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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.64 by root, Thu Oct 11 23:57:24 2007 UTC vs.
Revision 1.95 by root, Tue Mar 25 16:56:09 2008 UTC

…		…
		1	=head1 NAME
		2
1	=encoding utf-8	3	=encoding utf-8
2
3	=head1 NAME
4		4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		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	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)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
12	use JSON::XS;	12	use JSON::XS;
13		13
14	# exported functions, they croak on error	14	# exported functions, they croak on error
15	# and expect/generate UTF-8	15	# and expect/generate UTF-8
16		16
17	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
18	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
19		19
20	# OO-interface	20	# OO-interface
21		21
22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
24	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
25		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
26	=head1 DESCRIPTION	34	=head1 DESCRIPTION
27		35
28	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
29	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
30	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.
31		47
32	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
33	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
34	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
35	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
…		…
42		58
43	=head2 FEATURES	59	=head2 FEATURES
44		60
45	=over 4	61	=over 4
46		62
47	=item * correct unicode handling	63	=item * correct Unicode handling
48		64
49	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
50	it does so.	66	so, and even documents what "correct" means.
51		67
52	=item * round-trip integrity	68	=item * round-trip integrity
53		69
54	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
55	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.
56	(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
57	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
58		75
59	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
60		77
61	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,
62	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
63	feature).	80	feature).
64		81
65	=item * fast	82	=item * fast
66		83
67	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
68	of speed, too.	85	this module usually compares favourably in terms of speed, too.
69		86
70	=item * simple to use	87	=item * simple to use
71		88
72	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
73	interface.	90	oriented interface interface.
74		91
75	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
76		93
77	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
78	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
79	(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
80	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
81	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.
82		99
83	=back	100	=back
84		101
85	=cut	102	=cut
86		103
87	package JSON::XS;	104	package JSON::XS;
88		105
89	use strict;	106	use strict;
90		107
91	our $VERSION = '1.5';	108	our $VERSION = '2.1';
92	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
93		110
94	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		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	}
95		122
96	use Exporter;	123	use Exporter;
97	use XSLoader;	124	use XSLoader;
98		125
99	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
100		127
101	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
102	exported by default:	129	exported by default:
103		130
104	=over 4	131	=over 4
105		132
106	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
107		134
108	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
109	(that is, the string contains octets only). Croaks on error.	136	(that is, the string contains octets only). Croaks on error.
110		137
111	This function call is functionally identical to:	138	This function call is functionally identical to:
112		139
113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
114		141
115	except being faster.	142	except being faster.
116		143
117	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
118		145
119	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
120	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
121	reference. Croaks on error.	148	reference. Croaks on error.
122		149
123	This function call is functionally identical to:	150	This function call is functionally identical to:
124		151
…		…
145		172
146	=over 4	173	=over 4
147		174
148	=item 1. Perl strings can store characters with ordinal values > 255.	175	=item 1. Perl strings can store characters with ordinal values > 255.
149		176
150	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
151	Perl string - very natural.	178	Perl string - very natural.
152		179
153	=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.
154		181
155	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
156	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
157	locale-encoded text, octets/binary, or as Unicode, depending on various	184	string as locale-encoded text, octets/binary, or as Unicode, depending
158	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
159	I<use> that decides encoding, not any magical metadata.	186	data, it is I<use> that decides encoding, not any magical meta data.
160		187
161	=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
162	encoding of your string.	189	encoding of your string.
163		190
164	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
165	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
166	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
167	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
168	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
169	clear. Other possibilities exist, too.	196	clear. Other possibilities exist, too.
170		197
171	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
172	exist.	199	exist.
…		…
177	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
178	Unicode string encoded in UTF-8, giving you a binary string.	205	Unicode string encoded in UTF-8, giving you a binary string.
179		206
180	=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.
181		208
182	Its a fact. Learn to live with it.	209	It's a fact. Learn to live with it.
183		210
184	=back	211	=back
185		212
186	I hope this helps :)	213	I hope this helps :)
187		214
…		…
204	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]})
205	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
206		233
207	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
208		235
		236	=item $enabled = $json->get_ascii
		237
209	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
210	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
211	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
213	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
214	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
215	or any other superset of ASCII.	244	or any other superset of ASCII.
216		245
217	If C<$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
218	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
219	in a faster and more compact format.	248	in a faster and more compact format.
220		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
221	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
222	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
223	contain any 8 bit characters.	255	contain any 8 bit characters.
224		256
225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
226	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
227		259
228	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
229		261
		262	=item $enabled = $json->get_latin1
		263
230	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
231	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
232	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
233	latin1-encoded JSON text or a native unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
234	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
235	expects unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
236		270
237	If C<$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
238	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.
239		276
240	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
241	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
242	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
243	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
244	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
245	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
246	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.
247		284
248	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
249	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
250		287
251	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
252		291
253	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
254	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
255	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
256	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
257	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
258	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
259	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
260		299
261	If C<$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
262	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
263	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
264	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.
265		307
266	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
267		309
268	use Encode;	310	use Encode;
269	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
290	]	332	]
291	}	333	}
292		334
293	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
294		336
		337	=item $enabled = $json->get_indent
		338
295	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
296	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
297	into its own line, identing them properly.	341	into its own line, indenting them properly.
298		342
299	If C<$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
300	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
301		345
302	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
303		347
304	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
305		351
306	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
307	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
308		354
309	If C<$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
…		…
315	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
316		362
317	{"key" :"value"}	363	{"key" :"value"}
318		364
319	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
320		368
321	If C<$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
322	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
323	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
324	members.	372	members.
…		…
331	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
332		380
333	{"key": "value"}	381	{"key": "value"}
334		382
335	=item $json = $json->relaxed ([$enable])	383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
336		386
337	If C<$enable> is true (or missing), then C<decode> will accept some	387	If C<$enable> is true (or missing), then C<decode> will accept some
338	extensions to normal JSON syntax (see below). C<encode> will not be	388	extensions to normal JSON syntax (see below). C<encode> will not be
339	affected in anyway. I<Be aware that this option makes you accept invalid	389	affected in anyway. I<Be aware that this option makes you accept invalid
340	JSON texts as if they were valid!>. I suggest only to use this option to	390	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
377		427
378	=back	428	=back
379		429
380	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
381		431
		432	=item $enabled = $json->get_canonical
		433
382	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
383	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
384		436
385	If C<$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
386	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
387	of the same script).	439	of the same script).
388		440
389	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
390	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,
391	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,
392	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
393		445
394	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
395		447
396	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
397		451
398	If C<$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
399	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
400	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
401	values instead of croaking.	455	values instead of croaking.
…		…
411	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
412	=> "Hello, World!"	466	=> "Hello, World!"
413		467
414	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
415		469
		470	=item $enabled = $json->get_allow_blessed
		471
416	If C<$enable> is true (or missing), then the C<encode> method will not	472	If C<$enable> is true (or missing), then the C<encode> method will not
417	barf when it encounters a blessed reference. Instead, the value of the	473	barf when it encounters a blessed reference. Instead, the value of the
418	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
419	disabled or no C<to_json> method found) or a representation of the	475	disabled or no C<TO_JSON> method found) or a representation of the
420	object (C<convert_blessed> enabled and C<to_json> method found) is being	476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
421	encoded. Has no effect on C<decode>.	477	encoded. Has no effect on C<decode>.
422		478
423	If C<$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
424	exception when it encounters a blessed object.	480	exception when it encounters a blessed object.
425		481
426	=item $json = $json->convert_blessed ([$enable])	482	=item $json = $json->convert_blessed ([$enable])
		483
		484	=item $enabled = $json->get_convert_blessed
427		485
428	If C<$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
429	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
430	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
431	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
…		…
435	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>
436	returns other blessed objects, those will be handled in the same	494	returns other blessed objects, those will be handled in the same
437	way. C<TO_JSON> must take care of not causing an endless recursion cycle	495	way. C<TO_JSON> must take care of not causing an endless recursion cycle
438	(== crash) in this case. The name of C<TO_JSON> was chosen because other	496	(== crash) in this case. The name of C<TO_JSON> was chosen because other
439	methods called by the Perl core (== not by the user of the object) are	497	methods called by the Perl core (== not by the user of the object) are
440	usually in upper case letters and to avoid collisions with the C<to_json>	498	usually in upper case letters and to avoid collisions with any C<to_json>
441	function.	499	function or method.
442		500
443	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
444	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
445	enabled by this setting.	503	enabled by this setting.
446		504
…		…
488		546
489	As this callback gets called less often then the C<filter_json_object>	547	As this callback gets called less often then the C<filter_json_object>
490	one, decoding speed will not usually suffer as much. Therefore, single-key	548	one, decoding speed will not usually suffer as much. Therefore, single-key
491	objects make excellent targets to serialise Perl objects into, especially	549	objects make excellent targets to serialise Perl objects into, especially
492	as single-key JSON objects are as close to the type-tagged value concept	550	as single-key JSON objects are as close to the type-tagged value concept
493	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	551	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
494	support this in any way, so you need to make sure your data never looks	552	support this in any way, so you need to make sure your data never looks
495	like a serialised Perl hash.	553	like a serialised Perl hash.
496		554
497	Typical names for the single object key are C<__class_whatever__>, or	555	Typical names for the single object key are C<__class_whatever__>, or
498	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	556	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
522		580
523	{ __widget__ => $self->{id} }	581	{ __widget__ => $self->{id} }
524	}	582	}
525		583
526	=item $json = $json->shrink ([$enable])	584	=item $json = $json->shrink ([$enable])
		585
		586	=item $enabled = $json->get_shrink
527		587
528	Perl usually over-allocates memory a bit when allocating space for	588	Perl usually over-allocates memory a bit when allocating space for
529	strings. This flag optionally resizes strings generated by either	589	strings. This flag optionally resizes strings generated by either
530	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
531	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
…		…
549	strings that look like integers or floats into integers or floats	609	strings that look like integers or floats into integers or floats
550	internally (there is no difference on the Perl level), saving space.	610	internally (there is no difference on the Perl level), saving space.
551		611
552	=item $json = $json->max_depth ([$maximum_nesting_depth])	612	=item $json = $json->max_depth ([$maximum_nesting_depth])
553		613
		614	=item $max_depth = $json->get_max_depth
		615
554	Sets the maximum nesting level (default C<512>) accepted while encoding	616	Sets the maximum nesting level (default C<512>) accepted while encoding
555	or decoding. If the JSON text or Perl data structure has an equal or	617	or decoding. If the JSON text or Perl data structure has an equal or
556	higher nesting level then this limit, then the encoder and decoder will	618	higher nesting level then this limit, then the encoder and decoder will
557	stop and croak at that point.	619	stop and croak at that point.
558		620
…		…
569	used, which is rarely useful.	631	used, which is rarely useful.
570		632
571	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.
572		634
573	=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
574		638
575	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
576	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>
577	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
578	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
…		…
617	=> ([], 3)	681	=> ([], 3)
618		682
619	=back	683	=back
620		684
621		685
		686	=head1 INCREMENTAL PARSING
		687
		688	[This section is still EXPERIMENTAL]
		689
		690	In some cases, there is the need for incremental parsing of JSON
		691	texts. While this module always has to keep both JSON text and resulting
		692	Perl data structure in memory at one time, it does allow you to parse a
		693	JSON stream incrementally. It does so by accumulating text until it has
		694	a full JSON object, which it then can decode. This process is similar to
		695	using C<decode_prefix> to see if a full JSON object is available, but is
		696	much more efficient (JSON::XS will only attempt to parse the JSON text
		697	once it is sure it has enough text to get a decisive result, using a very
		698	simple but truly incremental parser).
		699
		700	The following two methods deal with this.
		701
		702	=over 4
		703
		704	=item [void, scalar or list context] = $json->incr_parse ([$string])
		705
		706	This is the central parsing function. It can both append new text and
		707	extract objects from the stream accumulated so far (both of these
		708	functions are optional).
		709
		710	If C<$string> is given, then this string is appended to the already
		711	existing JSON fragment stored in the C<$json> object.
		712
		713	After that, if the function is called in void context, it will simply
		714	return without doing anything further. This can be used to add more text
		715	in as many chunks as you want.
		716
		717	If the method is called in scalar context, then it will try to extract
		718	exactly I<one> JSON object. If that is successful, it will return this
		719	object, otherwise it will return C<undef>. This is the most common way of
		720	using the method.
		721
		722	And finally, in list context, it will try to extract as many objects
		723	from the stream as it can find and return them, or the empty list
		724	otherwise. For this to work, there must be no separators between the JSON
		725	objects or arrays, instead they must be concatenated back-to-back.
		726
		727	=item $lvalue_string = $json->incr_text
		728
		729	This method returns the currently stored JSON fragment as an lvalue, that
		730	is, you can manipulate it. This I<only> works when a preceding call to
		731	C<incr_parse> in I<scalar context> successfully returned an object. Under
		732	all other circumstances you must not call this function (I mean it.
		733	although in simple tests it might actually work, it I<will> fail under
		734	real world conditions). As a special exception, you can also call this
		735	method before having parsed anything.
		736
		737	This function is useful in two cases: a) finding the trailing text after a
		738	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		739	(such as commas).
		740
		741	=back
		742
		743	=head2 LIMITATIONS
		744
		745	All options that affect decoding are supported, except
		746	C<allow_nonref>. The reason for this is that it cannot be made to
		747	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		748	them back to back and still decode them perfectly. This does not hold true
		749	for JSON numbers, however.
		750
		751	For example, is the string C<1> a single JSON number, or is it simply the
		752	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		753	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		754	takes the conservative route and disallows this case.
		755
		756	=head2 EXAMPLES
		757
		758	Some examples will make all this clearer. First, a simple example that
		759	works similarly to C<decode_prefix>: We want to decode the JSON object at
		760	the start of a string and identify the portion after the JSON object:
		761
		762	my $text = "[1,2,3] hello";
		763
		764	my $json = new JSON::XS;
		765
		766	my $obj = $json->incr_parse ($text)
		767	or die "expected JSON object or array at beginning of string";
		768
		769	my $tail = $json->incr_text;
		770	# $tail now contains " hello"
		771
		772	Easy, isn't it?
		773
		774	Now for a more complicated example: Imagine a hypothetical protocol where
		775	you read some requests from a TCP stream, and each request is a JSON
		776	array, without any separation between them (in fact, it is often useful to
		777	use newlines as "separators", as these get interpreted as whitespace at
		778	the start of the JSON text, which makes it possible to test said protocol
		779	with C<telnet>...).
		780
		781	Here is how you'd do it (it is trivial to write this in an event-based
		782	manner):
		783
		784	my $json = new JSON::XS;
		785
		786	# read some data from the socket
		787	while (sysread $socket, my $buf, 4096) {
		788
		789	# split and decode as many requests as possible
		790	for my $request ($json->incr_parse ($buf)) {
		791	# act on the $request
		792	}
		793	}
		794
		795	Another complicated example: Assume you have a string with JSON objects
		796	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		797	[3]>). To parse them, we have to skip the commas between the JSON texts,
		798	and here is where the lvalue-ness of C<incr_text> comes in useful:
		799
		800	my $text = "[1],[2], [3]";
		801	my $json = new JSON::XS;
		802
		803	# void context, so no parsing done
		804	$json->incr_parse ($text);
		805
		806	# now extract as many objects as possible. note the
		807	# use of scalar context so incr_text can be called.
		808	while (my $obj = $json->incr_parse) {
		809	# do something with $obj
		810
		811	# now skip the optional comma
		812	$json->incr_text =~ s/^ \s* , //x;
		813	}
		814
		815	Now lets go for a very complex example: Assume that you have a gigantic
		816	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		817	but you cannot load it into memory fully (this has actually happened in
		818	the real world :).
		819
		820	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		821	can still help you: You implement a (very simple) array parser and let
		822	JSON decode the array elements, which are all full JSON objects on their
		823	own (this wouldn't work if the array elements could be JSON numbers, for
		824	example):
		825
		826	my $json = new JSON::XS;
		827
		828	# open the monster
		829	open my $fh, "<bigfile.json"
		830	or die "bigfile: $!";
		831
		832	# first parse the initial "["
		833	for (;;) {
		834	sysread $fh, my $buf, 65536
		835	or die "read error: $!";
		836	$json->incr_parse ($buf); # void context, so no parsing
		837
		838	# Exit the loop once we found and removed(!) the initial "[".
		839	# In essence, we are (ab-)using the $json object as a simple scalar
		840	# we append data to.
		841	last if $json->incr_text =~ s/^ \s* \[ //x;
		842	}
		843
		844	# now we have the skipped the initial "[", so continue
		845	# parsing all the elements.
		846	for (;;) {
		847	# in this loop we read data until we got a single JSON object
		848	for (;;) {
		849	if (my $obj = $json->incr_parse) {
		850	# do something with $obj
		851	last;
		852	}
		853
		854	# add more data
		855	sysread $fh, my $buf, 65536
		856	or die "read error: $!";
		857	$json->incr_parse ($buf); # void context, so no parsing
		858	}
		859
		860	# in this loop we read data until we either found and parsed the
		861	# separating "," between elements, or the final "]"
		862	for (;;) {
		863	# first skip whitespace
		864	$json->incr_text =~ s/^\s*//;
		865
		866	# if we find "]", we are done
		867	if ($json->incr_text =~ s/^\]//) {
		868	print "finished.\n";
		869	exit;
		870	}
		871
		872	# if we find ",", we can continue with the next element
		873	if ($json->incr_text =~ s/^,//) {
		874	last;
		875	}
		876
		877	# if we find anything else, we have a parse error!
		878	if (length $json->incr_text) {
		879	die "parse error near ", $json->incr_text;
		880	}
		881
		882	# else add more data
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886	}
		887
		888	This is a complex example, but most of the complexity comes from the fact
		889	that we are trying to be correct (bear with me if I am wrong, I never ran
		890	the above example :).
		891
		892
		893
622	=head1 MAPPING	894	=head1 MAPPING
623		895
624	This section describes how JSON::XS maps Perl values to JSON values and	896	This section describes how JSON::XS maps Perl values to JSON values and
625	vice versa. These mappings are designed to "do the right thing" in most	897	vice versa. These mappings are designed to "do the right thing" in most
626	circumstances automatically, preserving round-tripping characteristics	898	circumstances automatically, preserving round-tripping characteristics
627	(what you put in comes out as something equivalent).	899	(what you put in comes out as something equivalent).
628		900
629	For the more enlightened: note that in the following descriptions,	901	For the more enlightened: note that in the following descriptions,
630	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	902	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
631	refers to the abstract Perl language itself.	903	refers to the abstract Perl language itself.
632		904
633		905
634	=head2 JSON -> PERL	906	=head2 JSON -> PERL
635		907
636	=over 4	908	=over 4
637		909
638	=item object	910	=item object
639		911
640	A JSON object becomes a reference to a hash in Perl. No ordering of object	912	A JSON object becomes a reference to a hash in Perl. No ordering of object
641	keys is preserved (JSON does not preserver object key ordering itself).	913	keys is preserved (JSON does not preserve object key ordering itself).
642		914
643	=item array	915	=item array
644		916
645	A JSON array becomes a reference to an array in Perl.	917	A JSON array becomes a reference to an array in Perl.
646		918
…		…
654		926
655	A JSON number becomes either an integer, numeric (floating point) or	927	A JSON number becomes either an integer, numeric (floating point) or
656	string scalar in perl, depending on its range and any fractional parts. On	928	string scalar in perl, depending on its range and any fractional parts. On
657	the Perl level, there is no difference between those as Perl handles all	929	the Perl level, there is no difference between those as Perl handles all
658	the conversion details, but an integer may take slightly less memory and	930	the conversion details, but an integer may take slightly less memory and
659	might represent more values exactly than (floating point) numbers.	931	might represent more values exactly than floating point numbers.
660		932
661	If the number consists of digits only, JSON::XS will try to represent	933	If the number consists of digits only, JSON::XS will try to represent
662	it as an integer value. If that fails, it will try to represent it as	934	it as an integer value. If that fails, it will try to represent it as
663	a numeric (floating point) value if that is possible without loss of	935	a numeric (floating point) value if that is possible without loss of
664	precision. Otherwise it will preserve the number as a string value.	936	precision. Otherwise it will preserve the number as a string value (in
		937	which case you lose roundtripping ability, as the JSON number will be
		938	re-encoded toa JSON string).
665		939
666	Numbers containing a fractional or exponential part will always be	940	Numbers containing a fractional or exponential part will always be
667	represented as numeric (floating point) values, possibly at a loss of	941	represented as numeric (floating point) values, possibly at a loss of
668	precision.	942	precision (in which case you might lose perfect roundtripping ability, but
669		943	the JSON number will still be re-encoded as a JSON number).
670	This might create round-tripping problems as numbers might become strings,
671	but as Perl is typeless there is no other way to do it.
672		944
673	=item true, false	945	=item true, false
674		946
675	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	947	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
676	respectively. They are overloaded to act almost exactly like the numbers	948	respectively. They are overloaded to act almost exactly like the numbers
677	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	949	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
678	the C<JSON::XS::is_bool> function.	950	the C<JSON::XS::is_bool> function.
679		951
680	=item null	952	=item null
681		953
682	A JSON null atom becomes C<undef> in Perl.	954	A JSON null atom becomes C<undef> in Perl.
…		…
713	Other unblessed references are generally not allowed and will cause an	985	Other unblessed references are generally not allowed and will cause an
714	exception to be thrown, except for references to the integers C<0> and	986	exception to be thrown, except for references to the integers C<0> and
715	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	987	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
716	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	988	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
717		989
718	to_json [\0,JSON::XS::true] # yields [false,true]	990	encode_json [\0,JSON::XS::true] # yields [false,true]
719		991
720	=item JSON::XS::true, JSON::XS::false	992	=item JSON::XS::true, JSON::XS::false
721		993
722	These special values become JSON true and JSON false values,	994	These special values become JSON true and JSON false values,
723	respectively. You can also use C<\1> and C<\0> directly if you want.	995	respectively. You can also use C<\1> and C<\0> directly if you want.
724		996
725	=item blessed objects	997	=item blessed objects
726		998
727	Blessed objects are not allowed. JSON::XS currently tries to encode their	999	Blessed objects are not directly representable in JSON. See the
728	underlying representation (hash- or arrayref), but this behaviour might	1000	C<allow_blessed> and C<convert_blessed> methods on various options on
729	change in future versions.	1001	how to deal with this: basically, you can choose between throwing an
		1002	exception, encoding the reference as if it weren't blessed, or provide
		1003	your own serialiser method.
730		1004
731	=item simple scalars	1005	=item simple scalars
732		1006
733	Simple Perl scalars (any scalar that is not a reference) are the most	1007	Simple Perl scalars (any scalar that is not a reference) are the most
734	difficult objects to encode: JSON::XS will encode undefined scalars as	1008	difficult objects to encode: JSON::XS will encode undefined scalars as
735	JSON null value, scalars that have last been used in a string context	1009	JSON C<null> values, scalars that have last been used in a string context
736	before encoding as JSON strings and anything else as number value:	1010	before encoding as JSON strings, and anything else as number value:
737		1011
738	# dump as number	1012	# dump as number
739	to_json [2] # yields [2]	1013	encode_json [2] # yields [2]
740	to_json [-3.0e17] # yields [-3e+17]	1014	encode_json [-3.0e17] # yields [-3e+17]
741	my $value = 5; to_json [$value] # yields [5]	1015	my $value = 5; encode_json [$value] # yields [5]
742		1016
743	# used as string, so dump as string	1017	# used as string, so dump as string
744	print $value;	1018	print $value;
745	to_json [$value] # yields ["5"]	1019	encode_json [$value] # yields ["5"]
746		1020
747	# undef becomes null	1021	# undef becomes null
748	to_json [undef] # yields [null]	1022	encode_json [undef] # yields [null]
749		1023
750	You can force the type to be a string by stringifying it:	1024	You can force the type to be a JSON string by stringifying it:
751		1025
752	my $x = 3.1; # some variable containing a number	1026	my $x = 3.1; # some variable containing a number
753	"$x"; # stringified	1027	"$x"; # stringified
754	$x .= ""; # another, more awkward way to stringify	1028	$x .= ""; # another, more awkward way to stringify
755	print $x; # perl does it for you, too, quite often	1029	print $x; # perl does it for you, too, quite often
756		1030
757	You can force the type to be a number by numifying it:	1031	You can force the type to be a JSON number by numifying it:
758		1032
759	my $x = "3"; # some variable containing a string	1033	my $x = "3"; # some variable containing a string
760	$x += 0; # numify it, ensuring it will be dumped as a number	1034	$x += 0; # numify it, ensuring it will be dumped as a number
761	$x *= 1; # same thing, the choise is yours.	1035	$x *= 1; # same thing, the choice is yours.
762		1036
763	You can not currently output JSON booleans or force the type in other,	1037	You can not currently force the type in other, less obscure, ways. Tell me
764	less obscure, ways. Tell me if you need this capability.	1038	if you need this capability (but don't forget to explain why it's needed
		1039	:).
765		1040
766	=back	1041	=back
767		1042
768		1043
769	=head1 COMPARISON	1044	=head1 ENCODING/CODESET FLAG NOTES
770		1045
771	As already mentioned, this module was created because none of the existing	1046	The interested reader might have seen a number of flags that signify
772	JSON modules could be made to work correctly. First I will describe the	1047	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
773	problems (or pleasures) I encountered with various existing JSON modules,	1048	some confusion on what these do, so here is a short comparison:
774	followed by some benchmark values. JSON::XS was designed not to suffer	1049
775	from any of these problems or limitations.	1050	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1051	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1052	control whether C<encode> escapes character values outside their respective
		1053	codeset range. Neither of these flags conflict with each other, although
		1054	some combinations make less sense than others.
		1055
		1056	Care has been taken to make all flags symmetrical with respect to
		1057	C<encode> and C<decode>, that is, texts encoded with any combination of
		1058	these flag values will be correctly decoded when the same flags are used
		1059	- in general, if you use different flag settings while encoding vs. when
		1060	decoding you likely have a bug somewhere.
		1061
		1062	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1063	simply an abstract set of character-codepoint pairs, while an encoding
		1064	takes those codepoint numbers and I<encodes> them, in our case into
		1065	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1066	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1067	the same time, which can be confusing.
776		1068
777	=over 4	1069	=over 4
778		1070
779	=item JSON 1.07	1071	=item C<utf8> flag disabled
780		1072
781	Slow (but very portable, as it is written in pure Perl).	1073	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1074	and expect Unicode strings, that is, characters with high ordinal Unicode
		1075	values (> 255) will be encoded as such characters, and likewise such
		1076	characters are decoded as-is, no canges to them will be done, except
		1077	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1078	respectively (to Perl, these are the same thing in strings unless you do
		1079	funny/weird/dumb stuff).
782		1080
783	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1081	This is useful when you want to do the encoding yourself (e.g. when you
784	undocumented. One can get far by feeding it unicode strings and doing	1082	want to have UTF-16 encoded JSON texts) or when some other layer does
785	en-/decoding oneself, but unicode escapes are not working properly).	1083	the encoding for you (for example, when printing to a terminal using a
		1084	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1085	to UTF-8 encode your data first and have Perl encode it another time).
786		1086
787	No roundtripping (strings get clobbered if they look like numbers, e.g.	1087	=item C<utf8> flag enabled
788	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
789	decode into the number 2.
790		1088
791	=item JSON::PC 0.01	1089	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1090	characters using the corresponding UTF-8 multi-byte sequence, and will
		1091	expect your input strings to be encoded as UTF-8, that is, no "character"
		1092	of the input string must have any value > 255, as UTF-8 does not allow
		1093	that.
792		1094
793	Very fast.	1095	The C<utf8> flag therefore switches between two modes: disabled means you
		1096	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1097	octet/binary string in Perl.
794		1098
795	Undocumented/buggy Unicode handling.	1099	=item C<latin1> or C<ascii> flags enabled
796		1100
797	No roundtripping.	1101	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1102	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1103	characters as specified by the C<utf8> flag.
798		1104
799	Has problems handling many Perl values (e.g. regex results and other magic	1105	If C<utf8> is disabled, then the result is also correctly encoded in those
800	values will make it croak).	1106	character sets (as both are proper subsets of Unicode, meaning that a
		1107	Unicode string with all character values < 256 is the same thing as a
		1108	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1109	the same thing as an ASCII string in Perl).
801		1110
802	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1111	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
803	which is not a valid JSON text.	1112	regardless of these flags, just some more characters will be escaped using
		1113	C<\uXXXX> then before.
804		1114
805	Unmaintained (maintainer unresponsive for many months, bugs are not	1115	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
806	getting fixed).	1116	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1117	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1118	a subset of Unicode), while ASCII is.
807		1119
808	=item JSON::Syck 0.21	1120	Surprisingly, C<decode> will ignore these flags and so treat all input
		1121	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1122	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1123	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
809		1124
810	Very buggy (often crashes).	1125	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1126	they only govern when the JSON output engine escapes a character or not.
811		1127
812	Very inflexible (no human-readable format supported, format pretty much	1128	The main use for C<latin1> is to relatively efficiently store binary data
813	undocumented. I need at least a format for easy reading by humans and a	1129	as JSON, at the expense of breaking compatibility with most JSON decoders.
814	single-line compact format for use in a protocol, and preferably a way to
815	generate ASCII-only JSON texts).
816		1130
817	Completely broken (and confusingly documented) Unicode handling (unicode	1131	The main use for C<ascii> is to force the output to not contain characters
818	escapes are not working properly, you need to set ImplicitUnicode to	1132	with values > 127, which means you can interpret the resulting string
819	I<different> values on en- and decoding to get symmetric behaviour).	1133	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
820		1134	8-bit-encoding, and still get the same data structure back. This is useful
821	No roundtripping (simple cases work, but this depends on wether the scalar	1135	when your channel for JSON transfer is not 8-bit clean or the encoding
822	value was used in a numeric context or not).	1136	might be mangled in between (e.g. in mail), and works because ASCII is a
823		1137	proper subset of most 8-bit and multibyte encodings in use in the world.
824	Dumping hashes may skip hash values depending on iterator state.
825
826	Unmaintained (maintainer unresponsive for many months, bugs are not
827	getting fixed).
828
829	Does not check input for validity (i.e. will accept non-JSON input and
830	return "something" instead of raising an exception. This is a security
831	issue: imagine two banks transfering money between each other using
832	JSON. One bank might parse a given non-JSON request and deduct money,
833	while the other might reject the transaction with a syntax error. While a
834	good protocol will at least recover, that is extra unnecessary work and
835	the transaction will still not succeed).
836
837	=item JSON::DWIW 0.04
838
839	Very fast. Very natural. Very nice.
840
841	Undocumented unicode handling (but the best of the pack. Unicode escapes
842	still don't get parsed properly).
843
844	Very inflexible.
845
846	No roundtripping.
847
848	Does not generate valid JSON texts (key strings are often unquoted, empty keys
849	result in nothing being output)
850
851	Does not check input for validity.
852		1138
853	=back	1139	=back
854		1140
855		1141
856	=head2 JSON and YAML	1142	=head2 JSON and YAML
857		1143
858	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1144	You often hear that JSON is a subset of YAML. This is, however, a mass
859	however, a mass hysteria and very far from the truth. In general, there is	1145	hysteria(*) and very far from the truth (as of the time of this writing),
860	no way to configure JSON::XS to output a data structure as valid YAML.	1146	so let me state it clearly: I<in general, there is no way to configure
		1147	JSON::XS to output a data structure as valid YAML> that works in all
		1148	cases.
861		1149
862	If you really must use JSON::XS to generate YAML, you should use this	1150	If you really must use JSON::XS to generate YAML, you should use this
863	algorithm (subject to change in future versions):	1151	algorithm (subject to change in future versions):
864		1152
865	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1153	my $to_yaml = JSON::XS->new->utf8->space_after (1);
866	my $yaml = $to_yaml->encode ($ref) . "\n";	1154	my $yaml = $to_yaml->encode ($ref) . "\n";
867		1155
868	This will usually generate JSON texts that also parse as valid	1156	This will I<usually> generate JSON texts that also parse as valid
869	YAML. Please note that YAML has hardcoded limits on (simple) object key	1157	YAML. Please note that YAML has hardcoded limits on (simple) object key
870	lengths that JSON doesn't have, so you should make sure that your hash	1158	lengths that JSON doesn't have and also has different and incompatible
		1159	unicode handling, so you should make sure that your hash keys are
871	keys are noticably shorter than the 1024 characters YAML allows.	1160	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1161	you do not have characters with codepoint values outside the Unicode BMP
		1162	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1163	strings (which JSON::XS does not I<currently> generate, but other JSON
		1164	generators might).
872		1165
873	There might be other incompatibilities that I am not aware of. In general	1166	There might be other incompatibilities that I am not aware of (or the YAML
		1167	specification has been changed yet again - it does so quite often). In
874	you should not try to generate YAML with a JSON generator or vice versa,	1168	general you should not try to generate YAML with a JSON generator or vice
875	or try to parse JSON with a YAML parser or vice versa: chances are high	1169	versa, or try to parse JSON with a YAML parser or vice versa: chances are
876	that you will run into severe interoperability problems.	1170	high that you will run into severe interoperability problems when you
		1171	least expect it.
		1172
		1173	=over 4
		1174
		1175	=item (*)
		1176
		1177	I have been pressured multiple times by Brian Ingerson (one of the
		1178	authors of the YAML specification) to remove this paragraph, despite him
		1179	acknowledging that the actual incompatibilities exist. As I was personally
		1180	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1181	educate people about these issues, so others do not run into the same
		1182	problem again and again. After this, Brian called me a (quote)I<complete
		1183	and worthless idiot>(unquote).
		1184
		1185	In my opinion, instead of pressuring and insulting people who actually
		1186	clarify issues with YAML and the wrong statements of some of its
		1187	proponents, I would kindly suggest reading the JSON spec (which is not
		1188	that difficult or long) and finally make YAML compatible to it, and
		1189	educating users about the changes, instead of spreading lies about the
		1190	real compatibility for many I<years> and trying to silence people who
		1191	point out that it isn't true.
		1192
		1193	=back
877		1194
878		1195
879	=head2 SPEED	1196	=head2 SPEED
880		1197
881	It seems that JSON::XS is surprisingly fast, as shown in the following	1198	It seems that JSON::XS is surprisingly fast, as shown in the following
882	tables. They have been generated with the help of the C<eg/bench> program	1199	tables. They have been generated with the help of the C<eg/bench> program
883	in the JSON::XS distribution, to make it easy to compare on your own	1200	in the JSON::XS distribution, to make it easy to compare on your own
884	system.	1201	system.
885		1202
886	First comes a comparison between various modules using a very short	1203	First comes a comparison between various modules using
887	single-line JSON string:	1204	a very short single-line JSON string (also available at
		1205	L<http://dist.schmorp.de/misc/json/short.json>).
888		1206
889	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1207	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
890	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1208	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
891		1209
892	It shows the number of encodes/decodes per second (JSON::XS uses	1210	It shows the number of encodes/decodes per second (JSON::XS uses
893	the functional interface, while JSON::XS/2 uses the OO interface	1211	the functional interface, while JSON::XS/2 uses the OO interface
894	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1212	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
895	shrink). Higher is better:	1213	shrink). Higher is better:
896		1214
897	Storable \| 15779.925 \| 14169.946 \|
898	-----------+------------+------------+
899	module \| encode \| decode \|	1215	module \| encode \| decode \|
900	-----------\|------------\|------------\|	1216	-----------\|------------\|------------\|
901	JSON \| 4990.842 \| 4088.813 \|	1217	JSON 1.x \| 4990.842 \| 4088.813 \|
902	JSON::DWIW \| 51653.990 \| 71575.154 \|	1218	JSON::DWIW \| 51653.990 \| 71575.154 \|
903	JSON::PC \| 65948.176 \| 74631.744 \|	1219	JSON::PC \| 65948.176 \| 74631.744 \|
904	JSON::PP \| 8931.652 \| 3817.168 \|	1220	JSON::PP \| 8931.652 \| 3817.168 \|
905	JSON::Syck \| 24877.248 \| 27776.848 \|	1221	JSON::Syck \| 24877.248 \| 27776.848 \|
906	JSON::XS \| 388361.481 \| 227951.304 \|	1222	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
908	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1224	JSON::XS/3 \| 338250.323 \| 218453.333 \|
909	Storable \| 16500.016 \| 135300.129 \|	1225	Storable \| 16500.016 \| 135300.129 \|
910	-----------+------------+------------+	1226	-----------+------------+------------+
911		1227
912	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1228	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
913	about three times faster on decoding, and over fourty times faster	1229	about three times faster on decoding, and over forty times faster
914	than JSON, even with pretty-printing and key sorting. It also compares	1230	than JSON, even with pretty-printing and key sorting. It also compares
915	favourably to Storable for small amounts of data.	1231	favourably to Storable for small amounts of data.
916		1232
917	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1233	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
918	search API (http://nanoref.com/yahooapis/mgPdGg):	1234	search API (L<http://dist.schmorp.de/misc/json/long.json>).
919		1235
920	module \| encode \| decode \|	1236	module \| encode \| decode \|
921	-----------\|------------\|------------\|	1237	-----------\|------------\|------------\|
922	JSON \| 55.260 \| 34.971 \|	1238	JSON 1.x \| 55.260 \| 34.971 \|
923	JSON::DWIW \| 825.228 \| 1082.513 \|	1239	JSON::DWIW \| 825.228 \| 1082.513 \|
924	JSON::PC \| 3571.444 \| 2394.829 \|	1240	JSON::PC \| 3571.444 \| 2394.829 \|
925	JSON::PP \| 210.987 \| 32.574 \|	1241	JSON::PP \| 210.987 \| 32.574 \|
926	JSON::Syck \| 552.551 \| 787.544 \|	1242	JSON::Syck \| 552.551 \| 787.544 \|
927	JSON::XS \| 5780.463 \| 4854.519 \|	1243	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
931	-----------+------------+------------+	1247	-----------+------------+------------+
932		1248
933	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1249	Again, JSON::XS leads by far (except for Storable which non-surprisingly
934	decodes faster).	1250	decodes faster).
935		1251
936	On large strings containing lots of high unicode characters, some modules	1252	On large strings containing lots of high Unicode characters, some modules
937	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1253	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
938	will be broken due to missing (or wrong) unicode handling. Others refuse	1254	will be broken due to missing (or wrong) Unicode handling. Others refuse
939	to decode or encode properly, so it was impossible to prepare a fair	1255	to decode or encode properly, so it was impossible to prepare a fair
940	comparison table for that case.	1256	comparison table for that case.
941		1257
942		1258
943	=head1 SECURITY CONSIDERATIONS	1259	=head1 SECURITY CONSIDERATIONS
…		…
949	any buffer overflows. Obviously, this module should ensure that and I am	1265	any buffer overflows. Obviously, this module should ensure that and I am
950	trying hard on making that true, but you never know.	1266	trying hard on making that true, but you never know.
951		1267
952	Second, you need to avoid resource-starving attacks. That means you should	1268	Second, you need to avoid resource-starving attacks. That means you should
953	limit the size of JSON texts you accept, or make sure then when your	1269	limit the size of JSON texts you accept, or make sure then when your
954	resources run out, thats just fine (e.g. by using a separate process that	1270	resources run out, that's just fine (e.g. by using a separate process that
955	can crash safely). The size of a JSON text in octets or characters is	1271	can crash safely). The size of a JSON text in octets or characters is
956	usually a good indication of the size of the resources required to decode	1272	usually a good indication of the size of the resources required to decode
957	it into a Perl structure. While JSON::XS can check the size of the JSON	1273	it into a Perl structure. While JSON::XS can check the size of the JSON
958	text, it might be too late when you already have it in memory, so you	1274	text, it might be too late when you already have it in memory, so you
959	might want to check the size before you accept the string.	1275	might want to check the size before you accept the string.
960		1276
961	Third, JSON::XS recurses using the C stack when decoding objects and	1277	Third, JSON::XS recurses using the C stack when decoding objects and
962	arrays. The C stack is a limited resource: for instance, on my amd64	1278	arrays. The C stack is a limited resource: for instance, on my amd64
963	machine with 8MB of stack size I can decode around 180k nested arrays but	1279	machine with 8MB of stack size I can decode around 180k nested arrays but
964	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1280	only 14k nested JSON objects (due to perl itself recursing deeply on croak
965	to free the temporary). If that is exceeded, the program crashes. to be	1281	to free the temporary). If that is exceeded, the program crashes. To be
966	conservative, the default nesting limit is set to 512. If your process	1282	conservative, the default nesting limit is set to 512. If your process
967	has a smaller stack, you should adjust this setting accordingly with the	1283	has a smaller stack, you should adjust this setting accordingly with the
968	C<max_depth> method.	1284	C<max_depth> method.
969		1285
970	And last but least, something else could bomb you that I forgot to think	1286	Something else could bomb you, too, that I forgot to think of. In that
971	of. In that case, you get to keep the pieces. I am always open for hints,	1287	case, you get to keep the pieces. I am always open for hints, though...
972	though...	1288
		1289	Also keep in mind that JSON::XS might leak contents of your Perl data
		1290	structures in its error messages, so when you serialise sensitive
		1291	information you might want to make sure that exceptions thrown by JSON::XS
		1292	will not end up in front of untrusted eyes.
973		1293
974	If you are using JSON::XS to return packets to consumption	1294	If you are using JSON::XS to return packets to consumption
975	by javascript scripts in a browser you should have a look at	1295	by JavaScript scripts in a browser you should have a look at
976	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1296	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
977	you are vulnerable to some common attack vectors (which really are browser	1297	you are vulnerable to some common attack vectors (which really are browser
978	design bugs, but it is still you who will have to deal with it, as major	1298	design bugs, but it is still you who will have to deal with it, as major
979	browser developers care only for features, not about doing security	1299	browser developers care only for features, not about getting security
980	right).	1300	right).
981		1301
982		1302
983	=head1 THREADS	1303	=head1 THREADS
984		1304
985	This module is I<not> guarenteed to be thread safe and there are no	1305	This module is I<not> guaranteed to be thread safe and there are no
986	plans to change this until Perl gets thread support (as opposed to the	1306	plans to change this until Perl gets thread support (as opposed to the
987	horribly slow so-called "threads" which are simply slow and bloated	1307	horribly slow so-called "threads" which are simply slow and bloated
988	process simulations - use fork, its I<much> faster, cheaper, better).	1308	process simulations - use fork, it's I<much> faster, cheaper, better).
989		1309
990	(It might actually work, but you ahve ben warned).	1310	(It might actually work, but you have been warned).
991		1311
992		1312
993	=head1 BUGS	1313	=head1 BUGS
994		1314
995	While the goal of this module is to be correct, that unfortunately does	1315	While the goal of this module is to be correct, that unfortunately does
996	not mean its bug-free, only that I think its design is bug-free. It is	1316	not mean it's bug-free, only that I think its design is bug-free. It is
997	still relatively early in its development. If you keep reporting bugs they	1317	still relatively early in its development. If you keep reporting bugs they
998	will be fixed swiftly, though.	1318	will be fixed swiftly, though.
999		1319
1000	Please refrain from using rt.cpan.org or any other bug reporting	1320	Please refrain from using rt.cpan.org or any other bug reporting
1001	service. I put the contact address into my modules for a reason.	1321	service. I put the contact address into my modules for a reason.
…		…
1023	"--" => sub { $_[0] = ${$_[0]} - 1 },	1343	"--" => sub { $_[0] = ${$_[0]} - 1 },
1024	fallback => 1;	1344	fallback => 1;
1025		1345
1026	1;	1346	1;
1027		1347
		1348	=head1 SEE ALSO
		1349
		1350	The F<json_xs> command line utility for quick experiments.
		1351
1028	=head1 AUTHOR	1352	=head1 AUTHOR
1029		1353
1030	Marc Lehmann <schmorp@schmorp.de>	1354	Marc Lehmann <schmorp@schmorp.de>
1031	http://home.schmorp.de/	1355	http://home.schmorp.de/
1032		1356

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Revision 1.95 by root, Tue Mar 25 16:56:09 2008 UTC