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 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 $VERSION = 2.34; |
109 | our @ISA = qw(Exporter); |
107 | our @ISA = qw(Exporter); |
110 | |
108 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
109 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
112 | |
110 | |
113 | sub to_json($) { |
111 | sub to_json($) { |
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137 | |
135 | |
138 | This function call is functionally identical to: |
136 | This function call is functionally identical to: |
139 | |
137 | |
140 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
138 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
141 | |
139 | |
142 | except being faster. |
140 | Except being faster. |
143 | |
141 | |
144 | =item $perl_scalar = decode_json $json_text |
142 | =item $perl_scalar = decode_json $json_text |
145 | |
143 | |
146 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
144 | 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 |
145 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
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149 | |
147 | |
150 | This function call is functionally identical to: |
148 | This function call is functionally identical to: |
151 | |
149 | |
152 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
150 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
153 | |
151 | |
154 | except being faster. |
152 | Except being faster. |
155 | |
153 | |
156 | =item $is_boolean = JSON::XS::is_bool $scalar |
154 | =item $is_boolean = JSON::XS::is_bool $scalar |
157 | |
155 | |
158 | Returns true if the passed scalar represents either JSON::XS::true or |
156 | Returns true if the passed scalar represents either JSON::XS::true or |
159 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
157 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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197 | |
195 | |
198 | If you didn't know about that flag, just the better, pretend it doesn't |
196 | If you didn't know about that flag, just the better, pretend it doesn't |
199 | exist. |
197 | exist. |
200 | |
198 | |
201 | =item 4. A "Unicode String" is simply a string where each character can be |
199 | =item 4. A "Unicode String" is simply a string where each character can be |
202 | validly interpreted as a Unicode codepoint. |
200 | validly interpreted as a Unicode code point. |
203 | |
201 | |
204 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
202 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
205 | Unicode string encoded in UTF-8, giving you a binary string. |
203 | Unicode string encoded in UTF-8, giving you a binary string. |
206 | |
204 | |
207 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
205 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
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434 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
432 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
435 | by sorting their keys. This is adding a comparatively high overhead. |
433 | by sorting their keys. This is adding a comparatively high overhead. |
436 | |
434 | |
437 | If C<$enable> is false, then the C<encode> method will output key-value |
435 | 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 |
436 | pairs in the order Perl stores them (which will likely change between runs |
439 | of the same script). |
437 | of the same script, and can change even within the same run from 5.18 |
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438 | onwards). |
440 | |
439 | |
441 | This option is useful if you want the same data structure to be encoded as |
440 | 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, |
441 | 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, |
442 | the same hash might be encoded differently even if contains the same data, |
444 | as key-value pairs have no inherent ordering in Perl. |
443 | as key-value pairs have no inherent ordering in Perl. |
445 | |
444 | |
446 | This setting has no effect when decoding JSON texts. |
445 | This setting has no effect when decoding JSON texts. |
447 | |
446 | |
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447 | This setting has currently no effect on tied hashes. |
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448 | |
448 | =item $json = $json->allow_nonref ([$enable]) |
449 | =item $json = $json->allow_nonref ([$enable]) |
449 | |
450 | |
450 | =item $enabled = $json->get_allow_nonref |
451 | =item $enabled = $json->get_allow_nonref |
451 | |
452 | |
452 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
453 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
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462 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
463 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
463 | resulting in an invalid JSON text: |
464 | resulting in an invalid JSON text: |
464 | |
465 | |
465 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
466 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
466 | => "Hello, World!" |
467 | => "Hello, World!" |
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468 | |
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469 | =item $json = $json->allow_unknown ([$enable]) |
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470 | |
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471 | =item $enabled = $json->get_allow_unknown |
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472 | |
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473 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
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474 | exception when it encounters values it cannot represent in JSON (for |
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475 | example, filehandles) but instead will encode a JSON C<null> value. Note |
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476 | that blessed objects are not included here and are handled separately by |
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477 | c<allow_nonref>. |
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478 | |
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479 | If C<$enable> is false (the default), then C<encode> will throw an |
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480 | exception when it encounters anything it cannot encode as JSON. |
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481 | |
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482 | This option does not affect C<decode> in any way, and it is recommended to |
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483 | leave it off unless you know your communications partner. |
467 | |
484 | |
468 | =item $json = $json->allow_blessed ([$enable]) |
485 | =item $json = $json->allow_blessed ([$enable]) |
469 | |
486 | |
470 | =item $enabled = $json->get_allow_blessed |
487 | =item $enabled = $json->get_allow_blessed |
471 | |
488 | |
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612 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
629 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
613 | |
630 | |
614 | =item $max_depth = $json->get_max_depth |
631 | =item $max_depth = $json->get_max_depth |
615 | |
632 | |
616 | Sets the maximum nesting level (default C<512>) accepted while encoding |
633 | 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 |
634 | 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 |
635 | data structure, then the encoder and decoder will stop and croak at that |
619 | stop and croak at that point. |
636 | point. |
620 | |
637 | |
621 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
638 | 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<[> |
639 | 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 |
640 | characters without their matching closing parenthesis crossed to reach a |
624 | given character in a string. |
641 | given character in a string. |
625 | |
642 | |
626 | Setting the maximum depth to one disallows any nesting, so that ensures |
643 | Setting the maximum depth to one disallows any nesting, so that ensures |
627 | that the object is only a single hash/object or array. |
644 | that the object is only a single hash/object or array. |
628 | |
645 | |
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 |
646 | If no argument is given, the highest possible setting will be used, which |
631 | used, which is rarely useful. |
647 | is rarely useful. |
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648 | |
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649 | Note that nesting is implemented by recursion in C. The default value has |
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650 | been chosen to be as large as typical operating systems allow without |
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651 | crashing. |
632 | |
652 | |
633 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
653 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
634 | |
654 | |
635 | =item $json = $json->max_size ([$maximum_string_size]) |
655 | =item $json = $json->max_size ([$maximum_string_size]) |
636 | |
656 | |
637 | =item $max_size = $json->get_max_size |
657 | =item $max_size = $json->get_max_size |
638 | |
658 | |
639 | Set the maximum length a JSON text may have (in bytes) where decoding is |
659 | 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> |
660 | 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 |
661 | 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 |
662 | attempt to decode the string but throw an exception. This setting has no |
643 | effect on C<encode> (yet). |
663 | effect on C<encode> (yet). |
644 | |
664 | |
645 | The argument to C<max_size> will be rounded up to the next B<highest> |
665 | 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 |
666 | C<0> is specified). |
647 | limit check will be deactivated (same as when C<0> is specified). |
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648 | |
667 | |
649 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
668 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
650 | |
669 | |
651 | =item $json_text = $json->encode ($perl_scalar) |
670 | =item $json_text = $json->encode ($perl_scalar) |
652 | |
671 | |
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683 | =back |
702 | =back |
684 | |
703 | |
685 | |
704 | |
686 | =head1 INCREMENTAL PARSING |
705 | =head1 INCREMENTAL PARSING |
687 | |
706 | |
688 | [This section is still EXPERIMENTAL] |
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689 | |
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690 | In some cases, there is the need for incremental parsing of JSON |
707 | 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 |
708 | 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 |
709 | 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 |
710 | 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 |
711 | 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 |
712 | 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 |
713 | is much more efficient (and can be implemented with a minimum of method |
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714 | calls). |
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715 | |
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716 | 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 |
717 | has enough text to get a decisive result, using a very simple but |
698 | simple but truly incremental parser). |
718 | truly incremental parser. This means that it sometimes won't stop as |
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719 | early as the full parser, for example, it doesn't detect mismatched |
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720 | parentheses. The only thing it guarantees is that it starts decoding as |
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721 | soon as a syntactically valid JSON text has been seen. This means you need |
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722 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
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723 | parsing in the presence if syntax errors. |
699 | |
724 | |
700 | The following two methods deal with this. |
725 | The following methods implement this incremental parser. |
701 | |
726 | |
702 | =over 4 |
727 | =over 4 |
703 | |
728 | |
704 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
729 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
705 | |
730 | |
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714 | return without doing anything further. This can be used to add more text |
739 | return without doing anything further. This can be used to add more text |
715 | in as many chunks as you want. |
740 | in as many chunks as you want. |
716 | |
741 | |
717 | If the method is called in scalar context, then it will try to extract |
742 | 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 |
743 | 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 |
744 | object, otherwise it will return C<undef>. If there is a parse error, |
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745 | this method will croak just as C<decode> would do (one can then use |
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746 | C<incr_skip> to skip the errornous part). This is the most common way of |
720 | using the method. |
747 | using the method. |
721 | |
748 | |
722 | And finally, in list context, it will try to extract as many objects |
749 | 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 |
750 | 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 |
751 | 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. |
752 | objects or arrays, instead they must be concatenated back-to-back. If |
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753 | an error occurs, an exception will be raised as in the scalar context |
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754 | case. Note that in this case, any previously-parsed JSON texts will be |
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755 | lost. |
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756 | |
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757 | Example: Parse some JSON arrays/objects in a given string and return |
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758 | them. |
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759 | |
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760 | my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]"); |
726 | |
761 | |
727 | =item $lvalue_string = $json->incr_text |
762 | =item $lvalue_string = $json->incr_text |
728 | |
763 | |
729 | This method returns the currently stored JSON fragment as an lvalue, that |
764 | 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 |
765 | is, you can manipulate it. This I<only> works when a preceding call to |
… | |
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735 | method before having parsed anything. |
770 | method before having parsed anything. |
736 | |
771 | |
737 | This function is useful in two cases: a) finding the trailing text after a |
772 | 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 |
773 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
739 | (such as commas). |
774 | (such as commas). |
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775 | |
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776 | =item $json->incr_skip |
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777 | |
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778 | This will reset the state of the incremental parser and will remove |
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779 | the parsed text from the input buffer so far. This is useful after |
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780 | C<incr_parse> died, in which case the input buffer and incremental parser |
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781 | state is left unchanged, to skip the text parsed so far and to reset the |
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782 | parse state. |
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783 | |
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784 | The difference to C<incr_reset> is that only text until the parse error |
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785 | occured is removed. |
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786 | |
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787 | =item $json->incr_reset |
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788 | |
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789 | This completely resets the incremental parser, that is, after this call, |
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790 | it will be as if the parser had never parsed anything. |
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791 | |
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792 | This is useful if you want to repeatedly parse JSON objects and want to |
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793 | ignore any trailing data, which means you have to reset the parser after |
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794 | each successful decode. |
740 | |
795 | |
741 | =back |
796 | =back |
742 | |
797 | |
743 | =head2 LIMITATIONS |
798 | =head2 LIMITATIONS |
744 | |
799 | |
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940 | Numbers containing a fractional or exponential part will always be |
995 | Numbers containing a fractional or exponential part will always be |
941 | represented as numeric (floating point) values, possibly at a loss of |
996 | represented as numeric (floating point) values, possibly at a loss of |
942 | precision (in which case you might lose perfect roundtripping ability, but |
997 | precision (in which case you might lose perfect roundtripping ability, but |
943 | the JSON number will still be re-encoded as a JSON number). |
998 | the JSON number will still be re-encoded as a JSON number). |
944 | |
999 | |
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1000 | Note that precision is not accuracy - binary floating point values cannot |
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1001 | represent most decimal fractions exactly, and when converting from and to |
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1002 | floating point, JSON::XS only guarantees precision up to but not including |
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1003 | the leats significant bit. |
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1004 | |
945 | =item true, false |
1005 | =item true, false |
946 | |
1006 | |
947 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
1007 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
948 | respectively. They are overloaded to act almost exactly like the numbers |
1008 | respectively. They are overloaded to act almost exactly like the numbers |
949 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
1009 | C<1> and C<0>. You can check whether a scalar is a JSON boolean by using |
… | |
… | |
985 | Other unblessed references are generally not allowed and will cause an |
1045 | 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 |
1046 | 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 |
1047 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
988 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
1048 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
989 | |
1049 | |
990 | encode_json [\0,JSON::XS::true] # yields [false,true] |
1050 | encode_json [\0, JSON::XS::true] # yields [false,true] |
991 | |
1051 | |
992 | =item JSON::XS::true, JSON::XS::false |
1052 | =item JSON::XS::true, JSON::XS::false |
993 | |
1053 | |
994 | These special values become JSON true and JSON false values, |
1054 | These special values become JSON true and JSON false values, |
995 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1055 | respectively. You can also use C<\1> and C<\0> directly if you want. |
… | |
… | |
1035 | $x *= 1; # same thing, the choice is yours. |
1095 | $x *= 1; # same thing, the choice is yours. |
1036 | |
1096 | |
1037 | You can not currently force the type in other, less obscure, ways. Tell me |
1097 | 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 |
1098 | if you need this capability (but don't forget to explain why it's needed |
1039 | :). |
1099 | :). |
|
|
1100 | |
|
|
1101 | Note that numerical precision has the same meaning as under Perl (so |
|
|
1102 | binary to decimal conversion follows the same rules as in Perl, which |
|
|
1103 | can differ to other languages). Also, your perl interpreter might expose |
|
|
1104 | extensions to the floating point numbers of your platform, such as |
|
|
1105 | infinities or NaN's - these cannot be represented in JSON, and it is an |
|
|
1106 | error to pass those in. |
1040 | |
1107 | |
1041 | =back |
1108 | =back |
1042 | |
1109 | |
1043 | |
1110 | |
1044 | =head1 ENCODING/CODESET FLAG NOTES |
1111 | =head1 ENCODING/CODESET FLAG NOTES |
… | |
… | |
1137 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1204 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1138 | |
1205 | |
1139 | =back |
1206 | =back |
1140 | |
1207 | |
1141 | |
1208 | |
1142 | =head1 COMPARISON |
1209 | =head2 JSON and ECMAscript |
1143 | |
1210 | |
1144 | As already mentioned, this module was created because none of the existing |
1211 | JSON syntax is based on how literals are represented in javascript (the |
1145 | JSON modules could be made to work correctly. First I will describe the |
1212 | not-standardised predecessor of ECMAscript) which is presumably why it is |
1146 | problems (or pleasures) I encountered with various existing JSON modules, |
1213 | called "JavaScript Object Notation". |
1147 | followed by some benchmark values. JSON::XS was designed not to suffer |
|
|
1148 | from any of these problems or limitations. |
|
|
1149 | |
1214 | |
1150 | =over 4 |
1215 | However, JSON is not a subset (and also not a superset of course) of |
|
|
1216 | ECMAscript (the standard) or javascript (whatever browsers actually |
|
|
1217 | implement). |
1151 | |
1218 | |
1152 | =item JSON 2.xx |
1219 | If you want to use javascript's C<eval> function to "parse" JSON, you |
|
|
1220 | might run into parse errors for valid JSON texts, or the resulting data |
|
|
1221 | structure might not be queryable: |
1153 | |
1222 | |
1154 | A marvellous piece of engineering, this module either uses JSON::XS |
1223 | One of the problems is that U+2028 and U+2029 are valid characters inside |
1155 | directly when available (so will be 100% compatible with it, including |
1224 | JSON strings, but are not allowed in ECMAscript string literals, so the |
1156 | speed), or it uses JSON::PP, which is basically JSON::XS translated to |
1225 | following Perl fragment will not output something that can be guaranteed |
1157 | Pure Perl, which should be 100% compatible with JSON::XS, just a bit |
1226 | to be parsable by javascript's C<eval>: |
1158 | slower. |
|
|
1159 | |
1227 | |
1160 | You cannot really lose by using this module, especially as it tries very |
1228 | use JSON::XS; |
1161 | hard to work even with ancient Perl versions, while JSON::XS does not. |
|
|
1162 | |
1229 | |
1163 | =item JSON 1.07 |
1230 | print encode_json [chr 0x2028]; |
1164 | |
1231 | |
1165 | Slow (but very portable, as it is written in pure Perl). |
1232 | The right fix for this is to use a proper JSON parser in your javascript |
|
|
1233 | programs, and not rely on C<eval> (see for example Douglas Crockford's |
|
|
1234 | F<json2.js> parser). |
1166 | |
1235 | |
1167 | Undocumented/buggy Unicode handling (how JSON handles Unicode values is |
1236 | If this is not an option, you can, as a stop-gap measure, simply encode to |
1168 | undocumented. One can get far by feeding it Unicode strings and doing |
1237 | ASCII-only JSON: |
1169 | en-/decoding oneself, but Unicode escapes are not working properly). |
|
|
1170 | |
1238 | |
1171 | No round-tripping (strings get clobbered if they look like numbers, e.g. |
1239 | use JSON::XS; |
1172 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
|
|
1173 | decode into the number 2. |
|
|
1174 | |
1240 | |
1175 | =item JSON::PC 0.01 |
1241 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
1176 | |
1242 | |
1177 | Very fast. |
1243 | Note that this will enlarge the resulting JSON text quite a bit if you |
|
|
1244 | have many non-ASCII characters. You might be tempted to run some regexes |
|
|
1245 | to only escape U+2028 and U+2029, e.g.: |
1178 | |
1246 | |
1179 | Undocumented/buggy Unicode handling. |
1247 | # DO NOT USE THIS! |
|
|
1248 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
|
|
1249 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
|
|
1250 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
|
|
1251 | print $json; |
1180 | |
1252 | |
1181 | No round-tripping. |
1253 | Note that I<this is a bad idea>: the above only works for U+2028 and |
|
|
1254 | U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing |
|
|
1255 | javascript implementations, however, have issues with other characters as |
|
|
1256 | well - using C<eval> naively simply I<will> cause problems. |
1182 | |
1257 | |
1183 | Has problems handling many Perl values (e.g. regex results and other magic |
1258 | Another problem is that some javascript implementations reserve |
1184 | values will make it croak). |
1259 | some property names for their own purposes (which probably makes |
|
|
1260 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
|
|
1261 | C<__proto__> property name for its own purposes. |
1185 | |
1262 | |
1186 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
1263 | If that is a problem, you could parse try to filter the resulting JSON |
1187 | which is not a valid JSON text. |
1264 | output for these property strings, e.g.: |
1188 | |
1265 | |
1189 | Unmaintained (maintainer unresponsive for many months, bugs are not |
1266 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
1190 | getting fixed). |
|
|
1191 | |
1267 | |
1192 | =item JSON::Syck 0.21 |
1268 | This works because C<__proto__> is not valid outside of strings, so every |
|
|
1269 | occurence of C<"__proto__"\s*:> must be a string used as property name. |
1193 | |
1270 | |
1194 | Very buggy (often crashes). |
1271 | If you know of other incompatibilities, please let me know. |
1195 | |
|
|
1196 | Very inflexible (no human-readable format supported, format pretty much |
|
|
1197 | undocumented. I need at least a format for easy reading by humans and a |
|
|
1198 | single-line compact format for use in a protocol, and preferably a way to |
|
|
1199 | generate ASCII-only JSON texts). |
|
|
1200 | |
|
|
1201 | Completely broken (and confusingly documented) Unicode handling (Unicode |
|
|
1202 | escapes are not working properly, you need to set ImplicitUnicode to |
|
|
1203 | I<different> values on en- and decoding to get symmetric behaviour). |
|
|
1204 | |
|
|
1205 | No round-tripping (simple cases work, but this depends on whether the scalar |
|
|
1206 | value was used in a numeric context or not). |
|
|
1207 | |
|
|
1208 | Dumping hashes may skip hash values depending on iterator state. |
|
|
1209 | |
|
|
1210 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
1211 | getting fixed). |
|
|
1212 | |
|
|
1213 | Does not check input for validity (i.e. will accept non-JSON input and |
|
|
1214 | return "something" instead of raising an exception. This is a security |
|
|
1215 | issue: imagine two banks transferring money between each other using |
|
|
1216 | JSON. One bank might parse a given non-JSON request and deduct money, |
|
|
1217 | while the other might reject the transaction with a syntax error. While a |
|
|
1218 | good protocol will at least recover, that is extra unnecessary work and |
|
|
1219 | the transaction will still not succeed). |
|
|
1220 | |
|
|
1221 | =item JSON::DWIW 0.04 |
|
|
1222 | |
|
|
1223 | Very fast. Very natural. Very nice. |
|
|
1224 | |
|
|
1225 | Undocumented Unicode handling (but the best of the pack. Unicode escapes |
|
|
1226 | still don't get parsed properly). |
|
|
1227 | |
|
|
1228 | Very inflexible. |
|
|
1229 | |
|
|
1230 | No round-tripping. |
|
|
1231 | |
|
|
1232 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
|
|
1233 | result in nothing being output) |
|
|
1234 | |
|
|
1235 | Does not check input for validity. |
|
|
1236 | |
|
|
1237 | =back |
|
|
1238 | |
1272 | |
1239 | |
1273 | |
1240 | =head2 JSON and YAML |
1274 | =head2 JSON and YAML |
1241 | |
1275 | |
1242 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1276 | You often hear that JSON is a subset of YAML. This is, however, a mass |
… | |
… | |
1252 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1286 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1253 | |
1287 | |
1254 | This will I<usually> generate JSON texts that also parse as valid |
1288 | This will I<usually> generate JSON texts that also parse as valid |
1255 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1289 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1256 | lengths that JSON doesn't have and also has different and incompatible |
1290 | lengths that JSON doesn't have and also has different and incompatible |
1257 | unicode handling, so you should make sure that your hash keys are |
1291 | unicode character escape syntax, so you should make sure that your hash |
1258 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1292 | keys are noticeably shorter than the 1024 "stream characters" YAML allows |
1259 | you do not have characters with codepoint values outside the Unicode BMP |
1293 | and that you do not have characters with codepoint values outside the |
1260 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
1294 | Unicode BMP (basic multilingual page). YAML also does not allow C<\/> |
1261 | strings (which JSON::XS does not I<currently> generate, but other JSON |
1295 | sequences in strings (which JSON::XS does not I<currently> generate, but |
1262 | generators might). |
1296 | other JSON generators might). |
1263 | |
1297 | |
1264 | There might be other incompatibilities that I am not aware of (or the YAML |
1298 | There might be other incompatibilities that I am not aware of (or the YAML |
1265 | specification has been changed yet again - it does so quite often). In |
1299 | specification has been changed yet again - it does so quite often). In |
1266 | general you should not try to generate YAML with a JSON generator or vice |
1300 | general you should not try to generate YAML with a JSON generator or vice |
1267 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1301 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
… | |
… | |
1286 | that difficult or long) and finally make YAML compatible to it, and |
1320 | that difficult or long) and finally make YAML compatible to it, and |
1287 | educating users about the changes, instead of spreading lies about the |
1321 | educating users about the changes, instead of spreading lies about the |
1288 | real compatibility for many I<years> and trying to silence people who |
1322 | real compatibility for many I<years> and trying to silence people who |
1289 | point out that it isn't true. |
1323 | point out that it isn't true. |
1290 | |
1324 | |
|
|
1325 | Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even |
|
|
1326 | though the incompatibilities have been documented (and are known to Brian) |
|
|
1327 | for many years and the spec makes explicit claims that YAML is a superset |
|
|
1328 | of JSON. It would be so easy to fix, but apparently, bullying people and |
|
|
1329 | corrupting userdata is so much easier. |
|
|
1330 | |
1291 | =back |
1331 | =back |
1292 | |
1332 | |
1293 | |
1333 | |
1294 | =head2 SPEED |
1334 | =head2 SPEED |
1295 | |
1335 | |
… | |
… | |
1300 | |
1340 | |
1301 | First comes a comparison between various modules using |
1341 | First comes a comparison between various modules using |
1302 | a very short single-line JSON string (also available at |
1342 | a very short single-line JSON string (also available at |
1303 | L<http://dist.schmorp.de/misc/json/short.json>). |
1343 | L<http://dist.schmorp.de/misc/json/short.json>). |
1304 | |
1344 | |
1305 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1345 | {"method": "handleMessage", "params": ["user1", |
1306 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1346 | "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, |
|
|
1347 | 1, 0]} |
1307 | |
1348 | |
1308 | It shows the number of encodes/decodes per second (JSON::XS uses |
1349 | It shows the number of encodes/decodes per second (JSON::XS uses |
1309 | the functional interface, while JSON::XS/2 uses the OO interface |
1350 | the functional interface, while JSON::XS/2 uses the OO interface |
1310 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1351 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1311 | shrink). Higher is better: |
1352 | shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ |
|
|
1353 | uses the from_json method). Higher is better: |
1312 | |
1354 | |
1313 | module | encode | decode | |
1355 | module | encode | decode | |
1314 | -----------|------------|------------| |
1356 | --------------|------------|------------| |
1315 | JSON 1.x | 4990.842 | 4088.813 | |
1357 | JSON::DWIW/DS | 86302.551 | 102300.098 | |
1316 | JSON::DWIW | 51653.990 | 71575.154 | |
1358 | JSON::DWIW/FJ | 86302.551 | 75983.768 | |
1317 | JSON::PC | 65948.176 | 74631.744 | |
1359 | JSON::PP | 15827.562 | 6638.658 | |
1318 | JSON::PP | 8931.652 | 3817.168 | |
1360 | JSON::Syck | 63358.066 | 47662.545 | |
1319 | JSON::Syck | 24877.248 | 27776.848 | |
1361 | JSON::XS | 511500.488 | 511500.488 | |
1320 | JSON::XS | 388361.481 | 227951.304 | |
1362 | JSON::XS/2 | 291271.111 | 388361.481 | |
1321 | JSON::XS/2 | 227951.304 | 218453.333 | |
1363 | JSON::XS/3 | 361577.931 | 361577.931 | |
1322 | JSON::XS/3 | 338250.323 | 218453.333 | |
1364 | Storable | 66788.280 | 265462.278 | |
1323 | Storable | 16500.016 | 135300.129 | |
|
|
1324 | -----------+------------+------------+ |
1365 | --------------+------------+------------+ |
1325 | |
1366 | |
1326 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
1367 | That is, JSON::XS is almost six times faster than JSON::DWIW on encoding, |
1327 | about three times faster on decoding, and over forty times faster |
1368 | about five times faster on decoding, and over thirty to seventy times |
1328 | than JSON, even with pretty-printing and key sorting. It also compares |
1369 | faster than JSON's pure perl implementation. It also compares favourably |
1329 | favourably to Storable for small amounts of data. |
1370 | to Storable for small amounts of data. |
1330 | |
1371 | |
1331 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1372 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
1332 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1373 | search API (L<http://dist.schmorp.de/misc/json/long.json>). |
1333 | |
1374 | |
1334 | module | encode | decode | |
1375 | module | encode | decode | |
1335 | -----------|------------|------------| |
1376 | --------------|------------|------------| |
1336 | JSON 1.x | 55.260 | 34.971 | |
1377 | JSON::DWIW/DS | 1647.927 | 2673.916 | |
1337 | JSON::DWIW | 825.228 | 1082.513 | |
1378 | JSON::DWIW/FJ | 1630.249 | 2596.128 | |
1338 | JSON::PC | 3571.444 | 2394.829 | |
|
|
1339 | JSON::PP | 210.987 | 32.574 | |
1379 | JSON::PP | 400.640 | 62.311 | |
1340 | JSON::Syck | 552.551 | 787.544 | |
1380 | JSON::Syck | 1481.040 | 1524.869 | |
1341 | JSON::XS | 5780.463 | 4854.519 | |
1381 | JSON::XS | 20661.596 | 9541.183 | |
1342 | JSON::XS/2 | 3869.998 | 4798.975 | |
1382 | JSON::XS/2 | 10683.403 | 9416.938 | |
1343 | JSON::XS/3 | 5862.880 | 4798.975 | |
1383 | JSON::XS/3 | 20661.596 | 9400.054 | |
1344 | Storable | 4445.002 | 5235.027 | |
1384 | Storable | 19765.806 | 10000.725 | |
1345 | -----------+------------+------------+ |
1385 | --------------+------------+------------+ |
1346 | |
1386 | |
1347 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1387 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
1348 | decodes faster). |
1388 | decodes a bit faster). |
1349 | |
1389 | |
1350 | On large strings containing lots of high Unicode characters, some modules |
1390 | On large strings containing lots of high Unicode characters, some modules |
1351 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1391 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
1352 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1392 | will be broken due to missing (or wrong) Unicode handling. Others refuse |
1353 | to decode or encode properly, so it was impossible to prepare a fair |
1393 | to decode or encode properly, so it was impossible to prepare a fair |
… | |
… | |
1389 | information you might want to make sure that exceptions thrown by JSON::XS |
1429 | information you might want to make sure that exceptions thrown by JSON::XS |
1390 | will not end up in front of untrusted eyes. |
1430 | will not end up in front of untrusted eyes. |
1391 | |
1431 | |
1392 | If you are using JSON::XS to return packets to consumption |
1432 | If you are using JSON::XS to return packets to consumption |
1393 | by JavaScript scripts in a browser you should have a look at |
1433 | by JavaScript scripts in a browser you should have a look at |
1394 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether |
1434 | L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to |
1395 | you are vulnerable to some common attack vectors (which really are browser |
1435 | see whether you are vulnerable to some common attack vectors (which really |
1396 | design bugs, but it is still you who will have to deal with it, as major |
1436 | are browser design bugs, but it is still you who will have to deal with |
1397 | browser developers care only for features, not about getting security |
1437 | it, as major browser developers care only for features, not about getting |
1398 | right). |
1438 | security right). |
1399 | |
1439 | |
1400 | |
1440 | |
1401 | =head1 THREADS |
1441 | =head1 THREADS |
1402 | |
1442 | |
1403 | This module is I<not> guaranteed to be thread safe and there are no |
1443 | This module is I<not> guaranteed to be thread safe and there are no |
… | |
… | |
1406 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1446 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1407 | |
1447 | |
1408 | (It might actually work, but you have been warned). |
1448 | (It might actually work, but you have been warned). |
1409 | |
1449 | |
1410 | |
1450 | |
|
|
1451 | =head1 THE PERILS OF SETLOCALE |
|
|
1452 | |
|
|
1453 | Sometimes people avoid the Perl locale support and directly call the |
|
|
1454 | system's setlocale function with C<LC_ALL>. |
|
|
1455 | |
|
|
1456 | This breaks both perl and modules such as JSON::XS, as stringification of |
|
|
1457 | numbers no longer works correcly (e.g. C<$x = 0.1; print "$x"+1> might |
|
|
1458 | print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on |
|
|
1459 | perl to stringify numbers). |
|
|
1460 | |
|
|
1461 | The solution is simple: don't call C<setlocale>, or use it for only those |
|
|
1462 | categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>. |
|
|
1463 | |
|
|
1464 | If you need C<LC_NUMERIC>, you should enable it only around the code that |
|
|
1465 | actually needs it (avoiding stringification of numbers), and restore it |
|
|
1466 | afterwards. |
|
|
1467 | |
|
|
1468 | |
1411 | =head1 BUGS |
1469 | =head1 BUGS |
1412 | |
1470 | |
1413 | While the goal of this module is to be correct, that unfortunately does |
1471 | While the goal of this module is to be correct, that unfortunately does |
1414 | not mean it's bug-free, only that I think its design is bug-free. It is |
1472 | not mean it's bug-free, only that I think its design is bug-free. If you |
1415 | still relatively early in its development. If you keep reporting bugs they |
1473 | keep reporting bugs they will be fixed swiftly, though. |
1416 | will be fixed swiftly, though. |
|
|
1417 | |
1474 | |
1418 | Please refrain from using rt.cpan.org or any other bug reporting |
1475 | Please refrain from using rt.cpan.org or any other bug reporting |
1419 | service. I put the contact address into my modules for a reason. |
1476 | service. I put the contact address into my modules for a reason. |
1420 | |
1477 | |
1421 | =cut |
1478 | =cut |