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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.82 by root, Sun Dec 30 21:24:57 2007 UTC vs.
Revision 1.143 by root, Fri Oct 25 20:02:54 2013 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
4		6
5	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
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
35	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
36	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.
37		39
38	Beginning with version 2.0 of the JSON module, when both JSON and	40	Beginning with version 2.0 of the JSON module, when both JSON and
39	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be	41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
40	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
41	and methods). If JSON::XS is not available, it will fall back to the	43	and methods). If JSON::XS is not available, it will fall back to the
42	compatible JSON::PP module as backend, so using JSON instead of JSON::XS	44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
43	gives you a portable JSON API that can be fast when you need and doesn't	45	gives you a portable JSON API that can be fast when you need and doesn't
44	require a C compiler when that is a problem.	46	require a C compiler when that is a problem.
45		47
…		…
47	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
48	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
49	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
50	reports for other reasons.	52	reports for other reasons.
51		53
52	See COMPARISON, below, for a comparison to some other JSON modules.
53
54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
55	vice versa.	55	vice versa.
56		56
57	=head2 FEATURES	57	=head2 FEATURES
58		58
59	=over 4	59	=over 4
60		60
61	=item * correct Unicode handling	61	=item * correct Unicode handling
62		62
63	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
64	it does so.	64	so, and even documents what "correct" means.
65		65
66	=item * round-trip integrity	66	=item * round-trip integrity
67		67
68	When you serialise a perl data structure using only datatypes supported	68	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.	69	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	70	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
71	like a number).	71	it looks like a number). There I<are> minor exceptions to this, read the
		72	MAPPING section below to learn about those.
72		73
73	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
74		75
75	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
76	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
77	feature).	78	feature).
78		79
79	=item * fast	80	=item * fast
80		81
81	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
82	of speed, too.	83	this module usually compares favourably in terms of speed, too.
83		84
84	=item * simple to use	85	=item * simple to use
85		86
86	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
87	interface.	88	oriented interface.
88		89
89	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
90		91
91	You can choose between the most compact guaranteed single-line format	92	You can choose between the most compact guaranteed-single-line format
92	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
93	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
94	Unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
95	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
96		97
97	=back	98	=back
98		99
99	=cut	100	=cut
100		101
101	package JSON::XS;	102	package JSON::XS;
102		103
103	use strict;	104	use common::sense;
104		105
105	our $VERSION = '2.01';	106	our $VERSION = 2.34;
106	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
107		108
108	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
109
110	sub to_json($) {
111	require Carp;
112	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");
113	}
114
115	sub from_json($) {
116	require Carp;
117	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");
118	}
119		110
120	use Exporter;	111	use Exporter;
121	use XSLoader;	112	use XSLoader;
122		113
123	=head1 FUNCTIONAL INTERFACE	114	=head1 FUNCTIONAL INTERFACE
…		…
134		125
135	This function call is functionally identical to:	126	This function call is functionally identical to:
136		127
137	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	128	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
138		129
139	except being faster.	130	Except being faster.
140		131
141	=item $perl_scalar = decode_json $json_text	132	=item $perl_scalar = decode_json $json_text
142		133
143	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	134	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
144	to parse that as an UTF-8 encoded JSON text, returning the resulting	135	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
146		137
147	This function call is functionally identical to:	138	This function call is functionally identical to:
148		139
149	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	140	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
150		141
151	except being faster.	142	Except being faster.
152		143
153	=item $is_boolean = JSON::XS::is_bool $scalar	144	=item $is_boolean = JSON::XS::is_bool $scalar
154		145
155	Returns true if the passed scalar represents either JSON::XS::true or	146	Returns true if the passed scalar represents either JSON::XS::true or
156	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	147	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
174	This enables you to store Unicode characters as single characters in a	165	This enables you to store Unicode characters as single characters in a
175	Perl string - very natural.	166	Perl string - very natural.
176		167
177	=item 2. Perl does I<not> associate an encoding with your strings.	168	=item 2. Perl does I<not> associate an encoding with your strings.
178		169
179	Unless you force it to, e.g. when matching it against a regex, or printing	170	... until you force it to, e.g. when matching it against a regex, or
180	the scalar to a file, in which case Perl either interprets your string as	171	printing the scalar to a file, in which case Perl either interprets your
181	locale-encoded text, octets/binary, or as Unicode, depending on various	172	string as locale-encoded text, octets/binary, or as Unicode, depending
182	settings. In no case is an encoding stored together with your data, it is	173	on various settings. In no case is an encoding stored together with your
183	I<use> that decides encoding, not any magical metadata.	174	data, it is I<use> that decides encoding, not any magical meta data.
184		175
185	=item 3. The internal utf-8 flag has no meaning with regards to the	176	=item 3. The internal utf-8 flag has no meaning with regards to the
186	encoding of your string.	177	encoding of your string.
187		178
188	Just ignore that flag unless you debug a Perl bug, a module written in	179	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
194		185
195	If you didn't know about that flag, just the better, pretend it doesn't	186	If you didn't know about that flag, just the better, pretend it doesn't
196	exist.	187	exist.
197		188
198	=item 4. A "Unicode String" is simply a string where each character can be	189	=item 4. A "Unicode String" is simply a string where each character can be
199	validly interpreted as a Unicode codepoint.	190	validly interpreted as a Unicode code point.
200		191
201	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	192	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
202	Unicode string encoded in UTF-8, giving you a binary string.	193	Unicode string encoded in UTF-8, giving you a binary string.
203		194
204	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	195	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
242		233
243	If C<$enable> is false, then the C<encode> method will not escape Unicode	234	If C<$enable> is false, then the C<encode> method will not escape Unicode
244	characters unless required by the JSON syntax or other flags. This results	235	characters unless required by the JSON syntax or other flags. This results
245	in a faster and more compact format.	236	in a faster and more compact format.
246		237
		238	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		239	document.
		240
247	The main use for this flag is to produce JSON texts that can be	241	The main use for this flag is to produce JSON texts that can be
248	transmitted over a 7-bit channel, as the encoded JSON texts will not	242	transmitted over a 7-bit channel, as the encoded JSON texts will not
249	contain any 8 bit characters.	243	contain any 8 bit characters.
250		244
251	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	245	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
262	will not be affected in any way by this flag, as C<decode> by default	256	will not be affected in any way by this flag, as C<decode> by default
263	expects Unicode, which is a strict superset of latin1.	257	expects Unicode, which is a strict superset of latin1.
264		258
265	If C<$enable> is false, then the C<encode> method will not escape Unicode	259	If C<$enable> is false, then the C<encode> method will not escape Unicode
266	characters unless required by the JSON syntax or other flags.	260	characters unless required by the JSON syntax or other flags.
		261
		262	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		263	document.
267		264
268	The main use for this flag is efficiently encoding binary data as JSON	265	The main use for this flag is efficiently encoding binary data as JSON
269	text, as most octets will not be escaped, resulting in a smaller encoded	266	text, as most octets will not be escaped, resulting in a smaller encoded
270	size. The disadvantage is that the resulting JSON text is encoded	267	size. The disadvantage is that the resulting JSON text is encoded
271	in latin1 (and must correctly be treated as such when storing and	268	in latin1 (and must correctly be treated as such when storing and
…		…
290		287
291	If C<$enable> is false, then the C<encode> method will return the JSON	288	If C<$enable> is false, then the C<encode> method will return the JSON
292	string as a (non-encoded) Unicode string, while C<decode> expects thus a	289	string as a (non-encoded) Unicode string, while C<decode> expects thus a
293	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	290	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
294	to be done yourself, e.g. using the Encode module.	291	to be done yourself, e.g. using the Encode module.
		292
		293	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		294	document.
295		295
296	Example, output UTF-16BE-encoded JSON:	296	Example, output UTF-16BE-encoded JSON:
297		297
298	use Encode;	298	use Encode;
299	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	299	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
422	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	422	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
423	by sorting their keys. This is adding a comparatively high overhead.	423	by sorting their keys. This is adding a comparatively high overhead.
424		424
425	If C<$enable> is false, then the C<encode> method will output key-value	425	If C<$enable> is false, then the C<encode> method will output key-value
426	pairs in the order Perl stores them (which will likely change between runs	426	pairs in the order Perl stores them (which will likely change between runs
427	of the same script).	427	of the same script, and can change even within the same run from 5.18
		428	onwards).
428		429
429	This option is useful if you want the same data structure to be encoded as	430	This option is useful if you want the same data structure to be encoded as
430	the same JSON text (given the same overall settings). If it is disabled,	431	the same JSON text (given the same overall settings). If it is disabled,
431	the same hash might be encoded differently even if contains the same data,	432	the same hash might be encoded differently even if contains the same data,
432	as key-value pairs have no inherent ordering in Perl.	433	as key-value pairs have no inherent ordering in Perl.
433		434
434	This setting has no effect when decoding JSON texts.	435	This setting has no effect when decoding JSON texts.
435		436
		437	This setting has currently no effect on tied hashes.
		438
436	=item $json = $json->allow_nonref ([$enable])	439	=item $json = $json->allow_nonref ([$enable])
437		440
438	=item $enabled = $json->get_allow_nonref	441	=item $enabled = $json->get_allow_nonref
439		442
440	If C<$enable> is true (or missing), then the C<encode> method can convert a	443	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
450	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	453	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
451	resulting in an invalid JSON text:	454	resulting in an invalid JSON text:
452		455
453	JSON::XS->new->allow_nonref->encode ("Hello, World!")	456	JSON::XS->new->allow_nonref->encode ("Hello, World!")
454	=> "Hello, World!"	457	=> "Hello, World!"
		458
		459	=item $json = $json->allow_unknown ([$enable])
		460
		461	=item $enabled = $json->get_allow_unknown
		462
		463	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		464	exception when it encounters values it cannot represent in JSON (for
		465	example, filehandles) but instead will encode a JSON C<null> value. Note
		466	that blessed objects are not included here and are handled separately by
		467	c<allow_nonref>.
		468
		469	If C<$enable> is false (the default), then C<encode> will throw an
		470	exception when it encounters anything it cannot encode as JSON.
		471
		472	This option does not affect C<decode> in any way, and it is recommended to
		473	leave it off unless you know your communications partner.
455		474
456	=item $json = $json->allow_blessed ([$enable])	475	=item $json = $json->allow_blessed ([$enable])
457		476
458	=item $enabled = $json->get_allow_blessed	477	=item $enabled = $json->get_allow_blessed
459		478
…		…
600	=item $json = $json->max_depth ([$maximum_nesting_depth])	619	=item $json = $json->max_depth ([$maximum_nesting_depth])
601		620
602	=item $max_depth = $json->get_max_depth	621	=item $max_depth = $json->get_max_depth
603		622
604	Sets the maximum nesting level (default C<512>) accepted while encoding	623	Sets the maximum nesting level (default C<512>) accepted while encoding
605	or decoding. If the JSON text or Perl data structure has an equal or	624	or decoding. If a higher nesting level is detected in JSON text or a Perl
606	higher nesting level then this limit, then the encoder and decoder will	625	data structure, then the encoder and decoder will stop and croak at that
607	stop and croak at that point.	626	point.
608		627
609	Nesting level is defined by number of hash- or arrayrefs that the encoder	628	Nesting level is defined by number of hash- or arrayrefs that the encoder
610	needs to traverse to reach a given point or the number of C<{> or C<[>	629	needs to traverse to reach a given point or the number of C<{> or C<[>
611	characters without their matching closing parenthesis crossed to reach a	630	characters without their matching closing parenthesis crossed to reach a
612	given character in a string.	631	given character in a string.
613		632
614	Setting the maximum depth to one disallows any nesting, so that ensures	633	Setting the maximum depth to one disallows any nesting, so that ensures
615	that the object is only a single hash/object or array.	634	that the object is only a single hash/object or array.
616		635
617	The argument to C<max_depth> will be rounded up to the next highest power
618	of two. If no argument is given, the highest possible setting will be	636	If no argument is given, the highest possible setting will be used, which
619	used, which is rarely useful.	637	is rarely useful.
		638
		639	Note that nesting is implemented by recursion in C. The default value has
		640	been chosen to be as large as typical operating systems allow without
		641	crashing.
620		642
621	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	643	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
622		644
623	=item $json = $json->max_size ([$maximum_string_size])	645	=item $json = $json->max_size ([$maximum_string_size])
624		646
625	=item $max_size = $json->get_max_size	647	=item $max_size = $json->get_max_size
626		648
627	Set the maximum length a JSON text may have (in bytes) where decoding is	649	Set the maximum length a JSON text may have (in bytes) where decoding is
628	being attempted. The default is C<0>, meaning no limit. When C<decode>	650	being attempted. The default is C<0>, meaning no limit. When C<decode>
629	is called on a string longer then this number of characters it will not	651	is called on a string that is longer then this many bytes, it will not
630	attempt to decode the string but throw an exception. This setting has no	652	attempt to decode the string but throw an exception. This setting has no
631	effect on C<encode> (yet).	653	effect on C<encode> (yet).
632		654
633	The argument to C<max_size> will be rounded up to the next B<highest>	655	If no argument is given, the limit check will be deactivated (same as when
634	power of two (so may be more than requested). If no argument is given, the	656	C<0> is specified).
635	limit check will be deactivated (same as when C<0> is specified).
636		657
637	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	658	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
638		659
639	=item $json_text = $json->encode ($perl_scalar)	660	=item $json_text = $json->encode ($perl_scalar)
640		661
641	Converts the given Perl data structure (a simple scalar or a reference	662	Converts the given Perl value or data structure to its JSON
642	to a hash or array) to its JSON representation. Simple scalars will be	663	representation. Croaks on error.
643	converted into JSON string or number sequences, while references to arrays
644	become JSON arrays and references to hashes become JSON objects. Undefined
645	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
646	nor C<false> values will be generated.
647		664
648	=item $perl_scalar = $json->decode ($json_text)	665	=item $perl_scalar = $json->decode ($json_text)
649		666
650	The opposite of C<encode>: expects a JSON text and tries to parse it,	667	The opposite of C<encode>: expects a JSON text and tries to parse it,
651	returning the resulting simple scalar or reference. Croaks on error.	668	returning the resulting simple scalar or reference. Croaks on error.
652
653	JSON numbers and strings become simple Perl scalars. JSON arrays become
654	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
655	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
656		669
657	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	670	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
658		671
659	This works like the C<decode> method, but instead of raising an exception	672	This works like the C<decode> method, but instead of raising an exception
660	when there is trailing garbage after the first JSON object, it will	673	when there is trailing garbage after the first JSON object, it will
661	silently stop parsing there and return the number of characters consumed	674	silently stop parsing there and return the number of characters consumed
662	so far.	675	so far.
663		676
664	This is useful if your JSON texts are not delimited by an outer protocol	677	This is useful if your JSON texts are not delimited by an outer protocol
665	(which is not the brightest thing to do in the first place) and you need
666	to know where the JSON text ends.	678	and you need to know where the JSON text ends.
667		679
668	JSON::XS->new->decode_prefix ("[1] the tail")	680	JSON::XS->new->decode_prefix ("[1] the tail")
669	=> ([], 3)	681	=> ([], 3)
670		682
671	=back	683	=back
		684
		685
		686	=head1 INCREMENTAL PARSING
		687
		688	In some cases, there is the need for incremental parsing of JSON
		689	texts. While this module always has to keep both JSON text and resulting
		690	Perl data structure in memory at one time, it does allow you to parse a
		691	JSON stream incrementally. It does so by accumulating text until it has
		692	a full JSON object, which it then can decode. This process is similar to
		693	using C<decode_prefix> to see if a full JSON object is available, but
		694	is much more efficient (and can be implemented with a minimum of method
		695	calls).
		696
		697	JSON::XS will only attempt to parse the JSON text once it is sure it
		698	has enough text to get a decisive result, using a very simple but
		699	truly incremental parser. This means that it sometimes won't stop as
		700	early as the full parser, for example, it doesn't detect mismatched
		701	parentheses. The only thing it guarantees is that it starts decoding as
		702	soon as a syntactically valid JSON text has been seen. This means you need
		703	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		704	parsing in the presence if syntax errors.
		705
		706	The following methods implement this incremental parser.
		707
		708	=over 4
		709
		710	=item [void, scalar or list context] = $json->incr_parse ([$string])
		711
		712	This is the central parsing function. It can both append new text and
		713	extract objects from the stream accumulated so far (both of these
		714	functions are optional).
		715
		716	If C<$string> is given, then this string is appended to the already
		717	existing JSON fragment stored in the C<$json> object.
		718
		719	After that, if the function is called in void context, it will simply
		720	return without doing anything further. This can be used to add more text
		721	in as many chunks as you want.
		722
		723	If the method is called in scalar context, then it will try to extract
		724	exactly I<one> JSON object. If that is successful, it will return this
		725	object, otherwise it will return C<undef>. If there is a parse error,
		726	this method will croak just as C<decode> would do (one can then use
		727	C<incr_skip> to skip the erroneous part). This is the most common way of
		728	using the method.
		729
		730	And finally, in list context, it will try to extract as many objects
		731	from the stream as it can find and return them, or the empty list
		732	otherwise. For this to work, there must be no separators between the JSON
		733	objects or arrays, instead they must be concatenated back-to-back. If
		734	an error occurs, an exception will be raised as in the scalar context
		735	case. Note that in this case, any previously-parsed JSON texts will be
		736	lost.
		737
		738	Example: Parse some JSON arrays/objects in a given string and return
		739	them.
		740
		741	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		742
		743	=item $lvalue_string = $json->incr_text
		744
		745	This method returns the currently stored JSON fragment as an lvalue, that
		746	is, you can manipulate it. This I<only> works when a preceding call to
		747	C<incr_parse> in I<scalar context> successfully returned an object. Under
		748	all other circumstances you must not call this function (I mean it.
		749	although in simple tests it might actually work, it I<will> fail under
		750	real world conditions). As a special exception, you can also call this
		751	method before having parsed anything.
		752
		753	This function is useful in two cases: a) finding the trailing text after a
		754	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		755	(such as commas).
		756
		757	=item $json->incr_skip
		758
		759	This will reset the state of the incremental parser and will remove
		760	the parsed text from the input buffer so far. This is useful after
		761	C<incr_parse> died, in which case the input buffer and incremental parser
		762	state is left unchanged, to skip the text parsed so far and to reset the
		763	parse state.
		764
		765	The difference to C<incr_reset> is that only text until the parse error
		766	occurred is removed.
		767
		768	=item $json->incr_reset
		769
		770	This completely resets the incremental parser, that is, after this call,
		771	it will be as if the parser had never parsed anything.
		772
		773	This is useful if you want to repeatedly parse JSON objects and want to
		774	ignore any trailing data, which means you have to reset the parser after
		775	each successful decode.
		776
		777	=back
		778
		779	=head2 LIMITATIONS
		780
		781	All options that affect decoding are supported, except
		782	C<allow_nonref>. The reason for this is that it cannot be made to work
		783	sensibly: JSON objects and arrays are self-delimited, i.e. you can
		784	concatenate them back to back and still decode them perfectly. This does
		785	not hold true for JSON numbers, however.
		786
		787	For example, is the string C<1> a single JSON number, or is it simply the
		788	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		789	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		790	takes the conservative route and disallows this case.
		791
		792	=head2 EXAMPLES
		793
		794	Some examples will make all this clearer. First, a simple example that
		795	works similarly to C<decode_prefix>: We want to decode the JSON object at
		796	the start of a string and identify the portion after the JSON object:
		797
		798	my $text = "[1,2,3] hello";
		799
		800	my $json = new JSON::XS;
		801
		802	my $obj = $json->incr_parse ($text)
		803	or die "expected JSON object or array at beginning of string";
		804
		805	my $tail = $json->incr_text;
		806	# $tail now contains " hello"
		807
		808	Easy, isn't it?
		809
		810	Now for a more complicated example: Imagine a hypothetical protocol where
		811	you read some requests from a TCP stream, and each request is a JSON
		812	array, without any separation between them (in fact, it is often useful to
		813	use newlines as "separators", as these get interpreted as whitespace at
		814	the start of the JSON text, which makes it possible to test said protocol
		815	with C<telnet>...).
		816
		817	Here is how you'd do it (it is trivial to write this in an event-based
		818	manner):
		819
		820	my $json = new JSON::XS;
		821
		822	# read some data from the socket
		823	while (sysread $socket, my $buf, 4096) {
		824
		825	# split and decode as many requests as possible
		826	for my $request ($json->incr_parse ($buf)) {
		827	# act on the $request
		828	}
		829	}
		830
		831	Another complicated example: Assume you have a string with JSON objects
		832	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		833	[3]>). To parse them, we have to skip the commas between the JSON texts,
		834	and here is where the lvalue-ness of C<incr_text> comes in useful:
		835
		836	my $text = "[1],[2], [3]";
		837	my $json = new JSON::XS;
		838
		839	# void context, so no parsing done
		840	$json->incr_parse ($text);
		841
		842	# now extract as many objects as possible. note the
		843	# use of scalar context so incr_text can be called.
		844	while (my $obj = $json->incr_parse) {
		845	# do something with $obj
		846
		847	# now skip the optional comma
		848	$json->incr_text =~ s/^ \s* , //x;
		849	}
		850
		851	Now lets go for a very complex example: Assume that you have a gigantic
		852	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		853	but you cannot load it into memory fully (this has actually happened in
		854	the real world :).
		855
		856	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		857	can still help you: You implement a (very simple) array parser and let
		858	JSON decode the array elements, which are all full JSON objects on their
		859	own (this wouldn't work if the array elements could be JSON numbers, for
		860	example):
		861
		862	my $json = new JSON::XS;
		863
		864	# open the monster
		865	open my $fh, "<bigfile.json"
		866	or die "bigfile: $!";
		867
		868	# first parse the initial "["
		869	for (;;) {
		870	sysread $fh, my $buf, 65536
		871	or die "read error: $!";
		872	$json->incr_parse ($buf); # void context, so no parsing
		873
		874	# Exit the loop once we found and removed(!) the initial "[".
		875	# In essence, we are (ab-)using the $json object as a simple scalar
		876	# we append data to.
		877	last if $json->incr_text =~ s/^ \s* \[ //x;
		878	}
		879
		880	# now we have the skipped the initial "[", so continue
		881	# parsing all the elements.
		882	for (;;) {
		883	# in this loop we read data until we got a single JSON object
		884	for (;;) {
		885	if (my $obj = $json->incr_parse) {
		886	# do something with $obj
		887	last;
		888	}
		889
		890	# add more data
		891	sysread $fh, my $buf, 65536
		892	or die "read error: $!";
		893	$json->incr_parse ($buf); # void context, so no parsing
		894	}
		895
		896	# in this loop we read data until we either found and parsed the
		897	# separating "," between elements, or the final "]"
		898	for (;;) {
		899	# first skip whitespace
		900	$json->incr_text =~ s/^\s*//;
		901
		902	# if we find "]", we are done
		903	if ($json->incr_text =~ s/^\]//) {
		904	print "finished.\n";
		905	exit;
		906	}
		907
		908	# if we find ",", we can continue with the next element
		909	if ($json->incr_text =~ s/^,//) {
		910	last;
		911	}
		912
		913	# if we find anything else, we have a parse error!
		914	if (length $json->incr_text) {
		915	die "parse error near ", $json->incr_text;
		916	}
		917
		918	# else add more data
		919	sysread $fh, my $buf, 65536
		920	or die "read error: $!";
		921	$json->incr_parse ($buf); # void context, so no parsing
		922	}
		923
		924	This is a complex example, but most of the complexity comes from the fact
		925	that we are trying to be correct (bear with me if I am wrong, I never ran
		926	the above example :).
		927
672		928
673		929
674	=head1 MAPPING	930	=head1 MAPPING
675		931
676	This section describes how JSON::XS maps Perl values to JSON values and	932	This section describes how JSON::XS maps Perl values to JSON values and
…		…
706		962
707	A JSON number becomes either an integer, numeric (floating point) or	963	A JSON number becomes either an integer, numeric (floating point) or
708	string scalar in perl, depending on its range and any fractional parts. On	964	string scalar in perl, depending on its range and any fractional parts. On
709	the Perl level, there is no difference between those as Perl handles all	965	the Perl level, there is no difference between those as Perl handles all
710	the conversion details, but an integer may take slightly less memory and	966	the conversion details, but an integer may take slightly less memory and
711	might represent more values exactly than (floating point) numbers.	967	might represent more values exactly than floating point numbers.
712		968
713	If the number consists of digits only, JSON::XS will try to represent	969	If the number consists of digits only, JSON::XS will try to represent
714	it as an integer value. If that fails, it will try to represent it as	970	it as an integer value. If that fails, it will try to represent it as
715	a numeric (floating point) value if that is possible without loss of	971	a numeric (floating point) value if that is possible without loss of
716	precision. Otherwise it will preserve the number as a string value.	972	precision. Otherwise it will preserve the number as a string value (in
		973	which case you lose roundtripping ability, as the JSON number will be
		974	re-encoded to a JSON string).
717		975
718	Numbers containing a fractional or exponential part will always be	976	Numbers containing a fractional or exponential part will always be
719	represented as numeric (floating point) values, possibly at a loss of	977	represented as numeric (floating point) values, possibly at a loss of
720	precision.	978	precision (in which case you might lose perfect roundtripping ability, but
		979	the JSON number will still be re-encoded as a JSON number).
721		980
722	This might create round-tripping problems as numbers might become strings,	981	Note that precision is not accuracy - binary floating point values cannot
723	but as Perl is typeless there is no other way to do it.	982	represent most decimal fractions exactly, and when converting from and to
		983	floating point, JSON::XS only guarantees precision up to but not including
		984	the least significant bit.
724		985
725	=item true, false	986	=item true, false
726		987
727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	988	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
728	respectively. They are overloaded to act almost exactly like the numbers	989	respectively. They are overloaded to act almost exactly like the numbers
…		…
744		1005
745	=over 4	1006	=over 4
746		1007
747	=item hash references	1008	=item hash references
748		1009
749	Perl hash references become JSON objects. As there is no inherent ordering	1010	Perl hash references become JSON objects. As there is no inherent
750	in hash keys (or JSON objects), they will usually be encoded in a	1011	ordering in hash keys (or JSON objects), they will usually be encoded
751	pseudo-random order that can change between runs of the same program but	1012	in a pseudo-random order. JSON::XS can optionally sort the hash keys
752	stays generally the same within a single run of a program. JSON::XS can	1013	(determined by the I<canonical> flag), so the same datastructure will
753	optionally sort the hash keys (determined by the I<canonical> flag), so	1014	serialise to the same JSON text (given same settings and version of
754	the same datastructure will serialise to the same JSON text (given same	1015	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
755	settings and version of JSON::XS), but this incurs a runtime overhead	1016	e.g. when you want to compare some JSON text against another for equality.
756	and is only rarely useful, e.g. when you want to compare some JSON text
757	against another for equality.
758		1017
759	=item array references	1018	=item array references
760		1019
761	Perl array references become JSON arrays.	1020	Perl array references become JSON arrays.
762		1021
…		…
765	Other unblessed references are generally not allowed and will cause an	1024	Other unblessed references are generally not allowed and will cause an
766	exception to be thrown, except for references to the integers C<0> and	1025	exception to be thrown, except for references to the integers C<0> and
767	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1026	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
768	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1027	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
769		1028
770	encode_json [\0,JSON::XS::true] # yields [false,true]	1029	encode_json [\0, JSON::XS::true] # yields [false,true]
771		1030
772	=item JSON::XS::true, JSON::XS::false	1031	=item JSON::XS::true, JSON::XS::false
773		1032
774	These special values become JSON true and JSON false values,	1033	These special values become JSON true and JSON false values,
775	respectively. You can also use C<\1> and C<\0> directly if you want.	1034	respectively. You can also use C<\1> and C<\0> directly if you want.
776		1035
777	=item blessed objects	1036	=item blessed objects
778		1037
779	Blessed objects are not allowed. JSON::XS currently tries to encode their	1038	Blessed objects are not directly representable in JSON. See the
780	underlying representation (hash- or arrayref), but this behaviour might	1039	C<allow_blessed> and C<convert_blessed> methods on various options on
781	change in future versions.	1040	how to deal with this: basically, you can choose between throwing an
		1041	exception, encoding the reference as if it weren't blessed, or provide
		1042	your own serialiser method.
782		1043
783	=item simple scalars	1044	=item simple scalars
784		1045
785	Simple Perl scalars (any scalar that is not a reference) are the most	1046	Simple Perl scalars (any scalar that is not a reference) are the most
786	difficult objects to encode: JSON::XS will encode undefined scalars as	1047	difficult objects to encode: JSON::XS will encode undefined scalars as
787	JSON null value, scalars that have last been used in a string context	1048	JSON C<null> values, scalars that have last been used in a string context
788	before encoding as JSON strings and anything else as number value:	1049	before encoding as JSON strings, and anything else as number value:
789		1050
790	# dump as number	1051	# dump as number
791	encode_json [2] # yields [2]	1052	encode_json [2] # yields [2]
792	encode_json [-3.0e17] # yields [-3e+17]	1053	encode_json [-3.0e17] # yields [-3e+17]
793	my $value = 5; encode_json [$value] # yields [5]	1054	my $value = 5; encode_json [$value] # yields [5]
…		…
811	my $x = "3"; # some variable containing a string	1072	my $x = "3"; # some variable containing a string
812	$x += 0; # numify it, ensuring it will be dumped as a number	1073	$x += 0; # numify it, ensuring it will be dumped as a number
813	$x *= 1; # same thing, the choice is yours.	1074	$x *= 1; # same thing, the choice is yours.
814		1075
815	You can not currently force the type in other, less obscure, ways. Tell me	1076	You can not currently force the type in other, less obscure, ways. Tell me
816	if you need this capability.	1077	if you need this capability (but don't forget to explain why it's needed
		1078	:).
		1079
		1080	Note that numerical precision has the same meaning as under Perl (so
		1081	binary to decimal conversion follows the same rules as in Perl, which
		1082	can differ to other languages). Also, your perl interpreter might expose
		1083	extensions to the floating point numbers of your platform, such as
		1084	infinities or NaN's - these cannot be represented in JSON, and it is an
		1085	error to pass those in.
817		1086
818	=back	1087	=back
819		1088
820		1089
821	=head1 COMPARISON	1090	=head1 ENCODING/CODESET FLAG NOTES
822		1091
823	As already mentioned, this module was created because none of the existing	1092	The interested reader might have seen a number of flags that signify
824	JSON modules could be made to work correctly. First I will describe the	1093	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
825	problems (or pleasures) I encountered with various existing JSON modules,	1094	some confusion on what these do, so here is a short comparison:
826	followed by some benchmark values. JSON::XS was designed not to suffer	1095
827	from any of these problems or limitations.	1096	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1097	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1098	control whether C<encode> escapes character values outside their respective
		1099	codeset range. Neither of these flags conflict with each other, although
		1100	some combinations make less sense than others.
		1101
		1102	Care has been taken to make all flags symmetrical with respect to
		1103	C<encode> and C<decode>, that is, texts encoded with any combination of
		1104	these flag values will be correctly decoded when the same flags are used
		1105	- in general, if you use different flag settings while encoding vs. when
		1106	decoding you likely have a bug somewhere.
		1107
		1108	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1109	simply an abstract set of character-codepoint pairs, while an encoding
		1110	takes those codepoint numbers and I<encodes> them, in our case into
		1111	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1112	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1113	the same time, which can be confusing.
828		1114
829	=over 4	1115	=over 4
830		1116
831	=item JSON 1.07	1117	=item C<utf8> flag disabled
832		1118
833	Slow (but very portable, as it is written in pure Perl).	1119	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1120	and expect Unicode strings, that is, characters with high ordinal Unicode
		1121	values (> 255) will be encoded as such characters, and likewise such
		1122	characters are decoded as-is, no changes to them will be done, except
		1123	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1124	respectively (to Perl, these are the same thing in strings unless you do
		1125	funny/weird/dumb stuff).
834		1126
835	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1127	This is useful when you want to do the encoding yourself (e.g. when you
836	undocumented. One can get far by feeding it Unicode strings and doing	1128	want to have UTF-16 encoded JSON texts) or when some other layer does
837	en-/decoding oneself, but Unicode escapes are not working properly).	1129	the encoding for you (for example, when printing to a terminal using a
		1130	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1131	to UTF-8 encode your data first and have Perl encode it another time).
838		1132
839	No round-tripping (strings get clobbered if they look like numbers, e.g.	1133	=item C<utf8> flag enabled
840	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
841	decode into the number 2.
842		1134
843	=item JSON::PC 0.01	1135	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1136	characters using the corresponding UTF-8 multi-byte sequence, and will
		1137	expect your input strings to be encoded as UTF-8, that is, no "character"
		1138	of the input string must have any value > 255, as UTF-8 does not allow
		1139	that.
844		1140
845	Very fast.	1141	The C<utf8> flag therefore switches between two modes: disabled means you
		1142	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1143	octet/binary string in Perl.
846		1144
847	Undocumented/buggy Unicode handling.	1145	=item C<latin1> or C<ascii> flags enabled
848		1146
849	No round-tripping.	1147	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1148	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1149	characters as specified by the C<utf8> flag.
850		1150
851	Has problems handling many Perl values (e.g. regex results and other magic	1151	If C<utf8> is disabled, then the result is also correctly encoded in those
852	values will make it croak).	1152	character sets (as both are proper subsets of Unicode, meaning that a
		1153	Unicode string with all character values < 256 is the same thing as a
		1154	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1155	the same thing as an ASCII string in Perl).
853		1156
854	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1157	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
855	which is not a valid JSON text.	1158	regardless of these flags, just some more characters will be escaped using
		1159	C<\uXXXX> then before.
856		1160
857	Unmaintained (maintainer unresponsive for many months, bugs are not	1161	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
858	getting fixed).	1162	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1163	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1164	a subset of Unicode), while ASCII is.
859		1165
860	=item JSON::Syck 0.21	1166	Surprisingly, C<decode> will ignore these flags and so treat all input
		1167	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1168	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1169	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
861		1170
862	Very buggy (often crashes).	1171	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1172	they only govern when the JSON output engine escapes a character or not.
863		1173
864	Very inflexible (no human-readable format supported, format pretty much	1174	The main use for C<latin1> is to relatively efficiently store binary data
865	undocumented. I need at least a format for easy reading by humans and a	1175	as JSON, at the expense of breaking compatibility with most JSON decoders.
866	single-line compact format for use in a protocol, and preferably a way to
867	generate ASCII-only JSON texts).
868		1176
869	Completely broken (and confusingly documented) Unicode handling (Unicode	1177	The main use for C<ascii> is to force the output to not contain characters
870	escapes are not working properly, you need to set ImplicitUnicode to	1178	with values > 127, which means you can interpret the resulting string
871	I<different> values on en- and decoding to get symmetric behaviour).	1179	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
872		1180	8-bit-encoding, and still get the same data structure back. This is useful
873	No round-tripping (simple cases work, but this depends on whether the scalar	1181	when your channel for JSON transfer is not 8-bit clean or the encoding
874	value was used in a numeric context or not).	1182	might be mangled in between (e.g. in mail), and works because ASCII is a
875		1183	proper subset of most 8-bit and multibyte encodings in use in the world.
876	Dumping hashes may skip hash values depending on iterator state.
877
878	Unmaintained (maintainer unresponsive for many months, bugs are not
879	getting fixed).
880
881	Does not check input for validity (i.e. will accept non-JSON input and
882	return "something" instead of raising an exception. This is a security
883	issue: imagine two banks transferring money between each other using
884	JSON. One bank might parse a given non-JSON request and deduct money,
885	while the other might reject the transaction with a syntax error. While a
886	good protocol will at least recover, that is extra unnecessary work and
887	the transaction will still not succeed).
888
889	=item JSON::DWIW 0.04
890
891	Very fast. Very natural. Very nice.
892
893	Undocumented Unicode handling (but the best of the pack. Unicode escapes
894	still don't get parsed properly).
895
896	Very inflexible.
897
898	No round-tripping.
899
900	Does not generate valid JSON texts (key strings are often unquoted, empty keys
901	result in nothing being output)
902
903	Does not check input for validity.
904		1184
905	=back	1185	=back
906		1186
907		1187
		1188	=head2 JSON and ECMAscript
		1189
		1190	JSON syntax is based on how literals are represented in javascript (the
		1191	not-standardised predecessor of ECMAscript) which is presumably why it is
		1192	called "JavaScript Object Notation".
		1193
		1194	However, JSON is not a subset (and also not a superset of course) of
		1195	ECMAscript (the standard) or javascript (whatever browsers actually
		1196	implement).
		1197
		1198	If you want to use javascript's C<eval> function to "parse" JSON, you
		1199	might run into parse errors for valid JSON texts, or the resulting data
		1200	structure might not be queryable:
		1201
		1202	One of the problems is that U+2028 and U+2029 are valid characters inside
		1203	JSON strings, but are not allowed in ECMAscript string literals, so the
		1204	following Perl fragment will not output something that can be guaranteed
		1205	to be parsable by javascript's C<eval>:
		1206
		1207	use JSON::XS;
		1208
		1209	print encode_json [chr 0x2028];
		1210
		1211	The right fix for this is to use a proper JSON parser in your javascript
		1212	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1213	F<json2.js> parser).
		1214
		1215	If this is not an option, you can, as a stop-gap measure, simply encode to
		1216	ASCII-only JSON:
		1217
		1218	use JSON::XS;
		1219
		1220	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1221
		1222	Note that this will enlarge the resulting JSON text quite a bit if you
		1223	have many non-ASCII characters. You might be tempted to run some regexes
		1224	to only escape U+2028 and U+2029, e.g.:
		1225
		1226	# DO NOT USE THIS!
		1227	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1228	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1229	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1230	print $json;
		1231
		1232	Note that I<this is a bad idea>: the above only works for U+2028 and
		1233	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1234	javascript implementations, however, have issues with other characters as
		1235	well - using C<eval> naively simply I<will> cause problems.
		1236
		1237	Another problem is that some javascript implementations reserve
		1238	some property names for their own purposes (which probably makes
		1239	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1240	C<__proto__> property name for its own purposes.
		1241
		1242	If that is a problem, you could parse try to filter the resulting JSON
		1243	output for these property strings, e.g.:
		1244
		1245	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1246
		1247	This works because C<__proto__> is not valid outside of strings, so every
		1248	occurrence of C<"__proto__"\s*:> must be a string used as property name.
		1249
		1250	If you know of other incompatibilities, please let me know.
		1251
		1252
908	=head2 JSON and YAML	1253	=head2 JSON and YAML
909		1254
910	You often hear that JSON is a subset of YAML. This is, however, a mass	1255	You often hear that JSON is a subset of YAML. This is, however, a mass
911	hysteria(*) and very far from the truth. In general, there is no way to	1256	hysteria(*) and very far from the truth (as of the time of this writing),
		1257	so let me state it clearly: I<in general, there is no way to configure
912	configure JSON::XS to output a data structure as valid YAML that works for	1258	JSON::XS to output a data structure as valid YAML> that works in all
913	all cases.	1259	cases.
914		1260
915	If you really must use JSON::XS to generate YAML, you should use this	1261	If you really must use JSON::XS to generate YAML, you should use this
916	algorithm (subject to change in future versions):	1262	algorithm (subject to change in future versions):
917		1263
918	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1264	my $to_yaml = JSON::XS->new->utf8->space_after (1);
919	my $yaml = $to_yaml->encode ($ref) . "\n";	1265	my $yaml = $to_yaml->encode ($ref) . "\n";
920		1266
921	This will usually generate JSON texts that also parse as valid	1267	This will I<usually> generate JSON texts that also parse as valid
922	YAML. Please note that YAML has hardcoded limits on (simple) object key	1268	YAML. Please note that YAML has hardcoded limits on (simple) object key
923	lengths that JSON doesn't have and also has different and incompatible	1269	lengths that JSON doesn't have and also has different and incompatible
924	unicode handling, so you should make sure that your hash keys are	1270	unicode character escape syntax, so you should make sure that your hash
925	noticeably shorter than the 1024 "stream characters" YAML allows and that	1271	keys are noticeably shorter than the 1024 "stream characters" YAML allows
926	you do not have codepoints with values outside the Unicode BMP (basic	1272	and that you do not have characters with codepoint values outside the
927	multilingual page). YAML also does not allow C<\/> sequences in strings	1273	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
928	(which JSON::XS does not I<currently> generate).	1274	sequences in strings (which JSON::XS does not I<currently> generate, but
		1275	other JSON generators might).
929		1276
930	There might be other incompatibilities that I am not aware of. In general	1277	There might be other incompatibilities that I am not aware of (or the YAML
		1278	specification has been changed yet again - it does so quite often). In
931	you should not try to generate YAML with a JSON generator or vice versa,	1279	general you should not try to generate YAML with a JSON generator or vice
932	or try to parse JSON with a YAML parser or vice versa: chances are high	1280	versa, or try to parse JSON with a YAML parser or vice versa: chances are
933	that you will run into severe interoperability problems when you least	1281	high that you will run into severe interoperability problems when you
934	expect it.	1282	least expect it.
935		1283
936	=over 4	1284	=over 4
937		1285
938	=item (*)	1286	=item (*)
939		1287
940	This is spread actively by the YAML team, however. For many years now they	1288	I have been pressured multiple times by Brian Ingerson (one of the
941	claim YAML were a superset of JSON, even when proven otherwise.	1289	authors of the YAML specification) to remove this paragraph, despite him
		1290	acknowledging that the actual incompatibilities exist. As I was personally
		1291	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1292	educate people about these issues, so others do not run into the same
		1293	problem again and again. After this, Brian called me a (quote)I<complete
		1294	and worthless idiot>(unquote).
942		1295
943	Even the author of this manpage was at some point accused of providing	1296	In my opinion, instead of pressuring and insulting people who actually
944	"incorrect" information, despite the evidence presented (claims ranged	1297	clarify issues with YAML and the wrong statements of some of its
945	from "your documentation contains inaccurate and negative statements about	1298	proponents, I would kindly suggest reading the JSON spec (which is not
946	YAML" (the only negative comment is this footnote, and it didn't exist	1299	that difficult or long) and finally make YAML compatible to it, and
947	back then; the question on which claims were inaccurate was never answered	1300	educating users about the changes, instead of spreading lies about the
948	etc.) to "the YAML spec is not up-to-date" (the real and suppsedly	1301	real compatibility for many I<years> and trying to silence people who
949	JSON-compatible spec is apparently not currently publicly available)	1302	point out that it isn't true.
950	to actual requests to replace this section by incorrect information,
951	suppressing information about the real problem).
952		1303
953	So whenever you are told that YAML was a superset of JSON, first check	1304	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
954	wether it is really true (it might be when you check it, but it cetrainly	1305	though the incompatibilities have been documented (and are known to Brian)
955	is not true when this was written). I would much prefer if the YAML team	1306	for many years and the spec makes explicit claims that YAML is a superset
956	would spent their time on actually making JSON compatibility a truth	1307	of JSON. It would be so easy to fix, but apparently, bullying people and
957	(JSON, after all, has a very small and simple specification) instead of	1308	corrupting userdata is so much easier.
958	trying to lobby/force people into reporting untruths.
959		1309
960	=back	1310	=back
961		1311
962		1312
963	=head2 SPEED	1313	=head2 SPEED
…		…
965	It seems that JSON::XS is surprisingly fast, as shown in the following	1315	It seems that JSON::XS is surprisingly fast, as shown in the following
966	tables. They have been generated with the help of the C<eg/bench> program	1316	tables. They have been generated with the help of the C<eg/bench> program
967	in the JSON::XS distribution, to make it easy to compare on your own	1317	in the JSON::XS distribution, to make it easy to compare on your own
968	system.	1318	system.
969		1319
970	First comes a comparison between various modules using a very short	1320	First comes a comparison between various modules using
971	single-line JSON string:	1321	a very short single-line JSON string (also available at
		1322	L<http://dist.schmorp.de/misc/json/short.json>).
972		1323
973	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1324	{"method": "handleMessage", "params": ["user1",
974	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1325	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1326	1, 0]}
975		1327
976	It shows the number of encodes/decodes per second (JSON::XS uses	1328	It shows the number of encodes/decodes per second (JSON::XS uses
977	the functional interface, while JSON::XS/2 uses the OO interface	1329	the functional interface, while JSON::XS/2 uses the OO interface
978	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1330	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
979	shrink). Higher is better:	1331	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1332	uses the from_json method). Higher is better:
980		1333
981	module \| encode \| decode \|	1334	module \| encode \| decode \|
982	-----------\|------------\|------------\|	1335	--------------\|------------\|------------\|
983	JSON 1.x \| 4990.842 \| 4088.813 \|	1336	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
984	JSON::DWIW \| 51653.990 \| 71575.154 \|	1337	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
985	JSON::PC \| 65948.176 \| 74631.744 \|	1338	JSON::PP \| 15827.562 \| 6638.658 \|
986	JSON::PP \| 8931.652 \| 3817.168 \|	1339	JSON::Syck \| 63358.066 \| 47662.545 \|
987	JSON::Syck \| 24877.248 \| 27776.848 \|	1340	JSON::XS \| 511500.488 \| 511500.488 \|
988	JSON::XS \| 388361.481 \| 227951.304 \|	1341	JSON::XS/2 \| 291271.111 \| 388361.481 \|
989	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1342	JSON::XS/3 \| 361577.931 \| 361577.931 \|
990	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1343	Storable \| 66788.280 \| 265462.278 \|
991	Storable \| 16500.016 \| 135300.129 \|
992	-----------+------------+------------+	1344	--------------+------------+------------+
993		1345
994	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1346	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
995	about three times faster on decoding, and over forty times faster	1347	about five times faster on decoding, and over thirty to seventy times
996	than JSON, even with pretty-printing and key sorting. It also compares	1348	faster than JSON's pure perl implementation. It also compares favourably
997	favourably to Storable for small amounts of data.	1349	to Storable for small amounts of data.
998		1350
999	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1351	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1000	search API (http://nanoref.com/yahooapis/mgPdGg):	1352	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1001		1353
1002	module \| encode \| decode \|	1354	module \| encode \| decode \|
1003	-----------\|------------\|------------\|	1355	--------------\|------------\|------------\|
1004	JSON 1.x \| 55.260 \| 34.971 \|	1356	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1005	JSON::DWIW \| 825.228 \| 1082.513 \|	1357	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1006	JSON::PC \| 3571.444 \| 2394.829 \|
1007	JSON::PP \| 210.987 \| 32.574 \|	1358	JSON::PP \| 400.640 \| 62.311 \|
1008	JSON::Syck \| 552.551 \| 787.544 \|	1359	JSON::Syck \| 1481.040 \| 1524.869 \|
1009	JSON::XS \| 5780.463 \| 4854.519 \|	1360	JSON::XS \| 20661.596 \| 9541.183 \|
1010	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1361	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1011	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1362	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1012	Storable \| 4445.002 \| 5235.027 \|	1363	Storable \| 19765.806 \| 10000.725 \|
1013	-----------+------------+------------+	1364	--------------+------------+------------+
1014		1365
1015	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1366	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1016	decodes faster).	1367	decodes a bit faster).
1017		1368
1018	On large strings containing lots of high Unicode characters, some modules	1369	On large strings containing lots of high Unicode characters, some modules
1019	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1370	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1020	will be broken due to missing (or wrong) Unicode handling. Others refuse	1371	will be broken due to missing (or wrong) Unicode handling. Others refuse
1021	to decode or encode properly, so it was impossible to prepare a fair	1372	to decode or encode properly, so it was impossible to prepare a fair
…		…
1047	to free the temporary). If that is exceeded, the program crashes. To be	1398	to free the temporary). If that is exceeded, the program crashes. To be
1048	conservative, the default nesting limit is set to 512. If your process	1399	conservative, the default nesting limit is set to 512. If your process
1049	has a smaller stack, you should adjust this setting accordingly with the	1400	has a smaller stack, you should adjust this setting accordingly with the
1050	C<max_depth> method.	1401	C<max_depth> method.
1051		1402
1052	And last but least, something else could bomb you that I forgot to think	1403	Something else could bomb you, too, that I forgot to think of. In that
1053	of. In that case, you get to keep the pieces. I am always open for hints,	1404	case, you get to keep the pieces. I am always open for hints, though...
1054	though...	1405
		1406	Also keep in mind that JSON::XS might leak contents of your Perl data
		1407	structures in its error messages, so when you serialise sensitive
		1408	information you might want to make sure that exceptions thrown by JSON::XS
		1409	will not end up in front of untrusted eyes.
1055		1410
1056	If you are using JSON::XS to return packets to consumption	1411	If you are using JSON::XS to return packets to consumption
1057	by JavaScript scripts in a browser you should have a look at	1412	by JavaScript scripts in a browser you should have a look at
1058	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1413	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1059	you are vulnerable to some common attack vectors (which really are browser	1414	see whether you are vulnerable to some common attack vectors (which really
1060	design bugs, but it is still you who will have to deal with it, as major	1415	are browser design bugs, but it is still you who will have to deal with
1061	browser developers care only for features, not about getting security	1416	it, as major browser developers care only for features, not about getting
1062	right).	1417	security right).
1063		1418
1064		1419
1065	=head1 THREADS	1420	=head1 THREADS
1066		1421
1067	This module is I<not> guaranteed to be thread safe and there are no	1422	This module is I<not> guaranteed to be thread safe and there are no
1068	plans to change this until Perl gets thread support (as opposed to the	1423	plans to change this until Perl gets thread support (as opposed to the
1069	horribly slow so-called "threads" which are simply slow and bloated	1424	horribly slow so-called "threads" which are simply slow and bloated
1070	process simulations - use fork, its I<much> faster, cheaper, better).	1425	process simulations - use fork, it's I<much> faster, cheaper, better).
1071		1426
1072	(It might actually work, but you have been warned).	1427	(It might actually work, but you have been warned).
1073		1428
1074		1429
		1430	=head1 THE PERILS OF SETLOCALE
		1431
		1432	Sometimes people avoid the Perl locale support and directly call the
		1433	system's setlocale function with C<LC_ALL>.
		1434
		1435	This breaks both perl and modules such as JSON::XS, as stringification of
		1436	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1437	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1438	perl to stringify numbers).
		1439
		1440	The solution is simple: don't call C<setlocale>, or use it for only those
		1441	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1442
		1443	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1444	actually needs it (avoiding stringification of numbers), and restore it
		1445	afterwards.
		1446
		1447
1075	=head1 BUGS	1448	=head1 BUGS
1076		1449
1077	While the goal of this module is to be correct, that unfortunately does	1450	While the goal of this module is to be correct, that unfortunately does
1078	not mean its bug-free, only that I think its design is bug-free. It is	1451	not mean it's bug-free, only that I think its design is bug-free. If you
1079	still relatively early in its development. If you keep reporting bugs they	1452	keep reporting bugs they will be fixed swiftly, though.
1080	will be fixed swiftly, though.
1081		1453
1082	Please refrain from using rt.cpan.org or any other bug reporting	1454	Please refrain from using rt.cpan.org or any other bug reporting
1083	service. I put the contact address into my modules for a reason.	1455	service. I put the contact address into my modules for a reason.
1084		1456
1085	=cut	1457	=cut
…		…
1105	"--" => sub { $_[0] = ${$_[0]} - 1 },	1477	"--" => sub { $_[0] = ${$_[0]} - 1 },
1106	fallback => 1;	1478	fallback => 1;
1107		1479
1108	1;	1480	1;
1109		1481
		1482	=head1 SEE ALSO
		1483
		1484	The F<json_xs> command line utility for quick experiments.
		1485
1110	=head1 AUTHOR	1486	=head1 AUTHOR
1111		1487
1112	Marc Lehmann <schmorp@schmorp.de>	1488	Marc Lehmann <schmorp@schmorp.de>
1113	http://home.schmorp.de/	1489	http://home.schmorp.de/
1114		1490

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Comparing JSON-XS/XS.pm (file contents): Revision 1.82 by root, Sun Dec 30 21:24:57 2007 UTC vs. Revision 1.143 by root, Fri Oct 25 20:02:54 2013 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.82 by root, Sun Dec 30 21:24:57 2007 UTC vs.
Revision 1.143 by root, Fri Oct 25 20:02:54 2013 UTC