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1NAME 1NAME
2 JSON::XS - JSON serialising/deserialising, done correctly and fast 2 JSON::XS - JSON serialising/deserialising, done correctly and fast
3 3
4 JSON::XS - 正しくて高速な JSON 4 JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
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) 5 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7 6
8SYNOPSIS 7SYNOPSIS
9 use JSON::XS; 8 use JSON::XS;
10 9
… …
33 primary goal is to be *correct* and its secondary goal is to be *fast*. 32 primary goal is to be *correct* and its secondary goal is to be *fast*.
34 To reach the latter goal it was written in C. 33 To reach the latter goal it was written in C.
35 34
36 Beginning with version 2.0 of the JSON module, when both JSON and 35 Beginning with version 2.0 of the JSON module, when both JSON and
37 JSON::XS are installed, then JSON will fall back on JSON::XS (this can 36 JSON::XS are installed, then JSON will fall back on JSON::XS (this can
38 be overriden) with no overhead due to emulation (by inheritign 37 be overridden) with no overhead due to emulation (by inheriting
39 constructor and methods). If JSON::XS is not available, it will fall 38 constructor and methods). If JSON::XS is not available, it will fall
40 back to the compatible JSON::PP module as backend, so using JSON instead 39 back to the compatible JSON::PP module as backend, so using JSON instead
41 of JSON::XS gives you a portable JSON API that can be fast when you need 40 of JSON::XS gives you a portable JSON API that can be fast when you need
42 and doesn't require a C compiler when that is a problem. 41 and doesn't require a C compiler when that is a problem.
43 42
… …
45 to write yet another JSON module? While it seems there are many JSON 44 to write yet another JSON module? While it seems there are many JSON
46 modules, none of them correctly handle all corner cases, and in most 45 modules, none of them correctly handle all corner cases, and in most
47 cases their maintainers are unresponsive, gone missing, or not listening 46 cases their maintainers are unresponsive, gone missing, or not listening
48 to bug reports for other reasons. 47 to bug reports for other reasons.
49 48
50 See COMPARISON, below, for a comparison to some other JSON modules.
51
52 See MAPPING, below, on how JSON::XS maps perl values to JSON values and 49 See MAPPING, below, on how JSON::XS maps perl values to JSON values and
53 vice versa. 50 vice versa.
54 51
55 FEATURES 52 FEATURES
56 * correct Unicode handling 53 * correct Unicode handling
54
57 This module knows how to handle Unicode, and even documents how and 55 This module knows how to handle Unicode, documents how and when it
58 when it does so. 56 does so, and even documents what "correct" means.
59 57
60 * round-trip integrity 58 * round-trip integrity
59
61 When you serialise a perl data structure using only datatypes 60 When you serialise a perl data structure using only data types
62 supported by JSON, the deserialised data structure is identical on 61 supported by JSON, the deserialised data structure is identical on
63 the Perl level. (e.g. the string "2.0" doesn't suddenly become "2" 62 the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"
64 just because it looks like a number). 63 just because it looks like a number). There minor *are* exceptions
64 to this, read the MAPPING section below to learn about those.
65 65
66 * strict checking of JSON correctness 66 * strict checking of JSON correctness
67
67 There is no guessing, no generating of illegal JSON texts by 68 There is no guessing, no generating of illegal JSON texts by
68 default, and only JSON is accepted as input by default (the latter 69 default, and only JSON is accepted as input by default (the latter
69 is a security feature). 70 is a security feature).
70 71
71 * fast 72 * fast
72 Compared to other JSON modules, this module compares favourably in
73 terms of speed, too.
74 73
74 Compared to other JSON modules and other serialisers such as
75 Storable, this module usually compares favourably in terms of speed,
76 too.
77
75 * simple to use 78 * simple to use
79
76 This module has both a simple functional interface as well as an OO 80 This module has both a simple functional interface as well as an
77 interface. 81 object oriented interface interface.
78 82
79 * reasonably versatile output formats 83 * reasonably versatile output formats
84
80 You can choose between the most compact guaranteed single-line 85 You can choose between the most compact guaranteed-single-line
81 format possible (nice for simple line-based protocols), a pure-ascii 86 format possible (nice for simple line-based protocols), a pure-ASCII
82 format (for when your transport is not 8-bit clean, still supports 87 format (for when your transport is not 8-bit clean, still supports
83 the whole Unicode range), or a pretty-printed format (for when you 88 the whole Unicode range), or a pretty-printed format (for when you
84 want to read that stuff). Or you can combine those features in 89 want to read that stuff). Or you can combine those features in
85 whatever way you like. 90 whatever way you like.
86 91
… …
94 99
95 This function call is functionally identical to: 100 This function call is functionally identical to:
96 101
97 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 102 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
98 103
99 except being faster. 104 Except being faster.
100 105
101 $perl_scalar = decode_json $json_text 106 $perl_scalar = decode_json $json_text
102 The opposite of "encode_json": expects an UTF-8 (binary) string and 107 The opposite of "encode_json": expects an UTF-8 (binary) string and
103 tries to parse that as an UTF-8 encoded JSON text, returning the 108 tries to parse that as an UTF-8 encoded JSON text, returning the
104 resulting reference. Croaks on error. 109 resulting reference. Croaks on error.
105 110
106 This function call is functionally identical to: 111 This function call is functionally identical to:
107 112
108 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 113 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
109 114
110 except being faster. 115 Except being faster.
111 116
112 $is_boolean = JSON::XS::is_bool $scalar 117 $is_boolean = JSON::XS::is_bool $scalar
113 Returns true if the passed scalar represents either JSON::XS::true 118 Returns true if the passed scalar represents either JSON::XS::true
114 or JSON::XS::false, two constants that act like 1 and 0, 119 or JSON::XS::false, two constants that act like 1 and 0,
115 respectively and are used to represent JSON "true" and "false" 120 respectively and are used to represent JSON "true" and "false"
… …
125 1. Perl strings can store characters with ordinal values > 255. 130 1. Perl strings can store characters with ordinal values > 255.
126 This enables you to store Unicode characters as single characters in 131 This enables you to store Unicode characters as single characters in
127 a Perl string - very natural. 132 a Perl string - very natural.
128 133
129 2. Perl does *not* associate an encoding with your strings. 134 2. Perl does *not* associate an encoding with your strings.
130 Unless you force it to, e.g. when matching it against a regex, or 135 ... until you force it to, e.g. when matching it against a regex, or
131 printing the scalar to a file, in which case Perl either interprets 136 printing the scalar to a file, in which case Perl either interprets
132 your string as locale-encoded text, octets/binary, or as Unicode, 137 your string as locale-encoded text, octets/binary, or as Unicode,
133 depending on various settings. In no case is an encoding stored 138 depending on various settings. In no case is an encoding stored
134 together with your data, it is *use* that decides encoding, not any 139 together with your data, it is *use* that decides encoding, not any
135 magical metadata. 140 magical meta data.
136 141
137 3. The internal utf-8 flag has no meaning with regards to the encoding 142 3. The internal utf-8 flag has no meaning with regards to the encoding
138 of your string. 143 of your string.
139 Just ignore that flag unless you debug a Perl bug, a module written 144 Just ignore that flag unless you debug a Perl bug, a module written
140 in XS or want to dive into the internals of perl. Otherwise it will 145 in XS or want to dive into the internals of perl. Otherwise it will
… …
145 150
146 If you didn't know about that flag, just the better, pretend it 151 If you didn't know about that flag, just the better, pretend it
147 doesn't exist. 152 doesn't exist.
148 153
149 4. A "Unicode String" is simply a string where each character can be 154 4. A "Unicode String" is simply a string where each character can be
150 validly interpreted as a Unicode codepoint. 155 validly interpreted as a Unicode code point.
151 If you have UTF-8 encoded data, it is no longer a Unicode string, 156 If you have UTF-8 encoded data, it is no longer a Unicode string,
152 but a Unicode string encoded in UTF-8, giving you a binary string. 157 but a Unicode string encoded in UTF-8, giving you a binary string.
153 158
154 5. A string containing "high" (> 255) character values is *not* a UTF-8 159 5. A string containing "high" (> 255) character values is *not* a UTF-8
155 string. 160 string.
… …
185 190
186 If $enable is false, then the "encode" method will not escape 191 If $enable is false, then the "encode" method will not escape
187 Unicode characters unless required by the JSON syntax or other 192 Unicode characters unless required by the JSON syntax or other
188 flags. This results in a faster and more compact format. 193 flags. This results in a faster and more compact format.
189 194
195 See also the section *ENCODING/CODESET FLAG NOTES* later in this
196 document.
197
190 The main use for this flag is to produce JSON texts that can be 198 The main use for this flag is to produce JSON texts that can be
191 transmitted over a 7-bit channel, as the encoded JSON texts will not 199 transmitted over a 7-bit channel, as the encoded JSON texts will not
192 contain any 8 bit characters. 200 contain any 8 bit characters.
193 201
194 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 202 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
… …
205 superset of latin1. 213 superset of latin1.
206 214
207 If $enable is false, then the "encode" method will not escape 215 If $enable is false, then the "encode" method will not escape
208 Unicode characters unless required by the JSON syntax or other 216 Unicode characters unless required by the JSON syntax or other
209 flags. 217 flags.
218
219 See also the section *ENCODING/CODESET FLAG NOTES* later in this
220 document.
210 221
211 The main use for this flag is efficiently encoding binary data as 222 The main use for this flag is efficiently encoding binary data as
212 JSON text, as most octets will not be escaped, resulting in a 223 JSON text, as most octets will not be escaped, resulting in a
213 smaller encoded size. The disadvantage is that the resulting JSON 224 smaller encoded size. The disadvantage is that the resulting JSON
214 text is encoded in latin1 (and must correctly be treated as such 225 text is encoded in latin1 (and must correctly be treated as such
… …
234 If $enable is false, then the "encode" method will return the JSON 245 If $enable is false, then the "encode" method will return the JSON
235 string as a (non-encoded) Unicode string, while "decode" expects 246 string as a (non-encoded) Unicode string, while "decode" expects
236 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or 247 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
237 UTF-16) needs to be done yourself, e.g. using the Encode module. 248 UTF-16) needs to be done yourself, e.g. using the Encode module.
238 249
250 See also the section *ENCODING/CODESET FLAG NOTES* later in this
251 document.
252
239 Example, output UTF-16BE-encoded JSON: 253 Example, output UTF-16BE-encoded JSON:
240 254
241 use Encode; 255 use Encode;
242 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); 256 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
243 257
… …
318 If $enable is false (the default), then "decode" will only accept 332 If $enable is false (the default), then "decode" will only accept
319 valid JSON texts. 333 valid JSON texts.
320 334
321 Currently accepted extensions are: 335 Currently accepted extensions are:
322 336
323 * list items can have an end-comma 337 * list items can have an end-comma
338
324 JSON *separates* array elements and key-value pairs with commas. 339 JSON *separates* array elements and key-value pairs with commas.
325 This can be annoying if you write JSON texts manually and want 340 This can be annoying if you write JSON texts manually and want
326 to be able to quickly append elements, so this extension accepts 341 to be able to quickly append elements, so this extension accepts
327 comma at the end of such items not just between them: 342 comma at the end of such items not just between them:
328 343
… …
333 { 348 {
334 "k1": "v1", 349 "k1": "v1",
335 "k2": "v2", <- this comma not normally allowed 350 "k2": "v2", <- this comma not normally allowed
336 } 351 }
337 352
338 * shell-style '#'-comments 353 * shell-style '#'-comments
354
339 Whenever JSON allows whitespace, shell-style comments are 355 Whenever JSON allows whitespace, shell-style comments are
340 additionally allowed. They are terminated by the first 356 additionally allowed. They are terminated by the first
341 carriage-return or line-feed character, after which more 357 carriage-return or line-feed character, after which more
342 white-space and comments are allowed. 358 white-space and comments are allowed.
343 359
… …
379 Example, encode a Perl scalar as JSON value with enabled 395 Example, encode a Perl scalar as JSON value with enabled
380 "allow_nonref", resulting in an invalid JSON text: 396 "allow_nonref", resulting in an invalid JSON text:
381 397
382 JSON::XS->new->allow_nonref->encode ("Hello, World!") 398 JSON::XS->new->allow_nonref->encode ("Hello, World!")
383 => "Hello, World!" 399 => "Hello, World!"
400
401 $json = $json->allow_unknown ([$enable])
402 $enabled = $json->get_allow_unknown
403 If $enable is true (or missing), then "encode" will *not* throw an
404 exception when it encounters values it cannot represent in JSON (for
405 example, filehandles) but instead will encode a JSON "null" value.
406 Note that blessed objects are not included here and are handled
407 separately by c<allow_nonref>.
408
409 If $enable is false (the default), then "encode" will throw an
410 exception when it encounters anything it cannot encode as JSON.
411
412 This option does not affect "decode" in any way, and it is
413 recommended to leave it off unless you know your communications
414 partner.
384 415
385 $json = $json->allow_blessed ([$enable]) 416 $json = $json->allow_blessed ([$enable])
386 $enabled = $json->get_allow_blessed 417 $enabled = $json->get_allow_blessed
387 If $enable is true (or missing), then the "encode" method will not 418 If $enable is true (or missing), then the "encode" method will not
388 barf when it encounters a blessed reference. Instead, the value of 419 barf when it encounters a blessed reference. Instead, the value of
… …
523 saving space. 554 saving space.
524 555
525 $json = $json->max_depth ([$maximum_nesting_depth]) 556 $json = $json->max_depth ([$maximum_nesting_depth])
526 $max_depth = $json->get_max_depth 557 $max_depth = $json->get_max_depth
527 Sets the maximum nesting level (default 512) accepted while encoding 558 Sets the maximum nesting level (default 512) accepted while encoding
528 or decoding. If the JSON text or Perl data structure has an equal or 559 or decoding. If a higher nesting level is detected in JSON text or a
529 higher nesting level then this limit, then the encoder and decoder 560 Perl data structure, then the encoder and decoder will stop and
530 will stop and croak at that point. 561 croak at that point.
531 562
532 Nesting level is defined by number of hash- or arrayrefs that the 563 Nesting level is defined by number of hash- or arrayrefs that the
533 encoder needs to traverse to reach a given point or the number of 564 encoder needs to traverse to reach a given point or the number of
534 "{" or "[" characters without their matching closing parenthesis 565 "{" or "[" characters without their matching closing parenthesis
535 crossed to reach a given character in a string. 566 crossed to reach a given character in a string.
536 567
537 Setting the maximum depth to one disallows any nesting, so that 568 Setting the maximum depth to one disallows any nesting, so that
538 ensures that the object is only a single hash/object or array. 569 ensures that the object is only a single hash/object or array.
539 570
540 The argument to "max_depth" will be rounded up to the next highest
541 power of two. If no argument is given, the highest possible setting 571 If no argument is given, the highest possible setting will be used,
542 will be used, which is rarely useful. 572 which is rarely useful.
573
574 Note that nesting is implemented by recursion in C. The default
575 value has been chosen to be as large as typical operating systems
576 allow without crashing.
543 577
544 See SECURITY CONSIDERATIONS, below, for more info on why this is 578 See SECURITY CONSIDERATIONS, below, for more info on why this is
545 useful. 579 useful.
546 580
547 $json = $json->max_size ([$maximum_string_size]) 581 $json = $json->max_size ([$maximum_string_size])
548 $max_size = $json->get_max_size 582 $max_size = $json->get_max_size
549 Set the maximum length a JSON text may have (in bytes) where 583 Set the maximum length a JSON text may have (in bytes) where
550 decoding is being attempted. The default is 0, meaning no limit. 584 decoding is being attempted. The default is 0, meaning no limit.
551 When "decode" is called on a string longer then this number of 585 When "decode" is called on a string that is longer then this many
552 characters it will not attempt to decode the string but throw an 586 bytes, it will not attempt to decode the string but throw an
553 exception. This setting has no effect on "encode" (yet). 587 exception. This setting has no effect on "encode" (yet).
554 588
555 The argument to "max_size" will be rounded up to the next highest
556 power of two (so may be more than requested). If no argument is
557 given, the limit check will be deactivated (same as when 0 is 589 If no argument is given, the limit check will be deactivated (same
558 specified). 590 as when 0 is specified).
559 591
560 See SECURITY CONSIDERATIONS, below, for more info on why this is 592 See SECURITY CONSIDERATIONS, below, for more info on why this is
561 useful. 593 useful.
562 594
563 $json_text = $json->encode ($perl_scalar) 595 $json_text = $json->encode ($perl_scalar)
… …
588 and you need to know where the JSON text ends. 620 and you need to know where the JSON text ends.
589 621
590 JSON::XS->new->decode_prefix ("[1] the tail") 622 JSON::XS->new->decode_prefix ("[1] the tail")
591 => ([], 3) 623 => ([], 3)
592 624
625INCREMENTAL PARSING
626 In some cases, there is the need for incremental parsing of JSON texts.
627 While this module always has to keep both JSON text and resulting Perl
628 data structure in memory at one time, it does allow you to parse a JSON
629 stream incrementally. It does so by accumulating text until it has a
630 full JSON object, which it then can decode. This process is similar to
631 using "decode_prefix" to see if a full JSON object is available, but is
632 much more efficient (and can be implemented with a minimum of method
633 calls).
634
635 JSON::XS will only attempt to parse the JSON text once it is sure it has
636 enough text to get a decisive result, using a very simple but truly
637 incremental parser. This means that it sometimes won't stop as early as
638 the full parser, for example, it doesn't detect parenthese mismatches.
639 The only thing it guarantees is that it starts decoding as soon as a
640 syntactically valid JSON text has been seen. This means you need to set
641 resource limits (e.g. "max_size") to ensure the parser will stop parsing
642 in the presence if syntax errors.
643
644 The following methods implement this incremental parser.
645
646 [void, scalar or list context] = $json->incr_parse ([$string])
647 This is the central parsing function. It can both append new text
648 and extract objects from the stream accumulated so far (both of
649 these functions are optional).
650
651 If $string is given, then this string is appended to the already
652 existing JSON fragment stored in the $json object.
653
654 After that, if the function is called in void context, it will
655 simply return without doing anything further. This can be used to
656 add more text in as many chunks as you want.
657
658 If the method is called in scalar context, then it will try to
659 extract exactly *one* JSON object. If that is successful, it will
660 return this object, otherwise it will return "undef". If there is a
661 parse error, this method will croak just as "decode" would do (one
662 can then use "incr_skip" to skip the errornous part). This is the
663 most common way of using the method.
664
665 And finally, in list context, it will try to extract as many objects
666 from the stream as it can find and return them, or the empty list
667 otherwise. For this to work, there must be no separators between the
668 JSON objects or arrays, instead they must be concatenated
669 back-to-back. If an error occurs, an exception will be raised as in
670 the scalar context case. Note that in this case, any
671 previously-parsed JSON texts will be lost.
672
673 $lvalue_string = $json->incr_text
674 This method returns the currently stored JSON fragment as an lvalue,
675 that is, you can manipulate it. This *only* works when a preceding
676 call to "incr_parse" in *scalar context* successfully returned an
677 object. Under all other circumstances you must not call this
678 function (I mean it. although in simple tests it might actually
679 work, it *will* fail under real world conditions). As a special
680 exception, you can also call this method before having parsed
681 anything.
682
683 This function is useful in two cases: a) finding the trailing text
684 after a JSON object or b) parsing multiple JSON objects separated by
685 non-JSON text (such as commas).
686
687 $json->incr_skip
688 This will reset the state of the incremental parser and will remove
689 the parsed text from the input buffer so far. This is useful after
690 "incr_parse" died, in which case the input buffer and incremental
691 parser state is left unchanged, to skip the text parsed so far and
692 to reset the parse state.
693
694 The difference to "incr_reset" is that only text until the parse
695 error occured is removed.
696
697 $json->incr_reset
698 This completely resets the incremental parser, that is, after this
699 call, it will be as if the parser had never parsed anything.
700
701 This is useful if you want to repeatedly parse JSON objects and want
702 to ignore any trailing data, which means you have to reset the
703 parser after each successful decode.
704
705 LIMITATIONS
706 All options that affect decoding are supported, except "allow_nonref".
707 The reason for this is that it cannot be made to work sensibly: JSON
708 objects and arrays are self-delimited, i.e. you can concatenate them
709 back to back and still decode them perfectly. This does not hold true
710 for JSON numbers, however.
711
712 For example, is the string 1 a single JSON number, or is it simply the
713 start of 12? Or is 12 a single JSON number, or the concatenation of 1
714 and 2? In neither case you can tell, and this is why JSON::XS takes the
715 conservative route and disallows this case.
716
717 EXAMPLES
718 Some examples will make all this clearer. First, a simple example that
719 works similarly to "decode_prefix": We want to decode the JSON object at
720 the start of a string and identify the portion after the JSON object:
721
722 my $text = "[1,2,3] hello";
723
724 my $json = new JSON::XS;
725
726 my $obj = $json->incr_parse ($text)
727 or die "expected JSON object or array at beginning of string";
728
729 my $tail = $json->incr_text;
730 # $tail now contains " hello"
731
732 Easy, isn't it?
733
734 Now for a more complicated example: Imagine a hypothetical protocol
735 where you read some requests from a TCP stream, and each request is a
736 JSON array, without any separation between them (in fact, it is often
737 useful to use newlines as "separators", as these get interpreted as
738 whitespace at the start of the JSON text, which makes it possible to
739 test said protocol with "telnet"...).
740
741 Here is how you'd do it (it is trivial to write this in an event-based
742 manner):
743
744 my $json = new JSON::XS;
745
746 # read some data from the socket
747 while (sysread $socket, my $buf, 4096) {
748
749 # split and decode as many requests as possible
750 for my $request ($json->incr_parse ($buf)) {
751 # act on the $request
752 }
753 }
754
755 Another complicated example: Assume you have a string with JSON objects
756 or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
757 [3]"). To parse them, we have to skip the commas between the JSON texts,
758 and here is where the lvalue-ness of "incr_text" comes in useful:
759
760 my $text = "[1],[2], [3]";
761 my $json = new JSON::XS;
762
763 # void context, so no parsing done
764 $json->incr_parse ($text);
765
766 # now extract as many objects as possible. note the
767 # use of scalar context so incr_text can be called.
768 while (my $obj = $json->incr_parse) {
769 # do something with $obj
770
771 # now skip the optional comma
772 $json->incr_text =~ s/^ \s* , //x;
773 }
774
775 Now lets go for a very complex example: Assume that you have a gigantic
776 JSON array-of-objects, many gigabytes in size, and you want to parse it,
777 but you cannot load it into memory fully (this has actually happened in
778 the real world :).
779
780 Well, you lost, you have to implement your own JSON parser. But JSON::XS
781 can still help you: You implement a (very simple) array parser and let
782 JSON decode the array elements, which are all full JSON objects on their
783 own (this wouldn't work if the array elements could be JSON numbers, for
784 example):
785
786 my $json = new JSON::XS;
787
788 # open the monster
789 open my $fh, "<bigfile.json"
790 or die "bigfile: $!";
791
792 # first parse the initial "["
793 for (;;) {
794 sysread $fh, my $buf, 65536
795 or die "read error: $!";
796 $json->incr_parse ($buf); # void context, so no parsing
797
798 # Exit the loop once we found and removed(!) the initial "[".
799 # In essence, we are (ab-)using the $json object as a simple scalar
800 # we append data to.
801 last if $json->incr_text =~ s/^ \s* \[ //x;
802 }
803
804 # now we have the skipped the initial "[", so continue
805 # parsing all the elements.
806 for (;;) {
807 # in this loop we read data until we got a single JSON object
808 for (;;) {
809 if (my $obj = $json->incr_parse) {
810 # do something with $obj
811 last;
812 }
813
814 # add more data
815 sysread $fh, my $buf, 65536
816 or die "read error: $!";
817 $json->incr_parse ($buf); # void context, so no parsing
818 }
819
820 # in this loop we read data until we either found and parsed the
821 # separating "," between elements, or the final "]"
822 for (;;) {
823 # first skip whitespace
824 $json->incr_text =~ s/^\s*//;
825
826 # if we find "]", we are done
827 if ($json->incr_text =~ s/^\]//) {
828 print "finished.\n";
829 exit;
830 }
831
832 # if we find ",", we can continue with the next element
833 if ($json->incr_text =~ s/^,//) {
834 last;
835 }
836
837 # if we find anything else, we have a parse error!
838 if (length $json->incr_text) {
839 die "parse error near ", $json->incr_text;
840 }
841
842 # else add more data
843 sysread $fh, my $buf, 65536
844 or die "read error: $!";
845 $json->incr_parse ($buf); # void context, so no parsing
846 }
847
848 This is a complex example, but most of the complexity comes from the
849 fact that we are trying to be correct (bear with me if I am wrong, I
850 never ran the above example :).
851
593MAPPING 852MAPPING
594 This section describes how JSON::XS maps Perl values to JSON values and 853 This section describes how JSON::XS maps Perl values to JSON values and
595 vice versa. These mappings are designed to "do the right thing" in most 854 vice versa. These mappings are designed to "do the right thing" in most
596 circumstances automatically, preserving round-tripping characteristics 855 circumstances automatically, preserving round-tripping characteristics
597 (what you put in comes out as something equivalent). 856 (what you put in comes out as something equivalent).
… …
618 A JSON number becomes either an integer, numeric (floating point) or 877 A JSON number becomes either an integer, numeric (floating point) or
619 string scalar in perl, depending on its range and any fractional 878 string scalar in perl, depending on its range and any fractional
620 parts. On the Perl level, there is no difference between those as 879 parts. On the Perl level, there is no difference between those as
621 Perl handles all the conversion details, but an integer may take 880 Perl handles all the conversion details, but an integer may take
622 slightly less memory and might represent more values exactly than 881 slightly less memory and might represent more values exactly than
623 (floating point) numbers. 882 floating point numbers.
624 883
625 If the number consists of digits only, JSON::XS will try to 884 If the number consists of digits only, JSON::XS will try to
626 represent it as an integer value. If that fails, it will try to 885 represent it as an integer value. If that fails, it will try to
627 represent it as a numeric (floating point) value if that is possible 886 represent it as a numeric (floating point) value if that is possible
628 without loss of precision. Otherwise it will preserve the number as 887 without loss of precision. Otherwise it will preserve the number as
629 a string value. 888 a string value (in which case you lose roundtripping ability, as the
889 JSON number will be re-encoded toa JSON string).
630 890
631 Numbers containing a fractional or exponential part will always be 891 Numbers containing a fractional or exponential part will always be
632 represented as numeric (floating point) values, possibly at a loss 892 represented as numeric (floating point) values, possibly at a loss
633 of precision. 893 of precision (in which case you might lose perfect roundtripping
634 894 ability, but the JSON number will still be re-encoded as a JSON
635 This might create round-tripping problems as numbers might become 895 number).
636 strings, but as Perl is typeless there is no other way to do it.
637 896
638 true, false 897 true, false
639 These JSON atoms become "JSON::XS::true" and "JSON::XS::false", 898 These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
640 respectively. They are overloaded to act almost exactly like the 899 respectively. They are overloaded to act almost exactly like the
641 numbers 1 and 0. You can check whether a scalar is a JSON boolean by 900 numbers 1 and 0. You can check whether a scalar is a JSON boolean by
… …
669 an exception to be thrown, except for references to the integers 0 928 an exception to be thrown, except for references to the integers 0
670 and 1, which get turned into "false" and "true" atoms in JSON. You 929 and 1, which get turned into "false" and "true" atoms in JSON. You
671 can also use "JSON::XS::false" and "JSON::XS::true" to improve 930 can also use "JSON::XS::false" and "JSON::XS::true" to improve
672 readability. 931 readability.
673 932
674 encode_json [\0,JSON::XS::true] # yields [false,true] 933 encode_json [\0, JSON::XS::true] # yields [false,true]
675 934
676 JSON::XS::true, JSON::XS::false 935 JSON::XS::true, JSON::XS::false
677 These special values become JSON true and JSON false values, 936 These special values become JSON true and JSON false values,
678 respectively. You can also use "\1" and "\0" directly if you want. 937 respectively. You can also use "\1" and "\0" directly if you want.
679 938
680 blessed objects 939 blessed objects
681 Blessed objects are not allowed. JSON::XS currently tries to encode 940 Blessed objects are not directly representable in JSON. See the
682 their underlying representation (hash- or arrayref), but this 941 "allow_blessed" and "convert_blessed" methods on various options on
683 behaviour might change in future versions. 942 how to deal with this: basically, you can choose between throwing an
943 exception, encoding the reference as if it weren't blessed, or
944 provide your own serialiser method.
684 945
685 simple scalars 946 simple scalars
686 Simple Perl scalars (any scalar that is not a reference) are the 947 Simple Perl scalars (any scalar that is not a reference) are the
687 most difficult objects to encode: JSON::XS will encode undefined 948 most difficult objects to encode: JSON::XS will encode undefined
688 scalars as JSON null value, scalars that have last been used in a 949 scalars as JSON "null" values, scalars that have last been used in a
689 string context before encoding as JSON strings and anything else as 950 string context before encoding as JSON strings, and anything else as
690 number value: 951 number value:
691 952
692 # dump as number 953 # dump as number
693 encode_json [2] # yields [2] 954 encode_json [2] # yields [2]
694 encode_json [-3.0e17] # yields [-3e+17] 955 encode_json [-3.0e17] # yields [-3e+17]
… …
713 my $x = "3"; # some variable containing a string 974 my $x = "3"; # some variable containing a string
714 $x += 0; # numify it, ensuring it will be dumped as a number 975 $x += 0; # numify it, ensuring it will be dumped as a number
715 $x *= 1; # same thing, the choice is yours. 976 $x *= 1; # same thing, the choice is yours.
716 977
717 You can not currently force the type in other, less obscure, ways. 978 You can not currently force the type in other, less obscure, ways.
718 Tell me if you need this capability. 979 Tell me if you need this capability (but don't forget to explain why
980 it's needed :).
719 981
720COMPARISON 982ENCODING/CODESET FLAG NOTES
721 As already mentioned, this module was created because none of the 983 The interested reader might have seen a number of flags that signify
722 existing JSON modules could be made to work correctly. First I will 984 encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
723 describe the problems (or pleasures) I encountered with various existing 985 some confusion on what these do, so here is a short comparison:
724 JSON modules, followed by some benchmark values. JSON::XS was designed
725 not to suffer from any of these problems or limitations.
726 986
727 JSON 1.07 987 "utf8" controls whether the JSON text created by "encode" (and expected
728 Slow (but very portable, as it is written in pure Perl). 988 by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
989 control whether "encode" escapes character values outside their
990 respective codeset range. Neither of these flags conflict with each
991 other, although some combinations make less sense than others.
729 992
730 Undocumented/buggy Unicode handling (how JSON handles Unicode values 993 Care has been taken to make all flags symmetrical with respect to
731 is undocumented. One can get far by feeding it Unicode strings and 994 "encode" and "decode", that is, texts encoded with any combination of
732 doing en-/decoding oneself, but Unicode escapes are not working 995 these flag values will be correctly decoded when the same flags are used
996 - in general, if you use different flag settings while encoding vs. when
997 decoding you likely have a bug somewhere.
998
999 Below comes a verbose discussion of these flags. Note that a "codeset"
1000 is simply an abstract set of character-codepoint pairs, while an
1001 encoding takes those codepoint numbers and *encodes* them, in our case
1002 into octets. Unicode is (among other things) a codeset, UTF-8 is an
1003 encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets *and*
1004 encodings at the same time, which can be confusing.
1005
1006 "utf8" flag disabled
1007 When "utf8" is disabled (the default), then "encode"/"decode"
1008 generate and expect Unicode strings, that is, characters with high
1009 ordinal Unicode values (> 255) will be encoded as such characters,
1010 and likewise such characters are decoded as-is, no canges to them
1011 will be done, except "(re-)interpreting" them as Unicode codepoints
1012 or Unicode characters, respectively (to Perl, these are the same
1013 thing in strings unless you do funny/weird/dumb stuff).
1014
1015 This is useful when you want to do the encoding yourself (e.g. when
1016 you want to have UTF-16 encoded JSON texts) or when some other layer
1017 does the encoding for you (for example, when printing to a terminal
1018 using a filehandle that transparently encodes to UTF-8 you certainly
1019 do NOT want to UTF-8 encode your data first and have Perl encode it
1020 another time).
1021
1022 "utf8" flag enabled
1023 If the "utf8"-flag is enabled, "encode"/"decode" will encode all
1024 characters using the corresponding UTF-8 multi-byte sequence, and
1025 will expect your input strings to be encoded as UTF-8, that is, no
1026 "character" of the input string must have any value > 255, as UTF-8
1027 does not allow that.
1028
1029 The "utf8" flag therefore switches between two modes: disabled means
1030 you will get a Unicode string in Perl, enabled means you get an
1031 UTF-8 encoded octet/binary string in Perl.
1032
1033 "latin1" or "ascii" flags enabled
1034 With "latin1" (or "ascii") enabled, "encode" will escape characters
1035 with ordinal values > 255 (> 127 with "ascii") and encode the
1036 remaining characters as specified by the "utf8" flag.
1037
1038 If "utf8" is disabled, then the result is also correctly encoded in
1039 those character sets (as both are proper subsets of Unicode, meaning
1040 that a Unicode string with all character values < 256 is the same
1041 thing as a ISO-8859-1 string, and a Unicode string with all
1042 character values < 128 is the same thing as an ASCII string in
733 properly). 1043 Perl).
734 1044
735 No round-tripping (strings get clobbered if they look like numbers, 1045 If "utf8" is enabled, you still get a correct UTF-8-encoded string,
736 e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that 1046 regardless of these flags, just some more characters will be escaped
737 will decode into the number 2. 1047 using "\uXXXX" then before.
738 1048
739 JSON::PC 0.01 1049 Note that ISO-8859-1-*encoded* strings are not compatible with UTF-8
740 Very fast. 1050 encoding, while ASCII-encoded strings are. That is because the
1051 ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
1052 *codeset* being a subset of Unicode), while ASCII is.
741 1053
742 Undocumented/buggy Unicode handling. 1054 Surprisingly, "decode" will ignore these flags and so treat all
1055 input values as governed by the "utf8" flag. If it is disabled, this
1056 allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
1057 strict subsets of Unicode. If it is enabled, you can correctly
1058 decode UTF-8 encoded strings.
743 1059
744 No round-tripping. 1060 So neither "latin1" nor "ascii" are incompatible with the "utf8"
1061 flag - they only govern when the JSON output engine escapes a
1062 character or not.
745 1063
746 Has problems handling many Perl values (e.g. regex results and other 1064 The main use for "latin1" is to relatively efficiently store binary
747 magic values will make it croak). 1065 data as JSON, at the expense of breaking compatibility with most
1066 JSON decoders.
748 1067
749 Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}" 1068 The main use for "ascii" is to force the output to not contain
750 which is not a valid JSON text. 1069 characters with values > 127, which means you can interpret the
1070 resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
1071 any character set and 8-bit-encoding, and still get the same data
1072 structure back. This is useful when your channel for JSON transfer
1073 is not 8-bit clean or the encoding might be mangled in between (e.g.
1074 in mail), and works because ASCII is a proper subset of most 8-bit
1075 and multibyte encodings in use in the world.
751 1076
752 Unmaintained (maintainer unresponsive for many months, bugs are not 1077 JSON and ECMAscript
753 getting fixed). 1078 JSON syntax is based on how literals are represented in javascript (the
1079 not-standardised predecessor of ECMAscript) which is presumably why it
1080 is called "JavaScript Object Notation".
754 1081
755 JSON::Syck 0.21 1082 However, JSON is not a subset (and also not a superset of course) of
756 Very buggy (often crashes). 1083 ECMAscript (the standard) or javascript (whatever browsers actually
1084 implement).
757 1085
758 Very inflexible (no human-readable format supported, format pretty 1086 If you want to use javascript's "eval" function to "parse" JSON, you
759 much undocumented. I need at least a format for easy reading by 1087 might run into parse errors for valid JSON texts, or the resulting data
760 humans and a single-line compact format for use in a protocol, and 1088 structure might not be queryable:
761 preferably a way to generate ASCII-only JSON texts).
762 1089
763 Completely broken (and confusingly documented) Unicode handling 1090 One of the problems is that U+2028 and U+2029 are valid characters
764 (Unicode escapes are not working properly, you need to set 1091 inside JSON strings, but are not allowed in ECMAscript string literals,
765 ImplicitUnicode to *different* values on en- and decoding to get 1092 so the following Perl fragment will not output something that can be
766 symmetric behaviour). 1093 guaranteed to be parsable by javascript's "eval":
767 1094
768 No round-tripping (simple cases work, but this depends on whether 1095 use JSON::XS;
769 the scalar value was used in a numeric context or not).
770 1096
771 Dumping hashes may skip hash values depending on iterator state. 1097 print encode_json [chr 0x2028];
772 1098
773 Unmaintained (maintainer unresponsive for many months, bugs are not 1099 The right fix for this is to use a proper JSON parser in your javascript
774 getting fixed). 1100 programs, and not rely on "eval" (see for example Douglas Crockford's
1101 json2.js parser).
775 1102
776 Does not check input for validity (i.e. will accept non-JSON input 1103 If this is not an option, you can, as a stop-gap measure, simply encode
777 and return "something" instead of raising an exception. This is a 1104 to ASCII-only JSON:
778 security issue: imagine two banks transferring money between each
779 other using JSON. One bank might parse a given non-JSON request and
780 deduct money, while the other might reject the transaction with a
781 syntax error. While a good protocol will at least recover, that is
782 extra unnecessary work and the transaction will still not succeed).
783 1105
784 JSON::DWIW 0.04 1106 use JSON::XS;
785 Very fast. Very natural. Very nice.
786 1107
787 Undocumented Unicode handling (but the best of the pack. Unicode 1108 print JSON::XS->new->ascii->encode ([chr 0x2028]);
788 escapes still don't get parsed properly).
789 1109
790 Very inflexible. 1110 Note that this will enlarge the resulting JSON text quite a bit if you
1111 have many non-ASCII characters. You might be tempted to run some regexes
1112 to only escape U+2028 and U+2029, e.g.:
791 1113
792 No round-tripping. 1114 # DO NOT USE THIS!
1115 my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
1116 $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
1117 $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
1118 print $json;
793 1119
794 Does not generate valid JSON texts (key strings are often unquoted, 1120 Note that *this is a bad idea*: the above only works for U+2028 and
795 empty keys result in nothing being output) 1121 U+2029 and thus only for fully ECMAscript-compliant parsers. Many
1122 existing javascript implementations, however, have issues with other
1123 characters as well - using "eval" naively simply *will* cause problems.
796 1124
797 Does not check input for validity. 1125 Another problem is that some javascript implementations reserve some
1126 property names for their own purposes (which probably makes them
1127 non-ECMAscript-compliant). For example, Iceweasel reserves the
1128 "__proto__" property name for it's own purposes.
1129
1130 If that is a problem, you could parse try to filter the resulting JSON
1131 output for these property strings, e.g.:
1132
1133 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1134
1135 This works because "__proto__" is not valid outside of strings, so every
1136 occurence of ""__proto__"\s*:" must be a string used as property name.
1137
1138 If you know of other incompatibilities, please let me know.
798 1139
799 JSON and YAML 1140 JSON and YAML
800 You often hear that JSON is a subset (or a close subset) of YAML. This 1141 You often hear that JSON is a subset of YAML. This is, however, a mass
801 is, however, a mass hysteria and very far from the truth. In general, 1142 hysteria(*) and very far from the truth (as of the time of this
802 there is no way to configure JSON::XS to output a data structure as 1143 writing), so let me state it clearly: *in general, there is no way to
803 valid YAML. 1144 configure JSON::XS to output a data structure as valid YAML* that works
1145 in all cases.
804 1146
805 If you really must use JSON::XS to generate YAML, you should use this 1147 If you really must use JSON::XS to generate YAML, you should use this
806 algorithm (subject to change in future versions): 1148 algorithm (subject to change in future versions):
807 1149
808 my $to_yaml = JSON::XS->new->utf8->space_after (1); 1150 my $to_yaml = JSON::XS->new->utf8->space_after (1);
809 my $yaml = $to_yaml->encode ($ref) . "\n"; 1151 my $yaml = $to_yaml->encode ($ref) . "\n";
810 1152
811 This will usually generate JSON texts that also parse as valid YAML. 1153 This will *usually* generate JSON texts that also parse as valid YAML.
812 Please note that YAML has hardcoded limits on (simple) object key 1154 Please note that YAML has hardcoded limits on (simple) object key
813 lengths that JSON doesn't have, so you should make sure that your hash 1155 lengths that JSON doesn't have and also has different and incompatible
1156 unicode handling, so you should make sure that your hash keys are
814 keys are noticeably shorter than the 1024 characters YAML allows. 1157 noticeably shorter than the 1024 "stream characters" YAML allows and
1158 that you do not have characters with codepoint values outside the
1159 Unicode BMP (basic multilingual page). YAML also does not allow "\/"
1160 sequences in strings (which JSON::XS does not *currently* generate, but
1161 other JSON generators might).
815 1162
816 There might be other incompatibilities that I am not aware of. In 1163 There might be other incompatibilities that I am not aware of (or the
1164 YAML specification has been changed yet again - it does so quite often).
817 general you should not try to generate YAML with a JSON generator or 1165 In general you should not try to generate YAML with a JSON generator or
818 vice versa, or try to parse JSON with a YAML parser or vice versa: 1166 vice versa, or try to parse JSON with a YAML parser or vice versa:
819 chances are high that you will run into severe interoperability 1167 chances are high that you will run into severe interoperability problems
820 problems. 1168 when you least expect it.
1169
1170 (*) I have been pressured multiple times by Brian Ingerson (one of the
1171 authors of the YAML specification) to remove this paragraph, despite
1172 him acknowledging that the actual incompatibilities exist. As I was
1173 personally bitten by this "JSON is YAML" lie, I refused and said I
1174 will continue to educate people about these issues, so others do not
1175 run into the same problem again and again. After this, Brian called
1176 me a (quote)*complete and worthless idiot*(unquote).
1177
1178 In my opinion, instead of pressuring and insulting people who
1179 actually clarify issues with YAML and the wrong statements of some
1180 of its proponents, I would kindly suggest reading the JSON spec
1181 (which is not that difficult or long) and finally make YAML
1182 compatible to it, and educating users about the changes, instead of
1183 spreading lies about the real compatibility for many *years* and
1184 trying to silence people who point out that it isn't true.
821 1185
822 SPEED 1186 SPEED
823 It seems that JSON::XS is surprisingly fast, as shown in the following 1187 It seems that JSON::XS is surprisingly fast, as shown in the following
824 tables. They have been generated with the help of the "eg/bench" program 1188 tables. They have been generated with the help of the "eg/bench" program
825 in the JSON::XS distribution, to make it easy to compare on your own 1189 in the JSON::XS distribution, to make it easy to compare on your own
826 system. 1190 system.
827 1191
828 First comes a comparison between various modules using a very short 1192 First comes a comparison between various modules using a very short
829 single-line JSON string: 1193 single-line JSON string (also available at
1194 <http://dist.schmorp.de/misc/json/short.json>).
830 1195
831 {"method": "handleMessage", "params": ["user1", "we were just talking"], \ 1196 {"method": "handleMessage", "params": ["user1",
832 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} 1197 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1198 true, false]}
833 1199
834 It shows the number of encodes/decodes per second (JSON::XS uses the 1200 It shows the number of encodes/decodes per second (JSON::XS uses the
835 functional interface, while JSON::XS/2 uses the OO interface with 1201 functional interface, while JSON::XS/2 uses the OO interface with
836 pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). 1202 pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
837 Higher is better: 1203 Higher is better:
… …
853 encoding, about three times faster on decoding, and over forty times 1219 encoding, about three times faster on decoding, and over forty times
854 faster than JSON, even with pretty-printing and key sorting. It also 1220 faster than JSON, even with pretty-printing and key sorting. It also
855 compares favourably to Storable for small amounts of data. 1221 compares favourably to Storable for small amounts of data.
856 1222
857 Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1223 Using a longer test string (roughly 18KB, generated from Yahoo! Locals
858 search API (http://nanoref.com/yahooapis/mgPdGg): 1224 search API (<http://dist.schmorp.de/misc/json/long.json>).
859 1225
860 module | encode | decode | 1226 module | encode | decode |
861 -----------|------------|------------| 1227 -----------|------------|------------|
862 JSON 1.x | 55.260 | 34.971 | 1228 JSON 1.x | 55.260 | 34.971 |
863 JSON::DWIW | 825.228 | 1082.513 | 1229 JSON::DWIW | 825.228 | 1082.513 |
… …
900 Third, JSON::XS recurses using the C stack when decoding objects and 1266 Third, JSON::XS recurses using the C stack when decoding objects and
901 arrays. The C stack is a limited resource: for instance, on my amd64 1267 arrays. The C stack is a limited resource: for instance, on my amd64
902 machine with 8MB of stack size I can decode around 180k nested arrays 1268 machine with 8MB of stack size I can decode around 180k nested arrays
903 but only 14k nested JSON objects (due to perl itself recursing deeply on 1269 but only 14k nested JSON objects (due to perl itself recursing deeply on
904 croak to free the temporary). If that is exceeded, the program crashes. 1270 croak to free the temporary). If that is exceeded, the program crashes.
905 to be conservative, the default nesting limit is set to 512. If your 1271 To be conservative, the default nesting limit is set to 512. If your
906 process has a smaller stack, you should adjust this setting accordingly 1272 process has a smaller stack, you should adjust this setting accordingly
907 with the "max_depth" method. 1273 with the "max_depth" method.
908 1274
909 And last but least, something else could bomb you that I forgot to think 1275 Something else could bomb you, too, that I forgot to think of. In that
910 of. In that case, you get to keep the pieces. I am always open for 1276 case, you get to keep the pieces. I am always open for hints, though...
911 hints, though... 1277
1278 Also keep in mind that JSON::XS might leak contents of your Perl data
1279 structures in its error messages, so when you serialise sensitive
1280 information you might want to make sure that exceptions thrown by
1281 JSON::XS will not end up in front of untrusted eyes.
912 1282
913 If you are using JSON::XS to return packets to consumption by JavaScript 1283 If you are using JSON::XS to return packets to consumption by JavaScript
914 scripts in a browser you should have a look at 1284 scripts in a browser you should have a look at
915 <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1285 <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
916 you are vulnerable to some common attack vectors (which really are 1286 you are vulnerable to some common attack vectors (which really are
917 browser design bugs, but it is still you who will have to deal with it, 1287 browser design bugs, but it is still you who will have to deal with it,
918 as major browser developers care only for features, not about doing 1288 as major browser developers care only for features, not about getting
919 security right). 1289 security right).
920 1290
921THREADS 1291THREADS
922 This module is *not* guaranteed to be thread safe and there are no plans 1292 This module is *not* guaranteed to be thread safe and there are no plans
923 to change this until Perl gets thread support (as opposed to the 1293 to change this until Perl gets thread support (as opposed to the
924 horribly slow so-called "threads" which are simply slow and bloated 1294 horribly slow so-called "threads" which are simply slow and bloated
925 process simulations - use fork, its *much* faster, cheaper, better). 1295 process simulations - use fork, it's *much* faster, cheaper, better).
926 1296
927 (It might actually work, but you have been warned). 1297 (It might actually work, but you have been warned).
928 1298
929BUGS 1299BUGS
930 While the goal of this module is to be correct, that unfortunately does 1300 While the goal of this module is to be correct, that unfortunately does
931 not mean its bug-free, only that I think its design is bug-free. It is 1301 not mean it's bug-free, only that I think its design is bug-free. If you
932 still relatively early in its development. If you keep reporting bugs
933 they will be fixed swiftly, though. 1302 keep reporting bugs they will be fixed swiftly, though.
934 1303
935 Please refrain from using rt.cpan.org or any other bug reporting 1304 Please refrain from using rt.cpan.org or any other bug reporting
936 service. I put the contact address into my modules for a reason. 1305 service. I put the contact address into my modules for a reason.
1306
1307SEE ALSO
1308 The json_xs command line utility for quick experiments.
937 1309
938AUTHOR 1310AUTHOR
939 Marc Lehmann <schmorp@schmorp.de> 1311 Marc Lehmann <schmorp@schmorp.de>
940 http://home.schmorp.de/ 1312 http://home.schmorp.de/
941 1313

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