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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.89 by root, Wed Mar 19 13:54:53 2008 UTC

…		…
12	use JSON::XS;	12	use JSON::XS;
13		13
14	# exported functions, they croak on error	14	# exported functions, they croak on error
15	# and expect/generate UTF-8	15	# and expect/generate UTF-8
16		16
17	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
18	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
19		19
20	# OO-interface	20	# OO-interface
21		21
22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
24	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
25		25
		26	# Note that JSON version 2.0 and above will automatically use JSON::XS
		27	# if available, at virtually no speed overhead either, so you should
		28	# be able to just:
		29
		30	use JSON;
		31
		32	# and do the same things, except that you have a pure-perl fallback now.
		33
26	=head1 DESCRIPTION	34	=head1 DESCRIPTION
27		35
28	This module converts Perl data structures to JSON and vice versa. Its	36	This module converts Perl data structures to JSON and vice versa. Its
29	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
30	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
		39
		40	Beginning with version 2.0 of the JSON module, when both JSON and
		41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
		42	overriden) with no overhead due to emulation (by inheritign constructor
		43	and methods). If JSON::XS is not available, it will fall back to the
		44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
		45	gives you a portable JSON API that can be fast when you need and doesn't
		46	require a C compiler when that is a problem.
31		47
32	As this is the n-th-something JSON module on CPAN, what was the reason	48	As this is the n-th-something JSON module on CPAN, what was the reason
33	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
34	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
35	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
…		…
42		58
43	=head2 FEATURES	59	=head2 FEATURES
44		60
45	=over 4	61	=over 4
46		62
47	=item * correct unicode handling	63	=item * correct Unicode handling
48		64
49	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
50	it does so.	66	so, and even documents what "correct" means.
51		67
52	=item * round-trip integrity	68	=item * round-trip integrity
53		69
54	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
55	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
56	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
57	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
58		75
59	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
60		77
61	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
62	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
63	feature).	80	feature).
64		81
65	=item * fast	82	=item * fast
66		83
67	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
68	of speed, too.	85	this module usually compares favourably in terms of speed, too.
69		86
70	=item * simple to use	87	=item * simple to use
71		88
72	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an objetc
73	interface.	90	oriented interface interface.
74		91
75	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
76		93
77	You can choose between the most compact guarenteed single-line format	94	You can choose between the most compact guaranteed-single-line format
78	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
79	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
80	unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
81	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
82		99
83	=back	100	=back
84		101
85	=cut	102	=cut
86		103
87	package JSON::XS;	104	package JSON::XS;
88		105
89	use strict;	106	use strict;
90		107
91	our $VERSION = '1.5';	108	our $VERSION = '2.01';
92	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
93		110
94	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		114	require Carp;
		115	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		116	}
		117
		118	sub from_json($) {
		119	require Carp;
		120	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
		121	}
95		122
96	use Exporter;	123	use Exporter;
97	use XSLoader;	124	use XSLoader;
98		125
99	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
100		127
101	The following convinience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
102	exported by default:	129	exported by default:
103		130
104	=over 4	131	=over 4
105		132
106	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
107		134
108	Converts the given Perl data structure (a simple scalar or a reference to	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
109	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	136	(that is, the string contains octets only). Croaks on error.
110	octets only). Croaks on error.
111		137
112	This function call is functionally identical to:	138	This function call is functionally identical to:
113		139
114	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
115		141
116	except being faster.	142	except being faster.
117		143
118	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
119		145
120	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
121	parse that as an UTF-8 encoded JSON text, returning the resulting simple	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
122	scalar or reference. Croaks on error.	148	reference. Croaks on error.
123		149
124	This function call is functionally identical to:	150	This function call is functionally identical to:
125		151
126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
127		153
…		…
137	Perl.	163	Perl.
138		164
139	=back	165	=back
140		166
141		167
		168	=head1 A FEW NOTES ON UNICODE AND PERL
		169
		170	Since this often leads to confusion, here are a few very clear words on
		171	how Unicode works in Perl, modulo bugs.
		172
		173	=over 4
		174
		175	=item 1. Perl strings can store characters with ordinal values > 255.
		176
		177	This enables you to store Unicode characters as single characters in a
		178	Perl string - very natural.
		179
		180	=item 2. Perl does I<not> associate an encoding with your strings.
		181
		182	... until you force it to, e.g. when matching it against a regex, or
		183	printing the scalar to a file, in which case Perl either interprets your
		184	string as locale-encoded text, octets/binary, or as Unicode, depending
		185	on various settings. In no case is an encoding stored together with your
		186	data, it is I<use> that decides encoding, not any magical meta data.
		187
		188	=item 3. The internal utf-8 flag has no meaning with regards to the
		189	encoding of your string.
		190
		191	Just ignore that flag unless you debug a Perl bug, a module written in
		192	XS or want to dive into the internals of perl. Otherwise it will only
		193	confuse you, as, despite the name, it says nothing about how your string
		194	is encoded. You can have Unicode strings with that flag set, with that
		195	flag clear, and you can have binary data with that flag set and that flag
		196	clear. Other possibilities exist, too.
		197
		198	If you didn't know about that flag, just the better, pretend it doesn't
		199	exist.
		200
		201	=item 4. A "Unicode String" is simply a string where each character can be
		202	validly interpreted as a Unicode codepoint.
		203
		204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		205	Unicode string encoded in UTF-8, giving you a binary string.
		206
		207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		208
		209	It's a fact. Learn to live with it.
		210
		211	=back
		212
		213	I hope this helps :)
		214
		215
142	=head1 OBJECT-ORIENTED INTERFACE	216	=head1 OBJECT-ORIENTED INTERFACE
143		217
144	The object oriented interface lets you configure your own encoding or	218	The object oriented interface lets you configure your own encoding or
145	decoding style, within the limits of supported formats.	219	decoding style, within the limits of supported formats.
146		220
…		…
157	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})	231	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
158	=> {"a": [1, 2]}	232	=> {"a": [1, 2]}
159		233
160	=item $json = $json->ascii ([$enable])	234	=item $json = $json->ascii ([$enable])
161		235
		236	=item $enabled = $json->get_ascii
		237
162	If C<$enable> is true (or missing), then the C<encode> method will not	238	If C<$enable> is true (or missing), then the C<encode> method will not
163	generate characters outside the code range C<0..127> (which is ASCII). Any	239	generate characters outside the code range C<0..127> (which is ASCII). Any
164	unicode characters outside that range will be escaped using either a	240	Unicode characters outside that range will be escaped using either a
165	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	241	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
166	as per RFC4627. The resulting encoded JSON text can be treated as a native	242	as per RFC4627. The resulting encoded JSON text can be treated as a native
167	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,	243	Unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
168	or any other superset of ASCII.	244	or any other superset of ASCII.
169		245
170	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
171	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
172	in a faster and more compact format.	248	in a faster and more compact format.
…		…
178	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
179	=> ["\ud801\udc01"]	255	=> ["\ud801\udc01"]
180		256
181	=item $json = $json->latin1 ([$enable])	257	=item $json = $json->latin1 ([$enable])
182		258
		259	=item $enabled = $json->get_latin1
		260
183	If C<$enable> is true (or missing), then the C<encode> method will encode	261	If C<$enable> is true (or missing), then the C<encode> method will encode
184	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters	262	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
185	outside the code range C<0..255>. The resulting string can be treated as a	263	outside the code range C<0..255>. The resulting string can be treated as a
186	latin1-encoded JSON text or a native unicode string. The C<decode> method	264	latin1-encoded JSON text or a native Unicode string. The C<decode> method
187	will not be affected in any way by this flag, as C<decode> by default	265	will not be affected in any way by this flag, as C<decode> by default
188	expects unicode, which is a strict superset of latin1.	266	expects Unicode, which is a strict superset of latin1.
189		267
190	If C<$enable> is false, then the C<encode> method will not escape Unicode	268	If C<$enable> is false, then the C<encode> method will not escape Unicode
191	characters unless required by the JSON syntax or other flags.	269	characters unless required by the JSON syntax or other flags.
192		270
193	The main use for this flag is efficiently encoding binary data as JSON	271	The main use for this flag is efficiently encoding binary data as JSON
194	text, as most octets will not be escaped, resulting in a smaller encoded	272	text, as most octets will not be escaped, resulting in a smaller encoded
195	size. The disadvantage is that the resulting JSON text is encoded	273	size. The disadvantage is that the resulting JSON text is encoded
196	in latin1 (and must correctly be treated as such when storing and	274	in latin1 (and must correctly be treated as such when storing and
197	transfering), a rare encoding for JSON. It is therefore most useful when	275	transferring), a rare encoding for JSON. It is therefore most useful when
198	you want to store data structures known to contain binary data efficiently	276	you want to store data structures known to contain binary data efficiently
199	in files or databases, not when talking to other JSON encoders/decoders.	277	in files or databases, not when talking to other JSON encoders/decoders.
200		278
201	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]	279	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
202	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)	280	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
203		281
204	=item $json = $json->utf8 ([$enable])	282	=item $json = $json->utf8 ([$enable])
		283
		284	=item $enabled = $json->get_utf8
205		285
206	If C<$enable> is true (or missing), then the C<encode> method will encode	286	If C<$enable> is true (or missing), then the C<encode> method will encode
207	the JSON result into UTF-8, as required by many protocols, while the	287	the JSON result into UTF-8, as required by many protocols, while the
208	C<decode> method expects to be handled an UTF-8-encoded string. Please	288	C<decode> method expects to be handled an UTF-8-encoded string. Please
209	note that UTF-8-encoded strings do not contain any characters outside the	289	note that UTF-8-encoded strings do not contain any characters outside the
210	range C<0..255>, they are thus useful for bytewise/binary I/O. In future	290	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
211	versions, enabling this option might enable autodetection of the UTF-16	291	versions, enabling this option might enable autodetection of the UTF-16
212	and UTF-32 encoding families, as described in RFC4627.	292	and UTF-32 encoding families, as described in RFC4627.
213		293
214	If C<$enable> is false, then the C<encode> method will return the JSON	294	If C<$enable> is false, then the C<encode> method will return the JSON
215	string as a (non-encoded) unicode string, while C<decode> expects thus a	295	string as a (non-encoded) Unicode string, while C<decode> expects thus a
216	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	296	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
217	to be done yourself, e.g. using the Encode module.	297	to be done yourself, e.g. using the Encode module.
218		298
219	Example, output UTF-16BE-encoded JSON:	299	Example, output UTF-16BE-encoded JSON:
220		300
221	use Encode;	301	use Encode;
…		…
243	]	323	]
244	}	324	}
245		325
246	=item $json = $json->indent ([$enable])	326	=item $json = $json->indent ([$enable])
247		327
		328	=item $enabled = $json->get_indent
		329
248	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	330	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
249	format as output, putting every array member or object/hash key-value pair	331	format as output, putting every array member or object/hash key-value pair
250	into its own line, identing them properly.	332	into its own line, indenting them properly.
251		333
252	If C<$enable> is false, no newlines or indenting will be produced, and the	334	If C<$enable> is false, no newlines or indenting will be produced, and the
253	resulting JSON text is guarenteed not to contain any C<newlines>.	335	resulting JSON text is guaranteed not to contain any C<newlines>.
254		336
255	This setting has no effect when decoding JSON texts.	337	This setting has no effect when decoding JSON texts.
256		338
257	=item $json = $json->space_before ([$enable])	339	=item $json = $json->space_before ([$enable])
		340
		341	=item $enabled = $json->get_space_before
258		342
259	If C<$enable> is true (or missing), then the C<encode> method will add an extra	343	If C<$enable> is true (or missing), then the C<encode> method will add an extra
260	optional space before the C<:> separating keys from values in JSON objects.	344	optional space before the C<:> separating keys from values in JSON objects.
261		345
262	If C<$enable> is false, then the C<encode> method will not add any extra	346	If C<$enable> is false, then the C<encode> method will not add any extra
…		…
268	Example, space_before enabled, space_after and indent disabled:	352	Example, space_before enabled, space_after and indent disabled:
269		353
270	{"key" :"value"}	354	{"key" :"value"}
271		355
272	=item $json = $json->space_after ([$enable])	356	=item $json = $json->space_after ([$enable])
		357
		358	=item $enabled = $json->get_space_after
273		359
274	If C<$enable> is true (or missing), then the C<encode> method will add an extra	360	If C<$enable> is true (or missing), then the C<encode> method will add an extra
275	optional space after the C<:> separating keys from values in JSON objects	361	optional space after the C<:> separating keys from values in JSON objects
276	and extra whitespace after the C<,> separating key-value pairs and array	362	and extra whitespace after the C<,> separating key-value pairs and array
277	members.	363	members.
…		…
284	Example, space_before and indent disabled, space_after enabled:	370	Example, space_before and indent disabled, space_after enabled:
285		371
286	{"key": "value"}	372	{"key": "value"}
287		373
288	=item $json = $json->relaxed ([$enable])	374	=item $json = $json->relaxed ([$enable])
		375
		376	=item $enabled = $json->get_relaxed
289		377
290	If C<$enable> is true (or missing), then C<decode> will accept some	378	If C<$enable> is true (or missing), then C<decode> will accept some
291	extensions to normal JSON syntax (see below). C<encode> will not be	379	extensions to normal JSON syntax (see below). C<encode> will not be
292	affected in anyway. I<Be aware that this option makes you accept invalid	380	affected in anyway. I<Be aware that this option makes you accept invalid
293	JSON texts as if they were valid!>. I suggest only to use this option to	381	JSON texts as if they were valid!>. I suggest only to use this option to
…		…
330		418
331	=back	419	=back
332		420
333	=item $json = $json->canonical ([$enable])	421	=item $json = $json->canonical ([$enable])
334		422
		423	=item $enabled = $json->get_canonical
		424
335	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	425	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
336	by sorting their keys. This is adding a comparatively high overhead.	426	by sorting their keys. This is adding a comparatively high overhead.
337		427
338	If C<$enable> is false, then the C<encode> method will output key-value	428	If C<$enable> is false, then the C<encode> method will output key-value
339	pairs in the order Perl stores them (which will likely change between runs	429	pairs in the order Perl stores them (which will likely change between runs
340	of the same script).	430	of the same script).
341		431
342	This option is useful if you want the same data structure to be encoded as	432	This option is useful if you want the same data structure to be encoded as
343	the same JSON text (given the same overall settings). If it is disabled,	433	the same JSON text (given the same overall settings). If it is disabled,
344	the same hash migh be encoded differently even if contains the same data,	434	the same hash might be encoded differently even if contains the same data,
345	as key-value pairs have no inherent ordering in Perl.	435	as key-value pairs have no inherent ordering in Perl.
346		436
347	This setting has no effect when decoding JSON texts.	437	This setting has no effect when decoding JSON texts.
348		438
349	=item $json = $json->allow_nonref ([$enable])	439	=item $json = $json->allow_nonref ([$enable])
		440
		441	=item $enabled = $json->get_allow_nonref
350		442
351	If C<$enable> is true (or missing), then the C<encode> method can convert a	443	If C<$enable> is true (or missing), then the C<encode> method can convert a
352	non-reference into its corresponding string, number or null JSON value,	444	non-reference into its corresponding string, number or null JSON value,
353	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	445	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
354	values instead of croaking.	446	values instead of croaking.
…		…
364	JSON::XS->new->allow_nonref->encode ("Hello, World!")	456	JSON::XS->new->allow_nonref->encode ("Hello, World!")
365	=> "Hello, World!"	457	=> "Hello, World!"
366		458
367	=item $json = $json->allow_blessed ([$enable])	459	=item $json = $json->allow_blessed ([$enable])
368		460
		461	=item $enabled = $json->get_allow_blessed
		462
369	If C<$enable> is true (or missing), then the C<encode> method will not	463	If C<$enable> is true (or missing), then the C<encode> method will not
370	barf when it encounters a blessed reference. Instead, the value of the	464	barf when it encounters a blessed reference. Instead, the value of the
371	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>	465	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>
372	disabled or no C<to_json> method found) or a representation of the	466	disabled or no C<TO_JSON> method found) or a representation of the
373	object (C<convert_blessed> enabled and C<to_json> method found) is being	467	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
374	encoded. Has no effect on C<decode>.	468	encoded. Has no effect on C<decode>.
375		469
376	If C<$enable> is false (the default), then C<encode> will throw an	470	If C<$enable> is false (the default), then C<encode> will throw an
377	exception when it encounters a blessed object.	471	exception when it encounters a blessed object.
378		472
379	=item $json = $json->convert_blessed ([$enable])	473	=item $json = $json->convert_blessed ([$enable])
		474
		475	=item $enabled = $json->get_convert_blessed
380		476
381	If C<$enable> is true (or missing), then C<encode>, upon encountering a	477	If C<$enable> is true (or missing), then C<encode>, upon encountering a
382	blessed object, will check for the availability of the C<TO_JSON> method	478	blessed object, will check for the availability of the C<TO_JSON> method
383	on the object's class. If found, it will be called in scalar context	479	on the object's class. If found, it will be called in scalar context
384	and the resulting scalar will be encoded instead of the object. If no	480	and the resulting scalar will be encoded instead of the object. If no
…		…
388	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	484	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
389	returns other blessed objects, those will be handled in the same	485	returns other blessed objects, those will be handled in the same
390	way. C<TO_JSON> must take care of not causing an endless recursion cycle	486	way. C<TO_JSON> must take care of not causing an endless recursion cycle
391	(== crash) in this case. The name of C<TO_JSON> was chosen because other	487	(== crash) in this case. The name of C<TO_JSON> was chosen because other
392	methods called by the Perl core (== not by the user of the object) are	488	methods called by the Perl core (== not by the user of the object) are
393	usually in upper case letters and to avoid collisions with the C<to_json>	489	usually in upper case letters and to avoid collisions with any C<to_json>
394	function.	490	function or method.
395		491
396	This setting does not yet influence C<decode> in any way, but in the	492	This setting does not yet influence C<decode> in any way, but in the
397	future, global hooks might get installed that influence C<decode> and are	493	future, global hooks might get installed that influence C<decode> and are
398	enabled by this setting.	494	enabled by this setting.
399		495
…		…
441		537
442	As this callback gets called less often then the C<filter_json_object>	538	As this callback gets called less often then the C<filter_json_object>
443	one, decoding speed will not usually suffer as much. Therefore, single-key	539	one, decoding speed will not usually suffer as much. Therefore, single-key
444	objects make excellent targets to serialise Perl objects into, especially	540	objects make excellent targets to serialise Perl objects into, especially
445	as single-key JSON objects are as close to the type-tagged value concept	541	as single-key JSON objects are as close to the type-tagged value concept
446	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not	542	as JSON gets (it's basically an ID/VALUE tuple). Of course, JSON does not
447	support this in any way, so you need to make sure your data never looks	543	support this in any way, so you need to make sure your data never looks
448	like a serialised Perl hash.	544	like a serialised Perl hash.
449		545
450	Typical names for the single object key are C<__class_whatever__>, or	546	Typical names for the single object key are C<__class_whatever__>, or
451	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even	547	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
…		…
475		571
476	{ __widget__ => $self->{id} }	572	{ __widget__ => $self->{id} }
477	}	573	}
478		574
479	=item $json = $json->shrink ([$enable])	575	=item $json = $json->shrink ([$enable])
		576
		577	=item $enabled = $json->get_shrink
480		578
481	Perl usually over-allocates memory a bit when allocating space for	579	Perl usually over-allocates memory a bit when allocating space for
482	strings. This flag optionally resizes strings generated by either	580	strings. This flag optionally resizes strings generated by either
483	C<encode> or C<decode> to their minimum size possible. This can save	581	C<encode> or C<decode> to their minimum size possible. This can save
484	memory when your JSON texts are either very very long or you have many	582	memory when your JSON texts are either very very long or you have many
…		…
502	strings that look like integers or floats into integers or floats	600	strings that look like integers or floats into integers or floats
503	internally (there is no difference on the Perl level), saving space.	601	internally (there is no difference on the Perl level), saving space.
504		602
505	=item $json = $json->max_depth ([$maximum_nesting_depth])	603	=item $json = $json->max_depth ([$maximum_nesting_depth])
506		604
		605	=item $max_depth = $json->get_max_depth
		606
507	Sets the maximum nesting level (default C<512>) accepted while encoding	607	Sets the maximum nesting level (default C<512>) accepted while encoding
508	or decoding. If the JSON text or Perl data structure has an equal or	608	or decoding. If the JSON text or Perl data structure has an equal or
509	higher nesting level then this limit, then the encoder and decoder will	609	higher nesting level then this limit, then the encoder and decoder will
510	stop and croak at that point.	610	stop and croak at that point.
511		611
…		…
522	used, which is rarely useful.	622	used, which is rarely useful.
523		623
524	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
525		625
526	=item $json = $json->max_size ([$maximum_string_size])	626	=item $json = $json->max_size ([$maximum_string_size])
		627
		628	=item $max_size = $json->get_max_size
527		629
528	Set the maximum length a JSON text may have (in bytes) where decoding is	630	Set the maximum length a JSON text may have (in bytes) where decoding is
529	being attempted. The default is C<0>, meaning no limit. When C<decode>	631	being attempted. The default is C<0>, meaning no limit. When C<decode>
530	is called on a string longer then this number of characters it will not	632	is called on a string longer then this number of characters it will not
531	attempt to decode the string but throw an exception. This setting has no	633	attempt to decode the string but throw an exception. This setting has no
…		…
578	vice versa. These mappings are designed to "do the right thing" in most	680	vice versa. These mappings are designed to "do the right thing" in most
579	circumstances automatically, preserving round-tripping characteristics	681	circumstances automatically, preserving round-tripping characteristics
580	(what you put in comes out as something equivalent).	682	(what you put in comes out as something equivalent).
581		683
582	For the more enlightened: note that in the following descriptions,	684	For the more enlightened: note that in the following descriptions,
583	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	685	lowercase I<perl> refers to the Perl interpreter, while uppercase I<Perl>
584	refers to the abstract Perl language itself.	686	refers to the abstract Perl language itself.
585		687
586		688
587	=head2 JSON -> PERL	689	=head2 JSON -> PERL
588		690
589	=over 4	691	=over 4
590		692
591	=item object	693	=item object
592		694
593	A JSON object becomes a reference to a hash in Perl. No ordering of object	695	A JSON object becomes a reference to a hash in Perl. No ordering of object
594	keys is preserved (JSON does not preserver object key ordering itself).	696	keys is preserved (JSON does not preserve object key ordering itself).
595		697
596	=item array	698	=item array
597		699
598	A JSON array becomes a reference to an array in Perl.	700	A JSON array becomes a reference to an array in Perl.
599		701
…		…
607		709
608	A JSON number becomes either an integer, numeric (floating point) or	710	A JSON number becomes either an integer, numeric (floating point) or
609	string scalar in perl, depending on its range and any fractional parts. On	711	string scalar in perl, depending on its range and any fractional parts. On
610	the Perl level, there is no difference between those as Perl handles all	712	the Perl level, there is no difference between those as Perl handles all
611	the conversion details, but an integer may take slightly less memory and	713	the conversion details, but an integer may take slightly less memory and
612	might represent more values exactly than (floating point) numbers.	714	might represent more values exactly than floating point numbers.
613		715
614	If the number consists of digits only, JSON::XS will try to represent	716	If the number consists of digits only, JSON::XS will try to represent
615	it as an integer value. If that fails, it will try to represent it as	717	it as an integer value. If that fails, it will try to represent it as
616	a numeric (floating point) value if that is possible without loss of	718	a numeric (floating point) value if that is possible without loss of
617	precision. Otherwise it will preserve the number as a string value.	719	precision. Otherwise it will preserve the number as a string value (in
		720	which case you lose roundtripping ability, as the JSON number will be
		721	re-encoded toa JSON string).
618		722
619	Numbers containing a fractional or exponential part will always be	723	Numbers containing a fractional or exponential part will always be
620	represented as numeric (floating point) values, possibly at a loss of	724	represented as numeric (floating point) values, possibly at a loss of
621	precision.	725	precision (in which case you might lose perfect roundtripping ability, but
622		726	the JSON number will still be re-encoded as a JSON number).
623	This might create round-tripping problems as numbers might become strings,
624	but as Perl is typeless there is no other way to do it.
625		727
626	=item true, false	728	=item true, false
627		729
628	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	730	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
629	respectively. They are overloaded to act almost exactly like the numbers	731	respectively. They are overloaded to act almost exactly like the numbers
630	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using	732	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using
631	the C<JSON::XS::is_bool> function.	733	the C<JSON::XS::is_bool> function.
632		734
633	=item null	735	=item null
634		736
635	A JSON null atom becomes C<undef> in Perl.	737	A JSON null atom becomes C<undef> in Perl.
…		…
666	Other unblessed references are generally not allowed and will cause an	768	Other unblessed references are generally not allowed and will cause an
667	exception to be thrown, except for references to the integers C<0> and	769	exception to be thrown, except for references to the integers C<0> and
668	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	770	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
669	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	771	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
670		772
671	to_json [\0,JSON::XS::true] # yields [false,true]	773	encode_json [\0,JSON::XS::true] # yields [false,true]
672		774
673	=item JSON::XS::true, JSON::XS::false	775	=item JSON::XS::true, JSON::XS::false
674		776
675	These special values become JSON true and JSON false values,	777	These special values become JSON true and JSON false values,
676	respectively. You can also use C<\1> and C<\0> directly if you want.	778	respectively. You can also use C<\1> and C<\0> directly if you want.
677		779
678	=item blessed objects	780	=item blessed objects
679		781
680	Blessed objects are not allowed. JSON::XS currently tries to encode their	782	Blessed objects are not directly representable in JSON. See the
681	underlying representation (hash- or arrayref), but this behaviour might	783	C<allow_blessed> and C<convert_blessed> methods on various options on
682	change in future versions.	784	how to deal with this: basically, you can choose between throwing an
		785	exception, encoding the reference as if it weren't blessed, or provide
		786	your own serialiser method.
683		787
684	=item simple scalars	788	=item simple scalars
685		789
686	Simple Perl scalars (any scalar that is not a reference) are the most	790	Simple Perl scalars (any scalar that is not a reference) are the most
687	difficult objects to encode: JSON::XS will encode undefined scalars as	791	difficult objects to encode: JSON::XS will encode undefined scalars as
688	JSON null value, scalars that have last been used in a string context	792	JSON C<null> values, scalars that have last been used in a string context
689	before encoding as JSON strings and anything else as number value:	793	before encoding as JSON strings, and anything else as number value:
690		794
691	# dump as number	795	# dump as number
692	to_json [2] # yields [2]	796	encode_json [2] # yields [2]
693	to_json [-3.0e17] # yields [-3e+17]	797	encode_json [-3.0e17] # yields [-3e+17]
694	my $value = 5; to_json [$value] # yields [5]	798	my $value = 5; encode_json [$value] # yields [5]
695		799
696	# used as string, so dump as string	800	# used as string, so dump as string
697	print $value;	801	print $value;
698	to_json [$value] # yields ["5"]	802	encode_json [$value] # yields ["5"]
699		803
700	# undef becomes null	804	# undef becomes null
701	to_json [undef] # yields [null]	805	encode_json [undef] # yields [null]
702		806
703	You can force the type to be a string by stringifying it:	807	You can force the type to be a JSON string by stringifying it:
704		808
705	my $x = 3.1; # some variable containing a number	809	my $x = 3.1; # some variable containing a number
706	"$x"; # stringified	810	"$x"; # stringified
707	$x .= ""; # another, more awkward way to stringify	811	$x .= ""; # another, more awkward way to stringify
708	print $x; # perl does it for you, too, quite often	812	print $x; # perl does it for you, too, quite often
709		813
710	You can force the type to be a number by numifying it:	814	You can force the type to be a JSON number by numifying it:
711		815
712	my $x = "3"; # some variable containing a string	816	my $x = "3"; # some variable containing a string
713	$x += 0; # numify it, ensuring it will be dumped as a number	817	$x += 0; # numify it, ensuring it will be dumped as a number
714	$x *= 1; # same thing, the choise is yours.	818	$x *= 1; # same thing, the choice is yours.
715		819
716	You can not currently output JSON booleans or force the type in other,	820	You can not currently force the type in other, less obscure, ways. Tell me
717	less obscure, ways. Tell me if you need this capability.	821	if you need this capability (but don't forget to explain why its needed
		822	:).
		823
		824	=back
		825
		826
		827	=head1 ENCODING/CODESET FLAG NOTES
		828
		829	The interested reader might have seen a number of flags that signify
		830	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
		831	some confusion on what these do, so here is a short comparison:
		832
		833	C<utf8> controls wether the JSON text created by C<encode> (and expected
		834	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		835	control wether C<encode> escapes character values outside their respective
		836	codeset range. Neither of these flags conflict with each other, although
		837	some combinations make less sense than others.
		838
		839	Care has been taken to make all flags symmetrical with respect to
		840	C<encode> and C<decode>, that is, texts encoded with any combination of
		841	these flag values will be correctly decoded when the same flags are used
		842	- in general, if you use different flag settings while encoding vs. when
		843	decoding you likely have a bug somewhere.
		844
		845	Below comes a verbose discussion of these flags. Note that a "codeset" is
		846	simply an abstract set of character-codepoint pairs, while an encoding
		847	takes those codepoint numbers and I<encodes> them, in our case into
		848	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		849	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		850	the same time, which can be confusing.
		851
		852	=over 4
		853
		854	=item C<utf8> flag disabled
		855
		856	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		857	and expect Unicode strings, that is, characters with high ordinal Unicode
		858	values (> 255) will be encoded as such characters, and likewise such
		859	characters are decoded as-is, no canges to them will be done, except
		860	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		861	respectively (to Perl, these are the same thing in strings unless you do
		862	funny/weird/dumb stuff).
		863
		864	This is useful when you want to do the encoding yourself (e.g. when you
		865	want to have UTF-16 encoded JSON texts) or when some other layer does
		866	the encoding for you (for example, when printing to a terminal using a
		867	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		868	to UTF-8 encode your data first and have Perl encode it another time).
		869
		870	=item C<utf8> flag enabled
		871
		872	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		873	characters using the corresponding UTF-8 multi-byte sequence, and will
		874	expect your input strings to be encoded as UTF-8, that is, no "character"
		875	of the input string must have any value > 255, as UTF-8 does not allow
		876	that.
		877
		878	The C<utf8> flag therefore switches between two modes: disabled means you
		879	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		880	octet/binary string in Perl.
		881
		882	=item C<latin1> or C<ascii> flags enabled
		883
		884	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		885	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		886	characters as specified by the C<utf8> flag.
		887
		888	If C<utf8> is disabled, then the result is also correctly encoded in those
		889	character sets (as both are proper subsets of Unicode, meaning that a
		890	Unicode string with all character values < 256 is the same thing as a
		891	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		892	the same thing as an ASCII string in Perl).
		893
		894	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
		895	regardless of these flags, just some more characters will be escaped using
		896	C<\uXXXX> then before.
		897
		898	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
		899	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		900	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		901	a subset of Unicode), while ASCII is.
		902
		903	Surprisingly, C<decode> will ignore these flags and so treat all input
		904	values as governed by the C<utf8> flag. If it is disabled, this allows you
		905	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		906	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
		907
		908	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		909	they only govern when the JSON output engine escapes a character or not.
		910
		911	The main use for C<latin1> is to relatively efficiently store binary data
		912	as JSON, at the expense of breaking compatibility with most JSON decoders.
		913
		914	The main use for C<ascii> is to force the output to not contain characters
		915	with values > 127, which means you can interpret the resulting string
		916	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
		917	8-bit-encoding, and still get the same data structure back. This is useful
		918	when your channel for JSON transfer is not 8-bit clean or the encoding
		919	might be mangled in between (e.g. in mail), and works because ASCII is a
		920	proper subset of most 8-bit and multibyte encodings in use in the world.
718		921
719	=back	922	=back
720		923
721		924
722	=head1 COMPARISON	925	=head1 COMPARISON
…		…
727	followed by some benchmark values. JSON::XS was designed not to suffer	930	followed by some benchmark values. JSON::XS was designed not to suffer
728	from any of these problems or limitations.	931	from any of these problems or limitations.
729		932
730	=over 4	933	=over 4
731		934
		935	=item JSON 2.xx
		936
		937	A marvellous piece of engineering, this module either uses JSON::XS
		938	directly when available (so will be 100% compatible with it, including
		939	speed), or it uses JSON::PP, which is basically JSON::XS translated to
		940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
		941	slower.
		942
		943	You cannot really lose by using this module, especially as it tries very
		944	hard to work even with ancient Perl versions, while JSON::XS does not.
		945
732	=item JSON 1.07	946	=item JSON 1.07
733		947
734	Slow (but very portable, as it is written in pure Perl).	948	Slow (but very portable, as it is written in pure Perl).
735		949
736	Undocumented/buggy Unicode handling (how JSON handles unicode values is	950	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
737	undocumented. One can get far by feeding it unicode strings and doing	951	undocumented. One can get far by feeding it Unicode strings and doing
738	en-/decoding oneself, but unicode escapes are not working properly).	952	en-/decoding oneself, but Unicode escapes are not working properly).
739		953
740	No roundtripping (strings get clobbered if they look like numbers, e.g.	954	No round-tripping (strings get clobbered if they look like numbers, e.g.
741	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	955	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
742	decode into the number 2.	956	decode into the number 2.
743		957
744	=item JSON::PC 0.01	958	=item JSON::PC 0.01
745		959
746	Very fast.	960	Very fast.
747		961
748	Undocumented/buggy Unicode handling.	962	Undocumented/buggy Unicode handling.
749		963
750	No roundtripping.	964	No round-tripping.
751		965
752	Has problems handling many Perl values (e.g. regex results and other magic	966	Has problems handling many Perl values (e.g. regex results and other magic
753	values will make it croak).	967	values will make it croak).
754		968
755	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	969	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
…		…
765	Very inflexible (no human-readable format supported, format pretty much	979	Very inflexible (no human-readable format supported, format pretty much
766	undocumented. I need at least a format for easy reading by humans and a	980	undocumented. I need at least a format for easy reading by humans and a
767	single-line compact format for use in a protocol, and preferably a way to	981	single-line compact format for use in a protocol, and preferably a way to
768	generate ASCII-only JSON texts).	982	generate ASCII-only JSON texts).
769		983
770	Completely broken (and confusingly documented) Unicode handling (unicode	984	Completely broken (and confusingly documented) Unicode handling (Unicode
771	escapes are not working properly, you need to set ImplicitUnicode to	985	escapes are not working properly, you need to set ImplicitUnicode to
772	I<different> values on en- and decoding to get symmetric behaviour).	986	I<different> values on en- and decoding to get symmetric behaviour).
773		987
774	No roundtripping (simple cases work, but this depends on wether the scalar	988	No round-tripping (simple cases work, but this depends on whether the scalar
775	value was used in a numeric context or not).	989	value was used in a numeric context or not).
776		990
777	Dumping hashes may skip hash values depending on iterator state.	991	Dumping hashes may skip hash values depending on iterator state.
778		992
779	Unmaintained (maintainer unresponsive for many months, bugs are not	993	Unmaintained (maintainer unresponsive for many months, bugs are not
780	getting fixed).	994	getting fixed).
781		995
782	Does not check input for validity (i.e. will accept non-JSON input and	996	Does not check input for validity (i.e. will accept non-JSON input and
783	return "something" instead of raising an exception. This is a security	997	return "something" instead of raising an exception. This is a security
784	issue: imagine two banks transfering money between each other using	998	issue: imagine two banks transferring money between each other using
785	JSON. One bank might parse a given non-JSON request and deduct money,	999	JSON. One bank might parse a given non-JSON request and deduct money,
786	while the other might reject the transaction with a syntax error. While a	1000	while the other might reject the transaction with a syntax error. While a
787	good protocol will at least recover, that is extra unnecessary work and	1001	good protocol will at least recover, that is extra unnecessary work and
788	the transaction will still not succeed).	1002	the transaction will still not succeed).
789		1003
790	=item JSON::DWIW 0.04	1004	=item JSON::DWIW 0.04
791		1005
792	Very fast. Very natural. Very nice.	1006	Very fast. Very natural. Very nice.
793		1007
794	Undocumented unicode handling (but the best of the pack. Unicode escapes	1008	Undocumented Unicode handling (but the best of the pack. Unicode escapes
795	still don't get parsed properly).	1009	still don't get parsed properly).
796		1010
797	Very inflexible.	1011	Very inflexible.
798		1012
799	No roundtripping.	1013	No round-tripping.
800		1014
801	Does not generate valid JSON texts (key strings are often unquoted, empty keys	1015	Does not generate valid JSON texts (key strings are often unquoted, empty keys
802	result in nothing being output)	1016	result in nothing being output)
803		1017
804	Does not check input for validity.	1018	Does not check input for validity.
…		…
806	=back	1020	=back
807		1021
808		1022
809	=head2 JSON and YAML	1023	=head2 JSON and YAML
810		1024
811	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1025	You often hear that JSON is a subset of YAML. This is, however, a mass
812	however, a mass hysteria and very far from the truth. In general, there is	1026	hysteria(*) and very far from the truth. In general, there is no way to
813	no way to configure JSON::XS to output a data structure as valid YAML.	1027	configure JSON::XS to output a data structure as valid YAML that works for
		1028	all cases.
814		1029
815	If you really must use JSON::XS to generate YAML, you should use this	1030	If you really must use JSON::XS to generate YAML, you should use this
816	algorithm (subject to change in future versions):	1031	algorithm (subject to change in future versions):
817		1032
818	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1033	my $to_yaml = JSON::XS->new->utf8->space_after (1);
819	my $yaml = $to_yaml->encode ($ref) . "\n";	1034	my $yaml = $to_yaml->encode ($ref) . "\n";
820		1035
821	This will usually generate JSON texts that also parse as valid	1036	This will I<usually> generate JSON texts that also parse as valid
822	YAML. Please note that YAML has hardcoded limits on (simple) object key	1037	YAML. Please note that YAML has hardcoded limits on (simple) object key
823	lengths that JSON doesn't have, so you should make sure that your hash	1038	lengths that JSON doesn't have and also has different and incompatible
		1039	unicode handling, so you should make sure that your hash keys are
824	keys are noticably shorter than the 1024 characters YAML allows.	1040	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1041	you do not have codepoints with values outside the Unicode BMP (basic
		1042	multilingual page). YAML also does not allow C<\/> sequences in strings
		1043	(which JSON::XS does not I<currently> generate).
825		1044
826	There might be other incompatibilities that I am not aware of. In general	1045	There might be other incompatibilities that I am not aware of (or the YAML
		1046	specification has been changed yet again - it does so quite often). In
827	you should not try to generate YAML with a JSON generator or vice versa,	1047	general you should not try to generate YAML with a JSON generator or vice
828	or try to parse JSON with a YAML parser or vice versa: chances are high	1048	versa, or try to parse JSON with a YAML parser or vice versa: chances are
829	that you will run into severe interoperability problems.	1049	high that you will run into severe interoperability problems when you
		1050	least expect it.
		1051
		1052	=over 4
		1053
		1054	=item (*)
		1055
		1056	This is spread actively by the YAML team, however. For many years now they
		1057	claim YAML were a superset of JSON, even when proven otherwise.
		1058
		1059	Even the author of this manpage was at some point accused of providing
		1060	"incorrect" information, despite the evidence presented (claims ranged
		1061	from "your documentation contains inaccurate and negative statements about
		1062	YAML" (the only negative comment is this footnote, and it didn't exist
		1063	back then; the question on which claims were inaccurate was never answered
		1064	etc.) to "the YAML spec is not up-to-date" (the real and supposedly
		1065	JSON-compatible spec is apparently not currently publicly available)
		1066	to actual requests to replace this section by incorrect information,
		1067	suppressing information about the real problem).
		1068
		1069	So whenever you are told that YAML was a superset of JSON, first check
		1070	wether it is really true (it might be when you check it, but it certainly
		1071	was not true when this was written). I would much prefer if the YAML team
		1072	would spent their time on actually making JSON compatibility a truth
		1073	(JSON, after all, has a very small and simple specification) instead of
		1074	trying to lobby/force people into reporting untruths.
		1075
		1076	=back
830		1077
831		1078
832	=head2 SPEED	1079	=head2 SPEED
833		1080
834	It seems that JSON::XS is surprisingly fast, as shown in the following	1081	It seems that JSON::XS is surprisingly fast, as shown in the following
835	tables. They have been generated with the help of the C<eg/bench> program	1082	tables. They have been generated with the help of the C<eg/bench> program
836	in the JSON::XS distribution, to make it easy to compare on your own	1083	in the JSON::XS distribution, to make it easy to compare on your own
837	system.	1084	system.
838		1085
839	First comes a comparison between various modules using a very short	1086	First comes a comparison between various modules using
840	single-line JSON string:	1087	a very short single-line JSON string (also available at
		1088	L<http://dist.schmorp.de/misc/json/short.json>).
841		1089
842	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1090	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
843	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1091	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
844		1092
845	It shows the number of encodes/decodes per second (JSON::XS uses	1093	It shows the number of encodes/decodes per second (JSON::XS uses
846	the functional interface, while JSON::XS/2 uses the OO interface	1094	the functional interface, while JSON::XS/2 uses the OO interface
847	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1095	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
848	shrink). Higher is better:	1096	shrink). Higher is better:
849		1097
850	Storable \| 15779.925 \| 14169.946 \|
851	-----------+------------+------------+
852	module \| encode \| decode \|	1098	module \| encode \| decode \|
853	-----------\|------------\|------------\|	1099	-----------\|------------\|------------\|
854	JSON \| 4990.842 \| 4088.813 \|	1100	JSON 1.x \| 4990.842 \| 4088.813 \|
855	JSON::DWIW \| 51653.990 \| 71575.154 \|	1101	JSON::DWIW \| 51653.990 \| 71575.154 \|
856	JSON::PC \| 65948.176 \| 74631.744 \|	1102	JSON::PC \| 65948.176 \| 74631.744 \|
857	JSON::PP \| 8931.652 \| 3817.168 \|	1103	JSON::PP \| 8931.652 \| 3817.168 \|
858	JSON::Syck \| 24877.248 \| 27776.848 \|	1104	JSON::Syck \| 24877.248 \| 27776.848 \|
859	JSON::XS \| 388361.481 \| 227951.304 \|	1105	JSON::XS \| 388361.481 \| 227951.304 \|
…		…
861	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1107	JSON::XS/3 \| 338250.323 \| 218453.333 \|
862	Storable \| 16500.016 \| 135300.129 \|	1108	Storable \| 16500.016 \| 135300.129 \|
863	-----------+------------+------------+	1109	-----------+------------+------------+
864		1110
865	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1111	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
866	about three times faster on decoding, and over fourty times faster	1112	about three times faster on decoding, and over forty times faster
867	than JSON, even with pretty-printing and key sorting. It also compares	1113	than JSON, even with pretty-printing and key sorting. It also compares
868	favourably to Storable for small amounts of data.	1114	favourably to Storable for small amounts of data.
869		1115
870	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1116	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
871	search API (http://nanoref.com/yahooapis/mgPdGg):	1117	search API (L<http://dist.schmorp.de/misc/json/long.json>).
872		1118
873	module \| encode \| decode \|	1119	module \| encode \| decode \|
874	-----------\|------------\|------------\|	1120	-----------\|------------\|------------\|
875	JSON \| 55.260 \| 34.971 \|	1121	JSON 1.x \| 55.260 \| 34.971 \|
876	JSON::DWIW \| 825.228 \| 1082.513 \|	1122	JSON::DWIW \| 825.228 \| 1082.513 \|
877	JSON::PC \| 3571.444 \| 2394.829 \|	1123	JSON::PC \| 3571.444 \| 2394.829 \|
878	JSON::PP \| 210.987 \| 32.574 \|	1124	JSON::PP \| 210.987 \| 32.574 \|
879	JSON::Syck \| 552.551 \| 787.544 \|	1125	JSON::Syck \| 552.551 \| 787.544 \|
880	JSON::XS \| 5780.463 \| 4854.519 \|	1126	JSON::XS \| 5780.463 \| 4854.519 \|
…		…
884	-----------+------------+------------+	1130	-----------+------------+------------+
885		1131
886	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1132	Again, JSON::XS leads by far (except for Storable which non-surprisingly
887	decodes faster).	1133	decodes faster).
888		1134
889	On large strings containing lots of high unicode characters, some modules	1135	On large strings containing lots of high Unicode characters, some modules
890	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1136	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
891	will be broken due to missing (or wrong) unicode handling. Others refuse	1137	will be broken due to missing (or wrong) Unicode handling. Others refuse
892	to decode or encode properly, so it was impossible to prepare a fair	1138	to decode or encode properly, so it was impossible to prepare a fair
893	comparison table for that case.	1139	comparison table for that case.
894		1140
895		1141
896	=head1 SECURITY CONSIDERATIONS	1142	=head1 SECURITY CONSIDERATIONS
…		…
902	any buffer overflows. Obviously, this module should ensure that and I am	1148	any buffer overflows. Obviously, this module should ensure that and I am
903	trying hard on making that true, but you never know.	1149	trying hard on making that true, but you never know.
904		1150
905	Second, you need to avoid resource-starving attacks. That means you should	1151	Second, you need to avoid resource-starving attacks. That means you should
906	limit the size of JSON texts you accept, or make sure then when your	1152	limit the size of JSON texts you accept, or make sure then when your
907	resources run out, thats just fine (e.g. by using a separate process that	1153	resources run out, that's just fine (e.g. by using a separate process that
908	can crash safely). The size of a JSON text in octets or characters is	1154	can crash safely). The size of a JSON text in octets or characters is
909	usually a good indication of the size of the resources required to decode	1155	usually a good indication of the size of the resources required to decode
910	it into a Perl structure. While JSON::XS can check the size of the JSON	1156	it into a Perl structure. While JSON::XS can check the size of the JSON
911	text, it might be too late when you already have it in memory, so you	1157	text, it might be too late when you already have it in memory, so you
912	might want to check the size before you accept the string.	1158	might want to check the size before you accept the string.
913		1159
914	Third, JSON::XS recurses using the C stack when decoding objects and	1160	Third, JSON::XS recurses using the C stack when decoding objects and
915	arrays. The C stack is a limited resource: for instance, on my amd64	1161	arrays. The C stack is a limited resource: for instance, on my amd64
916	machine with 8MB of stack size I can decode around 180k nested arrays but	1162	machine with 8MB of stack size I can decode around 180k nested arrays but
917	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1163	only 14k nested JSON objects (due to perl itself recursing deeply on croak
918	to free the temporary). If that is exceeded, the program crashes. to be	1164	to free the temporary). If that is exceeded, the program crashes. To be
919	conservative, the default nesting limit is set to 512. If your process	1165	conservative, the default nesting limit is set to 512. If your process
920	has a smaller stack, you should adjust this setting accordingly with the	1166	has a smaller stack, you should adjust this setting accordingly with the
921	C<max_depth> method.	1167	C<max_depth> method.
922		1168
923	And last but least, something else could bomb you that I forgot to think	1169	Something else could bomb you, too, that I forgot to think of. In that
924	of. In that case, you get to keep the pieces. I am always open for hints,	1170	case, you get to keep the pieces. I am always open for hints, though...
925	though...	1171
		1172	Also keep in mind that JSON::XS might leak contents of your Perl data
		1173	structures in its error messages, so when you serialise sensitive
		1174	information you might want to make sure that exceptions thrown by JSON::XS
		1175	will not end up in front of untrusted eyes.
926		1176
927	If you are using JSON::XS to return packets to consumption	1177	If you are using JSON::XS to return packets to consumption
928	by javascript scripts in a browser you should have a look at	1178	by JavaScript scripts in a browser you should have a look at
929	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether	1179	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
930	you are vulnerable to some common attack vectors (which really are browser	1180	you are vulnerable to some common attack vectors (which really are browser
931	design bugs, but it is still you who will have to deal with it, as major	1181	design bugs, but it is still you who will have to deal with it, as major
932	browser developers care only for features, not about doing security	1182	browser developers care only for features, not about getting security
933	right).	1183	right).
		1184
		1185
		1186	=head1 THREADS
		1187
		1188	This module is I<not> guaranteed to be thread safe and there are no
		1189	plans to change this until Perl gets thread support (as opposed to the
		1190	horribly slow so-called "threads" which are simply slow and bloated
		1191	process simulations - use fork, its I<much> faster, cheaper, better).
		1192
		1193	(It might actually work, but you have been warned).
934		1194
935		1195
936	=head1 BUGS	1196	=head1 BUGS
937		1197
938	While the goal of this module is to be correct, that unfortunately does	1198	While the goal of this module is to be correct, that unfortunately does
939	not mean its bug-free, only that I think its design is bug-free. It is	1199	not mean its bug-free, only that I think its design is bug-free. It is
940	still relatively early in its development. If you keep reporting bugs they	1200	still relatively early in its development. If you keep reporting bugs they
941	will be fixed swiftly, though.	1201	will be fixed swiftly, though.
		1202
		1203	Please refrain from using rt.cpan.org or any other bug reporting
		1204	service. I put the contact address into my modules for a reason.
942		1205
943	=cut	1206	=cut
944		1207
945	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1208	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
946	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1209	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };

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Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC vs.
Revision 1.89 by root, Wed Mar 19 13:54:53 2008 UTC