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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs.
Revision 1.76 by root, Sun Dec 2 15:34:13 2007 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
		5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		7
5	=head1 SYNOPSIS	8	=head1 SYNOPSIS
6		9
7	use JSON::XS;	10	use JSON::XS;
		11
		12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
		14
		15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		17
		18	# OO-interface
		19
		20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		22	$perl_scalar = $coder->decode ($unicode_json_text);
8		23
9	=head1 DESCRIPTION	24	=head1 DESCRIPTION
10		25
11	This module converts Perl data structures to JSON and vice versa. Its	26	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	27	primary goal is to be I<correct> and its secondary goal is to be
25		40
26	=head2 FEATURES	41	=head2 FEATURES
27		42
28	=over 4	43	=over 4
29		44
30	=item * correct handling of unicode issues	45	=item * correct Unicode handling
31		46
32	This module knows how to handle Unicode, and even documents how and when	47	This module knows how to handle Unicode, and even documents how and when
33	it does so.	48	it does so.
34		49
35	=item * round-trip integrity	50	=item * round-trip integrity
36		51
37	When you serialise a perl data structure using only datatypes supported	52	When you serialise a perl data structure using only datatypes supported
38	by JSON, the deserialised data structure is identical on the Perl level.	53	by JSON, the deserialised data structure is identical on the Perl level.
39	(e.g. the string "2.0" doesn't suddenly become "2").	54	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		55	like a number).
40		56
41	=item * strict checking of JSON correctness	57	=item * strict checking of JSON correctness
42		58
43	There is no guessing, no generating of illegal JSON strings by default,	59	There is no guessing, no generating of illegal JSON texts by default,
44	and only JSON is accepted as input by default (the latter is a security	60	and only JSON is accepted as input by default (the latter is a security
45	feature).	61	feature).
46		62
47	=item * fast	63	=item * fast
48		64
…		…
54	This module has both a simple functional interface as well as an OO	70	This module has both a simple functional interface as well as an OO
55	interface.	71	interface.
56		72
57	=item * reasonably versatile output formats	73	=item * reasonably versatile output formats
58		74
59	You can choose between the most compact guarenteed single-line format	75	You can choose between the most compact guaranteed single-line format
60	possible (nice for simple line-based protocols), a pure-ascii format (for	76	possible (nice for simple line-based protocols), a pure-ascii format
61	when your transport is not 8-bit clean), or a pretty-printed format (for	77	(for when your transport is not 8-bit clean, still supports the whole
62	when you want to read that stuff). Or you can combine those features in	78	Unicode range), or a pretty-printed format (for when you want to read that
63	whatever way you like.	79	stuff). Or you can combine those features in whatever way you like.
64		80
65	=back	81	=back
66		82
67	=cut	83	=cut
68		84
69	package JSON::XS;	85	package JSON::XS;
70		86
71	BEGIN {	87	use strict;
		88
72	$VERSION = '0.3';	89	our $VERSION = '2.0';
73	@ISA = qw(Exporter);	90	our @ISA = qw(Exporter);
74		91
75	@EXPORT = qw(to_json from_json);	92	our @EXPORT = qw(to_json from_json);
76	require Exporter;
77		93
78	require XSLoader;	94	use Exporter;
79	XSLoader::load JSON::XS::, $VERSION;	95	use XSLoader;
80	}
81		96
82	=head1 FUNCTIONAL INTERFACE	97	=head1 FUNCTIONAL INTERFACE
83		98
84	The following convinience methods are provided by this module. They are	99	The following convenience methods are provided by this module. They are
85	exported by default:	100	exported by default:
86		101
87	=over 4	102	=over 4
88		103
89	=item $json_string = to_json $perl_scalar	104	=item $json_text = to_json $perl_scalar
90		105
91	Converts the given Perl data structure (a simple scalar or a reference to	106	Converts the given Perl data structure to a UTF-8 encoded, binary string
92	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	107	(that is, the string contains octets only). Croaks on error.
93	octets only). Croaks on error.
94		108
95	This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.	109	This function call is functionally identical to:
96		110
		111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		112
		113	except being faster.
		114
97	=item $perl_scalar = from_json $json_string	115	=item $perl_scalar = from_json $json_text
98		116
99	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
100	parse that as an UTF-8 encoded JSON string, returning the resulting simple	118	to parse that as an UTF-8 encoded JSON text, returning the resulting
101	scalar or reference. Croaks on error.	119	reference. Croaks on error.
102		120
103	This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.	121	This function call is functionally identical to:
		122
		123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		124
		125	except being faster.
		126
		127	=item $is_boolean = JSON::XS::is_bool $scalar
		128
		129	Returns true if the passed scalar represents either JSON::XS::true or
		130	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		131	and are used to represent JSON C<true> and C<false> values in Perl.
		132
		133	See MAPPING, below, for more information on how JSON values are mapped to
		134	Perl.
104		135
105	=back	136	=back
		137
		138
		139	=head1 A FEW NOTES ON UNICODE AND PERL
		140
		141	Since this often leads to confusion, here are a few very clear words on
		142	how Unicode works in Perl, modulo bugs.
		143
		144	=over 4
		145
		146	=item 1. Perl strings can store characters with ordinal values > 255.
		147
		148	This enables you to store Unicode characters as single characters in a
		149	Perl string - very natural.
		150
		151	=item 2. Perl does I<not> associate an encoding with your strings.
		152
		153	Unless you force it to, e.g. when matching it against a regex, or printing
		154	the scalar to a file, in which case Perl either interprets your string as
		155	locale-encoded text, octets/binary, or as Unicode, depending on various
		156	settings. In no case is an encoding stored together with your data, it is
		157	I<use> that decides encoding, not any magical metadata.
		158
		159	=item 3. The internal utf-8 flag has no meaning with regards to the
		160	encoding of your string.
		161
		162	Just ignore that flag unless you debug a Perl bug, a module written in
		163	XS or want to dive into the internals of perl. Otherwise it will only
		164	confuse you, as, despite the name, it says nothing about how your string
		165	is encoded. You can have Unicode strings with that flag set, with that
		166	flag clear, and you can have binary data with that flag set and that flag
		167	clear. Other possibilities exist, too.
		168
		169	If you didn't know about that flag, just the better, pretend it doesn't
		170	exist.
		171
		172	=item 4. A "Unicode String" is simply a string where each character can be
		173	validly interpreted as a Unicode codepoint.
		174
		175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		176	Unicode string encoded in UTF-8, giving you a binary string.
		177
		178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		179
		180	It's a fact. Learn to live with it.
		181
		182	=back
		183
		184	I hope this helps :)
		185
106		186
107	=head1 OBJECT-ORIENTED INTERFACE	187	=head1 OBJECT-ORIENTED INTERFACE
108		188
109	The object oriented interface lets you configure your own encoding or	189	The object oriented interface lets you configure your own encoding or
110	decoding style, within the limits of supported formats.	190	decoding style, within the limits of supported formats.
…		…
117	strings. All boolean flags described below are by default I<disabled>.	197	strings. All boolean flags described below are by default I<disabled>.
118		198
119	The mutators for flags all return the JSON object again and thus calls can	199	The mutators for flags all return the JSON object again and thus calls can
120	be chained:	200	be chained:
121		201
122	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	202	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
123	=> {"a": [1, 2]}	203	=> {"a": [1, 2]}
124		204
125	=item $json = $json->ascii ([$enable])	205	=item $json = $json->ascii ([$enable])
126		206
		207	=item $enabled = $json->get_ascii
		208
127	If C<$enable> is true (or missing), then the C<encode> method will	209	If C<$enable> is true (or missing), then the C<encode> method will not
128	not generate characters outside the code range C<0..127>. Any unicode	210	generate characters outside the code range C<0..127> (which is ASCII). Any
129	characters outside that range will be escaped using either a single	211	Unicode characters outside that range will be escaped using either a
130	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
131	RFC4627.	213	as per RFC4627. The resulting encoded JSON text can be treated as a native
		214	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		215	or any other superset of ASCII.
132		216
133	If C<$enable> is false, then the C<encode> method will not escape Unicode	217	If C<$enable> is false, then the C<encode> method will not escape Unicode
134	characters unless necessary.	218	characters unless required by the JSON syntax or other flags. This results
		219	in a faster and more compact format.
135		220
		221	The main use for this flag is to produce JSON texts that can be
		222	transmitted over a 7-bit channel, as the encoded JSON texts will not
		223	contain any 8 bit characters.
		224
136	JSON::XS->new->ascii (1)->encode (chr 0x10401)	225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
137	=> \ud801\udc01	226	=> ["\ud801\udc01"]
		227
		228	=item $json = $json->latin1 ([$enable])
		229
		230	=item $enabled = $json->get_latin1
		231
		232	If C<$enable> is true (or missing), then the C<encode> method will encode
		233	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		234	outside the code range C<0..255>. The resulting string can be treated as a
		235	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		236	will not be affected in any way by this flag, as C<decode> by default
		237	expects Unicode, which is a strict superset of latin1.
		238
		239	If C<$enable> is false, then the C<encode> method will not escape Unicode
		240	characters unless required by the JSON syntax or other flags.
		241
		242	The main use for this flag is efficiently encoding binary data as JSON
		243	text, as most octets will not be escaped, resulting in a smaller encoded
		244	size. The disadvantage is that the resulting JSON text is encoded
		245	in latin1 (and must correctly be treated as such when storing and
		246	transferring), a rare encoding for JSON. It is therefore most useful when
		247	you want to store data structures known to contain binary data efficiently
		248	in files or databases, not when talking to other JSON encoders/decoders.
		249
		250	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		251	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
138		252
139	=item $json = $json->utf8 ([$enable])	253	=item $json = $json->utf8 ([$enable])
140		254
		255	=item $enabled = $json->get_utf8
		256
141	If C<$enable> is true (or missing), then the C<encode> method will encode	257	If C<$enable> is true (or missing), then the C<encode> method will encode
142	the JSON string into UTF-8, as required by many protocols, while the	258	the JSON result into UTF-8, as required by many protocols, while the
143	C<decode> method expects to be handled an UTF-8-encoded string. Please	259	C<decode> method expects to be handled an UTF-8-encoded string. Please
144	note that UTF-8-encoded strings do not contain any characters outside the	260	note that UTF-8-encoded strings do not contain any characters outside the
145	range C<0..255>, they are thus useful for bytewise/binary I/O.	261	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		262	versions, enabling this option might enable autodetection of the UTF-16
		263	and UTF-32 encoding families, as described in RFC4627.
146		264
147	If C<$enable> is false, then the C<encode> method will return the JSON	265	If C<$enable> is false, then the C<encode> method will return the JSON
148	string as a (non-encoded) unicode string, while C<decode> expects thus a	266	string as a (non-encoded) Unicode string, while C<decode> expects thus a
149	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	267	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
150	to be done yourself, e.g. using the Encode module.	268	to be done yourself, e.g. using the Encode module.
		269
		270	Example, output UTF-16BE-encoded JSON:
		271
		272	use Encode;
		273	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		274
		275	Example, decode UTF-32LE-encoded JSON:
		276
		277	use Encode;
		278	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
151		279
152	=item $json = $json->pretty ([$enable])	280	=item $json = $json->pretty ([$enable])
153		281
154	This enables (or disables) all of the C<indent>, C<space_before> and	282	This enables (or disables) all of the C<indent>, C<space_before> and
155	C<space_after> (and in the future possibly more) flags in one call to	283	C<space_after> (and in the future possibly more) flags in one call to
156	generate the most readable (or most compact) form possible.	284	generate the most readable (or most compact) form possible.
		285
		286	Example, pretty-print some simple structure:
157		287
158	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	288	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
159	=>	289	=>
160	{	290	{
161	"a" : [	291	"a" : [
…		…
164	]	294	]
165	}	295	}
166		296
167	=item $json = $json->indent ([$enable])	297	=item $json = $json->indent ([$enable])
168		298
		299	=item $enabled = $json->get_indent
		300
169	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	301	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
170	format as output, putting every array member or object/hash key-value pair	302	format as output, putting every array member or object/hash key-value pair
171	into its own line, identing them properly.	303	into its own line, indenting them properly.
172		304
173	If C<$enable> is false, no newlines or indenting will be produced, and the	305	If C<$enable> is false, no newlines or indenting will be produced, and the
174	resulting JSON strings is guarenteed not to contain any C<newlines>.	306	resulting JSON text is guaranteed not to contain any C<newlines>.
175		307
176	This setting has no effect when decoding JSON strings.	308	This setting has no effect when decoding JSON texts.
177		309
178	=item $json = $json->space_before ([$enable])	310	=item $json = $json->space_before ([$enable])
		311
		312	=item $enabled = $json->get_space_before
179		313
180	If C<$enable> is true (or missing), then the C<encode> method will add an extra	314	If C<$enable> is true (or missing), then the C<encode> method will add an extra
181	optional space before the C<:> separating keys from values in JSON objects.	315	optional space before the C<:> separating keys from values in JSON objects.
182		316
183	If C<$enable> is false, then the C<encode> method will not add any extra	317	If C<$enable> is false, then the C<encode> method will not add any extra
184	space at those places.	318	space at those places.
185		319
186	This setting has no effect when decoding JSON strings. You will also most	320	This setting has no effect when decoding JSON texts. You will also
187	likely combine this setting with C<space_after>.	321	most likely combine this setting with C<space_after>.
		322
		323	Example, space_before enabled, space_after and indent disabled:
		324
		325	{"key" :"value"}
188		326
189	=item $json = $json->space_after ([$enable])	327	=item $json = $json->space_after ([$enable])
		328
		329	=item $enabled = $json->get_space_after
190		330
191	If C<$enable> is true (or missing), then the C<encode> method will add an extra	331	If C<$enable> is true (or missing), then the C<encode> method will add an extra
192	optional space after the C<:> separating keys from values in JSON objects	332	optional space after the C<:> separating keys from values in JSON objects
193	and extra whitespace after the C<,> separating key-value pairs and array	333	and extra whitespace after the C<,> separating key-value pairs and array
194	members.	334	members.
195		335
196	If C<$enable> is false, then the C<encode> method will not add any extra	336	If C<$enable> is false, then the C<encode> method will not add any extra
197	space at those places.	337	space at those places.
198		338
199	This setting has no effect when decoding JSON strings.	339	This setting has no effect when decoding JSON texts.
		340
		341	Example, space_before and indent disabled, space_after enabled:
		342
		343	{"key": "value"}
		344
		345	=item $json = $json->relaxed ([$enable])
		346
		347	=item $enabled = $json->get_relaxed
		348
		349	If C<$enable> is true (or missing), then C<decode> will accept some
		350	extensions to normal JSON syntax (see below). C<encode> will not be
		351	affected in anyway. I<Be aware that this option makes you accept invalid
		352	JSON texts as if they were valid!>. I suggest only to use this option to
		353	parse application-specific files written by humans (configuration files,
		354	resource files etc.)
		355
		356	If C<$enable> is false (the default), then C<decode> will only accept
		357	valid JSON texts.
		358
		359	Currently accepted extensions are:
		360
		361	=over 4
		362
		363	=item * list items can have an end-comma
		364
		365	JSON I<separates> array elements and key-value pairs with commas. This
		366	can be annoying if you write JSON texts manually and want to be able to
		367	quickly append elements, so this extension accepts comma at the end of
		368	such items not just between them:
		369
		370	[
		371	1,
		372	2, <- this comma not normally allowed
		373	]
		374	{
		375	"k1": "v1",
		376	"k2": "v2", <- this comma not normally allowed
		377	}
		378
		379	=item * shell-style '#'-comments
		380
		381	Whenever JSON allows whitespace, shell-style comments are additionally
		382	allowed. They are terminated by the first carriage-return or line-feed
		383	character, after which more white-space and comments are allowed.
		384
		385	[
		386	1, # this comment not allowed in JSON
		387	# neither this one...
		388	]
		389
		390	=back
200		391
201	=item $json = $json->canonical ([$enable])	392	=item $json = $json->canonical ([$enable])
		393
		394	=item $enabled = $json->get_canonical
202		395
203	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	396	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
204	by sorting their keys. This is adding a comparatively high overhead.	397	by sorting their keys. This is adding a comparatively high overhead.
205		398
206	If C<$enable> is false, then the C<encode> method will output key-value	399	If C<$enable> is false, then the C<encode> method will output key-value
207	pairs in the order Perl stores them (which will likely change between runs	400	pairs in the order Perl stores them (which will likely change between runs
208	of the same script).	401	of the same script).
209		402
210	This option is useful if you want the same data structure to be encoded as	403	This option is useful if you want the same data structure to be encoded as
211	the same JSON string (given the same overall settings). If it is disabled,	404	the same JSON text (given the same overall settings). If it is disabled,
212	the same hash migh be encoded differently even if contains the same data,	405	the same hash might be encoded differently even if contains the same data,
213	as key-value pairs have no inherent ordering in Perl.	406	as key-value pairs have no inherent ordering in Perl.
214		407
215	This setting has no effect when decoding JSON strings.	408	This setting has no effect when decoding JSON texts.
216		409
217	=item $json = $json->allow_nonref ([$enable])	410	=item $json = $json->allow_nonref ([$enable])
		411
		412	=item $enabled = $json->get_allow_nonref
218		413
219	If C<$enable> is true (or missing), then the C<encode> method can convert a	414	If C<$enable> is true (or missing), then the C<encode> method can convert a
220	non-reference into its corresponding string, number or null JSON value,	415	non-reference into its corresponding string, number or null JSON value,
221	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	416	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
222	values instead of croaking.	417	values instead of croaking.
223		418
224	If C<$enable> is false, then the C<encode> method will croak if it isn't	419	If C<$enable> is false, then the C<encode> method will croak if it isn't
225	passed an arrayref or hashref, as JSON strings must either be an object	420	passed an arrayref or hashref, as JSON texts must either be an object
226	or array. Likewise, C<decode> will croak if given something that is not a	421	or array. Likewise, C<decode> will croak if given something that is not a
227	JSON object or array.	422	JSON object or array.
228		423
		424	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		425	resulting in an invalid JSON text:
		426
		427	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		428	=> "Hello, World!"
		429
		430	=item $json = $json->allow_blessed ([$enable])
		431
		432	=item $enabled = $json->get_allow_blessed
		433
		434	If C<$enable> is true (or missing), then the C<encode> method will not
		435	barf when it encounters a blessed reference. Instead, the value of the
		436	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		437	disabled or no C<TO_JSON> method found) or a representation of the
		438	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		439	encoded. Has no effect on C<decode>.
		440
		441	If C<$enable> is false (the default), then C<encode> will throw an
		442	exception when it encounters a blessed object.
		443
		444	=item $json = $json->convert_blessed ([$enable])
		445
		446	=item $enabled = $json->get_convert_blessed
		447
		448	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		449	blessed object, will check for the availability of the C<TO_JSON> method
		450	on the object's class. If found, it will be called in scalar context
		451	and the resulting scalar will be encoded instead of the object. If no
		452	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		453	to do.
		454
		455	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		456	returns other blessed objects, those will be handled in the same
		457	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		458	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		459	methods called by the Perl core (== not by the user of the object) are
		460	usually in upper case letters and to avoid collisions with the C<to_json>
		461	function.
		462
		463	This setting does not yet influence C<decode> in any way, but in the
		464	future, global hooks might get installed that influence C<decode> and are
		465	enabled by this setting.
		466
		467	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		468	to do when a blessed object is found.
		469
		470	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		471
		472	When C<$coderef> is specified, it will be called from C<decode> each
		473	time it decodes a JSON object. The only argument is a reference to the
		474	newly-created hash. If the code references returns a single scalar (which
		475	need not be a reference), this value (i.e. a copy of that scalar to avoid
		476	aliasing) is inserted into the deserialised data structure. If it returns
		477	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		478	original deserialised hash will be inserted. This setting can slow down
		479	decoding considerably.
		480
		481	When C<$coderef> is omitted or undefined, any existing callback will
		482	be removed and C<decode> will not change the deserialised hash in any
		483	way.
		484
		485	Example, convert all JSON objects into the integer 5:
		486
		487	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		488	# returns [5]
		489	$js->decode ('[{}]')
		490	# throw an exception because allow_nonref is not enabled
		491	# so a lone 5 is not allowed.
		492	$js->decode ('{"a":1, "b":2}');
		493
		494	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		495
		496	Works remotely similar to C<filter_json_object>, but is only called for
		497	JSON objects having a single key named C<$key>.
		498
		499	This C<$coderef> is called before the one specified via
		500	C<filter_json_object>, if any. It gets passed the single value in the JSON
		501	object. If it returns a single value, it will be inserted into the data
		502	structure. If it returns nothing (not even C<undef> but the empty list),
		503	the callback from C<filter_json_object> will be called next, as if no
		504	single-key callback were specified.
		505
		506	If C<$coderef> is omitted or undefined, the corresponding callback will be
		507	disabled. There can only ever be one callback for a given key.
		508
		509	As this callback gets called less often then the C<filter_json_object>
		510	one, decoding speed will not usually suffer as much. Therefore, single-key
		511	objects make excellent targets to serialise Perl objects into, especially
		512	as single-key JSON objects are as close to the type-tagged value concept
		513	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		514	support this in any way, so you need to make sure your data never looks
		515	like a serialised Perl hash.
		516
		517	Typical names for the single object key are C<__class_whatever__>, or
		518	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		519	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		520	with real hashes.
		521
		522	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		523	into the corresponding C<< $WIDGET{<id>} >> object:
		524
		525	# return whatever is in $WIDGET{5}:
		526	JSON::XS
		527	->new
		528	->filter_json_single_key_object (__widget__ => sub {
		529	$WIDGET{ $_[0] }
		530	})
		531	->decode ('{"__widget__": 5')
		532
		533	# this can be used with a TO_JSON method in some "widget" class
		534	# for serialisation to json:
		535	sub WidgetBase::TO_JSON {
		536	my ($self) = @_;
		537
		538	unless ($self->{id}) {
		539	$self->{id} = ..get..some..id..;
		540	$WIDGET{$self->{id}} = $self;
		541	}
		542
		543	{ __widget__ => $self->{id} }
		544	}
		545
229	=item $json = $json->shrink ([$enable])	546	=item $json = $json->shrink ([$enable])
230		547
		548	=item $enabled = $json->get_shrink
		549
231	Perl usually over-allocates memory a bit when allocating space for	550	Perl usually over-allocates memory a bit when allocating space for
232	strings. This flag optionally resizes strings generated by either	551	strings. This flag optionally resizes strings generated by either
233	C<encode> or C<decode> to their minimum size possible. This can save	552	C<encode> or C<decode> to their minimum size possible. This can save
234	memory when your JSON strings are either very very long or you have many	553	memory when your JSON texts are either very very long or you have many
235	short strings. It will also try to downgrade any strings to octet-form	554	short strings. It will also try to downgrade any strings to octet-form
236	if possible: perl stores strings internally either in an encoding called	555	if possible: perl stores strings internally either in an encoding called
237	UTF-X or in octet-form. The latter cannot store everything but uses less	556	UTF-X or in octet-form. The latter cannot store everything but uses less
238	space in general.	557	space in general (and some buggy Perl or C code might even rely on that
		558	internal representation being used).
239		559
		560	The actual definition of what shrink does might change in future versions,
		561	but it will always try to save space at the expense of time.
		562
240	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	563	If C<$enable> is true (or missing), the string returned by C<encode> will
241	while all strings generated by C<decode> will also be shrunk-to-fit.	564	be shrunk-to-fit, while all strings generated by C<decode> will also be
		565	shrunk-to-fit.
242		566
243	If C<$enable> is false, then the normal perl allocation algorithms are used.	567	If C<$enable> is false, then the normal perl allocation algorithms are used.
244	If you work with your data, then this is likely to be faster.	568	If you work with your data, then this is likely to be faster.
245		569
246	In the future, this setting might control other things, such as converting	570	In the future, this setting might control other things, such as converting
247	strings that look like integers or floats into integers or floats	571	strings that look like integers or floats into integers or floats
248	internally (there is no difference on the Perl level), saving space.	572	internally (there is no difference on the Perl level), saving space.
249		573
		574	=item $json = $json->max_depth ([$maximum_nesting_depth])
		575
		576	=item $max_depth = $json->get_max_depth
		577
		578	Sets the maximum nesting level (default C<512>) accepted while encoding
		579	or decoding. If the JSON text or Perl data structure has an equal or
		580	higher nesting level then this limit, then the encoder and decoder will
		581	stop and croak at that point.
		582
		583	Nesting level is defined by number of hash- or arrayrefs that the encoder
		584	needs to traverse to reach a given point or the number of C<{> or C<[>
		585	characters without their matching closing parenthesis crossed to reach a
		586	given character in a string.
		587
		588	Setting the maximum depth to one disallows any nesting, so that ensures
		589	that the object is only a single hash/object or array.
		590
		591	The argument to C<max_depth> will be rounded up to the next highest power
		592	of two. If no argument is given, the highest possible setting will be
		593	used, which is rarely useful.
		594
		595	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		596
		597	=item $json = $json->max_size ([$maximum_string_size])
		598
		599	=item $max_size = $json->get_max_size
		600
		601	Set the maximum length a JSON text may have (in bytes) where decoding is
		602	being attempted. The default is C<0>, meaning no limit. When C<decode>
		603	is called on a string longer then this number of characters it will not
		604	attempt to decode the string but throw an exception. This setting has no
		605	effect on C<encode> (yet).
		606
		607	The argument to C<max_size> will be rounded up to the next B<highest>
		608	power of two (so may be more than requested). If no argument is given, the
		609	limit check will be deactivated (same as when C<0> is specified).
		610
		611	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		612
250	=item $json_string = $json->encode ($perl_scalar)	613	=item $json_text = $json->encode ($perl_scalar)
251		614
252	Converts the given Perl data structure (a simple scalar or a reference	615	Converts the given Perl data structure (a simple scalar or a reference
253	to a hash or array) to its JSON representation. Simple scalars will be	616	to a hash or array) to its JSON representation. Simple scalars will be
254	converted into JSON string or number sequences, while references to arrays	617	converted into JSON string or number sequences, while references to arrays
255	become JSON arrays and references to hashes become JSON objects. Undefined	618	become JSON arrays and references to hashes become JSON objects. Undefined
256	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	619	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
257	nor C<false> values will be generated.	620	nor C<false> values will be generated.
258		621
259	=item $perl_scalar = $json->decode ($json_string)	622	=item $perl_scalar = $json->decode ($json_text)
260		623
261	The opposite of C<encode>: expects a JSON string and tries to parse it,	624	The opposite of C<encode>: expects a JSON text and tries to parse it,
262	returning the resulting simple scalar or reference. Croaks on error.	625	returning the resulting simple scalar or reference. Croaks on error.
263		626
264	JSON numbers and strings become simple Perl scalars. JSON arrays become	627	JSON numbers and strings become simple Perl scalars. JSON arrays become
265	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	628	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
266	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	629	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
267		630
		631	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		632
		633	This works like the C<decode> method, but instead of raising an exception
		634	when there is trailing garbage after the first JSON object, it will
		635	silently stop parsing there and return the number of characters consumed
		636	so far.
		637
		638	This is useful if your JSON texts are not delimited by an outer protocol
		639	(which is not the brightest thing to do in the first place) and you need
		640	to know where the JSON text ends.
		641
		642	JSON::XS->new->decode_prefix ("[1] the tail")
		643	=> ([], 3)
		644
268	=back	645	=back
		646
269		647
270	=head1 MAPPING	648	=head1 MAPPING
271		649
272	This section describes how JSON::XS maps Perl values to JSON values and	650	This section describes how JSON::XS maps Perl values to JSON values and
273	vice versa. These mappings are designed to "do the right thing" in most	651	vice versa. These mappings are designed to "do the right thing" in most
274	circumstances automatically, preserving round-tripping characteristics	652	circumstances automatically, preserving round-tripping characteristics
275	(what you put in comes out as something equivalent).	653	(what you put in comes out as something equivalent).
276		654
277	For the more enlightened: note that in the following descriptions,	655	For the more enlightened: note that in the following descriptions,
278	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	656	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
279	refers to the abstract Perl language itself.	657	refers to the abstract Perl language itself.
280		658
		659
281	=head2 JSON -> PERL	660	=head2 JSON -> PERL
282		661
283	=over 4	662	=over 4
284		663
285	=item object	664	=item object
286		665
287	A JSON object becomes a reference to a hash in Perl. No ordering of object	666	A JSON object becomes a reference to a hash in Perl. No ordering of object
288	keys is preserved.	667	keys is preserved (JSON does not preserve object key ordering itself).
289		668
290	=item array	669	=item array
291		670
292	A JSON array becomes a reference to an array in Perl.	671	A JSON array becomes a reference to an array in Perl.
293		672
…		…
297	are represented by the same codepoints in the Perl string, so no manual	676	are represented by the same codepoints in the Perl string, so no manual
298	decoding is necessary.	677	decoding is necessary.
299		678
300	=item number	679	=item number
301		680
302	A JSON number becomes either an integer or numeric (floating point)	681	A JSON number becomes either an integer, numeric (floating point) or
303	scalar in perl, depending on its range and any fractional parts. On the	682	string scalar in perl, depending on its range and any fractional parts. On
304	Perl level, there is no difference between those as Perl handles all the	683	the Perl level, there is no difference between those as Perl handles all
305	conversion details, but an integer may take slightly less memory and might	684	the conversion details, but an integer may take slightly less memory and
306	represent more values exactly than (floating point) numbers.	685	might represent more values exactly than (floating point) numbers.
		686
		687	If the number consists of digits only, JSON::XS will try to represent
		688	it as an integer value. If that fails, it will try to represent it as
		689	a numeric (floating point) value if that is possible without loss of
		690	precision. Otherwise it will preserve the number as a string value.
		691
		692	Numbers containing a fractional or exponential part will always be
		693	represented as numeric (floating point) values, possibly at a loss of
		694	precision.
		695
		696	This might create round-tripping problems as numbers might become strings,
		697	but as Perl is typeless there is no other way to do it.
307		698
308	=item true, false	699	=item true, false
309		700
310	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	701	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
311	this process. Future versions might represent those values differently,	702	respectively. They are overloaded to act almost exactly like the numbers
312	but they will be guarenteed to act like these integers would normally in	703	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
313	Perl.	704	the C<JSON::XS::is_bool> function.
314		705
315	=item null	706	=item null
316		707
317	A JSON null atom becomes C<undef> in Perl.	708	A JSON null atom becomes C<undef> in Perl.
318		709
319	=back	710	=back
		711
320		712
321	=head2 PERL -> JSON	713	=head2 PERL -> JSON
322		714
323	The mapping from Perl to JSON is slightly more difficult, as Perl is a	715	The mapping from Perl to JSON is slightly more difficult, as Perl is a
324	truly typeless language, so we can only guess which JSON type is meant by	716	truly typeless language, so we can only guess which JSON type is meant by
…		…
327	=over 4	719	=over 4
328		720
329	=item hash references	721	=item hash references
330		722
331	Perl hash references become JSON objects. As there is no inherent ordering	723	Perl hash references become JSON objects. As there is no inherent ordering
332	in hash keys, they will usually be encoded in a pseudo-random order that	724	in hash keys (or JSON objects), they will usually be encoded in a
333	can change between runs of the same program but stays generally the same	725	pseudo-random order that can change between runs of the same program but
334	within the single run of a program. JSON::XS can optionally sort the hash	726	stays generally the same within a single run of a program. JSON::XS can
335	keys (determined by the I<canonical> flag), so the same datastructure	727	optionally sort the hash keys (determined by the I<canonical> flag), so
336	will serialise to the same JSON text (given same settings and version of	728	the same datastructure will serialise to the same JSON text (given same
337	JSON::XS), but this incurs a runtime overhead.	729	settings and version of JSON::XS), but this incurs a runtime overhead
		730	and is only rarely useful, e.g. when you want to compare some JSON text
		731	against another for equality.
338		732
339	=item array references	733	=item array references
340		734
341	Perl array references become JSON arrays.	735	Perl array references become JSON arrays.
		736
		737	=item other references
		738
		739	Other unblessed references are generally not allowed and will cause an
		740	exception to be thrown, except for references to the integers C<0> and
		741	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		742	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		743
		744	to_json [\0,JSON::XS::true] # yields [false,true]
		745
		746	=item JSON::XS::true, JSON::XS::false
		747
		748	These special values become JSON true and JSON false values,
		749	respectively. You can also use C<\1> and C<\0> directly if you want.
342		750
343	=item blessed objects	751	=item blessed objects
344		752
345	Blessed objects are not allowed. JSON::XS currently tries to encode their	753	Blessed objects are not allowed. JSON::XS currently tries to encode their
346	underlying representation (hash- or arrayref), but this behaviour might	754	underlying representation (hash- or arrayref), but this behaviour might
…		…
363	to_json [$value] # yields ["5"]	771	to_json [$value] # yields ["5"]
364		772
365	# undef becomes null	773	# undef becomes null
366	to_json [undef] # yields [null]	774	to_json [undef] # yields [null]
367		775
368	You can force the type to be a string by stringifying it:	776	You can force the type to be a JSON string by stringifying it:
369		777
370	my $x = 3.1; # some variable containing a number	778	my $x = 3.1; # some variable containing a number
371	"$x"; # stringified	779	"$x"; # stringified
372	$x .= ""; # another, more awkward way to stringify	780	$x .= ""; # another, more awkward way to stringify
373	print $x; # perl does it for you, too, quite often	781	print $x; # perl does it for you, too, quite often
374		782
375	You can force the type to be a number by numifying it:	783	You can force the type to be a JSON number by numifying it:
376		784
377	my $x = "3"; # some variable containing a string	785	my $x = "3"; # some variable containing a string
378	$x += 0; # numify it, ensuring it will be dumped as a number	786	$x += 0; # numify it, ensuring it will be dumped as a number
379	$x *= 1; # same thing, the choise is yours.	787	$x *= 1; # same thing, the choice is yours.
380		788
381	You can not currently output JSON booleans or force the type in other,	789	You can not currently force the type in other, less obscure, ways. Tell me
382	less obscure, ways. Tell me if you need this capability.	790	if you need this capability.
383
384	=item circular data structures
385
386	Those will be encoded until memory or stackspace runs out.
387		791
388	=back	792	=back
		793
389		794
390	=head1 COMPARISON	795	=head1 COMPARISON
391		796
392	As already mentioned, this module was created because none of the existing	797	As already mentioned, this module was created because none of the existing
393	JSON modules could be made to work correctly. First I will describe the	798	JSON modules could be made to work correctly. First I will describe the
…		…
399		804
400	=item JSON 1.07	805	=item JSON 1.07
401		806
402	Slow (but very portable, as it is written in pure Perl).	807	Slow (but very portable, as it is written in pure Perl).
403		808
404	Undocumented/buggy Unicode handling (how JSON handles unicode values is	809	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
405	undocumented. One can get far by feeding it unicode strings and doing	810	undocumented. One can get far by feeding it Unicode strings and doing
406	en-/decoding oneself, but unicode escapes are not working properly).	811	en-/decoding oneself, but Unicode escapes are not working properly).
407		812
408	No roundtripping (strings get clobbered if they look like numbers, e.g.	813	No round-tripping (strings get clobbered if they look like numbers, e.g.
409	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	814	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
410	decode into the number 2.	815	decode into the number 2.
411		816
412	=item JSON::PC 0.01	817	=item JSON::PC 0.01
413		818
414	Very fast.	819	Very fast.
415		820
416	Undocumented/buggy Unicode handling.	821	Undocumented/buggy Unicode handling.
417		822
418	No roundtripping.	823	No round-tripping.
419		824
420	Has problems handling many Perl values (e.g. regex results and other magic	825	Has problems handling many Perl values (e.g. regex results and other magic
421	values will make it croak).	826	values will make it croak).
422		827
423	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	828	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
424	which is not a valid JSON string.	829	which is not a valid JSON text.
425		830
426	Unmaintained (maintainer unresponsive for many months, bugs are not	831	Unmaintained (maintainer unresponsive for many months, bugs are not
427	getting fixed).	832	getting fixed).
428		833
429	=item JSON::Syck 0.21	834	=item JSON::Syck 0.21
…		…
431	Very buggy (often crashes).	836	Very buggy (often crashes).
432		837
433	Very inflexible (no human-readable format supported, format pretty much	838	Very inflexible (no human-readable format supported, format pretty much
434	undocumented. I need at least a format for easy reading by humans and a	839	undocumented. I need at least a format for easy reading by humans and a
435	single-line compact format for use in a protocol, and preferably a way to	840	single-line compact format for use in a protocol, and preferably a way to
436	generate ASCII-only JSON strings).	841	generate ASCII-only JSON texts).
437		842
438	Completely broken (and confusingly documented) Unicode handling (unicode	843	Completely broken (and confusingly documented) Unicode handling (Unicode
439	escapes are not working properly, you need to set ImplicitUnicode to	844	escapes are not working properly, you need to set ImplicitUnicode to
440	I<different> values on en- and decoding to get symmetric behaviour).	845	I<different> values on en- and decoding to get symmetric behaviour).
441		846
442	No roundtripping (simple cases work, but this depends on wether the scalar	847	No round-tripping (simple cases work, but this depends on whether the scalar
443	value was used in a numeric context or not).	848	value was used in a numeric context or not).
444		849
445	Dumping hashes may skip hash values depending on iterator state.	850	Dumping hashes may skip hash values depending on iterator state.
446		851
447	Unmaintained (maintainer unresponsive for many months, bugs are not	852	Unmaintained (maintainer unresponsive for many months, bugs are not
448	getting fixed).	853	getting fixed).
449		854
450	Does not check input for validity (i.e. will accept non-JSON input and	855	Does not check input for validity (i.e. will accept non-JSON input and
451	return "something" instead of raising an exception. This is a security	856	return "something" instead of raising an exception. This is a security
452	issue: imagine two banks transfering money between each other using	857	issue: imagine two banks transferring money between each other using
453	JSON. One bank might parse a given non-JSON request and deduct money,	858	JSON. One bank might parse a given non-JSON request and deduct money,
454	while the other might reject the transaction with a syntax error. While a	859	while the other might reject the transaction with a syntax error. While a
455	good protocol will at least recover, that is extra unnecessary work and	860	good protocol will at least recover, that is extra unnecessary work and
456	the transaction will still not succeed).	861	the transaction will still not succeed).
457		862
458	=item JSON::DWIW 0.04	863	=item JSON::DWIW 0.04
459		864
460	Very fast. Very natural. Very nice.	865	Very fast. Very natural. Very nice.
461		866
462	Undocumented unicode handling (but the best of the pack. Unicode escapes	867	Undocumented Unicode handling (but the best of the pack. Unicode escapes
463	still don't get parsed properly).	868	still don't get parsed properly).
464		869
465	Very inflexible.	870	Very inflexible.
466		871
467	No roundtripping.	872	No round-tripping.
468		873
469	Does not generate valid JSON (key strings are often unquoted, empty keys	874	Does not generate valid JSON texts (key strings are often unquoted, empty keys
470	result in nothing being output)	875	result in nothing being output)
471		876
472	Does not check input for validity.	877	Does not check input for validity.
473		878
474	=back	879	=back
		880
		881
		882	=head2 JSON and YAML
		883
		884	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		885	however, a mass hysteria and very far from the truth. In general, there is
		886	no way to configure JSON::XS to output a data structure as valid YAML.
		887
		888	If you really must use JSON::XS to generate YAML, you should use this
		889	algorithm (subject to change in future versions):
		890
		891	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		892	my $yaml = $to_yaml->encode ($ref) . "\n";
		893
		894	This will usually generate JSON texts that also parse as valid
		895	YAML. Please note that YAML has hardcoded limits on (simple) object key
		896	lengths that JSON doesn't have, so you should make sure that your hash
		897	keys are noticeably shorter than the 1024 characters YAML allows.
		898
		899	There might be other incompatibilities that I am not aware of. In general
		900	you should not try to generate YAML with a JSON generator or vice versa,
		901	or try to parse JSON with a YAML parser or vice versa: chances are high
		902	that you will run into severe interoperability problems.
		903
475		904
476	=head2 SPEED	905	=head2 SPEED
477		906
478	It seems that JSON::XS is surprisingly fast, as shown in the following	907	It seems that JSON::XS is surprisingly fast, as shown in the following
479	tables. They have been generated with the help of the C<eg/bench> program	908	tables. They have been generated with the help of the C<eg/bench> program
480	in the JSON::XS distribution, to make it easy to compare on your own	909	in the JSON::XS distribution, to make it easy to compare on your own
481	system.	910	system.
482		911
483	First is a comparison between various modules using a very simple JSON	912	First comes a comparison between various modules using a very short
		913	single-line JSON string:
		914
		915	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		916	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		917
484	string, showing the number of encodes/decodes per second (JSON::XS is	918	It shows the number of encodes/decodes per second (JSON::XS uses
485	the functional interface, while JSON::XS/2 is the OO interface with	919	the functional interface, while JSON::XS/2 uses the OO interface
486	pretty-printing and hashkey sorting enabled).	920	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		921	shrink). Higher is better:
487		922
488	module \| encode \| decode \|	923	module \| encode \| decode \|
489	-----------\|------------\|------------\|	924	-----------\|------------\|------------\|
490	JSON \| 14006 \| 6820 \|	925	JSON 1.x \| 4990.842 \| 4088.813 \|
491	JSON::DWIW \| 200937 \| 120386 \|	926	JSON::DWIW \| 51653.990 \| 71575.154 \|
492	JSON::PC \| 85065 \| 129366 \|	927	JSON::PC \| 65948.176 \| 74631.744 \|
493	JSON::Syck \| 59898 \| 44232 \|	928	JSON::PP \| 8931.652 \| 3817.168 \|
494	JSON::XS \| 1171478 \| 342435 \|	929	JSON::Syck \| 24877.248 \| 27776.848 \|
495	JSON::XS/2 \| 730760 \| 328714 \|	930	JSON::XS \| 388361.481 \| 227951.304 \|
		931	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		932	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		933	Storable \| 16500.016 \| 135300.129 \|
496	-----------+------------+------------+	934	-----------+------------+------------+
497		935
498	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	936	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		937	about three times faster on decoding, and over forty times faster
499	times faster than JSON, even with pretty-printing and key sorting.	938	than JSON, even with pretty-printing and key sorting. It also compares
		939	favourably to Storable for small amounts of data.
500		940
501	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	941	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
502	search API (http://nanoref.com/yahooapis/mgPdGg):	942	search API (http://nanoref.com/yahooapis/mgPdGg):
503		943
504	module \| encode \| decode \|	944	module \| encode \| decode \|
505	-----------\|------------\|------------\|	945	-----------\|------------\|------------\|
506	JSON \| 673 \| 38 \|	946	JSON 1.x \| 55.260 \| 34.971 \|
507	JSON::DWIW \| 5271 \| 770 \|	947	JSON::DWIW \| 825.228 \| 1082.513 \|
508	JSON::PC \| 9901 \| 2491 \|	948	JSON::PC \| 3571.444 \| 2394.829 \|
509	JSON::Syck \| 2360 \| 786 \|	949	JSON::PP \| 210.987 \| 32.574 \|
510	JSON::XS \| 37398 \| 3202 \|	950	JSON::Syck \| 552.551 \| 787.544 \|
511	JSON::XS/2 \| 13765 \| 3153 \|	951	JSON::XS \| 5780.463 \| 4854.519 \|
		952	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		953	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		954	Storable \| 4445.002 \| 5235.027 \|
512	-----------+------------+------------+	955	-----------+------------+------------+
513		956
514	Again, JSON::XS leads by far in the encoding case, while still beating	957	Again, JSON::XS leads by far (except for Storable which non-surprisingly
515	every other module in the decoding case.	958	decodes faster).
516		959
517	Last example is an almost 8MB large hash with many large binary values	960	On large strings containing lots of high Unicode characters, some modules
518	(PNG files), resulting in a lot of escaping:	961	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		962	will be broken due to missing (or wrong) Unicode handling. Others refuse
		963	to decode or encode properly, so it was impossible to prepare a fair
		964	comparison table for that case.
519		965
520	=head1 RESOURCE LIMITS
521		966
522	JSON::XS does not impose any limits on the size of JSON texts or Perl	967	=head1 SECURITY CONSIDERATIONS
523	values they represent - if your machine cna handle it, JSON::XS will	968
524	encode or decode it. Future versions might optionally impose structure	969	When you are using JSON in a protocol, talking to untrusted potentially
525	depth and memory use resource limits.	970	hostile creatures requires relatively few measures.
		971
		972	First of all, your JSON decoder should be secure, that is, should not have
		973	any buffer overflows. Obviously, this module should ensure that and I am
		974	trying hard on making that true, but you never know.
		975
		976	Second, you need to avoid resource-starving attacks. That means you should
		977	limit the size of JSON texts you accept, or make sure then when your
		978	resources run out, that's just fine (e.g. by using a separate process that
		979	can crash safely). The size of a JSON text in octets or characters is
		980	usually a good indication of the size of the resources required to decode
		981	it into a Perl structure. While JSON::XS can check the size of the JSON
		982	text, it might be too late when you already have it in memory, so you
		983	might want to check the size before you accept the string.
		984
		985	Third, JSON::XS recurses using the C stack when decoding objects and
		986	arrays. The C stack is a limited resource: for instance, on my amd64
		987	machine with 8MB of stack size I can decode around 180k nested arrays but
		988	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		989	to free the temporary). If that is exceeded, the program crashes. to be
		990	conservative, the default nesting limit is set to 512. If your process
		991	has a smaller stack, you should adjust this setting accordingly with the
		992	C<max_depth> method.
		993
		994	And last but least, something else could bomb you that I forgot to think
		995	of. In that case, you get to keep the pieces. I am always open for hints,
		996	though...
		997
		998	If you are using JSON::XS to return packets to consumption
		999	by JavaScript scripts in a browser you should have a look at
		1000	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1001	you are vulnerable to some common attack vectors (which really are browser
		1002	design bugs, but it is still you who will have to deal with it, as major
		1003	browser developers care only for features, not about doing security
		1004	right).
		1005
		1006
		1007	=head1 THREADS
		1008
		1009	This module is I<not> guaranteed to be thread safe and there are no
		1010	plans to change this until Perl gets thread support (as opposed to the
		1011	horribly slow so-called "threads" which are simply slow and bloated
		1012	process simulations - use fork, its I<much> faster, cheaper, better).
		1013
		1014	(It might actually work, but you have been warned).
		1015
526		1016
527	=head1 BUGS	1017	=head1 BUGS
528		1018
529	While the goal of this module is to be correct, that unfortunately does	1019	While the goal of this module is to be correct, that unfortunately does
530	not mean its bug-free, only that I think its design is bug-free. It is	1020	not mean its bug-free, only that I think its design is bug-free. It is
531	still very young and not well-tested. If you keep reporting bugs they will	1021	still relatively early in its development. If you keep reporting bugs they
532	be fixed swiftly, though.	1022	will be fixed swiftly, though.
		1023
		1024	Please refrain from using rt.cpan.org or any other bug reporting
		1025	service. I put the contact address into my modules for a reason.
533		1026
534	=cut	1027	=cut
		1028
		1029	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1030	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1031
		1032	sub true() { $true }
		1033	sub false() { $false }
		1034
		1035	sub is_bool($) {
		1036	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1037	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1038	}
		1039
		1040	XSLoader::load "JSON::XS", $VERSION;
		1041
		1042	package JSON::XS::Boolean;
		1043
		1044	use overload
		1045	"0+" => sub { ${$_[0]} },
		1046	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1047	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1048	fallback => 1;
535		1049
536	1;	1050	1;
537		1051
538	=head1 AUTHOR	1052	=head1 AUTHOR
539		1053

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Comparing JSON-XS/XS.pm (file contents): Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs. Revision 1.76 by root, Sun Dec 2 15:34:13 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs.
Revision 1.76 by root, Sun Dec 2 15:34:13 2007 UTC