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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.17 by root, Sat Mar 24 19:42:14 2007 UTC vs.
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
		5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		7
5	=head1 SYNOPSIS	8	=head1 SYNOPSIS
6		9
7	use JSON::XS;	10	use JSON::XS;
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 texts 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
…		…
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 = '0.5';	89	our $VERSION = '1.6';
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_text = 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:	109	This function call is functionally identical to:
107		110
108	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
109		112
110	except being faster.	113	except being faster.
111		114
112	=item $perl_scalar = from_json $json_text	115	=item $perl_scalar = from_json $json_text
113		116
114	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
115	parse that as an UTF-8 encoded JSON text, returning the resulting simple	118	to parse that as an UTF-8 encoded JSON text, returning the resulting
116	scalar or reference. Croaks on error.	119	reference. Croaks on error.
117		120
118	This function call is functionally identical to:	121	This function call is functionally identical to:
119		122
120	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
121		124
122	except being faster.	125	except being faster.
123		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.
		135
124	=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
125		186
126	=head1 OBJECT-ORIENTED INTERFACE	187	=head1 OBJECT-ORIENTED INTERFACE
127		188
128	The object oriented interface lets you configure your own encoding or	189	The object oriented interface lets you configure your own encoding or
129	decoding style, within the limits of supported formats.	190	decoding style, within the limits of supported formats.
…		…
141	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	202	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
142	=> {"a": [1, 2]}	203	=> {"a": [1, 2]}
143		204
144	=item $json = $json->ascii ([$enable])	205	=item $json = $json->ascii ([$enable])
145		206
		207	=item $enabled = $json->get_ascii
		208
146	If C<$enable> is true (or missing), then the C<encode> method will not	209	If C<$enable> is true (or missing), then the C<encode> method will not
147	generate characters outside the code range C<0..127> (which is ASCII). Any	210	generate characters outside the code range C<0..127> (which is ASCII). Any
148	unicode characters outside that range will be escaped using either a	211	Unicode characters outside that range will be escaped using either a
149	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
150	as per RFC4627.	213	as per RFC4627. The resulting encoded JSON text can be treated as a native
		214	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		215	or any other superset of ASCII.
151		216
152	If C<$enable> is false, then the C<encode> method will not escape Unicode	217	If C<$enable> is false, then the C<encode> method will not escape Unicode
153	characters unless required by the JSON syntax. This results in a faster	218	characters unless required by the JSON syntax or other flags. This results
154	and more compact format.	219	in a faster and more compact format.
		220
		221	The main use for this flag is to produce JSON texts that can be
		222	transmitted over a 7-bit channel, as the encoded JSON texts will not
		223	contain any 8 bit characters.
155		224
156	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
157	=> ["\ud801\udc01"]	226	=> ["\ud801\udc01"]
158		227
		228	=item $json = $json->latin1 ([$enable])
		229
		230	=item $enabled = $json->get_latin1
		231
		232	If C<$enable> is true (or missing), then the C<encode> method will encode
		233	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		234	outside the code range C<0..255>. The resulting string can be treated as a
		235	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		236	will not be affected in any way by this flag, as C<decode> by default
		237	expects Unicode, which is a strict superset of latin1.
		238
		239	If C<$enable> is false, then the C<encode> method will not escape Unicode
		240	characters unless required by the JSON syntax or other flags.
		241
		242	The main use for this flag is efficiently encoding binary data as JSON
		243	text, as most octets will not be escaped, resulting in a smaller encoded
		244	size. The disadvantage is that the resulting JSON text is encoded
		245	in latin1 (and must correctly be treated as such when storing and
		246	transferring), a rare encoding for JSON. It is therefore most useful when
		247	you want to store data structures known to contain binary data efficiently
		248	in files or databases, not when talking to other JSON encoders/decoders.
		249
		250	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		251	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		252
159	=item $json = $json->utf8 ([$enable])	253	=item $json = $json->utf8 ([$enable])
		254
		255	=item $enabled = $json->get_utf8
160		256
161	If C<$enable> is true (or missing), then the C<encode> method will encode	257	If C<$enable> is true (or missing), then the C<encode> method will encode
162	the JSON result into UTF-8, as required by many protocols, while the	258	the JSON result into UTF-8, as required by many protocols, while the
163	C<decode> method expects to be handled an UTF-8-encoded string. Please	259	C<decode> method expects to be handled an UTF-8-encoded string. Please
164	note that UTF-8-encoded strings do not contain any characters outside the	260	note that UTF-8-encoded strings do not contain any characters outside the
165	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	261	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
166	versions, enabling this option might enable autodetection of the UTF-16	262	versions, enabling this option might enable autodetection of the UTF-16
167	and UTF-32 encoding families, as described in RFC4627.	263	and UTF-32 encoding families, as described in RFC4627.
168		264
169	If C<$enable> is false, then the C<encode> method will return the JSON	265	If C<$enable> is false, then the C<encode> method will return the JSON
170	string as a (non-encoded) unicode string, while C<decode> expects thus a	266	string as a (non-encoded) Unicode string, while C<decode> expects thus a
171	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	267	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
172	to be done yourself, e.g. using the Encode module.	268	to be done yourself, e.g. using the Encode module.
173		269
174	Example, output UTF-16BE-encoded JSON:	270	Example, output UTF-16BE-encoded JSON:
175		271
176	use Encode;	272	use Encode;
…		…
180		276
181	use Encode;	277	use Encode;
182	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);	278	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
183		279
184	=item $json = $json->pretty ([$enable])	280	=item $json = $json->pretty ([$enable])
		281
		282	=item $enabled = $json->get_pretty
185		283
186	This enables (or disables) all of the C<indent>, C<space_before> and	284	This enables (or disables) all of the C<indent>, C<space_before> and
187	C<space_after> (and in the future possibly more) flags in one call to	285	C<space_after> (and in the future possibly more) flags in one call to
188	generate the most readable (or most compact) form possible.	286	generate the most readable (or most compact) form possible.
189		287
…		…
198	]	296	]
199	}	297	}
200		298
201	=item $json = $json->indent ([$enable])	299	=item $json = $json->indent ([$enable])
202		300
		301	=item $enabled = $json->get_indent
		302
203	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	303	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
204	format as output, putting every array member or object/hash key-value pair	304	format as output, putting every array member or object/hash key-value pair
205	into its own line, identing them properly.	305	into its own line, indenting them properly.
206		306
207	If C<$enable> is false, no newlines or indenting will be produced, and the	307	If C<$enable> is false, no newlines or indenting will be produced, and the
208	resulting JSON text is guarenteed not to contain any C<newlines>.	308	resulting JSON text is guaranteed not to contain any C<newlines>.
209		309
210	This setting has no effect when decoding JSON texts.	310	This setting has no effect when decoding JSON texts.
211		311
212	=item $json = $json->space_before ([$enable])	312	=item $json = $json->space_before ([$enable])
		313
		314	=item $enabled = $json->get_space_before
213		315
214	If C<$enable> is true (or missing), then the C<encode> method will add an extra	316	If C<$enable> is true (or missing), then the C<encode> method will add an extra
215	optional space before the C<:> separating keys from values in JSON objects.	317	optional space before the C<:> separating keys from values in JSON objects.
216		318
217	If C<$enable> is false, then the C<encode> method will not add any extra	319	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
223	Example, space_before enabled, space_after and indent disabled:	325	Example, space_before enabled, space_after and indent disabled:
224		326
225	{"key" :"value"}	327	{"key" :"value"}
226		328
227	=item $json = $json->space_after ([$enable])	329	=item $json = $json->space_after ([$enable])
		330
		331	=item $enabled = $json->get_space_after
228		332
229	If C<$enable> is true (or missing), then the C<encode> method will add an extra	333	If C<$enable> is true (or missing), then the C<encode> method will add an extra
230	optional space after the C<:> separating keys from values in JSON objects	334	optional space after the C<:> separating keys from values in JSON objects
231	and extra whitespace after the C<,> separating key-value pairs and array	335	and extra whitespace after the C<,> separating key-value pairs and array
232	members.	336	members.
…		…
238		342
239	Example, space_before and indent disabled, space_after enabled:	343	Example, space_before and indent disabled, space_after enabled:
240		344
241	{"key": "value"}	345	{"key": "value"}
242		346
		347	=item $json = $json->relaxed ([$enable])
		348
		349	=item $enabled = $json->get_relaxed
		350
		351	If C<$enable> is true (or missing), then C<decode> will accept some
		352	extensions to normal JSON syntax (see below). C<encode> will not be
		353	affected in anyway. I<Be aware that this option makes you accept invalid
		354	JSON texts as if they were valid!>. I suggest only to use this option to
		355	parse application-specific files written by humans (configuration files,
		356	resource files etc.)
		357
		358	If C<$enable> is false (the default), then C<decode> will only accept
		359	valid JSON texts.
		360
		361	Currently accepted extensions are:
		362
		363	=over 4
		364
		365	=item * list items can have an end-comma
		366
		367	JSON I<separates> array elements and key-value pairs with commas. This
		368	can be annoying if you write JSON texts manually and want to be able to
		369	quickly append elements, so this extension accepts comma at the end of
		370	such items not just between them:
		371
		372	[
		373	1,
		374	2, <- this comma not normally allowed
		375	]
		376	{
		377	"k1": "v1",
		378	"k2": "v2", <- this comma not normally allowed
		379	}
		380
		381	=item * shell-style '#'-comments
		382
		383	Whenever JSON allows whitespace, shell-style comments are additionally
		384	allowed. They are terminated by the first carriage-return or line-feed
		385	character, after which more white-space and comments are allowed.
		386
		387	[
		388	1, # this comment not allowed in JSON
		389	# neither this one...
		390	]
		391
		392	=back
		393
243	=item $json = $json->canonical ([$enable])	394	=item $json = $json->canonical ([$enable])
		395
		396	=item $enabled = $json->get_canonical
244		397
245	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	398	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
246	by sorting their keys. This is adding a comparatively high overhead.	399	by sorting their keys. This is adding a comparatively high overhead.
247		400
248	If C<$enable> is false, then the C<encode> method will output key-value	401	If C<$enable> is false, then the C<encode> method will output key-value
249	pairs in the order Perl stores them (which will likely change between runs	402	pairs in the order Perl stores them (which will likely change between runs
250	of the same script).	403	of the same script).
251		404
252	This option is useful if you want the same data structure to be encoded as	405	This option is useful if you want the same data structure to be encoded as
253	the same JSON text (given the same overall settings). If it is disabled,	406	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,	407	the same hash might be encoded differently even if contains the same data,
255	as key-value pairs have no inherent ordering in Perl.	408	as key-value pairs have no inherent ordering in Perl.
256		409
257	This setting has no effect when decoding JSON texts.	410	This setting has no effect when decoding JSON texts.
258		411
259	=item $json = $json->allow_nonref ([$enable])	412	=item $json = $json->allow_nonref ([$enable])
		413
		414	=item $enabled = $json->get_allow_nonref
260		415
261	If C<$enable> is true (or missing), then the C<encode> method can convert a	416	If C<$enable> is true (or missing), then the C<encode> method can convert a
262	non-reference into its corresponding string, number or null JSON value,	417	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	418	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
264	values instead of croaking.	419	values instead of croaking.
…		…
272	resulting in an invalid JSON text:	427	resulting in an invalid JSON text:
273		428
274	JSON::XS->new->allow_nonref->encode ("Hello, World!")	429	JSON::XS->new->allow_nonref->encode ("Hello, World!")
275	=> "Hello, World!"	430	=> "Hello, World!"
276		431
		432	=item $json = $json->allow_blessed ([$enable])
		433
		434	=item $enabled = $json->get_allow_bless
		435
		436	If C<$enable> is true (or missing), then the C<encode> method will not
		437	barf when it encounters a blessed reference. Instead, the value of the
		438	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		439	disabled or no C<to_json> method found) or a representation of the
		440	object (C<convert_blessed> enabled and C<to_json> method found) is being
		441	encoded. Has no effect on C<decode>.
		442
		443	If C<$enable> is false (the default), then C<encode> will throw an
		444	exception when it encounters a blessed object.
		445
		446	=item $json = $json->convert_blessed ([$enable])
		447
		448	=item $enabled = $json->get_convert_blessed
		449
		450	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		451	blessed object, will check for the availability of the C<TO_JSON> method
		452	on the object's class. If found, it will be called in scalar context
		453	and the resulting scalar will be encoded instead of the object. If no
		454	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		455	to do.
		456
		457	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		458	returns other blessed objects, those will be handled in the same
		459	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		460	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		461	methods called by the Perl core (== not by the user of the object) are
		462	usually in upper case letters and to avoid collisions with the C<to_json>
		463	function.
		464
		465	This setting does not yet influence C<decode> in any way, but in the
		466	future, global hooks might get installed that influence C<decode> and are
		467	enabled by this setting.
		468
		469	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		470	to do when a blessed object is found.
		471
		472	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		473
		474	When C<$coderef> is specified, it will be called from C<decode> each
		475	time it decodes a JSON object. The only argument is a reference to the
		476	newly-created hash. If the code references returns a single scalar (which
		477	need not be a reference), this value (i.e. a copy of that scalar to avoid
		478	aliasing) is inserted into the deserialised data structure. If it returns
		479	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		480	original deserialised hash will be inserted. This setting can slow down
		481	decoding considerably.
		482
		483	When C<$coderef> is omitted or undefined, any existing callback will
		484	be removed and C<decode> will not change the deserialised hash in any
		485	way.
		486
		487	Example, convert all JSON objects into the integer 5:
		488
		489	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		490	# returns [5]
		491	$js->decode ('[{}]')
		492	# throw an exception because allow_nonref is not enabled
		493	# so a lone 5 is not allowed.
		494	$js->decode ('{"a":1, "b":2}');
		495
		496	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		497
		498	Works remotely similar to C<filter_json_object>, but is only called for
		499	JSON objects having a single key named C<$key>.
		500
		501	This C<$coderef> is called before the one specified via
		502	C<filter_json_object>, if any. It gets passed the single value in the JSON
		503	object. If it returns a single value, it will be inserted into the data
		504	structure. If it returns nothing (not even C<undef> but the empty list),
		505	the callback from C<filter_json_object> will be called next, as if no
		506	single-key callback were specified.
		507
		508	If C<$coderef> is omitted or undefined, the corresponding callback will be
		509	disabled. There can only ever be one callback for a given key.
		510
		511	As this callback gets called less often then the C<filter_json_object>
		512	one, decoding speed will not usually suffer as much. Therefore, single-key
		513	objects make excellent targets to serialise Perl objects into, especially
		514	as single-key JSON objects are as close to the type-tagged value concept
		515	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		516	support this in any way, so you need to make sure your data never looks
		517	like a serialised Perl hash.
		518
		519	Typical names for the single object key are C<__class_whatever__>, or
		520	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		521	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		522	with real hashes.
		523
		524	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		525	into the corresponding C<< $WIDGET{<id>} >> object:
		526
		527	# return whatever is in $WIDGET{5}:
		528	JSON::XS
		529	->new
		530	->filter_json_single_key_object (__widget__ => sub {
		531	$WIDGET{ $_[0] }
		532	})
		533	->decode ('{"__widget__": 5')
		534
		535	# this can be used with a TO_JSON method in some "widget" class
		536	# for serialisation to json:
		537	sub WidgetBase::TO_JSON {
		538	my ($self) = @_;
		539
		540	unless ($self->{id}) {
		541	$self->{id} = ..get..some..id..;
		542	$WIDGET{$self->{id}} = $self;
		543	}
		544
		545	{ __widget__ => $self->{id} }
		546	}
		547
277	=item $json = $json->shrink ([$enable])	548	=item $json = $json->shrink ([$enable])
278		549
		550	=item $enabled = $json->get_shrink
		551
279	Perl usually over-allocates memory a bit when allocating space for	552	Perl usually over-allocates memory a bit when allocating space for
280	strings. This flag optionally resizes strings generated by either	553	strings. This flag optionally resizes strings generated by either
281	C<encode> or C<decode> to their minimum size possible. This can save	554	C<encode> or C<decode> to their minimum size possible. This can save
282	memory when your JSON texts are either very very long or you have many	555	memory when your JSON texts are either very very long or you have many
283	short strings. It will also try to downgrade any strings to octet-form	556	short strings. It will also try to downgrade any strings to octet-form
284	if possible: perl stores strings internally either in an encoding called	557	if possible: perl stores strings internally either in an encoding called
285	UTF-X or in octet-form. The latter cannot store everything but uses less	558	UTF-X or in octet-form. The latter cannot store everything but uses less
286	space in general.	559	space in general (and some buggy Perl or C code might even rely on that
		560	internal representation being used).
287		561
		562	The actual definition of what shrink does might change in future versions,
		563	but it will always try to save space at the expense of time.
		564
288	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	565	If C<$enable> is true (or missing), the string returned by C<encode> will
289	while all strings generated by C<decode> will also be shrunk-to-fit.	566	be shrunk-to-fit, while all strings generated by C<decode> will also be
		567	shrunk-to-fit.
290		568
291	If C<$enable> is false, then the normal perl allocation algorithms are used.	569	If C<$enable> is false, then the normal perl allocation algorithms are used.
292	If you work with your data, then this is likely to be faster.	570	If you work with your data, then this is likely to be faster.
293		571
294	In the future, this setting might control other things, such as converting	572	In the future, this setting might control other things, such as converting
295	strings that look like integers or floats into integers or floats	573	strings that look like integers or floats into integers or floats
296	internally (there is no difference on the Perl level), saving space.	574	internally (there is no difference on the Perl level), saving space.
		575
		576	=item $json = $json->max_depth ([$maximum_nesting_depth])
		577
		578	=item $max_depth = $json->get_max_depth
		579
		580	Sets the maximum nesting level (default C<512>) accepted while encoding
		581	or decoding. If the JSON text or Perl data structure has an equal or
		582	higher nesting level then this limit, then the encoder and decoder will
		583	stop and croak at that point.
		584
		585	Nesting level is defined by number of hash- or arrayrefs that the encoder
		586	needs to traverse to reach a given point or the number of C<{> or C<[>
		587	characters without their matching closing parenthesis crossed to reach a
		588	given character in a string.
		589
		590	Setting the maximum depth to one disallows any nesting, so that ensures
		591	that the object is only a single hash/object or array.
		592
		593	The argument to C<max_depth> will be rounded up to the next highest power
		594	of two. If no argument is given, the highest possible setting will be
		595	used, which is rarely useful.
		596
		597	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		598
		599	=item $json = $json->max_size ([$maximum_string_size])
		600
		601	=item $max_size = $json->get_max_size
		602
		603	Set the maximum length a JSON text may have (in bytes) where decoding is
		604	being attempted. The default is C<0>, meaning no limit. When C<decode>
		605	is called on a string longer then this number of characters it will not
		606	attempt to decode the string but throw an exception. This setting has no
		607	effect on C<encode> (yet).
		608
		609	The argument to C<max_size> will be rounded up to the next B<highest>
		610	power of two (so may be more than requested). If no argument is given, the
		611	limit check will be deactivated (same as when C<0> is specified).
		612
		613	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
297		614
298	=item $json_text = $json->encode ($perl_scalar)	615	=item $json_text = $json->encode ($perl_scalar)
299		616
300	Converts the given Perl data structure (a simple scalar or a reference	617	Converts the given Perl data structure (a simple scalar or a reference
301	to a hash or array) to its JSON representation. Simple scalars will be	618	to a hash or array) to its JSON representation. Simple scalars will be
…		…
311		628
312	JSON numbers and strings become simple Perl scalars. JSON arrays become	629	JSON numbers and strings become simple Perl scalars. JSON arrays become
313	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	630	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>.	631	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
315		632
		633	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		634
		635	This works like the C<decode> method, but instead of raising an exception
		636	when there is trailing garbage after the first JSON object, it will
		637	silently stop parsing there and return the number of characters consumed
		638	so far.
		639
		640	This is useful if your JSON texts are not delimited by an outer protocol
		641	(which is not the brightest thing to do in the first place) and you need
		642	to know where the JSON text ends.
		643
		644	JSON::XS->new->decode_prefix ("[1] the tail")
		645	=> ([], 3)
		646
316	=back	647	=back
		648
317		649
318	=head1 MAPPING	650	=head1 MAPPING
319		651
320	This section describes how JSON::XS maps Perl values to JSON values and	652	This section describes how JSON::XS maps Perl values to JSON values and
321	vice versa. These mappings are designed to "do the right thing" in most	653	vice versa. These mappings are designed to "do the right thing" in most
322	circumstances automatically, preserving round-tripping characteristics	654	circumstances automatically, preserving round-tripping characteristics
323	(what you put in comes out as something equivalent).	655	(what you put in comes out as something equivalent).
324		656
325	For the more enlightened: note that in the following descriptions,	657	For the more enlightened: note that in the following descriptions,
326	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	658	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
327	refers to the abstract Perl language itself.	659	refers to the abstract Perl language itself.
328		660
		661
329	=head2 JSON -> PERL	662	=head2 JSON -> PERL
330		663
331	=over 4	664	=over 4
332		665
333	=item object	666	=item object
334		667
335	A JSON object becomes a reference to a hash in Perl. No ordering of object	668	A JSON object becomes a reference to a hash in Perl. No ordering of object
336	keys is preserved (JSON does not preserver object key ordering itself).	669	keys is preserved (JSON does not preserve object key ordering itself).
337		670
338	=item array	671	=item array
339		672
340	A JSON array becomes a reference to an array in Perl.	673	A JSON array becomes a reference to an array in Perl.
341		674
…		…
345	are represented by the same codepoints in the Perl string, so no manual	678	are represented by the same codepoints in the Perl string, so no manual
346	decoding is necessary.	679	decoding is necessary.
347		680
348	=item number	681	=item number
349		682
350	A JSON number becomes either an integer or numeric (floating point)	683	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	684	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	685	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	686	the conversion details, but an integer may take slightly less memory and
354	represent more values exactly than (floating point) numbers.	687	might represent more values exactly than (floating point) numbers.
		688
		689	If the number consists of digits only, JSON::XS will try to represent
		690	it as an integer value. If that fails, it will try to represent it as
		691	a numeric (floating point) value if that is possible without loss of
		692	precision. Otherwise it will preserve the number as a string value.
		693
		694	Numbers containing a fractional or exponential part will always be
		695	represented as numeric (floating point) values, possibly at a loss of
		696	precision.
		697
		698	This might create round-tripping problems as numbers might become strings,
		699	but as Perl is typeless there is no other way to do it.
355		700
356	=item true, false	701	=item true, false
357		702
358	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	703	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
359	this process. Future versions might represent those values differently,	704	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	705	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
361	Perl.	706	the C<JSON::XS::is_bool> function.
362		707
363	=item null	708	=item null
364		709
365	A JSON null atom becomes C<undef> in Perl.	710	A JSON null atom becomes C<undef> in Perl.
366		711
367	=back	712	=back
		713
368		714
369	=head2 PERL -> JSON	715	=head2 PERL -> JSON
370		716
371	The mapping from Perl to JSON is slightly more difficult, as Perl is a	717	The mapping from Perl to JSON is slightly more difficult, as Perl is a
372	truly typeless language, so we can only guess which JSON type is meant by	718	truly typeless language, so we can only guess which JSON type is meant by
…		…
375	=over 4	721	=over 4
376		722
377	=item hash references	723	=item hash references
378		724
379	Perl hash references become JSON objects. As there is no inherent ordering	725	Perl hash references become JSON objects. As there is no inherent ordering
380	in hash keys, they will usually be encoded in a pseudo-random order that	726	in hash keys (or JSON objects), they will usually be encoded in a
381	can change between runs of the same program but stays generally the same	727	pseudo-random order that can change between runs of the same program but
382	within a single run of a program. JSON::XS can optionally sort the hash	728	stays generally the same within a single run of a program. JSON::XS can
383	keys (determined by the I<canonical> flag), so the same datastructure	729	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	730	the same datastructure will serialise to the same JSON text (given same
385	JSON::XS), but this incurs a runtime overhead.	731	settings and version of JSON::XS), but this incurs a runtime overhead
		732	and is only rarely useful, e.g. when you want to compare some JSON text
		733	against another for equality.
386		734
387	=item array references	735	=item array references
388		736
389	Perl array references become JSON arrays.	737	Perl array references become JSON arrays.
		738
		739	=item other references
		740
		741	Other unblessed references are generally not allowed and will cause an
		742	exception to be thrown, except for references to the integers C<0> and
		743	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		744	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		745
		746	to_json [\0,JSON::XS::true] # yields [false,true]
		747
		748	=item JSON::XS::true, JSON::XS::false
		749
		750	These special values become JSON true and JSON false values,
		751	respectively. You can also use C<\1> and C<\0> directly if you want.
390		752
391	=item blessed objects	753	=item blessed objects
392		754
393	Blessed objects are not allowed. JSON::XS currently tries to encode their	755	Blessed objects are not allowed. JSON::XS currently tries to encode their
394	underlying representation (hash- or arrayref), but this behaviour might	756	underlying representation (hash- or arrayref), but this behaviour might
…		…
411	to_json [$value] # yields ["5"]	773	to_json [$value] # yields ["5"]
412		774
413	# undef becomes null	775	# undef becomes null
414	to_json [undef] # yields [null]	776	to_json [undef] # yields [null]
415		777
416	You can force the type to be a string by stringifying it:	778	You can force the type to be a JSON string by stringifying it:
417		779
418	my $x = 3.1; # some variable containing a number	780	my $x = 3.1; # some variable containing a number
419	"$x"; # stringified	781	"$x"; # stringified
420	$x .= ""; # another, more awkward way to stringify	782	$x .= ""; # another, more awkward way to stringify
421	print $x; # perl does it for you, too, quite often	783	print $x; # perl does it for you, too, quite often
422		784
423	You can force the type to be a number by numifying it:	785	You can force the type to be a JSON number by numifying it:
424		786
425	my $x = "3"; # some variable containing a string	787	my $x = "3"; # some variable containing a string
426	$x += 0; # numify it, ensuring it will be dumped as a number	788	$x += 0; # numify it, ensuring it will be dumped as a number
427	$x *= 1; # same thing, the choise is yours.	789	$x *= 1; # same thing, the choice is yours.
428		790
429	You can not currently output JSON booleans or force the type in other,	791	You can not currently force the type in other, less obscure, ways. Tell me
430	less obscure, ways. Tell me if you need this capability.	792	if you need this capability.
431
432	=item circular data structures
433
434	Those will be encoded until memory or stackspace runs out.
435		793
436	=back	794	=back
		795
437		796
438	=head1 COMPARISON	797	=head1 COMPARISON
439		798
440	As already mentioned, this module was created because none of the existing	799	As already mentioned, this module was created because none of the existing
441	JSON modules could be made to work correctly. First I will describe the	800	JSON modules could be made to work correctly. First I will describe the
…		…
447		806
448	=item JSON 1.07	807	=item JSON 1.07
449		808
450	Slow (but very portable, as it is written in pure Perl).	809	Slow (but very portable, as it is written in pure Perl).
451		810
452	Undocumented/buggy Unicode handling (how JSON handles unicode values is	811	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
453	undocumented. One can get far by feeding it unicode strings and doing	812	undocumented. One can get far by feeding it Unicode strings and doing
454	en-/decoding oneself, but unicode escapes are not working properly).	813	en-/decoding oneself, but Unicode escapes are not working properly).
455		814
456	No roundtripping (strings get clobbered if they look like numbers, e.g.	815	No round-tripping (strings get clobbered if they look like numbers, e.g.
457	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	816	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
458	decode into the number 2.	817	decode into the number 2.
459		818
460	=item JSON::PC 0.01	819	=item JSON::PC 0.01
461		820
462	Very fast.	821	Very fast.
463		822
464	Undocumented/buggy Unicode handling.	823	Undocumented/buggy Unicode handling.
465		824
466	No roundtripping.	825	No round-tripping.
467		826
468	Has problems handling many Perl values (e.g. regex results and other magic	827	Has problems handling many Perl values (e.g. regex results and other magic
469	values will make it croak).	828	values will make it croak).
470		829
471	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	830	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
481	Very inflexible (no human-readable format supported, format pretty much	840	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	841	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	842	single-line compact format for use in a protocol, and preferably a way to
484	generate ASCII-only JSON texts).	843	generate ASCII-only JSON texts).
485		844
486	Completely broken (and confusingly documented) Unicode handling (unicode	845	Completely broken (and confusingly documented) Unicode handling (Unicode
487	escapes are not working properly, you need to set ImplicitUnicode to	846	escapes are not working properly, you need to set ImplicitUnicode to
488	I<different> values on en- and decoding to get symmetric behaviour).	847	I<different> values on en- and decoding to get symmetric behaviour).
489		848
490	No roundtripping (simple cases work, but this depends on wether the scalar	849	No round-tripping (simple cases work, but this depends on whether the scalar
491	value was used in a numeric context or not).	850	value was used in a numeric context or not).
492		851
493	Dumping hashes may skip hash values depending on iterator state.	852	Dumping hashes may skip hash values depending on iterator state.
494		853
495	Unmaintained (maintainer unresponsive for many months, bugs are not	854	Unmaintained (maintainer unresponsive for many months, bugs are not
496	getting fixed).	855	getting fixed).
497		856
498	Does not check input for validity (i.e. will accept non-JSON input and	857	Does not check input for validity (i.e. will accept non-JSON input and
499	return "something" instead of raising an exception. This is a security	858	return "something" instead of raising an exception. This is a security
500	issue: imagine two banks transfering money between each other using	859	issue: imagine two banks transferring money between each other using
501	JSON. One bank might parse a given non-JSON request and deduct money,	860	JSON. One bank might parse a given non-JSON request and deduct money,
502	while the other might reject the transaction with a syntax error. While a	861	while the other might reject the transaction with a syntax error. While a
503	good protocol will at least recover, that is extra unnecessary work and	862	good protocol will at least recover, that is extra unnecessary work and
504	the transaction will still not succeed).	863	the transaction will still not succeed).
505		864
506	=item JSON::DWIW 0.04	865	=item JSON::DWIW 0.04
507		866
508	Very fast. Very natural. Very nice.	867	Very fast. Very natural. Very nice.
509		868
510	Undocumented unicode handling (but the best of the pack. Unicode escapes	869	Undocumented Unicode handling (but the best of the pack. Unicode escapes
511	still don't get parsed properly).	870	still don't get parsed properly).
512		871
513	Very inflexible.	872	Very inflexible.
514		873
515	No roundtripping.	874	No round-tripping.
516		875
517	Does not generate valid JSON texts (key strings are often unquoted, empty keys	876	Does not generate valid JSON texts (key strings are often unquoted, empty keys
518	result in nothing being output)	877	result in nothing being output)
519		878
520	Does not check input for validity.	879	Does not check input for validity.
521		880
522	=back	881	=back
		882
		883
		884	=head2 JSON and YAML
		885
		886	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		887	however, a mass hysteria and very far from the truth. In general, there is
		888	no way to configure JSON::XS to output a data structure as valid YAML.
		889
		890	If you really must use JSON::XS to generate YAML, you should use this
		891	algorithm (subject to change in future versions):
		892
		893	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		894	my $yaml = $to_yaml->encode ($ref) . "\n";
		895
		896	This will usually generate JSON texts that also parse as valid
		897	YAML. Please note that YAML has hardcoded limits on (simple) object key
		898	lengths that JSON doesn't have, so you should make sure that your hash
		899	keys are noticeably shorter than the 1024 characters YAML allows.
		900
		901	There might be other incompatibilities that I am not aware of. In general
		902	you should not try to generate YAML with a JSON generator or vice versa,
		903	or try to parse JSON with a YAML parser or vice versa: chances are high
		904	that you will run into severe interoperability problems.
		905
523		906
524	=head2 SPEED	907	=head2 SPEED
525		908
526	It seems that JSON::XS is surprisingly fast, as shown in the following	909	It seems that JSON::XS is surprisingly fast, as shown in the following
527	tables. They have been generated with the help of the C<eg/bench> program	910	tables. They have been generated with the help of the C<eg/bench> program
528	in the JSON::XS distribution, to make it easy to compare on your own	911	in the JSON::XS distribution, to make it easy to compare on your own
529	system.	912	system.
530		913
531	First comes a comparison between various modules using a very short JSON	914	First comes a comparison between various modules using a very short
532	string (83 bytes), showing the number of encodes/decodes per second	915	single-line JSON string:
		916
		917	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		918	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		919
		920	It shows the number of encodes/decodes per second (JSON::XS uses
533	(JSON::XS is the functional interface, while JSON::XS/2 is the OO	921	the functional interface, while JSON::XS/2 uses the OO interface
534	interface with pretty-printing and hashkey sorting enabled). Higher is	922	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
535	better:	923	shrink). Higher is better:
536		924
537	module \| encode \| decode \|	925	module \| encode \| decode \|
538	-----------\|------------\|------------\|	926	-----------\|------------\|------------\|
539	JSON \| 14006 \| 6820 \|	927	JSON 1.x \| 4990.842 \| 4088.813 \|
540	JSON::DWIW \| 200937 \| 120386 \|	928	JSON::DWIW \| 51653.990 \| 71575.154 \|
541	JSON::PC \| 85065 \| 129366 \|	929	JSON::PC \| 65948.176 \| 74631.744 \|
542	JSON::Syck \| 59898 \| 44232 \|	930	JSON::PP \| 8931.652 \| 3817.168 \|
543	JSON::XS \| 1171478 \| 342435 \|	931	JSON::Syck \| 24877.248 \| 27776.848 \|
544	JSON::XS/2 \| 730760 \| 328714 \|	932	JSON::XS \| 388361.481 \| 227951.304 \|
		933	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		934	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		935	Storable \| 16500.016 \| 135300.129 \|
545	-----------+------------+------------+	936	-----------+------------+------------+
546		937
547	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	938	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		939	about three times faster on decoding, and over forty times faster
548	times faster than JSON, even with pretty-printing and key sorting.	940	than JSON, even with pretty-printing and key sorting. It also compares
		941	favourably to Storable for small amounts of data.
549		942
550	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	943	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
551	search API (http://nanoref.com/yahooapis/mgPdGg):	944	search API (http://nanoref.com/yahooapis/mgPdGg):
552		945
553	module \| encode \| decode \|	946	module \| encode \| decode \|
554	-----------\|------------\|------------\|	947	-----------\|------------\|------------\|
555	JSON \| 673 \| 38 \|	948	JSON 1.x \| 55.260 \| 34.971 \|
556	JSON::DWIW \| 5271 \| 770 \|	949	JSON::DWIW \| 825.228 \| 1082.513 \|
557	JSON::PC \| 9901 \| 2491 \|	950	JSON::PC \| 3571.444 \| 2394.829 \|
558	JSON::Syck \| 2360 \| 786 \|	951	JSON::PP \| 210.987 \| 32.574 \|
559	JSON::XS \| 37398 \| 3202 \|	952	JSON::Syck \| 552.551 \| 787.544 \|
560	JSON::XS/2 \| 13765 \| 3153 \|	953	JSON::XS \| 5780.463 \| 4854.519 \|
		954	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		955	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		956	Storable \| 4445.002 \| 5235.027 \|
561	-----------+------------+------------+	957	-----------+------------+------------+
562		958
563	Again, JSON::XS leads by far in the encoding case, while still beating	959	Again, JSON::XS leads by far (except for Storable which non-surprisingly
564	every other module in the decoding case.	960	decodes faster).
565		961
566	On large strings containing lots of unicode characters, some modules	962	On large strings containing lots of high Unicode characters, some modules
567	(such as JSON::PC) decode faster than JSON::XS, but the result will be	963	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
568	broken due to missing unicode handling. Others refuse to decode or encode	964	will be broken due to missing (or wrong) Unicode handling. Others refuse
569	properly, so it was impossible to prepare a fair comparison table for that	965	to decode or encode properly, so it was impossible to prepare a fair
570	case.	966	comparison table for that case.
571		967
572	=head1 RESOURCE LIMITS
573		968
574	JSON::XS does not impose any limits on the size of JSON texts or Perl	969	=head1 SECURITY CONSIDERATIONS
575	values they represent - if your machine can handle it, JSON::XS will	970
576	encode or decode it. Future versions might optionally impose structure	971	When you are using JSON in a protocol, talking to untrusted potentially
577	depth and memory use resource limits.	972	hostile creatures requires relatively few measures.
		973
		974	First of all, your JSON decoder should be secure, that is, should not have
		975	any buffer overflows. Obviously, this module should ensure that and I am
		976	trying hard on making that true, but you never know.
		977
		978	Second, you need to avoid resource-starving attacks. That means you should
		979	limit the size of JSON texts you accept, or make sure then when your
		980	resources run out, that's just fine (e.g. by using a separate process that
		981	can crash safely). The size of a JSON text in octets or characters is
		982	usually a good indication of the size of the resources required to decode
		983	it into a Perl structure. While JSON::XS can check the size of the JSON
		984	text, it might be too late when you already have it in memory, so you
		985	might want to check the size before you accept the string.
		986
		987	Third, JSON::XS recurses using the C stack when decoding objects and
		988	arrays. The C stack is a limited resource: for instance, on my amd64
		989	machine with 8MB of stack size I can decode around 180k nested arrays but
		990	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		991	to free the temporary). If that is exceeded, the program crashes. to be
		992	conservative, the default nesting limit is set to 512. If your process
		993	has a smaller stack, you should adjust this setting accordingly with the
		994	C<max_depth> method.
		995
		996	And last but least, something else could bomb you that I forgot to think
		997	of. In that case, you get to keep the pieces. I am always open for hints,
		998	though...
		999
		1000	If you are using JSON::XS to return packets to consumption
		1001	by JavaScript scripts in a browser you should have a look at
		1002	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1003	you are vulnerable to some common attack vectors (which really are browser
		1004	design bugs, but it is still you who will have to deal with it, as major
		1005	browser developers care only for features, not about doing security
		1006	right).
		1007
		1008
		1009	=head1 THREADS
		1010
		1011	This module is I<not> guaranteed to be thread safe and there are no
		1012	plans to change this until Perl gets thread support (as opposed to the
		1013	horribly slow so-called "threads" which are simply slow and bloated
		1014	process simulations - use fork, its I<much> faster, cheaper, better).
		1015
		1016	(It might actually work, but you have been warned).
		1017
578		1018
579	=head1 BUGS	1019	=head1 BUGS
580		1020
581	While the goal of this module is to be correct, that unfortunately does	1021	While the goal of this module is to be correct, that unfortunately does
582	not mean its bug-free, only that I think its design is bug-free. It is	1022	not mean its bug-free, only that I think its design is bug-free. It is
583	still very young and not well-tested. If you keep reporting bugs they will	1023	still relatively early in its development. If you keep reporting bugs they
584	be fixed swiftly, though.	1024	will be fixed swiftly, though.
		1025
		1026	Please refrain from using rt.cpan.org or any other bug reporting
		1027	service. I put the contact address into my modules for a reason.
585		1028
586	=cut	1029	=cut
		1030
		1031	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1032	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1033
		1034	sub true() { $true }
		1035	sub false() { $false }
		1036
		1037	sub is_bool($) {
		1038	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1039	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1040	}
		1041
		1042	XSLoader::load "JSON::XS", $VERSION;
		1043
		1044	package JSON::XS::Boolean;
		1045
		1046	use overload
		1047	"0+" => sub { ${$_[0]} },
		1048	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1049	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1050	fallback => 1;
587		1051
588	1;	1052	1;
589		1053
590	=head1 AUTHOR	1054	=head1 AUTHOR
591		1055

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Comparing JSON-XS/XS.pm (file contents): Revision 1.17 by root, Sat Mar 24 19:42:14 2007 UTC vs. Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.17 by root, Sat Mar 24 19:42:14 2007 UTC vs.
Revision 1.73 by root, Sun Nov 25 19:36:54 2007 UTC