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Revision 1.43 by root, Sat Jun 23 23:49:29 2007 UTC vs.
Revision 1.72 by root, Sun Nov 25 19:11:07 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);
… …
41 40
42=head2 FEATURES 41=head2 FEATURES
43 42
44=over 4 43=over 4
45 44
46=item * correct unicode handling 45=item * correct Unicode handling
47 46
48This 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
49it does so. 48it does so.
50 49
51=item * round-trip integrity 50=item * round-trip integrity
… …
71This 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
72interface. 71interface.
73 72
74=item * reasonably versatile output formats 73=item * reasonably versatile output formats
75 74
76You can choose between the most compact guarenteed single-line format 75You can choose between the most compact guaranteed single-line format
77possible (nice for simple line-based protocols), a pure-ascii format 76possible (nice for simple line-based protocols), a pure-ascii format
78(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
79unicode 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
80stuff). Or you can combine those features in whatever way you like. 79stuff). Or you can combine those features in whatever way you like.
81 80
82=back 81=back
83 82
84=cut 83=cut
85 84
86package JSON::XS; 85package JSON::XS;
87 86
88use strict; 87use strict;
89 88
90our $VERSION = '1.3'; 89our $VERSION = '1.53';
91our @ISA = qw(Exporter); 90our @ISA = qw(Exporter);
92 91
93our @EXPORT = qw(to_json from_json objToJson jsonToObj); 92our @EXPORT = qw(to_json from_json);
94 93
95use Exporter; 94use Exporter;
96use XSLoader; 95use XSLoader;
97 96
98=head1 FUNCTIONAL INTERFACE 97=head1 FUNCTIONAL INTERFACE
99 98
100The following convinience methods are provided by this module. They are 99The following convenience methods are provided by this module. They are
101exported by default: 100exported by default:
102 101
103=over 4 102=over 4
104 103
105=item $json_text = to_json $perl_scalar 104=item $json_text = to_json $perl_scalar
106 105
107Converts 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
108a 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.
109octets only). Croaks on error.
110 108
111This function call is functionally identical to: 109This function call is functionally identical to:
112 110
113 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114 112
115except being faster. 113except being faster.
116 114
117=item $perl_scalar = from_json $json_text 115=item $perl_scalar = from_json $json_text
118 116
119The 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
120parse 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
121scalar or reference. Croaks on error. 119reference. Croaks on error.
122 120
123This function call is functionally identical to: 121This function call is functionally identical to:
124 122
125 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 123 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
126 124
… …
136Perl. 134Perl.
137 135
138=back 136=back
139 137
140 138
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
141=head1 OBJECT-ORIENTED INTERFACE 187=head1 OBJECT-ORIENTED INTERFACE
142 188
143The object oriented interface lets you configure your own encoding or 189The object oriented interface lets you configure your own encoding or
144decoding style, within the limits of supported formats. 190decoding style, within the limits of supported formats.
145 191
… …
156 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 202 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
157 => {"a": [1, 2]} 203 => {"a": [1, 2]}
158 204
159=item $json = $json->ascii ([$enable]) 205=item $json = $json->ascii ([$enable])
160 206
207=item $enabled = $json->get_ascii
208
161If C<$enable> is true (or missing), then the C<encode> method will not 209If C<$enable> is true (or missing), then the C<encode> method will not
162generate characters outside the code range C<0..127> (which is ASCII). Any 210generate characters outside the code range C<0..127> (which is ASCII). Any
163unicode characters outside that range will be escaped using either a 211Unicode characters outside that range will be escaped using either a
164single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 212single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
165as per RFC4627. The resulting encoded JSON text can be treated as a native 213as per RFC4627. The resulting encoded JSON text can be treated as a native
166unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 214Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
167or any other superset of ASCII. 215or any other superset of ASCII.
168 216
169If C<$enable> is false, then the C<encode> method will not escape Unicode 217If 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 218characters unless required by the JSON syntax or other flags. This results
171in a faster and more compact format. 219in a faster and more compact format.
… …
177 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 225 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178 => ["\ud801\udc01"] 226 => ["\ud801\udc01"]
179 227
180=item $json = $json->latin1 ([$enable]) 228=item $json = $json->latin1 ([$enable])
181 229
230=item $enabled = $json->get_latin1
231
182If C<$enable> is true (or missing), then the C<encode> method will encode 232If C<$enable> is true (or missing), then the C<encode> method will encode
183the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 233the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
184outside the code range C<0..255>. The resulting string can be treated as a 234outside the code range C<0..255>. The resulting string can be treated as a
185latin1-encoded JSON text or a native unicode string. The C<decode> method 235latin1-encoded JSON text or a native Unicode string. The C<decode> method
186will not be affected in any way by this flag, as C<decode> by default 236will not be affected in any way by this flag, as C<decode> by default
187expects unicode, which is a strict superset of latin1. 237expects Unicode, which is a strict superset of latin1.
188 238
189If C<$enable> is false, then the C<encode> method will not escape Unicode 239If C<$enable> is false, then the C<encode> method will not escape Unicode
190characters unless required by the JSON syntax or other flags. 240characters unless required by the JSON syntax or other flags.
191 241
192The main use for this flag is efficiently encoding binary data as JSON 242The 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 243text, as most octets will not be escaped, resulting in a smaller encoded
194size. The disadvantage is that the resulting JSON text is encoded 244size. The disadvantage is that the resulting JSON text is encoded
195in latin1 (and must correctly be treated as such when storing and 245in latin1 (and must correctly be treated as such when storing and
196transfering), a rare encoding for JSON. It is therefore most useful when 246transferring), a rare encoding for JSON. It is therefore most useful when
197you want to store data structures known to contain binary data efficiently 247you want to store data structures known to contain binary data efficiently
198in files or databases, not when talking to other JSON encoders/decoders. 248in files or databases, not when talking to other JSON encoders/decoders.
199 249
200 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 250 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
201 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 251 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
202 252
203=item $json = $json->utf8 ([$enable]) 253=item $json = $json->utf8 ([$enable])
254
255=item $enabled = $json->get_utf8
204 256
205If C<$enable> is true (or missing), then the C<encode> method will encode 257If C<$enable> is true (or missing), then the C<encode> method will encode
206the JSON result into UTF-8, as required by many protocols, while the 258the JSON result into UTF-8, as required by many protocols, while the
207C<decode> method expects to be handled an UTF-8-encoded string. Please 259C<decode> method expects to be handled an UTF-8-encoded string. Please
208note that UTF-8-encoded strings do not contain any characters outside the 260note that UTF-8-encoded strings do not contain any characters outside the
209range C<0..255>, they are thus useful for bytewise/binary I/O. In future 261range C<0..255>, they are thus useful for bytewise/binary I/O. In future
210versions, enabling this option might enable autodetection of the UTF-16 262versions, enabling this option might enable autodetection of the UTF-16
211and UTF-32 encoding families, as described in RFC4627. 263and UTF-32 encoding families, as described in RFC4627.
212 264
213If C<$enable> is false, then the C<encode> method will return the JSON 265If 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 266string 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 267Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
216to be done yourself, e.g. using the Encode module. 268to be done yourself, e.g. using the Encode module.
217 269
218Example, output UTF-16BE-encoded JSON: 270Example, output UTF-16BE-encoded JSON:
219 271
220 use Encode; 272 use Encode;
… …
224 276
225 use Encode; 277 use Encode;
226 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); 278 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
227 279
228=item $json = $json->pretty ([$enable]) 280=item $json = $json->pretty ([$enable])
281
282=item $enabled = $json->get_pretty
229 283
230This enables (or disables) all of the C<indent>, C<space_before> and 284This enables (or disables) all of the C<indent>, C<space_before> and
231C<space_after> (and in the future possibly more) flags in one call to 285C<space_after> (and in the future possibly more) flags in one call to
232generate the most readable (or most compact) form possible. 286generate the most readable (or most compact) form possible.
233 287
… …
242 ] 296 ]
243 } 297 }
244 298
245=item $json = $json->indent ([$enable]) 299=item $json = $json->indent ([$enable])
246 300
301=item $enabled = $json->get_indent
302
247If C<$enable> is true (or missing), then the C<encode> method will use a multiline 303If C<$enable> is true (or missing), then the C<encode> method will use a multiline
248format as output, putting every array member or object/hash key-value pair 304format as output, putting every array member or object/hash key-value pair
249into its own line, identing them properly. 305into its own line, indenting them properly.
250 306
251If C<$enable> is false, no newlines or indenting will be produced, and the 307If C<$enable> is false, no newlines or indenting will be produced, and the
252resulting JSON text is guarenteed not to contain any C<newlines>. 308resulting JSON text is guaranteed not to contain any C<newlines>.
253 309
254This setting has no effect when decoding JSON texts. 310This setting has no effect when decoding JSON texts.
255 311
256=item $json = $json->space_before ([$enable]) 312=item $json = $json->space_before ([$enable])
313
314=item $enabled = $json->get_space_before
257 315
258If C<$enable> is true (or missing), then the C<encode> method will add an extra 316If C<$enable> is true (or missing), then the C<encode> method will add an extra
259optional space before the C<:> separating keys from values in JSON objects. 317optional space before the C<:> separating keys from values in JSON objects.
260 318
261If C<$enable> is false, then the C<encode> method will not add any extra 319If C<$enable> is false, then the C<encode> method will not add any extra
… …
267Example, space_before enabled, space_after and indent disabled: 325Example, space_before enabled, space_after and indent disabled:
268 326
269 {"key" :"value"} 327 {"key" :"value"}
270 328
271=item $json = $json->space_after ([$enable]) 329=item $json = $json->space_after ([$enable])
330
331=item $enabled = $json->get_space_after
272 332
273If C<$enable> is true (or missing), then the C<encode> method will add an extra 333If 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 334optional space after the C<:> separating keys from values in JSON objects
275and extra whitespace after the C<,> separating key-value pairs and array 335and extra whitespace after the C<,> separating key-value pairs and array
276members. 336members.
… …
282 342
283Example, space_before and indent disabled, space_after enabled: 343Example, space_before and indent disabled, space_after enabled:
284 344
285 {"key": "value"} 345 {"key": "value"}
286 346
347=item $json = $json->relaxed ([$enable])
348
349=item $enabled = $json->get_relaxed
350
351If C<$enable> is true (or missing), then C<decode> will accept some
352extensions to normal JSON syntax (see below). C<encode> will not be
353affected in anyway. I<Be aware that this option makes you accept invalid
354JSON texts as if they were valid!>. I suggest only to use this option to
355parse application-specific files written by humans (configuration files,
356resource files etc.)
357
358If C<$enable> is false (the default), then C<decode> will only accept
359valid JSON texts.
360
361Currently accepted extensions are:
362
363=over 4
364
365=item * list items can have an end-comma
366
367JSON I<separates> array elements and key-value pairs with commas. This
368can be annoying if you write JSON texts manually and want to be able to
369quickly append elements, so this extension accepts comma at the end of
370such items not just between them:
371
372 [
373 1,
374 2, <- this comma not normally allowed
375 ]
376 {
377 "k1": "v1",
378 "k2": "v2", <- this comma not normally allowed
379 }
380
381=item * shell-style '#'-comments
382
383Whenever JSON allows whitespace, shell-style comments are additionally
384allowed. They are terminated by the first carriage-return or line-feed
385character, after which more white-space and comments are allowed.
386
387 [
388 1, # this comment not allowed in JSON
389 # neither this one...
390 ]
391
392=back
393
287=item $json = $json->canonical ([$enable]) 394=item $json = $json->canonical ([$enable])
395
396=item $enabled = $json->get_canonical
288 397
289If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 398If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
290by sorting their keys. This is adding a comparatively high overhead. 399by sorting their keys. This is adding a comparatively high overhead.
291 400
292If C<$enable> is false, then the C<encode> method will output key-value 401If 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 402pairs in the order Perl stores them (which will likely change between runs
294of the same script). 403of the same script).
295 404
296This option is useful if you want the same data structure to be encoded as 405This 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, 406the 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, 407the same hash might be encoded differently even if contains the same data,
299as key-value pairs have no inherent ordering in Perl. 408as key-value pairs have no inherent ordering in Perl.
300 409
301This setting has no effect when decoding JSON texts. 410This setting has no effect when decoding JSON texts.
302 411
303=item $json = $json->allow_nonref ([$enable]) 412=item $json = $json->allow_nonref ([$enable])
413
414=item $enabled = $json->get_allow_nonref
304 415
305If C<$enable> is true (or missing), then the C<encode> method can convert a 416If 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, 417non-reference into its corresponding string, number or null JSON value,
307which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 418which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
308values instead of croaking. 419values instead of croaking.
… …
316resulting in an invalid JSON text: 427resulting in an invalid JSON text:
317 428
318 JSON::XS->new->allow_nonref->encode ("Hello, World!") 429 JSON::XS->new->allow_nonref->encode ("Hello, World!")
319 => "Hello, World!" 430 => "Hello, World!"
320 431
432=item $json = $json->allow_blessed ([$enable])
433
434=item $enabled = $json->get_allow_bless
435
436If C<$enable> is true (or missing), then the C<encode> method will not
437barf when it encounters a blessed reference. Instead, the value of the
438B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
439disabled or no C<to_json> method found) or a representation of the
440object (C<convert_blessed> enabled and C<to_json> method found) is being
441encoded. Has no effect on C<decode>.
442
443If C<$enable> is false (the default), then C<encode> will throw an
444exception when it encounters a blessed object.
445
446=item $json = $json->convert_blessed ([$enable])
447
448=item $enabled = $json->get_convert_blessed
449
450If C<$enable> is true (or missing), then C<encode>, upon encountering a
451blessed object, will check for the availability of the C<TO_JSON> method
452on the object's class. If found, it will be called in scalar context
453and the resulting scalar will be encoded instead of the object. If no
454C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
455to do.
456
457The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
458returns other blessed objects, those will be handled in the same
459way. C<TO_JSON> must take care of not causing an endless recursion cycle
460(== crash) in this case. The name of C<TO_JSON> was chosen because other
461methods called by the Perl core (== not by the user of the object) are
462usually in upper case letters and to avoid collisions with the C<to_json>
463function.
464
465This setting does not yet influence C<decode> in any way, but in the
466future, global hooks might get installed that influence C<decode> and are
467enabled by this setting.
468
469If C<$enable> is false, then the C<allow_blessed> setting will decide what
470to do when a blessed object is found.
471
472=item $json = $json->filter_json_object ([$coderef->($hashref)])
473
474When C<$coderef> is specified, it will be called from C<decode> each
475time it decodes a JSON object. The only argument is a reference to the
476newly-created hash. If the code references returns a single scalar (which
477need not be a reference), this value (i.e. a copy of that scalar to avoid
478aliasing) is inserted into the deserialised data structure. If it returns
479an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
480original deserialised hash will be inserted. This setting can slow down
481decoding considerably.
482
483When C<$coderef> is omitted or undefined, any existing callback will
484be removed and C<decode> will not change the deserialised hash in any
485way.
486
487Example, convert all JSON objects into the integer 5:
488
489 my $js = JSON::XS->new->filter_json_object (sub { 5 });
490 # returns [5]
491 $js->decode ('[{}]')
492 # throw an exception because allow_nonref is not enabled
493 # so a lone 5 is not allowed.
494 $js->decode ('{"a":1, "b":2}');
495
496=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
497
498Works remotely similar to C<filter_json_object>, but is only called for
499JSON objects having a single key named C<$key>.
500
501This C<$coderef> is called before the one specified via
502C<filter_json_object>, if any. It gets passed the single value in the JSON
503object. If it returns a single value, it will be inserted into the data
504structure. If it returns nothing (not even C<undef> but the empty list),
505the callback from C<filter_json_object> will be called next, as if no
506single-key callback were specified.
507
508If C<$coderef> is omitted or undefined, the corresponding callback will be
509disabled. There can only ever be one callback for a given key.
510
511As this callback gets called less often then the C<filter_json_object>
512one, decoding speed will not usually suffer as much. Therefore, single-key
513objects make excellent targets to serialise Perl objects into, especially
514as single-key JSON objects are as close to the type-tagged value concept
515as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
516support this in any way, so you need to make sure your data never looks
517like a serialised Perl hash.
518
519Typical names for the single object key are C<__class_whatever__>, or
520C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
521things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
522with real hashes.
523
524Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
525into the corresponding C<< $WIDGET{<id>} >> object:
526
527 # return whatever is in $WIDGET{5}:
528 JSON::XS
529 ->new
530 ->filter_json_single_key_object (__widget__ => sub {
531 $WIDGET{ $_[0] }
532 })
533 ->decode ('{"__widget__": 5')
534
535 # this can be used with a TO_JSON method in some "widget" class
536 # for serialisation to json:
537 sub WidgetBase::TO_JSON {
538 my ($self) = @_;
539
540 unless ($self->{id}) {
541 $self->{id} = ..get..some..id..;
542 $WIDGET{$self->{id}} = $self;
543 }
544
545 { __widget__ => $self->{id} }
546 }
547
321=item $json = $json->shrink ([$enable]) 548=item $json = $json->shrink ([$enable])
549
550=item $enabled = $json->get_shrink
322 551
323Perl usually over-allocates memory a bit when allocating space for 552Perl usually over-allocates memory a bit when allocating space for
324strings. This flag optionally resizes strings generated by either 553strings. This flag optionally resizes strings generated by either
325C<encode> or C<decode> to their minimum size possible. This can save 554C<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 555memory when your JSON texts are either very very long or you have many
… …
344strings that look like integers or floats into integers or floats 573strings that look like integers or floats into integers or floats
345internally (there is no difference on the Perl level), saving space. 574internally (there is no difference on the Perl level), saving space.
346 575
347=item $json = $json->max_depth ([$maximum_nesting_depth]) 576=item $json = $json->max_depth ([$maximum_nesting_depth])
348 577
578=item $max_depth = $json->get_max_depth
579
349Sets the maximum nesting level (default C<512>) accepted while encoding 580Sets the maximum nesting level (default C<512>) accepted while encoding
350or decoding. If the JSON text or Perl data structure has an equal or 581or 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 582higher nesting level then this limit, then the encoder and decoder will
352stop and croak at that point. 583stop and croak at that point.
353 584
… …
357given character in a string. 588given character in a string.
358 589
359Setting the maximum depth to one disallows any nesting, so that ensures 590Setting the maximum depth to one disallows any nesting, so that ensures
360that the object is only a single hash/object or array. 591that the object is only a single hash/object or array.
361 592
362The argument to C<max_depth> will be rounded up to the next nearest power 593The argument to C<max_depth> will be rounded up to the next highest power
363of two. 594of two. If no argument is given, the highest possible setting will be
595used, which is rarely useful.
596
597See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
598
599=item $json = $json->max_size ([$maximum_string_size])
600
601=item $max_size = $json->get_max_size
602
603Set the maximum length a JSON text may have (in bytes) where decoding is
604being attempted. The default is C<0>, meaning no limit. When C<decode>
605is called on a string longer then this number of characters it will not
606attempt to decode the string but throw an exception. This setting has no
607effect on C<encode> (yet).
608
609The argument to C<max_size> will be rounded up to the next B<highest>
610power of two (so may be more than requested). If no argument is given, the
611limit check will be deactivated (same as when C<0> is specified).
364 612
365See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 613See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
366 614
367=item $json_text = $json->encode ($perl_scalar) 615=item $json_text = $json->encode ($perl_scalar)
368 616
… …
405vice versa. These mappings are designed to "do the right thing" in most 653vice versa. These mappings are designed to "do the right thing" in most
406circumstances automatically, preserving round-tripping characteristics 654circumstances automatically, preserving round-tripping characteristics
407(what you put in comes out as something equivalent). 655(what you put in comes out as something equivalent).
408 656
409For the more enlightened: note that in the following descriptions, 657For the more enlightened: note that in the following descriptions,
410lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 658lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
411refers to the abstract Perl language itself. 659refers to the abstract Perl language itself.
412 660
413 661
414=head2 JSON -> PERL 662=head2 JSON -> PERL
415 663
416=over 4 664=over 4
417 665
418=item object 666=item object
419 667
420A JSON object becomes a reference to a hash in Perl. No ordering of object 668A 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). 669keys is preserved (JSON does not preserve object key ordering itself).
422 670
423=item array 671=item array
424 672
425A JSON array becomes a reference to an array in Perl. 673A JSON array becomes a reference to an array in Perl.
426 674
… …
430are represented by the same codepoints in the Perl string, so no manual 678are represented by the same codepoints in the Perl string, so no manual
431decoding is necessary. 679decoding is necessary.
432 680
433=item number 681=item number
434 682
435A JSON number becomes either an integer or numeric (floating point) 683A JSON number becomes either an integer, numeric (floating point) or
436scalar in perl, depending on its range and any fractional parts. On the 684string 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 685the Perl level, there is no difference between those as Perl handles all
438conversion details, but an integer may take slightly less memory and might 686the conversion details, but an integer may take slightly less memory and
439represent more values exactly than (floating point) numbers. 687might represent more values exactly than (floating point) numbers.
688
689If the number consists of digits only, JSON::XS will try to represent
690it as an integer value. If that fails, it will try to represent it as
691a numeric (floating point) value if that is possible without loss of
692precision. Otherwise it will preserve the number as a string value.
693
694Numbers containing a fractional or exponential part will always be
695represented as numeric (floating point) values, possibly at a loss of
696precision.
697
698This might create round-tripping problems as numbers might become strings,
699but as Perl is typeless there is no other way to do it.
440 700
441=item true, false 701=item true, false
442 702
443These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 703These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
444respectively. They are overloaded to act almost exactly like the numbers 704respectively. 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 705C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
446the C<JSON::XS::is_bool> function. 706the C<JSON::XS::is_bool> function.
447 707
448=item null 708=item null
449 709
450A JSON null atom becomes C<undef> in Perl. 710A JSON null atom becomes C<undef> in Perl.
… …
486 to_json [\0,JSON::XS::true] # yields [false,true] 746 to_json [\0,JSON::XS::true] # yields [false,true]
487 747
488=item JSON::XS::true, JSON::XS::false 748=item JSON::XS::true, JSON::XS::false
489 749
490These special values become JSON true and JSON false values, 750These special values become JSON true and JSON false values,
491respectively. You cna alos use C<\1> and C<\0> directly if you want. 751respectively. You can also use C<\1> and C<\0> directly if you want.
492 752
493=item blessed objects 753=item blessed objects
494 754
495Blessed objects are not allowed. JSON::XS currently tries to encode their 755Blessed objects are not allowed. JSON::XS currently tries to encode their
496underlying representation (hash- or arrayref), but this behaviour might 756underlying representation (hash- or arrayref), but this behaviour might
… …
513 to_json [$value] # yields ["5"] 773 to_json [$value] # yields ["5"]
514 774
515 # undef becomes null 775 # undef becomes null
516 to_json [undef] # yields [null] 776 to_json [undef] # yields [null]
517 777
518You can force the type to be a string by stringifying it: 778You can force the type to be a JSON string by stringifying it:
519 779
520 my $x = 3.1; # some variable containing a number 780 my $x = 3.1; # some variable containing a number
521 "$x"; # stringified 781 "$x"; # stringified
522 $x .= ""; # another, more awkward way to stringify 782 $x .= ""; # another, more awkward way to stringify
523 print $x; # perl does it for you, too, quite often 783 print $x; # perl does it for you, too, quite often
524 784
525You can force the type to be a number by numifying it: 785You can force the type to be a JSON number by numifying it:
526 786
527 my $x = "3"; # some variable containing a string 787 my $x = "3"; # some variable containing a string
528 $x += 0; # numify it, ensuring it will be dumped as a number 788 $x += 0; # numify it, ensuring it will be dumped as a number
529 $x *= 1; # same thing, the choise is yours. 789 $x *= 1; # same thing, the choice is yours.
530 790
531You can not currently output JSON booleans or force the type in other, 791You can not currently force the type in other, less obscure, ways. Tell me
532less obscure, ways. Tell me if you need this capability. 792if you need this capability.
533 793
534=back 794=back
535 795
536 796
537=head1 COMPARISON 797=head1 COMPARISON
… …
546 806
547=item JSON 1.07 807=item JSON 1.07
548 808
549Slow (but very portable, as it is written in pure Perl). 809Slow (but very portable, as it is written in pure Perl).
550 810
551Undocumented/buggy Unicode handling (how JSON handles unicode values is 811Undocumented/buggy Unicode handling (how JSON handles Unicode values is
552undocumented. One can get far by feeding it unicode strings and doing 812undocumented. One can get far by feeding it Unicode strings and doing
553en-/decoding oneself, but unicode escapes are not working properly). 813en-/decoding oneself, but Unicode escapes are not working properly).
554 814
555No roundtripping (strings get clobbered if they look like numbers, e.g. 815No 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 816the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
557decode into the number 2. 817decode into the number 2.
558 818
559=item JSON::PC 0.01 819=item JSON::PC 0.01
560 820
561Very fast. 821Very fast.
562 822
563Undocumented/buggy Unicode handling. 823Undocumented/buggy Unicode handling.
564 824
565No roundtripping. 825No round-tripping.
566 826
567Has problems handling many Perl values (e.g. regex results and other magic 827Has problems handling many Perl values (e.g. regex results and other magic
568values will make it croak). 828values will make it croak).
569 829
570Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 830Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
… …
580Very inflexible (no human-readable format supported, format pretty much 840Very inflexible (no human-readable format supported, format pretty much
581undocumented. I need at least a format for easy reading by humans and a 841undocumented. 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 842single-line compact format for use in a protocol, and preferably a way to
583generate ASCII-only JSON texts). 843generate ASCII-only JSON texts).
584 844
585Completely broken (and confusingly documented) Unicode handling (unicode 845Completely broken (and confusingly documented) Unicode handling (Unicode
586escapes are not working properly, you need to set ImplicitUnicode to 846escapes are not working properly, you need to set ImplicitUnicode to
587I<different> values on en- and decoding to get symmetric behaviour). 847I<different> values on en- and decoding to get symmetric behaviour).
588 848
589No roundtripping (simple cases work, but this depends on wether the scalar 849No round-tripping (simple cases work, but this depends on whether the scalar
590value was used in a numeric context or not). 850value was used in a numeric context or not).
591 851
592Dumping hashes may skip hash values depending on iterator state. 852Dumping hashes may skip hash values depending on iterator state.
593 853
594Unmaintained (maintainer unresponsive for many months, bugs are not 854Unmaintained (maintainer unresponsive for many months, bugs are not
595getting fixed). 855getting fixed).
596 856
597Does not check input for validity (i.e. will accept non-JSON input and 857Does not check input for validity (i.e. will accept non-JSON input and
598return "something" instead of raising an exception. This is a security 858return "something" instead of raising an exception. This is a security
599issue: imagine two banks transfering money between each other using 859issue: imagine two banks transferring money between each other using
600JSON. One bank might parse a given non-JSON request and deduct money, 860JSON. 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 861while the other might reject the transaction with a syntax error. While a
602good protocol will at least recover, that is extra unnecessary work and 862good protocol will at least recover, that is extra unnecessary work and
603the transaction will still not succeed). 863the transaction will still not succeed).
604 864
605=item JSON::DWIW 0.04 865=item JSON::DWIW 0.04
606 866
607Very fast. Very natural. Very nice. 867Very fast. Very natural. Very nice.
608 868
609Undocumented unicode handling (but the best of the pack. Unicode escapes 869Undocumented Unicode handling (but the best of the pack. Unicode escapes
610still don't get parsed properly). 870still don't get parsed properly).
611 871
612Very inflexible. 872Very inflexible.
613 873
614No roundtripping. 874No round-tripping.
615 875
616Does not generate valid JSON texts (key strings are often unquoted, empty keys 876Does not generate valid JSON texts (key strings are often unquoted, empty keys
617result in nothing being output) 877result in nothing being output)
618 878
619Does not check input for validity. 879Does not check input for validity.
… …
634 my $yaml = $to_yaml->encode ($ref) . "\n"; 894 my $yaml = $to_yaml->encode ($ref) . "\n";
635 895
636This will usually generate JSON texts that also parse as valid 896This will usually generate JSON texts that also parse as valid
637YAML. Please note that YAML has hardcoded limits on (simple) object key 897YAML. 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 898lengths that JSON doesn't have, so you should make sure that your hash
639keys are noticably shorter than the 1024 characters YAML allows. 899keys are noticeably shorter than the 1024 characters YAML allows.
640 900
641There might be other incompatibilities that I am not aware of. In general 901There 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, 902you 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 903or try to parse JSON with a YAML parser or vice versa: chances are high
644that you will run into severe interoperability problems. 904that you will run into severe interoperability problems.
… …
662with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 922with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
663shrink). Higher is better: 923shrink). Higher is better:
664 924
665 module | encode | decode | 925 module | encode | decode |
666 -----------|------------|------------| 926 -----------|------------|------------|
667 JSON | 7645.468 | 4208.613 | 927 JSON 1.x | 4990.842 | 4088.813 |
668 JSON::DWIW | 40721.398 | 77101.176 | 928 JSON::DWIW | 51653.990 | 71575.154 |
669 JSON::PC | 65948.176 | 78251.940 | 929 JSON::PC | 65948.176 | 74631.744 |
670 JSON::Syck | 22844.793 | 26479.192 | 930 JSON::PP | 8931.652 | 3817.168 |
931 JSON::Syck | 24877.248 | 27776.848 |
671 JSON::XS | 388361.481 | 199728.762 | 932 JSON::XS | 388361.481 | 227951.304 |
672 JSON::XS/2 | 218453.333 | 192399.266 | 933 JSON::XS/2 | 227951.304 | 218453.333 |
673 JSON::XS/3 | 338250.323 | 192399.266 | 934 JSON::XS/3 | 338250.323 | 218453.333 |
674 Storable | 15779.925 | 14169.946 | 935 Storable | 16500.016 | 135300.129 |
675 -----------+------------+------------+ 936 -----------+------------+------------+
676 937
677That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 938That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
678about three times faster on decoding, and over fourty times faster 939about three times faster on decoding, and over forty times faster
679than JSON, even with pretty-printing and key sorting. It also compares 940than JSON, even with pretty-printing and key sorting. It also compares
680favourably to Storable for small amounts of data. 941favourably to Storable for small amounts of data.
681 942
682Using a longer test string (roughly 18KB, generated from Yahoo! Locals 943Using a longer test string (roughly 18KB, generated from Yahoo! Locals
683search API (http://nanoref.com/yahooapis/mgPdGg): 944search API (http://nanoref.com/yahooapis/mgPdGg):
684 945
685 module | encode | decode | 946 module | encode | decode |
686 -----------|------------|------------| 947 -----------|------------|------------|
687 JSON | 254.685 | 37.665 | 948 JSON 1.x | 55.260 | 34.971 |
688 JSON::DWIW | 843.343 | 1049.731 | 949 JSON::DWIW | 825.228 | 1082.513 |
689 JSON::PC | 3602.116 | 2307.352 | 950 JSON::PC | 3571.444 | 2394.829 |
951 JSON::PP | 210.987 | 32.574 |
690 JSON::Syck | 505.107 | 787.899 | 952 JSON::Syck | 552.551 | 787.544 |
691 JSON::XS | 5747.196 | 3690.220 | 953 JSON::XS | 5780.463 | 4854.519 |
692 JSON::XS/2 | 3968.121 | 3676.634 | 954 JSON::XS/2 | 3869.998 | 4798.975 |
693 JSON::XS/3 | 6105.246 | 3662.508 | 955 JSON::XS/3 | 5862.880 | 4798.975 |
694 Storable | 4417.337 | 5285.161 | 956 Storable | 4445.002 | 5235.027 |
695 -----------+------------+------------+ 957 -----------+------------+------------+
696 958
697Again, JSON::XS leads by far (except for Storable which non-surprisingly 959Again, JSON::XS leads by far (except for Storable which non-surprisingly
698decodes faster). 960decodes faster).
699 961
700On large strings containing lots of high unicode characters, some modules 962On 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 963(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 964will be broken due to missing (or wrong) Unicode handling. Others refuse
703to decode or encode properly, so it was impossible to prepare a fair 965to decode or encode properly, so it was impossible to prepare a fair
704comparison table for that case. 966comparison table for that case.
705 967
706 968
707=head1 SECURITY CONSIDERATIONS 969=head1 SECURITY CONSIDERATIONS
… …
713any buffer overflows. Obviously, this module should ensure that and I am 975any buffer overflows. Obviously, this module should ensure that and I am
714trying hard on making that true, but you never know. 976trying hard on making that true, but you never know.
715 977
716Second, you need to avoid resource-starving attacks. That means you should 978Second, 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 979limit 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 980resources 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 981can 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 982usually a good indication of the size of the resources required to decode
721it into a Perl structure. 983it into a Perl structure. While JSON::XS can check the size of the JSON
984text, it might be too late when you already have it in memory, so you
985might want to check the size before you accept the string.
722 986
723Third, JSON::XS recurses using the C stack when decoding objects and 987Third, JSON::XS recurses using the C stack when decoding objects and
724arrays. The C stack is a limited resource: for instance, on my amd64 988arrays. 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 989machine 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 990only 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 996And 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, 997of. In that case, you get to keep the pieces. I am always open for hints,
734though... 998though...
735 999
736If you are using JSON::XS to return packets to consumption 1000If you are using JSON::XS to return packets to consumption
737by javascript scripts in a browser you should have a look at 1001by JavaScript scripts in a browser you should have a look at
738L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1002L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
739you are vulnerable to some common attack vectors (which really are browser 1003you 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 1004design 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 1005browser developers care only for features, not about doing security
742right). 1006right).
743 1007
744 1008
1009=head1 THREADS
1010
1011This module is I<not> guaranteed to be thread safe and there are no
1012plans to change this until Perl gets thread support (as opposed to the
1013horribly slow so-called "threads" which are simply slow and bloated
1014process simulations - use fork, its I<much> faster, cheaper, better).
1015
1016(It might actually work, but you have been warned).
1017
1018
745=head1 BUGS 1019=head1 BUGS
746 1020
747While the goal of this module is to be correct, that unfortunately does 1021While 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 1022not 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 1023still relatively early in its development. If you keep reporting bugs they
750will be fixed swiftly, though. 1024will be fixed swiftly, though.
751 1025
1026Please refrain from using rt.cpan.org or any other bug reporting
1027service. I put the contact address into my modules for a reason.
1028
752=cut 1029=cut
753 1030
754our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1031our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
755our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1032our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
756 1033
757sub true() { $true } 1034sub true() { $true }
758sub false() { $false } 1035sub false() { $false }
759 1036
760sub is_bool($) { 1037sub is_bool($) {
761 UNIVERSAL::isa $_[0], "JSON::XS::Boolean" 1038 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
762 or UNIVERSAL::isa $_[0], "JSON::Literal" 1039# or UNIVERSAL::isa $_[0], "JSON::Literal"
763} 1040}
764 1041
765XSLoader::load "JSON::XS", $VERSION; 1042XSLoader::load "JSON::XS", $VERSION;
766 1043
767package JSON::XS::Boolean; 1044package JSON::XS::Boolean;

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