… | |
… | |
26 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
26 | substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string |
27 | } |
27 | } |
28 | |
28 | |
29 | =head1 DESCRIPTION |
29 | =head1 DESCRIPTION |
30 | |
30 | |
31 | WARNING! This module is very new, and not very well tested (that's up to |
31 | WARNING! This module is very new, and not very well tested (that's up |
32 | you to do). Furthermore, details of the implementation might change freely |
32 | to you to do). Furthermore, details of the implementation might change |
33 | before version 1.0. And lastly, the object serialisation protocol depends |
33 | freely before version 1.0. And lastly, most extensions depend on an IANA |
34 | on a pending IANA assignment, and until that assignment is official, this |
34 | assignment, and until that assignment is official, this implementation is |
35 | implementation is not interoperable with other implementations (even |
35 | not interoperable with other implementations (even future versions of this |
36 | future versions of this module) until the assignment is done. |
36 | module) until the assignment is done. |
37 | |
37 | |
38 | You are still invited to try out CBOR, and this module. |
38 | You are still invited to try out CBOR, and this module. |
39 | |
39 | |
40 | This module converts Perl data structures to the Concise Binary Object |
40 | This module converts Perl data structures to the Concise Binary Object |
41 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
41 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
… | |
… | |
54 | data, the worse L<Storable> performs in comparison. |
54 | data, the worse L<Storable> performs in comparison. |
55 | |
55 | |
56 | As for compactness, C<CBOR::XS> encoded data structures are usually about |
56 | As for compactness, C<CBOR::XS> encoded data structures are usually about |
57 | 20% smaller than the same data encoded as (compact) JSON or L<Storable>. |
57 | 20% smaller than the same data encoded as (compact) JSON or L<Storable>. |
58 | |
58 | |
|
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59 | In addition to the core CBOR data format, this module implements a number |
|
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60 | of extensions, to support cyclic and self-referencing data structures |
|
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61 | (see C<allow_sharing>), string deduplication (see C<allow_stringref>) and |
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62 | scalar references (always enabled). |
|
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63 | |
59 | The primary goal of this module is to be I<correct> and the secondary goal |
64 | The primary goal of this module is to be I<correct> and the secondary goal |
60 | is to be I<fast>. To reach the latter goal it was written in C. |
65 | is to be I<fast>. To reach the latter goal it was written in C. |
61 | |
66 | |
62 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
67 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
63 | vice versa. |
68 | vice versa. |
… | |
… | |
156 | |
161 | |
157 | If no argument is given, the limit check will be deactivated (same as when |
162 | If no argument is given, the limit check will be deactivated (same as when |
158 | C<0> is specified). |
163 | C<0> is specified). |
159 | |
164 | |
160 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
165 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
|
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166 | |
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167 | =item $cbor = $cbor->allow_unknown ([$enable]) |
|
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168 | |
|
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169 | =item $enabled = $cbor->get_allow_unknown |
|
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170 | |
|
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171 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
|
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172 | exception when it encounters values it cannot represent in CBOR (for |
|
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173 | example, filehandles) but instead will encode a CBOR C<error> value. |
|
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174 | |
|
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175 | If C<$enable> is false (the default), then C<encode> will throw an |
|
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176 | exception when it encounters anything it cannot encode as CBOR. |
|
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177 | |
|
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178 | This option does not affect C<decode> in any way, and it is recommended to |
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179 | leave it off unless you know your communications partner. |
|
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180 | |
|
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181 | =item $cbor = $cbor->allow_sharing ([$enable]) |
|
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182 | |
|
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183 | =item $enabled = $cbor->get_allow_sharing |
|
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184 | |
|
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185 | If C<$enable> is true (or missing), then C<encode> will not double-encode |
|
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186 | values that have been referenced before (e.g. when the same object, such |
|
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187 | as an array, is referenced multiple times), but instead will emit a |
|
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188 | reference to the earlier value. |
|
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189 | |
|
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190 | This means that such values will only be encoded once, and will not result |
|
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191 | in a deep cloning of the value on decode, in decoders supporting the value |
|
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192 | sharing extension. |
|
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193 | |
|
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194 | It is recommended to leave it off unless you know your |
|
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195 | communication partner supports the value sharing extensions to CBOR |
|
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196 | (http://cbor.schmorp.de/value-sharing). |
|
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197 | |
|
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198 | Detecting shared values incurs a runtime overhead when values are encoded |
|
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199 | that have a reference counter large than one, and might unnecessarily |
|
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200 | increase the encoded size, as potentially shared values are encode as |
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201 | sharable whether or not they are actually shared. |
|
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202 | |
|
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203 | At the moment, only targets of references can be shared (e.g. scalars, |
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204 | arrays or hashes pointed to by a reference). Weirder constructs, such as |
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205 | an array with multiple "copies" of the I<same> string, which are hard but |
|
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206 | not impossible to create in Perl, are not supported (this is the same as |
|
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207 | for L<Storable>). |
|
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208 | |
|
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209 | If C<$enable> is false (the default), then C<encode> will encode |
|
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210 | exception when it encounters anything it cannot encode as CBOR. |
|
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211 | |
|
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212 | This option does not affect C<decode> in any way - shared values and |
|
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213 | references will always be decoded properly if present. |
|
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214 | |
|
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215 | =item $cbor = $cbor->allow_stringref ([$enable]) |
|
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216 | |
|
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217 | =item $enabled = $cbor->get_allow_stringref |
|
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218 | |
|
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219 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
|
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220 | the same string twice, but will instead encode a reference to the string |
|
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221 | instead. Depending on your data format. this can save a lot of space, but |
|
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222 | also results in a very large runtime overhead (expect encoding times to be |
|
|
223 | 2-4 times as high as without). |
|
|
224 | |
|
|
225 | It is recommended to leave it off unless you know your |
|
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226 | communications partner supports the stringref extension to CBOR |
|
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227 | (http://cbor.schmorp.de/stringref). |
|
|
228 | |
|
|
229 | If C<$enable> is false (the default), then C<encode> will encode |
|
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230 | exception when it encounters anything it cannot encode as CBOR. |
|
|
231 | |
|
|
232 | This option does not affect C<decode> in any way - string references will |
|
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233 | always be decoded properly if present. |
161 | |
234 | |
162 | =item $cbor_data = $cbor->encode ($perl_scalar) |
235 | =item $cbor_data = $cbor->encode ($perl_scalar) |
163 | |
236 | |
164 | Converts the given Perl data structure (a scalar value) to its CBOR |
237 | Converts the given Perl data structure (a scalar value) to its CBOR |
165 | representation. |
238 | representation. |
… | |
… | |
455 | =head1 MAGIC HEADER |
528 | =head1 MAGIC HEADER |
456 | |
529 | |
457 | There is no way to distinguish CBOR from other formats |
530 | There is no way to distinguish CBOR from other formats |
458 | programmatically. To make it easier to distinguish CBOR from other |
531 | programmatically. To make it easier to distinguish CBOR from other |
459 | formats, the CBOR specification has a special "magic string" that can be |
532 | formats, the CBOR specification has a special "magic string" that can be |
460 | prepended to any CBOR string without changing it's meaning. |
533 | prepended to any CBOR string without changing its meaning. |
461 | |
534 | |
462 | This string is available as C<$CBOR::XS::MAGIC>. This module does not |
535 | This string is available as C<$CBOR::XS::MAGIC>. This module does not |
463 | prepend this string tot he CBOR data it generates, but it will ignroe it |
536 | prepend this string to the CBOR data it generates, but it will ignore it |
464 | if present, so users can prepend this string as a "file type" indicator as |
537 | if present, so users can prepend this string as a "file type" indicator as |
465 | required. |
538 | required. |
466 | |
539 | |
467 | |
540 | |
468 | =head1 THE CBOR::XS::Tagged CLASS |
541 | =head1 THE CBOR::XS::Tagged CLASS |
… | |
… | |
551 | Wrap CBOR data in CBOR: |
624 | Wrap CBOR data in CBOR: |
552 | |
625 | |
553 | my $cbor_cbor = encode_cbor |
626 | my $cbor_cbor = encode_cbor |
554 | CBOR::XS::tag 24, |
627 | CBOR::XS::tag 24, |
555 | encode_cbor [1, 2, 3]; |
628 | encode_cbor [1, 2, 3]; |
|
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629 | |
|
|
630 | =head1 TAG HANDLING AND EXTENSIONS |
|
|
631 | |
|
|
632 | This section describes how this module handles specific tagged values and |
|
|
633 | extensions. If a tag is not mentioned here, then the default handling |
|
|
634 | applies (creating a CBOR::XS::Tagged object on decoding, and only encoding |
|
|
635 | the tag when explicitly requested). |
|
|
636 | |
|
|
637 | Future versions of this module reserve the right to special case |
|
|
638 | additional tags (such as bigfloat or base64url). |
|
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639 | |
|
|
640 | =over 4 |
|
|
641 | |
|
|
642 | =item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>) |
|
|
643 | |
|
|
644 | These tags are automatically created for serialisable objects using the |
|
|
645 | C<FREEZE/THAW> methods (the L<Types::Serialier> object serialisation |
|
|
646 | protocol). |
|
|
647 | |
|
|
648 | =item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
|
|
649 | |
|
|
650 | These tags are automatically decoded when encountered, resulting in |
|
|
651 | shared values in the decoded object. They are only encoded, however, when |
|
|
652 | C<allow_sharable> is enabled. |
|
|
653 | |
|
|
654 | =item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
|
|
655 | |
|
|
656 | These tags are automatically decoded when encountered. They are only |
|
|
657 | encoded, however, when C<allow_stringref> is enabled. |
|
|
658 | |
|
|
659 | =item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) |
|
|
660 | |
|
|
661 | This tag is automatically generated when a reference are encountered (with |
|
|
662 | the exception of hash and array refernces). It is converted to a reference |
|
|
663 | when decoding. |
|
|
664 | |
|
|
665 | =item 55799 (self-describe CBOR, RFC 7049) |
|
|
666 | |
|
|
667 | This value is not generated on encoding (unless explicitly requested by |
|
|
668 | the user), and is simply ignored when decoding. |
|
|
669 | |
|
|
670 | =back |
|
|
671 | |
556 | |
672 | |
557 | =head1 CBOR and JSON |
673 | =head1 CBOR and JSON |
558 | |
674 | |
559 | CBOR is supposed to implement a superset of the JSON data model, and is, |
675 | CBOR is supposed to implement a superset of the JSON data model, and is, |
560 | with some coercion, able to represent all JSON texts (something that other |
676 | with some coercion, able to represent all JSON texts (something that other |