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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs.
Revision 1.41 by root, Mon Jun 11 03:45:26 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
…		…
25		41
26	=head2 FEATURES	42	=head2 FEATURES
27		43
28	=over 4	44	=over 4
29		45
30	=item * correct handling of unicode issues	46	=item * correct unicode handling
31		47
32	This module knows how to handle Unicode, and even documents how and when	48	This module knows how to handle Unicode, and even documents how and when
33	it does so.	49	it does so.
34		50
35	=item * round-trip integrity	51	=item * round-trip integrity
36		52
37	When you serialise a perl data structure using only datatypes supported	53	When you serialise a perl data structure using only datatypes supported
38	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.
39	(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).
40		57
41	=item * strict checking of JSON correctness	58	=item * strict checking of JSON correctness
42		59
43	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,
44	and only JSON is accepted as input by default (the latter is a security	61	and only JSON is accepted as input by default (the latter is a security
45	feature).	62	feature).
46		63
47	=item * fast	64	=item * fast
48		65
…		…
55	interface.	72	interface.
56		73
57	=item * reasonably versatile output formats	74	=item * reasonably versatile output formats
58		75
59	You can choose between the most compact guarenteed single-line format	76	You can choose between the most compact guarenteed single-line format
60	possible (nice for simple line-based protocols), a pure-ascii format (for	77	possible (nice for simple line-based protocols), a pure-ascii format
61	when your transport is not 8-bit clean), or a pretty-printed format (for	78	(for when your transport is not 8-bit clean, still supports the whole
62	when you want to read that stuff). Or you can combine those features in	79	unicode range), or a pretty-printed format (for when you want to read that
63	whatever way you like.	80	stuff). Or you can combine those features in whatever way you like.
64		81
65	=back	82	=back
66		83
67	=cut	84	=cut
68		85
69	package JSON::XS;	86	package JSON::XS;
70		87
		88	use strict;
		89
71	BEGIN {	90	BEGIN {
72	$VERSION = '0.3';	91	our $VERSION = '1.24';
73	@ISA = qw(Exporter);	92	our @ISA = qw(Exporter);
74		93
75	@EXPORT = qw(to_json from_json);	94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);
76	require Exporter;	95	require Exporter;
77		96
78	require XSLoader;	97	require XSLoader;
79	XSLoader::load JSON::XS::, $VERSION;	98	XSLoader::load JSON::XS::, $VERSION;
80	}	99	}
…		…
84	The following convinience methods are provided by this module. They are	103	The following convinience methods are provided by this module. They are
85	exported by default:	104	exported by default:
86		105
87	=over 4	106	=over 4
88		107
89	=item $json_string = to_json $perl_scalar	108	=item $json_text = to_json $perl_scalar
90		109
91	Converts the given Perl data structure (a simple scalar or a reference to	110	Converts the given Perl data structure (a simple scalar or a reference to
92	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	111	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
93	octets only). Croaks on error.	112	octets only). Croaks on error.
94		113
95	This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.	114	This function call is functionally identical to:
96		115
		116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		117
		118	except being faster.
		119
97	=item $perl_scalar = from_json $json_string	120	=item $perl_scalar = from_json $json_text
98		121
99	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	122	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
100	parse that as an UTF-8 encoded JSON string, returning the resulting simple	123	parse that as an UTF-8 encoded JSON text, returning the resulting simple
101	scalar or reference. Croaks on error.	124	scalar or reference. Croaks on error.
102		125
103	This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.	126	This function call is functionally identical to:
		127
		128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		129
		130	except being faster.
104		131
105	=back	132	=back
		133
106		134
107	=head1 OBJECT-ORIENTED INTERFACE	135	=head1 OBJECT-ORIENTED INTERFACE
108		136
109	The object oriented interface lets you configure your own encoding or	137	The object oriented interface lets you configure your own encoding or
110	decoding style, within the limits of supported formats.	138	decoding style, within the limits of supported formats.
…		…
117	strings. All boolean flags described below are by default I<disabled>.	145	strings. All boolean flags described below are by default I<disabled>.
118		146
119	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
120	be chained:	148	be chained:
121		149
122	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]})
123	=> {"a": [1, 2]}	151	=> {"a": [1, 2]}
124		152
125	=item $json = $json->ascii ([$enable])	153	=item $json = $json->ascii ([$enable])
126		154
127	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
128	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
129	characters outside that range will be escaped using either a single	157	unicode characters outside that range will be escaped using either a
130	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
131	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.
132		162
133	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
134	characters unless necessary.	164	characters unless required by the JSON syntax or other flags. This results
		165	in a faster and more compact format.
135		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
136	JSON::XS->new->ascii (1)->encode (chr 0x10401)	171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
137	=> \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)
138		196
139	=item $json = $json->utf8 ([$enable])	197	=item $json = $json->utf8 ([$enable])
140		198
141	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
142	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
143	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
144	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
145	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.
146		206
147	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
148	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
149	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
150	to be done yourself, e.g. using the Encode module.	210	to be done yourself, e.g. using the Encode module.
151		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
152	=item $json = $json->pretty ([$enable])	222	=item $json = $json->pretty ([$enable])
153		223
154	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
155	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
156	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:
157		229
158	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	230	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
159	=>	231	=>
160	{	232	{
161	"a" : [	233	"a" : [
…		…
169	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	241	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
170	format as output, putting every array member or object/hash key-value pair	242	format as output, putting every array member or object/hash key-value pair
171	into its own line, identing them properly.	243	into its own line, identing them properly.
172		244
173	If C<$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
174	resulting JSON strings is guarenteed not to contain any C<newlines>.	246	resulting JSON text is guarenteed not to contain any C<newlines>.
175		247
176	This setting has no effect when decoding JSON strings.	248	This setting has no effect when decoding JSON texts.
177		249
178	=item $json = $json->space_before ([$enable])	250	=item $json = $json->space_before ([$enable])
179		251
180	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
181	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.
182		254
183	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
184	space at those places.	256	space at those places.
185		257
186	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
187	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"}
188		264
189	=item $json = $json->space_after ([$enable])	265	=item $json = $json->space_after ([$enable])
190		266
191	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
192	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
…		…
194	members.	270	members.
195		271
196	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
197	space at those places.	273	space at those places.
198		274
199	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"}
200		280
201	=item $json = $json->canonical ([$enable])	281	=item $json = $json->canonical ([$enable])
202		282
203	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
204	by sorting their keys. This is adding a comparatively high overhead.	284	by sorting their keys. This is adding a comparatively high overhead.
…		…
206	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
207	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
208	of the same script).	288	of the same script).
209		289
210	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
211	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,
212	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,
213	as key-value pairs have no inherent ordering in Perl.	293	as key-value pairs have no inherent ordering in Perl.
214		294
215	This setting has no effect when decoding JSON strings.	295	This setting has no effect when decoding JSON texts.
216		296
217	=item $json = $json->allow_nonref ([$enable])	297	=item $json = $json->allow_nonref ([$enable])
218		298
219	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
220	non-reference into its corresponding string, number or null JSON value,	300	non-reference into its corresponding string, number or null JSON value,
221	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
222	values instead of croaking.	302	values instead of croaking.
223		303
224	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
225	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
226	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
227	JSON object or array.	307	JSON object or array.
228		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
229	=item $json = $json->shrink ([$enable])	315	=item $json = $json->shrink ([$enable])
230		316
231	Perl usually over-allocates memory a bit when allocating space for	317	Perl usually over-allocates memory a bit when allocating space for
232	strings. This flag optionally resizes strings generated by either	318	strings. This flag optionally resizes strings generated by either
233	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
234	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
235	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
236	if possible: perl stores strings internally either in an encoding called	322	if possible: perl stores strings internally either in an encoding called
237	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
238	space in general.	324	space in general (and some buggy Perl or C code might even rely on that
		325	internal representation being used).
239		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
240	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
241	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.
242		333
243	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.
244	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.
245		336
246	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
247	strings that look like integers or floats into integers or floats	338	strings that look like integers or floats into integers or floats
248	internally (there is no difference on the Perl level), saving space.	339	internally (there is no difference on the Perl level), saving space.
249		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
250	=item $json_string = $json->encode ($perl_scalar)	361	=item $json_text = $json->encode ($perl_scalar)
251		362
252	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
253	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
254	converted into JSON string or number sequences, while references to arrays	365	converted into JSON string or number sequences, while references to arrays
255	become JSON arrays and references to hashes become JSON objects. Undefined	366	become JSON arrays and references to hashes become JSON objects. Undefined
256	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>
257	nor C<false> values will be generated.	368	nor C<false> values will be generated.
258		369
259	=item $perl_scalar = $json->decode ($json_string)	370	=item $perl_scalar = $json->decode ($json_text)
260		371
261	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,
262	returning the resulting simple scalar or reference. Croaks on error.	373	returning the resulting simple scalar or reference. Croaks on error.
263		374
264	JSON numbers and strings become simple Perl scalars. JSON arrays become	375	JSON numbers and strings become simple Perl scalars. JSON arrays become
265	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	376	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
266	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>.
267		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
268	=back	393	=back
		394
269		395
270	=head1 MAPPING	396	=head1 MAPPING
271		397
272	This section describes how JSON::XS maps Perl values to JSON values and	398	This section describes how JSON::XS maps Perl values to JSON values and
273	vice versa. These mappings are designed to "do the right thing" in most	399	vice versa. These mappings are designed to "do the right thing" in most
…		…
276		402
277	For the more enlightened: note that in the following descriptions,	403	For the more enlightened: note that in the following descriptions,
278	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	404	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
279	refers to the abstract Perl language itself.	405	refers to the abstract Perl language itself.
280		406
		407
281	=head2 JSON -> PERL	408	=head2 JSON -> PERL
282		409
283	=over 4	410	=over 4
284		411
285	=item object	412	=item object
286		413
287	A JSON object becomes a reference to a hash in Perl. No ordering of object	414	A JSON object becomes a reference to a hash in Perl. No ordering of object
288	keys is preserved.	415	keys is preserved (JSON does not preserver object key ordering itself).
289		416
290	=item array	417	=item array
291		418
292	A JSON array becomes a reference to an array in Perl.	419	A JSON array becomes a reference to an array in Perl.
293		420
…		…
316		443
317	A JSON null atom becomes C<undef> in Perl.	444	A JSON null atom becomes C<undef> in Perl.
318		445
319	=back	446	=back
320		447
		448
321	=head2 PERL -> JSON	449	=head2 PERL -> JSON
322		450
323	The mapping from Perl to JSON is slightly more difficult, as Perl is a	451	The mapping from Perl to JSON is slightly more difficult, as Perl is a
324	truly typeless language, so we can only guess which JSON type is meant by	452	truly typeless language, so we can only guess which JSON type is meant by
325	a Perl value.	453	a Perl value.
…		…
327	=over 4	455	=over 4
328		456
329	=item hash references	457	=item hash references
330		458
331	Perl hash references become JSON objects. As there is no inherent ordering	459	Perl hash references become JSON objects. As there is no inherent ordering
332	in hash keys, they will usually be encoded in a pseudo-random order that	460	in hash keys (or JSON objects), they will usually be encoded in a
333	can change between runs of the same program but stays generally the same	461	pseudo-random order that can change between runs of the same program but
334	within the single run of a program. JSON::XS can optionally sort the hash	462	stays generally the same within a single run of a program. JSON::XS can
335	keys (determined by the I<canonical> flag), so the same datastructure	463	optionally sort the hash keys (determined by the I<canonical> flag), so
336	will serialise to the same JSON text (given same settings and version of	464	the same datastructure will serialise to the same JSON text (given same
337	JSON::XS), but this incurs a runtime overhead.	465	settings and version of JSON::XS), but this incurs a runtime overhead
		466	and is only rarely useful, e.g. when you want to compare some JSON text
		467	against another for equality.
338		468
339	=item array references	469	=item array references
340		470
341	Perl array references become JSON arrays.	471	Perl array references become JSON arrays.
		472
		473	=item other references
		474
		475	Other unblessed references are generally not allowed and will cause an
		476	exception to be thrown, except for references to the integers C<0> and
		477	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		478	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		479
		480	to_json [\0,JSON::XS::true] # yields [false,true]
342		481
343	=item blessed objects	482	=item blessed objects
344		483
345	Blessed objects are not allowed. JSON::XS currently tries to encode their	484	Blessed objects are not allowed. JSON::XS currently tries to encode their
346	underlying representation (hash- or arrayref), but this behaviour might	485	underlying representation (hash- or arrayref), but this behaviour might
…		…
379	$x *= 1; # same thing, the choise is yours.	518	$x *= 1; # same thing, the choise is yours.
380		519
381	You can not currently output JSON booleans or force the type in other,	520	You can not currently output JSON booleans or force the type in other,
382	less obscure, ways. Tell me if you need this capability.	521	less obscure, ways. Tell me if you need this capability.
383		522
384	=item circular data structures
385
386	Those will be encoded until memory or stackspace runs out.
387
388	=back	523	=back
		524
389		525
390	=head1 COMPARISON	526	=head1 COMPARISON
391		527
392	As already mentioned, this module was created because none of the existing	528	As already mentioned, this module was created because none of the existing
393	JSON modules could be made to work correctly. First I will describe the	529	JSON modules could be made to work correctly. First I will describe the
…		…
419		555
420	Has problems handling many Perl values (e.g. regex results and other magic	556	Has problems handling many Perl values (e.g. regex results and other magic
421	values will make it croak).	557	values will make it croak).
422		558
423	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	559	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
424	which is not a valid JSON string.	560	which is not a valid JSON text.
425		561
426	Unmaintained (maintainer unresponsive for many months, bugs are not	562	Unmaintained (maintainer unresponsive for many months, bugs are not
427	getting fixed).	563	getting fixed).
428		564
429	=item JSON::Syck 0.21	565	=item JSON::Syck 0.21
…		…
431	Very buggy (often crashes).	567	Very buggy (often crashes).
432		568
433	Very inflexible (no human-readable format supported, format pretty much	569	Very inflexible (no human-readable format supported, format pretty much
434	undocumented. I need at least a format for easy reading by humans and a	570	undocumented. I need at least a format for easy reading by humans and a
435	single-line compact format for use in a protocol, and preferably a way to	571	single-line compact format for use in a protocol, and preferably a way to
436	generate ASCII-only JSON strings).	572	generate ASCII-only JSON texts).
437		573
438	Completely broken (and confusingly documented) Unicode handling (unicode	574	Completely broken (and confusingly documented) Unicode handling (unicode
439	escapes are not working properly, you need to set ImplicitUnicode to	575	escapes are not working properly, you need to set ImplicitUnicode to
440	I<different> values on en- and decoding to get symmetric behaviour).	576	I<different> values on en- and decoding to get symmetric behaviour).
441		577
…		…
464		600
465	Very inflexible.	601	Very inflexible.
466		602
467	No roundtripping.	603	No roundtripping.
468		604
469	Does not generate valid JSON (key strings are often unquoted, empty keys	605	Does not generate valid JSON texts (key strings are often unquoted, empty keys
470	result in nothing being output)	606	result in nothing being output)
471		607
472	Does not check input for validity.	608	Does not check input for validity.
473		609
474	=back	610	=back
		611
		612
		613	=head2 JSON and YAML
		614
		615	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		616	however, a mass hysteria and very far from the truth. In general, there is
		617	no way to configure JSON::XS to output a data structure as valid YAML.
		618
		619	If you really must use JSON::XS to generate YAML, you should use this
		620	algorithm (subject to change in future versions):
		621
		622	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		623	my $yaml = $to_yaml->encode ($ref) . "\n";
		624
		625	This will usually generate JSON texts that also parse as valid
		626	YAML. Please note that YAML has hardcoded limits on (simple) object key
		627	lengths that JSON doesn't have, so you should make sure that your hash
		628	keys are noticably shorter than the 1024 characters YAML allows.
		629
		630	There might be other incompatibilities that I am not aware of. In general
		631	you should not try to generate YAML with a JSON generator or vice versa,
		632	or try to parse JSON with a YAML parser or vice versa: chances are high
		633	that you will run into severe interoperability problems.
		634
475		635
476	=head2 SPEED	636	=head2 SPEED
477		637
478	It seems that JSON::XS is surprisingly fast, as shown in the following	638	It seems that JSON::XS is surprisingly fast, as shown in the following
479	tables. They have been generated with the help of the C<eg/bench> program	639	tables. They have been generated with the help of the C<eg/bench> program
480	in the JSON::XS distribution, to make it easy to compare on your own	640	in the JSON::XS distribution, to make it easy to compare on your own
481	system.	641	system.
482		642
483	First is a comparison between various modules using a very simple JSON	643	First comes a comparison between various modules using a very short
		644	single-line JSON string:
		645
		646	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		647	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		648
484	string, showing the number of encodes/decodes per second (JSON::XS is	649	It shows the number of encodes/decodes per second (JSON::XS uses
485	the functional interface, while JSON::XS/2 is the OO interface with	650	the functional interface, while JSON::XS/2 uses the OO interface
486	pretty-printing and hashkey sorting enabled).	651	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		652	shrink). Higher is better:
487		653
488	module \| encode \| decode \|	654	module \| encode \| decode \|
489	-----------\|------------\|------------\|	655	-----------\|------------\|------------\|
490	JSON \| 14006 \| 6820 \|	656	JSON \| 7645.468 \| 4208.613 \|
491	JSON::DWIW \| 200937 \| 120386 \|	657	JSON::DWIW \| 40721.398 \| 77101.176 \|
492	JSON::PC \| 85065 \| 129366 \|	658	JSON::PC \| 65948.176 \| 78251.940 \|
493	JSON::Syck \| 59898 \| 44232 \|	659	JSON::Syck \| 22844.793 \| 26479.192 \|
494	JSON::XS \| 1171478 \| 342435 \|	660	JSON::XS \| 388361.481 \| 199728.762 \|
495	JSON::XS/2 \| 730760 \| 328714 \|	661	JSON::XS/2 \| 218453.333 \| 192399.266 \|
		662	JSON::XS/3 \| 338250.323 \| 192399.266 \|
		663	Storable \| 15779.925 \| 14169.946 \|
496	-----------+------------+------------+	664	-----------+------------+------------+
497		665
498	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	666	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		667	about three times faster on decoding, and over fourty times faster
499	times faster than JSON, even with pretty-printing and key sorting.	668	than JSON, even with pretty-printing and key sorting. It also compares
		669	favourably to Storable for small amounts of data.
500		670
501	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	671	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
502	search API (http://nanoref.com/yahooapis/mgPdGg):	672	search API (http://nanoref.com/yahooapis/mgPdGg):
503		673
504	module \| encode \| decode \|	674	module \| encode \| decode \|
505	-----------\|------------\|------------\|	675	-----------\|------------\|------------\|
506	JSON \| 673 \| 38 \|	676	JSON \| 254.685 \| 37.665 \|
507	JSON::DWIW \| 5271 \| 770 \|	677	JSON::DWIW \| 843.343 \| 1049.731 \|
508	JSON::PC \| 9901 \| 2491 \|	678	JSON::PC \| 3602.116 \| 2307.352 \|
509	JSON::Syck \| 2360 \| 786 \|	679	JSON::Syck \| 505.107 \| 787.899 \|
510	JSON::XS \| 37398 \| 3202 \|	680	JSON::XS \| 5747.196 \| 3690.220 \|
511	JSON::XS/2 \| 13765 \| 3153 \|	681	JSON::XS/2 \| 3968.121 \| 3676.634 \|
		682	JSON::XS/3 \| 6105.246 \| 3662.508 \|
		683	Storable \| 4417.337 \| 5285.161 \|
512	-----------+------------+------------+	684	-----------+------------+------------+
513		685
514	Again, JSON::XS leads by far in the encoding case, while still beating	686	Again, JSON::XS leads by far (except for Storable which non-surprisingly
515	every other module in the decoding case.	687	decodes faster).
516		688
517	Last example is an almost 8MB large hash with many large binary values	689	On large strings containing lots of high unicode characters, some modules
518	(PNG files), resulting in a lot of escaping:	690	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		691	will be broken due to missing (or wrong) unicode handling. Others refuse
		692	to decode or encode properly, so it was impossible to prepare a fair
		693	comparison table for that case.
519		694
520	=head1 RESOURCE LIMITS
521		695
522	JSON::XS does not impose any limits on the size of JSON texts or Perl	696	=head1 SECURITY CONSIDERATIONS
523	values they represent - if your machine cna handle it, JSON::XS will	697
524	encode or decode it. Future versions might optionally impose structure	698	When you are using JSON in a protocol, talking to untrusted potentially
525	depth and memory use resource limits.	699	hostile creatures requires relatively few measures.
		700
		701	First of all, your JSON decoder should be secure, that is, should not have
		702	any buffer overflows. Obviously, this module should ensure that and I am
		703	trying hard on making that true, but you never know.
		704
		705	Second, you need to avoid resource-starving attacks. That means you should
		706	limit the size of JSON texts you accept, or make sure then when your
		707	resources run out, thats just fine (e.g. by using a separate process that
		708	can crash safely). The size of a JSON text in octets or characters is
		709	usually a good indication of the size of the resources required to decode
		710	it into a Perl structure.
		711
		712	Third, JSON::XS recurses using the C stack when decoding objects and
		713	arrays. The C stack is a limited resource: for instance, on my amd64
		714	machine with 8MB of stack size I can decode around 180k nested arrays but
		715	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		716	to free the temporary). If that is exceeded, the program crashes. to be
		717	conservative, the default nesting limit is set to 512. If your process
		718	has a smaller stack, you should adjust this setting accordingly with the
		719	C<max_depth> method.
		720
		721	And last but least, something else could bomb you that I forgot to think
		722	of. In that case, you get to keep the pieces. I am always open for hints,
		723	though...
		724
526		725
527	=head1 BUGS	726	=head1 BUGS
528		727
529	While the goal of this module is to be correct, that unfortunately does	728	While the goal of this module is to be correct, that unfortunately does
530	not mean its bug-free, only that I think its design is bug-free. It is	729	not mean its bug-free, only that I think its design is bug-free. It is
531	still very young and not well-tested. If you keep reporting bugs they will	730	still relatively early in its development. If you keep reporting bugs they
532	be fixed swiftly, though.	731	will be fixed swiftly, though.
533		732
534	=cut	733	=cut
		734
		735	sub true() { \1 }
		736	sub false() { \0 }
535		737
536	1;	738	1;
537		739
538	=head1 AUTHOR	740	=head1 AUTHOR
539		741

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Comparing JSON-XS/XS.pm (file contents): Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs. Revision 1.41 by root, Mon Jun 11 03:45:26 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.11 by root, Fri Mar 23 17:48:59 2007 UTC vs.
Revision 1.41 by root, Mon Jun 11 03:45:26 2007 UTC