… | |
… | |
12 | $perl_value = decode_cbor $binary_cbor_data; |
12 | $perl_value = decode_cbor $binary_cbor_data; |
13 | |
13 | |
14 | # OO-interface |
14 | # OO-interface |
15 | |
15 | |
16 | $coder = CBOR::XS->new; |
16 | $coder = CBOR::XS->new; |
17 | #TODO |
17 | $binary_cbor_data = $coder->encode ($perl_value); |
|
|
18 | $perl_value = $coder->decode ($binary_cbor_data); |
|
|
19 | |
|
|
20 | # prefix decoding |
|
|
21 | |
|
|
22 | my $many_cbor_strings = ...; |
|
|
23 | while (length $many_cbor_strings) { |
|
|
24 | my ($data, $length) = $cbor->decode_prefix ($many_cbor_strings); |
|
|
25 | # data was decoded |
|
|
26 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
|
|
27 | } |
18 | |
28 | |
19 | =head1 DESCRIPTION |
29 | =head1 DESCRIPTION |
20 | |
30 | |
21 | WARNING! THIS IS A PRE-ALPHA RELEASE! IT WILL CRASH, CORRUPT YOUR DATA AND |
31 | WARNING! This module is very new, and not very well tested (that's up |
22 | EAT YOUR CHILDREN! |
32 | to you to do). Furthermore, details of the implementation might change |
|
|
33 | freely before version 1.0. And lastly, most extensions depend on an IANA |
|
|
34 | assignment, and until that assignment is official, this implementation is |
|
|
35 | not interoperable with other implementations (even future versions of this |
|
|
36 | module) until the assignment is done. |
23 | |
37 | |
24 | This module converts Perl data structures to CBOR and vice versa. Its |
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 |
|
|
41 | 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 |
|
|
43 | can represent something in JSON, you should be able to represent it in |
|
|
44 | CBOR. |
|
|
45 | |
|
|
46 | In short, CBOR is a faster and very compact binary alternative to JSON, |
|
|
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>. |
|
|
58 | |
|
|
59 | In addition to the core CBOR data format, this module implements a number |
|
|
60 | of extensions, to support cyclic and self-referencing data structures |
|
|
61 | (see C<allow_sharing>), string deduplication (see C<pack_strings>) and |
|
|
62 | scalar references (always enabled). |
|
|
63 | |
25 | primary goal is to be I<correct> and its secondary goal is to be |
64 | The primary goal of this module is to be I<correct> and the secondary goal |
26 | I<fast>. To reach the latter goal it was written in C. |
65 | is to be I<fast>. To reach the latter goal it was written in C. |
27 | |
66 | |
28 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
67 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
29 | vice versa. |
68 | vice versa. |
30 | |
69 | |
31 | =cut |
70 | =cut |
32 | |
71 | |
33 | package CBOR::XS; |
72 | package CBOR::XS; |
34 | |
73 | |
35 | use common::sense; |
74 | use common::sense; |
36 | |
75 | |
37 | our $VERSION = 0.02; |
76 | our $VERSION = 0.09; |
38 | our @ISA = qw(Exporter); |
77 | our @ISA = qw(Exporter); |
39 | |
78 | |
40 | our @EXPORT = qw(encode_cbor decode_cbor); |
79 | our @EXPORT = qw(encode_cbor decode_cbor); |
41 | |
80 | |
42 | use Exporter; |
81 | use Exporter; |
43 | use XSLoader; |
82 | use XSLoader; |
44 | |
83 | |
|
|
84 | use Types::Serialiser; |
|
|
85 | |
45 | our $MAGIC = "\xd9\xd9\xf7"; |
86 | our $MAGIC = "\xd9\xd9\xf7"; |
46 | |
87 | |
47 | =head1 FUNCTIONAL INTERFACE |
88 | =head1 FUNCTIONAL INTERFACE |
48 | |
89 | |
49 | The following convenience methods are provided by this module. They are |
90 | The following convenience methods are provided by this module. They are |
… | |
… | |
77 | strings. All boolean flags described below are by default I<disabled>. |
118 | strings. All boolean flags described below are by default I<disabled>. |
78 | |
119 | |
79 | The mutators for flags all return the CBOR object again and thus calls can |
120 | The mutators for flags all return the CBOR object again and thus calls can |
80 | be chained: |
121 | be chained: |
81 | |
122 | |
82 | #TODO |
|
|
83 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
123 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
84 | |
124 | |
85 | =item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
125 | =item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
86 | |
126 | |
87 | =item $max_depth = $cbor->get_max_depth |
127 | =item $max_depth = $cbor->get_max_depth |
… | |
… | |
121 | If no argument is given, the limit check will be deactivated (same as when |
161 | If no argument is given, the limit check will be deactivated (same as when |
122 | C<0> is specified). |
162 | C<0> is specified). |
123 | |
163 | |
124 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
164 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
125 | |
165 | |
|
|
166 | =item $cbor = $cbor->allow_unknown ([$enable]) |
|
|
167 | |
|
|
168 | =item $enabled = $cbor->get_allow_unknown |
|
|
169 | |
|
|
170 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
|
|
171 | exception when it encounters values it cannot represent in CBOR (for |
|
|
172 | example, filehandles) but instead will encode a CBOR C<error> value. |
|
|
173 | |
|
|
174 | If C<$enable> is false (the default), then C<encode> will throw an |
|
|
175 | exception when it encounters anything it cannot encode as CBOR. |
|
|
176 | |
|
|
177 | This option does not affect C<decode> in any way, and it is recommended to |
|
|
178 | leave it off unless you know your communications partner. |
|
|
179 | |
|
|
180 | =item $cbor = $cbor->allow_sharing ([$enable]) |
|
|
181 | |
|
|
182 | =item $enabled = $cbor->get_allow_sharing |
|
|
183 | |
|
|
184 | If C<$enable> is true (or missing), then C<encode> will not double-encode |
|
|
185 | values that have been referenced before (e.g. when the same object, such |
|
|
186 | as an array, is referenced multiple times), but instead will emit a |
|
|
187 | reference to the earlier value. |
|
|
188 | |
|
|
189 | This means that such values will only be encoded once, and will not result |
|
|
190 | in a deep cloning of the value on decode, in decoders supporting the value |
|
|
191 | sharing extension. This also makes it possible to encode cyclic data |
|
|
192 | structures. |
|
|
193 | |
|
|
194 | It is recommended to leave it off unless you know your |
|
|
195 | communication partner supports the value sharing extensions to CBOR |
|
|
196 | (L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the |
|
|
197 | resulting data structure might be unusable. |
|
|
198 | |
|
|
199 | Detecting shared values incurs a runtime overhead when values are encoded |
|
|
200 | that have a reference counter large than one, and might unnecessarily |
|
|
201 | increase the encoded size, as potentially shared values are encode as |
|
|
202 | sharable whether or not they are actually shared. |
|
|
203 | |
|
|
204 | At the moment, only targets of references can be shared (e.g. scalars, |
|
|
205 | arrays or hashes pointed to by a reference). Weirder constructs, such as |
|
|
206 | an array with multiple "copies" of the I<same> string, which are hard but |
|
|
207 | not impossible to create in Perl, are not supported (this is the same as |
|
|
208 | with L<Storable>). |
|
|
209 | |
|
|
210 | If C<$enable> is false (the default), then C<encode> will encode shared |
|
|
211 | data structures repeatedly, unsharing them in the process. Cyclic data |
|
|
212 | structures cannot be encoded in this mode. |
|
|
213 | |
|
|
214 | This option does not affect C<decode> in any way - shared values and |
|
|
215 | references will always be decoded properly if present. |
|
|
216 | |
|
|
217 | =item $cbor = $cbor->pack_strings ([$enable]) |
|
|
218 | |
|
|
219 | =item $enabled = $cbor->get_pack_strings |
|
|
220 | |
|
|
221 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
|
|
222 | the same string twice, but will instead encode a reference to the string |
|
|
223 | instead. Depending on your data format, this can save a lot of space, but |
|
|
224 | also results in a very large runtime overhead (expect encoding times to be |
|
|
225 | 2-4 times as high as without). |
|
|
226 | |
|
|
227 | It is recommended to leave it off unless you know your |
|
|
228 | communications partner supports the stringref extension to CBOR |
|
|
229 | (L<http://cbor.schmorp.de/stringref>), as without decoder support, the |
|
|
230 | resulting data structure might not be usable. |
|
|
231 | |
|
|
232 | If C<$enable> is false (the default), then C<encode> will encode strings |
|
|
233 | the standard CBOR way. |
|
|
234 | |
|
|
235 | This option does not affect C<decode> in any way - string references will |
|
|
236 | always be decoded properly if present. |
|
|
237 | |
|
|
238 | =item $cbor = $cbor->filter ([$cb->($tag, $value)]) |
|
|
239 | |
|
|
240 | =item $cb_or_undef = $cbor->get_filter |
|
|
241 | |
|
|
242 | Sets or replaces the tagged value decoding filter (when C<$cb> is |
|
|
243 | specified) or clears the filter (if no argument or C<undef> is provided). |
|
|
244 | |
|
|
245 | The filter callback is called only during decoding, when a non-enforced |
|
|
246 | tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a |
|
|
247 | list of enforced tags). For specific tags, it's often better to provide a |
|
|
248 | default converter using the C<%CBOR::XS::FILTER> hash (see below). |
|
|
249 | |
|
|
250 | The first argument is the numerical tag, the second is the (decoded) value |
|
|
251 | that has been tagged. |
|
|
252 | |
|
|
253 | The filter function should return either exactly one value, which will |
|
|
254 | replace the tagged value in the decoded data structure, or no values, |
|
|
255 | which will result in default handling, which currently means the decoder |
|
|
256 | creates a C<CBOR::XS::Tagged> object to hold the tag and the value. |
|
|
257 | |
|
|
258 | When the filter is cleared (the default state), the default filter |
|
|
259 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
|
|
260 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
|
|
261 | a code reference that is called with tag and value, and is responsible for |
|
|
262 | decoding the value. If no entry exists, it returns no values. |
|
|
263 | |
|
|
264 | Example: decode all tags not handled internally into CBOR::XS::Tagged |
|
|
265 | objects, with no other special handling (useful when working with |
|
|
266 | potentially "unsafe" CBOR data). |
|
|
267 | |
|
|
268 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
|
|
269 | |
|
|
270 | Example: provide a global filter for tag 1347375694, converting the value |
|
|
271 | into some string form. |
|
|
272 | |
|
|
273 | $CBOR::XS::FILTER{1347375694} = sub { |
|
|
274 | my ($tag, $value); |
|
|
275 | |
|
|
276 | "tag 1347375694 value $value" |
|
|
277 | }; |
|
|
278 | |
126 | =item $cbor_data = $cbor->encode ($perl_scalar) |
279 | =item $cbor_data = $cbor->encode ($perl_scalar) |
127 | |
280 | |
128 | Converts the given Perl data structure (a scalar value) to its CBOR |
281 | Converts the given Perl data structure (a scalar value) to its CBOR |
129 | representation. |
282 | representation. |
130 | |
283 | |
… | |
… | |
170 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
323 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
171 | support, 64 bit integers will be truncated or otherwise corrupted. |
324 | support, 64 bit integers will be truncated or otherwise corrupted. |
172 | |
325 | |
173 | =item byte strings |
326 | =item byte strings |
174 | |
327 | |
175 | Byte strings will become octet strings in Perl (the byte values 0..255 |
328 | Byte strings will become octet strings in Perl (the Byte values 0..255 |
176 | will simply become characters of the same value in Perl). |
329 | will simply become characters of the same value in Perl). |
177 | |
330 | |
178 | =item UTF-8 strings |
331 | =item UTF-8 strings |
179 | |
332 | |
180 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
333 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
… | |
… | |
186 | |
339 | |
187 | CBOR arrays and CBOR maps will be converted into references to a Perl |
340 | CBOR arrays and CBOR maps will be converted into references to a Perl |
188 | array or hash, respectively. The keys of the map will be stringified |
341 | array or hash, respectively. The keys of the map will be stringified |
189 | during this process. |
342 | during this process. |
190 | |
343 | |
|
|
344 | =item null |
|
|
345 | |
|
|
346 | CBOR null becomes C<undef> in Perl. |
|
|
347 | |
191 | =item true, false |
348 | =item true, false, undefined |
192 | |
349 | |
193 | These CBOR values become C<CBOR::XS::true> and C<CBOR::XS::false>, |
350 | These CBOR values become C<Types:Serialiser::true>, |
|
|
351 | C<Types:Serialiser::false> and C<Types::Serialiser::error>, |
194 | respectively. They are overloaded to act almost exactly like the numbers |
352 | respectively. They are overloaded to act almost exactly like the numbers |
195 | C<1> and C<0>. You can check whether a scalar is a CBOR boolean by using |
353 | C<1> and C<0> (for true and false) or to throw an exception on access (for |
196 | the C<CBOR::XS::is_bool> function. |
354 | error). See the L<Types::Serialiser> manpage for details. |
197 | |
355 | |
198 | =item null, undefined |
356 | =item tagged values |
199 | |
357 | |
200 | CBOR null and undefined values becomes C<undef> in Perl (in the future, |
|
|
201 | Undefined may raise an exception or something else). |
|
|
202 | |
|
|
203 | =item tags |
|
|
204 | |
|
|
205 | Tagged items consists of a numeric tag and another CBOR value. The tag |
358 | Tagged items consists of a numeric tag and another CBOR value. |
206 | 55799 is ignored (this tag implements the magic header). |
|
|
207 | |
359 | |
208 | All other tags are currently converted into a L<CBOR::XS::Tagged> object, |
360 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
209 | which is simply a blessed array reference consistsing of the numeric tag |
361 | for details. |
210 | value followed by the (decoded) BOR value. |
|
|
211 | |
362 | |
212 | =item anything else |
363 | =item anything else |
213 | |
364 | |
214 | Anything else (e.g. unsupported simple values) will raise a decoding |
365 | Anything else (e.g. unsupported simple values) will raise a decoding |
215 | error. |
366 | error. |
… | |
… | |
245 | C<1>, which get turned into false and true in CBOR. |
396 | C<1>, which get turned into false and true in CBOR. |
246 | |
397 | |
247 | =item CBOR::XS::Tagged objects |
398 | =item CBOR::XS::Tagged objects |
248 | |
399 | |
249 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
400 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
250 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will be |
401 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
251 | encoded as appropriate for the value. |
402 | be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to |
|
|
403 | create such objects. |
252 | |
404 | |
253 | =item CBOR::XS::true, CBOR::XS::false |
405 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
254 | |
406 | |
255 | These special values become CBOR true and CBOR false values, |
407 | These special values become CBOR true, CBOR false and CBOR undefined |
256 | respectively. You can also use C<\1> and C<\0> directly if you want. |
408 | values, respectively. You can also use C<\1>, C<\0> and C<\undef> directly |
|
|
409 | if you want. |
257 | |
410 | |
258 | =item blessed objects |
411 | =item other blessed objects |
259 | |
412 | |
260 | Other blessed objects currently need to have a C<TO_CBOR> method. It |
413 | Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See |
261 | will be called on every object that is being serialised, and must return |
414 | L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this |
262 | something that can be encoded in CBOR. |
415 | module, and L<OBJECT SERIALISATION> for generic object serialisation. |
263 | |
416 | |
264 | =item simple scalars |
417 | =item simple scalars |
265 | |
418 | |
266 | TODO |
|
|
267 | Simple Perl scalars (any scalar that is not a reference) are the most |
419 | Simple Perl scalars (any scalar that is not a reference) are the most |
268 | difficult objects to encode: CBOR::XS will encode undefined scalars as |
420 | difficult objects to encode: CBOR::XS will encode undefined scalars as |
269 | CBOR null values, scalars that have last been used in a string context |
421 | CBOR null values, scalars that have last been used in a string context |
270 | before encoding as CBOR strings, and anything else as number value: |
422 | before encoding as CBOR strings, and anything else as number value: |
271 | |
423 | |
272 | # dump as number |
424 | # dump as number |
273 | encode_cbor [2] # yields [2] |
425 | encode_cbor [2] # yields [2] |
274 | encode_cbor [-3.0e17] # yields [-3e+17] |
426 | encode_cbor [-3.0e17] # yields [-3e+17] |
275 | my $value = 5; encode_cbor [$value] # yields [5] |
427 | my $value = 5; encode_cbor [$value] # yields [5] |
276 | |
428 | |
277 | # used as string, so dump as string |
429 | # used as string, so dump as string (either byte or text) |
278 | print $value; |
430 | print $value; |
279 | encode_cbor [$value] # yields ["5"] |
431 | encode_cbor [$value] # yields ["5"] |
280 | |
432 | |
281 | # undef becomes null |
433 | # undef becomes null |
282 | encode_cbor [undef] # yields [null] |
434 | encode_cbor [undef] # yields [null] |
… | |
… | |
285 | |
437 | |
286 | my $x = 3.1; # some variable containing a number |
438 | my $x = 3.1; # some variable containing a number |
287 | "$x"; # stringified |
439 | "$x"; # stringified |
288 | $x .= ""; # another, more awkward way to stringify |
440 | $x .= ""; # another, more awkward way to stringify |
289 | print $x; # perl does it for you, too, quite often |
441 | print $x; # perl does it for you, too, quite often |
|
|
442 | |
|
|
443 | You can force whether a string ie encoded as byte or text string by using |
|
|
444 | C<utf8::upgrade> and C<utf8::downgrade>): |
|
|
445 | |
|
|
446 | utf8::upgrade $x; # encode $x as text string |
|
|
447 | utf8::downgrade $x; # encode $x as byte string |
|
|
448 | |
|
|
449 | Perl doesn't define what operations up- and downgrade strings, so if the |
|
|
450 | difference between byte and text is important, you should up- or downgrade |
|
|
451 | your string as late as possible before encoding. |
290 | |
452 | |
291 | You can force the type to be a CBOR number by numifying it: |
453 | You can force the type to be a CBOR number by numifying it: |
292 | |
454 | |
293 | my $x = "3"; # some variable containing a string |
455 | my $x = "3"; # some variable containing a string |
294 | $x += 0; # numify it, ensuring it will be dumped as a number |
456 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
305 | represent numerical values are supported, but might suffer loss of |
467 | represent numerical values are supported, but might suffer loss of |
306 | precision. |
468 | precision. |
307 | |
469 | |
308 | =back |
470 | =back |
309 | |
471 | |
|
|
472 | =head2 OBJECT SERIALISATION |
310 | |
473 | |
|
|
474 | This module knows two way to serialise a Perl object: The CBOR-specific |
|
|
475 | way, and the generic way. |
|
|
476 | |
|
|
477 | Whenever the encoder encounters a Perl object that it cnanot serialise |
|
|
478 | directly (most of them), it will first look up the C<TO_CBOR> method on |
|
|
479 | it. |
|
|
480 | |
|
|
481 | If it has a C<TO_CBOR> method, it will call it with the object as only |
|
|
482 | argument, and expects exactly one return value, which it will then |
|
|
483 | substitute and encode it in the place of the object. |
|
|
484 | |
|
|
485 | Otherwise, it will look up the C<FREEZE> method. If it exists, it will |
|
|
486 | call it with the object as first argument, and the constant string C<CBOR> |
|
|
487 | as the second argument, to distinguish it from other serialisers. |
|
|
488 | |
|
|
489 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
490 | more). These will be encoded as CBOR perl object, together with the |
|
|
491 | classname. |
|
|
492 | |
|
|
493 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
|
|
494 | with an error. |
|
|
495 | |
|
|
496 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
|
|
497 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
|
|
498 | |
|
|
499 | When an encoded CBOR perl object is encountered by the decoder, it will |
|
|
500 | look up the C<THAW> method, by using the stored classname, and will fail |
|
|
501 | if the method cannot be found. |
|
|
502 | |
|
|
503 | After the lookup it will call the C<THAW> method with the stored classname |
|
|
504 | as first argument, the constant string C<CBOR> as second argument, and all |
|
|
505 | values returned by C<FREEZE> as remaining arguments. |
|
|
506 | |
|
|
507 | =head4 EXAMPLES |
|
|
508 | |
|
|
509 | Here is an example C<TO_CBOR> method: |
|
|
510 | |
|
|
511 | sub My::Object::TO_CBOR { |
|
|
512 | my ($obj) = @_; |
|
|
513 | |
|
|
514 | ["this is a serialised My::Object object", $obj->{id}] |
|
|
515 | } |
|
|
516 | |
|
|
517 | When a C<My::Object> is encoded to CBOR, it will instead encode a simple |
|
|
518 | array with two members: a string, and the "object id". Decoding this CBOR |
|
|
519 | string will yield a normal perl array reference in place of the object. |
|
|
520 | |
|
|
521 | A more useful and practical example would be a serialisation method for |
|
|
522 | the URI module. CBOR has a custom tag value for URIs, namely 32: |
|
|
523 | |
|
|
524 | sub URI::TO_CBOR { |
|
|
525 | my ($self) = @_; |
|
|
526 | my $uri = "$self"; # stringify uri |
|
|
527 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
|
|
528 | CBOR::XS::tagged 32, "$_[0]" |
|
|
529 | } |
|
|
530 | |
|
|
531 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
|
|
532 | URI. |
|
|
533 | |
|
|
534 | Decoding such an URI will not (currently) give you an URI object, but |
|
|
535 | instead a CBOR::XS::Tagged object with tag number 32 and the string - |
|
|
536 | exactly what was returned by C<TO_CBOR>. |
|
|
537 | |
|
|
538 | To serialise an object so it can automatically be deserialised, you need |
|
|
539 | to use C<FREEZE> and C<THAW>. To take the URI module as example, this |
|
|
540 | would be a possible implementation: |
|
|
541 | |
|
|
542 | sub URI::FREEZE { |
|
|
543 | my ($self, $serialiser) = @_; |
|
|
544 | "$self" # encode url string |
|
|
545 | } |
|
|
546 | |
|
|
547 | sub URI::THAW { |
|
|
548 | my ($class, $serialiser, $uri) = @_; |
|
|
549 | |
|
|
550 | $class->new ($uri) |
|
|
551 | } |
|
|
552 | |
|
|
553 | Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For |
|
|
554 | example, a C<FREEZE> method that returns "type", "id" and "variant" values |
|
|
555 | would cause an invocation of C<THAW> with 5 arguments: |
|
|
556 | |
|
|
557 | sub My::Object::FREEZE { |
|
|
558 | my ($self, $serialiser) = @_; |
|
|
559 | |
|
|
560 | ($self->{type}, $self->{id}, $self->{variant}) |
|
|
561 | } |
|
|
562 | |
|
|
563 | sub My::Object::THAW { |
|
|
564 | my ($class, $serialiser, $type, $id, $variant) = @_; |
|
|
565 | |
|
|
566 | $class-<new (type => $type, id => $id, variant => $variant) |
|
|
567 | } |
|
|
568 | |
|
|
569 | |
311 | =head2 MAGIC HEADER |
570 | =head1 MAGIC HEADER |
312 | |
571 | |
313 | There is no way to distinguish CBOR from other formats |
572 | There is no way to distinguish CBOR from other formats |
314 | programmatically. To make it easier to distinguish CBOR from other |
573 | programmatically. To make it easier to distinguish CBOR from other |
315 | formats, the CBOR specification has a special "magic string" that can be |
574 | formats, the CBOR specification has a special "magic string" that can be |
316 | prepended to any CBOR string without changing it's meaning. |
575 | prepended to any CBOR string without changing its meaning. |
317 | |
576 | |
318 | This string is available as C<$CBOR::XS::MAGIC>. This module does not |
577 | This string is available as C<$CBOR::XS::MAGIC>. This module does not |
319 | prepend this string tot he CBOR data it generates, but it will ignroe it |
578 | prepend this string to the CBOR data it generates, but it will ignore it |
320 | if present, so users can prepend this string as a "file type" indicator as |
579 | if present, so users can prepend this string as a "file type" indicator as |
321 | required. |
580 | required. |
322 | |
581 | |
323 | |
582 | |
|
|
583 | =head1 THE CBOR::XS::Tagged CLASS |
|
|
584 | |
|
|
585 | CBOR has the concept of tagged values - any CBOR value can be tagged with |
|
|
586 | a numeric 64 bit number, which are centrally administered. |
|
|
587 | |
|
|
588 | C<CBOR::XS> handles a few tags internally when en- or decoding. You can |
|
|
589 | also create tags yourself by encoding C<CBOR::XS::Tagged> objects, and the |
|
|
590 | decoder will create C<CBOR::XS::Tagged> objects itself when it hits an |
|
|
591 | unknown tag. |
|
|
592 | |
|
|
593 | These objects are simply blessed array references - the first member of |
|
|
594 | the array being the numerical tag, the second being the value. |
|
|
595 | |
|
|
596 | You can interact with C<CBOR::XS::Tagged> objects in the following ways: |
|
|
597 | |
|
|
598 | =over 4 |
|
|
599 | |
|
|
600 | =item $tagged = CBOR::XS::tag $tag, $value |
|
|
601 | |
|
|
602 | This function(!) creates a new C<CBOR::XS::Tagged> object using the given |
|
|
603 | C<$tag> (0..2**64-1) to tag the given C<$value> (which can be any Perl |
|
|
604 | value that can be encoded in CBOR, including serialisable Perl objects and |
|
|
605 | C<CBOR::XS::Tagged> objects). |
|
|
606 | |
|
|
607 | =item $tagged->[0] |
|
|
608 | |
|
|
609 | =item $tagged->[0] = $new_tag |
|
|
610 | |
|
|
611 | =item $tag = $tagged->tag |
|
|
612 | |
|
|
613 | =item $new_tag = $tagged->tag ($new_tag) |
|
|
614 | |
|
|
615 | Access/mutate the tag. |
|
|
616 | |
|
|
617 | =item $tagged->[1] |
|
|
618 | |
|
|
619 | =item $tagged->[1] = $new_value |
|
|
620 | |
|
|
621 | =item $value = $tagged->value |
|
|
622 | |
|
|
623 | =item $new_value = $tagged->value ($new_value) |
|
|
624 | |
|
|
625 | Access/mutate the tagged value. |
|
|
626 | |
|
|
627 | =back |
|
|
628 | |
|
|
629 | =cut |
|
|
630 | |
|
|
631 | sub tag($$) { |
|
|
632 | bless [@_], CBOR::XS::Tagged::; |
|
|
633 | } |
|
|
634 | |
|
|
635 | sub CBOR::XS::Tagged::tag { |
|
|
636 | $_[0][0] = $_[1] if $#_; |
|
|
637 | $_[0][0] |
|
|
638 | } |
|
|
639 | |
|
|
640 | sub CBOR::XS::Tagged::value { |
|
|
641 | $_[0][1] = $_[1] if $#_; |
|
|
642 | $_[0][1] |
|
|
643 | } |
|
|
644 | |
|
|
645 | =head2 EXAMPLES |
|
|
646 | |
|
|
647 | Here are some examples of C<CBOR::XS::Tagged> uses to tag objects. |
|
|
648 | |
|
|
649 | You can look up CBOR tag value and emanings in the IANA registry at |
|
|
650 | L<http://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml>. |
|
|
651 | |
|
|
652 | Prepend a magic header (C<$CBOR::XS::MAGIC>): |
|
|
653 | |
|
|
654 | my $cbor = encode_cbor CBOR::XS::tag 55799, $value; |
|
|
655 | # same as: |
|
|
656 | my $cbor = $CBOR::XS::MAGIC . encode_cbor $value; |
|
|
657 | |
|
|
658 | Serialise some URIs and a regex in an array: |
|
|
659 | |
|
|
660 | my $cbor = encode_cbor [ |
|
|
661 | (CBOR::XS::tag 32, "http://www.nethype.de/"), |
|
|
662 | (CBOR::XS::tag 32, "http://software.schmorp.de/"), |
|
|
663 | (CBOR::XS::tag 35, "^[Pp][Ee][Rr][lL]\$"), |
|
|
664 | ]; |
|
|
665 | |
|
|
666 | Wrap CBOR data in CBOR: |
|
|
667 | |
|
|
668 | my $cbor_cbor = encode_cbor |
|
|
669 | CBOR::XS::tag 24, |
|
|
670 | encode_cbor [1, 2, 3]; |
|
|
671 | |
|
|
672 | =head1 TAG HANDLING AND EXTENSIONS |
|
|
673 | |
|
|
674 | This section describes how this module handles specific tagged values |
|
|
675 | and extensions. If a tag is not mentioned here and no additional filters |
|
|
676 | are provided for it, then the default handling applies (creating a |
|
|
677 | CBOR::XS::Tagged object on decoding, and only encoding the tag when |
|
|
678 | explicitly requested). |
|
|
679 | |
|
|
680 | Tags not handled specifically are currently converted into a |
|
|
681 | L<CBOR::XS::Tagged> object, which is simply a blessed array reference |
|
|
682 | consisting of the numeric tag value followed by the (decoded) CBOR value. |
|
|
683 | |
|
|
684 | Future versions of this module reserve the right to special case |
|
|
685 | additional tags (such as base64url). |
|
|
686 | |
|
|
687 | =head2 ENFORCED TAGS |
|
|
688 | |
|
|
689 | These tags are always handled when decoding, and their handling cannot be |
|
|
690 | overriden by the user. |
|
|
691 | |
|
|
692 | =over 4 |
|
|
693 | |
|
|
694 | =item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>) |
|
|
695 | |
|
|
696 | These tags are automatically created (and decoded) for serialisable |
|
|
697 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
|
|
698 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
|
|
699 | |
|
|
700 | =item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
|
|
701 | |
|
|
702 | These tags are automatically decoded when encountered, resulting in |
|
|
703 | shared values in the decoded object. They are only encoded, however, when |
|
|
704 | C<allow_sharable> is enabled. |
|
|
705 | |
|
|
706 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
|
|
707 | |
|
|
708 | These tags are automatically decoded when encountered. They are only |
|
|
709 | encoded, however, when C<pack_strings> is enabled. |
|
|
710 | |
|
|
711 | =item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) |
|
|
712 | |
|
|
713 | This tag is automatically generated when a reference are encountered (with |
|
|
714 | the exception of hash and array refernces). It is converted to a reference |
|
|
715 | when decoding. |
|
|
716 | |
|
|
717 | =item 55799 (self-describe CBOR, RFC 7049) |
|
|
718 | |
|
|
719 | This value is not generated on encoding (unless explicitly requested by |
|
|
720 | the user), and is simply ignored when decoding. |
|
|
721 | |
|
|
722 | =back |
|
|
723 | |
|
|
724 | =head2 NON-ENFORCED TAGS |
|
|
725 | |
|
|
726 | These tags have default filters provided when decoding. Their handling can |
|
|
727 | be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by |
|
|
728 | providing a custom C<filter> callback when decoding. |
|
|
729 | |
|
|
730 | When they result in decoding into a specific Perl class, the module |
|
|
731 | usually provides a corresponding C<TO_CBOR> method as well. |
|
|
732 | |
|
|
733 | When any of these need to load additional modules that are not part of the |
|
|
734 | perl core distribution (e.g. L<URI>), it is (currently) up to the user to |
|
|
735 | provide these modules. The decoding usually fails with an exception if the |
|
|
736 | required module cannot be loaded. |
|
|
737 | |
|
|
738 | =over 4 |
|
|
739 | |
|
|
740 | =item 2, 3 (positive/negative bignum) |
|
|
741 | |
|
|
742 | These tags are decoded into L<Math::BigInt> objects. The corresponding |
|
|
743 | C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR |
|
|
744 | integers, and others into positive/negative CBOR bignums. |
|
|
745 | |
|
|
746 | =item 4, 5 (decimal fraction/bigfloat) |
|
|
747 | |
|
|
748 | Both decimal fractions and bigfloats are decoded into L<Math::BigFloat> |
|
|
749 | objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always> |
|
|
750 | encodes into a decimal fraction. |
|
|
751 | |
|
|
752 | CBOR cannot represent bigfloats with I<very> large exponents - conversion |
|
|
753 | of such big float objects is undefined. |
|
|
754 | |
|
|
755 | Also, NaN and infinities are not encoded properly. |
|
|
756 | |
|
|
757 | =item 21, 22, 23 (expected later JSON conversion) |
|
|
758 | |
|
|
759 | CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these |
|
|
760 | tags. |
|
|
761 | |
|
|
762 | =item 32 (URI) |
|
|
763 | |
|
|
764 | These objects decode into L<URI> objects. The corresponding |
|
|
765 | C<URI::TO_CBOR> method again results in a CBOR URI value. |
|
|
766 | |
|
|
767 | =back |
|
|
768 | |
|
|
769 | =cut |
|
|
770 | |
|
|
771 | our %FILTER = ( |
|
|
772 | # 0 # rfc4287 datetime, utf-8 |
|
|
773 | # 1 # unix timestamp, any |
|
|
774 | |
|
|
775 | 2 => sub { # pos bigint |
|
|
776 | require Math::BigInt; |
|
|
777 | Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
778 | }, |
|
|
779 | |
|
|
780 | 3 => sub { # neg bigint |
|
|
781 | require Math::BigInt; |
|
|
782 | -Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
783 | }, |
|
|
784 | |
|
|
785 | 4 => sub { # decimal fraction, array |
|
|
786 | require Math::BigFloat; |
|
|
787 | Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
|
|
788 | }, |
|
|
789 | |
|
|
790 | 5 => sub { # bigfloat, array |
|
|
791 | require Math::BigFloat; |
|
|
792 | scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2) |
|
|
793 | }, |
|
|
794 | |
|
|
795 | 21 => sub { pop }, # expected conversion to base64url encoding |
|
|
796 | 22 => sub { pop }, # expected conversion to base64 encoding |
|
|
797 | 23 => sub { pop }, # expected conversion to base16 encoding |
|
|
798 | |
|
|
799 | # 24 # embedded cbor, byte string |
|
|
800 | |
|
|
801 | 32 => sub { |
|
|
802 | require URI; |
|
|
803 | URI->new (pop) |
|
|
804 | }, |
|
|
805 | |
|
|
806 | # 33 # base64url rfc4648, utf-8 |
|
|
807 | # 34 # base64 rfc46484, utf-8 |
|
|
808 | # 35 # regex pcre/ecma262, utf-8 |
|
|
809 | # 36 # mime message rfc2045, utf-8 |
|
|
810 | ); |
|
|
811 | |
|
|
812 | |
324 | =head2 CBOR and JSON |
813 | =head1 CBOR and JSON |
325 | |
814 | |
326 | CBOR is supposed to implement a superset of the JSON data model, and is, |
815 | CBOR is supposed to implement a superset of the JSON data model, and is, |
327 | with some coercion, able to represent all JSON texts (something that other |
816 | with some coercion, able to represent all JSON texts (something that other |
328 | "binary JSON" formats such as BSON generally do not support). |
817 | "binary JSON" formats such as BSON generally do not support). |
329 | |
818 | |
… | |
… | |
409 | Please refrain from using rt.cpan.org or any other bug reporting |
898 | Please refrain from using rt.cpan.org or any other bug reporting |
410 | service. I put the contact address into my modules for a reason. |
899 | service. I put the contact address into my modules for a reason. |
411 | |
900 | |
412 | =cut |
901 | =cut |
413 | |
902 | |
414 | our $true = do { bless \(my $dummy = 1), "CBOR::XS::Boolean" }; |
903 | our %FILTER = ( |
415 | our $false = do { bless \(my $dummy = 0), "CBOR::XS::Boolean" }; |
904 | # 0 # rfc4287 datetime, utf-8 |
|
|
905 | # 1 # unix timestamp, any |
416 | |
906 | |
417 | sub true() { $true } |
907 | 2 => sub { # pos bigint |
418 | sub false() { $false } |
908 | require Math::BigInt; |
|
|
909 | Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
910 | }, |
419 | |
911 | |
420 | sub is_bool($) { |
912 | 3 => sub { # neg bigint |
421 | UNIVERSAL::isa $_[0], "CBOR::XS::Boolean" |
913 | require Math::BigInt; |
422 | # or UNIVERSAL::isa $_[0], "CBOR::Literal" |
914 | -Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
915 | }, |
|
|
916 | |
|
|
917 | 4 => sub { # decimal fraction, array |
|
|
918 | require Math::BigFloat; |
|
|
919 | Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
|
|
920 | }, |
|
|
921 | |
|
|
922 | 5 => sub { # bigfloat, array |
|
|
923 | require Math::BigFloat; |
|
|
924 | scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2) |
|
|
925 | }, |
|
|
926 | |
|
|
927 | 21 => sub { pop }, # expected conversion to base64url encoding |
|
|
928 | 22 => sub { pop }, # expected conversion to base64 encoding |
|
|
929 | 23 => sub { pop }, # expected conversion to base16 encoding |
|
|
930 | |
|
|
931 | # 24 # embedded cbor, byte string |
|
|
932 | |
|
|
933 | 32 => sub { |
|
|
934 | require URI; |
|
|
935 | URI->new (pop) |
|
|
936 | }, |
|
|
937 | |
|
|
938 | # 33 # base64url rfc4648, utf-8 |
|
|
939 | # 34 # base64 rfc46484, utf-8 |
|
|
940 | # 35 # regex pcre/ecma262, utf-8 |
|
|
941 | # 36 # mime message rfc2045, utf-8 |
|
|
942 | ); |
|
|
943 | |
|
|
944 | sub CBOR::XS::default_filter { |
|
|
945 | &{ $FILTER{$_[0]} or return } |
423 | } |
946 | } |
424 | |
947 | |
|
|
948 | sub URI::TO_CBOR { |
|
|
949 | my $uri = $_[0]->as_string; |
|
|
950 | utf8::upgrade $uri; |
|
|
951 | CBOR::XS::tag 32, $uri |
|
|
952 | } |
|
|
953 | |
|
|
954 | sub Math::BigInt::TO_CBOR { |
|
|
955 | if ($_[0] >= -2147483648 && $_[0] <= 2147483647) { |
|
|
956 | $_[0]->numify |
|
|
957 | } else { |
|
|
958 | my $hex = substr $_[0]->as_hex, 2; |
|
|
959 | $hex = "0$hex" if 1 & length $hex; # sigh |
|
|
960 | CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex |
|
|
961 | } |
|
|
962 | } |
|
|
963 | |
|
|
964 | sub Math::BigFloat::TO_CBOR { |
|
|
965 | my ($m, $e) = $_[0]->parts; |
|
|
966 | CBOR::XS::tag 4, [$e->numify, $m] |
|
|
967 | } |
|
|
968 | |
425 | XSLoader::load "CBOR::XS", $VERSION; |
969 | XSLoader::load "CBOR::XS", $VERSION; |
426 | |
|
|
427 | package CBOR::XS::Boolean; |
|
|
428 | |
|
|
429 | use overload |
|
|
430 | "0+" => sub { ${$_[0]} }, |
|
|
431 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
|
|
432 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
|
|
433 | fallback => 1; |
|
|
434 | |
|
|
435 | 1; |
|
|
436 | |
970 | |
437 | =head1 SEE ALSO |
971 | =head1 SEE ALSO |
438 | |
972 | |
439 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
973 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
440 | serialisation. |
974 | serialisation. |
441 | |
975 | |
|
|
976 | The L<Types::Serialiser> module provides the data model for true, false |
|
|
977 | and error values. |
|
|
978 | |
442 | =head1 AUTHOR |
979 | =head1 AUTHOR |
443 | |
980 | |
444 | Marc Lehmann <schmorp@schmorp.de> |
981 | Marc Lehmann <schmorp@schmorp.de> |
445 | http://home.schmorp.de/ |
982 | http://home.schmorp.de/ |
446 | |
983 | |
447 | =cut |
984 | =cut |
448 | |
985 | |
|
|
986 | 1 |
|
|
987 | |