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Revision 1.121 by root, Mon Jul 13 22:13:17 2009 UTC vs.
Revision 1.145 by root, Tue Oct 29 00:06:40 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 = '2.24'; 106our $VERSION = '3.0';
107our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
108 108
109our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json);
110
111sub to_json($) {
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;
113
114use Types::Serialiser ();
123 115
124=head1 FUNCTIONAL INTERFACE 116=head1 FUNCTIONAL INTERFACE
125 117
126The following convenience methods are provided by this module. They are 118The following convenience methods are provided by this module. They are
127exported by default: 119exported by default:
148This function call is functionally identical to: 140This function call is functionally identical to:
149 141
150 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 142 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
151 143
152Except being faster. 144Except being faster.
153
154=item $is_boolean = JSON::XS::is_bool $scalar
155
156Returns true if the passed scalar represents either JSON::XS::true or
157JSON::XS::false, two constants that act like C<1> and C<0>, respectively
158and are used to represent JSON C<true> and C<false> values in Perl.
159
160See MAPPING, below, for more information on how JSON values are mapped to
161Perl.
162 145
163=back 146=back
164 147
165 148
166=head1 A FEW NOTES ON UNICODE AND PERL 149=head1 A FEW NOTES ON UNICODE AND PERL
432If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 415If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
433by sorting their keys. This is adding a comparatively high overhead. 416by sorting their keys. This is adding a comparatively high overhead.
434 417
435If C<$enable> is false, then the C<encode> method will output key-value 418If 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 419pairs in the order Perl stores them (which will likely change between runs
437of the same script). 420of the same script, and can change even within the same run from 5.18
421onwards).
438 422
439This option is useful if you want the same data structure to be encoded as 423This 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, 424the 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, 425the same hash might be encoded differently even if contains the same data,
442as key-value pairs have no inherent ordering in Perl. 426as key-value pairs have no inherent ordering in Perl.
443 427
444This setting has no effect when decoding JSON texts. 428This setting has no effect when decoding JSON texts.
429
430This setting has currently no effect on tied hashes.
445 431
446=item $json = $json->allow_nonref ([$enable]) 432=item $json = $json->allow_nonref ([$enable])
447 433
448=item $enabled = $json->get_allow_nonref 434=item $enabled = $json->get_allow_nonref
449 435
664 650
665See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 651See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
666 652
667=item $json_text = $json->encode ($perl_scalar) 653=item $json_text = $json->encode ($perl_scalar)
668 654
669Converts the given Perl data structure (a simple scalar or a reference 655Converts the given Perl value or data structure to its JSON
670to a hash or array) to its JSON representation. Simple scalars will be 656representation. Croaks on error.
671converted into JSON string or number sequences, while references to arrays
672become JSON arrays and references to hashes become JSON objects. Undefined
673Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
674nor C<false> values will be generated.
675 657
676=item $perl_scalar = $json->decode ($json_text) 658=item $perl_scalar = $json->decode ($json_text)
677 659
678The opposite of C<encode>: expects a JSON text and tries to parse it, 660The opposite of C<encode>: expects a JSON text and tries to parse it,
679returning the resulting simple scalar or reference. Croaks on error. 661returning the resulting simple scalar or reference. Croaks on error.
680
681JSON numbers and strings become simple Perl scalars. JSON arrays become
682Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
683C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
684 662
685=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) 663=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
686 664
687This works like the C<decode> method, but instead of raising an exception 665This works like the C<decode> method, but instead of raising an exception
688when there is trailing garbage after the first JSON object, it will 666when there is trailing garbage after the first JSON object, it will
689silently stop parsing there and return the number of characters consumed 667silently stop parsing there and return the number of characters consumed
690so far. 668so far.
691 669
692This is useful if your JSON texts are not delimited by an outer protocol 670This is useful if your JSON texts are not delimited by an outer protocol
693(which is not the brightest thing to do in the first place) and you need
694to know where the JSON text ends. 671and you need to know where the JSON text ends.
695 672
696 JSON::XS->new->decode_prefix ("[1] the tail") 673 JSON::XS->new->decode_prefix ("[1] the tail")
697 => ([], 3) 674 => ([], 3)
698 675
699=back 676=back
711calls). 688calls).
712 689
713JSON::XS will only attempt to parse the JSON text once it is sure it 690JSON::XS will only attempt to parse the JSON text once it is sure it
714has enough text to get a decisive result, using a very simple but 691has enough text to get a decisive result, using a very simple but
715truly incremental parser. This means that it sometimes won't stop as 692truly incremental parser. This means that it sometimes won't stop as
716early as the full parser, for example, it doesn't detect parenthese 693early as the full parser, for example, it doesn't detect mismatched
717mismatches. The only thing it guarantees is that it starts decoding as 694parentheses. The only thing it guarantees is that it starts decoding as
718soon as a syntactically valid JSON text has been seen. This means you need 695soon as a syntactically valid JSON text has been seen. This means you need
719to set resource limits (e.g. C<max_size>) to ensure the parser will stop 696to set resource limits (e.g. C<max_size>) to ensure the parser will stop
720parsing in the presence if syntax errors. 697parsing in the presence if syntax errors.
721 698
722The following methods implement this incremental parser. 699The following methods implement this incremental parser.
738 715
739If the method is called in scalar context, then it will try to extract 716If the method is called in scalar context, then it will try to extract
740exactly I<one> JSON object. If that is successful, it will return this 717exactly I<one> JSON object. If that is successful, it will return this
741object, otherwise it will return C<undef>. If there is a parse error, 718object, otherwise it will return C<undef>. If there is a parse error,
742this method will croak just as C<decode> would do (one can then use 719this method will croak just as C<decode> would do (one can then use
743C<incr_skip> to skip the errornous part). This is the most common way of 720C<incr_skip> to skip the erroneous part). This is the most common way of
744using the method. 721using the method.
745 722
746And finally, in list context, it will try to extract as many objects 723And finally, in list context, it will try to extract as many objects
747from the stream as it can find and return them, or the empty list 724from the stream as it can find and return them, or the empty list
748otherwise. For this to work, there must be no separators between the JSON 725otherwise. For this to work, there must be no separators between the JSON
749objects or arrays, instead they must be concatenated back-to-back. If 726objects or arrays, instead they must be concatenated back-to-back. If
750an error occurs, an exception will be raised as in the scalar context 727an error occurs, an exception will be raised as in the scalar context
751case. Note that in this case, any previously-parsed JSON texts will be 728case. Note that in this case, any previously-parsed JSON texts will be
752lost. 729lost.
753 730
731Example: Parse some JSON arrays/objects in a given string and return
732them.
733
734 my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
735
754=item $lvalue_string = $json->incr_text 736=item $lvalue_string = $json->incr_text
755 737
756This method returns the currently stored JSON fragment as an lvalue, that 738This method returns the currently stored JSON fragment as an lvalue, that
757is, you can manipulate it. This I<only> works when a preceding call to 739is, you can manipulate it. This I<only> works when a preceding call to
758C<incr_parse> in I<scalar context> successfully returned an object. Under 740C<incr_parse> in I<scalar context> successfully returned an object. Under
772C<incr_parse> died, in which case the input buffer and incremental parser 754C<incr_parse> died, in which case the input buffer and incremental parser
773state is left unchanged, to skip the text parsed so far and to reset the 755state is left unchanged, to skip the text parsed so far and to reset the
774parse state. 756parse state.
775 757
776The difference to C<incr_reset> is that only text until the parse error 758The difference to C<incr_reset> is that only text until the parse error
777occured is removed. 759occurred is removed.
778 760
779=item $json->incr_reset 761=item $json->incr_reset
780 762
781This completely resets the incremental parser, that is, after this call, 763This completely resets the incremental parser, that is, after this call,
782it will be as if the parser had never parsed anything. 764it will be as if the parser had never parsed anything.
788=back 770=back
789 771
790=head2 LIMITATIONS 772=head2 LIMITATIONS
791 773
792All options that affect decoding are supported, except 774All options that affect decoding are supported, except
793C<allow_nonref>. The reason for this is that it cannot be made to 775C<allow_nonref>. The reason for this is that it cannot be made to work
794work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate 776sensibly: JSON objects and arrays are self-delimited, i.e. you can
795them back to back and still decode them perfectly. This does not hold true 777concatenate them back to back and still decode them perfectly. This does
796for JSON numbers, however. 778not hold true for JSON numbers, however.
797 779
798For example, is the string C<1> a single JSON number, or is it simply the 780For example, is the string C<1> a single JSON number, or is it simply the
799start of C<12>? Or is C<12> a single JSON number, or the concatenation 781start of C<12>? Or is C<12> a single JSON number, or the concatenation
800of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS 782of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
801takes the conservative route and disallows this case. 783takes the conservative route and disallows this case.
980If the number consists of digits only, JSON::XS will try to represent 962If the number consists of digits only, JSON::XS will try to represent
981it as an integer value. If that fails, it will try to represent it as 963it as an integer value. If that fails, it will try to represent it as
982a numeric (floating point) value if that is possible without loss of 964a numeric (floating point) value if that is possible without loss of
983precision. Otherwise it will preserve the number as a string value (in 965precision. Otherwise it will preserve the number as a string value (in
984which case you lose roundtripping ability, as the JSON number will be 966which case you lose roundtripping ability, as the JSON number will be
985re-encoded toa JSON string). 967re-encoded to a JSON string).
986 968
987Numbers containing a fractional or exponential part will always be 969Numbers containing a fractional or exponential part will always be
988represented as numeric (floating point) values, possibly at a loss of 970represented as numeric (floating point) values, possibly at a loss of
989precision (in which case you might lose perfect roundtripping ability, but 971precision (in which case you might lose perfect roundtripping ability, but
990the JSON number will still be re-encoded as a JSON number). 972the JSON number will still be re-encoded as a JSON number).
991 973
974Note that precision is not accuracy - binary floating point values cannot
975represent most decimal fractions exactly, and when converting from and to
976floating point, JSON::XS only guarantees precision up to but not including
977the least significant bit.
978
992=item true, false 979=item true, false
993 980
994These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 981These JSON atoms become C<Types::Serialiser::true> and
995respectively. They are overloaded to act almost exactly like the numbers 982C<Types::Serialiser::false>, respectively. They are overloaded to act
996C<1> and C<0>. You can check whether a scalar is a JSON boolean by using 983almost exactly like the numbers C<1> and C<0>. You can check whether
997the C<JSON::XS::is_bool> function. 984a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
985function (after C<use Types::Serialier>, of course).
998 986
999=item null 987=item null
1000 988
1001A JSON null atom becomes C<undef> in Perl. 989A JSON null atom becomes C<undef> in Perl.
990
991=item shell-style comments (C<< # I<text> >>)
992
993As a nonstandard extension to the JSON syntax that is enabled by the
994C<relaxed> setting, shell-style comments are allowed. They can start
995anywhere outside strings and go till the end of the line.
996
997=item tagged values (C<< (I<tag>)I<value> >>).
998
999Another nonstandard extension to the JSON syntax, enabled with the
1000C<allow_tags> setting, are tagged values. In this implementation, the
1001I<tag> must be a perl package/class name encoded as a JSON string, and the
1002I<value> must be a JSON array encoding optional constructor arguments.
1003
1004See "OBJECT SERIALISATION", below, for details.
1002 1005
1003=back 1006=back
1004 1007
1005 1008
1006=head2 PERL -> JSON 1009=head2 PERL -> JSON
1011 1014
1012=over 4 1015=over 4
1013 1016
1014=item hash references 1017=item hash references
1015 1018
1016Perl hash references become JSON objects. As there is no inherent ordering 1019Perl hash references become JSON objects. As there is no inherent
1017in hash keys (or JSON objects), they will usually be encoded in a 1020ordering in hash keys (or JSON objects), they will usually be encoded
1018pseudo-random order that can change between runs of the same program but 1021in a pseudo-random order. JSON::XS can optionally sort the hash keys
1019stays generally the same within a single run of a program. JSON::XS can 1022(determined by the I<canonical> flag), so the same datastructure will
1020optionally sort the hash keys (determined by the I<canonical> flag), so 1023serialise to the same JSON text (given same settings and version of
1021the same datastructure will serialise to the same JSON text (given same 1024JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1022settings and version of JSON::XS), but this incurs a runtime overhead 1025e.g. when you want to compare some JSON text against another for equality.
1023and is only rarely useful, e.g. when you want to compare some JSON text
1024against another for equality.
1025 1026
1026=item array references 1027=item array references
1027 1028
1028Perl array references become JSON arrays. 1029Perl array references become JSON arrays.
1029 1030
1030=item other references 1031=item other references
1031 1032
1032Other unblessed references are generally not allowed and will cause an 1033Other unblessed references are generally not allowed and will cause an
1033exception to be thrown, except for references to the integers C<0> and 1034exception to be thrown, except for references to the integers C<0> and
1034C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 1035C<1>, which get turned into C<false> and C<true> atoms in JSON.
1035also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1036 1036
1037Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
1038can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
1039and C<Types::Serialiser::true> to improve readability.
1040
1041 use Types::Serialiser;
1037 encode_json [\0, JSON::XS::true] # yields [false,true] 1042 encode_json [\0, Types::Serialiser::true] # yields [false,true]
1038 1043
1039=item JSON::XS::true, JSON::XS::false 1044=item Types::Serialiser::true, Types::Serialiser::false
1040 1045
1041These special values become JSON true and JSON false values, 1046These special values from the L<Types::Serialiser> module become JSON true
1042respectively. You can also use C<\1> and C<\0> directly if you want. 1047and JSON false values, respectively. You can also use C<\1> and C<\0>
1048directly if you want.
1043 1049
1044=item blessed objects 1050=item blessed objects
1045 1051
1046Blessed objects are not directly representable in JSON. See the 1052Blessed objects are not directly representable in JSON, but C<JSON::XS>
1047C<allow_blessed> and C<convert_blessed> methods on various options on 1053allows various ways of handling objects. See "OBJECT SERIALISATION",
1048how to deal with this: basically, you can choose between throwing an 1054below, for details.
1049exception, encoding the reference as if it weren't blessed, or provide
1050your own serialiser method.
1051 1055
1052=item simple scalars 1056=item simple scalars
1053 1057
1054Simple Perl scalars (any scalar that is not a reference) are the most 1058Simple Perl scalars (any scalar that is not a reference) are the most
1055difficult objects to encode: JSON::XS will encode undefined scalars as 1059difficult objects to encode: JSON::XS will encode undefined scalars as
1083 1087
1084You can not currently force the type in other, less obscure, ways. Tell me 1088You can not currently force the type in other, less obscure, ways. Tell me
1085if you need this capability (but don't forget to explain why it's needed 1089if you need this capability (but don't forget to explain why it's needed
1086:). 1090:).
1087 1091
1092Note that numerical precision has the same meaning as under Perl (so
1093binary to decimal conversion follows the same rules as in Perl, which
1094can differ to other languages). Also, your perl interpreter might expose
1095extensions to the floating point numbers of your platform, such as
1096infinities or NaN's - these cannot be represented in JSON, and it is an
1097error to pass those in.
1098
1088=back 1099=back
1100
1101=head2 OBJECT SERIALISATION
1102
1103As JSON cannot directly represent Perl objects, you have to choose between
1104a pure JSON representation (without the ability to deserialise the object
1105automatically again), and a nonstandard extension to the JSON syntax,
1106tagged values.
1107
1108=head3 SERIALISATION
1109
1110What happens when C<JSON::XS> encounters a Perl object depends on the
1111C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
1112used in this order:
1113
1114=over 4
1115
1116=item 1. C<allow_tags> is enabled and object has a C<FREEZE> method.
1117
1118In this case, C<JSON::XS> uses the L<Types::Serialiser> object
1119serialisation protocol to create a tagged JSON value, using a nonstandard
1120extension to the JSON syntax.
1121
1122This works by invoking the C<FREEZE> method on the object, with the first
1123argument being the object to serialise, and the second argument being the
1124constant string C<JSON> to distinguish it from other serialisers.
1125
1126The C<FREEZE> method can return any number of values (i.e. zero or
1127more). These values and the paclkage/classname of the object will then be
1128encoded as a tagged JSON value in the following format:
1129
1130 ("classname")[FREEZE return values...]
1131
1132For example, the hypothetical C<My::Object> C<FREEZE> method might use the
1133objects C<type> and C<id> members to encode the object:
1134
1135 sub My::Object::FREEZE {
1136 my ($self, $serialiser) = @_;
1137
1138 ($self->{type}, $self->{id})
1139 }
1140
1141=item 2. C<convert_blessed> is enabled and object has a C<TO_JSON> method.
1142
1143In this case, the C<TO_JSON> method of the object is invoked in scalar
1144context. It must return a single scalar that can be directly encoded into
1145JSON. This scalar replaces the object in the JSON text.
1146
1147For example, the following C<TO_JSON> method will convert all L<URI>
1148objects to JSON strings when serialised. The fatc that these values
1149originally were L<URI> objects is lost.
1150
1151 sub URI::TO_JSON {
1152 my ($uri) = @_;
1153 $uri->as_string
1154 }
1155
1156=item 3. C<allow_blessed> is enabled.
1157
1158The object will be serialised as a JSON null value.
1159
1160=item 4. none of the above
1161
1162If none of the settings are enabled or the respective methods are missing,
1163C<JSON::XS> throws an exception.
1164
1165=back
1166
1167=head3 DESERIALISATION
1168
1169For deserialisation there are only two cases to consider: either
1170nonstandard tagging was used, in which case C<allow_tags> decides,
1171or objects cannot be automatically be deserialised, in which
1172case you can use postprocessing or the C<filter_json_object> or
1173C<filter_json_single_key_object> callbacks to get some real objects our of
1174your JSON.
1175
1176This section only considers the tagged value case: I a tagged JSON object
1177is encountered during decoding and C<allow_tags> is disabled, a parse
1178error will result (as if tagged values were not part of the grammar).
1179
1180If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
1181of the package/classname used during serialisation. If there is no such
1182method, the decoding will fail with an error.
1183
1184Otherwise, the C<THAW> method is invoked with the classname as first
1185argument, the constant string C<JSON> as second argument, and all the
1186values from the JSON array (the values originally returned by the
1187C<FREEZE> method) as remaining arguments.
1188
1189The method must then return the object. While technically you can return
1190any Perl scalar, you might have to enable the C<enable_nonref> setting to
1191make that work in all cases, so better return an actual blessed reference.
1192
1193As an example, let's implement a C<THAW> function that regenerates the
1194C<My::Object> from the C<FREEZE> example earlier:
1195
1196 sub My::Object::THAW {
1197 my ($class, $serialiser, $type, $id) = @_;
1198
1199 $class->new (type => $type, id => $id)
1200 }
1089 1201
1090 1202
1091=head1 ENCODING/CODESET FLAG NOTES 1203=head1 ENCODING/CODESET FLAG NOTES
1092 1204
1093The interested reader might have seen a number of flags that signify 1205The interested reader might have seen a number of flags that signify
1118=item C<utf8> flag disabled 1230=item C<utf8> flag disabled
1119 1231
1120When C<utf8> is disabled (the default), then C<encode>/C<decode> generate 1232When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1121and expect Unicode strings, that is, characters with high ordinal Unicode 1233and expect Unicode strings, that is, characters with high ordinal Unicode
1122values (> 255) will be encoded as such characters, and likewise such 1234values (> 255) will be encoded as such characters, and likewise such
1123characters are decoded as-is, no canges to them will be done, except 1235characters are decoded as-is, no changes to them will be done, except
1124"(re-)interpreting" them as Unicode codepoints or Unicode characters, 1236"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1125respectively (to Perl, these are the same thing in strings unless you do 1237respectively (to Perl, these are the same thing in strings unless you do
1126funny/weird/dumb stuff). 1238funny/weird/dumb stuff).
1127 1239
1128This is useful when you want to do the encoding yourself (e.g. when you 1240This is useful when you want to do the encoding yourself (e.g. when you
1236well - using C<eval> naively simply I<will> cause problems. 1348well - using C<eval> naively simply I<will> cause problems.
1237 1349
1238Another problem is that some javascript implementations reserve 1350Another problem is that some javascript implementations reserve
1239some property names for their own purposes (which probably makes 1351some property names for their own purposes (which probably makes
1240them non-ECMAscript-compliant). For example, Iceweasel reserves the 1352them non-ECMAscript-compliant). For example, Iceweasel reserves the
1241C<__proto__> property name for it's own purposes. 1353C<__proto__> property name for its own purposes.
1242 1354
1243If that is a problem, you could parse try to filter the resulting JSON 1355If that is a problem, you could parse try to filter the resulting JSON
1244output for these property strings, e.g.: 1356output for these property strings, e.g.:
1245 1357
1246 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g; 1358 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1247 1359
1248This works because C<__proto__> is not valid outside of strings, so every 1360This works because C<__proto__> is not valid outside of strings, so every
1249occurence of C<"__proto__"\s*:> must be a string used as property name. 1361occurrence of C<"__proto__"\s*:> must be a string used as property name.
1250 1362
1251If you know of other incompatibilities, please let me know. 1363If you know of other incompatibilities, please let me know.
1252 1364
1253 1365
1254=head2 JSON and YAML 1366=head2 JSON and YAML
1266 my $yaml = $to_yaml->encode ($ref) . "\n"; 1378 my $yaml = $to_yaml->encode ($ref) . "\n";
1267 1379
1268This will I<usually> generate JSON texts that also parse as valid 1380This will I<usually> generate JSON texts that also parse as valid
1269YAML. Please note that YAML has hardcoded limits on (simple) object key 1381YAML. Please note that YAML has hardcoded limits on (simple) object key
1270lengths that JSON doesn't have and also has different and incompatible 1382lengths that JSON doesn't have and also has different and incompatible
1271unicode handling, so you should make sure that your hash keys are 1383unicode character escape syntax, so you should make sure that your hash
1272noticeably shorter than the 1024 "stream characters" YAML allows and that 1384keys are noticeably shorter than the 1024 "stream characters" YAML allows
1273you do not have characters with codepoint values outside the Unicode BMP 1385and that you do not have characters with codepoint values outside the
1274(basic multilingual page). YAML also does not allow C<\/> sequences in 1386Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1275strings (which JSON::XS does not I<currently> generate, but other JSON 1387sequences in strings (which JSON::XS does not I<currently> generate, but
1276generators might). 1388other JSON generators might).
1277 1389
1278There might be other incompatibilities that I am not aware of (or the YAML 1390There might be other incompatibilities that I am not aware of (or the YAML
1279specification has been changed yet again - it does so quite often). In 1391specification has been changed yet again - it does so quite often). In
1280general you should not try to generate YAML with a JSON generator or vice 1392general you should not try to generate YAML with a JSON generator or vice
1281versa, or try to parse JSON with a YAML parser or vice versa: chances are 1393versa, or try to parse JSON with a YAML parser or vice versa: chances are
1300that difficult or long) and finally make YAML compatible to it, and 1412that difficult or long) and finally make YAML compatible to it, and
1301educating users about the changes, instead of spreading lies about the 1413educating users about the changes, instead of spreading lies about the
1302real compatibility for many I<years> and trying to silence people who 1414real compatibility for many I<years> and trying to silence people who
1303point out that it isn't true. 1415point out that it isn't true.
1304 1416
1417Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
1418though the incompatibilities have been documented (and are known to Brian)
1419for many years and the spec makes explicit claims that YAML is a superset
1420of JSON. It would be so easy to fix, but apparently, bullying people and
1421corrupting userdata is so much easier.
1422
1305=back 1423=back
1306 1424
1307 1425
1308=head2 SPEED 1426=head2 SPEED
1309 1427
1316a very short single-line JSON string (also available at 1434a very short single-line JSON string (also available at
1317L<http://dist.schmorp.de/misc/json/short.json>). 1435L<http://dist.schmorp.de/misc/json/short.json>).
1318 1436
1319 {"method": "handleMessage", "params": ["user1", 1437 {"method": "handleMessage", "params": ["user1",
1320 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, 1438 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1321 true, false]} 1439 1, 0]}
1322 1440
1323It shows the number of encodes/decodes per second (JSON::XS uses 1441It shows the number of encodes/decodes per second (JSON::XS uses
1324the functional interface, while JSON::XS/2 uses the OO interface 1442the functional interface, while JSON::XS/2 uses the OO interface
1325with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 1443with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1326shrink). Higher is better: 1444shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
1445uses the from_json method). Higher is better:
1327 1446
1328 module | encode | decode | 1447 module | encode | decode |
1329 -----------|------------|------------| 1448 --------------|------------|------------|
1330 JSON 1.x | 4990.842 | 4088.813 | 1449 JSON::DWIW/DS | 86302.551 | 102300.098 |
1331 JSON::DWIW | 51653.990 | 71575.154 | 1450 JSON::DWIW/FJ | 86302.551 | 75983.768 |
1332 JSON::PC | 65948.176 | 74631.744 | 1451 JSON::PP | 15827.562 | 6638.658 |
1333 JSON::PP | 8931.652 | 3817.168 | 1452 JSON::Syck | 63358.066 | 47662.545 |
1334 JSON::Syck | 24877.248 | 27776.848 | 1453 JSON::XS | 511500.488 | 511500.488 |
1335 JSON::XS | 388361.481 | 227951.304 | 1454 JSON::XS/2 | 291271.111 | 388361.481 |
1336 JSON::XS/2 | 227951.304 | 218453.333 | 1455 JSON::XS/3 | 361577.931 | 361577.931 |
1337 JSON::XS/3 | 338250.323 | 218453.333 | 1456 Storable | 66788.280 | 265462.278 |
1338 Storable | 16500.016 | 135300.129 |
1339 -----------+------------+------------+ 1457 --------------+------------+------------+
1340 1458
1341That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 1459That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1342about three times faster on decoding, and over forty times faster 1460about five times faster on decoding, and over thirty to seventy times
1343than JSON, even with pretty-printing and key sorting. It also compares 1461faster than JSON's pure perl implementation. It also compares favourably
1344favourably to Storable for small amounts of data. 1462to Storable for small amounts of data.
1345 1463
1346Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1464Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1347search API (L<http://dist.schmorp.de/misc/json/long.json>). 1465search API (L<http://dist.schmorp.de/misc/json/long.json>).
1348 1466
1349 module | encode | decode | 1467 module | encode | decode |
1350 -----------|------------|------------| 1468 --------------|------------|------------|
1351 JSON 1.x | 55.260 | 34.971 | 1469 JSON::DWIW/DS | 1647.927 | 2673.916 |
1352 JSON::DWIW | 825.228 | 1082.513 | 1470 JSON::DWIW/FJ | 1630.249 | 2596.128 |
1353 JSON::PC | 3571.444 | 2394.829 |
1354 JSON::PP | 210.987 | 32.574 | 1471 JSON::PP | 400.640 | 62.311 |
1355 JSON::Syck | 552.551 | 787.544 | 1472 JSON::Syck | 1481.040 | 1524.869 |
1356 JSON::XS | 5780.463 | 4854.519 | 1473 JSON::XS | 20661.596 | 9541.183 |
1357 JSON::XS/2 | 3869.998 | 4798.975 | 1474 JSON::XS/2 | 10683.403 | 9416.938 |
1358 JSON::XS/3 | 5862.880 | 4798.975 | 1475 JSON::XS/3 | 20661.596 | 9400.054 |
1359 Storable | 4445.002 | 5235.027 | 1476 Storable | 19765.806 | 10000.725 |
1360 -----------+------------+------------+ 1477 --------------+------------+------------+
1361 1478
1362Again, JSON::XS leads by far (except for Storable which non-surprisingly 1479Again, JSON::XS leads by far (except for Storable which non-surprisingly
1363decodes faster). 1480decodes a bit faster).
1364 1481
1365On large strings containing lots of high Unicode characters, some modules 1482On large strings containing lots of high Unicode characters, some modules
1366(such as JSON::PC) seem to decode faster than JSON::XS, but the result 1483(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1367will be broken due to missing (or wrong) Unicode handling. Others refuse 1484will be broken due to missing (or wrong) Unicode handling. Others refuse
1368to decode or encode properly, so it was impossible to prepare a fair 1485to decode or encode properly, so it was impossible to prepare a fair
1404information you might want to make sure that exceptions thrown by JSON::XS 1521information you might want to make sure that exceptions thrown by JSON::XS
1405will not end up in front of untrusted eyes. 1522will not end up in front of untrusted eyes.
1406 1523
1407If you are using JSON::XS to return packets to consumption 1524If you are using JSON::XS to return packets to consumption
1408by JavaScript scripts in a browser you should have a look at 1525by JavaScript scripts in a browser you should have a look at
1409L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1526L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1410you are vulnerable to some common attack vectors (which really are browser 1527see whether you are vulnerable to some common attack vectors (which really
1411design bugs, but it is still you who will have to deal with it, as major 1528are browser design bugs, but it is still you who will have to deal with
1412browser developers care only for features, not about getting security 1529it, as major browser developers care only for features, not about getting
1413right). 1530security right).
1531
1532
1533=head1 INTEROPERABILITY WITH OTHER MODULES
1534
1535C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
1536constants. That means that the JSON true and false values will be
1537comaptible to true and false values of iother modules that do the same,
1538such as L<JSON::PP> and L<CBOR::XS>.
1414 1539
1415 1540
1416=head1 THREADS 1541=head1 THREADS
1417 1542
1418This module is I<not> guaranteed to be thread safe and there are no 1543This module is I<not> guaranteed to be thread safe and there are no
1421process simulations - use fork, it's I<much> faster, cheaper, better). 1546process simulations - use fork, it's I<much> faster, cheaper, better).
1422 1547
1423(It might actually work, but you have been warned). 1548(It might actually work, but you have been warned).
1424 1549
1425 1550
1551=head1 THE PERILS OF SETLOCALE
1552
1553Sometimes people avoid the Perl locale support and directly call the
1554system's setlocale function with C<LC_ALL>.
1555
1556This breaks both perl and modules such as JSON::XS, as stringification of
1557numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
1558print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
1559perl to stringify numbers).
1560
1561The solution is simple: don't call C<setlocale>, or use it for only those
1562categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
1563
1564If you need C<LC_NUMERIC>, you should enable it only around the code that
1565actually needs it (avoiding stringification of numbers), and restore it
1566afterwards.
1567
1568
1426=head1 BUGS 1569=head1 BUGS
1427 1570
1428While the goal of this module is to be correct, that unfortunately does 1571While the goal of this module is to be correct, that unfortunately does
1429not mean it's bug-free, only that I think its design is bug-free. If you 1572not mean it's bug-free, only that I think its design is bug-free. If you
1430keep reporting bugs they will be fixed swiftly, though. 1573keep reporting bugs they will be fixed swiftly, though.
1432Please refrain from using rt.cpan.org or any other bug reporting 1575Please refrain from using rt.cpan.org or any other bug reporting
1433service. I put the contact address into my modules for a reason. 1576service. I put the contact address into my modules for a reason.
1434 1577
1435=cut 1578=cut
1436 1579
1437our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1580BEGIN {
1438our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1581 *true = \$Types::Serialiser::true;
1582 *true = \&Types::Serialiser::true;
1583 *false = \$Types::Serialiser::false;
1584 *false = \&Types::Serialiser::false;
1585 *is_bool = \&Types::Serialiser::is_bool;
1439 1586
1440sub true() { $true } 1587 *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1441sub false() { $false }
1442
1443sub is_bool($) {
1444 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1445# or UNIVERSAL::isa $_[0], "JSON::Literal"
1446} 1588}
1447 1589
1448XSLoader::load "JSON::XS", $VERSION; 1590XSLoader::load "JSON::XS", $VERSION;
1449
1450package JSON::XS::Boolean;
1451
1452use overload
1453 "0+" => sub { ${$_[0]} },
1454 "++" => sub { $_[0] = ${$_[0]} + 1 },
1455 "--" => sub { $_[0] = ${$_[0]} - 1 },
1456 fallback => 1;
1457
14581;
1459 1591
1460=head1 SEE ALSO 1592=head1 SEE ALSO
1461 1593
1462The F<json_xs> command line utility for quick experiments. 1594The F<json_xs> command line utility for quick experiments.
1463 1595
1466 Marc Lehmann <schmorp@schmorp.de> 1598 Marc Lehmann <schmorp@schmorp.de>
1467 http://home.schmorp.de/ 1599 http://home.schmorp.de/
1468 1600
1469=cut 1601=cut
1470 1602
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