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1NAME 1NAME
2 JSON::XS - JSON serialising/deserialising, done correctly and fast 2 JSON::XS - JSON serialising/deserialising, done correctly and fast
3 3
4 JSON::XS - 正しくて高速な JSON 4 JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
5 シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) 5 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7 6
8SYNOPSIS 7SYNOPSIS
9 use JSON::XS; 8 use JSON::XS;
10 9
… …
21 $perl_scalar = $coder->decode ($unicode_json_text); 20 $perl_scalar = $coder->decode ($unicode_json_text);
22 21
23 # Note that JSON version 2.0 and above will automatically use JSON::XS 22 # Note that JSON version 2.0 and above will automatically use JSON::XS
24 # if available, at virtually no speed overhead either, so you should 23 # if available, at virtually no speed overhead either, so you should
25 # be able to just: 24 # be able to just:
26 25
27 use JSON; 26 use JSON;
28 27
29 # and do the same things, except that you have a pure-perl fallback now. 28 # and do the same things, except that you have a pure-perl fallback now.
30 29
31DESCRIPTION 30DESCRIPTION
32 This module converts Perl data structures to JSON and vice versa. Its 31 This module converts Perl data structures to JSON and vice versa. Its
… …
51 50
52 See MAPPING, below, on how JSON::XS maps perl values to JSON values and 51 See MAPPING, below, on how JSON::XS maps perl values to JSON values and
53 vice versa. 52 vice versa.
54 53
55 FEATURES 54 FEATURES
56 * correct Unicode handling 55 * correct Unicode handling
56
57 This module knows how to handle Unicode, and even documents how and 57 This module knows how to handle Unicode, documents how and when it
58 when it does so. 58 does so, and even documents what "correct" means.
59 59
60 * round-trip integrity 60 * round-trip integrity
61
61 When you serialise a perl data structure using only datatypes 62 When you serialise a perl data structure using only datatypes
62 supported by JSON, the deserialised data structure is identical on 63 supported by JSON, the deserialised data structure is identical on
63 the Perl level. (e.g. the string "2.0" doesn't suddenly become "2" 64 the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"
64 just because it looks like a number). 65 just because it looks like a number). There minor *are* exceptions
66 to this, read the MAPPING section below to learn about those.
65 67
66 * strict checking of JSON correctness 68 * strict checking of JSON correctness
69
67 There is no guessing, no generating of illegal JSON texts by 70 There is no guessing, no generating of illegal JSON texts by
68 default, and only JSON is accepted as input by default (the latter 71 default, and only JSON is accepted as input by default (the latter
69 is a security feature). 72 is a security feature).
70 73
71 * fast 74 * fast
72 Compared to other JSON modules, this module compares favourably in
73 terms of speed, too.
74 75
76 Compared to other JSON modules and other serialisers such as
77 Storable, this module usually compares favourably in terms of speed,
78 too.
79
75 * simple to use 80 * simple to use
81
76 This module has both a simple functional interface as well as an OO 82 This module has both a simple functional interface as well as an
77 interface. 83 objetc oriented interface interface.
78 84
79 * reasonably versatile output formats 85 * reasonably versatile output formats
86
80 You can choose between the most compact guaranteed single-line 87 You can choose between the most compact guaranteed-single-line
81 format possible (nice for simple line-based protocols), a pure-ascii 88 format possible (nice for simple line-based protocols), a pure-ascii
82 format (for when your transport is not 8-bit clean, still supports 89 format (for when your transport is not 8-bit clean, still supports
83 the whole Unicode range), or a pretty-printed format (for when you 90 the whole Unicode range), or a pretty-printed format (for when you
84 want to read that stuff). Or you can combine those features in 91 want to read that stuff). Or you can combine those features in
85 whatever way you like. 92 whatever way you like.
… …
125 1. Perl strings can store characters with ordinal values > 255. 132 1. Perl strings can store characters with ordinal values > 255.
126 This enables you to store Unicode characters as single characters in 133 This enables you to store Unicode characters as single characters in
127 a Perl string - very natural. 134 a Perl string - very natural.
128 135
129 2. Perl does *not* associate an encoding with your strings. 136 2. Perl does *not* associate an encoding with your strings.
130 Unless you force it to, e.g. when matching it against a regex, or 137 ... until you force it to, e.g. when matching it against a regex, or
131 printing the scalar to a file, in which case Perl either interprets 138 printing the scalar to a file, in which case Perl either interprets
132 your string as locale-encoded text, octets/binary, or as Unicode, 139 your string as locale-encoded text, octets/binary, or as Unicode,
133 depending on various settings. In no case is an encoding stored 140 depending on various settings. In no case is an encoding stored
134 together with your data, it is *use* that decides encoding, not any 141 together with your data, it is *use* that decides encoding, not any
135 magical metadata. 142 magical meta data.
136 143
137 3. The internal utf-8 flag has no meaning with regards to the encoding 144 3. The internal utf-8 flag has no meaning with regards to the encoding
138 of your string. 145 of your string.
139 Just ignore that flag unless you debug a Perl bug, a module written 146 Just ignore that flag unless you debug a Perl bug, a module written
140 in XS or want to dive into the internals of perl. Otherwise it will 147 in XS or want to dive into the internals of perl. Otherwise it will
… …
185 192
186 If $enable is false, then the "encode" method will not escape 193 If $enable is false, then the "encode" method will not escape
187 Unicode characters unless required by the JSON syntax or other 194 Unicode characters unless required by the JSON syntax or other
188 flags. This results in a faster and more compact format. 195 flags. This results in a faster and more compact format.
189 196
197 See also the section *ENCODING/CODESET FLAG NOTES* later in this
198 document.
199
190 The main use for this flag is to produce JSON texts that can be 200 The main use for this flag is to produce JSON texts that can be
191 transmitted over a 7-bit channel, as the encoded JSON texts will not 201 transmitted over a 7-bit channel, as the encoded JSON texts will not
192 contain any 8 bit characters. 202 contain any 8 bit characters.
193 203
194 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 204 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
… …
205 superset of latin1. 215 superset of latin1.
206 216
207 If $enable is false, then the "encode" method will not escape 217 If $enable is false, then the "encode" method will not escape
208 Unicode characters unless required by the JSON syntax or other 218 Unicode characters unless required by the JSON syntax or other
209 flags. 219 flags.
220
221 See also the section *ENCODING/CODESET FLAG NOTES* later in this
222 document.
210 223
211 The main use for this flag is efficiently encoding binary data as 224 The main use for this flag is efficiently encoding binary data as
212 JSON text, as most octets will not be escaped, resulting in a 225 JSON text, as most octets will not be escaped, resulting in a
213 smaller encoded size. The disadvantage is that the resulting JSON 226 smaller encoded size. The disadvantage is that the resulting JSON
214 text is encoded in latin1 (and must correctly be treated as such 227 text is encoded in latin1 (and must correctly be treated as such
… …
234 If $enable is false, then the "encode" method will return the JSON 247 If $enable is false, then the "encode" method will return the JSON
235 string as a (non-encoded) Unicode string, while "decode" expects 248 string as a (non-encoded) Unicode string, while "decode" expects
236 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or 249 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
237 UTF-16) needs to be done yourself, e.g. using the Encode module. 250 UTF-16) needs to be done yourself, e.g. using the Encode module.
238 251
252 See also the section *ENCODING/CODESET FLAG NOTES* later in this
253 document.
254
239 Example, output UTF-16BE-encoded JSON: 255 Example, output UTF-16BE-encoded JSON:
240 256
241 use Encode; 257 use Encode;
242 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); 258 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
243 259
… …
318 If $enable is false (the default), then "decode" will only accept 334 If $enable is false (the default), then "decode" will only accept
319 valid JSON texts. 335 valid JSON texts.
320 336
321 Currently accepted extensions are: 337 Currently accepted extensions are:
322 338
323 * list items can have an end-comma 339 * list items can have an end-comma
340
324 JSON *separates* array elements and key-value pairs with commas. 341 JSON *separates* array elements and key-value pairs with commas.
325 This can be annoying if you write JSON texts manually and want 342 This can be annoying if you write JSON texts manually and want
326 to be able to quickly append elements, so this extension accepts 343 to be able to quickly append elements, so this extension accepts
327 comma at the end of such items not just between them: 344 comma at the end of such items not just between them:
328 345
… …
333 { 350 {
334 "k1": "v1", 351 "k1": "v1",
335 "k2": "v2", <- this comma not normally allowed 352 "k2": "v2", <- this comma not normally allowed
336 } 353 }
337 354
338 * shell-style '#'-comments 355 * shell-style '#'-comments
356
339 Whenever JSON allows whitespace, shell-style comments are 357 Whenever JSON allows whitespace, shell-style comments are
340 additionally allowed. They are terminated by the first 358 additionally allowed. They are terminated by the first
341 carriage-return or line-feed character, after which more 359 carriage-return or line-feed character, after which more
342 white-space and comments are allowed. 360 white-space and comments are allowed.
343 361
… …
618 A JSON number becomes either an integer, numeric (floating point) or 636 A JSON number becomes either an integer, numeric (floating point) or
619 string scalar in perl, depending on its range and any fractional 637 string scalar in perl, depending on its range and any fractional
620 parts. On the Perl level, there is no difference between those as 638 parts. On the Perl level, there is no difference between those as
621 Perl handles all the conversion details, but an integer may take 639 Perl handles all the conversion details, but an integer may take
622 slightly less memory and might represent more values exactly than 640 slightly less memory and might represent more values exactly than
623 (floating point) numbers. 641 floating point numbers.
624 642
625 If the number consists of digits only, JSON::XS will try to 643 If the number consists of digits only, JSON::XS will try to
626 represent it as an integer value. If that fails, it will try to 644 represent it as an integer value. If that fails, it will try to
627 represent it as a numeric (floating point) value if that is possible 645 represent it as a numeric (floating point) value if that is possible
628 without loss of precision. Otherwise it will preserve the number as 646 without loss of precision. Otherwise it will preserve the number as
629 a string value. 647 a string value (in which case you lose roundtripping ability, as the
648 JSON number will be re-encoded toa JSON string).
630 649
631 Numbers containing a fractional or exponential part will always be 650 Numbers containing a fractional or exponential part will always be
632 represented as numeric (floating point) values, possibly at a loss 651 represented as numeric (floating point) values, possibly at a loss
633 of precision. 652 of precision (in which case you might lose perfect roundtripping
634 653 ability, but the JSON number will still be re-encoded as a JSON
635 This might create round-tripping problems as numbers might become 654 number).
636 strings, but as Perl is typeless there is no other way to do it.
637 655
638 true, false 656 true, false
639 These JSON atoms become "JSON::XS::true" and "JSON::XS::false", 657 These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
640 respectively. They are overloaded to act almost exactly like the 658 respectively. They are overloaded to act almost exactly like the
641 numbers 1 and 0. You can check whether a scalar is a JSON boolean by 659 numbers 1 and 0. You can check whether a scalar is a JSON boolean by
… …
676 JSON::XS::true, JSON::XS::false 694 JSON::XS::true, JSON::XS::false
677 These special values become JSON true and JSON false values, 695 These special values become JSON true and JSON false values,
678 respectively. You can also use "\1" and "\0" directly if you want. 696 respectively. You can also use "\1" and "\0" directly if you want.
679 697
680 blessed objects 698 blessed objects
681 Blessed objects are not allowed. JSON::XS currently tries to encode 699 Blessed objects are not directly representable in JSON. See the
682 their underlying representation (hash- or arrayref), but this 700 "allow_blessed" and "convert_blessed" methods on various options on
683 behaviour might change in future versions. 701 how to deal with this: basically, you can choose between throwing an
702 exception, encoding the reference as if it weren't blessed, or
703 provide your own serialiser method.
684 704
685 simple scalars 705 simple scalars
686 Simple Perl scalars (any scalar that is not a reference) are the 706 Simple Perl scalars (any scalar that is not a reference) are the
687 most difficult objects to encode: JSON::XS will encode undefined 707 most difficult objects to encode: JSON::XS will encode undefined
688 scalars as JSON null value, scalars that have last been used in a 708 scalars as JSON "null" values, scalars that have last been used in a
689 string context before encoding as JSON strings and anything else as 709 string context before encoding as JSON strings, and anything else as
690 number value: 710 number value:
691 711
692 # dump as number 712 # dump as number
693 encode_json [2] # yields [2] 713 encode_json [2] # yields [2]
694 encode_json [-3.0e17] # yields [-3e+17] 714 encode_json [-3.0e17] # yields [-3e+17]
… …
713 my $x = "3"; # some variable containing a string 733 my $x = "3"; # some variable containing a string
714 $x += 0; # numify it, ensuring it will be dumped as a number 734 $x += 0; # numify it, ensuring it will be dumped as a number
715 $x *= 1; # same thing, the choice is yours. 735 $x *= 1; # same thing, the choice is yours.
716 736
717 You can not currently force the type in other, less obscure, ways. 737 You can not currently force the type in other, less obscure, ways.
718 Tell me if you need this capability. 738 Tell me if you need this capability (but don't forget to explain why
739 its needed :).
740
741ENCODING/CODESET FLAG NOTES
742 The interested reader might have seen a number of flags that signify
743 encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
744 some confusion on what these do, so here is a short comparison:
745
746 "utf8" controls wether the JSON text created by "encode" (and expected
747 by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
748 control wether "encode" escapes character values outside their
749 respective codeset range. Neither of these flags conflict with each
750 other, although some combinations make less sense than others.
751
752 Care has been taken to make all flags symmetrical with respect to
753 "encode" and "decode", that is, texts encoded with any combination of
754 these flag values will be correctly decoded when the same flags are used
755 - in general, if you use different flag settings while encoding vs. when
756 decoding you likely have a bug somewhere.
757
758 Below comes a verbose discussion of these flags. Note that a "codeset"
759 is simply an abstract set of character-codepoint pairs, while an
760 encoding takes those codepoint numbers and *encodes* them, in our case
761 into octets. Unicode is (among other things) a codeset, UTF-8 is an
762 encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets *and*
763 encodings at the same time, which can be confusing.
764
765 "utf8" flag disabled
766 When "utf8" is disabled (the default), then "encode"/"decode"
767 generate and expect Unicode strings, that is, characters with high
768 ordinal Unicode values (> 255) will be encoded as such characters,
769 and likewise such characters are decoded as-is, no canges to them
770 will be done, except "(re-)interpreting" them as Unicode codepoints
771 or Unicode characters, respectively (to Perl, these are the same
772 thing in strings unless you do funny/weird/dumb stuff).
773
774 This is useful when you want to do the encoding yourself (e.g. when
775 you want to have UTF-16 encoded JSON texts) or when some other layer
776 does the encoding for you (for example, when printing to a terminal
777 using a filehandle that transparently encodes to UTF-8 you certainly
778 do NOT want to UTF-8 encode your data first and have Perl encode it
779 another time).
780
781 "utf8" flag enabled
782 If the "utf8"-flag is enabled, "encode"/"decode" will encode all
783 characters using the corresponding UTF-8 multi-byte sequence, and
784 will expect your input strings to be encoded as UTF-8, that is, no
785 "character" of the input string must have any value > 255, as UTF-8
786 does not allow that.
787
788 The "utf8" flag therefore switches between two modes: disabled means
789 you will get a Unicode string in Perl, enabled means you get an
790 UTF-8 encoded octet/binary string in Perl.
791
792 "latin1" or "ascii" flags enabled
793 With "latin1" (or "ascii") enabled, "encode" will escape characters
794 with ordinal values > 255 (> 127 with "ascii") and encode the
795 remaining characters as specified by the "utf8" flag.
796
797 If "utf8" is disabled, then the result is also correctly encoded in
798 those character sets (as both are proper subsets of Unicode, meaning
799 that a Unicode string with all character values < 256 is the same
800 thing as a ISO-8859-1 string, and a Unicode string with all
801 character values < 128 is the same thing as an ASCII string in
802 Perl).
803
804 If "utf8" is enabled, you still get a correct UTF-8-encoded string,
805 regardless of these flags, just some more characters will be escaped
806 using "\uXXXX" then before.
807
808 Note that ISO-8859-1-*encoded* strings are not compatible with UTF-8
809 encoding, while ASCII-encoded strings are. That is because the
810 ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
811 *codeset* being a subset of Unicode), while ASCII is.
812
813 Surprisingly, "decode" will ignore these flags and so treat all
814 input values as governed by the "utf8" flag. If it is disabled, this
815 allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
816 strict subsets of Unicode. If it is enabled, you can correctly
817 decode UTF-8 encoded strings.
818
819 So neither "latin1" nor "ascii" are incompatible with the "utf8"
820 flag - they only govern when the JSON output engine escapes a
821 character or not.
822
823 The main use for "latin1" is to relatively efficiently store binary
824 data as JSON, at the expense of breaking compatibility with most
825 JSON decoders.
826
827 The main use for "ascii" is to force the output to not contain
828 characters with values > 127, which means you can interpret the
829 resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
830 any character set and 8-bit-encoding, and still get the same data
831 structure back. This is useful when your channel for JSON transfer
832 is not 8-bit clean or the encoding might be mangled in between (e.g.
833 in mail), and works because ASCII is a proper subset of most 8-bit
834 and multibyte encodings in use in the world.
719 835
720COMPARISON 836COMPARISON
721 As already mentioned, this module was created because none of the 837 As already mentioned, this module was created because none of the
722 existing JSON modules could be made to work correctly. First I will 838 existing JSON modules could be made to work correctly. First I will
723 describe the problems (or pleasures) I encountered with various existing 839 describe the problems (or pleasures) I encountered with various existing
724 JSON modules, followed by some benchmark values. JSON::XS was designed 840 JSON modules, followed by some benchmark values. JSON::XS was designed
725 not to suffer from any of these problems or limitations. 841 not to suffer from any of these problems or limitations.
842
843 JSON 2.xx
844 A marvellous piece of engineering, this module either uses JSON::XS
845 directly when available (so will be 100% compatible with it,
846 including speed), or it uses JSON::PP, which is basically JSON::XS
847 translated to Pure Perl, which should be 100% compatible with
848 JSON::XS, just a bit slower.
849
850 You cannot really lose by using this module, especially as it tries
851 very hard to work even with ancient Perl versions, while JSON::XS
852 does not.
726 853
727 JSON 1.07 854 JSON 1.07
728 Slow (but very portable, as it is written in pure Perl). 855 Slow (but very portable, as it is written in pure Perl).
729 856
730 Undocumented/buggy Unicode handling (how JSON handles Unicode values 857 Undocumented/buggy Unicode handling (how JSON handles Unicode values
… …
795 empty keys result in nothing being output) 922 empty keys result in nothing being output)
796 923
797 Does not check input for validity. 924 Does not check input for validity.
798 925
799 JSON and YAML 926 JSON and YAML
800 You often hear that JSON is a subset (or a close subset) of YAML. This 927 You often hear that JSON is a subset of YAML. This is, however, a mass
801 is, however, a mass hysteria and very far from the truth. In general, 928 hysteria(*) and very far from the truth (as of the time of this
802 there is no way to configure JSON::XS to output a data structure as 929 writing), so let me state it clearly: *in general, there is no way to
803 valid YAML. 930 configure JSON::XS to output a data structure as valid YAML* that works
931 in all cases.
804 932
805 If you really must use JSON::XS to generate YAML, you should use this 933 If you really must use JSON::XS to generate YAML, you should use this
806 algorithm (subject to change in future versions): 934 algorithm (subject to change in future versions):
807 935
808 my $to_yaml = JSON::XS->new->utf8->space_after (1); 936 my $to_yaml = JSON::XS->new->utf8->space_after (1);
809 my $yaml = $to_yaml->encode ($ref) . "\n"; 937 my $yaml = $to_yaml->encode ($ref) . "\n";
810 938
811 This will usually generate JSON texts that also parse as valid YAML. 939 This will *usually* generate JSON texts that also parse as valid YAML.
812 Please note that YAML has hardcoded limits on (simple) object key 940 Please note that YAML has hardcoded limits on (simple) object key
813 lengths that JSON doesn't have, so you should make sure that your hash 941 lengths that JSON doesn't have and also has different and incompatible
942 unicode handling, so you should make sure that your hash keys are
814 keys are noticeably shorter than the 1024 characters YAML allows. 943 noticeably shorter than the 1024 "stream characters" YAML allows and
944 that you do not have characters with codepoint values outside the
945 Unicode BMP (basic multilingual page). YAML also does not allow "\/"
946 sequences in strings (which JSON::XS does not *currently* generate, but
947 other JSON generators might).
815 948
816 There might be other incompatibilities that I am not aware of. In 949 There might be other incompatibilities that I am not aware of (or the
950 YAML specification has been changed yet again - it does so quite often).
817 general you should not try to generate YAML with a JSON generator or 951 In general you should not try to generate YAML with a JSON generator or
818 vice versa, or try to parse JSON with a YAML parser or vice versa: 952 vice versa, or try to parse JSON with a YAML parser or vice versa:
819 chances are high that you will run into severe interoperability 953 chances are high that you will run into severe interoperability problems
820 problems. 954 when you least expect it.
955
956 (*) I have been pressured multiple times by Brian Ingerson (one of the
957 authors of the YAML specification) to remove this paragraph, despite
958 him acknowledging that the actual incompatibilities exist. As I was
959 personally bitten by this "JSON is YAML" lie, I refused and said I
960 will continue to educate people about these issues, so others do not
961 run into the same problem again and again. After this, Brian called
962 me a (quote)*complete and worthless idiot*(unquote).
963
964 In my opinion, instead of pressuring and insulting people who
965 actually clarify issues with YAML and the wrong statements of some
966 of its proponents, I would kindly suggest reading the JSON spec
967 (which is not that difficult or long) and finally make YAML
968 compatible to it, and educating users about the changes, instead of
969 spreading lies about the real compatibility for many *years* and
970 trying to silence people who point out that it isn't true.
821 971
822 SPEED 972 SPEED
823 It seems that JSON::XS is surprisingly fast, as shown in the following 973 It seems that JSON::XS is surprisingly fast, as shown in the following
824 tables. They have been generated with the help of the "eg/bench" program 974 tables. They have been generated with the help of the "eg/bench" program
825 in the JSON::XS distribution, to make it easy to compare on your own 975 in the JSON::XS distribution, to make it easy to compare on your own
826 system. 976 system.
827 977
828 First comes a comparison between various modules using a very short 978 First comes a comparison between various modules using a very short
829 single-line JSON string: 979 single-line JSON string (also available at
980 <http://dist.schmorp.de/misc/json/short.json>).
830 981
831 {"method": "handleMessage", "params": ["user1", "we were just talking"], \ 982 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
832 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} 983 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
833 984
834 It shows the number of encodes/decodes per second (JSON::XS uses the 985 It shows the number of encodes/decodes per second (JSON::XS uses the
… …
853 encoding, about three times faster on decoding, and over forty times 1004 encoding, about three times faster on decoding, and over forty times
854 faster than JSON, even with pretty-printing and key sorting. It also 1005 faster than JSON, even with pretty-printing and key sorting. It also
855 compares favourably to Storable for small amounts of data. 1006 compares favourably to Storable for small amounts of data.
856 1007
857 Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1008 Using a longer test string (roughly 18KB, generated from Yahoo! Locals
858 search API (http://nanoref.com/yahooapis/mgPdGg): 1009 search API (<http://dist.schmorp.de/misc/json/long.json>).
859 1010
860 module | encode | decode | 1011 module | encode | decode |
861 -----------|------------|------------| 1012 -----------|------------|------------|
862 JSON 1.x | 55.260 | 34.971 | 1013 JSON 1.x | 55.260 | 34.971 |
863 JSON::DWIW | 825.228 | 1082.513 | 1014 JSON::DWIW | 825.228 | 1082.513 |
… …
900 Third, JSON::XS recurses using the C stack when decoding objects and 1051 Third, JSON::XS recurses using the C stack when decoding objects and
901 arrays. The C stack is a limited resource: for instance, on my amd64 1052 arrays. The C stack is a limited resource: for instance, on my amd64
902 machine with 8MB of stack size I can decode around 180k nested arrays 1053 machine with 8MB of stack size I can decode around 180k nested arrays
903 but only 14k nested JSON objects (due to perl itself recursing deeply on 1054 but only 14k nested JSON objects (due to perl itself recursing deeply on
904 croak to free the temporary). If that is exceeded, the program crashes. 1055 croak to free the temporary). If that is exceeded, the program crashes.
905 to be conservative, the default nesting limit is set to 512. If your 1056 To be conservative, the default nesting limit is set to 512. If your
906 process has a smaller stack, you should adjust this setting accordingly 1057 process has a smaller stack, you should adjust this setting accordingly
907 with the "max_depth" method. 1058 with the "max_depth" method.
908 1059
909 And last but least, something else could bomb you that I forgot to think 1060 Something else could bomb you, too, that I forgot to think of. In that
910 of. In that case, you get to keep the pieces. I am always open for 1061 case, you get to keep the pieces. I am always open for hints, though...
911 hints, though... 1062
1063 Also keep in mind that JSON::XS might leak contents of your Perl data
1064 structures in its error messages, so when you serialise sensitive
1065 information you might want to make sure that exceptions thrown by
1066 JSON::XS will not end up in front of untrusted eyes.
912 1067
913 If you are using JSON::XS to return packets to consumption by JavaScript 1068 If you are using JSON::XS to return packets to consumption by JavaScript
914 scripts in a browser you should have a look at 1069 scripts in a browser you should have a look at
915 <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether 1070 <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
916 you are vulnerable to some common attack vectors (which really are 1071 you are vulnerable to some common attack vectors (which really are
917 browser design bugs, but it is still you who will have to deal with it, 1072 browser design bugs, but it is still you who will have to deal with it,
918 as major browser developers care only for features, not about doing 1073 as major browser developers care only for features, not about getting
919 security right). 1074 security right).
920 1075
921THREADS 1076THREADS
922 This module is *not* guaranteed to be thread safe and there are no plans 1077 This module is *not* guaranteed to be thread safe and there are no plans
923 to change this until Perl gets thread support (as opposed to the 1078 to change this until Perl gets thread support (as opposed to the

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