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Revision 1.36 by root, Wed May 23 22:07:43 2007 UTC vs.
Revision 1.116 by root, Tue Feb 17 23:41:20 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		19
19	# OO-interface	20	# OO-interface
20		21
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
23	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
24		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
25	=head1 DESCRIPTION	34	=head1 DESCRIPTION
26		35
27	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
28	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
29	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overridden) with no overhead due to emulation (by inheriting constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
30		47
31	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
32	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
33	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
34	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
35	reports for other reasons.	52	reports for other reasons.
36		53
37	See COMPARISON, below, for a comparison to some other JSON modules.
38
39	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
40	vice versa.	55	vice versa.
41		56
42	=head2 FEATURES	57	=head2 FEATURES
43		58
44	=over 4	59	=over 4
45		60
46	=item * correct unicode handling	61	=item * correct Unicode handling
47		62
48	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
49	it does so.	64	so, and even documents what "correct" means.
50		65
51	=item * round-trip integrity	66	=item * round-trip integrity
52		67
53	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
54	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
55	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
56	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
57		73
58	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
59		75
60	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
61	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
62	feature).	78	feature).
63		79
64	=item * fast	80	=item * fast
65		81
66	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
67	of speed, too.	83	this module usually compares favourably in terms of speed, too.
68		84
69	=item * simple to use	85	=item * simple to use
70		86
71	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
72	interface.	88	oriented interface interface.
73		89
74	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
75		91
76	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
77	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
78	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
79	unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
80	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
81		97
82	=back	98	=back
83		99
84	=cut	100	=cut
85		101
86	package JSON::XS;	102	package JSON::XS;
87		103
		104	no warnings;
88	use strict;	105	use strict;
89		106
90	BEGIN {
91	our $VERSION = '1.22';	107	our $VERSION = '2.232';
92	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
93		109
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
95	require Exporter;
96		111
		112	sub to_json($) {
97	require XSLoader;	113	require Carp;
98	XSLoader::load JSON::XS::, $VERSION;	114	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
99	}	115	}
100		116
		117	sub from_json($) {
		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
101	=head1 FUNCTIONAL INTERFACE	125	=head1 FUNCTIONAL INTERFACE
102		126
103	The following convinience methods are provided by this module. They are	127	The following convenience methods are provided by this module. They are
104	exported by default:	128	exported by default:
105		129
106	=over 4	130	=over 4
107		131
108	=item $json_text = to_json $perl_scalar	132	=item $json_text = encode_json $perl_scalar
109		133
110	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
111	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.
112	octets only). Croaks on error.
113		136
114	This function call is functionally identical to:	137	This function call is functionally identical to:
115		138
116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
117		140
118	except being faster.	141	Except being faster.
119		142
120	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
121		144
122	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
123	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
124	scalar or reference. Croaks on error.	147	reference. Croaks on error.
125		148
126	This function call is functionally identical to:	149	This function call is functionally identical to:
127		150
128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129		152
130	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.
131		163
132	=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 :)
133		213
134		214
135	=head1 OBJECT-ORIENTED INTERFACE	215	=head1 OBJECT-ORIENTED INTERFACE
136		216
137	The object oriented interface lets you configure your own encoding or	217	The object oriented interface lets you configure your own encoding or
…		…
150	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]})
151	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
152		232
153	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
154		234
		235	=item $enabled = $json->get_ascii
		236
155	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
156	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
157	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159	as per RFC4627. The resulting encoded JSON text can be treated as a native	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
160	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
161	or any other superset of ASCII.	243	or any other superset of ASCII.
162		244
163	If C<$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
164	characters unless required by the JSON syntax or other flags. This results	246	characters unless required by the JSON syntax or other flags. This results
165	in a faster and more compact format.	247	in a faster and more compact format.
166		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
167	The main use for this flag is to produce JSON texts that can be	252	The main use for this flag is to produce JSON texts that can be
168	transmitted over a 7-bit channel, as the encoded JSON texts will not	253	transmitted over a 7-bit channel, as the encoded JSON texts will not
169	contain any 8 bit characters.	254	contain any 8 bit characters.
170		255
171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
172	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
173		258
174	=item $json = $json->latin1 ([$enable])	259	=item $json = $json->latin1 ([$enable])
175		260
		261	=item $enabled = $json->get_latin1
		262
176	If C<$enable> is true (or missing), then the C<encode> method will encode	263	If C<$enable> is true (or missing), then the C<encode> method will encode
177	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
178	outside the code range C<0..255>. The resulting string can be treated as a	265	outside the code range C<0..255>. The resulting string can be treated as a
179	latin1-encoded JSON text or a native unicode string. The C<decode> method	266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
180	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
181	expects unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
182		269
183	If C<$enable> is false, then the C<encode> method will not escape Unicode	270	If C<$enable> is false, then the C<encode> method will not escape Unicode
184	characters unless required by the JSON syntax or other flags.	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.
185		275
186	The main use for this flag is efficiently encoding binary data as JSON	276	The main use for this flag is efficiently encoding binary data as JSON
187	text, as most octets will not be escaped, resulting in a smaller encoded	277	text, as most octets will not be escaped, resulting in a smaller encoded
188	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
189	in latin1 (and must correctly be treated as such when storing and	279	in latin1 (and must correctly be treated as such when storing and
190	transfering), a rare encoding for JSON. It is therefore most useful when	280	transferring), a rare encoding for JSON. It is therefore most useful when
191	you want to store data structures known to contain binary data efficiently	281	you want to store data structures known to contain binary data efficiently
192	in files or databases, not when talking to other JSON encoders/decoders.	282	in files or databases, not when talking to other JSON encoders/decoders.
193		283
194	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
195	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
196		286
197	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
198		290
199	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
200	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
201	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
202	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
203	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
204	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
205	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
206		298
207	If C<$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
208	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
209	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
210	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.
211		306
212	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
213		308
214	use Encode;	309	use Encode;
215	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
236	]	331	]
237	}	332	}
238		333
239	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
240		335
		336	=item $enabled = $json->get_indent
		337
241	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
242	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
243	into its own line, identing them properly.	340	into its own line, indenting them properly.
244		341
245	If C<$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
246	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
247		344
248	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
249		346
250	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
251		350
252	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
253	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
254		353
255	If C<$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
…		…
261	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
262		361
263	{"key" :"value"}	362	{"key" :"value"}
264		363
265	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
266		367
267	If C<$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
268	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
269	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
270	members.	371	members.
…		…
276		377
277	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
278		379
279	{"key": "value"}	380	{"key": "value"}
280		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
281	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
		430
		431	=item $enabled = $json->get_canonical
282		432
283	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
285		435
286	If C<$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
287	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
288	of the same script).	438	of the same script).
289		439
290	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
291	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,
292	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,
293	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
294		444
295	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
296		446
297	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
298		450
299	If C<$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
300	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
301	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
302	values instead of croaking.	454	values instead of croaking.
…		…
310	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
311		463
312	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
313	=> "Hello, World!"	465	=> "Hello, World!"
314		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
315	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
316		602
317	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
318	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
319	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
320	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
…		…
338	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
339	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
340		626
341	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
342		628
		629	=item $max_depth = $json->get_max_depth
		630
343	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
344	or decoding. If the JSON text or Perl data structure has an equal or	632	or decoding. If a higher nesting level is detected in JSON text or a Perl
345	higher nesting level then this limit, then the encoder and decoder will	633	data structure, then the encoder and decoder will stop and croak at that
346	stop and croak at that point.	634	point.
347		635
348	Nesting level is defined by number of hash- or arrayrefs that the encoder	636	Nesting level is defined by number of hash- or arrayrefs that the encoder
349	needs to traverse to reach a given point or the number of C<{> or C<[>	637	needs to traverse to reach a given point or the number of C<{> or C<[>
350	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
351	given character in a string.	639	given character in a string.
352		640
353	Setting the maximum depth to one disallows any nesting, so that ensures	641	Setting the maximum depth to one disallows any nesting, so that ensures
354	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
355		643
356	The argument to C<max_depth> will be rounded up to the next nearest power	644	If no argument is given, the highest possible setting will be used, which
357	of two.	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).
358		665
359	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	666	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360		667
361	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
362		669
…		…
391	=> ([], 3)	698	=> ([], 3)
392		699
393	=back	700	=back
394		701
395		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
		941
396	=head1 MAPPING	942	=head1 MAPPING
397		943
398	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
399	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
400	circumstances automatically, preserving round-tripping characteristics	946	circumstances automatically, preserving round-tripping characteristics
401	(what you put in comes out as something equivalent).	947	(what you put in comes out as something equivalent).
402		948
403	For the more enlightened: note that in the following descriptions,	949	For the more enlightened: note that in the following descriptions,
404	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>
405	refers to the abstract Perl language itself.	951	refers to the abstract Perl language itself.
406		952
		953
407	=head2 JSON -> PERL	954	=head2 JSON -> PERL
408		955
409	=over 4	956	=over 4
410		957
411	=item object	958	=item object
412		959
413	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
414	keys is preserved (JSON does not preserver object key ordering itself).	961	keys is preserved (JSON does not preserve object key ordering itself).
415		962
416	=item array	963	=item array
417		964
418	A JSON array becomes a reference to an array in Perl.	965	A JSON array becomes a reference to an array in Perl.
419		966
…		…
423	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
424	decoding is necessary.	971	decoding is necessary.
425		972
426	=item number	973	=item number
427		974
428	A JSON number becomes either an integer or numeric (floating point)	975	A JSON number becomes either an integer, numeric (floating point) or
429	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
430	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
431	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
432	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).
433		992
434	=item true, false	993	=item true, false
435		994
436	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>,
437	this process. Future versions might represent those values differently,	996	respectively. They are overloaded to act almost exactly like the numbers
438	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
439	Perl.	998	the C<JSON::XS::is_bool> function.
440		999
441	=item null	1000	=item null
442		1001
443	A JSON null atom becomes C<undef> in Perl.	1002	A JSON null atom becomes C<undef> in Perl.
444		1003
445	=back	1004	=back
		1005
446		1006
447	=head2 PERL -> JSON	1007	=head2 PERL -> JSON
448		1008
449	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
450	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
…		…
473	Other unblessed references are generally not allowed and will cause an	1033	Other unblessed references are generally not allowed and will cause an
474	exception to be thrown, except for references to the integers C<0> and	1034	exception to be thrown, except for references to the integers C<0> and
475	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1035	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
476	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1036	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
477		1037
478	to_json [\0,JSON::XS::true] # yields [false,true]	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.
479		1044
480	=item blessed objects	1045	=item blessed objects
481		1046
482	Blessed objects are not allowed. JSON::XS currently tries to encode their	1047	Blessed objects are not directly representable in JSON. See the
483	underlying representation (hash- or arrayref), but this behaviour might	1048	C<allow_blessed> and C<convert_blessed> methods on various options on
484	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.
485		1052
486	=item simple scalars	1053	=item simple scalars
487		1054
488	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
489	difficult objects to encode: JSON::XS will encode undefined scalars as	1056	difficult objects to encode: JSON::XS will encode undefined scalars as
490	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
491	before encoding as JSON strings and anything else as number value:	1058	before encoding as JSON strings, and anything else as number value:
492		1059
493	# dump as number	1060	# dump as number
494	to_json [2] # yields [2]	1061	encode_json [2] # yields [2]
495	to_json [-3.0e17] # yields [-3e+17]	1062	encode_json [-3.0e17] # yields [-3e+17]
496	my $value = 5; to_json [$value] # yields [5]	1063	my $value = 5; encode_json [$value] # yields [5]
497		1064
498	# used as string, so dump as string	1065	# used as string, so dump as string
499	print $value;	1066	print $value;
500	to_json [$value] # yields ["5"]	1067	encode_json [$value] # yields ["5"]
501		1068
502	# undef becomes null	1069	# undef becomes null
503	to_json [undef] # yields [null]	1070	encode_json [undef] # yields [null]
504		1071
505	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:
506		1073
507	my $x = 3.1; # some variable containing a number	1074	my $x = 3.1; # some variable containing a number
508	"$x"; # stringified	1075	"$x"; # stringified
509	$x .= ""; # another, more awkward way to stringify	1076	$x .= ""; # another, more awkward way to stringify
510	print $x; # perl does it for you, too, quite often	1077	print $x; # perl does it for you, too, quite often
511		1078
512	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:
513		1080
514	my $x = "3"; # some variable containing a string	1081	my $x = "3"; # some variable containing a string
515	$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
516	$x *= 1; # same thing, the choise is yours.	1083	$x *= 1; # same thing, the choice is yours.
517		1084
518	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
519	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
		1087	:).
520		1088
521	=back	1089	=back
522		1090
523		1091
524	=head1 COMPARISON	1092	=head1 ENCODING/CODESET FLAG NOTES
525		1093
526	As already mentioned, this module was created because none of the existing	1094	The interested reader might have seen a number of flags that signify
527	JSON modules could be made to work correctly. First I will describe the	1095	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
528	problems (or pleasures) I encountered with various existing JSON modules,	1096	some confusion on what these do, so here is a short comparison:
529	followed by some benchmark values. JSON::XS was designed not to suffer	1097
530	from any of these problems or limitations.	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.
531		1116
532	=over 4	1117	=over 4
533		1118
534	=item JSON 1.07	1119	=item C<utf8> flag disabled
535		1120
536	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).
537		1128
538	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
539	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
540	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).
541		1134
542	No roundtripping (strings get clobbered if they look like numbers, e.g.	1135	=item C<utf8> flag enabled
543	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
544	decode into the number 2.
545		1136
546	=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.
547		1142
548	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.
549		1146
550	Undocumented/buggy Unicode handling.	1147	=item C<latin1> or C<ascii> flags enabled
551		1148
552	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.
553		1152
554	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
555	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).
556		1158
557	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,
558	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.
559		1162
560	Unmaintained (maintainer unresponsive for many months, bugs are not	1163	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
561	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.
562		1167
563	=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.
564		1172
565	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.
566		1175
567	Very inflexible (no human-readable format supported, format pretty much	1176	The main use for C<latin1> is to relatively efficiently store binary data
568	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.
569	single-line compact format for use in a protocol, and preferably a way to
570	generate ASCII-only JSON texts).
571		1178
572	Completely broken (and confusingly documented) Unicode handling (unicode	1179	The main use for C<ascii> is to force the output to not contain characters
573	escapes are not working properly, you need to set ImplicitUnicode to	1180	with values > 127, which means you can interpret the resulting string
574	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
575		1182	8-bit-encoding, and still get the same data structure back. This is useful
576	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
577	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
578		1185	proper subset of most 8-bit and multibyte encodings in use in the world.
579	Dumping hashes may skip hash values depending on iterator state.
580
581	Unmaintained (maintainer unresponsive for many months, bugs are not
582	getting fixed).
583
584	Does not check input for validity (i.e. will accept non-JSON input and
585	return "something" instead of raising an exception. This is a security
586	issue: imagine two banks transfering money between each other using
587	JSON. One bank might parse a given non-JSON request and deduct money,
588	while the other might reject the transaction with a syntax error. While a
589	good protocol will at least recover, that is extra unnecessary work and
590	the transaction will still not succeed).
591
592	=item JSON::DWIW 0.04
593
594	Very fast. Very natural. Very nice.
595
596	Undocumented unicode handling (but the best of the pack. Unicode escapes
597	still don't get parsed properly).
598
599	Very inflexible.
600
601	No roundtripping.
602
603	Does not generate valid JSON texts (key strings are often unquoted, empty keys
604	result in nothing being output)
605
606	Does not check input for validity.
607		1186
608	=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>.
		1215
		1216	If this is not an option, you can, as a stop-gap measure, simply encode to
		1217	ASCII-only JSON:
		1218
		1219	use JSON::XS;
		1220
		1221	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1222
		1223	And if you are concerned about the size of the resulting JSON text, you
		1224	can run some regexes to only escape U+2028 and U+2029:
		1225
		1226	use JSON::XS;
		1227
		1228	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1229	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1230	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1231	print $json;
		1232
		1233	This works because U+2028/U+2029 are not allowed outside of strings and
		1234	are not used for syntax, so replacing them unconditionally just works.
		1235
		1236	Note, however, that fixing the broken JSON parser is better than working
		1237	around it in every other generator. The above regexes should work well in
		1238	other languages, as long as they operate on UTF-8. It is equally valid to
		1239	replace all occurences of U+2028/2029 directly by their \\u-escaped forms
		1240	in unicode texts, so they can simply be used to fix any parsers relying on
		1241	C<eval> by first applying the regexes on the encoded texts.
		1242
		1243	Note also that the above only works for U+2028 and U+2029 and thus
		1244	only for fully ECMAscript-compliant parsers. Many existing javascript
		1245	implementations misparse other characters as well. Best rely on a good
		1246	JSON parser, such as Douglas Crockfords F<json2.js>, which escapes the
		1247	above and many more problematic characters properly before passing them
		1248	into C<eval>.
		1249
		1250	Another problem is that some javascript implementations reserve
		1251	some property names for their own purposes (which probably makes
		1252	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1253	C<__proto__> property name for it's own purposes.
		1254
		1255	If that is a problem, you could parse try to filter the resulting JSON
		1256	output for these property strings, e.g.:
		1257
		1258	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1259
		1260	This works because C<__proto__> is not valid outside of strings, so every
		1261	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1262
		1263	If you know of other incompatibilities, please let me know.
		1264
		1265
		1266	=head2 JSON and YAML
		1267
		1268	You often hear that JSON is a subset of YAML. This is, however, a mass
		1269	hysteria(*) and very far from the truth (as of the time of this writing),
		1270	so let me state it clearly: I<in general, there is no way to configure
		1271	JSON::XS to output a data structure as valid YAML> that works in all
		1272	cases.
		1273
		1274	If you really must use JSON::XS to generate YAML, you should use this
		1275	algorithm (subject to change in future versions):
		1276
		1277	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1278	my $yaml = $to_yaml->encode ($ref) . "\n";
		1279
		1280	This will I<usually> generate JSON texts that also parse as valid
		1281	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1282	lengths that JSON doesn't have and also has different and incompatible
		1283	unicode handling, so you should make sure that your hash keys are
		1284	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1285	you do not have characters with codepoint values outside the Unicode BMP
		1286	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1287	strings (which JSON::XS does not I<currently> generate, but other JSON
		1288	generators might).
		1289
		1290	There might be other incompatibilities that I am not aware of (or the YAML
		1291	specification has been changed yet again - it does so quite often). In
		1292	general you should not try to generate YAML with a JSON generator or vice
		1293	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1294	high that you will run into severe interoperability problems when you
		1295	least expect it.
		1296
		1297	=over 4
		1298
		1299	=item (*)
		1300
		1301	I have been pressured multiple times by Brian Ingerson (one of the
		1302	authors of the YAML specification) to remove this paragraph, despite him
		1303	acknowledging that the actual incompatibilities exist. As I was personally
		1304	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1305	educate people about these issues, so others do not run into the same
		1306	problem again and again. After this, Brian called me a (quote)I<complete
		1307	and worthless idiot>(unquote).
		1308
		1309	In my opinion, instead of pressuring and insulting people who actually
		1310	clarify issues with YAML and the wrong statements of some of its
		1311	proponents, I would kindly suggest reading the JSON spec (which is not
		1312	that difficult or long) and finally make YAML compatible to it, and
		1313	educating users about the changes, instead of spreading lies about the
		1314	real compatibility for many I<years> and trying to silence people who
		1315	point out that it isn't true.
		1316
		1317	=back
		1318
609		1319
610	=head2 SPEED	1320	=head2 SPEED
611		1321
612	It seems that JSON::XS is surprisingly fast, as shown in the following	1322	It seems that JSON::XS is surprisingly fast, as shown in the following
613	tables. They have been generated with the help of the C<eg/bench> program	1323	tables. They have been generated with the help of the C<eg/bench> program
614	in the JSON::XS distribution, to make it easy to compare on your own	1324	in the JSON::XS distribution, to make it easy to compare on your own
615	system.	1325	system.
616		1326
617	First comes a comparison between various modules using a very short JSON	1327	First comes a comparison between various modules using
618	string:	1328	a very short single-line JSON string (also available at
		1329	L<http://dist.schmorp.de/misc/json/short.json>).
619		1330
620	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1331	{"method": "handleMessage", "params": ["user1",
		1332	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1333	true, false]}
621		1334
622	It shows the number of encodes/decodes per second (JSON::XS uses the	1335	It shows the number of encodes/decodes per second (JSON::XS uses
623	functional interface, while JSON::XS/2 uses the OO interface with	1336	the functional interface, while JSON::XS/2 uses the OO interface
624	pretty-printing and hashkey sorting enabled). Higher is better:	1337	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1338	shrink). Higher is better:
625		1339
626	module | encode | decode |	1340	module | encode | decode |
627	-----------|------------|------------|	1341	-----------|------------|------------|
628	JSON | 11488.516 | 7823.035 |	1342	JSON 1.x | 4990.842 | 4088.813 |
629	JSON::DWIW | 94708.054 | 129094.260 |	1343	JSON::DWIW | 51653.990 | 71575.154 |
630	JSON::PC | 63884.157 | 128528.212 |	1344	JSON::PC | 65948.176 | 74631.744 |
631	JSON::Syck | 34898.677 | 42096.911 |	1345	JSON::PP | 8931.652 | 3817.168 |
632	JSON::XS | 654027.064 | 396423.669 |	1346	JSON::Syck | 24877.248 | 27776.848 |
633	JSON::XS/2 | 371564.190 | 371725.613 |	1347	JSON::XS | 388361.481 | 227951.304 |
		1348	JSON::XS/2 | 227951.304 | 218453.333 |
		1349	JSON::XS/3 | 338250.323 | 218453.333 |
		1350	Storable | 16500.016 | 135300.129 |
634	-----------+------------+------------+	1351	-----------+------------+------------+
635		1352
636	That is, JSON::XS is more than six times faster than JSON::DWIW on	1353	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
637	encoding, more than three times faster on decoding, and about thirty times	1354	about three times faster on decoding, and over forty times faster
638	faster than JSON, even with pretty-printing and key sorting.	1355	than JSON, even with pretty-printing and key sorting. It also compares
		1356	favourably to Storable for small amounts of data.
639		1357
640	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1358	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
641	search API (http://nanoref.com/yahooapis/mgPdGg):	1359	search API (L<http://dist.schmorp.de/misc/json/long.json>).
642		1360
643	module | encode | decode |	1361	module | encode | decode |
644	-----------|------------|------------|	1362	-----------|------------|------------|
645	JSON | 273.023 | 44.674 |	1363	JSON 1.x | 55.260 | 34.971 |
646	JSON::DWIW | 1089.383 | 1145.704 |	1364	JSON::DWIW | 825.228 | 1082.513 |
647	JSON::PC | 3097.419 | 2393.921 |	1365	JSON::PC | 3571.444 | 2394.829 |
648	JSON::Syck | 514.060 | 843.053 |	1366	JSON::PP | 210.987 | 32.574 |
649	JSON::XS | 6479.668 | 3636.364 |	1367	JSON::Syck | 552.551 | 787.544 |
650	JSON::XS/2 | 3774.221 | 3599.124 |	1368	JSON::XS | 5780.463 | 4854.519 |
		1369	JSON::XS/2 | 3869.998 | 4798.975 |
		1370	JSON::XS/3 | 5862.880 | 4798.975 |
		1371	Storable | 4445.002 | 5235.027 |
651	-----------+------------+------------+	1372	-----------+------------+------------+
652		1373
653	Again, JSON::XS leads by far.	1374	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1375	decodes faster).
654		1376
655	On large strings containing lots of high unicode characters, some modules	1377	On large strings containing lots of high Unicode characters, some modules
656	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1378	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
657	will be broken due to missing (or wrong) unicode handling. Others refuse	1379	will be broken due to missing (or wrong) Unicode handling. Others refuse
658	to decode or encode properly, so it was impossible to prepare a fair	1380	to decode or encode properly, so it was impossible to prepare a fair
659	comparison table for that case.	1381	comparison table for that case.
660		1382
661		1383
662	=head1 SECURITY CONSIDERATIONS	1384	=head1 SECURITY CONSIDERATIONS
…		…
668	any buffer overflows. Obviously, this module should ensure that and I am	1390	any buffer overflows. Obviously, this module should ensure that and I am
669	trying hard on making that true, but you never know.	1391	trying hard on making that true, but you never know.
670		1392
671	Second, you need to avoid resource-starving attacks. That means you should	1393	Second, you need to avoid resource-starving attacks. That means you should
672	limit the size of JSON texts you accept, or make sure then when your	1394	limit the size of JSON texts you accept, or make sure then when your
673	resources run out, thats just fine (e.g. by using a separate process that	1395	resources run out, that's just fine (e.g. by using a separate process that
674	can crash safely). The size of a JSON text in octets or characters is	1396	can crash safely). The size of a JSON text in octets or characters is
675	usually a good indication of the size of the resources required to decode	1397	usually a good indication of the size of the resources required to decode
676	it into a Perl structure.	1398	it into a Perl structure. While JSON::XS can check the size of the JSON
		1399	text, it might be too late when you already have it in memory, so you
		1400	might want to check the size before you accept the string.
677		1401
678	Third, JSON::XS recurses using the C stack when decoding objects and	1402	Third, JSON::XS recurses using the C stack when decoding objects and
679	arrays. The C stack is a limited resource: for instance, on my amd64	1403	arrays. The C stack is a limited resource: for instance, on my amd64
680	machine with 8MB of stack size I can decode around 180k nested arrays but	1404	machine with 8MB of stack size I can decode around 180k nested arrays but
681	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1405	only 14k nested JSON objects (due to perl itself recursing deeply on croak
682	to free the temporary). If that is exceeded, the program crashes. to be	1406	to free the temporary). If that is exceeded, the program crashes. To be
683	conservative, the default nesting limit is set to 512. If your process	1407	conservative, the default nesting limit is set to 512. If your process
684	has a smaller stack, you should adjust this setting accordingly with the	1408	has a smaller stack, you should adjust this setting accordingly with the
685	C<max_depth> method.	1409	C<max_depth> method.
686		1410
687	And last but least, something else could bomb you that I forgot to think	1411	Something else could bomb you, too, that I forgot to think of. In that
688	of. In that case, you get to keep the pieces. I am always open for hints,	1412	case, you get to keep the pieces. I am always open for hints, though...
689	though...	1413
		1414	Also keep in mind that JSON::XS might leak contents of your Perl data
		1415	structures in its error messages, so when you serialise sensitive
		1416	information you might want to make sure that exceptions thrown by JSON::XS
		1417	will not end up in front of untrusted eyes.
		1418
		1419	If you are using JSON::XS to return packets to consumption
		1420	by JavaScript scripts in a browser you should have a look at
		1421	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1422	you are vulnerable to some common attack vectors (which really are browser
		1423	design bugs, but it is still you who will have to deal with it, as major
		1424	browser developers care only for features, not about getting security
		1425	right).
		1426
		1427
		1428	=head1 THREADS
		1429
		1430	This module is I<not> guaranteed to be thread safe and there are no
		1431	plans to change this until Perl gets thread support (as opposed to the
		1432	horribly slow so-called "threads" which are simply slow and bloated
		1433	process simulations - use fork, it's I<much> faster, cheaper, better).
		1434
		1435	(It might actually work, but you have been warned).
690		1436
691		1437
692	=head1 BUGS	1438	=head1 BUGS
693		1439
694	While the goal of this module is to be correct, that unfortunately does	1440	While the goal of this module is to be correct, that unfortunately does
695	not mean its bug-free, only that I think its design is bug-free. It is	1441	not mean it's bug-free, only that I think its design is bug-free. If you
696	still relatively early in its development. If you keep reporting bugs they	1442	keep reporting bugs they will be fixed swiftly, though.
697	will be fixed swiftly, though.	1443
		1444	Please refrain from using rt.cpan.org or any other bug reporting
		1445	service. I put the contact address into my modules for a reason.
698		1446
699	=cut	1447	=cut
700		1448
		1449	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1450	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1451
701	sub true() { \1 }	1452	sub true() { $true }
702	sub false() { \0 }	1453	sub false() { $false }
		1454
		1455	sub is_bool($) {
		1456	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1457	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1458	}
		1459
		1460	XSLoader::load "JSON::XS", $VERSION;
		1461
		1462	package JSON::XS::Boolean;
		1463
		1464	use overload
		1465	"0+" => sub { ${$_[0]} },
		1466	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1467	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1468	fallback => 1;
703		1469
704	1;	1470	1;
		1471
		1472	=head1 SEE ALSO
		1473
		1474	The F<json_xs> command line utility for quick experiments.
705		1475
706	=head1 AUTHOR	1476	=head1 AUTHOR
707		1477
708	Marc Lehmann <schmorp@schmorp.de>	1478	Marc Lehmann <schmorp@schmorp.de>
709	http://home.schmorp.de/	1479	http://home.schmorp.de/

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