… | |
… | |
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 | FUTURE DIRECTION: the motivation behind this option is to avoid |
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184 | *real* cycles - future versions of this module might chose to decode |
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185 | cyclic data structures using weak references when this option is |
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186 | off, instead of throwing an error. |
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187 | |
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188 | This option does not affect "encode" in any way - shared values and |
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189 | references will always be encoded properly if present. |
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190 | |
176 | $cbor = $cbor->allow_stringref ([$enable]) |
191 | $cbor = $cbor->pack_strings ([$enable]) |
177 | $enabled = $cbor->get_allow_stringref |
192 | $enabled = $cbor->get_pack_strings |
178 | If $enable is true (or missing), then "encode" will try not to |
193 | 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 |
194 | 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 |
195 | 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 |
196 | 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). |
197 | (expect encoding times to be 2-4 times as high as without). |
183 | |
198 | |
184 | It is recommended to leave it off unless you know your |
199 | It is recommended to leave it off unless you know your |
185 | communications partner supports the stringref extension to CBOR |
200 | communications partner supports the stringref extension to CBOR |
186 | (http://cbor.schmorp.de/stringref). |
201 | (<http://cbor.schmorp.de/stringref>), as without decoder support, |
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202 | the resulting data structure might not be usable. |
187 | |
203 | |
188 | If $enable is false (the default), then "encode" will encode |
204 | If $enable is false (the default), then "encode" will encode strings |
189 | exception when it encounters anything it cannot encode as CBOR. |
205 | the standard CBOR way. |
190 | |
206 | |
191 | This option does not affect "decode" in any way - string references |
207 | This option does not affect "decode" in any way - string references |
192 | will always be decoded properly if present. |
208 | will always be decoded properly if present. |
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209 | |
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210 | $cbor = $cbor->validate_utf8 ([$enable]) |
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211 | $enabled = $cbor->get_validate_utf8 |
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212 | If $enable is true (or missing), then "decode" will validate that |
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213 | elements (text strings) containing UTF-8 data in fact contain valid |
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214 | UTF-8 data (instead of blindly accepting it). This validation |
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215 | obviously takes extra time during decoding. |
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216 | |
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217 | The concept of "valid UTF-8" used is perl's concept, which is a |
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218 | superset of the official UTF-8. |
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219 | |
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220 | If $enable is false (the default), then "decode" will blindly accept |
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221 | UTF-8 data, marking them as valid UTF-8 in the resulting data |
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222 | structure regardless of whether thats true or not. |
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223 | |
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224 | Perl isn't too happy about corrupted UTF-8 in strings, but should |
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225 | generally not crash or do similarly evil things. Extensions might be |
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226 | not so forgiving, so it's recommended to turn on this setting if you |
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227 | receive untrusted CBOR. |
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228 | |
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229 | This option does not affect "encode" in any way - strings that are |
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230 | supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
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231 | string without checking whether that is, in fact, true or not. |
193 | |
232 | |
194 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
233 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
195 | $cb_or_undef = $cbor->get_filter |
234 | $cb_or_undef = $cbor->get_filter |
196 | Sets or replaces the tagged value decoding filter (when $cb is |
235 | Sets or replaces the tagged value decoding filter (when $cb is |
197 | specified) or clears the filter (if no argument or "undef" is |
236 | specified) or clears the filter (if no argument or "undef" is |
… | |
… | |
218 | it must be a code reference that is called with tag and value, and |
257 | it must be a code reference that is called with tag and value, and |
219 | is responsible for decoding the value. If no entry exists, it |
258 | is responsible for decoding the value. If no entry exists, it |
220 | returns no values. |
259 | returns no values. |
221 | |
260 | |
222 | Example: decode all tags not handled internally into |
261 | Example: decode all tags not handled internally into |
223 | CBOR::XS::Tagged objects, with no other special handling (useful |
262 | "CBOR::XS::Tagged" objects, with no other special handling (useful |
224 | when working with potentially "unsafe" CBOR data). |
263 | when working with potentially "unsafe" CBOR data). |
225 | |
264 | |
226 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
265 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
227 | |
266 | |
228 | Example: provide a global filter for tag 1347375694, converting the |
267 | Example: provide a global filter for tag 1347375694, converting the |
… | |
… | |
253 | the next one starts. |
292 | the next one starts. |
254 | |
293 | |
255 | CBOR::XS->new->decode_prefix ("......") |
294 | CBOR::XS->new->decode_prefix ("......") |
256 | => ("...", 3) |
295 | => ("...", 3) |
257 | |
296 | |
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297 | INCREMENTAL PARSING |
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298 | In some cases, there is the need for incremental parsing of JSON texts. |
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299 | While this module always has to keep both CBOR text and resulting Perl |
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300 | data structure in memory at one time, it does allow you to parse a CBOR |
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301 | stream incrementally, using a similar to using "decode_prefix" to see if |
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302 | a full CBOR object is available, but is much more efficient. |
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303 | |
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304 | It basically works by parsing as much of a CBOR string as possible - if |
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305 | the CBOR data is not complete yet, the pasrer will remember where it |
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306 | was, to be able to restart when more data has been accumulated. Once |
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307 | enough data is available to either decode a complete CBOR value or raise |
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308 | an error, a real decode will be attempted. |
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309 | |
|
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310 | A typical use case would be a network protocol that consists of sending |
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311 | and receiving CBOR-encoded messages. The solution that works with CBOR |
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312 | and about anything else is by prepending a length to every CBOR value, |
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313 | so the receiver knows how many octets to read. More compact (and |
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314 | slightly slower) would be to just send CBOR values back-to-back, as |
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315 | "CBOR::XS" knows where a CBOR value ends, and doesn't need an explicit |
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316 | length. |
|
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317 | |
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318 | The following methods help with this: |
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319 | |
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320 | @decoded = $cbor->incr_parse ($buffer) |
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321 | This method attempts to decode exactly one CBOR value from the |
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322 | beginning of the given $buffer. The value is removed from the |
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323 | $buffer on success. When $buffer doesn't contain a complete value |
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324 | yet, it returns nothing. Finally, when the $buffer doesn't start |
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325 | with something that could ever be a valid CBOR value, it raises an |
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326 | exception, just as "decode" would. In the latter case the decoder |
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327 | state is undefined and must be reset before being able to parse |
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328 | further. |
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329 | |
|
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330 | This method modifies the $buffer in place. When no CBOR value can be |
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331 | decoded, the decoder stores the current string offset. On the next |
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332 | call, continues decoding at the place where it stopped before. For |
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333 | this to make sense, the $buffer must begin with the same octets as |
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334 | on previous unsuccessful calls. |
|
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335 | |
|
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336 | You can call this method in scalar context, in which case it either |
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337 | returns a decoded value or "undef". This makes it impossible to |
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338 | distinguish between CBOR null values (which decode to "undef") and |
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339 | an unsuccessful decode, which is often acceptable. |
|
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340 | |
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341 | @decoded = $cbor->incr_parse_multiple ($buffer) |
|
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342 | Same as "incr_parse", but attempts to decode as many CBOR values as |
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343 | possible in one go, instead of at most one. Calls to "incr_parse" |
|
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344 | and "incr_parse_multiple" can be interleaved. |
|
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345 | |
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346 | $cbor->incr_reset |
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347 | Resets the incremental decoder. This throws away any saved state, so |
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348 | that subsequent calls to "incr_parse" or "incr_parse_multiple" start |
|
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349 | to parse a new CBOR value from the beginning of the $buffer again. |
|
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350 | |
|
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351 | This method can be caled at any time, but it *must* be called if you |
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352 | want to change your $buffer or there was a decoding error and you |
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353 | want to reuse the $cbor object for future incremental parsings. |
|
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354 | |
258 | MAPPING |
355 | MAPPING |
259 | This section describes how CBOR::XS maps Perl values to CBOR values and |
356 | This section describes how CBOR::XS maps Perl values to CBOR values and |
260 | vice versa. These mappings are designed to "do the right thing" in most |
357 | vice versa. These mappings are designed to "do the right thing" in most |
261 | circumstances automatically, preserving round-tripping characteristics |
358 | circumstances automatically, preserving round-tripping characteristics |
262 | (what you put in comes out as something equivalent). |
359 | (what you put in comes out as something equivalent). |
… | |
… | |
269 | integers |
366 | integers |
270 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
367 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
271 | support, 64 bit integers will be truncated or otherwise corrupted. |
368 | support, 64 bit integers will be truncated or otherwise corrupted. |
272 | |
369 | |
273 | byte strings |
370 | byte strings |
274 | Byte strings will become octet strings in Perl (the byte values |
371 | Byte strings will become octet strings in Perl (the Byte values |
275 | 0..255 will simply become characters of the same value in Perl). |
372 | 0..255 will simply become characters of the same value in Perl). |
276 | |
373 | |
277 | UTF-8 strings |
374 | UTF-8 strings |
278 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
375 | 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 |
376 | decoded into proper Unicode code points. At the moment, the validity |
… | |
… | |
297 | |
394 | |
298 | tagged values |
395 | tagged values |
299 | Tagged items consists of a numeric tag and another CBOR value. |
396 | Tagged items consists of a numeric tag and another CBOR value. |
300 | |
397 | |
301 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
398 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
302 | for details. |
399 | for details on which tags are handled how. |
303 | |
400 | |
304 | anything else |
401 | anything else |
305 | Anything else (e.g. unsupported simple values) will raise a decoding |
402 | Anything else (e.g. unsupported simple values) will raise a decoding |
306 | error. |
403 | error. |
307 | |
404 | |
308 | PERL -> CBOR |
405 | PERL -> CBOR |
309 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
406 | 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 |
407 | typeless language. That means this module can only guess which CBOR type |
311 | by a Perl value. |
408 | is meant by a perl value. |
312 | |
409 | |
313 | hash references |
410 | hash references |
314 | Perl hash references become CBOR maps. As there is no inherent |
411 | Perl hash references become CBOR maps. As there is no inherent |
315 | ordering in hash keys (or CBOR maps), they will usually be encoded |
412 | ordering in hash keys (or CBOR maps), they will usually be encoded |
316 | in a pseudo-random order. |
413 | in a pseudo-random order. This order can be different each time a |
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414 | hahs is encoded. |
317 | |
415 | |
318 | Currently, tied hashes will use the indefinite-length format, while |
416 | Currently, tied hashes will use the indefinite-length format, while |
319 | normal hashes will use the fixed-length format. |
417 | normal hashes will use the fixed-length format. |
320 | |
418 | |
321 | array references |
419 | array references |
322 | Perl array references become fixed-length CBOR arrays. |
420 | Perl array references become fixed-length CBOR arrays. |
323 | |
421 | |
324 | other references |
422 | other references |
325 | Other unblessed references are generally not allowed and will cause |
423 | Other unblessed references will be represented using the indirection |
326 | an exception to be thrown, except for references to the integers 0 |
424 | tag extension (tag value 22098, |
327 | and 1, which get turned into false and true in CBOR. |
425 | <http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
|
|
426 | to be able to decode these values somehow, by either "doing the |
|
|
427 | right thing", decoding into a generic tagged object, simply ignoring |
|
|
428 | the tag, or something else. |
328 | |
429 | |
329 | CBOR::XS::Tagged objects |
430 | CBOR::XS::Tagged objects |
330 | Objects of this type must be arrays consisting of a single "[tag, |
431 | 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 |
432 | 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 |
433 | value will be encoded as appropriate for the value. You must use |
333 | "CBOR::XS::tag" to create such objects. |
434 | "CBOR::XS::tag" to create such objects. |
334 | |
435 | |
335 | Types::Serialiser::true, Types::Serialiser::false, |
436 | Types::Serialiser::true, Types::Serialiser::false, |
336 | Types::Serialiser::error |
437 | Types::Serialiser::error |
337 | These special values become CBOR true, CBOR false and CBOR undefined |
438 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
… | |
353 | # dump as number |
454 | # dump as number |
354 | encode_cbor [2] # yields [2] |
455 | encode_cbor [2] # yields [2] |
355 | encode_cbor [-3.0e17] # yields [-3e+17] |
456 | encode_cbor [-3.0e17] # yields [-3e+17] |
356 | my $value = 5; encode_cbor [$value] # yields [5] |
457 | my $value = 5; encode_cbor [$value] # yields [5] |
357 | |
458 | |
358 | # used as string, so dump as string |
459 | # used as string, so dump as string (either byte or text) |
359 | print $value; |
460 | print $value; |
360 | encode_cbor [$value] # yields ["5"] |
461 | encode_cbor [$value] # yields ["5"] |
361 | |
462 | |
362 | # undef becomes null |
463 | # undef becomes null |
363 | encode_cbor [undef] # yields [null] |
464 | encode_cbor [undef] # yields [null] |
… | |
… | |
366 | |
467 | |
367 | my $x = 3.1; # some variable containing a number |
468 | my $x = 3.1; # some variable containing a number |
368 | "$x"; # stringified |
469 | "$x"; # stringified |
369 | $x .= ""; # another, more awkward way to stringify |
470 | $x .= ""; # another, more awkward way to stringify |
370 | print $x; # perl does it for you, too, quite often |
471 | print $x; # perl does it for you, too, quite often |
|
|
472 | |
|
|
473 | You can force whether a string ie encoded as byte or text string by |
|
|
474 | using "utf8::upgrade" and "utf8::downgrade"): |
|
|
475 | |
|
|
476 | utf8::upgrade $x; # encode $x as text string |
|
|
477 | utf8::downgrade $x; # encode $x as byte string |
|
|
478 | |
|
|
479 | Perl doesn't define what operations up- and downgrade strings, so if |
|
|
480 | the difference between byte and text is important, you should up- or |
|
|
481 | downgrade your string as late as possible before encoding. |
371 | |
482 | |
372 | You can force the type to be a CBOR number by numifying it: |
483 | You can force the type to be a CBOR number by numifying it: |
373 | |
484 | |
374 | my $x = "3"; # some variable containing a string |
485 | my $x = "3"; # some variable containing a string |
375 | $x += 0; # numify it, ensuring it will be dumped as a number |
486 | $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 |
496 | the IEEE double format will be used. Perls that use formats other |
386 | than IEEE double to represent numerical values are supported, but |
497 | than IEEE double to represent numerical values are supported, but |
387 | might suffer loss of precision. |
498 | might suffer loss of precision. |
388 | |
499 | |
389 | OBJECT SERIALISATION |
500 | OBJECT SERIALISATION |
|
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501 | This module implements both a CBOR-specific and the generic |
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502 | Types::Serialier object serialisation protocol. The following |
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503 | subsections explain both methods. |
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504 | |
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505 | ENCODING |
390 | This module knows two way to serialise a Perl object: The CBOR-specific |
506 | This module knows two way to serialise a Perl object: The CBOR-specific |
391 | way, and the generic way. |
507 | way, and the generic way. |
392 | |
508 | |
393 | Whenever the encoder encounters a Perl object that it cnanot serialise |
509 | 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 |
510 | directly (most of them), it will first look up the "TO_CBOR" method on |
395 | it. |
511 | it. |
396 | |
512 | |
397 | If it has a "TO_CBOR" method, it will call it with the object as only |
513 | 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 |
514 | argument, and expects exactly one return value, which it will then |
… | |
… | |
403 | "CBOR" as the second argument, to distinguish it from other serialisers. |
519 | "CBOR" as the second argument, to distinguish it from other serialisers. |
404 | |
520 | |
405 | The "FREEZE" method can return any number of values (i.e. zero or more). |
521 | 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. |
522 | These will be encoded as CBOR perl object, together with the classname. |
407 | |
523 | |
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524 | These methods *MUST NOT* change the data structure that is being |
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525 | serialised. Failure to comply to this can result in memory corruption - |
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526 | and worse. |
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527 | |
408 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
528 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
409 | with an error. |
529 | with an error. |
410 | |
530 | |
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531 | DECODING |
411 | Objects encoded via "TO_CBOR" cannot be automatically decoded, but |
532 | Objects encoded via "TO_CBOR" cannot (normally) be automatically |
412 | objects encoded via "FREEZE" can be decoded using the following |
533 | decoded, but objects encoded via "FREEZE" can be decoded using the |
413 | protocol: |
534 | following protocol: |
414 | |
535 | |
415 | When an encoded CBOR perl object is encountered by the decoder, it will |
536 | 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 |
537 | look up the "THAW" method, by using the stored classname, and will fail |
417 | if the method cannot be found. |
538 | if the method cannot be found. |
418 | |
539 | |
… | |
… | |
439 | |
560 | |
440 | sub URI::TO_CBOR { |
561 | sub URI::TO_CBOR { |
441 | my ($self) = @_; |
562 | my ($self) = @_; |
442 | my $uri = "$self"; # stringify uri |
563 | my $uri = "$self"; # stringify uri |
443 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
564 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
444 | CBOR::XS::tagged 32, "$_[0]" |
565 | CBOR::XS::tag 32, "$_[0]" |
445 | } |
566 | } |
446 | |
567 | |
447 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
568 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
448 | URI. |
569 | URI. |
449 | |
570 | |
… | |
… | |
568 | |
689 | |
569 | ENFORCED TAGS |
690 | ENFORCED TAGS |
570 | These tags are always handled when decoding, and their handling cannot |
691 | These tags are always handled when decoding, and their handling cannot |
571 | be overriden by the user. |
692 | be overriden by the user. |
572 | |
693 | |
573 | <unassigned> (perl-object, <http://cbor.schmorp.de/perl-object>) |
694 | 26 (perl-object, <http://cbor.schmorp.de/perl-object>) |
574 | These tags are automatically created (and decoded) for serialisable |
695 | These tags are automatically created (and decoded) for serialisable |
575 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
696 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
576 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
697 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
577 | |
698 | |
578 | <unassigned>, <unassigned> (sharable, sharedref, L |
699 | 28, 29 (shareable, sharedref, <http://cbor.schmorp.de/value-sharing>) |
579 | <http://cbor.schmorp.de/value-sharing>) |
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580 | These tags are automatically decoded when encountered, resulting in |
700 | These tags are automatically decoded when encountered (and they do |
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|
701 | not result in a cyclic data structure, see "allow_cycles"), |
581 | shared values in the decoded object. They are only encoded, however, |
702 | resulting in shared values in the decoded object. They are only |
582 | when "allow_sharable" is enabled. |
703 | encoded, however, when "allow_sharing" is enabled. |
583 | |
704 | |
584 | <unassigned>, <unassigned> (stringref-namespace, stringref, L |
705 | Not all shared values can be successfully decoded: values that |
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706 | reference themselves will *currently* decode as "undef" (this is not |
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707 | the same as a reference pointing to itself, which will be |
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708 | represented as a value that contains an indirect reference to itself |
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709 | - these will be decoded properly). |
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710 | |
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711 | Note that considerably more shared value data structures can be |
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712 | decoded than will be encoded - currently, only values pointed to by |
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713 | references will be shared, others will not. While non-reference |
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714 | shared values can be generated in Perl with some effort, they were |
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715 | considered too unimportant to be supported in the encoder. The |
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716 | decoder, however, will decode these values as shared values. |
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717 | |
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718 | 256, 25 (stringref-namespace, stringref, |
585 | <http://cbor.schmorp.de/stringref>) |
719 | <http://cbor.schmorp.de/stringref>) |
586 | These tags are automatically decoded when encountered. They are only |
720 | These tags are automatically decoded when encountered. They are only |
587 | encoded, however, when "allow_stringref" is enabled. |
721 | encoded, however, when "pack_strings" is enabled. |
588 | |
722 | |
589 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
723 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
590 | This tag is automatically generated when a reference are encountered |
724 | This tag is automatically generated when a reference are encountered |
591 | (with the exception of hash and array refernces). It is converted to |
725 | (with the exception of hash and array refernces). It is converted to |
592 | a reference when decoding. |
726 | a reference when decoding. |
… | |
… | |
605 | |
739 | |
606 | When any of these need to load additional modules that are not part of |
740 | 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 |
741 | 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 |
742 | to provide these modules. The decoding usually fails with an exception |
609 | if the required module cannot be loaded. |
743 | if the required module cannot be loaded. |
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744 | |
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745 | 0, 1 (date/time string, seconds since the epoch) |
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746 | These tags are decoded into Time::Piece objects. The corresponding |
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747 | "Time::Piece::TO_CBOR" method always encodes into tag 1 values |
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748 | currently. |
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749 | |
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750 | The Time::Piece API is generally surprisingly bad, and fractional |
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751 | seconds are only accidentally kept intact, so watch out. On the plus |
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752 | side, the module comes with perl since 5.10, which has to count for |
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753 | something. |
610 | |
754 | |
611 | 2, 3 (positive/negative bignum) |
755 | 2, 3 (positive/negative bignum) |
612 | These tags are decoded into Math::BigInt objects. The corresponding |
756 | These tags are decoded into Math::BigInt objects. The corresponding |
613 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
757 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
614 | CBOR integers, and others into positive/negative CBOR bignums. |
758 | CBOR integers, and others into positive/negative CBOR bignums. |
… | |
… | |
693 | uses long double to represent floating point values, they might not be |
837 | uses long double to represent floating point values, they might not be |
694 | encoded properly. Half precision types are accepted, but not encoded. |
838 | encoded properly. Half precision types are accepted, but not encoded. |
695 | |
839 | |
696 | Strict mode and canonical mode are not implemented. |
840 | Strict mode and canonical mode are not implemented. |
697 | |
841 | |
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842 | LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
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843 | On perls that were built without 64 bit integer support (these are rare |
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844 | nowadays, even on 32 bit architectures, as all major Perl distributions |
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845 | are built with 64 bit integer support), support for any kind of 64 bit |
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846 | integer in CBOR is very limited - most likely, these 64 bit values will |
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847 | be truncated, corrupted, or otherwise not decoded correctly. This also |
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848 | includes string, array and map sizes that are stored as 64 bit integers. |
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849 | |
698 | THREADS |
850 | THREADS |
699 | This module is *not* guaranteed to be thread safe and there are no plans |
851 | 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 |
852 | to change this until Perl gets thread support (as opposed to the |
701 | horribly slow so-called "threads" which are simply slow and bloated |
853 | horribly slow so-called "threads" which are simply slow and bloated |
702 | process simulations - use fork, it's *much* faster, cheaper, better). |
854 | process simulations - use fork, it's *much* faster, cheaper, better). |