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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

…		…
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
		8
		9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
		11
		12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		14
		15	# OO-interface
		16
		17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		19	$perl_scalar = $coder->decode ($unicode_json_text);
8		20
9	=head1 DESCRIPTION	21	=head1 DESCRIPTION
10		22
11	This module converts Perl data structures to JSON and vice versa. Its	23	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	24	primary goal is to be I<correct> and its secondary goal is to be
…		…
18	their maintainers are unresponsive, gone missing, or not listening to bug	30	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	31	reports for other reasons.
20		32
21	See COMPARISON, below, for a comparison to some other JSON modules.	33	See COMPARISON, below, for a comparison to some other JSON modules.
22		34
		35	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		36	vice versa.
		37
23	=head2 FEATURES	38	=head2 FEATURES
24		39
25	=over 4	40	=over 4
26		41
27	=item * correct handling of unicode issues	42	=item * correct unicode handling
28		43
29	This module knows how to handle Unicode, and even documents how it does so.	44	This module knows how to handle Unicode, and even documents how and when
		45	it does so.
30		46
31	=item * round-trip integrity	47	=item * round-trip integrity
32		48
33	When you serialise a perl data structure using only datatypes supported	49	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	50	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		52	like a number).
36		53
37	=item * strict checking of JSON correctness	54	=item * strict checking of JSON correctness
38		55
39	There is no guessing, no generating of illegal JSON strings by default,	56	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	57	and only JSON is accepted as input by default (the latter is a security
		58	feature).
41		59
42	=item * fast	60	=item * fast
43		61
44	compared to other JSON modules, this module compares favourably.	62	Compared to other JSON modules, this module compares favourably in terms
		63	of speed, too.
45		64
46	=item * simple to use	65	=item * simple to use
47		66
48	This module has both a simple functional interface as well as an OO	67	This module has both a simple functional interface as well as an OO
49	interface.	68	interface.
50		69
51	=item * reasonably versatile output formats	70	=item * reasonably versatile output formats
52		71
53	You can choose between the most compact format possible, a pure-ascii	72	You can choose between the most compact guarenteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	73	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	74	(for when your transport is not 8-bit clean, still supports the whole
		75	unicode range), or a pretty-printed format (for when you want to read that
		76	stuff). Or you can combine those features in whatever way you like.
56		77
57	=back	78	=back
58		79
59	=cut	80	=cut
60		81
61	package JSON::XS;	82	package JSON::XS;
62		83
63	BEGIN {	84	use strict;
		85
64	$VERSION = '0.1';	86	our $VERSION = '1.5';
65	@ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
66		88
67	@EXPORT = qw(to_json from_json);	89	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		90
70	require XSLoader;	91	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
72	}
73		93
74	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
75		95
76	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
77	exported by default:	97	exported by default:
78		98
79	=over 4	99	=over 4
80		100
81	=item $json_string = to_json $perl_scalar	101	=item $json_text = to_json $perl_scalar
82		102
83	Converts the given Perl data structure (a simple scalar or a reference to	103	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	105	octets only). Croaks on error.
86		106
87	This function call is functionally identical to C<< JSON::XS->new->utf8	107	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		108
		109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		110
		111	except being faster.
		112
90	=item $perl_scalar = from_json $json_string	113	=item $perl_scalar = from_json $json_text
91		114
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	116	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	117	scalar or reference. Croaks on error.
95		118
96	This function call is functionally identical to C<< JSON::XS->new->utf8	119	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	120
		121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		122
		123	except being faster.
		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
98		133
99	=back	134	=back
		135
100		136
101	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
102		138
103	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	147	strings. All boolean flags described below are by default I<disabled>.
112		148
113	The mutators for flags all return the JSON object again and thus calls can	149	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	150	be chained:
115		151
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	153	=> {"a": [1, 2]}
118		154
119	=item $json = $json->ascii ($enable)	155	=item $json = $json->ascii ([$enable])
120		156
121	If C<$enable> is true, then the C<encode> method will not generate	157	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	158	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	159	unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		161	as per RFC4627. The resulting encoded JSON text can be treated as a native
		162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		163	or any other superset of ASCII.
125		164
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	165	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	166	characters unless required by the JSON syntax or other flags. This results
		167	in a faster and more compact format.
128		168
		169	The main use for this flag is to produce JSON texts that can be
		170	transmitted over a 7-bit channel, as the encoded JSON texts will not
		171	contain any 8 bit characters.
		172
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	174	=> ["\ud801\udc01"]
131		175
		176	=item $json = $json->latin1 ([$enable])
		177
		178	If C<$enable> is true (or missing), then the C<encode> method will encode
		179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		180	outside the code range C<0..255>. The resulting string can be treated as a
		181	latin1-encoded JSON text or a native unicode string. The C<decode> method
		182	will not be affected in any way by this flag, as C<decode> by default
		183	expects unicode, which is a strict superset of latin1.
		184
		185	If C<$enable> is false, then the C<encode> method will not escape Unicode
		186	characters unless required by the JSON syntax or other flags.
		187
		188	The main use for this flag is efficiently encoding binary data as JSON
		189	text, as most octets will not be escaped, resulting in a smaller encoded
		190	size. The disadvantage is that the resulting JSON text is encoded
		191	in latin1 (and must correctly be treated as such when storing and
		192	transfering), a rare encoding for JSON. It is therefore most useful when
		193	you want to store data structures known to contain binary data efficiently
		194	in files or databases, not when talking to other JSON encoders/decoders.
		195
		196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		198
132	=item $json = $json->utf8 ($enable)	199	=item $json = $json->utf8 ([$enable])
133		200
134	If C<$enable> is true, then the C<encode> method will encode the JSON	201	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	202	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	203	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	204	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		206	versions, enabling this option might enable autodetection of the UTF-16
		207	and UTF-32 encoding families, as described in RFC4627.
139		208
140	If C<$enable> is false, then the C<encode> method will return the JSON	209	If C<$enable> is false, then the C<encode> method will return the JSON
141	string as a (non-encoded) unicode string, while C<decode> expects thus a	210	string as a (non-encoded) unicode string, while C<decode> expects thus a
142	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
143	to be done yourself, e.g. using the Encode module.	212	to be done yourself, e.g. using the Encode module.
144		213
		214	Example, output UTF-16BE-encoded JSON:
		215
		216	use Encode;
		217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		218
		219	Example, decode UTF-32LE-encoded JSON:
		220
		221	use Encode;
		222	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		223
145	=item $json = $json->pretty ($enable)	224	=item $json = $json->pretty ([$enable])
146		225
147	This enables (or disables) all of the C<indent>, C<space_before> and	226	This enables (or disables) all of the C<indent>, C<space_before> and
148	C<space_after> (and in the future possibly more) flags in one call to	227	C<space_after> (and in the future possibly more) flags in one call to
149	generate the most readable (or most compact) form possible.	228	generate the most readable (or most compact) form possible.
		229
		230	Example, pretty-print some simple structure:
150		231
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	232	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	233	=>
153	{	234	{
154	"a" : [	235	"a" : [
155	1,	236	1,
156	2	237	2
157	]	238	]
158	}	239	}
159		240
160	=item $json = $json->indent ($enable)	241	=item $json = $json->indent ([$enable])
161		242
162	If C<$enable> is true, then the C<encode> method will use a multiline	243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	244	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	245	into its own line, identing them properly.
165		246
166	If C<$enable> is false, no newlines or indenting will be produced, and the	247	If C<$enable> is false, no newlines or indenting will be produced, and the
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	248	resulting JSON text is guarenteed not to contain any C<newlines>.
168		249
169	This setting has no effect when decoding JSON strings.	250	This setting has no effect when decoding JSON texts.
170		251
171	=item $json = $json->space_before ($enable)	252	=item $json = $json->space_before ([$enable])
172		253
173	If C<$enable> is true, then the C<encode> method will add an extra	254	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	255	optional space before the C<:> separating keys from values in JSON objects.
175		256
176	If C<$enable> is false, then the C<encode> method will not add any extra	257	If C<$enable> is false, then the C<encode> method will not add any extra
177	space at those places.	258	space at those places.
178		259
179	This setting has no effect when decoding JSON strings. You will also most	260	This setting has no effect when decoding JSON texts. You will also
180	likely combine this setting with C<space_after>.	261	most likely combine this setting with C<space_after>.
181		262
		263	Example, space_before enabled, space_after and indent disabled:
		264
		265	{"key" :"value"}
		266
182	=item $json = $json->space_after ($enable)	267	=item $json = $json->space_after ([$enable])
183		268
184	If C<$enable> is true, then the C<encode> method will add an extra	269	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	270	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	271	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	272	members.
188		273
189	If C<$enable> is false, then the C<encode> method will not add any extra	274	If C<$enable> is false, then the C<encode> method will not add any extra
190	space at those places.	275	space at those places.
191		276
192	This setting has no effect when decoding JSON strings.	277	This setting has no effect when decoding JSON texts.
193		278
		279	Example, space_before and indent disabled, space_after enabled:
		280
		281	{"key": "value"}
		282
		283	=item $json = $json->relaxed ([$enable])
		284
		285	If C<$enable> is true (or missing), then C<decode> will accept some
		286	extensions to normal JSON syntax (see below). C<encode> will not be
		287	affected in anyway. I<Be aware that this option makes you accept invalid
		288	JSON texts as if they were valid!>. I suggest only to use this option to
		289	parse application-specific files written by humans (configuration files,
		290	resource files etc.)
		291
		292	If C<$enable> is false (the default), then C<decode> will only accept
		293	valid JSON texts.
		294
		295	Currently accepted extensions are:
		296
		297	=over 4
		298
		299	=item * list items can have an end-comma
		300
		301	JSON I<separates> array elements and key-value pairs with commas. This
		302	can be annoying if you write JSON texts manually and want to be able to
		303	quickly append elements, so this extension accepts comma at the end of
		304	such items not just between them:
		305
		306	[
		307	1,
		308	2, <- this comma not normally allowed
		309	]
		310	{
		311	"k1": "v1",
		312	"k2": "v2", <- this comma not normally allowed
		313	}
		314
		315	=back
		316
194	=item $json = $json->canonical ($enable)	317	=item $json = $json->canonical ([$enable])
195		318
196	If C<$enable> is true, then the C<encode> method will output JSON objects	319	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	320	by sorting their keys. This is adding a comparatively high overhead.
198		321
199	If C<$enable> is false, then the C<encode> method will output key-value	322	If C<$enable> is false, then the C<encode> method will output key-value
200	pairs in the order Perl stores them (which will likely change between runs	323	pairs in the order Perl stores them (which will likely change between runs
201	of the same script).	324	of the same script).
202		325
203	This option is useful if you want the same data structure to be encoded as	326	This option is useful if you want the same data structure to be encoded as
204	the same JSON string (given the same overall settings). If it is disabled,	327	the same JSON text (given the same overall settings). If it is disabled,
205	the same hash migh be encoded differently even if contains the same data,	328	the same hash migh be encoded differently even if contains the same data,
206	as key-value pairs have no inherent ordering in Perl.	329	as key-value pairs have no inherent ordering in Perl.
207		330
208	This setting has no effect when decoding JSON strings.	331	This setting has no effect when decoding JSON texts.
209		332
210	=item $json = $json->allow_nonref ($enable)	333	=item $json = $json->allow_nonref ([$enable])
211		334
212	If C<$enable> is true, then the C<encode> method can convert a	335	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	336	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	337	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	338	values instead of croaking.
216		339
217	If C<$enable> is false, then the C<encode> method will croak if it isn't	340	If C<$enable> is false, then the C<encode> method will croak if it isn't
218	passed an arrayref or hashref, as JSON strings must either be an object	341	passed an arrayref or hashref, as JSON texts must either be an object
219	or array. Likewise, C<decode> will croak if given something that is not a	342	or array. Likewise, C<decode> will croak if given something that is not a
220	JSON object or array.	343	JSON object or array.
221		344
		345	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		346	resulting in an invalid JSON text:
		347
		348	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		349	=> "Hello, World!"
		350
		351	=item $json = $json->allow_blessed ([$enable])
		352
		353	If C<$enable> is true (or missing), then the C<encode> method will not
		354	barf when it encounters a blessed reference. Instead, the value of the
		355	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		356	disabled or no C<to_json> method found) or a representation of the
		357	object (C<convert_blessed> enabled and C<to_json> method found) is being
		358	encoded. Has no effect on C<decode>.
		359
		360	If C<$enable> is false (the default), then C<encode> will throw an
		361	exception when it encounters a blessed object.
		362
		363	=item $json = $json->convert_blessed ([$enable])
		364
		365	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		366	blessed object, will check for the availability of the C<TO_JSON> method
		367	on the object's class. If found, it will be called in scalar context
		368	and the resulting scalar will be encoded instead of the object. If no
		369	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		370	to do.
		371
		372	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		373	returns other blessed objects, those will be handled in the same
		374	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		375	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		376	methods called by the Perl core (== not by the user of the object) are
		377	usually in upper case letters and to avoid collisions with the C<to_json>
		378	function.
		379
		380	This setting does not yet influence C<decode> in any way, but in the
		381	future, global hooks might get installed that influence C<decode> and are
		382	enabled by this setting.
		383
		384	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		385	to do when a blessed object is found.
		386
		387	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		388
		389	When C<$coderef> is specified, it will be called from C<decode> each
		390	time it decodes a JSON object. The only argument is a reference to the
		391	newly-created hash. If the code references returns a single scalar (which
		392	need not be a reference), this value (i.e. a copy of that scalar to avoid
		393	aliasing) is inserted into the deserialised data structure. If it returns
		394	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		395	original deserialised hash will be inserted. This setting can slow down
		396	decoding considerably.
		397
		398	When C<$coderef> is omitted or undefined, any existing callback will
		399	be removed and C<decode> will not change the deserialised hash in any
		400	way.
		401
		402	Example, convert all JSON objects into the integer 5:
		403
		404	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		405	# returns [5]
		406	$js->decode ('[{}]')
		407	# throw an exception because allow_nonref is not enabled
		408	# so a lone 5 is not allowed.
		409	$js->decode ('{"a":1, "b":2}');
		410
		411	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		412
		413	Works remotely similar to C<filter_json_object>, but is only called for
		414	JSON objects having a single key named C<$key>.
		415
		416	This C<$coderef> is called before the one specified via
		417	C<filter_json_object>, if any. It gets passed the single value in the JSON
		418	object. If it returns a single value, it will be inserted into the data
		419	structure. If it returns nothing (not even C<undef> but the empty list),
		420	the callback from C<filter_json_object> will be called next, as if no
		421	single-key callback were specified.
		422
		423	If C<$coderef> is omitted or undefined, the corresponding callback will be
		424	disabled. There can only ever be one callback for a given key.
		425
		426	As this callback gets called less often then the C<filter_json_object>
		427	one, decoding speed will not usually suffer as much. Therefore, single-key
		428	objects make excellent targets to serialise Perl objects into, especially
		429	as single-key JSON objects are as close to the type-tagged value concept
		430	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		431	support this in any way, so you need to make sure your data never looks
		432	like a serialised Perl hash.
		433
		434	Typical names for the single object key are C<__class_whatever__>, or
		435	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		436	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		437	with real hashes.
		438
		439	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		440	into the corresponding C<< $WIDGET{<id>} >> object:
		441
		442	# return whatever is in $WIDGET{5}:
		443	JSON::XS
		444	->new
		445	->filter_json_single_key_object (__widget__ => sub {
		446	$WIDGET{ $_[0] }
		447	})
		448	->decode ('{"__widget__": 5')
		449
		450	# this can be used with a TO_JSON method in some "widget" class
		451	# for serialisation to json:
		452	sub WidgetBase::TO_JSON {
		453	my ($self) = @_;
		454
		455	unless ($self->{id}) {
		456	$self->{id} = ..get..some..id..;
		457	$WIDGET{$self->{id}} = $self;
		458	}
		459
		460	{ __widget__ => $self->{id} }
		461	}
		462
		463	=item $json = $json->shrink ([$enable])
		464
		465	Perl usually over-allocates memory a bit when allocating space for
		466	strings. This flag optionally resizes strings generated by either
		467	C<encode> or C<decode> to their minimum size possible. This can save
		468	memory when your JSON texts are either very very long or you have many
		469	short strings. It will also try to downgrade any strings to octet-form
		470	if possible: perl stores strings internally either in an encoding called
		471	UTF-X or in octet-form. The latter cannot store everything but uses less
		472	space in general (and some buggy Perl or C code might even rely on that
		473	internal representation being used).
		474
		475	The actual definition of what shrink does might change in future versions,
		476	but it will always try to save space at the expense of time.
		477
		478	If C<$enable> is true (or missing), the string returned by C<encode> will
		479	be shrunk-to-fit, while all strings generated by C<decode> will also be
		480	shrunk-to-fit.
		481
		482	If C<$enable> is false, then the normal perl allocation algorithms are used.
		483	If you work with your data, then this is likely to be faster.
		484
		485	In the future, this setting might control other things, such as converting
		486	strings that look like integers or floats into integers or floats
		487	internally (there is no difference on the Perl level), saving space.
		488
		489	=item $json = $json->max_depth ([$maximum_nesting_depth])
		490
		491	Sets the maximum nesting level (default C<512>) accepted while encoding
		492	or decoding. If the JSON text or Perl data structure has an equal or
		493	higher nesting level then this limit, then the encoder and decoder will
		494	stop and croak at that point.
		495
		496	Nesting level is defined by number of hash- or arrayrefs that the encoder
		497	needs to traverse to reach a given point or the number of C<{> or C<[>
		498	characters without their matching closing parenthesis crossed to reach a
		499	given character in a string.
		500
		501	Setting the maximum depth to one disallows any nesting, so that ensures
		502	that the object is only a single hash/object or array.
		503
		504	The argument to C<max_depth> will be rounded up to the next highest power
		505	of two. If no argument is given, the highest possible setting will be
		506	used, which is rarely useful.
		507
		508	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		509
		510	=item $json = $json->max_size ([$maximum_string_size])
		511
		512	Set the maximum length a JSON text may have (in bytes) where decoding is
		513	being attempted. The default is C<0>, meaning no limit. When C<decode>
		514	is called on a string longer then this number of characters it will not
		515	attempt to decode the string but throw an exception. This setting has no
		516	effect on C<encode> (yet).
		517
		518	The argument to C<max_size> will be rounded up to the next B<highest>
		519	power of two (so may be more than requested). If no argument is given, the
		520	limit check will be deactivated (same as when C<0> is specified).
		521
		522	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		523
222	=item $json_string = $json->encode ($perl_scalar)	524	=item $json_text = $json->encode ($perl_scalar)
223		525
224	Converts the given Perl data structure (a simple scalar or a reference	526	Converts the given Perl data structure (a simple scalar or a reference
225	to a hash or array) to its JSON representation. Simple scalars will be	527	to a hash or array) to its JSON representation. Simple scalars will be
226	converted into JSON string or number sequences, while references to arrays	528	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	529	become JSON arrays and references to hashes become JSON objects. Undefined
228	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	530	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	531	nor C<false> values will be generated.
230		532
231	=item $perl_scalar = $json->decode ($json_string)	533	=item $perl_scalar = $json->decode ($json_text)
232		534
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	535	The opposite of C<encode>: expects a JSON text and tries to parse it,
234	returning the resulting simple scalar or reference. Croaks on error.	536	returning the resulting simple scalar or reference. Croaks on error.
235		537
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	538	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	539	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
238	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	540	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		541
		542	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		543
		544	This works like the C<decode> method, but instead of raising an exception
		545	when there is trailing garbage after the first JSON object, it will
		546	silently stop parsing there and return the number of characters consumed
		547	so far.
		548
		549	This is useful if your JSON texts are not delimited by an outer protocol
		550	(which is not the brightest thing to do in the first place) and you need
		551	to know where the JSON text ends.
		552
		553	JSON::XS->new->decode_prefix ("[1] the tail")
		554	=> ([], 3)
		555
240	=back	556	=back
		557
		558
		559	=head1 MAPPING
		560
		561	This section describes how JSON::XS maps Perl values to JSON values and
		562	vice versa. These mappings are designed to "do the right thing" in most
		563	circumstances automatically, preserving round-tripping characteristics
		564	(what you put in comes out as something equivalent).
		565
		566	For the more enlightened: note that in the following descriptions,
		567	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		568	refers to the abstract Perl language itself.
		569
		570
		571	=head2 JSON -> PERL
		572
		573	=over 4
		574
		575	=item object
		576
		577	A JSON object becomes a reference to a hash in Perl. No ordering of object
		578	keys is preserved (JSON does not preserver object key ordering itself).
		579
		580	=item array
		581
		582	A JSON array becomes a reference to an array in Perl.
		583
		584	=item string
		585
		586	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		587	are represented by the same codepoints in the Perl string, so no manual
		588	decoding is necessary.
		589
		590	=item number
		591
		592	A JSON number becomes either an integer, numeric (floating point) or
		593	string scalar in perl, depending on its range and any fractional parts. On
		594	the Perl level, there is no difference between those as Perl handles all
		595	the conversion details, but an integer may take slightly less memory and
		596	might represent more values exactly than (floating point) numbers.
		597
		598	If the number consists of digits only, JSON::XS will try to represent
		599	it as an integer value. If that fails, it will try to represent it as
		600	a numeric (floating point) value if that is possible without loss of
		601	precision. Otherwise it will preserve the number as a string value.
		602
		603	Numbers containing a fractional or exponential part will always be
		604	represented as numeric (floating point) values, possibly at a loss of
		605	precision.
		606
		607	This might create round-tripping problems as numbers might become strings,
		608	but as Perl is typeless there is no other way to do it.
		609
		610	=item true, false
		611
		612	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		613	respectively. They are overloaded to act almost exactly like the numbers
		614	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		615	the C<JSON::XS::is_bool> function.
		616
		617	=item null
		618
		619	A JSON null atom becomes C<undef> in Perl.
		620
		621	=back
		622
		623
		624	=head2 PERL -> JSON
		625
		626	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		627	truly typeless language, so we can only guess which JSON type is meant by
		628	a Perl value.
		629
		630	=over 4
		631
		632	=item hash references
		633
		634	Perl hash references become JSON objects. As there is no inherent ordering
		635	in hash keys (or JSON objects), they will usually be encoded in a
		636	pseudo-random order that can change between runs of the same program but
		637	stays generally the same within a single run of a program. JSON::XS can
		638	optionally sort the hash keys (determined by the I<canonical> flag), so
		639	the same datastructure will serialise to the same JSON text (given same
		640	settings and version of JSON::XS), but this incurs a runtime overhead
		641	and is only rarely useful, e.g. when you want to compare some JSON text
		642	against another for equality.
		643
		644	=item array references
		645
		646	Perl array references become JSON arrays.
		647
		648	=item other references
		649
		650	Other unblessed references are generally not allowed and will cause an
		651	exception to be thrown, except for references to the integers C<0> and
		652	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		653	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		654
		655	to_json [\0,JSON::XS::true] # yields [false,true]
		656
		657	=item JSON::XS::true, JSON::XS::false
		658
		659	These special values become JSON true and JSON false values,
		660	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		661
		662	=item blessed objects
		663
		664	Blessed objects are not allowed. JSON::XS currently tries to encode their
		665	underlying representation (hash- or arrayref), but this behaviour might
		666	change in future versions.
		667
		668	=item simple scalars
		669
		670	Simple Perl scalars (any scalar that is not a reference) are the most
		671	difficult objects to encode: JSON::XS will encode undefined scalars as
		672	JSON null value, scalars that have last been used in a string context
		673	before encoding as JSON strings and anything else as number value:
		674
		675	# dump as number
		676	to_json [2] # yields [2]
		677	to_json [-3.0e17] # yields [-3e+17]
		678	my $value = 5; to_json [$value] # yields [5]
		679
		680	# used as string, so dump as string
		681	print $value;
		682	to_json [$value] # yields ["5"]
		683
		684	# undef becomes null
		685	to_json [undef] # yields [null]
		686
		687	You can force the type to be a string by stringifying it:
		688
		689	my $x = 3.1; # some variable containing a number
		690	"$x"; # stringified
		691	$x .= ""; # another, more awkward way to stringify
		692	print $x; # perl does it for you, too, quite often
		693
		694	You can force the type to be a number by numifying it:
		695
		696	my $x = "3"; # some variable containing a string
		697	$x += 0; # numify it, ensuring it will be dumped as a number
		698	$x *= 1; # same thing, the choise is yours.
		699
		700	You can not currently output JSON booleans or force the type in other,
		701	less obscure, ways. Tell me if you need this capability.
		702
		703	=back
		704
241		705
242	=head1 COMPARISON	706	=head1 COMPARISON
243		707
244	As already mentioned, this module was created because none of the existing	708	As already mentioned, this module was created because none of the existing
245	JSON modules could be made to work correctly. First I will describe the	709	JSON modules could be made to work correctly. First I will describe the
…		…
271		735
272	Has problems handling many Perl values (e.g. regex results and other magic	736	Has problems handling many Perl values (e.g. regex results and other magic
273	values will make it croak).	737	values will make it croak).
274		738
275	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	739	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
276	which is not a valid JSON string.	740	which is not a valid JSON text.
277		741
278	Unmaintained (maintainer unresponsive for many months, bugs are not	742	Unmaintained (maintainer unresponsive for many months, bugs are not
279	getting fixed).	743	getting fixed).
280		744
281	=item JSON::Syck 0.21	745	=item JSON::Syck 0.21
…		…
283	Very buggy (often crashes).	747	Very buggy (often crashes).
284		748
285	Very inflexible (no human-readable format supported, format pretty much	749	Very inflexible (no human-readable format supported, format pretty much
286	undocumented. I need at least a format for easy reading by humans and a	750	undocumented. I need at least a format for easy reading by humans and a
287	single-line compact format for use in a protocol, and preferably a way to	751	single-line compact format for use in a protocol, and preferably a way to
288	generate ASCII-only JSON strings).	752	generate ASCII-only JSON texts).
289		753
290	Completely broken (and confusingly documented) Unicode handling (unicode	754	Completely broken (and confusingly documented) Unicode handling (unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	755	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	756	I<different> values on en- and decoding to get symmetric behaviour).
293		757
…		…
316		780
317	Very inflexible.	781	Very inflexible.
318		782
319	No roundtripping.	783	No roundtripping.
320		784
321	Does not generate valid JSON (key strings are often unquoted, empty keys	785	Does not generate valid JSON texts (key strings are often unquoted, empty keys
322	result in nothing being output)	786	result in nothing being output)
323		787
324	Does not check input for validity.	788	Does not check input for validity.
325		789
326	=back	790	=back
		791
		792
		793	=head2 JSON and YAML
		794
		795	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		796	however, a mass hysteria and very far from the truth. In general, there is
		797	no way to configure JSON::XS to output a data structure as valid YAML.
		798
		799	If you really must use JSON::XS to generate YAML, you should use this
		800	algorithm (subject to change in future versions):
		801
		802	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		803	my $yaml = $to_yaml->encode ($ref) . "\n";
		804
		805	This will usually generate JSON texts that also parse as valid
		806	YAML. Please note that YAML has hardcoded limits on (simple) object key
		807	lengths that JSON doesn't have, so you should make sure that your hash
		808	keys are noticably shorter than the 1024 characters YAML allows.
		809
		810	There might be other incompatibilities that I am not aware of. In general
		811	you should not try to generate YAML with a JSON generator or vice versa,
		812	or try to parse JSON with a YAML parser or vice versa: chances are high
		813	that you will run into severe interoperability problems.
		814
327		815
328	=head2 SPEED	816	=head2 SPEED
329		817
330	It seems that JSON::XS is surprisingly fast, as shown in the following	818	It seems that JSON::XS is surprisingly fast, as shown in the following
331	tables. They have been generated with the help of the C<eg/bench> program	819	tables. They have been generated with the help of the C<eg/bench> program
332	in the JSON::XS distribution, to make it easy to compare on your own	820	in the JSON::XS distribution, to make it easy to compare on your own
333	system.	821	system.
334		822
335	First is a comparison between various modules using a very simple JSON	823	First comes a comparison between various modules using a very short
		824	single-line JSON string:
		825
		826	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		827	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		828
336	string, showing the number of encodes/decodes per second (JSON::XS is	829	It shows the number of encodes/decodes per second (JSON::XS uses
337	the functional interface, while JSON::XS/2 is the OO interface with	830	the functional interface, while JSON::XS/2 uses the OO interface
338	pretty-printing and hashkey sorting enabled).	831	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		832	shrink). Higher is better:
339		833
		834	Storable \| 15779.925 \| 14169.946 \|
		835	-----------+------------+------------+
340	module \| encode \| decode \|	836	module \| encode \| decode \|
341	-----------\|------------\|------------\|	837	-----------\|------------\|------------\|
342	JSON \| 14006 \| 6820 \|	838	JSON \| 4990.842 \| 4088.813 \|
343	JSON::DWIW \| 200937 \| 120386 \|	839	JSON::DWIW \| 51653.990 \| 71575.154 \|
344	JSON::PC \| 85065 \| 129366 \|	840	JSON::PC \| 65948.176 \| 74631.744 \|
345	JSON::Syck \| 59898 \| 44232 \|	841	JSON::PP \| 8931.652 \| 3817.168 \|
346	JSON::XS \| 1171478 \| 342435 \|	842	JSON::Syck \| 24877.248 \| 27776.848 \|
347	JSON::XS/2 \| 730760 \| 328714 \|	843	JSON::XS \| 388361.481 \| 227951.304 \|
		844	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		845	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		846	Storable \| 16500.016 \| 135300.129 \|
348	-----------+------------+------------+	847	-----------+------------+------------+
349		848
350	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	849	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		850	about three times faster on decoding, and over fourty times faster
351	times faster than JSON, even with pretty-printing and key sorting.	851	than JSON, even with pretty-printing and key sorting. It also compares
		852	favourably to Storable for small amounts of data.
352		853
353	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	854	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
354	search API (http://nanoref.com/yahooapis/mgPdGg):	855	search API (http://nanoref.com/yahooapis/mgPdGg):
355		856
356	module \| encode \| decode \|	857	module \| encode \| decode \|
357	-----------\|------------\|------------\|	858	-----------\|------------\|------------\|
358	JSON \| 673 \| 38 \|	859	JSON \| 55.260 \| 34.971 \|
359	JSON::DWIW \| 5271 \| 770 \|	860	JSON::DWIW \| 825.228 \| 1082.513 \|
360	JSON::PC \| 9901 \| 2491 \|	861	JSON::PC \| 3571.444 \| 2394.829 \|
361	JSON::Syck \| 2360 \| 786 \|	862	JSON::PP \| 210.987 \| 32.574 \|
362	JSON::XS \| 37398 \| 3202 \|	863	JSON::Syck \| 552.551 \| 787.544 \|
363	JSON::XS/2 \| 13765 \| 3153 \|	864	JSON::XS \| 5780.463 \| 4854.519 \|
		865	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		866	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		867	Storable \| 4445.002 \| 5235.027 \|
364	-----------+------------+------------+	868	-----------+------------+------------+
365		869
366	Again, JSON::XS leads by far in the encoding case, while still beating	870	Again, JSON::XS leads by far (except for Storable which non-surprisingly
367	every other module in the decoding case.	871	decodes faster).
368		872
369	Last example is an almost 8MB large hash with many large binary values	873	On large strings containing lots of high unicode characters, some modules
370	(PNG files), resulting in a lot of escaping:	874	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		875	will be broken due to missing (or wrong) unicode handling. Others refuse
		876	to decode or encode properly, so it was impossible to prepare a fair
		877	comparison table for that case.
		878
		879
		880	=head1 SECURITY CONSIDERATIONS
		881
		882	When you are using JSON in a protocol, talking to untrusted potentially
		883	hostile creatures requires relatively few measures.
		884
		885	First of all, your JSON decoder should be secure, that is, should not have
		886	any buffer overflows. Obviously, this module should ensure that and I am
		887	trying hard on making that true, but you never know.
		888
		889	Second, you need to avoid resource-starving attacks. That means you should
		890	limit the size of JSON texts you accept, or make sure then when your
		891	resources run out, thats just fine (e.g. by using a separate process that
		892	can crash safely). The size of a JSON text in octets or characters is
		893	usually a good indication of the size of the resources required to decode
		894	it into a Perl structure. While JSON::XS can check the size of the JSON
		895	text, it might be too late when you already have it in memory, so you
		896	might want to check the size before you accept the string.
		897
		898	Third, JSON::XS recurses using the C stack when decoding objects and
		899	arrays. The C stack is a limited resource: for instance, on my amd64
		900	machine with 8MB of stack size I can decode around 180k nested arrays but
		901	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		902	to free the temporary). If that is exceeded, the program crashes. to be
		903	conservative, the default nesting limit is set to 512. If your process
		904	has a smaller stack, you should adjust this setting accordingly with the
		905	C<max_depth> method.
		906
		907	And last but least, something else could bomb you that I forgot to think
		908	of. In that case, you get to keep the pieces. I am always open for hints,
		909	though...
		910
		911	If you are using JSON::XS to return packets to consumption
		912	by javascript scripts in a browser you should have a look at
		913	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		914	you are vulnerable to some common attack vectors (which really are browser
		915	design bugs, but it is still you who will have to deal with it, as major
		916	browser developers care only for features, not about doing security
		917	right).
		918
371		919
372	=head1 BUGS	920	=head1 BUGS
373		921
374	While the goal of this module is to be correct, that unfortunately does	922	While the goal of this module is to be correct, that unfortunately does
375	not mean its bug-free, only that I think its design is bug-free. It is	923	not mean its bug-free, only that I think its design is bug-free. It is
376	still very young and not well-tested. If you keep reporting bugs they will	924	still relatively early in its development. If you keep reporting bugs they
377	be fixed swiftly, though.	925	will be fixed swiftly, though.
378		926
379	=cut	927	=cut
		928
		929	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		930	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		931
		932	sub true() { $true }
		933	sub false() { $false }
		934
		935	sub is_bool($) {
		936	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		937	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		938	}
		939
		940	XSLoader::load "JSON::XS", $VERSION;
		941
		942	package JSON::XS::Boolean;
		943
		944	use overload
		945	"0+" => sub { ${$_[0]} },
		946	"++" => sub { $_[0] = ${$_[0]} + 1 },
		947	"--" => sub { $_[0] = ${$_[0]} - 1 },
		948	fallback => 1;
380		949
381	1;	950	1;
382		951
383	=head1 AUTHOR	952	=head1 AUTHOR
384		953

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Comparing JSON-XS/XS.pm (file contents): Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs. Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.5 by root, Thu Mar 22 21:36:52 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC