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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC vs.
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14		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	overridden) with no overhead due to emulation (by inheriting constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
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 data types 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 object
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
		106	no warnings;
84	use strict;	107	use strict;
85		108
86	our $VERSION = '1.5';	109	our $VERSION = '2.2222';
87	our @ISA = qw(Exporter);	110	our @ISA = qw(Exporter);
88		111
89	our @EXPORT = qw(to_json from_json);	112	our @EXPORT = qw(encode_json decode_json to_json from_json);
		113
		114	sub to_json($) {
		115	require Carp;
		116	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");
		117	}
		118
		119	sub from_json($) {
		120	require Carp;
		121	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");
		122	}
90		123
91	use Exporter;	124	use Exporter;
92	use XSLoader;	125	use XSLoader;
93		126
94	=head1 FUNCTIONAL INTERFACE	127	=head1 FUNCTIONAL INTERFACE
95		128
96	The following convinience methods are provided by this module. They are	129	The following convenience methods are provided by this module. They are
97	exported by default:	130	exported by default:
98		131
99	=over 4	132	=over 4
100		133
101	=item $json_text = to_json $perl_scalar	134	=item $json_text = encode_json $perl_scalar
102		135
103	Converts the given Perl data structure (a simple scalar or a reference to	136	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	137	(that is, the string contains octets only). Croaks on error.
105	octets only). Croaks on error.
106		138
107	This function call is functionally identical to:	139	This function call is functionally identical to:
108		140
109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	141	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
110		142
111	except being faster.	143	Except being faster.
112		144
113	=item $perl_scalar = from_json $json_text	145	=item $perl_scalar = decode_json $json_text
114		146
115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	147	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	148	to parse that as an UTF-8 encoded JSON text, returning the resulting
117	scalar or reference. Croaks on error.	149	reference. Croaks on error.
118		150
119	This function call is functionally identical to:	151	This function call is functionally identical to:
120		152
121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	153	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
122		154
123	except being faster.	155	Except being faster.
124		156
125	=item $is_boolean = JSON::XS::is_bool $scalar	157	=item $is_boolean = JSON::XS::is_bool $scalar
126		158
127	Returns true if the passed scalar represents either JSON::XS::true or	159	Returns true if the passed scalar represents either JSON::XS::true or
128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	160	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
132	Perl.	164	Perl.
133		165
134	=back	166	=back
135		167
136		168
		169	=head1 A FEW NOTES ON UNICODE AND PERL
		170
		171	Since this often leads to confusion, here are a few very clear words on
		172	how Unicode works in Perl, modulo bugs.
		173
		174	=over 4
		175
		176	=item 1. Perl strings can store characters with ordinal values > 255.
		177
		178	This enables you to store Unicode characters as single characters in a
		179	Perl string - very natural.
		180
		181	=item 2. Perl does I<not> associate an encoding with your strings.
		182
		183	... until you force it to, e.g. when matching it against a regex, or
		184	printing the scalar to a file, in which case Perl either interprets your
		185	string as locale-encoded text, octets/binary, or as Unicode, depending
		186	on various settings. In no case is an encoding stored together with your
		187	data, it is I<use> that decides encoding, not any magical meta data.
		188
		189	=item 3. The internal utf-8 flag has no meaning with regards to the
		190	encoding of your string.
		191
		192	Just ignore that flag unless you debug a Perl bug, a module written in
		193	XS or want to dive into the internals of perl. Otherwise it will only
		194	confuse you, as, despite the name, it says nothing about how your string
		195	is encoded. You can have Unicode strings with that flag set, with that
		196	flag clear, and you can have binary data with that flag set and that flag
		197	clear. Other possibilities exist, too.
		198
		199	If you didn't know about that flag, just the better, pretend it doesn't
		200	exist.
		201
		202	=item 4. A "Unicode String" is simply a string where each character can be
		203	validly interpreted as a Unicode code point.
		204
		205	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		206	Unicode string encoded in UTF-8, giving you a binary string.
		207
		208	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		209
		210	It's a fact. Learn to live with it.
		211
		212	=back
		213
		214	I hope this helps :)
		215
		216
137	=head1 OBJECT-ORIENTED INTERFACE	217	=head1 OBJECT-ORIENTED INTERFACE
138		218
139	The object oriented interface lets you configure your own encoding or	219	The object oriented interface lets you configure your own encoding or
140	decoding style, within the limits of supported formats.	220	decoding style, within the limits of supported formats.
141		221
…		…
152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	232	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
153	=> {"a": [1, 2]}	233	=> {"a": [1, 2]}
154		234
155	=item $json = $json->ascii ([$enable])	235	=item $json = $json->ascii ([$enable])
156		236
		237	=item $enabled = $json->get_ascii
		238
157	If C<$enable> is true (or missing), then the C<encode> method will not	239	If C<$enable> is true (or missing), then the C<encode> method will not
158	generate characters outside the code range C<0..127> (which is ASCII). Any	240	generate characters outside the code range C<0..127> (which is ASCII). Any
159	unicode characters outside that range will be escaped using either a	241	Unicode characters outside that range will be escaped using either a
160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	242	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
161	as per RFC4627. The resulting encoded JSON text can be treated as a native	243	as per RFC4627. The resulting encoded JSON text can be treated as a native
162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	244	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
163	or any other superset of ASCII.	245	or any other superset of ASCII.
164		246
165	If C<$enable> is false, then the C<encode> method will not escape Unicode	247	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	248	characters unless required by the JSON syntax or other flags. This results
167	in a faster and more compact format.	249	in a faster and more compact format.
168		250
		251	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		252	document.
		253
169	The main use for this flag is to produce JSON texts that can be	254	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	255	transmitted over a 7-bit channel, as the encoded JSON texts will not
171	contain any 8 bit characters.	256	contain any 8 bit characters.
172		257
173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	258	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
174	=> ["\ud801\udc01"]	259	=> ["\ud801\udc01"]
175		260
176	=item $json = $json->latin1 ([$enable])	261	=item $json = $json->latin1 ([$enable])
177		262
		263	=item $enabled = $json->get_latin1
		264
178	If C<$enable> is true (or missing), then the C<encode> method will encode	265	If C<$enable> is true (or missing), then the C<encode> method will encode
179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	266	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
180	outside the code range C<0..255>. The resulting string can be treated as a	267	outside the code range C<0..255>. The resulting string can be treated as a
181	latin1-encoded JSON text or a native unicode string. The C<decode> method	268	latin1-encoded JSON text or a native Unicode string. The C<decode> method
182	will not be affected in any way by this flag, as C<decode> by default	269	will not be affected in any way by this flag, as C<decode> by default
183	expects unicode, which is a strict superset of latin1.	270	expects Unicode, which is a strict superset of latin1.
184		271
185	If C<$enable> is false, then the C<encode> method will not escape Unicode	272	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.	273	characters unless required by the JSON syntax or other flags.
		274
		275	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		276	document.
187		277
188	The main use for this flag is efficiently encoding binary data as JSON	278	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	279	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	280	size. The disadvantage is that the resulting JSON text is encoded
191	in latin1 (and must correctly be treated as such when storing and	281	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	282	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	283	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.	284	in files or databases, not when talking to other JSON encoders/decoders.
195		285
196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	286	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	287	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
198		288
199	=item $json = $json->utf8 ([$enable])	289	=item $json = $json->utf8 ([$enable])
		290
		291	=item $enabled = $json->get_utf8
200		292
201	If C<$enable> is true (or missing), then the C<encode> method will encode	293	If C<$enable> is true (or missing), then the C<encode> method will encode
202	the JSON result into UTF-8, as required by many protocols, while the	294	the JSON result into UTF-8, as required by many protocols, while the
203	C<decode> method expects to be handled an UTF-8-encoded string. Please	295	C<decode> method expects to be handled an UTF-8-encoded string. Please
204	note that UTF-8-encoded strings do not contain any characters outside the	296	note that UTF-8-encoded strings do not contain any characters outside the
205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	297	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
206	versions, enabling this option might enable autodetection of the UTF-16	298	versions, enabling this option might enable autodetection of the UTF-16
207	and UTF-32 encoding families, as described in RFC4627.	299	and UTF-32 encoding families, as described in RFC4627.
208		300
209	If C<$enable> is false, then the C<encode> method will return the JSON	301	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	302	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	303	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.	304	to be done yourself, e.g. using the Encode module.
		305
		306	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		307	document.
213		308
214	Example, output UTF-16BE-encoded JSON:	309	Example, output UTF-16BE-encoded JSON:
215		310
216	use Encode;	311	use Encode;
217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	312	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
238	]	333	]
239	}	334	}
240		335
241	=item $json = $json->indent ([$enable])	336	=item $json = $json->indent ([$enable])
242		337
		338	=item $enabled = $json->get_indent
		339
243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	340	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
244	format as output, putting every array member or object/hash key-value pair	341	format as output, putting every array member or object/hash key-value pair
245	into its own line, identing them properly.	342	into its own line, indenting them properly.
246		343
247	If C<$enable> is false, no newlines or indenting will be produced, and the	344	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>.	345	resulting JSON text is guaranteed not to contain any C<newlines>.
249		346
250	This setting has no effect when decoding JSON texts.	347	This setting has no effect when decoding JSON texts.
251		348
252	=item $json = $json->space_before ([$enable])	349	=item $json = $json->space_before ([$enable])
		350
		351	=item $enabled = $json->get_space_before
253		352
254	If C<$enable> is true (or missing), then the C<encode> method will add an extra	353	If C<$enable> is true (or missing), then the C<encode> method will add an extra
255	optional space before the C<:> separating keys from values in JSON objects.	354	optional space before the C<:> separating keys from values in JSON objects.
256		355
257	If C<$enable> is false, then the C<encode> method will not add any extra	356	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:	362	Example, space_before enabled, space_after and indent disabled:
264		363
265	{"key" :"value"}	364	{"key" :"value"}
266		365
267	=item $json = $json->space_after ([$enable])	366	=item $json = $json->space_after ([$enable])
		367
		368	=item $enabled = $json->get_space_after
268		369
269	If C<$enable> is true (or missing), then the C<encode> method will add an extra	370	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	371	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	372	and extra whitespace after the C<,> separating key-value pairs and array
272	members.	373	members.
…		…
279	Example, space_before and indent disabled, space_after enabled:	380	Example, space_before and indent disabled, space_after enabled:
280		381
281	{"key": "value"}	382	{"key": "value"}
282		383
283	=item $json = $json->relaxed ([$enable])	384	=item $json = $json->relaxed ([$enable])
		385
		386	=item $enabled = $json->get_relaxed
284		387
285	If C<$enable> is true (or missing), then C<decode> will accept some	388	If C<$enable> is true (or missing), then C<decode> will accept some
286	extensions to normal JSON syntax (see below). C<encode> will not be	389	extensions to normal JSON syntax (see below). C<encode> will not be
287	affected in anyway. I<Be aware that this option makes you accept invalid	390	affected in anyway. I<Be aware that this option makes you accept invalid
288	JSON texts as if they were valid!>. I suggest only to use this option to	391	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
325		428
326	=back	429	=back
327		430
328	=item $json = $json->canonical ([$enable])	431	=item $json = $json->canonical ([$enable])
329		432
		433	=item $enabled = $json->get_canonical
		434
330	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	435	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
331	by sorting their keys. This is adding a comparatively high overhead.	436	by sorting their keys. This is adding a comparatively high overhead.
332		437
333	If C<$enable> is false, then the C<encode> method will output key-value	438	If C<$enable> is false, then the C<encode> method will output key-value
334	pairs in the order Perl stores them (which will likely change between runs	439	pairs in the order Perl stores them (which will likely change between runs
335	of the same script).	440	of the same script).
336		441
337	This option is useful if you want the same data structure to be encoded as	442	This option is useful if you want the same data structure to be encoded as
338	the same JSON text (given the same overall settings). If it is disabled,	443	the same JSON text (given the same overall settings). If it is disabled,
339	the same hash migh be encoded differently even if contains the same data,	444	the same hash might be encoded differently even if contains the same data,
340	as key-value pairs have no inherent ordering in Perl.	445	as key-value pairs have no inherent ordering in Perl.
341		446
342	This setting has no effect when decoding JSON texts.	447	This setting has no effect when decoding JSON texts.
343		448
344	=item $json = $json->allow_nonref ([$enable])	449	=item $json = $json->allow_nonref ([$enable])
		450
		451	=item $enabled = $json->get_allow_nonref
345		452
346	If C<$enable> is true (or missing), then the C<encode> method can convert a	453	If C<$enable> is true (or missing), then the C<encode> method can convert a
347	non-reference into its corresponding string, number or null JSON value,	454	non-reference into its corresponding string, number or null JSON value,
348	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	455	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
349	values instead of croaking.	456	values instead of croaking.
…		…
357	resulting in an invalid JSON text:	464	resulting in an invalid JSON text:
358		465
359	JSON::XS->new->allow_nonref->encode ("Hello, World!")	466	JSON::XS->new->allow_nonref->encode ("Hello, World!")
360	=> "Hello, World!"	467	=> "Hello, World!"
361		468
		469	=item $json = $json->allow_unknown ([$enable])
		470
		471	=item $enabled = $json->get_allow_unknown
		472
		473	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		474	exception when it encounters values it cannot represent in JSON (for
		475	example, filehandles) but instead will encode a JSON C<null> value. Note
		476	that blessed objects are not included here and are handled separately by
		477	c<allow_nonref>.
		478
		479	If C<$enable> is false (the default), then C<encode> will throw an
		480	exception when it encounters anything it cannot encode as JSON.
		481
		482	This option does not affect C<decode> in any way, and it is recommended to
		483	leave it off unless you know your communications partner.
		484
362	=item $json = $json->allow_blessed ([$enable])	485	=item $json = $json->allow_blessed ([$enable])
		486
		487	=item $enabled = $json->get_allow_blessed
363		488
364	If C<$enable> is true (or missing), then the C<encode> method will not	489	If C<$enable> is true (or missing), then the C<encode> method will not
365	barf when it encounters a blessed reference. Instead, the value of the	490	barf when it encounters a blessed reference. Instead, the value of the
366	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	491	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
367	disabled or no C<to_json> method found) or a representation of the	492	disabled or no C<TO_JSON> method found) or a representation of the
368	object (C<convert_blessed> enabled and C<to_json> method found) is being	493	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
369	encoded. Has no effect on C<decode>.	494	encoded. Has no effect on C<decode>.
370		495
371	If C<$enable> is false (the default), then C<encode> will throw an	496	If C<$enable> is false (the default), then C<encode> will throw an
372	exception when it encounters a blessed object.	497	exception when it encounters a blessed object.
373		498
374	=item $json = $json->convert_blessed ([$enable])	499	=item $json = $json->convert_blessed ([$enable])
		500
		501	=item $enabled = $json->get_convert_blessed
375		502
376	If C<$enable> is true (or missing), then C<encode>, upon encountering a	503	If C<$enable> is true (or missing), then C<encode>, upon encountering a
377	blessed object, will check for the availability of the C<TO_JSON> method	504	blessed object, will check for the availability of the C<TO_JSON> method
378	on the object's class. If found, it will be called in scalar context	505	on the object's class. If found, it will be called in scalar context
379	and the resulting scalar will be encoded instead of the object. If no	506	and the resulting scalar will be encoded instead of the object. If no
…		…
383	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	510	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
384	returns other blessed objects, those will be handled in the same	511	returns other blessed objects, those will be handled in the same
385	way. C<TO_JSON> must take care of not causing an endless recursion cycle	512	way. C<TO_JSON> must take care of not causing an endless recursion cycle
386	(== crash) in this case. The name of C<TO_JSON> was chosen because other	513	(== crash) in this case. The name of C<TO_JSON> was chosen because other
387	methods called by the Perl core (== not by the user of the object) are	514	methods called by the Perl core (== not by the user of the object) are
388	usually in upper case letters and to avoid collisions with the C<to_json>	515	usually in upper case letters and to avoid collisions with any C<to_json>
389	function.	516	function or method.
390		517
391	This setting does not yet influence C<decode> in any way, but in the	518	This setting does not yet influence C<decode> in any way, but in the
392	future, global hooks might get installed that influence C<decode> and are	519	future, global hooks might get installed that influence C<decode> and are
393	enabled by this setting.	520	enabled by this setting.
394		521
…		…
436		563
437	As this callback gets called less often then the C<filter_json_object>	564	As this callback gets called less often then the C<filter_json_object>
438	one, decoding speed will not usually suffer as much. Therefore, single-key	565	one, decoding speed will not usually suffer as much. Therefore, single-key
439	objects make excellent targets to serialise Perl objects into, especially	566	objects make excellent targets to serialise Perl objects into, especially
440	as single-key JSON objects are as close to the type-tagged value concept	567	as single-key JSON objects are as close to the type-tagged value concept
441	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	568	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
442	support this in any way, so you need to make sure your data never looks	569	support this in any way, so you need to make sure your data never looks
443	like a serialised Perl hash.	570	like a serialised Perl hash.
444		571
445	Typical names for the single object key are C<__class_whatever__>, or	572	Typical names for the single object key are C<__class_whatever__>, or
446	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	573	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
470		597
471	{ __widget__ => $self->{id} }	598	{ __widget__ => $self->{id} }
472	}	599	}
473		600
474	=item $json = $json->shrink ([$enable])	601	=item $json = $json->shrink ([$enable])
		602
		603	=item $enabled = $json->get_shrink
475		604
476	Perl usually over-allocates memory a bit when allocating space for	605	Perl usually over-allocates memory a bit when allocating space for
477	strings. This flag optionally resizes strings generated by either	606	strings. This flag optionally resizes strings generated by either
478	C<encode> or C<decode> to their minimum size possible. This can save	607	C<encode> or C<decode> to their minimum size possible. This can save
479	memory when your JSON texts are either very very long or you have many	608	memory when your JSON texts are either very very long or you have many
…		…
497	strings that look like integers or floats into integers or floats	626	strings that look like integers or floats into integers or floats
498	internally (there is no difference on the Perl level), saving space.	627	internally (there is no difference on the Perl level), saving space.
499		628
500	=item $json = $json->max_depth ([$maximum_nesting_depth])	629	=item $json = $json->max_depth ([$maximum_nesting_depth])
501		630
		631	=item $max_depth = $json->get_max_depth
		632
502	Sets the maximum nesting level (default C<512>) accepted while encoding	633	Sets the maximum nesting level (default C<512>) accepted while encoding
503	or decoding. If the JSON text or Perl data structure has an equal or	634	or decoding. If a higher nesting level is detected in JSON text or a Perl
504	higher nesting level then this limit, then the encoder and decoder will	635	data structure, then the encoder and decoder will stop and croak at that
505	stop and croak at that point.	636	point.
506		637
507	Nesting level is defined by number of hash- or arrayrefs that the encoder	638	Nesting level is defined by number of hash- or arrayrefs that the encoder
508	needs to traverse to reach a given point or the number of C<{> or C<[>	639	needs to traverse to reach a given point or the number of C<{> or C<[>
509	characters without their matching closing parenthesis crossed to reach a	640	characters without their matching closing parenthesis crossed to reach a
510	given character in a string.	641	given character in a string.
511		642
512	Setting the maximum depth to one disallows any nesting, so that ensures	643	Setting the maximum depth to one disallows any nesting, so that ensures
513	that the object is only a single hash/object or array.	644	that the object is only a single hash/object or array.
514		645
515	The argument to C<max_depth> will be rounded up to the next highest power
516	of two. If no argument is given, the highest possible setting will be	646	If no argument is given, the highest possible setting will be used, which
517	used, which is rarely useful.	647	is rarely useful.
		648
		649	Note that nesting is implemented by recursion in C. The default value has
		650	been chosen to be as large as typical operating systems allow without
		651	crashing.
518		652
519	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	653	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
520		654
521	=item $json = $json->max_size ([$maximum_string_size])	655	=item $json = $json->max_size ([$maximum_string_size])
		656
		657	=item $max_size = $json->get_max_size
522		658
523	Set the maximum length a JSON text may have (in bytes) where decoding is	659	Set the maximum length a JSON text may have (in bytes) where decoding is
524	being attempted. The default is C<0>, meaning no limit. When C<decode>	660	being attempted. The default is C<0>, meaning no limit. When C<decode>
525	is called on a string longer then this number of characters it will not	661	is called on a string that is longer then this many bytes, it will not
526	attempt to decode the string but throw an exception. This setting has no	662	attempt to decode the string but throw an exception. This setting has no
527	effect on C<encode> (yet).	663	effect on C<encode> (yet).
528		664
529	The argument to C<max_size> will be rounded up to the next B<highest>	665	If no argument is given, the limit check will be deactivated (same as when
530	power of two (so may be more than requested). If no argument is given, the	666	C<0> is specified).
531	limit check will be deactivated (same as when C<0> is specified).
532		667
533	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	668	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
534		669
535	=item $json_text = $json->encode ($perl_scalar)	670	=item $json_text = $json->encode ($perl_scalar)
536		671
…		…
565	=> ([], 3)	700	=> ([], 3)
566		701
567	=back	702	=back
568		703
569		704
		705	=head1 INCREMENTAL PARSING
		706
		707	In some cases, there is the need for incremental parsing of JSON
		708	texts. While this module always has to keep both JSON text and resulting
		709	Perl data structure in memory at one time, it does allow you to parse a
		710	JSON stream incrementally. It does so by accumulating text until it has
		711	a full JSON object, which it then can decode. This process is similar to
		712	using C<decode_prefix> to see if a full JSON object is available, but
		713	is much more efficient (and can be implemented with a minimum of method
		714	calls).
		715
		716	JSON::XS will only attempt to parse the JSON text once it is sure it
		717	has enough text to get a decisive result, using a very simple but
		718	truly incremental parser. This means that it sometimes won't stop as
		719	early as the full parser, for example, it doesn't detect parenthese
		720	mismatches. The only thing it guarantees is that it starts decoding as
		721	soon as a syntactically valid JSON text has been seen. This means you need
		722	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		723	parsing in the presence if syntax errors.
		724
		725	The following methods implement this incremental parser.
		726
		727	=over 4
		728
		729	=item [void, scalar or list context] = $json->incr_parse ([$string])
		730
		731	This is the central parsing function. It can both append new text and
		732	extract objects from the stream accumulated so far (both of these
		733	functions are optional).
		734
		735	If C<$string> is given, then this string is appended to the already
		736	existing JSON fragment stored in the C<$json> object.
		737
		738	After that, if the function is called in void context, it will simply
		739	return without doing anything further. This can be used to add more text
		740	in as many chunks as you want.
		741
		742	If the method is called in scalar context, then it will try to extract
		743	exactly I<one> JSON object. If that is successful, it will return this
		744	object, otherwise it will return C<undef>. If there is a parse error,
		745	this method will croak just as C<decode> would do (one can then use
		746	C<incr_skip> to skip the errornous part). This is the most common way of
		747	using the method.
		748
		749	And finally, in list context, it will try to extract as many objects
		750	from the stream as it can find and return them, or the empty list
		751	otherwise. For this to work, there must be no separators between the JSON
		752	objects or arrays, instead they must be concatenated back-to-back. If
		753	an error occurs, an exception will be raised as in the scalar context
		754	case. Note that in this case, any previously-parsed JSON texts will be
		755	lost.
		756
		757	=item $lvalue_string = $json->incr_text
		758
		759	This method returns the currently stored JSON fragment as an lvalue, that
		760	is, you can manipulate it. This I<only> works when a preceding call to
		761	C<incr_parse> in I<scalar context> successfully returned an object. Under
		762	all other circumstances you must not call this function (I mean it.
		763	although in simple tests it might actually work, it I<will> fail under
		764	real world conditions). As a special exception, you can also call this
		765	method before having parsed anything.
		766
		767	This function is useful in two cases: a) finding the trailing text after a
		768	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		769	(such as commas).
		770
		771	=item $json->incr_skip
		772
		773	This will reset the state of the incremental parser and will remove the
		774	parsed text from the input buffer. This is useful after C<incr_parse>
		775	died, in which case the input buffer and incremental parser state is left
		776	unchanged, to skip the text parsed so far and to reset the parse state.
		777
		778	=item $json->incr_reset
		779
		780	This completely resets the incremental parser, that is, after this call,
		781	it will be as if the parser had never parsed anything.
		782
		783	This is useful if you want ot repeatedly parse JSON objects and want to
		784	ignore any trailing data, which means you have to reset the parser after
		785	each successful decode.
		786
		787	=back
		788
		789	=head2 LIMITATIONS
		790
		791	All options that affect decoding are supported, except
		792	C<allow_nonref>. The reason for this is that it cannot be made to
		793	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		794	them back to back and still decode them perfectly. This does not hold true
		795	for JSON numbers, however.
		796
		797	For example, is the string C<1> a single JSON number, or is it simply the
		798	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		799	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		800	takes the conservative route and disallows this case.
		801
		802	=head2 EXAMPLES
		803
		804	Some examples will make all this clearer. First, a simple example that
		805	works similarly to C<decode_prefix>: We want to decode the JSON object at
		806	the start of a string and identify the portion after the JSON object:
		807
		808	my $text = "[1,2,3] hello";
		809
		810	my $json = new JSON::XS;
		811
		812	my $obj = $json->incr_parse ($text)
		813	or die "expected JSON object or array at beginning of string";
		814
		815	my $tail = $json->incr_text;
		816	# $tail now contains " hello"
		817
		818	Easy, isn't it?
		819
		820	Now for a more complicated example: Imagine a hypothetical protocol where
		821	you read some requests from a TCP stream, and each request is a JSON
		822	array, without any separation between them (in fact, it is often useful to
		823	use newlines as "separators", as these get interpreted as whitespace at
		824	the start of the JSON text, which makes it possible to test said protocol
		825	with C<telnet>...).
		826
		827	Here is how you'd do it (it is trivial to write this in an event-based
		828	manner):
		829
		830	my $json = new JSON::XS;
		831
		832	# read some data from the socket
		833	while (sysread $socket, my $buf, 4096) {
		834
		835	# split and decode as many requests as possible
		836	for my $request ($json->incr_parse ($buf)) {
		837	# act on the $request
		838	}
		839	}
		840
		841	Another complicated example: Assume you have a string with JSON objects
		842	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		843	[3]>). To parse them, we have to skip the commas between the JSON texts,
		844	and here is where the lvalue-ness of C<incr_text> comes in useful:
		845
		846	my $text = "[1],[2], [3]";
		847	my $json = new JSON::XS;
		848
		849	# void context, so no parsing done
		850	$json->incr_parse ($text);
		851
		852	# now extract as many objects as possible. note the
		853	# use of scalar context so incr_text can be called.
		854	while (my $obj = $json->incr_parse) {
		855	# do something with $obj
		856
		857	# now skip the optional comma
		858	$json->incr_text =~ s/^ \s* , //x;
		859	}
		860
		861	Now lets go for a very complex example: Assume that you have a gigantic
		862	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		863	but you cannot load it into memory fully (this has actually happened in
		864	the real world :).
		865
		866	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		867	can still help you: You implement a (very simple) array parser and let
		868	JSON decode the array elements, which are all full JSON objects on their
		869	own (this wouldn't work if the array elements could be JSON numbers, for
		870	example):
		871
		872	my $json = new JSON::XS;
		873
		874	# open the monster
		875	open my $fh, "<bigfile.json"
		876	or die "bigfile: $!";
		877
		878	# first parse the initial "["
		879	for (;;) {
		880	sysread $fh, my $buf, 65536
		881	or die "read error: $!";
		882	$json->incr_parse ($buf); # void context, so no parsing
		883
		884	# Exit the loop once we found and removed(!) the initial "[".
		885	# In essence, we are (ab-)using the $json object as a simple scalar
		886	# we append data to.
		887	last if $json->incr_text =~ s/^ \s* \[ //x;
		888	}
		889
		890	# now we have the skipped the initial "[", so continue
		891	# parsing all the elements.
		892	for (;;) {
		893	# in this loop we read data until we got a single JSON object
		894	for (;;) {
		895	if (my $obj = $json->incr_parse) {
		896	# do something with $obj
		897	last;
		898	}
		899
		900	# add more data
		901	sysread $fh, my $buf, 65536
		902	or die "read error: $!";
		903	$json->incr_parse ($buf); # void context, so no parsing
		904	}
		905
		906	# in this loop we read data until we either found and parsed the
		907	# separating "," between elements, or the final "]"
		908	for (;;) {
		909	# first skip whitespace
		910	$json->incr_text =~ s/^\s*//;
		911
		912	# if we find "]", we are done
		913	if ($json->incr_text =~ s/^\]//) {
		914	print "finished.\n";
		915	exit;
		916	}
		917
		918	# if we find ",", we can continue with the next element
		919	if ($json->incr_text =~ s/^,//) {
		920	last;
		921	}
		922
		923	# if we find anything else, we have a parse error!
		924	if (length $json->incr_text) {
		925	die "parse error near ", $json->incr_text;
		926	}
		927
		928	# else add more data
		929	sysread $fh, my $buf, 65536
		930	or die "read error: $!";
		931	$json->incr_parse ($buf); # void context, so no parsing
		932	}
		933
		934	This is a complex example, but most of the complexity comes from the fact
		935	that we are trying to be correct (bear with me if I am wrong, I never ran
		936	the above example :).
		937
		938
		939
570	=head1 MAPPING	940	=head1 MAPPING
571		941
572	This section describes how JSON::XS maps Perl values to JSON values and	942	This section describes how JSON::XS maps Perl values to JSON values and
573	vice versa. These mappings are designed to "do the right thing" in most	943	vice versa. These mappings are designed to "do the right thing" in most
574	circumstances automatically, preserving round-tripping characteristics	944	circumstances automatically, preserving round-tripping characteristics
575	(what you put in comes out as something equivalent).	945	(what you put in comes out as something equivalent).
576		946
577	For the more enlightened: note that in the following descriptions,	947	For the more enlightened: note that in the following descriptions,
578	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	948	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
579	refers to the abstract Perl language itself.	949	refers to the abstract Perl language itself.
580		950
581		951
582	=head2 JSON -> PERL	952	=head2 JSON -> PERL
583		953
584	=over 4	954	=over 4
585		955
586	=item object	956	=item object
587		957
588	A JSON object becomes a reference to a hash in Perl. No ordering of object	958	A JSON object becomes a reference to a hash in Perl. No ordering of object
589	keys is preserved (JSON does not preserver object key ordering itself).	959	keys is preserved (JSON does not preserve object key ordering itself).
590		960
591	=item array	961	=item array
592		962
593	A JSON array becomes a reference to an array in Perl.	963	A JSON array becomes a reference to an array in Perl.
594		964
…		…
602		972
603	A JSON number becomes either an integer, numeric (floating point) or	973	A JSON number becomes either an integer, numeric (floating point) or
604	string scalar in perl, depending on its range and any fractional parts. On	974	string scalar in perl, depending on its range and any fractional parts. On
605	the Perl level, there is no difference between those as Perl handles all	975	the Perl level, there is no difference between those as Perl handles all
606	the conversion details, but an integer may take slightly less memory and	976	the conversion details, but an integer may take slightly less memory and
607	might represent more values exactly than (floating point) numbers.	977	might represent more values exactly than floating point numbers.
608		978
609	If the number consists of digits only, JSON::XS will try to represent	979	If the number consists of digits only, JSON::XS will try to represent
610	it as an integer value. If that fails, it will try to represent it as	980	it as an integer value. If that fails, it will try to represent it as
611	a numeric (floating point) value if that is possible without loss of	981	a numeric (floating point) value if that is possible without loss of
612	precision. Otherwise it will preserve the number as a string value.	982	precision. Otherwise it will preserve the number as a string value (in
		983	which case you lose roundtripping ability, as the JSON number will be
		984	re-encoded toa JSON string).
613		985
614	Numbers containing a fractional or exponential part will always be	986	Numbers containing a fractional or exponential part will always be
615	represented as numeric (floating point) values, possibly at a loss of	987	represented as numeric (floating point) values, possibly at a loss of
616	precision.	988	precision (in which case you might lose perfect roundtripping ability, but
617		989	the JSON number will still be re-encoded as a JSON number).
618	This might create round-tripping problems as numbers might become strings,
619	but as Perl is typeless there is no other way to do it.
620		990
621	=item true, false	991	=item true, false
622		992
623	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	993	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
624	respectively. They are overloaded to act almost exactly like the numbers	994	respectively. They are overloaded to act almost exactly like the numbers
625	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	995	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
626	the C<JSON::XS::is_bool> function.	996	the C<JSON::XS::is_bool> function.
627		997
628	=item null	998	=item null
629		999
630	A JSON null atom becomes C<undef> in Perl.	1000	A JSON null atom becomes C<undef> in Perl.
…		…
661	Other unblessed references are generally not allowed and will cause an	1031	Other unblessed references are generally not allowed and will cause an
662	exception to be thrown, except for references to the integers C<0> and	1032	exception to be thrown, except for references to the integers C<0> and
663	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1033	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
664	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1034	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
665		1035
666	to_json [\0,JSON::XS::true] # yields [false,true]	1036	encode_json [\0, JSON::XS::true] # yields [false,true]
667		1037
668	=item JSON::XS::true, JSON::XS::false	1038	=item JSON::XS::true, JSON::XS::false
669		1039
670	These special values become JSON true and JSON false values,	1040	These special values become JSON true and JSON false values,
671	respectively. You can also use C<\1> and C<\0> directly if you want.	1041	respectively. You can also use C<\1> and C<\0> directly if you want.
672		1042
673	=item blessed objects	1043	=item blessed objects
674		1044
675	Blessed objects are not allowed. JSON::XS currently tries to encode their	1045	Blessed objects are not directly representable in JSON. See the
676	underlying representation (hash- or arrayref), but this behaviour might	1046	C<allow_blessed> and C<convert_blessed> methods on various options on
677	change in future versions.	1047	how to deal with this: basically, you can choose between throwing an
		1048	exception, encoding the reference as if it weren't blessed, or provide
		1049	your own serialiser method.
678		1050
679	=item simple scalars	1051	=item simple scalars
680		1052
681	Simple Perl scalars (any scalar that is not a reference) are the most	1053	Simple Perl scalars (any scalar that is not a reference) are the most
682	difficult objects to encode: JSON::XS will encode undefined scalars as	1054	difficult objects to encode: JSON::XS will encode undefined scalars as
683	JSON null value, scalars that have last been used in a string context	1055	JSON C<null> values, scalars that have last been used in a string context
684	before encoding as JSON strings and anything else as number value:	1056	before encoding as JSON strings, and anything else as number value:
685		1057
686	# dump as number	1058	# dump as number
687	to_json [2] # yields [2]	1059	encode_json [2] # yields [2]
688	to_json [-3.0e17] # yields [-3e+17]	1060	encode_json [-3.0e17] # yields [-3e+17]
689	my $value = 5; to_json [$value] # yields [5]	1061	my $value = 5; encode_json [$value] # yields [5]
690		1062
691	# used as string, so dump as string	1063	# used as string, so dump as string
692	print $value;	1064	print $value;
693	to_json [$value] # yields ["5"]	1065	encode_json [$value] # yields ["5"]
694		1066
695	# undef becomes null	1067	# undef becomes null
696	to_json [undef] # yields [null]	1068	encode_json [undef] # yields [null]
697		1069
698	You can force the type to be a string by stringifying it:	1070	You can force the type to be a JSON string by stringifying it:
699		1071
700	my $x = 3.1; # some variable containing a number	1072	my $x = 3.1; # some variable containing a number
701	"$x"; # stringified	1073	"$x"; # stringified
702	$x .= ""; # another, more awkward way to stringify	1074	$x .= ""; # another, more awkward way to stringify
703	print $x; # perl does it for you, too, quite often	1075	print $x; # perl does it for you, too, quite often
704		1076
705	You can force the type to be a number by numifying it:	1077	You can force the type to be a JSON number by numifying it:
706		1078
707	my $x = "3"; # some variable containing a string	1079	my $x = "3"; # some variable containing a string
708	$x += 0; # numify it, ensuring it will be dumped as a number	1080	$x += 0; # numify it, ensuring it will be dumped as a number
709	$x *= 1; # same thing, the choise is yours.	1081	$x *= 1; # same thing, the choice is yours.
710		1082
711	You can not currently output JSON booleans or force the type in other,	1083	You can not currently force the type in other, less obscure, ways. Tell me
712	less obscure, ways. Tell me if you need this capability.	1084	if you need this capability (but don't forget to explain why it's needed
		1085	:).
713		1086
714	=back	1087	=back
715		1088
716		1089
717	=head1 COMPARISON	1090	=head1 ENCODING/CODESET FLAG NOTES
718		1091
719	As already mentioned, this module was created because none of the existing	1092	The interested reader might have seen a number of flags that signify
720	JSON modules could be made to work correctly. First I will describe the	1093	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
721	problems (or pleasures) I encountered with various existing JSON modules,	1094	some confusion on what these do, so here is a short comparison:
722	followed by some benchmark values. JSON::XS was designed not to suffer	1095
723	from any of these problems or limitations.	1096	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1097	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1098	control whether C<encode> escapes character values outside their respective
		1099	codeset range. Neither of these flags conflict with each other, although
		1100	some combinations make less sense than others.
		1101
		1102	Care has been taken to make all flags symmetrical with respect to
		1103	C<encode> and C<decode>, that is, texts encoded with any combination of
		1104	these flag values will be correctly decoded when the same flags are used
		1105	- in general, if you use different flag settings while encoding vs. when
		1106	decoding you likely have a bug somewhere.
		1107
		1108	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1109	simply an abstract set of character-codepoint pairs, while an encoding
		1110	takes those codepoint numbers and I<encodes> them, in our case into
		1111	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1112	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1113	the same time, which can be confusing.
724		1114
725	=over 4	1115	=over 4
726		1116
727	=item JSON 1.07	1117	=item C<utf8> flag disabled
728		1118
729	Slow (but very portable, as it is written in pure Perl).	1119	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1120	and expect Unicode strings, that is, characters with high ordinal Unicode
		1121	values (> 255) will be encoded as such characters, and likewise such
		1122	characters are decoded as-is, no canges to them will be done, except
		1123	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1124	respectively (to Perl, these are the same thing in strings unless you do
		1125	funny/weird/dumb stuff).
730		1126
731	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1127	This is useful when you want to do the encoding yourself (e.g. when you
732	undocumented. One can get far by feeding it unicode strings and doing	1128	want to have UTF-16 encoded JSON texts) or when some other layer does
733	en-/decoding oneself, but unicode escapes are not working properly).	1129	the encoding for you (for example, when printing to a terminal using a
		1130	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1131	to UTF-8 encode your data first and have Perl encode it another time).
734		1132
735	No roundtripping (strings get clobbered if they look like numbers, e.g.	1133	=item C<utf8> flag enabled
736	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
737	decode into the number 2.
738		1134
739	=item JSON::PC 0.01	1135	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1136	characters using the corresponding UTF-8 multi-byte sequence, and will
		1137	expect your input strings to be encoded as UTF-8, that is, no "character"
		1138	of the input string must have any value > 255, as UTF-8 does not allow
		1139	that.
740		1140
741	Very fast.	1141	The C<utf8> flag therefore switches between two modes: disabled means you
		1142	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1143	octet/binary string in Perl.
742		1144
743	Undocumented/buggy Unicode handling.	1145	=item C<latin1> or C<ascii> flags enabled
744		1146
745	No roundtripping.	1147	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1148	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1149	characters as specified by the C<utf8> flag.
746		1150
747	Has problems handling many Perl values (e.g. regex results and other magic	1151	If C<utf8> is disabled, then the result is also correctly encoded in those
748	values will make it croak).	1152	character sets (as both are proper subsets of Unicode, meaning that a
		1153	Unicode string with all character values < 256 is the same thing as a
		1154	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1155	the same thing as an ASCII string in Perl).
749		1156
750	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1157	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
751	which is not a valid JSON text.	1158	regardless of these flags, just some more characters will be escaped using
		1159	C<\uXXXX> then before.
752		1160
753	Unmaintained (maintainer unresponsive for many months, bugs are not	1161	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
754	getting fixed).	1162	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1163	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1164	a subset of Unicode), while ASCII is.
755		1165
756	=item JSON::Syck 0.21	1166	Surprisingly, C<decode> will ignore these flags and so treat all input
		1167	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1168	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1169	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
757		1170
758	Very buggy (often crashes).	1171	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1172	they only govern when the JSON output engine escapes a character or not.
759		1173
760	Very inflexible (no human-readable format supported, format pretty much	1174	The main use for C<latin1> is to relatively efficiently store binary data
761	undocumented. I need at least a format for easy reading by humans and a	1175	as JSON, at the expense of breaking compatibility with most JSON decoders.
762	single-line compact format for use in a protocol, and preferably a way to
763	generate ASCII-only JSON texts).
764		1176
765	Completely broken (and confusingly documented) Unicode handling (unicode	1177	The main use for C<ascii> is to force the output to not contain characters
766	escapes are not working properly, you need to set ImplicitUnicode to	1178	with values > 127, which means you can interpret the resulting string
767	I<different> values on en- and decoding to get symmetric behaviour).	1179	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
768		1180	8-bit-encoding, and still get the same data structure back. This is useful
769	No roundtripping (simple cases work, but this depends on wether the scalar	1181	when your channel for JSON transfer is not 8-bit clean or the encoding
770	value was used in a numeric context or not).	1182	might be mangled in between (e.g. in mail), and works because ASCII is a
771		1183	proper subset of most 8-bit and multibyte encodings in use in the world.
772	Dumping hashes may skip hash values depending on iterator state.
773
774	Unmaintained (maintainer unresponsive for many months, bugs are not
775	getting fixed).
776
777	Does not check input for validity (i.e. will accept non-JSON input and
778	return "something" instead of raising an exception. This is a security
779	issue: imagine two banks transfering money between each other using
780	JSON. One bank might parse a given non-JSON request and deduct money,
781	while the other might reject the transaction with a syntax error. While a
782	good protocol will at least recover, that is extra unnecessary work and
783	the transaction will still not succeed).
784
785	=item JSON::DWIW 0.04
786
787	Very fast. Very natural. Very nice.
788
789	Undocumented unicode handling (but the best of the pack. Unicode escapes
790	still don't get parsed properly).
791
792	Very inflexible.
793
794	No roundtripping.
795
796	Does not generate valid JSON texts (key strings are often unquoted, empty keys
797	result in nothing being output)
798
799	Does not check input for validity.
800		1184
801	=back	1185	=back
802		1186
803		1187
804	=head2 JSON and YAML	1188	=head2 JSON and YAML
805		1189
806	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1190	You often hear that JSON is a subset of YAML. This is, however, a mass
807	however, a mass hysteria and very far from the truth. In general, there is	1191	hysteria(*) and very far from the truth (as of the time of this writing),
808	no way to configure JSON::XS to output a data structure as valid YAML.	1192	so let me state it clearly: I<in general, there is no way to configure
		1193	JSON::XS to output a data structure as valid YAML> that works in all
		1194	cases.
809		1195
810	If you really must use JSON::XS to generate YAML, you should use this	1196	If you really must use JSON::XS to generate YAML, you should use this
811	algorithm (subject to change in future versions):	1197	algorithm (subject to change in future versions):
812		1198
813	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1199	my $to_yaml = JSON::XS->new->utf8->space_after (1);
814	my $yaml = $to_yaml->encode ($ref) . "\n";	1200	my $yaml = $to_yaml->encode ($ref) . "\n";
815		1201
816	This will usually generate JSON texts that also parse as valid	1202	This will I<usually> generate JSON texts that also parse as valid
817	YAML. Please note that YAML has hardcoded limits on (simple) object key	1203	YAML. Please note that YAML has hardcoded limits on (simple) object key
818	lengths that JSON doesn't have, so you should make sure that your hash	1204	lengths that JSON doesn't have and also has different and incompatible
		1205	unicode handling, so you should make sure that your hash keys are
819	keys are noticably shorter than the 1024 characters YAML allows.	1206	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1207	you do not have characters with codepoint values outside the Unicode BMP
		1208	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1209	strings (which JSON::XS does not I<currently> generate, but other JSON
		1210	generators might).
820		1211
821	There might be other incompatibilities that I am not aware of. In general	1212	There might be other incompatibilities that I am not aware of (or the YAML
		1213	specification has been changed yet again - it does so quite often). In
822	you should not try to generate YAML with a JSON generator or vice versa,	1214	general you should not try to generate YAML with a JSON generator or vice
823	or try to parse JSON with a YAML parser or vice versa: chances are high	1215	versa, or try to parse JSON with a YAML parser or vice versa: chances are
824	that you will run into severe interoperability problems.	1216	high that you will run into severe interoperability problems when you
		1217	least expect it.
		1218
		1219	=over 4
		1220
		1221	=item (*)
		1222
		1223	I have been pressured multiple times by Brian Ingerson (one of the
		1224	authors of the YAML specification) to remove this paragraph, despite him
		1225	acknowledging that the actual incompatibilities exist. As I was personally
		1226	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1227	educate people about these issues, so others do not run into the same
		1228	problem again and again. After this, Brian called me a (quote)I<complete
		1229	and worthless idiot>(unquote).
		1230
		1231	In my opinion, instead of pressuring and insulting people who actually
		1232	clarify issues with YAML and the wrong statements of some of its
		1233	proponents, I would kindly suggest reading the JSON spec (which is not
		1234	that difficult or long) and finally make YAML compatible to it, and
		1235	educating users about the changes, instead of spreading lies about the
		1236	real compatibility for many I<years> and trying to silence people who
		1237	point out that it isn't true.
		1238
		1239	=back
825		1240
826		1241
827	=head2 SPEED	1242	=head2 SPEED
828		1243
829	It seems that JSON::XS is surprisingly fast, as shown in the following	1244	It seems that JSON::XS is surprisingly fast, as shown in the following
830	tables. They have been generated with the help of the C<eg/bench> program	1245	tables. They have been generated with the help of the C<eg/bench> program
831	in the JSON::XS distribution, to make it easy to compare on your own	1246	in the JSON::XS distribution, to make it easy to compare on your own
832	system.	1247	system.
833		1248
834	First comes a comparison between various modules using a very short	1249	First comes a comparison between various modules using
835	single-line JSON string:	1250	a very short single-line JSON string (also available at
		1251	L<http://dist.schmorp.de/misc/json/short.json>).
836		1252
837	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1253	{"method": "handleMessage", "params": ["user1",
838	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1254	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1255	true, false]}
839		1256
840	It shows the number of encodes/decodes per second (JSON::XS uses	1257	It shows the number of encodes/decodes per second (JSON::XS uses
841	the functional interface, while JSON::XS/2 uses the OO interface	1258	the functional interface, while JSON::XS/2 uses the OO interface
842	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1259	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
843	shrink). Higher is better:	1260	shrink). Higher is better:
844		1261
845	Storable \| 15779.925 \| 14169.946 \|
846	-----------+------------+------------+
847	module \| encode \| decode \|	1262	module \| encode \| decode \|
848	-----------\|------------\|------------\|	1263	-----------\|------------\|------------\|
849	JSON \| 4990.842 \| 4088.813 \|	1264	JSON 1.x \| 4990.842 \| 4088.813 \|
850	JSON::DWIW \| 51653.990 \| 71575.154 \|	1265	JSON::DWIW \| 51653.990 \| 71575.154 \|
851	JSON::PC \| 65948.176 \| 74631.744 \|	1266	JSON::PC \| 65948.176 \| 74631.744 \|
852	JSON::PP \| 8931.652 \| 3817.168 \|	1267	JSON::PP \| 8931.652 \| 3817.168 \|
853	JSON::Syck \| 24877.248 \| 27776.848 \|	1268	JSON::Syck \| 24877.248 \| 27776.848 \|
854	JSON::XS \| 388361.481 \| 227951.304 \|	1269	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
856	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1271	JSON::XS/3 \| 338250.323 \| 218453.333 \|
857	Storable \| 16500.016 \| 135300.129 \|	1272	Storable \| 16500.016 \| 135300.129 \|
858	-----------+------------+------------+	1273	-----------+------------+------------+
859		1274
860	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1275	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
861	about three times faster on decoding, and over fourty times faster	1276	about three times faster on decoding, and over forty times faster
862	than JSON, even with pretty-printing and key sorting. It also compares	1277	than JSON, even with pretty-printing and key sorting. It also compares
863	favourably to Storable for small amounts of data.	1278	favourably to Storable for small amounts of data.
864		1279
865	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1280	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
866	search API (http://nanoref.com/yahooapis/mgPdGg):	1281	search API (L<http://dist.schmorp.de/misc/json/long.json>).
867		1282
868	module \| encode \| decode \|	1283	module \| encode \| decode \|
869	-----------\|------------\|------------\|	1284	-----------\|------------\|------------\|
870	JSON \| 55.260 \| 34.971 \|	1285	JSON 1.x \| 55.260 \| 34.971 \|
871	JSON::DWIW \| 825.228 \| 1082.513 \|	1286	JSON::DWIW \| 825.228 \| 1082.513 \|
872	JSON::PC \| 3571.444 \| 2394.829 \|	1287	JSON::PC \| 3571.444 \| 2394.829 \|
873	JSON::PP \| 210.987 \| 32.574 \|	1288	JSON::PP \| 210.987 \| 32.574 \|
874	JSON::Syck \| 552.551 \| 787.544 \|	1289	JSON::Syck \| 552.551 \| 787.544 \|
875	JSON::XS \| 5780.463 \| 4854.519 \|	1290	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
879	-----------+------------+------------+	1294	-----------+------------+------------+
880		1295
881	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1296	Again, JSON::XS leads by far (except for Storable which non-surprisingly
882	decodes faster).	1297	decodes faster).
883		1298
884	On large strings containing lots of high unicode characters, some modules	1299	On large strings containing lots of high Unicode characters, some modules
885	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1300	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
886	will be broken due to missing (or wrong) unicode handling. Others refuse	1301	will be broken due to missing (or wrong) Unicode handling. Others refuse
887	to decode or encode properly, so it was impossible to prepare a fair	1302	to decode or encode properly, so it was impossible to prepare a fair
888	comparison table for that case.	1303	comparison table for that case.
889		1304
890		1305
891	=head1 SECURITY CONSIDERATIONS	1306	=head1 SECURITY CONSIDERATIONS
…		…
897	any buffer overflows. Obviously, this module should ensure that and I am	1312	any buffer overflows. Obviously, this module should ensure that and I am
898	trying hard on making that true, but you never know.	1313	trying hard on making that true, but you never know.
899		1314
900	Second, you need to avoid resource-starving attacks. That means you should	1315	Second, you need to avoid resource-starving attacks. That means you should
901	limit the size of JSON texts you accept, or make sure then when your	1316	limit the size of JSON texts you accept, or make sure then when your
902	resources run out, thats just fine (e.g. by using a separate process that	1317	resources run out, that's just fine (e.g. by using a separate process that
903	can crash safely). The size of a JSON text in octets or characters is	1318	can crash safely). The size of a JSON text in octets or characters is
904	usually a good indication of the size of the resources required to decode	1319	usually a good indication of the size of the resources required to decode
905	it into a Perl structure. While JSON::XS can check the size of the JSON	1320	it into a Perl structure. While JSON::XS can check the size of the JSON
906	text, it might be too late when you already have it in memory, so you	1321	text, it might be too late when you already have it in memory, so you
907	might want to check the size before you accept the string.	1322	might want to check the size before you accept the string.
908		1323
909	Third, JSON::XS recurses using the C stack when decoding objects and	1324	Third, JSON::XS recurses using the C stack when decoding objects and
910	arrays. The C stack is a limited resource: for instance, on my amd64	1325	arrays. The C stack is a limited resource: for instance, on my amd64
911	machine with 8MB of stack size I can decode around 180k nested arrays but	1326	machine with 8MB of stack size I can decode around 180k nested arrays but
912	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1327	only 14k nested JSON objects (due to perl itself recursing deeply on croak
913	to free the temporary). If that is exceeded, the program crashes. to be	1328	to free the temporary). If that is exceeded, the program crashes. To be
914	conservative, the default nesting limit is set to 512. If your process	1329	conservative, the default nesting limit is set to 512. If your process
915	has a smaller stack, you should adjust this setting accordingly with the	1330	has a smaller stack, you should adjust this setting accordingly with the
916	C<max_depth> method.	1331	C<max_depth> method.
917		1332
918	And last but least, something else could bomb you that I forgot to think	1333	Something else could bomb you, too, that I forgot to think of. In that
919	of. In that case, you get to keep the pieces. I am always open for hints,	1334	case, you get to keep the pieces. I am always open for hints, though...
920	though...	1335
		1336	Also keep in mind that JSON::XS might leak contents of your Perl data
		1337	structures in its error messages, so when you serialise sensitive
		1338	information you might want to make sure that exceptions thrown by JSON::XS
		1339	will not end up in front of untrusted eyes.
921		1340
922	If you are using JSON::XS to return packets to consumption	1341	If you are using JSON::XS to return packets to consumption
923	by javascript scripts in a browser you should have a look at	1342	by JavaScript scripts in a browser you should have a look at
924	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1343	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
925	you are vulnerable to some common attack vectors (which really are browser	1344	you are vulnerable to some common attack vectors (which really are browser
926	design bugs, but it is still you who will have to deal with it, as major	1345	design bugs, but it is still you who will have to deal with it, as major
927	browser developers care only for features, not about doing security	1346	browser developers care only for features, not about getting security
928	right).	1347	right).
929		1348
930		1349
		1350	=head1 THREADS
		1351
		1352	This module is I<not> guaranteed to be thread safe and there are no
		1353	plans to change this until Perl gets thread support (as opposed to the
		1354	horribly slow so-called "threads" which are simply slow and bloated
		1355	process simulations - use fork, it's I<much> faster, cheaper, better).
		1356
		1357	(It might actually work, but you have been warned).
		1358
		1359
931	=head1 BUGS	1360	=head1 BUGS
932		1361
933	While the goal of this module is to be correct, that unfortunately does	1362	While the goal of this module is to be correct, that unfortunately does
934	not mean its bug-free, only that I think its design is bug-free. It is	1363	not mean it's bug-free, only that I think its design is bug-free. If you
935	still relatively early in its development. If you keep reporting bugs they	1364	keep reporting bugs they will be fixed swiftly, though.
936	will be fixed swiftly, though.	1365
		1366	Please refrain from using rt.cpan.org or any other bug reporting
		1367	service. I put the contact address into my modules for a reason.
937		1368
938	=cut	1369	=cut
939		1370
940	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1371	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
941	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1372	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
…		…
958	"--" => sub { $_[0] = ${$_[0]} - 1 },	1389	"--" => sub { $_[0] = ${$_[0]} - 1 },
959	fallback => 1;	1390	fallback => 1;
960		1391
961	1;	1392	1;
962		1393
		1394	=head1 SEE ALSO
		1395
		1396	The F<json_xs> command line utility for quick experiments.
		1397
963	=head1 AUTHOR	1398	=head1 AUTHOR
964		1399
965	Marc Lehmann <schmorp@schmorp.de>	1400	Marc Lehmann <schmorp@schmorp.de>
966	http://home.schmorp.de/	1401	http://home.schmorp.de/
967		1402

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Comparing JSON-XS/XS.pm (file contents): Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC vs. Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC vs.
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC