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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.7 by root, Fri Mar 23 15:10:55 2007 UTC vs.
Revision 1.43 by root, Sat Jun 23 23:49:29 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 = '1.3';
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
223	=item $json = $json->shrink ([$enable])	321	=item $json = $json->shrink ([$enable])
224		322
225	Perl usually over-allocates memory a bit when allocating space for	323	Perl usually over-allocates memory a bit when allocating space for
226	strings. This flag optionally resizes strings generated by either	324	strings. This flag optionally resizes strings generated by either
227	C<encode> or C<decode> to their minimum size possible. This can save	325	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	326	memory when your JSON texts are either very very long or you have many
229	short strings.	327	short strings. It will also try to downgrade any strings to octet-form
		328	if possible: perl stores strings internally either in an encoding called
		329	UTF-X or in octet-form. The latter cannot store everything but uses less
		330	space in general (and some buggy Perl or C code might even rely on that
		331	internal representation being used).
230		332
		333	The actual definition of what shrink does might change in future versions,
		334	but it will always try to save space at the expense of time.
		335
231	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	336	If C<$enable> is true (or missing), the string returned by C<encode> will
232	while all strings generated by C<decode> will also be shrunk-to-fit.	337	be shrunk-to-fit, while all strings generated by C<decode> will also be
		338	shrunk-to-fit.
233		339
234	If C<$enable> is false, then the normal perl allocation algorithms are used.	340	If C<$enable> is false, then the normal perl allocation algorithms are used.
235	If you work with your data, then this is likely to be faster.	341	If you work with your data, then this is likely to be faster.
236		342
237	In the future, this setting might control other things, such as converting	343	In the future, this setting might control other things, such as converting
238	strings that look like integers or floats into integers or floats	344	strings that look like integers or floats into integers or floats
239	internally (there is no difference on the Perl level), saving space.	345	internally (there is no difference on the Perl level), saving space.
240		346
		347	=item $json = $json->max_depth ([$maximum_nesting_depth])
		348
		349	Sets the maximum nesting level (default C<512>) accepted while encoding
		350	or decoding. If the JSON text or Perl data structure has an equal or
		351	higher nesting level then this limit, then the encoder and decoder will
		352	stop and croak at that point.
		353
		354	Nesting level is defined by number of hash- or arrayrefs that the encoder
		355	needs to traverse to reach a given point or the number of C<{> or C<[>
		356	characters without their matching closing parenthesis crossed to reach a
		357	given character in a string.
		358
		359	Setting the maximum depth to one disallows any nesting, so that ensures
		360	that the object is only a single hash/object or array.
		361
		362	The argument to C<max_depth> will be rounded up to the next nearest power
		363	of two.
		364
		365	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		366
241	=item $json_string = $json->encode ($perl_scalar)	367	=item $json_text = $json->encode ($perl_scalar)
242		368
243	Converts the given Perl data structure (a simple scalar or a reference	369	Converts the given Perl data structure (a simple scalar or a reference
244	to a hash or array) to its JSON representation. Simple scalars will be	370	to a hash or array) to its JSON representation. Simple scalars will be
245	converted into JSON string or number sequences, while references to arrays	371	converted into JSON string or number sequences, while references to arrays
246	become JSON arrays and references to hashes become JSON objects. Undefined	372	become JSON arrays and references to hashes become JSON objects. Undefined
247	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	373	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
248	nor C<false> values will be generated.	374	nor C<false> values will be generated.
249		375
250	=item $perl_scalar = $json->decode ($json_string)	376	=item $perl_scalar = $json->decode ($json_text)
251		377
252	The opposite of C<encode>: expects a JSON string and tries to parse it,	378	The opposite of C<encode>: expects a JSON text and tries to parse it,
253	returning the resulting simple scalar or reference. Croaks on error.	379	returning the resulting simple scalar or reference. Croaks on error.
254		380
255	JSON numbers and strings become simple Perl scalars. JSON arrays become	381	JSON numbers and strings become simple Perl scalars. JSON arrays become
256	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	382	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
257	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	383	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
258		384
		385	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		386
		387	This works like the C<decode> method, but instead of raising an exception
		388	when there is trailing garbage after the first JSON object, it will
		389	silently stop parsing there and return the number of characters consumed
		390	so far.
		391
		392	This is useful if your JSON texts are not delimited by an outer protocol
		393	(which is not the brightest thing to do in the first place) and you need
		394	to know where the JSON text ends.
		395
		396	JSON::XS->new->decode_prefix ("[1] the tail")
		397	=> ([], 3)
		398
259	=back	399	=back
		400
		401
		402	=head1 MAPPING
		403
		404	This section describes how JSON::XS maps Perl values to JSON values and
		405	vice versa. These mappings are designed to "do the right thing" in most
		406	circumstances automatically, preserving round-tripping characteristics
		407	(what you put in comes out as something equivalent).
		408
		409	For the more enlightened: note that in the following descriptions,
		410	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		411	refers to the abstract Perl language itself.
		412
		413
		414	=head2 JSON -> PERL
		415
		416	=over 4
		417
		418	=item object
		419
		420	A JSON object becomes a reference to a hash in Perl. No ordering of object
		421	keys is preserved (JSON does not preserver object key ordering itself).
		422
		423	=item array
		424
		425	A JSON array becomes a reference to an array in Perl.
		426
		427	=item string
		428
		429	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		430	are represented by the same codepoints in the Perl string, so no manual
		431	decoding is necessary.
		432
		433	=item number
		434
		435	A JSON number becomes either an integer or numeric (floating point)
		436	scalar in perl, depending on its range and any fractional parts. On the
		437	Perl level, there is no difference between those as Perl handles all the
		438	conversion details, but an integer may take slightly less memory and might
		439	represent more values exactly than (floating point) numbers.
		440
		441	=item true, false
		442
		443	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		444	respectively. They are overloaded to act almost exactly like the numbers
		445	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		446	the C<JSON::XS::is_bool> function.
		447
		448	=item null
		449
		450	A JSON null atom becomes C<undef> in Perl.
		451
		452	=back
		453
		454
		455	=head2 PERL -> JSON
		456
		457	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		458	truly typeless language, so we can only guess which JSON type is meant by
		459	a Perl value.
		460
		461	=over 4
		462
		463	=item hash references
		464
		465	Perl hash references become JSON objects. As there is no inherent ordering
		466	in hash keys (or JSON objects), they will usually be encoded in a
		467	pseudo-random order that can change between runs of the same program but
		468	stays generally the same within a single run of a program. JSON::XS can
		469	optionally sort the hash keys (determined by the I<canonical> flag), so
		470	the same datastructure will serialise to the same JSON text (given same
		471	settings and version of JSON::XS), but this incurs a runtime overhead
		472	and is only rarely useful, e.g. when you want to compare some JSON text
		473	against another for equality.
		474
		475	=item array references
		476
		477	Perl array references become JSON arrays.
		478
		479	=item other references
		480
		481	Other unblessed references are generally not allowed and will cause an
		482	exception to be thrown, except for references to the integers C<0> and
		483	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		484	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		485
		486	to_json [\0,JSON::XS::true] # yields [false,true]
		487
		488	=item JSON::XS::true, JSON::XS::false
		489
		490	These special values become JSON true and JSON false values,
		491	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		492
		493	=item blessed objects
		494
		495	Blessed objects are not allowed. JSON::XS currently tries to encode their
		496	underlying representation (hash- or arrayref), but this behaviour might
		497	change in future versions.
		498
		499	=item simple scalars
		500
		501	Simple Perl scalars (any scalar that is not a reference) are the most
		502	difficult objects to encode: JSON::XS will encode undefined scalars as
		503	JSON null value, scalars that have last been used in a string context
		504	before encoding as JSON strings and anything else as number value:
		505
		506	# dump as number
		507	to_json [2] # yields [2]
		508	to_json [-3.0e17] # yields [-3e+17]
		509	my $value = 5; to_json [$value] # yields [5]
		510
		511	# used as string, so dump as string
		512	print $value;
		513	to_json [$value] # yields ["5"]
		514
		515	# undef becomes null
		516	to_json [undef] # yields [null]
		517
		518	You can force the type to be a string by stringifying it:
		519
		520	my $x = 3.1; # some variable containing a number
		521	"$x"; # stringified
		522	$x .= ""; # another, more awkward way to stringify
		523	print $x; # perl does it for you, too, quite often
		524
		525	You can force the type to be a number by numifying it:
		526
		527	my $x = "3"; # some variable containing a string
		528	$x += 0; # numify it, ensuring it will be dumped as a number
		529	$x *= 1; # same thing, the choise is yours.
		530
		531	You can not currently output JSON booleans or force the type in other,
		532	less obscure, ways. Tell me if you need this capability.
		533
		534	=back
		535
260		536
261	=head1 COMPARISON	537	=head1 COMPARISON
262		538
263	As already mentioned, this module was created because none of the existing	539	As already mentioned, this module was created because none of the existing
264	JSON modules could be made to work correctly. First I will describe the	540	JSON modules could be made to work correctly. First I will describe the
…		…
290		566
291	Has problems handling many Perl values (e.g. regex results and other magic	567	Has problems handling many Perl values (e.g. regex results and other magic
292	values will make it croak).	568	values will make it croak).
293		569
294	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	570	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
295	which is not a valid JSON string.	571	which is not a valid JSON text.
296		572
297	Unmaintained (maintainer unresponsive for many months, bugs are not	573	Unmaintained (maintainer unresponsive for many months, bugs are not
298	getting fixed).	574	getting fixed).
299		575
300	=item JSON::Syck 0.21	576	=item JSON::Syck 0.21
…		…
302	Very buggy (often crashes).	578	Very buggy (often crashes).
303		579
304	Very inflexible (no human-readable format supported, format pretty much	580	Very inflexible (no human-readable format supported, format pretty much
305	undocumented. I need at least a format for easy reading by humans and a	581	undocumented. I need at least a format for easy reading by humans and a
306	single-line compact format for use in a protocol, and preferably a way to	582	single-line compact format for use in a protocol, and preferably a way to
307	generate ASCII-only JSON strings).	583	generate ASCII-only JSON texts).
308		584
309	Completely broken (and confusingly documented) Unicode handling (unicode	585	Completely broken (and confusingly documented) Unicode handling (unicode
310	escapes are not working properly, you need to set ImplicitUnicode to	586	escapes are not working properly, you need to set ImplicitUnicode to
311	I<different> values on en- and decoding to get symmetric behaviour).	587	I<different> values on en- and decoding to get symmetric behaviour).
312		588
…		…
335		611
336	Very inflexible.	612	Very inflexible.
337		613
338	No roundtripping.	614	No roundtripping.
339		615
340	Does not generate valid JSON (key strings are often unquoted, empty keys	616	Does not generate valid JSON texts (key strings are often unquoted, empty keys
341	result in nothing being output)	617	result in nothing being output)
342		618
343	Does not check input for validity.	619	Does not check input for validity.
344		620
345	=back	621	=back
		622
		623
		624	=head2 JSON and YAML
		625
		626	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		627	however, a mass hysteria and very far from the truth. In general, there is
		628	no way to configure JSON::XS to output a data structure as valid YAML.
		629
		630	If you really must use JSON::XS to generate YAML, you should use this
		631	algorithm (subject to change in future versions):
		632
		633	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		634	my $yaml = $to_yaml->encode ($ref) . "\n";
		635
		636	This will usually generate JSON texts that also parse as valid
		637	YAML. Please note that YAML has hardcoded limits on (simple) object key
		638	lengths that JSON doesn't have, so you should make sure that your hash
		639	keys are noticably shorter than the 1024 characters YAML allows.
		640
		641	There might be other incompatibilities that I am not aware of. In general
		642	you should not try to generate YAML with a JSON generator or vice versa,
		643	or try to parse JSON with a YAML parser or vice versa: chances are high
		644	that you will run into severe interoperability problems.
		645
346		646
347	=head2 SPEED	647	=head2 SPEED
348		648
349	It seems that JSON::XS is surprisingly fast, as shown in the following	649	It seems that JSON::XS is surprisingly fast, as shown in the following
350	tables. They have been generated with the help of the C<eg/bench> program	650	tables. They have been generated with the help of the C<eg/bench> program
351	in the JSON::XS distribution, to make it easy to compare on your own	651	in the JSON::XS distribution, to make it easy to compare on your own
352	system.	652	system.
353		653
354	First is a comparison between various modules using a very simple JSON	654	First comes a comparison between various modules using a very short
		655	single-line JSON string:
		656
		657	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		658	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		659
355	string, showing the number of encodes/decodes per second (JSON::XS is	660	It shows the number of encodes/decodes per second (JSON::XS uses
356	the functional interface, while JSON::XS/2 is the OO interface with	661	the functional interface, while JSON::XS/2 uses the OO interface
357	pretty-printing and hashkey sorting enabled).	662	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		663	shrink). Higher is better:
358		664
359	module \| encode \| decode \|	665	module \| encode \| decode \|
360	-----------\|------------\|------------\|	666	-----------\|------------\|------------\|
361	JSON \| 14006 \| 6820 \|	667	JSON \| 7645.468 \| 4208.613 \|
362	JSON::DWIW \| 200937 \| 120386 \|	668	JSON::DWIW \| 40721.398 \| 77101.176 \|
363	JSON::PC \| 85065 \| 129366 \|	669	JSON::PC \| 65948.176 \| 78251.940 \|
364	JSON::Syck \| 59898 \| 44232 \|	670	JSON::Syck \| 22844.793 \| 26479.192 \|
365	JSON::XS \| 1171478 \| 342435 \|	671	JSON::XS \| 388361.481 \| 199728.762 \|
366	JSON::XS/2 \| 730760 \| 328714 \|	672	JSON::XS/2 \| 218453.333 \| 192399.266 \|
		673	JSON::XS/3 \| 338250.323 \| 192399.266 \|
		674	Storable \| 15779.925 \| 14169.946 \|
367	-----------+------------+------------+	675	-----------+------------+------------+
368		676
369	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	677	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		678	about three times faster on decoding, and over fourty times faster
370	times faster than JSON, even with pretty-printing and key sorting.	679	than JSON, even with pretty-printing and key sorting. It also compares
		680	favourably to Storable for small amounts of data.
371		681
372	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	682	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
373	search API (http://nanoref.com/yahooapis/mgPdGg):	683	search API (http://nanoref.com/yahooapis/mgPdGg):
374		684
375	module \| encode \| decode \|	685	module \| encode \| decode \|
376	-----------\|------------\|------------\|	686	-----------\|------------\|------------\|
377	JSON \| 673 \| 38 \|	687	JSON \| 254.685 \| 37.665 \|
378	JSON::DWIW \| 5271 \| 770 \|	688	JSON::DWIW \| 843.343 \| 1049.731 \|
379	JSON::PC \| 9901 \| 2491 \|	689	JSON::PC \| 3602.116 \| 2307.352 \|
380	JSON::Syck \| 2360 \| 786 \|	690	JSON::Syck \| 505.107 \| 787.899 \|
381	JSON::XS \| 37398 \| 3202 \|	691	JSON::XS \| 5747.196 \| 3690.220 \|
382	JSON::XS/2 \| 13765 \| 3153 \|	692	JSON::XS/2 \| 3968.121 \| 3676.634 \|
		693	JSON::XS/3 \| 6105.246 \| 3662.508 \|
		694	Storable \| 4417.337 \| 5285.161 \|
383	-----------+------------+------------+	695	-----------+------------+------------+
384		696
385	Again, JSON::XS leads by far in the encoding case, while still beating	697	Again, JSON::XS leads by far (except for Storable which non-surprisingly
386	every other module in the decoding case.	698	decodes faster).
387		699
388	Last example is an almost 8MB large hash with many large binary values	700	On large strings containing lots of high unicode characters, some modules
389	(PNG files), resulting in a lot of escaping:	701	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		702	will be broken due to missing (or wrong) unicode handling. Others refuse
		703	to decode or encode properly, so it was impossible to prepare a fair
		704	comparison table for that case.
		705
		706
		707	=head1 SECURITY CONSIDERATIONS
		708
		709	When you are using JSON in a protocol, talking to untrusted potentially
		710	hostile creatures requires relatively few measures.
		711
		712	First of all, your JSON decoder should be secure, that is, should not have
		713	any buffer overflows. Obviously, this module should ensure that and I am
		714	trying hard on making that true, but you never know.
		715
		716	Second, you need to avoid resource-starving attacks. That means you should
		717	limit the size of JSON texts you accept, or make sure then when your
		718	resources run out, thats just fine (e.g. by using a separate process that
		719	can crash safely). The size of a JSON text in octets or characters is
		720	usually a good indication of the size of the resources required to decode
		721	it into a Perl structure.
		722
		723	Third, JSON::XS recurses using the C stack when decoding objects and
		724	arrays. The C stack is a limited resource: for instance, on my amd64
		725	machine with 8MB of stack size I can decode around 180k nested arrays but
		726	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		727	to free the temporary). If that is exceeded, the program crashes. to be
		728	conservative, the default nesting limit is set to 512. If your process
		729	has a smaller stack, you should adjust this setting accordingly with the
		730	C<max_depth> method.
		731
		732	And last but least, something else could bomb you that I forgot to think
		733	of. In that case, you get to keep the pieces. I am always open for hints,
		734	though...
		735
		736	If you are using JSON::XS to return packets to consumption
		737	by javascript scripts in a browser you should have a look at
		738	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		739	you are vulnerable to some common attack vectors (which really are browser
		740	design bugs, but it is still you who will have to deal with it, as major
		741	browser developers care only for features, not about doing security
		742	right).
		743
390		744
391	=head1 BUGS	745	=head1 BUGS
392		746
393	While the goal of this module is to be correct, that unfortunately does	747	While the goal of this module is to be correct, that unfortunately does
394	not mean its bug-free, only that I think its design is bug-free. It is	748	not mean its bug-free, only that I think its design is bug-free. It is
395	still very young and not well-tested. If you keep reporting bugs they will	749	still relatively early in its development. If you keep reporting bugs they
396	be fixed swiftly, though.	750	will be fixed swiftly, though.
397		751
398	=cut	752	=cut
		753
		754	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		755	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		756
		757	sub true() { $true }
		758	sub false() { $false }
		759
		760	sub is_bool($) {
		761	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		762	or UNIVERSAL::isa $_[0], "JSON::Literal"
		763	}
		764
		765	XSLoader::load "JSON::XS", $VERSION;
		766
		767	package JSON::XS::Boolean;
		768
		769	use overload
		770	"0+" => sub { ${$_[0]} },
		771	"++" => sub { $_[0] = ${$_[0]} + 1 },
		772	"--" => sub { $_[0] = ${$_[0]} - 1 },
		773	fallback => 1;
399		774
400	1;	775	1;
401		776
402	=head1 AUTHOR	777	=head1 AUTHOR
403		778

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Comparing JSON-XS/XS.pm (file contents): Revision 1.7 by root, Fri Mar 23 15:10:55 2007 UTC vs. Revision 1.43 by root, Sat Jun 23 23:49:29 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.7 by root, Fri Mar 23 15:10:55 2007 UTC vs.
Revision 1.43 by root, Sat Jun 23 23:49:29 2007 UTC