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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.93 by root, Sat Mar 22 22:21:33 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 (a simple scalar or a reference to	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
109	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	136	(that is, the string contains octets only). Croaks on error.
110	octets only). Croaks on error.
111		137
112	This function call is functionally identical to:	138	This function call is functionally identical to:
113		139
114	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115		141
116	except being faster.	142	except being faster.
117		143
118	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
119		145
120	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
121	parse that as an UTF-8 encoded JSON text, returning the resulting simple	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
122	scalar or reference. Croaks on error.	148	reference. Croaks on error.
123		149
124	This function call is functionally identical to:	150	This function call is functionally identical to:
125		151
126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127		153
…		…
137	Perl.	163	Perl.
138		164
139	=back	165	=back
140		166
141		167
		168	=head1 A FEW NOTES ON UNICODE AND PERL
		169
		170	Since this often leads to confusion, here are a few very clear words on
		171	how Unicode works in Perl, modulo bugs.
		172
		173	=over 4
		174
		175	=item 1. Perl strings can store characters with ordinal values > 255.
		176
		177	This enables you to store Unicode characters as single characters in a
		178	Perl string - very natural.
		179
		180	=item 2. Perl does I<not> associate an encoding with your strings.
		181
		182	... until you force it to, e.g. when matching it against a regex, or
		183	printing the scalar to a file, in which case Perl either interprets your
		184	string as locale-encoded text, octets/binary, or as Unicode, depending
		185	on various settings. In no case is an encoding stored together with your
		186	data, it is I<use> that decides encoding, not any magical meta data.
		187
		188	=item 3. The internal utf-8 flag has no meaning with regards to the
		189	encoding of your string.
		190
		191	Just ignore that flag unless you debug a Perl bug, a module written in
		192	XS or want to dive into the internals of perl. Otherwise it will only
		193	confuse you, as, despite the name, it says nothing about how your string
		194	is encoded. You can have Unicode strings with that flag set, with that
		195	flag clear, and you can have binary data with that flag set and that flag
		196	clear. Other possibilities exist, too.
		197
		198	If you didn't know about that flag, just the better, pretend it doesn't
		199	exist.
		200
		201	=item 4. A "Unicode String" is simply a string where each character can be
		202	validly interpreted as a Unicode codepoint.
		203
		204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		205	Unicode string encoded in UTF-8, giving you a binary string.
		206
		207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		208
		209	It's a fact. Learn to live with it.
		210
		211	=back
		212
		213	I hope this helps :)
		214
		215
142	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
143		217
144	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
145	decoding style, within the limits of supported formats.	219	decoding style, within the limits of supported formats.
146		220
…		…
157	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]})
158	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
159		233
160	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
161		235
		236	=item $enabled = $json->get_ascii
		237
162	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
163	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
164	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
165	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
166	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
167	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
168	or any other superset of ASCII.	244	or any other superset of ASCII.
169		245
170	If C<$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
171	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
172	in a faster and more compact format.	248	in a faster and more compact format.
173		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
174	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
175	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
176	contain any 8 bit characters.	255	contain any 8 bit characters.
177		256
178	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
179	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
180		259
181	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
182		261
		262	=item $enabled = $json->get_latin1
		263
183	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
184	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
185	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
186	latin1-encoded JSON text or a native unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
187	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
188	expects unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
189		270
190	If C<$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
191	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.
192		276
193	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
194	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
195	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
196	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
197	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
198	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
199	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.
200		284
201	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
202	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
203		287
204	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
205		291
206	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
207	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
208	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
209	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
210	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
211	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
212	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
213		299
214	If C<$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
215	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
216	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
217	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.
218		307
219	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
220		309
221	use Encode;	310	use Encode;
222	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
243	]	332	]
244	}	333	}
245		334
246	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
247		336
		337	=item $enabled = $json->get_indent
		338
248	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
249	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
250	into its own line, identing them properly.	341	into its own line, indenting them properly.
251		342
252	If C<$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
253	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
254		345
255	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
256		347
257	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
258		351
259	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
260	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
261		354
262	If C<$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
…		…
268	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
269		362
270	{"key" :"value"}	363	{"key" :"value"}
271		364
272	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
273		368
274	If C<$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
275	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
276	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
277	members.	372	members.
…		…
284	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
285		380
286	{"key": "value"}	381	{"key": "value"}
287		382
288	=item $json = $json->relaxed ([$enable])	383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
289		386
290	If C<$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
291	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
292	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
293	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
…		…
330		427
331	=back	428	=back
332		429
333	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
334		431
		432	=item $enabled = $json->get_canonical
		433
335	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
336	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
337		436
338	If C<$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
339	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
340	of the same script).	439	of the same script).
341		440
342	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
343	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,
344	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,
345	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
346		445
347	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
348		447
349	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
350		451
351	If C<$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
352	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
353	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
354	values instead of croaking.	455	values instead of croaking.
…		…
364	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
365	=> "Hello, World!"	466	=> "Hello, World!"
366		467
367	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
368		469
		470	=item $enabled = $json->get_allow_blessed
		471
369	If C<$enable> is true (or missing), then the C<encode> method will not	472	If C<$enable> is true (or missing), then the C<encode> method will not
370	barf when it encounters a blessed reference. Instead, the value of the	473	barf when it encounters a blessed reference. Instead, the value of the
371	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
372	disabled or no C<to_json> method found) or a representation of the	475	disabled or no C<TO_JSON> method found) or a representation of the
373	object (C<convert_blessed> enabled and C<to_json> method found) is being	476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
374	encoded. Has no effect on C<decode>.	477	encoded. Has no effect on C<decode>.
375		478
376	If C<$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
377	exception when it encounters a blessed object.	480	exception when it encounters a blessed object.
378		481
379	=item $json = $json->convert_blessed ([$enable])	482	=item $json = $json->convert_blessed ([$enable])
		483
		484	=item $enabled = $json->get_convert_blessed
380		485
381	If C<$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
382	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
383	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
384	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
…		…
388	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>
389	returns other blessed objects, those will be handled in the same	494	returns other blessed objects, those will be handled in the same
390	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
391	(== 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
392	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
393	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>
394	function.	499	function or method.
395		500
396	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
397	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
398	enabled by this setting.	503	enabled by this setting.
399		504
…		…
441		546
442	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>
443	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
444	objects make excellent targets to serialise Perl objects into, especially	549	objects make excellent targets to serialise Perl objects into, especially
445	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
446	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
447	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
448	like a serialised Perl hash.	553	like a serialised Perl hash.
449		554
450	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
451	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
…		…
475		580
476	{ __widget__ => $self->{id} }	581	{ __widget__ => $self->{id} }
477	}	582	}
478		583
479	=item $json = $json->shrink ([$enable])	584	=item $json = $json->shrink ([$enable])
		585
		586	=item $enabled = $json->get_shrink
480		587
481	Perl usually over-allocates memory a bit when allocating space for	588	Perl usually over-allocates memory a bit when allocating space for
482	strings. This flag optionally resizes strings generated by either	589	strings. This flag optionally resizes strings generated by either
483	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
484	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
…		…
502	strings that look like integers or floats into integers or floats	609	strings that look like integers or floats into integers or floats
503	internally (there is no difference on the Perl level), saving space.	610	internally (there is no difference on the Perl level), saving space.
504		611
505	=item $json = $json->max_depth ([$maximum_nesting_depth])	612	=item $json = $json->max_depth ([$maximum_nesting_depth])
506		613
		614	=item $max_depth = $json->get_max_depth
		615
507	Sets the maximum nesting level (default C<512>) accepted while encoding	616	Sets the maximum nesting level (default C<512>) accepted while encoding
508	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
509	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
510	stop and croak at that point.	619	stop and croak at that point.
511		620
…		…
522	used, which is rarely useful.	631	used, which is rarely useful.
523		632
524	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.
525		634
526	=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
527		638
528	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
529	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>
530	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
531	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
…		…
578	vice versa. These mappings are designed to "do the right thing" in most	689	vice versa. These mappings are designed to "do the right thing" in most
579	circumstances automatically, preserving round-tripping characteristics	690	circumstances automatically, preserving round-tripping characteristics
580	(what you put in comes out as something equivalent).	691	(what you put in comes out as something equivalent).
581		692
582	For the more enlightened: note that in the following descriptions,	693	For the more enlightened: note that in the following descriptions,
583	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	694	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
584	refers to the abstract Perl language itself.	695	refers to the abstract Perl language itself.
585		696
586		697
587	=head2 JSON -> PERL	698	=head2 JSON -> PERL
588		699
589	=over 4	700	=over 4
590		701
591	=item object	702	=item object
592		703
593	A JSON object becomes a reference to a hash in Perl. No ordering of object	704	A JSON object becomes a reference to a hash in Perl. No ordering of object
594	keys is preserved (JSON does not preserver object key ordering itself).	705	keys is preserved (JSON does not preserve object key ordering itself).
595		706
596	=item array	707	=item array
597		708
598	A JSON array becomes a reference to an array in Perl.	709	A JSON array becomes a reference to an array in Perl.
599		710
…		…
607		718
608	A JSON number becomes either an integer, numeric (floating point) or	719	A JSON number becomes either an integer, numeric (floating point) or
609	string scalar in perl, depending on its range and any fractional parts. On	720	string scalar in perl, depending on its range and any fractional parts. On
610	the Perl level, there is no difference between those as Perl handles all	721	the Perl level, there is no difference between those as Perl handles all
611	the conversion details, but an integer may take slightly less memory and	722	the conversion details, but an integer may take slightly less memory and
612	might represent more values exactly than (floating point) numbers.	723	might represent more values exactly than floating point numbers.
613		724
614	If the number consists of digits only, JSON::XS will try to represent	725	If the number consists of digits only, JSON::XS will try to represent
615	it as an integer value. If that fails, it will try to represent it as	726	it as an integer value. If that fails, it will try to represent it as
616	a numeric (floating point) value if that is possible without loss of	727	a numeric (floating point) value if that is possible without loss of
617	precision. Otherwise it will preserve the number as a string value.	728	precision. Otherwise it will preserve the number as a string value (in
		729	which case you lose roundtripping ability, as the JSON number will be
		730	re-encoded toa JSON string).
618		731
619	Numbers containing a fractional or exponential part will always be	732	Numbers containing a fractional or exponential part will always be
620	represented as numeric (floating point) values, possibly at a loss of	733	represented as numeric (floating point) values, possibly at a loss of
621	precision.	734	precision (in which case you might lose perfect roundtripping ability, but
622		735	the JSON number will still be re-encoded as a JSON number).
623	This might create round-tripping problems as numbers might become strings,
624	but as Perl is typeless there is no other way to do it.
625		736
626	=item true, false	737	=item true, false
627		738
628	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	739	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
629	respectively. They are overloaded to act almost exactly like the numbers	740	respectively. They are overloaded to act almost exactly like the numbers
630	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	741	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
631	the C<JSON::XS::is_bool> function.	742	the C<JSON::XS::is_bool> function.
632		743
633	=item null	744	=item null
634		745
635	A JSON null atom becomes C<undef> in Perl.	746	A JSON null atom becomes C<undef> in Perl.
…		…
666	Other unblessed references are generally not allowed and will cause an	777	Other unblessed references are generally not allowed and will cause an
667	exception to be thrown, except for references to the integers C<0> and	778	exception to be thrown, except for references to the integers C<0> and
668	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	779	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
669	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	780	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
670		781
671	to_json [\0,JSON::XS::true] # yields [false,true]	782	encode_json [\0,JSON::XS::true] # yields [false,true]
672		783
673	=item JSON::XS::true, JSON::XS::false	784	=item JSON::XS::true, JSON::XS::false
674		785
675	These special values become JSON true and JSON false values,	786	These special values become JSON true and JSON false values,
676	respectively. You can also use C<\1> and C<\0> directly if you want.	787	respectively. You can also use C<\1> and C<\0> directly if you want.
677		788
678	=item blessed objects	789	=item blessed objects
679		790
680	Blessed objects are not allowed. JSON::XS currently tries to encode their	791	Blessed objects are not directly representable in JSON. See the
681	underlying representation (hash- or arrayref), but this behaviour might	792	C<allow_blessed> and C<convert_blessed> methods on various options on
682	change in future versions.	793	how to deal with this: basically, you can choose between throwing an
		794	exception, encoding the reference as if it weren't blessed, or provide
		795	your own serialiser method.
683		796
684	=item simple scalars	797	=item simple scalars
685		798
686	Simple Perl scalars (any scalar that is not a reference) are the most	799	Simple Perl scalars (any scalar that is not a reference) are the most
687	difficult objects to encode: JSON::XS will encode undefined scalars as	800	difficult objects to encode: JSON::XS will encode undefined scalars as
688	JSON null value, scalars that have last been used in a string context	801	JSON C<null> values, scalars that have last been used in a string context
689	before encoding as JSON strings and anything else as number value:	802	before encoding as JSON strings, and anything else as number value:
690		803
691	# dump as number	804	# dump as number
692	to_json [2] # yields [2]	805	encode_json [2] # yields [2]
693	to_json [-3.0e17] # yields [-3e+17]	806	encode_json [-3.0e17] # yields [-3e+17]
694	my $value = 5; to_json [$value] # yields [5]	807	my $value = 5; encode_json [$value] # yields [5]
695		808
696	# used as string, so dump as string	809	# used as string, so dump as string
697	print $value;	810	print $value;
698	to_json [$value] # yields ["5"]	811	encode_json [$value] # yields ["5"]
699		812
700	# undef becomes null	813	# undef becomes null
701	to_json [undef] # yields [null]	814	encode_json [undef] # yields [null]
702		815
703	You can force the type to be a string by stringifying it:	816	You can force the type to be a JSON string by stringifying it:
704		817
705	my $x = 3.1; # some variable containing a number	818	my $x = 3.1; # some variable containing a number
706	"$x"; # stringified	819	"$x"; # stringified
707	$x .= ""; # another, more awkward way to stringify	820	$x .= ""; # another, more awkward way to stringify
708	print $x; # perl does it for you, too, quite often	821	print $x; # perl does it for you, too, quite often
709		822
710	You can force the type to be a number by numifying it:	823	You can force the type to be a JSON number by numifying it:
711		824
712	my $x = "3"; # some variable containing a string	825	my $x = "3"; # some variable containing a string
713	$x += 0; # numify it, ensuring it will be dumped as a number	826	$x += 0; # numify it, ensuring it will be dumped as a number
714	$x *= 1; # same thing, the choise is yours.	827	$x *= 1; # same thing, the choice is yours.
715		828
716	You can not currently output JSON booleans or force the type in other,	829	You can not currently force the type in other, less obscure, ways. Tell me
717	less obscure, ways. Tell me if you need this capability.	830	if you need this capability (but don't forget to explain why it's needed
		831	:).
		832
		833	=back
		834
		835
		836	=head1 ENCODING/CODESET FLAG NOTES
		837
		838	The interested reader might have seen a number of flags that signify
		839	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		840	some confusion on what these do, so here is a short comparison:
		841
		842	C<utf8> controls whether the JSON text created by C<encode> (and expected
		843	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		844	control whether C<encode> escapes character values outside their respective
		845	codeset range. Neither of these flags conflict with each other, although
		846	some combinations make less sense than others.
		847
		848	Care has been taken to make all flags symmetrical with respect to
		849	C<encode> and C<decode>, that is, texts encoded with any combination of
		850	these flag values will be correctly decoded when the same flags are used
		851	- in general, if you use different flag settings while encoding vs. when
		852	decoding you likely have a bug somewhere.
		853
		854	Below comes a verbose discussion of these flags. Note that a "codeset" is
		855	simply an abstract set of character-codepoint pairs, while an encoding
		856	takes those codepoint numbers and I<encodes> them, in our case into
		857	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		858	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		859	the same time, which can be confusing.
		860
		861	=over 4
		862
		863	=item C<utf8> flag disabled
		864
		865	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		866	and expect Unicode strings, that is, characters with high ordinal Unicode
		867	values (> 255) will be encoded as such characters, and likewise such
		868	characters are decoded as-is, no canges to them will be done, except
		869	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		870	respectively (to Perl, these are the same thing in strings unless you do
		871	funny/weird/dumb stuff).
		872
		873	This is useful when you want to do the encoding yourself (e.g. when you
		874	want to have UTF-16 encoded JSON texts) or when some other layer does
		875	the encoding for you (for example, when printing to a terminal using a
		876	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		877	to UTF-8 encode your data first and have Perl encode it another time).
		878
		879	=item C<utf8> flag enabled
		880
		881	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		882	characters using the corresponding UTF-8 multi-byte sequence, and will
		883	expect your input strings to be encoded as UTF-8, that is, no "character"
		884	of the input string must have any value > 255, as UTF-8 does not allow
		885	that.
		886
		887	The C<utf8> flag therefore switches between two modes: disabled means you
		888	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		889	octet/binary string in Perl.
		890
		891	=item C<latin1> or C<ascii> flags enabled
		892
		893	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		894	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		895	characters as specified by the C<utf8> flag.
		896
		897	If C<utf8> is disabled, then the result is also correctly encoded in those
		898	character sets (as both are proper subsets of Unicode, meaning that a
		899	Unicode string with all character values < 256 is the same thing as a
		900	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		901	the same thing as an ASCII string in Perl).
		902
		903	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		904	regardless of these flags, just some more characters will be escaped using
		905	C<\uXXXX> then before.
		906
		907	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		908	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		909	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		910	a subset of Unicode), while ASCII is.
		911
		912	Surprisingly, C<decode> will ignore these flags and so treat all input
		913	values as governed by the C<utf8> flag. If it is disabled, this allows you
		914	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		915	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		916
		917	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		918	they only govern when the JSON output engine escapes a character or not.
		919
		920	The main use for C<latin1> is to relatively efficiently store binary data
		921	as JSON, at the expense of breaking compatibility with most JSON decoders.
		922
		923	The main use for C<ascii> is to force the output to not contain characters
		924	with values > 127, which means you can interpret the resulting string
		925	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		926	8-bit-encoding, and still get the same data structure back. This is useful
		927	when your channel for JSON transfer is not 8-bit clean or the encoding
		928	might be mangled in between (e.g. in mail), and works because ASCII is a
		929	proper subset of most 8-bit and multibyte encodings in use in the world.
718		930
719	=back	931	=back
720		932
721		933
722	=head1 COMPARISON	934	=head1 COMPARISON
…		…
727	followed by some benchmark values. JSON::XS was designed not to suffer	939	followed by some benchmark values. JSON::XS was designed not to suffer
728	from any of these problems or limitations.	940	from any of these problems or limitations.
729		941
730	=over 4	942	=over 4
731		943
		944	=item JSON 2.xx
		945
		946	A marvellous piece of engineering, this module either uses JSON::XS
		947	directly when available (so will be 100% compatible with it, including
		948	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		949	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		950	slower.
		951
		952	You cannot really lose by using this module, especially as it tries very
		953	hard to work even with ancient Perl versions, while JSON::XS does not.
		954
732	=item JSON 1.07	955	=item JSON 1.07
733		956
734	Slow (but very portable, as it is written in pure Perl).	957	Slow (but very portable, as it is written in pure Perl).
735		958
736	Undocumented/buggy Unicode handling (how JSON handles unicode values is	959	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
737	undocumented. One can get far by feeding it unicode strings and doing	960	undocumented. One can get far by feeding it Unicode strings and doing
738	en-/decoding oneself, but unicode escapes are not working properly).	961	en-/decoding oneself, but Unicode escapes are not working properly).
739		962
740	No roundtripping (strings get clobbered if they look like numbers, e.g.	963	No round-tripping (strings get clobbered if they look like numbers, e.g.
741	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	964	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
742	decode into the number 2.	965	decode into the number 2.
743		966
744	=item JSON::PC 0.01	967	=item JSON::PC 0.01
745		968
746	Very fast.	969	Very fast.
747		970
748	Undocumented/buggy Unicode handling.	971	Undocumented/buggy Unicode handling.
749		972
750	No roundtripping.	973	No round-tripping.
751		974
752	Has problems handling many Perl values (e.g. regex results and other magic	975	Has problems handling many Perl values (e.g. regex results and other magic
753	values will make it croak).	976	values will make it croak).
754		977
755	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	978	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
765	Very inflexible (no human-readable format supported, format pretty much	988	Very inflexible (no human-readable format supported, format pretty much
766	undocumented. I need at least a format for easy reading by humans and a	989	undocumented. I need at least a format for easy reading by humans and a
767	single-line compact format for use in a protocol, and preferably a way to	990	single-line compact format for use in a protocol, and preferably a way to
768	generate ASCII-only JSON texts).	991	generate ASCII-only JSON texts).
769		992
770	Completely broken (and confusingly documented) Unicode handling (unicode	993	Completely broken (and confusingly documented) Unicode handling (Unicode
771	escapes are not working properly, you need to set ImplicitUnicode to	994	escapes are not working properly, you need to set ImplicitUnicode to
772	I<different> values on en- and decoding to get symmetric behaviour).	995	I<different> values on en- and decoding to get symmetric behaviour).
773		996
774	No roundtripping (simple cases work, but this depends on wether the scalar	997	No round-tripping (simple cases work, but this depends on whether the scalar
775	value was used in a numeric context or not).	998	value was used in a numeric context or not).
776		999
777	Dumping hashes may skip hash values depending on iterator state.	1000	Dumping hashes may skip hash values depending on iterator state.
778		1001
779	Unmaintained (maintainer unresponsive for many months, bugs are not	1002	Unmaintained (maintainer unresponsive for many months, bugs are not
780	getting fixed).	1003	getting fixed).
781		1004
782	Does not check input for validity (i.e. will accept non-JSON input and	1005	Does not check input for validity (i.e. will accept non-JSON input and
783	return "something" instead of raising an exception. This is a security	1006	return "something" instead of raising an exception. This is a security
784	issue: imagine two banks transfering money between each other using	1007	issue: imagine two banks transferring money between each other using
785	JSON. One bank might parse a given non-JSON request and deduct money,	1008	JSON. One bank might parse a given non-JSON request and deduct money,
786	while the other might reject the transaction with a syntax error. While a	1009	while the other might reject the transaction with a syntax error. While a
787	good protocol will at least recover, that is extra unnecessary work and	1010	good protocol will at least recover, that is extra unnecessary work and
788	the transaction will still not succeed).	1011	the transaction will still not succeed).
789		1012
790	=item JSON::DWIW 0.04	1013	=item JSON::DWIW 0.04
791		1014
792	Very fast. Very natural. Very nice.	1015	Very fast. Very natural. Very nice.
793		1016
794	Undocumented unicode handling (but the best of the pack. Unicode escapes	1017	Undocumented Unicode handling (but the best of the pack. Unicode escapes
795	still don't get parsed properly).	1018	still don't get parsed properly).
796		1019
797	Very inflexible.	1020	Very inflexible.
798		1021
799	No roundtripping.	1022	No round-tripping.
800		1023
801	Does not generate valid JSON texts (key strings are often unquoted, empty keys	1024	Does not generate valid JSON texts (key strings are often unquoted, empty keys
802	result in nothing being output)	1025	result in nothing being output)
803		1026
804	Does not check input for validity.	1027	Does not check input for validity.
…		…
806	=back	1029	=back
807		1030
808		1031
809	=head2 JSON and YAML	1032	=head2 JSON and YAML
810		1033
811	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1034	You often hear that JSON is a subset of YAML. This is, however, a mass
812	however, a mass hysteria and very far from the truth. In general, there is	1035	hysteria(*) and very far from the truth (as of the time of this writing),
813	no way to configure JSON::XS to output a data structure as valid YAML.	1036	so let me state it clearly: I<in general, there is no way to configure
		1037	JSON::XS to output a data structure as valid YAML> that works in all
		1038	cases.
814		1039
815	If you really must use JSON::XS to generate YAML, you should use this	1040	If you really must use JSON::XS to generate YAML, you should use this
816	algorithm (subject to change in future versions):	1041	algorithm (subject to change in future versions):
817		1042
818	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1043	my $to_yaml = JSON::XS->new->utf8->space_after (1);
819	my $yaml = $to_yaml->encode ($ref) . "\n";	1044	my $yaml = $to_yaml->encode ($ref) . "\n";
820		1045
821	This will usually generate JSON texts that also parse as valid	1046	This will I<usually> generate JSON texts that also parse as valid
822	YAML. Please note that YAML has hardcoded limits on (simple) object key	1047	YAML. Please note that YAML has hardcoded limits on (simple) object key
823	lengths that JSON doesn't have, so you should make sure that your hash	1048	lengths that JSON doesn't have and also has different and incompatible
		1049	unicode handling, so you should make sure that your hash keys are
824	keys are noticably shorter than the 1024 characters YAML allows.	1050	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1051	you do not have characters with codepoint values outside the Unicode BMP
		1052	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1053	strings (which JSON::XS does not I<currently> generate, but other JSON
		1054	generators might).
825		1055
826	There might be other incompatibilities that I am not aware of. In general	1056	There might be other incompatibilities that I am not aware of (or the YAML
		1057	specification has been changed yet again - it does so quite often). In
827	you should not try to generate YAML with a JSON generator or vice versa,	1058	general you should not try to generate YAML with a JSON generator or vice
828	or try to parse JSON with a YAML parser or vice versa: chances are high	1059	versa, or try to parse JSON with a YAML parser or vice versa: chances are
829	that you will run into severe interoperability problems.	1060	high that you will run into severe interoperability problems when you
		1061	least expect it.
		1062
		1063	=over 4
		1064
		1065	=item (*)
		1066
		1067	I have been pressured multiple times by Brian Ingerson (one of the
		1068	authors of the YAML specification) to remove this paragraph, despite him
		1069	acknowledging that the actual incompatibilities exist. As I was personally
		1070	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1071	educate people about these issues, so others do not run into the same
		1072	problem again and again. After this, Brian called me a (quote)I<complete
		1073	and worthless idiot>(unquote).
		1074
		1075	In my opinion, instead of pressuring and insulting people who actually
		1076	clarify issues with YAML and the wrong statements of some of its
		1077	proponents, I would kindly suggest reading the JSON spec (which is not
		1078	that difficult or long) and finally make YAML compatible to it, and
		1079	educating users about the changes, instead of spreading lies about the
		1080	real compatibility for many I<years> and trying to silence people who
		1081	point out that it isn't true.
		1082
		1083	=back
830		1084
831		1085
832	=head2 SPEED	1086	=head2 SPEED
833		1087
834	It seems that JSON::XS is surprisingly fast, as shown in the following	1088	It seems that JSON::XS is surprisingly fast, as shown in the following
835	tables. They have been generated with the help of the C<eg/bench> program	1089	tables. They have been generated with the help of the C<eg/bench> program
836	in the JSON::XS distribution, to make it easy to compare on your own	1090	in the JSON::XS distribution, to make it easy to compare on your own
837	system.	1091	system.
838		1092
839	First comes a comparison between various modules using a very short	1093	First comes a comparison between various modules using
840	single-line JSON string:	1094	a very short single-line JSON string (also available at
		1095	L<http://dist.schmorp.de/misc/json/short.json>).
841		1096
842	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1097	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
843	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1098	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
844		1099
845	It shows the number of encodes/decodes per second (JSON::XS uses	1100	It shows the number of encodes/decodes per second (JSON::XS uses
846	the functional interface, while JSON::XS/2 uses the OO interface	1101	the functional interface, while JSON::XS/2 uses the OO interface
847	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1102	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
848	shrink). Higher is better:	1103	shrink). Higher is better:
849		1104
850	Storable \| 15779.925 \| 14169.946 \|
851	-----------+------------+------------+
852	module \| encode \| decode \|	1105	module \| encode \| decode \|
853	-----------\|------------\|------------\|	1106	-----------\|------------\|------------\|
854	JSON \| 4990.842 \| 4088.813 \|	1107	JSON 1.x \| 4990.842 \| 4088.813 \|
855	JSON::DWIW \| 51653.990 \| 71575.154 \|	1108	JSON::DWIW \| 51653.990 \| 71575.154 \|
856	JSON::PC \| 65948.176 \| 74631.744 \|	1109	JSON::PC \| 65948.176 \| 74631.744 \|
857	JSON::PP \| 8931.652 \| 3817.168 \|	1110	JSON::PP \| 8931.652 \| 3817.168 \|
858	JSON::Syck \| 24877.248 \| 27776.848 \|	1111	JSON::Syck \| 24877.248 \| 27776.848 \|
859	JSON::XS \| 388361.481 \| 227951.304 \|	1112	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
861	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1114	JSON::XS/3 \| 338250.323 \| 218453.333 \|
862	Storable \| 16500.016 \| 135300.129 \|	1115	Storable \| 16500.016 \| 135300.129 \|
863	-----------+------------+------------+	1116	-----------+------------+------------+
864		1117
865	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1118	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
866	about three times faster on decoding, and over fourty times faster	1119	about three times faster on decoding, and over forty times faster
867	than JSON, even with pretty-printing and key sorting. It also compares	1120	than JSON, even with pretty-printing and key sorting. It also compares
868	favourably to Storable for small amounts of data.	1121	favourably to Storable for small amounts of data.
869		1122
870	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1123	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
871	search API (http://nanoref.com/yahooapis/mgPdGg):	1124	search API (L<http://dist.schmorp.de/misc/json/long.json>).
872		1125
873	module \| encode \| decode \|	1126	module \| encode \| decode \|
874	-----------\|------------\|------------\|	1127	-----------\|------------\|------------\|
875	JSON \| 55.260 \| 34.971 \|	1128	JSON 1.x \| 55.260 \| 34.971 \|
876	JSON::DWIW \| 825.228 \| 1082.513 \|	1129	JSON::DWIW \| 825.228 \| 1082.513 \|
877	JSON::PC \| 3571.444 \| 2394.829 \|	1130	JSON::PC \| 3571.444 \| 2394.829 \|
878	JSON::PP \| 210.987 \| 32.574 \|	1131	JSON::PP \| 210.987 \| 32.574 \|
879	JSON::Syck \| 552.551 \| 787.544 \|	1132	JSON::Syck \| 552.551 \| 787.544 \|
880	JSON::XS \| 5780.463 \| 4854.519 \|	1133	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
884	-----------+------------+------------+	1137	-----------+------------+------------+
885		1138
886	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1139	Again, JSON::XS leads by far (except for Storable which non-surprisingly
887	decodes faster).	1140	decodes faster).
888		1141
889	On large strings containing lots of high unicode characters, some modules	1142	On large strings containing lots of high Unicode characters, some modules
890	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1143	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
891	will be broken due to missing (or wrong) unicode handling. Others refuse	1144	will be broken due to missing (or wrong) Unicode handling. Others refuse
892	to decode or encode properly, so it was impossible to prepare a fair	1145	to decode or encode properly, so it was impossible to prepare a fair
893	comparison table for that case.	1146	comparison table for that case.
894		1147
895		1148
896	=head1 SECURITY CONSIDERATIONS	1149	=head1 SECURITY CONSIDERATIONS
…		…
902	any buffer overflows. Obviously, this module should ensure that and I am	1155	any buffer overflows. Obviously, this module should ensure that and I am
903	trying hard on making that true, but you never know.	1156	trying hard on making that true, but you never know.
904		1157
905	Second, you need to avoid resource-starving attacks. That means you should	1158	Second, you need to avoid resource-starving attacks. That means you should
906	limit the size of JSON texts you accept, or make sure then when your	1159	limit the size of JSON texts you accept, or make sure then when your
907	resources run out, thats just fine (e.g. by using a separate process that	1160	resources run out, that's just fine (e.g. by using a separate process that
908	can crash safely). The size of a JSON text in octets or characters is	1161	can crash safely). The size of a JSON text in octets or characters is
909	usually a good indication of the size of the resources required to decode	1162	usually a good indication of the size of the resources required to decode
910	it into a Perl structure. While JSON::XS can check the size of the JSON	1163	it into a Perl structure. While JSON::XS can check the size of the JSON
911	text, it might be too late when you already have it in memory, so you	1164	text, it might be too late when you already have it in memory, so you
912	might want to check the size before you accept the string.	1165	might want to check the size before you accept the string.
913		1166
914	Third, JSON::XS recurses using the C stack when decoding objects and	1167	Third, JSON::XS recurses using the C stack when decoding objects and
915	arrays. The C stack is a limited resource: for instance, on my amd64	1168	arrays. The C stack is a limited resource: for instance, on my amd64
916	machine with 8MB of stack size I can decode around 180k nested arrays but	1169	machine with 8MB of stack size I can decode around 180k nested arrays but
917	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1170	only 14k nested JSON objects (due to perl itself recursing deeply on croak
918	to free the temporary). If that is exceeded, the program crashes. to be	1171	to free the temporary). If that is exceeded, the program crashes. To be
919	conservative, the default nesting limit is set to 512. If your process	1172	conservative, the default nesting limit is set to 512. If your process
920	has a smaller stack, you should adjust this setting accordingly with the	1173	has a smaller stack, you should adjust this setting accordingly with the
921	C<max_depth> method.	1174	C<max_depth> method.
922		1175
923	And last but least, something else could bomb you that I forgot to think	1176	Something else could bomb you, too, that I forgot to think of. In that
924	of. In that case, you get to keep the pieces. I am always open for hints,	1177	case, you get to keep the pieces. I am always open for hints, though...
925	though...	1178
		1179	Also keep in mind that JSON::XS might leak contents of your Perl data
		1180	structures in its error messages, so when you serialise sensitive
		1181	information you might want to make sure that exceptions thrown by JSON::XS
		1182	will not end up in front of untrusted eyes.
926		1183
927	If you are using JSON::XS to return packets to consumption	1184	If you are using JSON::XS to return packets to consumption
928	by javascript scripts in a browser you should have a look at	1185	by JavaScript scripts in a browser you should have a look at
929	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1186	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
930	you are vulnerable to some common attack vectors (which really are browser	1187	you are vulnerable to some common attack vectors (which really are browser
931	design bugs, but it is still you who will have to deal with it, as major	1188	design bugs, but it is still you who will have to deal with it, as major
932	browser developers care only for features, not about doing security	1189	browser developers care only for features, not about getting security
933	right).	1190	right).
934		1191
935		1192
		1193	=head1 THREADS
		1194
		1195	This module is I<not> guaranteed to be thread safe and there are no
		1196	plans to change this until Perl gets thread support (as opposed to the
		1197	horribly slow so-called "threads" which are simply slow and bloated
		1198	process simulations - use fork, it's I<much> faster, cheaper, better).
		1199
		1200	(It might actually work, but you have been warned).
		1201
		1202
936	=head1 BUGS	1203	=head1 BUGS
937		1204
938	While the goal of this module is to be correct, that unfortunately does	1205	While the goal of this module is to be correct, that unfortunately does
939	not mean its bug-free, only that I think its design is bug-free. It is	1206	not mean it's bug-free, only that I think its design is bug-free. It is
940	still relatively early in its development. If you keep reporting bugs they	1207	still relatively early in its development. If you keep reporting bugs they
941	will be fixed swiftly, though.	1208	will be fixed swiftly, though.
		1209
		1210	Please refrain from using rt.cpan.org or any other bug reporting
		1211	service. I put the contact address into my modules for a reason.
942		1212
943	=cut	1213	=cut
944		1214
945	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1215	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
946	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1216	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
963	"--" => sub { $_[0] = ${$_[0]} - 1 },	1233	"--" => sub { $_[0] = ${$_[0]} - 1 },
964	fallback => 1;	1234	fallback => 1;
965		1235
966	1;	1236	1;
967		1237
		1238	=head1 SEE ALSO
		1239
		1240	The F<json_xs> command line utility for quick experiments.
		1241
968	=head1 AUTHOR	1242	=head1 AUTHOR
969		1243
970	Marc Lehmann <schmorp@schmorp.de>	1244	Marc Lehmann <schmorp@schmorp.de>
971	http://home.schmorp.de/	1245	http://home.schmorp.de/
972		1246

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Revision 1.93 by root, Sat Mar 22 22:21:33 2008 UTC