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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs.
Revision 1.91 by root, Thu Mar 20 02:11:21 2008 UTC

…		…
		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14		19
15	# OO-interface	20	# OO-interface
16		21
17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
19	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
20		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
21	=head1 DESCRIPTION	34	=head1 DESCRIPTION
22		35
23	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
24	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
25	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overriden) with no overhead due to emulation (by inheritign constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
26		47
27	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
28	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
29	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
30	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
37		58
38	=head2 FEATURES	59	=head2 FEATURES
39		60
40	=over 4	61	=over 4
41		62
42	=item * correct unicode handling	63	=item * correct Unicode handling
43		64
44	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
45	it does so.	66	so, and even documents what "correct" means.
46		67
47	=item * round-trip integrity	68	=item * round-trip integrity
48		69
49	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
50	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
52	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
53		75
54	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
55		77
56	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
57	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
58	feature).	80	feature).
59		81
60	=item * fast	82	=item * fast
61		83
62	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
63	of speed, too.	85	this module usually compares favourably in terms of speed, too.
64		86
65	=item * simple to use	87	=item * simple to use
66		88
67	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an objetc
68	interface.	90	oriented interface interface.
69		91
70	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
71		93
72	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
73	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
74	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
75	unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
76	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
77		99
78	=back	100	=back
79		101
80	=cut	102	=cut
81		103
82	package JSON::XS;	104	package JSON::XS;
83		105
84	use strict;	106	use strict;
85		107
86	our $VERSION = '1.4';	108	our $VERSION = '2.1';
87	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
88		110
89	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		114	require Carp;
		115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		116	}
		117
		118	sub from_json($) {
		119	require Carp;
		120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		121	}
90		122
91	use Exporter;	123	use Exporter;
92	use XSLoader;	124	use XSLoader;
93		125
94	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
95		127
96	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
97	exported by default:	129	exported by default:
98		130
99	=over 4	131	=over 4
100		132
101	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
102		134
103	Converts the given Perl data structure (a simple scalar or a reference to	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	136	(that is, the string contains octets only). Croaks on error.
105	octets only). Croaks on error.
106		137
107	This function call is functionally identical to:	138	This function call is functionally identical to:
108		139
109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110		141
111	except being faster.	142	except being faster.
112		143
113	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
114		145
115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
116	parse that as an UTF-8 encoded JSON text, returning the resulting simple	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
117	scalar or reference. Croaks on error.	148	reference. Croaks on error.
118		149
119	This function call is functionally identical to:	150	This function call is functionally identical to:
120		151
121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122		153
…		…
132	Perl.	163	Perl.
133		164
134	=back	165	=back
135		166
136		167
		168	=head1 A FEW NOTES ON UNICODE AND PERL
		169
		170	Since this often leads to confusion, here are a few very clear words on
		171	how Unicode works in Perl, modulo bugs.
		172
		173	=over 4
		174
		175	=item 1. Perl strings can store characters with ordinal values > 255.
		176
		177	This enables you to store Unicode characters as single characters in a
		178	Perl string - very natural.
		179
		180	=item 2. Perl does I<not> associate an encoding with your strings.
		181
		182	... until you force it to, e.g. when matching it against a regex, or
		183	printing the scalar to a file, in which case Perl either interprets your
		184	string as locale-encoded text, octets/binary, or as Unicode, depending
		185	on various settings. In no case is an encoding stored together with your
		186	data, it is I<use> that decides encoding, not any magical meta data.
		187
		188	=item 3. The internal utf-8 flag has no meaning with regards to the
		189	encoding of your string.
		190
		191	Just ignore that flag unless you debug a Perl bug, a module written in
		192	XS or want to dive into the internals of perl. Otherwise it will only
		193	confuse you, as, despite the name, it says nothing about how your string
		194	is encoded. You can have Unicode strings with that flag set, with that
		195	flag clear, and you can have binary data with that flag set and that flag
		196	clear. Other possibilities exist, too.
		197
		198	If you didn't know about that flag, just the better, pretend it doesn't
		199	exist.
		200
		201	=item 4. A "Unicode String" is simply a string where each character can be
		202	validly interpreted as a Unicode codepoint.
		203
		204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		205	Unicode string encoded in UTF-8, giving you a binary string.
		206
		207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		208
		209	It's a fact. Learn to live with it.
		210
		211	=back
		212
		213	I hope this helps :)
		214
		215
137	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
138		217
139	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
140	decoding style, within the limits of supported formats.	219	decoding style, within the limits of supported formats.
141		220
…		…
152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	231	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
153	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
154		233
155	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
156		235
		236	=item $enabled = $json->get_ascii
		237
157	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
158	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
159	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163	or any other superset of ASCII.	244	or any other superset of ASCII.
164		245
165	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
166	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
167	in a faster and more compact format.	248	in a faster and more compact format.
168		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
169	The main use for this flag is to produce JSON texts that can be	253	The main use for this flag is to produce JSON texts that can be
170	transmitted over a 7-bit channel, as the encoded JSON texts will not	254	transmitted over a 7-bit channel, as the encoded JSON texts will not
171	contain any 8 bit characters.	255	contain any 8 bit characters.
172		256
173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
175		259
176	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
177		261
		262	=item $enabled = $json->get_latin1
		263
178	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
181	latin1-encoded JSON text or a native unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
182	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
183	expects unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
184		270
185	If C<$enable> is false, then the C<encode> method will not escape Unicode	271	If C<$enable> is false, then the C<encode> method will not escape Unicode
186	characters unless required by the JSON syntax or other flags.	272	characters unless required by the JSON syntax or other flags.
		273
		274	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		275	document.
187		276
188	The main use for this flag is efficiently encoding binary data as JSON	277	The main use for this flag is efficiently encoding binary data as JSON
189	text, as most octets will not be escaped, resulting in a smaller encoded	278	text, as most octets will not be escaped, resulting in a smaller encoded
190	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
191	in latin1 (and must correctly be treated as such when storing and	280	in latin1 (and must correctly be treated as such when storing and
192	transfering), a rare encoding for JSON. It is therefore most useful when	281	transferring), a rare encoding for JSON. It is therefore most useful when
193	you want to store data structures known to contain binary data efficiently	282	you want to store data structures known to contain binary data efficiently
194	in files or databases, not when talking to other JSON encoders/decoders.	283	in files or databases, not when talking to other JSON encoders/decoders.
195		284
196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198		287
199	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
200		291
201	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
202	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
203	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
204	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
207	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
208		299
209	If C<$enable> is false, then the C<encode> method will return the JSON	300	If C<$enable> is false, then the C<encode> method will return the JSON
210	string as a (non-encoded) unicode string, while C<decode> expects thus a	301	string as a (non-encoded) Unicode string, while C<decode> expects thus a
211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	302	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
212	to be done yourself, e.g. using the Encode module.	303	to be done yourself, e.g. using the Encode module.
		304
		305	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		306	document.
213		307
214	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
215		309
216	use Encode;	310	use Encode;
217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
238	]	332	]
239	}	333	}
240		334
241	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
242		336
		337	=item $enabled = $json->get_indent
		338
243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
245	into its own line, identing them properly.	341	into its own line, indenting them properly.
246		342
247	If C<$enable> is false, no newlines or indenting will be produced, and the	343	If C<$enable> is false, no newlines or indenting will be produced, and the
248	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
249		345
250	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
251		347
252	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
253		351
254	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
255	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
256		354
257	If C<$enable> is false, then the C<encode> method will not add any extra	355	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
263	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
264		362
265	{"key" :"value"}	363	{"key" :"value"}
266		364
267	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
268		368
269	If C<$enable> is true (or missing), then the C<encode> method will add an extra	369	If C<$enable> is true (or missing), then the C<encode> method will add an extra
270	optional space after the C<:> separating keys from values in JSON objects	370	optional space after the C<:> separating keys from values in JSON objects
271	and extra whitespace after the C<,> separating key-value pairs and array	371	and extra whitespace after the C<,> separating key-value pairs and array
272	members.	372	members.
…		…
278		378
279	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
280		380
281	{"key": "value"}	381	{"key": "value"}
282		382
		383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
		386
		387	If C<$enable> is true (or missing), then C<decode> will accept some
		388	extensions to normal JSON syntax (see below). C<encode> will not be
		389	affected in anyway. I<Be aware that this option makes you accept invalid
		390	JSON texts as if they were valid!>. I suggest only to use this option to
		391	parse application-specific files written by humans (configuration files,
		392	resource files etc.)
		393
		394	If C<$enable> is false (the default), then C<decode> will only accept
		395	valid JSON texts.
		396
		397	Currently accepted extensions are:
		398
		399	=over 4
		400
		401	=item * list items can have an end-comma
		402
		403	JSON I<separates> array elements and key-value pairs with commas. This
		404	can be annoying if you write JSON texts manually and want to be able to
		405	quickly append elements, so this extension accepts comma at the end of
		406	such items not just between them:
		407
		408	[
		409	1,
		410	2, <- this comma not normally allowed
		411	]
		412	{
		413	"k1": "v1",
		414	"k2": "v2", <- this comma not normally allowed
		415	}
		416
		417	=item * shell-style '#'-comments
		418
		419	Whenever JSON allows whitespace, shell-style comments are additionally
		420	allowed. They are terminated by the first carriage-return or line-feed
		421	character, after which more white-space and comments are allowed.
		422
		423	[
		424	1, # this comment not allowed in JSON
		425	# neither this one...
		426	]
		427
		428	=back
		429
283	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
		431
		432	=item $enabled = $json->get_canonical
284		433
285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
287		436
288	If C<$enable> is false, then the C<encode> method will output key-value	437	If C<$enable> is false, then the C<encode> method will output key-value
289	pairs in the order Perl stores them (which will likely change between runs	438	pairs in the order Perl stores them (which will likely change between runs
290	of the same script).	439	of the same script).
291		440
292	This option is useful if you want the same data structure to be encoded as	441	This option is useful if you want the same data structure to be encoded as
293	the same JSON text (given the same overall settings). If it is disabled,	442	the same JSON text (given the same overall settings). If it is disabled,
294	the same hash migh be encoded differently even if contains the same data,	443	the same hash might be encoded differently even if contains the same data,
295	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
296		445
297	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
298		447
299	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
300		451
301	If C<$enable> is true (or missing), then the C<encode> method can convert a	452	If C<$enable> is true (or missing), then the C<encode> method can convert a
302	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
303	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304	values instead of croaking.	455	values instead of croaking.
…		…
314	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
315	=> "Hello, World!"	466	=> "Hello, World!"
316		467
317	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
318		469
		470	=item $enabled = $json->get_allow_blessed
		471
319	If C<$enable> is true (or missing), then the C<encode> method will not	472	If C<$enable> is true (or missing), then the C<encode> method will not
320	barf when it encounters a blessed reference. Instead, the value of the	473	barf when it encounters a blessed reference. Instead, the value of the
321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322	disabled or no C<to_json> method found) or a representation of the	475	disabled or no C<TO_JSON> method found) or a representation of the
323	object (C<convert_blessed> enabled and C<to_json> method found) is being	476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324	encoded. Has no effect on C<decode>.	477	encoded. Has no effect on C<decode>.
325		478
326	If C<$enable> is false (the default), then C<encode> will throw an	479	If C<$enable> is false (the default), then C<encode> will throw an
327	exception when it encounters a blessed object.	480	exception when it encounters a blessed object.
328		481
329	=item $json = $json->convert_blessed ([$enable])	482	=item $json = $json->convert_blessed ([$enable])
		483
		484	=item $enabled = $json->get_convert_blessed
330		485
331	If C<$enable> is true (or missing), then C<encode>, upon encountering a	486	If C<$enable> is true (or missing), then C<encode>, upon encountering a
332	blessed object, will check for the availability of the C<TO_JSON> method	487	blessed object, will check for the availability of the C<TO_JSON> method
333	on the object's class. If found, it will be called in scalar context	488	on the object's class. If found, it will be called in scalar context
334	and the resulting scalar will be encoded instead of the object. If no	489	and the resulting scalar will be encoded instead of the object. If no
…		…
338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
339	returns other blessed objects, those will be handled in the same	494	returns other blessed objects, those will be handled in the same
340	way. C<TO_JSON> must take care of not causing an endless recursion cycle	495	way. C<TO_JSON> must take care of not causing an endless recursion cycle
341	(== crash) in this case. The name of C<TO_JSON> was chosen because other	496	(== crash) in this case. The name of C<TO_JSON> was chosen because other
342	methods called by the Perl core (== not by the user of the object) are	497	methods called by the Perl core (== not by the user of the object) are
343	usually in upper case letters and to avoid collisions with the C<to_json>	498	usually in upper case letters and to avoid collisions with any C<to_json>
344	function.	499	function or method.
345		500
346	This setting does not yet influence C<decode> in any way, but in the	501	This setting does not yet influence C<decode> in any way, but in the
347	future, global hooks might get installed that influence C<decode> and are	502	future, global hooks might get installed that influence C<decode> and are
348	enabled by this setting.	503	enabled by this setting.
349		504
350	If C<$enable> is false, then the C<allow_blessed> setting will decide what	505	If C<$enable> is false, then the C<allow_blessed> setting will decide what
351	to do when a blessed object is found.	506	to do when a blessed object is found.
352		507
		508	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		509
		510	When C<$coderef> is specified, it will be called from C<decode> each
		511	time it decodes a JSON object. The only argument is a reference to the
		512	newly-created hash. If the code references returns a single scalar (which
		513	need not be a reference), this value (i.e. a copy of that scalar to avoid
		514	aliasing) is inserted into the deserialised data structure. If it returns
		515	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		516	original deserialised hash will be inserted. This setting can slow down
		517	decoding considerably.
		518
		519	When C<$coderef> is omitted or undefined, any existing callback will
		520	be removed and C<decode> will not change the deserialised hash in any
		521	way.
		522
		523	Example, convert all JSON objects into the integer 5:
		524
		525	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		526	# returns [5]
		527	$js->decode ('[{}]')
		528	# throw an exception because allow_nonref is not enabled
		529	# so a lone 5 is not allowed.
		530	$js->decode ('{"a":1, "b":2}');
		531
		532	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		533
		534	Works remotely similar to C<filter_json_object>, but is only called for
		535	JSON objects having a single key named C<$key>.
		536
		537	This C<$coderef> is called before the one specified via
		538	C<filter_json_object>, if any. It gets passed the single value in the JSON
		539	object. If it returns a single value, it will be inserted into the data
		540	structure. If it returns nothing (not even C<undef> but the empty list),
		541	the callback from C<filter_json_object> will be called next, as if no
		542	single-key callback were specified.
		543
		544	If C<$coderef> is omitted or undefined, the corresponding callback will be
		545	disabled. There can only ever be one callback for a given key.
		546
		547	As this callback gets called less often then the C<filter_json_object>
		548	one, decoding speed will not usually suffer as much. Therefore, single-key
		549	objects make excellent targets to serialise Perl objects into, especially
		550	as single-key JSON objects are as close to the type-tagged value concept
		551	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		552	support this in any way, so you need to make sure your data never looks
		553	like a serialised Perl hash.
		554
		555	Typical names for the single object key are C<__class_whatever__>, or
		556	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		557	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		558	with real hashes.
		559
		560	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		561	into the corresponding C<< $WIDGET{<id>} >> object:
		562
		563	# return whatever is in $WIDGET{5}:
		564	JSON::XS
		565	->new
		566	->filter_json_single_key_object (__widget__ => sub {
		567	$WIDGET{ $_[0] }
		568	})
		569	->decode ('{"__widget__": 5')
		570
		571	# this can be used with a TO_JSON method in some "widget" class
		572	# for serialisation to json:
		573	sub WidgetBase::TO_JSON {
		574	my ($self) = @_;
		575
		576	unless ($self->{id}) {
		577	$self->{id} = ..get..some..id..;
		578	$WIDGET{$self->{id}} = $self;
		579	}
		580
		581	{ __widget__ => $self->{id} }
		582	}
		583
353	=item $json = $json->shrink ([$enable])	584	=item $json = $json->shrink ([$enable])
		585
		586	=item $enabled = $json->get_shrink
354		587
355	Perl usually over-allocates memory a bit when allocating space for	588	Perl usually over-allocates memory a bit when allocating space for
356	strings. This flag optionally resizes strings generated by either	589	strings. This flag optionally resizes strings generated by either
357	C<encode> or C<decode> to their minimum size possible. This can save	590	C<encode> or C<decode> to their minimum size possible. This can save
358	memory when your JSON texts are either very very long or you have many	591	memory when your JSON texts are either very very long or you have many
…		…
376	strings that look like integers or floats into integers or floats	609	strings that look like integers or floats into integers or floats
377	internally (there is no difference on the Perl level), saving space.	610	internally (there is no difference on the Perl level), saving space.
378		611
379	=item $json = $json->max_depth ([$maximum_nesting_depth])	612	=item $json = $json->max_depth ([$maximum_nesting_depth])
380		613
		614	=item $max_depth = $json->get_max_depth
		615
381	Sets the maximum nesting level (default C<512>) accepted while encoding	616	Sets the maximum nesting level (default C<512>) accepted while encoding
382	or decoding. If the JSON text or Perl data structure has an equal or	617	or decoding. If the JSON text or Perl data structure has an equal or
383	higher nesting level then this limit, then the encoder and decoder will	618	higher nesting level then this limit, then the encoder and decoder will
384	stop and croak at that point.	619	stop and croak at that point.
385		620
…		…
396	used, which is rarely useful.	631	used, which is rarely useful.
397		632
398	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
399		634
400	=item $json = $json->max_size ([$maximum_string_size])	635	=item $json = $json->max_size ([$maximum_string_size])
		636
		637	=item $max_size = $json->get_max_size
401		638
402	Set the maximum length a JSON text may have (in bytes) where decoding is	639	Set the maximum length a JSON text may have (in bytes) where decoding is
403	being attempted. The default is C<0>, meaning no limit. When C<decode>	640	being attempted. The default is C<0>, meaning no limit. When C<decode>
404	is called on a string longer then this number of characters it will not	641	is called on a string longer then this number of characters it will not
405	attempt to decode the string but throw an exception. This setting has no	642	attempt to decode the string but throw an exception. This setting has no
…		…
452	vice versa. These mappings are designed to "do the right thing" in most	689	vice versa. These mappings are designed to "do the right thing" in most
453	circumstances automatically, preserving round-tripping characteristics	690	circumstances automatically, preserving round-tripping characteristics
454	(what you put in comes out as something equivalent).	691	(what you put in comes out as something equivalent).
455		692
456	For the more enlightened: note that in the following descriptions,	693	For the more enlightened: note that in the following descriptions,
457	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	694	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
458	refers to the abstract Perl language itself.	695	refers to the abstract Perl language itself.
459		696
460		697
461	=head2 JSON -> PERL	698	=head2 JSON -> PERL
462		699
463	=over 4	700	=over 4
464		701
465	=item object	702	=item object
466		703
467	A JSON object becomes a reference to a hash in Perl. No ordering of object	704	A JSON object becomes a reference to a hash in Perl. No ordering of object
468	keys is preserved (JSON does not preserver object key ordering itself).	705	keys is preserved (JSON does not preserve object key ordering itself).
469		706
470	=item array	707	=item array
471		708
472	A JSON array becomes a reference to an array in Perl.	709	A JSON array becomes a reference to an array in Perl.
473		710
…		…
477	are represented by the same codepoints in the Perl string, so no manual	714	are represented by the same codepoints in the Perl string, so no manual
478	decoding is necessary.	715	decoding is necessary.
479		716
480	=item number	717	=item number
481		718
482	A JSON number becomes either an integer or numeric (floating point)	719	A JSON number becomes either an integer, numeric (floating point) or
483	scalar in perl, depending on its range and any fractional parts. On the	720	string scalar in perl, depending on its range and any fractional parts. On
484	Perl level, there is no difference between those as Perl handles all the	721	the Perl level, there is no difference between those as Perl handles all
485	conversion details, but an integer may take slightly less memory and might	722	the conversion details, but an integer may take slightly less memory and
486	represent more values exactly than (floating point) numbers.	723	might represent more values exactly than floating point numbers.
		724
		725	If the number consists of digits only, JSON::XS will try to represent
		726	it as an integer value. If that fails, it will try to represent it as
		727	a numeric (floating point) value if that is possible without loss of
		728	precision. Otherwise it will preserve the number as a string value (in
		729	which case you lose roundtripping ability, as the JSON number will be
		730	re-encoded toa JSON string).
		731
		732	Numbers containing a fractional or exponential part will always be
		733	represented as numeric (floating point) values, possibly at a loss of
		734	precision (in which case you might lose perfect roundtripping ability, but
		735	the JSON number will still be re-encoded as a JSON number).
487		736
488	=item true, false	737	=item true, false
489		738
490	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	739	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
491	respectively. They are overloaded to act almost exactly like the numbers	740	respectively. They are overloaded to act almost exactly like the numbers
492	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	741	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
493	the C<JSON::XS::is_bool> function.	742	the C<JSON::XS::is_bool> function.
494		743
495	=item null	744	=item null
496		745
497	A JSON null atom becomes C<undef> in Perl.	746	A JSON null atom becomes C<undef> in Perl.
…		…
528	Other unblessed references are generally not allowed and will cause an	777	Other unblessed references are generally not allowed and will cause an
529	exception to be thrown, except for references to the integers C<0> and	778	exception to be thrown, except for references to the integers C<0> and
530	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	779	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
531	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	780	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
532		781
533	to_json [\0,JSON::XS::true] # yields [false,true]	782	encode_json [\0,JSON::XS::true] # yields [false,true]
534		783
535	=item JSON::XS::true, JSON::XS::false	784	=item JSON::XS::true, JSON::XS::false
536		785
537	These special values become JSON true and JSON false values,	786	These special values become JSON true and JSON false values,
538	respectively. You cna alos use C<\1> and C<\0> directly if you want.	787	respectively. You can also use C<\1> and C<\0> directly if you want.
539		788
540	=item blessed objects	789	=item blessed objects
541		790
542	Blessed objects are not allowed. JSON::XS currently tries to encode their	791	Blessed objects are not directly representable in JSON. See the
543	underlying representation (hash- or arrayref), but this behaviour might	792	C<allow_blessed> and C<convert_blessed> methods on various options on
544	change in future versions.	793	how to deal with this: basically, you can choose between throwing an
		794	exception, encoding the reference as if it weren't blessed, or provide
		795	your own serialiser method.
545		796
546	=item simple scalars	797	=item simple scalars
547		798
548	Simple Perl scalars (any scalar that is not a reference) are the most	799	Simple Perl scalars (any scalar that is not a reference) are the most
549	difficult objects to encode: JSON::XS will encode undefined scalars as	800	difficult objects to encode: JSON::XS will encode undefined scalars as
550	JSON null value, scalars that have last been used in a string context	801	JSON C<null> values, scalars that have last been used in a string context
551	before encoding as JSON strings and anything else as number value:	802	before encoding as JSON strings, and anything else as number value:
552		803
553	# dump as number	804	# dump as number
554	to_json [2] # yields [2]	805	encode_json [2] # yields [2]
555	to_json [-3.0e17] # yields [-3e+17]	806	encode_json [-3.0e17] # yields [-3e+17]
556	my $value = 5; to_json [$value] # yields [5]	807	my $value = 5; encode_json [$value] # yields [5]
557		808
558	# used as string, so dump as string	809	# used as string, so dump as string
559	print $value;	810	print $value;
560	to_json [$value] # yields ["5"]	811	encode_json [$value] # yields ["5"]
561		812
562	# undef becomes null	813	# undef becomes null
563	to_json [undef] # yields [null]	814	encode_json [undef] # yields [null]
564		815
565	You can force the type to be a string by stringifying it:	816	You can force the type to be a JSON string by stringifying it:
566		817
567	my $x = 3.1; # some variable containing a number	818	my $x = 3.1; # some variable containing a number
568	"$x"; # stringified	819	"$x"; # stringified
569	$x .= ""; # another, more awkward way to stringify	820	$x .= ""; # another, more awkward way to stringify
570	print $x; # perl does it for you, too, quite often	821	print $x; # perl does it for you, too, quite often
571		822
572	You can force the type to be a number by numifying it:	823	You can force the type to be a JSON number by numifying it:
573		824
574	my $x = "3"; # some variable containing a string	825	my $x = "3"; # some variable containing a string
575	$x += 0; # numify it, ensuring it will be dumped as a number	826	$x += 0; # numify it, ensuring it will be dumped as a number
576	$x *= 1; # same thing, the choise is yours.	827	$x *= 1; # same thing, the choice is yours.
577		828
578	You can not currently output JSON booleans or force the type in other,	829	You can not currently force the type in other, less obscure, ways. Tell me
579	less obscure, ways. Tell me if you need this capability.	830	if you need this capability (but don't forget to explain why it's needed
		831	:).
		832
		833	=back
		834
		835
		836	=head1 ENCODING/CODESET FLAG NOTES
		837
		838	The interested reader might have seen a number of flags that signify
		839	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		840	some confusion on what these do, so here is a short comparison:
		841
		842	C<utf8> controls whether the JSON text created by C<encode> (and expected
		843	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		844	control whether C<encode> escapes character values outside their respective
		845	codeset range. Neither of these flags conflict with each other, although
		846	some combinations make less sense than others.
		847
		848	Care has been taken to make all flags symmetrical with respect to
		849	C<encode> and C<decode>, that is, texts encoded with any combination of
		850	these flag values will be correctly decoded when the same flags are used
		851	- in general, if you use different flag settings while encoding vs. when
		852	decoding you likely have a bug somewhere.
		853
		854	Below comes a verbose discussion of these flags. Note that a "codeset" is
		855	simply an abstract set of character-codepoint pairs, while an encoding
		856	takes those codepoint numbers and I<encodes> them, in our case into
		857	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		858	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		859	the same time, which can be confusing.
		860
		861	=over 4
		862
		863	=item C<utf8> flag disabled
		864
		865	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		866	and expect Unicode strings, that is, characters with high ordinal Unicode
		867	values (> 255) will be encoded as such characters, and likewise such
		868	characters are decoded as-is, no canges to them will be done, except
		869	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		870	respectively (to Perl, these are the same thing in strings unless you do
		871	funny/weird/dumb stuff).
		872
		873	This is useful when you want to do the encoding yourself (e.g. when you
		874	want to have UTF-16 encoded JSON texts) or when some other layer does
		875	the encoding for you (for example, when printing to a terminal using a
		876	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		877	to UTF-8 encode your data first and have Perl encode it another time).
		878
		879	=item C<utf8> flag enabled
		880
		881	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		882	characters using the corresponding UTF-8 multi-byte sequence, and will
		883	expect your input strings to be encoded as UTF-8, that is, no "character"
		884	of the input string must have any value > 255, as UTF-8 does not allow
		885	that.
		886
		887	The C<utf8> flag therefore switches between two modes: disabled means you
		888	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		889	octet/binary string in Perl.
		890
		891	=item C<latin1> or C<ascii> flags enabled
		892
		893	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		894	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		895	characters as specified by the C<utf8> flag.
		896
		897	If C<utf8> is disabled, then the result is also correctly encoded in those
		898	character sets (as both are proper subsets of Unicode, meaning that a
		899	Unicode string with all character values < 256 is the same thing as a
		900	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		901	the same thing as an ASCII string in Perl).
		902
		903	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		904	regardless of these flags, just some more characters will be escaped using
		905	C<\uXXXX> then before.
		906
		907	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		908	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		909	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		910	a subset of Unicode), while ASCII is.
		911
		912	Surprisingly, C<decode> will ignore these flags and so treat all input
		913	values as governed by the C<utf8> flag. If it is disabled, this allows you
		914	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		915	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		916
		917	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		918	they only govern when the JSON output engine escapes a character or not.
		919
		920	The main use for C<latin1> is to relatively efficiently store binary data
		921	as JSON, at the expense of breaking compatibility with most JSON decoders.
		922
		923	The main use for C<ascii> is to force the output to not contain characters
		924	with values > 127, which means you can interpret the resulting string
		925	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		926	8-bit-encoding, and still get the same data structure back. This is useful
		927	when your channel for JSON transfer is not 8-bit clean or the encoding
		928	might be mangled in between (e.g. in mail), and works because ASCII is a
		929	proper subset of most 8-bit and multibyte encodings in use in the world.
580		930
581	=back	931	=back
582		932
583		933
584	=head1 COMPARISON	934	=head1 COMPARISON
…		…
589	followed by some benchmark values. JSON::XS was designed not to suffer	939	followed by some benchmark values. JSON::XS was designed not to suffer
590	from any of these problems or limitations.	940	from any of these problems or limitations.
591		941
592	=over 4	942	=over 4
593		943
		944	=item JSON 2.xx
		945
		946	A marvellous piece of engineering, this module either uses JSON::XS
		947	directly when available (so will be 100% compatible with it, including
		948	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		949	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		950	slower.
		951
		952	You cannot really lose by using this module, especially as it tries very
		953	hard to work even with ancient Perl versions, while JSON::XS does not.
		954
594	=item JSON 1.07	955	=item JSON 1.07
595		956
596	Slow (but very portable, as it is written in pure Perl).	957	Slow (but very portable, as it is written in pure Perl).
597		958
598	Undocumented/buggy Unicode handling (how JSON handles unicode values is	959	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
599	undocumented. One can get far by feeding it unicode strings and doing	960	undocumented. One can get far by feeding it Unicode strings and doing
600	en-/decoding oneself, but unicode escapes are not working properly).	961	en-/decoding oneself, but Unicode escapes are not working properly).
601		962
602	No roundtripping (strings get clobbered if they look like numbers, e.g.	963	No round-tripping (strings get clobbered if they look like numbers, e.g.
603	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	964	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
604	decode into the number 2.	965	decode into the number 2.
605		966
606	=item JSON::PC 0.01	967	=item JSON::PC 0.01
607		968
608	Very fast.	969	Very fast.
609		970
610	Undocumented/buggy Unicode handling.	971	Undocumented/buggy Unicode handling.
611		972
612	No roundtripping.	973	No round-tripping.
613		974
614	Has problems handling many Perl values (e.g. regex results and other magic	975	Has problems handling many Perl values (e.g. regex results and other magic
615	values will make it croak).	976	values will make it croak).
616		977
617	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	978	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
627	Very inflexible (no human-readable format supported, format pretty much	988	Very inflexible (no human-readable format supported, format pretty much
628	undocumented. I need at least a format for easy reading by humans and a	989	undocumented. I need at least a format for easy reading by humans and a
629	single-line compact format for use in a protocol, and preferably a way to	990	single-line compact format for use in a protocol, and preferably a way to
630	generate ASCII-only JSON texts).	991	generate ASCII-only JSON texts).
631		992
632	Completely broken (and confusingly documented) Unicode handling (unicode	993	Completely broken (and confusingly documented) Unicode handling (Unicode
633	escapes are not working properly, you need to set ImplicitUnicode to	994	escapes are not working properly, you need to set ImplicitUnicode to
634	I<different> values on en- and decoding to get symmetric behaviour).	995	I<different> values on en- and decoding to get symmetric behaviour).
635		996
636	No roundtripping (simple cases work, but this depends on wether the scalar	997	No round-tripping (simple cases work, but this depends on whether the scalar
637	value was used in a numeric context or not).	998	value was used in a numeric context or not).
638		999
639	Dumping hashes may skip hash values depending on iterator state.	1000	Dumping hashes may skip hash values depending on iterator state.
640		1001
641	Unmaintained (maintainer unresponsive for many months, bugs are not	1002	Unmaintained (maintainer unresponsive for many months, bugs are not
642	getting fixed).	1003	getting fixed).
643		1004
644	Does not check input for validity (i.e. will accept non-JSON input and	1005	Does not check input for validity (i.e. will accept non-JSON input and
645	return "something" instead of raising an exception. This is a security	1006	return "something" instead of raising an exception. This is a security
646	issue: imagine two banks transfering money between each other using	1007	issue: imagine two banks transferring money between each other using
647	JSON. One bank might parse a given non-JSON request and deduct money,	1008	JSON. One bank might parse a given non-JSON request and deduct money,
648	while the other might reject the transaction with a syntax error. While a	1009	while the other might reject the transaction with a syntax error. While a
649	good protocol will at least recover, that is extra unnecessary work and	1010	good protocol will at least recover, that is extra unnecessary work and
650	the transaction will still not succeed).	1011	the transaction will still not succeed).
651		1012
652	=item JSON::DWIW 0.04	1013	=item JSON::DWIW 0.04
653		1014
654	Very fast. Very natural. Very nice.	1015	Very fast. Very natural. Very nice.
655		1016
656	Undocumented unicode handling (but the best of the pack. Unicode escapes	1017	Undocumented Unicode handling (but the best of the pack. Unicode escapes
657	still don't get parsed properly).	1018	still don't get parsed properly).
658		1019
659	Very inflexible.	1020	Very inflexible.
660		1021
661	No roundtripping.	1022	No round-tripping.
662		1023
663	Does not generate valid JSON texts (key strings are often unquoted, empty keys	1024	Does not generate valid JSON texts (key strings are often unquoted, empty keys
664	result in nothing being output)	1025	result in nothing being output)
665		1026
666	Does not check input for validity.	1027	Does not check input for validity.
…		…
668	=back	1029	=back
669		1030
670		1031
671	=head2 JSON and YAML	1032	=head2 JSON and YAML
672		1033
673	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1034	You often hear that JSON is a subset of YAML. This is, however, a mass
674	however, a mass hysteria and very far from the truth. In general, there is	1035	hysteria(*) and very far from the truth (as of the time of this writing),
675	no way to configure JSON::XS to output a data structure as valid YAML.	1036	so let me state it clearly: I<in general, there is no way to configure
		1037	JSON::XS to output a data structure as valid YAML> that works in all
		1038	cases.
676		1039
677	If you really must use JSON::XS to generate YAML, you should use this	1040	If you really must use JSON::XS to generate YAML, you should use this
678	algorithm (subject to change in future versions):	1041	algorithm (subject to change in future versions):
679		1042
680	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1043	my $to_yaml = JSON::XS->new->utf8->space_after (1);
681	my $yaml = $to_yaml->encode ($ref) . "\n";	1044	my $yaml = $to_yaml->encode ($ref) . "\n";
682		1045
683	This will usually generate JSON texts that also parse as valid	1046	This will I<usually> generate JSON texts that also parse as valid
684	YAML. Please note that YAML has hardcoded limits on (simple) object key	1047	YAML. Please note that YAML has hardcoded limits on (simple) object key
685	lengths that JSON doesn't have, so you should make sure that your hash	1048	lengths that JSON doesn't have and also has different and incompatible
		1049	unicode handling, so you should make sure that your hash keys are
686	keys are noticably shorter than the 1024 characters YAML allows.	1050	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1051	you do not have characters with codepoint values outside the Unicode BMP
		1052	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1053	strings (which JSON::XS does not I<currently> generate, but other JSON
		1054	generators might).
687		1055
688	There might be other incompatibilities that I am not aware of. In general	1056	There might be other incompatibilities that I am not aware of (or the YAML
		1057	specification has been changed yet again - it does so quite often). In
689	you should not try to generate YAML with a JSON generator or vice versa,	1058	general you should not try to generate YAML with a JSON generator or vice
690	or try to parse JSON with a YAML parser or vice versa: chances are high	1059	versa, or try to parse JSON with a YAML parser or vice versa: chances are
691	that you will run into severe interoperability problems.	1060	high that you will run into severe interoperability problems when you
		1061	least expect it.
		1062
		1063	=over 4
		1064
		1065	=item (*)
		1066
		1067	I have been pressured multiple times by Brian Ingerson (one of the
		1068	authors of the YAML specification) to remove this paragraph, despite him
		1069	acknowledging that the actual incompatibilities exist. As I was personally
		1070	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1071	educate people about these issues, so others do not run into the same
		1072	problem again and again. After this, Brian called me a (quote)I<complete
		1073	and worthless idiot>(unquote).
		1074
		1075	In my opinion, instead of pressuring and insulting people who actually
		1076	clarify issues with YAML and the wrong statements of some of its
		1077	proponents, I would kindly suggest reading the JSON spec (which is not
		1078	that difficult or long) and finally make YAML compatible to it, and
		1079	educating users about the changes, instead of spreading lies about the
		1080	real compatibility for many I<years> and trying to silence people who
		1081	point out that it isn't true.
		1082
		1083	=back
692		1084
693		1085
694	=head2 SPEED	1086	=head2 SPEED
695		1087
696	It seems that JSON::XS is surprisingly fast, as shown in the following	1088	It seems that JSON::XS is surprisingly fast, as shown in the following
697	tables. They have been generated with the help of the C<eg/bench> program	1089	tables. They have been generated with the help of the C<eg/bench> program
698	in the JSON::XS distribution, to make it easy to compare on your own	1090	in the JSON::XS distribution, to make it easy to compare on your own
699	system.	1091	system.
700		1092
701	First comes a comparison between various modules using a very short	1093	First comes a comparison between various modules using
702	single-line JSON string:	1094	a very short single-line JSON string (also available at
		1095	L<http://dist.schmorp.de/misc/json/short.json>).
703		1096
704	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1097	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
705	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1098	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
706		1099
707	It shows the number of encodes/decodes per second (JSON::XS uses	1100	It shows the number of encodes/decodes per second (JSON::XS uses
708	the functional interface, while JSON::XS/2 uses the OO interface	1101	the functional interface, while JSON::XS/2 uses the OO interface
709	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1102	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
710	shrink). Higher is better:	1103	shrink). Higher is better:
711		1104
712	Storable \| 15779.925 \| 14169.946 \|
713	-----------+------------+------------+
714	module \| encode \| decode \|	1105	module \| encode \| decode \|
715	-----------\|------------\|------------\|	1106	-----------\|------------\|------------\|
716	JSON \| 4990.842 \| 4088.813 \|	1107	JSON 1.x \| 4990.842 \| 4088.813 \|
717	JSON::DWIW \| 51653.990 \| 71575.154 \|	1108	JSON::DWIW \| 51653.990 \| 71575.154 \|
718	JSON::PC \| 65948.176 \| 74631.744 \|	1109	JSON::PC \| 65948.176 \| 74631.744 \|
719	JSON::PP \| 8931.652 \| 3817.168 \|	1110	JSON::PP \| 8931.652 \| 3817.168 \|
720	JSON::Syck \| 24877.248 \| 27776.848 \|	1111	JSON::Syck \| 24877.248 \| 27776.848 \|
721	JSON::XS \| 388361.481 \| 227951.304 \|	1112	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
723	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1114	JSON::XS/3 \| 338250.323 \| 218453.333 \|
724	Storable \| 16500.016 \| 135300.129 \|	1115	Storable \| 16500.016 \| 135300.129 \|
725	-----------+------------+------------+	1116	-----------+------------+------------+
726		1117
727	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1118	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
728	about three times faster on decoding, and over fourty times faster	1119	about three times faster on decoding, and over forty times faster
729	than JSON, even with pretty-printing and key sorting. It also compares	1120	than JSON, even with pretty-printing and key sorting. It also compares
730	favourably to Storable for small amounts of data.	1121	favourably to Storable for small amounts of data.
731		1122
732	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1123	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
733	search API (http://nanoref.com/yahooapis/mgPdGg):	1124	search API (L<http://dist.schmorp.de/misc/json/long.json>).
734		1125
735	module \| encode \| decode \|	1126	module \| encode \| decode \|
736	-----------\|------------\|------------\|	1127	-----------\|------------\|------------\|
737	JSON \| 55.260 \| 34.971 \|	1128	JSON 1.x \| 55.260 \| 34.971 \|
738	JSON::DWIW \| 825.228 \| 1082.513 \|	1129	JSON::DWIW \| 825.228 \| 1082.513 \|
739	JSON::PC \| 3571.444 \| 2394.829 \|	1130	JSON::PC \| 3571.444 \| 2394.829 \|
740	JSON::PP \| 210.987 \| 32.574 \|	1131	JSON::PP \| 210.987 \| 32.574 \|
741	JSON::Syck \| 552.551 \| 787.544 \|	1132	JSON::Syck \| 552.551 \| 787.544 \|
742	JSON::XS \| 5780.463 \| 4854.519 \|	1133	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
746	-----------+------------+------------+	1137	-----------+------------+------------+
747		1138
748	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1139	Again, JSON::XS leads by far (except for Storable which non-surprisingly
749	decodes faster).	1140	decodes faster).
750		1141
751	On large strings containing lots of high unicode characters, some modules	1142	On large strings containing lots of high Unicode characters, some modules
752	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1143	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
753	will be broken due to missing (or wrong) unicode handling. Others refuse	1144	will be broken due to missing (or wrong) Unicode handling. Others refuse
754	to decode or encode properly, so it was impossible to prepare a fair	1145	to decode or encode properly, so it was impossible to prepare a fair
755	comparison table for that case.	1146	comparison table for that case.
756		1147
757		1148
758	=head1 SECURITY CONSIDERATIONS	1149	=head1 SECURITY CONSIDERATIONS
…		…
764	any buffer overflows. Obviously, this module should ensure that and I am	1155	any buffer overflows. Obviously, this module should ensure that and I am
765	trying hard on making that true, but you never know.	1156	trying hard on making that true, but you never know.
766		1157
767	Second, you need to avoid resource-starving attacks. That means you should	1158	Second, you need to avoid resource-starving attacks. That means you should
768	limit the size of JSON texts you accept, or make sure then when your	1159	limit the size of JSON texts you accept, or make sure then when your
769	resources run out, thats just fine (e.g. by using a separate process that	1160	resources run out, that's just fine (e.g. by using a separate process that
770	can crash safely). The size of a JSON text in octets or characters is	1161	can crash safely). The size of a JSON text in octets or characters is
771	usually a good indication of the size of the resources required to decode	1162	usually a good indication of the size of the resources required to decode
772	it into a Perl structure. While JSON::XS can check the size of the JSON	1163	it into a Perl structure. While JSON::XS can check the size of the JSON
773	text, it might be too late when you already have it in memory, so you	1164	text, it might be too late when you already have it in memory, so you
774	might want to check the size before you accept the string.	1165	might want to check the size before you accept the string.
775		1166
776	Third, JSON::XS recurses using the C stack when decoding objects and	1167	Third, JSON::XS recurses using the C stack when decoding objects and
777	arrays. The C stack is a limited resource: for instance, on my amd64	1168	arrays. The C stack is a limited resource: for instance, on my amd64
778	machine with 8MB of stack size I can decode around 180k nested arrays but	1169	machine with 8MB of stack size I can decode around 180k nested arrays but
779	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1170	only 14k nested JSON objects (due to perl itself recursing deeply on croak
780	to free the temporary). If that is exceeded, the program crashes. to be	1171	to free the temporary). If that is exceeded, the program crashes. To be
781	conservative, the default nesting limit is set to 512. If your process	1172	conservative, the default nesting limit is set to 512. If your process
782	has a smaller stack, you should adjust this setting accordingly with the	1173	has a smaller stack, you should adjust this setting accordingly with the
783	C<max_depth> method.	1174	C<max_depth> method.
784		1175
785	And last but least, something else could bomb you that I forgot to think	1176	Something else could bomb you, too, that I forgot to think of. In that
786	of. In that case, you get to keep the pieces. I am always open for hints,	1177	case, you get to keep the pieces. I am always open for hints, though...
787	though...	1178
		1179	Also keep in mind that JSON::XS might leak contents of your Perl data
		1180	structures in its error messages, so when you serialise sensitive
		1181	information you might want to make sure that exceptions thrown by JSON::XS
		1182	will not end up in front of untrusted eyes.
788		1183
789	If you are using JSON::XS to return packets to consumption	1184	If you are using JSON::XS to return packets to consumption
790	by javascript scripts in a browser you should have a look at	1185	by JavaScript scripts in a browser you should have a look at
791	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1186	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792	you are vulnerable to some common attack vectors (which really are browser	1187	you are vulnerable to some common attack vectors (which really are browser
793	design bugs, but it is still you who will have to deal with it, as major	1188	design bugs, but it is still you who will have to deal with it, as major
794	browser developers care only for features, not about doing security	1189	browser developers care only for features, not about getting security
795	right).	1190	right).
796		1191
797		1192
		1193	=head1 THREADS
		1194
		1195	This module is I<not> guaranteed to be thread safe and there are no
		1196	plans to change this until Perl gets thread support (as opposed to the
		1197	horribly slow so-called "threads" which are simply slow and bloated
		1198	process simulations - use fork, it's I<much> faster, cheaper, better).
		1199
		1200	(It might actually work, but you have been warned).
		1201
		1202
798	=head1 BUGS	1203	=head1 BUGS
799		1204
800	While the goal of this module is to be correct, that unfortunately does	1205	While the goal of this module is to be correct, that unfortunately does
801	not mean its bug-free, only that I think its design is bug-free. It is	1206	not mean it's bug-free, only that I think its design is bug-free. It is
802	still relatively early in its development. If you keep reporting bugs they	1207	still relatively early in its development. If you keep reporting bugs they
803	will be fixed swiftly, though.	1208	will be fixed swiftly, though.
		1209
		1210	Please refrain from using rt.cpan.org or any other bug reporting
		1211	service. I put the contact address into my modules for a reason.
804		1212
805	=cut	1213	=cut
806		1214
807	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1215	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1216	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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Comparing JSON-XS/XS.pm (file contents): Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs. Revision 1.91 by root, Thu Mar 20 02:11:21 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs.
Revision 1.91 by root, Thu Mar 20 02:11:21 2008 UTC