[ViewVC] Diff of: cvs/JSON-XS/XS.pm

Comparing JSON-XS/XS.pm (file contents):
Revision 1.30 by root, Mon Apr 9 06:37:40 2007 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 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 = '1.11';	107	our $VERSION = '2.2222';
92	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
93		109
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
95	require Exporter;
96		111
		112	sub to_json($) {
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<$enable> is true (or missing), then the C<encode> method will not
156	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
157	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159	as per RFC4627.	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
		242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		243	or any other superset of ASCII.
160		244
161	If C<$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
162	characters unless required by the JSON syntax. This results in a faster	246	characters unless required by the JSON syntax or other flags. This results
163	and more compact format.	247	in a faster and more compact format.
		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
		252	The main use for this flag is to produce JSON texts that can be
		253	transmitted over a 7-bit channel, as the encoded JSON texts will not
		254	contain any 8 bit characters.
164		255
165	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
166	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
167		258
		259	=item $json = $json->latin1 ([$enable])
		260
		261	=item $enabled = $json->get_latin1
		262
		263	If C<$enable> is true (or missing), then the C<encode> method will encode
		264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		265	outside the code range C<0..255>. The resulting string can be treated as a
		266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		267	will not be affected in any way by this flag, as C<decode> by default
		268	expects Unicode, which is a strict superset of latin1.
		269
		270	If C<$enable> is false, then the C<encode> method will not escape Unicode
		271	characters unless required by the JSON syntax or other flags.
		272
		273	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		274	document.
		275
		276	The main use for this flag is efficiently encoding binary data as JSON
		277	text, as most octets will not be escaped, resulting in a smaller encoded
		278	size. The disadvantage is that the resulting JSON text is encoded
		279	in latin1 (and must correctly be treated as such when storing and
		280	transferring), a rare encoding for JSON. It is therefore most useful when
		281	you want to store data structures known to contain binary data efficiently
		282	in files or databases, not when talking to other JSON encoders/decoders.
		283
		284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		286
168	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
169		290
170	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
171	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
172	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
173	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
174	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
175	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
176	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
177		298
178	If C<$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
179	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
180	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
181	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.
182		306
183	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
184		308
185	use Encode;	309	use Encode;
186	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
207	]	331	]
208	}	332	}
209		333
210	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
211		335
		336	=item $enabled = $json->get_indent
		337
212	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
213	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
214	into its own line, identing them properly.	340	into its own line, indenting them properly.
215		341
216	If C<$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
217	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
218		344
219	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
220		346
221	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
222		350
223	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
224	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
225		353
226	If C<$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
…		…
232	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
233		361
234	{"key" :"value"}	362	{"key" :"value"}
235		363
236	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
237		367
238	If C<$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
239	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
240	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
241	members.	371	members.
…		…
247		377
248	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
249		379
250	{"key": "value"}	380	{"key": "value"}
251		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
252	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
		430
		431	=item $enabled = $json->get_canonical
253		432
254	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
255	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
256		435
257	If C<$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
258	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
259	of the same script).	438	of the same script).
260		439
261	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
262	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,
263	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,
264	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
265		444
266	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
267		446
268	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
269		450
270	If C<$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
271	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
272	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
273	values instead of croaking.	454	values instead of croaking.
…		…
281	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
282		463
283	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
284	=> "Hello, World!"	465	=> "Hello, World!"
285		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
286	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
287		602
288	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
289	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
290	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
291	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
…		…
309	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
310	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
311		626
312	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
313		628
		629	=item $max_depth = $json->get_max_depth
		630
314	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
315	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
316	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
317	stop and croak at that point.	634	point.
318		635
319	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
320	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<[>
321	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
322	given character in a string.	639	given character in a string.
323		640
324	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
325	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
326		643
327	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
328	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).
329		665
330	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.
331		667
332	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
333		669
…		…
345		681
346	JSON numbers and strings become simple Perl scalars. JSON arrays become	682	JSON numbers and strings become simple Perl scalars. JSON arrays become
347	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	683	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
348	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	684	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
349		685
		686	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		687
		688	This works like the C<decode> method, but instead of raising an exception
		689	when there is trailing garbage after the first JSON object, it will
		690	silently stop parsing there and return the number of characters consumed
		691	so far.
		692
		693	This is useful if your JSON texts are not delimited by an outer protocol
		694	(which is not the brightest thing to do in the first place) and you need
		695	to know where the JSON text ends.
		696
		697	JSON::XS->new->decode_prefix ("[1] the tail")
		698	=> ([], 3)
		699
350	=back	700	=back
		701
		702
		703	=head1 INCREMENTAL PARSING
		704
		705	In some cases, there is the need for incremental parsing of JSON
		706	texts. While this module always has to keep both JSON text and resulting
		707	Perl data structure in memory at one time, it does allow you to parse a
		708	JSON stream incrementally. It does so by accumulating text until it has
		709	a full JSON object, which it then can decode. This process is similar to
		710	using C<decode_prefix> to see if a full JSON object is available, but
		711	is much more efficient (and can be implemented with a minimum of method
		712	calls).
		713
		714	JSON::XS will only attempt to parse the JSON text once it is sure it
		715	has enough text to get a decisive result, using a very simple but
		716	truly incremental parser. This means that it sometimes won't stop as
		717	early as the full parser, for example, it doesn't detect parenthese
		718	mismatches. The only thing it guarantees is that it starts decoding as
		719	soon as a syntactically valid JSON text has been seen. This means you need
		720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		721	parsing in the presence if syntax errors.
		722
		723	The following methods implement this incremental parser.
		724
		725	=over 4
		726
		727	=item [void, scalar or list context] = $json->incr_parse ([$string])
		728
		729	This is the central parsing function. It can both append new text and
		730	extract objects from the stream accumulated so far (both of these
		731	functions are optional).
		732
		733	If C<$string> is given, then this string is appended to the already
		734	existing JSON fragment stored in the C<$json> object.
		735
		736	After that, if the function is called in void context, it will simply
		737	return without doing anything further. This can be used to add more text
		738	in as many chunks as you want.
		739
		740	If the method is called in scalar context, then it will try to extract
		741	exactly I<one> JSON object. If that is successful, it will return this
		742	object, otherwise it will return C<undef>. If there is a parse error,
		743	this method will croak just as C<decode> would do (one can then use
		744	C<incr_skip> to skip the errornous part). This is the most common way of
		745	using the method.
		746
		747	And finally, in list context, it will try to extract as many objects
		748	from the stream as it can find and return them, or the empty list
		749	otherwise. For this to work, there must be no separators between the JSON
		750	objects or arrays, instead they must be concatenated back-to-back. If
		751	an error occurs, an exception will be raised as in the scalar context
		752	case. Note that in this case, any previously-parsed JSON texts will be
		753	lost.
		754
		755	=item $lvalue_string = $json->incr_text
		756
		757	This method returns the currently stored JSON fragment as an lvalue, that
		758	is, you can manipulate it. This I<only> works when a preceding call to
		759	C<incr_parse> in I<scalar context> successfully returned an object. Under
		760	all other circumstances you must not call this function (I mean it.
		761	although in simple tests it might actually work, it I<will> fail under
		762	real world conditions). As a special exception, you can also call this
		763	method before having parsed anything.
		764
		765	This function is useful in two cases: a) finding the trailing text after a
		766	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		767	(such as commas).
		768
		769	=item $json->incr_skip
		770
		771	This will reset the state of the incremental parser and will remove the
		772	parsed text from the input buffer. This is useful after C<incr_parse>
		773	died, in which case the input buffer and incremental parser state is left
		774	unchanged, to skip the text parsed so far and to reset the parse state.
		775
		776	=item $json->incr_reset
		777
		778	This completely resets the incremental parser, that is, after this call,
		779	it will be as if the parser had never parsed anything.
		780
		781	This is useful if you want ot repeatedly parse JSON objects and want to
		782	ignore any trailing data, which means you have to reset the parser after
		783	each successful decode.
		784
		785	=back
		786
		787	=head2 LIMITATIONS
		788
		789	All options that affect decoding are supported, except
		790	C<allow_nonref>. The reason for this is that it cannot be made to
		791	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		792	them back to back and still decode them perfectly. This does not hold true
		793	for JSON numbers, however.
		794
		795	For example, is the string C<1> a single JSON number, or is it simply the
		796	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		797	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		798	takes the conservative route and disallows this case.
		799
		800	=head2 EXAMPLES
		801
		802	Some examples will make all this clearer. First, a simple example that
		803	works similarly to C<decode_prefix>: We want to decode the JSON object at
		804	the start of a string and identify the portion after the JSON object:
		805
		806	my $text = "[1,2,3] hello";
		807
		808	my $json = new JSON::XS;
		809
		810	my $obj = $json->incr_parse ($text)
		811	or die "expected JSON object or array at beginning of string";
		812
		813	my $tail = $json->incr_text;
		814	# $tail now contains " hello"
		815
		816	Easy, isn't it?
		817
		818	Now for a more complicated example: Imagine a hypothetical protocol where
		819	you read some requests from a TCP stream, and each request is a JSON
		820	array, without any separation between them (in fact, it is often useful to
		821	use newlines as "separators", as these get interpreted as whitespace at
		822	the start of the JSON text, which makes it possible to test said protocol
		823	with C<telnet>...).
		824
		825	Here is how you'd do it (it is trivial to write this in an event-based
		826	manner):
		827
		828	my $json = new JSON::XS;
		829
		830	# read some data from the socket
		831	while (sysread $socket, my $buf, 4096) {
		832
		833	# split and decode as many requests as possible
		834	for my $request ($json->incr_parse ($buf)) {
		835	# act on the $request
		836	}
		837	}
		838
		839	Another complicated example: Assume you have a string with JSON objects
		840	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		841	[3]>). To parse them, we have to skip the commas between the JSON texts,
		842	and here is where the lvalue-ness of C<incr_text> comes in useful:
		843
		844	my $text = "[1],[2], [3]";
		845	my $json = new JSON::XS;
		846
		847	# void context, so no parsing done
		848	$json->incr_parse ($text);
		849
		850	# now extract as many objects as possible. note the
		851	# use of scalar context so incr_text can be called.
		852	while (my $obj = $json->incr_parse) {
		853	# do something with $obj
		854
		855	# now skip the optional comma
		856	$json->incr_text =~ s/^ \s* , //x;
		857	}
		858
		859	Now lets go for a very complex example: Assume that you have a gigantic
		860	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		861	but you cannot load it into memory fully (this has actually happened in
		862	the real world :).
		863
		864	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		865	can still help you: You implement a (very simple) array parser and let
		866	JSON decode the array elements, which are all full JSON objects on their
		867	own (this wouldn't work if the array elements could be JSON numbers, for
		868	example):
		869
		870	my $json = new JSON::XS;
		871
		872	# open the monster
		873	open my $fh, "<bigfile.json"
		874	or die "bigfile: $!";
		875
		876	# first parse the initial "["
		877	for (;;) {
		878	sysread $fh, my $buf, 65536
		879	or die "read error: $!";
		880	$json->incr_parse ($buf); # void context, so no parsing
		881
		882	# Exit the loop once we found and removed(!) the initial "[".
		883	# In essence, we are (ab-)using the $json object as a simple scalar
		884	# we append data to.
		885	last if $json->incr_text =~ s/^ \s* \[ //x;
		886	}
		887
		888	# now we have the skipped the initial "[", so continue
		889	# parsing all the elements.
		890	for (;;) {
		891	# in this loop we read data until we got a single JSON object
		892	for (;;) {
		893	if (my $obj = $json->incr_parse) {
		894	# do something with $obj
		895	last;
		896	}
		897
		898	# add more data
		899	sysread $fh, my $buf, 65536
		900	or die "read error: $!";
		901	$json->incr_parse ($buf); # void context, so no parsing
		902	}
		903
		904	# in this loop we read data until we either found and parsed the
		905	# separating "," between elements, or the final "]"
		906	for (;;) {
		907	# first skip whitespace
		908	$json->incr_text =~ s/^\s*//;
		909
		910	# if we find "]", we are done
		911	if ($json->incr_text =~ s/^\]//) {
		912	print "finished.\n";
		913	exit;
		914	}
		915
		916	# if we find ",", we can continue with the next element
		917	if ($json->incr_text =~ s/^,//) {
		918	last;
		919	}
		920
		921	# if we find anything else, we have a parse error!
		922	if (length $json->incr_text) {
		923	die "parse error near ", $json->incr_text;
		924	}
		925
		926	# else add more data
		927	sysread $fh, my $buf, 65536
		928	or die "read error: $!";
		929	$json->incr_parse ($buf); # void context, so no parsing
		930	}
		931
		932	This is a complex example, but most of the complexity comes from the fact
		933	that we are trying to be correct (bear with me if I am wrong, I never ran
		934	the above example :).
		935
351		936
352		937
353	=head1 MAPPING	938	=head1 MAPPING
354		939
355	This section describes how JSON::XS maps Perl values to JSON values and	940	This section describes how JSON::XS maps Perl values to JSON values and
356	vice versa. These mappings are designed to "do the right thing" in most	941	vice versa. These mappings are designed to "do the right thing" in most
357	circumstances automatically, preserving round-tripping characteristics	942	circumstances automatically, preserving round-tripping characteristics
358	(what you put in comes out as something equivalent).	943	(what you put in comes out as something equivalent).
359		944
360	For the more enlightened: note that in the following descriptions,	945	For the more enlightened: note that in the following descriptions,
361	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	946	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
362	refers to the abstract Perl language itself.	947	refers to the abstract Perl language itself.
363		948
		949
364	=head2 JSON -> PERL	950	=head2 JSON -> PERL
365		951
366	=over 4	952	=over 4
367		953
368	=item object	954	=item object
369		955
370	A JSON object becomes a reference to a hash in Perl. No ordering of object	956	A JSON object becomes a reference to a hash in Perl. No ordering of object
371	keys is preserved (JSON does not preserver object key ordering itself).	957	keys is preserved (JSON does not preserve object key ordering itself).
372		958
373	=item array	959	=item array
374		960
375	A JSON array becomes a reference to an array in Perl.	961	A JSON array becomes a reference to an array in Perl.
376		962
…		…
380	are represented by the same codepoints in the Perl string, so no manual	966	are represented by the same codepoints in the Perl string, so no manual
381	decoding is necessary.	967	decoding is necessary.
382		968
383	=item number	969	=item number
384		970
385	A JSON number becomes either an integer or numeric (floating point)	971	A JSON number becomes either an integer, numeric (floating point) or
386	scalar in perl, depending on its range and any fractional parts. On the	972	string scalar in perl, depending on its range and any fractional parts. On
387	Perl level, there is no difference between those as Perl handles all the	973	the Perl level, there is no difference between those as Perl handles all
388	conversion details, but an integer may take slightly less memory and might	974	the conversion details, but an integer may take slightly less memory and
389	represent more values exactly than (floating point) numbers.	975	might represent more values exactly than floating point numbers.
		976
		977	If the number consists of digits only, JSON::XS will try to represent
		978	it as an integer value. If that fails, it will try to represent it as
		979	a numeric (floating point) value if that is possible without loss of
		980	precision. Otherwise it will preserve the number as a string value (in
		981	which case you lose roundtripping ability, as the JSON number will be
		982	re-encoded toa JSON string).
		983
		984	Numbers containing a fractional or exponential part will always be
		985	represented as numeric (floating point) values, possibly at a loss of
		986	precision (in which case you might lose perfect roundtripping ability, but
		987	the JSON number will still be re-encoded as a JSON number).
390		988
391	=item true, false	989	=item true, false
392		990
393	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	991	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
394	this process. Future versions might represent those values differently,	992	respectively. They are overloaded to act almost exactly like the numbers
395	but they will be guarenteed to act like these integers would normally in	993	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
396	Perl.	994	the C<JSON::XS::is_bool> function.
397		995
398	=item null	996	=item null
399		997
400	A JSON null atom becomes C<undef> in Perl.	998	A JSON null atom becomes C<undef> in Perl.
401		999
402	=back	1000	=back
		1001
403		1002
404	=head2 PERL -> JSON	1003	=head2 PERL -> JSON
405		1004
406	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1005	The mapping from Perl to JSON is slightly more difficult, as Perl is a
407	truly typeless language, so we can only guess which JSON type is meant by	1006	truly typeless language, so we can only guess which JSON type is meant by
…		…
430	Other unblessed references are generally not allowed and will cause an	1029	Other unblessed references are generally not allowed and will cause an
431	exception to be thrown, except for references to the integers C<0> and	1030	exception to be thrown, except for references to the integers C<0> and
432	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1031	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
433	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1032	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
434		1033
435	to_json [\0,JSON::XS::true] # yields [false,true]	1034	encode_json [\0, JSON::XS::true] # yields [false,true]
		1035
		1036	=item JSON::XS::true, JSON::XS::false
		1037
		1038	These special values become JSON true and JSON false values,
		1039	respectively. You can also use C<\1> and C<\0> directly if you want.
436		1040
437	=item blessed objects	1041	=item blessed objects
438		1042
439	Blessed objects are not allowed. JSON::XS currently tries to encode their	1043	Blessed objects are not directly representable in JSON. See the
440	underlying representation (hash- or arrayref), but this behaviour might	1044	C<allow_blessed> and C<convert_blessed> methods on various options on
441	change in future versions.	1045	how to deal with this: basically, you can choose between throwing an
		1046	exception, encoding the reference as if it weren't blessed, or provide
		1047	your own serialiser method.
442		1048
443	=item simple scalars	1049	=item simple scalars
444		1050
445	Simple Perl scalars (any scalar that is not a reference) are the most	1051	Simple Perl scalars (any scalar that is not a reference) are the most
446	difficult objects to encode: JSON::XS will encode undefined scalars as	1052	difficult objects to encode: JSON::XS will encode undefined scalars as
447	JSON null value, scalars that have last been used in a string context	1053	JSON C<null> values, scalars that have last been used in a string context
448	before encoding as JSON strings and anything else as number value:	1054	before encoding as JSON strings, and anything else as number value:
449		1055
450	# dump as number	1056	# dump as number
451	to_json [2] # yields [2]	1057	encode_json [2] # yields [2]
452	to_json [-3.0e17] # yields [-3e+17]	1058	encode_json [-3.0e17] # yields [-3e+17]
453	my $value = 5; to_json [$value] # yields [5]	1059	my $value = 5; encode_json [$value] # yields [5]
454		1060
455	# used as string, so dump as string	1061	# used as string, so dump as string
456	print $value;	1062	print $value;
457	to_json [$value] # yields ["5"]	1063	encode_json [$value] # yields ["5"]
458		1064
459	# undef becomes null	1065	# undef becomes null
460	to_json [undef] # yields [null]	1066	encode_json [undef] # yields [null]
461		1067
462	You can force the type to be a string by stringifying it:	1068	You can force the type to be a JSON string by stringifying it:
463		1069
464	my $x = 3.1; # some variable containing a number	1070	my $x = 3.1; # some variable containing a number
465	"$x"; # stringified	1071	"$x"; # stringified
466	$x .= ""; # another, more awkward way to stringify	1072	$x .= ""; # another, more awkward way to stringify
467	print $x; # perl does it for you, too, quite often	1073	print $x; # perl does it for you, too, quite often
468		1074
469	You can force the type to be a number by numifying it:	1075	You can force the type to be a JSON number by numifying it:
470		1076
471	my $x = "3"; # some variable containing a string	1077	my $x = "3"; # some variable containing a string
472	$x += 0; # numify it, ensuring it will be dumped as a number	1078	$x += 0; # numify it, ensuring it will be dumped as a number
473	$x *= 1; # same thing, the choise is yours.	1079	$x *= 1; # same thing, the choice is yours.
474		1080
475	You can not currently output JSON booleans or force the type in other,	1081	You can not currently force the type in other, less obscure, ways. Tell me
476	less obscure, ways. Tell me if you need this capability.	1082	if you need this capability (but don't forget to explain why it's needed
		1083	:).
477		1084
478	=back	1085	=back
479		1086
480		1087
481	=head1 COMPARISON	1088	=head1 ENCODING/CODESET FLAG NOTES
482		1089
483	As already mentioned, this module was created because none of the existing	1090	The interested reader might have seen a number of flags that signify
484	JSON modules could be made to work correctly. First I will describe the	1091	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
485	problems (or pleasures) I encountered with various existing JSON modules,	1092	some confusion on what these do, so here is a short comparison:
486	followed by some benchmark values. JSON::XS was designed not to suffer	1093
487	from any of these problems or limitations.	1094	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1095	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1096	control whether C<encode> escapes character values outside their respective
		1097	codeset range. Neither of these flags conflict with each other, although
		1098	some combinations make less sense than others.
		1099
		1100	Care has been taken to make all flags symmetrical with respect to
		1101	C<encode> and C<decode>, that is, texts encoded with any combination of
		1102	these flag values will be correctly decoded when the same flags are used
		1103	- in general, if you use different flag settings while encoding vs. when
		1104	decoding you likely have a bug somewhere.
		1105
		1106	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1107	simply an abstract set of character-codepoint pairs, while an encoding
		1108	takes those codepoint numbers and I<encodes> them, in our case into
		1109	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1110	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1111	the same time, which can be confusing.
488		1112
489	=over 4	1113	=over 4
490		1114
491	=item JSON 1.07	1115	=item C<utf8> flag disabled
492		1116
493	Slow (but very portable, as it is written in pure Perl).	1117	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1118	and expect Unicode strings, that is, characters with high ordinal Unicode
		1119	values (> 255) will be encoded as such characters, and likewise such
		1120	characters are decoded as-is, no canges to them will be done, except
		1121	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1122	respectively (to Perl, these are the same thing in strings unless you do
		1123	funny/weird/dumb stuff).
494		1124
495	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1125	This is useful when you want to do the encoding yourself (e.g. when you
496	undocumented. One can get far by feeding it unicode strings and doing	1126	want to have UTF-16 encoded JSON texts) or when some other layer does
497	en-/decoding oneself, but unicode escapes are not working properly).	1127	the encoding for you (for example, when printing to a terminal using a
		1128	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1129	to UTF-8 encode your data first and have Perl encode it another time).
498		1130
499	No roundtripping (strings get clobbered if they look like numbers, e.g.	1131	=item C<utf8> flag enabled
500	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
501	decode into the number 2.
502		1132
503	=item JSON::PC 0.01	1133	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1134	characters using the corresponding UTF-8 multi-byte sequence, and will
		1135	expect your input strings to be encoded as UTF-8, that is, no "character"
		1136	of the input string must have any value > 255, as UTF-8 does not allow
		1137	that.
504		1138
505	Very fast.	1139	The C<utf8> flag therefore switches between two modes: disabled means you
		1140	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1141	octet/binary string in Perl.
506		1142
507	Undocumented/buggy Unicode handling.	1143	=item C<latin1> or C<ascii> flags enabled
508		1144
509	No roundtripping.	1145	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1146	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1147	characters as specified by the C<utf8> flag.
510		1148
511	Has problems handling many Perl values (e.g. regex results and other magic	1149	If C<utf8> is disabled, then the result is also correctly encoded in those
512	values will make it croak).	1150	character sets (as both are proper subsets of Unicode, meaning that a
		1151	Unicode string with all character values < 256 is the same thing as a
		1152	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1153	the same thing as an ASCII string in Perl).
513		1154
514	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1155	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
515	which is not a valid JSON text.	1156	regardless of these flags, just some more characters will be escaped using
		1157	C<\uXXXX> then before.
516		1158
517	Unmaintained (maintainer unresponsive for many months, bugs are not	1159	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
518	getting fixed).	1160	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1161	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1162	a subset of Unicode), while ASCII is.
519		1163
520	=item JSON::Syck 0.21	1164	Surprisingly, C<decode> will ignore these flags and so treat all input
		1165	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1166	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1167	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
521		1168
522	Very buggy (often crashes).	1169	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1170	they only govern when the JSON output engine escapes a character or not.
523		1171
524	Very inflexible (no human-readable format supported, format pretty much	1172	The main use for C<latin1> is to relatively efficiently store binary data
525	undocumented. I need at least a format for easy reading by humans and a	1173	as JSON, at the expense of breaking compatibility with most JSON decoders.
526	single-line compact format for use in a protocol, and preferably a way to
527	generate ASCII-only JSON texts).
528		1174
529	Completely broken (and confusingly documented) Unicode handling (unicode	1175	The main use for C<ascii> is to force the output to not contain characters
530	escapes are not working properly, you need to set ImplicitUnicode to	1176	with values > 127, which means you can interpret the resulting string
531	I<different> values on en- and decoding to get symmetric behaviour).	1177	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
532		1178	8-bit-encoding, and still get the same data structure back. This is useful
533	No roundtripping (simple cases work, but this depends on wether the scalar	1179	when your channel for JSON transfer is not 8-bit clean or the encoding
534	value was used in a numeric context or not).	1180	might be mangled in between (e.g. in mail), and works because ASCII is a
535		1181	proper subset of most 8-bit and multibyte encodings in use in the world.
536	Dumping hashes may skip hash values depending on iterator state.
537
538	Unmaintained (maintainer unresponsive for many months, bugs are not
539	getting fixed).
540
541	Does not check input for validity (i.e. will accept non-JSON input and
542	return "something" instead of raising an exception. This is a security
543	issue: imagine two banks transfering money between each other using
544	JSON. One bank might parse a given non-JSON request and deduct money,
545	while the other might reject the transaction with a syntax error. While a
546	good protocol will at least recover, that is extra unnecessary work and
547	the transaction will still not succeed).
548
549	=item JSON::DWIW 0.04
550
551	Very fast. Very natural. Very nice.
552
553	Undocumented unicode handling (but the best of the pack. Unicode escapes
554	still don't get parsed properly).
555
556	Very inflexible.
557
558	No roundtripping.
559
560	Does not generate valid JSON texts (key strings are often unquoted, empty keys
561	result in nothing being output)
562
563	Does not check input for validity.
564		1182
565	=back	1183	=back
		1184
		1185
		1186	=head2 JSON and YAML
		1187
		1188	You often hear that JSON is a subset of YAML. This is, however, a mass
		1189	hysteria(*) and very far from the truth (as of the time of this writing),
		1190	so let me state it clearly: I<in general, there is no way to configure
		1191	JSON::XS to output a data structure as valid YAML> that works in all
		1192	cases.
		1193
		1194	If you really must use JSON::XS to generate YAML, you should use this
		1195	algorithm (subject to change in future versions):
		1196
		1197	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1198	my $yaml = $to_yaml->encode ($ref) . "\n";
		1199
		1200	This will I<usually> generate JSON texts that also parse as valid
		1201	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1202	lengths that JSON doesn't have and also has different and incompatible
		1203	unicode handling, so you should make sure that your hash keys are
		1204	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1205	you do not have characters with codepoint values outside the Unicode BMP
		1206	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1207	strings (which JSON::XS does not I<currently> generate, but other JSON
		1208	generators might).
		1209
		1210	There might be other incompatibilities that I am not aware of (or the YAML
		1211	specification has been changed yet again - it does so quite often). In
		1212	general you should not try to generate YAML with a JSON generator or vice
		1213	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1214	high that you will run into severe interoperability problems when you
		1215	least expect it.
		1216
		1217	=over 4
		1218
		1219	=item (*)
		1220
		1221	I have been pressured multiple times by Brian Ingerson (one of the
		1222	authors of the YAML specification) to remove this paragraph, despite him
		1223	acknowledging that the actual incompatibilities exist. As I was personally
		1224	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1225	educate people about these issues, so others do not run into the same
		1226	problem again and again. After this, Brian called me a (quote)I<complete
		1227	and worthless idiot>(unquote).
		1228
		1229	In my opinion, instead of pressuring and insulting people who actually
		1230	clarify issues with YAML and the wrong statements of some of its
		1231	proponents, I would kindly suggest reading the JSON spec (which is not
		1232	that difficult or long) and finally make YAML compatible to it, and
		1233	educating users about the changes, instead of spreading lies about the
		1234	real compatibility for many I<years> and trying to silence people who
		1235	point out that it isn't true.
		1236
		1237	=back
		1238
566		1239
567	=head2 SPEED	1240	=head2 SPEED
568		1241
569	It seems that JSON::XS is surprisingly fast, as shown in the following	1242	It seems that JSON::XS is surprisingly fast, as shown in the following
570	tables. They have been generated with the help of the C<eg/bench> program	1243	tables. They have been generated with the help of the C<eg/bench> program
571	in the JSON::XS distribution, to make it easy to compare on your own	1244	in the JSON::XS distribution, to make it easy to compare on your own
572	system.	1245	system.
573		1246
574	First comes a comparison between various modules using a very short JSON	1247	First comes a comparison between various modules using
575	string:	1248	a very short single-line JSON string (also available at
		1249	L<http://dist.schmorp.de/misc/json/short.json>).
576		1250
577	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1251	{"method": "handleMessage", "params": ["user1",
		1252	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1253	true, false]}
578		1254
579	It shows the number of encodes/decodes per second (JSON::XS uses the	1255	It shows the number of encodes/decodes per second (JSON::XS uses
580	functional interface, while JSON::XS/2 uses the OO interface with	1256	the functional interface, while JSON::XS/2 uses the OO interface
581	pretty-printing and hashkey sorting enabled). Higher is better:	1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1258	shrink). Higher is better:
582		1259
583	module \| encode \| decode \|	1260	module \| encode \| decode \|
584	-----------\|------------\|------------\|	1261	-----------\|------------\|------------\|
585	JSON \| 11488.516 \| 7823.035 \|	1262	JSON 1.x \| 4990.842 \| 4088.813 \|
586	JSON::DWIW \| 94708.054 \| 129094.260 \|	1263	JSON::DWIW \| 51653.990 \| 71575.154 \|
587	JSON::PC \| 63884.157 \| 128528.212 \|	1264	JSON::PC \| 65948.176 \| 74631.744 \|
588	JSON::Syck \| 34898.677 \| 42096.911 \|	1265	JSON::PP \| 8931.652 \| 3817.168 \|
589	JSON::XS \| 654027.064 \| 396423.669 \|	1266	JSON::Syck \| 24877.248 \| 27776.848 \|
590	JSON::XS/2 \| 371564.190 \| 371725.613 \|	1267	JSON::XS \| 388361.481 \| 227951.304 \|
		1268	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		1269	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		1270	Storable \| 16500.016 \| 135300.129 \|
591	-----------+------------+------------+	1271	-----------+------------+------------+
592		1272
593	That is, JSON::XS is more than six times faster than JSON::DWIW on	1273	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
594	encoding, more than three times faster on decoding, and about thirty times	1274	about three times faster on decoding, and over forty times faster
595	faster than JSON, even with pretty-printing and key sorting.	1275	than JSON, even with pretty-printing and key sorting. It also compares
		1276	favourably to Storable for small amounts of data.
596		1277
597	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
598	search API (http://nanoref.com/yahooapis/mgPdGg):	1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).
599		1280
600	module \| encode \| decode \|	1281	module \| encode \| decode \|
601	-----------\|------------\|------------\|	1282	-----------\|------------\|------------\|
602	JSON \| 273.023 \| 44.674 \|	1283	JSON 1.x \| 55.260 \| 34.971 \|
603	JSON::DWIW \| 1089.383 \| 1145.704 \|	1284	JSON::DWIW \| 825.228 \| 1082.513 \|
604	JSON::PC \| 3097.419 \| 2393.921 \|	1285	JSON::PC \| 3571.444 \| 2394.829 \|
605	JSON::Syck \| 514.060 \| 843.053 \|	1286	JSON::PP \| 210.987 \| 32.574 \|
606	JSON::XS \| 6479.668 \| 3636.364 \|	1287	JSON::Syck \| 552.551 \| 787.544 \|
607	JSON::XS/2 \| 3774.221 \| 3599.124 \|	1288	JSON::XS \| 5780.463 \| 4854.519 \|
		1289	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		1290	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		1291	Storable \| 4445.002 \| 5235.027 \|
608	-----------+------------+------------+	1292	-----------+------------+------------+
609		1293
610	Again, JSON::XS leads by far.	1294	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1295	decodes faster).
611		1296
612	On large strings containing lots of high unicode characters, some modules	1297	On large strings containing lots of high Unicode characters, some modules
613	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1298	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
614	will be broken due to missing (or wrong) unicode handling. Others refuse	1299	will be broken due to missing (or wrong) Unicode handling. Others refuse
615	to decode or encode properly, so it was impossible to prepare a fair	1300	to decode or encode properly, so it was impossible to prepare a fair
616	comparison table for that case.	1301	comparison table for that case.
617		1302
618		1303
619	=head1 SECURITY CONSIDERATIONS	1304	=head1 SECURITY CONSIDERATIONS
…		…
625	any buffer overflows. Obviously, this module should ensure that and I am	1310	any buffer overflows. Obviously, this module should ensure that and I am
626	trying hard on making that true, but you never know.	1311	trying hard on making that true, but you never know.
627		1312
628	Second, you need to avoid resource-starving attacks. That means you should	1313	Second, you need to avoid resource-starving attacks. That means you should
629	limit the size of JSON texts you accept, or make sure then when your	1314	limit the size of JSON texts you accept, or make sure then when your
630	resources run out, thats just fine (e.g. by using a separate process that	1315	resources run out, that's just fine (e.g. by using a separate process that
631	can crash safely). The size of a JSON text in octets or characters is	1316	can crash safely). The size of a JSON text in octets or characters is
632	usually a good indication of the size of the resources required to decode	1317	usually a good indication of the size of the resources required to decode
633	it into a Perl structure.	1318	it into a Perl structure. While JSON::XS can check the size of the JSON
		1319	text, it might be too late when you already have it in memory, so you
		1320	might want to check the size before you accept the string.
634		1321
635	Third, JSON::XS recurses using the C stack when decoding objects and	1322	Third, JSON::XS recurses using the C stack when decoding objects and
636	arrays. The C stack is a limited resource: for instance, on my amd64	1323	arrays. The C stack is a limited resource: for instance, on my amd64
637	machine with 8MB of stack size I can decode around 180k nested arrays but	1324	machine with 8MB of stack size I can decode around 180k nested arrays but
638	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1325	only 14k nested JSON objects (due to perl itself recursing deeply on croak
639	to free the temporary). If that is exceeded, the program crashes. to be	1326	to free the temporary). If that is exceeded, the program crashes. To be
640	conservative, the default nesting limit is set to 512. If your process	1327	conservative, the default nesting limit is set to 512. If your process
641	has a smaller stack, you should adjust this setting accordingly with the	1328	has a smaller stack, you should adjust this setting accordingly with the
642	C<max_depth> method.	1329	C<max_depth> method.
643		1330
644	And last but least, something else could bomb you that I forgot to think	1331	Something else could bomb you, too, that I forgot to think of. In that
645	of. In that case, you get to keep the pieces. I am always open for hints,	1332	case, you get to keep the pieces. I am always open for hints, though...
646	though...	1333
		1334	Also keep in mind that JSON::XS might leak contents of your Perl data
		1335	structures in its error messages, so when you serialise sensitive
		1336	information you might want to make sure that exceptions thrown by JSON::XS
		1337	will not end up in front of untrusted eyes.
		1338
		1339	If you are using JSON::XS to return packets to consumption
		1340	by JavaScript scripts in a browser you should have a look at
		1341	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1342	you are vulnerable to some common attack vectors (which really are browser
		1343	design bugs, but it is still you who will have to deal with it, as major
		1344	browser developers care only for features, not about getting security
		1345	right).
		1346
		1347
		1348	=head1 THREADS
		1349
		1350	This module is I<not> guaranteed to be thread safe and there are no
		1351	plans to change this until Perl gets thread support (as opposed to the
		1352	horribly slow so-called "threads" which are simply slow and bloated
		1353	process simulations - use fork, it's I<much> faster, cheaper, better).
		1354
		1355	(It might actually work, but you have been warned).
647		1356
648		1357
649	=head1 BUGS	1358	=head1 BUGS
650		1359
651	While the goal of this module is to be correct, that unfortunately does	1360	While the goal of this module is to be correct, that unfortunately does
652	not mean its bug-free, only that I think its design is bug-free. It is	1361	not mean it's bug-free, only that I think its design is bug-free. If you
653	still relatively early in its development. If you keep reporting bugs they	1362	keep reporting bugs they will be fixed swiftly, though.
654	will be fixed swiftly, though.	1363
		1364	Please refrain from using rt.cpan.org or any other bug reporting
		1365	service. I put the contact address into my modules for a reason.
655		1366
656	=cut	1367	=cut
657		1368
		1369	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1370	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1371
658	sub true() { \1 }	1372	sub true() { $true }
659	sub false() { \0 }	1373	sub false() { $false }
		1374
		1375	sub is_bool($) {
		1376	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1377	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1378	}
		1379
		1380	XSLoader::load "JSON::XS", $VERSION;
		1381
		1382	package JSON::XS::Boolean;
		1383
		1384	use overload
		1385	"0+" => sub { ${$_[0]} },
		1386	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1388	fallback => 1;
660		1389
661	1;	1390	1;
		1391
		1392	=head1 SEE ALSO
		1393
		1394	The F<json_xs> command line utility for quick experiments.
662		1395
663	=head1 AUTHOR	1396	=head1 AUTHOR
664		1397
665	Marc Lehmann <schmorp@schmorp.de>	1398	Marc Lehmann <schmorp@schmorp.de>
666	http://home.schmorp.de/	1399	http://home.schmorp.de/

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Comparing JSON-XS/XS.pm (file contents): Revision 1.30 by root, Mon Apr 9 06:37:40 2007 UTC vs. Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.30 by root, Mon Apr 9 06:37:40 2007 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC