[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 1.129 by root, Tue Jan 19 01:02:19 2010 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, the deserialised data structure is identical on the Perl level.
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
71	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	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 $VERSION = '2.28';
106	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
107		108
108	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
109		110
110	sub to_json($) {	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 parenthese
		719	mismatches. 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	=item $lvalue_string = $json->incr_text
		757
		758	This method returns the currently stored JSON fragment as an lvalue, that
		759	is, you can manipulate it. This I<only> works when a preceding call to
		760	C<incr_parse> in I<scalar context> successfully returned an object. Under
		761	all other circumstances you must not call this function (I mean it.
		762	although in simple tests it might actually work, it I<will> fail under
		763	real world conditions). As a special exception, you can also call this
		764	method before having parsed anything.
		765
		766	This function is useful in two cases: a) finding the trailing text after a
		767	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		768	(such as commas).
		769
		770	=item $json->incr_skip
		771
		772	This will reset the state of the incremental parser and will remove
		773	the parsed text from the input buffer so far. This is useful after
		774	C<incr_parse> died, in which case the input buffer and incremental parser
		775	state is left unchanged, to skip the text parsed so far and to reset the
		776	parse state.
		777
		778	The difference to C<incr_reset> is that only text until the parse error
		779	occured is removed.
		780
		781	=item $json->incr_reset
		782
		783	This completely resets the incremental parser, that is, after this call,
		784	it will be as if the parser had never parsed anything.
		785
		786	This is useful if you want to repeatedly parse JSON objects and want to
		787	ignore any trailing data, which means you have to reset the parser after
		788	each successful decode.
		789
		790	=back
		791
		792	=head2 LIMITATIONS
		793
		794	All options that affect decoding are supported, except
		795	C<allow_nonref>. The reason for this is that it cannot be made to
		796	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		797	them back to back and still decode them perfectly. This does not hold true
		798	for JSON numbers, however.
		799
		800	For example, is the string C<1> a single JSON number, or is it simply the
		801	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		802	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		803	takes the conservative route and disallows this case.
		804
		805	=head2 EXAMPLES
		806
		807	Some examples will make all this clearer. First, a simple example that
		808	works similarly to C<decode_prefix>: We want to decode the JSON object at
		809	the start of a string and identify the portion after the JSON object:
		810
		811	my $text = "[1,2,3] hello";
		812
		813	my $json = new JSON::XS;
		814
		815	my $obj = $json->incr_parse ($text)
		816	or die "expected JSON object or array at beginning of string";
		817
		818	my $tail = $json->incr_text;
		819	# $tail now contains " hello"
		820
		821	Easy, isn't it?
		822
		823	Now for a more complicated example: Imagine a hypothetical protocol where
		824	you read some requests from a TCP stream, and each request is a JSON
		825	array, without any separation between them (in fact, it is often useful to
		826	use newlines as "separators", as these get interpreted as whitespace at
		827	the start of the JSON text, which makes it possible to test said protocol
		828	with C<telnet>...).
		829
		830	Here is how you'd do it (it is trivial to write this in an event-based
		831	manner):
		832
		833	my $json = new JSON::XS;
		834
		835	# read some data from the socket
		836	while (sysread $socket, my $buf, 4096) {
		837
		838	# split and decode as many requests as possible
		839	for my $request ($json->incr_parse ($buf)) {
		840	# act on the $request
		841	}
		842	}
		843
		844	Another complicated example: Assume you have a string with JSON objects
		845	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		846	[3]>). To parse them, we have to skip the commas between the JSON texts,
		847	and here is where the lvalue-ness of C<incr_text> comes in useful:
		848
		849	my $text = "[1],[2], [3]";
		850	my $json = new JSON::XS;
		851
		852	# void context, so no parsing done
		853	$json->incr_parse ($text);
		854
		855	# now extract as many objects as possible. note the
		856	# use of scalar context so incr_text can be called.
		857	while (my $obj = $json->incr_parse) {
		858	# do something with $obj
		859
		860	# now skip the optional comma
		861	$json->incr_text =~ s/^ \s* , //x;
		862	}
		863
		864	Now lets go for a very complex example: Assume that you have a gigantic
		865	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		866	but you cannot load it into memory fully (this has actually happened in
		867	the real world :).
		868
		869	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		870	can still help you: You implement a (very simple) array parser and let
		871	JSON decode the array elements, which are all full JSON objects on their
		872	own (this wouldn't work if the array elements could be JSON numbers, for
		873	example):
		874
		875	my $json = new JSON::XS;
		876
		877	# open the monster
		878	open my $fh, "<bigfile.json"
		879	or die "bigfile: $!";
		880
		881	# first parse the initial "["
		882	for (;;) {
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886
		887	# Exit the loop once we found and removed(!) the initial "[".
		888	# In essence, we are (ab-)using the $json object as a simple scalar
		889	# we append data to.
		890	last if $json->incr_text =~ s/^ \s* \[ //x;
		891	}
		892
		893	# now we have the skipped the initial "[", so continue
		894	# parsing all the elements.
		895	for (;;) {
		896	# in this loop we read data until we got a single JSON object
		897	for (;;) {
		898	if (my $obj = $json->incr_parse) {
		899	# do something with $obj
		900	last;
		901	}
		902
		903	# add more data
		904	sysread $fh, my $buf, 65536
		905	or die "read error: $!";
		906	$json->incr_parse ($buf); # void context, so no parsing
		907	}
		908
		909	# in this loop we read data until we either found and parsed the
		910	# separating "," between elements, or the final "]"
		911	for (;;) {
		912	# first skip whitespace
		913	$json->incr_text =~ s/^\s*//;
		914
		915	# if we find "]", we are done
		916	if ($json->incr_text =~ s/^\]//) {
		917	print "finished.\n";
		918	exit;
		919	}
		920
		921	# if we find ",", we can continue with the next element
		922	if ($json->incr_text =~ s/^,//) {
		923	last;
		924	}
		925
		926	# if we find anything else, we have a parse error!
		927	if (length $json->incr_text) {
		928	die "parse error near ", $json->incr_text;
		929	}
		930
		931	# else add more data
		932	sysread $fh, my $buf, 65536
		933	or die "read error: $!";
		934	$json->incr_parse ($buf); # void context, so no parsing
		935	}
		936
		937	This is a complex example, but most of the complexity comes from the fact
		938	that we are trying to be correct (bear with me if I am wrong, I never ran
		939	the above example :).
		940
		941
		942
674	=head1 MAPPING	943	=head1 MAPPING
675		944
676	This section describes how JSON::XS maps Perl values to JSON values and	945	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	946	vice versa. These mappings are designed to "do the right thing" in most
678	circumstances automatically, preserving round-tripping characteristics	947	circumstances automatically, preserving round-tripping characteristics
…		…
706		975
707	A JSON number becomes either an integer, numeric (floating point) or	976	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	977	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	978	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	979	the conversion details, but an integer may take slightly less memory and
711	might represent more values exactly than (floating point) numbers.	980	might represent more values exactly than floating point numbers.
712		981
713	If the number consists of digits only, JSON::XS will try to represent	982	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	983	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	984	a numeric (floating point) value if that is possible without loss of
716	precision. Otherwise it will preserve the number as a string value.	985	precision. Otherwise it will preserve the number as a string value (in
		986	which case you lose roundtripping ability, as the JSON number will be
		987	re-encoded toa JSON string).
717		988
718	Numbers containing a fractional or exponential part will always be	989	Numbers containing a fractional or exponential part will always be
719	represented as numeric (floating point) values, possibly at a loss of	990	represented as numeric (floating point) values, possibly at a loss of
720	precision.	991	precision (in which case you might lose perfect roundtripping ability, but
721		992	the JSON number will still be re-encoded as a JSON number).
722	This might create round-tripping problems as numbers might become strings,
723	but as Perl is typeless there is no other way to do it.
724		993
725	=item true, false	994	=item true, false
726		995
727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	996	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	997	respectively. They are overloaded to act almost exactly like the numbers
…		…
765	Other unblessed references are generally not allowed and will cause an	1034	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	1035	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	1036	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.	1037	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
769		1038
770	encode_json [\0,JSON::XS::true] # yields [false,true]	1039	encode_json [\0, JSON::XS::true] # yields [false,true]
771		1040
772	=item JSON::XS::true, JSON::XS::false	1041	=item JSON::XS::true, JSON::XS::false
773		1042
774	These special values become JSON true and JSON false values,	1043	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.	1044	respectively. You can also use C<\1> and C<\0> directly if you want.
…		…
813	my $x = "3"; # some variable containing a string	1082	my $x = "3"; # some variable containing a string
814	$x += 0; # numify it, ensuring it will be dumped as a number	1083	$x += 0; # numify it, ensuring it will be dumped as a number
815	$x *= 1; # same thing, the choice is yours.	1084	$x *= 1; # same thing, the choice is yours.
816		1085
817	You can not currently force the type in other, less obscure, ways. Tell me	1086	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	1087	if you need this capability (but don't forget to explain why it's needed
819	:).	1088	:).
820		1089
821	=back	1090	=back
822		1091
823		1092
824	=head1 COMPARISON	1093	=head1 ENCODING/CODESET FLAG NOTES
825		1094
826	As already mentioned, this module was created because none of the existing	1095	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	1096	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,	1097	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	1098
830	from any of these problems or limitations.	1099	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1100	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1101	control whether C<encode> escapes character values outside their respective
		1102	codeset range. Neither of these flags conflict with each other, although
		1103	some combinations make less sense than others.
		1104
		1105	Care has been taken to make all flags symmetrical with respect to
		1106	C<encode> and C<decode>, that is, texts encoded with any combination of
		1107	these flag values will be correctly decoded when the same flags are used
		1108	- in general, if you use different flag settings while encoding vs. when
		1109	decoding you likely have a bug somewhere.
		1110
		1111	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1112	simply an abstract set of character-codepoint pairs, while an encoding
		1113	takes those codepoint numbers and I<encodes> them, in our case into
		1114	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1115	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1116	the same time, which can be confusing.
831		1117
832	=over 4	1118	=over 4
833		1119
834	=item JSON 1.07	1120	=item C<utf8> flag disabled
835		1121
836	Slow (but very portable, as it is written in pure Perl).	1122	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1123	and expect Unicode strings, that is, characters with high ordinal Unicode
		1124	values (> 255) will be encoded as such characters, and likewise such
		1125	characters are decoded as-is, no canges to them will be done, except
		1126	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1127	respectively (to Perl, these are the same thing in strings unless you do
		1128	funny/weird/dumb stuff).
837		1129
838	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1130	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	1131	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).	1132	the encoding for you (for example, when printing to a terminal using a
		1133	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1134	to UTF-8 encode your data first and have Perl encode it another time).
841		1135
842	No round-tripping (strings get clobbered if they look like numbers, e.g.	1136	=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		1137
846	=item JSON::PC 0.01	1138	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1139	characters using the corresponding UTF-8 multi-byte sequence, and will
		1140	expect your input strings to be encoded as UTF-8, that is, no "character"
		1141	of the input string must have any value > 255, as UTF-8 does not allow
		1142	that.
847		1143
848	Very fast.	1144	The C<utf8> flag therefore switches between two modes: disabled means you
		1145	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1146	octet/binary string in Perl.
849		1147
850	Undocumented/buggy Unicode handling.	1148	=item C<latin1> or C<ascii> flags enabled
851		1149
852	No round-tripping.	1150	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1151	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1152	characters as specified by the C<utf8> flag.
853		1153
854	Has problems handling many Perl values (e.g. regex results and other magic	1154	If C<utf8> is disabled, then the result is also correctly encoded in those
855	values will make it croak).	1155	character sets (as both are proper subsets of Unicode, meaning that a
		1156	Unicode string with all character values < 256 is the same thing as a
		1157	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1158	the same thing as an ASCII string in Perl).
856		1159
857	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1160	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
858	which is not a valid JSON text.	1161	regardless of these flags, just some more characters will be escaped using
		1162	C<\uXXXX> then before.
859		1163
860	Unmaintained (maintainer unresponsive for many months, bugs are not	1164	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
861	getting fixed).	1165	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1166	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1167	a subset of Unicode), while ASCII is.
862		1168
863	=item JSON::Syck 0.21	1169	Surprisingly, C<decode> will ignore these flags and so treat all input
		1170	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1171	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1172	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
864		1173
865	Very buggy (often crashes).	1174	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1175	they only govern when the JSON output engine escapes a character or not.
866		1176
867	Very inflexible (no human-readable format supported, format pretty much	1177	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	1178	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		1179
872	Completely broken (and confusingly documented) Unicode handling (Unicode	1180	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	1181	with values > 127, which means you can interpret the resulting string
874	I<different> values on en- and decoding to get symmetric behaviour).	1182	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
875		1183	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	1184	when your channel for JSON transfer is not 8-bit clean or the encoding
877	value was used in a numeric context or not).	1185	might be mangled in between (e.g. in mail), and works because ASCII is a
878		1186	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		1187
908	=back	1188	=back
909		1189
910		1190
		1191	=head2 JSON and ECMAscript
		1192
		1193	JSON syntax is based on how literals are represented in javascript (the
		1194	not-standardised predecessor of ECMAscript) which is presumably why it is
		1195	called "JavaScript Object Notation".
		1196
		1197	However, JSON is not a subset (and also not a superset of course) of
		1198	ECMAscript (the standard) or javascript (whatever browsers actually
		1199	implement).
		1200
		1201	If you want to use javascript's C<eval> function to "parse" JSON, you
		1202	might run into parse errors for valid JSON texts, or the resulting data
		1203	structure might not be queryable:
		1204
		1205	One of the problems is that U+2028 and U+2029 are valid characters inside
		1206	JSON strings, but are not allowed in ECMAscript string literals, so the
		1207	following Perl fragment will not output something that can be guaranteed
		1208	to be parsable by javascript's C<eval>:
		1209
		1210	use JSON::XS;
		1211
		1212	print encode_json [chr 0x2028];
		1213
		1214	The right fix for this is to use a proper JSON parser in your javascript
		1215	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1216	F<json2.js> parser).
		1217
		1218	If this is not an option, you can, as a stop-gap measure, simply encode to
		1219	ASCII-only JSON:
		1220
		1221	use JSON::XS;
		1222
		1223	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1224
		1225	Note that this will enlarge the resulting JSON text quite a bit if you
		1226	have many non-ASCII characters. You might be tempted to run some regexes
		1227	to only escape U+2028 and U+2029, e.g.:
		1228
		1229	# DO NOT USE THIS!
		1230	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1231	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1232	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1233	print $json;
		1234
		1235	Note that I<this is a bad idea>: the above only works for U+2028 and
		1236	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1237	javascript implementations, however, have issues with other characters as
		1238	well - using C<eval> naively simply I<will> cause problems.
		1239
		1240	Another problem is that some javascript implementations reserve
		1241	some property names for their own purposes (which probably makes
		1242	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1243	C<__proto__> property name for it's own purposes.
		1244
		1245	If that is a problem, you could parse try to filter the resulting JSON
		1246	output for these property strings, e.g.:
		1247
		1248	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1249
		1250	This works because C<__proto__> is not valid outside of strings, so every
		1251	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1252
		1253	If you know of other incompatibilities, please let me know.
		1254
		1255
911	=head2 JSON and YAML	1256	=head2 JSON and YAML
912		1257
913	You often hear that JSON is a subset of YAML. This is, however, a mass	1258	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	1259	hysteria(*) and very far from the truth (as of the time of this writing),
		1260	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	1261	JSON::XS to output a data structure as valid YAML> that works in all
916	all cases.	1262	cases.
917		1263
918	If you really must use JSON::XS to generate YAML, you should use this	1264	If you really must use JSON::XS to generate YAML, you should use this
919	algorithm (subject to change in future versions):	1265	algorithm (subject to change in future versions):
920		1266
921	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1267	my $to_yaml = JSON::XS->new->utf8->space_after (1);
922	my $yaml = $to_yaml->encode ($ref) . "\n";	1268	my $yaml = $to_yaml->encode ($ref) . "\n";
923		1269
924	This will I<usually> generate JSON texts that also parse as valid	1270	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	1271	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	1272	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	1273	unicode character escape syntax, so you should make sure that your hash
928	noticeably shorter than the 1024 "stream characters" YAML allows and that	1274	keys are noticeably shorter than the 1024 "stream characters" YAML allows
929	you do not have codepoints with values outside the Unicode BMP (basic	1275	and that you do not have characters with codepoint values outside the
930	multilingual page). YAML also does not allow C<\/> sequences in strings	1276	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
931	(which JSON::XS does not I<currently> generate).	1277	sequences in strings (which JSON::XS does not I<currently> generate, but
		1278	other JSON generators might).
932		1279
933	There might be other incompatibilities that I am not aware of (or the YAML	1280	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	1281	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	1282	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	1283	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
939		1286
940	=over 4	1287	=over 4
941		1288
942	=item (*)	1289	=item (*)
943		1290
944	This is spread actively by the YAML team, however. For many years now they	1291	I have been pressured multiple times by Brian Ingerson (one of the
945	claim YAML were a superset of JSON, even when proven otherwise.	1292	authors of the YAML specification) to remove this paragraph, despite him
		1293	acknowledging that the actual incompatibilities exist. As I was personally
		1294	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1295	educate people about these issues, so others do not run into the same
		1296	problem again and again. After this, Brian called me a (quote)I<complete
		1297	and worthless idiot>(unquote).
946		1298
947	Even the author of this manpage was at some point accused of providing	1299	In my opinion, instead of pressuring and insulting people who actually
948	"incorrect" information, despite the evidence presented (claims ranged	1300	clarify issues with YAML and the wrong statements of some of its
949	from "your documentation contains inaccurate and negative statements about	1301	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	1302	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	1303	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	1304	real compatibility for many I<years> and trying to silence people who
953	JSON-compatible spec is apparently not currently publicly available)	1305	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		1306
957	So whenever you are told that YAML was a superset of JSON, first check	1307	Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
958	wether it is really true (it might be when you check it, but it certainly	1308	though the incompatibilities have been documented (and are known to
959	was not true when this was written). I would much prefer if the YAML team	1309	Brian) for many years and the spec makes explicit claims that YAML is a
960	would spent their time on actually making JSON compatibility a truth	1310	superset of JSON. It would be so easy to fix, but apparently, bullying and
961	(JSON, after all, has a very small and simple specification) instead of	1311	corrupting userdata is so much easier.
962	trying to lobby/force people into reporting untruths.
963		1312
964	=back	1313	=back
965		1314
966		1315
967	=head2 SPEED	1316	=head2 SPEED
…		…
969	It seems that JSON::XS is surprisingly fast, as shown in the following	1318	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	1319	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	1320	in the JSON::XS distribution, to make it easy to compare on your own
972	system.	1321	system.
973		1322
974	First comes a comparison between various modules using a very short	1323	First comes a comparison between various modules using
975	single-line JSON string:	1324	a very short single-line JSON string (also available at
		1325	L<http://dist.schmorp.de/misc/json/short.json>).
976		1326
977	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1327	{"method": "handleMessage", "params": ["user1",
978	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1328	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1329	1, 0]}
979		1330
980	It shows the number of encodes/decodes per second (JSON::XS uses	1331	It shows the number of encodes/decodes per second (JSON::XS uses
981	the functional interface, while JSON::XS/2 uses the OO interface	1332	the functional interface, while JSON::XS/2 uses the OO interface
982	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1333	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
983	shrink). Higher is better:	1334	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1335	uses the from_json method). Higher is better:
984		1336
985	module \| encode \| decode \|	1337	module \| encode \| decode \|
986	-----------\|------------\|------------\|	1338	--------------\|------------\|------------\|
987	JSON 1.x \| 4990.842 \| 4088.813 \|	1339	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
988	JSON::DWIW \| 51653.990 \| 71575.154 \|	1340	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
989	JSON::PC \| 65948.176 \| 74631.744 \|	1341	JSON::PP \| 15827.562 \| 6638.658 \|
990	JSON::PP \| 8931.652 \| 3817.168 \|	1342	JSON::Syck \| 63358.066 \| 47662.545 \|
991	JSON::Syck \| 24877.248 \| 27776.848 \|	1343	JSON::XS \| 511500.488 \| 511500.488 \|
992	JSON::XS \| 388361.481 \| 227951.304 \|	1344	JSON::XS/2 \| 291271.111 \| 388361.481 \|
993	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1345	JSON::XS/3 \| 361577.931 \| 361577.931 \|
994	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1346	Storable \| 66788.280 \| 265462.278 \|
995	Storable \| 16500.016 \| 135300.129 \|
996	-----------+------------+------------+	1347	--------------+------------+------------+
997		1348
998	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1349	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	1350	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	1351	faster than JSON's pure perl implementation. It also compares favourably
1001	favourably to Storable for small amounts of data.	1352	to Storable for small amounts of data.
1002		1353
1003	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1354	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1004	search API (http://nanoref.com/yahooapis/mgPdGg):	1355	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1005		1356
1006	module \| encode \| decode \|	1357	module \| encode \| decode \|
1007	-----------\|------------\|------------\|	1358	--------------\|------------\|------------\|
1008	JSON 1.x \| 55.260 \| 34.971 \|	1359	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1009	JSON::DWIW \| 825.228 \| 1082.513 \|	1360	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1010	JSON::PC \| 3571.444 \| 2394.829 \|
1011	JSON::PP \| 210.987 \| 32.574 \|	1361	JSON::PP \| 400.640 \| 62.311 \|
1012	JSON::Syck \| 552.551 \| 787.544 \|	1362	JSON::Syck \| 1481.040 \| 1524.869 \|
1013	JSON::XS \| 5780.463 \| 4854.519 \|	1363	JSON::XS \| 20661.596 \| 9541.183 \|
1014	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1364	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1015	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1365	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1016	Storable \| 4445.002 \| 5235.027 \|	1366	Storable \| 19765.806 \| 10000.725 \|
1017	-----------+------------+------------+	1367	--------------+------------+------------+
1018		1368
1019	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1369	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1020	decodes faster).	1370	decodes a bit faster).
1021		1371
1022	On large strings containing lots of high Unicode characters, some modules	1372	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	1373	(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	1374	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	1375	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	1401	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	1402	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	1403	has a smaller stack, you should adjust this setting accordingly with the
1054	C<max_depth> method.	1404	C<max_depth> method.
1055		1405
1056	And last but least, something else could bomb you that I forgot to think	1406	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,	1407	case, you get to keep the pieces. I am always open for hints, though...
1058	though...	1408
		1409	Also keep in mind that JSON::XS might leak contents of your Perl data
		1410	structures in its error messages, so when you serialise sensitive
		1411	information you might want to make sure that exceptions thrown by JSON::XS
		1412	will not end up in front of untrusted eyes.
1059		1413
1060	If you are using JSON::XS to return packets to consumption	1414	If you are using JSON::XS to return packets to consumption
1061	by JavaScript scripts in a browser you should have a look at	1415	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	1416	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	1417	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	1418	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	1419	it, as major browser developers care only for features, not about getting
1066	right).	1420	security right).
1067		1421
1068		1422
1069	=head1 THREADS	1423	=head1 THREADS
1070		1424
1071	This module is I<not> guaranteed to be thread safe and there are no	1425	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	1426	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	1427	horribly slow so-called "threads" which are simply slow and bloated
1074	process simulations - use fork, its I<much> faster, cheaper, better).	1428	process simulations - use fork, it's I<much> faster, cheaper, better).
1075		1429
1076	(It might actually work, but you have been warned).	1430	(It might actually work, but you have been warned).
1077		1431
1078		1432
1079	=head1 BUGS	1433	=head1 BUGS
1080		1434
1081	While the goal of this module is to be correct, that unfortunately does	1435	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	1436	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	1437	keep reporting bugs they will be fixed swiftly, though.
1084	will be fixed swiftly, though.
1085		1438
1086	Please refrain from using rt.cpan.org or any other bug reporting	1439	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.	1440	service. I put the contact address into my modules for a reason.
1088		1441
1089	=cut	1442	=cut
…		…
1109	"--" => sub { $_[0] = ${$_[0]} - 1 },	1462	"--" => sub { $_[0] = ${$_[0]} - 1 },
1110	fallback => 1;	1463	fallback => 1;
1111		1464
1112	1;	1465	1;
1113		1466
		1467	=head1 SEE ALSO
		1468
		1469	The F<json_xs> command line utility for quick experiments.
		1470
1114	=head1 AUTHOR	1471	=head1 AUTHOR
1115		1472
1116	Marc Lehmann <schmorp@schmorp.de>	1473	Marc Lehmann <schmorp@schmorp.de>
1117	http://home.schmorp.de/	1474	http://home.schmorp.de/
1118		1475

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Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs.
Revision 1.129 by root, Tue Jan 19 01:02:19 2010 UTC