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Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC vs.
Revision 1.80 by root, Sat Dec 29 17:22:39 2007 UTC

1=head1 NAME 1=head1 NAME
2 2
3JSON::XS - JSON serialising/deserialising, done correctly and fast 3JSON::XS - JSON serialising/deserialising, done correctly and fast
4
5JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4 7
5=head1 SYNOPSIS 8=head1 SYNOPSIS
6 9
7 use JSON::XS; 10 use JSON::XS;
8 11
9 # exported functions, they croak on error 12 # exported functions, they croak on error
10 # and expect/generate UTF-8 13 # and expect/generate UTF-8
11 14
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14 17
15 # OO-interface 18 # OO-interface
16 19
17 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
18 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
19 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
20 23
24 # Note that JSON version 2.0 and above will automatically use JSON::XS
25 # if available, at virtually no speed overhead either, so you should
26 # be able to just:
27
28 use JSON;
29
30 # and do the same things, except that you have a pure-perl fallback now.
31
21=head1 DESCRIPTION 32=head1 DESCRIPTION
22 33
23This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
24primary goal is to be I<correct> and its secondary goal is to be 35primary goal is to be I<correct> and its secondary goal is to be
25I<fast>. To reach the latter goal it was written in C. 36I<fast>. To reach the latter goal it was written in C.
37
38Beginning with version 2.0 of the JSON module, when both JSON and
39JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40overriden) with no overhead due to emulation (by inheritign constructor
41and methods). If JSON::XS is not available, it will fall back to the
42compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43gives you a portable JSON API that can be fast when you need and doesn't
44require a C compiler when that is a problem.
26 45
27As this is the n-th-something JSON module on CPAN, what was the reason 46As this is the n-th-something JSON module on CPAN, what was the reason
28to write yet another JSON module? While it seems there are many JSON 47to write yet another JSON module? While it seems there are many JSON
29modules, none of them correctly handle all corner cases, and in most cases 48modules, none of them correctly handle all corner cases, and in most cases
30their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
37 56
38=head2 FEATURES 57=head2 FEATURES
39 58
40=over 4 59=over 4
41 60
42=item * correct unicode handling 61=item * correct Unicode handling
43 62
44This module knows how to handle Unicode, and even documents how and when 63This module knows how to handle Unicode, and even documents how and when
45it does so. 64it does so.
46 65
47=item * round-trip integrity 66=item * round-trip integrity
67This module has both a simple functional interface as well as an OO 86This module has both a simple functional interface as well as an OO
68interface. 87interface.
69 88
70=item * reasonably versatile output formats 89=item * reasonably versatile output formats
71 90
72You can choose between the most compact guarenteed single-line format 91You can choose between the most compact guaranteed single-line format
73possible (nice for simple line-based protocols), a pure-ascii format 92possible (nice for simple line-based protocols), a pure-ascii format
74(for when your transport is not 8-bit clean, still supports the whole 93(for when your transport is not 8-bit clean, still supports the whole
75unicode range), or a pretty-printed format (for when you want to read that 94Unicode range), or a pretty-printed format (for when you want to read that
76stuff). Or you can combine those features in whatever way you like. 95stuff). Or you can combine those features in whatever way you like.
77 96
78=back 97=back
79 98
80=cut 99=cut
81 100
82package JSON::XS; 101package JSON::XS;
83 102
84use strict; 103use strict;
85 104
86our $VERSION = '1.5'; 105our $VERSION = '2.01';
87our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
88 107
89our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
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}
90 119
91use Exporter; 120use Exporter;
92use XSLoader; 121use XSLoader;
93 122
94=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
95 124
96The following convinience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
97exported by default: 126exported by default:
98 127
99=over 4 128=over 4
100 129
101=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
102 131
103Converts 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
104a 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.
105octets only). Croaks on error.
106 134
107This function call is functionally identical to: 135This function call is functionally identical to:
108 136
109 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110 138
111except being faster. 139except being faster.
112 140
113=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
114 142
115The 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
116parse 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
117scalar or reference. Croaks on error. 145reference. Croaks on error.
118 146
119This function call is functionally identical to: 147This function call is functionally identical to:
120 148
121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 149 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122 150
132Perl. 160Perl.
133 161
134=back 162=back
135 163
136 164
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
137=head1 OBJECT-ORIENTED INTERFACE 213=head1 OBJECT-ORIENTED INTERFACE
138 214
139The object oriented interface lets you configure your own encoding or 215The object oriented interface lets you configure your own encoding or
140decoding style, within the limits of supported formats. 216decoding style, within the limits of supported formats.
141 217
152 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]})
153 => {"a": [1, 2]} 229 => {"a": [1, 2]}
154 230
155=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
156 232
233=item $enabled = $json->get_ascii
234
157If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
158generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
159unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
160single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161as per RFC4627. The resulting encoded JSON text can be treated as a native 239as per RFC4627. The resulting encoded JSON text can be treated as a native
162unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, 240Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163or any other superset of ASCII. 241or any other superset of ASCII.
164 242
165If C<$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
166characters unless required by the JSON syntax or other flags. This results 244characters unless required by the JSON syntax or other flags. This results
167in a faster and more compact format. 245in a faster and more compact format.
173 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
175 253
176=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
177 255
256=item $enabled = $json->get_latin1
257
178If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
179the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
181latin1-encoded JSON text or a native unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
182will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
183expects unicode, which is a strict superset of latin1. 263expects Unicode, which is a strict superset of latin1.
184 264
185If C<$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
186characters unless required by the JSON syntax or other flags. 266characters unless required by the JSON syntax or other flags.
187 267
188The 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
189text, 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
190size. The disadvantage is that the resulting JSON text is encoded 270size. The disadvantage is that the resulting JSON text is encoded
191in latin1 (and must correctly be treated as such when storing and 271in latin1 (and must correctly be treated as such when storing and
192transfering), a rare encoding for JSON. It is therefore most useful when 272transferring), a rare encoding for JSON. It is therefore most useful when
193you want to store data structures known to contain binary data efficiently 273you want to store data structures known to contain binary data efficiently
194in files or databases, not when talking to other JSON encoders/decoders. 274in files or databases, not when talking to other JSON encoders/decoders.
195 275
196 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198 278
199=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
200 282
201If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
202the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
203C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
204note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
205range C<0..255>, they are thus useful for bytewise/binary I/O. In future 287range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206versions, enabling this option might enable autodetection of the UTF-16 288versions, enabling this option might enable autodetection of the UTF-16
207and UTF-32 encoding families, as described in RFC4627. 289and UTF-32 encoding families, as described in RFC4627.
208 290
209If C<$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
210string 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
211unicode 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
212to be done yourself, e.g. using the Encode module. 294to be done yourself, e.g. using the Encode module.
213 295
214Example, output UTF-16BE-encoded JSON: 296Example, output UTF-16BE-encoded JSON:
215 297
216 use Encode; 298 use Encode;
238 ] 320 ]
239 } 321 }
240 322
241=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
242 324
325=item $enabled = $json->get_indent
326
243If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
245into its own line, identing them properly. 329into its own line, indenting them properly.
246 330
247If C<$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
248resulting JSON text is guarenteed not to contain any C<newlines>. 332resulting JSON text is guaranteed not to contain any C<newlines>.
249 333
250This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
251 335
252=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
337
338=item $enabled = $json->get_space_before
253 339
254If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
255optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
256 342
257If C<$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
263Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
264 350
265 {"key" :"value"} 351 {"key" :"value"}
266 352
267=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
268 356
269If C<$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
270optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
271and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
272members. 360members.
279Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
280 368
281 {"key": "value"} 369 {"key": "value"}
282 370
283=item $json = $json->relaxed ([$enable]) 371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
284 374
285If C<$enable> is true (or missing), then C<decode> will accept some 375If C<$enable> is true (or missing), then C<decode> will accept some
286extensions to normal JSON syntax (see below). C<encode> will not be 376extensions to normal JSON syntax (see below). C<encode> will not be
287affected 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
288JSON 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
325 415
326=back 416=back
327 417
328=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
329 419
420=item $enabled = $json->get_canonical
421
330If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
331by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
332 424
333If C<$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
334pairs 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
335of the same script). 427of the same script).
336 428
337This 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
338the 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,
339the 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,
340as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
341 433
342This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
343 435
344=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
345 439
346If C<$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
347non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
348which 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
349values instead of croaking. 443values instead of croaking.
359 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
360 => "Hello, World!" 454 => "Hello, World!"
361 455
362=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
363 457
458=item $enabled = $json->get_allow_blessed
459
364If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
365barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
366B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
367disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
368object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
369encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
370 466
371If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
372exception when it encounters a blessed object. 468exception when it encounters a blessed object.
373 469
374=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
375 473
376If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
377blessed 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
378on 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
379and 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
383The 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>
384returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
385way. 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
386(== 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
387methods 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
388usually 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>
389function. 487function or method.
390 488
391This 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
392future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
393enabled by this setting. 491enabled by this setting.
394 492
436 534
437As 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>
438one, decoding speed will not usually suffer as much. Therefore, single-key 536one, decoding speed will not usually suffer as much. Therefore, single-key
439objects make excellent targets to serialise Perl objects into, especially 537objects make excellent targets to serialise Perl objects into, especially
440as 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
441as 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
442support 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
443like a serialised Perl hash. 541like a serialised Perl hash.
444 542
445Typical names for the single object key are C<__class_whatever__>, or 543Typical names for the single object key are C<__class_whatever__>, or
446C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
470 568
471 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
472 } 570 }
473 571
474=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
475 575
476Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
477strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
478C<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
479memory 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
497strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
498internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
499 599
500=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
501 601
602=item $max_depth = $json->get_max_depth
603
502Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
503or 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
504higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
505stop and croak at that point. 607stop and croak at that point.
506 608
517used, which is rarely useful. 619used, which is rarely useful.
518 620
519See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
520 622
521=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
522 626
523Set 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
524being 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>
525is 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
526attempt 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
573vice 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
574circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
575(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
576 680
577For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
578lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
579refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
580 684
581 685
582=head2 JSON -> PERL 686=head2 JSON -> PERL
583 687
584=over 4 688=over 4
585 689
586=item object 690=item object
587 691
588A 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
589keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
590 694
591=item array 695=item array
592 696
593A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
594 698
620 724
621=item true, false 725=item true, false
622 726
623These 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>,
624respectively. They are overloaded to act almost exactly like the numbers 728respectively. They are overloaded to act almost exactly like the numbers
625C<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
626the C<JSON::XS::is_bool> function. 730the C<JSON::XS::is_bool> function.
627 731
628=item null 732=item null
629 733
630A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
661Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
662exception 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
663C<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
664also 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.
665 769
666 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
667 771
668=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
669 773
670These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
671respectively. 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.
682difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
683JSON 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
684before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
685 789
686 # dump as number 790 # dump as number
687 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
688 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
689 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
690 794
691 # used as string, so dump as string 795 # used as string, so dump as string
692 print $value; 796 print $value;
693 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
694 798
695 # undef becomes null 799 # undef becomes null
696 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
697 801
698You can force the type to be a string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
699 803
700 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
701 "$x"; # stringified 805 "$x"; # stringified
702 $x .= ""; # another, more awkward way to stringify 806 $x .= ""; # another, more awkward way to stringify
703 print $x; # perl does it for you, too, quite often 807 print $x; # perl does it for you, too, quite often
704 808
705You can force the type to be a number by numifying it: 809You can force the type to be a JSON number by numifying it:
706 810
707 my $x = "3"; # some variable containing a string 811 my $x = "3"; # some variable containing a string
708 $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
709 $x *= 1; # same thing, the choise is yours. 813 $x *= 1; # same thing, the choice is yours.
710 814
711You 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
712less obscure, ways. Tell me if you need this capability. 816if you need this capability.
713 817
714=back 818=back
715 819
716 820
717=head1 COMPARISON 821=head1 COMPARISON
726 830
727=item JSON 1.07 831=item JSON 1.07
728 832
729Slow (but very portable, as it is written in pure Perl). 833Slow (but very portable, as it is written in pure Perl).
730 834
731Undocumented/buggy Unicode handling (how JSON handles unicode values is 835Undocumented/buggy Unicode handling (how JSON handles Unicode values is
732undocumented. One can get far by feeding it unicode strings and doing 836undocumented. One can get far by feeding it Unicode strings and doing
733en-/decoding oneself, but unicode escapes are not working properly). 837en-/decoding oneself, but Unicode escapes are not working properly).
734 838
735No roundtripping (strings get clobbered if they look like numbers, e.g. 839No round-tripping (strings get clobbered if they look like numbers, e.g.
736the 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
737decode into the number 2. 841decode into the number 2.
738 842
739=item JSON::PC 0.01 843=item JSON::PC 0.01
740 844
741Very fast. 845Very fast.
742 846
743Undocumented/buggy Unicode handling. 847Undocumented/buggy Unicode handling.
744 848
745No roundtripping. 849No round-tripping.
746 850
747Has 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
748values will make it croak). 852values will make it croak).
749 853
750Does 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}>
760Very inflexible (no human-readable format supported, format pretty much 864Very inflexible (no human-readable format supported, format pretty much
761undocumented. 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
762single-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
763generate ASCII-only JSON texts). 867generate ASCII-only JSON texts).
764 868
765Completely broken (and confusingly documented) Unicode handling (unicode 869Completely broken (and confusingly documented) Unicode handling (Unicode
766escapes are not working properly, you need to set ImplicitUnicode to 870escapes are not working properly, you need to set ImplicitUnicode to
767I<different> values on en- and decoding to get symmetric behaviour). 871I<different> values on en- and decoding to get symmetric behaviour).
768 872
769No roundtripping (simple cases work, but this depends on wether the scalar 873No round-tripping (simple cases work, but this depends on whether the scalar
770value was used in a numeric context or not). 874value was used in a numeric context or not).
771 875
772Dumping hashes may skip hash values depending on iterator state. 876Dumping hashes may skip hash values depending on iterator state.
773 877
774Unmaintained (maintainer unresponsive for many months, bugs are not 878Unmaintained (maintainer unresponsive for many months, bugs are not
775getting fixed). 879getting fixed).
776 880
777Does 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
778return "something" instead of raising an exception. This is a security 882return "something" instead of raising an exception. This is a security
779issue: imagine two banks transfering money between each other using 883issue: imagine two banks transferring money between each other using
780JSON. 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,
781while 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
782good protocol will at least recover, that is extra unnecessary work and 886good protocol will at least recover, that is extra unnecessary work and
783the transaction will still not succeed). 887the transaction will still not succeed).
784 888
785=item JSON::DWIW 0.04 889=item JSON::DWIW 0.04
786 890
787Very fast. Very natural. Very nice. 891Very fast. Very natural. Very nice.
788 892
789Undocumented unicode handling (but the best of the pack. Unicode escapes 893Undocumented Unicode handling (but the best of the pack. Unicode escapes
790still don't get parsed properly). 894still don't get parsed properly).
791 895
792Very inflexible. 896Very inflexible.
793 897
794No roundtripping. 898No round-tripping.
795 899
796Does 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
797result in nothing being output) 901result in nothing being output)
798 902
799Does not check input for validity. 903Does not check input for validity.
801=back 905=back
802 906
803 907
804=head2 JSON and YAML 908=head2 JSON and YAML
805 909
806You 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
807however, 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
808no 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.
809 914
810If 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
811algorithm (subject to change in future versions): 916algorithm (subject to change in future versions):
812 917
813 my $to_yaml = JSON::XS->new->utf8->space_after (1); 918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
814 my $yaml = $to_yaml->encode ($ref) . "\n"; 919 my $yaml = $to_yaml->encode ($ref) . "\n";
815 920
816This will usually generate JSON texts that also parse as valid 921This will usually generate JSON texts that also parse as valid
817YAML. Please note that YAML has hardcoded limits on (simple) object key 922YAML. Please note that YAML has hardcoded limits on (simple) object key
818lengths 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
819keys 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).
820 928
821There 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
822you 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,
823or 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
824that you will run into severe interoperability problems. 932that you will run into severe interoperability problems when you least
933expect it.
825 934
826 935
827=head2 SPEED 936=head2 SPEED
828 937
829It 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
840It shows the number of encodes/decodes per second (JSON::XS uses 949It shows the number of encodes/decodes per second (JSON::XS uses
841the functional interface, while JSON::XS/2 uses the OO interface 950the functional interface, while JSON::XS/2 uses the OO interface
842with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 951with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
843shrink). Higher is better: 952shrink). Higher is better:
844 953
845 Storable | 15779.925 | 14169.946 |
846 -----------+------------+------------+
847 module | encode | decode | 954 module | encode | decode |
848 -----------|------------|------------| 955 -----------|------------|------------|
849 JSON | 4990.842 | 4088.813 | 956 JSON 1.x | 4990.842 | 4088.813 |
850 JSON::DWIW | 51653.990 | 71575.154 | 957 JSON::DWIW | 51653.990 | 71575.154 |
851 JSON::PC | 65948.176 | 74631.744 | 958 JSON::PC | 65948.176 | 74631.744 |
852 JSON::PP | 8931.652 | 3817.168 | 959 JSON::PP | 8931.652 | 3817.168 |
853 JSON::Syck | 24877.248 | 27776.848 | 960 JSON::Syck | 24877.248 | 27776.848 |
854 JSON::XS | 388361.481 | 227951.304 | 961 JSON::XS | 388361.481 | 227951.304 |
856 JSON::XS/3 | 338250.323 | 218453.333 | 963 JSON::XS/3 | 338250.323 | 218453.333 |
857 Storable | 16500.016 | 135300.129 | 964 Storable | 16500.016 | 135300.129 |
858 -----------+------------+------------+ 965 -----------+------------+------------+
859 966
860That 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,
861about three times faster on decoding, and over fourty times faster 968about three times faster on decoding, and over forty times faster
862than JSON, even with pretty-printing and key sorting. It also compares 969than JSON, even with pretty-printing and key sorting. It also compares
863favourably to Storable for small amounts of data. 970favourably to Storable for small amounts of data.
864 971
865Using a longer test string (roughly 18KB, generated from Yahoo! Locals 972Using a longer test string (roughly 18KB, generated from Yahoo! Locals
866search API (http://nanoref.com/yahooapis/mgPdGg): 973search API (http://nanoref.com/yahooapis/mgPdGg):
867 974
868 module | encode | decode | 975 module | encode | decode |
869 -----------|------------|------------| 976 -----------|------------|------------|
870 JSON | 55.260 | 34.971 | 977 JSON 1.x | 55.260 | 34.971 |
871 JSON::DWIW | 825.228 | 1082.513 | 978 JSON::DWIW | 825.228 | 1082.513 |
872 JSON::PC | 3571.444 | 2394.829 | 979 JSON::PC | 3571.444 | 2394.829 |
873 JSON::PP | 210.987 | 32.574 | 980 JSON::PP | 210.987 | 32.574 |
874 JSON::Syck | 552.551 | 787.544 | 981 JSON::Syck | 552.551 | 787.544 |
875 JSON::XS | 5780.463 | 4854.519 | 982 JSON::XS | 5780.463 | 4854.519 |
879 -----------+------------+------------+ 986 -----------+------------+------------+
880 987
881Again, JSON::XS leads by far (except for Storable which non-surprisingly 988Again, JSON::XS leads by far (except for Storable which non-surprisingly
882decodes faster). 989decodes faster).
883 990
884On large strings containing lots of high unicode characters, some modules 991On large strings containing lots of high Unicode characters, some modules
885(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
886will be broken due to missing (or wrong) unicode handling. Others refuse 993will be broken due to missing (or wrong) Unicode handling. Others refuse
887to 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
888comparison table for that case. 995comparison table for that case.
889 996
890 997
891=head1 SECURITY CONSIDERATIONS 998=head1 SECURITY CONSIDERATIONS
897any buffer overflows. Obviously, this module should ensure that and I am 1004any buffer overflows. Obviously, this module should ensure that and I am
898trying hard on making that true, but you never know. 1005trying hard on making that true, but you never know.
899 1006
900Second, you need to avoid resource-starving attacks. That means you should 1007Second, you need to avoid resource-starving attacks. That means you should
901limit 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
902resources 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
903can 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
904usually 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
905it 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
906text, 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
907might want to check the size before you accept the string. 1014might want to check the size before you accept the string.
908 1015
909Third, JSON::XS recurses using the C stack when decoding objects and 1016Third, JSON::XS recurses using the C stack when decoding objects and
910arrays. 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
911machine 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
912only 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
913to 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
914conservative, the default nesting limit is set to 512. If your process 1021conservative, the default nesting limit is set to 512. If your process
915has a smaller stack, you should adjust this setting accordingly with the 1022has a smaller stack, you should adjust this setting accordingly with the
916C<max_depth> method. 1023C<max_depth> method.
917 1024
918And 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
919of. 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,
920though... 1027though...
921 1028
922If you are using JSON::XS to return packets to consumption 1029If you are using JSON::XS to return packets to consumption
923by javascript scripts in a browser you should have a look at 1030by JavaScript scripts in a browser you should have a look at
924L<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
925you are vulnerable to some common attack vectors (which really are browser 1032you are vulnerable to some common attack vectors (which really are browser
926design 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
927browser developers care only for features, not about doing security 1034browser developers care only for features, not about getting security
928right). 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).
929 1046
930 1047
931=head1 BUGS 1048=head1 BUGS
932 1049
933While 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
934not 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
935still relatively early in its development. If you keep reporting bugs they 1052still relatively early in its development. If you keep reporting bugs they
936will 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.
937 1057
938=cut 1058=cut
939 1059
940our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1060our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
941our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1061our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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