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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs.
Revision 1.86 by root, Wed Mar 19 03:17:38 2008 UTC

…		…
		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14		19
15	# OO-interface	20	# OO-interface
16		21
17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
19	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
20		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
21	=head1 DESCRIPTION	34	=head1 DESCRIPTION
22		35
23	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
24	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
25	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overriden) with no overhead due to emulation (by inheritign constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
26		47
27	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
28	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
29	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
30	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
37		58
38	=head2 FEATURES	59	=head2 FEATURES
39		60
40	=over 4	61	=over 4
41		62
42	=item * correct unicode handling	63	=item * correct Unicode handling
43		64
44	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
45	it does so.	66	so, and even documents what "correct" means.
46		67
47	=item * round-trip integrity	68	=item * round-trip integrity
48		69
49	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
50	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
52	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
53		75
54	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
55		77
56	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
57	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
58	feature).	80	feature).
59		81
60	=item * fast	82	=item * fast
61		83
62	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
63	of speed, too.	85	this module usually compares favourably in terms of speed, too.
64		86
65	=item * simple to use	87	=item * simple to use
66		88
67	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an objetc
68	interface.	90	oriented interface interface.
69		91
70	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
71		93
72	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
73	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
74	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
75	unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
76	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
77		99
78	=back	100	=back
79		101
80	=cut	102	=cut
81		103
82	package JSON::XS;	104	package JSON::XS;
83		105
84	use strict;	106	use strict;
85		107
86	our $VERSION = '1.4';	108	our $VERSION = '2.01';
87	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
88		110
89	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		114	require Carp;
		115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		116	}
		117
		118	sub from_json($) {
		119	require Carp;
		120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		121	}
90		122
91	use Exporter;	123	use Exporter;
92	use XSLoader;	124	use XSLoader;
93		125
94	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
95		127
96	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
97	exported by default:	129	exported by default:
98		130
99	=over 4	131	=over 4
100		132
101	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
102		134
103	Converts the given Perl data structure (a simple scalar or a reference to	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	136	(that is, the string contains octets only). Croaks on error.
105	octets only). Croaks on error.
106		137
107	This function call is functionally identical to:	138	This function call is functionally identical to:
108		139
109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110		141
111	except being faster.	142	except being faster.
112		143
113	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
114		145
115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
116	parse that as an UTF-8 encoded JSON text, returning the resulting simple	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
117	scalar or reference. Croaks on error.	148	reference. Croaks on error.
118		149
119	This function call is functionally identical to:	150	This function call is functionally identical to:
120		151
121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122		153
…		…
132	Perl.	163	Perl.
133		164
134	=back	165	=back
135		166
136		167
		168	=head1 A FEW NOTES ON UNICODE AND PERL
		169
		170	Since this often leads to confusion, here are a few very clear words on
		171	how Unicode works in Perl, modulo bugs.
		172
		173	=over 4
		174
		175	=item 1. Perl strings can store characters with ordinal values > 255.
		176
		177	This enables you to store Unicode characters as single characters in a
		178	Perl string - very natural.
		179
		180	=item 2. Perl does I<not> associate an encoding with your strings.
		181
		182	... until you force it to, e.g. when matching it against a regex, or
		183	printing the scalar to a file, in which case Perl either interprets your
		184	string as locale-encoded text, octets/binary, or as Unicode, depending
		185	on various settings. In no case is an encoding stored together with your
		186	data, it is I<use> that decides encoding, not any magical meta data.
		187
		188	=item 3. The internal utf-8 flag has no meaning with regards to the
		189	encoding of your string.
		190
		191	Just ignore that flag unless you debug a Perl bug, a module written in
		192	XS or want to dive into the internals of perl. Otherwise it will only
		193	confuse you, as, despite the name, it says nothing about how your string
		194	is encoded. You can have Unicode strings with that flag set, with that
		195	flag clear, and you can have binary data with that flag set and that flag
		196	clear. Other possibilities exist, too.
		197
		198	If you didn't know about that flag, just the better, pretend it doesn't
		199	exist.
		200
		201	=item 4. A "Unicode String" is simply a string where each character can be
		202	validly interpreted as a Unicode codepoint.
		203
		204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		205	Unicode string encoded in UTF-8, giving you a binary string.
		206
		207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		208
		209	It's a fact. Learn to live with it.
		210
		211	=back
		212
		213	I hope this helps :)
		214
		215
137	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
138		217
139	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
140	decoding style, within the limits of supported formats.	219	decoding style, within the limits of supported formats.
141		220
…		…
152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	231	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
153	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
154		233
155	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
156		235
		236	=item $enabled = $json->get_ascii
		237
157	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
158	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
159	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163	or any other superset of ASCII.	244	or any other superset of ASCII.
164		245
165	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
166	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
167	in a faster and more compact format.	248	in a faster and more compact format.
…		…
173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174	=> ["\ud801\udc01"]	255	=> ["\ud801\udc01"]
175		256
176	=item $json = $json->latin1 ([$enable])	257	=item $json = $json->latin1 ([$enable])
177		258
		259	=item $enabled = $json->get_latin1
		260
178	If C<$enable> is true (or missing), then the C<encode> method will encode	261	If C<$enable> is true (or missing), then the C<encode> method will encode
179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	262	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180	outside the code range C<0..255>. The resulting string can be treated as a	263	outside the code range C<0..255>. The resulting string can be treated as a
181	latin1-encoded JSON text or a native unicode string. The C<decode> method	264	latin1-encoded JSON text or a native Unicode string. The C<decode> method
182	will not be affected in any way by this flag, as C<decode> by default	265	will not be affected in any way by this flag, as C<decode> by default
183	expects unicode, which is a strict superset of latin1.	266	expects Unicode, which is a strict superset of latin1.
184		267
185	If C<$enable> is false, then the C<encode> method will not escape Unicode	268	If C<$enable> is false, then the C<encode> method will not escape Unicode
186	characters unless required by the JSON syntax or other flags.	269	characters unless required by the JSON syntax or other flags.
187		270
188	The main use for this flag is efficiently encoding binary data as JSON	271	The main use for this flag is efficiently encoding binary data as JSON
189	text, as most octets will not be escaped, resulting in a smaller encoded	272	text, as most octets will not be escaped, resulting in a smaller encoded
190	size. The disadvantage is that the resulting JSON text is encoded	273	size. The disadvantage is that the resulting JSON text is encoded
191	in latin1 (and must correctly be treated as such when storing and	274	in latin1 (and must correctly be treated as such when storing and
192	transfering), a rare encoding for JSON. It is therefore most useful when	275	transferring), a rare encoding for JSON. It is therefore most useful when
193	you want to store data structures known to contain binary data efficiently	276	you want to store data structures known to contain binary data efficiently
194	in files or databases, not when talking to other JSON encoders/decoders.	277	in files or databases, not when talking to other JSON encoders/decoders.
195		278
196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	279	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	280	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198		281
199	=item $json = $json->utf8 ([$enable])	282	=item $json = $json->utf8 ([$enable])
		283
		284	=item $enabled = $json->get_utf8
200		285
201	If C<$enable> is true (or missing), then the C<encode> method will encode	286	If C<$enable> is true (or missing), then the C<encode> method will encode
202	the JSON result into UTF-8, as required by many protocols, while the	287	the JSON result into UTF-8, as required by many protocols, while the
203	C<decode> method expects to be handled an UTF-8-encoded string. Please	288	C<decode> method expects to be handled an UTF-8-encoded string. Please
204	note that UTF-8-encoded strings do not contain any characters outside the	289	note that UTF-8-encoded strings do not contain any characters outside the
205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	290	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206	versions, enabling this option might enable autodetection of the UTF-16	291	versions, enabling this option might enable autodetection of the UTF-16
207	and UTF-32 encoding families, as described in RFC4627.	292	and UTF-32 encoding families, as described in RFC4627.
208		293
209	If C<$enable> is false, then the C<encode> method will return the JSON	294	If C<$enable> is false, then the C<encode> method will return the JSON
210	string as a (non-encoded) unicode string, while C<decode> expects thus a	295	string as a (non-encoded) Unicode string, while C<decode> expects thus a
211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	296	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
212	to be done yourself, e.g. using the Encode module.	297	to be done yourself, e.g. using the Encode module.
213		298
214	Example, output UTF-16BE-encoded JSON:	299	Example, output UTF-16BE-encoded JSON:
215		300
216	use Encode;	301	use Encode;
…		…
238	]	323	]
239	}	324	}
240		325
241	=item $json = $json->indent ([$enable])	326	=item $json = $json->indent ([$enable])
242		327
		328	=item $enabled = $json->get_indent
		329
243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	330	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244	format as output, putting every array member or object/hash key-value pair	331	format as output, putting every array member or object/hash key-value pair
245	into its own line, identing them properly.	332	into its own line, indenting them properly.
246		333
247	If C<$enable> is false, no newlines or indenting will be produced, and the	334	If C<$enable> is false, no newlines or indenting will be produced, and the
248	resulting JSON text is guarenteed not to contain any C<newlines>.	335	resulting JSON text is guaranteed not to contain any C<newlines>.
249		336
250	This setting has no effect when decoding JSON texts.	337	This setting has no effect when decoding JSON texts.
251		338
252	=item $json = $json->space_before ([$enable])	339	=item $json = $json->space_before ([$enable])
		340
		341	=item $enabled = $json->get_space_before
253		342
254	If C<$enable> is true (or missing), then the C<encode> method will add an extra	343	If C<$enable> is true (or missing), then the C<encode> method will add an extra
255	optional space before the C<:> separating keys from values in JSON objects.	344	optional space before the C<:> separating keys from values in JSON objects.
256		345
257	If C<$enable> is false, then the C<encode> method will not add any extra	346	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
263	Example, space_before enabled, space_after and indent disabled:	352	Example, space_before enabled, space_after and indent disabled:
264		353
265	{"key" :"value"}	354	{"key" :"value"}
266		355
267	=item $json = $json->space_after ([$enable])	356	=item $json = $json->space_after ([$enable])
		357
		358	=item $enabled = $json->get_space_after
268		359
269	If C<$enable> is true (or missing), then the C<encode> method will add an extra	360	If C<$enable> is true (or missing), then the C<encode> method will add an extra
270	optional space after the C<:> separating keys from values in JSON objects	361	optional space after the C<:> separating keys from values in JSON objects
271	and extra whitespace after the C<,> separating key-value pairs and array	362	and extra whitespace after the C<,> separating key-value pairs and array
272	members.	363	members.
…		…
278		369
279	Example, space_before and indent disabled, space_after enabled:	370	Example, space_before and indent disabled, space_after enabled:
280		371
281	{"key": "value"}	372	{"key": "value"}
282		373
		374	=item $json = $json->relaxed ([$enable])
		375
		376	=item $enabled = $json->get_relaxed
		377
		378	If C<$enable> is true (or missing), then C<decode> will accept some
		379	extensions to normal JSON syntax (see below). C<encode> will not be
		380	affected in anyway. I<Be aware that this option makes you accept invalid
		381	JSON texts as if they were valid!>. I suggest only to use this option to
		382	parse application-specific files written by humans (configuration files,
		383	resource files etc.)
		384
		385	If C<$enable> is false (the default), then C<decode> will only accept
		386	valid JSON texts.
		387
		388	Currently accepted extensions are:
		389
		390	=over 4
		391
		392	=item * list items can have an end-comma
		393
		394	JSON I<separates> array elements and key-value pairs with commas. This
		395	can be annoying if you write JSON texts manually and want to be able to
		396	quickly append elements, so this extension accepts comma at the end of
		397	such items not just between them:
		398
		399	[
		400	1,
		401	2, <- this comma not normally allowed
		402	]
		403	{
		404	"k1": "v1",
		405	"k2": "v2", <- this comma not normally allowed
		406	}
		407
		408	=item * shell-style '#'-comments
		409
		410	Whenever JSON allows whitespace, shell-style comments are additionally
		411	allowed. They are terminated by the first carriage-return or line-feed
		412	character, after which more white-space and comments are allowed.
		413
		414	[
		415	1, # this comment not allowed in JSON
		416	# neither this one...
		417	]
		418
		419	=back
		420
283	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
		422
		423	=item $enabled = $json->get_canonical
284		424
285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
287		427
288	If C<$enable> is false, then the C<encode> method will output key-value	428	If C<$enable> is false, then the C<encode> method will output key-value
289	pairs in the order Perl stores them (which will likely change between runs	429	pairs in the order Perl stores them (which will likely change between runs
290	of the same script).	430	of the same script).
291		431
292	This option is useful if you want the same data structure to be encoded as	432	This option is useful if you want the same data structure to be encoded as
293	the same JSON text (given the same overall settings). If it is disabled,	433	the same JSON text (given the same overall settings). If it is disabled,
294	the same hash migh be encoded differently even if contains the same data,	434	the same hash might be encoded differently even if contains the same data,
295	as key-value pairs have no inherent ordering in Perl.	435	as key-value pairs have no inherent ordering in Perl.
296		436
297	This setting has no effect when decoding JSON texts.	437	This setting has no effect when decoding JSON texts.
298		438
299	=item $json = $json->allow_nonref ([$enable])	439	=item $json = $json->allow_nonref ([$enable])
		440
		441	=item $enabled = $json->get_allow_nonref
300		442
301	If C<$enable> is true (or missing), then the C<encode> method can convert a	443	If C<$enable> is true (or missing), then the C<encode> method can convert a
302	non-reference into its corresponding string, number or null JSON value,	444	non-reference into its corresponding string, number or null JSON value,
303	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	445	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304	values instead of croaking.	446	values instead of croaking.
…		…
314	JSON::XS->new->allow_nonref->encode ("Hello, World!")	456	JSON::XS->new->allow_nonref->encode ("Hello, World!")
315	=> "Hello, World!"	457	=> "Hello, World!"
316		458
317	=item $json = $json->allow_blessed ([$enable])	459	=item $json = $json->allow_blessed ([$enable])
318		460
		461	=item $enabled = $json->get_allow_blessed
		462
319	If C<$enable> is true (or missing), then the C<encode> method will not	463	If C<$enable> is true (or missing), then the C<encode> method will not
320	barf when it encounters a blessed reference. Instead, the value of the	464	barf when it encounters a blessed reference. Instead, the value of the
321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	465	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322	disabled or no C<to_json> method found) or a representation of the	466	disabled or no C<TO_JSON> method found) or a representation of the
323	object (C<convert_blessed> enabled and C<to_json> method found) is being	467	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324	encoded. Has no effect on C<decode>.	468	encoded. Has no effect on C<decode>.
325		469
326	If C<$enable> is false (the default), then C<encode> will throw an	470	If C<$enable> is false (the default), then C<encode> will throw an
327	exception when it encounters a blessed object.	471	exception when it encounters a blessed object.
328		472
329	=item $json = $json->convert_blessed ([$enable])	473	=item $json = $json->convert_blessed ([$enable])
		474
		475	=item $enabled = $json->get_convert_blessed
330		476
331	If C<$enable> is true (or missing), then C<encode>, upon encountering a	477	If C<$enable> is true (or missing), then C<encode>, upon encountering a
332	blessed object, will check for the availability of the C<TO_JSON> method	478	blessed object, will check for the availability of the C<TO_JSON> method
333	on the object's class. If found, it will be called in scalar context	479	on the object's class. If found, it will be called in scalar context
334	and the resulting scalar will be encoded instead of the object. If no	480	and the resulting scalar will be encoded instead of the object. If no
…		…
338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	484	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
339	returns other blessed objects, those will be handled in the same	485	returns other blessed objects, those will be handled in the same
340	way. C<TO_JSON> must take care of not causing an endless recursion cycle	486	way. C<TO_JSON> must take care of not causing an endless recursion cycle
341	(== crash) in this case. The name of C<TO_JSON> was chosen because other	487	(== crash) in this case. The name of C<TO_JSON> was chosen because other
342	methods called by the Perl core (== not by the user of the object) are	488	methods called by the Perl core (== not by the user of the object) are
343	usually in upper case letters and to avoid collisions with the C<to_json>	489	usually in upper case letters and to avoid collisions with any C<to_json>
344	function.	490	function or method.
345		491
346	This setting does not yet influence C<decode> in any way, but in the	492	This setting does not yet influence C<decode> in any way, but in the
347	future, global hooks might get installed that influence C<decode> and are	493	future, global hooks might get installed that influence C<decode> and are
348	enabled by this setting.	494	enabled by this setting.
349		495
350	If C<$enable> is false, then the C<allow_blessed> setting will decide what	496	If C<$enable> is false, then the C<allow_blessed> setting will decide what
351	to do when a blessed object is found.	497	to do when a blessed object is found.
352		498
353	=item $json = $json->filter_json_object ([$coderef])	499	=item $json = $json->filter_json_object ([$coderef->($hashref)])
354		500
355	When C<$coderef> is specified, it will be called from C<decode> each	501	When C<$coderef> is specified, it will be called from C<decode> each
356	time it decodes a JSON object. The only argument is a reference to the	502	time it decodes a JSON object. The only argument is a reference to the
357	newly-created hash. If the code references returns a single scalar (which	503	newly-created hash. If the code references returns a single scalar (which
358	need not be a reference), this value (i.e. a copy of that scalar to avoid	504	need not be a reference), this value (i.e. a copy of that scalar to avoid
359	aliasing) is inserted into the deserialised data structure. If it returns	505	aliasing) is inserted into the deserialised data structure. If it returns
360	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the	506	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
361	original deserialised hash will be inserted. This setting can slow down	507	original deserialised hash will be inserted. This setting can slow down
362	decoding considerably.	508	decoding considerably.
363		509
364	When C<$coderef> is omitted or undefined, C<decode> will not change the	510	When C<$coderef> is omitted or undefined, any existing callback will
365	deserialised hash in any way. This is maximally fast.	511	be removed and C<decode> will not change the deserialised hash in any
		512	way.
366		513
367	Example, convert all JSON objects into the integer 5:	514	Example, convert all JSON objects into the integer 5:
368		515
369	my $js = JSON::XS->new->filter_json_object (sub { 5 });	516	my $js = JSON::XS->new->filter_json_object (sub { 5 });
370	# returns [5]	517	# returns [5]
371	$js->decode ('[{}]')	518	$js->decode ('[{}]')
372	# throw an exception because allow_nonref is not enabled:	519	# throw an exception because allow_nonref is not enabled
		520	# so a lone 5 is not allowed.
373	$js->decode ('{"a":1, "b":2}');	521	$js->decode ('{"a":1, "b":2}');
374		522
375	=item $json = $json->filter_json_single_key_object ([$coderef])	523	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
376		524
377	Works like C<filter_json_object>, but is only called for JSON objects	525	Works remotely similar to C<filter_json_object>, but is only called for
378	having only a single key.	526	JSON objects having a single key named C<$key>.
379		527
380	This C<$coderef> is called before the one specified via	528	This C<$coderef> is called before the one specified via
381	C<filter_json_object>, if any. If it returns something, that will be	529	C<filter_json_object>, if any. It gets passed the single value in the JSON
382	inserted into the data structure. If it returns nothing, the callback	530	object. If it returns a single value, it will be inserted into the data
383	from C<filter_json_object> will be called next. If you want to force	531	structure. If it returns nothing (not even C<undef> but the empty list),
384	insertion of single-key objects even in the presence of a mutating	532	the callback from C<filter_json_object> will be called next, as if no
385	C<filter_json_object> callback, simply return the passed hash.	533	single-key callback were specified.
		534
		535	If C<$coderef> is omitted or undefined, the corresponding callback will be
		536	disabled. There can only ever be one callback for a given key.
386		537
387	As this callback gets called less often then the C<filter_json_object>	538	As this callback gets called less often then the C<filter_json_object>
388	one, decoding speed will not usually suffer as much. Therefore, single-key	539	one, decoding speed will not usually suffer as much. Therefore, single-key
389	objects make excellent targets to serialise Perl objects into, especially	540	objects make excellent targets to serialise Perl objects into, especially
390	as single-key JSON objects are as close to the type-tagged value concept	541	as single-key JSON objects are as close to the type-tagged value concept
391	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	542	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
392	support this in any way, so you need to make sure your data never looks	543	support this in any way, so you need to make sure your data never looks
393	like a serialised Perl hash.	544	like a serialised Perl hash.
394		545
395	Typical names for the single object key are C<__class_whatever__>, or	546	Typical names for the single object key are C<__class_whatever__>, or
396	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	547	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
401	into the corresponding C<< $WIDGET{<id>} >> object:	552	into the corresponding C<< $WIDGET{<id>} >> object:
402		553
403	# return whatever is in $WIDGET{5}:	554	# return whatever is in $WIDGET{5}:
404	JSON::XS	555	JSON::XS
405	->new	556	->new
406	->filter_json_single_key_object (sub {	557	->filter_json_single_key_object (__widget__ => sub {
407	exists $_[0]{__widget__}
408	? $WIDGET{ $_[0]{__widget__} }	558	$WIDGET{ $_[0] }
409	: ()
410	})	559	})
411	->decode ('{"__widget__": 5')	560	->decode ('{"__widget__": 5')
412		561
413	# this can be used with a TO_JSON method in some "widget" class	562	# this can be used with a TO_JSON method in some "widget" class
414	# for serialisation to json:	563	# for serialisation to json:
…		…
422		571
423	{ __widget__ => $self->{id} }	572	{ __widget__ => $self->{id} }
424	}	573	}
425		574
426	=item $json = $json->shrink ([$enable])	575	=item $json = $json->shrink ([$enable])
		576
		577	=item $enabled = $json->get_shrink
427		578
428	Perl usually over-allocates memory a bit when allocating space for	579	Perl usually over-allocates memory a bit when allocating space for
429	strings. This flag optionally resizes strings generated by either	580	strings. This flag optionally resizes strings generated by either
430	C<encode> or C<decode> to their minimum size possible. This can save	581	C<encode> or C<decode> to their minimum size possible. This can save
431	memory when your JSON texts are either very very long or you have many	582	memory when your JSON texts are either very very long or you have many
…		…
449	strings that look like integers or floats into integers or floats	600	strings that look like integers or floats into integers or floats
450	internally (there is no difference on the Perl level), saving space.	601	internally (there is no difference on the Perl level), saving space.
451		602
452	=item $json = $json->max_depth ([$maximum_nesting_depth])	603	=item $json = $json->max_depth ([$maximum_nesting_depth])
453		604
		605	=item $max_depth = $json->get_max_depth
		606
454	Sets the maximum nesting level (default C<512>) accepted while encoding	607	Sets the maximum nesting level (default C<512>) accepted while encoding
455	or decoding. If the JSON text or Perl data structure has an equal or	608	or decoding. If the JSON text or Perl data structure has an equal or
456	higher nesting level then this limit, then the encoder and decoder will	609	higher nesting level then this limit, then the encoder and decoder will
457	stop and croak at that point.	610	stop and croak at that point.
458		611
…		…
469	used, which is rarely useful.	622	used, which is rarely useful.
470		623
471	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
472		625
473	=item $json = $json->max_size ([$maximum_string_size])	626	=item $json = $json->max_size ([$maximum_string_size])
		627
		628	=item $max_size = $json->get_max_size
474		629
475	Set the maximum length a JSON text may have (in bytes) where decoding is	630	Set the maximum length a JSON text may have (in bytes) where decoding is
476	being attempted. The default is C<0>, meaning no limit. When C<decode>	631	being attempted. The default is C<0>, meaning no limit. When C<decode>
477	is called on a string longer then this number of characters it will not	632	is called on a string longer then this number of characters it will not
478	attempt to decode the string but throw an exception. This setting has no	633	attempt to decode the string but throw an exception. This setting has no
…		…
525	vice versa. These mappings are designed to "do the right thing" in most	680	vice versa. These mappings are designed to "do the right thing" in most
526	circumstances automatically, preserving round-tripping characteristics	681	circumstances automatically, preserving round-tripping characteristics
527	(what you put in comes out as something equivalent).	682	(what you put in comes out as something equivalent).
528		683
529	For the more enlightened: note that in the following descriptions,	684	For the more enlightened: note that in the following descriptions,
530	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	685	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
531	refers to the abstract Perl language itself.	686	refers to the abstract Perl language itself.
532		687
533		688
534	=head2 JSON -> PERL	689	=head2 JSON -> PERL
535		690
536	=over 4	691	=over 4
537		692
538	=item object	693	=item object
539		694
540	A JSON object becomes a reference to a hash in Perl. No ordering of object	695	A JSON object becomes a reference to a hash in Perl. No ordering of object
541	keys is preserved (JSON does not preserver object key ordering itself).	696	keys is preserved (JSON does not preserve object key ordering itself).
542		697
543	=item array	698	=item array
544		699
545	A JSON array becomes a reference to an array in Perl.	700	A JSON array becomes a reference to an array in Perl.
546		701
…		…
550	are represented by the same codepoints in the Perl string, so no manual	705	are represented by the same codepoints in the Perl string, so no manual
551	decoding is necessary.	706	decoding is necessary.
552		707
553	=item number	708	=item number
554		709
555	A JSON number becomes either an integer or numeric (floating point)	710	A JSON number becomes either an integer, numeric (floating point) or
556	scalar in perl, depending on its range and any fractional parts. On the	711	string scalar in perl, depending on its range and any fractional parts. On
557	Perl level, there is no difference between those as Perl handles all the	712	the Perl level, there is no difference between those as Perl handles all
558	conversion details, but an integer may take slightly less memory and might	713	the conversion details, but an integer may take slightly less memory and
559	represent more values exactly than (floating point) numbers.	714	might represent more values exactly than floating point numbers.
		715
		716	If the number consists of digits only, JSON::XS will try to represent
		717	it as an integer value. If that fails, it will try to represent it as
		718	a numeric (floating point) value if that is possible without loss of
		719	precision. Otherwise it will preserve the number as a string value (in
		720	which case you lose roundtripping ability, as the JSON number will be
		721	re-encoded toa JSON string).
		722
		723	Numbers containing a fractional or exponential part will always be
		724	represented as numeric (floating point) values, possibly at a loss of
		725	precision (in which case you might lose perfect roundtripping ability, but
		726	the JSON number will still be re-encoded as a JSON number).
560		727
561	=item true, false	728	=item true, false
562		729
563	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	730	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
564	respectively. They are overloaded to act almost exactly like the numbers	731	respectively. They are overloaded to act almost exactly like the numbers
565	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	732	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
566	the C<JSON::XS::is_bool> function.	733	the C<JSON::XS::is_bool> function.
567		734
568	=item null	735	=item null
569		736
570	A JSON null atom becomes C<undef> in Perl.	737	A JSON null atom becomes C<undef> in Perl.
…		…
601	Other unblessed references are generally not allowed and will cause an	768	Other unblessed references are generally not allowed and will cause an
602	exception to be thrown, except for references to the integers C<0> and	769	exception to be thrown, except for references to the integers C<0> and
603	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	770	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
604	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	771	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
605		772
606	to_json [\0,JSON::XS::true] # yields [false,true]	773	encode_json [\0,JSON::XS::true] # yields [false,true]
607		774
608	=item JSON::XS::true, JSON::XS::false	775	=item JSON::XS::true, JSON::XS::false
609		776
610	These special values become JSON true and JSON false values,	777	These special values become JSON true and JSON false values,
611	respectively. You cna alos use C<\1> and C<\0> directly if you want.	778	respectively. You can also use C<\1> and C<\0> directly if you want.
612		779
613	=item blessed objects	780	=item blessed objects
614		781
615	Blessed objects are not allowed. JSON::XS currently tries to encode their	782	Blessed objects are not directly representable in JSON. See the
616	underlying representation (hash- or arrayref), but this behaviour might	783	C<allow_blessed> and C<convert_blessed> methods on various options on
617	change in future versions.	784	how to deal with this: basically, you can choose between throwing an
		785	exception, encoding the reference as if it weren't blessed, or provide
		786	your own serialiser method.
618		787
619	=item simple scalars	788	=item simple scalars
620		789
621	Simple Perl scalars (any scalar that is not a reference) are the most	790	Simple Perl scalars (any scalar that is not a reference) are the most
622	difficult objects to encode: JSON::XS will encode undefined scalars as	791	difficult objects to encode: JSON::XS will encode undefined scalars as
623	JSON null value, scalars that have last been used in a string context	792	JSON C<null> values, scalars that have last been used in a string context
624	before encoding as JSON strings and anything else as number value:	793	before encoding as JSON strings, and anything else as number value:
625		794
626	# dump as number	795	# dump as number
627	to_json [2] # yields [2]	796	encode_json [2] # yields [2]
628	to_json [-3.0e17] # yields [-3e+17]	797	encode_json [-3.0e17] # yields [-3e+17]
629	my $value = 5; to_json [$value] # yields [5]	798	my $value = 5; encode_json [$value] # yields [5]
630		799
631	# used as string, so dump as string	800	# used as string, so dump as string
632	print $value;	801	print $value;
633	to_json [$value] # yields ["5"]	802	encode_json [$value] # yields ["5"]
634		803
635	# undef becomes null	804	# undef becomes null
636	to_json [undef] # yields [null]	805	encode_json [undef] # yields [null]
637		806
638	You can force the type to be a string by stringifying it:	807	You can force the type to be a JSON string by stringifying it:
639		808
640	my $x = 3.1; # some variable containing a number	809	my $x = 3.1; # some variable containing a number
641	"$x"; # stringified	810	"$x"; # stringified
642	$x .= ""; # another, more awkward way to stringify	811	$x .= ""; # another, more awkward way to stringify
643	print $x; # perl does it for you, too, quite often	812	print $x; # perl does it for you, too, quite often
644		813
645	You can force the type to be a number by numifying it:	814	You can force the type to be a JSON number by numifying it:
646		815
647	my $x = "3"; # some variable containing a string	816	my $x = "3"; # some variable containing a string
648	$x += 0; # numify it, ensuring it will be dumped as a number	817	$x += 0; # numify it, ensuring it will be dumped as a number
649	$x *= 1; # same thing, the choise is yours.	818	$x *= 1; # same thing, the choice is yours.
650		819
651	You can not currently output JSON booleans or force the type in other,	820	You can not currently force the type in other, less obscure, ways. Tell me
652	less obscure, ways. Tell me if you need this capability.	821	if you need this capability (but don't forget to explain why its needed
		822	:).
		823
		824	=back
		825
		826
		827	=head1 ENCODING/CODESET FLAG NOTES
		828
		829	The interested reader might have seen a number of flags that signify
		830	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		831	some confusion on what these do, so here is a short comparison:
		832
		833	C<utf8> controls wether the JSON text created by C<encode> (and expected
		834	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		835	control wether C<encode> escapes character values outside their respective
		836	codeset range. Neither of these flags conflict with each other, although
		837	some combinations make less sense than others.
		838
		839	Care has been taken to make all flags symmetrical with respect to
		840	C<encode> and C<decode>, that is, texts encoded with any combination of
		841	these flag values will be correctly decoded when the same flags are used
		842	- in general, if you use different flag settings while encoding vs. when
		843	decoding you likely have a bug somewhere.
		844
		845	Below comes a verbose discussion of these flags. Note that a "codeset" is
		846	simply an abstract set of character-codepoint pairs, while an encoding
		847	takes those codepoint numbers and I<encodes> them, in our case into
		848	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		849	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		850	the same time, which can be confusing.
		851
		852	=over 4
		853
		854	=item C<utf8> flag disabled
		855
		856	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		857	and expect Unicode strings, that is, characters with high ordinal Unicode
		858	values (> 255) will be encoded as such characters, and likewise such
		859	characters are decoded as-is, no canges to them will be done, except
		860	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		861	respectively (to Perl, these are the same thing in strings unless you do
		862	funny/weird/dumb stuff).
		863
		864	This is useful when you want to do the encoding yourself (e.g. when you
		865	want to have UTF-16 encoded JSON texts) or when some other layer does
		866	the encoding for you (for example, when printing to a terminal using a
		867	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		868	to UTF-8 encode your data first and have Perl encode it another time).
		869
		870	=item C<utf8> flag enabled
		871
		872	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		873	characters using the corresponding UTF-8 multi-byte sequence, and will
		874	expect your input strings to be encoded as UTF-8, that is, no "character"
		875	of the input string must have any value > 255, as UTF-8 does not allow
		876	that.
		877
		878	The C<utf8> flag therefore switches between two modes: disabled means you
		879	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		880	octet/binary string in Perl.
		881
		882	=item C<latin1> or C<ascii> flags enabled
		883
		884	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		885	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		886	characters as specified by the C<utf8> flag.
		887
		888	If C<utf8> is disabled, then the result is also correctly encoded in those
		889	character sets (as both are proper subsets of Unicode, meaning that a
		890	Unicode string with all character values < 256 is the same thing as a
		891	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		892	the same thing as an ASCII string in Perl).
		893
		894	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		895	regardless of these flags, just some more characters will be escaped using
		896	C<\uXXXX> then before.
		897
		898	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		899	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		900	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		901	a subset of Unicode), while ASCII is.
		902
		903	Surprisingly, C<decode> will ignore these flags and so treat all input
		904	values as governed by the C<utf8> flag. If it is disabled, this allows you
		905	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		906	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		907
		908	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		909	they only govern when the JSON output engine escapes a character or not.
		910
		911	The main use for C<latin1> is to relatively efficiently store binary data
		912	as JSON, at the expense of breaking compatibility with most JSON decoders.
		913
		914	The main use for C<ascii> is to force the output to not contain characters
		915	with values > 127, which means you can interpret the resulting string
		916	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		917	8-bit-encoding, and still get the same data structure back. This is useful
		918	when your channel for JSON transfer is not 8-bit clean or the encoding
		919	might be mangled in between (e.g. in mail), and works because ASCII is a
		920	proper subset of most 8-bit and multibyte encodings in use in the world.
653		921
654	=back	922	=back
655		923
656		924
657	=head1 COMPARISON	925	=head1 COMPARISON
…		…
662	followed by some benchmark values. JSON::XS was designed not to suffer	930	followed by some benchmark values. JSON::XS was designed not to suffer
663	from any of these problems or limitations.	931	from any of these problems or limitations.
664		932
665	=over 4	933	=over 4
666		934
		935	=item JSON 2.xx
		936
		937	A marvellous piece of engineering, this module either uses JSON::XS
		938	directly when available (so will be 100% compatible with it, including
		939	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		941	slower.
		942
		943	You cannot really lose by using this module, especially as it tries very
		944	hard to work even with ancient Perl versions, while JSON::XS does not.
		945
667	=item JSON 1.07	946	=item JSON 1.07
668		947
669	Slow (but very portable, as it is written in pure Perl).	948	Slow (but very portable, as it is written in pure Perl).
670		949
671	Undocumented/buggy Unicode handling (how JSON handles unicode values is	950	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
672	undocumented. One can get far by feeding it unicode strings and doing	951	undocumented. One can get far by feeding it Unicode strings and doing
673	en-/decoding oneself, but unicode escapes are not working properly).	952	en-/decoding oneself, but Unicode escapes are not working properly).
674		953
675	No roundtripping (strings get clobbered if they look like numbers, e.g.	954	No round-tripping (strings get clobbered if they look like numbers, e.g.
676	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	955	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
677	decode into the number 2.	956	decode into the number 2.
678		957
679	=item JSON::PC 0.01	958	=item JSON::PC 0.01
680		959
681	Very fast.	960	Very fast.
682		961
683	Undocumented/buggy Unicode handling.	962	Undocumented/buggy Unicode handling.
684		963
685	No roundtripping.	964	No round-tripping.
686		965
687	Has problems handling many Perl values (e.g. regex results and other magic	966	Has problems handling many Perl values (e.g. regex results and other magic
688	values will make it croak).	967	values will make it croak).
689		968
690	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	969	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
700	Very inflexible (no human-readable format supported, format pretty much	979	Very inflexible (no human-readable format supported, format pretty much
701	undocumented. I need at least a format for easy reading by humans and a	980	undocumented. I need at least a format for easy reading by humans and a
702	single-line compact format for use in a protocol, and preferably a way to	981	single-line compact format for use in a protocol, and preferably a way to
703	generate ASCII-only JSON texts).	982	generate ASCII-only JSON texts).
704		983
705	Completely broken (and confusingly documented) Unicode handling (unicode	984	Completely broken (and confusingly documented) Unicode handling (Unicode
706	escapes are not working properly, you need to set ImplicitUnicode to	985	escapes are not working properly, you need to set ImplicitUnicode to
707	I<different> values on en- and decoding to get symmetric behaviour).	986	I<different> values on en- and decoding to get symmetric behaviour).
708		987
709	No roundtripping (simple cases work, but this depends on wether the scalar	988	No round-tripping (simple cases work, but this depends on whether the scalar
710	value was used in a numeric context or not).	989	value was used in a numeric context or not).
711		990
712	Dumping hashes may skip hash values depending on iterator state.	991	Dumping hashes may skip hash values depending on iterator state.
713		992
714	Unmaintained (maintainer unresponsive for many months, bugs are not	993	Unmaintained (maintainer unresponsive for many months, bugs are not
715	getting fixed).	994	getting fixed).
716		995
717	Does not check input for validity (i.e. will accept non-JSON input and	996	Does not check input for validity (i.e. will accept non-JSON input and
718	return "something" instead of raising an exception. This is a security	997	return "something" instead of raising an exception. This is a security
719	issue: imagine two banks transfering money between each other using	998	issue: imagine two banks transferring money between each other using
720	JSON. One bank might parse a given non-JSON request and deduct money,	999	JSON. One bank might parse a given non-JSON request and deduct money,
721	while the other might reject the transaction with a syntax error. While a	1000	while the other might reject the transaction with a syntax error. While a
722	good protocol will at least recover, that is extra unnecessary work and	1001	good protocol will at least recover, that is extra unnecessary work and
723	the transaction will still not succeed).	1002	the transaction will still not succeed).
724		1003
725	=item JSON::DWIW 0.04	1004	=item JSON::DWIW 0.04
726		1005
727	Very fast. Very natural. Very nice.	1006	Very fast. Very natural. Very nice.
728		1007
729	Undocumented unicode handling (but the best of the pack. Unicode escapes	1008	Undocumented Unicode handling (but the best of the pack. Unicode escapes
730	still don't get parsed properly).	1009	still don't get parsed properly).
731		1010
732	Very inflexible.	1011	Very inflexible.
733		1012
734	No roundtripping.	1013	No round-tripping.
735		1014
736	Does not generate valid JSON texts (key strings are often unquoted, empty keys	1015	Does not generate valid JSON texts (key strings are often unquoted, empty keys
737	result in nothing being output)	1016	result in nothing being output)
738		1017
739	Does not check input for validity.	1018	Does not check input for validity.
…		…
741	=back	1020	=back
742		1021
743		1022
744	=head2 JSON and YAML	1023	=head2 JSON and YAML
745		1024
746	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1025	You often hear that JSON is a subset of YAML. This is, however, a mass
747	however, a mass hysteria and very far from the truth. In general, there is	1026	hysteria(*) and very far from the truth. In general, there is no way to
748	no way to configure JSON::XS to output a data structure as valid YAML.	1027	configure JSON::XS to output a data structure as valid YAML that works for
		1028	all cases.
749		1029
750	If you really must use JSON::XS to generate YAML, you should use this	1030	If you really must use JSON::XS to generate YAML, you should use this
751	algorithm (subject to change in future versions):	1031	algorithm (subject to change in future versions):
752		1032
753	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1033	my $to_yaml = JSON::XS->new->utf8->space_after (1);
754	my $yaml = $to_yaml->encode ($ref) . "\n";	1034	my $yaml = $to_yaml->encode ($ref) . "\n";
755		1035
756	This will usually generate JSON texts that also parse as valid	1036	This will I<usually> generate JSON texts that also parse as valid
757	YAML. Please note that YAML has hardcoded limits on (simple) object key	1037	YAML. Please note that YAML has hardcoded limits on (simple) object key
758	lengths that JSON doesn't have, so you should make sure that your hash	1038	lengths that JSON doesn't have and also has different and incompatible
		1039	unicode handling, so you should make sure that your hash keys are
759	keys are noticably shorter than the 1024 characters YAML allows.	1040	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1041	you do not have codepoints with values outside the Unicode BMP (basic
		1042	multilingual page). YAML also does not allow C<\/> sequences in strings
		1043	(which JSON::XS does not I<currently> generate).
760		1044
761	There might be other incompatibilities that I am not aware of. In general	1045	There might be other incompatibilities that I am not aware of (or the YAML
		1046	specification has been changed yet again - it does so quite often). In
762	you should not try to generate YAML with a JSON generator or vice versa,	1047	general you should not try to generate YAML with a JSON generator or vice
763	or try to parse JSON with a YAML parser or vice versa: chances are high	1048	versa, or try to parse JSON with a YAML parser or vice versa: chances are
764	that you will run into severe interoperability problems.	1049	high that you will run into severe interoperability problems when you
		1050	least expect it.
		1051
		1052	=over 4
		1053
		1054	=item (*)
		1055
		1056	This is spread actively by the YAML team, however. For many years now they
		1057	claim YAML were a superset of JSON, even when proven otherwise.
		1058
		1059	Even the author of this manpage was at some point accused of providing
		1060	"incorrect" information, despite the evidence presented (claims ranged
		1061	from "your documentation contains inaccurate and negative statements about
		1062	YAML" (the only negative comment is this footnote, and it didn't exist
		1063	back then; the question on which claims were inaccurate was never answered
		1064	etc.) to "the YAML spec is not up-to-date" (the real and supposedly
		1065	JSON-compatible spec is apparently not currently publicly available)
		1066	to actual requests to replace this section by incorrect information,
		1067	suppressing information about the real problem).
		1068
		1069	So whenever you are told that YAML was a superset of JSON, first check
		1070	wether it is really true (it might be when you check it, but it certainly
		1071	was not true when this was written). I would much prefer if the YAML team
		1072	would spent their time on actually making JSON compatibility a truth
		1073	(JSON, after all, has a very small and simple specification) instead of
		1074	trying to lobby/force people into reporting untruths.
		1075
		1076	=back
765		1077
766		1078
767	=head2 SPEED	1079	=head2 SPEED
768		1080
769	It seems that JSON::XS is surprisingly fast, as shown in the following	1081	It seems that JSON::XS is surprisingly fast, as shown in the following
…		…
780	It shows the number of encodes/decodes per second (JSON::XS uses	1092	It shows the number of encodes/decodes per second (JSON::XS uses
781	the functional interface, while JSON::XS/2 uses the OO interface	1093	the functional interface, while JSON::XS/2 uses the OO interface
782	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1094	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
783	shrink). Higher is better:	1095	shrink). Higher is better:
784		1096
785	Storable \| 15779.925 \| 14169.946 \|
786	-----------+------------+------------+
787	module \| encode \| decode \|	1097	module \| encode \| decode \|
788	-----------\|------------\|------------\|	1098	-----------\|------------\|------------\|
789	JSON \| 4990.842 \| 4088.813 \|	1099	JSON 1.x \| 4990.842 \| 4088.813 \|
790	JSON::DWIW \| 51653.990 \| 71575.154 \|	1100	JSON::DWIW \| 51653.990 \| 71575.154 \|
791	JSON::PC \| 65948.176 \| 74631.744 \|	1101	JSON::PC \| 65948.176 \| 74631.744 \|
792	JSON::PP \| 8931.652 \| 3817.168 \|	1102	JSON::PP \| 8931.652 \| 3817.168 \|
793	JSON::Syck \| 24877.248 \| 27776.848 \|	1103	JSON::Syck \| 24877.248 \| 27776.848 \|
794	JSON::XS \| 388361.481 \| 227951.304 \|	1104	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
796	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1106	JSON::XS/3 \| 338250.323 \| 218453.333 \|
797	Storable \| 16500.016 \| 135300.129 \|	1107	Storable \| 16500.016 \| 135300.129 \|
798	-----------+------------+------------+	1108	-----------+------------+------------+
799		1109
800	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1110	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
801	about three times faster on decoding, and over fourty times faster	1111	about three times faster on decoding, and over forty times faster
802	than JSON, even with pretty-printing and key sorting. It also compares	1112	than JSON, even with pretty-printing and key sorting. It also compares
803	favourably to Storable for small amounts of data.	1113	favourably to Storable for small amounts of data.
804		1114
805	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1115	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
806	search API (http://nanoref.com/yahooapis/mgPdGg):	1116	search API (http://nanoref.com/yahooapis/mgPdGg):
807		1117
808	module \| encode \| decode \|	1118	module \| encode \| decode \|
809	-----------\|------------\|------------\|	1119	-----------\|------------\|------------\|
810	JSON \| 55.260 \| 34.971 \|	1120	JSON 1.x \| 55.260 \| 34.971 \|
811	JSON::DWIW \| 825.228 \| 1082.513 \|	1121	JSON::DWIW \| 825.228 \| 1082.513 \|
812	JSON::PC \| 3571.444 \| 2394.829 \|	1122	JSON::PC \| 3571.444 \| 2394.829 \|
813	JSON::PP \| 210.987 \| 32.574 \|	1123	JSON::PP \| 210.987 \| 32.574 \|
814	JSON::Syck \| 552.551 \| 787.544 \|	1124	JSON::Syck \| 552.551 \| 787.544 \|
815	JSON::XS \| 5780.463 \| 4854.519 \|	1125	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
819	-----------+------------+------------+	1129	-----------+------------+------------+
820		1130
821	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1131	Again, JSON::XS leads by far (except for Storable which non-surprisingly
822	decodes faster).	1132	decodes faster).
823		1133
824	On large strings containing lots of high unicode characters, some modules	1134	On large strings containing lots of high Unicode characters, some modules
825	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1135	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
826	will be broken due to missing (or wrong) unicode handling. Others refuse	1136	will be broken due to missing (or wrong) Unicode handling. Others refuse
827	to decode or encode properly, so it was impossible to prepare a fair	1137	to decode or encode properly, so it was impossible to prepare a fair
828	comparison table for that case.	1138	comparison table for that case.
829		1139
830		1140
831	=head1 SECURITY CONSIDERATIONS	1141	=head1 SECURITY CONSIDERATIONS
…		…
837	any buffer overflows. Obviously, this module should ensure that and I am	1147	any buffer overflows. Obviously, this module should ensure that and I am
838	trying hard on making that true, but you never know.	1148	trying hard on making that true, but you never know.
839		1149
840	Second, you need to avoid resource-starving attacks. That means you should	1150	Second, you need to avoid resource-starving attacks. That means you should
841	limit the size of JSON texts you accept, or make sure then when your	1151	limit the size of JSON texts you accept, or make sure then when your
842	resources run out, thats just fine (e.g. by using a separate process that	1152	resources run out, that's just fine (e.g. by using a separate process that
843	can crash safely). The size of a JSON text in octets or characters is	1153	can crash safely). The size of a JSON text in octets or characters is
844	usually a good indication of the size of the resources required to decode	1154	usually a good indication of the size of the resources required to decode
845	it into a Perl structure. While JSON::XS can check the size of the JSON	1155	it into a Perl structure. While JSON::XS can check the size of the JSON
846	text, it might be too late when you already have it in memory, so you	1156	text, it might be too late when you already have it in memory, so you
847	might want to check the size before you accept the string.	1157	might want to check the size before you accept the string.
848		1158
849	Third, JSON::XS recurses using the C stack when decoding objects and	1159	Third, JSON::XS recurses using the C stack when decoding objects and
850	arrays. The C stack is a limited resource: for instance, on my amd64	1160	arrays. The C stack is a limited resource: for instance, on my amd64
851	machine with 8MB of stack size I can decode around 180k nested arrays but	1161	machine with 8MB of stack size I can decode around 180k nested arrays but
852	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1162	only 14k nested JSON objects (due to perl itself recursing deeply on croak
853	to free the temporary). If that is exceeded, the program crashes. to be	1163	to free the temporary). If that is exceeded, the program crashes. To be
854	conservative, the default nesting limit is set to 512. If your process	1164	conservative, the default nesting limit is set to 512. If your process
855	has a smaller stack, you should adjust this setting accordingly with the	1165	has a smaller stack, you should adjust this setting accordingly with the
856	C<max_depth> method.	1166	C<max_depth> method.
857		1167
858	And last but least, something else could bomb you that I forgot to think	1168	Something else could bomb you, too, that I forgot to think of. In that
859	of. In that case, you get to keep the pieces. I am always open for hints,	1169	case, you get to keep the pieces. I am always open for hints, though...
860	though...	1170
		1171	Also keep in mind that JSON::XS might leak contents of your Perl data
		1172	structures in its error messages, so when you serialise sensitive
		1173	information you might want to make sure that exceptions thrown by JSON::XS
		1174	will not end up in front of untrusted eyes.
861		1175
862	If you are using JSON::XS to return packets to consumption	1176	If you are using JSON::XS to return packets to consumption
863	by javascript scripts in a browser you should have a look at	1177	by JavaScript scripts in a browser you should have a look at
864	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1178	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
865	you are vulnerable to some common attack vectors (which really are browser	1179	you are vulnerable to some common attack vectors (which really are browser
866	design bugs, but it is still you who will have to deal with it, as major	1180	design bugs, but it is still you who will have to deal with it, as major
867	browser developers care only for features, not about doing security	1181	browser developers care only for features, not about getting security
868	right).	1182	right).
		1183
		1184
		1185	=head1 THREADS
		1186
		1187	This module is I<not> guaranteed to be thread safe and there are no
		1188	plans to change this until Perl gets thread support (as opposed to the
		1189	horribly slow so-called "threads" which are simply slow and bloated
		1190	process simulations - use fork, its I<much> faster, cheaper, better).
		1191
		1192	(It might actually work, but you have been warned).
869		1193
870		1194
871	=head1 BUGS	1195	=head1 BUGS
872		1196
873	While the goal of this module is to be correct, that unfortunately does	1197	While the goal of this module is to be correct, that unfortunately does
874	not mean its bug-free, only that I think its design is bug-free. It is	1198	not mean its bug-free, only that I think its design is bug-free. It is
875	still relatively early in its development. If you keep reporting bugs they	1199	still relatively early in its development. If you keep reporting bugs they
876	will be fixed swiftly, though.	1200	will be fixed swiftly, though.
877		1201
		1202	Please refrain from using rt.cpan.org or any other bug reporting
		1203	service. I put the contact address into my modules for a reason.
		1204
878	=cut	1205	=cut
879		1206
880	our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };	1207	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
881	our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };	1208	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
882		1209
883	sub true() { $true }	1210	sub true() { $true }
884	sub false() { $false }	1211	sub false() { $false }
885		1212
886	sub is_bool($) {	1213	sub is_bool($) {

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs. Revision 1.86 by root, Wed Mar 19 03:17:38 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.51 by root, Mon Jul 2 01:12:27 2007 UTC vs.
Revision 1.86 by root, Wed Mar 19 03:17:38 2008 UTC