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Revision 1.140 by root, Thu Jun 27 11:45:17 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 $VERSION = '3.0';
107our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
108 108
109our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json);
110
111sub to_json($) {
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
… …
667 650
668See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 651See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
669 652
670=item $json_text = $json->encode ($perl_scalar) 653=item $json_text = $json->encode ($perl_scalar)
671 654
672Converts the given Perl data structure (a simple scalar or a reference 655Converts the given Perl value or data structure to its JSON
673to a hash or array) to its JSON representation. Simple scalars will be 656representation. Croaks on error.
674converted into JSON string or number sequences, while references to arrays
675become JSON arrays and references to hashes become JSON objects. Undefined
676Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
677nor C<false> values will be generated.
678 657
679=item $perl_scalar = $json->decode ($json_text) 658=item $perl_scalar = $json->decode ($json_text)
680 659
681The 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,
682returning the resulting simple scalar or reference. Croaks on error. 661returning the resulting simple scalar or reference. Croaks on error.
683
684JSON numbers and strings become simple Perl scalars. JSON arrays become
685Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
686C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
687 662
688=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) 663=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
689 664
690This 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
691when there is trailing garbage after the first JSON object, it will 666when there is trailing garbage after the first JSON object, it will
692silently stop parsing there and return the number of characters consumed 667silently stop parsing there and return the number of characters consumed
693so far. 668so far.
694 669
695This 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
696(which is not the brightest thing to do in the first place) and you need
697to know where the JSON text ends. 671and you need to know where the JSON text ends.
698 672
699 JSON::XS->new->decode_prefix ("[1] the tail") 673 JSON::XS->new->decode_prefix ("[1] the tail")
700 => ([], 3) 674 => ([], 3)
701 675
702=back 676=back
… …
796=back 770=back
797 771
798=head2 LIMITATIONS 772=head2 LIMITATIONS
799 773
800All options that affect decoding are supported, except 774All options that affect decoding are supported, except
801C<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
802work 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
803them 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
804for JSON numbers, however. 778not hold true for JSON numbers, however.
805 779
806For 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
807start 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
808of 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
809takes the conservative route and disallows this case. 783takes the conservative route and disallows this case.
… …
1002floating point, JSON::XS only guarantees precision up to but not including 976floating point, JSON::XS only guarantees precision up to but not including
1003the least significant bit. 977the least significant bit.
1004 978
1005=item true, false 979=item true, false
1006 980
1007These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 981These JSON atoms become C<Types::Serialiser::true> and
1008respectively. They are overloaded to act almost exactly like the numbers 982C<Types::Serialiser::false>, respectively. They are overloaded to act
1009C<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
1010the 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).
1011 986
1012=item null 987=item null
1013 988
1014A 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.
1015 1005
1016=back 1006=back
1017 1007
1018 1008
1019=head2 PERL -> JSON 1009=head2 PERL -> JSON
… …
1024 1014
1025=over 4 1015=over 4
1026 1016
1027=item hash references 1017=item hash references
1028 1018
1029Perl hash references become JSON objects. As there is no inherent ordering 1019Perl hash references become JSON objects. As there is no inherent
1030in hash keys (or JSON objects), they will usually be encoded in a 1020ordering in hash keys (or JSON objects), they will usually be encoded
1031pseudo-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
1032stays 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
1033optionally sort the hash keys (determined by the I<canonical> flag), so 1023serialise to the same JSON text (given same settings and version of
1034the same datastructure will serialise to the same JSON text (given same 1024JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1035settings 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.
1036and is only rarely useful, e.g. when you want to compare some JSON text
1037against another for equality.
1038 1026
1039=item array references 1027=item array references
1040 1028
1041Perl array references become JSON arrays. 1029Perl array references become JSON arrays.
1042 1030
1043=item other references 1031=item other references
1044 1032
1045Other unblessed references are generally not allowed and will cause an 1033Other unblessed references are generally not allowed and will cause an
1046exception 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
1047C<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.
1048also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1049 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;
1050 encode_json [\0, JSON::XS::true] # yields [false,true] 1042 encode_json [\0, Types::Serialiser::true] # yields [false,true]
1051 1043
1052=item JSON::XS::true, JSON::XS::false 1044=item Types::Serialiser::true, Types::Serialiser::false
1053 1045
1054These special values become JSON true and JSON false values, 1046These special values from the L<Types::Serialiser> module become JSON true
1055respectively. 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.
1056 1049
1057=item blessed objects 1050=item blessed objects
1058 1051
1059Blessed objects are not directly representable in JSON. See the 1052Blessed objects are not directly representable in JSON, but C<JSON::XS>
1060C<allow_blessed> and C<convert_blessed> methods on various options on 1053allows various ways of handling objects. See "OBJECT SERIALISATION",
1061how to deal with this: basically, you can choose between throwing an 1054below, for details.
1062exception, encoding the reference as if it weren't blessed, or provide
1063your own serialiser method.
1064 1055
1065=item simple scalars 1056=item simple scalars
1066 1057
1067Simple 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
1068difficult objects to encode: JSON::XS will encode undefined scalars as 1059difficult objects to encode: JSON::XS will encode undefined scalars as
… …
1104extensions to the floating point numbers of your platform, such as 1095extensions to the floating point numbers of your platform, such as
1105infinities 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
1106error to pass those in. 1097error to pass those in.
1107 1098
1108=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 }
1109 1201
1110 1202
1111=head1 ENCODING/CODESET FLAG NOTES 1203=head1 ENCODING/CODESET FLAG NOTES
1112 1204
1113The interested reader might have seen a number of flags that signify 1205The interested reader might have seen a number of flags that signify
… …
1436are 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
1437it, as major browser developers care only for features, not about getting 1529it, as major browser developers care only for features, not about getting
1438security right). 1530security right).
1439 1531
1440 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
1441=head1 THREADS 1541=head1 THREADS
1442 1542
1443This 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
1444plans 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
1445horribly slow so-called "threads" which are simply slow and bloated 1545horribly slow so-called "threads" which are simply slow and bloated
… …
1475Please refrain from using rt.cpan.org or any other bug reporting 1575Please refrain from using rt.cpan.org or any other bug reporting
1476service. I put the contact address into my modules for a reason. 1576service. I put the contact address into my modules for a reason.
1477 1577
1478=cut 1578=cut
1479 1579
1480our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1580BEGIN {
1481our $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;
1482 1586
1483sub true() { $true } 1587 *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1484sub false() { $false }
1485
1486sub is_bool($) {
1487 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1488# or UNIVERSAL::isa $_[0], "JSON::Literal"
1489} 1588}
1490 1589
1491XSLoader::load "JSON::XS", $VERSION; 1590XSLoader::load "JSON::XS", $VERSION;
1492
1493package JSON::XS::Boolean;
1494
1495use overload
1496 "0+" => sub { ${$_[0]} },
1497 "++" => sub { $_[0] = ${$_[0]} + 1 },
1498 "--" => sub { $_[0] = ${$_[0]} - 1 },
1499 fallback => 1;
1500
15011;
1502 1591
1503=head1 SEE ALSO 1592=head1 SEE ALSO
1504 1593
1505The F<json_xs> command line utility for quick experiments. 1594The F<json_xs> command line utility for quick experiments.
1506 1595
… …
1509 Marc Lehmann <schmorp@schmorp.de> 1598 Marc Lehmann <schmorp@schmorp.de>
1510 http://home.schmorp.de/ 1599 http://home.schmorp.de/
1511 1600
1512=cut 1601=cut
1513 1602
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