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112 | $json = $json->ascii ([$enable]) |
112 | $json = $json->ascii ([$enable]) |
113 | If $enable is true (or missing), then the "encode" method will not |
113 | If $enable is true (or missing), then the "encode" method will not |
114 | generate characters outside the code range 0..127 (which is ASCII). |
114 | generate characters outside the code range 0..127 (which is ASCII). |
115 | Any unicode characters outside that range will be escaped using |
115 | Any unicode characters outside that range will be escaped using |
116 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
116 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
117 | escape sequence, as per RFC4627. |
117 | escape sequence, as per RFC4627. The resulting encoded JSON text can |
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118 | be treated as a native unicode string, an ascii-encoded, |
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119 | latin1-encoded or UTF-8 encoded string, or any other superset of |
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120 | ASCII. |
118 | |
121 | |
119 | If $enable is false, then the "encode" method will not escape |
122 | If $enable is false, then the "encode" method will not escape |
120 | Unicode characters unless required by the JSON syntax. This results |
123 | Unicode characters unless required by the JSON syntax or other |
121 | in a faster and more compact format. |
124 | flags. This results in a faster and more compact format. |
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125 | |
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126 | The main use for this flag is to produce JSON texts that can be |
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127 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
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128 | contain any 8 bit characters. |
122 | |
129 | |
123 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
130 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
124 | => ["\ud801\udc01"] |
131 | => ["\ud801\udc01"] |
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132 | |
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133 | $json = $json->latin1 ([$enable]) |
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134 | If $enable is true (or missing), then the "encode" method will |
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135 | encode the resulting JSON text as latin1 (or iso-8859-1), escaping |
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136 | any characters outside the code range 0..255. The resulting string |
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137 | can be treated as a latin1-encoded JSON text or a native unicode |
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138 | string. The "decode" method will not be affected in any way by this |
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139 | flag, as "decode" by default expects unicode, which is a strict |
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140 | superset of latin1. |
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141 | |
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142 | If $enable is false, then the "encode" method will not escape |
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143 | Unicode characters unless required by the JSON syntax or other |
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144 | flags. |
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145 | |
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146 | The main use for this flag is efficiently encoding binary data as |
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147 | JSON text, as most octets will not be escaped, resulting in a |
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148 | smaller encoded size. The disadvantage is that the resulting JSON |
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149 | text is encoded in latin1 (and must correctly be treated as such |
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150 | when storing and transfering), a rare encoding for JSON. It is |
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151 | therefore most useful when you want to store data structures known |
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152 | to contain binary data efficiently in files or databases, not when |
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153 | talking to other JSON encoders/decoders. |
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154 | |
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155 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
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156 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
125 | |
157 | |
126 | $json = $json->utf8 ([$enable]) |
158 | $json = $json->utf8 ([$enable]) |
127 | If $enable is true (or missing), then the "encode" method will |
159 | If $enable is true (or missing), then the "encode" method will |
128 | encode the JSON result into UTF-8, as required by many protocols, |
160 | encode the JSON result into UTF-8, as required by many protocols, |
129 | while the "decode" method expects to be handled an UTF-8-encoded |
161 | while the "decode" method expects to be handled an UTF-8-encoded |
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245 | "encode" or "decode" to their minimum size possible. This can save |
277 | "encode" or "decode" to their minimum size possible. This can save |
246 | memory when your JSON texts are either very very long or you have |
278 | memory when your JSON texts are either very very long or you have |
247 | many short strings. It will also try to downgrade any strings to |
279 | many short strings. It will also try to downgrade any strings to |
248 | octet-form if possible: perl stores strings internally either in an |
280 | octet-form if possible: perl stores strings internally either in an |
249 | encoding called UTF-X or in octet-form. The latter cannot store |
281 | encoding called UTF-X or in octet-form. The latter cannot store |
250 | everything but uses less space in general. |
282 | everything but uses less space in general (and some buggy Perl or C |
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283 | code might even rely on that internal representation being used). |
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284 | |
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285 | The actual definition of what shrink does might change in future |
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286 | versions, but it will always try to save space at the expense of |
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287 | time. |
251 | |
288 | |
252 | If $enable is true (or missing), the string returned by "encode" |
289 | If $enable is true (or missing), the string returned by "encode" |
253 | will be shrunk-to-fit, while all strings generated by "decode" will |
290 | will be shrunk-to-fit, while all strings generated by "decode" will |
254 | also be shrunk-to-fit. |
291 | also be shrunk-to-fit. |
255 | |
292 | |
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260 | converting strings that look like integers or floats into integers |
297 | converting strings that look like integers or floats into integers |
261 | or floats internally (there is no difference on the Perl level), |
298 | or floats internally (there is no difference on the Perl level), |
262 | saving space. |
299 | saving space. |
263 | |
300 | |
264 | $json = $json->max_depth ([$maximum_nesting_depth]) |
301 | $json = $json->max_depth ([$maximum_nesting_depth]) |
265 | Sets the maximum nesting level (default 8192) accepted while |
302 | Sets the maximum nesting level (default 512) accepted while encoding |
266 | encoding or decoding. If the JSON text or Perl data structure has an |
303 | or decoding. If the JSON text or Perl data structure has an equal or |
267 | equal or higher nesting level then this limit, then the encoder and |
304 | higher nesting level then this limit, then the encoder and decoder |
268 | decoder will stop and croak at that point. |
305 | will stop and croak at that point. |
269 | |
306 | |
270 | Nesting level is defined by number of hash- or arrayrefs that the |
307 | Nesting level is defined by number of hash- or arrayrefs that the |
271 | encoder needs to traverse to reach a given point or the number of |
308 | encoder needs to traverse to reach a given point or the number of |
272 | "{" or "[" characters without their matching closing parenthesis |
309 | "{" or "[" characters without their matching closing parenthesis |
273 | crossed to reach a given character in a string. |
310 | crossed to reach a given character in a string. |
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296 | |
333 | |
297 | JSON numbers and strings become simple Perl scalars. JSON arrays |
334 | JSON numbers and strings become simple Perl scalars. JSON arrays |
298 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
335 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
299 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
336 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
300 | |
337 | |
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338 | ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
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339 | This works like the "decode" method, but instead of raising an |
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340 | exception when there is trailing garbage after the first JSON |
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341 | object, it will silently stop parsing there and return the number of |
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342 | characters consumed so far. |
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343 | |
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344 | This is useful if your JSON texts are not delimited by an outer |
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345 | protocol (which is not the brightest thing to do in the first place) |
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346 | and you need to know where the JSON text ends. |
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347 | |
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348 | JSON::XS->new->decode_prefix ("[1] the tail") |
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349 | => ([], 3) |
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350 | |
301 | MAPPING |
351 | MAPPING |
302 | This section describes how JSON::XS maps Perl values to JSON values and |
352 | This section describes how JSON::XS maps Perl values to JSON values and |
303 | vice versa. These mappings are designed to "do the right thing" in most |
353 | vice versa. These mappings are designed to "do the right thing" in most |
304 | circumstances automatically, preserving round-tripping characteristics |
354 | circumstances automatically, preserving round-tripping characteristics |
305 | (what you put in comes out as something equivalent). |
355 | (what you put in comes out as something equivalent). |
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344 | truly typeless language, so we can only guess which JSON type is meant |
394 | truly typeless language, so we can only guess which JSON type is meant |
345 | by a Perl value. |
395 | by a Perl value. |
346 | |
396 | |
347 | hash references |
397 | hash references |
348 | Perl hash references become JSON objects. As there is no inherent |
398 | Perl hash references become JSON objects. As there is no inherent |
349 | ordering in hash keys, they will usually be encoded in a |
399 | ordering in hash keys (or JSON objects), they will usually be |
350 | pseudo-random order that can change between runs of the same program |
400 | encoded in a pseudo-random order that can change between runs of the |
351 | but stays generally the same within a single run of a program. |
401 | same program but stays generally the same within a single run of a |
352 | JSON::XS can optionally sort the hash keys (determined by the |
402 | program. JSON::XS can optionally sort the hash keys (determined by |
353 | *canonical* flag), so the same datastructure will serialise to the |
403 | the *canonical* flag), so the same datastructure will serialise to |
354 | same JSON text (given same settings and version of JSON::XS), but |
404 | the same JSON text (given same settings and version of JSON::XS), |
355 | this incurs a runtime overhead. |
405 | but this incurs a runtime overhead and is only rarely useful, e.g. |
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406 | when you want to compare some JSON text against another for |
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407 | equality. |
356 | |
408 | |
357 | array references |
409 | array references |
358 | Perl array references become JSON arrays. |
410 | Perl array references become JSON arrays. |
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411 | |
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412 | other references |
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413 | Other unblessed references are generally not allowed and will cause |
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414 | an exception to be thrown, except for references to the integers 0 |
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415 | and 1, which get turned into "false" and "true" atoms in JSON. You |
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416 | can also use "JSON::XS::false" and "JSON::XS::true" to improve |
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417 | readability. |
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418 | |
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419 | to_json [\0,JSON::XS::true] # yields [false,true] |
359 | |
420 | |
360 | blessed objects |
421 | blessed objects |
361 | Blessed objects are not allowed. JSON::XS currently tries to encode |
422 | Blessed objects are not allowed. JSON::XS currently tries to encode |
362 | their underlying representation (hash- or arrayref), but this |
423 | their underlying representation (hash- or arrayref), but this |
363 | behaviour might change in future versions. |
424 | behaviour might change in future versions. |
… | |
… | |
394 | $x += 0; # numify it, ensuring it will be dumped as a number |
455 | $x += 0; # numify it, ensuring it will be dumped as a number |
395 | $x *= 1; # same thing, the choise is yours. |
456 | $x *= 1; # same thing, the choise is yours. |
396 | |
457 | |
397 | You can not currently output JSON booleans or force the type in |
458 | You can not currently output JSON booleans or force the type in |
398 | other, less obscure, ways. Tell me if you need this capability. |
459 | other, less obscure, ways. Tell me if you need this capability. |
399 | |
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400 | circular data structures |
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401 | Those will be encoded until memory or stackspace runs out. |
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402 | |
460 | |
403 | COMPARISON |
461 | COMPARISON |
404 | As already mentioned, this module was created because none of the |
462 | As already mentioned, this module was created because none of the |
405 | existing JSON modules could be made to work correctly. First I will |
463 | existing JSON modules could be made to work correctly. First I will |
406 | describe the problems (or pleasures) I encountered with various existing |
464 | describe the problems (or pleasures) I encountered with various existing |
… | |
… | |
545 | required to decode it into a Perl structure. |
603 | required to decode it into a Perl structure. |
546 | |
604 | |
547 | Third, JSON::XS recurses using the C stack when decoding objects and |
605 | Third, JSON::XS recurses using the C stack when decoding objects and |
548 | arrays. The C stack is a limited resource: for instance, on my amd64 |
606 | arrays. The C stack is a limited resource: for instance, on my amd64 |
549 | machine with 8MB of stack size I can decode around 180k nested arrays |
607 | machine with 8MB of stack size I can decode around 180k nested arrays |
550 | but only 14k nested JSON objects. If that is exceeded, the program |
608 | but only 14k nested JSON objects (due to perl itself recursing deeply on |
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609 | croak to free the temporary). If that is exceeded, the program crashes. |
551 | crashes. Thats why the default nesting limit is set to 8192. If your |
610 | to be conservative, the default nesting limit is set to 512. If your |
552 | process has a smaller stack, you should adjust this setting accordingly |
611 | process has a smaller stack, you should adjust this setting accordingly |
553 | with the "max_depth" method. |
612 | with the "max_depth" method. |
554 | |
613 | |
555 | And last but least, something else could bomb you that I forgot to think |
614 | And last but least, something else could bomb you that I forgot to think |
556 | of. In that case, you get to keep the pieces. I am alway sopen for |
615 | of. In that case, you get to keep the pieces. I am always open for |
557 | hints, though... |
616 | hints, though... |
558 | |
617 | |
559 | BUGS |
618 | BUGS |
560 | While the goal of this module is to be correct, that unfortunately does |
619 | While the goal of this module is to be correct, that unfortunately does |
561 | not mean its bug-free, only that I think its design is bug-free. It is |
620 | not mean its bug-free, only that I think its design is bug-free. It is |