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Revision 1.37 by root, Wed Jun 6 14:52:49 2007 UTC vs.
Revision 1.130 by root, Thu Mar 11 17:36:09 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		19
19	# OO-interface	20	# OO-interface
20		21
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
23	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
24		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
25	=head1 DESCRIPTION	34	=head1 DESCRIPTION
26		35
27	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
28	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
29	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overridden) with no overhead due to emulation (by inheriting constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
30		47
31	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
32	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
33	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
34	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
35	reports for other reasons.	52	reports for other reasons.
36		53
37	See COMPARISON, below, for a comparison to some other JSON modules.
38
39	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
40	vice versa.	55	vice versa.
41		56
42	=head2 FEATURES	57	=head2 FEATURES
43		58
44	=over 4	59	=over 4
45		60
46	=item * correct unicode handling	61	=item * correct Unicode handling
47		62
48	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
49	it does so.	64	so, and even documents what "correct" means.
50		65
51	=item * round-trip integrity	66	=item * round-trip integrity
52		67
53	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
54	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
55	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
56	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
57		73
58	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
59		75
60	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
61	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
62	feature).	78	feature).
63		79
64	=item * fast	80	=item * fast
65		81
66	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
67	of speed, too.	83	this module usually compares favourably in terms of speed, too.
68		84
69	=item * simple to use	85	=item * simple to use
70		86
71	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
72	interface.	88	oriented interface interface.
73		89
74	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
75		91
76	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
77	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
78	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
79	unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
80	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
81		97
82	=back	98	=back
83		99
84	=cut	100	=cut
85		101
86	package JSON::XS;	102	package JSON::XS;
87		103
88	use strict;	104	use common::sense;
89		105
90	BEGIN {
91	our $VERSION = '1.22';	106	our $VERSION = '2.28';
92	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
93		108
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
95	require Exporter;
96		110
		111	sub to_json($) {
97	require XSLoader;	112	require Carp;
98	XSLoader::load JSON::XS::, $VERSION;	113	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
99	}	114	}
100		115
		116	sub from_json($) {
		117	require Carp;
		118	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		119	}
		120
		121	use Exporter;
		122	use XSLoader;
		123
101	=head1 FUNCTIONAL INTERFACE	124	=head1 FUNCTIONAL INTERFACE
102		125
103	The following convinience methods are provided by this module. They are	126	The following convenience methods are provided by this module. They are
104	exported by default:	127	exported by default:
105		128
106	=over 4	129	=over 4
107		130
108	=item $json_text = to_json $perl_scalar	131	=item $json_text = encode_json $perl_scalar
109		132
110	Converts the given Perl data structure (a simple scalar or a reference to	133	Converts the given Perl data structure to a UTF-8 encoded, binary string
111	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	134	(that is, the string contains octets only). Croaks on error.
112	octets only). Croaks on error.
113		135
114	This function call is functionally identical to:	136	This function call is functionally identical to:
115		137
116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
117		139
118	except being faster.	140	Except being faster.
119		141
120	=item $perl_scalar = from_json $json_text	142	=item $perl_scalar = decode_json $json_text
121		143
122	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	144	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
123	parse that as an UTF-8 encoded JSON text, returning the resulting simple	145	to parse that as an UTF-8 encoded JSON text, returning the resulting
124	scalar or reference. Croaks on error.	146	reference. Croaks on error.
125		147
126	This function call is functionally identical to:	148	This function call is functionally identical to:
127		149
128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129		151
130	except being faster.	152	Except being faster.
		153
		154	=item $is_boolean = JSON::XS::is_bool $scalar
		155
		156	Returns true if the passed scalar represents either JSON::XS::true or
		157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		158	and are used to represent JSON C<true> and C<false> values in Perl.
		159
		160	See MAPPING, below, for more information on how JSON values are mapped to
		161	Perl.
131		162
132	=back	163	=back
		164
		165
		166	=head1 A FEW NOTES ON UNICODE AND PERL
		167
		168	Since this often leads to confusion, here are a few very clear words on
		169	how Unicode works in Perl, modulo bugs.
		170
		171	=over 4
		172
		173	=item 1. Perl strings can store characters with ordinal values > 255.
		174
		175	This enables you to store Unicode characters as single characters in a
		176	Perl string - very natural.
		177
		178	=item 2. Perl does I<not> associate an encoding with your strings.
		179
		180	... until you force it to, e.g. when matching it against a regex, or
		181	printing the scalar to a file, in which case Perl either interprets your
		182	string as locale-encoded text, octets/binary, or as Unicode, depending
		183	on various settings. In no case is an encoding stored together with your
		184	data, it is I<use> that decides encoding, not any magical meta data.
		185
		186	=item 3. The internal utf-8 flag has no meaning with regards to the
		187	encoding of your string.
		188
		189	Just ignore that flag unless you debug a Perl bug, a module written in
		190	XS or want to dive into the internals of perl. Otherwise it will only
		191	confuse you, as, despite the name, it says nothing about how your string
		192	is encoded. You can have Unicode strings with that flag set, with that
		193	flag clear, and you can have binary data with that flag set and that flag
		194	clear. Other possibilities exist, too.
		195
		196	If you didn't know about that flag, just the better, pretend it doesn't
		197	exist.
		198
		199	=item 4. A "Unicode String" is simply a string where each character can be
		200	validly interpreted as a Unicode code point.
		201
		202	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		203	Unicode string encoded in UTF-8, giving you a binary string.
		204
		205	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		206
		207	It's a fact. Learn to live with it.
		208
		209	=back
		210
		211	I hope this helps :)
133		212
134		213
135	=head1 OBJECT-ORIENTED INTERFACE	214	=head1 OBJECT-ORIENTED INTERFACE
136		215
137	The object oriented interface lets you configure your own encoding or	216	The object oriented interface lets you configure your own encoding or
…		…
150	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	229	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
151	=> {"a": [1, 2]}	230	=> {"a": [1, 2]}
152		231
153	=item $json = $json->ascii ([$enable])	232	=item $json = $json->ascii ([$enable])
154		233
		234	=item $enabled = $json->get_ascii
		235
155	If C<$enable> is true (or missing), then the C<encode> method will not	236	If C<$enable> is true (or missing), then the C<encode> method will not
156	generate characters outside the code range C<0..127> (which is ASCII). Any	237	generate characters outside the code range C<0..127> (which is ASCII). Any
157	unicode characters outside that range will be escaped using either a	238	Unicode characters outside that range will be escaped using either a
158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	239	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159	as per RFC4627. The resulting encoded JSON text can be treated as a native	240	as per RFC4627. The resulting encoded JSON text can be treated as a native
160	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	241	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
161	or any other superset of ASCII.	242	or any other superset of ASCII.
162		243
163	If C<$enable> is false, then the C<encode> method will not escape Unicode	244	If C<$enable> is false, then the C<encode> method will not escape Unicode
164	characters unless required by the JSON syntax or other flags. This results	245	characters unless required by the JSON syntax or other flags. This results
165	in a faster and more compact format.	246	in a faster and more compact format.
166		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
167	The main use for this flag is to produce JSON texts that can be	251	The main use for this flag is to produce JSON texts that can be
168	transmitted over a 7-bit channel, as the encoded JSON texts will not	252	transmitted over a 7-bit channel, as the encoded JSON texts will not
169	contain any 8 bit characters.	253	contain any 8 bit characters.
170		254
171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
172	=> ["\ud801\udc01"]	256	=> ["\ud801\udc01"]
173		257
174	=item $json = $json->latin1 ([$enable])	258	=item $json = $json->latin1 ([$enable])
175		259
		260	=item $enabled = $json->get_latin1
		261
176	If C<$enable> is true (or missing), then the C<encode> method will encode	262	If C<$enable> is true (or missing), then the C<encode> method will encode
177	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	263	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
178	outside the code range C<0..255>. The resulting string can be treated as a	264	outside the code range C<0..255>. The resulting string can be treated as a
179	latin1-encoded JSON text or a native unicode string. The C<decode> method	265	latin1-encoded JSON text or a native Unicode string. The C<decode> method
180	will not be affected in any way by this flag, as C<decode> by default	266	will not be affected in any way by this flag, as C<decode> by default
181	expects unicode, which is a strict superset of latin1.	267	expects Unicode, which is a strict superset of latin1.
182		268
183	If C<$enable> is false, then the C<encode> method will not escape Unicode	269	If C<$enable> is false, then the C<encode> method will not escape Unicode
184	characters unless required by the JSON syntax or other flags.	270	characters unless required by the JSON syntax or other flags.
		271
		272	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		273	document.
185		274
186	The main use for this flag is efficiently encoding binary data as JSON	275	The main use for this flag is efficiently encoding binary data as JSON
187	text, as most octets will not be escaped, resulting in a smaller encoded	276	text, as most octets will not be escaped, resulting in a smaller encoded
188	size. The disadvantage is that the resulting JSON text is encoded	277	size. The disadvantage is that the resulting JSON text is encoded
189	in latin1 (and must correctly be treated as such when storing and	278	in latin1 (and must correctly be treated as such when storing and
190	transfering), a rare encoding for JSON. It is therefore most useful when	279	transferring), a rare encoding for JSON. It is therefore most useful when
191	you want to store data structures known to contain binary data efficiently	280	you want to store data structures known to contain binary data efficiently
192	in files or databases, not when talking to other JSON encoders/decoders.	281	in files or databases, not when talking to other JSON encoders/decoders.
193		282
194	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	283	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
195	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	284	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
196		285
197	=item $json = $json->utf8 ([$enable])	286	=item $json = $json->utf8 ([$enable])
		287
		288	=item $enabled = $json->get_utf8
198		289
199	If C<$enable> is true (or missing), then the C<encode> method will encode	290	If C<$enable> is true (or missing), then the C<encode> method will encode
200	the JSON result into UTF-8, as required by many protocols, while the	291	the JSON result into UTF-8, as required by many protocols, while the
201	C<decode> method expects to be handled an UTF-8-encoded string. Please	292	C<decode> method expects to be handled an UTF-8-encoded string. Please
202	note that UTF-8-encoded strings do not contain any characters outside the	293	note that UTF-8-encoded strings do not contain any characters outside the
203	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	294	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
204	versions, enabling this option might enable autodetection of the UTF-16	295	versions, enabling this option might enable autodetection of the UTF-16
205	and UTF-32 encoding families, as described in RFC4627.	296	and UTF-32 encoding families, as described in RFC4627.
206		297
207	If C<$enable> is false, then the C<encode> method will return the JSON	298	If C<$enable> is false, then the C<encode> method will return the JSON
208	string as a (non-encoded) unicode string, while C<decode> expects thus a	299	string as a (non-encoded) Unicode string, while C<decode> expects thus a
209	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	300	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
210	to be done yourself, e.g. using the Encode module.	301	to be done yourself, e.g. using the Encode module.
		302
		303	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		304	document.
211		305
212	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
213		307
214	use Encode;	308	use Encode;
215	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
236	]	330	]
237	}	331	}
238		332
239	=item $json = $json->indent ([$enable])	333	=item $json = $json->indent ([$enable])
240		334
		335	=item $enabled = $json->get_indent
		336
241	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	337	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
242	format as output, putting every array member or object/hash key-value pair	338	format as output, putting every array member or object/hash key-value pair
243	into its own line, identing them properly.	339	into its own line, indenting them properly.
244		340
245	If C<$enable> is false, no newlines or indenting will be produced, and the	341	If C<$enable> is false, no newlines or indenting will be produced, and the
246	resulting JSON text is guarenteed not to contain any C<newlines>.	342	resulting JSON text is guaranteed not to contain any C<newlines>.
247		343
248	This setting has no effect when decoding JSON texts.	344	This setting has no effect when decoding JSON texts.
249		345
250	=item $json = $json->space_before ([$enable])	346	=item $json = $json->space_before ([$enable])
		347
		348	=item $enabled = $json->get_space_before
251		349
252	If C<$enable> is true (or missing), then the C<encode> method will add an extra	350	If C<$enable> is true (or missing), then the C<encode> method will add an extra
253	optional space before the C<:> separating keys from values in JSON objects.	351	optional space before the C<:> separating keys from values in JSON objects.
254		352
255	If C<$enable> is false, then the C<encode> method will not add any extra	353	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
261	Example, space_before enabled, space_after and indent disabled:	359	Example, space_before enabled, space_after and indent disabled:
262		360
263	{"key" :"value"}	361	{"key" :"value"}
264		362
265	=item $json = $json->space_after ([$enable])	363	=item $json = $json->space_after ([$enable])
		364
		365	=item $enabled = $json->get_space_after
266		366
267	If C<$enable> is true (or missing), then the C<encode> method will add an extra	367	If C<$enable> is true (or missing), then the C<encode> method will add an extra
268	optional space after the C<:> separating keys from values in JSON objects	368	optional space after the C<:> separating keys from values in JSON objects
269	and extra whitespace after the C<,> separating key-value pairs and array	369	and extra whitespace after the C<,> separating key-value pairs and array
270	members.	370	members.
…		…
276		376
277	Example, space_before and indent disabled, space_after enabled:	377	Example, space_before and indent disabled, space_after enabled:
278		378
279	{"key": "value"}	379	{"key": "value"}
280		380
		381	=item $json = $json->relaxed ([$enable])
		382
		383	=item $enabled = $json->get_relaxed
		384
		385	If C<$enable> is true (or missing), then C<decode> will accept some
		386	extensions to normal JSON syntax (see below). C<encode> will not be
		387	affected in anyway. I<Be aware that this option makes you accept invalid
		388	JSON texts as if they were valid!>. I suggest only to use this option to
		389	parse application-specific files written by humans (configuration files,
		390	resource files etc.)
		391
		392	If C<$enable> is false (the default), then C<decode> will only accept
		393	valid JSON texts.
		394
		395	Currently accepted extensions are:
		396
		397	=over 4
		398
		399	=item * list items can have an end-comma
		400
		401	JSON I<separates> array elements and key-value pairs with commas. This
		402	can be annoying if you write JSON texts manually and want to be able to
		403	quickly append elements, so this extension accepts comma at the end of
		404	such items not just between them:
		405
		406	[
		407	1,
		408	2, <- this comma not normally allowed
		409	]
		410	{
		411	"k1": "v1",
		412	"k2": "v2", <- this comma not normally allowed
		413	}
		414
		415	=item * shell-style '#'-comments
		416
		417	Whenever JSON allows whitespace, shell-style comments are additionally
		418	allowed. They are terminated by the first carriage-return or line-feed
		419	character, after which more white-space and comments are allowed.
		420
		421	[
		422	1, # this comment not allowed in JSON
		423	# neither this one...
		424	]
		425
		426	=back
		427
281	=item $json = $json->canonical ([$enable])	428	=item $json = $json->canonical ([$enable])
		429
		430	=item $enabled = $json->get_canonical
282		431
283	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	432	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284	by sorting their keys. This is adding a comparatively high overhead.	433	by sorting their keys. This is adding a comparatively high overhead.
285		434
286	If C<$enable> is false, then the C<encode> method will output key-value	435	If C<$enable> is false, then the C<encode> method will output key-value
287	pairs in the order Perl stores them (which will likely change between runs	436	pairs in the order Perl stores them (which will likely change between runs
288	of the same script).	437	of the same script).
289		438
290	This option is useful if you want the same data structure to be encoded as	439	This option is useful if you want the same data structure to be encoded as
291	the same JSON text (given the same overall settings). If it is disabled,	440	the same JSON text (given the same overall settings). If it is disabled,
292	the same hash migh be encoded differently even if contains the same data,	441	the same hash might be encoded differently even if contains the same data,
293	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
294		443
295	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
296		445
		446	This setting has currently no effect on tied hashes.
		447
297	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
298		451
299	If C<$enable> is true (or missing), then the C<encode> method can convert a	452	If C<$enable> is true (or missing), then the C<encode> method can convert a
300	non-reference into its corresponding string, number or null JSON value,	453	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	454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
302	values instead of croaking.	455	values instead of croaking.
…		…
310	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
311		464
312	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
313	=> "Hello, World!"	466	=> "Hello, World!"
314		467
		468	=item $json = $json->allow_unknown ([$enable])
		469
		470	=item $enabled = $json->get_allow_unknown
		471
		472	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		473	exception when it encounters values it cannot represent in JSON (for
		474	example, filehandles) but instead will encode a JSON C<null> value. Note
		475	that blessed objects are not included here and are handled separately by
		476	c<allow_nonref>.
		477
		478	If C<$enable> is false (the default), then C<encode> will throw an
		479	exception when it encounters anything it cannot encode as JSON.
		480
		481	This option does not affect C<decode> in any way, and it is recommended to
		482	leave it off unless you know your communications partner.
		483
		484	=item $json = $json->allow_blessed ([$enable])
		485
		486	=item $enabled = $json->get_allow_blessed
		487
		488	If C<$enable> is true (or missing), then the C<encode> method will not
		489	barf when it encounters a blessed reference. Instead, the value of the
		490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		491	disabled or no C<TO_JSON> method found) or a representation of the
		492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		493	encoded. Has no effect on C<decode>.
		494
		495	If C<$enable> is false (the default), then C<encode> will throw an
		496	exception when it encounters a blessed object.
		497
		498	=item $json = $json->convert_blessed ([$enable])
		499
		500	=item $enabled = $json->get_convert_blessed
		501
		502	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		503	blessed object, will check for the availability of the C<TO_JSON> method
		504	on the object's class. If found, it will be called in scalar context
		505	and the resulting scalar will be encoded instead of the object. If no
		506	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		507	to do.
		508
		509	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		510	returns other blessed objects, those will be handled in the same
		511	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		512	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		513	methods called by the Perl core (== not by the user of the object) are
		514	usually in upper case letters and to avoid collisions with any C<to_json>
		515	function or method.
		516
		517	This setting does not yet influence C<decode> in any way, but in the
		518	future, global hooks might get installed that influence C<decode> and are
		519	enabled by this setting.
		520
		521	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		522	to do when a blessed object is found.
		523
		524	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		525
		526	When C<$coderef> is specified, it will be called from C<decode> each
		527	time it decodes a JSON object. The only argument is a reference to the
		528	newly-created hash. If the code references returns a single scalar (which
		529	need not be a reference), this value (i.e. a copy of that scalar to avoid
		530	aliasing) is inserted into the deserialised data structure. If it returns
		531	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		532	original deserialised hash will be inserted. This setting can slow down
		533	decoding considerably.
		534
		535	When C<$coderef> is omitted or undefined, any existing callback will
		536	be removed and C<decode> will not change the deserialised hash in any
		537	way.
		538
		539	Example, convert all JSON objects into the integer 5:
		540
		541	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		542	# returns [5]
		543	$js->decode ('[{}]')
		544	# throw an exception because allow_nonref is not enabled
		545	# so a lone 5 is not allowed.
		546	$js->decode ('{"a":1, "b":2}');
		547
		548	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		549
		550	Works remotely similar to C<filter_json_object>, but is only called for
		551	JSON objects having a single key named C<$key>.
		552
		553	This C<$coderef> is called before the one specified via
		554	C<filter_json_object>, if any. It gets passed the single value in the JSON
		555	object. If it returns a single value, it will be inserted into the data
		556	structure. If it returns nothing (not even C<undef> but the empty list),
		557	the callback from C<filter_json_object> will be called next, as if no
		558	single-key callback were specified.
		559
		560	If C<$coderef> is omitted or undefined, the corresponding callback will be
		561	disabled. There can only ever be one callback for a given key.
		562
		563	As this callback gets called less often then the C<filter_json_object>
		564	one, decoding speed will not usually suffer as much. Therefore, single-key
		565	objects make excellent targets to serialise Perl objects into, especially
		566	as single-key JSON objects are as close to the type-tagged value concept
		567	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		568	support this in any way, so you need to make sure your data never looks
		569	like a serialised Perl hash.
		570
		571	Typical names for the single object key are C<__class_whatever__>, or
		572	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		573	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		574	with real hashes.
		575
		576	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		577	into the corresponding C<< $WIDGET{<id>} >> object:
		578
		579	# return whatever is in $WIDGET{5}:
		580	JSON::XS
		581	->new
		582	->filter_json_single_key_object (__widget__ => sub {
		583	$WIDGET{ $_[0] }
		584	})
		585	->decode ('{"__widget__": 5')
		586
		587	# this can be used with a TO_JSON method in some "widget" class
		588	# for serialisation to json:
		589	sub WidgetBase::TO_JSON {
		590	my ($self) = @_;
		591
		592	unless ($self->{id}) {
		593	$self->{id} = ..get..some..id..;
		594	$WIDGET{$self->{id}} = $self;
		595	}
		596
		597	{ __widget__ => $self->{id} }
		598	}
		599
315	=item $json = $json->shrink ([$enable])	600	=item $json = $json->shrink ([$enable])
		601
		602	=item $enabled = $json->get_shrink
316		603
317	Perl usually over-allocates memory a bit when allocating space for	604	Perl usually over-allocates memory a bit when allocating space for
318	strings. This flag optionally resizes strings generated by either	605	strings. This flag optionally resizes strings generated by either
319	C<encode> or C<decode> to their minimum size possible. This can save	606	C<encode> or C<decode> to their minimum size possible. This can save
320	memory when your JSON texts are either very very long or you have many	607	memory when your JSON texts are either very very long or you have many
…		…
338	strings that look like integers or floats into integers or floats	625	strings that look like integers or floats into integers or floats
339	internally (there is no difference on the Perl level), saving space.	626	internally (there is no difference on the Perl level), saving space.
340		627
341	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
342		629
		630	=item $max_depth = $json->get_max_depth
		631
343	Sets the maximum nesting level (default C<512>) accepted while encoding	632	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	633	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	634	data structure, then the encoder and decoder will stop and croak at that
346	stop and croak at that point.	635	point.
347		636
348	Nesting level is defined by number of hash- or arrayrefs that the encoder	637	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<[>	638	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	639	characters without their matching closing parenthesis crossed to reach a
351	given character in a string.	640	given character in a string.
352		641
353	Setting the maximum depth to one disallows any nesting, so that ensures	642	Setting the maximum depth to one disallows any nesting, so that ensures
354	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
355		644
356	The argument to C<max_depth> will be rounded up to the next nearest power	645	If no argument is given, the highest possible setting will be used, which
357	of two.	646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
		651
		652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		653
		654	=item $json = $json->max_size ([$maximum_string_size])
		655
		656	=item $max_size = $json->get_max_size
		657
		658	Set the maximum length a JSON text may have (in bytes) where decoding is
		659	being attempted. The default is C<0>, meaning no limit. When C<decode>
		660	is called on a string that is longer then this many bytes, it will not
		661	attempt to decode the string but throw an exception. This setting has no
		662	effect on C<encode> (yet).
		663
		664	If no argument is given, the limit check will be deactivated (same as when
		665	C<0> is specified).
358		666
359	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360		668
361	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
362		670
…		…
391	=> ([], 3)	699	=> ([], 3)
392		700
393	=back	701	=back
394		702
395		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	Example: Parse some JSON arrays/objects in a given string and return
		757	them.
		758
		759	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		760
		761	=item $lvalue_string = $json->incr_text
		762
		763	This method returns the currently stored JSON fragment as an lvalue, that
		764	is, you can manipulate it. This I<only> works when a preceding call to
		765	C<incr_parse> in I<scalar context> successfully returned an object. Under
		766	all other circumstances you must not call this function (I mean it.
		767	although in simple tests it might actually work, it I<will> fail under
		768	real world conditions). As a special exception, you can also call this
		769	method before having parsed anything.
		770
		771	This function is useful in two cases: a) finding the trailing text after a
		772	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		773	(such as commas).
		774
		775	=item $json->incr_skip
		776
		777	This will reset the state of the incremental parser and will remove
		778	the parsed text from the input buffer so far. This is useful after
		779	C<incr_parse> died, in which case the input buffer and incremental parser
		780	state is left unchanged, to skip the text parsed so far and to reset the
		781	parse state.
		782
		783	The difference to C<incr_reset> is that only text until the parse error
		784	occured is removed.
		785
		786	=item $json->incr_reset
		787
		788	This completely resets the incremental parser, that is, after this call,
		789	it will be as if the parser had never parsed anything.
		790
		791	This is useful if you want to repeatedly parse JSON objects and want to
		792	ignore any trailing data, which means you have to reset the parser after
		793	each successful decode.
		794
		795	=back
		796
		797	=head2 LIMITATIONS
		798
		799	All options that affect decoding are supported, except
		800	C<allow_nonref>. The reason for this is that it cannot be made to
		801	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		802	them back to back and still decode them perfectly. This does not hold true
		803	for JSON numbers, however.
		804
		805	For example, is the string C<1> a single JSON number, or is it simply the
		806	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		807	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		808	takes the conservative route and disallows this case.
		809
		810	=head2 EXAMPLES
		811
		812	Some examples will make all this clearer. First, a simple example that
		813	works similarly to C<decode_prefix>: We want to decode the JSON object at
		814	the start of a string and identify the portion after the JSON object:
		815
		816	my $text = "[1,2,3] hello";
		817
		818	my $json = new JSON::XS;
		819
		820	my $obj = $json->incr_parse ($text)
		821	or die "expected JSON object or array at beginning of string";
		822
		823	my $tail = $json->incr_text;
		824	# $tail now contains " hello"
		825
		826	Easy, isn't it?
		827
		828	Now for a more complicated example: Imagine a hypothetical protocol where
		829	you read some requests from a TCP stream, and each request is a JSON
		830	array, without any separation between them (in fact, it is often useful to
		831	use newlines as "separators", as these get interpreted as whitespace at
		832	the start of the JSON text, which makes it possible to test said protocol
		833	with C<telnet>...).
		834
		835	Here is how you'd do it (it is trivial to write this in an event-based
		836	manner):
		837
		838	my $json = new JSON::XS;
		839
		840	# read some data from the socket
		841	while (sysread $socket, my $buf, 4096) {
		842
		843	# split and decode as many requests as possible
		844	for my $request ($json->incr_parse ($buf)) {
		845	# act on the $request
		846	}
		847	}
		848
		849	Another complicated example: Assume you have a string with JSON objects
		850	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		851	[3]>). To parse them, we have to skip the commas between the JSON texts,
		852	and here is where the lvalue-ness of C<incr_text> comes in useful:
		853
		854	my $text = "[1],[2], [3]";
		855	my $json = new JSON::XS;
		856
		857	# void context, so no parsing done
		858	$json->incr_parse ($text);
		859
		860	# now extract as many objects as possible. note the
		861	# use of scalar context so incr_text can be called.
		862	while (my $obj = $json->incr_parse) {
		863	# do something with $obj
		864
		865	# now skip the optional comma
		866	$json->incr_text =~ s/^ \s* , //x;
		867	}
		868
		869	Now lets go for a very complex example: Assume that you have a gigantic
		870	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		871	but you cannot load it into memory fully (this has actually happened in
		872	the real world :).
		873
		874	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		875	can still help you: You implement a (very simple) array parser and let
		876	JSON decode the array elements, which are all full JSON objects on their
		877	own (this wouldn't work if the array elements could be JSON numbers, for
		878	example):
		879
		880	my $json = new JSON::XS;
		881
		882	# open the monster
		883	open my $fh, "<bigfile.json"
		884	or die "bigfile: $!";
		885
		886	# first parse the initial "["
		887	for (;;) {
		888	sysread $fh, my $buf, 65536
		889	or die "read error: $!";
		890	$json->incr_parse ($buf); # void context, so no parsing
		891
		892	# Exit the loop once we found and removed(!) the initial "[".
		893	# In essence, we are (ab-)using the $json object as a simple scalar
		894	# we append data to.
		895	last if $json->incr_text =~ s/^ \s* \[ //x;
		896	}
		897
		898	# now we have the skipped the initial "[", so continue
		899	# parsing all the elements.
		900	for (;;) {
		901	# in this loop we read data until we got a single JSON object
		902	for (;;) {
		903	if (my $obj = $json->incr_parse) {
		904	# do something with $obj
		905	last;
		906	}
		907
		908	# add more data
		909	sysread $fh, my $buf, 65536
		910	or die "read error: $!";
		911	$json->incr_parse ($buf); # void context, so no parsing
		912	}
		913
		914	# in this loop we read data until we either found and parsed the
		915	# separating "," between elements, or the final "]"
		916	for (;;) {
		917	# first skip whitespace
		918	$json->incr_text =~ s/^\s*//;
		919
		920	# if we find "]", we are done
		921	if ($json->incr_text =~ s/^\]//) {
		922	print "finished.\n";
		923	exit;
		924	}
		925
		926	# if we find ",", we can continue with the next element
		927	if ($json->incr_text =~ s/^,//) {
		928	last;
		929	}
		930
		931	# if we find anything else, we have a parse error!
		932	if (length $json->incr_text) {
		933	die "parse error near ", $json->incr_text;
		934	}
		935
		936	# else add more data
		937	sysread $fh, my $buf, 65536
		938	or die "read error: $!";
		939	$json->incr_parse ($buf); # void context, so no parsing
		940	}
		941
		942	This is a complex example, but most of the complexity comes from the fact
		943	that we are trying to be correct (bear with me if I am wrong, I never ran
		944	the above example :).
		945
		946
		947
396	=head1 MAPPING	948	=head1 MAPPING
397		949
398	This section describes how JSON::XS maps Perl values to JSON values and	950	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	951	vice versa. These mappings are designed to "do the right thing" in most
400	circumstances automatically, preserving round-tripping characteristics	952	circumstances automatically, preserving round-tripping characteristics
401	(what you put in comes out as something equivalent).	953	(what you put in comes out as something equivalent).
402		954
403	For the more enlightened: note that in the following descriptions,	955	For the more enlightened: note that in the following descriptions,
404	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	956	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
405	refers to the abstract Perl language itself.	957	refers to the abstract Perl language itself.
406		958
		959
407	=head2 JSON -> PERL	960	=head2 JSON -> PERL
408		961
409	=over 4	962	=over 4
410		963
411	=item object	964	=item object
412		965
413	A JSON object becomes a reference to a hash in Perl. No ordering of object	966	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).	967	keys is preserved (JSON does not preserve object key ordering itself).
415		968
416	=item array	969	=item array
417		970
418	A JSON array becomes a reference to an array in Perl.	971	A JSON array becomes a reference to an array in Perl.
419		972
…		…
423	are represented by the same codepoints in the Perl string, so no manual	976	are represented by the same codepoints in the Perl string, so no manual
424	decoding is necessary.	977	decoding is necessary.
425		978
426	=item number	979	=item number
427		980
428	A JSON number becomes either an integer or numeric (floating point)	981	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	982	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	983	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	984	the conversion details, but an integer may take slightly less memory and
432	represent more values exactly than (floating point) numbers.	985	might represent more values exactly than floating point numbers.
		986
		987	If the number consists of digits only, JSON::XS will try to represent
		988	it as an integer value. If that fails, it will try to represent it as
		989	a numeric (floating point) value if that is possible without loss of
		990	precision. Otherwise it will preserve the number as a string value (in
		991	which case you lose roundtripping ability, as the JSON number will be
		992	re-encoded toa JSON string).
		993
		994	Numbers containing a fractional or exponential part will always be
		995	represented as numeric (floating point) values, possibly at a loss of
		996	precision (in which case you might lose perfect roundtripping ability, but
		997	the JSON number will still be re-encoded as a JSON number).
433		998
434	=item true, false	999	=item true, false
435		1000
436	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	1001	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
437	this process. Future versions might represent those values differently,	1002	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	1003	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
439	Perl.	1004	the C<JSON::XS::is_bool> function.
440		1005
441	=item null	1006	=item null
442		1007
443	A JSON null atom becomes C<undef> in Perl.	1008	A JSON null atom becomes C<undef> in Perl.
444		1009
445	=back	1010	=back
		1011
446		1012
447	=head2 PERL -> JSON	1013	=head2 PERL -> JSON
448		1014
449	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1015	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	1016	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	1039	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	1040	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	1041	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.	1042	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
477		1043
478	to_json [\0,JSON::XS::true] # yields [false,true]	1044	encode_json [\0, JSON::XS::true] # yields [false,true]
		1045
		1046	=item JSON::XS::true, JSON::XS::false
		1047
		1048	These special values become JSON true and JSON false values,
		1049	respectively. You can also use C<\1> and C<\0> directly if you want.
479		1050
480	=item blessed objects	1051	=item blessed objects
481		1052
482	Blessed objects are not allowed. JSON::XS currently tries to encode their	1053	Blessed objects are not directly representable in JSON. See the
483	underlying representation (hash- or arrayref), but this behaviour might	1054	C<allow_blessed> and C<convert_blessed> methods on various options on
484	change in future versions.	1055	how to deal with this: basically, you can choose between throwing an
		1056	exception, encoding the reference as if it weren't blessed, or provide
		1057	your own serialiser method.
485		1058
486	=item simple scalars	1059	=item simple scalars
487		1060
488	Simple Perl scalars (any scalar that is not a reference) are the most	1061	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	1062	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	1063	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:	1064	before encoding as JSON strings, and anything else as number value:
492		1065
493	# dump as number	1066	# dump as number
494	to_json [2] # yields [2]	1067	encode_json [2] # yields [2]
495	to_json [-3.0e17] # yields [-3e+17]	1068	encode_json [-3.0e17] # yields [-3e+17]
496	my $value = 5; to_json [$value] # yields [5]	1069	my $value = 5; encode_json [$value] # yields [5]
497		1070
498	# used as string, so dump as string	1071	# used as string, so dump as string
499	print $value;	1072	print $value;
500	to_json [$value] # yields ["5"]	1073	encode_json [$value] # yields ["5"]
501		1074
502	# undef becomes null	1075	# undef becomes null
503	to_json [undef] # yields [null]	1076	encode_json [undef] # yields [null]
504		1077
505	You can force the type to be a string by stringifying it:	1078	You can force the type to be a JSON string by stringifying it:
506		1079
507	my $x = 3.1; # some variable containing a number	1080	my $x = 3.1; # some variable containing a number
508	"$x"; # stringified	1081	"$x"; # stringified
509	$x .= ""; # another, more awkward way to stringify	1082	$x .= ""; # another, more awkward way to stringify
510	print $x; # perl does it for you, too, quite often	1083	print $x; # perl does it for you, too, quite often
511		1084
512	You can force the type to be a number by numifying it:	1085	You can force the type to be a JSON number by numifying it:
513		1086
514	my $x = "3"; # some variable containing a string	1087	my $x = "3"; # some variable containing a string
515	$x += 0; # numify it, ensuring it will be dumped as a number	1088	$x += 0; # numify it, ensuring it will be dumped as a number
516	$x *= 1; # same thing, the choise is yours.	1089	$x *= 1; # same thing, the choice is yours.
517		1090
518	You can not currently output JSON booleans or force the type in other,	1091	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.	1092	if you need this capability (but don't forget to explain why it's needed
		1093	:).
520		1094
521	=back	1095	=back
522		1096
523		1097
524	=head1 COMPARISON	1098	=head1 ENCODING/CODESET FLAG NOTES
525		1099
526	As already mentioned, this module was created because none of the existing	1100	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	1101	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,	1102	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	1103
530	from any of these problems or limitations.	1104	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1105	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1106	control whether C<encode> escapes character values outside their respective
		1107	codeset range. Neither of these flags conflict with each other, although
		1108	some combinations make less sense than others.
		1109
		1110	Care has been taken to make all flags symmetrical with respect to
		1111	C<encode> and C<decode>, that is, texts encoded with any combination of
		1112	these flag values will be correctly decoded when the same flags are used
		1113	- in general, if you use different flag settings while encoding vs. when
		1114	decoding you likely have a bug somewhere.
		1115
		1116	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1117	simply an abstract set of character-codepoint pairs, while an encoding
		1118	takes those codepoint numbers and I<encodes> them, in our case into
		1119	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1120	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1121	the same time, which can be confusing.
531		1122
532	=over 4	1123	=over 4
533		1124
534	=item JSON 1.07	1125	=item C<utf8> flag disabled
535		1126
536	Slow (but very portable, as it is written in pure Perl).	1127	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1128	and expect Unicode strings, that is, characters with high ordinal Unicode
		1129	values (> 255) will be encoded as such characters, and likewise such
		1130	characters are decoded as-is, no canges to them will be done, except
		1131	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1132	respectively (to Perl, these are the same thing in strings unless you do
		1133	funny/weird/dumb stuff).
537		1134
538	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1135	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	1136	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).	1137	the encoding for you (for example, when printing to a terminal using a
		1138	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1139	to UTF-8 encode your data first and have Perl encode it another time).
541		1140
542	No roundtripping (strings get clobbered if they look like numbers, e.g.	1141	=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		1142
546	=item JSON::PC 0.01	1143	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1144	characters using the corresponding UTF-8 multi-byte sequence, and will
		1145	expect your input strings to be encoded as UTF-8, that is, no "character"
		1146	of the input string must have any value > 255, as UTF-8 does not allow
		1147	that.
547		1148
548	Very fast.	1149	The C<utf8> flag therefore switches between two modes: disabled means you
		1150	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1151	octet/binary string in Perl.
549		1152
550	Undocumented/buggy Unicode handling.	1153	=item C<latin1> or C<ascii> flags enabled
551		1154
552	No roundtripping.	1155	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1156	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1157	characters as specified by the C<utf8> flag.
553		1158
554	Has problems handling many Perl values (e.g. regex results and other magic	1159	If C<utf8> is disabled, then the result is also correctly encoded in those
555	values will make it croak).	1160	character sets (as both are proper subsets of Unicode, meaning that a
		1161	Unicode string with all character values < 256 is the same thing as a
		1162	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1163	the same thing as an ASCII string in Perl).
556		1164
557	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1165	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
558	which is not a valid JSON text.	1166	regardless of these flags, just some more characters will be escaped using
		1167	C<\uXXXX> then before.
559		1168
560	Unmaintained (maintainer unresponsive for many months, bugs are not	1169	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
561	getting fixed).	1170	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1171	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1172	a subset of Unicode), while ASCII is.
562		1173
563	=item JSON::Syck 0.21	1174	Surprisingly, C<decode> will ignore these flags and so treat all input
		1175	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1176	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1177	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
564		1178
565	Very buggy (often crashes).	1179	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1180	they only govern when the JSON output engine escapes a character or not.
566		1181
567	Very inflexible (no human-readable format supported, format pretty much	1182	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	1183	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		1184
572	Completely broken (and confusingly documented) Unicode handling (unicode	1185	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	1186	with values > 127, which means you can interpret the resulting string
574	I<different> values on en- and decoding to get symmetric behaviour).	1187	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
575		1188	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	1189	when your channel for JSON transfer is not 8-bit clean or the encoding
577	value was used in a numeric context or not).	1190	might be mangled in between (e.g. in mail), and works because ASCII is a
578		1191	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		1192
608	=back	1193	=back
		1194
		1195
		1196	=head2 JSON and ECMAscript
		1197
		1198	JSON syntax is based on how literals are represented in javascript (the
		1199	not-standardised predecessor of ECMAscript) which is presumably why it is
		1200	called "JavaScript Object Notation".
		1201
		1202	However, JSON is not a subset (and also not a superset of course) of
		1203	ECMAscript (the standard) or javascript (whatever browsers actually
		1204	implement).
		1205
		1206	If you want to use javascript's C<eval> function to "parse" JSON, you
		1207	might run into parse errors for valid JSON texts, or the resulting data
		1208	structure might not be queryable:
		1209
		1210	One of the problems is that U+2028 and U+2029 are valid characters inside
		1211	JSON strings, but are not allowed in ECMAscript string literals, so the
		1212	following Perl fragment will not output something that can be guaranteed
		1213	to be parsable by javascript's C<eval>:
		1214
		1215	use JSON::XS;
		1216
		1217	print encode_json [chr 0x2028];
		1218
		1219	The right fix for this is to use a proper JSON parser in your javascript
		1220	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1221	F<json2.js> parser).
		1222
		1223	If this is not an option, you can, as a stop-gap measure, simply encode to
		1224	ASCII-only JSON:
		1225
		1226	use JSON::XS;
		1227
		1228	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1229
		1230	Note that this will enlarge the resulting JSON text quite a bit if you
		1231	have many non-ASCII characters. You might be tempted to run some regexes
		1232	to only escape U+2028 and U+2029, e.g.:
		1233
		1234	# DO NOT USE THIS!
		1235	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1236	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1237	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1238	print $json;
		1239
		1240	Note that I<this is a bad idea>: the above only works for U+2028 and
		1241	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1242	javascript implementations, however, have issues with other characters as
		1243	well - using C<eval> naively simply I<will> cause problems.
		1244
		1245	Another problem is that some javascript implementations reserve
		1246	some property names for their own purposes (which probably makes
		1247	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1248	C<__proto__> property name for it's own purposes.
		1249
		1250	If that is a problem, you could parse try to filter the resulting JSON
		1251	output for these property strings, e.g.:
		1252
		1253	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1254
		1255	This works because C<__proto__> is not valid outside of strings, so every
		1256	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1257
		1258	If you know of other incompatibilities, please let me know.
		1259
		1260
		1261	=head2 JSON and YAML
		1262
		1263	You often hear that JSON is a subset of YAML. This is, however, a mass
		1264	hysteria(*) and very far from the truth (as of the time of this writing),
		1265	so let me state it clearly: I<in general, there is no way to configure
		1266	JSON::XS to output a data structure as valid YAML> that works in all
		1267	cases.
		1268
		1269	If you really must use JSON::XS to generate YAML, you should use this
		1270	algorithm (subject to change in future versions):
		1271
		1272	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1273	my $yaml = $to_yaml->encode ($ref) . "\n";
		1274
		1275	This will I<usually> generate JSON texts that also parse as valid
		1276	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1277	lengths that JSON doesn't have and also has different and incompatible
		1278	unicode character escape syntax, so you should make sure that your hash
		1279	keys are noticeably shorter than the 1024 "stream characters" YAML allows
		1280	and that you do not have characters with codepoint values outside the
		1281	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
		1282	sequences in strings (which JSON::XS does not I<currently> generate, but
		1283	other JSON generators might).
		1284
		1285	There might be other incompatibilities that I am not aware of (or the YAML
		1286	specification has been changed yet again - it does so quite often). In
		1287	general you should not try to generate YAML with a JSON generator or vice
		1288	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1289	high that you will run into severe interoperability problems when you
		1290	least expect it.
		1291
		1292	=over 4
		1293
		1294	=item (*)
		1295
		1296	I have been pressured multiple times by Brian Ingerson (one of the
		1297	authors of the YAML specification) to remove this paragraph, despite him
		1298	acknowledging that the actual incompatibilities exist. As I was personally
		1299	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1300	educate people about these issues, so others do not run into the same
		1301	problem again and again. After this, Brian called me a (quote)I<complete
		1302	and worthless idiot>(unquote).
		1303
		1304	In my opinion, instead of pressuring and insulting people who actually
		1305	clarify issues with YAML and the wrong statements of some of its
		1306	proponents, I would kindly suggest reading the JSON spec (which is not
		1307	that difficult or long) and finally make YAML compatible to it, and
		1308	educating users about the changes, instead of spreading lies about the
		1309	real compatibility for many I<years> and trying to silence people who
		1310	point out that it isn't true.
		1311
		1312	Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
		1313	though the incompatibilities have been documented (and are known to
		1314	Brian) for many years and the spec makes explicit claims that YAML is a
		1315	superset of JSON. It would be so easy to fix, but apparently, bullying and
		1316	corrupting userdata is so much easier.
		1317
		1318	=back
		1319
609		1320
610	=head2 SPEED	1321	=head2 SPEED
611		1322
612	It seems that JSON::XS is surprisingly fast, as shown in the following	1323	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	1324	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	1325	in the JSON::XS distribution, to make it easy to compare on your own
615	system.	1326	system.
616		1327
617	First comes a comparison between various modules using a very short	1328	First comes a comparison between various modules using
618	single-line JSON string:	1329	a very short single-line JSON string (also available at
		1330	L<http://dist.schmorp.de/misc/json/short.json>).
619		1331
620	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1332	{"method": "handleMessage", "params": ["user1",
621	"id": null, [1,11,234,-5,1e5,1e7, true, false]}	1333	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1334	1, 0]}
622		1335
623	It shows the number of encodes/decodes per second (JSON::XS uses the	1336	It shows the number of encodes/decodes per second (JSON::XS uses
624	functional interface, while JSON::XS/2 uses the OO interface with	1337	the functional interface, while JSON::XS/2 uses the OO interface
625	pretty-printing and hashkey sorting enabled). Higher is better:	1338	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1339	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1340	uses the from_json method). Higher is better:
626		1341
627	-----------+------------+------------+
628	module | encode | decode |	1342	module | encode | decode |
629	-----------|------------|------------|	1343	--------------|------------|------------|
630	JSON | 10597.029 | 5740.903 |	1344	JSON::DWIW/DS | 86302.551 | 102300.098 |
631	JSON::DWIW | 78251.940 | 98457.840 |	1345	JSON::DWIW/FJ | 86302.551 | 75983.768 |
632	JSON::PC | 70611.178 | 92794.336 |	1346	JSON::PP | 15827.562 | 6638.658 |
633	JSON::Syck | 28767.517 | 38199.490 |	1347	JSON::Syck | 63358.066 | 47662.545 |
634	JSON::XS | 419430.400 | 265462.278 |	1348	JSON::XS | 511500.488 | 511500.488 |
635	JSON::XS/2 | 279620.267 | 265462.278 |	1349	JSON::XS/2 | 291271.111 | 388361.481 |
636	JSON::XS/3 | 388361.481 | 265462.278 |	1350	JSON::XS/3 | 361577.931 | 361577.931 |
637	Storable | 16294.887 | 16844.594 |	1351	Storable | 66788.280 | 265462.278 |
638	-----------+------------+------------+	1352	--------------+------------+------------+
639		1353
640	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1354	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
641	about three times faster on decoding, and about fourty times faster	1355	about five times faster on decoding, and over thirty to seventy times
642	than JSON, even with pretty-printing and key sorting. It also compares	1356	faster than JSON's pure perl implementation. It also compares favourably
643	favourably to Storable for small amounts of data.	1357	to Storable for small amounts of data.
644		1358
645	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1359	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
646	search API (http://nanoref.com/yahooapis/mgPdGg):	1360	search API (L<http://dist.schmorp.de/misc/json/long.json>).
647		1361
648	module | encode | decode |	1362	module | encode | decode |
649	-----------|------------|------------|	1363	--------------|------------|------------|
650	JSON | 254.685 | 37.665 |	1364	JSON::DWIW/DS | 1647.927 | 2673.916 |
651	JSON::DWIW | 1014.244 | 1087.678 |	1365	JSON::DWIW/FJ | 1630.249 | 2596.128 |
652	JSON::PC | 3602.116 | 2307.352 |	1366	JSON::PP | 400.640 | 62.311 |
653	JSON::Syck | 558.035 | 776.263 |	1367	JSON::Syck | 1481.040 | 1524.869 |
654	JSON::XS | 5747.196 | 3543.684 |	1368	JSON::XS | 20661.596 | 9541.183 |
655	JSON::XS/2 | 3968.121 | 3589.170 |	1369	JSON::XS/2 | 10683.403 | 9416.938 |
656	JSON::XS/3 | 6105.246 | 3561.134 |	1370	JSON::XS/3 | 20661.596 | 9400.054 |
657	Storable | 4456.337 | 5320.020 |	1371	Storable | 19765.806 | 10000.725 |
658	-----------+------------+------------+	1372	--------------+------------+------------+
659		1373
660	Again, JSON::XS leads by far.	1374	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1375	decodes a bit faster).
661		1376
662	On large strings containing lots of high unicode characters, some modules	1377	On large strings containing lots of high Unicode characters, some modules
663	(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
664	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
665	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
666	comparison table for that case.	1381	comparison table for that case.
667		1382
668		1383
669	=head1 SECURITY CONSIDERATIONS	1384	=head1 SECURITY CONSIDERATIONS
…		…
675	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
676	trying hard on making that true, but you never know.	1391	trying hard on making that true, but you never know.
677		1392
678	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
679	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
680	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
681	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
682	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
683	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.
684		1401
685	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
686	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
687	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
688	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
689	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
690	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
691	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
692	C<max_depth> method.	1409	C<max_depth> method.
693		1410
694	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
695	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...
696	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://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
		1422	see whether you are vulnerable to some common attack vectors (which really
		1423	are browser design bugs, but it is still you who will have to deal with
		1424	it, as major browser developers care only for features, not about getting
		1425	security 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).
697		1436
698		1437
699	=head1 BUGS	1438	=head1 BUGS
700		1439
701	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
702	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
703	still relatively early in its development. If you keep reporting bugs they	1442	keep reporting bugs they will be fixed swiftly, though.
704	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.
705		1446
706	=cut	1447	=cut
707		1448
		1449	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1450	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1451
708	sub true() { \1 }	1452	sub true() { $true }
709	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;
710		1469
711	1;	1470	1;
		1471
		1472	=head1 SEE ALSO
		1473
		1474	The F<json_xs> command line utility for quick experiments.
712		1475
713	=head1 AUTHOR	1476	=head1 AUTHOR
714		1477
715	Marc Lehmann <schmorp@schmorp.de>	1478	Marc Lehmann <schmorp@schmorp.de>
716	http://home.schmorp.de/	1479	http://home.schmorp.de/

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