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Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC vs.
Revision 1.79 by root, Wed Dec 19 11:42:52 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
310 { 400 {
311 "k1": "v1", 401 "k1": "v1",
312 "k2": "v2", <- this comma not normally allowed 402 "k2": "v2", <- this comma not normally allowed
313 } 403 }
314 404
405=item * shell-style '#'-comments
406
407Whenever JSON allows whitespace, shell-style comments are additionally
408allowed. They are terminated by the first carriage-return or line-feed
409character, after which more white-space and comments are allowed.
410
411 [
412 1, # this comment not allowed in JSON
413 # neither this one...
414 ]
415
315=back 416=back
316 417
317=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
419
420=item $enabled = $json->get_canonical
318 421
319If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
320by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
321 424
322If C<$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
323pairs 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
324of the same script). 427of the same script).
325 428
326This 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
327the 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,
328the 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,
329as key-value pairs have no inherent ordering in Perl. 432as key-value pairs have no inherent ordering in Perl.
330 433
331This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
332 435
333=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
437
438=item $enabled = $json->get_allow_nonref
334 439
335If C<$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
336non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
337which 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
338values instead of croaking. 443values instead of croaking.
348 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
349 => "Hello, World!" 454 => "Hello, World!"
350 455
351=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
352 457
458=item $enabled = $json->get_allow_blessed
459
353If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
354barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
355B<convert_blessed> option will decide wether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
356disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
357object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
358encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
359 466
360If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
361exception when it encounters a blessed object. 468exception when it encounters a blessed object.
362 469
363=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
364 473
365If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
366blessed 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
367on 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
368and 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
372The 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>
373returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
374way. 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
375(== 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
376methods 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
377usually 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>
378function. 487function or method.
379 488
380This 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
381future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
382enabled by this setting. 491enabled by this setting.
383 492
425 534
426As 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>
427one, decoding speed will not usually suffer as much. Therefore, single-key 536one, decoding speed will not usually suffer as much. Therefore, single-key
428objects make excellent targets to serialise Perl objects into, especially 537objects make excellent targets to serialise Perl objects into, especially
429as 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
430as 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
431support 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
432like a serialised Perl hash. 541like a serialised Perl hash.
433 542
434Typical names for the single object key are C<__class_whatever__>, or 543Typical names for the single object key are C<__class_whatever__>, or
435C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even 544C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
459 568
460 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
461 } 570 }
462 571
463=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
464 575
465Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
466strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
467C<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
468memory 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
486strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
487internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
488 599
489=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
490 601
602=item $max_depth = $json->get_max_depth
603
491Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
492or 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
493higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
494stop and croak at that point. 607stop and croak at that point.
495 608
506used, which is rarely useful. 619used, which is rarely useful.
507 620
508See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
509 622
510=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
511 626
512Set 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
513being 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>
514is 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
515attempt 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
562vice 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
563circumstances automatically, preserving round-tripping characteristics 678circumstances automatically, preserving round-tripping characteristics
564(what you put in comes out as something equivalent). 679(what you put in comes out as something equivalent).
565 680
566For the more enlightened: note that in the following descriptions, 681For the more enlightened: note that in the following descriptions,
567lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 682lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
568refers to the abstract Perl language itself. 683refers to the abstract Perl language itself.
569 684
570 685
571=head2 JSON -> PERL 686=head2 JSON -> PERL
572 687
573=over 4 688=over 4
574 689
575=item object 690=item object
576 691
577A 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
578keys is preserved (JSON does not preserver object key ordering itself). 693keys is preserved (JSON does not preserve object key ordering itself).
579 694
580=item array 695=item array
581 696
582A JSON array becomes a reference to an array in Perl. 697A JSON array becomes a reference to an array in Perl.
583 698
609 724
610=item true, false 725=item true, false
611 726
612These 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>,
613respectively. They are overloaded to act almost exactly like the numbers 728respectively. They are overloaded to act almost exactly like the numbers
614C<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
615the C<JSON::XS::is_bool> function. 730the C<JSON::XS::is_bool> function.
616 731
617=item null 732=item null
618 733
619A JSON null atom becomes C<undef> in Perl. 734A JSON null atom becomes C<undef> in Perl.
650Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
651exception 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
652C<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
653also 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.
654 769
655 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
656 771
657=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
658 773
659These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
660respectively. You cna alos use C<\1> and C<\0> directly if you want. 775respectively. You can also use C<\1> and C<\0> directly if you want.
661 776
662=item blessed objects 777=item blessed objects
663 778
664Blessed objects are not allowed. JSON::XS currently tries to encode their 779Blessed objects are not allowed. JSON::XS currently tries to encode their
665underlying representation (hash- or arrayref), but this behaviour might 780underlying representation (hash- or arrayref), but this behaviour might
671difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
672JSON 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
673before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
674 789
675 # dump as number 790 # dump as number
676 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
677 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
678 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
679 794
680 # used as string, so dump as string 795 # used as string, so dump as string
681 print $value; 796 print $value;
682 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
683 798
684 # undef becomes null 799 # undef becomes null
685 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
686 801
687You can force the type to be a string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
688 803
689 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
690 "$x"; # stringified 805 "$x"; # stringified
691 $x .= ""; # another, more awkward way to stringify 806 $x .= ""; # another, more awkward way to stringify
692 print $x; # perl does it for you, too, quite often 807 print $x; # perl does it for you, too, quite often
693 808
694You can force the type to be a number by numifying it: 809You can force the type to be a JSON number by numifying it:
695 810
696 my $x = "3"; # some variable containing a string 811 my $x = "3"; # some variable containing a string
697 $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
698 $x *= 1; # same thing, the choise is yours. 813 $x *= 1; # same thing, the choice is yours.
699 814
700You 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
701less obscure, ways. Tell me if you need this capability. 816if you need this capability.
702 817
703=back 818=back
704 819
705 820
706=head1 COMPARISON 821=head1 COMPARISON
715 830
716=item JSON 1.07 831=item JSON 1.07
717 832
718Slow (but very portable, as it is written in pure Perl). 833Slow (but very portable, as it is written in pure Perl).
719 834
720Undocumented/buggy Unicode handling (how JSON handles unicode values is 835Undocumented/buggy Unicode handling (how JSON handles Unicode values is
721undocumented. One can get far by feeding it unicode strings and doing 836undocumented. One can get far by feeding it Unicode strings and doing
722en-/decoding oneself, but unicode escapes are not working properly). 837en-/decoding oneself, but Unicode escapes are not working properly).
723 838
724No roundtripping (strings get clobbered if they look like numbers, e.g. 839No round-tripping (strings get clobbered if they look like numbers, e.g.
725the 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
726decode into the number 2. 841decode into the number 2.
727 842
728=item JSON::PC 0.01 843=item JSON::PC 0.01
729 844
730Very fast. 845Very fast.
731 846
732Undocumented/buggy Unicode handling. 847Undocumented/buggy Unicode handling.
733 848
734No roundtripping. 849No round-tripping.
735 850
736Has 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
737values will make it croak). 852values will make it croak).
738 853
739Does 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}>
749Very inflexible (no human-readable format supported, format pretty much 864Very inflexible (no human-readable format supported, format pretty much
750undocumented. 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
751single-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
752generate ASCII-only JSON texts). 867generate ASCII-only JSON texts).
753 868
754Completely broken (and confusingly documented) Unicode handling (unicode 869Completely broken (and confusingly documented) Unicode handling (Unicode
755escapes are not working properly, you need to set ImplicitUnicode to 870escapes are not working properly, you need to set ImplicitUnicode to
756I<different> values on en- and decoding to get symmetric behaviour). 871I<different> values on en- and decoding to get symmetric behaviour).
757 872
758No roundtripping (simple cases work, but this depends on wether the scalar 873No round-tripping (simple cases work, but this depends on whether the scalar
759value was used in a numeric context or not). 874value was used in a numeric context or not).
760 875
761Dumping hashes may skip hash values depending on iterator state. 876Dumping hashes may skip hash values depending on iterator state.
762 877
763Unmaintained (maintainer unresponsive for many months, bugs are not 878Unmaintained (maintainer unresponsive for many months, bugs are not
764getting fixed). 879getting fixed).
765 880
766Does 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
767return "something" instead of raising an exception. This is a security 882return "something" instead of raising an exception. This is a security
768issue: imagine two banks transfering money between each other using 883issue: imagine two banks transferring money between each other using
769JSON. 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,
770while 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
771good protocol will at least recover, that is extra unnecessary work and 886good protocol will at least recover, that is extra unnecessary work and
772the transaction will still not succeed). 887the transaction will still not succeed).
773 888
774=item JSON::DWIW 0.04 889=item JSON::DWIW 0.04
775 890
776Very fast. Very natural. Very nice. 891Very fast. Very natural. Very nice.
777 892
778Undocumented unicode handling (but the best of the pack. Unicode escapes 893Undocumented Unicode handling (but the best of the pack. Unicode escapes
779still don't get parsed properly). 894still don't get parsed properly).
780 895
781Very inflexible. 896Very inflexible.
782 897
783No roundtripping. 898No round-tripping.
784 899
785Does 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
786result in nothing being output) 901result in nothing being output)
787 902
788Does not check input for validity. 903Does not check input for validity.
803 my $yaml = $to_yaml->encode ($ref) . "\n"; 918 my $yaml = $to_yaml->encode ($ref) . "\n";
804 919
805This will usually generate JSON texts that also parse as valid 920This will usually generate JSON texts that also parse as valid
806YAML. Please note that YAML has hardcoded limits on (simple) object key 921YAML. Please note that YAML has hardcoded limits on (simple) object key
807lengths that JSON doesn't have, so you should make sure that your hash 922lengths that JSON doesn't have, so you should make sure that your hash
808keys are noticably shorter than the 1024 characters YAML allows. 923keys are noticeably shorter than the 1024 characters YAML allows.
809 924
810There might be other incompatibilities that I am not aware of. In general 925There might be other incompatibilities that I am not aware of. In general
811you should not try to generate YAML with a JSON generator or vice versa, 926you should not try to generate YAML with a JSON generator or vice versa,
812or try to parse JSON with a YAML parser or vice versa: chances are high 927or try to parse JSON with a YAML parser or vice versa: chances are high
813that you will run into severe interoperability problems. 928that you will run into severe interoperability problems.
829It shows the number of encodes/decodes per second (JSON::XS uses 944It shows the number of encodes/decodes per second (JSON::XS uses
830the functional interface, while JSON::XS/2 uses the OO interface 945the functional interface, while JSON::XS/2 uses the OO interface
831with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 946with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
832shrink). Higher is better: 947shrink). Higher is better:
833 948
834 Storable | 15779.925 | 14169.946 |
835 -----------+------------+------------+
836 module | encode | decode | 949 module | encode | decode |
837 -----------|------------|------------| 950 -----------|------------|------------|
838 JSON | 4990.842 | 4088.813 | 951 JSON 1.x | 4990.842 | 4088.813 |
839 JSON::DWIW | 51653.990 | 71575.154 | 952 JSON::DWIW | 51653.990 | 71575.154 |
840 JSON::PC | 65948.176 | 74631.744 | 953 JSON::PC | 65948.176 | 74631.744 |
841 JSON::PP | 8931.652 | 3817.168 | 954 JSON::PP | 8931.652 | 3817.168 |
842 JSON::Syck | 24877.248 | 27776.848 | 955 JSON::Syck | 24877.248 | 27776.848 |
843 JSON::XS | 388361.481 | 227951.304 | 956 JSON::XS | 388361.481 | 227951.304 |
845 JSON::XS/3 | 338250.323 | 218453.333 | 958 JSON::XS/3 | 338250.323 | 218453.333 |
846 Storable | 16500.016 | 135300.129 | 959 Storable | 16500.016 | 135300.129 |
847 -----------+------------+------------+ 960 -----------+------------+------------+
848 961
849That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 962That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
850about three times faster on decoding, and over fourty times faster 963about three times faster on decoding, and over forty times faster
851than JSON, even with pretty-printing and key sorting. It also compares 964than JSON, even with pretty-printing and key sorting. It also compares
852favourably to Storable for small amounts of data. 965favourably to Storable for small amounts of data.
853 966
854Using a longer test string (roughly 18KB, generated from Yahoo! Locals 967Using a longer test string (roughly 18KB, generated from Yahoo! Locals
855search API (http://nanoref.com/yahooapis/mgPdGg): 968search API (http://nanoref.com/yahooapis/mgPdGg):
856 969
857 module | encode | decode | 970 module | encode | decode |
858 -----------|------------|------------| 971 -----------|------------|------------|
859 JSON | 55.260 | 34.971 | 972 JSON 1.x | 55.260 | 34.971 |
860 JSON::DWIW | 825.228 | 1082.513 | 973 JSON::DWIW | 825.228 | 1082.513 |
861 JSON::PC | 3571.444 | 2394.829 | 974 JSON::PC | 3571.444 | 2394.829 |
862 JSON::PP | 210.987 | 32.574 | 975 JSON::PP | 210.987 | 32.574 |
863 JSON::Syck | 552.551 | 787.544 | 976 JSON::Syck | 552.551 | 787.544 |
864 JSON::XS | 5780.463 | 4854.519 | 977 JSON::XS | 5780.463 | 4854.519 |
868 -----------+------------+------------+ 981 -----------+------------+------------+
869 982
870Again, JSON::XS leads by far (except for Storable which non-surprisingly 983Again, JSON::XS leads by far (except for Storable which non-surprisingly
871decodes faster). 984decodes faster).
872 985
873On large strings containing lots of high unicode characters, some modules 986On large strings containing lots of high Unicode characters, some modules
874(such as JSON::PC) seem to decode faster than JSON::XS, but the result 987(such as JSON::PC) seem to decode faster than JSON::XS, but the result
875will be broken due to missing (or wrong) unicode handling. Others refuse 988will be broken due to missing (or wrong) Unicode handling. Others refuse
876to decode or encode properly, so it was impossible to prepare a fair 989to decode or encode properly, so it was impossible to prepare a fair
877comparison table for that case. 990comparison table for that case.
878 991
879 992
880=head1 SECURITY CONSIDERATIONS 993=head1 SECURITY CONSIDERATIONS
886any buffer overflows. Obviously, this module should ensure that and I am 999any buffer overflows. Obviously, this module should ensure that and I am
887trying hard on making that true, but you never know. 1000trying hard on making that true, but you never know.
888 1001
889Second, you need to avoid resource-starving attacks. That means you should 1002Second, you need to avoid resource-starving attacks. That means you should
890limit the size of JSON texts you accept, or make sure then when your 1003limit the size of JSON texts you accept, or make sure then when your
891resources run out, thats just fine (e.g. by using a separate process that 1004resources run out, that's just fine (e.g. by using a separate process that
892can crash safely). The size of a JSON text in octets or characters is 1005can crash safely). The size of a JSON text in octets or characters is
893usually a good indication of the size of the resources required to decode 1006usually a good indication of the size of the resources required to decode
894it into a Perl structure. While JSON::XS can check the size of the JSON 1007it into a Perl structure. While JSON::XS can check the size of the JSON
895text, it might be too late when you already have it in memory, so you 1008text, it might be too late when you already have it in memory, so you
896might want to check the size before you accept the string. 1009might want to check the size before you accept the string.
897 1010
898Third, JSON::XS recurses using the C stack when decoding objects and 1011Third, JSON::XS recurses using the C stack when decoding objects and
899arrays. The C stack is a limited resource: for instance, on my amd64 1012arrays. The C stack is a limited resource: for instance, on my amd64
900machine with 8MB of stack size I can decode around 180k nested arrays but 1013machine with 8MB of stack size I can decode around 180k nested arrays but
901only 14k nested JSON objects (due to perl itself recursing deeply on croak 1014only 14k nested JSON objects (due to perl itself recursing deeply on croak
902to free the temporary). If that is exceeded, the program crashes. to be 1015to free the temporary). If that is exceeded, the program crashes. To be
903conservative, the default nesting limit is set to 512. If your process 1016conservative, the default nesting limit is set to 512. If your process
904has a smaller stack, you should adjust this setting accordingly with the 1017has a smaller stack, you should adjust this setting accordingly with the
905C<max_depth> method. 1018C<max_depth> method.
906 1019
907And last but least, something else could bomb you that I forgot to think 1020And last but least, something else could bomb you that I forgot to think
908of. In that case, you get to keep the pieces. I am always open for hints, 1021of. In that case, you get to keep the pieces. I am always open for hints,
909though... 1022though...
910 1023
911If you are using JSON::XS to return packets to consumption 1024If you are using JSON::XS to return packets to consumption
912by javascript scripts in a browser you should have a look at 1025by JavaScript scripts in a browser you should have a look at
913L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1026L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
914you are vulnerable to some common attack vectors (which really are browser 1027you are vulnerable to some common attack vectors (which really are browser
915design bugs, but it is still you who will have to deal with it, as major 1028design bugs, but it is still you who will have to deal with it, as major
916browser developers care only for features, not about doing security 1029browser developers care only for features, not about getting security
917right). 1030right).
1031
1032
1033=head1 THREADS
1034
1035This module is I<not> guaranteed to be thread safe and there are no
1036plans to change this until Perl gets thread support (as opposed to the
1037horribly slow so-called "threads" which are simply slow and bloated
1038process simulations - use fork, its I<much> faster, cheaper, better).
1039
1040(It might actually work, but you have been warned).
918 1041
919 1042
920=head1 BUGS 1043=head1 BUGS
921 1044
922While the goal of this module is to be correct, that unfortunately does 1045While the goal of this module is to be correct, that unfortunately does
923not mean its bug-free, only that I think its design is bug-free. It is 1046not mean its bug-free, only that I think its design is bug-free. It is
924still relatively early in its development. If you keep reporting bugs they 1047still relatively early in its development. If you keep reporting bugs they
925will be fixed swiftly, though. 1048will be fixed swiftly, though.
1049
1050Please refrain from using rt.cpan.org or any other bug reporting
1051service. I put the contact address into my modules for a reason.
926 1052
927=cut 1053=cut
928 1054
929our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1055our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
930our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1056our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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