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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.55 by root, Mon Jul 23 22:57:40 2007 UTC vs.
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 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 = '1.42';	107	our $VERSION = '2.23';
87	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
88		109
89	our @EXPORT = qw(to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
		111
		112	sub to_json($) {
		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
…		…
391		561
392	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>
393	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
394	objects make excellent targets to serialise Perl objects into, especially	564	objects make excellent targets to serialise Perl objects into, especially
395	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
396	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
397	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
398	like a serialised Perl hash.	568	like a serialised Perl hash.
399		569
400	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
401	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
…		…
425		595
426	{ __widget__ => $self->{id} }	596	{ __widget__ => $self->{id} }
427	}	597	}
428		598
429	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
430		602
431	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
432	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
433	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
434	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
…		…
452	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
453	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
454		626
455	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
456		628
		629	=item $max_depth = $json->get_max_depth
		630
457	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
458	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
459	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
460	stop and croak at that point.	634	point.
461		635
462	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
463	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<[>
464	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
465	given character in a string.	639	given character in a string.
466		640
467	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
468	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
469		643
470	The argument to C<max_depth> will be rounded up to the next highest power
471	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
472	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.
473		650
474	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.
475		652
476	=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
477		656
478	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
479	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>
480	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
481	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
482	effect on C<encode> (yet).	661	effect on C<encode> (yet).
483		662
484	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
485	power of two (so may be more than requested). If no argument is given, the	664	C<0> is specified).
486	limit check will be deactivated (same as when C<0> is specified).
487		665
488	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.
489		667
490	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
491		669
…		…
520	=> ([], 3)	698	=> ([], 3)
521		699
522	=back	700	=back
523		701
524		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 the
		772	parsed text from the input buffer. This is useful after C<incr_parse>
		773	died, in which case the input buffer and incremental parser state is left
		774	unchanged, to skip the text parsed so far and to reset the parse state.
		775
		776	=item $json->incr_reset
		777
		778	This completely resets the incremental parser, that is, after this call,
		779	it will be as if the parser had never parsed anything.
		780
		781	This is useful if you want ot repeatedly parse JSON objects and want to
		782	ignore any trailing data, which means you have to reset the parser after
		783	each successful decode.
		784
		785	=back
		786
		787	=head2 LIMITATIONS
		788
		789	All options that affect decoding are supported, except
		790	C<allow_nonref>. The reason for this is that it cannot be made to
		791	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		792	them back to back and still decode them perfectly. This does not hold true
		793	for JSON numbers, however.
		794
		795	For example, is the string C<1> a single JSON number, or is it simply the
		796	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		797	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		798	takes the conservative route and disallows this case.
		799
		800	=head2 EXAMPLES
		801
		802	Some examples will make all this clearer. First, a simple example that
		803	works similarly to C<decode_prefix>: We want to decode the JSON object at
		804	the start of a string and identify the portion after the JSON object:
		805
		806	my $text = "[1,2,3] hello";
		807
		808	my $json = new JSON::XS;
		809
		810	my $obj = $json->incr_parse ($text)
		811	or die "expected JSON object or array at beginning of string";
		812
		813	my $tail = $json->incr_text;
		814	# $tail now contains " hello"
		815
		816	Easy, isn't it?
		817
		818	Now for a more complicated example: Imagine a hypothetical protocol where
		819	you read some requests from a TCP stream, and each request is a JSON
		820	array, without any separation between them (in fact, it is often useful to
		821	use newlines as "separators", as these get interpreted as whitespace at
		822	the start of the JSON text, which makes it possible to test said protocol
		823	with C<telnet>...).
		824
		825	Here is how you'd do it (it is trivial to write this in an event-based
		826	manner):
		827
		828	my $json = new JSON::XS;
		829
		830	# read some data from the socket
		831	while (sysread $socket, my $buf, 4096) {
		832
		833	# split and decode as many requests as possible
		834	for my $request ($json->incr_parse ($buf)) {
		835	# act on the $request
		836	}
		837	}
		838
		839	Another complicated example: Assume you have a string with JSON objects
		840	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		841	[3]>). To parse them, we have to skip the commas between the JSON texts,
		842	and here is where the lvalue-ness of C<incr_text> comes in useful:
		843
		844	my $text = "[1],[2], [3]";
		845	my $json = new JSON::XS;
		846
		847	# void context, so no parsing done
		848	$json->incr_parse ($text);
		849
		850	# now extract as many objects as possible. note the
		851	# use of scalar context so incr_text can be called.
		852	while (my $obj = $json->incr_parse) {
		853	# do something with $obj
		854
		855	# now skip the optional comma
		856	$json->incr_text =~ s/^ \s* , //x;
		857	}
		858
		859	Now lets go for a very complex example: Assume that you have a gigantic
		860	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		861	but you cannot load it into memory fully (this has actually happened in
		862	the real world :).
		863
		864	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		865	can still help you: You implement a (very simple) array parser and let
		866	JSON decode the array elements, which are all full JSON objects on their
		867	own (this wouldn't work if the array elements could be JSON numbers, for
		868	example):
		869
		870	my $json = new JSON::XS;
		871
		872	# open the monster
		873	open my $fh, "<bigfile.json"
		874	or die "bigfile: $!";
		875
		876	# first parse the initial "["
		877	for (;;) {
		878	sysread $fh, my $buf, 65536
		879	or die "read error: $!";
		880	$json->incr_parse ($buf); # void context, so no parsing
		881
		882	# Exit the loop once we found and removed(!) the initial "[".
		883	# In essence, we are (ab-)using the $json object as a simple scalar
		884	# we append data to.
		885	last if $json->incr_text =~ s/^ \s* \[ //x;
		886	}
		887
		888	# now we have the skipped the initial "[", so continue
		889	# parsing all the elements.
		890	for (;;) {
		891	# in this loop we read data until we got a single JSON object
		892	for (;;) {
		893	if (my $obj = $json->incr_parse) {
		894	# do something with $obj
		895	last;
		896	}
		897
		898	# add more data
		899	sysread $fh, my $buf, 65536
		900	or die "read error: $!";
		901	$json->incr_parse ($buf); # void context, so no parsing
		902	}
		903
		904	# in this loop we read data until we either found and parsed the
		905	# separating "," between elements, or the final "]"
		906	for (;;) {
		907	# first skip whitespace
		908	$json->incr_text =~ s/^\s*//;
		909
		910	# if we find "]", we are done
		911	if ($json->incr_text =~ s/^\]//) {
		912	print "finished.\n";
		913	exit;
		914	}
		915
		916	# if we find ",", we can continue with the next element
		917	if ($json->incr_text =~ s/^,//) {
		918	last;
		919	}
		920
		921	# if we find anything else, we have a parse error!
		922	if (length $json->incr_text) {
		923	die "parse error near ", $json->incr_text;
		924	}
		925
		926	# else add more data
		927	sysread $fh, my $buf, 65536
		928	or die "read error: $!";
		929	$json->incr_parse ($buf); # void context, so no parsing
		930	}
		931
		932	This is a complex example, but most of the complexity comes from the fact
		933	that we are trying to be correct (bear with me if I am wrong, I never ran
		934	the above example :).
		935
		936
		937
525	=head1 MAPPING	938	=head1 MAPPING
526		939
527	This section describes how JSON::XS maps Perl values to JSON values and	940	This section describes how JSON::XS maps Perl values to JSON values and
528	vice versa. These mappings are designed to "do the right thing" in most	941	vice versa. These mappings are designed to "do the right thing" in most
529	circumstances automatically, preserving round-tripping characteristics	942	circumstances automatically, preserving round-tripping characteristics
530	(what you put in comes out as something equivalent).	943	(what you put in comes out as something equivalent).
531		944
532	For the more enlightened: note that in the following descriptions,	945	For the more enlightened: note that in the following descriptions,
533	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	946	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
534	refers to the abstract Perl language itself.	947	refers to the abstract Perl language itself.
535		948
536		949
537	=head2 JSON -> PERL	950	=head2 JSON -> PERL
538		951
539	=over 4	952	=over 4
540		953
541	=item object	954	=item object
542		955
543	A JSON object becomes a reference to a hash in Perl. No ordering of object	956	A JSON object becomes a reference to a hash in Perl. No ordering of object
544	keys is preserved (JSON does not preserver object key ordering itself).	957	keys is preserved (JSON does not preserve object key ordering itself).
545		958
546	=item array	959	=item array
547		960
548	A JSON array becomes a reference to an array in Perl.	961	A JSON array becomes a reference to an array in Perl.
549		962
…		…
553	are represented by the same codepoints in the Perl string, so no manual	966	are represented by the same codepoints in the Perl string, so no manual
554	decoding is necessary.	967	decoding is necessary.
555		968
556	=item number	969	=item number
557		970
558	A JSON number becomes either an integer or numeric (floating point)	971	A JSON number becomes either an integer, numeric (floating point) or
559	scalar in perl, depending on its range and any fractional parts. On the	972	string scalar in perl, depending on its range and any fractional parts. On
560	Perl level, there is no difference between those as Perl handles all the	973	the Perl level, there is no difference between those as Perl handles all
561	conversion details, but an integer may take slightly less memory and might	974	the conversion details, but an integer may take slightly less memory and
562	represent more values exactly than (floating point) numbers.	975	might represent more values exactly than floating point numbers.
		976
		977	If the number consists of digits only, JSON::XS will try to represent
		978	it as an integer value. If that fails, it will try to represent it as
		979	a numeric (floating point) value if that is possible without loss of
		980	precision. Otherwise it will preserve the number as a string value (in
		981	which case you lose roundtripping ability, as the JSON number will be
		982	re-encoded toa JSON string).
		983
		984	Numbers containing a fractional or exponential part will always be
		985	represented as numeric (floating point) values, possibly at a loss of
		986	precision (in which case you might lose perfect roundtripping ability, but
		987	the JSON number will still be re-encoded as a JSON number).
563		988
564	=item true, false	989	=item true, false
565		990
566	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	991	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
567	respectively. They are overloaded to act almost exactly like the numbers	992	respectively. They are overloaded to act almost exactly like the numbers
568	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	993	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
569	the C<JSON::XS::is_bool> function.	994	the C<JSON::XS::is_bool> function.
570		995
571	=item null	996	=item null
572		997
573	A JSON null atom becomes C<undef> in Perl.	998	A JSON null atom becomes C<undef> in Perl.
…		…
604	Other unblessed references are generally not allowed and will cause an	1029	Other unblessed references are generally not allowed and will cause an
605	exception to be thrown, except for references to the integers C<0> and	1030	exception to be thrown, except for references to the integers C<0> and
606	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1031	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
607	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1032	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
608		1033
609	to_json [\0,JSON::XS::true] # yields [false,true]	1034	encode_json [\0, JSON::XS::true] # yields [false,true]
610		1035
611	=item JSON::XS::true, JSON::XS::false	1036	=item JSON::XS::true, JSON::XS::false
612		1037
613	These special values become JSON true and JSON false values,	1038	These special values become JSON true and JSON false values,
614	respectively. You cna alos use C<\1> and C<\0> directly if you want.	1039	respectively. You can also use C<\1> and C<\0> directly if you want.
615		1040
616	=item blessed objects	1041	=item blessed objects
617		1042
618	Blessed objects are not allowed. JSON::XS currently tries to encode their	1043	Blessed objects are not directly representable in JSON. See the
619	underlying representation (hash- or arrayref), but this behaviour might	1044	C<allow_blessed> and C<convert_blessed> methods on various options on
620	change in future versions.	1045	how to deal with this: basically, you can choose between throwing an
		1046	exception, encoding the reference as if it weren't blessed, or provide
		1047	your own serialiser method.
621		1048
622	=item simple scalars	1049	=item simple scalars
623		1050
624	Simple Perl scalars (any scalar that is not a reference) are the most	1051	Simple Perl scalars (any scalar that is not a reference) are the most
625	difficult objects to encode: JSON::XS will encode undefined scalars as	1052	difficult objects to encode: JSON::XS will encode undefined scalars as
626	JSON null value, scalars that have last been used in a string context	1053	JSON C<null> values, scalars that have last been used in a string context
627	before encoding as JSON strings and anything else as number value:	1054	before encoding as JSON strings, and anything else as number value:
628		1055
629	# dump as number	1056	# dump as number
630	to_json [2] # yields [2]	1057	encode_json [2] # yields [2]
631	to_json [-3.0e17] # yields [-3e+17]	1058	encode_json [-3.0e17] # yields [-3e+17]
632	my $value = 5; to_json [$value] # yields [5]	1059	my $value = 5; encode_json [$value] # yields [5]
633		1060
634	# used as string, so dump as string	1061	# used as string, so dump as string
635	print $value;	1062	print $value;
636	to_json [$value] # yields ["5"]	1063	encode_json [$value] # yields ["5"]
637		1064
638	# undef becomes null	1065	# undef becomes null
639	to_json [undef] # yields [null]	1066	encode_json [undef] # yields [null]
640		1067
641	You can force the type to be a string by stringifying it:	1068	You can force the type to be a JSON string by stringifying it:
642		1069
643	my $x = 3.1; # some variable containing a number	1070	my $x = 3.1; # some variable containing a number
644	"$x"; # stringified	1071	"$x"; # stringified
645	$x .= ""; # another, more awkward way to stringify	1072	$x .= ""; # another, more awkward way to stringify
646	print $x; # perl does it for you, too, quite often	1073	print $x; # perl does it for you, too, quite often
647		1074
648	You can force the type to be a number by numifying it:	1075	You can force the type to be a JSON number by numifying it:
649		1076
650	my $x = "3"; # some variable containing a string	1077	my $x = "3"; # some variable containing a string
651	$x += 0; # numify it, ensuring it will be dumped as a number	1078	$x += 0; # numify it, ensuring it will be dumped as a number
652	$x *= 1; # same thing, the choise is yours.	1079	$x *= 1; # same thing, the choice is yours.
653		1080
654	You can not currently output JSON booleans or force the type in other,	1081	You can not currently force the type in other, less obscure, ways. Tell me
655	less obscure, ways. Tell me if you need this capability.	1082	if you need this capability (but don't forget to explain why it's needed
		1083	:).
656		1084
657	=back	1085	=back
658		1086
659		1087
660	=head1 COMPARISON	1088	=head1 ENCODING/CODESET FLAG NOTES
661		1089
662	As already mentioned, this module was created because none of the existing	1090	The interested reader might have seen a number of flags that signify
663	JSON modules could be made to work correctly. First I will describe the	1091	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
664	problems (or pleasures) I encountered with various existing JSON modules,	1092	some confusion on what these do, so here is a short comparison:
665	followed by some benchmark values. JSON::XS was designed not to suffer	1093
666	from any of these problems or limitations.	1094	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1095	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1096	control whether C<encode> escapes character values outside their respective
		1097	codeset range. Neither of these flags conflict with each other, although
		1098	some combinations make less sense than others.
		1099
		1100	Care has been taken to make all flags symmetrical with respect to
		1101	C<encode> and C<decode>, that is, texts encoded with any combination of
		1102	these flag values will be correctly decoded when the same flags are used
		1103	- in general, if you use different flag settings while encoding vs. when
		1104	decoding you likely have a bug somewhere.
		1105
		1106	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1107	simply an abstract set of character-codepoint pairs, while an encoding
		1108	takes those codepoint numbers and I<encodes> them, in our case into
		1109	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1110	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1111	the same time, which can be confusing.
667		1112
668	=over 4	1113	=over 4
669		1114
670	=item JSON 1.07	1115	=item C<utf8> flag disabled
671		1116
672	Slow (but very portable, as it is written in pure Perl).	1117	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1118	and expect Unicode strings, that is, characters with high ordinal Unicode
		1119	values (> 255) will be encoded as such characters, and likewise such
		1120	characters are decoded as-is, no canges to them will be done, except
		1121	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1122	respectively (to Perl, these are the same thing in strings unless you do
		1123	funny/weird/dumb stuff).
673		1124
674	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1125	This is useful when you want to do the encoding yourself (e.g. when you
675	undocumented. One can get far by feeding it unicode strings and doing	1126	want to have UTF-16 encoded JSON texts) or when some other layer does
676	en-/decoding oneself, but unicode escapes are not working properly).	1127	the encoding for you (for example, when printing to a terminal using a
		1128	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1129	to UTF-8 encode your data first and have Perl encode it another time).
677		1130
678	No roundtripping (strings get clobbered if they look like numbers, e.g.	1131	=item C<utf8> flag enabled
679	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
680	decode into the number 2.
681		1132
682	=item JSON::PC 0.01	1133	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1134	characters using the corresponding UTF-8 multi-byte sequence, and will
		1135	expect your input strings to be encoded as UTF-8, that is, no "character"
		1136	of the input string must have any value > 255, as UTF-8 does not allow
		1137	that.
683		1138
684	Very fast.	1139	The C<utf8> flag therefore switches between two modes: disabled means you
		1140	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1141	octet/binary string in Perl.
685		1142
686	Undocumented/buggy Unicode handling.	1143	=item C<latin1> or C<ascii> flags enabled
687		1144
688	No roundtripping.	1145	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1146	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1147	characters as specified by the C<utf8> flag.
689		1148
690	Has problems handling many Perl values (e.g. regex results and other magic	1149	If C<utf8> is disabled, then the result is also correctly encoded in those
691	values will make it croak).	1150	character sets (as both are proper subsets of Unicode, meaning that a
		1151	Unicode string with all character values < 256 is the same thing as a
		1152	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1153	the same thing as an ASCII string in Perl).
692		1154
693	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1155	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
694	which is not a valid JSON text.	1156	regardless of these flags, just some more characters will be escaped using
		1157	C<\uXXXX> then before.
695		1158
696	Unmaintained (maintainer unresponsive for many months, bugs are not	1159	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
697	getting fixed).	1160	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1161	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1162	a subset of Unicode), while ASCII is.
698		1163
699	=item JSON::Syck 0.21	1164	Surprisingly, C<decode> will ignore these flags and so treat all input
		1165	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1166	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1167	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
700		1168
701	Very buggy (often crashes).	1169	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1170	they only govern when the JSON output engine escapes a character or not.
702		1171
703	Very inflexible (no human-readable format supported, format pretty much	1172	The main use for C<latin1> is to relatively efficiently store binary data
704	undocumented. I need at least a format for easy reading by humans and a	1173	as JSON, at the expense of breaking compatibility with most JSON decoders.
705	single-line compact format for use in a protocol, and preferably a way to
706	generate ASCII-only JSON texts).
707		1174
708	Completely broken (and confusingly documented) Unicode handling (unicode	1175	The main use for C<ascii> is to force the output to not contain characters
709	escapes are not working properly, you need to set ImplicitUnicode to	1176	with values > 127, which means you can interpret the resulting string
710	I<different> values on en- and decoding to get symmetric behaviour).	1177	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
711		1178	8-bit-encoding, and still get the same data structure back. This is useful
712	No roundtripping (simple cases work, but this depends on wether the scalar	1179	when your channel for JSON transfer is not 8-bit clean or the encoding
713	value was used in a numeric context or not).	1180	might be mangled in between (e.g. in mail), and works because ASCII is a
714		1181	proper subset of most 8-bit and multibyte encodings in use in the world.
715	Dumping hashes may skip hash values depending on iterator state.
716
717	Unmaintained (maintainer unresponsive for many months, bugs are not
718	getting fixed).
719
720	Does not check input for validity (i.e. will accept non-JSON input and
721	return "something" instead of raising an exception. This is a security
722	issue: imagine two banks transfering money between each other using
723	JSON. One bank might parse a given non-JSON request and deduct money,
724	while the other might reject the transaction with a syntax error. While a
725	good protocol will at least recover, that is extra unnecessary work and
726	the transaction will still not succeed).
727
728	=item JSON::DWIW 0.04
729
730	Very fast. Very natural. Very nice.
731
732	Undocumented unicode handling (but the best of the pack. Unicode escapes
733	still don't get parsed properly).
734
735	Very inflexible.
736
737	No roundtripping.
738
739	Does not generate valid JSON texts (key strings are often unquoted, empty keys
740	result in nothing being output)
741
742	Does not check input for validity.
743		1182
744	=back	1183	=back
745		1184
746		1185
747	=head2 JSON and YAML	1186	=head2 JSON and YAML
748		1187
749	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1188	You often hear that JSON is a subset of YAML. This is, however, a mass
750	however, a mass hysteria and very far from the truth. In general, there is	1189	hysteria(*) and very far from the truth (as of the time of this writing),
751	no way to configure JSON::XS to output a data structure as valid YAML.	1190	so let me state it clearly: I<in general, there is no way to configure
		1191	JSON::XS to output a data structure as valid YAML> that works in all
		1192	cases.
752		1193
753	If you really must use JSON::XS to generate YAML, you should use this	1194	If you really must use JSON::XS to generate YAML, you should use this
754	algorithm (subject to change in future versions):	1195	algorithm (subject to change in future versions):
755		1196
756	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1197	my $to_yaml = JSON::XS->new->utf8->space_after (1);
757	my $yaml = $to_yaml->encode ($ref) . "\n";	1198	my $yaml = $to_yaml->encode ($ref) . "\n";
758		1199
759	This will usually generate JSON texts that also parse as valid	1200	This will I<usually> generate JSON texts that also parse as valid
760	YAML. Please note that YAML has hardcoded limits on (simple) object key	1201	YAML. Please note that YAML has hardcoded limits on (simple) object key
761	lengths that JSON doesn't have, so you should make sure that your hash	1202	lengths that JSON doesn't have and also has different and incompatible
		1203	unicode handling, so you should make sure that your hash keys are
762	keys are noticably shorter than the 1024 characters YAML allows.	1204	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1205	you do not have characters with codepoint values outside the Unicode BMP
		1206	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1207	strings (which JSON::XS does not I<currently> generate, but other JSON
		1208	generators might).
763		1209
764	There might be other incompatibilities that I am not aware of. In general	1210	There might be other incompatibilities that I am not aware of (or the YAML
		1211	specification has been changed yet again - it does so quite often). In
765	you should not try to generate YAML with a JSON generator or vice versa,	1212	general you should not try to generate YAML with a JSON generator or vice
766	or try to parse JSON with a YAML parser or vice versa: chances are high	1213	versa, or try to parse JSON with a YAML parser or vice versa: chances are
767	that you will run into severe interoperability problems.	1214	high that you will run into severe interoperability problems when you
		1215	least expect it.
		1216
		1217	=over 4
		1218
		1219	=item (*)
		1220
		1221	I have been pressured multiple times by Brian Ingerson (one of the
		1222	authors of the YAML specification) to remove this paragraph, despite him
		1223	acknowledging that the actual incompatibilities exist. As I was personally
		1224	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1225	educate people about these issues, so others do not run into the same
		1226	problem again and again. After this, Brian called me a (quote)I<complete
		1227	and worthless idiot>(unquote).
		1228
		1229	In my opinion, instead of pressuring and insulting people who actually
		1230	clarify issues with YAML and the wrong statements of some of its
		1231	proponents, I would kindly suggest reading the JSON spec (which is not
		1232	that difficult or long) and finally make YAML compatible to it, and
		1233	educating users about the changes, instead of spreading lies about the
		1234	real compatibility for many I<years> and trying to silence people who
		1235	point out that it isn't true.
		1236
		1237	=back
768		1238
769		1239
770	=head2 SPEED	1240	=head2 SPEED
771		1241
772	It seems that JSON::XS is surprisingly fast, as shown in the following	1242	It seems that JSON::XS is surprisingly fast, as shown in the following
773	tables. They have been generated with the help of the C<eg/bench> program	1243	tables. They have been generated with the help of the C<eg/bench> program
774	in the JSON::XS distribution, to make it easy to compare on your own	1244	in the JSON::XS distribution, to make it easy to compare on your own
775	system.	1245	system.
776		1246
777	First comes a comparison between various modules using a very short	1247	First comes a comparison between various modules using
778	single-line JSON string:	1248	a very short single-line JSON string (also available at
		1249	L<http://dist.schmorp.de/misc/json/short.json>).
779		1250
780	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1251	{"method": "handleMessage", "params": ["user1",
781	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1252	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1253	true, false]}
782		1254
783	It shows the number of encodes/decodes per second (JSON::XS uses	1255	It shows the number of encodes/decodes per second (JSON::XS uses
784	the functional interface, while JSON::XS/2 uses the OO interface	1256	the functional interface, while JSON::XS/2 uses the OO interface
785	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
786	shrink). Higher is better:	1258	shrink). Higher is better:
787		1259
788	Storable \| 15779.925 \| 14169.946 \|
789	-----------+------------+------------+
790	module \| encode \| decode \|	1260	module \| encode \| decode \|
791	-----------\|------------\|------------\|	1261	-----------\|------------\|------------\|
792	JSON \| 4990.842 \| 4088.813 \|	1262	JSON 1.x \| 4990.842 \| 4088.813 \|
793	JSON::DWIW \| 51653.990 \| 71575.154 \|	1263	JSON::DWIW \| 51653.990 \| 71575.154 \|
794	JSON::PC \| 65948.176 \| 74631.744 \|	1264	JSON::PC \| 65948.176 \| 74631.744 \|
795	JSON::PP \| 8931.652 \| 3817.168 \|	1265	JSON::PP \| 8931.652 \| 3817.168 \|
796	JSON::Syck \| 24877.248 \| 27776.848 \|	1266	JSON::Syck \| 24877.248 \| 27776.848 \|
797	JSON::XS \| 388361.481 \| 227951.304 \|	1267	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
799	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1269	JSON::XS/3 \| 338250.323 \| 218453.333 \|
800	Storable \| 16500.016 \| 135300.129 \|	1270	Storable \| 16500.016 \| 135300.129 \|
801	-----------+------------+------------+	1271	-----------+------------+------------+
802		1272
803	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1273	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
804	about three times faster on decoding, and over fourty times faster	1274	about three times faster on decoding, and over forty times faster
805	than JSON, even with pretty-printing and key sorting. It also compares	1275	than JSON, even with pretty-printing and key sorting. It also compares
806	favourably to Storable for small amounts of data.	1276	favourably to Storable for small amounts of data.
807		1277
808	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
809	search API (http://nanoref.com/yahooapis/mgPdGg):	1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).
810		1280
811	module \| encode \| decode \|	1281	module \| encode \| decode \|
812	-----------\|------------\|------------\|	1282	-----------\|------------\|------------\|
813	JSON \| 55.260 \| 34.971 \|	1283	JSON 1.x \| 55.260 \| 34.971 \|
814	JSON::DWIW \| 825.228 \| 1082.513 \|	1284	JSON::DWIW \| 825.228 \| 1082.513 \|
815	JSON::PC \| 3571.444 \| 2394.829 \|	1285	JSON::PC \| 3571.444 \| 2394.829 \|
816	JSON::PP \| 210.987 \| 32.574 \|	1286	JSON::PP \| 210.987 \| 32.574 \|
817	JSON::Syck \| 552.551 \| 787.544 \|	1287	JSON::Syck \| 552.551 \| 787.544 \|
818	JSON::XS \| 5780.463 \| 4854.519 \|	1288	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
822	-----------+------------+------------+	1292	-----------+------------+------------+
823		1293
824	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1294	Again, JSON::XS leads by far (except for Storable which non-surprisingly
825	decodes faster).	1295	decodes faster).
826		1296
827	On large strings containing lots of high unicode characters, some modules	1297	On large strings containing lots of high Unicode characters, some modules
828	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1298	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
829	will be broken due to missing (or wrong) unicode handling. Others refuse	1299	will be broken due to missing (or wrong) Unicode handling. Others refuse
830	to decode or encode properly, so it was impossible to prepare a fair	1300	to decode or encode properly, so it was impossible to prepare a fair
831	comparison table for that case.	1301	comparison table for that case.
832		1302
833		1303
834	=head1 SECURITY CONSIDERATIONS	1304	=head1 SECURITY CONSIDERATIONS
…		…
840	any buffer overflows. Obviously, this module should ensure that and I am	1310	any buffer overflows. Obviously, this module should ensure that and I am
841	trying hard on making that true, but you never know.	1311	trying hard on making that true, but you never know.
842		1312
843	Second, you need to avoid resource-starving attacks. That means you should	1313	Second, you need to avoid resource-starving attacks. That means you should
844	limit the size of JSON texts you accept, or make sure then when your	1314	limit the size of JSON texts you accept, or make sure then when your
845	resources run out, thats just fine (e.g. by using a separate process that	1315	resources run out, that's just fine (e.g. by using a separate process that
846	can crash safely). The size of a JSON text in octets or characters is	1316	can crash safely). The size of a JSON text in octets or characters is
847	usually a good indication of the size of the resources required to decode	1317	usually a good indication of the size of the resources required to decode
848	it into a Perl structure. While JSON::XS can check the size of the JSON	1318	it into a Perl structure. While JSON::XS can check the size of the JSON
849	text, it might be too late when you already have it in memory, so you	1319	text, it might be too late when you already have it in memory, so you
850	might want to check the size before you accept the string.	1320	might want to check the size before you accept the string.
851		1321
852	Third, JSON::XS recurses using the C stack when decoding objects and	1322	Third, JSON::XS recurses using the C stack when decoding objects and
853	arrays. The C stack is a limited resource: for instance, on my amd64	1323	arrays. The C stack is a limited resource: for instance, on my amd64
854	machine with 8MB of stack size I can decode around 180k nested arrays but	1324	machine with 8MB of stack size I can decode around 180k nested arrays but
855	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1325	only 14k nested JSON objects (due to perl itself recursing deeply on croak
856	to free the temporary). If that is exceeded, the program crashes. to be	1326	to free the temporary). If that is exceeded, the program crashes. To be
857	conservative, the default nesting limit is set to 512. If your process	1327	conservative, the default nesting limit is set to 512. If your process
858	has a smaller stack, you should adjust this setting accordingly with the	1328	has a smaller stack, you should adjust this setting accordingly with the
859	C<max_depth> method.	1329	C<max_depth> method.
860		1330
861	And last but least, something else could bomb you that I forgot to think	1331	Something else could bomb you, too, that I forgot to think of. In that
862	of. In that case, you get to keep the pieces. I am always open for hints,	1332	case, you get to keep the pieces. I am always open for hints, though...
863	though...	1333
		1334	Also keep in mind that JSON::XS might leak contents of your Perl data
		1335	structures in its error messages, so when you serialise sensitive
		1336	information you might want to make sure that exceptions thrown by JSON::XS
		1337	will not end up in front of untrusted eyes.
864		1338
865	If you are using JSON::XS to return packets to consumption	1339	If you are using JSON::XS to return packets to consumption
866	by javascript scripts in a browser you should have a look at	1340	by JavaScript scripts in a browser you should have a look at
867	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1341	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
868	you are vulnerable to some common attack vectors (which really are browser	1342	you are vulnerable to some common attack vectors (which really are browser
869	design bugs, but it is still you who will have to deal with it, as major	1343	design bugs, but it is still you who will have to deal with it, as major
870	browser developers care only for features, not about doing security	1344	browser developers care only for features, not about getting security
871	right).	1345	right).
872		1346
873		1347
		1348	=head1 THREADS
		1349
		1350	This module is I<not> guaranteed to be thread safe and there are no
		1351	plans to change this until Perl gets thread support (as opposed to the
		1352	horribly slow so-called "threads" which are simply slow and bloated
		1353	process simulations - use fork, it's I<much> faster, cheaper, better).
		1354
		1355	(It might actually work, but you have been warned).
		1356
		1357
874	=head1 BUGS	1358	=head1 BUGS
875		1359
876	While the goal of this module is to be correct, that unfortunately does	1360	While the goal of this module is to be correct, that unfortunately does
877	not mean its bug-free, only that I think its design is bug-free. It is	1361	not mean it's bug-free, only that I think its design is bug-free. If you
878	still relatively early in its development. If you keep reporting bugs they	1362	keep reporting bugs they will be fixed swiftly, though.
879	will be fixed swiftly, though.	1363
		1364	Please refrain from using rt.cpan.org or any other bug reporting
		1365	service. I put the contact address into my modules for a reason.
880		1366
881	=cut	1367	=cut
882		1368
883	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1369	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
884	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1370	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
901	"--" => sub { $_[0] = ${$_[0]} - 1 },	1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
902	fallback => 1;	1388	fallback => 1;
903		1389
904	1;	1390	1;
905		1391
		1392	=head1 SEE ALSO
		1393
		1394	The F<json_xs> command line utility for quick experiments.
		1395
906	=head1 AUTHOR	1396	=head1 AUTHOR
907		1397
908	Marc Lehmann <schmorp@schmorp.de>	1398	Marc Lehmann <schmorp@schmorp.de>
909	http://home.schmorp.de/	1399	http://home.schmorp.de/
910		1400

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Comparing JSON-XS/XS.pm (file contents): Revision 1.55 by root, Mon Jul 23 22:57:40 2007 UTC vs. Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.55 by root, Mon Jul 23 22:57:40 2007 UTC vs.
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC