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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.122 by root, Fri Jul 17 14:33:45 2009 UTC vs.
Revision 1.174 by root, Sun Feb 24 04:21:05 2019 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.
65		51
66	=item * round-trip integrity	52	=item * round-trip integrity
67		53
68	When you serialise a perl data structure using only data types supported	54	When you serialise a perl data structure using only data types supported
69	by JSON, the deserialised data structure is identical on the Perl level.	55	by JSON and Perl, the deserialised data structure is identical on the Perl
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	56	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
71	like a number). There minor I<are> exceptions to this, read the MAPPING	57	it looks like a number). There I<are> minor exceptions to this, read the
72	section below to learn about those.	58	MAPPING section below to learn about those.
73		59
74	=item * strict checking of JSON correctness	60	=item * strict checking of JSON correctness
75		61
76	There is no guessing, no generating of illegal JSON texts by default,	62	There is no guessing, no generating of illegal JSON texts by default,
77	and only JSON is accepted as input by default (the latter is a security	63	and only JSON is accepted as input by default (the latter is a security
…		…
83	this module usually compares favourably in terms of speed, too.	69	this module usually compares favourably in terms of speed, too.
84		70
85	=item * simple to use	71	=item * simple to use
86		72
87	This module has both a simple functional interface as well as an object	73	This module has both a simple functional interface as well as an object
88	oriented interface interface.	74	oriented interface.
89		75
90	=item * reasonably versatile output formats	76	=item * reasonably versatile output formats
91		77
92	You can choose between the most compact guaranteed-single-line format	78	You can choose between the most compact guaranteed-single-line format
93	possible (nice for simple line-based protocols), a pure-ASCII format	79	possible (nice for simple line-based protocols), a pure-ASCII format
…		…
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 = '2.24';	92	our $VERSION = '4.01';
107	our @ISA = qw(Exporter);	93	our @ISA = qw(Exporter);
108		94
109	our @EXPORT = qw(encode_json decode_json to_json from_json);	95	our @EXPORT = qw(encode_json decode_json);
110
111	sub to_json($) {
112	require Carp;
113	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");
114	}
115
116	sub from_json($) {
117	require Carp;
118	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");
119	}
120		96
121	use Exporter;	97	use Exporter;
122	use XSLoader;	98	use XSLoader;
123		99
		100	use Types::Serialiser ();
		101
124	=head1 FUNCTIONAL INTERFACE	102	=head1 FUNCTIONAL INTERFACE
125		103
126	The following convenience methods are provided by this module. They are	104	The following convenience methods are provided by this module. They are
127	exported by default:	105	exported by default:
128		106
129	=over 4	107	=over
130		108
131	=item $json_text = encode_json $perl_scalar	109	=item $json_text = encode_json $perl_scalar
132		110
133	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
134	(that is, the string contains octets only). Croaks on error.	112	(that is, the string contains octets only). Croaks on error.
…		…
139		117
140	Except being faster.	118	Except being faster.
141		119
142	=item $perl_scalar = decode_json $json_text	120	=item $perl_scalar = decode_json $json_text
143		121
144	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
145	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
146	reference. Croaks on error.	124	reference. Croaks on error.
147		125
148	This function call is functionally identical to:	126	This function call is functionally identical to:
149		127
150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
151		129
152	Except being faster.	130	Except being faster.
153
154	=item $is_boolean = JSON::XS::is_bool $scalar
155
156	Returns true if the passed scalar represents either JSON::XS::true or
157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
158	and are used to represent JSON C<true> and C<false> values in Perl.
159
160	See MAPPING, below, for more information on how JSON values are mapped to
161	Perl.
162		131
163	=back	132	=back
164		133
165		134
166	=head1 A FEW NOTES ON UNICODE AND PERL	135	=head1 A FEW NOTES ON UNICODE AND PERL
167		136
168	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
169	how Unicode works in Perl, modulo bugs.	138	how Unicode works in Perl, modulo bugs.
170		139
171	=over 4	140	=over
172		141
173	=item 1. Perl strings can store characters with ordinal values > 255.	142	=item 1. Perl strings can store characters with ordinal values > 255.
174		143
175	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
176	Perl string - very natural.	145	Perl string - very natural.
…		…
214	=head1 OBJECT-ORIENTED INTERFACE	183	=head1 OBJECT-ORIENTED INTERFACE
215		184
216	The object oriented interface lets you configure your own encoding or	185	The object oriented interface lets you configure your own encoding or
217	decoding style, within the limits of supported formats.	186	decoding style, within the limits of supported formats.
218		187
219	=over 4	188	=over
220		189
221	=item $json = new JSON::XS	190	=item $json = new JSON::XS
222		191
223	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
224	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>).
225		196
226	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
227	be chained:	198	be chained:
228		199
229	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]})
…		…
287		258
288	=item $enabled = $json->get_utf8	259	=item $enabled = $json->get_utf8
289		260
290	If C<$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
291	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
292	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
293	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
294	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
295	versions, enabling this option might enable autodetection of the UTF-16	266	versions, enabling this option might enable autodetection of the UTF-16
296	and UTF-32 encoding families, as described in RFC4627.	267	and UTF-32 encoding families, as described in RFC4627.
297		268
…		…
382		353
383	=item $enabled = $json->get_relaxed	354	=item $enabled = $json->get_relaxed
384		355
385	If C<$enable> is true (or missing), then C<decode> will accept some	356	If C<$enable> is true (or missing), then C<decode> will accept some
386	extensions to normal JSON syntax (see below). C<encode> will not be	357	extensions to normal JSON syntax (see below). C<encode> will not be
387	affected in anyway. I<Be aware that this option makes you accept invalid	358	affected in any way. I<Be aware that this option makes you accept invalid
388	JSON texts as if they were valid!>. I suggest only to use this option to	359	JSON texts as if they were valid!>. I suggest only to use this option to
389	parse application-specific files written by humans (configuration files,	360	parse application-specific files written by humans (configuration files,
390	resource files etc.)	361	resource files etc.)
391		362
392	If C<$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
393	valid JSON texts.	364	valid JSON texts.
394		365
395	Currently accepted extensions are:	366	Currently accepted extensions are:
396		367
397	=over 4	368	=over
398		369
399	=item * list items can have an end-comma	370	=item * list items can have an end-comma
400		371
401	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
402	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
…		…
421	[	392	[
422	1, # this comment not allowed in JSON	393	1, # this comment not allowed in JSON
423	# neither this one...	394	# neither this one...
424	]	395	]
425		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
426	=back	407	=back
427		408
428	=item $json = $json->canonical ([$enable])	409	=item $json = $json->canonical ([$enable])
429		410
430	=item $enabled = $json->get_canonical	411	=item $enabled = $json->get_canonical
…		…
432	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	413	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
433	by sorting their keys. This is adding a comparatively high overhead.	414	by sorting their keys. This is adding a comparatively high overhead.
434		415
435	If C<$enable> is false, then the C<encode> method will output key-value	416	If C<$enable> is false, then the C<encode> method will output key-value
436	pairs in the order Perl stores them (which will likely change between runs	417	pairs in the order Perl stores them (which will likely change between runs
437	of the same script).	418	of the same script, and can change even within the same run from 5.18
		419	onwards).
438		420
439	This option is useful if you want the same data structure to be encoded as	421	This option is useful if you want the same data structure to be encoded as
440	the same JSON text (given the same overall settings). If it is disabled,	422	the same JSON text (given the same overall settings). If it is disabled,
441	the same hash might be encoded differently even if contains the same data,	423	the same hash might be encoded differently even if contains the same data,
442	as key-value pairs have no inherent ordering in Perl.	424	as key-value pairs have no inherent ordering in Perl.
…		…
447		429
448	=item $json = $json->allow_nonref ([$enable])	430	=item $json = $json->allow_nonref ([$enable])
449		431
450	=item $enabled = $json->get_allow_nonref	432	=item $enabled = $json->get_allow_nonref
451		433
		434	Unlike other boolean options, this opotion is enabled by default beginning
		435	with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details.
		436
452	If C<$enable> is true (or missing), then the C<encode> method can convert a	437	If C<$enable> is true (or missing), then the C<encode> method can convert a
453	non-reference into its corresponding string, number or null JSON value,	438	non-reference into its corresponding string, number or null JSON value,
454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	439	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
455	values instead of croaking.	440	values instead of croaking.
456		441
457	If C<$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
458	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
459	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
460	JSON object or array.	445	JSON object or array.
461		446
462	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>,
463	resulting in an invalid JSON text:	448	resulting in an error:
464		449
465	JSON::XS->new->allow_nonref->encode ("Hello, World!")	450	JSON::XS->new->allow_nonref (0)->encode ("Hello, World!")
466	=> "Hello, World!"	451	=> hash- or arrayref expected...
467		452
468	=item $json = $json->allow_unknown ([$enable])	453	=item $json = $json->allow_unknown ([$enable])
469		454
470	=item $enabled = $json->get_allow_unknown	455	=item $enabled = $json->get_allow_unknown
471		456
…		…
483		468
484	=item $json = $json->allow_blessed ([$enable])	469	=item $json = $json->allow_blessed ([$enable])
485		470
486	=item $enabled = $json->get_allow_blessed	471	=item $enabled = $json->get_allow_blessed
487		472
		473	See L<OBJECT SERIALISATION> for details.
		474
488	If C<$enable> is true (or missing), then the C<encode> method will not	475	If C<$enable> is true (or missing), then the C<encode> method will not
489	barf when it encounters a blessed reference. Instead, the value of the	476	barf when it encounters a blessed reference that it cannot convert
490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	477	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
491	disabled or no C<TO_JSON> method found) or a representation of the
492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
493	encoded. Has no effect on C<decode>.
494		478
495	If C<$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
496	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>.
497		484
498	=item $json = $json->convert_blessed ([$enable])	485	=item $json = $json->convert_blessed ([$enable])
499		486
500	=item $enabled = $json->get_convert_blessed	487	=item $enabled = $json->get_convert_blessed
		488
		489	See L<OBJECT SERIALISATION> for details.
501		490
502	If C<$enable> is true (or missing), then C<encode>, upon encountering a	491	If C<$enable> is true (or missing), then C<encode>, upon encountering a
503	blessed object, will check for the availability of the C<TO_JSON> method	492	blessed object, will check for the availability of the C<TO_JSON> method
504	on the object's class. If found, it will be called in scalar context	493	on the object's class. If found, it will be called in scalar context and
505	and the resulting scalar will be encoded instead of the object. If no	494	the resulting scalar will be encoded instead of the object.
506	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
507	to do.
508		495
509	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	496	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
510	returns other blessed objects, those will be handled in the same	497	returns other blessed objects, those will be handled in the same
511	way. C<TO_JSON> must take care of not causing an endless recursion cycle	498	way. C<TO_JSON> must take care of not causing an endless recursion cycle
512	(== crash) in this case. The name of C<TO_JSON> was chosen because other	499	(== crash) in this case. The name of C<TO_JSON> was chosen because other
513	methods called by the Perl core (== not by the user of the object) are	500	methods called by the Perl core (== not by the user of the object) are
514	usually in upper case letters and to avoid collisions with any C<to_json>	501	usually in upper case letters and to avoid collisions with any C<to_json>
515	function or method.	502	function or method.
516		503
517	This setting does not yet influence C<decode> in any way, but in the	504	If C<$enable> is false (the default), then C<encode> will not consider
518	future, global hooks might get installed that influence C<decode> and are	505	this type of conversion.
519	enabled by this setting.
520		506
521	If C<$enable> is false, then the C<allow_blessed> setting will decide what	507	This setting has no effect on C<decode>.
522	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.
		526
		527	=item $json->boolean_values ([$false, $true])
		528
		529	=item ($false, $true) = $json->get_boolean_values
		530
		531	By default, JSON booleans will be decoded as overloaded
		532	C<$Types::Serialiser::false> and C<$Types::Serialiser::true> objects.
		533
		534	With this method you can specify your own boolean values for decoding -
		535	on decode, JSON C<false> will be decoded as a copy of C<$false>, and JSON
		536	C<true> will be decoded as C<$true> ("copy" here is the same thing as
		537	assigning a value to another variable, i.e. C<$copy = $false>).
		538
		539	Calling this method without any arguments will reset the booleans
		540	to their default values.
		541
		542	C<get_boolean_values> will return both C<$false> and C<$true> values, or
		543	the empty list when they are set to the default.
523		544
524	=item $json = $json->filter_json_object ([$coderef->($hashref)])	545	=item $json = $json->filter_json_object ([$coderef->($hashref)])
525		546
526	When C<$coderef> is specified, it will be called from C<decode> each	547	When C<$coderef> is specified, it will be called from C<decode> each
527	time it decodes a JSON object. The only argument is a reference to the	548	time it decodes a JSON object. The only argument is a reference to
528	newly-created hash. If the code references returns a single scalar (which	549	the newly-created hash. If the code reference returns a single scalar
529	need not be a reference), this value (i.e. a copy of that scalar to avoid	550	(which need not be a reference), this value (or rather a copy of it) is
530	aliasing) is inserted into the deserialised data structure. If it returns	551	inserted into the deserialised data structure. If it returns an empty
531	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the	552	list (NOTE: I<not> C<undef>, which is a valid scalar), the original
532	original deserialised hash will be inserted. This setting can slow down	553	deserialised hash will be inserted. This setting can slow down decoding
533	decoding considerably.	554	considerably.
534		555
535	When C<$coderef> is omitted or undefined, any existing callback will	556	When C<$coderef> is omitted or undefined, any existing callback will
536	be removed and C<decode> will not change the deserialised hash in any	557	be removed and C<decode> will not change the deserialised hash in any
537	way.	558	way.
538		559
…		…
666		687
667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	688	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
668		689
669	=item $json_text = $json->encode ($perl_scalar)	690	=item $json_text = $json->encode ($perl_scalar)
670		691
671	Converts the given Perl data structure (a simple scalar or a reference	692	Converts the given Perl value or data structure to its JSON
672	to a hash or array) to its JSON representation. Simple scalars will be	693	representation. Croaks on error.
673	converted into JSON string or number sequences, while references to arrays
674	become JSON arrays and references to hashes become JSON objects. Undefined
675	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
676	nor C<false> values will be generated.
677		694
678	=item $perl_scalar = $json->decode ($json_text)	695	=item $perl_scalar = $json->decode ($json_text)
679		696
680	The opposite of C<encode>: expects a JSON text and tries to parse it,	697	The opposite of C<encode>: expects a JSON text and tries to parse it,
681	returning the resulting simple scalar or reference. Croaks on error.	698	returning the resulting simple scalar or reference. Croaks on error.
682
683	JSON numbers and strings become simple Perl scalars. JSON arrays become
684	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
685	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
686		699
687	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	700	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
688		701
689	This works like the C<decode> method, but instead of raising an exception	702	This works like the C<decode> method, but instead of raising an exception
690	when there is trailing garbage after the first JSON object, it will	703	when there is trailing garbage after the first JSON object, it will
691	silently stop parsing there and return the number of characters consumed	704	silently stop parsing there and return the number of characters consumed
692	so far.	705	so far.
693		706
694	This is useful if your JSON texts are not delimited by an outer protocol	707	This is useful if your JSON texts are not delimited by an outer protocol
695	(which is not the brightest thing to do in the first place) and you need
696	to know where the JSON text ends.	708	and you need to know where the JSON text ends.
697		709
698	JSON::XS->new->decode_prefix ("[1] the tail")	710	JSON::XS->new->decode_prefix ("[1] the tail")
699	=> ([], 3)	711	=> ([1], 3)
700		712
701	=back	713	=back
702		714
703		715
704	=head1 INCREMENTAL PARSING	716	=head1 INCREMENTAL PARSING
…		…
713	calls).	725	calls).
714		726
715	JSON::XS will only attempt to parse the JSON text once it is sure it	727	JSON::XS will only attempt to parse the JSON text once it is sure it
716	has enough text to get a decisive result, using a very simple but	728	has enough text to get a decisive result, using a very simple but
717	truly incremental parser. This means that it sometimes won't stop as	729	truly incremental parser. This means that it sometimes won't stop as
718	early as the full parser, for example, it doesn't detect parenthese	730	early as the full parser, for example, it doesn't detect mismatched
719	mismatches. The only thing it guarantees is that it starts decoding as	731	parentheses. The only thing it guarantees is that it starts decoding as
720	soon as a syntactically valid JSON text has been seen. This means you need	732	soon as a syntactically valid JSON text has been seen. This means you need
721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop	733	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
722	parsing in the presence if syntax errors.	734	parsing in the presence if syntax errors.
723		735
724	The following methods implement this incremental parser.	736	The following methods implement this incremental parser.
725		737
726	=over 4	738	=over
727		739
728	=item [void, scalar or list context] = $json->incr_parse ([$string])	740	=item [void, scalar or list context] = $json->incr_parse ([$string])
729		741
730	This is the central parsing function. It can both append new text and	742	This is the central parsing function. It can both append new text and
731	extract objects from the stream accumulated so far (both of these	743	extract objects from the stream accumulated so far (both of these
…		…
740		752
741	If the method is called in scalar context, then it will try to extract	753	If the method is called in scalar context, then it will try to extract
742	exactly I<one> JSON object. If that is successful, it will return this	754	exactly I<one> JSON object. If that is successful, it will return this
743	object, otherwise it will return C<undef>. If there is a parse error,	755	object, otherwise it will return C<undef>. If there is a parse error,
744	this method will croak just as C<decode> would do (one can then use	756	this method will croak just as C<decode> would do (one can then use
745	C<incr_skip> to skip the errornous part). This is the most common way of	757	C<incr_skip> to skip the erroneous part). This is the most common way of
746	using the method.	758	using the method.
747		759
748	And finally, in list context, it will try to extract as many objects	760	And finally, in list context, it will try to extract as many objects
749	from the stream as it can find and return them, or the empty list	761	from the stream as it can find and return them, or the empty list
750	otherwise. For this to work, there must be no separators between the JSON	762	otherwise. For this to work, there must be no separators (other than
751	objects or arrays, instead they must be concatenated back-to-back. If	763	whitespace) between the JSON objects or arrays, instead they must be
752	an error occurs, an exception will be raised as in the scalar context	764	concatenated back-to-back. If an error occurs, an exception will be
753	case. Note that in this case, any previously-parsed JSON texts will be	765	raised as in the scalar context case. Note that in this case, any
754	lost.	766	previously-parsed JSON texts will be lost.
		767
		768	Example: Parse some JSON arrays/objects in a given string and return
		769	them.
		770
		771	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
755		772
756	=item $lvalue_string = $json->incr_text	773	=item $lvalue_string = $json->incr_text
757		774
758	This method returns the currently stored JSON fragment as an lvalue, that	775	This method returns the currently stored JSON fragment as an lvalue, that
759	is, you can manipulate it. This I<only> works when a preceding call to	776	is, you can manipulate it. This I<only> works when a preceding call to
…		…
761	all other circumstances you must not call this function (I mean it.	778	all other circumstances you must not call this function (I mean it.
762	although in simple tests it might actually work, it I<will> fail under	779	although in simple tests it might actually work, it I<will> fail under
763	real world conditions). As a special exception, you can also call this	780	real world conditions). As a special exception, you can also call this
764	method before having parsed anything.	781	method before having parsed anything.
765		782
		783	That means you can only use this function to look at or manipulate text
		784	before or after complete JSON objects, not while the parser is in the
		785	middle of parsing a JSON object.
		786
766	This function is useful in two cases: a) finding the trailing text after a	787	This function is useful in two cases: a) finding the trailing text after a
767	JSON object or b) parsing multiple JSON objects separated by non-JSON text	788	JSON object or b) parsing multiple JSON objects separated by non-JSON text
768	(such as commas).	789	(such as commas).
769		790
770	=item $json->incr_skip	791	=item $json->incr_skip
…		…
774	C<incr_parse> died, in which case the input buffer and incremental parser	795	C<incr_parse> died, in which case the input buffer and incremental parser
775	state is left unchanged, to skip the text parsed so far and to reset the	796	state is left unchanged, to skip the text parsed so far and to reset the
776	parse state.	797	parse state.
777		798
778	The difference to C<incr_reset> is that only text until the parse error	799	The difference to C<incr_reset> is that only text until the parse error
779	occured is removed.	800	occurred is removed.
780		801
781	=item $json->incr_reset	802	=item $json->incr_reset
782		803
783	This completely resets the incremental parser, that is, after this call,	804	This completely resets the incremental parser, that is, after this call,
784	it will be as if the parser had never parsed anything.	805	it will be as if the parser had never parsed anything.
…		…
789		810
790	=back	811	=back
791		812
792	=head2 LIMITATIONS	813	=head2 LIMITATIONS
793		814
794	All options that affect decoding are supported, except	815	The incremental parser is a non-exact parser: it works by gathering as
795	C<allow_nonref>. The reason for this is that it cannot be made to	816	much text as possible that I<could> be a valid JSON text, followed by
796	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate	817	trying to decode it.
797	them back to back and still decode them perfectly. This does not hold true
798	for JSON numbers, however.
799		818
800	For example, is the string C<1> a single JSON number, or is it simply the	819	That means it sometimes needs to read more data than strictly necessary to
801	start of C<12>? Or is C<12> a single JSON number, or the concatenation	820	diagnose an invalid JSON text. For example, after parsing the following
802	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS	821	fragment, the parser I<could> stop with an error, as this fragment
803	takes the conservative route and disallows this case.	822	I<cannot> be the beginning of a valid JSON text:
		823
		824	[,
		825
		826	In reality, hopwever, the parser might continue to read data until a
		827	length limit is exceeded or it finds a closing bracket.
804		828
805	=head2 EXAMPLES	829	=head2 EXAMPLES
806		830
807	Some examples will make all this clearer. First, a simple example that	831	Some examples will make all this clearer. First, a simple example that
808	works similarly to C<decode_prefix>: We want to decode the JSON object at	832	works similarly to C<decode_prefix>: We want to decode the JSON object at
…		…
952	refers to the abstract Perl language itself.	976	refers to the abstract Perl language itself.
953		977
954		978
955	=head2 JSON -> PERL	979	=head2 JSON -> PERL
956		980
957	=over 4	981	=over
958		982
959	=item object	983	=item object
960		984
961	A JSON object becomes a reference to a hash in Perl. No ordering of object	985	A JSON object becomes a reference to a hash in Perl. No ordering of object
962	keys is preserved (JSON does not preserve object key ordering itself).	986	keys is preserved (JSON does not preserve object key ordering itself).
…		…
982	If the number consists of digits only, JSON::XS will try to represent	1006	If the number consists of digits only, JSON::XS will try to represent
983	it as an integer value. If that fails, it will try to represent it as	1007	it as an integer value. If that fails, it will try to represent it as
984	a numeric (floating point) value if that is possible without loss of	1008	a numeric (floating point) value if that is possible without loss of
985	precision. Otherwise it will preserve the number as a string value (in	1009	precision. Otherwise it will preserve the number as a string value (in
986	which case you lose roundtripping ability, as the JSON number will be	1010	which case you lose roundtripping ability, as the JSON number will be
987	re-encoded toa JSON string).	1011	re-encoded to a JSON string).
988		1012
989	Numbers containing a fractional or exponential part will always be	1013	Numbers containing a fractional or exponential part will always be
990	represented as numeric (floating point) values, possibly at a loss of	1014	represented as numeric (floating point) values, possibly at a loss of
991	precision (in which case you might lose perfect roundtripping ability, but	1015	precision (in which case you might lose perfect roundtripping ability, but
992	the JSON number will still be re-encoded as a JSON number).	1016	the JSON number will still be re-encoded as a JSON number).
993		1017
		1018	Note that precision is not accuracy - binary floating point values cannot
		1019	represent most decimal fractions exactly, and when converting from and to
		1020	floating point, JSON::XS only guarantees precision up to but not including
		1021	the least significant bit.
		1022
994	=item true, false	1023	=item true, false
995		1024
996	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1025	These JSON atoms become C<Types::Serialiser::true> and
997	respectively. They are overloaded to act almost exactly like the numbers	1026	C<Types::Serialiser::false>, respectively. They are overloaded to act
998	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1027	almost exactly like the numbers C<1> and C<0>. You can check whether
999	the C<JSON::XS::is_bool> function.	1028	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1029	function (after C<use Types::Serialier>, of course).
1000		1030
1001	=item null	1031	=item null
1002		1032
1003	A JSON null atom becomes C<undef> in Perl.	1033	A JSON null atom becomes C<undef> in Perl.
		1034
		1035	=item shell-style comments (C<< # I<text> >>)
		1036
		1037	As a nonstandard extension to the JSON syntax that is enabled by the
		1038	C<relaxed> setting, shell-style comments are allowed. They can start
		1039	anywhere outside strings and go till the end of the line.
		1040
		1041	=item tagged values (C<< (I<tag>)I<value> >>).
		1042
		1043	Another nonstandard extension to the JSON syntax, enabled with the
		1044	C<allow_tags> setting, are tagged values. In this implementation, the
		1045	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1046	I<value> must be a JSON array encoding optional constructor arguments.
		1047
		1048	See L<OBJECT SERIALISATION>, below, for details.
1004		1049
1005	=back	1050	=back
1006		1051
1007		1052
1008	=head2 PERL -> JSON	1053	=head2 PERL -> JSON
1009		1054
1010	The mapping from Perl to JSON is slightly more difficult, as Perl is a	1055	The mapping from Perl to JSON is slightly more difficult, as Perl is a
1011	truly typeless language, so we can only guess which JSON type is meant by	1056	truly typeless language, so we can only guess which JSON type is meant by
1012	a Perl value.	1057	a Perl value.
1013		1058
1014	=over 4	1059	=over
1015		1060
1016	=item hash references	1061	=item hash references
1017		1062
1018	Perl hash references become JSON objects. As there is no inherent ordering	1063	Perl hash references become JSON objects. As there is no inherent
1019	in hash keys (or JSON objects), they will usually be encoded in a	1064	ordering in hash keys (or JSON objects), they will usually be encoded
1020	pseudo-random order that can change between runs of the same program but	1065	in a pseudo-random order. JSON::XS can optionally sort the hash keys
1021	stays generally the same within a single run of a program. JSON::XS can	1066	(determined by the I<canonical> flag), so the same datastructure will
1022	optionally sort the hash keys (determined by the I<canonical> flag), so	1067	serialise to the same JSON text (given same settings and version of
1023	the same datastructure will serialise to the same JSON text (given same	1068	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1024	settings and version of JSON::XS), but this incurs a runtime overhead	1069	e.g. when you want to compare some JSON text against another for equality.
1025	and is only rarely useful, e.g. when you want to compare some JSON text
1026	against another for equality.
1027		1070
1028	=item array references	1071	=item array references
1029		1072
1030	Perl array references become JSON arrays.	1073	Perl array references become JSON arrays.
1031		1074
1032	=item other references	1075	=item other references
1033		1076
1034	Other unblessed references are generally not allowed and will cause an	1077	Other unblessed references are generally not allowed and will cause an
1035	exception to be thrown, except for references to the integers C<0> and	1078	exception to be thrown, except for references to the integers C<0> and
1036	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1079	C<1>, which get turned into C<false> and C<true> atoms in JSON.
1037	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1038		1080
		1081	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1082	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1083	and C<Types::Serialiser::true> to improve readability.
		1084
		1085	use Types::Serialiser;
1039	encode_json [\0, JSON::XS::true] # yields [false,true]	1086	encode_json [\0, Types::Serialiser::true] # yields [false,true]
1040		1087
1041	=item JSON::XS::true, JSON::XS::false	1088	=item Types::Serialiser::true, Types::Serialiser::false
1042		1089
1043	These special values become JSON true and JSON false values,	1090	These special values from the L<Types::Serialiser> module become JSON true
1044	respectively. You can also use C<\1> and C<\0> directly if you want.	1091	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1092	directly if you want.
1045		1093
1046	=item blessed objects	1094	=item blessed objects
1047		1095
1048	Blessed objects are not directly representable in JSON. See the	1096	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1049	C<allow_blessed> and C<convert_blessed> methods on various options on	1097	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1050	how to deal with this: basically, you can choose between throwing an	1098	below, for details.
1051	exception, encoding the reference as if it weren't blessed, or provide
1052	your own serialiser method.
1053		1099
1054	=item simple scalars	1100	=item simple scalars
1055		1101
1056	Simple Perl scalars (any scalar that is not a reference) are the most	1102	Simple Perl scalars (any scalar that is not a reference) are the most
1057	difficult objects to encode: JSON::XS will encode undefined scalars as	1103	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1085		1131
1086	You can not currently force the type in other, less obscure, ways. Tell me	1132	You can not currently force the type in other, less obscure, ways. Tell me
1087	if you need this capability (but don't forget to explain why it's needed	1133	if you need this capability (but don't forget to explain why it's needed
1088	:).	1134	:).
1089		1135
		1136	Note that numerical precision has the same meaning as under Perl (so
		1137	binary to decimal conversion follows the same rules as in Perl, which
		1138	can differ to other languages). Also, your perl interpreter might expose
		1139	extensions to the floating point numbers of your platform, such as
		1140	infinities or NaN's - these cannot be represented in JSON, and it is an
		1141	error to pass those in.
		1142
1090	=back	1143	=back
		1144
		1145	=head2 OBJECT SERIALISATION
		1146
		1147	As JSON cannot directly represent Perl objects, you have to choose between
		1148	a pure JSON representation (without the ability to deserialise the object
		1149	automatically again), and a nonstandard extension to the JSON syntax,
		1150	tagged values.
		1151
		1152	=head3 SERIALISATION
		1153
		1154	What happens when C<JSON::XS> encounters a Perl object depends on the
		1155	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1156	used in this order:
		1157
		1158	=over
		1159
		1160	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1161
		1162	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1163	serialisation protocol to create a tagged JSON value, using a nonstandard
		1164	extension to the JSON syntax.
		1165
		1166	This works by invoking the C<FREEZE> method on the object, with the first
		1167	argument being the object to serialise, and the second argument being the
		1168	constant string C<JSON> to distinguish it from other serialisers.
		1169
		1170	The C<FREEZE> method can return any number of values (i.e. zero or
		1171	more). These values and the paclkage/classname of the object will then be
		1172	encoded as a tagged JSON value in the following format:
		1173
		1174	("classname")[FREEZE return values...]
		1175
		1176	e.g.:
		1177
		1178	("URI")["http://www.google.com/"]
		1179	("MyDate")[2013,10,29]
		1180	("ImageData::JPEG")["Z3...VlCg=="]
		1181
		1182	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1183	objects C<type> and C<id> members to encode the object:
		1184
		1185	sub My::Object::FREEZE {
		1186	my ($self, $serialiser) = @_;
		1187
		1188	($self->{type}, $self->{id})
		1189	}
		1190
		1191	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1192
		1193	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1194	context. It must return a single scalar that can be directly encoded into
		1195	JSON. This scalar replaces the object in the JSON text.
		1196
		1197	For example, the following C<TO_JSON> method will convert all L<URI>
		1198	objects to JSON strings when serialised. The fatc that these values
		1199	originally were L<URI> objects is lost.
		1200
		1201	sub URI::TO_JSON {
		1202	my ($uri) = @_;
		1203	$uri->as_string
		1204	}
		1205
		1206	=item 3. C<allow_blessed> is enabled.
		1207
		1208	The object will be serialised as a JSON null value.
		1209
		1210	=item 4. none of the above
		1211
		1212	If none of the settings are enabled or the respective methods are missing,
		1213	C<JSON::XS> throws an exception.
		1214
		1215	=back
		1216
		1217	=head3 DESERIALISATION
		1218
		1219	For deserialisation there are only two cases to consider: either
		1220	nonstandard tagging was used, in which case C<allow_tags> decides,
		1221	or objects cannot be automatically be deserialised, in which
		1222	case you can use postprocessing or the C<filter_json_object> or
		1223	C<filter_json_single_key_object> callbacks to get some real objects our of
		1224	your JSON.
		1225
		1226	This section only considers the tagged value case: I a tagged JSON object
		1227	is encountered during decoding and C<allow_tags> is disabled, a parse
		1228	error will result (as if tagged values were not part of the grammar).
		1229
		1230	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1231	of the package/classname used during serialisation (it will not attempt
		1232	to load the package as a Perl module). If there is no such method, the
		1233	decoding will fail with an error.
		1234
		1235	Otherwise, the C<THAW> method is invoked with the classname as first
		1236	argument, the constant string C<JSON> as second argument, and all the
		1237	values from the JSON array (the values originally returned by the
		1238	C<FREEZE> method) as remaining arguments.
		1239
		1240	The method must then return the object. While technically you can return
		1241	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1242	make that work in all cases, so better return an actual blessed reference.
		1243
		1244	As an example, let's implement a C<THAW> function that regenerates the
		1245	C<My::Object> from the C<FREEZE> example earlier:
		1246
		1247	sub My::Object::THAW {
		1248	my ($class, $serialiser, $type, $id) = @_;
		1249
		1250	$class->new (type => $type, id => $id)
		1251	}
1091		1252
1092		1253
1093	=head1 ENCODING/CODESET FLAG NOTES	1254	=head1 ENCODING/CODESET FLAG NOTES
1094		1255
1095	The interested reader might have seen a number of flags that signify	1256	The interested reader might have seen a number of flags that signify
…		…
1113	takes those codepoint numbers and I<encodes> them, in our case into	1274	takes those codepoint numbers and I<encodes> them, in our case into
1114	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,	1275	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
1115	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at	1276	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
1116	the same time, which can be confusing.	1277	the same time, which can be confusing.
1117		1278
1118	=over 4	1279	=over
1119		1280
1120	=item C<utf8> flag disabled	1281	=item C<utf8> flag disabled
1121		1282
1122	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1283	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1123	and expect Unicode strings, that is, characters with high ordinal Unicode	1284	and expect Unicode strings, that is, characters with high ordinal Unicode
1124	values (> 255) will be encoded as such characters, and likewise such	1285	values (> 255) will be encoded as such characters, and likewise such
1125	characters are decoded as-is, no canges to them will be done, except	1286	characters are decoded as-is, no changes to them will be done, except
1126	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1287	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1127	respectively (to Perl, these are the same thing in strings unless you do	1288	respectively (to Perl, these are the same thing in strings unless you do
1128	funny/weird/dumb stuff).	1289	funny/weird/dumb stuff).
1129		1290
1130	This is useful when you want to do the encoding yourself (e.g. when you	1291	This is useful when you want to do the encoding yourself (e.g. when you
…		…
1140	expect your input strings to be encoded as UTF-8, that is, no "character"	1301	expect your input strings to be encoded as UTF-8, that is, no "character"
1141	of the input string must have any value > 255, as UTF-8 does not allow	1302	of the input string must have any value > 255, as UTF-8 does not allow
1142	that.	1303	that.
1143		1304
1144	The C<utf8> flag therefore switches between two modes: disabled means you	1305	The C<utf8> flag therefore switches between two modes: disabled means you
1145	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded	1306	will get a Unicode string in Perl, enabled means you get a UTF-8 encoded
1146	octet/binary string in Perl.	1307	octet/binary string in Perl.
1147		1308
1148	=item C<latin1> or C<ascii> flags enabled	1309	=item C<latin1> or C<ascii> flags enabled
1149		1310
1150	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters	1311	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
…		…
1238	well - using C<eval> naively simply I<will> cause problems.	1399	well - using C<eval> naively simply I<will> cause problems.
1239		1400
1240	Another problem is that some javascript implementations reserve	1401	Another problem is that some javascript implementations reserve
1241	some property names for their own purposes (which probably makes	1402	some property names for their own purposes (which probably makes
1242	them non-ECMAscript-compliant). For example, Iceweasel reserves the	1403	them non-ECMAscript-compliant). For example, Iceweasel reserves the
1243	C<__proto__> property name for it's own purposes.	1404	C<__proto__> property name for its own purposes.
1244		1405
1245	If that is a problem, you could parse try to filter the resulting JSON	1406	If that is a problem, you could parse try to filter the resulting JSON
1246	output for these property strings, e.g.:	1407	output for these property strings, e.g.:
1247		1408
1248	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;	1409	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1249		1410
1250	This works because C<__proto__> is not valid outside of strings, so every	1411	This works because C<__proto__> is not valid outside of strings, so every
1251	occurence of C<"__proto__"\s*:> must be a string used as property name.	1412	occurrence of C<"__proto__"\s*:> must be a string used as property name.
1252		1413
1253	If you know of other incompatibilities, please let me know.	1414	If you know of other incompatibilities, please let me know.
1254		1415
1255		1416
1256	=head2 JSON and YAML	1417	=head2 JSON and YAML
…		…
1268	my $yaml = $to_yaml->encode ($ref) . "\n";	1429	my $yaml = $to_yaml->encode ($ref) . "\n";
1269		1430
1270	This will I<usually> generate JSON texts that also parse as valid	1431	This will I<usually> generate JSON texts that also parse as valid
1271	YAML. Please note that YAML has hardcoded limits on (simple) object key	1432	YAML. Please note that YAML has hardcoded limits on (simple) object key
1272	lengths that JSON doesn't have and also has different and incompatible	1433	lengths that JSON doesn't have and also has different and incompatible
1273	unicode handling, so you should make sure that your hash keys are	1434	unicode character escape syntax, so you should make sure that your hash
1274	noticeably shorter than the 1024 "stream characters" YAML allows and that	1435	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1275	you do not have characters with codepoint values outside the Unicode BMP	1436	and that you do not have characters with codepoint values outside the
1276	(basic multilingual page). YAML also does not allow C<\/> sequences in	1437	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1277	strings (which JSON::XS does not I<currently> generate, but other JSON	1438	sequences in strings (which JSON::XS does not I<currently> generate, but
1278	generators might).	1439	other JSON generators might).
1279		1440
1280	There might be other incompatibilities that I am not aware of (or the YAML	1441	There might be other incompatibilities that I am not aware of (or the YAML
1281	specification has been changed yet again - it does so quite often). In	1442	specification has been changed yet again - it does so quite often). In
1282	general you should not try to generate YAML with a JSON generator or vice	1443	general you should not try to generate YAML with a JSON generator or vice
1283	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1444	versa, or try to parse JSON with a YAML parser or vice versa: chances are
1284	high that you will run into severe interoperability problems when you	1445	high that you will run into severe interoperability problems when you
1285	least expect it.	1446	least expect it.
1286		1447
1287	=over 4	1448	=over
1288		1449
1289	=item (*)	1450	=item (*)
1290		1451
1291	I have been pressured multiple times by Brian Ingerson (one of the	1452	I have been pressured multiple times by Brian Ingerson (one of the
1292	authors of the YAML specification) to remove this paragraph, despite him	1453	authors of the YAML specification) to remove this paragraph, despite him
…		…
1302	that difficult or long) and finally make YAML compatible to it, and	1463	that difficult or long) and finally make YAML compatible to it, and
1303	educating users about the changes, instead of spreading lies about the	1464	educating users about the changes, instead of spreading lies about the
1304	real compatibility for many I<years> and trying to silence people who	1465	real compatibility for many I<years> and trying to silence people who
1305	point out that it isn't true.	1466	point out that it isn't true.
1306		1467
		1468	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1469	though the incompatibilities have been documented (and are known to Brian)
		1470	for many years and the spec makes explicit claims that YAML is a superset
		1471	of JSON. It would be so easy to fix, but apparently, bullying people and
		1472	corrupting userdata is so much easier.
		1473
1307	=back	1474	=back
1308		1475
1309		1476
1310	=head2 SPEED	1477	=head2 SPEED
1311		1478
…		…
1318	a very short single-line JSON string (also available at	1485	a very short single-line JSON string (also available at
1319	L<http://dist.schmorp.de/misc/json/short.json>).	1486	L<http://dist.schmorp.de/misc/json/short.json>).
1320		1487
1321	{"method": "handleMessage", "params": ["user1",	1488	{"method": "handleMessage", "params": ["user1",
1322	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,	1489	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1323	true, false]}	1490	1, 0]}
1324		1491
1325	It shows the number of encodes/decodes per second (JSON::XS uses	1492	It shows the number of encodes/decodes per second (JSON::XS uses
1326	the functional interface, while JSON::XS/2 uses the OO interface	1493	the functional interface, while JSON::XS/2 uses the OO interface
1327	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1494	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1328	shrink). Higher is better:	1495	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1496	uses the from_json method). Higher is better:
1329		1497
1330	module \| encode \| decode \|	1498	module \| encode \| decode \|
1331	-----------\|------------\|------------\|	1499	--------------\|------------\|------------\|
1332	JSON 1.x \| 4990.842 \| 4088.813 \|	1500	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1333	JSON::DWIW \| 51653.990 \| 71575.154 \|	1501	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1334	JSON::PC \| 65948.176 \| 74631.744 \|	1502	JSON::PP \| 15827.562 \| 6638.658 \|
1335	JSON::PP \| 8931.652 \| 3817.168 \|	1503	JSON::Syck \| 63358.066 \| 47662.545 \|
1336	JSON::Syck \| 24877.248 \| 27776.848 \|	1504	JSON::XS \| 511500.488 \| 511500.488 \|
1337	JSON::XS \| 388361.481 \| 227951.304 \|	1505	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1338	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1506	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1339	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1507	Storable \| 66788.280 \| 265462.278 \|
1340	Storable \| 16500.016 \| 135300.129 \|
1341	-----------+------------+------------+	1508	--------------+------------+------------+
1342		1509
1343	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1510	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1344	about three times faster on decoding, and over forty times faster	1511	about five times faster on decoding, and over thirty to seventy times
1345	than JSON, even with pretty-printing and key sorting. It also compares	1512	faster than JSON's pure perl implementation. It also compares favourably
1346	favourably to Storable for small amounts of data.	1513	to Storable for small amounts of data.
1347		1514
1348	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1515	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1349	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1516	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1350		1517
1351	module \| encode \| decode \|	1518	module \| encode \| decode \|
1352	-----------\|------------\|------------\|	1519	--------------\|------------\|------------\|
1353	JSON 1.x \| 55.260 \| 34.971 \|	1520	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1354	JSON::DWIW \| 825.228 \| 1082.513 \|	1521	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1355	JSON::PC \| 3571.444 \| 2394.829 \|
1356	JSON::PP \| 210.987 \| 32.574 \|	1522	JSON::PP \| 400.640 \| 62.311 \|
1357	JSON::Syck \| 552.551 \| 787.544 \|	1523	JSON::Syck \| 1481.040 \| 1524.869 \|
1358	JSON::XS \| 5780.463 \| 4854.519 \|	1524	JSON::XS \| 20661.596 \| 9541.183 \|
1359	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1525	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1360	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1526	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1361	Storable \| 4445.002 \| 5235.027 \|	1527	Storable \| 19765.806 \| 10000.725 \|
1362	-----------+------------+------------+	1528	--------------+------------+------------+
1363		1529
1364	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1530	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1365	decodes faster).	1531	decodes a bit faster).
1366		1532
1367	On large strings containing lots of high Unicode characters, some modules	1533	On large strings containing lots of high Unicode characters, some modules
1368	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1534	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1369	will be broken due to missing (or wrong) Unicode handling. Others refuse	1535	will be broken due to missing (or wrong) Unicode handling. Others refuse
1370	to decode or encode properly, so it was impossible to prepare a fair	1536	to decode or encode properly, so it was impossible to prepare a fair
…		…
1406	information you might want to make sure that exceptions thrown by JSON::XS	1572	information you might want to make sure that exceptions thrown by JSON::XS
1407	will not end up in front of untrusted eyes.	1573	will not end up in front of untrusted eyes.
1408		1574
1409	If you are using JSON::XS to return packets to consumption	1575	If you are using JSON::XS to return packets to consumption
1410	by JavaScript scripts in a browser you should have a look at	1576	by JavaScript scripts in a browser you should have a look at
1411	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1577	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1412	you are vulnerable to some common attack vectors (which really are browser	1578	see whether you are vulnerable to some common attack vectors (which really
1413	design bugs, but it is still you who will have to deal with it, as major	1579	are browser design bugs, but it is still you who will have to deal with
1414	browser developers care only for features, not about getting security	1580	it, as major browser developers care only for features, not about getting
1415	right).	1581	security right).
1416		1582
1417		1583
		1584	=head2 "OLD" VS. "NEW" JSON (RFC4627 VS. RFC7159)
		1585
		1586	JSON originally required JSON texts to represent an array or object -
		1587	scalar values were explicitly not allowed. This has changed, and versions
		1588	of JSON::XS beginning with C<4.0> reflect this by allowing scalar values
		1589	by default.
		1590
		1591	One reason why one might not want this is that this removes a fundamental
		1592	property of JSON texts, namely that they are self-delimited and
		1593	self-contained, or in other words, you could take any number of "old"
		1594	JSON texts and paste them together, and the result would be unambiguously
		1595	parseable:
		1596
		1597	[1,3]{"k":5}[][null] # four JSON texts, without doubt
		1598
		1599	By allowing scalars, this property is lost: in the following example, is
		1600	this one JSON text (the number 12) or two JSON texts (the numbers 1 and
		1601	2):
		1602
		1603	12 # could be 12, or 1 and 2
		1604
		1605	Another lost property of "old" JSON is that no lookahead is required to
		1606	know the end of a JSON text, i.e. the JSON text definitely ended at the
		1607	last C<]> or C<}> character, there was no need to read extra characters.
		1608
		1609	For example, a viable network protocol with "old" JSON was to simply
		1610	exchange JSON texts without delimiter. For "new" JSON, you have to use a
		1611	suitable delimiter (such as a newline) after every JSON text or ensure you
		1612	never encode/decode scalar values.
		1613
		1614	Most protocols do work by only transferring arrays or objects, and the
		1615	easiest way to avoid problems with the "new" JSON definition is to
		1616	explicitly disallow scalar values in your encoder and decoder:
		1617
		1618	$json_coder = JSON::XS->new->allow_nonref (0)
		1619
		1620	This is a somewhat unhappy situation, and the blame can fully be put on
		1621	JSON's inmventor, Douglas Crockford, who unilaterally changed the format
		1622	in 2006 without consulting the IETF, forcing the IETF to either fork the
		1623	format or go with it (as I was told, the IETF wasn't amused).
		1624
		1625
		1626	=head1 RELATIONSHIP WITH I-JSON
		1627
		1628	JSON is a somewhat sloppily-defined format - it carries around obvious
		1629	Javascript baggage, such as not really defining number range, probably
		1630	because Javascript only has one type of numbers: IEEE 64 bit floats
		1631	("binary64").
		1632
		1633	For this reaosn, RFC7493 defines "Internet JSON", which is a restricted
		1634	subset of JSON that is supposedly more interoperable on the internet.
		1635
		1636	While C<JSON::XS> does not offer specific support for I-JSON, it of course
		1637	accepts valid I-JSON and by default implements some of the limitations
		1638	of I-JSON, such as parsing numbers as perl numbers, which are usually a
		1639	superset of binary64 numbers.
		1640
		1641	To generate I-JSON, follow these rules:
		1642
		1643	=over
		1644
		1645	=item * always generate UTF-8
		1646
		1647	I-JSON must be encoded in UTF-8, the default for C<encode_json>.
		1648
		1649	=item * numbers should be within IEEE 754 binary64 range
		1650
		1651	Basically all existing perl installations use binary64 to represent
		1652	floating point numbers, so all you need to do is to avoid large integers.
		1653
		1654	=item * objects must not have duplicate keys
		1655
		1656	This is trivially done, as C<JSON::XS> does not allow duplicate keys.
		1657
		1658	=item * do not generate scalar JSON texts, use C<< ->allow_nonref (0) >>
		1659
		1660	I-JSON strongly requests you to only encode arrays and objects into JSON.
		1661
		1662	=item * times should be strings in ISO 8601 format
		1663
		1664	There are a myriad of modules on CPAN dealing with ISO 8601 - search for
		1665	C<ISO8601> on CPAN and use one.
		1666
		1667	=item * encode binary data as base64
		1668
		1669	While it's tempting to just dump binary data as a string (and let
		1670	C<JSON::XS> do the escaping), for I-JSON, it's I<recommended> to encode
		1671	binary data as base64.
		1672
		1673	=back
		1674
		1675	There are some other considerations - read RFC7493 for the details if
		1676	interested.
		1677
		1678
		1679	=head1 INTEROPERABILITY WITH OTHER MODULES
		1680
		1681	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1682	constants. That means that the JSON true and false values will be
		1683	comaptible to true and false values of other modules that do the same,
		1684	such as L<JSON::PP> and L<CBOR::XS>.
		1685
		1686
		1687	=head1 INTEROPERABILITY WITH OTHER JSON DECODERS
		1688
		1689	As long as you only serialise data that can be directly expressed in JSON,
		1690	C<JSON::XS> is incapable of generating invalid JSON output (modulo bugs,
		1691	but C<JSON::XS> has found more bugs in the official JSON testsuite (1)
		1692	than the official JSON testsuite has found in C<JSON::XS> (0)).
		1693
		1694	When you have trouble decoding JSON generated by this module using other
		1695	decoders, then it is very likely that you have an encoding mismatch or the
		1696	other decoder is broken.
		1697
		1698	When decoding, C<JSON::XS> is strict by default and will likely catch all
		1699	errors. There are currently two settings that change this: C<relaxed>
		1700	makes C<JSON::XS> accept (but not generate) some non-standard extensions,
		1701	and C<allow_tags> will allow you to encode and decode Perl objects, at the
		1702	cost of not outputting valid JSON anymore.
		1703
		1704	=head2 TAGGED VALUE SYNTAX AND STANDARD JSON EN/DECODERS
		1705
		1706	When you use C<allow_tags> to use the extended (and also nonstandard and
		1707	invalid) JSON syntax for serialised objects, and you still want to decode
		1708	the generated When you want to serialise objects, you can run a regex
		1709	to replace the tagged syntax by standard JSON arrays (it only works for
		1710	"normal" package names without comma, newlines or single colons). First,
		1711	the readable Perl version:
		1712
		1713	# if your FREEZE methods return no values, you need this replace first:
		1714	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[\s*\]/[$1]/gx;
		1715
		1716	# this works for non-empty constructor arg lists:
		1717	$json =~ s/$ \s* (" (?: [^\\":,]+\|\\.\|::)* ") \s* $ \s* \[/[$1,/gx;
		1718
		1719	And here is a less readable version that is easy to adapt to other
		1720	languages:
		1721
		1722	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/[$1,/g;
		1723
		1724	Here is an ECMAScript version (same regex):
		1725
		1726	json = json.replace (/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/g, "[$1,");
		1727
		1728	Since this syntax converts to standard JSON arrays, it might be hard to
		1729	distinguish serialised objects from normal arrays. You can prepend a
		1730	"magic number" as first array element to reduce chances of a collision:
		1731
		1732	$json =~ s/$\s("([^\\":,]+\|\\.\|::)")\s$\s\[/["XU1peReLzT4ggEllLanBYq4G9VzliwKF",$1,/g;
		1733
		1734	And after decoding the JSON text, you could walk the data
		1735	structure looking for arrays with a first element of
		1736	C<XU1peReLzT4ggEllLanBYq4G9VzliwKF>.
		1737
		1738	The same approach can be used to create the tagged format with another
		1739	encoder. First, you create an array with the magic string as first member,
		1740	the classname as second, and constructor arguments last, encode it as part
		1741	of your JSON structure, and then:
		1742
		1743	$json =~ s/\[\s"XU1peReLzT4ggEllLanBYq4G9VzliwKF"\s,\s("([^\\":,]+\|\\.\|::)")\s*,/($1)[/g;
		1744
		1745	Again, this has some limitations - the magic string must not be encoded
		1746	with character escapes, and the constructor arguments must be non-empty.
		1747
		1748
1418	=head1 THREADS	1749	=head1 (I-)THREADS
1419		1750
1420	This module is I<not> guaranteed to be thread safe and there are no	1751	This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
1421	plans to change this until Perl gets thread support (as opposed to the	1752	and there are no plans to change this. Note that perl's builtin so-called
1422	horribly slow so-called "threads" which are simply slow and bloated	1753	threads/ithreads are officially deprecated and should not be used.
1423	process simulations - use fork, it's I<much> faster, cheaper, better).
1424		1754
1425	(It might actually work, but you have been warned).	1755
		1756	=head1 THE PERILS OF SETLOCALE
		1757
		1758	Sometimes people avoid the Perl locale support and directly call the
		1759	system's setlocale function with C<LC_ALL>.
		1760
		1761	This breaks both perl and modules such as JSON::XS, as stringification of
		1762	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1763	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1764	perl to stringify numbers).
		1765
		1766	The solution is simple: don't call C<setlocale>, or use it for only those
		1767	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1768
		1769	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1770	actually needs it (avoiding stringification of numbers), and restore it
		1771	afterwards.
		1772
		1773
		1774	=head1 SOME HISTORY
		1775
		1776	At the time this module was created there already were a number of JSON
		1777	modules available on CPAN, so what was the reason to write yet another
		1778	JSON module? While it seems there are many JSON modules, none of them
		1779	correctly handled all corner cases, and in most cases their maintainers
		1780	are unresponsive, gone missing, or not listening to bug reports for other
		1781	reasons.
		1782
		1783	Beginning with version 2.0 of the JSON module, when both JSON and
		1784	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		1785	overridden) with no overhead due to emulation (by inheriting constructor
		1786	and methods). If JSON::XS is not available, it will fall back to the
		1787	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		1788	gives you a portable JSON API that can be fast when you need it and
		1789	doesn't require a C compiler when that is a problem.
		1790
		1791	Somewhere around version 3, this module was forked into
		1792	C<Cpanel::JSON::XS>, because its maintainer had serious trouble
		1793	understanding JSON and insisted on a fork with many bugs "fixed" that
		1794	weren't actually bugs, while spreading FUD about this module without
		1795	actually giving any details on his accusations. You be the judge, but
		1796	in my personal opinion, if you want quality, you will stay away from
		1797	dangerous forks like that.
1426		1798
1427		1799
1428	=head1 BUGS	1800	=head1 BUGS
1429		1801
1430	While the goal of this module is to be correct, that unfortunately does	1802	While the goal of this module is to be correct, that unfortunately does
…		…
1434	Please refrain from using rt.cpan.org or any other bug reporting	1806	Please refrain from using rt.cpan.org or any other bug reporting
1435	service. I put the contact address into my modules for a reason.	1807	service. I put the contact address into my modules for a reason.
1436		1808
1437	=cut	1809	=cut
1438		1810
1439	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1811	BEGIN {
1440	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1812	*true = \$Types::Serialiser::true;
		1813	*true = \&Types::Serialiser::true;
		1814	*false = \$Types::Serialiser::false;
		1815	*false = \&Types::Serialiser::false;
		1816	*is_bool = \&Types::Serialiser::is_bool;
1441		1817
1442	sub true() { $true }	1818	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1443	sub false() { $false }
1444
1445	sub is_bool($) {
1446	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1447	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1448	}	1819	}
1449		1820
1450	XSLoader::load "JSON::XS", $VERSION;	1821	XSLoader::load "JSON::XS", $VERSION;
1451
1452	package JSON::XS::Boolean;
1453
1454	use overload
1455	"0+" => sub { ${$_[0]} },
1456	"++" => sub { $_[0] = ${$_[0]} + 1 },
1457	"--" => sub { $_[0] = ${$_[0]} - 1 },
1458	fallback => 1;
1459
1460	1;
1461		1822
1462	=head1 SEE ALSO	1823	=head1 SEE ALSO
1463		1824
1464	The F<json_xs> command line utility for quick experiments.	1825	The F<json_xs> command line utility for quick experiments.
1465		1826
…		…
1468	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1469	http://home.schmorp.de/	1830	http://home.schmorp.de/
1470		1831
1471	=cut	1832	=cut
1472		1833
		1834	1
		1835

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Comparing JSON-XS/XS.pm (file contents): Revision 1.122 by root, Fri Jul 17 14:33:45 2009 UTC vs. Revision 1.174 by root, Sun Feb 24 04:21:05 2019 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.122 by root, Fri Jul 17 14:33:45 2009 UTC vs.
Revision 1.174 by root, Sun Feb 24 04:21:05 2019 UTC