… | |
… | |
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. |
|
|
55 | |
|
|
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 | |
… | |
… | |
101 | |
99 | |
102 | =cut |
100 | =cut |
103 | |
101 | |
104 | package JSON::XS; |
102 | package JSON::XS; |
105 | |
103 | |
|
|
104 | no warnings; |
106 | use strict; |
105 | use strict; |
107 | |
106 | |
108 | our $VERSION = '2.2'; |
107 | our $VERSION = '2.232'; |
109 | our @ISA = qw(Exporter); |
108 | our @ISA = qw(Exporter); |
110 | |
109 | |
111 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
110 | our @EXPORT = qw(encode_json decode_json to_json from_json); |
112 | |
111 | |
113 | sub to_json($) { |
112 | sub to_json($) { |
… | |
… | |
706 | 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 |
707 | 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 |
708 | 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 |
709 | 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 |
710 | 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 |
711 | 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 |
712 | 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 |
|
|
712 | calls). |
|
|
713 | |
|
|
714 | JSON::XS will only attempt to parse the JSON text once it is sure it |
713 | 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 |
714 | simple but truly incremental parser). |
716 | truly incremental parser. This means that it sometimes won't stop as |
|
|
717 | early as the full parser, for example, it doesn't detect parenthese |
|
|
718 | mismatches. The only thing it guarantees is that it starts decoding as |
|
|
719 | soon as a syntactically valid JSON text has been seen. This means you need |
|
|
720 | to set resource limits (e.g. C<max_size>) to ensure the parser will stop |
|
|
721 | parsing in the presence if syntax errors. |
715 | |
722 | |
716 | The following two methods deal with this. |
723 | The following methods implement this incremental parser. |
717 | |
724 | |
718 | =over 4 |
725 | =over 4 |
719 | |
726 | |
720 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
727 | =item [void, scalar or list context] = $json->incr_parse ([$string]) |
721 | |
728 | |
… | |
… | |
759 | 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 |
760 | (such as commas). |
767 | (such as commas). |
761 | |
768 | |
762 | =item $json->incr_skip |
769 | =item $json->incr_skip |
763 | |
770 | |
764 | 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 |
765 | 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 |
766 | 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 |
767 | 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 |
|
|
775 | parse state. |
|
|
776 | |
|
|
777 | The difference to C<incr_reset> is that only text until the parse error |
|
|
778 | occured is removed. |
768 | |
779 | |
769 | =item $json->incr_reset |
780 | =item $json->incr_reset |
770 | |
781 | |
771 | This completely resets the incremental parser, that is, after this call, |
782 | This completely resets the incremental parser, that is, after this call, |
772 | it will be as if the parser had never parsed anything. |
783 | it will be as if the parser had never parsed anything. |
773 | |
784 | |
774 | This is useful if you want ot repeatedly parse JSON objects and want to |
785 | This is useful if you want to repeatedly parse JSON objects and want to |
775 | ignore any trailing data, which means you have to reset the parser after |
786 | ignore any trailing data, which means you have to reset the parser after |
776 | each successful decode. |
787 | each successful decode. |
777 | |
788 | |
778 | =back |
789 | =back |
779 | |
790 | |
… | |
… | |
1172 | 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 |
1173 | 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 |
1174 | 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. |
1175 | |
1186 | |
1176 | =back |
1187 | =back |
|
|
1188 | |
|
|
1189 | |
|
|
1190 | =head2 JSON and ECMAscript |
|
|
1191 | |
|
|
1192 | JSON syntax is based on how literals are represented in javascript (the |
|
|
1193 | not-standardised predecessor of ECMAscript) which is presumably why it is |
|
|
1194 | called "JavaScript Object Notation". |
|
|
1195 | |
|
|
1196 | However, JSON is not a subset (and also not a superset of course) of |
|
|
1197 | ECMAscript (the standard) or javascript (whatever browsers actually |
|
|
1198 | implement). |
|
|
1199 | |
|
|
1200 | If you want to use javascript's C<eval> function to "parse" JSON, you |
|
|
1201 | might run into parse errors for valid JSON texts, or the resulting data |
|
|
1202 | structure might not be queryable: |
|
|
1203 | |
|
|
1204 | One of the problems is that U+2028 and U+2029 are valid characters inside |
|
|
1205 | JSON strings, but are not allowed in ECMAscript string literals, so the |
|
|
1206 | following Perl fragment will not output something that can be guaranteed |
|
|
1207 | to be parsable by javascript's C<eval>: |
|
|
1208 | |
|
|
1209 | use JSON::XS; |
|
|
1210 | |
|
|
1211 | print encode_json [chr 0x2028]; |
|
|
1212 | |
|
|
1213 | The right fix for this is to use a proper JSON parser in your javascript |
|
|
1214 | programs, and not rely on C<eval>. |
|
|
1215 | |
|
|
1216 | If this is not an option, you can, as a stop-gap measure, simply encode to |
|
|
1217 | ASCII-only JSON: |
|
|
1218 | |
|
|
1219 | use JSON::XS; |
|
|
1220 | |
|
|
1221 | print JSON::XS->new->ascii->encode ([chr 0x2028]); |
|
|
1222 | |
|
|
1223 | And if you are concerned about the size of the resulting JSON text, you |
|
|
1224 | can run some regexes to only escape U+2028 and U+2029: |
|
|
1225 | |
|
|
1226 | use JSON::XS; |
|
|
1227 | |
|
|
1228 | my $json = JSON::XS->new->utf8->encode ([chr 0x2028]); |
|
|
1229 | $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028 |
|
|
1230 | $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029 |
|
|
1231 | print $json; |
|
|
1232 | |
|
|
1233 | This works because U+2028/U+2029 are not allowed outside of strings and |
|
|
1234 | are not used for syntax, so replacing them unconditionally just works. |
|
|
1235 | |
|
|
1236 | Note, however, that fixing the broken JSON parser is better than working |
|
|
1237 | around it in every other generator. The above regexes should work well in |
|
|
1238 | other languages, as long as they operate on UTF-8. It is equally valid to |
|
|
1239 | replace all occurences of U+2028/2029 directly by their \\u-escaped forms |
|
|
1240 | in unicode texts, so they can simply be used to fix any parsers relying on |
|
|
1241 | C<eval> by first applying the regexes on the encoded texts. |
|
|
1242 | |
|
|
1243 | Note also that the above only works for U+2028 and U+2029 and thus |
|
|
1244 | only for fully ECMAscript-compliant parsers. Many existing javascript |
|
|
1245 | implementations misparse other characters as well. Best rely on a good |
|
|
1246 | JSON parser, such as Douglas Crockfords F<json2.js>, which escapes the |
|
|
1247 | above and many more problematic characters properly before passing them |
|
|
1248 | into C<eval>. |
|
|
1249 | |
|
|
1250 | Another problem is that some javascript implementations reserve |
|
|
1251 | some property names for their own purposes (which probably makes |
|
|
1252 | them non-ECMAscript-compliant). For example, Iceweasel reserves the |
|
|
1253 | C<__proto__> property name for it's own purposes. |
|
|
1254 | |
|
|
1255 | If that is a problem, you could parse try to filter the resulting JSON |
|
|
1256 | output for these property strings, e.g.: |
|
|
1257 | |
|
|
1258 | $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; |
|
|
1259 | |
|
|
1260 | This works because C<__proto__> is not valid outside of strings, so every |
|
|
1261 | occurence of C<"__proto__"\s*:> must be a string used as property name. |
|
|
1262 | |
|
|
1263 | If you know of other incompatibilities, please let me know. |
1177 | |
1264 | |
1178 | |
1265 | |
1179 | =head2 JSON and YAML |
1266 | =head2 JSON and YAML |
1180 | |
1267 | |
1181 | You often hear that JSON is a subset of YAML. This is, however, a mass |
1268 | You often hear that JSON is a subset of YAML. This is, however, a mass |