[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 1.148 by root, Tue Oct 29 00:19:45 2013 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 $VERSION = '3.0';
109	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
110		108
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
112
113	sub to_json($) {
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
		695
		696
		697	=head1 INCREMENTAL PARSING
		698
		699	In some cases, there is the need for incremental parsing of JSON
		700	texts. While this module always has to keep both JSON text and resulting
		701	Perl data structure in memory at one time, it does allow you to parse a
		702	JSON stream incrementally. It does so by accumulating text until it has
		703	a full JSON object, which it then can decode. This process is similar to
		704	using C<decode_prefix> to see if a full JSON object is available, but
		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
		709	has enough text to get a decisive result, using a very simple but
		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.
		716
		717	The following methods implement this incremental parser.
		718
		719	=over 4
		720
		721	=item [void, scalar or list context] = $json->incr_parse ([$string])
		722
		723	This is the central parsing function. It can both append new text and
		724	extract objects from the stream accumulated so far (both of these
		725	functions are optional).
		726
		727	If C<$string> is given, then this string is appended to the already
		728	existing JSON fragment stored in the C<$json> object.
		729
		730	After that, if the function is called in void context, it will simply
		731	return without doing anything further. This can be used to add more text
		732	in as many chunks as you want.
		733
		734	If the method is called in scalar context, then it will try to extract
		735	exactly I<one> JSON object. If that is successful, it will return this
		736	object, otherwise it will return C<undef>. If there is a parse error,
		737	this method will croak just as C<decode> would do (one can then use
		738	C<incr_skip> to skip the erroneous part). This is the most common way of
		739	using the method.
		740
		741	And finally, in list context, it will try to extract as many objects
		742	from the stream as it can find and return them, or the empty list
		743	otherwise. For this to work, there must be no separators between the JSON
		744	objects or arrays, instead they must be concatenated back-to-back. If
		745	an error occurs, an exception will be raised as in the scalar context
		746	case. Note that in this case, any previously-parsed JSON texts will be
		747	lost.
		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
		754	=item $lvalue_string = $json->incr_text
		755
		756	This method returns the currently stored JSON fragment as an lvalue, that
		757	is, you can manipulate it. This I<only> works when a preceding call to
		758	C<incr_parse> in I<scalar context> successfully returned an object. Under
		759	all other circumstances you must not call this function (I mean it.
		760	although in simple tests it might actually work, it I<will> fail under
		761	real world conditions). As a special exception, you can also call this
		762	method before having parsed anything.
		763
		764	This function is useful in two cases: a) finding the trailing text after a
		765	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		766	(such as commas).
		767
		768	=item $json->incr_skip
		769
		770	This will reset the state of the incremental parser and will remove
		771	the parsed text from the input buffer so far. This is useful after
		772	C<incr_parse> died, in which case the input buffer and incremental parser
		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.
		787
		788	=back
		789
		790	=head2 LIMITATIONS
		791
		792	All options that affect decoding are supported, except
		793	C<allow_nonref>. The reason for this is that it cannot be made to work
		794	sensibly: JSON objects and arrays are self-delimited, i.e. you can
		795	concatenate them back to back and still decode them perfectly. This does
		796	not hold true for JSON numbers, however.
		797
		798	For example, is the string C<1> a single JSON number, or is it simply the
		799	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		800	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		801	takes the conservative route and disallows this case.
		802
		803	=head2 EXAMPLES
		804
		805	Some examples will make all this clearer. First, a simple example that
		806	works similarly to C<decode_prefix>: We want to decode the JSON object at
		807	the start of a string and identify the portion after the JSON object:
		808
		809	my $text = "[1,2,3] hello";
		810
		811	my $json = new JSON::XS;
		812
		813	my $obj = $json->incr_parse ($text)
		814	or die "expected JSON object or array at beginning of string";
		815
		816	my $tail = $json->incr_text;
		817	# $tail now contains " hello"
		818
		819	Easy, isn't it?
		820
		821	Now for a more complicated example: Imagine a hypothetical protocol where
		822	you read some requests from a TCP stream, and each request is a JSON
		823	array, without any separation between them (in fact, it is often useful to
		824	use newlines as "separators", as these get interpreted as whitespace at
		825	the start of the JSON text, which makes it possible to test said protocol
		826	with C<telnet>...).
		827
		828	Here is how you'd do it (it is trivial to write this in an event-based
		829	manner):
		830
		831	my $json = new JSON::XS;
		832
		833	# read some data from the socket
		834	while (sysread $socket, my $buf, 4096) {
		835
		836	# split and decode as many requests as possible
		837	for my $request ($json->incr_parse ($buf)) {
		838	# act on the $request
		839	}
		840	}
		841
		842	Another complicated example: Assume you have a string with JSON objects
		843	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		844	[3]>). To parse them, we have to skip the commas between the JSON texts,
		845	and here is where the lvalue-ness of C<incr_text> comes in useful:
		846
		847	my $text = "[1],[2], [3]";
		848	my $json = new JSON::XS;
		849
		850	# void context, so no parsing done
		851	$json->incr_parse ($text);
		852
		853	# now extract as many objects as possible. note the
		854	# use of scalar context so incr_text can be called.
		855	while (my $obj = $json->incr_parse) {
		856	# do something with $obj
		857
		858	# now skip the optional comma
		859	$json->incr_text =~ s/^ \s* , //x;
		860	}
		861
		862	Now lets go for a very complex example: Assume that you have a gigantic
		863	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		864	but you cannot load it into memory fully (this has actually happened in
		865	the real world :).
		866
		867	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		868	can still help you: You implement a (very simple) array parser and let
		869	JSON decode the array elements, which are all full JSON objects on their
		870	own (this wouldn't work if the array elements could be JSON numbers, for
		871	example):
		872
		873	my $json = new JSON::XS;
		874
		875	# open the monster
		876	open my $fh, "<bigfile.json"
		877	or die "bigfile: $!";
		878
		879	# first parse the initial "["
		880	for (;;) {
		881	sysread $fh, my $buf, 65536
		882	or die "read error: $!";
		883	$json->incr_parse ($buf); # void context, so no parsing
		884
		885	# Exit the loop once we found and removed(!) the initial "[".
		886	# In essence, we are (ab-)using the $json object as a simple scalar
		887	# we append data to.
		888	last if $json->incr_text =~ s/^ \s* \[ //x;
		889	}
		890
		891	# now we have the skipped the initial "[", so continue
		892	# parsing all the elements.
		893	for (;;) {
		894	# in this loop we read data until we got a single JSON object
		895	for (;;) {
		896	if (my $obj = $json->incr_parse) {
		897	# do something with $obj
		898	last;
		899	}
		900
		901	# add more data
		902	sysread $fh, my $buf, 65536
		903	or die "read error: $!";
		904	$json->incr_parse ($buf); # void context, so no parsing
		905	}
		906
		907	# in this loop we read data until we either found and parsed the
		908	# separating "," between elements, or the final "]"
		909	for (;;) {
		910	# first skip whitespace
		911	$json->incr_text =~ s/^\s*//;
		912
		913	# if we find "]", we are done
		914	if ($json->incr_text =~ s/^\]//) {
		915	print "finished.\n";
		916	exit;
		917	}
		918
		919	# if we find ",", we can continue with the next element
		920	if ($json->incr_text =~ s/^,//) {
		921	last;
		922	}
		923
		924	# if we find anything else, we have a parse error!
		925	if (length $json->incr_text) {
		926	die "parse error near ", $json->incr_text;
		927	}
		928
		929	# else add more data
		930	sysread $fh, my $buf, 65536
		931	or die "read error: $!";
		932	$json->incr_parse ($buf); # void context, so no parsing
		933	}
		934
		935	This is a complex example, but most of the complexity comes from the fact
		936	that we are trying to be correct (bear with me if I am wrong, I never ran
		937	the above example :).
		938
684		939
685		940
686	=head1 MAPPING	941	=head1 MAPPING
687		942
688	This section describes how JSON::XS maps Perl values to JSON values and	943	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	980	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	981	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	982	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	983	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	984	which case you lose roundtripping ability, as the JSON number will be
730	re-encoded toa JSON string).	985	re-encoded to a JSON string).
731		986
732	Numbers containing a fractional or exponential part will always be	987	Numbers containing a fractional or exponential part will always be
733	represented as numeric (floating point) values, possibly at a loss of	988	represented as numeric (floating point) values, possibly at a loss of
734	precision (in which case you might lose perfect roundtripping ability, but	989	precision (in which case you might lose perfect roundtripping ability, but
735	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).
736		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
737	=item true, false	997	=item true, false
738		998
739	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	999	These JSON atoms become C<Types::Serialiser::true> and
740	respectively. They are overloaded to act almost exactly like the numbers	1000	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	1001	almost exactly like the numbers C<1> and C<0>. You can check whether
742	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).
743		1004
744	=item null	1005	=item null
745		1006
746	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.
747		1023
748	=back	1024	=back
749		1025
750		1026
751	=head2 PERL -> JSON	1027	=head2 PERL -> JSON
…		…
756		1032
757	=over 4	1033	=over 4
758		1034
759	=item hash references	1035	=item hash references
760		1036
761	Perl hash references become JSON objects. As there is no inherent ordering	1037	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	1038	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	1039	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	1040	(determined by the I<canonical> flag), so the same datastructure will
765	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
766	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,
767	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.
768	and is only rarely useful, e.g. when you want to compare some JSON text
769	against another for equality.
770		1044
771	=item array references	1045	=item array references
772		1046
773	Perl array references become JSON arrays.	1047	Perl array references become JSON arrays.
774		1048
775	=item other references	1049	=item other references
776		1050
777	Other unblessed references are generally not allowed and will cause an	1051	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	1052	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	1053	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		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;
782	encode_json [\0,JSON::XS::true] # yields [false,true]	1060	encode_json [\0, Types::Serialiser::true] # yields [false,true]
783		1061
784	=item JSON::XS::true, JSON::XS::false	1062	=item Types::Serialiser::true, Types::Serialiser::false
785		1063
786	These special values become JSON true and JSON false values,	1064	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.	1065	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1066	directly if you want.
788		1067
789	=item blessed objects	1068	=item blessed objects
790		1069
791	Blessed objects are not directly representable in JSON. See the	1070	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	1071	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
793	how to deal with this: basically, you can choose between throwing an	1072	below, for details.
794	exception, encoding the reference as if it weren't blessed, or provide
795	your own serialiser method.
796		1073
797	=item simple scalars	1074	=item simple scalars
798		1075
799	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
800	difficult objects to encode: JSON::XS will encode undefined scalars as	1077	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
828		1105
829	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
830	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
831	:).	1108	:).
832		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
833	=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 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	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1151	objects C<type> and C<id> members to encode the object:
		1152
		1153	sub My::Object::FREEZE {
		1154	my ($self, $serialiser) = @_;
		1155
		1156	($self->{type}, $self->{id})
		1157	}
		1158
		1159	=item 2. C<convert_blessed> is enabled and object has a C<TO_JSON> method.
		1160
		1161	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1162	context. It must return a single scalar that can be directly encoded into
		1163	JSON. This scalar replaces the object in the JSON text.
		1164
		1165	For example, the following C<TO_JSON> method will convert all L<URI>
		1166	objects to JSON strings when serialised. The fatc that these values
		1167	originally were L<URI> objects is lost.
		1168
		1169	sub URI::TO_JSON {
		1170	my ($uri) = @_;
		1171	$uri->as_string
		1172	}
		1173
		1174	=item 3. C<allow_blessed> is enabled.
		1175
		1176	The object will be serialised as a JSON null value.
		1177
		1178	=item 4. none of the above
		1179
		1180	If none of the settings are enabled or the respective methods are missing,
		1181	C<JSON::XS> throws an exception.
		1182
		1183	=back
		1184
		1185	=head3 DESERIALISATION
		1186
		1187	For deserialisation there are only two cases to consider: either
		1188	nonstandard tagging was used, in which case C<allow_tags> decides,
		1189	or objects cannot be automatically be deserialised, in which
		1190	case you can use postprocessing or the C<filter_json_object> or
		1191	C<filter_json_single_key_object> callbacks to get some real objects our of
		1192	your JSON.
		1193
		1194	This section only considers the tagged value case: I a tagged JSON object
		1195	is encountered during decoding and C<allow_tags> is disabled, a parse
		1196	error will result (as if tagged values were not part of the grammar).
		1197
		1198	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1199	of the package/classname used during serialisation (it will not attempt
		1200	to load the package as a Perl module). If there is no such method, the
		1201	decoding will fail with an error.
		1202
		1203	Otherwise, the C<THAW> method is invoked with the classname as first
		1204	argument, the constant string C<JSON> as second argument, and all the
		1205	values from the JSON array (the values originally returned by the
		1206	C<FREEZE> method) as remaining arguments.
		1207
		1208	The method must then return the object. While technically you can return
		1209	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1210	make that work in all cases, so better return an actual blessed reference.
		1211
		1212	As an example, let's implement a C<THAW> function that regenerates the
		1213	C<My::Object> from the C<FREEZE> example earlier:
		1214
		1215	sub My::Object::THAW {
		1216	my ($class, $serialiser, $type, $id) = @_;
		1217
		1218	$class->new (type => $type, id => $id)
		1219	}
834		1220
835		1221
836	=head1 ENCODING/CODESET FLAG NOTES	1222	=head1 ENCODING/CODESET FLAG NOTES
837		1223
838	The interested reader might have seen a number of flags that signify	1224	The interested reader might have seen a number of flags that signify
…		…
863	=item C<utf8> flag disabled	1249	=item C<utf8> flag disabled
864		1250
865	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1251	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	1252	and expect Unicode strings, that is, characters with high ordinal Unicode
867	values (> 255) will be encoded as such characters, and likewise such	1253	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	1254	characters are decoded as-is, no changes to them will be done, except
869	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1255	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
870	respectively (to Perl, these are the same thing in strings unless you do	1256	respectively (to Perl, these are the same thing in strings unless you do
871	funny/weird/dumb stuff).	1257	funny/weird/dumb stuff).
872		1258
873	This is useful when you want to do the encoding yourself (e.g. when you	1259	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.	1315	proper subset of most 8-bit and multibyte encodings in use in the world.
930		1316
931	=back	1317	=back
932		1318
933		1319
934	=head1 COMPARISON	1320	=head2 JSON and ECMAscript
935		1321
936	As already mentioned, this module was created because none of the existing	1322	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	1323	not-standardised predecessor of ECMAscript) which is presumably why it is
938	problems (or pleasures) I encountered with various existing JSON modules,	1324	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		1325
942	=over 4	1326	However, JSON is not a subset (and also not a superset of course) of
		1327	ECMAscript (the standard) or javascript (whatever browsers actually
		1328	implement).
943		1329
944	=item JSON 2.xx	1330	If you want to use javascript's C<eval> function to "parse" JSON, you
		1331	might run into parse errors for valid JSON texts, or the resulting data
		1332	structure might not be queryable:
945		1333
946	A marvellous piece of engineering, this module either uses JSON::XS	1334	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	1335	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	1336	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	1337	to be parsable by javascript's C<eval>:
950	slower.
951		1338
952	You cannot really lose by using this module, especially as it tries very	1339	use JSON::XS;
953	hard to work even with ancient Perl versions, while JSON::XS does not.
954		1340
955	=item JSON 1.07	1341	print encode_json [chr 0x2028];
956		1342
957	Slow (but very portable, as it is written in pure Perl).	1343	The right fix for this is to use a proper JSON parser in your javascript
		1344	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1345	F<json2.js> parser).
958		1346
959	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1347	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	1348	ASCII-only JSON:
961	en-/decoding oneself, but Unicode escapes are not working properly).
962		1349
963	No round-tripping (strings get clobbered if they look like numbers, e.g.	1350	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		1351
967	=item JSON::PC 0.01	1352	print JSON::XS->new->ascii->encode ([chr 0x2028]);
968		1353
969	Very fast.	1354	Note that this will enlarge the resulting JSON text quite a bit if you
		1355	have many non-ASCII characters. You might be tempted to run some regexes
		1356	to only escape U+2028 and U+2029, e.g.:
970		1357
971	Undocumented/buggy Unicode handling.	1358	# DO NOT USE THIS!
		1359	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1360	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1361	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1362	print $json;
972		1363
973	No round-tripping.	1364	Note that I<this is a bad idea>: the above only works for U+2028 and
		1365	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1366	javascript implementations, however, have issues with other characters as
		1367	well - using C<eval> naively simply I<will> cause problems.
974		1368
975	Has problems handling many Perl values (e.g. regex results and other magic	1369	Another problem is that some javascript implementations reserve
976	values will make it croak).	1370	some property names for their own purposes (which probably makes
		1371	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1372	C<__proto__> property name for its own purposes.
977		1373
978	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1374	If that is a problem, you could parse try to filter the resulting JSON
979	which is not a valid JSON text.	1375	output for these property strings, e.g.:
980		1376
981	Unmaintained (maintainer unresponsive for many months, bugs are not	1377	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
982	getting fixed).
983		1378
984	=item JSON::Syck 0.21	1379	This works because C<__proto__> is not valid outside of strings, so every
		1380	occurrence of C<"__proto__"\s*:> must be a string used as property name.
985		1381
986	Very buggy (often crashes).	1382	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		1383
1031		1384
1032	=head2 JSON and YAML	1385	=head2 JSON and YAML
1033		1386
1034	You often hear that JSON is a subset of YAML. This is, however, a mass	1387	You often hear that JSON is a subset of YAML. This is, however, a mass
…		…
1044	my $yaml = $to_yaml->encode ($ref) . "\n";	1397	my $yaml = $to_yaml->encode ($ref) . "\n";
1045		1398
1046	This will I<usually> generate JSON texts that also parse as valid	1399	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	1400	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	1401	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	1402	unicode character escape syntax, so you should make sure that your hash
1050	noticeably shorter than the 1024 "stream characters" YAML allows and that	1403	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1051	you do not have characters with codepoint values outside the Unicode BMP	1404	and that you do not have characters with codepoint values outside the
1052	(basic multilingual page). YAML also does not allow C<\/> sequences in	1405	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1053	strings (which JSON::XS does not I<currently> generate, but other JSON	1406	sequences in strings (which JSON::XS does not I<currently> generate, but
1054	generators might).	1407	other JSON generators might).
1055		1408
1056	There might be other incompatibilities that I am not aware of (or the YAML	1409	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	1410	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	1411	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	1412	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	1431	that difficult or long) and finally make YAML compatible to it, and
1079	educating users about the changes, instead of spreading lies about the	1432	educating users about the changes, instead of spreading lies about the
1080	real compatibility for many I<years> and trying to silence people who	1433	real compatibility for many I<years> and trying to silence people who
1081	point out that it isn't true.	1434	point out that it isn't true.
1082		1435
		1436	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1437	though the incompatibilities have been documented (and are known to Brian)
		1438	for many years and the spec makes explicit claims that YAML is a superset
		1439	of JSON. It would be so easy to fix, but apparently, bullying people and
		1440	corrupting userdata is so much easier.
		1441
1083	=back	1442	=back
1084		1443
1085		1444
1086	=head2 SPEED	1445	=head2 SPEED
1087		1446
…		…
1092		1451
1093	First comes a comparison between various modules using	1452	First comes a comparison between various modules using
1094	a very short single-line JSON string (also available at	1453	a very short single-line JSON string (also available at
1095	L<http://dist.schmorp.de/misc/json/short.json>).	1454	L<http://dist.schmorp.de/misc/json/short.json>).
1096		1455
1097	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1456	{"method": "handleMessage", "params": ["user1",
1098	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1457	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1458	1, 0]}
1099		1459
1100	It shows the number of encodes/decodes per second (JSON::XS uses	1460	It shows the number of encodes/decodes per second (JSON::XS uses
1101	the functional interface, while JSON::XS/2 uses the OO interface	1461	the functional interface, while JSON::XS/2 uses the OO interface
1102	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1462	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1103	shrink). Higher is better:	1463	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1464	uses the from_json method). Higher is better:
1104		1465
1105	module \| encode \| decode \|	1466	module \| encode \| decode \|
1106	-----------\|------------\|------------\|	1467	--------------\|------------\|------------\|
1107	JSON 1.x \| 4990.842 \| 4088.813 \|	1468	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1108	JSON::DWIW \| 51653.990 \| 71575.154 \|	1469	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1109	JSON::PC \| 65948.176 \| 74631.744 \|	1470	JSON::PP \| 15827.562 \| 6638.658 \|
1110	JSON::PP \| 8931.652 \| 3817.168 \|	1471	JSON::Syck \| 63358.066 \| 47662.545 \|
1111	JSON::Syck \| 24877.248 \| 27776.848 \|	1472	JSON::XS \| 511500.488 \| 511500.488 \|
1112	JSON::XS \| 388361.481 \| 227951.304 \|	1473	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1113	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1474	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1114	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1475	Storable \| 66788.280 \| 265462.278 \|
1115	Storable \| 16500.016 \| 135300.129 \|
1116	-----------+------------+------------+	1476	--------------+------------+------------+
1117		1477
1118	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1478	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	1479	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	1480	faster than JSON's pure perl implementation. It also compares favourably
1121	favourably to Storable for small amounts of data.	1481	to Storable for small amounts of data.
1122		1482
1123	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1483	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1124	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1484	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1125		1485
1126	module \| encode \| decode \|	1486	module \| encode \| decode \|
1127	-----------\|------------\|------------\|	1487	--------------\|------------\|------------\|
1128	JSON 1.x \| 55.260 \| 34.971 \|	1488	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1129	JSON::DWIW \| 825.228 \| 1082.513 \|	1489	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1130	JSON::PC \| 3571.444 \| 2394.829 \|
1131	JSON::PP \| 210.987 \| 32.574 \|	1490	JSON::PP \| 400.640 \| 62.311 \|
1132	JSON::Syck \| 552.551 \| 787.544 \|	1491	JSON::Syck \| 1481.040 \| 1524.869 \|
1133	JSON::XS \| 5780.463 \| 4854.519 \|	1492	JSON::XS \| 20661.596 \| 9541.183 \|
1134	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1493	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1135	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1494	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1136	Storable \| 4445.002 \| 5235.027 \|	1495	Storable \| 19765.806 \| 10000.725 \|
1137	-----------+------------+------------+	1496	--------------+------------+------------+
1138		1497
1139	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1498	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1140	decodes faster).	1499	decodes a bit faster).
1141		1500
1142	On large strings containing lots of high Unicode characters, some modules	1501	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	1502	(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	1503	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	1504	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	1540	information you might want to make sure that exceptions thrown by JSON::XS
1182	will not end up in front of untrusted eyes.	1541	will not end up in front of untrusted eyes.
1183		1542
1184	If you are using JSON::XS to return packets to consumption	1543	If you are using JSON::XS to return packets to consumption
1185	by JavaScript scripts in a browser you should have a look at	1544	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	1545	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	1546	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	1547	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	1548	it, as major browser developers care only for features, not about getting
1190	right).	1549	security right).
		1550
		1551
		1552	=head1 INTEROPERABILITY WITH OTHER MODULES
		1553
		1554	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1555	constants. That means that the JSON true and false values will be
		1556	comaptible to true and false values of iother modules that do the same,
		1557	such as L<JSON::PP> and L<CBOR::XS>.
1191		1558
1192		1559
1193	=head1 THREADS	1560	=head1 THREADS
1194		1561
1195	This module is I<not> guaranteed to be thread safe and there are no	1562	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).	1565	process simulations - use fork, it's I<much> faster, cheaper, better).
1199		1566
1200	(It might actually work, but you have been warned).	1567	(It might actually work, but you have been warned).
1201		1568
1202		1569
		1570	=head1 THE PERILS OF SETLOCALE
		1571
		1572	Sometimes people avoid the Perl locale support and directly call the
		1573	system's setlocale function with C<LC_ALL>.
		1574
		1575	This breaks both perl and modules such as JSON::XS, as stringification of
		1576	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1577	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1578	perl to stringify numbers).
		1579
		1580	The solution is simple: don't call C<setlocale>, or use it for only those
		1581	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1582
		1583	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1584	actually needs it (avoiding stringification of numbers), and restore it
		1585	afterwards.
		1586
		1587
1203	=head1 BUGS	1588	=head1 BUGS
1204		1589
1205	While the goal of this module is to be correct, that unfortunately does	1590	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	1591	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	1592	keep reporting bugs they will be fixed swiftly, though.
1208	will be fixed swiftly, though.
1209		1593
1210	Please refrain from using rt.cpan.org or any other bug reporting	1594	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.	1595	service. I put the contact address into my modules for a reason.
1212		1596
1213	=cut	1597	=cut
1214		1598
1215	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1599	BEGIN {
1216	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1600	*true = \$Types::Serialiser::true;
		1601	*true = \&Types::Serialiser::true;
		1602	*false = \$Types::Serialiser::false;
		1603	*false = \&Types::Serialiser::false;
		1604	*is_bool = \&Types::Serialiser::is_bool;
1217		1605
1218	sub true() { $true }	1606	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	}	1607	}
1225		1608
1226	XSLoader::load "JSON::XS", $VERSION;	1609	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		1610
1238	=head1 SEE ALSO	1611	=head1 SEE ALSO
1239		1612
1240	The F<json_xs> command line utility for quick experiments.	1613	The F<json_xs> command line utility for quick experiments.
1241		1614
…		…
1244	Marc Lehmann <schmorp@schmorp.de>	1617	Marc Lehmann <schmorp@schmorp.de>
1245	http://home.schmorp.de/	1618	http://home.schmorp.de/
1246		1619
1247	=cut	1620	=cut
1248		1621
		1622	1
		1623

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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 1.148 by root, Tue Oct 29 00:19:45 2013 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 1.148 by root, Tue Oct 29 00:19:45 2013 UTC