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Revision 1.53 by root, Mon Jul 2 07:39:31 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
16 19
17 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
18 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
19 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
20 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
21=head1 DESCRIPTION 32=head1 DESCRIPTION
22 33
23This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
24primary 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
25I<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.
26 45
27As 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
28to 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
29modules, 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
30their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
37 56
38=head2 FEATURES 57=head2 FEATURES
39 58
40=over 4 59=over 4
41 60
42=item * correct unicode handling 61=item * correct Unicode handling
43 62
44This 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
45it does so. 64it does so.
46 65
47=item * round-trip integrity 66=item * round-trip integrity
67This 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
68interface. 87interface.
69 88
70=item * reasonably versatile output formats 89=item * reasonably versatile output formats
71 90
72You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
73possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
74(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
75unicode 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
76stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
77 96
78=back 97=back
79 98
80=cut 99=cut
81 100
82package JSON::XS; 101package JSON::XS;
83 102
84use strict; 103use strict;
85 104
86our $VERSION = '1.4'; 105our $VERSION = '2.0';
87our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
88 107
89our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(to_json from_json);
90 109
91use Exporter; 110use Exporter;
92use XSLoader; 111use XSLoader;
93 112
94=head1 FUNCTIONAL INTERFACE 113=head1 FUNCTIONAL INTERFACE
95 114
96The following convinience methods are provided by this module. They are 115The following convenience methods are provided by this module. They are
97exported by default: 116exported by default:
98 117
99=over 4 118=over 4
100 119
101=item $json_text = to_json $perl_scalar 120=item $json_text = to_json $perl_scalar
102 121
103Converts 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
104a 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.
105octets only). Croaks on error.
106 124
107This function call is functionally identical to: 125This function call is functionally identical to:
108 126
109 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 127 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110 128
111except being faster. 129except being faster.
112 130
113=item $perl_scalar = from_json $json_text 131=item $perl_scalar = from_json $json_text
114 132
115The 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
116parse 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
117scalar or reference. Croaks on error. 135reference. Croaks on error.
118 136
119This function call is functionally identical to: 137This function call is functionally identical to:
120 138
121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 139 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122 140
132Perl. 150Perl.
133 151
134=back 152=back
135 153
136 154
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
137=head1 OBJECT-ORIENTED INTERFACE 203=head1 OBJECT-ORIENTED INTERFACE
138 204
139The object oriented interface lets you configure your own encoding or 205The object oriented interface lets you configure your own encoding or
140decoding style, within the limits of supported formats. 206decoding style, within the limits of supported formats.
141 207
152 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]})
153 => {"a": [1, 2]} 219 => {"a": [1, 2]}
154 220
155=item $json = $json->ascii ([$enable]) 221=item $json = $json->ascii ([$enable])
156 222
223=item $enabled = $json->get_ascii
224
157If C<$enable> is true (or missing), then the C<encode> method will not 225If C<$enable> is true (or missing), then the C<encode> method will not
158generate characters outside the code range C<0..127> (which is ASCII). Any 226generate characters outside the code range C<0..127> (which is ASCII). Any
159unicode characters outside that range will be escaped using either a 227Unicode characters outside that range will be escaped using either a
160single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 228single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161as per RFC4627. The resulting encoded JSON text can be treated as a native 229as per RFC4627. The resulting encoded JSON text can be treated as a native
162unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 230Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163or any other superset of ASCII. 231or any other superset of ASCII.
164 232
165If C<$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
166characters unless required by the JSON syntax or other flags. This results 234characters unless required by the JSON syntax or other flags. This results
167in a faster and more compact format. 235in a faster and more compact format.
173 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 241 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174 => ["\ud801\udc01"] 242 => ["\ud801\udc01"]
175 243
176=item $json = $json->latin1 ([$enable]) 244=item $json = $json->latin1 ([$enable])
177 245
246=item $enabled = $json->get_latin1
247
178If C<$enable> is true (or missing), then the C<encode> method will encode 248If C<$enable> is true (or missing), then the C<encode> method will encode
179the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 249the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180outside the code range C<0..255>. The resulting string can be treated as a 250outside the code range C<0..255>. The resulting string can be treated as a
181latin1-encoded JSON text or a native unicode string. The C<decode> method 251latin1-encoded JSON text or a native Unicode string. The C<decode> method
182will not be affected in any way by this flag, as C<decode> by default 252will not be affected in any way by this flag, as C<decode> by default
183expects unicode, which is a strict superset of latin1. 253expects Unicode, which is a strict superset of latin1.
184 254
185If C<$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
186characters unless required by the JSON syntax or other flags. 256characters unless required by the JSON syntax or other flags.
187 257
188The 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
189text, 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
190size. The disadvantage is that the resulting JSON text is encoded 260size. The disadvantage is that the resulting JSON text is encoded
191in latin1 (and must correctly be treated as such when storing and 261in latin1 (and must correctly be treated as such when storing and
192transfering), a rare encoding for JSON. It is therefore most useful when 262transferring), a rare encoding for JSON. It is therefore most useful when
193you want to store data structures known to contain binary data efficiently 263you want to store data structures known to contain binary data efficiently
194in files or databases, not when talking to other JSON encoders/decoders. 264in files or databases, not when talking to other JSON encoders/decoders.
195 265
196 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 266 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 267 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198 268
199=item $json = $json->utf8 ([$enable]) 269=item $json = $json->utf8 ([$enable])
270
271=item $enabled = $json->get_utf8
200 272
201If C<$enable> is true (or missing), then the C<encode> method will encode 273If C<$enable> is true (or missing), then the C<encode> method will encode
202the JSON result into UTF-8, as required by many protocols, while the 274the JSON result into UTF-8, as required by many protocols, while the
203C<decode> method expects to be handled an UTF-8-encoded string. Please 275C<decode> method expects to be handled an UTF-8-encoded string. Please
204note that UTF-8-encoded strings do not contain any characters outside the 276note that UTF-8-encoded strings do not contain any characters outside the
205range C<0..255>, they are thus useful for bytewise/binary I/O. In future 277range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206versions, enabling this option might enable autodetection of the UTF-16 278versions, enabling this option might enable autodetection of the UTF-16
207and UTF-32 encoding families, as described in RFC4627. 279and UTF-32 encoding families, as described in RFC4627.
208 280
209If C<$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
210string 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
211unicode 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
212to be done yourself, e.g. using the Encode module. 284to be done yourself, e.g. using the Encode module.
213 285
214Example, output UTF-16BE-encoded JSON: 286Example, output UTF-16BE-encoded JSON:
215 287
216 use Encode; 288 use Encode;
238 ] 310 ]
239 } 311 }
240 312
241=item $json = $json->indent ([$enable]) 313=item $json = $json->indent ([$enable])
242 314
315=item $enabled = $json->get_indent
316
243If C<$enable> is true (or missing), then the C<encode> method will use a multiline 317If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244format as output, putting every array member or object/hash key-value pair 318format as output, putting every array member or object/hash key-value pair
245into its own line, identing them properly. 319into its own line, indenting them properly.
246 320
247If C<$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
248resulting JSON text is guarenteed not to contain any C<newlines>. 322resulting JSON text is guaranteed not to contain any C<newlines>.
249 323
250This setting has no effect when decoding JSON texts. 324This setting has no effect when decoding JSON texts.
251 325
252=item $json = $json->space_before ([$enable]) 326=item $json = $json->space_before ([$enable])
327
328=item $enabled = $json->get_space_before
253 329
254If C<$enable> is true (or missing), then the C<encode> method will add an extra 330If C<$enable> is true (or missing), then the C<encode> method will add an extra
255optional space before the C<:> separating keys from values in JSON objects. 331optional space before the C<:> separating keys from values in JSON objects.
256 332
257If C<$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
263Example, space_before enabled, space_after and indent disabled: 339Example, space_before enabled, space_after and indent disabled:
264 340
265 {"key" :"value"} 341 {"key" :"value"}
266 342
267=item $json = $json->space_after ([$enable]) 343=item $json = $json->space_after ([$enable])
344
345=item $enabled = $json->get_space_after
268 346
269If C<$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
270optional space after the C<:> separating keys from values in JSON objects 348optional space after the C<:> separating keys from values in JSON objects
271and extra whitespace after the C<,> separating key-value pairs and array 349and extra whitespace after the C<,> separating key-value pairs and array
272members. 350members.
278 356
279Example, space_before and indent disabled, space_after enabled: 357Example, space_before and indent disabled, space_after enabled:
280 358
281 {"key": "value"} 359 {"key": "value"}
282 360
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
283=item $json = $json->canonical ([$enable]) 408=item $json = $json->canonical ([$enable])
409
410=item $enabled = $json->get_canonical
284 411
285If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 412If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286by sorting their keys. This is adding a comparatively high overhead. 413by sorting their keys. This is adding a comparatively high overhead.
287 414
288If C<$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
289pairs 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
290of the same script). 417of the same script).
291 418
292This 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
293the 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,
294the 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,
295as key-value pairs have no inherent ordering in Perl. 422as key-value pairs have no inherent ordering in Perl.
296 423
297This setting has no effect when decoding JSON texts. 424This setting has no effect when decoding JSON texts.
298 425
299=item $json = $json->allow_nonref ([$enable]) 426=item $json = $json->allow_nonref ([$enable])
427
428=item $enabled = $json->get_allow_nonref
300 429
301If C<$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
302non-reference into its corresponding string, number or null JSON value, 431non-reference into its corresponding string, number or null JSON value,
303which 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
304values instead of croaking. 433values instead of croaking.
314 JSON::XS->new->allow_nonref->encode ("Hello, World!") 443 JSON::XS->new->allow_nonref->encode ("Hello, World!")
315 => "Hello, World!" 444 => "Hello, World!"
316 445
317=item $json = $json->allow_blessed ([$enable]) 446=item $json = $json->allow_blessed ([$enable])
318 447
448=item $enabled = $json->get_allow_blessed
449
319If C<$enable> is true (or missing), then the C<encode> method will not 450If C<$enable> is true (or missing), then the C<encode> method will not
320barf when it encounters a blessed reference. Instead, the value of the 451barf when it encounters a blessed reference. Instead, the value of the
321B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 452B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322disabled or no C<to_json> method found) or a representation of the 453disabled or no C<TO_JSON> method found) or a representation of the
323object (C<convert_blessed> enabled and C<to_json> method found) is being 454object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324encoded. Has no effect on C<decode>. 455encoded. Has no effect on C<decode>.
325 456
326If C<$enable> is false (the default), then C<encode> will throw an 457If C<$enable> is false (the default), then C<encode> will throw an
327exception when it encounters a blessed object. 458exception when it encounters a blessed object.
328 459
329=item $json = $json->convert_blessed ([$enable]) 460=item $json = $json->convert_blessed ([$enable])
461
462=item $enabled = $json->get_convert_blessed
330 463
331If C<$enable> is true (or missing), then C<encode>, upon encountering a 464If C<$enable> is true (or missing), then C<encode>, upon encountering a
332blessed object, will check for the availability of the C<TO_JSON> method 465blessed object, will check for the availability of the C<TO_JSON> method
333on the object's class. If found, it will be called in scalar context 466on the object's class. If found, it will be called in scalar context
334and the resulting scalar will be encoded instead of the object. If no 467and the resulting scalar will be encoded instead of the object. If no
391 524
392As this callback gets called less often then the C<filter_json_object> 525As this callback gets called less often then the C<filter_json_object>
393one, decoding speed will not usually suffer as much. Therefore, single-key 526one, decoding speed will not usually suffer as much. Therefore, single-key
394objects make excellent targets to serialise Perl objects into, especially 527objects make excellent targets to serialise Perl objects into, especially
395as single-key JSON objects are as close to the type-tagged value concept 528as single-key JSON objects are as close to the type-tagged value concept
396as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not 529as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
397support this in any way, so you need to make sure your data never looks 530support this in any way, so you need to make sure your data never looks
398like a serialised Perl hash. 531like a serialised Perl hash.
399 532
400Typical names for the single object key are C<__class_whatever__>, or 533Typical names for the single object key are C<__class_whatever__>, or
401C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 534C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
425 558
426 { __widget__ => $self->{id} } 559 { __widget__ => $self->{id} }
427 } 560 }
428 561
429=item $json = $json->shrink ([$enable]) 562=item $json = $json->shrink ([$enable])
563
564=item $enabled = $json->get_shrink
430 565
431Perl usually over-allocates memory a bit when allocating space for 566Perl usually over-allocates memory a bit when allocating space for
432strings. This flag optionally resizes strings generated by either 567strings. This flag optionally resizes strings generated by either
433C<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
434memory 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
452strings that look like integers or floats into integers or floats 587strings that look like integers or floats into integers or floats
453internally (there is no difference on the Perl level), saving space. 588internally (there is no difference on the Perl level), saving space.
454 589
455=item $json = $json->max_depth ([$maximum_nesting_depth]) 590=item $json = $json->max_depth ([$maximum_nesting_depth])
456 591
592=item $max_depth = $json->get_max_depth
593
457Sets the maximum nesting level (default C<512>) accepted while encoding 594Sets the maximum nesting level (default C<512>) accepted while encoding
458or 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
459higher nesting level then this limit, then the encoder and decoder will 596higher nesting level then this limit, then the encoder and decoder will
460stop and croak at that point. 597stop and croak at that point.
461 598
472used, which is rarely useful. 609used, which is rarely useful.
473 610
474See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 611See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
475 612
476=item $json = $json->max_size ([$maximum_string_size]) 613=item $json = $json->max_size ([$maximum_string_size])
614
615=item $max_size = $json->get_max_size
477 616
478Set the maximum length a JSON text may have (in bytes) where decoding is 617Set the maximum length a JSON text may have (in bytes) where decoding is
479being attempted. The default is C<0>, meaning no limit. When C<decode> 618being attempted. The default is C<0>, meaning no limit. When C<decode>
480is called on a string longer then this number of characters it will not 619is called on a string longer then this number of characters it will not
481attempt to decode the string but throw an exception. This setting has no 620attempt to decode the string but throw an exception. This setting has no
528vice 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
529circumstances automatically, preserving round-tripping characteristics 668circumstances automatically, preserving round-tripping characteristics
530(what you put in comes out as something equivalent). 669(what you put in comes out as something equivalent).
531 670
532For the more enlightened: note that in the following descriptions, 671For the more enlightened: note that in the following descriptions,
533lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 672lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
534refers to the abstract Perl language itself. 673refers to the abstract Perl language itself.
535 674
536 675
537=head2 JSON -> PERL 676=head2 JSON -> PERL
538 677
539=over 4 678=over 4
540 679
541=item object 680=item object
542 681
543A 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
544keys is preserved (JSON does not preserver object key ordering itself). 683keys is preserved (JSON does not preserve object key ordering itself).
545 684
546=item array 685=item array
547 686
548A JSON array becomes a reference to an array in Perl. 687A JSON array becomes a reference to an array in Perl.
549 688
553are 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
554decoding is necessary. 693decoding is necessary.
555 694
556=item number 695=item number
557 696
558A JSON number becomes either an integer or numeric (floating point) 697A JSON number becomes either an integer, numeric (floating point) or
559scalar 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
560Perl 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
561conversion details, but an integer may take slightly less memory and might 700the conversion details, but an integer may take slightly less memory and
562represent 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.
563 714
564=item true, false 715=item true, false
565 716
566These 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>,
567respectively. They are overloaded to act almost exactly like the numbers 718respectively. They are overloaded to act almost exactly like the numbers
568C<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
569the C<JSON::XS::is_bool> function. 720the C<JSON::XS::is_bool> function.
570 721
571=item null 722=item null
572 723
573A JSON null atom becomes C<undef> in Perl. 724A JSON null atom becomes C<undef> in Perl.
609 to_json [\0,JSON::XS::true] # yields [false,true] 760 to_json [\0,JSON::XS::true] # yields [false,true]
610 761
611=item JSON::XS::true, JSON::XS::false 762=item JSON::XS::true, JSON::XS::false
612 763
613These special values become JSON true and JSON false values, 764These special values become JSON true and JSON false values,
614respectively. 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.
615 766
616=item blessed objects 767=item blessed objects
617 768
618Blessed objects are not allowed. JSON::XS currently tries to encode their 769Blessed objects are not allowed. JSON::XS currently tries to encode their
619underlying representation (hash- or arrayref), but this behaviour might 770underlying representation (hash- or arrayref), but this behaviour might
636 to_json [$value] # yields ["5"] 787 to_json [$value] # yields ["5"]
637 788
638 # undef becomes null 789 # undef becomes null
639 to_json [undef] # yields [null] 790 to_json [undef] # yields [null]
640 791
641You can force the type to be a string by stringifying it: 792You can force the type to be a JSON string by stringifying it:
642 793
643 my $x = 3.1; # some variable containing a number 794 my $x = 3.1; # some variable containing a number
644 "$x"; # stringified 795 "$x"; # stringified
645 $x .= ""; # another, more awkward way to stringify 796 $x .= ""; # another, more awkward way to stringify
646 print $x; # perl does it for you, too, quite often 797 print $x; # perl does it for you, too, quite often
647 798
648You can force the type to be a number by numifying it: 799You can force the type to be a JSON number by numifying it:
649 800
650 my $x = "3"; # some variable containing a string 801 my $x = "3"; # some variable containing a string
651 $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
652 $x *= 1; # same thing, the choise is yours. 803 $x *= 1; # same thing, the choice is yours.
653 804
654You 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
655less obscure, ways. Tell me if you need this capability. 806if you need this capability.
656 807
657=back 808=back
658 809
659 810
660=head1 COMPARISON 811=head1 COMPARISON
669 820
670=item JSON 1.07 821=item JSON 1.07
671 822
672Slow (but very portable, as it is written in pure Perl). 823Slow (but very portable, as it is written in pure Perl).
673 824
674Undocumented/buggy Unicode handling (how JSON handles unicode values is 825Undocumented/buggy Unicode handling (how JSON handles Unicode values is
675undocumented. One can get far by feeding it unicode strings and doing 826undocumented. One can get far by feeding it Unicode strings and doing
676en-/decoding oneself, but unicode escapes are not working properly). 827en-/decoding oneself, but Unicode escapes are not working properly).
677 828
678No roundtripping (strings get clobbered if they look like numbers, e.g. 829No round-tripping (strings get clobbered if they look like numbers, e.g.
679the 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
680decode into the number 2. 831decode into the number 2.
681 832
682=item JSON::PC 0.01 833=item JSON::PC 0.01
683 834
684Very fast. 835Very fast.
685 836
686Undocumented/buggy Unicode handling. 837Undocumented/buggy Unicode handling.
687 838
688No roundtripping. 839No round-tripping.
689 840
690Has 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
691values will make it croak). 842values will make it croak).
692 843
693Does 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}>
703Very inflexible (no human-readable format supported, format pretty much 854Very inflexible (no human-readable format supported, format pretty much
704undocumented. 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
705single-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
706generate ASCII-only JSON texts). 857generate ASCII-only JSON texts).
707 858
708Completely broken (and confusingly documented) Unicode handling (unicode 859Completely broken (and confusingly documented) Unicode handling (Unicode
709escapes are not working properly, you need to set ImplicitUnicode to 860escapes are not working properly, you need to set ImplicitUnicode to
710I<different> values on en- and decoding to get symmetric behaviour). 861I<different> values on en- and decoding to get symmetric behaviour).
711 862
712No roundtripping (simple cases work, but this depends on wether the scalar 863No round-tripping (simple cases work, but this depends on whether the scalar
713value was used in a numeric context or not). 864value was used in a numeric context or not).
714 865
715Dumping hashes may skip hash values depending on iterator state. 866Dumping hashes may skip hash values depending on iterator state.
716 867
717Unmaintained (maintainer unresponsive for many months, bugs are not 868Unmaintained (maintainer unresponsive for many months, bugs are not
718getting fixed). 869getting fixed).
719 870
720Does 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
721return "something" instead of raising an exception. This is a security 872return "something" instead of raising an exception. This is a security
722issue: imagine two banks transfering money between each other using 873issue: imagine two banks transferring money between each other using
723JSON. 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,
724while 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
725good protocol will at least recover, that is extra unnecessary work and 876good protocol will at least recover, that is extra unnecessary work and
726the transaction will still not succeed). 877the transaction will still not succeed).
727 878
728=item JSON::DWIW 0.04 879=item JSON::DWIW 0.04
729 880
730Very fast. Very natural. Very nice. 881Very fast. Very natural. Very nice.
731 882
732Undocumented unicode handling (but the best of the pack. Unicode escapes 883Undocumented Unicode handling (but the best of the pack. Unicode escapes
733still don't get parsed properly). 884still don't get parsed properly).
734 885
735Very inflexible. 886Very inflexible.
736 887
737No roundtripping. 888No round-tripping.
738 889
739Does 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
740result in nothing being output) 891result in nothing being output)
741 892
742Does not check input for validity. 893Does not check input for validity.
757 my $yaml = $to_yaml->encode ($ref) . "\n"; 908 my $yaml = $to_yaml->encode ($ref) . "\n";
758 909
759This will usually generate JSON texts that also parse as valid 910This will usually generate JSON texts that also parse as valid
760YAML. Please note that YAML has hardcoded limits on (simple) object key 911YAML. Please note that YAML has hardcoded limits on (simple) object key
761lengths 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
762keys are noticably shorter than the 1024 characters YAML allows. 913keys are noticeably shorter than the 1024 characters YAML allows.
763 914
764There 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
765you 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,
766or 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
767that you will run into severe interoperability problems. 918that you will run into severe interoperability problems.
783It shows the number of encodes/decodes per second (JSON::XS uses 934It shows the number of encodes/decodes per second (JSON::XS uses
784the functional interface, while JSON::XS/2 uses the OO interface 935the functional interface, while JSON::XS/2 uses the OO interface
785with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 936with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
786shrink). Higher is better: 937shrink). Higher is better:
787 938
788 Storable | 15779.925 | 14169.946 |
789 -----------+------------+------------+
790 module | encode | decode | 939 module | encode | decode |
791 -----------|------------|------------| 940 -----------|------------|------------|
792 JSON | 4990.842 | 4088.813 | 941 JSON 1.x | 4990.842 | 4088.813 |
793 JSON::DWIW | 51653.990 | 71575.154 | 942 JSON::DWIW | 51653.990 | 71575.154 |
794 JSON::PC | 65948.176 | 74631.744 | 943 JSON::PC | 65948.176 | 74631.744 |
795 JSON::PP | 8931.652 | 3817.168 | 944 JSON::PP | 8931.652 | 3817.168 |
796 JSON::Syck | 24877.248 | 27776.848 | 945 JSON::Syck | 24877.248 | 27776.848 |
797 JSON::XS | 388361.481 | 227951.304 | 946 JSON::XS | 388361.481 | 227951.304 |
799 JSON::XS/3 | 338250.323 | 218453.333 | 948 JSON::XS/3 | 338250.323 | 218453.333 |
800 Storable | 16500.016 | 135300.129 | 949 Storable | 16500.016 | 135300.129 |
801 -----------+------------+------------+ 950 -----------+------------+------------+
802 951
803That 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,
804about three times faster on decoding, and over fourty times faster 953about three times faster on decoding, and over forty times faster
805than JSON, even with pretty-printing and key sorting. It also compares 954than JSON, even with pretty-printing and key sorting. It also compares
806favourably to Storable for small amounts of data. 955favourably to Storable for small amounts of data.
807 956
808Using a longer test string (roughly 18KB, generated from Yahoo! Locals 957Using a longer test string (roughly 18KB, generated from Yahoo! Locals
809search API (http://nanoref.com/yahooapis/mgPdGg): 958search API (http://nanoref.com/yahooapis/mgPdGg):
810 959
811 module | encode | decode | 960 module | encode | decode |
812 -----------|------------|------------| 961 -----------|------------|------------|
813 JSON | 55.260 | 34.971 | 962 JSON 1.x | 55.260 | 34.971 |
814 JSON::DWIW | 825.228 | 1082.513 | 963 JSON::DWIW | 825.228 | 1082.513 |
815 JSON::PC | 3571.444 | 2394.829 | 964 JSON::PC | 3571.444 | 2394.829 |
816 JSON::PP | 210.987 | 32.574 | 965 JSON::PP | 210.987 | 32.574 |
817 JSON::Syck | 552.551 | 787.544 | 966 JSON::Syck | 552.551 | 787.544 |
818 JSON::XS | 5780.463 | 4854.519 | 967 JSON::XS | 5780.463 | 4854.519 |
822 -----------+------------+------------+ 971 -----------+------------+------------+
823 972
824Again, JSON::XS leads by far (except for Storable which non-surprisingly 973Again, JSON::XS leads by far (except for Storable which non-surprisingly
825decodes faster). 974decodes faster).
826 975
827On large strings containing lots of high unicode characters, some modules 976On large strings containing lots of high Unicode characters, some modules
828(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
829will be broken due to missing (or wrong) unicode handling. Others refuse 978will be broken due to missing (or wrong) Unicode handling. Others refuse
830to 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
831comparison table for that case. 980comparison table for that case.
832 981
833 982
834=head1 SECURITY CONSIDERATIONS 983=head1 SECURITY CONSIDERATIONS
840any buffer overflows. Obviously, this module should ensure that and I am 989any buffer overflows. Obviously, this module should ensure that and I am
841trying hard on making that true, but you never know. 990trying hard on making that true, but you never know.
842 991
843Second, you need to avoid resource-starving attacks. That means you should 992Second, you need to avoid resource-starving attacks. That means you should
844limit 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
845resources 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
846can 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
847usually 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
848it into a Perl structure. While JSON::XS can check the size of the JSON 997it into a Perl structure. While JSON::XS can check the size of the JSON
849text, it might be too late when you already have it in memory, so you 998text, it might be too late when you already have it in memory, so you
850might want to check the size before you accept the string. 999might want to check the size before you accept the string.
861And 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
862of. 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,
863though... 1012though...
864 1013
865If you are using JSON::XS to return packets to consumption 1014If you are using JSON::XS to return packets to consumption
866by javascript scripts in a browser you should have a look at 1015by JavaScript scripts in a browser you should have a look at
867L<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
868you are vulnerable to some common attack vectors (which really are browser 1017you are vulnerable to some common attack vectors (which really are browser
869design 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
870browser developers care only for features, not about doing security 1019browser developers care only for features, not about doing security
871right). 1020right).
872 1021
873 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
874=head1 BUGS 1033=head1 BUGS
875 1034
876While 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
877not 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
878still relatively early in its development. If you keep reporting bugs they 1037still relatively early in its development. If you keep reporting bugs they
879will be fixed swiftly, though. 1038will be fixed swiftly, though.
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.
880 1042
881=cut 1043=cut
882 1044
883our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1045our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
884our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1046our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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