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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs.
Revision 1.86 by root, Wed Mar 19 03:17:38 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
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
10	use JSON::XS;	12	use JSON::XS;
11		13
12	# exported functions, they croak on error	14	# exported functions, they croak on error
13	# and expect/generate UTF-8	15	# and expect/generate UTF-8
14		16
15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17		19
18	# OO-interface	20	# OO-interface
19		21
20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
22	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
23		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
24	=head1 DESCRIPTION	34	=head1 DESCRIPTION
25		35
26	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
27	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
28	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.
29		47
30	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
31	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
32	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
33	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
…		…
40		58
41	=head2 FEATURES	59	=head2 FEATURES
42		60
43	=over 4	61	=over 4
44		62
45	=item * correct unicode handling	63	=item * correct Unicode handling
46		64
47	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
48	it does so.	66	so, and even documents what "correct" means.
49		67
50	=item * round-trip integrity	68	=item * round-trip integrity
51		69
52	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
53	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.
54	(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
55	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
56		75
57	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
58		77
59	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,
60	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
61	feature).	80	feature).
62		81
63	=item * fast	82	=item * fast
64		83
65	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
66	of speed, too.	85	this module usually compares favourably in terms of speed, too.
67		86
68	=item * simple to use	87	=item * simple to use
69		88
70	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
71	interface.	90	oriented interface interface.
72		91
73	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
74		93
75	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
76	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
77	(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
78	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
79	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.
80		99
81	=back	100	=back
82		101
83	=cut	102	=cut
84		103
85	package JSON::XS;	104	package JSON::XS;
86		105
87	use strict;	106	use strict;
88		107
89	our $VERSION = '1.52';	108	our $VERSION = '2.01';
90	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
91		110
92	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		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	}
93		122
94	use Exporter;	123	use Exporter;
95	use XSLoader;	124	use XSLoader;
96		125
97	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
98		127
99	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
100	exported by default:	129	exported by default:
101		130
102	=over 4	131	=over 4
103		132
104	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
105		134
106	Converts the given Perl data structure to a UTF-8 encoded, binary string	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
107	(that is, the string contains octets only). Croaks on error.	136	(that is, the string contains octets only). Croaks on error.
108		137
109	This function call is functionally identical to:	138	This function call is functionally identical to:
110		139
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		141
113	except being faster.	142	except being faster.
114		143
115	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
116		145
117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
118	to parse that as an UTF-8 encoded JSON text, returning the resulting	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
119	reference. Croaks on error.	148	reference. Croaks on error.
120		149
121	This function call is functionally identical to:	150	This function call is functionally identical to:
122		151
…		…
143		172
144	=over 4	173	=over 4
145		174
146	=item 1. Perl strings can store characters with ordinal values > 255.	175	=item 1. Perl strings can store characters with ordinal values > 255.
147		176
148	This enables you to store unicode characters as single characters in a	177	This enables you to store Unicode characters as single characters in a
149	Perl string - very natural.	178	Perl string - very natural.
150		179
151	=item 2. Perl does I<not> associate an encoding with your strings.	180	=item 2. Perl does I<not> associate an encoding with your strings.
152		181
153	Unless you force it to, e.g. when matching it against a regex, or printing	182	... until you force it to, e.g. when matching it against a regex, or
154	the scalar to a file, in which case Perl either interprets your string as	183	printing the scalar to a file, in which case Perl either interprets your
155	locale-encoded text, octets/binary, or as Unicode, depending on various	184	string as locale-encoded text, octets/binary, or as Unicode, depending
156	settings. In no case is an encoding stored together with your data, it is	185	on various settings. In no case is an encoding stored together with your
157	I<use> that decides encoding, not any magical metadata.	186	data, it is I<use> that decides encoding, not any magical meta data.
158		187
159	=item 3. The internal utf-8 flag has no meaning with regards to the	188	=item 3. The internal utf-8 flag has no meaning with regards to the
160	encoding of your string.	189	encoding of your string.
161		190
162	Just ignore that flag unless you debug a Perl bug, a module written in	191	Just ignore that flag unless you debug a Perl bug, a module written in
163	XS or want to dive into the internals of perl. Otherwise it will only	192	XS or want to dive into the internals of perl. Otherwise it will only
164	confuse you, as, despite the name, it says nothing about how your string	193	confuse you, as, despite the name, it says nothing about how your string
165	is encoded. You can have unicode strings with that flag set, with that	194	is encoded. You can have Unicode strings with that flag set, with that
166	flag clear, and you can have binary data with that flag set and that flag	195	flag clear, and you can have binary data with that flag set and that flag
167	clear. Other possibilities exist, too.	196	clear. Other possibilities exist, too.
168		197
169	If you didn't know about that flag, just the better, pretend it doesn't	198	If you didn't know about that flag, just the better, pretend it doesn't
170	exist.	199	exist.
…		…
175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
176	Unicode string encoded in UTF-8, giving you a binary string.	205	Unicode string encoded in UTF-8, giving you a binary string.
177		206
178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
179		208
180	Its a fact. Learn to live with it.	209	It's a fact. Learn to live with it.
181		210
182	=back	211	=back
183		212
184	I hope this helps :)	213	I hope this helps :)
185		214
…		…
202	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]})
203	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
204		233
205	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
206		235
		236	=item $enabled = $json->get_ascii
		237
207	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
208	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
209	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
211	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
212	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
213	or any other superset of ASCII.	244	or any other superset of ASCII.
214		245
215	If C<$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
216	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
217	in a faster and more compact format.	248	in a faster and more compact format.
…		…
223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224	=> ["\ud801\udc01"]	255	=> ["\ud801\udc01"]
225		256
226	=item $json = $json->latin1 ([$enable])	257	=item $json = $json->latin1 ([$enable])
227		258
		259	=item $enabled = $json->get_latin1
		260
228	If C<$enable> is true (or missing), then the C<encode> method will encode	261	If C<$enable> is true (or missing), then the C<encode> method will encode
229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	262	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230	outside the code range C<0..255>. The resulting string can be treated as a	263	outside the code range C<0..255>. The resulting string can be treated as a
231	latin1-encoded JSON text or a native unicode string. The C<decode> method	264	latin1-encoded JSON text or a native Unicode string. The C<decode> method
232	will not be affected in any way by this flag, as C<decode> by default	265	will not be affected in any way by this flag, as C<decode> by default
233	expects unicode, which is a strict superset of latin1.	266	expects Unicode, which is a strict superset of latin1.
234		267
235	If C<$enable> is false, then the C<encode> method will not escape Unicode	268	If C<$enable> is false, then the C<encode> method will not escape Unicode
236	characters unless required by the JSON syntax or other flags.	269	characters unless required by the JSON syntax or other flags.
237		270
238	The main use for this flag is efficiently encoding binary data as JSON	271	The main use for this flag is efficiently encoding binary data as JSON
239	text, as most octets will not be escaped, resulting in a smaller encoded	272	text, as most octets will not be escaped, resulting in a smaller encoded
240	size. The disadvantage is that the resulting JSON text is encoded	273	size. The disadvantage is that the resulting JSON text is encoded
241	in latin1 (and must correctly be treated as such when storing and	274	in latin1 (and must correctly be treated as such when storing and
242	transfering), a rare encoding for JSON. It is therefore most useful when	275	transferring), a rare encoding for JSON. It is therefore most useful when
243	you want to store data structures known to contain binary data efficiently	276	you want to store data structures known to contain binary data efficiently
244	in files or databases, not when talking to other JSON encoders/decoders.	277	in files or databases, not when talking to other JSON encoders/decoders.
245		278
246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	279	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	280	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248		281
249	=item $json = $json->utf8 ([$enable])	282	=item $json = $json->utf8 ([$enable])
		283
		284	=item $enabled = $json->get_utf8
250		285
251	If C<$enable> is true (or missing), then the C<encode> method will encode	286	If C<$enable> is true (or missing), then the C<encode> method will encode
252	the JSON result into UTF-8, as required by many protocols, while the	287	the JSON result into UTF-8, as required by many protocols, while the
253	C<decode> method expects to be handled an UTF-8-encoded string. Please	288	C<decode> method expects to be handled an UTF-8-encoded string. Please
254	note that UTF-8-encoded strings do not contain any characters outside the	289	note that UTF-8-encoded strings do not contain any characters outside the
255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	290	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
256	versions, enabling this option might enable autodetection of the UTF-16	291	versions, enabling this option might enable autodetection of the UTF-16
257	and UTF-32 encoding families, as described in RFC4627.	292	and UTF-32 encoding families, as described in RFC4627.
258		293
259	If C<$enable> is false, then the C<encode> method will return the JSON	294	If C<$enable> is false, then the C<encode> method will return the JSON
260	string as a (non-encoded) unicode string, while C<decode> expects thus a	295	string as a (non-encoded) Unicode string, while C<decode> expects thus a
261	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	296	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
262	to be done yourself, e.g. using the Encode module.	297	to be done yourself, e.g. using the Encode module.
263		298
264	Example, output UTF-16BE-encoded JSON:	299	Example, output UTF-16BE-encoded JSON:
265		300
266	use Encode;	301	use Encode;
…		…
288	]	323	]
289	}	324	}
290		325
291	=item $json = $json->indent ([$enable])	326	=item $json = $json->indent ([$enable])
292		327
		328	=item $enabled = $json->get_indent
		329
293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	330	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294	format as output, putting every array member or object/hash key-value pair	331	format as output, putting every array member or object/hash key-value pair
295	into its own line, identing them properly.	332	into its own line, indenting them properly.
296		333
297	If C<$enable> is false, no newlines or indenting will be produced, and the	334	If C<$enable> is false, no newlines or indenting will be produced, and the
298	resulting JSON text is guarenteed not to contain any C<newlines>.	335	resulting JSON text is guaranteed not to contain any C<newlines>.
299		336
300	This setting has no effect when decoding JSON texts.	337	This setting has no effect when decoding JSON texts.
301		338
302	=item $json = $json->space_before ([$enable])	339	=item $json = $json->space_before ([$enable])
		340
		341	=item $enabled = $json->get_space_before
303		342
304	If C<$enable> is true (or missing), then the C<encode> method will add an extra	343	If C<$enable> is true (or missing), then the C<encode> method will add an extra
305	optional space before the C<:> separating keys from values in JSON objects.	344	optional space before the C<:> separating keys from values in JSON objects.
306		345
307	If C<$enable> is false, then the C<encode> method will not add any extra	346	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
313	Example, space_before enabled, space_after and indent disabled:	352	Example, space_before enabled, space_after and indent disabled:
314		353
315	{"key" :"value"}	354	{"key" :"value"}
316		355
317	=item $json = $json->space_after ([$enable])	356	=item $json = $json->space_after ([$enable])
		357
		358	=item $enabled = $json->get_space_after
318		359
319	If C<$enable> is true (or missing), then the C<encode> method will add an extra	360	If C<$enable> is true (or missing), then the C<encode> method will add an extra
320	optional space after the C<:> separating keys from values in JSON objects	361	optional space after the C<:> separating keys from values in JSON objects
321	and extra whitespace after the C<,> separating key-value pairs and array	362	and extra whitespace after the C<,> separating key-value pairs and array
322	members.	363	members.
…		…
329	Example, space_before and indent disabled, space_after enabled:	370	Example, space_before and indent disabled, space_after enabled:
330		371
331	{"key": "value"}	372	{"key": "value"}
332		373
333	=item $json = $json->relaxed ([$enable])	374	=item $json = $json->relaxed ([$enable])
		375
		376	=item $enabled = $json->get_relaxed
334		377
335	If C<$enable> is true (or missing), then C<decode> will accept some	378	If C<$enable> is true (or missing), then C<decode> will accept some
336	extensions to normal JSON syntax (see below). C<encode> will not be	379	extensions to normal JSON syntax (see below). C<encode> will not be
337	affected in anyway. I<Be aware that this option makes you accept invalid	380	affected in anyway. I<Be aware that this option makes you accept invalid
338	JSON texts as if they were valid!>. I suggest only to use this option to	381	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
375		418
376	=back	419	=back
377		420
378	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
379		422
		423	=item $enabled = $json->get_canonical
		424
380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
382		427
383	If C<$enable> is false, then the C<encode> method will output key-value	428	If C<$enable> is false, then the C<encode> method will output key-value
384	pairs in the order Perl stores them (which will likely change between runs	429	pairs in the order Perl stores them (which will likely change between runs
385	of the same script).	430	of the same script).
386		431
387	This option is useful if you want the same data structure to be encoded as	432	This option is useful if you want the same data structure to be encoded as
388	the same JSON text (given the same overall settings). If it is disabled,	433	the same JSON text (given the same overall settings). If it is disabled,
389	the same hash migh be encoded differently even if contains the same data,	434	the same hash might be encoded differently even if contains the same data,
390	as key-value pairs have no inherent ordering in Perl.	435	as key-value pairs have no inherent ordering in Perl.
391		436
392	This setting has no effect when decoding JSON texts.	437	This setting has no effect when decoding JSON texts.
393		438
394	=item $json = $json->allow_nonref ([$enable])	439	=item $json = $json->allow_nonref ([$enable])
		440
		441	=item $enabled = $json->get_allow_nonref
395		442
396	If C<$enable> is true (or missing), then the C<encode> method can convert a	443	If C<$enable> is true (or missing), then the C<encode> method can convert a
397	non-reference into its corresponding string, number or null JSON value,	444	non-reference into its corresponding string, number or null JSON value,
398	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	445	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
399	values instead of croaking.	446	values instead of croaking.
…		…
409	JSON::XS->new->allow_nonref->encode ("Hello, World!")	456	JSON::XS->new->allow_nonref->encode ("Hello, World!")
410	=> "Hello, World!"	457	=> "Hello, World!"
411		458
412	=item $json = $json->allow_blessed ([$enable])	459	=item $json = $json->allow_blessed ([$enable])
413		460
		461	=item $enabled = $json->get_allow_blessed
		462
414	If C<$enable> is true (or missing), then the C<encode> method will not	463	If C<$enable> is true (or missing), then the C<encode> method will not
415	barf when it encounters a blessed reference. Instead, the value of the	464	barf when it encounters a blessed reference. Instead, the value of the
416	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	465	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417	disabled or no C<to_json> method found) or a representation of the	466	disabled or no C<TO_JSON> method found) or a representation of the
418	object (C<convert_blessed> enabled and C<to_json> method found) is being	467	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419	encoded. Has no effect on C<decode>.	468	encoded. Has no effect on C<decode>.
420		469
421	If C<$enable> is false (the default), then C<encode> will throw an	470	If C<$enable> is false (the default), then C<encode> will throw an
422	exception when it encounters a blessed object.	471	exception when it encounters a blessed object.
423		472
424	=item $json = $json->convert_blessed ([$enable])	473	=item $json = $json->convert_blessed ([$enable])
		474
		475	=item $enabled = $json->get_convert_blessed
425		476
426	If C<$enable> is true (or missing), then C<encode>, upon encountering a	477	If C<$enable> is true (or missing), then C<encode>, upon encountering a
427	blessed object, will check for the availability of the C<TO_JSON> method	478	blessed object, will check for the availability of the C<TO_JSON> method
428	on the object's class. If found, it will be called in scalar context	479	on the object's class. If found, it will be called in scalar context
429	and the resulting scalar will be encoded instead of the object. If no	480	and the resulting scalar will be encoded instead of the object. If no
…		…
433	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	484	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
434	returns other blessed objects, those will be handled in the same	485	returns other blessed objects, those will be handled in the same
435	way. C<TO_JSON> must take care of not causing an endless recursion cycle	486	way. C<TO_JSON> must take care of not causing an endless recursion cycle
436	(== crash) in this case. The name of C<TO_JSON> was chosen because other	487	(== crash) in this case. The name of C<TO_JSON> was chosen because other
437	methods called by the Perl core (== not by the user of the object) are	488	methods called by the Perl core (== not by the user of the object) are
438	usually in upper case letters and to avoid collisions with the C<to_json>	489	usually in upper case letters and to avoid collisions with any C<to_json>
439	function.	490	function or method.
440		491
441	This setting does not yet influence C<decode> in any way, but in the	492	This setting does not yet influence C<decode> in any way, but in the
442	future, global hooks might get installed that influence C<decode> and are	493	future, global hooks might get installed that influence C<decode> and are
443	enabled by this setting.	494	enabled by this setting.
444		495
…		…
486		537
487	As this callback gets called less often then the C<filter_json_object>	538	As this callback gets called less often then the C<filter_json_object>
488	one, decoding speed will not usually suffer as much. Therefore, single-key	539	one, decoding speed will not usually suffer as much. Therefore, single-key
489	objects make excellent targets to serialise Perl objects into, especially	540	objects make excellent targets to serialise Perl objects into, especially
490	as single-key JSON objects are as close to the type-tagged value concept	541	as single-key JSON objects are as close to the type-tagged value concept
491	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	542	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
492	support this in any way, so you need to make sure your data never looks	543	support this in any way, so you need to make sure your data never looks
493	like a serialised Perl hash.	544	like a serialised Perl hash.
494		545
495	Typical names for the single object key are C<__class_whatever__>, or	546	Typical names for the single object key are C<__class_whatever__>, or
496	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	547	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
520		571
521	{ __widget__ => $self->{id} }	572	{ __widget__ => $self->{id} }
522	}	573	}
523		574
524	=item $json = $json->shrink ([$enable])	575	=item $json = $json->shrink ([$enable])
		576
		577	=item $enabled = $json->get_shrink
525		578
526	Perl usually over-allocates memory a bit when allocating space for	579	Perl usually over-allocates memory a bit when allocating space for
527	strings. This flag optionally resizes strings generated by either	580	strings. This flag optionally resizes strings generated by either
528	C<encode> or C<decode> to their minimum size possible. This can save	581	C<encode> or C<decode> to their minimum size possible. This can save
529	memory when your JSON texts are either very very long or you have many	582	memory when your JSON texts are either very very long or you have many
…		…
547	strings that look like integers or floats into integers or floats	600	strings that look like integers or floats into integers or floats
548	internally (there is no difference on the Perl level), saving space.	601	internally (there is no difference on the Perl level), saving space.
549		602
550	=item $json = $json->max_depth ([$maximum_nesting_depth])	603	=item $json = $json->max_depth ([$maximum_nesting_depth])
551		604
		605	=item $max_depth = $json->get_max_depth
		606
552	Sets the maximum nesting level (default C<512>) accepted while encoding	607	Sets the maximum nesting level (default C<512>) accepted while encoding
553	or decoding. If the JSON text or Perl data structure has an equal or	608	or decoding. If the JSON text or Perl data structure has an equal or
554	higher nesting level then this limit, then the encoder and decoder will	609	higher nesting level then this limit, then the encoder and decoder will
555	stop and croak at that point.	610	stop and croak at that point.
556		611
…		…
567	used, which is rarely useful.	622	used, which is rarely useful.
568		623
569	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
570		625
571	=item $json = $json->max_size ([$maximum_string_size])	626	=item $json = $json->max_size ([$maximum_string_size])
		627
		628	=item $max_size = $json->get_max_size
572		629
573	Set the maximum length a JSON text may have (in bytes) where decoding is	630	Set the maximum length a JSON text may have (in bytes) where decoding is
574	being attempted. The default is C<0>, meaning no limit. When C<decode>	631	being attempted. The default is C<0>, meaning no limit. When C<decode>
575	is called on a string longer then this number of characters it will not	632	is called on a string longer then this number of characters it will not
576	attempt to decode the string but throw an exception. This setting has no	633	attempt to decode the string but throw an exception. This setting has no
…		…
623	vice versa. These mappings are designed to "do the right thing" in most	680	vice versa. These mappings are designed to "do the right thing" in most
624	circumstances automatically, preserving round-tripping characteristics	681	circumstances automatically, preserving round-tripping characteristics
625	(what you put in comes out as something equivalent).	682	(what you put in comes out as something equivalent).
626		683
627	For the more enlightened: note that in the following descriptions,	684	For the more enlightened: note that in the following descriptions,
628	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	685	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
629	refers to the abstract Perl language itself.	686	refers to the abstract Perl language itself.
630		687
631		688
632	=head2 JSON -> PERL	689	=head2 JSON -> PERL
633		690
634	=over 4	691	=over 4
635		692
636	=item object	693	=item object
637		694
638	A JSON object becomes a reference to a hash in Perl. No ordering of object	695	A JSON object becomes a reference to a hash in Perl. No ordering of object
639	keys is preserved (JSON does not preserver object key ordering itself).	696	keys is preserved (JSON does not preserve object key ordering itself).
640		697
641	=item array	698	=item array
642		699
643	A JSON array becomes a reference to an array in Perl.	700	A JSON array becomes a reference to an array in Perl.
644		701
…		…
652		709
653	A JSON number becomes either an integer, numeric (floating point) or	710	A JSON number becomes either an integer, numeric (floating point) or
654	string scalar in perl, depending on its range and any fractional parts. On	711	string scalar in perl, depending on its range and any fractional parts. On
655	the Perl level, there is no difference between those as Perl handles all	712	the Perl level, there is no difference between those as Perl handles all
656	the conversion details, but an integer may take slightly less memory and	713	the conversion details, but an integer may take slightly less memory and
657	might represent more values exactly than (floating point) numbers.	714	might represent more values exactly than floating point numbers.
658		715
659	If the number consists of digits only, JSON::XS will try to represent	716	If the number consists of digits only, JSON::XS will try to represent
660	it as an integer value. If that fails, it will try to represent it as	717	it as an integer value. If that fails, it will try to represent it as
661	a numeric (floating point) value if that is possible without loss of	718	a numeric (floating point) value if that is possible without loss of
662	precision. Otherwise it will preserve the number as a string value.	719	precision. Otherwise it will preserve the number as a string value (in
		720	which case you lose roundtripping ability, as the JSON number will be
		721	re-encoded toa JSON string).
663		722
664	Numbers containing a fractional or exponential part will always be	723	Numbers containing a fractional or exponential part will always be
665	represented as numeric (floating point) values, possibly at a loss of	724	represented as numeric (floating point) values, possibly at a loss of
666	precision.	725	precision (in which case you might lose perfect roundtripping ability, but
667		726	the JSON number will still be re-encoded as a JSON number).
668	This might create round-tripping problems as numbers might become strings,
669	but as Perl is typeless there is no other way to do it.
670		727
671	=item true, false	728	=item true, false
672		729
673	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	730	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
674	respectively. They are overloaded to act almost exactly like the numbers	731	respectively. They are overloaded to act almost exactly like the numbers
675	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	732	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
676	the C<JSON::XS::is_bool> function.	733	the C<JSON::XS::is_bool> function.
677		734
678	=item null	735	=item null
679		736
680	A JSON null atom becomes C<undef> in Perl.	737	A JSON null atom becomes C<undef> in Perl.
…		…
711	Other unblessed references are generally not allowed and will cause an	768	Other unblessed references are generally not allowed and will cause an
712	exception to be thrown, except for references to the integers C<0> and	769	exception to be thrown, except for references to the integers C<0> and
713	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	770	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
714	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	771	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
715		772
716	to_json [\0,JSON::XS::true] # yields [false,true]	773	encode_json [\0,JSON::XS::true] # yields [false,true]
717		774
718	=item JSON::XS::true, JSON::XS::false	775	=item JSON::XS::true, JSON::XS::false
719		776
720	These special values become JSON true and JSON false values,	777	These special values become JSON true and JSON false values,
721	respectively. You can also use C<\1> and C<\0> directly if you want.	778	respectively. You can also use C<\1> and C<\0> directly if you want.
722		779
723	=item blessed objects	780	=item blessed objects
724		781
725	Blessed objects are not allowed. JSON::XS currently tries to encode their	782	Blessed objects are not directly representable in JSON. See the
726	underlying representation (hash- or arrayref), but this behaviour might	783	C<allow_blessed> and C<convert_blessed> methods on various options on
727	change in future versions.	784	how to deal with this: basically, you can choose between throwing an
		785	exception, encoding the reference as if it weren't blessed, or provide
		786	your own serialiser method.
728		787
729	=item simple scalars	788	=item simple scalars
730		789
731	Simple Perl scalars (any scalar that is not a reference) are the most	790	Simple Perl scalars (any scalar that is not a reference) are the most
732	difficult objects to encode: JSON::XS will encode undefined scalars as	791	difficult objects to encode: JSON::XS will encode undefined scalars as
733	JSON null value, scalars that have last been used in a string context	792	JSON C<null> values, scalars that have last been used in a string context
734	before encoding as JSON strings and anything else as number value:	793	before encoding as JSON strings, and anything else as number value:
735		794
736	# dump as number	795	# dump as number
737	to_json [2] # yields [2]	796	encode_json [2] # yields [2]
738	to_json [-3.0e17] # yields [-3e+17]	797	encode_json [-3.0e17] # yields [-3e+17]
739	my $value = 5; to_json [$value] # yields [5]	798	my $value = 5; encode_json [$value] # yields [5]
740		799
741	# used as string, so dump as string	800	# used as string, so dump as string
742	print $value;	801	print $value;
743	to_json [$value] # yields ["5"]	802	encode_json [$value] # yields ["5"]
744		803
745	# undef becomes null	804	# undef becomes null
746	to_json [undef] # yields [null]	805	encode_json [undef] # yields [null]
747		806
748	You can force the type to be a string by stringifying it:	807	You can force the type to be a JSON string by stringifying it:
749		808
750	my $x = 3.1; # some variable containing a number	809	my $x = 3.1; # some variable containing a number
751	"$x"; # stringified	810	"$x"; # stringified
752	$x .= ""; # another, more awkward way to stringify	811	$x .= ""; # another, more awkward way to stringify
753	print $x; # perl does it for you, too, quite often	812	print $x; # perl does it for you, too, quite often
754		813
755	You can force the type to be a number by numifying it:	814	You can force the type to be a JSON number by numifying it:
756		815
757	my $x = "3"; # some variable containing a string	816	my $x = "3"; # some variable containing a string
758	$x += 0; # numify it, ensuring it will be dumped as a number	817	$x += 0; # numify it, ensuring it will be dumped as a number
759	$x *= 1; # same thing, the choise is yours.	818	$x *= 1; # same thing, the choice is yours.
760		819
761	You can not currently output JSON booleans or force the type in other,	820	You can not currently force the type in other, less obscure, ways. Tell me
762	less obscure, ways. Tell me if you need this capability.	821	if you need this capability (but don't forget to explain why its needed
		822	:).
		823
		824	=back
		825
		826
		827	=head1 ENCODING/CODESET FLAG NOTES
		828
		829	The interested reader might have seen a number of flags that signify
		830	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		831	some confusion on what these do, so here is a short comparison:
		832
		833	C<utf8> controls wether the JSON text created by C<encode> (and expected
		834	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		835	control wether C<encode> escapes character values outside their respective
		836	codeset range. Neither of these flags conflict with each other, although
		837	some combinations make less sense than others.
		838
		839	Care has been taken to make all flags symmetrical with respect to
		840	C<encode> and C<decode>, that is, texts encoded with any combination of
		841	these flag values will be correctly decoded when the same flags are used
		842	- in general, if you use different flag settings while encoding vs. when
		843	decoding you likely have a bug somewhere.
		844
		845	Below comes a verbose discussion of these flags. Note that a "codeset" is
		846	simply an abstract set of character-codepoint pairs, while an encoding
		847	takes those codepoint numbers and I<encodes> them, in our case into
		848	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		849	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		850	the same time, which can be confusing.
		851
		852	=over 4
		853
		854	=item C<utf8> flag disabled
		855
		856	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		857	and expect Unicode strings, that is, characters with high ordinal Unicode
		858	values (> 255) will be encoded as such characters, and likewise such
		859	characters are decoded as-is, no canges to them will be done, except
		860	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		861	respectively (to Perl, these are the same thing in strings unless you do
		862	funny/weird/dumb stuff).
		863
		864	This is useful when you want to do the encoding yourself (e.g. when you
		865	want to have UTF-16 encoded JSON texts) or when some other layer does
		866	the encoding for you (for example, when printing to a terminal using a
		867	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		868	to UTF-8 encode your data first and have Perl encode it another time).
		869
		870	=item C<utf8> flag enabled
		871
		872	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		873	characters using the corresponding UTF-8 multi-byte sequence, and will
		874	expect your input strings to be encoded as UTF-8, that is, no "character"
		875	of the input string must have any value > 255, as UTF-8 does not allow
		876	that.
		877
		878	The C<utf8> flag therefore switches between two modes: disabled means you
		879	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		880	octet/binary string in Perl.
		881
		882	=item C<latin1> or C<ascii> flags enabled
		883
		884	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		885	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		886	characters as specified by the C<utf8> flag.
		887
		888	If C<utf8> is disabled, then the result is also correctly encoded in those
		889	character sets (as both are proper subsets of Unicode, meaning that a
		890	Unicode string with all character values < 256 is the same thing as a
		891	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		892	the same thing as an ASCII string in Perl).
		893
		894	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		895	regardless of these flags, just some more characters will be escaped using
		896	C<\uXXXX> then before.
		897
		898	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		899	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		900	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		901	a subset of Unicode), while ASCII is.
		902
		903	Surprisingly, C<decode> will ignore these flags and so treat all input
		904	values as governed by the C<utf8> flag. If it is disabled, this allows you
		905	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		906	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		907
		908	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		909	they only govern when the JSON output engine escapes a character or not.
		910
		911	The main use for C<latin1> is to relatively efficiently store binary data
		912	as JSON, at the expense of breaking compatibility with most JSON decoders.
		913
		914	The main use for C<ascii> is to force the output to not contain characters
		915	with values > 127, which means you can interpret the resulting string
		916	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		917	8-bit-encoding, and still get the same data structure back. This is useful
		918	when your channel for JSON transfer is not 8-bit clean or the encoding
		919	might be mangled in between (e.g. in mail), and works because ASCII is a
		920	proper subset of most 8-bit and multibyte encodings in use in the world.
763		921
764	=back	922	=back
765		923
766		924
767	=head1 COMPARISON	925	=head1 COMPARISON
…		…
772	followed by some benchmark values. JSON::XS was designed not to suffer	930	followed by some benchmark values. JSON::XS was designed not to suffer
773	from any of these problems or limitations.	931	from any of these problems or limitations.
774		932
775	=over 4	933	=over 4
776		934
		935	=item JSON 2.xx
		936
		937	A marvellous piece of engineering, this module either uses JSON::XS
		938	directly when available (so will be 100% compatible with it, including
		939	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		941	slower.
		942
		943	You cannot really lose by using this module, especially as it tries very
		944	hard to work even with ancient Perl versions, while JSON::XS does not.
		945
777	=item JSON 1.07	946	=item JSON 1.07
778		947
779	Slow (but very portable, as it is written in pure Perl).	948	Slow (but very portable, as it is written in pure Perl).
780		949
781	Undocumented/buggy Unicode handling (how JSON handles unicode values is	950	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
782	undocumented. One can get far by feeding it unicode strings and doing	951	undocumented. One can get far by feeding it Unicode strings and doing
783	en-/decoding oneself, but unicode escapes are not working properly).	952	en-/decoding oneself, but Unicode escapes are not working properly).
784		953
785	No roundtripping (strings get clobbered if they look like numbers, e.g.	954	No round-tripping (strings get clobbered if they look like numbers, e.g.
786	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	955	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
787	decode into the number 2.	956	decode into the number 2.
788		957
789	=item JSON::PC 0.01	958	=item JSON::PC 0.01
790		959
791	Very fast.	960	Very fast.
792		961
793	Undocumented/buggy Unicode handling.	962	Undocumented/buggy Unicode handling.
794		963
795	No roundtripping.	964	No round-tripping.
796		965
797	Has problems handling many Perl values (e.g. regex results and other magic	966	Has problems handling many Perl values (e.g. regex results and other magic
798	values will make it croak).	967	values will make it croak).
799		968
800	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	969	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
810	Very inflexible (no human-readable format supported, format pretty much	979	Very inflexible (no human-readable format supported, format pretty much
811	undocumented. I need at least a format for easy reading by humans and a	980	undocumented. I need at least a format for easy reading by humans and a
812	single-line compact format for use in a protocol, and preferably a way to	981	single-line compact format for use in a protocol, and preferably a way to
813	generate ASCII-only JSON texts).	982	generate ASCII-only JSON texts).
814		983
815	Completely broken (and confusingly documented) Unicode handling (unicode	984	Completely broken (and confusingly documented) Unicode handling (Unicode
816	escapes are not working properly, you need to set ImplicitUnicode to	985	escapes are not working properly, you need to set ImplicitUnicode to
817	I<different> values on en- and decoding to get symmetric behaviour).	986	I<different> values on en- and decoding to get symmetric behaviour).
818		987
819	No roundtripping (simple cases work, but this depends on wether the scalar	988	No round-tripping (simple cases work, but this depends on whether the scalar
820	value was used in a numeric context or not).	989	value was used in a numeric context or not).
821		990
822	Dumping hashes may skip hash values depending on iterator state.	991	Dumping hashes may skip hash values depending on iterator state.
823		992
824	Unmaintained (maintainer unresponsive for many months, bugs are not	993	Unmaintained (maintainer unresponsive for many months, bugs are not
825	getting fixed).	994	getting fixed).
826		995
827	Does not check input for validity (i.e. will accept non-JSON input and	996	Does not check input for validity (i.e. will accept non-JSON input and
828	return "something" instead of raising an exception. This is a security	997	return "something" instead of raising an exception. This is a security
829	issue: imagine two banks transfering money between each other using	998	issue: imagine two banks transferring money between each other using
830	JSON. One bank might parse a given non-JSON request and deduct money,	999	JSON. One bank might parse a given non-JSON request and deduct money,
831	while the other might reject the transaction with a syntax error. While a	1000	while the other might reject the transaction with a syntax error. While a
832	good protocol will at least recover, that is extra unnecessary work and	1001	good protocol will at least recover, that is extra unnecessary work and
833	the transaction will still not succeed).	1002	the transaction will still not succeed).
834		1003
835	=item JSON::DWIW 0.04	1004	=item JSON::DWIW 0.04
836		1005
837	Very fast. Very natural. Very nice.	1006	Very fast. Very natural. Very nice.
838		1007
839	Undocumented unicode handling (but the best of the pack. Unicode escapes	1008	Undocumented Unicode handling (but the best of the pack. Unicode escapes
840	still don't get parsed properly).	1009	still don't get parsed properly).
841		1010
842	Very inflexible.	1011	Very inflexible.
843		1012
844	No roundtripping.	1013	No round-tripping.
845		1014
846	Does not generate valid JSON texts (key strings are often unquoted, empty keys	1015	Does not generate valid JSON texts (key strings are often unquoted, empty keys
847	result in nothing being output)	1016	result in nothing being output)
848		1017
849	Does not check input for validity.	1018	Does not check input for validity.
…		…
851	=back	1020	=back
852		1021
853		1022
854	=head2 JSON and YAML	1023	=head2 JSON and YAML
855		1024
856	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1025	You often hear that JSON is a subset of YAML. This is, however, a mass
857	however, a mass hysteria and very far from the truth. In general, there is	1026	hysteria(*) and very far from the truth. In general, there is no way to
858	no way to configure JSON::XS to output a data structure as valid YAML.	1027	configure JSON::XS to output a data structure as valid YAML that works for
		1028	all cases.
859		1029
860	If you really must use JSON::XS to generate YAML, you should use this	1030	If you really must use JSON::XS to generate YAML, you should use this
861	algorithm (subject to change in future versions):	1031	algorithm (subject to change in future versions):
862		1032
863	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1033	my $to_yaml = JSON::XS->new->utf8->space_after (1);
864	my $yaml = $to_yaml->encode ($ref) . "\n";	1034	my $yaml = $to_yaml->encode ($ref) . "\n";
865		1035
866	This will usually generate JSON texts that also parse as valid	1036	This will I<usually> generate JSON texts that also parse as valid
867	YAML. Please note that YAML has hardcoded limits on (simple) object key	1037	YAML. Please note that YAML has hardcoded limits on (simple) object key
868	lengths that JSON doesn't have, so you should make sure that your hash	1038	lengths that JSON doesn't have and also has different and incompatible
		1039	unicode handling, so you should make sure that your hash keys are
869	keys are noticably shorter than the 1024 characters YAML allows.	1040	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1041	you do not have codepoints with values outside the Unicode BMP (basic
		1042	multilingual page). YAML also does not allow C<\/> sequences in strings
		1043	(which JSON::XS does not I<currently> generate).
870		1044
871	There might be other incompatibilities that I am not aware of. In general	1045	There might be other incompatibilities that I am not aware of (or the YAML
		1046	specification has been changed yet again - it does so quite often). In
872	you should not try to generate YAML with a JSON generator or vice versa,	1047	general you should not try to generate YAML with a JSON generator or vice
873	or try to parse JSON with a YAML parser or vice versa: chances are high	1048	versa, or try to parse JSON with a YAML parser or vice versa: chances are
874	that you will run into severe interoperability problems.	1049	high that you will run into severe interoperability problems when you
		1050	least expect it.
		1051
		1052	=over 4
		1053
		1054	=item (*)
		1055
		1056	This is spread actively by the YAML team, however. For many years now they
		1057	claim YAML were a superset of JSON, even when proven otherwise.
		1058
		1059	Even the author of this manpage was at some point accused of providing
		1060	"incorrect" information, despite the evidence presented (claims ranged
		1061	from "your documentation contains inaccurate and negative statements about
		1062	YAML" (the only negative comment is this footnote, and it didn't exist
		1063	back then; the question on which claims were inaccurate was never answered
		1064	etc.) to "the YAML spec is not up-to-date" (the real and supposedly
		1065	JSON-compatible spec is apparently not currently publicly available)
		1066	to actual requests to replace this section by incorrect information,
		1067	suppressing information about the real problem).
		1068
		1069	So whenever you are told that YAML was a superset of JSON, first check
		1070	wether it is really true (it might be when you check it, but it certainly
		1071	was not true when this was written). I would much prefer if the YAML team
		1072	would spent their time on actually making JSON compatibility a truth
		1073	(JSON, after all, has a very small and simple specification) instead of
		1074	trying to lobby/force people into reporting untruths.
		1075
		1076	=back
875		1077
876		1078
877	=head2 SPEED	1079	=head2 SPEED
878		1080
879	It seems that JSON::XS is surprisingly fast, as shown in the following	1081	It seems that JSON::XS is surprisingly fast, as shown in the following
…		…
890	It shows the number of encodes/decodes per second (JSON::XS uses	1092	It shows the number of encodes/decodes per second (JSON::XS uses
891	the functional interface, while JSON::XS/2 uses the OO interface	1093	the functional interface, while JSON::XS/2 uses the OO interface
892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1094	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893	shrink). Higher is better:	1095	shrink). Higher is better:
894		1096
895	Storable \| 15779.925 \| 14169.946 \|
896	-----------+------------+------------+
897	module \| encode \| decode \|	1097	module \| encode \| decode \|
898	-----------\|------------\|------------\|	1098	-----------\|------------\|------------\|
899	JSON \| 4990.842 \| 4088.813 \|	1099	JSON 1.x \| 4990.842 \| 4088.813 \|
900	JSON::DWIW \| 51653.990 \| 71575.154 \|	1100	JSON::DWIW \| 51653.990 \| 71575.154 \|
901	JSON::PC \| 65948.176 \| 74631.744 \|	1101	JSON::PC \| 65948.176 \| 74631.744 \|
902	JSON::PP \| 8931.652 \| 3817.168 \|	1102	JSON::PP \| 8931.652 \| 3817.168 \|
903	JSON::Syck \| 24877.248 \| 27776.848 \|	1103	JSON::Syck \| 24877.248 \| 27776.848 \|
904	JSON::XS \| 388361.481 \| 227951.304 \|	1104	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
906	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1106	JSON::XS/3 \| 338250.323 \| 218453.333 \|
907	Storable \| 16500.016 \| 135300.129 \|	1107	Storable \| 16500.016 \| 135300.129 \|
908	-----------+------------+------------+	1108	-----------+------------+------------+
909		1109
910	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1110	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
911	about three times faster on decoding, and over fourty times faster	1111	about three times faster on decoding, and over forty times faster
912	than JSON, even with pretty-printing and key sorting. It also compares	1112	than JSON, even with pretty-printing and key sorting. It also compares
913	favourably to Storable for small amounts of data.	1113	favourably to Storable for small amounts of data.
914		1114
915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1115	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916	search API (http://nanoref.com/yahooapis/mgPdGg):	1116	search API (http://nanoref.com/yahooapis/mgPdGg):
917		1117
918	module \| encode \| decode \|	1118	module \| encode \| decode \|
919	-----------\|------------\|------------\|	1119	-----------\|------------\|------------\|
920	JSON \| 55.260 \| 34.971 \|	1120	JSON 1.x \| 55.260 \| 34.971 \|
921	JSON::DWIW \| 825.228 \| 1082.513 \|	1121	JSON::DWIW \| 825.228 \| 1082.513 \|
922	JSON::PC \| 3571.444 \| 2394.829 \|	1122	JSON::PC \| 3571.444 \| 2394.829 \|
923	JSON::PP \| 210.987 \| 32.574 \|	1123	JSON::PP \| 210.987 \| 32.574 \|
924	JSON::Syck \| 552.551 \| 787.544 \|	1124	JSON::Syck \| 552.551 \| 787.544 \|
925	JSON::XS \| 5780.463 \| 4854.519 \|	1125	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
929	-----------+------------+------------+	1129	-----------+------------+------------+
930		1130
931	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1131	Again, JSON::XS leads by far (except for Storable which non-surprisingly
932	decodes faster).	1132	decodes faster).
933		1133
934	On large strings containing lots of high unicode characters, some modules	1134	On large strings containing lots of high Unicode characters, some modules
935	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1135	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
936	will be broken due to missing (or wrong) unicode handling. Others refuse	1136	will be broken due to missing (or wrong) Unicode handling. Others refuse
937	to decode or encode properly, so it was impossible to prepare a fair	1137	to decode or encode properly, so it was impossible to prepare a fair
938	comparison table for that case.	1138	comparison table for that case.
939		1139
940		1140
941	=head1 SECURITY CONSIDERATIONS	1141	=head1 SECURITY CONSIDERATIONS
…		…
947	any buffer overflows. Obviously, this module should ensure that and I am	1147	any buffer overflows. Obviously, this module should ensure that and I am
948	trying hard on making that true, but you never know.	1148	trying hard on making that true, but you never know.
949		1149
950	Second, you need to avoid resource-starving attacks. That means you should	1150	Second, you need to avoid resource-starving attacks. That means you should
951	limit the size of JSON texts you accept, or make sure then when your	1151	limit the size of JSON texts you accept, or make sure then when your
952	resources run out, thats just fine (e.g. by using a separate process that	1152	resources run out, that's just fine (e.g. by using a separate process that
953	can crash safely). The size of a JSON text in octets or characters is	1153	can crash safely). The size of a JSON text in octets or characters is
954	usually a good indication of the size of the resources required to decode	1154	usually a good indication of the size of the resources required to decode
955	it into a Perl structure. While JSON::XS can check the size of the JSON	1155	it into a Perl structure. While JSON::XS can check the size of the JSON
956	text, it might be too late when you already have it in memory, so you	1156	text, it might be too late when you already have it in memory, so you
957	might want to check the size before you accept the string.	1157	might want to check the size before you accept the string.
958		1158
959	Third, JSON::XS recurses using the C stack when decoding objects and	1159	Third, JSON::XS recurses using the C stack when decoding objects and
960	arrays. The C stack is a limited resource: for instance, on my amd64	1160	arrays. The C stack is a limited resource: for instance, on my amd64
961	machine with 8MB of stack size I can decode around 180k nested arrays but	1161	machine with 8MB of stack size I can decode around 180k nested arrays but
962	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1162	only 14k nested JSON objects (due to perl itself recursing deeply on croak
963	to free the temporary). If that is exceeded, the program crashes. to be	1163	to free the temporary). If that is exceeded, the program crashes. To be
964	conservative, the default nesting limit is set to 512. If your process	1164	conservative, the default nesting limit is set to 512. If your process
965	has a smaller stack, you should adjust this setting accordingly with the	1165	has a smaller stack, you should adjust this setting accordingly with the
966	C<max_depth> method.	1166	C<max_depth> method.
967		1167
968	And last but least, something else could bomb you that I forgot to think	1168	Something else could bomb you, too, that I forgot to think of. In that
969	of. In that case, you get to keep the pieces. I am always open for hints,	1169	case, you get to keep the pieces. I am always open for hints, though...
970	though...	1170
		1171	Also keep in mind that JSON::XS might leak contents of your Perl data
		1172	structures in its error messages, so when you serialise sensitive
		1173	information you might want to make sure that exceptions thrown by JSON::XS
		1174	will not end up in front of untrusted eyes.
971		1175
972	If you are using JSON::XS to return packets to consumption	1176	If you are using JSON::XS to return packets to consumption
973	by javascript scripts in a browser you should have a look at	1177	by JavaScript scripts in a browser you should have a look at
974	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1178	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
975	you are vulnerable to some common attack vectors (which really are browser	1179	you are vulnerable to some common attack vectors (which really are browser
976	design bugs, but it is still you who will have to deal with it, as major	1180	design bugs, but it is still you who will have to deal with it, as major
977	browser developers care only for features, not about doing security	1181	browser developers care only for features, not about getting security
978	right).	1182	right).
979		1183
980		1184
981	=head1 THREADS	1185	=head1 THREADS
982		1186
983	This module is I<not> guarenteed to be thread safe and there are no	1187	This module is I<not> guaranteed to be thread safe and there are no
984	plans to change this until Perl gets thread support (as opposed to the	1188	plans to change this until Perl gets thread support (as opposed to the
985	horribly slow so-called "threads" which are simply slow and bloated	1189	horribly slow so-called "threads" which are simply slow and bloated
986	process simulations - use fork, its I<much> faster, cheaper, better).	1190	process simulations - use fork, its I<much> faster, cheaper, better).
987		1191
988	(It might actually work, but you ahve ben warned).	1192	(It might actually work, but you have been warned).
989		1193
990		1194
991	=head1 BUGS	1195	=head1 BUGS
992		1196
993	While the goal of this module is to be correct, that unfortunately does	1197	While the goal of this module is to be correct, that unfortunately does

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Comparing JSON-XS/XS.pm (file contents): Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs. Revision 1.86 by root, Wed Mar 19 03:17:38 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.67 by root, Mon Oct 15 01:22:34 2007 UTC vs.
Revision 1.86 by root, Wed Mar 19 03:17:38 2008 UTC