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Revision 1.21 by root, Sun Mar 25 02:32:40 2007 UTC vs.
Revision 1.122 by root, Fri Jul 17 14:33:45 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
		446	This setting has currently no effect on tied hashes.
		447
265	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
266		451
267	If C<$enable> is true (or missing), then the C<encode> method can convert a	452	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,	453	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	454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
270	values instead of croaking.	455	values instead of croaking.
…		…
278	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
279		464
280	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
281	=> "Hello, World!"	466	=> "Hello, World!"
282		467
		468	=item $json = $json->allow_unknown ([$enable])
		469
		470	=item $enabled = $json->get_allow_unknown
		471
		472	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		473	exception when it encounters values it cannot represent in JSON (for
		474	example, filehandles) but instead will encode a JSON C<null> value. Note
		475	that blessed objects are not included here and are handled separately by
		476	c<allow_nonref>.
		477
		478	If C<$enable> is false (the default), then C<encode> will throw an
		479	exception when it encounters anything it cannot encode as JSON.
		480
		481	This option does not affect C<decode> in any way, and it is recommended to
		482	leave it off unless you know your communications partner.
		483
		484	=item $json = $json->allow_blessed ([$enable])
		485
		486	=item $enabled = $json->get_allow_blessed
		487
		488	If C<$enable> is true (or missing), then the C<encode> method will not
		489	barf when it encounters a blessed reference. Instead, the value of the
		490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		491	disabled or no C<TO_JSON> method found) or a representation of the
		492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		493	encoded. Has no effect on C<decode>.
		494
		495	If C<$enable> is false (the default), then C<encode> will throw an
		496	exception when it encounters a blessed object.
		497
		498	=item $json = $json->convert_blessed ([$enable])
		499
		500	=item $enabled = $json->get_convert_blessed
		501
		502	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		503	blessed object, will check for the availability of the C<TO_JSON> method
		504	on the object's class. If found, it will be called in scalar context
		505	and the resulting scalar will be encoded instead of the object. If no
		506	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		507	to do.
		508
		509	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		510	returns other blessed objects, those will be handled in the same
		511	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		512	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		513	methods called by the Perl core (== not by the user of the object) are
		514	usually in upper case letters and to avoid collisions with any C<to_json>
		515	function or method.
		516
		517	This setting does not yet influence C<decode> in any way, but in the
		518	future, global hooks might get installed that influence C<decode> and are
		519	enabled by this setting.
		520
		521	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		522	to do when a blessed object is found.
		523
		524	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		525
		526	When C<$coderef> is specified, it will be called from C<decode> each
		527	time it decodes a JSON object. The only argument is a reference to the
		528	newly-created hash. If the code references returns a single scalar (which
		529	need not be a reference), this value (i.e. a copy of that scalar to avoid
		530	aliasing) is inserted into the deserialised data structure. If it returns
		531	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		532	original deserialised hash will be inserted. This setting can slow down
		533	decoding considerably.
		534
		535	When C<$coderef> is omitted or undefined, any existing callback will
		536	be removed and C<decode> will not change the deserialised hash in any
		537	way.
		538
		539	Example, convert all JSON objects into the integer 5:
		540
		541	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		542	# returns [5]
		543	$js->decode ('[{}]')
		544	# throw an exception because allow_nonref is not enabled
		545	# so a lone 5 is not allowed.
		546	$js->decode ('{"a":1, "b":2}');
		547
		548	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		549
		550	Works remotely similar to C<filter_json_object>, but is only called for
		551	JSON objects having a single key named C<$key>.
		552
		553	This C<$coderef> is called before the one specified via
		554	C<filter_json_object>, if any. It gets passed the single value in the JSON
		555	object. If it returns a single value, it will be inserted into the data
		556	structure. If it returns nothing (not even C<undef> but the empty list),
		557	the callback from C<filter_json_object> will be called next, as if no
		558	single-key callback were specified.
		559
		560	If C<$coderef> is omitted or undefined, the corresponding callback will be
		561	disabled. There can only ever be one callback for a given key.
		562
		563	As this callback gets called less often then the C<filter_json_object>
		564	one, decoding speed will not usually suffer as much. Therefore, single-key
		565	objects make excellent targets to serialise Perl objects into, especially
		566	as single-key JSON objects are as close to the type-tagged value concept
		567	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		568	support this in any way, so you need to make sure your data never looks
		569	like a serialised Perl hash.
		570
		571	Typical names for the single object key are C<__class_whatever__>, or
		572	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		573	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		574	with real hashes.
		575
		576	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		577	into the corresponding C<< $WIDGET{<id>} >> object:
		578
		579	# return whatever is in $WIDGET{5}:
		580	JSON::XS
		581	->new
		582	->filter_json_single_key_object (__widget__ => sub {
		583	$WIDGET{ $_[0] }
		584	})
		585	->decode ('{"__widget__": 5')
		586
		587	# this can be used with a TO_JSON method in some "widget" class
		588	# for serialisation to json:
		589	sub WidgetBase::TO_JSON {
		590	my ($self) = @_;
		591
		592	unless ($self->{id}) {
		593	$self->{id} = ..get..some..id..;
		594	$WIDGET{$self->{id}} = $self;
		595	}
		596
		597	{ __widget__ => $self->{id} }
		598	}
		599
283	=item $json = $json->shrink ([$enable])	600	=item $json = $json->shrink ([$enable])
284		601
		602	=item $enabled = $json->get_shrink
		603
285	Perl usually over-allocates memory a bit when allocating space for	604	Perl usually over-allocates memory a bit when allocating space for
286	strings. This flag optionally resizes strings generated by either	605	strings. This flag optionally resizes strings generated by either
287	C<encode> or C<decode> to their minimum size possible. This can save	606	C<encode> or C<decode> to their minimum size possible. This can save
288	memory when your JSON texts are either very very long or you have many	607	memory when your JSON texts are either very very long or you have many
289	short strings. It will also try to downgrade any strings to octet-form	608	short strings. It will also try to downgrade any strings to octet-form
290	if possible: perl stores strings internally either in an encoding called	609	if possible: perl stores strings internally either in an encoding called
291	UTF-X or in octet-form. The latter cannot store everything but uses less	610	UTF-X or in octet-form. The latter cannot store everything but uses less
292	space in general.	611	space in general (and some buggy Perl or C code might even rely on that
		612	internal representation being used).
293		613
		614	The actual definition of what shrink does might change in future versions,
		615	but it will always try to save space at the expense of time.
		616
294	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	617	If C<$enable> is true (or missing), the string returned by C<encode> will
295	while all strings generated by C<decode> will also be shrunk-to-fit.	618	be shrunk-to-fit, while all strings generated by C<decode> will also be
		619	shrunk-to-fit.
296		620
297	If C<$enable> is false, then the normal perl allocation algorithms are used.	621	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.	622	If you work with your data, then this is likely to be faster.
299		623
300	In the future, this setting might control other things, such as converting	624	In the future, this setting might control other things, such as converting
301	strings that look like integers or floats into integers or floats	625	strings that look like integers or floats into integers or floats
302	internally (there is no difference on the Perl level), saving space.	626	internally (there is no difference on the Perl level), saving space.
		627
		628	=item $json = $json->max_depth ([$maximum_nesting_depth])
		629
		630	=item $max_depth = $json->get_max_depth
		631
		632	Sets the maximum nesting level (default C<512>) accepted while encoding
		633	or decoding. If a higher nesting level is detected in JSON text or a Perl
		634	data structure, then the encoder and decoder will stop and croak at that
		635	point.
		636
		637	Nesting level is defined by number of hash- or arrayrefs that the encoder
		638	needs to traverse to reach a given point or the number of C<{> or C<[>
		639	characters without their matching closing parenthesis crossed to reach a
		640	given character in a string.
		641
		642	Setting the maximum depth to one disallows any nesting, so that ensures
		643	that the object is only a single hash/object or array.
		644
		645	If no argument is given, the highest possible setting will be used, which
		646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
		651
		652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		653
		654	=item $json = $json->max_size ([$maximum_string_size])
		655
		656	=item $max_size = $json->get_max_size
		657
		658	Set the maximum length a JSON text may have (in bytes) where decoding is
		659	being attempted. The default is C<0>, meaning no limit. When C<decode>
		660	is called on a string that is longer then this many bytes, it will not
		661	attempt to decode the string but throw an exception. This setting has no
		662	effect on C<encode> (yet).
		663
		664	If no argument is given, the limit check will be deactivated (same as when
		665	C<0> is specified).
		666
		667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
303		668
304	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
305		670
306	Converts the given Perl data structure (a simple scalar or a reference	671	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	672	to a hash or array) to its JSON representation. Simple scalars will be
…		…
317		682
318	JSON numbers and strings become simple Perl scalars. JSON arrays become	683	JSON numbers and strings become simple Perl scalars. JSON arrays become
319	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	684	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>.	685	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
321		686
		687	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		688
		689	This works like the C<decode> method, but instead of raising an exception
		690	when there is trailing garbage after the first JSON object, it will
		691	silently stop parsing there and return the number of characters consumed
		692	so far.
		693
		694	This is useful if your JSON texts are not delimited by an outer protocol
		695	(which is not the brightest thing to do in the first place) and you need
		696	to know where the JSON text ends.
		697
		698	JSON::XS->new->decode_prefix ("[1] the tail")
		699	=> ([], 3)
		700
322	=back	701	=back
		702
		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	=item $lvalue_string = $json->incr_text
		757
		758	This method returns the currently stored JSON fragment as an lvalue, that
		759	is, you can manipulate it. This I<only> works when a preceding call to
		760	C<incr_parse> in I<scalar context> successfully returned an object. Under
		761	all other circumstances you must not call this function (I mean it.
		762	although in simple tests it might actually work, it I<will> fail under
		763	real world conditions). As a special exception, you can also call this
		764	method before having parsed anything.
		765
		766	This function is useful in two cases: a) finding the trailing text after a
		767	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		768	(such as commas).
		769
		770	=item $json->incr_skip
		771
		772	This will reset the state of the incremental parser and will remove
		773	the parsed text from the input buffer so far. This is useful after
		774	C<incr_parse> died, in which case the input buffer and incremental parser
		775	state is left unchanged, to skip the text parsed so far and to reset the
		776	parse state.
		777
		778	The difference to C<incr_reset> is that only text until the parse error
		779	occured is removed.
		780
		781	=item $json->incr_reset
		782
		783	This completely resets the incremental parser, that is, after this call,
		784	it will be as if the parser had never parsed anything.
		785
		786	This is useful if you want to repeatedly parse JSON objects and want to
		787	ignore any trailing data, which means you have to reset the parser after
		788	each successful decode.
		789
		790	=back
		791
		792	=head2 LIMITATIONS
		793
		794	All options that affect decoding are supported, except
		795	C<allow_nonref>. The reason for this is that it cannot be made to
		796	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		797	them back to back and still decode them perfectly. This does not hold true
		798	for JSON numbers, however.
		799
		800	For example, is the string C<1> a single JSON number, or is it simply the
		801	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		802	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		803	takes the conservative route and disallows this case.
		804
		805	=head2 EXAMPLES
		806
		807	Some examples will make all this clearer. First, a simple example that
		808	works similarly to C<decode_prefix>: We want to decode the JSON object at
		809	the start of a string and identify the portion after the JSON object:
		810
		811	my $text = "[1,2,3] hello";
		812
		813	my $json = new JSON::XS;
		814
		815	my $obj = $json->incr_parse ($text)
		816	or die "expected JSON object or array at beginning of string";
		817
		818	my $tail = $json->incr_text;
		819	# $tail now contains " hello"
		820
		821	Easy, isn't it?
		822
		823	Now for a more complicated example: Imagine a hypothetical protocol where
		824	you read some requests from a TCP stream, and each request is a JSON
		825	array, without any separation between them (in fact, it is often useful to
		826	use newlines as "separators", as these get interpreted as whitespace at
		827	the start of the JSON text, which makes it possible to test said protocol
		828	with C<telnet>...).
		829
		830	Here is how you'd do it (it is trivial to write this in an event-based
		831	manner):
		832
		833	my $json = new JSON::XS;
		834
		835	# read some data from the socket
		836	while (sysread $socket, my $buf, 4096) {
		837
		838	# split and decode as many requests as possible
		839	for my $request ($json->incr_parse ($buf)) {
		840	# act on the $request
		841	}
		842	}
		843
		844	Another complicated example: Assume you have a string with JSON objects
		845	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		846	[3]>). To parse them, we have to skip the commas between the JSON texts,
		847	and here is where the lvalue-ness of C<incr_text> comes in useful:
		848
		849	my $text = "[1],[2], [3]";
		850	my $json = new JSON::XS;
		851
		852	# void context, so no parsing done
		853	$json->incr_parse ($text);
		854
		855	# now extract as many objects as possible. note the
		856	# use of scalar context so incr_text can be called.
		857	while (my $obj = $json->incr_parse) {
		858	# do something with $obj
		859
		860	# now skip the optional comma
		861	$json->incr_text =~ s/^ \s* , //x;
		862	}
		863
		864	Now lets go for a very complex example: Assume that you have a gigantic
		865	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		866	but you cannot load it into memory fully (this has actually happened in
		867	the real world :).
		868
		869	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		870	can still help you: You implement a (very simple) array parser and let
		871	JSON decode the array elements, which are all full JSON objects on their
		872	own (this wouldn't work if the array elements could be JSON numbers, for
		873	example):
		874
		875	my $json = new JSON::XS;
		876
		877	# open the monster
		878	open my $fh, "<bigfile.json"
		879	or die "bigfile: $!";
		880
		881	# first parse the initial "["
		882	for (;;) {
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886
		887	# Exit the loop once we found and removed(!) the initial "[".
		888	# In essence, we are (ab-)using the $json object as a simple scalar
		889	# we append data to.
		890	last if $json->incr_text =~ s/^ \s* \[ //x;
		891	}
		892
		893	# now we have the skipped the initial "[", so continue
		894	# parsing all the elements.
		895	for (;;) {
		896	# in this loop we read data until we got a single JSON object
		897	for (;;) {
		898	if (my $obj = $json->incr_parse) {
		899	# do something with $obj
		900	last;
		901	}
		902
		903	# add more data
		904	sysread $fh, my $buf, 65536
		905	or die "read error: $!";
		906	$json->incr_parse ($buf); # void context, so no parsing
		907	}
		908
		909	# in this loop we read data until we either found and parsed the
		910	# separating "," between elements, or the final "]"
		911	for (;;) {
		912	# first skip whitespace
		913	$json->incr_text =~ s/^\s*//;
		914
		915	# if we find "]", we are done
		916	if ($json->incr_text =~ s/^\]//) {
		917	print "finished.\n";
		918	exit;
		919	}
		920
		921	# if we find ",", we can continue with the next element
		922	if ($json->incr_text =~ s/^,//) {
		923	last;
		924	}
		925
		926	# if we find anything else, we have a parse error!
		927	if (length $json->incr_text) {
		928	die "parse error near ", $json->incr_text;
		929	}
		930
		931	# else add more data
		932	sysread $fh, my $buf, 65536
		933	or die "read error: $!";
		934	$json->incr_parse ($buf); # void context, so no parsing
		935	}
		936
		937	This is a complex example, but most of the complexity comes from the fact
		938	that we are trying to be correct (bear with me if I am wrong, I never ran
		939	the above example :).
		940
		941
323		942
324	=head1 MAPPING	943	=head1 MAPPING
325		944
326	This section describes how JSON::XS maps Perl values to JSON values and	945	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	946	vice versa. These mappings are designed to "do the right thing" in most
328	circumstances automatically, preserving round-tripping characteristics	947	circumstances automatically, preserving round-tripping characteristics
329	(what you put in comes out as something equivalent).	948	(what you put in comes out as something equivalent).
330		949
331	For the more enlightened: note that in the following descriptions,	950	For the more enlightened: note that in the following descriptions,
332	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	951	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
333	refers to the abstract Perl language itself.	952	refers to the abstract Perl language itself.
334		953
		954
335	=head2 JSON -> PERL	955	=head2 JSON -> PERL
336		956
337	=over 4	957	=over 4
338		958
339	=item object	959	=item object
340		960
341	A JSON object becomes a reference to a hash in Perl. No ordering of object	961	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).	962	keys is preserved (JSON does not preserve object key ordering itself).
343		963
344	=item array	964	=item array
345		965
346	A JSON array becomes a reference to an array in Perl.	966	A JSON array becomes a reference to an array in Perl.
347		967
…		…
351	are represented by the same codepoints in the Perl string, so no manual	971	are represented by the same codepoints in the Perl string, so no manual
352	decoding is necessary.	972	decoding is necessary.
353		973
354	=item number	974	=item number
355		975
356	A JSON number becomes either an integer or numeric (floating point)	976	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	977	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	978	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	979	the conversion details, but an integer may take slightly less memory and
360	represent more values exactly than (floating point) numbers.	980	might represent more values exactly than floating point numbers.
		981
		982	If the number consists of digits only, JSON::XS will try to represent
		983	it as an integer value. If that fails, it will try to represent it as
		984	a numeric (floating point) value if that is possible without loss of
		985	precision. Otherwise it will preserve the number as a string value (in
		986	which case you lose roundtripping ability, as the JSON number will be
		987	re-encoded toa JSON string).
		988
		989	Numbers containing a fractional or exponential part will always be
		990	represented as numeric (floating point) values, possibly at a loss of
		991	precision (in which case you might lose perfect roundtripping ability, but
		992	the JSON number will still be re-encoded as a JSON number).
361		993
362	=item true, false	994	=item true, false
363		995
364	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	996	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
365	this process. Future versions might represent those values differently,	997	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	998	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
367	Perl.	999	the C<JSON::XS::is_bool> function.
368		1000
369	=item null	1001	=item null
370		1002
371	A JSON null atom becomes C<undef> in Perl.	1003	A JSON null atom becomes C<undef> in Perl.
372		1004
373	=back	1005	=back
		1006
374		1007
375	=head2 PERL -> JSON	1008	=head2 PERL -> JSON
376		1009
377	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1010	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	1011	truly typeless language, so we can only guess which JSON type is meant by
…		…
381	=over 4	1014	=over 4
382		1015
383	=item hash references	1016	=item hash references
384		1017
385	Perl hash references become JSON objects. As there is no inherent ordering	1018	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	1019	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	1020	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	1021	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	1022	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	1023	the same datastructure will serialise to the same JSON text (given same
391	JSON::XS), but this incurs a runtime overhead.	1024	settings and version of JSON::XS), but this incurs a runtime overhead
		1025	and is only rarely useful, e.g. when you want to compare some JSON text
		1026	against another for equality.
392		1027
393	=item array references	1028	=item array references
394		1029
395	Perl array references become JSON arrays.	1030	Perl array references become JSON arrays.
396		1031
		1032	=item other references
		1033
		1034	Other unblessed references are generally not allowed and will cause an
		1035	exception to be thrown, except for references to the integers C<0> and
		1036	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		1037	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		1038
		1039	encode_json [\0, JSON::XS::true] # yields [false,true]
		1040
		1041	=item JSON::XS::true, JSON::XS::false
		1042
		1043	These special values become JSON true and JSON false values,
		1044	respectively. You can also use C<\1> and C<\0> directly if you want.
		1045
397	=item blessed objects	1046	=item blessed objects
398		1047
399	Blessed objects are not allowed. JSON::XS currently tries to encode their	1048	Blessed objects are not directly representable in JSON. See the
400	underlying representation (hash- or arrayref), but this behaviour might	1049	C<allow_blessed> and C<convert_blessed> methods on various options on
401	change in future versions.	1050	how to deal with this: basically, you can choose between throwing an
		1051	exception, encoding the reference as if it weren't blessed, or provide
		1052	your own serialiser method.
402		1053
403	=item simple scalars	1054	=item simple scalars
404		1055
405	Simple Perl scalars (any scalar that is not a reference) are the most	1056	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	1057	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	1058	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:	1059	before encoding as JSON strings, and anything else as number value:
409		1060
410	# dump as number	1061	# dump as number
411	to_json [2] # yields [2]	1062	encode_json [2] # yields [2]
412	to_json [-3.0e17] # yields [-3e+17]	1063	encode_json [-3.0e17] # yields [-3e+17]
413	my $value = 5; to_json [$value] # yields [5]	1064	my $value = 5; encode_json [$value] # yields [5]
414		1065
415	# used as string, so dump as string	1066	# used as string, so dump as string
416	print $value;	1067	print $value;
417	to_json [$value] # yields ["5"]	1068	encode_json [$value] # yields ["5"]
418		1069
419	# undef becomes null	1070	# undef becomes null
420	to_json [undef] # yields [null]	1071	encode_json [undef] # yields [null]
421		1072
422	You can force the type to be a string by stringifying it:	1073	You can force the type to be a JSON string by stringifying it:
423		1074
424	my $x = 3.1; # some variable containing a number	1075	my $x = 3.1; # some variable containing a number
425	"$x"; # stringified	1076	"$x"; # stringified
426	$x .= ""; # another, more awkward way to stringify	1077	$x .= ""; # another, more awkward way to stringify
427	print $x; # perl does it for you, too, quite often	1078	print $x; # perl does it for you, too, quite often
428		1079
429	You can force the type to be a number by numifying it:	1080	You can force the type to be a JSON number by numifying it:
430		1081
431	my $x = "3"; # some variable containing a string	1082	my $x = "3"; # some variable containing a string
432	$x += 0; # numify it, ensuring it will be dumped as a number	1083	$x += 0; # numify it, ensuring it will be dumped as a number
433	$x *= 1; # same thing, the choise is yours.	1084	$x *= 1; # same thing, the choice is yours.
434		1085
435	You can not currently output JSON booleans or force the type in other,	1086	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.	1087	if you need this capability (but don't forget to explain why it's needed
437		1088	:).
438	=item circular data structures
439
440	Those will be encoded until memory or stackspace runs out.
441		1089
442	=back	1090	=back
443		1091
444	=head1 COMPARISON
445		1092
446	As already mentioned, this module was created because none of the existing	1093	=head1 ENCODING/CODESET FLAG NOTES
447	JSON modules could be made to work correctly. First I will describe the	1094
448	problems (or pleasures) I encountered with various existing JSON modules,	1095	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	1096	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
450	from any of these problems or limitations.	1097	some confusion on what these do, so here is a short comparison:
		1098
		1099	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1100	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1101	control whether C<encode> escapes character values outside their respective
		1102	codeset range. Neither of these flags conflict with each other, although
		1103	some combinations make less sense than others.
		1104
		1105	Care has been taken to make all flags symmetrical with respect to
		1106	C<encode> and C<decode>, that is, texts encoded with any combination of
		1107	these flag values will be correctly decoded when the same flags are used
		1108	- in general, if you use different flag settings while encoding vs. when
		1109	decoding you likely have a bug somewhere.
		1110
		1111	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1112	simply an abstract set of character-codepoint pairs, while an encoding
		1113	takes those codepoint numbers and I<encodes> them, in our case into
		1114	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1115	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1116	the same time, which can be confusing.
451		1117
452	=over 4	1118	=over 4
453		1119
454	=item JSON 1.07	1120	=item C<utf8> flag disabled
455		1121
456	Slow (but very portable, as it is written in pure Perl).	1122	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1123	and expect Unicode strings, that is, characters with high ordinal Unicode
		1124	values (> 255) will be encoded as such characters, and likewise such
		1125	characters are decoded as-is, no canges to them will be done, except
		1126	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1127	respectively (to Perl, these are the same thing in strings unless you do
		1128	funny/weird/dumb stuff).
457		1129
458	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1130	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	1131	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).	1132	the encoding for you (for example, when printing to a terminal using a
		1133	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1134	to UTF-8 encode your data first and have Perl encode it another time).
461		1135
462	No roundtripping (strings get clobbered if they look like numbers, e.g.	1136	=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		1137
466	=item JSON::PC 0.01	1138	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1139	characters using the corresponding UTF-8 multi-byte sequence, and will
		1140	expect your input strings to be encoded as UTF-8, that is, no "character"
		1141	of the input string must have any value > 255, as UTF-8 does not allow
		1142	that.
467		1143
468	Very fast.	1144	The C<utf8> flag therefore switches between two modes: disabled means you
		1145	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1146	octet/binary string in Perl.
469		1147
470	Undocumented/buggy Unicode handling.	1148	=item C<latin1> or C<ascii> flags enabled
471		1149
472	No roundtripping.	1150	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1151	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1152	characters as specified by the C<utf8> flag.
473		1153
474	Has problems handling many Perl values (e.g. regex results and other magic	1154	If C<utf8> is disabled, then the result is also correctly encoded in those
475	values will make it croak).	1155	character sets (as both are proper subsets of Unicode, meaning that a
		1156	Unicode string with all character values < 256 is the same thing as a
		1157	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1158	the same thing as an ASCII string in Perl).
476		1159
477	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1160	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
478	which is not a valid JSON text.	1161	regardless of these flags, just some more characters will be escaped using
		1162	C<\uXXXX> then before.
479		1163
480	Unmaintained (maintainer unresponsive for many months, bugs are not	1164	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
481	getting fixed).	1165	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1166	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1167	a subset of Unicode), while ASCII is.
482		1168
483	=item JSON::Syck 0.21	1169	Surprisingly, C<decode> will ignore these flags and so treat all input
		1170	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1171	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1172	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
484		1173
485	Very buggy (often crashes).	1174	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1175	they only govern when the JSON output engine escapes a character or not.
486		1176
487	Very inflexible (no human-readable format supported, format pretty much	1177	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	1178	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		1179
492	Completely broken (and confusingly documented) Unicode handling (unicode	1180	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	1181	with values > 127, which means you can interpret the resulting string
494	I<different> values on en- and decoding to get symmetric behaviour).	1182	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
495		1183	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	1184	when your channel for JSON transfer is not 8-bit clean or the encoding
497	value was used in a numeric context or not).	1185	might be mangled in between (e.g. in mail), and works because ASCII is a
498		1186	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		1187
528	=back	1188	=back
		1189
		1190
		1191	=head2 JSON and ECMAscript
		1192
		1193	JSON syntax is based on how literals are represented in javascript (the
		1194	not-standardised predecessor of ECMAscript) which is presumably why it is
		1195	called "JavaScript Object Notation".
		1196
		1197	However, JSON is not a subset (and also not a superset of course) of
		1198	ECMAscript (the standard) or javascript (whatever browsers actually
		1199	implement).
		1200
		1201	If you want to use javascript's C<eval> function to "parse" JSON, you
		1202	might run into parse errors for valid JSON texts, or the resulting data
		1203	structure might not be queryable:
		1204
		1205	One of the problems is that U+2028 and U+2029 are valid characters inside
		1206	JSON strings, but are not allowed in ECMAscript string literals, so the
		1207	following Perl fragment will not output something that can be guaranteed
		1208	to be parsable by javascript's C<eval>:
		1209
		1210	use JSON::XS;
		1211
		1212	print encode_json [chr 0x2028];
		1213
		1214	The right fix for this is to use a proper JSON parser in your javascript
		1215	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1216	F<json2.js> parser).
		1217
		1218	If this is not an option, you can, as a stop-gap measure, simply encode to
		1219	ASCII-only JSON:
		1220
		1221	use JSON::XS;
		1222
		1223	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1224
		1225	Note that this will enlarge the resulting JSON text quite a bit if you
		1226	have many non-ASCII characters. You might be tempted to run some regexes
		1227	to only escape U+2028 and U+2029, e.g.:
		1228
		1229	# DO NOT USE THIS!
		1230	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1231	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1232	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1233	print $json;
		1234
		1235	Note that I<this is a bad idea>: the above only works for U+2028 and
		1236	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1237	javascript implementations, however, have issues with other characters as
		1238	well - using C<eval> naively simply I<will> cause problems.
		1239
		1240	Another problem is that some javascript implementations reserve
		1241	some property names for their own purposes (which probably makes
		1242	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1243	C<__proto__> property name for it's own purposes.
		1244
		1245	If that is a problem, you could parse try to filter the resulting JSON
		1246	output for these property strings, e.g.:
		1247
		1248	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1249
		1250	This works because C<__proto__> is not valid outside of strings, so every
		1251	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1252
		1253	If you know of other incompatibilities, please let me know.
		1254
		1255
		1256	=head2 JSON and YAML
		1257
		1258	You often hear that JSON is a subset of YAML. This is, however, a mass
		1259	hysteria(*) and very far from the truth (as of the time of this writing),
		1260	so let me state it clearly: I<in general, there is no way to configure
		1261	JSON::XS to output a data structure as valid YAML> that works in all
		1262	cases.
		1263
		1264	If you really must use JSON::XS to generate YAML, you should use this
		1265	algorithm (subject to change in future versions):
		1266
		1267	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1268	my $yaml = $to_yaml->encode ($ref) . "\n";
		1269
		1270	This will I<usually> generate JSON texts that also parse as valid
		1271	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1272	lengths that JSON doesn't have and also has different and incompatible
		1273	unicode handling, so you should make sure that your hash keys are
		1274	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1275	you do not have characters with codepoint values outside the Unicode BMP
		1276	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1277	strings (which JSON::XS does not I<currently> generate, but other JSON
		1278	generators might).
		1279
		1280	There might be other incompatibilities that I am not aware of (or the YAML
		1281	specification has been changed yet again - it does so quite often). In
		1282	general you should not try to generate YAML with a JSON generator or vice
		1283	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1284	high that you will run into severe interoperability problems when you
		1285	least expect it.
		1286
		1287	=over 4
		1288
		1289	=item (*)
		1290
		1291	I have been pressured multiple times by Brian Ingerson (one of the
		1292	authors of the YAML specification) to remove this paragraph, despite him
		1293	acknowledging that the actual incompatibilities exist. As I was personally
		1294	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1295	educate people about these issues, so others do not run into the same
		1296	problem again and again. After this, Brian called me a (quote)I<complete
		1297	and worthless idiot>(unquote).
		1298
		1299	In my opinion, instead of pressuring and insulting people who actually
		1300	clarify issues with YAML and the wrong statements of some of its
		1301	proponents, I would kindly suggest reading the JSON spec (which is not
		1302	that difficult or long) and finally make YAML compatible to it, and
		1303	educating users about the changes, instead of spreading lies about the
		1304	real compatibility for many I<years> and trying to silence people who
		1305	point out that it isn't true.
		1306
		1307	=back
		1308
529		1309
530	=head2 SPEED	1310	=head2 SPEED
531		1311
532	It seems that JSON::XS is surprisingly fast, as shown in the following	1312	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	1313	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	1314	in the JSON::XS distribution, to make it easy to compare on your own
535	system.	1315	system.
536		1316
537	First comes a comparison between various modules using a very short JSON	1317	First comes a comparison between various modules using
538	string:	1318	a very short single-line JSON string (also available at
		1319	L<http://dist.schmorp.de/misc/json/short.json>).
539		1320
540	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1321	{"method": "handleMessage", "params": ["user1",
		1322	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1323	true, false]}
541		1324
542	It shows the number of encodes/decodes per second (JSON::XS uses the	1325	It shows the number of encodes/decodes per second (JSON::XS uses
543	functional interface, while JSON::XS/2 uses the OO interface with	1326	the functional interface, while JSON::XS/2 uses the OO interface
544	pretty-printing and hashkey sorting enabled). Higher is better:	1327	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1328	shrink). Higher is better:
545		1329
546	module | encode | decode |	1330	module | encode | decode |
547	-----------|------------|------------|	1331	-----------|------------|------------|
548	JSON | 11488.516 | 7823.035 |	1332	JSON 1.x | 4990.842 | 4088.813 |
549	JSON::DWIW | 94708.054 | 129094.260 |	1333	JSON::DWIW | 51653.990 | 71575.154 |
550	JSON::PC | 63884.157 | 128528.212 |	1334	JSON::PC | 65948.176 | 74631.744 |
551	JSON::Syck | 34898.677 | 42096.911 |	1335	JSON::PP | 8931.652 | 3817.168 |
552	JSON::XS | 654027.064 | 396423.669 |	1336	JSON::Syck | 24877.248 | 27776.848 |
553	JSON::XS/2 | 371564.190 | 371725.613 |	1337	JSON::XS | 388361.481 | 227951.304 |
		1338	JSON::XS/2 | 227951.304 | 218453.333 |
		1339	JSON::XS/3 | 338250.323 | 218453.333 |
		1340	Storable | 16500.016 | 135300.129 |
554	-----------+------------+------------+	1341	-----------+------------+------------+
555		1342
556	That is, JSON::XS is more than six times faster than JSON::DWIW on	1343	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	1344	about three times faster on decoding, and over forty times faster
558	faster than JSON, even with pretty-printing and key sorting.	1345	than JSON, even with pretty-printing and key sorting. It also compares
		1346	favourably to Storable for small amounts of data.
559		1347
560	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1348	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
561	search API (http://nanoref.com/yahooapis/mgPdGg):	1349	search API (L<http://dist.schmorp.de/misc/json/long.json>).
562		1350
563	module | encode | decode |	1351	module | encode | decode |
564	-----------|------------|------------|	1352	-----------|------------|------------|
565	JSON | 273.023 | 44.674 |	1353	JSON 1.x | 55.260 | 34.971 |
566	JSON::DWIW | 1089.383 | 1145.704 |	1354	JSON::DWIW | 825.228 | 1082.513 |
567	JSON::PC | 3097.419 | 2393.921 |	1355	JSON::PC | 3571.444 | 2394.829 |
568	JSON::Syck | 514.060 | 843.053 |	1356	JSON::PP | 210.987 | 32.574 |
569	JSON::XS | 6479.668 | 3636.364 |	1357	JSON::Syck | 552.551 | 787.544 |
570	JSON::XS/2 | 3774.221 | 3599.124 |	1358	JSON::XS | 5780.463 | 4854.519 |
		1359	JSON::XS/2 | 3869.998 | 4798.975 |
		1360	JSON::XS/3 | 5862.880 | 4798.975 |
		1361	Storable | 4445.002 | 5235.027 |
571	-----------+------------+------------+	1362	-----------+------------+------------+
572		1363
573	Again, JSON::XS leads by far.	1364	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1365	decodes faster).
574		1366
575	On large strings containing lots of high unicode characters, some modules	1367	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	1368	(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	1369	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	1370	to decode or encode properly, so it was impossible to prepare a fair
579	comparison table for that case.	1371	comparison table for that case.
580		1372
581	=head1 RESOURCE LIMITS
582		1373
583	JSON::XS does not impose any limits on the size of JSON texts or Perl	1374	=head1 SECURITY CONSIDERATIONS
584	values they represent - if your machine can handle it, JSON::XS will	1375
585	encode or decode it. Future versions might optionally impose structure	1376	When you are using JSON in a protocol, talking to untrusted potentially
586	depth and memory use resource limits.	1377	hostile creatures requires relatively few measures.
		1378
		1379	First of all, your JSON decoder should be secure, that is, should not have
		1380	any buffer overflows. Obviously, this module should ensure that and I am
		1381	trying hard on making that true, but you never know.
		1382
		1383	Second, you need to avoid resource-starving attacks. That means you should
		1384	limit the size of JSON texts you accept, or make sure then when your
		1385	resources run out, that's just fine (e.g. by using a separate process that
		1386	can crash safely). The size of a JSON text in octets or characters is
		1387	usually a good indication of the size of the resources required to decode
		1388	it into a Perl structure. While JSON::XS can check the size of the JSON
		1389	text, it might be too late when you already have it in memory, so you
		1390	might want to check the size before you accept the string.
		1391
		1392	Third, JSON::XS recurses using the C stack when decoding objects and
		1393	arrays. The C stack is a limited resource: for instance, on my amd64
		1394	machine with 8MB of stack size I can decode around 180k nested arrays but
		1395	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		1396	to free the temporary). If that is exceeded, the program crashes. To be
		1397	conservative, the default nesting limit is set to 512. If your process
		1398	has a smaller stack, you should adjust this setting accordingly with the
		1399	C<max_depth> method.
		1400
		1401	Something else could bomb you, too, that I forgot to think of. In that
		1402	case, you get to keep the pieces. I am always open for hints, though...
		1403
		1404	Also keep in mind that JSON::XS might leak contents of your Perl data
		1405	structures in its error messages, so when you serialise sensitive
		1406	information you might want to make sure that exceptions thrown by JSON::XS
		1407	will not end up in front of untrusted eyes.
		1408
		1409	If you are using JSON::XS to return packets to consumption
		1410	by JavaScript scripts in a browser you should have a look at
		1411	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1412	you are vulnerable to some common attack vectors (which really are browser
		1413	design bugs, but it is still you who will have to deal with it, as major
		1414	browser developers care only for features, not about getting security
		1415	right).
		1416
		1417
		1418	=head1 THREADS
		1419
		1420	This module is I<not> guaranteed to be thread safe and there are no
		1421	plans to change this until Perl gets thread support (as opposed to the
		1422	horribly slow so-called "threads" which are simply slow and bloated
		1423	process simulations - use fork, it's I<much> faster, cheaper, better).
		1424
		1425	(It might actually work, but you have been warned).
		1426
587		1427
588	=head1 BUGS	1428	=head1 BUGS
589		1429
590	While the goal of this module is to be correct, that unfortunately does	1430	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	1431	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	1432	keep reporting bugs they will be fixed swiftly, though.
593	be fixed swiftly, though.	1433
		1434	Please refrain from using rt.cpan.org or any other bug reporting
		1435	service. I put the contact address into my modules for a reason.
594		1436
595	=cut	1437	=cut
596		1438
		1439	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1440	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1441
		1442	sub true() { $true }
		1443	sub false() { $false }
		1444
		1445	sub is_bool($) {
		1446	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1447	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1448	}
		1449
		1450	XSLoader::load "JSON::XS", $VERSION;
		1451
		1452	package JSON::XS::Boolean;
		1453
		1454	use overload
		1455	"0+" => sub { ${$_[0]} },
		1456	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1457	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1458	fallback => 1;
		1459
597	1;	1460	1;
		1461
		1462	=head1 SEE ALSO
		1463
		1464	The F<json_xs> command line utility for quick experiments.
598		1465
599	=head1 AUTHOR	1466	=head1 AUTHOR
600		1467
601	Marc Lehmann <schmorp@schmorp.de>	1468	Marc Lehmann <schmorp@schmorp.de>
602	http://home.schmorp.de/	1469	http://home.schmorp.de/

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