… | |
… | |
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 IS A PRE-ALPHA RELEASE! IT WILL CRASH, CORRUPT YOUR DATA |
22 | EAT YOUR CHILDREN! |
32 | AND EAT YOUR CHILDREN! (Actually, apart from being untested and a bit |
|
|
33 | feature-limited, it might already be useful). |
23 | |
34 | |
24 | This module converts Perl data structures to CBOR and vice versa. Its |
35 | This module converts Perl data structures to the Concise Binary Object |
|
|
36 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
|
|
37 | format that aims to use a superset of the JSON data model, i.e. when you |
|
|
38 | can represent something in JSON, you should be able to represent it in |
|
|
39 | CBOR. |
|
|
40 | |
|
|
41 | This makes it a faster and more compact binary alternative to JSON, with |
|
|
42 | the added ability of supporting serialising of perl objects. |
|
|
43 | |
25 | primary goal is to be I<correct> and its secondary goal is to be |
44 | 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. |
45 | is to be I<fast>. To reach the latter goal it was written in C. |
27 | |
46 | |
28 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
47 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
29 | vice versa. |
48 | vice versa. |
30 | |
49 | |
31 | =cut |
50 | =cut |
32 | |
51 | |
33 | package CBOR::XS; |
52 | package CBOR::XS; |
34 | |
53 | |
35 | use common::sense; |
54 | use common::sense; |
36 | |
55 | |
37 | our $VERSION = 0.02; |
56 | our $VERSION = 0.03; |
38 | our @ISA = qw(Exporter); |
57 | our @ISA = qw(Exporter); |
39 | |
58 | |
40 | our @EXPORT = qw(encode_cbor decode_cbor); |
59 | our @EXPORT = qw(encode_cbor decode_cbor); |
41 | |
60 | |
42 | use Exporter; |
61 | use Exporter; |
43 | use XSLoader; |
62 | use XSLoader; |
|
|
63 | |
|
|
64 | use Types::Serialiser; |
44 | |
65 | |
45 | our $MAGIC = "\xd9\xd9\xf7"; |
66 | our $MAGIC = "\xd9\xd9\xf7"; |
46 | |
67 | |
47 | =head1 FUNCTIONAL INTERFACE |
68 | =head1 FUNCTIONAL INTERFACE |
48 | |
69 | |
… | |
… | |
186 | |
207 | |
187 | CBOR arrays and CBOR maps will be converted into references to a Perl |
208 | 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 |
209 | array or hash, respectively. The keys of the map will be stringified |
189 | during this process. |
210 | during this process. |
190 | |
211 | |
|
|
212 | =item null |
|
|
213 | |
|
|
214 | CBOR null becomes C<undef> in Perl. |
|
|
215 | |
191 | =item true, false |
216 | =item true, false, undefined |
192 | |
217 | |
193 | These CBOR values become C<CBOR::XS::true> and C<CBOR::XS::false>, |
218 | These CBOR values become C<Types:Serialiser::true>, |
|
|
219 | C<Types:Serialiser::false> and C<Types::Serialiser::error>, |
194 | respectively. They are overloaded to act almost exactly like the numbers |
220 | 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 |
221 | 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. |
222 | error). See the L<Types::Serialiser> manpage for details. |
197 | |
223 | |
198 | =item null, undefined |
224 | =item CBOR tag 256 (perl object) |
199 | |
225 | |
200 | CBOR null and undefined values becomes C<undef> in Perl (in the future, |
226 | The tag value C<256> (TODO: pending iana registration) will be used |
201 | Undefined may raise an exception or something else). |
227 | to deserialise a Perl object serialised with C<FREEZE>. See "OBJECT |
|
|
228 | SERIALISATION", below, for details. |
202 | |
229 | |
203 | =item tags |
230 | =item CBOR tag 55799 (magic header) |
204 | |
231 | |
|
|
232 | The tag 55799 is ignored (this tag implements the magic header). |
|
|
233 | |
|
|
234 | =item other CBOR tags |
|
|
235 | |
205 | Tagged items consists of a numeric tag and another CBOR value. The tag |
236 | Tagged items consists of a numeric tag and another CBOR value. Tags not |
206 | 55799 is ignored (this tag implements the magic header). |
237 | handled internally are currently converted into a L<CBOR::XS::Tagged> |
207 | |
|
|
208 | All other tags are currently converted into a L<CBOR::XS::Tagged> object, |
|
|
209 | which is simply a blessed array reference consistsing of the numeric tag |
238 | object, which is simply a blessed array reference consisting of the |
210 | value followed by the (decoded) BOR value. |
239 | numeric tag value followed by the (decoded) CBOR value. |
|
|
240 | |
|
|
241 | In the future, support for user-supplied conversions might get added. |
211 | |
242 | |
212 | =item anything else |
243 | =item anything else |
213 | |
244 | |
214 | Anything else (e.g. unsupported simple values) will raise a decoding |
245 | Anything else (e.g. unsupported simple values) will raise a decoding |
215 | error. |
246 | error. |
… | |
… | |
248 | |
279 | |
249 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
280 | 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 |
281 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will be |
251 | encoded as appropriate for the value. |
282 | encoded as appropriate for the value. |
252 | |
283 | |
253 | =item CBOR::XS::true, CBOR::XS::false |
284 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
254 | |
285 | |
255 | These special values become CBOR true and CBOR false values, |
286 | 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. |
287 | values, respectively. You can also use C<\1>, C<\0> and C<\undef> directly |
|
|
288 | if you want. |
257 | |
289 | |
258 | =item blessed objects |
290 | =item other blessed objects |
259 | |
291 | |
260 | Other blessed objects currently need to have a C<TO_CBOR> method. It |
292 | 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 |
293 | "OBJECT SERIALISATION", below, for details. |
262 | something that can be encoded in CBOR. |
|
|
263 | |
294 | |
264 | =item simple scalars |
295 | =item simple scalars |
265 | |
296 | |
266 | TODO |
297 | TODO |
267 | Simple Perl scalars (any scalar that is not a reference) are the most |
298 | Simple Perl scalars (any scalar that is not a reference) are the most |
… | |
… | |
305 | represent numerical values are supported, but might suffer loss of |
336 | represent numerical values are supported, but might suffer loss of |
306 | precision. |
337 | precision. |
307 | |
338 | |
308 | =back |
339 | =back |
309 | |
340 | |
|
|
341 | =head2 OBJECT SERIALISATION |
310 | |
342 | |
|
|
343 | This module knows two way to serialise a Perl object: The CBOR-specific |
|
|
344 | way, and the generic way. |
|
|
345 | |
|
|
346 | Whenever the encoder encounters a Perl object that it cnanot serialise |
|
|
347 | directly (most of them), it will first look up the C<TO_CBOR> method on |
|
|
348 | it. |
|
|
349 | |
|
|
350 | If it has a C<TO_CBOR> method, it will call it with the object as only |
|
|
351 | argument, and expects exactly one return value, which it will then |
|
|
352 | substitute and encode it in the place of the object. |
|
|
353 | |
|
|
354 | Otherwise, it will look up the C<FREEZE> method. If it exists, it will |
|
|
355 | call it with the object as first argument, and the constant string C<CBOR> |
|
|
356 | as the second argument, to distinguish it from other serialisers. |
|
|
357 | |
|
|
358 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
359 | more). These will be encoded as CBOR perl object, together with the |
|
|
360 | classname. |
|
|
361 | |
|
|
362 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
|
|
363 | with an error. |
|
|
364 | |
|
|
365 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
|
|
366 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
|
|
367 | |
|
|
368 | When an encoded CBOR perl object is encountered by the decoder, it will |
|
|
369 | look up the C<THAW> method, by using the stored classname, and will fail |
|
|
370 | if the method cannot be found. |
|
|
371 | |
|
|
372 | After the lookup it will call the C<THAW> method with the stored classname |
|
|
373 | as first argument, the constant string C<CBOR> as second argument, and all |
|
|
374 | values returned by C<FREEZE> as remaining arguments. |
|
|
375 | |
|
|
376 | =head4 EXAMPLES |
|
|
377 | |
|
|
378 | Here is an example C<TO_CBOR> method: |
|
|
379 | |
|
|
380 | sub My::Object::TO_CBOR { |
|
|
381 | my ($obj) = @_; |
|
|
382 | |
|
|
383 | ["this is a serialised My::Object object", $obj->{id}] |
|
|
384 | } |
|
|
385 | |
|
|
386 | When a C<My::Object> is encoded to CBOR, it will instead encode a simple |
|
|
387 | array with two members: a string, and the "object id". Decoding this CBOR |
|
|
388 | string will yield a normal perl array reference in place of the object. |
|
|
389 | |
|
|
390 | A more useful and practical example would be a serialisation method for |
|
|
391 | the URI module. CBOR has a custom tag value for URIs, namely 32: |
|
|
392 | |
|
|
393 | sub URI::TO_CBOR { |
|
|
394 | my ($self) = @_; |
|
|
395 | my $uri = "$self"; # stringify uri |
|
|
396 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
|
|
397 | CBOR::XS::tagged 32, "$_[0]" |
|
|
398 | } |
|
|
399 | |
|
|
400 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
|
|
401 | URI. |
|
|
402 | |
|
|
403 | Decoding such an URI will not (currently) give you an URI object, but |
|
|
404 | instead a CBOR::XS::Tagged object with tag number 32 and the string - |
|
|
405 | exactly what was returned by C<TO_CBOR>. |
|
|
406 | |
|
|
407 | To serialise an object so it can automatically be deserialised, you need |
|
|
408 | to use C<FREEZE> and C<THAW>. To take the URI module as example, this |
|
|
409 | would be a possible implementation: |
|
|
410 | |
|
|
411 | sub URI::FREEZE { |
|
|
412 | my ($self, $serialiser) = @_; |
|
|
413 | "$self" # encode url string |
|
|
414 | } |
|
|
415 | |
|
|
416 | sub URI::THAW { |
|
|
417 | my ($class, $serialiser, $uri) = @_; |
|
|
418 | |
|
|
419 | $class->new ($uri) |
|
|
420 | } |
|
|
421 | |
|
|
422 | Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For |
|
|
423 | example, a C<FREEZE> method that returns "type", "id" and "variant" values |
|
|
424 | would cause an invocation of C<THAW> with 5 arguments: |
|
|
425 | |
|
|
426 | sub My::Object::FREEZE { |
|
|
427 | my ($self, $serialiser) = @_; |
|
|
428 | |
|
|
429 | ($self->{type}, $self->{id}, $self->{variant}) |
|
|
430 | } |
|
|
431 | |
|
|
432 | sub My::Object::THAW { |
|
|
433 | my ($class, $serialiser, $type, $id, $variant) = @_; |
|
|
434 | |
|
|
435 | $class-<new (type => $type, id => $id, variant => $variant) |
|
|
436 | } |
|
|
437 | |
|
|
438 | |
311 | =head2 MAGIC HEADER |
439 | =head1 MAGIC HEADER |
312 | |
440 | |
313 | There is no way to distinguish CBOR from other formats |
441 | There is no way to distinguish CBOR from other formats |
314 | programmatically. To make it easier to distinguish CBOR from other |
442 | programmatically. To make it easier to distinguish CBOR from other |
315 | formats, the CBOR specification has a special "magic string" that can be |
443 | formats, the CBOR specification has a special "magic string" that can be |
316 | prepended to any CBOR string without changing it's meaning. |
444 | prepended to any CBOR string without changing it's meaning. |
… | |
… | |
319 | prepend this string tot he CBOR data it generates, but it will ignroe it |
447 | prepend this string tot he CBOR data it generates, but it will ignroe it |
320 | if present, so users can prepend this string as a "file type" indicator as |
448 | if present, so users can prepend this string as a "file type" indicator as |
321 | required. |
449 | required. |
322 | |
450 | |
323 | |
451 | |
324 | =head2 CBOR and JSON |
452 | =head1 CBOR and JSON |
325 | |
453 | |
326 | CBOR is supposed to implement a superset of the JSON data model, and is, |
454 | 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 |
455 | with some coercion, able to represent all JSON texts (something that other |
328 | "binary JSON" formats such as BSON generally do not support). |
456 | "binary JSON" formats such as BSON generally do not support). |
329 | |
457 | |
… | |
… | |
409 | Please refrain from using rt.cpan.org or any other bug reporting |
537 | 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. |
538 | service. I put the contact address into my modules for a reason. |
411 | |
539 | |
412 | =cut |
540 | =cut |
413 | |
541 | |
414 | our $true = do { bless \(my $dummy = 1), "CBOR::XS::Boolean" }; |
|
|
415 | our $false = do { bless \(my $dummy = 0), "CBOR::XS::Boolean" }; |
|
|
416 | |
|
|
417 | sub true() { $true } |
|
|
418 | sub false() { $false } |
|
|
419 | |
|
|
420 | sub is_bool($) { |
|
|
421 | UNIVERSAL::isa $_[0], "CBOR::XS::Boolean" |
|
|
422 | # or UNIVERSAL::isa $_[0], "CBOR::Literal" |
|
|
423 | } |
|
|
424 | |
|
|
425 | XSLoader::load "CBOR::XS", $VERSION; |
542 | 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 | |
543 | |
437 | =head1 SEE ALSO |
544 | =head1 SEE ALSO |
438 | |
545 | |
439 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
546 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
440 | serialisation. |
547 | serialisation. |
441 | |
548 | |
|
|
549 | The L<Types::Serialiser> module provides the data model for true, false |
|
|
550 | and error values. |
|
|
551 | |
442 | =head1 AUTHOR |
552 | =head1 AUTHOR |
443 | |
553 | |
444 | Marc Lehmann <schmorp@schmorp.de> |
554 | Marc Lehmann <schmorp@schmorp.de> |
445 | http://home.schmorp.de/ |
555 | http://home.schmorp.de/ |
446 | |
556 | |
447 | =cut |
557 | =cut |
448 | |
558 | |
|
|
559 | 1 |
|
|
560 | |