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Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs.
Revision 1.68 by root, Tue Oct 23 03:30:02 2007 UTC

1=head1 NAME 1=head1 NAME
2 2
3JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
4
5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4 7
5=head1 SYNOPSIS 8=head1 SYNOPSIS
6 9
7 use JSON::XS; 10 use JSON::XS;
8 11
… …
37 40
38=head2 FEATURES 41=head2 FEATURES
39 42
40=over 4 43=over 4
41 44
42=item * correct unicode handling 45=item * correct Unicode handling
43 46
44This module knows how to handle Unicode, and even documents how and when 47This module knows how to handle Unicode, and even documents how and when
45it does so. 48it does so.
46 49
47=item * round-trip integrity 50=item * round-trip integrity
… …
67This module has both a simple functional interface as well as an OO 70This module has both a simple functional interface as well as an OO
68interface. 71interface.
69 72
70=item * reasonably versatile output formats 73=item * reasonably versatile output formats
71 74
72You can choose between the most compact guarenteed single-line format 75You can choose between the most compact guaranteed single-line format
73possible (nice for simple line-based protocols), a pure-ascii format 76possible (nice for simple line-based protocols), a pure-ascii format
74(for when your transport is not 8-bit clean, still supports the whole 77(for when your transport is not 8-bit clean, still supports the whole
75unicode range), or a pretty-printed format (for when you want to read that 78Unicode range), or a pretty-printed format (for when you want to read that
76stuff). Or you can combine those features in whatever way you like. 79stuff). Or you can combine those features in whatever way you like.
77 80
78=back 81=back
79 82
80=cut 83=cut
81 84
82package JSON::XS; 85package JSON::XS;
83 86
84use strict; 87use strict;
85 88
86our $VERSION = '1.4'; 89our $VERSION = '1.52';
87our @ISA = qw(Exporter); 90our @ISA = qw(Exporter);
88 91
89our @EXPORT = qw(to_json from_json); 92our @EXPORT = qw(to_json from_json);
90 93
91use Exporter; 94use Exporter;
92use XSLoader; 95use XSLoader;
93 96
94=head1 FUNCTIONAL INTERFACE 97=head1 FUNCTIONAL INTERFACE
95 98
96The following convinience methods are provided by this module. They are 99The following convenience methods are provided by this module. They are
97exported by default: 100exported by default:
98 101
99=over 4 102=over 4
100 103
101=item $json_text = to_json $perl_scalar 104=item $json_text = to_json $perl_scalar
102 105
103Converts the given Perl data structure (a simple scalar or a reference to 106Converts the given Perl data structure to a UTF-8 encoded, binary string
104a hash or array) to a UTF-8 encoded, binary string (that is, the string contains 107(that is, the string contains octets only). Croaks on error.
105octets only). Croaks on error.
106 108
107This function call is functionally identical to: 109This function call is functionally identical to:
108 110
109 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110 112
111except being faster. 113except being faster.
112 114
113=item $perl_scalar = from_json $json_text 115=item $perl_scalar = from_json $json_text
114 116
115The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to 117The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
116parse that as an UTF-8 encoded JSON text, returning the resulting simple 118to parse that as an UTF-8 encoded JSON text, returning the resulting
117scalar or reference. Croaks on error. 119reference. Croaks on error.
118 120
119This function call is functionally identical to: 121This function call is functionally identical to:
120 122
121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 123 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122 124
… …
132Perl. 134Perl.
133 135
134=back 136=back
135 137
136 138
139=head1 A FEW NOTES ON UNICODE AND PERL
140
141Since this often leads to confusion, here are a few very clear words on
142how Unicode works in Perl, modulo bugs.
143
144=over 4
145
146=item 1. Perl strings can store characters with ordinal values > 255.
147
148This enables you to store Unicode characters as single characters in a
149Perl string - very natural.
150
151=item 2. Perl does I<not> associate an encoding with your strings.
152
153Unless you force it to, e.g. when matching it against a regex, or printing
154the scalar to a file, in which case Perl either interprets your string as
155locale-encoded text, octets/binary, or as Unicode, depending on various
156settings. In no case is an encoding stored together with your data, it is
157I<use> that decides encoding, not any magical metadata.
158
159=item 3. The internal utf-8 flag has no meaning with regards to the
160encoding of your string.
161
162Just ignore that flag unless you debug a Perl bug, a module written in
163XS or want to dive into the internals of perl. Otherwise it will only
164confuse you, as, despite the name, it says nothing about how your string
165is encoded. You can have Unicode strings with that flag set, with that
166flag clear, and you can have binary data with that flag set and that flag
167clear. Other possibilities exist, too.
168
169If you didn't know about that flag, just the better, pretend it doesn't
170exist.
171
172=item 4. A "Unicode String" is simply a string where each character can be
173validly interpreted as a Unicode codepoint.
174
175If you have UTF-8 encoded data, it is no longer a Unicode string, but a
176Unicode string encoded in UTF-8, giving you a binary string.
177
178=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
179
180It's a fact. Learn to live with it.
181
182=back
183
184I hope this helps :)
185
186
137=head1 OBJECT-ORIENTED INTERFACE 187=head1 OBJECT-ORIENTED INTERFACE
138 188
139The object oriented interface lets you configure your own encoding or 189The object oriented interface lets you configure your own encoding or
140decoding style, within the limits of supported formats. 190decoding style, within the limits of supported formats.
141 191
… …
154 204
155=item $json = $json->ascii ([$enable]) 205=item $json = $json->ascii ([$enable])
156 206
157If C<$enable> is true (or missing), then the C<encode> method will not 207If C<$enable> is true (or missing), then the C<encode> method will not
158generate characters outside the code range C<0..127> (which is ASCII). Any 208generate characters outside the code range C<0..127> (which is ASCII). Any
159unicode characters outside that range will be escaped using either a 209Unicode characters outside that range will be escaped using either a
160single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 210single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161as per RFC4627. The resulting encoded JSON text can be treated as a native 211as per RFC4627. The resulting encoded JSON text can be treated as a native
162unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 212Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163or any other superset of ASCII. 213or any other superset of ASCII.
164 214
165If C<$enable> is false, then the C<encode> method will not escape Unicode 215If C<$enable> is false, then the C<encode> method will not escape Unicode
166characters unless required by the JSON syntax or other flags. This results 216characters unless required by the JSON syntax or other flags. This results
167in a faster and more compact format. 217in a faster and more compact format.
… …
176=item $json = $json->latin1 ([$enable]) 226=item $json = $json->latin1 ([$enable])
177 227
178If C<$enable> is true (or missing), then the C<encode> method will encode 228If C<$enable> is true (or missing), then the C<encode> method will encode
179the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 229the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180outside the code range C<0..255>. The resulting string can be treated as a 230outside the code range C<0..255>. The resulting string can be treated as a
181latin1-encoded JSON text or a native unicode string. The C<decode> method 231latin1-encoded JSON text or a native Unicode string. The C<decode> method
182will not be affected in any way by this flag, as C<decode> by default 232will not be affected in any way by this flag, as C<decode> by default
183expects unicode, which is a strict superset of latin1. 233expects Unicode, which is a strict superset of latin1.
184 234
185If C<$enable> is false, then the C<encode> method will not escape Unicode 235If C<$enable> is false, then the C<encode> method will not escape Unicode
186characters unless required by the JSON syntax or other flags. 236characters unless required by the JSON syntax or other flags.
187 237
188The main use for this flag is efficiently encoding binary data as JSON 238The main use for this flag is efficiently encoding binary data as JSON
189text, as most octets will not be escaped, resulting in a smaller encoded 239text, as most octets will not be escaped, resulting in a smaller encoded
190size. The disadvantage is that the resulting JSON text is encoded 240size. The disadvantage is that the resulting JSON text is encoded
191in latin1 (and must correctly be treated as such when storing and 241in latin1 (and must correctly be treated as such when storing and
192transfering), a rare encoding for JSON. It is therefore most useful when 242transferring), a rare encoding for JSON. It is therefore most useful when
193you want to store data structures known to contain binary data efficiently 243you want to store data structures known to contain binary data efficiently
194in files or databases, not when talking to other JSON encoders/decoders. 244in files or databases, not when talking to other JSON encoders/decoders.
195 245
196 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 246 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 247 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
… …
205range C<0..255>, they are thus useful for bytewise/binary I/O. In future 255range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206versions, enabling this option might enable autodetection of the UTF-16 256versions, enabling this option might enable autodetection of the UTF-16
207and UTF-32 encoding families, as described in RFC4627. 257and UTF-32 encoding families, as described in RFC4627.
208 258
209If C<$enable> is false, then the C<encode> method will return the JSON 259If C<$enable> is false, then the C<encode> method will return the JSON
210string as a (non-encoded) unicode string, while C<decode> expects thus a 260string as a (non-encoded) Unicode string, while C<decode> expects thus a
211unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 261Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
212to be done yourself, e.g. using the Encode module. 262to be done yourself, e.g. using the Encode module.
213 263
214Example, output UTF-16BE-encoded JSON: 264Example, output UTF-16BE-encoded JSON:
215 265
216 use Encode; 266 use Encode;
… …
240 290
241=item $json = $json->indent ([$enable]) 291=item $json = $json->indent ([$enable])
242 292
243If C<$enable> is true (or missing), then the C<encode> method will use a multiline 293If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244format as output, putting every array member or object/hash key-value pair 294format as output, putting every array member or object/hash key-value pair
245into its own line, identing them properly. 295into its own line, indenting them properly.
246 296
247If C<$enable> is false, no newlines or indenting will be produced, and the 297If C<$enable> is false, no newlines or indenting will be produced, and the
248resulting JSON text is guarenteed not to contain any C<newlines>. 298resulting JSON text is guaranteed not to contain any C<newlines>.
249 299
250This setting has no effect when decoding JSON texts. 300This setting has no effect when decoding JSON texts.
251 301
252=item $json = $json->space_before ([$enable]) 302=item $json = $json->space_before ([$enable])
253 303
… …
278 328
279Example, space_before and indent disabled, space_after enabled: 329Example, space_before and indent disabled, space_after enabled:
280 330
281 {"key": "value"} 331 {"key": "value"}
282 332
333=item $json = $json->relaxed ([$enable])
334
335If C<$enable> is true (or missing), then C<decode> will accept some
336extensions to normal JSON syntax (see below). C<encode> will not be
337affected in anyway. I<Be aware that this option makes you accept invalid
338JSON texts as if they were valid!>. I suggest only to use this option to
339parse application-specific files written by humans (configuration files,
340resource files etc.)
341
342If C<$enable> is false (the default), then C<decode> will only accept
343valid JSON texts.
344
345Currently accepted extensions are:
346
347=over 4
348
349=item * list items can have an end-comma
350
351JSON I<separates> array elements and key-value pairs with commas. This
352can be annoying if you write JSON texts manually and want to be able to
353quickly append elements, so this extension accepts comma at the end of
354such items not just between them:
355
356 [
357 1,
358 2, <- this comma not normally allowed
359 ]
360 {
361 "k1": "v1",
362 "k2": "v2", <- this comma not normally allowed
363 }
364
365=item * shell-style '#'-comments
366
367Whenever JSON allows whitespace, shell-style comments are additionally
368allowed. They are terminated by the first carriage-return or line-feed
369character, after which more white-space and comments are allowed.
370
371 [
372 1, # this comment not allowed in JSON
373 # neither this one...
374 ]
375
376=back
377
283=item $json = $json->canonical ([$enable]) 378=item $json = $json->canonical ([$enable])
284 379
285If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 380If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286by sorting their keys. This is adding a comparatively high overhead. 381by sorting their keys. This is adding a comparatively high overhead.
287 382
… …
289pairs in the order Perl stores them (which will likely change between runs 384pairs in the order Perl stores them (which will likely change between runs
290of the same script). 385of the same script).
291 386
292This option is useful if you want the same data structure to be encoded as 387This option is useful if you want the same data structure to be encoded as
293the same JSON text (given the same overall settings). If it is disabled, 388the same JSON text (given the same overall settings). If it is disabled,
294the same hash migh be encoded differently even if contains the same data, 389the same hash might be encoded differently even if contains the same data,
295as key-value pairs have no inherent ordering in Perl. 390as key-value pairs have no inherent ordering in Perl.
296 391
297This setting has no effect when decoding JSON texts. 392This setting has no effect when decoding JSON texts.
298 393
299=item $json = $json->allow_nonref ([$enable]) 394=item $json = $json->allow_nonref ([$enable])
… …
316 411
317=item $json = $json->allow_blessed ([$enable]) 412=item $json = $json->allow_blessed ([$enable])
318 413
319If C<$enable> is true (or missing), then the C<encode> method will not 414If C<$enable> is true (or missing), then the C<encode> method will not
320barf when it encounters a blessed reference. Instead, the value of the 415barf when it encounters a blessed reference. Instead, the value of the
321B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 416B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322disabled or no C<to_json> method found) or a representation of the 417disabled or no C<to_json> method found) or a representation of the
323object (C<convert_blessed> enabled and C<to_json> method found) is being 418object (C<convert_blessed> enabled and C<to_json> method found) is being
324encoded. Has no effect on C<decode>. 419encoded. Has no effect on C<decode>.
325 420
326If C<$enable> is false (the default), then C<encode> will throw an 421If C<$enable> is false (the default), then C<encode> will throw an
… …
347future, global hooks might get installed that influence C<decode> and are 442future, global hooks might get installed that influence C<decode> and are
348enabled by this setting. 443enabled by this setting.
349 444
350If C<$enable> is false, then the C<allow_blessed> setting will decide what 445If C<$enable> is false, then the C<allow_blessed> setting will decide what
351to do when a blessed object is found. 446to do when a blessed object is found.
447
448=item $json = $json->filter_json_object ([$coderef->($hashref)])
449
450When C<$coderef> is specified, it will be called from C<decode> each
451time it decodes a JSON object. The only argument is a reference to the
452newly-created hash. If the code references returns a single scalar (which
453need not be a reference), this value (i.e. a copy of that scalar to avoid
454aliasing) is inserted into the deserialised data structure. If it returns
455an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
456original deserialised hash will be inserted. This setting can slow down
457decoding considerably.
458
459When C<$coderef> is omitted or undefined, any existing callback will
460be removed and C<decode> will not change the deserialised hash in any
461way.
462
463Example, convert all JSON objects into the integer 5:
464
465 my $js = JSON::XS->new->filter_json_object (sub { 5 });
466 # returns [5]
467 $js->decode ('[{}]')
468 # throw an exception because allow_nonref is not enabled
469 # so a lone 5 is not allowed.
470 $js->decode ('{"a":1, "b":2}');
471
472=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
473
474Works remotely similar to C<filter_json_object>, but is only called for
475JSON objects having a single key named C<$key>.
476
477This C<$coderef> is called before the one specified via
478C<filter_json_object>, if any. It gets passed the single value in the JSON
479object. If it returns a single value, it will be inserted into the data
480structure. If it returns nothing (not even C<undef> but the empty list),
481the callback from C<filter_json_object> will be called next, as if no
482single-key callback were specified.
483
484If C<$coderef> is omitted or undefined, the corresponding callback will be
485disabled. There can only ever be one callback for a given key.
486
487As this callback gets called less often then the C<filter_json_object>
488one, decoding speed will not usually suffer as much. Therefore, single-key
489objects make excellent targets to serialise Perl objects into, especially
490as single-key JSON objects are as close to the type-tagged value concept
491as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
492support this in any way, so you need to make sure your data never looks
493like a serialised Perl hash.
494
495Typical names for the single object key are C<__class_whatever__>, or
496C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
497things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
498with real hashes.
499
500Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
501into the corresponding C<< $WIDGET{<id>} >> object:
502
503 # return whatever is in $WIDGET{5}:
504 JSON::XS
505 ->new
506 ->filter_json_single_key_object (__widget__ => sub {
507 $WIDGET{ $_[0] }
508 })
509 ->decode ('{"__widget__": 5')
510
511 # this can be used with a TO_JSON method in some "widget" class
512 # for serialisation to json:
513 sub WidgetBase::TO_JSON {
514 my ($self) = @_;
515
516 unless ($self->{id}) {
517 $self->{id} = ..get..some..id..;
518 $WIDGET{$self->{id}} = $self;
519 }
520
521 { __widget__ => $self->{id} }
522 }
352 523
353=item $json = $json->shrink ([$enable]) 524=item $json = $json->shrink ([$enable])
354 525
355Perl usually over-allocates memory a bit when allocating space for 526Perl usually over-allocates memory a bit when allocating space for
356strings. This flag optionally resizes strings generated by either 527strings. This flag optionally resizes strings generated by either
… …
452vice versa. These mappings are designed to "do the right thing" in most 623vice versa. These mappings are designed to "do the right thing" in most
453circumstances automatically, preserving round-tripping characteristics 624circumstances automatically, preserving round-tripping characteristics
454(what you put in comes out as something equivalent). 625(what you put in comes out as something equivalent).
455 626
456For the more enlightened: note that in the following descriptions, 627For the more enlightened: note that in the following descriptions,
457lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 628lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
458refers to the abstract Perl language itself. 629refers to the abstract Perl language itself.
459 630
460 631
461=head2 JSON -> PERL 632=head2 JSON -> PERL
462 633
463=over 4 634=over 4
464 635
465=item object 636=item object
466 637
467A JSON object becomes a reference to a hash in Perl. No ordering of object 638A JSON object becomes a reference to a hash in Perl. No ordering of object
468keys is preserved (JSON does not preserver object key ordering itself). 639keys is preserved (JSON does not preserve object key ordering itself).
469 640
470=item array 641=item array
471 642
472A JSON array becomes a reference to an array in Perl. 643A JSON array becomes a reference to an array in Perl.
473 644
… …
477are represented by the same codepoints in the Perl string, so no manual 648are represented by the same codepoints in the Perl string, so no manual
478decoding is necessary. 649decoding is necessary.
479 650
480=item number 651=item number
481 652
482A JSON number becomes either an integer or numeric (floating point) 653A JSON number becomes either an integer, numeric (floating point) or
483scalar in perl, depending on its range and any fractional parts. On the 654string scalar in perl, depending on its range and any fractional parts. On
484Perl level, there is no difference between those as Perl handles all the 655the Perl level, there is no difference between those as Perl handles all
485conversion details, but an integer may take slightly less memory and might 656the conversion details, but an integer may take slightly less memory and
486represent more values exactly than (floating point) numbers. 657might represent more values exactly than (floating point) numbers.
658
659If the number consists of digits only, JSON::XS will try to represent
660it as an integer value. If that fails, it will try to represent it as
661a numeric (floating point) value if that is possible without loss of
662precision. Otherwise it will preserve the number as a string value.
663
664Numbers containing a fractional or exponential part will always be
665represented as numeric (floating point) values, possibly at a loss of
666precision.
667
668This might create round-tripping problems as numbers might become strings,
669but as Perl is typeless there is no other way to do it.
487 670
488=item true, false 671=item true, false
489 672
490These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 673These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
491respectively. They are overloaded to act almost exactly like the numbers 674respectively. They are overloaded to act almost exactly like the numbers
492C<1> and C<0>. You can check wether a scalar is a JSON boolean by using 675C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
493the C<JSON::XS::is_bool> function. 676the C<JSON::XS::is_bool> function.
494 677
495=item null 678=item null
496 679
497A JSON null atom becomes C<undef> in Perl. 680A JSON null atom becomes C<undef> in Perl.
… …
533 to_json [\0,JSON::XS::true] # yields [false,true] 716 to_json [\0,JSON::XS::true] # yields [false,true]
534 717
535=item JSON::XS::true, JSON::XS::false 718=item JSON::XS::true, JSON::XS::false
536 719
537These special values become JSON true and JSON false values, 720These special values become JSON true and JSON false values,
538respectively. You cna alos use C<\1> and C<\0> directly if you want. 721respectively. You can also use C<\1> and C<\0> directly if you want.
539 722
540=item blessed objects 723=item blessed objects
541 724
542Blessed objects are not allowed. JSON::XS currently tries to encode their 725Blessed objects are not allowed. JSON::XS currently tries to encode their
543underlying representation (hash- or arrayref), but this behaviour might 726underlying representation (hash- or arrayref), but this behaviour might
… …
560 to_json [$value] # yields ["5"] 743 to_json [$value] # yields ["5"]
561 744
562 # undef becomes null 745 # undef becomes null
563 to_json [undef] # yields [null] 746 to_json [undef] # yields [null]
564 747
565You can force the type to be a string by stringifying it: 748You can force the type to be a JSON string by stringifying it:
566 749
567 my $x = 3.1; # some variable containing a number 750 my $x = 3.1; # some variable containing a number
568 "$x"; # stringified 751 "$x"; # stringified
569 $x .= ""; # another, more awkward way to stringify 752 $x .= ""; # another, more awkward way to stringify
570 print $x; # perl does it for you, too, quite often 753 print $x; # perl does it for you, too, quite often
571 754
572You can force the type to be a number by numifying it: 755You can force the type to be a JSON number by numifying it:
573 756
574 my $x = "3"; # some variable containing a string 757 my $x = "3"; # some variable containing a string
575 $x += 0; # numify it, ensuring it will be dumped as a number 758 $x += 0; # numify it, ensuring it will be dumped as a number
576 $x *= 1; # same thing, the choise is yours. 759 $x *= 1; # same thing, the choice is yours.
577 760
578You can not currently output JSON booleans or force the type in other, 761You can not currently force the type in other, less obscure, ways. Tell me
579less obscure, ways. Tell me if you need this capability. 762if you need this capability.
580 763
581=back 764=back
582 765
583 766
584=head1 COMPARISON 767=head1 COMPARISON
… …
593 776
594=item JSON 1.07 777=item JSON 1.07
595 778
596Slow (but very portable, as it is written in pure Perl). 779Slow (but very portable, as it is written in pure Perl).
597 780
598Undocumented/buggy Unicode handling (how JSON handles unicode values is 781Undocumented/buggy Unicode handling (how JSON handles Unicode values is
599undocumented. One can get far by feeding it unicode strings and doing 782undocumented. One can get far by feeding it Unicode strings and doing
600en-/decoding oneself, but unicode escapes are not working properly). 783en-/decoding oneself, but Unicode escapes are not working properly).
601 784
602No roundtripping (strings get clobbered if they look like numbers, e.g. 785No roundtripping (strings get clobbered if they look like numbers, e.g.
603the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 786the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
604decode into the number 2. 787decode into the number 2.
605 788
… …
627Very inflexible (no human-readable format supported, format pretty much 810Very inflexible (no human-readable format supported, format pretty much
628undocumented. I need at least a format for easy reading by humans and a 811undocumented. I need at least a format for easy reading by humans and a
629single-line compact format for use in a protocol, and preferably a way to 812single-line compact format for use in a protocol, and preferably a way to
630generate ASCII-only JSON texts). 813generate ASCII-only JSON texts).
631 814
632Completely broken (and confusingly documented) Unicode handling (unicode 815Completely broken (and confusingly documented) Unicode handling (Unicode
633escapes are not working properly, you need to set ImplicitUnicode to 816escapes are not working properly, you need to set ImplicitUnicode to
634I<different> values on en- and decoding to get symmetric behaviour). 817I<different> values on en- and decoding to get symmetric behaviour).
635 818
636No roundtripping (simple cases work, but this depends on wether the scalar 819No roundtripping (simple cases work, but this depends on whether the scalar
637value was used in a numeric context or not). 820value was used in a numeric context or not).
638 821
639Dumping hashes may skip hash values depending on iterator state. 822Dumping hashes may skip hash values depending on iterator state.
640 823
641Unmaintained (maintainer unresponsive for many months, bugs are not 824Unmaintained (maintainer unresponsive for many months, bugs are not
642getting fixed). 825getting fixed).
643 826
644Does not check input for validity (i.e. will accept non-JSON input and 827Does not check input for validity (i.e. will accept non-JSON input and
645return "something" instead of raising an exception. This is a security 828return "something" instead of raising an exception. This is a security
646issue: imagine two banks transfering money between each other using 829issue: imagine two banks transferring money between each other using
647JSON. One bank might parse a given non-JSON request and deduct money, 830JSON. One bank might parse a given non-JSON request and deduct money,
648while the other might reject the transaction with a syntax error. While a 831while the other might reject the transaction with a syntax error. While a
649good protocol will at least recover, that is extra unnecessary work and 832good protocol will at least recover, that is extra unnecessary work and
650the transaction will still not succeed). 833the transaction will still not succeed).
651 834
652=item JSON::DWIW 0.04 835=item JSON::DWIW 0.04
653 836
654Very fast. Very natural. Very nice. 837Very fast. Very natural. Very nice.
655 838
656Undocumented unicode handling (but the best of the pack. Unicode escapes 839Undocumented Unicode handling (but the best of the pack. Unicode escapes
657still don't get parsed properly). 840still don't get parsed properly).
658 841
659Very inflexible. 842Very inflexible.
660 843
661No roundtripping. 844No roundtripping.
… …
681 my $yaml = $to_yaml->encode ($ref) . "\n"; 864 my $yaml = $to_yaml->encode ($ref) . "\n";
682 865
683This will usually generate JSON texts that also parse as valid 866This will usually generate JSON texts that also parse as valid
684YAML. Please note that YAML has hardcoded limits on (simple) object key 867YAML. Please note that YAML has hardcoded limits on (simple) object key
685lengths that JSON doesn't have, so you should make sure that your hash 868lengths that JSON doesn't have, so you should make sure that your hash
686keys are noticably shorter than the 1024 characters YAML allows. 869keys are noticeably shorter than the 1024 characters YAML allows.
687 870
688There might be other incompatibilities that I am not aware of. In general 871There might be other incompatibilities that I am not aware of. In general
689you should not try to generate YAML with a JSON generator or vice versa, 872you should not try to generate YAML with a JSON generator or vice versa,
690or try to parse JSON with a YAML parser or vice versa: chances are high 873or try to parse JSON with a YAML parser or vice versa: chances are high
691that you will run into severe interoperability problems. 874that you will run into severe interoperability problems.
… …
723 JSON::XS/3 | 338250.323 | 218453.333 | 906 JSON::XS/3 | 338250.323 | 218453.333 |
724 Storable | 16500.016 | 135300.129 | 907 Storable | 16500.016 | 135300.129 |
725 -----------+------------+------------+ 908 -----------+------------+------------+
726 909
727That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 910That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
728about three times faster on decoding, and over fourty times faster 911about three times faster on decoding, and over forty times faster
729than JSON, even with pretty-printing and key sorting. It also compares 912than JSON, even with pretty-printing and key sorting. It also compares
730favourably to Storable for small amounts of data. 913favourably to Storable for small amounts of data.
731 914
732Using a longer test string (roughly 18KB, generated from Yahoo! Locals 915Using a longer test string (roughly 18KB, generated from Yahoo! Locals
733search API (http://nanoref.com/yahooapis/mgPdGg): 916search API (http://nanoref.com/yahooapis/mgPdGg):
… …
746 -----------+------------+------------+ 929 -----------+------------+------------+
747 930
748Again, JSON::XS leads by far (except for Storable which non-surprisingly 931Again, JSON::XS leads by far (except for Storable which non-surprisingly
749decodes faster). 932decodes faster).
750 933
751On large strings containing lots of high unicode characters, some modules 934On large strings containing lots of high Unicode characters, some modules
752(such as JSON::PC) seem to decode faster than JSON::XS, but the result 935(such as JSON::PC) seem to decode faster than JSON::XS, but the result
753will be broken due to missing (or wrong) unicode handling. Others refuse 936will be broken due to missing (or wrong) Unicode handling. Others refuse
754to decode or encode properly, so it was impossible to prepare a fair 937to decode or encode properly, so it was impossible to prepare a fair
755comparison table for that case. 938comparison table for that case.
756 939
757 940
758=head1 SECURITY CONSIDERATIONS 941=head1 SECURITY CONSIDERATIONS
… …
764any buffer overflows. Obviously, this module should ensure that and I am 947any buffer overflows. Obviously, this module should ensure that and I am
765trying hard on making that true, but you never know. 948trying hard on making that true, but you never know.
766 949
767Second, you need to avoid resource-starving attacks. That means you should 950Second, you need to avoid resource-starving attacks. That means you should
768limit the size of JSON texts you accept, or make sure then when your 951limit the size of JSON texts you accept, or make sure then when your
769resources run out, thats just fine (e.g. by using a separate process that 952resources run out, that's just fine (e.g. by using a separate process that
770can crash safely). The size of a JSON text in octets or characters is 953can crash safely). The size of a JSON text in octets or characters is
771usually a good indication of the size of the resources required to decode 954usually a good indication of the size of the resources required to decode
772it into a Perl structure. While JSON::XS can check the size of the JSON 955it into a Perl structure. While JSON::XS can check the size of the JSON
773text, it might be too late when you already have it in memory, so you 956text, it might be too late when you already have it in memory, so you
774might want to check the size before you accept the string. 957might want to check the size before you accept the string.
… …
785And last but least, something else could bomb you that I forgot to think 968And last but least, something else could bomb you that I forgot to think
786of. In that case, you get to keep the pieces. I am always open for hints, 969of. In that case, you get to keep the pieces. I am always open for hints,
787though... 970though...
788 971
789If you are using JSON::XS to return packets to consumption 972If you are using JSON::XS to return packets to consumption
790by javascript scripts in a browser you should have a look at 973by JavaScript scripts in a browser you should have a look at
791L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 974L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792you are vulnerable to some common attack vectors (which really are browser 975you are vulnerable to some common attack vectors (which really are browser
793design bugs, but it is still you who will have to deal with it, as major 976design bugs, but it is still you who will have to deal with it, as major
794browser developers care only for features, not about doing security 977browser developers care only for features, not about doing security
795right). 978right).
796 979
797 980
981=head1 THREADS
982
983This module is I<not> guaranteed to be thread safe and there are no
984plans to change this until Perl gets thread support (as opposed to the
985horribly slow so-called "threads" which are simply slow and bloated
986process simulations - use fork, its I<much> faster, cheaper, better).
987
988(It might actually work, but you have been warned).
989
990
798=head1 BUGS 991=head1 BUGS
799 992
800While the goal of this module is to be correct, that unfortunately does 993While the goal of this module is to be correct, that unfortunately does
801not mean its bug-free, only that I think its design is bug-free. It is 994not mean its bug-free, only that I think its design is bug-free. It is
802still relatively early in its development. If you keep reporting bugs they 995still relatively early in its development. If you keep reporting bugs they
803will be fixed swiftly, though. 996will be fixed swiftly, though.
997
998Please refrain from using rt.cpan.org or any other bug reporting
999service. I put the contact address into my modules for a reason.
804 1000
805=cut 1001=cut
806 1002
807our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1003our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1004our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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