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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC vs.
Revision 1.167 by root, Tue Aug 28 16:16:17 2018 UTC

…		…
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	overridden) with no overhead due to emulation (by inheriting 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 it and
46	require a C compiler when that is a problem.	46	doesn't require a C compiler when that is a problem.
47		47
48	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
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
…		…
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 data types 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
…		…
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 object	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
…		…
101		99
102	=cut	100	=cut
103		101
104	package JSON::XS;	102	package JSON::XS;
105		103
106	no warnings;	104	use common::sense;
107	use strict;
108		105
109	our $VERSION = '2.2222';	106	our $VERSION = 3.04;
110	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
111		108
112	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
113
114	sub to_json($) {
115	require Carp;
116	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");
117	}
118
119	sub from_json($) {
120	require Carp;
121	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");
122	}
123		110
124	use Exporter;	111	use Exporter;
125	use XSLoader;	112	use XSLoader;
126		113
		114	use Types::Serialiser ();
		115
127	=head1 FUNCTIONAL INTERFACE	116	=head1 FUNCTIONAL INTERFACE
128		117
129	The following convenience methods are provided by this module. They are	118	The following convenience methods are provided by this module. They are
130	exported by default:	119	exported by default:
131		120
…		…
142		131
143	Except being faster.	132	Except being faster.
144		133
145	=item $perl_scalar = decode_json $json_text	134	=item $perl_scalar = decode_json $json_text
146		135
147	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	136	The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries
148	to parse that as an UTF-8 encoded JSON text, returning the resulting	137	to parse that as a UTF-8 encoded JSON text, returning the resulting
149	reference. Croaks on error.	138	reference. Croaks on error.
150		139
151	This function call is functionally identical to:	140	This function call is functionally identical to:
152		141
153	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	142	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
154		143
155	Except being faster.	144	Except being faster.
156
157	=item $is_boolean = JSON::XS::is_bool $scalar
158
159	Returns true if the passed scalar represents either JSON::XS::true or
160	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
161	and are used to represent JSON C<true> and C<false> values in Perl.
162
163	See MAPPING, below, for more information on how JSON values are mapped to
164	Perl.
165		145
166	=back	146	=back
167		147
168		148
169	=head1 A FEW NOTES ON UNICODE AND PERL	149	=head1 A FEW NOTES ON UNICODE AND PERL
…		…
290		270
291	=item $enabled = $json->get_utf8	271	=item $enabled = $json->get_utf8
292		272
293	If C<$enable> is true (or missing), then the C<encode> method will encode	273	If C<$enable> is true (or missing), then the C<encode> method will encode
294	the JSON result into UTF-8, as required by many protocols, while the	274	the JSON result into UTF-8, as required by many protocols, while the
295	C<decode> method expects to be handled an UTF-8-encoded string. Please	275	C<decode> method expects to be handed a UTF-8-encoded string. Please
296	note that UTF-8-encoded strings do not contain any characters outside the	276	note that UTF-8-encoded strings do not contain any characters outside the
297	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	277	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
298	versions, enabling this option might enable autodetection of the UTF-16	278	versions, enabling this option might enable autodetection of the UTF-16
299	and UTF-32 encoding families, as described in RFC4627.	279	and UTF-32 encoding families, as described in RFC4627.
300		280
…		…
385		365
386	=item $enabled = $json->get_relaxed	366	=item $enabled = $json->get_relaxed
387		367
388	If C<$enable> is true (or missing), then C<decode> will accept some	368	If C<$enable> is true (or missing), then C<decode> will accept some
389	extensions to normal JSON syntax (see below). C<encode> will not be	369	extensions to normal JSON syntax (see below). C<encode> will not be
390	affected in anyway. I<Be aware that this option makes you accept invalid	370	affected in any way. I<Be aware that this option makes you accept invalid
391	JSON texts as if they were valid!>. I suggest only to use this option to	371	JSON texts as if they were valid!>. I suggest only to use this option to
392	parse application-specific files written by humans (configuration files,	372	parse application-specific files written by humans (configuration files,
393	resource files etc.)	373	resource files etc.)
394		374
395	If C<$enable> is false (the default), then C<decode> will only accept	375	If C<$enable> is false (the default), then C<decode> will only accept
…		…
424	[	404	[
425	1, # this comment not allowed in JSON	405	1, # this comment not allowed in JSON
426	# neither this one...	406	# neither this one...
427	]	407	]
428		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
429	=back	419	=back
430		420
431	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
432		422
433	=item $enabled = $json->get_canonical	423	=item $enabled = $json->get_canonical
…		…
435	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
436	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
437		427
438	If C<$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
439	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
440	of the same script).	430	of the same script, and can change even within the same run from 5.18
		431	onwards).
441		432
442	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
443	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,
444	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,
445	as key-value pairs have no inherent ordering in Perl.	436	as key-value pairs have no inherent ordering in Perl.
446		437
447	This setting has no effect when decoding JSON texts.	438	This setting has no effect when decoding JSON texts.
		439
		440	This setting has currently no effect on tied hashes.
448		441
449	=item $json = $json->allow_nonref ([$enable])	442	=item $json = $json->allow_nonref ([$enable])
450		443
451	=item $enabled = $json->get_allow_nonref	444	=item $enabled = $json->get_allow_nonref
452		445
…		…
484		477
485	=item $json = $json->allow_blessed ([$enable])	478	=item $json = $json->allow_blessed ([$enable])
486		479
487	=item $enabled = $json->get_allow_blessed	480	=item $enabled = $json->get_allow_blessed
488		481
		482	See L<OBJECT SERIALISATION> for details.
		483
489	If C<$enable> is true (or missing), then the C<encode> method will not	484	If C<$enable> is true (or missing), then the C<encode> method will not
490	barf when it encounters a blessed reference. Instead, the value of the	485	barf when it encounters a blessed reference that it cannot convert
491	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	486	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
492	disabled or no C<TO_JSON> method found) or a representation of the
493	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
494	encoded. Has no effect on C<decode>.
495		487
496	If C<$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
497	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>.
498		493
499	=item $json = $json->convert_blessed ([$enable])	494	=item $json = $json->convert_blessed ([$enable])
500		495
501	=item $enabled = $json->get_convert_blessed	496	=item $enabled = $json->get_convert_blessed
		497
		498	See L<OBJECT SERIALISATION> for details.
502		499
503	If C<$enable> is true (or missing), then C<encode>, upon encountering a	500	If C<$enable> is true (or missing), then C<encode>, upon encountering a
504	blessed object, will check for the availability of the C<TO_JSON> method	501	blessed object, will check for the availability of the C<TO_JSON> method
505	on the object's class. If found, it will be called in scalar context	502	on the object's class. If found, it will be called in scalar context and
506	and the resulting scalar will be encoded instead of the object. If no	503	the resulting scalar will be encoded instead of the object.
507	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
508	to do.
509		504
510	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	505	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
511	returns other blessed objects, those will be handled in the same	506	returns other blessed objects, those will be handled in the same
512	way. C<TO_JSON> must take care of not causing an endless recursion cycle	507	way. C<TO_JSON> must take care of not causing an endless recursion cycle
513	(== crash) in this case. The name of C<TO_JSON> was chosen because other	508	(== crash) in this case. The name of C<TO_JSON> was chosen because other
514	methods called by the Perl core (== not by the user of the object) are	509	methods called by the Perl core (== not by the user of the object) are
515	usually in upper case letters and to avoid collisions with any C<to_json>	510	usually in upper case letters and to avoid collisions with any C<to_json>
516	function or method.	511	function or method.
517		512
518	This setting does not yet influence C<decode> in any way, but in the	513	If C<$enable> is false (the default), then C<encode> will not consider
519	future, global hooks might get installed that influence C<decode> and are	514	this type of conversion.
520	enabled by this setting.
521		515
522	If C<$enable> is false, then the C<allow_blessed> setting will decide what	516	This setting has no effect on C<decode>.
523	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.
524		535
525	=item $json = $json->filter_json_object ([$coderef->($hashref)])	536	=item $json = $json->filter_json_object ([$coderef->($hashref)])
526		537
527	When C<$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
528	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
…		…
667		678
668	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.
669		680
670	=item $json_text = $json->encode ($perl_scalar)	681	=item $json_text = $json->encode ($perl_scalar)
671		682
672	Converts the given Perl data structure (a simple scalar or a reference	683	Converts the given Perl value or data structure to its JSON
673	to a hash or array) to its JSON representation. Simple scalars will be	684	representation. Croaks on error.
674	converted into JSON string or number sequences, while references to arrays
675	become JSON arrays and references to hashes become JSON objects. Undefined
676	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
677	nor C<false> values will be generated.
678		685
679	=item $perl_scalar = $json->decode ($json_text)	686	=item $perl_scalar = $json->decode ($json_text)
680		687
681	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,
682	returning the resulting simple scalar or reference. Croaks on error.	689	returning the resulting simple scalar or reference. Croaks on error.
683
684	JSON numbers and strings become simple Perl scalars. JSON arrays become
685	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
686	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
687		690
688	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	691	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
689		692
690	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
691	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
692	silently stop parsing there and return the number of characters consumed	695	silently stop parsing there and return the number of characters consumed
693	so far.	696	so far.
694		697
695	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
696	(which is not the brightest thing to do in the first place) and you need
697	to know where the JSON text ends.	699	and you need to know where the JSON text ends.
698		700
699	JSON::XS->new->decode_prefix ("[1] the tail")	701	JSON::XS->new->decode_prefix ("[1] the tail")
700	=> ([], 3)	702	=> ([1], 3)
701		703
702	=back	704	=back
703		705
704		706
705	=head1 INCREMENTAL PARSING	707	=head1 INCREMENTAL PARSING
…		…
714	calls).	716	calls).
715		717
716	JSON::XS will only attempt to parse the JSON text once it is sure it	718	JSON::XS will only attempt to parse the JSON text once it is sure it
717	has enough text to get a decisive result, using a very simple but	719	has enough text to get a decisive result, using a very simple but
718	truly incremental parser. This means that it sometimes won't stop as	720	truly incremental parser. This means that it sometimes won't stop as
719	early as the full parser, for example, it doesn't detect parenthese	721	early as the full parser, for example, it doesn't detect mismatched
720	mismatches. The only thing it guarantees is that it starts decoding as	722	parentheses. The only thing it guarantees is that it starts decoding as
721	soon as a syntactically valid JSON text has been seen. This means you need	723	soon as a syntactically valid JSON text has been seen. This means you need
722	to set resource limits (e.g. C<max_size>) to ensure the parser will stop	724	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
723	parsing in the presence if syntax errors.	725	parsing in the presence if syntax errors.
724		726
725	The following methods implement this incremental parser.	727	The following methods implement this incremental parser.
…		…
741		743
742	If the method is called in scalar context, then it will try to extract	744	If the method is called in scalar context, then it will try to extract
743	exactly I<one> JSON object. If that is successful, it will return this	745	exactly I<one> JSON object. If that is successful, it will return this
744	object, otherwise it will return C<undef>. If there is a parse error,	746	object, otherwise it will return C<undef>. If there is a parse error,
745	this method will croak just as C<decode> would do (one can then use	747	this method will croak just as C<decode> would do (one can then use
746	C<incr_skip> to skip the errornous part). This is the most common way of	748	C<incr_skip> to skip the erroneous part). This is the most common way of
747	using the method.	749	using the method.
748		750
749	And finally, in list context, it will try to extract as many objects	751	And finally, in list context, it will try to extract as many objects
750	from the stream as it can find and return them, or the empty list	752	from the stream as it can find and return them, or the empty list
751	otherwise. For this to work, there must be no separators between the JSON	753	otherwise. For this to work, there must be no separators (other than
752	objects or arrays, instead they must be concatenated back-to-back. If	754	whitespace) between the JSON objects or arrays, instead they must be
753	an error occurs, an exception will be raised as in the scalar context	755	concatenated back-to-back. If an error occurs, an exception will be
754	case. Note that in this case, any previously-parsed JSON texts will be	756	raised as in the scalar context case. Note that in this case, any
755	lost.	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]");
756		763
757	=item $lvalue_string = $json->incr_text	764	=item $lvalue_string = $json->incr_text
758		765
759	This method returns the currently stored JSON fragment as an lvalue, that	766	This method returns the currently stored JSON fragment as an lvalue, that
760	is, you can manipulate it. This I<only> works when a preceding call to	767	is, you can manipulate it. This I<only> works when a preceding call to
…		…
762	all other circumstances you must not call this function (I mean it.	769	all other circumstances you must not call this function (I mean it.
763	although in simple tests it might actually work, it I<will> fail under	770	although in simple tests it might actually work, it I<will> fail under
764	real world conditions). As a special exception, you can also call this	771	real world conditions). As a special exception, you can also call this
765	method before having parsed anything.	772	method before having parsed anything.
766		773
		774	That means you can only use this function to look at or manipulate text
		775	before or after complete JSON objects, not while the parser is in the
		776	middle of parsing a JSON object.
		777
767	This function is useful in two cases: a) finding the trailing text after a	778	This function is useful in two cases: a) finding the trailing text after a
768	JSON object or b) parsing multiple JSON objects separated by non-JSON text	779	JSON object or b) parsing multiple JSON objects separated by non-JSON text
769	(such as commas).	780	(such as commas).
770		781
771	=item $json->incr_skip	782	=item $json->incr_skip
772		783
773	This will reset the state of the incremental parser and will remove the	784	This will reset the state of the incremental parser and will remove
774	parsed text from the input buffer. This is useful after C<incr_parse>	785	the parsed text from the input buffer so far. This is useful after
775	died, in which case the input buffer and incremental parser state is left	786	C<incr_parse> died, in which case the input buffer and incremental parser
776	unchanged, to skip the text parsed so far and to reset the parse state.	787	state is left unchanged, to skip the text parsed so far and to reset the
		788	parse state.
		789
		790	The difference to C<incr_reset> is that only text until the parse error
		791	occurred is removed.
777		792
778	=item $json->incr_reset	793	=item $json->incr_reset
779		794
780	This completely resets the incremental parser, that is, after this call,	795	This completely resets the incremental parser, that is, after this call,
781	it will be as if the parser had never parsed anything.	796	it will be as if the parser had never parsed anything.
782		797
783	This is useful if you want ot repeatedly parse JSON objects and want to	798	This is useful if you want to repeatedly parse JSON objects and want to
784	ignore any trailing data, which means you have to reset the parser after	799	ignore any trailing data, which means you have to reset the parser after
785	each successful decode.	800	each successful decode.
786		801
787	=back	802	=back
788		803
789	=head2 LIMITATIONS	804	=head2 LIMITATIONS
790		805
791	All options that affect decoding are supported, except	806	All options that affect decoding are supported, except
792	C<allow_nonref>. The reason for this is that it cannot be made to	807	C<allow_nonref>. The reason for this is that it cannot be made to work
793	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate	808	sensibly: JSON objects and arrays are self-delimited, i.e. you can
794	them back to back and still decode them perfectly. This does not hold true	809	concatenate them back to back and still decode them perfectly. This does
795	for JSON numbers, however.	810	not hold true for JSON numbers, however.
796		811
797	For example, is the string C<1> a single JSON number, or is it simply the	812	For example, is the string C<1> a single JSON number, or is it simply the
798	start of C<12>? Or is C<12> a single JSON number, or the concatenation	813	start of C<12>? Or is C<12> a single JSON number, or the concatenation
799	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS	814	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
800	takes the conservative route and disallows this case.	815	takes the conservative route and disallows this case.
…		…
979	If the number consists of digits only, JSON::XS will try to represent	994	If the number consists of digits only, JSON::XS will try to represent
980	it as an integer value. If that fails, it will try to represent it as	995	it as an integer value. If that fails, it will try to represent it as
981	a numeric (floating point) value if that is possible without loss of	996	a numeric (floating point) value if that is possible without loss of
982	precision. Otherwise it will preserve the number as a string value (in	997	precision. Otherwise it will preserve the number as a string value (in
983	which case you lose roundtripping ability, as the JSON number will be	998	which case you lose roundtripping ability, as the JSON number will be
984	re-encoded toa JSON string).	999	re-encoded to a JSON string).
985		1000
986	Numbers containing a fractional or exponential part will always be	1001	Numbers containing a fractional or exponential part will always be
987	represented as numeric (floating point) values, possibly at a loss of	1002	represented as numeric (floating point) values, possibly at a loss of
988	precision (in which case you might lose perfect roundtripping ability, but	1003	precision (in which case you might lose perfect roundtripping ability, but
989	the JSON number will still be re-encoded as a JSON number).	1004	the JSON number will still be re-encoded as a JSON number).
990		1005
		1006	Note that precision is not accuracy - binary floating point values cannot
		1007	represent most decimal fractions exactly, and when converting from and to
		1008	floating point, JSON::XS only guarantees precision up to but not including
		1009	the least significant bit.
		1010
991	=item true, false	1011	=item true, false
992		1012
993	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1013	These JSON atoms become C<Types::Serialiser::true> and
994	respectively. They are overloaded to act almost exactly like the numbers	1014	C<Types::Serialiser::false>, respectively. They are overloaded to act
995	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1015	almost exactly like the numbers C<1> and C<0>. You can check whether
996	the C<JSON::XS::is_bool> function.	1016	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1017	function (after C<use Types::Serialier>, of course).
997		1018
998	=item null	1019	=item null
999		1020
1000	A JSON null atom becomes C<undef> in Perl.	1021	A JSON null atom becomes C<undef> in Perl.
		1022
		1023	=item shell-style comments (C<< # I<text> >>)
		1024
		1025	As a nonstandard extension to the JSON syntax that is enabled by the
		1026	C<relaxed> setting, shell-style comments are allowed. They can start
		1027	anywhere outside strings and go till the end of the line.
		1028
		1029	=item tagged values (C<< (I<tag>)I<value> >>).
		1030
		1031	Another nonstandard extension to the JSON syntax, enabled with the
		1032	C<allow_tags> setting, are tagged values. In this implementation, the
		1033	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1034	I<value> must be a JSON array encoding optional constructor arguments.
		1035
		1036	See L<OBJECT SERIALISATION>, below, for details.
1001		1037
1002	=back	1038	=back
1003		1039
1004		1040
1005	=head2 PERL -> JSON	1041	=head2 PERL -> JSON
…		…
1010		1046
1011	=over 4	1047	=over 4
1012		1048
1013	=item hash references	1049	=item hash references
1014		1050
1015	Perl hash references become JSON objects. As there is no inherent ordering	1051	Perl hash references become JSON objects. As there is no inherent
1016	in hash keys (or JSON objects), they will usually be encoded in a	1052	ordering in hash keys (or JSON objects), they will usually be encoded
1017	pseudo-random order that can change between runs of the same program but	1053	in a pseudo-random order. JSON::XS can optionally sort the hash keys
1018	stays generally the same within a single run of a program. JSON::XS can	1054	(determined by the I<canonical> flag), so the same datastructure will
1019	optionally sort the hash keys (determined by the I<canonical> flag), so	1055	serialise to the same JSON text (given same settings and version of
1020	the same datastructure will serialise to the same JSON text (given same	1056	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1021	settings and version of JSON::XS), but this incurs a runtime overhead	1057	e.g. when you want to compare some JSON text against another for equality.
1022	and is only rarely useful, e.g. when you want to compare some JSON text
1023	against another for equality.
1024		1058
1025	=item array references	1059	=item array references
1026		1060
1027	Perl array references become JSON arrays.	1061	Perl array references become JSON arrays.
1028		1062
1029	=item other references	1063	=item other references
1030		1064
1031	Other unblessed references are generally not allowed and will cause an	1065	Other unblessed references are generally not allowed and will cause an
1032	exception to be thrown, except for references to the integers C<0> and	1066	exception to be thrown, except for references to the integers C<0> and
1033	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1067	C<1>, which get turned into C<false> and C<true> atoms in JSON.
1034	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1035		1068
		1069	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1070	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1071	and C<Types::Serialiser::true> to improve readability.
		1072
		1073	use Types::Serialiser;
1036	encode_json [\0, JSON::XS::true] # yields [false,true]	1074	encode_json [\0, Types::Serialiser::true] # yields [false,true]
1037		1075
1038	=item JSON::XS::true, JSON::XS::false	1076	=item Types::Serialiser::true, Types::Serialiser::false
1039		1077
1040	These special values become JSON true and JSON false values,	1078	These special values from the L<Types::Serialiser> module become JSON true
1041	respectively. You can also use C<\1> and C<\0> directly if you want.	1079	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1080	directly if you want.
1042		1081
1043	=item blessed objects	1082	=item blessed objects
1044		1083
1045	Blessed objects are not directly representable in JSON. See the	1084	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1046	C<allow_blessed> and C<convert_blessed> methods on various options on	1085	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1047	how to deal with this: basically, you can choose between throwing an	1086	below, for details.
1048	exception, encoding the reference as if it weren't blessed, or provide
1049	your own serialiser method.
1050		1087
1051	=item simple scalars	1088	=item simple scalars
1052		1089
1053	Simple Perl scalars (any scalar that is not a reference) are the most	1090	Simple Perl scalars (any scalar that is not a reference) are the most
1054	difficult objects to encode: JSON::XS will encode undefined scalars as	1091	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1082		1119
1083	You can not currently force the type in other, less obscure, ways. Tell me	1120	You can not currently force the type in other, less obscure, ways. Tell me
1084	if you need this capability (but don't forget to explain why it's needed	1121	if you need this capability (but don't forget to explain why it's needed
1085	:).	1122	:).
1086		1123
		1124	Note that numerical precision has the same meaning as under Perl (so
		1125	binary to decimal conversion follows the same rules as in Perl, which
		1126	can differ to other languages). Also, your perl interpreter might expose
		1127	extensions to the floating point numbers of your platform, such as
		1128	infinities or NaN's - these cannot be represented in JSON, and it is an
		1129	error to pass those in.
		1130
1087	=back	1131	=back
		1132
		1133	=head2 OBJECT SERIALISATION
		1134
		1135	As JSON cannot directly represent Perl objects, you have to choose between
		1136	a pure JSON representation (without the ability to deserialise the object
		1137	automatically again), and a nonstandard extension to the JSON syntax,
		1138	tagged values.
		1139
		1140	=head3 SERIALISATION
		1141
		1142	What happens when C<JSON::XS> encounters a Perl object depends on the
		1143	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1144	used in this order:
		1145
		1146	=over 4
		1147
		1148	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1149
		1150	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1151	serialisation protocol to create a tagged JSON value, using a nonstandard
		1152	extension to the JSON syntax.
		1153
		1154	This works by invoking the C<FREEZE> method on the object, with the first
		1155	argument being the object to serialise, and the second argument being the
		1156	constant string C<JSON> to distinguish it from other serialisers.
		1157
		1158	The C<FREEZE> method can return any number of values (i.e. zero or
		1159	more). These values and the paclkage/classname of the object will then be
		1160	encoded as a tagged JSON value in the following format:
		1161
		1162	("classname")[FREEZE return values...]
		1163
		1164	e.g.:
		1165
		1166	("URI")["http://www.google.com/"]
		1167	("MyDate")[2013,10,29]
		1168	("ImageData::JPEG")["Z3...VlCg=="]
		1169
		1170	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1171	objects C<type> and C<id> members to encode the object:
		1172
		1173	sub My::Object::FREEZE {
		1174	my ($self, $serialiser) = @_;
		1175
		1176	($self->{type}, $self->{id})
		1177	}
		1178
		1179	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1180
		1181	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1182	context. It must return a single scalar that can be directly encoded into
		1183	JSON. This scalar replaces the object in the JSON text.
		1184
		1185	For example, the following C<TO_JSON> method will convert all L<URI>
		1186	objects to JSON strings when serialised. The fatc that these values
		1187	originally were L<URI> objects is lost.
		1188
		1189	sub URI::TO_JSON {
		1190	my ($uri) = @_;
		1191	$uri->as_string
		1192	}
		1193
		1194	=item 3. C<allow_blessed> is enabled.
		1195
		1196	The object will be serialised as a JSON null value.
		1197
		1198	=item 4. none of the above
		1199
		1200	If none of the settings are enabled or the respective methods are missing,
		1201	C<JSON::XS> throws an exception.
		1202
		1203	=back
		1204
		1205	=head3 DESERIALISATION
		1206
		1207	For deserialisation there are only two cases to consider: either
		1208	nonstandard tagging was used, in which case C<allow_tags> decides,
		1209	or objects cannot be automatically be deserialised, in which
		1210	case you can use postprocessing or the C<filter_json_object> or
		1211	C<filter_json_single_key_object> callbacks to get some real objects our of
		1212	your JSON.
		1213
		1214	This section only considers the tagged value case: I a tagged JSON object
		1215	is encountered during decoding and C<allow_tags> is disabled, a parse
		1216	error will result (as if tagged values were not part of the grammar).
		1217
		1218	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1219	of the package/classname used during serialisation (it will not attempt
		1220	to load the package as a Perl module). If there is no such method, the
		1221	decoding will fail with an error.
		1222
		1223	Otherwise, the C<THAW> method is invoked with the classname as first
		1224	argument, the constant string C<JSON> as second argument, and all the
		1225	values from the JSON array (the values originally returned by the
		1226	C<FREEZE> method) as remaining arguments.
		1227
		1228	The method must then return the object. While technically you can return
		1229	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1230	make that work in all cases, so better return an actual blessed reference.
		1231
		1232	As an example, let's implement a C<THAW> function that regenerates the
		1233	C<My::Object> from the C<FREEZE> example earlier:
		1234
		1235	sub My::Object::THAW {
		1236	my ($class, $serialiser, $type, $id) = @_;
		1237
		1238	$class->new (type => $type, id => $id)
		1239	}
1088		1240
1089		1241
1090	=head1 ENCODING/CODESET FLAG NOTES	1242	=head1 ENCODING/CODESET FLAG NOTES
1091		1243
1092	The interested reader might have seen a number of flags that signify	1244	The interested reader might have seen a number of flags that signify
…		…
1117	=item C<utf8> flag disabled	1269	=item C<utf8> flag disabled
1118		1270
1119	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1271	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1120	and expect Unicode strings, that is, characters with high ordinal Unicode	1272	and expect Unicode strings, that is, characters with high ordinal Unicode
1121	values (> 255) will be encoded as such characters, and likewise such	1273	values (> 255) will be encoded as such characters, and likewise such
1122	characters are decoded as-is, no canges to them will be done, except	1274	characters are decoded as-is, no changes to them will be done, except
1123	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1275	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1124	respectively (to Perl, these are the same thing in strings unless you do	1276	respectively (to Perl, these are the same thing in strings unless you do
1125	funny/weird/dumb stuff).	1277	funny/weird/dumb stuff).
1126		1278
1127	This is useful when you want to do the encoding yourself (e.g. when you	1279	This is useful when you want to do the encoding yourself (e.g. when you
…		…
1137	expect your input strings to be encoded as UTF-8, that is, no "character"	1289	expect your input strings to be encoded as UTF-8, that is, no "character"
1138	of the input string must have any value > 255, as UTF-8 does not allow	1290	of the input string must have any value > 255, as UTF-8 does not allow
1139	that.	1291	that.
1140		1292
1141	The C<utf8> flag therefore switches between two modes: disabled means you	1293	The C<utf8> flag therefore switches between two modes: disabled means you
1142	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded	1294	will get a Unicode string in Perl, enabled means you get a UTF-8 encoded
1143	octet/binary string in Perl.	1295	octet/binary string in Perl.
1144		1296
1145	=item C<latin1> or C<ascii> flags enabled	1297	=item C<latin1> or C<ascii> flags enabled
1146		1298
1147	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters	1299	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
…		…
1183	proper subset of most 8-bit and multibyte encodings in use in the world.	1335	proper subset of most 8-bit and multibyte encodings in use in the world.
1184		1336
1185	=back	1337	=back
1186		1338
1187		1339
		1340	=head2 JSON and ECMAscript
		1341
		1342	JSON syntax is based on how literals are represented in javascript (the
		1343	not-standardised predecessor of ECMAscript) which is presumably why it is
		1344	called "JavaScript Object Notation".
		1345
		1346	However, JSON is not a subset (and also not a superset of course) of
		1347	ECMAscript (the standard) or javascript (whatever browsers actually
		1348	implement).
		1349
		1350	If you want to use javascript's C<eval> function to "parse" JSON, you
		1351	might run into parse errors for valid JSON texts, or the resulting data
		1352	structure might not be queryable:
		1353
		1354	One of the problems is that U+2028 and U+2029 are valid characters inside
		1355	JSON strings, but are not allowed in ECMAscript string literals, so the
		1356	following Perl fragment will not output something that can be guaranteed
		1357	to be parsable by javascript's C<eval>:
		1358
		1359	use JSON::XS;
		1360
		1361	print encode_json [chr 0x2028];
		1362
		1363	The right fix for this is to use a proper JSON parser in your javascript
		1364	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1365	F<json2.js> parser).
		1366
		1367	If this is not an option, you can, as a stop-gap measure, simply encode to
		1368	ASCII-only JSON:
		1369
		1370	use JSON::XS;
		1371
		1372	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1373
		1374	Note that this will enlarge the resulting JSON text quite a bit if you
		1375	have many non-ASCII characters. You might be tempted to run some regexes
		1376	to only escape U+2028 and U+2029, e.g.:
		1377
		1378	# DO NOT USE THIS!
		1379	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1380	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1381	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1382	print $json;
		1383
		1384	Note that I<this is a bad idea>: the above only works for U+2028 and
		1385	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1386	javascript implementations, however, have issues with other characters as
		1387	well - using C<eval> naively simply I<will> cause problems.
		1388
		1389	Another problem is that some javascript implementations reserve
		1390	some property names for their own purposes (which probably makes
		1391	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1392	C<__proto__> property name for its own purposes.
		1393
		1394	If that is a problem, you could parse try to filter the resulting JSON
		1395	output for these property strings, e.g.:
		1396
		1397	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1398
		1399	This works because C<__proto__> is not valid outside of strings, so every
		1400	occurrence of C<"__proto__"\s*:> must be a string used as property name.
		1401
		1402	If you know of other incompatibilities, please let me know.
		1403
		1404
1188	=head2 JSON and YAML	1405	=head2 JSON and YAML
1189		1406
1190	You often hear that JSON is a subset of YAML. This is, however, a mass	1407	You often hear that JSON is a subset of YAML. This is, however, a mass
1191	hysteria(*) and very far from the truth (as of the time of this writing),	1408	hysteria(*) and very far from the truth (as of the time of this writing),
1192	so let me state it clearly: I<in general, there is no way to configure	1409	so let me state it clearly: I<in general, there is no way to configure
…		…
1200	my $yaml = $to_yaml->encode ($ref) . "\n";	1417	my $yaml = $to_yaml->encode ($ref) . "\n";
1201		1418
1202	This will I<usually> generate JSON texts that also parse as valid	1419	This will I<usually> generate JSON texts that also parse as valid
1203	YAML. Please note that YAML has hardcoded limits on (simple) object key	1420	YAML. Please note that YAML has hardcoded limits on (simple) object key
1204	lengths that JSON doesn't have and also has different and incompatible	1421	lengths that JSON doesn't have and also has different and incompatible
1205	unicode handling, so you should make sure that your hash keys are	1422	unicode character escape syntax, so you should make sure that your hash
1206	noticeably shorter than the 1024 "stream characters" YAML allows and that	1423	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1207	you do not have characters with codepoint values outside the Unicode BMP	1424	and that you do not have characters with codepoint values outside the
1208	(basic multilingual page). YAML also does not allow C<\/> sequences in	1425	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1209	strings (which JSON::XS does not I<currently> generate, but other JSON	1426	sequences in strings (which JSON::XS does not I<currently> generate, but
1210	generators might).	1427	other JSON generators might).
1211		1428
1212	There might be other incompatibilities that I am not aware of (or the YAML	1429	There might be other incompatibilities that I am not aware of (or the YAML
1213	specification has been changed yet again - it does so quite often). In	1430	specification has been changed yet again - it does so quite often). In
1214	general you should not try to generate YAML with a JSON generator or vice	1431	general you should not try to generate YAML with a JSON generator or vice
1215	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1432	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1234	that difficult or long) and finally make YAML compatible to it, and	1451	that difficult or long) and finally make YAML compatible to it, and
1235	educating users about the changes, instead of spreading lies about the	1452	educating users about the changes, instead of spreading lies about the
1236	real compatibility for many I<years> and trying to silence people who	1453	real compatibility for many I<years> and trying to silence people who
1237	point out that it isn't true.	1454	point out that it isn't true.
1238		1455
		1456	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1457	though the incompatibilities have been documented (and are known to Brian)
		1458	for many years and the spec makes explicit claims that YAML is a superset
		1459	of JSON. It would be so easy to fix, but apparently, bullying people and
		1460	corrupting userdata is so much easier.
		1461
1239	=back	1462	=back
1240		1463
1241		1464
1242	=head2 SPEED	1465	=head2 SPEED
1243		1466
…		…
1250	a very short single-line JSON string (also available at	1473	a very short single-line JSON string (also available at
1251	L<http://dist.schmorp.de/misc/json/short.json>).	1474	L<http://dist.schmorp.de/misc/json/short.json>).
1252		1475
1253	{"method": "handleMessage", "params": ["user1",	1476	{"method": "handleMessage", "params": ["user1",
1254	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,	1477	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1255	true, false]}	1478	1, 0]}
1256		1479
1257	It shows the number of encodes/decodes per second (JSON::XS uses	1480	It shows the number of encodes/decodes per second (JSON::XS uses
1258	the functional interface, while JSON::XS/2 uses the OO interface	1481	the functional interface, while JSON::XS/2 uses the OO interface
1259	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1482	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1260	shrink). Higher is better:	1483	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1484	uses the from_json method). Higher is better:
1261		1485
1262	module \| encode \| decode \|	1486	module \| encode \| decode \|
1263	-----------\|------------\|------------\|	1487	--------------\|------------\|------------\|
1264	JSON 1.x \| 4990.842 \| 4088.813 \|	1488	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1265	JSON::DWIW \| 51653.990 \| 71575.154 \|	1489	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1266	JSON::PC \| 65948.176 \| 74631.744 \|	1490	JSON::PP \| 15827.562 \| 6638.658 \|
1267	JSON::PP \| 8931.652 \| 3817.168 \|	1491	JSON::Syck \| 63358.066 \| 47662.545 \|
1268	JSON::Syck \| 24877.248 \| 27776.848 \|	1492	JSON::XS \| 511500.488 \| 511500.488 \|
1269	JSON::XS \| 388361.481 \| 227951.304 \|	1493	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1270	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1494	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1271	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1495	Storable \| 66788.280 \| 265462.278 \|
1272	Storable \| 16500.016 \| 135300.129 \|
1273	-----------+------------+------------+	1496	--------------+------------+------------+
1274		1497
1275	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1498	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1276	about three times faster on decoding, and over forty times faster	1499	about five times faster on decoding, and over thirty to seventy times
1277	than JSON, even with pretty-printing and key sorting. It also compares	1500	faster than JSON's pure perl implementation. It also compares favourably
1278	favourably to Storable for small amounts of data.	1501	to Storable for small amounts of data.
1279		1502
1280	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1503	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1281	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1504	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1282		1505
1283	module \| encode \| decode \|	1506	module \| encode \| decode \|
1284	-----------\|------------\|------------\|	1507	--------------\|------------\|------------\|
1285	JSON 1.x \| 55.260 \| 34.971 \|	1508	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1286	JSON::DWIW \| 825.228 \| 1082.513 \|	1509	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1287	JSON::PC \| 3571.444 \| 2394.829 \|
1288	JSON::PP \| 210.987 \| 32.574 \|	1510	JSON::PP \| 400.640 \| 62.311 \|
1289	JSON::Syck \| 552.551 \| 787.544 \|	1511	JSON::Syck \| 1481.040 \| 1524.869 \|
1290	JSON::XS \| 5780.463 \| 4854.519 \|	1512	JSON::XS \| 20661.596 \| 9541.183 \|
1291	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1513	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1292	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1514	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1293	Storable \| 4445.002 \| 5235.027 \|	1515	Storable \| 19765.806 \| 10000.725 \|
1294	-----------+------------+------------+	1516	--------------+------------+------------+
1295		1517
1296	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1518	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1297	decodes faster).	1519	decodes a bit faster).
1298		1520
1299	On large strings containing lots of high Unicode characters, some modules	1521	On large strings containing lots of high Unicode characters, some modules
1300	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1522	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1301	will be broken due to missing (or wrong) Unicode handling. Others refuse	1523	will be broken due to missing (or wrong) Unicode handling. Others refuse
1302	to decode or encode properly, so it was impossible to prepare a fair	1524	to decode or encode properly, so it was impossible to prepare a fair
…		…
1338	information you might want to make sure that exceptions thrown by JSON::XS	1560	information you might want to make sure that exceptions thrown by JSON::XS
1339	will not end up in front of untrusted eyes.	1561	will not end up in front of untrusted eyes.
1340		1562
1341	If you are using JSON::XS to return packets to consumption	1563	If you are using JSON::XS to return packets to consumption
1342	by JavaScript scripts in a browser you should have a look at	1564	by JavaScript scripts in a browser you should have a look at
1343	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1565	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1344	you are vulnerable to some common attack vectors (which really are browser	1566	see whether you are vulnerable to some common attack vectors (which really
1345	design bugs, but it is still you who will have to deal with it, as major	1567	are browser design bugs, but it is still you who will have to deal with
1346	browser developers care only for features, not about getting security	1568	it, as major browser developers care only for features, not about getting
1347	right).	1569	security right).
1348		1570
1349		1571
		1572	=head1 "OLD" VS. "NEW" JSON (RFC 4627 VS. RFC 7159)
		1573
		1574	TL;DR: Due to security concerns, JSON::XS will not allow scalar data in
		1575	JSON texts by default - you need to create your own JSON::XS object and
		1576	enable C<allow_nonref>:
		1577
		1578
		1579	my $json = JSON::XS->new->allow_nonref;
		1580
		1581	$text = $json->encode ($data);
		1582	$data = $json->decode ($text);
		1583
		1584	The long version: JSON being an important and supposedly stable format,
		1585	the IETF standardised it as RFC 4627 in 2006. Unfortunately, the inventor
		1586	of JSON, Dougles Crockford, unilaterally changed the definition of JSON in
		1587	javascript. Rather than create a fork, the IETF decided to standardise the
		1588	new syntax (apparently, so Iw as told, without finding it very amusing).
		1589
		1590	The biggest difference between thed original JSON and the new JSON is that
		1591	the new JSON supports scalars (anything other than arrays and objects) at
		1592	the toplevel of a JSON text. While this is strictly backwards compatible
		1593	to older versions, it breaks a number of protocols that relied on sending
		1594	JSON back-to-back, and is a minor security concern.
		1595
		1596	For example, imagine you have two banks communicating, and on one side,
		1597	trhe JSON coder gets upgraded. Two messages, such as C<10> and C<1000>
		1598	might then be confused to mean C<101000>, something that couldn't happen
		1599	in the original JSON, because niether of these messages would be valid
		1600	JSON.
		1601
		1602	If one side accepts these messages, then an upgrade in the coder on either
		1603	side could result in this becoming exploitable.
		1604
		1605	This module has always allowed these messages as an optional extension, by
		1606	default disabled. The security concerns are the reason why the default is
		1607	still disabled, but future versions might/will likely upgrade to the newer
		1608	RFC as default format, so you are advised to check your implementation
		1609	and/or override the default with C<< ->allow_nonref (0) >> to ensure that
		1610	future versions are safe.
		1611
		1612
		1613	=head1 INTEROPERABILITY WITH OTHER MODULES
		1614
		1615	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1616	constants. That means that the JSON true and false values will be
		1617	comaptible to true and false values of other modules that do the same,
		1618	such as L<JSON::PP> and L<CBOR::XS>.
		1619
		1620
		1621	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1622
		1623	As long as you only serialise data that can be directly expressed in JSON,
		1624	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1625	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1626	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1627
		1628	When you have trouble decoding JSON generated by this module using other
		1629	decoders, then it is very likely that you have an encoding mismatch or the
		1630	other decoder is broken.
		1631
		1632	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1633	errors. There are currently two settings that change this: C<relaxed>
		1634	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1635	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1636	cost of not outputting valid JSON anymore.
		1637
		1638	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1639
		1640	When you use C<allow_tags> to use the extended (and also nonstandard and
		1641	invalid) JSON syntax for serialised objects, and you still want to decode
		1642	the generated When you want to serialise objects, you can run a regex
		1643	to replace the tagged syntax by standard JSON arrays (it only works for
		1644	"normal" package names without comma, newlines or single colons). First,
		1645	the readable Perl version:
		1646
		1647	# if your FREEZE methods return no values, you need this replace first:
		1648	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1649
		1650	# this works for non-empty constructor arg lists:
		1651	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1652
		1653	And here is a less readable version that is easy to adapt to other
		1654	languages:
		1655
		1656	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1657
		1658	Here is an ECMAScript version (same regex):
		1659
		1660	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1661
		1662	Since this syntax converts to standard JSON arrays, it might be hard to
		1663	distinguish serialised objects from normal arrays. You can prepend a
		1664	"magic number" as first array element to reduce chances of a collision:
		1665
		1666	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1667
		1668	And after decoding the JSON text, you could walk the data
		1669	structure looking for arrays with a first element of
		1670	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1671
		1672	The same approach can be used to create the tagged format with another
		1673	encoder. First, you create an array with the magic string as first member,
		1674	the classname as second, and constructor arguments last, encode it as part
		1675	of your JSON structure, and then:
		1676
		1677	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1678
		1679	Again, this has some limitations - the magic string must not be encoded
		1680	with character escapes, and the constructor arguments must be non-empty.
		1681
		1682
		1683	=head1 RFC7159
		1684
		1685	Since this module was written, Google has written a new JSON RFC, RFC 7159
		1686	(and RFC7158). Unfortunately, this RFC breaks compatibility with both the
		1687	original JSON specification on www.json.org and RFC4627.
		1688
		1689	As far as I can see, you can get partial compatibility when parsing by
		1690	using C<< ->allow_nonref >>. However, consider the security implications
		1691	of doing so.
		1692
		1693	I haven't decided yet when to break compatibility with RFC4627 by default
		1694	(and potentially leave applications insecure) and change the default to
		1695	follow RFC7159, but application authors are well advised to call C<<
		1696	->allow_nonref(0) >> even if this is the current default, if they cannot
		1697	handle non-reference values, in preparation for the day when the default
		1698	will change.
		1699
		1700
1350	=head1 THREADS	1701	=head1 (I-)THREADS
1351		1702
1352	This module is I<not> guaranteed to be thread safe and there are no	1703	This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
1353	plans to change this until Perl gets thread support (as opposed to the	1704	and there are no plans to change this. Note that perl's builtin so-called
1354	horribly slow so-called "threads" which are simply slow and bloated	1705	threads/ithreads are officially deprecated and should not be used.
1355	process simulations - use fork, it's I<much> faster, cheaper, better).
1356		1706
1357	(It might actually work, but you have been warned).	1707
		1708	=head1 THE PERILS OF SETLOCALE
		1709
		1710	Sometimes people avoid the Perl locale support and directly call the
		1711	system's setlocale function with C<LC_ALL>.
		1712
		1713	This breaks both perl and modules such as JSON::XS, as stringification of
		1714	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1715	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1716	perl to stringify numbers).
		1717
		1718	The solution is simple: don't call C<setlocale>, or use it for only those
		1719	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1720
		1721	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1722	actually needs it (avoiding stringification of numbers), and restore it
		1723	afterwards.
1358		1724
1359		1725
1360	=head1 BUGS	1726	=head1 BUGS
1361		1727
1362	While the goal of this module is to be correct, that unfortunately does	1728	While the goal of this module is to be correct, that unfortunately does
…		…
1366	Please refrain from using rt.cpan.org or any other bug reporting	1732	Please refrain from using rt.cpan.org or any other bug reporting
1367	service. I put the contact address into my modules for a reason.	1733	service. I put the contact address into my modules for a reason.
1368		1734
1369	=cut	1735	=cut
1370		1736
1371	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1737	BEGIN {
1372	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1738	*true = \$Types::Serialiser::true;
		1739	*true = \&Types::Serialiser::true;
		1740	*false = \$Types::Serialiser::false;
		1741	*false = \&Types::Serialiser::false;
		1742	*is_bool = \&Types::Serialiser::is_bool;
1373		1743
1374	sub true() { $true }	1744	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1375	sub false() { $false }
1376
1377	sub is_bool($) {
1378	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1379	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1380	}	1745	}
1381		1746
1382	XSLoader::load "JSON::XS", $VERSION;	1747	XSLoader::load "JSON::XS", $VERSION;
1383
1384	package JSON::XS::Boolean;
1385
1386	use overload
1387	"0+" => sub { ${$_[0]} },
1388	"++" => sub { $_[0] = ${$_[0]} + 1 },
1389	"--" => sub { $_[0] = ${$_[0]} - 1 },
1390	fallback => 1;
1391
1392	1;
1393		1748
1394	=head1 SEE ALSO	1749	=head1 SEE ALSO
1395		1750
1396	The F<json_xs> command line utility for quick experiments.	1751	The F<json_xs> command line utility for quick experiments.
1397		1752
…		…
1400	Marc Lehmann <schmorp@schmorp.de>	1755	Marc Lehmann <schmorp@schmorp.de>
1401	http://home.schmorp.de/	1756	http://home.schmorp.de/
1402		1757
1403	=cut	1758	=cut
1404		1759
		1760	1
		1761

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Comparing JSON-XS/XS.pm (file contents): Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC vs. Revision 1.167 by root, Tue Aug 28 16:16:17 2018 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC vs.
Revision 1.167 by root, Tue Aug 28 16:16:17 2018 UTC