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Revision 1.141 by root, Fri Oct 25 19:53:08 2013 UTC vs.
Revision 1.145 by root, Tue Oct 29 00:06:40 2013 UTC

… …
101 101
102package JSON::XS; 102package JSON::XS;
103 103
104use common::sense; 104use common::sense;
105 105
106our $VERSION = 2.34; 106our $VERSION = '3.0';
107our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
108 108
109our @EXPORT = qw(encode_json decode_json); 109our @EXPORT = qw(encode_json decode_json);
110 110
111use Exporter; 111use Exporter;
112use XSLoader; 112use XSLoader;
113
114use Types::Serialiser ();
113 115
114=head1 FUNCTIONAL INTERFACE 116=head1 FUNCTIONAL INTERFACE
115 117
116The following convenience methods are provided by this module. They are 118The following convenience methods are provided by this module. They are
117exported by default: 119exported by default:
… …
138This function call is functionally identical to: 140This function call is functionally identical to:
139 141
140 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 142 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
141 143
142Except being faster. 144Except being faster.
143
144=item $is_boolean = JSON::XS::is_bool $scalar
145
146Returns true if the passed scalar represents either JSON::XS::true or
147JSON::XS::false, two constants that act like C<1> and C<0>, respectively
148and are used to represent JSON C<true> and C<false> values in Perl.
149
150See MAPPING, below, for more information on how JSON values are mapped to
151Perl.
152 145
153=back 146=back
154 147
155 148
156=head1 A FEW NOTES ON UNICODE AND PERL 149=head1 A FEW NOTES ON UNICODE AND PERL
… …
673when there is trailing garbage after the first JSON object, it will 666when there is trailing garbage after the first JSON object, it will
674silently stop parsing there and return the number of characters consumed 667silently stop parsing there and return the number of characters consumed
675so far. 668so far.
676 669
677This 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
678(which is not the brightest thing to do in the first place) and you need
679to know where the JSON text ends. 671and you need to know where the JSON text ends.
680 672
681 JSON::XS->new->decode_prefix ("[1] the tail") 673 JSON::XS->new->decode_prefix ("[1] the tail")
682 => ([], 3) 674 => ([], 3)
683 675
684=back 676=back
… …
778=back 770=back
779 771
780=head2 LIMITATIONS 772=head2 LIMITATIONS
781 773
782All options that affect decoding are supported, except 774All options that affect decoding are supported, except
783C<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
784work 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
785them 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
786for JSON numbers, however. 778not hold true for JSON numbers, however.
787 779
788For 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
789start 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
790of 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
791takes the conservative route and disallows this case. 783takes the conservative route and disallows this case.
… …
984floating point, JSON::XS only guarantees precision up to but not including 976floating point, JSON::XS only guarantees precision up to but not including
985the least significant bit. 977the least significant bit.
986 978
987=item true, false 979=item true, false
988 980
989These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 981These JSON atoms become C<Types::Serialiser::true> and
990respectively. They are overloaded to act almost exactly like the numbers 982C<Types::Serialiser::false>, respectively. They are overloaded to act
991C<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
992the 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).
993 986
994=item null 987=item null
995 988
996A 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.
997 1005
998=back 1006=back
999 1007
1000 1008
1001=head2 PERL -> JSON 1009=head2 PERL -> JSON
… …
1006 1014
1007=over 4 1015=over 4
1008 1016
1009=item hash references 1017=item hash references
1010 1018
1011Perl hash references become JSON objects. As there is no inherent ordering 1019Perl hash references become JSON objects. As there is no inherent
1012in hash keys (or JSON objects), they will usually be encoded in a 1020ordering in hash keys (or JSON objects), they will usually be encoded
1013pseudo-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
1014stays 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
1015optionally sort the hash keys (determined by the I<canonical> flag), so 1023serialise to the same JSON text (given same settings and version of
1016the same datastructure will serialise to the same JSON text (given same 1024JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1017settings 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.
1018and is only rarely useful, e.g. when you want to compare some JSON text
1019against another for equality.
1020 1026
1021=item array references 1027=item array references
1022 1028
1023Perl array references become JSON arrays. 1029Perl array references become JSON arrays.
1024 1030
1025=item other references 1031=item other references
1026 1032
1027Other unblessed references are generally not allowed and will cause an 1033Other unblessed references are generally not allowed and will cause an
1028exception 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
1029C<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.
1030also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1031 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;
1032 encode_json [\0, JSON::XS::true] # yields [false,true] 1042 encode_json [\0, Types::Serialiser::true] # yields [false,true]
1033 1043
1034=item JSON::XS::true, JSON::XS::false 1044=item Types::Serialiser::true, Types::Serialiser::false
1035 1045
1036These special values become JSON true and JSON false values, 1046These special values from the L<Types::Serialiser> module become JSON true
1037respectively. 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.
1038 1049
1039=item blessed objects 1050=item blessed objects
1040 1051
1041Blessed objects are not directly representable in JSON. See the 1052Blessed objects are not directly representable in JSON, but C<JSON::XS>
1042C<allow_blessed> and C<convert_blessed> methods on various options on 1053allows various ways of handling objects. See "OBJECT SERIALISATION",
1043how to deal with this: basically, you can choose between throwing an 1054below, for details.
1044exception, encoding the reference as if it weren't blessed, or provide
1045your own serialiser method.
1046 1055
1047=item simple scalars 1056=item simple scalars
1048 1057
1049Simple 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
1050difficult objects to encode: JSON::XS will encode undefined scalars as 1059difficult objects to encode: JSON::XS will encode undefined scalars as
… …
1086extensions to the floating point numbers of your platform, such as 1095extensions to the floating point numbers of your platform, such as
1087infinities or NaN's - these cannot be represented in JSON, and it is an 1096infinities or NaN's - these cannot be represented in JSON, and it is an
1088error to pass those in. 1097error to pass those in.
1089 1098
1090=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 }
1091 1201
1092 1202
1093=head1 ENCODING/CODESET FLAG NOTES 1203=head1 ENCODING/CODESET FLAG NOTES
1094 1204
1095The interested reader might have seen a number of flags that signify 1205The interested reader might have seen a number of flags that signify
… …
1418are browser design bugs, but it is still you who will have to deal with 1528are browser design bugs, but it is still you who will have to deal with
1419it, as major browser developers care only for features, not about getting 1529it, as major browser developers care only for features, not about getting
1420security right). 1530security right).
1421 1531
1422 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>.
1539
1540
1423=head1 THREADS 1541=head1 THREADS
1424 1542
1425This 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
1426plans to change this until Perl gets thread support (as opposed to the 1544plans to change this until Perl gets thread support (as opposed to the
1427horribly slow so-called "threads" which are simply slow and bloated 1545horribly slow so-called "threads" which are simply slow and bloated
… …
1457Please refrain from using rt.cpan.org or any other bug reporting 1575Please refrain from using rt.cpan.org or any other bug reporting
1458service. I put the contact address into my modules for a reason. 1576service. I put the contact address into my modules for a reason.
1459 1577
1460=cut 1578=cut
1461 1579
1462our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1580BEGIN {
1463our $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;
1464 1586
1465sub true() { $true } 1587 *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1466sub false() { $false }
1467
1468sub is_bool($) {
1469 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1470# or UNIVERSAL::isa $_[0], "JSON::Literal"
1471} 1588}
1472 1589
1473XSLoader::load "JSON::XS", $VERSION; 1590XSLoader::load "JSON::XS", $VERSION;
1474
1475package JSON::XS::Boolean;
1476
1477use overload
1478 "0+" => sub { ${$_[0]} },
1479 "++" => sub { $_[0] = ${$_[0]} + 1 },
1480 "--" => sub { $_[0] = ${$_[0]} - 1 },
1481 fallback => 1;
1482
14831;
1484 1591
1485=head1 SEE ALSO 1592=head1 SEE ALSO
1486 1593
1487The F<json_xs> command line utility for quick experiments. 1594The F<json_xs> command line utility for quick experiments.
1488 1595
… …
1491 Marc Lehmann <schmorp@schmorp.de> 1598 Marc Lehmann <schmorp@schmorp.de>
1492 http://home.schmorp.de/ 1599 http://home.schmorp.de/
1493 1600
1494=cut 1601=cut
1495 1602
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