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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC

…		…
		1	=head1 NAME
		2
		3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
1	=encoding utf-8	5	=encoding utf-8
2
3	=head1 NAME
4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		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	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)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9		9
10	=head1 SYNOPSIS	10	=head1 SYNOPSIS
12	use JSON::XS;	12	use JSON::XS;
13		13
14	# exported functions, they croak on error	14	# exported functions, they croak on error
15	# and expect/generate UTF-8	15	# and expect/generate UTF-8
16		16
17	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
18	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
19		19
20	# OO-interface	20	# OO-interface
21		21
22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
24	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
25		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
26	=head1 DESCRIPTION	34	=head1 DESCRIPTION
27		35
28	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
29	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
30	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.
31		47
32	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
33	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
34	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
35	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
36	reports for other reasons.	52	reports for other reasons.
37		53
38	See COMPARISON, below, for a comparison to some other JSON modules.
39
40	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
41	vice versa.	55	vice versa.
42		56
43	=head2 FEATURES	57	=head2 FEATURES
44		58
45	=over 4	59	=over 4
46		60
47	=item * correct unicode handling	61	=item * correct Unicode handling
48		62
49	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
50	it does so.	64	so, and even documents what "correct" means.
51		65
52	=item * round-trip integrity	66	=item * round-trip integrity
53		67
54	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
55	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.
56	(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
57	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
58		73
59	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
60		75
61	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,
62	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
63	feature).	78	feature).
64		79
65	=item * fast	80	=item * fast
66		81
67	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
68	of speed, too.	83	this module usually compares favourably in terms of speed, too.
69		84
70	=item * simple to use	85	=item * simple to use
71		86
72	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
73	interface.	88	oriented interface interface.
74		89
75	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
76		91
77	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
78	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
79	(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
80	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
81	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.
82		97
83	=back	98	=back
84		99
85	=cut	100	=cut
86		101
87	package JSON::XS;	102	package JSON::XS;
88		103
		104	no warnings;
89	use strict;	105	use strict;
90		106
91	our $VERSION = '1.5';	107	our $VERSION = '2.23';
92	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
93		109
94	our @EXPORT = qw(to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
		111
		112	sub to_json($) {
		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	}
95		121
96	use Exporter;	122	use Exporter;
97	use XSLoader;	123	use XSLoader;
98		124
99	=head1 FUNCTIONAL INTERFACE	125	=head1 FUNCTIONAL INTERFACE
100		126
101	The following convinience methods are provided by this module. They are	127	The following convenience methods are provided by this module. They are
102	exported by default:	128	exported by default:
103		129
104	=over 4	130	=over 4
105		131
106	=item $json_text = to_json $perl_scalar	132	=item $json_text = encode_json $perl_scalar
107		133
108	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
109	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.
110	octets only). Croaks on error.
111		136
112	This function call is functionally identical to:	137	This function call is functionally identical to:
113		138
114	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115		140
116	except being faster.	141	Except being faster.
117		142
118	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
119		144
120	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
121	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
122	scalar or reference. Croaks on error.	147	reference. Croaks on error.
123		148
124	This function call is functionally identical to:	149	This function call is functionally identical to:
125		150
126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127		152
128	except being faster.	153	Except being faster.
129		154
130	=item $is_boolean = JSON::XS::is_bool $scalar	155	=item $is_boolean = JSON::XS::is_bool $scalar
131		156
132	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
133	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
…		…
137	Perl.	162	Perl.
138		163
139	=back	164	=back
140		165
141		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
142	=head1 OBJECT-ORIENTED INTERFACE	215	=head1 OBJECT-ORIENTED INTERFACE
143		216
144	The object oriented interface lets you configure your own encoding or	217	The object oriented interface lets you configure your own encoding or
145	decoding style, within the limits of supported formats.	218	decoding style, within the limits of supported formats.
146		219
…		…
157	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]})
158	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
159		232
160	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
161		234
		235	=item $enabled = $json->get_ascii
		236
162	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
163	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
164	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
165	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
166	as per RFC4627. The resulting encoded JSON text can be treated as a native	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
167	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
168	or any other superset of ASCII.	243	or any other superset of ASCII.
169		244
170	If C<$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
171	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
172	in a faster and more compact format.	247	in a faster and more compact format.
173		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
174	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
175	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
176	contain any 8 bit characters.	254	contain any 8 bit characters.
177		255
178	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
179	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
180		258
181	=item $json = $json->latin1 ([$enable])	259	=item $json = $json->latin1 ([$enable])
182		260
		261	=item $enabled = $json->get_latin1
		262
183	If C<$enable> is true (or missing), then the C<encode> method will encode	263	If C<$enable> is true (or missing), then the C<encode> method will encode
184	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
185	outside the code range C<0..255>. The resulting string can be treated as a	265	outside the code range C<0..255>. The resulting string can be treated as a
186	latin1-encoded JSON text or a native unicode string. The C<decode> method	266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
187	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
188	expects unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
189		269
190	If C<$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
191	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.
192		275
193	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
194	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
195	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
196	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
197	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
198	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
199	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.
200		283
201	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
202	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
203		286
204	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
205		290
206	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
207	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
208	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
209	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
210	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
211	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
212	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
213		298
214	If C<$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
215	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
216	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
217	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.
218		306
219	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
220		308
221	use Encode;	309	use Encode;
222	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
243	]	331	]
244	}	332	}
245		333
246	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
247		335
		336	=item $enabled = $json->get_indent
		337
248	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
249	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
250	into its own line, identing them properly.	340	into its own line, indenting them properly.
251		341
252	If C<$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
253	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
254		344
255	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
256		346
257	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
258		350
259	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
260	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
261		353
262	If C<$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
…		…
268	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
269		361
270	{"key" :"value"}	362	{"key" :"value"}
271		363
272	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
273		367
274	If C<$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
275	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
276	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
277	members.	371	members.
…		…
284	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
285		379
286	{"key": "value"}	380	{"key": "value"}
287		381
288	=item $json = $json->relaxed ([$enable])	382	=item $json = $json->relaxed ([$enable])
		383
		384	=item $enabled = $json->get_relaxed
289		385
290	If C<$enable> is true (or missing), then C<decode> will accept some	386	If C<$enable> is true (or missing), then C<decode> will accept some
291	extensions to normal JSON syntax (see below). C<encode> will not be	387	extensions to normal JSON syntax (see below). C<encode> will not be
292	affected in anyway. I<Be aware that this option makes you accept invalid	388	affected in anyway. I<Be aware that this option makes you accept invalid
293	JSON texts as if they were valid!>. I suggest only to use this option to	389	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
330		426
331	=back	427	=back
332		428
333	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
334		430
		431	=item $enabled = $json->get_canonical
		432
335	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
336	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
337		435
338	If C<$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
339	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
340	of the same script).	438	of the same script).
341		439
342	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
343	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,
344	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,
345	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
346		444
347	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
348		446
349	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
350		450
351	If C<$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
352	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
353	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
354	values instead of croaking.	454	values instead of croaking.
…		…
362	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
363		463
364	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
365	=> "Hello, World!"	465	=> "Hello, World!"
366		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
367	=item $json = $json->allow_blessed ([$enable])	483	=item $json = $json->allow_blessed ([$enable])
		484
		485	=item $enabled = $json->get_allow_blessed
368		486
369	If C<$enable> is true (or missing), then the C<encode> method will not	487	If C<$enable> is true (or missing), then the C<encode> method will not
370	barf when it encounters a blessed reference. Instead, the value of the	488	barf when it encounters a blessed reference. Instead, the value of the
371	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
372	disabled or no C<to_json> method found) or a representation of the	490	disabled or no C<TO_JSON> method found) or a representation of the
373	object (C<convert_blessed> enabled and C<to_json> method found) is being	491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
374	encoded. Has no effect on C<decode>.	492	encoded. Has no effect on C<decode>.
375		493
376	If C<$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
377	exception when it encounters a blessed object.	495	exception when it encounters a blessed object.
378		496
379	=item $json = $json->convert_blessed ([$enable])	497	=item $json = $json->convert_blessed ([$enable])
		498
		499	=item $enabled = $json->get_convert_blessed
380		500
381	If C<$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
382	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
383	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
384	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
…		…
388	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>
389	returns other blessed objects, those will be handled in the same	509	returns other blessed objects, those will be handled in the same
390	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
391	(== 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
392	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
393	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>
394	function.	514	function or method.
395		515
396	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
397	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
398	enabled by this setting.	518	enabled by this setting.
399		519
…		…
441		561
442	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>
443	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
444	objects make excellent targets to serialise Perl objects into, especially	564	objects make excellent targets to serialise Perl objects into, especially
445	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
446	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
447	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
448	like a serialised Perl hash.	568	like a serialised Perl hash.
449		569
450	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
451	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
…		…
475		595
476	{ __widget__ => $self->{id} }	596	{ __widget__ => $self->{id} }
477	}	597	}
478		598
479	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
480		602
481	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
482	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
483	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
484	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
…		…
502	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
503	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
504		626
505	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
506		628
		629	=item $max_depth = $json->get_max_depth
		630
507	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
508	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
509	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
510	stop and croak at that point.	634	point.
511		635
512	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
513	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<[>
514	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
515	given character in a string.	639	given character in a string.
516		640
517	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
518	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
519		643
520	The argument to C<max_depth> will be rounded up to the next highest power
521	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
522	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.
523		650
524	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.
525		652
526	=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
527		656
528	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
529	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>
530	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
531	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
532	effect on C<encode> (yet).	661	effect on C<encode> (yet).
533		662
534	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
535	power of two (so may be more than requested). If no argument is given, the	664	C<0> is specified).
536	limit check will be deactivated (same as when C<0> is specified).
537		665
538	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.
539		667
540	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
541		669
…		…
570	=> ([], 3)	698	=> ([], 3)
571		699
572	=back	700	=back
573		701
574		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
575	=head1 MAPPING	938	=head1 MAPPING
576		939
577	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
578	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
579	circumstances automatically, preserving round-tripping characteristics	942	circumstances automatically, preserving round-tripping characteristics
580	(what you put in comes out as something equivalent).	943	(what you put in comes out as something equivalent).
581		944
582	For the more enlightened: note that in the following descriptions,	945	For the more enlightened: note that in the following descriptions,
583	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>
584	refers to the abstract Perl language itself.	947	refers to the abstract Perl language itself.
585		948
586		949
587	=head2 JSON -> PERL	950	=head2 JSON -> PERL
588		951
589	=over 4	952	=over 4
590		953
591	=item object	954	=item object
592		955
593	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
594	keys is preserved (JSON does not preserver object key ordering itself).	957	keys is preserved (JSON does not preserve object key ordering itself).
595		958
596	=item array	959	=item array
597		960
598	A JSON array becomes a reference to an array in Perl.	961	A JSON array becomes a reference to an array in Perl.
599		962
…		…
607		970
608	A JSON number becomes either an integer, numeric (floating point) or	971	A JSON number becomes either an integer, numeric (floating point) or
609	string scalar in perl, depending on its range and any fractional parts. On	972	string scalar in perl, depending on its range and any fractional parts. On
610	the Perl level, there is no difference between those as Perl handles all	973	the Perl level, there is no difference between those as Perl handles all
611	the conversion details, but an integer may take slightly less memory and	974	the conversion details, but an integer may take slightly less memory and
612	might represent more values exactly than (floating point) numbers.	975	might represent more values exactly than floating point numbers.
613		976
614	If the number consists of digits only, JSON::XS will try to represent	977	If the number consists of digits only, JSON::XS will try to represent
615	it as an integer value. If that fails, it will try to represent it as	978	it as an integer value. If that fails, it will try to represent it as
616	a numeric (floating point) value if that is possible without loss of	979	a numeric (floating point) value if that is possible without loss of
617	precision. Otherwise it will preserve the number as a string value.	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).
618		983
619	Numbers containing a fractional or exponential part will always be	984	Numbers containing a fractional or exponential part will always be
620	represented as numeric (floating point) values, possibly at a loss of	985	represented as numeric (floating point) values, possibly at a loss of
621	precision.	986	precision (in which case you might lose perfect roundtripping ability, but
622		987	the JSON number will still be re-encoded as a JSON number).
623	This might create round-tripping problems as numbers might become strings,
624	but as Perl is typeless there is no other way to do it.
625		988
626	=item true, false	989	=item true, false
627		990
628	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>,
629	respectively. They are overloaded to act almost exactly like the numbers	992	respectively. They are overloaded to act almost exactly like the numbers
630	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
631	the C<JSON::XS::is_bool> function.	994	the C<JSON::XS::is_bool> function.
632		995
633	=item null	996	=item null
634		997
635	A JSON null atom becomes C<undef> in Perl.	998	A JSON null atom becomes C<undef> in Perl.
…		…
666	Other unblessed references are generally not allowed and will cause an	1029	Other unblessed references are generally not allowed and will cause an
667	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
668	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
669	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.
670		1033
671	to_json [\0,JSON::XS::true] # yields [false,true]	1034	encode_json [\0, JSON::XS::true] # yields [false,true]
672		1035
673	=item JSON::XS::true, JSON::XS::false	1036	=item JSON::XS::true, JSON::XS::false
674		1037
675	These special values become JSON true and JSON false values,	1038	These special values become JSON true and JSON false values,
676	respectively. You can also 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.
677		1040
678	=item blessed objects	1041	=item blessed objects
679		1042
680	Blessed objects are not allowed. JSON::XS currently tries to encode their	1043	Blessed objects are not directly representable in JSON. See the
681	underlying representation (hash- or arrayref), but this behaviour might	1044	C<allow_blessed> and C<convert_blessed> methods on various options on
682	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.
683		1048
684	=item simple scalars	1049	=item simple scalars
685		1050
686	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
687	difficult objects to encode: JSON::XS will encode undefined scalars as	1052	difficult objects to encode: JSON::XS will encode undefined scalars as
688	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
689	before encoding as JSON strings and anything else as number value:	1054	before encoding as JSON strings, and anything else as number value:
690		1055
691	# dump as number	1056	# dump as number
692	to_json [2] # yields [2]	1057	encode_json [2] # yields [2]
693	to_json [-3.0e17] # yields [-3e+17]	1058	encode_json [-3.0e17] # yields [-3e+17]
694	my $value = 5; to_json [$value] # yields [5]	1059	my $value = 5; encode_json [$value] # yields [5]
695		1060
696	# used as string, so dump as string	1061	# used as string, so dump as string
697	print $value;	1062	print $value;
698	to_json [$value] # yields ["5"]	1063	encode_json [$value] # yields ["5"]
699		1064
700	# undef becomes null	1065	# undef becomes null
701	to_json [undef] # yields [null]	1066	encode_json [undef] # yields [null]
702		1067
703	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:
704		1069
705	my $x = 3.1; # some variable containing a number	1070	my $x = 3.1; # some variable containing a number
706	"$x"; # stringified	1071	"$x"; # stringified
707	$x .= ""; # another, more awkward way to stringify	1072	$x .= ""; # another, more awkward way to stringify
708	print $x; # perl does it for you, too, quite often	1073	print $x; # perl does it for you, too, quite often
709		1074
710	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:
711		1076
712	my $x = "3"; # some variable containing a string	1077	my $x = "3"; # some variable containing a string
713	$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
714	$x *= 1; # same thing, the choise is yours.	1079	$x *= 1; # same thing, the choice is yours.
715		1080
716	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
717	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	:).
718		1084
719	=back	1085	=back
720		1086
721		1087
722	=head1 COMPARISON	1088	=head1 ENCODING/CODESET FLAG NOTES
723		1089
724	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
725	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
726	problems (or pleasures) I encountered with various existing JSON modules,	1092	some confusion on what these do, so here is a short comparison:
727	followed by some benchmark values. JSON::XS was designed not to suffer	1093
728	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.
729		1112
730	=over 4	1113	=over 4
731		1114
732	=item JSON 1.07	1115	=item C<utf8> flag disabled
733		1116
734	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).
735		1124
736	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
737	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
738	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).
739		1130
740	No roundtripping (strings get clobbered if they look like numbers, e.g.	1131	=item C<utf8> flag enabled
741	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
742	decode into the number 2.
743		1132
744	=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.
745		1138
746	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.
747		1142
748	Undocumented/buggy Unicode handling.	1143	=item C<latin1> or C<ascii> flags enabled
749		1144
750	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.
751		1148
752	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
753	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).
754		1154
755	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,
756	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.
757		1158
758	Unmaintained (maintainer unresponsive for many months, bugs are not	1159	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
759	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.
760		1163
761	=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.
762		1168
763	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.
764		1171
765	Very inflexible (no human-readable format supported, format pretty much	1172	The main use for C<latin1> is to relatively efficiently store binary data
766	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.
767	single-line compact format for use in a protocol, and preferably a way to
768	generate ASCII-only JSON texts).
769		1174
770	Completely broken (and confusingly documented) Unicode handling (unicode	1175	The main use for C<ascii> is to force the output to not contain characters
771	escapes are not working properly, you need to set ImplicitUnicode to	1176	with values > 127, which means you can interpret the resulting string
772	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
773		1178	8-bit-encoding, and still get the same data structure back. This is useful
774	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
775	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
776		1181	proper subset of most 8-bit and multibyte encodings in use in the world.
777	Dumping hashes may skip hash values depending on iterator state.
778
779	Unmaintained (maintainer unresponsive for many months, bugs are not
780	getting fixed).
781
782	Does not check input for validity (i.e. will accept non-JSON input and
783	return "something" instead of raising an exception. This is a security
784	issue: imagine two banks transfering money between each other using
785	JSON. One bank might parse a given non-JSON request and deduct money,
786	while the other might reject the transaction with a syntax error. While a
787	good protocol will at least recover, that is extra unnecessary work and
788	the transaction will still not succeed).
789
790	=item JSON::DWIW 0.04
791
792	Very fast. Very natural. Very nice.
793
794	Undocumented unicode handling (but the best of the pack. Unicode escapes
795	still don't get parsed properly).
796
797	Very inflexible.
798
799	No roundtripping.
800
801	Does not generate valid JSON texts (key strings are often unquoted, empty keys
802	result in nothing being output)
803
804	Does not check input for validity.
805		1182
806	=back	1183	=back
807		1184
808		1185
809	=head2 JSON and YAML	1186	=head2 JSON and YAML
810		1187
811	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
812	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),
813	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.
814		1193
815	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
816	algorithm (subject to change in future versions):	1195	algorithm (subject to change in future versions):
817		1196
818	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1197	my $to_yaml = JSON::XS->new->utf8->space_after (1);
819	my $yaml = $to_yaml->encode ($ref) . "\n";	1198	my $yaml = $to_yaml->encode ($ref) . "\n";
820		1199
821	This will usually generate JSON texts that also parse as valid	1200	This will I<usually> generate JSON texts that also parse as valid
822	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
823	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
824	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).
825		1209
826	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
827	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
828	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
829	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
830		1238
831		1239
832	=head2 SPEED	1240	=head2 SPEED
833		1241
834	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
835	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
836	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
837	system.	1245	system.
838		1246
839	First comes a comparison between various modules using a very short	1247	First comes a comparison between various modules using
840	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>).
841		1250
842	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1251	{"method": "handleMessage", "params": ["user1",
843	"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]}
844		1254
845	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
846	the functional interface, while JSON::XS/2 uses the OO interface	1256	the functional interface, while JSON::XS/2 uses the OO interface
847	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
848	shrink). Higher is better:	1258	shrink). Higher is better:
849		1259
850	Storable \| 15779.925 \| 14169.946 \|
851	-----------+------------+------------+
852	module \| encode \| decode \|	1260	module \| encode \| decode \|
853	-----------\|------------\|------------\|	1261	-----------\|------------\|------------\|
854	JSON \| 4990.842 \| 4088.813 \|	1262	JSON 1.x \| 4990.842 \| 4088.813 \|
855	JSON::DWIW \| 51653.990 \| 71575.154 \|	1263	JSON::DWIW \| 51653.990 \| 71575.154 \|
856	JSON::PC \| 65948.176 \| 74631.744 \|	1264	JSON::PC \| 65948.176 \| 74631.744 \|
857	JSON::PP \| 8931.652 \| 3817.168 \|	1265	JSON::PP \| 8931.652 \| 3817.168 \|
858	JSON::Syck \| 24877.248 \| 27776.848 \|	1266	JSON::Syck \| 24877.248 \| 27776.848 \|
859	JSON::XS \| 388361.481 \| 227951.304 \|	1267	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
861	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1269	JSON::XS/3 \| 338250.323 \| 218453.333 \|
862	Storable \| 16500.016 \| 135300.129 \|	1270	Storable \| 16500.016 \| 135300.129 \|
863	-----------+------------+------------+	1271	-----------+------------+------------+
864		1272
865	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,
866	about three times faster on decoding, and over fourty times faster	1274	about three times faster on decoding, and over forty times faster
867	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
868	favourably to Storable for small amounts of data.	1276	favourably to Storable for small amounts of data.
869		1277
870	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
871	search API (http://nanoref.com/yahooapis/mgPdGg):	1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).
872		1280
873	module \| encode \| decode \|	1281	module \| encode \| decode \|
874	-----------\|------------\|------------\|	1282	-----------\|------------\|------------\|
875	JSON \| 55.260 \| 34.971 \|	1283	JSON 1.x \| 55.260 \| 34.971 \|
876	JSON::DWIW \| 825.228 \| 1082.513 \|	1284	JSON::DWIW \| 825.228 \| 1082.513 \|
877	JSON::PC \| 3571.444 \| 2394.829 \|	1285	JSON::PC \| 3571.444 \| 2394.829 \|
878	JSON::PP \| 210.987 \| 32.574 \|	1286	JSON::PP \| 210.987 \| 32.574 \|
879	JSON::Syck \| 552.551 \| 787.544 \|	1287	JSON::Syck \| 552.551 \| 787.544 \|
880	JSON::XS \| 5780.463 \| 4854.519 \|	1288	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
884	-----------+------------+------------+	1292	-----------+------------+------------+
885		1293
886	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
887	decodes faster).	1295	decodes faster).
888		1296
889	On large strings containing lots of high unicode characters, some modules	1297	On large strings containing lots of high Unicode characters, some modules
890	(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
891	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
892	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
893	comparison table for that case.	1301	comparison table for that case.
894		1302
895		1303
896	=head1 SECURITY CONSIDERATIONS	1304	=head1 SECURITY CONSIDERATIONS
…		…
902	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
903	trying hard on making that true, but you never know.	1311	trying hard on making that true, but you never know.
904		1312
905	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
906	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
907	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
908	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
909	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
910	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
911	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
912	might want to check the size before you accept the string.	1320	might want to check the size before you accept the string.
913		1321
914	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
915	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
916	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
917	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
918	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
919	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
920	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
921	C<max_depth> method.	1329	C<max_depth> method.
922		1330
923	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
924	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...
925	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.
926		1338
927	If you are using JSON::XS to return packets to consumption	1339	If you are using JSON::XS to return packets to consumption
928	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
929	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
930	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
931	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
932	browser developers care only for features, not about doing security	1344	browser developers care only for features, not about getting security
933	right).	1345	right).
934		1346
935		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
936	=head1 BUGS	1358	=head1 BUGS
937		1359
938	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
939	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
940	still relatively early in its development. If you keep reporting bugs they	1362	keep reporting bugs they will be fixed swiftly, though.
941	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.
942		1366
943	=cut	1367	=cut
944		1368
945	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1369	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
946	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1370	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
963	"--" => sub { $_[0] = ${$_[0]} - 1 },	1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
964	fallback => 1;	1388	fallback => 1;
965		1389
966	1;	1390	1;
967		1391
		1392	=head1 SEE ALSO
		1393
		1394	The F<json_xs> command line utility for quick experiments.
		1395
968	=head1 AUTHOR	1396	=head1 AUTHOR
969		1397
970	Marc Lehmann <schmorp@schmorp.de>	1398	Marc Lehmann <schmorp@schmorp.de>
971	http://home.schmorp.de/	1399	http://home.schmorp.de/
972		1400

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Comparing JSON-XS/XS.pm (file contents): Revision 1.62 by root, Thu Oct 11 22:52:52 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 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC