… | |
… | |
21 | # data was decoded |
21 | # data was decoded |
22 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
22 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
23 | } |
23 | } |
24 | |
24 | |
25 | DESCRIPTION |
25 | DESCRIPTION |
26 | WARNING! This module is very new, and not very well tested (that's up to |
|
|
27 | you to do). Furthermore, details of the implementation might change |
|
|
28 | freely before version 1.0. And lastly, most extensions depend on an IANA |
|
|
29 | assignment, and until that assignment is official, this implementation |
|
|
30 | is not interoperable with other implementations (even future versions of |
|
|
31 | this module) until the assignment is done. |
|
|
32 | |
|
|
33 | You are still invited to try out CBOR, and this module. |
|
|
34 | |
|
|
35 | This module converts Perl data structures to the Concise Binary Object |
26 | This module converts Perl data structures to the Concise Binary Object |
36 | Representation (CBOR) and vice versa. CBOR is a fast binary |
27 | Representation (CBOR) and vice versa. CBOR is a fast binary |
37 | serialisation format that aims to use a superset of the JSON data model, |
28 | serialisation format that aims to use an (almost) superset of the JSON |
38 | i.e. when you can represent something in JSON, you should be able to |
29 | data model, i.e. when you can represent something useful in JSON, you |
39 | represent it in CBOR. |
30 | should be able to represent it in CBOR. |
40 | |
31 | |
41 | In short, CBOR is a faster and very compact binary alternative to JSON, |
32 | In short, CBOR is a faster and quite compact binary alternative to JSON, |
42 | with the added ability of supporting serialisation of Perl objects. |
33 | with the added ability of supporting serialisation of Perl objects. |
43 | (JSON often compresses better than CBOR though, so if you plan to |
34 | (JSON often compresses better than CBOR though, so if you plan to |
44 | compress the data later you might want to compare both formats first). |
35 | compress the data later and speed is less important you might want to |
|
|
36 | compare both formats first). |
45 | |
37 | |
46 | To give you a general idea about speed, with texts in the megabyte |
38 | To give you a general idea about speed, with texts in the megabyte |
47 | range, "CBOR::XS" usually encodes roughly twice as fast as Storable or |
39 | range, "CBOR::XS" usually encodes roughly twice as fast as Storable or |
48 | JSON::XS and decodes about 15%-30% faster than those. The shorter the |
40 | JSON::XS and decodes about 15%-30% faster than those. The shorter the |
49 | data, the worse Storable performs in comparison. |
41 | data, the worse Storable performs in comparison. |
50 | |
42 | |
51 | As for compactness, "CBOR::XS" encoded data structures are usually about |
43 | Regarding compactness, "CBOR::XS"-encoded data structures are usually |
52 | 20% smaller than the same data encoded as (compact) JSON or Storable. |
44 | about 20% smaller than the same data encoded as (compact) JSON or |
|
|
45 | Storable. |
53 | |
46 | |
54 | In addition to the core CBOR data format, this module implements a |
47 | In addition to the core CBOR data format, this module implements a |
55 | number of extensions, to support cyclic and self-referencing data |
48 | number of extensions, to support cyclic and shared data structures (see |
56 | structures (see "allow_sharing"), string deduplication (see |
49 | "allow_sharing"), string deduplication (see "pack_strings") and scalar |
57 | "allow_stringref") and scalar references (always enabled). |
50 | references (always enabled). |
58 | |
51 | |
59 | The primary goal of this module is to be *correct* and the secondary |
52 | The primary goal of this module is to be *correct* and the secondary |
60 | goal is to be *fast*. To reach the latter goal it was written in C. |
53 | goal is to be *fast*. To reach the latter goal it was written in C. |
61 | |
54 | |
62 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
55 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
… | |
… | |
147 | same object, such as an array, is referenced multiple times), but |
140 | same object, such as an array, is referenced multiple times), but |
148 | instead will emit a reference to the earlier value. |
141 | instead will emit a reference to the earlier value. |
149 | |
142 | |
150 | This means that such values will only be encoded once, and will not |
143 | This means that such values will only be encoded once, and will not |
151 | result in a deep cloning of the value on decode, in decoders |
144 | result in a deep cloning of the value on decode, in decoders |
152 | supporting the value sharing extension. |
145 | supporting the value sharing extension. This also makes it possible |
|
|
146 | to encode cyclic data structures. |
153 | |
147 | |
154 | It is recommended to leave it off unless you know your communication |
148 | It is recommended to leave it off unless you know your communication |
155 | partner supports the value sharing extensions to CBOR |
149 | partner supports the value sharing extensions to CBOR |
156 | (http://cbor.schmorp.de/value-sharing). |
150 | (<http://cbor.schmorp.de/value-sharing>), as without decoder |
|
|
151 | support, the resulting data structure might be unusable. |
157 | |
152 | |
158 | Detecting shared values incurs a runtime overhead when values are |
153 | Detecting shared values incurs a runtime overhead when values are |
159 | encoded that have a reference counter large than one, and might |
154 | encoded that have a reference counter large than one, and might |
160 | unnecessarily increase the encoded size, as potentially shared |
155 | unnecessarily increase the encoded size, as potentially shared |
161 | values are encode as sharable whether or not they are actually |
156 | values are encode as sharable whether or not they are actually |
… | |
… | |
163 | |
158 | |
164 | At the moment, only targets of references can be shared (e.g. |
159 | At the moment, only targets of references can be shared (e.g. |
165 | scalars, arrays or hashes pointed to by a reference). Weirder |
160 | scalars, arrays or hashes pointed to by a reference). Weirder |
166 | constructs, such as an array with multiple "copies" of the *same* |
161 | constructs, such as an array with multiple "copies" of the *same* |
167 | string, which are hard but not impossible to create in Perl, are not |
162 | string, which are hard but not impossible to create in Perl, are not |
168 | supported (this is the same as for Storable). |
163 | supported (this is the same as with Storable). |
169 | |
164 | |
170 | If $enable is false (the default), then "encode" will encode |
165 | If $enable is false (the default), then "encode" will encode shared |
171 | exception when it encounters anything it cannot encode as CBOR. |
166 | data structures repeatedly, unsharing them in the process. Cyclic |
|
|
167 | data structures cannot be encoded in this mode. |
172 | |
168 | |
173 | This option does not affect "decode" in any way - shared values and |
169 | This option does not affect "decode" in any way - shared values and |
174 | references will always be decoded properly if present. |
170 | references will always be decoded properly if present. |
175 | |
171 | |
176 | $cbor = $cbor->allow_stringref ([$enable]) |
172 | $cbor = $cbor->pack_strings ([$enable]) |
177 | $enabled = $cbor->get_allow_stringref |
173 | $enabled = $cbor->get_pack_strings |
178 | If $enable is true (or missing), then "encode" will try not to |
174 | If $enable is true (or missing), then "encode" will try not to |
179 | encode the same string twice, but will instead encode a reference to |
175 | encode the same string twice, but will instead encode a reference to |
180 | the string instead. Depending on your data format. this can save a |
176 | the string instead. Depending on your data format, this can save a |
181 | lot of space, but also results in a very large runtime overhead |
177 | lot of space, but also results in a very large runtime overhead |
182 | (expect encoding times to be 2-4 times as high as without). |
178 | (expect encoding times to be 2-4 times as high as without). |
183 | |
179 | |
184 | It is recommended to leave it off unless you know your |
180 | It is recommended to leave it off unless you know your |
185 | communications partner supports the stringref extension to CBOR |
181 | communications partner supports the stringref extension to CBOR |
186 | (http://cbor.schmorp.de/stringref). |
182 | (<http://cbor.schmorp.de/stringref>), as without decoder support, |
|
|
183 | the resulting data structure might not be usable. |
187 | |
184 | |
188 | If $enable is false (the default), then "encode" will encode |
185 | If $enable is false (the default), then "encode" will encode strings |
189 | exception when it encounters anything it cannot encode as CBOR. |
186 | the standard CBOR way. |
190 | |
187 | |
191 | This option does not affect "decode" in any way - string references |
188 | This option does not affect "decode" in any way - string references |
192 | will always be decoded properly if present. |
189 | will always be decoded properly if present. |
193 | |
190 | |
194 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
191 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
… | |
… | |
218 | it must be a code reference that is called with tag and value, and |
215 | it must be a code reference that is called with tag and value, and |
219 | is responsible for decoding the value. If no entry exists, it |
216 | is responsible for decoding the value. If no entry exists, it |
220 | returns no values. |
217 | returns no values. |
221 | |
218 | |
222 | Example: decode all tags not handled internally into |
219 | Example: decode all tags not handled internally into |
223 | CBOR::XS::Tagged objects, with no other special handling (useful |
220 | "CBOR::XS::Tagged" objects, with no other special handling (useful |
224 | when working with potentially "unsafe" CBOR data). |
221 | when working with potentially "unsafe" CBOR data). |
225 | |
222 | |
226 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
223 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
227 | |
224 | |
228 | Example: provide a global filter for tag 1347375694, converting the |
225 | Example: provide a global filter for tag 1347375694, converting the |
… | |
… | |
269 | integers |
266 | integers |
270 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
267 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
271 | support, 64 bit integers will be truncated or otherwise corrupted. |
268 | support, 64 bit integers will be truncated or otherwise corrupted. |
272 | |
269 | |
273 | byte strings |
270 | byte strings |
274 | Byte strings will become octet strings in Perl (the byte values |
271 | Byte strings will become octet strings in Perl (the Byte values |
275 | 0..255 will simply become characters of the same value in Perl). |
272 | 0..255 will simply become characters of the same value in Perl). |
276 | |
273 | |
277 | UTF-8 strings |
274 | UTF-8 strings |
278 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
275 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
279 | decoded into proper Unicode code points. At the moment, the validity |
276 | decoded into proper Unicode code points. At the moment, the validity |
… | |
… | |
297 | |
294 | |
298 | tagged values |
295 | tagged values |
299 | Tagged items consists of a numeric tag and another CBOR value. |
296 | Tagged items consists of a numeric tag and another CBOR value. |
300 | |
297 | |
301 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
298 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
302 | for details. |
299 | for details on which tags are handled how. |
303 | |
300 | |
304 | anything else |
301 | anything else |
305 | Anything else (e.g. unsupported simple values) will raise a decoding |
302 | Anything else (e.g. unsupported simple values) will raise a decoding |
306 | error. |
303 | error. |
307 | |
304 | |
308 | PERL -> CBOR |
305 | PERL -> CBOR |
309 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
306 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
310 | truly typeless language, so we can only guess which CBOR type is meant |
307 | typeless language. That means this module can only guess which CBOR type |
311 | by a Perl value. |
308 | is meant by a perl value. |
312 | |
309 | |
313 | hash references |
310 | hash references |
314 | Perl hash references become CBOR maps. As there is no inherent |
311 | Perl hash references become CBOR maps. As there is no inherent |
315 | ordering in hash keys (or CBOR maps), they will usually be encoded |
312 | ordering in hash keys (or CBOR maps), they will usually be encoded |
316 | in a pseudo-random order. |
313 | in a pseudo-random order. This order can be different each time a |
|
|
314 | hahs is encoded. |
317 | |
315 | |
318 | Currently, tied hashes will use the indefinite-length format, while |
316 | Currently, tied hashes will use the indefinite-length format, while |
319 | normal hashes will use the fixed-length format. |
317 | normal hashes will use the fixed-length format. |
320 | |
318 | |
321 | array references |
319 | array references |
322 | Perl array references become fixed-length CBOR arrays. |
320 | Perl array references become fixed-length CBOR arrays. |
323 | |
321 | |
324 | other references |
322 | other references |
325 | Other unblessed references are generally not allowed and will cause |
323 | Other unblessed references will be represented using the indirection |
326 | an exception to be thrown, except for references to the integers 0 |
324 | tag extension (tag value 22098, |
327 | and 1, which get turned into false and true in CBOR. |
325 | <http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
|
|
326 | to be able to decode these values somehow, by either "doing the |
|
|
327 | right thing", decoding into a generic tagged object, simply ignoring |
|
|
328 | the tag, or something else. |
328 | |
329 | |
329 | CBOR::XS::Tagged objects |
330 | CBOR::XS::Tagged objects |
330 | Objects of this type must be arrays consisting of a single "[tag, |
331 | Objects of this type must be arrays consisting of a single "[tag, |
331 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
332 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
332 | value will be encoded as appropriate for the value. You cna use |
333 | value will be encoded as appropriate for the value. You must use |
333 | "CBOR::XS::tag" to create such objects. |
334 | "CBOR::XS::tag" to create such objects. |
334 | |
335 | |
335 | Types::Serialiser::true, Types::Serialiser::false, |
336 | Types::Serialiser::true, Types::Serialiser::false, |
336 | Types::Serialiser::error |
337 | Types::Serialiser::error |
337 | These special values become CBOR true, CBOR false and CBOR undefined |
338 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
… | |
353 | # dump as number |
354 | # dump as number |
354 | encode_cbor [2] # yields [2] |
355 | encode_cbor [2] # yields [2] |
355 | encode_cbor [-3.0e17] # yields [-3e+17] |
356 | encode_cbor [-3.0e17] # yields [-3e+17] |
356 | my $value = 5; encode_cbor [$value] # yields [5] |
357 | my $value = 5; encode_cbor [$value] # yields [5] |
357 | |
358 | |
358 | # used as string, so dump as string |
359 | # used as string, so dump as string (either byte or text) |
359 | print $value; |
360 | print $value; |
360 | encode_cbor [$value] # yields ["5"] |
361 | encode_cbor [$value] # yields ["5"] |
361 | |
362 | |
362 | # undef becomes null |
363 | # undef becomes null |
363 | encode_cbor [undef] # yields [null] |
364 | encode_cbor [undef] # yields [null] |
… | |
… | |
366 | |
367 | |
367 | my $x = 3.1; # some variable containing a number |
368 | my $x = 3.1; # some variable containing a number |
368 | "$x"; # stringified |
369 | "$x"; # stringified |
369 | $x .= ""; # another, more awkward way to stringify |
370 | $x .= ""; # another, more awkward way to stringify |
370 | print $x; # perl does it for you, too, quite often |
371 | print $x; # perl does it for you, too, quite often |
|
|
372 | |
|
|
373 | You can force whether a string ie encoded as byte or text string by |
|
|
374 | using "utf8::upgrade" and "utf8::downgrade"): |
|
|
375 | |
|
|
376 | utf8::upgrade $x; # encode $x as text string |
|
|
377 | utf8::downgrade $x; # encode $x as byte string |
|
|
378 | |
|
|
379 | Perl doesn't define what operations up- and downgrade strings, so if |
|
|
380 | the difference between byte and text is important, you should up- or |
|
|
381 | downgrade your string as late as possible before encoding. |
371 | |
382 | |
372 | You can force the type to be a CBOR number by numifying it: |
383 | You can force the type to be a CBOR number by numifying it: |
373 | |
384 | |
374 | my $x = "3"; # some variable containing a string |
385 | my $x = "3"; # some variable containing a string |
375 | $x += 0; # numify it, ensuring it will be dumped as a number |
386 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
439 | |
450 | |
440 | sub URI::TO_CBOR { |
451 | sub URI::TO_CBOR { |
441 | my ($self) = @_; |
452 | my ($self) = @_; |
442 | my $uri = "$self"; # stringify uri |
453 | my $uri = "$self"; # stringify uri |
443 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
454 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
444 | CBOR::XS::tagged 32, "$_[0]" |
455 | CBOR::XS::tag 32, "$_[0]" |
445 | } |
456 | } |
446 | |
457 | |
447 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
458 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
448 | URI. |
459 | URI. |
449 | |
460 | |
… | |
… | |
568 | |
579 | |
569 | ENFORCED TAGS |
580 | ENFORCED TAGS |
570 | These tags are always handled when decoding, and their handling cannot |
581 | These tags are always handled when decoding, and their handling cannot |
571 | be overriden by the user. |
582 | be overriden by the user. |
572 | |
583 | |
573 | <unassigned> (perl-object, <http://cbor.schmorp.de/perl-object>) |
584 | 26 (perl-object, <http://cbor.schmorp.de/perl-object>) |
574 | These tags are automatically created (and decoded) for serialisable |
585 | These tags are automatically created (and decoded) for serialisable |
575 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
586 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
576 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
587 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
577 | |
588 | |
578 | <unassigned>, <unassigned> (sharable, sharedref, L |
589 | 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
579 | <http://cbor.schmorp.de/value-sharing>) |
|
|
580 | These tags are automatically decoded when encountered, resulting in |
590 | These tags are automatically decoded when encountered, resulting in |
581 | shared values in the decoded object. They are only encoded, however, |
591 | shared values in the decoded object. They are only encoded, however, |
582 | when "allow_sharable" is enabled. |
592 | when "allow_sharable" is enabled. |
583 | |
593 | |
584 | <unassigned>, <unassigned> (stringref-namespace, stringref, L |
594 | 256, 25 (stringref-namespace, stringref, L |
585 | <http://cbor.schmorp.de/stringref>) |
595 | <http://cbor.schmorp.de/stringref>) |
586 | These tags are automatically decoded when encountered. They are only |
596 | These tags are automatically decoded when encountered. They are only |
587 | encoded, however, when "allow_stringref" is enabled. |
597 | encoded, however, when "pack_strings" is enabled. |
588 | |
598 | |
589 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
599 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
590 | This tag is automatically generated when a reference are encountered |
600 | This tag is automatically generated when a reference are encountered |
591 | (with the exception of hash and array refernces). It is converted to |
601 | (with the exception of hash and array refernces). It is converted to |
592 | a reference when decoding. |
602 | a reference when decoding. |