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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.65 by root, Sat Oct 13 01:55:31 2007 UTC vs.
Revision 1.114 by root, Wed Jan 21 05:34:08 2009 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 = '1.51';	107	our $VERSION = '2.231';
92	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
93		109
94	our @EXPORT = qw(to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
		111
		112	sub to_json($) {
		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 to a UTF-8 encoded, binary string	134	Converts the given Perl data structure to a UTF-8 encoded, binary string
109	(that is, the string contains octets only). Croaks on error.	135	(that is, the string contains octets only). Croaks on error.
110		136
111	This function call is functionally identical to:	137	This function call is functionally identical to:
112		138
113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114		140
115	except being faster.	141	Except being faster.
116		142
117	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
118		144
119	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	145	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
120	to parse that as an UTF-8 encoded JSON text, returning the resulting	146	to parse that as an UTF-8 encoded JSON text, returning the resulting
121	reference. Croaks on error.	147	reference. Croaks on error.
122		148
123	This function call is functionally identical to:	149	This function call is functionally identical to:
124		150
125	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
126		152
127	except being faster.	153	Except being faster.
128		154
129	=item $is_boolean = JSON::XS::is_bool $scalar	155	=item $is_boolean = JSON::XS::is_bool $scalar
130		156
131	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
132	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
…		…
145		171
146	=over 4	172	=over 4
147		173
148	=item 1. Perl strings can store characters with ordinal values > 255.	174	=item 1. Perl strings can store characters with ordinal values > 255.
149		175
150	This enables you to store unicode characters as single characters in a	176	This enables you to store Unicode characters as single characters in a
151	Perl string - very natural.	177	Perl string - very natural.
152		178
153	=item 2. Perl does I<not> associate an encoding with your strings.	179	=item 2. Perl does I<not> associate an encoding with your strings.
154		180
155	Unless you force it to, e.g. when matching it against a regex, or printing	181	... until you force it to, e.g. when matching it against a regex, or
156	the scalar to a file, in which case Perl either interprets your string as	182	printing the scalar to a file, in which case Perl either interprets your
157	locale-encoded text, octets/binary, or as Unicode, depending on various	183	string as locale-encoded text, octets/binary, or as Unicode, depending
158	settings. In no case is an encoding stored together with your data, it is	184	on various settings. In no case is an encoding stored together with your
159	I<use> that decides encoding, not any magical metadata.	185	data, it is I<use> that decides encoding, not any magical meta data.
160		186
161	=item 3. The internal utf-8 flag has no meaning with regards to the	187	=item 3. The internal utf-8 flag has no meaning with regards to the
162	encoding of your string.	188	encoding of your string.
163		189
164	Just ignore that flag unless you debug a Perl bug, a module written in	190	Just ignore that flag unless you debug a Perl bug, a module written in
165	XS or want to dive into the internals of perl. Otherwise it will only	191	XS or want to dive into the internals of perl. Otherwise it will only
166	confuse you, as, despite the name, it says nothing about how your string	192	confuse you, as, despite the name, it says nothing about how your string
167	is encoded. You can have unicode strings with that flag set, with that	193	is encoded. You can have Unicode strings with that flag set, with that
168	flag clear, and you can have binary data with that flag set and that flag	194	flag clear, and you can have binary data with that flag set and that flag
169	clear. Other possibilities exist, too.	195	clear. Other possibilities exist, too.
170		196
171	If you didn't know about that flag, just the better, pretend it doesn't	197	If you didn't know about that flag, just the better, pretend it doesn't
172	exist.	198	exist.
173		199
174	=item 4. A "Unicode String" is simply a string where each character can be	200	=item 4. A "Unicode String" is simply a string where each character can be
175	validly interpreted as a Unicode codepoint.	201	validly interpreted as a Unicode code point.
176		202
177	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	203	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
178	Unicode string encoded in UTF-8, giving you a binary string.	204	Unicode string encoded in UTF-8, giving you a binary string.
179		205
180	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	206	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
181		207
182	Its a fact. Learn to live with it.	208	It's a fact. Learn to live with it.
183		209
184	=back	210	=back
185		211
186	I hope this helps :)	212	I hope this helps :)
187		213
…		…
204	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]})
205	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
206		232
207	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
208		234
		235	=item $enabled = $json->get_ascii
		236
209	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
210	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
211	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
213	as per RFC4627. The resulting encoded JSON text can be treated as a native	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
214	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
215	or any other superset of ASCII.	243	or any other superset of ASCII.
216		244
217	If C<$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
218	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
219	in a faster and more compact format.	247	in a faster and more compact format.
220		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
221	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
222	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
223	contain any 8 bit characters.	254	contain any 8 bit characters.
224		255
225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
226	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
227		258
228	=item $json = $json->latin1 ([$enable])	259	=item $json = $json->latin1 ([$enable])
229		260
		261	=item $enabled = $json->get_latin1
		262
230	If C<$enable> is true (or missing), then the C<encode> method will encode	263	If C<$enable> is true (or missing), then the C<encode> method will encode
231	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
232	outside the code range C<0..255>. The resulting string can be treated as a	265	outside the code range C<0..255>. The resulting string can be treated as a
233	latin1-encoded JSON text or a native unicode string. The C<decode> method	266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
234	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
235	expects unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
236		269
237	If C<$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
238	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.
239		275
240	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
241	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
242	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
243	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
244	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
245	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
246	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.
247		283
248	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
249	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
250		286
251	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
252		290
253	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
254	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
255	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
256	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
257	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
258	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
259	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
260		298
261	If C<$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
262	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
263	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
264	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.
265		306
266	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
267		308
268	use Encode;	309	use Encode;
269	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
290	]	331	]
291	}	332	}
292		333
293	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
294		335
		336	=item $enabled = $json->get_indent
		337
295	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
296	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
297	into its own line, identing them properly.	340	into its own line, indenting them properly.
298		341
299	If C<$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
300	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
301		344
302	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
303		346
304	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
305		350
306	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
307	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
308		353
309	If C<$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
…		…
315	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
316		361
317	{"key" :"value"}	362	{"key" :"value"}
318		363
319	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
320		367
321	If C<$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
322	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
323	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
324	members.	371	members.
…		…
331	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
332		379
333	{"key": "value"}	380	{"key": "value"}
334		381
335	=item $json = $json->relaxed ([$enable])	382	=item $json = $json->relaxed ([$enable])
		383
		384	=item $enabled = $json->get_relaxed
336		385
337	If C<$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
338	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
339	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
340	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
…		…
377		426
378	=back	427	=back
379		428
380	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
381		430
		431	=item $enabled = $json->get_canonical
		432
382	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
383	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
384		435
385	If C<$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
386	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
387	of the same script).	438	of the same script).
388		439
389	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
390	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,
391	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,
392	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
393		444
394	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
395		446
396	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
397		450
398	If C<$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
399	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
400	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
401	values instead of croaking.	454	values instead of croaking.
…		…
409	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
410		463
411	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
412	=> "Hello, World!"	465	=> "Hello, World!"
413		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
414	=item $json = $json->allow_blessed ([$enable])	483	=item $json = $json->allow_blessed ([$enable])
		484
		485	=item $enabled = $json->get_allow_blessed
415		486
416	If C<$enable> is true (or missing), then the C<encode> method will not	487	If C<$enable> is true (or missing), then the C<encode> method will not
417	barf when it encounters a blessed reference. Instead, the value of the	488	barf when it encounters a blessed reference. Instead, the value of the
418	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
419	disabled or no C<to_json> method found) or a representation of the	490	disabled or no C<TO_JSON> method found) or a representation of the
420	object (C<convert_blessed> enabled and C<to_json> method found) is being	491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
421	encoded. Has no effect on C<decode>.	492	encoded. Has no effect on C<decode>.
422		493
423	If C<$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
424	exception when it encounters a blessed object.	495	exception when it encounters a blessed object.
425		496
426	=item $json = $json->convert_blessed ([$enable])	497	=item $json = $json->convert_blessed ([$enable])
		498
		499	=item $enabled = $json->get_convert_blessed
427		500
428	If C<$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
429	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
430	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
431	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
…		…
435	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>
436	returns other blessed objects, those will be handled in the same	509	returns other blessed objects, those will be handled in the same
437	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
438	(== 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
439	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
440	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>
441	function.	514	function or method.
442		515
443	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
444	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
445	enabled by this setting.	518	enabled by this setting.
446		519
…		…
488		561
489	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>
490	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
491	objects make excellent targets to serialise Perl objects into, especially	564	objects make excellent targets to serialise Perl objects into, especially
492	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
493	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
494	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
495	like a serialised Perl hash.	568	like a serialised Perl hash.
496		569
497	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
498	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
…		…
522		595
523	{ __widget__ => $self->{id} }	596	{ __widget__ => $self->{id} }
524	}	597	}
525		598
526	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
527		602
528	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
529	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
530	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
531	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
…		…
549	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
550	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
551		626
552	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
553		628
		629	=item $max_depth = $json->get_max_depth
		630
554	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
555	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
556	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
557	stop and croak at that point.	634	point.
558		635
559	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
560	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<[>
561	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
562	given character in a string.	639	given character in a string.
563		640
564	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
565	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
566		643
567	The argument to C<max_depth> will be rounded up to the next highest power
568	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
569	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.
570		650
571	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.
572		652
573	=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
574		656
575	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
576	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>
577	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
578	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
579	effect on C<encode> (yet).	661	effect on C<encode> (yet).
580		662
581	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
582	power of two (so may be more than requested). If no argument is given, the	664	C<0> is specified).
583	limit check will be deactivated (same as when C<0> is specified).
584		665
585	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.
586		667
587	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
588		669
…		…
617	=> ([], 3)	698	=> ([], 3)
618		699
619	=back	700	=back
620		701
621		702
		703	=head1 INCREMENTAL PARSING
		704
		705	In some cases, there is the need for incremental parsing of JSON
		706	texts. While this module always has to keep both JSON text and resulting
		707	Perl data structure in memory at one time, it does allow you to parse a
		708	JSON stream incrementally. It does so by accumulating text until it has
		709	a full JSON object, which it then can decode. This process is similar to
		710	using C<decode_prefix> to see if a full JSON object is available, but
		711	is much more efficient (and can be implemented with a minimum of method
		712	calls).
		713
		714	JSON::XS will only attempt to parse the JSON text once it is sure it
		715	has enough text to get a decisive result, using a very simple but
		716	truly incremental parser. This means that it sometimes won't stop as
		717	early as the full parser, for example, it doesn't detect parenthese
		718	mismatches. The only thing it guarantees is that it starts decoding as
		719	soon as a syntactically valid JSON text has been seen. This means you need
		720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		721	parsing in the presence if syntax errors.
		722
		723	The following methods implement this incremental parser.
		724
		725	=over 4
		726
		727	=item [void, scalar or list context] = $json->incr_parse ([$string])
		728
		729	This is the central parsing function. It can both append new text and
		730	extract objects from the stream accumulated so far (both of these
		731	functions are optional).
		732
		733	If C<$string> is given, then this string is appended to the already
		734	existing JSON fragment stored in the C<$json> object.
		735
		736	After that, if the function is called in void context, it will simply
		737	return without doing anything further. This can be used to add more text
		738	in as many chunks as you want.
		739
		740	If the method is called in scalar context, then it will try to extract
		741	exactly I<one> JSON object. If that is successful, it will return this
		742	object, otherwise it will return C<undef>. If there is a parse error,
		743	this method will croak just as C<decode> would do (one can then use
		744	C<incr_skip> to skip the errornous part). This is the most common way of
		745	using the method.
		746
		747	And finally, in list context, it will try to extract as many objects
		748	from the stream as it can find and return them, or the empty list
		749	otherwise. For this to work, there must be no separators between the JSON
		750	objects or arrays, instead they must be concatenated back-to-back. If
		751	an error occurs, an exception will be raised as in the scalar context
		752	case. Note that in this case, any previously-parsed JSON texts will be
		753	lost.
		754
		755	=item $lvalue_string = $json->incr_text
		756
		757	This method returns the currently stored JSON fragment as an lvalue, that
		758	is, you can manipulate it. This I<only> works when a preceding call to
		759	C<incr_parse> in I<scalar context> successfully returned an object. Under
		760	all other circumstances you must not call this function (I mean it.
		761	although in simple tests it might actually work, it I<will> fail under
		762	real world conditions). As a special exception, you can also call this
		763	method before having parsed anything.
		764
		765	This function is useful in two cases: a) finding the trailing text after a
		766	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		767	(such as commas).
		768
		769	=item $json->incr_skip
		770
		771	This will reset the state of the incremental parser and will remove
		772	the parsed text from the input buffer so far. This is useful after
		773	C<incr_parse> died, in which case the input buffer and incremental parser
		774	state is left unchanged, to skip the text parsed so far and to reset the
		775	parse state.
		776
		777	The difference to C<incr_reset> is that only text until the parse error
		778	occured is removed.
		779
		780	=item $json->incr_reset
		781
		782	This completely resets the incremental parser, that is, after this call,
		783	it will be as if the parser had never parsed anything.
		784
		785	This is useful if you want to repeatedly parse JSON objects and want to
		786	ignore any trailing data, which means you have to reset the parser after
		787	each successful decode.
		788
		789	=back
		790
		791	=head2 LIMITATIONS
		792
		793	All options that affect decoding are supported, except
		794	C<allow_nonref>. The reason for this is that it cannot be made to
		795	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		796	them back to back and still decode them perfectly. This does not hold true
		797	for JSON numbers, however.
		798
		799	For example, is the string C<1> a single JSON number, or is it simply the
		800	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		801	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		802	takes the conservative route and disallows this case.
		803
		804	=head2 EXAMPLES
		805
		806	Some examples will make all this clearer. First, a simple example that
		807	works similarly to C<decode_prefix>: We want to decode the JSON object at
		808	the start of a string and identify the portion after the JSON object:
		809
		810	my $text = "[1,2,3] hello";
		811
		812	my $json = new JSON::XS;
		813
		814	my $obj = $json->incr_parse ($text)
		815	or die "expected JSON object or array at beginning of string";
		816
		817	my $tail = $json->incr_text;
		818	# $tail now contains " hello"
		819
		820	Easy, isn't it?
		821
		822	Now for a more complicated example: Imagine a hypothetical protocol where
		823	you read some requests from a TCP stream, and each request is a JSON
		824	array, without any separation between them (in fact, it is often useful to
		825	use newlines as "separators", as these get interpreted as whitespace at
		826	the start of the JSON text, which makes it possible to test said protocol
		827	with C<telnet>...).
		828
		829	Here is how you'd do it (it is trivial to write this in an event-based
		830	manner):
		831
		832	my $json = new JSON::XS;
		833
		834	# read some data from the socket
		835	while (sysread $socket, my $buf, 4096) {
		836
		837	# split and decode as many requests as possible
		838	for my $request ($json->incr_parse ($buf)) {
		839	# act on the $request
		840	}
		841	}
		842
		843	Another complicated example: Assume you have a string with JSON objects
		844	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		845	[3]>). To parse them, we have to skip the commas between the JSON texts,
		846	and here is where the lvalue-ness of C<incr_text> comes in useful:
		847
		848	my $text = "[1],[2], [3]";
		849	my $json = new JSON::XS;
		850
		851	# void context, so no parsing done
		852	$json->incr_parse ($text);
		853
		854	# now extract as many objects as possible. note the
		855	# use of scalar context so incr_text can be called.
		856	while (my $obj = $json->incr_parse) {
		857	# do something with $obj
		858
		859	# now skip the optional comma
		860	$json->incr_text =~ s/^ \s* , //x;
		861	}
		862
		863	Now lets go for a very complex example: Assume that you have a gigantic
		864	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		865	but you cannot load it into memory fully (this has actually happened in
		866	the real world :).
		867
		868	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		869	can still help you: You implement a (very simple) array parser and let
		870	JSON decode the array elements, which are all full JSON objects on their
		871	own (this wouldn't work if the array elements could be JSON numbers, for
		872	example):
		873
		874	my $json = new JSON::XS;
		875
		876	# open the monster
		877	open my $fh, "<bigfile.json"
		878	or die "bigfile: $!";
		879
		880	# first parse the initial "["
		881	for (;;) {
		882	sysread $fh, my $buf, 65536
		883	or die "read error: $!";
		884	$json->incr_parse ($buf); # void context, so no parsing
		885
		886	# Exit the loop once we found and removed(!) the initial "[".
		887	# In essence, we are (ab-)using the $json object as a simple scalar
		888	# we append data to.
		889	last if $json->incr_text =~ s/^ \s* \[ //x;
		890	}
		891
		892	# now we have the skipped the initial "[", so continue
		893	# parsing all the elements.
		894	for (;;) {
		895	# in this loop we read data until we got a single JSON object
		896	for (;;) {
		897	if (my $obj = $json->incr_parse) {
		898	# do something with $obj
		899	last;
		900	}
		901
		902	# add more data
		903	sysread $fh, my $buf, 65536
		904	or die "read error: $!";
		905	$json->incr_parse ($buf); # void context, so no parsing
		906	}
		907
		908	# in this loop we read data until we either found and parsed the
		909	# separating "," between elements, or the final "]"
		910	for (;;) {
		911	# first skip whitespace
		912	$json->incr_text =~ s/^\s*//;
		913
		914	# if we find "]", we are done
		915	if ($json->incr_text =~ s/^\]//) {
		916	print "finished.\n";
		917	exit;
		918	}
		919
		920	# if we find ",", we can continue with the next element
		921	if ($json->incr_text =~ s/^,//) {
		922	last;
		923	}
		924
		925	# if we find anything else, we have a parse error!
		926	if (length $json->incr_text) {
		927	die "parse error near ", $json->incr_text;
		928	}
		929
		930	# else add more data
		931	sysread $fh, my $buf, 65536
		932	or die "read error: $!";
		933	$json->incr_parse ($buf); # void context, so no parsing
		934	}
		935
		936	This is a complex example, but most of the complexity comes from the fact
		937	that we are trying to be correct (bear with me if I am wrong, I never ran
		938	the above example :).
		939
		940
		941
622	=head1 MAPPING	942	=head1 MAPPING
623		943
624	This section describes how JSON::XS maps Perl values to JSON values and	944	This section describes how JSON::XS maps Perl values to JSON values and
625	vice versa. These mappings are designed to "do the right thing" in most	945	vice versa. These mappings are designed to "do the right thing" in most
626	circumstances automatically, preserving round-tripping characteristics	946	circumstances automatically, preserving round-tripping characteristics
627	(what you put in comes out as something equivalent).	947	(what you put in comes out as something equivalent).
628		948
629	For the more enlightened: note that in the following descriptions,	949	For the more enlightened: note that in the following descriptions,
630	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	950	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
631	refers to the abstract Perl language itself.	951	refers to the abstract Perl language itself.
632		952
633		953
634	=head2 JSON -> PERL	954	=head2 JSON -> PERL
635		955
636	=over 4	956	=over 4
637		957
638	=item object	958	=item object
639		959
640	A JSON object becomes a reference to a hash in Perl. No ordering of object	960	A JSON object becomes a reference to a hash in Perl. No ordering of object
641	keys is preserved (JSON does not preserver object key ordering itself).	961	keys is preserved (JSON does not preserve object key ordering itself).
642		962
643	=item array	963	=item array
644		964
645	A JSON array becomes a reference to an array in Perl.	965	A JSON array becomes a reference to an array in Perl.
646		966
…		…
654		974
655	A JSON number becomes either an integer, numeric (floating point) or	975	A JSON number becomes either an integer, numeric (floating point) or
656	string scalar in perl, depending on its range and any fractional parts. On	976	string scalar in perl, depending on its range and any fractional parts. On
657	the Perl level, there is no difference between those as Perl handles all	977	the Perl level, there is no difference between those as Perl handles all
658	the conversion details, but an integer may take slightly less memory and	978	the conversion details, but an integer may take slightly less memory and
659	might represent more values exactly than (floating point) numbers.	979	might represent more values exactly than floating point numbers.
660		980
661	If the number consists of digits only, JSON::XS will try to represent	981	If the number consists of digits only, JSON::XS will try to represent
662	it as an integer value. If that fails, it will try to represent it as	982	it as an integer value. If that fails, it will try to represent it as
663	a numeric (floating point) value if that is possible without loss of	983	a numeric (floating point) value if that is possible without loss of
664	precision. Otherwise it will preserve the number as a string value.	984	precision. Otherwise it will preserve the number as a string value (in
		985	which case you lose roundtripping ability, as the JSON number will be
		986	re-encoded toa JSON string).
665		987
666	Numbers containing a fractional or exponential part will always be	988	Numbers containing a fractional or exponential part will always be
667	represented as numeric (floating point) values, possibly at a loss of	989	represented as numeric (floating point) values, possibly at a loss of
668	precision.	990	precision (in which case you might lose perfect roundtripping ability, but
669		991	the JSON number will still be re-encoded as a JSON number).
670	This might create round-tripping problems as numbers might become strings,
671	but as Perl is typeless there is no other way to do it.
672		992
673	=item true, false	993	=item true, false
674		994
675	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	995	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
676	respectively. They are overloaded to act almost exactly like the numbers	996	respectively. They are overloaded to act almost exactly like the numbers
677	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	997	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
678	the C<JSON::XS::is_bool> function.	998	the C<JSON::XS::is_bool> function.
679		999
680	=item null	1000	=item null
681		1001
682	A JSON null atom becomes C<undef> in Perl.	1002	A JSON null atom becomes C<undef> in Perl.
…		…
713	Other unblessed references are generally not allowed and will cause an	1033	Other unblessed references are generally not allowed and will cause an
714	exception to be thrown, except for references to the integers C<0> and	1034	exception to be thrown, except for references to the integers C<0> and
715	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1035	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
716	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1036	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
717		1037
718	to_json [\0,JSON::XS::true] # yields [false,true]	1038	encode_json [\0, JSON::XS::true] # yields [false,true]
719		1039
720	=item JSON::XS::true, JSON::XS::false	1040	=item JSON::XS::true, JSON::XS::false
721		1041
722	These special values become JSON true and JSON false values,	1042	These special values become JSON true and JSON false values,
723	respectively. You can also use C<\1> and C<\0> directly if you want.	1043	respectively. You can also use C<\1> and C<\0> directly if you want.
724		1044
725	=item blessed objects	1045	=item blessed objects
726		1046
727	Blessed objects are not allowed. JSON::XS currently tries to encode their	1047	Blessed objects are not directly representable in JSON. See the
728	underlying representation (hash- or arrayref), but this behaviour might	1048	C<allow_blessed> and C<convert_blessed> methods on various options on
729	change in future versions.	1049	how to deal with this: basically, you can choose between throwing an
		1050	exception, encoding the reference as if it weren't blessed, or provide
		1051	your own serialiser method.
730		1052
731	=item simple scalars	1053	=item simple scalars
732		1054
733	Simple Perl scalars (any scalar that is not a reference) are the most	1055	Simple Perl scalars (any scalar that is not a reference) are the most
734	difficult objects to encode: JSON::XS will encode undefined scalars as	1056	difficult objects to encode: JSON::XS will encode undefined scalars as
735	JSON null value, scalars that have last been used in a string context	1057	JSON C<null> values, scalars that have last been used in a string context
736	before encoding as JSON strings and anything else as number value:	1058	before encoding as JSON strings, and anything else as number value:
737		1059
738	# dump as number	1060	# dump as number
739	to_json [2] # yields [2]	1061	encode_json [2] # yields [2]
740	to_json [-3.0e17] # yields [-3e+17]	1062	encode_json [-3.0e17] # yields [-3e+17]
741	my $value = 5; to_json [$value] # yields [5]	1063	my $value = 5; encode_json [$value] # yields [5]
742		1064
743	# used as string, so dump as string	1065	# used as string, so dump as string
744	print $value;	1066	print $value;
745	to_json [$value] # yields ["5"]	1067	encode_json [$value] # yields ["5"]
746		1068
747	# undef becomes null	1069	# undef becomes null
748	to_json [undef] # yields [null]	1070	encode_json [undef] # yields [null]
749		1071
750	You can force the type to be a string by stringifying it:	1072	You can force the type to be a JSON string by stringifying it:
751		1073
752	my $x = 3.1; # some variable containing a number	1074	my $x = 3.1; # some variable containing a number
753	"$x"; # stringified	1075	"$x"; # stringified
754	$x .= ""; # another, more awkward way to stringify	1076	$x .= ""; # another, more awkward way to stringify
755	print $x; # perl does it for you, too, quite often	1077	print $x; # perl does it for you, too, quite often
756		1078
757	You can force the type to be a number by numifying it:	1079	You can force the type to be a JSON number by numifying it:
758		1080
759	my $x = "3"; # some variable containing a string	1081	my $x = "3"; # some variable containing a string
760	$x += 0; # numify it, ensuring it will be dumped as a number	1082	$x += 0; # numify it, ensuring it will be dumped as a number
761	$x *= 1; # same thing, the choise is yours.	1083	$x *= 1; # same thing, the choice is yours.
762		1084
763	You can not currently output JSON booleans or force the type in other,	1085	You can not currently force the type in other, less obscure, ways. Tell me
764	less obscure, ways. Tell me if you need this capability.	1086	if you need this capability (but don't forget to explain why it's needed
		1087	:).
765		1088
766	=back	1089	=back
767		1090
768		1091
769	=head1 COMPARISON	1092	=head1 ENCODING/CODESET FLAG NOTES
770		1093
771	As already mentioned, this module was created because none of the existing	1094	The interested reader might have seen a number of flags that signify
772	JSON modules could be made to work correctly. First I will describe the	1095	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
773	problems (or pleasures) I encountered with various existing JSON modules,	1096	some confusion on what these do, so here is a short comparison:
774	followed by some benchmark values. JSON::XS was designed not to suffer	1097
775	from any of these problems or limitations.	1098	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1099	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1100	control whether C<encode> escapes character values outside their respective
		1101	codeset range. Neither of these flags conflict with each other, although
		1102	some combinations make less sense than others.
		1103
		1104	Care has been taken to make all flags symmetrical with respect to
		1105	C<encode> and C<decode>, that is, texts encoded with any combination of
		1106	these flag values will be correctly decoded when the same flags are used
		1107	- in general, if you use different flag settings while encoding vs. when
		1108	decoding you likely have a bug somewhere.
		1109
		1110	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1111	simply an abstract set of character-codepoint pairs, while an encoding
		1112	takes those codepoint numbers and I<encodes> them, in our case into
		1113	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1114	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1115	the same time, which can be confusing.
776		1116
777	=over 4	1117	=over 4
778		1118
779	=item JSON 1.07	1119	=item C<utf8> flag disabled
780		1120
781	Slow (but very portable, as it is written in pure Perl).	1121	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1122	and expect Unicode strings, that is, characters with high ordinal Unicode
		1123	values (> 255) will be encoded as such characters, and likewise such
		1124	characters are decoded as-is, no canges to them will be done, except
		1125	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1126	respectively (to Perl, these are the same thing in strings unless you do
		1127	funny/weird/dumb stuff).
782		1128
783	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1129	This is useful when you want to do the encoding yourself (e.g. when you
784	undocumented. One can get far by feeding it unicode strings and doing	1130	want to have UTF-16 encoded JSON texts) or when some other layer does
785	en-/decoding oneself, but unicode escapes are not working properly).	1131	the encoding for you (for example, when printing to a terminal using a
		1132	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1133	to UTF-8 encode your data first and have Perl encode it another time).
786		1134
787	No roundtripping (strings get clobbered if they look like numbers, e.g.	1135	=item C<utf8> flag enabled
788	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
789	decode into the number 2.
790		1136
791	=item JSON::PC 0.01	1137	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1138	characters using the corresponding UTF-8 multi-byte sequence, and will
		1139	expect your input strings to be encoded as UTF-8, that is, no "character"
		1140	of the input string must have any value > 255, as UTF-8 does not allow
		1141	that.
792		1142
793	Very fast.	1143	The C<utf8> flag therefore switches between two modes: disabled means you
		1144	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1145	octet/binary string in Perl.
794		1146
795	Undocumented/buggy Unicode handling.	1147	=item C<latin1> or C<ascii> flags enabled
796		1148
797	No roundtripping.	1149	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1150	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1151	characters as specified by the C<utf8> flag.
798		1152
799	Has problems handling many Perl values (e.g. regex results and other magic	1153	If C<utf8> is disabled, then the result is also correctly encoded in those
800	values will make it croak).	1154	character sets (as both are proper subsets of Unicode, meaning that a
		1155	Unicode string with all character values < 256 is the same thing as a
		1156	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1157	the same thing as an ASCII string in Perl).
801		1158
802	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1159	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
803	which is not a valid JSON text.	1160	regardless of these flags, just some more characters will be escaped using
		1161	C<\uXXXX> then before.
804		1162
805	Unmaintained (maintainer unresponsive for many months, bugs are not	1163	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
806	getting fixed).	1164	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1165	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1166	a subset of Unicode), while ASCII is.
807		1167
808	=item JSON::Syck 0.21	1168	Surprisingly, C<decode> will ignore these flags and so treat all input
		1169	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1170	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1171	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
809		1172
810	Very buggy (often crashes).	1173	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1174	they only govern when the JSON output engine escapes a character or not.
811		1175
812	Very inflexible (no human-readable format supported, format pretty much	1176	The main use for C<latin1> is to relatively efficiently store binary data
813	undocumented. I need at least a format for easy reading by humans and a	1177	as JSON, at the expense of breaking compatibility with most JSON decoders.
814	single-line compact format for use in a protocol, and preferably a way to
815	generate ASCII-only JSON texts).
816		1178
817	Completely broken (and confusingly documented) Unicode handling (unicode	1179	The main use for C<ascii> is to force the output to not contain characters
818	escapes are not working properly, you need to set ImplicitUnicode to	1180	with values > 127, which means you can interpret the resulting string
819	I<different> values on en- and decoding to get symmetric behaviour).	1181	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
820		1182	8-bit-encoding, and still get the same data structure back. This is useful
821	No roundtripping (simple cases work, but this depends on wether the scalar	1183	when your channel for JSON transfer is not 8-bit clean or the encoding
822	value was used in a numeric context or not).	1184	might be mangled in between (e.g. in mail), and works because ASCII is a
823		1185	proper subset of most 8-bit and multibyte encodings in use in the world.
824	Dumping hashes may skip hash values depending on iterator state.
825
826	Unmaintained (maintainer unresponsive for many months, bugs are not
827	getting fixed).
828
829	Does not check input for validity (i.e. will accept non-JSON input and
830	return "something" instead of raising an exception. This is a security
831	issue: imagine two banks transfering money between each other using
832	JSON. One bank might parse a given non-JSON request and deduct money,
833	while the other might reject the transaction with a syntax error. While a
834	good protocol will at least recover, that is extra unnecessary work and
835	the transaction will still not succeed).
836
837	=item JSON::DWIW 0.04
838
839	Very fast. Very natural. Very nice.
840
841	Undocumented unicode handling (but the best of the pack. Unicode escapes
842	still don't get parsed properly).
843
844	Very inflexible.
845
846	No roundtripping.
847
848	Does not generate valid JSON texts (key strings are often unquoted, empty keys
849	result in nothing being output)
850
851	Does not check input for validity.
852		1186
853	=back	1187	=back
854		1188
855		1189
856	=head2 JSON and YAML	1190	=head2 JSON and YAML
857		1191
858	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1192	You often hear that JSON is a subset of YAML. This is, however, a mass
859	however, a mass hysteria and very far from the truth. In general, there is	1193	hysteria(*) and very far from the truth (as of the time of this writing),
860	no way to configure JSON::XS to output a data structure as valid YAML.	1194	so let me state it clearly: I<in general, there is no way to configure
		1195	JSON::XS to output a data structure as valid YAML> that works in all
		1196	cases.
861		1197
862	If you really must use JSON::XS to generate YAML, you should use this	1198	If you really must use JSON::XS to generate YAML, you should use this
863	algorithm (subject to change in future versions):	1199	algorithm (subject to change in future versions):
864		1200
865	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1201	my $to_yaml = JSON::XS->new->utf8->space_after (1);
866	my $yaml = $to_yaml->encode ($ref) . "\n";	1202	my $yaml = $to_yaml->encode ($ref) . "\n";
867		1203
868	This will usually generate JSON texts that also parse as valid	1204	This will I<usually> generate JSON texts that also parse as valid
869	YAML. Please note that YAML has hardcoded limits on (simple) object key	1205	YAML. Please note that YAML has hardcoded limits on (simple) object key
870	lengths that JSON doesn't have, so you should make sure that your hash	1206	lengths that JSON doesn't have and also has different and incompatible
		1207	unicode handling, so you should make sure that your hash keys are
871	keys are noticably shorter than the 1024 characters YAML allows.	1208	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1209	you do not have characters with codepoint values outside the Unicode BMP
		1210	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1211	strings (which JSON::XS does not I<currently> generate, but other JSON
		1212	generators might).
872		1213
873	There might be other incompatibilities that I am not aware of. In general	1214	There might be other incompatibilities that I am not aware of (or the YAML
		1215	specification has been changed yet again - it does so quite often). In
874	you should not try to generate YAML with a JSON generator or vice versa,	1216	general you should not try to generate YAML with a JSON generator or vice
875	or try to parse JSON with a YAML parser or vice versa: chances are high	1217	versa, or try to parse JSON with a YAML parser or vice versa: chances are
876	that you will run into severe interoperability problems.	1218	high that you will run into severe interoperability problems when you
		1219	least expect it.
		1220
		1221	=over 4
		1222
		1223	=item (*)
		1224
		1225	I have been pressured multiple times by Brian Ingerson (one of the
		1226	authors of the YAML specification) to remove this paragraph, despite him
		1227	acknowledging that the actual incompatibilities exist. As I was personally
		1228	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1229	educate people about these issues, so others do not run into the same
		1230	problem again and again. After this, Brian called me a (quote)I<complete
		1231	and worthless idiot>(unquote).
		1232
		1233	In my opinion, instead of pressuring and insulting people who actually
		1234	clarify issues with YAML and the wrong statements of some of its
		1235	proponents, I would kindly suggest reading the JSON spec (which is not
		1236	that difficult or long) and finally make YAML compatible to it, and
		1237	educating users about the changes, instead of spreading lies about the
		1238	real compatibility for many I<years> and trying to silence people who
		1239	point out that it isn't true.
		1240
		1241	=back
877		1242
878		1243
879	=head2 SPEED	1244	=head2 SPEED
880		1245
881	It seems that JSON::XS is surprisingly fast, as shown in the following	1246	It seems that JSON::XS is surprisingly fast, as shown in the following
882	tables. They have been generated with the help of the C<eg/bench> program	1247	tables. They have been generated with the help of the C<eg/bench> program
883	in the JSON::XS distribution, to make it easy to compare on your own	1248	in the JSON::XS distribution, to make it easy to compare on your own
884	system.	1249	system.
885		1250
886	First comes a comparison between various modules using a very short	1251	First comes a comparison between various modules using
887	single-line JSON string:	1252	a very short single-line JSON string (also available at
		1253	L<http://dist.schmorp.de/misc/json/short.json>).
888		1254
889	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1255	{"method": "handleMessage", "params": ["user1",
890	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1256	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1257	true, false]}
891		1258
892	It shows the number of encodes/decodes per second (JSON::XS uses	1259	It shows the number of encodes/decodes per second (JSON::XS uses
893	the functional interface, while JSON::XS/2 uses the OO interface	1260	the functional interface, while JSON::XS/2 uses the OO interface
894	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1261	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
895	shrink). Higher is better:	1262	shrink). Higher is better:
896		1263
897	Storable \| 15779.925 \| 14169.946 \|
898	-----------+------------+------------+
899	module \| encode \| decode \|	1264	module \| encode \| decode \|
900	-----------\|------------\|------------\|	1265	-----------\|------------\|------------\|
901	JSON \| 4990.842 \| 4088.813 \|	1266	JSON 1.x \| 4990.842 \| 4088.813 \|
902	JSON::DWIW \| 51653.990 \| 71575.154 \|	1267	JSON::DWIW \| 51653.990 \| 71575.154 \|
903	JSON::PC \| 65948.176 \| 74631.744 \|	1268	JSON::PC \| 65948.176 \| 74631.744 \|
904	JSON::PP \| 8931.652 \| 3817.168 \|	1269	JSON::PP \| 8931.652 \| 3817.168 \|
905	JSON::Syck \| 24877.248 \| 27776.848 \|	1270	JSON::Syck \| 24877.248 \| 27776.848 \|
906	JSON::XS \| 388361.481 \| 227951.304 \|	1271	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
908	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1273	JSON::XS/3 \| 338250.323 \| 218453.333 \|
909	Storable \| 16500.016 \| 135300.129 \|	1274	Storable \| 16500.016 \| 135300.129 \|
910	-----------+------------+------------+	1275	-----------+------------+------------+
911		1276
912	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1277	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
913	about three times faster on decoding, and over fourty times faster	1278	about three times faster on decoding, and over forty times faster
914	than JSON, even with pretty-printing and key sorting. It also compares	1279	than JSON, even with pretty-printing and key sorting. It also compares
915	favourably to Storable for small amounts of data.	1280	favourably to Storable for small amounts of data.
916		1281
917	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1282	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
918	search API (http://nanoref.com/yahooapis/mgPdGg):	1283	search API (L<http://dist.schmorp.de/misc/json/long.json>).
919		1284
920	module \| encode \| decode \|	1285	module \| encode \| decode \|
921	-----------\|------------\|------------\|	1286	-----------\|------------\|------------\|
922	JSON \| 55.260 \| 34.971 \|	1287	JSON 1.x \| 55.260 \| 34.971 \|
923	JSON::DWIW \| 825.228 \| 1082.513 \|	1288	JSON::DWIW \| 825.228 \| 1082.513 \|
924	JSON::PC \| 3571.444 \| 2394.829 \|	1289	JSON::PC \| 3571.444 \| 2394.829 \|
925	JSON::PP \| 210.987 \| 32.574 \|	1290	JSON::PP \| 210.987 \| 32.574 \|
926	JSON::Syck \| 552.551 \| 787.544 \|	1291	JSON::Syck \| 552.551 \| 787.544 \|
927	JSON::XS \| 5780.463 \| 4854.519 \|	1292	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
931	-----------+------------+------------+	1296	-----------+------------+------------+
932		1297
933	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1298	Again, JSON::XS leads by far (except for Storable which non-surprisingly
934	decodes faster).	1299	decodes faster).
935		1300
936	On large strings containing lots of high unicode characters, some modules	1301	On large strings containing lots of high Unicode characters, some modules
937	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1302	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
938	will be broken due to missing (or wrong) unicode handling. Others refuse	1303	will be broken due to missing (or wrong) Unicode handling. Others refuse
939	to decode or encode properly, so it was impossible to prepare a fair	1304	to decode or encode properly, so it was impossible to prepare a fair
940	comparison table for that case.	1305	comparison table for that case.
941		1306
942		1307
943	=head1 SECURITY CONSIDERATIONS	1308	=head1 SECURITY CONSIDERATIONS
…		…
949	any buffer overflows. Obviously, this module should ensure that and I am	1314	any buffer overflows. Obviously, this module should ensure that and I am
950	trying hard on making that true, but you never know.	1315	trying hard on making that true, but you never know.
951		1316
952	Second, you need to avoid resource-starving attacks. That means you should	1317	Second, you need to avoid resource-starving attacks. That means you should
953	limit the size of JSON texts you accept, or make sure then when your	1318	limit the size of JSON texts you accept, or make sure then when your
954	resources run out, thats just fine (e.g. by using a separate process that	1319	resources run out, that's just fine (e.g. by using a separate process that
955	can crash safely). The size of a JSON text in octets or characters is	1320	can crash safely). The size of a JSON text in octets or characters is
956	usually a good indication of the size of the resources required to decode	1321	usually a good indication of the size of the resources required to decode
957	it into a Perl structure. While JSON::XS can check the size of the JSON	1322	it into a Perl structure. While JSON::XS can check the size of the JSON
958	text, it might be too late when you already have it in memory, so you	1323	text, it might be too late when you already have it in memory, so you
959	might want to check the size before you accept the string.	1324	might want to check the size before you accept the string.
960		1325
961	Third, JSON::XS recurses using the C stack when decoding objects and	1326	Third, JSON::XS recurses using the C stack when decoding objects and
962	arrays. The C stack is a limited resource: for instance, on my amd64	1327	arrays. The C stack is a limited resource: for instance, on my amd64
963	machine with 8MB of stack size I can decode around 180k nested arrays but	1328	machine with 8MB of stack size I can decode around 180k nested arrays but
964	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1329	only 14k nested JSON objects (due to perl itself recursing deeply on croak
965	to free the temporary). If that is exceeded, the program crashes. to be	1330	to free the temporary). If that is exceeded, the program crashes. To be
966	conservative, the default nesting limit is set to 512. If your process	1331	conservative, the default nesting limit is set to 512. If your process
967	has a smaller stack, you should adjust this setting accordingly with the	1332	has a smaller stack, you should adjust this setting accordingly with the
968	C<max_depth> method.	1333	C<max_depth> method.
969		1334
970	And last but least, something else could bomb you that I forgot to think	1335	Something else could bomb you, too, that I forgot to think of. In that
971	of. In that case, you get to keep the pieces. I am always open for hints,	1336	case, you get to keep the pieces. I am always open for hints, though...
972	though...	1337
		1338	Also keep in mind that JSON::XS might leak contents of your Perl data
		1339	structures in its error messages, so when you serialise sensitive
		1340	information you might want to make sure that exceptions thrown by JSON::XS
		1341	will not end up in front of untrusted eyes.
973		1342
974	If you are using JSON::XS to return packets to consumption	1343	If you are using JSON::XS to return packets to consumption
975	by javascript scripts in a browser you should have a look at	1344	by JavaScript scripts in a browser you should have a look at
976	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1345	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
977	you are vulnerable to some common attack vectors (which really are browser	1346	you are vulnerable to some common attack vectors (which really are browser
978	design bugs, but it is still you who will have to deal with it, as major	1347	design bugs, but it is still you who will have to deal with it, as major
979	browser developers care only for features, not about doing security	1348	browser developers care only for features, not about getting security
980	right).	1349	right).
981		1350
982		1351
983	=head1 THREADS	1352	=head1 THREADS
984		1353
985	This module is I<not> guarenteed to be thread safe and there are no	1354	This module is I<not> guaranteed to be thread safe and there are no
986	plans to change this until Perl gets thread support (as opposed to the	1355	plans to change this until Perl gets thread support (as opposed to the
987	horribly slow so-called "threads" which are simply slow and bloated	1356	horribly slow so-called "threads" which are simply slow and bloated
988	process simulations - use fork, its I<much> faster, cheaper, better).	1357	process simulations - use fork, it's I<much> faster, cheaper, better).
989		1358
990	(It might actually work, but you ahve ben warned).	1359	(It might actually work, but you have been warned).
991		1360
992		1361
993	=head1 BUGS	1362	=head1 BUGS
994		1363
995	While the goal of this module is to be correct, that unfortunately does	1364	While the goal of this module is to be correct, that unfortunately does
996	not mean its bug-free, only that I think its design is bug-free. It is	1365	not mean it's bug-free, only that I think its design is bug-free. If you
997	still relatively early in its development. If you keep reporting bugs they	1366	keep reporting bugs they will be fixed swiftly, though.
998	will be fixed swiftly, though.
999		1367
1000	Please refrain from using rt.cpan.org or any other bug reporting	1368	Please refrain from using rt.cpan.org or any other bug reporting
1001	service. I put the contact address into my modules for a reason.	1369	service. I put the contact address into my modules for a reason.
1002		1370
1003	=cut	1371	=cut
…		…
1023	"--" => sub { $_[0] = ${$_[0]} - 1 },	1391	"--" => sub { $_[0] = ${$_[0]} - 1 },
1024	fallback => 1;	1392	fallback => 1;
1025		1393
1026	1;	1394	1;
1027		1395
		1396	=head1 SEE ALSO
		1397
		1398	The F<json_xs> command line utility for quick experiments.
		1399
1028	=head1 AUTHOR	1400	=head1 AUTHOR
1029		1401
1030	Marc Lehmann <schmorp@schmorp.de>	1402	Marc Lehmann <schmorp@schmorp.de>
1031	http://home.schmorp.de/	1403	http://home.schmorp.de/
1032		1404

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Comparing JSON-XS/XS.pm (file contents): Revision 1.65 by root, Sat Oct 13 01:55:31 2007 UTC vs. Revision 1.114 by root, Wed Jan 21 05:34:08 2009 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.65 by root, Sat Oct 13 01:55:31 2007 UTC vs.
Revision 1.114 by root, Wed Jan 21 05:34:08 2009 UTC