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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs.
Revision 1.44 by root, Mon Jun 25 04:08:17 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	# objToJson and jsonToObj aliases to to_json and from_json
		16	# are exported for compatibility to the JSON module,
		17	# but should not be used in new code.
		18
		19	# OO-interface
		20
		21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		23	$perl_scalar = $coder->decode ($unicode_json_text);
8		24
9	=head1 DESCRIPTION	25	=head1 DESCRIPTION
10		26
11	This module converts Perl data structures to JSON and vice versa. Its	27	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	28	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	34	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	35	reports for other reasons.
20		36
21	See COMPARISON, below, for a comparison to some other JSON modules.	37	See COMPARISON, below, for a comparison to some other JSON modules.
22		38
		39	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		40	vice versa.
		41
23	=head2 FEATURES	42	=head2 FEATURES
24		43
25	=over 4	44	=over 4
26		45
27	=item * correct handling of unicode issues	46	=item * correct unicode handling
28		47
29	This module knows how to handle Unicode, and even documents how it does so.	48	This module knows how to handle Unicode, and even documents how and when
		49	it does so.
30		50
31	=item * round-trip integrity	51	=item * round-trip integrity
32		52
33	When you serialise a perl data structure using only datatypes supported	53	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	54	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	55	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		56	like a number).
36		57
37	=item * strict checking of JSON correctness	58	=item * strict checking of JSON correctness
38		59
39	There is no guessing, no generating of illegal JSON strings by default,	60	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).	61	and only JSON is accepted as input by default (the latter is a security
		62	feature).
41		63
42	=item * fast	64	=item * fast
43		65
44	compared to other JSON modules, this module compares favourably.	66	Compared to other JSON modules, this module compares favourably in terms
		67	of speed, too.
45		68
46	=item * simple to use	69	=item * simple to use
47		70
48	This module has both a simple functional interface as well as an OO	71	This module has both a simple functional interface as well as an OO
49	interface.	72	interface.
50		73
51	=item * reasonably versatile output formats	74	=item * reasonably versatile output formats
52		75
53	You can choose between the most compact format possible, a pure-ascii	76	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	77	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	78	(for when your transport is not 8-bit clean, still supports the whole
		79	unicode range), or a pretty-printed format (for when you want to read that
		80	stuff). Or you can combine those features in whatever way you like.
56		81
57	=back	82	=back
58		83
59	=cut	84	=cut
60		85
61	package JSON::XS;	86	package JSON::XS;
62		87
63	BEGIN {	88	use strict;
		89
64	$VERSION = '0.2';	90	our $VERSION = '1.4';
65	@ISA = qw(Exporter);	91	our @ISA = qw(Exporter);
66		92
67	@EXPORT = qw(to_json from_json);	93	our @EXPORT = qw(to_json from_json objToJson jsonToObj);
68	require Exporter;
69		94
70	require XSLoader;	95	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	96	use XSLoader;
72	}
73		97
74	=head1 FUNCTIONAL INTERFACE	98	=head1 FUNCTIONAL INTERFACE
75		99
76	The following convinience methods are provided by this module. They are	100	The following convinience methods are provided by this module. They are
77	exported by default:	101	exported by default:
78		102
79	=over 4	103	=over 4
80		104
81	=item $json_string = to_json $perl_scalar	105	=item $json_text = to_json $perl_scalar
82		106
83	Converts the given Perl data structure (a simple scalar or a reference to	107	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	108	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	109	octets only). Croaks on error.
86		110
87	This function call is functionally identical to C<< JSON::XS->new->utf8	111	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		112
		113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		114
		115	except being faster.
		116
90	=item $perl_scalar = from_json $json_string	117	=item $perl_scalar = from_json $json_text
91		118
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	119	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	120	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	121	scalar or reference. Croaks on error.
95		122
96	This function call is functionally identical to C<< JSON::XS->new->utf8	123	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	124
		125	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		126
		127	except being faster.
		128
		129	=item $is_boolean = JSON::XS::is_bool $scalar
		130
		131	Returns true if the passed scalar represents either JSON::XS::true or
		132	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		133	and are used to represent JSON C<true> and C<false> values in Perl.
		134
		135	See MAPPING, below, for more information on how JSON values are mapped to
		136	Perl.
98		137
99	=back	138	=back
		139
100		140
101	=head1 OBJECT-ORIENTED INTERFACE	141	=head1 OBJECT-ORIENTED INTERFACE
102		142
103	The object oriented interface lets you configure your own encoding or	143	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	144	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	151	strings. All boolean flags described below are by default I<disabled>.
112		152
113	The mutators for flags all return the JSON object again and thus calls can	153	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	154	be chained:
115		155
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	156	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	157	=> {"a": [1, 2]}
118		158
119	=item $json = $json->ascii ([$enable])	159	=item $json = $json->ascii ([$enable])
120		160
121	If C<$enable> is true (or missing), then the C<encode> method will	161	If C<$enable> is true (or missing), then the C<encode> method will not
122	not generate characters outside the code range C<0..127>. Any unicode	162	generate characters outside the code range C<0..127> (which is ASCII). Any
123	characters outside that range will be escaped using either a single	163	unicode characters outside that range will be escaped using either a
124	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	164	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
125	RFC4627.	165	as per RFC4627. The resulting encoded JSON text can be treated as a native
		166	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		167	or any other superset of ASCII.
126		168
127	If C<$enable> is false, then the C<encode> method will not escape Unicode	169	If C<$enable> is false, then the C<encode> method will not escape Unicode
128	characters unless necessary.	170	characters unless required by the JSON syntax or other flags. This results
		171	in a faster and more compact format.
129		172
		173	The main use for this flag is to produce JSON texts that can be
		174	transmitted over a 7-bit channel, as the encoded JSON texts will not
		175	contain any 8 bit characters.
		176
130	JSON::XS->new->ascii (1)->encode (chr 0x10401)	177	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
131	=> \ud801\udc01	178	=> ["\ud801\udc01"]
		179
		180	=item $json = $json->latin1 ([$enable])
		181
		182	If C<$enable> is true (or missing), then the C<encode> method will encode
		183	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		184	outside the code range C<0..255>. The resulting string can be treated as a
		185	latin1-encoded JSON text or a native unicode string. The C<decode> method
		186	will not be affected in any way by this flag, as C<decode> by default
		187	expects unicode, which is a strict superset of latin1.
		188
		189	If C<$enable> is false, then the C<encode> method will not escape Unicode
		190	characters unless required by the JSON syntax or other flags.
		191
		192	The main use for this flag is efficiently encoding binary data as JSON
		193	text, as most octets will not be escaped, resulting in a smaller encoded
		194	size. The disadvantage is that the resulting JSON text is encoded
		195	in latin1 (and must correctly be treated as such when storing and
		196	transfering), a rare encoding for JSON. It is therefore most useful when
		197	you want to store data structures known to contain binary data efficiently
		198	in files or databases, not when talking to other JSON encoders/decoders.
		199
		200	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		201	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
132		202
133	=item $json = $json->utf8 ([$enable])	203	=item $json = $json->utf8 ([$enable])
134		204
135	If C<$enable> is true (or missing), then the C<encode> method will encode	205	If C<$enable> is true (or missing), then the C<encode> method will encode
136	the JSON string into UTF-8, as required by many protocols, while the	206	the JSON result into UTF-8, as required by many protocols, while the
137	C<decode> method expects to be handled an UTF-8-encoded string. Please	207	C<decode> method expects to be handled an UTF-8-encoded string. Please
138	note that UTF-8-encoded strings do not contain any characters outside the	208	note that UTF-8-encoded strings do not contain any characters outside the
139	range C<0..255>, they are thus useful for bytewise/binary I/O.	209	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		210	versions, enabling this option might enable autodetection of the UTF-16
		211	and UTF-32 encoding families, as described in RFC4627.
140		212
141	If C<$enable> is false, then the C<encode> method will return the JSON	213	If C<$enable> is false, then the C<encode> method will return the JSON
142	string as a (non-encoded) unicode string, while C<decode> expects thus a	214	string as a (non-encoded) unicode string, while C<decode> expects thus a
143	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	215	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
144	to be done yourself, e.g. using the Encode module.	216	to be done yourself, e.g. using the Encode module.
145		217
		218	Example, output UTF-16BE-encoded JSON:
		219
		220	use Encode;
		221	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		222
		223	Example, decode UTF-32LE-encoded JSON:
		224
		225	use Encode;
		226	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		227
146	=item $json = $json->pretty ([$enable])	228	=item $json = $json->pretty ([$enable])
147		229
148	This enables (or disables) all of the C<indent>, C<space_before> and	230	This enables (or disables) all of the C<indent>, C<space_before> and
149	C<space_after> (and in the future possibly more) flags in one call to	231	C<space_after> (and in the future possibly more) flags in one call to
150	generate the most readable (or most compact) form possible.	232	generate the most readable (or most compact) form possible.
		233
		234	Example, pretty-print some simple structure:
151		235
152	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	236	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
153	=>	237	=>
154	{	238	{
155	"a" : [	239	"a" : [
…		…
163	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	247	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
164	format as output, putting every array member or object/hash key-value pair	248	format as output, putting every array member or object/hash key-value pair
165	into its own line, identing them properly.	249	into its own line, identing them properly.
166		250
167	If C<$enable> is false, no newlines or indenting will be produced, and the	251	If C<$enable> is false, no newlines or indenting will be produced, and the
168	resulting JSON strings is guarenteed not to contain any C<newlines>.	252	resulting JSON text is guarenteed not to contain any C<newlines>.
169		253
170	This setting has no effect when decoding JSON strings.	254	This setting has no effect when decoding JSON texts.
171		255
172	=item $json = $json->space_before ([$enable])	256	=item $json = $json->space_before ([$enable])
173		257
174	If C<$enable> is true (or missing), then the C<encode> method will add an extra	258	If C<$enable> is true (or missing), then the C<encode> method will add an extra
175	optional space before the C<:> separating keys from values in JSON objects.	259	optional space before the C<:> separating keys from values in JSON objects.
176		260
177	If C<$enable> is false, then the C<encode> method will not add any extra	261	If C<$enable> is false, then the C<encode> method will not add any extra
178	space at those places.	262	space at those places.
179		263
180	This setting has no effect when decoding JSON strings. You will also most	264	This setting has no effect when decoding JSON texts. You will also
181	likely combine this setting with C<space_after>.	265	most likely combine this setting with C<space_after>.
		266
		267	Example, space_before enabled, space_after and indent disabled:
		268
		269	{"key" :"value"}
182		270
183	=item $json = $json->space_after ([$enable])	271	=item $json = $json->space_after ([$enable])
184		272
185	If C<$enable> is true (or missing), then the C<encode> method will add an extra	273	If C<$enable> is true (or missing), then the C<encode> method will add an extra
186	optional space after the C<:> separating keys from values in JSON objects	274	optional space after the C<:> separating keys from values in JSON objects
…		…
188	members.	276	members.
189		277
190	If C<$enable> is false, then the C<encode> method will not add any extra	278	If C<$enable> is false, then the C<encode> method will not add any extra
191	space at those places.	279	space at those places.
192		280
193	This setting has no effect when decoding JSON strings.	281	This setting has no effect when decoding JSON texts.
		282
		283	Example, space_before and indent disabled, space_after enabled:
		284
		285	{"key": "value"}
194		286
195	=item $json = $json->canonical ([$enable])	287	=item $json = $json->canonical ([$enable])
196		288
197	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	289	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
198	by sorting their keys. This is adding a comparatively high overhead.	290	by sorting their keys. This is adding a comparatively high overhead.
…		…
200	If C<$enable> is false, then the C<encode> method will output key-value	292	If C<$enable> is false, then the C<encode> method will output key-value
201	pairs in the order Perl stores them (which will likely change between runs	293	pairs in the order Perl stores them (which will likely change between runs
202	of the same script).	294	of the same script).
203		295
204	This option is useful if you want the same data structure to be encoded as	296	This option is useful if you want the same data structure to be encoded as
205	the same JSON string (given the same overall settings). If it is disabled,	297	the same JSON text (given the same overall settings). If it is disabled,
206	the same hash migh be encoded differently even if contains the same data,	298	the same hash migh be encoded differently even if contains the same data,
207	as key-value pairs have no inherent ordering in Perl.	299	as key-value pairs have no inherent ordering in Perl.
208		300
209	This setting has no effect when decoding JSON strings.	301	This setting has no effect when decoding JSON texts.
210		302
211	=item $json = $json->allow_nonref ([$enable])	303	=item $json = $json->allow_nonref ([$enable])
212		304
213	If C<$enable> is true (or missing), then the C<encode> method can convert a	305	If C<$enable> is true (or missing), then the C<encode> method can convert a
214	non-reference into its corresponding string, number or null JSON value,	306	non-reference into its corresponding string, number or null JSON value,
215	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	307	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
216	values instead of croaking.	308	values instead of croaking.
217		309
218	If C<$enable> is false, then the C<encode> method will croak if it isn't	310	If C<$enable> is false, then the C<encode> method will croak if it isn't
219	passed an arrayref or hashref, as JSON strings must either be an object	311	passed an arrayref or hashref, as JSON texts must either be an object
220	or array. Likewise, C<decode> will croak if given something that is not a	312	or array. Likewise, C<decode> will croak if given something that is not a
221	JSON object or array.	313	JSON object or array.
222		314
		315	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		316	resulting in an invalid JSON text:
		317
		318	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		319	=> "Hello, World!"
		320
		321	=item $json = $json->allow_blessed ([$enable])
		322
		323	If C<$enable> is true (or missing), then the C<encode> method will not
		324	barf when it encounters a blessed reference. Instead, the value of the
		325	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		326	disabled or no C<to_json> method found) or a representation of the
		327	object (C<convert_blessed> enabled and C<to_json> method found) is being
		328	encoded. Has no effect on C<decode>.
		329
		330	If C<$enable> is false (the default), then C<encode> will throw an
		331	exception when it encounters a blessed object.
		332
		333	=item $json = $json->convert_blessed ([$enable])
		334
		335	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		336	blessed object, will check for the availability of the C<TO_JSON> method
		337	on the object's class. If found, it will be called in scalar context
		338	and the resulting scalar will be encoded instead of the object. If no
		339	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		340	to do.
		341
		342	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		343	returns other blessed objects, those will be handled in the same
		344	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		345	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		346	methods called by the Perl core (== not the user of the object) are
		347	usually in upper case letters and to avoid collisions with the C<to_json>
		348	function.
		349
		350	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		351	to do when a blessed object is found.
		352
223	=item $json = $json->shrink ([$enable])	353	=item $json = $json->shrink ([$enable])
224		354
225	Perl usually over-allocates memory a bit when allocating space for	355	Perl usually over-allocates memory a bit when allocating space for
226	strings. This flag optionally resizes strings generated by either	356	strings. This flag optionally resizes strings generated by either
227	C<encode> or C<decode> to their minimum size possible. This can save	357	C<encode> or C<decode> to their minimum size possible. This can save
228	memory when your JSON strings are either very very long or you have many	358	memory when your JSON texts are either very very long or you have many
229	short strings. It will also try to downgrade any strings to octet-form	359	short strings. It will also try to downgrade any strings to octet-form
230	if possible: perl stores strings internally either in an encoding called	360	if possible: perl stores strings internally either in an encoding called
231	UTF-X or in octet-form. The latter cannot store everything but uses less	361	UTF-X or in octet-form. The latter cannot store everything but uses less
232	space in general.	362	space in general (and some buggy Perl or C code might even rely on that
		363	internal representation being used).
233		364
		365	The actual definition of what shrink does might change in future versions,
		366	but it will always try to save space at the expense of time.
		367
234	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	368	If C<$enable> is true (or missing), the string returned by C<encode> will
235	while all strings generated by C<decode> will also be shrunk-to-fit.	369	be shrunk-to-fit, while all strings generated by C<decode> will also be
		370	shrunk-to-fit.
236		371
237	If C<$enable> is false, then the normal perl allocation algorithms are used.	372	If C<$enable> is false, then the normal perl allocation algorithms are used.
238	If you work with your data, then this is likely to be faster.	373	If you work with your data, then this is likely to be faster.
239		374
240	In the future, this setting might control other things, such as converting	375	In the future, this setting might control other things, such as converting
241	strings that look like integers or floats into integers or floats	376	strings that look like integers or floats into integers or floats
242	internally (there is no difference on the Perl level), saving space.	377	internally (there is no difference on the Perl level), saving space.
243		378
		379	=item $json = $json->max_depth ([$maximum_nesting_depth])
		380
		381	Sets the maximum nesting level (default C<512>) accepted while encoding
		382	or decoding. If the JSON text or Perl data structure has an equal or
		383	higher nesting level then this limit, then the encoder and decoder will
		384	stop and croak at that point.
		385
		386	Nesting level is defined by number of hash- or arrayrefs that the encoder
		387	needs to traverse to reach a given point or the number of C<{> or C<[>
		388	characters without their matching closing parenthesis crossed to reach a
		389	given character in a string.
		390
		391	Setting the maximum depth to one disallows any nesting, so that ensures
		392	that the object is only a single hash/object or array.
		393
		394	The argument to C<max_depth> will be rounded up to the next nearest power
		395	of two.
		396
		397	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		398
244	=item $json_string = $json->encode ($perl_scalar)	399	=item $json_text = $json->encode ($perl_scalar)
245		400
246	Converts the given Perl data structure (a simple scalar or a reference	401	Converts the given Perl data structure (a simple scalar or a reference
247	to a hash or array) to its JSON representation. Simple scalars will be	402	to a hash or array) to its JSON representation. Simple scalars will be
248	converted into JSON string or number sequences, while references to arrays	403	converted into JSON string or number sequences, while references to arrays
249	become JSON arrays and references to hashes become JSON objects. Undefined	404	become JSON arrays and references to hashes become JSON objects. Undefined
250	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	405	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
251	nor C<false> values will be generated.	406	nor C<false> values will be generated.
252		407
253	=item $perl_scalar = $json->decode ($json_string)	408	=item $perl_scalar = $json->decode ($json_text)
254		409
255	The opposite of C<encode>: expects a JSON string and tries to parse it,	410	The opposite of C<encode>: expects a JSON text and tries to parse it,
256	returning the resulting simple scalar or reference. Croaks on error.	411	returning the resulting simple scalar or reference. Croaks on error.
257		412
258	JSON numbers and strings become simple Perl scalars. JSON arrays become	413	JSON numbers and strings become simple Perl scalars. JSON arrays become
259	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	414	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
260	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	415	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
261		416
		417	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		418
		419	This works like the C<decode> method, but instead of raising an exception
		420	when there is trailing garbage after the first JSON object, it will
		421	silently stop parsing there and return the number of characters consumed
		422	so far.
		423
		424	This is useful if your JSON texts are not delimited by an outer protocol
		425	(which is not the brightest thing to do in the first place) and you need
		426	to know where the JSON text ends.
		427
		428	JSON::XS->new->decode_prefix ("[1] the tail")
		429	=> ([], 3)
		430
262	=back	431	=back
		432
		433
		434	=head1 MAPPING
		435
		436	This section describes how JSON::XS maps Perl values to JSON values and
		437	vice versa. These mappings are designed to "do the right thing" in most
		438	circumstances automatically, preserving round-tripping characteristics
		439	(what you put in comes out as something equivalent).
		440
		441	For the more enlightened: note that in the following descriptions,
		442	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		443	refers to the abstract Perl language itself.
		444
		445
		446	=head2 JSON -> PERL
		447
		448	=over 4
		449
		450	=item object
		451
		452	A JSON object becomes a reference to a hash in Perl. No ordering of object
		453	keys is preserved (JSON does not preserver object key ordering itself).
		454
		455	=item array
		456
		457	A JSON array becomes a reference to an array in Perl.
		458
		459	=item string
		460
		461	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		462	are represented by the same codepoints in the Perl string, so no manual
		463	decoding is necessary.
		464
		465	=item number
		466
		467	A JSON number becomes either an integer or numeric (floating point)
		468	scalar in perl, depending on its range and any fractional parts. On the
		469	Perl level, there is no difference between those as Perl handles all the
		470	conversion details, but an integer may take slightly less memory and might
		471	represent more values exactly than (floating point) numbers.
		472
		473	=item true, false
		474
		475	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		476	respectively. They are overloaded to act almost exactly like the numbers
		477	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		478	the C<JSON::XS::is_bool> function.
		479
		480	=item null
		481
		482	A JSON null atom becomes C<undef> in Perl.
		483
		484	=back
		485
		486
		487	=head2 PERL -> JSON
		488
		489	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		490	truly typeless language, so we can only guess which JSON type is meant by
		491	a Perl value.
		492
		493	=over 4
		494
		495	=item hash references
		496
		497	Perl hash references become JSON objects. As there is no inherent ordering
		498	in hash keys (or JSON objects), they will usually be encoded in a
		499	pseudo-random order that can change between runs of the same program but
		500	stays generally the same within a single run of a program. JSON::XS can
		501	optionally sort the hash keys (determined by the I<canonical> flag), so
		502	the same datastructure will serialise to the same JSON text (given same
		503	settings and version of JSON::XS), but this incurs a runtime overhead
		504	and is only rarely useful, e.g. when you want to compare some JSON text
		505	against another for equality.
		506
		507	=item array references
		508
		509	Perl array references become JSON arrays.
		510
		511	=item other references
		512
		513	Other unblessed references are generally not allowed and will cause an
		514	exception to be thrown, except for references to the integers C<0> and
		515	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		516	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		517
		518	to_json [\0,JSON::XS::true] # yields [false,true]
		519
		520	=item JSON::XS::true, JSON::XS::false
		521
		522	These special values become JSON true and JSON false values,
		523	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		524
		525	=item blessed objects
		526
		527	Blessed objects are not allowed. JSON::XS currently tries to encode their
		528	underlying representation (hash- or arrayref), but this behaviour might
		529	change in future versions.
		530
		531	=item simple scalars
		532
		533	Simple Perl scalars (any scalar that is not a reference) are the most
		534	difficult objects to encode: JSON::XS will encode undefined scalars as
		535	JSON null value, scalars that have last been used in a string context
		536	before encoding as JSON strings and anything else as number value:
		537
		538	# dump as number
		539	to_json [2] # yields [2]
		540	to_json [-3.0e17] # yields [-3e+17]
		541	my $value = 5; to_json [$value] # yields [5]
		542
		543	# used as string, so dump as string
		544	print $value;
		545	to_json [$value] # yields ["5"]
		546
		547	# undef becomes null
		548	to_json [undef] # yields [null]
		549
		550	You can force the type to be a string by stringifying it:
		551
		552	my $x = 3.1; # some variable containing a number
		553	"$x"; # stringified
		554	$x .= ""; # another, more awkward way to stringify
		555	print $x; # perl does it for you, too, quite often
		556
		557	You can force the type to be a number by numifying it:
		558
		559	my $x = "3"; # some variable containing a string
		560	$x += 0; # numify it, ensuring it will be dumped as a number
		561	$x *= 1; # same thing, the choise is yours.
		562
		563	You can not currently output JSON booleans or force the type in other,
		564	less obscure, ways. Tell me if you need this capability.
		565
		566	=back
		567
263		568
264	=head1 COMPARISON	569	=head1 COMPARISON
265		570
266	As already mentioned, this module was created because none of the existing	571	As already mentioned, this module was created because none of the existing
267	JSON modules could be made to work correctly. First I will describe the	572	JSON modules could be made to work correctly. First I will describe the
…		…
293		598
294	Has problems handling many Perl values (e.g. regex results and other magic	599	Has problems handling many Perl values (e.g. regex results and other magic
295	values will make it croak).	600	values will make it croak).
296		601
297	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	602	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
298	which is not a valid JSON string.	603	which is not a valid JSON text.
299		604
300	Unmaintained (maintainer unresponsive for many months, bugs are not	605	Unmaintained (maintainer unresponsive for many months, bugs are not
301	getting fixed).	606	getting fixed).
302		607
303	=item JSON::Syck 0.21	608	=item JSON::Syck 0.21
…		…
305	Very buggy (often crashes).	610	Very buggy (often crashes).
306		611
307	Very inflexible (no human-readable format supported, format pretty much	612	Very inflexible (no human-readable format supported, format pretty much
308	undocumented. I need at least a format for easy reading by humans and a	613	undocumented. I need at least a format for easy reading by humans and a
309	single-line compact format for use in a protocol, and preferably a way to	614	single-line compact format for use in a protocol, and preferably a way to
310	generate ASCII-only JSON strings).	615	generate ASCII-only JSON texts).
311		616
312	Completely broken (and confusingly documented) Unicode handling (unicode	617	Completely broken (and confusingly documented) Unicode handling (unicode
313	escapes are not working properly, you need to set ImplicitUnicode to	618	escapes are not working properly, you need to set ImplicitUnicode to
314	I<different> values on en- and decoding to get symmetric behaviour).	619	I<different> values on en- and decoding to get symmetric behaviour).
315		620
…		…
338		643
339	Very inflexible.	644	Very inflexible.
340		645
341	No roundtripping.	646	No roundtripping.
342		647
343	Does not generate valid JSON (key strings are often unquoted, empty keys	648	Does not generate valid JSON texts (key strings are often unquoted, empty keys
344	result in nothing being output)	649	result in nothing being output)
345		650
346	Does not check input for validity.	651	Does not check input for validity.
347		652
348	=back	653	=back
		654
		655
		656	=head2 JSON and YAML
		657
		658	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		659	however, a mass hysteria and very far from the truth. In general, there is
		660	no way to configure JSON::XS to output a data structure as valid YAML.
		661
		662	If you really must use JSON::XS to generate YAML, you should use this
		663	algorithm (subject to change in future versions):
		664
		665	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		666	my $yaml = $to_yaml->encode ($ref) . "\n";
		667
		668	This will usually generate JSON texts that also parse as valid
		669	YAML. Please note that YAML has hardcoded limits on (simple) object key
		670	lengths that JSON doesn't have, so you should make sure that your hash
		671	keys are noticably shorter than the 1024 characters YAML allows.
		672
		673	There might be other incompatibilities that I am not aware of. In general
		674	you should not try to generate YAML with a JSON generator or vice versa,
		675	or try to parse JSON with a YAML parser or vice versa: chances are high
		676	that you will run into severe interoperability problems.
		677
349		678
350	=head2 SPEED	679	=head2 SPEED
351		680
352	It seems that JSON::XS is surprisingly fast, as shown in the following	681	It seems that JSON::XS is surprisingly fast, as shown in the following
353	tables. They have been generated with the help of the C<eg/bench> program	682	tables. They have been generated with the help of the C<eg/bench> program
354	in the JSON::XS distribution, to make it easy to compare on your own	683	in the JSON::XS distribution, to make it easy to compare on your own
355	system.	684	system.
356		685
357	First is a comparison between various modules using a very simple JSON	686	First comes a comparison between various modules using a very short
		687	single-line JSON string:
		688
		689	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		690	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		691
358	string, showing the number of encodes/decodes per second (JSON::XS is	692	It shows the number of encodes/decodes per second (JSON::XS uses
359	the functional interface, while JSON::XS/2 is the OO interface with	693	the functional interface, while JSON::XS/2 uses the OO interface
360	pretty-printing and hashkey sorting enabled).	694	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		695	shrink). Higher is better:
361		696
362	module \| encode \| decode \|	697	module \| encode \| decode \|
363	-----------\|------------\|------------\|	698	-----------\|------------\|------------\|
364	JSON \| 14006 \| 6820 \|	699	JSON \| 7645.468 \| 4208.613 \|
365	JSON::DWIW \| 200937 \| 120386 \|	700	JSON::DWIW \| 40721.398 \| 77101.176 \|
366	JSON::PC \| 85065 \| 129366 \|	701	JSON::PC \| 65948.176 \| 78251.940 \|
367	JSON::Syck \| 59898 \| 44232 \|	702	JSON::Syck \| 22844.793 \| 26479.192 \|
368	JSON::XS \| 1171478 \| 342435 \|	703	JSON::XS \| 388361.481 \| 199728.762 \|
369	JSON::XS/2 \| 730760 \| 328714 \|	704	JSON::XS/2 \| 218453.333 \| 192399.266 \|
		705	JSON::XS/3 \| 338250.323 \| 192399.266 \|
		706	Storable \| 15779.925 \| 14169.946 \|
370	-----------+------------+------------+	707	-----------+------------+------------+
371		708
372	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	709	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		710	about three times faster on decoding, and over fourty times faster
373	times faster than JSON, even with pretty-printing and key sorting.	711	than JSON, even with pretty-printing and key sorting. It also compares
		712	favourably to Storable for small amounts of data.
374		713
375	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	714	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
376	search API (http://nanoref.com/yahooapis/mgPdGg):	715	search API (http://nanoref.com/yahooapis/mgPdGg):
377		716
378	module \| encode \| decode \|	717	module \| encode \| decode \|
379	-----------\|------------\|------------\|	718	-----------\|------------\|------------\|
380	JSON \| 673 \| 38 \|	719	JSON \| 254.685 \| 37.665 \|
381	JSON::DWIW \| 5271 \| 770 \|	720	JSON::DWIW \| 843.343 \| 1049.731 \|
382	JSON::PC \| 9901 \| 2491 \|	721	JSON::PC \| 3602.116 \| 2307.352 \|
383	JSON::Syck \| 2360 \| 786 \|	722	JSON::Syck \| 505.107 \| 787.899 \|
384	JSON::XS \| 37398 \| 3202 \|	723	JSON::XS \| 5747.196 \| 3690.220 \|
385	JSON::XS/2 \| 13765 \| 3153 \|	724	JSON::XS/2 \| 3968.121 \| 3676.634 \|
		725	JSON::XS/3 \| 6105.246 \| 3662.508 \|
		726	Storable \| 4417.337 \| 5285.161 \|
386	-----------+------------+------------+	727	-----------+------------+------------+
387		728
388	Again, JSON::XS leads by far in the encoding case, while still beating	729	Again, JSON::XS leads by far (except for Storable which non-surprisingly
389	every other module in the decoding case.	730	decodes faster).
390		731
391	Last example is an almost 8MB large hash with many large binary values	732	On large strings containing lots of high unicode characters, some modules
392	(PNG files), resulting in a lot of escaping:	733	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		734	will be broken due to missing (or wrong) unicode handling. Others refuse
		735	to decode or encode properly, so it was impossible to prepare a fair
		736	comparison table for that case.
		737
		738
		739	=head1 SECURITY CONSIDERATIONS
		740
		741	When you are using JSON in a protocol, talking to untrusted potentially
		742	hostile creatures requires relatively few measures.
		743
		744	First of all, your JSON decoder should be secure, that is, should not have
		745	any buffer overflows. Obviously, this module should ensure that and I am
		746	trying hard on making that true, but you never know.
		747
		748	Second, you need to avoid resource-starving attacks. That means you should
		749	limit the size of JSON texts you accept, or make sure then when your
		750	resources run out, thats just fine (e.g. by using a separate process that
		751	can crash safely). The size of a JSON text in octets or characters is
		752	usually a good indication of the size of the resources required to decode
		753	it into a Perl structure.
		754
		755	Third, JSON::XS recurses using the C stack when decoding objects and
		756	arrays. The C stack is a limited resource: for instance, on my amd64
		757	machine with 8MB of stack size I can decode around 180k nested arrays but
		758	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		759	to free the temporary). If that is exceeded, the program crashes. to be
		760	conservative, the default nesting limit is set to 512. If your process
		761	has a smaller stack, you should adjust this setting accordingly with the
		762	C<max_depth> method.
		763
		764	And last but least, something else could bomb you that I forgot to think
		765	of. In that case, you get to keep the pieces. I am always open for hints,
		766	though...
		767
		768	If you are using JSON::XS to return packets to consumption
		769	by javascript scripts in a browser you should have a look at
		770	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		771	you are vulnerable to some common attack vectors (which really are browser
		772	design bugs, but it is still you who will have to deal with it, as major
		773	browser developers care only for features, not about doing security
		774	right).
		775
393		776
394	=head1 BUGS	777	=head1 BUGS
395		778
396	While the goal of this module is to be correct, that unfortunately does	779	While the goal of this module is to be correct, that unfortunately does
397	not mean its bug-free, only that I think its design is bug-free. It is	780	not mean its bug-free, only that I think its design is bug-free. It is
398	still very young and not well-tested. If you keep reporting bugs they will	781	still relatively early in its development. If you keep reporting bugs they
399	be fixed swiftly, though.	782	will be fixed swiftly, though.
400		783
401	=cut	784	=cut
		785
		786	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		787	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		788
		789	sub true() { $true }
		790	sub false() { $false }
		791
		792	sub is_bool($) {
		793	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		794	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		795	}
		796
		797	XSLoader::load "JSON::XS", $VERSION;
		798
		799	package JSON::XS::Boolean;
		800
		801	use overload
		802	"0+" => sub { ${$_[0]} },
		803	"++" => sub { $_[0] = ${$_[0]} + 1 },
		804	"--" => sub { $_[0] = ${$_[0]} - 1 },
		805	fallback => 1;
402		806
403	1;	807	1;
404		808
405	=head1 AUTHOR	809	=head1 AUTHOR
406		810

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Comparing JSON-XS/XS.pm (file contents): Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs. Revision 1.44 by root, Mon Jun 25 04:08:17 2007 UTC

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Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs.
Revision 1.44 by root, Mon Jun 25 04:08:17 2007 UTC