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Revision 1.72 by root, Sun Nov 25 19:11:07 2007 UTC vs.
Revision 1.80 by root, Sat Dec 29 17:22:39 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 = '1.53'; 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
276 302
277 use Encode; 303 use Encode;
278 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); 304 $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
279 305
280=item $json = $json->pretty ([$enable]) 306=item $json = $json->pretty ([$enable])
281
282=item $enabled = $json->get_pretty
283 307
284This enables (or disables) all of the C<indent>, C<space_before> and 308This enables (or disables) all of the C<indent>, C<space_before> and
285C<space_after> (and in the future possibly more) flags in one call to 309C<space_after> (and in the future possibly more) flags in one call to
286generate the most readable (or most compact) form possible. 310generate the most readable (or most compact) form possible.
287 311
429 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
430 => "Hello, World!" 454 => "Hello, World!"
431 455
432=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
433 457
434=item $enabled = $json->get_allow_bless 458=item $enabled = $json->get_allow_blessed
435 459
436If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
437barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
438B<convert_blessed> option will decide whether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
439disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
440object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
441encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
442 466
443If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
444exception when it encounters a blessed object. 468exception when it encounters a blessed object.
445 469
457The 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>
458returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
459way. 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
460(== 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
461methods 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
462usually 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>
463function. 487function or method.
464 488
465This 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
466future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
467enabled by this setting. 491enabled by this setting.
468 492
741Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
742exception 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
743C<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
744also 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.
745 769
746 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
747 771
748=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
749 773
750These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
751respectively. 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.
762difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
763JSON 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
764before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
765 789
766 # dump as number 790 # dump as number
767 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
768 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
769 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
770 794
771 # used as string, so dump as string 795 # used as string, so dump as string
772 print $value; 796 print $value;
773 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
774 798
775 # undef becomes null 799 # undef becomes null
776 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
777 801
778You 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:
779 803
780 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
781 "$x"; # stringified 805 "$x"; # stringified
881=back 905=back
882 906
883 907
884=head2 JSON and YAML 908=head2 JSON and YAML
885 909
886You 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
887however, 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
888no 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.
889 914
890If 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
891algorithm (subject to change in future versions): 916algorithm (subject to change in future versions):
892 917
893 my $to_yaml = JSON::XS->new->utf8->space_after (1); 918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
894 my $yaml = $to_yaml->encode ($ref) . "\n"; 919 my $yaml = $to_yaml->encode ($ref) . "\n";
895 920
896This will usually generate JSON texts that also parse as valid 921This will usually generate JSON texts that also parse as valid
897YAML. Please note that YAML has hardcoded limits on (simple) object key 922YAML. Please note that YAML has hardcoded limits on (simple) object key
898lengths 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
899keys 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).
900 928
901There might be other incompatibilities that I am not aware of. In general 929There might be other incompatibilities that I am not aware of. In general
902you should not try to generate YAML with a JSON generator or vice versa, 930you should not try to generate YAML with a JSON generator or vice versa,
903or try to parse JSON with a YAML parser or vice versa: chances are high 931or try to parse JSON with a YAML parser or vice versa: chances are high
904that you will run into severe interoperability problems. 932that you will run into severe interoperability problems when you least
933expect it.
905 934
906 935
907=head2 SPEED 936=head2 SPEED
908 937
909It seems that JSON::XS is surprisingly fast, as shown in the following 938It seems that JSON::XS is surprisingly fast, as shown in the following
986 1015
987Third, JSON::XS recurses using the C stack when decoding objects and 1016Third, JSON::XS recurses using the C stack when decoding objects and
988arrays. The C stack is a limited resource: for instance, on my amd64 1017arrays. The C stack is a limited resource: for instance, on my amd64
989machine with 8MB of stack size I can decode around 180k nested arrays but 1018machine with 8MB of stack size I can decode around 180k nested arrays but
990only 14k nested JSON objects (due to perl itself recursing deeply on croak 1019only 14k nested JSON objects (due to perl itself recursing deeply on croak
991to free the temporary). If that is exceeded, the program crashes. to be 1020to free the temporary). If that is exceeded, the program crashes. To be
992conservative, the default nesting limit is set to 512. If your process 1021conservative, the default nesting limit is set to 512. If your process
993has a smaller stack, you should adjust this setting accordingly with the 1022has a smaller stack, you should adjust this setting accordingly with the
994C<max_depth> method. 1023C<max_depth> method.
995 1024
996And last but least, something else could bomb you that I forgot to think 1025And last but least, something else could bomb you that I forgot to think
1000If you are using JSON::XS to return packets to consumption 1029If you are using JSON::XS to return packets to consumption
1001by JavaScript scripts in a browser you should have a look at 1030by JavaScript scripts in a browser you should have a look at
1002L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1031L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1003you are vulnerable to some common attack vectors (which really are browser 1032you are vulnerable to some common attack vectors (which really are browser
1004design bugs, but it is still you who will have to deal with it, as major 1033design bugs, but it is still you who will have to deal with it, as major
1005browser developers care only for features, not about doing security 1034browser developers care only for features, not about getting security
1006right). 1035right).
1007 1036
1008 1037
1009=head1 THREADS 1038=head1 THREADS
1010 1039

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