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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.27 by root, Tue Apr 3 01:25:40 2007 UTC vs.
Revision 1.95 by root, Tue Mar 25 16:56:09 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
		3	=encoding utf-8
		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
4		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, they croak on error	14	# exported functions, they croak on error
10	# and expect/generate UTF-8	15	# and expect/generate UTF-8
11		16
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		19
19	# OO-interface	20	# OO-interface
20		21
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
23	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
24		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
25	=head1 DESCRIPTION	34	=head1 DESCRIPTION
26		35
27	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
28	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
29	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.
30		47
31	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
32	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
33	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
34	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
41		58
42	=head2 FEATURES	59	=head2 FEATURES
43		60
44	=over 4	61	=over 4
45		62
46	=item * correct unicode handling	63	=item * correct Unicode handling
47		64
48	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
49	it does so.	66	so, and even documents what "correct" means.
50		67
51	=item * round-trip integrity	68	=item * round-trip integrity
52		69
53	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
54	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.
55	(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
56	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
57		75
58	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
59		77
60	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,
61	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
62	feature).	80	feature).
63		81
64	=item * fast	82	=item * fast
65		83
66	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
67	of speed, too.	85	this module usually compares favourably in terms of speed, too.
68		86
69	=item * simple to use	87	=item * simple to use
70		88
71	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
72	interface.	90	oriented interface interface.
73		91
74	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
75		93
76	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
77	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
78	(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
79	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
80	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.
81		99
82	=back	100	=back
83		101
84	=cut	102	=cut
85		103
86	package JSON::XS;	104	package JSON::XS;
87		105
88	use strict;	106	use strict;
89		107
90	BEGIN {
91	our $VERSION = '1.02';	108	our $VERSION = '2.1';
92	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
93		110
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
95	require Exporter;
96		112
		113	sub to_json($) {
97	require XSLoader;	114	require Carp;
98	XSLoader::load JSON::XS::, $VERSION;	115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
99	}	116	}
100		117
		118	sub from_json($) {
		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	}
		122
		123	use Exporter;
		124	use XSLoader;
		125
101	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
102		127
103	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
104	exported by default:	129	exported by default:
105		130
106	=over 4	131	=over 4
107		132
108	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
109		134
110	Converts the given Perl data structure (a simple scalar or a reference to	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
111	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	136	(that is, the string contains octets only). Croaks on error.
112	octets only). Croaks on error.
113		137
114	This function call is functionally identical to:	138	This function call is functionally identical to:
115		139
116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
117		141
118	except being faster.	142	except being faster.
119		143
120	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
121		145
122	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
123	parse that as an UTF-8 encoded JSON text, returning the resulting simple	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
124	scalar or reference. Croaks on error.	148	reference. Croaks on error.
125		149
126	This function call is functionally identical to:	150	This function call is functionally identical to:
127		151
128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129		153
130	except being faster.	154	except being faster.
131		155
		156	=item $is_boolean = JSON::XS::is_bool $scalar
		157
		158	Returns true if the passed scalar represents either JSON::XS::true or
		159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		160	and are used to represent JSON C<true> and C<false> values in Perl.
		161
		162	See MAPPING, below, for more information on how JSON values are mapped to
		163	Perl.
		164
132	=back	165	=back
		166
		167
		168	=head1 A FEW NOTES ON UNICODE AND PERL
		169
		170	Since this often leads to confusion, here are a few very clear words on
		171	how Unicode works in Perl, modulo bugs.
		172
		173	=over 4
		174
		175	=item 1. Perl strings can store characters with ordinal values > 255.
		176
		177	This enables you to store Unicode characters as single characters in a
		178	Perl string - very natural.
		179
		180	=item 2. Perl does I<not> associate an encoding with your strings.
		181
		182	... until you force it to, e.g. when matching it against a regex, or
		183	printing the scalar to a file, in which case Perl either interprets your
		184	string as locale-encoded text, octets/binary, or as Unicode, depending
		185	on various settings. In no case is an encoding stored together with your
		186	data, it is I<use> that decides encoding, not any magical meta data.
		187
		188	=item 3. The internal utf-8 flag has no meaning with regards to the
		189	encoding of your string.
		190
		191	Just ignore that flag unless you debug a Perl bug, a module written in
		192	XS or want to dive into the internals of perl. Otherwise it will only
		193	confuse you, as, despite the name, it says nothing about how your string
		194	is encoded. You can have Unicode strings with that flag set, with that
		195	flag clear, and you can have binary data with that flag set and that flag
		196	clear. Other possibilities exist, too.
		197
		198	If you didn't know about that flag, just the better, pretend it doesn't
		199	exist.
		200
		201	=item 4. A "Unicode String" is simply a string where each character can be
		202	validly interpreted as a Unicode codepoint.
		203
		204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		205	Unicode string encoded in UTF-8, giving you a binary string.
		206
		207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		208
		209	It's a fact. Learn to live with it.
		210
		211	=back
		212
		213	I hope this helps :)
133		214
134		215
135	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
136		217
137	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
…		…
150	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]})
151	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
152		233
153	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
154		235
		236	=item $enabled = $json->get_ascii
		237
155	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
156	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
157	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
159	as per RFC4627.	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
		243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		244	or any other superset of ASCII.
160		245
161	If C<$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
162	characters unless required by the JSON syntax. This results in a faster	247	characters unless required by the JSON syntax or other flags. This results
163	and more compact format.	248	in a faster and more compact format.
		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
		253	The main use for this flag is to produce JSON texts that can be
		254	transmitted over a 7-bit channel, as the encoded JSON texts will not
		255	contain any 8 bit characters.
164		256
165	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
166	=> ["\ud801\udc01"]	258	=> ["\ud801\udc01"]
167		259
		260	=item $json = $json->latin1 ([$enable])
		261
		262	=item $enabled = $json->get_latin1
		263
		264	If C<$enable> is true (or missing), then the C<encode> method will encode
		265	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		266	outside the code range C<0..255>. The resulting string can be treated as a
		267	latin1-encoded JSON text or a native Unicode string. The C<decode> method
		268	will not be affected in any way by this flag, as C<decode> by default
		269	expects Unicode, which is a strict superset of latin1.
		270
		271	If C<$enable> is false, then the C<encode> method will not escape Unicode
		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.
		276
		277	The main use for this flag is efficiently encoding binary data as JSON
		278	text, as most octets will not be escaped, resulting in a smaller encoded
		279	size. The disadvantage is that the resulting JSON text is encoded
		280	in latin1 (and must correctly be treated as such when storing and
		281	transferring), a rare encoding for JSON. It is therefore most useful when
		282	you want to store data structures known to contain binary data efficiently
		283	in files or databases, not when talking to other JSON encoders/decoders.
		284
		285	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		286	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		287
168	=item $json = $json->utf8 ([$enable])	288	=item $json = $json->utf8 ([$enable])
		289
		290	=item $enabled = $json->get_utf8
169		291
170	If C<$enable> is true (or missing), then the C<encode> method will encode	292	If C<$enable> is true (or missing), then the C<encode> method will encode
171	the JSON result into UTF-8, as required by many protocols, while the	293	the JSON result into UTF-8, as required by many protocols, while the
172	C<decode> method expects to be handled an UTF-8-encoded string. Please	294	C<decode> method expects to be handled an UTF-8-encoded string. Please
173	note that UTF-8-encoded strings do not contain any characters outside the	295	note that UTF-8-encoded strings do not contain any characters outside the
174	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	296	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
175	versions, enabling this option might enable autodetection of the UTF-16	297	versions, enabling this option might enable autodetection of the UTF-16
176	and UTF-32 encoding families, as described in RFC4627.	298	and UTF-32 encoding families, as described in RFC4627.
177		299
178	If C<$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
179	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
180	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
181	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.
182		307
183	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
184		309
185	use Encode;	310	use Encode;
186	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
207	]	332	]
208	}	333	}
209		334
210	=item $json = $json->indent ([$enable])	335	=item $json = $json->indent ([$enable])
211		336
		337	=item $enabled = $json->get_indent
		338
212	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	339	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
213	format as output, putting every array member or object/hash key-value pair	340	format as output, putting every array member or object/hash key-value pair
214	into its own line, identing them properly.	341	into its own line, indenting them properly.
215		342
216	If C<$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
217	resulting JSON text is guarenteed not to contain any C<newlines>.	344	resulting JSON text is guaranteed not to contain any C<newlines>.
218		345
219	This setting has no effect when decoding JSON texts.	346	This setting has no effect when decoding JSON texts.
220		347
221	=item $json = $json->space_before ([$enable])	348	=item $json = $json->space_before ([$enable])
		349
		350	=item $enabled = $json->get_space_before
222		351
223	If C<$enable> is true (or missing), then the C<encode> method will add an extra	352	If C<$enable> is true (or missing), then the C<encode> method will add an extra
224	optional space before the C<:> separating keys from values in JSON objects.	353	optional space before the C<:> separating keys from values in JSON objects.
225		354
226	If C<$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
…		…
232	Example, space_before enabled, space_after and indent disabled:	361	Example, space_before enabled, space_after and indent disabled:
233		362
234	{"key" :"value"}	363	{"key" :"value"}
235		364
236	=item $json = $json->space_after ([$enable])	365	=item $json = $json->space_after ([$enable])
		366
		367	=item $enabled = $json->get_space_after
237		368
238	If C<$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
239	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
240	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
241	members.	372	members.
…		…
247		378
248	Example, space_before and indent disabled, space_after enabled:	379	Example, space_before and indent disabled, space_after enabled:
249		380
250	{"key": "value"}	381	{"key": "value"}
251		382
		383	=item $json = $json->relaxed ([$enable])
		384
		385	=item $enabled = $json->get_relaxed
		386
		387	If C<$enable> is true (or missing), then C<decode> will accept some
		388	extensions to normal JSON syntax (see below). C<encode> will not be
		389	affected in anyway. I<Be aware that this option makes you accept invalid
		390	JSON texts as if they were valid!>. I suggest only to use this option to
		391	parse application-specific files written by humans (configuration files,
		392	resource files etc.)
		393
		394	If C<$enable> is false (the default), then C<decode> will only accept
		395	valid JSON texts.
		396
		397	Currently accepted extensions are:
		398
		399	=over 4
		400
		401	=item * list items can have an end-comma
		402
		403	JSON I<separates> array elements and key-value pairs with commas. This
		404	can be annoying if you write JSON texts manually and want to be able to
		405	quickly append elements, so this extension accepts comma at the end of
		406	such items not just between them:
		407
		408	[
		409	1,
		410	2, <- this comma not normally allowed
		411	]
		412	{
		413	"k1": "v1",
		414	"k2": "v2", <- this comma not normally allowed
		415	}
		416
		417	=item * shell-style '#'-comments
		418
		419	Whenever JSON allows whitespace, shell-style comments are additionally
		420	allowed. They are terminated by the first carriage-return or line-feed
		421	character, after which more white-space and comments are allowed.
		422
		423	[
		424	1, # this comment not allowed in JSON
		425	# neither this one...
		426	]
		427
		428	=back
		429
252	=item $json = $json->canonical ([$enable])	430	=item $json = $json->canonical ([$enable])
		431
		432	=item $enabled = $json->get_canonical
253		433
254	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	434	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
255	by sorting their keys. This is adding a comparatively high overhead.	435	by sorting their keys. This is adding a comparatively high overhead.
256		436
257	If C<$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
258	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
259	of the same script).	439	of the same script).
260		440
261	This option is useful if you want the same data structure to be encoded as	441	This option is useful if you want the same data structure to be encoded as
262	the same JSON text (given the same overall settings). If it is disabled,	442	the same JSON text (given the same overall settings). If it is disabled,
263	the same hash migh be encoded differently even if contains the same data,	443	the same hash might be encoded differently even if contains the same data,
264	as key-value pairs have no inherent ordering in Perl.	444	as key-value pairs have no inherent ordering in Perl.
265		445
266	This setting has no effect when decoding JSON texts.	446	This setting has no effect when decoding JSON texts.
267		447
268	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
		449
		450	=item $enabled = $json->get_allow_nonref
269		451
270	If C<$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
271	non-reference into its corresponding string, number or null JSON value,	453	non-reference into its corresponding string, number or null JSON value,
272	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
273	values instead of croaking.	455	values instead of croaking.
…		…
281	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
282		464
283	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
284	=> "Hello, World!"	466	=> "Hello, World!"
285		467
		468	=item $json = $json->allow_blessed ([$enable])
		469
		470	=item $enabled = $json->get_allow_blessed
		471
		472	If C<$enable> is true (or missing), then the C<encode> method will not
		473	barf when it encounters a blessed reference. Instead, the value of the
		474	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
		475	disabled or no C<TO_JSON> method found) or a representation of the
		476	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
		477	encoded. Has no effect on C<decode>.
		478
		479	If C<$enable> is false (the default), then C<encode> will throw an
		480	exception when it encounters a blessed object.
		481
		482	=item $json = $json->convert_blessed ([$enable])
		483
		484	=item $enabled = $json->get_convert_blessed
		485
		486	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		487	blessed object, will check for the availability of the C<TO_JSON> method
		488	on the object's class. If found, it will be called in scalar context
		489	and the resulting scalar will be encoded instead of the object. If no
		490	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		491	to do.
		492
		493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		494	returns other blessed objects, those will be handled in the same
		495	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		496	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		497	methods called by the Perl core (== not by the user of the object) are
		498	usually in upper case letters and to avoid collisions with any C<to_json>
		499	function or method.
		500
		501	This setting does not yet influence C<decode> in any way, but in the
		502	future, global hooks might get installed that influence C<decode> and are
		503	enabled by this setting.
		504
		505	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		506	to do when a blessed object is found.
		507
		508	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		509
		510	When C<$coderef> is specified, it will be called from C<decode> each
		511	time it decodes a JSON object. The only argument is a reference to the
		512	newly-created hash. If the code references returns a single scalar (which
		513	need not be a reference), this value (i.e. a copy of that scalar to avoid
		514	aliasing) is inserted into the deserialised data structure. If it returns
		515	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		516	original deserialised hash will be inserted. This setting can slow down
		517	decoding considerably.
		518
		519	When C<$coderef> is omitted or undefined, any existing callback will
		520	be removed and C<decode> will not change the deserialised hash in any
		521	way.
		522
		523	Example, convert all JSON objects into the integer 5:
		524
		525	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		526	# returns [5]
		527	$js->decode ('[{}]')
		528	# throw an exception because allow_nonref is not enabled
		529	# so a lone 5 is not allowed.
		530	$js->decode ('{"a":1, "b":2}');
		531
		532	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		533
		534	Works remotely similar to C<filter_json_object>, but is only called for
		535	JSON objects having a single key named C<$key>.
		536
		537	This C<$coderef> is called before the one specified via
		538	C<filter_json_object>, if any. It gets passed the single value in the JSON
		539	object. If it returns a single value, it will be inserted into the data
		540	structure. If it returns nothing (not even C<undef> but the empty list),
		541	the callback from C<filter_json_object> will be called next, as if no
		542	single-key callback were specified.
		543
		544	If C<$coderef> is omitted or undefined, the corresponding callback will be
		545	disabled. There can only ever be one callback for a given key.
		546
		547	As this callback gets called less often then the C<filter_json_object>
		548	one, decoding speed will not usually suffer as much. Therefore, single-key
		549	objects make excellent targets to serialise Perl objects into, especially
		550	as single-key JSON objects are as close to the type-tagged value concept
		551	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
		552	support this in any way, so you need to make sure your data never looks
		553	like a serialised Perl hash.
		554
		555	Typical names for the single object key are C<__class_whatever__>, or
		556	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		557	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		558	with real hashes.
		559
		560	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		561	into the corresponding C<< $WIDGET{<id>} >> object:
		562
		563	# return whatever is in $WIDGET{5}:
		564	JSON::XS
		565	->new
		566	->filter_json_single_key_object (__widget__ => sub {
		567	$WIDGET{ $_[0] }
		568	})
		569	->decode ('{"__widget__": 5')
		570
		571	# this can be used with a TO_JSON method in some "widget" class
		572	# for serialisation to json:
		573	sub WidgetBase::TO_JSON {
		574	my ($self) = @_;
		575
		576	unless ($self->{id}) {
		577	$self->{id} = ..get..some..id..;
		578	$WIDGET{$self->{id}} = $self;
		579	}
		580
		581	{ __widget__ => $self->{id} }
		582	}
		583
286	=item $json = $json->shrink ([$enable])	584	=item $json = $json->shrink ([$enable])
		585
		586	=item $enabled = $json->get_shrink
287		587
288	Perl usually over-allocates memory a bit when allocating space for	588	Perl usually over-allocates memory a bit when allocating space for
289	strings. This flag optionally resizes strings generated by either	589	strings. This flag optionally resizes strings generated by either
290	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
291	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
…		…
309	strings that look like integers or floats into integers or floats	609	strings that look like integers or floats into integers or floats
310	internally (there is no difference on the Perl level), saving space.	610	internally (there is no difference on the Perl level), saving space.
311		611
312	=item $json = $json->max_depth ([$maximum_nesting_depth])	612	=item $json = $json->max_depth ([$maximum_nesting_depth])
313		613
		614	=item $max_depth = $json->get_max_depth
		615
314	Sets the maximum nesting level (default C<4096>) accepted while encoding	616	Sets the maximum nesting level (default C<512>) accepted while encoding
315	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
316	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
317	stop and croak at that point.	619	stop and croak at that point.
318		620
319	Nesting level is defined by number of hash- or arrayrefs that the encoder	621	Nesting level is defined by number of hash- or arrayrefs that the encoder
…		…
322	given character in a string.	624	given character in a string.
323		625
324	Setting the maximum depth to one disallows any nesting, so that ensures	626	Setting the maximum depth to one disallows any nesting, so that ensures
325	that the object is only a single hash/object or array.	627	that the object is only a single hash/object or array.
326		628
327	The argument to C<max_depth> will be rounded up to the next nearest power	629	The argument to C<max_depth> will be rounded up to the next highest power
328	of two.	630	of two. If no argument is given, the highest possible setting will be
		631	used, which is rarely useful.
		632
		633	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		634
		635	=item $json = $json->max_size ([$maximum_string_size])
		636
		637	=item $max_size = $json->get_max_size
		638
		639	Set the maximum length a JSON text may have (in bytes) where decoding is
		640	being attempted. The default is C<0>, meaning no limit. When C<decode>
		641	is called on a string longer then this number of characters it will not
		642	attempt to decode the string but throw an exception. This setting has no
		643	effect on C<encode> (yet).
		644
		645	The argument to C<max_size> will be rounded up to the next B<highest>
		646	power of two (so may be more than requested). If no argument is given, the
		647	limit check will be deactivated (same as when C<0> is specified).
329		648
330	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	649	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
331		650
332	=item $json_text = $json->encode ($perl_scalar)	651	=item $json_text = $json->encode ($perl_scalar)
333		652
…		…
345		664
346	JSON numbers and strings become simple Perl scalars. JSON arrays become	665	JSON numbers and strings become simple Perl scalars. JSON arrays become
347	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	666	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
348	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	667	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
349		668
		669	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		670
		671	This works like the C<decode> method, but instead of raising an exception
		672	when there is trailing garbage after the first JSON object, it will
		673	silently stop parsing there and return the number of characters consumed
		674	so far.
		675
		676	This is useful if your JSON texts are not delimited by an outer protocol
		677	(which is not the brightest thing to do in the first place) and you need
		678	to know where the JSON text ends.
		679
		680	JSON::XS->new->decode_prefix ("[1] the tail")
		681	=> ([], 3)
		682
350	=back	683	=back
		684
		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
351		892
352		893
353	=head1 MAPPING	894	=head1 MAPPING
354		895
355	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
356	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
357	circumstances automatically, preserving round-tripping characteristics	898	circumstances automatically, preserving round-tripping characteristics
358	(what you put in comes out as something equivalent).	899	(what you put in comes out as something equivalent).
359		900
360	For the more enlightened: note that in the following descriptions,	901	For the more enlightened: note that in the following descriptions,
361	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	902	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
362	refers to the abstract Perl language itself.	903	refers to the abstract Perl language itself.
363		904
		905
364	=head2 JSON -> PERL	906	=head2 JSON -> PERL
365		907
366	=over 4	908	=over 4
367		909
368	=item object	910	=item object
369		911
370	A JSON object becomes a reference to a hash in Perl. No ordering of object	912	A JSON object becomes a reference to a hash in Perl. No ordering of object
371	keys is preserved (JSON does not preserver object key ordering itself).	913	keys is preserved (JSON does not preserve object key ordering itself).
372		914
373	=item array	915	=item array
374		916
375	A JSON array becomes a reference to an array in Perl.	917	A JSON array becomes a reference to an array in Perl.
376		918
…		…
380	are represented by the same codepoints in the Perl string, so no manual	922	are represented by the same codepoints in the Perl string, so no manual
381	decoding is necessary.	923	decoding is necessary.
382		924
383	=item number	925	=item number
384		926
385	A JSON number becomes either an integer or numeric (floating point)	927	A JSON number becomes either an integer, numeric (floating point) or
386	scalar in perl, depending on its range and any fractional parts. On the	928	string scalar in perl, depending on its range and any fractional parts. On
387	Perl level, there is no difference between those as Perl handles all the	929	the Perl level, there is no difference between those as Perl handles all
388	conversion details, but an integer may take slightly less memory and might	930	the conversion details, but an integer may take slightly less memory and
389	represent more values exactly than (floating point) numbers.	931	might represent more values exactly than floating point numbers.
		932
		933	If the number consists of digits only, JSON::XS will try to represent
		934	it as an integer value. If that fails, it will try to represent it as
		935	a numeric (floating point) value if that is possible without loss of
		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).
		939
		940	Numbers containing a fractional or exponential part will always be
		941	represented as numeric (floating point) values, possibly at a loss of
		942	precision (in which case you might lose perfect roundtripping ability, but
		943	the JSON number will still be re-encoded as a JSON number).
390		944
391	=item true, false	945	=item true, false
392		946
393	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	947	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
394	this process. Future versions might represent those values differently,	948	respectively. They are overloaded to act almost exactly like the numbers
395	but they will be guarenteed to act like these integers would normally in	949	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
396	Perl.	950	the C<JSON::XS::is_bool> function.
397		951
398	=item null	952	=item null
399		953
400	A JSON null atom becomes C<undef> in Perl.	954	A JSON null atom becomes C<undef> in Perl.
401		955
402	=back	956	=back
		957
403		958
404	=head2 PERL -> JSON	959	=head2 PERL -> JSON
405		960
406	The mapping from Perl to JSON is slightly more difficult, as Perl is a	961	The mapping from Perl to JSON is slightly more difficult, as Perl is a
407	truly typeless language, so we can only guess which JSON type is meant by	962	truly typeless language, so we can only guess which JSON type is meant by
…		…
430	Other unblessed references are generally not allowed and will cause an	985	Other unblessed references are generally not allowed and will cause an
431	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
432	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
433	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.
434		989
435	to_json [\0,JSON::XS::true] # yields [false,true]	990	encode_json [\0,JSON::XS::true] # yields [false,true]
		991
		992	=item JSON::XS::true, JSON::XS::false
		993
		994	These special values become JSON true and JSON false values,
		995	respectively. You can also use C<\1> and C<\0> directly if you want.
436		996
437	=item blessed objects	997	=item blessed objects
438		998
439	Blessed objects are not allowed. JSON::XS currently tries to encode their	999	Blessed objects are not directly representable in JSON. See the
440	underlying representation (hash- or arrayref), but this behaviour might	1000	C<allow_blessed> and C<convert_blessed> methods on various options on
441	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.
442		1004
443	=item simple scalars	1005	=item simple scalars
444		1006
445	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
446	difficult objects to encode: JSON::XS will encode undefined scalars as	1008	difficult objects to encode: JSON::XS will encode undefined scalars as
447	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
448	before encoding as JSON strings and anything else as number value:	1010	before encoding as JSON strings, and anything else as number value:
449		1011
450	# dump as number	1012	# dump as number
451	to_json [2] # yields [2]	1013	encode_json [2] # yields [2]
452	to_json [-3.0e17] # yields [-3e+17]	1014	encode_json [-3.0e17] # yields [-3e+17]
453	my $value = 5; to_json [$value] # yields [5]	1015	my $value = 5; encode_json [$value] # yields [5]
454		1016
455	# used as string, so dump as string	1017	# used as string, so dump as string
456	print $value;	1018	print $value;
457	to_json [$value] # yields ["5"]	1019	encode_json [$value] # yields ["5"]
458		1020
459	# undef becomes null	1021	# undef becomes null
460	to_json [undef] # yields [null]	1022	encode_json [undef] # yields [null]
461		1023
462	You can force the type to be a string by stringifying it:	1024	You can force the type to be a JSON string by stringifying it:
463		1025
464	my $x = 3.1; # some variable containing a number	1026	my $x = 3.1; # some variable containing a number
465	"$x"; # stringified	1027	"$x"; # stringified
466	$x .= ""; # another, more awkward way to stringify	1028	$x .= ""; # another, more awkward way to stringify
467	print $x; # perl does it for you, too, quite often	1029	print $x; # perl does it for you, too, quite often
468		1030
469	You can force the type to be a number by numifying it:	1031	You can force the type to be a JSON number by numifying it:
470		1032
471	my $x = "3"; # some variable containing a string	1033	my $x = "3"; # some variable containing a string
472	$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
473	$x *= 1; # same thing, the choise is yours.	1035	$x *= 1; # same thing, the choice is yours.
474		1036
475	You can not currently output JSON booleans or force the type in other,	1037	You can not currently force the type in other, less obscure, ways. Tell me
476	less obscure, ways. Tell me if you need this capability.	1038	if you need this capability (but don't forget to explain why it's needed
		1039	:).
477		1040
478	=back	1041	=back
479		1042
480		1043
481	=head1 COMPARISON	1044	=head1 ENCODING/CODESET FLAG NOTES
482		1045
483	As already mentioned, this module was created because none of the existing	1046	The interested reader might have seen a number of flags that signify
484	JSON modules could be made to work correctly. First I will describe the	1047	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
485	problems (or pleasures) I encountered with various existing JSON modules,	1048	some confusion on what these do, so here is a short comparison:
486	followed by some benchmark values. JSON::XS was designed not to suffer	1049
487	from any of these problems or limitations.	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.
488		1068
489	=over 4	1069	=over 4
490		1070
491	=item JSON 1.07	1071	=item C<utf8> flag disabled
492		1072
493	Slow (but very portable, as it is written in pure Perl).	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).
494		1080
495	Undocumented/buggy Unicode handling (how JSON handles unicode values is	1081	This is useful when you want to do the encoding yourself (e.g. when you
496	undocumented. One can get far by feeding it unicode strings and doing	1082	want to have UTF-16 encoded JSON texts) or when some other layer does
497	en-/decoding oneself, but unicode escapes are not working properly).	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).
498		1086
499	No roundtripping (strings get clobbered if they look like numbers, e.g.	1087	=item C<utf8> flag enabled
500	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
501	decode into the number 2.
502		1088
503	=item JSON::PC 0.01	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.
504		1094
505	Very fast.	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.
506		1098
507	Undocumented/buggy Unicode handling.	1099	=item C<latin1> or C<ascii> flags enabled
508		1100
509	No roundtripping.	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.
510		1104
511	Has problems handling many Perl values (e.g. regex results and other magic	1105	If C<utf8> is disabled, then the result is also correctly encoded in those
512	values will make it croak).	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).
513		1110
514	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1111	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
515	which is not a valid JSON text.	1112	regardless of these flags, just some more characters will be escaped using
		1113	C<\uXXXX> then before.
516		1114
517	Unmaintained (maintainer unresponsive for many months, bugs are not	1115	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
518	getting fixed).	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.
519		1119
520	=item JSON::Syck 0.21	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.
521		1124
522	Very buggy (often crashes).	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.
523		1127
524	Very inflexible (no human-readable format supported, format pretty much	1128	The main use for C<latin1> is to relatively efficiently store binary data
525	undocumented. I need at least a format for easy reading by humans and a	1129	as JSON, at the expense of breaking compatibility with most JSON decoders.
526	single-line compact format for use in a protocol, and preferably a way to
527	generate ASCII-only JSON texts).
528		1130
529	Completely broken (and confusingly documented) Unicode handling (unicode	1131	The main use for C<ascii> is to force the output to not contain characters
530	escapes are not working properly, you need to set ImplicitUnicode to	1132	with values > 127, which means you can interpret the resulting string
531	I<different> values on en- and decoding to get symmetric behaviour).	1133	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
532		1134	8-bit-encoding, and still get the same data structure back. This is useful
533	No roundtripping (simple cases work, but this depends on wether the scalar	1135	when your channel for JSON transfer is not 8-bit clean or the encoding
534	value was used in a numeric context or not).	1136	might be mangled in between (e.g. in mail), and works because ASCII is a
535		1137	proper subset of most 8-bit and multibyte encodings in use in the world.
536	Dumping hashes may skip hash values depending on iterator state.
537
538	Unmaintained (maintainer unresponsive for many months, bugs are not
539	getting fixed).
540
541	Does not check input for validity (i.e. will accept non-JSON input and
542	return "something" instead of raising an exception. This is a security
543	issue: imagine two banks transfering money between each other using
544	JSON. One bank might parse a given non-JSON request and deduct money,
545	while the other might reject the transaction with a syntax error. While a
546	good protocol will at least recover, that is extra unnecessary work and
547	the transaction will still not succeed).
548
549	=item JSON::DWIW 0.04
550
551	Very fast. Very natural. Very nice.
552
553	Undocumented unicode handling (but the best of the pack. Unicode escapes
554	still don't get parsed properly).
555
556	Very inflexible.
557
558	No roundtripping.
559
560	Does not generate valid JSON texts (key strings are often unquoted, empty keys
561	result in nothing being output)
562
563	Does not check input for validity.
564		1138
565	=back	1139	=back
		1140
		1141
		1142	=head2 JSON and YAML
		1143
		1144	You often hear that JSON is a subset of YAML. This is, however, a mass
		1145	hysteria(*) and very far from the truth (as of the time of this writing),
		1146	so let me state it clearly: I<in general, there is no way to configure
		1147	JSON::XS to output a data structure as valid YAML> that works in all
		1148	cases.
		1149
		1150	If you really must use JSON::XS to generate YAML, you should use this
		1151	algorithm (subject to change in future versions):
		1152
		1153	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		1154	my $yaml = $to_yaml->encode ($ref) . "\n";
		1155
		1156	This will I<usually> generate JSON texts that also parse as valid
		1157	YAML. Please note that YAML has hardcoded limits on (simple) object key
		1158	lengths that JSON doesn't have and also has different and incompatible
		1159	unicode handling, so you should make sure that your hash keys are
		1160	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1161	you do not have characters with codepoint values outside the Unicode BMP
		1162	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1163	strings (which JSON::XS does not I<currently> generate, but other JSON
		1164	generators might).
		1165
		1166	There might be other incompatibilities that I am not aware of (or the YAML
		1167	specification has been changed yet again - it does so quite often). In
		1168	general you should not try to generate YAML with a JSON generator or vice
		1169	versa, or try to parse JSON with a YAML parser or vice versa: chances are
		1170	high that you will run into severe interoperability problems when you
		1171	least expect it.
		1172
		1173	=over 4
		1174
		1175	=item (*)
		1176
		1177	I have been pressured multiple times by Brian Ingerson (one of the
		1178	authors of the YAML specification) to remove this paragraph, despite him
		1179	acknowledging that the actual incompatibilities exist. As I was personally
		1180	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1181	educate people about these issues, so others do not run into the same
		1182	problem again and again. After this, Brian called me a (quote)I<complete
		1183	and worthless idiot>(unquote).
		1184
		1185	In my opinion, instead of pressuring and insulting people who actually
		1186	clarify issues with YAML and the wrong statements of some of its
		1187	proponents, I would kindly suggest reading the JSON spec (which is not
		1188	that difficult or long) and finally make YAML compatible to it, and
		1189	educating users about the changes, instead of spreading lies about the
		1190	real compatibility for many I<years> and trying to silence people who
		1191	point out that it isn't true.
		1192
		1193	=back
		1194
566		1195
567	=head2 SPEED	1196	=head2 SPEED
568		1197
569	It seems that JSON::XS is surprisingly fast, as shown in the following	1198	It seems that JSON::XS is surprisingly fast, as shown in the following
570	tables. They have been generated with the help of the C<eg/bench> program	1199	tables. They have been generated with the help of the C<eg/bench> program
571	in the JSON::XS distribution, to make it easy to compare on your own	1200	in the JSON::XS distribution, to make it easy to compare on your own
572	system.	1201	system.
573		1202
574	First comes a comparison between various modules using a very short JSON	1203	First comes a comparison between various modules using
575	string:	1204	a very short single-line JSON string (also available at
		1205	L<http://dist.schmorp.de/misc/json/short.json>).
576		1206
577	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	1207	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		1208	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
578		1209
579	It shows the number of encodes/decodes per second (JSON::XS uses the	1210	It shows the number of encodes/decodes per second (JSON::XS uses
580	functional interface, while JSON::XS/2 uses the OO interface with	1211	the functional interface, while JSON::XS/2 uses the OO interface
581	pretty-printing and hashkey sorting enabled). Higher is better:	1212	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		1213	shrink). Higher is better:
582		1214
583	module \| encode \| decode \|	1215	module \| encode \| decode \|
584	-----------\|------------\|------------\|	1216	-----------\|------------\|------------\|
585	JSON \| 11488.516 \| 7823.035 \|	1217	JSON 1.x \| 4990.842 \| 4088.813 \|
586	JSON::DWIW \| 94708.054 \| 129094.260 \|	1218	JSON::DWIW \| 51653.990 \| 71575.154 \|
587	JSON::PC \| 63884.157 \| 128528.212 \|	1219	JSON::PC \| 65948.176 \| 74631.744 \|
588	JSON::Syck \| 34898.677 \| 42096.911 \|	1220	JSON::PP \| 8931.652 \| 3817.168 \|
589	JSON::XS \| 654027.064 \| 396423.669 \|	1221	JSON::Syck \| 24877.248 \| 27776.848 \|
590	JSON::XS/2 \| 371564.190 \| 371725.613 \|	1222	JSON::XS \| 388361.481 \| 227951.304 \|
		1223	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		1224	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		1225	Storable \| 16500.016 \| 135300.129 \|
591	-----------+------------+------------+	1226	-----------+------------+------------+
592		1227
593	That is, JSON::XS is more than six times faster than JSON::DWIW on	1228	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
594	encoding, more than three times faster on decoding, and about thirty times	1229	about three times faster on decoding, and over forty times faster
595	faster than JSON, even with pretty-printing and key sorting.	1230	than JSON, even with pretty-printing and key sorting. It also compares
		1231	favourably to Storable for small amounts of data.
596		1232
597	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1233	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
598	search API (http://nanoref.com/yahooapis/mgPdGg):	1234	search API (L<http://dist.schmorp.de/misc/json/long.json>).
599		1235
600	module \| encode \| decode \|	1236	module \| encode \| decode \|
601	-----------\|------------\|------------\|	1237	-----------\|------------\|------------\|
602	JSON \| 273.023 \| 44.674 \|	1238	JSON 1.x \| 55.260 \| 34.971 \|
603	JSON::DWIW \| 1089.383 \| 1145.704 \|	1239	JSON::DWIW \| 825.228 \| 1082.513 \|
604	JSON::PC \| 3097.419 \| 2393.921 \|	1240	JSON::PC \| 3571.444 \| 2394.829 \|
605	JSON::Syck \| 514.060 \| 843.053 \|	1241	JSON::PP \| 210.987 \| 32.574 \|
606	JSON::XS \| 6479.668 \| 3636.364 \|	1242	JSON::Syck \| 552.551 \| 787.544 \|
607	JSON::XS/2 \| 3774.221 \| 3599.124 \|	1243	JSON::XS \| 5780.463 \| 4854.519 \|
		1244	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		1245	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		1246	Storable \| 4445.002 \| 5235.027 \|
608	-----------+------------+------------+	1247	-----------+------------+------------+
609		1248
610	Again, JSON::XS leads by far.	1249	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		1250	decodes faster).
611		1251
612	On large strings containing lots of high unicode characters, some modules	1252	On large strings containing lots of high Unicode characters, some modules
613	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1253	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
614	will be broken due to missing (or wrong) unicode handling. Others refuse	1254	will be broken due to missing (or wrong) Unicode handling. Others refuse
615	to decode or encode properly, so it was impossible to prepare a fair	1255	to decode or encode properly, so it was impossible to prepare a fair
616	comparison table for that case.	1256	comparison table for that case.
617		1257
618		1258
619	=head1 SECURITY CONSIDERATIONS	1259	=head1 SECURITY CONSIDERATIONS
…		…
625	any buffer overflows. Obviously, this module should ensure that and I am	1265	any buffer overflows. Obviously, this module should ensure that and I am
626	trying hard on making that true, but you never know.	1266	trying hard on making that true, but you never know.
627		1267
628	Second, you need to avoid resource-starving attacks. That means you should	1268	Second, you need to avoid resource-starving attacks. That means you should
629	limit the size of JSON texts you accept, or make sure then when your	1269	limit the size of JSON texts you accept, or make sure then when your
630	resources run out, thats just fine (e.g. by using a separate process that	1270	resources run out, that's just fine (e.g. by using a separate process that
631	can crash safely). The size of a JSON text in octets or characters is	1271	can crash safely). The size of a JSON text in octets or characters is
632	usually a good indication of the size of the resources required to decode	1272	usually a good indication of the size of the resources required to decode
633	it into a Perl structure.	1273	it into a Perl structure. While JSON::XS can check the size of the JSON
		1274	text, it might be too late when you already have it in memory, so you
		1275	might want to check the size before you accept the string.
634		1276
635	Third, JSON::XS recurses using the C stack when decoding objects and	1277	Third, JSON::XS recurses using the C stack when decoding objects and
636	arrays. The C stack is a limited resource: for instance, on my amd64	1278	arrays. The C stack is a limited resource: for instance, on my amd64
637	machine with 8MB of stack size I can decode around 180k nested arrays	1279	machine with 8MB of stack size I can decode around 180k nested arrays but
638	but only 14k nested JSON objects. If that is exceeded, the program	1280	only 14k nested JSON objects (due to perl itself recursing deeply on croak
639	crashes. Thats why the default nesting limit is set to 4096. If your	1281	to free the temporary). If that is exceeded, the program crashes. To be
		1282	conservative, the default nesting limit is set to 512. If your process
640	process has a smaller stack, you should adjust this setting accordingly	1283	has a smaller stack, you should adjust this setting accordingly with the
641	with the C<max_depth> method.	1284	C<max_depth> method.
642		1285
643	And last but least, something else could bomb you that I forgot to think	1286	Something else could bomb you, too, that I forgot to think of. In that
644	of. In that case, you get to keep the pieces. I am alway sopen for hints,	1287	case, you get to keep the pieces. I am always open for hints, though...
645	though...	1288
		1289	Also keep in mind that JSON::XS might leak contents of your Perl data
		1290	structures in its error messages, so when you serialise sensitive
		1291	information you might want to make sure that exceptions thrown by JSON::XS
		1292	will not end up in front of untrusted eyes.
		1293
		1294	If you are using JSON::XS to return packets to consumption
		1295	by JavaScript scripts in a browser you should have a look at
		1296	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
		1297	you are vulnerable to some common attack vectors (which really are browser
		1298	design bugs, but it is still you who will have to deal with it, as major
		1299	browser developers care only for features, not about getting security
		1300	right).
		1301
		1302
		1303	=head1 THREADS
		1304
		1305	This module is I<not> guaranteed to be thread safe and there are no
		1306	plans to change this until Perl gets thread support (as opposed to the
		1307	horribly slow so-called "threads" which are simply slow and bloated
		1308	process simulations - use fork, it's I<much> faster, cheaper, better).
		1309
		1310	(It might actually work, but you have been warned).
646		1311
647		1312
648	=head1 BUGS	1313	=head1 BUGS
649		1314
650	While the goal of this module is to be correct, that unfortunately does	1315	While the goal of this module is to be correct, that unfortunately does
651	not mean its bug-free, only that I think its design is bug-free. It is	1316	not mean it's bug-free, only that I think its design is bug-free. It is
652	still relatively early in its development. If you keep reporting bugs they	1317	still relatively early in its development. If you keep reporting bugs they
653	will be fixed swiftly, though.	1318	will be fixed swiftly, though.
654		1319
		1320	Please refrain from using rt.cpan.org or any other bug reporting
		1321	service. I put the contact address into my modules for a reason.
		1322
655	=cut	1323	=cut
656		1324
		1325	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1326	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1327
657	sub true() { \1 }	1328	sub true() { $true }
658	sub false() { \0 }	1329	sub false() { $false }
		1330
		1331	sub is_bool($) {
		1332	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1333	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1334	}
		1335
		1336	XSLoader::load "JSON::XS", $VERSION;
		1337
		1338	package JSON::XS::Boolean;
		1339
		1340	use overload
		1341	"0+" => sub { ${$_[0]} },
		1342	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1343	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1344	fallback => 1;
659		1345
660	1;	1346	1;
		1347
		1348	=head1 SEE ALSO
		1349
		1350	The F<json_xs> command line utility for quick experiments.
661		1351
662	=head1 AUTHOR	1352	=head1 AUTHOR
663		1353
664	Marc Lehmann <schmorp@schmorp.de>	1354	Marc Lehmann <schmorp@schmorp.de>
665	http://home.schmorp.de/	1355	http://home.schmorp.de/

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.27 by root, Tue Apr 3 01:25:40 2007 UTC vs. Revision 1.95 by root, Tue Mar 25 16:56:09 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.27 by root, Tue Apr 3 01:25:40 2007 UTC vs.
Revision 1.95 by root, Tue Mar 25 16:56:09 2008 UTC