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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.63 by root, Thu Oct 11 23:07:43 2007 UTC

…		…
		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		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
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
		13
		14	# exported functions, they croak on error
		15	# and expect/generate UTF-8
		16
		17	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		18	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		19
		20	# OO-interface
		21
		22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		24	$perl_scalar = $coder->decode ($unicode_json_text);
8		25
9	=head1 DESCRIPTION	26	=head1 DESCRIPTION
10		27
11	This module converts Perl data structures to JSON and vice versa. Its	28	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	29	primary goal is to be I<correct> and its secondary goal is to be
18	their maintainers are unresponsive, gone missing, or not listening to bug	35	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	36	reports for other reasons.
20		37
21	See COMPARISON, below, for a comparison to some other JSON modules.	38	See COMPARISON, below, for a comparison to some other JSON modules.
22		39
		40	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		41	vice versa.
		42
23	=head2 FEATURES	43	=head2 FEATURES
24		44
25	=over 4	45	=over 4
26		46
27	=item * correct handling of unicode issues	47	=item * correct unicode handling
28		48
29	This module knows how to handle Unicode, and even documents how it does so.	49	This module knows how to handle Unicode, and even documents how and when
		50	it does so.
30		51
31	=item * round-trip integrity	52	=item * round-trip integrity
32		53
33	When you serialise a perl data structure using only datatypes supported	54	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	55	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	56	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		57	like a number).
36		58
37	=item * strict checking of JSON correctness	59	=item * strict checking of JSON correctness
38		60
39	There is no guessing, no generating of illegal JSON strings by default,	61	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	62	and only JSON is accepted as input by default (the latter is a security
		63	feature).
41		64
42	=item * fast	65	=item * fast
43		66
44	compared to other JSON modules, this module compares favourably.	67	Compared to other JSON modules, this module compares favourably in terms
		68	of speed, too.
45		69
46	=item * simple to use	70	=item * simple to use
47		71
48	This module has both a simple functional interface as well as an OO	72	This module has both a simple functional interface as well as an OO
49	interface.	73	interface.
50		74
51	=item * reasonably versatile output formats	75	=item * reasonably versatile output formats
52		76
53	You can choose between the most compact format possible, a pure-ascii	77	You can choose between the most compact guarenteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	78	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	79	(for when your transport is not 8-bit clean, still supports the whole
		80	unicode range), or a pretty-printed format (for when you want to read that
		81	stuff). Or you can combine those features in whatever way you like.
56		82
57	=back	83	=back
58		84
59	=cut	85	=cut
60		86
61	package JSON::XS;	87	package JSON::XS;
62		88
63	BEGIN {	89	use strict;
		90
64	$VERSION = '0.1';	91	our $VERSION = '1.5';
65	@ISA = qw(Exporter);	92	our @ISA = qw(Exporter);
66		93
67	@EXPORT = qw(to_json from_json);	94	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		95
70	require XSLoader;	96	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	97	use XSLoader;
72	}
73		98
74	=head1 FUNCTIONAL INTERFACE	99	=head1 FUNCTIONAL INTERFACE
75		100
76	The following convinience methods are provided by this module. They are	101	The following convinience methods are provided by this module. They are
77	exported by default:	102	exported by default:
78		103
79	=over 4	104	=over 4
80		105
81	=item $json_string = to_json $perl_scalar	106	=item $json_text = to_json $perl_scalar
82		107
83	Converts the given Perl data structure (a simple scalar or a reference to	108	Converts the given Perl data structure to a UTF-8 encoded, binary string
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	109	(that is, the string contains octets only). Croaks on error.
85	octets only). Croaks on error.
86		110
87	This function call is functionally identical to C<< JSON::XS->new->utf8	111	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		112
		113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		114
		115	except being faster.
		116
90	=item $perl_scalar = from_json $json_string	117	=item $perl_scalar = from_json $json_text
91		118
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	119	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	120	to parse that as an UTF-8 encoded JSON text, returning the resulting
94	scalar or reference. Croaks on error.	121	reference. Croaks on error.
95		122
96	This function call is functionally identical to C<< JSON::XS->new->utf8	123	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	124
		125	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		126
		127	except being faster.
		128
		129	=item $is_boolean = JSON::XS::is_bool $scalar
		130
		131	Returns true if the passed scalar represents either JSON::XS::true or
		132	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		133	and are used to represent JSON C<true> and C<false> values in Perl.
		134
		135	See MAPPING, below, for more information on how JSON values are mapped to
		136	Perl.
98		137
99	=back	138	=back
		139
		140
		141	=head1 A FEW NOTES ON UNICODE AND PERL
		142
		143	Since this often leads to confusion, here are a few very clear words on
		144	how Unicode works in Perl, modulo bugs.
		145
		146	=over 4
		147
		148	=item 1. Perl strings can store characters with ordinal values > 255.
		149
		150	This enables you to store unicode characters as single characters in a
		151	Perl string - very natural.
		152
		153	=item 2. Perl does I<not> associate an encoding with your strings.
		154
		155	Unless you force it to, e.g. when matching it against a regex, or printing
		156	the scalar to a file, in which case Perl either interprets your string as
		157	locale-encoded text, octets/binary, or as Unicode, depending on various
		158	settings. In no case is an encoding stored together with your data, it is
		159	I<use> that decides encoding, not any magical metadata.
		160
		161	=item 3. The internal utf-8 flag has no meaning with regards to the
		162	encoding of your string.
		163
		164	Just ignore that flag unless you debug a Perl bug, a module written in
		165	XS or want to dive into the internals of perl. Otherwise it will only
		166	confuse you, as, despite the name, it says nothing about how your string
		167	is encoded. You can have unicode strings with that flag set, with that
		168	flag clear, and you can have binary data with that flag set and that flag
		169	clear. Other possibilities exist, too.
		170
		171	If you didn't know about that flag, just the better, pretend it doesn't
		172	exist.
		173
		174	=item 4. A "Unicode String" is simply a string where each character can be
		175	validly interpreted as a Unicode codepoint.
		176
		177	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		178	Unicode string encoded in UTF-8, giving you a binary string.
		179
		180	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		181
		182	Its a fact. Learn to live with it.
		183
		184	=back
		185
		186	I hope this helps :)
		187
100		188
101	=head1 OBJECT-ORIENTED INTERFACE	189	=head1 OBJECT-ORIENTED INTERFACE
102		190
103	The object oriented interface lets you configure your own encoding or	191	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	192	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	199	strings. All boolean flags described below are by default I<disabled>.
112		200
113	The mutators for flags all return the JSON object again and thus calls can	201	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	202	be chained:
115		203
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	204	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	205	=> {"a": [1, 2]}
118		206
119	=item $json = $json->ascii ($enable)	207	=item $json = $json->ascii ([$enable])
120		208
121	If C<$enable> is true, then the C<encode> method will not generate	209	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	210	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	211	unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		213	as per RFC4627. The resulting encoded JSON text can be treated as a native
		214	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		215	or any other superset of ASCII.
125		216
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	217	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	218	characters unless required by the JSON syntax or other flags. This results
		219	in a faster and more compact format.
128		220
		221	The main use for this flag is to produce JSON texts that can be
		222	transmitted over a 7-bit channel, as the encoded JSON texts will not
		223	contain any 8 bit characters.
		224
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	226	=> ["\ud801\udc01"]
131		227
		228	=item $json = $json->latin1 ([$enable])
		229
		230	If C<$enable> is true (or missing), then the C<encode> method will encode
		231	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		232	outside the code range C<0..255>. The resulting string can be treated as a
		233	latin1-encoded JSON text or a native unicode string. The C<decode> method
		234	will not be affected in any way by this flag, as C<decode> by default
		235	expects unicode, which is a strict superset of latin1.
		236
		237	If C<$enable> is false, then the C<encode> method will not escape Unicode
		238	characters unless required by the JSON syntax or other flags.
		239
		240	The main use for this flag is efficiently encoding binary data as JSON
		241	text, as most octets will not be escaped, resulting in a smaller encoded
		242	size. The disadvantage is that the resulting JSON text is encoded
		243	in latin1 (and must correctly be treated as such when storing and
		244	transfering), a rare encoding for JSON. It is therefore most useful when
		245	you want to store data structures known to contain binary data efficiently
		246	in files or databases, not when talking to other JSON encoders/decoders.
		247
		248	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		249	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		250
132	=item $json = $json->utf8 ($enable)	251	=item $json = $json->utf8 ([$enable])
133		252
134	If C<$enable> is true, then the C<encode> method will encode the JSON	253	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	254	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	255	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	256	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	257	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		258	versions, enabling this option might enable autodetection of the UTF-16
		259	and UTF-32 encoding families, as described in RFC4627.
139		260
140	If C<$enable> is false, then the C<encode> method will return the JSON	261	If C<$enable> is false, then the C<encode> method will return the JSON
141	string as a (non-encoded) unicode string, while C<decode> expects thus a	262	string as a (non-encoded) unicode string, while C<decode> expects thus a
142	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	263	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
143	to be done yourself, e.g. using the Encode module.	264	to be done yourself, e.g. using the Encode module.
144		265
		266	Example, output UTF-16BE-encoded JSON:
		267
		268	use Encode;
		269	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		270
		271	Example, decode UTF-32LE-encoded JSON:
		272
		273	use Encode;
		274	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		275
145	=item $json = $json->pretty ($enable)	276	=item $json = $json->pretty ([$enable])
146		277
147	This enables (or disables) all of the C<indent>, C<space_before> and	278	This enables (or disables) all of the C<indent>, C<space_before> and
148	C<space_after> (and in the future possibly more) flags in one call to	279	C<space_after> (and in the future possibly more) flags in one call to
149	generate the most readable (or most compact) form possible.	280	generate the most readable (or most compact) form possible.
		281
		282	Example, pretty-print some simple structure:
150		283
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	284	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	285	=>
153	{	286	{
154	"a" : [	287	"a" : [
155	1,	288	1,
156	2	289	2
157	]	290	]
158	}	291	}
159		292
160	=item $json = $json->indent ($enable)	293	=item $json = $json->indent ([$enable])
161		294
162	If C<$enable> is true, then the C<encode> method will use a multiline	295	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	296	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	297	into its own line, identing them properly.
165		298
166	If C<$enable> is false, no newlines or indenting will be produced, and the	299	If C<$enable> is false, no newlines or indenting will be produced, and the
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	300	resulting JSON text is guarenteed not to contain any C<newlines>.
168		301
169	This setting has no effect when decoding JSON strings.	302	This setting has no effect when decoding JSON texts.
170		303
171	=item $json = $json->space_before ($enable)	304	=item $json = $json->space_before ([$enable])
172		305
173	If C<$enable> is true, then the C<encode> method will add an extra	306	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	307	optional space before the C<:> separating keys from values in JSON objects.
175		308
176	If C<$enable> is false, then the C<encode> method will not add any extra	309	If C<$enable> is false, then the C<encode> method will not add any extra
177	space at those places.	310	space at those places.
178		311
179	This setting has no effect when decoding JSON strings. You will also most	312	This setting has no effect when decoding JSON texts. You will also
180	likely combine this setting with C<space_after>.	313	most likely combine this setting with C<space_after>.
181		314
		315	Example, space_before enabled, space_after and indent disabled:
		316
		317	{"key" :"value"}
		318
182	=item $json = $json->space_after ($enable)	319	=item $json = $json->space_after ([$enable])
183		320
184	If C<$enable> is true, then the C<encode> method will add an extra	321	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	322	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	323	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	324	members.
188		325
189	If C<$enable> is false, then the C<encode> method will not add any extra	326	If C<$enable> is false, then the C<encode> method will not add any extra
190	space at those places.	327	space at those places.
191		328
192	This setting has no effect when decoding JSON strings.	329	This setting has no effect when decoding JSON texts.
193		330
		331	Example, space_before and indent disabled, space_after enabled:
		332
		333	{"key": "value"}
		334
		335	=item $json = $json->relaxed ([$enable])
		336
		337	If C<$enable> is true (or missing), then C<decode> will accept some
		338	extensions to normal JSON syntax (see below). C<encode> will not be
		339	affected in anyway. I<Be aware that this option makes you accept invalid
		340	JSON texts as if they were valid!>. I suggest only to use this option to
		341	parse application-specific files written by humans (configuration files,
		342	resource files etc.)
		343
		344	If C<$enable> is false (the default), then C<decode> will only accept
		345	valid JSON texts.
		346
		347	Currently accepted extensions are:
		348
		349	=over 4
		350
		351	=item * list items can have an end-comma
		352
		353	JSON I<separates> array elements and key-value pairs with commas. This
		354	can be annoying if you write JSON texts manually and want to be able to
		355	quickly append elements, so this extension accepts comma at the end of
		356	such items not just between them:
		357
		358	[
		359	1,
		360	2, <- this comma not normally allowed
		361	]
		362	{
		363	"k1": "v1",
		364	"k2": "v2", <- this comma not normally allowed
		365	}
		366
		367	=item * shell-style '#'-comments
		368
		369	Whenever JSON allows whitespace, shell-style comments are additionally
		370	allowed. They are terminated by the first carriage-return or line-feed
		371	character, after which more white-space and comments are allowed.
		372
		373	[
		374	1, # this comment not allowed in JSON
		375	# neither this one...
		376	]
		377
		378	=back
		379
194	=item $json = $json->canonical ($enable)	380	=item $json = $json->canonical ([$enable])
195		381
196	If C<$enable> is true, then the C<encode> method will output JSON objects	382	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	383	by sorting their keys. This is adding a comparatively high overhead.
198		384
199	If C<$enable> is false, then the C<encode> method will output key-value	385	If C<$enable> is false, then the C<encode> method will output key-value
200	pairs in the order Perl stores them (which will likely change between runs	386	pairs in the order Perl stores them (which will likely change between runs
201	of the same script).	387	of the same script).
202		388
203	This option is useful if you want the same data structure to be encoded as	389	This option is useful if you want the same data structure to be encoded as
204	the same JSON string (given the same overall settings). If it is disabled,	390	the same JSON text (given the same overall settings). If it is disabled,
205	the same hash migh be encoded differently even if contains the same data,	391	the same hash migh be encoded differently even if contains the same data,
206	as key-value pairs have no inherent ordering in Perl.	392	as key-value pairs have no inherent ordering in Perl.
207		393
208	This setting has no effect when decoding JSON strings.	394	This setting has no effect when decoding JSON texts.
209		395
210	=item $json = $json->allow_nonref ($enable)	396	=item $json = $json->allow_nonref ([$enable])
211		397
212	If C<$enable> is true, then the C<encode> method can convert a	398	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	399	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	400	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	401	values instead of croaking.
216		402
217	If C<$enable> is false, then the C<encode> method will croak if it isn't	403	If C<$enable> is false, then the C<encode> method will croak if it isn't
218	passed an arrayref or hashref, as JSON strings must either be an object	404	passed an arrayref or hashref, as JSON texts must either be an object
219	or array. Likewise, C<decode> will croak if given something that is not a	405	or array. Likewise, C<decode> will croak if given something that is not a
220	JSON object or array.	406	JSON object or array.
221		407
		408	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		409	resulting in an invalid JSON text:
		410
		411	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		412	=> "Hello, World!"
		413
		414	=item $json = $json->allow_blessed ([$enable])
		415
		416	If C<$enable> is true (or missing), then the C<encode> method will not
		417	barf when it encounters a blessed reference. Instead, the value of the
		418	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		419	disabled or no C<to_json> method found) or a representation of the
		420	object (C<convert_blessed> enabled and C<to_json> method found) is being
		421	encoded. Has no effect on C<decode>.
		422
		423	If C<$enable> is false (the default), then C<encode> will throw an
		424	exception when it encounters a blessed object.
		425
		426	=item $json = $json->convert_blessed ([$enable])
		427
		428	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		429	blessed object, will check for the availability of the C<TO_JSON> method
		430	on the object's class. If found, it will be called in scalar context
		431	and the resulting scalar will be encoded instead of the object. If no
		432	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		433	to do.
		434
		435	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		436	returns other blessed objects, those will be handled in the same
		437	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		438	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		439	methods called by the Perl core (== not by the user of the object) are
		440	usually in upper case letters and to avoid collisions with the C<to_json>
		441	function.
		442
		443	This setting does not yet influence C<decode> in any way, but in the
		444	future, global hooks might get installed that influence C<decode> and are
		445	enabled by this setting.
		446
		447	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		448	to do when a blessed object is found.
		449
		450	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		451
		452	When C<$coderef> is specified, it will be called from C<decode> each
		453	time it decodes a JSON object. The only argument is a reference to the
		454	newly-created hash. If the code references returns a single scalar (which
		455	need not be a reference), this value (i.e. a copy of that scalar to avoid
		456	aliasing) is inserted into the deserialised data structure. If it returns
		457	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		458	original deserialised hash will be inserted. This setting can slow down
		459	decoding considerably.
		460
		461	When C<$coderef> is omitted or undefined, any existing callback will
		462	be removed and C<decode> will not change the deserialised hash in any
		463	way.
		464
		465	Example, convert all JSON objects into the integer 5:
		466
		467	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		468	# returns [5]
		469	$js->decode ('[{}]')
		470	# throw an exception because allow_nonref is not enabled
		471	# so a lone 5 is not allowed.
		472	$js->decode ('{"a":1, "b":2}');
		473
		474	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		475
		476	Works remotely similar to C<filter_json_object>, but is only called for
		477	JSON objects having a single key named C<$key>.
		478
		479	This C<$coderef> is called before the one specified via
		480	C<filter_json_object>, if any. It gets passed the single value in the JSON
		481	object. If it returns a single value, it will be inserted into the data
		482	structure. If it returns nothing (not even C<undef> but the empty list),
		483	the callback from C<filter_json_object> will be called next, as if no
		484	single-key callback were specified.
		485
		486	If C<$coderef> is omitted or undefined, the corresponding callback will be
		487	disabled. There can only ever be one callback for a given key.
		488
		489	As this callback gets called less often then the C<filter_json_object>
		490	one, decoding speed will not usually suffer as much. Therefore, single-key
		491	objects make excellent targets to serialise Perl objects into, especially
		492	as single-key JSON objects are as close to the type-tagged value concept
		493	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		494	support this in any way, so you need to make sure your data never looks
		495	like a serialised Perl hash.
		496
		497	Typical names for the single object key are C<__class_whatever__>, or
		498	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		499	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		500	with real hashes.
		501
		502	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		503	into the corresponding C<< $WIDGET{<id>} >> object:
		504
		505	# return whatever is in $WIDGET{5}:
		506	JSON::XS
		507	->new
		508	->filter_json_single_key_object (__widget__ => sub {
		509	$WIDGET{ $_[0] }
		510	})
		511	->decode ('{"__widget__": 5')
		512
		513	# this can be used with a TO_JSON method in some "widget" class
		514	# for serialisation to json:
		515	sub WidgetBase::TO_JSON {
		516	my ($self) = @_;
		517
		518	unless ($self->{id}) {
		519	$self->{id} = ..get..some..id..;
		520	$WIDGET{$self->{id}} = $self;
		521	}
		522
		523	{ __widget__ => $self->{id} }
		524	}
		525
		526	=item $json = $json->shrink ([$enable])
		527
		528	Perl usually over-allocates memory a bit when allocating space for
		529	strings. This flag optionally resizes strings generated by either
		530	C<encode> or C<decode> to their minimum size possible. This can save
		531	memory when your JSON texts are either very very long or you have many
		532	short strings. It will also try to downgrade any strings to octet-form
		533	if possible: perl stores strings internally either in an encoding called
		534	UTF-X or in octet-form. The latter cannot store everything but uses less
		535	space in general (and some buggy Perl or C code might even rely on that
		536	internal representation being used).
		537
		538	The actual definition of what shrink does might change in future versions,
		539	but it will always try to save space at the expense of time.
		540
		541	If C<$enable> is true (or missing), the string returned by C<encode> will
		542	be shrunk-to-fit, while all strings generated by C<decode> will also be
		543	shrunk-to-fit.
		544
		545	If C<$enable> is false, then the normal perl allocation algorithms are used.
		546	If you work with your data, then this is likely to be faster.
		547
		548	In the future, this setting might control other things, such as converting
		549	strings that look like integers or floats into integers or floats
		550	internally (there is no difference on the Perl level), saving space.
		551
		552	=item $json = $json->max_depth ([$maximum_nesting_depth])
		553
		554	Sets the maximum nesting level (default C<512>) accepted while encoding
		555	or decoding. If the JSON text or Perl data structure has an equal or
		556	higher nesting level then this limit, then the encoder and decoder will
		557	stop and croak at that point.
		558
		559	Nesting level is defined by number of hash- or arrayrefs that the encoder
		560	needs to traverse to reach a given point or the number of C<{> or C<[>
		561	characters without their matching closing parenthesis crossed to reach a
		562	given character in a string.
		563
		564	Setting the maximum depth to one disallows any nesting, so that ensures
		565	that the object is only a single hash/object or array.
		566
		567	The argument to C<max_depth> will be rounded up to the next highest power
		568	of two. If no argument is given, the highest possible setting will be
		569	used, which is rarely useful.
		570
		571	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		572
		573	=item $json = $json->max_size ([$maximum_string_size])
		574
		575	Set the maximum length a JSON text may have (in bytes) where decoding is
		576	being attempted. The default is C<0>, meaning no limit. When C<decode>
		577	is called on a string longer then this number of characters it will not
		578	attempt to decode the string but throw an exception. This setting has no
		579	effect on C<encode> (yet).
		580
		581	The argument to C<max_size> will be rounded up to the next B<highest>
		582	power of two (so may be more than requested). If no argument is given, the
		583	limit check will be deactivated (same as when C<0> is specified).
		584
		585	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		586
222	=item $json_string = $json->encode ($perl_scalar)	587	=item $json_text = $json->encode ($perl_scalar)
223		588
224	Converts the given Perl data structure (a simple scalar or a reference	589	Converts the given Perl data structure (a simple scalar or a reference
225	to a hash or array) to its JSON representation. Simple scalars will be	590	to a hash or array) to its JSON representation. Simple scalars will be
226	converted into JSON string or number sequences, while references to arrays	591	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	592	become JSON arrays and references to hashes become JSON objects. Undefined
228	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	593	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	594	nor C<false> values will be generated.
230		595
231	=item $perl_scalar = $json->decode ($json_string)	596	=item $perl_scalar = $json->decode ($json_text)
232		597
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	598	The opposite of C<encode>: expects a JSON text and tries to parse it,
234	returning the resulting simple scalar or reference. Croaks on error.	599	returning the resulting simple scalar or reference. Croaks on error.
235		600
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	601	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	602	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
238	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	603	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		604
		605	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		606
		607	This works like the C<decode> method, but instead of raising an exception
		608	when there is trailing garbage after the first JSON object, it will
		609	silently stop parsing there and return the number of characters consumed
		610	so far.
		611
		612	This is useful if your JSON texts are not delimited by an outer protocol
		613	(which is not the brightest thing to do in the first place) and you need
		614	to know where the JSON text ends.
		615
		616	JSON::XS->new->decode_prefix ("[1] the tail")
		617	=> ([], 3)
		618
240	=back	619	=back
		620
		621
		622	=head1 MAPPING
		623
		624	This section describes how JSON::XS maps Perl values to JSON values and
		625	vice versa. These mappings are designed to "do the right thing" in most
		626	circumstances automatically, preserving round-tripping characteristics
		627	(what you put in comes out as something equivalent).
		628
		629	For the more enlightened: note that in the following descriptions,
		630	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		631	refers to the abstract Perl language itself.
		632
		633
		634	=head2 JSON -> PERL
		635
		636	=over 4
		637
		638	=item object
		639
		640	A JSON object becomes a reference to a hash in Perl. No ordering of object
		641	keys is preserved (JSON does not preserver object key ordering itself).
		642
		643	=item array
		644
		645	A JSON array becomes a reference to an array in Perl.
		646
		647	=item string
		648
		649	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		650	are represented by the same codepoints in the Perl string, so no manual
		651	decoding is necessary.
		652
		653	=item number
		654
		655	A JSON number becomes either an integer, numeric (floating point) or
		656	string scalar in perl, depending on its range and any fractional parts. On
		657	the Perl level, there is no difference between those as Perl handles all
		658	the conversion details, but an integer may take slightly less memory and
		659	might represent more values exactly than (floating point) numbers.
		660
		661	If the number consists of digits only, JSON::XS will try to represent
		662	it as an integer value. If that fails, it will try to represent it as
		663	a numeric (floating point) value if that is possible without loss of
		664	precision. Otherwise it will preserve the number as a string value.
		665
		666	Numbers containing a fractional or exponential part will always be
		667	represented as numeric (floating point) values, possibly at a loss of
		668	precision.
		669
		670	This might create round-tripping problems as numbers might become strings,
		671	but as Perl is typeless there is no other way to do it.
		672
		673	=item true, false
		674
		675	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		676	respectively. They are overloaded to act almost exactly like the numbers
		677	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		678	the C<JSON::XS::is_bool> function.
		679
		680	=item null
		681
		682	A JSON null atom becomes C<undef> in Perl.
		683
		684	=back
		685
		686
		687	=head2 PERL -> JSON
		688
		689	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		690	truly typeless language, so we can only guess which JSON type is meant by
		691	a Perl value.
		692
		693	=over 4
		694
		695	=item hash references
		696
		697	Perl hash references become JSON objects. As there is no inherent ordering
		698	in hash keys (or JSON objects), they will usually be encoded in a
		699	pseudo-random order that can change between runs of the same program but
		700	stays generally the same within a single run of a program. JSON::XS can
		701	optionally sort the hash keys (determined by the I<canonical> flag), so
		702	the same datastructure will serialise to the same JSON text (given same
		703	settings and version of JSON::XS), but this incurs a runtime overhead
		704	and is only rarely useful, e.g. when you want to compare some JSON text
		705	against another for equality.
		706
		707	=item array references
		708
		709	Perl array references become JSON arrays.
		710
		711	=item other references
		712
		713	Other unblessed references are generally not allowed and will cause an
		714	exception to be thrown, except for references to the integers C<0> and
		715	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		716	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		717
		718	to_json [\0,JSON::XS::true] # yields [false,true]
		719
		720	=item JSON::XS::true, JSON::XS::false
		721
		722	These special values become JSON true and JSON false values,
		723	respectively. You can also use C<\1> and C<\0> directly if you want.
		724
		725	=item blessed objects
		726
		727	Blessed objects are not allowed. JSON::XS currently tries to encode their
		728	underlying representation (hash- or arrayref), but this behaviour might
		729	change in future versions.
		730
		731	=item simple scalars
		732
		733	Simple Perl scalars (any scalar that is not a reference) are the most
		734	difficult objects to encode: JSON::XS will encode undefined scalars as
		735	JSON null value, scalars that have last been used in a string context
		736	before encoding as JSON strings and anything else as number value:
		737
		738	# dump as number
		739	to_json [2] # yields [2]
		740	to_json [-3.0e17] # yields [-3e+17]
		741	my $value = 5; to_json [$value] # yields [5]
		742
		743	# used as string, so dump as string
		744	print $value;
		745	to_json [$value] # yields ["5"]
		746
		747	# undef becomes null
		748	to_json [undef] # yields [null]
		749
		750	You can force the type to be a string by stringifying it:
		751
		752	my $x = 3.1; # some variable containing a number
		753	"$x"; # stringified
		754	$x .= ""; # another, more awkward way to stringify
		755	print $x; # perl does it for you, too, quite often
		756
		757	You can force the type to be a number by numifying it:
		758
		759	my $x = "3"; # some variable containing a string
		760	$x += 0; # numify it, ensuring it will be dumped as a number
		761	$x *= 1; # same thing, the choise is yours.
		762
		763	You can not currently output JSON booleans or force the type in other,
		764	less obscure, ways. Tell me if you need this capability.
		765
		766	=back
		767
241		768
242	=head1 COMPARISON	769	=head1 COMPARISON
243		770
244	As already mentioned, this module was created because none of the existing	771	As already mentioned, this module was created because none of the existing
245	JSON modules could be made to work correctly. First I will describe the	772	JSON modules could be made to work correctly. First I will describe the
…		…
271		798
272	Has problems handling many Perl values (e.g. regex results and other magic	799	Has problems handling many Perl values (e.g. regex results and other magic
273	values will make it croak).	800	values will make it croak).
274		801
275	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	802	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
276	which is not a valid JSON string.	803	which is not a valid JSON text.
277		804
278	Unmaintained (maintainer unresponsive for many months, bugs are not	805	Unmaintained (maintainer unresponsive for many months, bugs are not
279	getting fixed).	806	getting fixed).
280		807
281	=item JSON::Syck 0.21	808	=item JSON::Syck 0.21
…		…
283	Very buggy (often crashes).	810	Very buggy (often crashes).
284		811
285	Very inflexible (no human-readable format supported, format pretty much	812	Very inflexible (no human-readable format supported, format pretty much
286	undocumented. I need at least a format for easy reading by humans and a	813	undocumented. I need at least a format for easy reading by humans and a
287	single-line compact format for use in a protocol, and preferably a way to	814	single-line compact format for use in a protocol, and preferably a way to
288	generate ASCII-only JSON strings).	815	generate ASCII-only JSON texts).
289		816
290	Completely broken (and confusingly documented) Unicode handling (unicode	817	Completely broken (and confusingly documented) Unicode handling (unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	818	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	819	I<different> values on en- and decoding to get symmetric behaviour).
293		820
…		…
316		843
317	Very inflexible.	844	Very inflexible.
318		845
319	No roundtripping.	846	No roundtripping.
320		847
321	Does not generate valid JSON (key strings are often unquoted, empty keys	848	Does not generate valid JSON texts (key strings are often unquoted, empty keys
322	result in nothing being output)	849	result in nothing being output)
323		850
324	Does not check input for validity.	851	Does not check input for validity.
325		852
326	=back	853	=back
		854
		855
		856	=head2 JSON and YAML
		857
		858	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		859	however, a mass hysteria and very far from the truth. In general, there is
		860	no way to configure JSON::XS to output a data structure as valid YAML.
		861
		862	If you really must use JSON::XS to generate YAML, you should use this
		863	algorithm (subject to change in future versions):
		864
		865	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		866	my $yaml = $to_yaml->encode ($ref) . "\n";
		867
		868	This will usually generate JSON texts that also parse as valid
		869	YAML. Please note that YAML has hardcoded limits on (simple) object key
		870	lengths that JSON doesn't have, so you should make sure that your hash
		871	keys are noticably shorter than the 1024 characters YAML allows.
		872
		873	There might be other incompatibilities that I am not aware of. In general
		874	you should not try to generate YAML with a JSON generator or vice versa,
		875	or try to parse JSON with a YAML parser or vice versa: chances are high
		876	that you will run into severe interoperability problems.
		877
327		878
328	=head2 SPEED	879	=head2 SPEED
329		880
330	It seems that JSON::XS is surprisingly fast, as shown in the following	881	It seems that JSON::XS is surprisingly fast, as shown in the following
331	tables. They have been generated with the help of the C<eg/bench> program	882	tables. They have been generated with the help of the C<eg/bench> program
332	in the JSON::XS distribution, to make it easy to compare on your own	883	in the JSON::XS distribution, to make it easy to compare on your own
333	system.	884	system.
334		885
335	First is a comparison between various modules using a very simple JSON	886	First comes a comparison between various modules using a very short
		887	single-line JSON string:
		888
		889	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		890	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		891
336	string, showing the number of encodes/decodes per second (JSON::XS is	892	It shows the number of encodes/decodes per second (JSON::XS uses
337	the functional interface, while JSON::XS/2 is the OO interface with	893	the functional interface, while JSON::XS/2 uses the OO interface
338	pretty-printing and hashkey sorting enabled).	894	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		895	shrink). Higher is better:
339		896
		897	Storable \| 15779.925 \| 14169.946 \|
		898	-----------+------------+------------+
340	module \| encode \| decode \|	899	module \| encode \| decode \|
341	-----------\|------------\|------------\|	900	-----------\|------------\|------------\|
342	JSON \| 14006 \| 6820 \|	901	JSON \| 4990.842 \| 4088.813 \|
343	JSON::DWIW \| 200937 \| 120386 \|	902	JSON::DWIW \| 51653.990 \| 71575.154 \|
344	JSON::PC \| 85065 \| 129366 \|	903	JSON::PC \| 65948.176 \| 74631.744 \|
345	JSON::Syck \| 59898 \| 44232 \|	904	JSON::PP \| 8931.652 \| 3817.168 \|
346	JSON::XS \| 1171478 \| 342435 \|	905	JSON::Syck \| 24877.248 \| 27776.848 \|
347	JSON::XS/2 \| 730760 \| 328714 \|	906	JSON::XS \| 388361.481 \| 227951.304 \|
		907	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		908	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		909	Storable \| 16500.016 \| 135300.129 \|
348	-----------+------------+------------+	910	-----------+------------+------------+
349		911
350	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	912	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		913	about three times faster on decoding, and over fourty times faster
351	times faster than JSON, even with pretty-printing and key sorting.	914	than JSON, even with pretty-printing and key sorting. It also compares
		915	favourably to Storable for small amounts of data.
352		916
353	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	917	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
354	search API (http://nanoref.com/yahooapis/mgPdGg):	918	search API (http://nanoref.com/yahooapis/mgPdGg):
355		919
356	module \| encode \| decode \|	920	module \| encode \| decode \|
357	-----------\|------------\|------------\|	921	-----------\|------------\|------------\|
358	JSON \| 673 \| 38 \|	922	JSON \| 55.260 \| 34.971 \|
359	JSON::DWIW \| 5271 \| 770 \|	923	JSON::DWIW \| 825.228 \| 1082.513 \|
360	JSON::PC \| 9901 \| 2491 \|	924	JSON::PC \| 3571.444 \| 2394.829 \|
361	JSON::Syck \| 2360 \| 786 \|	925	JSON::PP \| 210.987 \| 32.574 \|
362	JSON::XS \| 37398 \| 3202 \|	926	JSON::Syck \| 552.551 \| 787.544 \|
363	JSON::XS/2 \| 13765 \| 3153 \|	927	JSON::XS \| 5780.463 \| 4854.519 \|
		928	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		929	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		930	Storable \| 4445.002 \| 5235.027 \|
364	-----------+------------+------------+	931	-----------+------------+------------+
365		932
366	Again, JSON::XS leads by far in the encoding case, while still beating	933	Again, JSON::XS leads by far (except for Storable which non-surprisingly
367	every other module in the decoding case.	934	decodes faster).
368		935
369	Last example is an almost 8MB large hash with many large binary values	936	On large strings containing lots of high unicode characters, some modules
370	(PNG files), resulting in a lot of escaping:	937	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		938	will be broken due to missing (or wrong) unicode handling. Others refuse
		939	to decode or encode properly, so it was impossible to prepare a fair
		940	comparison table for that case.
		941
		942
		943	=head1 SECURITY CONSIDERATIONS
		944
		945	When you are using JSON in a protocol, talking to untrusted potentially
		946	hostile creatures requires relatively few measures.
		947
		948	First of all, your JSON decoder should be secure, that is, should not have
		949	any buffer overflows. Obviously, this module should ensure that and I am
		950	trying hard on making that true, but you never know.
		951
		952	Second, you need to avoid resource-starving attacks. That means you should
		953	limit the size of JSON texts you accept, or make sure then when your
		954	resources run out, thats just fine (e.g. by using a separate process that
		955	can crash safely). The size of a JSON text in octets or characters is
		956	usually a good indication of the size of the resources required to decode
		957	it into a Perl structure. While JSON::XS can check the size of the JSON
		958	text, it might be too late when you already have it in memory, so you
		959	might want to check the size before you accept the string.
		960
		961	Third, JSON::XS recurses using the C stack when decoding objects and
		962	arrays. The C stack is a limited resource: for instance, on my amd64
		963	machine with 8MB of stack size I can decode around 180k nested arrays but
		964	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		965	to free the temporary). If that is exceeded, the program crashes. to be
		966	conservative, the default nesting limit is set to 512. If your process
		967	has a smaller stack, you should adjust this setting accordingly with the
		968	C<max_depth> method.
		969
		970	And last but least, something else could bomb you that I forgot to think
		971	of. In that case, you get to keep the pieces. I am always open for hints,
		972	though...
		973
		974	If you are using JSON::XS to return packets to consumption
		975	by javascript scripts in a browser you should have a look at
		976	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		977	you are vulnerable to some common attack vectors (which really are browser
		978	design bugs, but it is still you who will have to deal with it, as major
		979	browser developers care only for features, not about doing security
		980	right).
		981
371		982
372	=head1 BUGS	983	=head1 BUGS
373		984
374	While the goal of this module is to be correct, that unfortunately does	985	While the goal of this module is to be correct, that unfortunately does
375	not mean its bug-free, only that I think its design is bug-free. It is	986	not mean its bug-free, only that I think its design is bug-free. It is
376	still very young and not well-tested. If you keep reporting bugs they will	987	still relatively early in its development. If you keep reporting bugs they
377	be fixed swiftly, though.	988	will be fixed swiftly, though.
378		989
379	=cut	990	=cut
		991
		992	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		993	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		994
		995	sub true() { $true }
		996	sub false() { $false }
		997
		998	sub is_bool($) {
		999	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1000	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1001	}
		1002
		1003	XSLoader::load "JSON::XS", $VERSION;
		1004
		1005	package JSON::XS::Boolean;
		1006
		1007	use overload
		1008	"0+" => sub { ${$_[0]} },
		1009	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1010	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1011	fallback => 1;
380		1012
381	1;	1013	1;
382		1014
383	=head1 AUTHOR	1015	=head1 AUTHOR
384		1016

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Comparing JSON-XS/XS.pm (file contents): Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs. Revision 1.63 by root, Thu Oct 11 23:07:43 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.63 by root, Thu Oct 11 23:07:43 2007 UTC