1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
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3 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
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4 | |
3 | =encoding utf-8 |
5 | =encoding utf-8 |
4 | |
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5 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
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6 | |
6 | |
7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
7 | JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ |
8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
8 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
9 | |
9 | |
10 | =head1 SYNOPSIS |
10 | =head1 SYNOPSIS |
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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 |
40 | Beginning with version 2.0 of the JSON module, when both JSON and |
41 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
41 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can be |
42 | overriden) with no overhead due to emulation (by inheritign constructor |
42 | overridden) with no overhead due to emulation (by inheriting constructor |
43 | and methods). If JSON::XS is not available, it will fall back to the |
43 | and methods). If JSON::XS is not available, it will fall back to the |
44 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
44 | compatible JSON::PP module as backend, so using JSON instead of JSON::XS |
45 | gives you a portable JSON API that can be fast when you need and doesn't |
45 | gives you a portable JSON API that can be fast when you need and doesn't |
46 | require a C compiler when that is a problem. |
46 | require a C compiler when that is a problem. |
47 | |
47 | |
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49 | to write yet another JSON module? While it seems there are many JSON |
49 | to write yet another JSON module? While it seems there are many JSON |
50 | modules, none of them correctly handle all corner cases, and in most cases |
50 | modules, none of them correctly handle all corner cases, and in most cases |
51 | their maintainers are unresponsive, gone missing, or not listening to bug |
51 | their maintainers are unresponsive, gone missing, or not listening to bug |
52 | reports for other reasons. |
52 | reports for other reasons. |
53 | |
53 | |
54 | See COMPARISON, below, for a comparison to some other JSON modules. |
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55 | |
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56 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
54 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
57 | vice versa. |
55 | vice versa. |
58 | |
56 | |
59 | =head2 FEATURES |
57 | =head2 FEATURES |
60 | |
58 | |
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65 | This module knows how to handle Unicode, documents how and when it does |
63 | This module knows how to handle Unicode, documents how and when it does |
66 | so, and even documents what "correct" means. |
64 | so, and even documents what "correct" means. |
67 | |
65 | |
68 | =item * round-trip integrity |
66 | =item * round-trip integrity |
69 | |
67 | |
70 | When you serialise a perl data structure using only datatypes supported |
68 | When you serialise a perl data structure using only data types supported |
71 | by JSON, the deserialised data structure is identical on the Perl level. |
69 | by JSON and Perl, the deserialised data structure is identical on the Perl |
72 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
70 | level. (e.g. the string "2.0" doesn't suddenly become "2" just because |
73 | like a number). There minor I<are> exceptions to this, read the MAPPING |
71 | it looks like a number). There I<are> minor exceptions to this, read the |
74 | section below to learn about those. |
72 | MAPPING section below to learn about those. |
75 | |
73 | |
76 | =item * strict checking of JSON correctness |
74 | =item * strict checking of JSON correctness |
77 | |
75 | |
78 | There is no guessing, no generating of illegal JSON texts by default, |
76 | There is no guessing, no generating of illegal JSON texts by default, |
79 | and only JSON is accepted as input by default (the latter is a security |
77 | and only JSON is accepted as input by default (the latter is a security |
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84 | Compared to other JSON modules and other serialisers such as Storable, |
82 | Compared to other JSON modules and other serialisers such as Storable, |
85 | this module usually compares favourably in terms of speed, too. |
83 | this module usually compares favourably in terms of speed, too. |
86 | |
84 | |
87 | =item * simple to use |
85 | =item * simple to use |
88 | |
86 | |
89 | This module has both a simple functional interface as well as an objetc |
87 | This module has both a simple functional interface as well as an object |
90 | oriented interface interface. |
88 | oriented interface. |
91 | |
89 | |
92 | =item * reasonably versatile output formats |
90 | =item * reasonably versatile output formats |
93 | |
91 | |
94 | You can choose between the most compact guaranteed-single-line format |
92 | You can choose between the most compact guaranteed-single-line format |
95 | possible (nice for simple line-based protocols), a pure-ascii format |
93 | possible (nice for simple line-based protocols), a pure-ASCII format |
96 | (for when your transport is not 8-bit clean, still supports the whole |
94 | (for when your transport is not 8-bit clean, still supports the whole |
97 | Unicode range), or a pretty-printed format (for when you want to read that |
95 | Unicode range), or a pretty-printed format (for when you want to read that |
98 | stuff). Or you can combine those features in whatever way you like. |
96 | stuff). Or you can combine those features in whatever way you like. |
99 | |
97 | |
100 | =back |
98 | =back |
101 | |
99 | |
102 | =cut |
100 | =cut |
103 | |
101 | |
104 | package JSON::XS; |
102 | package JSON::XS; |
105 | |
103 | |
106 | use strict; |
104 | use common::sense; |
107 | |
105 | |
108 | our $VERSION = '2.1'; |
106 | our $VERSION = '3.0'; |
109 | our @ISA = qw(Exporter); |
107 | our @ISA = qw(Exporter); |
110 | |
108 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
109 | our @EXPORT = qw(encode_json decode_json); |
112 | |
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113 | sub to_json($) { |
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114 | require Carp; |
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115 | 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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116 | } |
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117 | |
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118 | sub from_json($) { |
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119 | require Carp; |
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120 | 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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121 | } |
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122 | |
110 | |
123 | use Exporter; |
111 | use Exporter; |
124 | use XSLoader; |
112 | use XSLoader; |
125 | |
113 | |
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114 | use Types::Serialiser (); |
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115 | |
126 | =head1 FUNCTIONAL INTERFACE |
116 | =head1 FUNCTIONAL INTERFACE |
127 | |
117 | |
128 | The following convenience methods are provided by this module. They are |
118 | The following convenience methods are provided by this module. They are |
129 | exported by default: |
119 | exported by default: |
130 | |
120 | |
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137 | |
127 | |
138 | This function call is functionally identical to: |
128 | This function call is functionally identical to: |
139 | |
129 | |
140 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
130 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
141 | |
131 | |
142 | except being faster. |
132 | Except being faster. |
143 | |
133 | |
144 | =item $perl_scalar = decode_json $json_text |
134 | =item $perl_scalar = decode_json $json_text |
145 | |
135 | |
146 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
136 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
147 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
137 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
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149 | |
139 | |
150 | This function call is functionally identical to: |
140 | This function call is functionally identical to: |
151 | |
141 | |
152 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
142 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
153 | |
143 | |
154 | except being faster. |
144 | Except being faster. |
155 | |
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156 | =item $is_boolean = JSON::XS::is_bool $scalar |
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157 | |
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158 | Returns true if the passed scalar represents either JSON::XS::true or |
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159 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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160 | and are used to represent JSON C<true> and C<false> values in Perl. |
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161 | |
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162 | See MAPPING, below, for more information on how JSON values are mapped to |
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163 | Perl. |
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164 | |
145 | |
165 | =back |
146 | =back |
166 | |
147 | |
167 | |
148 | |
168 | =head1 A FEW NOTES ON UNICODE AND PERL |
149 | =head1 A FEW NOTES ON UNICODE AND PERL |
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197 | |
178 | |
198 | If you didn't know about that flag, just the better, pretend it doesn't |
179 | If you didn't know about that flag, just the better, pretend it doesn't |
199 | exist. |
180 | exist. |
200 | |
181 | |
201 | =item 4. A "Unicode String" is simply a string where each character can be |
182 | =item 4. A "Unicode String" is simply a string where each character can be |
202 | validly interpreted as a Unicode codepoint. |
183 | validly interpreted as a Unicode code point. |
203 | |
184 | |
204 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
185 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
205 | Unicode string encoded in UTF-8, giving you a binary string. |
186 | Unicode string encoded in UTF-8, giving you a binary string. |
206 | |
187 | |
207 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
188 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
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434 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
415 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
435 | by sorting their keys. This is adding a comparatively high overhead. |
416 | by sorting their keys. This is adding a comparatively high overhead. |
436 | |
417 | |
437 | If C<$enable> is false, then the C<encode> method will output key-value |
418 | If C<$enable> is false, then the C<encode> method will output key-value |
438 | pairs in the order Perl stores them (which will likely change between runs |
419 | pairs in the order Perl stores them (which will likely change between runs |
439 | of the same script). |
420 | of the same script, and can change even within the same run from 5.18 |
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421 | onwards). |
440 | |
422 | |
441 | This option is useful if you want the same data structure to be encoded as |
423 | This option is useful if you want the same data structure to be encoded as |
442 | the same JSON text (given the same overall settings). If it is disabled, |
424 | the same JSON text (given the same overall settings). If it is disabled, |
443 | the same hash might be encoded differently even if contains the same data, |
425 | the same hash might be encoded differently even if contains the same data, |
444 | as key-value pairs have no inherent ordering in Perl. |
426 | as key-value pairs have no inherent ordering in Perl. |
445 | |
427 | |
446 | This setting has no effect when decoding JSON texts. |
428 | This setting has no effect when decoding JSON texts. |
447 | |
429 | |
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430 | This setting has currently no effect on tied hashes. |
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431 | |
448 | =item $json = $json->allow_nonref ([$enable]) |
432 | =item $json = $json->allow_nonref ([$enable]) |
449 | |
433 | |
450 | =item $enabled = $json->get_allow_nonref |
434 | =item $enabled = $json->get_allow_nonref |
451 | |
435 | |
452 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
436 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
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463 | resulting in an invalid JSON text: |
447 | resulting in an invalid JSON text: |
464 | |
448 | |
465 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
449 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
466 | => "Hello, World!" |
450 | => "Hello, World!" |
467 | |
451 | |
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452 | =item $json = $json->allow_unknown ([$enable]) |
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453 | |
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454 | =item $enabled = $json->get_allow_unknown |
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455 | |
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456 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
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457 | exception when it encounters values it cannot represent in JSON (for |
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458 | example, filehandles) but instead will encode a JSON C<null> value. Note |
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459 | that blessed objects are not included here and are handled separately by |
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460 | c<allow_nonref>. |
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461 | |
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462 | If C<$enable> is false (the default), then C<encode> will throw an |
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463 | exception when it encounters anything it cannot encode as JSON. |
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464 | |
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465 | This option does not affect C<decode> in any way, and it is recommended to |
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466 | leave it off unless you know your communications partner. |
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467 | |
468 | =item $json = $json->allow_blessed ([$enable]) |
468 | =item $json = $json->allow_blessed ([$enable]) |
469 | |
469 | |
470 | =item $enabled = $json->get_allow_blessed |
470 | =item $enabled = $json->get_allow_blessed |
471 | |
471 | |
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472 | See L<OBJECT SERIALISATION> for details. |
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473 | |
472 | If C<$enable> is true (or missing), then the C<encode> method will not |
474 | If C<$enable> is true (or missing), then the C<encode> method will not |
473 | barf when it encounters a blessed reference. Instead, the value of the |
475 | barf when it encounters a blessed reference that it cannot convert |
474 | B<convert_blessed> option will decide whether C<null> (C<convert_blessed> |
476 | otherwise. Instead, a JSON C<null> value is encoded instead of the object. |
475 | disabled or no C<TO_JSON> method found) or a representation of the |
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476 | object (C<convert_blessed> enabled and C<TO_JSON> method found) is being |
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477 | encoded. Has no effect on C<decode>. |
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478 | |
477 | |
479 | If C<$enable> is false (the default), then C<encode> will throw an |
478 | If C<$enable> is false (the default), then C<encode> will throw an |
480 | exception when it encounters a blessed object. |
479 | exception when it encounters a blessed object that it cannot convert |
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480 | otherwise. |
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481 | |
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482 | This setting has no effect on C<decode>. |
481 | |
483 | |
482 | =item $json = $json->convert_blessed ([$enable]) |
484 | =item $json = $json->convert_blessed ([$enable]) |
483 | |
485 | |
484 | =item $enabled = $json->get_convert_blessed |
486 | =item $enabled = $json->get_convert_blessed |
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487 | |
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488 | See "OBJECT SERIALISATION" for details. |
485 | |
489 | |
486 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
490 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
487 | blessed object, will check for the availability of the C<TO_JSON> method |
491 | blessed object, will check for the availability of the C<TO_JSON> method |
488 | on the object's class. If found, it will be called in scalar context |
492 | on the object's class. If found, it will be called in scalar context and |
489 | and the resulting scalar will be encoded instead of the object. If no |
493 | the resulting scalar will be encoded instead of the object. |
490 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
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491 | to do. |
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492 | |
494 | |
493 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
495 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
494 | returns other blessed objects, those will be handled in the same |
496 | returns other blessed objects, those will be handled in the same |
495 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
497 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
496 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
498 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
497 | methods called by the Perl core (== not by the user of the object) are |
499 | methods called by the Perl core (== not by the user of the object) are |
498 | usually in upper case letters and to avoid collisions with any C<to_json> |
500 | usually in upper case letters and to avoid collisions with any C<to_json> |
499 | function or method. |
501 | function or method. |
500 | |
502 | |
501 | This setting does not yet influence C<decode> in any way, but in the |
503 | If C<$enable> is false (the default), then C<encode> will not consider |
502 | future, global hooks might get installed that influence C<decode> and are |
504 | this type of conversion. |
503 | enabled by this setting. |
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504 | |
505 | |
505 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
506 | This setting has no effect on C<decode>. |
506 | to do when a blessed object is found. |
507 | |
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508 | =item $json = $json->allow_tags ([$enable]) |
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509 | |
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510 | =item $enabled = $json->allow_tags |
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511 | |
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512 | See "OBJECT SERIALISATION" for details. |
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513 | |
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514 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
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515 | blessed object, will check for the availability of the C<FREEZE> method on |
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516 | the object's class. If found, it will be used to serialise the object into |
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517 | a nonstandard tagged JSON value (that JSON decoders cannot decode). |
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518 | |
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519 | It also causes C<decode> to parse such tagged JSON values and deserialise |
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520 | them via a call to the C<THAW> method. |
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521 | |
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522 | If C<$enable> is false (the default), then C<encode> will not consider |
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523 | this type of conversion, and tagged JSON values will cause a parse error |
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524 | in C<decode>, as if tags were not part of the grammar. |
507 | |
525 | |
508 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
526 | =item $json = $json->filter_json_object ([$coderef->($hashref)]) |
509 | |
527 | |
510 | When C<$coderef> is specified, it will be called from C<decode> each |
528 | When C<$coderef> is specified, it will be called from C<decode> each |
511 | time it decodes a JSON object. The only argument is a reference to the |
529 | time it decodes a JSON object. The only argument is a reference to the |
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612 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
630 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
613 | |
631 | |
614 | =item $max_depth = $json->get_max_depth |
632 | =item $max_depth = $json->get_max_depth |
615 | |
633 | |
616 | Sets the maximum nesting level (default C<512>) accepted while encoding |
634 | Sets the maximum nesting level (default C<512>) accepted while encoding |
617 | or decoding. If the JSON text or Perl data structure has an equal or |
635 | or decoding. If a higher nesting level is detected in JSON text or a Perl |
618 | higher nesting level then this limit, then the encoder and decoder will |
636 | data structure, then the encoder and decoder will stop and croak at that |
619 | stop and croak at that point. |
637 | point. |
620 | |
638 | |
621 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
639 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
622 | needs to traverse to reach a given point or the number of C<{> or C<[> |
640 | needs to traverse to reach a given point or the number of C<{> or C<[> |
623 | characters without their matching closing parenthesis crossed to reach a |
641 | characters without their matching closing parenthesis crossed to reach a |
624 | given character in a string. |
642 | given character in a string. |
625 | |
643 | |
626 | Setting the maximum depth to one disallows any nesting, so that ensures |
644 | Setting the maximum depth to one disallows any nesting, so that ensures |
627 | that the object is only a single hash/object or array. |
645 | that the object is only a single hash/object or array. |
628 | |
646 | |
629 | The argument to C<max_depth> will be rounded up to the next highest power |
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630 | of two. If no argument is given, the highest possible setting will be |
647 | If no argument is given, the highest possible setting will be used, which |
631 | used, which is rarely useful. |
648 | is rarely useful. |
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649 | |
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650 | Note that nesting is implemented by recursion in C. The default value has |
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651 | been chosen to be as large as typical operating systems allow without |
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652 | crashing. |
632 | |
653 | |
633 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
654 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
634 | |
655 | |
635 | =item $json = $json->max_size ([$maximum_string_size]) |
656 | =item $json = $json->max_size ([$maximum_string_size]) |
636 | |
657 | |
637 | =item $max_size = $json->get_max_size |
658 | =item $max_size = $json->get_max_size |
638 | |
659 | |
639 | Set the maximum length a JSON text may have (in bytes) where decoding is |
660 | Set the maximum length a JSON text may have (in bytes) where decoding is |
640 | being attempted. The default is C<0>, meaning no limit. When C<decode> |
661 | being attempted. The default is C<0>, meaning no limit. When C<decode> |
641 | is called on a string longer then this number of characters it will not |
662 | is called on a string that is longer then this many bytes, it will not |
642 | attempt to decode the string but throw an exception. This setting has no |
663 | attempt to decode the string but throw an exception. This setting has no |
643 | effect on C<encode> (yet). |
664 | effect on C<encode> (yet). |
644 | |
665 | |
645 | The argument to C<max_size> will be rounded up to the next B<highest> |
666 | If no argument is given, the limit check will be deactivated (same as when |
646 | power of two (so may be more than requested). If no argument is given, the |
667 | C<0> is specified). |
647 | limit check will be deactivated (same as when C<0> is specified). |
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648 | |
668 | |
649 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
669 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
650 | |
670 | |
651 | =item $json_text = $json->encode ($perl_scalar) |
671 | =item $json_text = $json->encode ($perl_scalar) |
652 | |
672 | |
653 | Converts the given Perl data structure (a simple scalar or a reference |
673 | Converts the given Perl value or data structure to its JSON |
654 | to a hash or array) to its JSON representation. Simple scalars will be |
674 | representation. Croaks on error. |
655 | converted into JSON string or number sequences, while references to arrays |
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656 | become JSON arrays and references to hashes become JSON objects. Undefined |
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657 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
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658 | nor C<false> values will be generated. |
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659 | |
675 | |
660 | =item $perl_scalar = $json->decode ($json_text) |
676 | =item $perl_scalar = $json->decode ($json_text) |
661 | |
677 | |
662 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
678 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
663 | returning the resulting simple scalar or reference. Croaks on error. |
679 | returning the resulting simple scalar or reference. Croaks on error. |
664 | |
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665 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
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|
666 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
|
|
667 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
|
|
668 | |
680 | |
669 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
681 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
670 | |
682 | |
671 | This works like the C<decode> method, but instead of raising an exception |
683 | This works like the C<decode> method, but instead of raising an exception |
672 | when there is trailing garbage after the first JSON object, it will |
684 | when there is trailing garbage after the first JSON object, it will |
673 | silently stop parsing there and return the number of characters consumed |
685 | silently stop parsing there and return the number of characters consumed |
674 | so far. |
686 | so far. |
675 | |
687 | |
676 | This is useful if your JSON texts are not delimited by an outer protocol |
688 | This is useful if your JSON texts are not delimited by an outer protocol |
677 | (which is not the brightest thing to do in the first place) and you need |
|
|
678 | to know where the JSON text ends. |
689 | and you need to know where the JSON text ends. |
679 | |
690 | |
680 | JSON::XS->new->decode_prefix ("[1] the tail") |
691 | JSON::XS->new->decode_prefix ("[1] the tail") |
681 | => ([], 3) |
692 | => ([], 3) |
682 | |
693 | |
683 | =back |
694 | =back |
684 | |
695 | |
685 | |
696 | |
686 | =head1 INCREMENTAL PARSING |
697 | =head1 INCREMENTAL PARSING |
687 | |
|
|
688 | [This section is still EXPERIMENTAL] |
|
|
689 | |
698 | |
690 | In some cases, there is the need for incremental parsing of JSON |
699 | In some cases, there is the need for incremental parsing of JSON |
691 | texts. While this module always has to keep both JSON text and resulting |
700 | texts. While this module always has to keep both JSON text and resulting |
692 | Perl data structure in memory at one time, it does allow you to parse a |
701 | Perl data structure in memory at one time, it does allow you to parse a |
693 | JSON stream incrementally. It does so by accumulating text until it has |
702 | JSON stream incrementally. It does so by accumulating text until it has |
694 | a full JSON object, which it then can decode. This process is similar to |
703 | a full JSON object, which it then can decode. This process is similar to |
695 | using C<decode_prefix> to see if a full JSON object is available, but is |
704 | using C<decode_prefix> to see if a full JSON object is available, but |
696 | much more efficient (JSON::XS will only attempt to parse the JSON text |
705 | is much more efficient (and can be implemented with a minimum of method |
|
|
706 | calls). |
|
|
707 | |
|
|
708 | JSON::XS will only attempt to parse the JSON text once it is sure it |
697 | once it is sure it has enough text to get a decisive result, using a very |
709 | has enough text to get a decisive result, using a very simple but |
698 | simple but truly incremental parser). |
710 | truly incremental parser. This means that it sometimes won't stop as |
|
|
711 | early as the full parser, for example, it doesn't detect mismatched |
|
|
712 | parentheses. The only thing it guarantees is that it starts decoding as |
|
|
713 | soon as a syntactically valid JSON text has been seen. This means you need |
|
|
714 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
|
|
715 | parsing in the presence if syntax errors. |
699 | |
716 | |
700 | The following two methods deal with this. |
717 | The following methods implement this incremental parser. |
701 | |
718 | |
702 | =over 4 |
719 | =over 4 |
703 | |
720 | |
704 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
721 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
705 | |
722 | |
… | |
… | |
714 | return without doing anything further. This can be used to add more text |
731 | return without doing anything further. This can be used to add more text |
715 | in as many chunks as you want. |
732 | in as many chunks as you want. |
716 | |
733 | |
717 | If the method is called in scalar context, then it will try to extract |
734 | If the method is called in scalar context, then it will try to extract |
718 | exactly I<one> JSON object. If that is successful, it will return this |
735 | exactly I<one> JSON object. If that is successful, it will return this |
719 | object, otherwise it will return C<undef>. This is the most common way of |
736 | object, otherwise it will return C<undef>. If there is a parse error, |
|
|
737 | this method will croak just as C<decode> would do (one can then use |
|
|
738 | C<incr_skip> to skip the erroneous part). This is the most common way of |
720 | using the method. |
739 | using the method. |
721 | |
740 | |
722 | And finally, in list context, it will try to extract as many objects |
741 | And finally, in list context, it will try to extract as many objects |
723 | from the stream as it can find and return them, or the empty list |
742 | from the stream as it can find and return them, or the empty list |
724 | otherwise. For this to work, there must be no separators between the JSON |
743 | otherwise. For this to work, there must be no separators between the JSON |
725 | objects or arrays, instead they must be concatenated back-to-back. |
744 | objects or arrays, instead they must be concatenated back-to-back. If |
|
|
745 | an error occurs, an exception will be raised as in the scalar context |
|
|
746 | case. Note that in this case, any previously-parsed JSON texts will be |
|
|
747 | lost. |
|
|
748 | |
|
|
749 | Example: Parse some JSON arrays/objects in a given string and return |
|
|
750 | them. |
|
|
751 | |
|
|
752 | my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]"); |
726 | |
753 | |
727 | =item $lvalue_string = $json->incr_text |
754 | =item $lvalue_string = $json->incr_text |
728 | |
755 | |
729 | This method returns the currently stored JSON fragment as an lvalue, that |
756 | This method returns the currently stored JSON fragment as an lvalue, that |
730 | is, you can manipulate it. This I<only> works when a preceding call to |
757 | is, you can manipulate it. This I<only> works when a preceding call to |
… | |
… | |
736 | |
763 | |
737 | This function is useful in two cases: a) finding the trailing text after a |
764 | This function is useful in two cases: a) finding the trailing text after a |
738 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
765 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
739 | (such as commas). |
766 | (such as commas). |
740 | |
767 | |
|
|
768 | =item $json->incr_skip |
|
|
769 | |
|
|
770 | This will reset the state of the incremental parser and will remove |
|
|
771 | the parsed text from the input buffer so far. This is useful after |
|
|
772 | C<incr_parse> died, in which case the input buffer and incremental parser |
|
|
773 | state is left unchanged, to skip the text parsed so far and to reset the |
|
|
774 | parse state. |
|
|
775 | |
|
|
776 | The difference to C<incr_reset> is that only text until the parse error |
|
|
777 | occurred is removed. |
|
|
778 | |
|
|
779 | =item $json->incr_reset |
|
|
780 | |
|
|
781 | This completely resets the incremental parser, that is, after this call, |
|
|
782 | it will be as if the parser had never parsed anything. |
|
|
783 | |
|
|
784 | This is useful if you want to repeatedly parse JSON objects and want to |
|
|
785 | ignore any trailing data, which means you have to reset the parser after |
|
|
786 | each successful decode. |
|
|
787 | |
741 | =back |
788 | =back |
742 | |
789 | |
743 | =head2 LIMITATIONS |
790 | =head2 LIMITATIONS |
744 | |
791 | |
745 | All options that affect decoding are supported, except |
792 | All options that affect decoding are supported, except |
746 | C<allow_nonref>. The reason for this is that it cannot be made to |
793 | C<allow_nonref>. The reason for this is that it cannot be made to work |
747 | work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate |
794 | sensibly: JSON objects and arrays are self-delimited, i.e. you can |
748 | them back to back and still decode them perfectly. This does not hold true |
795 | concatenate them back to back and still decode them perfectly. This does |
749 | for JSON numbers, however. |
796 | not hold true for JSON numbers, however. |
750 | |
797 | |
751 | For example, is the string C<1> a single JSON number, or is it simply the |
798 | For example, is the string C<1> a single JSON number, or is it simply the |
752 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
799 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
753 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
800 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
754 | takes the conservative route and disallows this case. |
801 | takes the conservative route and disallows this case. |
… | |
… | |
933 | If the number consists of digits only, JSON::XS will try to represent |
980 | If the number consists of digits only, JSON::XS will try to represent |
934 | it as an integer value. If that fails, it will try to represent it as |
981 | it as an integer value. If that fails, it will try to represent it as |
935 | a numeric (floating point) value if that is possible without loss of |
982 | a numeric (floating point) value if that is possible without loss of |
936 | precision. Otherwise it will preserve the number as a string value (in |
983 | precision. Otherwise it will preserve the number as a string value (in |
937 | which case you lose roundtripping ability, as the JSON number will be |
984 | which case you lose roundtripping ability, as the JSON number will be |
938 | re-encoded toa JSON string). |
985 | re-encoded to a JSON string). |
939 | |
986 | |
940 | Numbers containing a fractional or exponential part will always be |
987 | Numbers containing a fractional or exponential part will always be |
941 | represented as numeric (floating point) values, possibly at a loss of |
988 | represented as numeric (floating point) values, possibly at a loss of |
942 | precision (in which case you might lose perfect roundtripping ability, but |
989 | precision (in which case you might lose perfect roundtripping ability, but |
943 | the JSON number will still be re-encoded as a JSON number). |
990 | the JSON number will still be re-encoded as a JSON number). |
944 | |
991 | |
|
|
992 | Note that precision is not accuracy - binary floating point values cannot |
|
|
993 | represent most decimal fractions exactly, and when converting from and to |
|
|
994 | floating point, JSON::XS only guarantees precision up to but not including |
|
|
995 | the least significant bit. |
|
|
996 | |
945 | =item true, false |
997 | =item true, false |
946 | |
998 | |
947 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
999 | These JSON atoms become C<Types::Serialiser::true> and |
948 | respectively. They are overloaded to act almost exactly like the numbers |
1000 | C<Types::Serialiser::false>, respectively. They are overloaded to act |
949 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
1001 | almost exactly like the numbers C<1> and C<0>. You can check whether |
950 | the C<JSON::XS::is_bool> function. |
1002 | a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool> |
|
|
1003 | function (after C<use Types::Serialier>, of course). |
951 | |
1004 | |
952 | =item null |
1005 | =item null |
953 | |
1006 | |
954 | A JSON null atom becomes C<undef> in Perl. |
1007 | A JSON null atom becomes C<undef> in Perl. |
|
|
1008 | |
|
|
1009 | =item shell-style comments (C<< # I<text> >>) |
|
|
1010 | |
|
|
1011 | As a nonstandard extension to the JSON syntax that is enabled by the |
|
|
1012 | C<relaxed> setting, shell-style comments are allowed. They can start |
|
|
1013 | anywhere outside strings and go till the end of the line. |
|
|
1014 | |
|
|
1015 | =item tagged values (C<< (I<tag>)I<value> >>). |
|
|
1016 | |
|
|
1017 | Another nonstandard extension to the JSON syntax, enabled with the |
|
|
1018 | C<allow_tags> setting, are tagged values. In this implementation, the |
|
|
1019 | I<tag> must be a perl package/class name encoded as a JSON string, and the |
|
|
1020 | I<value> must be a JSON array encoding optional constructor arguments. |
|
|
1021 | |
|
|
1022 | See "OBJECT SERIALISATION", below, for details. |
955 | |
1023 | |
956 | =back |
1024 | =back |
957 | |
1025 | |
958 | |
1026 | |
959 | =head2 PERL -> JSON |
1027 | =head2 PERL -> JSON |
… | |
… | |
964 | |
1032 | |
965 | =over 4 |
1033 | =over 4 |
966 | |
1034 | |
967 | =item hash references |
1035 | =item hash references |
968 | |
1036 | |
969 | Perl hash references become JSON objects. As there is no inherent ordering |
1037 | Perl hash references become JSON objects. As there is no inherent |
970 | in hash keys (or JSON objects), they will usually be encoded in a |
1038 | ordering in hash keys (or JSON objects), they will usually be encoded |
971 | pseudo-random order that can change between runs of the same program but |
1039 | in a pseudo-random order. JSON::XS can optionally sort the hash keys |
972 | stays generally the same within a single run of a program. JSON::XS can |
1040 | (determined by the I<canonical> flag), so the same datastructure will |
973 | optionally sort the hash keys (determined by the I<canonical> flag), so |
1041 | serialise to the same JSON text (given same settings and version of |
974 | the same datastructure will serialise to the same JSON text (given same |
1042 | JSON::XS), but this incurs a runtime overhead and is only rarely useful, |
975 | settings and version of JSON::XS), but this incurs a runtime overhead |
1043 | e.g. when you want to compare some JSON text against another for equality. |
976 | and is only rarely useful, e.g. when you want to compare some JSON text |
|
|
977 | against another for equality. |
|
|
978 | |
1044 | |
979 | =item array references |
1045 | =item array references |
980 | |
1046 | |
981 | Perl array references become JSON arrays. |
1047 | Perl array references become JSON arrays. |
982 | |
1048 | |
983 | =item other references |
1049 | =item other references |
984 | |
1050 | |
985 | Other unblessed references are generally not allowed and will cause an |
1051 | Other unblessed references are generally not allowed and will cause an |
986 | exception to be thrown, except for references to the integers C<0> and |
1052 | exception to be thrown, except for references to the integers C<0> and |
987 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1053 | C<1>, which get turned into C<false> and C<true> atoms in JSON. |
988 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
|
|
989 | |
1054 | |
|
|
1055 | Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you |
|
|
1056 | can also C<use Types::Serialiser> and then use C<Types::Serialiser::false> |
|
|
1057 | and C<Types::Serialiser::true> to improve readability. |
|
|
1058 | |
|
|
1059 | use Types::Serialiser; |
990 | encode_json [\0,JSON::XS::true] # yields [false,true] |
1060 | encode_json [\0, Types::Serialiser::true] # yields [false,true] |
991 | |
1061 | |
992 | =item JSON::XS::true, JSON::XS::false |
1062 | =item Types::Serialiser::true, Types::Serialiser::false |
993 | |
1063 | |
994 | These special values become JSON true and JSON false values, |
1064 | These special values from the L<Types::Serialiser> module become JSON true |
995 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1065 | and JSON false values, respectively. You can also use C<\1> and C<\0> |
|
|
1066 | directly if you want. |
996 | |
1067 | |
997 | =item blessed objects |
1068 | =item blessed objects |
998 | |
1069 | |
999 | Blessed objects are not directly representable in JSON. See the |
1070 | Blessed objects are not directly representable in JSON, but C<JSON::XS> |
1000 | C<allow_blessed> and C<convert_blessed> methods on various options on |
1071 | allows various ways of handling objects. See "OBJECT SERIALISATION", |
1001 | how to deal with this: basically, you can choose between throwing an |
1072 | below, for details. |
1002 | exception, encoding the reference as if it weren't blessed, or provide |
|
|
1003 | your own serialiser method. |
|
|
1004 | |
1073 | |
1005 | =item simple scalars |
1074 | =item simple scalars |
1006 | |
1075 | |
1007 | Simple Perl scalars (any scalar that is not a reference) are the most |
1076 | Simple Perl scalars (any scalar that is not a reference) are the most |
1008 | difficult objects to encode: JSON::XS will encode undefined scalars as |
1077 | difficult objects to encode: JSON::XS will encode undefined scalars as |
… | |
… | |
1036 | |
1105 | |
1037 | You can not currently force the type in other, less obscure, ways. Tell me |
1106 | You can not currently force the type in other, less obscure, ways. Tell me |
1038 | if you need this capability (but don't forget to explain why it's needed |
1107 | if you need this capability (but don't forget to explain why it's needed |
1039 | :). |
1108 | :). |
1040 | |
1109 | |
|
|
1110 | Note that numerical precision has the same meaning as under Perl (so |
|
|
1111 | binary to decimal conversion follows the same rules as in Perl, which |
|
|
1112 | can differ to other languages). Also, your perl interpreter might expose |
|
|
1113 | extensions to the floating point numbers of your platform, such as |
|
|
1114 | infinities or NaN's - these cannot be represented in JSON, and it is an |
|
|
1115 | error to pass those in. |
|
|
1116 | |
1041 | =back |
1117 | =back |
|
|
1118 | |
|
|
1119 | =head2 OBJECT SERIALISATION |
|
|
1120 | |
|
|
1121 | As JSON cannot directly represent Perl objects, you have to choose between |
|
|
1122 | a pure JSON representation (without the ability to deserialise the object |
|
|
1123 | automatically again), and a nonstandard extension to the JSON syntax, |
|
|
1124 | tagged values. |
|
|
1125 | |
|
|
1126 | =head3 SERIALISATION |
|
|
1127 | |
|
|
1128 | What happens when C<JSON::XS> encounters a Perl object depends on the |
|
|
1129 | C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are |
|
|
1130 | used in this order: |
|
|
1131 | |
|
|
1132 | =over 4 |
|
|
1133 | |
|
|
1134 | =item 1. C<allow_tags> is enabled and object has a C<FREEZE> method. |
|
|
1135 | |
|
|
1136 | In this case, C<JSON::XS> uses the L<Types::Serialiser> object |
|
|
1137 | serialisation protocol to create a tagged JSON value, using a nonstandard |
|
|
1138 | extension to the JSON syntax. |
|
|
1139 | |
|
|
1140 | This works by invoking the C<FREEZE> method on the object, with the first |
|
|
1141 | argument being the object to serialise, and the second argument being the |
|
|
1142 | constant string C<JSON> to distinguish it from other serialisers. |
|
|
1143 | |
|
|
1144 | The C<FREEZE> method can return any number of values (i.e. zero or |
|
|
1145 | more). These values and the paclkage/classname of the object will then be |
|
|
1146 | encoded as a tagged JSON value in the following format: |
|
|
1147 | |
|
|
1148 | ("classname")[FREEZE return values...] |
|
|
1149 | |
|
|
1150 | For example, the hypothetical C<My::Object> C<FREEZE> method might use the |
|
|
1151 | objects C<type> and C<id> members to encode the object: |
|
|
1152 | |
|
|
1153 | sub My::Object::FREEZE { |
|
|
1154 | my ($self, $serialiser) = @_; |
|
|
1155 | |
|
|
1156 | ($self->{type}, $self->{id}) |
|
|
1157 | } |
|
|
1158 | |
|
|
1159 | =item 2. C<convert_blessed> is enabled and object has a C<TO_JSON> method. |
|
|
1160 | |
|
|
1161 | In this case, the C<TO_JSON> method of the object is invoked in scalar |
|
|
1162 | context. It must return a single scalar that can be directly encoded into |
|
|
1163 | JSON. This scalar replaces the object in the JSON text. |
|
|
1164 | |
|
|
1165 | For example, the following C<TO_JSON> method will convert all L<URI> |
|
|
1166 | objects to JSON strings when serialised. The fatc that these values |
|
|
1167 | originally were L<URI> objects is lost. |
|
|
1168 | |
|
|
1169 | sub URI::TO_JSON { |
|
|
1170 | my ($uri) = @_; |
|
|
1171 | $uri->as_string |
|
|
1172 | } |
|
|
1173 | |
|
|
1174 | =item 3. C<allow_blessed> is enabled. |
|
|
1175 | |
|
|
1176 | The object will be serialised as a JSON null value. |
|
|
1177 | |
|
|
1178 | =item 4. none of the above |
|
|
1179 | |
|
|
1180 | If none of the settings are enabled or the respective methods are missing, |
|
|
1181 | C<JSON::XS> throws an exception. |
|
|
1182 | |
|
|
1183 | =back |
|
|
1184 | |
|
|
1185 | =head3 DESERIALISATION |
|
|
1186 | |
|
|
1187 | For deserialisation there are only two cases to consider: either |
|
|
1188 | nonstandard tagging was used, in which case C<allow_tags> decides, |
|
|
1189 | or objects cannot be automatically be deserialised, in which |
|
|
1190 | case you can use postprocessing or the C<filter_json_object> or |
|
|
1191 | C<filter_json_single_key_object> callbacks to get some real objects our of |
|
|
1192 | your JSON. |
|
|
1193 | |
|
|
1194 | This section only considers the tagged value case: I a tagged JSON object |
|
|
1195 | is encountered during decoding and C<allow_tags> is disabled, a parse |
|
|
1196 | error will result (as if tagged values were not part of the grammar). |
|
|
1197 | |
|
|
1198 | If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method |
|
|
1199 | of the package/classname used during serialisation (it will not attempt |
|
|
1200 | to load the package as a Perl module). If there is no such method, the |
|
|
1201 | decoding will fail with an error. |
|
|
1202 | |
|
|
1203 | Otherwise, the C<THAW> method is invoked with the classname as first |
|
|
1204 | argument, the constant string C<JSON> as second argument, and all the |
|
|
1205 | values from the JSON array (the values originally returned by the |
|
|
1206 | C<FREEZE> method) as remaining arguments. |
|
|
1207 | |
|
|
1208 | The method must then return the object. While technically you can return |
|
|
1209 | any Perl scalar, you might have to enable the C<enable_nonref> setting to |
|
|
1210 | make that work in all cases, so better return an actual blessed reference. |
|
|
1211 | |
|
|
1212 | As an example, let's implement a C<THAW> function that regenerates the |
|
|
1213 | C<My::Object> from the C<FREEZE> example earlier: |
|
|
1214 | |
|
|
1215 | sub My::Object::THAW { |
|
|
1216 | my ($class, $serialiser, $type, $id) = @_; |
|
|
1217 | |
|
|
1218 | $class->new (type => $type, id => $id) |
|
|
1219 | } |
1042 | |
1220 | |
1043 | |
1221 | |
1044 | =head1 ENCODING/CODESET FLAG NOTES |
1222 | =head1 ENCODING/CODESET FLAG NOTES |
1045 | |
1223 | |
1046 | The interested reader might have seen a number of flags that signify |
1224 | The interested reader might have seen a number of flags that signify |
… | |
… | |
1071 | =item C<utf8> flag disabled |
1249 | =item C<utf8> flag disabled |
1072 | |
1250 | |
1073 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1251 | When C<utf8> is disabled (the default), then C<encode>/C<decode> generate |
1074 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1252 | and expect Unicode strings, that is, characters with high ordinal Unicode |
1075 | values (> 255) will be encoded as such characters, and likewise such |
1253 | values (> 255) will be encoded as such characters, and likewise such |
1076 | characters are decoded as-is, no canges to them will be done, except |
1254 | characters are decoded as-is, no changes to them will be done, except |
1077 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1255 | "(re-)interpreting" them as Unicode codepoints or Unicode characters, |
1078 | respectively (to Perl, these are the same thing in strings unless you do |
1256 | respectively (to Perl, these are the same thing in strings unless you do |
1079 | funny/weird/dumb stuff). |
1257 | funny/weird/dumb stuff). |
1080 | |
1258 | |
1081 | This is useful when you want to do the encoding yourself (e.g. when you |
1259 | This is useful when you want to do the encoding yourself (e.g. when you |
… | |
… | |
1137 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1315 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1138 | |
1316 | |
1139 | =back |
1317 | =back |
1140 | |
1318 | |
1141 | |
1319 | |
|
|
1320 | =head2 JSON and ECMAscript |
|
|
1321 | |
|
|
1322 | JSON syntax is based on how literals are represented in javascript (the |
|
|
1323 | not-standardised predecessor of ECMAscript) which is presumably why it is |
|
|
1324 | called "JavaScript Object Notation". |
|
|
1325 | |
|
|
1326 | However, JSON is not a subset (and also not a superset of course) of |
|
|
1327 | ECMAscript (the standard) or javascript (whatever browsers actually |
|
|
1328 | implement). |
|
|
1329 | |
|
|
1330 | If you want to use javascript's C<eval> function to "parse" JSON, you |
|
|
1331 | might run into parse errors for valid JSON texts, or the resulting data |
|
|
1332 | structure might not be queryable: |
|
|
1333 | |
|
|
1334 | One of the problems is that U+2028 and U+2029 are valid characters inside |
|
|
1335 | JSON strings, but are not allowed in ECMAscript string literals, so the |
|
|
1336 | following Perl fragment will not output something that can be guaranteed |
|
|
1337 | to be parsable by javascript's C<eval>: |
|
|
1338 | |
|
|
1339 | use JSON::XS; |
|
|
1340 | |
|
|
1341 | print encode_json [chr 0x2028]; |
|
|
1342 | |
|
|
1343 | The right fix for this is to use a proper JSON parser in your javascript |
|
|
1344 | programs, and not rely on C<eval> (see for example Douglas Crockford's |
|
|
1345 | F<json2.js> parser). |
|
|
1346 | |
|
|
1347 | If this is not an option, you can, as a stop-gap measure, simply encode to |
|
|
1348 | ASCII-only JSON: |
|
|
1349 | |
|
|
1350 | use JSON::XS; |
|
|
1351 | |
|
|
1352 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
|
|
1353 | |
|
|
1354 | Note that this will enlarge the resulting JSON text quite a bit if you |
|
|
1355 | have many non-ASCII characters. You might be tempted to run some regexes |
|
|
1356 | to only escape U+2028 and U+2029, e.g.: |
|
|
1357 | |
|
|
1358 | # DO NOT USE THIS! |
|
|
1359 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
|
|
1360 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
|
|
1361 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
|
|
1362 | print $json; |
|
|
1363 | |
|
|
1364 | Note that I<this is a bad idea>: the above only works for U+2028 and |
|
|
1365 | U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing |
|
|
1366 | javascript implementations, however, have issues with other characters as |
|
|
1367 | well - using C<eval> naively simply I<will> cause problems. |
|
|
1368 | |
|
|
1369 | Another problem is that some javascript implementations reserve |
|
|
1370 | some property names for their own purposes (which probably makes |
|
|
1371 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
|
|
1372 | C<__proto__> property name for its own purposes. |
|
|
1373 | |
|
|
1374 | If that is a problem, you could parse try to filter the resulting JSON |
|
|
1375 | output for these property strings, e.g.: |
|
|
1376 | |
|
|
1377 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
|
|
1378 | |
|
|
1379 | This works because C<__proto__> is not valid outside of strings, so every |
|
|
1380 | occurrence of C<"__proto__"\s*:> must be a string used as property name. |
|
|
1381 | |
|
|
1382 | If you know of other incompatibilities, please let me know. |
|
|
1383 | |
|
|
1384 | |
1142 | =head2 JSON and YAML |
1385 | =head2 JSON and YAML |
1143 | |
1386 | |
1144 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1387 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1145 | hysteria(*) and very far from the truth (as of the time of this writing), |
1388 | hysteria(*) and very far from the truth (as of the time of this writing), |
1146 | so let me state it clearly: I<in general, there is no way to configure |
1389 | so let me state it clearly: I<in general, there is no way to configure |
… | |
… | |
1154 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1397 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1155 | |
1398 | |
1156 | This will I<usually> generate JSON texts that also parse as valid |
1399 | This will I<usually> generate JSON texts that also parse as valid |
1157 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1400 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1158 | lengths that JSON doesn't have and also has different and incompatible |
1401 | lengths that JSON doesn't have and also has different and incompatible |
1159 | unicode handling, so you should make sure that your hash keys are |
1402 | unicode character escape syntax, so you should make sure that your hash |
1160 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1403 | keys are noticeably shorter than the 1024 "stream characters" YAML allows |
1161 | you do not have characters with codepoint values outside the Unicode BMP |
1404 | and that you do not have characters with codepoint values outside the |
1162 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
1405 | Unicode BMP (basic multilingual page). YAML also does not allow C<\/> |
1163 | strings (which JSON::XS does not I<currently> generate, but other JSON |
1406 | sequences in strings (which JSON::XS does not I<currently> generate, but |
1164 | generators might). |
1407 | other JSON generators might). |
1165 | |
1408 | |
1166 | There might be other incompatibilities that I am not aware of (or the YAML |
1409 | There might be other incompatibilities that I am not aware of (or the YAML |
1167 | specification has been changed yet again - it does so quite often). In |
1410 | specification has been changed yet again - it does so quite often). In |
1168 | general you should not try to generate YAML with a JSON generator or vice |
1411 | general you should not try to generate YAML with a JSON generator or vice |
1169 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1412 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
… | |
… | |
1188 | that difficult or long) and finally make YAML compatible to it, and |
1431 | that difficult or long) and finally make YAML compatible to it, and |
1189 | educating users about the changes, instead of spreading lies about the |
1432 | educating users about the changes, instead of spreading lies about the |
1190 | real compatibility for many I<years> and trying to silence people who |
1433 | real compatibility for many I<years> and trying to silence people who |
1191 | point out that it isn't true. |
1434 | point out that it isn't true. |
1192 | |
1435 | |
|
|
1436 | Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even |
|
|
1437 | though the incompatibilities have been documented (and are known to Brian) |
|
|
1438 | for many years and the spec makes explicit claims that YAML is a superset |
|
|
1439 | of JSON. It would be so easy to fix, but apparently, bullying people and |
|
|
1440 | corrupting userdata is so much easier. |
|
|
1441 | |
1193 | =back |
1442 | =back |
1194 | |
1443 | |
1195 | |
1444 | |
1196 | =head2 SPEED |
1445 | =head2 SPEED |
1197 | |
1446 | |
… | |
… | |
1202 | |
1451 | |
1203 | First comes a comparison between various modules using |
1452 | First comes a comparison between various modules using |
1204 | a very short single-line JSON string (also available at |
1453 | a very short single-line JSON string (also available at |
1205 | L<http://dist.schmorp.de/misc/json/short.json>). |
1454 | L<http://dist.schmorp.de/misc/json/short.json>). |
1206 | |
1455 | |
1207 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1456 | {"method": "handleMessage", "params": ["user1", |
1208 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1457 | "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, |
|
|
1458 | 1, 0]} |
1209 | |
1459 | |
1210 | It shows the number of encodes/decodes per second (JSON::XS uses |
1460 | It shows the number of encodes/decodes per second (JSON::XS uses |
1211 | the functional interface, while JSON::XS/2 uses the OO interface |
1461 | the functional interface, while JSON::XS/2 uses the OO interface |
1212 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1462 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1213 | shrink). Higher is better: |
1463 | shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ |
|
|
1464 | uses the from_json method). Higher is better: |
1214 | |
1465 | |
1215 | module | encode | decode | |
1466 | module | encode | decode | |
1216 | -----------|------------|------------| |
1467 | --------------|------------|------------| |
1217 | JSON 1.x | 4990.842 | 4088.813 | |
1468 | JSON::DWIW/DS | 86302.551 | 102300.098 | |
1218 | JSON::DWIW | 51653.990 | 71575.154 | |
1469 | JSON::DWIW/FJ | 86302.551 | 75983.768 | |
1219 | JSON::PC | 65948.176 | 74631.744 | |
1470 | JSON::PP | 15827.562 | 6638.658 | |
1220 | JSON::PP | 8931.652 | 3817.168 | |
1471 | JSON::Syck | 63358.066 | 47662.545 | |
1221 | JSON::Syck | 24877.248 | 27776.848 | |
1472 | JSON::XS | 511500.488 | 511500.488 | |
1222 | JSON::XS | 388361.481 | 227951.304 | |
1473 | JSON::XS/2 | 291271.111 | 388361.481 | |
1223 | JSON::XS/2 | 227951.304 | 218453.333 | |
1474 | JSON::XS/3 | 361577.931 | 361577.931 | |
1224 | JSON::XS/3 | 338250.323 | 218453.333 | |
1475 | Storable | 66788.280 | 265462.278 | |
1225 | Storable | 16500.016 | 135300.129 | |
|
|
1226 | -----------+------------+------------+ |
1476 | --------------+------------+------------+ |
1227 | |
1477 | |
1228 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
1478 | That is, JSON::XS is almost six times faster than JSON::DWIW on encoding, |
1229 | about three times faster on decoding, and over forty times faster |
1479 | about five times faster on decoding, and over thirty to seventy times |
1230 | than JSON, even with pretty-printing and key sorting. It also compares |
1480 | faster than JSON's pure perl implementation. It also compares favourably |
1231 | favourably to Storable for small amounts of data. |
1481 | to Storable for small amounts of data. |
1232 | |
1482 | |
1233 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1483 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1234 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1484 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1235 | |
1485 | |
1236 | module | encode | decode | |
1486 | module | encode | decode | |
1237 | -----------|------------|------------| |
1487 | --------------|------------|------------| |
1238 | JSON 1.x | 55.260 | 34.971 | |
1488 | JSON::DWIW/DS | 1647.927 | 2673.916 | |
1239 | JSON::DWIW | 825.228 | 1082.513 | |
1489 | JSON::DWIW/FJ | 1630.249 | 2596.128 | |
1240 | JSON::PC | 3571.444 | 2394.829 | |
|
|
1241 | JSON::PP | 210.987 | 32.574 | |
1490 | JSON::PP | 400.640 | 62.311 | |
1242 | JSON::Syck | 552.551 | 787.544 | |
1491 | JSON::Syck | 1481.040 | 1524.869 | |
1243 | JSON::XS | 5780.463 | 4854.519 | |
1492 | JSON::XS | 20661.596 | 9541.183 | |
1244 | JSON::XS/2 | 3869.998 | 4798.975 | |
1493 | JSON::XS/2 | 10683.403 | 9416.938 | |
1245 | JSON::XS/3 | 5862.880 | 4798.975 | |
1494 | JSON::XS/3 | 20661.596 | 9400.054 | |
1246 | Storable | 4445.002 | 5235.027 | |
1495 | Storable | 19765.806 | 10000.725 | |
1247 | -----------+------------+------------+ |
1496 | --------------+------------+------------+ |
1248 | |
1497 | |
1249 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1498 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1250 | decodes faster). |
1499 | decodes a bit faster). |
1251 | |
1500 | |
1252 | On large strings containing lots of high Unicode characters, some modules |
1501 | On large strings containing lots of high Unicode characters, some modules |
1253 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1502 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1254 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1503 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1255 | to decode or encode properly, so it was impossible to prepare a fair |
1504 | to decode or encode properly, so it was impossible to prepare a fair |
… | |
… | |
1291 | information you might want to make sure that exceptions thrown by JSON::XS |
1540 | information you might want to make sure that exceptions thrown by JSON::XS |
1292 | will not end up in front of untrusted eyes. |
1541 | will not end up in front of untrusted eyes. |
1293 | |
1542 | |
1294 | If you are using JSON::XS to return packets to consumption |
1543 | If you are using JSON::XS to return packets to consumption |
1295 | by JavaScript scripts in a browser you should have a look at |
1544 | by JavaScript scripts in a browser you should have a look at |
1296 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether |
1545 | L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to |
1297 | you are vulnerable to some common attack vectors (which really are browser |
1546 | see whether you are vulnerable to some common attack vectors (which really |
1298 | design bugs, but it is still you who will have to deal with it, as major |
1547 | are browser design bugs, but it is still you who will have to deal with |
1299 | browser developers care only for features, not about getting security |
1548 | it, as major browser developers care only for features, not about getting |
1300 | right). |
1549 | security right). |
|
|
1550 | |
|
|
1551 | |
|
|
1552 | =head1 INTEROPERABILITY WITH OTHER MODULES |
|
|
1553 | |
|
|
1554 | C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean |
|
|
1555 | constants. That means that the JSON true and false values will be |
|
|
1556 | comaptible to true and false values of iother modules that do the same, |
|
|
1557 | such as L<JSON::PP> and L<CBOR::XS>. |
1301 | |
1558 | |
1302 | |
1559 | |
1303 | =head1 THREADS |
1560 | =head1 THREADS |
1304 | |
1561 | |
1305 | This module is I<not> guaranteed to be thread safe and there are no |
1562 | This module is I<not> guaranteed to be thread safe and there are no |
… | |
… | |
1308 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1565 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1309 | |
1566 | |
1310 | (It might actually work, but you have been warned). |
1567 | (It might actually work, but you have been warned). |
1311 | |
1568 | |
1312 | |
1569 | |
|
|
1570 | =head1 THE PERILS OF SETLOCALE |
|
|
1571 | |
|
|
1572 | Sometimes people avoid the Perl locale support and directly call the |
|
|
1573 | system's setlocale function with C<LC_ALL>. |
|
|
1574 | |
|
|
1575 | This breaks both perl and modules such as JSON::XS, as stringification of |
|
|
1576 | numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might |
|
|
1577 | print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on |
|
|
1578 | perl to stringify numbers). |
|
|
1579 | |
|
|
1580 | The solution is simple: don't call C<setlocale>, or use it for only those |
|
|
1581 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
|
|
1582 | |
|
|
1583 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
|
|
1584 | actually needs it (avoiding stringification of numbers), and restore it |
|
|
1585 | afterwards. |
|
|
1586 | |
|
|
1587 | |
1313 | =head1 BUGS |
1588 | =head1 BUGS |
1314 | |
1589 | |
1315 | While the goal of this module is to be correct, that unfortunately does |
1590 | While the goal of this module is to be correct, that unfortunately does |
1316 | not mean it's bug-free, only that I think its design is bug-free. It is |
1591 | not mean it's bug-free, only that I think its design is bug-free. If you |
1317 | still relatively early in its development. If you keep reporting bugs they |
1592 | keep reporting bugs they will be fixed swiftly, though. |
1318 | will be fixed swiftly, though. |
|
|
1319 | |
1593 | |
1320 | Please refrain from using rt.cpan.org or any other bug reporting |
1594 | Please refrain from using rt.cpan.org or any other bug reporting |
1321 | service. I put the contact address into my modules for a reason. |
1595 | service. I put the contact address into my modules for a reason. |
1322 | |
1596 | |
1323 | =cut |
1597 | =cut |
1324 | |
1598 | |
1325 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
1599 | BEGIN { |
1326 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
1600 | *true = \$Types::Serialiser::true; |
|
|
1601 | *true = \&Types::Serialiser::true; |
|
|
1602 | *false = \$Types::Serialiser::false; |
|
|
1603 | *false = \&Types::Serialiser::false; |
|
|
1604 | *is_bool = \&Types::Serialiser::is_bool; |
1327 | |
1605 | |
1328 | sub true() { $true } |
1606 | *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::; |
1329 | sub false() { $false } |
|
|
1330 | |
|
|
1331 | sub is_bool($) { |
|
|
1332 | UNIVERSAL::isa $_[0], "JSON::XS::Boolean" |
|
|
1333 | # or UNIVERSAL::isa $_[0], "JSON::Literal" |
|
|
1334 | } |
1607 | } |
1335 | |
1608 | |
1336 | XSLoader::load "JSON::XS", $VERSION; |
1609 | XSLoader::load "JSON::XS", $VERSION; |
1337 | |
|
|
1338 | package JSON::XS::Boolean; |
|
|
1339 | |
|
|
1340 | use overload |
|
|
1341 | "0+" => sub { ${$_[0]} }, |
|
|
1342 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
|
|
1343 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
|
|
1344 | fallback => 1; |
|
|
1345 | |
|
|
1346 | 1; |
|
|
1347 | |
1610 | |
1348 | =head1 SEE ALSO |
1611 | =head1 SEE ALSO |
1349 | |
1612 | |
1350 | The F<json_xs> command line utility for quick experiments. |
1613 | The F<json_xs> command line utility for quick experiments. |
1351 | |
1614 | |
… | |
… | |
1354 | Marc Lehmann <schmorp@schmorp.de> |
1617 | Marc Lehmann <schmorp@schmorp.de> |
1355 | http://home.schmorp.de/ |
1618 | http://home.schmorp.de/ |
1356 | |
1619 | |
1357 | =cut |
1620 | =cut |
1358 | |
1621 | |
|
|
1622 | 1 |
|
|
1623 | |