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Comparing JSON-XS/XS.pm (file contents):
Revision 1.77 by root, Tue Dec 4 10:37:42 2007 UTC vs.
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC

10 use JSON::XS; 10 use JSON::XS;
11 11
12 # exported functions, they croak on error 12 # exported functions, they croak on error
13 # and expect/generate UTF-8 13 # and expect/generate UTF-8
14 14
15 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 15 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 16 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17 17
18 # OO-interface 18 # OO-interface
19 19
20 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 20 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
21 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 21 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
100 100
101package JSON::XS; 101package JSON::XS;
102 102
103use strict; 103use strict;
104 104
105our $VERSION = '2.0'; 105our $VERSION = '2.01';
106our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
107 107
108our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
111 require Carp;
112 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");
113}
114
115sub from_json($) {
116 require Carp;
117 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");
118}
109 119
110use Exporter; 120use Exporter;
111use XSLoader; 121use XSLoader;
112 122
113=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
115The following convenience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
116exported by default: 126exported by default:
117 127
118=over 4 128=over 4
119 129
120=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
121 131
122Converts the given Perl data structure to a UTF-8 encoded, binary string 132Converts the given Perl data structure to a UTF-8 encoded, binary string
123(that is, the string contains octets only). Croaks on error. 133(that is, the string contains octets only). Croaks on error.
124 134
125This function call is functionally identical to: 135This function call is functionally identical to:
126 136
127 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
128 138
129except being faster. 139except being faster.
130 140
131=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
132 142
133The opposite of C<to_json>: expects an UTF-8 (binary) string and tries 143The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
134to parse that as an UTF-8 encoded JSON text, returning the resulting 144to parse that as an UTF-8 encoded JSON text, returning the resulting
135reference. Croaks on error. 145reference. Croaks on error.
136 146
137This function call is functionally identical to: 147This function call is functionally identical to:
138 148
471The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> 481The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
472returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
473way. C<TO_JSON> must take care of not causing an endless recursion cycle 483way. C<TO_JSON> must take care of not causing an endless recursion cycle
474(== crash) in this case. The name of C<TO_JSON> was chosen because other 484(== crash) in this case. The name of C<TO_JSON> was chosen because other
475methods called by the Perl core (== not by the user of the object) are 485methods called by the Perl core (== not by the user of the object) are
476usually in upper case letters and to avoid collisions with the C<to_json> 486usually in upper case letters and to avoid collisions with any C<to_json>
477function. 487function or method.
478 488
479This setting does not yet influence C<decode> in any way, but in the 489This setting does not yet influence C<decode> in any way, but in the
480future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
481enabled by this setting. 491enabled by this setting.
482 492
755Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
756exception to be thrown, except for references to the integers C<0> and 766exception to be thrown, except for references to the integers C<0> and
757C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 767C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
758also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 768also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
759 769
760 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
761 771
762=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
763 773
764These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
765respectively. You can also use C<\1> and C<\0> directly if you want. 775respectively. You can also use C<\1> and C<\0> directly if you want.
766 776
767=item blessed objects 777=item blessed objects
768 778
769Blessed objects are not allowed. JSON::XS currently tries to encode their 779Blessed objects are not directly representable in JSON. See the
770underlying representation (hash- or arrayref), but this behaviour might 780C<allow_blessed> and C<convert_blessed> methods on various options on
771change in future versions. 781how to deal with this: basically, you can choose between throwing an
782exception, encoding the reference as if it weren't blessed, or provide
783your own serialiser method.
772 784
773=item simple scalars 785=item simple scalars
774 786
775Simple Perl scalars (any scalar that is not a reference) are the most 787Simple Perl scalars (any scalar that is not a reference) are the most
776difficult objects to encode: JSON::XS will encode undefined scalars as 788difficult objects to encode: JSON::XS will encode undefined scalars as
777JSON null value, scalars that have last been used in a string context 789JSON C<null> values, scalars that have last been used in a string context
778before encoding as JSON strings and anything else as number value: 790before encoding as JSON strings, and anything else as number value:
779 791
780 # dump as number 792 # dump as number
781 to_json [2] # yields [2] 793 encode_json [2] # yields [2]
782 to_json [-3.0e17] # yields [-3e+17] 794 encode_json [-3.0e17] # yields [-3e+17]
783 my $value = 5; to_json [$value] # yields [5] 795 my $value = 5; encode_json [$value] # yields [5]
784 796
785 # used as string, so dump as string 797 # used as string, so dump as string
786 print $value; 798 print $value;
787 to_json [$value] # yields ["5"] 799 encode_json [$value] # yields ["5"]
788 800
789 # undef becomes null 801 # undef becomes null
790 to_json [undef] # yields [null] 802 encode_json [undef] # yields [null]
791 803
792You can force the type to be a JSON string by stringifying it: 804You can force the type to be a JSON string by stringifying it:
793 805
794 my $x = 3.1; # some variable containing a number 806 my $x = 3.1; # some variable containing a number
795 "$x"; # stringified 807 "$x"; # stringified
801 my $x = "3"; # some variable containing a string 813 my $x = "3"; # some variable containing a string
802 $x += 0; # numify it, ensuring it will be dumped as a number 814 $x += 0; # numify it, ensuring it will be dumped as a number
803 $x *= 1; # same thing, the choice is yours. 815 $x *= 1; # same thing, the choice is yours.
804 816
805You can not currently force the type in other, less obscure, ways. Tell me 817You can not currently force the type in other, less obscure, ways. Tell me
806if you need this capability. 818if you need this capability (but don't forget to explain why its needed
819:).
807 820
808=back 821=back
809 822
810 823
811=head1 COMPARISON 824=head1 COMPARISON
895=back 908=back
896 909
897 910
898=head2 JSON and YAML 911=head2 JSON and YAML
899 912
900You often hear that JSON is a subset (or a close subset) of YAML. This is, 913You often hear that JSON is a subset of YAML. This is, however, a mass
901however, a mass hysteria and very far from the truth. In general, there is 914hysteria(*) and very far from the truth. In general, there is no way to
902no way to configure JSON::XS to output a data structure as valid YAML. 915configure JSON::XS to output a data structure as valid YAML that works for
916all cases.
903 917
904If you really must use JSON::XS to generate YAML, you should use this 918If you really must use JSON::XS to generate YAML, you should use this
905algorithm (subject to change in future versions): 919algorithm (subject to change in future versions):
906 920
907 my $to_yaml = JSON::XS->new->utf8->space_after (1); 921 my $to_yaml = JSON::XS->new->utf8->space_after (1);
908 my $yaml = $to_yaml->encode ($ref) . "\n"; 922 my $yaml = $to_yaml->encode ($ref) . "\n";
909 923
910This will usually generate JSON texts that also parse as valid 924This will I<usually> generate JSON texts that also parse as valid
911YAML. Please note that YAML has hardcoded limits on (simple) object key 925YAML. Please note that YAML has hardcoded limits on (simple) object key
912lengths that JSON doesn't have, so you should make sure that your hash 926lengths that JSON doesn't have and also has different and incompatible
927unicode handling, so you should make sure that your hash keys are
913keys are noticeably shorter than the 1024 characters YAML allows. 928noticeably shorter than the 1024 "stream characters" YAML allows and that
929you do not have codepoints with values outside the Unicode BMP (basic
930multilingual page). YAML also does not allow C<\/> sequences in strings
931(which JSON::XS does not I<currently> generate).
914 932
915There might be other incompatibilities that I am not aware of. In general 933There might be other incompatibilities that I am not aware of (or the YAML
934specification has been changed yet again - it does so quite often). In
916you should not try to generate YAML with a JSON generator or vice versa, 935general you should not try to generate YAML with a JSON generator or vice
917or try to parse JSON with a YAML parser or vice versa: chances are high 936versa, or try to parse JSON with a YAML parser or vice versa: chances are
918that you will run into severe interoperability problems. 937high that you will run into severe interoperability problems when you
938least expect it.
939
940=over 4
941
942=item (*)
943
944This is spread actively by the YAML team, however. For many years now they
945claim YAML were a superset of JSON, even when proven otherwise.
946
947Even the author of this manpage was at some point accused of providing
948"incorrect" information, despite the evidence presented (claims ranged
949from "your documentation contains inaccurate and negative statements about
950YAML" (the only negative comment is this footnote, and it didn't exist
951back then; the question on which claims were inaccurate was never answered
952etc.) to "the YAML spec is not up-to-date" (the *real* and supposedly
953JSON-compatible spec is apparently not currently publicly available)
954to actual requests to replace this section by *incorrect* information,
955suppressing information about the real problem).
956
957So whenever you are told that YAML was a superset of JSON, first check
958wether it is really true (it might be when you check it, but it certainly
959was not true when this was written). I would much prefer if the YAML team
960would spent their time on actually making JSON compatibility a truth
961(JSON, after all, has a very small and simple specification) instead of
962trying to lobby/force people into reporting untruths.
963
964=back
919 965
920 966
921=head2 SPEED 967=head2 SPEED
922 968
923It seems that JSON::XS is surprisingly fast, as shown in the following 969It seems that JSON::XS is surprisingly fast, as shown in the following
1000 1046
1001Third, JSON::XS recurses using the C stack when decoding objects and 1047Third, JSON::XS recurses using the C stack when decoding objects and
1002arrays. The C stack is a limited resource: for instance, on my amd64 1048arrays. The C stack is a limited resource: for instance, on my amd64
1003machine with 8MB of stack size I can decode around 180k nested arrays but 1049machine with 8MB of stack size I can decode around 180k nested arrays but
1004only 14k nested JSON objects (due to perl itself recursing deeply on croak 1050only 14k nested JSON objects (due to perl itself recursing deeply on croak
1005to free the temporary). If that is exceeded, the program crashes. to be 1051to free the temporary). If that is exceeded, the program crashes. To be
1006conservative, the default nesting limit is set to 512. If your process 1052conservative, the default nesting limit is set to 512. If your process
1007has a smaller stack, you should adjust this setting accordingly with the 1053has a smaller stack, you should adjust this setting accordingly with the
1008C<max_depth> method. 1054C<max_depth> method.
1009 1055
1010And last but least, something else could bomb you that I forgot to think 1056And last but least, something else could bomb you that I forgot to think
1014If you are using JSON::XS to return packets to consumption 1060If you are using JSON::XS to return packets to consumption
1015by JavaScript scripts in a browser you should have a look at 1061by JavaScript scripts in a browser you should have a look at
1016L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1062L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1017you are vulnerable to some common attack vectors (which really are browser 1063you are vulnerable to some common attack vectors (which really are browser
1018design bugs, but it is still you who will have to deal with it, as major 1064design bugs, but it is still you who will have to deal with it, as major
1019browser developers care only for features, not about doing security 1065browser developers care only for features, not about getting security
1020right). 1066right).
1021 1067
1022 1068
1023=head1 THREADS 1069=head1 THREADS
1024 1070

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