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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.19 by root, Sat Mar 24 22:57:12 2007 UTC vs.
Revision 1.81 by root, Sat Dec 29 17:33:38 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;
8		11
9	# exported functions, croak on error	12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
10		14
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	15	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	16	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
13		17
14	# oo-interface	18	# OO-interface
15		19
16	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
17	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
18	$perl_scalar = $coder->decode ($unicode_json_text);	22	$perl_scalar = $coder->decode ($unicode_json_text);
19		23
		24	# Note that JSON version 2.0 and above will automatically use JSON::XS
		25	# if available, at virtually no speed overhead either, so you should
		26	# be able to just:
		27
		28	use JSON;
		29
		30	# and do the same things, except that you have a pure-perl fallback now.
		31
20	=head1 DESCRIPTION	32	=head1 DESCRIPTION
21		33
22	This module converts Perl data structures to JSON and vice versa. Its	34	This module converts Perl data structures to JSON and vice versa. Its
23	primary goal is to be I<correct> and its secondary goal is to be	35	primary goal is to be I<correct> and its secondary goal is to be
24	I<fast>. To reach the latter goal it was written in C.	36	I<fast>. To reach the latter goal it was written in C.
		37
		38	Beginning with version 2.0 of the JSON module, when both JSON and
		39	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		40	overriden) with no overhead due to emulation (by inheritign constructor
		41	and methods). If JSON::XS is not available, it will fall back to the
		42	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		43	gives you a portable JSON API that can be fast when you need and doesn't
		44	require a C compiler when that is a problem.
25		45
26	As this is the n-th-something JSON module on CPAN, what was the reason	46	As this is the n-th-something JSON module on CPAN, what was the reason
27	to write yet another JSON module? While it seems there are many JSON	47	to write yet another JSON module? While it seems there are many JSON
28	modules, none of them correctly handle all corner cases, and in most cases	48	modules, none of them correctly handle all corner cases, and in most cases
29	their maintainers are unresponsive, gone missing, or not listening to bug	49	their maintainers are unresponsive, gone missing, or not listening to bug
36		56
37	=head2 FEATURES	57	=head2 FEATURES
38		58
39	=over 4	59	=over 4
40		60
41	=item * correct handling of unicode issues	61	=item * correct Unicode handling
42		62
43	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, and even documents how and when
44	it does so.	64	it does so.
45		65
46	=item * round-trip integrity	66	=item * round-trip integrity
47		67
48	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only datatypes supported
49	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
50	(e.g. the string "2.0" doesn't suddenly become "2").	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		71	like a number).
51		72
52	=item * strict checking of JSON correctness	73	=item * strict checking of JSON correctness
53		74
54	There is no guessing, no generating of illegal JSON texts by default,	75	There is no guessing, no generating of illegal JSON texts by default,
55	and only JSON is accepted as input by default (the latter is a security	76	and only JSON is accepted as input by default (the latter is a security
…		…
65	This module has both a simple functional interface as well as an OO	86	This module has both a simple functional interface as well as an OO
66	interface.	87	interface.
67		88
68	=item * reasonably versatile output formats	89	=item * reasonably versatile output formats
69		90
70	You can choose between the most compact guarenteed single-line format	91	You can choose between the most compact guaranteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	92	possible (nice for simple line-based protocols), a pure-ascii format
72	when your transport is not 8-bit clean), or a pretty-printed format (for	93	(for when your transport is not 8-bit clean, still supports the whole
73	when you want to read that stuff). Or you can combine those features in	94	Unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	95	stuff). Or you can combine those features in whatever way you like.
75		96
76	=back	97	=back
77		98
78	=cut	99	=cut
79		100
80	package JSON::XS;	101	package JSON::XS;
81		102
82	BEGIN {	103	use strict;
		104
83	$VERSION = '0.7';	105	our $VERSION = '2.01';
84	@ISA = qw(Exporter);	106	our @ISA = qw(Exporter);
85		107
86	@EXPORT = qw(to_json from_json);	108	our @EXPORT = qw(encode_json decode_json to_json from_json);
87	require Exporter;
88		109
		110	sub to_json($) {
89	require XSLoader;	111	require Carp;
90	XSLoader::load JSON::XS::, $VERSION;	112	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
91	}	113	}
92		114
		115	sub from_json($) {
		116	require Carp;
		117	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		118	}
		119
		120	use Exporter;
		121	use XSLoader;
		122
93	=head1 FUNCTIONAL INTERFACE	123	=head1 FUNCTIONAL INTERFACE
94		124
95	The following convinience methods are provided by this module. They are	125	The following convenience methods are provided by this module. They are
96	exported by default:	126	exported by default:
97		127
98	=over 4	128	=over 4
99		129
100	=item $json_text = to_json $perl_scalar	130	=item $json_text = encode_json $perl_scalar
101		131
102	Converts the given Perl data structure (a simple scalar or a reference to	132	Converts the given Perl data structure to a UTF-8 encoded, binary string
103	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	133	(that is, the string contains octets only). Croaks on error.
104	octets only). Croaks on error.
105		134
106	This function call is functionally identical to:	135	This function call is functionally identical to:
107		136
108	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	137	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
109		138
110	except being faster.	139	except being faster.
111		140
112	=item $perl_scalar = from_json $json_text	141	=item $perl_scalar = decode_json $json_text
113		142
114	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	143	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
115	parse that as an UTF-8 encoded JSON text, returning the resulting simple	144	to parse that as an UTF-8 encoded JSON text, returning the resulting
116	scalar or reference. Croaks on error.	145	reference. Croaks on error.
117		146
118	This function call is functionally identical to:	147	This function call is functionally identical to:
119		148
120	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	149	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
121		150
122	except being faster.	151	except being faster.
123		152
		153	=item $is_boolean = JSON::XS::is_bool $scalar
		154
		155	Returns true if the passed scalar represents either JSON::XS::true or
		156	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		157	and are used to represent JSON C<true> and C<false> values in Perl.
		158
		159	See MAPPING, below, for more information on how JSON values are mapped to
		160	Perl.
		161
124	=back	162	=back
		163
		164
		165	=head1 A FEW NOTES ON UNICODE AND PERL
		166
		167	Since this often leads to confusion, here are a few very clear words on
		168	how Unicode works in Perl, modulo bugs.
		169
		170	=over 4
		171
		172	=item 1. Perl strings can store characters with ordinal values > 255.
		173
		174	This enables you to store Unicode characters as single characters in a
		175	Perl string - very natural.
		176
		177	=item 2. Perl does I<not> associate an encoding with your strings.
		178
		179	Unless you force it to, e.g. when matching it against a regex, or printing
		180	the scalar to a file, in which case Perl either interprets your string as
		181	locale-encoded text, octets/binary, or as Unicode, depending on various
		182	settings. In no case is an encoding stored together with your data, it is
		183	I<use> that decides encoding, not any magical metadata.
		184
		185	=item 3. The internal utf-8 flag has no meaning with regards to the
		186	encoding of your string.
		187
		188	Just ignore that flag unless you debug a Perl bug, a module written in
		189	XS or want to dive into the internals of perl. Otherwise it will only
		190	confuse you, as, despite the name, it says nothing about how your string
		191	is encoded. You can have Unicode strings with that flag set, with that
		192	flag clear, and you can have binary data with that flag set and that flag
		193	clear. Other possibilities exist, too.
		194
		195	If you didn't know about that flag, just the better, pretend it doesn't
		196	exist.
		197
		198	=item 4. A "Unicode String" is simply a string where each character can be
		199	validly interpreted as a Unicode codepoint.
		200
		201	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		202	Unicode string encoded in UTF-8, giving you a binary string.
		203
		204	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		205
		206	It's a fact. Learn to live with it.
		207
		208	=back
		209
		210	I hope this helps :)
		211
125		212
126	=head1 OBJECT-ORIENTED INTERFACE	213	=head1 OBJECT-ORIENTED INTERFACE
127		214
128	The object oriented interface lets you configure your own encoding or	215	The object oriented interface lets you configure your own encoding or
129	decoding style, within the limits of supported formats.	216	decoding style, within the limits of supported formats.
…		…
141	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	228	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
142	=> {"a": [1, 2]}	229	=> {"a": [1, 2]}
143		230
144	=item $json = $json->ascii ([$enable])	231	=item $json = $json->ascii ([$enable])
145		232
		233	=item $enabled = $json->get_ascii
		234
146	If C<$enable> is true (or missing), then the C<encode> method will not	235	If C<$enable> is true (or missing), then the C<encode> method will not
147	generate characters outside the code range C<0..127> (which is ASCII). Any	236	generate characters outside the code range C<0..127> (which is ASCII). Any
148	unicode characters outside that range will be escaped using either a	237	Unicode characters outside that range will be escaped using either a
149	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	238	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
150	as per RFC4627.	239	as per RFC4627. The resulting encoded JSON text can be treated as a native
		240	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		241	or any other superset of ASCII.
151		242
152	If C<$enable> is false, then the C<encode> method will not escape Unicode	243	If C<$enable> is false, then the C<encode> method will not escape Unicode
153	characters unless required by the JSON syntax. This results in a faster	244	characters unless required by the JSON syntax or other flags. This results
154	and more compact format.	245	in a faster and more compact format.
		246
		247	The main use for this flag is to produce JSON texts that can be
		248	transmitted over a 7-bit channel, as the encoded JSON texts will not
		249	contain any 8 bit characters.
155		250
156	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	251	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
157	=> ["\ud801\udc01"]	252	=> ["\ud801\udc01"]
158		253
		254	=item $json = $json->latin1 ([$enable])
		255
		256	=item $enabled = $json->get_latin1
		257
		258	If C<$enable> is true (or missing), then the C<encode> method will encode
		259	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		260	outside the code range C<0..255>. The resulting string can be treated as a
		261	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		262	will not be affected in any way by this flag, as C<decode> by default
		263	expects Unicode, which is a strict superset of latin1.
		264
		265	If C<$enable> is false, then the C<encode> method will not escape Unicode
		266	characters unless required by the JSON syntax or other flags.
		267
		268	The main use for this flag is efficiently encoding binary data as JSON
		269	text, as most octets will not be escaped, resulting in a smaller encoded
		270	size. The disadvantage is that the resulting JSON text is encoded
		271	in latin1 (and must correctly be treated as such when storing and
		272	transferring), a rare encoding for JSON. It is therefore most useful when
		273	you want to store data structures known to contain binary data efficiently
		274	in files or databases, not when talking to other JSON encoders/decoders.
		275
		276	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		277	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		278
159	=item $json = $json->utf8 ([$enable])	279	=item $json = $json->utf8 ([$enable])
		280
		281	=item $enabled = $json->get_utf8
160		282
161	If C<$enable> is true (or missing), then the C<encode> method will encode	283	If C<$enable> is true (or missing), then the C<encode> method will encode
162	the JSON result into UTF-8, as required by many protocols, while the	284	the JSON result into UTF-8, as required by many protocols, while the
163	C<decode> method expects to be handled an UTF-8-encoded string. Please	285	C<decode> method expects to be handled an UTF-8-encoded string. Please
164	note that UTF-8-encoded strings do not contain any characters outside the	286	note that UTF-8-encoded strings do not contain any characters outside the
165	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	287	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
166	versions, enabling this option might enable autodetection of the UTF-16	288	versions, enabling this option might enable autodetection of the UTF-16
167	and UTF-32 encoding families, as described in RFC4627.	289	and UTF-32 encoding families, as described in RFC4627.
168		290
169	If C<$enable> is false, then the C<encode> method will return the JSON	291	If C<$enable> is false, then the C<encode> method will return the JSON
170	string as a (non-encoded) unicode string, while C<decode> expects thus a	292	string as a (non-encoded) Unicode string, while C<decode> expects thus a
171	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	293	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
172	to be done yourself, e.g. using the Encode module.	294	to be done yourself, e.g. using the Encode module.
173		295
174	Example, output UTF-16BE-encoded JSON:	296	Example, output UTF-16BE-encoded JSON:
175		297
176	use Encode;	298	use Encode;
…		…
198	]	320	]
199	}	321	}
200		322
201	=item $json = $json->indent ([$enable])	323	=item $json = $json->indent ([$enable])
202		324
		325	=item $enabled = $json->get_indent
		326
203	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	327	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
204	format as output, putting every array member or object/hash key-value pair	328	format as output, putting every array member or object/hash key-value pair
205	into its own line, identing them properly.	329	into its own line, indenting them properly.
206		330
207	If C<$enable> is false, no newlines or indenting will be produced, and the	331	If C<$enable> is false, no newlines or indenting will be produced, and the
208	resulting JSON text is guarenteed not to contain any C<newlines>.	332	resulting JSON text is guaranteed not to contain any C<newlines>.
209		333
210	This setting has no effect when decoding JSON texts.	334	This setting has no effect when decoding JSON texts.
211		335
212	=item $json = $json->space_before ([$enable])	336	=item $json = $json->space_before ([$enable])
		337
		338	=item $enabled = $json->get_space_before
213		339
214	If C<$enable> is true (or missing), then the C<encode> method will add an extra	340	If C<$enable> is true (or missing), then the C<encode> method will add an extra
215	optional space before the C<:> separating keys from values in JSON objects.	341	optional space before the C<:> separating keys from values in JSON objects.
216		342
217	If C<$enable> is false, then the C<encode> method will not add any extra	343	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
223	Example, space_before enabled, space_after and indent disabled:	349	Example, space_before enabled, space_after and indent disabled:
224		350
225	{"key" :"value"}	351	{"key" :"value"}
226		352
227	=item $json = $json->space_after ([$enable])	353	=item $json = $json->space_after ([$enable])
		354
		355	=item $enabled = $json->get_space_after
228		356
229	If C<$enable> is true (or missing), then the C<encode> method will add an extra	357	If C<$enable> is true (or missing), then the C<encode> method will add an extra
230	optional space after the C<:> separating keys from values in JSON objects	358	optional space after the C<:> separating keys from values in JSON objects
231	and extra whitespace after the C<,> separating key-value pairs and array	359	and extra whitespace after the C<,> separating key-value pairs and array
232	members.	360	members.
…		…
238		366
239	Example, space_before and indent disabled, space_after enabled:	367	Example, space_before and indent disabled, space_after enabled:
240		368
241	{"key": "value"}	369	{"key": "value"}
242		370
		371	=item $json = $json->relaxed ([$enable])
		372
		373	=item $enabled = $json->get_relaxed
		374
		375	If C<$enable> is true (or missing), then C<decode> will accept some
		376	extensions to normal JSON syntax (see below). C<encode> will not be
		377	affected in anyway. I<Be aware that this option makes you accept invalid
		378	JSON texts as if they were valid!>. I suggest only to use this option to
		379	parse application-specific files written by humans (configuration files,
		380	resource files etc.)
		381
		382	If C<$enable> is false (the default), then C<decode> will only accept
		383	valid JSON texts.
		384
		385	Currently accepted extensions are:
		386
		387	=over 4
		388
		389	=item * list items can have an end-comma
		390
		391	JSON I<separates> array elements and key-value pairs with commas. This
		392	can be annoying if you write JSON texts manually and want to be able to
		393	quickly append elements, so this extension accepts comma at the end of
		394	such items not just between them:
		395
		396	[
		397	1,
		398	2, <- this comma not normally allowed
		399	]
		400	{
		401	"k1": "v1",
		402	"k2": "v2", <- this comma not normally allowed
		403	}
		404
		405	=item * shell-style '#'-comments
		406
		407	Whenever JSON allows whitespace, shell-style comments are additionally
		408	allowed. They are terminated by the first carriage-return or line-feed
		409	character, after which more white-space and comments are allowed.
		410
		411	[
		412	1, # this comment not allowed in JSON
		413	# neither this one...
		414	]
		415
		416	=back
		417
243	=item $json = $json->canonical ([$enable])	418	=item $json = $json->canonical ([$enable])
		419
		420	=item $enabled = $json->get_canonical
244		421
245	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	422	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
246	by sorting their keys. This is adding a comparatively high overhead.	423	by sorting their keys. This is adding a comparatively high overhead.
247		424
248	If C<$enable> is false, then the C<encode> method will output key-value	425	If C<$enable> is false, then the C<encode> method will output key-value
249	pairs in the order Perl stores them (which will likely change between runs	426	pairs in the order Perl stores them (which will likely change between runs
250	of the same script).	427	of the same script).
251		428
252	This option is useful if you want the same data structure to be encoded as	429	This option is useful if you want the same data structure to be encoded as
253	the same JSON text (given the same overall settings). If it is disabled,	430	the same JSON text (given the same overall settings). If it is disabled,
254	the same hash migh be encoded differently even if contains the same data,	431	the same hash might be encoded differently even if contains the same data,
255	as key-value pairs have no inherent ordering in Perl.	432	as key-value pairs have no inherent ordering in Perl.
256		433
257	This setting has no effect when decoding JSON texts.	434	This setting has no effect when decoding JSON texts.
258		435
259	=item $json = $json->allow_nonref ([$enable])	436	=item $json = $json->allow_nonref ([$enable])
		437
		438	=item $enabled = $json->get_allow_nonref
260		439
261	If C<$enable> is true (or missing), then the C<encode> method can convert a	440	If C<$enable> is true (or missing), then the C<encode> method can convert a
262	non-reference into its corresponding string, number or null JSON value,	441	non-reference into its corresponding string, number or null JSON value,
263	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	442	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
264	values instead of croaking.	443	values instead of croaking.
…		…
272	resulting in an invalid JSON text:	451	resulting in an invalid JSON text:
273		452
274	JSON::XS->new->allow_nonref->encode ("Hello, World!")	453	JSON::XS->new->allow_nonref->encode ("Hello, World!")
275	=> "Hello, World!"	454	=> "Hello, World!"
276		455
		456	=item $json = $json->allow_blessed ([$enable])
		457
		458	=item $enabled = $json->get_allow_blessed
		459
		460	If C<$enable> is true (or missing), then the C<encode> method will not
		461	barf when it encounters a blessed reference. Instead, the value of the
		462	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		463	disabled or no C<TO_JSON> method found) or a representation of the
		464	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		465	encoded. Has no effect on C<decode>.
		466
		467	If C<$enable> is false (the default), then C<encode> will throw an
		468	exception when it encounters a blessed object.
		469
		470	=item $json = $json->convert_blessed ([$enable])
		471
		472	=item $enabled = $json->get_convert_blessed
		473
		474	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		475	blessed object, will check for the availability of the C<TO_JSON> method
		476	on the object's class. If found, it will be called in scalar context
		477	and the resulting scalar will be encoded instead of the object. If no
		478	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		479	to do.
		480
		481	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		482	returns other blessed objects, those will be handled in the same
		483	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		484	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		485	methods called by the Perl core (== not by the user of the object) are
		486	usually in upper case letters and to avoid collisions with any C<to_json>
		487	function or method.
		488
		489	This setting does not yet influence C<decode> in any way, but in the
		490	future, global hooks might get installed that influence C<decode> and are
		491	enabled by this setting.
		492
		493	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		494	to do when a blessed object is found.
		495
		496	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		497
		498	When C<$coderef> is specified, it will be called from C<decode> each
		499	time it decodes a JSON object. The only argument is a reference to the
		500	newly-created hash. If the code references returns a single scalar (which
		501	need not be a reference), this value (i.e. a copy of that scalar to avoid
		502	aliasing) is inserted into the deserialised data structure. If it returns
		503	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		504	original deserialised hash will be inserted. This setting can slow down
		505	decoding considerably.
		506
		507	When C<$coderef> is omitted or undefined, any existing callback will
		508	be removed and C<decode> will not change the deserialised hash in any
		509	way.
		510
		511	Example, convert all JSON objects into the integer 5:
		512
		513	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		514	# returns [5]
		515	$js->decode ('[{}]')
		516	# throw an exception because allow_nonref is not enabled
		517	# so a lone 5 is not allowed.
		518	$js->decode ('{"a":1, "b":2}');
		519
		520	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		521
		522	Works remotely similar to C<filter_json_object>, but is only called for
		523	JSON objects having a single key named C<$key>.
		524
		525	This C<$coderef> is called before the one specified via
		526	C<filter_json_object>, if any. It gets passed the single value in the JSON
		527	object. If it returns a single value, it will be inserted into the data
		528	structure. If it returns nothing (not even C<undef> but the empty list),
		529	the callback from C<filter_json_object> will be called next, as if no
		530	single-key callback were specified.
		531
		532	If C<$coderef> is omitted or undefined, the corresponding callback will be
		533	disabled. There can only ever be one callback for a given key.
		534
		535	As this callback gets called less often then the C<filter_json_object>
		536	one, decoding speed will not usually suffer as much. Therefore, single-key
		537	objects make excellent targets to serialise Perl objects into, especially
		538	as single-key JSON objects are as close to the type-tagged value concept
		539	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		540	support this in any way, so you need to make sure your data never looks
		541	like a serialised Perl hash.
		542
		543	Typical names for the single object key are C<__class_whatever__>, or
		544	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		545	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		546	with real hashes.
		547
		548	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		549	into the corresponding C<< $WIDGET{<id>} >> object:
		550
		551	# return whatever is in $WIDGET{5}:
		552	JSON::XS
		553	->new
		554	->filter_json_single_key_object (__widget__ => sub {
		555	$WIDGET{ $_[0] }
		556	})
		557	->decode ('{"__widget__": 5')
		558
		559	# this can be used with a TO_JSON method in some "widget" class
		560	# for serialisation to json:
		561	sub WidgetBase::TO_JSON {
		562	my ($self) = @_;
		563
		564	unless ($self->{id}) {
		565	$self->{id} = ..get..some..id..;
		566	$WIDGET{$self->{id}} = $self;
		567	}
		568
		569	{ __widget__ => $self->{id} }
		570	}
		571
277	=item $json = $json->shrink ([$enable])	572	=item $json = $json->shrink ([$enable])
278		573
		574	=item $enabled = $json->get_shrink
		575
279	Perl usually over-allocates memory a bit when allocating space for	576	Perl usually over-allocates memory a bit when allocating space for
280	strings. This flag optionally resizes strings generated by either	577	strings. This flag optionally resizes strings generated by either
281	C<encode> or C<decode> to their minimum size possible. This can save	578	C<encode> or C<decode> to their minimum size possible. This can save
282	memory when your JSON texts are either very very long or you have many	579	memory when your JSON texts are either very very long or you have many
283	short strings. It will also try to downgrade any strings to octet-form	580	short strings. It will also try to downgrade any strings to octet-form
284	if possible: perl stores strings internally either in an encoding called	581	if possible: perl stores strings internally either in an encoding called
285	UTF-X or in octet-form. The latter cannot store everything but uses less	582	UTF-X or in octet-form. The latter cannot store everything but uses less
286	space in general.	583	space in general (and some buggy Perl or C code might even rely on that
		584	internal representation being used).
287		585
		586	The actual definition of what shrink does might change in future versions,
		587	but it will always try to save space at the expense of time.
		588
288	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	589	If C<$enable> is true (or missing), the string returned by C<encode> will
289	while all strings generated by C<decode> will also be shrunk-to-fit.	590	be shrunk-to-fit, while all strings generated by C<decode> will also be
		591	shrunk-to-fit.
290		592
291	If C<$enable> is false, then the normal perl allocation algorithms are used.	593	If C<$enable> is false, then the normal perl allocation algorithms are used.
292	If you work with your data, then this is likely to be faster.	594	If you work with your data, then this is likely to be faster.
293		595
294	In the future, this setting might control other things, such as converting	596	In the future, this setting might control other things, such as converting
295	strings that look like integers or floats into integers or floats	597	strings that look like integers or floats into integers or floats
296	internally (there is no difference on the Perl level), saving space.	598	internally (there is no difference on the Perl level), saving space.
		599
		600	=item $json = $json->max_depth ([$maximum_nesting_depth])
		601
		602	=item $max_depth = $json->get_max_depth
		603
		604	Sets the maximum nesting level (default C<512>) accepted while encoding
		605	or decoding. If the JSON text or Perl data structure has an equal or
		606	higher nesting level then this limit, then the encoder and decoder will
		607	stop and croak at that point.
		608
		609	Nesting level is defined by number of hash- or arrayrefs that the encoder
		610	needs to traverse to reach a given point or the number of C<{> or C<[>
		611	characters without their matching closing parenthesis crossed to reach a
		612	given character in a string.
		613
		614	Setting the maximum depth to one disallows any nesting, so that ensures
		615	that the object is only a single hash/object or array.
		616
		617	The argument to C<max_depth> will be rounded up to the next highest power
		618	of two. If no argument is given, the highest possible setting will be
		619	used, which is rarely useful.
		620
		621	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		622
		623	=item $json = $json->max_size ([$maximum_string_size])
		624
		625	=item $max_size = $json->get_max_size
		626
		627	Set the maximum length a JSON text may have (in bytes) where decoding is
		628	being attempted. The default is C<0>, meaning no limit. When C<decode>
		629	is called on a string longer then this number of characters it will not
		630	attempt to decode the string but throw an exception. This setting has no
		631	effect on C<encode> (yet).
		632
		633	The argument to C<max_size> will be rounded up to the next B<highest>
		634	power of two (so may be more than requested). If no argument is given, the
		635	limit check will be deactivated (same as when C<0> is specified).
		636
		637	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
297		638
298	=item $json_text = $json->encode ($perl_scalar)	639	=item $json_text = $json->encode ($perl_scalar)
299		640
300	Converts the given Perl data structure (a simple scalar or a reference	641	Converts the given Perl data structure (a simple scalar or a reference
301	to a hash or array) to its JSON representation. Simple scalars will be	642	to a hash or array) to its JSON representation. Simple scalars will be
…		…
311		652
312	JSON numbers and strings become simple Perl scalars. JSON arrays become	653	JSON numbers and strings become simple Perl scalars. JSON arrays become
313	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	654	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
314	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	655	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
315		656
		657	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		658
		659	This works like the C<decode> method, but instead of raising an exception
		660	when there is trailing garbage after the first JSON object, it will
		661	silently stop parsing there and return the number of characters consumed
		662	so far.
		663
		664	This is useful if your JSON texts are not delimited by an outer protocol
		665	(which is not the brightest thing to do in the first place) and you need
		666	to know where the JSON text ends.
		667
		668	JSON::XS->new->decode_prefix ("[1] the tail")
		669	=> ([], 3)
		670
316	=back	671	=back
		672
317		673
318	=head1 MAPPING	674	=head1 MAPPING
319		675
320	This section describes how JSON::XS maps Perl values to JSON values and	676	This section describes how JSON::XS maps Perl values to JSON values and
321	vice versa. These mappings are designed to "do the right thing" in most	677	vice versa. These mappings are designed to "do the right thing" in most
322	circumstances automatically, preserving round-tripping characteristics	678	circumstances automatically, preserving round-tripping characteristics
323	(what you put in comes out as something equivalent).	679	(what you put in comes out as something equivalent).
324		680
325	For the more enlightened: note that in the following descriptions,	681	For the more enlightened: note that in the following descriptions,
326	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	682	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
327	refers to the abstract Perl language itself.	683	refers to the abstract Perl language itself.
328		684
		685
329	=head2 JSON -> PERL	686	=head2 JSON -> PERL
330		687
331	=over 4	688	=over 4
332		689
333	=item object	690	=item object
334		691
335	A JSON object becomes a reference to a hash in Perl. No ordering of object	692	A JSON object becomes a reference to a hash in Perl. No ordering of object
336	keys is preserved (JSON does not preserver object key ordering itself).	693	keys is preserved (JSON does not preserve object key ordering itself).
337		694
338	=item array	695	=item array
339		696
340	A JSON array becomes a reference to an array in Perl.	697	A JSON array becomes a reference to an array in Perl.
341		698
…		…
345	are represented by the same codepoints in the Perl string, so no manual	702	are represented by the same codepoints in the Perl string, so no manual
346	decoding is necessary.	703	decoding is necessary.
347		704
348	=item number	705	=item number
349		706
350	A JSON number becomes either an integer or numeric (floating point)	707	A JSON number becomes either an integer, numeric (floating point) or
351	scalar in perl, depending on its range and any fractional parts. On the	708	string scalar in perl, depending on its range and any fractional parts. On
352	Perl level, there is no difference between those as Perl handles all the	709	the Perl level, there is no difference between those as Perl handles all
353	conversion details, but an integer may take slightly less memory and might	710	the conversion details, but an integer may take slightly less memory and
354	represent more values exactly than (floating point) numbers.	711	might represent more values exactly than (floating point) numbers.
		712
		713	If the number consists of digits only, JSON::XS will try to represent
		714	it as an integer value. If that fails, it will try to represent it as
		715	a numeric (floating point) value if that is possible without loss of
		716	precision. Otherwise it will preserve the number as a string value.
		717
		718	Numbers containing a fractional or exponential part will always be
		719	represented as numeric (floating point) values, possibly at a loss of
		720	precision.
		721
		722	This might create round-tripping problems as numbers might become strings,
		723	but as Perl is typeless there is no other way to do it.
355		724
356	=item true, false	725	=item true, false
357		726
358	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
359	this process. Future versions might represent those values differently,	728	respectively. They are overloaded to act almost exactly like the numbers
360	but they will be guarenteed to act like these integers would normally in	729	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
361	Perl.	730	the C<JSON::XS::is_bool> function.
362		731
363	=item null	732	=item null
364		733
365	A JSON null atom becomes C<undef> in Perl.	734	A JSON null atom becomes C<undef> in Perl.
366		735
367	=back	736	=back
		737
368		738
369	=head2 PERL -> JSON	739	=head2 PERL -> JSON
370		740
371	The mapping from Perl to JSON is slightly more difficult, as Perl is a	741	The mapping from Perl to JSON is slightly more difficult, as Perl is a
372	truly typeless language, so we can only guess which JSON type is meant by	742	truly typeless language, so we can only guess which JSON type is meant by
…		…
375	=over 4	745	=over 4
376		746
377	=item hash references	747	=item hash references
378		748
379	Perl hash references become JSON objects. As there is no inherent ordering	749	Perl hash references become JSON objects. As there is no inherent ordering
380	in hash keys, they will usually be encoded in a pseudo-random order that	750	in hash keys (or JSON objects), they will usually be encoded in a
381	can change between runs of the same program but stays generally the same	751	pseudo-random order that can change between runs of the same program but
382	within a single run of a program. JSON::XS can optionally sort the hash	752	stays generally the same within a single run of a program. JSON::XS can
383	keys (determined by the I<canonical> flag), so the same datastructure	753	optionally sort the hash keys (determined by the I<canonical> flag), so
384	will serialise to the same JSON text (given same settings and version of	754	the same datastructure will serialise to the same JSON text (given same
385	JSON::XS), but this incurs a runtime overhead.	755	settings and version of JSON::XS), but this incurs a runtime overhead
		756	and is only rarely useful, e.g. when you want to compare some JSON text
		757	against another for equality.
386		758
387	=item array references	759	=item array references
388		760
389	Perl array references become JSON arrays.	761	Perl array references become JSON arrays.
		762
		763	=item other references
		764
		765	Other unblessed references are generally not allowed and will cause an
		766	exception to be thrown, except for references to the integers C<0> and
		767	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		768	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		769
		770	encode_json [\0,JSON::XS::true] # yields [false,true]
		771
		772	=item JSON::XS::true, JSON::XS::false
		773
		774	These special values become JSON true and JSON false values,
		775	respectively. You can also use C<\1> and C<\0> directly if you want.
390		776
391	=item blessed objects	777	=item blessed objects
392		778
393	Blessed objects are not allowed. JSON::XS currently tries to encode their	779	Blessed objects are not allowed. JSON::XS currently tries to encode their
394	underlying representation (hash- or arrayref), but this behaviour might	780	underlying representation (hash- or arrayref), but this behaviour might
…		…
400	difficult objects to encode: JSON::XS will encode undefined scalars as	786	difficult objects to encode: JSON::XS will encode undefined scalars as
401	JSON null value, scalars that have last been used in a string context	787	JSON null value, scalars that have last been used in a string context
402	before encoding as JSON strings and anything else as number value:	788	before encoding as JSON strings and anything else as number value:
403		789
404	# dump as number	790	# dump as number
405	to_json [2] # yields [2]	791	encode_json [2] # yields [2]
406	to_json [-3.0e17] # yields [-3e+17]	792	encode_json [-3.0e17] # yields [-3e+17]
407	my $value = 5; to_json [$value] # yields [5]	793	my $value = 5; encode_json [$value] # yields [5]
408		794
409	# used as string, so dump as string	795	# used as string, so dump as string
410	print $value;	796	print $value;
411	to_json [$value] # yields ["5"]	797	encode_json [$value] # yields ["5"]
412		798
413	# undef becomes null	799	# undef becomes null
414	to_json [undef] # yields [null]	800	encode_json [undef] # yields [null]
415		801
416	You can force the type to be a string by stringifying it:	802	You can force the type to be a JSON string by stringifying it:
417		803
418	my $x = 3.1; # some variable containing a number	804	my $x = 3.1; # some variable containing a number
419	"$x"; # stringified	805	"$x"; # stringified
420	$x .= ""; # another, more awkward way to stringify	806	$x .= ""; # another, more awkward way to stringify
421	print $x; # perl does it for you, too, quite often	807	print $x; # perl does it for you, too, quite often
422		808
423	You can force the type to be a number by numifying it:	809	You can force the type to be a JSON number by numifying it:
424		810
425	my $x = "3"; # some variable containing a string	811	my $x = "3"; # some variable containing a string
426	$x += 0; # numify it, ensuring it will be dumped as a number	812	$x += 0; # numify it, ensuring it will be dumped as a number
427	$x *= 1; # same thing, the choise is yours.	813	$x *= 1; # same thing, the choice is yours.
428		814
429	You can not currently output JSON booleans or force the type in other,	815	You can not currently force the type in other, less obscure, ways. Tell me
430	less obscure, ways. Tell me if you need this capability.	816	if you need this capability.
431
432	=item circular data structures
433
434	Those will be encoded until memory or stackspace runs out.
435		817
436	=back	818	=back
		819
437		820
438	=head1 COMPARISON	821	=head1 COMPARISON
439		822
440	As already mentioned, this module was created because none of the existing	823	As already mentioned, this module was created because none of the existing
441	JSON modules could be made to work correctly. First I will describe the	824	JSON modules could be made to work correctly. First I will describe the
…		…
447		830
448	=item JSON 1.07	831	=item JSON 1.07
449		832
450	Slow (but very portable, as it is written in pure Perl).	833	Slow (but very portable, as it is written in pure Perl).
451		834
452	Undocumented/buggy Unicode handling (how JSON handles unicode values is	835	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
453	undocumented. One can get far by feeding it unicode strings and doing	836	undocumented. One can get far by feeding it Unicode strings and doing
454	en-/decoding oneself, but unicode escapes are not working properly).	837	en-/decoding oneself, but Unicode escapes are not working properly).
455		838
456	No roundtripping (strings get clobbered if they look like numbers, e.g.	839	No round-tripping (strings get clobbered if they look like numbers, e.g.
457	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	840	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
458	decode into the number 2.	841	decode into the number 2.
459		842
460	=item JSON::PC 0.01	843	=item JSON::PC 0.01
461		844
462	Very fast.	845	Very fast.
463		846
464	Undocumented/buggy Unicode handling.	847	Undocumented/buggy Unicode handling.
465		848
466	No roundtripping.	849	No round-tripping.
467		850
468	Has problems handling many Perl values (e.g. regex results and other magic	851	Has problems handling many Perl values (e.g. regex results and other magic
469	values will make it croak).	852	values will make it croak).
470		853
471	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	854	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
481	Very inflexible (no human-readable format supported, format pretty much	864	Very inflexible (no human-readable format supported, format pretty much
482	undocumented. I need at least a format for easy reading by humans and a	865	undocumented. I need at least a format for easy reading by humans and a
483	single-line compact format for use in a protocol, and preferably a way to	866	single-line compact format for use in a protocol, and preferably a way to
484	generate ASCII-only JSON texts).	867	generate ASCII-only JSON texts).
485		868
486	Completely broken (and confusingly documented) Unicode handling (unicode	869	Completely broken (and confusingly documented) Unicode handling (Unicode
487	escapes are not working properly, you need to set ImplicitUnicode to	870	escapes are not working properly, you need to set ImplicitUnicode to
488	I<different> values on en- and decoding to get symmetric behaviour).	871	I<different> values on en- and decoding to get symmetric behaviour).
489		872
490	No roundtripping (simple cases work, but this depends on wether the scalar	873	No round-tripping (simple cases work, but this depends on whether the scalar
491	value was used in a numeric context or not).	874	value was used in a numeric context or not).
492		875
493	Dumping hashes may skip hash values depending on iterator state.	876	Dumping hashes may skip hash values depending on iterator state.
494		877
495	Unmaintained (maintainer unresponsive for many months, bugs are not	878	Unmaintained (maintainer unresponsive for many months, bugs are not
496	getting fixed).	879	getting fixed).
497		880
498	Does not check input for validity (i.e. will accept non-JSON input and	881	Does not check input for validity (i.e. will accept non-JSON input and
499	return "something" instead of raising an exception. This is a security	882	return "something" instead of raising an exception. This is a security
500	issue: imagine two banks transfering money between each other using	883	issue: imagine two banks transferring money between each other using
501	JSON. One bank might parse a given non-JSON request and deduct money,	884	JSON. One bank might parse a given non-JSON request and deduct money,
502	while the other might reject the transaction with a syntax error. While a	885	while the other might reject the transaction with a syntax error. While a
503	good protocol will at least recover, that is extra unnecessary work and	886	good protocol will at least recover, that is extra unnecessary work and
504	the transaction will still not succeed).	887	the transaction will still not succeed).
505		888
506	=item JSON::DWIW 0.04	889	=item JSON::DWIW 0.04
507		890
508	Very fast. Very natural. Very nice.	891	Very fast. Very natural. Very nice.
509		892
510	Undocumented unicode handling (but the best of the pack. Unicode escapes	893	Undocumented Unicode handling (but the best of the pack. Unicode escapes
511	still don't get parsed properly).	894	still don't get parsed properly).
512		895
513	Very inflexible.	896	Very inflexible.
514		897
515	No roundtripping.	898	No round-tripping.
516		899
517	Does not generate valid JSON texts (key strings are often unquoted, empty keys	900	Does not generate valid JSON texts (key strings are often unquoted, empty keys
518	result in nothing being output)	901	result in nothing being output)
519		902
520	Does not check input for validity.	903	Does not check input for validity.
521		904
522	=back	905	=back
		906
		907
		908	=head2 JSON and YAML
		909
		910	You often hear that JSON is a subset of YAML. This is, however, a mass
		911	hysteria and very far from the truth. In general, there is no way to
		912	configure JSON::XS to output a data structure as valid YAML that works for
		913	all cases.
		914
		915	If you really must use JSON::XS to generate YAML, you should use this
		916	algorithm (subject to change in future versions):
		917
		918	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		919	my $yaml = $to_yaml->encode ($ref) . "\n";
		920
		921	This will usually generate JSON texts that also parse as valid
		922	YAML. Please note that YAML has hardcoded limits on (simple) object key
		923	lengths that JSON doesn't have and also has different and incompatible
		924	unicode handling, so you should make sure that your hash keys are
		925	noticeably shorter than the 1024 "stream characters" YAML allows and that
		926	you do not have codepoints with values outside the Unicode BMP (basic
		927	multilingual page). YAML also does not allow C<\/> sequences in strings
		928	(which JSON::XS does not I<currently> generate).
		929
		930	There might be other incompatibilities that I am not aware of. In general
		931	you should not try to generate YAML with a JSON generator or vice versa,
		932	or try to parse JSON with a YAML parser or vice versa: chances are high
		933	that you will run into severe interoperability problems when you least
		934	expect it.
		935
523		936
524	=head2 SPEED	937	=head2 SPEED
525		938
526	It seems that JSON::XS is surprisingly fast, as shown in the following	939	It seems that JSON::XS is surprisingly fast, as shown in the following
527	tables. They have been generated with the help of the C<eg/bench> program	940	tables. They have been generated with the help of the C<eg/bench> program
528	in the JSON::XS distribution, to make it easy to compare on your own	941	in the JSON::XS distribution, to make it easy to compare on your own
529	system.	942	system.
530		943
531	First comes a comparison between various modules using a very short JSON	944	First comes a comparison between various modules using a very short
532	string:	945	single-line JSON string:
533		946
534	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	947	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		948	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
535		949
536	It shows the number of encodes/decodes per second (JSON::XS uses the	950	It shows the number of encodes/decodes per second (JSON::XS uses
537	functional interface, while JSON::XS/2 uses the OO interface with	951	the functional interface, while JSON::XS/2 uses the OO interface
538	pretty-printing and hashkey sorting enabled). Higher is better:	952	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		953	shrink). Higher is better:
539		954
540	module \| encode \| decode \|	955	module \| encode \| decode \|
541	-----------\|------------\|------------\|	956	-----------\|------------\|------------\|
542	JSON \| 11488.516 \| 7823.035 \|	957	JSON 1.x \| 4990.842 \| 4088.813 \|
543	JSON::DWIW \| 94708.054 \| 129094.260 \|	958	JSON::DWIW \| 51653.990 \| 71575.154 \|
544	JSON::PC \| 63884.157 \| 128528.212 \|	959	JSON::PC \| 65948.176 \| 74631.744 \|
545	JSON::Syck \| 34898.677 \| 42096.911 \|	960	JSON::PP \| 8931.652 \| 3817.168 \|
546	JSON::XS \| 654027.064 \| 396423.669 \|	961	JSON::Syck \| 24877.248 \| 27776.848 \|
547	JSON::XS/2 \| 371564.190 \| 371725.613 \|	962	JSON::XS \| 388361.481 \| 227951.304 \|
		963	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		964	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		965	Storable \| 16500.016 \| 135300.129 \|
548	-----------+------------+------------+	966	-----------+------------+------------+
549		967
550	That is, JSON::XS is more than six times faster than JSON::DWIW on	968	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
551	encoding, more than three times faster on decoding, and about thirty times	969	about three times faster on decoding, and over forty times faster
552	faster than JSON, even with pretty-printing and key sorting.	970	than JSON, even with pretty-printing and key sorting. It also compares
		971	favourably to Storable for small amounts of data.
553		972
554	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	973	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
555	search API (http://nanoref.com/yahooapis/mgPdGg):	974	search API (http://nanoref.com/yahooapis/mgPdGg):
556		975
557	module \| encode \| decode \|	976	module \| encode \| decode \|
558	-----------\|------------\|------------\|	977	-----------\|------------\|------------\|
559	JSON \| 273.023 \| 44.674 \|	978	JSON 1.x \| 55.260 \| 34.971 \|
560	JSON::DWIW \| 1089.383 \| 1145.704 \|	979	JSON::DWIW \| 825.228 \| 1082.513 \|
561	JSON::PC \| 3097.419 \| 2393.921 \|	980	JSON::PC \| 3571.444 \| 2394.829 \|
562	JSON::Syck \| 514.060 \| 843.053 \|	981	JSON::PP \| 210.987 \| 32.574 \|
563	JSON::XS \| 6479.668 \| 3636.364 \|	982	JSON::Syck \| 552.551 \| 787.544 \|
564	JSON::XS/2 \| 3774.221 \| 3599.124 \|	983	JSON::XS \| 5780.463 \| 4854.519 \|
		984	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		985	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		986	Storable \| 4445.002 \| 5235.027 \|
565	-----------+------------+------------+	987	-----------+------------+------------+
566		988
567	Again, JSON::XS leads by far.	989	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		990	decodes faster).
568		991
569	On large strings containing lots of high unicode characters, some modules	992	On large strings containing lots of high Unicode characters, some modules
570	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	993	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
571	will be broken due to missing (or wrong) unicode handling. Others refuse	994	will be broken due to missing (or wrong) Unicode handling. Others refuse
572	to decode or encode properly, so it was impossible to prepare a fair	995	to decode or encode properly, so it was impossible to prepare a fair
573	comparison table for that case.	996	comparison table for that case.
574		997
575	=head1 RESOURCE LIMITS
576		998
577	JSON::XS does not impose any limits on the size of JSON texts or Perl	999	=head1 SECURITY CONSIDERATIONS
578	values they represent - if your machine can handle it, JSON::XS will	1000
579	encode or decode it. Future versions might optionally impose structure	1001	When you are using JSON in a protocol, talking to untrusted potentially
580	depth and memory use resource limits.	1002	hostile creatures requires relatively few measures.
		1003
		1004	First of all, your JSON decoder should be secure, that is, should not have
		1005	any buffer overflows. Obviously, this module should ensure that and I am
		1006	trying hard on making that true, but you never know.
		1007
		1008	Second, you need to avoid resource-starving attacks. That means you should
		1009	limit the size of JSON texts you accept, or make sure then when your
		1010	resources run out, that's just fine (e.g. by using a separate process that
		1011	can crash safely). The size of a JSON text in octets or characters is
		1012	usually a good indication of the size of the resources required to decode
		1013	it into a Perl structure. While JSON::XS can check the size of the JSON
		1014	text, it might be too late when you already have it in memory, so you
		1015	might want to check the size before you accept the string.
		1016
		1017	Third, JSON::XS recurses using the C stack when decoding objects and
		1018	arrays. The C stack is a limited resource: for instance, on my amd64
		1019	machine with 8MB of stack size I can decode around 180k nested arrays but
		1020	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		1021	to free the temporary). If that is exceeded, the program crashes. To be
		1022	conservative, the default nesting limit is set to 512. If your process
		1023	has a smaller stack, you should adjust this setting accordingly with the
		1024	C<max_depth> method.
		1025
		1026	And last but least, something else could bomb you that I forgot to think
		1027	of. In that case, you get to keep the pieces. I am always open for hints,
		1028	though...
		1029
		1030	If you are using JSON::XS to return packets to consumption
		1031	by JavaScript scripts in a browser you should have a look at
		1032	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1033	you are vulnerable to some common attack vectors (which really are browser
		1034	design bugs, but it is still you who will have to deal with it, as major
		1035	browser developers care only for features, not about getting security
		1036	right).
		1037
		1038
		1039	=head1 THREADS
		1040
		1041	This module is I<not> guaranteed to be thread safe and there are no
		1042	plans to change this until Perl gets thread support (as opposed to the
		1043	horribly slow so-called "threads" which are simply slow and bloated
		1044	process simulations - use fork, its I<much> faster, cheaper, better).
		1045
		1046	(It might actually work, but you have been warned).
		1047
581		1048
582	=head1 BUGS	1049	=head1 BUGS
583		1050
584	While the goal of this module is to be correct, that unfortunately does	1051	While the goal of this module is to be correct, that unfortunately does
585	not mean its bug-free, only that I think its design is bug-free. It is	1052	not mean its bug-free, only that I think its design is bug-free. It is
586	still very young and not well-tested. If you keep reporting bugs they will	1053	still relatively early in its development. If you keep reporting bugs they
587	be fixed swiftly, though.	1054	will be fixed swiftly, though.
		1055
		1056	Please refrain from using rt.cpan.org or any other bug reporting
		1057	service. I put the contact address into my modules for a reason.
588		1058
589	=cut	1059	=cut
		1060
		1061	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1062	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1063
		1064	sub true() { $true }
		1065	sub false() { $false }
		1066
		1067	sub is_bool($) {
		1068	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1069	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1070	}
		1071
		1072	XSLoader::load "JSON::XS", $VERSION;
		1073
		1074	package JSON::XS::Boolean;
		1075
		1076	use overload
		1077	"0+" => sub { ${$_[0]} },
		1078	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1079	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1080	fallback => 1;
590		1081
591	1;	1082	1;
592		1083
593	=head1 AUTHOR	1084	=head1 AUTHOR
594		1085

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Comparing JSON-XS/XS.pm (file contents): Revision 1.19 by root, Sat Mar 24 22:57:12 2007 UTC vs. Revision 1.81 by root, Sat Dec 29 17:33:38 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.19 by root, Sat Mar 24 22:57:12 2007 UTC vs.
Revision 1.81 by root, Sat Dec 29 17:33:38 2007 UTC