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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs.
Revision 1.99 by root, Thu Mar 27 06:37:35 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
		3	=encoding utf-8
		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 $VERSION = '2.2';
87	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
88		110
89	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		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.
168		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
169	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
170	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
171	contain any 8 bit characters.	255	contain any 8 bit characters.
172		256
173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
175		259
176	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
177		261
		262	=item $enabled = $json->get_latin1
		263
178	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
181	latin1-encoded JSON text or a native unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
182	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
183	expects unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
184		270
185	If C<$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
186	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.
187		276
188	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
189	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
190	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
191	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
192	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
193	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
194	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.
195		284
196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198		287
199	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
200		291
201	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
202	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
203	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
204	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
207	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
208		299
209	If C<$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
210	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
211	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
212	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.
213		307
214	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
215		309
216	use Encode;	310	use Encode;
217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
238	]	332	]
239	}	333	}
240		334
241	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
242		336
		337	=item $enabled = $json->get_indent
		338
243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
245	into its own line, identing them properly.	341	into its own line, indenting them properly.
246		342
247	If C<$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
248	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
249		345
250	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
251		347
252	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
253		351
254	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
255	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
256		354
257	If C<$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
…		…
263	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
264		362
265	{"key" :"value"}	363	{"key" :"value"}
266		364
267	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
268		368
269	If C<$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
270	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
271	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
272	members.	372	members.
…		…
278		378
279	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
280		380
281	{"key": "value"}	381	{"key": "value"}
282		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
283	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
		431
		432	=item $enabled = $json->get_canonical
284		433
285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
286	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
287		436
288	If C<$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
289	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
290	of the same script).	439	of the same script).
291		440
292	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
293	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,
294	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,
295	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
296		445
297	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
298		447
299	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
300		451
301	If C<$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
302	non-reference into its corresponding string, number or null JSON value,	453	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	454	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
304	values instead of croaking.	455	values instead of croaking.
…		…
312	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
313		464
314	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
315	=> "Hello, World!"	466	=> "Hello, World!"
316		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
317	=item $json = $json->allow_blessed ([$enable])	484	=item $json = $json->allow_blessed ([$enable])
		485
		486	=item $enabled = $json->get_allow_blessed
318		487
319	If C<$enable> is true (or missing), then the C<encode> method will not	488	If C<$enable> is true (or missing), then the C<encode> method will not
320	barf when it encounters a blessed reference. Instead, the value of the	489	barf when it encounters a blessed reference. Instead, the value of the
321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
322	disabled or no C<to_json> method found) or a representation of the	491	disabled or no C<TO_JSON> method found) or a representation of the
323	object (C<convert_blessed> enabled and C<to_json> method found) is being	492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
324	encoded. Has no effect on C<decode>.	493	encoded. Has no effect on C<decode>.
325		494
326	If C<$enable> is false (the default), then C<encode> will throw an	495	If C<$enable> is false (the default), then C<encode> will throw an
327	exception when it encounters a blessed object.	496	exception when it encounters a blessed object.
328		497
329	=item $json = $json->convert_blessed ([$enable])	498	=item $json = $json->convert_blessed ([$enable])
		499
		500	=item $enabled = $json->get_convert_blessed
330		501
331	If C<$enable> is true (or missing), then C<encode>, upon encountering a	502	If C<$enable> is true (or missing), then C<encode>, upon encountering a
332	blessed object, will check for the availability of the C<TO_JSON> method	503	blessed object, will check for the availability of the C<TO_JSON> method
333	on the object's class. If found, it will be called in scalar context	504	on the object's class. If found, it will be called in scalar context
334	and the resulting scalar will be encoded instead of the object. If no	505	and the resulting scalar will be encoded instead of the object. If no
…		…
338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	509	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
339	returns other blessed objects, those will be handled in the same	510	returns other blessed objects, those will be handled in the same
340	way. C<TO_JSON> must take care of not causing an endless recursion cycle	511	way. C<TO_JSON> must take care of not causing an endless recursion cycle
341	(== crash) in this case. The name of C<TO_JSON> was chosen because other	512	(== crash) in this case. The name of C<TO_JSON> was chosen because other
342	methods called by the Perl core (== not by the user of the object) are	513	methods called by the Perl core (== not by the user of the object) are
343	usually in upper case letters and to avoid collisions with the C<to_json>	514	usually in upper case letters and to avoid collisions with any C<to_json>
344	function.	515	function or method.
345		516
346	This setting does not yet influence C<decode> in any way, but in the	517	This setting does not yet influence C<decode> in any way, but in the
347	future, global hooks might get installed that influence C<decode> and are	518	future, global hooks might get installed that influence C<decode> and are
348	enabled by this setting.	519	enabled by this setting.
349		520
350	If C<$enable> is false, then the C<allow_blessed> setting will decide what	521	If C<$enable> is false, then the C<allow_blessed> setting will decide what
351	to do when a blessed object is found.	522	to do when a blessed object is found.
352		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
353	=item $json = $json->shrink ([$enable])	600	=item $json = $json->shrink ([$enable])
		601
		602	=item $enabled = $json->get_shrink
354		603
355	Perl usually over-allocates memory a bit when allocating space for	604	Perl usually over-allocates memory a bit when allocating space for
356	strings. This flag optionally resizes strings generated by either	605	strings. This flag optionally resizes strings generated by either
357	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
358	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
…		…
376	strings that look like integers or floats into integers or floats	625	strings that look like integers or floats into integers or floats
377	internally (there is no difference on the Perl level), saving space.	626	internally (there is no difference on the Perl level), saving space.
378		627
379	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
380		629
		630	=item $max_depth = $json->get_max_depth
		631
381	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
382	or decoding. If the JSON text or Perl data structure has an equal or	633	or decoding. If the JSON text or Perl data structure has an equal or
383	higher nesting level then this limit, then the encoder and decoder will	634	higher nesting level then this limit, then the encoder and decoder will
384	stop and croak at that point.	635	stop and croak at that point.
385		636
…		…
396	used, which is rarely useful.	647	used, which is rarely useful.
397		648
398	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	649	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
399		650
400	=item $json = $json->max_size ([$maximum_string_size])	651	=item $json = $json->max_size ([$maximum_string_size])
		652
		653	=item $max_size = $json->get_max_size
401		654
402	Set the maximum length a JSON text may have (in bytes) where decoding is	655	Set the maximum length a JSON text may have (in bytes) where decoding is
403	being attempted. The default is C<0>, meaning no limit. When C<decode>	656	being attempted. The default is C<0>, meaning no limit. When C<decode>
404	is called on a string longer then this number of characters it will not	657	is called on a string longer then this number of characters it will not
405	attempt to decode the string but throw an exception. This setting has no	658	attempt to decode the string but throw an exception. This setting has no
…		…
444	=> ([], 3)	697	=> ([], 3)
445		698
446	=back	699	=back
447		700
448		701
		702	=head1 INCREMENTAL PARSING
		703
		704	[This section and the API it details is still EXPERIMENTAL]
		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 is
		712	much more efficient (JSON::XS will only attempt to parse the JSON text
		713	once it is sure it has enough text to get a decisive result, using a very
		714	simple but truly incremental parser).
		715
		716	The following two methods deal with this.
		717
		718	=over 4
		719
		720	=item [void, scalar or list context] = $json->incr_parse ([$string])
		721
		722	This is the central parsing function. It can both append new text and
		723	extract objects from the stream accumulated so far (both of these
		724	functions are optional).
		725
		726	If C<$string> is given, then this string is appended to the already
		727	existing JSON fragment stored in the C<$json> object.
		728
		729	After that, if the function is called in void context, it will simply
		730	return without doing anything further. This can be used to add more text
		731	in as many chunks as you want.
		732
		733	If the method is called in scalar context, then it will try to extract
		734	exactly I<one> JSON object. If that is successful, it will return this
		735	object, otherwise it will return C<undef>. If there is a parse error,
		736	this method will croak just as C<decode> would do (one can then use
		737	C<incr_skip> to skip the errornous part). This is the most common way of
		738	using the method.
		739
		740	And finally, in list context, it will try to extract as many objects
		741	from the stream as it can find and return them, or the empty list
		742	otherwise. For this to work, there must be no separators between the JSON
		743	objects or arrays, instead they must be concatenated back-to-back. If
		744	an error occurs, an exception will be raised as in the scalar context
		745	case. Note that in this case, any previously-parsed JSON texts will be
		746	lost.
		747
		748	=item $lvalue_string = $json->incr_text
		749
		750	This method returns the currently stored JSON fragment as an lvalue, that
		751	is, you can manipulate it. This I<only> works when a preceding call to
		752	C<incr_parse> in I<scalar context> successfully returned an object. Under
		753	all other circumstances you must not call this function (I mean it.
		754	although in simple tests it might actually work, it I<will> fail under
		755	real world conditions). As a special exception, you can also call this
		756	method before having parsed anything.
		757
		758	This function is useful in two cases: a) finding the trailing text after a
		759	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		760	(such as commas).
		761
		762	=item $json->incr_skip
		763
		764	This will reset the state of the incremental parser and will remove the
		765	parsed text from the input buffer. This is useful after C<incr_parse>
		766	died, in which case the input buffer and incremental parser state is left
		767	unchanged, to skip the text parsed so far and to reset the parse state.
		768
		769	=back
		770
		771	=head2 LIMITATIONS
		772
		773	All options that affect decoding are supported, except
		774	C<allow_nonref>. The reason for this is that it cannot be made to
		775	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		776	them back to back and still decode them perfectly. This does not hold true
		777	for JSON numbers, however.
		778
		779	For example, is the string C<1> a single JSON number, or is it simply the
		780	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		781	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		782	takes the conservative route and disallows this case.
		783
		784	=head2 EXAMPLES
		785
		786	Some examples will make all this clearer. First, a simple example that
		787	works similarly to C<decode_prefix>: We want to decode the JSON object at
		788	the start of a string and identify the portion after the JSON object:
		789
		790	my $text = "[1,2,3] hello";
		791
		792	my $json = new JSON::XS;
		793
		794	my $obj = $json->incr_parse ($text)
		795	or die "expected JSON object or array at beginning of string";
		796
		797	my $tail = $json->incr_text;
		798	# $tail now contains " hello"
		799
		800	Easy, isn't it?
		801
		802	Now for a more complicated example: Imagine a hypothetical protocol where
		803	you read some requests from a TCP stream, and each request is a JSON
		804	array, without any separation between them (in fact, it is often useful to
		805	use newlines as "separators", as these get interpreted as whitespace at
		806	the start of the JSON text, which makes it possible to test said protocol
		807	with C<telnet>...).
		808
		809	Here is how you'd do it (it is trivial to write this in an event-based
		810	manner):
		811
		812	my $json = new JSON::XS;
		813
		814	# read some data from the socket
		815	while (sysread $socket, my $buf, 4096) {
		816
		817	# split and decode as many requests as possible
		818	for my $request ($json->incr_parse ($buf)) {
		819	# act on the $request
		820	}
		821	}
		822
		823	Another complicated example: Assume you have a string with JSON objects
		824	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		825	[3]>). To parse them, we have to skip the commas between the JSON texts,
		826	and here is where the lvalue-ness of C<incr_text> comes in useful:
		827
		828	my $text = "[1],[2], [3]";
		829	my $json = new JSON::XS;
		830
		831	# void context, so no parsing done
		832	$json->incr_parse ($text);
		833
		834	# now extract as many objects as possible. note the
		835	# use of scalar context so incr_text can be called.
		836	while (my $obj = $json->incr_parse) {
		837	# do something with $obj
		838
		839	# now skip the optional comma
		840	$json->incr_text =~ s/^ \s* , //x;
		841	}
		842
		843	Now lets go for a very complex example: Assume that you have a gigantic
		844	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		845	but you cannot load it into memory fully (this has actually happened in
		846	the real world :).
		847
		848	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		849	can still help you: You implement a (very simple) array parser and let
		850	JSON decode the array elements, which are all full JSON objects on their
		851	own (this wouldn't work if the array elements could be JSON numbers, for
		852	example):
		853
		854	my $json = new JSON::XS;
		855
		856	# open the monster
		857	open my $fh, "<bigfile.json"
		858	or die "bigfile: $!";
		859
		860	# first parse the initial "["
		861	for (;;) {
		862	sysread $fh, my $buf, 65536
		863	or die "read error: $!";
		864	$json->incr_parse ($buf); # void context, so no parsing
		865
		866	# Exit the loop once we found and removed(!) the initial "[".
		867	# In essence, we are (ab-)using the $json object as a simple scalar
		868	# we append data to.
		869	last if $json->incr_text =~ s/^ \s* \[ //x;
		870	}
		871
		872	# now we have the skipped the initial "[", so continue
		873	# parsing all the elements.
		874	for (;;) {
		875	# in this loop we read data until we got a single JSON object
		876	for (;;) {
		877	if (my $obj = $json->incr_parse) {
		878	# do something with $obj
		879	last;
		880	}
		881
		882	# add more data
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886	}
		887
		888	# in this loop we read data until we either found and parsed the
		889	# separating "," between elements, or the final "]"
		890	for (;;) {
		891	# first skip whitespace
		892	$json->incr_text =~ s/^\s*//;
		893
		894	# if we find "]", we are done
		895	if ($json->incr_text =~ s/^\]//) {
		896	print "finished.\n";
		897	exit;
		898	}
		899
		900	# if we find ",", we can continue with the next element
		901	if ($json->incr_text =~ s/^,//) {
		902	last;
		903	}
		904
		905	# if we find anything else, we have a parse error!
		906	if (length $json->incr_text) {
		907	die "parse error near ", $json->incr_text;
		908	}
		909
		910	# else add more data
		911	sysread $fh, my $buf, 65536
		912	or die "read error: $!";
		913	$json->incr_parse ($buf); # void context, so no parsing
		914	}
		915
		916	This is a complex example, but most of the complexity comes from the fact
		917	that we are trying to be correct (bear with me if I am wrong, I never ran
		918	the above example :).
		919
		920
		921
449	=head1 MAPPING	922	=head1 MAPPING
450		923
451	This section describes how JSON::XS maps Perl values to JSON values and	924	This section describes how JSON::XS maps Perl values to JSON values and
452	vice versa. These mappings are designed to "do the right thing" in most	925	vice versa. These mappings are designed to "do the right thing" in most
453	circumstances automatically, preserving round-tripping characteristics	926	circumstances automatically, preserving round-tripping characteristics
454	(what you put in comes out as something equivalent).	927	(what you put in comes out as something equivalent).
455		928
456	For the more enlightened: note that in the following descriptions,	929	For the more enlightened: note that in the following descriptions,
457	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	930	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
458	refers to the abstract Perl language itself.	931	refers to the abstract Perl language itself.
459		932
460		933
461	=head2 JSON -> PERL	934	=head2 JSON -> PERL
462		935
463	=over 4	936	=over 4
464		937
465	=item object	938	=item object
466		939
467	A JSON object becomes a reference to a hash in Perl. No ordering of object	940	A JSON object becomes a reference to a hash in Perl. No ordering of object
468	keys is preserved (JSON does not preserver object key ordering itself).	941	keys is preserved (JSON does not preserve object key ordering itself).
469		942
470	=item array	943	=item array
471		944
472	A JSON array becomes a reference to an array in Perl.	945	A JSON array becomes a reference to an array in Perl.
473		946
…		…
477	are represented by the same codepoints in the Perl string, so no manual	950	are represented by the same codepoints in the Perl string, so no manual
478	decoding is necessary.	951	decoding is necessary.
479		952
480	=item number	953	=item number
481		954
482	A JSON number becomes either an integer or numeric (floating point)	955	A JSON number becomes either an integer, numeric (floating point) or
483	scalar in perl, depending on its range and any fractional parts. On the	956	string scalar in perl, depending on its range and any fractional parts. On
484	Perl level, there is no difference between those as Perl handles all the	957	the Perl level, there is no difference between those as Perl handles all
485	conversion details, but an integer may take slightly less memory and might	958	the conversion details, but an integer may take slightly less memory and
486	represent more values exactly than (floating point) numbers.	959	might represent more values exactly than floating point numbers.
		960
		961	If the number consists of digits only, JSON::XS will try to represent
		962	it as an integer value. If that fails, it will try to represent it as
		963	a numeric (floating point) value if that is possible without loss of
		964	precision. Otherwise it will preserve the number as a string value (in
		965	which case you lose roundtripping ability, as the JSON number will be
		966	re-encoded toa JSON string).
		967
		968	Numbers containing a fractional or exponential part will always be
		969	represented as numeric (floating point) values, possibly at a loss of
		970	precision (in which case you might lose perfect roundtripping ability, but
		971	the JSON number will still be re-encoded as a JSON number).
487		972
488	=item true, false	973	=item true, false
489		974
490	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	975	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
491	respectively. They are overloaded to act almost exactly like the numbers	976	respectively. They are overloaded to act almost exactly like the numbers
492	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	977	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
493	the C<JSON::XS::is_bool> function.	978	the C<JSON::XS::is_bool> function.
494		979
495	=item null	980	=item null
496		981
497	A JSON null atom becomes C<undef> in Perl.	982	A JSON null atom becomes C<undef> in Perl.
…		…
528	Other unblessed references are generally not allowed and will cause an	1013	Other unblessed references are generally not allowed and will cause an
529	exception to be thrown, except for references to the integers C<0> and	1014	exception to be thrown, except for references to the integers C<0> and
530	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1015	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
531	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1016	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
532		1017
533	to_json [\0,JSON::XS::true] # yields [false,true]	1018	encode_json [\0,JSON::XS::true] # yields [false,true]
534		1019
535	=item JSON::XS::true, JSON::XS::false	1020	=item JSON::XS::true, JSON::XS::false
536		1021
537	These special values become JSON true and JSON false values,	1022	These special values become JSON true and JSON false values,
538	respectively. You cna alos use C<\1> and C<\0> directly if you want.	1023	respectively. You can also use C<\1> and C<\0> directly if you want.
539		1024
540	=item blessed objects	1025	=item blessed objects
541		1026
542	Blessed objects are not allowed. JSON::XS currently tries to encode their	1027	Blessed objects are not directly representable in JSON. See the
543	underlying representation (hash- or arrayref), but this behaviour might	1028	C<allow_blessed> and C<convert_blessed> methods on various options on
544	change in future versions.	1029	how to deal with this: basically, you can choose between throwing an
		1030	exception, encoding the reference as if it weren't blessed, or provide
		1031	your own serialiser method.
545		1032
546	=item simple scalars	1033	=item simple scalars
547		1034
548	Simple Perl scalars (any scalar that is not a reference) are the most	1035	Simple Perl scalars (any scalar that is not a reference) are the most
549	difficult objects to encode: JSON::XS will encode undefined scalars as	1036	difficult objects to encode: JSON::XS will encode undefined scalars as
550	JSON null value, scalars that have last been used in a string context	1037	JSON C<null> values, scalars that have last been used in a string context
551	before encoding as JSON strings and anything else as number value:	1038	before encoding as JSON strings, and anything else as number value:
552		1039
553	# dump as number	1040	# dump as number
554	to_json [2] # yields [2]	1041	encode_json [2] # yields [2]
555	to_json [-3.0e17] # yields [-3e+17]	1042	encode_json [-3.0e17] # yields [-3e+17]
556	my $value = 5; to_json [$value] # yields [5]	1043	my $value = 5; encode_json [$value] # yields [5]
557		1044
558	# used as string, so dump as string	1045	# used as string, so dump as string
559	print $value;	1046	print $value;
560	to_json [$value] # yields ["5"]	1047	encode_json [$value] # yields ["5"]
561		1048
562	# undef becomes null	1049	# undef becomes null
563	to_json [undef] # yields [null]	1050	encode_json [undef] # yields [null]
564		1051
565	You can force the type to be a string by stringifying it:	1052	You can force the type to be a JSON string by stringifying it:
566		1053
567	my $x = 3.1; # some variable containing a number	1054	my $x = 3.1; # some variable containing a number
568	"$x"; # stringified	1055	"$x"; # stringified
569	$x .= ""; # another, more awkward way to stringify	1056	$x .= ""; # another, more awkward way to stringify
570	print $x; # perl does it for you, too, quite often	1057	print $x; # perl does it for you, too, quite often
571		1058
572	You can force the type to be a number by numifying it:	1059	You can force the type to be a JSON number by numifying it:
573		1060
574	my $x = "3"; # some variable containing a string	1061	my $x = "3"; # some variable containing a string
575	$x += 0; # numify it, ensuring it will be dumped as a number	1062	$x += 0; # numify it, ensuring it will be dumped as a number
576	$x *= 1; # same thing, the choise is yours.	1063	$x *= 1; # same thing, the choice is yours.
577		1064
578	You can not currently output JSON booleans or force the type in other,	1065	You can not currently force the type in other, less obscure, ways. Tell me
579	less obscure, ways. Tell me if you need this capability.	1066	if you need this capability (but don't forget to explain why it's needed
		1067	:).
580		1068
581	=back	1069	=back
582		1070
583		1071
584	=head1 COMPARISON	1072	=head1 ENCODING/CODESET FLAG NOTES
585		1073
586	As already mentioned, this module was created because none of the existing	1074	The interested reader might have seen a number of flags that signify
587	JSON modules could be made to work correctly. First I will describe the	1075	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
588	problems (or pleasures) I encountered with various existing JSON modules,	1076	some confusion on what these do, so here is a short comparison:
589	followed by some benchmark values. JSON::XS was designed not to suffer	1077
590	from any of these problems or limitations.	1078	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1079	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1080	control whether C<encode> escapes character values outside their respective
		1081	codeset range. Neither of these flags conflict with each other, although
		1082	some combinations make less sense than others.
		1083
		1084	Care has been taken to make all flags symmetrical with respect to
		1085	C<encode> and C<decode>, that is, texts encoded with any combination of
		1086	these flag values will be correctly decoded when the same flags are used
		1087	- in general, if you use different flag settings while encoding vs. when
		1088	decoding you likely have a bug somewhere.
		1089
		1090	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1091	simply an abstract set of character-codepoint pairs, while an encoding
		1092	takes those codepoint numbers and I<encodes> them, in our case into
		1093	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1094	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1095	the same time, which can be confusing.
591		1096
592	=over 4	1097	=over 4
593		1098
594	=item JSON 1.07	1099	=item C<utf8> flag disabled
595		1100
596	Slow (but very portable, as it is written in pure Perl).	1101	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1102	and expect Unicode strings, that is, characters with high ordinal Unicode
		1103	values (> 255) will be encoded as such characters, and likewise such
		1104	characters are decoded as-is, no canges to them will be done, except
		1105	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1106	respectively (to Perl, these are the same thing in strings unless you do
		1107	funny/weird/dumb stuff).
597		1108
598	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1109	This is useful when you want to do the encoding yourself (e.g. when you
599	undocumented. One can get far by feeding it unicode strings and doing	1110	want to have UTF-16 encoded JSON texts) or when some other layer does
600	en-/decoding oneself, but unicode escapes are not working properly).	1111	the encoding for you (for example, when printing to a terminal using a
		1112	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1113	to UTF-8 encode your data first and have Perl encode it another time).
601		1114
602	No roundtripping (strings get clobbered if they look like numbers, e.g.	1115	=item C<utf8> flag enabled
603	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
604	decode into the number 2.
605		1116
606	=item JSON::PC 0.01	1117	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1118	characters using the corresponding UTF-8 multi-byte sequence, and will
		1119	expect your input strings to be encoded as UTF-8, that is, no "character"
		1120	of the input string must have any value > 255, as UTF-8 does not allow
		1121	that.
607		1122
608	Very fast.	1123	The C<utf8> flag therefore switches between two modes: disabled means you
		1124	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1125	octet/binary string in Perl.
609		1126
610	Undocumented/buggy Unicode handling.	1127	=item C<latin1> or C<ascii> flags enabled
611		1128
612	No roundtripping.	1129	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1130	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1131	characters as specified by the C<utf8> flag.
613		1132
614	Has problems handling many Perl values (e.g. regex results and other magic	1133	If C<utf8> is disabled, then the result is also correctly encoded in those
615	values will make it croak).	1134	character sets (as both are proper subsets of Unicode, meaning that a
		1135	Unicode string with all character values < 256 is the same thing as a
		1136	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1137	the same thing as an ASCII string in Perl).
616		1138
617	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1139	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
618	which is not a valid JSON text.	1140	regardless of these flags, just some more characters will be escaped using
		1141	C<\uXXXX> then before.
619		1142
620	Unmaintained (maintainer unresponsive for many months, bugs are not	1143	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
621	getting fixed).	1144	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1145	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1146	a subset of Unicode), while ASCII is.
622		1147
623	=item JSON::Syck 0.21	1148	Surprisingly, C<decode> will ignore these flags and so treat all input
		1149	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1150	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1151	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
624		1152
625	Very buggy (often crashes).	1153	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1154	they only govern when the JSON output engine escapes a character or not.
626		1155
627	Very inflexible (no human-readable format supported, format pretty much	1156	The main use for C<latin1> is to relatively efficiently store binary data
628	undocumented. I need at least a format for easy reading by humans and a	1157	as JSON, at the expense of breaking compatibility with most JSON decoders.
629	single-line compact format for use in a protocol, and preferably a way to
630	generate ASCII-only JSON texts).
631		1158
632	Completely broken (and confusingly documented) Unicode handling (unicode	1159	The main use for C<ascii> is to force the output to not contain characters
633	escapes are not working properly, you need to set ImplicitUnicode to	1160	with values > 127, which means you can interpret the resulting string
634	I<different> values on en- and decoding to get symmetric behaviour).	1161	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
635		1162	8-bit-encoding, and still get the same data structure back. This is useful
636	No roundtripping (simple cases work, but this depends on wether the scalar	1163	when your channel for JSON transfer is not 8-bit clean or the encoding
637	value was used in a numeric context or not).	1164	might be mangled in between (e.g. in mail), and works because ASCII is a
638		1165	proper subset of most 8-bit and multibyte encodings in use in the world.
639	Dumping hashes may skip hash values depending on iterator state.
640
641	Unmaintained (maintainer unresponsive for many months, bugs are not
642	getting fixed).
643
644	Does not check input for validity (i.e. will accept non-JSON input and
645	return "something" instead of raising an exception. This is a security
646	issue: imagine two banks transfering money between each other using
647	JSON. One bank might parse a given non-JSON request and deduct money,
648	while the other might reject the transaction with a syntax error. While a
649	good protocol will at least recover, that is extra unnecessary work and
650	the transaction will still not succeed).
651
652	=item JSON::DWIW 0.04
653
654	Very fast. Very natural. Very nice.
655
656	Undocumented unicode handling (but the best of the pack. Unicode escapes
657	still don't get parsed properly).
658
659	Very inflexible.
660
661	No roundtripping.
662
663	Does not generate valid JSON texts (key strings are often unquoted, empty keys
664	result in nothing being output)
665
666	Does not check input for validity.
667		1166
668	=back	1167	=back
669		1168
670		1169
671	=head2 JSON and YAML	1170	=head2 JSON and YAML
672		1171
673	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1172	You often hear that JSON is a subset of YAML. This is, however, a mass
674	however, a mass hysteria and very far from the truth. In general, there is	1173	hysteria(*) and very far from the truth (as of the time of this writing),
675	no way to configure JSON::XS to output a data structure as valid YAML.	1174	so let me state it clearly: I<in general, there is no way to configure
		1175	JSON::XS to output a data structure as valid YAML> that works in all
		1176	cases.
676		1177
677	If you really must use JSON::XS to generate YAML, you should use this	1178	If you really must use JSON::XS to generate YAML, you should use this
678	algorithm (subject to change in future versions):	1179	algorithm (subject to change in future versions):
679		1180
680	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1181	my $to_yaml = JSON::XS->new->utf8->space_after (1);
681	my $yaml = $to_yaml->encode ($ref) . "\n";	1182	my $yaml = $to_yaml->encode ($ref) . "\n";
682		1183
683	This will usually generate JSON texts that also parse as valid	1184	This will I<usually> generate JSON texts that also parse as valid
684	YAML. Please note that YAML has hardcoded limits on (simple) object key	1185	YAML. Please note that YAML has hardcoded limits on (simple) object key
685	lengths that JSON doesn't have, so you should make sure that your hash	1186	lengths that JSON doesn't have and also has different and incompatible
		1187	unicode handling, so you should make sure that your hash keys are
686	keys are noticably shorter than the 1024 characters YAML allows.	1188	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1189	you do not have characters with codepoint values outside the Unicode BMP
		1190	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1191	strings (which JSON::XS does not I<currently> generate, but other JSON
		1192	generators might).
687		1193
688	There might be other incompatibilities that I am not aware of. In general	1194	There might be other incompatibilities that I am not aware of (or the YAML
		1195	specification has been changed yet again - it does so quite often). In
689	you should not try to generate YAML with a JSON generator or vice versa,	1196	general you should not try to generate YAML with a JSON generator or vice
690	or try to parse JSON with a YAML parser or vice versa: chances are high	1197	versa, or try to parse JSON with a YAML parser or vice versa: chances are
691	that you will run into severe interoperability problems.	1198	high that you will run into severe interoperability problems when you
		1199	least expect it.
		1200
		1201	=over 4
		1202
		1203	=item (*)
		1204
		1205	I have been pressured multiple times by Brian Ingerson (one of the
		1206	authors of the YAML specification) to remove this paragraph, despite him
		1207	acknowledging that the actual incompatibilities exist. As I was personally
		1208	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1209	educate people about these issues, so others do not run into the same
		1210	problem again and again. After this, Brian called me a (quote)I<complete
		1211	and worthless idiot>(unquote).
		1212
		1213	In my opinion, instead of pressuring and insulting people who actually
		1214	clarify issues with YAML and the wrong statements of some of its
		1215	proponents, I would kindly suggest reading the JSON spec (which is not
		1216	that difficult or long) and finally make YAML compatible to it, and
		1217	educating users about the changes, instead of spreading lies about the
		1218	real compatibility for many I<years> and trying to silence people who
		1219	point out that it isn't true.
		1220
		1221	=back
692		1222
693		1223
694	=head2 SPEED	1224	=head2 SPEED
695		1225
696	It seems that JSON::XS is surprisingly fast, as shown in the following	1226	It seems that JSON::XS is surprisingly fast, as shown in the following
697	tables. They have been generated with the help of the C<eg/bench> program	1227	tables. They have been generated with the help of the C<eg/bench> program
698	in the JSON::XS distribution, to make it easy to compare on your own	1228	in the JSON::XS distribution, to make it easy to compare on your own
699	system.	1229	system.
700		1230
701	First comes a comparison between various modules using a very short	1231	First comes a comparison between various modules using
702	single-line JSON string:	1232	a very short single-line JSON string (also available at
		1233	L<http://dist.schmorp.de/misc/json/short.json>).
703		1234
704	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1235	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
705	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1236	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
706		1237
707	It shows the number of encodes/decodes per second (JSON::XS uses	1238	It shows the number of encodes/decodes per second (JSON::XS uses
708	the functional interface, while JSON::XS/2 uses the OO interface	1239	the functional interface, while JSON::XS/2 uses the OO interface
709	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1240	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
710	shrink). Higher is better:	1241	shrink). Higher is better:
711		1242
712	Storable \| 15779.925 \| 14169.946 \|
713	-----------+------------+------------+
714	module \| encode \| decode \|	1243	module \| encode \| decode \|
715	-----------\|------------\|------------\|	1244	-----------\|------------\|------------\|
716	JSON \| 4990.842 \| 4088.813 \|	1245	JSON 1.x \| 4990.842 \| 4088.813 \|
717	JSON::DWIW \| 51653.990 \| 71575.154 \|	1246	JSON::DWIW \| 51653.990 \| 71575.154 \|
718	JSON::PC \| 65948.176 \| 74631.744 \|	1247	JSON::PC \| 65948.176 \| 74631.744 \|
719	JSON::PP \| 8931.652 \| 3817.168 \|	1248	JSON::PP \| 8931.652 \| 3817.168 \|
720	JSON::Syck \| 24877.248 \| 27776.848 \|	1249	JSON::Syck \| 24877.248 \| 27776.848 \|
721	JSON::XS \| 388361.481 \| 227951.304 \|	1250	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
723	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1252	JSON::XS/3 \| 338250.323 \| 218453.333 \|
724	Storable \| 16500.016 \| 135300.129 \|	1253	Storable \| 16500.016 \| 135300.129 \|
725	-----------+------------+------------+	1254	-----------+------------+------------+
726		1255
727	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1256	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
728	about three times faster on decoding, and over fourty times faster	1257	about three times faster on decoding, and over forty times faster
729	than JSON, even with pretty-printing and key sorting. It also compares	1258	than JSON, even with pretty-printing and key sorting. It also compares
730	favourably to Storable for small amounts of data.	1259	favourably to Storable for small amounts of data.
731		1260
732	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1261	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
733	search API (http://nanoref.com/yahooapis/mgPdGg):	1262	search API (L<http://dist.schmorp.de/misc/json/long.json>).
734		1263
735	module \| encode \| decode \|	1264	module \| encode \| decode \|
736	-----------\|------------\|------------\|	1265	-----------\|------------\|------------\|
737	JSON \| 55.260 \| 34.971 \|	1266	JSON 1.x \| 55.260 \| 34.971 \|
738	JSON::DWIW \| 825.228 \| 1082.513 \|	1267	JSON::DWIW \| 825.228 \| 1082.513 \|
739	JSON::PC \| 3571.444 \| 2394.829 \|	1268	JSON::PC \| 3571.444 \| 2394.829 \|
740	JSON::PP \| 210.987 \| 32.574 \|	1269	JSON::PP \| 210.987 \| 32.574 \|
741	JSON::Syck \| 552.551 \| 787.544 \|	1270	JSON::Syck \| 552.551 \| 787.544 \|
742	JSON::XS \| 5780.463 \| 4854.519 \|	1271	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
746	-----------+------------+------------+	1275	-----------+------------+------------+
747		1276
748	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1277	Again, JSON::XS leads by far (except for Storable which non-surprisingly
749	decodes faster).	1278	decodes faster).
750		1279
751	On large strings containing lots of high unicode characters, some modules	1280	On large strings containing lots of high Unicode characters, some modules
752	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1281	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
753	will be broken due to missing (or wrong) unicode handling. Others refuse	1282	will be broken due to missing (or wrong) Unicode handling. Others refuse
754	to decode or encode properly, so it was impossible to prepare a fair	1283	to decode or encode properly, so it was impossible to prepare a fair
755	comparison table for that case.	1284	comparison table for that case.
756		1285
757		1286
758	=head1 SECURITY CONSIDERATIONS	1287	=head1 SECURITY CONSIDERATIONS
…		…
764	any buffer overflows. Obviously, this module should ensure that and I am	1293	any buffer overflows. Obviously, this module should ensure that and I am
765	trying hard on making that true, but you never know.	1294	trying hard on making that true, but you never know.
766		1295
767	Second, you need to avoid resource-starving attacks. That means you should	1296	Second, you need to avoid resource-starving attacks. That means you should
768	limit the size of JSON texts you accept, or make sure then when your	1297	limit the size of JSON texts you accept, or make sure then when your
769	resources run out, thats just fine (e.g. by using a separate process that	1298	resources run out, that's just fine (e.g. by using a separate process that
770	can crash safely). The size of a JSON text in octets or characters is	1299	can crash safely). The size of a JSON text in octets or characters is
771	usually a good indication of the size of the resources required to decode	1300	usually a good indication of the size of the resources required to decode
772	it into a Perl structure. While JSON::XS can check the size of the JSON	1301	it into a Perl structure. While JSON::XS can check the size of the JSON
773	text, it might be too late when you already have it in memory, so you	1302	text, it might be too late when you already have it in memory, so you
774	might want to check the size before you accept the string.	1303	might want to check the size before you accept the string.
775		1304
776	Third, JSON::XS recurses using the C stack when decoding objects and	1305	Third, JSON::XS recurses using the C stack when decoding objects and
777	arrays. The C stack is a limited resource: for instance, on my amd64	1306	arrays. The C stack is a limited resource: for instance, on my amd64
778	machine with 8MB of stack size I can decode around 180k nested arrays but	1307	machine with 8MB of stack size I can decode around 180k nested arrays but
779	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1308	only 14k nested JSON objects (due to perl itself recursing deeply on croak
780	to free the temporary). If that is exceeded, the program crashes. to be	1309	to free the temporary). If that is exceeded, the program crashes. To be
781	conservative, the default nesting limit is set to 512. If your process	1310	conservative, the default nesting limit is set to 512. If your process
782	has a smaller stack, you should adjust this setting accordingly with the	1311	has a smaller stack, you should adjust this setting accordingly with the
783	C<max_depth> method.	1312	C<max_depth> method.
784		1313
785	And last but least, something else could bomb you that I forgot to think	1314	Something else could bomb you, too, that I forgot to think of. In that
786	of. In that case, you get to keep the pieces. I am always open for hints,	1315	case, you get to keep the pieces. I am always open for hints, though...
787	though...	1316
		1317	Also keep in mind that JSON::XS might leak contents of your Perl data
		1318	structures in its error messages, so when you serialise sensitive
		1319	information you might want to make sure that exceptions thrown by JSON::XS
		1320	will not end up in front of untrusted eyes.
788		1321
789	If you are using JSON::XS to return packets to consumption	1322	If you are using JSON::XS to return packets to consumption
790	by javascript scripts in a browser you should have a look at	1323	by JavaScript scripts in a browser you should have a look at
791	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1324	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
792	you are vulnerable to some common attack vectors (which really are browser	1325	you are vulnerable to some common attack vectors (which really are browser
793	design bugs, but it is still you who will have to deal with it, as major	1326	design bugs, but it is still you who will have to deal with it, as major
794	browser developers care only for features, not about doing security	1327	browser developers care only for features, not about getting security
795	right).	1328	right).
796		1329
797		1330
		1331	=head1 THREADS
		1332
		1333	This module is I<not> guaranteed to be thread safe and there are no
		1334	plans to change this until Perl gets thread support (as opposed to the
		1335	horribly slow so-called "threads" which are simply slow and bloated
		1336	process simulations - use fork, it's I<much> faster, cheaper, better).
		1337
		1338	(It might actually work, but you have been warned).
		1339
		1340
798	=head1 BUGS	1341	=head1 BUGS
799		1342
800	While the goal of this module is to be correct, that unfortunately does	1343	While the goal of this module is to be correct, that unfortunately does
801	not mean its bug-free, only that I think its design is bug-free. It is	1344	not mean it's bug-free, only that I think its design is bug-free. It is
802	still relatively early in its development. If you keep reporting bugs they	1345	still relatively early in its development. If you keep reporting bugs they
803	will be fixed swiftly, though.	1346	will be fixed swiftly, though.
		1347
		1348	Please refrain from using rt.cpan.org or any other bug reporting
		1349	service. I put the contact address into my modules for a reason.
804		1350
805	=cut	1351	=cut
806		1352
807	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1353	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
808	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1354	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
825	"--" => sub { $_[0] = ${$_[0]} - 1 },	1371	"--" => sub { $_[0] = ${$_[0]} - 1 },
826	fallback => 1;	1372	fallback => 1;
827		1373
828	1;	1374	1;
829		1375
		1376	=head1 SEE ALSO
		1377
		1378	The F<json_xs> command line utility for quick experiments.
		1379
830	=head1 AUTHOR	1380	=head1 AUTHOR
831		1381
832	Marc Lehmann <schmorp@schmorp.de>	1382	Marc Lehmann <schmorp@schmorp.de>
833	http://home.schmorp.de/	1383	http://home.schmorp.de/
834		1384

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs. Revision 1.99 by root, Thu Mar 27 06:37:35 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.49 by root, Sun Jul 1 14:08:03 2007 UTC vs.
Revision 1.99 by root, Thu Mar 27 06:37:35 2008 UTC