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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 1.34 by root, Thu Mar 11 17:36:09 2010 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, the deserialised data structure is identical on
63	the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"	62	the Perl level. (e.g. the string "2.0" doesn't suddenly become "2"
64	just because it looks like a number).	63	just because it looks like a number). There minor are exceptions
		64	to this, read the MAPPING section below to learn about those.
65		65
66	* strict checking of JSON correctness	66	* strict checking of JSON correctness
		67
67	There is no guessing, no generating of illegal JSON texts by	68	There is no guessing, no generating of illegal JSON texts by
68	default, and only JSON is accepted as input by default (the latter	69	default, and only JSON is accepted as input by default (the latter
69	is a security feature).	70	is a security feature).
70		71
71	* fast	72	* fast
72	Compared to other JSON modules, this module compares favourably in
73	terms of speed, too.
74		73
		74	Compared to other JSON modules and other serialisers such as
		75	Storable, this module usually compares favourably in terms of speed,
		76	too.
		77
75	* simple to use	78	* simple to use
		79
76	This module has both a simple functional interface as well as an OO	80	This module has both a simple functional interface as well as an
77	interface.	81	object oriented interface interface.
78		82
79	* reasonably versatile output formats	83	* reasonably versatile output formats
		84
80	You can choose between the most compact guaranteed single-line	85	You can choose between the most compact guaranteed-single-line
81	format possible (nice for simple line-based protocols), a pure-ascii	86	format possible (nice for simple line-based protocols), a pure-ASCII
82	format (for when your transport is not 8-bit clean, still supports	87	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	88	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	89	want to read that stuff). Or you can combine those features in
85	whatever way you like.	90	whatever way you like.
86		91
…		…
94		99
95	This function call is functionally identical to:	100	This function call is functionally identical to:
96		101
97	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	102	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
98		103
99	except being faster.	104	Except being faster.
100		105
101	$perl_scalar = decode_json $json_text	106	$perl_scalar = decode_json $json_text
102	The opposite of "encode_json": expects an UTF-8 (binary) string and	107	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	108	tries to parse that as an UTF-8 encoded JSON text, returning the
104	resulting reference. Croaks on error.	109	resulting reference. Croaks on error.
105		110
106	This function call is functionally identical to:	111	This function call is functionally identical to:
107		112
108	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	113	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
109		114
110	except being faster.	115	Except being faster.
111		116
112	$is_boolean = JSON::XS::is_bool $scalar	117	$is_boolean = JSON::XS::is_bool $scalar
113	Returns true if the passed scalar represents either JSON::XS::true	118	Returns true if the passed scalar represents either JSON::XS::true
114	or JSON::XS::false, two constants that act like 1 and 0,	119	or JSON::XS::false, two constants that act like 1 and 0,
115	respectively and are used to represent JSON "true" and "false"	120	respectively and are used to represent JSON "true" and "false"
…		…
125	1. Perl strings can store characters with ordinal values > 255.	130	1. Perl strings can store characters with ordinal values > 255.
126	This enables you to store Unicode characters as single characters in	131	This enables you to store Unicode characters as single characters in
127	a Perl string - very natural.	132	a Perl string - very natural.
128		133
129	2. Perl does not associate an encoding with your strings.	134	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	135	... 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	136	printing the scalar to a file, in which case Perl either interprets
132	your string as locale-encoded text, octets/binary, or as Unicode,	137	your string as locale-encoded text, octets/binary, or as Unicode,
133	depending on various settings. In no case is an encoding stored	138	depending on various settings. In no case is an encoding stored
134	together with your data, it is use that decides encoding, not any	139	together with your data, it is use that decides encoding, not any
135	magical metadata.	140	magical meta data.
136		141
137	3. The internal utf-8 flag has no meaning with regards to the encoding	142	3. The internal utf-8 flag has no meaning with regards to the encoding
138	of your string.	143	of your string.
139	Just ignore that flag unless you debug a Perl bug, a module written	144	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	145	in XS or want to dive into the internals of perl. Otherwise it will
…		…
145		150
146	If you didn't know about that flag, just the better, pretend it	151	If you didn't know about that flag, just the better, pretend it
147	doesn't exist.	152	doesn't exist.
148		153
149	4. A "Unicode String" is simply a string where each character can be	154	4. A "Unicode String" is simply a string where each character can be
150	validly interpreted as a Unicode codepoint.	155	validly interpreted as a Unicode code point.
151	If you have UTF-8 encoded data, it is no longer a Unicode string,	156	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.	157	but a Unicode string encoded in UTF-8, giving you a binary string.
153		158
154	5. A string containing "high" (> 255) character values is not a UTF-8	159	5. A string containing "high" (> 255) character values is not a UTF-8
155	string.	160	string.
…		…
185		190
186	If $enable is false, then the "encode" method will not escape	191	If $enable is false, then the "encode" method will not escape
187	Unicode characters unless required by the JSON syntax or other	192	Unicode characters unless required by the JSON syntax or other
188	flags. This results in a faster and more compact format.	193	flags. This results in a faster and more compact format.
189		194
		195	See also the section ENCODING/CODESET FLAG NOTES later in this
		196	document.
		197
190	The main use for this flag is to produce JSON texts that can be	198	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	199	transmitted over a 7-bit channel, as the encoded JSON texts will not
192	contain any 8 bit characters.	200	contain any 8 bit characters.
193		201
194	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	202	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
205	superset of latin1.	213	superset of latin1.
206		214
207	If $enable is false, then the "encode" method will not escape	215	If $enable is false, then the "encode" method will not escape
208	Unicode characters unless required by the JSON syntax or other	216	Unicode characters unless required by the JSON syntax or other
209	flags.	217	flags.
		218
		219	See also the section ENCODING/CODESET FLAG NOTES later in this
		220	document.
210		221
211	The main use for this flag is efficiently encoding binary data as	222	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	223	JSON text, as most octets will not be escaped, resulting in a
213	smaller encoded size. The disadvantage is that the resulting JSON	224	smaller encoded size. The disadvantage is that the resulting JSON
214	text is encoded in latin1 (and must correctly be treated as such	225	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	245	If $enable is false, then the "encode" method will return the JSON
235	string as a (non-encoded) Unicode string, while "decode" expects	246	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	247	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.	248	UTF-16) needs to be done yourself, e.g. using the Encode module.
238		249
		250	See also the section ENCODING/CODESET FLAG NOTES later in this
		251	document.
		252
239	Example, output UTF-16BE-encoded JSON:	253	Example, output UTF-16BE-encoded JSON:
240		254
241	use Encode;	255	use Encode;
242	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	256	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
243		257
…		…
318	If $enable is false (the default), then "decode" will only accept	332	If $enable is false (the default), then "decode" will only accept
319	valid JSON texts.	333	valid JSON texts.
320		334
321	Currently accepted extensions are:	335	Currently accepted extensions are:
322		336
323	* list items can have an end-comma	337	* list items can have an end-comma
		338
324	JSON separates array elements and key-value pairs with commas.	339	JSON separates array elements and key-value pairs with commas.
325	This can be annoying if you write JSON texts manually and want	340	This can be annoying if you write JSON texts manually and want
326	to be able to quickly append elements, so this extension accepts	341	to be able to quickly append elements, so this extension accepts
327	comma at the end of such items not just between them:	342	comma at the end of such items not just between them:
328		343
…		…
333	{	348	{
334	"k1": "v1",	349	"k1": "v1",
335	"k2": "v2", <- this comma not normally allowed	350	"k2": "v2", <- this comma not normally allowed
336	}	351	}
337		352
338	* shell-style '#'-comments	353	* shell-style '#'-comments
		354
339	Whenever JSON allows whitespace, shell-style comments are	355	Whenever JSON allows whitespace, shell-style comments are
340	additionally allowed. They are terminated by the first	356	additionally allowed. They are terminated by the first
341	carriage-return or line-feed character, after which more	357	carriage-return or line-feed character, after which more
342	white-space and comments are allowed.	358	white-space and comments are allowed.
343		359
…		…
361	it is disabled, the same hash might be encoded differently even if	377	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	378	contains the same data, as key-value pairs have no inherent ordering
363	in Perl.	379	in Perl.
364		380
365	This setting has no effect when decoding JSON texts.	381	This setting has no effect when decoding JSON texts.
		382
		383	This setting has currently no effect on tied hashes.
366		384
367	$json = $json->allow_nonref ([$enable])	385	$json = $json->allow_nonref ([$enable])
368	$enabled = $json->get_allow_nonref	386	$enabled = $json->get_allow_nonref
369	If $enable is true (or missing), then the "encode" method can	387	If $enable is true (or missing), then the "encode" method can
370	convert a non-reference into its corresponding string, number or	388	convert a non-reference into its corresponding string, number or
…		…
379	Example, encode a Perl scalar as JSON value with enabled	397	Example, encode a Perl scalar as JSON value with enabled
380	"allow_nonref", resulting in an invalid JSON text:	398	"allow_nonref", resulting in an invalid JSON text:
381		399
382	JSON::XS->new->allow_nonref->encode ("Hello, World!")	400	JSON::XS->new->allow_nonref->encode ("Hello, World!")
383	=> "Hello, World!"	401	=> "Hello, World!"
		402
		403	$json = $json->allow_unknown ([$enable])
		404	$enabled = $json->get_allow_unknown
		405	If $enable is true (or missing), then "encode" will not throw an
		406	exception when it encounters values it cannot represent in JSON (for
		407	example, filehandles) but instead will encode a JSON "null" value.
		408	Note that blessed objects are not included here and are handled
		409	separately by c<allow_nonref>.
		410
		411	If $enable is false (the default), then "encode" will throw an
		412	exception when it encounters anything it cannot encode as JSON.
		413
		414	This option does not affect "decode" in any way, and it is
		415	recommended to leave it off unless you know your communications
		416	partner.
384		417
385	$json = $json->allow_blessed ([$enable])	418	$json = $json->allow_blessed ([$enable])
386	$enabled = $json->get_allow_blessed	419	$enabled = $json->get_allow_blessed
387	If $enable is true (or missing), then the "encode" method will not	420	If $enable is true (or missing), then the "encode" method will not
388	barf when it encounters a blessed reference. Instead, the value of	421	barf when it encounters a blessed reference. Instead, the value of
…		…
523	saving space.	556	saving space.
524		557
525	$json = $json->max_depth ([$maximum_nesting_depth])	558	$json = $json->max_depth ([$maximum_nesting_depth])
526	$max_depth = $json->get_max_depth	559	$max_depth = $json->get_max_depth
527	Sets the maximum nesting level (default 512) accepted while encoding	560	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	561	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	562	Perl data structure, then the encoder and decoder will stop and
530	will stop and croak at that point.	563	croak at that point.
531		564
532	Nesting level is defined by number of hash- or arrayrefs that the	565	Nesting level is defined by number of hash- or arrayrefs that the
533	encoder needs to traverse to reach a given point or the number of	566	encoder needs to traverse to reach a given point or the number of
534	"{" or "[" characters without their matching closing parenthesis	567	"{" or "[" characters without their matching closing parenthesis
535	crossed to reach a given character in a string.	568	crossed to reach a given character in a string.
536		569
537	Setting the maximum depth to one disallows any nesting, so that	570	Setting the maximum depth to one disallows any nesting, so that
538	ensures that the object is only a single hash/object or array.	571	ensures that the object is only a single hash/object or array.
539		572
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	573	If no argument is given, the highest possible setting will be used,
542	will be used, which is rarely useful.	574	which is rarely useful.
		575
		576	Note that nesting is implemented by recursion in C. The default
		577	value has been chosen to be as large as typical operating systems
		578	allow without crashing.
543		579
544	See SECURITY CONSIDERATIONS, below, for more info on why this is	580	See SECURITY CONSIDERATIONS, below, for more info on why this is
545	useful.	581	useful.
546		582
547	$json = $json->max_size ([$maximum_string_size])	583	$json = $json->max_size ([$maximum_string_size])
548	$max_size = $json->get_max_size	584	$max_size = $json->get_max_size
549	Set the maximum length a JSON text may have (in bytes) where	585	Set the maximum length a JSON text may have (in bytes) where
550	decoding is being attempted. The default is 0, meaning no limit.	586	decoding is being attempted. The default is 0, meaning no limit.
551	When "decode" is called on a string longer then this number of	587	When "decode" is called on a string that is longer then this many
552	characters it will not attempt to decode the string but throw an	588	bytes, it will not attempt to decode the string but throw an
553	exception. This setting has no effect on "encode" (yet).	589	exception. This setting has no effect on "encode" (yet).
554		590
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	591	If no argument is given, the limit check will be deactivated (same
558	specified).	592	as when 0 is specified).
559		593
560	See SECURITY CONSIDERATIONS, below, for more info on why this is	594	See SECURITY CONSIDERATIONS, below, for more info on why this is
561	useful.	595	useful.
562		596
563	$json_text = $json->encode ($perl_scalar)	597	$json_text = $json->encode ($perl_scalar)
…		…
588	and you need to know where the JSON text ends.	622	and you need to know where the JSON text ends.
589		623
590	JSON::XS->new->decode_prefix ("[1] the tail")	624	JSON::XS->new->decode_prefix ("[1] the tail")
591	=> ([], 3)	625	=> ([], 3)
592		626
		627	INCREMENTAL PARSING
		628	In some cases, there is the need for incremental parsing of JSON texts.
		629	While this module always has to keep both JSON text and resulting Perl
		630	data structure in memory at one time, it does allow you to parse a JSON
		631	stream incrementally. It does so by accumulating text until it has a
		632	full JSON object, which it then can decode. This process is similar to
		633	using "decode_prefix" to see if a full JSON object is available, but is
		634	much more efficient (and can be implemented with a minimum of method
		635	calls).
		636
		637	JSON::XS will only attempt to parse the JSON text once it is sure it has
		638	enough text to get a decisive result, using a very simple but truly
		639	incremental parser. This means that it sometimes won't stop as early as
		640	the full parser, for example, it doesn't detect parenthese mismatches.
		641	The only thing it guarantees is that it starts decoding as soon as a
		642	syntactically valid JSON text has been seen. This means you need to set
		643	resource limits (e.g. "max_size") to ensure the parser will stop parsing
		644	in the presence if syntax errors.
		645
		646	The following methods implement this incremental parser.
		647
		648	[void, scalar or list context] = $json->incr_parse ([$string])
		649	This is the central parsing function. It can both append new text
		650	and extract objects from the stream accumulated so far (both of
		651	these functions are optional).
		652
		653	If $string is given, then this string is appended to the already
		654	existing JSON fragment stored in the $json object.
		655
		656	After that, if the function is called in void context, it will
		657	simply return without doing anything further. This can be used to
		658	add more text in as many chunks as you want.
		659
		660	If the method is called in scalar context, then it will try to
		661	extract exactly one JSON object. If that is successful, it will
		662	return this object, otherwise it will return "undef". If there is a
		663	parse error, this method will croak just as "decode" would do (one
		664	can then use "incr_skip" to skip the errornous part). This is the
		665	most common way of using the method.
		666
		667	And finally, in list context, it will try to extract as many objects
		668	from the stream as it can find and return them, or the empty list
		669	otherwise. For this to work, there must be no separators between the
		670	JSON objects or arrays, instead they must be concatenated
		671	back-to-back. If an error occurs, an exception will be raised as in
		672	the scalar context case. Note that in this case, any
		673	previously-parsed JSON texts will be lost.
		674
		675	$lvalue_string = $json->incr_text
		676	This method returns the currently stored JSON fragment as an lvalue,
		677	that is, you can manipulate it. This only works when a preceding
		678	call to "incr_parse" in scalar context successfully returned an
		679	object. Under all other circumstances you must not call this
		680	function (I mean it. although in simple tests it might actually
		681	work, it will fail under real world conditions). As a special
		682	exception, you can also call this method before having parsed
		683	anything.
		684
		685	This function is useful in two cases: a) finding the trailing text
		686	after a JSON object or b) parsing multiple JSON objects separated by
		687	non-JSON text (such as commas).
		688
		689	$json->incr_skip
		690	This will reset the state of the incremental parser and will remove
		691	the parsed text from the input buffer so far. This is useful after
		692	"incr_parse" died, in which case the input buffer and incremental
		693	parser state is left unchanged, to skip the text parsed so far and
		694	to reset the parse state.
		695
		696	The difference to "incr_reset" is that only text until the parse
		697	error occured is removed.
		698
		699	$json->incr_reset
		700	This completely resets the incremental parser, that is, after this
		701	call, it will be as if the parser had never parsed anything.
		702
		703	This is useful if you want to repeatedly parse JSON objects and want
		704	to ignore any trailing data, which means you have to reset the
		705	parser after each successful decode.
		706
		707	LIMITATIONS
		708	All options that affect decoding are supported, except "allow_nonref".
		709	The reason for this is that it cannot be made to work sensibly: JSON
		710	objects and arrays are self-delimited, i.e. you can concatenate them
		711	back to back and still decode them perfectly. This does not hold true
		712	for JSON numbers, however.
		713
		714	For example, is the string 1 a single JSON number, or is it simply the
		715	start of 12? Or is 12 a single JSON number, or the concatenation of 1
		716	and 2? In neither case you can tell, and this is why JSON::XS takes the
		717	conservative route and disallows this case.
		718
		719	EXAMPLES
		720	Some examples will make all this clearer. First, a simple example that
		721	works similarly to "decode_prefix": We want to decode the JSON object at
		722	the start of a string and identify the portion after the JSON object:
		723
		724	my $text = "[1,2,3] hello";
		725
		726	my $json = new JSON::XS;
		727
		728	my $obj = $json->incr_parse ($text)
		729	or die "expected JSON object or array at beginning of string";
		730
		731	my $tail = $json->incr_text;
		732	# $tail now contains " hello"
		733
		734	Easy, isn't it?
		735
		736	Now for a more complicated example: Imagine a hypothetical protocol
		737	where you read some requests from a TCP stream, and each request is a
		738	JSON array, without any separation between them (in fact, it is often
		739	useful to use newlines as "separators", as these get interpreted as
		740	whitespace at the start of the JSON text, which makes it possible to
		741	test said protocol with "telnet"...).
		742
		743	Here is how you'd do it (it is trivial to write this in an event-based
		744	manner):
		745
		746	my $json = new JSON::XS;
		747
		748	# read some data from the socket
		749	while (sysread $socket, my $buf, 4096) {
		750
		751	# split and decode as many requests as possible
		752	for my $request ($json->incr_parse ($buf)) {
		753	# act on the $request
		754	}
		755	}
		756
		757	Another complicated example: Assume you have a string with JSON objects
		758	or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
		759	[3]"). To parse them, we have to skip the commas between the JSON texts,
		760	and here is where the lvalue-ness of "incr_text" comes in useful:
		761
		762	my $text = "[1],[2], [3]";
		763	my $json = new JSON::XS;
		764
		765	# void context, so no parsing done
		766	$json->incr_parse ($text);
		767
		768	# now extract as many objects as possible. note the
		769	# use of scalar context so incr_text can be called.
		770	while (my $obj = $json->incr_parse) {
		771	# do something with $obj
		772
		773	# now skip the optional comma
		774	$json->incr_text =~ s/^ \s* , //x;
		775	}
		776
		777	Now lets go for a very complex example: Assume that you have a gigantic
		778	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		779	but you cannot load it into memory fully (this has actually happened in
		780	the real world :).
		781
		782	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		783	can still help you: You implement a (very simple) array parser and let
		784	JSON decode the array elements, which are all full JSON objects on their
		785	own (this wouldn't work if the array elements could be JSON numbers, for
		786	example):
		787
		788	my $json = new JSON::XS;
		789
		790	# open the monster
		791	open my $fh, "<bigfile.json"
		792	or die "bigfile: $!";
		793
		794	# first parse the initial "["
		795	for (;;) {
		796	sysread $fh, my $buf, 65536
		797	or die "read error: $!";
		798	$json->incr_parse ($buf); # void context, so no parsing
		799
		800	# Exit the loop once we found and removed(!) the initial "[".
		801	# In essence, we are (ab-)using the $json object as a simple scalar
		802	# we append data to.
		803	last if $json->incr_text =~ s/^ \s* \[ //x;
		804	}
		805
		806	# now we have the skipped the initial "[", so continue
		807	# parsing all the elements.
		808	for (;;) {
		809	# in this loop we read data until we got a single JSON object
		810	for (;;) {
		811	if (my $obj = $json->incr_parse) {
		812	# do something with $obj
		813	last;
		814	}
		815
		816	# add more data
		817	sysread $fh, my $buf, 65536
		818	or die "read error: $!";
		819	$json->incr_parse ($buf); # void context, so no parsing
		820	}
		821
		822	# in this loop we read data until we either found and parsed the
		823	# separating "," between elements, or the final "]"
		824	for (;;) {
		825	# first skip whitespace
		826	$json->incr_text =~ s/^\s*//;
		827
		828	# if we find "]", we are done
		829	if ($json->incr_text =~ s/^\]//) {
		830	print "finished.\n";
		831	exit;
		832	}
		833
		834	# if we find ",", we can continue with the next element
		835	if ($json->incr_text =~ s/^,//) {
		836	last;
		837	}
		838
		839	# if we find anything else, we have a parse error!
		840	if (length $json->incr_text) {
		841	die "parse error near ", $json->incr_text;
		842	}
		843
		844	# else add more data
		845	sysread $fh, my $buf, 65536
		846	or die "read error: $!";
		847	$json->incr_parse ($buf); # void context, so no parsing
		848	}
		849
		850	This is a complex example, but most of the complexity comes from the
		851	fact that we are trying to be correct (bear with me if I am wrong, I
		852	never ran the above example :).
		853
593	MAPPING	854	MAPPING
594	This section describes how JSON::XS maps Perl values to JSON values and	855	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	856	vice versa. These mappings are designed to "do the right thing" in most
596	circumstances automatically, preserving round-tripping characteristics	857	circumstances automatically, preserving round-tripping characteristics
597	(what you put in comes out as something equivalent).	858	(what you put in comes out as something equivalent).
…		…
618	A JSON number becomes either an integer, numeric (floating point) or	879	A JSON number becomes either an integer, numeric (floating point) or
619	string scalar in perl, depending on its range and any fractional	880	string scalar in perl, depending on its range and any fractional
620	parts. On the Perl level, there is no difference between those as	881	parts. On the Perl level, there is no difference between those as
621	Perl handles all the conversion details, but an integer may take	882	Perl handles all the conversion details, but an integer may take
622	slightly less memory and might represent more values exactly than	883	slightly less memory and might represent more values exactly than
623	(floating point) numbers.	884	floating point numbers.
624		885
625	If the number consists of digits only, JSON::XS will try to	886	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	887	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	888	represent it as a numeric (floating point) value if that is possible
628	without loss of precision. Otherwise it will preserve the number as	889	without loss of precision. Otherwise it will preserve the number as
629	a string value.	890	a string value (in which case you lose roundtripping ability, as the
		891	JSON number will be re-encoded toa JSON string).
630		892
631	Numbers containing a fractional or exponential part will always be	893	Numbers containing a fractional or exponential part will always be
632	represented as numeric (floating point) values, possibly at a loss	894	represented as numeric (floating point) values, possibly at a loss
633	of precision.	895	of precision (in which case you might lose perfect roundtripping
634		896	ability, but the JSON number will still be re-encoded as a JSON
635	This might create round-tripping problems as numbers might become	897	number).
636	strings, but as Perl is typeless there is no other way to do it.
637		898
638	true, false	899	true, false
639	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",	900	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
640	respectively. They are overloaded to act almost exactly like the	901	respectively. They are overloaded to act almost exactly like the
641	numbers 1 and 0. You can check whether a scalar is a JSON boolean by	902	numbers 1 and 0. You can check whether a scalar is a JSON boolean by
…		…
669	an exception to be thrown, except for references to the integers 0	930	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	931	and 1, which get turned into "false" and "true" atoms in JSON. You
671	can also use "JSON::XS::false" and "JSON::XS::true" to improve	932	can also use "JSON::XS::false" and "JSON::XS::true" to improve
672	readability.	933	readability.
673		934
674	encode_json [\0,JSON::XS::true] # yields [false,true]	935	encode_json [\0, JSON::XS::true] # yields [false,true]
675		936
676	JSON::XS::true, JSON::XS::false	937	JSON::XS::true, JSON::XS::false
677	These special values become JSON true and JSON false values,	938	These special values become JSON true and JSON false values,
678	respectively. You can also use "\1" and "\0" directly if you want.	939	respectively. You can also use "\1" and "\0" directly if you want.
679		940
680	blessed objects	941	blessed objects
681	Blessed objects are not allowed. JSON::XS currently tries to encode	942	Blessed objects are not directly representable in JSON. See the
682	their underlying representation (hash- or arrayref), but this	943	"allow_blessed" and "convert_blessed" methods on various options on
683	behaviour might change in future versions.	944	how to deal with this: basically, you can choose between throwing an
		945	exception, encoding the reference as if it weren't blessed, or
		946	provide your own serialiser method.
684		947
685	simple scalars	948	simple scalars
686	Simple Perl scalars (any scalar that is not a reference) are the	949	Simple Perl scalars (any scalar that is not a reference) are the
687	most difficult objects to encode: JSON::XS will encode undefined	950	most difficult objects to encode: JSON::XS will encode undefined
688	scalars as JSON null value, scalars that have last been used in a	951	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	952	string context before encoding as JSON strings, and anything else as
690	number value:	953	number value:
691		954
692	# dump as number	955	# dump as number
693	encode_json [2] # yields [2]	956	encode_json [2] # yields [2]
694	encode_json [-3.0e17] # yields [-3e+17]	957	encode_json [-3.0e17] # yields [-3e+17]
…		…
713	my $x = "3"; # some variable containing a string	976	my $x = "3"; # some variable containing a string
714	$x += 0; # numify it, ensuring it will be dumped as a number	977	$x += 0; # numify it, ensuring it will be dumped as a number
715	$x *= 1; # same thing, the choice is yours.	978	$x *= 1; # same thing, the choice is yours.
716		979
717	You can not currently force the type in other, less obscure, ways.	980	You can not currently force the type in other, less obscure, ways.
718	Tell me if you need this capability.	981	Tell me if you need this capability (but don't forget to explain why
		982	it's needed :).
719		983
720	COMPARISON	984	ENCODING/CODESET FLAG NOTES
721	As already mentioned, this module was created because none of the	985	The interested reader might have seen a number of flags that signify
722	existing JSON modules could be made to work correctly. First I will	986	encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
723	describe the problems (or pleasures) I encountered with various existing	987	some confusion on what these do, so here is a short comparison:
724	JSON modules, followed by some benchmark values. JSON::XS was designed
725	not to suffer from any of these problems or limitations.
726		988
727	JSON 1.07	989	"utf8" controls whether the JSON text created by "encode" (and expected
728	Slow (but very portable, as it is written in pure Perl).	990	by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
		991	control whether "encode" escapes character values outside their
		992	respective codeset range. Neither of these flags conflict with each
		993	other, although some combinations make less sense than others.
729		994
730	Undocumented/buggy Unicode handling (how JSON handles Unicode values	995	Care has been taken to make all flags symmetrical with respect to
731	is undocumented. One can get far by feeding it Unicode strings and	996	"encode" and "decode", that is, texts encoded with any combination of
732	doing en-/decoding oneself, but Unicode escapes are not working	997	these flag values will be correctly decoded when the same flags are used
		998	- in general, if you use different flag settings while encoding vs. when
		999	decoding you likely have a bug somewhere.
		1000
		1001	Below comes a verbose discussion of these flags. Note that a "codeset"
		1002	is simply an abstract set of character-codepoint pairs, while an
		1003	encoding takes those codepoint numbers and encodes them, in our case
		1004	into octets. Unicode is (among other things) a codeset, UTF-8 is an
		1005	encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets and
		1006	encodings at the same time, which can be confusing.
		1007
		1008	"utf8" flag disabled
		1009	When "utf8" is disabled (the default), then "encode"/"decode"
		1010	generate and expect Unicode strings, that is, characters with high
		1011	ordinal Unicode values (> 255) will be encoded as such characters,
		1012	and likewise such characters are decoded as-is, no canges to them
		1013	will be done, except "(re-)interpreting" them as Unicode codepoints
		1014	or Unicode characters, respectively (to Perl, these are the same
		1015	thing in strings unless you do funny/weird/dumb stuff).
		1016
		1017	This is useful when you want to do the encoding yourself (e.g. when
		1018	you want to have UTF-16 encoded JSON texts) or when some other layer
		1019	does the encoding for you (for example, when printing to a terminal
		1020	using a filehandle that transparently encodes to UTF-8 you certainly
		1021	do NOT want to UTF-8 encode your data first and have Perl encode it
		1022	another time).
		1023
		1024	"utf8" flag enabled
		1025	If the "utf8"-flag is enabled, "encode"/"decode" will encode all
		1026	characters using the corresponding UTF-8 multi-byte sequence, and
		1027	will expect your input strings to be encoded as UTF-8, that is, no
		1028	"character" of the input string must have any value > 255, as UTF-8
		1029	does not allow that.
		1030
		1031	The "utf8" flag therefore switches between two modes: disabled means
		1032	you will get a Unicode string in Perl, enabled means you get an
		1033	UTF-8 encoded octet/binary string in Perl.
		1034
		1035	"latin1" or "ascii" flags enabled
		1036	With "latin1" (or "ascii") enabled, "encode" will escape characters
		1037	with ordinal values > 255 (> 127 with "ascii") and encode the
		1038	remaining characters as specified by the "utf8" flag.
		1039
		1040	If "utf8" is disabled, then the result is also correctly encoded in
		1041	those character sets (as both are proper subsets of Unicode, meaning
		1042	that a Unicode string with all character values < 256 is the same
		1043	thing as a ISO-8859-1 string, and a Unicode string with all
		1044	character values < 128 is the same thing as an ASCII string in
733	properly).	1045	Perl).
734		1046
735	No round-tripping (strings get clobbered if they look like numbers,	1047	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	1048	regardless of these flags, just some more characters will be escaped
737	will decode into the number 2.	1049	using "\uXXXX" then before.
738		1050
739	JSON::PC 0.01	1051	Note that ISO-8859-1-encoded strings are not compatible with UTF-8
740	Very fast.	1052	encoding, while ASCII-encoded strings are. That is because the
		1053	ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
		1054	codeset being a subset of Unicode), while ASCII is.
741		1055
742	Undocumented/buggy Unicode handling.	1056	Surprisingly, "decode" will ignore these flags and so treat all
		1057	input values as governed by the "utf8" flag. If it is disabled, this
		1058	allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
		1059	strict subsets of Unicode. If it is enabled, you can correctly
		1060	decode UTF-8 encoded strings.
743		1061
744	No round-tripping.	1062	So neither "latin1" nor "ascii" are incompatible with the "utf8"
		1063	flag - they only govern when the JSON output engine escapes a
		1064	character or not.
745		1065
746	Has problems handling many Perl values (e.g. regex results and other	1066	The main use for "latin1" is to relatively efficiently store binary
747	magic values will make it croak).	1067	data as JSON, at the expense of breaking compatibility with most
		1068	JSON decoders.
748		1069
749	Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}"	1070	The main use for "ascii" is to force the output to not contain
750	which is not a valid JSON text.	1071	characters with values > 127, which means you can interpret the
		1072	resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
		1073	any character set and 8-bit-encoding, and still get the same data
		1074	structure back. This is useful when your channel for JSON transfer
		1075	is not 8-bit clean or the encoding might be mangled in between (e.g.
		1076	in mail), and works because ASCII is a proper subset of most 8-bit
		1077	and multibyte encodings in use in the world.
751		1078
752	Unmaintained (maintainer unresponsive for many months, bugs are not	1079	JSON and ECMAscript
753	getting fixed).	1080	JSON syntax is based on how literals are represented in javascript (the
		1081	not-standardised predecessor of ECMAscript) which is presumably why it
		1082	is called "JavaScript Object Notation".
754		1083
755	JSON::Syck 0.21	1084	However, JSON is not a subset (and also not a superset of course) of
756	Very buggy (often crashes).	1085	ECMAscript (the standard) or javascript (whatever browsers actually
		1086	implement).
757		1087
758	Very inflexible (no human-readable format supported, format pretty	1088	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	1089	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	1090	structure might not be queryable:
761	preferably a way to generate ASCII-only JSON texts).
762		1091
763	Completely broken (and confusingly documented) Unicode handling	1092	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	1093	inside JSON strings, but are not allowed in ECMAscript string literals,
765	ImplicitUnicode to different values on en- and decoding to get	1094	so the following Perl fragment will not output something that can be
766	symmetric behaviour).	1095	guaranteed to be parsable by javascript's "eval":
767		1096
768	No round-tripping (simple cases work, but this depends on whether	1097	use JSON::XS;
769	the scalar value was used in a numeric context or not).
770		1098
771	Dumping hashes may skip hash values depending on iterator state.	1099	print encode_json [chr 0x2028];
772		1100
773	Unmaintained (maintainer unresponsive for many months, bugs are not	1101	The right fix for this is to use a proper JSON parser in your javascript
774	getting fixed).	1102	programs, and not rely on "eval" (see for example Douglas Crockford's
		1103	json2.js parser).
775		1104
776	Does not check input for validity (i.e. will accept non-JSON input	1105	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	1106	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		1107
784	JSON::DWIW 0.04	1108	use JSON::XS;
785	Very fast. Very natural. Very nice.
786		1109
787	Undocumented Unicode handling (but the best of the pack. Unicode	1110	print JSON::XS->new->ascii->encode ([chr 0x2028]);
788	escapes still don't get parsed properly).
789		1111
790	Very inflexible.	1112	Note that this will enlarge the resulting JSON text quite a bit if you
		1113	have many non-ASCII characters. You might be tempted to run some regexes
		1114	to only escape U+2028 and U+2029, e.g.:
791		1115
792	No round-tripping.	1116	# DO NOT USE THIS!
		1117	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1118	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1119	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1120	print $json;
793		1121
794	Does not generate valid JSON texts (key strings are often unquoted,	1122	Note that this is a bad idea: the above only works for U+2028 and
795	empty keys result in nothing being output)	1123	U+2029 and thus only for fully ECMAscript-compliant parsers. Many
		1124	existing javascript implementations, however, have issues with other
		1125	characters as well - using "eval" naively simply will cause problems.
796		1126
797	Does not check input for validity.	1127	Another problem is that some javascript implementations reserve some
		1128	property names for their own purposes (which probably makes them
		1129	non-ECMAscript-compliant). For example, Iceweasel reserves the
		1130	"__proto__" property name for it's own purposes.
		1131
		1132	If that is a problem, you could parse try to filter the resulting JSON
		1133	output for these property strings, e.g.:
		1134
		1135	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1136
		1137	This works because "__proto__" is not valid outside of strings, so every
		1138	occurence of ""__proto__"\s*:" must be a string used as property name.
		1139
		1140	If you know of other incompatibilities, please let me know.
798		1141
799	JSON and YAML	1142	JSON and YAML
800	You often hear that JSON is a subset (or a close subset) of YAML. This	1143	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,	1144	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	1145	writing), so let me state it clearly: *in general, there is no way to
803	valid YAML.	1146	configure JSON::XS to output a data structure as valid YAML* that works
		1147	in all cases.
804		1148
805	If you really must use JSON::XS to generate YAML, you should use this	1149	If you really must use JSON::XS to generate YAML, you should use this
806	algorithm (subject to change in future versions):	1150	algorithm (subject to change in future versions):
807		1151
808	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1152	my $to_yaml = JSON::XS->new->utf8->space_after (1);
809	my $yaml = $to_yaml->encode ($ref) . "\n";	1153	my $yaml = $to_yaml->encode ($ref) . "\n";
810		1154
811	This will usually generate JSON texts that also parse as valid YAML.	1155	This will usually generate JSON texts that also parse as valid YAML.
812	Please note that YAML has hardcoded limits on (simple) object key	1156	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	1157	lengths that JSON doesn't have and also has different and incompatible
		1158	unicode character escape syntax, so you should make sure that your hash
814	keys are noticeably shorter than the 1024 characters YAML allows.	1159	keys are noticeably shorter than the 1024 "stream characters" YAML
		1160	allows and that you do not have characters with codepoint values outside
		1161	the Unicode BMP (basic multilingual page). YAML also does not allow "\/"
		1162	sequences in strings (which JSON::XS does not currently generate, but
		1163	other JSON generators might).
815		1164
816	There might be other incompatibilities that I am not aware of. In	1165	There might be other incompatibilities that I am not aware of (or the
		1166	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	1167	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:	1168	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	1169	chances are high that you will run into severe interoperability problems
820	problems.	1170	when you least expect it.
		1171
		1172	(*) I have been pressured multiple times by Brian Ingerson (one of the
		1173	authors of the YAML specification) to remove this paragraph, despite
		1174	him acknowledging that the actual incompatibilities exist. As I was
		1175	personally bitten by this "JSON is YAML" lie, I refused and said I
		1176	will continue to educate people about these issues, so others do not
		1177	run into the same problem again and again. After this, Brian called
		1178	me a (quote)complete and worthless idiot(unquote).
		1179
		1180	In my opinion, instead of pressuring and insulting people who
		1181	actually clarify issues with YAML and the wrong statements of some
		1182	of its proponents, I would kindly suggest reading the JSON spec
		1183	(which is not that difficult or long) and finally make YAML
		1184	compatible to it, and educating users about the changes, instead of
		1185	spreading lies about the real compatibility for many years and
		1186	trying to silence people who point out that it isn't true.
		1187
		1188	Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON,
		1189	even though the incompatibilities have been documented (and are
		1190	known to Brian) for many years and the spec makes explicit claims
		1191	that YAML is a superset of JSON. It would be so easy to fix, but
		1192	apparently, bullying and corrupting userdata is so much easier.
821		1193
822	SPEED	1194	SPEED
823	It seems that JSON::XS is surprisingly fast, as shown in the following	1195	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	1196	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	1197	in the JSON::XS distribution, to make it easy to compare on your own
826	system.	1198	system.
827		1199
828	First comes a comparison between various modules using a very short	1200	First comes a comparison between various modules using a very short
829	single-line JSON string:	1201	single-line JSON string (also available at
		1202	<http://dist.schmorp.de/misc/json/short.json>).
830		1203
831	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1204	{"method": "handleMessage", "params": ["user1",
832	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1205	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1206	1, 0]}
833		1207
834	It shows the number of encodes/decodes per second (JSON::XS uses the	1208	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	1209	functional interface, while JSON::XS/2 uses the OO interface with
836	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).	1210	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink.
837	Higher is better:	1211	JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ uses
		1212	the from_json method). Higher is better:
838		1213
839	module \| encode \| decode \|	1214	module \| encode \| decode \|
840	-----------\|------------\|------------\|	1215	--------------\|------------\|------------\|
841	JSON 1.x \| 4990.842 \| 4088.813 \|	1216	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
842	JSON::DWIW \| 51653.990 \| 71575.154 \|	1217	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
843	JSON::PC \| 65948.176 \| 74631.744 \|	1218	JSON::PP \| 15827.562 \| 6638.658 \|
844	JSON::PP \| 8931.652 \| 3817.168 \|	1219	JSON::Syck \| 63358.066 \| 47662.545 \|
845	JSON::Syck \| 24877.248 \| 27776.848 \|	1220	JSON::XS \| 511500.488 \| 511500.488 \|
846	JSON::XS \| 388361.481 \| 227951.304 \|	1221	JSON::XS/2 \| 291271.111 \| 388361.481 \|
847	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1222	JSON::XS/3 \| 361577.931 \| 361577.931 \|
848	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1223	Storable \| 66788.280 \| 265462.278 \|
849	Storable \| 16500.016 \| 135300.129 \|
850	-----------+------------+------------+	1224	--------------+------------+------------+
851		1225
852	That is, JSON::XS is about five times faster than JSON::DWIW on	1226	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	1227	encoding, about five times faster on decoding, and over thirty to
854	faster than JSON, even with pretty-printing and key sorting. It also	1228	seventy times faster than JSON's pure perl implementation. It also
855	compares favourably to Storable for small amounts of data.	1229	compares favourably to Storable for small amounts of data.
856		1230
857	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1231	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
858	search API (http://nanoref.com/yahooapis/mgPdGg):	1232	search API (<http://dist.schmorp.de/misc/json/long.json>).
859		1233
860	module \| encode \| decode \|	1234	module \| encode \| decode \|
861	-----------\|------------\|------------\|	1235	--------------\|------------\|------------\|
862	JSON 1.x \| 55.260 \| 34.971 \|	1236	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
863	JSON::DWIW \| 825.228 \| 1082.513 \|	1237	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
864	JSON::PC \| 3571.444 \| 2394.829 \|
865	JSON::PP \| 210.987 \| 32.574 \|	1238	JSON::PP \| 400.640 \| 62.311 \|
866	JSON::Syck \| 552.551 \| 787.544 \|	1239	JSON::Syck \| 1481.040 \| 1524.869 \|
867	JSON::XS \| 5780.463 \| 4854.519 \|	1240	JSON::XS \| 20661.596 \| 9541.183 \|
868	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1241	JSON::XS/2 \| 10683.403 \| 9416.938 \|
869	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1242	JSON::XS/3 \| 20661.596 \| 9400.054 \|
870	Storable \| 4445.002 \| 5235.027 \|	1243	Storable \| 19765.806 \| 10000.725 \|
871	-----------+------------+------------+	1244	--------------+------------+------------+
872		1245
873	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1246	Again, JSON::XS leads by far (except for Storable which non-surprisingly
874	decodes faster).	1247	decodes a bit faster).
875		1248
876	On large strings containing lots of high Unicode characters, some	1249	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	1250	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	1251	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	1252	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	1273	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	1274	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	1275	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	1276	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.	1277	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	1278	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	1279	process has a smaller stack, you should adjust this setting accordingly
907	with the "max_depth" method.	1280	with the "max_depth" method.
908		1281
909	And last but least, something else could bomb you that I forgot to think	1282	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	1283	case, you get to keep the pieces. I am always open for hints, though...
911	hints, though...	1284
		1285	Also keep in mind that JSON::XS might leak contents of your Perl data
		1286	structures in its error messages, so when you serialise sensitive
		1287	information you might want to make sure that exceptions thrown by
		1288	JSON::XS will not end up in front of untrusted eyes.
912		1289
913	If you are using JSON::XS to return packets to consumption by JavaScript	1290	If you are using JSON::XS to return packets to consumption by JavaScript
914	scripts in a browser you should have a look at	1291	scripts in a browser you should have a look at
915	<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1292	<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/>
916	you are vulnerable to some common attack vectors (which really are	1293	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,	1294	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	1295	deal with it, as major browser developers care only for features, not
919	security right).	1296	about getting security right).
920		1297
921	THREADS	1298	THREADS
922	This module is not guaranteed to be thread safe and there are no plans	1299	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	1300	to change this until Perl gets thread support (as opposed to the
924	horribly slow so-called "threads" which are simply slow and bloated	1301	horribly slow so-called "threads" which are simply slow and bloated
925	process simulations - use fork, its much faster, cheaper, better).	1302	process simulations - use fork, it's much faster, cheaper, better).
926		1303
927	(It might actually work, but you have been warned).	1304	(It might actually work, but you have been warned).
928		1305
929	BUGS	1306	BUGS
930	While the goal of this module is to be correct, that unfortunately does	1307	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	1308	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.	1309	keep reporting bugs they will be fixed swiftly, though.
934		1310
935	Please refrain from using rt.cpan.org or any other bug reporting	1311	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.	1312	service. I put the contact address into my modules for a reason.
		1313
		1314	SEE ALSO
		1315	The json_xs command line utility for quick experiments.
937		1316
938	AUTHOR	1317	AUTHOR
939	Marc Lehmann <schmorp@schmorp.de>	1318	Marc Lehmann <schmorp@schmorp.de>
940	http://home.schmorp.de/	1319	http://home.schmorp.de/
941		1320

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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 1.34 by root, Thu Mar 11 17:36:09 2010 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 1.34 by root, Thu Mar 11 17:36:09 2010 UTC