… | |
… | |
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 |
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32 | to you to do). Furthermore, details of the implementation might change |
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33 | freely before version 1.0. And lastly, most extensions depend on an IANA |
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34 | assignment, and until that assignment is official, this implementation is |
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35 | not interoperable with other implementations (even future versions of this |
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36 | module) until the assignment is done. |
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37 | |
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38 | You are still invited to try out CBOR, and this module. |
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39 | |
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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 |
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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 |
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50 | L<Storable>. |
58 | |
51 | |
59 | In addition to the core CBOR data format, this module implements a number |
52 | In addition to the core CBOR data format, this module implements a |
60 | of extensions, to support cyclic and self-referencing data structures |
53 | number of extensions, to support cyclic and shared data structures (see |
61 | (see C<allow_sharing>), string deduplication (see C<pack_strings>) and |
54 | C<allow_sharing>), string deduplication (see C<pack_strings>) and scalar |
62 | scalar references (always enabled). |
55 | references (always enabled). |
63 | |
56 | |
64 | 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 |
65 | 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. |
66 | |
59 | |
67 | 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 |
… | |
… | |
71 | |
64 | |
72 | package CBOR::XS; |
65 | package CBOR::XS; |
73 | |
66 | |
74 | use common::sense; |
67 | use common::sense; |
75 | |
68 | |
76 | our $VERSION = 0.09; |
69 | our $VERSION = '1.0'; |
77 | our @ISA = qw(Exporter); |
70 | our @ISA = qw(Exporter); |
78 | |
71 | |
79 | our @EXPORT = qw(encode_cbor decode_cbor); |
72 | our @EXPORT = qw(encode_cbor decode_cbor); |
80 | |
73 | |
81 | use Exporter; |
74 | use Exporter; |
… | |
… | |
259 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
252 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
260 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
253 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
261 | a code reference that is called with tag and value, and is responsible for |
254 | a code reference that is called with tag and value, and is responsible for |
262 | decoding the value. If no entry exists, it returns no values. |
255 | decoding the value. If no entry exists, it returns no values. |
263 | |
256 | |
264 | Example: decode all tags not handled internally into CBOR::XS::Tagged |
257 | Example: decode all tags not handled internally into C<CBOR::XS::Tagged> |
265 | objects, with no other special handling (useful when working with |
258 | objects, with no other special handling (useful when working with |
266 | potentially "unsafe" CBOR data). |
259 | potentially "unsafe" CBOR data). |
267 | |
260 | |
268 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
261 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
269 | |
262 | |
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323 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
316 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
324 | support, 64 bit integers will be truncated or otherwise corrupted. |
317 | support, 64 bit integers will be truncated or otherwise corrupted. |
325 | |
318 | |
326 | =item byte strings |
319 | =item byte strings |
327 | |
320 | |
328 | Byte strings will become octet strings in Perl (the byte values 0..255 |
321 | Byte strings will become octet strings in Perl (the Byte values 0..255 |
329 | will simply become characters of the same value in Perl). |
322 | will simply become characters of the same value in Perl). |
330 | |
323 | |
331 | =item UTF-8 strings |
324 | =item UTF-8 strings |
332 | |
325 | |
333 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
326 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
… | |
… | |
356 | =item tagged values |
349 | =item tagged values |
357 | |
350 | |
358 | Tagged items consists of a numeric tag and another CBOR value. |
351 | Tagged items consists of a numeric tag and another CBOR value. |
359 | |
352 | |
360 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
353 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
361 | for details. |
354 | for details on which tags are handled how. |
362 | |
355 | |
363 | =item anything else |
356 | =item anything else |
364 | |
357 | |
365 | Anything else (e.g. unsupported simple values) will raise a decoding |
358 | Anything else (e.g. unsupported simple values) will raise a decoding |
366 | error. |
359 | error. |
… | |
… | |
369 | |
362 | |
370 | |
363 | |
371 | =head2 PERL -> CBOR |
364 | =head2 PERL -> CBOR |
372 | |
365 | |
373 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
366 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
374 | truly typeless language, so we can only guess which CBOR type is meant by |
367 | typeless language. That means this module can only guess which CBOR type |
375 | a Perl value. |
368 | is meant by a perl value. |
376 | |
369 | |
377 | =over 4 |
370 | =over 4 |
378 | |
371 | |
379 | =item hash references |
372 | =item hash references |
380 | |
373 | |
381 | Perl hash references become CBOR maps. As there is no inherent ordering in |
374 | Perl hash references become CBOR maps. As there is no inherent ordering in |
382 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
375 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
383 | order. |
376 | order. This order can be different each time a hahs is encoded. |
384 | |
377 | |
385 | Currently, tied hashes will use the indefinite-length format, while normal |
378 | Currently, tied hashes will use the indefinite-length format, while normal |
386 | hashes will use the fixed-length format. |
379 | hashes will use the fixed-length format. |
387 | |
380 | |
388 | =item array references |
381 | =item array references |
389 | |
382 | |
390 | Perl array references become fixed-length CBOR arrays. |
383 | Perl array references become fixed-length CBOR arrays. |
391 | |
384 | |
392 | =item other references |
385 | =item other references |
393 | |
386 | |
394 | Other unblessed references are generally not allowed and will cause an |
387 | Other unblessed references will be represented using |
395 | exception to be thrown, except for references to the integers C<0> and |
388 | the indirection tag extension (tag value C<22098>, |
396 | C<1>, which get turned into false and true in CBOR. |
389 | L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
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390 | to be able to decode these values somehow, by either "doing the right |
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391 | thing", decoding into a generic tagged object, simply ignoring the tag, or |
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392 | something else. |
397 | |
393 | |
398 | =item CBOR::XS::Tagged objects |
394 | =item CBOR::XS::Tagged objects |
399 | |
395 | |
400 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
396 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
401 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
397 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
402 | be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to |
398 | be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to |
403 | create such objects. |
399 | create such objects. |
404 | |
400 | |
405 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
401 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
406 | |
402 | |
407 | These special values become CBOR true, CBOR false and CBOR undefined |
403 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
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424 | # dump as number |
420 | # dump as number |
425 | encode_cbor [2] # yields [2] |
421 | encode_cbor [2] # yields [2] |
426 | encode_cbor [-3.0e17] # yields [-3e+17] |
422 | encode_cbor [-3.0e17] # yields [-3e+17] |
427 | my $value = 5; encode_cbor [$value] # yields [5] |
423 | my $value = 5; encode_cbor [$value] # yields [5] |
428 | |
424 | |
429 | # used as string, so dump as string |
425 | # used as string, so dump as string (either byte or text) |
430 | print $value; |
426 | print $value; |
431 | encode_cbor [$value] # yields ["5"] |
427 | encode_cbor [$value] # yields ["5"] |
432 | |
428 | |
433 | # undef becomes null |
429 | # undef becomes null |
434 | encode_cbor [undef] # yields [null] |
430 | encode_cbor [undef] # yields [null] |
… | |
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437 | |
433 | |
438 | my $x = 3.1; # some variable containing a number |
434 | my $x = 3.1; # some variable containing a number |
439 | "$x"; # stringified |
435 | "$x"; # stringified |
440 | $x .= ""; # another, more awkward way to stringify |
436 | $x .= ""; # another, more awkward way to stringify |
441 | print $x; # perl does it for you, too, quite often |
437 | print $x; # perl does it for you, too, quite often |
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438 | |
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439 | You can force whether a string ie encoded as byte or text string by using |
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440 | C<utf8::upgrade> and C<utf8::downgrade>): |
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441 | |
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442 | utf8::upgrade $x; # encode $x as text string |
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443 | utf8::downgrade $x; # encode $x as byte string |
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444 | |
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445 | Perl doesn't define what operations up- and downgrade strings, so if the |
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446 | difference between byte and text is important, you should up- or downgrade |
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447 | your string as late as possible before encoding. |
442 | |
448 | |
443 | You can force the type to be a CBOR number by numifying it: |
449 | You can force the type to be a CBOR number by numifying it: |
444 | |
450 | |
445 | my $x = "3"; # some variable containing a string |
451 | my $x = "3"; # some variable containing a string |
446 | $x += 0; # numify it, ensuring it will be dumped as a number |
452 | $x += 0; # numify it, ensuring it will be dumped as a number |
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459 | |
465 | |
460 | =back |
466 | =back |
461 | |
467 | |
462 | =head2 OBJECT SERIALISATION |
468 | =head2 OBJECT SERIALISATION |
463 | |
469 | |
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470 | This module implements both a CBOR-specific and the generic |
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471 | L<Types::Serialier> object serialisation protocol. The following |
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472 | subsections explain both methods. |
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473 | |
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474 | =head3 ENCODING |
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475 | |
464 | This module knows two way to serialise a Perl object: The CBOR-specific |
476 | This module knows two way to serialise a Perl object: The CBOR-specific |
465 | way, and the generic way. |
477 | way, and the generic way. |
466 | |
478 | |
467 | Whenever the encoder encounters a Perl object that it cnanot serialise |
479 | Whenever the encoder encounters a Perl object that it cannot serialise |
468 | directly (most of them), it will first look up the C<TO_CBOR> method on |
480 | directly (most of them), it will first look up the C<TO_CBOR> method on |
469 | it. |
481 | it. |
470 | |
482 | |
471 | If it has a C<TO_CBOR> method, it will call it with the object as only |
483 | If it has a C<TO_CBOR> method, it will call it with the object as only |
472 | argument, and expects exactly one return value, which it will then |
484 | argument, and expects exactly one return value, which it will then |
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… | |
478 | |
490 | |
479 | The C<FREEZE> method can return any number of values (i.e. zero or |
491 | The C<FREEZE> method can return any number of values (i.e. zero or |
480 | more). These will be encoded as CBOR perl object, together with the |
492 | more). These will be encoded as CBOR perl object, together with the |
481 | classname. |
493 | classname. |
482 | |
494 | |
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495 | These methods I<MUST NOT> change the data structure that is being |
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496 | serialised. Failure to comply to this can result in memory corruption - |
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497 | and worse. |
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498 | |
483 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
499 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
484 | with an error. |
500 | with an error. |
485 | |
501 | |
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502 | =head3 DECODING |
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503 | |
486 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
504 | Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded, |
487 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
505 | but objects encoded via C<FREEZE> can be decoded using the following |
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506 | protocol: |
488 | |
507 | |
489 | When an encoded CBOR perl object is encountered by the decoder, it will |
508 | When an encoded CBOR perl object is encountered by the decoder, it will |
490 | look up the C<THAW> method, by using the stored classname, and will fail |
509 | look up the C<THAW> method, by using the stored classname, and will fail |
491 | if the method cannot be found. |
510 | if the method cannot be found. |
492 | |
511 | |
493 | After the lookup it will call the C<THAW> method with the stored classname |
512 | After the lookup it will call the C<THAW> method with the stored classname |
494 | as first argument, the constant string C<CBOR> as second argument, and all |
513 | as first argument, the constant string C<CBOR> as second argument, and all |
495 | values returned by C<FREEZE> as remaining arguments. |
514 | values returned by C<FREEZE> as remaining arguments. |
496 | |
515 | |
497 | =head4 EXAMPLES |
516 | =head3 EXAMPLES |
498 | |
517 | |
499 | Here is an example C<TO_CBOR> method: |
518 | Here is an example C<TO_CBOR> method: |
500 | |
519 | |
501 | sub My::Object::TO_CBOR { |
520 | sub My::Object::TO_CBOR { |
502 | my ($obj) = @_; |
521 | my ($obj) = @_; |
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513 | |
532 | |
514 | sub URI::TO_CBOR { |
533 | sub URI::TO_CBOR { |
515 | my ($self) = @_; |
534 | my ($self) = @_; |
516 | my $uri = "$self"; # stringify uri |
535 | my $uri = "$self"; # stringify uri |
517 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
536 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
518 | CBOR::XS::tagged 32, "$_[0]" |
537 | CBOR::XS::tag 32, "$_[0]" |
519 | } |
538 | } |
520 | |
539 | |
521 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
540 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
522 | URI. |
541 | URI. |
523 | |
542 | |