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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs.
Revision 1.68 by root, Tue Oct 23 03:30:02 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 = to_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	16	$perl_hash_or_arrayref = from_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
36		40
37	=head2 FEATURES	41	=head2 FEATURES
38		42
39	=over 4	43	=over 4
40		44
41	=item * correct handling of unicode issues	45	=item * correct Unicode handling
42		46
43	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
44	it does so.	48	it does so.
45		49
46	=item * round-trip integrity	50	=item * round-trip integrity
47		51
48	When you serialise a perl data structure using only datatypes supported	52	When you serialise a perl data structure using only datatypes supported
49	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.
50	(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).
51		56
52	=item * strict checking of JSON correctness	57	=item * strict checking of JSON correctness
53		58
54	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,
55	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
56	feature).	61	feature).
57		62
58	=item * fast	63	=item * fast
59		64
…		…
65	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
66	interface.	71	interface.
67		72
68	=item * reasonably versatile output formats	73	=item * reasonably versatile output formats
69		74
70	You can choose between the most compact guarenteed single-line format	75	You can choose between the most compact guaranteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	76	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	77	(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	78	Unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	79	stuff). Or you can combine those features in whatever way you like.
75		80
76	=back	81	=back
77		82
78	=cut	83	=cut
79		84
80	package JSON::XS;	85	package JSON::XS;
81		86
82	BEGIN {	87	use strict;
		88
83	$VERSION = '0.3';	89	our $VERSION = '1.52';
84	@ISA = qw(Exporter);	90	our @ISA = qw(Exporter);
85		91
86	@EXPORT = qw(to_json from_json);	92	our @EXPORT = qw(to_json from_json);
87	require Exporter;
88		93
89	require XSLoader;	94	use Exporter;
90	XSLoader::load JSON::XS::, $VERSION;	95	use XSLoader;
91	}
92		96
93	=head1 FUNCTIONAL INTERFACE	97	=head1 FUNCTIONAL INTERFACE
94		98
95	The following convinience methods are provided by this module. They are	99	The following convenience methods are provided by this module. They are
96	exported by default:	100	exported by default:
97		101
98	=over 4	102	=over 4
99		103
100	=item $json_string = to_json $perl_scalar	104	=item $json_text = to_json $perl_scalar
101		105
102	Converts the given Perl data structure (a simple scalar or a reference to	106	Converts the given Perl data structure to a UTF-8 encoded, binary string
103	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	107	(that is, the string contains octets only). Croaks on error.
104	octets only). Croaks on error.
105		108
106	This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.	109	This function call is functionally identical to:
107		110
		111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		112
		113	except being faster.
		114
108	=item $perl_scalar = from_json $json_string	115	=item $perl_scalar = from_json $json_text
109		116
110	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
111	parse that as an UTF-8 encoded JSON string, returning the resulting simple	118	to parse that as an UTF-8 encoded JSON text, returning the resulting
112	scalar or reference. Croaks on error.	119	reference. Croaks on error.
113		120
114	This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($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.
115		135
116	=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
117		186
118	=head1 OBJECT-ORIENTED INTERFACE	187	=head1 OBJECT-ORIENTED INTERFACE
119		188
120	The object oriented interface lets you configure your own encoding or	189	The object oriented interface lets you configure your own encoding or
121	decoding style, within the limits of supported formats.	190	decoding style, within the limits of supported formats.
…		…
128	strings. All boolean flags described below are by default I<disabled>.	197	strings. All boolean flags described below are by default I<disabled>.
129		198
130	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
131	be chained:	200	be chained:
132		201
133	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]})
134	=> {"a": [1, 2]}	203	=> {"a": [1, 2]}
135		204
136	=item $json = $json->ascii ([$enable])	205	=item $json = $json->ascii ([$enable])
137		206
138	If C<$enable> is true (or missing), then the C<encode> method will	207	If C<$enable> is true (or missing), then the C<encode> method will not
139	not generate characters outside the code range C<0..127>. Any unicode	208	generate characters outside the code range C<0..127> (which is ASCII). Any
140	characters outside that range will be escaped using either a single	209	Unicode characters outside that range will be escaped using either a
141	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
142	RFC4627.	211	as per RFC4627. The resulting encoded JSON text can be treated as a native
		212	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		213	or any other superset of ASCII.
143		214
144	If C<$enable> is false, then the C<encode> method will not escape Unicode	215	If C<$enable> is false, then the C<encode> method will not escape Unicode
145	characters unless necessary.	216	characters unless required by the JSON syntax or other flags. This results
		217	in a faster and more compact format.
146		218
		219	The main use for this flag is to produce JSON texts that can be
		220	transmitted over a 7-bit channel, as the encoded JSON texts will not
		221	contain any 8 bit characters.
		222
147	JSON::XS->new->ascii (1)->encode (chr 0x10401)	223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
148	=> \ud801\udc01	224	=> ["\ud801\udc01"]
		225
		226	=item $json = $json->latin1 ([$enable])
		227
		228	If C<$enable> is true (or missing), then the C<encode> method will encode
		229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		230	outside the code range C<0..255>. The resulting string can be treated as a
		231	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		232	will not be affected in any way by this flag, as C<decode> by default
		233	expects Unicode, which is a strict superset of latin1.
		234
		235	If C<$enable> is false, then the C<encode> method will not escape Unicode
		236	characters unless required by the JSON syntax or other flags.
		237
		238	The main use for this flag is efficiently encoding binary data as JSON
		239	text, as most octets will not be escaped, resulting in a smaller encoded
		240	size. The disadvantage is that the resulting JSON text is encoded
		241	in latin1 (and must correctly be treated as such when storing and
		242	transferring), a rare encoding for JSON. It is therefore most useful when
		243	you want to store data structures known to contain binary data efficiently
		244	in files or databases, not when talking to other JSON encoders/decoders.
		245
		246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
149		248
150	=item $json = $json->utf8 ([$enable])	249	=item $json = $json->utf8 ([$enable])
151		250
152	If C<$enable> is true (or missing), then the C<encode> method will encode	251	If C<$enable> is true (or missing), then the C<encode> method will encode
153	the JSON string into UTF-8, as required by many protocols, while the	252	the JSON result into UTF-8, as required by many protocols, while the
154	C<decode> method expects to be handled an UTF-8-encoded string. Please	253	C<decode> method expects to be handled an UTF-8-encoded string. Please
155	note that UTF-8-encoded strings do not contain any characters outside the	254	note that UTF-8-encoded strings do not contain any characters outside the
156	range C<0..255>, they are thus useful for bytewise/binary I/O.	255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		256	versions, enabling this option might enable autodetection of the UTF-16
		257	and UTF-32 encoding families, as described in RFC4627.
157		258
158	If C<$enable> is false, then the C<encode> method will return the JSON	259	If C<$enable> is false, then the C<encode> method will return the JSON
159	string as a (non-encoded) unicode string, while C<decode> expects thus a	260	string as a (non-encoded) Unicode string, while C<decode> expects thus a
160	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	261	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
161	to be done yourself, e.g. using the Encode module.	262	to be done yourself, e.g. using the Encode module.
162		263
163	Example, output UTF-16-encoded JSON:	264	Example, output UTF-16BE-encoded JSON:
		265
		266	use Encode;
		267	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		268
		269	Example, decode UTF-32LE-encoded JSON:
		270
		271	use Encode;
		272	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
164		273
165	=item $json = $json->pretty ([$enable])	274	=item $json = $json->pretty ([$enable])
166		275
167	This enables (or disables) all of the C<indent>, C<space_before> and	276	This enables (or disables) all of the C<indent>, C<space_before> and
168	C<space_after> (and in the future possibly more) flags in one call to	277	C<space_after> (and in the future possibly more) flags in one call to
…		…
181		290
182	=item $json = $json->indent ([$enable])	291	=item $json = $json->indent ([$enable])
183		292
184	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
185	format as output, putting every array member or object/hash key-value pair	294	format as output, putting every array member or object/hash key-value pair
186	into its own line, identing them properly.	295	into its own line, indenting them properly.
187		296
188	If C<$enable> is false, no newlines or indenting will be produced, and the	297	If C<$enable> is false, no newlines or indenting will be produced, and the
189	resulting JSON strings is guarenteed not to contain any C<newlines>.	298	resulting JSON text is guaranteed not to contain any C<newlines>.
190		299
191	This setting has no effect when decoding JSON strings.	300	This setting has no effect when decoding JSON texts.
192		301
193	=item $json = $json->space_before ([$enable])	302	=item $json = $json->space_before ([$enable])
194		303
195	If C<$enable> is true (or missing), then the C<encode> method will add an extra	304	If C<$enable> is true (or missing), then the C<encode> method will add an extra
196	optional space before the C<:> separating keys from values in JSON objects.	305	optional space before the C<:> separating keys from values in JSON objects.
197		306
198	If C<$enable> is false, then the C<encode> method will not add any extra	307	If C<$enable> is false, then the C<encode> method will not add any extra
199	space at those places.	308	space at those places.
200		309
201	This setting has no effect when decoding JSON strings. You will also most	310	This setting has no effect when decoding JSON texts. You will also
202	likely combine this setting with C<space_after>.	311	most likely combine this setting with C<space_after>.
203		312
204	Example, space_before enabled, space_after and indent disabled:	313	Example, space_before enabled, space_after and indent disabled:
205		314
206	{"key" :"value"}	315	{"key" :"value"}
207		316
…		…
213	members.	322	members.
214		323
215	If C<$enable> is false, then the C<encode> method will not add any extra	324	If C<$enable> is false, then the C<encode> method will not add any extra
216	space at those places.	325	space at those places.
217		326
218	This setting has no effect when decoding JSON strings.	327	This setting has no effect when decoding JSON texts.
219		328
220	Example, space_before and indent disabled, space_after enabled:	329	Example, space_before and indent disabled, space_after enabled:
221		330
222	{"key": "value"}	331	{"key": "value"}
		332
		333	=item $json = $json->relaxed ([$enable])
		334
		335	If C<$enable> is true (or missing), then C<decode> will accept some
		336	extensions to normal JSON syntax (see below). C<encode> will not be
		337	affected in anyway. I<Be aware that this option makes you accept invalid
		338	JSON texts as if they were valid!>. I suggest only to use this option to
		339	parse application-specific files written by humans (configuration files,
		340	resource files etc.)
		341
		342	If C<$enable> is false (the default), then C<decode> will only accept
		343	valid JSON texts.
		344
		345	Currently accepted extensions are:
		346
		347	=over 4
		348
		349	=item * list items can have an end-comma
		350
		351	JSON I<separates> array elements and key-value pairs with commas. This
		352	can be annoying if you write JSON texts manually and want to be able to
		353	quickly append elements, so this extension accepts comma at the end of
		354	such items not just between them:
		355
		356	[
		357	1,
		358	2, <- this comma not normally allowed
		359	]
		360	{
		361	"k1": "v1",
		362	"k2": "v2", <- this comma not normally allowed
		363	}
		364
		365	=item * shell-style '#'-comments
		366
		367	Whenever JSON allows whitespace, shell-style comments are additionally
		368	allowed. They are terminated by the first carriage-return or line-feed
		369	character, after which more white-space and comments are allowed.
		370
		371	[
		372	1, # this comment not allowed in JSON
		373	# neither this one...
		374	]
		375
		376	=back
223		377
224	=item $json = $json->canonical ([$enable])	378	=item $json = $json->canonical ([$enable])
225		379
226	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
227	by sorting their keys. This is adding a comparatively high overhead.	381	by sorting their keys. This is adding a comparatively high overhead.
…		…
229	If C<$enable> is false, then the C<encode> method will output key-value	383	If C<$enable> is false, then the C<encode> method will output key-value
230	pairs in the order Perl stores them (which will likely change between runs	384	pairs in the order Perl stores them (which will likely change between runs
231	of the same script).	385	of the same script).
232		386
233	This option is useful if you want the same data structure to be encoded as	387	This option is useful if you want the same data structure to be encoded as
234	the same JSON string (given the same overall settings). If it is disabled,	388	the same JSON text (given the same overall settings). If it is disabled,
235	the same hash migh be encoded differently even if contains the same data,	389	the same hash might be encoded differently even if contains the same data,
236	as key-value pairs have no inherent ordering in Perl.	390	as key-value pairs have no inherent ordering in Perl.
237		391
238	This setting has no effect when decoding JSON strings.	392	This setting has no effect when decoding JSON texts.
239		393
240	=item $json = $json->allow_nonref ([$enable])	394	=item $json = $json->allow_nonref ([$enable])
241		395
242	If C<$enable> is true (or missing), then the C<encode> method can convert a	396	If C<$enable> is true (or missing), then the C<encode> method can convert a
243	non-reference into its corresponding string, number or null JSON value,	397	non-reference into its corresponding string, number or null JSON value,
244	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	398	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
245	values instead of croaking.	399	values instead of croaking.
246		400
247	If C<$enable> is false, then the C<encode> method will croak if it isn't	401	If C<$enable> is false, then the C<encode> method will croak if it isn't
248	passed an arrayref or hashref, as JSON strings must either be an object	402	passed an arrayref or hashref, as JSON texts must either be an object
249	or array. Likewise, C<decode> will croak if given something that is not a	403	or array. Likewise, C<decode> will croak if given something that is not a
250	JSON object or array.	404	JSON object or array.
251		405
252	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	406	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
253	resulting in an invalid JSON text:	407	resulting in an invalid JSON text:
254		408
255	JSON::XS->new->allow_nonref->encode ("Hello, World!")	409	JSON::XS->new->allow_nonref->encode ("Hello, World!")
256	=> "Hello, World!"	410	=> "Hello, World!"
257		411
		412	=item $json = $json->allow_blessed ([$enable])
		413
		414	If C<$enable> is true (or missing), then the C<encode> method will not
		415	barf when it encounters a blessed reference. Instead, the value of the
		416	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		417	disabled or no C<to_json> method found) or a representation of the
		418	object (C<convert_blessed> enabled and C<to_json> method found) is being
		419	encoded. Has no effect on C<decode>.
		420
		421	If C<$enable> is false (the default), then C<encode> will throw an
		422	exception when it encounters a blessed object.
		423
		424	=item $json = $json->convert_blessed ([$enable])
		425
		426	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		427	blessed object, will check for the availability of the C<TO_JSON> method
		428	on the object's class. If found, it will be called in scalar context
		429	and the resulting scalar will be encoded instead of the object. If no
		430	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		431	to do.
		432
		433	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		434	returns other blessed objects, those will be handled in the same
		435	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		436	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		437	methods called by the Perl core (== not by the user of the object) are
		438	usually in upper case letters and to avoid collisions with the C<to_json>
		439	function.
		440
		441	This setting does not yet influence C<decode> in any way, but in the
		442	future, global hooks might get installed that influence C<decode> and are
		443	enabled by this setting.
		444
		445	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		446	to do when a blessed object is found.
		447
		448	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		449
		450	When C<$coderef> is specified, it will be called from C<decode> each
		451	time it decodes a JSON object. The only argument is a reference to the
		452	newly-created hash. If the code references returns a single scalar (which
		453	need not be a reference), this value (i.e. a copy of that scalar to avoid
		454	aliasing) is inserted into the deserialised data structure. If it returns
		455	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		456	original deserialised hash will be inserted. This setting can slow down
		457	decoding considerably.
		458
		459	When C<$coderef> is omitted or undefined, any existing callback will
		460	be removed and C<decode> will not change the deserialised hash in any
		461	way.
		462
		463	Example, convert all JSON objects into the integer 5:
		464
		465	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		466	# returns [5]
		467	$js->decode ('[{}]')
		468	# throw an exception because allow_nonref is not enabled
		469	# so a lone 5 is not allowed.
		470	$js->decode ('{"a":1, "b":2}');
		471
		472	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		473
		474	Works remotely similar to C<filter_json_object>, but is only called for
		475	JSON objects having a single key named C<$key>.
		476
		477	This C<$coderef> is called before the one specified via
		478	C<filter_json_object>, if any. It gets passed the single value in the JSON
		479	object. If it returns a single value, it will be inserted into the data
		480	structure. If it returns nothing (not even C<undef> but the empty list),
		481	the callback from C<filter_json_object> will be called next, as if no
		482	single-key callback were specified.
		483
		484	If C<$coderef> is omitted or undefined, the corresponding callback will be
		485	disabled. There can only ever be one callback for a given key.
		486
		487	As this callback gets called less often then the C<filter_json_object>
		488	one, decoding speed will not usually suffer as much. Therefore, single-key
		489	objects make excellent targets to serialise Perl objects into, especially
		490	as single-key JSON objects are as close to the type-tagged value concept
		491	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		492	support this in any way, so you need to make sure your data never looks
		493	like a serialised Perl hash.
		494
		495	Typical names for the single object key are C<__class_whatever__>, or
		496	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		497	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		498	with real hashes.
		499
		500	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		501	into the corresponding C<< $WIDGET{<id>} >> object:
		502
		503	# return whatever is in $WIDGET{5}:
		504	JSON::XS
		505	->new
		506	->filter_json_single_key_object (__widget__ => sub {
		507	$WIDGET{ $_[0] }
		508	})
		509	->decode ('{"__widget__": 5')
		510
		511	# this can be used with a TO_JSON method in some "widget" class
		512	# for serialisation to json:
		513	sub WidgetBase::TO_JSON {
		514	my ($self) = @_;
		515
		516	unless ($self->{id}) {
		517	$self->{id} = ..get..some..id..;
		518	$WIDGET{$self->{id}} = $self;
		519	}
		520
		521	{ __widget__ => $self->{id} }
		522	}
		523
258	=item $json = $json->shrink ([$enable])	524	=item $json = $json->shrink ([$enable])
259		525
260	Perl usually over-allocates memory a bit when allocating space for	526	Perl usually over-allocates memory a bit when allocating space for
261	strings. This flag optionally resizes strings generated by either	527	strings. This flag optionally resizes strings generated by either
262	C<encode> or C<decode> to their minimum size possible. This can save	528	C<encode> or C<decode> to their minimum size possible. This can save
263	memory when your JSON strings are either very very long or you have many	529	memory when your JSON texts are either very very long or you have many
264	short strings. It will also try to downgrade any strings to octet-form	530	short strings. It will also try to downgrade any strings to octet-form
265	if possible: perl stores strings internally either in an encoding called	531	if possible: perl stores strings internally either in an encoding called
266	UTF-X or in octet-form. The latter cannot store everything but uses less	532	UTF-X or in octet-form. The latter cannot store everything but uses less
267	space in general.	533	space in general (and some buggy Perl or C code might even rely on that
		534	internal representation being used).
268		535
		536	The actual definition of what shrink does might change in future versions,
		537	but it will always try to save space at the expense of time.
		538
269	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	539	If C<$enable> is true (or missing), the string returned by C<encode> will
270	while all strings generated by C<decode> will also be shrunk-to-fit.	540	be shrunk-to-fit, while all strings generated by C<decode> will also be
		541	shrunk-to-fit.
271		542
272	If C<$enable> is false, then the normal perl allocation algorithms are used.	543	If C<$enable> is false, then the normal perl allocation algorithms are used.
273	If you work with your data, then this is likely to be faster.	544	If you work with your data, then this is likely to be faster.
274		545
275	In the future, this setting might control other things, such as converting	546	In the future, this setting might control other things, such as converting
276	strings that look like integers or floats into integers or floats	547	strings that look like integers or floats into integers or floats
277	internally (there is no difference on the Perl level), saving space.	548	internally (there is no difference on the Perl level), saving space.
278		549
		550	=item $json = $json->max_depth ([$maximum_nesting_depth])
		551
		552	Sets the maximum nesting level (default C<512>) accepted while encoding
		553	or decoding. If the JSON text or Perl data structure has an equal or
		554	higher nesting level then this limit, then the encoder and decoder will
		555	stop and croak at that point.
		556
		557	Nesting level is defined by number of hash- or arrayrefs that the encoder
		558	needs to traverse to reach a given point or the number of C<{> or C<[>
		559	characters without their matching closing parenthesis crossed to reach a
		560	given character in a string.
		561
		562	Setting the maximum depth to one disallows any nesting, so that ensures
		563	that the object is only a single hash/object or array.
		564
		565	The argument to C<max_depth> will be rounded up to the next highest power
		566	of two. If no argument is given, the highest possible setting will be
		567	used, which is rarely useful.
		568
		569	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		570
		571	=item $json = $json->max_size ([$maximum_string_size])
		572
		573	Set the maximum length a JSON text may have (in bytes) where decoding is
		574	being attempted. The default is C<0>, meaning no limit. When C<decode>
		575	is called on a string longer then this number of characters it will not
		576	attempt to decode the string but throw an exception. This setting has no
		577	effect on C<encode> (yet).
		578
		579	The argument to C<max_size> will be rounded up to the next B<highest>
		580	power of two (so may be more than requested). If no argument is given, the
		581	limit check will be deactivated (same as when C<0> is specified).
		582
		583	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		584
279	=item $json_string = $json->encode ($perl_scalar)	585	=item $json_text = $json->encode ($perl_scalar)
280		586
281	Converts the given Perl data structure (a simple scalar or a reference	587	Converts the given Perl data structure (a simple scalar or a reference
282	to a hash or array) to its JSON representation. Simple scalars will be	588	to a hash or array) to its JSON representation. Simple scalars will be
283	converted into JSON string or number sequences, while references to arrays	589	converted into JSON string or number sequences, while references to arrays
284	become JSON arrays and references to hashes become JSON objects. Undefined	590	become JSON arrays and references to hashes become JSON objects. Undefined
285	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	591	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
286	nor C<false> values will be generated.	592	nor C<false> values will be generated.
287		593
288	=item $perl_scalar = $json->decode ($json_string)	594	=item $perl_scalar = $json->decode ($json_text)
289		595
290	The opposite of C<encode>: expects a JSON string and tries to parse it,	596	The opposite of C<encode>: expects a JSON text and tries to parse it,
291	returning the resulting simple scalar or reference. Croaks on error.	597	returning the resulting simple scalar or reference. Croaks on error.
292		598
293	JSON numbers and strings become simple Perl scalars. JSON arrays become	599	JSON numbers and strings become simple Perl scalars. JSON arrays become
294	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	600	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
295	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	601	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
296		602
		603	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		604
		605	This works like the C<decode> method, but instead of raising an exception
		606	when there is trailing garbage after the first JSON object, it will
		607	silently stop parsing there and return the number of characters consumed
		608	so far.
		609
		610	This is useful if your JSON texts are not delimited by an outer protocol
		611	(which is not the brightest thing to do in the first place) and you need
		612	to know where the JSON text ends.
		613
		614	JSON::XS->new->decode_prefix ("[1] the tail")
		615	=> ([], 3)
		616
297	=back	617	=back
		618
298		619
299	=head1 MAPPING	620	=head1 MAPPING
300		621
301	This section describes how JSON::XS maps Perl values to JSON values and	622	This section describes how JSON::XS maps Perl values to JSON values and
302	vice versa. These mappings are designed to "do the right thing" in most	623	vice versa. These mappings are designed to "do the right thing" in most
303	circumstances automatically, preserving round-tripping characteristics	624	circumstances automatically, preserving round-tripping characteristics
304	(what you put in comes out as something equivalent).	625	(what you put in comes out as something equivalent).
305		626
306	For the more enlightened: note that in the following descriptions,	627	For the more enlightened: note that in the following descriptions,
307	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	628	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
308	refers to the abstract Perl language itself.	629	refers to the abstract Perl language itself.
309		630
		631
310	=head2 JSON -> PERL	632	=head2 JSON -> PERL
311		633
312	=over 4	634	=over 4
313		635
314	=item object	636	=item object
315		637
316	A JSON object becomes a reference to a hash in Perl. No ordering of object	638	A JSON object becomes a reference to a hash in Perl. No ordering of object
317	keys is preserved.	639	keys is preserved (JSON does not preserve object key ordering itself).
318		640
319	=item array	641	=item array
320		642
321	A JSON array becomes a reference to an array in Perl.	643	A JSON array becomes a reference to an array in Perl.
322		644
…		…
326	are represented by the same codepoints in the Perl string, so no manual	648	are represented by the same codepoints in the Perl string, so no manual
327	decoding is necessary.	649	decoding is necessary.
328		650
329	=item number	651	=item number
330		652
331	A JSON number becomes either an integer or numeric (floating point)	653	A JSON number becomes either an integer, numeric (floating point) or
332	scalar in perl, depending on its range and any fractional parts. On the	654	string scalar in perl, depending on its range and any fractional parts. On
333	Perl level, there is no difference between those as Perl handles all the	655	the Perl level, there is no difference between those as Perl handles all
334	conversion details, but an integer may take slightly less memory and might	656	the conversion details, but an integer may take slightly less memory and
335	represent more values exactly than (floating point) numbers.	657	might represent more values exactly than (floating point) numbers.
		658
		659	If the number consists of digits only, JSON::XS will try to represent
		660	it as an integer value. If that fails, it will try to represent it as
		661	a numeric (floating point) value if that is possible without loss of
		662	precision. Otherwise it will preserve the number as a string value.
		663
		664	Numbers containing a fractional or exponential part will always be
		665	represented as numeric (floating point) values, possibly at a loss of
		666	precision.
		667
		668	This might create round-tripping problems as numbers might become strings,
		669	but as Perl is typeless there is no other way to do it.
336		670
337	=item true, false	671	=item true, false
338		672
339	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	673	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
340	this process. Future versions might represent those values differently,	674	respectively. They are overloaded to act almost exactly like the numbers
341	but they will be guarenteed to act like these integers would normally in	675	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
342	Perl.	676	the C<JSON::XS::is_bool> function.
343		677
344	=item null	678	=item null
345		679
346	A JSON null atom becomes C<undef> in Perl.	680	A JSON null atom becomes C<undef> in Perl.
347		681
348	=back	682	=back
		683
349		684
350	=head2 PERL -> JSON	685	=head2 PERL -> JSON
351		686
352	The mapping from Perl to JSON is slightly more difficult, as Perl is a	687	The mapping from Perl to JSON is slightly more difficult, as Perl is a
353	truly typeless language, so we can only guess which JSON type is meant by	688	truly typeless language, so we can only guess which JSON type is meant by
…		…
356	=over 4	691	=over 4
357		692
358	=item hash references	693	=item hash references
359		694
360	Perl hash references become JSON objects. As there is no inherent ordering	695	Perl hash references become JSON objects. As there is no inherent ordering
361	in hash keys, they will usually be encoded in a pseudo-random order that	696	in hash keys (or JSON objects), they will usually be encoded in a
362	can change between runs of the same program but stays generally the same	697	pseudo-random order that can change between runs of the same program but
363	within the single run of a program. JSON::XS can optionally sort the hash	698	stays generally the same within a single run of a program. JSON::XS can
364	keys (determined by the I<canonical> flag), so the same datastructure	699	optionally sort the hash keys (determined by the I<canonical> flag), so
365	will serialise to the same JSON text (given same settings and version of	700	the same datastructure will serialise to the same JSON text (given same
366	JSON::XS), but this incurs a runtime overhead.	701	settings and version of JSON::XS), but this incurs a runtime overhead
		702	and is only rarely useful, e.g. when you want to compare some JSON text
		703	against another for equality.
367		704
368	=item array references	705	=item array references
369		706
370	Perl array references become JSON arrays.	707	Perl array references become JSON arrays.
		708
		709	=item other references
		710
		711	Other unblessed references are generally not allowed and will cause an
		712	exception to be thrown, except for references to the integers C<0> and
		713	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		714	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		715
		716	to_json [\0,JSON::XS::true] # yields [false,true]
		717
		718	=item JSON::XS::true, JSON::XS::false
		719
		720	These special values become JSON true and JSON false values,
		721	respectively. You can also use C<\1> and C<\0> directly if you want.
371		722
372	=item blessed objects	723	=item blessed objects
373		724
374	Blessed objects are not allowed. JSON::XS currently tries to encode their	725	Blessed objects are not allowed. JSON::XS currently tries to encode their
375	underlying representation (hash- or arrayref), but this behaviour might	726	underlying representation (hash- or arrayref), but this behaviour might
…		…
392	to_json [$value] # yields ["5"]	743	to_json [$value] # yields ["5"]
393		744
394	# undef becomes null	745	# undef becomes null
395	to_json [undef] # yields [null]	746	to_json [undef] # yields [null]
396		747
397	You can force the type to be a string by stringifying it:	748	You can force the type to be a JSON string by stringifying it:
398		749
399	my $x = 3.1; # some variable containing a number	750	my $x = 3.1; # some variable containing a number
400	"$x"; # stringified	751	"$x"; # stringified
401	$x .= ""; # another, more awkward way to stringify	752	$x .= ""; # another, more awkward way to stringify
402	print $x; # perl does it for you, too, quite often	753	print $x; # perl does it for you, too, quite often
403		754
404	You can force the type to be a number by numifying it:	755	You can force the type to be a JSON number by numifying it:
405		756
406	my $x = "3"; # some variable containing a string	757	my $x = "3"; # some variable containing a string
407	$x += 0; # numify it, ensuring it will be dumped as a number	758	$x += 0; # numify it, ensuring it will be dumped as a number
408	$x *= 1; # same thing, the choise is yours.	759	$x *= 1; # same thing, the choice is yours.
409		760
410	You can not currently output JSON booleans or force the type in other,	761	You can not currently force the type in other, less obscure, ways. Tell me
411	less obscure, ways. Tell me if you need this capability.	762	if you need this capability.
412
413	=item circular data structures
414
415	Those will be encoded until memory or stackspace runs out.
416		763
417	=back	764	=back
		765
418		766
419	=head1 COMPARISON	767	=head1 COMPARISON
420		768
421	As already mentioned, this module was created because none of the existing	769	As already mentioned, this module was created because none of the existing
422	JSON modules could be made to work correctly. First I will describe the	770	JSON modules could be made to work correctly. First I will describe the
…		…
428		776
429	=item JSON 1.07	777	=item JSON 1.07
430		778
431	Slow (but very portable, as it is written in pure Perl).	779	Slow (but very portable, as it is written in pure Perl).
432		780
433	Undocumented/buggy Unicode handling (how JSON handles unicode values is	781	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
434	undocumented. One can get far by feeding it unicode strings and doing	782	undocumented. One can get far by feeding it Unicode strings and doing
435	en-/decoding oneself, but unicode escapes are not working properly).	783	en-/decoding oneself, but Unicode escapes are not working properly).
436		784
437	No roundtripping (strings get clobbered if they look like numbers, e.g.	785	No roundtripping (strings get clobbered if they look like numbers, e.g.
438	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	786	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
439	decode into the number 2.	787	decode into the number 2.
440		788
…		…
448		796
449	Has problems handling many Perl values (e.g. regex results and other magic	797	Has problems handling many Perl values (e.g. regex results and other magic
450	values will make it croak).	798	values will make it croak).
451		799
452	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	800	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
453	which is not a valid JSON string.	801	which is not a valid JSON text.
454		802
455	Unmaintained (maintainer unresponsive for many months, bugs are not	803	Unmaintained (maintainer unresponsive for many months, bugs are not
456	getting fixed).	804	getting fixed).
457		805
458	=item JSON::Syck 0.21	806	=item JSON::Syck 0.21
…		…
460	Very buggy (often crashes).	808	Very buggy (often crashes).
461		809
462	Very inflexible (no human-readable format supported, format pretty much	810	Very inflexible (no human-readable format supported, format pretty much
463	undocumented. I need at least a format for easy reading by humans and a	811	undocumented. I need at least a format for easy reading by humans and a
464	single-line compact format for use in a protocol, and preferably a way to	812	single-line compact format for use in a protocol, and preferably a way to
465	generate ASCII-only JSON strings).	813	generate ASCII-only JSON texts).
466		814
467	Completely broken (and confusingly documented) Unicode handling (unicode	815	Completely broken (and confusingly documented) Unicode handling (Unicode
468	escapes are not working properly, you need to set ImplicitUnicode to	816	escapes are not working properly, you need to set ImplicitUnicode to
469	I<different> values on en- and decoding to get symmetric behaviour).	817	I<different> values on en- and decoding to get symmetric behaviour).
470		818
471	No roundtripping (simple cases work, but this depends on wether the scalar	819	No roundtripping (simple cases work, but this depends on whether the scalar
472	value was used in a numeric context or not).	820	value was used in a numeric context or not).
473		821
474	Dumping hashes may skip hash values depending on iterator state.	822	Dumping hashes may skip hash values depending on iterator state.
475		823
476	Unmaintained (maintainer unresponsive for many months, bugs are not	824	Unmaintained (maintainer unresponsive for many months, bugs are not
477	getting fixed).	825	getting fixed).
478		826
479	Does not check input for validity (i.e. will accept non-JSON input and	827	Does not check input for validity (i.e. will accept non-JSON input and
480	return "something" instead of raising an exception. This is a security	828	return "something" instead of raising an exception. This is a security
481	issue: imagine two banks transfering money between each other using	829	issue: imagine two banks transferring money between each other using
482	JSON. One bank might parse a given non-JSON request and deduct money,	830	JSON. One bank might parse a given non-JSON request and deduct money,
483	while the other might reject the transaction with a syntax error. While a	831	while the other might reject the transaction with a syntax error. While a
484	good protocol will at least recover, that is extra unnecessary work and	832	good protocol will at least recover, that is extra unnecessary work and
485	the transaction will still not succeed).	833	the transaction will still not succeed).
486		834
487	=item JSON::DWIW 0.04	835	=item JSON::DWIW 0.04
488		836
489	Very fast. Very natural. Very nice.	837	Very fast. Very natural. Very nice.
490		838
491	Undocumented unicode handling (but the best of the pack. Unicode escapes	839	Undocumented Unicode handling (but the best of the pack. Unicode escapes
492	still don't get parsed properly).	840	still don't get parsed properly).
493		841
494	Very inflexible.	842	Very inflexible.
495		843
496	No roundtripping.	844	No roundtripping.
497		845
498	Does not generate valid JSON (key strings are often unquoted, empty keys	846	Does not generate valid JSON texts (key strings are often unquoted, empty keys
499	result in nothing being output)	847	result in nothing being output)
500		848
501	Does not check input for validity.	849	Does not check input for validity.
502		850
503	=back	851	=back
		852
		853
		854	=head2 JSON and YAML
		855
		856	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		857	however, a mass hysteria and very far from the truth. In general, there is
		858	no way to configure JSON::XS to output a data structure as valid YAML.
		859
		860	If you really must use JSON::XS to generate YAML, you should use this
		861	algorithm (subject to change in future versions):
		862
		863	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		864	my $yaml = $to_yaml->encode ($ref) . "\n";
		865
		866	This will usually generate JSON texts that also parse as valid
		867	YAML. Please note that YAML has hardcoded limits on (simple) object key
		868	lengths that JSON doesn't have, so you should make sure that your hash
		869	keys are noticeably shorter than the 1024 characters YAML allows.
		870
		871	There might be other incompatibilities that I am not aware of. In general
		872	you should not try to generate YAML with a JSON generator or vice versa,
		873	or try to parse JSON with a YAML parser or vice versa: chances are high
		874	that you will run into severe interoperability problems.
		875
504		876
505	=head2 SPEED	877	=head2 SPEED
506		878
507	It seems that JSON::XS is surprisingly fast, as shown in the following	879	It seems that JSON::XS is surprisingly fast, as shown in the following
508	tables. They have been generated with the help of the C<eg/bench> program	880	tables. They have been generated with the help of the C<eg/bench> program
509	in the JSON::XS distribution, to make it easy to compare on your own	881	in the JSON::XS distribution, to make it easy to compare on your own
510	system.	882	system.
511		883
512	First comes a comparison between various modules using a very short JSON	884	First comes a comparison between various modules using a very short
513	string (83 bytes), showing the number of encodes/decodes per second	885	single-line JSON string:
		886
		887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		888	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		889
		890	It shows the number of encodes/decodes per second (JSON::XS uses
514	(JSON::XS is the functional interface, while JSON::XS/2 is the OO	891	the functional interface, while JSON::XS/2 uses the OO interface
515	interface with pretty-printing and hashkey sorting enabled). Higher is	892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
516	better:	893	shrink). Higher is better:
517		894
		895	Storable \| 15779.925 \| 14169.946 \|
		896	-----------+------------+------------+
518	module \| encode \| decode \|	897	module \| encode \| decode \|
519	-----------\|------------\|------------\|	898	-----------\|------------\|------------\|
520	JSON \| 14006 \| 6820 \|	899	JSON \| 4990.842 \| 4088.813 \|
521	JSON::DWIW \| 200937 \| 120386 \|	900	JSON::DWIW \| 51653.990 \| 71575.154 \|
522	JSON::PC \| 85065 \| 129366 \|	901	JSON::PC \| 65948.176 \| 74631.744 \|
523	JSON::Syck \| 59898 \| 44232 \|	902	JSON::PP \| 8931.652 \| 3817.168 \|
524	JSON::XS \| 1171478 \| 342435 \|	903	JSON::Syck \| 24877.248 \| 27776.848 \|
525	JSON::XS/2 \| 730760 \| 328714 \|	904	JSON::XS \| 388361.481 \| 227951.304 \|
		905	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		906	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		907	Storable \| 16500.016 \| 135300.129 \|
526	-----------+------------+------------+	908	-----------+------------+------------+
527		909
528	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	910	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		911	about three times faster on decoding, and over forty times faster
529	times faster than JSON, even with pretty-printing and key sorting.	912	than JSON, even with pretty-printing and key sorting. It also compares
		913	favourably to Storable for small amounts of data.
530		914
531	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
532	search API (http://nanoref.com/yahooapis/mgPdGg):	916	search API (http://nanoref.com/yahooapis/mgPdGg):
533		917
534	module \| encode \| decode \|	918	module \| encode \| decode \|
535	-----------\|------------\|------------\|	919	-----------\|------------\|------------\|
536	JSON \| 673 \| 38 \|	920	JSON \| 55.260 \| 34.971 \|
537	JSON::DWIW \| 5271 \| 770 \|	921	JSON::DWIW \| 825.228 \| 1082.513 \|
538	JSON::PC \| 9901 \| 2491 \|	922	JSON::PC \| 3571.444 \| 2394.829 \|
539	JSON::Syck \| 2360 \| 786 \|	923	JSON::PP \| 210.987 \| 32.574 \|
540	JSON::XS \| 37398 \| 3202 \|	924	JSON::Syck \| 552.551 \| 787.544 \|
541	JSON::XS/2 \| 13765 \| 3153 \|	925	JSON::XS \| 5780.463 \| 4854.519 \|
		926	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		927	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		928	Storable \| 4445.002 \| 5235.027 \|
542	-----------+------------+------------+	929	-----------+------------+------------+
543		930
544	Again, JSON::XS leads by far in the encoding case, while still beating	931	Again, JSON::XS leads by far (except for Storable which non-surprisingly
545	every other module in the decoding case.	932	decodes faster).
546		933
547	On large strings containing lots of unicode characters, some modules	934	On large strings containing lots of high Unicode characters, some modules
548	(such as JSON::PC) decode faster than JSON::XS, but the result will be	935	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
549	broken due to missing unicode handling. Others refuse to decode or encode	936	will be broken due to missing (or wrong) Unicode handling. Others refuse
550	properly, so it was impossible to prepare a fair comparison table for that	937	to decode or encode properly, so it was impossible to prepare a fair
551	case.	938	comparison table for that case.
552		939
553	=head1 RESOURCE LIMITS
554		940
555	JSON::XS does not impose any limits on the size of JSON texts or Perl	941	=head1 SECURITY CONSIDERATIONS
556	values they represent - if your machine can handle it, JSON::XS will	942
557	encode or decode it. Future versions might optionally impose structure	943	When you are using JSON in a protocol, talking to untrusted potentially
558	depth and memory use resource limits.	944	hostile creatures requires relatively few measures.
		945
		946	First of all, your JSON decoder should be secure, that is, should not have
		947	any buffer overflows. Obviously, this module should ensure that and I am
		948	trying hard on making that true, but you never know.
		949
		950	Second, you need to avoid resource-starving attacks. That means you should
		951	limit the size of JSON texts you accept, or make sure then when your
		952	resources run out, that's just fine (e.g. by using a separate process that
		953	can crash safely). The size of a JSON text in octets or characters is
		954	usually a good indication of the size of the resources required to decode
		955	it into a Perl structure. While JSON::XS can check the size of the JSON
		956	text, it might be too late when you already have it in memory, so you
		957	might want to check the size before you accept the string.
		958
		959	Third, JSON::XS recurses using the C stack when decoding objects and
		960	arrays. The C stack is a limited resource: for instance, on my amd64
		961	machine with 8MB of stack size I can decode around 180k nested arrays but
		962	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		963	to free the temporary). If that is exceeded, the program crashes. to be
		964	conservative, the default nesting limit is set to 512. If your process
		965	has a smaller stack, you should adjust this setting accordingly with the
		966	C<max_depth> method.
		967
		968	And last but least, something else could bomb you that I forgot to think
		969	of. In that case, you get to keep the pieces. I am always open for hints,
		970	though...
		971
		972	If you are using JSON::XS to return packets to consumption
		973	by JavaScript scripts in a browser you should have a look at
		974	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		975	you are vulnerable to some common attack vectors (which really are browser
		976	design bugs, but it is still you who will have to deal with it, as major
		977	browser developers care only for features, not about doing security
		978	right).
		979
		980
		981	=head1 THREADS
		982
		983	This module is I<not> guaranteed to be thread safe and there are no
		984	plans to change this until Perl gets thread support (as opposed to the
		985	horribly slow so-called "threads" which are simply slow and bloated
		986	process simulations - use fork, its I<much> faster, cheaper, better).
		987
		988	(It might actually work, but you have been warned).
		989
559		990
560	=head1 BUGS	991	=head1 BUGS
561		992
562	While the goal of this module is to be correct, that unfortunately does	993	While the goal of this module is to be correct, that unfortunately does
563	not mean its bug-free, only that I think its design is bug-free. It is	994	not mean its bug-free, only that I think its design is bug-free. It is
564	still very young and not well-tested. If you keep reporting bugs they will	995	still relatively early in its development. If you keep reporting bugs they
565	be fixed swiftly, though.	996	will be fixed swiftly, though.
		997
		998	Please refrain from using rt.cpan.org or any other bug reporting
		999	service. I put the contact address into my modules for a reason.
566		1000
567	=cut	1001	=cut
		1002
		1003	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1004	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1005
		1006	sub true() { $true }
		1007	sub false() { $false }
		1008
		1009	sub is_bool($) {
		1010	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1011	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1012	}
		1013
		1014	XSLoader::load "JSON::XS", $VERSION;
		1015
		1016	package JSON::XS::Boolean;
		1017
		1018	use overload
		1019	"0+" => sub { ${$_[0]} },
		1020	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1021	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1022	fallback => 1;
568		1023
569	1;	1024	1;
570		1025
571	=head1 AUTHOR	1026	=head1 AUTHOR
572		1027

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Comparing JSON-XS/XS.pm (file contents): Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs. Revision 1.68 by root, Tue Oct 23 03:30:02 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs.
Revision 1.68 by root, Tue Oct 23 03:30:02 2007 UTC