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

Comparing JSON-XS/README (file contents):
Revision 1.20 by root, Tue Nov 13 22:59:08 2007 UTC vs.
Revision 1.24 by root, Thu Mar 27 06:37:35 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	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
11	# exported functions, they croak on error	10	# exported functions, they croak on error
12	# and expect/generate UTF-8	11	# and expect/generate UTF-8
13		12
14	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	13	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
15	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	14	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
16		15
17	# OO-interface	16	# OO-interface
18		17
19	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	18	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
20	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	19	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
21	$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.
22		29
23	DESCRIPTION	30	DESCRIPTION
24	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
25	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.
26	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.
27		42
28	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
29	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
30	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
31	cases their maintainers are unresponsive, gone missing, or not listening	46	cases their maintainers are unresponsive, gone missing, or not listening
35		50
36	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
37	vice versa.	52	vice versa.
38		53
39	FEATURES	54	FEATURES
40	* correct Unicode handling	55	* correct Unicode handling
		56
41	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
42	when it does so.	58	does so, and even documents what "correct" means.
43		59
44	* round-trip integrity	60	* round-trip integrity
		61
45	When you serialise a perl data structure using only datatypes	62	When you serialise a perl data structure using only datatypes
46	supported by JSON, the deserialised data structure is identical on	63	supported by JSON, the deserialised data structure is identical on
47	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"
48	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.
49		67
50	* strict checking of JSON correctness	68	* strict checking of JSON correctness
		69
51	There is no guessing, no generating of illegal JSON texts by	70	There is no guessing, no generating of illegal JSON texts by
52	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
53	is a security feature).	72	is a security feature).
54		73
55	* fast	74	* fast
56	Compared to other JSON modules, this module compares favourably in
57	terms of speed, too.
58		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
59	* simple to use	80	* simple to use
		81
60	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
61	interface.	83	objetc oriented interface interface.
62		84
63	* reasonably versatile output formats	85	* reasonably versatile output formats
		86
64	You can choose between the most compact guaranteed single-line	87	You can choose between the most compact guaranteed-single-line
65	format possible (nice for simple line-based protocols), a pure-ascii	88	format possible (nice for simple line-based protocols), a pure-ascii
66	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
67	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
68	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
69	whatever way you like.	92	whatever way you like.
70		93
71	FUNCTIONAL INTERFACE	94	FUNCTIONAL INTERFACE
72	The following convenience methods are provided by this module. They are	95	The following convenience methods are provided by this module. They are
73	exported by default:	96	exported by default:
74		97
75	$json_text = to_json $perl_scalar	98	$json_text = encode_json $perl_scalar
76	Converts the given Perl data structure to a UTF-8 encoded, binary	99	Converts the given Perl data structure to a UTF-8 encoded, binary
77	string (that is, the string contains octets only). Croaks on error.	100	string (that is, the string contains octets only). Croaks on error.
78		101
79	This function call is functionally identical to:	102	This function call is functionally identical to:
80		103
81	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	104	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
82		105
83	except being faster.	106	except being faster.
84		107
85	$perl_scalar = from_json $json_text	108	$perl_scalar = decode_json $json_text
86	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
87	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
88	resulting reference. Croaks on error.	111	resulting reference. Croaks on error.
89		112
90	This function call is functionally identical to:	113	This function call is functionally identical to:
91		114
…		…
109	1. Perl strings can store characters with ordinal values > 255.	132	1. Perl strings can store characters with ordinal values > 255.
110	This enables you to store Unicode characters as single characters in	133	This enables you to store Unicode characters as single characters in
111	a Perl string - very natural.	134	a Perl string - very natural.
112		135
113	2. Perl does not associate an encoding with your strings.	136	2. Perl does not associate an encoding with your strings.
114	Unless you force it to, e.g. when matching it against a regex, or	137	... until you force it to, e.g. when matching it against a regex, or
115	printing the scalar to a file, in which case Perl either interprets	138	printing the scalar to a file, in which case Perl either interprets
116	your string as locale-encoded text, octets/binary, or as Unicode,	139	your string as locale-encoded text, octets/binary, or as Unicode,
117	depending on various settings. In no case is an encoding stored	140	depending on various settings. In no case is an encoding stored
118	together with your data, it is use that decides encoding, not any	141	together with your data, it is use that decides encoding, not any
119	magical metadata.	142	magical meta data.
120		143
121	3. The internal utf-8 flag has no meaning with regards to the encoding	144	3. The internal utf-8 flag has no meaning with regards to the encoding
122	of your string.	145	of your string.
123	Just ignore that flag unless you debug a Perl bug, a module written	146	Just ignore that flag unless you debug a Perl bug, a module written
124	in XS or want to dive into the internals of perl. Otherwise it will	147	in XS or want to dive into the internals of perl. Otherwise it will
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155		178
156	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]})
157	=> {"a": [1, 2]}	180	=> {"a": [1, 2]}
158		181
159	$json = $json->ascii ([$enable])	182	$json = $json->ascii ([$enable])
		183	$enabled = $json->get_ascii
160	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
161	generate characters outside the code range 0..127 (which is ASCII).	185	generate characters outside the code range 0..127 (which is ASCII).
162	Any Unicode characters outside that range will be escaped using	186	Any Unicode characters outside that range will be escaped using
163	either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL	187	either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL
164	escape sequence, as per RFC4627. The resulting encoded JSON text can	188	escape sequence, as per RFC4627. The resulting encoded JSON text can
…		…
168		192
169	If $enable is false, then the "encode" method will not escape	193	If $enable is false, then the "encode" method will not escape
170	Unicode characters unless required by the JSON syntax or other	194	Unicode characters unless required by the JSON syntax or other
171	flags. This results in a faster and more compact format.	195	flags. This results in a faster and more compact format.
172		196
		197	See also the section ENCODING/CODESET FLAG NOTES later in this
		198	document.
		199
173	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
174	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
175	contain any 8 bit characters.	202	contain any 8 bit characters.
176		203
177	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	204	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178	=> ["\ud801\udc01"]	205	=> ["\ud801\udc01"]
179		206
180	$json = $json->latin1 ([$enable])	207	$json = $json->latin1 ([$enable])
		208	$enabled = $json->get_latin1
181	If $enable is true (or missing), then the "encode" method will	209	If $enable is true (or missing), then the "encode" method will
182	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
183	any characters outside the code range 0..255. The resulting string	211	any characters outside the code range 0..255. The resulting string
184	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
185	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
…		…
187	superset of latin1.	215	superset of latin1.
188		216
189	If $enable is false, then the "encode" method will not escape	217	If $enable is false, then the "encode" method will not escape
190	Unicode characters unless required by the JSON syntax or other	218	Unicode characters unless required by the JSON syntax or other
191	flags.	219	flags.
		220
		221	See also the section ENCODING/CODESET FLAG NOTES later in this
		222	document.
192		223
193	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
194	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
195	smaller encoded size. The disadvantage is that the resulting JSON	226	smaller encoded size. The disadvantage is that the resulting JSON
196	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
…		…
201		232
202	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	233	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
203	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	234	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
204		235
205	$json = $json->utf8 ([$enable])	236	$json = $json->utf8 ([$enable])
		237	$enabled = $json->get_utf8
206	If $enable is true (or missing), then the "encode" method will	238	If $enable is true (or missing), then the "encode" method will
207	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,
208	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
209	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
210	characters outside the range 0..255, they are thus useful for	242	characters outside the range 0..255, they are thus useful for
…		…
215	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
216	string as a (non-encoded) Unicode string, while "decode" expects	248	string as a (non-encoded) Unicode string, while "decode" expects
217	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
218	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.
219		251
		252	See also the section ENCODING/CODESET FLAG NOTES later in this
		253	document.
		254
220	Example, output UTF-16BE-encoded JSON:	255	Example, output UTF-16BE-encoded JSON:
221		256
222	use Encode;	257	use Encode;
223	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	258	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
224		259
…		…
242	2	277	2
243	]	278	]
244	}	279	}
245		280
246	$json = $json->indent ([$enable])	281	$json = $json->indent ([$enable])
		282	$enabled = $json->get_indent
247	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
248	multiline format as output, putting every array member or	284	multiline format as output, putting every array member or
249	object/hash key-value pair into its own line, indenting them	285	object/hash key-value pair into its own line, indenting them
250	properly.	286	properly.
251		287
…		…
253	the resulting JSON text is guaranteed not to contain any "newlines".	289	the resulting JSON text is guaranteed not to contain any "newlines".
254		290
255	This setting has no effect when decoding JSON texts.	291	This setting has no effect when decoding JSON texts.
256		292
257	$json = $json->space_before ([$enable])	293	$json = $json->space_before ([$enable])
		294	$enabled = $json->get_space_before
258	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
259	an extra optional space before the ":" separating keys from values	296	an extra optional space before the ":" separating keys from values
260	in JSON objects.	297	in JSON objects.
261		298
262	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
…		…
268	Example, space_before enabled, space_after and indent disabled:	305	Example, space_before enabled, space_after and indent disabled:
269		306
270	{"key" :"value"}	307	{"key" :"value"}
271		308
272	$json = $json->space_after ([$enable])	309	$json = $json->space_after ([$enable])
		310	$enabled = $json->get_space_after
273	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
274	an extra optional space after the ":" separating keys from values in	312	an extra optional space after the ":" separating keys from values in
275	JSON objects and extra whitespace after the "," separating key-value	313	JSON objects and extra whitespace after the "," separating key-value
276	pairs and array members.	314	pairs and array members.
277		315
…		…
283	Example, space_before and indent disabled, space_after enabled:	321	Example, space_before and indent disabled, space_after enabled:
284		322
285	{"key": "value"}	323	{"key": "value"}
286		324
287	$json = $json->relaxed ([$enable])	325	$json = $json->relaxed ([$enable])
		326	$enabled = $json->get_relaxed
288	If $enable is true (or missing), then "decode" will accept some	327	If $enable is true (or missing), then "decode" will accept some
289	extensions to normal JSON syntax (see below). "encode" will not be	328	extensions to normal JSON syntax (see below). "encode" will not be
290	affected in anyway. *Be aware that this option makes you accept	329	affected in anyway. *Be aware that this option makes you accept
291	invalid JSON texts as if they were valid!*. I suggest only to use	330	invalid JSON texts as if they were valid!*. I suggest only to use
292	this option to parse application-specific files written by humans	331	this option to parse application-specific files written by humans
…		…
295	If $enable is false (the default), then "decode" will only accept	334	If $enable is false (the default), then "decode" will only accept
296	valid JSON texts.	335	valid JSON texts.
297		336
298	Currently accepted extensions are:	337	Currently accepted extensions are:
299		338
300	* list items can have an end-comma	339	* list items can have an end-comma
		340
301	JSON separates array elements and key-value pairs with commas.	341	JSON separates array elements and key-value pairs with commas.
302	This can be annoying if you write JSON texts manually and want	342	This can be annoying if you write JSON texts manually and want
303	to be able to quickly append elements, so this extension accepts	343	to be able to quickly append elements, so this extension accepts
304	comma at the end of such items not just between them:	344	comma at the end of such items not just between them:
305		345
…		…
310	{	350	{
311	"k1": "v1",	351	"k1": "v1",
312	"k2": "v2", <- this comma not normally allowed	352	"k2": "v2", <- this comma not normally allowed
313	}	353	}
314		354
315	* shell-style '#'-comments	355	* shell-style '#'-comments
		356
316	Whenever JSON allows whitespace, shell-style comments are	357	Whenever JSON allows whitespace, shell-style comments are
317	additionally allowed. They are terminated by the first	358	additionally allowed. They are terminated by the first
318	carriage-return or line-feed character, after which more	359	carriage-return or line-feed character, after which more
319	white-space and comments are allowed.	360	white-space and comments are allowed.
320		361
…		…
322	1, # this comment not allowed in JSON	363	1, # this comment not allowed in JSON
323	# neither this one...	364	# neither this one...
324	]	365	]
325		366
326	$json = $json->canonical ([$enable])	367	$json = $json->canonical ([$enable])
		368	$enabled = $json->get_canonical
327	If $enable is true (or missing), then the "encode" method will	369	If $enable is true (or missing), then the "encode" method will
328	output JSON objects by sorting their keys. This is adding a	370	output JSON objects by sorting their keys. This is adding a
329	comparatively high overhead.	371	comparatively high overhead.
330		372
331	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
…		…
339	in Perl.	381	in Perl.
340		382
341	This setting has no effect when decoding JSON texts.	383	This setting has no effect when decoding JSON texts.
342		384
343	$json = $json->allow_nonref ([$enable])	385	$json = $json->allow_nonref ([$enable])
		386	$enabled = $json->get_allow_nonref
344	If $enable is true (or missing), then the "encode" method can	387	If $enable is true (or missing), then the "encode" method can
345	convert a non-reference into its corresponding string, number or	388	convert a non-reference into its corresponding string, number or
346	null JSON value, which is an extension to RFC4627. Likewise,	389	null JSON value, which is an extension to RFC4627. Likewise,
347	"decode" will accept those JSON values instead of croaking.	390	"decode" will accept those JSON values instead of croaking.
348		391
…		…
356		399
357	JSON::XS->new->allow_nonref->encode ("Hello, World!")	400	JSON::XS->new->allow_nonref->encode ("Hello, World!")
358	=> "Hello, World!"	401	=> "Hello, World!"
359		402
360	$json = $json->allow_blessed ([$enable])	403	$json = $json->allow_blessed ([$enable])
		404	$enabled = $json->get_allow_blessed
361	If $enable is true (or missing), then the "encode" method will not	405	If $enable is true (or missing), then the "encode" method will not
362	barf when it encounters a blessed reference. Instead, the value of	406	barf when it encounters a blessed reference. Instead, the value of
363	the convert_blessed option will decide whether "null"	407	the convert_blessed option will decide whether "null"
364	("convert_blessed" disabled or no "to_json" method found) or a	408	("convert_blessed" disabled or no "TO_JSON" method found) or a
365	representation of the object ("convert_blessed" enabled and	409	representation of the object ("convert_blessed" enabled and
366	"to_json" method found) is being encoded. Has no effect on "decode".	410	"TO_JSON" method found) is being encoded. Has no effect on "decode".
367		411
368	If $enable is false (the default), then "encode" will throw an	412	If $enable is false (the default), then "encode" will throw an
369	exception when it encounters a blessed object.	413	exception when it encounters a blessed object.
370		414
371	$json = $json->convert_blessed ([$enable])	415	$json = $json->convert_blessed ([$enable])
		416	$enabled = $json->get_convert_blessed
372	If $enable is true (or missing), then "encode", upon encountering a	417	If $enable is true (or missing), then "encode", upon encountering a
373	blessed object, will check for the availability of the "TO_JSON"	418	blessed object, will check for the availability of the "TO_JSON"
374	method on the object's class. If found, it will be called in scalar	419	method on the object's class. If found, it will be called in scalar
375	context and the resulting scalar will be encoded instead of the	420	context and the resulting scalar will be encoded instead of the
376	object. If no "TO_JSON" method is found, the value of	421	object. If no "TO_JSON" method is found, the value of
…		…
380	returns other blessed objects, those will be handled in the same	425	returns other blessed objects, those will be handled in the same
381	way. "TO_JSON" must take care of not causing an endless recursion	426	way. "TO_JSON" must take care of not causing an endless recursion
382	cycle (== crash) in this case. The name of "TO_JSON" was chosen	427	cycle (== crash) in this case. The name of "TO_JSON" was chosen
383	because other methods called by the Perl core (== not by the user of	428	because other methods called by the Perl core (== not by the user of
384	the object) are usually in upper case letters and to avoid	429	the object) are usually in upper case letters and to avoid
385	collisions with the "to_json" function.	430	collisions with any "to_json" function or method.
386		431
387	This setting does not yet influence "decode" in any way, but in the	432	This setting does not yet influence "decode" in any way, but in the
388	future, global hooks might get installed that influence "decode" and	433	future, global hooks might get installed that influence "decode" and
389	are enabled by this setting.	434	are enabled by this setting.
390		435
…		…
466		511
467	{ __widget__ => $self->{id} }	512	{ __widget__ => $self->{id} }
468	}	513	}
469		514
470	$json = $json->shrink ([$enable])	515	$json = $json->shrink ([$enable])
		516	$enabled = $json->get_shrink
471	Perl usually over-allocates memory a bit when allocating space for	517	Perl usually over-allocates memory a bit when allocating space for
472	strings. This flag optionally resizes strings generated by either	518	strings. This flag optionally resizes strings generated by either
473	"encode" or "decode" to their minimum size possible. This can save	519	"encode" or "decode" to their minimum size possible. This can save
474	memory when your JSON texts are either very very long or you have	520	memory when your JSON texts are either very very long or you have
475	many short strings. It will also try to downgrade any strings to	521	many short strings. It will also try to downgrade any strings to
…		…
493	converting strings that look like integers or floats into integers	539	converting strings that look like integers or floats into integers
494	or floats internally (there is no difference on the Perl level),	540	or floats internally (there is no difference on the Perl level),
495	saving space.	541	saving space.
496		542
497	$json = $json->max_depth ([$maximum_nesting_depth])	543	$json = $json->max_depth ([$maximum_nesting_depth])
		544	$max_depth = $json->get_max_depth
498	Sets the maximum nesting level (default 512) accepted while encoding	545	Sets the maximum nesting level (default 512) accepted while encoding
499	or decoding. If the JSON text or Perl data structure has an equal or	546	or decoding. If the JSON text or Perl data structure has an equal or
500	higher nesting level then this limit, then the encoder and decoder	547	higher nesting level then this limit, then the encoder and decoder
501	will stop and croak at that point.	548	will stop and croak at that point.
502		549
…		…
514		561
515	See SECURITY CONSIDERATIONS, below, for more info on why this is	562	See SECURITY CONSIDERATIONS, below, for more info on why this is
516	useful.	563	useful.
517		564
518	$json = $json->max_size ([$maximum_string_size])	565	$json = $json->max_size ([$maximum_string_size])
		566	$max_size = $json->get_max_size
519	Set the maximum length a JSON text may have (in bytes) where	567	Set the maximum length a JSON text may have (in bytes) where
520	decoding is being attempted. The default is 0, meaning no limit.	568	decoding is being attempted. The default is 0, meaning no limit.
521	When "decode" is called on a string longer then this number of	569	When "decode" is called on a string longer then this number of
522	characters it will not attempt to decode the string but throw an	570	characters it will not attempt to decode the string but throw an
523	exception. This setting has no effect on "encode" (yet).	571	exception. This setting has no effect on "encode" (yet).
…		…
558	and you need to know where the JSON text ends.	606	and you need to know where the JSON text ends.
559		607
560	JSON::XS->new->decode_prefix ("[1] the tail")	608	JSON::XS->new->decode_prefix ("[1] the tail")
561	=> ([], 3)	609	=> ([], 3)
562		610
		611	INCREMENTAL PARSING
		612	[This section and the API it details is still EXPERIMENTAL]
		613
		614	In some cases, there is the need for incremental parsing of JSON texts.
		615	While this module always has to keep both JSON text and resulting Perl
		616	data structure in memory at one time, it does allow you to parse a JSON
		617	stream incrementally. It does so by accumulating text until it has a
		618	full JSON object, which it then can decode. This process is similar to
		619	using "decode_prefix" to see if a full JSON object is available, but is
		620	much more efficient (JSON::XS will only attempt to parse the JSON text
		621	once it is sure it has enough text to get a decisive result, using a
		622	very simple but truly incremental parser).
		623
		624	The following two methods deal with this.
		625
		626	[void, scalar or list context] = $json->incr_parse ([$string])
		627	This is the central parsing function. It can both append new text
		628	and extract objects from the stream accumulated so far (both of
		629	these functions are optional).
		630
		631	If $string is given, then this string is appended to the already
		632	existing JSON fragment stored in the $json object.
		633
		634	After that, if the function is called in void context, it will
		635	simply return without doing anything further. This can be used to
		636	add more text in as many chunks as you want.
		637
		638	If the method is called in scalar context, then it will try to
		639	extract exactly one JSON object. If that is successful, it will
		640	return this object, otherwise it will return "undef". If there is a
		641	parse error, this method will croak just as "decode" would do (one
		642	can then use "incr_skip" to skip the errornous part). This is the
		643	most common way of using the method.
		644
		645	And finally, in list context, it will try to extract as many objects
		646	from the stream as it can find and return them, or the empty list
		647	otherwise. For this to work, there must be no separators between the
		648	JSON objects or arrays, instead they must be concatenated
		649	back-to-back. If an error occurs, an exception will be raised as in
		650	the scalar context case. Note that in this case, any
		651	previously-parsed JSON texts will be lost.
		652
		653	$lvalue_string = $json->incr_text
		654	This method returns the currently stored JSON fragment as an lvalue,
		655	that is, you can manipulate it. This only works when a preceding
		656	call to "incr_parse" in scalar context successfully returned an
		657	object. Under all other circumstances you must not call this
		658	function (I mean it. although in simple tests it might actually
		659	work, it will fail under real world conditions). As a special
		660	exception, you can also call this method before having parsed
		661	anything.
		662
		663	This function is useful in two cases: a) finding the trailing text
		664	after a JSON object or b) parsing multiple JSON objects separated by
		665	non-JSON text (such as commas).
		666
		667	$json->incr_skip
		668	This will reset the state of the incremental parser and will remove
		669	the parsed text from the input buffer. This is useful after
		670	"incr_parse" died, in which case the input buffer and incremental
		671	parser state is left unchanged, to skip the text parsed so far and
		672	to reset the parse state.
		673
		674	LIMITATIONS
		675	All options that affect decoding are supported, except "allow_nonref".
		676	The reason for this is that it cannot be made to work sensibly: JSON
		677	objects and arrays are self-delimited, i.e. you can concatenate them
		678	back to back and still decode them perfectly. This does not hold true
		679	for JSON numbers, however.
		680
		681	For example, is the string 1 a single JSON number, or is it simply the
		682	start of 12? Or is 12 a single JSON number, or the concatenation of 1
		683	and 2? In neither case you can tell, and this is why JSON::XS takes the
		684	conservative route and disallows this case.
		685
		686	EXAMPLES
		687	Some examples will make all this clearer. First, a simple example that
		688	works similarly to "decode_prefix": We want to decode the JSON object at
		689	the start of a string and identify the portion after the JSON object:
		690
		691	my $text = "[1,2,3] hello";
		692
		693	my $json = new JSON::XS;
		694
		695	my $obj = $json->incr_parse ($text)
		696	or die "expected JSON object or array at beginning of string";
		697
		698	my $tail = $json->incr_text;
		699	# $tail now contains " hello"
		700
		701	Easy, isn't it?
		702
		703	Now for a more complicated example: Imagine a hypothetical protocol
		704	where you read some requests from a TCP stream, and each request is a
		705	JSON array, without any separation between them (in fact, it is often
		706	useful to use newlines as "separators", as these get interpreted as
		707	whitespace at the start of the JSON text, which makes it possible to
		708	test said protocol with "telnet"...).
		709
		710	Here is how you'd do it (it is trivial to write this in an event-based
		711	manner):
		712
		713	my $json = new JSON::XS;
		714
		715	# read some data from the socket
		716	while (sysread $socket, my $buf, 4096) {
		717
		718	# split and decode as many requests as possible
		719	for my $request ($json->incr_parse ($buf)) {
		720	# act on the $request
		721	}
		722	}
		723
		724	Another complicated example: Assume you have a string with JSON objects
		725	or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
		726	[3]"). To parse them, we have to skip the commas between the JSON texts,
		727	and here is where the lvalue-ness of "incr_text" comes in useful:
		728
		729	my $text = "[1],[2], [3]";
		730	my $json = new JSON::XS;
		731
		732	# void context, so no parsing done
		733	$json->incr_parse ($text);
		734
		735	# now extract as many objects as possible. note the
		736	# use of scalar context so incr_text can be called.
		737	while (my $obj = $json->incr_parse) {
		738	# do something with $obj
		739
		740	# now skip the optional comma
		741	$json->incr_text =~ s/^ \s* , //x;
		742	}
		743
		744	Now lets go for a very complex example: Assume that you have a gigantic
		745	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		746	but you cannot load it into memory fully (this has actually happened in
		747	the real world :).
		748
		749	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		750	can still help you: You implement a (very simple) array parser and let
		751	JSON decode the array elements, which are all full JSON objects on their
		752	own (this wouldn't work if the array elements could be JSON numbers, for
		753	example):
		754
		755	my $json = new JSON::XS;
		756
		757	# open the monster
		758	open my $fh, "<bigfile.json"
		759	or die "bigfile: $!";
		760
		761	# first parse the initial "["
		762	for (;;) {
		763	sysread $fh, my $buf, 65536
		764	or die "read error: $!";
		765	$json->incr_parse ($buf); # void context, so no parsing
		766
		767	# Exit the loop once we found and removed(!) the initial "[".
		768	# In essence, we are (ab-)using the $json object as a simple scalar
		769	# we append data to.
		770	last if $json->incr_text =~ s/^ \s* \[ //x;
		771	}
		772
		773	# now we have the skipped the initial "[", so continue
		774	# parsing all the elements.
		775	for (;;) {
		776	# in this loop we read data until we got a single JSON object
		777	for (;;) {
		778	if (my $obj = $json->incr_parse) {
		779	# do something with $obj
		780	last;
		781	}
		782
		783	# add more data
		784	sysread $fh, my $buf, 65536
		785	or die "read error: $!";
		786	$json->incr_parse ($buf); # void context, so no parsing
		787	}
		788
		789	# in this loop we read data until we either found and parsed the
		790	# separating "," between elements, or the final "]"
		791	for (;;) {
		792	# first skip whitespace
		793	$json->incr_text =~ s/^\s*//;
		794
		795	# if we find "]", we are done
		796	if ($json->incr_text =~ s/^\]//) {
		797	print "finished.\n";
		798	exit;
		799	}
		800
		801	# if we find ",", we can continue with the next element
		802	if ($json->incr_text =~ s/^,//) {
		803	last;
		804	}
		805
		806	# if we find anything else, we have a parse error!
		807	if (length $json->incr_text) {
		808	die "parse error near ", $json->incr_text;
		809	}
		810
		811	# else add more data
		812	sysread $fh, my $buf, 65536
		813	or die "read error: $!";
		814	$json->incr_parse ($buf); # void context, so no parsing
		815	}
		816
		817	This is a complex example, but most of the complexity comes from the
		818	fact that we are trying to be correct (bear with me if I am wrong, I
		819	never ran the above example :).
		820
563	MAPPING	821	MAPPING
564	This section describes how JSON::XS maps Perl values to JSON values and	822	This section describes how JSON::XS maps Perl values to JSON values and
565	vice versa. These mappings are designed to "do the right thing" in most	823	vice versa. These mappings are designed to "do the right thing" in most
566	circumstances automatically, preserving round-tripping characteristics	824	circumstances automatically, preserving round-tripping characteristics
567	(what you put in comes out as something equivalent).	825	(what you put in comes out as something equivalent).
…		…
588	A JSON number becomes either an integer, numeric (floating point) or	846	A JSON number becomes either an integer, numeric (floating point) or
589	string scalar in perl, depending on its range and any fractional	847	string scalar in perl, depending on its range and any fractional
590	parts. On the Perl level, there is no difference between those as	848	parts. On the Perl level, there is no difference between those as
591	Perl handles all the conversion details, but an integer may take	849	Perl handles all the conversion details, but an integer may take
592	slightly less memory and might represent more values exactly than	850	slightly less memory and might represent more values exactly than
593	(floating point) numbers.	851	floating point numbers.
594		852
595	If the number consists of digits only, JSON::XS will try to	853	If the number consists of digits only, JSON::XS will try to
596	represent it as an integer value. If that fails, it will try to	854	represent it as an integer value. If that fails, it will try to
597	represent it as a numeric (floating point) value if that is possible	855	represent it as a numeric (floating point) value if that is possible
598	without loss of precision. Otherwise it will preserve the number as	856	without loss of precision. Otherwise it will preserve the number as
599	a string value.	857	a string value (in which case you lose roundtripping ability, as the
		858	JSON number will be re-encoded toa JSON string).
600		859
601	Numbers containing a fractional or exponential part will always be	860	Numbers containing a fractional or exponential part will always be
602	represented as numeric (floating point) values, possibly at a loss	861	represented as numeric (floating point) values, possibly at a loss
603	of precision.	862	of precision (in which case you might lose perfect roundtripping
604		863	ability, but the JSON number will still be re-encoded as a JSON
605	This might create round-tripping problems as numbers might become	864	number).
606	strings, but as Perl is typeless there is no other way to do it.
607		865
608	true, false	866	true, false
609	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",	867	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
610	respectively. They are overloaded to act almost exactly like the	868	respectively. They are overloaded to act almost exactly like the
611	numbers 1 and 0. You can check whether a scalar is a JSON boolean by	869	numbers 1 and 0. You can check whether a scalar is a JSON boolean by
…		…
639	an exception to be thrown, except for references to the integers 0	897	an exception to be thrown, except for references to the integers 0
640	and 1, which get turned into "false" and "true" atoms in JSON. You	898	and 1, which get turned into "false" and "true" atoms in JSON. You
641	can also use "JSON::XS::false" and "JSON::XS::true" to improve	899	can also use "JSON::XS::false" and "JSON::XS::true" to improve
642	readability.	900	readability.
643		901
644	to_json [\0,JSON::XS::true] # yields [false,true]	902	encode_json [\0,JSON::XS::true] # yields [false,true]
645		903
646	JSON::XS::true, JSON::XS::false	904	JSON::XS::true, JSON::XS::false
647	These special values become JSON true and JSON false values,	905	These special values become JSON true and JSON false values,
648	respectively. You can also use "\1" and "\0" directly if you want.	906	respectively. You can also use "\1" and "\0" directly if you want.
649		907
650	blessed objects	908	blessed objects
651	Blessed objects are not allowed. JSON::XS currently tries to encode	909	Blessed objects are not directly representable in JSON. See the
652	their underlying representation (hash- or arrayref), but this	910	"allow_blessed" and "convert_blessed" methods on various options on
653	behaviour might change in future versions.	911	how to deal with this: basically, you can choose between throwing an
		912	exception, encoding the reference as if it weren't blessed, or
		913	provide your own serialiser method.
654		914
655	simple scalars	915	simple scalars
656	Simple Perl scalars (any scalar that is not a reference) are the	916	Simple Perl scalars (any scalar that is not a reference) are the
657	most difficult objects to encode: JSON::XS will encode undefined	917	most difficult objects to encode: JSON::XS will encode undefined
658	scalars as JSON null value, scalars that have last been used in a	918	scalars as JSON "null" values, scalars that have last been used in a
659	string context before encoding as JSON strings and anything else as	919	string context before encoding as JSON strings, and anything else as
660	number value:	920	number value:
661		921
662	# dump as number	922	# dump as number
663	to_json [2] # yields [2]	923	encode_json [2] # yields [2]
664	to_json [-3.0e17] # yields [-3e+17]	924	encode_json [-3.0e17] # yields [-3e+17]
665	my $value = 5; to_json [$value] # yields [5]	925	my $value = 5; encode_json [$value] # yields [5]
666		926
667	# used as string, so dump as string	927	# used as string, so dump as string
668	print $value;	928	print $value;
669	to_json [$value] # yields ["5"]	929	encode_json [$value] # yields ["5"]
670		930
671	# undef becomes null	931	# undef becomes null
672	to_json [undef] # yields [null]	932	encode_json [undef] # yields [null]
673		933
674	You can force the type to be a JSON string by stringifying it:	934	You can force the type to be a JSON string by stringifying it:
675		935
676	my $x = 3.1; # some variable containing a number	936	my $x = 3.1; # some variable containing a number
677	"$x"; # stringified	937	"$x"; # stringified
…		…
683	my $x = "3"; # some variable containing a string	943	my $x = "3"; # some variable containing a string
684	$x += 0; # numify it, ensuring it will be dumped as a number	944	$x += 0; # numify it, ensuring it will be dumped as a number
685	$x *= 1; # same thing, the choice is yours.	945	$x *= 1; # same thing, the choice is yours.
686		946
687	You can not currently force the type in other, less obscure, ways.	947	You can not currently force the type in other, less obscure, ways.
688	Tell me if you need this capability.	948	Tell me if you need this capability (but don't forget to explain why
		949	it's needed :).
689		950
690	COMPARISON	951	ENCODING/CODESET FLAG NOTES
691	As already mentioned, this module was created because none of the	952	The interested reader might have seen a number of flags that signify
692	existing JSON modules could be made to work correctly. First I will	953	encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
693	describe the problems (or pleasures) I encountered with various existing	954	some confusion on what these do, so here is a short comparison:
694	JSON modules, followed by some benchmark values. JSON::XS was designed
695	not to suffer from any of these problems or limitations.
696		955
697	JSON 1.07	956	"utf8" controls whether the JSON text created by "encode" (and expected
698	Slow (but very portable, as it is written in pure Perl).	957	by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
		958	control whether "encode" escapes character values outside their
		959	respective codeset range. Neither of these flags conflict with each
		960	other, although some combinations make less sense than others.
699		961
700	Undocumented/buggy Unicode handling (how JSON handles Unicode values	962	Care has been taken to make all flags symmetrical with respect to
701	is undocumented. One can get far by feeding it Unicode strings and	963	"encode" and "decode", that is, texts encoded with any combination of
702	doing en-/decoding oneself, but Unicode escapes are not working	964	these flag values will be correctly decoded when the same flags are used
		965	- in general, if you use different flag settings while encoding vs. when
		966	decoding you likely have a bug somewhere.
		967
		968	Below comes a verbose discussion of these flags. Note that a "codeset"
		969	is simply an abstract set of character-codepoint pairs, while an
		970	encoding takes those codepoint numbers and encodes them, in our case
		971	into octets. Unicode is (among other things) a codeset, UTF-8 is an
		972	encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets and
		973	encodings at the same time, which can be confusing.
		974
		975	"utf8" flag disabled
		976	When "utf8" is disabled (the default), then "encode"/"decode"
		977	generate and expect Unicode strings, that is, characters with high
		978	ordinal Unicode values (> 255) will be encoded as such characters,
		979	and likewise such characters are decoded as-is, no canges to them
		980	will be done, except "(re-)interpreting" them as Unicode codepoints
		981	or Unicode characters, respectively (to Perl, these are the same
		982	thing in strings unless you do funny/weird/dumb stuff).
		983
		984	This is useful when you want to do the encoding yourself (e.g. when
		985	you want to have UTF-16 encoded JSON texts) or when some other layer
		986	does the encoding for you (for example, when printing to a terminal
		987	using a filehandle that transparently encodes to UTF-8 you certainly
		988	do NOT want to UTF-8 encode your data first and have Perl encode it
		989	another time).
		990
		991	"utf8" flag enabled
		992	If the "utf8"-flag is enabled, "encode"/"decode" will encode all
		993	characters using the corresponding UTF-8 multi-byte sequence, and
		994	will expect your input strings to be encoded as UTF-8, that is, no
		995	"character" of the input string must have any value > 255, as UTF-8
		996	does not allow that.
		997
		998	The "utf8" flag therefore switches between two modes: disabled means
		999	you will get a Unicode string in Perl, enabled means you get an
		1000	UTF-8 encoded octet/binary string in Perl.
		1001
		1002	"latin1" or "ascii" flags enabled
		1003	With "latin1" (or "ascii") enabled, "encode" will escape characters
		1004	with ordinal values > 255 (> 127 with "ascii") and encode the
		1005	remaining characters as specified by the "utf8" flag.
		1006
		1007	If "utf8" is disabled, then the result is also correctly encoded in
		1008	those character sets (as both are proper subsets of Unicode, meaning
		1009	that a Unicode string with all character values < 256 is the same
		1010	thing as a ISO-8859-1 string, and a Unicode string with all
		1011	character values < 128 is the same thing as an ASCII string in
703	properly).	1012	Perl).
704		1013
705	No round-tripping (strings get clobbered if they look like numbers,	1014	If "utf8" is enabled, you still get a correct UTF-8-encoded string,
706	e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that	1015	regardless of these flags, just some more characters will be escaped
707	will decode into the number 2.	1016	using "\uXXXX" then before.
708		1017
709	JSON::PC 0.01	1018	Note that ISO-8859-1-encoded strings are not compatible with UTF-8
710	Very fast.	1019	encoding, while ASCII-encoded strings are. That is because the
		1020	ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
		1021	codeset being a subset of Unicode), while ASCII is.
711		1022
712	Undocumented/buggy Unicode handling.	1023	Surprisingly, "decode" will ignore these flags and so treat all
		1024	input values as governed by the "utf8" flag. If it is disabled, this
		1025	allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
		1026	strict subsets of Unicode. If it is enabled, you can correctly
		1027	decode UTF-8 encoded strings.
713		1028
714	No round-tripping.	1029	So neither "latin1" nor "ascii" are incompatible with the "utf8"
		1030	flag - they only govern when the JSON output engine escapes a
		1031	character or not.
715		1032
716	Has problems handling many Perl values (e.g. regex results and other	1033	The main use for "latin1" is to relatively efficiently store binary
717	magic values will make it croak).	1034	data as JSON, at the expense of breaking compatibility with most
		1035	JSON decoders.
718		1036
719	Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}"	1037	The main use for "ascii" is to force the output to not contain
720	which is not a valid JSON text.	1038	characters with values > 127, which means you can interpret the
721		1039	resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
722	Unmaintained (maintainer unresponsive for many months, bugs are not	1040	any character set and 8-bit-encoding, and still get the same data
723	getting fixed).	1041	structure back. This is useful when your channel for JSON transfer
724		1042	is not 8-bit clean or the encoding might be mangled in between (e.g.
725	JSON::Syck 0.21	1043	in mail), and works because ASCII is a proper subset of most 8-bit
726	Very buggy (often crashes).	1044	and multibyte encodings in use in the world.
727
728	Very inflexible (no human-readable format supported, format pretty
729	much undocumented. I need at least a format for easy reading by
730	humans and a single-line compact format for use in a protocol, and
731	preferably a way to generate ASCII-only JSON texts).
732
733	Completely broken (and confusingly documented) Unicode handling
734	(Unicode escapes are not working properly, you need to set
735	ImplicitUnicode to different values on en- and decoding to get
736	symmetric behaviour).
737
738	No round-tripping (simple cases work, but this depends on whether
739	the scalar value was used in a numeric context or not).
740
741	Dumping hashes may skip hash values depending on iterator state.
742
743	Unmaintained (maintainer unresponsive for many months, bugs are not
744	getting fixed).
745
746	Does not check input for validity (i.e. will accept non-JSON input
747	and return "something" instead of raising an exception. This is a
748	security issue: imagine two banks transferring money between each
749	other using JSON. One bank might parse a given non-JSON request and
750	deduct money, while the other might reject the transaction with a
751	syntax error. While a good protocol will at least recover, that is
752	extra unnecessary work and the transaction will still not succeed).
753
754	JSON::DWIW 0.04
755	Very fast. Very natural. Very nice.
756
757	Undocumented Unicode handling (but the best of the pack. Unicode
758	escapes still don't get parsed properly).
759
760	Very inflexible.
761
762	No round-tripping.
763
764	Does not generate valid JSON texts (key strings are often unquoted,
765	empty keys result in nothing being output)
766
767	Does not check input for validity.
768		1045
769	JSON and YAML	1046	JSON and YAML
770	You often hear that JSON is a subset (or a close subset) of YAML. This	1047	You often hear that JSON is a subset of YAML. This is, however, a mass
771	is, however, a mass hysteria and very far from the truth. In general,	1048	hysteria(*) and very far from the truth (as of the time of this
772	there is no way to configure JSON::XS to output a data structure as	1049	writing), so let me state it clearly: *in general, there is no way to
773	valid YAML.	1050	configure JSON::XS to output a data structure as valid YAML* that works
		1051	in all cases.
774		1052
775	If you really must use JSON::XS to generate YAML, you should use this	1053	If you really must use JSON::XS to generate YAML, you should use this
776	algorithm (subject to change in future versions):	1054	algorithm (subject to change in future versions):
777		1055
778	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1056	my $to_yaml = JSON::XS->new->utf8->space_after (1);
779	my $yaml = $to_yaml->encode ($ref) . "\n";	1057	my $yaml = $to_yaml->encode ($ref) . "\n";
780		1058
781	This will usually generate JSON texts that also parse as valid YAML.	1059	This will usually generate JSON texts that also parse as valid YAML.
782	Please note that YAML has hardcoded limits on (simple) object key	1060	Please note that YAML has hardcoded limits on (simple) object key
783	lengths that JSON doesn't have, so you should make sure that your hash	1061	lengths that JSON doesn't have and also has different and incompatible
		1062	unicode handling, so you should make sure that your hash keys are
784	keys are noticeably shorter than the 1024 characters YAML allows.	1063	noticeably shorter than the 1024 "stream characters" YAML allows and
		1064	that you do not have characters with codepoint values outside the
		1065	Unicode BMP (basic multilingual page). YAML also does not allow "\/"
		1066	sequences in strings (which JSON::XS does not currently generate, but
		1067	other JSON generators might).
785		1068
786	There might be other incompatibilities that I am not aware of. In	1069	There might be other incompatibilities that I am not aware of (or the
		1070	YAML specification has been changed yet again - it does so quite often).
787	general you should not try to generate YAML with a JSON generator or	1071	In general you should not try to generate YAML with a JSON generator or
788	vice versa, or try to parse JSON with a YAML parser or vice versa:	1072	vice versa, or try to parse JSON with a YAML parser or vice versa:
789	chances are high that you will run into severe interoperability	1073	chances are high that you will run into severe interoperability problems
790	problems.	1074	when you least expect it.
		1075
		1076	(*) I have been pressured multiple times by Brian Ingerson (one of the
		1077	authors of the YAML specification) to remove this paragraph, despite
		1078	him acknowledging that the actual incompatibilities exist. As I was
		1079	personally bitten by this "JSON is YAML" lie, I refused and said I
		1080	will continue to educate people about these issues, so others do not
		1081	run into the same problem again and again. After this, Brian called
		1082	me a (quote)complete and worthless idiot(unquote).
		1083
		1084	In my opinion, instead of pressuring and insulting people who
		1085	actually clarify issues with YAML and the wrong statements of some
		1086	of its proponents, I would kindly suggest reading the JSON spec
		1087	(which is not that difficult or long) and finally make YAML
		1088	compatible to it, and educating users about the changes, instead of
		1089	spreading lies about the real compatibility for many years and
		1090	trying to silence people who point out that it isn't true.
791		1091
792	SPEED	1092	SPEED
793	It seems that JSON::XS is surprisingly fast, as shown in the following	1093	It seems that JSON::XS is surprisingly fast, as shown in the following
794	tables. They have been generated with the help of the "eg/bench" program	1094	tables. They have been generated with the help of the "eg/bench" program
795	in the JSON::XS distribution, to make it easy to compare on your own	1095	in the JSON::XS distribution, to make it easy to compare on your own
796	system.	1096	system.
797		1097
798	First comes a comparison between various modules using a very short	1098	First comes a comparison between various modules using a very short
799	single-line JSON string:	1099	single-line JSON string (also available at
		1100	<http://dist.schmorp.de/misc/json/short.json>).
800		1101
801	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1102	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
802	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1103	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
803		1104
804	It shows the number of encodes/decodes per second (JSON::XS uses the	1105	It shows the number of encodes/decodes per second (JSON::XS uses the
805	functional interface, while JSON::XS/2 uses the OO interface with	1106	functional interface, while JSON::XS/2 uses the OO interface with
806	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).	1107	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
807	Higher is better:	1108	Higher is better:
808		1109
809	Storable \| 15779.925 \| 14169.946 \|
810	-----------+------------+------------+
811	module \| encode \| decode \|	1110	module \| encode \| decode \|
812	-----------\|------------\|------------\|	1111	-----------\|------------\|------------\|
813	JSON \| 4990.842 \| 4088.813 \|	1112	JSON 1.x \| 4990.842 \| 4088.813 \|
814	JSON::DWIW \| 51653.990 \| 71575.154 \|	1113	JSON::DWIW \| 51653.990 \| 71575.154 \|
815	JSON::PC \| 65948.176 \| 74631.744 \|	1114	JSON::PC \| 65948.176 \| 74631.744 \|
816	JSON::PP \| 8931.652 \| 3817.168 \|	1115	JSON::PP \| 8931.652 \| 3817.168 \|
817	JSON::Syck \| 24877.248 \| 27776.848 \|	1116	JSON::Syck \| 24877.248 \| 27776.848 \|
818	JSON::XS \| 388361.481 \| 227951.304 \|	1117	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
825	encoding, about three times faster on decoding, and over forty times	1124	encoding, about three times faster on decoding, and over forty times
826	faster than JSON, even with pretty-printing and key sorting. It also	1125	faster than JSON, even with pretty-printing and key sorting. It also
827	compares favourably to Storable for small amounts of data.	1126	compares favourably to Storable for small amounts of data.
828		1127
829	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1128	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
830	search API (http://nanoref.com/yahooapis/mgPdGg):	1129	search API (<http://dist.schmorp.de/misc/json/long.json>).
831		1130
832	module \| encode \| decode \|	1131	module \| encode \| decode \|
833	-----------\|------------\|------------\|	1132	-----------\|------------\|------------\|
834	JSON \| 55.260 \| 34.971 \|	1133	JSON 1.x \| 55.260 \| 34.971 \|
835	JSON::DWIW \| 825.228 \| 1082.513 \|	1134	JSON::DWIW \| 825.228 \| 1082.513 \|
836	JSON::PC \| 3571.444 \| 2394.829 \|	1135	JSON::PC \| 3571.444 \| 2394.829 \|
837	JSON::PP \| 210.987 \| 32.574 \|	1136	JSON::PP \| 210.987 \| 32.574 \|
838	JSON::Syck \| 552.551 \| 787.544 \|	1137	JSON::Syck \| 552.551 \| 787.544 \|
839	JSON::XS \| 5780.463 \| 4854.519 \|	1138	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
872	Third, JSON::XS recurses using the C stack when decoding objects and	1171	Third, JSON::XS recurses using the C stack when decoding objects and
873	arrays. The C stack is a limited resource: for instance, on my amd64	1172	arrays. The C stack is a limited resource: for instance, on my amd64
874	machine with 8MB of stack size I can decode around 180k nested arrays	1173	machine with 8MB of stack size I can decode around 180k nested arrays
875	but only 14k nested JSON objects (due to perl itself recursing deeply on	1174	but only 14k nested JSON objects (due to perl itself recursing deeply on
876	croak to free the temporary). If that is exceeded, the program crashes.	1175	croak to free the temporary). If that is exceeded, the program crashes.
877	to be conservative, the default nesting limit is set to 512. If your	1176	To be conservative, the default nesting limit is set to 512. If your
878	process has a smaller stack, you should adjust this setting accordingly	1177	process has a smaller stack, you should adjust this setting accordingly
879	with the "max_depth" method.	1178	with the "max_depth" method.
880		1179
881	And last but least, something else could bomb you that I forgot to think	1180	Something else could bomb you, too, that I forgot to think of. In that
882	of. In that case, you get to keep the pieces. I am always open for	1181	case, you get to keep the pieces. I am always open for hints, though...
883	hints, though...	1182
		1183	Also keep in mind that JSON::XS might leak contents of your Perl data
		1184	structures in its error messages, so when you serialise sensitive
		1185	information you might want to make sure that exceptions thrown by
		1186	JSON::XS will not end up in front of untrusted eyes.
884		1187
885	If you are using JSON::XS to return packets to consumption by JavaScript	1188	If you are using JSON::XS to return packets to consumption by JavaScript
886	scripts in a browser you should have a look at	1189	scripts in a browser you should have a look at
887	<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1190	<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
888	you are vulnerable to some common attack vectors (which really are	1191	you are vulnerable to some common attack vectors (which really are
889	browser design bugs, but it is still you who will have to deal with it,	1192	browser design bugs, but it is still you who will have to deal with it,
890	as major browser developers care only for features, not about doing	1193	as major browser developers care only for features, not about getting
891	security right).	1194	security right).
892		1195
893	THREADS	1196	THREADS
894	This module is not guaranteed to be thread safe and there are no plans	1197	This module is not guaranteed to be thread safe and there are no plans
895	to change this until Perl gets thread support (as opposed to the	1198	to change this until Perl gets thread support (as opposed to the
896	horribly slow so-called "threads" which are simply slow and bloated	1199	horribly slow so-called "threads" which are simply slow and bloated
897	process simulations - use fork, its much faster, cheaper, better).	1200	process simulations - use fork, it's much faster, cheaper, better).
898		1201
899	(It might actually work, but you have been warned).	1202	(It might actually work, but you have been warned).
900		1203
901	BUGS	1204	BUGS
902	While the goal of this module is to be correct, that unfortunately does	1205	While the goal of this module is to be correct, that unfortunately does
903	not mean its bug-free, only that I think its design is bug-free. It is	1206	not mean it's bug-free, only that I think its design is bug-free. It is
904	still relatively early in its development. If you keep reporting bugs	1207	still relatively early in its development. If you keep reporting bugs
905	they will be fixed swiftly, though.	1208	they will be fixed swiftly, though.
906		1209
907	Please refrain from using rt.cpan.org or any other bug reporting	1210	Please refrain from using rt.cpan.org or any other bug reporting
908	service. I put the contact address into my modules for a reason.	1211	service. I put the contact address into my modules for a reason.
		1212
		1213	SEE ALSO
		1214	The json_xs command line utility for quick experiments.
909		1215
910	AUTHOR	1216	AUTHOR
911	Marc Lehmann <schmorp@schmorp.de>	1217	Marc Lehmann <schmorp@schmorp.de>
912	http://home.schmorp.de/	1218	http://home.schmorp.de/
913		1219

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Comparing JSON-XS/README (file contents):
Revision 1.20 by root, Tue Nov 13 22:59:08 2007 UTC vs.
Revision 1.24 by root, Thu Mar 27 06:37:35 2008 UTC