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Revision 1.47 by root, Mon Jun 25 06:57:42 2007 UTC vs.
Revision 1.121 by root, Mon Jul 13 22:13:17 2009 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
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		19
19	# OO-interface	20	# OO-interface
20		21
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
23	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
24		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
25	=head1 DESCRIPTION	34	=head1 DESCRIPTION
26		35
27	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
28	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
29	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.
30		47
31	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
32	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
33	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
34	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
35	reports for other reasons.	52	reports for other reasons.
36		53
37	See COMPARISON, below, for a comparison to some other JSON modules.
38
39	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
40	vice versa.	55	vice versa.
41		56
42	=head2 FEATURES	57	=head2 FEATURES
43		58
44	=over 4	59	=over 4
45		60
46	=item * correct unicode handling	61	=item * correct Unicode handling
47		62
48	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
49	it does so.	64	so, and even documents what "correct" means.
50		65
51	=item * round-trip integrity	66	=item * round-trip integrity
52		67
53	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
54	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
55	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
56	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
57		73
58	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
59		75
60	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
61	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
62	feature).	78	feature).
63		79
64	=item * fast	80	=item * fast
65		81
66	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
67	of speed, too.	83	this module usually compares favourably in terms of speed, too.
68		84
69	=item * simple to use	85	=item * simple to use
70		86
71	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
72	interface.	88	oriented interface interface.
73		89
74	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
75		91
76	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
77	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
78	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
79	unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
80	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
81		97
82	=back	98	=back
83		99
84	=cut	100	=cut
85		101
86	package JSON::XS;	102	package JSON::XS;
87		103
88	use strict;	104	use common::sense;
89		105
90	our $VERSION = '1.4';	106	our $VERSION = '2.24';
91	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
92		108
93	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
		110
		111	sub to_json($) {
		112	require Carp;
		113	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");
		114	}
		115
		116	sub from_json($) {
		117	require Carp;
		118	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");
		119	}
94		120
95	use Exporter;	121	use Exporter;
96	use XSLoader;	122	use XSLoader;
97		123
98	=head1 FUNCTIONAL INTERFACE	124	=head1 FUNCTIONAL INTERFACE
99		125
100	The following convinience methods are provided by this module. They are	126	The following convenience methods are provided by this module. They are
101	exported by default:	127	exported by default:
102		128
103	=over 4	129	=over 4
104		130
105	=item $json_text = to_json $perl_scalar	131	=item $json_text = encode_json $perl_scalar
106		132
107	Converts the given Perl data structure (a simple scalar or a reference to	133	Converts the given Perl data structure to a UTF-8 encoded, binary string
108	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	134	(that is, the string contains octets only). Croaks on error.
109	octets only). Croaks on error.
110		135
111	This function call is functionally identical to:	136	This function call is functionally identical to:
112		137
113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114		139
115	except being faster.	140	Except being faster.
116		141
117	=item $perl_scalar = from_json $json_text	142	=item $perl_scalar = decode_json $json_text
118		143
119	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	144	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
120	parse that as an UTF-8 encoded JSON text, returning the resulting simple	145	to parse that as an UTF-8 encoded JSON text, returning the resulting
121	scalar or reference. Croaks on error.	146	reference. Croaks on error.
122		147
123	This function call is functionally identical to:	148	This function call is functionally identical to:
124		149
125	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
126		151
127	except being faster.	152	Except being faster.
128		153
129	=item $is_boolean = JSON::XS::is_bool $scalar	154	=item $is_boolean = JSON::XS::is_bool $scalar
130		155
131	Returns true if the passed scalar represents either JSON::XS::true or	156	Returns true if the passed scalar represents either JSON::XS::true or
132	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
136	Perl.	161	Perl.
137		162
138	=back	163	=back
139		164
140		165
		166	=head1 A FEW NOTES ON UNICODE AND PERL
		167
		168	Since this often leads to confusion, here are a few very clear words on
		169	how Unicode works in Perl, modulo bugs.
		170
		171	=over 4
		172
		173	=item 1. Perl strings can store characters with ordinal values > 255.
		174
		175	This enables you to store Unicode characters as single characters in a
		176	Perl string - very natural.
		177
		178	=item 2. Perl does I<not> associate an encoding with your strings.
		179
		180	... until you force it to, e.g. when matching it against a regex, or
		181	printing the scalar to a file, in which case Perl either interprets your
		182	string as locale-encoded text, octets/binary, or as Unicode, depending
		183	on various settings. In no case is an encoding stored together with your
		184	data, it is I<use> that decides encoding, not any magical meta data.
		185
		186	=item 3. The internal utf-8 flag has no meaning with regards to the
		187	encoding of your string.
		188
		189	Just ignore that flag unless you debug a Perl bug, a module written in
		190	XS or want to dive into the internals of perl. Otherwise it will only
		191	confuse you, as, despite the name, it says nothing about how your string
		192	is encoded. You can have Unicode strings with that flag set, with that
		193	flag clear, and you can have binary data with that flag set and that flag
		194	clear. Other possibilities exist, too.
		195
		196	If you didn't know about that flag, just the better, pretend it doesn't
		197	exist.
		198
		199	=item 4. A "Unicode String" is simply a string where each character can be
		200	validly interpreted as a Unicode code point.
		201
		202	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		203	Unicode string encoded in UTF-8, giving you a binary string.
		204
		205	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		206
		207	It's a fact. Learn to live with it.
		208
		209	=back
		210
		211	I hope this helps :)
		212
		213
141	=head1 OBJECT-ORIENTED INTERFACE	214	=head1 OBJECT-ORIENTED INTERFACE
142		215
143	The object oriented interface lets you configure your own encoding or	216	The object oriented interface lets you configure your own encoding or
144	decoding style, within the limits of supported formats.	217	decoding style, within the limits of supported formats.
145		218
…		…
156	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	229	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
157	=> {"a": [1, 2]}	230	=> {"a": [1, 2]}
158		231
159	=item $json = $json->ascii ([$enable])	232	=item $json = $json->ascii ([$enable])
160		233
		234	=item $enabled = $json->get_ascii
		235
161	If C<$enable> is true (or missing), then the C<encode> method will not	236	If C<$enable> is true (or missing), then the C<encode> method will not
162	generate characters outside the code range C<0..127> (which is ASCII). Any	237	generate characters outside the code range C<0..127> (which is ASCII). Any
163	unicode characters outside that range will be escaped using either a	238	Unicode characters outside that range will be escaped using either a
164	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	239	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
165	as per RFC4627. The resulting encoded JSON text can be treated as a native	240	as per RFC4627. The resulting encoded JSON text can be treated as a native
166	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	241	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
167	or any other superset of ASCII.	242	or any other superset of ASCII.
168		243
169	If C<$enable> is false, then the C<encode> method will not escape Unicode	244	If C<$enable> is false, then the C<encode> method will not escape Unicode
170	characters unless required by the JSON syntax or other flags. This results	245	characters unless required by the JSON syntax or other flags. This results
171	in a faster and more compact format.	246	in a faster and more compact format.
172		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
173	The main use for this flag is to produce JSON texts that can be	251	The main use for this flag is to produce JSON texts that can be
174	transmitted over a 7-bit channel, as the encoded JSON texts will not	252	transmitted over a 7-bit channel, as the encoded JSON texts will not
175	contain any 8 bit characters.	253	contain any 8 bit characters.
176		254
177	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178	=> ["\ud801\udc01"]	256	=> ["\ud801\udc01"]
179		257
180	=item $json = $json->latin1 ([$enable])	258	=item $json = $json->latin1 ([$enable])
181		259
		260	=item $enabled = $json->get_latin1
		261
182	If C<$enable> is true (or missing), then the C<encode> method will encode	262	If C<$enable> is true (or missing), then the C<encode> method will encode
183	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	263	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
184	outside the code range C<0..255>. The resulting string can be treated as a	264	outside the code range C<0..255>. The resulting string can be treated as a
185	latin1-encoded JSON text or a native unicode string. The C<decode> method	265	latin1-encoded JSON text or a native Unicode string. The C<decode> method
186	will not be affected in any way by this flag, as C<decode> by default	266	will not be affected in any way by this flag, as C<decode> by default
187	expects unicode, which is a strict superset of latin1.	267	expects Unicode, which is a strict superset of latin1.
188		268
189	If C<$enable> is false, then the C<encode> method will not escape Unicode	269	If C<$enable> is false, then the C<encode> method will not escape Unicode
190	characters unless required by the JSON syntax or other flags.	270	characters unless required by the JSON syntax or other flags.
		271
		272	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		273	document.
191		274
192	The main use for this flag is efficiently encoding binary data as JSON	275	The main use for this flag is efficiently encoding binary data as JSON
193	text, as most octets will not be escaped, resulting in a smaller encoded	276	text, as most octets will not be escaped, resulting in a smaller encoded
194	size. The disadvantage is that the resulting JSON text is encoded	277	size. The disadvantage is that the resulting JSON text is encoded
195	in latin1 (and must correctly be treated as such when storing and	278	in latin1 (and must correctly be treated as such when storing and
196	transfering), a rare encoding for JSON. It is therefore most useful when	279	transferring), a rare encoding for JSON. It is therefore most useful when
197	you want to store data structures known to contain binary data efficiently	280	you want to store data structures known to contain binary data efficiently
198	in files or databases, not when talking to other JSON encoders/decoders.	281	in files or databases, not when talking to other JSON encoders/decoders.
199		282
200	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	283	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
201	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	284	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
202		285
203	=item $json = $json->utf8 ([$enable])	286	=item $json = $json->utf8 ([$enable])
		287
		288	=item $enabled = $json->get_utf8
204		289
205	If C<$enable> is true (or missing), then the C<encode> method will encode	290	If C<$enable> is true (or missing), then the C<encode> method will encode
206	the JSON result into UTF-8, as required by many protocols, while the	291	the JSON result into UTF-8, as required by many protocols, while the
207	C<decode> method expects to be handled an UTF-8-encoded string. Please	292	C<decode> method expects to be handled an UTF-8-encoded string. Please
208	note that UTF-8-encoded strings do not contain any characters outside the	293	note that UTF-8-encoded strings do not contain any characters outside the
209	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	294	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
210	versions, enabling this option might enable autodetection of the UTF-16	295	versions, enabling this option might enable autodetection of the UTF-16
211	and UTF-32 encoding families, as described in RFC4627.	296	and UTF-32 encoding families, as described in RFC4627.
212		297
213	If C<$enable> is false, then the C<encode> method will return the JSON	298	If C<$enable> is false, then the C<encode> method will return the JSON
214	string as a (non-encoded) unicode string, while C<decode> expects thus a	299	string as a (non-encoded) Unicode string, while C<decode> expects thus a
215	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	300	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
216	to be done yourself, e.g. using the Encode module.	301	to be done yourself, e.g. using the Encode module.
		302
		303	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		304	document.
217		305
218	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
219		307
220	use Encode;	308	use Encode;
221	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
242	]	330	]
243	}	331	}
244		332
245	=item $json = $json->indent ([$enable])	333	=item $json = $json->indent ([$enable])
246		334
		335	=item $enabled = $json->get_indent
		336
247	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	337	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
248	format as output, putting every array member or object/hash key-value pair	338	format as output, putting every array member or object/hash key-value pair
249	into its own line, identing them properly.	339	into its own line, indenting them properly.
250		340
251	If C<$enable> is false, no newlines or indenting will be produced, and the	341	If C<$enable> is false, no newlines or indenting will be produced, and the
252	resulting JSON text is guarenteed not to contain any C<newlines>.	342	resulting JSON text is guaranteed not to contain any C<newlines>.
253		343
254	This setting has no effect when decoding JSON texts.	344	This setting has no effect when decoding JSON texts.
255		345
256	=item $json = $json->space_before ([$enable])	346	=item $json = $json->space_before ([$enable])
		347
		348	=item $enabled = $json->get_space_before
257		349
258	If C<$enable> is true (or missing), then the C<encode> method will add an extra	350	If C<$enable> is true (or missing), then the C<encode> method will add an extra
259	optional space before the C<:> separating keys from values in JSON objects.	351	optional space before the C<:> separating keys from values in JSON objects.
260		352
261	If C<$enable> is false, then the C<encode> method will not add any extra	353	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
267	Example, space_before enabled, space_after and indent disabled:	359	Example, space_before enabled, space_after and indent disabled:
268		360
269	{"key" :"value"}	361	{"key" :"value"}
270		362
271	=item $json = $json->space_after ([$enable])	363	=item $json = $json->space_after ([$enable])
		364
		365	=item $enabled = $json->get_space_after
272		366
273	If C<$enable> is true (or missing), then the C<encode> method will add an extra	367	If C<$enable> is true (or missing), then the C<encode> method will add an extra
274	optional space after the C<:> separating keys from values in JSON objects	368	optional space after the C<:> separating keys from values in JSON objects
275	and extra whitespace after the C<,> separating key-value pairs and array	369	and extra whitespace after the C<,> separating key-value pairs and array
276	members.	370	members.
…		…
282		376
283	Example, space_before and indent disabled, space_after enabled:	377	Example, space_before and indent disabled, space_after enabled:
284		378
285	{"key": "value"}	379	{"key": "value"}
286		380
		381	=item $json = $json->relaxed ([$enable])
		382
		383	=item $enabled = $json->get_relaxed
		384
		385	If C<$enable> is true (or missing), then C<decode> will accept some
		386	extensions to normal JSON syntax (see below). C<encode> will not be
		387	affected in anyway. I<Be aware that this option makes you accept invalid
		388	JSON texts as if they were valid!>. I suggest only to use this option to
		389	parse application-specific files written by humans (configuration files,
		390	resource files etc.)
		391
		392	If C<$enable> is false (the default), then C<decode> will only accept
		393	valid JSON texts.
		394
		395	Currently accepted extensions are:
		396
		397	=over 4
		398
		399	=item * list items can have an end-comma
		400
		401	JSON I<separates> array elements and key-value pairs with commas. This
		402	can be annoying if you write JSON texts manually and want to be able to
		403	quickly append elements, so this extension accepts comma at the end of
		404	such items not just between them:
		405
		406	[
		407	1,
		408	2, <- this comma not normally allowed
		409	]
		410	{
		411	"k1": "v1",
		412	"k2": "v2", <- this comma not normally allowed
		413	}
		414
		415	=item * shell-style '#'-comments
		416
		417	Whenever JSON allows whitespace, shell-style comments are additionally
		418	allowed. They are terminated by the first carriage-return or line-feed
		419	character, after which more white-space and comments are allowed.
		420
		421	[
		422	1, # this comment not allowed in JSON
		423	# neither this one...
		424	]
		425
		426	=back
		427
287	=item $json = $json->canonical ([$enable])	428	=item $json = $json->canonical ([$enable])
		429
		430	=item $enabled = $json->get_canonical
288		431
289	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	432	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
290	by sorting their keys. This is adding a comparatively high overhead.	433	by sorting their keys. This is adding a comparatively high overhead.
291		434
292	If C<$enable> is false, then the C<encode> method will output key-value	435	If C<$enable> is false, then the C<encode> method will output key-value
293	pairs in the order Perl stores them (which will likely change between runs	436	pairs in the order Perl stores them (which will likely change between runs
294	of the same script).	437	of the same script).
295		438
296	This option is useful if you want the same data structure to be encoded as	439	This option is useful if you want the same data structure to be encoded as
297	the same JSON text (given the same overall settings). If it is disabled,	440	the same JSON text (given the same overall settings). If it is disabled,
298	the same hash migh be encoded differently even if contains the same data,	441	the same hash might be encoded differently even if contains the same data,
299	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
300		443
301	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
302		445
303	=item $json = $json->allow_nonref ([$enable])	446	=item $json = $json->allow_nonref ([$enable])
		447
		448	=item $enabled = $json->get_allow_nonref
304		449
305	If C<$enable> is true (or missing), then the C<encode> method can convert a	450	If C<$enable> is true (or missing), then the C<encode> method can convert a
306	non-reference into its corresponding string, number or null JSON value,	451	non-reference into its corresponding string, number or null JSON value,
307	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	452	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
308	values instead of croaking.	453	values instead of croaking.
…		…
316	resulting in an invalid JSON text:	461	resulting in an invalid JSON text:
317		462
318	JSON::XS->new->allow_nonref->encode ("Hello, World!")	463	JSON::XS->new->allow_nonref->encode ("Hello, World!")
319	=> "Hello, World!"	464	=> "Hello, World!"
320		465
		466	=item $json = $json->allow_unknown ([$enable])
		467
		468	=item $enabled = $json->get_allow_unknown
		469
		470	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		471	exception when it encounters values it cannot represent in JSON (for
		472	example, filehandles) but instead will encode a JSON C<null> value. Note
		473	that blessed objects are not included here and are handled separately by
		474	c<allow_nonref>.
		475
		476	If C<$enable> is false (the default), then C<encode> will throw an
		477	exception when it encounters anything it cannot encode as JSON.
		478
		479	This option does not affect C<decode> in any way, and it is recommended to
		480	leave it off unless you know your communications partner.
		481
321	=item $json = $json->allow_blessed ([$enable])	482	=item $json = $json->allow_blessed ([$enable])
		483
		484	=item $enabled = $json->get_allow_blessed
322		485
323	If C<$enable> is true (or missing), then the C<encode> method will not	486	If C<$enable> is true (or missing), then the C<encode> method will not
324	barf when it encounters a blessed reference. Instead, the value of the	487	barf when it encounters a blessed reference. Instead, the value of the
325	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	488	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
326	disabled or no C<to_json> method found) or a representation of the	489	disabled or no C<TO_JSON> method found) or a representation of the
327	object (C<convert_blessed> enabled and C<to_json> method found) is being	490	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
328	encoded. Has no effect on C<decode>.	491	encoded. Has no effect on C<decode>.
329		492
330	If C<$enable> is false (the default), then C<encode> will throw an	493	If C<$enable> is false (the default), then C<encode> will throw an
331	exception when it encounters a blessed object.	494	exception when it encounters a blessed object.
332		495
333	=item $json = $json->convert_blessed ([$enable])	496	=item $json = $json->convert_blessed ([$enable])
		497
		498	=item $enabled = $json->get_convert_blessed
334		499
335	If C<$enable> is true (or missing), then C<encode>, upon encountering a	500	If C<$enable> is true (or missing), then C<encode>, upon encountering a
336	blessed object, will check for the availability of the C<TO_JSON> method	501	blessed object, will check for the availability of the C<TO_JSON> method
337	on the object's class. If found, it will be called in scalar context	502	on the object's class. If found, it will be called in scalar context
338	and the resulting scalar will be encoded instead of the object. If no	503	and the resulting scalar will be encoded instead of the object. If no
…		…
342	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	507	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
343	returns other blessed objects, those will be handled in the same	508	returns other blessed objects, those will be handled in the same
344	way. C<TO_JSON> must take care of not causing an endless recursion cycle	509	way. C<TO_JSON> must take care of not causing an endless recursion cycle
345	(== crash) in this case. The name of C<TO_JSON> was chosen because other	510	(== crash) in this case. The name of C<TO_JSON> was chosen because other
346	methods called by the Perl core (== not by the user of the object) are	511	methods called by the Perl core (== not by the user of the object) are
347	usually in upper case letters and to avoid collisions with the C<to_json>	512	usually in upper case letters and to avoid collisions with any C<to_json>
348	function.	513	function or method.
349		514
350	This setting does not yet influence C<decode> in any way, but in the	515	This setting does not yet influence C<decode> in any way, but in the
351	future, global hooks might get installed that influence C<decode> and are	516	future, global hooks might get installed that influence C<decode> and are
352	enabled by this setting.	517	enabled by this setting.
353		518
354	If C<$enable> is false, then the C<allow_blessed> setting will decide what	519	If C<$enable> is false, then the C<allow_blessed> setting will decide what
355	to do when a blessed object is found.	520	to do when a blessed object is found.
356		521
		522	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		523
		524	When C<$coderef> is specified, it will be called from C<decode> each
		525	time it decodes a JSON object. The only argument is a reference to the
		526	newly-created hash. If the code references returns a single scalar (which
		527	need not be a reference), this value (i.e. a copy of that scalar to avoid
		528	aliasing) is inserted into the deserialised data structure. If it returns
		529	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		530	original deserialised hash will be inserted. This setting can slow down
		531	decoding considerably.
		532
		533	When C<$coderef> is omitted or undefined, any existing callback will
		534	be removed and C<decode> will not change the deserialised hash in any
		535	way.
		536
		537	Example, convert all JSON objects into the integer 5:
		538
		539	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		540	# returns [5]
		541	$js->decode ('[{}]')
		542	# throw an exception because allow_nonref is not enabled
		543	# so a lone 5 is not allowed.
		544	$js->decode ('{"a":1, "b":2}');
		545
		546	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		547
		548	Works remotely similar to C<filter_json_object>, but is only called for
		549	JSON objects having a single key named C<$key>.
		550
		551	This C<$coderef> is called before the one specified via
		552	C<filter_json_object>, if any. It gets passed the single value in the JSON
		553	object. If it returns a single value, it will be inserted into the data
		554	structure. If it returns nothing (not even C<undef> but the empty list),
		555	the callback from C<filter_json_object> will be called next, as if no
		556	single-key callback were specified.
		557
		558	If C<$coderef> is omitted or undefined, the corresponding callback will be
		559	disabled. There can only ever be one callback for a given key.
		560
		561	As this callback gets called less often then the C<filter_json_object>
		562	one, decoding speed will not usually suffer as much. Therefore, single-key
		563	objects make excellent targets to serialise Perl objects into, especially
		564	as single-key JSON objects are as close to the type-tagged value concept
		565	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		566	support this in any way, so you need to make sure your data never looks
		567	like a serialised Perl hash.
		568
		569	Typical names for the single object key are C<__class_whatever__>, or
		570	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		571	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		572	with real hashes.
		573
		574	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		575	into the corresponding C<< $WIDGET{<id>} >> object:
		576
		577	# return whatever is in $WIDGET{5}:
		578	JSON::XS
		579	->new
		580	->filter_json_single_key_object (__widget__ => sub {
		581	$WIDGET{ $_[0] }
		582	})
		583	->decode ('{"__widget__": 5')
		584
		585	# this can be used with a TO_JSON method in some "widget" class
		586	# for serialisation to json:
		587	sub WidgetBase::TO_JSON {
		588	my ($self) = @_;
		589
		590	unless ($self->{id}) {
		591	$self->{id} = ..get..some..id..;
		592	$WIDGET{$self->{id}} = $self;
		593	}
		594
		595	{ __widget__ => $self->{id} }
		596	}
		597
357	=item $json = $json->shrink ([$enable])	598	=item $json = $json->shrink ([$enable])
		599
		600	=item $enabled = $json->get_shrink
358		601
359	Perl usually over-allocates memory a bit when allocating space for	602	Perl usually over-allocates memory a bit when allocating space for
360	strings. This flag optionally resizes strings generated by either	603	strings. This flag optionally resizes strings generated by either
361	C<encode> or C<decode> to their minimum size possible. This can save	604	C<encode> or C<decode> to their minimum size possible. This can save
362	memory when your JSON texts are either very very long or you have many	605	memory when your JSON texts are either very very long or you have many
…		…
380	strings that look like integers or floats into integers or floats	623	strings that look like integers or floats into integers or floats
381	internally (there is no difference on the Perl level), saving space.	624	internally (there is no difference on the Perl level), saving space.
382		625
383	=item $json = $json->max_depth ([$maximum_nesting_depth])	626	=item $json = $json->max_depth ([$maximum_nesting_depth])
384		627
		628	=item $max_depth = $json->get_max_depth
		629
385	Sets the maximum nesting level (default C<512>) accepted while encoding	630	Sets the maximum nesting level (default C<512>) accepted while encoding
386	or decoding. If the JSON text or Perl data structure has an equal or	631	or decoding. If a higher nesting level is detected in JSON text or a Perl
387	higher nesting level then this limit, then the encoder and decoder will	632	data structure, then the encoder and decoder will stop and croak at that
388	stop and croak at that point.	633	point.
389		634
390	Nesting level is defined by number of hash- or arrayrefs that the encoder	635	Nesting level is defined by number of hash- or arrayrefs that the encoder
391	needs to traverse to reach a given point or the number of C<{> or C<[>	636	needs to traverse to reach a given point or the number of C<{> or C<[>
392	characters without their matching closing parenthesis crossed to reach a	637	characters without their matching closing parenthesis crossed to reach a
393	given character in a string.	638	given character in a string.
394		639
395	Setting the maximum depth to one disallows any nesting, so that ensures	640	Setting the maximum depth to one disallows any nesting, so that ensures
396	that the object is only a single hash/object or array.	641	that the object is only a single hash/object or array.
397		642
398	The argument to C<max_depth> will be rounded up to the next highest power
399	of two. If no argument is given, the highest possible setting will be	643	If no argument is given, the highest possible setting will be used, which
400	used, which is rarely useful.	644	is rarely useful.
		645
		646	Note that nesting is implemented by recursion in C. The default value has
		647	been chosen to be as large as typical operating systems allow without
		648	crashing.
401		649
402	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	650	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
403		651
404	=item $json = $json->max_size ([$maximum_string_size])	652	=item $json = $json->max_size ([$maximum_string_size])
		653
		654	=item $max_size = $json->get_max_size
405		655
406	Set the maximum length a JSON text may have (in bytes) where decoding is	656	Set the maximum length a JSON text may have (in bytes) where decoding is
407	being attempted. The default is C<0>, meaning no limit. When C<decode>	657	being attempted. The default is C<0>, meaning no limit. When C<decode>
408	is called on a string longer then this number of characters it will not	658	is called on a string that is longer then this many bytes, it will not
409	attempt to decode the string but throw an exception. This setting has no	659	attempt to decode the string but throw an exception. This setting has no
410	effect on C<encode> (yet).	660	effect on C<encode> (yet).
411		661
412	The argument to C<max_size> will be rounded up to the next B<highest>	662	If no argument is given, the limit check will be deactivated (same as when
413	power of two (so may be more than requested). If no argument is given, the	663	C<0> is specified).
414	limit check will be deactivated (same as when C<0> is specified).
415		664
416	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	665	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
417		666
418	=item $json_text = $json->encode ($perl_scalar)	667	=item $json_text = $json->encode ($perl_scalar)
419		668
…		…
448	=> ([], 3)	697	=> ([], 3)
449		698
450	=back	699	=back
451		700
452		701
		702	=head1 INCREMENTAL PARSING
		703
		704	In some cases, there is the need for incremental parsing of JSON
		705	texts. While this module always has to keep both JSON text and resulting
		706	Perl data structure in memory at one time, it does allow you to parse a
		707	JSON stream incrementally. It does so by accumulating text until it has
		708	a full JSON object, which it then can decode. This process is similar to
		709	using C<decode_prefix> to see if a full JSON object is available, but
		710	is much more efficient (and can be implemented with a minimum of method
		711	calls).
		712
		713	JSON::XS will only attempt to parse the JSON text once it is sure it
		714	has enough text to get a decisive result, using a very simple but
		715	truly incremental parser. This means that it sometimes won't stop as
		716	early as the full parser, for example, it doesn't detect parenthese
		717	mismatches. The only thing it guarantees is that it starts decoding as
		718	soon as a syntactically valid JSON text has been seen. This means you need
		719	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		720	parsing in the presence if syntax errors.
		721
		722	The following methods implement this incremental parser.
		723
		724	=over 4
		725
		726	=item [void, scalar or list context] = $json->incr_parse ([$string])
		727
		728	This is the central parsing function. It can both append new text and
		729	extract objects from the stream accumulated so far (both of these
		730	functions are optional).
		731
		732	If C<$string> is given, then this string is appended to the already
		733	existing JSON fragment stored in the C<$json> object.
		734
		735	After that, if the function is called in void context, it will simply
		736	return without doing anything further. This can be used to add more text
		737	in as many chunks as you want.
		738
		739	If the method is called in scalar context, then it will try to extract
		740	exactly I<one> JSON object. If that is successful, it will return this
		741	object, otherwise it will return C<undef>. If there is a parse error,
		742	this method will croak just as C<decode> would do (one can then use
		743	C<incr_skip> to skip the errornous part). This is the most common way of
		744	using the method.
		745
		746	And finally, in list context, it will try to extract as many objects
		747	from the stream as it can find and return them, or the empty list
		748	otherwise. For this to work, there must be no separators between the JSON
		749	objects or arrays, instead they must be concatenated back-to-back. If
		750	an error occurs, an exception will be raised as in the scalar context
		751	case. Note that in this case, any previously-parsed JSON texts will be
		752	lost.
		753
		754	=item $lvalue_string = $json->incr_text
		755
		756	This method returns the currently stored JSON fragment as an lvalue, that
		757	is, you can manipulate it. This I<only> works when a preceding call to
		758	C<incr_parse> in I<scalar context> successfully returned an object. Under
		759	all other circumstances you must not call this function (I mean it.
		760	although in simple tests it might actually work, it I<will> fail under
		761	real world conditions). As a special exception, you can also call this
		762	method before having parsed anything.
		763
		764	This function is useful in two cases: a) finding the trailing text after a
		765	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		766	(such as commas).
		767
		768	=item $json->incr_skip
		769
		770	This will reset the state of the incremental parser and will remove
		771	the parsed text from the input buffer so far. This is useful after
		772	C<incr_parse> died, in which case the input buffer and incremental parser
		773	state is left unchanged, to skip the text parsed so far and to reset the
		774	parse state.
		775
		776	The difference to C<incr_reset> is that only text until the parse error
		777	occured is removed.
		778
		779	=item $json->incr_reset
		780
		781	This completely resets the incremental parser, that is, after this call,
		782	it will be as if the parser had never parsed anything.
		783
		784	This is useful if you want to repeatedly parse JSON objects and want to
		785	ignore any trailing data, which means you have to reset the parser after
		786	each successful decode.
		787
		788	=back
		789
		790	=head2 LIMITATIONS
		791
		792	All options that affect decoding are supported, except
		793	C<allow_nonref>. The reason for this is that it cannot be made to
		794	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		795	them back to back and still decode them perfectly. This does not hold true
		796	for JSON numbers, however.
		797
		798	For example, is the string C<1> a single JSON number, or is it simply the
		799	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		800	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		801	takes the conservative route and disallows this case.
		802
		803	=head2 EXAMPLES
		804
		805	Some examples will make all this clearer. First, a simple example that
		806	works similarly to C<decode_prefix>: We want to decode the JSON object at
		807	the start of a string and identify the portion after the JSON object:
		808
		809	my $text = "[1,2,3] hello";
		810
		811	my $json = new JSON::XS;
		812
		813	my $obj = $json->incr_parse ($text)
		814	or die "expected JSON object or array at beginning of string";
		815
		816	my $tail = $json->incr_text;
		817	# $tail now contains " hello"
		818
		819	Easy, isn't it?
		820
		821	Now for a more complicated example: Imagine a hypothetical protocol where
		822	you read some requests from a TCP stream, and each request is a JSON
		823	array, without any separation between them (in fact, it is often useful to
		824	use newlines as "separators", as these get interpreted as whitespace at
		825	the start of the JSON text, which makes it possible to test said protocol
		826	with C<telnet>...).
		827
		828	Here is how you'd do it (it is trivial to write this in an event-based
		829	manner):
		830
		831	my $json = new JSON::XS;
		832
		833	# read some data from the socket
		834	while (sysread $socket, my $buf, 4096) {
		835
		836	# split and decode as many requests as possible
		837	for my $request ($json->incr_parse ($buf)) {
		838	# act on the $request
		839	}
		840	}
		841
		842	Another complicated example: Assume you have a string with JSON objects
		843	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		844	[3]>). To parse them, we have to skip the commas between the JSON texts,
		845	and here is where the lvalue-ness of C<incr_text> comes in useful:
		846
		847	my $text = "[1],[2], [3]";
		848	my $json = new JSON::XS;
		849
		850	# void context, so no parsing done
		851	$json->incr_parse ($text);
		852
		853	# now extract as many objects as possible. note the
		854	# use of scalar context so incr_text can be called.
		855	while (my $obj = $json->incr_parse) {
		856	# do something with $obj
		857
		858	# now skip the optional comma
		859	$json->incr_text =~ s/^ \s* , //x;
		860	}
		861
		862	Now lets go for a very complex example: Assume that you have a gigantic
		863	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		864	but you cannot load it into memory fully (this has actually happened in
		865	the real world :).
		866
		867	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		868	can still help you: You implement a (very simple) array parser and let
		869	JSON decode the array elements, which are all full JSON objects on their
		870	own (this wouldn't work if the array elements could be JSON numbers, for
		871	example):
		872
		873	my $json = new JSON::XS;
		874
		875	# open the monster
		876	open my $fh, "<bigfile.json"
		877	or die "bigfile: $!";
		878
		879	# first parse the initial "["
		880	for (;;) {
		881	sysread $fh, my $buf, 65536
		882	or die "read error: $!";
		883	$json->incr_parse ($buf); # void context, so no parsing
		884
		885	# Exit the loop once we found and removed(!) the initial "[".
		886	# In essence, we are (ab-)using the $json object as a simple scalar
		887	# we append data to.
		888	last if $json->incr_text =~ s/^ \s* \[ //x;
		889	}
		890
		891	# now we have the skipped the initial "[", so continue
		892	# parsing all the elements.
		893	for (;;) {
		894	# in this loop we read data until we got a single JSON object
		895	for (;;) {
		896	if (my $obj = $json->incr_parse) {
		897	# do something with $obj
		898	last;
		899	}
		900
		901	# add more data
		902	sysread $fh, my $buf, 65536
		903	or die "read error: $!";
		904	$json->incr_parse ($buf); # void context, so no parsing
		905	}
		906
		907	# in this loop we read data until we either found and parsed the
		908	# separating "," between elements, or the final "]"
		909	for (;;) {
		910	# first skip whitespace
		911	$json->incr_text =~ s/^\s*//;
		912
		913	# if we find "]", we are done
		914	if ($json->incr_text =~ s/^\]//) {
		915	print "finished.\n";
		916	exit;
		917	}
		918
		919	# if we find ",", we can continue with the next element
		920	if ($json->incr_text =~ s/^,//) {
		921	last;
		922	}
		923
		924	# if we find anything else, we have a parse error!
		925	if (length $json->incr_text) {
		926	die "parse error near ", $json->incr_text;
		927	}
		928
		929	# else add more data
		930	sysread $fh, my $buf, 65536
		931	or die "read error: $!";
		932	$json->incr_parse ($buf); # void context, so no parsing
		933	}
		934
		935	This is a complex example, but most of the complexity comes from the fact
		936	that we are trying to be correct (bear with me if I am wrong, I never ran
		937	the above example :).
		938
		939
		940
453	=head1 MAPPING	941	=head1 MAPPING
454		942
455	This section describes how JSON::XS maps Perl values to JSON values and	943	This section describes how JSON::XS maps Perl values to JSON values and
456	vice versa. These mappings are designed to "do the right thing" in most	944	vice versa. These mappings are designed to "do the right thing" in most
457	circumstances automatically, preserving round-tripping characteristics	945	circumstances automatically, preserving round-tripping characteristics
458	(what you put in comes out as something equivalent).	946	(what you put in comes out as something equivalent).
459		947
460	For the more enlightened: note that in the following descriptions,	948	For the more enlightened: note that in the following descriptions,
461	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	949	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
462	refers to the abstract Perl language itself.	950	refers to the abstract Perl language itself.
463		951
464		952
465	=head2 JSON -> PERL	953	=head2 JSON -> PERL
466		954
467	=over 4	955	=over 4
468		956
469	=item object	957	=item object
470		958
471	A JSON object becomes a reference to a hash in Perl. No ordering of object	959	A JSON object becomes a reference to a hash in Perl. No ordering of object
472	keys is preserved (JSON does not preserver object key ordering itself).	960	keys is preserved (JSON does not preserve object key ordering itself).
473		961
474	=item array	962	=item array
475		963
476	A JSON array becomes a reference to an array in Perl.	964	A JSON array becomes a reference to an array in Perl.
477		965
…		…
481	are represented by the same codepoints in the Perl string, so no manual	969	are represented by the same codepoints in the Perl string, so no manual
482	decoding is necessary.	970	decoding is necessary.
483		971
484	=item number	972	=item number
485		973
486	A JSON number becomes either an integer or numeric (floating point)	974	A JSON number becomes either an integer, numeric (floating point) or
487	scalar in perl, depending on its range and any fractional parts. On the	975	string scalar in perl, depending on its range and any fractional parts. On
488	Perl level, there is no difference between those as Perl handles all the	976	the Perl level, there is no difference between those as Perl handles all
489	conversion details, but an integer may take slightly less memory and might	977	the conversion details, but an integer may take slightly less memory and
490	represent more values exactly than (floating point) numbers.	978	might represent more values exactly than floating point numbers.
		979
		980	If the number consists of digits only, JSON::XS will try to represent
		981	it as an integer value. If that fails, it will try to represent it as
		982	a numeric (floating point) value if that is possible without loss of
		983	precision. Otherwise it will preserve the number as a string value (in
		984	which case you lose roundtripping ability, as the JSON number will be
		985	re-encoded toa JSON string).
		986
		987	Numbers containing a fractional or exponential part will always be
		988	represented as numeric (floating point) values, possibly at a loss of
		989	precision (in which case you might lose perfect roundtripping ability, but
		990	the JSON number will still be re-encoded as a JSON number).
491		991
492	=item true, false	992	=item true, false
493		993
494	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	994	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
495	respectively. They are overloaded to act almost exactly like the numbers	995	respectively. They are overloaded to act almost exactly like the numbers
496	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	996	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
497	the C<JSON::XS::is_bool> function.	997	the C<JSON::XS::is_bool> function.
498		998
499	=item null	999	=item null
500		1000
501	A JSON null atom becomes C<undef> in Perl.	1001	A JSON null atom becomes C<undef> in Perl.
…		…
532	Other unblessed references are generally not allowed and will cause an	1032	Other unblessed references are generally not allowed and will cause an
533	exception to be thrown, except for references to the integers C<0> and	1033	exception to be thrown, except for references to the integers C<0> and
534	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1034	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
535	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1035	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
536		1036
537	to_json [\0,JSON::XS::true] # yields [false,true]	1037	encode_json [\0, JSON::XS::true] # yields [false,true]
538		1038
539	=item JSON::XS::true, JSON::XS::false	1039	=item JSON::XS::true, JSON::XS::false
540		1040
541	These special values become JSON true and JSON false values,	1041	These special values become JSON true and JSON false values,
542	respectively. You cna alos use C<\1> and C<\0> directly if you want.	1042	respectively. You can also use C<\1> and C<\0> directly if you want.
543		1043
544	=item blessed objects	1044	=item blessed objects
545		1045
546	Blessed objects are not allowed. JSON::XS currently tries to encode their	1046	Blessed objects are not directly representable in JSON. See the
547	underlying representation (hash- or arrayref), but this behaviour might	1047	C<allow_blessed> and C<convert_blessed> methods on various options on
548	change in future versions.	1048	how to deal with this: basically, you can choose between throwing an
		1049	exception, encoding the reference as if it weren't blessed, or provide
		1050	your own serialiser method.
549		1051
550	=item simple scalars	1052	=item simple scalars
551		1053
552	Simple Perl scalars (any scalar that is not a reference) are the most	1054	Simple Perl scalars (any scalar that is not a reference) are the most
553	difficult objects to encode: JSON::XS will encode undefined scalars as	1055	difficult objects to encode: JSON::XS will encode undefined scalars as
554	JSON null value, scalars that have last been used in a string context	1056	JSON C<null> values, scalars that have last been used in a string context
555	before encoding as JSON strings and anything else as number value:	1057	before encoding as JSON strings, and anything else as number value:
556		1058
557	# dump as number	1059	# dump as number
558	to_json [2] # yields [2]	1060	encode_json [2] # yields [2]
559	to_json [-3.0e17] # yields [-3e+17]	1061	encode_json [-3.0e17] # yields [-3e+17]
560	my $value = 5; to_json [$value] # yields [5]	1062	my $value = 5; encode_json [$value] # yields [5]
561		1063
562	# used as string, so dump as string	1064	# used as string, so dump as string
563	print $value;	1065	print $value;
564	to_json [$value] # yields ["5"]	1066	encode_json [$value] # yields ["5"]
565		1067
566	# undef becomes null	1068	# undef becomes null
567	to_json [undef] # yields [null]	1069	encode_json [undef] # yields [null]
568		1070
569	You can force the type to be a string by stringifying it:	1071	You can force the type to be a JSON string by stringifying it:
570		1072
571	my $x = 3.1; # some variable containing a number	1073	my $x = 3.1; # some variable containing a number
572	"$x"; # stringified	1074	"$x"; # stringified
573	$x .= ""; # another, more awkward way to stringify	1075	$x .= ""; # another, more awkward way to stringify
574	print $x; # perl does it for you, too, quite often	1076	print $x; # perl does it for you, too, quite often
575		1077
576	You can force the type to be a number by numifying it:	1078	You can force the type to be a JSON number by numifying it:
577		1079
578	my $x = "3"; # some variable containing a string	1080	my $x = "3"; # some variable containing a string
579	$x += 0; # numify it, ensuring it will be dumped as a number	1081	$x += 0; # numify it, ensuring it will be dumped as a number
580	$x *= 1; # same thing, the choise is yours.	1082	$x *= 1; # same thing, the choice is yours.
581		1083
582	You can not currently output JSON booleans or force the type in other,	1084	You can not currently force the type in other, less obscure, ways. Tell me
583	less obscure, ways. Tell me if you need this capability.	1085	if you need this capability (but don't forget to explain why it's needed
		1086	:).
584		1087
585	=back	1088	=back
586		1089
587		1090
588	=head1 COMPARISON	1091	=head1 ENCODING/CODESET FLAG NOTES
589		1092
590	As already mentioned, this module was created because none of the existing	1093	The interested reader might have seen a number of flags that signify
591	JSON modules could be made to work correctly. First I will describe the	1094	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
592	problems (or pleasures) I encountered with various existing JSON modules,	1095	some confusion on what these do, so here is a short comparison:
593	followed by some benchmark values. JSON::XS was designed not to suffer	1096
594	from any of these problems or limitations.	1097	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1098	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1099	control whether C<encode> escapes character values outside their respective
		1100	codeset range. Neither of these flags conflict with each other, although
		1101	some combinations make less sense than others.
		1102
		1103	Care has been taken to make all flags symmetrical with respect to
		1104	C<encode> and C<decode>, that is, texts encoded with any combination of
		1105	these flag values will be correctly decoded when the same flags are used
		1106	- in general, if you use different flag settings while encoding vs. when
		1107	decoding you likely have a bug somewhere.
		1108
		1109	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1110	simply an abstract set of character-codepoint pairs, while an encoding
		1111	takes those codepoint numbers and I<encodes> them, in our case into
		1112	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1113	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1114	the same time, which can be confusing.
595		1115
596	=over 4	1116	=over 4
597		1117
598	=item JSON 1.07	1118	=item C<utf8> flag disabled
599		1119
600	Slow (but very portable, as it is written in pure Perl).	1120	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1121	and expect Unicode strings, that is, characters with high ordinal Unicode
		1122	values (> 255) will be encoded as such characters, and likewise such
		1123	characters are decoded as-is, no canges to them will be done, except
		1124	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1125	respectively (to Perl, these are the same thing in strings unless you do
		1126	funny/weird/dumb stuff).
601		1127
602	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1128	This is useful when you want to do the encoding yourself (e.g. when you
603	undocumented. One can get far by feeding it unicode strings and doing	1129	want to have UTF-16 encoded JSON texts) or when some other layer does
604	en-/decoding oneself, but unicode escapes are not working properly).	1130	the encoding for you (for example, when printing to a terminal using a
		1131	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1132	to UTF-8 encode your data first and have Perl encode it another time).
605		1133
606	No roundtripping (strings get clobbered if they look like numbers, e.g.	1134	=item C<utf8> flag enabled
607	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
608	decode into the number 2.
609		1135
610	=item JSON::PC 0.01	1136	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1137	characters using the corresponding UTF-8 multi-byte sequence, and will
		1138	expect your input strings to be encoded as UTF-8, that is, no "character"
		1139	of the input string must have any value > 255, as UTF-8 does not allow
		1140	that.
611		1141
612	Very fast.	1142	The C<utf8> flag therefore switches between two modes: disabled means you
		1143	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1144	octet/binary string in Perl.
613		1145
614	Undocumented/buggy Unicode handling.	1146	=item C<latin1> or C<ascii> flags enabled
615		1147
616	No roundtripping.	1148	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1149	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1150	characters as specified by the C<utf8> flag.
617		1151
618	Has problems handling many Perl values (e.g. regex results and other magic	1152	If C<utf8> is disabled, then the result is also correctly encoded in those
619	values will make it croak).	1153	character sets (as both are proper subsets of Unicode, meaning that a
		1154	Unicode string with all character values < 256 is the same thing as a
		1155	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1156	the same thing as an ASCII string in Perl).
620		1157
621	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1158	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
622	which is not a valid JSON text.	1159	regardless of these flags, just some more characters will be escaped using
		1160	C<\uXXXX> then before.
623		1161
624	Unmaintained (maintainer unresponsive for many months, bugs are not	1162	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
625	getting fixed).	1163	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1164	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1165	a subset of Unicode), while ASCII is.
626		1166
627	=item JSON::Syck 0.21	1167	Surprisingly, C<decode> will ignore these flags and so treat all input
		1168	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1169	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1170	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
628		1171
629	Very buggy (often crashes).	1172	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1173	they only govern when the JSON output engine escapes a character or not.
630		1174
631	Very inflexible (no human-readable format supported, format pretty much	1175	The main use for C<latin1> is to relatively efficiently store binary data
632	undocumented. I need at least a format for easy reading by humans and a	1176	as JSON, at the expense of breaking compatibility with most JSON decoders.
633	single-line compact format for use in a protocol, and preferably a way to
634	generate ASCII-only JSON texts).
635		1177
636	Completely broken (and confusingly documented) Unicode handling (unicode	1178	The main use for C<ascii> is to force the output to not contain characters
637	escapes are not working properly, you need to set ImplicitUnicode to	1179	with values > 127, which means you can interpret the resulting string
638	I<different> values on en- and decoding to get symmetric behaviour).	1180	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
639		1181	8-bit-encoding, and still get the same data structure back. This is useful
640	No roundtripping (simple cases work, but this depends on wether the scalar	1182	when your channel for JSON transfer is not 8-bit clean or the encoding
641	value was used in a numeric context or not).	1183	might be mangled in between (e.g. in mail), and works because ASCII is a
642		1184	proper subset of most 8-bit and multibyte encodings in use in the world.
643	Dumping hashes may skip hash values depending on iterator state.
644
645	Unmaintained (maintainer unresponsive for many months, bugs are not
646	getting fixed).
647
648	Does not check input for validity (i.e. will accept non-JSON input and
649	return "something" instead of raising an exception. This is a security
650	issue: imagine two banks transfering money between each other using
651	JSON. One bank might parse a given non-JSON request and deduct money,
652	while the other might reject the transaction with a syntax error. While a
653	good protocol will at least recover, that is extra unnecessary work and
654	the transaction will still not succeed).
655
656	=item JSON::DWIW 0.04
657
658	Very fast. Very natural. Very nice.
659
660	Undocumented unicode handling (but the best of the pack. Unicode escapes
661	still don't get parsed properly).
662
663	Very inflexible.
664
665	No roundtripping.
666
667	Does not generate valid JSON texts (key strings are often unquoted, empty keys
668	result in nothing being output)
669
670	Does not check input for validity.
671		1185
672	=back	1186	=back
673		1187
674		1188
		1189	=head2 JSON and ECMAscript
		1190
		1191	JSON syntax is based on how literals are represented in javascript (the
		1192	not-standardised predecessor of ECMAscript) which is presumably why it is
		1193	called "JavaScript Object Notation".
		1194
		1195	However, JSON is not a subset (and also not a superset of course) of
		1196	ECMAscript (the standard) or javascript (whatever browsers actually
		1197	implement).
		1198
		1199	If you want to use javascript's C<eval> function to "parse" JSON, you
		1200	might run into parse errors for valid JSON texts, or the resulting data
		1201	structure might not be queryable:
		1202
		1203	One of the problems is that U+2028 and U+2029 are valid characters inside
		1204	JSON strings, but are not allowed in ECMAscript string literals, so the
		1205	following Perl fragment will not output something that can be guaranteed
		1206	to be parsable by javascript's C<eval>:
		1207
		1208	use JSON::XS;
		1209
		1210	print encode_json [chr 0x2028];
		1211
		1212	The right fix for this is to use a proper JSON parser in your javascript
		1213	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1214	F<json2.js> parser).
		1215
		1216	If this is not an option, you can, as a stop-gap measure, simply encode to
		1217	ASCII-only JSON:
		1218
		1219	use JSON::XS;
		1220
		1221	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1222
		1223	Note that this will enlarge the resulting JSON text quite a bit if you
		1224	have many non-ASCII characters. You might be tempted to run some regexes
		1225	to only escape U+2028 and U+2029, e.g.:
		1226
		1227	# DO NOT USE THIS!
		1228	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1229	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1230	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1231	print $json;
		1232
		1233	Note that I<this is a bad idea>: the above only works for U+2028 and
		1234	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1235	javascript implementations, however, have issues with other characters as
		1236	well - using C<eval> naively simply I<will> cause problems.
		1237
		1238	Another problem is that some javascript implementations reserve
		1239	some property names for their own purposes (which probably makes
		1240	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1241	C<__proto__> property name for it's own purposes.
		1242
		1243	If that is a problem, you could parse try to filter the resulting JSON
		1244	output for these property strings, e.g.:
		1245
		1246	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1247
		1248	This works because C<__proto__> is not valid outside of strings, so every
		1249	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1250
		1251	If you know of other incompatibilities, please let me know.
		1252
		1253
675	=head2 JSON and YAML	1254	=head2 JSON and YAML
676		1255
677	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1256	You often hear that JSON is a subset of YAML. This is, however, a mass
678	however, a mass hysteria and very far from the truth. In general, there is	1257	hysteria(*) and very far from the truth (as of the time of this writing),
679	no way to configure JSON::XS to output a data structure as valid YAML.	1258	so let me state it clearly: I<in general, there is no way to configure
		1259	JSON::XS to output a data structure as valid YAML> that works in all
		1260	cases.
680		1261
681	If you really must use JSON::XS to generate YAML, you should use this	1262	If you really must use JSON::XS to generate YAML, you should use this
682	algorithm (subject to change in future versions):	1263	algorithm (subject to change in future versions):
683		1264
684	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1265	my $to_yaml = JSON::XS->new->utf8->space_after (1);
685	my $yaml = $to_yaml->encode ($ref) . "\n";	1266	my $yaml = $to_yaml->encode ($ref) . "\n";
686		1267
687	This will usually generate JSON texts that also parse as valid	1268	This will I<usually> generate JSON texts that also parse as valid
688	YAML. Please note that YAML has hardcoded limits on (simple) object key	1269	YAML. Please note that YAML has hardcoded limits on (simple) object key
689	lengths that JSON doesn't have, so you should make sure that your hash	1270	lengths that JSON doesn't have and also has different and incompatible
		1271	unicode handling, so you should make sure that your hash keys are
690	keys are noticably shorter than the 1024 characters YAML allows.	1272	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1273	you do not have characters with codepoint values outside the Unicode BMP
		1274	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1275	strings (which JSON::XS does not I<currently> generate, but other JSON
		1276	generators might).
691		1277
692	There might be other incompatibilities that I am not aware of. In general	1278	There might be other incompatibilities that I am not aware of (or the YAML
		1279	specification has been changed yet again - it does so quite often). In
693	you should not try to generate YAML with a JSON generator or vice versa,	1280	general you should not try to generate YAML with a JSON generator or vice
694	or try to parse JSON with a YAML parser or vice versa: chances are high	1281	versa, or try to parse JSON with a YAML parser or vice versa: chances are
695	that you will run into severe interoperability problems.	1282	high that you will run into severe interoperability problems when you
		1283	least expect it.
		1284
		1285	=over 4
		1286
		1287	=item (*)
		1288
		1289	I have been pressured multiple times by Brian Ingerson (one of the
		1290	authors of the YAML specification) to remove this paragraph, despite him
		1291	acknowledging that the actual incompatibilities exist. As I was personally
		1292	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1293	educate people about these issues, so others do not run into the same
		1294	problem again and again. After this, Brian called me a (quote)I<complete
		1295	and worthless idiot>(unquote).
		1296
		1297	In my opinion, instead of pressuring and insulting people who actually
		1298	clarify issues with YAML and the wrong statements of some of its
		1299	proponents, I would kindly suggest reading the JSON spec (which is not
		1300	that difficult or long) and finally make YAML compatible to it, and
		1301	educating users about the changes, instead of spreading lies about the
		1302	real compatibility for many I<years> and trying to silence people who
		1303	point out that it isn't true.
		1304
		1305	=back
696		1306
697		1307
698	=head2 SPEED	1308	=head2 SPEED
699		1309
700	It seems that JSON::XS is surprisingly fast, as shown in the following	1310	It seems that JSON::XS is surprisingly fast, as shown in the following
701	tables. They have been generated with the help of the C<eg/bench> program	1311	tables. They have been generated with the help of the C<eg/bench> program
702	in the JSON::XS distribution, to make it easy to compare on your own	1312	in the JSON::XS distribution, to make it easy to compare on your own
703	system.	1313	system.
704		1314
705	First comes a comparison between various modules using a very short	1315	First comes a comparison between various modules using
706	single-line JSON string:	1316	a very short single-line JSON string (also available at
		1317	L<http://dist.schmorp.de/misc/json/short.json>).
707		1318
708	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1319	{"method": "handleMessage", "params": ["user1",
709	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1320	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1321	true, false]}
710		1322
711	It shows the number of encodes/decodes per second (JSON::XS uses	1323	It shows the number of encodes/decodes per second (JSON::XS uses
712	the functional interface, while JSON::XS/2 uses the OO interface	1324	the functional interface, while JSON::XS/2 uses the OO interface
713	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1325	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
714	shrink). Higher is better:	1326	shrink). Higher is better:
715		1327
716	module | encode | decode |	1328	module | encode | decode |
717	-----------|------------|------------|	1329	-----------|------------|------------|
718	JSON | 7645.468 | 4208.613 |	1330	JSON 1.x | 4990.842 | 4088.813 |
719	JSON::DWIW | 40721.398 | 77101.176 |	1331	JSON::DWIW | 51653.990 | 71575.154 |
720	JSON::PC | 65948.176 | 78251.940 |	1332	JSON::PC | 65948.176 | 74631.744 |
721	JSON::Syck | 22844.793 | 26479.192 |	1333	JSON::PP | 8931.652 | 3817.168 |
		1334	JSON::Syck | 24877.248 | 27776.848 |
722	JSON::XS | 388361.481 | 199728.762 |	1335	JSON::XS | 388361.481 | 227951.304 |
723	JSON::XS/2 | 218453.333 | 192399.266 |	1336	JSON::XS/2 | 227951.304 | 218453.333 |
724	JSON::XS/3 | 338250.323 | 192399.266 |	1337	JSON::XS/3 | 338250.323 | 218453.333 |
725	Storable | 15779.925 | 14169.946 |	1338	Storable | 16500.016 | 135300.129 |
726	-----------+------------+------------+	1339	-----------+------------+------------+
727		1340
728	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1341	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
729	about three times faster on decoding, and over fourty times faster	1342	about three times faster on decoding, and over forty times faster
730	than JSON, even with pretty-printing and key sorting. It also compares	1343	than JSON, even with pretty-printing and key sorting. It also compares
731	favourably to Storable for small amounts of data.	1344	favourably to Storable for small amounts of data.
732		1345
733	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1346	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
734	search API (http://nanoref.com/yahooapis/mgPdGg):	1347	search API (L<http://dist.schmorp.de/misc/json/long.json>).
735		1348
736	module | encode | decode |	1349	module | encode | decode |
737	-----------|------------|------------|	1350	-----------|------------|------------|
738	JSON | 254.685 | 37.665 |	1351	JSON 1.x | 55.260 | 34.971 |
739	JSON::DWIW | 843.343 | 1049.731 |	1352	JSON::DWIW | 825.228 | 1082.513 |
740	JSON::PC | 3602.116 | 2307.352 |	1353	JSON::PC | 3571.444 | 2394.829 |
		1354	JSON::PP | 210.987 | 32.574 |
741	JSON::Syck | 505.107 | 787.899 |	1355	JSON::Syck | 552.551 | 787.544 |
742	JSON::XS | 5747.196 | 3690.220 |	1356	JSON::XS | 5780.463 | 4854.519 |
743	JSON::XS/2 | 3968.121 | 3676.634 |	1357	JSON::XS/2 | 3869.998 | 4798.975 |
744	JSON::XS/3 | 6105.246 | 3662.508 |	1358	JSON::XS/3 | 5862.880 | 4798.975 |
745	Storable | 4417.337 | 5285.161 |	1359	Storable | 4445.002 | 5235.027 |
746	-----------+------------+------------+	1360	-----------+------------+------------+
747		1361
748	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1362	Again, JSON::XS leads by far (except for Storable which non-surprisingly
749	decodes faster).	1363	decodes faster).
750		1364
751	On large strings containing lots of high unicode characters, some modules	1365	On large strings containing lots of high Unicode characters, some modules
752	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1366	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
753	will be broken due to missing (or wrong) unicode handling. Others refuse	1367	will be broken due to missing (or wrong) Unicode handling. Others refuse
754	to decode or encode properly, so it was impossible to prepare a fair	1368	to decode or encode properly, so it was impossible to prepare a fair
755	comparison table for that case.	1369	comparison table for that case.
756		1370
757		1371
758	=head1 SECURITY CONSIDERATIONS	1372	=head1 SECURITY CONSIDERATIONS
…		…
764	any buffer overflows. Obviously, this module should ensure that and I am	1378	any buffer overflows. Obviously, this module should ensure that and I am
765	trying hard on making that true, but you never know.	1379	trying hard on making that true, but you never know.
766		1380
767	Second, you need to avoid resource-starving attacks. That means you should	1381	Second, you need to avoid resource-starving attacks. That means you should
768	limit the size of JSON texts you accept, or make sure then when your	1382	limit the size of JSON texts you accept, or make sure then when your
769	resources run out, thats just fine (e.g. by using a separate process that	1383	resources run out, that's just fine (e.g. by using a separate process that
770	can crash safely). The size of a JSON text in octets or characters is	1384	can crash safely). The size of a JSON text in octets or characters is
771	usually a good indication of the size of the resources required to decode	1385	usually a good indication of the size of the resources required to decode
772	it into a Perl structure. While JSON::XS can check the size of the JSON	1386	it into a Perl structure. While JSON::XS can check the size of the JSON
773	text, it might be too late when you already have it in memory, so you	1387	text, it might be too late when you already have it in memory, so you
774	might want to check the size before you accept the string.	1388	might want to check the size before you accept the string.
775		1389
776	Third, JSON::XS recurses using the C stack when decoding objects and	1390	Third, JSON::XS recurses using the C stack when decoding objects and
777	arrays. The C stack is a limited resource: for instance, on my amd64	1391	arrays. The C stack is a limited resource: for instance, on my amd64
778	machine with 8MB of stack size I can decode around 180k nested arrays but	1392	machine with 8MB of stack size I can decode around 180k nested arrays but
779	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1393	only 14k nested JSON objects (due to perl itself recursing deeply on croak
780	to free the temporary). If that is exceeded, the program crashes. to be	1394	to free the temporary). If that is exceeded, the program crashes. To be
781	conservative, the default nesting limit is set to 512. If your process	1395	conservative, the default nesting limit is set to 512. If your process
782	has a smaller stack, you should adjust this setting accordingly with the	1396	has a smaller stack, you should adjust this setting accordingly with the
783	C<max_depth> method.	1397	C<max_depth> method.
784		1398
785	And last but least, something else could bomb you that I forgot to think	1399	Something else could bomb you, too, that I forgot to think of. In that
786	of. In that case, you get to keep the pieces. I am always open for hints,	1400	case, you get to keep the pieces. I am always open for hints, though...
787	though...	1401
		1402	Also keep in mind that JSON::XS might leak contents of your Perl data
		1403	structures in its error messages, so when you serialise sensitive
		1404	information you might want to make sure that exceptions thrown by JSON::XS
		1405	will not end up in front of untrusted eyes.
788		1406
789	If you are using JSON::XS to return packets to consumption	1407	If you are using JSON::XS to return packets to consumption
790	by javascript scripts in a browser you should have a look at	1408	by JavaScript scripts in a browser you should have a look at
791	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1409	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792	you are vulnerable to some common attack vectors (which really are browser	1410	you are vulnerable to some common attack vectors (which really are browser
793	design bugs, but it is still you who will have to deal with it, as major	1411	design bugs, but it is still you who will have to deal with it, as major
794	browser developers care only for features, not about doing security	1412	browser developers care only for features, not about getting security
795	right).	1413	right).
796		1414
797		1415
		1416	=head1 THREADS
		1417
		1418	This module is I<not> guaranteed to be thread safe and there are no
		1419	plans to change this until Perl gets thread support (as opposed to the
		1420	horribly slow so-called "threads" which are simply slow and bloated
		1421	process simulations - use fork, it's I<much> faster, cheaper, better).
		1422
		1423	(It might actually work, but you have been warned).
		1424
		1425
798	=head1 BUGS	1426	=head1 BUGS
799		1427
800	While the goal of this module is to be correct, that unfortunately does	1428	While the goal of this module is to be correct, that unfortunately does
801	not mean its bug-free, only that I think its design is bug-free. It is	1429	not mean it's bug-free, only that I think its design is bug-free. If you
802	still relatively early in its development. If you keep reporting bugs they	1430	keep reporting bugs they will be fixed swiftly, though.
803	will be fixed swiftly, though.	1431
		1432	Please refrain from using rt.cpan.org or any other bug reporting
		1433	service. I put the contact address into my modules for a reason.
804		1434
805	=cut	1435	=cut
806		1436
807	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1437	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1438	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
825	"--" => sub { $_[0] = ${$_[0]} - 1 },	1455	"--" => sub { $_[0] = ${$_[0]} - 1 },
826	fallback => 1;	1456	fallback => 1;
827		1457
828	1;	1458	1;
829		1459
		1460	=head1 SEE ALSO
		1461
		1462	The F<json_xs> command line utility for quick experiments.
		1463
830	=head1 AUTHOR	1464	=head1 AUTHOR
831		1465
832	Marc Lehmann <schmorp@schmorp.de>	1466	Marc Lehmann <schmorp@schmorp.de>
833	http://home.schmorp.de/	1467	http://home.schmorp.de/
834		1468

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