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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.70 by root, Tue Nov 13 22:59:08 2007 UTC vs.
Revision 1.130 by root, Thu Mar 11 17:36:09 2010 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
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
10	use JSON::XS;	12	use JSON::XS;
11		13
12	# exported functions, they croak on error	14	# exported functions, they croak on error
13	# and expect/generate UTF-8	15	# and expect/generate UTF-8
14		16
15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17		19
18	# OO-interface	20	# OO-interface
19		21
20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
22	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
23		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
24	=head1 DESCRIPTION	34	=head1 DESCRIPTION
25		35
26	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
27	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
28	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.
29		47
30	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
31	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
32	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
33	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
34	reports for other reasons.	52	reports for other reasons.
35		53
36	See COMPARISON, below, for a comparison to some other JSON modules.
37
38	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
39	vice versa.	55	vice versa.
40		56
41	=head2 FEATURES	57	=head2 FEATURES
42		58
43	=over 4	59	=over 4
44		60
45	=item * correct Unicode handling	61	=item * correct Unicode handling
46		62
47	This module knows how to handle Unicode, and even documents how and when	63	This module knows how to handle Unicode, documents how and when it does
48	it does so.	64	so, and even documents what "correct" means.
49		65
50	=item * round-trip integrity	66	=item * round-trip integrity
51		67
52	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
53	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
54	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
55	like a number).	71	like a number). There minor I<are> exceptions to this, read the MAPPING
		72	section below to learn about those.
56		73
57	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
58		75
59	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
60	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
61	feature).	78	feature).
62		79
63	=item * fast	80	=item * fast
64		81
65	Compared to other JSON modules, this module compares favourably in terms	82	Compared to other JSON modules and other serialisers such as Storable,
66	of speed, too.	83	this module usually compares favourably in terms of speed, too.
67		84
68	=item * simple to use	85	=item * simple to use
69		86
70	This module has both a simple functional interface as well as an OO	87	This module has both a simple functional interface as well as an object
71	interface.	88	oriented interface interface.
72		89
73	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
74		91
75	You can choose between the most compact guaranteed single-line format	92	You can choose between the most compact guaranteed-single-line format
76	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
77	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
78	Unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
79	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
80		97
81	=back	98	=back
82		99
83	=cut	100	=cut
84		101
85	package JSON::XS;	102	package JSON::XS;
86		103
87	use strict;	104	use common::sense;
88		105
89	our $VERSION = '1.53';	106	our $VERSION = '2.28';
90	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
91		108
92	our @EXPORT = qw(to_json from_json);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
		110
		111	sub to_json($) {
		112	require Carp;
		113	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");
		114	}
		115
		116	sub from_json($) {
		117	require Carp;
		118	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");
		119	}
93		120
94	use Exporter;	121	use Exporter;
95	use XSLoader;	122	use XSLoader;
96		123
97	=head1 FUNCTIONAL INTERFACE	124	=head1 FUNCTIONAL INTERFACE
…		…
99	The following convenience methods are provided by this module. They are	126	The following convenience methods are provided by this module. They are
100	exported by default:	127	exported by default:
101		128
102	=over 4	129	=over 4
103		130
104	=item $json_text = to_json $perl_scalar	131	=item $json_text = encode_json $perl_scalar
105		132
106	Converts the given Perl data structure to a UTF-8 encoded, binary string	133	Converts the given Perl data structure to a UTF-8 encoded, binary string
107	(that is, the string contains octets only). Croaks on error.	134	(that is, the string contains octets only). Croaks on error.
108		135
109	This function call is functionally identical to:	136	This function call is functionally identical to:
110		137
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		139
113	except being faster.	140	Except being faster.
114		141
115	=item $perl_scalar = from_json $json_text	142	=item $perl_scalar = decode_json $json_text
116		143
117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	144	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
118	to parse that as an UTF-8 encoded JSON text, returning the resulting	145	to parse that as an UTF-8 encoded JSON text, returning the resulting
119	reference. Croaks on error.	146	reference. Croaks on error.
120		147
121	This function call is functionally identical to:	148	This function call is functionally identical to:
122		149
123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
124		151
125	except being faster.	152	Except being faster.
126		153
127	=item $is_boolean = JSON::XS::is_bool $scalar	154	=item $is_boolean = JSON::XS::is_bool $scalar
128		155
129	Returns true if the passed scalar represents either JSON::XS::true or	156	Returns true if the passed scalar represents either JSON::XS::true or
130	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
148	This enables you to store Unicode characters as single characters in a	175	This enables you to store Unicode characters as single characters in a
149	Perl string - very natural.	176	Perl string - very natural.
150		177
151	=item 2. Perl does I<not> associate an encoding with your strings.	178	=item 2. Perl does I<not> associate an encoding with your strings.
152		179
153	Unless you force it to, e.g. when matching it against a regex, or printing	180	... until you force it to, e.g. when matching it against a regex, or
154	the scalar to a file, in which case Perl either interprets your string as	181	printing the scalar to a file, in which case Perl either interprets your
155	locale-encoded text, octets/binary, or as Unicode, depending on various	182	string as locale-encoded text, octets/binary, or as Unicode, depending
156	settings. In no case is an encoding stored together with your data, it is	183	on various settings. In no case is an encoding stored together with your
157	I<use> that decides encoding, not any magical metadata.	184	data, it is I<use> that decides encoding, not any magical meta data.
158		185
159	=item 3. The internal utf-8 flag has no meaning with regards to the	186	=item 3. The internal utf-8 flag has no meaning with regards to the
160	encoding of your string.	187	encoding of your string.
161		188
162	Just ignore that flag unless you debug a Perl bug, a module written in	189	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
168		195
169	If you didn't know about that flag, just the better, pretend it doesn't	196	If you didn't know about that flag, just the better, pretend it doesn't
170	exist.	197	exist.
171		198
172	=item 4. A "Unicode String" is simply a string where each character can be	199	=item 4. A "Unicode String" is simply a string where each character can be
173	validly interpreted as a Unicode codepoint.	200	validly interpreted as a Unicode code point.
174		201
175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	202	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
176	Unicode string encoded in UTF-8, giving you a binary string.	203	Unicode string encoded in UTF-8, giving you a binary string.
177		204
178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	205	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
201		228
202	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	229	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
203	=> {"a": [1, 2]}	230	=> {"a": [1, 2]}
204		231
205	=item $json = $json->ascii ([$enable])	232	=item $json = $json->ascii ([$enable])
		233
		234	=item $enabled = $json->get_ascii
206		235
207	If C<$enable> is true (or missing), then the C<encode> method will not	236	If C<$enable> is true (or missing), then the C<encode> method will not
208	generate characters outside the code range C<0..127> (which is ASCII). Any	237	generate characters outside the code range C<0..127> (which is ASCII). Any
209	Unicode characters outside that range will be escaped using either a	238	Unicode characters outside that range will be escaped using either a
210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	239	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
…		…
214		243
215	If C<$enable> is false, then the C<encode> method will not escape Unicode	244	If C<$enable> is false, then the C<encode> method will not escape Unicode
216	characters unless required by the JSON syntax or other flags. This results	245	characters unless required by the JSON syntax or other flags. This results
217	in a faster and more compact format.	246	in a faster and more compact format.
218		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
219	The main use for this flag is to produce JSON texts that can be	251	The main use for this flag is to produce JSON texts that can be
220	transmitted over a 7-bit channel, as the encoded JSON texts will not	252	transmitted over a 7-bit channel, as the encoded JSON texts will not
221	contain any 8 bit characters.	253	contain any 8 bit characters.
222		254
223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224	=> ["\ud801\udc01"]	256	=> ["\ud801\udc01"]
225		257
226	=item $json = $json->latin1 ([$enable])	258	=item $json = $json->latin1 ([$enable])
		259
		260	=item $enabled = $json->get_latin1
227		261
228	If C<$enable> is true (or missing), then the C<encode> method will encode	262	If C<$enable> is true (or missing), then the C<encode> method will encode
229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	263	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230	outside the code range C<0..255>. The resulting string can be treated as a	264	outside the code range C<0..255>. The resulting string can be treated as a
231	latin1-encoded JSON text or a native Unicode string. The C<decode> method	265	latin1-encoded JSON text or a native Unicode string. The C<decode> method
232	will not be affected in any way by this flag, as C<decode> by default	266	will not be affected in any way by this flag, as C<decode> by default
233	expects Unicode, which is a strict superset of latin1.	267	expects Unicode, which is a strict superset of latin1.
234		268
235	If C<$enable> is false, then the C<encode> method will not escape Unicode	269	If C<$enable> is false, then the C<encode> method will not escape Unicode
236	characters unless required by the JSON syntax or other flags.	270	characters unless required by the JSON syntax or other flags.
		271
		272	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		273	document.
237		274
238	The main use for this flag is efficiently encoding binary data as JSON	275	The main use for this flag is efficiently encoding binary data as JSON
239	text, as most octets will not be escaped, resulting in a smaller encoded	276	text, as most octets will not be escaped, resulting in a smaller encoded
240	size. The disadvantage is that the resulting JSON text is encoded	277	size. The disadvantage is that the resulting JSON text is encoded
241	in latin1 (and must correctly be treated as such when storing and	278	in latin1 (and must correctly be treated as such when storing and
…		…
246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	283	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	284	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248		285
249	=item $json = $json->utf8 ([$enable])	286	=item $json = $json->utf8 ([$enable])
250		287
		288	=item $enabled = $json->get_utf8
		289
251	If C<$enable> is true (or missing), then the C<encode> method will encode	290	If C<$enable> is true (or missing), then the C<encode> method will encode
252	the JSON result into UTF-8, as required by many protocols, while the	291	the JSON result into UTF-8, as required by many protocols, while the
253	C<decode> method expects to be handled an UTF-8-encoded string. Please	292	C<decode> method expects to be handled an UTF-8-encoded string. Please
254	note that UTF-8-encoded strings do not contain any characters outside the	293	note that UTF-8-encoded strings do not contain any characters outside the
255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	294	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
…		…
258		297
259	If C<$enable> is false, then the C<encode> method will return the JSON	298	If C<$enable> is false, then the C<encode> method will return the JSON
260	string as a (non-encoded) Unicode string, while C<decode> expects thus a	299	string as a (non-encoded) Unicode string, while C<decode> expects thus a
261	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	300	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
262	to be done yourself, e.g. using the Encode module.	301	to be done yourself, e.g. using the Encode module.
		302
		303	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		304	document.
263		305
264	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
265		307
266	use Encode;	308	use Encode;
267	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
288	]	330	]
289	}	331	}
290		332
291	=item $json = $json->indent ([$enable])	333	=item $json = $json->indent ([$enable])
292		334
		335	=item $enabled = $json->get_indent
		336
293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	337	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294	format as output, putting every array member or object/hash key-value pair	338	format as output, putting every array member or object/hash key-value pair
295	into its own line, indenting them properly.	339	into its own line, indenting them properly.
296		340
297	If C<$enable> is false, no newlines or indenting will be produced, and the	341	If C<$enable> is false, no newlines or indenting will be produced, and the
…		…
299		343
300	This setting has no effect when decoding JSON texts.	344	This setting has no effect when decoding JSON texts.
301		345
302	=item $json = $json->space_before ([$enable])	346	=item $json = $json->space_before ([$enable])
303		347
		348	=item $enabled = $json->get_space_before
		349
304	If C<$enable> is true (or missing), then the C<encode> method will add an extra	350	If C<$enable> is true (or missing), then the C<encode> method will add an extra
305	optional space before the C<:> separating keys from values in JSON objects.	351	optional space before the C<:> separating keys from values in JSON objects.
306		352
307	If C<$enable> is false, then the C<encode> method will not add any extra	353	If C<$enable> is false, then the C<encode> method will not add any extra
308	space at those places.	354	space at those places.
…		…
313	Example, space_before enabled, space_after and indent disabled:	359	Example, space_before enabled, space_after and indent disabled:
314		360
315	{"key" :"value"}	361	{"key" :"value"}
316		362
317	=item $json = $json->space_after ([$enable])	363	=item $json = $json->space_after ([$enable])
		364
		365	=item $enabled = $json->get_space_after
318		366
319	If C<$enable> is true (or missing), then the C<encode> method will add an extra	367	If C<$enable> is true (or missing), then the C<encode> method will add an extra
320	optional space after the C<:> separating keys from values in JSON objects	368	optional space after the C<:> separating keys from values in JSON objects
321	and extra whitespace after the C<,> separating key-value pairs and array	369	and extra whitespace after the C<,> separating key-value pairs and array
322	members.	370	members.
…		…
329	Example, space_before and indent disabled, space_after enabled:	377	Example, space_before and indent disabled, space_after enabled:
330		378
331	{"key": "value"}	379	{"key": "value"}
332		380
333	=item $json = $json->relaxed ([$enable])	381	=item $json = $json->relaxed ([$enable])
		382
		383	=item $enabled = $json->get_relaxed
334		384
335	If C<$enable> is true (or missing), then C<decode> will accept some	385	If C<$enable> is true (or missing), then C<decode> will accept some
336	extensions to normal JSON syntax (see below). C<encode> will not be	386	extensions to normal JSON syntax (see below). C<encode> will not be
337	affected in anyway. I<Be aware that this option makes you accept invalid	387	affected in anyway. I<Be aware that this option makes you accept invalid
338	JSON texts as if they were valid!>. I suggest only to use this option to	388	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
375		425
376	=back	426	=back
377		427
378	=item $json = $json->canonical ([$enable])	428	=item $json = $json->canonical ([$enable])
379		429
		430	=item $enabled = $json->get_canonical
		431
380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	432	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381	by sorting their keys. This is adding a comparatively high overhead.	433	by sorting their keys. This is adding a comparatively high overhead.
382		434
383	If C<$enable> is false, then the C<encode> method will output key-value	435	If C<$enable> is false, then the C<encode> method will output key-value
384	pairs in the order Perl stores them (which will likely change between runs	436	pairs in the order Perl stores them (which will likely change between runs
…		…
389	the same hash might be encoded differently even if contains the same data,	441	the same hash might be encoded differently even if contains the same data,
390	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
391		443
392	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
393		445
		446	This setting has currently no effect on tied hashes.
		447
394	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
395		451
396	If C<$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
397	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
398	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
399	values instead of croaking.	455	values instead of croaking.
…		…
407	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
408		464
409	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
410	=> "Hello, World!"	466	=> "Hello, World!"
411		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
412	=item $json = $json->allow_blessed ([$enable])	484	=item $json = $json->allow_blessed ([$enable])
		485
		486	=item $enabled = $json->get_allow_blessed
413		487
414	If C<$enable> is true (or missing), then the C<encode> method will not	488	If C<$enable> is true (or missing), then the C<encode> method will not
415	barf when it encounters a blessed reference. Instead, the value of the	489	barf when it encounters a blessed reference. Instead, the value of the
416	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	490	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417	disabled or no C<to_json> method found) or a representation of the	491	disabled or no C<TO_JSON> method found) or a representation of the
418	object (C<convert_blessed> enabled and C<to_json> method found) is being	492	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419	encoded. Has no effect on C<decode>.	493	encoded. Has no effect on C<decode>.
420		494
421	If C<$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
422	exception when it encounters a blessed object.	496	exception when it encounters a blessed object.
423		497
424	=item $json = $json->convert_blessed ([$enable])	498	=item $json = $json->convert_blessed ([$enable])
		499
		500	=item $enabled = $json->get_convert_blessed
425		501
426	If C<$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
427	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
428	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
429	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
…		…
433	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>
434	returns other blessed objects, those will be handled in the same	510	returns other blessed objects, those will be handled in the same
435	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
436	(== 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
437	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
438	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>
439	function.	515	function or method.
440		516
441	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
442	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
443	enabled by this setting.	519	enabled by this setting.
444		520
…		…
520		596
521	{ __widget__ => $self->{id} }	597	{ __widget__ => $self->{id} }
522	}	598	}
523		599
524	=item $json = $json->shrink ([$enable])	600	=item $json = $json->shrink ([$enable])
		601
		602	=item $enabled = $json->get_shrink
525		603
526	Perl usually over-allocates memory a bit when allocating space for	604	Perl usually over-allocates memory a bit when allocating space for
527	strings. This flag optionally resizes strings generated by either	605	strings. This flag optionally resizes strings generated by either
528	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
529	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
…		…
547	strings that look like integers or floats into integers or floats	625	strings that look like integers or floats into integers or floats
548	internally (there is no difference on the Perl level), saving space.	626	internally (there is no difference on the Perl level), saving space.
549		627
550	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
551		629
		630	=item $max_depth = $json->get_max_depth
		631
552	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
553	or decoding. If the JSON text or Perl data structure has an equal or	633	or decoding. If a higher nesting level is detected in JSON text or a Perl
554	higher nesting level then this limit, then the encoder and decoder will	634	data structure, then the encoder and decoder will stop and croak at that
555	stop and croak at that point.	635	point.
556		636
557	Nesting level is defined by number of hash- or arrayrefs that the encoder	637	Nesting level is defined by number of hash- or arrayrefs that the encoder
558	needs to traverse to reach a given point or the number of C<{> or C<[>	638	needs to traverse to reach a given point or the number of C<{> or C<[>
559	characters without their matching closing parenthesis crossed to reach a	639	characters without their matching closing parenthesis crossed to reach a
560	given character in a string.	640	given character in a string.
561		641
562	Setting the maximum depth to one disallows any nesting, so that ensures	642	Setting the maximum depth to one disallows any nesting, so that ensures
563	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
564		644
565	The argument to C<max_depth> will be rounded up to the next highest power
566	of two. If no argument is given, the highest possible setting will be	645	If no argument is given, the highest possible setting will be used, which
567	used, which is rarely useful.	646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
568		651
569	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
570		653
571	=item $json = $json->max_size ([$maximum_string_size])	654	=item $json = $json->max_size ([$maximum_string_size])
		655
		656	=item $max_size = $json->get_max_size
572		657
573	Set the maximum length a JSON text may have (in bytes) where decoding is	658	Set the maximum length a JSON text may have (in bytes) where decoding is
574	being attempted. The default is C<0>, meaning no limit. When C<decode>	659	being attempted. The default is C<0>, meaning no limit. When C<decode>
575	is called on a string longer then this number of characters it will not	660	is called on a string that is longer then this many bytes, it will not
576	attempt to decode the string but throw an exception. This setting has no	661	attempt to decode the string but throw an exception. This setting has no
577	effect on C<encode> (yet).	662	effect on C<encode> (yet).
578		663
579	The argument to C<max_size> will be rounded up to the next B<highest>	664	If no argument is given, the limit check will be deactivated (same as when
580	power of two (so may be more than requested). If no argument is given, the	665	C<0> is specified).
581	limit check will be deactivated (same as when C<0> is specified).
582		666
583	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
584		668
585	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
586		670
…		…
615	=> ([], 3)	699	=> ([], 3)
616		700
617	=back	701	=back
618		702
619		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	Example: Parse some JSON arrays/objects in a given string and return
		757	them.
		758
		759	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		760
		761	=item $lvalue_string = $json->incr_text
		762
		763	This method returns the currently stored JSON fragment as an lvalue, that
		764	is, you can manipulate it. This I<only> works when a preceding call to
		765	C<incr_parse> in I<scalar context> successfully returned an object. Under
		766	all other circumstances you must not call this function (I mean it.
		767	although in simple tests it might actually work, it I<will> fail under
		768	real world conditions). As a special exception, you can also call this
		769	method before having parsed anything.
		770
		771	This function is useful in two cases: a) finding the trailing text after a
		772	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		773	(such as commas).
		774
		775	=item $json->incr_skip
		776
		777	This will reset the state of the incremental parser and will remove
		778	the parsed text from the input buffer so far. This is useful after
		779	C<incr_parse> died, in which case the input buffer and incremental parser
		780	state is left unchanged, to skip the text parsed so far and to reset the
		781	parse state.
		782
		783	The difference to C<incr_reset> is that only text until the parse error
		784	occured is removed.
		785
		786	=item $json->incr_reset
		787
		788	This completely resets the incremental parser, that is, after this call,
		789	it will be as if the parser had never parsed anything.
		790
		791	This is useful if you want to repeatedly parse JSON objects and want to
		792	ignore any trailing data, which means you have to reset the parser after
		793	each successful decode.
		794
		795	=back
		796
		797	=head2 LIMITATIONS
		798
		799	All options that affect decoding are supported, except
		800	C<allow_nonref>. The reason for this is that it cannot be made to
		801	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		802	them back to back and still decode them perfectly. This does not hold true
		803	for JSON numbers, however.
		804
		805	For example, is the string C<1> a single JSON number, or is it simply the
		806	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		807	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		808	takes the conservative route and disallows this case.
		809
		810	=head2 EXAMPLES
		811
		812	Some examples will make all this clearer. First, a simple example that
		813	works similarly to C<decode_prefix>: We want to decode the JSON object at
		814	the start of a string and identify the portion after the JSON object:
		815
		816	my $text = "[1,2,3] hello";
		817
		818	my $json = new JSON::XS;
		819
		820	my $obj = $json->incr_parse ($text)
		821	or die "expected JSON object or array at beginning of string";
		822
		823	my $tail = $json->incr_text;
		824	# $tail now contains " hello"
		825
		826	Easy, isn't it?
		827
		828	Now for a more complicated example: Imagine a hypothetical protocol where
		829	you read some requests from a TCP stream, and each request is a JSON
		830	array, without any separation between them (in fact, it is often useful to
		831	use newlines as "separators", as these get interpreted as whitespace at
		832	the start of the JSON text, which makes it possible to test said protocol
		833	with C<telnet>...).
		834
		835	Here is how you'd do it (it is trivial to write this in an event-based
		836	manner):
		837
		838	my $json = new JSON::XS;
		839
		840	# read some data from the socket
		841	while (sysread $socket, my $buf, 4096) {
		842
		843	# split and decode as many requests as possible
		844	for my $request ($json->incr_parse ($buf)) {
		845	# act on the $request
		846	}
		847	}
		848
		849	Another complicated example: Assume you have a string with JSON objects
		850	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		851	[3]>). To parse them, we have to skip the commas between the JSON texts,
		852	and here is where the lvalue-ness of C<incr_text> comes in useful:
		853
		854	my $text = "[1],[2], [3]";
		855	my $json = new JSON::XS;
		856
		857	# void context, so no parsing done
		858	$json->incr_parse ($text);
		859
		860	# now extract as many objects as possible. note the
		861	# use of scalar context so incr_text can be called.
		862	while (my $obj = $json->incr_parse) {
		863	# do something with $obj
		864
		865	# now skip the optional comma
		866	$json->incr_text =~ s/^ \s* , //x;
		867	}
		868
		869	Now lets go for a very complex example: Assume that you have a gigantic
		870	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		871	but you cannot load it into memory fully (this has actually happened in
		872	the real world :).
		873
		874	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		875	can still help you: You implement a (very simple) array parser and let
		876	JSON decode the array elements, which are all full JSON objects on their
		877	own (this wouldn't work if the array elements could be JSON numbers, for
		878	example):
		879
		880	my $json = new JSON::XS;
		881
		882	# open the monster
		883	open my $fh, "<bigfile.json"
		884	or die "bigfile: $!";
		885
		886	# first parse the initial "["
		887	for (;;) {
		888	sysread $fh, my $buf, 65536
		889	or die "read error: $!";
		890	$json->incr_parse ($buf); # void context, so no parsing
		891
		892	# Exit the loop once we found and removed(!) the initial "[".
		893	# In essence, we are (ab-)using the $json object as a simple scalar
		894	# we append data to.
		895	last if $json->incr_text =~ s/^ \s* \[ //x;
		896	}
		897
		898	# now we have the skipped the initial "[", so continue
		899	# parsing all the elements.
		900	for (;;) {
		901	# in this loop we read data until we got a single JSON object
		902	for (;;) {
		903	if (my $obj = $json->incr_parse) {
		904	# do something with $obj
		905	last;
		906	}
		907
		908	# add more data
		909	sysread $fh, my $buf, 65536
		910	or die "read error: $!";
		911	$json->incr_parse ($buf); # void context, so no parsing
		912	}
		913
		914	# in this loop we read data until we either found and parsed the
		915	# separating "," between elements, or the final "]"
		916	for (;;) {
		917	# first skip whitespace
		918	$json->incr_text =~ s/^\s*//;
		919
		920	# if we find "]", we are done
		921	if ($json->incr_text =~ s/^\]//) {
		922	print "finished.\n";
		923	exit;
		924	}
		925
		926	# if we find ",", we can continue with the next element
		927	if ($json->incr_text =~ s/^,//) {
		928	last;
		929	}
		930
		931	# if we find anything else, we have a parse error!
		932	if (length $json->incr_text) {
		933	die "parse error near ", $json->incr_text;
		934	}
		935
		936	# else add more data
		937	sysread $fh, my $buf, 65536
		938	or die "read error: $!";
		939	$json->incr_parse ($buf); # void context, so no parsing
		940	}
		941
		942	This is a complex example, but most of the complexity comes from the fact
		943	that we are trying to be correct (bear with me if I am wrong, I never ran
		944	the above example :).
		945
		946
		947
620	=head1 MAPPING	948	=head1 MAPPING
621		949
622	This section describes how JSON::XS maps Perl values to JSON values and	950	This section describes how JSON::XS maps Perl values to JSON values and
623	vice versa. These mappings are designed to "do the right thing" in most	951	vice versa. These mappings are designed to "do the right thing" in most
624	circumstances automatically, preserving round-tripping characteristics	952	circumstances automatically, preserving round-tripping characteristics
…		…
652		980
653	A JSON number becomes either an integer, numeric (floating point) or	981	A JSON number becomes either an integer, numeric (floating point) or
654	string scalar in perl, depending on its range and any fractional parts. On	982	string scalar in perl, depending on its range and any fractional parts. On
655	the Perl level, there is no difference between those as Perl handles all	983	the Perl level, there is no difference between those as Perl handles all
656	the conversion details, but an integer may take slightly less memory and	984	the conversion details, but an integer may take slightly less memory and
657	might represent more values exactly than (floating point) numbers.	985	might represent more values exactly than floating point numbers.
658		986
659	If the number consists of digits only, JSON::XS will try to represent	987	If the number consists of digits only, JSON::XS will try to represent
660	it as an integer value. If that fails, it will try to represent it as	988	it as an integer value. If that fails, it will try to represent it as
661	a numeric (floating point) value if that is possible without loss of	989	a numeric (floating point) value if that is possible without loss of
662	precision. Otherwise it will preserve the number as a string value.	990	precision. Otherwise it will preserve the number as a string value (in
		991	which case you lose roundtripping ability, as the JSON number will be
		992	re-encoded toa JSON string).
663		993
664	Numbers containing a fractional or exponential part will always be	994	Numbers containing a fractional or exponential part will always be
665	represented as numeric (floating point) values, possibly at a loss of	995	represented as numeric (floating point) values, possibly at a loss of
666	precision.	996	precision (in which case you might lose perfect roundtripping ability, but
667		997	the JSON number will still be re-encoded as a JSON number).
668	This might create round-tripping problems as numbers might become strings,
669	but as Perl is typeless there is no other way to do it.
670		998
671	=item true, false	999	=item true, false
672		1000
673	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	1001	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
674	respectively. They are overloaded to act almost exactly like the numbers	1002	respectively. They are overloaded to act almost exactly like the numbers
…		…
711	Other unblessed references are generally not allowed and will cause an	1039	Other unblessed references are generally not allowed and will cause an
712	exception to be thrown, except for references to the integers C<0> and	1040	exception to be thrown, except for references to the integers C<0> and
713	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1041	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
714	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1042	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
715		1043
716	to_json [\0,JSON::XS::true] # yields [false,true]	1044	encode_json [\0, JSON::XS::true] # yields [false,true]
717		1045
718	=item JSON::XS::true, JSON::XS::false	1046	=item JSON::XS::true, JSON::XS::false
719		1047
720	These special values become JSON true and JSON false values,	1048	These special values become JSON true and JSON false values,
721	respectively. You can also use C<\1> and C<\0> directly if you want.	1049	respectively. You can also use C<\1> and C<\0> directly if you want.
722		1050
723	=item blessed objects	1051	=item blessed objects
724		1052
725	Blessed objects are not allowed. JSON::XS currently tries to encode their	1053	Blessed objects are not directly representable in JSON. See the
726	underlying representation (hash- or arrayref), but this behaviour might	1054	C<allow_blessed> and C<convert_blessed> methods on various options on
727	change in future versions.	1055	how to deal with this: basically, you can choose between throwing an
		1056	exception, encoding the reference as if it weren't blessed, or provide
		1057	your own serialiser method.
728		1058
729	=item simple scalars	1059	=item simple scalars
730		1060
731	Simple Perl scalars (any scalar that is not a reference) are the most	1061	Simple Perl scalars (any scalar that is not a reference) are the most
732	difficult objects to encode: JSON::XS will encode undefined scalars as	1062	difficult objects to encode: JSON::XS will encode undefined scalars as
733	JSON null value, scalars that have last been used in a string context	1063	JSON C<null> values, scalars that have last been used in a string context
734	before encoding as JSON strings and anything else as number value:	1064	before encoding as JSON strings, and anything else as number value:
735		1065
736	# dump as number	1066	# dump as number
737	to_json [2] # yields [2]	1067	encode_json [2] # yields [2]
738	to_json [-3.0e17] # yields [-3e+17]	1068	encode_json [-3.0e17] # yields [-3e+17]
739	my $value = 5; to_json [$value] # yields [5]	1069	my $value = 5; encode_json [$value] # yields [5]
740		1070
741	# used as string, so dump as string	1071	# used as string, so dump as string
742	print $value;	1072	print $value;
743	to_json [$value] # yields ["5"]	1073	encode_json [$value] # yields ["5"]
744		1074
745	# undef becomes null	1075	# undef becomes null
746	to_json [undef] # yields [null]	1076	encode_json [undef] # yields [null]
747		1077
748	You can force the type to be a JSON string by stringifying it:	1078	You can force the type to be a JSON string by stringifying it:
749		1079
750	my $x = 3.1; # some variable containing a number	1080	my $x = 3.1; # some variable containing a number
751	"$x"; # stringified	1081	"$x"; # stringified
…		…
757	my $x = "3"; # some variable containing a string	1087	my $x = "3"; # some variable containing a string
758	$x += 0; # numify it, ensuring it will be dumped as a number	1088	$x += 0; # numify it, ensuring it will be dumped as a number
759	$x *= 1; # same thing, the choice is yours.	1089	$x *= 1; # same thing, the choice is yours.
760		1090
761	You can not currently force the type in other, less obscure, ways. Tell me	1091	You can not currently force the type in other, less obscure, ways. Tell me
762	if you need this capability.	1092	if you need this capability (but don't forget to explain why it's needed
		1093	:).
763		1094
764	=back	1095	=back
765		1096
766		1097
767	=head1 COMPARISON	1098	=head1 ENCODING/CODESET FLAG NOTES
768		1099
769	As already mentioned, this module was created because none of the existing	1100	The interested reader might have seen a number of flags that signify
770	JSON modules could be made to work correctly. First I will describe the	1101	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
771	problems (or pleasures) I encountered with various existing JSON modules,	1102	some confusion on what these do, so here is a short comparison:
772	followed by some benchmark values. JSON::XS was designed not to suffer	1103
773	from any of these problems or limitations.	1104	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1105	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1106	control whether C<encode> escapes character values outside their respective
		1107	codeset range. Neither of these flags conflict with each other, although
		1108	some combinations make less sense than others.
		1109
		1110	Care has been taken to make all flags symmetrical with respect to
		1111	C<encode> and C<decode>, that is, texts encoded with any combination of
		1112	these flag values will be correctly decoded when the same flags are used
		1113	- in general, if you use different flag settings while encoding vs. when
		1114	decoding you likely have a bug somewhere.
		1115
		1116	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1117	simply an abstract set of character-codepoint pairs, while an encoding
		1118	takes those codepoint numbers and I<encodes> them, in our case into
		1119	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1120	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1121	the same time, which can be confusing.
774		1122
775	=over 4	1123	=over 4
776		1124
777	=item JSON 1.07	1125	=item C<utf8> flag disabled
778		1126
779	Slow (but very portable, as it is written in pure Perl).	1127	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1128	and expect Unicode strings, that is, characters with high ordinal Unicode
		1129	values (> 255) will be encoded as such characters, and likewise such
		1130	characters are decoded as-is, no canges to them will be done, except
		1131	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1132	respectively (to Perl, these are the same thing in strings unless you do
		1133	funny/weird/dumb stuff).
780		1134
781	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1135	This is useful when you want to do the encoding yourself (e.g. when you
782	undocumented. One can get far by feeding it Unicode strings and doing	1136	want to have UTF-16 encoded JSON texts) or when some other layer does
783	en-/decoding oneself, but Unicode escapes are not working properly).	1137	the encoding for you (for example, when printing to a terminal using a
		1138	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1139	to UTF-8 encode your data first and have Perl encode it another time).
784		1140
785	No round-tripping (strings get clobbered if they look like numbers, e.g.	1141	=item C<utf8> flag enabled
786	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
787	decode into the number 2.
788		1142
789	=item JSON::PC 0.01	1143	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1144	characters using the corresponding UTF-8 multi-byte sequence, and will
		1145	expect your input strings to be encoded as UTF-8, that is, no "character"
		1146	of the input string must have any value > 255, as UTF-8 does not allow
		1147	that.
790		1148
791	Very fast.	1149	The C<utf8> flag therefore switches between two modes: disabled means you
		1150	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1151	octet/binary string in Perl.
792		1152
793	Undocumented/buggy Unicode handling.	1153	=item C<latin1> or C<ascii> flags enabled
794		1154
795	No round-tripping.	1155	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1156	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1157	characters as specified by the C<utf8> flag.
796		1158
797	Has problems handling many Perl values (e.g. regex results and other magic	1159	If C<utf8> is disabled, then the result is also correctly encoded in those
798	values will make it croak).	1160	character sets (as both are proper subsets of Unicode, meaning that a
		1161	Unicode string with all character values < 256 is the same thing as a
		1162	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1163	the same thing as an ASCII string in Perl).
799		1164
800	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1165	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
801	which is not a valid JSON text.	1166	regardless of these flags, just some more characters will be escaped using
		1167	C<\uXXXX> then before.
802		1168
803	Unmaintained (maintainer unresponsive for many months, bugs are not	1169	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
804	getting fixed).	1170	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1171	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1172	a subset of Unicode), while ASCII is.
805		1173
806	=item JSON::Syck 0.21	1174	Surprisingly, C<decode> will ignore these flags and so treat all input
		1175	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1176	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1177	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
807		1178
808	Very buggy (often crashes).	1179	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1180	they only govern when the JSON output engine escapes a character or not.
809		1181
810	Very inflexible (no human-readable format supported, format pretty much	1182	The main use for C<latin1> is to relatively efficiently store binary data
811	undocumented. I need at least a format for easy reading by humans and a	1183	as JSON, at the expense of breaking compatibility with most JSON decoders.
812	single-line compact format for use in a protocol, and preferably a way to
813	generate ASCII-only JSON texts).
814		1184
815	Completely broken (and confusingly documented) Unicode handling (Unicode	1185	The main use for C<ascii> is to force the output to not contain characters
816	escapes are not working properly, you need to set ImplicitUnicode to	1186	with values > 127, which means you can interpret the resulting string
817	I<different> values on en- and decoding to get symmetric behaviour).	1187	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
818		1188	8-bit-encoding, and still get the same data structure back. This is useful
819	No round-tripping (simple cases work, but this depends on whether the scalar	1189	when your channel for JSON transfer is not 8-bit clean or the encoding
820	value was used in a numeric context or not).	1190	might be mangled in between (e.g. in mail), and works because ASCII is a
821		1191	proper subset of most 8-bit and multibyte encodings in use in the world.
822	Dumping hashes may skip hash values depending on iterator state.
823
824	Unmaintained (maintainer unresponsive for many months, bugs are not
825	getting fixed).
826
827	Does not check input for validity (i.e. will accept non-JSON input and
828	return "something" instead of raising an exception. This is a security
829	issue: imagine two banks transferring money between each other using
830	JSON. One bank might parse a given non-JSON request and deduct money,
831	while the other might reject the transaction with a syntax error. While a
832	good protocol will at least recover, that is extra unnecessary work and
833	the transaction will still not succeed).
834
835	=item JSON::DWIW 0.04
836
837	Very fast. Very natural. Very nice.
838
839	Undocumented Unicode handling (but the best of the pack. Unicode escapes
840	still don't get parsed properly).
841
842	Very inflexible.
843
844	No round-tripping.
845
846	Does not generate valid JSON texts (key strings are often unquoted, empty keys
847	result in nothing being output)
848
849	Does not check input for validity.
850		1192
851	=back	1193	=back
852		1194
853		1195
		1196	=head2 JSON and ECMAscript
		1197
		1198	JSON syntax is based on how literals are represented in javascript (the
		1199	not-standardised predecessor of ECMAscript) which is presumably why it is
		1200	called "JavaScript Object Notation".
		1201
		1202	However, JSON is not a subset (and also not a superset of course) of
		1203	ECMAscript (the standard) or javascript (whatever browsers actually
		1204	implement).
		1205
		1206	If you want to use javascript's C<eval> function to "parse" JSON, you
		1207	might run into parse errors for valid JSON texts, or the resulting data
		1208	structure might not be queryable:
		1209
		1210	One of the problems is that U+2028 and U+2029 are valid characters inside
		1211	JSON strings, but are not allowed in ECMAscript string literals, so the
		1212	following Perl fragment will not output something that can be guaranteed
		1213	to be parsable by javascript's C<eval>:
		1214
		1215	use JSON::XS;
		1216
		1217	print encode_json [chr 0x2028];
		1218
		1219	The right fix for this is to use a proper JSON parser in your javascript
		1220	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1221	F<json2.js> parser).
		1222
		1223	If this is not an option, you can, as a stop-gap measure, simply encode to
		1224	ASCII-only JSON:
		1225
		1226	use JSON::XS;
		1227
		1228	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1229
		1230	Note that this will enlarge the resulting JSON text quite a bit if you
		1231	have many non-ASCII characters. You might be tempted to run some regexes
		1232	to only escape U+2028 and U+2029, e.g.:
		1233
		1234	# DO NOT USE THIS!
		1235	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1236	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1237	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1238	print $json;
		1239
		1240	Note that I<this is a bad idea>: the above only works for U+2028 and
		1241	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1242	javascript implementations, however, have issues with other characters as
		1243	well - using C<eval> naively simply I<will> cause problems.
		1244
		1245	Another problem is that some javascript implementations reserve
		1246	some property names for their own purposes (which probably makes
		1247	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1248	C<__proto__> property name for it's own purposes.
		1249
		1250	If that is a problem, you could parse try to filter the resulting JSON
		1251	output for these property strings, e.g.:
		1252
		1253	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1254
		1255	This works because C<__proto__> is not valid outside of strings, so every
		1256	occurence of C<"__proto__"\s*:> must be a string used as property name.
		1257
		1258	If you know of other incompatibilities, please let me know.
		1259
		1260
854	=head2 JSON and YAML	1261	=head2 JSON and YAML
855		1262
856	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1263	You often hear that JSON is a subset of YAML. This is, however, a mass
857	however, a mass hysteria and very far from the truth. In general, there is	1264	hysteria(*) and very far from the truth (as of the time of this writing),
858	no way to configure JSON::XS to output a data structure as valid YAML.	1265	so let me state it clearly: I<in general, there is no way to configure
		1266	JSON::XS to output a data structure as valid YAML> that works in all
		1267	cases.
859		1268
860	If you really must use JSON::XS to generate YAML, you should use this	1269	If you really must use JSON::XS to generate YAML, you should use this
861	algorithm (subject to change in future versions):	1270	algorithm (subject to change in future versions):
862		1271
863	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1272	my $to_yaml = JSON::XS->new->utf8->space_after (1);
864	my $yaml = $to_yaml->encode ($ref) . "\n";	1273	my $yaml = $to_yaml->encode ($ref) . "\n";
865		1274
866	This will usually generate JSON texts that also parse as valid	1275	This will I<usually> generate JSON texts that also parse as valid
867	YAML. Please note that YAML has hardcoded limits on (simple) object key	1276	YAML. Please note that YAML has hardcoded limits on (simple) object key
868	lengths that JSON doesn't have, so you should make sure that your hash	1277	lengths that JSON doesn't have and also has different and incompatible
		1278	unicode character escape syntax, so you should make sure that your hash
869	keys are noticeably shorter than the 1024 characters YAML allows.	1279	keys are noticeably shorter than the 1024 "stream characters" YAML allows
		1280	and that you do not have characters with codepoint values outside the
		1281	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
		1282	sequences in strings (which JSON::XS does not I<currently> generate, but
		1283	other JSON generators might).
870		1284
871	There might be other incompatibilities that I am not aware of. In general	1285	There might be other incompatibilities that I am not aware of (or the YAML
		1286	specification has been changed yet again - it does so quite often). In
872	you should not try to generate YAML with a JSON generator or vice versa,	1287	general you should not try to generate YAML with a JSON generator or vice
873	or try to parse JSON with a YAML parser or vice versa: chances are high	1288	versa, or try to parse JSON with a YAML parser or vice versa: chances are
874	that you will run into severe interoperability problems.	1289	high that you will run into severe interoperability problems when you
		1290	least expect it.
		1291
		1292	=over 4
		1293
		1294	=item (*)
		1295
		1296	I have been pressured multiple times by Brian Ingerson (one of the
		1297	authors of the YAML specification) to remove this paragraph, despite him
		1298	acknowledging that the actual incompatibilities exist. As I was personally
		1299	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1300	educate people about these issues, so others do not run into the same
		1301	problem again and again. After this, Brian called me a (quote)I<complete
		1302	and worthless idiot>(unquote).
		1303
		1304	In my opinion, instead of pressuring and insulting people who actually
		1305	clarify issues with YAML and the wrong statements of some of its
		1306	proponents, I would kindly suggest reading the JSON spec (which is not
		1307	that difficult or long) and finally make YAML compatible to it, and
		1308	educating users about the changes, instead of spreading lies about the
		1309	real compatibility for many I<years> and trying to silence people who
		1310	point out that it isn't true.
		1311
		1312	Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
		1313	though the incompatibilities have been documented (and are known to
		1314	Brian) for many years and the spec makes explicit claims that YAML is a
		1315	superset of JSON. It would be so easy to fix, but apparently, bullying and
		1316	corrupting userdata is so much easier.
		1317
		1318	=back
875		1319
876		1320
877	=head2 SPEED	1321	=head2 SPEED
878		1322
879	It seems that JSON::XS is surprisingly fast, as shown in the following	1323	It seems that JSON::XS is surprisingly fast, as shown in the following
880	tables. They have been generated with the help of the C<eg/bench> program	1324	tables. They have been generated with the help of the C<eg/bench> program
881	in the JSON::XS distribution, to make it easy to compare on your own	1325	in the JSON::XS distribution, to make it easy to compare on your own
882	system.	1326	system.
883		1327
884	First comes a comparison between various modules using a very short	1328	First comes a comparison between various modules using
885	single-line JSON string:	1329	a very short single-line JSON string (also available at
		1330	L<http://dist.schmorp.de/misc/json/short.json>).
886		1331
887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1332	{"method": "handleMessage", "params": ["user1",
888	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1333	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1334	1, 0]}
889		1335
890	It shows the number of encodes/decodes per second (JSON::XS uses	1336	It shows the number of encodes/decodes per second (JSON::XS uses
891	the functional interface, while JSON::XS/2 uses the OO interface	1337	the functional interface, while JSON::XS/2 uses the OO interface
892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1338	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893	shrink). Higher is better:	1339	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1340	uses the from_json method). Higher is better:
894		1341
895	Storable \| 15779.925 \| 14169.946 \|
896	-----------+------------+------------+
897	module \| encode \| decode \|	1342	module \| encode \| decode \|
898	-----------\|------------\|------------\|	1343	--------------\|------------\|------------\|
899	JSON \| 4990.842 \| 4088.813 \|	1344	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
900	JSON::DWIW \| 51653.990 \| 71575.154 \|	1345	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
901	JSON::PC \| 65948.176 \| 74631.744 \|	1346	JSON::PP \| 15827.562 \| 6638.658 \|
902	JSON::PP \| 8931.652 \| 3817.168 \|	1347	JSON::Syck \| 63358.066 \| 47662.545 \|
903	JSON::Syck \| 24877.248 \| 27776.848 \|	1348	JSON::XS \| 511500.488 \| 511500.488 \|
904	JSON::XS \| 388361.481 \| 227951.304 \|	1349	JSON::XS/2 \| 291271.111 \| 388361.481 \|
905	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1350	JSON::XS/3 \| 361577.931 \| 361577.931 \|
906	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1351	Storable \| 66788.280 \| 265462.278 \|
907	Storable \| 16500.016 \| 135300.129 \|
908	-----------+------------+------------+	1352	--------------+------------+------------+
909		1353
910	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1354	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
911	about three times faster on decoding, and over forty times faster	1355	about five times faster on decoding, and over thirty to seventy times
912	than JSON, even with pretty-printing and key sorting. It also compares	1356	faster than JSON's pure perl implementation. It also compares favourably
913	favourably to Storable for small amounts of data.	1357	to Storable for small amounts of data.
914		1358
915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1359	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916	search API (http://nanoref.com/yahooapis/mgPdGg):	1360	search API (L<http://dist.schmorp.de/misc/json/long.json>).
917		1361
918	module \| encode \| decode \|	1362	module \| encode \| decode \|
919	-----------\|------------\|------------\|	1363	--------------\|------------\|------------\|
920	JSON \| 55.260 \| 34.971 \|	1364	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
921	JSON::DWIW \| 825.228 \| 1082.513 \|	1365	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
922	JSON::PC \| 3571.444 \| 2394.829 \|
923	JSON::PP \| 210.987 \| 32.574 \|	1366	JSON::PP \| 400.640 \| 62.311 \|
924	JSON::Syck \| 552.551 \| 787.544 \|	1367	JSON::Syck \| 1481.040 \| 1524.869 \|
925	JSON::XS \| 5780.463 \| 4854.519 \|	1368	JSON::XS \| 20661.596 \| 9541.183 \|
926	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1369	JSON::XS/2 \| 10683.403 \| 9416.938 \|
927	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1370	JSON::XS/3 \| 20661.596 \| 9400.054 \|
928	Storable \| 4445.002 \| 5235.027 \|	1371	Storable \| 19765.806 \| 10000.725 \|
929	-----------+------------+------------+	1372	--------------+------------+------------+
930		1373
931	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1374	Again, JSON::XS leads by far (except for Storable which non-surprisingly
932	decodes faster).	1375	decodes a bit faster).
933		1376
934	On large strings containing lots of high Unicode characters, some modules	1377	On large strings containing lots of high Unicode characters, some modules
935	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1378	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
936	will be broken due to missing (or wrong) Unicode handling. Others refuse	1379	will be broken due to missing (or wrong) Unicode handling. Others refuse
937	to decode or encode properly, so it was impossible to prepare a fair	1380	to decode or encode properly, so it was impossible to prepare a fair
…		…
958		1401
959	Third, JSON::XS recurses using the C stack when decoding objects and	1402	Third, JSON::XS recurses using the C stack when decoding objects and
960	arrays. The C stack is a limited resource: for instance, on my amd64	1403	arrays. The C stack is a limited resource: for instance, on my amd64
961	machine with 8MB of stack size I can decode around 180k nested arrays but	1404	machine with 8MB of stack size I can decode around 180k nested arrays but
962	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1405	only 14k nested JSON objects (due to perl itself recursing deeply on croak
963	to free the temporary). If that is exceeded, the program crashes. to be	1406	to free the temporary). If that is exceeded, the program crashes. To be
964	conservative, the default nesting limit is set to 512. If your process	1407	conservative, the default nesting limit is set to 512. If your process
965	has a smaller stack, you should adjust this setting accordingly with the	1408	has a smaller stack, you should adjust this setting accordingly with the
966	C<max_depth> method.	1409	C<max_depth> method.
967		1410
968	And last but least, something else could bomb you that I forgot to think	1411	Something else could bomb you, too, that I forgot to think of. In that
969	of. In that case, you get to keep the pieces. I am always open for hints,	1412	case, you get to keep the pieces. I am always open for hints, though...
970	though...	1413
		1414	Also keep in mind that JSON::XS might leak contents of your Perl data
		1415	structures in its error messages, so when you serialise sensitive
		1416	information you might want to make sure that exceptions thrown by JSON::XS
		1417	will not end up in front of untrusted eyes.
971		1418
972	If you are using JSON::XS to return packets to consumption	1419	If you are using JSON::XS to return packets to consumption
973	by JavaScript scripts in a browser you should have a look at	1420	by JavaScript scripts in a browser you should have a look at
974	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1421	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
975	you are vulnerable to some common attack vectors (which really are browser	1422	see whether you are vulnerable to some common attack vectors (which really
976	design bugs, but it is still you who will have to deal with it, as major	1423	are browser design bugs, but it is still you who will have to deal with
977	browser developers care only for features, not about doing security	1424	it, as major browser developers care only for features, not about getting
978	right).	1425	security right).
979		1426
980		1427
981	=head1 THREADS	1428	=head1 THREADS
982		1429
983	This module is I<not> guaranteed to be thread safe and there are no	1430	This module is I<not> guaranteed to be thread safe and there are no
984	plans to change this until Perl gets thread support (as opposed to the	1431	plans to change this until Perl gets thread support (as opposed to the
985	horribly slow so-called "threads" which are simply slow and bloated	1432	horribly slow so-called "threads" which are simply slow and bloated
986	process simulations - use fork, its I<much> faster, cheaper, better).	1433	process simulations - use fork, it's I<much> faster, cheaper, better).
987		1434
988	(It might actually work, but you have been warned).	1435	(It might actually work, but you have been warned).
989		1436
990		1437
991	=head1 BUGS	1438	=head1 BUGS
992		1439
993	While the goal of this module is to be correct, that unfortunately does	1440	While the goal of this module is to be correct, that unfortunately does
994	not mean its bug-free, only that I think its design is bug-free. It is	1441	not mean it's bug-free, only that I think its design is bug-free. If you
995	still relatively early in its development. If you keep reporting bugs they	1442	keep reporting bugs they will be fixed swiftly, though.
996	will be fixed swiftly, though.
997		1443
998	Please refrain from using rt.cpan.org or any other bug reporting	1444	Please refrain from using rt.cpan.org or any other bug reporting
999	service. I put the contact address into my modules for a reason.	1445	service. I put the contact address into my modules for a reason.
1000		1446
1001	=cut	1447	=cut
…		…
1021	"--" => sub { $_[0] = ${$_[0]} - 1 },	1467	"--" => sub { $_[0] = ${$_[0]} - 1 },
1022	fallback => 1;	1468	fallback => 1;
1023		1469
1024	1;	1470	1;
1025		1471
		1472	=head1 SEE ALSO
		1473
		1474	The F<json_xs> command line utility for quick experiments.
		1475
1026	=head1 AUTHOR	1476	=head1 AUTHOR
1027		1477
1028	Marc Lehmann <schmorp@schmorp.de>	1478	Marc Lehmann <schmorp@schmorp.de>
1029	http://home.schmorp.de/	1479	http://home.schmorp.de/
1030		1480

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Comparing JSON-XS/XS.pm (file contents): Revision 1.70 by root, Tue Nov 13 22:59:08 2007 UTC vs. Revision 1.130 by root, Thu Mar 11 17:36:09 2010 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.70 by root, Tue Nov 13 22:59:08 2007 UTC vs.
Revision 1.130 by root, Thu Mar 11 17:36:09 2010 UTC