[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 1.94 by root, Tue Mar 25 07:46:15 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
		2
		3	=encoding utf-8
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
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)
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	overriden) with no overhead due to emulation (by inheritign constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
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 datatypes 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 objetc
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
…		…
84		103
85	package JSON::XS;	104	package JSON::XS;
86		105
87	use strict;	106	use strict;
88		107
89	our $VERSION = '1.53';	108	our $VERSION = '2.1';
90	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
91		110
92	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		114	require Carp;
		115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		116	}
		117
		118	sub from_json($) {
		119	require Carp;
		120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		121	}
93		122
94	use Exporter;	123	use Exporter;
95	use XSLoader;	124	use XSLoader;
96		125
97	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
…		…
99	The following convenience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
100	exported by default:	129	exported by default:
101		130
102	=over 4	131	=over 4
103		132
104	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
105		134
106	Converts the given Perl data structure to a UTF-8 encoded, binary string	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
107	(that is, the string contains octets only). Croaks on error.	136	(that is, the string contains octets only). Croaks on error.
108		137
109	This function call is functionally identical to:	138	This function call is functionally identical to:
110		139
111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
112		141
113	except being faster.	142	except being faster.
114		143
115	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
116		145
117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	146	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	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
119	reference. Croaks on error.	148	reference. Croaks on error.
120		149
121	This function call is functionally identical to:	150	This function call is functionally identical to:
122		151
…		…
148	This enables you to store Unicode characters as single characters in a	177	This enables you to store Unicode characters as single characters in a
149	Perl string - very natural.	178	Perl string - very natural.
150		179
151	=item 2. Perl does I<not> associate an encoding with your strings.	180	=item 2. Perl does I<not> associate an encoding with your strings.
152		181
153	Unless you force it to, e.g. when matching it against a regex, or printing	182	... 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	183	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	184	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	185	on various settings. In no case is an encoding stored together with your
157	I<use> that decides encoding, not any magical metadata.	186	data, it is I<use> that decides encoding, not any magical meta data.
158		187
159	=item 3. The internal utf-8 flag has no meaning with regards to the	188	=item 3. The internal utf-8 flag has no meaning with regards to the
160	encoding of your string.	189	encoding of your string.
161		190
162	Just ignore that flag unless you debug a Perl bug, a module written in	191	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
201		230
202	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	231	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
203	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
204		233
205	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
		235
		236	=item $enabled = $json->get_ascii
206		237
207	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
208	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
209	Unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
…		…
214		245
215	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
216	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
217	in a faster and more compact format.	248	in a faster and more compact format.
218		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
219	The main use for this flag is to produce JSON texts that can be	253	The main use for this flag is to produce JSON texts that can be
220	transmitted over a 7-bit channel, as the encoded JSON texts will not	254	transmitted over a 7-bit channel, as the encoded JSON texts will not
221	contain any 8 bit characters.	255	contain any 8 bit characters.
222		256
223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
224	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
225		259
226	=item $json = $json->latin1 ([$enable])	260	=item $json = $json->latin1 ([$enable])
		261
		262	=item $enabled = $json->get_latin1
227		263
228	If C<$enable> is true (or missing), then the C<encode> method will encode	264	If C<$enable> is true (or missing), then the C<encode> method will encode
229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
230	outside the code range C<0..255>. The resulting string can be treated as a	266	outside the code range C<0..255>. The resulting string can be treated as a
231	latin1-encoded JSON text or a native Unicode string. The C<decode> method	267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
232	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
233	expects Unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
234		270
235	If C<$enable> is false, then the C<encode> method will not escape Unicode	271	If C<$enable> is false, then the C<encode> method will not escape Unicode
236	characters unless required by the JSON syntax or other flags.	272	characters unless required by the JSON syntax or other flags.
		273
		274	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		275	document.
237		276
238	The main use for this flag is efficiently encoding binary data as JSON	277	The main use for this flag is efficiently encoding binary data as JSON
239	text, as most octets will not be escaped, resulting in a smaller encoded	278	text, as most octets will not be escaped, resulting in a smaller encoded
240	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
241	in latin1 (and must correctly be treated as such when storing and	280	in latin1 (and must correctly be treated as such when storing and
…		…
246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
248		287
249	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
250		289
		290	=item $enabled = $json->get_utf8
		291
251	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
252	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
253	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
254	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
255	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
…		…
258		299
259	If C<$enable> is false, then the C<encode> method will return the JSON	300	If C<$enable> is false, then the C<encode> method will return the JSON
260	string as a (non-encoded) Unicode string, while C<decode> expects thus a	301	string as a (non-encoded) Unicode string, while C<decode> expects thus a
261	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	302	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
262	to be done yourself, e.g. using the Encode module.	303	to be done yourself, e.g. using the Encode module.
		304
		305	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		306	document.
263		307
264	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
265		309
266	use Encode;	310	use Encode;
267	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
288	]	332	]
289	}	333	}
290		334
291	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
292		336
		337	=item $enabled = $json->get_indent
		338
293	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
294	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
295	into its own line, indenting them properly.	341	into its own line, indenting them properly.
296		342
297	If C<$enable> is false, no newlines or indenting will be produced, and the	343	If C<$enable> is false, no newlines or indenting will be produced, and the
…		…
299		345
300	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
301		347
302	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
303		349
		350	=item $enabled = $json->get_space_before
		351
304	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
305	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
306		354
307	If C<$enable> is false, then the C<encode> method will not add any extra	355	If C<$enable> is false, then the C<encode> method will not add any extra
308	space at those places.	356	space at those places.
…		…
313	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
314		362
315	{"key" :"value"}	363	{"key" :"value"}
316		364
317	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
318		368
319	If C<$enable> is true (or missing), then the C<encode> method will add an extra	369	If C<$enable> is true (or missing), then the C<encode> method will add an extra
320	optional space after the C<:> separating keys from values in JSON objects	370	optional space after the C<:> separating keys from values in JSON objects
321	and extra whitespace after the C<,> separating key-value pairs and array	371	and extra whitespace after the C<,> separating key-value pairs and array
322	members.	372	members.
…		…
329	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
330		380
331	{"key": "value"}	381	{"key": "value"}
332		382
333	=item $json = $json->relaxed ([$enable])	383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
334		386
335	If C<$enable> is true (or missing), then C<decode> will accept some	387	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	388	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	389	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	390	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
375		427
376	=back	428	=back
377		429
378	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
379		431
		432	=item $enabled = $json->get_canonical
		433
380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
381	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
382		436
383	If C<$enable> is false, then the C<encode> method will output key-value	437	If C<$enable> is false, then the C<encode> method will output key-value
384	pairs in the order Perl stores them (which will likely change between runs	438	pairs in the order Perl stores them (which will likely change between runs
…		…
391		445
392	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
393		447
394	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
395		449
		450	=item $enabled = $json->get_allow_nonref
		451
396	If C<$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.
400		456
…		…
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
412	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
413		469
		470	=item $enabled = $json->get_allow_blessed
		471
414	If C<$enable> is true (or missing), then the C<encode> method will not	472	If C<$enable> is true (or missing), then the C<encode> method will not
415	barf when it encounters a blessed reference. Instead, the value of the	473	barf when it encounters a blessed reference. Instead, the value of the
416	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
417	disabled or no C<to_json> method found) or a representation of the	475	disabled or no C<TO_JSON> method found) or a representation of the
418	object (C<convert_blessed> enabled and C<to_json> method found) is being	476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
419	encoded. Has no effect on C<decode>.	477	encoded. Has no effect on C<decode>.
420		478
421	If C<$enable> is false (the default), then C<encode> will throw an	479	If C<$enable> is false (the default), then C<encode> will throw an
422	exception when it encounters a blessed object.	480	exception when it encounters a blessed object.
423		481
424	=item $json = $json->convert_blessed ([$enable])	482	=item $json = $json->convert_blessed ([$enable])
		483
		484	=item $enabled = $json->get_convert_blessed
425		485
426	If C<$enable> is true (or missing), then C<encode>, upon encountering a	486	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	487	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	488	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	489	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>	493	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	494	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	495	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	496	(== 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	497	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>	498	usually in upper case letters and to avoid collisions with any C<to_json>
439	function.	499	function or method.
440		500
441	This setting does not yet influence C<decode> in any way, but in the	501	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	502	future, global hooks might get installed that influence C<decode> and are
443	enabled by this setting.	503	enabled by this setting.
444		504
…		…
520		580
521	{ __widget__ => $self->{id} }	581	{ __widget__ => $self->{id} }
522	}	582	}
523		583
524	=item $json = $json->shrink ([$enable])	584	=item $json = $json->shrink ([$enable])
		585
		586	=item $enabled = $json->get_shrink
525		587
526	Perl usually over-allocates memory a bit when allocating space for	588	Perl usually over-allocates memory a bit when allocating space for
527	strings. This flag optionally resizes strings generated by either	589	strings. This flag optionally resizes strings generated by either
528	C<encode> or C<decode> to their minimum size possible. This can save	590	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	591	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	609	strings that look like integers or floats into integers or floats
548	internally (there is no difference on the Perl level), saving space.	610	internally (there is no difference on the Perl level), saving space.
549		611
550	=item $json = $json->max_depth ([$maximum_nesting_depth])	612	=item $json = $json->max_depth ([$maximum_nesting_depth])
551		613
		614	=item $max_depth = $json->get_max_depth
		615
552	Sets the maximum nesting level (default C<512>) accepted while encoding	616	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	617	or decoding. If the JSON text or Perl data structure has an equal or
554	higher nesting level then this limit, then the encoder and decoder will	618	higher nesting level then this limit, then the encoder and decoder will
555	stop and croak at that point.	619	stop and croak at that point.
556		620
…		…
567	used, which is rarely useful.	631	used, which is rarely useful.
568		632
569	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
570		634
571	=item $json = $json->max_size ([$maximum_string_size])	635	=item $json = $json->max_size ([$maximum_string_size])
		636
		637	=item $max_size = $json->get_max_size
572		638
573	Set the maximum length a JSON text may have (in bytes) where decoding is	639	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>	640	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	641	is called on a string longer then this number of characters it will not
576	attempt to decode the string but throw an exception. This setting has no	642	attempt to decode the string but throw an exception. This setting has no
…		…
615	=> ([], 3)	681	=> ([], 3)
616		682
617	=back	683	=back
618		684
619		685
		686	=head1 INCREMENTAL PARSING
		687
		688	[This section is still EXPERIMENTAL]
		689
		690	In some cases, there is the need for incremental parsing of JSON
		691	texts. While this module always has to keep both JSON text and resulting
		692	Perl data structure in memory at one time, it does allow you to parse a
		693	JSON stream incrementally. It does so by accumulating text until it has
		694	a full JSON object, which it then can decode. This process is similar to
		695	using C<decode_prefix> to see if a full JSON object is available, but is
		696	much more efficient (JSON::XS will only attempt to parse the JSON text
		697	once it is sure it has enough text to get a decisive result, using a very
		698	simple but truly incremental parser).
		699
		700	The following two methods deal with this.
		701
		702	=over 4
		703
		704	=item [void, scalar or list context] = $json->incr_parse ([$string])
		705
		706	This is the central parsing function. It can both append new text and
		707	extract objects from the stream accumulated so far (both of these
		708	functions are optional).
		709
		710	If C<$string> is given, then this string is appended to the already
		711	existing JSON fragment stored in the C<$json> object.
		712
		713	After that, if the function is called in void context, it will simply
		714	return without doing anything further. This can be used to add more text
		715	in as many chunks as you want.
		716
		717	If the method is called in scalar context, then it will try to extract
		718	exactly I<one> JSON object. If that is successful, it will return this
		719	object, otherwise it will return C<undef>. This is the most common way of
		720	using the method.
		721
		722	And finally, in list context, it will try to extract as many objects
		723	from the stream as it can find and return them, or the empty list
		724	otherwise. For this to work, there must be no separators between the JSON
		725	objects or arrays, instead they must be concatenated back-to-back.
		726
		727	=item $lvalue_string = $json->incr_text
		728
		729	This method returns the currently stored JSON fragment as an lvalue, that
		730	is, you can manipulate it. This I<only> works when a preceding call to
		731	C<incr_parse> in I<scalar context> successfully returned an object. Under
		732	all other circumstances you must not call this function (I mean it.
		733	although in simple tests it might actually work, it I<will> fail under
		734	real world conditions). As a special exception, you can also call this
		735	method before having parsed anything.
		736
		737	This function is useful in two cases: a) finding the trailing text after a
		738	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		739	(such as commas).
		740
		741	=back
		742
		743	=head2 LIMITATIONS
		744
		745	All options that affect decoding are supported, except
		746	C<allow_nonref>. The reason for this is that it cannot be made to
		747	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		748	them back to back and still decode them perfectly. This does not hold true
		749	for JSON numbers, however.
		750
		751	For example, is the string C<1> a single JSON number, or is it simply the
		752	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		753	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		754	takes the conservative route and disallows this case.
		755
		756	=head2 EXAMPLES
		757
		758	Some examples will make all this clearer. First, a simple example that
		759	works similarly to C<decode_prefix>: We want to decode the JSON object at
		760	the start of a string and identify the portion after the JSON object:
		761
		762	my $text = "[1,2,3] hello";
		763
		764	my $json = new JSON::XS;
		765
		766	my $obj = $json->incr_parse ($text)
		767	or die "expected JSON object or array at beginning of string";
		768
		769	my $tail = $json->incr_text;
		770	# $tail now contains " hello"
		771
		772	Easy, isn't it?
		773
		774	Now for a more complicated example: Imagine a hypothetical protocol where
		775	you read some requests from a TCP stream, and each request is a JSON
		776	array, without any separation between them (in fact, it is often useful to
		777	use newlines as "separators", as these get interpreted as whitespace at
		778	the start of the JSON text, which makes it possible to test said protocol
		779	with C<telnet>...).
		780
		781	Here is how you'd do it (it is trivial to write this in an event-based
		782	manner):
		783
		784	my $json = new JSON::XS;
		785
		786	# read some data from the socket
		787	while (sysread $socket, my $buf, 4096) {
		788
		789	# split and decode as many requests as possible
		790	for my $request ($json->incr_parse ($buf)) {
		791	# act on the $request
		792	}
		793	}
		794
		795	Another complicated example: Assume you have a string with JSON objects
		796	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		797	[3]>). To parse them, we have to skip the commas between the JSON texts,
		798	and here is where the lvalue-ness of C<incr_text> comes in useful:
		799
		800	my $text = "[1],[2], [3]";
		801	my $json = new JSON::XS;
		802
		803	# void context, so no parsing done
		804	$json->incr_parse ($text);
		805
		806	# now extract as many objects as possible. note the
		807	# use of scalar context so incr_text can be called.
		808	while (my $obj = $json->incr_parse) {
		809	# do something with $obj
		810
		811	# now skip the optional comma
		812	$json->incr_text =~ s/^ \s* , //x;
		813	}
		814
		815	Now lets go for a very complex example: Assume that you have a gigantic
		816	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		817	but you cannot load it into memory fully (this has actually happened in
		818	the real world :).
		819
		820	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		821	can still help you: You implement a (very simple) array parser and let
		822	JSON decode the array elements, which are all full JSON objects on their
		823	own (this wouldn't work if the array elements could be JSON numbers, for
		824	example):
		825
		826	my $json = new JSON::XS;
		827
		828	# open the monster
		829	open my $fh, "<bigfile.json"
		830	or die "bigfile: $!";
		831
		832	# first parse the initial "["
		833	for (;;) {
		834	sysread $fh, my $buf, 65536
		835	or die "read error: $!";
		836	$json->incr_parse ($buf); # void context, so no parsing
		837
		838	# Exit the loop once we found and removed(!) the initial "[".
		839	# In essence, we are (ab-)using the $json object as a simple scalar
		840	# we append data to.
		841	last if $json->incr_text =~ s/^ \s* \[ //x;
		842	}
		843
		844	# now we have the skipped the initial "[", so continue
		845	# parsing all the elements.
		846	for (;;) {
		847	# in this loop we read data until we got a single JSON object
		848	for (;;) {
		849	if (my $obj = $json->incr_parse) {
		850	# do something with $obj
		851	last;
		852	}
		853
		854	# add more data
		855	sysread $fh, my $buf, 65536
		856	or die "read error: $!";
		857	$json->incr_parse ($buf); # void context, so no parsing
		858	}
		859
		860	# in this loop we read data until we either found and parsed the
		861	# separating "," between elements, or the final "]"
		862	for (;;) {
		863	# first skip whitespace
		864	$json->incr_text =~ s/^\s*//;
		865
		866	# if we find "]", we are done
		867	if ($json->incr_text =~ s/^\]//) {
		868	print "finished.\n";
		869	exit;
		870	}
		871
		872	# if we find ",", we can continue with the next element
		873	if ($json->incr_text =~ s/^,//) {
		874	last;
		875	}
		876
		877	# if we find anything else, we have a parse error!
		878	if (length $json->incr_text) {
		879	die "parse error near ", $json->incr_text;
		880	}
		881
		882	# else add more data
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886	}
		887
		888	This is a complex example, but most of the complexity comes from the fact
		889	that we are trying to be correct (bear with me if I am wrong, I never ran
		890	the above example :).
		891
		892
		893
620	=head1 MAPPING	894	=head1 MAPPING
621		895
622	This section describes how JSON::XS maps Perl values to JSON values and	896	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	897	vice versa. These mappings are designed to "do the right thing" in most
624	circumstances automatically, preserving round-tripping characteristics	898	circumstances automatically, preserving round-tripping characteristics
…		…
652		926
653	A JSON number becomes either an integer, numeric (floating point) or	927	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	928	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	929	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	930	the conversion details, but an integer may take slightly less memory and
657	might represent more values exactly than (floating point) numbers.	931	might represent more values exactly than floating point numbers.
658		932
659	If the number consists of digits only, JSON::XS will try to represent	933	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	934	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	935	a numeric (floating point) value if that is possible without loss of
662	precision. Otherwise it will preserve the number as a string value.	936	precision. Otherwise it will preserve the number as a string value (in
		937	which case you lose roundtripping ability, as the JSON number will be
		938	re-encoded toa JSON string).
663		939
664	Numbers containing a fractional or exponential part will always be	940	Numbers containing a fractional or exponential part will always be
665	represented as numeric (floating point) values, possibly at a loss of	941	represented as numeric (floating point) values, possibly at a loss of
666	precision.	942	precision (in which case you might lose perfect roundtripping ability, but
667		943	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		944
671	=item true, false	945	=item true, false
672		946
673	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	947	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	948	respectively. They are overloaded to act almost exactly like the numbers
…		…
711	Other unblessed references are generally not allowed and will cause an	985	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	986	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	987	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.	988	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
715		989
716	to_json [\0,JSON::XS::true] # yields [false,true]	990	encode_json [\0,JSON::XS::true] # yields [false,true]
717		991
718	=item JSON::XS::true, JSON::XS::false	992	=item JSON::XS::true, JSON::XS::false
719		993
720	These special values become JSON true and JSON false values,	994	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.	995	respectively. You can also use C<\1> and C<\0> directly if you want.
722		996
723	=item blessed objects	997	=item blessed objects
724		998
725	Blessed objects are not allowed. JSON::XS currently tries to encode their	999	Blessed objects are not directly representable in JSON. See the
726	underlying representation (hash- or arrayref), but this behaviour might	1000	C<allow_blessed> and C<convert_blessed> methods on various options on
727	change in future versions.	1001	how to deal with this: basically, you can choose between throwing an
		1002	exception, encoding the reference as if it weren't blessed, or provide
		1003	your own serialiser method.
728		1004
729	=item simple scalars	1005	=item simple scalars
730		1006
731	Simple Perl scalars (any scalar that is not a reference) are the most	1007	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	1008	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	1009	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:	1010	before encoding as JSON strings, and anything else as number value:
735		1011
736	# dump as number	1012	# dump as number
737	to_json [2] # yields [2]	1013	encode_json [2] # yields [2]
738	to_json [-3.0e17] # yields [-3e+17]	1014	encode_json [-3.0e17] # yields [-3e+17]
739	my $value = 5; to_json [$value] # yields [5]	1015	my $value = 5; encode_json [$value] # yields [5]
740		1016
741	# used as string, so dump as string	1017	# used as string, so dump as string
742	print $value;	1018	print $value;
743	to_json [$value] # yields ["5"]	1019	encode_json [$value] # yields ["5"]
744		1020
745	# undef becomes null	1021	# undef becomes null
746	to_json [undef] # yields [null]	1022	encode_json [undef] # yields [null]
747		1023
748	You can force the type to be a JSON string by stringifying it:	1024	You can force the type to be a JSON string by stringifying it:
749		1025
750	my $x = 3.1; # some variable containing a number	1026	my $x = 3.1; # some variable containing a number
751	"$x"; # stringified	1027	"$x"; # stringified
…		…
757	my $x = "3"; # some variable containing a string	1033	my $x = "3"; # some variable containing a string
758	$x += 0; # numify it, ensuring it will be dumped as a number	1034	$x += 0; # numify it, ensuring it will be dumped as a number
759	$x *= 1; # same thing, the choice is yours.	1035	$x *= 1; # same thing, the choice is yours.
760		1036
761	You can not currently force the type in other, less obscure, ways. Tell me	1037	You can not currently force the type in other, less obscure, ways. Tell me
762	if you need this capability.	1038	if you need this capability (but don't forget to explain why it's needed
		1039	:).
		1040
		1041	=back
		1042
		1043
		1044	=head1 ENCODING/CODESET FLAG NOTES
		1045
		1046	The interested reader might have seen a number of flags that signify
		1047	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		1048	some confusion on what these do, so here is a short comparison:
		1049
		1050	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1051	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1052	control whether C<encode> escapes character values outside their respective
		1053	codeset range. Neither of these flags conflict with each other, although
		1054	some combinations make less sense than others.
		1055
		1056	Care has been taken to make all flags symmetrical with respect to
		1057	C<encode> and C<decode>, that is, texts encoded with any combination of
		1058	these flag values will be correctly decoded when the same flags are used
		1059	- in general, if you use different flag settings while encoding vs. when
		1060	decoding you likely have a bug somewhere.
		1061
		1062	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1063	simply an abstract set of character-codepoint pairs, while an encoding
		1064	takes those codepoint numbers and I<encodes> them, in our case into
		1065	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1066	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1067	the same time, which can be confusing.
		1068
		1069	=over 4
		1070
		1071	=item C<utf8> flag disabled
		1072
		1073	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1074	and expect Unicode strings, that is, characters with high ordinal Unicode
		1075	values (> 255) will be encoded as such characters, and likewise such
		1076	characters are decoded as-is, no canges to them will be done, except
		1077	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1078	respectively (to Perl, these are the same thing in strings unless you do
		1079	funny/weird/dumb stuff).
		1080
		1081	This is useful when you want to do the encoding yourself (e.g. when you
		1082	want to have UTF-16 encoded JSON texts) or when some other layer does
		1083	the encoding for you (for example, when printing to a terminal using a
		1084	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1085	to UTF-8 encode your data first and have Perl encode it another time).
		1086
		1087	=item C<utf8> flag enabled
		1088
		1089	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1090	characters using the corresponding UTF-8 multi-byte sequence, and will
		1091	expect your input strings to be encoded as UTF-8, that is, no "character"
		1092	of the input string must have any value > 255, as UTF-8 does not allow
		1093	that.
		1094
		1095	The C<utf8> flag therefore switches between two modes: disabled means you
		1096	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1097	octet/binary string in Perl.
		1098
		1099	=item C<latin1> or C<ascii> flags enabled
		1100
		1101	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1102	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1103	characters as specified by the C<utf8> flag.
		1104
		1105	If C<utf8> is disabled, then the result is also correctly encoded in those
		1106	character sets (as both are proper subsets of Unicode, meaning that a
		1107	Unicode string with all character values < 256 is the same thing as a
		1108	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1109	the same thing as an ASCII string in Perl).
		1110
		1111	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		1112	regardless of these flags, just some more characters will be escaped using
		1113	C<\uXXXX> then before.
		1114
		1115	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		1116	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1117	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1118	a subset of Unicode), while ASCII is.
		1119
		1120	Surprisingly, C<decode> will ignore these flags and so treat all input
		1121	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1122	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1123	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		1124
		1125	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1126	they only govern when the JSON output engine escapes a character or not.
		1127
		1128	The main use for C<latin1> is to relatively efficiently store binary data
		1129	as JSON, at the expense of breaking compatibility with most JSON decoders.
		1130
		1131	The main use for C<ascii> is to force the output to not contain characters
		1132	with values > 127, which means you can interpret the resulting string
		1133	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		1134	8-bit-encoding, and still get the same data structure back. This is useful
		1135	when your channel for JSON transfer is not 8-bit clean or the encoding
		1136	might be mangled in between (e.g. in mail), and works because ASCII is a
		1137	proper subset of most 8-bit and multibyte encodings in use in the world.
763		1138
764	=back	1139	=back
765		1140
766		1141
767	=head1 COMPARISON	1142	=head1 COMPARISON
…		…
771	problems (or pleasures) I encountered with various existing JSON modules,	1146	problems (or pleasures) I encountered with various existing JSON modules,
772	followed by some benchmark values. JSON::XS was designed not to suffer	1147	followed by some benchmark values. JSON::XS was designed not to suffer
773	from any of these problems or limitations.	1148	from any of these problems or limitations.
774		1149
775	=over 4	1150	=over 4
		1151
		1152	=item JSON 2.xx
		1153
		1154	A marvellous piece of engineering, this module either uses JSON::XS
		1155	directly when available (so will be 100% compatible with it, including
		1156	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		1157	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		1158	slower.
		1159
		1160	You cannot really lose by using this module, especially as it tries very
		1161	hard to work even with ancient Perl versions, while JSON::XS does not.
776		1162
777	=item JSON 1.07	1163	=item JSON 1.07
778		1164
779	Slow (but very portable, as it is written in pure Perl).	1165	Slow (but very portable, as it is written in pure Perl).
780		1166
…		…
851	=back	1237	=back
852		1238
853		1239
854	=head2 JSON and YAML	1240	=head2 JSON and YAML
855		1241
856	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1242	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	1243	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.	1244	so let me state it clearly: I<in general, there is no way to configure
		1245	JSON::XS to output a data structure as valid YAML> that works in all
		1246	cases.
859		1247
860	If you really must use JSON::XS to generate YAML, you should use this	1248	If you really must use JSON::XS to generate YAML, you should use this
861	algorithm (subject to change in future versions):	1249	algorithm (subject to change in future versions):
862		1250
863	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1251	my $to_yaml = JSON::XS->new->utf8->space_after (1);
864	my $yaml = $to_yaml->encode ($ref) . "\n";	1252	my $yaml = $to_yaml->encode ($ref) . "\n";
865		1253
866	This will usually generate JSON texts that also parse as valid	1254	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	1255	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	1256	lengths that JSON doesn't have and also has different and incompatible
		1257	unicode handling, so you should make sure that your hash keys are
869	keys are noticeably shorter than the 1024 characters YAML allows.	1258	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1259	you do not have characters with codepoint values outside the Unicode BMP
		1260	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1261	strings (which JSON::XS does not I<currently> generate, but other JSON
		1262	generators might).
870		1263
871	There might be other incompatibilities that I am not aware of. In general	1264	There might be other incompatibilities that I am not aware of (or the YAML
		1265	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,	1266	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	1267	versa, or try to parse JSON with a YAML parser or vice versa: chances are
874	that you will run into severe interoperability problems.	1268	high that you will run into severe interoperability problems when you
		1269	least expect it.
		1270
		1271	=over 4
		1272
		1273	=item (*)
		1274
		1275	I have been pressured multiple times by Brian Ingerson (one of the
		1276	authors of the YAML specification) to remove this paragraph, despite him
		1277	acknowledging that the actual incompatibilities exist. As I was personally
		1278	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1279	educate people about these issues, so others do not run into the same
		1280	problem again and again. After this, Brian called me a (quote)I<complete
		1281	and worthless idiot>(unquote).
		1282
		1283	In my opinion, instead of pressuring and insulting people who actually
		1284	clarify issues with YAML and the wrong statements of some of its
		1285	proponents, I would kindly suggest reading the JSON spec (which is not
		1286	that difficult or long) and finally make YAML compatible to it, and
		1287	educating users about the changes, instead of spreading lies about the
		1288	real compatibility for many I<years> and trying to silence people who
		1289	point out that it isn't true.
		1290
		1291	=back
875		1292
876		1293
877	=head2 SPEED	1294	=head2 SPEED
878		1295
879	It seems that JSON::XS is surprisingly fast, as shown in the following	1296	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	1297	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	1298	in the JSON::XS distribution, to make it easy to compare on your own
882	system.	1299	system.
883		1300
884	First comes a comparison between various modules using a very short	1301	First comes a comparison between various modules using
885	single-line JSON string:	1302	a very short single-line JSON string (also available at
		1303	L<http://dist.schmorp.de/misc/json/short.json>).
886		1304
887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1305	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
888	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1306	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
889		1307
890	It shows the number of encodes/decodes per second (JSON::XS uses	1308	It shows the number of encodes/decodes per second (JSON::XS uses
891	the functional interface, while JSON::XS/2 uses the OO interface	1309	the functional interface, while JSON::XS/2 uses the OO interface
892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1310	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
893	shrink). Higher is better:	1311	shrink). Higher is better:
894		1312
895	Storable \| 15779.925 \| 14169.946 \|
896	-----------+------------+------------+
897	module \| encode \| decode \|	1313	module \| encode \| decode \|
898	-----------\|------------\|------------\|	1314	-----------\|------------\|------------\|
899	JSON \| 4990.842 \| 4088.813 \|	1315	JSON 1.x \| 4990.842 \| 4088.813 \|
900	JSON::DWIW \| 51653.990 \| 71575.154 \|	1316	JSON::DWIW \| 51653.990 \| 71575.154 \|
901	JSON::PC \| 65948.176 \| 74631.744 \|	1317	JSON::PC \| 65948.176 \| 74631.744 \|
902	JSON::PP \| 8931.652 \| 3817.168 \|	1318	JSON::PP \| 8931.652 \| 3817.168 \|
903	JSON::Syck \| 24877.248 \| 27776.848 \|	1319	JSON::Syck \| 24877.248 \| 27776.848 \|
904	JSON::XS \| 388361.481 \| 227951.304 \|	1320	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
911	about three times faster on decoding, and over forty times faster	1327	about three times faster on decoding, and over forty times faster
912	than JSON, even with pretty-printing and key sorting. It also compares	1328	than JSON, even with pretty-printing and key sorting. It also compares
913	favourably to Storable for small amounts of data.	1329	favourably to Storable for small amounts of data.
914		1330
915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1331	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
916	search API (http://nanoref.com/yahooapis/mgPdGg):	1332	search API (L<http://dist.schmorp.de/misc/json/long.json>).
917		1333
918	module \| encode \| decode \|	1334	module \| encode \| decode \|
919	-----------\|------------\|------------\|	1335	-----------\|------------\|------------\|
920	JSON \| 55.260 \| 34.971 \|	1336	JSON 1.x \| 55.260 \| 34.971 \|
921	JSON::DWIW \| 825.228 \| 1082.513 \|	1337	JSON::DWIW \| 825.228 \| 1082.513 \|
922	JSON::PC \| 3571.444 \| 2394.829 \|	1338	JSON::PC \| 3571.444 \| 2394.829 \|
923	JSON::PP \| 210.987 \| 32.574 \|	1339	JSON::PP \| 210.987 \| 32.574 \|
924	JSON::Syck \| 552.551 \| 787.544 \|	1340	JSON::Syck \| 552.551 \| 787.544 \|
925	JSON::XS \| 5780.463 \| 4854.519 \|	1341	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
958		1374
959	Third, JSON::XS recurses using the C stack when decoding objects and	1375	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	1376	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	1377	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	1378	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	1379	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	1380	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	1381	has a smaller stack, you should adjust this setting accordingly with the
966	C<max_depth> method.	1382	C<max_depth> method.
967		1383
968	And last but least, something else could bomb you that I forgot to think	1384	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,	1385	case, you get to keep the pieces. I am always open for hints, though...
970	though...	1386
		1387	Also keep in mind that JSON::XS might leak contents of your Perl data
		1388	structures in its error messages, so when you serialise sensitive
		1389	information you might want to make sure that exceptions thrown by JSON::XS
		1390	will not end up in front of untrusted eyes.
971		1391
972	If you are using JSON::XS to return packets to consumption	1392	If you are using JSON::XS to return packets to consumption
973	by JavaScript scripts in a browser you should have a look at	1393	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	1394	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	1395	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	1396	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	1397	browser developers care only for features, not about getting security
978	right).	1398	right).
979		1399
980		1400
981	=head1 THREADS	1401	=head1 THREADS
982		1402
983	This module is I<not> guaranteed to be thread safe and there are no	1403	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	1404	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	1405	horribly slow so-called "threads" which are simply slow and bloated
986	process simulations - use fork, its I<much> faster, cheaper, better).	1406	process simulations - use fork, it's I<much> faster, cheaper, better).
987		1407
988	(It might actually work, but you have been warned).	1408	(It might actually work, but you have been warned).
989		1409
990		1410
991	=head1 BUGS	1411	=head1 BUGS
992		1412
993	While the goal of this module is to be correct, that unfortunately does	1413	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	1414	not mean it's bug-free, only that I think its design is bug-free. It is
995	still relatively early in its development. If you keep reporting bugs they	1415	still relatively early in its development. If you keep reporting bugs they
996	will be fixed swiftly, though.	1416	will be fixed swiftly, though.
997		1417
998	Please refrain from using rt.cpan.org or any other bug reporting	1418	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.	1419	service. I put the contact address into my modules for a reason.
…		…
1021	"--" => sub { $_[0] = ${$_[0]} - 1 },	1441	"--" => sub { $_[0] = ${$_[0]} - 1 },
1022	fallback => 1;	1442	fallback => 1;
1023		1443
1024	1;	1444	1;
1025		1445
		1446	=head1 SEE ALSO
		1447
		1448	The F<json_xs> command line utility for quick experiments.
		1449
1026	=head1 AUTHOR	1450	=head1 AUTHOR
1027		1451
1028	Marc Lehmann <schmorp@schmorp.de>	1452	Marc Lehmann <schmorp@schmorp.de>
1029	http://home.schmorp.de/	1453	http://home.schmorp.de/
1030		1454

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.70 by root, Tue Nov 13 22:59:08 2007 UTC vs. Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.70 by root, Tue Nov 13 22:59:08 2007 UTC vs.
Revision 1.94 by root, Tue Mar 25 07:46:15 2008 UTC