[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 1.50 by root, Mon Jul 2 00:29:38 2007 UTC

…		…
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
		8
		9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
		11
		12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		14
		15	# OO-interface
		16
		17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		19	$perl_scalar = $coder->decode ($unicode_json_text);
8		20
9	=head1 DESCRIPTION	21	=head1 DESCRIPTION
10		22
11	This module converts Perl data structures to JSON and vice versa. Its	23	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	24	primary goal is to be I<correct> and its secondary goal is to be
…		…
18	their maintainers are unresponsive, gone missing, or not listening to bug	30	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	31	reports for other reasons.
20		32
21	See COMPARISON, below, for a comparison to some other JSON modules.	33	See COMPARISON, below, for a comparison to some other JSON modules.
22		34
		35	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		36	vice versa.
		37
23	=head2 FEATURES	38	=head2 FEATURES
24		39
25	=over 4	40	=over 4
26		41
27	=item * correct handling of unicode issues	42	=item * correct unicode handling
28		43
29	This module knows how to handle Unicode, and even documents how it does so.	44	This module knows how to handle Unicode, and even documents how and when
		45	it does so.
30		46
31	=item * round-trip integrity	47	=item * round-trip integrity
32		48
33	When you serialise a perl data structure using only datatypes supported	49	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	50	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		52	like a number).
36		53
37	=item * strict checking of JSON correctness	54	=item * strict checking of JSON correctness
38		55
39	There is no guessing, no generating of illegal JSON strings by default,	56	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	57	and only JSON is accepted as input by default (the latter is a security
		58	feature).
41		59
42	=item * fast	60	=item * fast
43		61
44	compared to other JSON modules, this module compares favourably.	62	Compared to other JSON modules, this module compares favourably in terms
		63	of speed, too.
45		64
46	=item * simple to use	65	=item * simple to use
47		66
48	This module has both a simple functional interface as well as an OO	67	This module has both a simple functional interface as well as an OO
49	interface.	68	interface.
50		69
51	=item * reasonably versatile output formats	70	=item * reasonably versatile output formats
52		71
53	You can choose between the most compact format possible, a pure-ascii	72	You can choose between the most compact guarenteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	73	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	74	(for when your transport is not 8-bit clean, still supports the whole
		75	unicode range), or a pretty-printed format (for when you want to read that
		76	stuff). Or you can combine those features in whatever way you like.
56		77
57	=back	78	=back
58		79
59	=cut	80	=cut
60		81
61	package JSON::XS;	82	package JSON::XS;
62		83
63	BEGIN {	84	use strict;
		85
64	$VERSION = '0.1';	86	our $VERSION = '1.4';
65	@ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
66		88
67	@EXPORT = qw(to_json from_json);	89	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		90
70	require XSLoader;	91	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
72	}
73		93
74	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
75		95
76	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
77	exported by default:	97	exported by default:
78		98
79	=over 4	99	=over 4
80		100
81	=item $json_string = to_json $perl_scalar	101	=item $json_text = to_json $perl_scalar
82		102
83	Converts the given Perl data structure (a simple scalar or a reference to	103	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	105	octets only). Croaks on error.
86		106
87	This function call is functionally identical to C<< JSON::XS->new->utf8	107	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		108
		109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		110
		111	except being faster.
		112
90	=item $perl_scalar = from_json $json_string	113	=item $perl_scalar = from_json $json_text
91		114
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	116	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	117	scalar or reference. Croaks on error.
95		118
96	This function call is functionally identical to C<< JSON::XS->new->utf8	119	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	120
		121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		122
		123	except being faster.
		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
98		133
99	=back	134	=back
		135
100		136
101	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
102		138
103	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	147	strings. All boolean flags described below are by default I<disabled>.
112		148
113	The mutators for flags all return the JSON object again and thus calls can	149	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	150	be chained:
115		151
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	153	=> {"a": [1, 2]}
118		154
119	=item $json = $json->ascii ($enable)	155	=item $json = $json->ascii ([$enable])
120		156
121	If C<$enable> is true, then the C<encode> method will not generate	157	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	158	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	159	unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		161	as per RFC4627. The resulting encoded JSON text can be treated as a native
		162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		163	or any other superset of ASCII.
125		164
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	165	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	166	characters unless required by the JSON syntax or other flags. This results
		167	in a faster and more compact format.
128		168
		169	The main use for this flag is to produce JSON texts that can be
		170	transmitted over a 7-bit channel, as the encoded JSON texts will not
		171	contain any 8 bit characters.
		172
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	174	=> ["\ud801\udc01"]
131		175
		176	=item $json = $json->latin1 ([$enable])
		177
		178	If C<$enable> is true (or missing), then the C<encode> method will encode
		179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		180	outside the code range C<0..255>. The resulting string can be treated as a
		181	latin1-encoded JSON text or a native unicode string. The C<decode> method
		182	will not be affected in any way by this flag, as C<decode> by default
		183	expects unicode, which is a strict superset of latin1.
		184
		185	If C<$enable> is false, then the C<encode> method will not escape Unicode
		186	characters unless required by the JSON syntax or other flags.
		187
		188	The main use for this flag is efficiently encoding binary data as JSON
		189	text, as most octets will not be escaped, resulting in a smaller encoded
		190	size. The disadvantage is that the resulting JSON text is encoded
		191	in latin1 (and must correctly be treated as such when storing and
		192	transfering), a rare encoding for JSON. It is therefore most useful when
		193	you want to store data structures known to contain binary data efficiently
		194	in files or databases, not when talking to other JSON encoders/decoders.
		195
		196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		198
132	=item $json = $json->utf8 ($enable)	199	=item $json = $json->utf8 ([$enable])
133		200
134	If C<$enable> is true, then the C<encode> method will encode the JSON	201	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	202	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	203	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	204	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		206	versions, enabling this option might enable autodetection of the UTF-16
		207	and UTF-32 encoding families, as described in RFC4627.
139		208
140	If C<$enable> is false, then the C<encode> method will return the JSON	209	If C<$enable> is false, then the C<encode> method will return the JSON
141	string as a (non-encoded) unicode string, while C<decode> expects thus a	210	string as a (non-encoded) unicode string, while C<decode> expects thus a
142	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
143	to be done yourself, e.g. using the Encode module.	212	to be done yourself, e.g. using the Encode module.
144		213
		214	Example, output UTF-16BE-encoded JSON:
		215
		216	use Encode;
		217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		218
		219	Example, decode UTF-32LE-encoded JSON:
		220
		221	use Encode;
		222	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		223
145	=item $json = $json->pretty ($enable)	224	=item $json = $json->pretty ([$enable])
146		225
147	This enables (or disables) all of the C<indent>, C<space_before> and	226	This enables (or disables) all of the C<indent>, C<space_before> and
148	C<space_after> (and in the future possibly more) flags in one call to	227	C<space_after> (and in the future possibly more) flags in one call to
149	generate the most readable (or most compact) form possible.	228	generate the most readable (or most compact) form possible.
		229
		230	Example, pretty-print some simple structure:
150		231
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	232	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	233	=>
153	{	234	{
154	"a" : [	235	"a" : [
155	1,	236	1,
156	2	237	2
157	]	238	]
158	}	239	}
159		240
160	=item $json = $json->indent ($enable)	241	=item $json = $json->indent ([$enable])
161		242
162	If C<$enable> is true, then the C<encode> method will use a multiline	243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	244	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	245	into its own line, identing them properly.
165		246
166	If C<$enable> is false, no newlines or indenting will be produced, and the	247	If C<$enable> is false, no newlines or indenting will be produced, and the
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	248	resulting JSON text is guarenteed not to contain any C<newlines>.
168		249
169	This setting has no effect when decoding JSON strings.	250	This setting has no effect when decoding JSON texts.
170		251
171	=item $json = $json->space_before ($enable)	252	=item $json = $json->space_before ([$enable])
172		253
173	If C<$enable> is true, then the C<encode> method will add an extra	254	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	255	optional space before the C<:> separating keys from values in JSON objects.
175		256
176	If C<$enable> is false, then the C<encode> method will not add any extra	257	If C<$enable> is false, then the C<encode> method will not add any extra
177	space at those places.	258	space at those places.
178		259
179	This setting has no effect when decoding JSON strings. You will also most	260	This setting has no effect when decoding JSON texts. You will also
180	likely combine this setting with C<space_after>.	261	most likely combine this setting with C<space_after>.
181		262
		263	Example, space_before enabled, space_after and indent disabled:
		264
		265	{"key" :"value"}
		266
182	=item $json = $json->space_after ($enable)	267	=item $json = $json->space_after ([$enable])
183		268
184	If C<$enable> is true, then the C<encode> method will add an extra	269	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	270	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	271	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	272	members.
188		273
189	If C<$enable> is false, then the C<encode> method will not add any extra	274	If C<$enable> is false, then the C<encode> method will not add any extra
190	space at those places.	275	space at those places.
191		276
192	This setting has no effect when decoding JSON strings.	277	This setting has no effect when decoding JSON texts.
193		278
		279	Example, space_before and indent disabled, space_after enabled:
		280
		281	{"key": "value"}
		282
194	=item $json = $json->canonical ($enable)	283	=item $json = $json->canonical ([$enable])
195		284
196	If C<$enable> is true, then the C<encode> method will output JSON objects	285	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	286	by sorting their keys. This is adding a comparatively high overhead.
198		287
199	If C<$enable> is false, then the C<encode> method will output key-value	288	If C<$enable> is false, then the C<encode> method will output key-value
200	pairs in the order Perl stores them (which will likely change between runs	289	pairs in the order Perl stores them (which will likely change between runs
201	of the same script).	290	of the same script).
202		291
203	This option is useful if you want the same data structure to be encoded as	292	This option is useful if you want the same data structure to be encoded as
204	the same JSON string (given the same overall settings). If it is disabled,	293	the same JSON text (given the same overall settings). If it is disabled,
205	the same hash migh be encoded differently even if contains the same data,	294	the same hash migh be encoded differently even if contains the same data,
206	as key-value pairs have no inherent ordering in Perl.	295	as key-value pairs have no inherent ordering in Perl.
207		296
208	This setting has no effect when decoding JSON strings.	297	This setting has no effect when decoding JSON texts.
209		298
210	=item $json = $json->allow_nonref ($enable)	299	=item $json = $json->allow_nonref ([$enable])
211		300
212	If C<$enable> is true, then the C<encode> method can convert a	301	If C<$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,	302	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	303	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	304	values instead of croaking.
216		305
217	If C<$enable> is false, then the C<encode> method will croak if it isn't	306	If C<$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	307	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	308	or array. Likewise, C<decode> will croak if given something that is not a
220	JSON object or array.	309	JSON object or array.
221		310
		311	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		312	resulting in an invalid JSON text:
		313
		314	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		315	=> "Hello, World!"
		316
		317	=item $json = $json->allow_blessed ([$enable])
		318
		319	If C<$enable> is true (or missing), then the C<encode> method will not
		320	barf when it encounters a blessed reference. Instead, the value of the
		321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		322	disabled or no C<to_json> method found) or a representation of the
		323	object (C<convert_blessed> enabled and C<to_json> method found) is being
		324	encoded. Has no effect on C<decode>.
		325
		326	If C<$enable> is false (the default), then C<encode> will throw an
		327	exception when it encounters a blessed object.
		328
		329	=item $json = $json->convert_blessed ([$enable])
		330
		331	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		332	blessed object, will check for the availability of the C<TO_JSON> method
		333	on the object's class. If found, it will be called in scalar context
		334	and the resulting scalar will be encoded instead of the object. If no
		335	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		336	to do.
		337
		338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		339	returns other blessed objects, those will be handled in the same
		340	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		341	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		342	methods called by the Perl core (== not by the user of the object) are
		343	usually in upper case letters and to avoid collisions with the C<to_json>
		344	function.
		345
		346	This setting does not yet influence C<decode> in any way, but in the
		347	future, global hooks might get installed that influence C<decode> and are
		348	enabled by this setting.
		349
		350	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		351	to do when a blessed object is found.
		352
		353	=item $json = $json->shrink ([$enable])
		354
		355	Perl usually over-allocates memory a bit when allocating space for
		356	strings. This flag optionally resizes strings generated by either
		357	C<encode> or C<decode> to their minimum size possible. This can save
		358	memory when your JSON texts are either very very long or you have many
		359	short strings. It will also try to downgrade any strings to octet-form
		360	if possible: perl stores strings internally either in an encoding called
		361	UTF-X or in octet-form. The latter cannot store everything but uses less
		362	space in general (and some buggy Perl or C code might even rely on that
		363	internal representation being used).
		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
		368	If C<$enable> is true (or missing), the string returned by C<encode> will
		369	be shrunk-to-fit, while all strings generated by C<decode> will also be
		370	shrunk-to-fit.
		371
		372	If C<$enable> is false, then the normal perl allocation algorithms are used.
		373	If you work with your data, then this is likely to be faster.
		374
		375	In the future, this setting might control other things, such as converting
		376	strings that look like integers or floats into integers or floats
		377	internally (there is no difference on the Perl level), saving space.
		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 highest power
		395	of two. If no argument is given, the highest possible setting will be
		396	used, which is rarely useful.
		397
		398	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		399
		400	=item $json = $json->max_size ([$maximum_string_size])
		401
		402	Set the maximum length a JSON text may have (in bytes) where decoding is
		403	being attempted. The default is C<0>, meaning no limit. When C<decode>
		404	is called on a string longer then this number of characters it will not
		405	attempt to decode the string but throw an exception. This setting has no
		406	effect on C<encode> (yet).
		407
		408	The argument to C<max_size> will be rounded up to the next B<highest>
		409	power of two (so may be more than requested). If no argument is given, the
		410	limit check will be deactivated (same as when C<0> is specified).
		411
		412	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		413
222	=item $json_string = $json->encode ($perl_scalar)	414	=item $json_text = $json->encode ($perl_scalar)
223		415
224	Converts the given Perl data structure (a simple scalar or a reference	416	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	417	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	418	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	419	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>	420	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	421	nor C<false> values will be generated.
230		422
231	=item $perl_scalar = $json->decode ($json_string)	423	=item $perl_scalar = $json->decode ($json_text)
232		424
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	425	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.	426	returning the resulting simple scalar or reference. Croaks on error.
235		427
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	428	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	429	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>.	430	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		431
		432	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		433
		434	This works like the C<decode> method, but instead of raising an exception
		435	when there is trailing garbage after the first JSON object, it will
		436	silently stop parsing there and return the number of characters consumed
		437	so far.
		438
		439	This is useful if your JSON texts are not delimited by an outer protocol
		440	(which is not the brightest thing to do in the first place) and you need
		441	to know where the JSON text ends.
		442
		443	JSON::XS->new->decode_prefix ("[1] the tail")
		444	=> ([], 3)
		445
240	=back	446	=back
		447
		448
		449	=head1 MAPPING
		450
		451	This section describes how JSON::XS maps Perl values to JSON values and
		452	vice versa. These mappings are designed to "do the right thing" in most
		453	circumstances automatically, preserving round-tripping characteristics
		454	(what you put in comes out as something equivalent).
		455
		456	For the more enlightened: note that in the following descriptions,
		457	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		458	refers to the abstract Perl language itself.
		459
		460
		461	=head2 JSON -> PERL
		462
		463	=over 4
		464
		465	=item object
		466
		467	A JSON object becomes a reference to a hash in Perl. No ordering of object
		468	keys is preserved (JSON does not preserver object key ordering itself).
		469
		470	=item array
		471
		472	A JSON array becomes a reference to an array in Perl.
		473
		474	=item string
		475
		476	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		477	are represented by the same codepoints in the Perl string, so no manual
		478	decoding is necessary.
		479
		480	=item number
		481
		482	A JSON number becomes either an integer or numeric (floating point)
		483	scalar in perl, depending on its range and any fractional parts. On the
		484	Perl level, there is no difference between those as Perl handles all the
		485	conversion details, but an integer may take slightly less memory and might
		486	represent more values exactly than (floating point) numbers.
		487
		488	=item true, false
		489
		490	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		491	respectively. They are overloaded to act almost exactly like the numbers
		492	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		493	the C<JSON::XS::is_bool> function.
		494
		495	=item null
		496
		497	A JSON null atom becomes C<undef> in Perl.
		498
		499	=back
		500
		501
		502	=head2 PERL -> JSON
		503
		504	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		505	truly typeless language, so we can only guess which JSON type is meant by
		506	a Perl value.
		507
		508	=over 4
		509
		510	=item hash references
		511
		512	Perl hash references become JSON objects. As there is no inherent ordering
		513	in hash keys (or JSON objects), they will usually be encoded in a
		514	pseudo-random order that can change between runs of the same program but
		515	stays generally the same within a single run of a program. JSON::XS can
		516	optionally sort the hash keys (determined by the I<canonical> flag), so
		517	the same datastructure will serialise to the same JSON text (given same
		518	settings and version of JSON::XS), but this incurs a runtime overhead
		519	and is only rarely useful, e.g. when you want to compare some JSON text
		520	against another for equality.
		521
		522	=item array references
		523
		524	Perl array references become JSON arrays.
		525
		526	=item other references
		527
		528	Other unblessed references are generally not allowed and will cause an
		529	exception to be thrown, except for references to the integers C<0> and
		530	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		531	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		532
		533	to_json [\0,JSON::XS::true] # yields [false,true]
		534
		535	=item JSON::XS::true, JSON::XS::false
		536
		537	These special values become JSON true and JSON false values,
		538	respectively. You cna alos use C<\1> and C<\0> directly if you want.
		539
		540	=item blessed objects
		541
		542	Blessed objects are not allowed. JSON::XS currently tries to encode their
		543	underlying representation (hash- or arrayref), but this behaviour might
		544	change in future versions.
		545
		546	=item simple scalars
		547
		548	Simple Perl scalars (any scalar that is not a reference) are the most
		549	difficult objects to encode: JSON::XS will encode undefined scalars as
		550	JSON null value, scalars that have last been used in a string context
		551	before encoding as JSON strings and anything else as number value:
		552
		553	# dump as number
		554	to_json [2] # yields [2]
		555	to_json [-3.0e17] # yields [-3e+17]
		556	my $value = 5; to_json [$value] # yields [5]
		557
		558	# used as string, so dump as string
		559	print $value;
		560	to_json [$value] # yields ["5"]
		561
		562	# undef becomes null
		563	to_json [undef] # yields [null]
		564
		565	You can force the type to be a string by stringifying it:
		566
		567	my $x = 3.1; # some variable containing a number
		568	"$x"; # stringified
		569	$x .= ""; # another, more awkward way to stringify
		570	print $x; # perl does it for you, too, quite often
		571
		572	You can force the type to be a number by numifying it:
		573
		574	my $x = "3"; # some variable containing a string
		575	$x += 0; # numify it, ensuring it will be dumped as a number
		576	$x *= 1; # same thing, the choise is yours.
		577
		578	You can not currently output JSON booleans or force the type in other,
		579	less obscure, ways. Tell me if you need this capability.
		580
		581	=back
		582
241		583
242	=head1 COMPARISON	584	=head1 COMPARISON
243		585
244	As already mentioned, this module was created because none of the existing	586	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	587	JSON modules could be made to work correctly. First I will describe the
246	problems (or pleasures) I encountered with various existing JSON modules,	588	problems (or pleasures) I encountered with various existing JSON modules,
247	followed by some benchmark values.	589	followed by some benchmark values. JSON::XS was designed not to suffer
		590	from any of these problems or limitations.
248		591
249	=over 4	592	=over 4
250		593
251	=item JSON	594	=item JSON 1.07
252		595
253	Slow (but very portable, as it is written in pure Perl).	596	Slow (but very portable, as it is written in pure Perl).
254		597
255	Undocumented/buggy Unicode handling (how JSON handles unicode values is	598	Undocumented/buggy Unicode handling (how JSON handles unicode values is
256	undocumented. One can get far by feeding it unicode strings and doing	599	undocumented. One can get far by feeding it unicode strings and doing
…		…
258		601
259	No roundtripping (strings get clobbered if they look like numbers, e.g.	602	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	603	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.	604	decode into the number 2.
262		605
263	=item JSON::PC	606	=item JSON::PC 0.01
264		607
265	Very fast.	608	Very fast.
		609
		610	Undocumented/buggy Unicode handling.
		611
		612	No roundtripping.
		613
		614	Has problems handling many Perl values (e.g. regex results and other magic
		615	values will make it croak).
		616
		617	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		618	which is not a valid JSON text.
		619
		620	Unmaintained (maintainer unresponsive for many months, bugs are not
		621	getting fixed).
		622
		623	=item JSON::Syck 0.21
		624
		625	Very buggy (often crashes).
266		626
267	Very inflexible (no human-readable format supported, format pretty much	627	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	628	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	629	single-line compact format for use in a protocol, and preferably a way to
270	generate ASCII-only JSON strings).	630	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		631
290	Completely broken (and confusingly documented) Unicode handling (unicode	632	Completely broken (and confusingly documented) Unicode handling (unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	633	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	634	I<different> values on en- and decoding to get symmetric behaviour).
293		635
…		…
305	JSON. One bank might parse a given non-JSON request and deduct money,	647	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	648	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	649	good protocol will at least recover, that is extra unnecessary work and
308	the transaction will still not succeed).	650	the transaction will still not succeed).
309		651
310	=item JSON::DWIW	652	=item JSON::DWIW 0.04
311		653
312	Very fast. Very natural. Very nice.	654	Very fast. Very natural. Very nice.
313		655
314	Undocumented unicode handling (but the best of the pack. Unicode escapes	656	Undocumented unicode handling (but the best of the pack. Unicode escapes
315	still don't get parsed properly).	657	still don't get parsed properly).
316		658
317	Very inflexible.	659	Very inflexible.
318		660
319	No roundtripping.	661	No roundtripping.
320		662
		663	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		664	result in nothing being output)
		665
321	Does not check input for validity.	666	Does not check input for validity.
322		667
323	=back	668	=back
324		669
		670
		671	=head2 JSON and YAML
		672
		673	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		674	however, a mass hysteria and very far from the truth. In general, there is
		675	no way to configure JSON::XS to output a data structure as valid YAML.
		676
		677	If you really must use JSON::XS to generate YAML, you should use this
		678	algorithm (subject to change in future versions):
		679
		680	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		681	my $yaml = $to_yaml->encode ($ref) . "\n";
		682
		683	This will usually generate JSON texts that also parse as valid
		684	YAML. Please note that YAML has hardcoded limits on (simple) object key
		685	lengths that JSON doesn't have, so you should make sure that your hash
		686	keys are noticably shorter than the 1024 characters YAML allows.
		687
		688	There might be other incompatibilities that I am not aware of. In general
		689	you should not try to generate YAML with a JSON generator or vice versa,
		690	or try to parse JSON with a YAML parser or vice versa: chances are high
		691	that you will run into severe interoperability problems.
		692
		693
325	=head2 SPEED	694	=head2 SPEED
326		695
		696	It seems that JSON::XS is surprisingly fast, as shown in the following
		697	tables. They have been generated with the help of the C<eg/bench> program
		698	in the JSON::XS distribution, to make it easy to compare on your own
		699	system.
		700
		701	First comes a comparison between various modules using a very short
		702	single-line JSON string:
		703
		704	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		705	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		706
		707	It shows the number of encodes/decodes per second (JSON::XS uses
		708	the functional interface, while JSON::XS/2 uses the OO interface
		709	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		710	shrink). Higher is better:
		711
		712	Storable \| 15779.925 \| 14169.946 \|
		713	-----------+------------+------------+
		714	module \| encode \| decode \|
		715	-----------\|------------\|------------\|
		716	JSON \| 4990.842 \| 4088.813 \|
		717	JSON::DWIW \| 51653.990 \| 71575.154 \|
		718	JSON::PC \| 65948.176 \| 74631.744 \|
		719	JSON::PP \| 8931.652 \| 3817.168 \|
		720	JSON::Syck \| 24877.248 \| 27776.848 \|
		721	JSON::XS \| 388361.481 \| 227951.304 \|
		722	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		723	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		724	Storable \| 16500.016 \| 135300.129 \|
		725	-----------+------------+------------+
		726
		727	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		728	about three times faster on decoding, and over fourty times faster
		729	than JSON, even with pretty-printing and key sorting. It also compares
		730	favourably to Storable for small amounts of data.
		731
		732	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		733	search API (http://nanoref.com/yahooapis/mgPdGg):
		734
		735	module \| encode \| decode \|
		736	-----------\|------------\|------------\|
		737	JSON \| 55.260 \| 34.971 \|
		738	JSON::DWIW \| 825.228 \| 1082.513 \|
		739	JSON::PC \| 3571.444 \| 2394.829 \|
		740	JSON::PP \| 210.987 \| 32.574 \|
		741	JSON::Syck \| 552.551 \| 787.544 \|
		742	JSON::XS \| 5780.463 \| 4854.519 \|
		743	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		744	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		745	Storable \| 4445.002 \| 5235.027 \|
		746	-----------+------------+------------+
		747
		748	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		749	decodes faster).
		750
		751	On large strings containing lots of high unicode characters, some modules
		752	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		753	will be broken due to missing (or wrong) unicode handling. Others refuse
		754	to decode or encode properly, so it was impossible to prepare a fair
		755	comparison table for that case.
		756
		757
		758	=head1 SECURITY CONSIDERATIONS
		759
		760	When you are using JSON in a protocol, talking to untrusted potentially
		761	hostile creatures requires relatively few measures.
		762
		763	First of all, your JSON decoder should be secure, that is, should not have
		764	any buffer overflows. Obviously, this module should ensure that and I am
		765	trying hard on making that true, but you never know.
		766
		767	Second, you need to avoid resource-starving attacks. That means you should
		768	limit the size of JSON texts you accept, or make sure then when your
		769	resources run out, thats just fine (e.g. by using a separate process that
		770	can crash safely). The size of a JSON text in octets or characters is
		771	usually a good indication of the size of the resources required to decode
		772	it into a Perl structure. While JSON::XS can check the size of the JSON
		773	text, it might be too late when you already have it in memory, so you
		774	might want to check the size before you accept the string.
		775
		776	Third, JSON::XS recurses using the C stack when decoding objects and
		777	arrays. The C stack is a limited resource: for instance, on my amd64
		778	machine with 8MB of stack size I can decode around 180k nested arrays but
		779	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		780	to free the temporary). If that is exceeded, the program crashes. to be
		781	conservative, the default nesting limit is set to 512. If your process
		782	has a smaller stack, you should adjust this setting accordingly with the
		783	C<max_depth> method.
		784
		785	And last but least, something else could bomb you that I forgot to think
		786	of. In that case, you get to keep the pieces. I am always open for hints,
		787	though...
		788
		789	If you are using JSON::XS to return packets to consumption
		790	by javascript scripts in a browser you should have a look at
		791	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		792	you are vulnerable to some common attack vectors (which really are browser
		793	design bugs, but it is still you who will have to deal with it, as major
		794	browser developers care only for features, not about doing security
		795	right).
		796
		797
		798	=head1 BUGS
		799
		800	While the goal of this module is to be correct, that unfortunately does
		801	not mean its bug-free, only that I think its design is bug-free. It is
		802	still relatively early in its development. If you keep reporting bugs they
		803	will be fixed swiftly, though.
		804
327	=cut	805	=cut
		806
		807	our $true = do { bless \(my $dummy = "1"), "JSON::XS::Boolean" };
		808	our $false = do { bless \(my $dummy = "0"), "JSON::XS::Boolean" };
		809
		810	sub true() { $true }
		811	sub false() { $false }
		812
		813	sub is_bool($) {
		814	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		815	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		816	}
		817
		818	XSLoader::load "JSON::XS", $VERSION;
		819
		820	package JSON::XS::Boolean;
		821
		822	use overload
		823	"0+" => sub { ${$_[0]} },
		824	"++" => sub { $_[0] = ${$_[0]} + 1 },
		825	"--" => sub { $_[0] = ${$_[0]} - 1 },
		826	fallback => 1;
328		827
329	1;	828	1;
330		829
331	=head1 AUTHOR	830	=head1 AUTHOR
332		831

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Revision 1.50 by root, Mon Jul 2 00:29:38 2007 UTC