[ViewVC] Diff of: cvs/JSON-XS/README

Comparing JSON-XS/README (file contents):
Revision 1.22 by root, Wed Dec 5 10:59:27 2007 UTC vs.
Revision 1.40 by root, Fri Feb 26 21:46:45 2016 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	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	シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	5	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		6
8	SYNOPSIS	7	SYNOPSIS
9	use JSON::XS;	8	use JSON::XS;
10		9
33	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.
34	To reach the latter goal it was written in C.	33	To reach the latter goal it was written in C.
35		34
36	Beginning with version 2.0 of the JSON module, when both JSON and	35	Beginning with version 2.0 of the JSON module, when both JSON and
37	JSON::XS are installed, then JSON will fall back on JSON::XS (this can	36	JSON::XS are installed, then JSON will fall back on JSON::XS (this can
38	be overriden) with no overhead due to emulation (by inheritign	37	be overridden) with no overhead due to emulation (by inheriting
39	constructor and methods). If JSON::XS is not available, it will fall	38	constructor and methods). If JSON::XS is not available, it will fall
40	back to the compatible JSON::PP module as backend, so using JSON instead	39	back to the compatible JSON::PP module as backend, so using JSON instead
41	of JSON::XS gives you a portable JSON API that can be fast when you need	40	of JSON::XS gives you a portable JSON API that can be fast when you need
42	and doesn't require a C compiler when that is a problem.	41	and doesn't require a C compiler when that is a problem.
43		42
…		…
45	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
46	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
47	cases their maintainers are unresponsive, gone missing, or not listening	46	cases their maintainers are unresponsive, gone missing, or not listening
48	to bug reports for other reasons.	47	to bug reports for other reasons.
49		48
50	See COMPARISON, below, for a comparison to some other JSON modules.
51
52	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	49	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
53	vice versa.	50	vice versa.
54		51
55	FEATURES	52	FEATURES
56	* correct Unicode handling	53	* correct Unicode handling
		54
57	This module knows how to handle Unicode, and even documents how and	55	This module knows how to handle Unicode, documents how and when it
58	when it does so.	56	does so, and even documents what "correct" means.
59		57
60	* round-trip integrity	58	* round-trip integrity
		59
61	When you serialise a perl data structure using only datatypes	60	When you serialise a perl data structure using only data types
62	supported by JSON, the deserialised data structure is identical on	61	supported by JSON and Perl, the deserialised data structure is
63	the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"	62	identical on the Perl level. (e.g. the string "2.0" doesn't suddenly
64	just because it looks like a number).	63	become "2" just because it looks like a number). There are minor
		64	exceptions to this, read the MAPPING section below to learn about
		65	those.
65		66
66	* strict checking of JSON correctness	67	* strict checking of JSON correctness
		68
67	There is no guessing, no generating of illegal JSON texts by	69	There is no guessing, no generating of illegal JSON texts by
68	default, and only JSON is accepted as input by default (the latter	70	default, and only JSON is accepted as input by default (the latter
69	is a security feature).	71	is a security feature).
70		72
71	* fast	73	* fast
72	Compared to other JSON modules, this module compares favourably in
73	terms of speed, too.
74		74
		75	Compared to other JSON modules and other serialisers such as
		76	Storable, this module usually compares favourably in terms of speed,
		77	too.
		78
75	* simple to use	79	* simple to use
		80
76	This module has both a simple functional interface as well as an OO	81	This module has both a simple functional interface as well as an
77	interface.	82	object oriented interface.
78		83
79	* reasonably versatile output formats	84	* reasonably versatile output formats
		85
80	You can choose between the most compact guaranteed single-line	86	You can choose between the most compact guaranteed-single-line
81	format possible (nice for simple line-based protocols), a pure-ascii	87	format possible (nice for simple line-based protocols), a pure-ASCII
82	format (for when your transport is not 8-bit clean, still supports	88	format (for when your transport is not 8-bit clean, still supports
83	the whole Unicode range), or a pretty-printed format (for when you	89	the whole Unicode range), or a pretty-printed format (for when you
84	want to read that stuff). Or you can combine those features in	90	want to read that stuff). Or you can combine those features in
85	whatever way you like.	91	whatever way you like.
86		92
…		…
94		100
95	This function call is functionally identical to:	101	This function call is functionally identical to:
96		102
97	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	103	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
98		104
99	except being faster.	105	Except being faster.
100		106
101	$perl_scalar = decode_json $json_text	107	$perl_scalar = decode_json $json_text
102	The opposite of "encode_json": expects an UTF-8 (binary) string and	108	The opposite of "encode_json": expects an UTF-8 (binary) string and
103	tries to parse that as an UTF-8 encoded JSON text, returning the	109	tries to parse that as an UTF-8 encoded JSON text, returning the
104	resulting reference. Croaks on error.	110	resulting reference. Croaks on error.
105		111
106	This function call is functionally identical to:	112	This function call is functionally identical to:
107		113
108	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	114	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
109		115
110	except being faster.	116	Except being faster.
111
112	$is_boolean = JSON::XS::is_bool $scalar
113	Returns true if the passed scalar represents either JSON::XS::true
114	or JSON::XS::false, two constants that act like 1 and 0,
115	respectively and are used to represent JSON "true" and "false"
116	values in Perl.
117
118	See MAPPING, below, for more information on how JSON values are
119	mapped to Perl.
120		117
121	A FEW NOTES ON UNICODE AND PERL	118	A FEW NOTES ON UNICODE AND PERL
122	Since this often leads to confusion, here are a few very clear words on	119	Since this often leads to confusion, here are a few very clear words on
123	how Unicode works in Perl, modulo bugs.	120	how Unicode works in Perl, modulo bugs.
124		121
125	1. Perl strings can store characters with ordinal values > 255.	122	1. Perl strings can store characters with ordinal values > 255.
126	This enables you to store Unicode characters as single characters in	123	This enables you to store Unicode characters as single characters in
127	a Perl string - very natural.	124	a Perl string - very natural.
128		125
129	2. Perl does not associate an encoding with your strings.	126	2. Perl does not associate an encoding with your strings.
130	Unless you force it to, e.g. when matching it against a regex, or	127	... until you force it to, e.g. when matching it against a regex, or
131	printing the scalar to a file, in which case Perl either interprets	128	printing the scalar to a file, in which case Perl either interprets
132	your string as locale-encoded text, octets/binary, or as Unicode,	129	your string as locale-encoded text, octets/binary, or as Unicode,
133	depending on various settings. In no case is an encoding stored	130	depending on various settings. In no case is an encoding stored
134	together with your data, it is use that decides encoding, not any	131	together with your data, it is use that decides encoding, not any
135	magical metadata.	132	magical meta data.
136		133
137	3. The internal utf-8 flag has no meaning with regards to the encoding	134	3. The internal utf-8 flag has no meaning with regards to the encoding
138	of your string.	135	of your string.
139	Just ignore that flag unless you debug a Perl bug, a module written	136	Just ignore that flag unless you debug a Perl bug, a module written
140	in XS or want to dive into the internals of perl. Otherwise it will	137	in XS or want to dive into the internals of perl. Otherwise it will
…		…
145		142
146	If you didn't know about that flag, just the better, pretend it	143	If you didn't know about that flag, just the better, pretend it
147	doesn't exist.	144	doesn't exist.
148		145
149	4. A "Unicode String" is simply a string where each character can be	146	4. A "Unicode String" is simply a string where each character can be
150	validly interpreted as a Unicode codepoint.	147	validly interpreted as a Unicode code point.
151	If you have UTF-8 encoded data, it is no longer a Unicode string,	148	If you have UTF-8 encoded data, it is no longer a Unicode string,
152	but a Unicode string encoded in UTF-8, giving you a binary string.	149	but a Unicode string encoded in UTF-8, giving you a binary string.
153		150
154	5. A string containing "high" (> 255) character values is not a UTF-8	151	5. A string containing "high" (> 255) character values is not a UTF-8
155	string.	152	string.
…		…
185		182
186	If $enable is false, then the "encode" method will not escape	183	If $enable is false, then the "encode" method will not escape
187	Unicode characters unless required by the JSON syntax or other	184	Unicode characters unless required by the JSON syntax or other
188	flags. This results in a faster and more compact format.	185	flags. This results in a faster and more compact format.
189		186
		187	See also the section ENCODING/CODESET FLAG NOTES later in this
		188	document.
		189
190	The main use for this flag is to produce JSON texts that can be	190	The main use for this flag is to produce JSON texts that can be
191	transmitted over a 7-bit channel, as the encoded JSON texts will not	191	transmitted over a 7-bit channel, as the encoded JSON texts will not
192	contain any 8 bit characters.	192	contain any 8 bit characters.
193		193
194	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	194	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
205	superset of latin1.	205	superset of latin1.
206		206
207	If $enable is false, then the "encode" method will not escape	207	If $enable is false, then the "encode" method will not escape
208	Unicode characters unless required by the JSON syntax or other	208	Unicode characters unless required by the JSON syntax or other
209	flags.	209	flags.
		210
		211	See also the section ENCODING/CODESET FLAG NOTES later in this
		212	document.
210		213
211	The main use for this flag is efficiently encoding binary data as	214	The main use for this flag is efficiently encoding binary data as
212	JSON text, as most octets will not be escaped, resulting in a	215	JSON text, as most octets will not be escaped, resulting in a
213	smaller encoded size. The disadvantage is that the resulting JSON	216	smaller encoded size. The disadvantage is that the resulting JSON
214	text is encoded in latin1 (and must correctly be treated as such	217	text is encoded in latin1 (and must correctly be treated as such
…		…
234	If $enable is false, then the "encode" method will return the JSON	237	If $enable is false, then the "encode" method will return the JSON
235	string as a (non-encoded) Unicode string, while "decode" expects	238	string as a (non-encoded) Unicode string, while "decode" expects
236	thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or	239	thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
237	UTF-16) needs to be done yourself, e.g. using the Encode module.	240	UTF-16) needs to be done yourself, e.g. using the Encode module.
238		241
		242	See also the section ENCODING/CODESET FLAG NOTES later in this
		243	document.
		244
239	Example, output UTF-16BE-encoded JSON:	245	Example, output UTF-16BE-encoded JSON:
240		246
241	use Encode;	247	use Encode;
242	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	248	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
243		249
…		…
318	If $enable is false (the default), then "decode" will only accept	324	If $enable is false (the default), then "decode" will only accept
319	valid JSON texts.	325	valid JSON texts.
320		326
321	Currently accepted extensions are:	327	Currently accepted extensions are:
322		328
323	* list items can have an end-comma	329	* list items can have an end-comma
		330
324	JSON separates array elements and key-value pairs with commas.	331	JSON separates array elements and key-value pairs with commas.
325	This can be annoying if you write JSON texts manually and want	332	This can be annoying if you write JSON texts manually and want
326	to be able to quickly append elements, so this extension accepts	333	to be able to quickly append elements, so this extension accepts
327	comma at the end of such items not just between them:	334	comma at the end of such items not just between them:
328		335
…		…
333	{	340	{
334	"k1": "v1",	341	"k1": "v1",
335	"k2": "v2", <- this comma not normally allowed	342	"k2": "v2", <- this comma not normally allowed
336	}	343	}
337		344
338	* shell-style '#'-comments	345	* shell-style '#'-comments
		346
339	Whenever JSON allows whitespace, shell-style comments are	347	Whenever JSON allows whitespace, shell-style comments are
340	additionally allowed. They are terminated by the first	348	additionally allowed. They are terminated by the first
341	carriage-return or line-feed character, after which more	349	carriage-return or line-feed character, after which more
342	white-space and comments are allowed.	350	white-space and comments are allowed.
343		351
344	[	352	[
345	1, # this comment not allowed in JSON	353	1, # this comment not allowed in JSON
346	# neither this one...	354	# neither this one...
		355	]
		356
		357	* literal ASCII TAB characters in strings
		358
		359	Literal ASCII TAB characters are now allowed in strings (and
		360	treated as "\t").
		361
		362	[
		363	"Hello\tWorld",
		364	"Hello<TAB>World", # literal <TAB> would not normally be allowed
347	]	365	]
348		366
349	$json = $json->canonical ([$enable])	367	$json = $json->canonical ([$enable])
350	$enabled = $json->get_canonical	368	$enabled = $json->get_canonical
351	If $enable is true (or missing), then the "encode" method will	369	If $enable is true (or missing), then the "encode" method will
352	output JSON objects by sorting their keys. This is adding a	370	output JSON objects by sorting their keys. This is adding a
353	comparatively high overhead.	371	comparatively high overhead.
354		372
355	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
356	pairs in the order Perl stores them (which will likely change	374	pairs in the order Perl stores them (which will likely change
357	between runs of the same script).	375	between runs of the same script, and can change even within the same
		376	run from 5.18 onwards).
358		377
359	This option is useful if you want the same data structure to be	378	This option is useful if you want the same data structure to be
360	encoded as the same JSON text (given the same overall settings). If	379	encoded as the same JSON text (given the same overall settings). If
361	it is disabled, the same hash might be encoded differently even if	380	it is disabled, the same hash might be encoded differently even if
362	contains the same data, as key-value pairs have no inherent ordering	381	contains the same data, as key-value pairs have no inherent ordering
363	in Perl.	382	in Perl.
364		383
365	This setting has no effect when decoding JSON texts.	384	This setting has no effect when decoding JSON texts.
		385
		386	This setting has currently no effect on tied hashes.
366		387
367	$json = $json->allow_nonref ([$enable])	388	$json = $json->allow_nonref ([$enable])
368	$enabled = $json->get_allow_nonref	389	$enabled = $json->get_allow_nonref
369	If $enable is true (or missing), then the "encode" method can	390	If $enable is true (or missing), then the "encode" method can
370	convert a non-reference into its corresponding string, number or	391	convert a non-reference into its corresponding string, number or
…		…
380	"allow_nonref", resulting in an invalid JSON text:	401	"allow_nonref", resulting in an invalid JSON text:
381		402
382	JSON::XS->new->allow_nonref->encode ("Hello, World!")	403	JSON::XS->new->allow_nonref->encode ("Hello, World!")
383	=> "Hello, World!"	404	=> "Hello, World!"
384		405
		406	$json = $json->allow_unknown ([$enable])
		407	$enabled = $json->get_allow_unknown
		408	If $enable is true (or missing), then "encode" will not throw an
		409	exception when it encounters values it cannot represent in JSON (for
		410	example, filehandles) but instead will encode a JSON "null" value.
		411	Note that blessed objects are not included here and are handled
		412	separately by c<allow_nonref>.
		413
		414	If $enable is false (the default), then "encode" will throw an
		415	exception when it encounters anything it cannot encode as JSON.
		416
		417	This option does not affect "decode" in any way, and it is
		418	recommended to leave it off unless you know your communications
		419	partner.
		420
385	$json = $json->allow_blessed ([$enable])	421	$json = $json->allow_blessed ([$enable])
386	$enabled = $json->get_allow_blessed	422	$enabled = $json->get_allow_blessed
		423	See "OBJECT SERIALISATION" for details.
		424
387	If $enable is true (or missing), then the "encode" method will not	425	If $enable is true (or missing), then the "encode" method will not
388	barf when it encounters a blessed reference. Instead, the value of	426	barf when it encounters a blessed reference that it cannot convert
389	the convert_blessed option will decide whether "null"	427	otherwise. Instead, a JSON "null" value is encoded instead of the
390	("convert_blessed" disabled or no "TO_JSON" method found) or a	428	object.
391	representation of the object ("convert_blessed" enabled and
392	"TO_JSON" method found) is being encoded. Has no effect on "decode".
393		429
394	If $enable is false (the default), then "encode" will throw an	430	If $enable is false (the default), then "encode" will throw an
395	exception when it encounters a blessed object.	431	exception when it encounters a blessed object that it cannot convert
		432	otherwise.
		433
		434	This setting has no effect on "decode".
396		435
397	$json = $json->convert_blessed ([$enable])	436	$json = $json->convert_blessed ([$enable])
398	$enabled = $json->get_convert_blessed	437	$enabled = $json->get_convert_blessed
		438	See "OBJECT SERIALISATION" for details.
		439
399	If $enable is true (or missing), then "encode", upon encountering a	440	If $enable is true (or missing), then "encode", upon encountering a
400	blessed object, will check for the availability of the "TO_JSON"	441	blessed object, will check for the availability of the "TO_JSON"
401	method on the object's class. If found, it will be called in scalar	442	method on the object's class. If found, it will be called in scalar
402	context and the resulting scalar will be encoded instead of the	443	context and the resulting scalar will be encoded instead of the
403	object. If no "TO_JSON" method is found, the value of	444	object.
404	"allow_blessed" will decide what to do.
405		445
406	The "TO_JSON" method may safely call die if it wants. If "TO_JSON"	446	The "TO_JSON" method may safely call die if it wants. If "TO_JSON"
407	returns other blessed objects, those will be handled in the same	447	returns other blessed objects, those will be handled in the same
408	way. "TO_JSON" must take care of not causing an endless recursion	448	way. "TO_JSON" must take care of not causing an endless recursion
409	cycle (== crash) in this case. The name of "TO_JSON" was chosen	449	cycle (== crash) in this case. The name of "TO_JSON" was chosen
410	because other methods called by the Perl core (== not by the user of	450	because other methods called by the Perl core (== not by the user of
411	the object) are usually in upper case letters and to avoid	451	the object) are usually in upper case letters and to avoid
412	collisions with any "to_json" function or method.	452	collisions with any "to_json" function or method.
413		453
414	This setting does not yet influence "decode" in any way, but in the	454	If $enable is false (the default), then "encode" will not consider
415	future, global hooks might get installed that influence "decode" and	455	this type of conversion.
416	are enabled by this setting.
417		456
418	If $enable is false, then the "allow_blessed" setting will decide	457	This setting has no effect on "decode".
419	what to do when a blessed object is found.	458
		459	$json = $json->allow_tags ([$enable])
		460	$enabled = $json->allow_tags
		461	See "OBJECT SERIALISATION" for details.
		462
		463	If $enable is true (or missing), then "encode", upon encountering a
		464	blessed object, will check for the availability of the "FREEZE"
		465	method on the object's class. If found, it will be used to serialise
		466	the object into a nonstandard tagged JSON value (that JSON decoders
		467	cannot decode).
		468
		469	It also causes "decode" to parse such tagged JSON values and
		470	deserialise them via a call to the "THAW" method.
		471
		472	If $enable is false (the default), then "encode" will not consider
		473	this type of conversion, and tagged JSON values will cause a parse
		474	error in "decode", as if tags were not part of the grammar.
420		475
421	$json = $json->filter_json_object ([$coderef->($hashref)])	476	$json = $json->filter_json_object ([$coderef->($hashref)])
422	When $coderef is specified, it will be called from "decode" each	477	When $coderef is specified, it will be called from "decode" each
423	time it decodes a JSON object. The only argument is a reference to	478	time it decodes a JSON object. The only argument is a reference to
424	the newly-created hash. If the code references returns a single	479	the newly-created hash. If the code references returns a single
…		…
523	saving space.	578	saving space.
524		579
525	$json = $json->max_depth ([$maximum_nesting_depth])	580	$json = $json->max_depth ([$maximum_nesting_depth])
526	$max_depth = $json->get_max_depth	581	$max_depth = $json->get_max_depth
527	Sets the maximum nesting level (default 512) accepted while encoding	582	Sets the maximum nesting level (default 512) accepted while encoding
528	or decoding. If the JSON text or Perl data structure has an equal or	583	or decoding. If a higher nesting level is detected in JSON text or a
529	higher nesting level then this limit, then the encoder and decoder	584	Perl data structure, then the encoder and decoder will stop and
530	will stop and croak at that point.	585	croak at that point.
531		586
532	Nesting level is defined by number of hash- or arrayrefs that the	587	Nesting level is defined by number of hash- or arrayrefs that the
533	encoder needs to traverse to reach a given point or the number of	588	encoder needs to traverse to reach a given point or the number of
534	"{" or "[" characters without their matching closing parenthesis	589	"{" or "[" characters without their matching closing parenthesis
535	crossed to reach a given character in a string.	590	crossed to reach a given character in a string.
536		591
537	Setting the maximum depth to one disallows any nesting, so that	592	Setting the maximum depth to one disallows any nesting, so that
538	ensures that the object is only a single hash/object or array.	593	ensures that the object is only a single hash/object or array.
539		594
540	The argument to "max_depth" will be rounded up to the next highest
541	power of two. If no argument is given, the highest possible setting	595	If no argument is given, the highest possible setting will be used,
542	will be used, which is rarely useful.	596	which is rarely useful.
		597
		598	Note that nesting is implemented by recursion in C. The default
		599	value has been chosen to be as large as typical operating systems
		600	allow without crashing.
543		601
544	See SECURITY CONSIDERATIONS, below, for more info on why this is	602	See SECURITY CONSIDERATIONS, below, for more info on why this is
545	useful.	603	useful.
546		604
547	$json = $json->max_size ([$maximum_string_size])	605	$json = $json->max_size ([$maximum_string_size])
548	$max_size = $json->get_max_size	606	$max_size = $json->get_max_size
549	Set the maximum length a JSON text may have (in bytes) where	607	Set the maximum length a JSON text may have (in bytes) where
550	decoding is being attempted. The default is 0, meaning no limit.	608	decoding is being attempted. The default is 0, meaning no limit.
551	When "decode" is called on a string longer then this number of	609	When "decode" is called on a string that is longer then this many
552	characters it will not attempt to decode the string but throw an	610	bytes, it will not attempt to decode the string but throw an
553	exception. This setting has no effect on "encode" (yet).	611	exception. This setting has no effect on "encode" (yet).
554		612
555	The argument to "max_size" will be rounded up to the next highest
556	power of two (so may be more than requested). If no argument is
557	given, the limit check will be deactivated (same as when 0 is	613	If no argument is given, the limit check will be deactivated (same
558	specified).	614	as when 0 is specified).
559		615
560	See SECURITY CONSIDERATIONS, below, for more info on why this is	616	See SECURITY CONSIDERATIONS, below, for more info on why this is
561	useful.	617	useful.
562		618
563	$json_text = $json->encode ($perl_scalar)	619	$json_text = $json->encode ($perl_scalar)
564	Converts the given Perl data structure (a simple scalar or a	620	Converts the given Perl value or data structure to its JSON
565	reference to a hash or array) to its JSON representation. Simple	621	representation. Croaks on error.
566	scalars will be converted into JSON string or number sequences,
567	while references to arrays become JSON arrays and references to
568	hashes become JSON objects. Undefined Perl values (e.g. "undef")
569	become JSON "null" values. Neither "true" nor "false" values will be
570	generated.
571		622
572	$perl_scalar = $json->decode ($json_text)	623	$perl_scalar = $json->decode ($json_text)
573	The opposite of "encode": expects a JSON text and tries to parse it,	624	The opposite of "encode": expects a JSON text and tries to parse it,
574	returning the resulting simple scalar or reference. Croaks on error.	625	returning the resulting simple scalar or reference. Croaks on error.
575
576	JSON numbers and strings become simple Perl scalars. JSON arrays
577	become Perl arrayrefs and JSON objects become Perl hashrefs. "true"
578	becomes 1, "false" becomes 0 and "null" becomes "undef".
579		626
580	($perl_scalar, $characters) = $json->decode_prefix ($json_text)	627	($perl_scalar, $characters) = $json->decode_prefix ($json_text)
581	This works like the "decode" method, but instead of raising an	628	This works like the "decode" method, but instead of raising an
582	exception when there is trailing garbage after the first JSON	629	exception when there is trailing garbage after the first JSON
583	object, it will silently stop parsing there and return the number of	630	object, it will silently stop parsing there and return the number of
584	characters consumed so far.	631	characters consumed so far.
585		632
586	This is useful if your JSON texts are not delimited by an outer	633	This is useful if your JSON texts are not delimited by an outer
587	protocol (which is not the brightest thing to do in the first place)
588	and you need to know where the JSON text ends.	634	protocol and you need to know where the JSON text ends.
589		635
590	JSON::XS->new->decode_prefix ("[1] the tail")	636	JSON::XS->new->decode_prefix ("[1] the tail")
591	=> ([], 3)	637	=> ([1], 3)
		638
		639	INCREMENTAL PARSING
		640	In some cases, there is the need for incremental parsing of JSON texts.
		641	While this module always has to keep both JSON text and resulting Perl
		642	data structure in memory at one time, it does allow you to parse a JSON
		643	stream incrementally. It does so by accumulating text until it has a
		644	full JSON object, which it then can decode. This process is similar to
		645	using "decode_prefix" to see if a full JSON object is available, but is
		646	much more efficient (and can be implemented with a minimum of method
		647	calls).
		648
		649	JSON::XS will only attempt to parse the JSON text once it is sure it has
		650	enough text to get a decisive result, using a very simple but truly
		651	incremental parser. This means that it sometimes won't stop as early as
		652	the full parser, for example, it doesn't detect mismatched parentheses.
		653	The only thing it guarantees is that it starts decoding as soon as a
		654	syntactically valid JSON text has been seen. This means you need to set
		655	resource limits (e.g. "max_size") to ensure the parser will stop parsing
		656	in the presence if syntax errors.
		657
		658	The following methods implement this incremental parser.
		659
		660	[void, scalar or list context] = $json->incr_parse ([$string])
		661	This is the central parsing function. It can both append new text
		662	and extract objects from the stream accumulated so far (both of
		663	these functions are optional).
		664
		665	If $string is given, then this string is appended to the already
		666	existing JSON fragment stored in the $json object.
		667
		668	After that, if the function is called in void context, it will
		669	simply return without doing anything further. This can be used to
		670	add more text in as many chunks as you want.
		671
		672	If the method is called in scalar context, then it will try to
		673	extract exactly one JSON object. If that is successful, it will
		674	return this object, otherwise it will return "undef". If there is a
		675	parse error, this method will croak just as "decode" would do (one
		676	can then use "incr_skip" to skip the erroneous part). This is the
		677	most common way of using the method.
		678
		679	And finally, in list context, it will try to extract as many objects
		680	from the stream as it can find and return them, or the empty list
		681	otherwise. For this to work, there must be no separators between the
		682	JSON objects or arrays, instead they must be concatenated
		683	back-to-back. If an error occurs, an exception will be raised as in
		684	the scalar context case. Note that in this case, any
		685	previously-parsed JSON texts will be lost.
		686
		687	Example: Parse some JSON arrays/objects in a given string and return
		688	them.
		689
		690	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		691
		692	$lvalue_string = $json->incr_text
		693	This method returns the currently stored JSON fragment as an lvalue,
		694	that is, you can manipulate it. This only works when a preceding
		695	call to "incr_parse" in scalar context successfully returned an
		696	object. Under all other circumstances you must not call this
		697	function (I mean it. although in simple tests it might actually
		698	work, it will fail under real world conditions). As a special
		699	exception, you can also call this method before having parsed
		700	anything.
		701
		702	This function is useful in two cases: a) finding the trailing text
		703	after a JSON object or b) parsing multiple JSON objects separated by
		704	non-JSON text (such as commas).
		705
		706	$json->incr_skip
		707	This will reset the state of the incremental parser and will remove
		708	the parsed text from the input buffer so far. This is useful after
		709	"incr_parse" died, in which case the input buffer and incremental
		710	parser state is left unchanged, to skip the text parsed so far and
		711	to reset the parse state.
		712
		713	The difference to "incr_reset" is that only text until the parse
		714	error occurred is removed.
		715
		716	$json->incr_reset
		717	This completely resets the incremental parser, that is, after this
		718	call, it will be as if the parser had never parsed anything.
		719
		720	This is useful if you want to repeatedly parse JSON objects and want
		721	to ignore any trailing data, which means you have to reset the
		722	parser after each successful decode.
		723
		724	LIMITATIONS
		725	All options that affect decoding are supported, except "allow_nonref".
		726	The reason for this is that it cannot be made to work sensibly: JSON
		727	objects and arrays are self-delimited, i.e. you can concatenate them
		728	back to back and still decode them perfectly. This does not hold true
		729	for JSON numbers, however.
		730
		731	For example, is the string 1 a single JSON number, or is it simply the
		732	start of 12? Or is 12 a single JSON number, or the concatenation of 1
		733	and 2? In neither case you can tell, and this is why JSON::XS takes the
		734	conservative route and disallows this case.
		735
		736	EXAMPLES
		737	Some examples will make all this clearer. First, a simple example that
		738	works similarly to "decode_prefix": We want to decode the JSON object at
		739	the start of a string and identify the portion after the JSON object:
		740
		741	my $text = "[1,2,3] hello";
		742
		743	my $json = new JSON::XS;
		744
		745	my $obj = $json->incr_parse ($text)
		746	or die "expected JSON object or array at beginning of string";
		747
		748	my $tail = $json->incr_text;
		749	# $tail now contains " hello"
		750
		751	Easy, isn't it?
		752
		753	Now for a more complicated example: Imagine a hypothetical protocol
		754	where you read some requests from a TCP stream, and each request is a
		755	JSON array, without any separation between them (in fact, it is often
		756	useful to use newlines as "separators", as these get interpreted as
		757	whitespace at the start of the JSON text, which makes it possible to
		758	test said protocol with "telnet"...).
		759
		760	Here is how you'd do it (it is trivial to write this in an event-based
		761	manner):
		762
		763	my $json = new JSON::XS;
		764
		765	# read some data from the socket
		766	while (sysread $socket, my $buf, 4096) {
		767
		768	# split and decode as many requests as possible
		769	for my $request ($json->incr_parse ($buf)) {
		770	# act on the $request
		771	}
		772	}
		773
		774	Another complicated example: Assume you have a string with JSON objects
		775	or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
		776	[3]"). To parse them, we have to skip the commas between the JSON texts,
		777	and here is where the lvalue-ness of "incr_text" comes in useful:
		778
		779	my $text = "[1],[2], [3]";
		780	my $json = new JSON::XS;
		781
		782	# void context, so no parsing done
		783	$json->incr_parse ($text);
		784
		785	# now extract as many objects as possible. note the
		786	# use of scalar context so incr_text can be called.
		787	while (my $obj = $json->incr_parse) {
		788	# do something with $obj
		789
		790	# now skip the optional comma
		791	$json->incr_text =~ s/^ \s* , //x;
		792	}
		793
		794	Now lets go for a very complex example: Assume that you have a gigantic
		795	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		796	but you cannot load it into memory fully (this has actually happened in
		797	the real world :).
		798
		799	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		800	can still help you: You implement a (very simple) array parser and let
		801	JSON decode the array elements, which are all full JSON objects on their
		802	own (this wouldn't work if the array elements could be JSON numbers, for
		803	example):
		804
		805	my $json = new JSON::XS;
		806
		807	# open the monster
		808	open my $fh, "<bigfile.json"
		809	or die "bigfile: $!";
		810
		811	# first parse the initial "["
		812	for (;;) {
		813	sysread $fh, my $buf, 65536
		814	or die "read error: $!";
		815	$json->incr_parse ($buf); # void context, so no parsing
		816
		817	# Exit the loop once we found and removed(!) the initial "[".
		818	# In essence, we are (ab-)using the $json object as a simple scalar
		819	# we append data to.
		820	last if $json->incr_text =~ s/^ \s* \[ //x;
		821	}
		822
		823	# now we have the skipped the initial "[", so continue
		824	# parsing all the elements.
		825	for (;;) {
		826	# in this loop we read data until we got a single JSON object
		827	for (;;) {
		828	if (my $obj = $json->incr_parse) {
		829	# do something with $obj
		830	last;
		831	}
		832
		833	# add more data
		834	sysread $fh, my $buf, 65536
		835	or die "read error: $!";
		836	$json->incr_parse ($buf); # void context, so no parsing
		837	}
		838
		839	# in this loop we read data until we either found and parsed the
		840	# separating "," between elements, or the final "]"
		841	for (;;) {
		842	# first skip whitespace
		843	$json->incr_text =~ s/^\s*//;
		844
		845	# if we find "]", we are done
		846	if ($json->incr_text =~ s/^\]//) {
		847	print "finished.\n";
		848	exit;
		849	}
		850
		851	# if we find ",", we can continue with the next element
		852	if ($json->incr_text =~ s/^,//) {
		853	last;
		854	}
		855
		856	# if we find anything else, we have a parse error!
		857	if (length $json->incr_text) {
		858	die "parse error near ", $json->incr_text;
		859	}
		860
		861	# else add more data
		862	sysread $fh, my $buf, 65536
		863	or die "read error: $!";
		864	$json->incr_parse ($buf); # void context, so no parsing
		865	}
		866
		867	This is a complex example, but most of the complexity comes from the
		868	fact that we are trying to be correct (bear with me if I am wrong, I
		869	never ran the above example :).
592		870
593	MAPPING	871	MAPPING
594	This section describes how JSON::XS maps Perl values to JSON values and	872	This section describes how JSON::XS maps Perl values to JSON values and
595	vice versa. These mappings are designed to "do the right thing" in most	873	vice versa. These mappings are designed to "do the right thing" in most
596	circumstances automatically, preserving round-tripping characteristics	874	circumstances automatically, preserving round-tripping characteristics
…		…
618	A JSON number becomes either an integer, numeric (floating point) or	896	A JSON number becomes either an integer, numeric (floating point) or
619	string scalar in perl, depending on its range and any fractional	897	string scalar in perl, depending on its range and any fractional
620	parts. On the Perl level, there is no difference between those as	898	parts. On the Perl level, there is no difference between those as
621	Perl handles all the conversion details, but an integer may take	899	Perl handles all the conversion details, but an integer may take
622	slightly less memory and might represent more values exactly than	900	slightly less memory and might represent more values exactly than
623	(floating point) numbers.	901	floating point numbers.
624		902
625	If the number consists of digits only, JSON::XS will try to	903	If the number consists of digits only, JSON::XS will try to
626	represent it as an integer value. If that fails, it will try to	904	represent it as an integer value. If that fails, it will try to
627	represent it as a numeric (floating point) value if that is possible	905	represent it as a numeric (floating point) value if that is possible
628	without loss of precision. Otherwise it will preserve the number as	906	without loss of precision. Otherwise it will preserve the number as
629	a string value.	907	a string value (in which case you lose roundtripping ability, as the
		908	JSON number will be re-encoded to a JSON string).
630		909
631	Numbers containing a fractional or exponential part will always be	910	Numbers containing a fractional or exponential part will always be
632	represented as numeric (floating point) values, possibly at a loss	911	represented as numeric (floating point) values, possibly at a loss
633	of precision.	912	of precision (in which case you might lose perfect roundtripping
		913	ability, but the JSON number will still be re-encoded as a JSON
		914	number).
634		915
635	This might create round-tripping problems as numbers might become	916	Note that precision is not accuracy - binary floating point values
636	strings, but as Perl is typeless there is no other way to do it.	917	cannot represent most decimal fractions exactly, and when converting
		918	from and to floating point, JSON::XS only guarantees precision up to
		919	but not including the least significant bit.
637		920
638	true, false	921	true, false
639	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",	922	These JSON atoms become "Types::Serialiser::true" and
640	respectively. They are overloaded to act almost exactly like the	923	"Types::Serialiser::false", respectively. They are overloaded to act
641	numbers 1 and 0. You can check whether a scalar is a JSON boolean by	924	almost exactly like the numbers 1 and 0. You can check whether a
642	using the "JSON::XS::is_bool" function.	925	scalar is a JSON boolean by using the "Types::Serialiser::is_bool"
		926	function (after "use Types::Serialier", of course).
643		927
644	null	928	null
645	A JSON null atom becomes "undef" in Perl.	929	A JSON null atom becomes "undef" in Perl.
		930
		931	shell-style comments ("# text")
		932	As a nonstandard extension to the JSON syntax that is enabled by the
		933	"relaxed" setting, shell-style comments are allowed. They can start
		934	anywhere outside strings and go till the end of the line.
		935
		936	tagged values ("(tag)value").
		937	Another nonstandard extension to the JSON syntax, enabled with the
		938	"allow_tags" setting, are tagged values. In this implementation, the
		939	tag must be a perl package/class name encoded as a JSON string,
		940	and the value must be a JSON array encoding optional constructor
		941	arguments.
		942
		943	See "OBJECT SERIALISATION", below, for details.
646		944
647	PERL -> JSON	945	PERL -> JSON
648	The mapping from Perl to JSON is slightly more difficult, as Perl is a	946	The mapping from Perl to JSON is slightly more difficult, as Perl is a
649	truly typeless language, so we can only guess which JSON type is meant	947	truly typeless language, so we can only guess which JSON type is meant
650	by a Perl value.	948	by a Perl value.
651		949
652	hash references	950	hash references
653	Perl hash references become JSON objects. As there is no inherent	951	Perl hash references become JSON objects. As there is no inherent
654	ordering in hash keys (or JSON objects), they will usually be	952	ordering in hash keys (or JSON objects), they will usually be
655	encoded in a pseudo-random order that can change between runs of the	953	encoded in a pseudo-random order. JSON::XS can optionally sort the
656	same program but stays generally the same within a single run of a	954	hash keys (determined by the canonical flag), so the same
657	program. JSON::XS can optionally sort the hash keys (determined by	955	datastructure will serialise to the same JSON text (given same
658	the canonical flag), so the same datastructure will serialise to	956	settings and version of JSON::XS), but this incurs a runtime
659	the same JSON text (given same settings and version of JSON::XS),	957	overhead and is only rarely useful, e.g. when you want to compare
660	but this incurs a runtime overhead and is only rarely useful, e.g.	958	some JSON text against another for equality.
661	when you want to compare some JSON text against another for
662	equality.
663		959
664	array references	960	array references
665	Perl array references become JSON arrays.	961	Perl array references become JSON arrays.
666		962
667	other references	963	other references
668	Other unblessed references are generally not allowed and will cause	964	Other unblessed references are generally not allowed and will cause
669	an exception to be thrown, except for references to the integers 0	965	an exception to be thrown, except for references to the integers 0
670	and 1, which get turned into "false" and "true" atoms in JSON. You	966	and 1, which get turned into "false" and "true" atoms in JSON.
671	can also use "JSON::XS::false" and "JSON::XS::true" to improve	967
		968	Since "JSON::XS" uses the boolean model from Types::Serialiser, you
		969	can also "use Types::Serialiser" and then use
		970	"Types::Serialiser::false" and "Types::Serialiser::true" to improve
672	readability.	971	readability.
673		972
		973	use Types::Serialiser;
674	encode_json [\0,JSON::XS::true] # yields [false,true]	974	encode_json [\0, Types::Serialiser::true] # yields [false,true]
675		975
676	JSON::XS::true, JSON::XS::false	976	Types::Serialiser::true, Types::Serialiser::false
677	These special values become JSON true and JSON false values,	977	These special values from the Types::Serialiser module become JSON
678	respectively. You can also use "\1" and "\0" directly if you want.	978	true and JSON false values, respectively. You can also use "\1" and
		979	"\0" directly if you want.
679		980
680	blessed objects	981	blessed objects
681	Blessed objects are not allowed. JSON::XS currently tries to encode	982	Blessed objects are not directly representable in JSON, but
682	their underlying representation (hash- or arrayref), but this	983	"JSON::XS" allows various ways of handling objects. See "OBJECT
683	behaviour might change in future versions.	984	SERIALISATION", below, for details.
684		985
685	simple scalars	986	simple scalars
686	Simple Perl scalars (any scalar that is not a reference) are the	987	Simple Perl scalars (any scalar that is not a reference) are the
687	most difficult objects to encode: JSON::XS will encode undefined	988	most difficult objects to encode: JSON::XS will encode undefined
688	scalars as JSON null value, scalars that have last been used in a	989	scalars as JSON "null" values, scalars that have last been used in a
689	string context before encoding as JSON strings and anything else as	990	string context before encoding as JSON strings, and anything else as
690	number value:	991	number value:
691		992
692	# dump as number	993	# dump as number
693	encode_json [2] # yields [2]	994	encode_json [2] # yields [2]
694	encode_json [-3.0e17] # yields [-3e+17]	995	encode_json [-3.0e17] # yields [-3e+17]
…		…
713	my $x = "3"; # some variable containing a string	1014	my $x = "3"; # some variable containing a string
714	$x += 0; # numify it, ensuring it will be dumped as a number	1015	$x += 0; # numify it, ensuring it will be dumped as a number
715	$x *= 1; # same thing, the choice is yours.	1016	$x *= 1; # same thing, the choice is yours.
716		1017
717	You can not currently force the type in other, less obscure, ways.	1018	You can not currently force the type in other, less obscure, ways.
718	Tell me if you need this capability.	1019	Tell me if you need this capability (but don't forget to explain why
		1020	it's needed :).
719		1021
720	COMPARISON	1022	Note that numerical precision has the same meaning as under Perl (so
721	As already mentioned, this module was created because none of the	1023	binary to decimal conversion follows the same rules as in Perl,
722	existing JSON modules could be made to work correctly. First I will	1024	which can differ to other languages). Also, your perl interpreter
723	describe the problems (or pleasures) I encountered with various existing	1025	might expose extensions to the floating point numbers of your
724	JSON modules, followed by some benchmark values. JSON::XS was designed	1026	platform, such as infinities or NaN's - these cannot be represented
725	not to suffer from any of these problems or limitations.	1027	in JSON, and it is an error to pass those in.
726		1028
727	JSON 1.07	1029	OBJECT SERIALISATION
728	Slow (but very portable, as it is written in pure Perl).	1030	As JSON cannot directly represent Perl objects, you have to choose
		1031	between a pure JSON representation (without the ability to deserialise
		1032	the object automatically again), and a nonstandard extension to the JSON
		1033	syntax, tagged values.
729		1034
730	Undocumented/buggy Unicode handling (how JSON handles Unicode values	1035	SERIALISATION
731	is undocumented. One can get far by feeding it Unicode strings and	1036	What happens when "JSON::XS" encounters a Perl object depends on the
732	doing en-/decoding oneself, but Unicode escapes are not working	1037	"allow_blessed", "convert_blessed" and "allow_tags" settings, which are
		1038	used in this order:
		1039
		1040	1. "allow_tags" is enabled and the object has a "FREEZE" method.
		1041	In this case, "JSON::XS" uses the Types::Serialiser object
		1042	serialisation protocol to create a tagged JSON value, using a
		1043	nonstandard extension to the JSON syntax.
		1044
		1045	This works by invoking the "FREEZE" method on the object, with the
		1046	first argument being the object to serialise, and the second
		1047	argument being the constant string "JSON" to distinguish it from
		1048	other serialisers.
		1049
		1050	The "FREEZE" method can return any number of values (i.e. zero or
		1051	more). These values and the paclkage/classname of the object will
		1052	then be encoded as a tagged JSON value in the following format:
		1053
		1054	("classname")[FREEZE return values...]
		1055
		1056	e.g.:
		1057
		1058	("URI")["http://www.google.com/"]
		1059	("MyDate")[2013,10,29]
		1060	("ImageData::JPEG")["Z3...VlCg=="]
		1061
		1062	For example, the hypothetical "My::Object" "FREEZE" method might use
		1063	the objects "type" and "id" members to encode the object:
		1064
		1065	sub My::Object::FREEZE {
		1066	my ($self, $serialiser) = @_;
		1067
		1068	($self->{type}, $self->{id})
		1069	}
		1070
		1071	2. "convert_blessed" is enabled and the object has a "TO_JSON" method.
		1072	In this case, the "TO_JSON" method of the object is invoked in
		1073	scalar context. It must return a single scalar that can be directly
		1074	encoded into JSON. This scalar replaces the object in the JSON text.
		1075
		1076	For example, the following "TO_JSON" method will convert all URI
		1077	objects to JSON strings when serialised. The fatc that these values
		1078	originally were URI objects is lost.
		1079
		1080	sub URI::TO_JSON {
		1081	my ($uri) = @_;
		1082	$uri->as_string
		1083	}
		1084
		1085	3. "allow_blessed" is enabled.
		1086	The object will be serialised as a JSON null value.
		1087
		1088	4. none of the above
		1089	If none of the settings are enabled or the respective methods are
		1090	missing, "JSON::XS" throws an exception.
		1091
		1092	DESERIALISATION
		1093	For deserialisation there are only two cases to consider: either
		1094	nonstandard tagging was used, in which case "allow_tags" decides, or
		1095	objects cannot be automatically be deserialised, in which case you can
		1096	use postprocessing or the "filter_json_object" or
		1097	"filter_json_single_key_object" callbacks to get some real objects our
		1098	of your JSON.
		1099
		1100	This section only considers the tagged value case: I a tagged JSON
		1101	object is encountered during decoding and "allow_tags" is disabled, a
		1102	parse error will result (as if tagged values were not part of the
		1103	grammar).
		1104
		1105	If "allow_tags" is enabled, "JSON::XS" will look up the "THAW" method of
		1106	the package/classname used during serialisation (it will not attempt to
		1107	load the package as a Perl module). If there is no such method, the
		1108	decoding will fail with an error.
		1109
		1110	Otherwise, the "THAW" method is invoked with the classname as first
		1111	argument, the constant string "JSON" as second argument, and all the
		1112	values from the JSON array (the values originally returned by the
		1113	"FREEZE" method) as remaining arguments.
		1114
		1115	The method must then return the object. While technically you can return
		1116	any Perl scalar, you might have to enable the "enable_nonref" setting to
		1117	make that work in all cases, so better return an actual blessed
		1118	reference.
		1119
		1120	As an example, let's implement a "THAW" function that regenerates the
		1121	"My::Object" from the "FREEZE" example earlier:
		1122
		1123	sub My::Object::THAW {
		1124	my ($class, $serialiser, $type, $id) = @_;
		1125
		1126	$class->new (type => $type, id => $id)
		1127	}
		1128
		1129	ENCODING/CODESET FLAG NOTES
		1130	The interested reader might have seen a number of flags that signify
		1131	encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
		1132	some confusion on what these do, so here is a short comparison:
		1133
		1134	"utf8" controls whether the JSON text created by "encode" (and expected
		1135	by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
		1136	control whether "encode" escapes character values outside their
		1137	respective codeset range. Neither of these flags conflict with each
		1138	other, although some combinations make less sense than others.
		1139
		1140	Care has been taken to make all flags symmetrical with respect to
		1141	"encode" and "decode", that is, texts encoded with any combination of
		1142	these flag values will be correctly decoded when the same flags are used
		1143	- in general, if you use different flag settings while encoding vs. when
		1144	decoding you likely have a bug somewhere.
		1145
		1146	Below comes a verbose discussion of these flags. Note that a "codeset"
		1147	is simply an abstract set of character-codepoint pairs, while an
		1148	encoding takes those codepoint numbers and encodes them, in our case
		1149	into octets. Unicode is (among other things) a codeset, UTF-8 is an
		1150	encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets and
		1151	encodings at the same time, which can be confusing.
		1152
		1153	"utf8" flag disabled
		1154	When "utf8" is disabled (the default), then "encode"/"decode"
		1155	generate and expect Unicode strings, that is, characters with high
		1156	ordinal Unicode values (> 255) will be encoded as such characters,
		1157	and likewise such characters are decoded as-is, no changes to them
		1158	will be done, except "(re-)interpreting" them as Unicode codepoints
		1159	or Unicode characters, respectively (to Perl, these are the same
		1160	thing in strings unless you do funny/weird/dumb stuff).
		1161
		1162	This is useful when you want to do the encoding yourself (e.g. when
		1163	you want to have UTF-16 encoded JSON texts) or when some other layer
		1164	does the encoding for you (for example, when printing to a terminal
		1165	using a filehandle that transparently encodes to UTF-8 you certainly
		1166	do NOT want to UTF-8 encode your data first and have Perl encode it
		1167	another time).
		1168
		1169	"utf8" flag enabled
		1170	If the "utf8"-flag is enabled, "encode"/"decode" will encode all
		1171	characters using the corresponding UTF-8 multi-byte sequence, and
		1172	will expect your input strings to be encoded as UTF-8, that is, no
		1173	"character" of the input string must have any value > 255, as UTF-8
		1174	does not allow that.
		1175
		1176	The "utf8" flag therefore switches between two modes: disabled means
		1177	you will get a Unicode string in Perl, enabled means you get an
		1178	UTF-8 encoded octet/binary string in Perl.
		1179
		1180	"latin1" or "ascii" flags enabled
		1181	With "latin1" (or "ascii") enabled, "encode" will escape characters
		1182	with ordinal values > 255 (> 127 with "ascii") and encode the
		1183	remaining characters as specified by the "utf8" flag.
		1184
		1185	If "utf8" is disabled, then the result is also correctly encoded in
		1186	those character sets (as both are proper subsets of Unicode, meaning
		1187	that a Unicode string with all character values < 256 is the same
		1188	thing as a ISO-8859-1 string, and a Unicode string with all
		1189	character values < 128 is the same thing as an ASCII string in
733	properly).	1190	Perl).
734		1191
735	No round-tripping (strings get clobbered if they look like numbers,	1192	If "utf8" is enabled, you still get a correct UTF-8-encoded string,
736	e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that	1193	regardless of these flags, just some more characters will be escaped
737	will decode into the number 2.	1194	using "\uXXXX" then before.
738		1195
739	JSON::PC 0.01	1196	Note that ISO-8859-1-encoded strings are not compatible with UTF-8
740	Very fast.	1197	encoding, while ASCII-encoded strings are. That is because the
		1198	ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
		1199	codeset being a subset of Unicode), while ASCII is.
741		1200
742	Undocumented/buggy Unicode handling.	1201	Surprisingly, "decode" will ignore these flags and so treat all
		1202	input values as governed by the "utf8" flag. If it is disabled, this
		1203	allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
		1204	strict subsets of Unicode. If it is enabled, you can correctly
		1205	decode UTF-8 encoded strings.
743		1206
744	No round-tripping.	1207	So neither "latin1" nor "ascii" are incompatible with the "utf8"
		1208	flag - they only govern when the JSON output engine escapes a
		1209	character or not.
745		1210
746	Has problems handling many Perl values (e.g. regex results and other	1211	The main use for "latin1" is to relatively efficiently store binary
747	magic values will make it croak).	1212	data as JSON, at the expense of breaking compatibility with most
		1213	JSON decoders.
748		1214
749	Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}"	1215	The main use for "ascii" is to force the output to not contain
750	which is not a valid JSON text.	1216	characters with values > 127, which means you can interpret the
		1217	resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
		1218	any character set and 8-bit-encoding, and still get the same data
		1219	structure back. This is useful when your channel for JSON transfer
		1220	is not 8-bit clean or the encoding might be mangled in between (e.g.
		1221	in mail), and works because ASCII is a proper subset of most 8-bit
		1222	and multibyte encodings in use in the world.
751		1223
752	Unmaintained (maintainer unresponsive for many months, bugs are not	1224	JSON and ECMAscript
753	getting fixed).	1225	JSON syntax is based on how literals are represented in javascript (the
		1226	not-standardised predecessor of ECMAscript) which is presumably why it
		1227	is called "JavaScript Object Notation".
754		1228
755	JSON::Syck 0.21	1229	However, JSON is not a subset (and also not a superset of course) of
756	Very buggy (often crashes).	1230	ECMAscript (the standard) or javascript (whatever browsers actually
		1231	implement).
757		1232
758	Very inflexible (no human-readable format supported, format pretty	1233	If you want to use javascript's "eval" function to "parse" JSON, you
759	much undocumented. I need at least a format for easy reading by	1234	might run into parse errors for valid JSON texts, or the resulting data
760	humans and a single-line compact format for use in a protocol, and	1235	structure might not be queryable:
761	preferably a way to generate ASCII-only JSON texts).
762		1236
763	Completely broken (and confusingly documented) Unicode handling	1237	One of the problems is that U+2028 and U+2029 are valid characters
764	(Unicode escapes are not working properly, you need to set	1238	inside JSON strings, but are not allowed in ECMAscript string literals,
765	ImplicitUnicode to different values on en- and decoding to get	1239	so the following Perl fragment will not output something that can be
766	symmetric behaviour).	1240	guaranteed to be parsable by javascript's "eval":
767		1241
768	No round-tripping (simple cases work, but this depends on whether	1242	use JSON::XS;
769	the scalar value was used in a numeric context or not).
770		1243
771	Dumping hashes may skip hash values depending on iterator state.	1244	print encode_json [chr 0x2028];
772		1245
773	Unmaintained (maintainer unresponsive for many months, bugs are not	1246	The right fix for this is to use a proper JSON parser in your javascript
774	getting fixed).	1247	programs, and not rely on "eval" (see for example Douglas Crockford's
		1248	json2.js parser).
775		1249
776	Does not check input for validity (i.e. will accept non-JSON input	1250	If this is not an option, you can, as a stop-gap measure, simply encode
777	and return "something" instead of raising an exception. This is a	1251	to ASCII-only JSON:
778	security issue: imagine two banks transferring money between each
779	other using JSON. One bank might parse a given non-JSON request and
780	deduct money, while the other might reject the transaction with a
781	syntax error. While a good protocol will at least recover, that is
782	extra unnecessary work and the transaction will still not succeed).
783		1252
784	JSON::DWIW 0.04	1253	use JSON::XS;
785	Very fast. Very natural. Very nice.
786		1254
787	Undocumented Unicode handling (but the best of the pack. Unicode	1255	print JSON::XS->new->ascii->encode ([chr 0x2028]);
788	escapes still don't get parsed properly).
789		1256
790	Very inflexible.	1257	Note that this will enlarge the resulting JSON text quite a bit if you
		1258	have many non-ASCII characters. You might be tempted to run some regexes
		1259	to only escape U+2028 and U+2029, e.g.:
791		1260
792	No round-tripping.	1261	# DO NOT USE THIS!
		1262	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1263	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1264	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1265	print $json;
793		1266
794	Does not generate valid JSON texts (key strings are often unquoted,	1267	Note that this is a bad idea: the above only works for U+2028 and
795	empty keys result in nothing being output)	1268	U+2029 and thus only for fully ECMAscript-compliant parsers. Many
		1269	existing javascript implementations, however, have issues with other
		1270	characters as well - using "eval" naively simply will cause problems.
796		1271
797	Does not check input for validity.	1272	Another problem is that some javascript implementations reserve some
		1273	property names for their own purposes (which probably makes them
		1274	non-ECMAscript-compliant). For example, Iceweasel reserves the
		1275	"__proto__" property name for its own purposes.
		1276
		1277	If that is a problem, you could parse try to filter the resulting JSON
		1278	output for these property strings, e.g.:
		1279
		1280	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1281
		1282	This works because "__proto__" is not valid outside of strings, so every
		1283	occurrence of ""__proto__"\s*:" must be a string used as property name.
		1284
		1285	If you know of other incompatibilities, please let me know.
798		1286
799	JSON and YAML	1287	JSON and YAML
800	You often hear that JSON is a subset (or a close subset) of YAML. This	1288	You often hear that JSON is a subset of YAML. This is, however, a mass
801	is, however, a mass hysteria and very far from the truth. In general,	1289	hysteria(*) and very far from the truth (as of the time of this
802	there is no way to configure JSON::XS to output a data structure as	1290	writing), so let me state it clearly: *in general, there is no way to
803	valid YAML.	1291	configure JSON::XS to output a data structure as valid YAML* that works
		1292	in all cases.
804		1293
805	If you really must use JSON::XS to generate YAML, you should use this	1294	If you really must use JSON::XS to generate YAML, you should use this
806	algorithm (subject to change in future versions):	1295	algorithm (subject to change in future versions):
807		1296
808	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1297	my $to_yaml = JSON::XS->new->utf8->space_after (1);
809	my $yaml = $to_yaml->encode ($ref) . "\n";	1298	my $yaml = $to_yaml->encode ($ref) . "\n";
810		1299
811	This will usually generate JSON texts that also parse as valid YAML.	1300	This will usually generate JSON texts that also parse as valid YAML.
812	Please note that YAML has hardcoded limits on (simple) object key	1301	Please note that YAML has hardcoded limits on (simple) object key
813	lengths that JSON doesn't have, so you should make sure that your hash	1302	lengths that JSON doesn't have and also has different and incompatible
		1303	unicode character escape syntax, so you should make sure that your hash
814	keys are noticeably shorter than the 1024 characters YAML allows.	1304	keys are noticeably shorter than the 1024 "stream characters" YAML
		1305	allows and that you do not have characters with codepoint values outside
		1306	the Unicode BMP (basic multilingual page). YAML also does not allow "\/"
		1307	sequences in strings (which JSON::XS does not currently generate, but
		1308	other JSON generators might).
815		1309
816	There might be other incompatibilities that I am not aware of. In	1310	There might be other incompatibilities that I am not aware of (or the
		1311	YAML specification has been changed yet again - it does so quite often).
817	general you should not try to generate YAML with a JSON generator or	1312	In general you should not try to generate YAML with a JSON generator or
818	vice versa, or try to parse JSON with a YAML parser or vice versa:	1313	vice versa, or try to parse JSON with a YAML parser or vice versa:
819	chances are high that you will run into severe interoperability	1314	chances are high that you will run into severe interoperability problems
820	problems.	1315	when you least expect it.
		1316
		1317	(*) I have been pressured multiple times by Brian Ingerson (one of the
		1318	authors of the YAML specification) to remove this paragraph, despite
		1319	him acknowledging that the actual incompatibilities exist. As I was
		1320	personally bitten by this "JSON is YAML" lie, I refused and said I
		1321	will continue to educate people about these issues, so others do not
		1322	run into the same problem again and again. After this, Brian called
		1323	me a (quote)complete and worthless idiot(unquote).
		1324
		1325	In my opinion, instead of pressuring and insulting people who
		1326	actually clarify issues with YAML and the wrong statements of some
		1327	of its proponents, I would kindly suggest reading the JSON spec
		1328	(which is not that difficult or long) and finally make YAML
		1329	compatible to it, and educating users about the changes, instead of
		1330	spreading lies about the real compatibility for many years and
		1331	trying to silence people who point out that it isn't true.
		1332
		1333	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON,
		1334	even though the incompatibilities have been documented (and are
		1335	known to Brian) for many years and the spec makes explicit claims
		1336	that YAML is a superset of JSON. It would be so easy to fix, but
		1337	apparently, bullying people and corrupting userdata is so much
		1338	easier.
821		1339
822	SPEED	1340	SPEED
823	It seems that JSON::XS is surprisingly fast, as shown in the following	1341	It seems that JSON::XS is surprisingly fast, as shown in the following
824	tables. They have been generated with the help of the "eg/bench" program	1342	tables. They have been generated with the help of the "eg/bench" program
825	in the JSON::XS distribution, to make it easy to compare on your own	1343	in the JSON::XS distribution, to make it easy to compare on your own
826	system.	1344	system.
827		1345
828	First comes a comparison between various modules using a very short	1346	First comes a comparison between various modules using a very short
829	single-line JSON string:	1347	single-line JSON string (also available at
		1348	<http://dist.schmorp.de/misc/json/short.json>).
830		1349
831	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1350	{"method": "handleMessage", "params": ["user1",
832	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1351	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1352	1, 0]}
833		1353
834	It shows the number of encodes/decodes per second (JSON::XS uses the	1354	It shows the number of encodes/decodes per second (JSON::XS uses the
835	functional interface, while JSON::XS/2 uses the OO interface with	1355	functional interface, while JSON::XS/2 uses the OO interface with
836	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).	1356	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink.
837	Higher is better:	1357	JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ uses
		1358	the from_json method). Higher is better:
838		1359
839	module \| encode \| decode \|	1360	module \| encode \| decode \|
840	-----------\|------------\|------------\|	1361	--------------\|------------\|------------\|
841	JSON 1.x \| 4990.842 \| 4088.813 \|	1362	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
842	JSON::DWIW \| 51653.990 \| 71575.154 \|	1363	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
843	JSON::PC \| 65948.176 \| 74631.744 \|	1364	JSON::PP \| 15827.562 \| 6638.658 \|
844	JSON::PP \| 8931.652 \| 3817.168 \|	1365	JSON::Syck \| 63358.066 \| 47662.545 \|
845	JSON::Syck \| 24877.248 \| 27776.848 \|	1366	JSON::XS \| 511500.488 \| 511500.488 \|
846	JSON::XS \| 388361.481 \| 227951.304 \|	1367	JSON::XS/2 \| 291271.111 \| 388361.481 \|
847	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1368	JSON::XS/3 \| 361577.931 \| 361577.931 \|
848	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1369	Storable \| 66788.280 \| 265462.278 \|
849	Storable \| 16500.016 \| 135300.129 \|
850	-----------+------------+------------+	1370	--------------+------------+------------+
851		1371
852	That is, JSON::XS is about five times faster than JSON::DWIW on	1372	That is, JSON::XS is almost six times faster than JSON::DWIW on
853	encoding, about three times faster on decoding, and over forty times	1373	encoding, about five times faster on decoding, and over thirty to
854	faster than JSON, even with pretty-printing and key sorting. It also	1374	seventy times faster than JSON's pure perl implementation. It also
855	compares favourably to Storable for small amounts of data.	1375	compares favourably to Storable for small amounts of data.
856		1376
857	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1377	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
858	search API (http://nanoref.com/yahooapis/mgPdGg):	1378	search API (<http://dist.schmorp.de/misc/json/long.json>).
859		1379
860	module \| encode \| decode \|	1380	module \| encode \| decode \|
861	-----------\|------------\|------------\|	1381	--------------\|------------\|------------\|
862	JSON 1.x \| 55.260 \| 34.971 \|	1382	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
863	JSON::DWIW \| 825.228 \| 1082.513 \|	1383	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
864	JSON::PC \| 3571.444 \| 2394.829 \|
865	JSON::PP \| 210.987 \| 32.574 \|	1384	JSON::PP \| 400.640 \| 62.311 \|
866	JSON::Syck \| 552.551 \| 787.544 \|	1385	JSON::Syck \| 1481.040 \| 1524.869 \|
867	JSON::XS \| 5780.463 \| 4854.519 \|	1386	JSON::XS \| 20661.596 \| 9541.183 \|
868	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1387	JSON::XS/2 \| 10683.403 \| 9416.938 \|
869	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1388	JSON::XS/3 \| 20661.596 \| 9400.054 \|
870	Storable \| 4445.002 \| 5235.027 \|	1389	Storable \| 19765.806 \| 10000.725 \|
871	-----------+------------+------------+	1390	--------------+------------+------------+
872		1391
873	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1392	Again, JSON::XS leads by far (except for Storable which non-surprisingly
874	decodes faster).	1393	decodes a bit faster).
875		1394
876	On large strings containing lots of high Unicode characters, some	1395	On large strings containing lots of high Unicode characters, some
877	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the	1396	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
878	result will be broken due to missing (or wrong) Unicode handling. Others	1397	result will be broken due to missing (or wrong) Unicode handling. Others
879	refuse to decode or encode properly, so it was impossible to prepare a	1398	refuse to decode or encode properly, so it was impossible to prepare a
…		…
900	Third, JSON::XS recurses using the C stack when decoding objects and	1419	Third, JSON::XS recurses using the C stack when decoding objects and
901	arrays. The C stack is a limited resource: for instance, on my amd64	1420	arrays. The C stack is a limited resource: for instance, on my amd64
902	machine with 8MB of stack size I can decode around 180k nested arrays	1421	machine with 8MB of stack size I can decode around 180k nested arrays
903	but only 14k nested JSON objects (due to perl itself recursing deeply on	1422	but only 14k nested JSON objects (due to perl itself recursing deeply on
904	croak to free the temporary). If that is exceeded, the program crashes.	1423	croak to free the temporary). If that is exceeded, the program crashes.
905	to be conservative, the default nesting limit is set to 512. If your	1424	To be conservative, the default nesting limit is set to 512. If your
906	process has a smaller stack, you should adjust this setting accordingly	1425	process has a smaller stack, you should adjust this setting accordingly
907	with the "max_depth" method.	1426	with the "max_depth" method.
908		1427
909	And last but least, something else could bomb you that I forgot to think	1428	Something else could bomb you, too, that I forgot to think of. In that
910	of. In that case, you get to keep the pieces. I am always open for	1429	case, you get to keep the pieces. I am always open for hints, though...
911	hints, though...	1430
		1431	Also keep in mind that JSON::XS might leak contents of your Perl data
		1432	structures in its error messages, so when you serialise sensitive
		1433	information you might want to make sure that exceptions thrown by
		1434	JSON::XS will not end up in front of untrusted eyes.
912		1435
913	If you are using JSON::XS to return packets to consumption by JavaScript	1436	If you are using JSON::XS to return packets to consumption by JavaScript
914	scripts in a browser you should have a look at	1437	scripts in a browser you should have a look at
915	<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1438	<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/>
916	you are vulnerable to some common attack vectors (which really are	1439	to see whether you are vulnerable to some common attack vectors (which
917	browser design bugs, but it is still you who will have to deal with it,	1440	really are browser design bugs, but it is still you who will have to
918	as major browser developers care only for features, not about doing	1441	deal with it, as major browser developers care only for features, not
919	security right).	1442	about getting security right).
		1443
		1444	"OLD" VS. "NEW" JSON (RFC 4627 VS. RFC 7159)
		1445	TL;DR: Due to security concerns, JSON::XS will not allow scalar data in
		1446	JSON texts by default - you need to create your own JSON::XS object and
		1447	enable "allow_nonref":
		1448
		1449	my $json = JSON::XS->new->allow_nonref;
		1450
		1451	$text = $json->encode ($data);
		1452	$data = $json->decode ($text);
		1453
		1454	The long version: JSON being an important and supposedly stable format,
		1455	the IETF standardised it as RFC 4627 in 2006. Unfortunately, the
		1456	inventor of JSON, Dougles Crockford, unilaterally changed the definition
		1457	of JSON in javascript. Rather than create a fork, the IETF decided to
		1458	standardise the new syntax (apparently, so Iw as told, without finding
		1459	it very amusing).
		1460
		1461	The biggest difference between thed original JSON and the new JSON is
		1462	that the new JSON supports scalars (anything other than arrays and
		1463	objects) at the toplevel of a JSON text. While this is strictly
		1464	backwards compatible to older versions, it breaks a number of protocols
		1465	that relied on sending JSON back-to-back, and is a minor security
		1466	concern.
		1467
		1468	For example, imagine you have two banks communicating, and on one side,
		1469	trhe JSON coder gets upgraded. Two messages, such as 10 and 1000 might
		1470	then be confused to mean 101000, something that couldn't happen in the
		1471	original JSON, because niether of these messages would be valid JSON.
		1472
		1473	If one side accepts these messages, then an upgrade in the coder on
		1474	either side could result in this becoming exploitable.
		1475
		1476	This module has always allowed these messages as an optional extension,
		1477	by default disabled. The security concerns are the reason why the
		1478	default is still disabled, but future versions might/will likely upgrade
		1479	to the newer RFC as default format, so you are advised to check your
		1480	implementation and/or override the default with "->allow_nonref (0)" to
		1481	ensure that future versions are safe.
		1482
		1483	INTEROPERABILITY WITH OTHER MODULES
		1484	"JSON::XS" uses the Types::Serialiser module to provide boolean
		1485	constants. That means that the JSON true and false values will be
		1486	comaptible to true and false values of iother modules that do the same,
		1487	such as JSON::PP and CBOR::XS.
		1488
		1489	INTEROPERABILITY WITH OTHER JSON DECODERS
		1490	As long as you only serialise data that can be directly expressed in
		1491	JSON, "JSON::XS" is incapable of generating invalid JSON output (modulo
		1492	bugs, but "JSON::XS" has found more bugs in the official JSON testsuite
		1493	(1) than the official JSON testsuite has found in "JSON::XS" (0)).
		1494
		1495	When you have trouble decoding JSON generated by this module using other
		1496	decoders, then it is very likely that you have an encoding mismatch or
		1497	the other decoder is broken.
		1498
		1499	When decoding, "JSON::XS" is strict by default and will likely catch all
		1500	errors. There are currently two settings that change this: "relaxed"
		1501	makes "JSON::XS" accept (but not generate) some non-standard extensions,
		1502	and "allow_tags" will allow you to encode and decode Perl objects, at
		1503	the cost of not outputting valid JSON anymore.
		1504
		1505	TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1506	When you use "allow_tags" to use the extended (and also nonstandard and
		1507	invalid) JSON syntax for serialised objects, and you still want to
		1508	decode the generated When you want to serialise objects, you can run a
		1509	regex to replace the tagged syntax by standard JSON arrays (it only
		1510	works for "normal" packagesnames without comma, newlines or single
		1511	colons). First, the readable Perl version:
		1512
		1513	# if your FREEZE methods return no values, you need this replace first:
		1514	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1515
		1516	# this works for non-empty constructor arg lists:
		1517	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1518
		1519	And here is a less readable version that is easy to adapt to other
		1520	languages:
		1521
		1522	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1523
		1524	Here is an ECMAScript version (same regex):
		1525
		1526	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1527
		1528	Since this syntax converts to standard JSON arrays, it might be hard to
		1529	distinguish serialised objects from normal arrays. You can prepend a
		1530	"magic number" as first array element to reduce chances of a collision:
		1531
		1532	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1533
		1534	And after decoding the JSON text, you could walk the data structure
		1535	looking for arrays with a first element of
		1536	"XU1peReLzT4ggEllLanBYq4G9VzliwKF".
		1537
		1538	The same approach can be used to create the tagged format with another
		1539	encoder. First, you create an array with the magic string as first
		1540	member, the classname as second, and constructor arguments last, encode
		1541	it as part of your JSON structure, and then:
		1542
		1543	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1544
		1545	Again, this has some limitations - the magic string must not be encoded
		1546	with character escapes, and the constructor arguments must be non-empty.
		1547
		1548	RFC7159
		1549	Since this module was written, Google has written a new JSON RFC, RFC
		1550	7159 (and RFC7158). Unfortunately, this RFC breaks compatibility with
		1551	both the original JSON specification on www.json.org and RFC4627.
		1552
		1553	As far as I can see, you can get partial compatibility when parsing by
		1554	using "->allow_nonref". However, consider thew security implications of
		1555	doing so.
		1556
		1557	I haven't decided yet when to break compatibility with RFC4627 by
		1558	default (and potentially leave applications insecure) and change the
		1559	default to follow RFC7159, but application authors are well advised to
		1560	call "->allow_nonref(0)" even if this is the current default, if they
		1561	cannot handle non-reference values, in preparation for the day when the4
		1562	default will change.
920		1563
921	THREADS	1564	THREADS
922	This module is not guaranteed to be thread safe and there are no plans	1565	This module is not guaranteed to be thread safe and there are no plans
923	to change this until Perl gets thread support (as opposed to the	1566	to change this until Perl gets thread support (as opposed to the
924	horribly slow so-called "threads" which are simply slow and bloated	1567	horribly slow so-called "threads" which are simply slow and bloated
925	process simulations - use fork, its much faster, cheaper, better).	1568	process simulations - use fork, it's much faster, cheaper, better).
926		1569
927	(It might actually work, but you have been warned).	1570	(It might actually work, but you have been warned).
		1571
		1572	THE PERILS OF SETLOCALE
		1573	Sometimes people avoid the Perl locale support and directly call the
		1574	system's setlocale function with "LC_ALL".
		1575
		1576	This breaks both perl and modules such as JSON::XS, as stringification
		1577	of numbers no longer works correctly (e.g. "$x = 0.1; print "$x"+1"
		1578	might print 1, and JSON::XS might output illegal JSON as JSON::XS relies
		1579	on perl to stringify numbers).
		1580
		1581	The solution is simple: don't call "setlocale", or use it for only those
		1582	categories you need, such as "LC_MESSAGES" or "LC_CTYPE".
		1583
		1584	If you need "LC_NUMERIC", you should enable it only around the code that
		1585	actually needs it (avoiding stringification of numbers), and restore it
		1586	afterwards.
928		1587
929	BUGS	1588	BUGS
930	While the goal of this module is to be correct, that unfortunately does	1589	While the goal of this module is to be correct, that unfortunately does
931	not mean its bug-free, only that I think its design is bug-free. It is	1590	not mean it's bug-free, only that I think its design is bug-free. If you
932	still relatively early in its development. If you keep reporting bugs
933	they will be fixed swiftly, though.	1591	keep reporting bugs they will be fixed swiftly, though.
934		1592
935	Please refrain from using rt.cpan.org or any other bug reporting	1593	Please refrain from using rt.cpan.org or any other bug reporting
936	service. I put the contact address into my modules for a reason.	1594	service. I put the contact address into my modules for a reason.
		1595
		1596	SEE ALSO
		1597	The json_xs command line utility for quick experiments.
937		1598
938	AUTHOR	1599	AUTHOR
939	Marc Lehmann <schmorp@schmorp.de>	1600	Marc Lehmann <schmorp@schmorp.de>
940	http://home.schmorp.de/	1601	http://home.schmorp.de/
941		1602

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Comparing JSON-XS/README (file contents): Revision 1.22 by root, Wed Dec 5 10:59:27 2007 UTC vs. Revision 1.40 by root, Fri Feb 26 21:46:45 2016 UTC

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Comparing JSON-XS/README (file contents):
Revision 1.22 by root, Wed Dec 5 10:59:27 2007 UTC vs.
Revision 1.40 by root, Fri Feb 26 21:46:45 2016 UTC