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Comparing JSON-XS/README (file contents):
Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC vs.
Revision 1.25 by root, Wed Apr 16 18:38:38 2008 UTC

…		…
1	NAME	1	NAME
2	JSON::XS - JSON serialising/deserialising, done correctly and fast	2	JSON::XS - JSON serialising/deserialising, done correctly and fast
3		3
		4	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		5	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		6
4	SYNOPSIS	7	SYNOPSIS
5	use JSON::XS;	8	use JSON::XS;
6		9
7	# exported functions, they croak on error	10	# exported functions, they croak on error
8	# and expect/generate UTF-8	11	# and expect/generate UTF-8
9		12
10	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	13	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
11	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	14	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
12		15
13	# OO-interface	16	# OO-interface
14		17
15	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	18	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
16	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	19	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
17	$perl_scalar = $coder->decode ($unicode_json_text);	20	$perl_scalar = $coder->decode ($unicode_json_text);
		21
		22	# Note that JSON version 2.0 and above will automatically use JSON::XS
		23	# if available, at virtually no speed overhead either, so you should
		24	# be able to just:
		25
		26	use JSON;
		27
		28	# and do the same things, except that you have a pure-perl fallback now.
18		29
19	DESCRIPTION	30	DESCRIPTION
20	This module converts Perl data structures to JSON and vice versa. Its	31	This module converts Perl data structures to JSON and vice versa. Its
21	primary goal is to be correct and its secondary goal is to be fast.	32	primary goal is to be correct and its secondary goal is to be fast.
22	To reach the latter goal it was written in C.	33	To reach the latter goal it was written in C.
		34
		35	Beginning with version 2.0 of the JSON module, when both JSON and
		36	JSON::XS are installed, then JSON will fall back on JSON::XS (this can
		37	be overriden) with no overhead due to emulation (by inheritign
		38	constructor and methods). If JSON::XS is not available, it will fall
		39	back to the compatible JSON::PP module as backend, so using JSON instead
		40	of JSON::XS gives you a portable JSON API that can be fast when you need
		41	and doesn't require a C compiler when that is a problem.
23		42
24	As this is the n-th-something JSON module on CPAN, what was the reason	43	As this is the n-th-something JSON module on CPAN, what was the reason
25	to write yet another JSON module? While it seems there are many JSON	44	to write yet another JSON module? While it seems there are many JSON
26	modules, none of them correctly handle all corner cases, and in most	45	modules, none of them correctly handle all corner cases, and in most
27	cases their maintainers are unresponsive, gone missing, or not listening	46	cases their maintainers are unresponsive, gone missing, or not listening
31		50
32	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	51	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
33	vice versa.	52	vice versa.
34		53
35	FEATURES	54	FEATURES
36	* correct unicode handling	55	* correct Unicode handling
		56
37	This module knows how to handle Unicode, and even documents how and	57	This module knows how to handle Unicode, documents how and when it
38	when it does so.	58	does so, and even documents what "correct" means.
39		59
40	* round-trip integrity	60	* round-trip integrity
		61
41	When you serialise a perl data structure using only datatypes	62	When you serialise a perl data structure using only datatypes
42	supported by JSON, the deserialised data structure is identical on	63	supported by JSON, the deserialised data structure is identical on
43	the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"	64	the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"
44	just because it looks like a number).	65	just because it looks like a number). There minor are exceptions
		66	to this, read the MAPPING section below to learn about those.
45		67
46	* strict checking of JSON correctness	68	* strict checking of JSON correctness
		69
47	There is no guessing, no generating of illegal JSON texts by	70	There is no guessing, no generating of illegal JSON texts by
48	default, and only JSON is accepted as input by default (the latter	71	default, and only JSON is accepted as input by default (the latter
49	is a security feature).	72	is a security feature).
50		73
51	* fast	74	* fast
52	Compared to other JSON modules, this module compares favourably in
53	terms of speed, too.
54		75
		76	Compared to other JSON modules and other serialisers such as
		77	Storable, this module usually compares favourably in terms of speed,
		78	too.
		79
55	* simple to use	80	* simple to use
		81
56	This module has both a simple functional interface as well as an OO	82	This module has both a simple functional interface as well as an
57	interface.	83	objetc oriented interface interface.
58		84
59	* reasonably versatile output formats	85	* reasonably versatile output formats
		86
60	You can choose between the most compact guarenteed single-line	87	You can choose between the most compact guaranteed-single-line
61	format possible (nice for simple line-based protocols), a pure-ascii	88	format possible (nice for simple line-based protocols), a pure-ascii
62	format (for when your transport is not 8-bit clean, still supports	89	format (for when your transport is not 8-bit clean, still supports
63	the whole unicode range), or a pretty-printed format (for when you	90	the whole Unicode range), or a pretty-printed format (for when you
64	want to read that stuff). Or you can combine those features in	91	want to read that stuff). Or you can combine those features in
65	whatever way you like.	92	whatever way you like.
66		93
67	FUNCTIONAL INTERFACE	94	FUNCTIONAL INTERFACE
68	The following convinience methods are provided by this module. They are	95	The following convenience methods are provided by this module. They are
69	exported by default:	96	exported by default:
70		97
71	$json_text = to_json $perl_scalar	98	$json_text = encode_json $perl_scalar
72	Converts the given Perl data structure (a simple scalar or a	99	Converts the given Perl data structure to a UTF-8 encoded, binary
73	reference to a hash or array) to a UTF-8 encoded, binary string
74	(that is, the string contains octets only). Croaks on error.	100	string (that is, the string contains octets only). Croaks on error.
75		101
76	This function call is functionally identical to:	102	This function call is functionally identical to:
77		103
78	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	104	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
79		105
80	except being faster.	106	except being faster.
81		107
82	$perl_scalar = from_json $json_text	108	$perl_scalar = decode_json $json_text
83	The opposite of "to_json": expects an UTF-8 (binary) string and	109	The opposite of "encode_json": expects an UTF-8 (binary) string and
84	tries to parse that as an UTF-8 encoded JSON text, returning the	110	tries to parse that as an UTF-8 encoded JSON text, returning the
85	resulting simple scalar or reference. Croaks on error.	111	resulting reference. Croaks on error.
86		112
87	This function call is functionally identical to:	113	This function call is functionally identical to:
88		114
89	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	115	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
90		116
…		…
97	values in Perl.	123	values in Perl.
98		124
99	See MAPPING, below, for more information on how JSON values are	125	See MAPPING, below, for more information on how JSON values are
100	mapped to Perl.	126	mapped to Perl.
101		127
		128	A FEW NOTES ON UNICODE AND PERL
		129	Since this often leads to confusion, here are a few very clear words on
		130	how Unicode works in Perl, modulo bugs.
		131
		132	1. Perl strings can store characters with ordinal values > 255.
		133	This enables you to store Unicode characters as single characters in
		134	a Perl string - very natural.
		135
		136	2. Perl does not associate an encoding with your strings.
		137	... until you force it to, e.g. when matching it against a regex, or
		138	printing the scalar to a file, in which case Perl either interprets
		139	your string as locale-encoded text, octets/binary, or as Unicode,
		140	depending on various settings. In no case is an encoding stored
		141	together with your data, it is use that decides encoding, not any
		142	magical meta data.
		143
		144	3. The internal utf-8 flag has no meaning with regards to the encoding
		145	of your string.
		146	Just ignore that flag unless you debug a Perl bug, a module written
		147	in XS or want to dive into the internals of perl. Otherwise it will
		148	only confuse you, as, despite the name, it says nothing about how
		149	your string is encoded. You can have Unicode strings with that flag
		150	set, with that flag clear, and you can have binary data with that
		151	flag set and that flag clear. Other possibilities exist, too.
		152
		153	If you didn't know about that flag, just the better, pretend it
		154	doesn't exist.
		155
		156	4. A "Unicode String" is simply a string where each character can be
		157	validly interpreted as a Unicode codepoint.
		158	If you have UTF-8 encoded data, it is no longer a Unicode string,
		159	but a Unicode string encoded in UTF-8, giving you a binary string.
		160
		161	5. A string containing "high" (> 255) character values is not a UTF-8
		162	string.
		163	It's a fact. Learn to live with it.
		164
		165	I hope this helps :)
		166
102	OBJECT-ORIENTED INTERFACE	167	OBJECT-ORIENTED INTERFACE
103	The object oriented interface lets you configure your own encoding or	168	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	169	decoding style, within the limits of supported formats.
105		170
106	$json = new JSON::XS	171	$json = new JSON::XS
…		…
113		178
114	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	179	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
115	=> {"a": [1, 2]}	180	=> {"a": [1, 2]}
116		181
117	$json = $json->ascii ([$enable])	182	$json = $json->ascii ([$enable])
		183	$enabled = $json->get_ascii
118	If $enable is true (or missing), then the "encode" method will not	184	If $enable is true (or missing), then the "encode" method will not
119	generate characters outside the code range 0..127 (which is ASCII).	185	generate characters outside the code range 0..127 (which is ASCII).
120	Any unicode characters outside that range will be escaped using	186	Any Unicode characters outside that range will be escaped using
121	either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL	187	either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL
122	escape sequence, as per RFC4627. The resulting encoded JSON text can	188	escape sequence, as per RFC4627. The resulting encoded JSON text can
123	be treated as a native unicode string, an ascii-encoded,	189	be treated as a native Unicode string, an ascii-encoded,
124	latin1-encoded or UTF-8 encoded string, or any other superset of	190	latin1-encoded or UTF-8 encoded string, or any other superset of
125	ASCII.	191	ASCII.
126		192
127	If $enable is false, then the "encode" method will not escape	193	If $enable is false, then the "encode" method will not escape
128	Unicode characters unless required by the JSON syntax or other	194	Unicode characters unless required by the JSON syntax or other
129	flags. This results in a faster and more compact format.	195	flags. This results in a faster and more compact format.
130		196
		197	See also the section ENCODING/CODESET FLAG NOTES later in this
		198	document.
		199
131	The main use for this flag is to produce JSON texts that can be	200	The main use for this flag is to produce JSON texts that can be
132	transmitted over a 7-bit channel, as the encoded JSON texts will not	201	transmitted over a 7-bit channel, as the encoded JSON texts will not
133	contain any 8 bit characters.	202	contain any 8 bit characters.
134		203
135	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	204	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
136	=> ["\ud801\udc01"]	205	=> ["\ud801\udc01"]
137		206
138	$json = $json->latin1 ([$enable])	207	$json = $json->latin1 ([$enable])
		208	$enabled = $json->get_latin1
139	If $enable is true (or missing), then the "encode" method will	209	If $enable is true (or missing), then the "encode" method will
140	encode the resulting JSON text as latin1 (or iso-8859-1), escaping	210	encode the resulting JSON text as latin1 (or iso-8859-1), escaping
141	any characters outside the code range 0..255. The resulting string	211	any characters outside the code range 0..255. The resulting string
142	can be treated as a latin1-encoded JSON text or a native unicode	212	can be treated as a latin1-encoded JSON text or a native Unicode
143	string. The "decode" method will not be affected in any way by this	213	string. The "decode" method will not be affected in any way by this
144	flag, as "decode" by default expects unicode, which is a strict	214	flag, as "decode" by default expects Unicode, which is a strict
145	superset of latin1.	215	superset of latin1.
146		216
147	If $enable is false, then the "encode" method will not escape	217	If $enable is false, then the "encode" method will not escape
148	Unicode characters unless required by the JSON syntax or other	218	Unicode characters unless required by the JSON syntax or other
149	flags.	219	flags.
		220
		221	See also the section ENCODING/CODESET FLAG NOTES later in this
		222	document.
150		223
151	The main use for this flag is efficiently encoding binary data as	224	The main use for this flag is efficiently encoding binary data as
152	JSON text, as most octets will not be escaped, resulting in a	225	JSON text, as most octets will not be escaped, resulting in a
153	smaller encoded size. The disadvantage is that the resulting JSON	226	smaller encoded size. The disadvantage is that the resulting JSON
154	text is encoded in latin1 (and must correctly be treated as such	227	text is encoded in latin1 (and must correctly be treated as such
155	when storing and transfering), a rare encoding for JSON. It is	228	when storing and transferring), a rare encoding for JSON. It is
156	therefore most useful when you want to store data structures known	229	therefore most useful when you want to store data structures known
157	to contain binary data efficiently in files or databases, not when	230	to contain binary data efficiently in files or databases, not when
158	talking to other JSON encoders/decoders.	231	talking to other JSON encoders/decoders.
159		232
160	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	233	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
161	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	234	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
162		235
163	$json = $json->utf8 ([$enable])	236	$json = $json->utf8 ([$enable])
		237	$enabled = $json->get_utf8
164	If $enable is true (or missing), then the "encode" method will	238	If $enable is true (or missing), then the "encode" method will
165	encode the JSON result into UTF-8, as required by many protocols,	239	encode the JSON result into UTF-8, as required by many protocols,
166	while the "decode" method expects to be handled an UTF-8-encoded	240	while the "decode" method expects to be handled an UTF-8-encoded
167	string. Please note that UTF-8-encoded strings do not contain any	241	string. Please note that UTF-8-encoded strings do not contain any
168	characters outside the range 0..255, they are thus useful for	242	characters outside the range 0..255, they are thus useful for
169	bytewise/binary I/O. In future versions, enabling this option might	243	bytewise/binary I/O. In future versions, enabling this option might
170	enable autodetection of the UTF-16 and UTF-32 encoding families, as	244	enable autodetection of the UTF-16 and UTF-32 encoding families, as
171	described in RFC4627.	245	described in RFC4627.
172		246
173	If $enable is false, then the "encode" method will return the JSON	247	If $enable is false, then the "encode" method will return the JSON
174	string as a (non-encoded) unicode string, while "decode" expects	248	string as a (non-encoded) Unicode string, while "decode" expects
175	thus a unicode string. Any decoding or encoding (e.g. to UTF-8 or	249	thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
176	UTF-16) needs to be done yourself, e.g. using the Encode module.	250	UTF-16) needs to be done yourself, e.g. using the Encode module.
		251
		252	See also the section ENCODING/CODESET FLAG NOTES later in this
		253	document.
177		254
178	Example, output UTF-16BE-encoded JSON:	255	Example, output UTF-16BE-encoded JSON:
179		256
180	use Encode;	257	use Encode;
181	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	258	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
200	2	277	2
201	]	278	]
202	}	279	}
203		280
204	$json = $json->indent ([$enable])	281	$json = $json->indent ([$enable])
		282	$enabled = $json->get_indent
205	If $enable is true (or missing), then the "encode" method will use a	283	If $enable is true (or missing), then the "encode" method will use a
206	multiline format as output, putting every array member or	284	multiline format as output, putting every array member or
207	object/hash key-value pair into its own line, identing them	285	object/hash key-value pair into its own line, indenting them
208	properly.	286	properly.
209		287
210	If $enable is false, no newlines or indenting will be produced, and	288	If $enable is false, no newlines or indenting will be produced, and
211	the resulting JSON text is guarenteed not to contain any "newlines".	289	the resulting JSON text is guaranteed not to contain any "newlines".
212		290
213	This setting has no effect when decoding JSON texts.	291	This setting has no effect when decoding JSON texts.
214		292
215	$json = $json->space_before ([$enable])	293	$json = $json->space_before ([$enable])
		294	$enabled = $json->get_space_before
216	If $enable is true (or missing), then the "encode" method will add	295	If $enable is true (or missing), then the "encode" method will add
217	an extra optional space before the ":" separating keys from values	296	an extra optional space before the ":" separating keys from values
218	in JSON objects.	297	in JSON objects.
219		298
220	If $enable is false, then the "encode" method will not add any extra	299	If $enable is false, then the "encode" method will not add any extra
…		…
226	Example, space_before enabled, space_after and indent disabled:	305	Example, space_before enabled, space_after and indent disabled:
227		306
228	{"key" :"value"}	307	{"key" :"value"}
229		308
230	$json = $json->space_after ([$enable])	309	$json = $json->space_after ([$enable])
		310	$enabled = $json->get_space_after
231	If $enable is true (or missing), then the "encode" method will add	311	If $enable is true (or missing), then the "encode" method will add
232	an extra optional space after the ":" separating keys from values in	312	an extra optional space after the ":" separating keys from values in
233	JSON objects and extra whitespace after the "," separating key-value	313	JSON objects and extra whitespace after the "," separating key-value
234	pairs and array members.	314	pairs and array members.
235		315
…		…
240		320
241	Example, space_before and indent disabled, space_after enabled:	321	Example, space_before and indent disabled, space_after enabled:
242		322
243	{"key": "value"}	323	{"key": "value"}
244		324
		325	$json = $json->relaxed ([$enable])
		326	$enabled = $json->get_relaxed
		327	If $enable is true (or missing), then "decode" will accept some
		328	extensions to normal JSON syntax (see below). "encode" will not be
		329	affected in anyway. *Be aware that this option makes you accept
		330	invalid JSON texts as if they were valid!*. I suggest only to use
		331	this option to parse application-specific files written by humans
		332	(configuration files, resource files etc.)
		333
		334	If $enable is false (the default), then "decode" will only accept
		335	valid JSON texts.
		336
		337	Currently accepted extensions are:
		338
		339	* list items can have an end-comma
		340
		341	JSON separates array elements and key-value pairs with commas.
		342	This can be annoying if you write JSON texts manually and want
		343	to be able to quickly append elements, so this extension accepts
		344	comma at the end of such items not just between them:
		345
		346	[
		347	1,
		348	2, <- this comma not normally allowed
		349	]
		350	{
		351	"k1": "v1",
		352	"k2": "v2", <- this comma not normally allowed
		353	}
		354
		355	* shell-style '#'-comments
		356
		357	Whenever JSON allows whitespace, shell-style comments are
		358	additionally allowed. They are terminated by the first
		359	carriage-return or line-feed character, after which more
		360	white-space and comments are allowed.
		361
		362	[
		363	1, # this comment not allowed in JSON
		364	# neither this one...
		365	]
		366
245	$json = $json->canonical ([$enable])	367	$json = $json->canonical ([$enable])
		368	$enabled = $json->get_canonical
246	If $enable is true (or missing), then the "encode" method will	369	If $enable is true (or missing), then the "encode" method will
247	output JSON objects by sorting their keys. This is adding a	370	output JSON objects by sorting their keys. This is adding a
248	comparatively high overhead.	371	comparatively high overhead.
249		372
250	If $enable is false, then the "encode" method will output key-value	373	If $enable is false, then the "encode" method will output key-value
251	pairs in the order Perl stores them (which will likely change	374	pairs in the order Perl stores them (which will likely change
252	between runs of the same script).	375	between runs of the same script).
253		376
254	This option is useful if you want the same data structure to be	377	This option is useful if you want the same data structure to be
255	encoded as the same JSON text (given the same overall settings). If	378	encoded as the same JSON text (given the same overall settings). If
256	it is disabled, the same hash migh be encoded differently even if	379	it is disabled, the same hash might be encoded differently even if
257	contains the same data, as key-value pairs have no inherent ordering	380	contains the same data, as key-value pairs have no inherent ordering
258	in Perl.	381	in Perl.
259		382
260	This setting has no effect when decoding JSON texts.	383	This setting has no effect when decoding JSON texts.
261		384
262	$json = $json->allow_nonref ([$enable])	385	$json = $json->allow_nonref ([$enable])
		386	$enabled = $json->get_allow_nonref
263	If $enable is true (or missing), then the "encode" method can	387	If $enable is true (or missing), then the "encode" method can
264	convert a non-reference into its corresponding string, number or	388	convert a non-reference into its corresponding string, number or
265	null JSON value, which is an extension to RFC4627. Likewise,	389	null JSON value, which is an extension to RFC4627. Likewise,
266	"decode" will accept those JSON values instead of croaking.	390	"decode" will accept those JSON values instead of croaking.
267		391
…		…
274	"allow_nonref", resulting in an invalid JSON text:	398	"allow_nonref", resulting in an invalid JSON text:
275		399
276	JSON::XS->new->allow_nonref->encode ("Hello, World!")	400	JSON::XS->new->allow_nonref->encode ("Hello, World!")
277	=> "Hello, World!"	401	=> "Hello, World!"
278		402
		403	$json = $json->allow_unknown ([$enable])
		404	$enabled = $json->get_allow_unknown
		405	If $enable is true (or missing), then "encode" will not throw an
		406	exception when it encounters values it cannot represent in JSON (for
		407	example, filehandles) but instead will encode a JSON "null" value.
		408	Note that blessed objects are not included here and are handled
		409	separately by c<allow_nonref>.
		410
		411	If $enable is false (the default), then "encode" will throw an
		412	exception when it encounters anything it cannot encode as JSON.
		413
		414	This option does not affect "decode" in any way, and it is
		415	recommended to leave it off unless you know your communications
		416	partner.
		417
279	$json = $json->allow_blessed ([$enable])	418	$json = $json->allow_blessed ([$enable])
		419	$enabled = $json->get_allow_blessed
280	If $enable is true (or missing), then the "encode" method will not	420	If $enable is true (or missing), then the "encode" method will not
281	barf when it encounters a blessed reference. Instead, the value of	421	barf when it encounters a blessed reference. Instead, the value of
282	the convert_blessed option will decide wether "null"	422	the convert_blessed option will decide whether "null"
283	("convert_blessed" disabled or no "to_json" method found) or a	423	("convert_blessed" disabled or no "TO_JSON" method found) or a
284	representation of the object ("convert_blessed" enabled and	424	representation of the object ("convert_blessed" enabled and
285	"to_json" method found) is being encoded. Has no effect on "decode".	425	"TO_JSON" method found) is being encoded. Has no effect on "decode".
286		426
287	If $enable is false (the default), then "encode" will throw an	427	If $enable is false (the default), then "encode" will throw an
288	exception when it encounters a blessed object.	428	exception when it encounters a blessed object.
289		429
290	$json = $json->convert_blessed ([$enable])	430	$json = $json->convert_blessed ([$enable])
		431	$enabled = $json->get_convert_blessed
291	If $enable is true (or missing), then "encode", upon encountering a	432	If $enable is true (or missing), then "encode", upon encountering a
292	blessed object, will check for the availability of the "TO_JSON"	433	blessed object, will check for the availability of the "TO_JSON"
293	method on the object's class. If found, it will be called in scalar	434	method on the object's class. If found, it will be called in scalar
294	context and the resulting scalar will be encoded instead of the	435	context and the resulting scalar will be encoded instead of the
295	object. If no "TO_JSON" method is found, the value of	436	object. If no "TO_JSON" method is found, the value of
…		…
299	returns other blessed objects, those will be handled in the same	440	returns other blessed objects, those will be handled in the same
300	way. "TO_JSON" must take care of not causing an endless recursion	441	way. "TO_JSON" must take care of not causing an endless recursion
301	cycle (== crash) in this case. The name of "TO_JSON" was chosen	442	cycle (== crash) in this case. The name of "TO_JSON" was chosen
302	because other methods called by the Perl core (== not by the user of	443	because other methods called by the Perl core (== not by the user of
303	the object) are usually in upper case letters and to avoid	444	the object) are usually in upper case letters and to avoid
304	collisions with the "to_json" function.	445	collisions with any "to_json" function or method.
305		446
306	This setting does not yet influence "decode" in any way, but in the	447	This setting does not yet influence "decode" in any way, but in the
307	future, global hooks might get installed that influence "decode" and	448	future, global hooks might get installed that influence "decode" and
308	are enabled by this setting.	449	are enabled by this setting.
309		450
…		…
350		491
351	As this callback gets called less often then the	492	As this callback gets called less often then the
352	"filter_json_object" one, decoding speed will not usually suffer as	493	"filter_json_object" one, decoding speed will not usually suffer as
353	much. Therefore, single-key objects make excellent targets to	494	much. Therefore, single-key objects make excellent targets to
354	serialise Perl objects into, especially as single-key JSON objects	495	serialise Perl objects into, especially as single-key JSON objects
355	are as close to the type-tagged value concept as JSON gets (its	496	are as close to the type-tagged value concept as JSON gets (it's
356	basically an ID/VALUE tuple). Of course, JSON does not support this	497	basically an ID/VALUE tuple). Of course, JSON does not support this
357	in any way, so you need to make sure your data never looks like a	498	in any way, so you need to make sure your data never looks like a
358	serialised Perl hash.	499	serialised Perl hash.
359		500
360	Typical names for the single object key are "__class_whatever__", or	501	Typical names for the single object key are "__class_whatever__", or
…		…
385		526
386	{ __widget__ => $self->{id} }	527	{ __widget__ => $self->{id} }
387	}	528	}
388		529
389	$json = $json->shrink ([$enable])	530	$json = $json->shrink ([$enable])
		531	$enabled = $json->get_shrink
390	Perl usually over-allocates memory a bit when allocating space for	532	Perl usually over-allocates memory a bit when allocating space for
391	strings. This flag optionally resizes strings generated by either	533	strings. This flag optionally resizes strings generated by either
392	"encode" or "decode" to their minimum size possible. This can save	534	"encode" or "decode" to their minimum size possible. This can save
393	memory when your JSON texts are either very very long or you have	535	memory when your JSON texts are either very very long or you have
394	many short strings. It will also try to downgrade any strings to	536	many short strings. It will also try to downgrade any strings to
…		…
412	converting strings that look like integers or floats into integers	554	converting strings that look like integers or floats into integers
413	or floats internally (there is no difference on the Perl level),	555	or floats internally (there is no difference on the Perl level),
414	saving space.	556	saving space.
415		557
416	$json = $json->max_depth ([$maximum_nesting_depth])	558	$json = $json->max_depth ([$maximum_nesting_depth])
		559	$max_depth = $json->get_max_depth
417	Sets the maximum nesting level (default 512) accepted while encoding	560	Sets the maximum nesting level (default 512) accepted while encoding
418	or decoding. If the JSON text or Perl data structure has an equal or	561	or decoding. If a higher nesting level is detected in JSON text or a
419	higher nesting level then this limit, then the encoder and decoder	562	Perl data structure, then the encoder and decoder will stop and
420	will stop and croak at that point.	563	croak at that point.
421		564
422	Nesting level is defined by number of hash- or arrayrefs that the	565	Nesting level is defined by number of hash- or arrayrefs that the
423	encoder needs to traverse to reach a given point or the number of	566	encoder needs to traverse to reach a given point or the number of
424	"{" or "[" characters without their matching closing parenthesis	567	"{" or "[" characters without their matching closing parenthesis
425	crossed to reach a given character in a string.	568	crossed to reach a given character in a string.
426		569
427	Setting the maximum depth to one disallows any nesting, so that	570	Setting the maximum depth to one disallows any nesting, so that
428	ensures that the object is only a single hash/object or array.	571	ensures that the object is only a single hash/object or array.
429		572
430	The argument to "max_depth" will be rounded up to the next highest
431	power of two. If no argument is given, the highest possible setting	573	If no argument is given, the highest possible setting will be used,
432	will be used, which is rarely useful.	574	which is rarely useful.
		575
		576	Note that nesting is implemented by recursion in C. The default
		577	value has been chosen to be as large as typical operating systems
		578	allow without crashing.
433		579
434	See SECURITY CONSIDERATIONS, below, for more info on why this is	580	See SECURITY CONSIDERATIONS, below, for more info on why this is
435	useful.	581	useful.
436		582
437	$json = $json->max_size ([$maximum_string_size])	583	$json = $json->max_size ([$maximum_string_size])
		584	$max_size = $json->get_max_size
438	Set the maximum length a JSON text may have (in bytes) where	585	Set the maximum length a JSON text may have (in bytes) where
439	decoding is being attempted. The default is 0, meaning no limit.	586	decoding is being attempted. The default is 0, meaning no limit.
440	When "decode" is called on a string longer then this number of	587	When "decode" is called on a string that is longer then this many
441	characters it will not attempt to decode the string but throw an	588	bytes, it will not attempt to decode the string but throw an
442	exception. This setting has no effect on "encode" (yet).	589	exception. This setting has no effect on "encode" (yet).
443		590
444	The argument to "max_size" will be rounded up to the next highest
445	power of two (so may be more than requested). If no argument is
446	given, the limit check will be deactivated (same as when 0 is	591	If no argument is given, the limit check will be deactivated (same
447	specified).	592	as when 0 is specified).
448		593
449	See SECURITY CONSIDERATIONS, below, for more info on why this is	594	See SECURITY CONSIDERATIONS, below, for more info on why this is
450	useful.	595	useful.
451		596
452	$json_text = $json->encode ($perl_scalar)	597	$json_text = $json->encode ($perl_scalar)
…		…
477	and you need to know where the JSON text ends.	622	and you need to know where the JSON text ends.
478		623
479	JSON::XS->new->decode_prefix ("[1] the tail")	624	JSON::XS->new->decode_prefix ("[1] the tail")
480	=> ([], 3)	625	=> ([], 3)
481		626
		627	INCREMENTAL PARSING
		628	[This section and the API it details is still EXPERIMENTAL]
		629
		630	In some cases, there is the need for incremental parsing of JSON texts.
		631	While this module always has to keep both JSON text and resulting Perl
		632	data structure in memory at one time, it does allow you to parse a JSON
		633	stream incrementally. It does so by accumulating text until it has a
		634	full JSON object, which it then can decode. This process is similar to
		635	using "decode_prefix" to see if a full JSON object is available, but is
		636	much more efficient (JSON::XS will only attempt to parse the JSON text
		637	once it is sure it has enough text to get a decisive result, using a
		638	very simple but truly incremental parser).
		639
		640	The following two methods deal with this.
		641
		642	[void, scalar or list context] = $json->incr_parse ([$string])
		643	This is the central parsing function. It can both append new text
		644	and extract objects from the stream accumulated so far (both of
		645	these functions are optional).
		646
		647	If $string is given, then this string is appended to the already
		648	existing JSON fragment stored in the $json object.
		649
		650	After that, if the function is called in void context, it will
		651	simply return without doing anything further. This can be used to
		652	add more text in as many chunks as you want.
		653
		654	If the method is called in scalar context, then it will try to
		655	extract exactly one JSON object. If that is successful, it will
		656	return this object, otherwise it will return "undef". If there is a
		657	parse error, this method will croak just as "decode" would do (one
		658	can then use "incr_skip" to skip the errornous part). This is the
		659	most common way of using the method.
		660
		661	And finally, in list context, it will try to extract as many objects
		662	from the stream as it can find and return them, or the empty list
		663	otherwise. For this to work, there must be no separators between the
		664	JSON objects or arrays, instead they must be concatenated
		665	back-to-back. If an error occurs, an exception will be raised as in
		666	the scalar context case. Note that in this case, any
		667	previously-parsed JSON texts will be lost.
		668
		669	$lvalue_string = $json->incr_text
		670	This method returns the currently stored JSON fragment as an lvalue,
		671	that is, you can manipulate it. This only works when a preceding
		672	call to "incr_parse" in scalar context successfully returned an
		673	object. Under all other circumstances you must not call this
		674	function (I mean it. although in simple tests it might actually
		675	work, it will fail under real world conditions). As a special
		676	exception, you can also call this method before having parsed
		677	anything.
		678
		679	This function is useful in two cases: a) finding the trailing text
		680	after a JSON object or b) parsing multiple JSON objects separated by
		681	non-JSON text (such as commas).
		682
		683	$json->incr_skip
		684	This will reset the state of the incremental parser and will remove
		685	the parsed text from the input buffer. This is useful after
		686	"incr_parse" died, in which case the input buffer and incremental
		687	parser state is left unchanged, to skip the text parsed so far and
		688	to reset the parse state.
		689
		690	LIMITATIONS
		691	All options that affect decoding are supported, except "allow_nonref".
		692	The reason for this is that it cannot be made to work sensibly: JSON
		693	objects and arrays are self-delimited, i.e. you can concatenate them
		694	back to back and still decode them perfectly. This does not hold true
		695	for JSON numbers, however.
		696
		697	For example, is the string 1 a single JSON number, or is it simply the
		698	start of 12? Or is 12 a single JSON number, or the concatenation of 1
		699	and 2? In neither case you can tell, and this is why JSON::XS takes the
		700	conservative route and disallows this case.
		701
		702	EXAMPLES
		703	Some examples will make all this clearer. First, a simple example that
		704	works similarly to "decode_prefix": We want to decode the JSON object at
		705	the start of a string and identify the portion after the JSON object:
		706
		707	my $text = "[1,2,3] hello";
		708
		709	my $json = new JSON::XS;
		710
		711	my $obj = $json->incr_parse ($text)
		712	or die "expected JSON object or array at beginning of string";
		713
		714	my $tail = $json->incr_text;
		715	# $tail now contains " hello"
		716
		717	Easy, isn't it?
		718
		719	Now for a more complicated example: Imagine a hypothetical protocol
		720	where you read some requests from a TCP stream, and each request is a
		721	JSON array, without any separation between them (in fact, it is often
		722	useful to use newlines as "separators", as these get interpreted as
		723	whitespace at the start of the JSON text, which makes it possible to
		724	test said protocol with "telnet"...).
		725
		726	Here is how you'd do it (it is trivial to write this in an event-based
		727	manner):
		728
		729	my $json = new JSON::XS;
		730
		731	# read some data from the socket
		732	while (sysread $socket, my $buf, 4096) {
		733
		734	# split and decode as many requests as possible
		735	for my $request ($json->incr_parse ($buf)) {
		736	# act on the $request
		737	}
		738	}
		739
		740	Another complicated example: Assume you have a string with JSON objects
		741	or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
		742	[3]"). To parse them, we have to skip the commas between the JSON texts,
		743	and here is where the lvalue-ness of "incr_text" comes in useful:
		744
		745	my $text = "[1],[2], [3]";
		746	my $json = new JSON::XS;
		747
		748	# void context, so no parsing done
		749	$json->incr_parse ($text);
		750
		751	# now extract as many objects as possible. note the
		752	# use of scalar context so incr_text can be called.
		753	while (my $obj = $json->incr_parse) {
		754	# do something with $obj
		755
		756	# now skip the optional comma
		757	$json->incr_text =~ s/^ \s* , //x;
		758	}
		759
		760	Now lets go for a very complex example: Assume that you have a gigantic
		761	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		762	but you cannot load it into memory fully (this has actually happened in
		763	the real world :).
		764
		765	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		766	can still help you: You implement a (very simple) array parser and let
		767	JSON decode the array elements, which are all full JSON objects on their
		768	own (this wouldn't work if the array elements could be JSON numbers, for
		769	example):
		770
		771	my $json = new JSON::XS;
		772
		773	# open the monster
		774	open my $fh, "<bigfile.json"
		775	or die "bigfile: $!";
		776
		777	# first parse the initial "["
		778	for (;;) {
		779	sysread $fh, my $buf, 65536
		780	or die "read error: $!";
		781	$json->incr_parse ($buf); # void context, so no parsing
		782
		783	# Exit the loop once we found and removed(!) the initial "[".
		784	# In essence, we are (ab-)using the $json object as a simple scalar
		785	# we append data to.
		786	last if $json->incr_text =~ s/^ \s* \[ //x;
		787	}
		788
		789	# now we have the skipped the initial "[", so continue
		790	# parsing all the elements.
		791	for (;;) {
		792	# in this loop we read data until we got a single JSON object
		793	for (;;) {
		794	if (my $obj = $json->incr_parse) {
		795	# do something with $obj
		796	last;
		797	}
		798
		799	# add more data
		800	sysread $fh, my $buf, 65536
		801	or die "read error: $!";
		802	$json->incr_parse ($buf); # void context, so no parsing
		803	}
		804
		805	# in this loop we read data until we either found and parsed the
		806	# separating "," between elements, or the final "]"
		807	for (;;) {
		808	# first skip whitespace
		809	$json->incr_text =~ s/^\s*//;
		810
		811	# if we find "]", we are done
		812	if ($json->incr_text =~ s/^\]//) {
		813	print "finished.\n";
		814	exit;
		815	}
		816
		817	# if we find ",", we can continue with the next element
		818	if ($json->incr_text =~ s/^,//) {
		819	last;
		820	}
		821
		822	# if we find anything else, we have a parse error!
		823	if (length $json->incr_text) {
		824	die "parse error near ", $json->incr_text;
		825	}
		826
		827	# else add more data
		828	sysread $fh, my $buf, 65536
		829	or die "read error: $!";
		830	$json->incr_parse ($buf); # void context, so no parsing
		831	}
		832
		833	This is a complex example, but most of the complexity comes from the
		834	fact that we are trying to be correct (bear with me if I am wrong, I
		835	never ran the above example :).
		836
482	MAPPING	837	MAPPING
483	This section describes how JSON::XS maps Perl values to JSON values and	838	This section describes how JSON::XS maps Perl values to JSON values and
484	vice versa. These mappings are designed to "do the right thing" in most	839	vice versa. These mappings are designed to "do the right thing" in most
485	circumstances automatically, preserving round-tripping characteristics	840	circumstances automatically, preserving round-tripping characteristics
486	(what you put in comes out as something equivalent).	841	(what you put in comes out as something equivalent).
487		842
488	For the more enlightened: note that in the following descriptions,	843	For the more enlightened: note that in the following descriptions,
489	lowercase perl refers to the Perl interpreter, while uppcercase Perl	844	lowercase perl refers to the Perl interpreter, while uppercase Perl
490	refers to the abstract Perl language itself.	845	refers to the abstract Perl language itself.
491		846
492	JSON -> PERL	847	JSON -> PERL
493	object	848	object
494	A JSON object becomes a reference to a hash in Perl. No ordering of	849	A JSON object becomes a reference to a hash in Perl. No ordering of
495	object keys is preserved (JSON does not preserver object key	850	object keys is preserved (JSON does not preserve object key ordering
496	ordering itself).	851	itself).
497		852
498	array	853	array
499	A JSON array becomes a reference to an array in Perl.	854	A JSON array becomes a reference to an array in Perl.
500		855
501	string	856	string
…		…
507	A JSON number becomes either an integer, numeric (floating point) or	862	A JSON number becomes either an integer, numeric (floating point) or
508	string scalar in perl, depending on its range and any fractional	863	string scalar in perl, depending on its range and any fractional
509	parts. On the Perl level, there is no difference between those as	864	parts. On the Perl level, there is no difference between those as
510	Perl handles all the conversion details, but an integer may take	865	Perl handles all the conversion details, but an integer may take
511	slightly less memory and might represent more values exactly than	866	slightly less memory and might represent more values exactly than
512	(floating point) numbers.	867	floating point numbers.
513		868
514	If the number consists of digits only, JSON::XS will try to	869	If the number consists of digits only, JSON::XS will try to
515	represent it as an integer value. If that fails, it will try to	870	represent it as an integer value. If that fails, it will try to
516	represent it as a numeric (floating point) value if that is possible	871	represent it as a numeric (floating point) value if that is possible
517	without loss of precision. Otherwise it will preserve the number as	872	without loss of precision. Otherwise it will preserve the number as
518	a string value.	873	a string value (in which case you lose roundtripping ability, as the
		874	JSON number will be re-encoded toa JSON string).
519		875
520	Numbers containing a fractional or exponential part will always be	876	Numbers containing a fractional or exponential part will always be
521	represented as numeric (floating point) values, possibly at a loss	877	represented as numeric (floating point) values, possibly at a loss
522	of precision.	878	of precision (in which case you might lose perfect roundtripping
523		879	ability, but the JSON number will still be re-encoded as a JSON
524	This might create round-tripping problems as numbers might become	880	number).
525	strings, but as Perl is typeless there is no other way to do it.
526		881
527	true, false	882	true, false
528	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",	883	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
529	respectively. They are overloaded to act almost exactly like the	884	respectively. They are overloaded to act almost exactly like the
530	numbers 1 and 0. You can check wether a scalar is a JSON boolean by	885	numbers 1 and 0. You can check whether a scalar is a JSON boolean by
531	using the "JSON::XS::is_bool" function.	886	using the "JSON::XS::is_bool" function.
532		887
533	null	888	null
534	A JSON null atom becomes "undef" in Perl.	889	A JSON null atom becomes "undef" in Perl.
535		890
…		…
558	an exception to be thrown, except for references to the integers 0	913	an exception to be thrown, except for references to the integers 0
559	and 1, which get turned into "false" and "true" atoms in JSON. You	914	and 1, which get turned into "false" and "true" atoms in JSON. You
560	can also use "JSON::XS::false" and "JSON::XS::true" to improve	915	can also use "JSON::XS::false" and "JSON::XS::true" to improve
561	readability.	916	readability.
562		917
563	to_json [\0,JSON::XS::true] # yields [false,true]	918	encode_json [\0,JSON::XS::true] # yields [false,true]
564		919
565	JSON::XS::true, JSON::XS::false	920	JSON::XS::true, JSON::XS::false
566	These special values become JSON true and JSON false values,	921	These special values become JSON true and JSON false values,
567	respectively. You cna alos use "\1" and "\0" directly if you want.	922	respectively. You can also use "\1" and "\0" directly if you want.
568		923
569	blessed objects	924	blessed objects
570	Blessed objects are not allowed. JSON::XS currently tries to encode	925	Blessed objects are not directly representable in JSON. See the
571	their underlying representation (hash- or arrayref), but this	926	"allow_blessed" and "convert_blessed" methods on various options on
572	behaviour might change in future versions.	927	how to deal with this: basically, you can choose between throwing an
		928	exception, encoding the reference as if it weren't blessed, or
		929	provide your own serialiser method.
573		930
574	simple scalars	931	simple scalars
575	Simple Perl scalars (any scalar that is not a reference) are the	932	Simple Perl scalars (any scalar that is not a reference) are the
576	most difficult objects to encode: JSON::XS will encode undefined	933	most difficult objects to encode: JSON::XS will encode undefined
577	scalars as JSON null value, scalars that have last been used in a	934	scalars as JSON "null" values, scalars that have last been used in a
578	string context before encoding as JSON strings and anything else as	935	string context before encoding as JSON strings, and anything else as
579	number value:	936	number value:
580		937
581	# dump as number	938	# dump as number
582	to_json [2] # yields [2]	939	encode_json [2] # yields [2]
583	to_json [-3.0e17] # yields [-3e+17]	940	encode_json [-3.0e17] # yields [-3e+17]
584	my $value = 5; to_json [$value] # yields [5]	941	my $value = 5; encode_json [$value] # yields [5]
585		942
586	# used as string, so dump as string	943	# used as string, so dump as string
587	print $value;	944	print $value;
588	to_json [$value] # yields ["5"]	945	encode_json [$value] # yields ["5"]
589		946
590	# undef becomes null	947	# undef becomes null
591	to_json [undef] # yields [null]	948	encode_json [undef] # yields [null]
592		949
593	You can force the type to be a string by stringifying it:	950	You can force the type to be a JSON string by stringifying it:
594		951
595	my $x = 3.1; # some variable containing a number	952	my $x = 3.1; # some variable containing a number
596	"$x"; # stringified	953	"$x"; # stringified
597	$x .= ""; # another, more awkward way to stringify	954	$x .= ""; # another, more awkward way to stringify
598	print $x; # perl does it for you, too, quite often	955	print $x; # perl does it for you, too, quite often
599		956
600	You can force the type to be a number by numifying it:	957	You can force the type to be a JSON number by numifying it:
601		958
602	my $x = "3"; # some variable containing a string	959	my $x = "3"; # some variable containing a string
603	$x += 0; # numify it, ensuring it will be dumped as a number	960	$x += 0; # numify it, ensuring it will be dumped as a number
604	$x *= 1; # same thing, the choise is yours.	961	$x *= 1; # same thing, the choice is yours.
605		962
606	You can not currently output JSON booleans or force the type in	963	You can not currently force the type in other, less obscure, ways.
607	other, less obscure, ways. Tell me if you need this capability.	964	Tell me if you need this capability (but don't forget to explain why
		965	it's needed :).
608		966
609	COMPARISON	967	ENCODING/CODESET FLAG NOTES
610	As already mentioned, this module was created because none of the	968	The interested reader might have seen a number of flags that signify
611	existing JSON modules could be made to work correctly. First I will	969	encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
612	describe the problems (or pleasures) I encountered with various existing	970	some confusion on what these do, so here is a short comparison:
613	JSON modules, followed by some benchmark values. JSON::XS was designed
614	not to suffer from any of these problems or limitations.
615		971
616	JSON 1.07	972	"utf8" controls whether the JSON text created by "encode" (and expected
617	Slow (but very portable, as it is written in pure Perl).	973	by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
		974	control whether "encode" escapes character values outside their
		975	respective codeset range. Neither of these flags conflict with each
		976	other, although some combinations make less sense than others.
618		977
619	Undocumented/buggy Unicode handling (how JSON handles unicode values	978	Care has been taken to make all flags symmetrical with respect to
620	is undocumented. One can get far by feeding it unicode strings and	979	"encode" and "decode", that is, texts encoded with any combination of
621	doing en-/decoding oneself, but unicode escapes are not working	980	these flag values will be correctly decoded when the same flags are used
		981	- in general, if you use different flag settings while encoding vs. when
		982	decoding you likely have a bug somewhere.
		983
		984	Below comes a verbose discussion of these flags. Note that a "codeset"
		985	is simply an abstract set of character-codepoint pairs, while an
		986	encoding takes those codepoint numbers and encodes them, in our case
		987	into octets. Unicode is (among other things) a codeset, UTF-8 is an
		988	encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets and
		989	encodings at the same time, which can be confusing.
		990
		991	"utf8" flag disabled
		992	When "utf8" is disabled (the default), then "encode"/"decode"
		993	generate and expect Unicode strings, that is, characters with high
		994	ordinal Unicode values (> 255) will be encoded as such characters,
		995	and likewise such characters are decoded as-is, no canges to them
		996	will be done, except "(re-)interpreting" them as Unicode codepoints
		997	or Unicode characters, respectively (to Perl, these are the same
		998	thing in strings unless you do funny/weird/dumb stuff).
		999
		1000	This is useful when you want to do the encoding yourself (e.g. when
		1001	you want to have UTF-16 encoded JSON texts) or when some other layer
		1002	does the encoding for you (for example, when printing to a terminal
		1003	using a filehandle that transparently encodes to UTF-8 you certainly
		1004	do NOT want to UTF-8 encode your data first and have Perl encode it
		1005	another time).
		1006
		1007	"utf8" flag enabled
		1008	If the "utf8"-flag is enabled, "encode"/"decode" will encode all
		1009	characters using the corresponding UTF-8 multi-byte sequence, and
		1010	will expect your input strings to be encoded as UTF-8, that is, no
		1011	"character" of the input string must have any value > 255, as UTF-8
		1012	does not allow that.
		1013
		1014	The "utf8" flag therefore switches between two modes: disabled means
		1015	you will get a Unicode string in Perl, enabled means you get an
		1016	UTF-8 encoded octet/binary string in Perl.
		1017
		1018	"latin1" or "ascii" flags enabled
		1019	With "latin1" (or "ascii") enabled, "encode" will escape characters
		1020	with ordinal values > 255 (> 127 with "ascii") and encode the
		1021	remaining characters as specified by the "utf8" flag.
		1022
		1023	If "utf8" is disabled, then the result is also correctly encoded in
		1024	those character sets (as both are proper subsets of Unicode, meaning
		1025	that a Unicode string with all character values < 256 is the same
		1026	thing as a ISO-8859-1 string, and a Unicode string with all
		1027	character values < 128 is the same thing as an ASCII string in
622	properly).	1028	Perl).
623		1029
624	No roundtripping (strings get clobbered if they look like numbers,	1030	If "utf8" is enabled, you still get a correct UTF-8-encoded string,
625	e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that	1031	regardless of these flags, just some more characters will be escaped
626	will decode into the number 2.	1032	using "\uXXXX" then before.
627		1033
628	JSON::PC 0.01	1034	Note that ISO-8859-1-encoded strings are not compatible with UTF-8
629	Very fast.	1035	encoding, while ASCII-encoded strings are. That is because the
		1036	ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
		1037	codeset being a subset of Unicode), while ASCII is.
630		1038
631	Undocumented/buggy Unicode handling.	1039	Surprisingly, "decode" will ignore these flags and so treat all
		1040	input values as governed by the "utf8" flag. If it is disabled, this
		1041	allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
		1042	strict subsets of Unicode. If it is enabled, you can correctly
		1043	decode UTF-8 encoded strings.
632		1044
633	No roundtripping.	1045	So neither "latin1" nor "ascii" are incompatible with the "utf8"
		1046	flag - they only govern when the JSON output engine escapes a
		1047	character or not.
634		1048
635	Has problems handling many Perl values (e.g. regex results and other	1049	The main use for "latin1" is to relatively efficiently store binary
636	magic values will make it croak).	1050	data as JSON, at the expense of breaking compatibility with most
		1051	JSON decoders.
637		1052
638	Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}"	1053	The main use for "ascii" is to force the output to not contain
639	which is not a valid JSON text.	1054	characters with values > 127, which means you can interpret the
640		1055	resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
641	Unmaintained (maintainer unresponsive for many months, bugs are not	1056	any character set and 8-bit-encoding, and still get the same data
642	getting fixed).	1057	structure back. This is useful when your channel for JSON transfer
643		1058	is not 8-bit clean or the encoding might be mangled in between (e.g.
644	JSON::Syck 0.21	1059	in mail), and works because ASCII is a proper subset of most 8-bit
645	Very buggy (often crashes).	1060	and multibyte encodings in use in the world.
646
647	Very inflexible (no human-readable format supported, format pretty
648	much undocumented. I need at least a format for easy reading by
649	humans and a single-line compact format for use in a protocol, and
650	preferably a way to generate ASCII-only JSON texts).
651
652	Completely broken (and confusingly documented) Unicode handling
653	(unicode escapes are not working properly, you need to set
654	ImplicitUnicode to different values on en- and decoding to get
655	symmetric behaviour).
656
657	No roundtripping (simple cases work, but this depends on wether the
658	scalar value was used in a numeric context or not).
659
660	Dumping hashes may skip hash values depending on iterator state.
661
662	Unmaintained (maintainer unresponsive for many months, bugs are not
663	getting fixed).
664
665	Does not check input for validity (i.e. will accept non-JSON input
666	and return "something" instead of raising an exception. This is a
667	security issue: imagine two banks transfering money between each
668	other using JSON. One bank might parse a given non-JSON request and
669	deduct money, while the other might reject the transaction with a
670	syntax error. While a good protocol will at least recover, that is
671	extra unnecessary work and the transaction will still not succeed).
672
673	JSON::DWIW 0.04
674	Very fast. Very natural. Very nice.
675
676	Undocumented unicode handling (but the best of the pack. Unicode
677	escapes still don't get parsed properly).
678
679	Very inflexible.
680
681	No roundtripping.
682
683	Does not generate valid JSON texts (key strings are often unquoted,
684	empty keys result in nothing being output)
685
686	Does not check input for validity.
687		1061
688	JSON and YAML	1062	JSON and YAML
689	You often hear that JSON is a subset (or a close subset) of YAML. This	1063	You often hear that JSON is a subset of YAML. This is, however, a mass
690	is, however, a mass hysteria and very far from the truth. In general,	1064	hysteria(*) and very far from the truth (as of the time of this
691	there is no way to configure JSON::XS to output a data structure as	1065	writing), so let me state it clearly: *in general, there is no way to
692	valid YAML.	1066	configure JSON::XS to output a data structure as valid YAML* that works
		1067	in all cases.
693		1068
694	If you really must use JSON::XS to generate YAML, you should use this	1069	If you really must use JSON::XS to generate YAML, you should use this
695	algorithm (subject to change in future versions):	1070	algorithm (subject to change in future versions):
696		1071
697	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1072	my $to_yaml = JSON::XS->new->utf8->space_after (1);
698	my $yaml = $to_yaml->encode ($ref) . "\n";	1073	my $yaml = $to_yaml->encode ($ref) . "\n";
699		1074
700	This will usually generate JSON texts that also parse as valid YAML.	1075	This will usually generate JSON texts that also parse as valid YAML.
701	Please note that YAML has hardcoded limits on (simple) object key	1076	Please note that YAML has hardcoded limits on (simple) object key
702	lengths that JSON doesn't have, so you should make sure that your hash	1077	lengths that JSON doesn't have and also has different and incompatible
		1078	unicode handling, so you should make sure that your hash keys are
703	keys are noticably shorter than the 1024 characters YAML allows.	1079	noticeably shorter than the 1024 "stream characters" YAML allows and
		1080	that you do not have characters with codepoint values outside the
		1081	Unicode BMP (basic multilingual page). YAML also does not allow "\/"
		1082	sequences in strings (which JSON::XS does not currently generate, but
		1083	other JSON generators might).
704		1084
705	There might be other incompatibilities that I am not aware of. In	1085	There might be other incompatibilities that I am not aware of (or the
		1086	YAML specification has been changed yet again - it does so quite often).
706	general you should not try to generate YAML with a JSON generator or	1087	In general you should not try to generate YAML with a JSON generator or
707	vice versa, or try to parse JSON with a YAML parser or vice versa:	1088	vice versa, or try to parse JSON with a YAML parser or vice versa:
708	chances are high that you will run into severe interoperability	1089	chances are high that you will run into severe interoperability problems
709	problems.	1090	when you least expect it.
		1091
		1092	(*) I have been pressured multiple times by Brian Ingerson (one of the
		1093	authors of the YAML specification) to remove this paragraph, despite
		1094	him acknowledging that the actual incompatibilities exist. As I was
		1095	personally bitten by this "JSON is YAML" lie, I refused and said I
		1096	will continue to educate people about these issues, so others do not
		1097	run into the same problem again and again. After this, Brian called
		1098	me a (quote)complete and worthless idiot(unquote).
		1099
		1100	In my opinion, instead of pressuring and insulting people who
		1101	actually clarify issues with YAML and the wrong statements of some
		1102	of its proponents, I would kindly suggest reading the JSON spec
		1103	(which is not that difficult or long) and finally make YAML
		1104	compatible to it, and educating users about the changes, instead of
		1105	spreading lies about the real compatibility for many years and
		1106	trying to silence people who point out that it isn't true.
710		1107
711	SPEED	1108	SPEED
712	It seems that JSON::XS is surprisingly fast, as shown in the following	1109	It seems that JSON::XS is surprisingly fast, as shown in the following
713	tables. They have been generated with the help of the "eg/bench" program	1110	tables. They have been generated with the help of the "eg/bench" program
714	in the JSON::XS distribution, to make it easy to compare on your own	1111	in the JSON::XS distribution, to make it easy to compare on your own
715	system.	1112	system.
716		1113
717	First comes a comparison between various modules using a very short	1114	First comes a comparison between various modules using a very short
718	single-line JSON string:	1115	single-line JSON string (also available at
		1116	<http://dist.schmorp.de/misc/json/short.json>).
719		1117
720	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1118	{"method": "handleMessage", "params": ["user1",
721	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1119	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1120	true, false]}
722		1121
723	It shows the number of encodes/decodes per second (JSON::XS uses the	1122	It shows the number of encodes/decodes per second (JSON::XS uses the
724	functional interface, while JSON::XS/2 uses the OO interface with	1123	functional interface, while JSON::XS/2 uses the OO interface with
725	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).	1124	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
726	Higher is better:	1125	Higher is better:
727		1126
728	Storable \| 15779.925 \| 14169.946 \|
729	-----------+------------+------------+
730	module \| encode \| decode \|	1127	module \| encode \| decode \|
731	-----------\|------------\|------------\|	1128	-----------\|------------\|------------\|
732	JSON \| 4990.842 \| 4088.813 \|	1129	JSON 1.x \| 4990.842 \| 4088.813 \|
733	JSON::DWIW \| 51653.990 \| 71575.154 \|	1130	JSON::DWIW \| 51653.990 \| 71575.154 \|
734	JSON::PC \| 65948.176 \| 74631.744 \|	1131	JSON::PC \| 65948.176 \| 74631.744 \|
735	JSON::PP \| 8931.652 \| 3817.168 \|	1132	JSON::PP \| 8931.652 \| 3817.168 \|
736	JSON::Syck \| 24877.248 \| 27776.848 \|	1133	JSON::Syck \| 24877.248 \| 27776.848 \|
737	JSON::XS \| 388361.481 \| 227951.304 \|	1134	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
739	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1136	JSON::XS/3 \| 338250.323 \| 218453.333 \|
740	Storable \| 16500.016 \| 135300.129 \|	1137	Storable \| 16500.016 \| 135300.129 \|
741	-----------+------------+------------+	1138	-----------+------------+------------+
742		1139
743	That is, JSON::XS is about five times faster than JSON::DWIW on	1140	That is, JSON::XS is about five times faster than JSON::DWIW on
744	encoding, about three times faster on decoding, and over fourty times	1141	encoding, about three times faster on decoding, and over forty times
745	faster than JSON, even with pretty-printing and key sorting. It also	1142	faster than JSON, even with pretty-printing and key sorting. It also
746	compares favourably to Storable for small amounts of data.	1143	compares favourably to Storable for small amounts of data.
747		1144
748	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1145	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
749	search API (http://nanoref.com/yahooapis/mgPdGg):	1146	search API (<http://dist.schmorp.de/misc/json/long.json>).
750		1147
751	module \| encode \| decode \|	1148	module \| encode \| decode \|
752	-----------\|------------\|------------\|	1149	-----------\|------------\|------------\|
753	JSON \| 55.260 \| 34.971 \|	1150	JSON 1.x \| 55.260 \| 34.971 \|
754	JSON::DWIW \| 825.228 \| 1082.513 \|	1151	JSON::DWIW \| 825.228 \| 1082.513 \|
755	JSON::PC \| 3571.444 \| 2394.829 \|	1152	JSON::PC \| 3571.444 \| 2394.829 \|
756	JSON::PP \| 210.987 \| 32.574 \|	1153	JSON::PP \| 210.987 \| 32.574 \|
757	JSON::Syck \| 552.551 \| 787.544 \|	1154	JSON::Syck \| 552.551 \| 787.544 \|
758	JSON::XS \| 5780.463 \| 4854.519 \|	1155	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
762	-----------+------------+------------+	1159	-----------+------------+------------+
763		1160
764	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1161	Again, JSON::XS leads by far (except for Storable which non-surprisingly
765	decodes faster).	1162	decodes faster).
766		1163
767	On large strings containing lots of high unicode characters, some	1164	On large strings containing lots of high Unicode characters, some
768	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the	1165	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
769	result will be broken due to missing (or wrong) unicode handling. Others	1166	result will be broken due to missing (or wrong) Unicode handling. Others
770	refuse to decode or encode properly, so it was impossible to prepare a	1167	refuse to decode or encode properly, so it was impossible to prepare a
771	fair comparison table for that case.	1168	fair comparison table for that case.
772		1169
773	SECURITY CONSIDERATIONS	1170	SECURITY CONSIDERATIONS
774	When you are using JSON in a protocol, talking to untrusted potentially	1171	When you are using JSON in a protocol, talking to untrusted potentially
…		…
778	have any buffer overflows. Obviously, this module should ensure that and	1175	have any buffer overflows. Obviously, this module should ensure that and
779	I am trying hard on making that true, but you never know.	1176	I am trying hard on making that true, but you never know.
780		1177
781	Second, you need to avoid resource-starving attacks. That means you	1178	Second, you need to avoid resource-starving attacks. That means you
782	should limit the size of JSON texts you accept, or make sure then when	1179	should limit the size of JSON texts you accept, or make sure then when
783	your resources run out, thats just fine (e.g. by using a separate	1180	your resources run out, that's just fine (e.g. by using a separate
784	process that can crash safely). The size of a JSON text in octets or	1181	process that can crash safely). The size of a JSON text in octets or
785	characters is usually a good indication of the size of the resources	1182	characters is usually a good indication of the size of the resources
786	required to decode it into a Perl structure. While JSON::XS can check	1183	required to decode it into a Perl structure. While JSON::XS can check
787	the size of the JSON text, it might be too late when you already have it	1184	the size of the JSON text, it might be too late when you already have it
788	in memory, so you might want to check the size before you accept the	1185	in memory, so you might want to check the size before you accept the
…		…
791	Third, JSON::XS recurses using the C stack when decoding objects and	1188	Third, JSON::XS recurses using the C stack when decoding objects and
792	arrays. The C stack is a limited resource: for instance, on my amd64	1189	arrays. The C stack is a limited resource: for instance, on my amd64
793	machine with 8MB of stack size I can decode around 180k nested arrays	1190	machine with 8MB of stack size I can decode around 180k nested arrays
794	but only 14k nested JSON objects (due to perl itself recursing deeply on	1191	but only 14k nested JSON objects (due to perl itself recursing deeply on
795	croak to free the temporary). If that is exceeded, the program crashes.	1192	croak to free the temporary). If that is exceeded, the program crashes.
796	to be conservative, the default nesting limit is set to 512. If your	1193	To be conservative, the default nesting limit is set to 512. If your
797	process has a smaller stack, you should adjust this setting accordingly	1194	process has a smaller stack, you should adjust this setting accordingly
798	with the "max_depth" method.	1195	with the "max_depth" method.
799		1196
800	And last but least, something else could bomb you that I forgot to think	1197	Something else could bomb you, too, that I forgot to think of. In that
801	of. In that case, you get to keep the pieces. I am always open for	1198	case, you get to keep the pieces. I am always open for hints, though...
802	hints, though...
803		1199
		1200	Also keep in mind that JSON::XS might leak contents of your Perl data
		1201	structures in its error messages, so when you serialise sensitive
		1202	information you might want to make sure that exceptions thrown by
		1203	JSON::XS will not end up in front of untrusted eyes.
		1204
804	If you are using JSON::XS to return packets to consumption by javascript	1205	If you are using JSON::XS to return packets to consumption by JavaScript
805	scripts in a browser you should have a look at	1206	scripts in a browser you should have a look at
806	<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1207	<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
807	you are vulnerable to some common attack vectors (which really are	1208	you are vulnerable to some common attack vectors (which really are
808	browser design bugs, but it is still you who will have to deal with it,	1209	browser design bugs, but it is still you who will have to deal with it,
809	as major browser developers care only for features, not about doing	1210	as major browser developers care only for features, not about getting
810	security right).	1211	security right).
		1212
		1213	THREADS
		1214	This module is not guaranteed to be thread safe and there are no plans
		1215	to change this until Perl gets thread support (as opposed to the
		1216	horribly slow so-called "threads" which are simply slow and bloated
		1217	process simulations - use fork, it's much faster, cheaper, better).
		1218
		1219	(It might actually work, but you have been warned).
811		1220
812	BUGS	1221	BUGS
813	While the goal of this module is to be correct, that unfortunately does	1222	While the goal of this module is to be correct, that unfortunately does
814	not mean its bug-free, only that I think its design is bug-free. It is	1223	not mean it's bug-free, only that I think its design is bug-free. It is
815	still relatively early in its development. If you keep reporting bugs	1224	still relatively early in its development. If you keep reporting bugs
816	they will be fixed swiftly, though.	1225	they will be fixed swiftly, though.
		1226
		1227	Please refrain from using rt.cpan.org or any other bug reporting
		1228	service. I put the contact address into my modules for a reason.
		1229
		1230	SEE ALSO
		1231	The json_xs command line utility for quick experiments.
817		1232
818	AUTHOR	1233	AUTHOR
819	Marc Lehmann <schmorp@schmorp.de>	1234	Marc Lehmann <schmorp@schmorp.de>
820	http://home.schmorp.de/	1235	http://home.schmorp.de/
821		1236

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Comparing JSON-XS/README (file contents): Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC vs. Revision 1.25 by root, Wed Apr 16 18:38:38 2008 UTC

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Comparing JSON-XS/README (file contents):
Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC vs.
Revision 1.25 by root, Wed Apr 16 18:38:38 2008 UTC