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Revision 1.71 by root, Sun Nov 25 14:23:57 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 = '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
201 227
202 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 228 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
203 => {"a": [1, 2]} 229 => {"a": [1, 2]}
204 230
205=item $json = $json->ascii ([$enable]) 231=item $json = $json->ascii ([$enable])
232
233=item $enabled = $json->get_ascii
206 234
207If C<$enable> is true (or missing), then the C<encode> method will not 235If C<$enable> is true (or missing), then the C<encode> method will not
208generate characters outside the code range C<0..127> (which is ASCII). Any 236generate characters outside the code range C<0..127> (which is ASCII). Any
209Unicode characters outside that range will be escaped using either a 237Unicode characters outside that range will be escaped using either a
210single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, 238single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
223 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 251 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224 => ["\ud801\udc01"] 252 => ["\ud801\udc01"]
225 253
226=item $json = $json->latin1 ([$enable]) 254=item $json = $json->latin1 ([$enable])
227 255
256=item $enabled = $json->get_latin1
257
228If C<$enable> is true (or missing), then the C<encode> method will encode 258If C<$enable> is true (or missing), then the C<encode> method will encode
229the resulting JSON text as latin1 (or iso-8859-1), escaping any characters 259the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230outside the code range C<0..255>. The resulting string can be treated as a 260outside the code range C<0..255>. The resulting string can be treated as a
231latin1-encoded JSON text or a native Unicode string. The C<decode> method 261latin1-encoded JSON text or a native Unicode string. The C<decode> method
232will not be affected in any way by this flag, as C<decode> by default 262will not be affected in any way by this flag, as C<decode> by default
245 275
246 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 276 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 277 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248 278
249=item $json = $json->utf8 ([$enable]) 279=item $json = $json->utf8 ([$enable])
280
281=item $enabled = $json->get_utf8
250 282
251If C<$enable> is true (or missing), then the C<encode> method will encode 283If C<$enable> is true (or missing), then the C<encode> method will encode
252the JSON result into UTF-8, as required by many protocols, while the 284the JSON result into UTF-8, as required by many protocols, while the
253C<decode> method expects to be handled an UTF-8-encoded string. Please 285C<decode> method expects to be handled an UTF-8-encoded string. Please
254note that UTF-8-encoded strings do not contain any characters outside the 286note that UTF-8-encoded strings do not contain any characters outside the
288 ] 320 ]
289 } 321 }
290 322
291=item $json = $json->indent ([$enable]) 323=item $json = $json->indent ([$enable])
292 324
325=item $enabled = $json->get_indent
326
293If C<$enable> is true (or missing), then the C<encode> method will use a multiline 327If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294format as output, putting every array member or object/hash key-value pair 328format as output, putting every array member or object/hash key-value pair
295into its own line, indenting them properly. 329into its own line, indenting them properly.
296 330
297If C<$enable> is false, no newlines or indenting will be produced, and the 331If C<$enable> is false, no newlines or indenting will be produced, and the
299 333
300This setting has no effect when decoding JSON texts. 334This setting has no effect when decoding JSON texts.
301 335
302=item $json = $json->space_before ([$enable]) 336=item $json = $json->space_before ([$enable])
303 337
338=item $enabled = $json->get_space_before
339
304If C<$enable> is true (or missing), then the C<encode> method will add an extra 340If C<$enable> is true (or missing), then the C<encode> method will add an extra
305optional space before the C<:> separating keys from values in JSON objects. 341optional space before the C<:> separating keys from values in JSON objects.
306 342
307If C<$enable> is false, then the C<encode> method will not add any extra 343If C<$enable> is false, then the C<encode> method will not add any extra
308space at those places. 344space at those places.
313Example, space_before enabled, space_after and indent disabled: 349Example, space_before enabled, space_after and indent disabled:
314 350
315 {"key" :"value"} 351 {"key" :"value"}
316 352
317=item $json = $json->space_after ([$enable]) 353=item $json = $json->space_after ([$enable])
354
355=item $enabled = $json->get_space_after
318 356
319If C<$enable> is true (or missing), then the C<encode> method will add an extra 357If C<$enable> is true (or missing), then the C<encode> method will add an extra
320optional space after the C<:> separating keys from values in JSON objects 358optional space after the C<:> separating keys from values in JSON objects
321and extra whitespace after the C<,> separating key-value pairs and array 359and extra whitespace after the C<,> separating key-value pairs and array
322members. 360members.
329Example, space_before and indent disabled, space_after enabled: 367Example, space_before and indent disabled, space_after enabled:
330 368
331 {"key": "value"} 369 {"key": "value"}
332 370
333=item $json = $json->relaxed ([$enable]) 371=item $json = $json->relaxed ([$enable])
372
373=item $enabled = $json->get_relaxed
334 374
335If C<$enable> is true (or missing), then C<decode> will accept some 375If C<$enable> is true (or missing), then C<decode> will accept some
336extensions to normal JSON syntax (see below). C<encode> will not be 376extensions to normal JSON syntax (see below). C<encode> will not be
337affected in anyway. I<Be aware that this option makes you accept invalid 377affected in anyway. I<Be aware that this option makes you accept invalid
338JSON texts as if they were valid!>. I suggest only to use this option to 378JSON texts as if they were valid!>. I suggest only to use this option to
375 415
376=back 416=back
377 417
378=item $json = $json->canonical ([$enable]) 418=item $json = $json->canonical ([$enable])
379 419
420=item $enabled = $json->get_canonical
421
380If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 422If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381by sorting their keys. This is adding a comparatively high overhead. 423by sorting their keys. This is adding a comparatively high overhead.
382 424
383If C<$enable> is false, then the C<encode> method will output key-value 425If C<$enable> is false, then the C<encode> method will output key-value
384pairs in the order Perl stores them (which will likely change between runs 426pairs in the order Perl stores them (which will likely change between runs
391 433
392This setting has no effect when decoding JSON texts. 434This setting has no effect when decoding JSON texts.
393 435
394=item $json = $json->allow_nonref ([$enable]) 436=item $json = $json->allow_nonref ([$enable])
395 437
438=item $enabled = $json->get_allow_nonref
439
396If C<$enable> is true (or missing), then the C<encode> method can convert a 440If C<$enable> is true (or missing), then the C<encode> method can convert a
397non-reference into its corresponding string, number or null JSON value, 441non-reference into its corresponding string, number or null JSON value,
398which is an extension to RFC4627. Likewise, C<decode> will accept those JSON 442which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
399values instead of croaking. 443values instead of croaking.
400 444
409 JSON::XS->new->allow_nonref->encode ("Hello, World!") 453 JSON::XS->new->allow_nonref->encode ("Hello, World!")
410 => "Hello, World!" 454 => "Hello, World!"
411 455
412=item $json = $json->allow_blessed ([$enable]) 456=item $json = $json->allow_blessed ([$enable])
413 457
458=item $enabled = $json->get_allow_blessed
459
414If C<$enable> is true (or missing), then the C<encode> method will not 460If C<$enable> is true (or missing), then the C<encode> method will not
415barf when it encounters a blessed reference. Instead, the value of the 461barf when it encounters a blessed reference. Instead, the value of the
416B<convert_blessed> option will decide whether C<null> (C<convert_blessed> 462B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417disabled or no C<to_json> method found) or a representation of the 463disabled or no C<TO_JSON> method found) or a representation of the
418object (C<convert_blessed> enabled and C<to_json> method found) is being 464object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419encoded. Has no effect on C<decode>. 465encoded. Has no effect on C<decode>.
420 466
421If C<$enable> is false (the default), then C<encode> will throw an 467If C<$enable> is false (the default), then C<encode> will throw an
422exception when it encounters a blessed object. 468exception when it encounters a blessed object.
423 469
424=item $json = $json->convert_blessed ([$enable]) 470=item $json = $json->convert_blessed ([$enable])
471
472=item $enabled = $json->get_convert_blessed
425 473
426If C<$enable> is true (or missing), then C<encode>, upon encountering a 474If C<$enable> is true (or missing), then C<encode>, upon encountering a
427blessed object, will check for the availability of the C<TO_JSON> method 475blessed object, will check for the availability of the C<TO_JSON> method
428on the object's class. If found, it will be called in scalar context 476on the object's class. If found, it will be called in scalar context
429and the resulting scalar will be encoded instead of the object. If no 477and the resulting scalar will be encoded instead of the object. If no
433The 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>
434returns other blessed objects, those will be handled in the same 482returns other blessed objects, those will be handled in the same
435way. 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
436(== 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
437methods 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
438usually 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>
439function. 487function or method.
440 488
441This 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
442future, global hooks might get installed that influence C<decode> and are 490future, global hooks might get installed that influence C<decode> and are
443enabled by this setting. 491enabled by this setting.
444 492
520 568
521 { __widget__ => $self->{id} } 569 { __widget__ => $self->{id} }
522 } 570 }
523 571
524=item $json = $json->shrink ([$enable]) 572=item $json = $json->shrink ([$enable])
573
574=item $enabled = $json->get_shrink
525 575
526Perl usually over-allocates memory a bit when allocating space for 576Perl usually over-allocates memory a bit when allocating space for
527strings. This flag optionally resizes strings generated by either 577strings. This flag optionally resizes strings generated by either
528C<encode> or C<decode> to their minimum size possible. This can save 578C<encode> or C<decode> to their minimum size possible. This can save
529memory when your JSON texts are either very very long or you have many 579memory when your JSON texts are either very very long or you have many
547strings that look like integers or floats into integers or floats 597strings that look like integers or floats into integers or floats
548internally (there is no difference on the Perl level), saving space. 598internally (there is no difference on the Perl level), saving space.
549 599
550=item $json = $json->max_depth ([$maximum_nesting_depth]) 600=item $json = $json->max_depth ([$maximum_nesting_depth])
551 601
602=item $max_depth = $json->get_max_depth
603
552Sets the maximum nesting level (default C<512>) accepted while encoding 604Sets the maximum nesting level (default C<512>) accepted while encoding
553or decoding. If the JSON text or Perl data structure has an equal or 605or decoding. If the JSON text or Perl data structure has an equal or
554higher nesting level then this limit, then the encoder and decoder will 606higher nesting level then this limit, then the encoder and decoder will
555stop and croak at that point. 607stop and croak at that point.
556 608
567used, which is rarely useful. 619used, which is rarely useful.
568 620
569See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 621See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
570 622
571=item $json = $json->max_size ([$maximum_string_size]) 623=item $json = $json->max_size ([$maximum_string_size])
624
625=item $max_size = $json->get_max_size
572 626
573Set the maximum length a JSON text may have (in bytes) where decoding is 627Set the maximum length a JSON text may have (in bytes) where decoding is
574being attempted. The default is C<0>, meaning no limit. When C<decode> 628being attempted. The default is C<0>, meaning no limit. When C<decode>
575is called on a string longer then this number of characters it will not 629is called on a string longer then this number of characters it will not
576attempt to decode the string but throw an exception. This setting has no 630attempt to decode the string but throw an exception. This setting has no
711Other unblessed references are generally not allowed and will cause an 765Other unblessed references are generally not allowed and will cause an
712exception 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
713C<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
714also 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.
715 769
716 to_json [\0,JSON::XS::true] # yields [false,true] 770 encode_json [\0,JSON::XS::true] # yields [false,true]
717 771
718=item JSON::XS::true, JSON::XS::false 772=item JSON::XS::true, JSON::XS::false
719 773
720These special values become JSON true and JSON false values, 774These special values become JSON true and JSON false values,
721respectively. 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.
732difficult objects to encode: JSON::XS will encode undefined scalars as 786difficult objects to encode: JSON::XS will encode undefined scalars as
733JSON 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
734before encoding as JSON strings and anything else as number value: 788before encoding as JSON strings and anything else as number value:
735 789
736 # dump as number 790 # dump as number
737 to_json [2] # yields [2] 791 encode_json [2] # yields [2]
738 to_json [-3.0e17] # yields [-3e+17] 792 encode_json [-3.0e17] # yields [-3e+17]
739 my $value = 5; to_json [$value] # yields [5] 793 my $value = 5; encode_json [$value] # yields [5]
740 794
741 # used as string, so dump as string 795 # used as string, so dump as string
742 print $value; 796 print $value;
743 to_json [$value] # yields ["5"] 797 encode_json [$value] # yields ["5"]
744 798
745 # undef becomes null 799 # undef becomes null
746 to_json [undef] # yields [null] 800 encode_json [undef] # yields [null]
747 801
748You 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:
749 803
750 my $x = 3.1; # some variable containing a number 804 my $x = 3.1; # some variable containing a number
751 "$x"; # stringified 805 "$x"; # stringified
851=back 905=back
852 906
853 907
854=head2 JSON and YAML 908=head2 JSON and YAML
855 909
856You 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
857however, 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
858no 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.
859 914
860If 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
861algorithm (subject to change in future versions): 916algorithm (subject to change in future versions):
862 917
863 my $to_yaml = JSON::XS->new->utf8->space_after (1); 918 my $to_yaml = JSON::XS->new->utf8->space_after (1);
864 my $yaml = $to_yaml->encode ($ref) . "\n"; 919 my $yaml = $to_yaml->encode ($ref) . "\n";
865 920
866This will usually generate JSON texts that also parse as valid 921This will usually generate JSON texts that also parse as valid
867YAML. Please note that YAML has hardcoded limits on (simple) object key 922YAML. Please note that YAML has hardcoded limits on (simple) object key
868lengths 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
869keys 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).
870 929
871There 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
872you 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,
873or 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
874that you will run into severe interoperability problems. 933that you will run into severe interoperability problems when you least
934expect it.
875 935
876 936
877=head2 SPEED 937=head2 SPEED
878 938
879It 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
892with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables 952with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893shrink). Higher is better: 953shrink). Higher is better:
894 954
895 module | encode | decode | 955 module | encode | decode |
896 -----------|------------|------------| 956 -----------|------------|------------|
897 JSON | 4990.842 | 4088.813 | 957 JSON 1.x | 4990.842 | 4088.813 |
898 JSON::DWIW | 51653.990 | 71575.154 | 958 JSON::DWIW | 51653.990 | 71575.154 |
899 JSON::PC | 65948.176 | 74631.744 | 959 JSON::PC | 65948.176 | 74631.744 |
900 JSON::PP | 8931.652 | 3817.168 | 960 JSON::PP | 8931.652 | 3817.168 |
901 JSON::Syck | 24877.248 | 27776.848 | 961 JSON::Syck | 24877.248 | 27776.848 |
902 JSON::XS | 388361.481 | 227951.304 | 962 JSON::XS | 388361.481 | 227951.304 |
913Using a longer test string (roughly 18KB, generated from Yahoo! Locals 973Using a longer test string (roughly 18KB, generated from Yahoo! Locals
914search API (http://nanoref.com/yahooapis/mgPdGg): 974search API (http://nanoref.com/yahooapis/mgPdGg):
915 975
916 module | encode | decode | 976 module | encode | decode |
917 -----------|------------|------------| 977 -----------|------------|------------|
918 JSON | 55.260 | 34.971 | 978 JSON 1.x | 55.260 | 34.971 |
919 JSON::DWIW | 825.228 | 1082.513 | 979 JSON::DWIW | 825.228 | 1082.513 |
920 JSON::PC | 3571.444 | 2394.829 | 980 JSON::PC | 3571.444 | 2394.829 |
921 JSON::PP | 210.987 | 32.574 | 981 JSON::PP | 210.987 | 32.574 |
922 JSON::Syck | 552.551 | 787.544 | 982 JSON::Syck | 552.551 | 787.544 |
923 JSON::XS | 5780.463 | 4854.519 | 983 JSON::XS | 5780.463 | 4854.519 |
956 1016
957Third, JSON::XS recurses using the C stack when decoding objects and 1017Third, JSON::XS recurses using the C stack when decoding objects and
958arrays. 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
959machine 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
960only 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
961to 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
962conservative, the default nesting limit is set to 512. If your process 1022conservative, the default nesting limit is set to 512. If your process
963has a smaller stack, you should adjust this setting accordingly with the 1023has a smaller stack, you should adjust this setting accordingly with the
964C<max_depth> method. 1024C<max_depth> method.
965 1025
966And 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
970If you are using JSON::XS to return packets to consumption 1030If you are using JSON::XS to return packets to consumption
971by JavaScript scripts in a browser you should have a look at 1031by JavaScript scripts in a browser you should have a look at
972L<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
973you are vulnerable to some common attack vectors (which really are browser 1033you are vulnerable to some common attack vectors (which really are browser
974design 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
975browser developers care only for features, not about doing security 1035browser developers care only for features, not about getting security
976right). 1036right).
977 1037
978 1038
979=head1 THREADS 1039=head1 THREADS
980 1040

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