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Revision 1.43 by root, Sat Jun 23 23:49:29 2007 UTC vs.
Revision 1.77 by root, Tue Dec 4 10:37:42 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
9 # exported functions, they croak on error 12 # exported functions, they croak on error
10 # and expect/generate UTF-8 13 # and expect/generate UTF-8
11 14
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
14
15 # objToJson and jsonToObj aliases to to_json and from_json
16 # are exported for compatibility to the JSON module,
17 # but should not be used in new code.
18 17
19 # OO-interface 18 # OO-interface
20 19
21 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
22 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
23 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
24 23
24 # Note that JSON version 2.0 and above will automatically use JSON::XS
25 # if available, at virtually no speed overhead either, so you should
26 # be able to just:
27
28 use JSON;
29
30 # and do the same things, except that you have a pure-perl fallback now.
31
25=head1 DESCRIPTION 32=head1 DESCRIPTION
26 33
27This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
28primary goal is to be I<correct> and its secondary goal is to be 35primary goal is to be I<correct> and its secondary goal is to be
29I<fast>. To reach the latter goal it was written in C. 36I<fast>. To reach the latter goal it was written in C.
37
38Beginning with version 2.0 of the JSON module, when both JSON and
39JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40overriden) with no overhead due to emulation (by inheritign constructor
41and methods). If JSON::XS is not available, it will fall back to the
42compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43gives you a portable JSON API that can be fast when you need and doesn't
44require a C compiler when that is a problem.
30 45
31As this is the n-th-something JSON module on CPAN, what was the reason 46As this is the n-th-something JSON module on CPAN, what was the reason
32to write yet another JSON module? While it seems there are many JSON 47to write yet another JSON module? While it seems there are many JSON
33modules, none of them correctly handle all corner cases, and in most cases 48modules, none of them correctly handle all corner cases, and in most cases
34their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
… …
41 56
42=head2 FEATURES 57=head2 FEATURES
43 58
44=over 4 59=over 4
45 60
46=item * correct unicode handling 61=item * correct Unicode handling
47 62
48This module knows how to handle Unicode, and even documents how and when 63This module knows how to handle Unicode, and even documents how and when
49it does so. 64it does so.
50 65
51=item * round-trip integrity 66=item * round-trip integrity
… …
71This module has both a simple functional interface as well as an OO 86This module has both a simple functional interface as well as an OO
72interface. 87interface.
73 88
74=item * reasonably versatile output formats 89=item * reasonably versatile output formats
75 90
76You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
77possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
78(for when your transport is not 8-bit clean, still supports the whole 93(for when your transport is not 8-bit clean, still supports the whole
79unicode range), or a pretty-printed format (for when you want to read that 94Unicode range), or a pretty-printed format (for when you want to read that
80stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
81 96
82=back 97=back
83 98
84=cut 99=cut
85 100
86package JSON::XS; 101package JSON::XS;
87 102
88use strict; 103use strict;
89 104
90our $VERSION = '1.3'; 105our $VERSION = '2.0';
91our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
92 107
93our @EXPORT = qw(to_json from_json objToJson jsonToObj); 108our @EXPORT = qw(to_json from_json);
94 109
95use Exporter; 110use Exporter;
96use XSLoader; 111use XSLoader;
97 112
98=head1 FUNCTIONAL INTERFACE 113=head1 FUNCTIONAL INTERFACE
99 114
100The following convinience methods are provided by this module. They are 115The following convenience methods are provided by this module. They are
101exported by default: 116exported by default:
102 117
103=over 4 118=over 4
104 119
105=item $json_text = to_json $perl_scalar 120=item $json_text = to_json $perl_scalar
106 121
107Converts the given Perl data structure (a simple scalar or a reference to 122Converts the given Perl data structure to a UTF-8 encoded, binary string
108a hash or array) to a UTF-8 encoded, binary string (that is, the string contains 123(that is, the string contains octets only). Croaks on error.
109octets only). Croaks on error.
110 124
111This function call is functionally identical to: 125This function call is functionally identical to:
112 126
113 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 127 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114 128
115except being faster. 129except being faster.
116 130
117=item $perl_scalar = from_json $json_text 131=item $perl_scalar = from_json $json_text
118 132
119The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to 133The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
120parse that as an UTF-8 encoded JSON text, returning the resulting simple 134to parse that as an UTF-8 encoded JSON text, returning the resulting
121scalar or reference. Croaks on error. 135reference. Croaks on error.
122 136
123This function call is functionally identical to: 137This function call is functionally identical to:
124 138
125 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 139 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
126 140
… …
136Perl. 150Perl.
137 151
138=back 152=back
139 153
140 154
155=head1 A FEW NOTES ON UNICODE AND PERL
156
157Since this often leads to confusion, here are a few very clear words on
158how Unicode works in Perl, modulo bugs.
159
160=over 4
161
162=item 1. Perl strings can store characters with ordinal values > 255.
163
164This enables you to store Unicode characters as single characters in a
165Perl string - very natural.
166
167=item 2. Perl does I<not> associate an encoding with your strings.
168
169Unless you force it to, e.g. when matching it against a regex, or printing
170the scalar to a file, in which case Perl either interprets your string as
171locale-encoded text, octets/binary, or as Unicode, depending on various
172settings. In no case is an encoding stored together with your data, it is
173I<use> that decides encoding, not any magical metadata.
174
175=item 3. The internal utf-8 flag has no meaning with regards to the
176encoding of your string.
177
178Just ignore that flag unless you debug a Perl bug, a module written in
179XS or want to dive into the internals of perl. Otherwise it will only
180confuse you, as, despite the name, it says nothing about how your string
181is encoded. You can have Unicode strings with that flag set, with that
182flag clear, and you can have binary data with that flag set and that flag
183clear. Other possibilities exist, too.
184
185If you didn't know about that flag, just the better, pretend it doesn't
186exist.
187
188=item 4. A "Unicode String" is simply a string where each character can be
189validly interpreted as a Unicode codepoint.
190
191If you have UTF-8 encoded data, it is no longer a Unicode string, but a
192Unicode string encoded in UTF-8, giving you a binary string.
193
194=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
195
196It's a fact. Learn to live with it.
197
198=back
199
200I hope this helps :)
201
202
141=head1 OBJECT-ORIENTED INTERFACE 203=head1 OBJECT-ORIENTED INTERFACE
142 204
143The object oriented interface lets you configure your own encoding or 205The object oriented interface lets you configure your own encoding or
144decoding style, within the limits of supported formats. 206decoding style, within the limits of supported formats.
145 207
… …
156 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 218 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
157 => {"a": [1, 2]} 219 => {"a": [1, 2]}
158 220
159=item $json = $json->ascii ([$enable]) 221=item $json = $json->ascii ([$enable])
160 222
223=item $enabled = $json->get_ascii
224
161If C<$enable> is true (or missing), then the C<encode> method will not 225If C<$enable> is true (or missing), then the C<encode> method will not
162generate characters outside the code range C<0..127> (which is ASCII). Any 226generate characters outside the code range C<0..127> (which is ASCII). Any
163unicode characters outside that range will be escaped using either a 227Unicode characters outside that range will be escaped using either a
164single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 228single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
165as per RFC4627. The resulting encoded JSON text can be treated as a native 229as per RFC4627. The resulting encoded JSON text can be treated as a native
166unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 230Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
167or any other superset of ASCII. 231or any other superset of ASCII.
168 232
169If C<$enable> is false, then the C<encode> method will not escape Unicode 233If C<$enable> is false, then the C<encode> method will not escape Unicode
170characters unless required by the JSON syntax or other flags. This results 234characters unless required by the JSON syntax or other flags. This results
171in a faster and more compact format. 235in a faster and more compact format.
… …
177 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 241 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178 => ["\ud801\udc01"] 242 => ["\ud801\udc01"]
179 243
180=item $json = $json->latin1 ([$enable]) 244=item $json = $json->latin1 ([$enable])
181 245
246=item $enabled = $json->get_latin1
247
182If C<$enable> is true (or missing), then the C<encode> method will encode 248If C<$enable> is true (or missing), then the C<encode> method will encode
183the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 249the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
184outside the code range C<0..255>. The resulting string can be treated as a 250outside the code range C<0..255>. The resulting string can be treated as a
185latin1-encoded JSON text or a native unicode string. The C<decode> method 251latin1-encoded JSON text or a native Unicode string. The C<decode> method
186will not be affected in any way by this flag, as C<decode> by default 252will not be affected in any way by this flag, as C<decode> by default
187expects unicode, which is a strict superset of latin1. 253expects Unicode, which is a strict superset of latin1.
188 254
189If C<$enable> is false, then the C<encode> method will not escape Unicode 255If C<$enable> is false, then the C<encode> method will not escape Unicode
190characters unless required by the JSON syntax or other flags. 256characters unless required by the JSON syntax or other flags.
191 257
192The main use for this flag is efficiently encoding binary data as JSON 258The main use for this flag is efficiently encoding binary data as JSON
193text, as most octets will not be escaped, resulting in a smaller encoded 259text, as most octets will not be escaped, resulting in a smaller encoded
194size. The disadvantage is that the resulting JSON text is encoded 260size. The disadvantage is that the resulting JSON text is encoded
195in latin1 (and must correctly be treated as such when storing and 261in latin1 (and must correctly be treated as such when storing and
196transfering), a rare encoding for JSON. It is therefore most useful when 262transferring), a rare encoding for JSON. It is therefore most useful when
197you want to store data structures known to contain binary data efficiently 263you want to store data structures known to contain binary data efficiently
198in files or databases, not when talking to other JSON encoders/decoders. 264in files or databases, not when talking to other JSON encoders/decoders.
199 265
200 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 266 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
201 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 267 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
202 268
203=item $json = $json->utf8 ([$enable]) 269=item $json = $json->utf8 ([$enable])
270
271=item $enabled = $json->get_utf8
204 272
205If C<$enable> is true (or missing), then the C<encode> method will encode 273If C<$enable> is true (or missing), then the C<encode> method will encode
206the JSON result into UTF-8, as required by many protocols, while the 274the JSON result into UTF-8, as required by many protocols, while the
207C<decode> method expects to be handled an UTF-8-encoded string. Please 275C<decode> method expects to be handled an UTF-8-encoded string. Please
208note that UTF-8-encoded strings do not contain any characters outside the 276note that UTF-8-encoded strings do not contain any characters outside the
209range C<0..255>, they are thus useful for bytewise/binary I/O. In future 277range C<0..255>, they are thus useful for bytewise/binary I/O. In future
210versions, enabling this option might enable autodetection of the UTF-16 278versions, enabling this option might enable autodetection of the UTF-16
211and UTF-32 encoding families, as described in RFC4627. 279and UTF-32 encoding families, as described in RFC4627.
212 280
213If C<$enable> is false, then the C<encode> method will return the JSON 281If C<$enable> is false, then the C<encode> method will return the JSON
214string as a (non-encoded) unicode string, while C<decode> expects thus a 282string as a (non-encoded) Unicode string, while C<decode> expects thus a
215unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 283Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
216to be done yourself, e.g. using the Encode module. 284to be done yourself, e.g. using the Encode module.
217 285
218Example, output UTF-16BE-encoded JSON: 286Example, output UTF-16BE-encoded JSON:
219 287
220 use Encode; 288 use Encode;
… …
242 ] 310 ]
243 } 311 }
244 312
245=item $json = $json->indent ([$enable]) 313=item $json = $json->indent ([$enable])
246 314
315=item $enabled = $json->get_indent
316
247If C<$enable> is true (or missing), then the C<encode> method will use a multiline 317If C<$enable> is true (or missing), then the C<encode> method will use a multiline
248format as output, putting every array member or object/hash key-value pair 318format as output, putting every array member or object/hash key-value pair
249into its own line, identing them properly. 319into its own line, indenting them properly.
250 320
251If C<$enable> is false, no newlines or indenting will be produced, and the 321If C<$enable> is false, no newlines or indenting will be produced, and the
252resulting JSON text is guarenteed not to contain any C<newlines>. 322resulting JSON text is guaranteed not to contain any C<newlines>.
253 323
254This setting has no effect when decoding JSON texts. 324This setting has no effect when decoding JSON texts.
255 325
256=item $json = $json->space_before ([$enable]) 326=item $json = $json->space_before ([$enable])
327
328=item $enabled = $json->get_space_before
257 329
258If C<$enable> is true (or missing), then the C<encode> method will add an extra 330If C<$enable> is true (or missing), then the C<encode> method will add an extra
259optional space before the C<:> separating keys from values in JSON objects. 331optional space before the C<:> separating keys from values in JSON objects.
260 332
261If C<$enable> is false, then the C<encode> method will not add any extra 333If C<$enable> is false, then the C<encode> method will not add any extra
… …
267Example, space_before enabled, space_after and indent disabled: 339Example, space_before enabled, space_after and indent disabled:
268 340
269 {"key" :"value"} 341 {"key" :"value"}
270 342
271=item $json = $json->space_after ([$enable]) 343=item $json = $json->space_after ([$enable])
344
345=item $enabled = $json->get_space_after
272 346
273If C<$enable> is true (or missing), then the C<encode> method will add an extra 347If C<$enable> is true (or missing), then the C<encode> method will add an extra
274optional space after the C<:> separating keys from values in JSON objects 348optional space after the C<:> separating keys from values in JSON objects
275and extra whitespace after the C<,> separating key-value pairs and array 349and extra whitespace after the C<,> separating key-value pairs and array
276members. 350members.
… …
282 356
283Example, space_before and indent disabled, space_after enabled: 357Example, space_before and indent disabled, space_after enabled:
284 358
285 {"key": "value"} 359 {"key": "value"}
286 360
361=item $json = $json->relaxed ([$enable])
362
363=item $enabled = $json->get_relaxed
364
365If C<$enable> is true (or missing), then C<decode> will accept some
366extensions to normal JSON syntax (see below). C<encode> will not be
367affected in anyway. I<Be aware that this option makes you accept invalid
368JSON texts as if they were valid!>. I suggest only to use this option to
369parse application-specific files written by humans (configuration files,
370resource files etc.)
371
372If C<$enable> is false (the default), then C<decode> will only accept
373valid JSON texts.
374
375Currently accepted extensions are:
376
377=over 4
378
379=item * list items can have an end-comma
380
381JSON I<separates> array elements and key-value pairs with commas. This
382can be annoying if you write JSON texts manually and want to be able to
383quickly append elements, so this extension accepts comma at the end of
384such items not just between them:
385
386 [
387 1,
388 2, <- this comma not normally allowed
389 ]
390 {
391 "k1": "v1",
392 "k2": "v2", <- this comma not normally allowed
393 }
394
395=item * shell-style '#'-comments
396
397Whenever JSON allows whitespace, shell-style comments are additionally
398allowed. They are terminated by the first carriage-return or line-feed
399character, after which more white-space and comments are allowed.
400
401 [
402 1, # this comment not allowed in JSON
403 # neither this one...
404 ]
405
406=back
407
287=item $json = $json->canonical ([$enable]) 408=item $json = $json->canonical ([$enable])
409
410=item $enabled = $json->get_canonical
288 411
289If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 412If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
290by sorting their keys. This is adding a comparatively high overhead. 413by sorting their keys. This is adding a comparatively high overhead.
291 414
292If C<$enable> is false, then the C<encode> method will output key-value 415If C<$enable> is false, then the C<encode> method will output key-value
293pairs in the order Perl stores them (which will likely change between runs 416pairs in the order Perl stores them (which will likely change between runs
294of the same script). 417of the same script).
295 418
296This option is useful if you want the same data structure to be encoded as 419This option is useful if you want the same data structure to be encoded as
297the same JSON text (given the same overall settings). If it is disabled, 420the same JSON text (given the same overall settings). If it is disabled,
298the same hash migh be encoded differently even if contains the same data, 421the same hash might be encoded differently even if contains the same data,
299as key-value pairs have no inherent ordering in Perl. 422as key-value pairs have no inherent ordering in Perl.
300 423
301This setting has no effect when decoding JSON texts. 424This setting has no effect when decoding JSON texts.
302 425
303=item $json = $json->allow_nonref ([$enable]) 426=item $json = $json->allow_nonref ([$enable])
427
428=item $enabled = $json->get_allow_nonref
304 429
305If C<$enable> is true (or missing), then the C<encode> method can convert a 430If C<$enable> is true (or missing), then the C<encode> method can convert a
306non-reference into its corresponding string, number or null JSON value, 431non-reference into its corresponding string, number or null JSON value,
307which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 432which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
308values instead of croaking. 433values instead of croaking.
… …
316resulting in an invalid JSON text: 441resulting in an invalid JSON text:
317 442
318 JSON::XS->new->allow_nonref->encode ("Hello, World!") 443 JSON::XS->new->allow_nonref->encode ("Hello, World!")
319 => "Hello, World!" 444 => "Hello, World!"
320 445
446=item $json = $json->allow_blessed ([$enable])
447
448=item $enabled = $json->get_allow_blessed
449
450If C<$enable> is true (or missing), then the C<encode> method will not
451barf when it encounters a blessed reference. Instead, the value of the
452B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
453disabled or no C<TO_JSON> method found) or a representation of the
454object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
455encoded. Has no effect on C<decode>.
456
457If C<$enable> is false (the default), then C<encode> will throw an
458exception when it encounters a blessed object.
459
460=item $json = $json->convert_blessed ([$enable])
461
462=item $enabled = $json->get_convert_blessed
463
464If C<$enable> is true (or missing), then C<encode>, upon encountering a
465blessed object, will check for the availability of the C<TO_JSON> method
466on the object's class. If found, it will be called in scalar context
467and the resulting scalar will be encoded instead of the object. If no
468C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
469to do.
470
471The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
472returns other blessed objects, those will be handled in the same
473way. C<TO_JSON> must take care of not causing an endless recursion cycle
474(== crash) in this case. The name of C<TO_JSON> was chosen because other
475methods called by the Perl core (== not by the user of the object) are
476usually in upper case letters and to avoid collisions with the C<to_json>
477function.
478
479This setting does not yet influence C<decode> in any way, but in the
480future, global hooks might get installed that influence C<decode> and are
481enabled by this setting.
482
483If C<$enable> is false, then the C<allow_blessed> setting will decide what
484to do when a blessed object is found.
485
486=item $json = $json->filter_json_object ([$coderef->($hashref)])
487
488When C<$coderef> is specified, it will be called from C<decode> each
489time it decodes a JSON object. The only argument is a reference to the
490newly-created hash. If the code references returns a single scalar (which
491need not be a reference), this value (i.e. a copy of that scalar to avoid
492aliasing) is inserted into the deserialised data structure. If it returns
493an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
494original deserialised hash will be inserted. This setting can slow down
495decoding considerably.
496
497When C<$coderef> is omitted or undefined, any existing callback will
498be removed and C<decode> will not change the deserialised hash in any
499way.
500
501Example, convert all JSON objects into the integer 5:
502
503 my $js = JSON::XS->new->filter_json_object (sub { 5 });
504 # returns [5]
505 $js->decode ('[{}]')
506 # throw an exception because allow_nonref is not enabled
507 # so a lone 5 is not allowed.
508 $js->decode ('{"a":1, "b":2}');
509
510=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
511
512Works remotely similar to C<filter_json_object>, but is only called for
513JSON objects having a single key named C<$key>.
514
515This C<$coderef> is called before the one specified via
516C<filter_json_object>, if any. It gets passed the single value in the JSON
517object. If it returns a single value, it will be inserted into the data
518structure. If it returns nothing (not even C<undef> but the empty list),
519the callback from C<filter_json_object> will be called next, as if no
520single-key callback were specified.
521
522If C<$coderef> is omitted or undefined, the corresponding callback will be
523disabled. There can only ever be one callback for a given key.
524
525As this callback gets called less often then the C<filter_json_object>
526one, decoding speed will not usually suffer as much. Therefore, single-key
527objects make excellent targets to serialise Perl objects into, especially
528as single-key JSON objects are as close to the type-tagged value concept
529as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
530support this in any way, so you need to make sure your data never looks
531like a serialised Perl hash.
532
533Typical names for the single object key are C<__class_whatever__>, or
534C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
535things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
536with real hashes.
537
538Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
539into the corresponding C<< $WIDGET{<id>} >> object:
540
541 # return whatever is in $WIDGET{5}:
542 JSON::XS
543 ->new
544 ->filter_json_single_key_object (__widget__ => sub {
545 $WIDGET{ $_[0] }
546 })
547 ->decode ('{"__widget__": 5')
548
549 # this can be used with a TO_JSON method in some "widget" class
550 # for serialisation to json:
551 sub WidgetBase::TO_JSON {
552 my ($self) = @_;
553
554 unless ($self->{id}) {
555 $self->{id} = ..get..some..id..;
556 $WIDGET{$self->{id}} = $self;
557 }
558
559 { __widget__ => $self->{id} }
560 }
561
321=item $json = $json->shrink ([$enable]) 562=item $json = $json->shrink ([$enable])
563
564=item $enabled = $json->get_shrink
322 565
323Perl usually over-allocates memory a bit when allocating space for 566Perl usually over-allocates memory a bit when allocating space for
324strings. This flag optionally resizes strings generated by either 567strings. This flag optionally resizes strings generated by either
325C<encode> or C<decode> to their minimum size possible. This can save 568C<encode> or C<decode> to their minimum size possible. This can save
326memory when your JSON texts are either very very long or you have many 569memory when your JSON texts are either very very long or you have many
… …
344strings that look like integers or floats into integers or floats 587strings that look like integers or floats into integers or floats
345internally (there is no difference on the Perl level), saving space. 588internally (there is no difference on the Perl level), saving space.
346 589
347=item $json = $json->max_depth ([$maximum_nesting_depth]) 590=item $json = $json->max_depth ([$maximum_nesting_depth])
348 591
592=item $max_depth = $json->get_max_depth
593
349Sets the maximum nesting level (default C<512>) accepted while encoding 594Sets the maximum nesting level (default C<512>) accepted while encoding
350or decoding. If the JSON text or Perl data structure has an equal or 595or decoding. If the JSON text or Perl data structure has an equal or
351higher nesting level then this limit, then the encoder and decoder will 596higher nesting level then this limit, then the encoder and decoder will
352stop and croak at that point. 597stop and croak at that point.
353 598
… …
357given character in a string. 602given character in a string.
358 603
359Setting the maximum depth to one disallows any nesting, so that ensures 604Setting the maximum depth to one disallows any nesting, so that ensures
360that the object is only a single hash/object or array. 605that the object is only a single hash/object or array.
361 606
362The argument to C<max_depth> will be rounded up to the next nearest power 607The argument to C<max_depth> will be rounded up to the next highest power
363of two. 608of two. If no argument is given, the highest possible setting will be
609used, which is rarely useful.
610
611See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
612
613=item $json = $json->max_size ([$maximum_string_size])
614
615=item $max_size = $json->get_max_size
616
617Set the maximum length a JSON text may have (in bytes) where decoding is
618being attempted. The default is C<0>, meaning no limit. When C<decode>
619is called on a string longer then this number of characters it will not
620attempt to decode the string but throw an exception. This setting has no
621effect on C<encode> (yet).
622
623The argument to C<max_size> will be rounded up to the next B<highest>
624power of two (so may be more than requested). If no argument is given, the
625limit check will be deactivated (same as when C<0> is specified).
364 626
365See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 627See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
366 628
367=item $json_text = $json->encode ($perl_scalar) 629=item $json_text = $json->encode ($perl_scalar)
368 630
… …
405vice versa. These mappings are designed to "do the right thing" in most 667vice versa. These mappings are designed to "do the right thing" in most
406circumstances automatically, preserving round-tripping characteristics 668circumstances automatically, preserving round-tripping characteristics
407(what you put in comes out as something equivalent). 669(what you put in comes out as something equivalent).
408 670
409For the more enlightened: note that in the following descriptions, 671For the more enlightened: note that in the following descriptions,
410lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 672lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
411refers to the abstract Perl language itself. 673refers to the abstract Perl language itself.
412 674
413 675
414=head2 JSON -> PERL 676=head2 JSON -> PERL
415 677
416=over 4 678=over 4
417 679
418=item object 680=item object
419 681
420A JSON object becomes a reference to a hash in Perl. No ordering of object 682A JSON object becomes a reference to a hash in Perl. No ordering of object
421keys is preserved (JSON does not preserver object key ordering itself). 683keys is preserved (JSON does not preserve object key ordering itself).
422 684
423=item array 685=item array
424 686
425A JSON array becomes a reference to an array in Perl. 687A JSON array becomes a reference to an array in Perl.
426 688
… …
430are represented by the same codepoints in the Perl string, so no manual 692are represented by the same codepoints in the Perl string, so no manual
431decoding is necessary. 693decoding is necessary.
432 694
433=item number 695=item number
434 696
435A JSON number becomes either an integer or numeric (floating point) 697A JSON number becomes either an integer, numeric (floating point) or
436scalar in perl, depending on its range and any fractional parts. On the 698string scalar in perl, depending on its range and any fractional parts. On
437Perl level, there is no difference between those as Perl handles all the 699the Perl level, there is no difference between those as Perl handles all
438conversion details, but an integer may take slightly less memory and might 700the conversion details, but an integer may take slightly less memory and
439represent more values exactly than (floating point) numbers. 701might represent more values exactly than (floating point) numbers.
702
703If the number consists of digits only, JSON::XS will try to represent
704it as an integer value. If that fails, it will try to represent it as
705a numeric (floating point) value if that is possible without loss of
706precision. Otherwise it will preserve the number as a string value.
707
708Numbers containing a fractional or exponential part will always be
709represented as numeric (floating point) values, possibly at a loss of
710precision.
711
712This might create round-tripping problems as numbers might become strings,
713but as Perl is typeless there is no other way to do it.
440 714
441=item true, false 715=item true, false
442 716
443These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 717These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
444respectively. They are overloaded to act almost exactly like the numbers 718respectively. They are overloaded to act almost exactly like the numbers
445C<1> and C<0>. You can check wether a scalar is a JSON boolean by using 719C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
446the C<JSON::XS::is_bool> function. 720the C<JSON::XS::is_bool> function.
447 721
448=item null 722=item null
449 723
450A JSON null atom becomes C<undef> in Perl. 724A JSON null atom becomes C<undef> in Perl.
… …
486 to_json [\0,JSON::XS::true] # yields [false,true] 760 to_json [\0,JSON::XS::true] # yields [false,true]
487 761
488=item JSON::XS::true, JSON::XS::false 762=item JSON::XS::true, JSON::XS::false
489 763
490These special values become JSON true and JSON false values, 764These special values become JSON true and JSON false values,
491respectively. You cna alos use C<\1> and C<\0> directly if you want. 765respectively. You can also use C<\1> and C<\0> directly if you want.
492 766
493=item blessed objects 767=item blessed objects
494 768
495Blessed objects are not allowed. JSON::XS currently tries to encode their 769Blessed objects are not allowed. JSON::XS currently tries to encode their
496underlying representation (hash- or arrayref), but this behaviour might 770underlying representation (hash- or arrayref), but this behaviour might
… …
513 to_json [$value] # yields ["5"] 787 to_json [$value] # yields ["5"]
514 788
515 # undef becomes null 789 # undef becomes null
516 to_json [undef] # yields [null] 790 to_json [undef] # yields [null]
517 791
518You can force the type to be a string by stringifying it: 792You can force the type to be a JSON string by stringifying it:
519 793
520 my $x = 3.1; # some variable containing a number 794 my $x = 3.1; # some variable containing a number
521 "$x"; # stringified 795 "$x"; # stringified
522 $x .= ""; # another, more awkward way to stringify 796 $x .= ""; # another, more awkward way to stringify
523 print $x; # perl does it for you, too, quite often 797 print $x; # perl does it for you, too, quite often
524 798
525You can force the type to be a number by numifying it: 799You can force the type to be a JSON number by numifying it:
526 800
527 my $x = "3"; # some variable containing a string 801 my $x = "3"; # some variable containing a string
528 $x += 0; # numify it, ensuring it will be dumped as a number 802 $x += 0; # numify it, ensuring it will be dumped as a number
529 $x *= 1; # same thing, the choise is yours. 803 $x *= 1; # same thing, the choice is yours.
530 804
531You can not currently output JSON booleans or force the type in other, 805You can not currently force the type in other, less obscure, ways. Tell me
532less obscure, ways. Tell me if you need this capability. 806if you need this capability.
533 807
534=back 808=back
535 809
536 810
537=head1 COMPARISON 811=head1 COMPARISON
… …
546 820
547=item JSON 1.07 821=item JSON 1.07
548 822
549Slow (but very portable, as it is written in pure Perl). 823Slow (but very portable, as it is written in pure Perl).
550 824
551Undocumented/buggy Unicode handling (how JSON handles unicode values is 825Undocumented/buggy Unicode handling (how JSON handles Unicode values is
552undocumented. One can get far by feeding it unicode strings and doing 826undocumented. One can get far by feeding it Unicode strings and doing
553en-/decoding oneself, but unicode escapes are not working properly). 827en-/decoding oneself, but Unicode escapes are not working properly).
554 828
555No roundtripping (strings get clobbered if they look like numbers, e.g. 829No round-tripping (strings get clobbered if they look like numbers, e.g.
556the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 830the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
557decode into the number 2. 831decode into the number 2.
558 832
559=item JSON::PC 0.01 833=item JSON::PC 0.01
560 834
561Very fast. 835Very fast.
562 836
563Undocumented/buggy Unicode handling. 837Undocumented/buggy Unicode handling.
564 838
565No roundtripping. 839No round-tripping.
566 840
567Has problems handling many Perl values (e.g. regex results and other magic 841Has problems handling many Perl values (e.g. regex results and other magic
568values will make it croak). 842values will make it croak).
569 843
570Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 844Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
… …
580Very inflexible (no human-readable format supported, format pretty much 854Very inflexible (no human-readable format supported, format pretty much
581undocumented. I need at least a format for easy reading by humans and a 855undocumented. I need at least a format for easy reading by humans and a
582single-line compact format for use in a protocol, and preferably a way to 856single-line compact format for use in a protocol, and preferably a way to
583generate ASCII-only JSON texts). 857generate ASCII-only JSON texts).
584 858
585Completely broken (and confusingly documented) Unicode handling (unicode 859Completely broken (and confusingly documented) Unicode handling (Unicode
586escapes are not working properly, you need to set ImplicitUnicode to 860escapes are not working properly, you need to set ImplicitUnicode to
587I<different> values on en- and decoding to get symmetric behaviour). 861I<different> values on en- and decoding to get symmetric behaviour).
588 862
589No roundtripping (simple cases work, but this depends on wether the scalar 863No round-tripping (simple cases work, but this depends on whether the scalar
590value was used in a numeric context or not). 864value was used in a numeric context or not).
591 865
592Dumping hashes may skip hash values depending on iterator state. 866Dumping hashes may skip hash values depending on iterator state.
593 867
594Unmaintained (maintainer unresponsive for many months, bugs are not 868Unmaintained (maintainer unresponsive for many months, bugs are not
595getting fixed). 869getting fixed).
596 870
597Does not check input for validity (i.e. will accept non-JSON input and 871Does not check input for validity (i.e. will accept non-JSON input and
598return "something" instead of raising an exception. This is a security 872return "something" instead of raising an exception. This is a security
599issue: imagine two banks transfering money between each other using 873issue: imagine two banks transferring money between each other using
600JSON. One bank might parse a given non-JSON request and deduct money, 874JSON. One bank might parse a given non-JSON request and deduct money,
601while the other might reject the transaction with a syntax error. While a 875while the other might reject the transaction with a syntax error. While a
602good protocol will at least recover, that is extra unnecessary work and 876good protocol will at least recover, that is extra unnecessary work and
603the transaction will still not succeed). 877the transaction will still not succeed).
604 878
605=item JSON::DWIW 0.04 879=item JSON::DWIW 0.04
606 880
607Very fast. Very natural. Very nice. 881Very fast. Very natural. Very nice.
608 882
609Undocumented unicode handling (but the best of the pack. Unicode escapes 883Undocumented Unicode handling (but the best of the pack. Unicode escapes
610still don't get parsed properly). 884still don't get parsed properly).
611 885
612Very inflexible. 886Very inflexible.
613 887
614No roundtripping. 888No round-tripping.
615 889
616Does not generate valid JSON texts (key strings are often unquoted, empty keys 890Does not generate valid JSON texts (key strings are often unquoted, empty keys
617result in nothing being output) 891result in nothing being output)
618 892
619Does not check input for validity. 893Does not check input for validity.
… …
634 my $yaml = $to_yaml->encode ($ref) . "\n"; 908 my $yaml = $to_yaml->encode ($ref) . "\n";
635 909
636This will usually generate JSON texts that also parse as valid 910This will usually generate JSON texts that also parse as valid
637YAML. Please note that YAML has hardcoded limits on (simple) object key 911YAML. Please note that YAML has hardcoded limits on (simple) object key
638lengths that JSON doesn't have, so you should make sure that your hash 912lengths that JSON doesn't have, so you should make sure that your hash
639keys are noticably shorter than the 1024 characters YAML allows. 913keys are noticeably shorter than the 1024 characters YAML allows.
640 914
641There might be other incompatibilities that I am not aware of. In general 915There might be other incompatibilities that I am not aware of. In general
642you should not try to generate YAML with a JSON generator or vice versa, 916you should not try to generate YAML with a JSON generator or vice versa,
643or try to parse JSON with a YAML parser or vice versa: chances are high 917or try to parse JSON with a YAML parser or vice versa: chances are high
644that you will run into severe interoperability problems. 918that you will run into severe interoperability problems.
… …
662with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 936with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
663shrink). Higher is better: 937shrink). Higher is better:
664 938
665 module | encode | decode | 939 module | encode | decode |
666 -----------|------------|------------| 940 -----------|------------|------------|
667 JSON | 7645.468 | 4208.613 | 941 JSON 1.x | 4990.842 | 4088.813 |
668 JSON::DWIW | 40721.398 | 77101.176 | 942 JSON::DWIW | 51653.990 | 71575.154 |
669 JSON::PC | 65948.176 | 78251.940 | 943 JSON::PC | 65948.176 | 74631.744 |
670 JSON::Syck | 22844.793 | 26479.192 | 944 JSON::PP | 8931.652 | 3817.168 |
945 JSON::Syck | 24877.248 | 27776.848 |
671 JSON::XS | 388361.481 | 199728.762 | 946 JSON::XS | 388361.481 | 227951.304 |
672 JSON::XS/2 | 218453.333 | 192399.266 | 947 JSON::XS/2 | 227951.304 | 218453.333 |
673 JSON::XS/3 | 338250.323 | 192399.266 | 948 JSON::XS/3 | 338250.323 | 218453.333 |
674 Storable | 15779.925 | 14169.946 | 949 Storable | 16500.016 | 135300.129 |
675 -----------+------------+------------+ 950 -----------+------------+------------+
676 951
677That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 952That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
678about three times faster on decoding, and over fourty times faster 953about three times faster on decoding, and over forty times faster
679than JSON, even with pretty-printing and key sorting. It also compares 954than JSON, even with pretty-printing and key sorting. It also compares
680favourably to Storable for small amounts of data. 955favourably to Storable for small amounts of data.
681 956
682Using a longer test string (roughly 18KB, generated from Yahoo! Locals 957Using a longer test string (roughly 18KB, generated from Yahoo! Locals
683search API (http://nanoref.com/yahooapis/mgPdGg): 958search API (http://nanoref.com/yahooapis/mgPdGg):
684 959
685 module | encode | decode | 960 module | encode | decode |
686 -----------|------------|------------| 961 -----------|------------|------------|
687 JSON | 254.685 | 37.665 | 962 JSON 1.x | 55.260 | 34.971 |
688 JSON::DWIW | 843.343 | 1049.731 | 963 JSON::DWIW | 825.228 | 1082.513 |
689 JSON::PC | 3602.116 | 2307.352 | 964 JSON::PC | 3571.444 | 2394.829 |
965 JSON::PP | 210.987 | 32.574 |
690 JSON::Syck | 505.107 | 787.899 | 966 JSON::Syck | 552.551 | 787.544 |
691 JSON::XS | 5747.196 | 3690.220 | 967 JSON::XS | 5780.463 | 4854.519 |
692 JSON::XS/2 | 3968.121 | 3676.634 | 968 JSON::XS/2 | 3869.998 | 4798.975 |
693 JSON::XS/3 | 6105.246 | 3662.508 | 969 JSON::XS/3 | 5862.880 | 4798.975 |
694 Storable | 4417.337 | 5285.161 | 970 Storable | 4445.002 | 5235.027 |
695 -----------+------------+------------+ 971 -----------+------------+------------+
696 972
697Again, JSON::XS leads by far (except for Storable which non-surprisingly 973Again, JSON::XS leads by far (except for Storable which non-surprisingly
698decodes faster). 974decodes faster).
699 975
700On large strings containing lots of high unicode characters, some modules 976On large strings containing lots of high Unicode characters, some modules
701(such as JSON::PC) seem to decode faster than JSON::XS, but the result 977(such as JSON::PC) seem to decode faster than JSON::XS, but the result
702will be broken due to missing (or wrong) unicode handling. Others refuse 978will be broken due to missing (or wrong) Unicode handling. Others refuse
703to decode or encode properly, so it was impossible to prepare a fair 979to decode or encode properly, so it was impossible to prepare a fair
704comparison table for that case. 980comparison table for that case.
705 981
706 982
707=head1 SECURITY CONSIDERATIONS 983=head1 SECURITY CONSIDERATIONS
… …
713any buffer overflows. Obviously, this module should ensure that and I am 989any buffer overflows. Obviously, this module should ensure that and I am
714trying hard on making that true, but you never know. 990trying hard on making that true, but you never know.
715 991
716Second, you need to avoid resource-starving attacks. That means you should 992Second, you need to avoid resource-starving attacks. That means you should
717limit the size of JSON texts you accept, or make sure then when your 993limit the size of JSON texts you accept, or make sure then when your
718resources run out, thats just fine (e.g. by using a separate process that 994resources run out, that's just fine (e.g. by using a separate process that
719can crash safely). The size of a JSON text in octets or characters is 995can crash safely). The size of a JSON text in octets or characters is
720usually a good indication of the size of the resources required to decode 996usually a good indication of the size of the resources required to decode
721it into a Perl structure. 997it into a Perl structure. While JSON::XS can check the size of the JSON
998text, it might be too late when you already have it in memory, so you
999might want to check the size before you accept the string.
722 1000
723Third, JSON::XS recurses using the C stack when decoding objects and 1001Third, JSON::XS recurses using the C stack when decoding objects and
724arrays. The C stack is a limited resource: for instance, on my amd64 1002arrays. The C stack is a limited resource: for instance, on my amd64
725machine with 8MB of stack size I can decode around 180k nested arrays but 1003machine with 8MB of stack size I can decode around 180k nested arrays but
726only 14k nested JSON objects (due to perl itself recursing deeply on croak 1004only 14k nested JSON objects (due to perl itself recursing deeply on croak
… …
732And last but least, something else could bomb you that I forgot to think 1010And last but least, something else could bomb you that I forgot to think
733of. In that case, you get to keep the pieces. I am always open for hints, 1011of. In that case, you get to keep the pieces. I am always open for hints,
734though... 1012though...
735 1013
736If you are using JSON::XS to return packets to consumption 1014If you are using JSON::XS to return packets to consumption
737by javascript scripts in a browser you should have a look at 1015by JavaScript scripts in a browser you should have a look at
738L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1016L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
739you are vulnerable to some common attack vectors (which really are browser 1017you are vulnerable to some common attack vectors (which really are browser
740design bugs, but it is still you who will have to deal with it, as major 1018design bugs, but it is still you who will have to deal with it, as major
741browser developers care only for features, not about doing security 1019browser developers care only for features, not about doing security
742right). 1020right).
743 1021
744 1022
1023=head1 THREADS
1024
1025This module is I<not> guaranteed to be thread safe and there are no
1026plans to change this until Perl gets thread support (as opposed to the
1027horribly slow so-called "threads" which are simply slow and bloated
1028process simulations - use fork, its I<much> faster, cheaper, better).
1029
1030(It might actually work, but you have been warned).
1031
1032
745=head1 BUGS 1033=head1 BUGS
746 1034
747While the goal of this module is to be correct, that unfortunately does 1035While the goal of this module is to be correct, that unfortunately does
748not mean its bug-free, only that I think its design is bug-free. It is 1036not mean its bug-free, only that I think its design is bug-free. It is
749still relatively early in its development. If you keep reporting bugs they 1037still relatively early in its development. If you keep reporting bugs they
750will be fixed swiftly, though. 1038will be fixed swiftly, though.
751 1039
1040Please refrain from using rt.cpan.org or any other bug reporting
1041service. I put the contact address into my modules for a reason.
1042
752=cut 1043=cut
753 1044
754our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1045our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
755our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1046our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
756 1047
757sub true() { $true } 1048sub true() { $true }
758sub false() { $false } 1049sub false() { $false }
759 1050
760sub is_bool($) { 1051sub is_bool($) {
761 UNIVERSAL::isa $_[0], "JSON::XS::Boolean" 1052 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
762 or UNIVERSAL::isa $_[0], "JSON::Literal" 1053# or UNIVERSAL::isa $_[0], "JSON::Literal"
763} 1054}
764 1055
765XSLoader::load "JSON::XS", $VERSION; 1056XSLoader::load "JSON::XS", $VERSION;
766 1057
767package JSON::XS::Boolean; 1058package JSON::XS::Boolean;

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