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Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC vs.
Revision 1.144 by root, Mon Oct 28 23:19:54 2013 UTC

49to write yet another JSON module? While it seems there are many JSON 49to write yet another JSON module? While it seems there are many JSON
50modules, none of them correctly handle all corner cases, and in most cases 50modules, none of them correctly handle all corner cases, and in most cases
51their maintainers are unresponsive, gone missing, or not listening to bug 51their maintainers are unresponsive, gone missing, or not listening to bug
52reports for other reasons. 52reports for other reasons.
53 53
54See COMPARISON, below, for a comparison to some other JSON modules.
55
56See MAPPING, below, on how JSON::XS maps perl values to JSON values and 54See MAPPING, below, on how JSON::XS maps perl values to JSON values and
57vice versa. 55vice versa.
58 56
59=head2 FEATURES 57=head2 FEATURES
60 58
66so, and even documents what "correct" means. 64so, and even documents what "correct" means.
67 65
68=item * round-trip integrity 66=item * round-trip integrity
69 67
70When you serialise a perl data structure using only data types supported 68When you serialise a perl data structure using only data types supported
71by JSON, the deserialised data structure is identical on the Perl level. 69by JSON and Perl, the deserialised data structure is identical on the Perl
72(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
73like 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
74section below to learn about those. 72MAPPING section below to learn about those.
75 73
76=item * strict checking of JSON correctness 74=item * strict checking of JSON correctness
77 75
78There is no guessing, no generating of illegal JSON texts by default, 76There is no guessing, no generating of illegal JSON texts by default,
79and 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
85this module usually compares favourably in terms of speed, too. 83this module usually compares favourably in terms of speed, too.
86 84
87=item * simple to use 85=item * simple to use
88 86
89This 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
90oriented interface interface. 88oriented interface.
91 89
92=item * reasonably versatile output formats 90=item * reasonably versatile output formats
93 91
94You can choose between the most compact guaranteed-single-line format 92You can choose between the most compact guaranteed-single-line format
95possible (nice for simple line-based protocols), a pure-ASCII format 93possible (nice for simple line-based protocols), a pure-ASCII format
101 99
102=cut 100=cut
103 101
104package JSON::XS; 102package JSON::XS;
105 103
106use strict; 104use common::sense;
107 105
108our $VERSION = '2.22'; 106our $VERSION = 2.34;
109our @ISA = qw(Exporter); 107our @ISA = qw(Exporter);
110 108
111our @EXPORT = qw(encode_json decode_json to_json from_json); 109our @EXPORT = qw(encode_json decode_json);
112
113sub to_json($) {
114 require Carp;
115 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");
116}
117
118sub from_json($) {
119 require Carp;
120 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");
121}
122 110
123use Exporter; 111use Exporter;
124use XSLoader; 112use XSLoader;
113
114use Types::Serialiser ();
125 115
126=head1 FUNCTIONAL INTERFACE 116=head1 FUNCTIONAL INTERFACE
127 117
128The following convenience methods are provided by this module. They are 118The following convenience methods are provided by this module. They are
129exported by default: 119exported by default:
150This function call is functionally identical to: 140This function call is functionally identical to:
151 141
152 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 142 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153 143
154Except being faster. 144Except being faster.
155
156=item $is_boolean = JSON::XS::is_bool $scalar
157
158Returns true if the passed scalar represents either JSON::XS::true or
159JSON::XS::false, two constants that act like C<1> and C<0>, respectively
160and are used to represent JSON C<true> and C<false> values in Perl.
161
162See MAPPING, below, for more information on how JSON values are mapped to
163Perl.
164 145
165=back 146=back
166 147
167 148
168=head1 A FEW NOTES ON UNICODE AND PERL 149=head1 A FEW NOTES ON UNICODE AND PERL
434If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 415If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
435by sorting their keys. This is adding a comparatively high overhead. 416by sorting their keys. This is adding a comparatively high overhead.
436 417
437If C<$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
438pairs 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
439of the same script). 420of the same script, and can change even within the same run from 5.18
421onwards).
440 422
441This 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
442the 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,
443the 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,
444as key-value pairs have no inherent ordering in Perl. 426as key-value pairs have no inherent ordering in Perl.
445 427
446This 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.
447 431
448=item $json = $json->allow_nonref ([$enable]) 432=item $json = $json->allow_nonref ([$enable])
449 433
450=item $enabled = $json->get_allow_nonref 434=item $enabled = $json->get_allow_nonref
451 435
666 650
667See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 651See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
668 652
669=item $json_text = $json->encode ($perl_scalar) 653=item $json_text = $json->encode ($perl_scalar)
670 654
671Converts the given Perl data structure (a simple scalar or a reference 655Converts the given Perl value or data structure to its JSON
672to a hash or array) to its JSON representation. Simple scalars will be 656representation. Croaks on error.
673converted into JSON string or number sequences, while references to arrays
674become JSON arrays and references to hashes become JSON objects. Undefined
675Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
676nor C<false> values will be generated.
677 657
678=item $perl_scalar = $json->decode ($json_text) 658=item $perl_scalar = $json->decode ($json_text)
679 659
680The 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,
681returning the resulting simple scalar or reference. Croaks on error. 661returning the resulting simple scalar or reference. Croaks on error.
682
683JSON numbers and strings become simple Perl scalars. JSON arrays become
684Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
685C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
686 662
687=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) 663=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
688 664
689This 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
690when there is trailing garbage after the first JSON object, it will 666when there is trailing garbage after the first JSON object, it will
691silently stop parsing there and return the number of characters consumed 667silently stop parsing there and return the number of characters consumed
692so far. 668so far.
693 669
694This 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
695(which is not the brightest thing to do in the first place) and you need
696to know where the JSON text ends. 671and you need to know where the JSON text ends.
697 672
698 JSON::XS->new->decode_prefix ("[1] the tail") 673 JSON::XS->new->decode_prefix ("[1] the tail")
699 => ([], 3) 674 => ([], 3)
700 675
701=back 676=back
713calls). 688calls).
714 689
715JSON::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
716has 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
717truly incremental parser. This means that it sometimes won't stop as 692truly incremental parser. This means that it sometimes won't stop as
718early as the full parser, for example, it doesn't detect parenthese 693early as the full parser, for example, it doesn't detect mismatched
719mismatches. The only thing it guarantees is that it starts decoding as 694parentheses. The only thing it guarantees is that it starts decoding as
720soon as a syntactically valid JSON text has been seen. This means you need 695soon as a syntactically valid JSON text has been seen. This means you need
721to set resource limits (e.g. C<max_size>) to ensure the parser will stop 696to set resource limits (e.g. C<max_size>) to ensure the parser will stop
722parsing in the presence if syntax errors. 697parsing in the presence if syntax errors.
723 698
724The following methods implement this incremental parser. 699The following methods implement this incremental parser.
740 715
741If 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
742exactly 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
743object, 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,
744this 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
745C<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
746using the method. 721using the method.
747 722
748And 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
749from 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
750otherwise. 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
751objects or arrays, instead they must be concatenated back-to-back. If 726objects or arrays, instead they must be concatenated back-to-back. If
752an 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
753case. 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
754lost. 729lost.
755 730
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
756=item $lvalue_string = $json->incr_text 736=item $lvalue_string = $json->incr_text
757 737
758This method returns the currently stored JSON fragment as an lvalue, that 738This method returns the currently stored JSON fragment as an lvalue, that
759is, 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
760C<incr_parse> in I<scalar context> successfully returned an object. Under 740C<incr_parse> in I<scalar context> successfully returned an object. Under
767JSON 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
768(such as commas). 748(such as commas).
769 749
770=item $json->incr_skip 750=item $json->incr_skip
771 751
772This will reset the state of the incremental parser and will remove the 752This will reset the state of the incremental parser and will remove
773parsed 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
774died, 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
775unchanged, 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.
776 760
777=item $json->incr_reset 761=item $json->incr_reset
778 762
779This completely resets the incremental parser, that is, after this call, 763This completely resets the incremental parser, that is, after this call,
780it will be as if the parser had never parsed anything. 764it will be as if the parser had never parsed anything.
781 765
782This 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
783ignore 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
784each successful decode. 768each successful decode.
785 769
786=back 770=back
787 771
788=head2 LIMITATIONS 772=head2 LIMITATIONS
789 773
790All options that affect decoding are supported, except 774All options that affect decoding are supported, except
791C<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
792work 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
793them 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
794for JSON numbers, however. 778not hold true for JSON numbers, however.
795 779
796For 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
797start 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
798of 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
799takes the conservative route and disallows this case. 783takes the conservative route and disallows this case.
978If 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
979it 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
980a numeric (floating point) value if that is possible without loss of 964a numeric (floating point) value if that is possible without loss of
981precision. Otherwise it will preserve the number as a string value (in 965precision. Otherwise it will preserve the number as a string value (in
982which case you lose roundtripping ability, as the JSON number will be 966which case you lose roundtripping ability, as the JSON number will be
983re-encoded toa JSON string). 967re-encoded to a JSON string).
984 968
985Numbers containing a fractional or exponential part will always be 969Numbers containing a fractional or exponential part will always be
986represented as numeric (floating point) values, possibly at a loss of 970represented as numeric (floating point) values, possibly at a loss of
987precision (in which case you might lose perfect roundtripping ability, but 971precision (in which case you might lose perfect roundtripping ability, but
988the JSON number will still be re-encoded as a JSON number). 972the JSON number will still be re-encoded as a JSON number).
989 973
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
990=item true, false 979=item true, false
991 980
992These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, 981These JSON atoms become C<Types::Serialiser::true> and
993respectively. They are overloaded to act almost exactly like the numbers 982C<Types::Serialiser::false>, respectively. They are overloaded to act
994C<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
995the 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).
996 986
997=item null 987=item null
998 988
999A JSON null atom becomes C<undef> in Perl. 989A JSON null atom becomes C<undef> in Perl.
1000 990
1009 999
1010=over 4 1000=over 4
1011 1001
1012=item hash references 1002=item hash references
1013 1003
1014Perl hash references become JSON objects. As there is no inherent ordering 1004Perl hash references become JSON objects. As there is no inherent
1015in hash keys (or JSON objects), they will usually be encoded in a 1005ordering in hash keys (or JSON objects), they will usually be encoded
1016pseudo-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
1017stays 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
1018optionally sort the hash keys (determined by the I<canonical> flag), so 1008serialise to the same JSON text (given same settings and version of
1019the same datastructure will serialise to the same JSON text (given same 1009JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1020settings 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.
1021and is only rarely useful, e.g. when you want to compare some JSON text
1022against another for equality.
1023 1011
1024=item array references 1012=item array references
1025 1013
1026Perl array references become JSON arrays. 1014Perl array references become JSON arrays.
1027 1015
1028=item other references 1016=item other references
1029 1017
1030Other unblessed references are generally not allowed and will cause an 1018Other unblessed references are generally not allowed and will cause an
1031exception 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
1032C<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.
1033also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1034 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;
1035 encode_json [\0, JSON::XS::true] # yields [false,true] 1027 encode_json [\0, Types::Serialiser::true] # yields [false,true]
1036 1028
1037=item JSON::XS::true, JSON::XS::false 1029=item Types::Serialiser::true, Types::Serialiser::false
1038 1030
1039These special values become JSON true and JSON false values, 1031These special values from the L<Types::Serialiser> module become JSON true
1040respectively. 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.
1041 1034
1042=item blessed objects 1035=item blessed objects
1043 1036
1044Blessed objects are not directly representable in JSON. See the 1037Blessed objects are not directly representable in JSON. See the
1045C<allow_blessed> and C<convert_blessed> methods on various options on 1038C<allow_blessed> and C<convert_blessed> methods on various options on
1080 $x *= 1; # same thing, the choice is yours. 1073 $x *= 1; # same thing, the choice is yours.
1081 1074
1082You 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
1083if 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
1084:). 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.
1085 1085
1086=back 1086=back
1087 1087
1088 1088
1089=head1 ENCODING/CODESET FLAG NOTES 1089=head1 ENCODING/CODESET FLAG NOTES
1116=item C<utf8> flag disabled 1116=item C<utf8> flag disabled
1117 1117
1118When 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
1119and expect Unicode strings, that is, characters with high ordinal Unicode 1119and expect Unicode strings, that is, characters with high ordinal Unicode
1120values (> 255) will be encoded as such characters, and likewise such 1120values (> 255) will be encoded as such characters, and likewise such
1121characters 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
1122"(re-)interpreting" them as Unicode codepoints or Unicode characters, 1122"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1123respectively (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
1124funny/weird/dumb stuff). 1124funny/weird/dumb stuff).
1125 1125
1126This 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
1182proper 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.
1183 1183
1184=back 1184=back
1185 1185
1186 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
1187=head2 JSON and YAML 1252=head2 JSON and YAML
1188 1253
1189You 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
1190hysteria(*) 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),
1191so 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
1199 my $yaml = $to_yaml->encode ($ref) . "\n"; 1264 my $yaml = $to_yaml->encode ($ref) . "\n";
1200 1265
1201This will I<usually> generate JSON texts that also parse as valid 1266This will I<usually> generate JSON texts that also parse as valid
1202YAML. Please note that YAML has hardcoded limits on (simple) object key 1267YAML. Please note that YAML has hardcoded limits on (simple) object key
1203lengths that JSON doesn't have and also has different and incompatible 1268lengths that JSON doesn't have and also has different and incompatible
1204unicode handling, so you should make sure that your hash keys are 1269unicode character escape syntax, so you should make sure that your hash
1205noticeably shorter than the 1024 "stream characters" YAML allows and that 1270keys are noticeably shorter than the 1024 "stream characters" YAML allows
1206you do not have characters with codepoint values outside the Unicode BMP 1271and that you do not have characters with codepoint values outside the
1207(basic multilingual page). YAML also does not allow C<\/> sequences in 1272Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1208strings (which JSON::XS does not I<currently> generate, but other JSON 1273sequences in strings (which JSON::XS does not I<currently> generate, but
1209generators might). 1274other JSON generators might).
1210 1275
1211There 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
1212specification has been changed yet again - it does so quite often). In 1277specification has been changed yet again - it does so quite often). In
1213general 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
1214versa, 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
1233that difficult or long) and finally make YAML compatible to it, and 1298that difficult or long) and finally make YAML compatible to it, and
1234educating users about the changes, instead of spreading lies about the 1299educating users about the changes, instead of spreading lies about the
1235real compatibility for many I<years> and trying to silence people who 1300real compatibility for many I<years> and trying to silence people who
1236point out that it isn't true. 1301point out that it isn't true.
1237 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
1238=back 1309=back
1239 1310
1240 1311
1241=head2 SPEED 1312=head2 SPEED
1242 1313
1249a very short single-line JSON string (also available at 1320a very short single-line JSON string (also available at
1250L<http://dist.schmorp.de/misc/json/short.json>). 1321L<http://dist.schmorp.de/misc/json/short.json>).
1251 1322
1252 {"method": "handleMessage", "params": ["user1", 1323 {"method": "handleMessage", "params": ["user1",
1253 "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,
1254 true, false]} 1325 1, 0]}
1255 1326
1256It shows the number of encodes/decodes per second (JSON::XS uses 1327It shows the number of encodes/decodes per second (JSON::XS uses
1257the functional interface, while JSON::XS/2 uses the OO interface 1328the functional interface, while JSON::XS/2 uses the OO interface
1258with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 1329with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1259shrink). Higher is better: 1330shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
1331uses the from_json method). Higher is better:
1260 1332
1261 module | encode | decode | 1333 module | encode | decode |
1262 -----------|------------|------------| 1334 --------------|------------|------------|
1263 JSON 1.x | 4990.842 | 4088.813 | 1335 JSON::DWIW/DS | 86302.551 | 102300.098 |
1264 JSON::DWIW | 51653.990 | 71575.154 | 1336 JSON::DWIW/FJ | 86302.551 | 75983.768 |
1265 JSON::PC | 65948.176 | 74631.744 | 1337 JSON::PP | 15827.562 | 6638.658 |
1266 JSON::PP | 8931.652 | 3817.168 | 1338 JSON::Syck | 63358.066 | 47662.545 |
1267 JSON::Syck | 24877.248 | 27776.848 | 1339 JSON::XS | 511500.488 | 511500.488 |
1268 JSON::XS | 388361.481 | 227951.304 | 1340 JSON::XS/2 | 291271.111 | 388361.481 |
1269 JSON::XS/2 | 227951.304 | 218453.333 | 1341 JSON::XS/3 | 361577.931 | 361577.931 |
1270 JSON::XS/3 | 338250.323 | 218453.333 | 1342 Storable | 66788.280 | 265462.278 |
1271 Storable | 16500.016 | 135300.129 |
1272 -----------+------------+------------+ 1343 --------------+------------+------------+
1273 1344
1274That 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,
1275about three times faster on decoding, and over forty times faster 1346about five times faster on decoding, and over thirty to seventy times
1276than JSON, even with pretty-printing and key sorting. It also compares 1347faster than JSON's pure perl implementation. It also compares favourably
1277favourably to Storable for small amounts of data. 1348to Storable for small amounts of data.
1278 1349
1279Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1350Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1280search API (L<http://dist.schmorp.de/misc/json/long.json>). 1351search API (L<http://dist.schmorp.de/misc/json/long.json>).
1281 1352
1282 module | encode | decode | 1353 module | encode | decode |
1283 -----------|------------|------------| 1354 --------------|------------|------------|
1284 JSON 1.x | 55.260 | 34.971 | 1355 JSON::DWIW/DS | 1647.927 | 2673.916 |
1285 JSON::DWIW | 825.228 | 1082.513 | 1356 JSON::DWIW/FJ | 1630.249 | 2596.128 |
1286 JSON::PC | 3571.444 | 2394.829 |
1287 JSON::PP | 210.987 | 32.574 | 1357 JSON::PP | 400.640 | 62.311 |
1288 JSON::Syck | 552.551 | 787.544 | 1358 JSON::Syck | 1481.040 | 1524.869 |
1289 JSON::XS | 5780.463 | 4854.519 | 1359 JSON::XS | 20661.596 | 9541.183 |
1290 JSON::XS/2 | 3869.998 | 4798.975 | 1360 JSON::XS/2 | 10683.403 | 9416.938 |
1291 JSON::XS/3 | 5862.880 | 4798.975 | 1361 JSON::XS/3 | 20661.596 | 9400.054 |
1292 Storable | 4445.002 | 5235.027 | 1362 Storable | 19765.806 | 10000.725 |
1293 -----------+------------+------------+ 1363 --------------+------------+------------+
1294 1364
1295Again, JSON::XS leads by far (except for Storable which non-surprisingly 1365Again, JSON::XS leads by far (except for Storable which non-surprisingly
1296decodes faster). 1366decodes a bit faster).
1297 1367
1298On large strings containing lots of high Unicode characters, some modules 1368On large strings containing lots of high Unicode characters, some modules
1299(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
1300will be broken due to missing (or wrong) Unicode handling. Others refuse 1370will be broken due to missing (or wrong) Unicode handling. Others refuse
1301to 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
1337information 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
1338will not end up in front of untrusted eyes. 1408will not end up in front of untrusted eyes.
1339 1409
1340If you are using JSON::XS to return packets to consumption 1410If you are using JSON::XS to return packets to consumption
1341by JavaScript scripts in a browser you should have a look at 1411by JavaScript scripts in a browser you should have a look at
1342L<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
1343you are vulnerable to some common attack vectors (which really are browser 1413see whether you are vulnerable to some common attack vectors (which really
1344design 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
1345browser developers care only for features, not about getting security 1415it, as major browser developers care only for features, not about getting
1346right). 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>.
1347 1425
1348 1426
1349=head1 THREADS 1427=head1 THREADS
1350 1428
1351This 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
1354process simulations - use fork, it's I<much> faster, cheaper, better). 1432process simulations - use fork, it's I<much> faster, cheaper, better).
1355 1433
1356(It might actually work, but you have been warned). 1434(It might actually work, but you have been warned).
1357 1435
1358 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
1359=head1 BUGS 1455=head1 BUGS
1360 1456
1361While 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
1362not 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
1363keep reporting bugs they will be fixed swiftly, though. 1459keep reporting bugs they will be fixed swiftly, though.
1365Please refrain from using rt.cpan.org or any other bug reporting 1461Please refrain from using rt.cpan.org or any other bug reporting
1366service. I put the contact address into my modules for a reason. 1462service. I put the contact address into my modules for a reason.
1367 1463
1368=cut 1464=cut
1369 1465
1370our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; 1466BEGIN {
1371our $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;
1372 1472
1373sub true() { $true } 1473 *JSON::XS::Boolean:: = *Types::Serialiser::Boolean::;
1374sub false() { $false }
1375
1376sub is_bool($) {
1377 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1378# or UNIVERSAL::isa $_[0], "JSON::Literal"
1379} 1474}
1380 1475
1381XSLoader::load "JSON::XS", $VERSION; 1476XSLoader::load "JSON::XS", $VERSION;
1382
1383package JSON::XS::Boolean;
1384
1385use overload
1386 "0+" => sub { ${$_[0]} },
1387 "++" => sub { $_[0] = ${$_[0]} + 1 },
1388 "--" => sub { $_[0] = ${$_[0]} - 1 },
1389 fallback => 1;
1390
13911;
1392 1477
1393=head1 SEE ALSO 1478=head1 SEE ALSO
1394 1479
1395The F<json_xs> command line utility for quick experiments. 1480The F<json_xs> command line utility for quick experiments.
1396 1481
1399 Marc Lehmann <schmorp@schmorp.de> 1484 Marc Lehmann <schmorp@schmorp.de>
1400 http://home.schmorp.de/ 1485 http://home.schmorp.de/
1401 1486
1402=cut 1487=cut
1403 1488
14891
1490

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