[ViewVC] Diff of: cvs/JSON-XS/XS.pm

Comparing JSON-XS/XS.pm (file contents):
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC vs.
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
10	use JSON::XS;	12	use JSON::XS;
11		13
12	# exported functions, they croak on error	14	# exported functions, they croak on error
13	# and expect/generate UTF-8	15	# and expect/generate UTF-8
14		16
15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17		19
18	# OO-interface	20	# OO-interface
19		21
20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
22	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
23		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
24	=head1 DESCRIPTION	34	=head1 DESCRIPTION
25		35
26	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
27	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
28	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overridden) with no overhead due to emulation (by inheriting constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
29		47
30	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
31	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
32	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
33	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
…		…
42		60
43	=over 4	61	=over 4
44		62
45	=item * correct Unicode handling	63	=item * correct Unicode handling
46		64
47	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
48	it does so.	66	so, and even documents what "correct" means.
49		67
50	=item * round-trip integrity	68	=item * round-trip integrity
51		69
52	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only data types supported
53	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
54	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
55	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
56		75
57	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
58		77
59	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
60	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
61	feature).	80	feature).
62		81
63	=item * fast	82	=item * fast
64		83
65	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
66	of speed, too.	85	this module usually compares favourably in terms of speed, too.
67		86
68	=item * simple to use	87	=item * simple to use
69		88
70	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an object
71	interface.	90	oriented interface interface.
72		91
73	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
74		93
75	You can choose between the most compact guaranteed single-line format	94	You can choose between the most compact guaranteed-single-line format
76	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ASCII format
77	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
78	Unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
79	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
80		99
81	=back	100	=back
82		101
83	=cut	102	=cut
84		103
85	package JSON::XS;	104	package JSON::XS;
86		105
		106	no warnings;
87	use strict;	107	use strict;
88		108
89	our $VERSION = '1.6';	109	our $VERSION = '2.2222';
90	our @ISA = qw(Exporter);	110	our @ISA = qw(Exporter);
91		111
92	our @EXPORT = qw(to_json from_json);	112	our @EXPORT = qw(encode_json decode_json to_json from_json);
		113
		114	sub to_json($) {
		115	require Carp;
		116	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");
		117	}
		118
		119	sub from_json($) {
		120	require Carp;
		121	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");
		122	}
93		123
94	use Exporter;	124	use Exporter;
95	use XSLoader;	125	use XSLoader;
96		126
97	=head1 FUNCTIONAL INTERFACE	127	=head1 FUNCTIONAL INTERFACE
…		…
99	The following convenience methods are provided by this module. They are	129	The following convenience methods are provided by this module. They are
100	exported by default:	130	exported by default:
101		131
102	=over 4	132	=over 4
103		133
104	=item $json_text = to_json $perl_scalar	134	=item $json_text = encode_json $perl_scalar
105		135
106	Converts the given Perl data structure to a UTF-8 encoded, binary string	136	Converts the given Perl data structure to a UTF-8 encoded, binary string
107	(that is, the string contains octets only). Croaks on error.	137	(that is, the string contains octets only). Croaks on error.
108		138
109	This function call is functionally identical to:	139	This function call is functionally identical to:
110		140
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	141	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		142
113	except being faster.	143	Except being faster.
114		144
115	=item $perl_scalar = from_json $json_text	145	=item $perl_scalar = decode_json $json_text
116		146
117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	147	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
118	to parse that as an UTF-8 encoded JSON text, returning the resulting	148	to parse that as an UTF-8 encoded JSON text, returning the resulting
119	reference. Croaks on error.	149	reference. Croaks on error.
120		150
121	This function call is functionally identical to:	151	This function call is functionally identical to:
122		152
123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	153	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
124		154
125	except being faster.	155	Except being faster.
126		156
127	=item $is_boolean = JSON::XS::is_bool $scalar	157	=item $is_boolean = JSON::XS::is_bool $scalar
128		158
129	Returns true if the passed scalar represents either JSON::XS::true or	159	Returns true if the passed scalar represents either JSON::XS::true or
130	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	160	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
148	This enables you to store Unicode characters as single characters in a	178	This enables you to store Unicode characters as single characters in a
149	Perl string - very natural.	179	Perl string - very natural.
150		180
151	=item 2. Perl does I<not> associate an encoding with your strings.	181	=item 2. Perl does I<not> associate an encoding with your strings.
152		182
153	Unless you force it to, e.g. when matching it against a regex, or printing	183	... until you force it to, e.g. when matching it against a regex, or
154	the scalar to a file, in which case Perl either interprets your string as	184	printing the scalar to a file, in which case Perl either interprets your
155	locale-encoded text, octets/binary, or as Unicode, depending on various	185	string as locale-encoded text, octets/binary, or as Unicode, depending
156	settings. In no case is an encoding stored together with your data, it is	186	on various settings. In no case is an encoding stored together with your
157	I<use> that decides encoding, not any magical metadata.	187	data, it is I<use> that decides encoding, not any magical meta data.
158		188
159	=item 3. The internal utf-8 flag has no meaning with regards to the	189	=item 3. The internal utf-8 flag has no meaning with regards to the
160	encoding of your string.	190	encoding of your string.
161		191
162	Just ignore that flag unless you debug a Perl bug, a module written in	192	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
168		198
169	If you didn't know about that flag, just the better, pretend it doesn't	199	If you didn't know about that flag, just the better, pretend it doesn't
170	exist.	200	exist.
171		201
172	=item 4. A "Unicode String" is simply a string where each character can be	202	=item 4. A "Unicode String" is simply a string where each character can be
173	validly interpreted as a Unicode codepoint.	203	validly interpreted as a Unicode code point.
174		204
175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	205	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
176	Unicode string encoded in UTF-8, giving you a binary string.	206	Unicode string encoded in UTF-8, giving you a binary string.
177		207
178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	208	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
216		246
217	If C<$enable> is false, then the C<encode> method will not escape Unicode	247	If C<$enable> is false, then the C<encode> method will not escape Unicode
218	characters unless required by the JSON syntax or other flags. This results	248	characters unless required by the JSON syntax or other flags. This results
219	in a faster and more compact format.	249	in a faster and more compact format.
220		250
		251	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		252	document.
		253
221	The main use for this flag is to produce JSON texts that can be	254	The main use for this flag is to produce JSON texts that can be
222	transmitted over a 7-bit channel, as the encoded JSON texts will not	255	transmitted over a 7-bit channel, as the encoded JSON texts will not
223	contain any 8 bit characters.	256	contain any 8 bit characters.
224		257
225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	258	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
236	will not be affected in any way by this flag, as C<decode> by default	269	will not be affected in any way by this flag, as C<decode> by default
237	expects Unicode, which is a strict superset of latin1.	270	expects Unicode, which is a strict superset of latin1.
238		271
239	If C<$enable> is false, then the C<encode> method will not escape Unicode	272	If C<$enable> is false, then the C<encode> method will not escape Unicode
240	characters unless required by the JSON syntax or other flags.	273	characters unless required by the JSON syntax or other flags.
		274
		275	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		276	document.
241		277
242	The main use for this flag is efficiently encoding binary data as JSON	278	The main use for this flag is efficiently encoding binary data as JSON
243	text, as most octets will not be escaped, resulting in a smaller encoded	279	text, as most octets will not be escaped, resulting in a smaller encoded
244	size. The disadvantage is that the resulting JSON text is encoded	280	size. The disadvantage is that the resulting JSON text is encoded
245	in latin1 (and must correctly be treated as such when storing and	281	in latin1 (and must correctly be treated as such when storing and
…		…
265	If C<$enable> is false, then the C<encode> method will return the JSON	301	If C<$enable> is false, then the C<encode> method will return the JSON
266	string as a (non-encoded) Unicode string, while C<decode> expects thus a	302	string as a (non-encoded) Unicode string, while C<decode> expects thus a
267	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	303	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
268	to be done yourself, e.g. using the Encode module.	304	to be done yourself, e.g. using the Encode module.
269		305
		306	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		307	document.
		308
270	Example, output UTF-16BE-encoded JSON:	309	Example, output UTF-16BE-encoded JSON:
271		310
272	use Encode;	311	use Encode;
273	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	312	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
274		313
…		…
276		315
277	use Encode;	316	use Encode;
278	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);	317	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
279		318
280	=item $json = $json->pretty ([$enable])	319	=item $json = $json->pretty ([$enable])
281
282	=item $enabled = $json->get_pretty
283		320
284	This enables (or disables) all of the C<indent>, C<space_before> and	321	This enables (or disables) all of the C<indent>, C<space_before> and
285	C<space_after> (and in the future possibly more) flags in one call to	322	C<space_after> (and in the future possibly more) flags in one call to
286	generate the most readable (or most compact) form possible.	323	generate the most readable (or most compact) form possible.
287		324
…		…
427	resulting in an invalid JSON text:	464	resulting in an invalid JSON text:
428		465
429	JSON::XS->new->allow_nonref->encode ("Hello, World!")	466	JSON::XS->new->allow_nonref->encode ("Hello, World!")
430	=> "Hello, World!"	467	=> "Hello, World!"
431		468
		469	=item $json = $json->allow_unknown ([$enable])
		470
		471	=item $enabled = $json->get_allow_unknown
		472
		473	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		474	exception when it encounters values it cannot represent in JSON (for
		475	example, filehandles) but instead will encode a JSON C<null> value. Note
		476	that blessed objects are not included here and are handled separately by
		477	c<allow_nonref>.
		478
		479	If C<$enable> is false (the default), then C<encode> will throw an
		480	exception when it encounters anything it cannot encode as JSON.
		481
		482	This option does not affect C<decode> in any way, and it is recommended to
		483	leave it off unless you know your communications partner.
		484
432	=item $json = $json->allow_blessed ([$enable])	485	=item $json = $json->allow_blessed ([$enable])
433		486
434	=item $enabled = $json->get_allow_bless	487	=item $enabled = $json->get_allow_blessed
435		488
436	If C<$enable> is true (or missing), then the C<encode> method will not	489	If C<$enable> is true (or missing), then the C<encode> method will not
437	barf when it encounters a blessed reference. Instead, the value of the	490	barf when it encounters a blessed reference. Instead, the value of the
438	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	491	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
439	disabled or no C<to_json> method found) or a representation of the	492	disabled or no C<TO_JSON> method found) or a representation of the
440	object (C<convert_blessed> enabled and C<to_json> method found) is being	493	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
441	encoded. Has no effect on C<decode>.	494	encoded. Has no effect on C<decode>.
442		495
443	If C<$enable> is false (the default), then C<encode> will throw an	496	If C<$enable> is false (the default), then C<encode> will throw an
444	exception when it encounters a blessed object.	497	exception when it encounters a blessed object.
445		498
…		…
457	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	510	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
458	returns other blessed objects, those will be handled in the same	511	returns other blessed objects, those will be handled in the same
459	way. C<TO_JSON> must take care of not causing an endless recursion cycle	512	way. 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	513	(== crash) in this case. The name of C<TO_JSON> was chosen because other
461	methods called by the Perl core (== not by the user of the object) are	514	methods called by the Perl core (== not by the user of the object) are
462	usually in upper case letters and to avoid collisions with the C<to_json>	515	usually in upper case letters and to avoid collisions with any C<to_json>
463	function.	516	function or method.
464		517
465	This setting does not yet influence C<decode> in any way, but in the	518	This setting does not yet influence C<decode> in any way, but in the
466	future, global hooks might get installed that influence C<decode> and are	519	future, global hooks might get installed that influence C<decode> and are
467	enabled by this setting.	520	enabled by this setting.
468		521
…		…
576	=item $json = $json->max_depth ([$maximum_nesting_depth])	629	=item $json = $json->max_depth ([$maximum_nesting_depth])
577		630
578	=item $max_depth = $json->get_max_depth	631	=item $max_depth = $json->get_max_depth
579		632
580	Sets the maximum nesting level (default C<512>) accepted while encoding	633	Sets the maximum nesting level (default C<512>) accepted while encoding
581	or decoding. If the JSON text or Perl data structure has an equal or	634	or decoding. If a higher nesting level is detected in JSON text or a Perl
582	higher nesting level then this limit, then the encoder and decoder will	635	data structure, then the encoder and decoder will stop and croak at that
583	stop and croak at that point.	636	point.
584		637
585	Nesting level is defined by number of hash- or arrayrefs that the encoder	638	Nesting level is defined by number of hash- or arrayrefs that the encoder
586	needs to traverse to reach a given point or the number of C<{> or C<[>	639	needs to traverse to reach a given point or the number of C<{> or C<[>
587	characters without their matching closing parenthesis crossed to reach a	640	characters without their matching closing parenthesis crossed to reach a
588	given character in a string.	641	given character in a string.
589		642
590	Setting the maximum depth to one disallows any nesting, so that ensures	643	Setting the maximum depth to one disallows any nesting, so that ensures
591	that the object is only a single hash/object or array.	644	that the object is only a single hash/object or array.
592		645
593	The argument to C<max_depth> will be rounded up to the next highest power
594	of two. If no argument is given, the highest possible setting will be	646	If no argument is given, the highest possible setting will be used, which
595	used, which is rarely useful.	647	is rarely useful.
		648
		649	Note that nesting is implemented by recursion in C. The default value has
		650	been chosen to be as large as typical operating systems allow without
		651	crashing.
596		652
597	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	653	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
598		654
599	=item $json = $json->max_size ([$maximum_string_size])	655	=item $json = $json->max_size ([$maximum_string_size])
600		656
601	=item $max_size = $json->get_max_size	657	=item $max_size = $json->get_max_size
602		658
603	Set the maximum length a JSON text may have (in bytes) where decoding is	659	Set the maximum length a JSON text may have (in bytes) where decoding is
604	being attempted. The default is C<0>, meaning no limit. When C<decode>	660	being attempted. The default is C<0>, meaning no limit. When C<decode>
605	is called on a string longer then this number of characters it will not	661	is called on a string that is longer then this many bytes, it will not
606	attempt to decode the string but throw an exception. This setting has no	662	attempt to decode the string but throw an exception. This setting has no
607	effect on C<encode> (yet).	663	effect on C<encode> (yet).
608		664
609	The argument to C<max_size> will be rounded up to the next B<highest>	665	If no argument is given, the limit check will be deactivated (same as when
610	power of two (so may be more than requested). If no argument is given, the	666	C<0> is specified).
611	limit check will be deactivated (same as when C<0> is specified).
612		667
613	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	668	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
614		669
615	=item $json_text = $json->encode ($perl_scalar)	670	=item $json_text = $json->encode ($perl_scalar)
616		671
…		…
645	=> ([], 3)	700	=> ([], 3)
646		701
647	=back	702	=back
648		703
649		704
		705	=head1 INCREMENTAL PARSING
		706
		707	In some cases, there is the need for incremental parsing of JSON
		708	texts. While this module always has to keep both JSON text and resulting
		709	Perl data structure in memory at one time, it does allow you to parse a
		710	JSON stream incrementally. It does so by accumulating text until it has
		711	a full JSON object, which it then can decode. This process is similar to
		712	using C<decode_prefix> to see if a full JSON object is available, but
		713	is much more efficient (and can be implemented with a minimum of method
		714	calls).
		715
		716	JSON::XS will only attempt to parse the JSON text once it is sure it
		717	has enough text to get a decisive result, using a very simple but
		718	truly incremental parser. This means that it sometimes won't stop as
		719	early as the full parser, for example, it doesn't detect parenthese
		720	mismatches. The only thing it guarantees is that it starts decoding as
		721	soon as a syntactically valid JSON text has been seen. This means you need
		722	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		723	parsing in the presence if syntax errors.
		724
		725	The following methods implement this incremental parser.
		726
		727	=over 4
		728
		729	=item [void, scalar or list context] = $json->incr_parse ([$string])
		730
		731	This is the central parsing function. It can both append new text and
		732	extract objects from the stream accumulated so far (both of these
		733	functions are optional).
		734
		735	If C<$string> is given, then this string is appended to the already
		736	existing JSON fragment stored in the C<$json> object.
		737
		738	After that, if the function is called in void context, it will simply
		739	return without doing anything further. This can be used to add more text
		740	in as many chunks as you want.
		741
		742	If the method is called in scalar context, then it will try to extract
		743	exactly I<one> JSON object. If that is successful, it will return this
		744	object, otherwise it will return C<undef>. If there is a parse error,
		745	this method will croak just as C<decode> would do (one can then use
		746	C<incr_skip> to skip the errornous part). This is the most common way of
		747	using the method.
		748
		749	And finally, in list context, it will try to extract as many objects
		750	from the stream as it can find and return them, or the empty list
		751	otherwise. For this to work, there must be no separators between the JSON
		752	objects or arrays, instead they must be concatenated back-to-back. If
		753	an error occurs, an exception will be raised as in the scalar context
		754	case. Note that in this case, any previously-parsed JSON texts will be
		755	lost.
		756
		757	=item $lvalue_string = $json->incr_text
		758
		759	This method returns the currently stored JSON fragment as an lvalue, that
		760	is, you can manipulate it. This I<only> works when a preceding call to
		761	C<incr_parse> in I<scalar context> successfully returned an object. Under
		762	all other circumstances you must not call this function (I mean it.
		763	although in simple tests it might actually work, it I<will> fail under
		764	real world conditions). As a special exception, you can also call this
		765	method before having parsed anything.
		766
		767	This function is useful in two cases: a) finding the trailing text after a
		768	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		769	(such as commas).
		770
		771	=item $json->incr_skip
		772
		773	This will reset the state of the incremental parser and will remove the
		774	parsed text from the input buffer. This is useful after C<incr_parse>
		775	died, in which case the input buffer and incremental parser state is left
		776	unchanged, to skip the text parsed so far and to reset the parse state.
		777
		778	=item $json->incr_reset
		779
		780	This completely resets the incremental parser, that is, after this call,
		781	it will be as if the parser had never parsed anything.
		782
		783	This is useful if you want ot repeatedly parse JSON objects and want to
		784	ignore any trailing data, which means you have to reset the parser after
		785	each successful decode.
		786
		787	=back
		788
		789	=head2 LIMITATIONS
		790
		791	All options that affect decoding are supported, except
		792	C<allow_nonref>. The reason for this is that it cannot be made to
		793	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		794	them back to back and still decode them perfectly. This does not hold true
		795	for JSON numbers, however.
		796
		797	For example, is the string C<1> a single JSON number, or is it simply the
		798	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		799	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		800	takes the conservative route and disallows this case.
		801
		802	=head2 EXAMPLES
		803
		804	Some examples will make all this clearer. First, a simple example that
		805	works similarly to C<decode_prefix>: We want to decode the JSON object at
		806	the start of a string and identify the portion after the JSON object:
		807
		808	my $text = "[1,2,3] hello";
		809
		810	my $json = new JSON::XS;
		811
		812	my $obj = $json->incr_parse ($text)
		813	or die "expected JSON object or array at beginning of string";
		814
		815	my $tail = $json->incr_text;
		816	# $tail now contains " hello"
		817
		818	Easy, isn't it?
		819
		820	Now for a more complicated example: Imagine a hypothetical protocol where
		821	you read some requests from a TCP stream, and each request is a JSON
		822	array, without any separation between them (in fact, it is often useful to
		823	use newlines as "separators", as these get interpreted as whitespace at
		824	the start of the JSON text, which makes it possible to test said protocol
		825	with C<telnet>...).
		826
		827	Here is how you'd do it (it is trivial to write this in an event-based
		828	manner):
		829
		830	my $json = new JSON::XS;
		831
		832	# read some data from the socket
		833	while (sysread $socket, my $buf, 4096) {
		834
		835	# split and decode as many requests as possible
		836	for my $request ($json->incr_parse ($buf)) {
		837	# act on the $request
		838	}
		839	}
		840
		841	Another complicated example: Assume you have a string with JSON objects
		842	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		843	[3]>). To parse them, we have to skip the commas between the JSON texts,
		844	and here is where the lvalue-ness of C<incr_text> comes in useful:
		845
		846	my $text = "[1],[2], [3]";
		847	my $json = new JSON::XS;
		848
		849	# void context, so no parsing done
		850	$json->incr_parse ($text);
		851
		852	# now extract as many objects as possible. note the
		853	# use of scalar context so incr_text can be called.
		854	while (my $obj = $json->incr_parse) {
		855	# do something with $obj
		856
		857	# now skip the optional comma
		858	$json->incr_text =~ s/^ \s* , //x;
		859	}
		860
		861	Now lets go for a very complex example: Assume that you have a gigantic
		862	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		863	but you cannot load it into memory fully (this has actually happened in
		864	the real world :).
		865
		866	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		867	can still help you: You implement a (very simple) array parser and let
		868	JSON decode the array elements, which are all full JSON objects on their
		869	own (this wouldn't work if the array elements could be JSON numbers, for
		870	example):
		871
		872	my $json = new JSON::XS;
		873
		874	# open the monster
		875	open my $fh, "<bigfile.json"
		876	or die "bigfile: $!";
		877
		878	# first parse the initial "["
		879	for (;;) {
		880	sysread $fh, my $buf, 65536
		881	or die "read error: $!";
		882	$json->incr_parse ($buf); # void context, so no parsing
		883
		884	# Exit the loop once we found and removed(!) the initial "[".
		885	# In essence, we are (ab-)using the $json object as a simple scalar
		886	# we append data to.
		887	last if $json->incr_text =~ s/^ \s* \[ //x;
		888	}
		889
		890	# now we have the skipped the initial "[", so continue
		891	# parsing all the elements.
		892	for (;;) {
		893	# in this loop we read data until we got a single JSON object
		894	for (;;) {
		895	if (my $obj = $json->incr_parse) {
		896	# do something with $obj
		897	last;
		898	}
		899
		900	# add more data
		901	sysread $fh, my $buf, 65536
		902	or die "read error: $!";
		903	$json->incr_parse ($buf); # void context, so no parsing
		904	}
		905
		906	# in this loop we read data until we either found and parsed the
		907	# separating "," between elements, or the final "]"
		908	for (;;) {
		909	# first skip whitespace
		910	$json->incr_text =~ s/^\s*//;
		911
		912	# if we find "]", we are done
		913	if ($json->incr_text =~ s/^\]//) {
		914	print "finished.\n";
		915	exit;
		916	}
		917
		918	# if we find ",", we can continue with the next element
		919	if ($json->incr_text =~ s/^,//) {
		920	last;
		921	}
		922
		923	# if we find anything else, we have a parse error!
		924	if (length $json->incr_text) {
		925	die "parse error near ", $json->incr_text;
		926	}
		927
		928	# else add more data
		929	sysread $fh, my $buf, 65536
		930	or die "read error: $!";
		931	$json->incr_parse ($buf); # void context, so no parsing
		932	}
		933
		934	This is a complex example, but most of the complexity comes from the fact
		935	that we are trying to be correct (bear with me if I am wrong, I never ran
		936	the above example :).
		937
		938
		939
650	=head1 MAPPING	940	=head1 MAPPING
651		941
652	This section describes how JSON::XS maps Perl values to JSON values and	942	This section describes how JSON::XS maps Perl values to JSON values and
653	vice versa. These mappings are designed to "do the right thing" in most	943	vice versa. These mappings are designed to "do the right thing" in most
654	circumstances automatically, preserving round-tripping characteristics	944	circumstances automatically, preserving round-tripping characteristics
…		…
682		972
683	A JSON number becomes either an integer, numeric (floating point) or	973	A JSON number becomes either an integer, numeric (floating point) or
684	string scalar in perl, depending on its range and any fractional parts. On	974	string scalar in perl, depending on its range and any fractional parts. On
685	the Perl level, there is no difference between those as Perl handles all	975	the Perl level, there is no difference between those as Perl handles all
686	the conversion details, but an integer may take slightly less memory and	976	the conversion details, but an integer may take slightly less memory and
687	might represent more values exactly than (floating point) numbers.	977	might represent more values exactly than floating point numbers.
688		978
689	If the number consists of digits only, JSON::XS will try to represent	979	If the number consists of digits only, JSON::XS will try to represent
690	it as an integer value. If that fails, it will try to represent it as	980	it as an integer value. If that fails, it will try to represent it as
691	a numeric (floating point) value if that is possible without loss of	981	a numeric (floating point) value if that is possible without loss of
692	precision. Otherwise it will preserve the number as a string value.	982	precision. Otherwise it will preserve the number as a string value (in
		983	which case you lose roundtripping ability, as the JSON number will be
		984	re-encoded toa JSON string).
693		985
694	Numbers containing a fractional or exponential part will always be	986	Numbers containing a fractional or exponential part will always be
695	represented as numeric (floating point) values, possibly at a loss of	987	represented as numeric (floating point) values, possibly at a loss of
696	precision.	988	precision (in which case you might lose perfect roundtripping ability, but
697		989	the JSON number will still be re-encoded as a JSON number).
698	This might create round-tripping problems as numbers might become strings,
699	but as Perl is typeless there is no other way to do it.
700		990
701	=item true, false	991	=item true, false
702		992
703	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	993	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
704	respectively. They are overloaded to act almost exactly like the numbers	994	respectively. They are overloaded to act almost exactly like the numbers
…		…
741	Other unblessed references are generally not allowed and will cause an	1031	Other unblessed references are generally not allowed and will cause an
742	exception to be thrown, except for references to the integers C<0> and	1032	exception to be thrown, except for references to the integers C<0> and
743	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1033	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
744	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1034	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
745		1035
746	to_json [\0,JSON::XS::true] # yields [false,true]	1036	encode_json [\0, JSON::XS::true] # yields [false,true]
747		1037
748	=item JSON::XS::true, JSON::XS::false	1038	=item JSON::XS::true, JSON::XS::false
749		1039
750	These special values become JSON true and JSON false values,	1040	These special values become JSON true and JSON false values,
751	respectively. You can also use C<\1> and C<\0> directly if you want.	1041	respectively. You can also use C<\1> and C<\0> directly if you want.
752		1042
753	=item blessed objects	1043	=item blessed objects
754		1044
755	Blessed objects are not allowed. JSON::XS currently tries to encode their	1045	Blessed objects are not directly representable in JSON. See the
756	underlying representation (hash- or arrayref), but this behaviour might	1046	C<allow_blessed> and C<convert_blessed> methods on various options on
757	change in future versions.	1047	how to deal with this: basically, you can choose between throwing an
		1048	exception, encoding the reference as if it weren't blessed, or provide
		1049	your own serialiser method.
758		1050
759	=item simple scalars	1051	=item simple scalars
760		1052
761	Simple Perl scalars (any scalar that is not a reference) are the most	1053	Simple Perl scalars (any scalar that is not a reference) are the most
762	difficult objects to encode: JSON::XS will encode undefined scalars as	1054	difficult objects to encode: JSON::XS will encode undefined scalars as
763	JSON null value, scalars that have last been used in a string context	1055	JSON C<null> values, scalars that have last been used in a string context
764	before encoding as JSON strings and anything else as number value:	1056	before encoding as JSON strings, and anything else as number value:
765		1057
766	# dump as number	1058	# dump as number
767	to_json [2] # yields [2]	1059	encode_json [2] # yields [2]
768	to_json [-3.0e17] # yields [-3e+17]	1060	encode_json [-3.0e17] # yields [-3e+17]
769	my $value = 5; to_json [$value] # yields [5]	1061	my $value = 5; encode_json [$value] # yields [5]
770		1062
771	# used as string, so dump as string	1063	# used as string, so dump as string
772	print $value;	1064	print $value;
773	to_json [$value] # yields ["5"]	1065	encode_json [$value] # yields ["5"]
774		1066
775	# undef becomes null	1067	# undef becomes null
776	to_json [undef] # yields [null]	1068	encode_json [undef] # yields [null]
777		1069
778	You can force the type to be a JSON string by stringifying it:	1070	You can force the type to be a JSON string by stringifying it:
779		1071
780	my $x = 3.1; # some variable containing a number	1072	my $x = 3.1; # some variable containing a number
781	"$x"; # stringified	1073	"$x"; # stringified
…		…
787	my $x = "3"; # some variable containing a string	1079	my $x = "3"; # some variable containing a string
788	$x += 0; # numify it, ensuring it will be dumped as a number	1080	$x += 0; # numify it, ensuring it will be dumped as a number
789	$x *= 1; # same thing, the choice is yours.	1081	$x *= 1; # same thing, the choice is yours.
790		1082
791	You can not currently force the type in other, less obscure, ways. Tell me	1083	You can not currently force the type in other, less obscure, ways. Tell me
792	if you need this capability.	1084	if you need this capability (but don't forget to explain why it's needed
		1085	:).
793		1086
794	=back	1087	=back
795		1088
796		1089
797	=head1 COMPARISON	1090	=head1 ENCODING/CODESET FLAG NOTES
798		1091
799	As already mentioned, this module was created because none of the existing	1092	The interested reader might have seen a number of flags that signify
800	JSON modules could be made to work correctly. First I will describe the	1093	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
801	problems (or pleasures) I encountered with various existing JSON modules,	1094	some confusion on what these do, so here is a short comparison:
802	followed by some benchmark values. JSON::XS was designed not to suffer	1095
803	from any of these problems or limitations.	1096	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1097	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1098	control whether C<encode> escapes character values outside their respective
		1099	codeset range. Neither of these flags conflict with each other, although
		1100	some combinations make less sense than others.
		1101
		1102	Care has been taken to make all flags symmetrical with respect to
		1103	C<encode> and C<decode>, that is, texts encoded with any combination of
		1104	these flag values will be correctly decoded when the same flags are used
		1105	- in general, if you use different flag settings while encoding vs. when
		1106	decoding you likely have a bug somewhere.
		1107
		1108	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1109	simply an abstract set of character-codepoint pairs, while an encoding
		1110	takes those codepoint numbers and I<encodes> them, in our case into
		1111	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1112	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1113	the same time, which can be confusing.
804		1114
805	=over 4	1115	=over 4
806		1116
807	=item JSON 1.07	1117	=item C<utf8> flag disabled
808		1118
809	Slow (but very portable, as it is written in pure Perl).	1119	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1120	and expect Unicode strings, that is, characters with high ordinal Unicode
		1121	values (> 255) will be encoded as such characters, and likewise such
		1122	characters are decoded as-is, no canges to them will be done, except
		1123	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1124	respectively (to Perl, these are the same thing in strings unless you do
		1125	funny/weird/dumb stuff).
810		1126
811	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1127	This is useful when you want to do the encoding yourself (e.g. when you
812	undocumented. One can get far by feeding it Unicode strings and doing	1128	want to have UTF-16 encoded JSON texts) or when some other layer does
813	en-/decoding oneself, but Unicode escapes are not working properly).	1129	the encoding for you (for example, when printing to a terminal using a
		1130	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1131	to UTF-8 encode your data first and have Perl encode it another time).
814		1132
815	No round-tripping (strings get clobbered if they look like numbers, e.g.	1133	=item C<utf8> flag enabled
816	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
817	decode into the number 2.
818		1134
819	=item JSON::PC 0.01	1135	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1136	characters using the corresponding UTF-8 multi-byte sequence, and will
		1137	expect your input strings to be encoded as UTF-8, that is, no "character"
		1138	of the input string must have any value > 255, as UTF-8 does not allow
		1139	that.
820		1140
821	Very fast.	1141	The C<utf8> flag therefore switches between two modes: disabled means you
		1142	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1143	octet/binary string in Perl.
822		1144
823	Undocumented/buggy Unicode handling.	1145	=item C<latin1> or C<ascii> flags enabled
824		1146
825	No round-tripping.	1147	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1148	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1149	characters as specified by the C<utf8> flag.
826		1150
827	Has problems handling many Perl values (e.g. regex results and other magic	1151	If C<utf8> is disabled, then the result is also correctly encoded in those
828	values will make it croak).	1152	character sets (as both are proper subsets of Unicode, meaning that a
		1153	Unicode string with all character values < 256 is the same thing as a
		1154	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1155	the same thing as an ASCII string in Perl).
829		1156
830	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1157	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
831	which is not a valid JSON text.	1158	regardless of these flags, just some more characters will be escaped using
		1159	C<\uXXXX> then before.
832		1160
833	Unmaintained (maintainer unresponsive for many months, bugs are not	1161	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
834	getting fixed).	1162	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1163	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1164	a subset of Unicode), while ASCII is.
835		1165
836	=item JSON::Syck 0.21	1166	Surprisingly, C<decode> will ignore these flags and so treat all input
		1167	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1168	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1169	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
837		1170
838	Very buggy (often crashes).	1171	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1172	they only govern when the JSON output engine escapes a character or not.
839		1173
840	Very inflexible (no human-readable format supported, format pretty much	1174	The main use for C<latin1> is to relatively efficiently store binary data
841	undocumented. I need at least a format for easy reading by humans and a	1175	as JSON, at the expense of breaking compatibility with most JSON decoders.
842	single-line compact format for use in a protocol, and preferably a way to
843	generate ASCII-only JSON texts).
844		1176
845	Completely broken (and confusingly documented) Unicode handling (Unicode	1177	The main use for C<ascii> is to force the output to not contain characters
846	escapes are not working properly, you need to set ImplicitUnicode to	1178	with values > 127, which means you can interpret the resulting string
847	I<different> values on en- and decoding to get symmetric behaviour).	1179	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
848		1180	8-bit-encoding, and still get the same data structure back. This is useful
849	No round-tripping (simple cases work, but this depends on whether the scalar	1181	when your channel for JSON transfer is not 8-bit clean or the encoding
850	value was used in a numeric context or not).	1182	might be mangled in between (e.g. in mail), and works because ASCII is a
851		1183	proper subset of most 8-bit and multibyte encodings in use in the world.
852	Dumping hashes may skip hash values depending on iterator state.
853
854	Unmaintained (maintainer unresponsive for many months, bugs are not
855	getting fixed).
856
857	Does not check input for validity (i.e. will accept non-JSON input and
858	return "something" instead of raising an exception. This is a security
859	issue: imagine two banks transferring money between each other using
860	JSON. One bank might parse a given non-JSON request and deduct money,
861	while the other might reject the transaction with a syntax error. While a
862	good protocol will at least recover, that is extra unnecessary work and
863	the transaction will still not succeed).
864
865	=item JSON::DWIW 0.04
866
867	Very fast. Very natural. Very nice.
868
869	Undocumented Unicode handling (but the best of the pack. Unicode escapes
870	still don't get parsed properly).
871
872	Very inflexible.
873
874	No round-tripping.
875
876	Does not generate valid JSON texts (key strings are often unquoted, empty keys
877	result in nothing being output)
878
879	Does not check input for validity.
880		1184
881	=back	1185	=back
882		1186
883		1187
884	=head2 JSON and YAML	1188	=head2 JSON and YAML
885		1189
886	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1190	You often hear that JSON is a subset of YAML. This is, however, a mass
887	however, a mass hysteria and very far from the truth. In general, there is	1191	hysteria(*) and very far from the truth (as of the time of this writing),
888	no way to configure JSON::XS to output a data structure as valid YAML.	1192	so let me state it clearly: I<in general, there is no way to configure
		1193	JSON::XS to output a data structure as valid YAML> that works in all
		1194	cases.
889		1195
890	If you really must use JSON::XS to generate YAML, you should use this	1196	If you really must use JSON::XS to generate YAML, you should use this
891	algorithm (subject to change in future versions):	1197	algorithm (subject to change in future versions):
892		1198
893	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1199	my $to_yaml = JSON::XS->new->utf8->space_after (1);
894	my $yaml = $to_yaml->encode ($ref) . "\n";	1200	my $yaml = $to_yaml->encode ($ref) . "\n";
895		1201
896	This will usually generate JSON texts that also parse as valid	1202	This will I<usually> generate JSON texts that also parse as valid
897	YAML. Please note that YAML has hardcoded limits on (simple) object key	1203	YAML. Please note that YAML has hardcoded limits on (simple) object key
898	lengths that JSON doesn't have, so you should make sure that your hash	1204	lengths that JSON doesn't have and also has different and incompatible
		1205	unicode handling, so you should make sure that your hash keys are
899	keys are noticeably shorter than the 1024 characters YAML allows.	1206	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1207	you do not have characters with codepoint values outside the Unicode BMP
		1208	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1209	strings (which JSON::XS does not I<currently> generate, but other JSON
		1210	generators might).
900		1211
901	There might be other incompatibilities that I am not aware of. In general	1212	There might be other incompatibilities that I am not aware of (or the YAML
		1213	specification has been changed yet again - it does so quite often). In
902	you should not try to generate YAML with a JSON generator or vice versa,	1214	general you should not try to generate YAML with a JSON generator or vice
903	or try to parse JSON with a YAML parser or vice versa: chances are high	1215	versa, or try to parse JSON with a YAML parser or vice versa: chances are
904	that you will run into severe interoperability problems.	1216	high that you will run into severe interoperability problems when you
		1217	least expect it.
		1218
		1219	=over 4
		1220
		1221	=item (*)
		1222
		1223	I have been pressured multiple times by Brian Ingerson (one of the
		1224	authors of the YAML specification) to remove this paragraph, despite him
		1225	acknowledging that the actual incompatibilities exist. As I was personally
		1226	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1227	educate people about these issues, so others do not run into the same
		1228	problem again and again. After this, Brian called me a (quote)I<complete
		1229	and worthless idiot>(unquote).
		1230
		1231	In my opinion, instead of pressuring and insulting people who actually
		1232	clarify issues with YAML and the wrong statements of some of its
		1233	proponents, I would kindly suggest reading the JSON spec (which is not
		1234	that difficult or long) and finally make YAML compatible to it, and
		1235	educating users about the changes, instead of spreading lies about the
		1236	real compatibility for many I<years> and trying to silence people who
		1237	point out that it isn't true.
		1238
		1239	=back
905		1240
906		1241
907	=head2 SPEED	1242	=head2 SPEED
908		1243
909	It seems that JSON::XS is surprisingly fast, as shown in the following	1244	It seems that JSON::XS is surprisingly fast, as shown in the following
910	tables. They have been generated with the help of the C<eg/bench> program	1245	tables. They have been generated with the help of the C<eg/bench> program
911	in the JSON::XS distribution, to make it easy to compare on your own	1246	in the JSON::XS distribution, to make it easy to compare on your own
912	system.	1247	system.
913		1248
914	First comes a comparison between various modules using a very short	1249	First comes a comparison between various modules using
915	single-line JSON string:	1250	a very short single-line JSON string (also available at
		1251	L<http://dist.schmorp.de/misc/json/short.json>).
916		1252
917	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1253	{"method": "handleMessage", "params": ["user1",
918	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1254	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1255	true, false]}
919		1256
920	It shows the number of encodes/decodes per second (JSON::XS uses	1257	It shows the number of encodes/decodes per second (JSON::XS uses
921	the functional interface, while JSON::XS/2 uses the OO interface	1258	the functional interface, while JSON::XS/2 uses the OO interface
922	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1259	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
923	shrink). Higher is better:	1260	shrink). Higher is better:
…		…
939	about three times faster on decoding, and over forty times faster	1276	about three times faster on decoding, and over forty times faster
940	than JSON, even with pretty-printing and key sorting. It also compares	1277	than JSON, even with pretty-printing and key sorting. It also compares
941	favourably to Storable for small amounts of data.	1278	favourably to Storable for small amounts of data.
942		1279
943	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1280	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
944	search API (http://nanoref.com/yahooapis/mgPdGg):	1281	search API (L<http://dist.schmorp.de/misc/json/long.json>).
945		1282
946	module \| encode \| decode \|	1283	module \| encode \| decode \|
947	-----------\|------------\|------------\|	1284	-----------\|------------\|------------\|
948	JSON 1.x \| 55.260 \| 34.971 \|	1285	JSON 1.x \| 55.260 \| 34.971 \|
949	JSON::DWIW \| 825.228 \| 1082.513 \|	1286	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
986		1323
987	Third, JSON::XS recurses using the C stack when decoding objects and	1324	Third, JSON::XS recurses using the C stack when decoding objects and
988	arrays. The C stack is a limited resource: for instance, on my amd64	1325	arrays. The C stack is a limited resource: for instance, on my amd64
989	machine with 8MB of stack size I can decode around 180k nested arrays but	1326	machine with 8MB of stack size I can decode around 180k nested arrays but
990	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1327	only 14k nested JSON objects (due to perl itself recursing deeply on croak
991	to free the temporary). If that is exceeded, the program crashes. to be	1328	to free the temporary). If that is exceeded, the program crashes. To be
992	conservative, the default nesting limit is set to 512. If your process	1329	conservative, the default nesting limit is set to 512. If your process
993	has a smaller stack, you should adjust this setting accordingly with the	1330	has a smaller stack, you should adjust this setting accordingly with the
994	C<max_depth> method.	1331	C<max_depth> method.
995		1332
996	And last but least, something else could bomb you that I forgot to think	1333	Something else could bomb you, too, that I forgot to think of. In that
997	of. In that case, you get to keep the pieces. I am always open for hints,	1334	case, you get to keep the pieces. I am always open for hints, though...
998	though...	1335
		1336	Also keep in mind that JSON::XS might leak contents of your Perl data
		1337	structures in its error messages, so when you serialise sensitive
		1338	information you might want to make sure that exceptions thrown by JSON::XS
		1339	will not end up in front of untrusted eyes.
999		1340
1000	If you are using JSON::XS to return packets to consumption	1341	If you are using JSON::XS to return packets to consumption
1001	by JavaScript scripts in a browser you should have a look at	1342	by JavaScript scripts in a browser you should have a look at
1002	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1343	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1003	you are vulnerable to some common attack vectors (which really are browser	1344	you are vulnerable to some common attack vectors (which really are browser
1004	design bugs, but it is still you who will have to deal with it, as major	1345	design bugs, but it is still you who will have to deal with it, as major
1005	browser developers care only for features, not about doing security	1346	browser developers care only for features, not about getting security
1006	right).	1347	right).
1007		1348
1008		1349
1009	=head1 THREADS	1350	=head1 THREADS
1010		1351
1011	This module is I<not> guaranteed to be thread safe and there are no	1352	This module is I<not> guaranteed to be thread safe and there are no
1012	plans to change this until Perl gets thread support (as opposed to the	1353	plans to change this until Perl gets thread support (as opposed to the
1013	horribly slow so-called "threads" which are simply slow and bloated	1354	horribly slow so-called "threads" which are simply slow and bloated
1014	process simulations - use fork, its I<much> faster, cheaper, better).	1355	process simulations - use fork, it's I<much> faster, cheaper, better).
1015		1356
1016	(It might actually work, but you have been warned).	1357	(It might actually work, but you have been warned).
1017		1358
1018		1359
1019	=head1 BUGS	1360	=head1 BUGS
1020		1361
1021	While the goal of this module is to be correct, that unfortunately does	1362	While the goal of this module is to be correct, that unfortunately does
1022	not mean its bug-free, only that I think its design is bug-free. It is	1363	not mean it's bug-free, only that I think its design is bug-free. If you
1023	still relatively early in its development. If you keep reporting bugs they	1364	keep reporting bugs they will be fixed swiftly, though.
1024	will be fixed swiftly, though.
1025		1365
1026	Please refrain from using rt.cpan.org or any other bug reporting	1366	Please refrain from using rt.cpan.org or any other bug reporting
1027	service. I put the contact address into my modules for a reason.	1367	service. I put the contact address into my modules for a reason.
1028		1368
1029	=cut	1369	=cut
…		…
1049	"--" => sub { $_[0] = ${$_[0]} - 1 },	1389	"--" => sub { $_[0] = ${$_[0]} - 1 },
1050	fallback => 1;	1390	fallback => 1;
1051		1391
1052	1;	1392	1;
1053		1393
		1394	=head1 SEE ALSO
		1395
		1396	The F<json_xs> command line utility for quick experiments.
		1397
1054	=head1 AUTHOR	1398	=head1 AUTHOR
1055		1399
1056	Marc Lehmann <schmorp@schmorp.de>	1400	Marc Lehmann <schmorp@schmorp.de>
1057	http://home.schmorp.de/	1401	http://home.schmorp.de/
1058		1402

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Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC vs.
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC