ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/JSON-XS/XS.pm
(Generate patch)

Comparing JSON-XS/XS.pm (file contents):
Revision 1.113 by root, Thu Nov 20 03:59:53 2008 UTC vs.
Revision 1.144 by root, Mon Oct 28 23:19:54 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
99 99
100=cut 100=cut
101 101
102package JSON::XS; 102package JSON::XS;
103 103
104no warnings; 104use common::sense;
105use strict;
106 105
107our $VERSION = '2.231'; 106our $VERSION = 2.34;
108our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
109 108
110our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json);
111
112sub to_json($) {
113 require Carp;
114 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");
115}
116
117sub from_json($) {
118 require Carp;
119 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");
120}
121 110
122use Exporter; 111use Exporter;
123use XSLoader; 112use XSLoader;
113
114use Types::Serialiser ();
124 115
125=head1 FUNCTIONAL INTERFACE 116=head1 FUNCTIONAL INTERFACE
126 117
127The following convenience methods are provided by this module. They are 118The following convenience methods are provided by this module. They are
128exported by default: 119exported by default:
149This function call is functionally identical to: 140This function call is functionally identical to:
150 141
151 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 142 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
152 143
153Except being faster. 144Except being faster.
154
155=item $is_boolean = JSON::XS::is_bool $scalar
156
157Returns true if the passed scalar represents either JSON::XS::true or
158JSON::XS::false, two constants that act like C<1> and C<0>, respectively
159and are used to represent JSON C<true> and C<false> values in Perl.
160
161See MAPPING, below, for more information on how JSON values are mapped to
162Perl.
163 145
164=back 146=back
165 147
166 148
167=head1 A FEW NOTES ON UNICODE AND PERL 149=head1 A FEW NOTES ON UNICODE AND PERL
433If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 415If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
434by sorting their keys. This is adding a comparatively high overhead. 416by sorting their keys. This is adding a comparatively high overhead.
435 417
436If C<$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
437pairs 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
438of the same script). 420of the same script, and can change even within the same run from 5.18
421onwards).
439 422
440This 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
441the 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,
442the 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,
443as key-value pairs have no inherent ordering in Perl. 426as key-value pairs have no inherent ordering in Perl.
444 427
445This 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.
446 431
447=item $json = $json->allow_nonref ([$enable]) 432=item $json = $json->allow_nonref ([$enable])
448 433
449=item $enabled = $json->get_allow_nonref 434=item $enabled = $json->get_allow_nonref
450 435
665 650
666See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 651See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
667 652
668=item $json_text = $json->encode ($perl_scalar) 653=item $json_text = $json->encode ($perl_scalar)
669 654
670Converts the given Perl data structure (a simple scalar or a reference 655Converts the given Perl value or data structure to its JSON
671to a hash or array) to its JSON representation. Simple scalars will be 656representation. Croaks on error.
672converted into JSON string or number sequences, while references to arrays
673become JSON arrays and references to hashes become JSON objects. Undefined
674Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
675nor C<false> values will be generated.
676 657
677=item $perl_scalar = $json->decode ($json_text) 658=item $perl_scalar = $json->decode ($json_text)
678 659
679The 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,
680returning the resulting simple scalar or reference. Croaks on error. 661returning the resulting simple scalar or reference. Croaks on error.
681
682JSON numbers and strings become simple Perl scalars. JSON arrays become
683Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
684C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
685 662
686=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) 663=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
687 664
688This 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
689when there is trailing garbage after the first JSON object, it will 666when there is trailing garbage after the first JSON object, it will
690silently stop parsing there and return the number of characters consumed 667silently stop parsing there and return the number of characters consumed
691so far. 668so far.
692 669
693This 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
694(which is not the brightest thing to do in the first place) and you need
695to know where the JSON text ends. 671and you need to know where the JSON text ends.
696 672
697 JSON::XS->new->decode_prefix ("[1] the tail") 673 JSON::XS->new->decode_prefix ("[1] the tail")
698 => ([], 3) 674 => ([], 3)
699 675
700=back 676=back
712calls). 688calls).
713 689
714JSON::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
715has 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
716truly incremental parser. This means that it sometimes won't stop as 692truly incremental parser. This means that it sometimes won't stop as
717early as the full parser, for example, it doesn't detect parenthese 693early as the full parser, for example, it doesn't detect mismatched
718mismatches. The only thing it guarantees is that it starts decoding as 694parentheses. The only thing it guarantees is that it starts decoding as
719soon 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
720to 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
721parsing in the presence if syntax errors. 697parsing in the presence if syntax errors.
722 698
723The following methods implement this incremental parser. 699The following methods implement this incremental parser.
739 715
740If 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
741exactly 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
742object, 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,
743this 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
744C<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
745using the method. 721using the method.
746 722
747And 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
748from 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
749otherwise. 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
750objects or arrays, instead they must be concatenated back-to-back. If 726objects or arrays, instead they must be concatenated back-to-back. If
751an 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
752case. 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
753lost. 729lost.
754 730
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
755=item $lvalue_string = $json->incr_text 736=item $lvalue_string = $json->incr_text
756 737
757This method returns the currently stored JSON fragment as an lvalue, that 738This method returns the currently stored JSON fragment as an lvalue, that
758is, 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
759C<incr_parse> in I<scalar context> successfully returned an object. Under 740C<incr_parse> in I<scalar context> successfully returned an object. Under
766JSON object or b) parsing multiple JSON objects separated by non-JSON text 747JSON object or b) parsing multiple JSON objects separated by non-JSON text
767(such as commas). 748(such as commas).
768 749
769=item $json->incr_skip 750=item $json->incr_skip
770 751
771This will reset the state of the incremental parser and will remove the 752This will reset the state of the incremental parser and will remove
772parsed text from the input buffer. This is useful after C<incr_parse> 753the parsed text from the input buffer so far. This is useful after
773died, in which case the input buffer and incremental parser state is left 754C<incr_parse> died, in which case the input buffer and incremental parser
774unchanged, to skip the text parsed so far and to reset the parse state. 755state is left unchanged, to skip the text parsed so far and to reset the
756parse state.
757
758The difference to C<incr_reset> is that only text until the parse error
759occurred is removed.
775 760
776=item $json->incr_reset 761=item $json->incr_reset
777 762
778This completely resets the incremental parser, that is, after this call, 763This completely resets the incremental parser, that is, after this call,
779it will be as if the parser had never parsed anything. 764it will be as if the parser had never parsed anything.
780 765
781This is useful if you want ot repeatedly parse JSON objects and want to 766This is useful if you want to repeatedly parse JSON objects and want to
782ignore any trailing data, which means you have to reset the parser after 767ignore any trailing data, which means you have to reset the parser after
783each successful decode. 768each successful decode.
784 769
785=back 770=back
786 771
787=head2 LIMITATIONS 772=head2 LIMITATIONS
788 773
789All options that affect decoding are supported, except 774All options that affect decoding are supported, except
790C<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
791work 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
792them 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
793for JSON numbers, however. 778not hold true for JSON numbers, however.
794 779
795For 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
796start 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
797of 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
798takes the conservative route and disallows this case. 783takes the conservative route and disallows this case.
977If 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
978it 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
979a numeric (floating point) value if that is possible without loss of 964a numeric (floating point) value if that is possible without loss of
980precision. Otherwise it will preserve the number as a string value (in 965precision. Otherwise it will preserve the number as a string value (in
981which case you lose roundtripping ability, as the JSON number will be 966which case you lose roundtripping ability, as the JSON number will be
982re-encoded toa JSON string). 967re-encoded to a JSON string).
983 968
984Numbers containing a fractional or exponential part will always be 969Numbers containing a fractional or exponential part will always be
985represented as numeric (floating point) values, possibly at a loss of 970represented as numeric (floating point) values, possibly at a loss of
986precision (in which case you might lose perfect roundtripping ability, but 971precision (in which case you might lose perfect roundtripping ability, but
987the JSON number will still be re-encoded as a JSON number). 972the JSON number will still be re-encoded as a JSON number).
988 973
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
989=item true, false 979=item true, false
990 980
991These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 981These JSON atoms become C<Types::Serialiser::true> and
992respectively. They are overloaded to act almost exactly like the numbers 982C<Types::Serialiser::false>, respectively. They are overloaded to act
993C<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
994the 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).
995 986
996=item null 987=item null
997 988
998A JSON null atom becomes C<undef> in Perl. 989A JSON null atom becomes C<undef> in Perl.
999 990
1008 999
1009=over 4 1000=over 4
1010 1001
1011=item hash references 1002=item hash references
1012 1003
1013Perl hash references become JSON objects. As there is no inherent ordering 1004Perl hash references become JSON objects. As there is no inherent
1014in hash keys (or JSON objects), they will usually be encoded in a 1005ordering in hash keys (or JSON objects), they will usually be encoded
1015pseudo-random order that can change between runs of the same program but 1006in a pseudo-random order. JSON::XS can optionally sort the hash keys
1016stays generally the same within a single run of a program. JSON::XS can 1007(determined by the I<canonical> flag), so the same datastructure will
1017optionally sort the hash keys (determined by the I<canonical> flag), so 1008serialise to the same JSON text (given same settings and version of
1018the same datastructure will serialise to the same JSON text (given same 1009JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1019settings and version of JSON::XS), but this incurs a runtime overhead 1010e.g. when you want to compare some JSON text against another for equality.
1020and is only rarely useful, e.g. when you want to compare some JSON text
1021against another for equality.
1022 1011
1023=item array references 1012=item array references
1024 1013
1025Perl array references become JSON arrays. 1014Perl array references become JSON arrays.
1026 1015
1027=item other references 1016=item other references
1028 1017
1029Other unblessed references are generally not allowed and will cause an 1018Other unblessed references are generally not allowed and will cause an
1030exception to be thrown, except for references to the integers C<0> and 1019exception to be thrown, except for references to the integers C<0> and
1031C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 1020C<1>, which get turned into C<false> and C<true> atoms in JSON.
1032also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1033 1021
1022Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
1023can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
1024and C<Types::Serialiser::true> to improve readability.
1025
1026 use Types::Serialiser;
1034 encode_json [\0, JSON::XS::true] # yields [false,true] 1027 encode_json [\0, Types::Serialiser::true] # yields [false,true]
1035 1028
1036=item JSON::XS::true, JSON::XS::false 1029=item Types::Serialiser::true, Types::Serialiser::false
1037 1030
1038These special values become JSON true and JSON false values, 1031These special values from the L<Types::Serialiser> module become JSON true
1039respectively. You can also use C<\1> and C<\0> directly if you want. 1032and JSON false values, respectively. You can also use C<\1> and C<\0>
1033directly if you want.
1040 1034
1041=item blessed objects 1035=item blessed objects
1042 1036
1043Blessed objects are not directly representable in JSON. See the 1037Blessed objects are not directly representable in JSON. See the
1044C<allow_blessed> and C<convert_blessed> methods on various options on 1038C<allow_blessed> and C<convert_blessed> methods on various options on
1079 $x *= 1; # same thing, the choice is yours. 1073 $x *= 1; # same thing, the choice is yours.
1080 1074
1081You can not currently force the type in other, less obscure, ways. Tell me 1075You can not currently force the type in other, less obscure, ways. Tell me
1082if you need this capability (but don't forget to explain why it's needed 1076if you need this capability (but don't forget to explain why it's needed
1083:). 1077:).
1078
1079Note that numerical precision has the same meaning as under Perl (so
1080binary to decimal conversion follows the same rules as in Perl, which
1081can differ to other languages). Also, your perl interpreter might expose
1082extensions to the floating point numbers of your platform, such as
1083infinities or NaN's - these cannot be represented in JSON, and it is an
1084error to pass those in.
1084 1085
1085=back 1086=back
1086 1087
1087 1088
1088=head1 ENCODING/CODESET FLAG NOTES 1089=head1 ENCODING/CODESET FLAG NOTES
1115=item C<utf8> flag disabled 1116=item C<utf8> flag disabled
1116 1117
1117When C<utf8> is disabled (the default), then C<encode>/C<decode> generate 1118When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1118and expect Unicode strings, that is, characters with high ordinal Unicode 1119and expect Unicode strings, that is, characters with high ordinal Unicode
1119values (> 255) will be encoded as such characters, and likewise such 1120values (> 255) will be encoded as such characters, and likewise such
1120characters are decoded as-is, no canges to them will be done, except 1121characters are decoded as-is, no changes to them will be done, except
1121"(re-)interpreting" them as Unicode codepoints or Unicode characters, 1122"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1122respectively (to Perl, these are the same thing in strings unless you do 1123respectively (to Perl, these are the same thing in strings unless you do
1123funny/weird/dumb stuff). 1124funny/weird/dumb stuff).
1124 1125
1125This is useful when you want to do the encoding yourself (e.g. when you 1126This is useful when you want to do the encoding yourself (e.g. when you
1181proper subset of most 8-bit and multibyte encodings in use in the world. 1182proper subset of most 8-bit and multibyte encodings in use in the world.
1182 1183
1183=back 1184=back
1184 1185
1185 1186
1187=head2 JSON and ECMAscript
1188
1189JSON syntax is based on how literals are represented in javascript (the
1190not-standardised predecessor of ECMAscript) which is presumably why it is
1191called "JavaScript Object Notation".
1192
1193However, JSON is not a subset (and also not a superset of course) of
1194ECMAscript (the standard) or javascript (whatever browsers actually
1195implement).
1196
1197If you want to use javascript's C<eval> function to "parse" JSON, you
1198might run into parse errors for valid JSON texts, or the resulting data
1199structure might not be queryable:
1200
1201One of the problems is that U+2028 and U+2029 are valid characters inside
1202JSON strings, but are not allowed in ECMAscript string literals, so the
1203following Perl fragment will not output something that can be guaranteed
1204to be parsable by javascript's C<eval>:
1205
1206 use JSON::XS;
1207
1208 print encode_json [chr 0x2028];
1209
1210The right fix for this is to use a proper JSON parser in your javascript
1211programs, and not rely on C<eval> (see for example Douglas Crockford's
1212F<json2.js> parser).
1213
1214If this is not an option, you can, as a stop-gap measure, simply encode to
1215ASCII-only JSON:
1216
1217 use JSON::XS;
1218
1219 print JSON::XS->new->ascii->encode ([chr 0x2028]);
1220
1221Note that this will enlarge the resulting JSON text quite a bit if you
1222have many non-ASCII characters. You might be tempted to run some regexes
1223to only escape U+2028 and U+2029, e.g.:
1224
1225 # DO NOT USE THIS!
1226 my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
1227 $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
1228 $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
1229 print $json;
1230
1231Note that I<this is a bad idea>: the above only works for U+2028 and
1232U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
1233javascript implementations, however, have issues with other characters as
1234well - using C<eval> naively simply I<will> cause problems.
1235
1236Another problem is that some javascript implementations reserve
1237some property names for their own purposes (which probably makes
1238them non-ECMAscript-compliant). For example, Iceweasel reserves the
1239C<__proto__> property name for its own purposes.
1240
1241If that is a problem, you could parse try to filter the resulting JSON
1242output for these property strings, e.g.:
1243
1244 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1245
1246This works because C<__proto__> is not valid outside of strings, so every
1247occurrence of C<"__proto__"\s*:> must be a string used as property name.
1248
1249If you know of other incompatibilities, please let me know.
1250
1251
1186=head2 JSON and YAML 1252=head2 JSON and YAML
1187 1253
1188You often hear that JSON is a subset of YAML. This is, however, a mass 1254You often hear that JSON is a subset of YAML. This is, however, a mass
1189hysteria(*) and very far from the truth (as of the time of this writing), 1255hysteria(*) and very far from the truth (as of the time of this writing),
1190so let me state it clearly: I<in general, there is no way to configure 1256so let me state it clearly: I<in general, there is no way to configure
1198 my $yaml = $to_yaml->encode ($ref) . "\n"; 1264 my $yaml = $to_yaml->encode ($ref) . "\n";
1199 1265
1200This will I<usually> generate JSON texts that also parse as valid 1266This will I<usually> generate JSON texts that also parse as valid
1201YAML. Please note that YAML has hardcoded limits on (simple) object key 1267YAML. Please note that YAML has hardcoded limits on (simple) object key
1202lengths that JSON doesn't have and also has different and incompatible 1268lengths that JSON doesn't have and also has different and incompatible
1203unicode handling, so you should make sure that your hash keys are 1269unicode character escape syntax, so you should make sure that your hash
1204noticeably shorter than the 1024 "stream characters" YAML allows and that 1270keys are noticeably shorter than the 1024 "stream characters" YAML allows
1205you do not have characters with codepoint values outside the Unicode BMP 1271and that you do not have characters with codepoint values outside the
1206(basic multilingual page). YAML also does not allow C<\/> sequences in 1272Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1207strings (which JSON::XS does not I<currently> generate, but other JSON 1273sequences in strings (which JSON::XS does not I<currently> generate, but
1208generators might). 1274other JSON generators might).
1209 1275
1210There might be other incompatibilities that I am not aware of (or the YAML 1276There might be other incompatibilities that I am not aware of (or the YAML
1211specification has been changed yet again - it does so quite often). In 1277specification has been changed yet again - it does so quite often). In
1212general you should not try to generate YAML with a JSON generator or vice 1278general you should not try to generate YAML with a JSON generator or vice
1213versa, or try to parse JSON with a YAML parser or vice versa: chances are 1279versa, or try to parse JSON with a YAML parser or vice versa: chances are
1232that difficult or long) and finally make YAML compatible to it, and 1298that difficult or long) and finally make YAML compatible to it, and
1233educating users about the changes, instead of spreading lies about the 1299educating users about the changes, instead of spreading lies about the
1234real compatibility for many I<years> and trying to silence people who 1300real compatibility for many I<years> and trying to silence people who
1235point out that it isn't true. 1301point out that it isn't true.
1236 1302
1303Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
1304though the incompatibilities have been documented (and are known to Brian)
1305for many years and the spec makes explicit claims that YAML is a superset
1306of JSON. It would be so easy to fix, but apparently, bullying people and
1307corrupting userdata is so much easier.
1308
1237=back 1309=back
1238 1310
1239 1311
1240=head2 SPEED 1312=head2 SPEED
1241 1313
1248a very short single-line JSON string (also available at 1320a very short single-line JSON string (also available at
1249L<http://dist.schmorp.de/misc/json/short.json>). 1321L<http://dist.schmorp.de/misc/json/short.json>).
1250 1322
1251 {"method": "handleMessage", "params": ["user1", 1323 {"method": "handleMessage", "params": ["user1",
1252 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7, 1324 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1253 true, false]} 1325 1, 0]}
1254 1326
1255It shows the number of encodes/decodes per second (JSON::XS uses 1327It shows the number of encodes/decodes per second (JSON::XS uses
1256the functional interface, while JSON::XS/2 uses the OO interface 1328the functional interface, while JSON::XS/2 uses the OO interface
1257with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 1329with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1258shrink). Higher is better: 1330shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
1331uses the from_json method). Higher is better:
1259 1332
1260 module | encode | decode | 1333 module | encode | decode |
1261 -----------|------------|------------| 1334 --------------|------------|------------|
1262 JSON 1.x | 4990.842 | 4088.813 | 1335 JSON::DWIW/DS | 86302.551 | 102300.098 |
1263 JSON::DWIW | 51653.990 | 71575.154 | 1336 JSON::DWIW/FJ | 86302.551 | 75983.768 |
1264 JSON::PC | 65948.176 | 74631.744 | 1337 JSON::PP | 15827.562 | 6638.658 |
1265 JSON::PP | 8931.652 | 3817.168 | 1338 JSON::Syck | 63358.066 | 47662.545 |
1266 JSON::Syck | 24877.248 | 27776.848 | 1339 JSON::XS | 511500.488 | 511500.488 |
1267 JSON::XS | 388361.481 | 227951.304 | 1340 JSON::XS/2 | 291271.111 | 388361.481 |
1268 JSON::XS/2 | 227951.304 | 218453.333 | 1341 JSON::XS/3 | 361577.931 | 361577.931 |
1269 JSON::XS/3 | 338250.323 | 218453.333 | 1342 Storable | 66788.280 | 265462.278 |
1270 Storable | 16500.016 | 135300.129 |
1271 -----------+------------+------------+ 1343 --------------+------------+------------+
1272 1344
1273That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 1345That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1274about three times faster on decoding, and over forty times faster 1346about five times faster on decoding, and over thirty to seventy times
1275than JSON, even with pretty-printing and key sorting. It also compares 1347faster than JSON's pure perl implementation. It also compares favourably
1276favourably to Storable for small amounts of data. 1348to Storable for small amounts of data.
1277 1349
1278Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1350Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1279search API (L<http://dist.schmorp.de/misc/json/long.json>). 1351search API (L<http://dist.schmorp.de/misc/json/long.json>).
1280 1352
1281 module | encode | decode | 1353 module | encode | decode |
1282 -----------|------------|------------| 1354 --------------|------------|------------|
1283 JSON 1.x | 55.260 | 34.971 | 1355 JSON::DWIW/DS | 1647.927 | 2673.916 |
1284 JSON::DWIW | 825.228 | 1082.513 | 1356 JSON::DWIW/FJ | 1630.249 | 2596.128 |
1285 JSON::PC | 3571.444 | 2394.829 |
1286 JSON::PP | 210.987 | 32.574 | 1357 JSON::PP | 400.640 | 62.311 |
1287 JSON::Syck | 552.551 | 787.544 | 1358 JSON::Syck | 1481.040 | 1524.869 |
1288 JSON::XS | 5780.463 | 4854.519 | 1359 JSON::XS | 20661.596 | 9541.183 |
1289 JSON::XS/2 | 3869.998 | 4798.975 | 1360 JSON::XS/2 | 10683.403 | 9416.938 |
1290 JSON::XS/3 | 5862.880 | 4798.975 | 1361 JSON::XS/3 | 20661.596 | 9400.054 |
1291 Storable | 4445.002 | 5235.027 | 1362 Storable | 19765.806 | 10000.725 |
1292 -----------+------------+------------+ 1363 --------------+------------+------------+
1293 1364
1294Again, JSON::XS leads by far (except for Storable which non-surprisingly 1365Again, JSON::XS leads by far (except for Storable which non-surprisingly
1295decodes faster). 1366decodes a bit faster).
1296 1367
1297On large strings containing lots of high Unicode characters, some modules 1368On large strings containing lots of high Unicode characters, some modules
1298(such as JSON::PC) seem to decode faster than JSON::XS, but the result 1369(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1299will be broken due to missing (or wrong) Unicode handling. Others refuse 1370will be broken due to missing (or wrong) Unicode handling. Others refuse
1300to decode or encode properly, so it was impossible to prepare a fair 1371to decode or encode properly, so it was impossible to prepare a fair
1336information you might want to make sure that exceptions thrown by JSON::XS 1407information you might want to make sure that exceptions thrown by JSON::XS
1337will not end up in front of untrusted eyes. 1408will not end up in front of untrusted eyes.
1338 1409
1339If you are using JSON::XS to return packets to consumption 1410If you are using JSON::XS to return packets to consumption
1340by JavaScript scripts in a browser you should have a look at 1411by JavaScript scripts in a browser you should have a look at
1341L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1412L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1342you are vulnerable to some common attack vectors (which really are browser 1413see whether you are vulnerable to some common attack vectors (which really
1343design bugs, but it is still you who will have to deal with it, as major 1414are browser design bugs, but it is still you who will have to deal with
1344browser developers care only for features, not about getting security 1415it, as major browser developers care only for features, not about getting
1345right). 1416security right).
1417
1418
1419=head1 INTEROPERABILITY WITH OTHER MODULES
1420
1421C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
1422constants. That means that the JSON true and false values will be
1423comaptible to true and false values of iother modules that do the same,
1424such as L<JSON::PP> and L<CBOR::XS>.
1346 1425
1347 1426
1348=head1 THREADS 1427=head1 THREADS
1349 1428
1350This module is I<not> guaranteed to be thread safe and there are no 1429This module is I<not> guaranteed to be thread safe and there are no
1353process simulations - use fork, it's I<much> faster, cheaper, better). 1432process simulations - use fork, it's I<much> faster, cheaper, better).
1354 1433
1355(It might actually work, but you have been warned). 1434(It might actually work, but you have been warned).
1356 1435
1357 1436
1437=head1 THE PERILS OF SETLOCALE
1438
1439Sometimes people avoid the Perl locale support and directly call the
1440system's setlocale function with C<LC_ALL>.
1441
1442This breaks both perl and modules such as JSON::XS, as stringification of
1443numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
1444print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
1445perl to stringify numbers).
1446
1447The solution is simple: don't call C<setlocale>, or use it for only those
1448categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
1449
1450If you need C<LC_NUMERIC>, you should enable it only around the code that
1451actually needs it (avoiding stringification of numbers), and restore it
1452afterwards.
1453
1454
1358=head1 BUGS 1455=head1 BUGS
1359 1456
1360While the goal of this module is to be correct, that unfortunately does 1457While the goal of this module is to be correct, that unfortunately does
1361not mean it's bug-free, only that I think its design is bug-free. If you 1458not mean it's bug-free, only that I think its design is bug-free. If you
1362keep reporting bugs they will be fixed swiftly, though. 1459keep reporting bugs they will be fixed swiftly, though.
1364Please refrain from using rt.cpan.org or any other bug reporting 1461Please refrain from using rt.cpan.org or any other bug reporting
1365service. I put the contact address into my modules for a reason. 1462service. I put the contact address into my modules for a reason.
1366 1463
1367=cut 1464=cut
1368 1465
1369our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1466BEGIN {
1370our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; 1467 *true = \$Types::Serialiser::true;
1468 *true = \&Types::Serialiser::true;
1469 *false = \$Types::Serialiser::false;
1470 *false = \&Types::Serialiser::false;
1471 *is_bool = \&Types::Serialiser::is_bool;
1371 1472
1372sub true() { $true } 1473 *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1373sub false() { $false }
1374
1375sub is_bool($) {
1376 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1377# or UNIVERSAL::isa $_[0], "JSON::Literal"
1378} 1474}
1379 1475
1380XSLoader::load "JSON::XS", $VERSION; 1476XSLoader::load "JSON::XS", $VERSION;
1381
1382package JSON::XS::Boolean;
1383
1384use overload
1385 "0+" => sub { ${$_[0]} },
1386 "++" => sub { $_[0] = ${$_[0]} + 1 },
1387 "--" => sub { $_[0] = ${$_[0]} - 1 },
1388 fallback => 1;
1389
13901;
1391 1477
1392=head1 SEE ALSO 1478=head1 SEE ALSO
1393 1479
1394The F<json_xs> command line utility for quick experiments. 1480The F<json_xs> command line utility for quick experiments.
1395 1481
1398 Marc Lehmann <schmorp@schmorp.de> 1484 Marc Lehmann <schmorp@schmorp.de>
1399 http://home.schmorp.de/ 1485 http://home.schmorp.de/
1400 1486
1401=cut 1487=cut
1402 1488
14891
1490

Diff Legend

Removed lines
+ Added lines
< Changed lines
> Changed lines