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Revision 1.130 by root, Thu Mar 11 17:36:09 2010 UTC vs.
Revision 1.141 by root, Fri Oct 25 19:53:08 2013 UTC

64so, and even documents what "correct" means. 64so, and even documents what "correct" means.
65 65
66=item * round-trip integrity 66=item * round-trip integrity
67 67
68When you serialise a perl data structure using only data types supported 68When you serialise a perl data structure using only data types supported
69by JSON, the deserialised data structure is identical on the Perl level. 69by JSON and Perl, the deserialised data structure is identical on the Perl
70(e.g. the string "2.0" doesn't suddenly become "2" just because it looks 70level. (e.g. the string "2.0" doesn't suddenly become "2" just because
71like a number). There minor I<are> exceptions to this, read the MAPPING 71it looks like a number). There I<are> minor exceptions to this, read the
72section below to learn about those. 72MAPPING section below to learn about those.
73 73
74=item * strict checking of JSON correctness 74=item * strict checking of JSON correctness
75 75
76There is no guessing, no generating of illegal JSON texts by default, 76There is no guessing, no generating of illegal JSON texts by default,
77and only JSON is accepted as input by default (the latter is a security 77and only JSON is accepted as input by default (the latter is a security
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 $VERSION = 2.34;
107our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
108 108
109our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json);
110
111sub to_json($) {
112 require Carp;
113 Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
114}
115
116sub from_json($) {
117 require Carp;
118 Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
119}
120 110
121use Exporter; 111use Exporter;
122use XSLoader; 112use XSLoader;
123 113
124=head1 FUNCTIONAL INTERFACE 114=head1 FUNCTIONAL INTERFACE
432If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
433by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
434 424
435If C<$enable> is false, then the C<encode> method will output key-value 425If 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 426pairs in the order Perl stores them (which will likely change between runs
437of the same script). 427of the same script, and can change even within the same run from 5.18
428onwards).
438 429
439This option is useful if you want the same data structure to be encoded as 430This 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, 431the 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, 432the same hash might be encoded differently even if contains the same data,
442as key-value pairs have no inherent ordering in Perl. 433as key-value pairs have no inherent ordering in Perl.
666 657
667See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 658See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
668 659
669=item $json_text = $json->encode ($perl_scalar) 660=item $json_text = $json->encode ($perl_scalar)
670 661
671Converts the given Perl data structure (a simple scalar or a reference 662Converts the given Perl value or data structure to its JSON
672to a hash or array) to its JSON representation. Simple scalars will be 663representation. Croaks on error.
673converted into JSON string or number sequences, while references to arrays
674become JSON arrays and references to hashes become JSON objects. Undefined
675Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
676nor C<false> values will be generated.
677 664
678=item $perl_scalar = $json->decode ($json_text) 665=item $perl_scalar = $json->decode ($json_text)
679 666
680The opposite of C<encode>: expects a JSON text and tries to parse it, 667The opposite of C<encode>: expects a JSON text and tries to parse it,
681returning the resulting simple scalar or reference. Croaks on error. 668returning the resulting simple scalar or reference. Croaks on error.
682
683JSON numbers and strings become simple Perl scalars. JSON arrays become
684Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
685C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
686 669
687=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) 670=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
688 671
689This works like the C<decode> method, but instead of raising an exception 672This works like the C<decode> method, but instead of raising an exception
690when there is trailing garbage after the first JSON object, it will 673when there is trailing garbage after the first JSON object, it will
713calls). 696calls).
714 697
715JSON::XS will only attempt to parse the JSON text once it is sure it 698JSON::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 699has enough text to get a decisive result, using a very simple but
717truly incremental parser. This means that it sometimes won't stop as 700truly incremental parser. This means that it sometimes won't stop as
718early as the full parser, for example, it doesn't detect parenthese 701early as the full parser, for example, it doesn't detect mismatched
719mismatches. The only thing it guarantees is that it starts decoding as 702parentheses. 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 703soon 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 704to set resource limits (e.g. C<max_size>) to ensure the parser will stop
722parsing in the presence if syntax errors. 705parsing in the presence if syntax errors.
723 706
724The following methods implement this incremental parser. 707The following methods implement this incremental parser.
740 723
741If the method is called in scalar context, then it will try to extract 724If 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 725exactly 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, 726object, 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 727this 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 728C<incr_skip> to skip the erroneous part). This is the most common way of
746using the method. 729using the method.
747 730
748And finally, in list context, it will try to extract as many objects 731And 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 732from 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 733otherwise. 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 762C<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 763state is left unchanged, to skip the text parsed so far and to reset the
781parse state. 764parse state.
782 765
783The difference to C<incr_reset> is that only text until the parse error 766The difference to C<incr_reset> is that only text until the parse error
784occured is removed. 767occurred is removed.
785 768
786=item $json->incr_reset 769=item $json->incr_reset
787 770
788This completely resets the incremental parser, that is, after this call, 771This completely resets the incremental parser, that is, after this call,
789it will be as if the parser had never parsed anything. 772it will be as if the parser had never parsed anything.
987If the number consists of digits only, JSON::XS will try to represent 970If 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 971it 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 972a numeric (floating point) value if that is possible without loss of
990precision. Otherwise it will preserve the number as a string value (in 973precision. Otherwise it will preserve the number as a string value (in
991which case you lose roundtripping ability, as the JSON number will be 974which case you lose roundtripping ability, as the JSON number will be
992re-encoded toa JSON string). 975re-encoded to a JSON string).
993 976
994Numbers containing a fractional or exponential part will always be 977Numbers containing a fractional or exponential part will always be
995represented as numeric (floating point) values, possibly at a loss of 978represented as numeric (floating point) values, possibly at a loss of
996precision (in which case you might lose perfect roundtripping ability, but 979precision (in which case you might lose perfect roundtripping ability, but
997the JSON number will still be re-encoded as a JSON number). 980the JSON number will still be re-encoded as a JSON number).
981
982Note that precision is not accuracy - binary floating point values cannot
983represent most decimal fractions exactly, and when converting from and to
984floating point, JSON::XS only guarantees precision up to but not including
985the least significant bit.
998 986
999=item true, false 987=item true, false
1000 988
1001These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 989These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
1002respectively. They are overloaded to act almost exactly like the numbers 990respectively. They are overloaded to act almost exactly like the numbers
1090 1078
1091You can not currently force the type in other, less obscure, ways. Tell me 1079You can not currently force the type in other, less obscure, ways. Tell me
1092if you need this capability (but don't forget to explain why it's needed 1080if you need this capability (but don't forget to explain why it's needed
1093:). 1081:).
1094 1082
1083Note that numerical precision has the same meaning as under Perl (so
1084binary to decimal conversion follows the same rules as in Perl, which
1085can differ to other languages). Also, your perl interpreter might expose
1086extensions to the floating point numbers of your platform, such as
1087infinities or NaN's - these cannot be represented in JSON, and it is an
1088error to pass those in.
1089
1095=back 1090=back
1096 1091
1097 1092
1098=head1 ENCODING/CODESET FLAG NOTES 1093=head1 ENCODING/CODESET FLAG NOTES
1099 1094
1125=item C<utf8> flag disabled 1120=item C<utf8> flag disabled
1126 1121
1127When C<utf8> is disabled (the default), then C<encode>/C<decode> generate 1122When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1128and expect Unicode strings, that is, characters with high ordinal Unicode 1123and expect Unicode strings, that is, characters with high ordinal Unicode
1129values (> 255) will be encoded as such characters, and likewise such 1124values (> 255) will be encoded as such characters, and likewise such
1130characters are decoded as-is, no canges to them will be done, except 1125characters are decoded as-is, no changes to them will be done, except
1131"(re-)interpreting" them as Unicode codepoints or Unicode characters, 1126"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1132respectively (to Perl, these are the same thing in strings unless you do 1127respectively (to Perl, these are the same thing in strings unless you do
1133funny/weird/dumb stuff). 1128funny/weird/dumb stuff).
1134 1129
1135This is useful when you want to do the encoding yourself (e.g. when you 1130This is useful when you want to do the encoding yourself (e.g. when you
1243well - using C<eval> naively simply I<will> cause problems. 1238well - using C<eval> naively simply I<will> cause problems.
1244 1239
1245Another problem is that some javascript implementations reserve 1240Another problem is that some javascript implementations reserve
1246some property names for their own purposes (which probably makes 1241some property names for their own purposes (which probably makes
1247them non-ECMAscript-compliant). For example, Iceweasel reserves the 1242them non-ECMAscript-compliant). For example, Iceweasel reserves the
1248C<__proto__> property name for it's own purposes. 1243C<__proto__> property name for its own purposes.
1249 1244
1250If that is a problem, you could parse try to filter the resulting JSON 1245If that is a problem, you could parse try to filter the resulting JSON
1251output for these property strings, e.g.: 1246output for these property strings, e.g.:
1252 1247
1253 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; 1248 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1254 1249
1255This works because C<__proto__> is not valid outside of strings, so every 1250This works because C<__proto__> is not valid outside of strings, so every
1256occurence of C<"__proto__"\s*:> must be a string used as property name. 1251occurrence of C<"__proto__"\s*:> must be a string used as property name.
1257 1252
1258If you know of other incompatibilities, please let me know. 1253If you know of other incompatibilities, please let me know.
1259 1254
1260 1255
1261=head2 JSON and YAML 1256=head2 JSON and YAML
1307that difficult or long) and finally make YAML compatible to it, and 1302that difficult or long) and finally make YAML compatible to it, and
1308educating users about the changes, instead of spreading lies about the 1303educating users about the changes, instead of spreading lies about the
1309real compatibility for many I<years> and trying to silence people who 1304real compatibility for many I<years> and trying to silence people who
1310point out that it isn't true. 1305point out that it isn't true.
1311 1306
1312Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even 1307Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
1313though the incompatibilities have been documented (and are known to 1308though the incompatibilities have been documented (and are known to Brian)
1314Brian) for many years and the spec makes explicit claims that YAML is a 1309for many years and the spec makes explicit claims that YAML is a superset
1315superset of JSON. It would be so easy to fix, but apparently, bullying and 1310of JSON. It would be so easy to fix, but apparently, bullying people and
1316corrupting userdata is so much easier. 1311corrupting userdata is so much easier.
1317 1312
1318=back 1313=back
1319 1314
1320 1315
1433process simulations - use fork, it's I<much> faster, cheaper, better). 1428process simulations - use fork, it's I<much> faster, cheaper, better).
1434 1429
1435(It might actually work, but you have been warned). 1430(It might actually work, but you have been warned).
1436 1431
1437 1432
1433=head1 THE PERILS OF SETLOCALE
1434
1435Sometimes people avoid the Perl locale support and directly call the
1436system's setlocale function with C<LC_ALL>.
1437
1438This breaks both perl and modules such as JSON::XS, as stringification of
1439numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
1440print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
1441perl to stringify numbers).
1442
1443The solution is simple: don't call C<setlocale>, or use it for only those
1444categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
1445
1446If you need C<LC_NUMERIC>, you should enable it only around the code that
1447actually needs it (avoiding stringification of numbers), and restore it
1448afterwards.
1449
1450
1438=head1 BUGS 1451=head1 BUGS
1439 1452
1440While the goal of this module is to be correct, that unfortunately does 1453While the goal of this module is to be correct, that unfortunately does
1441not mean it's bug-free, only that I think its design is bug-free. If you 1454not mean it's bug-free, only that I think its design is bug-free. If you
1442keep reporting bugs they will be fixed swiftly, though. 1455keep reporting bugs they will be fixed swiftly, though.

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