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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 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		4
		5	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)
		7
5	=head1 SYNOPSIS	8	=head1 SYNOPSIS
6		9
7	use JSON::XS;	10	use JSON::XS;
		11
		12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
		14
		15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		17
		18	# OO-interface
		19
		20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		22	$perl_scalar = $coder->decode ($unicode_json_text);
8		23
9	=head1 DESCRIPTION	24	=head1 DESCRIPTION
10		25
11	This module converts Perl data structures to JSON and vice versa. Its	26	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	27	primary goal is to be I<correct> and its secondary goal is to be
18	their maintainers are unresponsive, gone missing, or not listening to bug	33	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	34	reports for other reasons.
20		35
21	See COMPARISON, below, for a comparison to some other JSON modules.	36	See COMPARISON, below, for a comparison to some other JSON modules.
22		37
		38	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		39	vice versa.
		40
23	=head2 FEATURES	41	=head2 FEATURES
24		42
25	=over 4	43	=over 4
26		44
27	=item * correct handling of unicode issues	45	=item * correct Unicode handling
28		46
29	This module knows how to handle Unicode, and even documents how it does so.	47	This module knows how to handle Unicode, and even documents how and when
		48	it does so.
30		49
31	=item * round-trip integrity	50	=item * round-trip integrity
32		51
33	When you serialise a perl data structure using only datatypes supported	52	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	53	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	54	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		55	like a number).
36		56
37	=item * strict checking of JSON correctness	57	=item * strict checking of JSON correctness
38		58
39	There is no guessing, no generating of illegal JSON strings by default,	59	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	60	and only JSON is accepted as input by default (the latter is a security
		61	feature).
41		62
42	=item * fast	63	=item * fast
43		64
44	compared to other JSON modules, this module compares favourably.	65	Compared to other JSON modules, this module compares favourably in terms
		66	of speed, too.
45		67
46	=item * simple to use	68	=item * simple to use
47		69
48	This module has both a simple functional interface as well as an OO	70	This module has both a simple functional interface as well as an OO
49	interface.	71	interface.
50		72
51	=item * reasonably versatile output formats	73	=item * reasonably versatile output formats
52		74
53	You can choose between the most compact format possible, a pure-ascii	75	You can choose between the most compact guaranteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	76	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	77	(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
		79	stuff). Or you can combine those features in whatever way you like.
56		80
57	=back	81	=back
58		82
59	=cut	83	=cut
60		84
61	package JSON::XS;	85	package JSON::XS;
62		86
63	BEGIN {	87	use strict;
		88
64	$VERSION = '0.1';	89	our $VERSION = '1.6';
65	@ISA = qw(Exporter);	90	our @ISA = qw(Exporter);
66		91
67	@EXPORT = qw(to_json from_json);	92	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		93
70	require XSLoader;	94	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	95	use XSLoader;
72	}
73		96
74	=head1 FUNCTIONAL INTERFACE	97	=head1 FUNCTIONAL INTERFACE
75		98
76	The following convinience methods are provided by this module. They are	99	The following convenience methods are provided by this module. They are
77	exported by default:	100	exported by default:
78		101
79	=over 4	102	=over 4
80		103
81	=item $json_string = to_json $perl_scalar	104	=item $json_text = to_json $perl_scalar
82		105
83	Converts the given Perl data structure (a simple scalar or a reference to	106	Converts the given Perl data structure to a UTF-8 encoded, binary string
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	107	(that is, the string contains octets only). Croaks on error.
85	octets only). Croaks on error.
86		108
87	This function call is functionally identical to C<< JSON::XS->new->utf8	109	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		110
		111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		112
		113	except being faster.
		114
90	=item $perl_scalar = from_json $json_string	115	=item $perl_scalar = from_json $json_text
91		116
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	118	to parse that as an UTF-8 encoded JSON text, returning the resulting
94	scalar or reference. Croaks on error.	119	reference. Croaks on error.
95		120
96	This function call is functionally identical to C<< JSON::XS->new->utf8	121	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	122
		123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		124
		125	except being faster.
		126
		127	=item $is_boolean = JSON::XS::is_bool $scalar
		128
		129	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
		131	and are used to represent JSON C<true> and C<false> values in Perl.
		132
		133	See MAPPING, below, for more information on how JSON values are mapped to
		134	Perl.
98		135
99	=back	136	=back
		137
		138
		139	=head1 A FEW NOTES ON UNICODE AND PERL
		140
		141	Since this often leads to confusion, here are a few very clear words on
		142	how Unicode works in Perl, modulo bugs.
		143
		144	=over 4
		145
		146	=item 1. Perl strings can store characters with ordinal values > 255.
		147
		148	This enables you to store Unicode characters as single characters in a
		149	Perl string - very natural.
		150
		151	=item 2. Perl does I<not> associate an encoding with your strings.
		152
		153	Unless you force it to, e.g. when matching it against a regex, or printing
		154	the scalar to a file, in which case Perl either interprets your string as
		155	locale-encoded text, octets/binary, or as Unicode, depending on various
		156	settings. In no case is an encoding stored together with your data, it is
		157	I<use> that decides encoding, not any magical metadata.
		158
		159	=item 3. The internal utf-8 flag has no meaning with regards to the
		160	encoding of your string.
		161
		162	Just ignore that flag unless you debug a Perl bug, a module written in
		163	XS or want to dive into the internals of perl. Otherwise it will only
		164	confuse you, as, despite the name, it says nothing about how your string
		165	is encoded. You can have Unicode strings with that flag set, with that
		166	flag clear, and you can have binary data with that flag set and that flag
		167	clear. Other possibilities exist, too.
		168
		169	If you didn't know about that flag, just the better, pretend it doesn't
		170	exist.
		171
		172	=item 4. A "Unicode String" is simply a string where each character can be
		173	validly interpreted as a Unicode codepoint.
		174
		175	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.
		177
		178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		179
		180	It's a fact. Learn to live with it.
		181
		182	=back
		183
		184	I hope this helps :)
		185
100		186
101	=head1 OBJECT-ORIENTED INTERFACE	187	=head1 OBJECT-ORIENTED INTERFACE
102		188
103	The object oriented interface lets you configure your own encoding or	189	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	190	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	197	strings. All boolean flags described below are by default I<disabled>.
112		198
113	The mutators for flags all return the JSON object again and thus calls can	199	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	200	be chained:
115		201
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	202	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	203	=> {"a": [1, 2]}
118		204
119	=item $json = $json->ascii ($enable)	205	=item $json = $json->ascii ([$enable])
120		206
		207	=item $enabled = $json->get_ascii
		208
121	If C<$enable> is true, then the C<encode> method will not generate	209	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	210	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	211	Unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		213	as per RFC4627. The resulting encoded JSON text can be treated as a native
		214	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		215	or any other superset of ASCII.
125		216
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	217	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	218	characters unless required by the JSON syntax or other flags. This results
		219	in a faster and more compact format.
128		220
		221	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
		223	contain any 8 bit characters.
		224
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	226	=> ["\ud801\udc01"]
131		227
		228	=item $json = $json->latin1 ([$enable])
		229
		230	=item $enabled = $json->get_latin1
		231
		232	If C<$enable> is true (or missing), then the C<encode> method will encode
		233	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		234	outside the code range C<0..255>. The resulting string can be treated as a
		235	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		236	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.
		238
		239	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.
		241
		242	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
		244	size. The disadvantage is that the resulting JSON text is encoded
		245	in latin1 (and must correctly be treated as such when storing and
		246	transferring), a rare encoding for JSON. It is therefore most useful when
		247	you want to store data structures known to contain binary data efficiently
		248	in files or databases, not when talking to other JSON encoders/decoders.
		249
		250	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		251	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		252
132	=item $json = $json->utf8 ($enable)	253	=item $json = $json->utf8 ([$enable])
133		254
		255	=item $enabled = $json->get_utf8
		256
134	If C<$enable> is true, then the C<encode> method will encode the JSON	257	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	258	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	259	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	260	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	261	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		262	versions, enabling this option might enable autodetection of the UTF-16
		263	and UTF-32 encoding families, as described in RFC4627.
139		264
140	If C<$enable> is false, then the C<encode> method will return the JSON	265	If C<$enable> is false, then the C<encode> method will return the JSON
141	string as a (non-encoded) unicode string, while C<decode> expects thus a	266	string as a (non-encoded) Unicode string, while C<decode> expects thus a
142	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	267	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
143	to be done yourself, e.g. using the Encode module.	268	to be done yourself, e.g. using the Encode module.
144		269
		270	Example, output UTF-16BE-encoded JSON:
		271
		272	use Encode;
		273	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		274
		275	Example, decode UTF-32LE-encoded JSON:
		276
		277	use Encode;
		278	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		279
145	=item $json = $json->pretty ($enable)	280	=item $json = $json->pretty ([$enable])
		281
		282	=item $enabled = $json->get_pretty
146		283
147	This enables (or disables) all of the C<indent>, C<space_before> and	284	This enables (or disables) all of the C<indent>, C<space_before> and
148	C<space_after> (and in the future possibly more) flags in one call to	285	C<space_after> (and in the future possibly more) flags in one call to
149	generate the most readable (or most compact) form possible.	286	generate the most readable (or most compact) form possible.
		287
		288	Example, pretty-print some simple structure:
150		289
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	290	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	291	=>
153	{	292	{
154	"a" : [	293	"a" : [
155	1,	294	1,
156	2	295	2
157	]	296	]
158	}	297	}
159		298
160	=item $json = $json->indent ($enable)	299	=item $json = $json->indent ([$enable])
161		300
		301	=item $enabled = $json->get_indent
		302
162	If C<$enable> is true, then the C<encode> method will use a multiline	303	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	304	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	305	into its own line, indenting them properly.
165		306
166	If C<$enable> is false, no newlines or indenting will be produced, and the	307	If C<$enable> is false, no newlines or indenting will be produced, and the
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	308	resulting JSON text is guaranteed not to contain any C<newlines>.
168		309
169	This setting has no effect when decoding JSON strings.	310	This setting has no effect when decoding JSON texts.
170		311
171	=item $json = $json->space_before ($enable)	312	=item $json = $json->space_before ([$enable])
172		313
		314	=item $enabled = $json->get_space_before
		315
173	If C<$enable> is true, then the C<encode> method will add an extra	316	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	317	optional space before the C<:> separating keys from values in JSON objects.
175		318
176	If C<$enable> is false, then the C<encode> method will not add any extra	319	If C<$enable> is false, then the C<encode> method will not add any extra
177	space at those places.	320	space at those places.
178		321
179	This setting has no effect when decoding JSON strings. You will also most	322	This setting has no effect when decoding JSON texts. You will also
180	likely combine this setting with C<space_after>.	323	most likely combine this setting with C<space_after>.
181		324
		325	Example, space_before enabled, space_after and indent disabled:
		326
		327	{"key" :"value"}
		328
182	=item $json = $json->space_after ($enable)	329	=item $json = $json->space_after ([$enable])
183		330
		331	=item $enabled = $json->get_space_after
		332
184	If C<$enable> is true, then the C<encode> method will add an extra	333	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	334	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	335	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	336	members.
188		337
189	If C<$enable> is false, then the C<encode> method will not add any extra	338	If C<$enable> is false, then the C<encode> method will not add any extra
190	space at those places.	339	space at those places.
191		340
192	This setting has no effect when decoding JSON strings.	341	This setting has no effect when decoding JSON texts.
193		342
		343	Example, space_before and indent disabled, space_after enabled:
		344
		345	{"key": "value"}
		346
		347	=item $json = $json->relaxed ([$enable])
		348
		349	=item $enabled = $json->get_relaxed
		350
		351	If C<$enable> is true (or missing), then C<decode> will accept some
		352	extensions to normal JSON syntax (see below). C<encode> will not be
		353	affected in anyway. I<Be aware that this option makes you accept invalid
		354	JSON texts as if they were valid!>. I suggest only to use this option to
		355	parse application-specific files written by humans (configuration files,
		356	resource files etc.)
		357
		358	If C<$enable> is false (the default), then C<decode> will only accept
		359	valid JSON texts.
		360
		361	Currently accepted extensions are:
		362
		363	=over 4
		364
		365	=item * list items can have an end-comma
		366
		367	JSON I<separates> array elements and key-value pairs with commas. This
		368	can be annoying if you write JSON texts manually and want to be able to
		369	quickly append elements, so this extension accepts comma at the end of
		370	such items not just between them:
		371
		372	[
		373	1,
		374	2, <- this comma not normally allowed
		375	]
		376	{
		377	"k1": "v1",
		378	"k2": "v2", <- this comma not normally allowed
		379	}
		380
		381	=item * shell-style '#'-comments
		382
		383	Whenever JSON allows whitespace, shell-style comments are additionally
		384	allowed. They are terminated by the first carriage-return or line-feed
		385	character, after which more white-space and comments are allowed.
		386
		387	[
		388	1, # this comment not allowed in JSON
		389	# neither this one...
		390	]
		391
		392	=back
		393
194	=item $json = $json->canonical ($enable)	394	=item $json = $json->canonical ([$enable])
195		395
		396	=item $enabled = $json->get_canonical
		397
196	If C<$enable> is true, then the C<encode> method will output JSON objects	398	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	399	by sorting their keys. This is adding a comparatively high overhead.
198		400
199	If C<$enable> is false, then the C<encode> method will output key-value	401	If C<$enable> is false, then the C<encode> method will output key-value
200	pairs in the order Perl stores them (which will likely change between runs	402	pairs in the order Perl stores them (which will likely change between runs
201	of the same script).	403	of the same script).
202		404
203	This option is useful if you want the same data structure to be encoded as	405	This option is useful if you want the same data structure to be encoded as
204	the same JSON string (given the same overall settings). If it is disabled,	406	the same JSON text (given the same overall settings). If it is disabled,
205	the same hash migh be encoded differently even if contains the same data,	407	the same hash might be encoded differently even if contains the same data,
206	as key-value pairs have no inherent ordering in Perl.	408	as key-value pairs have no inherent ordering in Perl.
207		409
208	This setting has no effect when decoding JSON strings.	410	This setting has no effect when decoding JSON texts.
209		411
210	=item $json = $json->allow_nonref ($enable)	412	=item $json = $json->allow_nonref ([$enable])
211		413
		414	=item $enabled = $json->get_allow_nonref
		415
212	If C<$enable> is true, then the C<encode> method can convert a	416	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	417	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	418	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	419	values instead of croaking.
216		420
217	If C<$enable> is false, then the C<encode> method will croak if it isn't	421	If C<$enable> is false, then the C<encode> method will croak if it isn't
218	passed an arrayref or hashref, as JSON strings must either be an object	422	passed an arrayref or hashref, as JSON texts must either be an object
219	or array. Likewise, C<decode> will croak if given something that is not a	423	or array. Likewise, C<decode> will croak if given something that is not a
220	JSON object or array.	424	JSON object or array.
221		425
		426	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		427	resulting in an invalid JSON text:
		428
		429	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		430	=> "Hello, World!"
		431
		432	=item $json = $json->allow_blessed ([$enable])
		433
		434	=item $enabled = $json->get_allow_bless
		435
		436	If C<$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
		438	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
		440	object (C<convert_blessed> enabled and C<to_json> method found) is being
		441	encoded. Has no effect on C<decode>.
		442
		443	If C<$enable> is false (the default), then C<encode> will throw an
		444	exception when it encounters a blessed object.
		445
		446	=item $json = $json->convert_blessed ([$enable])
		447
		448	=item $enabled = $json->get_convert_blessed
		449
		450	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		451	blessed object, will check for the availability of the C<TO_JSON> method
		452	on the object's class. If found, it will be called in scalar context
		453	and the resulting scalar will be encoded instead of the object. If no
		454	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		455	to do.
		456
		457	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
		459	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
		461	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>
		463	function.
		464
		465	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
		467	enabled by this setting.
		468
		469	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		470	to do when a blessed object is found.
		471
		472	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		473
		474	When C<$coderef> is specified, it will be called from C<decode> each
		475	time it decodes a JSON object. The only argument is a reference to the
		476	newly-created hash. If the code references returns a single scalar (which
		477	need not be a reference), this value (i.e. a copy of that scalar to avoid
		478	aliasing) is inserted into the deserialised data structure. If it returns
		479	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		480	original deserialised hash will be inserted. This setting can slow down
		481	decoding considerably.
		482
		483	When C<$coderef> is omitted or undefined, any existing callback will
		484	be removed and C<decode> will not change the deserialised hash in any
		485	way.
		486
		487	Example, convert all JSON objects into the integer 5:
		488
		489	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		490	# returns [5]
		491	$js->decode ('[{}]')
		492	# throw an exception because allow_nonref is not enabled
		493	# so a lone 5 is not allowed.
		494	$js->decode ('{"a":1, "b":2}');
		495
		496	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		497
		498	Works remotely similar to C<filter_json_object>, but is only called for
		499	JSON objects having a single key named C<$key>.
		500
		501	This C<$coderef> is called before the one specified via
		502	C<filter_json_object>, if any. It gets passed the single value in the JSON
		503	object. If it returns a single value, it will be inserted into the data
		504	structure. If it returns nothing (not even C<undef> but the empty list),
		505	the callback from C<filter_json_object> will be called next, as if no
		506	single-key callback were specified.
		507
		508	If C<$coderef> is omitted or undefined, the corresponding callback will be
		509	disabled. There can only ever be one callback for a given key.
		510
		511	As this callback gets called less often then the C<filter_json_object>
		512	one, decoding speed will not usually suffer as much. Therefore, single-key
		513	objects make excellent targets to serialise Perl objects into, especially
		514	as single-key JSON objects are as close to the type-tagged value concept
		515	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		516	support this in any way, so you need to make sure your data never looks
		517	like a serialised Perl hash.
		518
		519	Typical names for the single object key are C<__class_whatever__>, or
		520	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		521	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		522	with real hashes.
		523
		524	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		525	into the corresponding C<< $WIDGET{<id>} >> object:
		526
		527	# return whatever is in $WIDGET{5}:
		528	JSON::XS
		529	->new
		530	->filter_json_single_key_object (__widget__ => sub {
		531	$WIDGET{ $_[0] }
		532	})
		533	->decode ('{"__widget__": 5')
		534
		535	# this can be used with a TO_JSON method in some "widget" class
		536	# for serialisation to json:
		537	sub WidgetBase::TO_JSON {
		538	my ($self) = @_;
		539
		540	unless ($self->{id}) {
		541	$self->{id} = ..get..some..id..;
		542	$WIDGET{$self->{id}} = $self;
		543	}
		544
		545	{ __widget__ => $self->{id} }
		546	}
		547
		548	=item $json = $json->shrink ([$enable])
		549
		550	=item $enabled = $json->get_shrink
		551
		552	Perl usually over-allocates memory a bit when allocating space for
		553	strings. This flag optionally resizes strings generated by either
		554	C<encode> or C<decode> to their minimum size possible. This can save
		555	memory when your JSON texts are either very very long or you have many
		556	short strings. It will also try to downgrade any strings to octet-form
		557	if possible: perl stores strings internally either in an encoding called
		558	UTF-X or in octet-form. The latter cannot store everything but uses less
		559	space in general (and some buggy Perl or C code might even rely on that
		560	internal representation being used).
		561
		562	The actual definition of what shrink does might change in future versions,
		563	but it will always try to save space at the expense of time.
		564
		565	If C<$enable> is true (or missing), the string returned by C<encode> will
		566	be shrunk-to-fit, while all strings generated by C<decode> will also be
		567	shrunk-to-fit.
		568
		569	If C<$enable> is false, then the normal perl allocation algorithms are used.
		570	If you work with your data, then this is likely to be faster.
		571
		572	In the future, this setting might control other things, such as converting
		573	strings that look like integers or floats into integers or floats
		574	internally (there is no difference on the Perl level), saving space.
		575
		576	=item $json = $json->max_depth ([$maximum_nesting_depth])
		577
		578	=item $max_depth = $json->get_max_depth
		579
		580	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
		582	higher nesting level then this limit, then the encoder and decoder will
		583	stop and croak at that point.
		584
		585	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<[>
		587	characters without their matching closing parenthesis crossed to reach a
		588	given character in a string.
		589
		590	Setting the maximum depth to one disallows any nesting, so that ensures
		591	that the object is only a single hash/object or array.
		592
		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
		595	used, which is rarely useful.
		596
		597	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		598
		599	=item $json = $json->max_size ([$maximum_string_size])
		600
		601	=item $max_size = $json->get_max_size
		602
		603	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>
		605	is called on a string longer then this number of characters it will not
		606	attempt to decode the string but throw an exception. This setting has no
		607	effect on C<encode> (yet).
		608
		609	The argument to C<max_size> will be rounded up to the next B<highest>
		610	power of two (so may be more than requested). If no argument is given, the
		611	limit check will be deactivated (same as when C<0> is specified).
		612
		613	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		614
222	=item $json_string = $json->encode ($perl_scalar)	615	=item $json_text = $json->encode ($perl_scalar)
223		616
224	Converts the given Perl data structure (a simple scalar or a reference	617	Converts the given Perl data structure (a simple scalar or a reference
225	to a hash or array) to its JSON representation. Simple scalars will be	618	to a hash or array) to its JSON representation. Simple scalars will be
226	converted into JSON string or number sequences, while references to arrays	619	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	620	become JSON arrays and references to hashes become JSON objects. Undefined
228	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	621	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	622	nor C<false> values will be generated.
230		623
231	=item $perl_scalar = $json->decode ($json_string)	624	=item $perl_scalar = $json->decode ($json_text)
232		625
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	626	The opposite of C<encode>: expects a JSON text and tries to parse it,
234	returning the resulting simple scalar or reference. Croaks on error.	627	returning the resulting simple scalar or reference. Croaks on error.
235		628
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	629	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	630	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
238	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	631	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		632
		633	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		634
		635	This works like the C<decode> method, but instead of raising an exception
		636	when there is trailing garbage after the first JSON object, it will
		637	silently stop parsing there and return the number of characters consumed
		638	so far.
		639
		640	This is useful if your JSON texts are not delimited by an outer protocol
		641	(which is not the brightest thing to do in the first place) and you need
		642	to know where the JSON text ends.
		643
		644	JSON::XS->new->decode_prefix ("[1] the tail")
		645	=> ([], 3)
		646
240	=back	647	=back
		648
		649
		650	=head1 MAPPING
		651
		652	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
		654	circumstances automatically, preserving round-tripping characteristics
		655	(what you put in comes out as something equivalent).
		656
		657	For the more enlightened: note that in the following descriptions,
		658	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
		659	refers to the abstract Perl language itself.
		660
		661
		662	=head2 JSON -> PERL
		663
		664	=over 4
		665
		666	=item object
		667
		668	A JSON object becomes a reference to a hash in Perl. No ordering of object
		669	keys is preserved (JSON does not preserve object key ordering itself).
		670
		671	=item array
		672
		673	A JSON array becomes a reference to an array in Perl.
		674
		675	=item string
		676
		677	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		678	are represented by the same codepoints in the Perl string, so no manual
		679	decoding is necessary.
		680
		681	=item number
		682
		683	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
		685	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
		687	might represent more values exactly than (floating point) numbers.
		688
		689	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
		691	a numeric (floating point) value if that is possible without loss of
		692	precision. Otherwise it will preserve the number as a string value.
		693
		694	Numbers containing a fractional or exponential part will always be
		695	represented as numeric (floating point) values, possibly at a loss of
		696	precision.
		697
		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
		701	=item true, false
		702
		703	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
		705	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
		706	the C<JSON::XS::is_bool> function.
		707
		708	=item null
		709
		710	A JSON null atom becomes C<undef> in Perl.
		711
		712	=back
		713
		714
		715	=head2 PERL -> JSON
		716
		717	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		718	truly typeless language, so we can only guess which JSON type is meant by
		719	a Perl value.
		720
		721	=over 4
		722
		723	=item hash references
		724
		725	Perl hash references become JSON objects. As there is no inherent ordering
		726	in hash keys (or JSON objects), they will usually be encoded in a
		727	pseudo-random order that can change between runs of the same program but
		728	stays generally the same within a single run of a program. JSON::XS can
		729	optionally sort the hash keys (determined by the I<canonical> flag), so
		730	the same datastructure will serialise to the same JSON text (given same
		731	settings and version of JSON::XS), but this incurs a runtime overhead
		732	and is only rarely useful, e.g. when you want to compare some JSON text
		733	against another for equality.
		734
		735	=item array references
		736
		737	Perl array references become JSON arrays.
		738
		739	=item other references
		740
		741	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
		743	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.
		745
		746	to_json [\0,JSON::XS::true] # yields [false,true]
		747
		748	=item JSON::XS::true, JSON::XS::false
		749
		750	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.
		752
		753	=item blessed objects
		754
		755	Blessed objects are not allowed. JSON::XS currently tries to encode their
		756	underlying representation (hash- or arrayref), but this behaviour might
		757	change in future versions.
		758
		759	=item simple scalars
		760
		761	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
		763	JSON null value, scalars that have last been used in a string context
		764	before encoding as JSON strings and anything else as number value:
		765
		766	# dump as number
		767	to_json [2] # yields [2]
		768	to_json [-3.0e17] # yields [-3e+17]
		769	my $value = 5; to_json [$value] # yields [5]
		770
		771	# used as string, so dump as string
		772	print $value;
		773	to_json [$value] # yields ["5"]
		774
		775	# undef becomes null
		776	to_json [undef] # yields [null]
		777
		778	You can force the type to be a JSON string by stringifying it:
		779
		780	my $x = 3.1; # some variable containing a number
		781	"$x"; # stringified
		782	$x .= ""; # another, more awkward way to stringify
		783	print $x; # perl does it for you, too, quite often
		784
		785	You can force the type to be a JSON number by numifying it:
		786
		787	my $x = "3"; # some variable containing a string
		788	$x += 0; # numify it, ensuring it will be dumped as a number
		789	$x *= 1; # same thing, the choice is yours.
		790
		791	You can not currently force the type in other, less obscure, ways. Tell me
		792	if you need this capability.
		793
		794	=back
		795
241		796
242	=head1 COMPARISON	797	=head1 COMPARISON
243		798
244	As already mentioned, this module was created because none of the existing	799	As already mentioned, this module was created because none of the existing
245	JSON modules could be made to work correctly. First I will describe the	800	JSON modules could be made to work correctly. First I will describe the
…		…
251		806
252	=item JSON 1.07	807	=item JSON 1.07
253		808
254	Slow (but very portable, as it is written in pure Perl).	809	Slow (but very portable, as it is written in pure Perl).
255		810
256	Undocumented/buggy Unicode handling (how JSON handles unicode values is	811	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
257	undocumented. One can get far by feeding it unicode strings and doing	812	undocumented. One can get far by feeding it Unicode strings and doing
258	en-/decoding oneself, but unicode escapes are not working properly).	813	en-/decoding oneself, but Unicode escapes are not working properly).
259		814
260	No roundtripping (strings get clobbered if they look like numbers, e.g.	815	No round-tripping (strings get clobbered if they look like numbers, e.g.
261	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	816	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
262	decode into the number 2.	817	decode into the number 2.
263		818
264	=item JSON::PC 0.01	819	=item JSON::PC 0.01
265		820
266	Very fast.	821	Very fast.
267		822
268	Undocumented/buggy Unicode handling.	823	Undocumented/buggy Unicode handling.
269		824
270	No roundtripping.	825	No round-tripping.
271		826
272	Has problems handling many Perl values (e.g. regex results and other magic	827	Has problems handling many Perl values (e.g. regex results and other magic
273	values will make it croak).	828	values will make it croak).
274		829
275	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	830	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
276	which is not a valid JSON string.	831	which is not a valid JSON text.
277		832
278	Unmaintained (maintainer unresponsive for many months, bugs are not	833	Unmaintained (maintainer unresponsive for many months, bugs are not
279	getting fixed).	834	getting fixed).
280		835
281	=item JSON::Syck 0.21	836	=item JSON::Syck 0.21
…		…
283	Very buggy (often crashes).	838	Very buggy (often crashes).
284		839
285	Very inflexible (no human-readable format supported, format pretty much	840	Very inflexible (no human-readable format supported, format pretty much
286	undocumented. I need at least a format for easy reading by humans and a	841	undocumented. I need at least a format for easy reading by humans and a
287	single-line compact format for use in a protocol, and preferably a way to	842	single-line compact format for use in a protocol, and preferably a way to
288	generate ASCII-only JSON strings).	843	generate ASCII-only JSON texts).
289		844
290	Completely broken (and confusingly documented) Unicode handling (unicode	845	Completely broken (and confusingly documented) Unicode handling (Unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	846	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	847	I<different> values on en- and decoding to get symmetric behaviour).
293		848
294	No roundtripping (simple cases work, but this depends on wether the scalar	849	No round-tripping (simple cases work, but this depends on whether the scalar
295	value was used in a numeric context or not).	850	value was used in a numeric context or not).
296		851
297	Dumping hashes may skip hash values depending on iterator state.	852	Dumping hashes may skip hash values depending on iterator state.
298		853
299	Unmaintained (maintainer unresponsive for many months, bugs are not	854	Unmaintained (maintainer unresponsive for many months, bugs are not
300	getting fixed).	855	getting fixed).
301		856
302	Does not check input for validity (i.e. will accept non-JSON input and	857	Does not check input for validity (i.e. will accept non-JSON input and
303	return "something" instead of raising an exception. This is a security	858	return "something" instead of raising an exception. This is a security
304	issue: imagine two banks transfering money between each other using	859	issue: imagine two banks transferring money between each other using
305	JSON. One bank might parse a given non-JSON request and deduct money,	860	JSON. One bank might parse a given non-JSON request and deduct money,
306	while the other might reject the transaction with a syntax error. While a	861	while the other might reject the transaction with a syntax error. While a
307	good protocol will at least recover, that is extra unnecessary work and	862	good protocol will at least recover, that is extra unnecessary work and
308	the transaction will still not succeed).	863	the transaction will still not succeed).
309		864
310	=item JSON::DWIW 0.04	865	=item JSON::DWIW 0.04
311		866
312	Very fast. Very natural. Very nice.	867	Very fast. Very natural. Very nice.
313		868
314	Undocumented unicode handling (but the best of the pack. Unicode escapes	869	Undocumented Unicode handling (but the best of the pack. Unicode escapes
315	still don't get parsed properly).	870	still don't get parsed properly).
316		871
317	Very inflexible.	872	Very inflexible.
318		873
319	No roundtripping.	874	No round-tripping.
320		875
321	Does not generate valid JSON (key strings are often unquoted, empty keys	876	Does not generate valid JSON texts (key strings are often unquoted, empty keys
322	result in nothing being output)	877	result in nothing being output)
323		878
324	Does not check input for validity.	879	Does not check input for validity.
325		880
326	=back	881	=back
		882
		883
		884	=head2 JSON and YAML
		885
		886	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		887	however, a mass hysteria and very far from the truth. In general, there is
		888	no way to configure JSON::XS to output a data structure as valid YAML.
		889
		890	If you really must use JSON::XS to generate YAML, you should use this
		891	algorithm (subject to change in future versions):
		892
		893	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		894	my $yaml = $to_yaml->encode ($ref) . "\n";
		895
		896	This will usually generate JSON texts that also parse as valid
		897	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
		899	keys are noticeably shorter than the 1024 characters YAML allows.
		900
		901	There might be other incompatibilities that I am not aware of. In general
		902	you should not try to generate YAML with a JSON generator or vice versa,
		903	or try to parse JSON with a YAML parser or vice versa: chances are high
		904	that you will run into severe interoperability problems.
		905
327		906
328	=head2 SPEED	907	=head2 SPEED
329		908
330	It seems that JSON::XS is surprisingly fast, as shown in the following	909	It seems that JSON::XS is surprisingly fast, as shown in the following
331	tables. They have been generated with the help of the C<eg/bench> program	910	tables. They have been generated with the help of the C<eg/bench> program
332	in the JSON::XS distribution, to make it easy to compare on your own	911	in the JSON::XS distribution, to make it easy to compare on your own
333	system.	912	system.
334		913
335	First is a comparison between various modules using a very simple JSON	914	First comes a comparison between various modules using a very short
		915	single-line JSON string:
		916
		917	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		918	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		919
336	string, showing the number of encodes/decodes per second (JSON::XS is	920	It shows the number of encodes/decodes per second (JSON::XS uses
337	the functional interface, while JSON::XS/2 is the OO interface with	921	the functional interface, while JSON::XS/2 uses the OO interface
338	pretty-printing and hashkey sorting enabled).	922	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		923	shrink). Higher is better:
339		924
340	module \| encode \| decode \|	925	module \| encode \| decode \|
341	-----------\|------------\|------------\|	926	-----------\|------------\|------------\|
342	JSON \| 14006 \| 6820 \|	927	JSON 1.x \| 4990.842 \| 4088.813 \|
343	JSON::DWIW \| 200937 \| 120386 \|	928	JSON::DWIW \| 51653.990 \| 71575.154 \|
344	JSON::PC \| 85065 \| 129366 \|	929	JSON::PC \| 65948.176 \| 74631.744 \|
345	JSON::Syck \| 59898 \| 44232 \|	930	JSON::PP \| 8931.652 \| 3817.168 \|
346	JSON::XS \| 1171478 \| 342435 \|	931	JSON::Syck \| 24877.248 \| 27776.848 \|
347	JSON::XS/2 \| 730760 \| 328714 \|	932	JSON::XS \| 388361.481 \| 227951.304 \|
		933	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		934	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		935	Storable \| 16500.016 \| 135300.129 \|
348	-----------+------------+------------+	936	-----------+------------+------------+
349		937
350	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	938	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		939	about three times faster on decoding, and over forty times faster
351	times faster than JSON, even with pretty-printing and key sorting.	940	than JSON, even with pretty-printing and key sorting. It also compares
		941	favourably to Storable for small amounts of data.
352		942
353	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	943	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
354	search API (http://nanoref.com/yahooapis/mgPdGg):	944	search API (http://nanoref.com/yahooapis/mgPdGg):
355		945
356	module \| encode \| decode \|	946	module \| encode \| decode \|
357	-----------\|------------\|------------\|	947	-----------\|------------\|------------\|
358	JSON \| 673 \| 38 \|	948	JSON 1.x \| 55.260 \| 34.971 \|
359	JSON::DWIW \| 5271 \| 770 \|	949	JSON::DWIW \| 825.228 \| 1082.513 \|
360	JSON::PC \| 9901 \| 2491 \|	950	JSON::PC \| 3571.444 \| 2394.829 \|
361	JSON::Syck \| 2360 \| 786 \|	951	JSON::PP \| 210.987 \| 32.574 \|
362	JSON::XS \| 37398 \| 3202 \|	952	JSON::Syck \| 552.551 \| 787.544 \|
363	JSON::XS/2 \| 13765 \| 3153 \|	953	JSON::XS \| 5780.463 \| 4854.519 \|
		954	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		955	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		956	Storable \| 4445.002 \| 5235.027 \|
364	-----------+------------+------------+	957	-----------+------------+------------+
365		958
366	Again, JSON::XS leads by far in the encoding case, while still beating	959	Again, JSON::XS leads by far (except for Storable which non-surprisingly
367	every other module in the decoding case.	960	decodes faster).
368		961
369	Last example is an almost 8MB large hash with many large binary values	962	On large strings containing lots of high Unicode characters, some modules
370	(PNG files), resulting in a lot of escaping:	963	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		964	will be broken due to missing (or wrong) Unicode handling. Others refuse
		965	to decode or encode properly, so it was impossible to prepare a fair
		966	comparison table for that case.
		967
		968
		969	=head1 SECURITY CONSIDERATIONS
		970
		971	When you are using JSON in a protocol, talking to untrusted potentially
		972	hostile creatures requires relatively few measures.
		973
		974	First of all, your JSON decoder should be secure, that is, should not have
		975	any buffer overflows. Obviously, this module should ensure that and I am
		976	trying hard on making that true, but you never know.
		977
		978	Second, you need to avoid resource-starving attacks. That means you should
		979	limit the size of JSON texts you accept, or make sure then when your
		980	resources run out, that's just fine (e.g. by using a separate process that
		981	can crash safely). The size of a JSON text in octets or characters is
		982	usually a good indication of the size of the resources required to decode
		983	it into a Perl structure. While JSON::XS can check the size of the JSON
		984	text, it might be too late when you already have it in memory, so you
		985	might want to check the size before you accept the string.
		986
		987	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
		989	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
		991	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
		993	has a smaller stack, you should adjust this setting accordingly with the
		994	C<max_depth> method.
		995
		996	And last but least, something else could bomb you that I forgot to think
		997	of. In that case, you get to keep the pieces. I am always open for hints,
		998	though...
		999
		1000	If you are using JSON::XS to return packets to consumption
		1001	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
		1003	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
		1005	browser developers care only for features, not about doing security
		1006	right).
		1007
		1008
		1009	=head1 THREADS
		1010
		1011	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
		1013	horribly slow so-called "threads" which are simply slow and bloated
		1014	process simulations - use fork, its I<much> faster, cheaper, better).
		1015
		1016	(It might actually work, but you have been warned).
		1017
371		1018
372	=head1 BUGS	1019	=head1 BUGS
373		1020
374	While the goal of this module is to be correct, that unfortunately does	1021	While the goal of this module is to be correct, that unfortunately does
375	not mean its bug-free, only that I think its design is bug-free. It is	1022	not mean its bug-free, only that I think its design is bug-free. It is
376	still very young and not well-tested. If you keep reporting bugs they will	1023	still relatively early in its development. If you keep reporting bugs they
377	be fixed swiftly, though.	1024	will be fixed swiftly, though.
		1025
		1026	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.
378		1028
379	=cut	1029	=cut
		1030
		1031	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1032	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1033
		1034	sub true() { $true }
		1035	sub false() { $false }
		1036
		1037	sub is_bool($) {
		1038	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1039	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1040	}
		1041
		1042	XSLoader::load "JSON::XS", $VERSION;
		1043
		1044	package JSON::XS::Boolean;
		1045
		1046	use overload
		1047	"0+" => sub { ${$_[0]} },
		1048	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1049	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1050	fallback => 1;
380		1051
381	1;	1052	1;
382		1053
383	=head1 AUTHOR	1054	=head1 AUTHOR
384		1055

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Comparing JSON-XS/XS.pm (file contents): Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs. Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC