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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.3 by root, Thu Mar 22 18:10:29 2007 UTC vs.
Revision 1.45 by root, Mon Jun 25 04:16:46 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 = '0.1';	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<$enable> is true, then the C<encode> method will not generate	161	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	162	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	163	unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	164	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		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.
125		168
126	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
127	characters unless necessary.	170	characters unless required by the JSON syntax or other flags. This results
		171	in a faster and more compact format.
128		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
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	177	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	178	=> ["\ud801\udc01"]
131		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)
		202
132	=item $json = $json->utf8 ($enable)	203	=item $json = $json->utf8 ([$enable])
133		204
134	If C<$enable> is true, then the C<encode> method will encode the JSON	205	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	206	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	207	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	208	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	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.
139		212
140	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
141	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
142	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
143	to be done yourself, e.g. using the Encode module.	216	to be done yourself, e.g. using the Encode module.
144		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
145	=item $json = $json->pretty ($enable)	228	=item $json = $json->pretty ([$enable])
146		229
147	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
148	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
149	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:
150		235
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	236	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	237	=>
153	{	238	{
154	"a" : [	239	"a" : [
155	1,	240	1,
156	2	241	2
157	]	242	]
158	}	243	}
159		244
160	=item $json = $json->indent ($enable)	245	=item $json = $json->indent ([$enable])
161		246
162	If C<$enable> is true, then the C<encode> method will use a multiline	247	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	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
164	into its own line, identing them properly.	249	into its own line, identing them properly.
165		250
166	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
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	252	resulting JSON text is guarenteed not to contain any C<newlines>.
168		253
169	This setting has no effect when decoding JSON strings.	254	This setting has no effect when decoding JSON texts.
170		255
171	=item $json = $json->space_before ($enable)	256	=item $json = $json->space_before ([$enable])
172		257
173	If C<$enable> is true, then the C<encode> method will add an extra	258	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	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.
175		260
176	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
177	space at those places.	262	space at those places.
178		263
179	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
180	likely combine this setting with C<space_after>.	265	most likely combine this setting with C<space_after>.
181		266
		267	Example, space_before enabled, space_after and indent disabled:
		268
		269	{"key" :"value"}
		270
182	=item $json = $json->space_after ($enable)	271	=item $json = $json->space_after ([$enable])
183		272
184	If C<$enable> is true, then the C<encode> method will add an extra	273	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	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
186	and extra whitespace after the C<,> separating key-value pairs and array	275	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	276	members.
188		277
189	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
190	space at those places.	279	space at those places.
191		280
192	This setting has no effect when decoding JSON strings.	281	This setting has no effect when decoding JSON texts.
193		282
		283	Example, space_before and indent disabled, space_after enabled:
		284
		285	{"key": "value"}
		286
194	=item $json = $json->canonical ($enable)	287	=item $json = $json->canonical ([$enable])
195		288
196	If C<$enable> is true, then the C<encode> method will output JSON objects	289	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	290	by sorting their keys. This is adding a comparatively high overhead.
198		291
199	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
200	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
201	of the same script).	294	of the same script).
202		295
203	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
204	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,
205	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,
206	as key-value pairs have no inherent ordering in Perl.	299	as key-value pairs have no inherent ordering in Perl.
207		300
208	This setting has no effect when decoding JSON strings.	301	This setting has no effect when decoding JSON texts.
209		302
210	=item $json = $json->allow_nonref ($enable)	303	=item $json = $json->allow_nonref ([$enable])
211		304
212	If C<$enable> is true, then the C<encode> method can convert a	305	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	306	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	307	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	308	values instead of croaking.
216		309
217	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
218	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
219	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
220	JSON object or array.	313	JSON object or array.
221		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<$enable> is true (or missing), then C<encode>, upon encountering a
		336	blessed object, will check for the availability of the C<TO_JSON> method
		337	on the object's class. If found, it will be called in scalar context
		338	and the resulting scalar will be encoded instead of the object. If no
		339	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		340	to do.
		341
		342	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		343	returns other blessed objects, those will be handled in the same
		344	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		345	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		346	methods called by the Perl core (== not the user of the object) are
		347	usually in upper case letters and to avoid collisions with the C<to_json>
		348	function.
		349
		350	This setting does not yet influence C<decode> in any way, but in the
		351	future, global hooks might get installed that influence C<decode> and are
		352	enabled by this setting.
		353
		354	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		355	to do when a blessed object is found.
		356
		357	=item $json = $json->shrink ([$enable])
		358
		359	Perl usually over-allocates memory a bit when allocating space for
		360	strings. This flag optionally resizes strings generated by either
		361	C<encode> or C<decode> to their minimum size possible. This can save
		362	memory when your JSON texts are either very very long or you have many
		363	short strings. It will also try to downgrade any strings to octet-form
		364	if possible: perl stores strings internally either in an encoding called
		365	UTF-X or in octet-form. The latter cannot store everything but uses less
		366	space in general (and some buggy Perl or C code might even rely on that
		367	internal representation being used).
		368
		369	The actual definition of what shrink does might change in future versions,
		370	but it will always try to save space at the expense of time.
		371
		372	If C<$enable> is true (or missing), the string returned by C<encode> will
		373	be shrunk-to-fit, while all strings generated by C<decode> will also be
		374	shrunk-to-fit.
		375
		376	If C<$enable> is false, then the normal perl allocation algorithms are used.
		377	If you work with your data, then this is likely to be faster.
		378
		379	In the future, this setting might control other things, such as converting
		380	strings that look like integers or floats into integers or floats
		381	internally (there is no difference on the Perl level), saving space.
		382
		383	=item $json = $json->max_depth ([$maximum_nesting_depth])
		384
		385	Sets the maximum nesting level (default C<512>) accepted while encoding
		386	or decoding. If the JSON text or Perl data structure has an equal or
		387	higher nesting level then this limit, then the encoder and decoder will
		388	stop and croak at that point.
		389
		390	Nesting level is defined by number of hash- or arrayrefs that the encoder
		391	needs to traverse to reach a given point or the number of C<{> or C<[>
		392	characters without their matching closing parenthesis crossed to reach a
		393	given character in a string.
		394
		395	Setting the maximum depth to one disallows any nesting, so that ensures
		396	that the object is only a single hash/object or array.
		397
		398	The argument to C<max_depth> will be rounded up to the next nearest power
		399	of two.
		400
		401	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		402
222	=item $json_string = $json->encode ($perl_scalar)	403	=item $json_text = $json->encode ($perl_scalar)
223		404
224	Converts the given Perl data structure (a simple scalar or a reference	405	Converts the given Perl data structure (a simple scalar or a reference
225	to a hash or array) to its JSON representation. Simple scalars will be	406	to a hash or array) to its JSON representation. Simple scalars will be
226	converted into JSON string or number sequences, while references to arrays	407	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	408	become JSON arrays and references to hashes become JSON objects. Undefined
228	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	409	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	410	nor C<false> values will be generated.
230		411
231	=item $perl_scalar = $json->decode ($json_string)	412	=item $perl_scalar = $json->decode ($json_text)
232		413
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	414	The opposite of C<encode>: expects a JSON text and tries to parse it,
234	returning the resulting simple scalar or reference. Croaks on error.	415	returning the resulting simple scalar or reference. Croaks on error.
235		416
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	417	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	418	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
238	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	419	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		420
		421	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		422
		423	This works like the C<decode> method, but instead of raising an exception
		424	when there is trailing garbage after the first JSON object, it will
		425	silently stop parsing there and return the number of characters consumed
		426	so far.
		427
		428	This is useful if your JSON texts are not delimited by an outer protocol
		429	(which is not the brightest thing to do in the first place) and you need
		430	to know where the JSON text ends.
		431
		432	JSON::XS->new->decode_prefix ("[1] the tail")
		433	=> ([], 3)
		434
240	=back	435	=back
		436
		437
		438	=head1 MAPPING
		439
		440	This section describes how JSON::XS maps Perl values to JSON values and
		441	vice versa. These mappings are designed to "do the right thing" in most
		442	circumstances automatically, preserving round-tripping characteristics
		443	(what you put in comes out as something equivalent).
		444
		445	For the more enlightened: note that in the following descriptions,
		446	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		447	refers to the abstract Perl language itself.
		448
		449
		450	=head2 JSON -> PERL
		451
		452	=over 4
		453
		454	=item object
		455
		456	A JSON object becomes a reference to a hash in Perl. No ordering of object
		457	keys is preserved (JSON does not preserver object key ordering itself).
		458
		459	=item array
		460
		461	A JSON array becomes a reference to an array in Perl.
		462
		463	=item string
		464
		465	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		466	are represented by the same codepoints in the Perl string, so no manual
		467	decoding is necessary.
		468
		469	=item number
		470
		471	A JSON number becomes either an integer or numeric (floating point)
		472	scalar in perl, depending on its range and any fractional parts. On the
		473	Perl level, there is no difference between those as Perl handles all the
		474	conversion details, but an integer may take slightly less memory and might
		475	represent more values exactly than (floating point) numbers.
		476
		477	=item true, false
		478
		479	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		480	respectively. They are overloaded to act almost exactly like the numbers
		481	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		482	the C<JSON::XS::is_bool> function.
		483
		484	=item null
		485
		486	A JSON null atom becomes C<undef> in Perl.
		487
		488	=back
		489
		490
		491	=head2 PERL -> JSON
		492
		493	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		494	truly typeless language, so we can only guess which JSON type is meant by
		495	a Perl value.
		496
		497	=over 4
		498
		499	=item hash references
		500
		501	Perl hash references become JSON objects. As there is no inherent ordering
		502	in hash keys (or JSON objects), they will usually be encoded in a
		503	pseudo-random order that can change between runs of the same program but
		504	stays generally the same within a single run of a program. JSON::XS can
		505	optionally sort the hash keys (determined by the I<canonical> flag), so
		506	the same datastructure will serialise to the same JSON text (given same
		507	settings and version of JSON::XS), but this incurs a runtime overhead
		508	and is only rarely useful, e.g. when you want to compare some JSON text
		509	against another for equality.
		510
		511	=item array references
		512
		513	Perl array references become JSON arrays.
		514
		515	=item other references
		516
		517	Other unblessed references are generally not allowed and will cause an
		518	exception to be thrown, except for references to the integers C<0> and
		519	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		520	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		521
		522	to_json [\0,JSON::XS::true] # yields [false,true]
		523
		524	=item JSON::XS::true, JSON::XS::false
		525
		526	These special values become JSON true and JSON false values,
		527	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		528
		529	=item blessed objects
		530
		531	Blessed objects are not allowed. JSON::XS currently tries to encode their
		532	underlying representation (hash- or arrayref), but this behaviour might
		533	change in future versions.
		534
		535	=item simple scalars
		536
		537	Simple Perl scalars (any scalar that is not a reference) are the most
		538	difficult objects to encode: JSON::XS will encode undefined scalars as
		539	JSON null value, scalars that have last been used in a string context
		540	before encoding as JSON strings and anything else as number value:
		541
		542	# dump as number
		543	to_json [2] # yields [2]
		544	to_json [-3.0e17] # yields [-3e+17]
		545	my $value = 5; to_json [$value] # yields [5]
		546
		547	# used as string, so dump as string
		548	print $value;
		549	to_json [$value] # yields ["5"]
		550
		551	# undef becomes null
		552	to_json [undef] # yields [null]
		553
		554	You can force the type to be a string by stringifying it:
		555
		556	my $x = 3.1; # some variable containing a number
		557	"$x"; # stringified
		558	$x .= ""; # another, more awkward way to stringify
		559	print $x; # perl does it for you, too, quite often
		560
		561	You can force the type to be a number by numifying it:
		562
		563	my $x = "3"; # some variable containing a string
		564	$x += 0; # numify it, ensuring it will be dumped as a number
		565	$x *= 1; # same thing, the choise is yours.
		566
		567	You can not currently output JSON booleans or force the type in other,
		568	less obscure, ways. Tell me if you need this capability.
		569
		570	=back
		571
241		572
242	=head1 COMPARISON	573	=head1 COMPARISON
243		574
244	As already mentioned, this module was created because none of the existing	575	As already mentioned, this module was created because none of the existing
245	JSON modules could be made to work correctly. First I will describe the	576	JSON modules could be made to work correctly. First I will describe the
246	problems (or pleasures) I encountered with various existing JSON modules,	577	problems (or pleasures) I encountered with various existing JSON modules,
247	followed by some benchmark values.	578	followed by some benchmark values. JSON::XS was designed not to suffer
		579	from any of these problems or limitations.
248		580
249	=over 4	581	=over 4
250		582
251	=item JSON	583	=item JSON 1.07
252		584
253	Slow (but very portable, as it is written in pure Perl).	585	Slow (but very portable, as it is written in pure Perl).
254		586
255	Undocumented/buggy Unicode handling (how JSON handles unicode values is	587	Undocumented/buggy Unicode handling (how JSON handles unicode values is
256	undocumented. One can get far by feeding it unicode strings and doing	588	undocumented. One can get far by feeding it unicode strings and doing
…		…
258		590
259	No roundtripping (strings get clobbered if they look like numbers, e.g.	591	No roundtripping (strings get clobbered if they look like numbers, e.g.
260	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	592	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
261	decode into the number 2.	593	decode into the number 2.
262		594
263	=item JSON::PC	595	=item JSON::PC 0.01
264		596
265	Very fast.	597	Very fast.
		598
		599	Undocumented/buggy Unicode handling.
		600
		601	No roundtripping.
		602
		603	Has problems handling many Perl values (e.g. regex results and other magic
		604	values will make it croak).
		605
		606	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		607	which is not a valid JSON text.
		608
		609	Unmaintained (maintainer unresponsive for many months, bugs are not
		610	getting fixed).
		611
		612	=item JSON::Syck 0.21
		613
		614	Very buggy (often crashes).
266		615
267	Very inflexible (no human-readable format supported, format pretty much	616	Very inflexible (no human-readable format supported, format pretty much
268	undocumented. I need at least a format for easy reading by humans and a	617	undocumented. I need at least a format for easy reading by humans and a
269	single-line compact format for use in a protocol, and preferably a way to	618	single-line compact format for use in a protocol, and preferably a way to
270	generate ASCII-only JSON strings).	619	generate ASCII-only JSON texts).
271
272	Undocumented/buggy Unicode handling.
273
274	No roundtripping.
275
276	Has problems handling many Perl values.
277
278	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
279	which is not a valid JSON string.
280
281	Unmaintained (maintainer unresponsive for many months, bugs are not
282	getting fixed).
283
284	=item JSON::Syck
285
286	Very buggy (often crashes).
287
288	Very inflexible.
289		620
290	Completely broken (and confusingly documented) Unicode handling (unicode	621	Completely broken (and confusingly documented) Unicode handling (unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	622	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	623	I<different> values on en- and decoding to get symmetric behaviour).
293		624
…		…
305	JSON. One bank might parse a given non-JSON request and deduct money,	636	JSON. One bank might parse a given non-JSON request and deduct money,
306	while the other might reject the transaction with a syntax error. While a	637	while the other might reject the transaction with a syntax error. While a
307	good protocol will at least recover, that is extra unnecessary work and	638	good protocol will at least recover, that is extra unnecessary work and
308	the transaction will still not succeed).	639	the transaction will still not succeed).
309		640
310	=item JSON::DWIW	641	=item JSON::DWIW 0.04
311		642
312	Very fast. Very natural. Very nice.	643	Very fast. Very natural. Very nice.
313		644
314	Undocumented unicode handling (but the best of the pack. Unicode escapes	645	Undocumented unicode handling (but the best of the pack. Unicode escapes
315	still don't get parsed properly).	646	still don't get parsed properly).
316		647
317	Very inflexible.	648	Very inflexible.
318		649
319	No roundtripping.	650	No roundtripping.
320		651
		652	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		653	result in nothing being output)
		654
321	Does not check input for validity.	655	Does not check input for validity.
322		656
323	=back	657	=back
324		658
		659
		660	=head2 JSON and YAML
		661
		662	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		663	however, a mass hysteria and very far from the truth. In general, there is
		664	no way to configure JSON::XS to output a data structure as valid YAML.
		665
		666	If you really must use JSON::XS to generate YAML, you should use this
		667	algorithm (subject to change in future versions):
		668
		669	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		670	my $yaml = $to_yaml->encode ($ref) . "\n";
		671
		672	This will usually generate JSON texts that also parse as valid
		673	YAML. Please note that YAML has hardcoded limits on (simple) object key
		674	lengths that JSON doesn't have, so you should make sure that your hash
		675	keys are noticably shorter than the 1024 characters YAML allows.
		676
		677	There might be other incompatibilities that I am not aware of. In general
		678	you should not try to generate YAML with a JSON generator or vice versa,
		679	or try to parse JSON with a YAML parser or vice versa: chances are high
		680	that you will run into severe interoperability problems.
		681
		682
325	=head2 SPEED	683	=head2 SPEED
326		684
		685	It seems that JSON::XS is surprisingly fast, as shown in the following
		686	tables. They have been generated with the help of the C<eg/bench> program
		687	in the JSON::XS distribution, to make it easy to compare on your own
		688	system.
		689
		690	First comes a comparison between various modules using a very short
		691	single-line JSON string:
		692
		693	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		694	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		695
		696	It shows the number of encodes/decodes per second (JSON::XS uses
		697	the functional interface, while JSON::XS/2 uses the OO interface
		698	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		699	shrink). Higher is better:
		700
		701	module \| encode \| decode \|
		702	-----------\|------------\|------------\|
		703	JSON \| 7645.468 \| 4208.613 \|
		704	JSON::DWIW \| 40721.398 \| 77101.176 \|
		705	JSON::PC \| 65948.176 \| 78251.940 \|
		706	JSON::Syck \| 22844.793 \| 26479.192 \|
		707	JSON::XS \| 388361.481 \| 199728.762 \|
		708	JSON::XS/2 \| 218453.333 \| 192399.266 \|
		709	JSON::XS/3 \| 338250.323 \| 192399.266 \|
		710	Storable \| 15779.925 \| 14169.946 \|
		711	-----------+------------+------------+
		712
		713	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		714	about three times faster on decoding, and over fourty times faster
		715	than JSON, even with pretty-printing and key sorting. It also compares
		716	favourably to Storable for small amounts of data.
		717
		718	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		719	search API (http://nanoref.com/yahooapis/mgPdGg):
		720
		721	module \| encode \| decode \|
		722	-----------\|------------\|------------\|
		723	JSON \| 254.685 \| 37.665 \|
		724	JSON::DWIW \| 843.343 \| 1049.731 \|
		725	JSON::PC \| 3602.116 \| 2307.352 \|
		726	JSON::Syck \| 505.107 \| 787.899 \|
		727	JSON::XS \| 5747.196 \| 3690.220 \|
		728	JSON::XS/2 \| 3968.121 \| 3676.634 \|
		729	JSON::XS/3 \| 6105.246 \| 3662.508 \|
		730	Storable \| 4417.337 \| 5285.161 \|
		731	-----------+------------+------------+
		732
		733	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		734	decodes faster).
		735
		736	On large strings containing lots of high unicode characters, some modules
		737	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		738	will be broken due to missing (or wrong) unicode handling. Others refuse
		739	to decode or encode properly, so it was impossible to prepare a fair
		740	comparison table for that case.
		741
		742
		743	=head1 SECURITY CONSIDERATIONS
		744
		745	When you are using JSON in a protocol, talking to untrusted potentially
		746	hostile creatures requires relatively few measures.
		747
		748	First of all, your JSON decoder should be secure, that is, should not have
		749	any buffer overflows. Obviously, this module should ensure that and I am
		750	trying hard on making that true, but you never know.
		751
		752	Second, you need to avoid resource-starving attacks. That means you should
		753	limit the size of JSON texts you accept, or make sure then when your
		754	resources run out, thats just fine (e.g. by using a separate process that
		755	can crash safely). The size of a JSON text in octets or characters is
		756	usually a good indication of the size of the resources required to decode
		757	it into a Perl structure.
		758
		759	Third, JSON::XS recurses using the C stack when decoding objects and
		760	arrays. The C stack is a limited resource: for instance, on my amd64
		761	machine with 8MB of stack size I can decode around 180k nested arrays but
		762	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		763	to free the temporary). If that is exceeded, the program crashes. to be
		764	conservative, the default nesting limit is set to 512. If your process
		765	has a smaller stack, you should adjust this setting accordingly with the
		766	C<max_depth> method.
		767
		768	And last but least, something else could bomb you that I forgot to think
		769	of. In that case, you get to keep the pieces. I am always open for hints,
		770	though...
		771
		772	If you are using JSON::XS to return packets to consumption
		773	by javascript scripts in a browser you should have a look at
		774	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		775	you are vulnerable to some common attack vectors (which really are browser
		776	design bugs, but it is still you who will have to deal with it, as major
		777	browser developers care only for features, not about doing security
		778	right).
		779
		780
		781	=head1 BUGS
		782
		783	While the goal of this module is to be correct, that unfortunately does
		784	not mean its bug-free, only that I think its design is bug-free. It is
		785	still relatively early in its development. If you keep reporting bugs they
		786	will be fixed swiftly, though.
		787
327	=cut	788	=cut
		789
		790	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		791	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		792
		793	sub true() { $true }
		794	sub false() { $false }
		795
		796	sub is_bool($) {
		797	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		798	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		799	}
		800
		801	XSLoader::load "JSON::XS", $VERSION;
		802
		803	package JSON::XS::Boolean;
		804
		805	use overload
		806	"0+" => sub { ${$_[0]} },
		807	"++" => sub { $_[0] = ${$_[0]} + 1 },
		808	"--" => sub { $_[0] = ${$_[0]} - 1 },
		809	fallback => 1;
328		810
329	1;	811	1;
330		812
331	=head1 AUTHOR	813	=head1 AUTHOR
332		814

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Revision 1.45 by root, Mon Jun 25 04:16:46 2007 UTC