ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/JSON-XS/README
(Generate patch)

Comparing JSON-XS/README (file contents):
Revision 1.8 by root, Sun Mar 25 22:11:06 2007 UTC vs.
Revision 1.18 by root, Tue Aug 28 02:06:06 2007 UTC

… …
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
97OBJECT-ORIENTED INTERFACE 102OBJECT-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
273 * shell-style '#'-comments
274 Whenever JSON allows whitespace, shell-style comments are
275 additionally allowed. They are terminated by the first
276 carriage-return or line-feed character, after which more
277 white-space and comments are allowed.
278
279 [
280 1, # this comment not allowed in JSON
281 # neither this one...
282 ]
283
208 $json = $json->canonical ([$enable]) 284 $json = $json->canonical ([$enable])
209 If $enable is true (or missing), then the "encode" method will 285 If $enable is true (or missing), then the "encode" method will
210 output JSON objects by sorting their keys. This is adding a 286 output JSON objects by sorting their keys. This is adding a
211 comparatively high overhead. 287 comparatively high overhead.
212 288
… …
236 Example, encode a Perl scalar as JSON value with enabled 312 Example, encode a Perl scalar as JSON value with enabled
237 "allow_nonref", resulting in an invalid JSON text: 313 "allow_nonref", resulting in an invalid JSON text:
238 314
239 JSON::XS->new->allow_nonref->encode ("Hello, World!") 315 JSON::XS->new->allow_nonref->encode ("Hello, World!")
240 => "Hello, World!" 316 => "Hello, World!"
317
318 $json = $json->allow_blessed ([$enable])
319 If $enable is true (or missing), then the "encode" method will not
320 barf when it encounters a blessed reference. Instead, the value of
321 the convert_blessed option will decide wether "null"
322 ("convert_blessed" disabled or no "to_json" method found) or a
323 representation of the object ("convert_blessed" enabled and
324 "to_json" method found) is being encoded. Has no effect on "decode".
325
326 If $enable is false (the default), then "encode" will throw an
327 exception when it encounters a blessed object.
328
329 $json = $json->convert_blessed ([$enable])
330 If $enable is true (or missing), then "encode", upon encountering a
331 blessed object, will check for the availability of the "TO_JSON"
332 method on the object's class. If found, it will be called in scalar
333 context and the resulting scalar will be encoded instead of the
334 object. If no "TO_JSON" method is found, the value of
335 "allow_blessed" will decide what to do.
336
337 The "TO_JSON" method may safely call die if it wants. If "TO_JSON"
338 returns other blessed objects, those will be handled in the same
339 way. "TO_JSON" must take care of not causing an endless recursion
340 cycle (== crash) in this case. The name of "TO_JSON" was chosen
341 because other methods called by the Perl core (== not by the user of
342 the object) are usually in upper case letters and to avoid
343 collisions with the "to_json" function.
344
345 This setting does not yet influence "decode" in any way, but in the
346 future, global hooks might get installed that influence "decode" and
347 are enabled by this setting.
348
349 If $enable is false, then the "allow_blessed" setting will decide
350 what to do when a blessed object is found.
351
352 $json = $json->filter_json_object ([$coderef->($hashref)])
353 When $coderef is specified, it will be called from "decode" each
354 time it decodes a JSON object. The only argument is a reference to
355 the newly-created hash. If the code references returns a single
356 scalar (which need not be a reference), this value (i.e. a copy of
357 that scalar to avoid aliasing) is inserted into the deserialised
358 data structure. If it returns an empty list (NOTE: *not* "undef",
359 which is a valid scalar), the original deserialised hash will be
360 inserted. This setting can slow down decoding considerably.
361
362 When $coderef is omitted or undefined, any existing callback will be
363 removed and "decode" will not change the deserialised hash in any
364 way.
365
366 Example, convert all JSON objects into the integer 5:
367
368 my $js = JSON::XS->new->filter_json_object (sub { 5 });
369 # returns [5]
370 $js->decode ('[{}]')
371 # throw an exception because allow_nonref is not enabled
372 # so a lone 5 is not allowed.
373 $js->decode ('{"a":1, "b":2}');
374
375 $json = $json->filter_json_single_key_object ($key [=>
376 $coderef->($value)])
377 Works remotely similar to "filter_json_object", but is only called
378 for JSON objects having a single key named $key.
379
380 This $coderef is called before the one specified via
381 "filter_json_object", if any. It gets passed the single value in the
382 JSON object. If it returns a single value, it will be inserted into
383 the data structure. If it returns nothing (not even "undef" but the
384 empty list), the callback from "filter_json_object" will be called
385 next, as if no single-key callback were specified.
386
387 If $coderef is omitted or undefined, the corresponding callback will
388 be disabled. There can only ever be one callback for a given key.
389
390 As this callback gets called less often then the
391 "filter_json_object" one, decoding speed will not usually suffer as
392 much. Therefore, single-key objects make excellent targets to
393 serialise Perl objects into, especially as single-key JSON objects
394 are as close to the type-tagged value concept as JSON gets (its
395 basically an ID/VALUE tuple). Of course, JSON does not support this
396 in any way, so you need to make sure your data never looks like a
397 serialised Perl hash.
398
399 Typical names for the single object key are "__class_whatever__", or
400 "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even
401 things like "__class_md5sum(classname)__", to reduce the risk of
402 clashing with real hashes.
403
404 Example, decode JSON objects of the form "{ "__widget__" => <id> }"
405 into the corresponding $WIDGET{<id>} object:
406
407 # return whatever is in $WIDGET{5}:
408 JSON::XS
409 ->new
410 ->filter_json_single_key_object (__widget__ => sub {
411 $WIDGET{ $_[0] }
412 })
413 ->decode ('{"__widget__": 5')
414
415 # this can be used with a TO_JSON method in some "widget" class
416 # for serialisation to json:
417 sub WidgetBase::TO_JSON {
418 my ($self) = @_;
419
420 unless ($self->{id}) {
421 $self->{id} = ..get..some..id..;
422 $WIDGET{$self->{id}} = $self;
423 }
424
425 { __widget__ => $self->{id} }
426 }
241 427
242 $json = $json->shrink ([$enable]) 428 $json = $json->shrink ([$enable])
243 Perl usually over-allocates memory a bit when allocating space for 429 Perl usually over-allocates memory a bit when allocating space for
244 strings. This flag optionally resizes strings generated by either 430 strings. This flag optionally resizes strings generated by either
245 "encode" or "decode" to their minimum size possible. This can save 431 "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 432 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 433 many short strings. It will also try to downgrade any strings to
248 octet-form if possible: perl stores strings internally either in an 434 octet-form if possible: perl stores strings internally either in an
249 encoding called UTF-X or in octet-form. The latter cannot store 435 encoding called UTF-X or in octet-form. The latter cannot store
250 everything but uses less space in general. 436 everything but uses less space in general (and some buggy Perl or C
437 code might even rely on that internal representation being used).
438
439 The actual definition of what shrink does might change in future
440 versions, but it will always try to save space at the expense of
441 time.
251 442
252 If $enable is true (or missing), the string returned by "encode" 443 If $enable is true (or missing), the string returned by "encode"
253 will be shrunk-to-fit, while all strings generated by "decode" will 444 will be shrunk-to-fit, while all strings generated by "decode" will
254 also be shrunk-to-fit. 445 also be shrunk-to-fit.
255 446
… …
260 converting strings that look like integers or floats into integers 451 converting strings that look like integers or floats into integers
261 or floats internally (there is no difference on the Perl level), 452 or floats internally (there is no difference on the Perl level),
262 saving space. 453 saving space.
263 454
264 $json = $json->max_depth ([$maximum_nesting_depth]) 455 $json = $json->max_depth ([$maximum_nesting_depth])
265 Sets the maximum nesting level (default 8192) accepted while 456 Sets the maximum nesting level (default 512) accepted while encoding
266 encoding or decoding. If the JSON text or Perl data structure has an 457 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 458 higher nesting level then this limit, then the encoder and decoder
268 decoder will stop and croak at that point. 459 will stop and croak at that point.
269 460
270 Nesting level is defined by number of hash- or arrayrefs that the 461 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 462 encoder needs to traverse to reach a given point or the number of
272 "{" or "[" characters without their matching closing parenthesis 463 "{" or "[" characters without their matching closing parenthesis
273 crossed to reach a given character in a string. 464 crossed to reach a given character in a string.
274 465
275 Setting the maximum depth to one disallows any nesting, so that 466 Setting the maximum depth to one disallows any nesting, so that
276 ensures that the object is only a single hash/object or array. 467 ensures that the object is only a single hash/object or array.
277 468
278 The argument to "max_depth" will be rounded up to the next nearest 469 The argument to "max_depth" will be rounded up to the next highest
279 power of two. 470 power of two. If no argument is given, the highest possible setting
471 will be used, which is rarely useful.
472
473 See SECURITY CONSIDERATIONS, below, for more info on why this is
474 useful.
475
476 $json = $json->max_size ([$maximum_string_size])
477 Set the maximum length a JSON text may have (in bytes) where
478 decoding is being attempted. The default is 0, meaning no limit.
479 When "decode" is called on a string longer then this number of
480 characters it will not attempt to decode the string but throw an
481 exception. This setting has no effect on "encode" (yet).
482
483 The argument to "max_size" will be rounded up to the next highest
484 power of two (so may be more than requested). If no argument is
485 given, the limit check will be deactivated (same as when 0 is
486 specified).
280 487
281 See SECURITY CONSIDERATIONS, below, for more info on why this is 488 See SECURITY CONSIDERATIONS, below, for more info on why this is
282 useful. 489 useful.
283 490
284 $json_text = $json->encode ($perl_scalar) 491 $json_text = $json->encode ($perl_scalar)
… …
296 503
297 JSON numbers and strings become simple Perl scalars. JSON arrays 504 JSON numbers and strings become simple Perl scalars. JSON arrays
298 become Perl arrayrefs and JSON objects become Perl hashrefs. "true" 505 become Perl arrayrefs and JSON objects become Perl hashrefs. "true"
299 becomes 1, "false" becomes 0 and "null" becomes "undef". 506 becomes 1, "false" becomes 0 and "null" becomes "undef".
300 507
508 ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
509 This works like the "decode" method, but instead of raising an
510 exception when there is trailing garbage after the first JSON
511 object, it will silently stop parsing there and return the number of
512 characters consumed so far.
513
514 This is useful if your JSON texts are not delimited by an outer
515 protocol (which is not the brightest thing to do in the first place)
516 and you need to know where the JSON text ends.
517
518 JSON::XS->new->decode_prefix ("[1] the tail")
519 => ([], 3)
520
301MAPPING 521MAPPING
302 This section describes how JSON::XS maps Perl values to JSON values and 522 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 523 vice versa. These mappings are designed to "do the right thing" in most
304 circumstances automatically, preserving round-tripping characteristics 524 circumstances automatically, preserving round-tripping characteristics
305 (what you put in comes out as something equivalent). 525 (what you put in comes out as something equivalent).
… …
321 A JSON string becomes a string scalar in Perl - Unicode codepoints 541 A JSON string becomes a string scalar in Perl - Unicode codepoints
322 in JSON are represented by the same codepoints in the Perl string, 542 in JSON are represented by the same codepoints in the Perl string,
323 so no manual decoding is necessary. 543 so no manual decoding is necessary.
324 544
325 number 545 number
326 A JSON number becomes either an integer or numeric (floating point) 546 A JSON number becomes either an integer, numeric (floating point) or
327 scalar in perl, depending on its range and any fractional parts. On 547 string scalar in perl, depending on its range and any fractional
328 the Perl level, there is no difference between those as Perl handles 548 parts. On the Perl level, there is no difference between those as
329 all the conversion details, but an integer may take slightly less 549 Perl handles all the conversion details, but an integer may take
330 memory and might represent more values exactly than (floating point) 550 slightly less memory and might represent more values exactly than
331 numbers. 551 (floating point) numbers.
552
553 If the number consists of digits only, JSON::XS will try to
554 represent it as an integer value. If that fails, it will try to
555 represent it as a numeric (floating point) value if that is possible
556 without loss of precision. Otherwise it will preserve the number as
557 a string value.
558
559 Numbers containing a fractional or exponential part will always be
560 represented as numeric (floating point) values, possibly at a loss
561 of precision.
562
563 This might create round-tripping problems as numbers might become
564 strings, but as Perl is typeless there is no other way to do it.
332 565
333 true, false 566 true, false
334 These JSON atoms become 0, 1, respectively. Information is lost in 567 These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
335 this process. Future versions might represent those values 568 respectively. They are overloaded to act almost exactly like the
336 differently, but they will be guarenteed to act like these integers 569 numbers 1 and 0. You can check wether a scalar is a JSON boolean by
337 would normally in Perl. 570 using the "JSON::XS::is_bool" function.
338 571
339 null 572 null
340 A JSON null atom becomes "undef" in Perl. 573 A JSON null atom becomes "undef" in Perl.
341 574
342 PERL -> JSON 575 PERL -> JSON
… …
344 truly typeless language, so we can only guess which JSON type is meant 577 truly typeless language, so we can only guess which JSON type is meant
345 by a Perl value. 578 by a Perl value.
346 579
347 hash references 580 hash references
348 Perl hash references become JSON objects. As there is no inherent 581 Perl hash references become JSON objects. As there is no inherent
349 ordering in hash keys, they will usually be encoded in a 582 ordering in hash keys (or JSON objects), they will usually be
350 pseudo-random order that can change between runs of the same program 583 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. 584 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 585 program. JSON::XS can optionally sort the hash keys (determined by
353 *canonical* flag), so the same datastructure will serialise to the 586 the *canonical* flag), so the same datastructure will serialise to
354 same JSON text (given same settings and version of JSON::XS), but 587 the same JSON text (given same settings and version of JSON::XS),
355 this incurs a runtime overhead. 588 but this incurs a runtime overhead and is only rarely useful, e.g.
589 when you want to compare some JSON text against another for
590 equality.
356 591
357 array references 592 array references
358 Perl array references become JSON arrays. 593 Perl array references become JSON arrays.
594
595 other references
596 Other unblessed references are generally not allowed and will cause
597 an exception to be thrown, except for references to the integers 0
598 and 1, which get turned into "false" and "true" atoms in JSON. You
599 can also use "JSON::XS::false" and "JSON::XS::true" to improve
600 readability.
601
602 to_json [\0,JSON::XS::true] # yields [false,true]
603
604 JSON::XS::true, JSON::XS::false
605 These special values become JSON true and JSON false values,
606 respectively. You cna alos use "\1" and "\0" directly if you want.
359 607
360 blessed objects 608 blessed objects
361 Blessed objects are not allowed. JSON::XS currently tries to encode 609 Blessed objects are not allowed. JSON::XS currently tries to encode
362 their underlying representation (hash- or arrayref), but this 610 their underlying representation (hash- or arrayref), but this
363 behaviour might change in future versions. 611 behaviour might change in future versions.
… …
394 $x += 0; # numify it, ensuring it will be dumped as a number 642 $x += 0; # numify it, ensuring it will be dumped as a number
395 $x *= 1; # same thing, the choise is yours. 643 $x *= 1; # same thing, the choise is yours.
396 644
397 You can not currently output JSON booleans or force the type in 645 You can not currently output JSON booleans or force the type in
398 other, less obscure, ways. Tell me if you need this capability. 646 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.
402 647
403COMPARISON 648COMPARISON
404 As already mentioned, this module was created because none of the 649 As already mentioned, this module was created because none of the
405 existing JSON modules could be made to work correctly. First I will 650 existing JSON modules could be made to work correctly. First I will
406 describe the problems (or pleasures) I encountered with various existing 651 describe the problems (or pleasures) I encountered with various existing
… …
477 Does not generate valid JSON texts (key strings are often unquoted, 722 Does not generate valid JSON texts (key strings are often unquoted,
478 empty keys result in nothing being output) 723 empty keys result in nothing being output)
479 724
480 Does not check input for validity. 725 Does not check input for validity.
481 726
727 JSON and YAML
728 You often hear that JSON is a subset (or a close subset) of YAML. This
729 is, however, a mass hysteria and very far from the truth. In general,
730 there is no way to configure JSON::XS to output a data structure as
731 valid YAML.
732
733 If you really must use JSON::XS to generate YAML, you should use this
734 algorithm (subject to change in future versions):
735
736 my $to_yaml = JSON::XS->new->utf8->space_after (1);
737 my $yaml = $to_yaml->encode ($ref) . "\n";
738
739 This will usually generate JSON texts that also parse as valid YAML.
740 Please note that YAML has hardcoded limits on (simple) object key
741 lengths that JSON doesn't have, so you should make sure that your hash
742 keys are noticably shorter than the 1024 characters YAML allows.
743
744 There might be other incompatibilities that I am not aware of. In
745 general you should not try to generate YAML with a JSON generator or
746 vice versa, or try to parse JSON with a YAML parser or vice versa:
747 chances are high that you will run into severe interoperability
748 problems.
749
482 SPEED 750 SPEED
483 It seems that JSON::XS is surprisingly fast, as shown in the following 751 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 752 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 753 in the JSON::XS distribution, to make it easy to compare on your own
486 system. 754 system.
487 755
488 First comes a comparison between various modules using a very short JSON 756 First comes a comparison between various modules using a very short
489 string: 757 single-line JSON string:
490 758
491 {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} 759 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
760 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
492 761
493 It shows the number of encodes/decodes per second (JSON::XS uses the 762 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 763 functional interface, while JSON::XS/2 uses the OO interface with
495 pretty-printing and hashkey sorting enabled). Higher is better: 764 pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
765 Higher is better:
496 766
767 Storable | 15779.925 | 14169.946 |
768 -----------+------------+------------+
497 module | encode | decode | 769 module | encode | decode |
498 -----------|------------|------------| 770 -----------|------------|------------|
499 JSON | 11488.516 | 7823.035 | 771 JSON | 4990.842 | 4088.813 |
500 JSON::DWIW | 94708.054 | 129094.260 | 772 JSON::DWIW | 51653.990 | 71575.154 |
501 JSON::PC | 63884.157 | 128528.212 | 773 JSON::PC | 65948.176 | 74631.744 |
774 JSON::PP | 8931.652 | 3817.168 |
502 JSON::Syck | 34898.677 | 42096.911 | 775 JSON::Syck | 24877.248 | 27776.848 |
503 JSON::XS | 654027.064 | 396423.669 | 776 JSON::XS | 388361.481 | 227951.304 |
504 JSON::XS/2 | 371564.190 | 371725.613 | 777 JSON::XS/2 | 227951.304 | 218453.333 |
778 JSON::XS/3 | 338250.323 | 218453.333 |
779 Storable | 16500.016 | 135300.129 |
505 -----------+------------+------------+ 780 -----------+------------+------------+
506 781
507 That is, JSON::XS is more than six times faster than JSON::DWIW on 782 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 783 encoding, about three times faster on decoding, and over fourty times
509 times faster than JSON, even with pretty-printing and key sorting. 784 faster than JSON, even with pretty-printing and key sorting. It also
785 compares favourably to Storable for small amounts of data.
510 786
511 Using a longer test string (roughly 18KB, generated from Yahoo! Locals 787 Using a longer test string (roughly 18KB, generated from Yahoo! Locals
512 search API (http://nanoref.com/yahooapis/mgPdGg): 788 search API (http://nanoref.com/yahooapis/mgPdGg):
513 789
514 module | encode | decode | 790 module | encode | decode |
515 -----------|------------|------------| 791 -----------|------------|------------|
516 JSON | 273.023 | 44.674 | 792 JSON | 55.260 | 34.971 |
517 JSON::DWIW | 1089.383 | 1145.704 | 793 JSON::DWIW | 825.228 | 1082.513 |
518 JSON::PC | 3097.419 | 2393.921 | 794 JSON::PC | 3571.444 | 2394.829 |
519 JSON::Syck | 514.060 | 843.053 | 795 JSON::PP | 210.987 | 32.574 |
520 JSON::XS | 6479.668 | 3636.364 | 796 JSON::Syck | 552.551 | 787.544 |
521 JSON::XS/2 | 3774.221 | 3599.124 | 797 JSON::XS | 5780.463 | 4854.519 |
798 JSON::XS/2 | 3869.998 | 4798.975 |
799 JSON::XS/3 | 5862.880 | 4798.975 |
800 Storable | 4445.002 | 5235.027 |
522 -----------+------------+------------+ 801 -----------+------------+------------+
523 802
524 Again, JSON::XS leads by far. 803 Again, JSON::XS leads by far (except for Storable which non-surprisingly
804 decodes faster).
525 805
526 On large strings containing lots of high unicode characters, some 806 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 807 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 808 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 809 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 820 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 821 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 822 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 823 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 824 characters is usually a good indication of the size of the resources
545 required to decode it into a Perl structure. 825 required to decode it into a Perl structure. While JSON::XS can check
826 the size of the JSON text, it might be too late when you already have it
827 in memory, so you might want to check the size before you accept the
828 string.
546 829
547 Third, JSON::XS recurses using the C stack when decoding objects and 830 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 831 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 832 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 833 but only 14k nested JSON objects (due to perl itself recursing deeply on
834 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 835 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 836 process has a smaller stack, you should adjust this setting accordingly
553 with the "max_depth" method. 837 with the "max_depth" method.
554 838
555 And last but least, something else could bomb you that I forgot to think 839 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 840 of. In that case, you get to keep the pieces. I am always open for
557 hints, though... 841 hints, though...
842
843 If you are using JSON::XS to return packets to consumption by javascript
844 scripts in a browser you should have a look at
845 <http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
846 you are vulnerable to some common attack vectors (which really are
847 browser design bugs, but it is still you who will have to deal with it,
848 as major browser developers care only for features, not about doing
849 security right).
558 850
559BUGS 851BUGS
560 While the goal of this module is to be correct, that unfortunately does 852 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 853 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 854 still relatively early in its development. If you keep reporting bugs

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines