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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.9 by root, Fri Mar 23 16:00:19 2007 UTC vs.
Revision 1.37 by root, Wed Jun 6 14:52:49 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
		88	use strict;
		89
63	BEGIN {	90	BEGIN {
64	$VERSION = '0.3';	91	our $VERSION = '1.22';
65	@ISA = qw(Exporter);	92	our @ISA = qw(Exporter);
66		93
67	@EXPORT = qw(to_json from_json);	94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);
68	require Exporter;	95	require Exporter;
69		96
70	require XSLoader;	97	require XSLoader;
71	XSLoader::load JSON::XS::, $VERSION;	98	XSLoader::load JSON::XS::, $VERSION;
72	}	99	}
…		…
76	The following convinience methods are provided by this module. They are	103	The following convinience methods are provided by this module. They are
77	exported by default:	104	exported by default:
78		105
79	=over 4	106	=over 4
80		107
81	=item $json_string = to_json $perl_scalar	108	=item $json_text = to_json $perl_scalar
82		109
83	Converts the given Perl data structure (a simple scalar or a reference to	110	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	111	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	112	octets only). Croaks on error.
86		113
87	This function call is functionally identical to C<< JSON::XS->new->utf8	114	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		115
		116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		117
		118	except being faster.
		119
90	=item $perl_scalar = from_json $json_string	120	=item $perl_scalar = from_json $json_text
91		121
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	122	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	123	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	124	scalar or reference. Croaks on error.
95		125
96	This function call is functionally identical to C<< JSON::XS->new->utf8	126	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	127
		128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		129
		130	except being faster.
98		131
99	=back	132	=back
		133
100		134
101	=head1 OBJECT-ORIENTED INTERFACE	135	=head1 OBJECT-ORIENTED INTERFACE
102		136
103	The object oriented interface lets you configure your own encoding or	137	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	138	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	145	strings. All boolean flags described below are by default I<disabled>.
112		146
113	The mutators for flags all return the JSON object again and thus calls can	147	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	148	be chained:
115		149
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	150	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	151	=> {"a": [1, 2]}
118		152
119	=item $json = $json->ascii ([$enable])	153	=item $json = $json->ascii ([$enable])
120		154
121	If C<$enable> is true (or missing), then the C<encode> method will	155	If C<$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	156	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	157	unicode characters outside that range will be escaped using either a
124	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
125	RFC4627.	159	as per RFC4627. The resulting encoded JSON text can be treated as a native
		160	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		161	or any other superset of ASCII.
126		162
127	If C<$enable> is false, then the C<encode> method will not escape Unicode	163	If C<$enable> is false, then the C<encode> method will not escape Unicode
128	characters unless necessary.	164	characters unless required by the JSON syntax or other flags. This results
		165	in a faster and more compact format.
129		166
		167	The main use for this flag is to produce JSON texts that can be
		168	transmitted over a 7-bit channel, as the encoded JSON texts will not
		169	contain any 8 bit characters.
		170
130	JSON::XS->new->ascii (1)->encode (chr 0x10401)	171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
131	=> \ud801\udc01	172	=> ["\ud801\udc01"]
		173
		174	=item $json = $json->latin1 ([$enable])
		175
		176	If C<$enable> is true (or missing), then the C<encode> method will encode
		177	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		178	outside the code range C<0..255>. The resulting string can be treated as a
		179	latin1-encoded JSON text or a native unicode string. The C<decode> method
		180	will not be affected in any way by this flag, as C<decode> by default
		181	expects unicode, which is a strict superset of latin1.
		182
		183	If C<$enable> is false, then the C<encode> method will not escape Unicode
		184	characters unless required by the JSON syntax or other flags.
		185
		186	The main use for this flag is efficiently encoding binary data as JSON
		187	text, as most octets will not be escaped, resulting in a smaller encoded
		188	size. The disadvantage is that the resulting JSON text is encoded
		189	in latin1 (and must correctly be treated as such when storing and
		190	transfering), a rare encoding for JSON. It is therefore most useful when
		191	you want to store data structures known to contain binary data efficiently
		192	in files or databases, not when talking to other JSON encoders/decoders.
		193
		194	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		195	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
132		196
133	=item $json = $json->utf8 ([$enable])	197	=item $json = $json->utf8 ([$enable])
134		198
135	If C<$enable> is true (or missing), then the C<encode> method will encode	199	If C<$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	200	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	201	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	202	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.	203	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		204	versions, enabling this option might enable autodetection of the UTF-16
		205	and UTF-32 encoding families, as described in RFC4627.
140		206
141	If C<$enable> is false, then the C<encode> method will return the JSON	207	If C<$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	208	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	209	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.	210	to be done yourself, e.g. using the Encode module.
145		211
		212	Example, output UTF-16BE-encoded JSON:
		213
		214	use Encode;
		215	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		216
		217	Example, decode UTF-32LE-encoded JSON:
		218
		219	use Encode;
		220	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		221
146	=item $json = $json->pretty ([$enable])	222	=item $json = $json->pretty ([$enable])
147		223
148	This enables (or disables) all of the C<indent>, C<space_before> and	224	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	225	C<space_after> (and in the future possibly more) flags in one call to
150	generate the most readable (or most compact) form possible.	226	generate the most readable (or most compact) form possible.
		227
		228	Example, pretty-print some simple structure:
151		229
152	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	230	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
153	=>	231	=>
154	{	232	{
155	"a" : [	233	"a" : [
…		…
163	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	241	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
164	format as output, putting every array member or object/hash key-value pair	242	format as output, putting every array member or object/hash key-value pair
165	into its own line, identing them properly.	243	into its own line, identing them properly.
166		244
167	If C<$enable> is false, no newlines or indenting will be produced, and the	245	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>.	246	resulting JSON text is guarenteed not to contain any C<newlines>.
169		247
170	This setting has no effect when decoding JSON strings.	248	This setting has no effect when decoding JSON texts.
171		249
172	=item $json = $json->space_before ([$enable])	250	=item $json = $json->space_before ([$enable])
173		251
174	If C<$enable> is true (or missing), then the C<encode> method will add an extra	252	If C<$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.	253	optional space before the C<:> separating keys from values in JSON objects.
176		254
177	If C<$enable> is false, then the C<encode> method will not add any extra	255	If C<$enable> is false, then the C<encode> method will not add any extra
178	space at those places.	256	space at those places.
179		257
180	This setting has no effect when decoding JSON strings. You will also most	258	This setting has no effect when decoding JSON texts. You will also
181	likely combine this setting with C<space_after>.	259	most likely combine this setting with C<space_after>.
		260
		261	Example, space_before enabled, space_after and indent disabled:
		262
		263	{"key" :"value"}
182		264
183	=item $json = $json->space_after ([$enable])	265	=item $json = $json->space_after ([$enable])
184		266
185	If C<$enable> is true (or missing), then the C<encode> method will add an extra	267	If C<$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	268	optional space after the C<:> separating keys from values in JSON objects
…		…
188	members.	270	members.
189		271
190	If C<$enable> is false, then the C<encode> method will not add any extra	272	If C<$enable> is false, then the C<encode> method will not add any extra
191	space at those places.	273	space at those places.
192		274
193	This setting has no effect when decoding JSON strings.	275	This setting has no effect when decoding JSON texts.
		276
		277	Example, space_before and indent disabled, space_after enabled:
		278
		279	{"key": "value"}
194		280
195	=item $json = $json->canonical ([$enable])	281	=item $json = $json->canonical ([$enable])
196		282
197	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	283	If C<$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.	284	by sorting their keys. This is adding a comparatively high overhead.
…		…
200	If C<$enable> is false, then the C<encode> method will output key-value	286	If C<$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	287	pairs in the order Perl stores them (which will likely change between runs
202	of the same script).	288	of the same script).
203		289
204	This option is useful if you want the same data structure to be encoded as	290	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,	291	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,	292	the same hash migh be encoded differently even if contains the same data,
207	as key-value pairs have no inherent ordering in Perl.	293	as key-value pairs have no inherent ordering in Perl.
208		294
209	This setting has no effect when decoding JSON strings.	295	This setting has no effect when decoding JSON texts.
210		296
211	=item $json = $json->allow_nonref ([$enable])	297	=item $json = $json->allow_nonref ([$enable])
212		298
213	If C<$enable> is true (or missing), then the C<encode> method can convert a	299	If C<$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,	300	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	301	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
216	values instead of croaking.	302	values instead of croaking.
217		303
218	If C<$enable> is false, then the C<encode> method will croak if it isn't	304	If C<$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	305	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	306	or array. Likewise, C<decode> will croak if given something that is not a
221	JSON object or array.	307	JSON object or array.
222		308
		309	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		310	resulting in an invalid JSON text:
		311
		312	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		313	=> "Hello, World!"
		314
223	=item $json = $json->shrink ([$enable])	315	=item $json = $json->shrink ([$enable])
224		316
225	Perl usually over-allocates memory a bit when allocating space for	317	Perl usually over-allocates memory a bit when allocating space for
226	strings. This flag optionally resizes strings generated by either	318	strings. This flag optionally resizes strings generated by either
227	C<encode> or C<decode> to their minimum size possible. This can save	319	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	320	memory when your JSON texts are either very very long or you have many
229	short strings. It will also try to downgrade any strings to octet-form	321	short strings. It will also try to downgrade any strings to octet-form
230	if possible: perl stores strings internally either in an encoding called	322	if possible: perl stores strings internally either in an encoding called
231	UTF-X or in octet-form. The latter cannot store everything but uses less	323	UTF-X or in octet-form. The latter cannot store everything but uses less
232	space in general.	324	space in general (and some buggy Perl or C code might even rely on that
		325	internal representation being used).
233		326
		327	The actual definition of what shrink does might change in future versions,
		328	but it will always try to save space at the expense of time.
		329
234	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	330	If C<$enable> is true (or missing), the string returned by C<encode> will
235	while all strings generated by C<decode> will also be shrunk-to-fit.	331	be shrunk-to-fit, while all strings generated by C<decode> will also be
		332	shrunk-to-fit.
236		333
237	If C<$enable> is false, then the normal perl allocation algorithms are used.	334	If C<$enable> is false, then the normal perl allocation algorithms are used.
238	If you work with your data, then this is likely to be faster.	335	If you work with your data, then this is likely to be faster.
239		336
240	In the future, this setting might control other things, such as converting	337	In the future, this setting might control other things, such as converting
241	strings that look like integers or floats into integers or floats	338	strings that look like integers or floats into integers or floats
242	internally (there is no difference on the Perl level), saving space.	339	internally (there is no difference on the Perl level), saving space.
243		340
		341	=item $json = $json->max_depth ([$maximum_nesting_depth])
		342
		343	Sets the maximum nesting level (default C<512>) accepted while encoding
		344	or decoding. If the JSON text or Perl data structure has an equal or
		345	higher nesting level then this limit, then the encoder and decoder will
		346	stop and croak at that point.
		347
		348	Nesting level is defined by number of hash- or arrayrefs that the encoder
		349	needs to traverse to reach a given point or the number of C<{> or C<[>
		350	characters without their matching closing parenthesis crossed to reach a
		351	given character in a string.
		352
		353	Setting the maximum depth to one disallows any nesting, so that ensures
		354	that the object is only a single hash/object or array.
		355
		356	The argument to C<max_depth> will be rounded up to the next nearest power
		357	of two.
		358
		359	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		360
244	=item $json_string = $json->encode ($perl_scalar)	361	=item $json_text = $json->encode ($perl_scalar)
245		362
246	Converts the given Perl data structure (a simple scalar or a reference	363	Converts the given Perl data structure (a simple scalar or a reference
247	to a hash or array) to its JSON representation. Simple scalars will be	364	to a hash or array) to its JSON representation. Simple scalars will be
248	converted into JSON string or number sequences, while references to arrays	365	converted into JSON string or number sequences, while references to arrays
249	become JSON arrays and references to hashes become JSON objects. Undefined	366	become JSON arrays and references to hashes become JSON objects. Undefined
250	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	367	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
251	nor C<false> values will be generated.	368	nor C<false> values will be generated.
252		369
253	=item $perl_scalar = $json->decode ($json_string)	370	=item $perl_scalar = $json->decode ($json_text)
254		371
255	The opposite of C<encode>: expects a JSON string and tries to parse it,	372	The opposite of C<encode>: expects a JSON text and tries to parse it,
256	returning the resulting simple scalar or reference. Croaks on error.	373	returning the resulting simple scalar or reference. Croaks on error.
257		374
258	JSON numbers and strings become simple Perl scalars. JSON arrays become	375	JSON numbers and strings become simple Perl scalars. JSON arrays become
259	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	376	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
260	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	377	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
261		378
		379	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		380
		381	This works like the C<decode> method, but instead of raising an exception
		382	when there is trailing garbage after the first JSON object, it will
		383	silently stop parsing there and return the number of characters consumed
		384	so far.
		385
		386	This is useful if your JSON texts are not delimited by an outer protocol
		387	(which is not the brightest thing to do in the first place) and you need
		388	to know where the JSON text ends.
		389
		390	JSON::XS->new->decode_prefix ("[1] the tail")
		391	=> ([], 3)
		392
262	=back	393	=back
		394
		395
		396	=head1 MAPPING
		397
		398	This section describes how JSON::XS maps Perl values to JSON values and
		399	vice versa. These mappings are designed to "do the right thing" in most
		400	circumstances automatically, preserving round-tripping characteristics
		401	(what you put in comes out as something equivalent).
		402
		403	For the more enlightened: note that in the following descriptions,
		404	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		405	refers to the abstract Perl language itself.
		406
		407	=head2 JSON -> PERL
		408
		409	=over 4
		410
		411	=item object
		412
		413	A JSON object becomes a reference to a hash in Perl. No ordering of object
		414	keys is preserved (JSON does not preserver object key ordering itself).
		415
		416	=item array
		417
		418	A JSON array becomes a reference to an array in Perl.
		419
		420	=item string
		421
		422	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		423	are represented by the same codepoints in the Perl string, so no manual
		424	decoding is necessary.
		425
		426	=item number
		427
		428	A JSON number becomes either an integer or numeric (floating point)
		429	scalar in perl, depending on its range and any fractional parts. On the
		430	Perl level, there is no difference between those as Perl handles all the
		431	conversion details, but an integer may take slightly less memory and might
		432	represent more values exactly than (floating point) numbers.
		433
		434	=item true, false
		435
		436	These JSON atoms become C<0>, C<1>, respectively. Information is lost in
		437	this process. Future versions might represent those values differently,
		438	but they will be guarenteed to act like these integers would normally in
		439	Perl.
		440
		441	=item null
		442
		443	A JSON null atom becomes C<undef> in Perl.
		444
		445	=back
		446
		447	=head2 PERL -> JSON
		448
		449	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		450	truly typeless language, so we can only guess which JSON type is meant by
		451	a Perl value.
		452
		453	=over 4
		454
		455	=item hash references
		456
		457	Perl hash references become JSON objects. As there is no inherent ordering
		458	in hash keys (or JSON objects), they will usually be encoded in a
		459	pseudo-random order that can change between runs of the same program but
		460	stays generally the same within a single run of a program. JSON::XS can
		461	optionally sort the hash keys (determined by the I<canonical> flag), so
		462	the same datastructure will serialise to the same JSON text (given same
		463	settings and version of JSON::XS), but this incurs a runtime overhead
		464	and is only rarely useful, e.g. when you want to compare some JSON text
		465	against another for equality.
		466
		467	=item array references
		468
		469	Perl array references become JSON arrays.
		470
		471	=item other references
		472
		473	Other unblessed references are generally not allowed and will cause an
		474	exception to be thrown, except for references to the integers C<0> and
		475	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		476	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		477
		478	to_json [\0,JSON::XS::true] # yields [false,true]
		479
		480	=item blessed objects
		481
		482	Blessed objects are not allowed. JSON::XS currently tries to encode their
		483	underlying representation (hash- or arrayref), but this behaviour might
		484	change in future versions.
		485
		486	=item simple scalars
		487
		488	Simple Perl scalars (any scalar that is not a reference) are the most
		489	difficult objects to encode: JSON::XS will encode undefined scalars as
		490	JSON null value, scalars that have last been used in a string context
		491	before encoding as JSON strings and anything else as number value:
		492
		493	# dump as number
		494	to_json [2] # yields [2]
		495	to_json [-3.0e17] # yields [-3e+17]
		496	my $value = 5; to_json [$value] # yields [5]
		497
		498	# used as string, so dump as string
		499	print $value;
		500	to_json [$value] # yields ["5"]
		501
		502	# undef becomes null
		503	to_json [undef] # yields [null]
		504
		505	You can force the type to be a string by stringifying it:
		506
		507	my $x = 3.1; # some variable containing a number
		508	"$x"; # stringified
		509	$x .= ""; # another, more awkward way to stringify
		510	print $x; # perl does it for you, too, quite often
		511
		512	You can force the type to be a number by numifying it:
		513
		514	my $x = "3"; # some variable containing a string
		515	$x += 0; # numify it, ensuring it will be dumped as a number
		516	$x *= 1; # same thing, the choise is yours.
		517
		518	You can not currently output JSON booleans or force the type in other,
		519	less obscure, ways. Tell me if you need this capability.
		520
		521	=back
		522
263		523
264	=head1 COMPARISON	524	=head1 COMPARISON
265		525
266	As already mentioned, this module was created because none of the existing	526	As already mentioned, this module was created because none of the existing
267	JSON modules could be made to work correctly. First I will describe the	527	JSON modules could be made to work correctly. First I will describe the
…		…
293		553
294	Has problems handling many Perl values (e.g. regex results and other magic	554	Has problems handling many Perl values (e.g. regex results and other magic
295	values will make it croak).	555	values will make it croak).
296		556
297	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	557	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
298	which is not a valid JSON string.	558	which is not a valid JSON text.
299		559
300	Unmaintained (maintainer unresponsive for many months, bugs are not	560	Unmaintained (maintainer unresponsive for many months, bugs are not
301	getting fixed).	561	getting fixed).
302		562
303	=item JSON::Syck 0.21	563	=item JSON::Syck 0.21
…		…
305	Very buggy (often crashes).	565	Very buggy (often crashes).
306		566
307	Very inflexible (no human-readable format supported, format pretty much	567	Very inflexible (no human-readable format supported, format pretty much
308	undocumented. I need at least a format for easy reading by humans and a	568	undocumented. I need at least a format for easy reading by humans and a
309	single-line compact format for use in a protocol, and preferably a way to	569	single-line compact format for use in a protocol, and preferably a way to
310	generate ASCII-only JSON strings).	570	generate ASCII-only JSON texts).
311		571
312	Completely broken (and confusingly documented) Unicode handling (unicode	572	Completely broken (and confusingly documented) Unicode handling (unicode
313	escapes are not working properly, you need to set ImplicitUnicode to	573	escapes are not working properly, you need to set ImplicitUnicode to
314	I<different> values on en- and decoding to get symmetric behaviour).	574	I<different> values on en- and decoding to get symmetric behaviour).
315		575
…		…
338		598
339	Very inflexible.	599	Very inflexible.
340		600
341	No roundtripping.	601	No roundtripping.
342		602
343	Does not generate valid JSON (key strings are often unquoted, empty keys	603	Does not generate valid JSON texts (key strings are often unquoted, empty keys
344	result in nothing being output)	604	result in nothing being output)
345		605
346	Does not check input for validity.	606	Does not check input for validity.
347		607
348	=back	608	=back
…		…
352	It seems that JSON::XS is surprisingly fast, as shown in the following	612	It seems that JSON::XS is surprisingly fast, as shown in the following
353	tables. They have been generated with the help of the C<eg/bench> program	613	tables. They have been generated with the help of the C<eg/bench> program
354	in the JSON::XS distribution, to make it easy to compare on your own	614	in the JSON::XS distribution, to make it easy to compare on your own
355	system.	615	system.
356		616
357	First is a comparison between various modules using a very simple JSON	617	First comes a comparison between various modules using a very short
		618	single-line JSON string:
		619
		620	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		621	"id": null, [1,11,234,-5,1e5,1e7, true, false]}
		622
358	string, showing the number of encodes/decodes per second (JSON::XS is	623	It shows the number of encodes/decodes per second (JSON::XS uses the
359	the functional interface, while JSON::XS/2 is the OO interface with	624	functional interface, while JSON::XS/2 uses the OO interface with
360	pretty-printing and hashkey sorting enabled).	625	pretty-printing and hashkey sorting enabled). Higher is better:
361		626
		627	-----------+------------+------------+
362	module \| encode \| decode \|	628	module \| encode \| decode \|
363	-----------\|------------\|------------\|	629	-----------\|------------\|------------\|
364	JSON \| 14006 \| 6820 \|	630	JSON \| 10597.029 \| 5740.903 \|
365	JSON::DWIW \| 200937 \| 120386 \|	631	JSON::DWIW \| 78251.940 \| 98457.840 \|
366	JSON::PC \| 85065 \| 129366 \|	632	JSON::PC \| 70611.178 \| 92794.336 \|
367	JSON::Syck \| 59898 \| 44232 \|	633	JSON::Syck \| 28767.517 \| 38199.490 \|
368	JSON::XS \| 1171478 \| 342435 \|	634	JSON::XS \| 419430.400 \| 265462.278 \|
369	JSON::XS/2 \| 730760 \| 328714 \|	635	JSON::XS/2 \| 279620.267 \| 265462.278 \|
		636	JSON::XS/3 \| 388361.481 \| 265462.278 \|
		637	Storable \| 16294.887 \| 16844.594 \|
370	-----------+------------+------------+	638	-----------+------------+------------+
371		639
372	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	640	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		641	about three times faster on decoding, and about fourty times faster
373	times faster than JSON, even with pretty-printing and key sorting.	642	than JSON, even with pretty-printing and key sorting. It also compares
		643	favourably to Storable for small amounts of data.
374		644
375	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	645	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
376	search API (http://nanoref.com/yahooapis/mgPdGg):	646	search API (http://nanoref.com/yahooapis/mgPdGg):
377		647
378	module \| encode \| decode \|	648	module \| encode \| decode \|
379	-----------\|------------\|------------\|	649	-----------\|------------\|------------\|
380	JSON \| 673 \| 38 \|	650	JSON \| 254.685 \| 37.665 \|
381	JSON::DWIW \| 5271 \| 770 \|	651	JSON::DWIW \| 1014.244 \| 1087.678 \|
382	JSON::PC \| 9901 \| 2491 \|	652	JSON::PC \| 3602.116 \| 2307.352 \|
383	JSON::Syck \| 2360 \| 786 \|	653	JSON::Syck \| 558.035 \| 776.263 \|
384	JSON::XS \| 37398 \| 3202 \|	654	JSON::XS \| 5747.196 \| 3543.684 \|
385	JSON::XS/2 \| 13765 \| 3153 \|	655	JSON::XS/2 \| 3968.121 \| 3589.170 \|
		656	JSON::XS/3 \| 6105.246 \| 3561.134 \|
		657	Storable \| 4456.337 \| 5320.020 \|
386	-----------+------------+------------+	658	-----------+------------+------------+
387		659
388	Again, JSON::XS leads by far in the encoding case, while still beating	660	Again, JSON::XS leads by far.
389	every other module in the decoding case.
390		661
391	Last example is an almost 8MB large hash with many large binary values	662	On large strings containing lots of high unicode characters, some modules
392	(PNG files), resulting in a lot of escaping:	663	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		664	will be broken due to missing (or wrong) unicode handling. Others refuse
		665	to decode or encode properly, so it was impossible to prepare a fair
		666	comparison table for that case.
		667
		668
		669	=head1 SECURITY CONSIDERATIONS
		670
		671	When you are using JSON in a protocol, talking to untrusted potentially
		672	hostile creatures requires relatively few measures.
		673
		674	First of all, your JSON decoder should be secure, that is, should not have
		675	any buffer overflows. Obviously, this module should ensure that and I am
		676	trying hard on making that true, but you never know.
		677
		678	Second, you need to avoid resource-starving attacks. That means you should
		679	limit the size of JSON texts you accept, or make sure then when your
		680	resources run out, thats just fine (e.g. by using a separate process that
		681	can crash safely). The size of a JSON text in octets or characters is
		682	usually a good indication of the size of the resources required to decode
		683	it into a Perl structure.
		684
		685	Third, JSON::XS recurses using the C stack when decoding objects and
		686	arrays. The C stack is a limited resource: for instance, on my amd64
		687	machine with 8MB of stack size I can decode around 180k nested arrays but
		688	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		689	to free the temporary). If that is exceeded, the program crashes. to be
		690	conservative, the default nesting limit is set to 512. If your process
		691	has a smaller stack, you should adjust this setting accordingly with the
		692	C<max_depth> method.
		693
		694	And last but least, something else could bomb you that I forgot to think
		695	of. In that case, you get to keep the pieces. I am always open for hints,
		696	though...
		697
393		698
394	=head1 BUGS	699	=head1 BUGS
395		700
396	While the goal of this module is to be correct, that unfortunately does	701	While the goal of this module is to be correct, that unfortunately does
397	not mean its bug-free, only that I think its design is bug-free. It is	702	not mean its bug-free, only that I think its design is bug-free. It is
398	still very young and not well-tested. If you keep reporting bugs they will	703	still relatively early in its development. If you keep reporting bugs they
399	be fixed swiftly, though.	704	will be fixed swiftly, though.
400		705
401	=cut	706	=cut
		707
		708	sub true() { \1 }
		709	sub false() { \0 }
402		710
403	1;	711	1;
404		712
405	=head1 AUTHOR	713	=head1 AUTHOR
406		714

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Revision 1.37 by root, Wed Jun 6 14:52:49 2007 UTC