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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs.
Revision 1.135 by root, Wed Jun 1 13:01:09 2011 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
35	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
36	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
37		39
38	Beginning with version 2.0 of the JSON module, when both JSON and	40	Beginning with version 2.0 of the JSON module, when both JSON and
39	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be	41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
41	and methods). If JSON::XS is not available, it will fall back to the	43	and methods). If JSON::XS is not available, it will fall back to the
42	compatible JSON::PP module as backend, so using JSON instead of JSON::XS	44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43	gives you a portable JSON API that can be fast when you need and doesn't	45	gives you a portable JSON API that can be fast when you need and doesn't
44	require a C compiler when that is a problem.	46	require a C compiler when that is a problem.
45		47
…		…
47	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
48	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
49	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
50	reports for other reasons.	52	reports for other reasons.
51		53
52	See COMPARISON, below, for a comparison to some other JSON modules.
53
54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
55	vice versa.	55	vice versa.
56		56
57	=head2 FEATURES	57	=head2 FEATURES
58		58
59	=over 4	59	=over 4
60		60
61	=item * correct Unicode handling	61	=item * correct Unicode handling
62		62
63	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
64	it does so.	64	so, and even documents what "correct" means.
65		65
66	=item * round-trip integrity	66	=item * round-trip integrity
67		67
68	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
69	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON and Perl, the deserialised data structure is identical on the Perl
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
71	like a number).	71	it looks like a number). There I<are> minor exceptions to this, read the
		72	MAPPING section below to learn about those.
72		73
73	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
74		75
75	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
76	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
77	feature).	78	feature).
78		79
79	=item * fast	80	=item * fast
80		81
81	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
82	of speed, too.	83	this module usually compares favourably in terms of speed, too.
83		84
84	=item * simple to use	85	=item * simple to use
85		86
86	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
87	interface.	88	oriented interface interface.
88		89
89	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
90		91
91	You can choose between the most compact guaranteed single-line format	92	You can choose between the most compact guaranteed-single-line format
92	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
93	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
94	Unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
95	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
96		97
97	=back	98	=back
98		99
99	=cut	100	=cut
100		101
101	package JSON::XS;	102	package JSON::XS;
102		103
103	use strict;	104	use common::sense;
104		105
105	our $VERSION = '2.01';	106	our $VERSION = '2.3';
106	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
107		108
108	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
109		110
110	sub to_json($) {	111	sub to_json($) {
…		…
134		135
135	This function call is functionally identical to:	136	This function call is functionally identical to:
136		137
137	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
138		139
139	except being faster.	140	Except being faster.
140		141
141	=item $perl_scalar = decode_json $json_text	142	=item $perl_scalar = decode_json $json_text
142		143
143	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	144	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
144	to parse that as an UTF-8 encoded JSON text, returning the resulting	145	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
146		147
147	This function call is functionally identical to:	148	This function call is functionally identical to:
148		149
149	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
150		151
151	except being faster.	152	Except being faster.
152		153
153	=item $is_boolean = JSON::XS::is_bool $scalar	154	=item $is_boolean = JSON::XS::is_bool $scalar
154		155
155	Returns true if the passed scalar represents either JSON::XS::true or	156	Returns true if the passed scalar represents either JSON::XS::true or
156	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
174	This enables you to store Unicode characters as single characters in a	175	This enables you to store Unicode characters as single characters in a
175	Perl string - very natural.	176	Perl string - very natural.
176		177
177	=item 2. Perl does I<not> associate an encoding with your strings.	178	=item 2. Perl does I<not> associate an encoding with your strings.
178		179
179	Unless you force it to, e.g. when matching it against a regex, or printing	180	... until you force it to, e.g. when matching it against a regex, or
180	the scalar to a file, in which case Perl either interprets your string as	181	printing the scalar to a file, in which case Perl either interprets your
181	locale-encoded text, octets/binary, or as Unicode, depending on various	182	string as locale-encoded text, octets/binary, or as Unicode, depending
182	settings. In no case is an encoding stored together with your data, it is	183	on various settings. In no case is an encoding stored together with your
183	I<use> that decides encoding, not any magical metadata.	184	data, it is I<use> that decides encoding, not any magical meta data.
184		185
185	=item 3. The internal utf-8 flag has no meaning with regards to the	186	=item 3. The internal utf-8 flag has no meaning with regards to the
186	encoding of your string.	187	encoding of your string.
187		188
188	Just ignore that flag unless you debug a Perl bug, a module written in	189	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
194		195
195	If you didn't know about that flag, just the better, pretend it doesn't	196	If you didn't know about that flag, just the better, pretend it doesn't
196	exist.	197	exist.
197		198
198	=item 4. A "Unicode String" is simply a string where each character can be	199	=item 4. A "Unicode String" is simply a string where each character can be
199	validly interpreted as a Unicode codepoint.	200	validly interpreted as a Unicode code point.
200		201
201	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	202	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
202	Unicode string encoded in UTF-8, giving you a binary string.	203	Unicode string encoded in UTF-8, giving you a binary string.
203		204
204	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	205	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
242		243
243	If C<$enable> is false, then the C<encode> method will not escape Unicode	244	If C<$enable> is false, then the C<encode> method will not escape Unicode
244	characters unless required by the JSON syntax or other flags. This results	245	characters unless required by the JSON syntax or other flags. This results
245	in a faster and more compact format.	246	in a faster and more compact format.
246		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
247	The main use for this flag is to produce JSON texts that can be	251	The main use for this flag is to produce JSON texts that can be
248	transmitted over a 7-bit channel, as the encoded JSON texts will not	252	transmitted over a 7-bit channel, as the encoded JSON texts will not
249	contain any 8 bit characters.	253	contain any 8 bit characters.
250		254
251	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
262	will not be affected in any way by this flag, as C<decode> by default	266	will not be affected in any way by this flag, as C<decode> by default
263	expects Unicode, which is a strict superset of latin1.	267	expects Unicode, which is a strict superset of latin1.
264		268
265	If C<$enable> is false, then the C<encode> method will not escape Unicode	269	If C<$enable> is false, then the C<encode> method will not escape Unicode
266	characters unless required by the JSON syntax or other flags.	270	characters unless required by the JSON syntax or other flags.
		271
		272	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		273	document.
267		274
268	The main use for this flag is efficiently encoding binary data as JSON	275	The main use for this flag is efficiently encoding binary data as JSON
269	text, as most octets will not be escaped, resulting in a smaller encoded	276	text, as most octets will not be escaped, resulting in a smaller encoded
270	size. The disadvantage is that the resulting JSON text is encoded	277	size. The disadvantage is that the resulting JSON text is encoded
271	in latin1 (and must correctly be treated as such when storing and	278	in latin1 (and must correctly be treated as such when storing and
…		…
290		297
291	If C<$enable> is false, then the C<encode> method will return the JSON	298	If C<$enable> is false, then the C<encode> method will return the JSON
292	string as a (non-encoded) Unicode string, while C<decode> expects thus a	299	string as a (non-encoded) Unicode string, while C<decode> expects thus a
293	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	300	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
294	to be done yourself, e.g. using the Encode module.	301	to be done yourself, e.g. using the Encode module.
		302
		303	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		304	document.
295		305
296	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
297		307
298	use Encode;	308	use Encode;
299	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
431	the same hash might be encoded differently even if contains the same data,	441	the same hash might be encoded differently even if contains the same data,
432	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
433		443
434	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
435		445
		446	This setting has currently no effect on tied hashes.
		447
436	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
437		449
438	=item $enabled = $json->get_allow_nonref	450	=item $enabled = $json->get_allow_nonref
439		451
440	If C<$enable> is true (or missing), then the C<encode> method can convert a	452	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
450	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	462	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
451	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
452		464
453	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
454	=> "Hello, World!"	466	=> "Hello, World!"
		467
		468	=item $json = $json->allow_unknown ([$enable])
		469
		470	=item $enabled = $json->get_allow_unknown
		471
		472	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		473	exception when it encounters values it cannot represent in JSON (for
		474	example, filehandles) but instead will encode a JSON C<null> value. Note
		475	that blessed objects are not included here and are handled separately by
		476	c<allow_nonref>.
		477
		478	If C<$enable> is false (the default), then C<encode> will throw an
		479	exception when it encounters anything it cannot encode as JSON.
		480
		481	This option does not affect C<decode> in any way, and it is recommended to
		482	leave it off unless you know your communications partner.
455		483
456	=item $json = $json->allow_blessed ([$enable])	484	=item $json = $json->allow_blessed ([$enable])
457		485
458	=item $enabled = $json->get_allow_blessed	486	=item $enabled = $json->get_allow_blessed
459		487
…		…
600	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
601		629
602	=item $max_depth = $json->get_max_depth	630	=item $max_depth = $json->get_max_depth
603		631
604	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
605	or decoding. If the JSON text or Perl data structure has an equal or	633	or decoding. If a higher nesting level is detected in JSON text or a Perl
606	higher nesting level then this limit, then the encoder and decoder will	634	data structure, then the encoder and decoder will stop and croak at that
607	stop and croak at that point.	635	point.
608		636
609	Nesting level is defined by number of hash- or arrayrefs that the encoder	637	Nesting level is defined by number of hash- or arrayrefs that the encoder
610	needs to traverse to reach a given point or the number of C<{> or C<[>	638	needs to traverse to reach a given point or the number of C<{> or C<[>
611	characters without their matching closing parenthesis crossed to reach a	639	characters without their matching closing parenthesis crossed to reach a
612	given character in a string.	640	given character in a string.
613		641
614	Setting the maximum depth to one disallows any nesting, so that ensures	642	Setting the maximum depth to one disallows any nesting, so that ensures
615	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
616		644
617	The argument to C<max_depth> will be rounded up to the next highest power
618	of two. If no argument is given, the highest possible setting will be	645	If no argument is given, the highest possible setting will be used, which
619	used, which is rarely useful.	646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
620		651
621	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
622		653
623	=item $json = $json->max_size ([$maximum_string_size])	654	=item $json = $json->max_size ([$maximum_string_size])
624		655
625	=item $max_size = $json->get_max_size	656	=item $max_size = $json->get_max_size
626		657
627	Set the maximum length a JSON text may have (in bytes) where decoding is	658	Set the maximum length a JSON text may have (in bytes) where decoding is
628	being attempted. The default is C<0>, meaning no limit. When C<decode>	659	being attempted. The default is C<0>, meaning no limit. When C<decode>
629	is called on a string longer then this number of characters it will not	660	is called on a string that is longer then this many bytes, it will not
630	attempt to decode the string but throw an exception. This setting has no	661	attempt to decode the string but throw an exception. This setting has no
631	effect on C<encode> (yet).	662	effect on C<encode> (yet).
632		663
633	The argument to C<max_size> will be rounded up to the next B<highest>	664	If no argument is given, the limit check will be deactivated (same as when
634	power of two (so may be more than requested). If no argument is given, the	665	C<0> is specified).
635	limit check will be deactivated (same as when C<0> is specified).
636		666
637	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
638		668
639	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
640		670
…		…
669	=> ([], 3)	699	=> ([], 3)
670		700
671	=back	701	=back
672		702
673		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect mismatched
		719	parentheses. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	Example: Parse some JSON arrays/objects in a given string and return
		757	them.
		758
		759	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		760
		761	=item $lvalue_string = $json->incr_text
		762
		763	This method returns the currently stored JSON fragment as an lvalue, that
		764	is, you can manipulate it. This I<only> works when a preceding call to
		765	C<incr_parse> in I<scalar context> successfully returned an object. Under
		766	all other circumstances you must not call this function (I mean it.
		767	although in simple tests it might actually work, it I<will> fail under
		768	real world conditions). As a special exception, you can also call this
		769	method before having parsed anything.
		770
		771	This function is useful in two cases: a) finding the trailing text after a
		772	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		773	(such as commas).
		774
		775	=item $json->incr_skip
		776
		777	This will reset the state of the incremental parser and will remove
		778	the parsed text from the input buffer so far. This is useful after
		779	C<incr_parse> died, in which case the input buffer and incremental parser
		780	state is left unchanged, to skip the text parsed so far and to reset the
		781	parse state.
		782
		783	The difference to C<incr_reset> is that only text until the parse error
		784	occured is removed.
		785
		786	=item $json->incr_reset
		787
		788	This completely resets the incremental parser, that is, after this call,
		789	it will be as if the parser had never parsed anything.
		790
		791	This is useful if you want to repeatedly parse JSON objects and want to
		792	ignore any trailing data, which means you have to reset the parser after
		793	each successful decode.
		794
		795	=back
		796
		797	=head2 LIMITATIONS
		798
		799	All options that affect decoding are supported, except
		800	C<allow_nonref>. The reason for this is that it cannot be made to
		801	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		802	them back to back and still decode them perfectly. This does not hold true
		803	for JSON numbers, however.
		804
		805	For example, is the string C<1> a single JSON number, or is it simply the
		806	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		807	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		808	takes the conservative route and disallows this case.
		809
		810	=head2 EXAMPLES
		811
		812	Some examples will make all this clearer. First, a simple example that
		813	works similarly to C<decode_prefix>: We want to decode the JSON object at
		814	the start of a string and identify the portion after the JSON object:
		815
		816	my $text = "[1,2,3] hello";
		817
		818	my $json = new JSON::XS;
		819
		820	my $obj = $json->incr_parse ($text)
		821	or die "expected JSON object or array at beginning of string";
		822
		823	my $tail = $json->incr_text;
		824	# $tail now contains " hello"
		825
		826	Easy, isn't it?
		827
		828	Now for a more complicated example: Imagine a hypothetical protocol where
		829	you read some requests from a TCP stream, and each request is a JSON
		830	array, without any separation between them (in fact, it is often useful to
		831	use newlines as "separators", as these get interpreted as whitespace at
		832	the start of the JSON text, which makes it possible to test said protocol
		833	with C<telnet>...).
		834
		835	Here is how you'd do it (it is trivial to write this in an event-based
		836	manner):
		837
		838	my $json = new JSON::XS;
		839
		840	# read some data from the socket
		841	while (sysread $socket, my $buf, 4096) {
		842
		843	# split and decode as many requests as possible
		844	for my $request ($json->incr_parse ($buf)) {
		845	# act on the $request
		846	}
		847	}
		848
		849	Another complicated example: Assume you have a string with JSON objects
		850	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		851	[3]>). To parse them, we have to skip the commas between the JSON texts,
		852	and here is where the lvalue-ness of C<incr_text> comes in useful:
		853
		854	my $text = "[1],[2], [3]";
		855	my $json = new JSON::XS;
		856
		857	# void context, so no parsing done
		858	$json->incr_parse ($text);
		859
		860	# now extract as many objects as possible. note the
		861	# use of scalar context so incr_text can be called.
		862	while (my $obj = $json->incr_parse) {
		863	# do something with $obj
		864
		865	# now skip the optional comma
		866	$json->incr_text =~ s/^ \s* , //x;
		867	}
		868
		869	Now lets go for a very complex example: Assume that you have a gigantic
		870	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		871	but you cannot load it into memory fully (this has actually happened in
		872	the real world :).
		873
		874	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		875	can still help you: You implement a (very simple) array parser and let
		876	JSON decode the array elements, which are all full JSON objects on their
		877	own (this wouldn't work if the array elements could be JSON numbers, for
		878	example):
		879
		880	my $json = new JSON::XS;
		881
		882	# open the monster
		883	open my $fh, "<bigfile.json"
		884	or die "bigfile: $!";
		885
		886	# first parse the initial "["
		887	for (;;) {
		888	sysread $fh, my $buf, 65536
		889	or die "read error: $!";
		890	$json->incr_parse ($buf); # void context, so no parsing
		891
		892	# Exit the loop once we found and removed(!) the initial "[".
		893	# In essence, we are (ab-)using the $json object as a simple scalar
		894	# we append data to.
		895	last if $json->incr_text =~ s/^ \s* \[ //x;
		896	}
		897
		898	# now we have the skipped the initial "[", so continue
		899	# parsing all the elements.
		900	for (;;) {
		901	# in this loop we read data until we got a single JSON object
		902	for (;;) {
		903	if (my $obj = $json->incr_parse) {
		904	# do something with $obj
		905	last;
		906	}
		907
		908	# add more data
		909	sysread $fh, my $buf, 65536
		910	or die "read error: $!";
		911	$json->incr_parse ($buf); # void context, so no parsing
		912	}
		913
		914	# in this loop we read data until we either found and parsed the
		915	# separating "," between elements, or the final "]"
		916	for (;;) {
		917	# first skip whitespace
		918	$json->incr_text =~ s/^\s*//;
		919
		920	# if we find "]", we are done
		921	if ($json->incr_text =~ s/^\]//) {
		922	print "finished.\n";
		923	exit;
		924	}
		925
		926	# if we find ",", we can continue with the next element
		927	if ($json->incr_text =~ s/^,//) {
		928	last;
		929	}
		930
		931	# if we find anything else, we have a parse error!
		932	if (length $json->incr_text) {
		933	die "parse error near ", $json->incr_text;
		934	}
		935
		936	# else add more data
		937	sysread $fh, my $buf, 65536
		938	or die "read error: $!";
		939	$json->incr_parse ($buf); # void context, so no parsing
		940	}
		941
		942	This is a complex example, but most of the complexity comes from the fact
		943	that we are trying to be correct (bear with me if I am wrong, I never ran
		944	the above example :).
		945
		946
		947
674	=head1 MAPPING	948	=head1 MAPPING
675		949
676	This section describes how JSON::XS maps Perl values to JSON values and	950	This section describes how JSON::XS maps Perl values to JSON values and
677	vice versa. These mappings are designed to "do the right thing" in most	951	vice versa. These mappings are designed to "do the right thing" in most
678	circumstances automatically, preserving round-tripping characteristics	952	circumstances automatically, preserving round-tripping characteristics
…		…
706		980
707	A JSON number becomes either an integer, numeric (floating point) or	981	A JSON number becomes either an integer, numeric (floating point) or
708	string scalar in perl, depending on its range and any fractional parts. On	982	string scalar in perl, depending on its range and any fractional parts. On
709	the Perl level, there is no difference between those as Perl handles all	983	the Perl level, there is no difference between those as Perl handles all
710	the conversion details, but an integer may take slightly less memory and	984	the conversion details, but an integer may take slightly less memory and
711	might represent more values exactly than (floating point) numbers.	985	might represent more values exactly than floating point numbers.
712		986
713	If the number consists of digits only, JSON::XS will try to represent	987	If the number consists of digits only, JSON::XS will try to represent
714	it as an integer value. If that fails, it will try to represent it as	988	it as an integer value. If that fails, it will try to represent it as
715	a numeric (floating point) value if that is possible without loss of	989	a numeric (floating point) value if that is possible without loss of
716	precision. Otherwise it will preserve the number as a string value.	990	precision. Otherwise it will preserve the number as a string value (in
		991	which case you lose roundtripping ability, as the JSON number will be
		992	re-encoded toa JSON string).
717		993
718	Numbers containing a fractional or exponential part will always be	994	Numbers containing a fractional or exponential part will always be
719	represented as numeric (floating point) values, possibly at a loss of	995	represented as numeric (floating point) values, possibly at a loss of
720	precision.	996	precision (in which case you might lose perfect roundtripping ability, but
		997	the JSON number will still be re-encoded as a JSON number).
721		998
722	This might create round-tripping problems as numbers might become strings,	999	Note that precision is not accuracy - binary floating point values cannot
723	but as Perl is typeless there is no other way to do it.	1000	represent most decimal fractions exactly, and when converting from and to
		1001	floating point, JSON::XS only guarantees precision up to but not including
		1002	the leats significant bit.
724		1003
725	=item true, false	1004	=item true, false
726		1005
727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1006	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
728	respectively. They are overloaded to act almost exactly like the numbers	1007	respectively. They are overloaded to act almost exactly like the numbers
…		…
765	Other unblessed references are generally not allowed and will cause an	1044	Other unblessed references are generally not allowed and will cause an
766	exception to be thrown, except for references to the integers C<0> and	1045	exception to be thrown, except for references to the integers C<0> and
767	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1046	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
768	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1047	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
769		1048
770	encode_json [\0,JSON::XS::true] # yields [false,true]	1049	encode_json [\0, JSON::XS::true] # yields [false,true]
771		1050
772	=item JSON::XS::true, JSON::XS::false	1051	=item JSON::XS::true, JSON::XS::false
773		1052
774	These special values become JSON true and JSON false values,	1053	These special values become JSON true and JSON false values,
775	respectively. You can also use C<\1> and C<\0> directly if you want.	1054	respectively. You can also use C<\1> and C<\0> directly if you want.
…		…
813	my $x = "3"; # some variable containing a string	1092	my $x = "3"; # some variable containing a string
814	$x += 0; # numify it, ensuring it will be dumped as a number	1093	$x += 0; # numify it, ensuring it will be dumped as a number
815	$x *= 1; # same thing, the choice is yours.	1094	$x *= 1; # same thing, the choice is yours.
816		1095
817	You can not currently force the type in other, less obscure, ways. Tell me	1096	You can not currently force the type in other, less obscure, ways. Tell me
818	if you need this capability (but don't forget to explain why its needed	1097	if you need this capability (but don't forget to explain why it's needed
819	:).	1098	:).
820		1099
		1100	Note that numerical precision has the same meaning as under Perl (so
		1101	binary to decimal conversion follows the same rules as in Perl, which
		1102	can differ to other languages). Also, your perl interpreter might expose
		1103	extensions to the floating point numbers of your platform, such as
		1104	infinities or NaN's - these cannot be represented in JSON, and it is an
		1105	error to pass those in.
		1106
821	=back	1107	=back
822		1108
823		1109
824	=head1 COMPARISON	1110	=head1 ENCODING/CODESET FLAG NOTES
825		1111
826	As already mentioned, this module was created because none of the existing	1112	The interested reader might have seen a number of flags that signify
827	JSON modules could be made to work correctly. First I will describe the	1113	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
828	problems (or pleasures) I encountered with various existing JSON modules,	1114	some confusion on what these do, so here is a short comparison:
829	followed by some benchmark values. JSON::XS was designed not to suffer	1115
830	from any of these problems or limitations.	1116	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1117	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1118	control whether C<encode> escapes character values outside their respective
		1119	codeset range. Neither of these flags conflict with each other, although
		1120	some combinations make less sense than others.
		1121
		1122	Care has been taken to make all flags symmetrical with respect to
		1123	C<encode> and C<decode>, that is, texts encoded with any combination of
		1124	these flag values will be correctly decoded when the same flags are used
		1125	- in general, if you use different flag settings while encoding vs. when
		1126	decoding you likely have a bug somewhere.
		1127
		1128	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1129	simply an abstract set of character-codepoint pairs, while an encoding
		1130	takes those codepoint numbers and I<encodes> them, in our case into
		1131	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1132	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1133	the same time, which can be confusing.
831		1134
832	=over 4	1135	=over 4
833		1136
834	=item JSON 1.07	1137	=item C<utf8> flag disabled
835		1138
836	Slow (but very portable, as it is written in pure Perl).	1139	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1140	and expect Unicode strings, that is, characters with high ordinal Unicode
		1141	values (> 255) will be encoded as such characters, and likewise such
		1142	characters are decoded as-is, no canges to them will be done, except
		1143	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1144	respectively (to Perl, these are the same thing in strings unless you do
		1145	funny/weird/dumb stuff).
837		1146
838	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1147	This is useful when you want to do the encoding yourself (e.g. when you
839	undocumented. One can get far by feeding it Unicode strings and doing	1148	want to have UTF-16 encoded JSON texts) or when some other layer does
840	en-/decoding oneself, but Unicode escapes are not working properly).	1149	the encoding for you (for example, when printing to a terminal using a
		1150	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1151	to UTF-8 encode your data first and have Perl encode it another time).
841		1152
842	No round-tripping (strings get clobbered if they look like numbers, e.g.	1153	=item C<utf8> flag enabled
843	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
844	decode into the number 2.
845		1154
846	=item JSON::PC 0.01	1155	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1156	characters using the corresponding UTF-8 multi-byte sequence, and will
		1157	expect your input strings to be encoded as UTF-8, that is, no "character"
		1158	of the input string must have any value > 255, as UTF-8 does not allow
		1159	that.
847		1160
848	Very fast.	1161	The C<utf8> flag therefore switches between two modes: disabled means you
		1162	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1163	octet/binary string in Perl.
849		1164
850	Undocumented/buggy Unicode handling.	1165	=item C<latin1> or C<ascii> flags enabled
851		1166
852	No round-tripping.	1167	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1168	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1169	characters as specified by the C<utf8> flag.
853		1170
854	Has problems handling many Perl values (e.g. regex results and other magic	1171	If C<utf8> is disabled, then the result is also correctly encoded in those
855	values will make it croak).	1172	character sets (as both are proper subsets of Unicode, meaning that a
		1173	Unicode string with all character values < 256 is the same thing as a
		1174	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1175	the same thing as an ASCII string in Perl).
856		1176
857	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1177	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
858	which is not a valid JSON text.	1178	regardless of these flags, just some more characters will be escaped using
		1179	C<\uXXXX> then before.
859		1180
860	Unmaintained (maintainer unresponsive for many months, bugs are not	1181	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
861	getting fixed).	1182	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1183	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1184	a subset of Unicode), while ASCII is.
862		1185
863	=item JSON::Syck 0.21	1186	Surprisingly, C<decode> will ignore these flags and so treat all input
		1187	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1188	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1189	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
864		1190
865	Very buggy (often crashes).	1191	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1192	they only govern when the JSON output engine escapes a character or not.
866		1193
867	Very inflexible (no human-readable format supported, format pretty much	1194	The main use for C<latin1> is to relatively efficiently store binary data
868	undocumented. I need at least a format for easy reading by humans and a	1195	as JSON, at the expense of breaking compatibility with most JSON decoders.
869	single-line compact format for use in a protocol, and preferably a way to
870	generate ASCII-only JSON texts).
871		1196
872	Completely broken (and confusingly documented) Unicode handling (Unicode	1197	The main use for C<ascii> is to force the output to not contain characters
873	escapes are not working properly, you need to set ImplicitUnicode to	1198	with values > 127, which means you can interpret the resulting string
874	I<different> values on en- and decoding to get symmetric behaviour).	1199	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
875		1200	8-bit-encoding, and still get the same data structure back. This is useful
876	No round-tripping (simple cases work, but this depends on whether the scalar	1201	when your channel for JSON transfer is not 8-bit clean or the encoding
877	value was used in a numeric context or not).	1202	might be mangled in between (e.g. in mail), and works because ASCII is a
878		1203	proper subset of most 8-bit and multibyte encodings in use in the world.
879	Dumping hashes may skip hash values depending on iterator state.
880
881	Unmaintained (maintainer unresponsive for many months, bugs are not
882	getting fixed).
883
884	Does not check input for validity (i.e. will accept non-JSON input and
885	return "something" instead of raising an exception. This is a security
886	issue: imagine two banks transferring money between each other using
887	JSON. One bank might parse a given non-JSON request and deduct money,
888	while the other might reject the transaction with a syntax error. While a
889	good protocol will at least recover, that is extra unnecessary work and
890	the transaction will still not succeed).
891
892	=item JSON::DWIW 0.04
893
894	Very fast. Very natural. Very nice.
895
896	Undocumented Unicode handling (but the best of the pack. Unicode escapes
897	still don't get parsed properly).
898
899	Very inflexible.
900
901	No round-tripping.
902
903	Does not generate valid JSON texts (key strings are often unquoted, empty keys
904	result in nothing being output)
905
906	Does not check input for validity.
907		1204
908	=back	1205	=back
909		1206
910		1207
		1208	=head2 JSON and ECMAscript
		1209
		1210	JSON syntax is based on how literals are represented in javascript (the
		1211	not-standardised predecessor of ECMAscript) which is presumably why it is
		1212	called "JavaScript Object Notation".
		1213
		1214	However, JSON is not a subset (and also not a superset of course) of
		1215	ECMAscript (the standard) or javascript (whatever browsers actually
		1216	implement).
		1217
		1218	If you want to use javascript's C<eval> function to "parse" JSON, you
		1219	might run into parse errors for valid JSON texts, or the resulting data
		1220	structure might not be queryable:
		1221
		1222	One of the problems is that U+2028 and U+2029 are valid characters inside
		1223	JSON strings, but are not allowed in ECMAscript string literals, so the
		1224	following Perl fragment will not output something that can be guaranteed
		1225	to be parsable by javascript's C<eval>:
		1226
		1227	use JSON::XS;
		1228
		1229	print encode_json [chr 0x2028];
		1230
		1231	The right fix for this is to use a proper JSON parser in your javascript
		1232	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1233	F<json2.js> parser).
		1234
		1235	If this is not an option, you can, as a stop-gap measure, simply encode to
		1236	ASCII-only JSON:
		1237
		1238	use JSON::XS;
		1239
		1240	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1241
		1242	Note that this will enlarge the resulting JSON text quite a bit if you
		1243	have many non-ASCII characters. You might be tempted to run some regexes
		1244	to only escape U+2028 and U+2029, e.g.:
		1245
		1246	# DO NOT USE THIS!
		1247	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1248	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1249	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1250	print $json;
		1251
		1252	Note that I<this is a bad idea>: the above only works for U+2028 and
		1253	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1254	javascript implementations, however, have issues with other characters as
		1255	well - using C<eval> naively simply I<will> cause problems.
		1256
		1257	Another problem is that some javascript implementations reserve
		1258	some property names for their own purposes (which probably makes
		1259	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1260	C<__proto__> property name for its own purposes.
		1261
		1262	If that is a problem, you could parse try to filter the resulting JSON
		1263	output for these property strings, e.g.:
		1264
		1265	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1266
		1267	This works because C<__proto__> is not valid outside of strings, so every
		1268	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1269
		1270	If you know of other incompatibilities, please let me know.
		1271
		1272
911	=head2 JSON and YAML	1273	=head2 JSON and YAML
912		1274
913	You often hear that JSON is a subset of YAML. This is, however, a mass	1275	You often hear that JSON is a subset of YAML. This is, however, a mass
914	hysteria(*) and very far from the truth. In general, there is no way to	1276	hysteria(*) and very far from the truth (as of the time of this writing),
		1277	so let me state it clearly: I<in general, there is no way to configure
915	configure JSON::XS to output a data structure as valid YAML that works for	1278	JSON::XS to output a data structure as valid YAML> that works in all
916	all cases.	1279	cases.
917		1280
918	If you really must use JSON::XS to generate YAML, you should use this	1281	If you really must use JSON::XS to generate YAML, you should use this
919	algorithm (subject to change in future versions):	1282	algorithm (subject to change in future versions):
920		1283
921	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1284	my $to_yaml = JSON::XS->new->utf8->space_after (1);
922	my $yaml = $to_yaml->encode ($ref) . "\n";	1285	my $yaml = $to_yaml->encode ($ref) . "\n";
923		1286
924	This will I<usually> generate JSON texts that also parse as valid	1287	This will I<usually> generate JSON texts that also parse as valid
925	YAML. Please note that YAML has hardcoded limits on (simple) object key	1288	YAML. Please note that YAML has hardcoded limits on (simple) object key
926	lengths that JSON doesn't have and also has different and incompatible	1289	lengths that JSON doesn't have and also has different and incompatible
927	unicode handling, so you should make sure that your hash keys are	1290	unicode character escape syntax, so you should make sure that your hash
928	noticeably shorter than the 1024 "stream characters" YAML allows and that	1291	keys are noticeably shorter than the 1024 "stream characters" YAML allows
929	you do not have codepoints with values outside the Unicode BMP (basic	1292	and that you do not have characters with codepoint values outside the
930	multilingual page). YAML also does not allow C<\/> sequences in strings	1293	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
931	(which JSON::XS does not I<currently> generate).	1294	sequences in strings (which JSON::XS does not I<currently> generate, but
		1295	other JSON generators might).
932		1296
933	There might be other incompatibilities that I am not aware of (or the YAML	1297	There might be other incompatibilities that I am not aware of (or the YAML
934	specification has been changed yet again - it does so quite often). In	1298	specification has been changed yet again - it does so quite often). In
935	general you should not try to generate YAML with a JSON generator or vice	1299	general you should not try to generate YAML with a JSON generator or vice
936	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1300	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
939		1303
940	=over 4	1304	=over 4
941		1305
942	=item (*)	1306	=item (*)
943		1307
944	This is spread actively by the YAML team, however. For many years now they	1308	I have been pressured multiple times by Brian Ingerson (one of the
945	claim YAML were a superset of JSON, even when proven otherwise.	1309	authors of the YAML specification) to remove this paragraph, despite him
		1310	acknowledging that the actual incompatibilities exist. As I was personally
		1311	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1312	educate people about these issues, so others do not run into the same
		1313	problem again and again. After this, Brian called me a (quote)I<complete
		1314	and worthless idiot>(unquote).
946		1315
947	Even the author of this manpage was at some point accused of providing	1316	In my opinion, instead of pressuring and insulting people who actually
948	"incorrect" information, despite the evidence presented (claims ranged	1317	clarify issues with YAML and the wrong statements of some of its
949	from "your documentation contains inaccurate and negative statements about	1318	proponents, I would kindly suggest reading the JSON spec (which is not
950	YAML" (the only negative comment is this footnote, and it didn't exist	1319	that difficult or long) and finally make YAML compatible to it, and
951	back then; the question on which claims were inaccurate was never answered	1320	educating users about the changes, instead of spreading lies about the
952	etc.) to "the YAML spec is not up-to-date" (the real and supposedly	1321	real compatibility for many I<years> and trying to silence people who
953	JSON-compatible spec is apparently not currently publicly available)	1322	point out that it isn't true.
954	to actual requests to replace this section by incorrect information,
955	suppressing information about the real problem).
956		1323
957	So whenever you are told that YAML was a superset of JSON, first check	1324	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
958	wether it is really true (it might be when you check it, but it certainly	1325	though the incompatibilities have been documented (and are known to Brian)
959	was not true when this was written). I would much prefer if the YAML team	1326	for many years and the spec makes explicit claims that YAML is a superset
960	would spent their time on actually making JSON compatibility a truth	1327	of JSON. It would be so easy to fix, but apparently, bullying people and
961	(JSON, after all, has a very small and simple specification) instead of	1328	corrupting userdata is so much easier.
962	trying to lobby/force people into reporting untruths.
963		1329
964	=back	1330	=back
965		1331
966		1332
967	=head2 SPEED	1333	=head2 SPEED
…		…
969	It seems that JSON::XS is surprisingly fast, as shown in the following	1335	It seems that JSON::XS is surprisingly fast, as shown in the following
970	tables. They have been generated with the help of the C<eg/bench> program	1336	tables. They have been generated with the help of the C<eg/bench> program
971	in the JSON::XS distribution, to make it easy to compare on your own	1337	in the JSON::XS distribution, to make it easy to compare on your own
972	system.	1338	system.
973		1339
974	First comes a comparison between various modules using a very short	1340	First comes a comparison between various modules using
975	single-line JSON string:	1341	a very short single-line JSON string (also available at
		1342	L<http://dist.schmorp.de/misc/json/short.json>).
976		1343
977	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1344	{"method": "handleMessage", "params": ["user1",
978	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1345	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1346	1, 0]}
979		1347
980	It shows the number of encodes/decodes per second (JSON::XS uses	1348	It shows the number of encodes/decodes per second (JSON::XS uses
981	the functional interface, while JSON::XS/2 uses the OO interface	1349	the functional interface, while JSON::XS/2 uses the OO interface
982	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1350	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
983	shrink). Higher is better:	1351	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1352	uses the from_json method). Higher is better:
984		1353
985	module \| encode \| decode \|	1354	module \| encode \| decode \|
986	-----------\|------------\|------------\|	1355	--------------\|------------\|------------\|
987	JSON 1.x \| 4990.842 \| 4088.813 \|	1356	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
988	JSON::DWIW \| 51653.990 \| 71575.154 \|	1357	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
989	JSON::PC \| 65948.176 \| 74631.744 \|	1358	JSON::PP \| 15827.562 \| 6638.658 \|
990	JSON::PP \| 8931.652 \| 3817.168 \|	1359	JSON::Syck \| 63358.066 \| 47662.545 \|
991	JSON::Syck \| 24877.248 \| 27776.848 \|	1360	JSON::XS \| 511500.488 \| 511500.488 \|
992	JSON::XS \| 388361.481 \| 227951.304 \|	1361	JSON::XS/2 \| 291271.111 \| 388361.481 \|
993	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1362	JSON::XS/3 \| 361577.931 \| 361577.931 \|
994	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1363	Storable \| 66788.280 \| 265462.278 \|
995	Storable \| 16500.016 \| 135300.129 \|
996	-----------+------------+------------+	1364	--------------+------------+------------+
997		1365
998	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1366	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
999	about three times faster on decoding, and over forty times faster	1367	about five times faster on decoding, and over thirty to seventy times
1000	than JSON, even with pretty-printing and key sorting. It also compares	1368	faster than JSON's pure perl implementation. It also compares favourably
1001	favourably to Storable for small amounts of data.	1369	to Storable for small amounts of data.
1002		1370
1003	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1371	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1004	search API (http://nanoref.com/yahooapis/mgPdGg):	1372	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1005		1373
1006	module \| encode \| decode \|	1374	module \| encode \| decode \|
1007	-----------\|------------\|------------\|	1375	--------------\|------------\|------------\|
1008	JSON 1.x \| 55.260 \| 34.971 \|	1376	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1009	JSON::DWIW \| 825.228 \| 1082.513 \|	1377	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1010	JSON::PC \| 3571.444 \| 2394.829 \|
1011	JSON::PP \| 210.987 \| 32.574 \|	1378	JSON::PP \| 400.640 \| 62.311 \|
1012	JSON::Syck \| 552.551 \| 787.544 \|	1379	JSON::Syck \| 1481.040 \| 1524.869 \|
1013	JSON::XS \| 5780.463 \| 4854.519 \|	1380	JSON::XS \| 20661.596 \| 9541.183 \|
1014	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1381	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1015	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1382	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1016	Storable \| 4445.002 \| 5235.027 \|	1383	Storable \| 19765.806 \| 10000.725 \|
1017	-----------+------------+------------+	1384	--------------+------------+------------+
1018		1385
1019	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1386	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1020	decodes faster).	1387	decodes a bit faster).
1021		1388
1022	On large strings containing lots of high Unicode characters, some modules	1389	On large strings containing lots of high Unicode characters, some modules
1023	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1390	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1024	will be broken due to missing (or wrong) Unicode handling. Others refuse	1391	will be broken due to missing (or wrong) Unicode handling. Others refuse
1025	to decode or encode properly, so it was impossible to prepare a fair	1392	to decode or encode properly, so it was impossible to prepare a fair
…		…
1051	to free the temporary). If that is exceeded, the program crashes. To be	1418	to free the temporary). If that is exceeded, the program crashes. To be
1052	conservative, the default nesting limit is set to 512. If your process	1419	conservative, the default nesting limit is set to 512. If your process
1053	has a smaller stack, you should adjust this setting accordingly with the	1420	has a smaller stack, you should adjust this setting accordingly with the
1054	C<max_depth> method.	1421	C<max_depth> method.
1055		1422
1056	And last but least, something else could bomb you that I forgot to think	1423	Something else could bomb you, too, that I forgot to think of. In that
1057	of. In that case, you get to keep the pieces. I am always open for hints,	1424	case, you get to keep the pieces. I am always open for hints, though...
1058	though...	1425
		1426	Also keep in mind that JSON::XS might leak contents of your Perl data
		1427	structures in its error messages, so when you serialise sensitive
		1428	information you might want to make sure that exceptions thrown by JSON::XS
		1429	will not end up in front of untrusted eyes.
1059		1430
1060	If you are using JSON::XS to return packets to consumption	1431	If you are using JSON::XS to return packets to consumption
1061	by JavaScript scripts in a browser you should have a look at	1432	by JavaScript scripts in a browser you should have a look at
1062	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1433	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1063	you are vulnerable to some common attack vectors (which really are browser	1434	see whether you are vulnerable to some common attack vectors (which really
1064	design bugs, but it is still you who will have to deal with it, as major	1435	are browser design bugs, but it is still you who will have to deal with
1065	browser developers care only for features, not about getting security	1436	it, as major browser developers care only for features, not about getting
1066	right).	1437	security right).
1067		1438
1068		1439
1069	=head1 THREADS	1440	=head1 THREADS
1070		1441
1071	This module is I<not> guaranteed to be thread safe and there are no	1442	This module is I<not> guaranteed to be thread safe and there are no
1072	plans to change this until Perl gets thread support (as opposed to the	1443	plans to change this until Perl gets thread support (as opposed to the
1073	horribly slow so-called "threads" which are simply slow and bloated	1444	horribly slow so-called "threads" which are simply slow and bloated
1074	process simulations - use fork, its I<much> faster, cheaper, better).	1445	process simulations - use fork, it's I<much> faster, cheaper, better).
1075		1446
1076	(It might actually work, but you have been warned).	1447	(It might actually work, but you have been warned).
1077		1448
1078		1449
1079	=head1 BUGS	1450	=head1 BUGS
1080		1451
1081	While the goal of this module is to be correct, that unfortunately does	1452	While the goal of this module is to be correct, that unfortunately does
1082	not mean its bug-free, only that I think its design is bug-free. It is	1453	not mean it's bug-free, only that I think its design is bug-free. If you
1083	still relatively early in its development. If you keep reporting bugs they	1454	keep reporting bugs they will be fixed swiftly, though.
1084	will be fixed swiftly, though.
1085		1455
1086	Please refrain from using rt.cpan.org or any other bug reporting	1456	Please refrain from using rt.cpan.org or any other bug reporting
1087	service. I put the contact address into my modules for a reason.	1457	service. I put the contact address into my modules for a reason.
1088		1458
1089	=cut	1459	=cut
…		…
1109	"--" => sub { $_[0] = ${$_[0]} - 1 },	1479	"--" => sub { $_[0] = ${$_[0]} - 1 },
1110	fallback => 1;	1480	fallback => 1;
1111		1481
1112	1;	1482	1;
1113		1483
		1484	=head1 SEE ALSO
		1485
		1486	The F<json_xs> command line utility for quick experiments.
		1487
1114	=head1 AUTHOR	1488	=head1 AUTHOR
1115		1489
1116	Marc Lehmann <schmorp@schmorp.de>	1490	Marc Lehmann <schmorp@schmorp.de>
1117	http://home.schmorp.de/	1491	http://home.schmorp.de/
1118		1492

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs.
Revision 1.135 by root, Wed Jun 1 13:01:09 2011 UTC