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Revision 1.66 by root, Sun Oct 14 20:02:57 2007 UTC vs.
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC

10 use JSON::XS; 10 use JSON::XS;
11 11
12 # exported functions, they croak on error 12 # exported functions, they croak on error
13 # and expect/generate UTF-8 13 # and expect/generate UTF-8
14 14
15 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17 17
18 # OO-interface 18 # OO-interface
19 19
20 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
21 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
22 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
23 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
24=head1 DESCRIPTION 32=head1 DESCRIPTION
25 33
26This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
27primary 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
28I<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.
29 45
30As 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
31to 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
32modules, 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
33their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
40 56
41=head2 FEATURES 57=head2 FEATURES
42 58
43=over 4 59=over 4
44 60
45=item * correct unicode handling 61=item * correct Unicode handling
46 62
47This 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
48it does so. 64it does so.
49 65
50=item * round-trip integrity 66=item * round-trip integrity
70This 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
71interface. 87interface.
72 88
73=item * reasonably versatile output formats 89=item * reasonably versatile output formats
74 90
75You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
76possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
77(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
78unicode 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
79stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
80 96
81=back 97=back
82 98
83=cut 99=cut
84 100
85package JSON::XS; 101package JSON::XS;
86 102
87use strict; 103use strict;
88 104
89our $VERSION = '1.51'; 105our $VERSION = '2.01';
90our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
91 107
92our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
111 require Carp;
112 Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
113}
114
115sub from_json($) {
116 require Carp;
117 Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
118}
93 119
94use Exporter; 120use Exporter;
95use XSLoader; 121use XSLoader;
96 122
97=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
98 124
99The following convinience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
100exported by default: 126exported by default:
101 127
102=over 4 128=over 4
103 129
104=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
105 131
106Converts the given Perl data structure to a UTF-8 encoded, binary string 132Converts the given Perl data structure to a UTF-8 encoded, binary string
107(that is, the string contains octets only). Croaks on error. 133(that is, the string contains octets only). Croaks on error.
108 134
109This function call is functionally identical to: 135This function call is functionally identical to:
110 136
111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112 138
113except being faster. 139except being faster.
114 140
115=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
116 142
117The opposite of C<to_json>: expects an UTF-8 (binary) string and tries 143The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
118to parse that as an UTF-8 encoded JSON text, returning the resulting 144to parse that as an UTF-8 encoded JSON text, returning the resulting
119reference. Croaks on error. 145reference. Croaks on error.
120 146
121This function call is functionally identical to: 147This function call is functionally identical to:
122 148
143 169
144=over 4 170=over 4
145 171
146=item 1. Perl strings can store characters with ordinal values > 255. 172=item 1. Perl strings can store characters with ordinal values > 255.
147 173
148This enables you to store unicode characters as single characters in a 174This enables you to store Unicode characters as single characters in a
149Perl string - very natural. 175Perl string - very natural.
150 176
151=item 2. Perl does I<not> associate an encoding with your strings. 177=item 2. Perl does I<not> associate an encoding with your strings.
152 178
153Unless you force it to, e.g. when matching it against a regex, or printing 179Unless you force it to, e.g. when matching it against a regex, or printing
160encoding of your string. 186encoding of your string.
161 187
162Just ignore that flag unless you debug a Perl bug, a module written in 188Just 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 189XS 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 190confuse 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 191is 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 192flag clear, and you can have binary data with that flag set and that flag
167clear. Other possibilities exist, too. 193clear. Other possibilities exist, too.
168 194
169If you didn't know about that flag, just the better, pretend it doesn't 195If you didn't know about that flag, just the better, pretend it doesn't
170exist. 196exist.
175If you have UTF-8 encoded data, it is no longer a Unicode string, but a 201If 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. 202Unicode string encoded in UTF-8, giving you a binary string.
177 203
178=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. 204=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
179 205
180Its a fact. Learn to live with it. 206It's a fact. Learn to live with it.
181 207
182=back 208=back
183 209
184I hope this helps :) 210I hope this helps :)
185 211
202 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 228 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
203 => {"a": [1, 2]} 229 => {"a": [1, 2]}
204 230
205=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
206 232
233=item $enabled = $json->get_ascii
234
207If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
208generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
209unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
210single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
211as per RFC4627. The resulting encoded JSON text can be treated as a native 239as per RFC4627. The resulting encoded JSON text can be treated as a native
212unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 240Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
213or any other superset of ASCII. 241or any other superset of ASCII.
214 242
215If C<$enable> is false, then the C<encode> method will not escape Unicode 243If C<$enable> is false, then the C<encode> method will not escape Unicode
216characters unless required by the JSON syntax or other flags. This results 244characters unless required by the JSON syntax or other flags. This results
217in a faster and more compact format. 245in a faster and more compact format.
223 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
225 253
226=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
227 255
256=item $enabled = $json->get_latin1
257
228If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
229the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
231latin1-encoded JSON text or a native unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
232will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
233expects unicode, which is a strict superset of latin1. 263expects Unicode, which is a strict superset of latin1.
234 264
235If C<$enable> is false, then the C<encode> method will not escape Unicode 265If C<$enable> is false, then the C<encode> method will not escape Unicode
236characters unless required by the JSON syntax or other flags. 266characters unless required by the JSON syntax or other flags.
237 267
238The main use for this flag is efficiently encoding binary data as JSON 268The main use for this flag is efficiently encoding binary data as JSON
239text, as most octets will not be escaped, resulting in a smaller encoded 269text, as most octets will not be escaped, resulting in a smaller encoded
240size. The disadvantage is that the resulting JSON text is encoded 270size. The disadvantage is that the resulting JSON text is encoded
241in latin1 (and must correctly be treated as such when storing and 271in latin1 (and must correctly be treated as such when storing and
242transfering), a rare encoding for JSON. It is therefore most useful when 272transferring), a rare encoding for JSON. It is therefore most useful when
243you want to store data structures known to contain binary data efficiently 273you want to store data structures known to contain binary data efficiently
244in files or databases, not when talking to other JSON encoders/decoders. 274in files or databases, not when talking to other JSON encoders/decoders.
245 275
246 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248 278
249=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
250 282
251If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
252the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
253C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
254note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
255range C<0..255>, they are thus useful for bytewise/binary I/O. In future 287range C<0..255>, they are thus useful for bytewise/binary I/O. In future
256versions, enabling this option might enable autodetection of the UTF-16 288versions, enabling this option might enable autodetection of the UTF-16
257and UTF-32 encoding families, as described in RFC4627. 289and UTF-32 encoding families, as described in RFC4627.
258 290
259If C<$enable> is false, then the C<encode> method will return the JSON 291If C<$enable> is false, then the C<encode> method will return the JSON
260string as a (non-encoded) unicode string, while C<decode> expects thus a 292string as a (non-encoded) Unicode string, while C<decode> expects thus a
261unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs 293Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
262to be done yourself, e.g. using the Encode module. 294to be done yourself, e.g. using the Encode module.
263 295
264Example, output UTF-16BE-encoded JSON: 296Example, output UTF-16BE-encoded JSON:
265 297
266 use Encode; 298 use Encode;
288 ] 320 ]
289 } 321 }
290 322
291=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
292 324
325=item $enabled = $json->get_indent
326
293If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
295into its own line, identing them properly. 329into its own line, indenting them properly.
296 330
297If C<$enable> is false, no newlines or indenting will be produced, and the 331If C<$enable> is false, no newlines or indenting will be produced, and the
298resulting JSON text is guarenteed not to contain any C<newlines>. 332resulting JSON text is guaranteed not to contain any C<newlines>.
299 333
300This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
301 335
302=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
337
338=item $enabled = $json->get_space_before
303 339
304If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
305optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
306 342
307If C<$enable> is false, then the C<encode> method will not add any extra 343If C<$enable> is false, then the C<encode> method will not add any extra
313Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
314 350
315 {"key" :"value"} 351 {"key" :"value"}
316 352
317=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
318 356
319If C<$enable> is true (or missing), then the C<encode> method will add an extra 357If C<$enable> is true (or missing), then the C<encode> method will add an extra
320optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
321and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
322members. 360members.
329Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
330 368
331 {"key": "value"} 369 {"key": "value"}
332 370
333=item $json = $json->relaxed ([$enable]) 371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
334 374
335If C<$enable> is true (or missing), then C<decode> will accept some 375If C<$enable> is true (or missing), then C<decode> will accept some
336extensions to normal JSON syntax (see below). C<encode> will not be 376extensions to normal JSON syntax (see below). C<encode> will not be
337affected in anyway. I<Be aware that this option makes you accept invalid 377affected in anyway. I<Be aware that this option makes you accept invalid
338JSON texts as if they were valid!>. I suggest only to use this option to 378JSON texts as if they were valid!>. I suggest only to use this option to
375 415
376=back 416=back
377 417
378=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
379 419
420=item $enabled = $json->get_canonical
421
380If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
382 424
383If C<$enable> is false, then the C<encode> method will output key-value 425If C<$enable> is false, then the C<encode> method will output key-value
384pairs in the order Perl stores them (which will likely change between runs 426pairs in the order Perl stores them (which will likely change between runs
385of the same script). 427of the same script).
386 428
387This option is useful if you want the same data structure to be encoded as 429This option is useful if you want the same data structure to be encoded as
388the same JSON text (given the same overall settings). If it is disabled, 430the same JSON text (given the same overall settings). If it is disabled,
389the same hash migh be encoded differently even if contains the same data, 431the same hash might be encoded differently even if contains the same data,
390as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
391 433
392This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
393 435
394=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
395 439
396If C<$enable> is true (or missing), then the C<encode> method can convert a 440If C<$enable> is true (or missing), then the C<encode> method can convert a
397non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
398which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 442which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
399values instead of croaking. 443values instead of croaking.
409 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
410 => "Hello, World!" 454 => "Hello, World!"
411 455
412=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
413 457
458=item $enabled = $json->get_allow_blessed
459
414If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
415barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
416B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
418object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
420 466
421If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
422exception when it encounters a blessed object. 468exception when it encounters a blessed object.
423 469
424=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
425 473
426If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
427blessed object, will check for the availability of the C<TO_JSON> method 475blessed object, will check for the availability of the C<TO_JSON> method
428on the object's class. If found, it will be called in scalar context 476on the object's class. If found, it will be called in scalar context
429and the resulting scalar will be encoded instead of the object. If no 477and the resulting scalar will be encoded instead of the object. If no
433The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> 481The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
434returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
435way. C<TO_JSON> must take care of not causing an endless recursion cycle 483way. C<TO_JSON> must take care of not causing an endless recursion cycle
436(== crash) in this case. The name of C<TO_JSON> was chosen because other 484(== crash) in this case. The name of C<TO_JSON> was chosen because other
437methods called by the Perl core (== not by the user of the object) are 485methods called by the Perl core (== not by the user of the object) are
438usually in upper case letters and to avoid collisions with the C<to_json> 486usually in upper case letters and to avoid collisions with any C<to_json>
439function. 487function or method.
440 488
441This setting does not yet influence C<decode> in any way, but in the 489This setting does not yet influence C<decode> in any way, but in the
442future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
443enabled by this setting. 491enabled by this setting.
444 492
486 534
487As this callback gets called less often then the C<filter_json_object> 535As this callback gets called less often then the C<filter_json_object>
488one, decoding speed will not usually suffer as much. Therefore, single-key 536one, decoding speed will not usually suffer as much. Therefore, single-key
489objects make excellent targets to serialise Perl objects into, especially 537objects make excellent targets to serialise Perl objects into, especially
490as single-key JSON objects are as close to the type-tagged value concept 538as single-key JSON objects are as close to the type-tagged value concept
491as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not 539as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
492support this in any way, so you need to make sure your data never looks 540support this in any way, so you need to make sure your data never looks
493like a serialised Perl hash. 541like a serialised Perl hash.
494 542
495Typical names for the single object key are C<__class_whatever__>, or 543Typical names for the single object key are C<__class_whatever__>, or
496C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
520 568
521 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
522 } 570 }
523 571
524=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
525 575
526Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
527strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
528C<encode> or C<decode> to their minimum size possible. This can save 578C<encode> or C<decode> to their minimum size possible. This can save
529memory when your JSON texts are either very very long or you have many 579memory when your JSON texts are either very very long or you have many
547strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
548internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
549 599
550=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
551 601
602=item $max_depth = $json->get_max_depth
603
552Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
553or decoding. If the JSON text or Perl data structure has an equal or 605or decoding. If the JSON text or Perl data structure has an equal or
554higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
555stop and croak at that point. 607stop and croak at that point.
556 608
567used, which is rarely useful. 619used, which is rarely useful.
568 620
569See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
570 622
571=item $json = $json->max_size ([$maximum_string_size]) 623=item $json = $json->max_size ([$maximum_string_size])
624
625=item $max_size = $json->get_max_size
572 626
573Set the maximum length a JSON text may have (in bytes) where decoding is 627Set the maximum length a JSON text may have (in bytes) where decoding is
574being attempted. The default is C<0>, meaning no limit. When C<decode> 628being attempted. The default is C<0>, meaning no limit. When C<decode>
575is called on a string longer then this number of characters it will not 629is called on a string longer then this number of characters it will not
576attempt to decode the string but throw an exception. This setting has no 630attempt to decode the string but throw an exception. This setting has no
623vice versa. These mappings are designed to "do the right thing" in most 677vice versa. These mappings are designed to "do the right thing" in most
624circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
625(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
626 680
627For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
628lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
629refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
630 684
631 685
632=head2 JSON -> PERL 686=head2 JSON -> PERL
633 687
634=over 4 688=over 4
635 689
636=item object 690=item object
637 691
638A JSON object becomes a reference to a hash in Perl. No ordering of object 692A JSON object becomes a reference to a hash in Perl. No ordering of object
639keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
640 694
641=item array 695=item array
642 696
643A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
644 698
670 724
671=item true, false 725=item true, false
672 726
673These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 727These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
674respectively. They are overloaded to act almost exactly like the numbers 728respectively. They are overloaded to act almost exactly like the numbers
675C<1> and C<0>. You can check wether a scalar is a JSON boolean by using 729C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
676the C<JSON::XS::is_bool> function. 730the C<JSON::XS::is_bool> function.
677 731
678=item null 732=item null
679 733
680A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
711Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
712exception to be thrown, except for references to the integers C<0> and 766exception to be thrown, except for references to the integers C<0> and
713C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 767C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
714also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 768also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
715 769
716 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
717 771
718=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
719 773
720These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
721respectively. You can also use C<\1> and C<\0> directly if you want. 775respectively. You can also use C<\1> and C<\0> directly if you want.
722 776
723=item blessed objects 777=item blessed objects
724 778
725Blessed objects are not allowed. JSON::XS currently tries to encode their 779Blessed objects are not directly representable in JSON. See the
726underlying representation (hash- or arrayref), but this behaviour might 780C<allow_blessed> and C<convert_blessed> methods on various options on
727change in future versions. 781how to deal with this: basically, you can choose between throwing an
782exception, encoding the reference as if it weren't blessed, or provide
783your own serialiser method.
728 784
729=item simple scalars 785=item simple scalars
730 786
731Simple Perl scalars (any scalar that is not a reference) are the most 787Simple Perl scalars (any scalar that is not a reference) are the most
732difficult objects to encode: JSON::XS will encode undefined scalars as 788difficult objects to encode: JSON::XS will encode undefined scalars as
733JSON null value, scalars that have last been used in a string context 789JSON C<null> values, scalars that have last been used in a string context
734before encoding as JSON strings and anything else as number value: 790before encoding as JSON strings, and anything else as number value:
735 791
736 # dump as number 792 # dump as number
737 to_json [2] # yields [2] 793 encode_json [2] # yields [2]
738 to_json [-3.0e17] # yields [-3e+17] 794 encode_json [-3.0e17] # yields [-3e+17]
739 my $value = 5; to_json [$value] # yields [5] 795 my $value = 5; encode_json [$value] # yields [5]
740 796
741 # used as string, so dump as string 797 # used as string, so dump as string
742 print $value; 798 print $value;
743 to_json [$value] # yields ["5"] 799 encode_json [$value] # yields ["5"]
744 800
745 # undef becomes null 801 # undef becomes null
746 to_json [undef] # yields [null] 802 encode_json [undef] # yields [null]
747 803
748You can force the type to be a string by stringifying it: 804You can force the type to be a JSON string by stringifying it:
749 805
750 my $x = 3.1; # some variable containing a number 806 my $x = 3.1; # some variable containing a number
751 "$x"; # stringified 807 "$x"; # stringified
752 $x .= ""; # another, more awkward way to stringify 808 $x .= ""; # another, more awkward way to stringify
753 print $x; # perl does it for you, too, quite often 809 print $x; # perl does it for you, too, quite often
754 810
755You can force the type to be a number by numifying it: 811You can force the type to be a JSON number by numifying it:
756 812
757 my $x = "3"; # some variable containing a string 813 my $x = "3"; # some variable containing a string
758 $x += 0; # numify it, ensuring it will be dumped as a number 814 $x += 0; # numify it, ensuring it will be dumped as a number
759 $x *= 1; # same thing, the choise is yours. 815 $x *= 1; # same thing, the choice is yours.
760 816
761You can not currently output JSON booleans or force the type in other, 817You can not currently force the type in other, less obscure, ways. Tell me
762less obscure, ways. Tell me if you need this capability. 818if you need this capability (but don't forget to explain why its needed
819:).
763 820
764=back 821=back
765 822
766 823
767=head1 COMPARISON 824=head1 COMPARISON
776 833
777=item JSON 1.07 834=item JSON 1.07
778 835
779Slow (but very portable, as it is written in pure Perl). 836Slow (but very portable, as it is written in pure Perl).
780 837
781Undocumented/buggy Unicode handling (how JSON handles unicode values is 838Undocumented/buggy Unicode handling (how JSON handles Unicode values is
782undocumented. One can get far by feeding it unicode strings and doing 839undocumented. One can get far by feeding it Unicode strings and doing
783en-/decoding oneself, but unicode escapes are not working properly). 840en-/decoding oneself, but Unicode escapes are not working properly).
784 841
785No roundtripping (strings get clobbered if they look like numbers, e.g. 842No round-tripping (strings get clobbered if they look like numbers, e.g.
786the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 843the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
787decode into the number 2. 844decode into the number 2.
788 845
789=item JSON::PC 0.01 846=item JSON::PC 0.01
790 847
791Very fast. 848Very fast.
792 849
793Undocumented/buggy Unicode handling. 850Undocumented/buggy Unicode handling.
794 851
795No roundtripping. 852No round-tripping.
796 853
797Has problems handling many Perl values (e.g. regex results and other magic 854Has problems handling many Perl values (e.g. regex results and other magic
798values will make it croak). 855values will make it croak).
799 856
800Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 857Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
810Very inflexible (no human-readable format supported, format pretty much 867Very inflexible (no human-readable format supported, format pretty much
811undocumented. I need at least a format for easy reading by humans and a 868undocumented. I need at least a format for easy reading by humans and a
812single-line compact format for use in a protocol, and preferably a way to 869single-line compact format for use in a protocol, and preferably a way to
813generate ASCII-only JSON texts). 870generate ASCII-only JSON texts).
814 871
815Completely broken (and confusingly documented) Unicode handling (unicode 872Completely broken (and confusingly documented) Unicode handling (Unicode
816escapes are not working properly, you need to set ImplicitUnicode to 873escapes are not working properly, you need to set ImplicitUnicode to
817I<different> values on en- and decoding to get symmetric behaviour). 874I<different> values on en- and decoding to get symmetric behaviour).
818 875
819No roundtripping (simple cases work, but this depends on wether the scalar 876No round-tripping (simple cases work, but this depends on whether the scalar
820value was used in a numeric context or not). 877value was used in a numeric context or not).
821 878
822Dumping hashes may skip hash values depending on iterator state. 879Dumping hashes may skip hash values depending on iterator state.
823 880
824Unmaintained (maintainer unresponsive for many months, bugs are not 881Unmaintained (maintainer unresponsive for many months, bugs are not
825getting fixed). 882getting fixed).
826 883
827Does not check input for validity (i.e. will accept non-JSON input and 884Does not check input for validity (i.e. will accept non-JSON input and
828return "something" instead of raising an exception. This is a security 885return "something" instead of raising an exception. This is a security
829issue: imagine two banks transfering money between each other using 886issue: imagine two banks transferring money between each other using
830JSON. One bank might parse a given non-JSON request and deduct money, 887JSON. One bank might parse a given non-JSON request and deduct money,
831while the other might reject the transaction with a syntax error. While a 888while the other might reject the transaction with a syntax error. While a
832good protocol will at least recover, that is extra unnecessary work and 889good protocol will at least recover, that is extra unnecessary work and
833the transaction will still not succeed). 890the transaction will still not succeed).
834 891
835=item JSON::DWIW 0.04 892=item JSON::DWIW 0.04
836 893
837Very fast. Very natural. Very nice. 894Very fast. Very natural. Very nice.
838 895
839Undocumented unicode handling (but the best of the pack. Unicode escapes 896Undocumented Unicode handling (but the best of the pack. Unicode escapes
840still don't get parsed properly). 897still don't get parsed properly).
841 898
842Very inflexible. 899Very inflexible.
843 900
844No roundtripping. 901No round-tripping.
845 902
846Does not generate valid JSON texts (key strings are often unquoted, empty keys 903Does not generate valid JSON texts (key strings are often unquoted, empty keys
847result in nothing being output) 904result in nothing being output)
848 905
849Does not check input for validity. 906Does not check input for validity.
851=back 908=back
852 909
853 910
854=head2 JSON and YAML 911=head2 JSON and YAML
855 912
856You often hear that JSON is a subset (or a close subset) of YAML. This is, 913You often hear that JSON is a subset of YAML. This is, however, a mass
857however, a mass hysteria and very far from the truth. In general, there is 914hysteria(*) and very far from the truth. In general, there is no way to
858no way to configure JSON::XS to output a data structure as valid YAML. 915configure JSON::XS to output a data structure as valid YAML that works for
916all cases.
859 917
860If you really must use JSON::XS to generate YAML, you should use this 918If you really must use JSON::XS to generate YAML, you should use this
861algorithm (subject to change in future versions): 919algorithm (subject to change in future versions):
862 920
863 my $to_yaml = JSON::XS->new->utf8->space_after (1); 921 my $to_yaml = JSON::XS->new->utf8->space_after (1);
864 my $yaml = $to_yaml->encode ($ref) . "\n"; 922 my $yaml = $to_yaml->encode ($ref) . "\n";
865 923
866This will usually generate JSON texts that also parse as valid 924This will I<usually> generate JSON texts that also parse as valid
867YAML. Please note that YAML has hardcoded limits on (simple) object key 925YAML. Please note that YAML has hardcoded limits on (simple) object key
868lengths that JSON doesn't have, so you should make sure that your hash 926lengths that JSON doesn't have and also has different and incompatible
927unicode handling, so you should make sure that your hash keys are
869keys are noticably shorter than the 1024 characters YAML allows. 928noticeably shorter than the 1024 "stream characters" YAML allows and that
929you do not have codepoints with values outside the Unicode BMP (basic
930multilingual page). YAML also does not allow C<\/> sequences in strings
931(which JSON::XS does not I<currently> generate).
870 932
871There might be other incompatibilities that I am not aware of. In general 933There might be other incompatibilities that I am not aware of (or the YAML
934specification has been changed yet again - it does so quite often). In
872you should not try to generate YAML with a JSON generator or vice versa, 935general you should not try to generate YAML with a JSON generator or vice
873or try to parse JSON with a YAML parser or vice versa: chances are high 936versa, or try to parse JSON with a YAML parser or vice versa: chances are
874that you will run into severe interoperability problems. 937high that you will run into severe interoperability problems when you
938least expect it.
939
940=over 4
941
942=item (*)
943
944This is spread actively by the YAML team, however. For many years now they
945claim YAML were a superset of JSON, even when proven otherwise.
946
947Even the author of this manpage was at some point accused of providing
948"incorrect" information, despite the evidence presented (claims ranged
949from "your documentation contains inaccurate and negative statements about
950YAML" (the only negative comment is this footnote, and it didn't exist
951back then; the question on which claims were inaccurate was never answered
952etc.) to "the YAML spec is not up-to-date" (the *real* and supposedly
953JSON-compatible spec is apparently not currently publicly available)
954to actual requests to replace this section by *incorrect* information,
955suppressing information about the real problem).
956
957So whenever you are told that YAML was a superset of JSON, first check
958wether it is really true (it might be when you check it, but it certainly
959was not true when this was written). I would much prefer if the YAML team
960would spent their time on actually making JSON compatibility a truth
961(JSON, after all, has a very small and simple specification) instead of
962trying to lobby/force people into reporting untruths.
963
964=back
875 965
876 966
877=head2 SPEED 967=head2 SPEED
878 968
879It seems that JSON::XS is surprisingly fast, as shown in the following 969It seems that JSON::XS is surprisingly fast, as shown in the following
890It shows the number of encodes/decodes per second (JSON::XS uses 980It shows the number of encodes/decodes per second (JSON::XS uses
891the functional interface, while JSON::XS/2 uses the OO interface 981the functional interface, while JSON::XS/2 uses the OO interface
892with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 982with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893shrink). Higher is better: 983shrink). Higher is better:
894 984
895 Storable | 15779.925 | 14169.946 |
896 -----------+------------+------------+
897 module | encode | decode | 985 module | encode | decode |
898 -----------|------------|------------| 986 -----------|------------|------------|
899 JSON | 4990.842 | 4088.813 | 987 JSON 1.x | 4990.842 | 4088.813 |
900 JSON::DWIW | 51653.990 | 71575.154 | 988 JSON::DWIW | 51653.990 | 71575.154 |
901 JSON::PC | 65948.176 | 74631.744 | 989 JSON::PC | 65948.176 | 74631.744 |
902 JSON::PP | 8931.652 | 3817.168 | 990 JSON::PP | 8931.652 | 3817.168 |
903 JSON::Syck | 24877.248 | 27776.848 | 991 JSON::Syck | 24877.248 | 27776.848 |
904 JSON::XS | 388361.481 | 227951.304 | 992 JSON::XS | 388361.481 | 227951.304 |
906 JSON::XS/3 | 338250.323 | 218453.333 | 994 JSON::XS/3 | 338250.323 | 218453.333 |
907 Storable | 16500.016 | 135300.129 | 995 Storable | 16500.016 | 135300.129 |
908 -----------+------------+------------+ 996 -----------+------------+------------+
909 997
910That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 998That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
911about three times faster on decoding, and over fourty times faster 999about three times faster on decoding, and over forty times faster
912than JSON, even with pretty-printing and key sorting. It also compares 1000than JSON, even with pretty-printing and key sorting. It also compares
913favourably to Storable for small amounts of data. 1001favourably to Storable for small amounts of data.
914 1002
915Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1003Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916search API (http://nanoref.com/yahooapis/mgPdGg): 1004search API (http://nanoref.com/yahooapis/mgPdGg):
917 1005
918 module | encode | decode | 1006 module | encode | decode |
919 -----------|------------|------------| 1007 -----------|------------|------------|
920 JSON | 55.260 | 34.971 | 1008 JSON 1.x | 55.260 | 34.971 |
921 JSON::DWIW | 825.228 | 1082.513 | 1009 JSON::DWIW | 825.228 | 1082.513 |
922 JSON::PC | 3571.444 | 2394.829 | 1010 JSON::PC | 3571.444 | 2394.829 |
923 JSON::PP | 210.987 | 32.574 | 1011 JSON::PP | 210.987 | 32.574 |
924 JSON::Syck | 552.551 | 787.544 | 1012 JSON::Syck | 552.551 | 787.544 |
925 JSON::XS | 5780.463 | 4854.519 | 1013 JSON::XS | 5780.463 | 4854.519 |
929 -----------+------------+------------+ 1017 -----------+------------+------------+
930 1018
931Again, JSON::XS leads by far (except for Storable which non-surprisingly 1019Again, JSON::XS leads by far (except for Storable which non-surprisingly
932decodes faster). 1020decodes faster).
933 1021
934On large strings containing lots of high unicode characters, some modules 1022On large strings containing lots of high Unicode characters, some modules
935(such as JSON::PC) seem to decode faster than JSON::XS, but the result 1023(such as JSON::PC) seem to decode faster than JSON::XS, but the result
936will be broken due to missing (or wrong) unicode handling. Others refuse 1024will be broken due to missing (or wrong) Unicode handling. Others refuse
937to decode or encode properly, so it was impossible to prepare a fair 1025to decode or encode properly, so it was impossible to prepare a fair
938comparison table for that case. 1026comparison table for that case.
939 1027
940 1028
941=head1 SECURITY CONSIDERATIONS 1029=head1 SECURITY CONSIDERATIONS
947any buffer overflows. Obviously, this module should ensure that and I am 1035any buffer overflows. Obviously, this module should ensure that and I am
948trying hard on making that true, but you never know. 1036trying hard on making that true, but you never know.
949 1037
950Second, you need to avoid resource-starving attacks. That means you should 1038Second, you need to avoid resource-starving attacks. That means you should
951limit the size of JSON texts you accept, or make sure then when your 1039limit the size of JSON texts you accept, or make sure then when your
952resources run out, thats just fine (e.g. by using a separate process that 1040resources run out, that's just fine (e.g. by using a separate process that
953can crash safely). The size of a JSON text in octets or characters is 1041can crash safely). The size of a JSON text in octets or characters is
954usually a good indication of the size of the resources required to decode 1042usually a good indication of the size of the resources required to decode
955it into a Perl structure. While JSON::XS can check the size of the JSON 1043it into a Perl structure. While JSON::XS can check the size of the JSON
956text, it might be too late when you already have it in memory, so you 1044text, it might be too late when you already have it in memory, so you
957might want to check the size before you accept the string. 1045might want to check the size before you accept the string.
958 1046
959Third, JSON::XS recurses using the C stack when decoding objects and 1047Third, JSON::XS recurses using the C stack when decoding objects and
960arrays. The C stack is a limited resource: for instance, on my amd64 1048arrays. The C stack is a limited resource: for instance, on my amd64
961machine with 8MB of stack size I can decode around 180k nested arrays but 1049machine with 8MB of stack size I can decode around 180k nested arrays but
962only 14k nested JSON objects (due to perl itself recursing deeply on croak 1050only 14k nested JSON objects (due to perl itself recursing deeply on croak
963to free the temporary). If that is exceeded, the program crashes. to be 1051to free the temporary). If that is exceeded, the program crashes. To be
964conservative, the default nesting limit is set to 512. If your process 1052conservative, the default nesting limit is set to 512. If your process
965has a smaller stack, you should adjust this setting accordingly with the 1053has a smaller stack, you should adjust this setting accordingly with the
966C<max_depth> method. 1054C<max_depth> method.
967 1055
968And last but least, something else could bomb you that I forgot to think 1056And last but least, something else could bomb you that I forgot to think
969of. In that case, you get to keep the pieces. I am always open for hints, 1057of. In that case, you get to keep the pieces. I am always open for hints,
970though... 1058though...
971 1059
972If you are using JSON::XS to return packets to consumption 1060If you are using JSON::XS to return packets to consumption
973by javascript scripts in a browser you should have a look at 1061by JavaScript scripts in a browser you should have a look at
974L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1062L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
975you are vulnerable to some common attack vectors (which really are browser 1063you are vulnerable to some common attack vectors (which really are browser
976design bugs, but it is still you who will have to deal with it, as major 1064design bugs, but it is still you who will have to deal with it, as major
977browser developers care only for features, not about doing security 1065browser developers care only for features, not about getting security
978right). 1066right).
979 1067
980 1068
981=head1 THREADS 1069=head1 THREADS
982 1070
983This module is I<not> guarenteed to be thread safe and there are no 1071This module is I<not> guaranteed to be thread safe and there are no
984plans to change this until Perl gets thread support (as opposed to the 1072plans to change this until Perl gets thread support (as opposed to the
985horribly slow so-called "threads" which are simply slow and bloated 1073horribly slow so-called "threads" which are simply slow and bloated
986process simulations - use fork, its I<much> faster, cheaper, better). 1074process simulations - use fork, its I<much> faster, cheaper, better).
987 1075
988(It might actually work, but you ahve ben warned). 1076(It might actually work, but you have been warned).
989 1077
990 1078
991=head1 BUGS 1079=head1 BUGS
992 1080
993While the goal of this module is to be correct, that unfortunately does 1081While the goal of this module is to be correct, that unfortunately does

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