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Revision 1.21 by root, Sun Mar 25 02:32:40 2007 UTC vs.
Revision 1.118 by root, Thu Feb 19 01:13:46 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
		104	no warnings;
86	use strict;	105	use strict;
87		106
88	BEGIN {
89	our $VERSION = '0.8';	107	our $VERSION = '2.2311';
90	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
91		109
92	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
93	require Exporter;
94		111
		112	sub to_json($) {
95	require XSLoader;	113	require Carp;
96	XSLoader::load JSON::XS::, $VERSION;	114	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
97	}	115	}
98		116
		117	sub from_json($) {
		118	require Carp;
		119	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");
		120	}
		121
		122	use Exporter;
		123	use XSLoader;
		124
99	=head1 FUNCTIONAL INTERFACE	125	=head1 FUNCTIONAL INTERFACE
100		126
101	The following convinience methods are provided by this module. They are	127	The following convenience methods are provided by this module. They are
102	exported by default:	128	exported by default:
103		129
104	=over 4	130	=over 4
105		131
106	=item $json_text = to_json $perl_scalar	132	=item $json_text = encode_json $perl_scalar
107		133
108	Converts the given Perl data structure (a simple scalar or a reference to	134	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	135	(that is, the string contains octets only). Croaks on error.
110	octets only). Croaks on error.
111		136
112	This function call is functionally identical to:	137	This function call is functionally identical to:
113		138
114	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115		140
116	except being faster.	141	Except being faster.
117		142
118	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
119		144
120	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	145	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	146	to parse that as an UTF-8 encoded JSON text, returning the resulting
122	scalar or reference. Croaks on error.	147	reference. Croaks on error.
123		148
124	This function call is functionally identical to:	149	This function call is functionally identical to:
125		150
126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127		152
128	except being faster.	153	Except being faster.
		154
		155	=item $is_boolean = JSON::XS::is_bool $scalar
		156
		157	Returns true if the passed scalar represents either JSON::XS::true or
		158	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		159	and are used to represent JSON C<true> and C<false> values in Perl.
		160
		161	See MAPPING, below, for more information on how JSON values are mapped to
		162	Perl.
129		163
130	=back	164	=back
		165
		166
		167	=head1 A FEW NOTES ON UNICODE AND PERL
		168
		169	Since this often leads to confusion, here are a few very clear words on
		170	how Unicode works in Perl, modulo bugs.
		171
		172	=over 4
		173
		174	=item 1. Perl strings can store characters with ordinal values > 255.
		175
		176	This enables you to store Unicode characters as single characters in a
		177	Perl string - very natural.
		178
		179	=item 2. Perl does I<not> associate an encoding with your strings.
		180
		181	... until you force it to, e.g. when matching it against a regex, or
		182	printing the scalar to a file, in which case Perl either interprets your
		183	string as locale-encoded text, octets/binary, or as Unicode, depending
		184	on various settings. In no case is an encoding stored together with your
		185	data, it is I<use> that decides encoding, not any magical meta data.
		186
		187	=item 3. The internal utf-8 flag has no meaning with regards to the
		188	encoding of your string.
		189
		190	Just ignore that flag unless you debug a Perl bug, a module written in
		191	XS or want to dive into the internals of perl. Otherwise it will only
		192	confuse you, as, despite the name, it says nothing about how your string
		193	is encoded. You can have Unicode strings with that flag set, with that
		194	flag clear, and you can have binary data with that flag set and that flag
		195	clear. Other possibilities exist, too.
		196
		197	If you didn't know about that flag, just the better, pretend it doesn't
		198	exist.
		199
		200	=item 4. A "Unicode String" is simply a string where each character can be
		201	validly interpreted as a Unicode code point.
		202
		203	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		204	Unicode string encoded in UTF-8, giving you a binary string.
		205
		206	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		207
		208	It's a fact. Learn to live with it.
		209
		210	=back
		211
		212	I hope this helps :)
		213
131		214
132	=head1 OBJECT-ORIENTED INTERFACE	215	=head1 OBJECT-ORIENTED INTERFACE
133		216
134	The object oriented interface lets you configure your own encoding or	217	The object oriented interface lets you configure your own encoding or
135	decoding style, within the limits of supported formats.	218	decoding style, within the limits of supported formats.
…		…
147	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	230	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
148	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
149		232
150	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
151		234
		235	=item $enabled = $json->get_ascii
		236
152	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
153	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
154	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
155	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
156	as per RFC4627.	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
		242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		243	or any other superset of ASCII.
157		244
158	If C<$enable> is false, then the C<encode> method will not escape Unicode	245	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	246	characters unless required by the JSON syntax or other flags. This results
160	and more compact format.	247	in a faster and more compact format.
		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
		252	The main use for this flag is to produce JSON texts that can be
		253	transmitted over a 7-bit channel, as the encoded JSON texts will not
		254	contain any 8 bit characters.
161		255
162	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
163	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
164		258
		259	=item $json = $json->latin1 ([$enable])
		260
		261	=item $enabled = $json->get_latin1
		262
		263	If C<$enable> is true (or missing), then the C<encode> method will encode
		264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		265	outside the code range C<0..255>. The resulting string can be treated as a
		266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		267	will not be affected in any way by this flag, as C<decode> by default
		268	expects Unicode, which is a strict superset of latin1.
		269
		270	If C<$enable> is false, then the C<encode> method will not escape Unicode
		271	characters unless required by the JSON syntax or other flags.
		272
		273	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		274	document.
		275
		276	The main use for this flag is efficiently encoding binary data as JSON
		277	text, as most octets will not be escaped, resulting in a smaller encoded
		278	size. The disadvantage is that the resulting JSON text is encoded
		279	in latin1 (and must correctly be treated as such when storing and
		280	transferring), a rare encoding for JSON. It is therefore most useful when
		281	you want to store data structures known to contain binary data efficiently
		282	in files or databases, not when talking to other JSON encoders/decoders.
		283
		284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		286
165	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
166		290
167	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
168	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
169	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
170	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
171	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
172	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
173	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
174		298
175	If C<$enable> is false, then the C<encode> method will return the JSON	299	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	300	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	301	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.	302	to be done yourself, e.g. using the Encode module.
		303
		304	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		305	document.
179		306
180	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
181		308
182	use Encode;	309	use Encode;
183	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
204	]	331	]
205	}	332	}
206		333
207	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
208		335
		336	=item $enabled = $json->get_indent
		337
209	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
210	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
211	into its own line, identing them properly.	340	into its own line, indenting them properly.
212		341
213	If C<$enable> is false, no newlines or indenting will be produced, and the	342	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>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
215		344
216	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
217		346
218	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
219		350
220	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
221	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
222		353
223	If C<$enable> is false, then the C<encode> method will not add any extra	354	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:	360	Example, space_before enabled, space_after and indent disabled:
230		361
231	{"key" :"value"}	362	{"key" :"value"}
232		363
233	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
234		367
235	If C<$enable> is true (or missing), then the C<encode> method will add an extra	368	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	369	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	370	and extra whitespace after the C<,> separating key-value pairs and array
238	members.	371	members.
…		…
244		377
245	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
246		379
247	{"key": "value"}	380	{"key": "value"}
248		381
		382	=item $json = $json->relaxed ([$enable])
		383
		384	=item $enabled = $json->get_relaxed
		385
		386	If C<$enable> is true (or missing), then C<decode> will accept some
		387	extensions to normal JSON syntax (see below). C<encode> will not be
		388	affected in anyway. I<Be aware that this option makes you accept invalid
		389	JSON texts as if they were valid!>. I suggest only to use this option to
		390	parse application-specific files written by humans (configuration files,
		391	resource files etc.)
		392
		393	If C<$enable> is false (the default), then C<decode> will only accept
		394	valid JSON texts.
		395
		396	Currently accepted extensions are:
		397
		398	=over 4
		399
		400	=item * list items can have an end-comma
		401
		402	JSON I<separates> array elements and key-value pairs with commas. This
		403	can be annoying if you write JSON texts manually and want to be able to
		404	quickly append elements, so this extension accepts comma at the end of
		405	such items not just between them:
		406
		407	[
		408	1,
		409	2, <- this comma not normally allowed
		410	]
		411	{
		412	"k1": "v1",
		413	"k2": "v2", <- this comma not normally allowed
		414	}
		415
		416	=item * shell-style '#'-comments
		417
		418	Whenever JSON allows whitespace, shell-style comments are additionally
		419	allowed. They are terminated by the first carriage-return or line-feed
		420	character, after which more white-space and comments are allowed.
		421
		422	[
		423	1, # this comment not allowed in JSON
		424	# neither this one...
		425	]
		426
		427	=back
		428
249	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
		430
		431	=item $enabled = $json->get_canonical
250		432
251	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
252	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
253		435
254	If C<$enable> is false, then the C<encode> method will output key-value	436	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	437	pairs in the order Perl stores them (which will likely change between runs
256	of the same script).	438	of the same script).
257		439
258	This option is useful if you want the same data structure to be encoded as	440	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,	441	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,	442	the same hash might be encoded differently even if contains the same data,
261	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
262		444
263	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
264		446
265	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
266		450
267	If C<$enable> is true (or missing), then the C<encode> method can convert a	451	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,	452	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	453	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
270	values instead of croaking.	454	values instead of croaking.
…		…
278	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
279		463
280	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
281	=> "Hello, World!"	465	=> "Hello, World!"
282		466
		467	=item $json = $json->allow_unknown ([$enable])
		468
		469	=item $enabled = $json->get_allow_unknown
		470
		471	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		472	exception when it encounters values it cannot represent in JSON (for
		473	example, filehandles) but instead will encode a JSON C<null> value. Note
		474	that blessed objects are not included here and are handled separately by
		475	c<allow_nonref>.
		476
		477	If C<$enable> is false (the default), then C<encode> will throw an
		478	exception when it encounters anything it cannot encode as JSON.
		479
		480	This option does not affect C<decode> in any way, and it is recommended to
		481	leave it off unless you know your communications partner.
		482
		483	=item $json = $json->allow_blessed ([$enable])
		484
		485	=item $enabled = $json->get_allow_blessed
		486
		487	If C<$enable> is true (or missing), then the C<encode> method will not
		488	barf when it encounters a blessed reference. Instead, the value of the
		489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		490	disabled or no C<TO_JSON> method found) or a representation of the
		491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		492	encoded. Has no effect on C<decode>.
		493
		494	If C<$enable> is false (the default), then C<encode> will throw an
		495	exception when it encounters a blessed object.
		496
		497	=item $json = $json->convert_blessed ([$enable])
		498
		499	=item $enabled = $json->get_convert_blessed
		500
		501	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		502	blessed object, will check for the availability of the C<TO_JSON> method
		503	on the object's class. If found, it will be called in scalar context
		504	and the resulting scalar will be encoded instead of the object. If no
		505	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		506	to do.
		507
		508	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		509	returns other blessed objects, those will be handled in the same
		510	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		511	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		512	methods called by the Perl core (== not by the user of the object) are
		513	usually in upper case letters and to avoid collisions with any C<to_json>
		514	function or method.
		515
		516	This setting does not yet influence C<decode> in any way, but in the
		517	future, global hooks might get installed that influence C<decode> and are
		518	enabled by this setting.
		519
		520	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		521	to do when a blessed object is found.
		522
		523	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		524
		525	When C<$coderef> is specified, it will be called from C<decode> each
		526	time it decodes a JSON object. The only argument is a reference to the
		527	newly-created hash. If the code references returns a single scalar (which
		528	need not be a reference), this value (i.e. a copy of that scalar to avoid
		529	aliasing) is inserted into the deserialised data structure. If it returns
		530	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		531	original deserialised hash will be inserted. This setting can slow down
		532	decoding considerably.
		533
		534	When C<$coderef> is omitted or undefined, any existing callback will
		535	be removed and C<decode> will not change the deserialised hash in any
		536	way.
		537
		538	Example, convert all JSON objects into the integer 5:
		539
		540	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		541	# returns [5]
		542	$js->decode ('[{}]')
		543	# throw an exception because allow_nonref is not enabled
		544	# so a lone 5 is not allowed.
		545	$js->decode ('{"a":1, "b":2}');
		546
		547	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		548
		549	Works remotely similar to C<filter_json_object>, but is only called for
		550	JSON objects having a single key named C<$key>.
		551
		552	This C<$coderef> is called before the one specified via
		553	C<filter_json_object>, if any. It gets passed the single value in the JSON
		554	object. If it returns a single value, it will be inserted into the data
		555	structure. If it returns nothing (not even C<undef> but the empty list),
		556	the callback from C<filter_json_object> will be called next, as if no
		557	single-key callback were specified.
		558
		559	If C<$coderef> is omitted or undefined, the corresponding callback will be
		560	disabled. There can only ever be one callback for a given key.
		561
		562	As this callback gets called less often then the C<filter_json_object>
		563	one, decoding speed will not usually suffer as much. Therefore, single-key
		564	objects make excellent targets to serialise Perl objects into, especially
		565	as single-key JSON objects are as close to the type-tagged value concept
		566	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		567	support this in any way, so you need to make sure your data never looks
		568	like a serialised Perl hash.
		569
		570	Typical names for the single object key are C<__class_whatever__>, or
		571	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		572	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		573	with real hashes.
		574
		575	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		576	into the corresponding C<< $WIDGET{<id>} >> object:
		577
		578	# return whatever is in $WIDGET{5}:
		579	JSON::XS
		580	->new
		581	->filter_json_single_key_object (__widget__ => sub {
		582	$WIDGET{ $_[0] }
		583	})
		584	->decode ('{"__widget__": 5')
		585
		586	# this can be used with a TO_JSON method in some "widget" class
		587	# for serialisation to json:
		588	sub WidgetBase::TO_JSON {
		589	my ($self) = @_;
		590
		591	unless ($self->{id}) {
		592	$self->{id} = ..get..some..id..;
		593	$WIDGET{$self->{id}} = $self;
		594	}
		595
		596	{ __widget__ => $self->{id} }
		597	}
		598
283	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
284		600
		601	=item $enabled = $json->get_shrink
		602
285	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
286	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
287	C<encode> or C<decode> to their minimum size possible. This can save	605	C<encode> or C<decode> to their minimum size possible. This can save
288	memory when your JSON texts are either very very long or you have many	606	memory when your JSON texts are either very very long or you have many
289	short strings. It will also try to downgrade any strings to octet-form	607	short strings. It will also try to downgrade any strings to octet-form
290	if possible: perl stores strings internally either in an encoding called	608	if possible: perl stores strings internally either in an encoding called
291	UTF-X or in octet-form. The latter cannot store everything but uses less	609	UTF-X or in octet-form. The latter cannot store everything but uses less
292	space in general.	610	space in general (and some buggy Perl or C code might even rely on that
		611	internal representation being used).
293		612
		613	The actual definition of what shrink does might change in future versions,
		614	but it will always try to save space at the expense of time.
		615
294	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	616	If C<$enable> is true (or missing), the string returned by C<encode> will
295	while all strings generated by C<decode> will also be shrunk-to-fit.	617	be shrunk-to-fit, while all strings generated by C<decode> will also be
		618	shrunk-to-fit.
296		619
297	If C<$enable> is false, then the normal perl allocation algorithms are used.	620	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.	621	If you work with your data, then this is likely to be faster.
299		622
300	In the future, this setting might control other things, such as converting	623	In the future, this setting might control other things, such as converting
301	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
302	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
		626
		627	=item $json = $json->max_depth ([$maximum_nesting_depth])
		628
		629	=item $max_depth = $json->get_max_depth
		630
		631	Sets the maximum nesting level (default C<512>) accepted while encoding
		632	or decoding. If a higher nesting level is detected in JSON text or a Perl
		633	data structure, then the encoder and decoder will stop and croak at that
		634	point.
		635
		636	Nesting level is defined by number of hash- or arrayrefs that the encoder
		637	needs to traverse to reach a given point or the number of C<{> or C<[>
		638	characters without their matching closing parenthesis crossed to reach a
		639	given character in a string.
		640
		641	Setting the maximum depth to one disallows any nesting, so that ensures
		642	that the object is only a single hash/object or array.
		643
		644	If no argument is given, the highest possible setting will be used, which
		645	is rarely useful.
		646
		647	Note that nesting is implemented by recursion in C. The default value has
		648	been chosen to be as large as typical operating systems allow without
		649	crashing.
		650
		651	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		652
		653	=item $json = $json->max_size ([$maximum_string_size])
		654
		655	=item $max_size = $json->get_max_size
		656
		657	Set the maximum length a JSON text may have (in bytes) where decoding is
		658	being attempted. The default is C<0>, meaning no limit. When C<decode>
		659	is called on a string that is longer then this many bytes, it will not
		660	attempt to decode the string but throw an exception. This setting has no
		661	effect on C<encode> (yet).
		662
		663	If no argument is given, the limit check will be deactivated (same as when
		664	C<0> is specified).
		665
		666	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
303		667
304	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
305		669
306	Converts the given Perl data structure (a simple scalar or a reference	670	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	671	to a hash or array) to its JSON representation. Simple scalars will be
…		…
317		681
318	JSON numbers and strings become simple Perl scalars. JSON arrays become	682	JSON numbers and strings become simple Perl scalars. JSON arrays become
319	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	683	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>.	684	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
321		685
		686	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		687
		688	This works like the C<decode> method, but instead of raising an exception
		689	when there is trailing garbage after the first JSON object, it will
		690	silently stop parsing there and return the number of characters consumed
		691	so far.
		692
		693	This is useful if your JSON texts are not delimited by an outer protocol
		694	(which is not the brightest thing to do in the first place) and you need
		695	to know where the JSON text ends.
		696
		697	JSON::XS->new->decode_prefix ("[1] the tail")
		698	=> ([], 3)
		699
322	=back	700	=back
		701
		702
		703	=head1 INCREMENTAL PARSING
		704
		705	In some cases, there is the need for incremental parsing of JSON
		706	texts. While this module always has to keep both JSON text and resulting
		707	Perl data structure in memory at one time, it does allow you to parse a
		708	JSON stream incrementally. It does so by accumulating text until it has
		709	a full JSON object, which it then can decode. This process is similar to
		710	using C<decode_prefix> to see if a full JSON object is available, but
		711	is much more efficient (and can be implemented with a minimum of method
		712	calls).
		713
		714	JSON::XS will only attempt to parse the JSON text once it is sure it
		715	has enough text to get a decisive result, using a very simple but
		716	truly incremental parser. This means that it sometimes won't stop as
		717	early as the full parser, for example, it doesn't detect parenthese
		718	mismatches. The only thing it guarantees is that it starts decoding as
		719	soon as a syntactically valid JSON text has been seen. This means you need
		720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		721	parsing in the presence if syntax errors.
		722
		723	The following methods implement this incremental parser.
		724
		725	=over 4
		726
		727	=item [void, scalar or list context] = $json->incr_parse ([$string])
		728
		729	This is the central parsing function. It can both append new text and
		730	extract objects from the stream accumulated so far (both of these
		731	functions are optional).
		732
		733	If C<$string> is given, then this string is appended to the already
		734	existing JSON fragment stored in the C<$json> object.
		735
		736	After that, if the function is called in void context, it will simply
		737	return without doing anything further. This can be used to add more text
		738	in as many chunks as you want.
		739
		740	If the method is called in scalar context, then it will try to extract
		741	exactly I<one> JSON object. If that is successful, it will return this
		742	object, otherwise it will return C<undef>. If there is a parse error,
		743	this method will croak just as C<decode> would do (one can then use
		744	C<incr_skip> to skip the errornous part). This is the most common way of
		745	using the method.
		746
		747	And finally, in list context, it will try to extract as many objects
		748	from the stream as it can find and return them, or the empty list
		749	otherwise. For this to work, there must be no separators between the JSON
		750	objects or arrays, instead they must be concatenated back-to-back. If
		751	an error occurs, an exception will be raised as in the scalar context
		752	case. Note that in this case, any previously-parsed JSON texts will be
		753	lost.
		754
		755	=item $lvalue_string = $json->incr_text
		756
		757	This method returns the currently stored JSON fragment as an lvalue, that
		758	is, you can manipulate it. This I<only> works when a preceding call to
		759	C<incr_parse> in I<scalar context> successfully returned an object. Under
		760	all other circumstances you must not call this function (I mean it.
		761	although in simple tests it might actually work, it I<will> fail under
		762	real world conditions). As a special exception, you can also call this
		763	method before having parsed anything.
		764
		765	This function is useful in two cases: a) finding the trailing text after a
		766	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		767	(such as commas).
		768
		769	=item $json->incr_skip
		770
		771	This will reset the state of the incremental parser and will remove
		772	the parsed text from the input buffer so far. This is useful after
		773	C<incr_parse> died, in which case the input buffer and incremental parser
		774	state is left unchanged, to skip the text parsed so far and to reset the
		775	parse state.
		776
		777	The difference to C<incr_reset> is that only text until the parse error
		778	occured is removed.
		779
		780	=item $json->incr_reset
		781
		782	This completely resets the incremental parser, that is, after this call,
		783	it will be as if the parser had never parsed anything.
		784
		785	This is useful if you want to repeatedly parse JSON objects and want to
		786	ignore any trailing data, which means you have to reset the parser after
		787	each successful decode.
		788
		789	=back
		790
		791	=head2 LIMITATIONS
		792
		793	All options that affect decoding are supported, except
		794	C<allow_nonref>. The reason for this is that it cannot be made to
		795	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		796	them back to back and still decode them perfectly. This does not hold true
		797	for JSON numbers, however.
		798
		799	For example, is the string C<1> a single JSON number, or is it simply the
		800	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		801	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		802	takes the conservative route and disallows this case.
		803
		804	=head2 EXAMPLES
		805
		806	Some examples will make all this clearer. First, a simple example that
		807	works similarly to C<decode_prefix>: We want to decode the JSON object at
		808	the start of a string and identify the portion after the JSON object:
		809
		810	my $text = "[1,2,3] hello";
		811
		812	my $json = new JSON::XS;
		813
		814	my $obj = $json->incr_parse ($text)
		815	or die "expected JSON object or array at beginning of string";
		816
		817	my $tail = $json->incr_text;
		818	# $tail now contains " hello"
		819
		820	Easy, isn't it?
		821
		822	Now for a more complicated example: Imagine a hypothetical protocol where
		823	you read some requests from a TCP stream, and each request is a JSON
		824	array, without any separation between them (in fact, it is often useful to
		825	use newlines as "separators", as these get interpreted as whitespace at
		826	the start of the JSON text, which makes it possible to test said protocol
		827	with C<telnet>...).
		828
		829	Here is how you'd do it (it is trivial to write this in an event-based
		830	manner):
		831
		832	my $json = new JSON::XS;
		833
		834	# read some data from the socket
		835	while (sysread $socket, my $buf, 4096) {
		836
		837	# split and decode as many requests as possible
		838	for my $request ($json->incr_parse ($buf)) {
		839	# act on the $request
		840	}
		841	}
		842
		843	Another complicated example: Assume you have a string with JSON objects
		844	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		845	[3]>). To parse them, we have to skip the commas between the JSON texts,
		846	and here is where the lvalue-ness of C<incr_text> comes in useful:
		847
		848	my $text = "[1],[2], [3]";
		849	my $json = new JSON::XS;
		850
		851	# void context, so no parsing done
		852	$json->incr_parse ($text);
		853
		854	# now extract as many objects as possible. note the
		855	# use of scalar context so incr_text can be called.
		856	while (my $obj = $json->incr_parse) {
		857	# do something with $obj
		858
		859	# now skip the optional comma
		860	$json->incr_text =~ s/^ \s* , //x;
		861	}
		862
		863	Now lets go for a very complex example: Assume that you have a gigantic
		864	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		865	but you cannot load it into memory fully (this has actually happened in
		866	the real world :).
		867
		868	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		869	can still help you: You implement a (very simple) array parser and let
		870	JSON decode the array elements, which are all full JSON objects on their
		871	own (this wouldn't work if the array elements could be JSON numbers, for
		872	example):
		873
		874	my $json = new JSON::XS;
		875
		876	# open the monster
		877	open my $fh, "<bigfile.json"
		878	or die "bigfile: $!";
		879
		880	# first parse the initial "["
		881	for (;;) {
		882	sysread $fh, my $buf, 65536
		883	or die "read error: $!";
		884	$json->incr_parse ($buf); # void context, so no parsing
		885
		886	# Exit the loop once we found and removed(!) the initial "[".
		887	# In essence, we are (ab-)using the $json object as a simple scalar
		888	# we append data to.
		889	last if $json->incr_text =~ s/^ \s* \[ //x;
		890	}
		891
		892	# now we have the skipped the initial "[", so continue
		893	# parsing all the elements.
		894	for (;;) {
		895	# in this loop we read data until we got a single JSON object
		896	for (;;) {
		897	if (my $obj = $json->incr_parse) {
		898	# do something with $obj
		899	last;
		900	}
		901
		902	# add more data
		903	sysread $fh, my $buf, 65536
		904	or die "read error: $!";
		905	$json->incr_parse ($buf); # void context, so no parsing
		906	}
		907
		908	# in this loop we read data until we either found and parsed the
		909	# separating "," between elements, or the final "]"
		910	for (;;) {
		911	# first skip whitespace
		912	$json->incr_text =~ s/^\s*//;
		913
		914	# if we find "]", we are done
		915	if ($json->incr_text =~ s/^\]//) {
		916	print "finished.\n";
		917	exit;
		918	}
		919
		920	# if we find ",", we can continue with the next element
		921	if ($json->incr_text =~ s/^,//) {
		922	last;
		923	}
		924
		925	# if we find anything else, we have a parse error!
		926	if (length $json->incr_text) {
		927	die "parse error near ", $json->incr_text;
		928	}
		929
		930	# else add more data
		931	sysread $fh, my $buf, 65536
		932	or die "read error: $!";
		933	$json->incr_parse ($buf); # void context, so no parsing
		934	}
		935
		936	This is a complex example, but most of the complexity comes from the fact
		937	that we are trying to be correct (bear with me if I am wrong, I never ran
		938	the above example :).
		939
		940
323		941
324	=head1 MAPPING	942	=head1 MAPPING
325		943
326	This section describes how JSON::XS maps Perl values to JSON values and	944	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	945	vice versa. These mappings are designed to "do the right thing" in most
328	circumstances automatically, preserving round-tripping characteristics	946	circumstances automatically, preserving round-tripping characteristics
329	(what you put in comes out as something equivalent).	947	(what you put in comes out as something equivalent).
330		948
331	For the more enlightened: note that in the following descriptions,	949	For the more enlightened: note that in the following descriptions,
332	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	950	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
333	refers to the abstract Perl language itself.	951	refers to the abstract Perl language itself.
334		952
		953
335	=head2 JSON -> PERL	954	=head2 JSON -> PERL
336		955
337	=over 4	956	=over 4
338		957
339	=item object	958	=item object
340		959
341	A JSON object becomes a reference to a hash in Perl. No ordering of object	960	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).	961	keys is preserved (JSON does not preserve object key ordering itself).
343		962
344	=item array	963	=item array
345		964
346	A JSON array becomes a reference to an array in Perl.	965	A JSON array becomes a reference to an array in Perl.
347		966
…		…
351	are represented by the same codepoints in the Perl string, so no manual	970	are represented by the same codepoints in the Perl string, so no manual
352	decoding is necessary.	971	decoding is necessary.
353		972
354	=item number	973	=item number
355		974
356	A JSON number becomes either an integer or numeric (floating point)	975	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	976	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	977	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	978	the conversion details, but an integer may take slightly less memory and
360	represent more values exactly than (floating point) numbers.	979	might represent more values exactly than floating point numbers.
		980
		981	If the number consists of digits only, JSON::XS will try to represent
		982	it as an integer value. If that fails, it will try to represent it as
		983	a numeric (floating point) value if that is possible without loss of
		984	precision. Otherwise it will preserve the number as a string value (in
		985	which case you lose roundtripping ability, as the JSON number will be
		986	re-encoded toa JSON string).
		987
		988	Numbers containing a fractional or exponential part will always be
		989	represented as numeric (floating point) values, possibly at a loss of
		990	precision (in which case you might lose perfect roundtripping ability, but
		991	the JSON number will still be re-encoded as a JSON number).
361		992
362	=item true, false	993	=item true, false
363		994
364	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	995	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
365	this process. Future versions might represent those values differently,	996	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	997	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
367	Perl.	998	the C<JSON::XS::is_bool> function.
368		999
369	=item null	1000	=item null
370		1001
371	A JSON null atom becomes C<undef> in Perl.	1002	A JSON null atom becomes C<undef> in Perl.
372		1003
373	=back	1004	=back
		1005
374		1006
375	=head2 PERL -> JSON	1007	=head2 PERL -> JSON
376		1008
377	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1009	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	1010	truly typeless language, so we can only guess which JSON type is meant by
…		…
381	=over 4	1013	=over 4
382		1014
383	=item hash references	1015	=item hash references
384		1016
385	Perl hash references become JSON objects. As there is no inherent ordering	1017	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	1018	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	1019	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	1020	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	1021	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	1022	the same datastructure will serialise to the same JSON text (given same
391	JSON::XS), but this incurs a runtime overhead.	1023	settings and version of JSON::XS), but this incurs a runtime overhead
		1024	and is only rarely useful, e.g. when you want to compare some JSON text
		1025	against another for equality.
392		1026
393	=item array references	1027	=item array references
394		1028
395	Perl array references become JSON arrays.	1029	Perl array references become JSON arrays.
396		1030
		1031	=item other references
		1032
		1033	Other unblessed references are generally not allowed and will cause an
		1034	exception to be thrown, except for references to the integers C<0> and
		1035	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		1036	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		1037
		1038	encode_json [\0, JSON::XS::true] # yields [false,true]
		1039
		1040	=item JSON::XS::true, JSON::XS::false
		1041
		1042	These special values become JSON true and JSON false values,
		1043	respectively. You can also use C<\1> and C<\0> directly if you want.
		1044
397	=item blessed objects	1045	=item blessed objects
398		1046
399	Blessed objects are not allowed. JSON::XS currently tries to encode their	1047	Blessed objects are not directly representable in JSON. See the
400	underlying representation (hash- or arrayref), but this behaviour might	1048	C<allow_blessed> and C<convert_blessed> methods on various options on
401	change in future versions.	1049	how to deal with this: basically, you can choose between throwing an
		1050	exception, encoding the reference as if it weren't blessed, or provide
		1051	your own serialiser method.
402		1052
403	=item simple scalars	1053	=item simple scalars
404		1054
405	Simple Perl scalars (any scalar that is not a reference) are the most	1055	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	1056	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	1057	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:	1058	before encoding as JSON strings, and anything else as number value:
409		1059
410	# dump as number	1060	# dump as number
411	to_json [2] # yields [2]	1061	encode_json [2] # yields [2]
412	to_json [-3.0e17] # yields [-3e+17]	1062	encode_json [-3.0e17] # yields [-3e+17]
413	my $value = 5; to_json [$value] # yields [5]	1063	my $value = 5; encode_json [$value] # yields [5]
414		1064
415	# used as string, so dump as string	1065	# used as string, so dump as string
416	print $value;	1066	print $value;
417	to_json [$value] # yields ["5"]	1067	encode_json [$value] # yields ["5"]
418		1068
419	# undef becomes null	1069	# undef becomes null
420	to_json [undef] # yields [null]	1070	encode_json [undef] # yields [null]
421		1071
422	You can force the type to be a string by stringifying it:	1072	You can force the type to be a JSON string by stringifying it:
423		1073
424	my $x = 3.1; # some variable containing a number	1074	my $x = 3.1; # some variable containing a number
425	"$x"; # stringified	1075	"$x"; # stringified
426	$x .= ""; # another, more awkward way to stringify	1076	$x .= ""; # another, more awkward way to stringify
427	print $x; # perl does it for you, too, quite often	1077	print $x; # perl does it for you, too, quite often
428		1078
429	You can force the type to be a number by numifying it:	1079	You can force the type to be a JSON number by numifying it:
430		1080
431	my $x = "3"; # some variable containing a string	1081	my $x = "3"; # some variable containing a string
432	$x += 0; # numify it, ensuring it will be dumped as a number	1082	$x += 0; # numify it, ensuring it will be dumped as a number
433	$x *= 1; # same thing, the choise is yours.	1083	$x *= 1; # same thing, the choice is yours.
434		1084
435	You can not currently output JSON booleans or force the type in other,	1085	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.	1086	if you need this capability (but don't forget to explain why it's needed
437		1087	:).
438	=item circular data structures
439
440	Those will be encoded until memory or stackspace runs out.
441		1088
442	=back	1089	=back
443		1090
444	=head1 COMPARISON
445		1091
446	As already mentioned, this module was created because none of the existing	1092	=head1 ENCODING/CODESET FLAG NOTES
447	JSON modules could be made to work correctly. First I will describe the	1093
448	problems (or pleasures) I encountered with various existing JSON modules,	1094	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	1095	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
450	from any of these problems or limitations.	1096	some confusion on what these do, so here is a short comparison:
		1097
		1098	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1099	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1100	control whether C<encode> escapes character values outside their respective
		1101	codeset range. Neither of these flags conflict with each other, although
		1102	some combinations make less sense than others.
		1103
		1104	Care has been taken to make all flags symmetrical with respect to
		1105	C<encode> and C<decode>, that is, texts encoded with any combination of
		1106	these flag values will be correctly decoded when the same flags are used
		1107	- in general, if you use different flag settings while encoding vs. when
		1108	decoding you likely have a bug somewhere.
		1109
		1110	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1111	simply an abstract set of character-codepoint pairs, while an encoding
		1112	takes those codepoint numbers and I<encodes> them, in our case into
		1113	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1114	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1115	the same time, which can be confusing.
451		1116
452	=over 4	1117	=over 4
453		1118
454	=item JSON 1.07	1119	=item C<utf8> flag disabled
455		1120
456	Slow (but very portable, as it is written in pure Perl).	1121	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1122	and expect Unicode strings, that is, characters with high ordinal Unicode
		1123	values (> 255) will be encoded as such characters, and likewise such
		1124	characters are decoded as-is, no canges to them will be done, except
		1125	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1126	respectively (to Perl, these are the same thing in strings unless you do
		1127	funny/weird/dumb stuff).
457		1128
458	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1129	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	1130	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).	1131	the encoding for you (for example, when printing to a terminal using a
		1132	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1133	to UTF-8 encode your data first and have Perl encode it another time).
461		1134
462	No roundtripping (strings get clobbered if they look like numbers, e.g.	1135	=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		1136
466	=item JSON::PC 0.01	1137	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1138	characters using the corresponding UTF-8 multi-byte sequence, and will
		1139	expect your input strings to be encoded as UTF-8, that is, no "character"
		1140	of the input string must have any value > 255, as UTF-8 does not allow
		1141	that.
467		1142
468	Very fast.	1143	The C<utf8> flag therefore switches between two modes: disabled means you
		1144	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1145	octet/binary string in Perl.
469		1146
470	Undocumented/buggy Unicode handling.	1147	=item C<latin1> or C<ascii> flags enabled
471		1148
472	No roundtripping.	1149	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1150	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1151	characters as specified by the C<utf8> flag.
473		1152
474	Has problems handling many Perl values (e.g. regex results and other magic	1153	If C<utf8> is disabled, then the result is also correctly encoded in those
475	values will make it croak).	1154	character sets (as both are proper subsets of Unicode, meaning that a
		1155	Unicode string with all character values < 256 is the same thing as a
		1156	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1157	the same thing as an ASCII string in Perl).
476		1158
477	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1159	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
478	which is not a valid JSON text.	1160	regardless of these flags, just some more characters will be escaped using
		1161	C<\uXXXX> then before.
479		1162
480	Unmaintained (maintainer unresponsive for many months, bugs are not	1163	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
481	getting fixed).	1164	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1165	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1166	a subset of Unicode), while ASCII is.
482		1167
483	=item JSON::Syck 0.21	1168	Surprisingly, C<decode> will ignore these flags and so treat all input
		1169	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1170	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1171	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
484		1172
485	Very buggy (often crashes).	1173	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1174	they only govern when the JSON output engine escapes a character or not.
486		1175
487	Very inflexible (no human-readable format supported, format pretty much	1176	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	1177	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		1178
492	Completely broken (and confusingly documented) Unicode handling (unicode	1179	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	1180	with values > 127, which means you can interpret the resulting string
494	I<different> values on en- and decoding to get symmetric behaviour).	1181	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
495		1182	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	1183	when your channel for JSON transfer is not 8-bit clean or the encoding
497	value was used in a numeric context or not).	1184	might be mangled in between (e.g. in mail), and works because ASCII is a
498		1185	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		1186
528	=back	1187	=back
		1188
		1189
		1190	=head2 JSON and ECMAscript
		1191
		1192	JSON syntax is based on how literals are represented in javascript (the
		1193	not-standardised predecessor of ECMAscript) which is presumably why it is
		1194	called "JavaScript Object Notation".
		1195
		1196	However, JSON is not a subset (and also not a superset of course) of
		1197	ECMAscript (the standard) or javascript (whatever browsers actually
		1198	implement).
		1199
		1200	If you want to use javascript's C<eval> function to "parse" JSON, you
		1201	might run into parse errors for valid JSON texts, or the resulting data
		1202	structure might not be queryable:
		1203
		1204	One of the problems is that U+2028 and U+2029 are valid characters inside
		1205	JSON strings, but are not allowed in ECMAscript string literals, so the
		1206	following Perl fragment will not output something that can be guaranteed
		1207	to be parsable by javascript's C<eval>:
		1208
		1209	use JSON::XS;
		1210
		1211	print encode_json [chr 0x2028];
		1212
		1213	The right fix for this is to use a proper JSON parser in your javascript
		1214	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1215	F<json2.js> parser).
		1216
		1217	If this is not an option, you can, as a stop-gap measure, simply encode to
		1218	ASCII-only JSON:
		1219
		1220	use JSON::XS;
		1221
		1222	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1223
		1224	Note that this will enlarge the resulting JSON text quite a bit if you
		1225	have many non-ASCII characters. You might be tempted to run some regexes
		1226	to only escape U+2028 and U+2029, e.g.:
		1227
		1228	# DO NOT USE THIS!
		1229	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1230	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1231	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1232	print $json;
		1233
		1234	Note that I<this is a bad idea>: the above only works for U+2028 and
		1235	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1236	javascript implementations, however, have issues with other characters as
		1237	well - using C<eval> naively simply I<will> cause problems.
		1238
		1239	Another problem is that some javascript implementations reserve
		1240	some property names for their own purposes (which probably makes
		1241	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1242	C<__proto__> property name for it's own purposes.
		1243
		1244	If that is a problem, you could parse try to filter the resulting JSON
		1245	output for these property strings, e.g.:
		1246
		1247	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1248
		1249	This works because C<__proto__> is not valid outside of strings, so every
		1250	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1251
		1252	If you know of other incompatibilities, please let me know.
		1253
		1254
		1255	=head2 JSON and YAML
		1256
		1257	You often hear that JSON is a subset of YAML. This is, however, a mass
		1258	hysteria(*) and very far from the truth (as of the time of this writing),
		1259	so let me state it clearly: I<in general, there is no way to configure
		1260	JSON::XS to output a data structure as valid YAML> that works in all
		1261	cases.
		1262
		1263	If you really must use JSON::XS to generate YAML, you should use this
		1264	algorithm (subject to change in future versions):
		1265
		1266	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1267	my $yaml = $to_yaml->encode ($ref) . "\n";
		1268
		1269	This will I<usually> generate JSON texts that also parse as valid
		1270	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1271	lengths that JSON doesn't have and also has different and incompatible
		1272	unicode handling, so you should make sure that your hash keys are
		1273	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1274	you do not have characters with codepoint values outside the Unicode BMP
		1275	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1276	strings (which JSON::XS does not I<currently> generate, but other JSON
		1277	generators might).
		1278
		1279	There might be other incompatibilities that I am not aware of (or the YAML
		1280	specification has been changed yet again - it does so quite often). In
		1281	general you should not try to generate YAML with a JSON generator or vice
		1282	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1283	high that you will run into severe interoperability problems when you
		1284	least expect it.
		1285
		1286	=over 4
		1287
		1288	=item (*)
		1289
		1290	I have been pressured multiple times by Brian Ingerson (one of the
		1291	authors of the YAML specification) to remove this paragraph, despite him
		1292	acknowledging that the actual incompatibilities exist. As I was personally
		1293	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1294	educate people about these issues, so others do not run into the same
		1295	problem again and again. After this, Brian called me a (quote)I<complete
		1296	and worthless idiot>(unquote).
		1297
		1298	In my opinion, instead of pressuring and insulting people who actually
		1299	clarify issues with YAML and the wrong statements of some of its
		1300	proponents, I would kindly suggest reading the JSON spec (which is not
		1301	that difficult or long) and finally make YAML compatible to it, and
		1302	educating users about the changes, instead of spreading lies about the
		1303	real compatibility for many I<years> and trying to silence people who
		1304	point out that it isn't true.
		1305
		1306	=back
		1307
529		1308
530	=head2 SPEED	1309	=head2 SPEED
531		1310
532	It seems that JSON::XS is surprisingly fast, as shown in the following	1311	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	1312	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	1313	in the JSON::XS distribution, to make it easy to compare on your own
535	system.	1314	system.
536		1315
537	First comes a comparison between various modules using a very short JSON	1316	First comes a comparison between various modules using
538	string:	1317	a very short single-line JSON string (also available at
		1318	L<http://dist.schmorp.de/misc/json/short.json>).
539		1319
540	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1320	{"method": "handleMessage", "params": ["user1",
		1321	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1322	true, false]}
541		1323
542	It shows the number of encodes/decodes per second (JSON::XS uses the	1324	It shows the number of encodes/decodes per second (JSON::XS uses
543	functional interface, while JSON::XS/2 uses the OO interface with	1325	the functional interface, while JSON::XS/2 uses the OO interface
544	pretty-printing and hashkey sorting enabled). Higher is better:	1326	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1327	shrink). Higher is better:
545		1328
546	module | encode | decode |	1329	module | encode | decode |
547	-----------|------------|------------|	1330	-----------|------------|------------|
548	JSON | 11488.516 | 7823.035 |	1331	JSON 1.x | 4990.842 | 4088.813 |
549	JSON::DWIW | 94708.054 | 129094.260 |	1332	JSON::DWIW | 51653.990 | 71575.154 |
550	JSON::PC | 63884.157 | 128528.212 |	1333	JSON::PC | 65948.176 | 74631.744 |
551	JSON::Syck | 34898.677 | 42096.911 |	1334	JSON::PP | 8931.652 | 3817.168 |
552	JSON::XS | 654027.064 | 396423.669 |	1335	JSON::Syck | 24877.248 | 27776.848 |
553	JSON::XS/2 | 371564.190 | 371725.613 |	1336	JSON::XS | 388361.481 | 227951.304 |
		1337	JSON::XS/2 | 227951.304 | 218453.333 |
		1338	JSON::XS/3 | 338250.323 | 218453.333 |
		1339	Storable | 16500.016 | 135300.129 |
554	-----------+------------+------------+	1340	-----------+------------+------------+
555		1341
556	That is, JSON::XS is more than six times faster than JSON::DWIW on	1342	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	1343	about three times faster on decoding, and over forty times faster
558	faster than JSON, even with pretty-printing and key sorting.	1344	than JSON, even with pretty-printing and key sorting. It also compares
		1345	favourably to Storable for small amounts of data.
559		1346
560	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1347	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
561	search API (http://nanoref.com/yahooapis/mgPdGg):	1348	search API (L<http://dist.schmorp.de/misc/json/long.json>).
562		1349
563	module | encode | decode |	1350	module | encode | decode |
564	-----------|------------|------------|	1351	-----------|------------|------------|
565	JSON | 273.023 | 44.674 |	1352	JSON 1.x | 55.260 | 34.971 |
566	JSON::DWIW | 1089.383 | 1145.704 |	1353	JSON::DWIW | 825.228 | 1082.513 |
567	JSON::PC | 3097.419 | 2393.921 |	1354	JSON::PC | 3571.444 | 2394.829 |
568	JSON::Syck | 514.060 | 843.053 |	1355	JSON::PP | 210.987 | 32.574 |
569	JSON::XS | 6479.668 | 3636.364 |	1356	JSON::Syck | 552.551 | 787.544 |
570	JSON::XS/2 | 3774.221 | 3599.124 |	1357	JSON::XS | 5780.463 | 4854.519 |
		1358	JSON::XS/2 | 3869.998 | 4798.975 |
		1359	JSON::XS/3 | 5862.880 | 4798.975 |
		1360	Storable | 4445.002 | 5235.027 |
571	-----------+------------+------------+	1361	-----------+------------+------------+
572		1362
573	Again, JSON::XS leads by far.	1363	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1364	decodes faster).
574		1365
575	On large strings containing lots of high unicode characters, some modules	1366	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	1367	(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	1368	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	1369	to decode or encode properly, so it was impossible to prepare a fair
579	comparison table for that case.	1370	comparison table for that case.
580		1371
581	=head1 RESOURCE LIMITS
582		1372
583	JSON::XS does not impose any limits on the size of JSON texts or Perl	1373	=head1 SECURITY CONSIDERATIONS
584	values they represent - if your machine can handle it, JSON::XS will	1374
585	encode or decode it. Future versions might optionally impose structure	1375	When you are using JSON in a protocol, talking to untrusted potentially
586	depth and memory use resource limits.	1376	hostile creatures requires relatively few measures.
		1377
		1378	First of all, your JSON decoder should be secure, that is, should not have
		1379	any buffer overflows. Obviously, this module should ensure that and I am
		1380	trying hard on making that true, but you never know.
		1381
		1382	Second, you need to avoid resource-starving attacks. That means you should
		1383	limit the size of JSON texts you accept, or make sure then when your
		1384	resources run out, that's just fine (e.g. by using a separate process that
		1385	can crash safely). The size of a JSON text in octets or characters is
		1386	usually a good indication of the size of the resources required to decode
		1387	it into a Perl structure. While JSON::XS can check the size of the JSON
		1388	text, it might be too late when you already have it in memory, so you
		1389	might want to check the size before you accept the string.
		1390
		1391	Third, JSON::XS recurses using the C stack when decoding objects and
		1392	arrays. The C stack is a limited resource: for instance, on my amd64
		1393	machine with 8MB of stack size I can decode around 180k nested arrays but
		1394	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		1395	to free the temporary). If that is exceeded, the program crashes. To be
		1396	conservative, the default nesting limit is set to 512. If your process
		1397	has a smaller stack, you should adjust this setting accordingly with the
		1398	C<max_depth> method.
		1399
		1400	Something else could bomb you, too, that I forgot to think of. In that
		1401	case, you get to keep the pieces. I am always open for hints, though...
		1402
		1403	Also keep in mind that JSON::XS might leak contents of your Perl data
		1404	structures in its error messages, so when you serialise sensitive
		1405	information you might want to make sure that exceptions thrown by JSON::XS
		1406	will not end up in front of untrusted eyes.
		1407
		1408	If you are using JSON::XS to return packets to consumption
		1409	by JavaScript scripts in a browser you should have a look at
		1410	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1411	you are vulnerable to some common attack vectors (which really are browser
		1412	design bugs, but it is still you who will have to deal with it, as major
		1413	browser developers care only for features, not about getting security
		1414	right).
		1415
		1416
		1417	=head1 THREADS
		1418
		1419	This module is I<not> guaranteed to be thread safe and there are no
		1420	plans to change this until Perl gets thread support (as opposed to the
		1421	horribly slow so-called "threads" which are simply slow and bloated
		1422	process simulations - use fork, it's I<much> faster, cheaper, better).
		1423
		1424	(It might actually work, but you have been warned).
		1425
587		1426
588	=head1 BUGS	1427	=head1 BUGS
589		1428
590	While the goal of this module is to be correct, that unfortunately does	1429	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	1430	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	1431	keep reporting bugs they will be fixed swiftly, though.
593	be fixed swiftly, though.	1432
		1433	Please refrain from using rt.cpan.org or any other bug reporting
		1434	service. I put the contact address into my modules for a reason.
594		1435
595	=cut	1436	=cut
596		1437
		1438	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1439	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1440
		1441	sub true() { $true }
		1442	sub false() { $false }
		1443
		1444	sub is_bool($) {
		1445	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1446	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1447	}
		1448
		1449	XSLoader::load "JSON::XS", $VERSION;
		1450
		1451	package JSON::XS::Boolean;
		1452
		1453	use overload
		1454	"0+" => sub { ${$_[0]} },
		1455	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1456	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1457	fallback => 1;
		1458
597	1;	1459	1;
		1460
		1461	=head1 SEE ALSO
		1462
		1463	The F<json_xs> command line utility for quick experiments.
598		1464
599	=head1 AUTHOR	1465	=head1 AUTHOR
600		1466
601	Marc Lehmann <schmorp@schmorp.de>	1467	Marc Lehmann <schmorp@schmorp.de>
602	http://home.schmorp.de/	1468	http://home.schmorp.de/

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