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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.69 by root, Tue Oct 23 03:31:14 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
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
…		…
42		60
43	=over 4	61	=over 4
44		62
45	=item * correct Unicode handling	63	=item * correct Unicode handling
46		64
47	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
48	it does so.	66	so, and even documents what "correct" means.
49		67
50	=item * round-trip integrity	68	=item * round-trip integrity
51		69
52	When you serialise a perl data structure using only datatypes supported	70	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.	71	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	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
55	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
56		75
57	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
58		77
59	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,
60	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
61	feature).	80	feature).
62		81
63	=item * fast	82	=item * fast
64		83
65	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
66	of speed, too.	85	this module usually compares favourably in terms of speed, too.
67		86
68	=item * simple to use	87	=item * simple to use
69		88
70	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
71	interface.	90	oriented interface interface.
72		91
73	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
74		93
75	You can choose between the most compact guaranteed single-line format	94	You can choose between the most compact guaranteed-single-line format
76	possible (nice for simple line-based protocols), a pure-ascii format	95	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	96	(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	97	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.	98	stuff). Or you can combine those features in whatever way you like.
80		99
81	=back	100	=back
82		101
83	=cut	102	=cut
84		103
85	package JSON::XS;	104	package JSON::XS;
86		105
		106	no warnings;
87	use strict;	107	use strict;
88		108
89	our $VERSION = '1.52';	109	our $VERSION = '2.2222';
90	our @ISA = qw(Exporter);	110	our @ISA = qw(Exporter);
91		111
92	our @EXPORT = qw(to_json from_json);	112	our @EXPORT = qw(encode_json decode_json to_json from_json);
		113
		114	sub to_json($) {
		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	}
93		123
94	use Exporter;	124	use Exporter;
95	use XSLoader;	125	use XSLoader;
96		126
97	=head1 FUNCTIONAL INTERFACE	127	=head1 FUNCTIONAL INTERFACE
…		…
99	The following convenience methods are provided by this module. They are	129	The following convenience methods are provided by this module. They are
100	exported by default:	130	exported by default:
101		131
102	=over 4	132	=over 4
103		133
104	=item $json_text = to_json $perl_scalar	134	=item $json_text = encode_json $perl_scalar
105		135
106	Converts the given Perl data structure to a UTF-8 encoded, binary string	136	Converts the given Perl data structure to a UTF-8 encoded, binary string
107	(that is, the string contains octets only). Croaks on error.	137	(that is, the string contains octets only). Croaks on error.
108		138
109	This function call is functionally identical to:	139	This function call is functionally identical to:
110		140
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	141	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		142
113	except being faster.	143	Except being faster.
114		144
115	=item $perl_scalar = from_json $json_text	145	=item $perl_scalar = decode_json $json_text
116		146
117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	147	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	148	to parse that as an UTF-8 encoded JSON text, returning the resulting
119	reference. Croaks on error.	149	reference. Croaks on error.
120		150
121	This function call is functionally identical to:	151	This function call is functionally identical to:
122		152
123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	153	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
124		154
125	except being faster.	155	Except being faster.
126		156
127	=item $is_boolean = JSON::XS::is_bool $scalar	157	=item $is_boolean = JSON::XS::is_bool $scalar
128		158
129	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
130	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
…		…
148	This enables you to store Unicode characters as single characters in a	178	This enables you to store Unicode characters as single characters in a
149	Perl string - very natural.	179	Perl string - very natural.
150		180
151	=item 2. Perl does I<not> associate an encoding with your strings.	181	=item 2. Perl does I<not> associate an encoding with your strings.
152		182
153	Unless you force it to, e.g. when matching it against a regex, or printing	183	... 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	184	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	185	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	186	on various settings. In no case is an encoding stored together with your
157	I<use> that decides encoding, not any magical metadata.	187	data, it is I<use> that decides encoding, not any magical meta data.
158		188
159	=item 3. The internal utf-8 flag has no meaning with regards to the	189	=item 3. The internal utf-8 flag has no meaning with regards to the
160	encoding of your string.	190	encoding of your string.
161		191
162	Just ignore that flag unless you debug a Perl bug, a module written in	192	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
168		198
169	If you didn't know about that flag, just the better, pretend it doesn't	199	If you didn't know about that flag, just the better, pretend it doesn't
170	exist.	200	exist.
171		201
172	=item 4. A "Unicode String" is simply a string where each character can be	202	=item 4. A "Unicode String" is simply a string where each character can be
173	validly interpreted as a Unicode codepoint.	203	validly interpreted as a Unicode code point.
174		204
175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	205	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.	206	Unicode string encoded in UTF-8, giving you a binary string.
177		207
178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	208	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
201		231
202	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]})
203	=> {"a": [1, 2]}	233	=> {"a": [1, 2]}
204		234
205	=item $json = $json->ascii ([$enable])	235	=item $json = $json->ascii ([$enable])
		236
		237	=item $enabled = $json->get_ascii
206		238
207	If C<$enable> is true (or missing), then the C<encode> method will not	239	If C<$enable> is true (or missing), then the C<encode> method will not
208	generate characters outside the code range C<0..127> (which is ASCII). Any	240	generate characters outside the code range C<0..127> (which is ASCII). Any
209	Unicode characters outside that range will be escaped using either a	241	Unicode characters outside that range will be escaped using either a
210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	242	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
…		…
214		246
215	If C<$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
216	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
217	in a faster and more compact format.	249	in a faster and more compact format.
218		250
		251	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		252	document.
		253
219	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
220	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
221	contain any 8 bit characters.	256	contain any 8 bit characters.
222		257
223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	258	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224	=> ["\ud801\udc01"]	259	=> ["\ud801\udc01"]
225		260
226	=item $json = $json->latin1 ([$enable])	261	=item $json = $json->latin1 ([$enable])
		262
		263	=item $enabled = $json->get_latin1
227		264
228	If C<$enable> is true (or missing), then the C<encode> method will encode	265	If C<$enable> is true (or missing), then the C<encode> method will encode
229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	266	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230	outside the code range C<0..255>. The resulting string can be treated as a	267	outside the code range C<0..255>. The resulting string can be treated as a
231	latin1-encoded JSON text or a native Unicode string. The C<decode> method	268	latin1-encoded JSON text or a native Unicode string. The C<decode> method
232	will not be affected in any way by this flag, as C<decode> by default	269	will not be affected in any way by this flag, as C<decode> by default
233	expects Unicode, which is a strict superset of latin1.	270	expects Unicode, which is a strict superset of latin1.
234		271
235	If C<$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
236	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.
237		277
238	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
239	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
240	size. The disadvantage is that the resulting JSON text is encoded	280	size. The disadvantage is that the resulting JSON text is encoded
241	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
…		…
246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	286	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	287	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248		288
249	=item $json = $json->utf8 ([$enable])	289	=item $json = $json->utf8 ([$enable])
250		290
		291	=item $enabled = $json->get_utf8
		292
251	If C<$enable> is true (or missing), then the C<encode> method will encode	293	If C<$enable> is true (or missing), then the C<encode> method will encode
252	the JSON result into UTF-8, as required by many protocols, while the	294	the JSON result into UTF-8, as required by many protocols, while the
253	C<decode> method expects to be handled an UTF-8-encoded string. Please	295	C<decode> method expects to be handled an UTF-8-encoded string. Please
254	note that UTF-8-encoded strings do not contain any characters outside the	296	note that UTF-8-encoded strings do not contain any characters outside the
255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	297	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
…		…
258		300
259	If C<$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
260	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
261	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
262	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.
263		308
264	Example, output UTF-16BE-encoded JSON:	309	Example, output UTF-16BE-encoded JSON:
265		310
266	use Encode;	311	use Encode;
267	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	312	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
288	]	333	]
289	}	334	}
290		335
291	=item $json = $json->indent ([$enable])	336	=item $json = $json->indent ([$enable])
292		337
		338	=item $enabled = $json->get_indent
		339
293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	340	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294	format as output, putting every array member or object/hash key-value pair	341	format as output, putting every array member or object/hash key-value pair
295	into its own line, indenting them properly.	342	into its own line, indenting them properly.
296		343
297	If C<$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
…		…
299		346
300	This setting has no effect when decoding JSON texts.	347	This setting has no effect when decoding JSON texts.
301		348
302	=item $json = $json->space_before ([$enable])	349	=item $json = $json->space_before ([$enable])
303		350
		351	=item $enabled = $json->get_space_before
		352
304	If C<$enable> is true (or missing), then the C<encode> method will add an extra	353	If C<$enable> is true (or missing), then the C<encode> method will add an extra
305	optional space before the C<:> separating keys from values in JSON objects.	354	optional space before the C<:> separating keys from values in JSON objects.
306		355
307	If C<$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
308	space at those places.	357	space at those places.
…		…
313	Example, space_before enabled, space_after and indent disabled:	362	Example, space_before enabled, space_after and indent disabled:
314		363
315	{"key" :"value"}	364	{"key" :"value"}
316		365
317	=item $json = $json->space_after ([$enable])	366	=item $json = $json->space_after ([$enable])
		367
		368	=item $enabled = $json->get_space_after
318		369
319	If C<$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
320	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
321	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
322	members.	373	members.
…		…
329	Example, space_before and indent disabled, space_after enabled:	380	Example, space_before and indent disabled, space_after enabled:
330		381
331	{"key": "value"}	382	{"key": "value"}
332		383
333	=item $json = $json->relaxed ([$enable])	384	=item $json = $json->relaxed ([$enable])
		385
		386	=item $enabled = $json->get_relaxed
334		387
335	If C<$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
336	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
337	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
338	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
…		…
375		428
376	=back	429	=back
377		430
378	=item $json = $json->canonical ([$enable])	431	=item $json = $json->canonical ([$enable])
379		432
		433	=item $enabled = $json->get_canonical
		434
380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	435	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381	by sorting their keys. This is adding a comparatively high overhead.	436	by sorting their keys. This is adding a comparatively high overhead.
382		437
383	If C<$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
384	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
…		…
391		446
392	This setting has no effect when decoding JSON texts.	447	This setting has no effect when decoding JSON texts.
393		448
394	=item $json = $json->allow_nonref ([$enable])	449	=item $json = $json->allow_nonref ([$enable])
395		450
		451	=item $enabled = $json->get_allow_nonref
		452
396	If C<$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
397	non-reference into its corresponding string, number or null JSON value,	454	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	455	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
399	values instead of croaking.	456	values instead of croaking.
400		457
…		…
407	resulting in an invalid JSON text:	464	resulting in an invalid JSON text:
408		465
409	JSON::XS->new->allow_nonref->encode ("Hello, World!")	466	JSON::XS->new->allow_nonref->encode ("Hello, World!")
410	=> "Hello, World!"	467	=> "Hello, World!"
411		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
412	=item $json = $json->allow_blessed ([$enable])	485	=item $json = $json->allow_blessed ([$enable])
		486
		487	=item $enabled = $json->get_allow_blessed
413		488
414	If C<$enable> is true (or missing), then the C<encode> method will not	489	If C<$enable> is true (or missing), then the C<encode> method will not
415	barf when it encounters a blessed reference. Instead, the value of the	490	barf when it encounters a blessed reference. Instead, the value of the
416	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	491	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417	disabled or no C<to_json> method found) or a representation of the	492	disabled or no C<TO_JSON> method found) or a representation of the
418	object (C<convert_blessed> enabled and C<to_json> method found) is being	493	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419	encoded. Has no effect on C<decode>.	494	encoded. Has no effect on C<decode>.
420		495
421	If C<$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
422	exception when it encounters a blessed object.	497	exception when it encounters a blessed object.
423		498
424	=item $json = $json->convert_blessed ([$enable])	499	=item $json = $json->convert_blessed ([$enable])
		500
		501	=item $enabled = $json->get_convert_blessed
425		502
426	If C<$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
427	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
428	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
429	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
…		…
433	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>
434	returns other blessed objects, those will be handled in the same	511	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	512	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	513	(== 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	514	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>	515	usually in upper case letters and to avoid collisions with any C<to_json>
439	function.	516	function or method.
440		517
441	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
442	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
443	enabled by this setting.	520	enabled by this setting.
444		521
…		…
520		597
521	{ __widget__ => $self->{id} }	598	{ __widget__ => $self->{id} }
522	}	599	}
523		600
524	=item $json = $json->shrink ([$enable])	601	=item $json = $json->shrink ([$enable])
		602
		603	=item $enabled = $json->get_shrink
525		604
526	Perl usually over-allocates memory a bit when allocating space for	605	Perl usually over-allocates memory a bit when allocating space for
527	strings. This flag optionally resizes strings generated by either	606	strings. This flag optionally resizes strings generated by either
528	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
529	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
…		…
547	strings that look like integers or floats into integers or floats	626	strings that look like integers or floats into integers or floats
548	internally (there is no difference on the Perl level), saving space.	627	internally (there is no difference on the Perl level), saving space.
549		628
550	=item $json = $json->max_depth ([$maximum_nesting_depth])	629	=item $json = $json->max_depth ([$maximum_nesting_depth])
551		630
		631	=item $max_depth = $json->get_max_depth
		632
552	Sets the maximum nesting level (default C<512>) accepted while encoding	633	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	634	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	635	data structure, then the encoder and decoder will stop and croak at that
555	stop and croak at that point.	636	point.
556		637
557	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
558	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<[>
559	characters without their matching closing parenthesis crossed to reach a	640	characters without their matching closing parenthesis crossed to reach a
560	given character in a string.	641	given character in a string.
561		642
562	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
563	that the object is only a single hash/object or array.	644	that the object is only a single hash/object or array.
564		645
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	646	If no argument is given, the highest possible setting will be used, which
567	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.
568		652
569	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.
570		654
571	=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
572		658
573	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
574	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>
575	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
576	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
577	effect on C<encode> (yet).	663	effect on C<encode> (yet).
578		664
579	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
580	power of two (so may be more than requested). If no argument is given, the	666	C<0> is specified).
581	limit check will be deactivated (same as when C<0> is specified).
582		667
583	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.
584		669
585	=item $json_text = $json->encode ($perl_scalar)	670	=item $json_text = $json->encode ($perl_scalar)
586		671
…		…
615	=> ([], 3)	700	=> ([], 3)
616		701
617	=back	702	=back
618		703
619		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
620	=head1 MAPPING	940	=head1 MAPPING
621		941
622	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
623	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
624	circumstances automatically, preserving round-tripping characteristics	944	circumstances automatically, preserving round-tripping characteristics
…		…
652		972
653	A JSON number becomes either an integer, numeric (floating point) or	973	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	974	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	975	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	976	the conversion details, but an integer may take slightly less memory and
657	might represent more values exactly than (floating point) numbers.	977	might represent more values exactly than floating point numbers.
658		978
659	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
660	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
661	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
662	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).
663		985
664	Numbers containing a fractional or exponential part will always be	986	Numbers containing a fractional or exponential part will always be
665	represented as numeric (floating point) values, possibly at a loss of	987	represented as numeric (floating point) values, possibly at a loss of
666	precision.	988	precision (in which case you might lose perfect roundtripping ability, but
667		989	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		990
671	=item true, false	991	=item true, false
672		992
673	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>,
674	respectively. They are overloaded to act almost exactly like the numbers	994	respectively. They are overloaded to act almost exactly like the numbers
…		…
711	Other unblessed references are generally not allowed and will cause an	1031	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	1032	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	1033	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.	1034	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
715		1035
716	to_json [\0,JSON::XS::true] # yields [false,true]	1036	encode_json [\0, JSON::XS::true] # yields [false,true]
717		1037
718	=item JSON::XS::true, JSON::XS::false	1038	=item JSON::XS::true, JSON::XS::false
719		1039
720	These special values become JSON true and JSON false values,	1040	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.	1041	respectively. You can also use C<\1> and C<\0> directly if you want.
722		1042
723	=item blessed objects	1043	=item blessed objects
724		1044
725	Blessed objects are not allowed. JSON::XS currently tries to encode their	1045	Blessed objects are not directly representable in JSON. See the
726	underlying representation (hash- or arrayref), but this behaviour might	1046	C<allow_blessed> and C<convert_blessed> methods on various options on
727	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.
728		1050
729	=item simple scalars	1051	=item simple scalars
730		1052
731	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
732	difficult objects to encode: JSON::XS will encode undefined scalars as	1054	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	1055	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:	1056	before encoding as JSON strings, and anything else as number value:
735		1057
736	# dump as number	1058	# dump as number
737	to_json [2] # yields [2]	1059	encode_json [2] # yields [2]
738	to_json [-3.0e17] # yields [-3e+17]	1060	encode_json [-3.0e17] # yields [-3e+17]
739	my $value = 5; to_json [$value] # yields [5]	1061	my $value = 5; encode_json [$value] # yields [5]
740		1062
741	# used as string, so dump as string	1063	# used as string, so dump as string
742	print $value;	1064	print $value;
743	to_json [$value] # yields ["5"]	1065	encode_json [$value] # yields ["5"]
744		1066
745	# undef becomes null	1067	# undef becomes null
746	to_json [undef] # yields [null]	1068	encode_json [undef] # yields [null]
747		1069
748	You can force the type to be a JSON string by stringifying it:	1070	You can force the type to be a JSON string by stringifying it:
749		1071
750	my $x = 3.1; # some variable containing a number	1072	my $x = 3.1; # some variable containing a number
751	"$x"; # stringified	1073	"$x"; # stringified
…		…
757	my $x = "3"; # some variable containing a string	1079	my $x = "3"; # some variable containing a string
758	$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
759	$x *= 1; # same thing, the choice is yours.	1081	$x *= 1; # same thing, the choice is yours.
760		1082
761	You can not currently force the type in other, less obscure, ways. Tell me	1083	You can not currently force the type in other, less obscure, ways. Tell me
762	if you need this capability.	1084	if you need this capability (but don't forget to explain why it's needed
		1085	:).
763		1086
764	=back	1087	=back
765		1088
766		1089
767	=head1 COMPARISON	1090	=head1 ENCODING/CODESET FLAG NOTES
768		1091
769	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
770	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
771	problems (or pleasures) I encountered with various existing JSON modules,	1094	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	1095
773	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.
774		1114
775	=over 4	1115	=over 4
776		1116
777	=item JSON 1.07	1117	=item C<utf8> flag disabled
778		1118
779	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).
780		1126
781	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
782	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
783	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).
784		1132
785	No round-tripping (strings get clobbered if they look like numbers, e.g.	1133	=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		1134
789	=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.
790		1140
791	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.
792		1144
793	Undocumented/buggy Unicode handling.	1145	=item C<latin1> or C<ascii> flags enabled
794		1146
795	No round-tripping.	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.
796		1150
797	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
798	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).
799		1156
800	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,
801	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.
802		1160
803	Unmaintained (maintainer unresponsive for many months, bugs are not	1161	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
804	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.
805		1165
806	=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.
807		1170
808	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.
809		1173
810	Very inflexible (no human-readable format supported, format pretty much	1174	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	1175	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		1176
815	Completely broken (and confusingly documented) Unicode handling (Unicode	1177	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	1178	with values > 127, which means you can interpret the resulting string
817	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
818		1180	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	1181	when your channel for JSON transfer is not 8-bit clean or the encoding
820	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
821		1183	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		1184
851	=back	1185	=back
852		1186
853		1187
854	=head2 JSON and YAML	1188	=head2 JSON and YAML
855		1189
856	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
857	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),
858	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.
859		1195
860	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
861	algorithm (subject to change in future versions):	1197	algorithm (subject to change in future versions):
862		1198
863	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1199	my $to_yaml = JSON::XS->new->utf8->space_after (1);
864	my $yaml = $to_yaml->encode ($ref) . "\n";	1200	my $yaml = $to_yaml->encode ($ref) . "\n";
865		1201
866	This will usually generate JSON texts that also parse as valid	1202	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	1203	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	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
869	keys are noticeably 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).
870		1211
871	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
872	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
873	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
874	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
875		1240
876		1241
877	=head2 SPEED	1242	=head2 SPEED
878		1243
879	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
880	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
881	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
882	system.	1247	system.
883		1248
884	First comes a comparison between various modules using a very short	1249	First comes a comparison between various modules using
885	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>).
886		1252
887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1253	{"method": "handleMessage", "params": ["user1",
888	"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]}
889		1256
890	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
891	the functional interface, while JSON::XS/2 uses the OO interface	1258	the functional interface, while JSON::XS/2 uses the OO interface
892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1259	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893	shrink). Higher is better:	1260	shrink). Higher is better:
894		1261
895	Storable \| 15779.925 \| 14169.946 \|
896	-----------+------------+------------+
897	module \| encode \| decode \|	1262	module \| encode \| decode \|
898	-----------\|------------\|------------\|	1263	-----------\|------------\|------------\|
899	JSON \| 4990.842 \| 4088.813 \|	1264	JSON 1.x \| 4990.842 \| 4088.813 \|
900	JSON::DWIW \| 51653.990 \| 71575.154 \|	1265	JSON::DWIW \| 51653.990 \| 71575.154 \|
901	JSON::PC \| 65948.176 \| 74631.744 \|	1266	JSON::PC \| 65948.176 \| 74631.744 \|
902	JSON::PP \| 8931.652 \| 3817.168 \|	1267	JSON::PP \| 8931.652 \| 3817.168 \|
903	JSON::Syck \| 24877.248 \| 27776.848 \|	1268	JSON::Syck \| 24877.248 \| 27776.848 \|
904	JSON::XS \| 388361.481 \| 227951.304 \|	1269	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
911	about three times faster on decoding, and over forty times faster	1276	about three times faster on decoding, and over forty times faster
912	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
913	favourably to Storable for small amounts of data.	1278	favourably to Storable for small amounts of data.
914		1279
915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1280	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916	search API (http://nanoref.com/yahooapis/mgPdGg):	1281	search API (L<http://dist.schmorp.de/misc/json/long.json>).
917		1282
918	module \| encode \| decode \|	1283	module \| encode \| decode \|
919	-----------\|------------\|------------\|	1284	-----------\|------------\|------------\|
920	JSON \| 55.260 \| 34.971 \|	1285	JSON 1.x \| 55.260 \| 34.971 \|
921	JSON::DWIW \| 825.228 \| 1082.513 \|	1286	JSON::DWIW \| 825.228 \| 1082.513 \|
922	JSON::PC \| 3571.444 \| 2394.829 \|	1287	JSON::PC \| 3571.444 \| 2394.829 \|
923	JSON::PP \| 210.987 \| 32.574 \|	1288	JSON::PP \| 210.987 \| 32.574 \|
924	JSON::Syck \| 552.551 \| 787.544 \|	1289	JSON::Syck \| 552.551 \| 787.544 \|
925	JSON::XS \| 5780.463 \| 4854.519 \|	1290	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
958		1323
959	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
960	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
961	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
962	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
963	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
964	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
965	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
966	C<max_depth> method.	1331	C<max_depth> method.
967		1332
968	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
969	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...
970	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.
971		1340
972	If you are using JSON::XS to return packets to consumption	1341	If you are using JSON::XS to return packets to consumption
973	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
974	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1343	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
975	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
976	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
977	browser developers care only for features, not about doing security	1346	browser developers care only for features, not about getting security
978	right).	1347	right).
979		1348
980		1349
981	=head1 THREADS	1350	=head1 THREADS
982		1351
983	This module is I<not> guaranteed to be thread safe and there are no	1352	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	1353	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	1354	horribly slow so-called "threads" which are simply slow and bloated
986	process simulations - use fork, its I<much> faster, cheaper, better).	1355	process simulations - use fork, it's I<much> faster, cheaper, better).
987		1356
988	(It might actually work, but you have been warned).	1357	(It might actually work, but you have been warned).
989		1358
990		1359
991	=head1 BUGS	1360	=head1 BUGS
992		1361
993	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
994	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
995	still relatively early in its development. If you keep reporting bugs they	1364	keep reporting bugs they will be fixed swiftly, though.
996	will be fixed swiftly, though.
997		1365
998	Please refrain from using rt.cpan.org or any other bug reporting	1366	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.	1367	service. I put the contact address into my modules for a reason.
1000		1368
1001	=cut	1369	=cut
…		…
1021	"--" => sub { $_[0] = ${$_[0]} - 1 },	1389	"--" => sub { $_[0] = ${$_[0]} - 1 },
1022	fallback => 1;	1390	fallback => 1;
1023		1391
1024	1;	1392	1;
1025		1393
		1394	=head1 SEE ALSO
		1395
		1396	The F<json_xs> command line utility for quick experiments.
		1397
1026	=head1 AUTHOR	1398	=head1 AUTHOR
1027		1399
1028	Marc Lehmann <schmorp@schmorp.de>	1400	Marc Lehmann <schmorp@schmorp.de>
1029	http://home.schmorp.de/	1401	http://home.schmorp.de/
1030		1402

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.69 by root, Tue Oct 23 03:31:14 2007 UTC vs. Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.69 by root, Tue Oct 23 03:31:14 2007 UTC vs.
Revision 1.110 by root, Sun Jul 20 17:55:19 2008 UTC