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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.144 by root, Mon Oct 28 23:19:54 2013 UTC vs.
Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC

…		…
35		35
36	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
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
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
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
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.
47
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
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
52	reports for other reasons.
53
54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	40	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
55	vice versa.	41	vice versa.
56		42
57	=head2 FEATURES	43	=head2 FEATURES
58		44
59	=over 4	45	=over
60		46
61	=item * correct Unicode handling	47	=item * correct Unicode handling
62		48
63	This module knows how to handle Unicode, documents how and when it does	49	This module knows how to handle Unicode, documents how and when it does
64	so, and even documents what "correct" means.	50	so, and even documents what "correct" means.
…		…
101		87
102	package JSON::XS;	88	package JSON::XS;
103		89
104	use common::sense;	90	use common::sense;
105		91
106	our $VERSION = 2.34;	92	our $VERSION = '4.0';
107	our @ISA = qw(Exporter);	93	our @ISA = qw(Exporter);
108		94
109	our @EXPORT = qw(encode_json decode_json);	95	our @EXPORT = qw(encode_json decode_json);
110		96
111	use Exporter;	97	use Exporter;
…		…
116	=head1 FUNCTIONAL INTERFACE	102	=head1 FUNCTIONAL INTERFACE
117		103
118	The following convenience methods are provided by this module. They are	104	The following convenience methods are provided by this module. They are
119	exported by default:	105	exported by default:
120		106
121	=over 4	107	=over
122		108
123	=item $json_text = encode_json $perl_scalar	109	=item $json_text = encode_json $perl_scalar
124		110
125	Converts the given Perl data structure to a UTF-8 encoded, binary string	111	Converts the given Perl data structure to a UTF-8 encoded, binary string
126	(that is, the string contains octets only). Croaks on error.	112	(that is, the string contains octets only). Croaks on error.
…		…
131		117
132	Except being faster.	118	Except being faster.
133		119
134	=item $perl_scalar = decode_json $json_text	120	=item $perl_scalar = decode_json $json_text
135		121
136	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	122	The opposite of C<encode_json>: expects a UTF-8 (binary) string and tries
137	to parse that as an UTF-8 encoded JSON text, returning the resulting	123	to parse that as a UTF-8 encoded JSON text, returning the resulting
138	reference. Croaks on error.	124	reference. Croaks on error.
139		125
140	This function call is functionally identical to:	126	This function call is functionally identical to:
141		127
142	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
…		…
149	=head1 A FEW NOTES ON UNICODE AND PERL	135	=head1 A FEW NOTES ON UNICODE AND PERL
150		136
151	Since this often leads to confusion, here are a few very clear words on	137	Since this often leads to confusion, here are a few very clear words on
152	how Unicode works in Perl, modulo bugs.	138	how Unicode works in Perl, modulo bugs.
153		139
154	=over 4	140	=over
155		141
156	=item 1. Perl strings can store characters with ordinal values > 255.	142	=item 1. Perl strings can store characters with ordinal values > 255.
157		143
158	This enables you to store Unicode characters as single characters in a	144	This enables you to store Unicode characters as single characters in a
159	Perl string - very natural.	145	Perl string - very natural.
…		…
197	=head1 OBJECT-ORIENTED INTERFACE	183	=head1 OBJECT-ORIENTED INTERFACE
198		184
199	The object oriented interface lets you configure your own encoding or	185	The object oriented interface lets you configure your own encoding or
200	decoding style, within the limits of supported formats.	186	decoding style, within the limits of supported formats.
201		187
202	=over 4	188	=over
203		189
204	=item $json = new JSON::XS	190	=item $json = new JSON::XS
205		191
206	Creates a new JSON::XS object that can be used to de/encode JSON	192	Creates a new JSON::XS object that can be used to de/encode JSON
207	strings. All boolean flags described below are by default I<disabled>.	193	strings. All boolean flags described below are by default I<disabled>
		194	(with the exception of C<allow_nonref>, which defaults to I<enabled> since
		195	version C<4.0>).
208		196
209	The mutators for flags all return the JSON object again and thus calls can	197	The mutators for flags all return the JSON object again and thus calls can
210	be chained:	198	be chained:
211		199
212	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	200	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
…		…
270		258
271	=item $enabled = $json->get_utf8	259	=item $enabled = $json->get_utf8
272		260
273	If C<$enable> is true (or missing), then the C<encode> method will encode	261	If C<$enable> is true (or missing), then the C<encode> method will encode
274	the JSON result into UTF-8, as required by many protocols, while the	262	the JSON result into UTF-8, as required by many protocols, while the
275	C<decode> method expects to be handled an UTF-8-encoded string. Please	263	C<decode> method expects to be handed a UTF-8-encoded string. Please
276	note that UTF-8-encoded strings do not contain any characters outside the	264	note that UTF-8-encoded strings do not contain any characters outside the
277	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	265	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
278	versions, enabling this option might enable autodetection of the UTF-16	266	versions, enabling this option might enable autodetection of the UTF-16
279	and UTF-32 encoding families, as described in RFC4627.	267	and UTF-32 encoding families, as described in RFC4627.
280		268
…		…
365		353
366	=item $enabled = $json->get_relaxed	354	=item $enabled = $json->get_relaxed
367		355
368	If C<$enable> is true (or missing), then C<decode> will accept some	356	If C<$enable> is true (or missing), then C<decode> will accept some
369	extensions to normal JSON syntax (see below). C<encode> will not be	357	extensions to normal JSON syntax (see below). C<encode> will not be
370	affected in anyway. I<Be aware that this option makes you accept invalid	358	affected in any way. I<Be aware that this option makes you accept invalid
371	JSON texts as if they were valid!>. I suggest only to use this option to	359	JSON texts as if they were valid!>. I suggest only to use this option to
372	parse application-specific files written by humans (configuration files,	360	parse application-specific files written by humans (configuration files,
373	resource files etc.)	361	resource files etc.)
374		362
375	If C<$enable> is false (the default), then C<decode> will only accept	363	If C<$enable> is false (the default), then C<decode> will only accept
376	valid JSON texts.	364	valid JSON texts.
377		365
378	Currently accepted extensions are:	366	Currently accepted extensions are:
379		367
380	=over 4	368	=over
381		369
382	=item * list items can have an end-comma	370	=item * list items can have an end-comma
383		371
384	JSON I<separates> array elements and key-value pairs with commas. This	372	JSON I<separates> array elements and key-value pairs with commas. This
385	can be annoying if you write JSON texts manually and want to be able to	373	can be annoying if you write JSON texts manually and want to be able to
…		…
404	[	392	[
405	1, # this comment not allowed in JSON	393	1, # this comment not allowed in JSON
406	# neither this one...	394	# neither this one...
407	]	395	]
408		396
		397	=item * literal ASCII TAB characters in strings
		398
		399	Literal ASCII TAB characters are now allowed in strings (and treated as
		400	C<\t>).
		401
		402	[
		403	"Hello\tWorld",
		404	"Hello<TAB>World", # literal <TAB> would not normally be allowed
		405	]
		406
409	=back	407	=back
410		408
411	=item $json = $json->canonical ([$enable])	409	=item $json = $json->canonical ([$enable])
412		410
413	=item $enabled = $json->get_canonical	411	=item $enabled = $json->get_canonical
…		…
431		429
432	=item $json = $json->allow_nonref ([$enable])	430	=item $json = $json->allow_nonref ([$enable])
433		431
434	=item $enabled = $json->get_allow_nonref	432	=item $enabled = $json->get_allow_nonref
435		433
		434	Unlike other boolean options, this opotion is enabled by default beginning
		435	with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details.
		436
436	If C<$enable> is true (or missing), then the C<encode> method can convert a	437	If C<$enable> is true (or missing), then the C<encode> method can convert a
437	non-reference into its corresponding string, number or null JSON value,	438	non-reference into its corresponding string, number or null JSON value,
438	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	439	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
439	values instead of croaking.	440	values instead of croaking.
440		441
441	If C<$enable> is false, then the C<encode> method will croak if it isn't	442	If C<$enable> is false, then the C<encode> method will croak if it isn't
442	passed an arrayref or hashref, as JSON texts must either be an object	443	passed an arrayref or hashref, as JSON texts must either be an object
443	or array. Likewise, C<decode> will croak if given something that is not a	444	or array. Likewise, C<decode> will croak if given something that is not a
444	JSON object or array.	445	JSON object or array.
445		446
446	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	447	Example, encode a Perl scalar as JSON value without enabled C<allow_nonref>,
447	resulting in an invalid JSON text:	448	resulting in an error:
448		449
449	JSON::XS->new->allow_nonref->encode ("Hello, World!")	450	JSON::XS->new->allow_nonref (0)->encode ("Hello, World!")
450	=> "Hello, World!"	451	=> hash- or arrayref expected...
451		452
452	=item $json = $json->allow_unknown ([$enable])	453	=item $json = $json->allow_unknown ([$enable])
453		454
454	=item $enabled = $json->get_allow_unknown	455	=item $enabled = $json->get_allow_unknown
455		456
…		…
467		468
468	=item $json = $json->allow_blessed ([$enable])	469	=item $json = $json->allow_blessed ([$enable])
469		470
470	=item $enabled = $json->get_allow_blessed	471	=item $enabled = $json->get_allow_blessed
471		472
		473	See L<OBJECT SERIALISATION> for details.
		474
472	If C<$enable> is true (or missing), then the C<encode> method will not	475	If C<$enable> is true (or missing), then the C<encode> method will not
473	barf when it encounters a blessed reference. Instead, the value of the	476	barf when it encounters a blessed reference that it cannot convert
474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	477	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
475	disabled or no C<TO_JSON> method found) or a representation of the
476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
477	encoded. Has no effect on C<decode>.
478		478
479	If C<$enable> is false (the default), then C<encode> will throw an	479	If C<$enable> is false (the default), then C<encode> will throw an
480	exception when it encounters a blessed object.	480	exception when it encounters a blessed object that it cannot convert
		481	otherwise.
		482
		483	This setting has no effect on C<decode>.
481		484
482	=item $json = $json->convert_blessed ([$enable])	485	=item $json = $json->convert_blessed ([$enable])
483		486
484	=item $enabled = $json->get_convert_blessed	487	=item $enabled = $json->get_convert_blessed
		488
		489	See L<OBJECT SERIALISATION> for details.
485		490
486	If C<$enable> is true (or missing), then C<encode>, upon encountering a	491	If C<$enable> is true (or missing), then C<encode>, upon encountering a
487	blessed object, will check for the availability of the C<TO_JSON> method	492	blessed object, will check for the availability of the C<TO_JSON> method
488	on the object's class. If found, it will be called in scalar context	493	on the object's class. If found, it will be called in scalar context and
489	and the resulting scalar will be encoded instead of the object. If no	494	the resulting scalar will be encoded instead of the object.
490	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
491	to do.
492		495
493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	496	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
494	returns other blessed objects, those will be handled in the same	497	returns other blessed objects, those will be handled in the same
495	way. C<TO_JSON> must take care of not causing an endless recursion cycle	498	way. C<TO_JSON> must take care of not causing an endless recursion cycle
496	(== crash) in this case. The name of C<TO_JSON> was chosen because other	499	(== crash) in this case. The name of C<TO_JSON> was chosen because other
497	methods called by the Perl core (== not by the user of the object) are	500	methods called by the Perl core (== not by the user of the object) are
498	usually in upper case letters and to avoid collisions with any C<to_json>	501	usually in upper case letters and to avoid collisions with any C<to_json>
499	function or method.	502	function or method.
500		503
501	This setting does not yet influence C<decode> in any way, but in the	504	If C<$enable> is false (the default), then C<encode> will not consider
502	future, global hooks might get installed that influence C<decode> and are	505	this type of conversion.
503	enabled by this setting.
504		506
505	If C<$enable> is false, then the C<allow_blessed> setting will decide what	507	This setting has no effect on C<decode>.
506	to do when a blessed object is found.	508
		509	=item $json = $json->allow_tags ([$enable])
		510
		511	=item $enabled = $json->get_allow_tags
		512
		513	See L<OBJECT SERIALISATION> for details.
		514
		515	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		516	blessed object, will check for the availability of the C<FREEZE> method on
		517	the object's class. If found, it will be used to serialise the object into
		518	a nonstandard tagged JSON value (that JSON decoders cannot decode).
		519
		520	It also causes C<decode> to parse such tagged JSON values and deserialise
		521	them via a call to the C<THAW> method.
		522
		523	If C<$enable> is false (the default), then C<encode> will not consider
		524	this type of conversion, and tagged JSON values will cause a parse error
		525	in C<decode>, as if tags were not part of the grammar.
507		526
508	=item $json = $json->filter_json_object ([$coderef->($hashref)])	527	=item $json = $json->filter_json_object ([$coderef->($hashref)])
509		528
510	When C<$coderef> is specified, it will be called from C<decode> each	529	When C<$coderef> is specified, it will be called from C<decode> each
511	time it decodes a JSON object. The only argument is a reference to the	530	time it decodes a JSON object. The only argument is a reference to
512	newly-created hash. If the code references returns a single scalar (which	531	the newly-created hash. If the code reference returns a single scalar
513	need not be a reference), this value (i.e. a copy of that scalar to avoid	532	(which need not be a reference), this value (or rather a copy of it) is
514	aliasing) is inserted into the deserialised data structure. If it returns	533	inserted into the deserialised data structure. If it returns an empty
515	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the	534	list (NOTE: I<not> C<undef>, which is a valid scalar), the original
516	original deserialised hash will be inserted. This setting can slow down	535	deserialised hash will be inserted. This setting can slow down decoding
517	decoding considerably.	536	considerably.
518		537
519	When C<$coderef> is omitted or undefined, any existing callback will	538	When C<$coderef> is omitted or undefined, any existing callback will
520	be removed and C<decode> will not change the deserialised hash in any	539	be removed and C<decode> will not change the deserialised hash in any
521	way.	540	way.
522		541
…		…
669		688
670	This is useful if your JSON texts are not delimited by an outer protocol	689	This is useful if your JSON texts are not delimited by an outer protocol
671	and you need to know where the JSON text ends.	690	and you need to know where the JSON text ends.
672		691
673	JSON::XS->new->decode_prefix ("[1] the tail")	692	JSON::XS->new->decode_prefix ("[1] the tail")
674	=> ([], 3)	693	=> ([1], 3)
675		694
676	=back	695	=back
677		696
678		697
679	=head1 INCREMENTAL PARSING	698	=head1 INCREMENTAL PARSING
…		…
696	to set resource limits (e.g. C<max_size>) to ensure the parser will stop	715	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
697	parsing in the presence if syntax errors.	716	parsing in the presence if syntax errors.
698		717
699	The following methods implement this incremental parser.	718	The following methods implement this incremental parser.
700		719
701	=over 4	720	=over
702		721
703	=item [void, scalar or list context] = $json->incr_parse ([$string])	722	=item [void, scalar or list context] = $json->incr_parse ([$string])
704		723
705	This is the central parsing function. It can both append new text and	724	This is the central parsing function. It can both append new text and
706	extract objects from the stream accumulated so far (both of these	725	extract objects from the stream accumulated so far (both of these
…		…
720	C<incr_skip> to skip the erroneous part). This is the most common way of	739	C<incr_skip> to skip the erroneous part). This is the most common way of
721	using the method.	740	using the method.
722		741
723	And finally, in list context, it will try to extract as many objects	742	And finally, in list context, it will try to extract as many objects
724	from the stream as it can find and return them, or the empty list	743	from the stream as it can find and return them, or the empty list
725	otherwise. For this to work, there must be no separators between the JSON	744	otherwise. For this to work, there must be no separators (other than
726	objects or arrays, instead they must be concatenated back-to-back. If	745	whitespace) between the JSON objects or arrays, instead they must be
727	an error occurs, an exception will be raised as in the scalar context	746	concatenated back-to-back. If an error occurs, an exception will be
728	case. Note that in this case, any previously-parsed JSON texts will be	747	raised as in the scalar context case. Note that in this case, any
729	lost.	748	previously-parsed JSON texts will be lost.
730		749
731	Example: Parse some JSON arrays/objects in a given string and return	750	Example: Parse some JSON arrays/objects in a given string and return
732	them.	751	them.
733		752
734	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");	753	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
…		…
741	all other circumstances you must not call this function (I mean it.	760	all other circumstances you must not call this function (I mean it.
742	although in simple tests it might actually work, it I<will> fail under	761	although in simple tests it might actually work, it I<will> fail under
743	real world conditions). As a special exception, you can also call this	762	real world conditions). As a special exception, you can also call this
744	method before having parsed anything.	763	method before having parsed anything.
745		764
		765	That means you can only use this function to look at or manipulate text
		766	before or after complete JSON objects, not while the parser is in the
		767	middle of parsing a JSON object.
		768
746	This function is useful in two cases: a) finding the trailing text after a	769	This function is useful in two cases: a) finding the trailing text after a
747	JSON object or b) parsing multiple JSON objects separated by non-JSON text	770	JSON object or b) parsing multiple JSON objects separated by non-JSON text
748	(such as commas).	771	(such as commas).
749		772
750	=item $json->incr_skip	773	=item $json->incr_skip
…		…
769		792
770	=back	793	=back
771		794
772	=head2 LIMITATIONS	795	=head2 LIMITATIONS
773		796
774	All options that affect decoding are supported, except	797	The incremental parser is a non-exact parser: it works by gathering as
775	C<allow_nonref>. The reason for this is that it cannot be made to work	798	much text as possible that I<could> be a valid JSON text, followed by
776	sensibly: JSON objects and arrays are self-delimited, i.e. you can	799	trying to decode it.
777	concatenate them back to back and still decode them perfectly. This does
778	not hold true for JSON numbers, however.
779		800
780	For example, is the string C<1> a single JSON number, or is it simply the	801	That means it sometimes needs to read more data than strictly necessary to
781	start of C<12>? Or is C<12> a single JSON number, or the concatenation	802	diagnose an invalid JSON text. For example, after parsing the following
782	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS	803	fragment, the parser I<could> stop with an error, as this fragment
783	takes the conservative route and disallows this case.	804	I<cannot> be the beginning of a valid JSON text:
		805
		806	[,
		807
		808	In reality, hopwever, the parser might continue to read data until a
		809	length limit is exceeded or it finds a closing bracket.
784		810
785	=head2 EXAMPLES	811	=head2 EXAMPLES
786		812
787	Some examples will make all this clearer. First, a simple example that	813	Some examples will make all this clearer. First, a simple example that
788	works similarly to C<decode_prefix>: We want to decode the JSON object at	814	works similarly to C<decode_prefix>: We want to decode the JSON object at
…		…
932	refers to the abstract Perl language itself.	958	refers to the abstract Perl language itself.
933		959
934		960
935	=head2 JSON -> PERL	961	=head2 JSON -> PERL
936		962
937	=over 4	963	=over
938		964
939	=item object	965	=item object
940		966
941	A JSON object becomes a reference to a hash in Perl. No ordering of object	967	A JSON object becomes a reference to a hash in Perl. No ordering of object
942	keys is preserved (JSON does not preserve object key ordering itself).	968	keys is preserved (JSON does not preserve object key ordering itself).
…		…
986		1012
987	=item null	1013	=item null
988		1014
989	A JSON null atom becomes C<undef> in Perl.	1015	A JSON null atom becomes C<undef> in Perl.
990		1016
		1017	=item shell-style comments (C<< # I<text> >>)
		1018
		1019	As a nonstandard extension to the JSON syntax that is enabled by the
		1020	C<relaxed> setting, shell-style comments are allowed. They can start
		1021	anywhere outside strings and go till the end of the line.
		1022
		1023	=item tagged values (C<< (I<tag>)I<value> >>).
		1024
		1025	Another nonstandard extension to the JSON syntax, enabled with the
		1026	C<allow_tags> setting, are tagged values. In this implementation, the
		1027	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1028	I<value> must be a JSON array encoding optional constructor arguments.
		1029
		1030	See L<OBJECT SERIALISATION>, below, for details.
		1031
991	=back	1032	=back
992		1033
993		1034
994	=head2 PERL -> JSON	1035	=head2 PERL -> JSON
995		1036
996	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1037	The mapping from Perl to JSON is slightly more difficult, as Perl is a
997	truly typeless language, so we can only guess which JSON type is meant by	1038	truly typeless language, so we can only guess which JSON type is meant by
998	a Perl value.	1039	a Perl value.
999		1040
1000	=over 4	1041	=over
1001		1042
1002	=item hash references	1043	=item hash references
1003		1044
1004	Perl hash references become JSON objects. As there is no inherent	1045	Perl hash references become JSON objects. As there is no inherent
1005	ordering in hash keys (or JSON objects), they will usually be encoded	1046	ordering in hash keys (or JSON objects), they will usually be encoded
…		…
1032	and JSON false values, respectively. You can also use C<\1> and C<\0>	1073	and JSON false values, respectively. You can also use C<\1> and C<\0>
1033	directly if you want.	1074	directly if you want.
1034		1075
1035	=item blessed objects	1076	=item blessed objects
1036		1077
1037	Blessed objects are not directly representable in JSON. See the	1078	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1038	C<allow_blessed> and C<convert_blessed> methods on various options on	1079	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1039	how to deal with this: basically, you can choose between throwing an	1080	below, for details.
1040	exception, encoding the reference as if it weren't blessed, or provide
1041	your own serialiser method.
1042		1081
1043	=item simple scalars	1082	=item simple scalars
1044		1083
1045	Simple Perl scalars (any scalar that is not a reference) are the most	1084	Simple Perl scalars (any scalar that is not a reference) are the most
1046	difficult objects to encode: JSON::XS will encode undefined scalars as	1085	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1083	infinities or NaN's - these cannot be represented in JSON, and it is an	1122	infinities or NaN's - these cannot be represented in JSON, and it is an
1084	error to pass those in.	1123	error to pass those in.
1085		1124
1086	=back	1125	=back
1087		1126
		1127	=head2 OBJECT SERIALISATION
		1128
		1129	As JSON cannot directly represent Perl objects, you have to choose between
		1130	a pure JSON representation (without the ability to deserialise the object
		1131	automatically again), and a nonstandard extension to the JSON syntax,
		1132	tagged values.
		1133
		1134	=head3 SERIALISATION
		1135
		1136	What happens when C<JSON::XS> encounters a Perl object depends on the
		1137	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1138	used in this order:
		1139
		1140	=over
		1141
		1142	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1143
		1144	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1145	serialisation protocol to create a tagged JSON value, using a nonstandard
		1146	extension to the JSON syntax.
		1147
		1148	This works by invoking the C<FREEZE> method on the object, with the first
		1149	argument being the object to serialise, and the second argument being the
		1150	constant string C<JSON> to distinguish it from other serialisers.
		1151
		1152	The C<FREEZE> method can return any number of values (i.e. zero or
		1153	more). These values and the paclkage/classname of the object will then be
		1154	encoded as a tagged JSON value in the following format:
		1155
		1156	("classname")[FREEZE return values...]
		1157
		1158	e.g.:
		1159
		1160	("URI")["http://www.google.com/"]
		1161	("MyDate")[2013,10,29]
		1162	("ImageData::JPEG")["Z3...VlCg=="]
		1163
		1164	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1165	objects C<type> and C<id> members to encode the object:
		1166
		1167	sub My::Object::FREEZE {
		1168	my ($self, $serialiser) = @_;
		1169
		1170	($self->{type}, $self->{id})
		1171	}
		1172
		1173	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1174
		1175	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1176	context. It must return a single scalar that can be directly encoded into
		1177	JSON. This scalar replaces the object in the JSON text.
		1178
		1179	For example, the following C<TO_JSON> method will convert all L<URI>
		1180	objects to JSON strings when serialised. The fatc that these values
		1181	originally were L<URI> objects is lost.
		1182
		1183	sub URI::TO_JSON {
		1184	my ($uri) = @_;
		1185	$uri->as_string
		1186	}
		1187
		1188	=item 3. C<allow_blessed> is enabled.
		1189
		1190	The object will be serialised as a JSON null value.
		1191
		1192	=item 4. none of the above
		1193
		1194	If none of the settings are enabled or the respective methods are missing,
		1195	C<JSON::XS> throws an exception.
		1196
		1197	=back
		1198
		1199	=head3 DESERIALISATION
		1200
		1201	For deserialisation there are only two cases to consider: either
		1202	nonstandard tagging was used, in which case C<allow_tags> decides,
		1203	or objects cannot be automatically be deserialised, in which
		1204	case you can use postprocessing or the C<filter_json_object> or
		1205	C<filter_json_single_key_object> callbacks to get some real objects our of
		1206	your JSON.
		1207
		1208	This section only considers the tagged value case: I a tagged JSON object
		1209	is encountered during decoding and C<allow_tags> is disabled, a parse
		1210	error will result (as if tagged values were not part of the grammar).
		1211
		1212	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1213	of the package/classname used during serialisation (it will not attempt
		1214	to load the package as a Perl module). If there is no such method, the
		1215	decoding will fail with an error.
		1216
		1217	Otherwise, the C<THAW> method is invoked with the classname as first
		1218	argument, the constant string C<JSON> as second argument, and all the
		1219	values from the JSON array (the values originally returned by the
		1220	C<FREEZE> method) as remaining arguments.
		1221
		1222	The method must then return the object. While technically you can return
		1223	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1224	make that work in all cases, so better return an actual blessed reference.
		1225
		1226	As an example, let's implement a C<THAW> function that regenerates the
		1227	C<My::Object> from the C<FREEZE> example earlier:
		1228
		1229	sub My::Object::THAW {
		1230	my ($class, $serialiser, $type, $id) = @_;
		1231
		1232	$class->new (type => $type, id => $id)
		1233	}
		1234
1088		1235
1089	=head1 ENCODING/CODESET FLAG NOTES	1236	=head1 ENCODING/CODESET FLAG NOTES
1090		1237
1091	The interested reader might have seen a number of flags that signify	1238	The interested reader might have seen a number of flags that signify
1092	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be	1239	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
…		…
1109	takes those codepoint numbers and I<encodes> them, in our case into	1256	takes those codepoint numbers and I<encodes> them, in our case into
1110	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,	1257	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
1111	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at	1258	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
1112	the same time, which can be confusing.	1259	the same time, which can be confusing.
1113		1260
1114	=over 4	1261	=over
1115		1262
1116	=item C<utf8> flag disabled	1263	=item C<utf8> flag disabled
1117		1264
1118	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1265	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1119	and expect Unicode strings, that is, characters with high ordinal Unicode	1266	and expect Unicode strings, that is, characters with high ordinal Unicode
…		…
1136	expect your input strings to be encoded as UTF-8, that is, no "character"	1283	expect your input strings to be encoded as UTF-8, that is, no "character"
1137	of the input string must have any value > 255, as UTF-8 does not allow	1284	of the input string must have any value > 255, as UTF-8 does not allow
1138	that.	1285	that.
1139		1286
1140	The C<utf8> flag therefore switches between two modes: disabled means you	1287	The C<utf8> flag therefore switches between two modes: disabled means you
1141	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded	1288	will get a Unicode string in Perl, enabled means you get a UTF-8 encoded
1142	octet/binary string in Perl.	1289	octet/binary string in Perl.
1143		1290
1144	=item C<latin1> or C<ascii> flags enabled	1291	=item C<latin1> or C<ascii> flags enabled
1145		1292
1146	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters	1293	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
…		…
1278	general you should not try to generate YAML with a JSON generator or vice	1425	general you should not try to generate YAML with a JSON generator or vice
1279	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1426	versa, or try to parse JSON with a YAML parser or vice versa: chances are
1280	high that you will run into severe interoperability problems when you	1427	high that you will run into severe interoperability problems when you
1281	least expect it.	1428	least expect it.
1282		1429
1283	=over 4	1430	=over
1284		1431
1285	=item (*)	1432	=item (*)
1286		1433
1287	I have been pressured multiple times by Brian Ingerson (one of the	1434	I have been pressured multiple times by Brian Ingerson (one of the
1288	authors of the YAML specification) to remove this paragraph, despite him	1435	authors of the YAML specification) to remove this paragraph, despite him
…		…
1414	are browser design bugs, but it is still you who will have to deal with	1561	are browser design bugs, but it is still you who will have to deal with
1415	it, as major browser developers care only for features, not about getting	1562	it, as major browser developers care only for features, not about getting
1416	security right).	1563	security right).
1417		1564
1418		1565
		1566	=head2 "OLD" VS. "NEW" JSON (RFC4627 VS. RFC7159)
		1567
		1568	JSON originally required JSON texts to represent an array or object -
		1569	scalar values were explicitly not allowed. This has changed, and versions
		1570	of JSON::XS beginning with C<4.0> reflect this by allowing scalar values
		1571	by default.
		1572
		1573	One reason why one might not want this is that this removes a fundamental
		1574	property of JSON texts, namely that they are self-delimited and
		1575	self-contained, or in other words, you could take any number of "old"
		1576	JSON texts and paste them together, and the result would be unambiguously
		1577	parseable:
		1578
		1579	[1,3]{"k":5}[][null] # four JSON texts, without doubt
		1580
		1581	By allowing scalars, this property is lost: in the following example, is
		1582	this one JSON text (the number 12) or two JSON texts (the numbers 1 and
		1583	2):
		1584
		1585	12 # could be 12, or 1 and 2
		1586
		1587	Another lost property of "old" JSON is that no lookahead is required to
		1588	know the end of a JSON text, i.e. the JSON text definitely ended at the
		1589	last C<]> or C<}> character, there was no need to read extra characters.
		1590
		1591	For example, a viable network protocol with "old" JSON was to simply
		1592	exchange JSON texts without delimiter. For "new" JSON, you have to use a
		1593	suitable delimiter (such as a newline) after every JSON text or ensure you
		1594	never encode/decode scalar values.
		1595
		1596	Most protocols do work by only transferring arrays or objects, and the
		1597	easiest way to avoid problems with the "new" JSON definition is to
		1598	explicitly disallow scalar values in your encoder and decoder:
		1599
		1600	$json_coder = JSON::XS->new->allow_nonref (0)
		1601
		1602	This is a somewhat unhappy situation, and the blame can fully be put on
		1603	JSON's inmventor, Douglas Crockford, who unilaterally changed the format
		1604	in 2006 without consulting the IETF, forcing the IETF to either fork the
		1605	format or go with it (as I was told, the IETF wasn't amused).
		1606
		1607
		1608	=head1 RELATIONSHIP WITH I-JSON
		1609
		1610	JSON is a somewhat sloppily-defined format - it carries around obvious
		1611	Javascript baggage, such as not really defining number range, probably
		1612	because Javascript only has one type of numbers: IEEE 64 bit floats
		1613	("binary64").
		1614
		1615	For this reaosn, RFC7493 defines "Internet JSON", which is a restricted
		1616	subset of JSON that is supposedly more interoperable on the internet.
		1617
		1618	While C<JSON::XS> does not offer specific support for I-JSON, it of course
		1619	accepts valid I-JSON and by default implements some of the limitations
		1620	of I-JSON, such as parsing numbers as perl numbers, which are usually a
		1621	superset of binary64 numbers.
		1622
		1623	To generate I-JSON, follow these rules:
		1624
		1625	=over
		1626
		1627	=item * always generate UTF-8
		1628
		1629	I-JSON must be encoded in UTF-8, the default for C<encode_json>.
		1630
		1631	=item * numbers should be within IEEE 754 binary64 range
		1632
		1633	Basically all existing perl installations use binary64 to represent
		1634	floating point numbers, so all you need to do is to avoid large integers.
		1635
		1636	=item * objects must not have duplicate keys
		1637
		1638	This is trivially done, as C<JSON::XS> does not allow duplicate keys.
		1639
		1640	=item * do not generate scalar JSON texts, use C<< ->allow_nonref (0) >>
		1641
		1642	I-JSON strongly requests you to only encode arrays and objects into JSON.
		1643
		1644	=item * times should be strings in ISO 8601 format
		1645
		1646	There are a myriad of modules on CPAN dealing with ISO 8601 - search for
		1647	C<ISO8601> on CPAN and use one.
		1648
		1649	=item * encode binary data as base64
		1650
		1651	While it's tempting to just dump binary data as a string (and let
		1652	C<JSON::XS> do the escaping), for I-JSON, it's I<recommended> to encode
		1653	binary data as base64.
		1654
		1655	=back
		1656
		1657	There are some other considerations - read RFC7493 for the details if
		1658	interested.
		1659
		1660
1419	=head1 INTEROPERABILITY WITH OTHER MODULES	1661	=head1 INTEROPERABILITY WITH OTHER MODULES
1420		1662
1421	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean	1663	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
1422	constants. That means that the JSON true and false values will be	1664	constants. That means that the JSON true and false values will be
1423	comaptible to true and false values of iother modules that do the same,	1665	comaptible to true and false values of other modules that do the same,
1424	such as L<JSON::PP> and L<CBOR::XS>.	1666	such as L<JSON::PP> and L<CBOR::XS>.
1425		1667
1426		1668
		1669	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1670
		1671	As long as you only serialise data that can be directly expressed in JSON,
		1672	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1673	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1674	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1675
		1676	When you have trouble decoding JSON generated by this module using other
		1677	decoders, then it is very likely that you have an encoding mismatch or the
		1678	other decoder is broken.
		1679
		1680	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1681	errors. There are currently two settings that change this: C<relaxed>
		1682	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1683	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1684	cost of not outputting valid JSON anymore.
		1685
		1686	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1687
		1688	When you use C<allow_tags> to use the extended (and also nonstandard and
		1689	invalid) JSON syntax for serialised objects, and you still want to decode
		1690	the generated When you want to serialise objects, you can run a regex
		1691	to replace the tagged syntax by standard JSON arrays (it only works for
		1692	"normal" package names without comma, newlines or single colons). First,
		1693	the readable Perl version:
		1694
		1695	# if your FREEZE methods return no values, you need this replace first:
		1696	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1697
		1698	# this works for non-empty constructor arg lists:
		1699	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1700
		1701	And here is a less readable version that is easy to adapt to other
		1702	languages:
		1703
		1704	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1705
		1706	Here is an ECMAScript version (same regex):
		1707
		1708	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1709
		1710	Since this syntax converts to standard JSON arrays, it might be hard to
		1711	distinguish serialised objects from normal arrays. You can prepend a
		1712	"magic number" as first array element to reduce chances of a collision:
		1713
		1714	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1715
		1716	And after decoding the JSON text, you could walk the data
		1717	structure looking for arrays with a first element of
		1718	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1719
		1720	The same approach can be used to create the tagged format with another
		1721	encoder. First, you create an array with the magic string as first member,
		1722	the classname as second, and constructor arguments last, encode it as part
		1723	of your JSON structure, and then:
		1724
		1725	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1726
		1727	Again, this has some limitations - the magic string must not be encoded
		1728	with character escapes, and the constructor arguments must be non-empty.
		1729
		1730
1427	=head1 THREADS	1731	=head1 (I-)THREADS
1428		1732
1429	This module is I<not> guaranteed to be thread safe and there are no	1733	This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
1430	plans to change this until Perl gets thread support (as opposed to the	1734	and there are no plans to change this. Note that perl's builtin so-called
1431	horribly slow so-called "threads" which are simply slow and bloated	1735	threads/ithreads are officially deprecated and should not be used.
1432	process simulations - use fork, it's I<much> faster, cheaper, better).
1433
1434	(It might actually work, but you have been warned).
1435		1736
1436		1737
1437	=head1 THE PERILS OF SETLOCALE	1738	=head1 THE PERILS OF SETLOCALE
1438		1739
1439	Sometimes people avoid the Perl locale support and directly call the	1740	Sometimes people avoid the Perl locale support and directly call the
…		…
1448	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.	1749	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
1449		1750
1450	If you need C<LC_NUMERIC>, you should enable it only around the code that	1751	If you need C<LC_NUMERIC>, you should enable it only around the code that
1451	actually needs it (avoiding stringification of numbers), and restore it	1752	actually needs it (avoiding stringification of numbers), and restore it
1452	afterwards.	1753	afterwards.
		1754
		1755
		1756	=head1 SOME HISTORY
		1757
		1758	At the time this module was created there already were a number of JSON
		1759	modules available on CPAN, so what was the reason to write yet another
		1760	JSON module? While it seems there are many JSON modules, none of them
		1761	correctly handled all corner cases, and in most cases their maintainers
		1762	are unresponsive, gone missing, or not listening to bug reports for other
		1763	reasons.
		1764
		1765	Beginning with version 2.0 of the JSON module, when both JSON and
		1766	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		1767	overridden) with no overhead due to emulation (by inheriting constructor
		1768	and methods). If JSON::XS is not available, it will fall back to the
		1769	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		1770	gives you a portable JSON API that can be fast when you need it and
		1771	doesn't require a C compiler when that is a problem.
		1772
		1773	Somewhere around version 3, this module was forked into
		1774	C<Cpanel::JSON::XS>, because its maintainer had serious trouble
		1775	understanding JSON and insisted on a fork with many bugs "fixed" that
		1776	weren't actually bugs, while spreading FUD about this module without
		1777	actually giving any details on his accusations. You be the judge, but
		1778	in my personal opinion, if you want quality, you will stay away from
		1779	dangerous forks like that.
1453		1780
1454		1781
1455	=head1 BUGS	1782	=head1 BUGS
1456		1783
1457	While the goal of this module is to be correct, that unfortunately does	1784	While the goal of this module is to be correct, that unfortunately does

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Comparing JSON-XS/XS.pm (file contents): Revision 1.144 by root, Mon Oct 28 23:19:54 2013 UTC vs. Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.144 by root, Mon Oct 28 23:19:54 2013 UTC vs.
Revision 1.170 by root, Thu Nov 15 22:35:35 2018 UTC