… | |
… | |
7 | # exported functions, they croak on error |
7 | # exported functions, they croak on error |
8 | # and expect/generate UTF-8 |
8 | # and expect/generate UTF-8 |
9 | |
9 | |
10 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
10 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
11 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
11 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
12 | |
|
|
13 | # objToJson and jsonToObj aliases to to_json and from_json |
|
|
14 | # are exported for compatibility to the JSON module, |
|
|
15 | # but should not be used in new code. |
|
|
16 | |
12 | |
17 | # OO-interface |
13 | # OO-interface |
18 | |
14 | |
19 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
15 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
20 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
16 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
… | |
… | |
92 | |
88 | |
93 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
89 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
94 | |
90 | |
95 | except being faster. |
91 | except being faster. |
96 | |
92 | |
|
|
93 | $is_boolean = JSON::XS::is_bool $scalar |
|
|
94 | Returns true if the passed scalar represents either JSON::XS::true |
|
|
95 | or JSON::XS::false, two constants that act like 1 and 0, |
|
|
96 | respectively and are used to represent JSON "true" and "false" |
|
|
97 | values in Perl. |
|
|
98 | |
|
|
99 | See MAPPING, below, for more information on how JSON values are |
|
|
100 | mapped to Perl. |
|
|
101 | |
97 | OBJECT-ORIENTED INTERFACE |
102 | OBJECT-ORIENTED INTERFACE |
98 | The object oriented interface lets you configure your own encoding or |
103 | The object oriented interface lets you configure your own encoding or |
99 | decoding style, within the limits of supported formats. |
104 | decoding style, within the limits of supported formats. |
100 | |
105 | |
101 | $json = new JSON::XS |
106 | $json = new JSON::XS |
… | |
… | |
112 | $json = $json->ascii ([$enable]) |
117 | $json = $json->ascii ([$enable]) |
113 | If $enable is true (or missing), then the "encode" method will not |
118 | If $enable is true (or missing), then the "encode" method will not |
114 | generate characters outside the code range 0..127 (which is ASCII). |
119 | generate characters outside the code range 0..127 (which is ASCII). |
115 | Any unicode characters outside that range will be escaped using |
120 | Any unicode characters outside that range will be escaped using |
116 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
121 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
117 | escape sequence, as per RFC4627. |
122 | escape sequence, as per RFC4627. The resulting encoded JSON text can |
|
|
123 | be treated as a native unicode string, an ascii-encoded, |
|
|
124 | latin1-encoded or UTF-8 encoded string, or any other superset of |
|
|
125 | ASCII. |
118 | |
126 | |
119 | If $enable is false, then the "encode" method will not escape |
127 | If $enable is false, then the "encode" method will not escape |
120 | Unicode characters unless required by the JSON syntax. This results |
128 | Unicode characters unless required by the JSON syntax or other |
121 | in a faster and more compact format. |
129 | flags. This results in a faster and more compact format. |
|
|
130 | |
|
|
131 | The main use for this flag is to produce JSON texts that can be |
|
|
132 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
|
|
133 | contain any 8 bit characters. |
122 | |
134 | |
123 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
135 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
124 | => ["\ud801\udc01"] |
136 | => ["\ud801\udc01"] |
|
|
137 | |
|
|
138 | $json = $json->latin1 ([$enable]) |
|
|
139 | If $enable is true (or missing), then the "encode" method will |
|
|
140 | encode the resulting JSON text as latin1 (or iso-8859-1), escaping |
|
|
141 | any characters outside the code range 0..255. The resulting string |
|
|
142 | can be treated as a latin1-encoded JSON text or a native unicode |
|
|
143 | string. The "decode" method will not be affected in any way by this |
|
|
144 | flag, as "decode" by default expects unicode, which is a strict |
|
|
145 | superset of latin1. |
|
|
146 | |
|
|
147 | If $enable is false, then the "encode" method will not escape |
|
|
148 | Unicode characters unless required by the JSON syntax or other |
|
|
149 | flags. |
|
|
150 | |
|
|
151 | The main use for this flag is efficiently encoding binary data as |
|
|
152 | JSON text, as most octets will not be escaped, resulting in a |
|
|
153 | smaller encoded size. The disadvantage is that the resulting JSON |
|
|
154 | text is encoded in latin1 (and must correctly be treated as such |
|
|
155 | when storing and transfering), a rare encoding for JSON. It is |
|
|
156 | therefore most useful when you want to store data structures known |
|
|
157 | to contain binary data efficiently in files or databases, not when |
|
|
158 | talking to other JSON encoders/decoders. |
|
|
159 | |
|
|
160 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
|
|
161 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
125 | |
162 | |
126 | $json = $json->utf8 ([$enable]) |
163 | $json = $json->utf8 ([$enable]) |
127 | If $enable is true (or missing), then the "encode" method will |
164 | If $enable is true (or missing), then the "encode" method will |
128 | encode the JSON result into UTF-8, as required by many protocols, |
165 | 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 |
166 | while the "decode" method expects to be handled an UTF-8-encoded |
… | |
… | |
203 | |
240 | |
204 | Example, space_before and indent disabled, space_after enabled: |
241 | Example, space_before and indent disabled, space_after enabled: |
205 | |
242 | |
206 | {"key": "value"} |
243 | {"key": "value"} |
207 | |
244 | |
|
|
245 | $json = $json->relaxed ([$enable]) |
|
|
246 | If $enable is true (or missing), then "decode" will accept some |
|
|
247 | extensions to normal JSON syntax (see below). "encode" will not be |
|
|
248 | affected in anyway. *Be aware that this option makes you accept |
|
|
249 | invalid JSON texts as if they were valid!*. I suggest only to use |
|
|
250 | this option to parse application-specific files written by humans |
|
|
251 | (configuration files, resource files etc.) |
|
|
252 | |
|
|
253 | If $enable is false (the default), then "decode" will only accept |
|
|
254 | valid JSON texts. |
|
|
255 | |
|
|
256 | Currently accepted extensions are: |
|
|
257 | |
|
|
258 | * list items can have an end-comma |
|
|
259 | JSON *separates* array elements and key-value pairs with commas. |
|
|
260 | This can be annoying if you write JSON texts manually and want |
|
|
261 | to be able to quickly append elements, so this extension accepts |
|
|
262 | comma at the end of such items not just between them: |
|
|
263 | |
|
|
264 | [ |
|
|
265 | 1, |
|
|
266 | 2, <- this comma not normally allowed |
|
|
267 | ] |
|
|
268 | { |
|
|
269 | "k1": "v1", |
|
|
270 | "k2": "v2", <- this comma not normally allowed |
|
|
271 | } |
|
|
272 | |
208 | $json = $json->canonical ([$enable]) |
273 | $json = $json->canonical ([$enable]) |
209 | If $enable is true (or missing), then the "encode" method will |
274 | If $enable is true (or missing), then the "encode" method will |
210 | output JSON objects by sorting their keys. This is adding a |
275 | output JSON objects by sorting their keys. This is adding a |
211 | comparatively high overhead. |
276 | comparatively high overhead. |
212 | |
277 | |
… | |
… | |
236 | Example, encode a Perl scalar as JSON value with enabled |
301 | Example, encode a Perl scalar as JSON value with enabled |
237 | "allow_nonref", resulting in an invalid JSON text: |
302 | "allow_nonref", resulting in an invalid JSON text: |
238 | |
303 | |
239 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
304 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
240 | => "Hello, World!" |
305 | => "Hello, World!" |
|
|
306 | |
|
|
307 | $json = $json->allow_blessed ([$enable]) |
|
|
308 | If $enable is true (or missing), then the "encode" method will not |
|
|
309 | barf when it encounters a blessed reference. Instead, the value of |
|
|
310 | the convert_blessed option will decide wether "null" |
|
|
311 | ("convert_blessed" disabled or no "to_json" method found) or a |
|
|
312 | representation of the object ("convert_blessed" enabled and |
|
|
313 | "to_json" method found) is being encoded. Has no effect on "decode". |
|
|
314 | |
|
|
315 | If $enable is false (the default), then "encode" will throw an |
|
|
316 | exception when it encounters a blessed object. |
|
|
317 | |
|
|
318 | $json = $json->convert_blessed ([$enable]) |
|
|
319 | If $enable is true (or missing), then "encode", upon encountering a |
|
|
320 | blessed object, will check for the availability of the "TO_JSON" |
|
|
321 | method on the object's class. If found, it will be called in scalar |
|
|
322 | context and the resulting scalar will be encoded instead of the |
|
|
323 | object. If no "TO_JSON" method is found, the value of |
|
|
324 | "allow_blessed" will decide what to do. |
|
|
325 | |
|
|
326 | The "TO_JSON" method may safely call die if it wants. If "TO_JSON" |
|
|
327 | returns other blessed objects, those will be handled in the same |
|
|
328 | way. "TO_JSON" must take care of not causing an endless recursion |
|
|
329 | cycle (== crash) in this case. The name of "TO_JSON" was chosen |
|
|
330 | because other methods called by the Perl core (== not by the user of |
|
|
331 | the object) are usually in upper case letters and to avoid |
|
|
332 | collisions with the "to_json" function. |
|
|
333 | |
|
|
334 | This setting does not yet influence "decode" in any way, but in the |
|
|
335 | future, global hooks might get installed that influence "decode" and |
|
|
336 | are enabled by this setting. |
|
|
337 | |
|
|
338 | If $enable is false, then the "allow_blessed" setting will decide |
|
|
339 | what to do when a blessed object is found. |
|
|
340 | |
|
|
341 | $json = $json->filter_json_object ([$coderef->($hashref)]) |
|
|
342 | When $coderef is specified, it will be called from "decode" each |
|
|
343 | time it decodes a JSON object. The only argument is a reference to |
|
|
344 | the newly-created hash. If the code references returns a single |
|
|
345 | scalar (which need not be a reference), this value (i.e. a copy of |
|
|
346 | that scalar to avoid aliasing) is inserted into the deserialised |
|
|
347 | data structure. If it returns an empty list (NOTE: *not* "undef", |
|
|
348 | which is a valid scalar), the original deserialised hash will be |
|
|
349 | inserted. This setting can slow down decoding considerably. |
|
|
350 | |
|
|
351 | When $coderef is omitted or undefined, any existing callback will be |
|
|
352 | removed and "decode" will not change the deserialised hash in any |
|
|
353 | way. |
|
|
354 | |
|
|
355 | Example, convert all JSON objects into the integer 5: |
|
|
356 | |
|
|
357 | my $js = JSON::XS->new->filter_json_object (sub { 5 }); |
|
|
358 | # returns [5] |
|
|
359 | $js->decode ('[{}]') |
|
|
360 | # throw an exception because allow_nonref is not enabled |
|
|
361 | # so a lone 5 is not allowed. |
|
|
362 | $js->decode ('{"a":1, "b":2}'); |
|
|
363 | |
|
|
364 | $json = $json->filter_json_single_key_object ($key [=> |
|
|
365 | $coderef->($value)]) |
|
|
366 | Works remotely similar to "filter_json_object", but is only called |
|
|
367 | for JSON objects having a single key named $key. |
|
|
368 | |
|
|
369 | This $coderef is called before the one specified via |
|
|
370 | "filter_json_object", if any. It gets passed the single value in the |
|
|
371 | JSON object. If it returns a single value, it will be inserted into |
|
|
372 | the data structure. If it returns nothing (not even "undef" but the |
|
|
373 | empty list), the callback from "filter_json_object" will be called |
|
|
374 | next, as if no single-key callback were specified. |
|
|
375 | |
|
|
376 | If $coderef is omitted or undefined, the corresponding callback will |
|
|
377 | be disabled. There can only ever be one callback for a given key. |
|
|
378 | |
|
|
379 | As this callback gets called less often then the |
|
|
380 | "filter_json_object" one, decoding speed will not usually suffer as |
|
|
381 | much. Therefore, single-key objects make excellent targets to |
|
|
382 | serialise Perl objects into, especially as single-key JSON objects |
|
|
383 | are as close to the type-tagged value concept as JSON gets (its |
|
|
384 | basically an ID/VALUE tuple). Of course, JSON does not support this |
|
|
385 | in any way, so you need to make sure your data never looks like a |
|
|
386 | serialised Perl hash. |
|
|
387 | |
|
|
388 | Typical names for the single object key are "__class_whatever__", or |
|
|
389 | "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even |
|
|
390 | things like "__class_md5sum(classname)__", to reduce the risk of |
|
|
391 | clashing with real hashes. |
|
|
392 | |
|
|
393 | Example, decode JSON objects of the form "{ "__widget__" => <id> }" |
|
|
394 | into the corresponding $WIDGET{<id>} object: |
|
|
395 | |
|
|
396 | # return whatever is in $WIDGET{5}: |
|
|
397 | JSON::XS |
|
|
398 | ->new |
|
|
399 | ->filter_json_single_key_object (__widget__ => sub { |
|
|
400 | $WIDGET{ $_[0] } |
|
|
401 | }) |
|
|
402 | ->decode ('{"__widget__": 5') |
|
|
403 | |
|
|
404 | # this can be used with a TO_JSON method in some "widget" class |
|
|
405 | # for serialisation to json: |
|
|
406 | sub WidgetBase::TO_JSON { |
|
|
407 | my ($self) = @_; |
|
|
408 | |
|
|
409 | unless ($self->{id}) { |
|
|
410 | $self->{id} = ..get..some..id..; |
|
|
411 | $WIDGET{$self->{id}} = $self; |
|
|
412 | } |
|
|
413 | |
|
|
414 | { __widget__ => $self->{id} } |
|
|
415 | } |
241 | |
416 | |
242 | $json = $json->shrink ([$enable]) |
417 | $json = $json->shrink ([$enable]) |
243 | Perl usually over-allocates memory a bit when allocating space for |
418 | Perl usually over-allocates memory a bit when allocating space for |
244 | strings. This flag optionally resizes strings generated by either |
419 | strings. This flag optionally resizes strings generated by either |
245 | "encode" or "decode" to their minimum size possible. This can save |
420 | "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 |
421 | 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 |
422 | many short strings. It will also try to downgrade any strings to |
248 | octet-form if possible: perl stores strings internally either in an |
423 | octet-form if possible: perl stores strings internally either in an |
249 | encoding called UTF-X or in octet-form. The latter cannot store |
424 | encoding called UTF-X or in octet-form. The latter cannot store |
250 | everything but uses less space in general. |
425 | everything but uses less space in general (and some buggy Perl or C |
|
|
426 | code might even rely on that internal representation being used). |
|
|
427 | |
|
|
428 | The actual definition of what shrink does might change in future |
|
|
429 | versions, but it will always try to save space at the expense of |
|
|
430 | time. |
251 | |
431 | |
252 | If $enable is true (or missing), the string returned by "encode" |
432 | If $enable is true (or missing), the string returned by "encode" |
253 | will be shrunk-to-fit, while all strings generated by "decode" will |
433 | will be shrunk-to-fit, while all strings generated by "decode" will |
254 | also be shrunk-to-fit. |
434 | also be shrunk-to-fit. |
255 | |
435 | |
… | |
… | |
260 | converting strings that look like integers or floats into integers |
440 | converting strings that look like integers or floats into integers |
261 | or floats internally (there is no difference on the Perl level), |
441 | or floats internally (there is no difference on the Perl level), |
262 | saving space. |
442 | saving space. |
263 | |
443 | |
264 | $json = $json->max_depth ([$maximum_nesting_depth]) |
444 | $json = $json->max_depth ([$maximum_nesting_depth]) |
265 | Sets the maximum nesting level (default 8192) accepted while |
445 | Sets the maximum nesting level (default 512) accepted while encoding |
266 | encoding or decoding. If the JSON text or Perl data structure has an |
446 | 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 |
447 | higher nesting level then this limit, then the encoder and decoder |
268 | decoder will stop and croak at that point. |
448 | will stop and croak at that point. |
269 | |
449 | |
270 | Nesting level is defined by number of hash- or arrayrefs that the |
450 | 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 |
451 | encoder needs to traverse to reach a given point or the number of |
272 | "{" or "[" characters without their matching closing parenthesis |
452 | "{" or "[" characters without their matching closing parenthesis |
273 | crossed to reach a given character in a string. |
453 | crossed to reach a given character in a string. |
274 | |
454 | |
275 | Setting the maximum depth to one disallows any nesting, so that |
455 | Setting the maximum depth to one disallows any nesting, so that |
276 | ensures that the object is only a single hash/object or array. |
456 | ensures that the object is only a single hash/object or array. |
277 | |
457 | |
278 | The argument to "max_depth" will be rounded up to the next nearest |
458 | The argument to "max_depth" will be rounded up to the next highest |
279 | power of two. |
459 | power of two. If no argument is given, the highest possible setting |
|
|
460 | will be used, which is rarely useful. |
|
|
461 | |
|
|
462 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
|
|
463 | useful. |
|
|
464 | |
|
|
465 | $json = $json->max_size ([$maximum_string_size]) |
|
|
466 | Set the maximum length a JSON text may have (in bytes) where |
|
|
467 | decoding is being attempted. The default is 0, meaning no limit. |
|
|
468 | When "decode" is called on a string longer then this number of |
|
|
469 | characters it will not attempt to decode the string but throw an |
|
|
470 | exception. This setting has no effect on "encode" (yet). |
|
|
471 | |
|
|
472 | The argument to "max_size" will be rounded up to the next highest |
|
|
473 | power of two (so may be more than requested). If no argument is |
|
|
474 | given, the limit check will be deactivated (same as when 0 is |
|
|
475 | specified). |
280 | |
476 | |
281 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
477 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
282 | useful. |
478 | useful. |
283 | |
479 | |
284 | $json_text = $json->encode ($perl_scalar) |
480 | $json_text = $json->encode ($perl_scalar) |
… | |
… | |
296 | |
492 | |
297 | JSON numbers and strings become simple Perl scalars. JSON arrays |
493 | JSON numbers and strings become simple Perl scalars. JSON arrays |
298 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
494 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
299 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
495 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
300 | |
496 | |
|
|
497 | ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
|
|
498 | This works like the "decode" method, but instead of raising an |
|
|
499 | exception when there is trailing garbage after the first JSON |
|
|
500 | object, it will silently stop parsing there and return the number of |
|
|
501 | characters consumed so far. |
|
|
502 | |
|
|
503 | This is useful if your JSON texts are not delimited by an outer |
|
|
504 | protocol (which is not the brightest thing to do in the first place) |
|
|
505 | and you need to know where the JSON text ends. |
|
|
506 | |
|
|
507 | JSON::XS->new->decode_prefix ("[1] the tail") |
|
|
508 | => ([], 3) |
|
|
509 | |
301 | MAPPING |
510 | MAPPING |
302 | This section describes how JSON::XS maps Perl values to JSON values and |
511 | 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 |
512 | vice versa. These mappings are designed to "do the right thing" in most |
304 | circumstances automatically, preserving round-tripping characteristics |
513 | circumstances automatically, preserving round-tripping characteristics |
305 | (what you put in comes out as something equivalent). |
514 | (what you put in comes out as something equivalent). |
… | |
… | |
321 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
530 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
322 | in JSON are represented by the same codepoints in the Perl string, |
531 | in JSON are represented by the same codepoints in the Perl string, |
323 | so no manual decoding is necessary. |
532 | so no manual decoding is necessary. |
324 | |
533 | |
325 | number |
534 | number |
326 | A JSON number becomes either an integer or numeric (floating point) |
535 | A JSON number becomes either an integer, numeric (floating point) or |
327 | scalar in perl, depending on its range and any fractional parts. On |
536 | string scalar in perl, depending on its range and any fractional |
328 | the Perl level, there is no difference between those as Perl handles |
537 | parts. On the Perl level, there is no difference between those as |
329 | all the conversion details, but an integer may take slightly less |
538 | Perl handles all the conversion details, but an integer may take |
330 | memory and might represent more values exactly than (floating point) |
539 | slightly less memory and might represent more values exactly than |
331 | numbers. |
540 | (floating point) numbers. |
|
|
541 | |
|
|
542 | If the number consists of digits only, JSON::XS will try to |
|
|
543 | represent it as an integer value. If that fails, it will try to |
|
|
544 | represent it as a numeric (floating point) value if that is possible |
|
|
545 | without loss of precision. Otherwise it will preserve the number as |
|
|
546 | a string value. |
|
|
547 | |
|
|
548 | Numbers containing a fractional or exponential part will always be |
|
|
549 | represented as numeric (floating point) values, possibly at a loss |
|
|
550 | of precision. |
|
|
551 | |
|
|
552 | This might create round-tripping problems as numbers might become |
|
|
553 | strings, but as Perl is typeless there is no other way to do it. |
332 | |
554 | |
333 | true, false |
555 | true, false |
334 | These JSON atoms become 0, 1, respectively. Information is lost in |
556 | These JSON atoms become "JSON::XS::true" and "JSON::XS::false", |
335 | this process. Future versions might represent those values |
557 | respectively. They are overloaded to act almost exactly like the |
336 | differently, but they will be guarenteed to act like these integers |
558 | numbers 1 and 0. You can check wether a scalar is a JSON boolean by |
337 | would normally in Perl. |
559 | using the "JSON::XS::is_bool" function. |
338 | |
560 | |
339 | null |
561 | null |
340 | A JSON null atom becomes "undef" in Perl. |
562 | A JSON null atom becomes "undef" in Perl. |
341 | |
563 | |
342 | PERL -> JSON |
564 | PERL -> JSON |
… | |
… | |
344 | truly typeless language, so we can only guess which JSON type is meant |
566 | truly typeless language, so we can only guess which JSON type is meant |
345 | by a Perl value. |
567 | by a Perl value. |
346 | |
568 | |
347 | hash references |
569 | hash references |
348 | Perl hash references become JSON objects. As there is no inherent |
570 | Perl hash references become JSON objects. As there is no inherent |
349 | ordering in hash keys, they will usually be encoded in a |
571 | ordering in hash keys (or JSON objects), they will usually be |
350 | pseudo-random order that can change between runs of the same program |
572 | 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. |
573 | 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 |
574 | program. JSON::XS can optionally sort the hash keys (determined by |
353 | *canonical* flag), so the same datastructure will serialise to the |
575 | the *canonical* flag), so the same datastructure will serialise to |
354 | same JSON text (given same settings and version of JSON::XS), but |
576 | the same JSON text (given same settings and version of JSON::XS), |
355 | this incurs a runtime overhead. |
577 | but this incurs a runtime overhead and is only rarely useful, e.g. |
|
|
578 | when you want to compare some JSON text against another for |
|
|
579 | equality. |
356 | |
580 | |
357 | array references |
581 | array references |
358 | Perl array references become JSON arrays. |
582 | Perl array references become JSON arrays. |
|
|
583 | |
|
|
584 | other references |
|
|
585 | Other unblessed references are generally not allowed and will cause |
|
|
586 | an exception to be thrown, except for references to the integers 0 |
|
|
587 | and 1, which get turned into "false" and "true" atoms in JSON. You |
|
|
588 | can also use "JSON::XS::false" and "JSON::XS::true" to improve |
|
|
589 | readability. |
|
|
590 | |
|
|
591 | to_json [\0,JSON::XS::true] # yields [false,true] |
|
|
592 | |
|
|
593 | JSON::XS::true, JSON::XS::false |
|
|
594 | These special values become JSON true and JSON false values, |
|
|
595 | respectively. You cna alos use "\1" and "\0" directly if you want. |
359 | |
596 | |
360 | blessed objects |
597 | blessed objects |
361 | Blessed objects are not allowed. JSON::XS currently tries to encode |
598 | Blessed objects are not allowed. JSON::XS currently tries to encode |
362 | their underlying representation (hash- or arrayref), but this |
599 | their underlying representation (hash- or arrayref), but this |
363 | behaviour might change in future versions. |
600 | behaviour might change in future versions. |
… | |
… | |
394 | $x += 0; # numify it, ensuring it will be dumped as a number |
631 | $x += 0; # numify it, ensuring it will be dumped as a number |
395 | $x *= 1; # same thing, the choise is yours. |
632 | $x *= 1; # same thing, the choise is yours. |
396 | |
633 | |
397 | You can not currently output JSON booleans or force the type in |
634 | You can not currently output JSON booleans or force the type in |
398 | other, less obscure, ways. Tell me if you need this capability. |
635 | other, less obscure, ways. Tell me if you need this capability. |
399 | |
|
|
400 | circular data structures |
|
|
401 | Those will be encoded until memory or stackspace runs out. |
|
|
402 | |
636 | |
403 | COMPARISON |
637 | COMPARISON |
404 | As already mentioned, this module was created because none of the |
638 | As already mentioned, this module was created because none of the |
405 | existing JSON modules could be made to work correctly. First I will |
639 | existing JSON modules could be made to work correctly. First I will |
406 | describe the problems (or pleasures) I encountered with various existing |
640 | describe the problems (or pleasures) I encountered with various existing |
… | |
… | |
477 | Does not generate valid JSON texts (key strings are often unquoted, |
711 | Does not generate valid JSON texts (key strings are often unquoted, |
478 | empty keys result in nothing being output) |
712 | empty keys result in nothing being output) |
479 | |
713 | |
480 | Does not check input for validity. |
714 | Does not check input for validity. |
481 | |
715 | |
|
|
716 | JSON and YAML |
|
|
717 | You often hear that JSON is a subset (or a close subset) of YAML. This |
|
|
718 | is, however, a mass hysteria and very far from the truth. In general, |
|
|
719 | there is no way to configure JSON::XS to output a data structure as |
|
|
720 | valid YAML. |
|
|
721 | |
|
|
722 | If you really must use JSON::XS to generate YAML, you should use this |
|
|
723 | algorithm (subject to change in future versions): |
|
|
724 | |
|
|
725 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
|
|
726 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
|
|
727 | |
|
|
728 | This will usually generate JSON texts that also parse as valid YAML. |
|
|
729 | Please note that YAML has hardcoded limits on (simple) object key |
|
|
730 | lengths that JSON doesn't have, so you should make sure that your hash |
|
|
731 | keys are noticably shorter than the 1024 characters YAML allows. |
|
|
732 | |
|
|
733 | There might be other incompatibilities that I am not aware of. In |
|
|
734 | general you should not try to generate YAML with a JSON generator or |
|
|
735 | vice versa, or try to parse JSON with a YAML parser or vice versa: |
|
|
736 | chances are high that you will run into severe interoperability |
|
|
737 | problems. |
|
|
738 | |
482 | SPEED |
739 | SPEED |
483 | It seems that JSON::XS is surprisingly fast, as shown in the following |
740 | It seems that JSON::XS is surprisingly fast, as shown in the following |
484 | tables. They have been generated with the help of the "eg/bench" program |
741 | tables. They have been generated with the help of the "eg/bench" program |
485 | in the JSON::XS distribution, to make it easy to compare on your own |
742 | in the JSON::XS distribution, to make it easy to compare on your own |
486 | system. |
743 | system. |
487 | |
744 | |
488 | First comes a comparison between various modules using a very short JSON |
745 | First comes a comparison between various modules using a very short |
489 | string: |
746 | single-line JSON string: |
490 | |
747 | |
491 | {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} |
748 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
|
|
749 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
492 | |
750 | |
493 | It shows the number of encodes/decodes per second (JSON::XS uses the |
751 | It shows the number of encodes/decodes per second (JSON::XS uses the |
494 | functional interface, while JSON::XS/2 uses the OO interface with |
752 | functional interface, while JSON::XS/2 uses the OO interface with |
495 | pretty-printing and hashkey sorting enabled). Higher is better: |
753 | pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). |
|
|
754 | Higher is better: |
496 | |
755 | |
|
|
756 | Storable | 15779.925 | 14169.946 | |
|
|
757 | -----------+------------+------------+ |
497 | module | encode | decode | |
758 | module | encode | decode | |
498 | -----------|------------|------------| |
759 | -----------|------------|------------| |
499 | JSON | 11488.516 | 7823.035 | |
760 | JSON | 4990.842 | 4088.813 | |
500 | JSON::DWIW | 94708.054 | 129094.260 | |
761 | JSON::DWIW | 51653.990 | 71575.154 | |
501 | JSON::PC | 63884.157 | 128528.212 | |
762 | JSON::PC | 65948.176 | 74631.744 | |
|
|
763 | JSON::PP | 8931.652 | 3817.168 | |
502 | JSON::Syck | 34898.677 | 42096.911 | |
764 | JSON::Syck | 24877.248 | 27776.848 | |
503 | JSON::XS | 654027.064 | 396423.669 | |
765 | JSON::XS | 388361.481 | 227951.304 | |
504 | JSON::XS/2 | 371564.190 | 371725.613 | |
766 | JSON::XS/2 | 227951.304 | 218453.333 | |
|
|
767 | JSON::XS/3 | 338250.323 | 218453.333 | |
|
|
768 | Storable | 16500.016 | 135300.129 | |
505 | -----------+------------+------------+ |
769 | -----------+------------+------------+ |
506 | |
770 | |
507 | That is, JSON::XS is more than six times faster than JSON::DWIW on |
771 | That is, JSON::XS is about five times faster than JSON::DWIW on |
508 | encoding, more than three times faster on decoding, and about thirty |
772 | encoding, about three times faster on decoding, and over fourty times |
509 | times faster than JSON, even with pretty-printing and key sorting. |
773 | faster than JSON, even with pretty-printing and key sorting. It also |
|
|
774 | compares favourably to Storable for small amounts of data. |
510 | |
775 | |
511 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
776 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
512 | search API (http://nanoref.com/yahooapis/mgPdGg): |
777 | search API (http://nanoref.com/yahooapis/mgPdGg): |
513 | |
778 | |
514 | module | encode | decode | |
779 | module | encode | decode | |
515 | -----------|------------|------------| |
780 | -----------|------------|------------| |
516 | JSON | 273.023 | 44.674 | |
781 | JSON | 55.260 | 34.971 | |
517 | JSON::DWIW | 1089.383 | 1145.704 | |
782 | JSON::DWIW | 825.228 | 1082.513 | |
518 | JSON::PC | 3097.419 | 2393.921 | |
783 | JSON::PC | 3571.444 | 2394.829 | |
519 | JSON::Syck | 514.060 | 843.053 | |
784 | JSON::PP | 210.987 | 32.574 | |
520 | JSON::XS | 6479.668 | 3636.364 | |
785 | JSON::Syck | 552.551 | 787.544 | |
521 | JSON::XS/2 | 3774.221 | 3599.124 | |
786 | JSON::XS | 5780.463 | 4854.519 | |
|
|
787 | JSON::XS/2 | 3869.998 | 4798.975 | |
|
|
788 | JSON::XS/3 | 5862.880 | 4798.975 | |
|
|
789 | Storable | 4445.002 | 5235.027 | |
522 | -----------+------------+------------+ |
790 | -----------+------------+------------+ |
523 | |
791 | |
524 | Again, JSON::XS leads by far. |
792 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
|
|
793 | decodes faster). |
525 | |
794 | |
526 | On large strings containing lots of high unicode characters, some |
795 | On large strings containing lots of high unicode characters, some |
527 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
796 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
528 | result will be broken due to missing (or wrong) unicode handling. Others |
797 | result will be broken due to missing (or wrong) unicode handling. Others |
529 | refuse to decode or encode properly, so it was impossible to prepare a |
798 | refuse to decode or encode properly, so it was impossible to prepare a |
… | |
… | |
540 | Second, you need to avoid resource-starving attacks. That means you |
809 | Second, you need to avoid resource-starving attacks. That means you |
541 | should limit the size of JSON texts you accept, or make sure then when |
810 | should limit the size of JSON texts you accept, or make sure then when |
542 | your resources run out, thats just fine (e.g. by using a separate |
811 | your resources run out, thats just fine (e.g. by using a separate |
543 | process that can crash safely). The size of a JSON text in octets or |
812 | process that can crash safely). The size of a JSON text in octets or |
544 | characters is usually a good indication of the size of the resources |
813 | characters is usually a good indication of the size of the resources |
545 | required to decode it into a Perl structure. |
814 | required to decode it into a Perl structure. While JSON::XS can check |
|
|
815 | the size of the JSON text, it might be too late when you already have it |
|
|
816 | in memory, so you might want to check the size before you accept the |
|
|
817 | string. |
546 | |
818 | |
547 | Third, JSON::XS recurses using the C stack when decoding objects and |
819 | 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 |
820 | 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 |
821 | 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 |
822 | but only 14k nested JSON objects (due to perl itself recursing deeply on |
|
|
823 | 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 |
824 | 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 |
825 | process has a smaller stack, you should adjust this setting accordingly |
553 | with the "max_depth" method. |
826 | with the "max_depth" method. |
554 | |
827 | |
555 | And last but least, something else could bomb you that I forgot to think |
828 | 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 |
829 | of. In that case, you get to keep the pieces. I am always open for |
557 | hints, though... |
830 | hints, though... |
|
|
831 | |
|
|
832 | If you are using JSON::XS to return packets to consumption by javascript |
|
|
833 | scripts in a browser you should have a look at |
|
|
834 | <http://jpsykes.com/47/practical-csrf-and-json-security> to see wether |
|
|
835 | you are vulnerable to some common attack vectors (which really are |
|
|
836 | browser design bugs, but it is still you who will have to deal with it, |
|
|
837 | as major browser developers care only for features, not about doing |
|
|
838 | security right). |
558 | |
839 | |
559 | BUGS |
840 | BUGS |
560 | While the goal of this module is to be correct, that unfortunately does |
841 | 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 |
842 | not mean its bug-free, only that I think its design is bug-free. It is |
562 | still relatively early in its development. If you keep reporting bugs |
843 | still relatively early in its development. If you keep reporting bugs |