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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs.
Revision 1.77 by root, Tue Dec 4 10:37:42 2007 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		4
		5	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)
		7
5	=head1 SYNOPSIS	8	=head1 SYNOPSIS
6		9
7	use JSON::XS;	10	use JSON::XS;
8		11
9	# exported functions, croak on error	12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
10		14
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
13		17
14	# oo-interface	18	# OO-interface
15		19
16	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
17	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
18	$perl_scalar = $coder->decode ($unicode_json_text);	22	$perl_scalar = $coder->decode ($unicode_json_text);
19		23
		24	# Note that JSON version 2.0 and above will automatically use JSON::XS
		25	# if available, at virtually no speed overhead either, so you should
		26	# be able to just:
		27
		28	use JSON;
		29
		30	# and do the same things, except that you have a pure-perl fallback now.
		31
20	=head1 DESCRIPTION	32	=head1 DESCRIPTION
21		33
22	This module converts Perl data structures to JSON and vice versa. Its	34	This module converts Perl data structures to JSON and vice versa. Its
23	primary goal is to be I<correct> and its secondary goal is to be	35	primary goal is to be I<correct> and its secondary goal is to be
24	I<fast>. To reach the latter goal it was written in C.	36	I<fast>. To reach the latter goal it was written in C.
		37
		38	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
		40	overriden) with no overhead due to emulation (by inheritign constructor
		41	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
		43	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.
25		45
26	As this is the n-th-something JSON module on CPAN, what was the reason	46	As this is the n-th-something JSON module on CPAN, what was the reason
27	to write yet another JSON module? While it seems there are many JSON	47	to write yet another JSON module? While it seems there are many JSON
28	modules, none of them correctly handle all corner cases, and in most cases	48	modules, none of them correctly handle all corner cases, and in most cases
29	their maintainers are unresponsive, gone missing, or not listening to bug	49	their maintainers are unresponsive, gone missing, or not listening to bug
36		56
37	=head2 FEATURES	57	=head2 FEATURES
38		58
39	=over 4	59	=over 4
40		60
41	=item * correct handling of unicode issues	61	=item * correct Unicode handling
42		62
43	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, and even documents how and when
44	it does so.	64	it does so.
45		65
46	=item * round-trip integrity	66	=item * round-trip integrity
47		67
48	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only datatypes supported
49	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
50	(e.g. the string "2.0" doesn't suddenly become "2").	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		71	like a number).
51		72
52	=item * strict checking of JSON correctness	73	=item * strict checking of JSON correctness
53		74
54	There is no guessing, no generating of illegal JSON strings by default,	75	There is no guessing, no generating of illegal JSON texts by default,
55	and only JSON is accepted as input by default (the latter is a security	76	and only JSON is accepted as input by default (the latter is a security
56	feature).	77	feature).
57		78
58	=item * fast	79	=item * fast
59		80
…		…
65	This module has both a simple functional interface as well as an OO	86	This module has both a simple functional interface as well as an OO
66	interface.	87	interface.
67		88
68	=item * reasonably versatile output formats	89	=item * reasonably versatile output formats
69		90
70	You can choose between the most compact guarenteed single-line format	91	You can choose between the most compact guaranteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	92	possible (nice for simple line-based protocols), a pure-ascii format
72	when your transport is not 8-bit clean), or a pretty-printed format (for	93	(for when your transport is not 8-bit clean, still supports the whole
73	when you want to read that stuff). Or you can combine those features in	94	Unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	95	stuff). Or you can combine those features in whatever way you like.
75		96
76	=back	97	=back
77		98
78	=cut	99	=cut
79		100
80	package JSON::XS;	101	package JSON::XS;
81		102
82	BEGIN {	103	use strict;
		104
83	$VERSION = '0.3';	105	our $VERSION = '2.0';
84	@ISA = qw(Exporter);	106	our @ISA = qw(Exporter);
85		107
86	@EXPORT = qw(to_json from_json);	108	our @EXPORT = qw(to_json from_json);
87	require Exporter;
88		109
89	require XSLoader;	110	use Exporter;
90	XSLoader::load JSON::XS::, $VERSION;	111	use XSLoader;
91	}
92		112
93	=head1 FUNCTIONAL INTERFACE	113	=head1 FUNCTIONAL INTERFACE
94		114
95	The following convinience methods are provided by this module. They are	115	The following convenience methods are provided by this module. They are
96	exported by default:	116	exported by default:
97		117
98	=over 4	118	=over 4
99		119
100	=item $json_string = to_json $perl_scalar	120	=item $json_text = to_json $perl_scalar
101		121
102	Converts the given Perl data structure (a simple scalar or a reference to	122	Converts the given Perl data structure to a UTF-8 encoded, binary string
103	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	123	(that is, the string contains octets only). Croaks on error.
104	octets only). Croaks on error.
105		124
106	This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.	125	This function call is functionally identical to:
107		126
		127	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		128
		129	except being faster.
		130
108	=item $perl_scalar = from_json $json_string	131	=item $perl_scalar = from_json $json_text
109		132
110	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	133	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
111	parse that as an UTF-8 encoded JSON string, returning the resulting simple	134	to parse that as an UTF-8 encoded JSON text, returning the resulting
112	scalar or reference. Croaks on error.	135	reference. Croaks on error.
113		136
114	This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.	137	This function call is functionally identical to:
		138
		139	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		140
		141	except being faster.
		142
		143	=item $is_boolean = JSON::XS::is_bool $scalar
		144
		145	Returns true if the passed scalar represents either JSON::XS::true or
		146	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		147	and are used to represent JSON C<true> and C<false> values in Perl.
		148
		149	See MAPPING, below, for more information on how JSON values are mapped to
		150	Perl.
115		151
116	=back	152	=back
		153
		154
		155	=head1 A FEW NOTES ON UNICODE AND PERL
		156
		157	Since this often leads to confusion, here are a few very clear words on
		158	how Unicode works in Perl, modulo bugs.
		159
		160	=over 4
		161
		162	=item 1. Perl strings can store characters with ordinal values > 255.
		163
		164	This enables you to store Unicode characters as single characters in a
		165	Perl string - very natural.
		166
		167	=item 2. Perl does I<not> associate an encoding with your strings.
		168
		169	Unless you force it to, e.g. when matching it against a regex, or printing
		170	the scalar to a file, in which case Perl either interprets your string as
		171	locale-encoded text, octets/binary, or as Unicode, depending on various
		172	settings. In no case is an encoding stored together with your data, it is
		173	I<use> that decides encoding, not any magical metadata.
		174
		175	=item 3. The internal utf-8 flag has no meaning with regards to the
		176	encoding of your string.
		177
		178	Just ignore that flag unless you debug a Perl bug, a module written in
		179	XS or want to dive into the internals of perl. Otherwise it will only
		180	confuse you, as, despite the name, it says nothing about how your string
		181	is encoded. You can have Unicode strings with that flag set, with that
		182	flag clear, and you can have binary data with that flag set and that flag
		183	clear. Other possibilities exist, too.
		184
		185	If you didn't know about that flag, just the better, pretend it doesn't
		186	exist.
		187
		188	=item 4. A "Unicode String" is simply a string where each character can be
		189	validly interpreted as a Unicode codepoint.
		190
		191	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		192	Unicode string encoded in UTF-8, giving you a binary string.
		193
		194	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		195
		196	It's a fact. Learn to live with it.
		197
		198	=back
		199
		200	I hope this helps :)
		201
117		202
118	=head1 OBJECT-ORIENTED INTERFACE	203	=head1 OBJECT-ORIENTED INTERFACE
119		204
120	The object oriented interface lets you configure your own encoding or	205	The object oriented interface lets you configure your own encoding or
121	decoding style, within the limits of supported formats.	206	decoding style, within the limits of supported formats.
…		…
128	strings. All boolean flags described below are by default I<disabled>.	213	strings. All boolean flags described below are by default I<disabled>.
129		214
130	The mutators for flags all return the JSON object again and thus calls can	215	The mutators for flags all return the JSON object again and thus calls can
131	be chained:	216	be chained:
132		217
133	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	218	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
134	=> {"a": [1, 2]}	219	=> {"a": [1, 2]}
135		220
136	=item $json = $json->ascii ([$enable])	221	=item $json = $json->ascii ([$enable])
137		222
		223	=item $enabled = $json->get_ascii
		224
138	If C<$enable> is true (or missing), then the C<encode> method will	225	If C<$enable> is true (or missing), then the C<encode> method will not
139	not generate characters outside the code range C<0..127>. Any unicode	226	generate characters outside the code range C<0..127> (which is ASCII). Any
140	characters outside that range will be escaped using either a single	227	Unicode characters outside that range will be escaped using either a
141	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	228	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
142	RFC4627.	229	as per RFC4627. The resulting encoded JSON text can be treated as a native
		230	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		231	or any other superset of ASCII.
143		232
144	If C<$enable> is false, then the C<encode> method will not escape Unicode	233	If C<$enable> is false, then the C<encode> method will not escape Unicode
145	characters unless necessary.	234	characters unless required by the JSON syntax or other flags. This results
		235	in a faster and more compact format.
146		236
		237	The main use for this flag is to produce JSON texts that can be
		238	transmitted over a 7-bit channel, as the encoded JSON texts will not
		239	contain any 8 bit characters.
		240
147	JSON::XS->new->ascii (1)->encode (chr 0x10401)	241	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
148	=> \ud801\udc01	242	=> ["\ud801\udc01"]
		243
		244	=item $json = $json->latin1 ([$enable])
		245
		246	=item $enabled = $json->get_latin1
		247
		248	If C<$enable> is true (or missing), then the C<encode> method will encode
		249	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		250	outside the code range C<0..255>. The resulting string can be treated as a
		251	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		252	will not be affected in any way by this flag, as C<decode> by default
		253	expects Unicode, which is a strict superset of latin1.
		254
		255	If C<$enable> is false, then the C<encode> method will not escape Unicode
		256	characters unless required by the JSON syntax or other flags.
		257
		258	The main use for this flag is efficiently encoding binary data as JSON
		259	text, as most octets will not be escaped, resulting in a smaller encoded
		260	size. The disadvantage is that the resulting JSON text is encoded
		261	in latin1 (and must correctly be treated as such when storing and
		262	transferring), a rare encoding for JSON. It is therefore most useful when
		263	you want to store data structures known to contain binary data efficiently
		264	in files or databases, not when talking to other JSON encoders/decoders.
		265
		266	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		267	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
149		268
150	=item $json = $json->utf8 ([$enable])	269	=item $json = $json->utf8 ([$enable])
151		270
		271	=item $enabled = $json->get_utf8
		272
152	If C<$enable> is true (or missing), then the C<encode> method will encode	273	If C<$enable> is true (or missing), then the C<encode> method will encode
153	the JSON string into UTF-8, as required by many protocols, while the	274	the JSON result into UTF-8, as required by many protocols, while the
154	C<decode> method expects to be handled an UTF-8-encoded string. Please	275	C<decode> method expects to be handled an UTF-8-encoded string. Please
155	note that UTF-8-encoded strings do not contain any characters outside the	276	note that UTF-8-encoded strings do not contain any characters outside the
156	range C<0..255>, they are thus useful for bytewise/binary I/O.	277	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		278	versions, enabling this option might enable autodetection of the UTF-16
		279	and UTF-32 encoding families, as described in RFC4627.
157		280
158	If C<$enable> is false, then the C<encode> method will return the JSON	281	If C<$enable> is false, then the C<encode> method will return the JSON
159	string as a (non-encoded) unicode string, while C<decode> expects thus a	282	string as a (non-encoded) Unicode string, while C<decode> expects thus a
160	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	283	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
161	to be done yourself, e.g. using the Encode module.	284	to be done yourself, e.g. using the Encode module.
162		285
163	Example, output UTF-16-encoded JSON:	286	Example, output UTF-16BE-encoded JSON:
		287
		288	use Encode;
		289	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		290
		291	Example, decode UTF-32LE-encoded JSON:
		292
		293	use Encode;
		294	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
164		295
165	=item $json = $json->pretty ([$enable])	296	=item $json = $json->pretty ([$enable])
166		297
167	This enables (or disables) all of the C<indent>, C<space_before> and	298	This enables (or disables) all of the C<indent>, C<space_before> and
168	C<space_after> (and in the future possibly more) flags in one call to	299	C<space_after> (and in the future possibly more) flags in one call to
…		…
179	]	310	]
180	}	311	}
181		312
182	=item $json = $json->indent ([$enable])	313	=item $json = $json->indent ([$enable])
183		314
		315	=item $enabled = $json->get_indent
		316
184	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	317	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
185	format as output, putting every array member or object/hash key-value pair	318	format as output, putting every array member or object/hash key-value pair
186	into its own line, identing them properly.	319	into its own line, indenting them properly.
187		320
188	If C<$enable> is false, no newlines or indenting will be produced, and the	321	If C<$enable> is false, no newlines or indenting will be produced, and the
189	resulting JSON strings is guarenteed not to contain any C<newlines>.	322	resulting JSON text is guaranteed not to contain any C<newlines>.
190		323
191	This setting has no effect when decoding JSON strings.	324	This setting has no effect when decoding JSON texts.
192		325
193	=item $json = $json->space_before ([$enable])	326	=item $json = $json->space_before ([$enable])
		327
		328	=item $enabled = $json->get_space_before
194		329
195	If C<$enable> is true (or missing), then the C<encode> method will add an extra	330	If C<$enable> is true (or missing), then the C<encode> method will add an extra
196	optional space before the C<:> separating keys from values in JSON objects.	331	optional space before the C<:> separating keys from values in JSON objects.
197		332
198	If C<$enable> is false, then the C<encode> method will not add any extra	333	If C<$enable> is false, then the C<encode> method will not add any extra
199	space at those places.	334	space at those places.
200		335
201	This setting has no effect when decoding JSON strings. You will also most	336	This setting has no effect when decoding JSON texts. You will also
202	likely combine this setting with C<space_after>.	337	most likely combine this setting with C<space_after>.
203		338
204	Example, space_before enabled, space_after and indent disabled:	339	Example, space_before enabled, space_after and indent disabled:
205		340
206	{"key" :"value"}	341	{"key" :"value"}
207		342
208	=item $json = $json->space_after ([$enable])	343	=item $json = $json->space_after ([$enable])
		344
		345	=item $enabled = $json->get_space_after
209		346
210	If C<$enable> is true (or missing), then the C<encode> method will add an extra	347	If C<$enable> is true (or missing), then the C<encode> method will add an extra
211	optional space after the C<:> separating keys from values in JSON objects	348	optional space after the C<:> separating keys from values in JSON objects
212	and extra whitespace after the C<,> separating key-value pairs and array	349	and extra whitespace after the C<,> separating key-value pairs and array
213	members.	350	members.
214		351
215	If C<$enable> is false, then the C<encode> method will not add any extra	352	If C<$enable> is false, then the C<encode> method will not add any extra
216	space at those places.	353	space at those places.
217		354
218	This setting has no effect when decoding JSON strings.	355	This setting has no effect when decoding JSON texts.
219		356
220	Example, space_before and indent disabled, space_after enabled:	357	Example, space_before and indent disabled, space_after enabled:
221		358
222	{"key": "value"}	359	{"key": "value"}
223		360
		361	=item $json = $json->relaxed ([$enable])
		362
		363	=item $enabled = $json->get_relaxed
		364
		365	If C<$enable> is true (or missing), then C<decode> will accept some
		366	extensions to normal JSON syntax (see below). C<encode> will not be
		367	affected in anyway. I<Be aware that this option makes you accept invalid
		368	JSON texts as if they were valid!>. I suggest only to use this option to
		369	parse application-specific files written by humans (configuration files,
		370	resource files etc.)
		371
		372	If C<$enable> is false (the default), then C<decode> will only accept
		373	valid JSON texts.
		374
		375	Currently accepted extensions are:
		376
		377	=over 4
		378
		379	=item * list items can have an end-comma
		380
		381	JSON I<separates> array elements and key-value pairs with commas. This
		382	can be annoying if you write JSON texts manually and want to be able to
		383	quickly append elements, so this extension accepts comma at the end of
		384	such items not just between them:
		385
		386	[
		387	1,
		388	2, <- this comma not normally allowed
		389	]
		390	{
		391	"k1": "v1",
		392	"k2": "v2", <- this comma not normally allowed
		393	}
		394
		395	=item * shell-style '#'-comments
		396
		397	Whenever JSON allows whitespace, shell-style comments are additionally
		398	allowed. They are terminated by the first carriage-return or line-feed
		399	character, after which more white-space and comments are allowed.
		400
		401	[
		402	1, # this comment not allowed in JSON
		403	# neither this one...
		404	]
		405
		406	=back
		407
224	=item $json = $json->canonical ([$enable])	408	=item $json = $json->canonical ([$enable])
		409
		410	=item $enabled = $json->get_canonical
225		411
226	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	412	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
227	by sorting their keys. This is adding a comparatively high overhead.	413	by sorting their keys. This is adding a comparatively high overhead.
228		414
229	If C<$enable> is false, then the C<encode> method will output key-value	415	If C<$enable> is false, then the C<encode> method will output key-value
230	pairs in the order Perl stores them (which will likely change between runs	416	pairs in the order Perl stores them (which will likely change between runs
231	of the same script).	417	of the same script).
232		418
233	This option is useful if you want the same data structure to be encoded as	419	This option is useful if you want the same data structure to be encoded as
234	the same JSON string (given the same overall settings). If it is disabled,	420	the same JSON text (given the same overall settings). If it is disabled,
235	the same hash migh be encoded differently even if contains the same data,	421	the same hash might be encoded differently even if contains the same data,
236	as key-value pairs have no inherent ordering in Perl.	422	as key-value pairs have no inherent ordering in Perl.
237		423
238	This setting has no effect when decoding JSON strings.	424	This setting has no effect when decoding JSON texts.
239		425
240	=item $json = $json->allow_nonref ([$enable])	426	=item $json = $json->allow_nonref ([$enable])
		427
		428	=item $enabled = $json->get_allow_nonref
241		429
242	If C<$enable> is true (or missing), then the C<encode> method can convert a	430	If C<$enable> is true (or missing), then the C<encode> method can convert a
243	non-reference into its corresponding string, number or null JSON value,	431	non-reference into its corresponding string, number or null JSON value,
244	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	432	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
245	values instead of croaking.	433	values instead of croaking.
246		434
247	If C<$enable> is false, then the C<encode> method will croak if it isn't	435	If C<$enable> is false, then the C<encode> method will croak if it isn't
248	passed an arrayref or hashref, as JSON strings must either be an object	436	passed an arrayref or hashref, as JSON texts must either be an object
249	or array. Likewise, C<decode> will croak if given something that is not a	437	or array. Likewise, C<decode> will croak if given something that is not a
250	JSON object or array.	438	JSON object or array.
251		439
252	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	440	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
253	resulting in an invalid JSON text:	441	resulting in an invalid JSON text:
254		442
255	JSON::XS->new->allow_nonref->encode ("Hello, World!")	443	JSON::XS->new->allow_nonref->encode ("Hello, World!")
256	=> "Hello, World!"	444	=> "Hello, World!"
257		445
		446	=item $json = $json->allow_blessed ([$enable])
		447
		448	=item $enabled = $json->get_allow_blessed
		449
		450	If C<$enable> is true (or missing), then the C<encode> method will not
		451	barf when it encounters a blessed reference. Instead, the value of the
		452	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		453	disabled or no C<TO_JSON> method found) or a representation of the
		454	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		455	encoded. Has no effect on C<decode>.
		456
		457	If C<$enable> is false (the default), then C<encode> will throw an
		458	exception when it encounters a blessed object.
		459
		460	=item $json = $json->convert_blessed ([$enable])
		461
		462	=item $enabled = $json->get_convert_blessed
		463
		464	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		465	blessed object, will check for the availability of the C<TO_JSON> method
		466	on the object's class. If found, it will be called in scalar context
		467	and the resulting scalar will be encoded instead of the object. If no
		468	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		469	to do.
		470
		471	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		472	returns other blessed objects, those will be handled in the same
		473	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		474	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		475	methods called by the Perl core (== not by the user of the object) are
		476	usually in upper case letters and to avoid collisions with the C<to_json>
		477	function.
		478
		479	This setting does not yet influence C<decode> in any way, but in the
		480	future, global hooks might get installed that influence C<decode> and are
		481	enabled by this setting.
		482
		483	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		484	to do when a blessed object is found.
		485
		486	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		487
		488	When C<$coderef> is specified, it will be called from C<decode> each
		489	time it decodes a JSON object. The only argument is a reference to the
		490	newly-created hash. If the code references returns a single scalar (which
		491	need not be a reference), this value (i.e. a copy of that scalar to avoid
		492	aliasing) is inserted into the deserialised data structure. If it returns
		493	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		494	original deserialised hash will be inserted. This setting can slow down
		495	decoding considerably.
		496
		497	When C<$coderef> is omitted or undefined, any existing callback will
		498	be removed and C<decode> will not change the deserialised hash in any
		499	way.
		500
		501	Example, convert all JSON objects into the integer 5:
		502
		503	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		504	# returns [5]
		505	$js->decode ('[{}]')
		506	# throw an exception because allow_nonref is not enabled
		507	# so a lone 5 is not allowed.
		508	$js->decode ('{"a":1, "b":2}');
		509
		510	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		511
		512	Works remotely similar to C<filter_json_object>, but is only called for
		513	JSON objects having a single key named C<$key>.
		514
		515	This C<$coderef> is called before the one specified via
		516	C<filter_json_object>, if any. It gets passed the single value in the JSON
		517	object. If it returns a single value, it will be inserted into the data
		518	structure. If it returns nothing (not even C<undef> but the empty list),
		519	the callback from C<filter_json_object> will be called next, as if no
		520	single-key callback were specified.
		521
		522	If C<$coderef> is omitted or undefined, the corresponding callback will be
		523	disabled. There can only ever be one callback for a given key.
		524
		525	As this callback gets called less often then the C<filter_json_object>
		526	one, decoding speed will not usually suffer as much. Therefore, single-key
		527	objects make excellent targets to serialise Perl objects into, especially
		528	as single-key JSON objects are as close to the type-tagged value concept
		529	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		530	support this in any way, so you need to make sure your data never looks
		531	like a serialised Perl hash.
		532
		533	Typical names for the single object key are C<__class_whatever__>, or
		534	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		535	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		536	with real hashes.
		537
		538	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		539	into the corresponding C<< $WIDGET{<id>} >> object:
		540
		541	# return whatever is in $WIDGET{5}:
		542	JSON::XS
		543	->new
		544	->filter_json_single_key_object (__widget__ => sub {
		545	$WIDGET{ $_[0] }
		546	})
		547	->decode ('{"__widget__": 5')
		548
		549	# this can be used with a TO_JSON method in some "widget" class
		550	# for serialisation to json:
		551	sub WidgetBase::TO_JSON {
		552	my ($self) = @_;
		553
		554	unless ($self->{id}) {
		555	$self->{id} = ..get..some..id..;
		556	$WIDGET{$self->{id}} = $self;
		557	}
		558
		559	{ __widget__ => $self->{id} }
		560	}
		561
258	=item $json = $json->shrink ([$enable])	562	=item $json = $json->shrink ([$enable])
259		563
		564	=item $enabled = $json->get_shrink
		565
260	Perl usually over-allocates memory a bit when allocating space for	566	Perl usually over-allocates memory a bit when allocating space for
261	strings. This flag optionally resizes strings generated by either	567	strings. This flag optionally resizes strings generated by either
262	C<encode> or C<decode> to their minimum size possible. This can save	568	C<encode> or C<decode> to their minimum size possible. This can save
263	memory when your JSON strings are either very very long or you have many	569	memory when your JSON texts are either very very long or you have many
264	short strings. It will also try to downgrade any strings to octet-form	570	short strings. It will also try to downgrade any strings to octet-form
265	if possible: perl stores strings internally either in an encoding called	571	if possible: perl stores strings internally either in an encoding called
266	UTF-X or in octet-form. The latter cannot store everything but uses less	572	UTF-X or in octet-form. The latter cannot store everything but uses less
267	space in general.	573	space in general (and some buggy Perl or C code might even rely on that
		574	internal representation being used).
268		575
		576	The actual definition of what shrink does might change in future versions,
		577	but it will always try to save space at the expense of time.
		578
269	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	579	If C<$enable> is true (or missing), the string returned by C<encode> will
270	while all strings generated by C<decode> will also be shrunk-to-fit.	580	be shrunk-to-fit, while all strings generated by C<decode> will also be
		581	shrunk-to-fit.
271		582
272	If C<$enable> is false, then the normal perl allocation algorithms are used.	583	If C<$enable> is false, then the normal perl allocation algorithms are used.
273	If you work with your data, then this is likely to be faster.	584	If you work with your data, then this is likely to be faster.
274		585
275	In the future, this setting might control other things, such as converting	586	In the future, this setting might control other things, such as converting
276	strings that look like integers or floats into integers or floats	587	strings that look like integers or floats into integers or floats
277	internally (there is no difference on the Perl level), saving space.	588	internally (there is no difference on the Perl level), saving space.
278		589
		590	=item $json = $json->max_depth ([$maximum_nesting_depth])
		591
		592	=item $max_depth = $json->get_max_depth
		593
		594	Sets the maximum nesting level (default C<512>) accepted while encoding
		595	or decoding. If the JSON text or Perl data structure has an equal or
		596	higher nesting level then this limit, then the encoder and decoder will
		597	stop and croak at that point.
		598
		599	Nesting level is defined by number of hash- or arrayrefs that the encoder
		600	needs to traverse to reach a given point or the number of C<{> or C<[>
		601	characters without their matching closing parenthesis crossed to reach a
		602	given character in a string.
		603
		604	Setting the maximum depth to one disallows any nesting, so that ensures
		605	that the object is only a single hash/object or array.
		606
		607	The argument to C<max_depth> will be rounded up to the next highest power
		608	of two. If no argument is given, the highest possible setting will be
		609	used, which is rarely useful.
		610
		611	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		612
		613	=item $json = $json->max_size ([$maximum_string_size])
		614
		615	=item $max_size = $json->get_max_size
		616
		617	Set the maximum length a JSON text may have (in bytes) where decoding is
		618	being attempted. The default is C<0>, meaning no limit. When C<decode>
		619	is called on a string longer then this number of characters it will not
		620	attempt to decode the string but throw an exception. This setting has no
		621	effect on C<encode> (yet).
		622
		623	The argument to C<max_size> will be rounded up to the next B<highest>
		624	power of two (so may be more than requested). If no argument is given, the
		625	limit check will be deactivated (same as when C<0> is specified).
		626
		627	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		628
279	=item $json_string = $json->encode ($perl_scalar)	629	=item $json_text = $json->encode ($perl_scalar)
280		630
281	Converts the given Perl data structure (a simple scalar or a reference	631	Converts the given Perl data structure (a simple scalar or a reference
282	to a hash or array) to its JSON representation. Simple scalars will be	632	to a hash or array) to its JSON representation. Simple scalars will be
283	converted into JSON string or number sequences, while references to arrays	633	converted into JSON string or number sequences, while references to arrays
284	become JSON arrays and references to hashes become JSON objects. Undefined	634	become JSON arrays and references to hashes become JSON objects. Undefined
285	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	635	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
286	nor C<false> values will be generated.	636	nor C<false> values will be generated.
287		637
288	=item $perl_scalar = $json->decode ($json_string)	638	=item $perl_scalar = $json->decode ($json_text)
289		639
290	The opposite of C<encode>: expects a JSON string and tries to parse it,	640	The opposite of C<encode>: expects a JSON text and tries to parse it,
291	returning the resulting simple scalar or reference. Croaks on error.	641	returning the resulting simple scalar or reference. Croaks on error.
292		642
293	JSON numbers and strings become simple Perl scalars. JSON arrays become	643	JSON numbers and strings become simple Perl scalars. JSON arrays become
294	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	644	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
295	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	645	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
296		646
		647	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		648
		649	This works like the C<decode> method, but instead of raising an exception
		650	when there is trailing garbage after the first JSON object, it will
		651	silently stop parsing there and return the number of characters consumed
		652	so far.
		653
		654	This is useful if your JSON texts are not delimited by an outer protocol
		655	(which is not the brightest thing to do in the first place) and you need
		656	to know where the JSON text ends.
		657
		658	JSON::XS->new->decode_prefix ("[1] the tail")
		659	=> ([], 3)
		660
297	=back	661	=back
		662
298		663
299	=head1 MAPPING	664	=head1 MAPPING
300		665
301	This section describes how JSON::XS maps Perl values to JSON values and	666	This section describes how JSON::XS maps Perl values to JSON values and
302	vice versa. These mappings are designed to "do the right thing" in most	667	vice versa. These mappings are designed to "do the right thing" in most
303	circumstances automatically, preserving round-tripping characteristics	668	circumstances automatically, preserving round-tripping characteristics
304	(what you put in comes out as something equivalent).	669	(what you put in comes out as something equivalent).
305		670
306	For the more enlightened: note that in the following descriptions,	671	For the more enlightened: note that in the following descriptions,
307	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	672	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
308	refers to the abstract Perl language itself.	673	refers to the abstract Perl language itself.
309		674
		675
310	=head2 JSON -> PERL	676	=head2 JSON -> PERL
311		677
312	=over 4	678	=over 4
313		679
314	=item object	680	=item object
315		681
316	A JSON object becomes a reference to a hash in Perl. No ordering of object	682	A JSON object becomes a reference to a hash in Perl. No ordering of object
317	keys is preserved.	683	keys is preserved (JSON does not preserve object key ordering itself).
318		684
319	=item array	685	=item array
320		686
321	A JSON array becomes a reference to an array in Perl.	687	A JSON array becomes a reference to an array in Perl.
322		688
…		…
326	are represented by the same codepoints in the Perl string, so no manual	692	are represented by the same codepoints in the Perl string, so no manual
327	decoding is necessary.	693	decoding is necessary.
328		694
329	=item number	695	=item number
330		696
331	A JSON number becomes either an integer or numeric (floating point)	697	A JSON number becomes either an integer, numeric (floating point) or
332	scalar in perl, depending on its range and any fractional parts. On the	698	string scalar in perl, depending on its range and any fractional parts. On
333	Perl level, there is no difference between those as Perl handles all the	699	the Perl level, there is no difference between those as Perl handles all
334	conversion details, but an integer may take slightly less memory and might	700	the conversion details, but an integer may take slightly less memory and
335	represent more values exactly than (floating point) numbers.	701	might represent more values exactly than (floating point) numbers.
		702
		703	If the number consists of digits only, JSON::XS will try to represent
		704	it as an integer value. If that fails, it will try to represent it as
		705	a numeric (floating point) value if that is possible without loss of
		706	precision. Otherwise it will preserve the number as a string value.
		707
		708	Numbers containing a fractional or exponential part will always be
		709	represented as numeric (floating point) values, possibly at a loss of
		710	precision.
		711
		712	This might create round-tripping problems as numbers might become strings,
		713	but as Perl is typeless there is no other way to do it.
336		714
337	=item true, false	715	=item true, false
338		716
339	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	717	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
340	this process. Future versions might represent those values differently,	718	respectively. They are overloaded to act almost exactly like the numbers
341	but they will be guarenteed to act like these integers would normally in	719	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
342	Perl.	720	the C<JSON::XS::is_bool> function.
343		721
344	=item null	722	=item null
345		723
346	A JSON null atom becomes C<undef> in Perl.	724	A JSON null atom becomes C<undef> in Perl.
347		725
348	=back	726	=back
		727
349		728
350	=head2 PERL -> JSON	729	=head2 PERL -> JSON
351		730
352	The mapping from Perl to JSON is slightly more difficult, as Perl is a	731	The mapping from Perl to JSON is slightly more difficult, as Perl is a
353	truly typeless language, so we can only guess which JSON type is meant by	732	truly typeless language, so we can only guess which JSON type is meant by
…		…
356	=over 4	735	=over 4
357		736
358	=item hash references	737	=item hash references
359		738
360	Perl hash references become JSON objects. As there is no inherent ordering	739	Perl hash references become JSON objects. As there is no inherent ordering
361	in hash keys, they will usually be encoded in a pseudo-random order that	740	in hash keys (or JSON objects), they will usually be encoded in a
362	can change between runs of the same program but stays generally the same	741	pseudo-random order that can change between runs of the same program but
363	within the single run of a program. JSON::XS can optionally sort the hash	742	stays generally the same within a single run of a program. JSON::XS can
364	keys (determined by the I<canonical> flag), so the same datastructure	743	optionally sort the hash keys (determined by the I<canonical> flag), so
365	will serialise to the same JSON text (given same settings and version of	744	the same datastructure will serialise to the same JSON text (given same
366	JSON::XS), but this incurs a runtime overhead.	745	settings and version of JSON::XS), but this incurs a runtime overhead
		746	and is only rarely useful, e.g. when you want to compare some JSON text
		747	against another for equality.
367		748
368	=item array references	749	=item array references
369		750
370	Perl array references become JSON arrays.	751	Perl array references become JSON arrays.
		752
		753	=item other references
		754
		755	Other unblessed references are generally not allowed and will cause an
		756	exception to be thrown, except for references to the integers C<0> and
		757	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		758	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		759
		760	to_json [\0,JSON::XS::true] # yields [false,true]
		761
		762	=item JSON::XS::true, JSON::XS::false
		763
		764	These special values become JSON true and JSON false values,
		765	respectively. You can also use C<\1> and C<\0> directly if you want.
371		766
372	=item blessed objects	767	=item blessed objects
373		768
374	Blessed objects are not allowed. JSON::XS currently tries to encode their	769	Blessed objects are not allowed. JSON::XS currently tries to encode their
375	underlying representation (hash- or arrayref), but this behaviour might	770	underlying representation (hash- or arrayref), but this behaviour might
…		…
392	to_json [$value] # yields ["5"]	787	to_json [$value] # yields ["5"]
393		788
394	# undef becomes null	789	# undef becomes null
395	to_json [undef] # yields [null]	790	to_json [undef] # yields [null]
396		791
397	You can force the type to be a string by stringifying it:	792	You can force the type to be a JSON string by stringifying it:
398		793
399	my $x = 3.1; # some variable containing a number	794	my $x = 3.1; # some variable containing a number
400	"$x"; # stringified	795	"$x"; # stringified
401	$x .= ""; # another, more awkward way to stringify	796	$x .= ""; # another, more awkward way to stringify
402	print $x; # perl does it for you, too, quite often	797	print $x; # perl does it for you, too, quite often
403		798
404	You can force the type to be a number by numifying it:	799	You can force the type to be a JSON number by numifying it:
405		800
406	my $x = "3"; # some variable containing a string	801	my $x = "3"; # some variable containing a string
407	$x += 0; # numify it, ensuring it will be dumped as a number	802	$x += 0; # numify it, ensuring it will be dumped as a number
408	$x *= 1; # same thing, the choise is yours.	803	$x *= 1; # same thing, the choice is yours.
409		804
410	You can not currently output JSON booleans or force the type in other,	805	You can not currently force the type in other, less obscure, ways. Tell me
411	less obscure, ways. Tell me if you need this capability.	806	if you need this capability.
412
413	=item circular data structures
414
415	Those will be encoded until memory or stackspace runs out.
416		807
417	=back	808	=back
		809
418		810
419	=head1 COMPARISON	811	=head1 COMPARISON
420		812
421	As already mentioned, this module was created because none of the existing	813	As already mentioned, this module was created because none of the existing
422	JSON modules could be made to work correctly. First I will describe the	814	JSON modules could be made to work correctly. First I will describe the
…		…
428		820
429	=item JSON 1.07	821	=item JSON 1.07
430		822
431	Slow (but very portable, as it is written in pure Perl).	823	Slow (but very portable, as it is written in pure Perl).
432		824
433	Undocumented/buggy Unicode handling (how JSON handles unicode values is	825	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
434	undocumented. One can get far by feeding it unicode strings and doing	826	undocumented. One can get far by feeding it Unicode strings and doing
435	en-/decoding oneself, but unicode escapes are not working properly).	827	en-/decoding oneself, but Unicode escapes are not working properly).
436		828
437	No roundtripping (strings get clobbered if they look like numbers, e.g.	829	No round-tripping (strings get clobbered if they look like numbers, e.g.
438	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	830	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
439	decode into the number 2.	831	decode into the number 2.
440		832
441	=item JSON::PC 0.01	833	=item JSON::PC 0.01
442		834
443	Very fast.	835	Very fast.
444		836
445	Undocumented/buggy Unicode handling.	837	Undocumented/buggy Unicode handling.
446		838
447	No roundtripping.	839	No round-tripping.
448		840
449	Has problems handling many Perl values (e.g. regex results and other magic	841	Has problems handling many Perl values (e.g. regex results and other magic
450	values will make it croak).	842	values will make it croak).
451		843
452	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	844	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
453	which is not a valid JSON string.	845	which is not a valid JSON text.
454		846
455	Unmaintained (maintainer unresponsive for many months, bugs are not	847	Unmaintained (maintainer unresponsive for many months, bugs are not
456	getting fixed).	848	getting fixed).
457		849
458	=item JSON::Syck 0.21	850	=item JSON::Syck 0.21
…		…
460	Very buggy (often crashes).	852	Very buggy (often crashes).
461		853
462	Very inflexible (no human-readable format supported, format pretty much	854	Very inflexible (no human-readable format supported, format pretty much
463	undocumented. I need at least a format for easy reading by humans and a	855	undocumented. I need at least a format for easy reading by humans and a
464	single-line compact format for use in a protocol, and preferably a way to	856	single-line compact format for use in a protocol, and preferably a way to
465	generate ASCII-only JSON strings).	857	generate ASCII-only JSON texts).
466		858
467	Completely broken (and confusingly documented) Unicode handling (unicode	859	Completely broken (and confusingly documented) Unicode handling (Unicode
468	escapes are not working properly, you need to set ImplicitUnicode to	860	escapes are not working properly, you need to set ImplicitUnicode to
469	I<different> values on en- and decoding to get symmetric behaviour).	861	I<different> values on en- and decoding to get symmetric behaviour).
470		862
471	No roundtripping (simple cases work, but this depends on wether the scalar	863	No round-tripping (simple cases work, but this depends on whether the scalar
472	value was used in a numeric context or not).	864	value was used in a numeric context or not).
473		865
474	Dumping hashes may skip hash values depending on iterator state.	866	Dumping hashes may skip hash values depending on iterator state.
475		867
476	Unmaintained (maintainer unresponsive for many months, bugs are not	868	Unmaintained (maintainer unresponsive for many months, bugs are not
477	getting fixed).	869	getting fixed).
478		870
479	Does not check input for validity (i.e. will accept non-JSON input and	871	Does not check input for validity (i.e. will accept non-JSON input and
480	return "something" instead of raising an exception. This is a security	872	return "something" instead of raising an exception. This is a security
481	issue: imagine two banks transfering money between each other using	873	issue: imagine two banks transferring money between each other using
482	JSON. One bank might parse a given non-JSON request and deduct money,	874	JSON. One bank might parse a given non-JSON request and deduct money,
483	while the other might reject the transaction with a syntax error. While a	875	while the other might reject the transaction with a syntax error. While a
484	good protocol will at least recover, that is extra unnecessary work and	876	good protocol will at least recover, that is extra unnecessary work and
485	the transaction will still not succeed).	877	the transaction will still not succeed).
486		878
487	=item JSON::DWIW 0.04	879	=item JSON::DWIW 0.04
488		880
489	Very fast. Very natural. Very nice.	881	Very fast. Very natural. Very nice.
490		882
491	Undocumented unicode handling (but the best of the pack. Unicode escapes	883	Undocumented Unicode handling (but the best of the pack. Unicode escapes
492	still don't get parsed properly).	884	still don't get parsed properly).
493		885
494	Very inflexible.	886	Very inflexible.
495		887
496	No roundtripping.	888	No round-tripping.
497		889
498	Does not generate valid JSON (key strings are often unquoted, empty keys	890	Does not generate valid JSON texts (key strings are often unquoted, empty keys
499	result in nothing being output)	891	result in nothing being output)
500		892
501	Does not check input for validity.	893	Does not check input for validity.
502		894
503	=back	895	=back
		896
		897
		898	=head2 JSON and YAML
		899
		900	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		901	however, a mass hysteria and very far from the truth. In general, there is
		902	no way to configure JSON::XS to output a data structure as valid YAML.
		903
		904	If you really must use JSON::XS to generate YAML, you should use this
		905	algorithm (subject to change in future versions):
		906
		907	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		908	my $yaml = $to_yaml->encode ($ref) . "\n";
		909
		910	This will usually generate JSON texts that also parse as valid
		911	YAML. Please note that YAML has hardcoded limits on (simple) object key
		912	lengths that JSON doesn't have, so you should make sure that your hash
		913	keys are noticeably shorter than the 1024 characters YAML allows.
		914
		915	There might be other incompatibilities that I am not aware of. In general
		916	you should not try to generate YAML with a JSON generator or vice versa,
		917	or try to parse JSON with a YAML parser or vice versa: chances are high
		918	that you will run into severe interoperability problems.
		919
504		920
505	=head2 SPEED	921	=head2 SPEED
506		922
507	It seems that JSON::XS is surprisingly fast, as shown in the following	923	It seems that JSON::XS is surprisingly fast, as shown in the following
508	tables. They have been generated with the help of the C<eg/bench> program	924	tables. They have been generated with the help of the C<eg/bench> program
509	in the JSON::XS distribution, to make it easy to compare on your own	925	in the JSON::XS distribution, to make it easy to compare on your own
510	system.	926	system.
511		927
512	First comes a comparison between various modules using a very short JSON	928	First comes a comparison between various modules using a very short
513	string (83 bytes), showing the number of encodes/decodes per second	929	single-line JSON string:
		930
		931	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		932	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		933
		934	It shows the number of encodes/decodes per second (JSON::XS uses
514	(JSON::XS is the functional interface, while JSON::XS/2 is the OO	935	the functional interface, while JSON::XS/2 uses the OO interface
515	interface with pretty-printing and hashkey sorting enabled). Higher is	936	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
516	better:	937	shrink). Higher is better:
517		938
518	module \| encode \| decode \|	939	module \| encode \| decode \|
519	-----------\|------------\|------------\|	940	-----------\|------------\|------------\|
520	JSON \| 14006 \| 6820 \|	941	JSON 1.x \| 4990.842 \| 4088.813 \|
521	JSON::DWIW \| 200937 \| 120386 \|	942	JSON::DWIW \| 51653.990 \| 71575.154 \|
522	JSON::PC \| 85065 \| 129366 \|	943	JSON::PC \| 65948.176 \| 74631.744 \|
523	JSON::Syck \| 59898 \| 44232 \|	944	JSON::PP \| 8931.652 \| 3817.168 \|
524	JSON::XS \| 1171478 \| 342435 \|	945	JSON::Syck \| 24877.248 \| 27776.848 \|
525	JSON::XS/2 \| 730760 \| 328714 \|	946	JSON::XS \| 388361.481 \| 227951.304 \|
		947	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		948	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		949	Storable \| 16500.016 \| 135300.129 \|
526	-----------+------------+------------+	950	-----------+------------+------------+
527		951
528	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	952	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		953	about three times faster on decoding, and over forty times faster
529	times faster than JSON, even with pretty-printing and key sorting.	954	than JSON, even with pretty-printing and key sorting. It also compares
		955	favourably to Storable for small amounts of data.
530		956
531	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	957	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
532	search API (http://nanoref.com/yahooapis/mgPdGg):	958	search API (http://nanoref.com/yahooapis/mgPdGg):
533		959
534	module \| encode \| decode \|	960	module \| encode \| decode \|
535	-----------\|------------\|------------\|	961	-----------\|------------\|------------\|
536	JSON \| 673 \| 38 \|	962	JSON 1.x \| 55.260 \| 34.971 \|
537	JSON::DWIW \| 5271 \| 770 \|	963	JSON::DWIW \| 825.228 \| 1082.513 \|
538	JSON::PC \| 9901 \| 2491 \|	964	JSON::PC \| 3571.444 \| 2394.829 \|
539	JSON::Syck \| 2360 \| 786 \|	965	JSON::PP \| 210.987 \| 32.574 \|
540	JSON::XS \| 37398 \| 3202 \|	966	JSON::Syck \| 552.551 \| 787.544 \|
541	JSON::XS/2 \| 13765 \| 3153 \|	967	JSON::XS \| 5780.463 \| 4854.519 \|
		968	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		969	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		970	Storable \| 4445.002 \| 5235.027 \|
542	-----------+------------+------------+	971	-----------+------------+------------+
543		972
544	Again, JSON::XS leads by far in the encoding case, while still beating	973	Again, JSON::XS leads by far (except for Storable which non-surprisingly
545	every other module in the decoding case.	974	decodes faster).
546		975
547	On large strings containing lots of unicode characters, some modules	976	On large strings containing lots of high Unicode characters, some modules
548	(such as JSON::PC) decode faster than JSON::XS, but the result will be	977	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
549	broken due to missing unicode handling. Others refuse to decode or encode	978	will be broken due to missing (or wrong) Unicode handling. Others refuse
550	properly, so it was impossible to prepare a fair comparison table for that	979	to decode or encode properly, so it was impossible to prepare a fair
551	case.	980	comparison table for that case.
552		981
553	=head1 RESOURCE LIMITS
554		982
555	JSON::XS does not impose any limits on the size of JSON texts or Perl	983	=head1 SECURITY CONSIDERATIONS
556	values they represent - if your machine can handle it, JSON::XS will	984
557	encode or decode it. Future versions might optionally impose structure	985	When you are using JSON in a protocol, talking to untrusted potentially
558	depth and memory use resource limits.	986	hostile creatures requires relatively few measures.
		987
		988	First of all, your JSON decoder should be secure, that is, should not have
		989	any buffer overflows. Obviously, this module should ensure that and I am
		990	trying hard on making that true, but you never know.
		991
		992	Second, you need to avoid resource-starving attacks. That means you should
		993	limit the size of JSON texts you accept, or make sure then when your
		994	resources run out, that's just fine (e.g. by using a separate process that
		995	can crash safely). The size of a JSON text in octets or characters is
		996	usually a good indication of the size of the resources required to decode
		997	it into a Perl structure. While JSON::XS can check the size of the JSON
		998	text, it might be too late when you already have it in memory, so you
		999	might want to check the size before you accept the string.
		1000
		1001	Third, JSON::XS recurses using the C stack when decoding objects and
		1002	arrays. The C stack is a limited resource: for instance, on my amd64
		1003	machine with 8MB of stack size I can decode around 180k nested arrays but
		1004	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		1005	to free the temporary). If that is exceeded, the program crashes. to be
		1006	conservative, the default nesting limit is set to 512. If your process
		1007	has a smaller stack, you should adjust this setting accordingly with the
		1008	C<max_depth> method.
		1009
		1010	And last but least, something else could bomb you that I forgot to think
		1011	of. In that case, you get to keep the pieces. I am always open for hints,
		1012	though...
		1013
		1014	If you are using JSON::XS to return packets to consumption
		1015	by JavaScript scripts in a browser you should have a look at
		1016	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1017	you are vulnerable to some common attack vectors (which really are browser
		1018	design bugs, but it is still you who will have to deal with it, as major
		1019	browser developers care only for features, not about doing security
		1020	right).
		1021
		1022
		1023	=head1 THREADS
		1024
		1025	This module is I<not> guaranteed to be thread safe and there are no
		1026	plans to change this until Perl gets thread support (as opposed to the
		1027	horribly slow so-called "threads" which are simply slow and bloated
		1028	process simulations - use fork, its I<much> faster, cheaper, better).
		1029
		1030	(It might actually work, but you have been warned).
		1031
559		1032
560	=head1 BUGS	1033	=head1 BUGS
561		1034
562	While the goal of this module is to be correct, that unfortunately does	1035	While the goal of this module is to be correct, that unfortunately does
563	not mean its bug-free, only that I think its design is bug-free. It is	1036	not mean its bug-free, only that I think its design is bug-free. It is
564	still very young and not well-tested. If you keep reporting bugs they will	1037	still relatively early in its development. If you keep reporting bugs they
565	be fixed swiftly, though.	1038	will be fixed swiftly, though.
		1039
		1040	Please refrain from using rt.cpan.org or any other bug reporting
		1041	service. I put the contact address into my modules for a reason.
566		1042
567	=cut	1043	=cut
		1044
		1045	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1046	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1047
		1048	sub true() { $true }
		1049	sub false() { $false }
		1050
		1051	sub is_bool($) {
		1052	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1053	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1054	}
		1055
		1056	XSLoader::load "JSON::XS", $VERSION;
		1057
		1058	package JSON::XS::Boolean;
		1059
		1060	use overload
		1061	"0+" => sub { ${$_[0]} },
		1062	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1063	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1064	fallback => 1;
568		1065
569	1;	1066	1;
570		1067
571	=head1 AUTHOR	1068	=head1 AUTHOR
572		1069

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Comparing JSON-XS/XS.pm (file contents): Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs. Revision 1.77 by root, Tue Dec 4 10:37:42 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.13 by root, Fri Mar 23 18:37:30 2007 UTC vs.
Revision 1.77 by root, Tue Dec 4 10:37:42 2007 UTC