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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.98 by root, Wed Mar 26 02:36:18 2008 UTC vs.
Revision 1.153 by root, Sun Mar 2 20:41:14 2014 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
		3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
3	=encoding utf-8	5	=encoding utf-8
4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		6
7	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
8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9		9
10	=head1 SYNOPSIS	10	=head1 SYNOPSIS
37	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
38	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.
39		39
40	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
41	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
42	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
43	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
44	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
45	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
46	require a C compiler when that is a problem.	46	require a C compiler when that is a problem.
47		47
…		…
49	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
50	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
51	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
52	reports for other reasons.	52	reports for other reasons.
53		53
54	See COMPARISON, below, for a comparison to some other JSON modules.
55
56	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
57	vice versa.	55	vice versa.
58		56
59	=head2 FEATURES	57	=head2 FEATURES
60		58
…		…
65	This module knows how to handle Unicode, documents how and when it does	63	This module knows how to handle Unicode, documents how and when it does
66	so, and even documents what "correct" means.	64	so, and even documents what "correct" means.
67		65
68	=item * round-trip integrity	66	=item * round-trip integrity
69		67
70	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
71	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
72	(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
73	like a number). There minor I<are> exceptions to this, read the MAPPING	71	it looks like a number). There I<are> minor exceptions to this, read the
74	section below to learn about those.	72	MAPPING section below to learn about those.
75		73
76	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
77		75
78	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,
79	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
…		…
84	Compared to other JSON modules and other serialisers such as Storable,	82	Compared to other JSON modules and other serialisers such as Storable,
85	this module usually compares favourably in terms of speed, too.	83	this module usually compares favourably in terms of speed, too.
86		84
87	=item * simple to use	85	=item * simple to use
88		86
89	This module has both a simple functional interface as well as an objetc	87	This module has both a simple functional interface as well as an object
90	oriented interface interface.	88	oriented interface.
91		89
92	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
93		91
94	You can choose between the most compact guaranteed-single-line format	92	You can choose between the most compact guaranteed-single-line format
95	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
96	(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
97	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
98	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.
99		97
100	=back	98	=back
101		99
102	=cut	100	=cut
103		101
104	package JSON::XS;	102	package JSON::XS;
105		103
106	use strict;	104	use common::sense;
107		105
108	our $VERSION = '2.1';	106	our $VERSION = 3.01;
109	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
110		108
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
112
113	sub to_json($) {
114	require Carp;
115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
116	}
117
118	sub from_json($) {
119	require Carp;
120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
121	}
122		110
123	use Exporter;	111	use Exporter;
124	use XSLoader;	112	use XSLoader;
125		113
		114	use Types::Serialiser ();
		115
126	=head1 FUNCTIONAL INTERFACE	116	=head1 FUNCTIONAL INTERFACE
127		117
128	The following convenience methods are provided by this module. They are	118	The following convenience methods are provided by this module. They are
129	exported by default:	119	exported by default:
130		120
…		…
137		127
138	This function call is functionally identical to:	128	This function call is functionally identical to:
139		129
140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	130	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141		131
142	except being faster.	132	Except being faster.
143		133
144	=item $perl_scalar = decode_json $json_text	134	=item $perl_scalar = decode_json $json_text
145		135
146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	136	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
147	to parse that as an UTF-8 encoded JSON text, returning the resulting	137	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
149		139
150	This function call is functionally identical to:	140	This function call is functionally identical to:
151		141
152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	142	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153		143
154	except being faster.	144	Except being faster.
155
156	=item $is_boolean = JSON::XS::is_bool $scalar
157
158	Returns true if the passed scalar represents either JSON::XS::true or
159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
160	and are used to represent JSON C<true> and C<false> values in Perl.
161
162	See MAPPING, below, for more information on how JSON values are mapped to
163	Perl.
164		145
165	=back	146	=back
166		147
167		148
168	=head1 A FEW NOTES ON UNICODE AND PERL	149	=head1 A FEW NOTES ON UNICODE AND PERL
…		…
197		178
198	If you didn't know about that flag, just the better, pretend it doesn't	179	If you didn't know about that flag, just the better, pretend it doesn't
199	exist.	180	exist.
200		181
201	=item 4. A "Unicode String" is simply a string where each character can be	182	=item 4. A "Unicode String" is simply a string where each character can be
202	validly interpreted as a Unicode codepoint.	183	validly interpreted as a Unicode code point.
203		184
204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	185	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205	Unicode string encoded in UTF-8, giving you a binary string.	186	Unicode string encoded in UTF-8, giving you a binary string.
206		187
207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	188	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	415	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
435	by sorting their keys. This is adding a comparatively high overhead.	416	by sorting their keys. This is adding a comparatively high overhead.
436		417
437	If C<$enable> is false, then the C<encode> method will output key-value	418	If C<$enable> is false, then the C<encode> method will output key-value
438	pairs in the order Perl stores them (which will likely change between runs	419	pairs in the order Perl stores them (which will likely change between runs
439	of the same script).	420	of the same script, and can change even within the same run from 5.18
		421	onwards).
440		422
441	This option is useful if you want the same data structure to be encoded as	423	This option is useful if you want the same data structure to be encoded as
442	the same JSON text (given the same overall settings). If it is disabled,	424	the same JSON text (given the same overall settings). If it is disabled,
443	the same hash might be encoded differently even if contains the same data,	425	the same hash might be encoded differently even if contains the same data,
444	as key-value pairs have no inherent ordering in Perl.	426	as key-value pairs have no inherent ordering in Perl.
445		427
446	This setting has no effect when decoding JSON texts.	428	This setting has no effect when decoding JSON texts.
447		429
		430	This setting has currently no effect on tied hashes.
		431
448	=item $json = $json->allow_nonref ([$enable])	432	=item $json = $json->allow_nonref ([$enable])
449		433
450	=item $enabled = $json->get_allow_nonref	434	=item $enabled = $json->get_allow_nonref
451		435
452	If C<$enable> is true (or missing), then the C<encode> method can convert a	436	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
463	resulting in an invalid JSON text:	447	resulting in an invalid JSON text:
464		448
465	JSON::XS->new->allow_nonref->encode ("Hello, World!")	449	JSON::XS->new->allow_nonref->encode ("Hello, World!")
466	=> "Hello, World!"	450	=> "Hello, World!"
467		451
		452	=item $json = $json->allow_unknown ([$enable])
		453
		454	=item $enabled = $json->get_allow_unknown
		455
		456	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		457	exception when it encounters values it cannot represent in JSON (for
		458	example, filehandles) but instead will encode a JSON C<null> value. Note
		459	that blessed objects are not included here and are handled separately by
		460	c<allow_nonref>.
		461
		462	If C<$enable> is false (the default), then C<encode> will throw an
		463	exception when it encounters anything it cannot encode as JSON.
		464
		465	This option does not affect C<decode> in any way, and it is recommended to
		466	leave it off unless you know your communications partner.
		467
468	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
469		469
470	=item $enabled = $json->get_allow_blessed	470	=item $enabled = $json->get_allow_blessed
471		471
		472	See L<OBJECT SERIALISATION> for details.
		473
472	If C<$enable> is true (or missing), then the C<encode> method will not	474	If C<$enable> is true (or missing), then the C<encode> method will not
473	barf when it encounters a blessed reference. Instead, the value of the	475	barf when it encounters a blessed reference that it cannot convert
474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	476	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
475	disabled or no C<TO_JSON> method found) or a representation of the
476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
477	encoded. Has no effect on C<decode>.
478		477
479	If C<$enable> is false (the default), then C<encode> will throw an	478	If C<$enable> is false (the default), then C<encode> will throw an
480	exception when it encounters a blessed object.	479	exception when it encounters a blessed object that it cannot convert
		480	otherwise.
		481
		482	This setting has no effect on C<decode>.
481		483
482	=item $json = $json->convert_blessed ([$enable])	484	=item $json = $json->convert_blessed ([$enable])
483		485
484	=item $enabled = $json->get_convert_blessed	486	=item $enabled = $json->get_convert_blessed
		487
		488	See L<OBJECT SERIALISATION> for details.
485		489
486	If C<$enable> is true (or missing), then C<encode>, upon encountering a	490	If C<$enable> is true (or missing), then C<encode>, upon encountering a
487	blessed object, will check for the availability of the C<TO_JSON> method	491	blessed object, will check for the availability of the C<TO_JSON> method
488	on the object's class. If found, it will be called in scalar context	492	on the object's class. If found, it will be called in scalar context and
489	and the resulting scalar will be encoded instead of the object. If no	493	the resulting scalar will be encoded instead of the object.
490	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
491	to do.
492		494
493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	495	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
494	returns other blessed objects, those will be handled in the same	496	returns other blessed objects, those will be handled in the same
495	way. C<TO_JSON> must take care of not causing an endless recursion cycle	497	way. C<TO_JSON> must take care of not causing an endless recursion cycle
496	(== crash) in this case. The name of C<TO_JSON> was chosen because other	498	(== crash) in this case. The name of C<TO_JSON> was chosen because other
497	methods called by the Perl core (== not by the user of the object) are	499	methods called by the Perl core (== not by the user of the object) are
498	usually in upper case letters and to avoid collisions with any C<to_json>	500	usually in upper case letters and to avoid collisions with any C<to_json>
499	function or method.	501	function or method.
500		502
501	This setting does not yet influence C<decode> in any way, but in the	503	If C<$enable> is false (the default), then C<encode> will not consider
502	future, global hooks might get installed that influence C<decode> and are	504	this type of conversion.
503	enabled by this setting.
504		505
505	If C<$enable> is false, then the C<allow_blessed> setting will decide what	506	This setting has no effect on C<decode>.
506	to do when a blessed object is found.	507
		508	=item $json = $json->allow_tags ([$enable])
		509
		510	=item $enabled = $json->allow_tags
		511
		512	See L<OBJECT SERIALISATION> for details.
		513
		514	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		515	blessed object, will check for the availability of the C<FREEZE> method on
		516	the object's class. If found, it will be used to serialise the object into
		517	a nonstandard tagged JSON value (that JSON decoders cannot decode).
		518
		519	It also causes C<decode> to parse such tagged JSON values and deserialise
		520	them via a call to the C<THAW> method.
		521
		522	If C<$enable> is false (the default), then C<encode> will not consider
		523	this type of conversion, and tagged JSON values will cause a parse error
		524	in C<decode>, as if tags were not part of the grammar.
507		525
508	=item $json = $json->filter_json_object ([$coderef->($hashref)])	526	=item $json = $json->filter_json_object ([$coderef->($hashref)])
509		527
510	When C<$coderef> is specified, it will be called from C<decode> each	528	When C<$coderef> is specified, it will be called from C<decode> each
511	time it decodes a JSON object. The only argument is a reference to the	529	time it decodes a JSON object. The only argument is a reference to the
…		…
612	=item $json = $json->max_depth ([$maximum_nesting_depth])	630	=item $json = $json->max_depth ([$maximum_nesting_depth])
613		631
614	=item $max_depth = $json->get_max_depth	632	=item $max_depth = $json->get_max_depth
615		633
616	Sets the maximum nesting level (default C<512>) accepted while encoding	634	Sets the maximum nesting level (default C<512>) accepted while encoding
617	or decoding. If the JSON text or Perl data structure has an equal or	635	or decoding. If a higher nesting level is detected in JSON text or a Perl
618	higher nesting level then this limit, then the encoder and decoder will	636	data structure, then the encoder and decoder will stop and croak at that
619	stop and croak at that point.	637	point.
620		638
621	Nesting level is defined by number of hash- or arrayrefs that the encoder	639	Nesting level is defined by number of hash- or arrayrefs that the encoder
622	needs to traverse to reach a given point or the number of C<{> or C<[>	640	needs to traverse to reach a given point or the number of C<{> or C<[>
623	characters without their matching closing parenthesis crossed to reach a	641	characters without their matching closing parenthesis crossed to reach a
624	given character in a string.	642	given character in a string.
625		643
626	Setting the maximum depth to one disallows any nesting, so that ensures	644	Setting the maximum depth to one disallows any nesting, so that ensures
627	that the object is only a single hash/object or array.	645	that the object is only a single hash/object or array.
628		646
629	The argument to C<max_depth> will be rounded up to the next highest power
630	of two. If no argument is given, the highest possible setting will be	647	If no argument is given, the highest possible setting will be used, which
631	used, which is rarely useful.	648	is rarely useful.
		649
		650	Note that nesting is implemented by recursion in C. The default value has
		651	been chosen to be as large as typical operating systems allow without
		652	crashing.
632		653
633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	654	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
634		655
635	=item $json = $json->max_size ([$maximum_string_size])	656	=item $json = $json->max_size ([$maximum_string_size])
636		657
637	=item $max_size = $json->get_max_size	658	=item $max_size = $json->get_max_size
638		659
639	Set the maximum length a JSON text may have (in bytes) where decoding is	660	Set the maximum length a JSON text may have (in bytes) where decoding is
640	being attempted. The default is C<0>, meaning no limit. When C<decode>	661	being attempted. The default is C<0>, meaning no limit. When C<decode>
641	is called on a string longer then this number of characters it will not	662	is called on a string that is longer then this many bytes, it will not
642	attempt to decode the string but throw an exception. This setting has no	663	attempt to decode the string but throw an exception. This setting has no
643	effect on C<encode> (yet).	664	effect on C<encode> (yet).
644		665
645	The argument to C<max_size> will be rounded up to the next B<highest>	666	If no argument is given, the limit check will be deactivated (same as when
646	power of two (so may be more than requested). If no argument is given, the	667	C<0> is specified).
647	limit check will be deactivated (same as when C<0> is specified).
648		668
649	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	669	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
650		670
651	=item $json_text = $json->encode ($perl_scalar)	671	=item $json_text = $json->encode ($perl_scalar)
652		672
653	Converts the given Perl data structure (a simple scalar or a reference	673	Converts the given Perl value or data structure to its JSON
654	to a hash or array) to its JSON representation. Simple scalars will be	674	representation. Croaks on error.
655	converted into JSON string or number sequences, while references to arrays
656	become JSON arrays and references to hashes become JSON objects. Undefined
657	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
658	nor C<false> values will be generated.
659		675
660	=item $perl_scalar = $json->decode ($json_text)	676	=item $perl_scalar = $json->decode ($json_text)
661		677
662	The opposite of C<encode>: expects a JSON text and tries to parse it,	678	The opposite of C<encode>: expects a JSON text and tries to parse it,
663	returning the resulting simple scalar or reference. Croaks on error.	679	returning the resulting simple scalar or reference. Croaks on error.
664
665	JSON numbers and strings become simple Perl scalars. JSON arrays become
666	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
667	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
668		680
669	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	681	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
670		682
671	This works like the C<decode> method, but instead of raising an exception	683	This works like the C<decode> method, but instead of raising an exception
672	when there is trailing garbage after the first JSON object, it will	684	when there is trailing garbage after the first JSON object, it will
673	silently stop parsing there and return the number of characters consumed	685	silently stop parsing there and return the number of characters consumed
674	so far.	686	so far.
675		687
676	This is useful if your JSON texts are not delimited by an outer protocol	688	This is useful if your JSON texts are not delimited by an outer protocol
677	(which is not the brightest thing to do in the first place) and you need
678	to know where the JSON text ends.	689	and you need to know where the JSON text ends.
679		690
680	JSON::XS->new->decode_prefix ("[1] the tail")	691	JSON::XS->new->decode_prefix ("[1] the tail")
681	=> ([], 3)	692	=> ([], 3)
682		693
683	=back	694	=back
684		695
685		696
686	=head1 INCREMENTAL PARSING	697	=head1 INCREMENTAL PARSING
687
688	[This section and the API it details is still EXPERIMENTAL]
689		698
690	In some cases, there is the need for incremental parsing of JSON	699	In some cases, there is the need for incremental parsing of JSON
691	texts. While this module always has to keep both JSON text and resulting	700	texts. While this module always has to keep both JSON text and resulting
692	Perl data structure in memory at one time, it does allow you to parse a	701	Perl data structure in memory at one time, it does allow you to parse a
693	JSON stream incrementally. It does so by accumulating text until it has	702	JSON stream incrementally. It does so by accumulating text until it has
694	a full JSON object, which it then can decode. This process is similar to	703	a full JSON object, which it then can decode. This process is similar to
695	using C<decode_prefix> to see if a full JSON object is available, but is	704	using C<decode_prefix> to see if a full JSON object is available, but
696	much more efficient (JSON::XS will only attempt to parse the JSON text	705	is much more efficient (and can be implemented with a minimum of method
		706	calls).
		707
		708	JSON::XS will only attempt to parse the JSON text once it is sure it
697	once it is sure it has enough text to get a decisive result, using a very	709	has enough text to get a decisive result, using a very simple but
698	simple but truly incremental parser).	710	truly incremental parser. This means that it sometimes won't stop as
		711	early as the full parser, for example, it doesn't detect mismatched
		712	parentheses. The only thing it guarantees is that it starts decoding as
		713	soon as a syntactically valid JSON text has been seen. This means you need
		714	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		715	parsing in the presence if syntax errors.
699		716
700	The following two methods deal with this.	717	The following methods implement this incremental parser.
701		718
702	=over 4	719	=over 4
703		720
704	=item [void, scalar or list context] = $json->incr_parse ([$string])	721	=item [void, scalar or list context] = $json->incr_parse ([$string])
705		722
…		…
716		733
717	If the method is called in scalar context, then it will try to extract	734	If the method is called in scalar context, then it will try to extract
718	exactly I<one> JSON object. If that is successful, it will return this	735	exactly I<one> JSON object. If that is successful, it will return this
719	object, otherwise it will return C<undef>. If there is a parse error,	736	object, otherwise it will return C<undef>. If there is a parse error,
720	this method will croak just as C<decode> would do (one can then use	737	this method will croak just as C<decode> would do (one can then use
721	C<incr_skip> to skip the errornous part). This is the most common way of	738	C<incr_skip> to skip the erroneous part). This is the most common way of
722	using the method.	739	using the method.
723		740
724	And finally, in list context, it will try to extract as many objects	741	And finally, in list context, it will try to extract as many objects
725	from the stream as it can find and return them, or the empty list	742	from the stream as it can find and return them, or the empty list
726	otherwise. For this to work, there must be no separators between the JSON	743	otherwise. For this to work, there must be no separators between the JSON
727	objects or arrays, instead they must be concatenated back-to-back. If	744	objects or arrays, instead they must be concatenated back-to-back. If
728	an error occurs, an exception will be raised as in the scalar context	745	an error occurs, an exception will be raised as in the scalar context
729	case. Note that in this case, any previously-parsed JSON texts will be	746	case. Note that in this case, any previously-parsed JSON texts will be
730	lost.	747	lost.
731		748
		749	Example: Parse some JSON arrays/objects in a given string and return
		750	them.
		751
		752	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		753
732	=item $lvalue_string = $json->incr_text	754	=item $lvalue_string = $json->incr_text
733		755
734	This method returns the currently stored JSON fragment as an lvalue, that	756	This method returns the currently stored JSON fragment as an lvalue, that
735	is, you can manipulate it. This I<only> works when a preceding call to	757	is, you can manipulate it. This I<only> works when a preceding call to
736	C<incr_parse> in I<scalar context> successfully returned an object. Under	758	C<incr_parse> in I<scalar context> successfully returned an object. Under
…		…
743	JSON object or b) parsing multiple JSON objects separated by non-JSON text	765	JSON object or b) parsing multiple JSON objects separated by non-JSON text
744	(such as commas).	766	(such as commas).
745		767
746	=item $json->incr_skip	768	=item $json->incr_skip
747		769
748	This will reset the state of the incremental parser and will remove the	770	This will reset the state of the incremental parser and will remove
749	parsed text from the input buffer. This is useful after C<incr_parse>	771	the parsed text from the input buffer so far. This is useful after
750	died, in which case the input buffer and incremental parser state is left	772	C<incr_parse> died, in which case the input buffer and incremental parser
751	unchanged, to skip the text parsed so far and to reset the parse state.	773	state is left unchanged, to skip the text parsed so far and to reset the
		774	parse state.
		775
		776	The difference to C<incr_reset> is that only text until the parse error
		777	occurred is removed.
		778
		779	=item $json->incr_reset
		780
		781	This completely resets the incremental parser, that is, after this call,
		782	it will be as if the parser had never parsed anything.
		783
		784	This is useful if you want to repeatedly parse JSON objects and want to
		785	ignore any trailing data, which means you have to reset the parser after
		786	each successful decode.
752		787
753	=back	788	=back
754		789
755	=head2 LIMITATIONS	790	=head2 LIMITATIONS
756		791
757	All options that affect decoding are supported, except	792	All options that affect decoding are supported, except
758	C<allow_nonref>. The reason for this is that it cannot be made to	793	C<allow_nonref>. The reason for this is that it cannot be made to work
759	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate	794	sensibly: JSON objects and arrays are self-delimited, i.e. you can
760	them back to back and still decode them perfectly. This does not hold true	795	concatenate them back to back and still decode them perfectly. This does
761	for JSON numbers, however.	796	not hold true for JSON numbers, however.
762		797
763	For example, is the string C<1> a single JSON number, or is it simply the	798	For example, is the string C<1> a single JSON number, or is it simply the
764	start of C<12>? Or is C<12> a single JSON number, or the concatenation	799	start of C<12>? Or is C<12> a single JSON number, or the concatenation
765	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS	800	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
766	takes the conservative route and disallows this case.	801	takes the conservative route and disallows this case.
…		…
945	If the number consists of digits only, JSON::XS will try to represent	980	If the number consists of digits only, JSON::XS will try to represent
946	it as an integer value. If that fails, it will try to represent it as	981	it as an integer value. If that fails, it will try to represent it as
947	a numeric (floating point) value if that is possible without loss of	982	a numeric (floating point) value if that is possible without loss of
948	precision. Otherwise it will preserve the number as a string value (in	983	precision. Otherwise it will preserve the number as a string value (in
949	which case you lose roundtripping ability, as the JSON number will be	984	which case you lose roundtripping ability, as the JSON number will be
950	re-encoded toa JSON string).	985	re-encoded to a JSON string).
951		986
952	Numbers containing a fractional or exponential part will always be	987	Numbers containing a fractional or exponential part will always be
953	represented as numeric (floating point) values, possibly at a loss of	988	represented as numeric (floating point) values, possibly at a loss of
954	precision (in which case you might lose perfect roundtripping ability, but	989	precision (in which case you might lose perfect roundtripping ability, but
955	the JSON number will still be re-encoded as a JSON number).	990	the JSON number will still be re-encoded as a JSON number).
956		991
		992	Note that precision is not accuracy - binary floating point values cannot
		993	represent most decimal fractions exactly, and when converting from and to
		994	floating point, JSON::XS only guarantees precision up to but not including
		995	the least significant bit.
		996
957	=item true, false	997	=item true, false
958		998
959	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	999	These JSON atoms become C<Types::Serialiser::true> and
960	respectively. They are overloaded to act almost exactly like the numbers	1000	C<Types::Serialiser::false>, respectively. They are overloaded to act
961	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1001	almost exactly like the numbers C<1> and C<0>. You can check whether
962	the C<JSON::XS::is_bool> function.	1002	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1003	function (after C<use Types::Serialier>, of course).
963		1004
964	=item null	1005	=item null
965		1006
966	A JSON null atom becomes C<undef> in Perl.	1007	A JSON null atom becomes C<undef> in Perl.
		1008
		1009	=item shell-style comments (C<< # I<text> >>)
		1010
		1011	As a nonstandard extension to the JSON syntax that is enabled by the
		1012	C<relaxed> setting, shell-style comments are allowed. They can start
		1013	anywhere outside strings and go till the end of the line.
		1014
		1015	=item tagged values (C<< (I<tag>)I<value> >>).
		1016
		1017	Another nonstandard extension to the JSON syntax, enabled with the
		1018	C<allow_tags> setting, are tagged values. In this implementation, the
		1019	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1020	I<value> must be a JSON array encoding optional constructor arguments.
		1021
		1022	See L<OBJECT SERIALISATION>, below, for details.
967		1023
968	=back	1024	=back
969		1025
970		1026
971	=head2 PERL -> JSON	1027	=head2 PERL -> JSON
…		…
976		1032
977	=over 4	1033	=over 4
978		1034
979	=item hash references	1035	=item hash references
980		1036
981	Perl hash references become JSON objects. As there is no inherent ordering	1037	Perl hash references become JSON objects. As there is no inherent
982	in hash keys (or JSON objects), they will usually be encoded in a	1038	ordering in hash keys (or JSON objects), they will usually be encoded
983	pseudo-random order that can change between runs of the same program but	1039	in a pseudo-random order. JSON::XS can optionally sort the hash keys
984	stays generally the same within a single run of a program. JSON::XS can	1040	(determined by the I<canonical> flag), so the same datastructure will
985	optionally sort the hash keys (determined by the I<canonical> flag), so	1041	serialise to the same JSON text (given same settings and version of
986	the same datastructure will serialise to the same JSON text (given same	1042	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
987	settings and version of JSON::XS), but this incurs a runtime overhead	1043	e.g. when you want to compare some JSON text against another for equality.
988	and is only rarely useful, e.g. when you want to compare some JSON text
989	against another for equality.
990		1044
991	=item array references	1045	=item array references
992		1046
993	Perl array references become JSON arrays.	1047	Perl array references become JSON arrays.
994		1048
995	=item other references	1049	=item other references
996		1050
997	Other unblessed references are generally not allowed and will cause an	1051	Other unblessed references are generally not allowed and will cause an
998	exception to be thrown, except for references to the integers C<0> and	1052	exception to be thrown, except for references to the integers C<0> and
999	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1053	C<1>, which get turned into C<false> and C<true> atoms in JSON.
1000	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1001		1054
		1055	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1056	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1057	and C<Types::Serialiser::true> to improve readability.
		1058
		1059	use Types::Serialiser;
1002	encode_json [\0,JSON::XS::true] # yields [false,true]	1060	encode_json [\0, Types::Serialiser::true] # yields [false,true]
1003		1061
1004	=item JSON::XS::true, JSON::XS::false	1062	=item Types::Serialiser::true, Types::Serialiser::false
1005		1063
1006	These special values become JSON true and JSON false values,	1064	These special values from the L<Types::Serialiser> module become JSON true
1007	respectively. You can also use C<\1> and C<\0> directly if you want.	1065	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1066	directly if you want.
1008		1067
1009	=item blessed objects	1068	=item blessed objects
1010		1069
1011	Blessed objects are not directly representable in JSON. See the	1070	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1012	C<allow_blessed> and C<convert_blessed> methods on various options on	1071	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1013	how to deal with this: basically, you can choose between throwing an	1072	below, for details.
1014	exception, encoding the reference as if it weren't blessed, or provide
1015	your own serialiser method.
1016		1073
1017	=item simple scalars	1074	=item simple scalars
1018		1075
1019	Simple Perl scalars (any scalar that is not a reference) are the most	1076	Simple Perl scalars (any scalar that is not a reference) are the most
1020	difficult objects to encode: JSON::XS will encode undefined scalars as	1077	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1048		1105
1049	You can not currently force the type in other, less obscure, ways. Tell me	1106	You can not currently force the type in other, less obscure, ways. Tell me
1050	if you need this capability (but don't forget to explain why it's needed	1107	if you need this capability (but don't forget to explain why it's needed
1051	:).	1108	:).
1052		1109
		1110	Note that numerical precision has the same meaning as under Perl (so
		1111	binary to decimal conversion follows the same rules as in Perl, which
		1112	can differ to other languages). Also, your perl interpreter might expose
		1113	extensions to the floating point numbers of your platform, such as
		1114	infinities or NaN's - these cannot be represented in JSON, and it is an
		1115	error to pass those in.
		1116
1053	=back	1117	=back
		1118
		1119	=head2 OBJECT SERIALISATION
		1120
		1121	As JSON cannot directly represent Perl objects, you have to choose between
		1122	a pure JSON representation (without the ability to deserialise the object
		1123	automatically again), and a nonstandard extension to the JSON syntax,
		1124	tagged values.
		1125
		1126	=head3 SERIALISATION
		1127
		1128	What happens when C<JSON::XS> encounters a Perl object depends on the
		1129	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1130	used in this order:
		1131
		1132	=over 4
		1133
		1134	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1135
		1136	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1137	serialisation protocol to create a tagged JSON value, using a nonstandard
		1138	extension to the JSON syntax.
		1139
		1140	This works by invoking the C<FREEZE> method on the object, with the first
		1141	argument being the object to serialise, and the second argument being the
		1142	constant string C<JSON> to distinguish it from other serialisers.
		1143
		1144	The C<FREEZE> method can return any number of values (i.e. zero or
		1145	more). These values and the paclkage/classname of the object will then be
		1146	encoded as a tagged JSON value in the following format:
		1147
		1148	("classname")[FREEZE return values...]
		1149
		1150	e.g.:
		1151
		1152	("URI")["http://www.google.com/"]
		1153	("MyDate")[2013,10,29]
		1154	("ImageData::JPEG")["Z3...VlCg=="]
		1155
		1156	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1157	objects C<type> and C<id> members to encode the object:
		1158
		1159	sub My::Object::FREEZE {
		1160	my ($self, $serialiser) = @_;
		1161
		1162	($self->{type}, $self->{id})
		1163	}
		1164
		1165	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1166
		1167	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1168	context. It must return a single scalar that can be directly encoded into
		1169	JSON. This scalar replaces the object in the JSON text.
		1170
		1171	For example, the following C<TO_JSON> method will convert all L<URI>
		1172	objects to JSON strings when serialised. The fatc that these values
		1173	originally were L<URI> objects is lost.
		1174
		1175	sub URI::TO_JSON {
		1176	my ($uri) = @_;
		1177	$uri->as_string
		1178	}
		1179
		1180	=item 3. C<allow_blessed> is enabled.
		1181
		1182	The object will be serialised as a JSON null value.
		1183
		1184	=item 4. none of the above
		1185
		1186	If none of the settings are enabled or the respective methods are missing,
		1187	C<JSON::XS> throws an exception.
		1188
		1189	=back
		1190
		1191	=head3 DESERIALISATION
		1192
		1193	For deserialisation there are only two cases to consider: either
		1194	nonstandard tagging was used, in which case C<allow_tags> decides,
		1195	or objects cannot be automatically be deserialised, in which
		1196	case you can use postprocessing or the C<filter_json_object> or
		1197	C<filter_json_single_key_object> callbacks to get some real objects our of
		1198	your JSON.
		1199
		1200	This section only considers the tagged value case: I a tagged JSON object
		1201	is encountered during decoding and C<allow_tags> is disabled, a parse
		1202	error will result (as if tagged values were not part of the grammar).
		1203
		1204	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1205	of the package/classname used during serialisation (it will not attempt
		1206	to load the package as a Perl module). If there is no such method, the
		1207	decoding will fail with an error.
		1208
		1209	Otherwise, the C<THAW> method is invoked with the classname as first
		1210	argument, the constant string C<JSON> as second argument, and all the
		1211	values from the JSON array (the values originally returned by the
		1212	C<FREEZE> method) as remaining arguments.
		1213
		1214	The method must then return the object. While technically you can return
		1215	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1216	make that work in all cases, so better return an actual blessed reference.
		1217
		1218	As an example, let's implement a C<THAW> function that regenerates the
		1219	C<My::Object> from the C<FREEZE> example earlier:
		1220
		1221	sub My::Object::THAW {
		1222	my ($class, $serialiser, $type, $id) = @_;
		1223
		1224	$class->new (type => $type, id => $id)
		1225	}
1054		1226
1055		1227
1056	=head1 ENCODING/CODESET FLAG NOTES	1228	=head1 ENCODING/CODESET FLAG NOTES
1057		1229
1058	The interested reader might have seen a number of flags that signify	1230	The interested reader might have seen a number of flags that signify
…		…
1083	=item C<utf8> flag disabled	1255	=item C<utf8> flag disabled
1084		1256
1085	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1257	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1086	and expect Unicode strings, that is, characters with high ordinal Unicode	1258	and expect Unicode strings, that is, characters with high ordinal Unicode
1087	values (> 255) will be encoded as such characters, and likewise such	1259	values (> 255) will be encoded as such characters, and likewise such
1088	characters are decoded as-is, no canges to them will be done, except	1260	characters are decoded as-is, no changes to them will be done, except
1089	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1261	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1090	respectively (to Perl, these are the same thing in strings unless you do	1262	respectively (to Perl, these are the same thing in strings unless you do
1091	funny/weird/dumb stuff).	1263	funny/weird/dumb stuff).
1092		1264
1093	This is useful when you want to do the encoding yourself (e.g. when you	1265	This is useful when you want to do the encoding yourself (e.g. when you
…		…
1149	proper subset of most 8-bit and multibyte encodings in use in the world.	1321	proper subset of most 8-bit and multibyte encodings in use in the world.
1150		1322
1151	=back	1323	=back
1152		1324
1153		1325
		1326	=head2 JSON and ECMAscript
		1327
		1328	JSON syntax is based on how literals are represented in javascript (the
		1329	not-standardised predecessor of ECMAscript) which is presumably why it is
		1330	called "JavaScript Object Notation".
		1331
		1332	However, JSON is not a subset (and also not a superset of course) of
		1333	ECMAscript (the standard) or javascript (whatever browsers actually
		1334	implement).
		1335
		1336	If you want to use javascript's C<eval> function to "parse" JSON, you
		1337	might run into parse errors for valid JSON texts, or the resulting data
		1338	structure might not be queryable:
		1339
		1340	One of the problems is that U+2028 and U+2029 are valid characters inside
		1341	JSON strings, but are not allowed in ECMAscript string literals, so the
		1342	following Perl fragment will not output something that can be guaranteed
		1343	to be parsable by javascript's C<eval>:
		1344
		1345	use JSON::XS;
		1346
		1347	print encode_json [chr 0x2028];
		1348
		1349	The right fix for this is to use a proper JSON parser in your javascript
		1350	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1351	F<json2.js> parser).
		1352
		1353	If this is not an option, you can, as a stop-gap measure, simply encode to
		1354	ASCII-only JSON:
		1355
		1356	use JSON::XS;
		1357
		1358	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1359
		1360	Note that this will enlarge the resulting JSON text quite a bit if you
		1361	have many non-ASCII characters. You might be tempted to run some regexes
		1362	to only escape U+2028 and U+2029, e.g.:
		1363
		1364	# DO NOT USE THIS!
		1365	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1366	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1367	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1368	print $json;
		1369
		1370	Note that I<this is a bad idea>: the above only works for U+2028 and
		1371	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1372	javascript implementations, however, have issues with other characters as
		1373	well - using C<eval> naively simply I<will> cause problems.
		1374
		1375	Another problem is that some javascript implementations reserve
		1376	some property names for their own purposes (which probably makes
		1377	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1378	C<__proto__> property name for its own purposes.
		1379
		1380	If that is a problem, you could parse try to filter the resulting JSON
		1381	output for these property strings, e.g.:
		1382
		1383	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1384
		1385	This works because C<__proto__> is not valid outside of strings, so every
		1386	occurrence of C<"__proto__"\s*:> must be a string used as property name.
		1387
		1388	If you know of other incompatibilities, please let me know.
		1389
		1390
1154	=head2 JSON and YAML	1391	=head2 JSON and YAML
1155		1392
1156	You often hear that JSON is a subset of YAML. This is, however, a mass	1393	You often hear that JSON is a subset of YAML. This is, however, a mass
1157	hysteria(*) and very far from the truth (as of the time of this writing),	1394	hysteria(*) and very far from the truth (as of the time of this writing),
1158	so let me state it clearly: I<in general, there is no way to configure	1395	so let me state it clearly: I<in general, there is no way to configure
…		…
1166	my $yaml = $to_yaml->encode ($ref) . "\n";	1403	my $yaml = $to_yaml->encode ($ref) . "\n";
1167		1404
1168	This will I<usually> generate JSON texts that also parse as valid	1405	This will I<usually> generate JSON texts that also parse as valid
1169	YAML. Please note that YAML has hardcoded limits on (simple) object key	1406	YAML. Please note that YAML has hardcoded limits on (simple) object key
1170	lengths that JSON doesn't have and also has different and incompatible	1407	lengths that JSON doesn't have and also has different and incompatible
1171	unicode handling, so you should make sure that your hash keys are	1408	unicode character escape syntax, so you should make sure that your hash
1172	noticeably shorter than the 1024 "stream characters" YAML allows and that	1409	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1173	you do not have characters with codepoint values outside the Unicode BMP	1410	and that you do not have characters with codepoint values outside the
1174	(basic multilingual page). YAML also does not allow C<\/> sequences in	1411	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1175	strings (which JSON::XS does not I<currently> generate, but other JSON	1412	sequences in strings (which JSON::XS does not I<currently> generate, but
1176	generators might).	1413	other JSON generators might).
1177		1414
1178	There might be other incompatibilities that I am not aware of (or the YAML	1415	There might be other incompatibilities that I am not aware of (or the YAML
1179	specification has been changed yet again - it does so quite often). In	1416	specification has been changed yet again - it does so quite often). In
1180	general you should not try to generate YAML with a JSON generator or vice	1417	general you should not try to generate YAML with a JSON generator or vice
1181	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1418	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1200	that difficult or long) and finally make YAML compatible to it, and	1437	that difficult or long) and finally make YAML compatible to it, and
1201	educating users about the changes, instead of spreading lies about the	1438	educating users about the changes, instead of spreading lies about the
1202	real compatibility for many I<years> and trying to silence people who	1439	real compatibility for many I<years> and trying to silence people who
1203	point out that it isn't true.	1440	point out that it isn't true.
1204		1441
		1442	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1443	though the incompatibilities have been documented (and are known to Brian)
		1444	for many years and the spec makes explicit claims that YAML is a superset
		1445	of JSON. It would be so easy to fix, but apparently, bullying people and
		1446	corrupting userdata is so much easier.
		1447
1205	=back	1448	=back
1206		1449
1207		1450
1208	=head2 SPEED	1451	=head2 SPEED
1209		1452
…		…
1214		1457
1215	First comes a comparison between various modules using	1458	First comes a comparison between various modules using
1216	a very short single-line JSON string (also available at	1459	a very short single-line JSON string (also available at
1217	L<http://dist.schmorp.de/misc/json/short.json>).	1460	L<http://dist.schmorp.de/misc/json/short.json>).
1218		1461
1219	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1462	{"method": "handleMessage", "params": ["user1",
1220	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1463	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1464	1, 0]}
1221		1465
1222	It shows the number of encodes/decodes per second (JSON::XS uses	1466	It shows the number of encodes/decodes per second (JSON::XS uses
1223	the functional interface, while JSON::XS/2 uses the OO interface	1467	the functional interface, while JSON::XS/2 uses the OO interface
1224	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1468	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1225	shrink). Higher is better:	1469	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1470	uses the from_json method). Higher is better:
1226		1471
1227	module \| encode \| decode \|	1472	module \| encode \| decode \|
1228	-----------\|------------\|------------\|	1473	--------------\|------------\|------------\|
1229	JSON 1.x \| 4990.842 \| 4088.813 \|	1474	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1230	JSON::DWIW \| 51653.990 \| 71575.154 \|	1475	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1231	JSON::PC \| 65948.176 \| 74631.744 \|	1476	JSON::PP \| 15827.562 \| 6638.658 \|
1232	JSON::PP \| 8931.652 \| 3817.168 \|	1477	JSON::Syck \| 63358.066 \| 47662.545 \|
1233	JSON::Syck \| 24877.248 \| 27776.848 \|	1478	JSON::XS \| 511500.488 \| 511500.488 \|
1234	JSON::XS \| 388361.481 \| 227951.304 \|	1479	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1235	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1480	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1236	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1481	Storable \| 66788.280 \| 265462.278 \|
1237	Storable \| 16500.016 \| 135300.129 \|
1238	-----------+------------+------------+	1482	--------------+------------+------------+
1239		1483
1240	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1484	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1241	about three times faster on decoding, and over forty times faster	1485	about five times faster on decoding, and over thirty to seventy times
1242	than JSON, even with pretty-printing and key sorting. It also compares	1486	faster than JSON's pure perl implementation. It also compares favourably
1243	favourably to Storable for small amounts of data.	1487	to Storable for small amounts of data.
1244		1488
1245	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1489	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1246	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1490	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1247		1491
1248	module \| encode \| decode \|	1492	module \| encode \| decode \|
1249	-----------\|------------\|------------\|	1493	--------------\|------------\|------------\|
1250	JSON 1.x \| 55.260 \| 34.971 \|	1494	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1251	JSON::DWIW \| 825.228 \| 1082.513 \|	1495	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1252	JSON::PC \| 3571.444 \| 2394.829 \|
1253	JSON::PP \| 210.987 \| 32.574 \|	1496	JSON::PP \| 400.640 \| 62.311 \|
1254	JSON::Syck \| 552.551 \| 787.544 \|	1497	JSON::Syck \| 1481.040 \| 1524.869 \|
1255	JSON::XS \| 5780.463 \| 4854.519 \|	1498	JSON::XS \| 20661.596 \| 9541.183 \|
1256	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1499	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1257	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1500	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1258	Storable \| 4445.002 \| 5235.027 \|	1501	Storable \| 19765.806 \| 10000.725 \|
1259	-----------+------------+------------+	1502	--------------+------------+------------+
1260		1503
1261	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1504	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1262	decodes faster).	1505	decodes a bit faster).
1263		1506
1264	On large strings containing lots of high Unicode characters, some modules	1507	On large strings containing lots of high Unicode characters, some modules
1265	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1508	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1266	will be broken due to missing (or wrong) Unicode handling. Others refuse	1509	will be broken due to missing (or wrong) Unicode handling. Others refuse
1267	to decode or encode properly, so it was impossible to prepare a fair	1510	to decode or encode properly, so it was impossible to prepare a fair
…		…
1303	information you might want to make sure that exceptions thrown by JSON::XS	1546	information you might want to make sure that exceptions thrown by JSON::XS
1304	will not end up in front of untrusted eyes.	1547	will not end up in front of untrusted eyes.
1305		1548
1306	If you are using JSON::XS to return packets to consumption	1549	If you are using JSON::XS to return packets to consumption
1307	by JavaScript scripts in a browser you should have a look at	1550	by JavaScript scripts in a browser you should have a look at
1308	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1551	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1309	you are vulnerable to some common attack vectors (which really are browser	1552	see whether you are vulnerable to some common attack vectors (which really
1310	design bugs, but it is still you who will have to deal with it, as major	1553	are browser design bugs, but it is still you who will have to deal with
1311	browser developers care only for features, not about getting security	1554	it, as major browser developers care only for features, not about getting
1312	right).	1555	security right).
		1556
		1557
		1558	=head1 INTEROPERABILITY WITH OTHER MODULES
		1559
		1560	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1561	constants. That means that the JSON true and false values will be
		1562	comaptible to true and false values of iother modules that do the same,
		1563	such as L<JSON::PP> and L<CBOR::XS>.
		1564
		1565
		1566	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1567
		1568	As long as you only serialise data that can be directly expressed in JSON,
		1569	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1570	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1571	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1572
		1573	When you have trouble decoding JSON generated by this module using other
		1574	decoders, then it is very likely that you have an encoding mismatch or the
		1575	other decoder is broken.
		1576
		1577	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1578	errors. There are currently two settings that change this: C<relaxed>
		1579	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1580	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1581	cost of not outputting valid JSON anymore.
		1582
		1583	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1584
		1585	When you use C<allow_tags> to use the extended (and also nonstandard and
		1586	invalid) JSON syntax for serialised objects, and you still want to decode
		1587	the generated When you want to serialise objects, you can run a regex
		1588	to replace the tagged syntax by standard JSON arrays (it only works for
		1589	"normal" packagesnames without comma, newlines or single colons). First,
		1590	the readable Perl version:
		1591
		1592	# if your FREEZE methods return no values, you need this replace first:
		1593	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1594
		1595	# this works for non-empty constructor arg lists:
		1596	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1597
		1598	And here is a less readable version that is easy to adapt to other
		1599	languages:
		1600
		1601	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1602
		1603	Here is an ECMAScript version (same regex):
		1604
		1605	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1606
		1607	Since this syntax converts to standard JSON arrays, it might be hard to
		1608	distinguish serialised objects from normal arrays. You can prepend a
		1609	"magic number" as first array element to reduce chances of a collision:
		1610
		1611	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1612
		1613	And after decoding the JSON text, you could walk the data
		1614	structure looking for arrays with a first element of
		1615	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1616
		1617	The same approach cna be used to create the tagged format with another
		1618	encoder. First, you create an array with the magic string as first member,
		1619	the classname as second, and constructor arguments last, encode it as part
		1620	of your JSON structure, and then:
		1621
		1622	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1623
		1624	Again, this has some limitations - the magic string must not be encoded
		1625	with character escapes, and the constructor arguments must be non-empty.
		1626
		1627
		1628	=head1 RFC7158
		1629
		1630	Since this module was written, Google has written a new JSON RFC, RFC
		1631	7158. Unfortunately, this RFC breaks compatibility with both the original
		1632	JSON specification on www.json.org and RFC4627.
		1633
		1634	As far as I can see, you can get partial compatibility when parsing by
		1635	using C<< ->allow_nonref >>. However, consider thew security implications
		1636	of doing so.
		1637
		1638	I haven't decided yet whether to break compatibility with RFC4627 by
		1639	default (and potentially leave applications insecure), or change the
		1640	default to follow RFC7158.
1313		1641
1314		1642
1315	=head1 THREADS	1643	=head1 THREADS
1316		1644
1317	This module is I<not> guaranteed to be thread safe and there are no	1645	This module is I<not> guaranteed to be thread safe and there are no
…		…
1320	process simulations - use fork, it's I<much> faster, cheaper, better).	1648	process simulations - use fork, it's I<much> faster, cheaper, better).
1321		1649
1322	(It might actually work, but you have been warned).	1650	(It might actually work, but you have been warned).
1323		1651
1324		1652
		1653	=head1 THE PERILS OF SETLOCALE
		1654
		1655	Sometimes people avoid the Perl locale support and directly call the
		1656	system's setlocale function with C<LC_ALL>.
		1657
		1658	This breaks both perl and modules such as JSON::XS, as stringification of
		1659	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1660	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1661	perl to stringify numbers).
		1662
		1663	The solution is simple: don't call C<setlocale>, or use it for only those
		1664	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1665
		1666	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1667	actually needs it (avoiding stringification of numbers), and restore it
		1668	afterwards.
		1669
		1670
1325	=head1 BUGS	1671	=head1 BUGS
1326		1672
1327	While the goal of this module is to be correct, that unfortunately does	1673	While the goal of this module is to be correct, that unfortunately does
1328	not mean it's bug-free, only that I think its design is bug-free. It is	1674	not mean it's bug-free, only that I think its design is bug-free. If you
1329	still relatively early in its development. If you keep reporting bugs they	1675	keep reporting bugs they will be fixed swiftly, though.
1330	will be fixed swiftly, though.
1331		1676
1332	Please refrain from using rt.cpan.org or any other bug reporting	1677	Please refrain from using rt.cpan.org or any other bug reporting
1333	service. I put the contact address into my modules for a reason.	1678	service. I put the contact address into my modules for a reason.
1334		1679
1335	=cut	1680	=cut
1336		1681
1337	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1682	BEGIN {
1338	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1683	*true = \$Types::Serialiser::true;
		1684	*true = \&Types::Serialiser::true;
		1685	*false = \$Types::Serialiser::false;
		1686	*false = \&Types::Serialiser::false;
		1687	*is_bool = \&Types::Serialiser::is_bool;
1339		1688
1340	sub true() { $true }	1689	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1341	sub false() { $false }
1342
1343	sub is_bool($) {
1344	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1345	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1346	}	1690	}
1347		1691
1348	XSLoader::load "JSON::XS", $VERSION;	1692	XSLoader::load "JSON::XS", $VERSION;
1349
1350	package JSON::XS::Boolean;
1351
1352	use overload
1353	"0+" => sub { ${$_[0]} },
1354	"++" => sub { $_[0] = ${$_[0]} + 1 },
1355	"--" => sub { $_[0] = ${$_[0]} - 1 },
1356	fallback => 1;
1357
1358	1;
1359		1693
1360	=head1 SEE ALSO	1694	=head1 SEE ALSO
1361		1695
1362	The F<json_xs> command line utility for quick experiments.	1696	The F<json_xs> command line utility for quick experiments.
1363		1697
…		…
1366	Marc Lehmann <schmorp@schmorp.de>	1700	Marc Lehmann <schmorp@schmorp.de>
1367	http://home.schmorp.de/	1701	http://home.schmorp.de/
1368		1702
1369	=cut	1703	=cut
1370		1704
		1705	1
		1706

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Comparing JSON-XS/XS.pm (file contents): Revision 1.98 by root, Wed Mar 26 02:36:18 2008 UTC vs. Revision 1.153 by root, Sun Mar 2 20:41:14 2014 UTC

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Revision 1.98 by root, Wed Mar 26 02:36:18 2008 UTC vs.
Revision 1.153 by root, Sun Mar 2 20:41:14 2014 UTC