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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
4		6
5	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
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
10	use JSON::XS;	12	use JSON::XS;
11		13
12	# exported functions, they croak on error	14	# exported functions, they croak on error
13	# and expect/generate UTF-8	15	# and expect/generate UTF-8
14		16
15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17		19
18	# OO-interface	20	# OO-interface
19		21
20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
22	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
23		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
24	=head1 DESCRIPTION	34	=head1 DESCRIPTION
25		35
26	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
27	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
28	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.
29		47
30	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
31	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
32	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
33	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
34	reports for other reasons.	52	reports for other reasons.
35		53
36	See COMPARISON, below, for a comparison to some other JSON modules.
37
38	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
39	vice versa.	55	vice versa.
40		56
41	=head2 FEATURES	57	=head2 FEATURES
42		58
43	=over 4	59	=over 4
44		60
45	=item * correct unicode handling	61	=item * correct Unicode handling
46		62
47	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
48	it does so.	64	so, and even documents what "correct" means.
49		65
50	=item * round-trip integrity	66	=item * round-trip integrity
51		67
52	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
53	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.
54	(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
55	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
56		73
57	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
58		75
59	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,
60	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
61	feature).	78	feature).
62		79
63	=item * fast	80	=item * fast
64		81
65	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
66	of speed, too.	83	this module usually compares favourably in terms of speed, too.
67		84
68	=item * simple to use	85	=item * simple to use
69		86
70	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
71	interface.	88	oriented interface interface.
72		89
73	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
74		91
75	You can choose between the most compact guarenteed single-line format	92	You can choose between the most compact guaranteed-single-line format
76	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
77	(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
78	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
79	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.
80		97
81	=back	98	=back
82		99
83	=cut	100	=cut
84		101
85	package JSON::XS;	102	package JSON::XS;
86		103
		104	no warnings;
87	use strict;	105	use strict;
88		106
89	our $VERSION = '1.52';	107	our $VERSION = '2.2222';
90	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
91		109
92	our @EXPORT = qw(to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
		111
		112	sub to_json($) {
		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	}
93		121
94	use Exporter;	122	use Exporter;
95	use XSLoader;	123	use XSLoader;
96		124
97	=head1 FUNCTIONAL INTERFACE	125	=head1 FUNCTIONAL INTERFACE
98		126
99	The following convinience methods are provided by this module. They are	127	The following convenience methods are provided by this module. They are
100	exported by default:	128	exported by default:
101		129
102	=over 4	130	=over 4
103		131
104	=item $json_text = to_json $perl_scalar	132	=item $json_text = encode_json $perl_scalar
105		133
106	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
107	(that is, the string contains octets only). Croaks on error.	135	(that is, the string contains octets only). Croaks on error.
108		136
109	This function call is functionally identical to:	137	This function call is functionally identical to:
110		138
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		140
113	except being faster.	141	Except being faster.
114		142
115	=item $perl_scalar = from_json $json_text	143	=item $perl_scalar = decode_json $json_text
116		144
117	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
118	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
119	reference. Croaks on error.	147	reference. Croaks on error.
120		148
121	This function call is functionally identical to:	149	This function call is functionally identical to:
122		150
123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
124		152
125	except being faster.	153	Except being faster.
126		154
127	=item $is_boolean = JSON::XS::is_bool $scalar	155	=item $is_boolean = JSON::XS::is_bool $scalar
128		156
129	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
130	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
…		…
143		171
144	=over 4	172	=over 4
145		173
146	=item 1. Perl strings can store characters with ordinal values > 255.	174	=item 1. Perl strings can store characters with ordinal values > 255.
147		175
148	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
149	Perl string - very natural.	177	Perl string - very natural.
150		178
151	=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.
152		180
153	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
154	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
155	locale-encoded text, octets/binary, or as Unicode, depending on various	183	string as locale-encoded text, octets/binary, or as Unicode, depending
156	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
157	I<use> that decides encoding, not any magical metadata.	185	data, it is I<use> that decides encoding, not any magical meta data.
158		186
159	=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
160	encoding of your string.	188	encoding of your string.
161		189
162	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
163	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
164	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
165	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
166	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
167	clear. Other possibilities exist, too.	195	clear. Other possibilities exist, too.
168		196
169	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
170	exist.	198	exist.
171		199
172	=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
173	validly interpreted as a Unicode codepoint.	201	validly interpreted as a Unicode code point.
174		202
175	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
176	Unicode string encoded in UTF-8, giving you a binary string.	204	Unicode string encoded in UTF-8, giving you a binary string.
177		205
178	=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.
179		207
180	Its a fact. Learn to live with it.	208	It's a fact. Learn to live with it.
181		209
182	=back	210	=back
183		211
184	I hope this helps :)	212	I hope this helps :)
185		213
…		…
202	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]})
203	=> {"a": [1, 2]}	231	=> {"a": [1, 2]}
204		232
205	=item $json = $json->ascii ([$enable])	233	=item $json = $json->ascii ([$enable])
206		234
		235	=item $enabled = $json->get_ascii
		236
207	If C<$enable> is true (or missing), then the C<encode> method will not	237	If C<$enable> is true (or missing), then the C<encode> method will not
208	generate characters outside the code range C<0..127> (which is ASCII). Any	238	generate characters outside the code range C<0..127> (which is ASCII). Any
209	unicode characters outside that range will be escaped using either a	239	Unicode characters outside that range will be escaped using either a
210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	240	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
211	as per RFC4627. The resulting encoded JSON text can be treated as a native	241	as per RFC4627. The resulting encoded JSON text can be treated as a native
212	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	242	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
213	or any other superset of ASCII.	243	or any other superset of ASCII.
214		244
215	If C<$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
216	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
217	in a faster and more compact format.	247	in a faster and more compact format.
218		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
219	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
220	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
221	contain any 8 bit characters.	254	contain any 8 bit characters.
222		255
223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224	=> ["\ud801\udc01"]	257	=> ["\ud801\udc01"]
225		258
226	=item $json = $json->latin1 ([$enable])	259	=item $json = $json->latin1 ([$enable])
227		260
		261	=item $enabled = $json->get_latin1
		262
228	If C<$enable> is true (or missing), then the C<encode> method will encode	263	If C<$enable> is true (or missing), then the C<encode> method will encode
229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	264	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230	outside the code range C<0..255>. The resulting string can be treated as a	265	outside the code range C<0..255>. The resulting string can be treated as a
231	latin1-encoded JSON text or a native unicode string. The C<decode> method	266	latin1-encoded JSON text or a native Unicode string. The C<decode> method
232	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
233	expects unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
234		269
235	If C<$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
236	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.
237		275
238	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
239	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
240	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
241	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
242	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
243	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
244	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.
245		283
246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	284	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	285	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248		286
249	=item $json = $json->utf8 ([$enable])	287	=item $json = $json->utf8 ([$enable])
		288
		289	=item $enabled = $json->get_utf8
250		290
251	If C<$enable> is true (or missing), then the C<encode> method will encode	291	If C<$enable> is true (or missing), then the C<encode> method will encode
252	the JSON result into UTF-8, as required by many protocols, while the	292	the JSON result into UTF-8, as required by many protocols, while the
253	C<decode> method expects to be handled an UTF-8-encoded string. Please	293	C<decode> method expects to be handled an UTF-8-encoded string. Please
254	note that UTF-8-encoded strings do not contain any characters outside the	294	note that UTF-8-encoded strings do not contain any characters outside the
255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	295	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
256	versions, enabling this option might enable autodetection of the UTF-16	296	versions, enabling this option might enable autodetection of the UTF-16
257	and UTF-32 encoding families, as described in RFC4627.	297	and UTF-32 encoding families, as described in RFC4627.
258		298
259	If C<$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
260	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
261	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
262	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.
263		306
264	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
265		308
266	use Encode;	309	use Encode;
267	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
288	]	331	]
289	}	332	}
290		333
291	=item $json = $json->indent ([$enable])	334	=item $json = $json->indent ([$enable])
292		335
		336	=item $enabled = $json->get_indent
		337
293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	338	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294	format as output, putting every array member or object/hash key-value pair	339	format as output, putting every array member or object/hash key-value pair
295	into its own line, identing them properly.	340	into its own line, indenting them properly.
296		341
297	If C<$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
298	resulting JSON text is guarenteed not to contain any C<newlines>.	343	resulting JSON text is guaranteed not to contain any C<newlines>.
299		344
300	This setting has no effect when decoding JSON texts.	345	This setting has no effect when decoding JSON texts.
301		346
302	=item $json = $json->space_before ([$enable])	347	=item $json = $json->space_before ([$enable])
		348
		349	=item $enabled = $json->get_space_before
303		350
304	If C<$enable> is true (or missing), then the C<encode> method will add an extra	351	If C<$enable> is true (or missing), then the C<encode> method will add an extra
305	optional space before the C<:> separating keys from values in JSON objects.	352	optional space before the C<:> separating keys from values in JSON objects.
306		353
307	If C<$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
…		…
313	Example, space_before enabled, space_after and indent disabled:	360	Example, space_before enabled, space_after and indent disabled:
314		361
315	{"key" :"value"}	362	{"key" :"value"}
316		363
317	=item $json = $json->space_after ([$enable])	364	=item $json = $json->space_after ([$enable])
		365
		366	=item $enabled = $json->get_space_after
318		367
319	If C<$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
320	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
321	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
322	members.	371	members.
…		…
329	Example, space_before and indent disabled, space_after enabled:	378	Example, space_before and indent disabled, space_after enabled:
330		379
331	{"key": "value"}	380	{"key": "value"}
332		381
333	=item $json = $json->relaxed ([$enable])	382	=item $json = $json->relaxed ([$enable])
		383
		384	=item $enabled = $json->get_relaxed
334		385
335	If C<$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
336	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
337	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
338	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
…		…
375		426
376	=back	427	=back
377		428
378	=item $json = $json->canonical ([$enable])	429	=item $json = $json->canonical ([$enable])
379		430
		431	=item $enabled = $json->get_canonical
		432
380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381	by sorting their keys. This is adding a comparatively high overhead.	434	by sorting their keys. This is adding a comparatively high overhead.
382		435
383	If C<$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
384	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
385	of the same script).	438	of the same script).
386		439
387	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
388	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,
389	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,
390	as key-value pairs have no inherent ordering in Perl.	443	as key-value pairs have no inherent ordering in Perl.
391		444
392	This setting has no effect when decoding JSON texts.	445	This setting has no effect when decoding JSON texts.
393		446
394	=item $json = $json->allow_nonref ([$enable])	447	=item $json = $json->allow_nonref ([$enable])
		448
		449	=item $enabled = $json->get_allow_nonref
395		450
396	If C<$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
397	non-reference into its corresponding string, number or null JSON value,	452	non-reference into its corresponding string, number or null JSON value,
398	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
399	values instead of croaking.	454	values instead of croaking.
…		…
407	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
408		463
409	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
410	=> "Hello, World!"	465	=> "Hello, World!"
411		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
412	=item $json = $json->allow_blessed ([$enable])	483	=item $json = $json->allow_blessed ([$enable])
		484
		485	=item $enabled = $json->get_allow_blessed
413		486
414	If C<$enable> is true (or missing), then the C<encode> method will not	487	If C<$enable> is true (or missing), then the C<encode> method will not
415	barf when it encounters a blessed reference. Instead, the value of the	488	barf when it encounters a blessed reference. Instead, the value of the
416	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417	disabled or no C<to_json> method found) or a representation of the	490	disabled or no C<TO_JSON> method found) or a representation of the
418	object (C<convert_blessed> enabled and C<to_json> method found) is being	491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419	encoded. Has no effect on C<decode>.	492	encoded. Has no effect on C<decode>.
420		493
421	If C<$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
422	exception when it encounters a blessed object.	495	exception when it encounters a blessed object.
423		496
424	=item $json = $json->convert_blessed ([$enable])	497	=item $json = $json->convert_blessed ([$enable])
		498
		499	=item $enabled = $json->get_convert_blessed
425		500
426	If C<$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
427	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
428	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
429	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
…		…
433	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>
434	returns other blessed objects, those will be handled in the same	509	returns other blessed objects, those will be handled in the same
435	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
436	(== 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
437	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
438	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>
439	function.	514	function or method.
440		515
441	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
442	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
443	enabled by this setting.	518	enabled by this setting.
444		519
…		…
486		561
487	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>
488	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
489	objects make excellent targets to serialise Perl objects into, especially	564	objects make excellent targets to serialise Perl objects into, especially
490	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
491	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
492	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
493	like a serialised Perl hash.	568	like a serialised Perl hash.
494		569
495	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
496	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
…		…
520		595
521	{ __widget__ => $self->{id} }	596	{ __widget__ => $self->{id} }
522	}	597	}
523		598
524	=item $json = $json->shrink ([$enable])	599	=item $json = $json->shrink ([$enable])
		600
		601	=item $enabled = $json->get_shrink
525		602
526	Perl usually over-allocates memory a bit when allocating space for	603	Perl usually over-allocates memory a bit when allocating space for
527	strings. This flag optionally resizes strings generated by either	604	strings. This flag optionally resizes strings generated by either
528	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
529	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
…		…
547	strings that look like integers or floats into integers or floats	624	strings that look like integers or floats into integers or floats
548	internally (there is no difference on the Perl level), saving space.	625	internally (there is no difference on the Perl level), saving space.
549		626
550	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
551		628
		629	=item $max_depth = $json->get_max_depth
		630
552	Sets the maximum nesting level (default C<512>) accepted while encoding	631	Sets the maximum nesting level (default C<512>) accepted while encoding
553	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
554	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
555	stop and croak at that point.	634	point.
556		635
557	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
558	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<[>
559	characters without their matching closing parenthesis crossed to reach a	638	characters without their matching closing parenthesis crossed to reach a
560	given character in a string.	639	given character in a string.
561		640
562	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
563	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
564		643
565	The argument to C<max_depth> will be rounded up to the next highest power
566	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
567	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.
568		650
569	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.
570		652
571	=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
572		656
573	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
574	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>
575	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
576	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
577	effect on C<encode> (yet).	661	effect on C<encode> (yet).
578		662
579	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
580	power of two (so may be more than requested). If no argument is given, the	664	C<0> is specified).
581	limit check will be deactivated (same as when C<0> is specified).
582		665
583	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.
584		667
585	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
586		669
…		…
615	=> ([], 3)	698	=> ([], 3)
616		699
617	=back	700	=back
618		701
619		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
620	=head1 MAPPING	938	=head1 MAPPING
621		939
622	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
623	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
624	circumstances automatically, preserving round-tripping characteristics	942	circumstances automatically, preserving round-tripping characteristics
625	(what you put in comes out as something equivalent).	943	(what you put in comes out as something equivalent).
626		944
627	For the more enlightened: note that in the following descriptions,	945	For the more enlightened: note that in the following descriptions,
628	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>
629	refers to the abstract Perl language itself.	947	refers to the abstract Perl language itself.
630		948
631		949
632	=head2 JSON -> PERL	950	=head2 JSON -> PERL
633		951
634	=over 4	952	=over 4
635		953
636	=item object	954	=item object
637		955
638	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
639	keys is preserved (JSON does not preserver object key ordering itself).	957	keys is preserved (JSON does not preserve object key ordering itself).
640		958
641	=item array	959	=item array
642		960
643	A JSON array becomes a reference to an array in Perl.	961	A JSON array becomes a reference to an array in Perl.
644		962
…		…
652		970
653	A JSON number becomes either an integer, numeric (floating point) or	971	A JSON number becomes either an integer, numeric (floating point) or
654	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
655	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
656	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
657	might represent more values exactly than (floating point) numbers.	975	might represent more values exactly than floating point numbers.
658		976
659	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
660	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
661	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
662	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).
663		983
664	Numbers containing a fractional or exponential part will always be	984	Numbers containing a fractional or exponential part will always be
665	represented as numeric (floating point) values, possibly at a loss of	985	represented as numeric (floating point) values, possibly at a loss of
666	precision.	986	precision (in which case you might lose perfect roundtripping ability, but
667		987	the JSON number will still be re-encoded as a JSON number).
668	This might create round-tripping problems as numbers might become strings,
669	but as Perl is typeless there is no other way to do it.
670		988
671	=item true, false	989	=item true, false
672		990
673	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>,
674	respectively. They are overloaded to act almost exactly like the numbers	992	respectively. They are overloaded to act almost exactly like the numbers
675	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
676	the C<JSON::XS::is_bool> function.	994	the C<JSON::XS::is_bool> function.
677		995
678	=item null	996	=item null
679		997
680	A JSON null atom becomes C<undef> in Perl.	998	A JSON null atom becomes C<undef> in Perl.
…		…
711	Other unblessed references are generally not allowed and will cause an	1029	Other unblessed references are generally not allowed and will cause an
712	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
713	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
714	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.
715		1033
716	to_json [\0,JSON::XS::true] # yields [false,true]	1034	encode_json [\0, JSON::XS::true] # yields [false,true]
717		1035
718	=item JSON::XS::true, JSON::XS::false	1036	=item JSON::XS::true, JSON::XS::false
719		1037
720	These special values become JSON true and JSON false values,	1038	These special values become JSON true and JSON false values,
721	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.
722		1040
723	=item blessed objects	1041	=item blessed objects
724		1042
725	Blessed objects are not allowed. JSON::XS currently tries to encode their	1043	Blessed objects are not directly representable in JSON. See the
726	underlying representation (hash- or arrayref), but this behaviour might	1044	C<allow_blessed> and C<convert_blessed> methods on various options on
727	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.
728		1048
729	=item simple scalars	1049	=item simple scalars
730		1050
731	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
732	difficult objects to encode: JSON::XS will encode undefined scalars as	1052	difficult objects to encode: JSON::XS will encode undefined scalars as
733	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
734	before encoding as JSON strings and anything else as number value:	1054	before encoding as JSON strings, and anything else as number value:
735		1055
736	# dump as number	1056	# dump as number
737	to_json [2] # yields [2]	1057	encode_json [2] # yields [2]
738	to_json [-3.0e17] # yields [-3e+17]	1058	encode_json [-3.0e17] # yields [-3e+17]
739	my $value = 5; to_json [$value] # yields [5]	1059	my $value = 5; encode_json [$value] # yields [5]
740		1060
741	# used as string, so dump as string	1061	# used as string, so dump as string
742	print $value;	1062	print $value;
743	to_json [$value] # yields ["5"]	1063	encode_json [$value] # yields ["5"]
744		1064
745	# undef becomes null	1065	# undef becomes null
746	to_json [undef] # yields [null]	1066	encode_json [undef] # yields [null]
747		1067
748	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:
749		1069
750	my $x = 3.1; # some variable containing a number	1070	my $x = 3.1; # some variable containing a number
751	"$x"; # stringified	1071	"$x"; # stringified
752	$x .= ""; # another, more awkward way to stringify	1072	$x .= ""; # another, more awkward way to stringify
753	print $x; # perl does it for you, too, quite often	1073	print $x; # perl does it for you, too, quite often
754		1074
755	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:
756		1076
757	my $x = "3"; # some variable containing a string	1077	my $x = "3"; # some variable containing a string
758	$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
759	$x *= 1; # same thing, the choise is yours.	1079	$x *= 1; # same thing, the choice is yours.
760		1080
761	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
762	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	:).
763		1084
764	=back	1085	=back
765		1086
766		1087
767	=head1 COMPARISON	1088	=head1 ENCODING/CODESET FLAG NOTES
768		1089
769	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
770	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
771	problems (or pleasures) I encountered with various existing JSON modules,	1092	some confusion on what these do, so here is a short comparison:
772	followed by some benchmark values. JSON::XS was designed not to suffer	1093
773	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.
774		1112
775	=over 4	1113	=over 4
776		1114
777	=item JSON 1.07	1115	=item C<utf8> flag disabled
778		1116
779	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).
780		1124
781	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
782	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
783	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).
784		1130
785	No roundtripping (strings get clobbered if they look like numbers, e.g.	1131	=item C<utf8> flag enabled
786	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
787	decode into the number 2.
788		1132
789	=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.
790		1138
791	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.
792		1142
793	Undocumented/buggy Unicode handling.	1143	=item C<latin1> or C<ascii> flags enabled
794		1144
795	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.
796		1148
797	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
798	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).
799		1154
800	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,
801	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.
802		1158
803	Unmaintained (maintainer unresponsive for many months, bugs are not	1159	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
804	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.
805		1163
806	=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.
807		1168
808	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.
809		1171
810	Very inflexible (no human-readable format supported, format pretty much	1172	The main use for C<latin1> is to relatively efficiently store binary data
811	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.
812	single-line compact format for use in a protocol, and preferably a way to
813	generate ASCII-only JSON texts).
814		1174
815	Completely broken (and confusingly documented) Unicode handling (unicode	1175	The main use for C<ascii> is to force the output to not contain characters
816	escapes are not working properly, you need to set ImplicitUnicode to	1176	with values > 127, which means you can interpret the resulting string
817	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
818		1178	8-bit-encoding, and still get the same data structure back. This is useful
819	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
820	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
821		1181	proper subset of most 8-bit and multibyte encodings in use in the world.
822	Dumping hashes may skip hash values depending on iterator state.
823
824	Unmaintained (maintainer unresponsive for many months, bugs are not
825	getting fixed).
826
827	Does not check input for validity (i.e. will accept non-JSON input and
828	return "something" instead of raising an exception. This is a security
829	issue: imagine two banks transfering money between each other using
830	JSON. One bank might parse a given non-JSON request and deduct money,
831	while the other might reject the transaction with a syntax error. While a
832	good protocol will at least recover, that is extra unnecessary work and
833	the transaction will still not succeed).
834
835	=item JSON::DWIW 0.04
836
837	Very fast. Very natural. Very nice.
838
839	Undocumented unicode handling (but the best of the pack. Unicode escapes
840	still don't get parsed properly).
841
842	Very inflexible.
843
844	No roundtripping.
845
846	Does not generate valid JSON texts (key strings are often unquoted, empty keys
847	result in nothing being output)
848
849	Does not check input for validity.
850		1182
851	=back	1183	=back
852		1184
853		1185
854	=head2 JSON and YAML	1186	=head2 JSON and YAML
855		1187
856	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
857	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),
858	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.
859		1193
860	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
861	algorithm (subject to change in future versions):	1195	algorithm (subject to change in future versions):
862		1196
863	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1197	my $to_yaml = JSON::XS->new->utf8->space_after (1);
864	my $yaml = $to_yaml->encode ($ref) . "\n";	1198	my $yaml = $to_yaml->encode ($ref) . "\n";
865		1199
866	This will usually generate JSON texts that also parse as valid	1200	This will I<usually> generate JSON texts that also parse as valid
867	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
868	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
869	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).
870		1209
871	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
872	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
873	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
874	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
875		1238
876		1239
877	=head2 SPEED	1240	=head2 SPEED
878		1241
879	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
880	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
881	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
882	system.	1245	system.
883		1246
884	First comes a comparison between various modules using a very short	1247	First comes a comparison between various modules using
885	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>).
886		1250
887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1251	{"method": "handleMessage", "params": ["user1",
888	"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]}
889		1254
890	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
891	the functional interface, while JSON::XS/2 uses the OO interface	1256	the functional interface, while JSON::XS/2 uses the OO interface
892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893	shrink). Higher is better:	1258	shrink). Higher is better:
894		1259
895	Storable \| 15779.925 \| 14169.946 \|
896	-----------+------------+------------+
897	module \| encode \| decode \|	1260	module \| encode \| decode \|
898	-----------\|------------\|------------\|	1261	-----------\|------------\|------------\|
899	JSON \| 4990.842 \| 4088.813 \|	1262	JSON 1.x \| 4990.842 \| 4088.813 \|
900	JSON::DWIW \| 51653.990 \| 71575.154 \|	1263	JSON::DWIW \| 51653.990 \| 71575.154 \|
901	JSON::PC \| 65948.176 \| 74631.744 \|	1264	JSON::PC \| 65948.176 \| 74631.744 \|
902	JSON::PP \| 8931.652 \| 3817.168 \|	1265	JSON::PP \| 8931.652 \| 3817.168 \|
903	JSON::Syck \| 24877.248 \| 27776.848 \|	1266	JSON::Syck \| 24877.248 \| 27776.848 \|
904	JSON::XS \| 388361.481 \| 227951.304 \|	1267	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
906	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1269	JSON::XS/3 \| 338250.323 \| 218453.333 \|
907	Storable \| 16500.016 \| 135300.129 \|	1270	Storable \| 16500.016 \| 135300.129 \|
908	-----------+------------+------------+	1271	-----------+------------+------------+
909		1272
910	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,
911	about three times faster on decoding, and over fourty times faster	1274	about three times faster on decoding, and over forty times faster
912	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
913	favourably to Storable for small amounts of data.	1276	favourably to Storable for small amounts of data.
914		1277
915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916	search API (http://nanoref.com/yahooapis/mgPdGg):	1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).
917		1280
918	module \| encode \| decode \|	1281	module \| encode \| decode \|
919	-----------\|------------\|------------\|	1282	-----------\|------------\|------------\|
920	JSON \| 55.260 \| 34.971 \|	1283	JSON 1.x \| 55.260 \| 34.971 \|
921	JSON::DWIW \| 825.228 \| 1082.513 \|	1284	JSON::DWIW \| 825.228 \| 1082.513 \|
922	JSON::PC \| 3571.444 \| 2394.829 \|	1285	JSON::PC \| 3571.444 \| 2394.829 \|
923	JSON::PP \| 210.987 \| 32.574 \|	1286	JSON::PP \| 210.987 \| 32.574 \|
924	JSON::Syck \| 552.551 \| 787.544 \|	1287	JSON::Syck \| 552.551 \| 787.544 \|
925	JSON::XS \| 5780.463 \| 4854.519 \|	1288	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
929	-----------+------------+------------+	1292	-----------+------------+------------+
930		1293
931	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
932	decodes faster).	1295	decodes faster).
933		1296
934	On large strings containing lots of high unicode characters, some modules	1297	On large strings containing lots of high Unicode characters, some modules
935	(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
936	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
937	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
938	comparison table for that case.	1301	comparison table for that case.
939		1302
940		1303
941	=head1 SECURITY CONSIDERATIONS	1304	=head1 SECURITY CONSIDERATIONS
…		…
947	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
948	trying hard on making that true, but you never know.	1311	trying hard on making that true, but you never know.
949		1312
950	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
951	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
952	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
953	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
954	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
955	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
956	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
957	might want to check the size before you accept the string.	1320	might want to check the size before you accept the string.
958		1321
959	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
960	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
961	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
962	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
963	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
964	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
965	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
966	C<max_depth> method.	1329	C<max_depth> method.
967		1330
968	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
969	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...
970	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.
971		1338
972	If you are using JSON::XS to return packets to consumption	1339	If you are using JSON::XS to return packets to consumption
973	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
974	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
975	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
976	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
977	browser developers care only for features, not about doing security	1344	browser developers care only for features, not about getting security
978	right).	1345	right).
979		1346
980		1347
981	=head1 THREADS	1348	=head1 THREADS
982		1349
983	This module is I<not> guarenteed to be thread safe and there are no	1350	This module is I<not> guaranteed to be thread safe and there are no
984	plans to change this until Perl gets thread support (as opposed to the	1351	plans to change this until Perl gets thread support (as opposed to the
985	horribly slow so-called "threads" which are simply slow and bloated	1352	horribly slow so-called "threads" which are simply slow and bloated
986	process simulations - use fork, its I<much> faster, cheaper, better).	1353	process simulations - use fork, it's I<much> faster, cheaper, better).
987		1354
988	(It might actually work, but you ahve ben warned).	1355	(It might actually work, but you have been warned).
989		1356
990		1357
991	=head1 BUGS	1358	=head1 BUGS
992		1359
993	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
994	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
995	still relatively early in its development. If you keep reporting bugs they	1362	keep reporting bugs they will be fixed swiftly, though.
996	will be fixed swiftly, though.
997		1363
998	Please refrain from using rt.cpan.org or any other bug reporting	1364	Please refrain from using rt.cpan.org or any other bug reporting
999	service. I put the contact address into my modules for a reason.	1365	service. I put the contact address into my modules for a reason.
1000		1366
1001	=cut	1367	=cut
…		…
1021	"--" => sub { $_[0] = ${$_[0]} - 1 },	1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
1022	fallback => 1;	1388	fallback => 1;
1023		1389
1024	1;	1390	1;
1025		1391
		1392	=head1 SEE ALSO
		1393
		1394	The F<json_xs> command line utility for quick experiments.
		1395
1026	=head1 AUTHOR	1396	=head1 AUTHOR
1027		1397
1028	Marc Lehmann <schmorp@schmorp.de>	1398	Marc Lehmann <schmorp@schmorp.de>
1029	http://home.schmorp.de/	1399	http://home.schmorp.de/
1030		1400

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Comparing JSON-XS/XS.pm (file contents): Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs. Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC