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178 | code that isn't prepared for this will not leak memory. |
178 | code that isn't prepared for this will not leak memory. |
179 | |
179 | |
180 | If $enable is false (the default), then "decode" will throw an error |
180 | If $enable is false (the default), then "decode" will throw an error |
181 | when it encounters a self-referential/cyclic data structure. |
181 | when it encounters a self-referential/cyclic data structure. |
182 | |
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 | |
183 | This option does not affect "encode" in any way - shared values and |
188 | This option does not affect "encode" in any way - shared values and |
184 | references will always be decoded properly if present. |
189 | references will always be encoded properly if present. |
185 | |
190 | |
186 | $cbor = $cbor->pack_strings ([$enable]) |
191 | $cbor = $cbor->pack_strings ([$enable]) |
187 | $enabled = $cbor->get_pack_strings |
192 | $enabled = $cbor->get_pack_strings |
188 | 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 |
189 | 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 |
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286 | protocol and you need to know where the first CBOR string ends amd |
291 | protocol and you need to know where the first CBOR string ends amd |
287 | the next one starts. |
292 | the next one starts. |
288 | |
293 | |
289 | CBOR::XS->new->decode_prefix ("......") |
294 | CBOR::XS->new->decode_prefix ("......") |
290 | => ("...", 3) |
295 | => ("...", 3) |
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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. |
291 | |
354 | |
292 | MAPPING |
355 | MAPPING |
293 | 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 |
294 | 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 |
295 | circumstances automatically, preserving round-tripping characteristics |
358 | circumstances automatically, preserving round-tripping characteristics |