[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 1.77 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;
		11
		12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
		14
		15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		17
		18	# OO-interface
		19
		20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		22	$perl_scalar = $coder->decode ($unicode_json_text);
		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.
8		31
9	=head1 DESCRIPTION	32	=head1 DESCRIPTION
10		33
11	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
12	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
13	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.
14		45
15	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
16	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
17	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
18	their maintainers are unresponsive, gone missing, or not listening to bug	49	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	50	reports for other reasons.
20		51
21	See COMPARISON, below, for a comparison to some other JSON modules.	52	See COMPARISON, below, for a comparison to some other JSON modules.
22		53
		54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		55	vice versa.
		56
23	=head2 FEATURES	57	=head2 FEATURES
24		58
25	=over 4	59	=over 4
26		60
27	=item * correct handling of unicode issues	61	=item * correct Unicode handling
28		62
29	This module knows how to handle Unicode, and even documents how it does so.	63	This module knows how to handle Unicode, and even documents how and when
		64	it does so.
30		65
31	=item * round-trip integrity	66	=item * round-trip integrity
32		67
33	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only datatypes supported
34	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.
35	(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).
36		72
37	=item * strict checking of JSON correctness	73	=item * strict checking of JSON correctness
38		74
39	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,
40	and only JSON is accepted as input (the latter is a security feature).	76	and only JSON is accepted as input by default (the latter is a security
		77	feature).
41		78
42	=item * fast	79	=item * fast
43		80
44	compared to other JSON modules, this module compares favourably.	81	Compared to other JSON modules, this module compares favourably in terms
		82	of speed, too.
45		83
46	=item * simple to use	84	=item * simple to use
47		85
48	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
49	interface.	87	interface.
50		88
51	=item * reasonably versatile output formats	89	=item * reasonably versatile output formats
52		90
53	You can choose between the most compact format possible, a pure-ascii	91	You can choose between the most compact guaranteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	92	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	93	(for when your transport is not 8-bit clean, still supports the whole
		94	Unicode range), or a pretty-printed format (for when you want to read that
		95	stuff). Or you can combine those features in whatever way you like.
56		96
57	=back	97	=back
58		98
59	=cut	99	=cut
60		100
61	package JSON::XS;	101	package JSON::XS;
62		102
63	BEGIN {	103	use strict;
		104
64	$VERSION = '0.1';	105	our $VERSION = '2.0';
65	@ISA = qw(Exporter);	106	our @ISA = qw(Exporter);
66		107
67	@EXPORT = qw(to_json from_json);	108	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		109
70	require XSLoader;	110	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	111	use XSLoader;
72	}
73		112
74	=head1 FUNCTIONAL INTERFACE	113	=head1 FUNCTIONAL INTERFACE
75		114
76	The following convinience methods are provided by this module. They are	115	The following convenience methods are provided by this module. They are
77	exported by default:	116	exported by default:
78		117
79	=over 4	118	=over 4
80		119
81	=item $json_string = to_json $perl_scalar	120	=item $json_text = to_json $perl_scalar
82		121
83	Converts the given Perl data structure (a simple scalar or a reference to	122	Converts the given Perl data structure to a UTF-8 encoded, binary string
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	123	(that is, the string contains octets only). Croaks on error.
85	octets only). Croaks on error.
86		124
87	This function call is functionally identical to C<< JSON::XS->new->utf8	125	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		126
		127	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		128
		129	except being faster.
		130
90	=item $perl_scalar = from_json $json_string	131	=item $perl_scalar = from_json $json_text
91		132
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	133	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	134	to parse that as an UTF-8 encoded JSON text, returning the resulting
94	scalar or reference. Croaks on error.	135	reference. Croaks on error.
95		136
96	This function call is functionally identical to C<< JSON::XS->new->utf8	137	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	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.
98		151
99	=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
100		202
101	=head1 OBJECT-ORIENTED INTERFACE	203	=head1 OBJECT-ORIENTED INTERFACE
102		204
103	The object oriented interface lets you configure your own encoding or	205	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	206	decoding style, within the limits of supported formats.
111	strings. All boolean flags described below are by default I<disabled>.	213	strings. All boolean flags described below are by default I<disabled>.
112		214
113	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
114	be chained:	216	be chained:
115		217
116	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]})
117	=> {"a": [1, 2]}	219	=> {"a": [1, 2]}
118		220
119	=item $json = $json->ascii ($enable)	221	=item $json = $json->ascii ([$enable])
120		222
		223	=item $enabled = $json->get_ascii
		224
121	If C<$enable> is true, then the C<encode> method will not generate	225	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	226	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	227	Unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	228	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		229	as per RFC4627. The resulting encoded JSON text can be treated as a native
		230	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		231	or any other superset of ASCII.
125		232
126	If C<$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
127	characters unless necessary.	234	characters unless required by the JSON syntax or other flags. This results
		235	in a faster and more compact format.
128		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
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	241	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	242	=> ["\ud801\udc01"]
131		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)
		268
132	=item $json = $json->utf8 ($enable)	269	=item $json = $json->utf8 ([$enable])
133		270
		271	=item $enabled = $json->get_utf8
		272
134	If C<$enable> is true, then the C<encode> method will encode the JSON	273	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	274	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	275	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	276	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	277	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		278	versions, enabling this option might enable autodetection of the UTF-16
		279	and UTF-32 encoding families, as described in RFC4627.
139		280
140	If C<$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
141	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
142	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
143	to be done yourself, e.g. using the Encode module.	284	to be done yourself, e.g. using the Encode module.
144		285
		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);
		295
145	=item $json = $json->pretty ($enable)	296	=item $json = $json->pretty ([$enable])
146		297
147	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
148	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
149	generate the most readable (or most compact) form possible.	300	generate the most readable (or most compact) form possible.
		301
		302	Example, pretty-print some simple structure:
150		303
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	304	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	305	=>
153	{	306	{
154	"a" : [	307	"a" : [
155	1,	308	1,
156	2	309	2
157	]	310	]
158	}	311	}
159		312
160	=item $json = $json->indent ($enable)	313	=item $json = $json->indent ([$enable])
161		314
		315	=item $enabled = $json->get_indent
		316
162	If C<$enable> is true, then the C<encode> method will use a multiline	317	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	318	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	319	into its own line, indenting them properly.
165		320
166	If C<$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
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	322	resulting JSON text is guaranteed not to contain any C<newlines>.
168		323
169	This setting has no effect when decoding JSON strings.	324	This setting has no effect when decoding JSON texts.
170		325
171	=item $json = $json->space_before ($enable)	326	=item $json = $json->space_before ([$enable])
172		327
		328	=item $enabled = $json->get_space_before
		329
173	If C<$enable> is true, then the C<encode> method will add an extra	330	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	331	optional space before the C<:> separating keys from values in JSON objects.
175		332
176	If C<$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
177	space at those places.	334	space at those places.
178		335
179	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
180	likely combine this setting with C<space_after>.	337	most likely combine this setting with C<space_after>.
181		338
		339	Example, space_before enabled, space_after and indent disabled:
		340
		341	{"key" :"value"}
		342
182	=item $json = $json->space_after ($enable)	343	=item $json = $json->space_after ([$enable])
183		344
		345	=item $enabled = $json->get_space_after
		346
184	If C<$enable> is true, then the C<encode> method will add an extra	347	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	348	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	349	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	350	members.
188		351
189	If C<$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
190	space at those places.	353	space at those places.
191		354
192	This setting has no effect when decoding JSON strings.	355	This setting has no effect when decoding JSON texts.
193		356
		357	Example, space_before and indent disabled, space_after enabled:
		358
		359	{"key": "value"}
		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
194	=item $json = $json->canonical ($enable)	408	=item $json = $json->canonical ([$enable])
195		409
		410	=item $enabled = $json->get_canonical
		411
196	If C<$enable> is true, then the C<encode> method will output JSON objects	412	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	413	by sorting their keys. This is adding a comparatively high overhead.
198		414
199	If C<$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
200	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
201	of the same script).	417	of the same script).
202		418
203	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
204	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,
205	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,
206	as key-value pairs have no inherent ordering in Perl.	422	as key-value pairs have no inherent ordering in Perl.
207		423
208	This setting has no effect when decoding JSON strings.	424	This setting has no effect when decoding JSON texts.
209		425
210	=item $json = $json->allow_nonref ($enable)	426	=item $json = $json->allow_nonref ([$enable])
211		427
		428	=item $enabled = $json->get_allow_nonref
		429
212	If C<$enable> is true, then the C<encode> method can convert a	430	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	431	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	432	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	433	values instead of croaking.
216		434
217	If C<$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
218	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
219	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
220	JSON object or array.	438	JSON object or array.
221		439
		440	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		441	resulting in an invalid JSON text:
		442
		443	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		444	=> "Hello, World!"
		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
		562	=item $json = $json->shrink ([$enable])
		563
		564	=item $enabled = $json->get_shrink
		565
		566	Perl usually over-allocates memory a bit when allocating space for
		567	strings. This flag optionally resizes strings generated by either
		568	C<encode> or C<decode> to their minimum size possible. This can save
		569	memory when your JSON texts are either very very long or you have many
		570	short strings. It will also try to downgrade any strings to octet-form
		571	if possible: perl stores strings internally either in an encoding called
		572	UTF-X or in octet-form. The latter cannot store everything but uses less
		573	space in general (and some buggy Perl or C code might even rely on that
		574	internal representation being used).
		575
		576	The actual definition of what shrink does might change in future versions,
		577	but it will always try to save space at the expense of time.
		578
		579	If C<$enable> is true (or missing), the string returned by C<encode> will
		580	be shrunk-to-fit, while all strings generated by C<decode> will also be
		581	shrunk-to-fit.
		582
		583	If C<$enable> is false, then the normal perl allocation algorithms are used.
		584	If you work with your data, then this is likely to be faster.
		585
		586	In the future, this setting might control other things, such as converting
		587	strings that look like integers or floats into integers or floats
		588	internally (there is no difference on the Perl level), saving space.
		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
222	=item $json_string = $json->encode ($perl_scalar)	629	=item $json_text = $json->encode ($perl_scalar)
223		630
224	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
225	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
226	converted into JSON string or number sequences, while references to arrays	633	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	634	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>	635	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	636	nor C<false> values will be generated.
230		637
231	=item $perl_scalar = $json->decode ($json_string)	638	=item $perl_scalar = $json->decode ($json_text)
232		639
233	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,
234	returning the resulting simple scalar or reference. Croaks on error.	641	returning the resulting simple scalar or reference. Croaks on error.
235		642
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	643	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	644	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>.	645	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		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
240	=back	661	=back
		662
		663
		664	=head1 MAPPING
		665
		666	This section describes how JSON::XS maps Perl values to JSON values and
		667	vice versa. These mappings are designed to "do the right thing" in most
		668	circumstances automatically, preserving round-tripping characteristics
		669	(what you put in comes out as something equivalent).
		670
		671	For the more enlightened: note that in the following descriptions,
		672	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
		673	refers to the abstract Perl language itself.
		674
		675
		676	=head2 JSON -> PERL
		677
		678	=over 4
		679
		680	=item object
		681
		682	A JSON object becomes a reference to a hash in Perl. No ordering of object
		683	keys is preserved (JSON does not preserve object key ordering itself).
		684
		685	=item array
		686
		687	A JSON array becomes a reference to an array in Perl.
		688
		689	=item string
		690
		691	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		692	are represented by the same codepoints in the Perl string, so no manual
		693	decoding is necessary.
		694
		695	=item number
		696
		697	A JSON number becomes either an integer, numeric (floating point) or
		698	string scalar in perl, depending on its range and any fractional parts. On
		699	the Perl level, there is no difference between those as Perl handles all
		700	the conversion details, but an integer may take slightly less memory and
		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.
		714
		715	=item true, false
		716
		717	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		718	respectively. They are overloaded to act almost exactly like the numbers
		719	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
		720	the C<JSON::XS::is_bool> function.
		721
		722	=item null
		723
		724	A JSON null atom becomes C<undef> in Perl.
		725
		726	=back
		727
		728
		729	=head2 PERL -> JSON
		730
		731	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		732	truly typeless language, so we can only guess which JSON type is meant by
		733	a Perl value.
		734
		735	=over 4
		736
		737	=item hash references
		738
		739	Perl hash references become JSON objects. As there is no inherent ordering
		740	in hash keys (or JSON objects), they will usually be encoded in a
		741	pseudo-random order that can change between runs of the same program but
		742	stays generally the same within a single run of a program. JSON::XS can
		743	optionally sort the hash keys (determined by the I<canonical> flag), so
		744	the same datastructure will serialise to the same JSON text (given same
		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.
		748
		749	=item array references
		750
		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.
		766
		767	=item blessed objects
		768
		769	Blessed objects are not allowed. JSON::XS currently tries to encode their
		770	underlying representation (hash- or arrayref), but this behaviour might
		771	change in future versions.
		772
		773	=item simple scalars
		774
		775	Simple Perl scalars (any scalar that is not a reference) are the most
		776	difficult objects to encode: JSON::XS will encode undefined scalars as
		777	JSON null value, scalars that have last been used in a string context
		778	before encoding as JSON strings and anything else as number value:
		779
		780	# dump as number
		781	to_json [2] # yields [2]
		782	to_json [-3.0e17] # yields [-3e+17]
		783	my $value = 5; to_json [$value] # yields [5]
		784
		785	# used as string, so dump as string
		786	print $value;
		787	to_json [$value] # yields ["5"]
		788
		789	# undef becomes null
		790	to_json [undef] # yields [null]
		791
		792	You can force the type to be a JSON string by stringifying it:
		793
		794	my $x = 3.1; # some variable containing a number
		795	"$x"; # stringified
		796	$x .= ""; # another, more awkward way to stringify
		797	print $x; # perl does it for you, too, quite often
		798
		799	You can force the type to be a JSON number by numifying it:
		800
		801	my $x = "3"; # some variable containing a string
		802	$x += 0; # numify it, ensuring it will be dumped as a number
		803	$x *= 1; # same thing, the choice is yours.
		804
		805	You can not currently force the type in other, less obscure, ways. Tell me
		806	if you need this capability.
		807
		808	=back
		809
241		810
242	=head1 COMPARISON	811	=head1 COMPARISON
243		812
244	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
245	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
…		…
251		820
252	=item JSON 1.07	821	=item JSON 1.07
253		822
254	Slow (but very portable, as it is written in pure Perl).	823	Slow (but very portable, as it is written in pure Perl).
255		824
256	Undocumented/buggy Unicode handling (how JSON handles unicode values is	825	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
257	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
258	en-/decoding oneself, but unicode escapes are not working properly).	827	en-/decoding oneself, but Unicode escapes are not working properly).
259		828
260	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.
261	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
262	decode into the number 2.	831	decode into the number 2.
263		832
264	=item JSON::PC 0.01	833	=item JSON::PC 0.01
265		834
266	Very fast.	835	Very fast.
267		836
268	Undocumented/buggy Unicode handling.	837	Undocumented/buggy Unicode handling.
269		838
270	No roundtripping.	839	No round-tripping.
271		840
272	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
273	values will make it croak).	842	values will make it croak).
274		843
275	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}>
276	which is not a valid JSON string.	845	which is not a valid JSON text.
277		846
278	Unmaintained (maintainer unresponsive for many months, bugs are not	847	Unmaintained (maintainer unresponsive for many months, bugs are not
279	getting fixed).	848	getting fixed).
280		849
281	=item JSON::Syck 0.21	850	=item JSON::Syck 0.21
…		…
283	Very buggy (often crashes).	852	Very buggy (often crashes).
284		853
285	Very inflexible (no human-readable format supported, format pretty much	854	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	855	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	856	single-line compact format for use in a protocol, and preferably a way to
288	generate ASCII-only JSON strings).	857	generate ASCII-only JSON texts).
289		858
290	Completely broken (and confusingly documented) Unicode handling (unicode	859	Completely broken (and confusingly documented) Unicode handling (Unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	860	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	861	I<different> values on en- and decoding to get symmetric behaviour).
293		862
294	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
295	value was used in a numeric context or not).	864	value was used in a numeric context or not).
296		865
297	Dumping hashes may skip hash values depending on iterator state.	866	Dumping hashes may skip hash values depending on iterator state.
298		867
299	Unmaintained (maintainer unresponsive for many months, bugs are not	868	Unmaintained (maintainer unresponsive for many months, bugs are not
300	getting fixed).	869	getting fixed).
301		870
302	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
303	return "something" instead of raising an exception. This is a security	872	return "something" instead of raising an exception. This is a security
304	issue: imagine two banks transfering money between each other using	873	issue: imagine two banks transferring money between each other using
305	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,
306	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
307	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
308	the transaction will still not succeed).	877	the transaction will still not succeed).
309		878
310	=item JSON::DWIW 0.04	879	=item JSON::DWIW 0.04
311		880
312	Very fast. Very natural. Very nice.	881	Very fast. Very natural. Very nice.
313		882
314	Undocumented unicode handling (but the best of the pack. Unicode escapes	883	Undocumented Unicode handling (but the best of the pack. Unicode escapes
315	still don't get parsed properly).	884	still don't get parsed properly).
316		885
317	Very inflexible.	886	Very inflexible.
318		887
319	No roundtripping.	888	No round-tripping.
320		889
321	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
322	result in nothing being output)	891	result in nothing being output)
323		892
324	Does not check input for validity.	893	Does not check input for validity.
325		894
326	=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
327		920
328	=head2 SPEED	921	=head2 SPEED
329		922
330	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
331	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
332	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
333	system.	926	system.
334		927
335	First is a comparison between various modules using a very simple JSON	928	First comes a comparison between various modules using a very short
		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
336	string, showing the number of encodes/decodes per second (JSON::XS is	934	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	935	the functional interface, while JSON::XS/2 uses the OO interface
338	pretty-printing and hashkey sorting enabled).	936	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		937	shrink). Higher is better:
339		938
340	module \| encode \| decode \|	939	module \| encode \| decode \|
341	-----------\|------------\|------------\|	940	-----------\|------------\|------------\|
342	JSON \| 14006 \| 6820 \|	941	JSON 1.x \| 4990.842 \| 4088.813 \|
343	JSON::DWIW \| 200937 \| 120386 \|	942	JSON::DWIW \| 51653.990 \| 71575.154 \|
344	JSON::PC \| 85065 \| 129366 \|	943	JSON::PC \| 65948.176 \| 74631.744 \|
345	JSON::Syck \| 59898 \| 44232 \|	944	JSON::PP \| 8931.652 \| 3817.168 \|
346	JSON::XS \| 1171478 \| 342435 \|	945	JSON::Syck \| 24877.248 \| 27776.848 \|
347	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 \|
348	-----------+------------+------------+	950	-----------+------------+------------+
349		951
350	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
351	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.
352		956
353	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	957	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
354	search API (http://nanoref.com/yahooapis/mgPdGg):	958	search API (http://nanoref.com/yahooapis/mgPdGg):
355		959
356	module \| encode \| decode \|	960	module \| encode \| decode \|
357	-----------\|------------\|------------\|	961	-----------\|------------\|------------\|
358	JSON \| 673 \| 38 \|	962	JSON 1.x \| 55.260 \| 34.971 \|
359	JSON::DWIW \| 5271 \| 770 \|	963	JSON::DWIW \| 825.228 \| 1082.513 \|
360	JSON::PC \| 9901 \| 2491 \|	964	JSON::PC \| 3571.444 \| 2394.829 \|
361	JSON::Syck \| 2360 \| 786 \|	965	JSON::PP \| 210.987 \| 32.574 \|
362	JSON::XS \| 37398 \| 3202 \|	966	JSON::Syck \| 552.551 \| 787.544 \|
363	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 \|
364	-----------+------------+------------+	971	-----------+------------+------------+
365		972
366	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
367	every other module in the decoding case.	974	decodes faster).
368		975
369	Last example is an almost 8MB large hash with many large binary values	976	On large strings containing lots of high Unicode characters, some modules
370	(PNG files), resulting in a lot of escaping:	977	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		978	will be broken due to missing (or wrong) Unicode handling. Others refuse
		979	to decode or encode properly, so it was impossible to prepare a fair
		980	comparison table for that case.
		981
		982
		983	=head1 SECURITY CONSIDERATIONS
		984
		985	When you are using JSON in a protocol, talking to untrusted potentially
		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
371		1032
372	=head1 BUGS	1033	=head1 BUGS
373		1034
374	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
375	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
376	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
377	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.
378		1042
379	=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;
380		1065
381	1;	1066	1;
382		1067
383	=head1 AUTHOR	1068	=head1 AUTHOR
384		1069

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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 1.77 by root, Tue Dec 4 10:37:42 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 1.77 by root, Tue Dec 4 10:37:42 2007 UTC