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Revision 1.21 by root, Sun Mar 25 02:32:40 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		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)
		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, croak on error	14	# exported functions, they croak on error
		15	# and expect/generate UTF-8
10		16
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
13		19
14	# objToJson and jsonToObj are exported for JSON
15	# compatibility, but should not be used in new code.
16
17	# oo-interface	20	# OO-interface
18		21
19	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
20	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
21	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
22		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
23	=head1 DESCRIPTION	34	=head1 DESCRIPTION
24		35
25	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
26	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
27	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.
28		47
29	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
30	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
31	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
32	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
33	reports for other reasons.	52	reports for other reasons.
34		53
35	See COMPARISON, below, for a comparison to some other JSON modules.
36
37	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
38	vice versa.	55	vice versa.
39		56
40	=head2 FEATURES	57	=head2 FEATURES
41		58
42	=over 4	59	=over 4
43		60
44	=item * correct unicode handling	61	=item * correct Unicode handling
45		62
46	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
47	it does so.	64	so, and even documents what "correct" means.
48		65
49	=item * round-trip integrity	66	=item * round-trip integrity
50		67
51	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
52	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.
53	(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
54	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
55		73
56	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
57		75
58	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,
59	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
60	feature).	78	feature).
61		79
62	=item * fast	80	=item * fast
63		81
64	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
65	of speed, too.	83	this module usually compares favourably in terms of speed, too.
66		84
67	=item * simple to use	85	=item * simple to use
68		86
69	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
70	interface.	88	oriented interface interface.
71		89
72	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
73		91
74	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
75	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
76	(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
77	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
78	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.
79		97
80	=back	98	=back
81		99
82	=cut	100	=cut
83		101
84	package JSON::XS;	102	package JSON::XS;
85		103
86	use strict;	104	use common::sense;
87		105
88	BEGIN {
89	our $VERSION = '0.8';	106	our $VERSION = '2.24';
90	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
91		108
92	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
93	require Exporter;
94		110
		111	sub to_json($) {
95	require XSLoader;	112	require Carp;
96	XSLoader::load JSON::XS::, $VERSION;	113	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
97	}	114	}
98		115
		116	sub from_json($) {
		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	}
		120
		121	use Exporter;
		122	use XSLoader;
		123
99	=head1 FUNCTIONAL INTERFACE	124	=head1 FUNCTIONAL INTERFACE
100		125
101	The following convinience methods are provided by this module. They are	126	The following convenience methods are provided by this module. They are
102	exported by default:	127	exported by default:
103		128
104	=over 4	129	=over 4
105		130
106	=item $json_text = to_json $perl_scalar	131	=item $json_text = encode_json $perl_scalar
107		132
108	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
109	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.
110	octets only). Croaks on error.
111		135
112	This function call is functionally identical to:	136	This function call is functionally identical to:
113		137
114	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115		139
116	except being faster.	140	Except being faster.
117		141
118	=item $perl_scalar = from_json $json_text	142	=item $perl_scalar = decode_json $json_text
119		143
120	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
121	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
122	scalar or reference. Croaks on error.	146	reference. Croaks on error.
123		147
124	This function call is functionally identical to:	148	This function call is functionally identical to:
125		149
126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127		151
128	except being faster.	152	Except being faster.
		153
		154	=item $is_boolean = JSON::XS::is_bool $scalar
		155
		156	Returns true if the passed scalar represents either JSON::XS::true or
		157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		158	and are used to represent JSON C<true> and C<false> values in Perl.
		159
		160	See MAPPING, below, for more information on how JSON values are mapped to
		161	Perl.
129		162
130	=back	163	=back
		164
		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
131		213
132	=head1 OBJECT-ORIENTED INTERFACE	214	=head1 OBJECT-ORIENTED INTERFACE
133		215
134	The object oriented interface lets you configure your own encoding or	216	The object oriented interface lets you configure your own encoding or
135	decoding style, within the limits of supported formats.	217	decoding style, within the limits of supported formats.
…		…
147	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]})
148	=> {"a": [1, 2]}	230	=> {"a": [1, 2]}
149		231
150	=item $json = $json->ascii ([$enable])	232	=item $json = $json->ascii ([$enable])
151		233
		234	=item $enabled = $json->get_ascii
		235
152	If C<$enable> is true (or missing), then the C<encode> method will not	236	If C<$enable> is true (or missing), then the C<encode> method will not
153	generate characters outside the code range C<0..127> (which is ASCII). Any	237	generate characters outside the code range C<0..127> (which is ASCII). Any
154	unicode characters outside that range will be escaped using either a	238	Unicode characters outside that range will be escaped using either a
155	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	239	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
156	as per RFC4627.	240	as per RFC4627. The resulting encoded JSON text can be treated as a native
		241	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		242	or any other superset of ASCII.
157		243
158	If C<$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
159	characters unless required by the JSON syntax. This results in a faster	245	characters unless required by the JSON syntax or other flags. This results
160	and more compact format.	246	in a faster and more compact format.
		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
		251	The main use for this flag is to produce JSON texts that can be
		252	transmitted over a 7-bit channel, as the encoded JSON texts will not
		253	contain any 8 bit characters.
161		254
162	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
163	=> ["\ud801\udc01"]	256	=> ["\ud801\udc01"]
164		257
		258	=item $json = $json->latin1 ([$enable])
		259
		260	=item $enabled = $json->get_latin1
		261
		262	If C<$enable> is true (or missing), then the C<encode> method will encode
		263	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		264	outside the code range C<0..255>. The resulting string can be treated as a
		265	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		266	will not be affected in any way by this flag, as C<decode> by default
		267	expects Unicode, which is a strict superset of latin1.
		268
		269	If C<$enable> is false, then the C<encode> method will not escape Unicode
		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.
		274
		275	The main use for this flag is efficiently encoding binary data as JSON
		276	text, as most octets will not be escaped, resulting in a smaller encoded
		277	size. The disadvantage is that the resulting JSON text is encoded
		278	in latin1 (and must correctly be treated as such when storing and
		279	transferring), a rare encoding for JSON. It is therefore most useful when
		280	you want to store data structures known to contain binary data efficiently
		281	in files or databases, not when talking to other JSON encoders/decoders.
		282
		283	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		284	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		285
165	=item $json = $json->utf8 ([$enable])	286	=item $json = $json->utf8 ([$enable])
		287
		288	=item $enabled = $json->get_utf8
166		289
167	If C<$enable> is true (or missing), then the C<encode> method will encode	290	If C<$enable> is true (or missing), then the C<encode> method will encode
168	the JSON result into UTF-8, as required by many protocols, while the	291	the JSON result into UTF-8, as required by many protocols, while the
169	C<decode> method expects to be handled an UTF-8-encoded string. Please	292	C<decode> method expects to be handled an UTF-8-encoded string. Please
170	note that UTF-8-encoded strings do not contain any characters outside the	293	note that UTF-8-encoded strings do not contain any characters outside the
171	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	294	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
172	versions, enabling this option might enable autodetection of the UTF-16	295	versions, enabling this option might enable autodetection of the UTF-16
173	and UTF-32 encoding families, as described in RFC4627.	296	and UTF-32 encoding families, as described in RFC4627.
174		297
175	If C<$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
176	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
177	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
178	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.
179		305
180	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
181		307
182	use Encode;	308	use Encode;
183	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
204	]	330	]
205	}	331	}
206		332
207	=item $json = $json->indent ([$enable])	333	=item $json = $json->indent ([$enable])
208		334
		335	=item $enabled = $json->get_indent
		336
209	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	337	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
210	format as output, putting every array member or object/hash key-value pair	338	format as output, putting every array member or object/hash key-value pair
211	into its own line, identing them properly.	339	into its own line, indenting them properly.
212		340
213	If C<$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
214	resulting JSON text is guarenteed not to contain any C<newlines>.	342	resulting JSON text is guaranteed not to contain any C<newlines>.
215		343
216	This setting has no effect when decoding JSON texts.	344	This setting has no effect when decoding JSON texts.
217		345
218	=item $json = $json->space_before ([$enable])	346	=item $json = $json->space_before ([$enable])
		347
		348	=item $enabled = $json->get_space_before
219		349
220	If C<$enable> is true (or missing), then the C<encode> method will add an extra	350	If C<$enable> is true (or missing), then the C<encode> method will add an extra
221	optional space before the C<:> separating keys from values in JSON objects.	351	optional space before the C<:> separating keys from values in JSON objects.
222		352
223	If C<$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
…		…
229	Example, space_before enabled, space_after and indent disabled:	359	Example, space_before enabled, space_after and indent disabled:
230		360
231	{"key" :"value"}	361	{"key" :"value"}
232		362
233	=item $json = $json->space_after ([$enable])	363	=item $json = $json->space_after ([$enable])
		364
		365	=item $enabled = $json->get_space_after
234		366
235	If C<$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
236	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
237	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
238	members.	370	members.
…		…
244		376
245	Example, space_before and indent disabled, space_after enabled:	377	Example, space_before and indent disabled, space_after enabled:
246		378
247	{"key": "value"}	379	{"key": "value"}
248		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
249	=item $json = $json->canonical ([$enable])	428	=item $json = $json->canonical ([$enable])
		429
		430	=item $enabled = $json->get_canonical
250		431
251	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	432	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
252	by sorting their keys. This is adding a comparatively high overhead.	433	by sorting their keys. This is adding a comparatively high overhead.
253		434
254	If C<$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
255	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
256	of the same script).	437	of the same script).
257		438
258	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
259	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,
260	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,
261	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
262		443
263	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
264		445
265	=item $json = $json->allow_nonref ([$enable])	446	=item $json = $json->allow_nonref ([$enable])
		447
		448	=item $enabled = $json->get_allow_nonref
266		449
267	If C<$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
268	non-reference into its corresponding string, number or null JSON value,	451	non-reference into its corresponding string, number or null JSON value,
269	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
270	values instead of croaking.	453	values instead of croaking.
…		…
278	resulting in an invalid JSON text:	461	resulting in an invalid JSON text:
279		462
280	JSON::XS->new->allow_nonref->encode ("Hello, World!")	463	JSON::XS->new->allow_nonref->encode ("Hello, World!")
281	=> "Hello, World!"	464	=> "Hello, World!"
282		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
		482	=item $json = $json->allow_blessed ([$enable])
		483
		484	=item $enabled = $json->get_allow_blessed
		485
		486	If C<$enable> is true (or missing), then the C<encode> method will not
		487	barf when it encounters a blessed reference. Instead, the value of the
		488	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		489	disabled or no C<TO_JSON> method found) or a representation of the
		490	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		491	encoded. Has no effect on C<decode>.
		492
		493	If C<$enable> is false (the default), then C<encode> will throw an
		494	exception when it encounters a blessed object.
		495
		496	=item $json = $json->convert_blessed ([$enable])
		497
		498	=item $enabled = $json->get_convert_blessed
		499
		500	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		501	blessed object, will check for the availability of the C<TO_JSON> method
		502	on the object's class. If found, it will be called in scalar context
		503	and the resulting scalar will be encoded instead of the object. If no
		504	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		505	to do.
		506
		507	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		508	returns other blessed objects, those will be handled in the same
		509	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		510	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		511	methods called by the Perl core (== not by the user of the object) are
		512	usually in upper case letters and to avoid collisions with any C<to_json>
		513	function or method.
		514
		515	This setting does not yet influence C<decode> in any way, but in the
		516	future, global hooks might get installed that influence C<decode> and are
		517	enabled by this setting.
		518
		519	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		520	to do when a blessed object is found.
		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
283	=item $json = $json->shrink ([$enable])	598	=item $json = $json->shrink ([$enable])
284		599
		600	=item $enabled = $json->get_shrink
		601
285	Perl usually over-allocates memory a bit when allocating space for	602	Perl usually over-allocates memory a bit when allocating space for
286	strings. This flag optionally resizes strings generated by either	603	strings. This flag optionally resizes strings generated by either
287	C<encode> or C<decode> to their minimum size possible. This can save	604	C<encode> or C<decode> to their minimum size possible. This can save
288	memory when your JSON texts are either very very long or you have many	605	memory when your JSON texts are either very very long or you have many
289	short strings. It will also try to downgrade any strings to octet-form	606	short strings. It will also try to downgrade any strings to octet-form
290	if possible: perl stores strings internally either in an encoding called	607	if possible: perl stores strings internally either in an encoding called
291	UTF-X or in octet-form. The latter cannot store everything but uses less	608	UTF-X or in octet-form. The latter cannot store everything but uses less
292	space in general.	609	space in general (and some buggy Perl or C code might even rely on that
		610	internal representation being used).
293		611
		612	The actual definition of what shrink does might change in future versions,
		613	but it will always try to save space at the expense of time.
		614
294	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	615	If C<$enable> is true (or missing), the string returned by C<encode> will
295	while all strings generated by C<decode> will also be shrunk-to-fit.	616	be shrunk-to-fit, while all strings generated by C<decode> will also be
		617	shrunk-to-fit.
296		618
297	If C<$enable> is false, then the normal perl allocation algorithms are used.	619	If C<$enable> is false, then the normal perl allocation algorithms are used.
298	If you work with your data, then this is likely to be faster.	620	If you work with your data, then this is likely to be faster.
299		621
300	In the future, this setting might control other things, such as converting	622	In the future, this setting might control other things, such as converting
301	strings that look like integers or floats into integers or floats	623	strings that look like integers or floats into integers or floats
302	internally (there is no difference on the Perl level), saving space.	624	internally (there is no difference on the Perl level), saving space.
		625
		626	=item $json = $json->max_depth ([$maximum_nesting_depth])
		627
		628	=item $max_depth = $json->get_max_depth
		629
		630	Sets the maximum nesting level (default C<512>) accepted while encoding
		631	or decoding. If a higher nesting level is detected in JSON text or a Perl
		632	data structure, then the encoder and decoder will stop and croak at that
		633	point.
		634
		635	Nesting level is defined by number of hash- or arrayrefs that the encoder
		636	needs to traverse to reach a given point or the number of C<{> or C<[>
		637	characters without their matching closing parenthesis crossed to reach a
		638	given character in a string.
		639
		640	Setting the maximum depth to one disallows any nesting, so that ensures
		641	that the object is only a single hash/object or array.
		642
		643	If no argument is given, the highest possible setting will be used, which
		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.
		649
		650	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		651
		652	=item $json = $json->max_size ([$maximum_string_size])
		653
		654	=item $max_size = $json->get_max_size
		655
		656	Set the maximum length a JSON text may have (in bytes) where decoding is
		657	being attempted. The default is C<0>, meaning no limit. When C<decode>
		658	is called on a string that is longer then this many bytes, it will not
		659	attempt to decode the string but throw an exception. This setting has no
		660	effect on C<encode> (yet).
		661
		662	If no argument is given, the limit check will be deactivated (same as when
		663	C<0> is specified).
		664
		665	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
303		666
304	=item $json_text = $json->encode ($perl_scalar)	667	=item $json_text = $json->encode ($perl_scalar)
305		668
306	Converts the given Perl data structure (a simple scalar or a reference	669	Converts the given Perl data structure (a simple scalar or a reference
307	to a hash or array) to its JSON representation. Simple scalars will be	670	to a hash or array) to its JSON representation. Simple scalars will be
…		…
317		680
318	JSON numbers and strings become simple Perl scalars. JSON arrays become	681	JSON numbers and strings become simple Perl scalars. JSON arrays become
319	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	682	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
320	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	683	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
321		684
		685	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		686
		687	This works like the C<decode> method, but instead of raising an exception
		688	when there is trailing garbage after the first JSON object, it will
		689	silently stop parsing there and return the number of characters consumed
		690	so far.
		691
		692	This is useful if your JSON texts are not delimited by an outer protocol
		693	(which is not the brightest thing to do in the first place) and you need
		694	to know where the JSON text ends.
		695
		696	JSON::XS->new->decode_prefix ("[1] the tail")
		697	=> ([], 3)
		698
322	=back	699	=back
		700
		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
323		940
324	=head1 MAPPING	941	=head1 MAPPING
325		942
326	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
327	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
328	circumstances automatically, preserving round-tripping characteristics	945	circumstances automatically, preserving round-tripping characteristics
329	(what you put in comes out as something equivalent).	946	(what you put in comes out as something equivalent).
330		947
331	For the more enlightened: note that in the following descriptions,	948	For the more enlightened: note that in the following descriptions,
332	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>
333	refers to the abstract Perl language itself.	950	refers to the abstract Perl language itself.
334		951
		952
335	=head2 JSON -> PERL	953	=head2 JSON -> PERL
336		954
337	=over 4	955	=over 4
338		956
339	=item object	957	=item object
340		958
341	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
342	keys is preserved (JSON does not preserver object key ordering itself).	960	keys is preserved (JSON does not preserve object key ordering itself).
343		961
344	=item array	962	=item array
345		963
346	A JSON array becomes a reference to an array in Perl.	964	A JSON array becomes a reference to an array in Perl.
347		965
…		…
351	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
352	decoding is necessary.	970	decoding is necessary.
353		971
354	=item number	972	=item number
355		973
356	A JSON number becomes either an integer or numeric (floating point)	974	A JSON number becomes either an integer, numeric (floating point) or
357	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
358	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
359	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
360	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).
361		991
362	=item true, false	992	=item true, false
363		993
364	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	994	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
365	this process. Future versions might represent those values differently,	995	respectively. They are overloaded to act almost exactly like the numbers
366	but they will be guarenteed to act like these integers would normally in	996	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
367	Perl.	997	the C<JSON::XS::is_bool> function.
368		998
369	=item null	999	=item null
370		1000
371	A JSON null atom becomes C<undef> in Perl.	1001	A JSON null atom becomes C<undef> in Perl.
372		1002
373	=back	1003	=back
		1004
374		1005
375	=head2 PERL -> JSON	1006	=head2 PERL -> JSON
376		1007
377	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1008	The mapping from Perl to JSON is slightly more difficult, as Perl is a
378	truly typeless language, so we can only guess which JSON type is meant by	1009	truly typeless language, so we can only guess which JSON type is meant by
…		…
381	=over 4	1012	=over 4
382		1013
383	=item hash references	1014	=item hash references
384		1015
385	Perl hash references become JSON objects. As there is no inherent ordering	1016	Perl hash references become JSON objects. As there is no inherent ordering
386	in hash keys, they will usually be encoded in a pseudo-random order that	1017	in hash keys (or JSON objects), they will usually be encoded in a
387	can change between runs of the same program but stays generally the same	1018	pseudo-random order that can change between runs of the same program but
388	within a single run of a program. JSON::XS can optionally sort the hash	1019	stays generally the same within a single run of a program. JSON::XS can
389	keys (determined by the I<canonical> flag), so the same datastructure	1020	optionally sort the hash keys (determined by the I<canonical> flag), so
390	will serialise to the same JSON text (given same settings and version of	1021	the same datastructure will serialise to the same JSON text (given same
391	JSON::XS), but this incurs a runtime overhead.	1022	settings and version of JSON::XS), but this incurs a runtime overhead
		1023	and is only rarely useful, e.g. when you want to compare some JSON text
		1024	against another for equality.
392		1025
393	=item array references	1026	=item array references
394		1027
395	Perl array references become JSON arrays.	1028	Perl array references become JSON arrays.
396		1029
		1030	=item other references
		1031
		1032	Other unblessed references are generally not allowed and will cause an
		1033	exception to be thrown, except for references to the integers C<0> and
		1034	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		1035	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		1036
		1037	encode_json [\0, JSON::XS::true] # yields [false,true]
		1038
		1039	=item JSON::XS::true, JSON::XS::false
		1040
		1041	These special values become JSON true and JSON false values,
		1042	respectively. You can also use C<\1> and C<\0> directly if you want.
		1043
397	=item blessed objects	1044	=item blessed objects
398		1045
399	Blessed objects are not allowed. JSON::XS currently tries to encode their	1046	Blessed objects are not directly representable in JSON. See the
400	underlying representation (hash- or arrayref), but this behaviour might	1047	C<allow_blessed> and C<convert_blessed> methods on various options on
401	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.
402		1051
403	=item simple scalars	1052	=item simple scalars
404		1053
405	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
406	difficult objects to encode: JSON::XS will encode undefined scalars as	1055	difficult objects to encode: JSON::XS will encode undefined scalars as
407	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
408	before encoding as JSON strings and anything else as number value:	1057	before encoding as JSON strings, and anything else as number value:
409		1058
410	# dump as number	1059	# dump as number
411	to_json [2] # yields [2]	1060	encode_json [2] # yields [2]
412	to_json [-3.0e17] # yields [-3e+17]	1061	encode_json [-3.0e17] # yields [-3e+17]
413	my $value = 5; to_json [$value] # yields [5]	1062	my $value = 5; encode_json [$value] # yields [5]
414		1063
415	# used as string, so dump as string	1064	# used as string, so dump as string
416	print $value;	1065	print $value;
417	to_json [$value] # yields ["5"]	1066	encode_json [$value] # yields ["5"]
418		1067
419	# undef becomes null	1068	# undef becomes null
420	to_json [undef] # yields [null]	1069	encode_json [undef] # yields [null]
421		1070
422	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:
423		1072
424	my $x = 3.1; # some variable containing a number	1073	my $x = 3.1; # some variable containing a number
425	"$x"; # stringified	1074	"$x"; # stringified
426	$x .= ""; # another, more awkward way to stringify	1075	$x .= ""; # another, more awkward way to stringify
427	print $x; # perl does it for you, too, quite often	1076	print $x; # perl does it for you, too, quite often
428		1077
429	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:
430		1079
431	my $x = "3"; # some variable containing a string	1080	my $x = "3"; # some variable containing a string
432	$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
433	$x *= 1; # same thing, the choise is yours.	1082	$x *= 1; # same thing, the choice is yours.
434		1083
435	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
436	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
437		1086	:).
438	=item circular data structures
439
440	Those will be encoded until memory or stackspace runs out.
441		1087
442	=back	1088	=back
443		1089
444	=head1 COMPARISON
445		1090
446	As already mentioned, this module was created because none of the existing	1091	=head1 ENCODING/CODESET FLAG NOTES
447	JSON modules could be made to work correctly. First I will describe the	1092
448	problems (or pleasures) I encountered with various existing JSON modules,	1093	The interested reader might have seen a number of flags that signify
449	followed by some benchmark values. JSON::XS was designed not to suffer	1094	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
450	from any of these problems or limitations.	1095	some confusion on what these do, so here is a short comparison:
		1096
		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.
451		1115
452	=over 4	1116	=over 4
453		1117
454	=item JSON 1.07	1118	=item C<utf8> flag disabled
455		1119
456	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).
457		1127
458	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
459	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
460	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).
461		1133
462	No roundtripping (strings get clobbered if they look like numbers, e.g.	1134	=item C<utf8> flag enabled
463	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
464	decode into the number 2.
465		1135
466	=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.
467		1141
468	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.
469		1145
470	Undocumented/buggy Unicode handling.	1146	=item C<latin1> or C<ascii> flags enabled
471		1147
472	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.
473		1151
474	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
475	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).
476		1157
477	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,
478	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.
479		1161
480	Unmaintained (maintainer unresponsive for many months, bugs are not	1162	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
481	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.
482		1166
483	=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.
484		1171
485	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.
486		1174
487	Very inflexible (no human-readable format supported, format pretty much	1175	The main use for C<latin1> is to relatively efficiently store binary data
488	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.
489	single-line compact format for use in a protocol, and preferably a way to
490	generate ASCII-only JSON texts).
491		1177
492	Completely broken (and confusingly documented) Unicode handling (unicode	1178	The main use for C<ascii> is to force the output to not contain characters
493	escapes are not working properly, you need to set ImplicitUnicode to	1179	with values > 127, which means you can interpret the resulting string
494	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
495		1181	8-bit-encoding, and still get the same data structure back. This is useful
496	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
497	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
498		1184	proper subset of most 8-bit and multibyte encodings in use in the world.
499	Dumping hashes may skip hash values depending on iterator state.
500
501	Unmaintained (maintainer unresponsive for many months, bugs are not
502	getting fixed).
503
504	Does not check input for validity (i.e. will accept non-JSON input and
505	return "something" instead of raising an exception. This is a security
506	issue: imagine two banks transfering money between each other using
507	JSON. One bank might parse a given non-JSON request and deduct money,
508	while the other might reject the transaction with a syntax error. While a
509	good protocol will at least recover, that is extra unnecessary work and
510	the transaction will still not succeed).
511
512	=item JSON::DWIW 0.04
513
514	Very fast. Very natural. Very nice.
515
516	Undocumented unicode handling (but the best of the pack. Unicode escapes
517	still don't get parsed properly).
518
519	Very inflexible.
520
521	No roundtripping.
522
523	Does not generate valid JSON texts (key strings are often unquoted, empty keys
524	result in nothing being output)
525
526	Does not check input for validity.
527		1185
528	=back	1186	=back
		1187
		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
		1254	=head2 JSON and YAML
		1255
		1256	You often hear that JSON is a subset of YAML. This is, however, a mass
		1257	hysteria(*) and very far from the truth (as of the time of this writing),
		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.
		1261
		1262	If you really must use JSON::XS to generate YAML, you should use this
		1263	algorithm (subject to change in future versions):
		1264
		1265	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1266	my $yaml = $to_yaml->encode ($ref) . "\n";
		1267
		1268	This will I<usually> generate JSON texts that also parse as valid
		1269	YAML. Please note that YAML has hardcoded limits on (simple) object key
		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
		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).
		1277
		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
		1280	general you should not try to generate YAML with a JSON generator or vice
		1281	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		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
		1306
529		1307
530	=head2 SPEED	1308	=head2 SPEED
531		1309
532	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
533	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
534	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
535	system.	1313	system.
536		1314
537	First comes a comparison between various modules using a very short JSON	1315	First comes a comparison between various modules using
538	string:	1316	a very short single-line JSON string (also available at
		1317	L<http://dist.schmorp.de/misc/json/short.json>).
539		1318
540	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1319	{"method": "handleMessage", "params": ["user1",
		1320	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1321	true, false]}
541		1322
542	It shows the number of encodes/decodes per second (JSON::XS uses the	1323	It shows the number of encodes/decodes per second (JSON::XS uses
543	functional interface, while JSON::XS/2 uses the OO interface with	1324	the functional interface, while JSON::XS/2 uses the OO interface
544	pretty-printing and hashkey sorting enabled). Higher is better:	1325	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1326	shrink). Higher is better:
545		1327
546	module | encode | decode |	1328	module | encode | decode |
547	-----------|------------|------------|	1329	-----------|------------|------------|
548	JSON | 11488.516 | 7823.035 |	1330	JSON 1.x | 4990.842 | 4088.813 |
549	JSON::DWIW | 94708.054 | 129094.260 |	1331	JSON::DWIW | 51653.990 | 71575.154 |
550	JSON::PC | 63884.157 | 128528.212 |	1332	JSON::PC | 65948.176 | 74631.744 |
551	JSON::Syck | 34898.677 | 42096.911 |	1333	JSON::PP | 8931.652 | 3817.168 |
552	JSON::XS | 654027.064 | 396423.669 |	1334	JSON::Syck | 24877.248 | 27776.848 |
553	JSON::XS/2 | 371564.190 | 371725.613 |	1335	JSON::XS | 388361.481 | 227951.304 |
		1336	JSON::XS/2 | 227951.304 | 218453.333 |
		1337	JSON::XS/3 | 338250.323 | 218453.333 |
		1338	Storable | 16500.016 | 135300.129 |
554	-----------+------------+------------+	1339	-----------+------------+------------+
555		1340
556	That is, JSON::XS is more than six times faster than JSON::DWIW on	1341	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
557	encoding, more than three times faster on decoding, and about thirty times	1342	about three times faster on decoding, and over forty times faster
558	faster than JSON, even with pretty-printing and key sorting.	1343	than JSON, even with pretty-printing and key sorting. It also compares
		1344	favourably to Storable for small amounts of data.
559		1345
560	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1346	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
561	search API (http://nanoref.com/yahooapis/mgPdGg):	1347	search API (L<http://dist.schmorp.de/misc/json/long.json>).
562		1348
563	module | encode | decode |	1349	module | encode | decode |
564	-----------|------------|------------|	1350	-----------|------------|------------|
565	JSON | 273.023 | 44.674 |	1351	JSON 1.x | 55.260 | 34.971 |
566	JSON::DWIW | 1089.383 | 1145.704 |	1352	JSON::DWIW | 825.228 | 1082.513 |
567	JSON::PC | 3097.419 | 2393.921 |	1353	JSON::PC | 3571.444 | 2394.829 |
568	JSON::Syck | 514.060 | 843.053 |	1354	JSON::PP | 210.987 | 32.574 |
569	JSON::XS | 6479.668 | 3636.364 |	1355	JSON::Syck | 552.551 | 787.544 |
570	JSON::XS/2 | 3774.221 | 3599.124 |	1356	JSON::XS | 5780.463 | 4854.519 |
		1357	JSON::XS/2 | 3869.998 | 4798.975 |
		1358	JSON::XS/3 | 5862.880 | 4798.975 |
		1359	Storable | 4445.002 | 5235.027 |
571	-----------+------------+------------+	1360	-----------+------------+------------+
572		1361
573	Again, JSON::XS leads by far.	1362	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1363	decodes faster).
574		1364
575	On large strings containing lots of high unicode characters, some modules	1365	On large strings containing lots of high Unicode characters, some modules
576	(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
577	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
578	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
579	comparison table for that case.	1369	comparison table for that case.
580		1370
581	=head1 RESOURCE LIMITS
582		1371
583	JSON::XS does not impose any limits on the size of JSON texts or Perl	1372	=head1 SECURITY CONSIDERATIONS
584	values they represent - if your machine can handle it, JSON::XS will	1373
585	encode or decode it. Future versions might optionally impose structure	1374	When you are using JSON in a protocol, talking to untrusted potentially
586	depth and memory use resource limits.	1375	hostile creatures requires relatively few measures.
		1376
		1377	First of all, your JSON decoder should be secure, that is, should not have
		1378	any buffer overflows. Obviously, this module should ensure that and I am
		1379	trying hard on making that true, but you never know.
		1380
		1381	Second, you need to avoid resource-starving attacks. That means you should
		1382	limit the size of JSON texts you accept, or make sure then when your
		1383	resources run out, that's just fine (e.g. by using a separate process that
		1384	can crash safely). The size of a JSON text in octets or characters is
		1385	usually a good indication of the size of the resources required to decode
		1386	it into a Perl structure. While JSON::XS can check the size of the JSON
		1387	text, it might be too late when you already have it in memory, so you
		1388	might want to check the size before you accept the string.
		1389
		1390	Third, JSON::XS recurses using the C stack when decoding objects and
		1391	arrays. The C stack is a limited resource: for instance, on my amd64
		1392	machine with 8MB of stack size I can decode around 180k nested arrays but
		1393	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		1394	to free the temporary). If that is exceeded, the program crashes. To be
		1395	conservative, the default nesting limit is set to 512. If your process
		1396	has a smaller stack, you should adjust this setting accordingly with the
		1397	C<max_depth> method.
		1398
		1399	Something else could bomb you, too, that I forgot to think of. In that
		1400	case, you get to keep the pieces. I am always open for hints, 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.
		1406
		1407	If you are using JSON::XS to return packets to consumption
		1408	by JavaScript scripts in a browser you should have a look at
		1409	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1410	you are vulnerable to some common attack vectors (which really are browser
		1411	design bugs, but it is still you who will have to deal with it, as major
		1412	browser developers care only for features, not about getting security
		1413	right).
		1414
		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
587		1425
588	=head1 BUGS	1426	=head1 BUGS
589		1427
590	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
591	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
592	still very young and not well-tested. If you keep reporting bugs they will	1430	keep reporting bugs they will be fixed swiftly, though.
593	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.
594		1434
595	=cut	1435	=cut
596		1436
		1437	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1438	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1439
		1440	sub true() { $true }
		1441	sub false() { $false }
		1442
		1443	sub is_bool($) {
		1444	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1445	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1446	}
		1447
		1448	XSLoader::load "JSON::XS", $VERSION;
		1449
		1450	package JSON::XS::Boolean;
		1451
		1452	use overload
		1453	"0+" => sub { ${$_[0]} },
		1454	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1455	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1456	fallback => 1;
		1457
597	1;	1458	1;
		1459
		1460	=head1 SEE ALSO
		1461
		1462	The F<json_xs> command line utility for quick experiments.
598		1463
599	=head1 AUTHOR	1464	=head1 AUTHOR
600		1465
601	Marc Lehmann <schmorp@schmorp.de>	1466	Marc Lehmann <schmorp@schmorp.de>
602	http://home.schmorp.de/	1467	http://home.schmorp.de/

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