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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs.
Revision 1.118 by root, Thu Feb 19 01:13:46 2009 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
		5	=encoding utf-8
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14		19
15	# OO-interface	20	# OO-interface
16		21
17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
19	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
20		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
21	=head1 DESCRIPTION	34	=head1 DESCRIPTION
22		35
23	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
24	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
25	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overridden) with no overhead due to emulation (by inheriting constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
26		47
27	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
28	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
29	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
30	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
31	reports for other reasons.	52	reports for other reasons.
32		53
33	See COMPARISON, below, for a comparison to some other JSON modules.
34
35	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
36	vice versa.	55	vice versa.
37		56
38	=head2 FEATURES	57	=head2 FEATURES
39		58
40	=over 4	59	=over 4
41		60
42	=item * correct unicode handling	61	=item * correct Unicode handling
43		62
44	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
45	it does so.	64	so, and even documents what "correct" means.
46		65
47	=item * round-trip integrity	66	=item * round-trip integrity
48		67
49	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
50	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
52	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
53		73
54	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
55		75
56	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
57	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
58	feature).	78	feature).
59		79
60	=item * fast	80	=item * fast
61		81
62	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
63	of speed, too.	83	this module usually compares favourably in terms of speed, too.
64		84
65	=item * simple to use	85	=item * simple to use
66		86
67	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
68	interface.	88	oriented interface interface.
69		89
70	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
71		91
72	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
73	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
74	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
75	unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
76	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
77		97
78	=back	98	=back
79		99
80	=cut	100	=cut
81		101
82	package JSON::XS;	102	package JSON::XS;
83		103
		104	no warnings;
84	use strict;	105	use strict;
85		106
86	our $VERSION = '1.4';	107	our $VERSION = '2.2311';
87	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
88		109
89	our @EXPORT = qw(to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
		111
		112	sub to_json($) {
		113	require Carp;
		114	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		115	}
		116
		117	sub from_json($) {
		118	require Carp;
		119	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		120	}
90		121
91	use Exporter;	122	use Exporter;
92	use XSLoader;	123	use XSLoader;
93		124
94	=head1 FUNCTIONAL INTERFACE	125	=head1 FUNCTIONAL INTERFACE
95		126
96	The following convinience methods are provided by this module. They are	127	The following convenience methods are provided by this module. They are
97	exported by default:	128	exported by default:
98		129
99	=over 4	130	=over 4
100		131
101	=item $json_text = to_json $perl_scalar	132	=item $json_text = encode_json $perl_scalar
102		133
103	Converts the given Perl data structure (a simple scalar or a reference to	134	Converts the given Perl data structure to a UTF-8 encoded, binary string
104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	135	(that is, the string contains octets only). Croaks on error.
105	octets only). Croaks on error.
106		136
107	This function call is functionally identical to:	137	This function call is functionally identical to:
108		138
109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110		140
111	except being faster.	141	Except being faster.
112		142
113	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
114		144
115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	145	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
116	parse that as an UTF-8 encoded JSON text, returning the resulting simple	146	to parse that as an UTF-8 encoded JSON text, returning the resulting
117	scalar or reference. Croaks on error.	147	reference. Croaks on error.
118		148
119	This function call is functionally identical to:	149	This function call is functionally identical to:
120		150
121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122		152
123	except being faster.	153	Except being faster.
124		154
125	=item $is_boolean = JSON::XS::is_bool $scalar	155	=item $is_boolean = JSON::XS::is_bool $scalar
126		156
127	Returns true if the passed scalar represents either JSON::XS::true or	157	Returns true if the passed scalar represents either JSON::XS::true or
128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	158	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
132	Perl.	162	Perl.
133		163
134	=back	164	=back
135		165
136		166
		167	=head1 A FEW NOTES ON UNICODE AND PERL
		168
		169	Since this often leads to confusion, here are a few very clear words on
		170	how Unicode works in Perl, modulo bugs.
		171
		172	=over 4
		173
		174	=item 1. Perl strings can store characters with ordinal values > 255.
		175
		176	This enables you to store Unicode characters as single characters in a
		177	Perl string - very natural.
		178
		179	=item 2. Perl does I<not> associate an encoding with your strings.
		180
		181	... until you force it to, e.g. when matching it against a regex, or
		182	printing the scalar to a file, in which case Perl either interprets your
		183	string as locale-encoded text, octets/binary, or as Unicode, depending
		184	on various settings. In no case is an encoding stored together with your
		185	data, it is I<use> that decides encoding, not any magical meta data.
		186
		187	=item 3. The internal utf-8 flag has no meaning with regards to the
		188	encoding of your string.
		189
		190	Just ignore that flag unless you debug a Perl bug, a module written in
		191	XS or want to dive into the internals of perl. Otherwise it will only
		192	confuse you, as, despite the name, it says nothing about how your string
		193	is encoded. You can have Unicode strings with that flag set, with that
		194	flag clear, and you can have binary data with that flag set and that flag
		195	clear. Other possibilities exist, too.
		196
		197	If you didn't know about that flag, just the better, pretend it doesn't
		198	exist.
		199
		200	=item 4. A "Unicode String" is simply a string where each character can be
		201	validly interpreted as a Unicode code point.
		202
		203	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		204	Unicode string encoded in UTF-8, giving you a binary string.
		205
		206	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		207
		208	It's a fact. Learn to live with it.
		209
		210	=back
		211
		212	I hope this helps :)
		213
		214
137	=head1 OBJECT-ORIENTED INTERFACE	215	=head1 OBJECT-ORIENTED INTERFACE
138		216
139	The object oriented interface lets you configure your own encoding or	217	The object oriented interface lets you configure your own encoding or
140	decoding style, within the limits of supported formats.	218	decoding style, within the limits of supported formats.
141		219
…		…
152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	230	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
153	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
154		232
155	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
156		234
		235	=item $enabled = $json->get_ascii
		236
157	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
158	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
159	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161	as per RFC4627. The resulting encoded JSON text can be treated as a native	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163	or any other superset of ASCII.	243	or any other superset of ASCII.
164		244
165	If C<$enable> is false, then the C<encode> method will not escape Unicode	245	If C<$enable> is false, then the C<encode> method will not escape Unicode
166	characters unless required by the JSON syntax or other flags. This results	246	characters unless required by the JSON syntax or other flags. This results
167	in a faster and more compact format.	247	in a faster and more compact format.
168		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
169	The main use for this flag is to produce JSON texts that can be	252	The main use for this flag is to produce JSON texts that can be
170	transmitted over a 7-bit channel, as the encoded JSON texts will not	253	transmitted over a 7-bit channel, as the encoded JSON texts will not
171	contain any 8 bit characters.	254	contain any 8 bit characters.
172		255
173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
175		258
176	=item $json = $json->latin1 ([$enable])	259	=item $json = $json->latin1 ([$enable])
177		260
		261	=item $enabled = $json->get_latin1
		262
178	If C<$enable> is true (or missing), then the C<encode> method will encode	263	If C<$enable> is true (or missing), then the C<encode> method will encode
179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180	outside the code range C<0..255>. The resulting string can be treated as a	265	outside the code range C<0..255>. The resulting string can be treated as a
181	latin1-encoded JSON text or a native unicode string. The C<decode> method	266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
182	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
183	expects unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
184		269
185	If C<$enable> is false, then the C<encode> method will not escape Unicode	270	If C<$enable> is false, then the C<encode> method will not escape Unicode
186	characters unless required by the JSON syntax or other flags.	271	characters unless required by the JSON syntax or other flags.
		272
		273	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		274	document.
187		275
188	The main use for this flag is efficiently encoding binary data as JSON	276	The main use for this flag is efficiently encoding binary data as JSON
189	text, as most octets will not be escaped, resulting in a smaller encoded	277	text, as most octets will not be escaped, resulting in a smaller encoded
190	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
191	in latin1 (and must correctly be treated as such when storing and	279	in latin1 (and must correctly be treated as such when storing and
192	transfering), a rare encoding for JSON. It is therefore most useful when	280	transferring), a rare encoding for JSON. It is therefore most useful when
193	you want to store data structures known to contain binary data efficiently	281	you want to store data structures known to contain binary data efficiently
194	in files or databases, not when talking to other JSON encoders/decoders.	282	in files or databases, not when talking to other JSON encoders/decoders.
195		283
196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198		286
199	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
200		290
201	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
202	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
203	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
204	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
207	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
208		298
209	If C<$enable> is false, then the C<encode> method will return the JSON	299	If C<$enable> is false, then the C<encode> method will return the JSON
210	string as a (non-encoded) unicode string, while C<decode> expects thus a	300	string as a (non-encoded) Unicode string, while C<decode> expects thus a
211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	301	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
212	to be done yourself, e.g. using the Encode module.	302	to be done yourself, e.g. using the Encode module.
		303
		304	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		305	document.
213		306
214	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
215		308
216	use Encode;	309	use Encode;
217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
238	]	331	]
239	}	332	}
240		333
241	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
242		335
		336	=item $enabled = $json->get_indent
		337
243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
245	into its own line, identing them properly.	340	into its own line, indenting them properly.
246		341
247	If C<$enable> is false, no newlines or indenting will be produced, and the	342	If C<$enable> is false, no newlines or indenting will be produced, and the
248	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
249		344
250	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
251		346
252	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
253		350
254	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
255	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
256		353
257	If C<$enable> is false, then the C<encode> method will not add any extra	354	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
263	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
264		361
265	{"key" :"value"}	362	{"key" :"value"}
266		363
267	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
268		367
269	If C<$enable> is true (or missing), then the C<encode> method will add an extra	368	If C<$enable> is true (or missing), then the C<encode> method will add an extra
270	optional space after the C<:> separating keys from values in JSON objects	369	optional space after the C<:> separating keys from values in JSON objects
271	and extra whitespace after the C<,> separating key-value pairs and array	370	and extra whitespace after the C<,> separating key-value pairs and array
272	members.	371	members.
…		…
278		377
279	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
280		379
281	{"key": "value"}	380	{"key": "value"}
282		381
		382	=item $json = $json->relaxed ([$enable])
		383
		384	=item $enabled = $json->get_relaxed
		385
		386	If C<$enable> is true (or missing), then C<decode> will accept some
		387	extensions to normal JSON syntax (see below). C<encode> will not be
		388	affected in anyway. I<Be aware that this option makes you accept invalid
		389	JSON texts as if they were valid!>. I suggest only to use this option to
		390	parse application-specific files written by humans (configuration files,
		391	resource files etc.)
		392
		393	If C<$enable> is false (the default), then C<decode> will only accept
		394	valid JSON texts.
		395
		396	Currently accepted extensions are:
		397
		398	=over 4
		399
		400	=item * list items can have an end-comma
		401
		402	JSON I<separates> array elements and key-value pairs with commas. This
		403	can be annoying if you write JSON texts manually and want to be able to
		404	quickly append elements, so this extension accepts comma at the end of
		405	such items not just between them:
		406
		407	[
		408	1,
		409	2, <- this comma not normally allowed
		410	]
		411	{
		412	"k1": "v1",
		413	"k2": "v2", <- this comma not normally allowed
		414	}
		415
		416	=item * shell-style '#'-comments
		417
		418	Whenever JSON allows whitespace, shell-style comments are additionally
		419	allowed. They are terminated by the first carriage-return or line-feed
		420	character, after which more white-space and comments are allowed.
		421
		422	[
		423	1, # this comment not allowed in JSON
		424	# neither this one...
		425	]
		426
		427	=back
		428
283	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
		430
		431	=item $enabled = $json->get_canonical
284		432
285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
287		435
288	If C<$enable> is false, then the C<encode> method will output key-value	436	If C<$enable> is false, then the C<encode> method will output key-value
289	pairs in the order Perl stores them (which will likely change between runs	437	pairs in the order Perl stores them (which will likely change between runs
290	of the same script).	438	of the same script).
291		439
292	This option is useful if you want the same data structure to be encoded as	440	This option is useful if you want the same data structure to be encoded as
293	the same JSON text (given the same overall settings). If it is disabled,	441	the same JSON text (given the same overall settings). If it is disabled,
294	the same hash migh be encoded differently even if contains the same data,	442	the same hash might be encoded differently even if contains the same data,
295	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
296		444
297	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
298		446
299	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
300		450
301	If C<$enable> is true (or missing), then the C<encode> method can convert a	451	If C<$enable> is true (or missing), then the C<encode> method can convert a
302	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
303	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	453	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304	values instead of croaking.	454	values instead of croaking.
…		…
312	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
313		463
314	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
315	=> "Hello, World!"	465	=> "Hello, World!"
316		466
		467	=item $json = $json->allow_unknown ([$enable])
		468
		469	=item $enabled = $json->get_allow_unknown
		470
		471	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		472	exception when it encounters values it cannot represent in JSON (for
		473	example, filehandles) but instead will encode a JSON C<null> value. Note
		474	that blessed objects are not included here and are handled separately by
		475	c<allow_nonref>.
		476
		477	If C<$enable> is false (the default), then C<encode> will throw an
		478	exception when it encounters anything it cannot encode as JSON.
		479
		480	This option does not affect C<decode> in any way, and it is recommended to
		481	leave it off unless you know your communications partner.
		482
317	=item $json = $json->allow_blessed ([$enable])	483	=item $json = $json->allow_blessed ([$enable])
		484
		485	=item $enabled = $json->get_allow_blessed
318		486
319	If C<$enable> is true (or missing), then the C<encode> method will not	487	If C<$enable> is true (or missing), then the C<encode> method will not
320	barf when it encounters a blessed reference. Instead, the value of the	488	barf when it encounters a blessed reference. Instead, the value of the
321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322	disabled or no C<to_json> method found) or a representation of the	490	disabled or no C<TO_JSON> method found) or a representation of the
323	object (C<convert_blessed> enabled and C<to_json> method found) is being	491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324	encoded. Has no effect on C<decode>.	492	encoded. Has no effect on C<decode>.
325		493
326	If C<$enable> is false (the default), then C<encode> will throw an	494	If C<$enable> is false (the default), then C<encode> will throw an
327	exception when it encounters a blessed object.	495	exception when it encounters a blessed object.
328		496
329	=item $json = $json->convert_blessed ([$enable])	497	=item $json = $json->convert_blessed ([$enable])
		498
		499	=item $enabled = $json->get_convert_blessed
330		500
331	If C<$enable> is true (or missing), then C<encode>, upon encountering a	501	If C<$enable> is true (or missing), then C<encode>, upon encountering a
332	blessed object, will check for the availability of the C<TO_JSON> method	502	blessed object, will check for the availability of the C<TO_JSON> method
333	on the object's class. If found, it will be called in scalar context	503	on the object's class. If found, it will be called in scalar context
334	and the resulting scalar will be encoded instead of the object. If no	504	and the resulting scalar will be encoded instead of the object. If no
…		…
338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	508	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
339	returns other blessed objects, those will be handled in the same	509	returns other blessed objects, those will be handled in the same
340	way. C<TO_JSON> must take care of not causing an endless recursion cycle	510	way. C<TO_JSON> must take care of not causing an endless recursion cycle
341	(== crash) in this case. The name of C<TO_JSON> was chosen because other	511	(== crash) in this case. The name of C<TO_JSON> was chosen because other
342	methods called by the Perl core (== not by the user of the object) are	512	methods called by the Perl core (== not by the user of the object) are
343	usually in upper case letters and to avoid collisions with the C<to_json>	513	usually in upper case letters and to avoid collisions with any C<to_json>
344	function.	514	function or method.
345		515
346	This setting does not yet influence C<decode> in any way, but in the	516	This setting does not yet influence C<decode> in any way, but in the
347	future, global hooks might get installed that influence C<decode> and are	517	future, global hooks might get installed that influence C<decode> and are
348	enabled by this setting.	518	enabled by this setting.
349		519
350	If C<$enable> is false, then the C<allow_blessed> setting will decide what	520	If C<$enable> is false, then the C<allow_blessed> setting will decide what
351	to do when a blessed object is found.	521	to do when a blessed object is found.
352		522
353	=item $json = $json->filter_json_object ([$coderef])	523	=item $json = $json->filter_json_object ([$coderef->($hashref)])
354		524
355	When C<$coderef> is specified, it will be called from C<decode> each	525	When C<$coderef> is specified, it will be called from C<decode> each
356	time it decodes a JSON object. The only argument is a reference to the	526	time it decodes a JSON object. The only argument is a reference to the
357	newly-created hash. If the code references returns a single scalar (which	527	newly-created hash. If the code references returns a single scalar (which
358	need not be a reference), this value (i.e. a copy of that scalar to avoid	528	need not be a reference), this value (i.e. a copy of that scalar to avoid
359	aliasing) is inserted into the deserialised data structure. If it returns	529	aliasing) is inserted into the deserialised data structure. If it returns
360	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the	530	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
361	original deserialised hash will be inserted. This setting can slow down	531	original deserialised hash will be inserted. This setting can slow down
362	decoding considerably.	532	decoding considerably.
363		533
364	When C<$coderef> is omitted or undefined, C<decode> will not change the	534	When C<$coderef> is omitted or undefined, any existing callback will
365	deserialised hash in any way. This is maximally fast.	535	be removed and C<decode> will not change the deserialised hash in any
		536	way.
366		537
367	Example, convert all JSON objects into the integer 5:	538	Example, convert all JSON objects into the integer 5:
368		539
369	my $js = JSON::XS->new->filter_json_object (sub { 5 });	540	my $js = JSON::XS->new->filter_json_object (sub { 5 });
370	# returns [5]	541	# returns [5]
371	$js->decode ('[{}]')	542	$js->decode ('[{}]')
372	# throw an exception because allow_nonref is not enabled:	543	# throw an exception because allow_nonref is not enabled
		544	# so a lone 5 is not allowed.
373	$js->decode ('{"a":1, "b":2}');	545	$js->decode ('{"a":1, "b":2}');
374		546
375	=item $json = $json->filter_json_single_key_object ([$coderef])	547	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
376		548
377	Works like C<filter_json_object>, but is only called for JSON objects	549	Works remotely similar to C<filter_json_object>, but is only called for
378	having only a single key.	550	JSON objects having a single key named C<$key>.
379		551
380	This C<$coderef> is called before the one specified via	552	This C<$coderef> is called before the one specified via
381	C<filter_json_object>, if any. If it returns something, that will be	553	C<filter_json_object>, if any. It gets passed the single value in the JSON
382	inserted into the data structure. If it returns nothing, the callback	554	object. If it returns a single value, it will be inserted into the data
383	from C<filter_json_object> will be called next. If you want to force	555	structure. If it returns nothing (not even C<undef> but the empty list),
384	insertion of single-key objects even in the presence of a mutating	556	the callback from C<filter_json_object> will be called next, as if no
385	C<filter_json_object> callback, simply return the passed hash.	557	single-key callback were specified.
		558
		559	If C<$coderef> is omitted or undefined, the corresponding callback will be
		560	disabled. There can only ever be one callback for a given key.
386		561
387	As this callback gets called less often then the C<filter_json_object>	562	As this callback gets called less often then the C<filter_json_object>
388	one, decoding speed will not usually suffer as much. Therefore, single-key	563	one, decoding speed will not usually suffer as much. Therefore, single-key
389	objects make excellent targets to serialise Perl objects into, especially	564	objects make excellent targets to serialise Perl objects into, especially
390	as single-key JSON objects are as close to the type-tagged value concept	565	as single-key JSON objects are as close to the type-tagged value concept
391	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	566	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
392	support this in any way, so you need to make sure your data never looks	567	support this in any way, so you need to make sure your data never looks
393	like a serialised Perl hash.	568	like a serialised Perl hash.
394		569
395	Typical names for the single object key are C<__class_whatever__>, or	570	Typical names for the single object key are C<__class_whatever__>, or
396	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	571	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
401	into the corresponding C<< $WIDGET{<id>} >> object:	576	into the corresponding C<< $WIDGET{<id>} >> object:
402		577
403	# return whatever is in $WIDGET{5}:	578	# return whatever is in $WIDGET{5}:
404	JSON::XS	579	JSON::XS
405	->new	580	->new
406	->filter_json_single_key_object (sub {	581	->filter_json_single_key_object (__widget__ => sub {
407	exists $_[0]{__widget__}
408	? $WIDGET{ $_[0]{__widget__} }	582	$WIDGET{ $_[0] }
409	: ()
410	})	583	})
411	->decode ('{"__widget__": 5')	584	->decode ('{"__widget__": 5')
412		585
413	# this can be used with a TO_JSON method in some "widget" class	586	# this can be used with a TO_JSON method in some "widget" class
414	# for serialisation to json:	587	# for serialisation to json:
…		…
422		595
423	{ __widget__ => $self->{id} }	596	{ __widget__ => $self->{id} }
424	}	597	}
425		598
426	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
427		602
428	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
429	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
430	C<encode> or C<decode> to their minimum size possible. This can save	605	C<encode> or C<decode> to their minimum size possible. This can save
431	memory when your JSON texts are either very very long or you have many	606	memory when your JSON texts are either very very long or you have many
…		…
449	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
450	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
451		626
452	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
453		628
		629	=item $max_depth = $json->get_max_depth
		630
454	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
455	or decoding. If the JSON text or Perl data structure has an equal or	632	or decoding. If a higher nesting level is detected in JSON text or a Perl
456	higher nesting level then this limit, then the encoder and decoder will	633	data structure, then the encoder and decoder will stop and croak at that
457	stop and croak at that point.	634	point.
458		635
459	Nesting level is defined by number of hash- or arrayrefs that the encoder	636	Nesting level is defined by number of hash- or arrayrefs that the encoder
460	needs to traverse to reach a given point or the number of C<{> or C<[>	637	needs to traverse to reach a given point or the number of C<{> or C<[>
461	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
462	given character in a string.	639	given character in a string.
463		640
464	Setting the maximum depth to one disallows any nesting, so that ensures	641	Setting the maximum depth to one disallows any nesting, so that ensures
465	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
466		643
467	The argument to C<max_depth> will be rounded up to the next highest power
468	of two. If no argument is given, the highest possible setting will be	644	If no argument is given, the highest possible setting will be used, which
469	used, which is rarely useful.	645	is rarely useful.
		646
		647	Note that nesting is implemented by recursion in C. The default value has
		648	been chosen to be as large as typical operating systems allow without
		649	crashing.
470		650
471	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	651	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
472		652
473	=item $json = $json->max_size ([$maximum_string_size])	653	=item $json = $json->max_size ([$maximum_string_size])
		654
		655	=item $max_size = $json->get_max_size
474		656
475	Set the maximum length a JSON text may have (in bytes) where decoding is	657	Set the maximum length a JSON text may have (in bytes) where decoding is
476	being attempted. The default is C<0>, meaning no limit. When C<decode>	658	being attempted. The default is C<0>, meaning no limit. When C<decode>
477	is called on a string longer then this number of characters it will not	659	is called on a string that is longer then this many bytes, it will not
478	attempt to decode the string but throw an exception. This setting has no	660	attempt to decode the string but throw an exception. This setting has no
479	effect on C<encode> (yet).	661	effect on C<encode> (yet).
480		662
481	The argument to C<max_size> will be rounded up to the next B<highest>	663	If no argument is given, the limit check will be deactivated (same as when
482	power of two (so may be more than requested). If no argument is given, the	664	C<0> is specified).
483	limit check will be deactivated (same as when C<0> is specified).
484		665
485	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	666	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
486		667
487	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
488		669
…		…
517	=> ([], 3)	698	=> ([], 3)
518		699
519	=back	700	=back
520		701
521		702
		703	=head1 INCREMENTAL PARSING
		704
		705	In some cases, there is the need for incremental parsing of JSON
		706	texts. While this module always has to keep both JSON text and resulting
		707	Perl data structure in memory at one time, it does allow you to parse a
		708	JSON stream incrementally. It does so by accumulating text until it has
		709	a full JSON object, which it then can decode. This process is similar to
		710	using C<decode_prefix> to see if a full JSON object is available, but
		711	is much more efficient (and can be implemented with a minimum of method
		712	calls).
		713
		714	JSON::XS will only attempt to parse the JSON text once it is sure it
		715	has enough text to get a decisive result, using a very simple but
		716	truly incremental parser. This means that it sometimes won't stop as
		717	early as the full parser, for example, it doesn't detect parenthese
		718	mismatches. The only thing it guarantees is that it starts decoding as
		719	soon as a syntactically valid JSON text has been seen. This means you need
		720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		721	parsing in the presence if syntax errors.
		722
		723	The following methods implement this incremental parser.
		724
		725	=over 4
		726
		727	=item [void, scalar or list context] = $json->incr_parse ([$string])
		728
		729	This is the central parsing function. It can both append new text and
		730	extract objects from the stream accumulated so far (both of these
		731	functions are optional).
		732
		733	If C<$string> is given, then this string is appended to the already
		734	existing JSON fragment stored in the C<$json> object.
		735
		736	After that, if the function is called in void context, it will simply
		737	return without doing anything further. This can be used to add more text
		738	in as many chunks as you want.
		739
		740	If the method is called in scalar context, then it will try to extract
		741	exactly I<one> JSON object. If that is successful, it will return this
		742	object, otherwise it will return C<undef>. If there is a parse error,
		743	this method will croak just as C<decode> would do (one can then use
		744	C<incr_skip> to skip the errornous part). This is the most common way of
		745	using the method.
		746
		747	And finally, in list context, it will try to extract as many objects
		748	from the stream as it can find and return them, or the empty list
		749	otherwise. For this to work, there must be no separators between the JSON
		750	objects or arrays, instead they must be concatenated back-to-back. If
		751	an error occurs, an exception will be raised as in the scalar context
		752	case. Note that in this case, any previously-parsed JSON texts will be
		753	lost.
		754
		755	=item $lvalue_string = $json->incr_text
		756
		757	This method returns the currently stored JSON fragment as an lvalue, that
		758	is, you can manipulate it. This I<only> works when a preceding call to
		759	C<incr_parse> in I<scalar context> successfully returned an object. Under
		760	all other circumstances you must not call this function (I mean it.
		761	although in simple tests it might actually work, it I<will> fail under
		762	real world conditions). As a special exception, you can also call this
		763	method before having parsed anything.
		764
		765	This function is useful in two cases: a) finding the trailing text after a
		766	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		767	(such as commas).
		768
		769	=item $json->incr_skip
		770
		771	This will reset the state of the incremental parser and will remove
		772	the parsed text from the input buffer so far. This is useful after
		773	C<incr_parse> died, in which case the input buffer and incremental parser
		774	state is left unchanged, to skip the text parsed so far and to reset the
		775	parse state.
		776
		777	The difference to C<incr_reset> is that only text until the parse error
		778	occured is removed.
		779
		780	=item $json->incr_reset
		781
		782	This completely resets the incremental parser, that is, after this call,
		783	it will be as if the parser had never parsed anything.
		784
		785	This is useful if you want to repeatedly parse JSON objects and want to
		786	ignore any trailing data, which means you have to reset the parser after
		787	each successful decode.
		788
		789	=back
		790
		791	=head2 LIMITATIONS
		792
		793	All options that affect decoding are supported, except
		794	C<allow_nonref>. The reason for this is that it cannot be made to
		795	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		796	them back to back and still decode them perfectly. This does not hold true
		797	for JSON numbers, however.
		798
		799	For example, is the string C<1> a single JSON number, or is it simply the
		800	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		801	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		802	takes the conservative route and disallows this case.
		803
		804	=head2 EXAMPLES
		805
		806	Some examples will make all this clearer. First, a simple example that
		807	works similarly to C<decode_prefix>: We want to decode the JSON object at
		808	the start of a string and identify the portion after the JSON object:
		809
		810	my $text = "[1,2,3] hello";
		811
		812	my $json = new JSON::XS;
		813
		814	my $obj = $json->incr_parse ($text)
		815	or die "expected JSON object or array at beginning of string";
		816
		817	my $tail = $json->incr_text;
		818	# $tail now contains " hello"
		819
		820	Easy, isn't it?
		821
		822	Now for a more complicated example: Imagine a hypothetical protocol where
		823	you read some requests from a TCP stream, and each request is a JSON
		824	array, without any separation between them (in fact, it is often useful to
		825	use newlines as "separators", as these get interpreted as whitespace at
		826	the start of the JSON text, which makes it possible to test said protocol
		827	with C<telnet>...).
		828
		829	Here is how you'd do it (it is trivial to write this in an event-based
		830	manner):
		831
		832	my $json = new JSON::XS;
		833
		834	# read some data from the socket
		835	while (sysread $socket, my $buf, 4096) {
		836
		837	# split and decode as many requests as possible
		838	for my $request ($json->incr_parse ($buf)) {
		839	# act on the $request
		840	}
		841	}
		842
		843	Another complicated example: Assume you have a string with JSON objects
		844	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		845	[3]>). To parse them, we have to skip the commas between the JSON texts,
		846	and here is where the lvalue-ness of C<incr_text> comes in useful:
		847
		848	my $text = "[1],[2], [3]";
		849	my $json = new JSON::XS;
		850
		851	# void context, so no parsing done
		852	$json->incr_parse ($text);
		853
		854	# now extract as many objects as possible. note the
		855	# use of scalar context so incr_text can be called.
		856	while (my $obj = $json->incr_parse) {
		857	# do something with $obj
		858
		859	# now skip the optional comma
		860	$json->incr_text =~ s/^ \s* , //x;
		861	}
		862
		863	Now lets go for a very complex example: Assume that you have a gigantic
		864	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		865	but you cannot load it into memory fully (this has actually happened in
		866	the real world :).
		867
		868	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		869	can still help you: You implement a (very simple) array parser and let
		870	JSON decode the array elements, which are all full JSON objects on their
		871	own (this wouldn't work if the array elements could be JSON numbers, for
		872	example):
		873
		874	my $json = new JSON::XS;
		875
		876	# open the monster
		877	open my $fh, "<bigfile.json"
		878	or die "bigfile: $!";
		879
		880	# first parse the initial "["
		881	for (;;) {
		882	sysread $fh, my $buf, 65536
		883	or die "read error: $!";
		884	$json->incr_parse ($buf); # void context, so no parsing
		885
		886	# Exit the loop once we found and removed(!) the initial "[".
		887	# In essence, we are (ab-)using the $json object as a simple scalar
		888	# we append data to.
		889	last if $json->incr_text =~ s/^ \s* \[ //x;
		890	}
		891
		892	# now we have the skipped the initial "[", so continue
		893	# parsing all the elements.
		894	for (;;) {
		895	# in this loop we read data until we got a single JSON object
		896	for (;;) {
		897	if (my $obj = $json->incr_parse) {
		898	# do something with $obj
		899	last;
		900	}
		901
		902	# add more data
		903	sysread $fh, my $buf, 65536
		904	or die "read error: $!";
		905	$json->incr_parse ($buf); # void context, so no parsing
		906	}
		907
		908	# in this loop we read data until we either found and parsed the
		909	# separating "," between elements, or the final "]"
		910	for (;;) {
		911	# first skip whitespace
		912	$json->incr_text =~ s/^\s*//;
		913
		914	# if we find "]", we are done
		915	if ($json->incr_text =~ s/^\]//) {
		916	print "finished.\n";
		917	exit;
		918	}
		919
		920	# if we find ",", we can continue with the next element
		921	if ($json->incr_text =~ s/^,//) {
		922	last;
		923	}
		924
		925	# if we find anything else, we have a parse error!
		926	if (length $json->incr_text) {
		927	die "parse error near ", $json->incr_text;
		928	}
		929
		930	# else add more data
		931	sysread $fh, my $buf, 65536
		932	or die "read error: $!";
		933	$json->incr_parse ($buf); # void context, so no parsing
		934	}
		935
		936	This is a complex example, but most of the complexity comes from the fact
		937	that we are trying to be correct (bear with me if I am wrong, I never ran
		938	the above example :).
		939
		940
		941
522	=head1 MAPPING	942	=head1 MAPPING
523		943
524	This section describes how JSON::XS maps Perl values to JSON values and	944	This section describes how JSON::XS maps Perl values to JSON values and
525	vice versa. These mappings are designed to "do the right thing" in most	945	vice versa. These mappings are designed to "do the right thing" in most
526	circumstances automatically, preserving round-tripping characteristics	946	circumstances automatically, preserving round-tripping characteristics
527	(what you put in comes out as something equivalent).	947	(what you put in comes out as something equivalent).
528		948
529	For the more enlightened: note that in the following descriptions,	949	For the more enlightened: note that in the following descriptions,
530	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	950	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
531	refers to the abstract Perl language itself.	951	refers to the abstract Perl language itself.
532		952
533		953
534	=head2 JSON -> PERL	954	=head2 JSON -> PERL
535		955
536	=over 4	956	=over 4
537		957
538	=item object	958	=item object
539		959
540	A JSON object becomes a reference to a hash in Perl. No ordering of object	960	A JSON object becomes a reference to a hash in Perl. No ordering of object
541	keys is preserved (JSON does not preserver object key ordering itself).	961	keys is preserved (JSON does not preserve object key ordering itself).
542		962
543	=item array	963	=item array
544		964
545	A JSON array becomes a reference to an array in Perl.	965	A JSON array becomes a reference to an array in Perl.
546		966
…		…
550	are represented by the same codepoints in the Perl string, so no manual	970	are represented by the same codepoints in the Perl string, so no manual
551	decoding is necessary.	971	decoding is necessary.
552		972
553	=item number	973	=item number
554		974
555	A JSON number becomes either an integer or numeric (floating point)	975	A JSON number becomes either an integer, numeric (floating point) or
556	scalar in perl, depending on its range and any fractional parts. On the	976	string scalar in perl, depending on its range and any fractional parts. On
557	Perl level, there is no difference between those as Perl handles all the	977	the Perl level, there is no difference between those as Perl handles all
558	conversion details, but an integer may take slightly less memory and might	978	the conversion details, but an integer may take slightly less memory and
559	represent more values exactly than (floating point) numbers.	979	might represent more values exactly than floating point numbers.
		980
		981	If the number consists of digits only, JSON::XS will try to represent
		982	it as an integer value. If that fails, it will try to represent it as
		983	a numeric (floating point) value if that is possible without loss of
		984	precision. Otherwise it will preserve the number as a string value (in
		985	which case you lose roundtripping ability, as the JSON number will be
		986	re-encoded toa JSON string).
		987
		988	Numbers containing a fractional or exponential part will always be
		989	represented as numeric (floating point) values, possibly at a loss of
		990	precision (in which case you might lose perfect roundtripping ability, but
		991	the JSON number will still be re-encoded as a JSON number).
560		992
561	=item true, false	993	=item true, false
562		994
563	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	995	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
564	respectively. They are overloaded to act almost exactly like the numbers	996	respectively. They are overloaded to act almost exactly like the numbers
565	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	997	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
566	the C<JSON::XS::is_bool> function.	998	the C<JSON::XS::is_bool> function.
567		999
568	=item null	1000	=item null
569		1001
570	A JSON null atom becomes C<undef> in Perl.	1002	A JSON null atom becomes C<undef> in Perl.
…		…
601	Other unblessed references are generally not allowed and will cause an	1033	Other unblessed references are generally not allowed and will cause an
602	exception to be thrown, except for references to the integers C<0> and	1034	exception to be thrown, except for references to the integers C<0> and
603	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1035	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
604	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1036	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
605		1037
606	to_json [\0,JSON::XS::true] # yields [false,true]	1038	encode_json [\0, JSON::XS::true] # yields [false,true]
607		1039
608	=item JSON::XS::true, JSON::XS::false	1040	=item JSON::XS::true, JSON::XS::false
609		1041
610	These special values become JSON true and JSON false values,	1042	These special values become JSON true and JSON false values,
611	respectively. You cna alos use C<\1> and C<\0> directly if you want.	1043	respectively. You can also use C<\1> and C<\0> directly if you want.
612		1044
613	=item blessed objects	1045	=item blessed objects
614		1046
615	Blessed objects are not allowed. JSON::XS currently tries to encode their	1047	Blessed objects are not directly representable in JSON. See the
616	underlying representation (hash- or arrayref), but this behaviour might	1048	C<allow_blessed> and C<convert_blessed> methods on various options on
617	change in future versions.	1049	how to deal with this: basically, you can choose between throwing an
		1050	exception, encoding the reference as if it weren't blessed, or provide
		1051	your own serialiser method.
618		1052
619	=item simple scalars	1053	=item simple scalars
620		1054
621	Simple Perl scalars (any scalar that is not a reference) are the most	1055	Simple Perl scalars (any scalar that is not a reference) are the most
622	difficult objects to encode: JSON::XS will encode undefined scalars as	1056	difficult objects to encode: JSON::XS will encode undefined scalars as
623	JSON null value, scalars that have last been used in a string context	1057	JSON C<null> values, scalars that have last been used in a string context
624	before encoding as JSON strings and anything else as number value:	1058	before encoding as JSON strings, and anything else as number value:
625		1059
626	# dump as number	1060	# dump as number
627	to_json [2] # yields [2]	1061	encode_json [2] # yields [2]
628	to_json [-3.0e17] # yields [-3e+17]	1062	encode_json [-3.0e17] # yields [-3e+17]
629	my $value = 5; to_json [$value] # yields [5]	1063	my $value = 5; encode_json [$value] # yields [5]
630		1064
631	# used as string, so dump as string	1065	# used as string, so dump as string
632	print $value;	1066	print $value;
633	to_json [$value] # yields ["5"]	1067	encode_json [$value] # yields ["5"]
634		1068
635	# undef becomes null	1069	# undef becomes null
636	to_json [undef] # yields [null]	1070	encode_json [undef] # yields [null]
637		1071
638	You can force the type to be a string by stringifying it:	1072	You can force the type to be a JSON string by stringifying it:
639		1073
640	my $x = 3.1; # some variable containing a number	1074	my $x = 3.1; # some variable containing a number
641	"$x"; # stringified	1075	"$x"; # stringified
642	$x .= ""; # another, more awkward way to stringify	1076	$x .= ""; # another, more awkward way to stringify
643	print $x; # perl does it for you, too, quite often	1077	print $x; # perl does it for you, too, quite often
644		1078
645	You can force the type to be a number by numifying it:	1079	You can force the type to be a JSON number by numifying it:
646		1080
647	my $x = "3"; # some variable containing a string	1081	my $x = "3"; # some variable containing a string
648	$x += 0; # numify it, ensuring it will be dumped as a number	1082	$x += 0; # numify it, ensuring it will be dumped as a number
649	$x *= 1; # same thing, the choise is yours.	1083	$x *= 1; # same thing, the choice is yours.
650		1084
651	You can not currently output JSON booleans or force the type in other,	1085	You can not currently force the type in other, less obscure, ways. Tell me
652	less obscure, ways. Tell me if you need this capability.	1086	if you need this capability (but don't forget to explain why it's needed
		1087	:).
653		1088
654	=back	1089	=back
655		1090
656		1091
657	=head1 COMPARISON	1092	=head1 ENCODING/CODESET FLAG NOTES
658		1093
659	As already mentioned, this module was created because none of the existing	1094	The interested reader might have seen a number of flags that signify
660	JSON modules could be made to work correctly. First I will describe the	1095	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
661	problems (or pleasures) I encountered with various existing JSON modules,	1096	some confusion on what these do, so here is a short comparison:
662	followed by some benchmark values. JSON::XS was designed not to suffer	1097
663	from any of these problems or limitations.	1098	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1099	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1100	control whether C<encode> escapes character values outside their respective
		1101	codeset range. Neither of these flags conflict with each other, although
		1102	some combinations make less sense than others.
		1103
		1104	Care has been taken to make all flags symmetrical with respect to
		1105	C<encode> and C<decode>, that is, texts encoded with any combination of
		1106	these flag values will be correctly decoded when the same flags are used
		1107	- in general, if you use different flag settings while encoding vs. when
		1108	decoding you likely have a bug somewhere.
		1109
		1110	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1111	simply an abstract set of character-codepoint pairs, while an encoding
		1112	takes those codepoint numbers and I<encodes> them, in our case into
		1113	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1114	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1115	the same time, which can be confusing.
664		1116
665	=over 4	1117	=over 4
666		1118
667	=item JSON 1.07	1119	=item C<utf8> flag disabled
668		1120
669	Slow (but very portable, as it is written in pure Perl).	1121	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1122	and expect Unicode strings, that is, characters with high ordinal Unicode
		1123	values (> 255) will be encoded as such characters, and likewise such
		1124	characters are decoded as-is, no canges to them will be done, except
		1125	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1126	respectively (to Perl, these are the same thing in strings unless you do
		1127	funny/weird/dumb stuff).
670		1128
671	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1129	This is useful when you want to do the encoding yourself (e.g. when you
672	undocumented. One can get far by feeding it unicode strings and doing	1130	want to have UTF-16 encoded JSON texts) or when some other layer does
673	en-/decoding oneself, but unicode escapes are not working properly).	1131	the encoding for you (for example, when printing to a terminal using a
		1132	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1133	to UTF-8 encode your data first and have Perl encode it another time).
674		1134
675	No roundtripping (strings get clobbered if they look like numbers, e.g.	1135	=item C<utf8> flag enabled
676	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
677	decode into the number 2.
678		1136
679	=item JSON::PC 0.01	1137	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1138	characters using the corresponding UTF-8 multi-byte sequence, and will
		1139	expect your input strings to be encoded as UTF-8, that is, no "character"
		1140	of the input string must have any value > 255, as UTF-8 does not allow
		1141	that.
680		1142
681	Very fast.	1143	The C<utf8> flag therefore switches between two modes: disabled means you
		1144	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1145	octet/binary string in Perl.
682		1146
683	Undocumented/buggy Unicode handling.	1147	=item C<latin1> or C<ascii> flags enabled
684		1148
685	No roundtripping.	1149	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1150	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1151	characters as specified by the C<utf8> flag.
686		1152
687	Has problems handling many Perl values (e.g. regex results and other magic	1153	If C<utf8> is disabled, then the result is also correctly encoded in those
688	values will make it croak).	1154	character sets (as both are proper subsets of Unicode, meaning that a
		1155	Unicode string with all character values < 256 is the same thing as a
		1156	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1157	the same thing as an ASCII string in Perl).
689		1158
690	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1159	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
691	which is not a valid JSON text.	1160	regardless of these flags, just some more characters will be escaped using
		1161	C<\uXXXX> then before.
692		1162
693	Unmaintained (maintainer unresponsive for many months, bugs are not	1163	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
694	getting fixed).	1164	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1165	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1166	a subset of Unicode), while ASCII is.
695		1167
696	=item JSON::Syck 0.21	1168	Surprisingly, C<decode> will ignore these flags and so treat all input
		1169	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1170	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1171	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
697		1172
698	Very buggy (often crashes).	1173	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1174	they only govern when the JSON output engine escapes a character or not.
699		1175
700	Very inflexible (no human-readable format supported, format pretty much	1176	The main use for C<latin1> is to relatively efficiently store binary data
701	undocumented. I need at least a format for easy reading by humans and a	1177	as JSON, at the expense of breaking compatibility with most JSON decoders.
702	single-line compact format for use in a protocol, and preferably a way to
703	generate ASCII-only JSON texts).
704		1178
705	Completely broken (and confusingly documented) Unicode handling (unicode	1179	The main use for C<ascii> is to force the output to not contain characters
706	escapes are not working properly, you need to set ImplicitUnicode to	1180	with values > 127, which means you can interpret the resulting string
707	I<different> values on en- and decoding to get symmetric behaviour).	1181	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
708		1182	8-bit-encoding, and still get the same data structure back. This is useful
709	No roundtripping (simple cases work, but this depends on wether the scalar	1183	when your channel for JSON transfer is not 8-bit clean or the encoding
710	value was used in a numeric context or not).	1184	might be mangled in between (e.g. in mail), and works because ASCII is a
711		1185	proper subset of most 8-bit and multibyte encodings in use in the world.
712	Dumping hashes may skip hash values depending on iterator state.
713
714	Unmaintained (maintainer unresponsive for many months, bugs are not
715	getting fixed).
716
717	Does not check input for validity (i.e. will accept non-JSON input and
718	return "something" instead of raising an exception. This is a security
719	issue: imagine two banks transfering money between each other using
720	JSON. One bank might parse a given non-JSON request and deduct money,
721	while the other might reject the transaction with a syntax error. While a
722	good protocol will at least recover, that is extra unnecessary work and
723	the transaction will still not succeed).
724
725	=item JSON::DWIW 0.04
726
727	Very fast. Very natural. Very nice.
728
729	Undocumented unicode handling (but the best of the pack. Unicode escapes
730	still don't get parsed properly).
731
732	Very inflexible.
733
734	No roundtripping.
735
736	Does not generate valid JSON texts (key strings are often unquoted, empty keys
737	result in nothing being output)
738
739	Does not check input for validity.
740		1186
741	=back	1187	=back
742		1188
743		1189
		1190	=head2 JSON and ECMAscript
		1191
		1192	JSON syntax is based on how literals are represented in javascript (the
		1193	not-standardised predecessor of ECMAscript) which is presumably why it is
		1194	called "JavaScript Object Notation".
		1195
		1196	However, JSON is not a subset (and also not a superset of course) of
		1197	ECMAscript (the standard) or javascript (whatever browsers actually
		1198	implement).
		1199
		1200	If you want to use javascript's C<eval> function to "parse" JSON, you
		1201	might run into parse errors for valid JSON texts, or the resulting data
		1202	structure might not be queryable:
		1203
		1204	One of the problems is that U+2028 and U+2029 are valid characters inside
		1205	JSON strings, but are not allowed in ECMAscript string literals, so the
		1206	following Perl fragment will not output something that can be guaranteed
		1207	to be parsable by javascript's C<eval>:
		1208
		1209	use JSON::XS;
		1210
		1211	print encode_json [chr 0x2028];
		1212
		1213	The right fix for this is to use a proper JSON parser in your javascript
		1214	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1215	F<json2.js> parser).
		1216
		1217	If this is not an option, you can, as a stop-gap measure, simply encode to
		1218	ASCII-only JSON:
		1219
		1220	use JSON::XS;
		1221
		1222	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1223
		1224	Note that this will enlarge the resulting JSON text quite a bit if you
		1225	have many non-ASCII characters. You might be tempted to run some regexes
		1226	to only escape U+2028 and U+2029, e.g.:
		1227
		1228	# DO NOT USE THIS!
		1229	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1230	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1231	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1232	print $json;
		1233
		1234	Note that I<this is a bad idea>: the above only works for U+2028 and
		1235	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1236	javascript implementations, however, have issues with other characters as
		1237	well - using C<eval> naively simply I<will> cause problems.
		1238
		1239	Another problem is that some javascript implementations reserve
		1240	some property names for their own purposes (which probably makes
		1241	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1242	C<__proto__> property name for it's own purposes.
		1243
		1244	If that is a problem, you could parse try to filter the resulting JSON
		1245	output for these property strings, e.g.:
		1246
		1247	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1248
		1249	This works because C<__proto__> is not valid outside of strings, so every
		1250	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1251
		1252	If you know of other incompatibilities, please let me know.
		1253
		1254
744	=head2 JSON and YAML	1255	=head2 JSON and YAML
745		1256
746	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1257	You often hear that JSON is a subset of YAML. This is, however, a mass
747	however, a mass hysteria and very far from the truth. In general, there is	1258	hysteria(*) and very far from the truth (as of the time of this writing),
748	no way to configure JSON::XS to output a data structure as valid YAML.	1259	so let me state it clearly: I<in general, there is no way to configure
		1260	JSON::XS to output a data structure as valid YAML> that works in all
		1261	cases.
749		1262
750	If you really must use JSON::XS to generate YAML, you should use this	1263	If you really must use JSON::XS to generate YAML, you should use this
751	algorithm (subject to change in future versions):	1264	algorithm (subject to change in future versions):
752		1265
753	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1266	my $to_yaml = JSON::XS->new->utf8->space_after (1);
754	my $yaml = $to_yaml->encode ($ref) . "\n";	1267	my $yaml = $to_yaml->encode ($ref) . "\n";
755		1268
756	This will usually generate JSON texts that also parse as valid	1269	This will I<usually> generate JSON texts that also parse as valid
757	YAML. Please note that YAML has hardcoded limits on (simple) object key	1270	YAML. Please note that YAML has hardcoded limits on (simple) object key
758	lengths that JSON doesn't have, so you should make sure that your hash	1271	lengths that JSON doesn't have and also has different and incompatible
		1272	unicode handling, so you should make sure that your hash keys are
759	keys are noticably shorter than the 1024 characters YAML allows.	1273	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1274	you do not have characters with codepoint values outside the Unicode BMP
		1275	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1276	strings (which JSON::XS does not I<currently> generate, but other JSON
		1277	generators might).
760		1278
761	There might be other incompatibilities that I am not aware of. In general	1279	There might be other incompatibilities that I am not aware of (or the YAML
		1280	specification has been changed yet again - it does so quite often). In
762	you should not try to generate YAML with a JSON generator or vice versa,	1281	general you should not try to generate YAML with a JSON generator or vice
763	or try to parse JSON with a YAML parser or vice versa: chances are high	1282	versa, or try to parse JSON with a YAML parser or vice versa: chances are
764	that you will run into severe interoperability problems.	1283	high that you will run into severe interoperability problems when you
		1284	least expect it.
		1285
		1286	=over 4
		1287
		1288	=item (*)
		1289
		1290	I have been pressured multiple times by Brian Ingerson (one of the
		1291	authors of the YAML specification) to remove this paragraph, despite him
		1292	acknowledging that the actual incompatibilities exist. As I was personally
		1293	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1294	educate people about these issues, so others do not run into the same
		1295	problem again and again. After this, Brian called me a (quote)I<complete
		1296	and worthless idiot>(unquote).
		1297
		1298	In my opinion, instead of pressuring and insulting people who actually
		1299	clarify issues with YAML and the wrong statements of some of its
		1300	proponents, I would kindly suggest reading the JSON spec (which is not
		1301	that difficult or long) and finally make YAML compatible to it, and
		1302	educating users about the changes, instead of spreading lies about the
		1303	real compatibility for many I<years> and trying to silence people who
		1304	point out that it isn't true.
		1305
		1306	=back
765		1307
766		1308
767	=head2 SPEED	1309	=head2 SPEED
768		1310
769	It seems that JSON::XS is surprisingly fast, as shown in the following	1311	It seems that JSON::XS is surprisingly fast, as shown in the following
770	tables. They have been generated with the help of the C<eg/bench> program	1312	tables. They have been generated with the help of the C<eg/bench> program
771	in the JSON::XS distribution, to make it easy to compare on your own	1313	in the JSON::XS distribution, to make it easy to compare on your own
772	system.	1314	system.
773		1315
774	First comes a comparison between various modules using a very short	1316	First comes a comparison between various modules using
775	single-line JSON string:	1317	a very short single-line JSON string (also available at
		1318	L<http://dist.schmorp.de/misc/json/short.json>).
776		1319
777	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1320	{"method": "handleMessage", "params": ["user1",
778	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1321	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1322	true, false]}
779		1323
780	It shows the number of encodes/decodes per second (JSON::XS uses	1324	It shows the number of encodes/decodes per second (JSON::XS uses
781	the functional interface, while JSON::XS/2 uses the OO interface	1325	the functional interface, while JSON::XS/2 uses the OO interface
782	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1326	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
783	shrink). Higher is better:	1327	shrink). Higher is better:
784		1328
785	Storable \| 15779.925 \| 14169.946 \|
786	-----------+------------+------------+
787	module \| encode \| decode \|	1329	module \| encode \| decode \|
788	-----------\|------------\|------------\|	1330	-----------\|------------\|------------\|
789	JSON \| 4990.842 \| 4088.813 \|	1331	JSON 1.x \| 4990.842 \| 4088.813 \|
790	JSON::DWIW \| 51653.990 \| 71575.154 \|	1332	JSON::DWIW \| 51653.990 \| 71575.154 \|
791	JSON::PC \| 65948.176 \| 74631.744 \|	1333	JSON::PC \| 65948.176 \| 74631.744 \|
792	JSON::PP \| 8931.652 \| 3817.168 \|	1334	JSON::PP \| 8931.652 \| 3817.168 \|
793	JSON::Syck \| 24877.248 \| 27776.848 \|	1335	JSON::Syck \| 24877.248 \| 27776.848 \|
794	JSON::XS \| 388361.481 \| 227951.304 \|	1336	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
796	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1338	JSON::XS/3 \| 338250.323 \| 218453.333 \|
797	Storable \| 16500.016 \| 135300.129 \|	1339	Storable \| 16500.016 \| 135300.129 \|
798	-----------+------------+------------+	1340	-----------+------------+------------+
799		1341
800	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1342	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
801	about three times faster on decoding, and over fourty times faster	1343	about three times faster on decoding, and over forty times faster
802	than JSON, even with pretty-printing and key sorting. It also compares	1344	than JSON, even with pretty-printing and key sorting. It also compares
803	favourably to Storable for small amounts of data.	1345	favourably to Storable for small amounts of data.
804		1346
805	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1347	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
806	search API (http://nanoref.com/yahooapis/mgPdGg):	1348	search API (L<http://dist.schmorp.de/misc/json/long.json>).
807		1349
808	module \| encode \| decode \|	1350	module \| encode \| decode \|
809	-----------\|------------\|------------\|	1351	-----------\|------------\|------------\|
810	JSON \| 55.260 \| 34.971 \|	1352	JSON 1.x \| 55.260 \| 34.971 \|
811	JSON::DWIW \| 825.228 \| 1082.513 \|	1353	JSON::DWIW \| 825.228 \| 1082.513 \|
812	JSON::PC \| 3571.444 \| 2394.829 \|	1354	JSON::PC \| 3571.444 \| 2394.829 \|
813	JSON::PP \| 210.987 \| 32.574 \|	1355	JSON::PP \| 210.987 \| 32.574 \|
814	JSON::Syck \| 552.551 \| 787.544 \|	1356	JSON::Syck \| 552.551 \| 787.544 \|
815	JSON::XS \| 5780.463 \| 4854.519 \|	1357	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
819	-----------+------------+------------+	1361	-----------+------------+------------+
820		1362
821	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1363	Again, JSON::XS leads by far (except for Storable which non-surprisingly
822	decodes faster).	1364	decodes faster).
823		1365
824	On large strings containing lots of high unicode characters, some modules	1366	On large strings containing lots of high Unicode characters, some modules
825	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1367	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
826	will be broken due to missing (or wrong) unicode handling. Others refuse	1368	will be broken due to missing (or wrong) Unicode handling. Others refuse
827	to decode or encode properly, so it was impossible to prepare a fair	1369	to decode or encode properly, so it was impossible to prepare a fair
828	comparison table for that case.	1370	comparison table for that case.
829		1371
830		1372
831	=head1 SECURITY CONSIDERATIONS	1373	=head1 SECURITY CONSIDERATIONS
…		…
837	any buffer overflows. Obviously, this module should ensure that and I am	1379	any buffer overflows. Obviously, this module should ensure that and I am
838	trying hard on making that true, but you never know.	1380	trying hard on making that true, but you never know.
839		1381
840	Second, you need to avoid resource-starving attacks. That means you should	1382	Second, you need to avoid resource-starving attacks. That means you should
841	limit the size of JSON texts you accept, or make sure then when your	1383	limit the size of JSON texts you accept, or make sure then when your
842	resources run out, thats just fine (e.g. by using a separate process that	1384	resources run out, that's just fine (e.g. by using a separate process that
843	can crash safely). The size of a JSON text in octets or characters is	1385	can crash safely). The size of a JSON text in octets or characters is
844	usually a good indication of the size of the resources required to decode	1386	usually a good indication of the size of the resources required to decode
845	it into a Perl structure. While JSON::XS can check the size of the JSON	1387	it into a Perl structure. While JSON::XS can check the size of the JSON
846	text, it might be too late when you already have it in memory, so you	1388	text, it might be too late when you already have it in memory, so you
847	might want to check the size before you accept the string.	1389	might want to check the size before you accept the string.
848		1390
849	Third, JSON::XS recurses using the C stack when decoding objects and	1391	Third, JSON::XS recurses using the C stack when decoding objects and
850	arrays. The C stack is a limited resource: for instance, on my amd64	1392	arrays. The C stack is a limited resource: for instance, on my amd64
851	machine with 8MB of stack size I can decode around 180k nested arrays but	1393	machine with 8MB of stack size I can decode around 180k nested arrays but
852	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1394	only 14k nested JSON objects (due to perl itself recursing deeply on croak
853	to free the temporary). If that is exceeded, the program crashes. to be	1395	to free the temporary). If that is exceeded, the program crashes. To be
854	conservative, the default nesting limit is set to 512. If your process	1396	conservative, the default nesting limit is set to 512. If your process
855	has a smaller stack, you should adjust this setting accordingly with the	1397	has a smaller stack, you should adjust this setting accordingly with the
856	C<max_depth> method.	1398	C<max_depth> method.
857		1399
858	And last but least, something else could bomb you that I forgot to think	1400	Something else could bomb you, too, that I forgot to think of. In that
859	of. In that case, you get to keep the pieces. I am always open for hints,	1401	case, you get to keep the pieces. I am always open for hints, though...
860	though...	1402
		1403	Also keep in mind that JSON::XS might leak contents of your Perl data
		1404	structures in its error messages, so when you serialise sensitive
		1405	information you might want to make sure that exceptions thrown by JSON::XS
		1406	will not end up in front of untrusted eyes.
861		1407
862	If you are using JSON::XS to return packets to consumption	1408	If you are using JSON::XS to return packets to consumption
863	by javascript scripts in a browser you should have a look at	1409	by JavaScript scripts in a browser you should have a look at
864	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1410	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
865	you are vulnerable to some common attack vectors (which really are browser	1411	you are vulnerable to some common attack vectors (which really are browser
866	design bugs, but it is still you who will have to deal with it, as major	1412	design bugs, but it is still you who will have to deal with it, as major
867	browser developers care only for features, not about doing security	1413	browser developers care only for features, not about getting security
868	right).	1414	right).
869		1415
870		1416
		1417	=head1 THREADS
		1418
		1419	This module is I<not> guaranteed to be thread safe and there are no
		1420	plans to change this until Perl gets thread support (as opposed to the
		1421	horribly slow so-called "threads" which are simply slow and bloated
		1422	process simulations - use fork, it's I<much> faster, cheaper, better).
		1423
		1424	(It might actually work, but you have been warned).
		1425
		1426
871	=head1 BUGS	1427	=head1 BUGS
872		1428
873	While the goal of this module is to be correct, that unfortunately does	1429	While the goal of this module is to be correct, that unfortunately does
874	not mean its bug-free, only that I think its design is bug-free. It is	1430	not mean it's bug-free, only that I think its design is bug-free. If you
875	still relatively early in its development. If you keep reporting bugs they	1431	keep reporting bugs they will be fixed swiftly, though.
876	will be fixed swiftly, though.	1432
		1433	Please refrain from using rt.cpan.org or any other bug reporting
		1434	service. I put the contact address into my modules for a reason.
877		1435
878	=cut	1436	=cut
879		1437
880	our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };	1438	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
881	our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };	1439	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
882		1440
883	sub true() { $true }	1441	sub true() { $true }
884	sub false() { $false }	1442	sub false() { $false }
885		1443
886	sub is_bool($) {	1444	sub is_bool($) {
…		…
898	"--" => sub { $_[0] = ${$_[0]} - 1 },	1456	"--" => sub { $_[0] = ${$_[0]} - 1 },
899	fallback => 1;	1457	fallback => 1;
900		1458
901	1;	1459	1;
902		1460
		1461	=head1 SEE ALSO
		1462
		1463	The F<json_xs> command line utility for quick experiments.
		1464
903	=head1 AUTHOR	1465	=head1 AUTHOR
904		1466
905	Marc Lehmann <schmorp@schmorp.de>	1467	Marc Lehmann <schmorp@schmorp.de>
906	http://home.schmorp.de/	1468	http://home.schmorp.de/
907		1469

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs. Revision 1.118 by root, Thu Feb 19 01:13:46 2009 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs.
Revision 1.118 by root, Thu Feb 19 01:13:46 2009 UTC