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Comparing JSON-XS/XS.pm (file contents):
Revision 1.74 by root, Wed Nov 28 13:57:15 2007 UTC vs.
Revision 1.81 by root, Sat Dec 29 17:33:38 2007 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);
22 $perl_scalar = $coder->decode ($unicode_json_text); 22 $perl_scalar = $coder->decode ($unicode_json_text);
23 23
24 # Note that JSON version 2.0 and above will automatically use JSON::XS
25 # if available, at virtually no speed overhead either, so you should
26 # be able to just:
27
28 use JSON;
29
30 # and do the same things, except that you have a pure-perl fallback now.
31
24=head1 DESCRIPTION 32=head1 DESCRIPTION
25 33
26This module converts Perl data structures to JSON and vice versa. Its 34This module converts Perl data structures to JSON and vice versa. Its
27primary goal is to be I<correct> and its secondary goal is to be 35primary goal is to be I<correct> and its secondary goal is to be
28I<fast>. To reach the latter goal it was written in C. 36I<fast>. To reach the latter goal it was written in C.
37
38Beginning with version 2.0 of the JSON module, when both JSON and
39JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40overriden) with no overhead due to emulation (by inheritign constructor
41and methods). If JSON::XS is not available, it will fall back to the
42compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43gives you a portable JSON API that can be fast when you need and doesn't
44require a C compiler when that is a problem.
29 45
30As this is the n-th-something JSON module on CPAN, what was the reason 46As this is the n-th-something JSON module on CPAN, what was the reason
31to write yet another JSON module? While it seems there are many JSON 47to write yet another JSON module? While it seems there are many JSON
32modules, none of them correctly handle all corner cases, and in most cases 48modules, none of them correctly handle all corner cases, and in most cases
33their maintainers are unresponsive, gone missing, or not listening to bug 49their maintainers are unresponsive, gone missing, or not listening to bug
84 100
85package JSON::XS; 101package JSON::XS;
86 102
87use strict; 103use strict;
88 104
89our $VERSION = '2.0'; 105our $VERSION = '2.01';
90our @ISA = qw(Exporter); 106our @ISA = qw(Exporter);
91 107
92our @EXPORT = qw(to_json from_json); 108our @EXPORT = qw(encode_json decode_json to_json from_json);
109
110sub to_json($) {
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}
93 119
94use Exporter; 120use Exporter;
95use XSLoader; 121use XSLoader;
96 122
97=head1 FUNCTIONAL INTERFACE 123=head1 FUNCTIONAL INTERFACE
99The following convenience methods are provided by this module. They are 125The following convenience methods are provided by this module. They are
100exported by default: 126exported by default:
101 127
102=over 4 128=over 4
103 129
104=item $json_text = to_json $perl_scalar 130=item $json_text = encode_json $perl_scalar
105 131
106Converts 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
107(that is, the string contains octets only). Croaks on error. 133(that is, the string contains octets only). Croaks on error.
108 134
109This function call is functionally identical to: 135This function call is functionally identical to:
110 136
111 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 137 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112 138
113except being faster. 139except being faster.
114 140
115=item $perl_scalar = from_json $json_text 141=item $perl_scalar = decode_json $json_text
116 142
117The 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
118to 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
119reference. Croaks on error. 145reference. Croaks on error.
120 146
121This function call is functionally identical to: 147This function call is functionally identical to:
122 148
427 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
428 => "Hello, World!" 454 => "Hello, World!"
429 455
430=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
431 457
432=item $enabled = $json->get_allow_bless 458=item $enabled = $json->get_allow_blessed
433 459
434If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
435barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
436B<convert_blessed> option will decide whether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
437disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
438object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
439encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
440 466
441If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
442exception when it encounters a blessed object. 468exception when it encounters a blessed object.
443 469
455The 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>
456returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
457way. 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
458(== 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
459methods 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
460usually 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>
461function. 487function or method.
462 488
463This 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
464future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
465enabled by this setting. 491enabled by this setting.
466 492
739Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
740exception 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
741C<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
742also 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.
743 769
744 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
745 771
746=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
747 773
748These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
749respectively. 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.
760difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
761JSON null value, scalars that have last been used in a string context 787JSON null value, scalars that have last been used in a string context
762before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
763 789
764 # dump as number 790 # dump as number
765 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
766 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
767 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
768 794
769 # used as string, so dump as string 795 # used as string, so dump as string
770 print $value; 796 print $value;
771 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
772 798
773 # undef becomes null 799 # undef becomes null
774 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
775 801
776You can force the type to be a JSON string by stringifying it: 802You can force the type to be a JSON string by stringifying it:
777 803
778 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
779 "$x"; # stringified 805 "$x"; # stringified
879=back 905=back
880 906
881 907
882=head2 JSON and YAML 908=head2 JSON and YAML
883 909
884You often hear that JSON is a subset (or a close subset) of YAML. This is, 910You often hear that JSON is a subset of YAML. This is, however, a mass
885however, a mass hysteria and very far from the truth. In general, there is 911hysteria and very far from the truth. In general, there is no way to
886no way to configure JSON::XS to output a data structure as valid YAML. 912configure JSON::XS to output a data structure as valid YAML that works for
913all cases.
887 914
888If you really must use JSON::XS to generate YAML, you should use this 915If you really must use JSON::XS to generate YAML, you should use this
889algorithm (subject to change in future versions): 916algorithm (subject to change in future versions):
890 917
891 my $to_yaml = JSON::XS->new->utf8->space_after (1); 918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
892 my $yaml = $to_yaml->encode ($ref) . "\n"; 919 my $yaml = $to_yaml->encode ($ref) . "\n";
893 920
894This will usually generate JSON texts that also parse as valid 921This will usually generate JSON texts that also parse as valid
895YAML. Please note that YAML has hardcoded limits on (simple) object key 922YAML. Please note that YAML has hardcoded limits on (simple) object key
896lengths that JSON doesn't have, so you should make sure that your hash 923lengths that JSON doesn't have and also has different and incompatible
924unicode handling, so you should make sure that your hash keys are
897keys are noticeably shorter than the 1024 characters YAML allows. 925noticeably shorter than the 1024 "stream characters" YAML allows and that
926you do not have codepoints with values outside the Unicode BMP (basic
927multilingual page). YAML also does not allow C<\/> sequences in strings
928(which JSON::XS does not I<currently> generate).
898 929
899There might be other incompatibilities that I am not aware of. In general 930There might be other incompatibilities that I am not aware of. In general
900you should not try to generate YAML with a JSON generator or vice versa, 931you should not try to generate YAML with a JSON generator or vice versa,
901or try to parse JSON with a YAML parser or vice versa: chances are high 932or try to parse JSON with a YAML parser or vice versa: chances are high
902that you will run into severe interoperability problems. 933that you will run into severe interoperability problems when you least
934expect it.
903 935
904 936
905=head2 SPEED 937=head2 SPEED
906 938
907It seems that JSON::XS is surprisingly fast, as shown in the following 939It seems that JSON::XS is surprisingly fast, as shown in the following
984 1016
985Third, JSON::XS recurses using the C stack when decoding objects and 1017Third, JSON::XS recurses using the C stack when decoding objects and
986arrays. The C stack is a limited resource: for instance, on my amd64 1018arrays. The C stack is a limited resource: for instance, on my amd64
987machine with 8MB of stack size I can decode around 180k nested arrays but 1019machine with 8MB of stack size I can decode around 180k nested arrays but
988only 14k nested JSON objects (due to perl itself recursing deeply on croak 1020only 14k nested JSON objects (due to perl itself recursing deeply on croak
989to free the temporary). If that is exceeded, the program crashes. to be 1021to free the temporary). If that is exceeded, the program crashes. To be
990conservative, the default nesting limit is set to 512. If your process 1022conservative, the default nesting limit is set to 512. If your process
991has a smaller stack, you should adjust this setting accordingly with the 1023has a smaller stack, you should adjust this setting accordingly with the
992C<max_depth> method. 1024C<max_depth> method.
993 1025
994And last but least, something else could bomb you that I forgot to think 1026And last but least, something else could bomb you that I forgot to think
998If you are using JSON::XS to return packets to consumption 1030If you are using JSON::XS to return packets to consumption
999by JavaScript scripts in a browser you should have a look at 1031by JavaScript scripts in a browser you should have a look at
1000L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1032L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1001you are vulnerable to some common attack vectors (which really are browser 1033you are vulnerable to some common attack vectors (which really are browser
1002design bugs, but it is still you who will have to deal with it, as major 1034design bugs, but it is still you who will have to deal with it, as major
1003browser developers care only for features, not about doing security 1035browser developers care only for features, not about getting security
1004right). 1036right).
1005 1037
1006 1038
1007=head1 THREADS 1039=head1 THREADS
1008 1040

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