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, 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 | |
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104 | no warnings; |
106 | use strict; |
105 | use strict; |
107 | |
106 | |
108 | our $VERSION = '2.2'; |
107 | our $VERSION = '2.24'; |
109 | our @ISA = qw(Exporter); |
108 | our @ISA = qw(Exporter); |
110 | |
109 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
110 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
112 | |
111 | |
113 | sub to_json($) { |
112 | sub to_json($) { |
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137 | |
136 | |
138 | This function call is functionally identical to: |
137 | This function call is functionally identical to: |
139 | |
138 | |
140 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
139 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
141 | |
140 | |
142 | except being faster. |
141 | Except being faster. |
143 | |
142 | |
144 | =item $perl_scalar = decode_json $json_text |
143 | =item $perl_scalar = decode_json $json_text |
145 | |
144 | |
146 | The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries |
145 | 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 |
146 | to parse that as an UTF-8 encoded JSON text, returning the resulting |
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149 | |
148 | |
150 | This function call is functionally identical to: |
149 | This function call is functionally identical to: |
151 | |
150 | |
152 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
151 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
153 | |
152 | |
154 | except being faster. |
153 | Except being faster. |
155 | |
154 | |
156 | =item $is_boolean = JSON::XS::is_bool $scalar |
155 | =item $is_boolean = JSON::XS::is_bool $scalar |
157 | |
156 | |
158 | Returns true if the passed scalar represents either JSON::XS::true or |
157 | 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 |
158 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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197 | |
196 | |
198 | If you didn't know about that flag, just the better, pretend it doesn't |
197 | If you didn't know about that flag, just the better, pretend it doesn't |
199 | exist. |
198 | exist. |
200 | |
199 | |
201 | =item 4. A "Unicode String" is simply a string where each character can be |
200 | =item 4. A "Unicode String" is simply a string where each character can be |
202 | validly interpreted as a Unicode codepoint. |
201 | validly interpreted as a Unicode code point. |
203 | |
202 | |
204 | If you have UTF-8 encoded data, it is no longer a Unicode string, but a |
203 | 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. |
204 | Unicode string encoded in UTF-8, giving you a binary string. |
206 | |
205 | |
207 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
206 | =item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string. |
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701 | =back |
700 | =back |
702 | |
701 | |
703 | |
702 | |
704 | =head1 INCREMENTAL PARSING |
703 | =head1 INCREMENTAL PARSING |
705 | |
704 | |
706 | [This section and the API it details is still EXPERIMENTAL] |
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707 | |
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708 | In some cases, there is the need for incremental parsing of JSON |
705 | In some cases, there is the need for incremental parsing of JSON |
709 | texts. While this module always has to keep both JSON text and resulting |
706 | texts. While this module always has to keep both JSON text and resulting |
710 | Perl data structure in memory at one time, it does allow you to parse a |
707 | Perl data structure in memory at one time, it does allow you to parse a |
711 | JSON stream incrementally. It does so by accumulating text until it has |
708 | JSON stream incrementally. It does so by accumulating text until it has |
712 | a full JSON object, which it then can decode. This process is similar to |
709 | a full JSON object, which it then can decode. This process is similar to |
713 | using C<decode_prefix> to see if a full JSON object is available, but is |
710 | using C<decode_prefix> to see if a full JSON object is available, but |
714 | much more efficient (JSON::XS will only attempt to parse the JSON text |
711 | is much more efficient (and can be implemented with a minimum of method |
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712 | calls). |
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713 | |
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714 | JSON::XS will only attempt to parse the JSON text once it is sure it |
715 | once it is sure it has enough text to get a decisive result, using a very |
715 | has enough text to get a decisive result, using a very simple but |
716 | simple but truly incremental parser). |
716 | truly incremental parser. This means that it sometimes won't stop as |
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717 | early as the full parser, for example, it doesn't detect parenthese |
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718 | mismatches. The only thing it guarantees is that it starts decoding as |
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719 | soon as a syntactically valid JSON text has been seen. This means you need |
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720 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
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721 | parsing in the presence if syntax errors. |
717 | |
722 | |
718 | The following two methods deal with this. |
723 | The following methods implement this incremental parser. |
719 | |
724 | |
720 | =over 4 |
725 | =over 4 |
721 | |
726 | |
722 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
727 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
723 | |
728 | |
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761 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
766 | JSON object or b) parsing multiple JSON objects separated by non-JSON text |
762 | (such as commas). |
767 | (such as commas). |
763 | |
768 | |
764 | =item $json->incr_skip |
769 | =item $json->incr_skip |
765 | |
770 | |
766 | This will reset the state of the incremental parser and will remove the |
771 | This will reset the state of the incremental parser and will remove |
767 | parsed text from the input buffer. This is useful after C<incr_parse> |
772 | the parsed text from the input buffer so far. This is useful after |
768 | died, in which case the input buffer and incremental parser state is left |
773 | C<incr_parse> died, in which case the input buffer and incremental parser |
769 | unchanged, to skip the text parsed so far and to reset the parse state. |
774 | state is left unchanged, to skip the text parsed so far and to reset the |
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775 | parse state. |
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776 | |
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777 | The difference to C<incr_reset> is that only text until the parse error |
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778 | occured is removed. |
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779 | |
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780 | =item $json->incr_reset |
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781 | |
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782 | This completely resets the incremental parser, that is, after this call, |
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783 | it will be as if the parser had never parsed anything. |
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784 | |
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785 | This is useful if you want to repeatedly parse JSON objects and want to |
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786 | ignore any trailing data, which means you have to reset the parser after |
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787 | each successful decode. |
770 | |
788 | |
771 | =back |
789 | =back |
772 | |
790 | |
773 | =head2 LIMITATIONS |
791 | =head2 LIMITATIONS |
774 | |
792 | |
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1015 | Other unblessed references are generally not allowed and will cause an |
1033 | Other unblessed references are generally not allowed and will cause an |
1016 | exception to be thrown, except for references to the integers C<0> and |
1034 | exception to be thrown, except for references to the integers C<0> and |
1017 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1035 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
1018 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
1036 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
1019 | |
1037 | |
1020 | encode_json [\0,JSON::XS::true] # yields [false,true] |
1038 | encode_json [\0, JSON::XS::true] # yields [false,true] |
1021 | |
1039 | |
1022 | =item JSON::XS::true, JSON::XS::false |
1040 | =item JSON::XS::true, JSON::XS::false |
1023 | |
1041 | |
1024 | These special values become JSON true and JSON false values, |
1042 | These special values become JSON true and JSON false values, |
1025 | respectively. You can also use C<\1> and C<\0> directly if you want. |
1043 | respectively. You can also use C<\1> and C<\0> directly if you want. |
… | |
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1165 | when your channel for JSON transfer is not 8-bit clean or the encoding |
1183 | when your channel for JSON transfer is not 8-bit clean or the encoding |
1166 | might be mangled in between (e.g. in mail), and works because ASCII is a |
1184 | might be mangled in between (e.g. in mail), and works because ASCII is a |
1167 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1185 | proper subset of most 8-bit and multibyte encodings in use in the world. |
1168 | |
1186 | |
1169 | =back |
1187 | =back |
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1188 | |
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1189 | |
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1190 | =head2 JSON and ECMAscript |
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1191 | |
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1192 | JSON syntax is based on how literals are represented in javascript (the |
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1193 | not-standardised predecessor of ECMAscript) which is presumably why it is |
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1194 | called "JavaScript Object Notation". |
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1195 | |
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1196 | However, JSON is not a subset (and also not a superset of course) of |
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1197 | ECMAscript (the standard) or javascript (whatever browsers actually |
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1198 | implement). |
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1199 | |
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1200 | If you want to use javascript's C<eval> function to "parse" JSON, you |
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1201 | might run into parse errors for valid JSON texts, or the resulting data |
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1202 | structure might not be queryable: |
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1203 | |
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1204 | One of the problems is that U+2028 and U+2029 are valid characters inside |
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1205 | JSON strings, but are not allowed in ECMAscript string literals, so the |
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1206 | following Perl fragment will not output something that can be guaranteed |
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1207 | to be parsable by javascript's C<eval>: |
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1208 | |
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1209 | use JSON::XS; |
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1210 | |
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1211 | print encode_json [chr 0x2028]; |
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1212 | |
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1213 | The right fix for this is to use a proper JSON parser in your javascript |
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1214 | programs, and not rely on C<eval> (see for example Douglas Crockford's |
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1215 | F<json2.js> parser). |
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1216 | |
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1217 | If this is not an option, you can, as a stop-gap measure, simply encode to |
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1218 | ASCII-only JSON: |
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1219 | |
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1220 | use JSON::XS; |
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1221 | |
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1222 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
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1223 | |
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1224 | Note that this will enlarge the resulting JSON text quite a bit if you |
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1225 | have many non-ASCII characters. You might be tempted to run some regexes |
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1226 | to only escape U+2028 and U+2029, e.g.: |
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1227 | |
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1228 | # DO NOT USE THIS! |
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1229 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
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1230 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
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1231 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
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1232 | print $json; |
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1233 | |
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1234 | Note that I<this is a bad idea>: the above only works for U+2028 and |
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1235 | U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing |
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1236 | javascript implementations, however, have issues with other characters as |
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1237 | well - using C<eval> naively simply I<will> cause problems. |
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1238 | |
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1239 | Another problem is that some javascript implementations reserve |
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1240 | some property names for their own purposes (which probably makes |
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1241 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
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1242 | C<__proto__> property name for it's own purposes. |
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1243 | |
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1244 | If that is a problem, you could parse try to filter the resulting JSON |
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1245 | output for these property strings, e.g.: |
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1246 | |
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1247 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
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1248 | |
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1249 | This works because C<__proto__> is not valid outside of strings, so every |
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1250 | occurence of C<"__proto__"\s*:> must be a string used as property name. |
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1251 | |
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1252 | If you know of other incompatibilities, please let me know. |
1170 | |
1253 | |
1171 | |
1254 | |
1172 | =head2 JSON and YAML |
1255 | =head2 JSON and YAML |
1173 | |
1256 | |
1174 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1257 | You often hear that JSON is a subset of YAML. This is, however, a mass |
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1342 | |
1425 | |
1343 | |
1426 | |
1344 | =head1 BUGS |
1427 | =head1 BUGS |
1345 | |
1428 | |
1346 | While the goal of this module is to be correct, that unfortunately does |
1429 | While the goal of this module is to be correct, that unfortunately does |
1347 | not mean it's bug-free, only that I think its design is bug-free. It is |
1430 | not mean it's bug-free, only that I think its design is bug-free. If you |
1348 | still relatively early in its development. If you keep reporting bugs they |
1431 | keep reporting bugs they will be fixed swiftly, though. |
1349 | will be fixed swiftly, though. |
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1350 | |
1432 | |
1351 | Please refrain from using rt.cpan.org or any other bug reporting |
1433 | Please refrain from using rt.cpan.org or any other bug reporting |
1352 | service. I put the contact address into my modules for a reason. |
1434 | service. I put the contact address into my modules for a reason. |
1353 | |
1435 | |
1354 | =cut |
1436 | =cut |