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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.42 by root, Thu Jun 14 23:58:57 2007 UTC vs.
Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		19
19	# OO-interface	20	# OO-interface
20		21
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
23	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
24		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
25	=head1 DESCRIPTION	34	=head1 DESCRIPTION
26		35
27	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
28	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
29	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	overridden) with no overhead due to emulation (by inheriting 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.
30		47
31	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
32	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
33	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
34	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
41		58
42	=head2 FEATURES	59	=head2 FEATURES
43		60
44	=over 4	61	=over 4
45		62
46	=item * correct unicode handling	63	=item * correct Unicode handling
47		64
48	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
49	it does so.	66	so, and even documents what "correct" means.
50		67
51	=item * round-trip integrity	68	=item * round-trip integrity
52		69
53	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only data types supported
54	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.
55	(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
56	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
57		75
58	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
59		77
60	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,
61	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
62	feature).	80	feature).
63		81
64	=item * fast	82	=item * fast
65		83
66	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
67	of speed, too.	85	this module usually compares favourably in terms of speed, too.
68		86
69	=item * simple to use	87	=item * simple to use
70		88
71	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 object
72	interface.	90	oriented interface interface.
73		91
74	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
75		93
76	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
77	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ASCII format
78	(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
79	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
80	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.
81		99
82	=back	100	=back
83		101
84	=cut	102	=cut
85		103
86	package JSON::XS;	104	package JSON::XS;
87		105
88	use strict;	106	use strict;
89		107
90	BEGIN {
91	our $VERSION = '1.24';	108	our $VERSION = '2.22';
92	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
93		110
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
95	require Exporter;
96		112
		113	sub to_json($) {
97	require XSLoader;	114	require Carp;
98	XSLoader::load JSON::XS::, $VERSION;	115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
99	}	116	}
100		117
		118	sub from_json($) {
		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	}
		122
		123	use Exporter;
		124	use XSLoader;
		125
101	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
102		127
103	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
104	exported by default:	129	exported by default:
105		130
106	=over 4	131	=over 4
107		132
108	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
109		134
110	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
111	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.
112	octets only). Croaks on error.
113		137
114	This function call is functionally identical to:	138	This function call is functionally identical to:
115		139
116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
117		141
118	except being faster.	142	Except being faster.
119		143
120	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
121		145
122	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
123	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
124	scalar or reference. Croaks on error.	148	reference. Croaks on error.
125		149
126	This function call is functionally identical to:	150	This function call is functionally identical to:
127		151
128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129		153
130	except being faster.	154	Except being faster.
		155
		156	=item $is_boolean = JSON::XS::is_bool $scalar
		157
		158	Returns true if the passed scalar represents either JSON::XS::true or
		159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		160	and are used to represent JSON C<true> and C<false> values in Perl.
		161
		162	See MAPPING, below, for more information on how JSON values are mapped to
		163	Perl.
131		164
132	=back	165	=back
		166
		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 code point.
		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 :)
133		214
134		215
135	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
136		217
137	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
…		…
150	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]})
151	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
152		233
153	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
154		235
		236	=item $enabled = $json->get_ascii
		237
155	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
156	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
157	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
160	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
161	or any other superset of ASCII.	244	or any other superset of ASCII.
162		245
163	If C<$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
164	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
165	in a faster and more compact format.	248	in a faster and more compact format.
166		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
167	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
168	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
169	contain any 8 bit characters.	255	contain any 8 bit characters.
170		256
171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
172	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
173		259
174	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
175		261
		262	=item $enabled = $json->get_latin1
		263
176	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
177	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
178	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
179	latin1-encoded JSON text or a native unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
180	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
181	expects unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
182		270
183	If C<$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
184	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.
185		276
186	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
187	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
188	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
189	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
190	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
191	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
192	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.
193		284
194	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
195	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
196		287
197	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
198		291
199	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
200	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
201	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
202	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
203	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
204	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
205	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
206		299
207	If C<$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
208	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
209	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
210	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.
211		307
212	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
213		309
214	use Encode;	310	use Encode;
215	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
236	]	332	]
237	}	333	}
238		334
239	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
240		336
		337	=item $enabled = $json->get_indent
		338
241	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
242	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
243	into its own line, identing them properly.	341	into its own line, indenting them properly.
244		342
245	If C<$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
246	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
247		345
248	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
249		347
250	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
251		351
252	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
253	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
254		354
255	If C<$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
…		…
261	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
262		362
263	{"key" :"value"}	363	{"key" :"value"}
264		364
265	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
266		368
267	If C<$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
268	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
269	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
270	members.	372	members.
…		…
276		378
277	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
278		380
279	{"key": "value"}	381	{"key": "value"}
280		382
		383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
		386
		387	If C<$enable> is true (or missing), then C<decode> will accept some
		388	extensions to normal JSON syntax (see below). C<encode> will not be
		389	affected in anyway. I<Be aware that this option makes you accept invalid
		390	JSON texts as if they were valid!>. I suggest only to use this option to
		391	parse application-specific files written by humans (configuration files,
		392	resource files etc.)
		393
		394	If C<$enable> is false (the default), then C<decode> will only accept
		395	valid JSON texts.
		396
		397	Currently accepted extensions are:
		398
		399	=over 4
		400
		401	=item * list items can have an end-comma
		402
		403	JSON I<separates> array elements and key-value pairs with commas. This
		404	can be annoying if you write JSON texts manually and want to be able to
		405	quickly append elements, so this extension accepts comma at the end of
		406	such items not just between them:
		407
		408	[
		409	1,
		410	2, <- this comma not normally allowed
		411	]
		412	{
		413	"k1": "v1",
		414	"k2": "v2", <- this comma not normally allowed
		415	}
		416
		417	=item * shell-style '#'-comments
		418
		419	Whenever JSON allows whitespace, shell-style comments are additionally
		420	allowed. They are terminated by the first carriage-return or line-feed
		421	character, after which more white-space and comments are allowed.
		422
		423	[
		424	1, # this comment not allowed in JSON
		425	# neither this one...
		426	]
		427
		428	=back
		429
281	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
		431
		432	=item $enabled = $json->get_canonical
282		433
283	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
285		436
286	If C<$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
287	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
288	of the same script).	439	of the same script).
289		440
290	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
291	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,
292	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,
293	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
294		445
295	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
296		447
297	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
298		451
299	If C<$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
300	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
301	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
302	values instead of croaking.	455	values instead of croaking.
…		…
310	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
311		464
312	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
313	=> "Hello, World!"	466	=> "Hello, World!"
314		467
		468	=item $json = $json->allow_unknown ([$enable])
		469
		470	=item $enabled = $json->get_allow_unknown
		471
		472	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		473	exception when it encounters values it cannot represent in JSON (for
		474	example, filehandles) but instead will encode a JSON C<null> value. Note
		475	that blessed objects are not included here and are handled separately by
		476	c<allow_nonref>.
		477
		478	If C<$enable> is false (the default), then C<encode> will throw an
		479	exception when it encounters anything it cannot encode as JSON.
		480
		481	This option does not affect C<decode> in any way, and it is recommended to
		482	leave it off unless you know your communications partner.
		483
		484	=item $json = $json->allow_blessed ([$enable])
		485
		486	=item $enabled = $json->get_allow_blessed
		487
		488	If C<$enable> is true (or missing), then the C<encode> method will not
		489	barf when it encounters a blessed reference. Instead, the value of the
		490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		491	disabled or no C<TO_JSON> method found) or a representation of the
		492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		493	encoded. Has no effect on C<decode>.
		494
		495	If C<$enable> is false (the default), then C<encode> will throw an
		496	exception when it encounters a blessed object.
		497
		498	=item $json = $json->convert_blessed ([$enable])
		499
		500	=item $enabled = $json->get_convert_blessed
		501
		502	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		503	blessed object, will check for the availability of the C<TO_JSON> method
		504	on the object's class. If found, it will be called in scalar context
		505	and the resulting scalar will be encoded instead of the object. If no
		506	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		507	to do.
		508
		509	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		510	returns other blessed objects, those will be handled in the same
		511	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		512	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		513	methods called by the Perl core (== not by the user of the object) are
		514	usually in upper case letters and to avoid collisions with any C<to_json>
		515	function or method.
		516
		517	This setting does not yet influence C<decode> in any way, but in the
		518	future, global hooks might get installed that influence C<decode> and are
		519	enabled by this setting.
		520
		521	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		522	to do when a blessed object is found.
		523
		524	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		525
		526	When C<$coderef> is specified, it will be called from C<decode> each
		527	time it decodes a JSON object. The only argument is a reference to the
		528	newly-created hash. If the code references returns a single scalar (which
		529	need not be a reference), this value (i.e. a copy of that scalar to avoid
		530	aliasing) is inserted into the deserialised data structure. If it returns
		531	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		532	original deserialised hash will be inserted. This setting can slow down
		533	decoding considerably.
		534
		535	When C<$coderef> is omitted or undefined, any existing callback will
		536	be removed and C<decode> will not change the deserialised hash in any
		537	way.
		538
		539	Example, convert all JSON objects into the integer 5:
		540
		541	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		542	# returns [5]
		543	$js->decode ('[{}]')
		544	# throw an exception because allow_nonref is not enabled
		545	# so a lone 5 is not allowed.
		546	$js->decode ('{"a":1, "b":2}');
		547
		548	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		549
		550	Works remotely similar to C<filter_json_object>, but is only called for
		551	JSON objects having a single key named C<$key>.
		552
		553	This C<$coderef> is called before the one specified via
		554	C<filter_json_object>, if any. It gets passed the single value in the JSON
		555	object. If it returns a single value, it will be inserted into the data
		556	structure. If it returns nothing (not even C<undef> but the empty list),
		557	the callback from C<filter_json_object> will be called next, as if no
		558	single-key callback were specified.
		559
		560	If C<$coderef> is omitted or undefined, the corresponding callback will be
		561	disabled. There can only ever be one callback for a given key.
		562
		563	As this callback gets called less often then the C<filter_json_object>
		564	one, decoding speed will not usually suffer as much. Therefore, single-key
		565	objects make excellent targets to serialise Perl objects into, especially
		566	as single-key JSON objects are as close to the type-tagged value concept
		567	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		568	support this in any way, so you need to make sure your data never looks
		569	like a serialised Perl hash.
		570
		571	Typical names for the single object key are C<__class_whatever__>, or
		572	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		573	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		574	with real hashes.
		575
		576	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		577	into the corresponding C<< $WIDGET{<id>} >> object:
		578
		579	# return whatever is in $WIDGET{5}:
		580	JSON::XS
		581	->new
		582	->filter_json_single_key_object (__widget__ => sub {
		583	$WIDGET{ $_[0] }
		584	})
		585	->decode ('{"__widget__": 5')
		586
		587	# this can be used with a TO_JSON method in some "widget" class
		588	# for serialisation to json:
		589	sub WidgetBase::TO_JSON {
		590	my ($self) = @_;
		591
		592	unless ($self->{id}) {
		593	$self->{id} = ..get..some..id..;
		594	$WIDGET{$self->{id}} = $self;
		595	}
		596
		597	{ __widget__ => $self->{id} }
		598	}
		599
315	=item $json = $json->shrink ([$enable])	600	=item $json = $json->shrink ([$enable])
		601
		602	=item $enabled = $json->get_shrink
316		603
317	Perl usually over-allocates memory a bit when allocating space for	604	Perl usually over-allocates memory a bit when allocating space for
318	strings. This flag optionally resizes strings generated by either	605	strings. This flag optionally resizes strings generated by either
319	C<encode> or C<decode> to their minimum size possible. This can save	606	C<encode> or C<decode> to their minimum size possible. This can save
320	memory when your JSON texts are either very very long or you have many	607	memory when your JSON texts are either very very long or you have many
…		…
338	strings that look like integers or floats into integers or floats	625	strings that look like integers or floats into integers or floats
339	internally (there is no difference on the Perl level), saving space.	626	internally (there is no difference on the Perl level), saving space.
340		627
341	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
342		629
		630	=item $max_depth = $json->get_max_depth
		631
343	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
344	or decoding. If the JSON text or Perl data structure has an equal or	633	or decoding. If a higher nesting level is detected in JSON text or a Perl
345	higher nesting level then this limit, then the encoder and decoder will	634	data structure, then the encoder and decoder will stop and croak at that
346	stop and croak at that point.	635	point.
347		636
348	Nesting level is defined by number of hash- or arrayrefs that the encoder	637	Nesting level is defined by number of hash- or arrayrefs that the encoder
349	needs to traverse to reach a given point or the number of C<{> or C<[>	638	needs to traverse to reach a given point or the number of C<{> or C<[>
350	characters without their matching closing parenthesis crossed to reach a	639	characters without their matching closing parenthesis crossed to reach a
351	given character in a string.	640	given character in a string.
352		641
353	Setting the maximum depth to one disallows any nesting, so that ensures	642	Setting the maximum depth to one disallows any nesting, so that ensures
354	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
355		644
356	The argument to C<max_depth> will be rounded up to the next nearest power	645	If no argument is given, the highest possible setting will be used, which
357	of two.	646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
		651
		652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		653
		654	=item $json = $json->max_size ([$maximum_string_size])
		655
		656	=item $max_size = $json->get_max_size
		657
		658	Set the maximum length a JSON text may have (in bytes) where decoding is
		659	being attempted. The default is C<0>, meaning no limit. When C<decode>
		660	is called on a string that is longer then this many bytes, it will not
		661	attempt to decode the string but throw an exception. This setting has no
		662	effect on C<encode> (yet).
		663
		664	If no argument is given, the limit check will be deactivated (same as when
		665	C<0> is specified).
358		666
359	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360		668
361	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
362		670
…		…
391	=> ([], 3)	699	=> ([], 3)
392		700
393	=back	701	=back
394		702
395		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	=item $lvalue_string = $json->incr_text
		757
		758	This method returns the currently stored JSON fragment as an lvalue, that
		759	is, you can manipulate it. This I<only> works when a preceding call to
		760	C<incr_parse> in I<scalar context> successfully returned an object. Under
		761	all other circumstances you must not call this function (I mean it.
		762	although in simple tests it might actually work, it I<will> fail under
		763	real world conditions). As a special exception, you can also call this
		764	method before having parsed anything.
		765
		766	This function is useful in two cases: a) finding the trailing text after a
		767	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		768	(such as commas).
		769
		770	=item $json->incr_skip
		771
		772	This will reset the state of the incremental parser and will remove the
		773	parsed text from the input buffer. This is useful after C<incr_parse>
		774	died, in which case the input buffer and incremental parser state is left
		775	unchanged, to skip the text parsed so far and to reset the parse state.
		776
		777	=item $json->incr_reset
		778
		779	This completely resets the incremental parser, that is, after this call,
		780	it will be as if the parser had never parsed anything.
		781
		782	This is useful if you want ot repeatedly parse JSON objects and want to
		783	ignore any trailing data, which means you have to reset the parser after
		784	each successful decode.
		785
		786	=back
		787
		788	=head2 LIMITATIONS
		789
		790	All options that affect decoding are supported, except
		791	C<allow_nonref>. The reason for this is that it cannot be made to
		792	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		793	them back to back and still decode them perfectly. This does not hold true
		794	for JSON numbers, however.
		795
		796	For example, is the string C<1> a single JSON number, or is it simply the
		797	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		798	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		799	takes the conservative route and disallows this case.
		800
		801	=head2 EXAMPLES
		802
		803	Some examples will make all this clearer. First, a simple example that
		804	works similarly to C<decode_prefix>: We want to decode the JSON object at
		805	the start of a string and identify the portion after the JSON object:
		806
		807	my $text = "[1,2,3] hello";
		808
		809	my $json = new JSON::XS;
		810
		811	my $obj = $json->incr_parse ($text)
		812	or die "expected JSON object or array at beginning of string";
		813
		814	my $tail = $json->incr_text;
		815	# $tail now contains " hello"
		816
		817	Easy, isn't it?
		818
		819	Now for a more complicated example: Imagine a hypothetical protocol where
		820	you read some requests from a TCP stream, and each request is a JSON
		821	array, without any separation between them (in fact, it is often useful to
		822	use newlines as "separators", as these get interpreted as whitespace at
		823	the start of the JSON text, which makes it possible to test said protocol
		824	with C<telnet>...).
		825
		826	Here is how you'd do it (it is trivial to write this in an event-based
		827	manner):
		828
		829	my $json = new JSON::XS;
		830
		831	# read some data from the socket
		832	while (sysread $socket, my $buf, 4096) {
		833
		834	# split and decode as many requests as possible
		835	for my $request ($json->incr_parse ($buf)) {
		836	# act on the $request
		837	}
		838	}
		839
		840	Another complicated example: Assume you have a string with JSON objects
		841	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		842	[3]>). To parse them, we have to skip the commas between the JSON texts,
		843	and here is where the lvalue-ness of C<incr_text> comes in useful:
		844
		845	my $text = "[1],[2], [3]";
		846	my $json = new JSON::XS;
		847
		848	# void context, so no parsing done
		849	$json->incr_parse ($text);
		850
		851	# now extract as many objects as possible. note the
		852	# use of scalar context so incr_text can be called.
		853	while (my $obj = $json->incr_parse) {
		854	# do something with $obj
		855
		856	# now skip the optional comma
		857	$json->incr_text =~ s/^ \s* , //x;
		858	}
		859
		860	Now lets go for a very complex example: Assume that you have a gigantic
		861	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		862	but you cannot load it into memory fully (this has actually happened in
		863	the real world :).
		864
		865	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		866	can still help you: You implement a (very simple) array parser and let
		867	JSON decode the array elements, which are all full JSON objects on their
		868	own (this wouldn't work if the array elements could be JSON numbers, for
		869	example):
		870
		871	my $json = new JSON::XS;
		872
		873	# open the monster
		874	open my $fh, "<bigfile.json"
		875	or die "bigfile: $!";
		876
		877	# first parse the initial "["
		878	for (;;) {
		879	sysread $fh, my $buf, 65536
		880	or die "read error: $!";
		881	$json->incr_parse ($buf); # void context, so no parsing
		882
		883	# Exit the loop once we found and removed(!) the initial "[".
		884	# In essence, we are (ab-)using the $json object as a simple scalar
		885	# we append data to.
		886	last if $json->incr_text =~ s/^ \s* \[ //x;
		887	}
		888
		889	# now we have the skipped the initial "[", so continue
		890	# parsing all the elements.
		891	for (;;) {
		892	# in this loop we read data until we got a single JSON object
		893	for (;;) {
		894	if (my $obj = $json->incr_parse) {
		895	# do something with $obj
		896	last;
		897	}
		898
		899	# add more data
		900	sysread $fh, my $buf, 65536
		901	or die "read error: $!";
		902	$json->incr_parse ($buf); # void context, so no parsing
		903	}
		904
		905	# in this loop we read data until we either found and parsed the
		906	# separating "," between elements, or the final "]"
		907	for (;;) {
		908	# first skip whitespace
		909	$json->incr_text =~ s/^\s*//;
		910
		911	# if we find "]", we are done
		912	if ($json->incr_text =~ s/^\]//) {
		913	print "finished.\n";
		914	exit;
		915	}
		916
		917	# if we find ",", we can continue with the next element
		918	if ($json->incr_text =~ s/^,//) {
		919	last;
		920	}
		921
		922	# if we find anything else, we have a parse error!
		923	if (length $json->incr_text) {
		924	die "parse error near ", $json->incr_text;
		925	}
		926
		927	# else add more data
		928	sysread $fh, my $buf, 65536
		929	or die "read error: $!";
		930	$json->incr_parse ($buf); # void context, so no parsing
		931	}
		932
		933	This is a complex example, but most of the complexity comes from the fact
		934	that we are trying to be correct (bear with me if I am wrong, I never ran
		935	the above example :).
		936
		937
		938
396	=head1 MAPPING	939	=head1 MAPPING
397		940
398	This section describes how JSON::XS maps Perl values to JSON values and	941	This section describes how JSON::XS maps Perl values to JSON values and
399	vice versa. These mappings are designed to "do the right thing" in most	942	vice versa. These mappings are designed to "do the right thing" in most
400	circumstances automatically, preserving round-tripping characteristics	943	circumstances automatically, preserving round-tripping characteristics
401	(what you put in comes out as something equivalent).	944	(what you put in comes out as something equivalent).
402		945
403	For the more enlightened: note that in the following descriptions,	946	For the more enlightened: note that in the following descriptions,
404	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	947	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
405	refers to the abstract Perl language itself.	948	refers to the abstract Perl language itself.
406		949
407		950
408	=head2 JSON -> PERL	951	=head2 JSON -> PERL
409		952
410	=over 4	953	=over 4
411		954
412	=item object	955	=item object
413		956
414	A JSON object becomes a reference to a hash in Perl. No ordering of object	957	A JSON object becomes a reference to a hash in Perl. No ordering of object
415	keys is preserved (JSON does not preserver object key ordering itself).	958	keys is preserved (JSON does not preserve object key ordering itself).
416		959
417	=item array	960	=item array
418		961
419	A JSON array becomes a reference to an array in Perl.	962	A JSON array becomes a reference to an array in Perl.
420		963
…		…
424	are represented by the same codepoints in the Perl string, so no manual	967	are represented by the same codepoints in the Perl string, so no manual
425	decoding is necessary.	968	decoding is necessary.
426		969
427	=item number	970	=item number
428		971
429	A JSON number becomes either an integer or numeric (floating point)	972	A JSON number becomes either an integer, numeric (floating point) or
430	scalar in perl, depending on its range and any fractional parts. On the	973	string scalar in perl, depending on its range and any fractional parts. On
431	Perl level, there is no difference between those as Perl handles all the	974	the Perl level, there is no difference between those as Perl handles all
432	conversion details, but an integer may take slightly less memory and might	975	the conversion details, but an integer may take slightly less memory and
433	represent more values exactly than (floating point) numbers.	976	might represent more values exactly than floating point numbers.
		977
		978	If the number consists of digits only, JSON::XS will try to represent
		979	it as an integer value. If that fails, it will try to represent it as
		980	a numeric (floating point) value if that is possible without loss of
		981	precision. Otherwise it will preserve the number as a string value (in
		982	which case you lose roundtripping ability, as the JSON number will be
		983	re-encoded toa JSON string).
		984
		985	Numbers containing a fractional or exponential part will always be
		986	represented as numeric (floating point) values, possibly at a loss of
		987	precision (in which case you might lose perfect roundtripping ability, but
		988	the JSON number will still be re-encoded as a JSON number).
434		989
435	=item true, false	990	=item true, false
436		991
437	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	992	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
438	this process. Future versions might represent those values differently,	993	respectively. They are overloaded to act almost exactly like the numbers
439	but they will be guarenteed to act like these integers would normally in	994	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
440	Perl.	995	the C<JSON::XS::is_bool> function.
441		996
442	=item null	997	=item null
443		998
444	A JSON null atom becomes C<undef> in Perl.	999	A JSON null atom becomes C<undef> in Perl.
445		1000
…		…
475	Other unblessed references are generally not allowed and will cause an	1030	Other unblessed references are generally not allowed and will cause an
476	exception to be thrown, except for references to the integers C<0> and	1031	exception to be thrown, except for references to the integers C<0> and
477	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1032	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
478	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1033	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
479		1034
480	to_json [\0,JSON::XS::true] # yields [false,true]	1035	encode_json [\0, JSON::XS::true] # yields [false,true]
		1036
		1037	=item JSON::XS::true, JSON::XS::false
		1038
		1039	These special values become JSON true and JSON false values,
		1040	respectively. You can also use C<\1> and C<\0> directly if you want.
481		1041
482	=item blessed objects	1042	=item blessed objects
483		1043
484	Blessed objects are not allowed. JSON::XS currently tries to encode their	1044	Blessed objects are not directly representable in JSON. See the
485	underlying representation (hash- or arrayref), but this behaviour might	1045	C<allow_blessed> and C<convert_blessed> methods on various options on
486	change in future versions.	1046	how to deal with this: basically, you can choose between throwing an
		1047	exception, encoding the reference as if it weren't blessed, or provide
		1048	your own serialiser method.
487		1049
488	=item simple scalars	1050	=item simple scalars
489		1051
490	Simple Perl scalars (any scalar that is not a reference) are the most	1052	Simple Perl scalars (any scalar that is not a reference) are the most
491	difficult objects to encode: JSON::XS will encode undefined scalars as	1053	difficult objects to encode: JSON::XS will encode undefined scalars as
492	JSON null value, scalars that have last been used in a string context	1054	JSON C<null> values, scalars that have last been used in a string context
493	before encoding as JSON strings and anything else as number value:	1055	before encoding as JSON strings, and anything else as number value:
494		1056
495	# dump as number	1057	# dump as number
496	to_json [2] # yields [2]	1058	encode_json [2] # yields [2]
497	to_json [-3.0e17] # yields [-3e+17]	1059	encode_json [-3.0e17] # yields [-3e+17]
498	my $value = 5; to_json [$value] # yields [5]	1060	my $value = 5; encode_json [$value] # yields [5]
499		1061
500	# used as string, so dump as string	1062	# used as string, so dump as string
501	print $value;	1063	print $value;
502	to_json [$value] # yields ["5"]	1064	encode_json [$value] # yields ["5"]
503		1065
504	# undef becomes null	1066	# undef becomes null
505	to_json [undef] # yields [null]	1067	encode_json [undef] # yields [null]
506		1068
507	You can force the type to be a string by stringifying it:	1069	You can force the type to be a JSON string by stringifying it:
508		1070
509	my $x = 3.1; # some variable containing a number	1071	my $x = 3.1; # some variable containing a number
510	"$x"; # stringified	1072	"$x"; # stringified
511	$x .= ""; # another, more awkward way to stringify	1073	$x .= ""; # another, more awkward way to stringify
512	print $x; # perl does it for you, too, quite often	1074	print $x; # perl does it for you, too, quite often
513		1075
514	You can force the type to be a number by numifying it:	1076	You can force the type to be a JSON number by numifying it:
515		1077
516	my $x = "3"; # some variable containing a string	1078	my $x = "3"; # some variable containing a string
517	$x += 0; # numify it, ensuring it will be dumped as a number	1079	$x += 0; # numify it, ensuring it will be dumped as a number
518	$x *= 1; # same thing, the choise is yours.	1080	$x *= 1; # same thing, the choice is yours.
519		1081
520	You can not currently output JSON booleans or force the type in other,	1082	You can not currently force the type in other, less obscure, ways. Tell me
521	less obscure, ways. Tell me if you need this capability.	1083	if you need this capability (but don't forget to explain why it's needed
		1084	:).
522		1085
523	=back	1086	=back
524		1087
525		1088
526	=head1 COMPARISON	1089	=head1 ENCODING/CODESET FLAG NOTES
527		1090
528	As already mentioned, this module was created because none of the existing	1091	The interested reader might have seen a number of flags that signify
529	JSON modules could be made to work correctly. First I will describe the	1092	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
530	problems (or pleasures) I encountered with various existing JSON modules,	1093	some confusion on what these do, so here is a short comparison:
531	followed by some benchmark values. JSON::XS was designed not to suffer	1094
532	from any of these problems or limitations.	1095	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1096	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1097	control whether C<encode> escapes character values outside their respective
		1098	codeset range. Neither of these flags conflict with each other, although
		1099	some combinations make less sense than others.
		1100
		1101	Care has been taken to make all flags symmetrical with respect to
		1102	C<encode> and C<decode>, that is, texts encoded with any combination of
		1103	these flag values will be correctly decoded when the same flags are used
		1104	- in general, if you use different flag settings while encoding vs. when
		1105	decoding you likely have a bug somewhere.
		1106
		1107	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1108	simply an abstract set of character-codepoint pairs, while an encoding
		1109	takes those codepoint numbers and I<encodes> them, in our case into
		1110	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1111	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1112	the same time, which can be confusing.
533		1113
534	=over 4	1114	=over 4
535		1115
536	=item JSON 1.07	1116	=item C<utf8> flag disabled
537		1117
538	Slow (but very portable, as it is written in pure Perl).	1118	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1119	and expect Unicode strings, that is, characters with high ordinal Unicode
		1120	values (> 255) will be encoded as such characters, and likewise such
		1121	characters are decoded as-is, no canges to them will be done, except
		1122	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1123	respectively (to Perl, these are the same thing in strings unless you do
		1124	funny/weird/dumb stuff).
539		1125
540	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1126	This is useful when you want to do the encoding yourself (e.g. when you
541	undocumented. One can get far by feeding it unicode strings and doing	1127	want to have UTF-16 encoded JSON texts) or when some other layer does
542	en-/decoding oneself, but unicode escapes are not working properly).	1128	the encoding for you (for example, when printing to a terminal using a
		1129	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1130	to UTF-8 encode your data first and have Perl encode it another time).
543		1131
544	No roundtripping (strings get clobbered if they look like numbers, e.g.	1132	=item C<utf8> flag enabled
545	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
546	decode into the number 2.
547		1133
548	=item JSON::PC 0.01	1134	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1135	characters using the corresponding UTF-8 multi-byte sequence, and will
		1136	expect your input strings to be encoded as UTF-8, that is, no "character"
		1137	of the input string must have any value > 255, as UTF-8 does not allow
		1138	that.
549		1139
550	Very fast.	1140	The C<utf8> flag therefore switches between two modes: disabled means you
		1141	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1142	octet/binary string in Perl.
551		1143
552	Undocumented/buggy Unicode handling.	1144	=item C<latin1> or C<ascii> flags enabled
553		1145
554	No roundtripping.	1146	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1147	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1148	characters as specified by the C<utf8> flag.
555		1149
556	Has problems handling many Perl values (e.g. regex results and other magic	1150	If C<utf8> is disabled, then the result is also correctly encoded in those
557	values will make it croak).	1151	character sets (as both are proper subsets of Unicode, meaning that a
		1152	Unicode string with all character values < 256 is the same thing as a
		1153	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1154	the same thing as an ASCII string in Perl).
558		1155
559	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1156	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
560	which is not a valid JSON text.	1157	regardless of these flags, just some more characters will be escaped using
		1158	C<\uXXXX> then before.
561		1159
562	Unmaintained (maintainer unresponsive for many months, bugs are not	1160	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
563	getting fixed).	1161	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1162	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1163	a subset of Unicode), while ASCII is.
564		1164
565	=item JSON::Syck 0.21	1165	Surprisingly, C<decode> will ignore these flags and so treat all input
		1166	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1167	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1168	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
566		1169
567	Very buggy (often crashes).	1170	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1171	they only govern when the JSON output engine escapes a character or not.
568		1172
569	Very inflexible (no human-readable format supported, format pretty much	1173	The main use for C<latin1> is to relatively efficiently store binary data
570	undocumented. I need at least a format for easy reading by humans and a	1174	as JSON, at the expense of breaking compatibility with most JSON decoders.
571	single-line compact format for use in a protocol, and preferably a way to
572	generate ASCII-only JSON texts).
573		1175
574	Completely broken (and confusingly documented) Unicode handling (unicode	1176	The main use for C<ascii> is to force the output to not contain characters
575	escapes are not working properly, you need to set ImplicitUnicode to	1177	with values > 127, which means you can interpret the resulting string
576	I<different> values on en- and decoding to get symmetric behaviour).	1178	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
577		1179	8-bit-encoding, and still get the same data structure back. This is useful
578	No roundtripping (simple cases work, but this depends on wether the scalar	1180	when your channel for JSON transfer is not 8-bit clean or the encoding
579	value was used in a numeric context or not).	1181	might be mangled in between (e.g. in mail), and works because ASCII is a
580		1182	proper subset of most 8-bit and multibyte encodings in use in the world.
581	Dumping hashes may skip hash values depending on iterator state.
582
583	Unmaintained (maintainer unresponsive for many months, bugs are not
584	getting fixed).
585
586	Does not check input for validity (i.e. will accept non-JSON input and
587	return "something" instead of raising an exception. This is a security
588	issue: imagine two banks transfering money between each other using
589	JSON. One bank might parse a given non-JSON request and deduct money,
590	while the other might reject the transaction with a syntax error. While a
591	good protocol will at least recover, that is extra unnecessary work and
592	the transaction will still not succeed).
593
594	=item JSON::DWIW 0.04
595
596	Very fast. Very natural. Very nice.
597
598	Undocumented unicode handling (but the best of the pack. Unicode escapes
599	still don't get parsed properly).
600
601	Very inflexible.
602
603	No roundtripping.
604
605	Does not generate valid JSON texts (key strings are often unquoted, empty keys
606	result in nothing being output)
607
608	Does not check input for validity.
609		1183
610	=back	1184	=back
611		1185
612		1186
613	=head2 JSON and YAML	1187	=head2 JSON and YAML
614		1188
615	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1189	You often hear that JSON is a subset of YAML. This is, however, a mass
616	however, a mass hysteria and very far from the truth. In general, there is	1190	hysteria(*) and very far from the truth (as of the time of this writing),
617	no way to configure JSON::XS to output a data structure as valid YAML.	1191	so let me state it clearly: I<in general, there is no way to configure
		1192	JSON::XS to output a data structure as valid YAML> that works in all
		1193	cases.
618		1194
619	If you really must use JSON::XS to generate YAML, you should use this	1195	If you really must use JSON::XS to generate YAML, you should use this
620	algorithm (subject to change in future versions):	1196	algorithm (subject to change in future versions):
621		1197
622	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1198	my $to_yaml = JSON::XS->new->utf8->space_after (1);
623	my $yaml = $to_yaml->encode ($ref) . "\n";	1199	my $yaml = $to_yaml->encode ($ref) . "\n";
624		1200
625	This will usually generate JSON texts that also parse as valid	1201	This will I<usually> generate JSON texts that also parse as valid
626	YAML. Please note that YAML has hardcoded limits on (simple) object key	1202	YAML. Please note that YAML has hardcoded limits on (simple) object key
627	lengths that JSON doesn't have, so you should make sure that your hash	1203	lengths that JSON doesn't have and also has different and incompatible
		1204	unicode handling, so you should make sure that your hash keys are
628	keys are noticably shorter than the 1024 characters YAML allows.	1205	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1206	you do not have characters with codepoint values outside the Unicode BMP
		1207	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1208	strings (which JSON::XS does not I<currently> generate, but other JSON
		1209	generators might).
629		1210
630	There might be other incompatibilities that I am not aware of. In general	1211	There might be other incompatibilities that I am not aware of (or the YAML
		1212	specification has been changed yet again - it does so quite often). In
631	you should not try to generate YAML with a JSON generator or vice versa,	1213	general you should not try to generate YAML with a JSON generator or vice
632	or try to parse JSON with a YAML parser or vice versa: chances are high	1214	versa, or try to parse JSON with a YAML parser or vice versa: chances are
633	that you will run into severe interoperability problems.	1215	high that you will run into severe interoperability problems when you
		1216	least expect it.
		1217
		1218	=over 4
		1219
		1220	=item (*)
		1221
		1222	I have been pressured multiple times by Brian Ingerson (one of the
		1223	authors of the YAML specification) to remove this paragraph, despite him
		1224	acknowledging that the actual incompatibilities exist. As I was personally
		1225	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1226	educate people about these issues, so others do not run into the same
		1227	problem again and again. After this, Brian called me a (quote)I<complete
		1228	and worthless idiot>(unquote).
		1229
		1230	In my opinion, instead of pressuring and insulting people who actually
		1231	clarify issues with YAML and the wrong statements of some of its
		1232	proponents, I would kindly suggest reading the JSON spec (which is not
		1233	that difficult or long) and finally make YAML compatible to it, and
		1234	educating users about the changes, instead of spreading lies about the
		1235	real compatibility for many I<years> and trying to silence people who
		1236	point out that it isn't true.
		1237
		1238	=back
634		1239
635		1240
636	=head2 SPEED	1241	=head2 SPEED
637		1242
638	It seems that JSON::XS is surprisingly fast, as shown in the following	1243	It seems that JSON::XS is surprisingly fast, as shown in the following
639	tables. They have been generated with the help of the C<eg/bench> program	1244	tables. They have been generated with the help of the C<eg/bench> program
640	in the JSON::XS distribution, to make it easy to compare on your own	1245	in the JSON::XS distribution, to make it easy to compare on your own
641	system.	1246	system.
642		1247
643	First comes a comparison between various modules using a very short	1248	First comes a comparison between various modules using
644	single-line JSON string:	1249	a very short single-line JSON string (also available at
		1250	L<http://dist.schmorp.de/misc/json/short.json>).
645		1251
646	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1252	{"method": "handleMessage", "params": ["user1",
647	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1253	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1254	true, false]}
648		1255
649	It shows the number of encodes/decodes per second (JSON::XS uses	1256	It shows the number of encodes/decodes per second (JSON::XS uses
650	the functional interface, while JSON::XS/2 uses the OO interface	1257	the functional interface, while JSON::XS/2 uses the OO interface
651	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1258	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
652	shrink). Higher is better:	1259	shrink). Higher is better:
653		1260
654	module \| encode \| decode \|	1261	module \| encode \| decode \|
655	-----------\|------------\|------------\|	1262	-----------\|------------\|------------\|
656	JSON \| 7645.468 \| 4208.613 \|	1263	JSON 1.x \| 4990.842 \| 4088.813 \|
657	JSON::DWIW \| 40721.398 \| 77101.176 \|	1264	JSON::DWIW \| 51653.990 \| 71575.154 \|
658	JSON::PC \| 65948.176 \| 78251.940 \|	1265	JSON::PC \| 65948.176 \| 74631.744 \|
659	JSON::Syck \| 22844.793 \| 26479.192 \|	1266	JSON::PP \| 8931.652 \| 3817.168 \|
		1267	JSON::Syck \| 24877.248 \| 27776.848 \|
660	JSON::XS \| 388361.481 \| 199728.762 \|	1268	JSON::XS \| 388361.481 \| 227951.304 \|
661	JSON::XS/2 \| 218453.333 \| 192399.266 \|	1269	JSON::XS/2 \| 227951.304 \| 218453.333 \|
662	JSON::XS/3 \| 338250.323 \| 192399.266 \|	1270	JSON::XS/3 \| 338250.323 \| 218453.333 \|
663	Storable \| 15779.925 \| 14169.946 \|	1271	Storable \| 16500.016 \| 135300.129 \|
664	-----------+------------+------------+	1272	-----------+------------+------------+
665		1273
666	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1274	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
667	about three times faster on decoding, and over fourty times faster	1275	about three times faster on decoding, and over forty times faster
668	than JSON, even with pretty-printing and key sorting. It also compares	1276	than JSON, even with pretty-printing and key sorting. It also compares
669	favourably to Storable for small amounts of data.	1277	favourably to Storable for small amounts of data.
670		1278
671	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1279	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
672	search API (http://nanoref.com/yahooapis/mgPdGg):	1280	search API (L<http://dist.schmorp.de/misc/json/long.json>).
673		1281
674	module \| encode \| decode \|	1282	module \| encode \| decode \|
675	-----------\|------------\|------------\|	1283	-----------\|------------\|------------\|
676	JSON \| 254.685 \| 37.665 \|	1284	JSON 1.x \| 55.260 \| 34.971 \|
677	JSON::DWIW \| 843.343 \| 1049.731 \|	1285	JSON::DWIW \| 825.228 \| 1082.513 \|
678	JSON::PC \| 3602.116 \| 2307.352 \|	1286	JSON::PC \| 3571.444 \| 2394.829 \|
		1287	JSON::PP \| 210.987 \| 32.574 \|
679	JSON::Syck \| 505.107 \| 787.899 \|	1288	JSON::Syck \| 552.551 \| 787.544 \|
680	JSON::XS \| 5747.196 \| 3690.220 \|	1289	JSON::XS \| 5780.463 \| 4854.519 \|
681	JSON::XS/2 \| 3968.121 \| 3676.634 \|	1290	JSON::XS/2 \| 3869.998 \| 4798.975 \|
682	JSON::XS/3 \| 6105.246 \| 3662.508 \|	1291	JSON::XS/3 \| 5862.880 \| 4798.975 \|
683	Storable \| 4417.337 \| 5285.161 \|	1292	Storable \| 4445.002 \| 5235.027 \|
684	-----------+------------+------------+	1293	-----------+------------+------------+
685		1294
686	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1295	Again, JSON::XS leads by far (except for Storable which non-surprisingly
687	decodes faster).	1296	decodes faster).
688		1297
689	On large strings containing lots of high unicode characters, some modules	1298	On large strings containing lots of high Unicode characters, some modules
690	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1299	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
691	will be broken due to missing (or wrong) unicode handling. Others refuse	1300	will be broken due to missing (or wrong) Unicode handling. Others refuse
692	to decode or encode properly, so it was impossible to prepare a fair	1301	to decode or encode properly, so it was impossible to prepare a fair
693	comparison table for that case.	1302	comparison table for that case.
694		1303
695		1304
696	=head1 SECURITY CONSIDERATIONS	1305	=head1 SECURITY CONSIDERATIONS
…		…
702	any buffer overflows. Obviously, this module should ensure that and I am	1311	any buffer overflows. Obviously, this module should ensure that and I am
703	trying hard on making that true, but you never know.	1312	trying hard on making that true, but you never know.
704		1313
705	Second, you need to avoid resource-starving attacks. That means you should	1314	Second, you need to avoid resource-starving attacks. That means you should
706	limit the size of JSON texts you accept, or make sure then when your	1315	limit the size of JSON texts you accept, or make sure then when your
707	resources run out, thats just fine (e.g. by using a separate process that	1316	resources run out, that's just fine (e.g. by using a separate process that
708	can crash safely). The size of a JSON text in octets or characters is	1317	can crash safely). The size of a JSON text in octets or characters is
709	usually a good indication of the size of the resources required to decode	1318	usually a good indication of the size of the resources required to decode
710	it into a Perl structure.	1319	it into a Perl structure. While JSON::XS can check the size of the JSON
		1320	text, it might be too late when you already have it in memory, so you
		1321	might want to check the size before you accept the string.
711		1322
712	Third, JSON::XS recurses using the C stack when decoding objects and	1323	Third, JSON::XS recurses using the C stack when decoding objects and
713	arrays. The C stack is a limited resource: for instance, on my amd64	1324	arrays. The C stack is a limited resource: for instance, on my amd64
714	machine with 8MB of stack size I can decode around 180k nested arrays but	1325	machine with 8MB of stack size I can decode around 180k nested arrays but
715	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1326	only 14k nested JSON objects (due to perl itself recursing deeply on croak
716	to free the temporary). If that is exceeded, the program crashes. to be	1327	to free the temporary). If that is exceeded, the program crashes. To be
717	conservative, the default nesting limit is set to 512. If your process	1328	conservative, the default nesting limit is set to 512. If your process
718	has a smaller stack, you should adjust this setting accordingly with the	1329	has a smaller stack, you should adjust this setting accordingly with the
719	C<max_depth> method.	1330	C<max_depth> method.
720		1331
721	And last but least, something else could bomb you that I forgot to think	1332	Something else could bomb you, too, that I forgot to think of. In that
722	of. In that case, you get to keep the pieces. I am always open for hints,	1333	case, you get to keep the pieces. I am always open for hints, though...
723	though...	1334
		1335	Also keep in mind that JSON::XS might leak contents of your Perl data
		1336	structures in its error messages, so when you serialise sensitive
		1337	information you might want to make sure that exceptions thrown by JSON::XS
		1338	will not end up in front of untrusted eyes.
724		1339
725	If you are using JSON::XS to return packets to consumption	1340	If you are using JSON::XS to return packets to consumption
726	by javascript scripts in a browser you should have a look at	1341	by JavaScript scripts in a browser you should have a look at
727	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1342	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
728	you are vulnerable to some common attack vectors (which really are browser	1343	you are vulnerable to some common attack vectors (which really are browser
729	design bugs, but it is still you who will have to deal with it, as major	1344	design bugs, but it is still you who will have to deal with it, as major
730	browser developers care only for features, not about doing security	1345	browser developers care only for features, not about getting security
731	right).	1346	right).
732		1347
733		1348
		1349	=head1 THREADS
		1350
		1351	This module is I<not> guaranteed to be thread safe and there are no
		1352	plans to change this until Perl gets thread support (as opposed to the
		1353	horribly slow so-called "threads" which are simply slow and bloated
		1354	process simulations - use fork, it's I<much> faster, cheaper, better).
		1355
		1356	(It might actually work, but you have been warned).
		1357
		1358
734	=head1 BUGS	1359	=head1 BUGS
735		1360
736	While the goal of this module is to be correct, that unfortunately does	1361	While the goal of this module is to be correct, that unfortunately does
737	not mean its bug-free, only that I think its design is bug-free. It is	1362	not mean it's bug-free, only that I think its design is bug-free. If you
738	still relatively early in its development. If you keep reporting bugs they	1363	keep reporting bugs they will be fixed swiftly, though.
739	will be fixed swiftly, though.	1364
		1365	Please refrain from using rt.cpan.org or any other bug reporting
		1366	service. I put the contact address into my modules for a reason.
740		1367
741	=cut	1368	=cut
742		1369
		1370	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1371	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1372
743	sub true() { \1 }	1373	sub true() { $true }
744	sub false() { \0 }	1374	sub false() { $false }
		1375
		1376	sub is_bool($) {
		1377	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1378	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1379	}
		1380
		1381	XSLoader::load "JSON::XS", $VERSION;
		1382
		1383	package JSON::XS::Boolean;
		1384
		1385	use overload
		1386	"0+" => sub { ${$_[0]} },
		1387	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1388	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1389	fallback => 1;
745		1390
746	1;	1391	1;
		1392
		1393	=head1 SEE ALSO
		1394
		1395	The F<json_xs> command line utility for quick experiments.
747		1396
748	=head1 AUTHOR	1397	=head1 AUTHOR
749		1398
750	Marc Lehmann <schmorp@schmorp.de>	1399	Marc Lehmann <schmorp@schmorp.de>
751	http://home.schmorp.de/	1400	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing JSON-XS/XS.pm (file contents): Revision 1.42 by root, Thu Jun 14 23:58:57 2007 UTC vs. Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.42 by root, Thu Jun 14 23:58:57 2007 UTC vs.
Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC