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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.17 by root, Wed Oct 30 10:11:04 2013 UTC vs.
Revision 1.57 by root, Mon Apr 25 21:57:57 2016 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 module is very new, and not very well tested (that's up to
32	you to do). Furthermore, details of the implementation might change freely
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.
39
40	This module converts Perl data structures to the Concise Binary Object	31	This module converts Perl data structures to the Concise Binary Object
41	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation	32	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
42	format that aims to use a superset of the JSON data model, i.e. when you	33	format that aims to use an (almost) superset of the JSON data model, i.e.
43	can represent something in JSON, you should be able to represent it in	34	when you can represent something useful in JSON, you should be able to
44	CBOR.	35	represent it in CBOR.
45		36
46	In short, CBOR is a faster and very compact binary alternative to JSON,	37	In short, CBOR is a faster and quite compact binary alternative to JSON,
47	with the added ability of supporting serialisation of Perl objects. (JSON	38	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	39	often compresses better than CBOR though, so if you plan to compress the
49	data later you might want to compare both formats first).	40	data later and speed is less important you might want to compare both
		41	formats first).
50		42
51	To give you a general idea about speed, with texts in the megabyte range,	43	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	44	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	45	L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
54	data, the worse L<Storable> performs in comparison.	46	data, the worse L<Storable> performs in comparison.
55		47
56	As for compactness, C<CBOR::XS> encoded data structures are usually about	48	Regarding compactness, C<CBOR::XS>-encoded data structures are usually
57	20% smaller than the same data encoded as (compact) JSON or L<Storable>.	49	about 20% smaller than the same data encoded as (compact) JSON or
		50	L<Storable>.
		51
		52	In addition to the core CBOR data format, this module implements a
		53	number of extensions, to support cyclic and shared data structures
		54	(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
		55	C<pack_strings>) and scalar references (always enabled).
58		56
59	The primary goal of this module is to be I<correct> and the secondary goal	57	The primary goal of this module is to be I<correct> and the secondary goal
60	is to be I<fast>. To reach the latter goal it was written in C.	58	is to be I<fast>. To reach the latter goal it was written in C.
61		59
62	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and	60	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
…		…
66		64
67	package CBOR::XS;	65	package CBOR::XS;
68		66
69	use common::sense;	67	use common::sense;
70		68
71	our $VERSION = 0.08;	69	our $VERSION = 1.5;
72	our @ISA = qw(Exporter);	70	our @ISA = qw(Exporter);
73		71
74	our @EXPORT = qw(encode_cbor decode_cbor);	72	our @EXPORT = qw(encode_cbor decode_cbor);
75		73
76	use Exporter;	74	use Exporter;
…		…
113	strings. All boolean flags described below are by default I<disabled>.	111	strings. All boolean flags described below are by default I<disabled>.
114		112
115	The mutators for flags all return the CBOR object again and thus calls can	113	The mutators for flags all return the CBOR object again and thus calls can
116	be chained:	114	be chained:
117		115
118	#TODO
119	my $cbor = CBOR::XS->new->encode ({a => [1,2]});	116	my $cbor = CBOR::XS->new->encode ({a => [1,2]});
120		117
121	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])	118	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
122		119
123	=item $max_depth = $cbor->get_max_depth	120	=item $max_depth = $cbor->get_max_depth
…		…
157	If no argument is given, the limit check will be deactivated (same as when	154	If no argument is given, the limit check will be deactivated (same as when
158	C<0> is specified).	155	C<0> is specified).
159		156
160	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	157	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
161		158
		159	=item $cbor = $cbor->allow_unknown ([$enable])
		160
		161	=item $enabled = $cbor->get_allow_unknown
		162
		163	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		164	exception when it encounters values it cannot represent in CBOR (for
		165	example, filehandles) but instead will encode a CBOR C<error> value.
		166
		167	If C<$enable> is false (the default), then C<encode> will throw an
		168	exception when it encounters anything it cannot encode as CBOR.
		169
		170	This option does not affect C<decode> in any way, and it is recommended to
		171	leave it off unless you know your communications partner.
		172
		173	=item $cbor = $cbor->allow_sharing ([$enable])
		174
		175	=item $enabled = $cbor->get_allow_sharing
		176
		177	If C<$enable> is true (or missing), then C<encode> will not double-encode
		178	values that have been referenced before (e.g. when the same object, such
		179	as an array, is referenced multiple times), but instead will emit a
		180	reference to the earlier value.
		181
		182	This means that such values will only be encoded once, and will not result
		183	in a deep cloning of the value on decode, in decoders supporting the value
		184	sharing extension. This also makes it possible to encode cyclic data
		185	structures (which need C<allow_cycles> to ne enabled to be decoded by this
		186	module).
		187
		188	It is recommended to leave it off unless you know your
		189	communication partner supports the value sharing extensions to CBOR
		190	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
		191	resulting data structure might be unusable.
		192
		193	Detecting shared values incurs a runtime overhead when values are encoded
		194	that have a reference counter large than one, and might unnecessarily
		195	increase the encoded size, as potentially shared values are encode as
		196	shareable whether or not they are actually shared.
		197
		198	At the moment, only targets of references can be shared (e.g. scalars,
		199	arrays or hashes pointed to by a reference). Weirder constructs, such as
		200	an array with multiple "copies" of the I<same> string, which are hard but
		201	not impossible to create in Perl, are not supported (this is the same as
		202	with L<Storable>).
		203
		204	If C<$enable> is false (the default), then C<encode> will encode shared
		205	data structures repeatedly, unsharing them in the process. Cyclic data
		206	structures cannot be encoded in this mode.
		207
		208	This option does not affect C<decode> in any way - shared values and
		209	references will always be decoded properly if present.
		210
		211	=item $cbor = $cbor->allow_cycles ([$enable])
		212
		213	=item $enabled = $cbor->get_allow_cycles
		214
		215	If C<$enable> is true (or missing), then C<decode> will happily decode
		216	self-referential (cyclic) data structures. By default these will not be
		217	decoded, as they need manual cleanup to avoid memory leaks, so code that
		218	isn't prepared for this will not leak memory.
		219
		220	If C<$enable> is false (the default), then C<decode> will throw an error
		221	when it encounters a self-referential/cyclic data structure.
		222
		223	FUTURE DIRECTION: the motivation behind this option is to avoid I<real>
		224	cycles - future versions of this module might chose to decode cyclic data
		225	structures using weak references when this option is off, instead of
		226	throwing an error.
		227
		228	This option does not affect C<encode> in any way - shared values and
		229	references will always be encoded properly if present.
		230
		231	=item $cbor = $cbor->pack_strings ([$enable])
		232
		233	=item $enabled = $cbor->get_pack_strings
		234
		235	If C<$enable> is true (or missing), then C<encode> will try not to encode
		236	the same string twice, but will instead encode a reference to the string
		237	instead. Depending on your data format, this can save a lot of space, but
		238	also results in a very large runtime overhead (expect encoding times to be
		239	2-4 times as high as without).
		240
		241	It is recommended to leave it off unless you know your
		242	communications partner supports the stringref extension to CBOR
		243	(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
		244	resulting data structure might not be usable.
		245
		246	If C<$enable> is false (the default), then C<encode> will encode strings
		247	the standard CBOR way.
		248
		249	This option does not affect C<decode> in any way - string references will
		250	always be decoded properly if present.
		251
		252	=item $cbor = $cbor->text_keys ([$enable])
		253
		254	=item $enabled = $cbor->get_text_keys
		255
		256	If C<$enabled> is true (or missing), then C<encode> will encode all
		257	perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed.
		258
		259	If C<$enable> is false (the default), then C<encode> will encode hash keys
		260	normally - upgraded perl strings (strings internally encoded as UTF-8) as
		261	CBOR text strings, and downgraded perl strings as CBOR byte strings.
		262
		263	This option does not affect C<decode> in any way.
		264
		265	This option is useful for interoperability with CBOR decoders that don't
		266	treat byte strings as a form of text. It is especially useful as Perl
		267	gives very little control over hash keys.
		268
		269	Enabling this option can be slow, as all downgraded hash keys that are
		270	encoded need to be scanned and converted to UTF-8.
		271
		272	=item $cbor = $cbor->text_strings ([$enable])
		273
		274	=item $enabled = $cbor->get_text_strings
		275
		276	This option works similar to C<text_keys>, above, but works on all strings
		277	(including hash keys), so C<text_keys> has no further effect after
		278	enabling C<text_strings>.
		279
		280	If C<$enabled> is true (or missing), then C<encode> will encode all perl
		281	strings as CBOR text strings/UTF-8 strings, upgrading them as needed.
		282
		283	If C<$enable> is false (the default), then C<encode> will encode strings
		284	normally (but see C<text_keys>) - upgraded perl strings (strings
		285	internally encoded as UTF-8) as CBOR text strings, and downgraded perl
		286	strings as CBOR byte strings.
		287
		288	This option does not affect C<decode> in any way.
		289
		290	This option has similar advantages and disadvantages as C<text_keys>. In
		291	addition, this option effectively removes the ability to encode byte
		292	strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely
		293	on this, such as bignum encoding, so this option is mainly useful for very
		294	simple data.
		295
		296	=item $cbor = $cbor->validate_utf8 ([$enable])
		297
		298	=item $enabled = $cbor->get_validate_utf8
		299
		300	If C<$enable> is true (or missing), then C<decode> will validate that
		301	elements (text strings) containing UTF-8 data in fact contain valid UTF-8
		302	data (instead of blindly accepting it). This validation obviously takes
		303	extra time during decoding.
		304
		305	The concept of "valid UTF-8" used is perl's concept, which is a superset
		306	of the official UTF-8.
		307
		308	If C<$enable> is false (the default), then C<decode> will blindly accept
		309	UTF-8 data, marking them as valid UTF-8 in the resulting data structure
		310	regardless of whether that's true or not.
		311
		312	Perl isn't too happy about corrupted UTF-8 in strings, but should
		313	generally not crash or do similarly evil things. Extensions might be not
		314	so forgiving, so it's recommended to turn on this setting if you receive
		315	untrusted CBOR.
		316
		317	This option does not affect C<encode> in any way - strings that are
		318	supposedly valid UTF-8 will simply be dumped into the resulting CBOR
		319	string without checking whether that is, in fact, true or not.
		320
		321	=item $cbor = $cbor->filter ([$cb->($tag, $value)])
		322
		323	=item $cb_or_undef = $cbor->get_filter
		324
		325	Sets or replaces the tagged value decoding filter (when C<$cb> is
		326	specified) or clears the filter (if no argument or C<undef> is provided).
		327
		328	The filter callback is called only during decoding, when a non-enforced
		329	tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a
		330	list of enforced tags). For specific tags, it's often better to provide a
		331	default converter using the C<%CBOR::XS::FILTER> hash (see below).
		332
		333	The first argument is the numerical tag, the second is the (decoded) value
		334	that has been tagged.
		335
		336	The filter function should return either exactly one value, which will
		337	replace the tagged value in the decoded data structure, or no values,
		338	which will result in default handling, which currently means the decoder
		339	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
		340
		341	When the filter is cleared (the default state), the default filter
		342	function, C<CBOR::XS::default_filter>, is used. This function simply looks
		343	up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be
		344	a code reference that is called with tag and value, and is responsible for
		345	decoding the value. If no entry exists, it returns no values.
		346
		347	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
		348	objects, with no other special handling (useful when working with
		349	potentially "unsafe" CBOR data).
		350
		351	CBOR::XS->new->filter (sub { })->decode ($cbor_data);
		352
		353	Example: provide a global filter for tag 1347375694, converting the value
		354	into some string form.
		355
		356	$CBOR::XS::FILTER{1347375694} = sub {
		357	my ($tag, $value);
		358
		359	"tag 1347375694 value $value"
		360	};
		361
162	=item $cbor_data = $cbor->encode ($perl_scalar)	362	=item $cbor_data = $cbor->encode ($perl_scalar)
163		363
164	Converts the given Perl data structure (a scalar value) to its CBOR	364	Converts the given Perl data structure (a scalar value) to its CBOR
165	representation.	365	representation.
166		366
…		…
179	and you need to know where the first CBOR string ends amd the next one	379	and you need to know where the first CBOR string ends amd the next one
180	starts.	380	starts.
181		381
182	CBOR::XS->new->decode_prefix ("......")	382	CBOR::XS->new->decode_prefix ("......")
183	=> ("...", 3)	383	=> ("...", 3)
		384
		385	=back
		386
		387	=head2 INCREMENTAL PARSING
		388
		389	In some cases, there is the need for incremental parsing of JSON
		390	texts. While this module always has to keep both CBOR text and resulting
		391	Perl data structure in memory at one time, it does allow you to parse a
		392	CBOR stream incrementally, using a similar to using "decode_prefix" to see
		393	if a full CBOR object is available, but is much more efficient.
		394
		395	It basically works by parsing as much of a CBOR string as possible - if
		396	the CBOR data is not complete yet, the pasrer will remember where it was,
		397	to be able to restart when more data has been accumulated. Once enough
		398	data is available to either decode a complete CBOR value or raise an
		399	error, a real decode will be attempted.
		400
		401	A typical use case would be a network protocol that consists of sending
		402	and receiving CBOR-encoded messages. The solution that works with CBOR and
		403	about anything else is by prepending a length to every CBOR value, so the
		404	receiver knows how many octets to read. More compact (and slightly slower)
		405	would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
		406	a CBOR value ends, and doesn't need an explicit length.
		407
		408	The following methods help with this:
		409
		410	=over 4
		411
		412	=item @decoded = $cbor->incr_parse ($buffer)
		413
		414	This method attempts to decode exactly one CBOR value from the beginning
		415	of the given C<$buffer>. The value is removed from the C<$buffer> on
		416	success. When C<$buffer> doesn't contain a complete value yet, it returns
		417	nothing. Finally, when the C<$buffer> doesn't start with something
		418	that could ever be a valid CBOR value, it raises an exception, just as
		419	C<decode> would. In the latter case the decoder state is undefined and
		420	must be reset before being able to parse further.
		421
		422	This method modifies the C<$buffer> in place. When no CBOR value can be
		423	decoded, the decoder stores the current string offset. On the next call,
		424	continues decoding at the place where it stopped before. For this to make
		425	sense, the C<$buffer> must begin with the same octets as on previous
		426	unsuccessful calls.
		427
		428	You can call this method in scalar context, in which case it either
		429	returns a decoded value or C<undef>. This makes it impossible to
		430	distinguish between CBOR null values (which decode to C<undef>) and an
		431	unsuccessful decode, which is often acceptable.
		432
		433	=item @decoded = $cbor->incr_parse_multiple ($buffer)
		434
		435	Same as C<incr_parse>, but attempts to decode as many CBOR values as
		436	possible in one go, instead of at most one. Calls to C<incr_parse> and
		437	C<incr_parse_multiple> can be interleaved.
		438
		439	=item $cbor->incr_reset
		440
		441	Resets the incremental decoder. This throws away any saved state, so that
		442	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
		443	a new CBOR value from the beginning of the C<$buffer> again.
		444
		445	This method can be caled at any time, but it I<must> be called if you want
		446	to change your C<$buffer> or there was a decoding error and you want to
		447	reuse the C<$cbor> object for future incremental parsings.
184		448
185	=back	449	=back
186		450
187		451
188	=head1 MAPPING	452	=head1 MAPPING
…		…
206	CBOR integers become (numeric) perl scalars. On perls without 64 bit	470	CBOR integers become (numeric) perl scalars. On perls without 64 bit
207	support, 64 bit integers will be truncated or otherwise corrupted.	471	support, 64 bit integers will be truncated or otherwise corrupted.
208		472
209	=item byte strings	473	=item byte strings
210		474
211	Byte strings will become octet strings in Perl (the byte values 0..255	475	Byte strings will become octet strings in Perl (the Byte values 0..255
212	will simply become characters of the same value in Perl).	476	will simply become characters of the same value in Perl).
213		477
214	=item UTF-8 strings	478	=item UTF-8 strings
215		479
216	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be	480	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
…		…
234	C<Types:Serialiser::false> and C<Types::Serialiser::error>,	498	C<Types:Serialiser::false> and C<Types::Serialiser::error>,
235	respectively. They are overloaded to act almost exactly like the numbers	499	respectively. They are overloaded to act almost exactly like the numbers
236	C<1> and C<0> (for true and false) or to throw an exception on access (for	500	C<1> and C<0> (for true and false) or to throw an exception on access (for
237	error). See the L<Types::Serialiser> manpage for details.	501	error). See the L<Types::Serialiser> manpage for details.
238		502
239	=item CBOR tag 256 (perl object)	503	=item tagged values
240		504
241	The tag value C<256> (TODO: pending iana registration) will be used
242	to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT
243	SERIALISATION>, below, for details.
244
245	=item CBOR tag 55799 (magic header)
246
247	The tag 55799 is ignored (this tag implements the magic header).
248
249	=item other CBOR tags
250
251	Tagged items consists of a numeric tag and another CBOR value. Tags not	505	Tagged items consists of a numeric tag and another CBOR value.
252	handled internally are currently converted into a L<CBOR::XS::Tagged>
253	object, which is simply a blessed array reference consisting of the
254	numeric tag value followed by the (decoded) CBOR value.
255		506
256	In the future, support for user-supplied conversions might get added.	507	See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
		508	for details on which tags are handled how.
257		509
258	=item anything else	510	=item anything else
259		511
260	Anything else (e.g. unsupported simple values) will raise a decoding	512	Anything else (e.g. unsupported simple values) will raise a decoding
261	error.	513	error.
…		…
264		516
265		517
266	=head2 PERL -> CBOR	518	=head2 PERL -> CBOR
267		519
268	The mapping from Perl to CBOR is slightly more difficult, as Perl is a	520	The mapping from Perl to CBOR is slightly more difficult, as Perl is a
269	truly typeless language, so we can only guess which CBOR type is meant by	521	typeless language. That means this module can only guess which CBOR type
270	a Perl value.	522	is meant by a perl value.
271		523
272	=over 4	524	=over 4
273		525
274	=item hash references	526	=item hash references
275		527
276	Perl hash references become CBOR maps. As there is no inherent ordering in	528	Perl hash references become CBOR maps. As there is no inherent ordering in
277	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random	529	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
278	order.	530	order. This order can be different each time a hash is encoded.
279		531
280	Currently, tied hashes will use the indefinite-length format, while normal	532	Currently, tied hashes will use the indefinite-length format, while normal
281	hashes will use the fixed-length format.	533	hashes will use the fixed-length format.
282		534
283	=item array references	535	=item array references
284		536
285	Perl array references become fixed-length CBOR arrays.	537	Perl array references become fixed-length CBOR arrays.
286		538
287	=item other references	539	=item other references
288		540
289	Other unblessed references are generally not allowed and will cause an	541	Other unblessed references will be represented using
290	exception to be thrown, except for references to the integers C<0> and	542	the indirection tag extension (tag value C<22098>,
291	C<1>, which get turned into false and true in CBOR.	543	L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
		544	to be able to decode these values somehow, by either "doing the right
		545	thing", decoding into a generic tagged object, simply ignoring the tag, or
		546	something else.
292		547
293	=item CBOR::XS::Tagged objects	548	=item CBOR::XS::Tagged objects
294		549
295	Objects of this type must be arrays consisting of a single C<[tag, value]>	550	Objects of this type must be arrays consisting of a single C<[tag, value]>
296	pair. The (numerical) tag will be encoded as a CBOR tag, the value will	551	pair. The (numerical) tag will be encoded as a CBOR tag, the value will
297	be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to	552	be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
298	create such objects.	553	create such objects.
299		554
300	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error	555	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
301		556
302	These special values become CBOR true, CBOR false and CBOR undefined	557	These special values become CBOR true, CBOR false and CBOR undefined
…		…
304	if you want.	559	if you want.
305		560
306	=item other blessed objects	561	=item other blessed objects
307		562
308	Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See	563	Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See
309	L<OBJECT SERIALISATION>, below, for details.	564	L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this
		565	module, and L<OBJECT SERIALISATION> for generic object serialisation.
310		566
311	=item simple scalars	567	=item simple scalars
312		568
313	TODO
314	Simple Perl scalars (any scalar that is not a reference) are the most	569	Simple Perl scalars (any scalar that is not a reference) are the most
315	difficult objects to encode: CBOR::XS will encode undefined scalars as	570	difficult objects to encode: CBOR::XS will encode undefined scalars as
316	CBOR null values, scalars that have last been used in a string context	571	CBOR null values, scalars that have last been used in a string context
317	before encoding as CBOR strings, and anything else as number value:	572	before encoding as CBOR strings, and anything else as number value:
318		573
319	# dump as number	574	# dump as number
320	encode_cbor [2] # yields [2]	575	encode_cbor [2] # yields [2]
321	encode_cbor [-3.0e17] # yields [-3e+17]	576	encode_cbor [-3.0e17] # yields [-3e+17]
322	my $value = 5; encode_cbor [$value] # yields [5]	577	my $value = 5; encode_cbor [$value] # yields [5]
323		578
324	# used as string, so dump as string	579	# used as string, so dump as string (either byte or text)
325	print $value;	580	print $value;
326	encode_cbor [$value] # yields ["5"]	581	encode_cbor [$value] # yields ["5"]
327		582
328	# undef becomes null	583	# undef becomes null
329	encode_cbor [undef] # yields [null]	584	encode_cbor [undef] # yields [null]
…		…
332		587
333	my $x = 3.1; # some variable containing a number	588	my $x = 3.1; # some variable containing a number
334	"$x"; # stringified	589	"$x"; # stringified
335	$x .= ""; # another, more awkward way to stringify	590	$x .= ""; # another, more awkward way to stringify
336	print $x; # perl does it for you, too, quite often	591	print $x; # perl does it for you, too, quite often
		592
		593	You can force whether a string is encoded as byte or text string by using
		594	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):
		595
		596	utf8::upgrade $x; # encode $x as text string
		597	utf8::downgrade $x; # encode $x as byte string
		598
		599	Perl doesn't define what operations up- and downgrade strings, so if the
		600	difference between byte and text is important, you should up- or downgrade
		601	your string as late as possible before encoding. You can also force the
		602	use of CBOR text strings by using C<text_keys> or C<text_strings>.
337		603
338	You can force the type to be a CBOR number by numifying it:	604	You can force the type to be a CBOR number by numifying it:
339		605
340	my $x = "3"; # some variable containing a string	606	my $x = "3"; # some variable containing a string
341	$x += 0; # numify it, ensuring it will be dumped as a number	607	$x += 0; # numify it, ensuring it will be dumped as a number
…		…
354		620
355	=back	621	=back
356		622
357	=head2 OBJECT SERIALISATION	623	=head2 OBJECT SERIALISATION
358		624
		625	This module implements both a CBOR-specific and the generic
		626	L<Types::Serialier> object serialisation protocol. The following
		627	subsections explain both methods.
		628
		629	=head3 ENCODING
		630
359	This module knows two way to serialise a Perl object: The CBOR-specific	631	This module knows two way to serialise a Perl object: The CBOR-specific
360	way, and the generic way.	632	way, and the generic way.
361		633
362	Whenever the encoder encounters a Perl object that it cnanot serialise	634	Whenever the encoder encounters a Perl object that it cannot serialise
363	directly (most of them), it will first look up the C<TO_CBOR> method on	635	directly (most of them), it will first look up the C<TO_CBOR> method on
364	it.	636	it.
365		637
366	If it has a C<TO_CBOR> method, it will call it with the object as only	638	If it has a C<TO_CBOR> method, it will call it with the object as only
367	argument, and expects exactly one return value, which it will then	639	argument, and expects exactly one return value, which it will then
…		…
373		645
374	The C<FREEZE> method can return any number of values (i.e. zero or	646	The C<FREEZE> method can return any number of values (i.e. zero or
375	more). These will be encoded as CBOR perl object, together with the	647	more). These will be encoded as CBOR perl object, together with the
376	classname.	648	classname.
377		649
		650	These methods I<MUST NOT> change the data structure that is being
		651	serialised. Failure to comply to this can result in memory corruption -
		652	and worse.
		653
378	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail	654	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
379	with an error.	655	with an error.
380		656
		657	=head3 DECODING
		658
381	Objects encoded via C<TO_CBOR> cannot be automatically decoded, but	659	Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
382	objects encoded via C<FREEZE> can be decoded using the following protocol:	660	but objects encoded via C<FREEZE> can be decoded using the following
		661	protocol:
383		662
384	When an encoded CBOR perl object is encountered by the decoder, it will	663	When an encoded CBOR perl object is encountered by the decoder, it will
385	look up the C<THAW> method, by using the stored classname, and will fail	664	look up the C<THAW> method, by using the stored classname, and will fail
386	if the method cannot be found.	665	if the method cannot be found.
387		666
388	After the lookup it will call the C<THAW> method with the stored classname	667	After the lookup it will call the C<THAW> method with the stored classname
389	as first argument, the constant string C<CBOR> as second argument, and all	668	as first argument, the constant string C<CBOR> as second argument, and all
390	values returned by C<FREEZE> as remaining arguments.	669	values returned by C<FREEZE> as remaining arguments.
391		670
392	=head4 EXAMPLES	671	=head3 EXAMPLES
393		672
394	Here is an example C<TO_CBOR> method:	673	Here is an example C<TO_CBOR> method:
395		674
396	sub My::Object::TO_CBOR {	675	sub My::Object::TO_CBOR {
397	my ($obj) = @_;	676	my ($obj) = @_;
…		…
408		687
409	sub URI::TO_CBOR {	688	sub URI::TO_CBOR {
410	my ($self) = @_;	689	my ($self) = @_;
411	my $uri = "$self"; # stringify uri	690	my $uri = "$self"; # stringify uri
412	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string	691	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
413	CBOR::XS::tagged 32, "$_[0]"	692	CBOR::XS::tag 32, "$_[0]"
414	}	693	}
415		694
416	This will encode URIs as a UTF-8 string with tag 32, which indicates an	695	This will encode URIs as a UTF-8 string with tag 32, which indicates an
417	URI.	696	URI.
418		697
…		…
429	"$self" # encode url string	708	"$self" # encode url string
430	}	709	}
431		710
432	sub URI::THAW {	711	sub URI::THAW {
433	my ($class, $serialiser, $uri) = @_;	712	my ($class, $serialiser, $uri) = @_;
434
435	$class->new ($uri)	713	$class->new ($uri)
436	}	714	}
437		715
438	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For	716	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
439	example, a C<FREEZE> method that returns "type", "id" and "variant" values	717	example, a C<FREEZE> method that returns "type", "id" and "variant" values
…		…
455	=head1 MAGIC HEADER	733	=head1 MAGIC HEADER
456		734
457	There is no way to distinguish CBOR from other formats	735	There is no way to distinguish CBOR from other formats
458	programmatically. To make it easier to distinguish CBOR from other	736	programmatically. To make it easier to distinguish CBOR from other
459	formats, the CBOR specification has a special "magic string" that can be	737	formats, the CBOR specification has a special "magic string" that can be
460	prepended to any CBOR string without changing it's meaning.	738	prepended to any CBOR string without changing its meaning.
461		739
462	This string is available as C<$CBOR::XS::MAGIC>. This module does not	740	This string is available as C<$CBOR::XS::MAGIC>. This module does not
463	prepend this string tot he CBOR data it generates, but it will ignroe it	741	prepend this string to the CBOR data it generates, but it will ignore it
464	if present, so users can prepend this string as a "file type" indicator as	742	if present, so users can prepend this string as a "file type" indicator as
465	required.	743	required.
466		744
467		745
468	=head1 THE CBOR::XS::Tagged CLASS	746	=head1 THE CBOR::XS::Tagged CLASS
…		…
551	Wrap CBOR data in CBOR:	829	Wrap CBOR data in CBOR:
552		830
553	my $cbor_cbor = encode_cbor	831	my $cbor_cbor = encode_cbor
554	CBOR::XS::tag 24,	832	CBOR::XS::tag 24,
555	encode_cbor [1, 2, 3];	833	encode_cbor [1, 2, 3];
		834
		835	=head1 TAG HANDLING AND EXTENSIONS
		836
		837	This section describes how this module handles specific tagged values
		838	and extensions. If a tag is not mentioned here and no additional filters
		839	are provided for it, then the default handling applies (creating a
		840	CBOR::XS::Tagged object on decoding, and only encoding the tag when
		841	explicitly requested).
		842
		843	Tags not handled specifically are currently converted into a
		844	L<CBOR::XS::Tagged> object, which is simply a blessed array reference
		845	consisting of the numeric tag value followed by the (decoded) CBOR value.
		846
		847	Future versions of this module reserve the right to special case
		848	additional tags (such as base64url).
		849
		850	=head2 ENFORCED TAGS
		851
		852	These tags are always handled when decoding, and their handling cannot be
		853	overridden by the user.
		854
		855	=over 4
		856
		857	=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
		858
		859	These tags are automatically created (and decoded) for serialisable
		860	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
		861	serialisation protocol). See L<OBJECT SERIALISATION> for details.
		862
		863	=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
		864
		865	These tags are automatically decoded when encountered (and they do not
		866	result in a cyclic data structure, see C<allow_cycles>), resulting in
		867	shared values in the decoded object. They are only encoded, however, when
		868	C<allow_sharing> is enabled.
		869
		870	Not all shared values can be successfully decoded: values that reference
		871	themselves will I<currently> decode as C<undef> (this is not the same
		872	as a reference pointing to itself, which will be represented as a value
		873	that contains an indirect reference to itself - these will be decoded
		874	properly).
		875
		876	Note that considerably more shared value data structures can be decoded
		877	than will be encoded - currently, only values pointed to by references
		878	will be shared, others will not. While non-reference shared values can be
		879	generated in Perl with some effort, they were considered too unimportant
		880	to be supported in the encoder. The decoder, however, will decode these
		881	values as shared values.
		882
		883	=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
		884
		885	These tags are automatically decoded when encountered. They are only
		886	encoded, however, when C<pack_strings> is enabled.
		887
		888	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
		889
		890	This tag is automatically generated when a reference are encountered (with
		891	the exception of hash and array references). It is converted to a reference
		892	when decoding.
		893
		894	=item 55799 (self-describe CBOR, RFC 7049)
		895
		896	This value is not generated on encoding (unless explicitly requested by
		897	the user), and is simply ignored when decoding.
		898
		899	=back
		900
		901	=head2 NON-ENFORCED TAGS
		902
		903	These tags have default filters provided when decoding. Their handling can
		904	be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
		905	providing a custom C<filter> callback when decoding.
		906
		907	When they result in decoding into a specific Perl class, the module
		908	usually provides a corresponding C<TO_CBOR> method as well.
		909
		910	When any of these need to load additional modules that are not part of the
		911	perl core distribution (e.g. L<URI>), it is (currently) up to the user to
		912	provide these modules. The decoding usually fails with an exception if the
		913	required module cannot be loaded.
		914
		915	=over 4
		916
		917	=item 0, 1 (date/time string, seconds since the epoch)
		918
		919	These tags are decoded into L<Time::Piece> objects. The corresponding
		920	C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
		921
		922	The L<Time::Piece> API is generally surprisingly bad, and fractional
		923	seconds are only accidentally kept intact, so watch out. On the plus side,
		924	the module comes with perl since 5.10, which has to count for something.
		925
		926	=item 2, 3 (positive/negative bignum)
		927
		928	These tags are decoded into L<Math::BigInt> objects. The corresponding
		929	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
		930	integers, and others into positive/negative CBOR bignums.
		931
		932	=item 4, 5, 264, 265 (decimal fraction/bigfloat)
		933
		934	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
		935	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
		936	encodes into a decimal fraction (either tag 4 or 264).
		937
		938	NaN and infinities are not encoded properly, as they cannot be represented
		939	in CBOR.
		940
		941	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		942
		943	=item 21, 22, 23 (expected later JSON conversion)
		944
		945	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
		946	tags.
		947
		948	=item 32 (URI)
		949
		950	These objects decode into L<URI> objects. The corresponding
		951	C<URI::TO_CBOR> method again results in a CBOR URI value.
		952
		953	=back
		954
		955	=cut
556		956
557	=head1 CBOR and JSON	957	=head1 CBOR and JSON
558		958
559	CBOR is supposed to implement a superset of the JSON data model, and is,	959	CBOR is supposed to implement a superset of the JSON data model, and is,
560	with some coercion, able to represent all JSON texts (something that other	960	with some coercion, able to represent all JSON texts (something that other
…		…
602	Also keep in mind that CBOR::XS might leak contents of your Perl data	1002	Also keep in mind that CBOR::XS might leak contents of your Perl data
603	structures in its error messages, so when you serialise sensitive	1003	structures in its error messages, so when you serialise sensitive
604	information you might want to make sure that exceptions thrown by CBOR::XS	1004	information you might want to make sure that exceptions thrown by CBOR::XS
605	will not end up in front of untrusted eyes.	1005	will not end up in front of untrusted eyes.
606		1006
		1007
		1008	=head1 BIGNUM SECURITY CONSIDERATIONS
		1009
		1010	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
		1011	L<Math::BigFloat> that tries to encode the number in the simplest possible
		1012	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
		1013	4) or an arbitrary-exponent decimal fraction (tag 264).
		1014
		1015	It will also understand base-2 bigfloat or arbitrary-exponent bigfloats
		1016	(tags 5 and 265), but it will never generate these on its own.
		1017
		1018	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
		1019	decimal fractions is generally fast. Decoding bigints can be slow for very
		1020	big numbers, and decoding bigfloats or arbitrary-exponent bigfloats can be
		1021	extremely slow (minutes, decades) for large exponents.
		1022
		1023	Additionally, L<Math::BigInt> can take advantage of other bignum
		1024	libraries, such as L<Math::GMP>, which cannot handle big
		1025	floats with large exponents, and might simply abort or crash your program,
		1026	due to their code quality.
		1027
		1028	This can be a concern if you want to parse untrusted CBOR. If it is, you
		1029	need to disable decoding of tag 2 (bigint) and 3 (negative bigint) types,
		1030	which will also disable bigfloat support (to be sure, you can also disable
		1031	types 4, 5, 264 and 265).
		1032
		1033
607	=head1 CBOR IMPLEMENTATION NOTES	1034	=head1 CBOR IMPLEMENTATION NOTES
608		1035
609	This section contains some random implementation notes. They do not	1036	This section contains some random implementation notes. They do not
610	describe guaranteed behaviour, but merely behaviour as-is implemented	1037	describe guaranteed behaviour, but merely behaviour as-is implemented
611	right now.	1038	right now.
…		…
619	Only the double data type is supported for NV data types - when Perl uses	1046	Only the double data type is supported for NV data types - when Perl uses
620	long double to represent floating point values, they might not be encoded	1047	long double to represent floating point values, they might not be encoded
621	properly. Half precision types are accepted, but not encoded.	1048	properly. Half precision types are accepted, but not encoded.
622		1049
623	Strict mode and canonical mode are not implemented.	1050	Strict mode and canonical mode are not implemented.
		1051
		1052
		1053	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
		1054
		1055	On perls that were built without 64 bit integer support (these are rare
		1056	nowadays, even on 32 bit architectures, as all major Perl distributions
		1057	are built with 64 bit integer support), support for any kind of 64 bit
		1058	integer in CBOR is very limited - most likely, these 64 bit values will
		1059	be truncated, corrupted, or otherwise not decoded correctly. This also
		1060	includes string, array and map sizes that are stored as 64 bit integers.
624		1061
625		1062
626	=head1 THREADS	1063	=head1 THREADS
627		1064
628	This module is I<not> guaranteed to be thread safe and there are no	1065	This module is I<not> guaranteed to be thread safe and there are no
…		…
642	Please refrain from using rt.cpan.org or any other bug reporting	1079	Please refrain from using rt.cpan.org or any other bug reporting
643	service. I put the contact address into my modules for a reason.	1080	service. I put the contact address into my modules for a reason.
644		1081
645	=cut	1082	=cut
646		1083
		1084	our %FILTER = (
		1085	0 => sub { # rfc4287 datetime, utf-8
		1086	require Time::Piece;
		1087	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
		1088	# from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
		1089	# else either. Whats incredibe over standard strptime totally escapes me.
		1090	# doesn't do fractional times, either. sigh.
		1091	# In fact, it's all a lie, it uses whatever strptime it wants, and of course,
		1092	# they are all incompatible. The openbsd one simply ignores %z (but according to the
		1093	# docs, it would be much more incredibly flexible indeed. If it worked, that is.).
		1094	scalar eval {
		1095	my $s = $_[1];
		1096
		1097	$s =~ s/Z$/+00:00/;
		1098	$s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
		1099	or die;
		1100
		1101	my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
		1102	my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
		1103
		1104	Time::Piece::gmtime ($d->epoch + $b)
		1105	} \|\| die "corrupted CBOR date/time string ($_[0])";
		1106	},
		1107
		1108	1 => sub { # seconds since the epoch, possibly fractional
		1109	require Time::Piece;
		1110	scalar Time::Piece::gmtime (pop)
		1111	},
		1112
		1113	2 => sub { # pos bigint
		1114	require Math::BigInt;
		1115	Math::BigInt->new ("0x" . unpack "H*", pop)
		1116	},
		1117
		1118	3 => sub { # neg bigint
		1119	require Math::BigInt;
		1120	-Math::BigInt->new ("0x" . unpack "H*", pop)
		1121	},
		1122
		1123	4 => sub { # decimal fraction, array
		1124	require Math::BigFloat;
		1125	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1126	},
		1127
		1128	5 => sub { # bigfloat, array
		1129	require Math::BigFloat;
		1130	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1131	},
		1132
		1133	21 => sub { pop }, # expected conversion to base64url encoding
		1134	22 => sub { pop }, # expected conversion to base64 encoding
		1135	23 => sub { pop }, # expected conversion to base16 encoding
		1136
		1137	# 24 # embedded cbor, byte string
		1138
		1139	32 => sub {
		1140	require URI;
		1141	URI->new (pop)
		1142	},
		1143
		1144	# 33 # base64url rfc4648, utf-8
		1145	# 34 # base64 rfc46484, utf-8
		1146	# 35 # regex pcre/ecma262, utf-8
		1147	# 36 # mime message rfc2045, utf-8
		1148
		1149	264 => sub { # decimal fraction with arbitrary exponent
		1150	require Math::BigFloat;
		1151	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1152	},
		1153
		1154	265 => sub { # bigfloat with arbitrary exponent
		1155	require Math::BigFloat;
		1156	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1157	},
		1158	);
		1159
		1160	sub CBOR::XS::default_filter {
		1161	&{ $FILTER{$_[0]} or return }
		1162	}
		1163
		1164	sub URI::TO_CBOR {
		1165	my $uri = $_[0]->as_string;
		1166	utf8::upgrade $uri;
		1167	tag 32, $uri
		1168	}
		1169
		1170	sub Math::BigInt::TO_CBOR {
		1171	if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
		1172	$_[0]->numify
		1173	} else {
		1174	my $hex = substr $_[0]->as_hex, 2;
		1175	$hex = "0$hex" if 1 & length $hex; # sigh
		1176	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
		1177	}
		1178	}
		1179
		1180	sub Math::BigFloat::TO_CBOR {
		1181	my ($m, $e) = $_[0]->parts;
		1182
		1183	-9223372036854775808 <= $e && $e <= 18446744073709551615
		1184	? tag 4, [$e->numify, $m]
		1185	: tag 264, [$e, $m]
		1186	}
		1187
		1188	sub Time::Piece::TO_CBOR {
		1189	tag 1, 0 + $_[0]->epoch
		1190	}
		1191
647	XSLoader::load "CBOR::XS", $VERSION;	1192	XSLoader::load "CBOR::XS", $VERSION;
648		1193
649	=head1 SEE ALSO	1194	=head1 SEE ALSO
650		1195
651	The L<JSON> and L<JSON::XS> modules that do similar, but human-readable,	1196	The L<JSON> and L<JSON::XS> modules that do similar, but human-readable,

Diff Legend

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

Comparing CBOR-XS/XS.pm (file contents): Revision 1.17 by root, Wed Oct 30 10:11:04 2013 UTC vs. Revision 1.57 by root, Mon Apr 25 21:57:57 2016 UTC

Diff Legend

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.17 by root, Wed Oct 30 10:11:04 2013 UTC vs.
Revision 1.57 by root, Mon Apr 25 21:57:57 2016 UTC