… | |
… | |
35 | |
35 | |
36 | This module converts Perl data structures to JSON and vice versa. Its |
36 | This module converts Perl data structures to JSON and vice versa. Its |
37 | primary goal is to be I<correct> and its secondary goal is to be |
37 | primary goal is to be I<correct> and its secondary goal is to be |
38 | I<fast>. To reach the latter goal it was written in C. |
38 | I<fast>. To reach the latter goal it was written in C. |
39 | |
39 | |
40 | Beginning with version 2.0 of the JSON module, when both JSON and |
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41 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
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42 | overridden) with no overhead due to emulation (by inheriting constructor |
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43 | and methods). If JSON::XS is not available, it will fall back to the |
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44 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
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45 | gives you a portable JSON API that can be fast when you need and doesn't |
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46 | require a C compiler when that is a problem. |
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47 | |
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48 | As this is the n-th-something JSON module on CPAN, what was the reason |
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49 | to write yet another JSON module? While it seems there are many JSON |
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50 | modules, none of them correctly handle all corner cases, and in most cases |
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51 | their maintainers are unresponsive, gone missing, or not listening to bug |
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52 | reports for other reasons. |
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53 | |
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54 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
40 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
55 | vice versa. |
41 | vice versa. |
56 | |
42 | |
57 | =head2 FEATURES |
43 | =head2 FEATURES |
58 | |
44 | |
59 | =over 4 |
45 | =over |
60 | |
46 | |
61 | =item * correct Unicode handling |
47 | =item * correct Unicode handling |
62 | |
48 | |
63 | This module knows how to handle Unicode, documents how and when it does |
49 | This module knows how to handle Unicode, documents how and when it does |
64 | so, and even documents what "correct" means. |
50 | so, and even documents what "correct" means. |
65 | |
51 | |
66 | =item * round-trip integrity |
52 | =item * round-trip integrity |
67 | |
53 | |
68 | When you serialise a perl data structure using only data types supported |
54 | When you serialise a perl data structure using only data types supported |
69 | by JSON, the deserialised data structure is identical on the Perl level. |
55 | by JSON and Perl, the deserialised data structure is identical on the Perl |
70 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
56 | level. (e.g. the string "2.0" doesn't suddenly become "2" just because |
71 | like a number). There minor I<are> exceptions to this, read the MAPPING |
57 | it looks like a number). There I<are> minor exceptions to this, read the |
72 | section below to learn about those. |
58 | MAPPING section below to learn about those. |
73 | |
59 | |
74 | =item * strict checking of JSON correctness |
60 | =item * strict checking of JSON correctness |
75 | |
61 | |
76 | There is no guessing, no generating of illegal JSON texts by default, |
62 | There is no guessing, no generating of illegal JSON texts by default, |
77 | and only JSON is accepted as input by default (the latter is a security |
63 | and only JSON is accepted as input by default (the latter is a security |
… | |
… | |
83 | this module usually compares favourably in terms of speed, too. |
69 | this module usually compares favourably in terms of speed, too. |
84 | |
70 | |
85 | =item * simple to use |
71 | =item * simple to use |
86 | |
72 | |
87 | This module has both a simple functional interface as well as an object |
73 | This module has both a simple functional interface as well as an object |
88 | oriented interface interface. |
74 | oriented interface. |
89 | |
75 | |
90 | =item * reasonably versatile output formats |
76 | =item * reasonably versatile output formats |
91 | |
77 | |
92 | You can choose between the most compact guaranteed-single-line format |
78 | You can choose between the most compact guaranteed-single-line format |
93 | possible (nice for simple line-based protocols), a pure-ASCII format |
79 | possible (nice for simple line-based protocols), a pure-ASCII format |
… | |
… | |
99 | |
85 | |
100 | =cut |
86 | =cut |
101 | |
87 | |
102 | package JSON::XS; |
88 | package JSON::XS; |
103 | |
89 | |
104 | no warnings; |
90 | use common::sense; |
105 | use strict; |
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106 | |
91 | |
107 | our $VERSION = '2.231'; |
92 | our $VERSION = '4.0'; |
108 | our @ISA = qw(Exporter); |
93 | our @ISA = qw(Exporter); |
109 | |
94 | |
110 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
95 | our @EXPORT = qw(encode_json decode_json); |
111 | |
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112 | sub to_json($) { |
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113 | require Carp; |
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114 | 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"); |
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115 | } |
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116 | |
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117 | sub from_json($) { |
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118 | require Carp; |
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119 | 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"); |
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120 | } |
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121 | |
96 | |
122 | use Exporter; |
97 | use Exporter; |
123 | use XSLoader; |
98 | use XSLoader; |
124 | |
99 | |
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100 | use Types::Serialiser (); |
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101 | |
125 | =head1 FUNCTIONAL INTERFACE |
102 | =head1 FUNCTIONAL INTERFACE |
126 | |
103 | |
127 | The following convenience methods are provided by this module. They are |
104 | The following convenience methods are provided by this module. They are |
128 | exported by default: |
105 | exported by default: |
129 | |
106 | |
130 | =over 4 |
107 | =over |
131 | |
108 | |
132 | =item $json_text = encode_json $perl_scalar |
109 | =item $json_text = encode_json $perl_scalar |
133 | |
110 | |
134 | Converts the given Perl data structure to a UTF-8 encoded, binary string |
111 | Converts the given Perl data structure to a UTF-8 encoded, binary string |
135 | (that is, the string contains octets only). Croaks on error. |
112 | (that is, the string contains octets only). Croaks on error. |
… | |
… | |
140 | |
117 | |
141 | Except being faster. |
118 | Except being faster. |
142 | |
119 | |
143 | =item $perl_scalar = decode_json $json_text |
120 | =item $perl_scalar = decode_json $json_text |
144 | |
121 | |
145 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
122 | The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries |
146 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
123 | to parse that as a UTF-8 encoded JSON text, returning the resulting |
147 | reference. Croaks on error. |
124 | reference. Croaks on error. |
148 | |
125 | |
149 | This function call is functionally identical to: |
126 | This function call is functionally identical to: |
150 | |
127 | |
151 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
128 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
152 | |
129 | |
153 | Except being faster. |
130 | Except being faster. |
154 | |
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155 | =item $is_boolean = JSON::XS::is_bool $scalar |
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156 | |
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157 | Returns true if the passed scalar represents either JSON::XS::true or |
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158 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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159 | and are used to represent JSON C<true> and C<false> values in Perl. |
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160 | |
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161 | See MAPPING, below, for more information on how JSON values are mapped to |
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162 | Perl. |
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163 | |
131 | |
164 | =back |
132 | =back |
165 | |
133 | |
166 | |
134 | |
167 | =head1 A FEW NOTES ON UNICODE AND PERL |
135 | =head1 A FEW NOTES ON UNICODE AND PERL |
168 | |
136 | |
169 | Since this often leads to confusion, here are a few very clear words on |
137 | Since this often leads to confusion, here are a few very clear words on |
170 | how Unicode works in Perl, modulo bugs. |
138 | how Unicode works in Perl, modulo bugs. |
171 | |
139 | |
172 | =over 4 |
140 | =over |
173 | |
141 | |
174 | =item 1. Perl strings can store characters with ordinal values > 255. |
142 | =item 1. Perl strings can store characters with ordinal values > 255. |
175 | |
143 | |
176 | This enables you to store Unicode characters as single characters in a |
144 | This enables you to store Unicode characters as single characters in a |
177 | Perl string - very natural. |
145 | Perl string - very natural. |
… | |
… | |
215 | =head1 OBJECT-ORIENTED INTERFACE |
183 | =head1 OBJECT-ORIENTED INTERFACE |
216 | |
184 | |
217 | The object oriented interface lets you configure your own encoding or |
185 | The object oriented interface lets you configure your own encoding or |
218 | decoding style, within the limits of supported formats. |
186 | decoding style, within the limits of supported formats. |
219 | |
187 | |
220 | =over 4 |
188 | =over |
221 | |
189 | |
222 | =item $json = new JSON::XS |
190 | =item $json = new JSON::XS |
223 | |
191 | |
224 | Creates a new JSON::XS object that can be used to de/encode JSON |
192 | Creates a new JSON::XS object that can be used to de/encode JSON |
225 | strings. All boolean flags described below are by default I<disabled>. |
193 | strings. All boolean flags described below are by default I<disabled> |
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194 | (with the exception of C<allow_nonref>, which defaults to I<enabled> since |
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195 | version C<4.0>). |
226 | |
196 | |
227 | The mutators for flags all return the JSON object again and thus calls can |
197 | The mutators for flags all return the JSON object again and thus calls can |
228 | be chained: |
198 | be chained: |
229 | |
199 | |
230 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
200 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
… | |
… | |
288 | |
258 | |
289 | =item $enabled = $json->get_utf8 |
259 | =item $enabled = $json->get_utf8 |
290 | |
260 | |
291 | If C<$enable> is true (or missing), then the C<encode> method will encode |
261 | If C<$enable> is true (or missing), then the C<encode> method will encode |
292 | the JSON result into UTF-8, as required by many protocols, while the |
262 | the JSON result into UTF-8, as required by many protocols, while the |
293 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
263 | C<decode> method expects to be handed a UTF-8-encoded string. Please |
294 | note that UTF-8-encoded strings do not contain any characters outside the |
264 | note that UTF-8-encoded strings do not contain any characters outside the |
295 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
265 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
296 | versions, enabling this option might enable autodetection of the UTF-16 |
266 | versions, enabling this option might enable autodetection of the UTF-16 |
297 | and UTF-32 encoding families, as described in RFC4627. |
267 | and UTF-32 encoding families, as described in RFC4627. |
298 | |
268 | |
… | |
… | |
383 | |
353 | |
384 | =item $enabled = $json->get_relaxed |
354 | =item $enabled = $json->get_relaxed |
385 | |
355 | |
386 | If C<$enable> is true (or missing), then C<decode> will accept some |
356 | If C<$enable> is true (or missing), then C<decode> will accept some |
387 | extensions to normal JSON syntax (see below). C<encode> will not be |
357 | extensions to normal JSON syntax (see below). C<encode> will not be |
388 | affected in anyway. I<Be aware that this option makes you accept invalid |
358 | affected in any way. I<Be aware that this option makes you accept invalid |
389 | JSON texts as if they were valid!>. I suggest only to use this option to |
359 | JSON texts as if they were valid!>. I suggest only to use this option to |
390 | parse application-specific files written by humans (configuration files, |
360 | parse application-specific files written by humans (configuration files, |
391 | resource files etc.) |
361 | resource files etc.) |
392 | |
362 | |
393 | If C<$enable> is false (the default), then C<decode> will only accept |
363 | If C<$enable> is false (the default), then C<decode> will only accept |
394 | valid JSON texts. |
364 | valid JSON texts. |
395 | |
365 | |
396 | Currently accepted extensions are: |
366 | Currently accepted extensions are: |
397 | |
367 | |
398 | =over 4 |
368 | =over |
399 | |
369 | |
400 | =item * list items can have an end-comma |
370 | =item * list items can have an end-comma |
401 | |
371 | |
402 | JSON I<separates> array elements and key-value pairs with commas. This |
372 | JSON I<separates> array elements and key-value pairs with commas. This |
403 | can be annoying if you write JSON texts manually and want to be able to |
373 | can be annoying if you write JSON texts manually and want to be able to |
… | |
… | |
422 | [ |
392 | [ |
423 | 1, # this comment not allowed in JSON |
393 | 1, # this comment not allowed in JSON |
424 | # neither this one... |
394 | # neither this one... |
425 | ] |
395 | ] |
426 | |
396 | |
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397 | =item * literal ASCII TAB characters in strings |
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398 | |
|
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399 | Literal ASCII TAB characters are now allowed in strings (and treated as |
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400 | C<\t>). |
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401 | |
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402 | [ |
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403 | "Hello\tWorld", |
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404 | "Hello<TAB>World", # literal <TAB> would not normally be allowed |
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405 | ] |
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406 | |
427 | =back |
407 | =back |
428 | |
408 | |
429 | =item $json = $json->canonical ([$enable]) |
409 | =item $json = $json->canonical ([$enable]) |
430 | |
410 | |
431 | =item $enabled = $json->get_canonical |
411 | =item $enabled = $json->get_canonical |
… | |
… | |
433 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
413 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
434 | by sorting their keys. This is adding a comparatively high overhead. |
414 | by sorting their keys. This is adding a comparatively high overhead. |
435 | |
415 | |
436 | If C<$enable> is false, then the C<encode> method will output key-value |
416 | If C<$enable> is false, then the C<encode> method will output key-value |
437 | pairs in the order Perl stores them (which will likely change between runs |
417 | pairs in the order Perl stores them (which will likely change between runs |
438 | of the same script). |
418 | of the same script, and can change even within the same run from 5.18 |
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419 | onwards). |
439 | |
420 | |
440 | This option is useful if you want the same data structure to be encoded as |
421 | This option is useful if you want the same data structure to be encoded as |
441 | the same JSON text (given the same overall settings). If it is disabled, |
422 | the same JSON text (given the same overall settings). If it is disabled, |
442 | the same hash might be encoded differently even if contains the same data, |
423 | the same hash might be encoded differently even if contains the same data, |
443 | as key-value pairs have no inherent ordering in Perl. |
424 | as key-value pairs have no inherent ordering in Perl. |
444 | |
425 | |
445 | This setting has no effect when decoding JSON texts. |
426 | This setting has no effect when decoding JSON texts. |
446 | |
427 | |
|
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428 | This setting has currently no effect on tied hashes. |
|
|
429 | |
447 | =item $json = $json->allow_nonref ([$enable]) |
430 | =item $json = $json->allow_nonref ([$enable]) |
448 | |
431 | |
449 | =item $enabled = $json->get_allow_nonref |
432 | =item $enabled = $json->get_allow_nonref |
|
|
433 | |
|
|
434 | Unlike other boolean options, this opotion is enabled by default beginning |
|
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435 | with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details. |
450 | |
436 | |
451 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
437 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
452 | non-reference into its corresponding string, number or null JSON value, |
438 | non-reference into its corresponding string, number or null JSON value, |
453 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
439 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
454 | values instead of croaking. |
440 | values instead of croaking. |
… | |
… | |
456 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
442 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
457 | passed an arrayref or hashref, as JSON texts must either be an object |
443 | passed an arrayref or hashref, as JSON texts must either be an object |
458 | or array. Likewise, C<decode> will croak if given something that is not a |
444 | or array. Likewise, C<decode> will croak if given something that is not a |
459 | JSON object or array. |
445 | JSON object or array. |
460 | |
446 | |
461 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
447 | Example, encode a Perl scalar as JSON value without enabled C<allow_nonref>, |
462 | resulting in an invalid JSON text: |
448 | resulting in an error: |
463 | |
449 | |
464 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
450 | JSON::XS->new->allow_nonref (0)->encode ("Hello, World!") |
465 | => "Hello, World!" |
451 | => hash- or arrayref expected... |
466 | |
452 | |
467 | =item $json = $json->allow_unknown ([$enable]) |
453 | =item $json = $json->allow_unknown ([$enable]) |
468 | |
454 | |
469 | =item $enabled = $json->get_allow_unknown |
455 | =item $enabled = $json->get_allow_unknown |
470 | |
456 | |
… | |
… | |
482 | |
468 | |
483 | =item $json = $json->allow_blessed ([$enable]) |
469 | =item $json = $json->allow_blessed ([$enable]) |
484 | |
470 | |
485 | =item $enabled = $json->get_allow_blessed |
471 | =item $enabled = $json->get_allow_blessed |
486 | |
472 | |
|
|
473 | See L<OBJECT SERIALISATION> for details. |
|
|
474 | |
487 | If C<$enable> is true (or missing), then the C<encode> method will not |
475 | If C<$enable> is true (or missing), then the C<encode> method will not |
488 | barf when it encounters a blessed reference. Instead, the value of the |
476 | barf when it encounters a blessed reference that it cannot convert |
489 | B<convert_blessed> option will decide whether C<null> (C<convert_blessed> |
477 | otherwise. Instead, a JSON C<null> value is encoded instead of the object. |
490 | disabled or no C<TO_JSON> method found) or a representation of the |
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491 | object (C<convert_blessed> enabled and C<TO_JSON> method found) is being |
|
|
492 | encoded. Has no effect on C<decode>. |
|
|
493 | |
478 | |
494 | If C<$enable> is false (the default), then C<encode> will throw an |
479 | If C<$enable> is false (the default), then C<encode> will throw an |
495 | exception when it encounters a blessed object. |
480 | exception when it encounters a blessed object that it cannot convert |
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481 | otherwise. |
|
|
482 | |
|
|
483 | This setting has no effect on C<decode>. |
496 | |
484 | |
497 | =item $json = $json->convert_blessed ([$enable]) |
485 | =item $json = $json->convert_blessed ([$enable]) |
498 | |
486 | |
499 | =item $enabled = $json->get_convert_blessed |
487 | =item $enabled = $json->get_convert_blessed |
|
|
488 | |
|
|
489 | See L<OBJECT SERIALISATION> for details. |
500 | |
490 | |
501 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
491 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
502 | blessed object, will check for the availability of the C<TO_JSON> method |
492 | blessed object, will check for the availability of the C<TO_JSON> method |
503 | on the object's class. If found, it will be called in scalar context |
493 | on the object's class. If found, it will be called in scalar context and |
504 | and the resulting scalar will be encoded instead of the object. If no |
494 | the resulting scalar will be encoded instead of the object. |
505 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
|
|
506 | to do. |
|
|
507 | |
495 | |
508 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
496 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
509 | returns other blessed objects, those will be handled in the same |
497 | returns other blessed objects, those will be handled in the same |
510 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
498 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
511 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
499 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
512 | methods called by the Perl core (== not by the user of the object) are |
500 | methods called by the Perl core (== not by the user of the object) are |
513 | usually in upper case letters and to avoid collisions with any C<to_json> |
501 | usually in upper case letters and to avoid collisions with any C<to_json> |
514 | function or method. |
502 | function or method. |
515 | |
503 | |
516 | This setting does not yet influence C<decode> in any way, but in the |
504 | If C<$enable> is false (the default), then C<encode> will not consider |
517 | future, global hooks might get installed that influence C<decode> and are |
505 | this type of conversion. |
518 | enabled by this setting. |
|
|
519 | |
506 | |
520 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
507 | This setting has no effect on C<decode>. |
521 | to do when a blessed object is found. |
508 | |
|
|
509 | =item $json = $json->allow_tags ([$enable]) |
|
|
510 | |
|
|
511 | =item $enabled = $json->get_allow_tags |
|
|
512 | |
|
|
513 | See L<OBJECT SERIALISATION> for details. |
|
|
514 | |
|
|
515 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
|
|
516 | blessed object, will check for the availability of the C<FREEZE> method on |
|
|
517 | the object's class. If found, it will be used to serialise the object into |
|
|
518 | a nonstandard tagged JSON value (that JSON decoders cannot decode). |
|
|
519 | |
|
|
520 | It also causes C<decode> to parse such tagged JSON values and deserialise |
|
|
521 | them via a call to the C<THAW> method. |
|
|
522 | |
|
|
523 | If C<$enable> is false (the default), then C<encode> will not consider |
|
|
524 | this type of conversion, and tagged JSON values will cause a parse error |
|
|
525 | in C<decode>, as if tags were not part of the grammar. |
|
|
526 | |
|
|
527 | =item $json->boolean_values ([$false, $true]) |
|
|
528 | |
|
|
529 | =item ($false, $true) = $json->get_boolean_values |
|
|
530 | |
|
|
531 | By default, JSON booleans will be decoded as overloaded |
|
|
532 | C<$Types::Serialiser::false> and C<$Types::Serialiser::true> objects. |
|
|
533 | |
|
|
534 | With this method you can specify your own boolean values for decoding - |
|
|
535 | on decode, JSON C<false> will be decoded as a copy of C<$false>, and JSON |
|
|
536 | C<true> will be decoded as C<$true> ("copy" here is the same thing as |
|
|
537 | assigning a value to another variable, i.e. C<$copy = $false>). |
|
|
538 | |
|
|
539 | Calling this method without any arguments will reset the booleans |
|
|
540 | to their default values. |
|
|
541 | |
|
|
542 | C<get_boolean_values> will return both C<$false> and C<$true> values, or |
|
|
543 | the empty list when they are set to the default. |
522 | |
544 | |
523 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
545 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
524 | |
546 | |
525 | When C<$coderef> is specified, it will be called from C<decode> each |
547 | When C<$coderef> is specified, it will be called from C<decode> each |
526 | time it decodes a JSON object. The only argument is a reference to the |
548 | time it decodes a JSON object. The only argument is a reference to |
527 | newly-created hash. If the code references returns a single scalar (which |
549 | the newly-created hash. If the code reference returns a single scalar |
528 | need not be a reference), this value (i.e. a copy of that scalar to avoid |
550 | (which need not be a reference), this value (or rather a copy of it) is |
529 | aliasing) is inserted into the deserialised data structure. If it returns |
551 | inserted into the deserialised data structure. If it returns an empty |
530 | an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the |
552 | list (NOTE: I<not> C<undef>, which is a valid scalar), the original |
531 | original deserialised hash will be inserted. This setting can slow down |
553 | deserialised hash will be inserted. This setting can slow down decoding |
532 | decoding considerably. |
554 | considerably. |
533 | |
555 | |
534 | When C<$coderef> is omitted or undefined, any existing callback will |
556 | When C<$coderef> is omitted or undefined, any existing callback will |
535 | be removed and C<decode> will not change the deserialised hash in any |
557 | be removed and C<decode> will not change the deserialised hash in any |
536 | way. |
558 | way. |
537 | |
559 | |
… | |
… | |
665 | |
687 | |
666 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
688 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
667 | |
689 | |
668 | =item $json_text = $json->encode ($perl_scalar) |
690 | =item $json_text = $json->encode ($perl_scalar) |
669 | |
691 | |
670 | Converts the given Perl data structure (a simple scalar or a reference |
692 | Converts the given Perl value or data structure to its JSON |
671 | to a hash or array) to its JSON representation. Simple scalars will be |
693 | representation. Croaks on error. |
672 | converted into JSON string or number sequences, while references to arrays |
|
|
673 | become JSON arrays and references to hashes become JSON objects. Undefined |
|
|
674 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
|
|
675 | nor C<false> values will be generated. |
|
|
676 | |
694 | |
677 | =item $perl_scalar = $json->decode ($json_text) |
695 | =item $perl_scalar = $json->decode ($json_text) |
678 | |
696 | |
679 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
697 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
680 | returning the resulting simple scalar or reference. Croaks on error. |
698 | returning the resulting simple scalar or reference. Croaks on error. |
681 | |
|
|
682 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
|
|
683 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
|
|
684 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
|
|
685 | |
699 | |
686 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
700 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
687 | |
701 | |
688 | This works like the C<decode> method, but instead of raising an exception |
702 | This works like the C<decode> method, but instead of raising an exception |
689 | when there is trailing garbage after the first JSON object, it will |
703 | when there is trailing garbage after the first JSON object, it will |
690 | silently stop parsing there and return the number of characters consumed |
704 | silently stop parsing there and return the number of characters consumed |
691 | so far. |
705 | so far. |
692 | |
706 | |
693 | This is useful if your JSON texts are not delimited by an outer protocol |
707 | This is useful if your JSON texts are not delimited by an outer protocol |
694 | (which is not the brightest thing to do in the first place) and you need |
|
|
695 | to know where the JSON text ends. |
708 | and you need to know where the JSON text ends. |
696 | |
709 | |
697 | JSON::XS->new->decode_prefix ("[1] the tail") |
710 | JSON::XS->new->decode_prefix ("[1] the tail") |
698 | => ([], 3) |
711 | => ([1], 3) |
699 | |
712 | |
700 | =back |
713 | =back |
701 | |
714 | |
702 | |
715 | |
703 | =head1 INCREMENTAL PARSING |
716 | =head1 INCREMENTAL PARSING |
… | |
… | |
712 | calls). |
725 | calls). |
713 | |
726 | |
714 | JSON::XS will only attempt to parse the JSON text once it is sure it |
727 | JSON::XS will only attempt to parse the JSON text once it is sure it |
715 | has enough text to get a decisive result, using a very simple but |
728 | has enough text to get a decisive result, using a very simple but |
716 | truly incremental parser. This means that it sometimes won't stop as |
729 | truly incremental parser. This means that it sometimes won't stop as |
717 | early as the full parser, for example, it doesn't detect parenthese |
730 | early as the full parser, for example, it doesn't detect mismatched |
718 | mismatches. The only thing it guarantees is that it starts decoding as |
731 | parentheses. The only thing it guarantees is that it starts decoding as |
719 | soon as a syntactically valid JSON text has been seen. This means you need |
732 | soon as a syntactically valid JSON text has been seen. This means you need |
720 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
733 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
721 | parsing in the presence if syntax errors. |
734 | parsing in the presence if syntax errors. |
722 | |
735 | |
723 | The following methods implement this incremental parser. |
736 | The following methods implement this incremental parser. |
724 | |
737 | |
725 | =over 4 |
738 | =over |
726 | |
739 | |
727 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
740 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
728 | |
741 | |
729 | This is the central parsing function. It can both append new text and |
742 | This is the central parsing function. It can both append new text and |
730 | extract objects from the stream accumulated so far (both of these |
743 | extract objects from the stream accumulated so far (both of these |
… | |
… | |
739 | |
752 | |
740 | If the method is called in scalar context, then it will try to extract |
753 | If the method is called in scalar context, then it will try to extract |
741 | exactly I<one> JSON object. If that is successful, it will return this |
754 | exactly I<one> JSON object. If that is successful, it will return this |
742 | object, otherwise it will return C<undef>. If there is a parse error, |
755 | object, otherwise it will return C<undef>. If there is a parse error, |
743 | this method will croak just as C<decode> would do (one can then use |
756 | this method will croak just as C<decode> would do (one can then use |
744 | C<incr_skip> to skip the errornous part). This is the most common way of |
757 | C<incr_skip> to skip the erroneous part). This is the most common way of |
745 | using the method. |
758 | using the method. |
746 | |
759 | |
747 | And finally, in list context, it will try to extract as many objects |
760 | And finally, in list context, it will try to extract as many objects |
748 | from the stream as it can find and return them, or the empty list |
761 | from the stream as it can find and return them, or the empty list |
749 | otherwise. For this to work, there must be no separators between the JSON |
762 | otherwise. For this to work, there must be no separators (other than |
750 | objects or arrays, instead they must be concatenated back-to-back. If |
763 | whitespace) between the JSON objects or arrays, instead they must be |
751 | an error occurs, an exception will be raised as in the scalar context |
764 | concatenated back-to-back. If an error occurs, an exception will be |
752 | case. Note that in this case, any previously-parsed JSON texts will be |
765 | raised as in the scalar context case. Note that in this case, any |
753 | lost. |
766 | previously-parsed JSON texts will be lost. |
|
|
767 | |
|
|
768 | Example: Parse some JSON arrays/objects in a given string and return |
|
|
769 | them. |
|
|
770 | |
|
|
771 | my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]"); |
754 | |
772 | |
755 | =item $lvalue_string = $json->incr_text |
773 | =item $lvalue_string = $json->incr_text |
756 | |
774 | |
757 | This method returns the currently stored JSON fragment as an lvalue, that |
775 | This method returns the currently stored JSON fragment as an lvalue, that |
758 | is, you can manipulate it. This I<only> works when a preceding call to |
776 | is, you can manipulate it. This I<only> works when a preceding call to |
… | |
… | |
760 | all other circumstances you must not call this function (I mean it. |
778 | all other circumstances you must not call this function (I mean it. |
761 | although in simple tests it might actually work, it I<will> fail under |
779 | although in simple tests it might actually work, it I<will> fail under |
762 | real world conditions). As a special exception, you can also call this |
780 | real world conditions). As a special exception, you can also call this |
763 | method before having parsed anything. |
781 | method before having parsed anything. |
764 | |
782 | |
|
|
783 | That means you can only use this function to look at or manipulate text |
|
|
784 | before or after complete JSON objects, not while the parser is in the |
|
|
785 | middle of parsing a JSON object. |
|
|
786 | |
765 | This function is useful in two cases: a) finding the trailing text after a |
787 | This function is useful in two cases: a) finding the trailing text after a |
766 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
788 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
767 | (such as commas). |
789 | (such as commas). |
768 | |
790 | |
769 | =item $json->incr_skip |
791 | =item $json->incr_skip |
… | |
… | |
773 | C<incr_parse> died, in which case the input buffer and incremental parser |
795 | C<incr_parse> died, in which case the input buffer and incremental parser |
774 | state is left unchanged, to skip the text parsed so far and to reset the |
796 | state is left unchanged, to skip the text parsed so far and to reset the |
775 | parse state. |
797 | parse state. |
776 | |
798 | |
777 | The difference to C<incr_reset> is that only text until the parse error |
799 | The difference to C<incr_reset> is that only text until the parse error |
778 | occured is removed. |
800 | occurred is removed. |
779 | |
801 | |
780 | =item $json->incr_reset |
802 | =item $json->incr_reset |
781 | |
803 | |
782 | This completely resets the incremental parser, that is, after this call, |
804 | This completely resets the incremental parser, that is, after this call, |
783 | it will be as if the parser had never parsed anything. |
805 | it will be as if the parser had never parsed anything. |
… | |
… | |
788 | |
810 | |
789 | =back |
811 | =back |
790 | |
812 | |
791 | =head2 LIMITATIONS |
813 | =head2 LIMITATIONS |
792 | |
814 | |
793 | All options that affect decoding are supported, except |
815 | The incremental parser is a non-exact parser: it works by gathering as |
794 | C<allow_nonref>. The reason for this is that it cannot be made to |
816 | much text as possible that I<could> be a valid JSON text, followed by |
795 | work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate |
817 | trying to decode it. |
796 | them back to back and still decode them perfectly. This does not hold true |
|
|
797 | for JSON numbers, however. |
|
|
798 | |
818 | |
799 | For example, is the string C<1> a single JSON number, or is it simply the |
819 | That means it sometimes needs to read more data than strictly necessary to |
800 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
820 | diagnose an invalid JSON text. For example, after parsing the following |
801 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
821 | fragment, the parser I<could> stop with an error, as this fragment |
802 | takes the conservative route and disallows this case. |
822 | I<cannot> be the beginning of a valid JSON text: |
|
|
823 | |
|
|
824 | [, |
|
|
825 | |
|
|
826 | In reality, hopwever, the parser might continue to read data until a |
|
|
827 | length limit is exceeded or it finds a closing bracket. |
803 | |
828 | |
804 | =head2 EXAMPLES |
829 | =head2 EXAMPLES |
805 | |
830 | |
806 | Some examples will make all this clearer. First, a simple example that |
831 | Some examples will make all this clearer. First, a simple example that |
807 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
832 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
… | |
… | |
951 | refers to the abstract Perl language itself. |
976 | refers to the abstract Perl language itself. |
952 | |
977 | |
953 | |
978 | |
954 | =head2 JSON -> PERL |
979 | =head2 JSON -> PERL |
955 | |
980 | |
956 | =over 4 |
981 | =over |
957 | |
982 | |
958 | =item object |
983 | =item object |
959 | |
984 | |
960 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
985 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
961 | keys is preserved (JSON does not preserve object key ordering itself). |
986 | keys is preserved (JSON does not preserve object key ordering itself). |
… | |
… | |
981 | If the number consists of digits only, JSON::XS will try to represent |
1006 | If the number consists of digits only, JSON::XS will try to represent |
982 | it as an integer value. If that fails, it will try to represent it as |
1007 | it as an integer value. If that fails, it will try to represent it as |
983 | a numeric (floating point) value if that is possible without loss of |
1008 | a numeric (floating point) value if that is possible without loss of |
984 | precision. Otherwise it will preserve the number as a string value (in |
1009 | precision. Otherwise it will preserve the number as a string value (in |
985 | which case you lose roundtripping ability, as the JSON number will be |
1010 | which case you lose roundtripping ability, as the JSON number will be |
986 | re-encoded toa JSON string). |
1011 | re-encoded to a JSON string). |
987 | |
1012 | |
988 | Numbers containing a fractional or exponential part will always be |
1013 | Numbers containing a fractional or exponential part will always be |
989 | represented as numeric (floating point) values, possibly at a loss of |
1014 | represented as numeric (floating point) values, possibly at a loss of |
990 | precision (in which case you might lose perfect roundtripping ability, but |
1015 | precision (in which case you might lose perfect roundtripping ability, but |
991 | the JSON number will still be re-encoded as a JSON number). |
1016 | the JSON number will still be re-encoded as a JSON number). |
992 | |
1017 | |
|
|
1018 | Note that precision is not accuracy - binary floating point values cannot |
|
|
1019 | represent most decimal fractions exactly, and when converting from and to |
|
|
1020 | floating point, JSON::XS only guarantees precision up to but not including |
|
|
1021 | the least significant bit. |
|
|
1022 | |
993 | =item true, false |
1023 | =item true, false |
994 | |
1024 | |
995 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
1025 | These JSON atoms become C<Types::Serialiser::true> and |
996 | respectively. They are overloaded to act almost exactly like the numbers |
1026 | C<Types::Serialiser::false>, respectively. They are overloaded to act |
997 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
1027 | almost exactly like the numbers C<1> and C<0>. You can check whether |
998 | the C<JSON::XS::is_bool> function. |
1028 | a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool> |
|
|
1029 | function (after C<use Types::Serialier>, of course). |
999 | |
1030 | |
1000 | =item null |
1031 | =item null |
1001 | |
1032 | |
1002 | A JSON null atom becomes C<undef> in Perl. |
1033 | A JSON null atom becomes C<undef> in Perl. |
|
|
1034 | |
|
|
1035 | =item shell-style comments (C<< # I<text> >>) |
|
|
1036 | |
|
|
1037 | As a nonstandard extension to the JSON syntax that is enabled by the |
|
|
1038 | C<relaxed> setting, shell-style comments are allowed. They can start |
|
|
1039 | anywhere outside strings and go till the end of the line. |
|
|
1040 | |
|
|
1041 | =item tagged values (C<< (I<tag>)I<value> >>). |
|
|
1042 | |
|
|
1043 | Another nonstandard extension to the JSON syntax, enabled with the |
|
|
1044 | C<allow_tags> setting, are tagged values. In this implementation, the |
|
|
1045 | I<tag> must be a perl package/class name encoded as a JSON string, and the |
|
|
1046 | I<value> must be a JSON array encoding optional constructor arguments. |
|
|
1047 | |
|
|
1048 | See L<OBJECT SERIALISATION>, below, for details. |
1003 | |
1049 | |
1004 | =back |
1050 | =back |
1005 | |
1051 | |
1006 | |
1052 | |
1007 | =head2 PERL -> JSON |
1053 | =head2 PERL -> JSON |
1008 | |
1054 | |
1009 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
1055 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
1010 | truly typeless language, so we can only guess which JSON type is meant by |
1056 | truly typeless language, so we can only guess which JSON type is meant by |
1011 | a Perl value. |
1057 | a Perl value. |
1012 | |
1058 | |
1013 | =over 4 |
1059 | =over |
1014 | |
1060 | |
1015 | =item hash references |
1061 | =item hash references |
1016 | |
1062 | |
1017 | Perl hash references become JSON objects. As there is no inherent ordering |
1063 | Perl hash references become JSON objects. As there is no inherent |
1018 | in hash keys (or JSON objects), they will usually be encoded in a |
1064 | ordering in hash keys (or JSON objects), they will usually be encoded |
1019 | pseudo-random order that can change between runs of the same program but |
1065 | in a pseudo-random order. JSON::XS can optionally sort the hash keys |
1020 | stays generally the same within a single run of a program. JSON::XS can |
1066 | (determined by the I<canonical> flag), so the same datastructure will |
1021 | optionally sort the hash keys (determined by the I<canonical> flag), so |
1067 | serialise to the same JSON text (given same settings and version of |
1022 | the same datastructure will serialise to the same JSON text (given same |
1068 | JSON::XS), but this incurs a runtime overhead and is only rarely useful, |
1023 | settings and version of JSON::XS), but this incurs a runtime overhead |
1069 | e.g. when you want to compare some JSON text against another for equality. |
1024 | and is only rarely useful, e.g. when you want to compare some JSON text |
|
|
1025 | against another for equality. |
|
|
1026 | |
1070 | |
1027 | =item array references |
1071 | =item array references |
1028 | |
1072 | |
1029 | Perl array references become JSON arrays. |
1073 | Perl array references become JSON arrays. |
1030 | |
1074 | |
1031 | =item other references |
1075 | =item other references |
1032 | |
1076 | |
1033 | Other unblessed references are generally not allowed and will cause an |
1077 | Other unblessed references are generally not allowed and will cause an |
1034 | exception to be thrown, except for references to the integers C<0> and |
1078 | exception to be thrown, except for references to the integers C<0> and |
1035 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1079 | C<1>, which get turned into C<false> and C<true> atoms in JSON. |
1036 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
|
|
1037 | |
1080 | |
|
|
1081 | Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you |
|
|
1082 | can also C<use Types::Serialiser> and then use C<Types::Serialiser::false> |
|
|
1083 | and C<Types::Serialiser::true> to improve readability. |
|
|
1084 | |
|
|
1085 | use Types::Serialiser; |
1038 | encode_json [\0, JSON::XS::true] # yields [false,true] |
1086 | encode_json [\0, Types::Serialiser::true] # yields [false,true] |
1039 | |
1087 | |
1040 | =item JSON::XS::true, JSON::XS::false |
1088 | =item Types::Serialiser::true, Types::Serialiser::false |
1041 | |
1089 | |
1042 | These special values become JSON true and JSON false values, |
1090 | These special values from the L<Types::Serialiser> module become JSON true |
1043 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1091 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
|
|
1092 | directly if you want. |
1044 | |
1093 | |
1045 | =item blessed objects |
1094 | =item blessed objects |
1046 | |
1095 | |
1047 | Blessed objects are not directly representable in JSON. See the |
1096 | Blessed objects are not directly representable in JSON, but C<JSON::XS> |
1048 | C<allow_blessed> and C<convert_blessed> methods on various options on |
1097 | allows various ways of handling objects. See L<OBJECT SERIALISATION>, |
1049 | how to deal with this: basically, you can choose between throwing an |
1098 | below, for details. |
1050 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
1051 | your own serialiser method. |
|
|
1052 | |
1099 | |
1053 | =item simple scalars |
1100 | =item simple scalars |
1054 | |
1101 | |
1055 | Simple Perl scalars (any scalar that is not a reference) are the most |
1102 | Simple Perl scalars (any scalar that is not a reference) are the most |
1056 | difficult objects to encode: JSON::XS will encode undefined scalars as |
1103 | difficult objects to encode: JSON::XS will encode undefined scalars as |
… | |
… | |
1084 | |
1131 | |
1085 | You can not currently force the type in other, less obscure, ways. Tell me |
1132 | You can not currently force the type in other, less obscure, ways. Tell me |
1086 | if you need this capability (but don't forget to explain why it's needed |
1133 | if you need this capability (but don't forget to explain why it's needed |
1087 | :). |
1134 | :). |
1088 | |
1135 | |
|
|
1136 | Note that numerical precision has the same meaning as under Perl (so |
|
|
1137 | binary to decimal conversion follows the same rules as in Perl, which |
|
|
1138 | can differ to other languages). Also, your perl interpreter might expose |
|
|
1139 | extensions to the floating point numbers of your platform, such as |
|
|
1140 | infinities or NaN's - these cannot be represented in JSON, and it is an |
|
|
1141 | error to pass those in. |
|
|
1142 | |
1089 | =back |
1143 | =back |
|
|
1144 | |
|
|
1145 | =head2 OBJECT SERIALISATION |
|
|
1146 | |
|
|
1147 | As JSON cannot directly represent Perl objects, you have to choose between |
|
|
1148 | a pure JSON representation (without the ability to deserialise the object |
|
|
1149 | automatically again), and a nonstandard extension to the JSON syntax, |
|
|
1150 | tagged values. |
|
|
1151 | |
|
|
1152 | =head3 SERIALISATION |
|
|
1153 | |
|
|
1154 | What happens when C<JSON::XS> encounters a Perl object depends on the |
|
|
1155 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
|
|
1156 | used in this order: |
|
|
1157 | |
|
|
1158 | =over |
|
|
1159 | |
|
|
1160 | =item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method. |
|
|
1161 | |
|
|
1162 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
|
|
1163 | serialisation protocol to create a tagged JSON value, using a nonstandard |
|
|
1164 | extension to the JSON syntax. |
|
|
1165 | |
|
|
1166 | This works by invoking the C<FREEZE> method on the object, with the first |
|
|
1167 | argument being the object to serialise, and the second argument being the |
|
|
1168 | constant string C<JSON> to distinguish it from other serialisers. |
|
|
1169 | |
|
|
1170 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
1171 | more). These values and the paclkage/classname of the object will then be |
|
|
1172 | encoded as a tagged JSON value in the following format: |
|
|
1173 | |
|
|
1174 | ("classname")[FREEZE return values...] |
|
|
1175 | |
|
|
1176 | e.g.: |
|
|
1177 | |
|
|
1178 | ("URI")["http://www.google.com/"] |
|
|
1179 | ("MyDate")[2013,10,29] |
|
|
1180 | ("ImageData::JPEG")["Z3...VlCg=="] |
|
|
1181 | |
|
|
1182 | For example, the hypothetical C<My::Object> C<FREEZE> method might use the |
|
|
1183 | objects C<type> and C<id> members to encode the object: |
|
|
1184 | |
|
|
1185 | sub My::Object::FREEZE { |
|
|
1186 | my ($self, $serialiser) = @_; |
|
|
1187 | |
|
|
1188 | ($self->{type}, $self->{id}) |
|
|
1189 | } |
|
|
1190 | |
|
|
1191 | =item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method. |
|
|
1192 | |
|
|
1193 | In this case, the C<TO_JSON> method of the object is invoked in scalar |
|
|
1194 | context. It must return a single scalar that can be directly encoded into |
|
|
1195 | JSON. This scalar replaces the object in the JSON text. |
|
|
1196 | |
|
|
1197 | For example, the following C<TO_JSON> method will convert all L<URI> |
|
|
1198 | objects to JSON strings when serialised. The fatc that these values |
|
|
1199 | originally were L<URI> objects is lost. |
|
|
1200 | |
|
|
1201 | sub URI::TO_JSON { |
|
|
1202 | my ($uri) = @_; |
|
|
1203 | $uri->as_string |
|
|
1204 | } |
|
|
1205 | |
|
|
1206 | =item 3. C<allow_blessed> is enabled. |
|
|
1207 | |
|
|
1208 | The object will be serialised as a JSON null value. |
|
|
1209 | |
|
|
1210 | =item 4. none of the above |
|
|
1211 | |
|
|
1212 | If none of the settings are enabled or the respective methods are missing, |
|
|
1213 | C<JSON::XS> throws an exception. |
|
|
1214 | |
|
|
1215 | =back |
|
|
1216 | |
|
|
1217 | =head3 DESERIALISATION |
|
|
1218 | |
|
|
1219 | For deserialisation there are only two cases to consider: either |
|
|
1220 | nonstandard tagging was used, in which case C<allow_tags> decides, |
|
|
1221 | or objects cannot be automatically be deserialised, in which |
|
|
1222 | case you can use postprocessing or the C<filter_json_object> or |
|
|
1223 | C<filter_json_single_key_object> callbacks to get some real objects our of |
|
|
1224 | your JSON. |
|
|
1225 | |
|
|
1226 | This section only considers the tagged value case: I a tagged JSON object |
|
|
1227 | is encountered during decoding and C<allow_tags> is disabled, a parse |
|
|
1228 | error will result (as if tagged values were not part of the grammar). |
|
|
1229 | |
|
|
1230 | If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method |
|
|
1231 | of the package/classname used during serialisation (it will not attempt |
|
|
1232 | to load the package as a Perl module). If there is no such method, the |
|
|
1233 | decoding will fail with an error. |
|
|
1234 | |
|
|
1235 | Otherwise, the C<THAW> method is invoked with the classname as first |
|
|
1236 | argument, the constant string C<JSON> as second argument, and all the |
|
|
1237 | values from the JSON array (the values originally returned by the |
|
|
1238 | C<FREEZE> method) as remaining arguments. |
|
|
1239 | |
|
|
1240 | The method must then return the object. While technically you can return |
|
|
1241 | any Perl scalar, you might have to enable the C<enable_nonref> setting to |
|
|
1242 | make that work in all cases, so better return an actual blessed reference. |
|
|
1243 | |
|
|
1244 | As an example, let's implement a C<THAW> function that regenerates the |
|
|
1245 | C<My::Object> from the C<FREEZE> example earlier: |
|
|
1246 | |
|
|
1247 | sub My::Object::THAW { |
|
|
1248 | my ($class, $serialiser, $type, $id) = @_; |
|
|
1249 | |
|
|
1250 | $class->new (type => $type, id => $id) |
|
|
1251 | } |
1090 | |
1252 | |
1091 | |
1253 | |
1092 | =head1 ENCODING/CODESET FLAG NOTES |
1254 | =head1 ENCODING/CODESET FLAG NOTES |
1093 | |
1255 | |
1094 | The interested reader might have seen a number of flags that signify |
1256 | The interested reader might have seen a number of flags that signify |
… | |
… | |
1112 | takes those codepoint numbers and I<encodes> them, in our case into |
1274 | takes those codepoint numbers and I<encodes> them, in our case into |
1113 | octets. Unicode is (among other things) a codeset, UTF-8 is an encoding, |
1275 | octets. Unicode is (among other things) a codeset, UTF-8 is an encoding, |
1114 | and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at |
1276 | and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at |
1115 | the same time, which can be confusing. |
1277 | the same time, which can be confusing. |
1116 | |
1278 | |
1117 | =over 4 |
1279 | =over |
1118 | |
1280 | |
1119 | =item C<utf8> flag disabled |
1281 | =item C<utf8> flag disabled |
1120 | |
1282 | |
1121 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1283 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1122 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1284 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1123 | values (> 255) will be encoded as such characters, and likewise such |
1285 | values (> 255) will be encoded as such characters, and likewise such |
1124 | characters are decoded as-is, no canges to them will be done, except |
1286 | characters are decoded as-is, no changes to them will be done, except |
1125 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1287 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1126 | respectively (to Perl, these are the same thing in strings unless you do |
1288 | respectively (to Perl, these are the same thing in strings unless you do |
1127 | funny/weird/dumb stuff). |
1289 | funny/weird/dumb stuff). |
1128 | |
1290 | |
1129 | This is useful when you want to do the encoding yourself (e.g. when you |
1291 | This is useful when you want to do the encoding yourself (e.g. when you |
… | |
… | |
1139 | expect your input strings to be encoded as UTF-8, that is, no "character" |
1301 | expect your input strings to be encoded as UTF-8, that is, no "character" |
1140 | of the input string must have any value > 255, as UTF-8 does not allow |
1302 | of the input string must have any value > 255, as UTF-8 does not allow |
1141 | that. |
1303 | that. |
1142 | |
1304 | |
1143 | The C<utf8> flag therefore switches between two modes: disabled means you |
1305 | The C<utf8> flag therefore switches between two modes: disabled means you |
1144 | will get a Unicode string in Perl, enabled means you get an UTF-8 encoded |
1306 | will get a Unicode string in Perl, enabled means you get a UTF-8 encoded |
1145 | octet/binary string in Perl. |
1307 | octet/binary string in Perl. |
1146 | |
1308 | |
1147 | =item C<latin1> or C<ascii> flags enabled |
1309 | =item C<latin1> or C<ascii> flags enabled |
1148 | |
1310 | |
1149 | With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters |
1311 | With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters |
… | |
… | |
1185 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1347 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1186 | |
1348 | |
1187 | =back |
1349 | =back |
1188 | |
1350 | |
1189 | |
1351 | |
|
|
1352 | =head2 JSON and ECMAscript |
|
|
1353 | |
|
|
1354 | JSON syntax is based on how literals are represented in javascript (the |
|
|
1355 | not-standardised predecessor of ECMAscript) which is presumably why it is |
|
|
1356 | called "JavaScript Object Notation". |
|
|
1357 | |
|
|
1358 | However, JSON is not a subset (and also not a superset of course) of |
|
|
1359 | ECMAscript (the standard) or javascript (whatever browsers actually |
|
|
1360 | implement). |
|
|
1361 | |
|
|
1362 | If you want to use javascript's C<eval> function to "parse" JSON, you |
|
|
1363 | might run into parse errors for valid JSON texts, or the resulting data |
|
|
1364 | structure might not be queryable: |
|
|
1365 | |
|
|
1366 | One of the problems is that U+2028 and U+2029 are valid characters inside |
|
|
1367 | JSON strings, but are not allowed in ECMAscript string literals, so the |
|
|
1368 | following Perl fragment will not output something that can be guaranteed |
|
|
1369 | to be parsable by javascript's C<eval>: |
|
|
1370 | |
|
|
1371 | use JSON::XS; |
|
|
1372 | |
|
|
1373 | print encode_json [chr 0x2028]; |
|
|
1374 | |
|
|
1375 | The right fix for this is to use a proper JSON parser in your javascript |
|
|
1376 | programs, and not rely on C<eval> (see for example Douglas Crockford's |
|
|
1377 | F<json2.js> parser). |
|
|
1378 | |
|
|
1379 | If this is not an option, you can, as a stop-gap measure, simply encode to |
|
|
1380 | ASCII-only JSON: |
|
|
1381 | |
|
|
1382 | use JSON::XS; |
|
|
1383 | |
|
|
1384 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
|
|
1385 | |
|
|
1386 | Note that this will enlarge the resulting JSON text quite a bit if you |
|
|
1387 | have many non-ASCII characters. You might be tempted to run some regexes |
|
|
1388 | to only escape U+2028 and U+2029, e.g.: |
|
|
1389 | |
|
|
1390 | # DO NOT USE THIS! |
|
|
1391 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
|
|
1392 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
|
|
1393 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
|
|
1394 | print $json; |
|
|
1395 | |
|
|
1396 | Note that I<this is a bad idea>: the above only works for U+2028 and |
|
|
1397 | U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing |
|
|
1398 | javascript implementations, however, have issues with other characters as |
|
|
1399 | well - using C<eval> naively simply I<will> cause problems. |
|
|
1400 | |
|
|
1401 | Another problem is that some javascript implementations reserve |
|
|
1402 | some property names for their own purposes (which probably makes |
|
|
1403 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
|
|
1404 | C<__proto__> property name for its own purposes. |
|
|
1405 | |
|
|
1406 | If that is a problem, you could parse try to filter the resulting JSON |
|
|
1407 | output for these property strings, e.g.: |
|
|
1408 | |
|
|
1409 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
|
|
1410 | |
|
|
1411 | This works because C<__proto__> is not valid outside of strings, so every |
|
|
1412 | occurrence of C<"__proto__"\s*:> must be a string used as property name. |
|
|
1413 | |
|
|
1414 | If you know of other incompatibilities, please let me know. |
|
|
1415 | |
|
|
1416 | |
1190 | =head2 JSON and YAML |
1417 | =head2 JSON and YAML |
1191 | |
1418 | |
1192 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1419 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1193 | hysteria(*) and very far from the truth (as of the time of this writing), |
1420 | hysteria(*) and very far from the truth (as of the time of this writing), |
1194 | so let me state it clearly: I<in general, there is no way to configure |
1421 | so let me state it clearly: I<in general, there is no way to configure |
… | |
… | |
1202 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1429 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1203 | |
1430 | |
1204 | This will I<usually> generate JSON texts that also parse as valid |
1431 | This will I<usually> generate JSON texts that also parse as valid |
1205 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1432 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1206 | lengths that JSON doesn't have and also has different and incompatible |
1433 | lengths that JSON doesn't have and also has different and incompatible |
1207 | unicode handling, so you should make sure that your hash keys are |
1434 | unicode character escape syntax, so you should make sure that your hash |
1208 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1435 | keys are noticeably shorter than the 1024 "stream characters" YAML allows |
1209 | you do not have characters with codepoint values outside the Unicode BMP |
1436 | and that you do not have characters with codepoint values outside the |
1210 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
1437 | Unicode BMP (basic multilingual page). YAML also does not allow C<\/> |
1211 | strings (which JSON::XS does not I<currently> generate, but other JSON |
1438 | sequences in strings (which JSON::XS does not I<currently> generate, but |
1212 | generators might). |
1439 | other JSON generators might). |
1213 | |
1440 | |
1214 | There might be other incompatibilities that I am not aware of (or the YAML |
1441 | There might be other incompatibilities that I am not aware of (or the YAML |
1215 | specification has been changed yet again - it does so quite often). In |
1442 | specification has been changed yet again - it does so quite often). In |
1216 | general you should not try to generate YAML with a JSON generator or vice |
1443 | general you should not try to generate YAML with a JSON generator or vice |
1217 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1444 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1218 | high that you will run into severe interoperability problems when you |
1445 | high that you will run into severe interoperability problems when you |
1219 | least expect it. |
1446 | least expect it. |
1220 | |
1447 | |
1221 | =over 4 |
1448 | =over |
1222 | |
1449 | |
1223 | =item (*) |
1450 | =item (*) |
1224 | |
1451 | |
1225 | I have been pressured multiple times by Brian Ingerson (one of the |
1452 | I have been pressured multiple times by Brian Ingerson (one of the |
1226 | authors of the YAML specification) to remove this paragraph, despite him |
1453 | authors of the YAML specification) to remove this paragraph, despite him |
… | |
… | |
1236 | that difficult or long) and finally make YAML compatible to it, and |
1463 | that difficult or long) and finally make YAML compatible to it, and |
1237 | educating users about the changes, instead of spreading lies about the |
1464 | educating users about the changes, instead of spreading lies about the |
1238 | real compatibility for many I<years> and trying to silence people who |
1465 | real compatibility for many I<years> and trying to silence people who |
1239 | point out that it isn't true. |
1466 | point out that it isn't true. |
1240 | |
1467 | |
|
|
1468 | Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even |
|
|
1469 | though the incompatibilities have been documented (and are known to Brian) |
|
|
1470 | for many years and the spec makes explicit claims that YAML is a superset |
|
|
1471 | of JSON. It would be so easy to fix, but apparently, bullying people and |
|
|
1472 | corrupting userdata is so much easier. |
|
|
1473 | |
1241 | =back |
1474 | =back |
1242 | |
1475 | |
1243 | |
1476 | |
1244 | =head2 SPEED |
1477 | =head2 SPEED |
1245 | |
1478 | |
… | |
… | |
1252 | a very short single-line JSON string (also available at |
1485 | a very short single-line JSON string (also available at |
1253 | L<http://dist.schmorp.de/misc/json/short.json>). |
1486 | L<http://dist.schmorp.de/misc/json/short.json>). |
1254 | |
1487 | |
1255 | {"method": "handleMessage", "params": ["user1", |
1488 | {"method": "handleMessage", "params": ["user1", |
1256 | "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, |
1489 | "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, |
1257 | true, false]} |
1490 | 1, 0]} |
1258 | |
1491 | |
1259 | It shows the number of encodes/decodes per second (JSON::XS uses |
1492 | It shows the number of encodes/decodes per second (JSON::XS uses |
1260 | the functional interface, while JSON::XS/2 uses the OO interface |
1493 | the functional interface, while JSON::XS/2 uses the OO interface |
1261 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1494 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1262 | shrink). Higher is better: |
1495 | shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ |
|
|
1496 | uses the from_json method). Higher is better: |
1263 | |
1497 | |
1264 | module | encode | decode | |
1498 | module | encode | decode | |
1265 | -----------|------------|------------| |
1499 | --------------|------------|------------| |
1266 | JSON 1.x | 4990.842 | 4088.813 | |
1500 | JSON::DWIW/DS | 86302.551 | 102300.098 | |
1267 | JSON::DWIW | 51653.990 | 71575.154 | |
1501 | JSON::DWIW/FJ | 86302.551 | 75983.768 | |
1268 | JSON::PC | 65948.176 | 74631.744 | |
1502 | JSON::PP | 15827.562 | 6638.658 | |
1269 | JSON::PP | 8931.652 | 3817.168 | |
1503 | JSON::Syck | 63358.066 | 47662.545 | |
1270 | JSON::Syck | 24877.248 | 27776.848 | |
1504 | JSON::XS | 511500.488 | 511500.488 | |
1271 | JSON::XS | 388361.481 | 227951.304 | |
1505 | JSON::XS/2 | 291271.111 | 388361.481 | |
1272 | JSON::XS/2 | 227951.304 | 218453.333 | |
1506 | JSON::XS/3 | 361577.931 | 361577.931 | |
1273 | JSON::XS/3 | 338250.323 | 218453.333 | |
1507 | Storable | 66788.280 | 265462.278 | |
1274 | Storable | 16500.016 | 135300.129 | |
|
|
1275 | -----------+------------+------------+ |
1508 | --------------+------------+------------+ |
1276 | |
1509 | |
1277 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
1510 | That is, JSON::XS is almost six times faster than JSON::DWIW on encoding, |
1278 | about three times faster on decoding, and over forty times faster |
1511 | about five times faster on decoding, and over thirty to seventy times |
1279 | than JSON, even with pretty-printing and key sorting. It also compares |
1512 | faster than JSON's pure perl implementation. It also compares favourably |
1280 | favourably to Storable for small amounts of data. |
1513 | to Storable for small amounts of data. |
1281 | |
1514 | |
1282 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1515 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1283 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1516 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1284 | |
1517 | |
1285 | module | encode | decode | |
1518 | module | encode | decode | |
1286 | -----------|------------|------------| |
1519 | --------------|------------|------------| |
1287 | JSON 1.x | 55.260 | 34.971 | |
1520 | JSON::DWIW/DS | 1647.927 | 2673.916 | |
1288 | JSON::DWIW | 825.228 | 1082.513 | |
1521 | JSON::DWIW/FJ | 1630.249 | 2596.128 | |
1289 | JSON::PC | 3571.444 | 2394.829 | |
|
|
1290 | JSON::PP | 210.987 | 32.574 | |
1522 | JSON::PP | 400.640 | 62.311 | |
1291 | JSON::Syck | 552.551 | 787.544 | |
1523 | JSON::Syck | 1481.040 | 1524.869 | |
1292 | JSON::XS | 5780.463 | 4854.519 | |
1524 | JSON::XS | 20661.596 | 9541.183 | |
1293 | JSON::XS/2 | 3869.998 | 4798.975 | |
1525 | JSON::XS/2 | 10683.403 | 9416.938 | |
1294 | JSON::XS/3 | 5862.880 | 4798.975 | |
1526 | JSON::XS/3 | 20661.596 | 9400.054 | |
1295 | Storable | 4445.002 | 5235.027 | |
1527 | Storable | 19765.806 | 10000.725 | |
1296 | -----------+------------+------------+ |
1528 | --------------+------------+------------+ |
1297 | |
1529 | |
1298 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1530 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1299 | decodes faster). |
1531 | decodes a bit faster). |
1300 | |
1532 | |
1301 | On large strings containing lots of high Unicode characters, some modules |
1533 | On large strings containing lots of high Unicode characters, some modules |
1302 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1534 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1303 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1535 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1304 | to decode or encode properly, so it was impossible to prepare a fair |
1536 | to decode or encode properly, so it was impossible to prepare a fair |
… | |
… | |
1340 | information you might want to make sure that exceptions thrown by JSON::XS |
1572 | information you might want to make sure that exceptions thrown by JSON::XS |
1341 | will not end up in front of untrusted eyes. |
1573 | will not end up in front of untrusted eyes. |
1342 | |
1574 | |
1343 | If you are using JSON::XS to return packets to consumption |
1575 | If you are using JSON::XS to return packets to consumption |
1344 | by JavaScript scripts in a browser you should have a look at |
1576 | by JavaScript scripts in a browser you should have a look at |
1345 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether |
1577 | L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to |
1346 | you are vulnerable to some common attack vectors (which really are browser |
1578 | see whether you are vulnerable to some common attack vectors (which really |
1347 | design bugs, but it is still you who will have to deal with it, as major |
1579 | are browser design bugs, but it is still you who will have to deal with |
1348 | browser developers care only for features, not about getting security |
1580 | it, as major browser developers care only for features, not about getting |
1349 | right). |
1581 | security right). |
1350 | |
1582 | |
1351 | |
1583 | |
|
|
1584 | =head2 "OLD" VS. "NEW" JSON (RFC4627 VS. RFC7159) |
|
|
1585 | |
|
|
1586 | JSON originally required JSON texts to represent an array or object - |
|
|
1587 | scalar values were explicitly not allowed. This has changed, and versions |
|
|
1588 | of JSON::XS beginning with C<4.0> reflect this by allowing scalar values |
|
|
1589 | by default. |
|
|
1590 | |
|
|
1591 | One reason why one might not want this is that this removes a fundamental |
|
|
1592 | property of JSON texts, namely that they are self-delimited and |
|
|
1593 | self-contained, or in other words, you could take any number of "old" |
|
|
1594 | JSON texts and paste them together, and the result would be unambiguously |
|
|
1595 | parseable: |
|
|
1596 | |
|
|
1597 | [1,3]{"k":5}[][null] # four JSON texts, without doubt |
|
|
1598 | |
|
|
1599 | By allowing scalars, this property is lost: in the following example, is |
|
|
1600 | this one JSON text (the number 12) or two JSON texts (the numbers 1 and |
|
|
1601 | 2): |
|
|
1602 | |
|
|
1603 | 12 # could be 12, or 1 and 2 |
|
|
1604 | |
|
|
1605 | Another lost property of "old" JSON is that no lookahead is required to |
|
|
1606 | know the end of a JSON text, i.e. the JSON text definitely ended at the |
|
|
1607 | last C<]> or C<}> character, there was no need to read extra characters. |
|
|
1608 | |
|
|
1609 | For example, a viable network protocol with "old" JSON was to simply |
|
|
1610 | exchange JSON texts without delimiter. For "new" JSON, you have to use a |
|
|
1611 | suitable delimiter (such as a newline) after every JSON text or ensure you |
|
|
1612 | never encode/decode scalar values. |
|
|
1613 | |
|
|
1614 | Most protocols do work by only transferring arrays or objects, and the |
|
|
1615 | easiest way to avoid problems with the "new" JSON definition is to |
|
|
1616 | explicitly disallow scalar values in your encoder and decoder: |
|
|
1617 | |
|
|
1618 | $json_coder = JSON::XS->new->allow_nonref (0) |
|
|
1619 | |
|
|
1620 | This is a somewhat unhappy situation, and the blame can fully be put on |
|
|
1621 | JSON's inmventor, Douglas Crockford, who unilaterally changed the format |
|
|
1622 | in 2006 without consulting the IETF, forcing the IETF to either fork the |
|
|
1623 | format or go with it (as I was told, the IETF wasn't amused). |
|
|
1624 | |
|
|
1625 | |
|
|
1626 | =head1 RELATIONSHIP WITH I-JSON |
|
|
1627 | |
|
|
1628 | JSON is a somewhat sloppily-defined format - it carries around obvious |
|
|
1629 | Javascript baggage, such as not really defining number range, probably |
|
|
1630 | because Javascript only has one type of numbers: IEEE 64 bit floats |
|
|
1631 | ("binary64"). |
|
|
1632 | |
|
|
1633 | For this reaosn, RFC7493 defines "Internet JSON", which is a restricted |
|
|
1634 | subset of JSON that is supposedly more interoperable on the internet. |
|
|
1635 | |
|
|
1636 | While C<JSON::XS> does not offer specific support for I-JSON, it of course |
|
|
1637 | accepts valid I-JSON and by default implements some of the limitations |
|
|
1638 | of I-JSON, such as parsing numbers as perl numbers, which are usually a |
|
|
1639 | superset of binary64 numbers. |
|
|
1640 | |
|
|
1641 | To generate I-JSON, follow these rules: |
|
|
1642 | |
|
|
1643 | =over |
|
|
1644 | |
|
|
1645 | =item * always generate UTF-8 |
|
|
1646 | |
|
|
1647 | I-JSON must be encoded in UTF-8, the default for C<encode_json>. |
|
|
1648 | |
|
|
1649 | =item * numbers should be within IEEE 754 binary64 range |
|
|
1650 | |
|
|
1651 | Basically all existing perl installations use binary64 to represent |
|
|
1652 | floating point numbers, so all you need to do is to avoid large integers. |
|
|
1653 | |
|
|
1654 | =item * objects must not have duplicate keys |
|
|
1655 | |
|
|
1656 | This is trivially done, as C<JSON::XS> does not allow duplicate keys. |
|
|
1657 | |
|
|
1658 | =item * do not generate scalar JSON texts, use C<< ->allow_nonref (0) >> |
|
|
1659 | |
|
|
1660 | I-JSON strongly requests you to only encode arrays and objects into JSON. |
|
|
1661 | |
|
|
1662 | =item * times should be strings in ISO 8601 format |
|
|
1663 | |
|
|
1664 | There are a myriad of modules on CPAN dealing with ISO 8601 - search for |
|
|
1665 | C<ISO8601> on CPAN and use one. |
|
|
1666 | |
|
|
1667 | =item * encode binary data as base64 |
|
|
1668 | |
|
|
1669 | While it's tempting to just dump binary data as a string (and let |
|
|
1670 | C<JSON::XS> do the escaping), for I-JSON, it's I<recommended> to encode |
|
|
1671 | binary data as base64. |
|
|
1672 | |
|
|
1673 | =back |
|
|
1674 | |
|
|
1675 | There are some other considerations - read RFC7493 for the details if |
|
|
1676 | interested. |
|
|
1677 | |
|
|
1678 | |
|
|
1679 | =head1 INTEROPERABILITY WITH OTHER MODULES |
|
|
1680 | |
|
|
1681 | C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean |
|
|
1682 | constants. That means that the JSON true and false values will be |
|
|
1683 | comaptible to true and false values of other modules that do the same, |
|
|
1684 | such as L<JSON::PP> and L<CBOR::XS>. |
|
|
1685 | |
|
|
1686 | |
|
|
1687 | =head1 INTEROPERABILITY WITH OTHER JSON DECODERS |
|
|
1688 | |
|
|
1689 | As long as you only serialise data that can be directly expressed in JSON, |
|
|
1690 | C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs, |
|
|
1691 | but C<JSON::XS> has found more bugs in the official JSON testsuite (1) |
|
|
1692 | than the official JSON testsuite has found in C<JSON::XS> (0)). |
|
|
1693 | |
|
|
1694 | When you have trouble decoding JSON generated by this module using other |
|
|
1695 | decoders, then it is very likely that you have an encoding mismatch or the |
|
|
1696 | other decoder is broken. |
|
|
1697 | |
|
|
1698 | When decoding, C<JSON::XS> is strict by default and will likely catch all |
|
|
1699 | errors. There are currently two settings that change this: C<relaxed> |
|
|
1700 | makes C<JSON::XS> accept (but not generate) some non-standard extensions, |
|
|
1701 | and C<allow_tags> will allow you to encode and decode Perl objects, at the |
|
|
1702 | cost of not outputting valid JSON anymore. |
|
|
1703 | |
|
|
1704 | =head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS |
|
|
1705 | |
|
|
1706 | When you use C<allow_tags> to use the extended (and also nonstandard and |
|
|
1707 | invalid) JSON syntax for serialised objects, and you still want to decode |
|
|
1708 | the generated When you want to serialise objects, you can run a regex |
|
|
1709 | to replace the tagged syntax by standard JSON arrays (it only works for |
|
|
1710 | "normal" package names without comma, newlines or single colons). First, |
|
|
1711 | the readable Perl version: |
|
|
1712 | |
|
|
1713 | # if your FREEZE methods return no values, you need this replace first: |
|
|
1714 | $json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[\s*\]/[$1]/gx; |
|
|
1715 | |
|
|
1716 | # this works for non-empty constructor arg lists: |
|
|
1717 | $json =~ s/\( \s* (" (?: [^\\":,]+|\\.|::)* ") \s* \) \s* \[/[$1,/gx; |
|
|
1718 | |
|
|
1719 | And here is a less readable version that is easy to adapt to other |
|
|
1720 | languages: |
|
|
1721 | |
|
|
1722 | $json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/[$1,/g; |
|
|
1723 | |
|
|
1724 | Here is an ECMAScript version (same regex): |
|
|
1725 | |
|
|
1726 | json = json.replace (/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/g, "[$1,"); |
|
|
1727 | |
|
|
1728 | Since this syntax converts to standard JSON arrays, it might be hard to |
|
|
1729 | distinguish serialised objects from normal arrays. You can prepend a |
|
|
1730 | "magic number" as first array element to reduce chances of a collision: |
|
|
1731 | |
|
|
1732 | $json =~ s/\(\s*("([^\\":,]+|\\.|::)*")\s*\)\s*\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g; |
|
|
1733 | |
|
|
1734 | And after decoding the JSON text, you could walk the data |
|
|
1735 | structure looking for arrays with a first element of |
|
|
1736 | C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>. |
|
|
1737 | |
|
|
1738 | The same approach can be used to create the tagged format with another |
|
|
1739 | encoder. First, you create an array with the magic string as first member, |
|
|
1740 | the classname as second, and constructor arguments last, encode it as part |
|
|
1741 | of your JSON structure, and then: |
|
|
1742 | |
|
|
1743 | $json =~ s/\[\s*"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s*,\s*("([^\\":,]+|\\.|::)*")\s*,/($1)[/g; |
|
|
1744 | |
|
|
1745 | Again, this has some limitations - the magic string must not be encoded |
|
|
1746 | with character escapes, and the constructor arguments must be non-empty. |
|
|
1747 | |
|
|
1748 | |
1352 | =head1 THREADS |
1749 | =head1 (I-)THREADS |
1353 | |
1750 | |
1354 | This module is I<not> guaranteed to be thread safe and there are no |
1751 | This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe |
1355 | plans to change this until Perl gets thread support (as opposed to the |
1752 | and there are no plans to change this. Note that perl's builtin so-called |
1356 | horribly slow so-called "threads" which are simply slow and bloated |
1753 | threads/ithreads are officially deprecated and should not be used. |
1357 | process simulations - use fork, it's I<much> faster, cheaper, better). |
|
|
1358 | |
1754 | |
1359 | (It might actually work, but you have been warned). |
1755 | |
|
|
1756 | =head1 THE PERILS OF SETLOCALE |
|
|
1757 | |
|
|
1758 | Sometimes people avoid the Perl locale support and directly call the |
|
|
1759 | system's setlocale function with C<LC_ALL>. |
|
|
1760 | |
|
|
1761 | This breaks both perl and modules such as JSON::XS, as stringification of |
|
|
1762 | numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might |
|
|
1763 | print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on |
|
|
1764 | perl to stringify numbers). |
|
|
1765 | |
|
|
1766 | The solution is simple: don't call C<setlocale>, or use it for only those |
|
|
1767 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
|
|
1768 | |
|
|
1769 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
|
|
1770 | actually needs it (avoiding stringification of numbers), and restore it |
|
|
1771 | afterwards. |
|
|
1772 | |
|
|
1773 | |
|
|
1774 | =head1 SOME HISTORY |
|
|
1775 | |
|
|
1776 | At the time this module was created there already were a number of JSON |
|
|
1777 | modules available on CPAN, so what was the reason to write yet another |
|
|
1778 | JSON module? While it seems there are many JSON modules, none of them |
|
|
1779 | correctly handled all corner cases, and in most cases their maintainers |
|
|
1780 | are unresponsive, gone missing, or not listening to bug reports for other |
|
|
1781 | reasons. |
|
|
1782 | |
|
|
1783 | Beginning with version 2.0 of the JSON module, when both JSON and |
|
|
1784 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
|
|
1785 | overridden) with no overhead due to emulation (by inheriting constructor |
|
|
1786 | and methods). If JSON::XS is not available, it will fall back to the |
|
|
1787 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
|
|
1788 | gives you a portable JSON API that can be fast when you need it and |
|
|
1789 | doesn't require a C compiler when that is a problem. |
|
|
1790 | |
|
|
1791 | Somewhere around version 3, this module was forked into |
|
|
1792 | C<Cpanel::JSON::XS>, because its maintainer had serious trouble |
|
|
1793 | understanding JSON and insisted on a fork with many bugs "fixed" that |
|
|
1794 | weren't actually bugs, while spreading FUD about this module without |
|
|
1795 | actually giving any details on his accusations. You be the judge, but |
|
|
1796 | in my personal opinion, if you want quality, you will stay away from |
|
|
1797 | dangerous forks like that. |
1360 | |
1798 | |
1361 | |
1799 | |
1362 | =head1 BUGS |
1800 | =head1 BUGS |
1363 | |
1801 | |
1364 | While the goal of this module is to be correct, that unfortunately does |
1802 | While the goal of this module is to be correct, that unfortunately does |
… | |
… | |
1368 | Please refrain from using rt.cpan.org or any other bug reporting |
1806 | Please refrain from using rt.cpan.org or any other bug reporting |
1369 | service. I put the contact address into my modules for a reason. |
1807 | service. I put the contact address into my modules for a reason. |
1370 | |
1808 | |
1371 | =cut |
1809 | =cut |
1372 | |
1810 | |
1373 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
1811 | BEGIN { |
1374 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
1812 | *true = \$Types::Serialiser::true; |
|
|
1813 | *true = \&Types::Serialiser::true; |
|
|
1814 | *false = \$Types::Serialiser::false; |
|
|
1815 | *false = \&Types::Serialiser::false; |
|
|
1816 | *is_bool = \&Types::Serialiser::is_bool; |
1375 | |
1817 | |
1376 | sub true() { $true } |
1818 | *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::; |
1377 | sub false() { $false } |
|
|
1378 | |
|
|
1379 | sub is_bool($) { |
|
|
1380 | UNIVERSAL::isa $_[0], "JSON::XS::Boolean" |
|
|
1381 | # or UNIVERSAL::isa $_[0], "JSON::Literal" |
|
|
1382 | } |
1819 | } |
1383 | |
1820 | |
1384 | XSLoader::load "JSON::XS", $VERSION; |
1821 | XSLoader::load "JSON::XS", $VERSION; |
1385 | |
|
|
1386 | package JSON::XS::Boolean; |
|
|
1387 | |
|
|
1388 | use overload |
|
|
1389 | "0+" => sub { ${$_[0]} }, |
|
|
1390 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
|
|
1391 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
|
|
1392 | fallback => 1; |
|
|
1393 | |
|
|
1394 | 1; |
|
|
1395 | |
1822 | |
1396 | =head1 SEE ALSO |
1823 | =head1 SEE ALSO |
1397 | |
1824 | |
1398 | The F<json_xs> command line utility for quick experiments. |
1825 | The F<json_xs> command line utility for quick experiments. |
1399 | |
1826 | |
… | |
… | |
1402 | Marc Lehmann <schmorp@schmorp.de> |
1829 | Marc Lehmann <schmorp@schmorp.de> |
1403 | http://home.schmorp.de/ |
1830 | http://home.schmorp.de/ |
1404 | |
1831 | |
1405 | =cut |
1832 | =cut |
1406 | |
1833 | |
|
|
1834 | 1 |
|
|
1835 | |