[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 1.73 by root, Sun Nov 25 19:36:54 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 = '1.6';
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.
151		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);
		279
152	=item $json = $json->pretty ([$enable])	280	=item $json = $json->pretty ([$enable])
		281
		282	=item $enabled = $json->get_pretty
153		283
154	This enables (or disables) all of the C<indent>, C<space_before> and	284	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	285	C<space_after> (and in the future possibly more) flags in one call to
156	generate the most readable (or most compact) form possible.	286	generate the most readable (or most compact) form possible.
		287
		288	Example, pretty-print some simple structure:
157		289
158	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	290	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
159	=>	291	=>
160	{	292	{
161	"a" : [	293	"a" : [
…		…
164	]	296	]
165	}	297	}
166		298
167	=item $json = $json->indent ([$enable])	299	=item $json = $json->indent ([$enable])
168		300
		301	=item $enabled = $json->get_indent
		302
169	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	303	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
170	format as output, putting every array member or object/hash key-value pair	304	format as output, putting every array member or object/hash key-value pair
171	into its own line, identing them properly.	305	into its own line, indenting them properly.
172		306
173	If C<$enable> is false, no newlines or indenting will be produced, and the	307	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>.	308	resulting JSON text is guaranteed not to contain any C<newlines>.
175		309
176	This setting has no effect when decoding JSON strings.	310	This setting has no effect when decoding JSON texts.
177		311
178	=item $json = $json->space_before ([$enable])	312	=item $json = $json->space_before ([$enable])
		313
		314	=item $enabled = $json->get_space_before
179		315
180	If C<$enable> is true (or missing), then the C<encode> method will add an extra	316	If C<$enable> is true (or missing), then the C<encode> method will add an extra
181	optional space before the C<:> separating keys from values in JSON objects.	317	optional space before the C<:> separating keys from values in JSON objects.
182		318
183	If C<$enable> is false, then the C<encode> method will not add any extra	319	If C<$enable> is false, then the C<encode> method will not add any extra
184	space at those places.	320	space at those places.
185		321
186	This setting has no effect when decoding JSON strings. You will also most	322	This setting has no effect when decoding JSON texts. You will also
187	likely combine this setting with C<space_after>.	323	most likely combine this setting with C<space_after>.
		324
		325	Example, space_before enabled, space_after and indent disabled:
		326
		327	{"key" :"value"}
188		328
189	=item $json = $json->space_after ([$enable])	329	=item $json = $json->space_after ([$enable])
		330
		331	=item $enabled = $json->get_space_after
190		332
191	If C<$enable> is true (or missing), then the C<encode> method will add an extra	333	If C<$enable> is true (or missing), then the C<encode> method will add an extra
192	optional space after the C<:> separating keys from values in JSON objects	334	optional space after the C<:> separating keys from values in JSON objects
193	and extra whitespace after the C<,> separating key-value pairs and array	335	and extra whitespace after the C<,> separating key-value pairs and array
194	members.	336	members.
195		337
196	If C<$enable> is false, then the C<encode> method will not add any extra	338	If C<$enable> is false, then the C<encode> method will not add any extra
197	space at those places.	339	space at those places.
198		340
199	This setting has no effect when decoding JSON strings.	341	This setting has no effect when decoding JSON texts.
		342
		343	Example, space_before and indent disabled, space_after enabled:
		344
		345	{"key": "value"}
		346
		347	=item $json = $json->relaxed ([$enable])
		348
		349	=item $enabled = $json->get_relaxed
		350
		351	If C<$enable> is true (or missing), then C<decode> will accept some
		352	extensions to normal JSON syntax (see below). C<encode> will not be
		353	affected in anyway. I<Be aware that this option makes you accept invalid
		354	JSON texts as if they were valid!>. I suggest only to use this option to
		355	parse application-specific files written by humans (configuration files,
		356	resource files etc.)
		357
		358	If C<$enable> is false (the default), then C<decode> will only accept
		359	valid JSON texts.
		360
		361	Currently accepted extensions are:
		362
		363	=over 4
		364
		365	=item * list items can have an end-comma
		366
		367	JSON I<separates> array elements and key-value pairs with commas. This
		368	can be annoying if you write JSON texts manually and want to be able to
		369	quickly append elements, so this extension accepts comma at the end of
		370	such items not just between them:
		371
		372	[
		373	1,
		374	2, <- this comma not normally allowed
		375	]
		376	{
		377	"k1": "v1",
		378	"k2": "v2", <- this comma not normally allowed
		379	}
		380
		381	=item * shell-style '#'-comments
		382
		383	Whenever JSON allows whitespace, shell-style comments are additionally
		384	allowed. They are terminated by the first carriage-return or line-feed
		385	character, after which more white-space and comments are allowed.
		386
		387	[
		388	1, # this comment not allowed in JSON
		389	# neither this one...
		390	]
		391
		392	=back
200		393
201	=item $json = $json->canonical ([$enable])	394	=item $json = $json->canonical ([$enable])
		395
		396	=item $enabled = $json->get_canonical
202		397
203	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	398	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
204	by sorting their keys. This is adding a comparatively high overhead.	399	by sorting their keys. This is adding a comparatively high overhead.
205		400
206	If C<$enable> is false, then the C<encode> method will output key-value	401	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	402	pairs in the order Perl stores them (which will likely change between runs
208	of the same script).	403	of the same script).
209		404
210	This option is useful if you want the same data structure to be encoded as	405	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,	406	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,	407	the same hash might be encoded differently even if contains the same data,
213	as key-value pairs have no inherent ordering in Perl.	408	as key-value pairs have no inherent ordering in Perl.
214		409
215	This setting has no effect when decoding JSON strings.	410	This setting has no effect when decoding JSON texts.
216		411
217	=item $json = $json->allow_nonref ([$enable])	412	=item $json = $json->allow_nonref ([$enable])
		413
		414	=item $enabled = $json->get_allow_nonref
218		415
219	If C<$enable> is true (or missing), then the C<encode> method can convert a	416	If C<$enable> is true (or missing), then the C<encode> method can convert a
220	non-reference into its corresponding string, number or null JSON value,	417	non-reference into its corresponding string, number or null JSON value,
221	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	418	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
222	values instead of croaking.	419	values instead of croaking.
223		420
224	If C<$enable> is false, then the C<encode> method will croak if it isn't	421	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	422	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	423	or array. Likewise, C<decode> will croak if given something that is not a
227	JSON object or array.	424	JSON object or array.
228		425
		426	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		427	resulting in an invalid JSON text:
		428
		429	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		430	=> "Hello, World!"
		431
		432	=item $json = $json->allow_blessed ([$enable])
		433
		434	=item $enabled = $json->get_allow_bless
		435
		436	If C<$enable> is true (or missing), then the C<encode> method will not
		437	barf when it encounters a blessed reference. Instead, the value of the
		438	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		439	disabled or no C<to_json> method found) or a representation of the
		440	object (C<convert_blessed> enabled and C<to_json> method found) is being
		441	encoded. Has no effect on C<decode>.
		442
		443	If C<$enable> is false (the default), then C<encode> will throw an
		444	exception when it encounters a blessed object.
		445
		446	=item $json = $json->convert_blessed ([$enable])
		447
		448	=item $enabled = $json->get_convert_blessed
		449
		450	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		451	blessed object, will check for the availability of the C<TO_JSON> method
		452	on the object's class. If found, it will be called in scalar context
		453	and the resulting scalar will be encoded instead of the object. If no
		454	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		455	to do.
		456
		457	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		458	returns other blessed objects, those will be handled in the same
		459	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		460	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		461	methods called by the Perl core (== not by the user of the object) are
		462	usually in upper case letters and to avoid collisions with the C<to_json>
		463	function.
		464
		465	This setting does not yet influence C<decode> in any way, but in the
		466	future, global hooks might get installed that influence C<decode> and are
		467	enabled by this setting.
		468
		469	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		470	to do when a blessed object is found.
		471
		472	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		473
		474	When C<$coderef> is specified, it will be called from C<decode> each
		475	time it decodes a JSON object. The only argument is a reference to the
		476	newly-created hash. If the code references returns a single scalar (which
		477	need not be a reference), this value (i.e. a copy of that scalar to avoid
		478	aliasing) is inserted into the deserialised data structure. If it returns
		479	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		480	original deserialised hash will be inserted. This setting can slow down
		481	decoding considerably.
		482
		483	When C<$coderef> is omitted or undefined, any existing callback will
		484	be removed and C<decode> will not change the deserialised hash in any
		485	way.
		486
		487	Example, convert all JSON objects into the integer 5:
		488
		489	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		490	# returns [5]
		491	$js->decode ('[{}]')
		492	# throw an exception because allow_nonref is not enabled
		493	# so a lone 5 is not allowed.
		494	$js->decode ('{"a":1, "b":2}');
		495
		496	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		497
		498	Works remotely similar to C<filter_json_object>, but is only called for
		499	JSON objects having a single key named C<$key>.
		500
		501	This C<$coderef> is called before the one specified via
		502	C<filter_json_object>, if any. It gets passed the single value in the JSON
		503	object. If it returns a single value, it will be inserted into the data
		504	structure. If it returns nothing (not even C<undef> but the empty list),
		505	the callback from C<filter_json_object> will be called next, as if no
		506	single-key callback were specified.
		507
		508	If C<$coderef> is omitted or undefined, the corresponding callback will be
		509	disabled. There can only ever be one callback for a given key.
		510
		511	As this callback gets called less often then the C<filter_json_object>
		512	one, decoding speed will not usually suffer as much. Therefore, single-key
		513	objects make excellent targets to serialise Perl objects into, especially
		514	as single-key JSON objects are as close to the type-tagged value concept
		515	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		516	support this in any way, so you need to make sure your data never looks
		517	like a serialised Perl hash.
		518
		519	Typical names for the single object key are C<__class_whatever__>, or
		520	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		521	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		522	with real hashes.
		523
		524	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		525	into the corresponding C<< $WIDGET{<id>} >> object:
		526
		527	# return whatever is in $WIDGET{5}:
		528	JSON::XS
		529	->new
		530	->filter_json_single_key_object (__widget__ => sub {
		531	$WIDGET{ $_[0] }
		532	})
		533	->decode ('{"__widget__": 5')
		534
		535	# this can be used with a TO_JSON method in some "widget" class
		536	# for serialisation to json:
		537	sub WidgetBase::TO_JSON {
		538	my ($self) = @_;
		539
		540	unless ($self->{id}) {
		541	$self->{id} = ..get..some..id..;
		542	$WIDGET{$self->{id}} = $self;
		543	}
		544
		545	{ __widget__ => $self->{id} }
		546	}
		547
229	=item $json = $json->shrink ([$enable])	548	=item $json = $json->shrink ([$enable])
230		549
		550	=item $enabled = $json->get_shrink
		551
231	Perl usually over-allocates memory a bit when allocating space for	552	Perl usually over-allocates memory a bit when allocating space for
232	strings. This flag optionally resizes strings generated by either	553	strings. This flag optionally resizes strings generated by either
233	C<encode> or C<decode> to their minimum size possible. This can save	554	C<encode> or C<decode> to their minimum size possible. This can save
234	memory when your JSON strings are either very very long or you have many	555	memory when your JSON texts are either very very long or you have many
235	short strings. It will also try to downgrade any strings to octet-form	556	short strings. It will also try to downgrade any strings to octet-form
236	if possible: perl stores strings internally either in an encoding called	557	if possible: perl stores strings internally either in an encoding called
237	UTF-X or in octet-form. The latter cannot store everything but uses less	558	UTF-X or in octet-form. The latter cannot store everything but uses less
238	space in general.	559	space in general (and some buggy Perl or C code might even rely on that
		560	internal representation being used).
239		561
		562	The actual definition of what shrink does might change in future versions,
		563	but it will always try to save space at the expense of time.
		564
240	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	565	If C<$enable> is true (or missing), the string returned by C<encode> will
241	while all strings generated by C<decode> will also be shrunk-to-fit.	566	be shrunk-to-fit, while all strings generated by C<decode> will also be
		567	shrunk-to-fit.
242		568
243	If C<$enable> is false, then the normal perl allocation algorithms are used.	569	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.	570	If you work with your data, then this is likely to be faster.
245		571
246	In the future, this setting might control other things, such as converting	572	In the future, this setting might control other things, such as converting
247	strings that look like integers or floats into integers or floats	573	strings that look like integers or floats into integers or floats
248	internally (there is no difference on the Perl level), saving space.	574	internally (there is no difference on the Perl level), saving space.
249		575
		576	=item $json = $json->max_depth ([$maximum_nesting_depth])
		577
		578	=item $max_depth = $json->get_max_depth
		579
		580	Sets the maximum nesting level (default C<512>) accepted while encoding
		581	or decoding. If the JSON text or Perl data structure has an equal or
		582	higher nesting level then this limit, then the encoder and decoder will
		583	stop and croak at that point.
		584
		585	Nesting level is defined by number of hash- or arrayrefs that the encoder
		586	needs to traverse to reach a given point or the number of C<{> or C<[>
		587	characters without their matching closing parenthesis crossed to reach a
		588	given character in a string.
		589
		590	Setting the maximum depth to one disallows any nesting, so that ensures
		591	that the object is only a single hash/object or array.
		592
		593	The argument to C<max_depth> will be rounded up to the next highest power
		594	of two. If no argument is given, the highest possible setting will be
		595	used, which is rarely useful.
		596
		597	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		598
		599	=item $json = $json->max_size ([$maximum_string_size])
		600
		601	=item $max_size = $json->get_max_size
		602
		603	Set the maximum length a JSON text may have (in bytes) where decoding is
		604	being attempted. The default is C<0>, meaning no limit. When C<decode>
		605	is called on a string longer then this number of characters it will not
		606	attempt to decode the string but throw an exception. This setting has no
		607	effect on C<encode> (yet).
		608
		609	The argument to C<max_size> will be rounded up to the next B<highest>
		610	power of two (so may be more than requested). If no argument is given, the
		611	limit check will be deactivated (same as when C<0> is specified).
		612
		613	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		614
250	=item $json_string = $json->encode ($perl_scalar)	615	=item $json_text = $json->encode ($perl_scalar)
251		616
252	Converts the given Perl data structure (a simple scalar or a reference	617	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	618	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	619	converted into JSON string or number sequences, while references to arrays
255	become JSON arrays and references to hashes become JSON objects. Undefined	620	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>	621	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
257	nor C<false> values will be generated.	622	nor C<false> values will be generated.
258		623
259	=item $perl_scalar = $json->decode ($json_string)	624	=item $perl_scalar = $json->decode ($json_text)
260		625
261	The opposite of C<encode>: expects a JSON string and tries to parse it,	626	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.	627	returning the resulting simple scalar or reference. Croaks on error.
263		628
264	JSON numbers and strings become simple Perl scalars. JSON arrays become	629	JSON numbers and strings become simple Perl scalars. JSON arrays become
265	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	630	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>.	631	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
267		632
		633	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		634
		635	This works like the C<decode> method, but instead of raising an exception
		636	when there is trailing garbage after the first JSON object, it will
		637	silently stop parsing there and return the number of characters consumed
		638	so far.
		639
		640	This is useful if your JSON texts are not delimited by an outer protocol
		641	(which is not the brightest thing to do in the first place) and you need
		642	to know where the JSON text ends.
		643
		644	JSON::XS->new->decode_prefix ("[1] the tail")
		645	=> ([], 3)
		646
268	=back	647	=back
		648
269		649
270	=head1 MAPPING	650	=head1 MAPPING
271		651
272	This section describes how JSON::XS maps Perl values to JSON values and	652	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	653	vice versa. These mappings are designed to "do the right thing" in most
274	circumstances automatically, preserving round-tripping characteristics	654	circumstances automatically, preserving round-tripping characteristics
275	(what you put in comes out as something equivalent).	655	(what you put in comes out as something equivalent).
276		656
277	For the more enlightened: note that in the following descriptions,	657	For the more enlightened: note that in the following descriptions,
278	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	658	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
279	refers to the abstract Perl language itself.	659	refers to the abstract Perl language itself.
280		660
		661
281	=head2 JSON -> PERL	662	=head2 JSON -> PERL
282		663
283	=over 4	664	=over 4
284		665
285	=item object	666	=item object
286		667
287	A JSON object becomes a reference to a hash in Perl. No ordering of object	668	A JSON object becomes a reference to a hash in Perl. No ordering of object
288	keys is preserved.	669	keys is preserved (JSON does not preserve object key ordering itself).
289		670
290	=item array	671	=item array
291		672
292	A JSON array becomes a reference to an array in Perl.	673	A JSON array becomes a reference to an array in Perl.
293		674
…		…
297	are represented by the same codepoints in the Perl string, so no manual	678	are represented by the same codepoints in the Perl string, so no manual
298	decoding is necessary.	679	decoding is necessary.
299		680
300	=item number	681	=item number
301		682
302	A JSON number becomes either an integer or numeric (floating point)	683	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	684	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	685	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	686	the conversion details, but an integer may take slightly less memory and
306	represent more values exactly than (floating point) numbers.	687	might represent more values exactly than (floating point) numbers.
		688
		689	If the number consists of digits only, JSON::XS will try to represent
		690	it as an integer value. If that fails, it will try to represent it as
		691	a numeric (floating point) value if that is possible without loss of
		692	precision. Otherwise it will preserve the number as a string value.
		693
		694	Numbers containing a fractional or exponential part will always be
		695	represented as numeric (floating point) values, possibly at a loss of
		696	precision.
		697
		698	This might create round-tripping problems as numbers might become strings,
		699	but as Perl is typeless there is no other way to do it.
307		700
308	=item true, false	701	=item true, false
309		702
310	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	703	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
311	this process. Future versions might represent those values differently,	704	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	705	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
313	Perl.	706	the C<JSON::XS::is_bool> function.
314		707
315	=item null	708	=item null
316		709
317	A JSON null atom becomes C<undef> in Perl.	710	A JSON null atom becomes C<undef> in Perl.
318		711
319	=back	712	=back
		713
320		714
321	=head2 PERL -> JSON	715	=head2 PERL -> JSON
322		716
323	The mapping from Perl to JSON is slightly more difficult, as Perl is a	717	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	718	truly typeless language, so we can only guess which JSON type is meant by
…		…
327	=over 4	721	=over 4
328		722
329	=item hash references	723	=item hash references
330		724
331	Perl hash references become JSON objects. As there is no inherent ordering	725	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	726	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	727	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	728	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	729	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	730	the same datastructure will serialise to the same JSON text (given same
337	JSON::XS), but this incurs a runtime overhead.	731	settings and version of JSON::XS), but this incurs a runtime overhead
		732	and is only rarely useful, e.g. when you want to compare some JSON text
		733	against another for equality.
338		734
339	=item array references	735	=item array references
340		736
341	Perl array references become JSON arrays.	737	Perl array references become JSON arrays.
		738
		739	=item other references
		740
		741	Other unblessed references are generally not allowed and will cause an
		742	exception to be thrown, except for references to the integers C<0> and
		743	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		744	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		745
		746	to_json [\0,JSON::XS::true] # yields [false,true]
		747
		748	=item JSON::XS::true, JSON::XS::false
		749
		750	These special values become JSON true and JSON false values,
		751	respectively. You can also use C<\1> and C<\0> directly if you want.
342		752
343	=item blessed objects	753	=item blessed objects
344		754
345	Blessed objects are not allowed. JSON::XS currently tries to encode their	755	Blessed objects are not allowed. JSON::XS currently tries to encode their
346	underlying representation (hash- or arrayref), but this behaviour might	756	underlying representation (hash- or arrayref), but this behaviour might
…		…
363	to_json [$value] # yields ["5"]	773	to_json [$value] # yields ["5"]
364		774
365	# undef becomes null	775	# undef becomes null
366	to_json [undef] # yields [null]	776	to_json [undef] # yields [null]
367		777
368	You can force the type to be a string by stringifying it:	778	You can force the type to be a JSON string by stringifying it:
369		779
370	my $x = 3.1; # some variable containing a number	780	my $x = 3.1; # some variable containing a number
371	"$x"; # stringified	781	"$x"; # stringified
372	$x .= ""; # another, more awkward way to stringify	782	$x .= ""; # another, more awkward way to stringify
373	print $x; # perl does it for you, too, quite often	783	print $x; # perl does it for you, too, quite often
374		784
375	You can force the type to be a number by numifying it:	785	You can force the type to be a JSON number by numifying it:
376		786
377	my $x = "3"; # some variable containing a string	787	my $x = "3"; # some variable containing a string
378	$x += 0; # numify it, ensuring it will be dumped as a number	788	$x += 0; # numify it, ensuring it will be dumped as a number
379	$x *= 1; # same thing, the choise is yours.	789	$x *= 1; # same thing, the choice is yours.
380		790
381	You can not currently output JSON booleans or force the type in other,	791	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.	792	if you need this capability.
383
384	=item circular data structures
385
386	Those will be encoded until memory or stackspace runs out.
387		793
388	=back	794	=back
		795
389		796
390	=head1 COMPARISON	797	=head1 COMPARISON
391		798
392	As already mentioned, this module was created because none of the existing	799	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	800	JSON modules could be made to work correctly. First I will describe the
…		…
399		806
400	=item JSON 1.07	807	=item JSON 1.07
401		808
402	Slow (but very portable, as it is written in pure Perl).	809	Slow (but very portable, as it is written in pure Perl).
403		810
404	Undocumented/buggy Unicode handling (how JSON handles unicode values is	811	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
405	undocumented. One can get far by feeding it unicode strings and doing	812	undocumented. One can get far by feeding it Unicode strings and doing
406	en-/decoding oneself, but unicode escapes are not working properly).	813	en-/decoding oneself, but Unicode escapes are not working properly).
407		814
408	No roundtripping (strings get clobbered if they look like numbers, e.g.	815	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	816	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.	817	decode into the number 2.
411		818
412	=item JSON::PC 0.01	819	=item JSON::PC 0.01
413		820
414	Very fast.	821	Very fast.
415		822
416	Undocumented/buggy Unicode handling.	823	Undocumented/buggy Unicode handling.
417		824
418	No roundtripping.	825	No round-tripping.
419		826
420	Has problems handling many Perl values (e.g. regex results and other magic	827	Has problems handling many Perl values (e.g. regex results and other magic
421	values will make it croak).	828	values will make it croak).
422		829
423	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	830	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
424	which is not a valid JSON string.	831	which is not a valid JSON text.
425		832
426	Unmaintained (maintainer unresponsive for many months, bugs are not	833	Unmaintained (maintainer unresponsive for many months, bugs are not
427	getting fixed).	834	getting fixed).
428		835
429	=item JSON::Syck 0.21	836	=item JSON::Syck 0.21
…		…
431	Very buggy (often crashes).	838	Very buggy (often crashes).
432		839
433	Very inflexible (no human-readable format supported, format pretty much	840	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	841	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	842	single-line compact format for use in a protocol, and preferably a way to
436	generate ASCII-only JSON strings).	843	generate ASCII-only JSON texts).
437		844
438	Completely broken (and confusingly documented) Unicode handling (unicode	845	Completely broken (and confusingly documented) Unicode handling (Unicode
439	escapes are not working properly, you need to set ImplicitUnicode to	846	escapes are not working properly, you need to set ImplicitUnicode to
440	I<different> values on en- and decoding to get symmetric behaviour).	847	I<different> values on en- and decoding to get symmetric behaviour).
441		848
442	No roundtripping (simple cases work, but this depends on wether the scalar	849	No round-tripping (simple cases work, but this depends on whether the scalar
443	value was used in a numeric context or not).	850	value was used in a numeric context or not).
444		851
445	Dumping hashes may skip hash values depending on iterator state.	852	Dumping hashes may skip hash values depending on iterator state.
446		853
447	Unmaintained (maintainer unresponsive for many months, bugs are not	854	Unmaintained (maintainer unresponsive for many months, bugs are not
448	getting fixed).	855	getting fixed).
449		856
450	Does not check input for validity (i.e. will accept non-JSON input and	857	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	858	return "something" instead of raising an exception. This is a security
452	issue: imagine two banks transfering money between each other using	859	issue: imagine two banks transferring money between each other using
453	JSON. One bank might parse a given non-JSON request and deduct money,	860	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	861	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	862	good protocol will at least recover, that is extra unnecessary work and
456	the transaction will still not succeed).	863	the transaction will still not succeed).
457		864
458	=item JSON::DWIW 0.04	865	=item JSON::DWIW 0.04
459		866
460	Very fast. Very natural. Very nice.	867	Very fast. Very natural. Very nice.
461		868
462	Undocumented unicode handling (but the best of the pack. Unicode escapes	869	Undocumented Unicode handling (but the best of the pack. Unicode escapes
463	still don't get parsed properly).	870	still don't get parsed properly).
464		871
465	Very inflexible.	872	Very inflexible.
466		873
467	No roundtripping.	874	No round-tripping.
468		875
469	Does not generate valid JSON (key strings are often unquoted, empty keys	876	Does not generate valid JSON texts (key strings are often unquoted, empty keys
470	result in nothing being output)	877	result in nothing being output)
471		878
472	Does not check input for validity.	879	Does not check input for validity.
473		880
474	=back	881	=back
		882
		883
		884	=head2 JSON and YAML
		885
		886	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		887	however, a mass hysteria and very far from the truth. In general, there is
		888	no way to configure JSON::XS to output a data structure as valid YAML.
		889
		890	If you really must use JSON::XS to generate YAML, you should use this
		891	algorithm (subject to change in future versions):
		892
		893	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		894	my $yaml = $to_yaml->encode ($ref) . "\n";
		895
		896	This will usually generate JSON texts that also parse as valid
		897	YAML. Please note that YAML has hardcoded limits on (simple) object key
		898	lengths that JSON doesn't have, so you should make sure that your hash
		899	keys are noticeably shorter than the 1024 characters YAML allows.
		900
		901	There might be other incompatibilities that I am not aware of. In general
		902	you should not try to generate YAML with a JSON generator or vice versa,
		903	or try to parse JSON with a YAML parser or vice versa: chances are high
		904	that you will run into severe interoperability problems.
		905
475		906
476	=head2 SPEED	907	=head2 SPEED
477		908
478	It seems that JSON::XS is surprisingly fast, as shown in the following	909	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	910	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	911	in the JSON::XS distribution, to make it easy to compare on your own
481	system.	912	system.
482		913
483	First is a comparison between various modules using a very simple JSON	914	First comes a comparison between various modules using a very short
		915	single-line JSON string:
		916
		917	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		918	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		919
484	string, showing the number of encodes/decodes per second (JSON::XS is	920	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	921	the functional interface, while JSON::XS/2 uses the OO interface
486	pretty-printing and hashkey sorting enabled).	922	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		923	shrink). Higher is better:
487		924
488	module \| encode \| decode \|	925	module \| encode \| decode \|
489	-----------\|------------\|------------\|	926	-----------\|------------\|------------\|
490	JSON \| 14006 \| 6820 \|	927	JSON 1.x \| 4990.842 \| 4088.813 \|
491	JSON::DWIW \| 200937 \| 120386 \|	928	JSON::DWIW \| 51653.990 \| 71575.154 \|
492	JSON::PC \| 85065 \| 129366 \|	929	JSON::PC \| 65948.176 \| 74631.744 \|
493	JSON::Syck \| 59898 \| 44232 \|	930	JSON::PP \| 8931.652 \| 3817.168 \|
494	JSON::XS \| 1171478 \| 342435 \|	931	JSON::Syck \| 24877.248 \| 27776.848 \|
495	JSON::XS/2 \| 730760 \| 328714 \|	932	JSON::XS \| 388361.481 \| 227951.304 \|
		933	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		934	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		935	Storable \| 16500.016 \| 135300.129 \|
496	-----------+------------+------------+	936	-----------+------------+------------+
497		937
498	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	938	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		939	about three times faster on decoding, and over forty times faster
499	times faster than JSON, even with pretty-printing and key sorting.	940	than JSON, even with pretty-printing and key sorting. It also compares
		941	favourably to Storable for small amounts of data.
500		942
501	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	943	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
502	search API (http://nanoref.com/yahooapis/mgPdGg):	944	search API (http://nanoref.com/yahooapis/mgPdGg):
503		945
504	module \| encode \| decode \|	946	module \| encode \| decode \|
505	-----------\|------------\|------------\|	947	-----------\|------------\|------------\|
506	JSON \| 673 \| 38 \|	948	JSON 1.x \| 55.260 \| 34.971 \|
507	JSON::DWIW \| 5271 \| 770 \|	949	JSON::DWIW \| 825.228 \| 1082.513 \|
508	JSON::PC \| 9901 \| 2491 \|	950	JSON::PC \| 3571.444 \| 2394.829 \|
509	JSON::Syck \| 2360 \| 786 \|	951	JSON::PP \| 210.987 \| 32.574 \|
510	JSON::XS \| 37398 \| 3202 \|	952	JSON::Syck \| 552.551 \| 787.544 \|
511	JSON::XS/2 \| 13765 \| 3153 \|	953	JSON::XS \| 5780.463 \| 4854.519 \|
		954	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		955	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		956	Storable \| 4445.002 \| 5235.027 \|
512	-----------+------------+------------+	957	-----------+------------+------------+
513		958
514	Again, JSON::XS leads by far in the encoding case, while still beating	959	Again, JSON::XS leads by far (except for Storable which non-surprisingly
515	every other module in the decoding case.	960	decodes faster).
516		961
517	Last example is an almost 8MB large hash with many large binary values	962	On large strings containing lots of high Unicode characters, some modules
518	(PNG files), resulting in a lot of escaping:	963	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		964	will be broken due to missing (or wrong) Unicode handling. Others refuse
		965	to decode or encode properly, so it was impossible to prepare a fair
		966	comparison table for that case.
519		967
520	=head1 RESOURCE LIMITS
521		968
522	JSON::XS does not impose any limits on the size of JSON texts or Perl	969	=head1 SECURITY CONSIDERATIONS
523	values they represent - if your machine cna handle it, JSON::XS will	970
524	encode or decode it. Future versions might optionally impose structure	971	When you are using JSON in a protocol, talking to untrusted potentially
525	depth and memory use resource limits.	972	hostile creatures requires relatively few measures.
		973
		974	First of all, your JSON decoder should be secure, that is, should not have
		975	any buffer overflows. Obviously, this module should ensure that and I am
		976	trying hard on making that true, but you never know.
		977
		978	Second, you need to avoid resource-starving attacks. That means you should
		979	limit the size of JSON texts you accept, or make sure then when your
		980	resources run out, that's just fine (e.g. by using a separate process that
		981	can crash safely). The size of a JSON text in octets or characters is
		982	usually a good indication of the size of the resources required to decode
		983	it into a Perl structure. While JSON::XS can check the size of the JSON
		984	text, it might be too late when you already have it in memory, so you
		985	might want to check the size before you accept the string.
		986
		987	Third, JSON::XS recurses using the C stack when decoding objects and
		988	arrays. The C stack is a limited resource: for instance, on my amd64
		989	machine with 8MB of stack size I can decode around 180k nested arrays but
		990	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		991	to free the temporary). If that is exceeded, the program crashes. to be
		992	conservative, the default nesting limit is set to 512. If your process
		993	has a smaller stack, you should adjust this setting accordingly with the
		994	C<max_depth> method.
		995
		996	And last but least, something else could bomb you that I forgot to think
		997	of. In that case, you get to keep the pieces. I am always open for hints,
		998	though...
		999
		1000	If you are using JSON::XS to return packets to consumption
		1001	by JavaScript scripts in a browser you should have a look at
		1002	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1003	you are vulnerable to some common attack vectors (which really are browser
		1004	design bugs, but it is still you who will have to deal with it, as major
		1005	browser developers care only for features, not about doing security
		1006	right).
		1007
		1008
		1009	=head1 THREADS
		1010
		1011	This module is I<not> guaranteed to be thread safe and there are no
		1012	plans to change this until Perl gets thread support (as opposed to the
		1013	horribly slow so-called "threads" which are simply slow and bloated
		1014	process simulations - use fork, its I<much> faster, cheaper, better).
		1015
		1016	(It might actually work, but you have been warned).
		1017
526		1018
527	=head1 BUGS	1019	=head1 BUGS
528		1020
529	While the goal of this module is to be correct, that unfortunately does	1021	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	1022	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	1023	still relatively early in its development. If you keep reporting bugs they
532	be fixed swiftly, though.	1024	will be fixed swiftly, though.
		1025
		1026	Please refrain from using rt.cpan.org or any other bug reporting
		1027	service. I put the contact address into my modules for a reason.
533		1028
534	=cut	1029	=cut
		1030
		1031	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1032	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1033
		1034	sub true() { $true }
		1035	sub false() { $false }
		1036
		1037	sub is_bool($) {
		1038	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1039	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1040	}
		1041
		1042	XSLoader::load "JSON::XS", $VERSION;
		1043
		1044	package JSON::XS::Boolean;
		1045
		1046	use overload
		1047	"0+" => sub { ${$_[0]} },
		1048	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1049	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1050	fallback => 1;
535		1051
536	1;	1052	1;
537		1053
538	=head1 AUTHOR	1054	=head1 AUTHOR
539		1055

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing JSON-XS/XS.pm (file contents): Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs. Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs.
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC