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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.2 by root, Thu Mar 22 17:28:50 2007 UTC vs.
Revision 1.54 by root, Tue Jul 10 16:22:31 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 = '1.41';
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)->pretty(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
		173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
		174	=> ["\ud801\udc01"]
		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
129	=item $json = $json->utf8 ($enable)	199	=item $json = $json->utf8 ([$enable])
130		200
131	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
132	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
133	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
134	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
135	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.
136		208
137	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
138	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
139	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
140	to be done yourself, e.g. using the Encode module.	212	to be done yourself, e.g. using the Encode module.
141		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
142	=item $json = $json->pretty ($enabla)	224	=item $json = $json->pretty ([$enable])
143		225
144	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
145	C<space_after> (and in the future possibly more) settings in one call to	227	C<space_after> (and in the future possibly more) flags in one call to
146	generate the most readable (or most compact) form possible.	228	generate the most readable (or most compact) form possible.
147		229
		230	Example, pretty-print some simple structure:
		231
		232	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
		233	=>
		234	{
		235	"a" : [
		236	1,
		237	2
		238	]
		239	}
		240
148	=item $json = $json->indent ($enable)	241	=item $json = $json->indent ([$enable])
149		242
150	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
151	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
152	into its own line, identing them properly.	245	into its own line, identing them properly.
153		246
154	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
155	resulting JSON strings is guarenteed not to contain any C<newlines>.	248	resulting JSON text is guarenteed not to contain any C<newlines>.
156		249
157	This setting has no effect when decoding JSON strings.	250	This setting has no effect when decoding JSON texts.
158		251
159	=item $json = $json->space_before ($enable)	252	=item $json = $json->space_before ([$enable])
160		253
161	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
162	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.
163		256
164	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
165	space at those places.	258	space at those places.
166		259
167	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
168	likely combine this setting with C<space_after>.	261	most likely combine this setting with C<space_after>.
169		262
		263	Example, space_before enabled, space_after and indent disabled:
		264
		265	{"key" :"value"}
		266
170	=item $json = $json->space_after ($enable)	267	=item $json = $json->space_after ([$enable])
171		268
172	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
173	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
174	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
175	members.	272	members.
176		273
177	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
178	space at those places.	275	space at those places.
179		276
180	This setting has no effect when decoding JSON strings.	277	This setting has no effect when decoding JSON texts.
181		278
		279	Example, space_before and indent disabled, space_after enabled:
		280
		281	{"key": "value"}
		282
182	=item $json = $json->canonical ($enable)	283	=item $json = $json->canonical ([$enable])
183		284
184	If C<$enable> is true, then the C<encode> method will output JSON objects	285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
185	by sorting their keys. This is adding a comparatively high overhead.	286	by sorting their keys. This is adding a comparatively high overhead.
186		287
187	If C<$enable> is false, then the C<encode> method will output key-value	288	If C<$enable> is false, then the C<encode> method will output key-value
188	pairs in the order Perl stores them (which will likely change between runs	289	pairs in the order Perl stores them (which will likely change between runs
189	of the same script).	290	of the same script).
190		291
191	This option is useful if you want the same data structure to be encoded as	292	This option is useful if you want the same data structure to be encoded as
192	the same JSON string (given the same overall settings). If it is disabled,	293	the same JSON text (given the same overall settings). If it is disabled,
193	the same hash migh be encoded differently even if contains the same data,	294	the same hash migh be encoded differently even if contains the same data,
194	as key-value pairs have no inherent ordering in Perl.	295	as key-value pairs have no inherent ordering in Perl.
195		296
196	This setting has no effect when decoding JSON strings.	297	This setting has no effect when decoding JSON texts.
197		298
		299	=item $json = $json->allow_nonref ([$enable])
		300
		301	If C<$enable> is true (or missing), then the C<encode> method can convert a
		302	non-reference into its corresponding string, number or null JSON value,
		303	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
		304	values instead of croaking.
		305
		306	If C<$enable> is false, then the C<encode> method will croak if it isn't
		307	passed an arrayref or hashref, as JSON texts must either be an object
		308	or array. Likewise, C<decode> will croak if given something that is not a
		309	JSON object or array.
		310
		311	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		312	resulting in an invalid JSON text:
		313
		314	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		315	=> "Hello, World!"
		316
		317	=item $json = $json->allow_blessed ([$enable])
		318
		319	If C<$enable> is true (or missing), then the C<encode> method will not
		320	barf when it encounters a blessed reference. Instead, the value of the
		321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		322	disabled or no C<to_json> method found) or a representation of the
		323	object (C<convert_blessed> enabled and C<to_json> method found) is being
		324	encoded. Has no effect on C<decode>.
		325
		326	If C<$enable> is false (the default), then C<encode> will throw an
		327	exception when it encounters a blessed object.
		328
		329	=item $json = $json->convert_blessed ([$enable])
		330
		331	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		332	blessed object, will check for the availability of the C<TO_JSON> method
		333	on the object's class. If found, it will be called in scalar context
		334	and the resulting scalar will be encoded instead of the object. If no
		335	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		336	to do.
		337
		338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		339	returns other blessed objects, those will be handled in the same
		340	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		341	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		342	methods called by the Perl core (== not by the user of the object) are
		343	usually in upper case letters and to avoid collisions with the C<to_json>
		344	function.
		345
		346	This setting does not yet influence C<decode> in any way, but in the
		347	future, global hooks might get installed that influence C<decode> and are
		348	enabled by this setting.
		349
		350	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		351	to do when a blessed object is found.
		352
		353	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		354
		355	When C<$coderef> is specified, it will be called from C<decode> each
		356	time it decodes a JSON object. The only argument is a reference to the
		357	newly-created hash. If the code references returns a single scalar (which
		358	need not be a reference), this value (i.e. a copy of that scalar to avoid
		359	aliasing) is inserted into the deserialised data structure. If it returns
		360	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		361	original deserialised hash will be inserted. This setting can slow down
		362	decoding considerably.
		363
		364	When C<$coderef> is omitted or undefined, any existing callback will
		365	be removed and C<decode> will not change the deserialised hash in any
		366	way.
		367
		368	Example, convert all JSON objects into the integer 5:
		369
		370	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		371	# returns [5]
		372	$js->decode ('[{}]')
		373	# throw an exception because allow_nonref is not enabled
		374	# so a lone 5 is not allowed.
		375	$js->decode ('{"a":1, "b":2}');
		376
		377	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		378
		379	Works remotely similar to C<filter_json_object>, but is only called for
		380	JSON objects having a single key named C<$key>.
		381
		382	This C<$coderef> is called before the one specified via
		383	C<filter_json_object>, if any. It gets passed the single value in the JSON
		384	object. If it returns a single value, it will be inserted into the data
		385	structure. If it returns nothing (not even C<undef> but the empty list),
		386	the callback from C<filter_json_object> will be called next, as if no
		387	single-key callback were specified.
		388
		389	If C<$coderef> is omitted or undefined, the corresponding callback will be
		390	disabled. There can only ever be one callback for a given key.
		391
		392	As this callback gets called less often then the C<filter_json_object>
		393	one, decoding speed will not usually suffer as much. Therefore, single-key
		394	objects make excellent targets to serialise Perl objects into, especially
		395	as single-key JSON objects are as close to the type-tagged value concept
		396	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		397	support this in any way, so you need to make sure your data never looks
		398	like a serialised Perl hash.
		399
		400	Typical names for the single object key are C<__class_whatever__>, or
		401	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		402	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		403	with real hashes.
		404
		405	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		406	into the corresponding C<< $WIDGET{<id>} >> object:
		407
		408	# return whatever is in $WIDGET{5}:
		409	JSON::XS
		410	->new
		411	->filter_json_single_key_object (__widget__ => sub {
		412	$WIDGET{ $_[0] }
		413	})
		414	->decode ('{"__widget__": 5')
		415
		416	# this can be used with a TO_JSON method in some "widget" class
		417	# for serialisation to json:
		418	sub WidgetBase::TO_JSON {
		419	my ($self) = @_;
		420
		421	unless ($self->{id}) {
		422	$self->{id} = ..get..some..id..;
		423	$WIDGET{$self->{id}} = $self;
		424	}
		425
		426	{ __widget__ => $self->{id} }
		427	}
		428
		429	=item $json = $json->shrink ([$enable])
		430
		431	Perl usually over-allocates memory a bit when allocating space for
		432	strings. This flag optionally resizes strings generated by either
		433	C<encode> or C<decode> to their minimum size possible. This can save
		434	memory when your JSON texts are either very very long or you have many
		435	short strings. It will also try to downgrade any strings to octet-form
		436	if possible: perl stores strings internally either in an encoding called
		437	UTF-X or in octet-form. The latter cannot store everything but uses less
		438	space in general (and some buggy Perl or C code might even rely on that
		439	internal representation being used).
		440
		441	The actual definition of what shrink does might change in future versions,
		442	but it will always try to save space at the expense of time.
		443
		444	If C<$enable> is true (or missing), the string returned by C<encode> will
		445	be shrunk-to-fit, while all strings generated by C<decode> will also be
		446	shrunk-to-fit.
		447
		448	If C<$enable> is false, then the normal perl allocation algorithms are used.
		449	If you work with your data, then this is likely to be faster.
		450
		451	In the future, this setting might control other things, such as converting
		452	strings that look like integers or floats into integers or floats
		453	internally (there is no difference on the Perl level), saving space.
		454
		455	=item $json = $json->max_depth ([$maximum_nesting_depth])
		456
		457	Sets the maximum nesting level (default C<512>) accepted while encoding
		458	or decoding. If the JSON text or Perl data structure has an equal or
		459	higher nesting level then this limit, then the encoder and decoder will
		460	stop and croak at that point.
		461
		462	Nesting level is defined by number of hash- or arrayrefs that the encoder
		463	needs to traverse to reach a given point or the number of C<{> or C<[>
		464	characters without their matching closing parenthesis crossed to reach a
		465	given character in a string.
		466
		467	Setting the maximum depth to one disallows any nesting, so that ensures
		468	that the object is only a single hash/object or array.
		469
		470	The argument to C<max_depth> will be rounded up to the next highest power
		471	of two. If no argument is given, the highest possible setting will be
		472	used, which is rarely useful.
		473
		474	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		475
		476	=item $json = $json->max_size ([$maximum_string_size])
		477
		478	Set the maximum length a JSON text may have (in bytes) where decoding is
		479	being attempted. The default is C<0>, meaning no limit. When C<decode>
		480	is called on a string longer then this number of characters it will not
		481	attempt to decode the string but throw an exception. This setting has no
		482	effect on C<encode> (yet).
		483
		484	The argument to C<max_size> will be rounded up to the next B<highest>
		485	power of two (so may be more than requested). If no argument is given, the
		486	limit check will be deactivated (same as when C<0> is specified).
		487
		488	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		489
198	=item $json_string = $json->encode ($perl_scalar)	490	=item $json_text = $json->encode ($perl_scalar)
199		491
200	Converts the given Perl data structure (a simple scalar or a reference	492	Converts the given Perl data structure (a simple scalar or a reference
201	to a hash or array) to its JSON representation. Simple scalars will be	493	to a hash or array) to its JSON representation. Simple scalars will be
202	converted into JSON string or number sequences, while references to arrays	494	converted into JSON string or number sequences, while references to arrays
203	become JSON arrays and references to hashes become JSON objects. Undefined	495	become JSON arrays and references to hashes become JSON objects. Undefined
204	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	496	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
205	nor C<false> values will be generated.	497	nor C<false> values will be generated.
206		498
207	=item $perl_scalar = $json->decode ($json_string)	499	=item $perl_scalar = $json->decode ($json_text)
208		500
209	The opposite of C<encode>: expects a JSON string and tries to parse it,	501	The opposite of C<encode>: expects a JSON text and tries to parse it,
210	returning the resulting simple scalar or reference. Croaks on error.	502	returning the resulting simple scalar or reference. Croaks on error.
211		503
212	JSON numbers and strings become simple Perl scalars. JSON arrays become	504	JSON numbers and strings become simple Perl scalars. JSON arrays become
213	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	505	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
214	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	506	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
215		507
		508	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		509
		510	This works like the C<decode> method, but instead of raising an exception
		511	when there is trailing garbage after the first JSON object, it will
		512	silently stop parsing there and return the number of characters consumed
		513	so far.
		514
		515	This is useful if your JSON texts are not delimited by an outer protocol
		516	(which is not the brightest thing to do in the first place) and you need
		517	to know where the JSON text ends.
		518
		519	JSON::XS->new->decode_prefix ("[1] the tail")
		520	=> ([], 3)
		521
216	=back	522	=back
217		523
		524
		525	=head1 MAPPING
		526
		527	This section describes how JSON::XS maps Perl values to JSON values and
		528	vice versa. These mappings are designed to "do the right thing" in most
		529	circumstances automatically, preserving round-tripping characteristics
		530	(what you put in comes out as something equivalent).
		531
		532	For the more enlightened: note that in the following descriptions,
		533	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		534	refers to the abstract Perl language itself.
		535
		536
		537	=head2 JSON -> PERL
		538
		539	=over 4
		540
		541	=item object
		542
		543	A JSON object becomes a reference to a hash in Perl. No ordering of object
		544	keys is preserved (JSON does not preserver object key ordering itself).
		545
		546	=item array
		547
		548	A JSON array becomes a reference to an array in Perl.
		549
		550	=item string
		551
		552	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		553	are represented by the same codepoints in the Perl string, so no manual
		554	decoding is necessary.
		555
		556	=item number
		557
		558	A JSON number becomes either an integer or numeric (floating point)
		559	scalar in perl, depending on its range and any fractional parts. On the
		560	Perl level, there is no difference between those as Perl handles all the
		561	conversion details, but an integer may take slightly less memory and might
		562	represent more values exactly than (floating point) numbers.
		563
		564	=item true, false
		565
		566	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		567	respectively. They are overloaded to act almost exactly like the numbers
		568	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		569	the C<JSON::XS::is_bool> function.
		570
		571	=item null
		572
		573	A JSON null atom becomes C<undef> in Perl.
		574
		575	=back
		576
		577
		578	=head2 PERL -> JSON
		579
		580	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		581	truly typeless language, so we can only guess which JSON type is meant by
		582	a Perl value.
		583
		584	=over 4
		585
		586	=item hash references
		587
		588	Perl hash references become JSON objects. As there is no inherent ordering
		589	in hash keys (or JSON objects), they will usually be encoded in a
		590	pseudo-random order that can change between runs of the same program but
		591	stays generally the same within a single run of a program. JSON::XS can
		592	optionally sort the hash keys (determined by the I<canonical> flag), so
		593	the same datastructure will serialise to the same JSON text (given same
		594	settings and version of JSON::XS), but this incurs a runtime overhead
		595	and is only rarely useful, e.g. when you want to compare some JSON text
		596	against another for equality.
		597
		598	=item array references
		599
		600	Perl array references become JSON arrays.
		601
		602	=item other references
		603
		604	Other unblessed references are generally not allowed and will cause an
		605	exception to be thrown, except for references to the integers C<0> and
		606	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		607	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		608
		609	to_json [\0,JSON::XS::true] # yields [false,true]
		610
		611	=item JSON::XS::true, JSON::XS::false
		612
		613	These special values become JSON true and JSON false values,
		614	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		615
		616	=item blessed objects
		617
		618	Blessed objects are not allowed. JSON::XS currently tries to encode their
		619	underlying representation (hash- or arrayref), but this behaviour might
		620	change in future versions.
		621
		622	=item simple scalars
		623
		624	Simple Perl scalars (any scalar that is not a reference) are the most
		625	difficult objects to encode: JSON::XS will encode undefined scalars as
		626	JSON null value, scalars that have last been used in a string context
		627	before encoding as JSON strings and anything else as number value:
		628
		629	# dump as number
		630	to_json [2] # yields [2]
		631	to_json [-3.0e17] # yields [-3e+17]
		632	my $value = 5; to_json [$value] # yields [5]
		633
		634	# used as string, so dump as string
		635	print $value;
		636	to_json [$value] # yields ["5"]
		637
		638	# undef becomes null
		639	to_json [undef] # yields [null]
		640
		641	You can force the type to be a string by stringifying it:
		642
		643	my $x = 3.1; # some variable containing a number
		644	"$x"; # stringified
		645	$x .= ""; # another, more awkward way to stringify
		646	print $x; # perl does it for you, too, quite often
		647
		648	You can force the type to be a number by numifying it:
		649
		650	my $x = "3"; # some variable containing a string
		651	$x += 0; # numify it, ensuring it will be dumped as a number
		652	$x *= 1; # same thing, the choise is yours.
		653
		654	You can not currently output JSON booleans or force the type in other,
		655	less obscure, ways. Tell me if you need this capability.
		656
		657	=back
		658
		659
		660	=head1 COMPARISON
		661
		662	As already mentioned, this module was created because none of the existing
		663	JSON modules could be made to work correctly. First I will describe the
		664	problems (or pleasures) I encountered with various existing JSON modules,
		665	followed by some benchmark values. JSON::XS was designed not to suffer
		666	from any of these problems or limitations.
		667
		668	=over 4
		669
		670	=item JSON 1.07
		671
		672	Slow (but very portable, as it is written in pure Perl).
		673
		674	Undocumented/buggy Unicode handling (how JSON handles unicode values is
		675	undocumented. One can get far by feeding it unicode strings and doing
		676	en-/decoding oneself, but unicode escapes are not working properly).
		677
		678	No roundtripping (strings get clobbered if they look like numbers, e.g.
		679	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
		680	decode into the number 2.
		681
		682	=item JSON::PC 0.01
		683
		684	Very fast.
		685
		686	Undocumented/buggy Unicode handling.
		687
		688	No roundtripping.
		689
		690	Has problems handling many Perl values (e.g. regex results and other magic
		691	values will make it croak).
		692
		693	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		694	which is not a valid JSON text.
		695
		696	Unmaintained (maintainer unresponsive for many months, bugs are not
		697	getting fixed).
		698
		699	=item JSON::Syck 0.21
		700
		701	Very buggy (often crashes).
		702
		703	Very inflexible (no human-readable format supported, format pretty much
		704	undocumented. I need at least a format for easy reading by humans and a
		705	single-line compact format for use in a protocol, and preferably a way to
		706	generate ASCII-only JSON texts).
		707
		708	Completely broken (and confusingly documented) Unicode handling (unicode
		709	escapes are not working properly, you need to set ImplicitUnicode to
		710	I<different> values on en- and decoding to get symmetric behaviour).
		711
		712	No roundtripping (simple cases work, but this depends on wether the scalar
		713	value was used in a numeric context or not).
		714
		715	Dumping hashes may skip hash values depending on iterator state.
		716
		717	Unmaintained (maintainer unresponsive for many months, bugs are not
		718	getting fixed).
		719
		720	Does not check input for validity (i.e. will accept non-JSON input and
		721	return "something" instead of raising an exception. This is a security
		722	issue: imagine two banks transfering money between each other using
		723	JSON. One bank might parse a given non-JSON request and deduct money,
		724	while the other might reject the transaction with a syntax error. While a
		725	good protocol will at least recover, that is extra unnecessary work and
		726	the transaction will still not succeed).
		727
		728	=item JSON::DWIW 0.04
		729
		730	Very fast. Very natural. Very nice.
		731
		732	Undocumented unicode handling (but the best of the pack. Unicode escapes
		733	still don't get parsed properly).
		734
		735	Very inflexible.
		736
		737	No roundtripping.
		738
		739	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		740	result in nothing being output)
		741
		742	Does not check input for validity.
		743
		744	=back
		745
		746
		747	=head2 JSON and YAML
		748
		749	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		750	however, a mass hysteria and very far from the truth. In general, there is
		751	no way to configure JSON::XS to output a data structure as valid YAML.
		752
		753	If you really must use JSON::XS to generate YAML, you should use this
		754	algorithm (subject to change in future versions):
		755
		756	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		757	my $yaml = $to_yaml->encode ($ref) . "\n";
		758
		759	This will usually generate JSON texts that also parse as valid
		760	YAML. Please note that YAML has hardcoded limits on (simple) object key
		761	lengths that JSON doesn't have, so you should make sure that your hash
		762	keys are noticably shorter than the 1024 characters YAML allows.
		763
		764	There might be other incompatibilities that I am not aware of. In general
		765	you should not try to generate YAML with a JSON generator or vice versa,
		766	or try to parse JSON with a YAML parser or vice versa: chances are high
		767	that you will run into severe interoperability problems.
		768
		769
		770	=head2 SPEED
		771
		772	It seems that JSON::XS is surprisingly fast, as shown in the following
		773	tables. They have been generated with the help of the C<eg/bench> program
		774	in the JSON::XS distribution, to make it easy to compare on your own
		775	system.
		776
		777	First comes a comparison between various modules using a very short
		778	single-line JSON string:
		779
		780	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		781	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		782
		783	It shows the number of encodes/decodes per second (JSON::XS uses
		784	the functional interface, while JSON::XS/2 uses the OO interface
		785	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		786	shrink). Higher is better:
		787
		788	Storable \| 15779.925 \| 14169.946 \|
		789	-----------+------------+------------+
		790	module \| encode \| decode \|
		791	-----------\|------------\|------------\|
		792	JSON \| 4990.842 \| 4088.813 \|
		793	JSON::DWIW \| 51653.990 \| 71575.154 \|
		794	JSON::PC \| 65948.176 \| 74631.744 \|
		795	JSON::PP \| 8931.652 \| 3817.168 \|
		796	JSON::Syck \| 24877.248 \| 27776.848 \|
		797	JSON::XS \| 388361.481 \| 227951.304 \|
		798	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		799	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		800	Storable \| 16500.016 \| 135300.129 \|
		801	-----------+------------+------------+
		802
		803	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		804	about three times faster on decoding, and over fourty times faster
		805	than JSON, even with pretty-printing and key sorting. It also compares
		806	favourably to Storable for small amounts of data.
		807
		808	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		809	search API (http://nanoref.com/yahooapis/mgPdGg):
		810
		811	module \| encode \| decode \|
		812	-----------\|------------\|------------\|
		813	JSON \| 55.260 \| 34.971 \|
		814	JSON::DWIW \| 825.228 \| 1082.513 \|
		815	JSON::PC \| 3571.444 \| 2394.829 \|
		816	JSON::PP \| 210.987 \| 32.574 \|
		817	JSON::Syck \| 552.551 \| 787.544 \|
		818	JSON::XS \| 5780.463 \| 4854.519 \|
		819	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		820	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		821	Storable \| 4445.002 \| 5235.027 \|
		822	-----------+------------+------------+
		823
		824	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		825	decodes faster).
		826
		827	On large strings containing lots of high unicode characters, some modules
		828	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		829	will be broken due to missing (or wrong) unicode handling. Others refuse
		830	to decode or encode properly, so it was impossible to prepare a fair
		831	comparison table for that case.
		832
		833
		834	=head1 SECURITY CONSIDERATIONS
		835
		836	When you are using JSON in a protocol, talking to untrusted potentially
		837	hostile creatures requires relatively few measures.
		838
		839	First of all, your JSON decoder should be secure, that is, should not have
		840	any buffer overflows. Obviously, this module should ensure that and I am
		841	trying hard on making that true, but you never know.
		842
		843	Second, you need to avoid resource-starving attacks. That means you should
		844	limit the size of JSON texts you accept, or make sure then when your
		845	resources run out, thats just fine (e.g. by using a separate process that
		846	can crash safely). The size of a JSON text in octets or characters is
		847	usually a good indication of the size of the resources required to decode
		848	it into a Perl structure. While JSON::XS can check the size of the JSON
		849	text, it might be too late when you already have it in memory, so you
		850	might want to check the size before you accept the string.
		851
		852	Third, JSON::XS recurses using the C stack when decoding objects and
		853	arrays. The C stack is a limited resource: for instance, on my amd64
		854	machine with 8MB of stack size I can decode around 180k nested arrays but
		855	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		856	to free the temporary). If that is exceeded, the program crashes. to be
		857	conservative, the default nesting limit is set to 512. If your process
		858	has a smaller stack, you should adjust this setting accordingly with the
		859	C<max_depth> method.
		860
		861	And last but least, something else could bomb you that I forgot to think
		862	of. In that case, you get to keep the pieces. I am always open for hints,
		863	though...
		864
		865	If you are using JSON::XS to return packets to consumption
		866	by javascript scripts in a browser you should have a look at
		867	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		868	you are vulnerable to some common attack vectors (which really are browser
		869	design bugs, but it is still you who will have to deal with it, as major
		870	browser developers care only for features, not about doing security
		871	right).
		872
		873
		874	=head1 BUGS
		875
		876	While the goal of this module is to be correct, that unfortunately does
		877	not mean its bug-free, only that I think its design is bug-free. It is
		878	still relatively early in its development. If you keep reporting bugs they
		879	will be fixed swiftly, though.
		880
218	=cut	881	=cut
		882
		883	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		884	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		885
		886	sub true() { $true }
		887	sub false() { $false }
		888
		889	sub is_bool($) {
		890	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		891	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		892	}
		893
		894	XSLoader::load "JSON::XS", $VERSION;
		895
		896	package JSON::XS::Boolean;
		897
		898	use overload
		899	"0+" => sub { ${$_[0]} },
		900	"++" => sub { $_[0] = ${$_[0]} + 1 },
		901	"--" => sub { $_[0] = ${$_[0]} - 1 },
		902	fallback => 1;
219		903
220	1;	904	1;
221		905
222	=head1 AUTHOR	906	=head1 AUTHOR
223		907

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Revision 1.54 by root, Tue Jul 10 16:22:31 2007 UTC