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Revision 1.20 by root, Tue Nov 13 22:59:08 2007 UTC

1NAME 1NAME
2 JSON::XS - JSON serialising/deserialising, done correctly and fast 2 JSON::XS - JSON serialising/deserialising, done correctly and fast
3
4 JSON::XS - 正しくて高速な JSON
5 シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
3 7
4SYNOPSIS 8SYNOPSIS
5 use JSON::XS; 9 use JSON::XS;
6 10
7 # exported functions, they croak on error 11 # exported functions, they croak on error
… …
31 35
32 See MAPPING, below, on how JSON::XS maps perl values to JSON values and 36 See MAPPING, below, on how JSON::XS maps perl values to JSON values and
33 vice versa. 37 vice versa.
34 38
35 FEATURES 39 FEATURES
36 * correct unicode handling 40 * correct Unicode handling
37 This module knows how to handle Unicode, and even documents how and 41 This module knows how to handle Unicode, and even documents how and
38 when it does so. 42 when it does so.
39 43
40 * round-trip integrity 44 * round-trip integrity
41 When you serialise a perl data structure using only datatypes 45 When you serialise a perl data structure using only datatypes
… …
55 * simple to use 59 * simple to use
56 This module has both a simple functional interface as well as an OO 60 This module has both a simple functional interface as well as an OO
57 interface. 61 interface.
58 62
59 * reasonably versatile output formats 63 * reasonably versatile output formats
60 You can choose between the most compact guarenteed single-line 64 You can choose between the most compact guaranteed single-line
61 format possible (nice for simple line-based protocols), a pure-ascii 65 format possible (nice for simple line-based protocols), a pure-ascii
62 format (for when your transport is not 8-bit clean, still supports 66 format (for when your transport is not 8-bit clean, still supports
63 the whole unicode range), or a pretty-printed format (for when you 67 the whole Unicode range), or a pretty-printed format (for when you
64 want to read that stuff). Or you can combine those features in 68 want to read that stuff). Or you can combine those features in
65 whatever way you like. 69 whatever way you like.
66 70
67FUNCTIONAL INTERFACE 71FUNCTIONAL INTERFACE
68 The following convinience methods are provided by this module. They are 72 The following convenience methods are provided by this module. They are
69 exported by default: 73 exported by default:
70 74
71 $json_text = to_json $perl_scalar 75 $json_text = to_json $perl_scalar
72 Converts the given Perl data structure (a simple scalar or a 76 Converts the given Perl data structure to a UTF-8 encoded, binary
73 reference to a hash or array) to a UTF-8 encoded, binary string
74 (that is, the string contains octets only). Croaks on error. 77 string (that is, the string contains octets only). Croaks on error.
75 78
76 This function call is functionally identical to: 79 This function call is functionally identical to:
77 80
78 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 81 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
79 82
80 except being faster. 83 except being faster.
81 84
82 $perl_scalar = from_json $json_text 85 $perl_scalar = from_json $json_text
83 The opposite of "to_json": expects an UTF-8 (binary) string and 86 The opposite of "to_json": expects an UTF-8 (binary) string and
84 tries to parse that as an UTF-8 encoded JSON text, returning the 87 tries to parse that as an UTF-8 encoded JSON text, returning the
85 resulting simple scalar or reference. Croaks on error. 88 resulting reference. Croaks on error.
86 89
87 This function call is functionally identical to: 90 This function call is functionally identical to:
88 91
89 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 92 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
90 93
… …
97 values in Perl. 100 values in Perl.
98 101
99 See MAPPING, below, for more information on how JSON values are 102 See MAPPING, below, for more information on how JSON values are
100 mapped to Perl. 103 mapped to Perl.
101 104
105A FEW NOTES ON UNICODE AND PERL
106 Since this often leads to confusion, here are a few very clear words on
107 how Unicode works in Perl, modulo bugs.
108
109 1. Perl strings can store characters with ordinal values > 255.
110 This enables you to store Unicode characters as single characters in
111 a Perl string - very natural.
112
113 2. Perl does *not* associate an encoding with your strings.
114 Unless you force it to, e.g. when matching it against a regex, or
115 printing the scalar to a file, in which case Perl either interprets
116 your string as locale-encoded text, octets/binary, or as Unicode,
117 depending on various settings. In no case is an encoding stored
118 together with your data, it is *use* that decides encoding, not any
119 magical metadata.
120
121 3. The internal utf-8 flag has no meaning with regards to the encoding
122 of your string.
123 Just ignore that flag unless you debug a Perl bug, a module written
124 in XS or want to dive into the internals of perl. Otherwise it will
125 only confuse you, as, despite the name, it says nothing about how
126 your string is encoded. You can have Unicode strings with that flag
127 set, with that flag clear, and you can have binary data with that
128 flag set and that flag clear. Other possibilities exist, too.
129
130 If you didn't know about that flag, just the better, pretend it
131 doesn't exist.
132
133 4. A "Unicode String" is simply a string where each character can be
134 validly interpreted as a Unicode codepoint.
135 If you have UTF-8 encoded data, it is no longer a Unicode string,
136 but a Unicode string encoded in UTF-8, giving you a binary string.
137
138 5. A string containing "high" (> 255) character values is *not* a UTF-8
139 string.
140 It's a fact. Learn to live with it.
141
142 I hope this helps :)
143
102OBJECT-ORIENTED INTERFACE 144OBJECT-ORIENTED INTERFACE
103 The object oriented interface lets you configure your own encoding or 145 The object oriented interface lets you configure your own encoding or
104 decoding style, within the limits of supported formats. 146 decoding style, within the limits of supported formats.
105 147
106 $json = new JSON::XS 148 $json = new JSON::XS
… …
115 => {"a": [1, 2]} 157 => {"a": [1, 2]}
116 158
117 $json = $json->ascii ([$enable]) 159 $json = $json->ascii ([$enable])
118 If $enable is true (or missing), then the "encode" method will not 160 If $enable is true (or missing), then the "encode" method will not
119 generate characters outside the code range 0..127 (which is ASCII). 161 generate characters outside the code range 0..127 (which is ASCII).
120 Any unicode characters outside that range will be escaped using 162 Any Unicode characters outside that range will be escaped using
121 either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL 163 either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL
122 escape sequence, as per RFC4627. The resulting encoded JSON text can 164 escape sequence, as per RFC4627. The resulting encoded JSON text can
123 be treated as a native unicode string, an ascii-encoded, 165 be treated as a native Unicode string, an ascii-encoded,
124 latin1-encoded or UTF-8 encoded string, or any other superset of 166 latin1-encoded or UTF-8 encoded string, or any other superset of
125 ASCII. 167 ASCII.
126 168
127 If $enable is false, then the "encode" method will not escape 169 If $enable is false, then the "encode" method will not escape
128 Unicode characters unless required by the JSON syntax or other 170 Unicode characters unless required by the JSON syntax or other
… …
137 179
138 $json = $json->latin1 ([$enable]) 180 $json = $json->latin1 ([$enable])
139 If $enable is true (or missing), then the "encode" method will 181 If $enable is true (or missing), then the "encode" method will
140 encode the resulting JSON text as latin1 (or iso-8859-1), escaping 182 encode the resulting JSON text as latin1 (or iso-8859-1), escaping
141 any characters outside the code range 0..255. The resulting string 183 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 184 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 185 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 186 flag, as "decode" by default expects Unicode, which is a strict
145 superset of latin1. 187 superset of latin1.
146 188
147 If $enable is false, then the "encode" method will not escape 189 If $enable is false, then the "encode" method will not escape
148 Unicode characters unless required by the JSON syntax or other 190 Unicode characters unless required by the JSON syntax or other
149 flags. 191 flags.
150 192
151 The main use for this flag is efficiently encoding binary data as 193 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 194 JSON text, as most octets will not be escaped, resulting in a
153 smaller encoded size. The disadvantage is that the resulting JSON 195 smaller encoded size. The disadvantage is that the resulting JSON
154 text is encoded in latin1 (and must correctly be treated as such 196 text is encoded in latin1 (and must correctly be treated as such
155 when storing and transfering), a rare encoding for JSON. It is 197 when storing and transferring), a rare encoding for JSON. It is
156 therefore most useful when you want to store data structures known 198 therefore most useful when you want to store data structures known
157 to contain binary data efficiently in files or databases, not when 199 to contain binary data efficiently in files or databases, not when
158 talking to other JSON encoders/decoders. 200 talking to other JSON encoders/decoders.
159 201
160 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 202 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
… …
169 bytewise/binary I/O. In future versions, enabling this option might 211 bytewise/binary I/O. In future versions, enabling this option might
170 enable autodetection of the UTF-16 and UTF-32 encoding families, as 212 enable autodetection of the UTF-16 and UTF-32 encoding families, as
171 described in RFC4627. 213 described in RFC4627.
172 214
173 If $enable is false, then the "encode" method will return the JSON 215 If $enable is false, then the "encode" method will return the JSON
174 string as a (non-encoded) unicode string, while "decode" expects 216 string as a (non-encoded) Unicode string, while "decode" expects
175 thus a unicode string. Any decoding or encoding (e.g. to UTF-8 or 217 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
176 UTF-16) needs to be done yourself, e.g. using the Encode module. 218 UTF-16) needs to be done yourself, e.g. using the Encode module.
177 219
178 Example, output UTF-16BE-encoded JSON: 220 Example, output UTF-16BE-encoded JSON:
179 221
180 use Encode; 222 use Encode;
… …
202 } 244 }
203 245
204 $json = $json->indent ([$enable]) 246 $json = $json->indent ([$enable])
205 If $enable is true (or missing), then the "encode" method will use a 247 If $enable is true (or missing), then the "encode" method will use a
206 multiline format as output, putting every array member or 248 multiline format as output, putting every array member or
207 object/hash key-value pair into its own line, identing them 249 object/hash key-value pair into its own line, indenting them
208 properly. 250 properly.
209 251
210 If $enable is false, no newlines or indenting will be produced, and 252 If $enable is false, no newlines or indenting will be produced, and
211 the resulting JSON text is guarenteed not to contain any "newlines". 253 the resulting JSON text is guaranteed not to contain any "newlines".
212 254
213 This setting has no effect when decoding JSON texts. 255 This setting has no effect when decoding JSON texts.
214 256
215 $json = $json->space_before ([$enable]) 257 $json = $json->space_before ([$enable])
216 If $enable is true (or missing), then the "encode" method will add 258 If $enable is true (or missing), then the "encode" method will add
… …
240 282
241 Example, space_before and indent disabled, space_after enabled: 283 Example, space_before and indent disabled, space_after enabled:
242 284
243 {"key": "value"} 285 {"key": "value"}
244 286
287 $json = $json->relaxed ([$enable])
288 If $enable is true (or missing), then "decode" will accept some
289 extensions to normal JSON syntax (see below). "encode" will not be
290 affected in anyway. *Be aware that this option makes you accept
291 invalid JSON texts as if they were valid!*. I suggest only to use
292 this option to parse application-specific files written by humans
293 (configuration files, resource files etc.)
294
295 If $enable is false (the default), then "decode" will only accept
296 valid JSON texts.
297
298 Currently accepted extensions are:
299
300 * list items can have an end-comma
301 JSON *separates* array elements and key-value pairs with commas.
302 This can be annoying if you write JSON texts manually and want
303 to be able to quickly append elements, so this extension accepts
304 comma at the end of such items not just between them:
305
306 [
307 1,
308 2, <- this comma not normally allowed
309 ]
310 {
311 "k1": "v1",
312 "k2": "v2", <- this comma not normally allowed
313 }
314
315 * shell-style '#'-comments
316 Whenever JSON allows whitespace, shell-style comments are
317 additionally allowed. They are terminated by the first
318 carriage-return or line-feed character, after which more
319 white-space and comments are allowed.
320
321 [
322 1, # this comment not allowed in JSON
323 # neither this one...
324 ]
325
245 $json = $json->canonical ([$enable]) 326 $json = $json->canonical ([$enable])
246 If $enable is true (or missing), then the "encode" method will 327 If $enable is true (or missing), then the "encode" method will
247 output JSON objects by sorting their keys. This is adding a 328 output JSON objects by sorting their keys. This is adding a
248 comparatively high overhead. 329 comparatively high overhead.
249 330
… …
251 pairs in the order Perl stores them (which will likely change 332 pairs in the order Perl stores them (which will likely change
252 between runs of the same script). 333 between runs of the same script).
253 334
254 This option is useful if you want the same data structure to be 335 This option is useful if you want the same data structure to be
255 encoded as the same JSON text (given the same overall settings). If 336 encoded as the same JSON text (given the same overall settings). If
256 it is disabled, the same hash migh be encoded differently even if 337 it is disabled, the same hash might be encoded differently even if
257 contains the same data, as key-value pairs have no inherent ordering 338 contains the same data, as key-value pairs have no inherent ordering
258 in Perl. 339 in Perl.
259 340
260 This setting has no effect when decoding JSON texts. 341 This setting has no effect when decoding JSON texts.
261 342
… …
277 => "Hello, World!" 358 => "Hello, World!"
278 359
279 $json = $json->allow_blessed ([$enable]) 360 $json = $json->allow_blessed ([$enable])
280 If $enable is true (or missing), then the "encode" method will not 361 If $enable is true (or missing), then the "encode" method will not
281 barf when it encounters a blessed reference. Instead, the value of 362 barf when it encounters a blessed reference. Instead, the value of
282 the convert_blessed option will decide wether "null" 363 the convert_blessed option will decide whether "null"
283 ("convert_blessed" disabled or no "to_json" method found) or a 364 ("convert_blessed" disabled or no "to_json" method found) or a
284 representation of the object ("convert_blessed" enabled and 365 representation of the object ("convert_blessed" enabled and
285 "to_json" method found) is being encoded. Has no effect on "decode". 366 "to_json" method found) is being encoded. Has no effect on "decode".
286 367
287 If $enable is false (the default), then "encode" will throw an 368 If $enable is false (the default), then "encode" will throw an
… …
350 431
351 As this callback gets called less often then the 432 As this callback gets called less often then the
352 "filter_json_object" one, decoding speed will not usually suffer as 433 "filter_json_object" one, decoding speed will not usually suffer as
353 much. Therefore, single-key objects make excellent targets to 434 much. Therefore, single-key objects make excellent targets to
354 serialise Perl objects into, especially as single-key JSON objects 435 serialise Perl objects into, especially as single-key JSON objects
355 are as close to the type-tagged value concept as JSON gets (its 436 are as close to the type-tagged value concept as JSON gets (it's
356 basically an ID/VALUE tuple). Of course, JSON does not support this 437 basically an ID/VALUE tuple). Of course, JSON does not support this
357 in any way, so you need to make sure your data never looks like a 438 in any way, so you need to make sure your data never looks like a
358 serialised Perl hash. 439 serialised Perl hash.
359 440
360 Typical names for the single object key are "__class_whatever__", or 441 Typical names for the single object key are "__class_whatever__", or
… …
484 vice versa. These mappings are designed to "do the right thing" in most 565 vice versa. These mappings are designed to "do the right thing" in most
485 circumstances automatically, preserving round-tripping characteristics 566 circumstances automatically, preserving round-tripping characteristics
486 (what you put in comes out as something equivalent). 567 (what you put in comes out as something equivalent).
487 568
488 For the more enlightened: note that in the following descriptions, 569 For the more enlightened: note that in the following descriptions,
489 lowercase *perl* refers to the Perl interpreter, while uppcercase *Perl* 570 lowercase *perl* refers to the Perl interpreter, while uppercase *Perl*
490 refers to the abstract Perl language itself. 571 refers to the abstract Perl language itself.
491 572
492 JSON -> PERL 573 JSON -> PERL
493 object 574 object
494 A JSON object becomes a reference to a hash in Perl. No ordering of 575 A JSON object becomes a reference to a hash in Perl. No ordering of
495 object keys is preserved (JSON does not preserver object key 576 object keys is preserved (JSON does not preserve object key ordering
496 ordering itself). 577 itself).
497 578
498 array 579 array
499 A JSON array becomes a reference to an array in Perl. 580 A JSON array becomes a reference to an array in Perl.
500 581
501 string 582 string
502 A JSON string becomes a string scalar in Perl - Unicode codepoints 583 A JSON string becomes a string scalar in Perl - Unicode codepoints
503 in JSON are represented by the same codepoints in the Perl string, 584 in JSON are represented by the same codepoints in the Perl string,
504 so no manual decoding is necessary. 585 so no manual decoding is necessary.
505 586
506 number 587 number
507 A JSON number becomes either an integer or numeric (floating point) 588 A JSON number becomes either an integer, numeric (floating point) or
508 scalar in perl, depending on its range and any fractional parts. On 589 string scalar in perl, depending on its range and any fractional
509 the Perl level, there is no difference between those as Perl handles 590 parts. On the Perl level, there is no difference between those as
510 all the conversion details, but an integer may take slightly less 591 Perl handles all the conversion details, but an integer may take
511 memory and might represent more values exactly than (floating point) 592 slightly less memory and might represent more values exactly than
512 numbers. 593 (floating point) numbers.
594
595 If the number consists of digits only, JSON::XS will try to
596 represent it as an integer value. If that fails, it will try to
597 represent it as a numeric (floating point) value if that is possible
598 without loss of precision. Otherwise it will preserve the number as
599 a string value.
600
601 Numbers containing a fractional or exponential part will always be
602 represented as numeric (floating point) values, possibly at a loss
603 of precision.
604
605 This might create round-tripping problems as numbers might become
606 strings, but as Perl is typeless there is no other way to do it.
513 607
514 true, false 608 true, false
515 These JSON atoms become "JSON::XS::true" and "JSON::XS::false", 609 These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
516 respectively. They are overloaded to act almost exactly like the 610 respectively. They are overloaded to act almost exactly like the
517 numbers 1 and 0. You can check wether a scalar is a JSON boolean by 611 numbers 1 and 0. You can check whether a scalar is a JSON boolean by
518 using the "JSON::XS::is_bool" function. 612 using the "JSON::XS::is_bool" function.
519 613
520 null 614 null
521 A JSON null atom becomes "undef" in Perl. 615 A JSON null atom becomes "undef" in Perl.
522 616
… …
549 643
550 to_json [\0,JSON::XS::true] # yields [false,true] 644 to_json [\0,JSON::XS::true] # yields [false,true]
551 645
552 JSON::XS::true, JSON::XS::false 646 JSON::XS::true, JSON::XS::false
553 These special values become JSON true and JSON false values, 647 These special values become JSON true and JSON false values,
554 respectively. You cna alos use "\1" and "\0" directly if you want. 648 respectively. You can also use "\1" and "\0" directly if you want.
555 649
556 blessed objects 650 blessed objects
557 Blessed objects are not allowed. JSON::XS currently tries to encode 651 Blessed objects are not allowed. JSON::XS currently tries to encode
558 their underlying representation (hash- or arrayref), but this 652 their underlying representation (hash- or arrayref), but this
559 behaviour might change in future versions. 653 behaviour might change in future versions.
… …
575 to_json [$value] # yields ["5"] 669 to_json [$value] # yields ["5"]
576 670
577 # undef becomes null 671 # undef becomes null
578 to_json [undef] # yields [null] 672 to_json [undef] # yields [null]
579 673
580 You can force the type to be a string by stringifying it: 674 You can force the type to be a JSON string by stringifying it:
581 675
582 my $x = 3.1; # some variable containing a number 676 my $x = 3.1; # some variable containing a number
583 "$x"; # stringified 677 "$x"; # stringified
584 $x .= ""; # another, more awkward way to stringify 678 $x .= ""; # another, more awkward way to stringify
585 print $x; # perl does it for you, too, quite often 679 print $x; # perl does it for you, too, quite often
586 680
587 You can force the type to be a number by numifying it: 681 You can force the type to be a JSON number by numifying it:
588 682
589 my $x = "3"; # some variable containing a string 683 my $x = "3"; # some variable containing a string
590 $x += 0; # numify it, ensuring it will be dumped as a number 684 $x += 0; # numify it, ensuring it will be dumped as a number
591 $x *= 1; # same thing, the choise is yours. 685 $x *= 1; # same thing, the choice is yours.
592 686
593 You can not currently output JSON booleans or force the type in 687 You can not currently force the type in other, less obscure, ways.
594 other, less obscure, ways. Tell me if you need this capability. 688 Tell me if you need this capability.
595 689
596COMPARISON 690COMPARISON
597 As already mentioned, this module was created because none of the 691 As already mentioned, this module was created because none of the
598 existing JSON modules could be made to work correctly. First I will 692 existing JSON modules could be made to work correctly. First I will
599 describe the problems (or pleasures) I encountered with various existing 693 describe the problems (or pleasures) I encountered with various existing
… …
601 not to suffer from any of these problems or limitations. 695 not to suffer from any of these problems or limitations.
602 696
603 JSON 1.07 697 JSON 1.07
604 Slow (but very portable, as it is written in pure Perl). 698 Slow (but very portable, as it is written in pure Perl).
605 699
606 Undocumented/buggy Unicode handling (how JSON handles unicode values 700 Undocumented/buggy Unicode handling (how JSON handles Unicode values
607 is undocumented. One can get far by feeding it unicode strings and 701 is undocumented. One can get far by feeding it Unicode strings and
608 doing en-/decoding oneself, but unicode escapes are not working 702 doing en-/decoding oneself, but Unicode escapes are not working
609 properly). 703 properly).
610 704
611 No roundtripping (strings get clobbered if they look like numbers, 705 No round-tripping (strings get clobbered if they look like numbers,
612 e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that 706 e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that
613 will decode into the number 2. 707 will decode into the number 2.
614 708
615 JSON::PC 0.01 709 JSON::PC 0.01
616 Very fast. 710 Very fast.
617 711
618 Undocumented/buggy Unicode handling. 712 Undocumented/buggy Unicode handling.
619 713
620 No roundtripping. 714 No round-tripping.
621 715
622 Has problems handling many Perl values (e.g. regex results and other 716 Has problems handling many Perl values (e.g. regex results and other
623 magic values will make it croak). 717 magic values will make it croak).
624 718
625 Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}" 719 Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}"
… …
635 much undocumented. I need at least a format for easy reading by 729 much undocumented. I need at least a format for easy reading by
636 humans and a single-line compact format for use in a protocol, and 730 humans and a single-line compact format for use in a protocol, and
637 preferably a way to generate ASCII-only JSON texts). 731 preferably a way to generate ASCII-only JSON texts).
638 732
639 Completely broken (and confusingly documented) Unicode handling 733 Completely broken (and confusingly documented) Unicode handling
640 (unicode escapes are not working properly, you need to set 734 (Unicode escapes are not working properly, you need to set
641 ImplicitUnicode to *different* values on en- and decoding to get 735 ImplicitUnicode to *different* values on en- and decoding to get
642 symmetric behaviour). 736 symmetric behaviour).
643 737
644 No roundtripping (simple cases work, but this depends on wether the 738 No round-tripping (simple cases work, but this depends on whether
645 scalar value was used in a numeric context or not). 739 the scalar value was used in a numeric context or not).
646 740
647 Dumping hashes may skip hash values depending on iterator state. 741 Dumping hashes may skip hash values depending on iterator state.
648 742
649 Unmaintained (maintainer unresponsive for many months, bugs are not 743 Unmaintained (maintainer unresponsive for many months, bugs are not
650 getting fixed). 744 getting fixed).
651 745
652 Does not check input for validity (i.e. will accept non-JSON input 746 Does not check input for validity (i.e. will accept non-JSON input
653 and return "something" instead of raising an exception. This is a 747 and return "something" instead of raising an exception. This is a
654 security issue: imagine two banks transfering money between each 748 security issue: imagine two banks transferring money between each
655 other using JSON. One bank might parse a given non-JSON request and 749 other using JSON. One bank might parse a given non-JSON request and
656 deduct money, while the other might reject the transaction with a 750 deduct money, while the other might reject the transaction with a
657 syntax error. While a good protocol will at least recover, that is 751 syntax error. While a good protocol will at least recover, that is
658 extra unnecessary work and the transaction will still not succeed). 752 extra unnecessary work and the transaction will still not succeed).
659 753
660 JSON::DWIW 0.04 754 JSON::DWIW 0.04
661 Very fast. Very natural. Very nice. 755 Very fast. Very natural. Very nice.
662 756
663 Undocumented unicode handling (but the best of the pack. Unicode 757 Undocumented Unicode handling (but the best of the pack. Unicode
664 escapes still don't get parsed properly). 758 escapes still don't get parsed properly).
665 759
666 Very inflexible. 760 Very inflexible.
667 761
668 No roundtripping. 762 No round-tripping.
669 763
670 Does not generate valid JSON texts (key strings are often unquoted, 764 Does not generate valid JSON texts (key strings are often unquoted,
671 empty keys result in nothing being output) 765 empty keys result in nothing being output)
672 766
673 Does not check input for validity. 767 Does not check input for validity.
… …
685 my $yaml = $to_yaml->encode ($ref) . "\n"; 779 my $yaml = $to_yaml->encode ($ref) . "\n";
686 780
687 This will usually generate JSON texts that also parse as valid YAML. 781 This will usually generate JSON texts that also parse as valid YAML.
688 Please note that YAML has hardcoded limits on (simple) object key 782 Please note that YAML has hardcoded limits on (simple) object key
689 lengths that JSON doesn't have, so you should make sure that your hash 783 lengths that JSON doesn't have, so you should make sure that your hash
690 keys are noticably shorter than the 1024 characters YAML allows. 784 keys are noticeably shorter than the 1024 characters YAML allows.
691 785
692 There might be other incompatibilities that I am not aware of. In 786 There might be other incompatibilities that I am not aware of. In
693 general you should not try to generate YAML with a JSON generator or 787 general you should not try to generate YAML with a JSON generator or
694 vice versa, or try to parse JSON with a YAML parser or vice versa: 788 vice versa, or try to parse JSON with a YAML parser or vice versa:
695 chances are high that you will run into severe interoperability 789 chances are high that you will run into severe interoperability
… …
726 JSON::XS/3 | 338250.323 | 218453.333 | 820 JSON::XS/3 | 338250.323 | 218453.333 |
727 Storable | 16500.016 | 135300.129 | 821 Storable | 16500.016 | 135300.129 |
728 -----------+------------+------------+ 822 -----------+------------+------------+
729 823
730 That is, JSON::XS is about five times faster than JSON::DWIW on 824 That is, JSON::XS is about five times faster than JSON::DWIW on
731 encoding, about three times faster on decoding, and over fourty times 825 encoding, about three times faster on decoding, and over forty times
732 faster than JSON, even with pretty-printing and key sorting. It also 826 faster than JSON, even with pretty-printing and key sorting. It also
733 compares favourably to Storable for small amounts of data. 827 compares favourably to Storable for small amounts of data.
734 828
735 Using a longer test string (roughly 18KB, generated from Yahoo! Locals 829 Using a longer test string (roughly 18KB, generated from Yahoo! Locals
736 search API (http://nanoref.com/yahooapis/mgPdGg): 830 search API (http://nanoref.com/yahooapis/mgPdGg):
… …
749 -----------+------------+------------+ 843 -----------+------------+------------+
750 844
751 Again, JSON::XS leads by far (except for Storable which non-surprisingly 845 Again, JSON::XS leads by far (except for Storable which non-surprisingly
752 decodes faster). 846 decodes faster).
753 847
754 On large strings containing lots of high unicode characters, some 848 On large strings containing lots of high Unicode characters, some
755 modules (such as JSON::PC) seem to decode faster than JSON::XS, but the 849 modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
756 result will be broken due to missing (or wrong) unicode handling. Others 850 result will be broken due to missing (or wrong) Unicode handling. Others
757 refuse to decode or encode properly, so it was impossible to prepare a 851 refuse to decode or encode properly, so it was impossible to prepare a
758 fair comparison table for that case. 852 fair comparison table for that case.
759 853
760SECURITY CONSIDERATIONS 854SECURITY CONSIDERATIONS
761 When you are using JSON in a protocol, talking to untrusted potentially 855 When you are using JSON in a protocol, talking to untrusted potentially
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765 have any buffer overflows. Obviously, this module should ensure that and 859 have any buffer overflows. Obviously, this module should ensure that and
766 I am trying hard on making that true, but you never know. 860 I am trying hard on making that true, but you never know.
767 861
768 Second, you need to avoid resource-starving attacks. That means you 862 Second, you need to avoid resource-starving attacks. That means you
769 should limit the size of JSON texts you accept, or make sure then when 863 should limit the size of JSON texts you accept, or make sure then when
770 your resources run out, thats just fine (e.g. by using a separate 864 your resources run out, that's just fine (e.g. by using a separate
771 process that can crash safely). The size of a JSON text in octets or 865 process that can crash safely). The size of a JSON text in octets or
772 characters is usually a good indication of the size of the resources 866 characters is usually a good indication of the size of the resources
773 required to decode it into a Perl structure. While JSON::XS can check 867 required to decode it into a Perl structure. While JSON::XS can check
774 the size of the JSON text, it might be too late when you already have it 868 the size of the JSON text, it might be too late when you already have it
775 in memory, so you might want to check the size before you accept the 869 in memory, so you might want to check the size before you accept the
… …
786 880
787 And last but least, something else could bomb you that I forgot to think 881 And last but least, something else could bomb you that I forgot to think
788 of. In that case, you get to keep the pieces. I am always open for 882 of. In that case, you get to keep the pieces. I am always open for
789 hints, though... 883 hints, though...
790 884
791 If you are using JSON::XS to return packets to consumption by javascript 885 If you are using JSON::XS to return packets to consumption by JavaScript
792 scripts in a browser you should have a look at 886 scripts in a browser you should have a look at
793 <http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 887 <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
794 you are vulnerable to some common attack vectors (which really are 888 you are vulnerable to some common attack vectors (which really are
795 browser design bugs, but it is still you who will have to deal with it, 889 browser design bugs, but it is still you who will have to deal with it,
796 as major browser developers care only for features, not about doing 890 as major browser developers care only for features, not about doing
797 security right). 891 security right).
892
893THREADS
894 This module is *not* guaranteed to be thread safe and there are no plans
895 to change this until Perl gets thread support (as opposed to the
896 horribly slow so-called "threads" which are simply slow and bloated
897 process simulations - use fork, its *much* faster, cheaper, better).
898
899 (It might actually work, but you have been warned).
798 900
799BUGS 901BUGS
800 While the goal of this module is to be correct, that unfortunately does 902 While the goal of this module is to be correct, that unfortunately does
801 not mean its bug-free, only that I think its design is bug-free. It is 903 not mean its bug-free, only that I think its design is bug-free. It is
802 still relatively early in its development. If you keep reporting bugs 904 still relatively early in its development. If you keep reporting bugs
803 they will be fixed swiftly, though. 905 they will be fixed swiftly, though.
804 906
907 Please refrain from using rt.cpan.org or any other bug reporting
908 service. I put the contact address into my modules for a reason.
909
805AUTHOR 910AUTHOR
806 Marc Lehmann <schmorp@schmorp.de> 911 Marc Lehmann <schmorp@schmorp.de>
807 http://home.schmorp.de/ 912 http://home.schmorp.de/
808 913

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