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1 | =head1 NAME |
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2 | |
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3 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
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4 | |
1 | =encoding utf-8 |
5 | =encoding utf-8 |
2 | |
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3 | =head1 NAME |
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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, the deserialised data structure is identical on the Perl level. |
72 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
70 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
73 | like a number). There minor I<are> exceptions to this, read the MAPPING |
71 | like a number). There minor I<are> exceptions to this, read the MAPPING |
74 | section below to learn about those. |
72 | section below to learn about those. |
75 | |
73 | |
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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 $VERSION = '2.26'; |
109 | our @ISA = qw(Exporter); |
107 | our @ISA = qw(Exporter); |
110 | |
108 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
109 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
112 | |
110 | |
113 | sub to_json($) { |
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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443 | the same hash might be encoded differently even if contains the same data, |
441 | the same hash might be encoded differently even if contains the same data, |
444 | as key-value pairs have no inherent ordering in Perl. |
442 | as key-value pairs have no inherent ordering in Perl. |
445 | |
443 | |
446 | This setting has no effect when decoding JSON texts. |
444 | This setting has no effect when decoding JSON texts. |
447 | |
445 | |
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446 | This setting has currently no effect on tied hashes. |
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447 | |
448 | =item $json = $json->allow_nonref ([$enable]) |
448 | =item $json = $json->allow_nonref ([$enable]) |
449 | |
449 | |
450 | =item $enabled = $json->get_allow_nonref |
450 | =item $enabled = $json->get_allow_nonref |
451 | |
451 | |
452 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
452 | 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>, |
462 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
463 | resulting in an invalid JSON text: |
463 | resulting in an invalid JSON text: |
464 | |
464 | |
465 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
465 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
466 | => "Hello, World!" |
466 | => "Hello, World!" |
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467 | |
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468 | =item $json = $json->allow_unknown ([$enable]) |
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469 | |
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470 | =item $enabled = $json->get_allow_unknown |
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471 | |
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472 | If C<$enable> is true (or missing), then C<encode> will I<not> throw an |
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473 | exception when it encounters values it cannot represent in JSON (for |
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474 | example, filehandles) but instead will encode a JSON C<null> value. Note |
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475 | that blessed objects are not included here and are handled separately by |
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476 | c<allow_nonref>. |
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477 | |
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478 | If C<$enable> is false (the default), then C<encode> will throw an |
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479 | exception when it encounters anything it cannot encode as JSON. |
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480 | |
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481 | This option does not affect C<decode> in any way, and it is recommended to |
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482 | leave it off unless you know your communications partner. |
467 | |
483 | |
468 | =item $json = $json->allow_blessed ([$enable]) |
484 | =item $json = $json->allow_blessed ([$enable]) |
469 | |
485 | |
470 | =item $enabled = $json->get_allow_blessed |
486 | =item $enabled = $json->get_allow_blessed |
471 | |
487 | |
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612 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
628 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
613 | |
629 | |
614 | =item $max_depth = $json->get_max_depth |
630 | =item $max_depth = $json->get_max_depth |
615 | |
631 | |
616 | Sets the maximum nesting level (default C<512>) accepted while encoding |
632 | 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 |
633 | 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 |
634 | data structure, then the encoder and decoder will stop and croak at that |
619 | stop and croak at that point. |
635 | point. |
620 | |
636 | |
621 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
637 | 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<[> |
638 | 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 |
639 | characters without their matching closing parenthesis crossed to reach a |
624 | given character in a string. |
640 | given character in a string. |
625 | |
641 | |
626 | Setting the maximum depth to one disallows any nesting, so that ensures |
642 | Setting the maximum depth to one disallows any nesting, so that ensures |
627 | that the object is only a single hash/object or array. |
643 | that the object is only a single hash/object or array. |
628 | |
644 | |
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 |
645 | If no argument is given, the highest possible setting will be used, which |
631 | used, which is rarely useful. |
646 | is rarely useful. |
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647 | |
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648 | Note that nesting is implemented by recursion in C. The default value has |
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649 | been chosen to be as large as typical operating systems allow without |
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650 | crashing. |
632 | |
651 | |
633 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
652 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
634 | |
653 | |
635 | =item $json = $json->max_size ([$maximum_string_size]) |
654 | =item $json = $json->max_size ([$maximum_string_size]) |
636 | |
655 | |
637 | =item $max_size = $json->get_max_size |
656 | =item $max_size = $json->get_max_size |
638 | |
657 | |
639 | Set the maximum length a JSON text may have (in bytes) where decoding is |
658 | 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> |
659 | 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 |
660 | 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 |
661 | attempt to decode the string but throw an exception. This setting has no |
643 | effect on C<encode> (yet). |
662 | effect on C<encode> (yet). |
644 | |
663 | |
645 | The argument to C<max_size> will be rounded up to the next B<highest> |
664 | 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 |
665 | C<0> is specified). |
647 | limit check will be deactivated (same as when C<0> is specified). |
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648 | |
666 | |
649 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
667 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
650 | |
668 | |
651 | =item $json_text = $json->encode ($perl_scalar) |
669 | =item $json_text = $json->encode ($perl_scalar) |
652 | |
670 | |
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679 | |
697 | |
680 | JSON::XS->new->decode_prefix ("[1] the tail") |
698 | JSON::XS->new->decode_prefix ("[1] the tail") |
681 | => ([], 3) |
699 | => ([], 3) |
682 | |
700 | |
683 | =back |
701 | =back |
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702 | |
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703 | |
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704 | =head1 INCREMENTAL PARSING |
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705 | |
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706 | In some cases, there is the need for incremental parsing of JSON |
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707 | texts. While this module always has to keep both JSON text and resulting |
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708 | Perl data structure in memory at one time, it does allow you to parse a |
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709 | JSON stream incrementally. It does so by accumulating text until it has |
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710 | a full JSON object, which it then can decode. This process is similar to |
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711 | using C<decode_prefix> to see if a full JSON object is available, but |
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712 | is much more efficient (and can be implemented with a minimum of method |
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713 | calls). |
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714 | |
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715 | JSON::XS will only attempt to parse the JSON text once it is sure it |
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716 | has enough text to get a decisive result, using a very simple but |
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717 | truly incremental parser. This means that it sometimes won't stop as |
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718 | early as the full parser, for example, it doesn't detect parenthese |
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719 | mismatches. The only thing it guarantees is that it starts decoding as |
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720 | soon as a syntactically valid JSON text has been seen. This means you need |
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721 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
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722 | parsing in the presence if syntax errors. |
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723 | |
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724 | The following methods implement this incremental parser. |
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725 | |
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726 | =over 4 |
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727 | |
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728 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
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729 | |
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730 | This is the central parsing function. It can both append new text and |
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731 | extract objects from the stream accumulated so far (both of these |
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732 | functions are optional). |
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733 | |
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734 | If C<$string> is given, then this string is appended to the already |
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735 | existing JSON fragment stored in the C<$json> object. |
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736 | |
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737 | After that, if the function is called in void context, it will simply |
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738 | return without doing anything further. This can be used to add more text |
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739 | in as many chunks as you want. |
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740 | |
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741 | If the method is called in scalar context, then it will try to extract |
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742 | exactly I<one> JSON object. If that is successful, it will return this |
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743 | object, otherwise it will return C<undef>. If there is a parse error, |
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744 | this method will croak just as C<decode> would do (one can then use |
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745 | C<incr_skip> to skip the errornous part). This is the most common way of |
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746 | using the method. |
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747 | |
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748 | And finally, in list context, it will try to extract as many objects |
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749 | from the stream as it can find and return them, or the empty list |
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750 | otherwise. For this to work, there must be no separators between the JSON |
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751 | objects or arrays, instead they must be concatenated back-to-back. If |
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752 | an error occurs, an exception will be raised as in the scalar context |
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753 | case. Note that in this case, any previously-parsed JSON texts will be |
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754 | lost. |
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755 | |
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756 | =item $lvalue_string = $json->incr_text |
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757 | |
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758 | This method returns the currently stored JSON fragment as an lvalue, that |
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759 | is, you can manipulate it. This I<only> works when a preceding call to |
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760 | C<incr_parse> in I<scalar context> successfully returned an object. Under |
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761 | all other circumstances you must not call this function (I mean it. |
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762 | although in simple tests it might actually work, it I<will> fail under |
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763 | real world conditions). As a special exception, you can also call this |
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764 | method before having parsed anything. |
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765 | |
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766 | This function is useful in two cases: a) finding the trailing text after a |
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767 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
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768 | (such as commas). |
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769 | |
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770 | =item $json->incr_skip |
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771 | |
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772 | This will reset the state of the incremental parser and will remove |
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773 | the parsed text from the input buffer so far. This is useful after |
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774 | C<incr_parse> died, in which case the input buffer and incremental parser |
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775 | state is left unchanged, to skip the text parsed so far and to reset the |
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776 | parse state. |
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777 | |
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778 | The difference to C<incr_reset> is that only text until the parse error |
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779 | occured is removed. |
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780 | |
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781 | =item $json->incr_reset |
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782 | |
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783 | This completely resets the incremental parser, that is, after this call, |
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784 | it will be as if the parser had never parsed anything. |
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785 | |
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786 | This is useful if you want to repeatedly parse JSON objects and want to |
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787 | ignore any trailing data, which means you have to reset the parser after |
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788 | each successful decode. |
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789 | |
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790 | =back |
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791 | |
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792 | =head2 LIMITATIONS |
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793 | |
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794 | All options that affect decoding are supported, except |
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795 | C<allow_nonref>. The reason for this is that it cannot be made to |
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796 | work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate |
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797 | them back to back and still decode them perfectly. This does not hold true |
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798 | for JSON numbers, however. |
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799 | |
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800 | For example, is the string C<1> a single JSON number, or is it simply the |
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801 | start of C<12>? Or is C<12> a single JSON number, or the concatenation |
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802 | of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS |
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803 | takes the conservative route and disallows this case. |
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804 | |
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805 | =head2 EXAMPLES |
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806 | |
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807 | Some examples will make all this clearer. First, a simple example that |
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808 | works similarly to C<decode_prefix>: We want to decode the JSON object at |
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809 | the start of a string and identify the portion after the JSON object: |
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810 | |
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811 | my $text = "[1,2,3] hello"; |
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812 | |
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813 | my $json = new JSON::XS; |
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814 | |
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815 | my $obj = $json->incr_parse ($text) |
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816 | or die "expected JSON object or array at beginning of string"; |
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817 | |
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818 | my $tail = $json->incr_text; |
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819 | # $tail now contains " hello" |
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820 | |
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821 | Easy, isn't it? |
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822 | |
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823 | Now for a more complicated example: Imagine a hypothetical protocol where |
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824 | you read some requests from a TCP stream, and each request is a JSON |
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825 | array, without any separation between them (in fact, it is often useful to |
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826 | use newlines as "separators", as these get interpreted as whitespace at |
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827 | the start of the JSON text, which makes it possible to test said protocol |
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828 | with C<telnet>...). |
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829 | |
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830 | Here is how you'd do it (it is trivial to write this in an event-based |
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831 | manner): |
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832 | |
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833 | my $json = new JSON::XS; |
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834 | |
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835 | # read some data from the socket |
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836 | while (sysread $socket, my $buf, 4096) { |
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837 | |
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838 | # split and decode as many requests as possible |
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839 | for my $request ($json->incr_parse ($buf)) { |
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840 | # act on the $request |
|
|
841 | } |
|
|
842 | } |
|
|
843 | |
|
|
844 | Another complicated example: Assume you have a string with JSON objects |
|
|
845 | or arrays, all separated by (optional) comma characters (e.g. C<[1],[2], |
|
|
846 | [3]>). To parse them, we have to skip the commas between the JSON texts, |
|
|
847 | and here is where the lvalue-ness of C<incr_text> comes in useful: |
|
|
848 | |
|
|
849 | my $text = "[1],[2], [3]"; |
|
|
850 | my $json = new JSON::XS; |
|
|
851 | |
|
|
852 | # void context, so no parsing done |
|
|
853 | $json->incr_parse ($text); |
|
|
854 | |
|
|
855 | # now extract as many objects as possible. note the |
|
|
856 | # use of scalar context so incr_text can be called. |
|
|
857 | while (my $obj = $json->incr_parse) { |
|
|
858 | # do something with $obj |
|
|
859 | |
|
|
860 | # now skip the optional comma |
|
|
861 | $json->incr_text =~ s/^ \s* , //x; |
|
|
862 | } |
|
|
863 | |
|
|
864 | Now lets go for a very complex example: Assume that you have a gigantic |
|
|
865 | JSON array-of-objects, many gigabytes in size, and you want to parse it, |
|
|
866 | but you cannot load it into memory fully (this has actually happened in |
|
|
867 | the real world :). |
|
|
868 | |
|
|
869 | Well, you lost, you have to implement your own JSON parser. But JSON::XS |
|
|
870 | can still help you: You implement a (very simple) array parser and let |
|
|
871 | JSON decode the array elements, which are all full JSON objects on their |
|
|
872 | own (this wouldn't work if the array elements could be JSON numbers, for |
|
|
873 | example): |
|
|
874 | |
|
|
875 | my $json = new JSON::XS; |
|
|
876 | |
|
|
877 | # open the monster |
|
|
878 | open my $fh, "<bigfile.json" |
|
|
879 | or die "bigfile: $!"; |
|
|
880 | |
|
|
881 | # first parse the initial "[" |
|
|
882 | for (;;) { |
|
|
883 | sysread $fh, my $buf, 65536 |
|
|
884 | or die "read error: $!"; |
|
|
885 | $json->incr_parse ($buf); # void context, so no parsing |
|
|
886 | |
|
|
887 | # Exit the loop once we found and removed(!) the initial "[". |
|
|
888 | # In essence, we are (ab-)using the $json object as a simple scalar |
|
|
889 | # we append data to. |
|
|
890 | last if $json->incr_text =~ s/^ \s* \[ //x; |
|
|
891 | } |
|
|
892 | |
|
|
893 | # now we have the skipped the initial "[", so continue |
|
|
894 | # parsing all the elements. |
|
|
895 | for (;;) { |
|
|
896 | # in this loop we read data until we got a single JSON object |
|
|
897 | for (;;) { |
|
|
898 | if (my $obj = $json->incr_parse) { |
|
|
899 | # do something with $obj |
|
|
900 | last; |
|
|
901 | } |
|
|
902 | |
|
|
903 | # add more data |
|
|
904 | sysread $fh, my $buf, 65536 |
|
|
905 | or die "read error: $!"; |
|
|
906 | $json->incr_parse ($buf); # void context, so no parsing |
|
|
907 | } |
|
|
908 | |
|
|
909 | # in this loop we read data until we either found and parsed the |
|
|
910 | # separating "," between elements, or the final "]" |
|
|
911 | for (;;) { |
|
|
912 | # first skip whitespace |
|
|
913 | $json->incr_text =~ s/^\s*//; |
|
|
914 | |
|
|
915 | # if we find "]", we are done |
|
|
916 | if ($json->incr_text =~ s/^\]//) { |
|
|
917 | print "finished.\n"; |
|
|
918 | exit; |
|
|
919 | } |
|
|
920 | |
|
|
921 | # if we find ",", we can continue with the next element |
|
|
922 | if ($json->incr_text =~ s/^,//) { |
|
|
923 | last; |
|
|
924 | } |
|
|
925 | |
|
|
926 | # if we find anything else, we have a parse error! |
|
|
927 | if (length $json->incr_text) { |
|
|
928 | die "parse error near ", $json->incr_text; |
|
|
929 | } |
|
|
930 | |
|
|
931 | # else add more data |
|
|
932 | sysread $fh, my $buf, 65536 |
|
|
933 | or die "read error: $!"; |
|
|
934 | $json->incr_parse ($buf); # void context, so no parsing |
|
|
935 | } |
|
|
936 | |
|
|
937 | This is a complex example, but most of the complexity comes from the fact |
|
|
938 | that we are trying to be correct (bear with me if I am wrong, I never ran |
|
|
939 | the above example :). |
|
|
940 | |
684 | |
941 | |
685 | |
942 | |
686 | =head1 MAPPING |
943 | =head1 MAPPING |
687 | |
944 | |
688 | This section describes how JSON::XS maps Perl values to JSON values and |
945 | This section describes how JSON::XS maps Perl values to JSON values and |
… | |
… | |
777 | Other unblessed references are generally not allowed and will cause an |
1034 | Other unblessed references are generally not allowed and will cause an |
778 | exception to be thrown, except for references to the integers C<0> and |
1035 | exception to be thrown, except for references to the integers C<0> and |
779 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1036 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
780 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
1037 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
781 | |
1038 | |
782 | encode_json [\0,JSON::XS::true] # yields [false,true] |
1039 | encode_json [\0, JSON::XS::true] # yields [false,true] |
783 | |
1040 | |
784 | =item JSON::XS::true, JSON::XS::false |
1041 | =item JSON::XS::true, JSON::XS::false |
785 | |
1042 | |
786 | These special values become JSON true and JSON false values, |
1043 | These special values become JSON true and JSON false values, |
787 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1044 | respectively. You can also use C<\1> and C<\0> directly if you want. |
… | |
… | |
825 | my $x = "3"; # some variable containing a string |
1082 | my $x = "3"; # some variable containing a string |
826 | $x += 0; # numify it, ensuring it will be dumped as a number |
1083 | $x += 0; # numify it, ensuring it will be dumped as a number |
827 | $x *= 1; # same thing, the choice is yours. |
1084 | $x *= 1; # same thing, the choice is yours. |
828 | |
1085 | |
829 | You can not currently force the type in other, less obscure, ways. Tell me |
1086 | You can not currently force the type in other, less obscure, ways. Tell me |
830 | if you need this capability (but don't forget to explain why its needed |
1087 | if you need this capability (but don't forget to explain why it's needed |
831 | :). |
1088 | :). |
832 | |
1089 | |
833 | =back |
1090 | =back |
834 | |
1091 | |
835 | |
1092 | |
… | |
… | |
837 | |
1094 | |
838 | The interested reader might have seen a number of flags that signify |
1095 | The interested reader might have seen a number of flags that signify |
839 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
1096 | encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be |
840 | some confusion on what these do, so here is a short comparison: |
1097 | some confusion on what these do, so here is a short comparison: |
841 | |
1098 | |
842 | C<utf8> controls wether the JSON text created by C<encode> (and expected |
1099 | C<utf8> controls whether the JSON text created by C<encode> (and expected |
843 | by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only |
1100 | by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only |
844 | control wether C<encode> escapes character values outside their respective |
1101 | control whether C<encode> escapes character values outside their respective |
845 | codeset range. Neither of these flags conflict with each other, although |
1102 | codeset range. Neither of these flags conflict with each other, although |
846 | some combinations make less sense than others. |
1103 | some combinations make less sense than others. |
847 | |
1104 | |
848 | Care has been taken to make all flags symmetrical with respect to |
1105 | Care has been taken to make all flags symmetrical with respect to |
849 | C<encode> and C<decode>, that is, texts encoded with any combination of |
1106 | C<encode> and C<decode>, that is, texts encoded with any combination of |
… | |
… | |
929 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1186 | proper subset of most 8-bit and multibyte encodings in use in the world. |
930 | |
1187 | |
931 | =back |
1188 | =back |
932 | |
1189 | |
933 | |
1190 | |
934 | =head1 COMPARISON |
1191 | =head2 JSON and ECMAscript |
935 | |
1192 | |
936 | As already mentioned, this module was created because none of the existing |
1193 | JSON syntax is based on how literals are represented in javascript (the |
937 | JSON modules could be made to work correctly. First I will describe the |
1194 | not-standardised predecessor of ECMAscript) which is presumably why it is |
938 | problems (or pleasures) I encountered with various existing JSON modules, |
1195 | called "JavaScript Object Notation". |
939 | followed by some benchmark values. JSON::XS was designed not to suffer |
|
|
940 | from any of these problems or limitations. |
|
|
941 | |
1196 | |
942 | =over 4 |
1197 | However, JSON is not a subset (and also not a superset of course) of |
|
|
1198 | ECMAscript (the standard) or javascript (whatever browsers actually |
|
|
1199 | implement). |
943 | |
1200 | |
944 | =item JSON 2.xx |
1201 | If you want to use javascript's C<eval> function to "parse" JSON, you |
|
|
1202 | might run into parse errors for valid JSON texts, or the resulting data |
|
|
1203 | structure might not be queryable: |
945 | |
1204 | |
946 | A marvellous piece of engineering, this module either uses JSON::XS |
1205 | One of the problems is that U+2028 and U+2029 are valid characters inside |
947 | directly when available (so will be 100% compatible with it, including |
1206 | JSON strings, but are not allowed in ECMAscript string literals, so the |
948 | speed), or it uses JSON::PP, which is basically JSON::XS translated to |
1207 | following Perl fragment will not output something that can be guaranteed |
949 | Pure Perl, which should be 100% compatible with JSON::XS, just a bit |
1208 | to be parsable by javascript's C<eval>: |
950 | slower. |
|
|
951 | |
1209 | |
952 | You cannot really lose by using this module, especially as it tries very |
1210 | use JSON::XS; |
953 | hard to work even with ancient Perl versions, while JSON::XS does not. |
|
|
954 | |
1211 | |
955 | =item JSON 1.07 |
1212 | print encode_json [chr 0x2028]; |
956 | |
1213 | |
957 | Slow (but very portable, as it is written in pure Perl). |
1214 | The right fix for this is to use a proper JSON parser in your javascript |
|
|
1215 | programs, and not rely on C<eval> (see for example Douglas Crockford's |
|
|
1216 | F<json2.js> parser). |
958 | |
1217 | |
959 | Undocumented/buggy Unicode handling (how JSON handles Unicode values is |
1218 | If this is not an option, you can, as a stop-gap measure, simply encode to |
960 | undocumented. One can get far by feeding it Unicode strings and doing |
1219 | ASCII-only JSON: |
961 | en-/decoding oneself, but Unicode escapes are not working properly). |
|
|
962 | |
1220 | |
963 | No round-tripping (strings get clobbered if they look like numbers, e.g. |
1221 | use JSON::XS; |
964 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
|
|
965 | decode into the number 2. |
|
|
966 | |
1222 | |
967 | =item JSON::PC 0.01 |
1223 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
968 | |
1224 | |
969 | Very fast. |
1225 | Note that this will enlarge the resulting JSON text quite a bit if you |
|
|
1226 | have many non-ASCII characters. You might be tempted to run some regexes |
|
|
1227 | to only escape U+2028 and U+2029, e.g.: |
970 | |
1228 | |
971 | Undocumented/buggy Unicode handling. |
1229 | # DO NOT USE THIS! |
|
|
1230 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
|
|
1231 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
|
|
1232 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
|
|
1233 | print $json; |
972 | |
1234 | |
973 | No round-tripping. |
1235 | Note that I<this is a bad idea>: the above only works for U+2028 and |
|
|
1236 | U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing |
|
|
1237 | javascript implementations, however, have issues with other characters as |
|
|
1238 | well - using C<eval> naively simply I<will> cause problems. |
974 | |
1239 | |
975 | Has problems handling many Perl values (e.g. regex results and other magic |
1240 | Another problem is that some javascript implementations reserve |
976 | values will make it croak). |
1241 | some property names for their own purposes (which probably makes |
|
|
1242 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
|
|
1243 | C<__proto__> property name for it's own purposes. |
977 | |
1244 | |
978 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
1245 | If that is a problem, you could parse try to filter the resulting JSON |
979 | which is not a valid JSON text. |
1246 | output for these property strings, e.g.: |
980 | |
1247 | |
981 | Unmaintained (maintainer unresponsive for many months, bugs are not |
1248 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
982 | getting fixed). |
|
|
983 | |
1249 | |
984 | =item JSON::Syck 0.21 |
1250 | This works because C<__proto__> is not valid outside of strings, so every |
|
|
1251 | occurence of C<"__proto__"\s*:> must be a string used as property name. |
985 | |
1252 | |
986 | Very buggy (often crashes). |
1253 | If you know of other incompatibilities, please let me know. |
987 | |
|
|
988 | Very inflexible (no human-readable format supported, format pretty much |
|
|
989 | undocumented. I need at least a format for easy reading by humans and a |
|
|
990 | single-line compact format for use in a protocol, and preferably a way to |
|
|
991 | generate ASCII-only JSON texts). |
|
|
992 | |
|
|
993 | Completely broken (and confusingly documented) Unicode handling (Unicode |
|
|
994 | escapes are not working properly, you need to set ImplicitUnicode to |
|
|
995 | I<different> values on en- and decoding to get symmetric behaviour). |
|
|
996 | |
|
|
997 | No round-tripping (simple cases work, but this depends on whether the scalar |
|
|
998 | value was used in a numeric context or not). |
|
|
999 | |
|
|
1000 | Dumping hashes may skip hash values depending on iterator state. |
|
|
1001 | |
|
|
1002 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
1003 | getting fixed). |
|
|
1004 | |
|
|
1005 | Does not check input for validity (i.e. will accept non-JSON input and |
|
|
1006 | return "something" instead of raising an exception. This is a security |
|
|
1007 | issue: imagine two banks transferring money between each other using |
|
|
1008 | JSON. One bank might parse a given non-JSON request and deduct money, |
|
|
1009 | while the other might reject the transaction with a syntax error. While a |
|
|
1010 | good protocol will at least recover, that is extra unnecessary work and |
|
|
1011 | the transaction will still not succeed). |
|
|
1012 | |
|
|
1013 | =item JSON::DWIW 0.04 |
|
|
1014 | |
|
|
1015 | Very fast. Very natural. Very nice. |
|
|
1016 | |
|
|
1017 | Undocumented Unicode handling (but the best of the pack. Unicode escapes |
|
|
1018 | still don't get parsed properly). |
|
|
1019 | |
|
|
1020 | Very inflexible. |
|
|
1021 | |
|
|
1022 | No round-tripping. |
|
|
1023 | |
|
|
1024 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
|
|
1025 | result in nothing being output) |
|
|
1026 | |
|
|
1027 | Does not check input for validity. |
|
|
1028 | |
|
|
1029 | =back |
|
|
1030 | |
1254 | |
1031 | |
1255 | |
1032 | =head2 JSON and YAML |
1256 | =head2 JSON and YAML |
1033 | |
1257 | |
1034 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1258 | You often hear that JSON is a subset of YAML. This is, however, a mass |
… | |
… | |
1044 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1268 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
1045 | |
1269 | |
1046 | This will I<usually> generate JSON texts that also parse as valid |
1270 | This will I<usually> generate JSON texts that also parse as valid |
1047 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1271 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
1048 | lengths that JSON doesn't have and also has different and incompatible |
1272 | lengths that JSON doesn't have and also has different and incompatible |
1049 | unicode handling, so you should make sure that your hash keys are |
1273 | unicode character escape syntax, so you should make sure that your hash |
1050 | noticeably shorter than the 1024 "stream characters" YAML allows and that |
1274 | keys are noticeably shorter than the 1024 "stream characters" YAML allows |
1051 | you do not have characters with codepoint values outside the Unicode BMP |
1275 | and that you do not have characters with codepoint values outside the |
1052 | (basic multilingual page). YAML also does not allow C<\/> sequences in |
1276 | Unicode BMP (basic multilingual page). YAML also does not allow C<\/> |
1053 | strings (which JSON::XS does not I<currently> generate, but other JSON |
1277 | sequences in strings (which JSON::XS does not I<currently> generate, but |
1054 | generators might). |
1278 | other JSON generators might). |
1055 | |
1279 | |
1056 | There might be other incompatibilities that I am not aware of (or the YAML |
1280 | There might be other incompatibilities that I am not aware of (or the YAML |
1057 | specification has been changed yet again - it does so quite often). In |
1281 | specification has been changed yet again - it does so quite often). In |
1058 | general you should not try to generate YAML with a JSON generator or vice |
1282 | general you should not try to generate YAML with a JSON generator or vice |
1059 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
1283 | versa, or try to parse JSON with a YAML parser or vice versa: chances are |
… | |
… | |
1078 | that difficult or long) and finally make YAML compatible to it, and |
1302 | that difficult or long) and finally make YAML compatible to it, and |
1079 | educating users about the changes, instead of spreading lies about the |
1303 | educating users about the changes, instead of spreading lies about the |
1080 | real compatibility for many I<years> and trying to silence people who |
1304 | real compatibility for many I<years> and trying to silence people who |
1081 | point out that it isn't true. |
1305 | point out that it isn't true. |
1082 | |
1306 | |
|
|
1307 | Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even |
|
|
1308 | though the incompatibilities have been documented (and are known to |
|
|
1309 | Brian) for many years and the spec makes explicit claims that YAML is a |
|
|
1310 | superset of JSON. It would be so easy to fix, but apparently, bullying and |
|
|
1311 | corrupting userdata is so much easier. |
|
|
1312 | |
1083 | =back |
1313 | =back |
1084 | |
1314 | |
1085 | |
1315 | |
1086 | =head2 SPEED |
1316 | =head2 SPEED |
1087 | |
1317 | |
… | |
… | |
1092 | |
1322 | |
1093 | First comes a comparison between various modules using |
1323 | First comes a comparison between various modules using |
1094 | a very short single-line JSON string (also available at |
1324 | a very short single-line JSON string (also available at |
1095 | L<http://dist.schmorp.de/misc/json/short.json>). |
1325 | L<http://dist.schmorp.de/misc/json/short.json>). |
1096 | |
1326 | |
1097 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
1327 | {"method": "handleMessage", "params": ["user1", |
1098 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
1328 | "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, |
|
|
1329 | true, false]} |
1099 | |
1330 | |
1100 | It shows the number of encodes/decodes per second (JSON::XS uses |
1331 | It shows the number of encodes/decodes per second (JSON::XS uses |
1101 | the functional interface, while JSON::XS/2 uses the OO interface |
1332 | the functional interface, while JSON::XS/2 uses the OO interface |
1102 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1333 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
1103 | shrink). Higher is better: |
1334 | shrink). Higher is better: |
… | |
… | |
1193 | =head1 THREADS |
1424 | =head1 THREADS |
1194 | |
1425 | |
1195 | This module is I<not> guaranteed to be thread safe and there are no |
1426 | This module is I<not> guaranteed to be thread safe and there are no |
1196 | plans to change this until Perl gets thread support (as opposed to the |
1427 | plans to change this until Perl gets thread support (as opposed to the |
1197 | horribly slow so-called "threads" which are simply slow and bloated |
1428 | horribly slow so-called "threads" which are simply slow and bloated |
1198 | process simulations - use fork, its I<much> faster, cheaper, better). |
1429 | process simulations - use fork, it's I<much> faster, cheaper, better). |
1199 | |
1430 | |
1200 | (It might actually work, but you have been warned). |
1431 | (It might actually work, but you have been warned). |
1201 | |
1432 | |
1202 | |
1433 | |
1203 | =head1 BUGS |
1434 | =head1 BUGS |
1204 | |
1435 | |
1205 | While the goal of this module is to be correct, that unfortunately does |
1436 | While the goal of this module is to be correct, that unfortunately does |
1206 | not mean its bug-free, only that I think its design is bug-free. It is |
1437 | not mean it's bug-free, only that I think its design is bug-free. If you |
1207 | still relatively early in its development. If you keep reporting bugs they |
1438 | keep reporting bugs they will be fixed swiftly, though. |
1208 | will be fixed swiftly, though. |
|
|
1209 | |
1439 | |
1210 | Please refrain from using rt.cpan.org or any other bug reporting |
1440 | Please refrain from using rt.cpan.org or any other bug reporting |
1211 | service. I put the contact address into my modules for a reason. |
1441 | service. I put the contact address into my modules for a reason. |
1212 | |
1442 | |
1213 | =cut |
1443 | =cut |
… | |
… | |
1233 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
1463 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
1234 | fallback => 1; |
1464 | fallback => 1; |
1235 | |
1465 | |
1236 | 1; |
1466 | 1; |
1237 | |
1467 | |
|
|
1468 | =head1 SEE ALSO |
|
|
1469 | |
|
|
1470 | The F<json_xs> command line utility for quick experiments. |
|
|
1471 | |
1238 | =head1 AUTHOR |
1472 | =head1 AUTHOR |
1239 | |
1473 | |
1240 | Marc Lehmann <schmorp@schmorp.de> |
1474 | Marc Lehmann <schmorp@schmorp.de> |
1241 | http://home.schmorp.de/ |
1475 | http://home.schmorp.de/ |
1242 | |
1476 | |