… | |
… | |
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 |
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27 | you to do). Furthermore, details of the implementation might change |
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28 | freely before version 1.0. And lastly, most extensions depend on an IANA |
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29 | assignment, and until that assignment is official, this implementation |
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30 | is not interoperable with other implementations (even future versions of |
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31 | this module) until the assignment is done. |
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32 | |
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33 | You are still invited to try out CBOR, and this module. |
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34 | |
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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 |
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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 |
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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" and "allow_cycles"), string deduplication (see |
57 | "allow_stringref") and scalar references (always enabled). |
50 | "pack_strings") and scalar 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 |
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146 | to encode cyclic data structures (which need "allow_cycles" to ne |
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147 | enabled to be decoded by this module). |
153 | |
148 | |
154 | It is recommended to leave it off unless you know your communication |
149 | It is recommended to leave it off unless you know your communication |
155 | partner supports the value sharing extensions to CBOR |
150 | partner supports the value sharing extensions to CBOR |
156 | (http://cbor.schmorp.de/value-sharing). |
151 | (<http://cbor.schmorp.de/value-sharing>), as without decoder |
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152 | support, the resulting data structure might be unusable. |
157 | |
153 | |
158 | Detecting shared values incurs a runtime overhead when values are |
154 | Detecting shared values incurs a runtime overhead when values are |
159 | encoded that have a reference counter large than one, and might |
155 | encoded that have a reference counter large than one, and might |
160 | unnecessarily increase the encoded size, as potentially shared |
156 | unnecessarily increase the encoded size, as potentially shared |
161 | values are encode as sharable whether or not they are actually |
157 | values are encode as shareable whether or not they are actually |
162 | shared. |
158 | shared. |
163 | |
159 | |
164 | At the moment, only targets of references can be shared (e.g. |
160 | At the moment, only targets of references can be shared (e.g. |
165 | scalars, arrays or hashes pointed to by a reference). Weirder |
161 | scalars, arrays or hashes pointed to by a reference). Weirder |
166 | constructs, such as an array with multiple "copies" of the *same* |
162 | 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 |
163 | string, which are hard but not impossible to create in Perl, are not |
168 | supported (this is the same as for Storable). |
164 | supported (this is the same as with Storable). |
169 | |
165 | |
170 | If $enable is false (the default), then "encode" will encode |
166 | If $enable is false (the default), then "encode" will encode shared |
171 | exception when it encounters anything it cannot encode as CBOR. |
167 | data structures repeatedly, unsharing them in the process. Cyclic |
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168 | data structures cannot be encoded in this mode. |
172 | |
169 | |
173 | This option does not affect "decode" in any way - shared values and |
170 | This option does not affect "decode" in any way - shared values and |
174 | references will always be decoded properly if present. |
171 | references will always be decoded properly if present. |
175 | |
172 | |
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173 | $cbor = $cbor->allow_cycles ([$enable]) |
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174 | $enabled = $cbor->get_allow_cycles |
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175 | If $enable is true (or missing), then "decode" will happily decode |
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176 | self-referential (cyclic) data structures. By default these will not |
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177 | be decoded, as they need manual cleanup to avoid memory leaks, so |
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178 | code that isn't prepared for this will not leak memory. |
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179 | |
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180 | If $enable is false (the default), then "decode" will throw an error |
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181 | when it encounters a self-referential/cyclic data structure. |
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182 | |
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183 | This option does not affect "encode" in any way - shared values and |
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184 | references will always be decoded properly if present. |
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185 | |
176 | $cbor = $cbor->allow_stringref ([$enable]) |
186 | $cbor = $cbor->pack_strings ([$enable]) |
177 | $enabled = $cbor->get_allow_stringref |
187 | $enabled = $cbor->get_pack_strings |
178 | If $enable is true (or missing), then "encode" will try not to |
188 | 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 |
189 | 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 |
190 | 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 |
191 | 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). |
192 | (expect encoding times to be 2-4 times as high as without). |
183 | |
193 | |
184 | It is recommended to leave it off unless you know your |
194 | It is recommended to leave it off unless you know your |
185 | communications partner supports the stringref extension to CBOR |
195 | communications partner supports the stringref extension to CBOR |
186 | (http://cbor.schmorp.de/stringref). |
196 | (<http://cbor.schmorp.de/stringref>), as without decoder support, |
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197 | the resulting data structure might not be usable. |
187 | |
198 | |
188 | If $enable is false (the default), then "encode" will encode |
199 | If $enable is false (the default), then "encode" will encode strings |
189 | exception when it encounters anything it cannot encode as CBOR. |
200 | the standard CBOR way. |
190 | |
201 | |
191 | This option does not affect "decode" in any way - string references |
202 | This option does not affect "decode" in any way - string references |
192 | will always be decoded properly if present. |
203 | will always be decoded properly if present. |
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204 | |
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205 | $cbor = $cbor->validate_utf8 ([$enable]) |
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206 | $enabled = $cbor->get_validate_utf8 |
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207 | If $enable is true (or missing), then "decode" will validate that |
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208 | elements (text strings) containing UTF-8 data in fact contain valid |
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209 | UTF-8 data (instead of blindly accepting it). This validation |
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210 | obviously takes extra time during decoding. |
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211 | |
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212 | The concept of "valid UTF-8" used is perl's concept, which is a |
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213 | superset of the official UTF-8. |
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214 | |
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215 | If $enable is false (the default), then "decode" will blindly accept |
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216 | UTF-8 data, marking them as valid UTF-8 in the resulting data |
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217 | structure regardless of whether thats true or not. |
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218 | |
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219 | Perl isn't too happy about corrupted UTF-8 in strings, but should |
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220 | generally not crash or do similarly evil things. Extensions might be |
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221 | not so forgiving, so it's recommended to turn on this setting if you |
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222 | receive untrusted CBOR. |
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223 | |
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224 | This option does not affect "encode" in any way - strings that are |
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225 | supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
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226 | string without checking whether that is, in fact, true or not. |
193 | |
227 | |
194 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
228 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
195 | $cb_or_undef = $cbor->get_filter |
229 | $cb_or_undef = $cbor->get_filter |
196 | Sets or replaces the tagged value decoding filter (when $cb is |
230 | Sets or replaces the tagged value decoding filter (when $cb is |
197 | specified) or clears the filter (if no argument or "undef" is |
231 | specified) or clears the filter (if no argument or "undef" is |
… | |
… | |
218 | it must be a code reference that is called with tag and value, and |
252 | it must be a code reference that is called with tag and value, and |
219 | is responsible for decoding the value. If no entry exists, it |
253 | is responsible for decoding the value. If no entry exists, it |
220 | returns no values. |
254 | returns no values. |
221 | |
255 | |
222 | Example: decode all tags not handled internally into |
256 | Example: decode all tags not handled internally into |
223 | CBOR::XS::Tagged objects, with no other special handling (useful |
257 | "CBOR::XS::Tagged" objects, with no other special handling (useful |
224 | when working with potentially "unsafe" CBOR data). |
258 | when working with potentially "unsafe" CBOR data). |
225 | |
259 | |
226 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
260 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
227 | |
261 | |
228 | Example: provide a global filter for tag 1347375694, converting the |
262 | Example: provide a global filter for tag 1347375694, converting the |
… | |
… | |
269 | integers |
303 | integers |
270 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
304 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
271 | support, 64 bit integers will be truncated or otherwise corrupted. |
305 | support, 64 bit integers will be truncated or otherwise corrupted. |
272 | |
306 | |
273 | byte strings |
307 | byte strings |
274 | Byte strings will become octet strings in Perl (the byte values |
308 | Byte strings will become octet strings in Perl (the Byte values |
275 | 0..255 will simply become characters of the same value in Perl). |
309 | 0..255 will simply become characters of the same value in Perl). |
276 | |
310 | |
277 | UTF-8 strings |
311 | UTF-8 strings |
278 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
312 | 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 |
313 | decoded into proper Unicode code points. At the moment, the validity |
… | |
… | |
297 | |
331 | |
298 | tagged values |
332 | tagged values |
299 | Tagged items consists of a numeric tag and another CBOR value. |
333 | Tagged items consists of a numeric tag and another CBOR value. |
300 | |
334 | |
301 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
335 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
302 | for details. |
336 | for details on which tags are handled how. |
303 | |
337 | |
304 | anything else |
338 | anything else |
305 | Anything else (e.g. unsupported simple values) will raise a decoding |
339 | Anything else (e.g. unsupported simple values) will raise a decoding |
306 | error. |
340 | error. |
307 | |
341 | |
308 | PERL -> CBOR |
342 | PERL -> CBOR |
309 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
343 | 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 |
344 | typeless language. That means this module can only guess which CBOR type |
311 | by a Perl value. |
345 | is meant by a perl value. |
312 | |
346 | |
313 | hash references |
347 | hash references |
314 | Perl hash references become CBOR maps. As there is no inherent |
348 | Perl hash references become CBOR maps. As there is no inherent |
315 | ordering in hash keys (or CBOR maps), they will usually be encoded |
349 | ordering in hash keys (or CBOR maps), they will usually be encoded |
316 | in a pseudo-random order. |
350 | in a pseudo-random order. This order can be different each time a |
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351 | hahs is encoded. |
317 | |
352 | |
318 | Currently, tied hashes will use the indefinite-length format, while |
353 | Currently, tied hashes will use the indefinite-length format, while |
319 | normal hashes will use the fixed-length format. |
354 | normal hashes will use the fixed-length format. |
320 | |
355 | |
321 | array references |
356 | array references |
322 | Perl array references become fixed-length CBOR arrays. |
357 | Perl array references become fixed-length CBOR arrays. |
323 | |
358 | |
324 | other references |
359 | other references |
325 | Other unblessed references are generally not allowed and will cause |
360 | Other unblessed references will be represented using the indirection |
326 | an exception to be thrown, except for references to the integers 0 |
361 | tag extension (tag value 22098, |
327 | and 1, which get turned into false and true in CBOR. |
362 | <http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
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363 | to be able to decode these values somehow, by either "doing the |
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364 | right thing", decoding into a generic tagged object, simply ignoring |
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365 | the tag, or something else. |
328 | |
366 | |
329 | CBOR::XS::Tagged objects |
367 | CBOR::XS::Tagged objects |
330 | Objects of this type must be arrays consisting of a single "[tag, |
368 | 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 |
369 | 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 |
370 | value will be encoded as appropriate for the value. You must use |
333 | "CBOR::XS::tag" to create such objects. |
371 | "CBOR::XS::tag" to create such objects. |
334 | |
372 | |
335 | Types::Serialiser::true, Types::Serialiser::false, |
373 | Types::Serialiser::true, Types::Serialiser::false, |
336 | Types::Serialiser::error |
374 | Types::Serialiser::error |
337 | These special values become CBOR true, CBOR false and CBOR undefined |
375 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
… | |
353 | # dump as number |
391 | # dump as number |
354 | encode_cbor [2] # yields [2] |
392 | encode_cbor [2] # yields [2] |
355 | encode_cbor [-3.0e17] # yields [-3e+17] |
393 | encode_cbor [-3.0e17] # yields [-3e+17] |
356 | my $value = 5; encode_cbor [$value] # yields [5] |
394 | my $value = 5; encode_cbor [$value] # yields [5] |
357 | |
395 | |
358 | # used as string, so dump as string |
396 | # used as string, so dump as string (either byte or text) |
359 | print $value; |
397 | print $value; |
360 | encode_cbor [$value] # yields ["5"] |
398 | encode_cbor [$value] # yields ["5"] |
361 | |
399 | |
362 | # undef becomes null |
400 | # undef becomes null |
363 | encode_cbor [undef] # yields [null] |
401 | encode_cbor [undef] # yields [null] |
… | |
… | |
366 | |
404 | |
367 | my $x = 3.1; # some variable containing a number |
405 | my $x = 3.1; # some variable containing a number |
368 | "$x"; # stringified |
406 | "$x"; # stringified |
369 | $x .= ""; # another, more awkward way to stringify |
407 | $x .= ""; # another, more awkward way to stringify |
370 | print $x; # perl does it for you, too, quite often |
408 | print $x; # perl does it for you, too, quite often |
|
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409 | |
|
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410 | You can force whether a string ie encoded as byte or text string by |
|
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411 | using "utf8::upgrade" and "utf8::downgrade"): |
|
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412 | |
|
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413 | utf8::upgrade $x; # encode $x as text string |
|
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414 | utf8::downgrade $x; # encode $x as byte string |
|
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415 | |
|
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416 | Perl doesn't define what operations up- and downgrade strings, so if |
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417 | the difference between byte and text is important, you should up- or |
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418 | downgrade your string as late as possible before encoding. |
371 | |
419 | |
372 | You can force the type to be a CBOR number by numifying it: |
420 | You can force the type to be a CBOR number by numifying it: |
373 | |
421 | |
374 | my $x = "3"; # some variable containing a string |
422 | my $x = "3"; # some variable containing a string |
375 | $x += 0; # numify it, ensuring it will be dumped as a number |
423 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
385 | the IEEE double format will be used. Perls that use formats other |
433 | the IEEE double format will be used. Perls that use formats other |
386 | than IEEE double to represent numerical values are supported, but |
434 | than IEEE double to represent numerical values are supported, but |
387 | might suffer loss of precision. |
435 | might suffer loss of precision. |
388 | |
436 | |
389 | OBJECT SERIALISATION |
437 | OBJECT SERIALISATION |
|
|
438 | This module implements both a CBOR-specific and the generic |
|
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439 | Types::Serialier object serialisation protocol. The following |
|
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440 | subsections explain both methods. |
|
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441 | |
|
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442 | ENCODING |
390 | This module knows two way to serialise a Perl object: The CBOR-specific |
443 | This module knows two way to serialise a Perl object: The CBOR-specific |
391 | way, and the generic way. |
444 | way, and the generic way. |
392 | |
445 | |
393 | Whenever the encoder encounters a Perl object that it cnanot serialise |
446 | Whenever the encoder encounters a Perl object that it cannot serialise |
394 | directly (most of them), it will first look up the "TO_CBOR" method on |
447 | directly (most of them), it will first look up the "TO_CBOR" method on |
395 | it. |
448 | it. |
396 | |
449 | |
397 | If it has a "TO_CBOR" method, it will call it with the object as only |
450 | If it has a "TO_CBOR" method, it will call it with the object as only |
398 | argument, and expects exactly one return value, which it will then |
451 | argument, and expects exactly one return value, which it will then |
… | |
… | |
403 | "CBOR" as the second argument, to distinguish it from other serialisers. |
456 | "CBOR" as the second argument, to distinguish it from other serialisers. |
404 | |
457 | |
405 | The "FREEZE" method can return any number of values (i.e. zero or more). |
458 | The "FREEZE" method can return any number of values (i.e. zero or more). |
406 | These will be encoded as CBOR perl object, together with the classname. |
459 | These will be encoded as CBOR perl object, together with the classname. |
407 | |
460 | |
|
|
461 | These methods *MUST NOT* change the data structure that is being |
|
|
462 | serialised. Failure to comply to this can result in memory corruption - |
|
|
463 | and worse. |
|
|
464 | |
408 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
465 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
409 | with an error. |
466 | with an error. |
410 | |
467 | |
|
|
468 | DECODING |
411 | Objects encoded via "TO_CBOR" cannot be automatically decoded, but |
469 | Objects encoded via "TO_CBOR" cannot (normally) be automatically |
412 | objects encoded via "FREEZE" can be decoded using the following |
470 | decoded, but objects encoded via "FREEZE" can be decoded using the |
413 | protocol: |
471 | following protocol: |
414 | |
472 | |
415 | When an encoded CBOR perl object is encountered by the decoder, it will |
473 | When an encoded CBOR perl object is encountered by the decoder, it will |
416 | look up the "THAW" method, by using the stored classname, and will fail |
474 | look up the "THAW" method, by using the stored classname, and will fail |
417 | if the method cannot be found. |
475 | if the method cannot be found. |
418 | |
476 | |
… | |
… | |
439 | |
497 | |
440 | sub URI::TO_CBOR { |
498 | sub URI::TO_CBOR { |
441 | my ($self) = @_; |
499 | my ($self) = @_; |
442 | my $uri = "$self"; # stringify uri |
500 | my $uri = "$self"; # stringify uri |
443 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
501 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
444 | CBOR::XS::tagged 32, "$_[0]" |
502 | CBOR::XS::tag 32, "$_[0]" |
445 | } |
503 | } |
446 | |
504 | |
447 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
505 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
448 | URI. |
506 | URI. |
449 | |
507 | |
… | |
… | |
568 | |
626 | |
569 | ENFORCED TAGS |
627 | ENFORCED TAGS |
570 | These tags are always handled when decoding, and their handling cannot |
628 | These tags are always handled when decoding, and their handling cannot |
571 | be overriden by the user. |
629 | be overriden by the user. |
572 | |
630 | |
573 | <unassigned> (perl-object, <http://cbor.schmorp.de/perl-object>) |
631 | 26 (perl-object, <http://cbor.schmorp.de/perl-object>) |
574 | These tags are automatically created (and decoded) for serialisable |
632 | These tags are automatically created (and decoded) for serialisable |
575 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
633 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
576 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
634 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
577 | |
635 | |
578 | <unassigned>, <unassigned> (sharable, sharedref, L |
636 | 28, 29 (shareable, 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 |
637 | These tags are automatically decoded when encountered (and they do |
|
|
638 | not result in a cyclic data structure, see "allow_cycles"), |
581 | shared values in the decoded object. They are only encoded, however, |
639 | resulting in shared values in the decoded object. They are only |
582 | when "allow_sharable" is enabled. |
640 | encoded, however, when "allow_sharing" is enabled. |
583 | |
641 | |
584 | <unassigned>, <unassigned> (stringref-namespace, stringref, L |
642 | Not all shared values can be successfully decoded: values that |
|
|
643 | reference themselves will *currently* decode as "undef" (this is not |
|
|
644 | the same as a reference pointing to itself, which will be |
|
|
645 | represented as a value that contains an indirect reference to itself |
|
|
646 | - these will be decoded properly). |
|
|
647 | |
|
|
648 | Note that considerably more shared value data structures can be |
|
|
649 | decoded than will be encoded - currently, only values pointed to by |
|
|
650 | references will be shared, others will not. While non-reference |
|
|
651 | shared values can be generated in Perl with some effort, they were |
|
|
652 | considered too unimportant to be supported in the encoder. The |
|
|
653 | decoder, however, will decode these values as shared values. |
|
|
654 | |
|
|
655 | 256, 25 (stringref-namespace, stringref, L |
585 | <http://cbor.schmorp.de/stringref>) |
656 | <http://cbor.schmorp.de/stringref>) |
586 | These tags are automatically decoded when encountered. They are only |
657 | These tags are automatically decoded when encountered. They are only |
587 | encoded, however, when "allow_stringref" is enabled. |
658 | encoded, however, when "pack_strings" is enabled. |
588 | |
659 | |
589 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
660 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
590 | This tag is automatically generated when a reference are encountered |
661 | This tag is automatically generated when a reference are encountered |
591 | (with the exception of hash and array refernces). It is converted to |
662 | (with the exception of hash and array refernces). It is converted to |
592 | a reference when decoding. |
663 | a reference when decoding. |
… | |
… | |
605 | |
676 | |
606 | When any of these need to load additional modules that are not part of |
677 | When any of these need to load additional modules that are not part of |
607 | the perl core distribution (e.g. URI), it is (currently) up to the user |
678 | the perl core distribution (e.g. URI), it is (currently) up to the user |
608 | to provide these modules. The decoding usually fails with an exception |
679 | to provide these modules. The decoding usually fails with an exception |
609 | if the required module cannot be loaded. |
680 | if the required module cannot be loaded. |
|
|
681 | |
|
|
682 | 0, 1 (date/time string, seconds since the epoch) |
|
|
683 | These tags are decoded into Time::Piece objects. The corresponding |
|
|
684 | "Time::Piece::TO_CBOR" method always encodes into tag 1 values |
|
|
685 | currently. |
|
|
686 | |
|
|
687 | The Time::Piece API is generally surprisingly bad, and fractional |
|
|
688 | seconds are only accidentally kept intact, so watch out. On the plus |
|
|
689 | side, the module comes with perl since 5.10, which has to count for |
|
|
690 | something. |
610 | |
691 | |
611 | 2, 3 (positive/negative bignum) |
692 | 2, 3 (positive/negative bignum) |
612 | These tags are decoded into Math::BigInt objects. The corresponding |
693 | These tags are decoded into Math::BigInt objects. The corresponding |
613 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
694 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
614 | CBOR integers, and others into positive/negative CBOR bignums. |
695 | CBOR integers, and others into positive/negative CBOR bignums. |
… | |
… | |
693 | uses long double to represent floating point values, they might not be |
774 | uses long double to represent floating point values, they might not be |
694 | encoded properly. Half precision types are accepted, but not encoded. |
775 | encoded properly. Half precision types are accepted, but not encoded. |
695 | |
776 | |
696 | Strict mode and canonical mode are not implemented. |
777 | Strict mode and canonical mode are not implemented. |
697 | |
778 | |
|
|
779 | LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
780 | On perls that were built without 64 bit integer support (these are rare |
|
|
781 | nowadays, even on 32 bit architectures), support for any kind of 64 bit |
|
|
782 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
783 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
784 | includes string, array and map sizes that are stored as 64 bit integers. |
|
|
785 | |
698 | THREADS |
786 | THREADS |
699 | This module is *not* guaranteed to be thread safe and there are no plans |
787 | This module is *not* guaranteed to be thread safe and there are no plans |
700 | to change this until Perl gets thread support (as opposed to the |
788 | to change this until Perl gets thread support (as opposed to the |
701 | horribly slow so-called "threads" which are simply slow and bloated |
789 | horribly slow so-called "threads" which are simply slow and bloated |
702 | process simulations - use fork, it's *much* faster, cheaper, better). |
790 | process simulations - use fork, it's *much* faster, cheaper, better). |