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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC vs.
Revision 1.171 by root, Thu Nov 15 22:49:06 2018 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
		3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
3	=encoding utf-8	5	=encoding utf-8
4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		6
7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9		9
10	=head1 SYNOPSIS	10	=head1 SYNOPSIS
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	overriden) with no overhead due to emulation (by inheritign 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 COMPARISON, below, for a comparison to some other JSON modules.
55
56	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	40	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
57	vice versa.	41	vice versa.
58		42
59	=head2 FEATURES	43	=head2 FEATURES
60		44
61	=over 4	45	=over
62		46
63	=item * correct Unicode handling	47	=item * correct Unicode handling
64		48
65	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
66	so, and even documents what "correct" means.	50	so, and even documents what "correct" means.
67		51
68	=item * round-trip integrity	52	=item * round-trip integrity
69		53
70	When you serialise a perl data structure using only datatypes supported	54	When you serialise a perl data structure using only data types supported
71	by JSON, the deserialised data structure is identical on the Perl level.	55	by JSON and Perl, the deserialised data structure is identical on the Perl
72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	56	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
73	like a number). There minor I<are> exceptions to this, read the MAPPING	57	it looks like a number). There I<are> minor exceptions to this, read the
74	section below to learn about those.	58	MAPPING section below to learn about those.
75		59
76	=item * strict checking of JSON correctness	60	=item * strict checking of JSON correctness
77		61
78	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,
79	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
…		…
84	Compared to other JSON modules and other serialisers such as Storable,	68	Compared to other JSON modules and other serialisers such as Storable,
85	this module usually compares favourably in terms of speed, too.	69	this module usually compares favourably in terms of speed, too.
86		70
87	=item * simple to use	71	=item * simple to use
88		72
89	This module has both a simple functional interface as well as an objetc	73	This module has both a simple functional interface as well as an object
90	oriented interface interface.	74	oriented interface.
91		75
92	=item * reasonably versatile output formats	76	=item * reasonably versatile output formats
93		77
94	You can choose between the most compact guaranteed-single-line format	78	You can choose between the most compact guaranteed-single-line format
95	possible (nice for simple line-based protocols), a pure-ascii format	79	possible (nice for simple line-based protocols), a pure-ASCII format
96	(for when your transport is not 8-bit clean, still supports the whole	80	(for when your transport is not 8-bit clean, still supports the whole
97	Unicode range), or a pretty-printed format (for when you want to read that	81	Unicode range), or a pretty-printed format (for when you want to read that
98	stuff). Or you can combine those features in whatever way you like.	82	stuff). Or you can combine those features in whatever way you like.
99		83
100	=back	84	=back
101		85
102	=cut	86	=cut
103		87
104	package JSON::XS;	88	package JSON::XS;
105		89
106	use strict;	90	use common::sense;
107		91
108	our $VERSION = '2.1';	92	our $VERSION = '4.0';
109	our @ISA = qw(Exporter);	93	our @ISA = qw(Exporter);
110		94
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	95	our @EXPORT = qw(encode_json decode_json);
112
113	sub to_json($) {
114	require Carp;
115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
116	}
117
118	sub from_json($) {
119	require Carp;
120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
121	}
122		96
123	use Exporter;	97	use Exporter;
124	use XSLoader;	98	use XSLoader;
125		99
		100	use Types::Serialiser ();
		101
126	=head1 FUNCTIONAL INTERFACE	102	=head1 FUNCTIONAL INTERFACE
127		103
128	The following convenience methods are provided by this module. They are	104	The following convenience methods are provided by this module. They are
129	exported by default:	105	exported by default:
130		106
131	=over 4	107	=over
132		108
133	=item $json_text = encode_json $perl_scalar	109	=item $json_text = encode_json $perl_scalar
134		110
135	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
136	(that is, the string contains octets only). Croaks on error.	112	(that is, the string contains octets only). Croaks on error.
137		113
138	This function call is functionally identical to:	114	This function call is functionally identical to:
139		115
140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141		117
142	except being faster.	118	Except being faster.
143		119
144	=item $perl_scalar = decode_json $json_text	120	=item $perl_scalar = decode_json $json_text
145		121
146	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
147	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
148	reference. Croaks on error.	124	reference. Croaks on error.
149		125
150	This function call is functionally identical to:	126	This function call is functionally identical to:
151		127
152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153		129
154	except being faster.	130	Except being faster.
155
156	=item $is_boolean = JSON::XS::is_bool $scalar
157
158	Returns true if the passed scalar represents either JSON::XS::true or
159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
160	and are used to represent JSON C<true> and C<false> values in Perl.
161
162	See MAPPING, below, for more information on how JSON values are mapped to
163	Perl.
164		131
165	=back	132	=back
166		133
167		134
168	=head1 A FEW NOTES ON UNICODE AND PERL	135	=head1 A FEW NOTES ON UNICODE AND PERL
169		136
170	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
171	how Unicode works in Perl, modulo bugs.	138	how Unicode works in Perl, modulo bugs.
172		139
173	=over 4	140	=over
174		141
175	=item 1. Perl strings can store characters with ordinal values > 255.	142	=item 1. Perl strings can store characters with ordinal values > 255.
176		143
177	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
178	Perl string - very natural.	145	Perl string - very natural.
…		…
197		164
198	If you didn't know about that flag, just the better, pretend it doesn't	165	If you didn't know about that flag, just the better, pretend it doesn't
199	exist.	166	exist.
200		167
201	=item 4. A "Unicode String" is simply a string where each character can be	168	=item 4. A "Unicode String" is simply a string where each character can be
202	validly interpreted as a Unicode codepoint.	169	validly interpreted as a Unicode code point.
203		170
204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	171	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205	Unicode string encoded in UTF-8, giving you a binary string.	172	Unicode string encoded in UTF-8, giving you a binary string.
206		173
207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	174	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
216	=head1 OBJECT-ORIENTED INTERFACE	183	=head1 OBJECT-ORIENTED INTERFACE
217		184
218	The object oriented interface lets you configure your own encoding or	185	The object oriented interface lets you configure your own encoding or
219	decoding style, within the limits of supported formats.	186	decoding style, within the limits of supported formats.
220		187
221	=over 4	188	=over
222		189
223	=item $json = new JSON::XS	190	=item $json = new JSON::XS
224		191
225	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
226	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>).
227		196
228	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
229	be chained:	198	be chained:
230		199
231	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]})
…		…
289		258
290	=item $enabled = $json->get_utf8	259	=item $enabled = $json->get_utf8
291		260
292	If C<$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
293	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
294	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
295	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
296	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
297	versions, enabling this option might enable autodetection of the UTF-16	266	versions, enabling this option might enable autodetection of the UTF-16
298	and UTF-32 encoding families, as described in RFC4627.	267	and UTF-32 encoding families, as described in RFC4627.
299		268
…		…
384		353
385	=item $enabled = $json->get_relaxed	354	=item $enabled = $json->get_relaxed
386		355
387	If C<$enable> is true (or missing), then C<decode> will accept some	356	If C<$enable> is true (or missing), then C<decode> will accept some
388	extensions to normal JSON syntax (see below). C<encode> will not be	357	extensions to normal JSON syntax (see below). C<encode> will not be
389	affected in anyway. I<Be aware that this option makes you accept invalid	358	affected in any way. I<Be aware that this option makes you accept invalid
390	JSON texts as if they were valid!>. I suggest only to use this option to	359	JSON texts as if they were valid!>. I suggest only to use this option to
391	parse application-specific files written by humans (configuration files,	360	parse application-specific files written by humans (configuration files,
392	resource files etc.)	361	resource files etc.)
393		362
394	If C<$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
395	valid JSON texts.	364	valid JSON texts.
396		365
397	Currently accepted extensions are:	366	Currently accepted extensions are:
398		367
399	=over 4	368	=over
400		369
401	=item * list items can have an end-comma	370	=item * list items can have an end-comma
402		371
403	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
404	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
…		…
423	[	392	[
424	1, # this comment not allowed in JSON	393	1, # this comment not allowed in JSON
425	# neither this one...	394	# neither this one...
426	]	395	]
427		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
428	=back	407	=back
429		408
430	=item $json = $json->canonical ([$enable])	409	=item $json = $json->canonical ([$enable])
431		410
432	=item $enabled = $json->get_canonical	411	=item $enabled = $json->get_canonical
…		…
434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	413	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
435	by sorting their keys. This is adding a comparatively high overhead.	414	by sorting their keys. This is adding a comparatively high overhead.
436		415
437	If C<$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
438	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
439	of the same script).	418	of the same script, and can change even within the same run from 5.18
		419	onwards).
440		420
441	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
442	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,
443	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,
444	as key-value pairs have no inherent ordering in Perl.	424	as key-value pairs have no inherent ordering in Perl.
445		425
446	This setting has no effect when decoding JSON texts.	426	This setting has no effect when decoding JSON texts.
447		427
		428	This setting has currently no effect on tied hashes.
		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 = $json->get_allow_nonref
		433
		434	Unlike other boolean options, this opotion is enabled by default beginning
		435	with version C<4.0>. See L<SECURITY CONSIDERATIONS> for the gory details.
451		436
452	If C<$enable> is true (or missing), then the C<encode> method can convert a	437	If C<$enable> is true (or missing), then the C<encode> method can convert a
453	non-reference into its corresponding string, number or null JSON value,	438	non-reference into its corresponding string, number or null JSON value,
454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	439	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
455	values instead of croaking.	440	values instead of croaking.
…		…
457	If C<$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...
		452
		453	=item $json = $json->allow_unknown ([$enable])
		454
		455	=item $enabled = $json->get_allow_unknown
		456
		457	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		458	exception when it encounters values it cannot represent in JSON (for
		459	example, filehandles) but instead will encode a JSON C<null> value. Note
		460	that blessed objects are not included here and are handled separately by
		461	c<allow_nonref>.
		462
		463	If C<$enable> is false (the default), then C<encode> will throw an
		464	exception when it encounters anything it cannot encode as JSON.
		465
		466	This option does not affect C<decode> in any way, and it is recommended to
		467	leave it off unless you know your communications partner.
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.
		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.
507		544
508	=item $json = $json->filter_json_object ([$coderef->($hashref)])	545	=item $json = $json->filter_json_object ([$coderef->($hashref)])
509		546
510	When C<$coderef> is specified, it will be called from C<decode> each	547	When C<$coderef> is specified, it will be called from C<decode> each
511	time it decodes a JSON object. The only argument is a reference to the	548	time it decodes a JSON object. The only argument is a reference to
512	newly-created hash. If the code references returns a single scalar (which	549	the newly-created hash. If the code reference returns a single scalar
513	need not be a reference), this value (i.e. a copy of that scalar to avoid	550	(which need not be a reference), this value (or rather a copy of it) is
514	aliasing) is inserted into the deserialised data structure. If it returns	551	inserted into the deserialised data structure. If it returns an empty
515	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the	552	list (NOTE: I<not> C<undef>, which is a valid scalar), the original
516	original deserialised hash will be inserted. This setting can slow down	553	deserialised hash will be inserted. This setting can slow down decoding
517	decoding considerably.	554	considerably.
518		555
519	When C<$coderef> is omitted or undefined, any existing callback will	556	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	557	be removed and C<decode> will not change the deserialised hash in any
521	way.	558	way.
522		559
…		…
612	=item $json = $json->max_depth ([$maximum_nesting_depth])	649	=item $json = $json->max_depth ([$maximum_nesting_depth])
613		650
614	=item $max_depth = $json->get_max_depth	651	=item $max_depth = $json->get_max_depth
615		652
616	Sets the maximum nesting level (default C<512>) accepted while encoding	653	Sets the maximum nesting level (default C<512>) accepted while encoding
617	or decoding. If the JSON text or Perl data structure has an equal or	654	or decoding. If a higher nesting level is detected in JSON text or a Perl
618	higher nesting level then this limit, then the encoder and decoder will	655	data structure, then the encoder and decoder will stop and croak at that
619	stop and croak at that point.	656	point.
620		657
621	Nesting level is defined by number of hash- or arrayrefs that the encoder	658	Nesting level is defined by number of hash- or arrayrefs that the encoder
622	needs to traverse to reach a given point or the number of C<{> or C<[>	659	needs to traverse to reach a given point or the number of C<{> or C<[>
623	characters without their matching closing parenthesis crossed to reach a	660	characters without their matching closing parenthesis crossed to reach a
624	given character in a string.	661	given character in a string.
625		662
626	Setting the maximum depth to one disallows any nesting, so that ensures	663	Setting the maximum depth to one disallows any nesting, so that ensures
627	that the object is only a single hash/object or array.	664	that the object is only a single hash/object or array.
628		665
629	The argument to C<max_depth> will be rounded up to the next highest power
630	of two. If no argument is given, the highest possible setting will be	666	If no argument is given, the highest possible setting will be used, which
631	used, which is rarely useful.	667	is rarely useful.
		668
		669	Note that nesting is implemented by recursion in C. The default value has
		670	been chosen to be as large as typical operating systems allow without
		671	crashing.
632		672
633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	673	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
634		674
635	=item $json = $json->max_size ([$maximum_string_size])	675	=item $json = $json->max_size ([$maximum_string_size])
636		676
637	=item $max_size = $json->get_max_size	677	=item $max_size = $json->get_max_size
638		678
639	Set the maximum length a JSON text may have (in bytes) where decoding is	679	Set the maximum length a JSON text may have (in bytes) where decoding is
640	being attempted. The default is C<0>, meaning no limit. When C<decode>	680	being attempted. The default is C<0>, meaning no limit. When C<decode>
641	is called on a string longer then this number of characters it will not	681	is called on a string that is longer then this many bytes, it will not
642	attempt to decode the string but throw an exception. This setting has no	682	attempt to decode the string but throw an exception. This setting has no
643	effect on C<encode> (yet).	683	effect on C<encode> (yet).
644		684
645	The argument to C<max_size> will be rounded up to the next B<highest>	685	If no argument is given, the limit check will be deactivated (same as when
646	power of two (so may be more than requested). If no argument is given, the	686	C<0> is specified).
647	limit check will be deactivated (same as when C<0> is specified).
648		687
649	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.
650		689
651	=item $json_text = $json->encode ($perl_scalar)	690	=item $json_text = $json->encode ($perl_scalar)
652		691
653	Converts the given Perl data structure (a simple scalar or a reference	692	Converts the given Perl value or data structure to its JSON
654	to a hash or array) to its JSON representation. Simple scalars will be	693	representation. Croaks on error.
655	converted into JSON string or number sequences, while references to arrays
656	become JSON arrays and references to hashes become JSON objects. Undefined
657	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
658	nor C<false> values will be generated.
659		694
660	=item $perl_scalar = $json->decode ($json_text)	695	=item $perl_scalar = $json->decode ($json_text)
661		696
662	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,
663	returning the resulting simple scalar or reference. Croaks on error.	698	returning the resulting simple scalar or reference. Croaks on error.
664
665	JSON numbers and strings become simple Perl scalars. JSON arrays become
666	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
667	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
668		699
669	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	700	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
670		701
671	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
672	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
673	silently stop parsing there and return the number of characters consumed	704	silently stop parsing there and return the number of characters consumed
674	so far.	705	so far.
675		706
676	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
677	(which is not the brightest thing to do in the first place) and you need
678	to know where the JSON text ends.	708	and you need to know where the JSON text ends.
679		709
680	JSON::XS->new->decode_prefix ("[1] the tail")	710	JSON::XS->new->decode_prefix ("[1] the tail")
681	=> ([], 3)	711	=> ([1], 3)
682		712
683	=back	713	=back
684		714
685		715
686	=head1 INCREMENTAL PARSING	716	=head1 INCREMENTAL PARSING
687
688	[This section is still EXPERIMENTAL]
689		717
690	In some cases, there is the need for incremental parsing of JSON	718	In some cases, there is the need for incremental parsing of JSON
691	texts. While this module always has to keep both JSON text and resulting	719	texts. While this module always has to keep both JSON text and resulting
692	Perl data structure in memory at one time, it does allow you to parse a	720	Perl data structure in memory at one time, it does allow you to parse a
693	JSON stream incrementally. It does so by accumulating text until it has	721	JSON stream incrementally. It does so by accumulating text until it has
694	a full JSON object, which it then can decode. This process is similar to	722	a full JSON object, which it then can decode. This process is similar to
695	using C<decode_prefix> to see if a full JSON object is available, but is	723	using C<decode_prefix> to see if a full JSON object is available, but
696	much more efficient (JSON::XS will only attempt to parse the JSON text	724	is much more efficient (and can be implemented with a minimum of method
		725	calls).
		726
		727	JSON::XS will only attempt to parse the JSON text once it is sure it
697	once it is sure it has enough text to get a decisive result, using a very	728	has enough text to get a decisive result, using a very simple but
698	simple but truly incremental parser).	729	truly incremental parser. This means that it sometimes won't stop as
		730	early as the full parser, for example, it doesn't detect mismatched
		731	parentheses. The only thing it guarantees is that it starts decoding as
		732	soon as a syntactically valid JSON text has been seen. This means you need
		733	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		734	parsing in the presence if syntax errors.
699		735
700	The following two methods deal with this.	736	The following methods implement this incremental parser.
701		737
702	=over 4	738	=over
703		739
704	=item [void, scalar or list context] = $json->incr_parse ([$string])	740	=item [void, scalar or list context] = $json->incr_parse ([$string])
705		741
706	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
707	extract objects from the stream accumulated so far (both of these	743	extract objects from the stream accumulated so far (both of these
…		…
714	return without doing anything further. This can be used to add more text	750	return without doing anything further. This can be used to add more text
715	in as many chunks as you want.	751	in as many chunks as you want.
716		752
717	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
718	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
719	object, otherwise it will return C<undef>. This is the most common way of	755	object, otherwise it will return C<undef>. If there is a parse error,
		756	this method will croak just as C<decode> would do (one can then use
		757	C<incr_skip> to skip the erroneous part). This is the most common way of
720	using the method.	758	using the method.
721		759
722	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
723	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
724	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
725	objects or arrays, instead they must be concatenated back-to-back.	763	whitespace) between the JSON objects or arrays, instead they must be
		764	concatenated back-to-back. If an error occurs, an exception will be
		765	raised as in the scalar context case. Note that in this case, any
		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]");
726		772
727	=item $lvalue_string = $json->incr_text	773	=item $lvalue_string = $json->incr_text
728		774
729	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
730	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
…		…
732	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.
733	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
734	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
735	method before having parsed anything.	781	method before having parsed anything.
736		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
737	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
738	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
739	(such as commas).	789	(such as commas).
740		790
		791	=item $json->incr_skip
		792
		793	This will reset the state of the incremental parser and will remove
		794	the parsed text from the input buffer so far. This is useful after
		795	C<incr_parse> died, in which case the input buffer and incremental parser
		796	state is left unchanged, to skip the text parsed so far and to reset the
		797	parse state.
		798
		799	The difference to C<incr_reset> is that only text until the parse error
		800	occurred is removed.
		801
		802	=item $json->incr_reset
		803
		804	This completely resets the incremental parser, that is, after this call,
		805	it will be as if the parser had never parsed anything.
		806
		807	This is useful if you want to repeatedly parse JSON objects and want to
		808	ignore any trailing data, which means you have to reset the parser after
		809	each successful decode.
		810
741	=back	811	=back
742		812
743	=head2 LIMITATIONS	813	=head2 LIMITATIONS
744		814
745	All options that affect decoding are supported, except	815	The incremental parser is a non-exact parser: it works by gathering as
746	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
747	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate	817	trying to decode it.
748	them back to back and still decode them perfectly. This does not hold true
749	for JSON numbers, however.
750		818
751	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
752	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
753	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
754	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.
755		828
756	=head2 EXAMPLES	829	=head2 EXAMPLES
757		830
758	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
759	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
…		…
903	refers to the abstract Perl language itself.	976	refers to the abstract Perl language itself.
904		977
905		978
906	=head2 JSON -> PERL	979	=head2 JSON -> PERL
907		980
908	=over 4	981	=over
909		982
910	=item object	983	=item object
911		984
912	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
913	keys is preserved (JSON does not preserve object key ordering itself).	986	keys is preserved (JSON does not preserve object key ordering itself).
…		…
933	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
934	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
935	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
936	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
937	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
938	re-encoded toa JSON string).	1011	re-encoded to a JSON string).
939		1012
940	Numbers containing a fractional or exponential part will always be	1013	Numbers containing a fractional or exponential part will always be
941	represented as numeric (floating point) values, possibly at a loss of	1014	represented as numeric (floating point) values, possibly at a loss of
942	precision (in which case you might lose perfect roundtripping ability, but	1015	precision (in which case you might lose perfect roundtripping ability, but
943	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).
944		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
945	=item true, false	1023	=item true, false
946		1024
947	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1025	These JSON atoms become C<Types::Serialiser::true> and
948	respectively. They are overloaded to act almost exactly like the numbers	1026	C<Types::Serialiser::false>, respectively. They are overloaded to act
949	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
950	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).
951		1030
952	=item null	1031	=item null
953		1032
954	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.
955		1049
956	=back	1050	=back
957		1051
958		1052
959	=head2 PERL -> JSON	1053	=head2 PERL -> JSON
960		1054
961	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
962	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
963	a Perl value.	1057	a Perl value.
964		1058
965	=over 4	1059	=over
966		1060
967	=item hash references	1061	=item hash references
968		1062
969	Perl hash references become JSON objects. As there is no inherent ordering	1063	Perl hash references become JSON objects. As there is no inherent
970	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
971	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
972	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
973	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
974	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,
975	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.
976	and is only rarely useful, e.g. when you want to compare some JSON text
977	against another for equality.
978		1070
979	=item array references	1071	=item array references
980		1072
981	Perl array references become JSON arrays.	1073	Perl array references become JSON arrays.
982		1074
983	=item other references	1075	=item other references
984		1076
985	Other unblessed references are generally not allowed and will cause an	1077	Other unblessed references are generally not allowed and will cause an
986	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
987	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.
988	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
989		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;
990	encode_json [\0,JSON::XS::true] # yields [false,true]	1086	encode_json [\0, Types::Serialiser::true] # yields [false,true]
991		1087
992	=item JSON::XS::true, JSON::XS::false	1088	=item Types::Serialiser::true, Types::Serialiser::false
993		1089
994	These special values become JSON true and JSON false values,	1090	These special values from the L<Types::Serialiser> module become JSON true
995	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.
996		1093
997	=item blessed objects	1094	=item blessed objects
998		1095
999	Blessed objects are not directly representable in JSON. See the	1096	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1000	C<allow_blessed> and C<convert_blessed> methods on various options on	1097	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1001	how to deal with this: basically, you can choose between throwing an	1098	below, for details.
1002	exception, encoding the reference as if it weren't blessed, or provide
1003	your own serialiser method.
1004		1099
1005	=item simple scalars	1100	=item simple scalars
1006		1101
1007	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
1008	difficult objects to encode: JSON::XS will encode undefined scalars as	1103	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1036		1131
1037	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
1038	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
1039	:).	1134	:).
1040		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
1041	=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	}
1042		1252
1043		1253
1044	=head1 ENCODING/CODESET FLAG NOTES	1254	=head1 ENCODING/CODESET FLAG NOTES
1045		1255
1046	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
…		…
1064	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
1065	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,
1066	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
1067	the same time, which can be confusing.	1277	the same time, which can be confusing.
1068		1278
1069	=over 4	1279	=over
1070		1280
1071	=item C<utf8> flag disabled	1281	=item C<utf8> flag disabled
1072		1282
1073	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
1074	and expect Unicode strings, that is, characters with high ordinal Unicode	1284	and expect Unicode strings, that is, characters with high ordinal Unicode
1075	values (> 255) will be encoded as such characters, and likewise such	1285	values (> 255) will be encoded as such characters, and likewise such
1076	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
1077	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1287	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1078	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
1079	funny/weird/dumb stuff).	1289	funny/weird/dumb stuff).
1080		1290
1081	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
…		…
1091	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"
1092	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
1093	that.	1303	that.
1094		1304
1095	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
1096	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
1097	octet/binary string in Perl.	1307	octet/binary string in Perl.
1098		1308
1099	=item C<latin1> or C<ascii> flags enabled	1309	=item C<latin1> or C<ascii> flags enabled
1100		1310
1101	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
…		…
1137	proper subset of most 8-bit and multibyte encodings in use in the world.	1347	proper subset of most 8-bit and multibyte encodings in use in the world.
1138		1348
1139	=back	1349	=back
1140		1350
1141		1351
1142	=head1 COMPARISON	1352	=head2 JSON and ECMAscript
1143		1353
1144	As already mentioned, this module was created because none of the existing	1354	JSON syntax is based on how literals are represented in javascript (the
1145	JSON modules could be made to work correctly. First I will describe the	1355	not-standardised predecessor of ECMAscript) which is presumably why it is
1146	problems (or pleasures) I encountered with various existing JSON modules,	1356	called "JavaScript Object Notation".
1147	followed by some benchmark values. JSON::XS was designed not to suffer
1148	from any of these problems or limitations.
1149		1357
1150	=over 4	1358	However, JSON is not a subset (and also not a superset of course) of
		1359	ECMAscript (the standard) or javascript (whatever browsers actually
		1360	implement).
1151		1361
1152	=item JSON 2.xx	1362	If you want to use javascript's C<eval> function to "parse" JSON, you
		1363	might run into parse errors for valid JSON texts, or the resulting data
		1364	structure might not be queryable:
1153		1365
1154	A marvellous piece of engineering, this module either uses JSON::XS	1366	One of the problems is that U+2028 and U+2029 are valid characters inside
1155	directly when available (so will be 100% compatible with it, including	1367	JSON strings, but are not allowed in ECMAscript string literals, so the
1156	speed), or it uses JSON::PP, which is basically JSON::XS translated to	1368	following Perl fragment will not output something that can be guaranteed
1157	Pure Perl, which should be 100% compatible with JSON::XS, just a bit	1369	to be parsable by javascript's C<eval>:
1158	slower.
1159		1370
1160	You cannot really lose by using this module, especially as it tries very	1371	use JSON::XS;
1161	hard to work even with ancient Perl versions, while JSON::XS does not.
1162		1372
1163	=item JSON 1.07	1373	print encode_json [chr 0x2028];
1164		1374
1165	Slow (but very portable, as it is written in pure Perl).	1375	The right fix for this is to use a proper JSON parser in your javascript
		1376	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1377	F<json2.js> parser).
1166		1378
1167	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1379	If this is not an option, you can, as a stop-gap measure, simply encode to
1168	undocumented. One can get far by feeding it Unicode strings and doing	1380	ASCII-only JSON:
1169	en-/decoding oneself, but Unicode escapes are not working properly).
1170		1381
1171	No round-tripping (strings get clobbered if they look like numbers, e.g.	1382	use JSON::XS;
1172	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
1173	decode into the number 2.
1174		1383
1175	=item JSON::PC 0.01	1384	print JSON::XS->new->ascii->encode ([chr 0x2028]);
1176		1385
1177	Very fast.	1386	Note that this will enlarge the resulting JSON text quite a bit if you
		1387	have many non-ASCII characters. You might be tempted to run some regexes
		1388	to only escape U+2028 and U+2029, e.g.:
1178		1389
1179	Undocumented/buggy Unicode handling.	1390	# DO NOT USE THIS!
		1391	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1392	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1393	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1394	print $json;
1180		1395
1181	No round-tripping.	1396	Note that I<this is a bad idea>: the above only works for U+2028 and
		1397	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1398	javascript implementations, however, have issues with other characters as
		1399	well - using C<eval> naively simply I<will> cause problems.
1182		1400
1183	Has problems handling many Perl values (e.g. regex results and other magic	1401	Another problem is that some javascript implementations reserve
1184	values will make it croak).	1402	some property names for their own purposes (which probably makes
		1403	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1404	C<__proto__> property name for its own purposes.
1185		1405
1186	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1406	If that is a problem, you could parse try to filter the resulting JSON
1187	which is not a valid JSON text.	1407	output for these property strings, e.g.:
1188		1408
1189	Unmaintained (maintainer unresponsive for many months, bugs are not	1409	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1190	getting fixed).
1191		1410
1192	=item JSON::Syck 0.21	1411	This works because C<__proto__> is not valid outside of strings, so every
		1412	occurrence of C<"__proto__"\s*:> must be a string used as property name.
1193		1413
1194	Very buggy (often crashes).	1414	If you know of other incompatibilities, please let me know.
1195
1196	Very inflexible (no human-readable format supported, format pretty much
1197	undocumented. I need at least a format for easy reading by humans and a
1198	single-line compact format for use in a protocol, and preferably a way to
1199	generate ASCII-only JSON texts).
1200
1201	Completely broken (and confusingly documented) Unicode handling (Unicode
1202	escapes are not working properly, you need to set ImplicitUnicode to
1203	I<different> values on en- and decoding to get symmetric behaviour).
1204
1205	No round-tripping (simple cases work, but this depends on whether the scalar
1206	value was used in a numeric context or not).
1207
1208	Dumping hashes may skip hash values depending on iterator state.
1209
1210	Unmaintained (maintainer unresponsive for many months, bugs are not
1211	getting fixed).
1212
1213	Does not check input for validity (i.e. will accept non-JSON input and
1214	return "something" instead of raising an exception. This is a security
1215	issue: imagine two banks transferring money between each other using
1216	JSON. One bank might parse a given non-JSON request and deduct money,
1217	while the other might reject the transaction with a syntax error. While a
1218	good protocol will at least recover, that is extra unnecessary work and
1219	the transaction will still not succeed).
1220
1221	=item JSON::DWIW 0.04
1222
1223	Very fast. Very natural. Very nice.
1224
1225	Undocumented Unicode handling (but the best of the pack. Unicode escapes
1226	still don't get parsed properly).
1227
1228	Very inflexible.
1229
1230	No round-tripping.
1231
1232	Does not generate valid JSON texts (key strings are often unquoted, empty keys
1233	result in nothing being output)
1234
1235	Does not check input for validity.
1236
1237	=back
1238		1415
1239		1416
1240	=head2 JSON and YAML	1417	=head2 JSON and YAML
1241		1418
1242	You often hear that JSON is a subset of YAML. This is, however, a mass	1419	You often hear that JSON is a subset of YAML. This is, however, a mass
…		…
1252	my $yaml = $to_yaml->encode ($ref) . "\n";	1429	my $yaml = $to_yaml->encode ($ref) . "\n";
1253		1430
1254	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
1255	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
1256	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
1257	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
1258	noticeably shorter than the 1024 "stream characters" YAML allows and that	1435	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1259	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
1260	(basic multilingual page). YAML also does not allow C<\/> sequences in	1437	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1261	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
1262	generators might).	1439	other JSON generators might).
1263		1440
1264	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
1265	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
1266	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
1267	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
1268	high that you will run into severe interoperability problems when you	1445	high that you will run into severe interoperability problems when you
1269	least expect it.	1446	least expect it.
1270		1447
1271	=over 4	1448	=over
1272		1449
1273	=item (*)	1450	=item (*)
1274		1451
1275	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
1276	authors of the YAML specification) to remove this paragraph, despite him	1453	authors of the YAML specification) to remove this paragraph, despite him
…		…
1286	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
1287	educating users about the changes, instead of spreading lies about the	1464	educating users about the changes, instead of spreading lies about the
1288	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
1289	point out that it isn't true.	1466	point out that it isn't true.
1290		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
1291	=back	1474	=back
1292		1475
1293		1476
1294	=head2 SPEED	1477	=head2 SPEED
1295		1478
…		…
1300		1483
1301	First comes a comparison between various modules using	1484	First comes a comparison between various modules using
1302	a very short single-line JSON string (also available at	1485	a very short single-line JSON string (also available at
1303	L<http://dist.schmorp.de/misc/json/short.json>).	1486	L<http://dist.schmorp.de/misc/json/short.json>).
1304		1487
1305	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1488	{"method": "handleMessage", "params": ["user1",
1306	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1489	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1490	1, 0]}
1307		1491
1308	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
1309	the functional interface, while JSON::XS/2 uses the OO interface	1493	the functional interface, while JSON::XS/2 uses the OO interface
1310	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1494	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1311	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:
1312		1497
1313	module \| encode \| decode \|	1498	module \| encode \| decode \|
1314	-----------\|------------\|------------\|	1499	--------------\|------------\|------------\|
1315	JSON 1.x \| 4990.842 \| 4088.813 \|	1500	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1316	JSON::DWIW \| 51653.990 \| 71575.154 \|	1501	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1317	JSON::PC \| 65948.176 \| 74631.744 \|	1502	JSON::PP \| 15827.562 \| 6638.658 \|
1318	JSON::PP \| 8931.652 \| 3817.168 \|	1503	JSON::Syck \| 63358.066 \| 47662.545 \|
1319	JSON::Syck \| 24877.248 \| 27776.848 \|	1504	JSON::XS \| 511500.488 \| 511500.488 \|
1320	JSON::XS \| 388361.481 \| 227951.304 \|	1505	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1321	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1506	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1322	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1507	Storable \| 66788.280 \| 265462.278 \|
1323	Storable \| 16500.016 \| 135300.129 \|
1324	-----------+------------+------------+	1508	--------------+------------+------------+
1325		1509
1326	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,
1327	about three times faster on decoding, and over forty times faster	1511	about five times faster on decoding, and over thirty to seventy times
1328	than JSON, even with pretty-printing and key sorting. It also compares	1512	faster than JSON's pure perl implementation. It also compares favourably
1329	favourably to Storable for small amounts of data.	1513	to Storable for small amounts of data.
1330		1514
1331	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1515	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1332	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1516	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1333		1517
1334	module \| encode \| decode \|	1518	module \| encode \| decode \|
1335	-----------\|------------\|------------\|	1519	--------------\|------------\|------------\|
1336	JSON 1.x \| 55.260 \| 34.971 \|	1520	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1337	JSON::DWIW \| 825.228 \| 1082.513 \|	1521	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1338	JSON::PC \| 3571.444 \| 2394.829 \|
1339	JSON::PP \| 210.987 \| 32.574 \|	1522	JSON::PP \| 400.640 \| 62.311 \|
1340	JSON::Syck \| 552.551 \| 787.544 \|	1523	JSON::Syck \| 1481.040 \| 1524.869 \|
1341	JSON::XS \| 5780.463 \| 4854.519 \|	1524	JSON::XS \| 20661.596 \| 9541.183 \|
1342	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1525	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1343	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1526	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1344	Storable \| 4445.002 \| 5235.027 \|	1527	Storable \| 19765.806 \| 10000.725 \|
1345	-----------+------------+------------+	1528	--------------+------------+------------+
1346		1529
1347	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
1348	decodes faster).	1531	decodes a bit faster).
1349		1532
1350	On large strings containing lots of high Unicode characters, some modules	1533	On large strings containing lots of high Unicode characters, some modules
1351	(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
1352	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
1353	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
…		…
1389	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
1390	will not end up in front of untrusted eyes.	1573	will not end up in front of untrusted eyes.
1391		1574
1392	If you are using JSON::XS to return packets to consumption	1575	If you are using JSON::XS to return packets to consumption
1393	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
1394	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
1395	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
1396	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
1397	browser developers care only for features, not about getting security	1580	it, as major browser developers care only for features, not about getting
1398	right).	1581	security right).
1399		1582
1400		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*,/($1)[/g;
		1744
		1745	Again, this has some limitations - the magic string must not be encoded
		1746	with character escapes, and the constructor arguments must be non-empty.
		1747
		1748
1401	=head1 THREADS	1749	=head1 (I-)THREADS
1402		1750
1403	This module is I<not> guaranteed to be thread safe and there are no	1751	This module is I<not> guaranteed to be ithread (or MULTIPLICITY-) safe
1404	plans to change this until Perl gets thread support (as opposed to the	1752	and there are no plans to change this. Note that perl's builtin so-called
1405	horribly slow so-called "threads" which are simply slow and bloated	1753	threads/ithreads are officially deprecated and should not be used.
1406	process simulations - use fork, it's I<much> faster, cheaper, better).
1407		1754
1408	(It might actually work, but you have been warned).	1755
		1756	=head1 THE PERILS OF SETLOCALE
		1757
		1758	Sometimes people avoid the Perl locale support and directly call the
		1759	system's setlocale function with C<LC_ALL>.
		1760
		1761	This breaks both perl and modules such as JSON::XS, as stringification of
		1762	numbers no longer works correctly (e.g. C<$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.
1409		1798
1410		1799
1411	=head1 BUGS	1800	=head1 BUGS
1412		1801
1413	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
1414	not mean it's bug-free, only that I think its design is bug-free. It is	1803	not mean it's bug-free, only that I think its design is bug-free. If you
1415	still relatively early in its development. If you keep reporting bugs they	1804	keep reporting bugs they will be fixed swiftly, though.
1416	will be fixed swiftly, though.
1417		1805
1418	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
1419	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.
1420		1808
1421	=cut	1809	=cut
1422		1810
1423	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1811	BEGIN {
1424	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;
1425		1817
1426	sub true() { $true }	1818	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1427	sub false() { $false }
1428
1429	sub is_bool($) {
1430	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1431	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1432	}	1819	}
1433		1820
1434	XSLoader::load "JSON::XS", $VERSION;	1821	XSLoader::load "JSON::XS", $VERSION;
1435
1436	package JSON::XS::Boolean;
1437
1438	use overload
1439	"0+" => sub { ${$_[0]} },
1440	"++" => sub { $_[0] = ${$_[0]} + 1 },
1441	"--" => sub { $_[0] = ${$_[0]} - 1 },
1442	fallback => 1;
1443
1444	1;
1445		1822
1446	=head1 SEE ALSO	1823	=head1 SEE ALSO
1447		1824
1448	The F<json_xs> command line utility for quick experiments.	1825	The F<json_xs> command line utility for quick experiments.
1449		1826
…		…
1452	Marc Lehmann <schmorp@schmorp.de>	1829	Marc Lehmann <schmorp@schmorp.de>
1453	http://home.schmorp.de/	1830	http://home.schmorp.de/
1454		1831
1455	=cut	1832	=cut
1456		1833
		1834	1
		1835

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Comparing JSON-XS/XS.pm (file contents): Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC vs. Revision 1.171 by root, Thu Nov 15 22:49:06 2018 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC vs.
Revision 1.171 by root, Thu Nov 15 22:49:06 2018 UTC