… | |
… | |
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, the object serialisation protocol |
|
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29 | depends on a pending IANA assignment, and until that assignment is |
|
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30 | official, this implementation is not interoperable with other |
|
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31 | implementations (even future versions of this module) until the |
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32 | assignment is done. |
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33 | |
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34 | You are still invited to try out CBOR, and this module. |
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35 | |
|
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36 | This module converts Perl data structures to the Concise Binary Object |
26 | This module converts Perl data structures to the Concise Binary Object |
37 | Representation (CBOR) and vice versa. CBOR is a fast binary |
27 | Representation (CBOR) and vice versa. CBOR is a fast binary |
38 | 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 |
39 | 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 |
40 | represent it in CBOR. |
30 | should be able to represent it in CBOR. |
41 | |
31 | |
42 | 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, |
43 | with the added ability of supporting serialisation of Perl objects. |
33 | with the added ability of supporting serialisation of Perl objects. |
44 | (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 |
45 | 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). |
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37 | |
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38 | To give you a general idea about speed, with texts in the megabyte |
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39 | range, "CBOR::XS" usually encodes roughly twice as fast as Storable or |
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40 | JSON::XS and decodes about 15%-30% faster than those. The shorter the |
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41 | data, the worse Storable performs in comparison. |
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42 | |
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43 | Regarding compactness, "CBOR::XS"-encoded data structures are usually |
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44 | about 20% smaller than the same data encoded as (compact) JSON or |
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45 | Storable. |
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46 | |
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47 | In addition to the core CBOR data format, this module implements a |
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48 | number of extensions, to support cyclic and shared data structures (see |
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49 | "allow_sharing" and "allow_cycles"), string deduplication (see |
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50 | "pack_strings") and scalar references (always enabled). |
46 | |
51 | |
47 | 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 |
48 | 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. |
49 | |
54 | |
50 | 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 |
… | |
… | |
72 | *disabled*. |
77 | *disabled*. |
73 | |
78 | |
74 | The mutators for flags all return the CBOR object again and thus |
79 | The mutators for flags all return the CBOR object again and thus |
75 | calls can be chained: |
80 | calls can be chained: |
76 | |
81 | |
77 | #TODO my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
82 | my $cbor = CBOR::XS->new->encode ({a => [1,2]}); |
78 | |
83 | |
79 | $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
84 | $cbor = $cbor->max_depth ([$maximum_nesting_depth]) |
80 | $max_depth = $cbor->get_max_depth |
85 | $max_depth = $cbor->get_max_depth |
81 | Sets the maximum nesting level (default 512) accepted while encoding |
86 | Sets the maximum nesting level (default 512) accepted while encoding |
82 | or decoding. If a higher nesting level is detected in CBOR data or a |
87 | or decoding. If a higher nesting level is detected in CBOR data or a |
… | |
… | |
113 | as when 0 is specified). |
118 | as when 0 is specified). |
114 | |
119 | |
115 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
120 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
116 | useful. |
121 | useful. |
117 | |
122 | |
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123 | $cbor = $cbor->allow_unknown ([$enable]) |
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124 | $enabled = $cbor->get_allow_unknown |
|
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125 | If $enable is true (or missing), then "encode" will *not* throw an |
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126 | exception when it encounters values it cannot represent in CBOR (for |
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127 | example, filehandles) but instead will encode a CBOR "error" value. |
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128 | |
|
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129 | If $enable is false (the default), then "encode" will throw an |
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130 | exception when it encounters anything it cannot encode as CBOR. |
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131 | |
|
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132 | This option does not affect "decode" in any way, and it is |
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133 | recommended to leave it off unless you know your communications |
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134 | partner. |
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135 | |
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136 | $cbor = $cbor->allow_sharing ([$enable]) |
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137 | $enabled = $cbor->get_allow_sharing |
|
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138 | If $enable is true (or missing), then "encode" will not |
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139 | double-encode values that have been referenced before (e.g. when the |
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140 | same object, such as an array, is referenced multiple times), but |
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141 | instead will emit a reference to the earlier value. |
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142 | |
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143 | This means that such values will only be encoded once, and will not |
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144 | result in a deep cloning of the value on decode, in decoders |
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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). |
|
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148 | |
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149 | It is recommended to leave it off unless you know your communication |
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150 | partner supports the value sharing extensions to CBOR |
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151 | (<http://cbor.schmorp.de/value-sharing>), as without decoder |
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152 | support, the resulting data structure might be unusable. |
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153 | |
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154 | Detecting shared values incurs a runtime overhead when values are |
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155 | encoded that have a reference counter large than one, and might |
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156 | unnecessarily increase the encoded size, as potentially shared |
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157 | values are encode as shareable whether or not they are actually |
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158 | shared. |
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159 | |
|
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160 | At the moment, only targets of references can be shared (e.g. |
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161 | scalars, arrays or hashes pointed to by a reference). Weirder |
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162 | constructs, such as an array with multiple "copies" of the *same* |
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163 | string, which are hard but not impossible to create in Perl, are not |
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164 | supported (this is the same as with Storable). |
|
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165 | |
|
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166 | If $enable is false (the default), then "encode" will encode shared |
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167 | data structures repeatedly, unsharing them in the process. Cyclic |
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168 | data structures cannot be encoded in this mode. |
|
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169 | |
|
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170 | This option does not affect "decode" in any way - shared values and |
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171 | references will always be decoded properly if present. |
|
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172 | |
|
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173 | $cbor = $cbor->allow_cycles ([$enable]) |
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174 | $enabled = $cbor->get_allow_cycles |
|
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175 | If $enable is true (or missing), then "decode" will happily decode |
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176 | self-referential (cyclic) data structures. By default these will not |
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177 | be decoded, as they need manual cleanup to avoid memory leaks, so |
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178 | code that isn't prepared for this will not leak memory. |
|
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179 | |
|
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180 | If $enable is false (the default), then "decode" will throw an error |
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181 | when it encounters a self-referential/cyclic data structure. |
|
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182 | |
|
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183 | This option does not affect "encode" in any way - shared values and |
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184 | references will always be decoded properly if present. |
|
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185 | |
|
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186 | $cbor = $cbor->pack_strings ([$enable]) |
|
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187 | $enabled = $cbor->get_pack_strings |
|
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188 | If $enable is true (or missing), then "encode" will try not to |
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189 | encode the same string twice, but will instead encode a reference to |
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190 | the string instead. Depending on your data format, this can save a |
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191 | lot of space, but also results in a very large runtime overhead |
|
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192 | (expect encoding times to be 2-4 times as high as without). |
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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 | communications partner supports the stringref extension to CBOR |
|
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196 | (<http://cbor.schmorp.de/stringref>), as without decoder support, |
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197 | the resulting data structure might not be usable. |
|
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198 | |
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199 | If $enable is false (the default), then "encode" will encode strings |
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200 | the standard CBOR way. |
|
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201 | |
|
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202 | This option does not affect "decode" in any way - string references |
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203 | will always be decoded properly if present. |
|
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204 | |
|
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205 | $cbor = $cbor->validate_utf8 ([$enable]) |
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206 | $enabled = $cbor->get_validate_utf8 |
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207 | If $enable is true (or missing), then "decode" will validate that |
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208 | elements (text strings) containing UTF-8 data in fact contain valid |
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209 | UTF-8 data (instead of blindly accepting it). This validation |
|
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210 | obviously takes extra time during decoding. |
|
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211 | |
|
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212 | The concept of "valid UTF-8" used is perl's concept, which is a |
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213 | superset of the official UTF-8. |
|
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214 | |
|
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215 | If $enable is false (the default), then "decode" will blindly accept |
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216 | UTF-8 data, marking them as valid UTF-8 in the resulting data |
|
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217 | structure regardless of whether thats true or not. |
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218 | |
|
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219 | Perl isn't too happy about corrupted UTF-8 in strings, but should |
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220 | generally not crash or do similarly evil things. Extensions might be |
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221 | not so forgiving, so it's recommended to turn on this setting if you |
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222 | receive untrusted CBOR. |
|
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223 | |
|
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224 | This option does not affect "encode" in any way - strings that are |
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225 | supposedly valid UTF-8 will simply be dumped into the resulting CBOR |
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226 | string without checking whether that is, in fact, true or not. |
|
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227 | |
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228 | $cbor = $cbor->filter ([$cb->($tag, $value)]) |
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229 | $cb_or_undef = $cbor->get_filter |
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230 | Sets or replaces the tagged value decoding filter (when $cb is |
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231 | specified) or clears the filter (if no argument or "undef" is |
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232 | provided). |
|
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233 | |
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234 | The filter callback is called only during decoding, when a |
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235 | non-enforced tagged value has been decoded (see "TAG HANDLING AND |
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236 | EXTENSIONS" for a list of enforced tags). For specific tags, it's |
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237 | often better to provide a default converter using the |
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238 | %CBOR::XS::FILTER hash (see below). |
|
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239 | |
|
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240 | The first argument is the numerical tag, the second is the (decoded) |
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241 | value that has been tagged. |
|
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242 | |
|
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243 | The filter function should return either exactly one value, which |
|
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244 | will replace the tagged value in the decoded data structure, or no |
|
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245 | values, which will result in default handling, which currently means |
|
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246 | the decoder creates a "CBOR::XS::Tagged" object to hold the tag and |
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247 | the value. |
|
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248 | |
|
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249 | When the filter is cleared (the default state), the default filter |
|
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250 | function, "CBOR::XS::default_filter", is used. This function simply |
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251 | looks up the tag in the %CBOR::XS::FILTER hash. If an entry exists |
|
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252 | it must be a code reference that is called with tag and value, and |
|
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253 | is responsible for decoding the value. If no entry exists, it |
|
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254 | returns no values. |
|
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255 | |
|
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256 | Example: decode all tags not handled internally into |
|
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257 | "CBOR::XS::Tagged" objects, with no other special handling (useful |
|
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258 | when working with potentially "unsafe" CBOR data). |
|
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259 | |
|
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260 | CBOR::XS->new->filter (sub { })->decode ($cbor_data); |
|
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261 | |
|
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262 | Example: provide a global filter for tag 1347375694, converting the |
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263 | value into some string form. |
|
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264 | |
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265 | $CBOR::XS::FILTER{1347375694} = sub { |
|
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266 | my ($tag, $value); |
|
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267 | |
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268 | "tag 1347375694 value $value" |
|
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269 | }; |
|
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270 | |
118 | $cbor_data = $cbor->encode ($perl_scalar) |
271 | $cbor_data = $cbor->encode ($perl_scalar) |
119 | Converts the given Perl data structure (a scalar value) to its CBOR |
272 | Converts the given Perl data structure (a scalar value) to its CBOR |
120 | representation. |
273 | representation. |
121 | |
274 | |
122 | $perl_scalar = $cbor->decode ($cbor_data) |
275 | $perl_scalar = $cbor->decode ($cbor_data) |
… | |
… | |
150 | integers |
303 | integers |
151 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
304 | CBOR integers become (numeric) perl scalars. On perls without 64 bit |
152 | support, 64 bit integers will be truncated or otherwise corrupted. |
305 | support, 64 bit integers will be truncated or otherwise corrupted. |
153 | |
306 | |
154 | byte strings |
307 | byte strings |
155 | Byte strings will become octet strings in Perl (the byte values |
308 | Byte strings will become octet strings in Perl (the Byte values |
156 | 0..255 will simply become characters of the same value in Perl). |
309 | 0..255 will simply become characters of the same value in Perl). |
157 | |
310 | |
158 | UTF-8 strings |
311 | UTF-8 strings |
159 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
312 | UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be |
160 | decoded into proper Unicode code points. At the moment, the validity |
313 | decoded into proper Unicode code points. At the moment, the validity |
… | |
… | |
174 | "Types:Serialiser::false" and "Types::Serialiser::error", |
327 | "Types:Serialiser::false" and "Types::Serialiser::error", |
175 | respectively. They are overloaded to act almost exactly like the |
328 | respectively. They are overloaded to act almost exactly like the |
176 | numbers 1 and 0 (for true and false) or to throw an exception on |
329 | numbers 1 and 0 (for true and false) or to throw an exception on |
177 | access (for error). See the Types::Serialiser manpage for details. |
330 | access (for error). See the Types::Serialiser manpage for details. |
178 | |
331 | |
179 | CBOR tag 256 (perl object) |
332 | tagged values |
180 | The tag value 256 (TODO: pending iana registration) will be used to |
|
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181 | deserialise a Perl object serialised with "FREEZE". See OBJECT |
|
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182 | SERIALISATION, below, for details. |
|
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183 | |
|
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184 | CBOR tag 55799 (magic header) |
|
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185 | The tag 55799 is ignored (this tag implements the magic header). |
|
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186 | |
|
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187 | other CBOR tags |
|
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188 | Tagged items consists of a numeric tag and another CBOR value. Tags |
333 | Tagged items consists of a numeric tag and another CBOR value. |
189 | not handled internally are currently converted into a |
|
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190 | CBOR::XS::Tagged object, which is simply a blessed array reference |
|
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191 | consisting of the numeric tag value followed by the (decoded) CBOR |
|
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192 | value. |
|
|
193 | |
334 | |
194 | In the future, support for user-supplied conversions might get |
335 | See "TAG HANDLING AND EXTENSIONS" and the description of "->filter" |
195 | added. |
336 | for details on which tags are handled how. |
196 | |
337 | |
197 | anything else |
338 | anything else |
198 | Anything else (e.g. unsupported simple values) will raise a decoding |
339 | Anything else (e.g. unsupported simple values) will raise a decoding |
199 | error. |
340 | error. |
200 | |
341 | |
201 | PERL -> CBOR |
342 | PERL -> CBOR |
202 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
343 | The mapping from Perl to CBOR is slightly more difficult, as Perl is a |
203 | truly typeless language, so we can only guess which CBOR type is meant |
344 | typeless language. That means this module can only guess which CBOR type |
204 | by a Perl value. |
345 | is meant by a perl value. |
205 | |
346 | |
206 | hash references |
347 | hash references |
207 | Perl hash references become CBOR maps. As there is no inherent |
348 | Perl hash references become CBOR maps. As there is no inherent |
208 | ordering in hash keys (or CBOR maps), they will usually be encoded |
349 | ordering in hash keys (or CBOR maps), they will usually be encoded |
209 | in a pseudo-random order. |
350 | in a pseudo-random order. This order can be different each time a |
|
|
351 | hahs is encoded. |
210 | |
352 | |
211 | Currently, tied hashes will use the indefinite-length format, while |
353 | Currently, tied hashes will use the indefinite-length format, while |
212 | normal hashes will use the fixed-length format. |
354 | normal hashes will use the fixed-length format. |
213 | |
355 | |
214 | array references |
356 | array references |
215 | Perl array references become fixed-length CBOR arrays. |
357 | Perl array references become fixed-length CBOR arrays. |
216 | |
358 | |
217 | other references |
359 | other references |
218 | Other unblessed references are generally not allowed and will cause |
360 | Other unblessed references will be represented using the indirection |
219 | an exception to be thrown, except for references to the integers 0 |
361 | tag extension (tag value 22098, |
220 | and 1, which get turned into false and true in CBOR. |
362 | <http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed |
|
|
363 | to be able to decode these values somehow, by either "doing the |
|
|
364 | right thing", decoding into a generic tagged object, simply ignoring |
|
|
365 | the tag, or something else. |
221 | |
366 | |
222 | CBOR::XS::Tagged objects |
367 | CBOR::XS::Tagged objects |
223 | Objects of this type must be arrays consisting of a single "[tag, |
368 | Objects of this type must be arrays consisting of a single "[tag, |
224 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
369 | value]" pair. The (numerical) tag will be encoded as a CBOR tag, the |
225 | value will be encoded as appropriate for the value. You cna use |
370 | value will be encoded as appropriate for the value. You must use |
226 | "CBOR::XS::tag" to create such objects. |
371 | "CBOR::XS::tag" to create such objects. |
227 | |
372 | |
228 | Types::Serialiser::true, Types::Serialiser::false, |
373 | Types::Serialiser::true, Types::Serialiser::false, |
229 | Types::Serialiser::error |
374 | Types::Serialiser::error |
230 | These special values become CBOR true, CBOR false and CBOR undefined |
375 | These special values become CBOR true, CBOR false and CBOR undefined |
231 | values, respectively. You can also use "\1", "\0" and "\undef" |
376 | values, respectively. You can also use "\1", "\0" and "\undef" |
232 | directly if you want. |
377 | directly if you want. |
233 | |
378 | |
234 | other blessed objects |
379 | other blessed objects |
235 | Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See |
380 | Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See |
236 | "OBJECT SERIALISATION", below, for details. |
381 | "TAG HANDLING AND EXTENSIONS" for specific classes handled by this |
|
|
382 | module, and "OBJECT SERIALISATION" for generic object serialisation. |
237 | |
383 | |
238 | simple scalars |
384 | simple scalars |
239 | TODO Simple Perl scalars (any scalar that is not a reference) are |
385 | Simple Perl scalars (any scalar that is not a reference) are the |
240 | the most difficult objects to encode: CBOR::XS will encode undefined |
386 | most difficult objects to encode: CBOR::XS will encode undefined |
241 | scalars as CBOR null values, scalars that have last been used in a |
387 | scalars as CBOR null values, scalars that have last been used in a |
242 | string context before encoding as CBOR strings, and anything else as |
388 | string context before encoding as CBOR strings, and anything else as |
243 | number value: |
389 | number value: |
244 | |
390 | |
245 | # dump as number |
391 | # dump as number |
246 | encode_cbor [2] # yields [2] |
392 | encode_cbor [2] # yields [2] |
247 | encode_cbor [-3.0e17] # yields [-3e+17] |
393 | encode_cbor [-3.0e17] # yields [-3e+17] |
248 | my $value = 5; encode_cbor [$value] # yields [5] |
394 | my $value = 5; encode_cbor [$value] # yields [5] |
249 | |
395 | |
250 | # used as string, so dump as string |
396 | # used as string, so dump as string (either byte or text) |
251 | print $value; |
397 | print $value; |
252 | encode_cbor [$value] # yields ["5"] |
398 | encode_cbor [$value] # yields ["5"] |
253 | |
399 | |
254 | # undef becomes null |
400 | # undef becomes null |
255 | encode_cbor [undef] # yields [null] |
401 | encode_cbor [undef] # yields [null] |
… | |
… | |
258 | |
404 | |
259 | my $x = 3.1; # some variable containing a number |
405 | my $x = 3.1; # some variable containing a number |
260 | "$x"; # stringified |
406 | "$x"; # stringified |
261 | $x .= ""; # another, more awkward way to stringify |
407 | $x .= ""; # another, more awkward way to stringify |
262 | print $x; # perl does it for you, too, quite often |
408 | print $x; # perl does it for you, too, quite often |
|
|
409 | |
|
|
410 | You can force whether a string ie encoded as byte or text string by |
|
|
411 | using "utf8::upgrade" and "utf8::downgrade"): |
|
|
412 | |
|
|
413 | utf8::upgrade $x; # encode $x as text string |
|
|
414 | utf8::downgrade $x; # encode $x as byte string |
|
|
415 | |
|
|
416 | Perl doesn't define what operations up- and downgrade strings, so if |
|
|
417 | the difference between byte and text is important, you should up- or |
|
|
418 | downgrade your string as late as possible before encoding. |
263 | |
419 | |
264 | You can force the type to be a CBOR number by numifying it: |
420 | You can force the type to be a CBOR number by numifying it: |
265 | |
421 | |
266 | my $x = "3"; # some variable containing a string |
422 | my $x = "3"; # some variable containing a string |
267 | $x += 0; # numify it, ensuring it will be dumped as a number |
423 | $x += 0; # numify it, ensuring it will be dumped as a number |
… | |
… | |
277 | the IEEE double format will be used. Perls that use formats other |
433 | the IEEE double format will be used. Perls that use formats other |
278 | than IEEE double to represent numerical values are supported, but |
434 | than IEEE double to represent numerical values are supported, but |
279 | might suffer loss of precision. |
435 | might suffer loss of precision. |
280 | |
436 | |
281 | OBJECT SERIALISATION |
437 | OBJECT SERIALISATION |
|
|
438 | This module implements both a CBOR-specific and the generic |
|
|
439 | Types::Serialier object serialisation protocol. The following |
|
|
440 | subsections explain both methods. |
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441 | |
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442 | ENCODING |
282 | This module knows two way to serialise a Perl object: The CBOR-specific |
443 | This module knows two way to serialise a Perl object: The CBOR-specific |
283 | way, and the generic way. |
444 | way, and the generic way. |
284 | |
445 | |
285 | Whenever the encoder encounters a Perl object that it cnanot serialise |
446 | Whenever the encoder encounters a Perl object that it cannot serialise |
286 | directly (most of them), it will first look up the "TO_CBOR" method on |
447 | directly (most of them), it will first look up the "TO_CBOR" method on |
287 | it. |
448 | it. |
288 | |
449 | |
289 | If it has a "TO_CBOR" method, it will call it with the object as only |
450 | If it has a "TO_CBOR" method, it will call it with the object as only |
290 | argument, and expects exactly one return value, which it will then |
451 | argument, and expects exactly one return value, which it will then |
… | |
… | |
295 | "CBOR" as the second argument, to distinguish it from other serialisers. |
456 | "CBOR" as the second argument, to distinguish it from other serialisers. |
296 | |
457 | |
297 | The "FREEZE" method can return any number of values (i.e. zero or more). |
458 | The "FREEZE" method can return any number of values (i.e. zero or more). |
298 | These will be encoded as CBOR perl object, together with the classname. |
459 | These will be encoded as CBOR perl object, together with the classname. |
299 | |
460 | |
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461 | These methods *MUST NOT* change the data structure that is being |
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462 | serialised. Failure to comply to this can result in memory corruption - |
|
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463 | and worse. |
|
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464 | |
300 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
465 | If an object supports neither "TO_CBOR" nor "FREEZE", encoding will fail |
301 | with an error. |
466 | with an error. |
302 | |
467 | |
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468 | DECODING |
303 | Objects encoded via "TO_CBOR" cannot be automatically decoded, but |
469 | Objects encoded via "TO_CBOR" cannot (normally) be automatically |
304 | objects encoded via "FREEZE" can be decoded using the following |
470 | decoded, but objects encoded via "FREEZE" can be decoded using the |
305 | protocol: |
471 | following protocol: |
306 | |
472 | |
307 | When an encoded CBOR perl object is encountered by the decoder, it will |
473 | When an encoded CBOR perl object is encountered by the decoder, it will |
308 | look up the "THAW" method, by using the stored classname, and will fail |
474 | look up the "THAW" method, by using the stored classname, and will fail |
309 | if the method cannot be found. |
475 | if the method cannot be found. |
310 | |
476 | |
… | |
… | |
331 | |
497 | |
332 | sub URI::TO_CBOR { |
498 | sub URI::TO_CBOR { |
333 | my ($self) = @_; |
499 | my ($self) = @_; |
334 | my $uri = "$self"; # stringify uri |
500 | my $uri = "$self"; # stringify uri |
335 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
501 | utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string |
336 | CBOR::XS::tagged 32, "$_[0]" |
502 | CBOR::XS::tag 32, "$_[0]" |
337 | } |
503 | } |
338 | |
504 | |
339 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
505 | This will encode URIs as a UTF-8 string with tag 32, which indicates an |
340 | URI. |
506 | URI. |
341 | |
507 | |
… | |
… | |
376 | |
542 | |
377 | MAGIC HEADER |
543 | MAGIC HEADER |
378 | There is no way to distinguish CBOR from other formats programmatically. |
544 | There is no way to distinguish CBOR from other formats programmatically. |
379 | To make it easier to distinguish CBOR from other formats, the CBOR |
545 | To make it easier to distinguish CBOR from other formats, the CBOR |
380 | specification has a special "magic string" that can be prepended to any |
546 | specification has a special "magic string" that can be prepended to any |
381 | CBOR string without changing it's meaning. |
547 | CBOR string without changing its meaning. |
382 | |
548 | |
383 | This string is available as $CBOR::XS::MAGIC. This module does not |
549 | This string is available as $CBOR::XS::MAGIC. This module does not |
384 | prepend this string tot he CBOR data it generates, but it will ignroe it |
550 | prepend this string to the CBOR data it generates, but it will ignore it |
385 | if present, so users can prepend this string as a "file type" indicator |
551 | if present, so users can prepend this string as a "file type" indicator |
386 | as required. |
552 | as required. |
387 | |
553 | |
388 | THE CBOR::XS::Tagged CLASS |
554 | THE CBOR::XS::Tagged CLASS |
389 | CBOR has the concept of tagged values - any CBOR value can be tagged |
555 | CBOR has the concept of tagged values - any CBOR value can be tagged |
… | |
… | |
440 | Wrap CBOR data in CBOR: |
606 | Wrap CBOR data in CBOR: |
441 | |
607 | |
442 | my $cbor_cbor = encode_cbor |
608 | my $cbor_cbor = encode_cbor |
443 | CBOR::XS::tag 24, |
609 | CBOR::XS::tag 24, |
444 | encode_cbor [1, 2, 3]; |
610 | encode_cbor [1, 2, 3]; |
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611 | |
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612 | TAG HANDLING AND EXTENSIONS |
|
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613 | This section describes how this module handles specific tagged values |
|
|
614 | and extensions. If a tag is not mentioned here and no additional filters |
|
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615 | are provided for it, then the default handling applies (creating a |
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616 | CBOR::XS::Tagged object on decoding, and only encoding the tag when |
|
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617 | explicitly requested). |
|
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618 | |
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619 | Tags not handled specifically are currently converted into a |
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620 | CBOR::XS::Tagged object, which is simply a blessed array reference |
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621 | consisting of the numeric tag value followed by the (decoded) CBOR |
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622 | value. |
|
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623 | |
|
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624 | Future versions of this module reserve the right to special case |
|
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625 | additional tags (such as base64url). |
|
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626 | |
|
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627 | ENFORCED TAGS |
|
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628 | These tags are always handled when decoding, and their handling cannot |
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629 | be overriden by the user. |
|
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630 | |
|
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631 | 26 (perl-object, <http://cbor.schmorp.de/perl-object>) |
|
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632 | These tags are automatically created (and decoded) for serialisable |
|
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633 | objects using the "FREEZE/THAW" methods (the Types::Serialier object |
|
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634 | serialisation protocol). See "OBJECT SERIALISATION" for details. |
|
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635 | |
|
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636 | 28, 29 (shareable, sharedref, L <http://cbor.schmorp.de/value-sharing>) |
|
|
637 | These tags are automatically decoded when encountered (and they do |
|
|
638 | not result in a cyclic data structure, see "allow_cycles"), |
|
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639 | resulting in shared values in the decoded object. They are only |
|
|
640 | encoded, however, when "allow_sharing" is enabled. |
|
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641 | |
|
|
642 | Not all shared values can be successfully decoded: values that |
|
|
643 | reference themselves will *currently* decode as "undef" (this is not |
|
|
644 | the same as a reference pointing to itself, which will be |
|
|
645 | represented as a value that contains an indirect reference to itself |
|
|
646 | - these will be decoded properly). |
|
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647 | |
|
|
648 | Note that considerably more shared value data structures can be |
|
|
649 | decoded than will be encoded - currently, only values pointed to by |
|
|
650 | references will be shared, others will not. While non-reference |
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|
651 | shared values can be generated in Perl with some effort, they were |
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|
652 | considered too unimportant to be supported in the encoder. The |
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653 | decoder, however, will decode these values as shared values. |
|
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654 | |
|
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655 | 256, 25 (stringref-namespace, stringref, L |
|
|
656 | <http://cbor.schmorp.de/stringref>) |
|
|
657 | These tags are automatically decoded when encountered. They are only |
|
|
658 | encoded, however, when "pack_strings" is enabled. |
|
|
659 | |
|
|
660 | 22098 (indirection, <http://cbor.schmorp.de/indirection>) |
|
|
661 | This tag is automatically generated when a reference are encountered |
|
|
662 | (with the exception of hash and array refernces). It is converted to |
|
|
663 | a reference when decoding. |
|
|
664 | |
|
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665 | 55799 (self-describe CBOR, RFC 7049) |
|
|
666 | This value is not generated on encoding (unless explicitly requested |
|
|
667 | by the user), and is simply ignored when decoding. |
|
|
668 | |
|
|
669 | NON-ENFORCED TAGS |
|
|
670 | These tags have default filters provided when decoding. Their handling |
|
|
671 | can be overriden by changing the %CBOR::XS::FILTER entry for the tag, or |
|
|
672 | by providing a custom "filter" callback when decoding. |
|
|
673 | |
|
|
674 | When they result in decoding into a specific Perl class, the module |
|
|
675 | usually provides a corresponding "TO_CBOR" method as well. |
|
|
676 | |
|
|
677 | When any of these need to load additional modules that are not part of |
|
|
678 | the perl core distribution (e.g. URI), it is (currently) up to the user |
|
|
679 | to provide these modules. The decoding usually fails with an exception |
|
|
680 | if the required module cannot be loaded. |
|
|
681 | |
|
|
682 | 0, 1 (date/time string, seconds since the epoch) |
|
|
683 | These tags are decoded into Time::Piece objects. The corresponding |
|
|
684 | "Time::Piece::TO_CBOR" method always encodes into tag 1 values |
|
|
685 | currently. |
|
|
686 | |
|
|
687 | The Time::Piece API is generally surprisingly bad, and fractional |
|
|
688 | seconds are only accidentally kept intact, so watch out. On the plus |
|
|
689 | side, the module comes with perl since 5.10, which has to count for |
|
|
690 | something. |
|
|
691 | |
|
|
692 | 2, 3 (positive/negative bignum) |
|
|
693 | These tags are decoded into Math::BigInt objects. The corresponding |
|
|
694 | "Math::BigInt::TO_CBOR" method encodes "small" bigints into normal |
|
|
695 | CBOR integers, and others into positive/negative CBOR bignums. |
|
|
696 | |
|
|
697 | 4, 5 (decimal fraction/bigfloat) |
|
|
698 | Both decimal fractions and bigfloats are decoded into Math::BigFloat |
|
|
699 | objects. The corresponding "Math::BigFloat::TO_CBOR" method *always* |
|
|
700 | encodes into a decimal fraction. |
|
|
701 | |
|
|
702 | CBOR cannot represent bigfloats with *very* large exponents - |
|
|
703 | conversion of such big float objects is undefined. |
|
|
704 | |
|
|
705 | Also, NaN and infinities are not encoded properly. |
|
|
706 | |
|
|
707 | 21, 22, 23 (expected later JSON conversion) |
|
|
708 | CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore |
|
|
709 | these tags. |
|
|
710 | |
|
|
711 | 32 (URI) |
|
|
712 | These objects decode into URI objects. The corresponding |
|
|
713 | "URI::TO_CBOR" method again results in a CBOR URI value. |
445 | |
714 | |
446 | CBOR and JSON |
715 | CBOR and JSON |
447 | CBOR is supposed to implement a superset of the JSON data model, and is, |
716 | CBOR is supposed to implement a superset of the JSON data model, and is, |
448 | with some coercion, able to represent all JSON texts (something that |
717 | with some coercion, able to represent all JSON texts (something that |
449 | other "binary JSON" formats such as BSON generally do not support). |
718 | other "binary JSON" formats such as BSON generally do not support). |
… | |
… | |
505 | uses long double to represent floating point values, they might not be |
774 | uses long double to represent floating point values, they might not be |
506 | encoded properly. Half precision types are accepted, but not encoded. |
775 | encoded properly. Half precision types are accepted, but not encoded. |
507 | |
776 | |
508 | Strict mode and canonical mode are not implemented. |
777 | Strict mode and canonical mode are not implemented. |
509 | |
778 | |
|
|
779 | LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT |
|
|
780 | On perls that were built without 64 bit integer support (these are rare |
|
|
781 | nowadays, even on 32 bit architectures), support for any kind of 64 bit |
|
|
782 | integer in CBOR is very limited - most likely, these 64 bit values will |
|
|
783 | be truncated, corrupted, or otherwise not decoded correctly. This also |
|
|
784 | includes string, array and map sizes that are stored as 64 bit integers. |
|
|
785 | |
510 | THREADS |
786 | THREADS |
511 | This module is *not* guaranteed to be thread safe and there are no plans |
787 | This module is *not* guaranteed to be thread safe and there are no plans |
512 | to change this until Perl gets thread support (as opposed to the |
788 | to change this until Perl gets thread support (as opposed to the |
513 | horribly slow so-called "threads" which are simply slow and bloated |
789 | horribly slow so-called "threads" which are simply slow and bloated |
514 | process simulations - use fork, it's *much* faster, cheaper, better). |
790 | process simulations - use fork, it's *much* faster, cheaper, better). |