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Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.80 by root, Sat Dec 29 17:22:39 2007 UTC

1=encoding utf-8
2
3=head1 NAME 1=head1 NAME
4 2
5JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
6 4
7JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ 5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
12 use JSON::XS; 10 use JSON::XS;
13 11
14 # exported functions, they croak on error 12 # exported functions, they croak on error
15 # and expect/generate UTF-8 13 # and expect/generate UTF-8
16 14
17 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
18 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
19 17
20 # OO-interface 18 # OO-interface
21 19
22 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
23 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
24 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
25 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
26=head1 DESCRIPTION 32=head1 DESCRIPTION
27 33
28This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
29primary 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
30I<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.
31 45
32As 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
33to 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
34modules, 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
35their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
42 56
43=head2 FEATURES 57=head2 FEATURES
44 58
45=over 4 59=over 4
46 60
47=item * correct unicode handling 61=item * correct Unicode handling
48 62
49This 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
50it does so. 64it does so.
51 65
52=item * round-trip integrity 66=item * round-trip integrity
72This 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
73interface. 87interface.
74 88
75=item * reasonably versatile output formats 89=item * reasonably versatile output formats
76 90
77You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
78possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
79(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
80unicode 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
81stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
82 96
83=back 97=back
84 98
85=cut 99=cut
86 100
87package JSON::XS; 101package JSON::XS;
88 102
89use strict; 103use strict;
90 104
91our $VERSION = '1.5'; 105our $VERSION = '2.01';
92our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
93 107
94our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
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}
95 119
96use Exporter; 120use Exporter;
97use XSLoader; 121use XSLoader;
98 122
99=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
100 124
101The following convinience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
102exported by default: 126exported by default:
103 127
104=over 4 128=over 4
105 129
106=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
107 131
108Converts the given Perl data structure (a simple scalar or a reference to 132Converts the given Perl data structure to a UTF-8 encoded, binary string
109a hash or array) to a UTF-8 encoded, binary string (that is, the string contains 133(that is, the string contains octets only). Croaks on error.
110octets only). Croaks on error.
111 134
112This function call is functionally identical to: 135This function call is functionally identical to:
113 136
114 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115 138
116except being faster. 139except being faster.
117 140
118=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
119 142
120The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to 143The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
121parse that as an UTF-8 encoded JSON text, returning the resulting simple 144to parse that as an UTF-8 encoded JSON text, returning the resulting
122scalar or reference. Croaks on error. 145reference. Croaks on error.
123 146
124This function call is functionally identical to: 147This function call is functionally identical to:
125 148
126 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 149 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127 150
137Perl. 160Perl.
138 161
139=back 162=back
140 163
141 164
165=head1 A FEW NOTES ON UNICODE AND PERL
166
167Since this often leads to confusion, here are a few very clear words on
168how Unicode works in Perl, modulo bugs.
169
170=over 4
171
172=item 1. Perl strings can store characters with ordinal values > 255.
173
174This enables you to store Unicode characters as single characters in a
175Perl string - very natural.
176
177=item 2. Perl does I<not> associate an encoding with your strings.
178
179Unless you force it to, e.g. when matching it against a regex, or printing
180the scalar to a file, in which case Perl either interprets your string as
181locale-encoded text, octets/binary, or as Unicode, depending on various
182settings. In no case is an encoding stored together with your data, it is
183I<use> that decides encoding, not any magical metadata.
184
185=item 3. The internal utf-8 flag has no meaning with regards to the
186encoding of your string.
187
188Just ignore that flag unless you debug a Perl bug, a module written in
189XS or want to dive into the internals of perl. Otherwise it will only
190confuse you, as, despite the name, it says nothing about how your string
191is encoded. You can have Unicode strings with that flag set, with that
192flag clear, and you can have binary data with that flag set and that flag
193clear. Other possibilities exist, too.
194
195If you didn't know about that flag, just the better, pretend it doesn't
196exist.
197
198=item 4. A "Unicode String" is simply a string where each character can be
199validly interpreted as a Unicode codepoint.
200
201If you have UTF-8 encoded data, it is no longer a Unicode string, but a
202Unicode string encoded in UTF-8, giving you a binary string.
203
204=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
205
206It's a fact. Learn to live with it.
207
208=back
209
210I hope this helps :)
211
212
142=head1 OBJECT-ORIENTED INTERFACE 213=head1 OBJECT-ORIENTED INTERFACE
143 214
144The object oriented interface lets you configure your own encoding or 215The object oriented interface lets you configure your own encoding or
145decoding style, within the limits of supported formats. 216decoding style, within the limits of supported formats.
146 217
157 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]})
158 => {"a": [1, 2]} 229 => {"a": [1, 2]}
159 230
160=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
161 232
233=item $enabled = $json->get_ascii
234
162If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
163generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
164unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
165single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
166as per RFC4627. The resulting encoded JSON text can be treated as a native 239as per RFC4627. The resulting encoded JSON text can be treated as a native
167unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 240Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
168or any other superset of ASCII. 241or any other superset of ASCII.
169 242
170If C<$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
171characters unless required by the JSON syntax or other flags. This results 244characters unless required by the JSON syntax or other flags. This results
172in a faster and more compact format. 245in a faster and more compact format.
178 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
179 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
180 253
181=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
182 255
256=item $enabled = $json->get_latin1
257
183If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
184the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
185outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
186latin1-encoded JSON text or a native unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
187will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
188expects unicode, which is a strict superset of latin1. 263expects Unicode, which is a strict superset of latin1.
189 264
190If C<$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
191characters unless required by the JSON syntax or other flags. 266characters unless required by the JSON syntax or other flags.
192 267
193The 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
194text, 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
195size. The disadvantage is that the resulting JSON text is encoded 270size. The disadvantage is that the resulting JSON text is encoded
196in latin1 (and must correctly be treated as such when storing and 271in latin1 (and must correctly be treated as such when storing and
197transfering), a rare encoding for JSON. It is therefore most useful when 272transferring), a rare encoding for JSON. It is therefore most useful when
198you want to store data structures known to contain binary data efficiently 273you want to store data structures known to contain binary data efficiently
199in files or databases, not when talking to other JSON encoders/decoders. 274in files or databases, not when talking to other JSON encoders/decoders.
200 275
201 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
202 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
203 278
204=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
205 282
206If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
207the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
208C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
209note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
210range C<0..255>, they are thus useful for bytewise/binary I/O. In future 287range C<0..255>, they are thus useful for bytewise/binary I/O. In future
211versions, enabling this option might enable autodetection of the UTF-16 288versions, enabling this option might enable autodetection of the UTF-16
212and UTF-32 encoding families, as described in RFC4627. 289and UTF-32 encoding families, as described in RFC4627.
213 290
214If C<$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
215string 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
216unicode 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
217to be done yourself, e.g. using the Encode module. 294to be done yourself, e.g. using the Encode module.
218 295
219Example, output UTF-16BE-encoded JSON: 296Example, output UTF-16BE-encoded JSON:
220 297
221 use Encode; 298 use Encode;
243 ] 320 ]
244 } 321 }
245 322
246=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
247 324
325=item $enabled = $json->get_indent
326
248If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
249format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
250into its own line, identing them properly. 329into its own line, indenting them properly.
251 330
252If C<$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
253resulting JSON text is guarenteed not to contain any C<newlines>. 332resulting JSON text is guaranteed not to contain any C<newlines>.
254 333
255This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
256 335
257=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
337
338=item $enabled = $json->get_space_before
258 339
259If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
260optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
261 342
262If C<$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
268Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
269 350
270 {"key" :"value"} 351 {"key" :"value"}
271 352
272=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
273 356
274If C<$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
275optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
276and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
277members. 360members.
284Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
285 368
286 {"key": "value"} 369 {"key": "value"}
287 370
288=item $json = $json->relaxed ([$enable]) 371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
289 374
290If C<$enable> is true (or missing), then C<decode> will accept some 375If C<$enable> is true (or missing), then C<decode> will accept some
291extensions to normal JSON syntax (see below). C<encode> will not be 376extensions to normal JSON syntax (see below). C<encode> will not be
292affected 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
293JSON 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
330 415
331=back 416=back
332 417
333=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
334 419
420=item $enabled = $json->get_canonical
421
335If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
336by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
337 424
338If C<$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
339pairs 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
340of the same script). 427of the same script).
341 428
342This 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
343the 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,
344the 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,
345as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
346 433
347This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
348 435
349=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
350 439
351If C<$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
352non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
353which 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
354values instead of croaking. 443values instead of croaking.
364 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
365 => "Hello, World!" 454 => "Hello, World!"
366 455
367=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
368 457
458=item $enabled = $json->get_allow_blessed
459
369If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
370barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
371B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
372disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
373object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
374encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
375 466
376If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
377exception when it encounters a blessed object. 468exception when it encounters a blessed object.
378 469
379=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
380 473
381If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
382blessed 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
383on 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
384and 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
388The 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>
389returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
390way. 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
391(== 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
392methods 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
393usually 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>
394function. 487function or method.
395 488
396This 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
397future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
398enabled by this setting. 491enabled by this setting.
399 492
441 534
442As 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>
443one, decoding speed will not usually suffer as much. Therefore, single-key 536one, decoding speed will not usually suffer as much. Therefore, single-key
444objects make excellent targets to serialise Perl objects into, especially 537objects make excellent targets to serialise Perl objects into, especially
445as 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
446as 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
447support 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
448like a serialised Perl hash. 541like a serialised Perl hash.
449 542
450Typical names for the single object key are C<__class_whatever__>, or 543Typical names for the single object key are C<__class_whatever__>, or
451C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
475 568
476 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
477 } 570 }
478 571
479=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
480 575
481Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
482strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
483C<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
484memory 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
502strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
503internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
504 599
505=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
506 601
602=item $max_depth = $json->get_max_depth
603
507Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
508or 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
509higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
510stop and croak at that point. 607stop and croak at that point.
511 608
522used, which is rarely useful. 619used, which is rarely useful.
523 620
524See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
525 622
526=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
527 626
528Set 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
529being 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>
530is 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
531attempt 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
578vice 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
579circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
580(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
581 680
582For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
583lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
584refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
585 684
586 685
587=head2 JSON -> PERL 686=head2 JSON -> PERL
588 687
589=over 4 688=over 4
590 689
591=item object 690=item object
592 691
593A 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
594keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
595 694
596=item array 695=item array
597 696
598A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
599 698
625 724
626=item true, false 725=item true, false
627 726
628These 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>,
629respectively. They are overloaded to act almost exactly like the numbers 728respectively. They are overloaded to act almost exactly like the numbers
630C<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
631the C<JSON::XS::is_bool> function. 730the C<JSON::XS::is_bool> function.
632 731
633=item null 732=item null
634 733
635A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
666Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
667exception 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
668C<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
669also 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.
670 769
671 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
672 771
673=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
674 773
675These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
676respectively. 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.
687difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
688JSON null value, scalars that have last been used in a string context 787JSON null value, scalars that have last been used in a string context
689before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
690 789
691 # dump as number 790 # dump as number
692 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
693 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
694 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
695 794
696 # used as string, so dump as string 795 # used as string, so dump as string
697 print $value; 796 print $value;
698 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
699 798
700 # undef becomes null 799 # undef becomes null
701 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
702 801
703You can force the type to be a string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
704 803
705 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
706 "$x"; # stringified 805 "$x"; # stringified
707 $x .= ""; # another, more awkward way to stringify 806 $x .= ""; # another, more awkward way to stringify
708 print $x; # perl does it for you, too, quite often 807 print $x; # perl does it for you, too, quite often
709 808
710You can force the type to be a number by numifying it: 809You can force the type to be a JSON number by numifying it:
711 810
712 my $x = "3"; # some variable containing a string 811 my $x = "3"; # some variable containing a string
713 $x += 0; # numify it, ensuring it will be dumped as a number 812 $x += 0; # numify it, ensuring it will be dumped as a number
714 $x *= 1; # same thing, the choise is yours. 813 $x *= 1; # same thing, the choice is yours.
715 814
716You can not currently output JSON booleans or force the type in other, 815You can not currently force the type in other, less obscure, ways. Tell me
717less obscure, ways. Tell me if you need this capability. 816if you need this capability.
718 817
719=back 818=back
720 819
721 820
722=head1 COMPARISON 821=head1 COMPARISON
731 830
732=item JSON 1.07 831=item JSON 1.07
733 832
734Slow (but very portable, as it is written in pure Perl). 833Slow (but very portable, as it is written in pure Perl).
735 834
736Undocumented/buggy Unicode handling (how JSON handles unicode values is 835Undocumented/buggy Unicode handling (how JSON handles Unicode values is
737undocumented. One can get far by feeding it unicode strings and doing 836undocumented. One can get far by feeding it Unicode strings and doing
738en-/decoding oneself, but unicode escapes are not working properly). 837en-/decoding oneself, but Unicode escapes are not working properly).
739 838
740No roundtripping (strings get clobbered if they look like numbers, e.g. 839No round-tripping (strings get clobbered if they look like numbers, e.g.
741the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will 840the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
742decode into the number 2. 841decode into the number 2.
743 842
744=item JSON::PC 0.01 843=item JSON::PC 0.01
745 844
746Very fast. 845Very fast.
747 846
748Undocumented/buggy Unicode handling. 847Undocumented/buggy Unicode handling.
749 848
750No roundtripping. 849No round-tripping.
751 850
752Has problems handling many Perl values (e.g. regex results and other magic 851Has problems handling many Perl values (e.g. regex results and other magic
753values will make it croak). 852values will make it croak).
754 853
755Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> 854Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
765Very inflexible (no human-readable format supported, format pretty much 864Very inflexible (no human-readable format supported, format pretty much
766undocumented. I need at least a format for easy reading by humans and a 865undocumented. I need at least a format for easy reading by humans and a
767single-line compact format for use in a protocol, and preferably a way to 866single-line compact format for use in a protocol, and preferably a way to
768generate ASCII-only JSON texts). 867generate ASCII-only JSON texts).
769 868
770Completely broken (and confusingly documented) Unicode handling (unicode 869Completely broken (and confusingly documented) Unicode handling (Unicode
771escapes are not working properly, you need to set ImplicitUnicode to 870escapes are not working properly, you need to set ImplicitUnicode to
772I<different> values on en- and decoding to get symmetric behaviour). 871I<different> values on en- and decoding to get symmetric behaviour).
773 872
774No roundtripping (simple cases work, but this depends on wether the scalar 873No round-tripping (simple cases work, but this depends on whether the scalar
775value was used in a numeric context or not). 874value was used in a numeric context or not).
776 875
777Dumping hashes may skip hash values depending on iterator state. 876Dumping hashes may skip hash values depending on iterator state.
778 877
779Unmaintained (maintainer unresponsive for many months, bugs are not 878Unmaintained (maintainer unresponsive for many months, bugs are not
780getting fixed). 879getting fixed).
781 880
782Does not check input for validity (i.e. will accept non-JSON input and 881Does not check input for validity (i.e. will accept non-JSON input and
783return "something" instead of raising an exception. This is a security 882return "something" instead of raising an exception. This is a security
784issue: imagine two banks transfering money between each other using 883issue: imagine two banks transferring money between each other using
785JSON. One bank might parse a given non-JSON request and deduct money, 884JSON. One bank might parse a given non-JSON request and deduct money,
786while the other might reject the transaction with a syntax error. While a 885while the other might reject the transaction with a syntax error. While a
787good protocol will at least recover, that is extra unnecessary work and 886good protocol will at least recover, that is extra unnecessary work and
788the transaction will still not succeed). 887the transaction will still not succeed).
789 888
790=item JSON::DWIW 0.04 889=item JSON::DWIW 0.04
791 890
792Very fast. Very natural. Very nice. 891Very fast. Very natural. Very nice.
793 892
794Undocumented unicode handling (but the best of the pack. Unicode escapes 893Undocumented Unicode handling (but the best of the pack. Unicode escapes
795still don't get parsed properly). 894still don't get parsed properly).
796 895
797Very inflexible. 896Very inflexible.
798 897
799No roundtripping. 898No round-tripping.
800 899
801Does not generate valid JSON texts (key strings are often unquoted, empty keys 900Does not generate valid JSON texts (key strings are often unquoted, empty keys
802result in nothing being output) 901result in nothing being output)
803 902
804Does not check input for validity. 903Does not check input for validity.
806=back 905=back
807 906
808 907
809=head2 JSON and YAML 908=head2 JSON and YAML
810 909
811You often hear that JSON is a subset (or a close subset) of YAML. This is, 910You often hear that JSON is a subset of YAML. This is, however, a mass
812however, a mass hysteria and very far from the truth. In general, there is 911hysteria and very far from the truth. In general, there is no way to
813no way to configure JSON::XS to output a data structure as valid YAML. 912configure JSON::XS to output a data structure as valid YAML that works for
913all cases.
814 914
815If you really must use JSON::XS to generate YAML, you should use this 915If you really must use JSON::XS to generate YAML, you should use this
816algorithm (subject to change in future versions): 916algorithm (subject to change in future versions):
817 917
818 my $to_yaml = JSON::XS->new->utf8->space_after (1); 918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
819 my $yaml = $to_yaml->encode ($ref) . "\n"; 919 my $yaml = $to_yaml->encode ($ref) . "\n";
820 920
821This will usually generate JSON texts that also parse as valid 921This will usually generate JSON texts that also parse as valid
822YAML. Please note that YAML has hardcoded limits on (simple) object key 922YAML. Please note that YAML has hardcoded limits on (simple) object key
823lengths that JSON doesn't have, so you should make sure that your hash 923lengths that JSON doesn't have and also has different and incompatible
924unicode handling, so you should make sure that your hash keys are
824keys are noticably shorter than the 1024 characters YAML allows. 925noticeably shorter than the 1024 "stream characters" YAML allows and that
926you do not have codepoints with values outside the Unicode BMP (basic
927multilingual page).
825 928
826There might be other incompatibilities that I am not aware of. In general 929There might be other incompatibilities that I am not aware of. In general
827you should not try to generate YAML with a JSON generator or vice versa, 930you should not try to generate YAML with a JSON generator or vice versa,
828or try to parse JSON with a YAML parser or vice versa: chances are high 931or try to parse JSON with a YAML parser or vice versa: chances are high
829that you will run into severe interoperability problems. 932that you will run into severe interoperability problems when you least
933expect it.
830 934
831 935
832=head2 SPEED 936=head2 SPEED
833 937
834It seems that JSON::XS is surprisingly fast, as shown in the following 938It seems that JSON::XS is surprisingly fast, as shown in the following
845It shows the number of encodes/decodes per second (JSON::XS uses 949It shows the number of encodes/decodes per second (JSON::XS uses
846the functional interface, while JSON::XS/2 uses the OO interface 950the functional interface, while JSON::XS/2 uses the OO interface
847with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 951with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
848shrink). Higher is better: 952shrink). Higher is better:
849 953
850 Storable | 15779.925 | 14169.946 |
851 -----------+------------+------------+
852 module | encode | decode | 954 module | encode | decode |
853 -----------|------------|------------| 955 -----------|------------|------------|
854 JSON | 4990.842 | 4088.813 | 956 JSON 1.x | 4990.842 | 4088.813 |
855 JSON::DWIW | 51653.990 | 71575.154 | 957 JSON::DWIW | 51653.990 | 71575.154 |
856 JSON::PC | 65948.176 | 74631.744 | 958 JSON::PC | 65948.176 | 74631.744 |
857 JSON::PP | 8931.652 | 3817.168 | 959 JSON::PP | 8931.652 | 3817.168 |
858 JSON::Syck | 24877.248 | 27776.848 | 960 JSON::Syck | 24877.248 | 27776.848 |
859 JSON::XS | 388361.481 | 227951.304 | 961 JSON::XS | 388361.481 | 227951.304 |
861 JSON::XS/3 | 338250.323 | 218453.333 | 963 JSON::XS/3 | 338250.323 | 218453.333 |
862 Storable | 16500.016 | 135300.129 | 964 Storable | 16500.016 | 135300.129 |
863 -----------+------------+------------+ 965 -----------+------------+------------+
864 966
865That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 967That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
866about three times faster on decoding, and over fourty times faster 968about three times faster on decoding, and over forty times faster
867than JSON, even with pretty-printing and key sorting. It also compares 969than JSON, even with pretty-printing and key sorting. It also compares
868favourably to Storable for small amounts of data. 970favourably to Storable for small amounts of data.
869 971
870Using a longer test string (roughly 18KB, generated from Yahoo! Locals 972Using a longer test string (roughly 18KB, generated from Yahoo! Locals
871search API (http://nanoref.com/yahooapis/mgPdGg): 973search API (http://nanoref.com/yahooapis/mgPdGg):
872 974
873 module | encode | decode | 975 module | encode | decode |
874 -----------|------------|------------| 976 -----------|------------|------------|
875 JSON | 55.260 | 34.971 | 977 JSON 1.x | 55.260 | 34.971 |
876 JSON::DWIW | 825.228 | 1082.513 | 978 JSON::DWIW | 825.228 | 1082.513 |
877 JSON::PC | 3571.444 | 2394.829 | 979 JSON::PC | 3571.444 | 2394.829 |
878 JSON::PP | 210.987 | 32.574 | 980 JSON::PP | 210.987 | 32.574 |
879 JSON::Syck | 552.551 | 787.544 | 981 JSON::Syck | 552.551 | 787.544 |
880 JSON::XS | 5780.463 | 4854.519 | 982 JSON::XS | 5780.463 | 4854.519 |
884 -----------+------------+------------+ 986 -----------+------------+------------+
885 987
886Again, JSON::XS leads by far (except for Storable which non-surprisingly 988Again, JSON::XS leads by far (except for Storable which non-surprisingly
887decodes faster). 989decodes faster).
888 990
889On large strings containing lots of high unicode characters, some modules 991On large strings containing lots of high Unicode characters, some modules
890(such as JSON::PC) seem to decode faster than JSON::XS, but the result 992(such as JSON::PC) seem to decode faster than JSON::XS, but the result
891will be broken due to missing (or wrong) unicode handling. Others refuse 993will be broken due to missing (or wrong) Unicode handling. Others refuse
892to decode or encode properly, so it was impossible to prepare a fair 994to decode or encode properly, so it was impossible to prepare a fair
893comparison table for that case. 995comparison table for that case.
894 996
895 997
896=head1 SECURITY CONSIDERATIONS 998=head1 SECURITY CONSIDERATIONS
902any buffer overflows. Obviously, this module should ensure that and I am 1004any buffer overflows. Obviously, this module should ensure that and I am
903trying hard on making that true, but you never know. 1005trying hard on making that true, but you never know.
904 1006
905Second, you need to avoid resource-starving attacks. That means you should 1007Second, you need to avoid resource-starving attacks. That means you should
906limit the size of JSON texts you accept, or make sure then when your 1008limit the size of JSON texts you accept, or make sure then when your
907resources run out, thats just fine (e.g. by using a separate process that 1009resources run out, that's just fine (e.g. by using a separate process that
908can crash safely). The size of a JSON text in octets or characters is 1010can crash safely). The size of a JSON text in octets or characters is
909usually a good indication of the size of the resources required to decode 1011usually a good indication of the size of the resources required to decode
910it into a Perl structure. While JSON::XS can check the size of the JSON 1012it into a Perl structure. While JSON::XS can check the size of the JSON
911text, it might be too late when you already have it in memory, so you 1013text, it might be too late when you already have it in memory, so you
912might want to check the size before you accept the string. 1014might want to check the size before you accept the string.
913 1015
914Third, JSON::XS recurses using the C stack when decoding objects and 1016Third, JSON::XS recurses using the C stack when decoding objects and
915arrays. The C stack is a limited resource: for instance, on my amd64 1017arrays. The C stack is a limited resource: for instance, on my amd64
916machine with 8MB of stack size I can decode around 180k nested arrays but 1018machine with 8MB of stack size I can decode around 180k nested arrays but
917only 14k nested JSON objects (due to perl itself recursing deeply on croak 1019only 14k nested JSON objects (due to perl itself recursing deeply on croak
918to free the temporary). If that is exceeded, the program crashes. to be 1020to free the temporary). If that is exceeded, the program crashes. To be
919conservative, the default nesting limit is set to 512. If your process 1021conservative, the default nesting limit is set to 512. If your process
920has a smaller stack, you should adjust this setting accordingly with the 1022has a smaller stack, you should adjust this setting accordingly with the
921C<max_depth> method. 1023C<max_depth> method.
922 1024
923And last but least, something else could bomb you that I forgot to think 1025And last but least, something else could bomb you that I forgot to think
924of. In that case, you get to keep the pieces. I am always open for hints, 1026of. In that case, you get to keep the pieces. I am always open for hints,
925though... 1027though...
926 1028
927If you are using JSON::XS to return packets to consumption 1029If you are using JSON::XS to return packets to consumption
928by javascript scripts in a browser you should have a look at 1030by JavaScript scripts in a browser you should have a look at
929L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1031L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
930you are vulnerable to some common attack vectors (which really are browser 1032you are vulnerable to some common attack vectors (which really are browser
931design bugs, but it is still you who will have to deal with it, as major 1033design bugs, but it is still you who will have to deal with it, as major
932browser developers care only for features, not about doing security 1034browser developers care only for features, not about getting security
933right). 1035right).
1036
1037
1038=head1 THREADS
1039
1040This module is I<not> guaranteed to be thread safe and there are no
1041plans to change this until Perl gets thread support (as opposed to the
1042horribly slow so-called "threads" which are simply slow and bloated
1043process simulations - use fork, its I<much> faster, cheaper, better).
1044
1045(It might actually work, but you have been warned).
934 1046
935 1047
936=head1 BUGS 1048=head1 BUGS
937 1049
938While the goal of this module is to be correct, that unfortunately does 1050While the goal of this module is to be correct, that unfortunately does
939not mean its bug-free, only that I think its design is bug-free. It is 1051not mean its bug-free, only that I think its design is bug-free. It is
940still relatively early in its development. If you keep reporting bugs they 1052still relatively early in its development. If you keep reporting bugs they
941will be fixed swiftly, though. 1053will be fixed swiftly, though.
1054
1055Please refrain from using rt.cpan.org or any other bug reporting
1056service. I put the contact address into my modules for a reason.
942 1057
943=cut 1058=cut
944 1059
945our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1060our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
946our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1061our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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