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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.93 by root, Sat Mar 22 22:21:33 2008 UTC vs.
Revision 1.158 by root, Thu Sep 1 11:38:39 2016 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 $VERSION = 3.02;
109	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
110		108
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
112
113	sub to_json($) {
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.
…		…
423	[	404	[
424	1, # this comment not allowed in JSON	405	1, # this comment not allowed in JSON
425	# neither this one...	406	# neither this one...
426	]	407	]
427		408
		409	=item * literal ASCII TAB characters in strings
		410
		411	Literal ASCII TAB characters are now allowed in strings (and treated as
		412	C<\t>).
		413
		414	[
		415	"Hello\tWorld",
		416	"Hello<TAB>World", # literal <TAB> would not normally be allowed
		417	]
		418
428	=back	419	=back
429		420
430	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
431		422
432	=item $enabled = $json->get_canonical	423	=item $enabled = $json->get_canonical
…		…
434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
435	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
436		427
437	If C<$enable> is false, then the C<encode> method will output key-value	428	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	429	pairs in the order Perl stores them (which will likely change between runs
439	of the same script).	430	of the same script, and can change even within the same run from 5.18
		431	onwards).
440		432
441	This option is useful if you want the same data structure to be encoded as	433	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,	434	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,	435	the same hash might be encoded differently even if contains the same data,
444	as key-value pairs have no inherent ordering in Perl.	436	as key-value pairs have no inherent ordering in Perl.
445		437
446	This setting has no effect when decoding JSON texts.	438	This setting has no effect when decoding JSON texts.
447		439
		440	This setting has currently no effect on tied hashes.
		441
448	=item $json = $json->allow_nonref ([$enable])	442	=item $json = $json->allow_nonref ([$enable])
449		443
450	=item $enabled = $json->get_allow_nonref	444	=item $enabled = $json->get_allow_nonref
451		445
452	If C<$enable> is true (or missing), then the C<encode> method can convert a	446	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
463	resulting in an invalid JSON text:	457	resulting in an invalid JSON text:
464		458
465	JSON::XS->new->allow_nonref->encode ("Hello, World!")	459	JSON::XS->new->allow_nonref->encode ("Hello, World!")
466	=> "Hello, World!"	460	=> "Hello, World!"
467		461
		462	=item $json = $json->allow_unknown ([$enable])
		463
		464	=item $enabled = $json->get_allow_unknown
		465
		466	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		467	exception when it encounters values it cannot represent in JSON (for
		468	example, filehandles) but instead will encode a JSON C<null> value. Note
		469	that blessed objects are not included here and are handled separately by
		470	c<allow_nonref>.
		471
		472	If C<$enable> is false (the default), then C<encode> will throw an
		473	exception when it encounters anything it cannot encode as JSON.
		474
		475	This option does not affect C<decode> in any way, and it is recommended to
		476	leave it off unless you know your communications partner.
		477
468	=item $json = $json->allow_blessed ([$enable])	478	=item $json = $json->allow_blessed ([$enable])
469		479
470	=item $enabled = $json->get_allow_blessed	480	=item $enabled = $json->get_allow_blessed
471		481
		482	See L<OBJECT SERIALISATION> for details.
		483
472	If C<$enable> is true (or missing), then the C<encode> method will not	484	If C<$enable> is true (or missing), then the C<encode> method will not
473	barf when it encounters a blessed reference. Instead, the value of the	485	barf when it encounters a blessed reference that it cannot convert
474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	486	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
475	disabled or no C<TO_JSON> method found) or a representation of the
476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
477	encoded. Has no effect on C<decode>.
478		487
479	If C<$enable> is false (the default), then C<encode> will throw an	488	If C<$enable> is false (the default), then C<encode> will throw an
480	exception when it encounters a blessed object.	489	exception when it encounters a blessed object that it cannot convert
		490	otherwise.
		491
		492	This setting has no effect on C<decode>.
481		493
482	=item $json = $json->convert_blessed ([$enable])	494	=item $json = $json->convert_blessed ([$enable])
483		495
484	=item $enabled = $json->get_convert_blessed	496	=item $enabled = $json->get_convert_blessed
		497
		498	See L<OBJECT SERIALISATION> for details.
485		499
486	If C<$enable> is true (or missing), then C<encode>, upon encountering a	500	If C<$enable> is true (or missing), then C<encode>, upon encountering a
487	blessed object, will check for the availability of the C<TO_JSON> method	501	blessed object, will check for the availability of the C<TO_JSON> method
488	on the object's class. If found, it will be called in scalar context	502	on the object's class. If found, it will be called in scalar context and
489	and the resulting scalar will be encoded instead of the object. If no	503	the resulting scalar will be encoded instead of the object.
490	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
491	to do.
492		504
493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	505	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
494	returns other blessed objects, those will be handled in the same	506	returns other blessed objects, those will be handled in the same
495	way. C<TO_JSON> must take care of not causing an endless recursion cycle	507	way. C<TO_JSON> must take care of not causing an endless recursion cycle
496	(== crash) in this case. The name of C<TO_JSON> was chosen because other	508	(== crash) in this case. The name of C<TO_JSON> was chosen because other
497	methods called by the Perl core (== not by the user of the object) are	509	methods called by the Perl core (== not by the user of the object) are
498	usually in upper case letters and to avoid collisions with any C<to_json>	510	usually in upper case letters and to avoid collisions with any C<to_json>
499	function or method.	511	function or method.
500		512
501	This setting does not yet influence C<decode> in any way, but in the	513	If C<$enable> is false (the default), then C<encode> will not consider
502	future, global hooks might get installed that influence C<decode> and are	514	this type of conversion.
503	enabled by this setting.
504		515
505	If C<$enable> is false, then the C<allow_blessed> setting will decide what	516	This setting has no effect on C<decode>.
506	to do when a blessed object is found.	517
		518	=item $json = $json->allow_tags ([$enable])
		519
		520	=item $enabled = $json->allow_tags
		521
		522	See L<OBJECT SERIALISATION> for details.
		523
		524	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		525	blessed object, will check for the availability of the C<FREEZE> method on
		526	the object's class. If found, it will be used to serialise the object into
		527	a nonstandard tagged JSON value (that JSON decoders cannot decode).
		528
		529	It also causes C<decode> to parse such tagged JSON values and deserialise
		530	them via a call to the C<THAW> method.
		531
		532	If C<$enable> is false (the default), then C<encode> will not consider
		533	this type of conversion, and tagged JSON values will cause a parse error
		534	in C<decode>, as if tags were not part of the grammar.
507		535
508	=item $json = $json->filter_json_object ([$coderef->($hashref)])	536	=item $json = $json->filter_json_object ([$coderef->($hashref)])
509		537
510	When C<$coderef> is specified, it will be called from C<decode> each	538	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	539	time it decodes a JSON object. The only argument is a reference to the
…		…
612	=item $json = $json->max_depth ([$maximum_nesting_depth])	640	=item $json = $json->max_depth ([$maximum_nesting_depth])
613		641
614	=item $max_depth = $json->get_max_depth	642	=item $max_depth = $json->get_max_depth
615		643
616	Sets the maximum nesting level (default C<512>) accepted while encoding	644	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	645	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	646	data structure, then the encoder and decoder will stop and croak at that
619	stop and croak at that point.	647	point.
620		648
621	Nesting level is defined by number of hash- or arrayrefs that the encoder	649	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<[>	650	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	651	characters without their matching closing parenthesis crossed to reach a
624	given character in a string.	652	given character in a string.
625		653
626	Setting the maximum depth to one disallows any nesting, so that ensures	654	Setting the maximum depth to one disallows any nesting, so that ensures
627	that the object is only a single hash/object or array.	655	that the object is only a single hash/object or array.
628		656
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	657	If no argument is given, the highest possible setting will be used, which
631	used, which is rarely useful.	658	is rarely useful.
		659
		660	Note that nesting is implemented by recursion in C. The default value has
		661	been chosen to be as large as typical operating systems allow without
		662	crashing.
632		663
633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	664	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
634		665
635	=item $json = $json->max_size ([$maximum_string_size])	666	=item $json = $json->max_size ([$maximum_string_size])
636		667
637	=item $max_size = $json->get_max_size	668	=item $max_size = $json->get_max_size
638		669
639	Set the maximum length a JSON text may have (in bytes) where decoding is	670	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>	671	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	672	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	673	attempt to decode the string but throw an exception. This setting has no
643	effect on C<encode> (yet).	674	effect on C<encode> (yet).
644		675
645	The argument to C<max_size> will be rounded up to the next B<highest>	676	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	677	C<0> is specified).
647	limit check will be deactivated (same as when C<0> is specified).
648		678
649	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	679	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
650		680
651	=item $json_text = $json->encode ($perl_scalar)	681	=item $json_text = $json->encode ($perl_scalar)
652		682
653	Converts the given Perl data structure (a simple scalar or a reference	683	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	684	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		685
660	=item $perl_scalar = $json->decode ($json_text)	686	=item $perl_scalar = $json->decode ($json_text)
661		687
662	The opposite of C<encode>: expects a JSON text and tries to parse it,	688	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.	689	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		690
669	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	691	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
670		692
671	This works like the C<decode> method, but instead of raising an exception	693	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	694	when there is trailing garbage after the first JSON object, it will
673	silently stop parsing there and return the number of characters consumed	695	silently stop parsing there and return the number of characters consumed
674	so far.	696	so far.
675		697
676	This is useful if your JSON texts are not delimited by an outer protocol	698	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.	699	and you need to know where the JSON text ends.
679		700
680	JSON::XS->new->decode_prefix ("[1] the tail")	701	JSON::XS->new->decode_prefix ("[1] the tail")
681	=> ([], 3)	702	=> ([1], 3)
682		703
683	=back	704	=back
		705
		706
		707	=head1 INCREMENTAL PARSING
		708
		709	In some cases, there is the need for incremental parsing of JSON
		710	texts. While this module always has to keep both JSON text and resulting
		711	Perl data structure in memory at one time, it does allow you to parse a
		712	JSON stream incrementally. It does so by accumulating text until it has
		713	a full JSON object, which it then can decode. This process is similar to
		714	using C<decode_prefix> to see if a full JSON object is available, but
		715	is much more efficient (and can be implemented with a minimum of method
		716	calls).
		717
		718	JSON::XS will only attempt to parse the JSON text once it is sure it
		719	has enough text to get a decisive result, using a very simple but
		720	truly incremental parser. This means that it sometimes won't stop as
		721	early as the full parser, for example, it doesn't detect mismatched
		722	parentheses. The only thing it guarantees is that it starts decoding as
		723	soon as a syntactically valid JSON text has been seen. This means you need
		724	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		725	parsing in the presence if syntax errors.
		726
		727	The following methods implement this incremental parser.
		728
		729	=over 4
		730
		731	=item [void, scalar or list context] = $json->incr_parse ([$string])
		732
		733	This is the central parsing function. It can both append new text and
		734	extract objects from the stream accumulated so far (both of these
		735	functions are optional).
		736
		737	If C<$string> is given, then this string is appended to the already
		738	existing JSON fragment stored in the C<$json> object.
		739
		740	After that, if the function is called in void context, it will simply
		741	return without doing anything further. This can be used to add more text
		742	in as many chunks as you want.
		743
		744	If the method is called in scalar context, then it will try to extract
		745	exactly I<one> JSON object. If that is successful, it will return this
		746	object, otherwise it will return C<undef>. If there is a parse error,
		747	this method will croak just as C<decode> would do (one can then use
		748	C<incr_skip> to skip the erroneous part). This is the most common way of
		749	using the method.
		750
		751	And finally, in list context, it will try to extract as many objects
		752	from the stream as it can find and return them, or the empty list
		753	otherwise. For this to work, there must be no separators (other than
		754	whitespace) between the JSON objects or arrays, instead they must be
		755	concatenated back-to-back. If an error occurs, an exception will be
		756	raised as in the scalar context case. Note that in this case, any
		757	previously-parsed JSON texts will be lost.
		758
		759	Example: Parse some JSON arrays/objects in a given string and return
		760	them.
		761
		762	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		763
		764	=item $lvalue_string = $json->incr_text
		765
		766	This method returns the currently stored JSON fragment as an lvalue, that
		767	is, you can manipulate it. This I<only> works when a preceding call to
		768	C<incr_parse> in I<scalar context> successfully returned an object. Under
		769	all other circumstances you must not call this function (I mean it.
		770	although in simple tests it might actually work, it I<will> fail under
		771	real world conditions). As a special exception, you can also call this
		772	method before having parsed anything.
		773
		774	This function is useful in two cases: a) finding the trailing text after a
		775	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		776	(such as commas).
		777
		778	=item $json->incr_skip
		779
		780	This will reset the state of the incremental parser and will remove
		781	the parsed text from the input buffer so far. This is useful after
		782	C<incr_parse> died, in which case the input buffer and incremental parser
		783	state is left unchanged, to skip the text parsed so far and to reset the
		784	parse state.
		785
		786	The difference to C<incr_reset> is that only text until the parse error
		787	occurred is removed.
		788
		789	=item $json->incr_reset
		790
		791	This completely resets the incremental parser, that is, after this call,
		792	it will be as if the parser had never parsed anything.
		793
		794	This is useful if you want to repeatedly parse JSON objects and want to
		795	ignore any trailing data, which means you have to reset the parser after
		796	each successful decode.
		797
		798	=back
		799
		800	=head2 LIMITATIONS
		801
		802	All options that affect decoding are supported, except
		803	C<allow_nonref>. The reason for this is that it cannot be made to work
		804	sensibly: JSON objects and arrays are self-delimited, i.e. you can
		805	concatenate them back to back and still decode them perfectly. This does
		806	not hold true for JSON numbers, however.
		807
		808	For example, is the string C<1> a single JSON number, or is it simply the
		809	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		810	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		811	takes the conservative route and disallows this case.
		812
		813	=head2 EXAMPLES
		814
		815	Some examples will make all this clearer. First, a simple example that
		816	works similarly to C<decode_prefix>: We want to decode the JSON object at
		817	the start of a string and identify the portion after the JSON object:
		818
		819	my $text = "[1,2,3] hello";
		820
		821	my $json = new JSON::XS;
		822
		823	my $obj = $json->incr_parse ($text)
		824	or die "expected JSON object or array at beginning of string";
		825
		826	my $tail = $json->incr_text;
		827	# $tail now contains " hello"
		828
		829	Easy, isn't it?
		830
		831	Now for a more complicated example: Imagine a hypothetical protocol where
		832	you read some requests from a TCP stream, and each request is a JSON
		833	array, without any separation between them (in fact, it is often useful to
		834	use newlines as "separators", as these get interpreted as whitespace at
		835	the start of the JSON text, which makes it possible to test said protocol
		836	with C<telnet>...).
		837
		838	Here is how you'd do it (it is trivial to write this in an event-based
		839	manner):
		840
		841	my $json = new JSON::XS;
		842
		843	# read some data from the socket
		844	while (sysread $socket, my $buf, 4096) {
		845
		846	# split and decode as many requests as possible
		847	for my $request ($json->incr_parse ($buf)) {
		848	# act on the $request
		849	}
		850	}
		851
		852	Another complicated example: Assume you have a string with JSON objects
		853	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		854	[3]>). To parse them, we have to skip the commas between the JSON texts,
		855	and here is where the lvalue-ness of C<incr_text> comes in useful:
		856
		857	my $text = "[1],[2], [3]";
		858	my $json = new JSON::XS;
		859
		860	# void context, so no parsing done
		861	$json->incr_parse ($text);
		862
		863	# now extract as many objects as possible. note the
		864	# use of scalar context so incr_text can be called.
		865	while (my $obj = $json->incr_parse) {
		866	# do something with $obj
		867
		868	# now skip the optional comma
		869	$json->incr_text =~ s/^ \s* , //x;
		870	}
		871
		872	Now lets go for a very complex example: Assume that you have a gigantic
		873	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		874	but you cannot load it into memory fully (this has actually happened in
		875	the real world :).
		876
		877	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		878	can still help you: You implement a (very simple) array parser and let
		879	JSON decode the array elements, which are all full JSON objects on their
		880	own (this wouldn't work if the array elements could be JSON numbers, for
		881	example):
		882
		883	my $json = new JSON::XS;
		884
		885	# open the monster
		886	open my $fh, "<bigfile.json"
		887	or die "bigfile: $!";
		888
		889	# first parse the initial "["
		890	for (;;) {
		891	sysread $fh, my $buf, 65536
		892	or die "read error: $!";
		893	$json->incr_parse ($buf); # void context, so no parsing
		894
		895	# Exit the loop once we found and removed(!) the initial "[".
		896	# In essence, we are (ab-)using the $json object as a simple scalar
		897	# we append data to.
		898	last if $json->incr_text =~ s/^ \s* \[ //x;
		899	}
		900
		901	# now we have the skipped the initial "[", so continue
		902	# parsing all the elements.
		903	for (;;) {
		904	# in this loop we read data until we got a single JSON object
		905	for (;;) {
		906	if (my $obj = $json->incr_parse) {
		907	# do something with $obj
		908	last;
		909	}
		910
		911	# add more data
		912	sysread $fh, my $buf, 65536
		913	or die "read error: $!";
		914	$json->incr_parse ($buf); # void context, so no parsing
		915	}
		916
		917	# in this loop we read data until we either found and parsed the
		918	# separating "," between elements, or the final "]"
		919	for (;;) {
		920	# first skip whitespace
		921	$json->incr_text =~ s/^\s*//;
		922
		923	# if we find "]", we are done
		924	if ($json->incr_text =~ s/^\]//) {
		925	print "finished.\n";
		926	exit;
		927	}
		928
		929	# if we find ",", we can continue with the next element
		930	if ($json->incr_text =~ s/^,//) {
		931	last;
		932	}
		933
		934	# if we find anything else, we have a parse error!
		935	if (length $json->incr_text) {
		936	die "parse error near ", $json->incr_text;
		937	}
		938
		939	# else add more data
		940	sysread $fh, my $buf, 65536
		941	or die "read error: $!";
		942	$json->incr_parse ($buf); # void context, so no parsing
		943	}
		944
		945	This is a complex example, but most of the complexity comes from the fact
		946	that we are trying to be correct (bear with me if I am wrong, I never ran
		947	the above example :).
		948
684		949
685		950
686	=head1 MAPPING	951	=head1 MAPPING
687		952
688	This section describes how JSON::XS maps Perl values to JSON values and	953	This section describes how JSON::XS maps Perl values to JSON values and
…		…
725	If the number consists of digits only, JSON::XS will try to represent	990	If the number consists of digits only, JSON::XS will try to represent
726	it as an integer value. If that fails, it will try to represent it as	991	it as an integer value. If that fails, it will try to represent it as
727	a numeric (floating point) value if that is possible without loss of	992	a numeric (floating point) value if that is possible without loss of
728	precision. Otherwise it will preserve the number as a string value (in	993	precision. Otherwise it will preserve the number as a string value (in
729	which case you lose roundtripping ability, as the JSON number will be	994	which case you lose roundtripping ability, as the JSON number will be
730	re-encoded toa JSON string).	995	re-encoded to a JSON string).
731		996
732	Numbers containing a fractional or exponential part will always be	997	Numbers containing a fractional or exponential part will always be
733	represented as numeric (floating point) values, possibly at a loss of	998	represented as numeric (floating point) values, possibly at a loss of
734	precision (in which case you might lose perfect roundtripping ability, but	999	precision (in which case you might lose perfect roundtripping ability, but
735	the JSON number will still be re-encoded as a JSON number).	1000	the JSON number will still be re-encoded as a JSON number).
736		1001
		1002	Note that precision is not accuracy - binary floating point values cannot
		1003	represent most decimal fractions exactly, and when converting from and to
		1004	floating point, JSON::XS only guarantees precision up to but not including
		1005	the least significant bit.
		1006
737	=item true, false	1007	=item true, false
738		1008
739	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1009	These JSON atoms become C<Types::Serialiser::true> and
740	respectively. They are overloaded to act almost exactly like the numbers	1010	C<Types::Serialiser::false>, respectively. They are overloaded to act
741	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1011	almost exactly like the numbers C<1> and C<0>. You can check whether
742	the C<JSON::XS::is_bool> function.	1012	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1013	function (after C<use Types::Serialier>, of course).
743		1014
744	=item null	1015	=item null
745		1016
746	A JSON null atom becomes C<undef> in Perl.	1017	A JSON null atom becomes C<undef> in Perl.
		1018
		1019	=item shell-style comments (C<< # I<text> >>)
		1020
		1021	As a nonstandard extension to the JSON syntax that is enabled by the
		1022	C<relaxed> setting, shell-style comments are allowed. They can start
		1023	anywhere outside strings and go till the end of the line.
		1024
		1025	=item tagged values (C<< (I<tag>)I<value> >>).
		1026
		1027	Another nonstandard extension to the JSON syntax, enabled with the
		1028	C<allow_tags> setting, are tagged values. In this implementation, the
		1029	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1030	I<value> must be a JSON array encoding optional constructor arguments.
		1031
		1032	See L<OBJECT SERIALISATION>, below, for details.
747		1033
748	=back	1034	=back
749		1035
750		1036
751	=head2 PERL -> JSON	1037	=head2 PERL -> JSON
…		…
756		1042
757	=over 4	1043	=over 4
758		1044
759	=item hash references	1045	=item hash references
760		1046
761	Perl hash references become JSON objects. As there is no inherent ordering	1047	Perl hash references become JSON objects. As there is no inherent
762	in hash keys (or JSON objects), they will usually be encoded in a	1048	ordering in hash keys (or JSON objects), they will usually be encoded
763	pseudo-random order that can change between runs of the same program but	1049	in a pseudo-random order. JSON::XS can optionally sort the hash keys
764	stays generally the same within a single run of a program. JSON::XS can	1050	(determined by the I<canonical> flag), so the same datastructure will
765	optionally sort the hash keys (determined by the I<canonical> flag), so	1051	serialise to the same JSON text (given same settings and version of
766	the same datastructure will serialise to the same JSON text (given same	1052	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
767	settings and version of JSON::XS), but this incurs a runtime overhead	1053	e.g. when you want to compare some JSON text against another for equality.
768	and is only rarely useful, e.g. when you want to compare some JSON text
769	against another for equality.
770		1054
771	=item array references	1055	=item array references
772		1056
773	Perl array references become JSON arrays.	1057	Perl array references become JSON arrays.
774		1058
775	=item other references	1059	=item other references
776		1060
777	Other unblessed references are generally not allowed and will cause an	1061	Other unblessed references are generally not allowed and will cause an
778	exception to be thrown, except for references to the integers C<0> and	1062	exception to be thrown, except for references to the integers C<0> and
779	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1063	C<1>, which get turned into C<false> and C<true> atoms in JSON.
780	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
781		1064
		1065	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1066	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1067	and C<Types::Serialiser::true> to improve readability.
		1068
		1069	use Types::Serialiser;
782	encode_json [\0,JSON::XS::true] # yields [false,true]	1070	encode_json [\0, Types::Serialiser::true] # yields [false,true]
783		1071
784	=item JSON::XS::true, JSON::XS::false	1072	=item Types::Serialiser::true, Types::Serialiser::false
785		1073
786	These special values become JSON true and JSON false values,	1074	These special values from the L<Types::Serialiser> module become JSON true
787	respectively. You can also use C<\1> and C<\0> directly if you want.	1075	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1076	directly if you want.
788		1077
789	=item blessed objects	1078	=item blessed objects
790		1079
791	Blessed objects are not directly representable in JSON. See the	1080	Blessed objects are not directly representable in JSON, but C<JSON::XS>
792	C<allow_blessed> and C<convert_blessed> methods on various options on	1081	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
793	how to deal with this: basically, you can choose between throwing an	1082	below, for details.
794	exception, encoding the reference as if it weren't blessed, or provide
795	your own serialiser method.
796		1083
797	=item simple scalars	1084	=item simple scalars
798		1085
799	Simple Perl scalars (any scalar that is not a reference) are the most	1086	Simple Perl scalars (any scalar that is not a reference) are the most
800	difficult objects to encode: JSON::XS will encode undefined scalars as	1087	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
828		1115
829	You can not currently force the type in other, less obscure, ways. Tell me	1116	You can not currently force the type in other, less obscure, ways. Tell me
830	if you need this capability (but don't forget to explain why it's needed	1117	if you need this capability (but don't forget to explain why it's needed
831	:).	1118	:).
832		1119
		1120	Note that numerical precision has the same meaning as under Perl (so
		1121	binary to decimal conversion follows the same rules as in Perl, which
		1122	can differ to other languages). Also, your perl interpreter might expose
		1123	extensions to the floating point numbers of your platform, such as
		1124	infinities or NaN's - these cannot be represented in JSON, and it is an
		1125	error to pass those in.
		1126
833	=back	1127	=back
		1128
		1129	=head2 OBJECT SERIALISATION
		1130
		1131	As JSON cannot directly represent Perl objects, you have to choose between
		1132	a pure JSON representation (without the ability to deserialise the object
		1133	automatically again), and a nonstandard extension to the JSON syntax,
		1134	tagged values.
		1135
		1136	=head3 SERIALISATION
		1137
		1138	What happens when C<JSON::XS> encounters a Perl object depends on the
		1139	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1140	used in this order:
		1141
		1142	=over 4
		1143
		1144	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1145
		1146	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1147	serialisation protocol to create a tagged JSON value, using a nonstandard
		1148	extension to the JSON syntax.
		1149
		1150	This works by invoking the C<FREEZE> method on the object, with the first
		1151	argument being the object to serialise, and the second argument being the
		1152	constant string C<JSON> to distinguish it from other serialisers.
		1153
		1154	The C<FREEZE> method can return any number of values (i.e. zero or
		1155	more). These values and the paclkage/classname of the object will then be
		1156	encoded as a tagged JSON value in the following format:
		1157
		1158	("classname")[FREEZE return values...]
		1159
		1160	e.g.:
		1161
		1162	("URI")["http://www.google.com/"]
		1163	("MyDate")[2013,10,29]
		1164	("ImageData::JPEG")["Z3...VlCg=="]
		1165
		1166	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1167	objects C<type> and C<id> members to encode the object:
		1168
		1169	sub My::Object::FREEZE {
		1170	my ($self, $serialiser) = @_;
		1171
		1172	($self->{type}, $self->{id})
		1173	}
		1174
		1175	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1176
		1177	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1178	context. It must return a single scalar that can be directly encoded into
		1179	JSON. This scalar replaces the object in the JSON text.
		1180
		1181	For example, the following C<TO_JSON> method will convert all L<URI>
		1182	objects to JSON strings when serialised. The fatc that these values
		1183	originally were L<URI> objects is lost.
		1184
		1185	sub URI::TO_JSON {
		1186	my ($uri) = @_;
		1187	$uri->as_string
		1188	}
		1189
		1190	=item 3. C<allow_blessed> is enabled.
		1191
		1192	The object will be serialised as a JSON null value.
		1193
		1194	=item 4. none of the above
		1195
		1196	If none of the settings are enabled or the respective methods are missing,
		1197	C<JSON::XS> throws an exception.
		1198
		1199	=back
		1200
		1201	=head3 DESERIALISATION
		1202
		1203	For deserialisation there are only two cases to consider: either
		1204	nonstandard tagging was used, in which case C<allow_tags> decides,
		1205	or objects cannot be automatically be deserialised, in which
		1206	case you can use postprocessing or the C<filter_json_object> or
		1207	C<filter_json_single_key_object> callbacks to get some real objects our of
		1208	your JSON.
		1209
		1210	This section only considers the tagged value case: I a tagged JSON object
		1211	is encountered during decoding and C<allow_tags> is disabled, a parse
		1212	error will result (as if tagged values were not part of the grammar).
		1213
		1214	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1215	of the package/classname used during serialisation (it will not attempt
		1216	to load the package as a Perl module). If there is no such method, the
		1217	decoding will fail with an error.
		1218
		1219	Otherwise, the C<THAW> method is invoked with the classname as first
		1220	argument, the constant string C<JSON> as second argument, and all the
		1221	values from the JSON array (the values originally returned by the
		1222	C<FREEZE> method) as remaining arguments.
		1223
		1224	The method must then return the object. While technically you can return
		1225	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1226	make that work in all cases, so better return an actual blessed reference.
		1227
		1228	As an example, let's implement a C<THAW> function that regenerates the
		1229	C<My::Object> from the C<FREEZE> example earlier:
		1230
		1231	sub My::Object::THAW {
		1232	my ($class, $serialiser, $type, $id) = @_;
		1233
		1234	$class->new (type => $type, id => $id)
		1235	}
834		1236
835		1237
836	=head1 ENCODING/CODESET FLAG NOTES	1238	=head1 ENCODING/CODESET FLAG NOTES
837		1239
838	The interested reader might have seen a number of flags that signify	1240	The interested reader might have seen a number of flags that signify
…		…
863	=item C<utf8> flag disabled	1265	=item C<utf8> flag disabled
864		1266
865	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1267	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
866	and expect Unicode strings, that is, characters with high ordinal Unicode	1268	and expect Unicode strings, that is, characters with high ordinal Unicode
867	values (> 255) will be encoded as such characters, and likewise such	1269	values (> 255) will be encoded as such characters, and likewise such
868	characters are decoded as-is, no canges to them will be done, except	1270	characters are decoded as-is, no changes to them will be done, except
869	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1271	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
870	respectively (to Perl, these are the same thing in strings unless you do	1272	respectively (to Perl, these are the same thing in strings unless you do
871	funny/weird/dumb stuff).	1273	funny/weird/dumb stuff).
872		1274
873	This is useful when you want to do the encoding yourself (e.g. when you	1275	This is useful when you want to do the encoding yourself (e.g. when you
…		…
929	proper subset of most 8-bit and multibyte encodings in use in the world.	1331	proper subset of most 8-bit and multibyte encodings in use in the world.
930		1332
931	=back	1333	=back
932		1334
933		1335
934	=head1 COMPARISON	1336	=head2 JSON and ECMAscript
935		1337
936	As already mentioned, this module was created because none of the existing	1338	JSON syntax is based on how literals are represented in javascript (the
937	JSON modules could be made to work correctly. First I will describe the	1339	not-standardised predecessor of ECMAscript) which is presumably why it is
938	problems (or pleasures) I encountered with various existing JSON modules,	1340	called "JavaScript Object Notation".
939	followed by some benchmark values. JSON::XS was designed not to suffer
940	from any of these problems or limitations.
941		1341
942	=over 4	1342	However, JSON is not a subset (and also not a superset of course) of
		1343	ECMAscript (the standard) or javascript (whatever browsers actually
		1344	implement).
943		1345
944	=item JSON 2.xx	1346	If you want to use javascript's C<eval> function to "parse" JSON, you
		1347	might run into parse errors for valid JSON texts, or the resulting data
		1348	structure might not be queryable:
945		1349
946	A marvellous piece of engineering, this module either uses JSON::XS	1350	One of the problems is that U+2028 and U+2029 are valid characters inside
947	directly when available (so will be 100% compatible with it, including	1351	JSON strings, but are not allowed in ECMAscript string literals, so the
948	speed), or it uses JSON::PP, which is basically JSON::XS translated to	1352	following Perl fragment will not output something that can be guaranteed
949	Pure Perl, which should be 100% compatible with JSON::XS, just a bit	1353	to be parsable by javascript's C<eval>:
950	slower.
951		1354
952	You cannot really lose by using this module, especially as it tries very	1355	use JSON::XS;
953	hard to work even with ancient Perl versions, while JSON::XS does not.
954		1356
955	=item JSON 1.07	1357	print encode_json [chr 0x2028];
956		1358
957	Slow (but very portable, as it is written in pure Perl).	1359	The right fix for this is to use a proper JSON parser in your javascript
		1360	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1361	F<json2.js> parser).
958		1362
959	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1363	If this is not an option, you can, as a stop-gap measure, simply encode to
960	undocumented. One can get far by feeding it Unicode strings and doing	1364	ASCII-only JSON:
961	en-/decoding oneself, but Unicode escapes are not working properly).
962		1365
963	No round-tripping (strings get clobbered if they look like numbers, e.g.	1366	use JSON::XS;
964	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
965	decode into the number 2.
966		1367
967	=item JSON::PC 0.01	1368	print JSON::XS->new->ascii->encode ([chr 0x2028]);
968		1369
969	Very fast.	1370	Note that this will enlarge the resulting JSON text quite a bit if you
		1371	have many non-ASCII characters. You might be tempted to run some regexes
		1372	to only escape U+2028 and U+2029, e.g.:
970		1373
971	Undocumented/buggy Unicode handling.	1374	# DO NOT USE THIS!
		1375	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1376	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1377	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1378	print $json;
972		1379
973	No round-tripping.	1380	Note that I<this is a bad idea>: the above only works for U+2028 and
		1381	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1382	javascript implementations, however, have issues with other characters as
		1383	well - using C<eval> naively simply I<will> cause problems.
974		1384
975	Has problems handling many Perl values (e.g. regex results and other magic	1385	Another problem is that some javascript implementations reserve
976	values will make it croak).	1386	some property names for their own purposes (which probably makes
		1387	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1388	C<__proto__> property name for its own purposes.
977		1389
978	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1390	If that is a problem, you could parse try to filter the resulting JSON
979	which is not a valid JSON text.	1391	output for these property strings, e.g.:
980		1392
981	Unmaintained (maintainer unresponsive for many months, bugs are not	1393	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
982	getting fixed).
983		1394
984	=item JSON::Syck 0.21	1395	This works because C<__proto__> is not valid outside of strings, so every
		1396	occurrence of C<"__proto__"\s*:> must be a string used as property name.
985		1397
986	Very buggy (often crashes).	1398	If you know of other incompatibilities, please let me know.
987
988	Very inflexible (no human-readable format supported, format pretty much
989	undocumented. I need at least a format for easy reading by humans and a
990	single-line compact format for use in a protocol, and preferably a way to
991	generate ASCII-only JSON texts).
992
993	Completely broken (and confusingly documented) Unicode handling (Unicode
994	escapes are not working properly, you need to set ImplicitUnicode to
995	I<different> values on en- and decoding to get symmetric behaviour).
996
997	No round-tripping (simple cases work, but this depends on whether the scalar
998	value was used in a numeric context or not).
999
1000	Dumping hashes may skip hash values depending on iterator state.
1001
1002	Unmaintained (maintainer unresponsive for many months, bugs are not
1003	getting fixed).
1004
1005	Does not check input for validity (i.e. will accept non-JSON input and
1006	return "something" instead of raising an exception. This is a security
1007	issue: imagine two banks transferring money between each other using
1008	JSON. One bank might parse a given non-JSON request and deduct money,
1009	while the other might reject the transaction with a syntax error. While a
1010	good protocol will at least recover, that is extra unnecessary work and
1011	the transaction will still not succeed).
1012
1013	=item JSON::DWIW 0.04
1014
1015	Very fast. Very natural. Very nice.
1016
1017	Undocumented Unicode handling (but the best of the pack. Unicode escapes
1018	still don't get parsed properly).
1019
1020	Very inflexible.
1021
1022	No round-tripping.
1023
1024	Does not generate valid JSON texts (key strings are often unquoted, empty keys
1025	result in nothing being output)
1026
1027	Does not check input for validity.
1028
1029	=back
1030		1399
1031		1400
1032	=head2 JSON and YAML	1401	=head2 JSON and YAML
1033		1402
1034	You often hear that JSON is a subset of YAML. This is, however, a mass	1403	You often hear that JSON is a subset of YAML. This is, however, a mass
…		…
1044	my $yaml = $to_yaml->encode ($ref) . "\n";	1413	my $yaml = $to_yaml->encode ($ref) . "\n";
1045		1414
1046	This will I<usually> generate JSON texts that also parse as valid	1415	This will I<usually> generate JSON texts that also parse as valid
1047	YAML. Please note that YAML has hardcoded limits on (simple) object key	1416	YAML. Please note that YAML has hardcoded limits on (simple) object key
1048	lengths that JSON doesn't have and also has different and incompatible	1417	lengths that JSON doesn't have and also has different and incompatible
1049	unicode handling, so you should make sure that your hash keys are	1418	unicode character escape syntax, so you should make sure that your hash
1050	noticeably shorter than the 1024 "stream characters" YAML allows and that	1419	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1051	you do not have characters with codepoint values outside the Unicode BMP	1420	and that you do not have characters with codepoint values outside the
1052	(basic multilingual page). YAML also does not allow C<\/> sequences in	1421	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1053	strings (which JSON::XS does not I<currently> generate, but other JSON	1422	sequences in strings (which JSON::XS does not I<currently> generate, but
1054	generators might).	1423	other JSON generators might).
1055		1424
1056	There might be other incompatibilities that I am not aware of (or the YAML	1425	There might be other incompatibilities that I am not aware of (or the YAML
1057	specification has been changed yet again - it does so quite often). In	1426	specification has been changed yet again - it does so quite often). In
1058	general you should not try to generate YAML with a JSON generator or vice	1427	general you should not try to generate YAML with a JSON generator or vice
1059	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1428	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1078	that difficult or long) and finally make YAML compatible to it, and	1447	that difficult or long) and finally make YAML compatible to it, and
1079	educating users about the changes, instead of spreading lies about the	1448	educating users about the changes, instead of spreading lies about the
1080	real compatibility for many I<years> and trying to silence people who	1449	real compatibility for many I<years> and trying to silence people who
1081	point out that it isn't true.	1450	point out that it isn't true.
1082		1451
		1452	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1453	though the incompatibilities have been documented (and are known to Brian)
		1454	for many years and the spec makes explicit claims that YAML is a superset
		1455	of JSON. It would be so easy to fix, but apparently, bullying people and
		1456	corrupting userdata is so much easier.
		1457
1083	=back	1458	=back
1084		1459
1085		1460
1086	=head2 SPEED	1461	=head2 SPEED
1087		1462
…		…
1092		1467
1093	First comes a comparison between various modules using	1468	First comes a comparison between various modules using
1094	a very short single-line JSON string (also available at	1469	a very short single-line JSON string (also available at
1095	L<http://dist.schmorp.de/misc/json/short.json>).	1470	L<http://dist.schmorp.de/misc/json/short.json>).
1096		1471
1097	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1472	{"method": "handleMessage", "params": ["user1",
1098	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1473	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1474	1, 0]}
1099		1475
1100	It shows the number of encodes/decodes per second (JSON::XS uses	1476	It shows the number of encodes/decodes per second (JSON::XS uses
1101	the functional interface, while JSON::XS/2 uses the OO interface	1477	the functional interface, while JSON::XS/2 uses the OO interface
1102	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1478	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1103	shrink). Higher is better:	1479	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1480	uses the from_json method). Higher is better:
1104		1481
1105	module \| encode \| decode \|	1482	module \| encode \| decode \|
1106	-----------\|------------\|------------\|	1483	--------------\|------------\|------------\|
1107	JSON 1.x \| 4990.842 \| 4088.813 \|	1484	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1108	JSON::DWIW \| 51653.990 \| 71575.154 \|	1485	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1109	JSON::PC \| 65948.176 \| 74631.744 \|	1486	JSON::PP \| 15827.562 \| 6638.658 \|
1110	JSON::PP \| 8931.652 \| 3817.168 \|	1487	JSON::Syck \| 63358.066 \| 47662.545 \|
1111	JSON::Syck \| 24877.248 \| 27776.848 \|	1488	JSON::XS \| 511500.488 \| 511500.488 \|
1112	JSON::XS \| 388361.481 \| 227951.304 \|	1489	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1113	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1490	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1114	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1491	Storable \| 66788.280 \| 265462.278 \|
1115	Storable \| 16500.016 \| 135300.129 \|
1116	-----------+------------+------------+	1492	--------------+------------+------------+
1117		1493
1118	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1494	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1119	about three times faster on decoding, and over forty times faster	1495	about five times faster on decoding, and over thirty to seventy times
1120	than JSON, even with pretty-printing and key sorting. It also compares	1496	faster than JSON's pure perl implementation. It also compares favourably
1121	favourably to Storable for small amounts of data.	1497	to Storable for small amounts of data.
1122		1498
1123	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1499	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1124	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1500	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1125		1501
1126	module \| encode \| decode \|	1502	module \| encode \| decode \|
1127	-----------\|------------\|------------\|	1503	--------------\|------------\|------------\|
1128	JSON 1.x \| 55.260 \| 34.971 \|	1504	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1129	JSON::DWIW \| 825.228 \| 1082.513 \|	1505	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1130	JSON::PC \| 3571.444 \| 2394.829 \|
1131	JSON::PP \| 210.987 \| 32.574 \|	1506	JSON::PP \| 400.640 \| 62.311 \|
1132	JSON::Syck \| 552.551 \| 787.544 \|	1507	JSON::Syck \| 1481.040 \| 1524.869 \|
1133	JSON::XS \| 5780.463 \| 4854.519 \|	1508	JSON::XS \| 20661.596 \| 9541.183 \|
1134	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1509	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1135	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1510	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1136	Storable \| 4445.002 \| 5235.027 \|	1511	Storable \| 19765.806 \| 10000.725 \|
1137	-----------+------------+------------+	1512	--------------+------------+------------+
1138		1513
1139	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1514	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1140	decodes faster).	1515	decodes a bit faster).
1141		1516
1142	On large strings containing lots of high Unicode characters, some modules	1517	On large strings containing lots of high Unicode characters, some modules
1143	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1518	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1144	will be broken due to missing (or wrong) Unicode handling. Others refuse	1519	will be broken due to missing (or wrong) Unicode handling. Others refuse
1145	to decode or encode properly, so it was impossible to prepare a fair	1520	to decode or encode properly, so it was impossible to prepare a fair
…		…
1181	information you might want to make sure that exceptions thrown by JSON::XS	1556	information you might want to make sure that exceptions thrown by JSON::XS
1182	will not end up in front of untrusted eyes.	1557	will not end up in front of untrusted eyes.
1183		1558
1184	If you are using JSON::XS to return packets to consumption	1559	If you are using JSON::XS to return packets to consumption
1185	by JavaScript scripts in a browser you should have a look at	1560	by JavaScript scripts in a browser you should have a look at
1186	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1561	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1187	you are vulnerable to some common attack vectors (which really are browser	1562	see whether you are vulnerable to some common attack vectors (which really
1188	design bugs, but it is still you who will have to deal with it, as major	1563	are browser design bugs, but it is still you who will have to deal with
1189	browser developers care only for features, not about getting security	1564	it, as major browser developers care only for features, not about getting
1190	right).	1565	security right).
		1566
		1567
		1568	=head1 "OLD" VS. "NEW" JSON (RFC 4627 VS. RFC 7159)
		1569
		1570	TL;DR: Due to security concerns, JSON::XS will not allow scalar data in
		1571	JSON texts by default - you need to create your own JSON::XS object and
		1572	enable C<allow_nonref>:
		1573
		1574
		1575	my $json = JSON::XS->new->allow_nonref;
		1576
		1577	$text = $json->encode ($data);
		1578	$data = $json->decode ($text);
		1579
		1580	The long version: JSON being an important and supposedly stable format,
		1581	the IETF standardised it as RFC 4627 in 2006. Unfortunately, the inventor
		1582	of JSON, Dougles Crockford, unilaterally changed the definition of JSON in
		1583	javascript. Rather than create a fork, the IETF decided to standardise the
		1584	new syntax (apparently, so Iw as told, without finding it very amusing).
		1585
		1586	The biggest difference between thed original JSON and the new JSON is that
		1587	the new JSON supports scalars (anything other than arrays and objects) at
		1588	the toplevel of a JSON text. While this is strictly backwards compatible
		1589	to older versions, it breaks a number of protocols that relied on sending
		1590	JSON back-to-back, and is a minor security concern.
		1591
		1592	For example, imagine you have two banks communicating, and on one side,
		1593	trhe JSON coder gets upgraded. Two messages, such as C<10> and C<1000>
		1594	might then be confused to mean C<101000>, something that couldn't happen
		1595	in the original JSON, because niether of these messages would be valid
		1596	JSON.
		1597
		1598	If one side accepts these messages, then an upgrade in the coder on either
		1599	side could result in this becoming exploitable.
		1600
		1601	This module has always allowed these messages as an optional extension, by
		1602	default disabled. The security concerns are the reason why the default is
		1603	still disabled, but future versions might/will likely upgrade to the newer
		1604	RFC as default format, so you are advised to check your implementation
		1605	and/or override the default with C<< ->allow_nonref (0) >> to ensure that
		1606	future versions are safe.
		1607
		1608
		1609	=head1 INTEROPERABILITY WITH OTHER MODULES
		1610
		1611	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1612	constants. That means that the JSON true and false values will be
		1613	comaptible to true and false values of iother modules that do the same,
		1614	such as L<JSON::PP> and L<CBOR::XS>.
		1615
		1616
		1617	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1618
		1619	As long as you only serialise data that can be directly expressed in JSON,
		1620	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1621	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1622	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1623
		1624	When you have trouble decoding JSON generated by this module using other
		1625	decoders, then it is very likely that you have an encoding mismatch or the
		1626	other decoder is broken.
		1627
		1628	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1629	errors. There are currently two settings that change this: C<relaxed>
		1630	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1631	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1632	cost of not outputting valid JSON anymore.
		1633
		1634	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1635
		1636	When you use C<allow_tags> to use the extended (and also nonstandard and
		1637	invalid) JSON syntax for serialised objects, and you still want to decode
		1638	the generated When you want to serialise objects, you can run a regex
		1639	to replace the tagged syntax by standard JSON arrays (it only works for
		1640	"normal" packagesnames without comma, newlines or single colons). First,
		1641	the readable Perl version:
		1642
		1643	# if your FREEZE methods return no values, you need this replace first:
		1644	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1645
		1646	# this works for non-empty constructor arg lists:
		1647	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1648
		1649	And here is a less readable version that is easy to adapt to other
		1650	languages:
		1651
		1652	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1653
		1654	Here is an ECMAScript version (same regex):
		1655
		1656	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1657
		1658	Since this syntax converts to standard JSON arrays, it might be hard to
		1659	distinguish serialised objects from normal arrays. You can prepend a
		1660	"magic number" as first array element to reduce chances of a collision:
		1661
		1662	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1663
		1664	And after decoding the JSON text, you could walk the data
		1665	structure looking for arrays with a first element of
		1666	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1667
		1668	The same approach can be used to create the tagged format with another
		1669	encoder. First, you create an array with the magic string as first member,
		1670	the classname as second, and constructor arguments last, encode it as part
		1671	of your JSON structure, and then:
		1672
		1673	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1674
		1675	Again, this has some limitations - the magic string must not be encoded
		1676	with character escapes, and the constructor arguments must be non-empty.
		1677
		1678
		1679	=head1 RFC7159
		1680
		1681	Since this module was written, Google has written a new JSON RFC, RFC 7159
		1682	(and RFC7158). Unfortunately, this RFC breaks compatibility with both the
		1683	original JSON specification on www.json.org and RFC4627.
		1684
		1685	As far as I can see, you can get partial compatibility when parsing by
		1686	using C<< ->allow_nonref >>. However, consider thew security implications
		1687	of doing so.
		1688
		1689	I haven't decided yet when to break compatibility with RFC4627 by default
		1690	(and potentially leave applications insecure) and change the default to
		1691	follow RFC7159, but application authors are well advised to call C<<
		1692	->allow_nonref(0) >> even if this is the current default, if they cannot
		1693	handle non-reference values, in preparation for the day when the4 default
		1694	will change.
1191		1695
1192		1696
1193	=head1 THREADS	1697	=head1 THREADS
1194		1698
1195	This module is I<not> guaranteed to be thread safe and there are no	1699	This module is I<not> guaranteed to be thread safe and there are no
…		…
1198	process simulations - use fork, it's I<much> faster, cheaper, better).	1702	process simulations - use fork, it's I<much> faster, cheaper, better).
1199		1703
1200	(It might actually work, but you have been warned).	1704	(It might actually work, but you have been warned).
1201		1705
1202		1706
		1707	=head1 THE PERILS OF SETLOCALE
		1708
		1709	Sometimes people avoid the Perl locale support and directly call the
		1710	system's setlocale function with C<LC_ALL>.
		1711
		1712	This breaks both perl and modules such as JSON::XS, as stringification of
		1713	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1714	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1715	perl to stringify numbers).
		1716
		1717	The solution is simple: don't call C<setlocale>, or use it for only those
		1718	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1719
		1720	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1721	actually needs it (avoiding stringification of numbers), and restore it
		1722	afterwards.
		1723
		1724
1203	=head1 BUGS	1725	=head1 BUGS
1204		1726
1205	While the goal of this module is to be correct, that unfortunately does	1727	While the goal of this module is to be correct, that unfortunately does
1206	not mean it's bug-free, only that I think its design is bug-free. It is	1728	not mean it's bug-free, only that I think its design is bug-free. If you
1207	still relatively early in its development. If you keep reporting bugs they	1729	keep reporting bugs they will be fixed swiftly, though.
1208	will be fixed swiftly, though.
1209		1730
1210	Please refrain from using rt.cpan.org or any other bug reporting	1731	Please refrain from using rt.cpan.org or any other bug reporting
1211	service. I put the contact address into my modules for a reason.	1732	service. I put the contact address into my modules for a reason.
1212		1733
1213	=cut	1734	=cut
1214		1735
1215	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1736	BEGIN {
1216	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1737	*true = \$Types::Serialiser::true;
		1738	*true = \&Types::Serialiser::true;
		1739	*false = \$Types::Serialiser::false;
		1740	*false = \&Types::Serialiser::false;
		1741	*is_bool = \&Types::Serialiser::is_bool;
1217		1742
1218	sub true() { $true }	1743	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1219	sub false() { $false }
1220
1221	sub is_bool($) {
1222	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1223	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1224	}	1744	}
1225		1745
1226	XSLoader::load "JSON::XS", $VERSION;	1746	XSLoader::load "JSON::XS", $VERSION;
1227
1228	package JSON::XS::Boolean;
1229
1230	use overload
1231	"0+" => sub { ${$_[0]} },
1232	"++" => sub { $_[0] = ${$_[0]} + 1 },
1233	"--" => sub { $_[0] = ${$_[0]} - 1 },
1234	fallback => 1;
1235
1236	1;
1237		1747
1238	=head1 SEE ALSO	1748	=head1 SEE ALSO
1239		1749
1240	The F<json_xs> command line utility for quick experiments.	1750	The F<json_xs> command line utility for quick experiments.
1241		1751
…		…
1244	Marc Lehmann <schmorp@schmorp.de>	1754	Marc Lehmann <schmorp@schmorp.de>
1245	http://home.schmorp.de/	1755	http://home.schmorp.de/
1246		1756
1247	=cut	1757	=cut
1248		1758
		1759	1
		1760

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Comparing JSON-XS/XS.pm (file contents): Revision 1.93 by root, Sat Mar 22 22:21:33 2008 UTC vs. Revision 1.158 by root, Thu Sep 1 11:38:39 2016 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.93 by root, Sat Mar 22 22:21:33 2008 UTC vs.
Revision 1.158 by root, Thu Sep 1 11:38:39 2016 UTC