBOR string without changing its meaning.
210		501
211	This string is available as $CBOR::XS::MAGIC. This module does not	502	This string is available as $CBOR::XS::MAGIC. This module does not
212	prepend this string tot he CBOR data it generates, but it will ignroe it	503	prepend this string to the CBOR data it generates, but it will ignore it
213	if present, so users can prepend this string as a "file type" indicator	504	if present, so users can prepend this string as a "file type" indicator
214	as required.	505	as required.
215		506
		507	THE CBOR::XS::Tagged CLASS
		508	CBOR has the concept of tagged values - any CBOR value can be tagged
		509	with a numeric 64 bit number, which are centrally administered.
		510
		511	"CBOR::XS" handles a few tags internally when en- or decoding. You can
		512	also create tags yourself by encoding "CBOR::XS::Tagged" objects, and
		513	the decoder will create "CBOR::XS::Tagged" objects itself when it hits
		514	an unknown tag.
		515
		516	These objects are simply blessed array references - the first member of
		517	the array being the numerical tag, the second being the value.
		518
		519	You can interact with "CBOR::XS::Tagged" objects in the following ways:
		520
		521	$tagged = CBOR::XS::tag $tag, $value
		522	This function(!) creates a new "CBOR::XS::Tagged" object using the
		523	given $tag (0..2**64-1) to tag the given $value (which can be any
		524	Perl value that can be encoded in CBOR, including serialisable Perl
		525	objects and "CBOR::XS::Tagged" objects).
		526
		527	$tagged->[0]
		528	$tagged->[0] = $new_tag
		529	$tag = $tagged->tag
		530	$new_tag = $tagged->tag ($new_tag)
		531	Access/mutate the tag.
		532
		533	$tagged->[1]
		534	$tagged->[1] = $new_value
		535	$value = $tagged->value
		536	$new_value = $tagged->value ($new_value)
		537	Access/mutate the tagged value.
		538
		539	EXAMPLES
		540	Here are some examples of "CBOR::XS::Tagged" uses to tag objects.
		541
		542	You can look up CBOR tag value and emanings in the IANA registry at
		543	<http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml>.
		544
		545	Prepend a magic header ($CBOR::XS::MAGIC):
		546
		547	my $cbor = encode_cbor CBOR::XS::tag 55799, $value;
		548	# same as:
		549	my $cbor = $CBOR::XS::MAGIC . encode_cbor $value;
		550
		551	Serialise some URIs and a regex in an array:
		552
		553	my $cbor = encode_cbor [
		554	(CBOR::XS::tag 32, "http://www.nethype.de/"),
		555	(CBOR::XS::tag 32, "http://software.schmorp.de/"),
		556	(CBOR::XS::tag 35, "^[Pp][Ee][Rr][lL]\$"),
		557	];
		558
		559	Wrap CBOR data in CBOR:
		560
		561	my $cbor_cbor = encode_cbor
		562	CBOR::XS::tag 24,
		563	encode_cbor [1, 2, 3];
		564
		565	TAG HANDLING AND EXTENSIONS
		566	This section describes how this module handles specific tagged values
		567	and extensions. If a tag is not mentioned here and no additional filters
		568	are provided for it, then the default handling applies (creating a
		569	CBOR::XS::Tagged object on decoding, and only encoding the tag when
		570	explicitly requested).
		571
		572	Tags not handled specifically are currently converted into a
		573	CBOR::XS::Tagged object, which is simply a blessed array reference
		574	consisting of the numeric tag value followed by the (decoded) CBOR
		575	value.
		576
		577	Future versions of this module reserve the right to special case
		578	additional tags (such as base64url).
		579
		580	ENFORCED TAGS
		581	These tags are always handled when decoding, and their handling cannot
		582	be overriden by the user.
		583
		584	26 (perl-object, <http://cbor.schmorp.de/perl-object>)
		585	These tags are automatically created (and decoded) for serialisable
		586	objects using the "FREEZE/THAW" methods (the Types::Serialier object
		587	serialisation protocol). See "OBJECT SERIALISATION" for details.
		588
		589	28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)
		590	These tags are automatically decoded when encountered, resulting in
		591	shared values in the decoded object. They are only encoded, however,
		592	when "allow_sharable" is enabled.
		593
		594	256, 25 (stringref-namespace, stringref, L
		595	<http://cbor.schmorp.de/stringref>)
		596	These tags are automatically decoded when encountered. They are only
		597	encoded, however, when "pack_strings" is enabled.
		598
		599	22098 (indirection, <http://cbor.schmorp.de/indirection>)
		600	This tag is automatically generated when a reference are encountered
		601	(with the exception of hash and array refernces). It is converted to
		602	a reference when decoding.
		603
		604	55799 (self-describe CBOR, RFC 7049)
		605	This value is not generated on encoding (unless explicitly requested
		606	by the user), and is simply ignored when decoding.
		607
		608	NON-ENFORCED TAGS
		609	These tags have default filters provided when decoding. Their handling
		610	can be overriden by changing the %CBOR::XS::FILTER entry for the tag, or
		611	by providing a custom "filter" callback when decoding.
		612
		613	When they result in decoding into a specific Perl class, the module
		614	usually provides a corresponding "TO_CBOR" method as well.
		615
		616	When any of these need to load additional modules that are not part of
		617	the perl core distribution (e.g. URI), it is (currently) up to the user
		618	to provide these modules. The decoding usually fails with an exception
		619	if the required module cannot be loaded.
		620
		621	2, 3 (positive/negative bignum)
		622	These tags are decoded into Math::BigInt objects. The corresponding
		623	"Math::BigInt::TO_CBOR" method encodes "small" bigints into normal
		624	CBOR integers, and others into positive/negative CBOR bignums.
		625
		626	4, 5 (decimal fraction/bigfloat)
		627	Both decimal fractions and bigfloats are decoded into Math::BigFloat
		628	objects. The corresponding "Math::BigFloat::TO_CBOR" method always
		629	encodes into a decimal fraction.
		630
		631	CBOR cannot represent bigfloats with very large exponents -
		632	conversion of such big float objects is undefined.
		633
		634	Also, NaN and infinities are not encoded properly.
		635
		636	21, 22, 23 (expected later JSON conversion)
		637	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore
		638	these tags.
		639
		640	32 (URI)
		641	These objects decode into URI objects. The corresponding
		642	"URI::TO_CBOR" method again results in a CBOR URI value.
		643
216	CBOR and JSON	644	CBOR and JSON
217	TODO	645	CBOR is supposed to implement a superset of the JSON data model, and is,
		646	with some coercion, able to represent all JSON texts (something that
		647	other "binary JSON" formats such as BSON generally do not support).
		648
		649	CBOR implements some extra hints and support for JSON interoperability,
		650	and the spec offers further guidance for conversion between CBOR and
		651	JSON. None of this is currently implemented in CBOR, and the guidelines
		652	in the spec do not result in correct round-tripping of data. If JSON
		653	interoperability is improved in the future, then the goal will be to
		654	ensure that decoded JSON data will round-trip encoding and decoding to
		655	CBOR intact.
218		656
219	SECURITY CONSIDERATIONS	657	SECURITY CONSIDERATIONS
220	When you are using CBOR in a protocol, talking to untrusted potentially	658	When you are using CBOR in a protocol, talking to untrusted potentially
221	hostile creatures requires relatively few measures.	659	hostile creatures requires relatively few measures.
222		660
…		…
285		723
286	SEE ALSO	724	SEE ALSO
287	The JSON and JSON::XS modules that do similar, but human-readable,	725	The JSON and JSON::XS modules that do similar, but human-readable,
288	serialisation.	726	serialisation.
289		727
		728	The Types::Serialiser module provides the data model for true, false and
		729	error values.
		730
290	AUTHOR	731	AUTHOR
291	Marc Lehmann <schmorp@schmorp.de>	732	Marc Lehmann <schmorp@schmorp.de>
292	http://home.schmorp.de/	733	http://home.schmorp.de/
293		734

Diff Legend

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

Comparing CBOR-XS/README (file contents): Revision 1.3 by root, Sat Oct 26 11:08:34 2013 UTC vs. Revision 1.10 by root, Thu Nov 28 16:09:04 2013 UTC

Diff Legend

Comparing CBOR-XS/README (file contents):
Revision 1.3 by root, Sat Oct 26 11:08:34 2013 UTC vs.
Revision 1.10 by root, Thu Nov 28 16:09:04 2013 UTC