… | |
… | |
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 |
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32 | you to do). Furthermore, details of the implementation might change freely |
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33 | before version 1.0. And lastly, the object serialisation protocol depends |
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34 | on a pending IANA assignment, and until that assignment is official, this |
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35 | implementation is not interoperable with other implementations (even |
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36 | future versions of this module) until the assignment is done. |
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37 | |
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38 | You are still invited to try out CBOR, and this module. |
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39 | |
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40 | This module converts Perl data structures to the Concise Binary Object |
31 | This module converts Perl data structures to the Concise Binary Object |
41 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
32 | Representation (CBOR) and vice versa. CBOR is a fast binary serialisation |
42 | format that aims to use a superset of the JSON data model, i.e. when you |
33 | format that aims to use an (almost) superset of the JSON data model, i.e. |
43 | can represent something in JSON, you should be able to represent it in |
34 | when you can represent something useful in JSON, you should be able to |
44 | CBOR. |
35 | represent it in CBOR. |
45 | |
36 | |
46 | In short, CBOR is a faster and very compact binary alternative to JSON, |
37 | In short, CBOR is a faster and quite compact binary alternative to JSON, |
47 | with the added ability of supporting serialisation of Perl objects. (JSON |
38 | with the added ability of supporting serialisation of Perl objects. (JSON |
48 | often compresses better than CBOR though, so if you plan to compress the |
39 | often compresses better than CBOR though, so if you plan to compress the |
49 | data later you might want to compare both formats first). |
40 | data later and speed is less important you might want to compare both |
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41 | formats first). |
50 | |
42 | |
51 | To give you a general idea about speed, with texts in the megabyte range, |
43 | To give you a general idea about speed, with texts in the megabyte range, |
52 | C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or |
44 | C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or |
53 | L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the |
45 | L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the |
54 | data, the worse L<Storable> performs in comparison. |
46 | data, the worse L<Storable> performs in comparison. |
55 | |
47 | |
56 | As for compactness, C<CBOR::XS> encoded data structures are usually about |
48 | Regarding compactness, C<CBOR::XS>-encoded data structures are usually |
57 | 20% smaller than the same data encoded as (compact) JSON or L<Storable>. |
49 | about 20% smaller than the same data encoded as (compact) JSON or |
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50 | L<Storable>. |
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51 | |
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52 | In addition to the core CBOR data format, this module implements a |
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53 | number of extensions, to support cyclic and shared data structures |
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54 | (see C<allow_sharing> and C<allow_cycles>), string deduplication (see |
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55 | C<pack_strings>) and scalar references (always enabled). |
58 | |
56 | |
59 | The primary goal of this module is to be I<correct> and the secondary goal |
57 | 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. |
58 | is to be I<fast>. To reach the latter goal it was written in C. |
61 | |
59 | |
62 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
60 | See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and |
… | |
… | |
66 | |
64 | |
67 | package CBOR::XS; |
65 | package CBOR::XS; |
68 | |
66 | |
69 | use common::sense; |
67 | use common::sense; |
70 | |
68 | |
71 | our $VERSION = 0.08; |
69 | our $VERSION = '1.0'; |
72 | our @ISA = qw(Exporter); |
70 | our @ISA = qw(Exporter); |
73 | |
71 | |
74 | our @EXPORT = qw(encode_cbor decode_cbor); |
72 | our @EXPORT = qw(encode_cbor decode_cbor); |
75 | |
73 | |
76 | use Exporter; |
74 | use Exporter; |
… | |
… | |
113 | strings. All boolean flags described below are by default I<disabled>. |
111 | strings. All boolean flags described below are by default I<disabled>. |
114 | |
112 | |
115 | The mutators for flags all return the CBOR object again and thus calls can |
113 | The mutators for flags all return the CBOR object again and thus calls can |
116 | be chained: |
114 | be chained: |
117 | |
115 | |
118 | #TODO |
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119 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
116 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
120 | |
117 | |
121 | =item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
118 | =item $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
122 | |
119 | |
123 | =item $max_depth = $cbor->get_max_depth |
120 | =item $max_depth = $cbor->get_max_depth |
… | |
… | |
157 | If no argument is given, the limit check will be deactivated (same as when |
154 | If no argument is given, the limit check will be deactivated (same as when |
158 | C<0> is specified). |
155 | C<0> is specified). |
159 | |
156 | |
160 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
157 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
161 | |
158 | |
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159 | =item $cbor = $cbor->allow_unknown ([$enable]) |
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160 | |
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161 | =item $enabled = $cbor->get_allow_unknown |
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162 | |
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163 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
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164 | exception when it encounters values it cannot represent in CBOR (for |
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165 | example, filehandles) but instead will encode a CBOR C<error> value. |
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166 | |
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167 | If C<$enable> is false (the default), then C<encode> will throw an |
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168 | exception when it encounters anything it cannot encode as CBOR. |
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169 | |
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170 | This option does not affect C<decode> in any way, and it is recommended to |
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171 | leave it off unless you know your communications partner. |
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172 | |
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173 | =item $cbor = $cbor->allow_sharing ([$enable]) |
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174 | |
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175 | =item $enabled = $cbor->get_allow_sharing |
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176 | |
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177 | If C<$enable> is true (or missing), then C<encode> will not double-encode |
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178 | values that have been referenced before (e.g. when the same object, such |
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179 | as an array, is referenced multiple times), but instead will emit a |
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180 | reference to the earlier value. |
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181 | |
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182 | This means that such values will only be encoded once, and will not result |
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183 | in a deep cloning of the value on decode, in decoders supporting the value |
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184 | sharing extension. This also makes it possible to encode cyclic data |
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185 | structures (which need C<allow_cycles> to ne enabled to be decoded by this |
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186 | module). |
|
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187 | |
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188 | It is recommended to leave it off unless you know your |
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189 | communication partner supports the value sharing extensions to CBOR |
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190 | (L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the |
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191 | resulting data structure might be unusable. |
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192 | |
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193 | Detecting shared values incurs a runtime overhead when values are encoded |
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194 | that have a reference counter large than one, and might unnecessarily |
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195 | increase the encoded size, as potentially shared values are encode as |
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196 | shareable whether or not they are actually shared. |
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197 | |
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198 | At the moment, only targets of references can be shared (e.g. scalars, |
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199 | arrays or hashes pointed to by a reference). Weirder constructs, such as |
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200 | an array with multiple "copies" of the I<same> string, which are hard but |
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201 | not impossible to create in Perl, are not supported (this is the same as |
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202 | with L<Storable>). |
|
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203 | |
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204 | If C<$enable> is false (the default), then C<encode> will encode shared |
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205 | data structures repeatedly, unsharing them in the process. Cyclic data |
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206 | structures cannot be encoded in this mode. |
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207 | |
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208 | This option does not affect C<decode> in any way - shared values and |
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209 | references will always be decoded properly if present. |
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210 | |
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211 | =item $cbor = $cbor->allow_cycles ([$enable]) |
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212 | |
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213 | =item $enabled = $cbor->get_allow_cycles |
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214 | |
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215 | If C<$enable> is true (or missing), then C<decode> will happily decode |
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216 | self-referential (cyclic) data structures. By default these will not be |
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217 | decoded, as they need manual cleanup to avoid memory leaks, so code that |
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218 | isn't prepared for this will not leak memory. |
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219 | |
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220 | If C<$enable> is false (the default), then C<decode> will throw an error |
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221 | when it encounters a self-referential/cyclic data structure. |
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222 | |
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223 | This option does not affect C<encode> in any way - shared values and |
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224 | references will always be decoded properly if present. |
|
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225 | |
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226 | =item $cbor = $cbor->pack_strings ([$enable]) |
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227 | |
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228 | =item $enabled = $cbor->get_pack_strings |
|
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229 | |
|
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230 | If C<$enable> is true (or missing), then C<encode> will try not to encode |
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231 | the same string twice, but will instead encode a reference to the string |
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232 | instead. Depending on your data format, this can save a lot of space, but |
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233 | also results in a very large runtime overhead (expect encoding times to be |
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234 | 2-4 times as high as without). |
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235 | |
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236 | It is recommended to leave it off unless you know your |
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237 | communications partner supports the stringref extension to CBOR |
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238 | (L<http://cbor.schmorp.de/stringref>), as without decoder support, the |
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239 | resulting data structure might not be usable. |
|
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240 | |
|
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241 | If C<$enable> is false (the default), then C<encode> will encode strings |
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242 | the standard CBOR way. |
|
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243 | |
|
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244 | This option does not affect C<decode> in any way - string references will |
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245 | always be decoded properly if present. |
|
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246 | |
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247 | =item $cbor = $cbor->filter ([$cb->($tag, $value)]) |
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248 | |
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249 | =item $cb_or_undef = $cbor->get_filter |
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250 | |
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251 | Sets or replaces the tagged value decoding filter (when C<$cb> is |
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252 | specified) or clears the filter (if no argument or C<undef> is provided). |
|
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253 | |
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254 | The filter callback is called only during decoding, when a non-enforced |
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255 | tagged value has been decoded (see L<TAG HANDLING AND EXTENSIONS> for a |
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256 | list of enforced tags). For specific tags, it's often better to provide a |
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257 | default converter using the C<%CBOR::XS::FILTER> hash (see below). |
|
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258 | |
|
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259 | The first argument is the numerical tag, the second is the (decoded) value |
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260 | that has been tagged. |
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261 | |
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262 | The filter function should return either exactly one value, which will |
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263 | replace the tagged value in the decoded data structure, or no values, |
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264 | which will result in default handling, which currently means the decoder |
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265 | creates a C<CBOR::XS::Tagged> object to hold the tag and the value. |
|
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266 | |
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267 | When the filter is cleared (the default state), the default filter |
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268 | function, C<CBOR::XS::default_filter>, is used. This function simply looks |
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269 | up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be |
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270 | a code reference that is called with tag and value, and is responsible for |
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271 | decoding the value. If no entry exists, it returns no values. |
|
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272 | |
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273 | Example: decode all tags not handled internally into C<CBOR::XS::Tagged> |
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274 | objects, with no other special handling (useful when working with |
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275 | potentially "unsafe" CBOR data). |
|
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276 | |
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277 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
|
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278 | |
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279 | Example: provide a global filter for tag 1347375694, converting the value |
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280 | into some string form. |
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281 | |
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282 | $CBOR::XS::FILTER{1347375694} = sub { |
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283 | my ($tag, $value); |
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284 | |
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285 | "tag 1347375694 value $value" |
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286 | }; |
|
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287 | |
162 | =item $cbor_data = $cbor->encode ($perl_scalar) |
288 | =item $cbor_data = $cbor->encode ($perl_scalar) |
163 | |
289 | |
164 | Converts the given Perl data structure (a scalar value) to its CBOR |
290 | Converts the given Perl data structure (a scalar value) to its CBOR |
165 | representation. |
291 | representation. |
166 | |
292 | |
… | |
… | |
206 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
332 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
207 | support, 64 bit integers will be truncated or otherwise corrupted. |
333 | support, 64 bit integers will be truncated or otherwise corrupted. |
208 | |
334 | |
209 | =item byte strings |
335 | =item byte strings |
210 | |
336 | |
211 | Byte strings will become octet strings in Perl (the byte values 0..255 |
337 | Byte strings will become octet strings in Perl (the Byte values 0..255 |
212 | will simply become characters of the same value in Perl). |
338 | will simply become characters of the same value in Perl). |
213 | |
339 | |
214 | =item UTF-8 strings |
340 | =item UTF-8 strings |
215 | |
341 | |
216 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
342 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
… | |
… | |
234 | C<Types:Serialiser::false> and C<Types::Serialiser::error>, |
360 | C<Types:Serialiser::false> and C<Types::Serialiser::error>, |
235 | respectively. They are overloaded to act almost exactly like the numbers |
361 | respectively. They are overloaded to act almost exactly like the numbers |
236 | C<1> and C<0> (for true and false) or to throw an exception on access (for |
362 | C<1> and C<0> (for true and false) or to throw an exception on access (for |
237 | error). See the L<Types::Serialiser> manpage for details. |
363 | error). See the L<Types::Serialiser> manpage for details. |
238 | |
364 | |
239 | =item CBOR tag 256 (perl object) |
365 | =item tagged values |
240 | |
366 | |
241 | The tag value C<256> (TODO: pending iana registration) will be used |
|
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242 | to deserialise a Perl object serialised with C<FREEZE>. See L<OBJECT |
|
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243 | SERIALISATION>, below, for details. |
|
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244 | |
|
|
245 | =item CBOR tag 55799 (magic header) |
|
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246 | |
|
|
247 | The tag 55799 is ignored (this tag implements the magic header). |
|
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248 | |
|
|
249 | =item other CBOR tags |
|
|
250 | |
|
|
251 | Tagged items consists of a numeric tag and another CBOR value. Tags not |
367 | Tagged items consists of a numeric tag and another CBOR value. |
252 | handled internally are currently converted into a L<CBOR::XS::Tagged> |
|
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253 | object, which is simply a blessed array reference consisting of the |
|
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254 | numeric tag value followed by the (decoded) CBOR value. |
|
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255 | |
368 | |
256 | In the future, support for user-supplied conversions might get added. |
369 | See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >> |
|
|
370 | for details on which tags are handled how. |
257 | |
371 | |
258 | =item anything else |
372 | =item anything else |
259 | |
373 | |
260 | Anything else (e.g. unsupported simple values) will raise a decoding |
374 | Anything else (e.g. unsupported simple values) will raise a decoding |
261 | error. |
375 | error. |
… | |
… | |
264 | |
378 | |
265 | |
379 | |
266 | =head2 PERL -> CBOR |
380 | =head2 PERL -> CBOR |
267 | |
381 | |
268 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
382 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
269 | truly typeless language, so we can only guess which CBOR type is meant by |
383 | typeless language. That means this module can only guess which CBOR type |
270 | a Perl value. |
384 | is meant by a perl value. |
271 | |
385 | |
272 | =over 4 |
386 | =over 4 |
273 | |
387 | |
274 | =item hash references |
388 | =item hash references |
275 | |
389 | |
276 | Perl hash references become CBOR maps. As there is no inherent ordering in |
390 | Perl hash references become CBOR maps. As there is no inherent ordering in |
277 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
391 | hash keys (or CBOR maps), they will usually be encoded in a pseudo-random |
278 | order. |
392 | order. This order can be different each time a hahs is encoded. |
279 | |
393 | |
280 | Currently, tied hashes will use the indefinite-length format, while normal |
394 | Currently, tied hashes will use the indefinite-length format, while normal |
281 | hashes will use the fixed-length format. |
395 | hashes will use the fixed-length format. |
282 | |
396 | |
283 | =item array references |
397 | =item array references |
284 | |
398 | |
285 | Perl array references become fixed-length CBOR arrays. |
399 | Perl array references become fixed-length CBOR arrays. |
286 | |
400 | |
287 | =item other references |
401 | =item other references |
288 | |
402 | |
289 | Other unblessed references are generally not allowed and will cause an |
403 | Other unblessed references will be represented using |
290 | exception to be thrown, except for references to the integers C<0> and |
404 | the indirection tag extension (tag value C<22098>, |
291 | C<1>, which get turned into false and true in CBOR. |
405 | L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
|
|
406 | to be able to decode these values somehow, by either "doing the right |
|
|
407 | thing", decoding into a generic tagged object, simply ignoring the tag, or |
|
|
408 | something else. |
292 | |
409 | |
293 | =item CBOR::XS::Tagged objects |
410 | =item CBOR::XS::Tagged objects |
294 | |
411 | |
295 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
412 | Objects of this type must be arrays consisting of a single C<[tag, value]> |
296 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
413 | pair. The (numerical) tag will be encoded as a CBOR tag, the value will |
297 | be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to |
414 | be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to |
298 | create such objects. |
415 | create such objects. |
299 | |
416 | |
300 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
417 | =item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error |
301 | |
418 | |
302 | These special values become CBOR true, CBOR false and CBOR undefined |
419 | These special values become CBOR true, CBOR false and CBOR undefined |
… | |
… | |
304 | if you want. |
421 | if you want. |
305 | |
422 | |
306 | =item other blessed objects |
423 | =item other blessed objects |
307 | |
424 | |
308 | Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See |
425 | Other blessed objects are serialised via C<TO_CBOR> or C<FREEZE>. See |
309 | L<OBJECT SERIALISATION>, below, for details. |
426 | L<TAG HANDLING AND EXTENSIONS> for specific classes handled by this |
|
|
427 | module, and L<OBJECT SERIALISATION> for generic object serialisation. |
310 | |
428 | |
311 | =item simple scalars |
429 | =item simple scalars |
312 | |
430 | |
313 | TODO |
|
|
314 | Simple Perl scalars (any scalar that is not a reference) are the most |
431 | Simple Perl scalars (any scalar that is not a reference) are the most |
315 | difficult objects to encode: CBOR::XS will encode undefined scalars as |
432 | difficult objects to encode: CBOR::XS will encode undefined scalars as |
316 | CBOR null values, scalars that have last been used in a string context |
433 | CBOR null values, scalars that have last been used in a string context |
317 | before encoding as CBOR strings, and anything else as number value: |
434 | before encoding as CBOR strings, and anything else as number value: |
318 | |
435 | |
319 | # dump as number |
436 | # dump as number |
320 | encode_cbor [2] # yields [2] |
437 | encode_cbor [2] # yields [2] |
321 | encode_cbor [-3.0e17] # yields [-3e+17] |
438 | encode_cbor [-3.0e17] # yields [-3e+17] |
322 | my $value = 5; encode_cbor [$value] # yields [5] |
439 | my $value = 5; encode_cbor [$value] # yields [5] |
323 | |
440 | |
324 | # used as string, so dump as string |
441 | # used as string, so dump as string (either byte or text) |
325 | print $value; |
442 | print $value; |
326 | encode_cbor [$value] # yields ["5"] |
443 | encode_cbor [$value] # yields ["5"] |
327 | |
444 | |
328 | # undef becomes null |
445 | # undef becomes null |
329 | encode_cbor [undef] # yields [null] |
446 | encode_cbor [undef] # yields [null] |
… | |
… | |
332 | |
449 | |
333 | my $x = 3.1; # some variable containing a number |
450 | my $x = 3.1; # some variable containing a number |
334 | "$x"; # stringified |
451 | "$x"; # stringified |
335 | $x .= ""; # another, more awkward way to stringify |
452 | $x .= ""; # another, more awkward way to stringify |
336 | print $x; # perl does it for you, too, quite often |
453 | print $x; # perl does it for you, too, quite often |
|
|
454 | |
|
|
455 | You can force whether a string ie encoded as byte or text string by using |
|
|
456 | C<utf8::upgrade> and C<utf8::downgrade>): |
|
|
457 | |
|
|
458 | utf8::upgrade $x; # encode $x as text string |
|
|
459 | utf8::downgrade $x; # encode $x as byte string |
|
|
460 | |
|
|
461 | Perl doesn't define what operations up- and downgrade strings, so if the |
|
|
462 | difference between byte and text is important, you should up- or downgrade |
|
|
463 | your string as late as possible before encoding. |
337 | |
464 | |
338 | You can force the type to be a CBOR number by numifying it: |
465 | You can force the type to be a CBOR number by numifying it: |
339 | |
466 | |
340 | my $x = "3"; # some variable containing a string |
467 | my $x = "3"; # some variable containing a string |
341 | $x += 0; # numify it, ensuring it will be dumped as a number |
468 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
354 | |
481 | |
355 | =back |
482 | =back |
356 | |
483 | |
357 | =head2 OBJECT SERIALISATION |
484 | =head2 OBJECT SERIALISATION |
358 | |
485 | |
|
|
486 | This module implements both a CBOR-specific and the generic |
|
|
487 | L<Types::Serialier> object serialisation protocol. The following |
|
|
488 | subsections explain both methods. |
|
|
489 | |
|
|
490 | =head3 ENCODING |
|
|
491 | |
359 | This module knows two way to serialise a Perl object: The CBOR-specific |
492 | This module knows two way to serialise a Perl object: The CBOR-specific |
360 | way, and the generic way. |
493 | way, and the generic way. |
361 | |
494 | |
362 | Whenever the encoder encounters a Perl object that it cnanot serialise |
495 | Whenever the encoder encounters a Perl object that it cannot serialise |
363 | directly (most of them), it will first look up the C<TO_CBOR> method on |
496 | directly (most of them), it will first look up the C<TO_CBOR> method on |
364 | it. |
497 | it. |
365 | |
498 | |
366 | If it has a C<TO_CBOR> method, it will call it with the object as only |
499 | If it has a C<TO_CBOR> method, it will call it with the object as only |
367 | argument, and expects exactly one return value, which it will then |
500 | argument, and expects exactly one return value, which it will then |
… | |
… | |
373 | |
506 | |
374 | The C<FREEZE> method can return any number of values (i.e. zero or |
507 | The C<FREEZE> method can return any number of values (i.e. zero or |
375 | more). These will be encoded as CBOR perl object, together with the |
508 | more). These will be encoded as CBOR perl object, together with the |
376 | classname. |
509 | classname. |
377 | |
510 | |
|
|
511 | These methods I<MUST NOT> change the data structure that is being |
|
|
512 | serialised. Failure to comply to this can result in memory corruption - |
|
|
513 | and worse. |
|
|
514 | |
378 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
515 | If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail |
379 | with an error. |
516 | with an error. |
380 | |
517 | |
|
|
518 | =head3 DECODING |
|
|
519 | |
381 | Objects encoded via C<TO_CBOR> cannot be automatically decoded, but |
520 | Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded, |
382 | objects encoded via C<FREEZE> can be decoded using the following protocol: |
521 | but objects encoded via C<FREEZE> can be decoded using the following |
|
|
522 | protocol: |
383 | |
523 | |
384 | When an encoded CBOR perl object is encountered by the decoder, it will |
524 | When an encoded CBOR perl object is encountered by the decoder, it will |
385 | look up the C<THAW> method, by using the stored classname, and will fail |
525 | look up the C<THAW> method, by using the stored classname, and will fail |
386 | if the method cannot be found. |
526 | if the method cannot be found. |
387 | |
527 | |
388 | After the lookup it will call the C<THAW> method with the stored classname |
528 | After the lookup it will call the C<THAW> method with the stored classname |
389 | as first argument, the constant string C<CBOR> as second argument, and all |
529 | as first argument, the constant string C<CBOR> as second argument, and all |
390 | values returned by C<FREEZE> as remaining arguments. |
530 | values returned by C<FREEZE> as remaining arguments. |
391 | |
531 | |
392 | =head4 EXAMPLES |
532 | =head3 EXAMPLES |
393 | |
533 | |
394 | Here is an example C<TO_CBOR> method: |
534 | Here is an example C<TO_CBOR> method: |
395 | |
535 | |
396 | sub My::Object::TO_CBOR { |
536 | sub My::Object::TO_CBOR { |
397 | my ($obj) = @_; |
537 | my ($obj) = @_; |
… | |
… | |
408 | |
548 | |
409 | sub URI::TO_CBOR { |
549 | sub URI::TO_CBOR { |
410 | my ($self) = @_; |
550 | my ($self) = @_; |
411 | my $uri = "$self"; # stringify uri |
551 | my $uri = "$self"; # stringify uri |
412 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
552 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
413 | CBOR::XS::tagged 32, "$_[0]" |
553 | CBOR::XS::tag 32, "$_[0]" |
414 | } |
554 | } |
415 | |
555 | |
416 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
556 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
417 | URI. |
557 | URI. |
418 | |
558 | |
… | |
… | |
455 | =head1 MAGIC HEADER |
595 | =head1 MAGIC HEADER |
456 | |
596 | |
457 | There is no way to distinguish CBOR from other formats |
597 | There is no way to distinguish CBOR from other formats |
458 | programmatically. To make it easier to distinguish CBOR from other |
598 | programmatically. To make it easier to distinguish CBOR from other |
459 | formats, the CBOR specification has a special "magic string" that can be |
599 | formats, the CBOR specification has a special "magic string" that can be |
460 | prepended to any CBOR string without changing it's meaning. |
600 | prepended to any CBOR string without changing its meaning. |
461 | |
601 | |
462 | This string is available as C<$CBOR::XS::MAGIC>. This module does not |
602 | 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 |
603 | 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 |
604 | if present, so users can prepend this string as a "file type" indicator as |
465 | required. |
605 | required. |
466 | |
606 | |
467 | |
607 | |
468 | =head1 THE CBOR::XS::Tagged CLASS |
608 | =head1 THE CBOR::XS::Tagged CLASS |
… | |
… | |
551 | Wrap CBOR data in CBOR: |
691 | Wrap CBOR data in CBOR: |
552 | |
692 | |
553 | my $cbor_cbor = encode_cbor |
693 | my $cbor_cbor = encode_cbor |
554 | CBOR::XS::tag 24, |
694 | CBOR::XS::tag 24, |
555 | encode_cbor [1, 2, 3]; |
695 | encode_cbor [1, 2, 3]; |
|
|
696 | |
|
|
697 | =head1 TAG HANDLING AND EXTENSIONS |
|
|
698 | |
|
|
699 | This section describes how this module handles specific tagged values |
|
|
700 | and extensions. If a tag is not mentioned here and no additional filters |
|
|
701 | are provided for it, then the default handling applies (creating a |
|
|
702 | CBOR::XS::Tagged object on decoding, and only encoding the tag when |
|
|
703 | explicitly requested). |
|
|
704 | |
|
|
705 | Tags not handled specifically are currently converted into a |
|
|
706 | L<CBOR::XS::Tagged> object, which is simply a blessed array reference |
|
|
707 | consisting of the numeric tag value followed by the (decoded) CBOR value. |
|
|
708 | |
|
|
709 | Future versions of this module reserve the right to special case |
|
|
710 | additional tags (such as base64url). |
|
|
711 | |
|
|
712 | =head2 ENFORCED TAGS |
|
|
713 | |
|
|
714 | These tags are always handled when decoding, and their handling cannot be |
|
|
715 | overriden by the user. |
|
|
716 | |
|
|
717 | =over 4 |
|
|
718 | |
|
|
719 | =item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>) |
|
|
720 | |
|
|
721 | These tags are automatically created (and decoded) for serialisable |
|
|
722 | objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object |
|
|
723 | serialisation protocol). See L<OBJECT SERIALISATION> for details. |
|
|
724 | |
|
|
725 | =item 28, 29 (shareable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
|
|
726 | |
|
|
727 | These tags are automatically decoded when encountered (and they do not |
|
|
728 | result in a cyclic data structure, see C<allow_cycles>), resulting in |
|
|
729 | shared values in the decoded object. They are only encoded, however, when |
|
|
730 | C<allow_sharing> is enabled. |
|
|
731 | |
|
|
732 | Not all shared values can be successfully decoded: values that reference |
|
|
733 | themselves will I<currently> decode as C<undef> (this is not the same |
|
|
734 | as a reference pointing to itself, which will be represented as a value |
|
|
735 | that contains an indirect reference to itself - these will be decoded |
|
|
736 | properly). |
|
|
737 | |
|
|
738 | Note that considerably more shared value data structures can be decoded |
|
|
739 | than will be encoded - currently, only values pointed to by references |
|
|
740 | will be shared, others will not. While non-reference shared values can be |
|
|
741 | generated in Perl with some effort, they were considered too unimportant |
|
|
742 | to be supported in the encoder. The decoder, however, will decode these |
|
|
743 | values as shared values. |
|
|
744 | |
|
|
745 | =item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>) |
|
|
746 | |
|
|
747 | These tags are automatically decoded when encountered. They are only |
|
|
748 | encoded, however, when C<pack_strings> is enabled. |
|
|
749 | |
|
|
750 | =item 22098 (indirection, L<http://cbor.schmorp.de/indirection>) |
|
|
751 | |
|
|
752 | This tag is automatically generated when a reference are encountered (with |
|
|
753 | the exception of hash and array refernces). It is converted to a reference |
|
|
754 | when decoding. |
|
|
755 | |
|
|
756 | =item 55799 (self-describe CBOR, RFC 7049) |
|
|
757 | |
|
|
758 | This value is not generated on encoding (unless explicitly requested by |
|
|
759 | the user), and is simply ignored when decoding. |
|
|
760 | |
|
|
761 | =back |
|
|
762 | |
|
|
763 | =head2 NON-ENFORCED TAGS |
|
|
764 | |
|
|
765 | These tags have default filters provided when decoding. Their handling can |
|
|
766 | be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by |
|
|
767 | providing a custom C<filter> callback when decoding. |
|
|
768 | |
|
|
769 | When they result in decoding into a specific Perl class, the module |
|
|
770 | usually provides a corresponding C<TO_CBOR> method as well. |
|
|
771 | |
|
|
772 | When any of these need to load additional modules that are not part of the |
|
|
773 | perl core distribution (e.g. L<URI>), it is (currently) up to the user to |
|
|
774 | provide these modules. The decoding usually fails with an exception if the |
|
|
775 | required module cannot be loaded. |
|
|
776 | |
|
|
777 | =over 4 |
|
|
778 | |
|
|
779 | =item 2, 3 (positive/negative bignum) |
|
|
780 | |
|
|
781 | These tags are decoded into L<Math::BigInt> objects. The corresponding |
|
|
782 | C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR |
|
|
783 | integers, and others into positive/negative CBOR bignums. |
|
|
784 | |
|
|
785 | =item 4, 5 (decimal fraction/bigfloat) |
|
|
786 | |
|
|
787 | Both decimal fractions and bigfloats are decoded into L<Math::BigFloat> |
|
|
788 | objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always> |
|
|
789 | encodes into a decimal fraction. |
|
|
790 | |
|
|
791 | CBOR cannot represent bigfloats with I<very> large exponents - conversion |
|
|
792 | of such big float objects is undefined. |
|
|
793 | |
|
|
794 | Also, NaN and infinities are not encoded properly. |
|
|
795 | |
|
|
796 | =item 21, 22, 23 (expected later JSON conversion) |
|
|
797 | |
|
|
798 | CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these |
|
|
799 | tags. |
|
|
800 | |
|
|
801 | =item 32 (URI) |
|
|
802 | |
|
|
803 | These objects decode into L<URI> objects. The corresponding |
|
|
804 | C<URI::TO_CBOR> method again results in a CBOR URI value. |
|
|
805 | |
|
|
806 | =back |
|
|
807 | |
|
|
808 | =cut |
|
|
809 | |
|
|
810 | our %FILTER = ( |
|
|
811 | # 0 # rfc4287 datetime, utf-8 |
|
|
812 | # 1 # unix timestamp, any |
|
|
813 | |
|
|
814 | 2 => sub { # pos bigint |
|
|
815 | require Math::BigInt; |
|
|
816 | Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
817 | }, |
|
|
818 | |
|
|
819 | 3 => sub { # neg bigint |
|
|
820 | require Math::BigInt; |
|
|
821 | -Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
822 | }, |
|
|
823 | |
|
|
824 | 4 => sub { # decimal fraction, array |
|
|
825 | require Math::BigFloat; |
|
|
826 | Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
|
|
827 | }, |
|
|
828 | |
|
|
829 | 5 => sub { # bigfloat, array |
|
|
830 | require Math::BigFloat; |
|
|
831 | scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2) |
|
|
832 | }, |
|
|
833 | |
|
|
834 | 21 => sub { pop }, # expected conversion to base64url encoding |
|
|
835 | 22 => sub { pop }, # expected conversion to base64 encoding |
|
|
836 | 23 => sub { pop }, # expected conversion to base16 encoding |
|
|
837 | |
|
|
838 | # 24 # embedded cbor, byte string |
|
|
839 | |
|
|
840 | 32 => sub { |
|
|
841 | require URI; |
|
|
842 | URI->new (pop) |
|
|
843 | }, |
|
|
844 | |
|
|
845 | # 33 # base64url rfc4648, utf-8 |
|
|
846 | # 34 # base64 rfc46484, utf-8 |
|
|
847 | # 35 # regex pcre/ecma262, utf-8 |
|
|
848 | # 36 # mime message rfc2045, utf-8 |
|
|
849 | ); |
|
|
850 | |
556 | |
851 | |
557 | =head1 CBOR and JSON |
852 | =head1 CBOR and JSON |
558 | |
853 | |
559 | CBOR is supposed to implement a superset of the JSON data model, and is, |
854 | 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 |
855 | with some coercion, able to represent all JSON texts (something that other |
… | |
… | |
621 | properly. Half precision types are accepted, but not encoded. |
916 | properly. Half precision types are accepted, but not encoded. |
622 | |
917 | |
623 | Strict mode and canonical mode are not implemented. |
918 | Strict mode and canonical mode are not implemented. |
624 | |
919 | |
625 | |
920 | |
|
|
921 | =head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
922 | |
|
|
923 | On perls that were built without 64 bit integer support (these are rare |
|
|
924 | nowadays, even on 32 bit architectures), support for any kind of 64 bit |
|
|
925 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
926 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
927 | includes string, array and map sizes that are stored as 64 bit integers. |
|
|
928 | |
|
|
929 | |
626 | =head1 THREADS |
930 | =head1 THREADS |
627 | |
931 | |
628 | This module is I<not> guaranteed to be thread safe and there are no |
932 | This module is I<not> guaranteed to be thread safe and there are no |
629 | plans to change this until Perl gets thread support (as opposed to the |
933 | plans to change this until Perl gets thread support (as opposed to the |
630 | horribly slow so-called "threads" which are simply slow and bloated |
934 | horribly slow so-called "threads" which are simply slow and bloated |
… | |
… | |
642 | Please refrain from using rt.cpan.org or any other bug reporting |
946 | Please refrain from using rt.cpan.org or any other bug reporting |
643 | service. I put the contact address into my modules for a reason. |
947 | service. I put the contact address into my modules for a reason. |
644 | |
948 | |
645 | =cut |
949 | =cut |
646 | |
950 | |
|
|
951 | our %FILTER = ( |
|
|
952 | # 0 # rfc4287 datetime, utf-8 |
|
|
953 | # 1 # unix timestamp, any |
|
|
954 | |
|
|
955 | 2 => sub { # pos bigint |
|
|
956 | require Math::BigInt; |
|
|
957 | Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
958 | }, |
|
|
959 | |
|
|
960 | 3 => sub { # neg bigint |
|
|
961 | require Math::BigInt; |
|
|
962 | -Math::BigInt->new ("0x" . unpack "H*", pop) |
|
|
963 | }, |
|
|
964 | |
|
|
965 | 4 => sub { # decimal fraction, array |
|
|
966 | require Math::BigFloat; |
|
|
967 | Math::BigFloat->new ($_[1][1] . "E" . $_[1][0]) |
|
|
968 | }, |
|
|
969 | |
|
|
970 | 5 => sub { # bigfloat, array |
|
|
971 | require Math::BigFloat; |
|
|
972 | scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2) |
|
|
973 | }, |
|
|
974 | |
|
|
975 | 21 => sub { pop }, # expected conversion to base64url encoding |
|
|
976 | 22 => sub { pop }, # expected conversion to base64 encoding |
|
|
977 | 23 => sub { pop }, # expected conversion to base16 encoding |
|
|
978 | |
|
|
979 | # 24 # embedded cbor, byte string |
|
|
980 | |
|
|
981 | 32 => sub { |
|
|
982 | require URI; |
|
|
983 | URI->new (pop) |
|
|
984 | }, |
|
|
985 | |
|
|
986 | # 33 # base64url rfc4648, utf-8 |
|
|
987 | # 34 # base64 rfc46484, utf-8 |
|
|
988 | # 35 # regex pcre/ecma262, utf-8 |
|
|
989 | # 36 # mime message rfc2045, utf-8 |
|
|
990 | ); |
|
|
991 | |
|
|
992 | sub CBOR::XS::default_filter { |
|
|
993 | &{ $FILTER{$_[0]} or return } |
|
|
994 | } |
|
|
995 | |
|
|
996 | sub URI::TO_CBOR { |
|
|
997 | my $uri = $_[0]->as_string; |
|
|
998 | utf8::upgrade $uri; |
|
|
999 | CBOR::XS::tag 32, $uri |
|
|
1000 | } |
|
|
1001 | |
|
|
1002 | sub Math::BigInt::TO_CBOR { |
|
|
1003 | if ($_[0] >= -2147483648 && $_[0] <= 2147483647) { |
|
|
1004 | $_[0]->numify |
|
|
1005 | } else { |
|
|
1006 | my $hex = substr $_[0]->as_hex, 2; |
|
|
1007 | $hex = "0$hex" if 1 & length $hex; # sigh |
|
|
1008 | CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex |
|
|
1009 | } |
|
|
1010 | } |
|
|
1011 | |
|
|
1012 | sub Math::BigFloat::TO_CBOR { |
|
|
1013 | my ($m, $e) = $_[0]->parts; |
|
|
1014 | CBOR::XS::tag 4, [$e->numify, $m] |
|
|
1015 | } |
|
|
1016 | |
647 | XSLoader::load "CBOR::XS", $VERSION; |
1017 | XSLoader::load "CBOR::XS", $VERSION; |
648 | |
1018 | |
649 | =head1 SEE ALSO |
1019 | =head1 SEE ALSO |
650 | |
1020 | |
651 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |
1021 | The L<JSON> and L<JSON::XS> modules that do similar, but human-readable, |