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Comparing JSON-XS/XS.pm (file contents):
Revision 1.131 by root, Thu Mar 11 19:31:37 2010 UTC vs.
Revision 1.140 by root, Thu Jun 27 11:45:17 2013 UTC

83this module usually compares favourably in terms of speed, too. 83this module usually compares favourably in terms of speed, too.
84 84
85=item * simple to use 85=item * simple to use
86 86
87This module has both a simple functional interface as well as an object 87This module has both a simple functional interface as well as an object
88oriented interface interface. 88oriented interface.
89 89
90=item * reasonably versatile output formats 90=item * reasonably versatile output formats
91 91
92You can choose between the most compact guaranteed-single-line format 92You can choose between the most compact guaranteed-single-line format
93possible (nice for simple line-based protocols), a pure-ASCII format 93possible (nice for simple line-based protocols), a pure-ASCII format
101 101
102package JSON::XS; 102package JSON::XS;
103 103
104use common::sense; 104use common::sense;
105 105
106our $VERSION = '2.28'; 106our $VERSION = 2.34;
107our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
108 108
109our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json to_json from_json);
110 110
111sub to_json($) { 111sub to_json($) {
432If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 432If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
433by sorting their keys. This is adding a comparatively high overhead. 433by sorting their keys. This is adding a comparatively high overhead.
434 434
435If C<$enable> is false, then the C<encode> method will output key-value 435If C<$enable> is false, then the C<encode> method will output key-value
436pairs in the order Perl stores them (which will likely change between runs 436pairs in the order Perl stores them (which will likely change between runs
437of the same script). 437of the same script, and can change even within the same run from 5.18
438onwards).
438 439
439This option is useful if you want the same data structure to be encoded as 440This option is useful if you want the same data structure to be encoded as
440the same JSON text (given the same overall settings). If it is disabled, 441the same JSON text (given the same overall settings). If it is disabled,
441the same hash might be encoded differently even if contains the same data, 442the same hash might be encoded differently even if contains the same data,
442as key-value pairs have no inherent ordering in Perl. 443as key-value pairs have no inherent ordering in Perl.
713calls). 714calls).
714 715
715JSON::XS will only attempt to parse the JSON text once it is sure it 716JSON::XS will only attempt to parse the JSON text once it is sure it
716has enough text to get a decisive result, using a very simple but 717has enough text to get a decisive result, using a very simple but
717truly incremental parser. This means that it sometimes won't stop as 718truly incremental parser. This means that it sometimes won't stop as
718early as the full parser, for example, it doesn't detect parenthese 719early as the full parser, for example, it doesn't detect mismatched
719mismatches. The only thing it guarantees is that it starts decoding as 720parentheses. The only thing it guarantees is that it starts decoding as
720soon as a syntactically valid JSON text has been seen. This means you need 721soon as a syntactically valid JSON text has been seen. This means you need
721to set resource limits (e.g. C<max_size>) to ensure the parser will stop 722to set resource limits (e.g. C<max_size>) to ensure the parser will stop
722parsing in the presence if syntax errors. 723parsing in the presence if syntax errors.
723 724
724The following methods implement this incremental parser. 725The following methods implement this incremental parser.
740 741
741If the method is called in scalar context, then it will try to extract 742If the method is called in scalar context, then it will try to extract
742exactly I<one> JSON object. If that is successful, it will return this 743exactly I<one> JSON object. If that is successful, it will return this
743object, otherwise it will return C<undef>. If there is a parse error, 744object, otherwise it will return C<undef>. If there is a parse error,
744this method will croak just as C<decode> would do (one can then use 745this method will croak just as C<decode> would do (one can then use
745C<incr_skip> to skip the errornous part). This is the most common way of 746C<incr_skip> to skip the erroneous part). This is the most common way of
746using the method. 747using the method.
747 748
748And finally, in list context, it will try to extract as many objects 749And finally, in list context, it will try to extract as many objects
749from the stream as it can find and return them, or the empty list 750from the stream as it can find and return them, or the empty list
750otherwise. For this to work, there must be no separators between the JSON 751otherwise. For this to work, there must be no separators between the JSON
779C<incr_parse> died, in which case the input buffer and incremental parser 780C<incr_parse> died, in which case the input buffer and incremental parser
780state is left unchanged, to skip the text parsed so far and to reset the 781state is left unchanged, to skip the text parsed so far and to reset the
781parse state. 782parse state.
782 783
783The difference to C<incr_reset> is that only text until the parse error 784The difference to C<incr_reset> is that only text until the parse error
784occured is removed. 785occurred is removed.
785 786
786=item $json->incr_reset 787=item $json->incr_reset
787 788
788This completely resets the incremental parser, that is, after this call, 789This completely resets the incremental parser, that is, after this call,
789it will be as if the parser had never parsed anything. 790it will be as if the parser had never parsed anything.
987If the number consists of digits only, JSON::XS will try to represent 988If the number consists of digits only, JSON::XS will try to represent
988it as an integer value. If that fails, it will try to represent it as 989it as an integer value. If that fails, it will try to represent it as
989a numeric (floating point) value if that is possible without loss of 990a numeric (floating point) value if that is possible without loss of
990precision. Otherwise it will preserve the number as a string value (in 991precision. Otherwise it will preserve the number as a string value (in
991which case you lose roundtripping ability, as the JSON number will be 992which case you lose roundtripping ability, as the JSON number will be
992re-encoded toa JSON string). 993re-encoded to a JSON string).
993 994
994Numbers containing a fractional or exponential part will always be 995Numbers containing a fractional or exponential part will always be
995represented as numeric (floating point) values, possibly at a loss of 996represented as numeric (floating point) values, possibly at a loss of
996precision (in which case you might lose perfect roundtripping ability, but 997precision (in which case you might lose perfect roundtripping ability, but
997the JSON number will still be re-encoded as a JSON number). 998the JSON number will still be re-encoded as a JSON number).
998 999
999Note that precision is not accuracy - binary floating point values cannot 1000Note that precision is not accuracy - binary floating point values cannot
1000represent most decimal fractions exactly, and when converting from and to 1001represent most decimal fractions exactly, and when converting from and to
1001floating point, JSON::XS only guarantees precision up to but not including 1002floating point, JSON::XS only guarantees precision up to but not including
1002the leats significant bit. 1003the least significant bit.
1003 1004
1004=item true, false 1005=item true, false
1005 1006
1006These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 1007These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
1007respectively. They are overloaded to act almost exactly like the numbers 1008respectively. They are overloaded to act almost exactly like the numbers
1137=item C<utf8> flag disabled 1138=item C<utf8> flag disabled
1138 1139
1139When C<utf8> is disabled (the default), then C<encode>/C<decode> generate 1140When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1140and expect Unicode strings, that is, characters with high ordinal Unicode 1141and expect Unicode strings, that is, characters with high ordinal Unicode
1141values (> 255) will be encoded as such characters, and likewise such 1142values (> 255) will be encoded as such characters, and likewise such
1142characters are decoded as-is, no canges to them will be done, except 1143characters are decoded as-is, no changes to them will be done, except
1143"(re-)interpreting" them as Unicode codepoints or Unicode characters, 1144"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1144respectively (to Perl, these are the same thing in strings unless you do 1145respectively (to Perl, these are the same thing in strings unless you do
1145funny/weird/dumb stuff). 1146funny/weird/dumb stuff).
1146 1147
1147This is useful when you want to do the encoding yourself (e.g. when you 1148This is useful when you want to do the encoding yourself (e.g. when you
1255well - using C<eval> naively simply I<will> cause problems. 1256well - using C<eval> naively simply I<will> cause problems.
1256 1257
1257Another problem is that some javascript implementations reserve 1258Another problem is that some javascript implementations reserve
1258some property names for their own purposes (which probably makes 1259some property names for their own purposes (which probably makes
1259them non-ECMAscript-compliant). For example, Iceweasel reserves the 1260them non-ECMAscript-compliant). For example, Iceweasel reserves the
1260C<__proto__> property name for it's own purposes. 1261C<__proto__> property name for its own purposes.
1261 1262
1262If that is a problem, you could parse try to filter the resulting JSON 1263If that is a problem, you could parse try to filter the resulting JSON
1263output for these property strings, e.g.: 1264output for these property strings, e.g.:
1264 1265
1265 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; 1266 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1266 1267
1267This works because C<__proto__> is not valid outside of strings, so every 1268This works because C<__proto__> is not valid outside of strings, so every
1268occurence of C<"__proto__"\s*:> must be a string used as property name. 1269occurrence of C<"__proto__"\s*:> must be a string used as property name.
1269 1270
1270If you know of other incompatibilities, please let me know. 1271If you know of other incompatibilities, please let me know.
1271 1272
1272 1273
1273=head2 JSON and YAML 1274=head2 JSON and YAML
1319that difficult or long) and finally make YAML compatible to it, and 1320that difficult or long) and finally make YAML compatible to it, and
1320educating users about the changes, instead of spreading lies about the 1321educating users about the changes, instead of spreading lies about the
1321real compatibility for many I<years> and trying to silence people who 1322real compatibility for many I<years> and trying to silence people who
1322point out that it isn't true. 1323point out that it isn't true.
1323 1324
1324Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even 1325Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
1325though the incompatibilities have been documented (and are known to 1326though the incompatibilities have been documented (and are known to Brian)
1326Brian) for many years and the spec makes explicit claims that YAML is a 1327for many years and the spec makes explicit claims that YAML is a superset
1327superset of JSON. It would be so easy to fix, but apparently, bullying and 1328of JSON. It would be so easy to fix, but apparently, bullying people and
1328corrupting userdata is so much easier. 1329corrupting userdata is so much easier.
1329 1330
1330=back 1331=back
1331 1332
1332 1333
1445process simulations - use fork, it's I<much> faster, cheaper, better). 1446process simulations - use fork, it's I<much> faster, cheaper, better).
1446 1447
1447(It might actually work, but you have been warned). 1448(It might actually work, but you have been warned).
1448 1449
1449 1450
1451=head1 THE PERILS OF SETLOCALE
1452
1453Sometimes people avoid the Perl locale support and directly call the
1454system's setlocale function with C<LC_ALL>.
1455
1456This breaks both perl and modules such as JSON::XS, as stringification of
1457numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
1458print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
1459perl to stringify numbers).
1460
1461The solution is simple: don't call C<setlocale>, or use it for only those
1462categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
1463
1464If you need C<LC_NUMERIC>, you should enable it only around the code that
1465actually needs it (avoiding stringification of numbers), and restore it
1466afterwards.
1467
1468
1450=head1 BUGS 1469=head1 BUGS
1451 1470
1452While the goal of this module is to be correct, that unfortunately does 1471While the goal of this module is to be correct, that unfortunately does
1453not mean it's bug-free, only that I think its design is bug-free. If you 1472not mean it's bug-free, only that I think its design is bug-free. If you
1454keep reporting bugs they will be fixed swiftly, though. 1473keep reporting bugs they will be fixed swiftly, though.

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