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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

…		…
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
		8
		9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
		11
		12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		14
		15	# OO-interface
		16
		17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		19	$perl_scalar = $coder->decode ($unicode_json_text);
8		20
9	=head1 DESCRIPTION	21	=head1 DESCRIPTION
10		22
11	This module converts Perl data structures to JSON and vice versa. Its	23	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	24	primary goal is to be I<correct> and its secondary goal is to be
…		…
25		37
26	=head2 FEATURES	38	=head2 FEATURES
27		39
28	=over 4	40	=over 4
29		41
30	=item * correct handling of unicode issues	42	=item * correct unicode handling
31		43
32	This module knows how to handle Unicode, and even documents how and when	44	This module knows how to handle Unicode, and even documents how and when
33	it does so.	45	it does so.
34		46
35	=item * round-trip integrity	47	=item * round-trip integrity
36		48
37	When you serialise a perl data structure using only datatypes supported	49	When you serialise a perl data structure using only datatypes supported
38	by JSON, the deserialised data structure is identical on the Perl level.	50	by JSON, the deserialised data structure is identical on the Perl level.
39	(e.g. the string "2.0" doesn't suddenly become "2").	51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		52	like a number).
40		53
41	=item * strict checking of JSON correctness	54	=item * strict checking of JSON correctness
42		55
43	There is no guessing, no generating of illegal JSON strings by default,	56	There is no guessing, no generating of illegal JSON texts by default,
44	and only JSON is accepted as input by default (the latter is a security	57	and only JSON is accepted as input by default (the latter is a security
45	feature).	58	feature).
46		59
47	=item * fast	60	=item * fast
48		61
…		…
55	interface.	68	interface.
56		69
57	=item * reasonably versatile output formats	70	=item * reasonably versatile output formats
58		71
59	You can choose between the most compact guarenteed single-line format	72	You can choose between the most compact guarenteed single-line format
60	possible (nice for simple line-based protocols), a pure-ascii format (for	73	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	74	(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	75	unicode range), or a pretty-printed format (for when you want to read that
63	whatever way you like.	76	stuff). Or you can combine those features in whatever way you like.
64		77
65	=back	78	=back
66		79
67	=cut	80	=cut
68		81
69	package JSON::XS;	82	package JSON::XS;
70		83
71	BEGIN {	84	use strict;
		85
72	$VERSION = '0.3';	86	our $VERSION = '1.5';
73	@ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
74		88
75	@EXPORT = qw(to_json from_json);	89	our @EXPORT = qw(to_json from_json);
76	require Exporter;
77		90
78	require XSLoader;	91	use Exporter;
79	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
80	}
81		93
82	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
83		95
84	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
85	exported by default:	97	exported by default:
86		98
87	=over 4	99	=over 4
88		100
89	=item $json_string = to_json $perl_scalar	101	=item $json_text = to_json $perl_scalar
90		102
91	Converts the given Perl data structure (a simple scalar or a reference to	103	Converts the given Perl data structure (a simple scalar or a reference to
92	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
93	octets only). Croaks on error.	105	octets only). Croaks on error.
94		106
95	This function call is functionally identical to C<< JSON::XS->new->utf8->encode ($perl_scalar) >>.	107	This function call is functionally identical to:
96		108
		109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		110
		111	except being faster.
		112
97	=item $perl_scalar = from_json $json_string	113	=item $perl_scalar = from_json $json_text
98		114
99	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
100	parse that as an UTF-8 encoded JSON string, returning the resulting simple	116	parse that as an UTF-8 encoded JSON text, returning the resulting simple
101	scalar or reference. Croaks on error.	117	scalar or reference. Croaks on error.
102		118
103	This function call is functionally identical to C<< JSON::XS->new->utf8->decode ($json_string) >>.	119	This function call is functionally identical to:
		120
		121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		122
		123	except being faster.
		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
104		133
105	=back	134	=back
		135
106		136
107	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
108		138
109	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
110	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
117	strings. All boolean flags described below are by default I<disabled>.	147	strings. All boolean flags described below are by default I<disabled>.
118		148
119	The mutators for flags all return the JSON object again and thus calls can	149	The mutators for flags all return the JSON object again and thus calls can
120	be chained:	150	be chained:
121		151
122	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
123	=> {"a": [1, 2]}	153	=> {"a": [1, 2]}
124		154
125	=item $json = $json->ascii ([$enable])	155	=item $json = $json->ascii ([$enable])
126		156
127	If C<$enable> is true (or missing), then the C<encode> method will	157	If C<$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	158	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	159	unicode characters outside that range will be escaped using either a
130	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
131	RFC4627.	161	as per RFC4627. The resulting encoded JSON text can be treated as a native
		162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		163	or any other superset of ASCII.
132		164
133	If C<$enable> is false, then the C<encode> method will not escape Unicode	165	If C<$enable> is false, then the C<encode> method will not escape Unicode
134	characters unless necessary.	166	characters unless required by the JSON syntax or other flags. This results
		167	in a faster and more compact format.
135		168
		169	The main use for this flag is to produce JSON texts that can be
		170	transmitted over a 7-bit channel, as the encoded JSON texts will not
		171	contain any 8 bit characters.
		172
136	JSON::XS->new->ascii (1)->encode (chr 0x10401)	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
137	=> \ud801\udc01	174	=> ["\ud801\udc01"]
		175
		176	=item $json = $json->latin1 ([$enable])
		177
		178	If C<$enable> is true (or missing), then the C<encode> method will encode
		179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		180	outside the code range C<0..255>. The resulting string can be treated as a
		181	latin1-encoded JSON text or a native unicode string. The C<decode> method
		182	will not be affected in any way by this flag, as C<decode> by default
		183	expects unicode, which is a strict superset of latin1.
		184
		185	If C<$enable> is false, then the C<encode> method will not escape Unicode
		186	characters unless required by the JSON syntax or other flags.
		187
		188	The main use for this flag is efficiently encoding binary data as JSON
		189	text, as most octets will not be escaped, resulting in a smaller encoded
		190	size. The disadvantage is that the resulting JSON text is encoded
		191	in latin1 (and must correctly be treated as such when storing and
		192	transfering), a rare encoding for JSON. It is therefore most useful when
		193	you want to store data structures known to contain binary data efficiently
		194	in files or databases, not when talking to other JSON encoders/decoders.
		195
		196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
138		198
139	=item $json = $json->utf8 ([$enable])	199	=item $json = $json->utf8 ([$enable])
140		200
141	If C<$enable> is true (or missing), then the C<encode> method will encode	201	If C<$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	202	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	203	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	204	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.	205	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		206	versions, enabling this option might enable autodetection of the UTF-16
		207	and UTF-32 encoding families, as described in RFC4627.
146		208
147	If C<$enable> is false, then the C<encode> method will return the JSON	209	If C<$enable> is false, then the C<encode> method will return the JSON
148	string as a (non-encoded) unicode string, while C<decode> expects thus a	210	string as a (non-encoded) unicode string, while C<decode> expects thus a
149	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	211	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
150	to be done yourself, e.g. using the Encode module.	212	to be done yourself, e.g. using the Encode module.
151		213
		214	Example, output UTF-16BE-encoded JSON:
		215
		216	use Encode;
		217	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		218
		219	Example, decode UTF-32LE-encoded JSON:
		220
		221	use Encode;
		222	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		223
152	=item $json = $json->pretty ([$enable])	224	=item $json = $json->pretty ([$enable])
153		225
154	This enables (or disables) all of the C<indent>, C<space_before> and	226	This enables (or disables) all of the C<indent>, C<space_before> and
155	C<space_after> (and in the future possibly more) flags in one call to	227	C<space_after> (and in the future possibly more) flags in one call to
156	generate the most readable (or most compact) form possible.	228	generate the most readable (or most compact) form possible.
		229
		230	Example, pretty-print some simple structure:
157		231
158	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	232	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
159	=>	233	=>
160	{	234	{
161	"a" : [	235	"a" : [
…		…
169	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
170	format as output, putting every array member or object/hash key-value pair	244	format as output, putting every array member or object/hash key-value pair
171	into its own line, identing them properly.	245	into its own line, identing them properly.
172		246
173	If C<$enable> is false, no newlines or indenting will be produced, and the	247	If C<$enable> is false, no newlines or indenting will be produced, and the
174	resulting JSON strings is guarenteed not to contain any C<newlines>.	248	resulting JSON text is guarenteed not to contain any C<newlines>.
175		249
176	This setting has no effect when decoding JSON strings.	250	This setting has no effect when decoding JSON texts.
177		251
178	=item $json = $json->space_before ([$enable])	252	=item $json = $json->space_before ([$enable])
179		253
180	If C<$enable> is true (or missing), then the C<encode> method will add an extra	254	If C<$enable> is true (or missing), then the C<encode> method will add an extra
181	optional space before the C<:> separating keys from values in JSON objects.	255	optional space before the C<:> separating keys from values in JSON objects.
182		256
183	If C<$enable> is false, then the C<encode> method will not add any extra	257	If C<$enable> is false, then the C<encode> method will not add any extra
184	space at those places.	258	space at those places.
185		259
186	This setting has no effect when decoding JSON strings. You will also most	260	This setting has no effect when decoding JSON texts. You will also
187	likely combine this setting with C<space_after>.	261	most likely combine this setting with C<space_after>.
		262
		263	Example, space_before enabled, space_after and indent disabled:
		264
		265	{"key" :"value"}
188		266
189	=item $json = $json->space_after ([$enable])	267	=item $json = $json->space_after ([$enable])
190		268
191	If C<$enable> is true (or missing), then the C<encode> method will add an extra	269	If C<$enable> is true (or missing), then the C<encode> method will add an extra
192	optional space after the C<:> separating keys from values in JSON objects	270	optional space after the C<:> separating keys from values in JSON objects
…		…
194	members.	272	members.
195		273
196	If C<$enable> is false, then the C<encode> method will not add any extra	274	If C<$enable> is false, then the C<encode> method will not add any extra
197	space at those places.	275	space at those places.
198		276
199	This setting has no effect when decoding JSON strings.	277	This setting has no effect when decoding JSON texts.
		278
		279	Example, space_before and indent disabled, space_after enabled:
		280
		281	{"key": "value"}
		282
		283	=item $json = $json->relaxed ([$enable])
		284
		285	If C<$enable> is true (or missing), then C<decode> will accept some
		286	extensions to normal JSON syntax (see below). C<encode> will not be
		287	affected in anyway. I<Be aware that this option makes you accept invalid
		288	JSON texts as if they were valid!>. I suggest only to use this option to
		289	parse application-specific files written by humans (configuration files,
		290	resource files etc.)
		291
		292	If C<$enable> is false (the default), then C<decode> will only accept
		293	valid JSON texts.
		294
		295	Currently accepted extensions are:
		296
		297	=over 4
		298
		299	=item * list items can have an end-comma
		300
		301	JSON I<separates> array elements and key-value pairs with commas. This
		302	can be annoying if you write JSON texts manually and want to be able to
		303	quickly append elements, so this extension accepts comma at the end of
		304	such items not just between them:
		305
		306	[
		307	1,
		308	2, <- this comma not normally allowed
		309	]
		310	{
		311	"k1": "v1",
		312	"k2": "v2", <- this comma not normally allowed
		313	}
		314
		315	=back
200		316
201	=item $json = $json->canonical ([$enable])	317	=item $json = $json->canonical ([$enable])
202		318
203	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	319	If C<$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.	320	by sorting their keys. This is adding a comparatively high overhead.
…		…
206	If C<$enable> is false, then the C<encode> method will output key-value	322	If C<$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	323	pairs in the order Perl stores them (which will likely change between runs
208	of the same script).	324	of the same script).
209		325
210	This option is useful if you want the same data structure to be encoded as	326	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,	327	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,	328	the same hash migh be encoded differently even if contains the same data,
213	as key-value pairs have no inherent ordering in Perl.	329	as key-value pairs have no inherent ordering in Perl.
214		330
215	This setting has no effect when decoding JSON strings.	331	This setting has no effect when decoding JSON texts.
216		332
217	=item $json = $json->allow_nonref ([$enable])	333	=item $json = $json->allow_nonref ([$enable])
218		334
219	If C<$enable> is true (or missing), then the C<encode> method can convert a	335	If C<$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,	336	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	337	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
222	values instead of croaking.	338	values instead of croaking.
223		339
224	If C<$enable> is false, then the C<encode> method will croak if it isn't	340	If C<$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	341	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	342	or array. Likewise, C<decode> will croak if given something that is not a
227	JSON object or array.	343	JSON object or array.
228		344
		345	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		346	resulting in an invalid JSON text:
		347
		348	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		349	=> "Hello, World!"
		350
		351	=item $json = $json->allow_blessed ([$enable])
		352
		353	If C<$enable> is true (or missing), then the C<encode> method will not
		354	barf when it encounters a blessed reference. Instead, the value of the
		355	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		356	disabled or no C<to_json> method found) or a representation of the
		357	object (C<convert_blessed> enabled and C<to_json> method found) is being
		358	encoded. Has no effect on C<decode>.
		359
		360	If C<$enable> is false (the default), then C<encode> will throw an
		361	exception when it encounters a blessed object.
		362
		363	=item $json = $json->convert_blessed ([$enable])
		364
		365	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		366	blessed object, will check for the availability of the C<TO_JSON> method
		367	on the object's class. If found, it will be called in scalar context
		368	and the resulting scalar will be encoded instead of the object. If no
		369	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		370	to do.
		371
		372	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		373	returns other blessed objects, those will be handled in the same
		374	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		375	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		376	methods called by the Perl core (== not by the user of the object) are
		377	usually in upper case letters and to avoid collisions with the C<to_json>
		378	function.
		379
		380	This setting does not yet influence C<decode> in any way, but in the
		381	future, global hooks might get installed that influence C<decode> and are
		382	enabled by this setting.
		383
		384	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		385	to do when a blessed object is found.
		386
		387	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		388
		389	When C<$coderef> is specified, it will be called from C<decode> each
		390	time it decodes a JSON object. The only argument is a reference to the
		391	newly-created hash. If the code references returns a single scalar (which
		392	need not be a reference), this value (i.e. a copy of that scalar to avoid
		393	aliasing) is inserted into the deserialised data structure. If it returns
		394	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		395	original deserialised hash will be inserted. This setting can slow down
		396	decoding considerably.
		397
		398	When C<$coderef> is omitted or undefined, any existing callback will
		399	be removed and C<decode> will not change the deserialised hash in any
		400	way.
		401
		402	Example, convert all JSON objects into the integer 5:
		403
		404	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		405	# returns [5]
		406	$js->decode ('[{}]')
		407	# throw an exception because allow_nonref is not enabled
		408	# so a lone 5 is not allowed.
		409	$js->decode ('{"a":1, "b":2}');
		410
		411	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		412
		413	Works remotely similar to C<filter_json_object>, but is only called for
		414	JSON objects having a single key named C<$key>.
		415
		416	This C<$coderef> is called before the one specified via
		417	C<filter_json_object>, if any. It gets passed the single value in the JSON
		418	object. If it returns a single value, it will be inserted into the data
		419	structure. If it returns nothing (not even C<undef> but the empty list),
		420	the callback from C<filter_json_object> will be called next, as if no
		421	single-key callback were specified.
		422
		423	If C<$coderef> is omitted or undefined, the corresponding callback will be
		424	disabled. There can only ever be one callback for a given key.
		425
		426	As this callback gets called less often then the C<filter_json_object>
		427	one, decoding speed will not usually suffer as much. Therefore, single-key
		428	objects make excellent targets to serialise Perl objects into, especially
		429	as single-key JSON objects are as close to the type-tagged value concept
		430	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		431	support this in any way, so you need to make sure your data never looks
		432	like a serialised Perl hash.
		433
		434	Typical names for the single object key are C<__class_whatever__>, or
		435	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		436	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		437	with real hashes.
		438
		439	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		440	into the corresponding C<< $WIDGET{<id>} >> object:
		441
		442	# return whatever is in $WIDGET{5}:
		443	JSON::XS
		444	->new
		445	->filter_json_single_key_object (__widget__ => sub {
		446	$WIDGET{ $_[0] }
		447	})
		448	->decode ('{"__widget__": 5')
		449
		450	# this can be used with a TO_JSON method in some "widget" class
		451	# for serialisation to json:
		452	sub WidgetBase::TO_JSON {
		453	my ($self) = @_;
		454
		455	unless ($self->{id}) {
		456	$self->{id} = ..get..some..id..;
		457	$WIDGET{$self->{id}} = $self;
		458	}
		459
		460	{ __widget__ => $self->{id} }
		461	}
		462
229	=item $json = $json->shrink ([$enable])	463	=item $json = $json->shrink ([$enable])
230		464
231	Perl usually over-allocates memory a bit when allocating space for	465	Perl usually over-allocates memory a bit when allocating space for
232	strings. This flag optionally resizes strings generated by either	466	strings. This flag optionally resizes strings generated by either
233	C<encode> or C<decode> to their minimum size possible. This can save	467	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	468	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	469	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	470	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	471	UTF-X or in octet-form. The latter cannot store everything but uses less
238	space in general.	472	space in general (and some buggy Perl or C code might even rely on that
		473	internal representation being used).
239		474
		475	The actual definition of what shrink does might change in future versions,
		476	but it will always try to save space at the expense of time.
		477
240	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	478	If C<$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.	479	be shrunk-to-fit, while all strings generated by C<decode> will also be
		480	shrunk-to-fit.
242		481
243	If C<$enable> is false, then the normal perl allocation algorithms are used.	482	If C<$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.	483	If you work with your data, then this is likely to be faster.
245		484
246	In the future, this setting might control other things, such as converting	485	In the future, this setting might control other things, such as converting
247	strings that look like integers or floats into integers or floats	486	strings that look like integers or floats into integers or floats
248	internally (there is no difference on the Perl level), saving space.	487	internally (there is no difference on the Perl level), saving space.
249		488
		489	=item $json = $json->max_depth ([$maximum_nesting_depth])
		490
		491	Sets the maximum nesting level (default C<512>) accepted while encoding
		492	or decoding. If the JSON text or Perl data structure has an equal or
		493	higher nesting level then this limit, then the encoder and decoder will
		494	stop and croak at that point.
		495
		496	Nesting level is defined by number of hash- or arrayrefs that the encoder
		497	needs to traverse to reach a given point or the number of C<{> or C<[>
		498	characters without their matching closing parenthesis crossed to reach a
		499	given character in a string.
		500
		501	Setting the maximum depth to one disallows any nesting, so that ensures
		502	that the object is only a single hash/object or array.
		503
		504	The argument to C<max_depth> will be rounded up to the next highest power
		505	of two. If no argument is given, the highest possible setting will be
		506	used, which is rarely useful.
		507
		508	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		509
		510	=item $json = $json->max_size ([$maximum_string_size])
		511
		512	Set the maximum length a JSON text may have (in bytes) where decoding is
		513	being attempted. The default is C<0>, meaning no limit. When C<decode>
		514	is called on a string longer then this number of characters it will not
		515	attempt to decode the string but throw an exception. This setting has no
		516	effect on C<encode> (yet).
		517
		518	The argument to C<max_size> will be rounded up to the next B<highest>
		519	power of two (so may be more than requested). If no argument is given, the
		520	limit check will be deactivated (same as when C<0> is specified).
		521
		522	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		523
250	=item $json_string = $json->encode ($perl_scalar)	524	=item $json_text = $json->encode ($perl_scalar)
251		525
252	Converts the given Perl data structure (a simple scalar or a reference	526	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	527	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	528	converted into JSON string or number sequences, while references to arrays
255	become JSON arrays and references to hashes become JSON objects. Undefined	529	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>	530	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
257	nor C<false> values will be generated.	531	nor C<false> values will be generated.
258		532
259	=item $perl_scalar = $json->decode ($json_string)	533	=item $perl_scalar = $json->decode ($json_text)
260		534
261	The opposite of C<encode>: expects a JSON string and tries to parse it,	535	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.	536	returning the resulting simple scalar or reference. Croaks on error.
263		537
264	JSON numbers and strings become simple Perl scalars. JSON arrays become	538	JSON numbers and strings become simple Perl scalars. JSON arrays become
265	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	539	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>.	540	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
267		541
		542	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		543
		544	This works like the C<decode> method, but instead of raising an exception
		545	when there is trailing garbage after the first JSON object, it will
		546	silently stop parsing there and return the number of characters consumed
		547	so far.
		548
		549	This is useful if your JSON texts are not delimited by an outer protocol
		550	(which is not the brightest thing to do in the first place) and you need
		551	to know where the JSON text ends.
		552
		553	JSON::XS->new->decode_prefix ("[1] the tail")
		554	=> ([], 3)
		555
268	=back	556	=back
		557
269		558
270	=head1 MAPPING	559	=head1 MAPPING
271		560
272	This section describes how JSON::XS maps Perl values to JSON values and	561	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	562	vice versa. These mappings are designed to "do the right thing" in most
…		…
276		565
277	For the more enlightened: note that in the following descriptions,	566	For the more enlightened: note that in the following descriptions,
278	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	567	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
279	refers to the abstract Perl language itself.	568	refers to the abstract Perl language itself.
280		569
		570
281	=head2 JSON -> PERL	571	=head2 JSON -> PERL
282		572
283	=over 4	573	=over 4
284		574
285	=item object	575	=item object
286		576
287	A JSON object becomes a reference to a hash in Perl. No ordering of object	577	A JSON object becomes a reference to a hash in Perl. No ordering of object
288	keys is preserved.	578	keys is preserved (JSON does not preserver object key ordering itself).
289		579
290	=item array	580	=item array
291		581
292	A JSON array becomes a reference to an array in Perl.	582	A JSON array becomes a reference to an array in Perl.
293		583
…		…
297	are represented by the same codepoints in the Perl string, so no manual	587	are represented by the same codepoints in the Perl string, so no manual
298	decoding is necessary.	588	decoding is necessary.
299		589
300	=item number	590	=item number
301		591
302	A JSON number becomes either an integer or numeric (floating point)	592	A JSON number becomes either an integer, numeric (floating point) or
303	scalar in perl, depending on its range and any fractional parts. On the	593	string scalar in perl, depending on its range and any fractional parts. On
304	Perl level, there is no difference between those as Perl handles all the	594	the Perl level, there is no difference between those as Perl handles all
305	conversion details, but an integer may take slightly less memory and might	595	the conversion details, but an integer may take slightly less memory and
306	represent more values exactly than (floating point) numbers.	596	might represent more values exactly than (floating point) numbers.
		597
		598	If the number consists of digits only, JSON::XS will try to represent
		599	it as an integer value. If that fails, it will try to represent it as
		600	a numeric (floating point) value if that is possible without loss of
		601	precision. Otherwise it will preserve the number as a string value.
		602
		603	Numbers containing a fractional or exponential part will always be
		604	represented as numeric (floating point) values, possibly at a loss of
		605	precision.
		606
		607	This might create round-tripping problems as numbers might become strings,
		608	but as Perl is typeless there is no other way to do it.
307		609
308	=item true, false	610	=item true, false
309		611
310	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	612	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
311	this process. Future versions might represent those values differently,	613	respectively. They are overloaded to act almost exactly like the numbers
312	but they will be guarenteed to act like these integers would normally in	614	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
313	Perl.	615	the C<JSON::XS::is_bool> function.
314		616
315	=item null	617	=item null
316		618
317	A JSON null atom becomes C<undef> in Perl.	619	A JSON null atom becomes C<undef> in Perl.
318		620
319	=back	621	=back
		622
320		623
321	=head2 PERL -> JSON	624	=head2 PERL -> JSON
322		625
323	The mapping from Perl to JSON is slightly more difficult, as Perl is a	626	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	627	truly typeless language, so we can only guess which JSON type is meant by
…		…
327	=over 4	630	=over 4
328		631
329	=item hash references	632	=item hash references
330		633
331	Perl hash references become JSON objects. As there is no inherent ordering	634	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	635	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	636	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	637	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	638	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	639	the same datastructure will serialise to the same JSON text (given same
337	JSON::XS), but this incurs a runtime overhead.	640	settings and version of JSON::XS), but this incurs a runtime overhead
		641	and is only rarely useful, e.g. when you want to compare some JSON text
		642	against another for equality.
338		643
339	=item array references	644	=item array references
340		645
341	Perl array references become JSON arrays.	646	Perl array references become JSON arrays.
		647
		648	=item other references
		649
		650	Other unblessed references are generally not allowed and will cause an
		651	exception to be thrown, except for references to the integers C<0> and
		652	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		653	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		654
		655	to_json [\0,JSON::XS::true] # yields [false,true]
		656
		657	=item JSON::XS::true, JSON::XS::false
		658
		659	These special values become JSON true and JSON false values,
		660	respectively. You cna alos use C<\1> and C<\0> directly if you want.
342		661
343	=item blessed objects	662	=item blessed objects
344		663
345	Blessed objects are not allowed. JSON::XS currently tries to encode their	664	Blessed objects are not allowed. JSON::XS currently tries to encode their
346	underlying representation (hash- or arrayref), but this behaviour might	665	underlying representation (hash- or arrayref), but this behaviour might
…		…
380		699
381	You can not currently output JSON booleans or force the type in other,	700	You can not currently output JSON booleans or force the type in other,
382	less obscure, ways. Tell me if you need this capability.	701	less obscure, ways. Tell me if you need this capability.
383		702
384	=back	703	=back
		704
385		705
386	=head1 COMPARISON	706	=head1 COMPARISON
387		707
388	As already mentioned, this module was created because none of the existing	708	As already mentioned, this module was created because none of the existing
389	JSON modules could be made to work correctly. First I will describe the	709	JSON modules could be made to work correctly. First I will describe the
…		…
415		735
416	Has problems handling many Perl values (e.g. regex results and other magic	736	Has problems handling many Perl values (e.g. regex results and other magic
417	values will make it croak).	737	values will make it croak).
418		738
419	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	739	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
420	which is not a valid JSON string.	740	which is not a valid JSON text.
421		741
422	Unmaintained (maintainer unresponsive for many months, bugs are not	742	Unmaintained (maintainer unresponsive for many months, bugs are not
423	getting fixed).	743	getting fixed).
424		744
425	=item JSON::Syck 0.21	745	=item JSON::Syck 0.21
…		…
427	Very buggy (often crashes).	747	Very buggy (often crashes).
428		748
429	Very inflexible (no human-readable format supported, format pretty much	749	Very inflexible (no human-readable format supported, format pretty much
430	undocumented. I need at least a format for easy reading by humans and a	750	undocumented. I need at least a format for easy reading by humans and a
431	single-line compact format for use in a protocol, and preferably a way to	751	single-line compact format for use in a protocol, and preferably a way to
432	generate ASCII-only JSON strings).	752	generate ASCII-only JSON texts).
433		753
434	Completely broken (and confusingly documented) Unicode handling (unicode	754	Completely broken (and confusingly documented) Unicode handling (unicode
435	escapes are not working properly, you need to set ImplicitUnicode to	755	escapes are not working properly, you need to set ImplicitUnicode to
436	I<different> values on en- and decoding to get symmetric behaviour).	756	I<different> values on en- and decoding to get symmetric behaviour).
437		757
…		…
460		780
461	Very inflexible.	781	Very inflexible.
462		782
463	No roundtripping.	783	No roundtripping.
464		784
465	Does not generate valid JSON (key strings are often unquoted, empty keys	785	Does not generate valid JSON texts (key strings are often unquoted, empty keys
466	result in nothing being output)	786	result in nothing being output)
467		787
468	Does not check input for validity.	788	Does not check input for validity.
469		789
470	=back	790	=back
		791
		792
		793	=head2 JSON and YAML
		794
		795	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		796	however, a mass hysteria and very far from the truth. In general, there is
		797	no way to configure JSON::XS to output a data structure as valid YAML.
		798
		799	If you really must use JSON::XS to generate YAML, you should use this
		800	algorithm (subject to change in future versions):
		801
		802	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		803	my $yaml = $to_yaml->encode ($ref) . "\n";
		804
		805	This will usually generate JSON texts that also parse as valid
		806	YAML. Please note that YAML has hardcoded limits on (simple) object key
		807	lengths that JSON doesn't have, so you should make sure that your hash
		808	keys are noticably shorter than the 1024 characters YAML allows.
		809
		810	There might be other incompatibilities that I am not aware of. In general
		811	you should not try to generate YAML with a JSON generator or vice versa,
		812	or try to parse JSON with a YAML parser or vice versa: chances are high
		813	that you will run into severe interoperability problems.
		814
471		815
472	=head2 SPEED	816	=head2 SPEED
473		817
474	It seems that JSON::XS is surprisingly fast, as shown in the following	818	It seems that JSON::XS is surprisingly fast, as shown in the following
475	tables. They have been generated with the help of the C<eg/bench> program	819	tables. They have been generated with the help of the C<eg/bench> program
476	in the JSON::XS distribution, to make it easy to compare on your own	820	in the JSON::XS distribution, to make it easy to compare on your own
477	system.	821	system.
478		822
479	First is a comparison between various modules using a very simple JSON	823	First comes a comparison between various modules using a very short
		824	single-line JSON string:
		825
		826	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		827	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		828
480	string, showing the number of encodes/decodes per second (JSON::XS is	829	It shows the number of encodes/decodes per second (JSON::XS uses
481	the functional interface, while JSON::XS/2 is the OO interface with	830	the functional interface, while JSON::XS/2 uses the OO interface
482	pretty-printing and hashkey sorting enabled).	831	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		832	shrink). Higher is better:
483		833
		834	Storable \| 15779.925 \| 14169.946 \|
		835	-----------+------------+------------+
484	module \| encode \| decode \|	836	module \| encode \| decode \|
485	-----------\|------------\|------------\|	837	-----------\|------------\|------------\|
486	JSON \| 14006 \| 6820 \|	838	JSON \| 4990.842 \| 4088.813 \|
487	JSON::DWIW \| 200937 \| 120386 \|	839	JSON::DWIW \| 51653.990 \| 71575.154 \|
488	JSON::PC \| 85065 \| 129366 \|	840	JSON::PC \| 65948.176 \| 74631.744 \|
489	JSON::Syck \| 59898 \| 44232 \|	841	JSON::PP \| 8931.652 \| 3817.168 \|
490	JSON::XS \| 1171478 \| 342435 \|	842	JSON::Syck \| 24877.248 \| 27776.848 \|
491	JSON::XS/2 \| 730760 \| 328714 \|	843	JSON::XS \| 388361.481 \| 227951.304 \|
		844	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		845	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		846	Storable \| 16500.016 \| 135300.129 \|
492	-----------+------------+------------+	847	-----------+------------+------------+
493		848
494	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	849	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		850	about three times faster on decoding, and over fourty times faster
495	times faster than JSON, even with pretty-printing and key sorting.	851	than JSON, even with pretty-printing and key sorting. It also compares
		852	favourably to Storable for small amounts of data.
496		853
497	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	854	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
498	search API (http://nanoref.com/yahooapis/mgPdGg):	855	search API (http://nanoref.com/yahooapis/mgPdGg):
499		856
500	module \| encode \| decode \|	857	module \| encode \| decode \|
501	-----------\|------------\|------------\|	858	-----------\|------------\|------------\|
502	JSON \| 673 \| 38 \|	859	JSON \| 55.260 \| 34.971 \|
503	JSON::DWIW \| 5271 \| 770 \|	860	JSON::DWIW \| 825.228 \| 1082.513 \|
504	JSON::PC \| 9901 \| 2491 \|	861	JSON::PC \| 3571.444 \| 2394.829 \|
505	JSON::Syck \| 2360 \| 786 \|	862	JSON::PP \| 210.987 \| 32.574 \|
506	JSON::XS \| 37398 \| 3202 \|	863	JSON::Syck \| 552.551 \| 787.544 \|
507	JSON::XS/2 \| 13765 \| 3153 \|	864	JSON::XS \| 5780.463 \| 4854.519 \|
		865	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		866	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		867	Storable \| 4445.002 \| 5235.027 \|
508	-----------+------------+------------+	868	-----------+------------+------------+
509		869
510	Again, JSON::XS leads by far in the encoding case, while still beating	870	Again, JSON::XS leads by far (except for Storable which non-surprisingly
511	every other module in the decoding case.	871	decodes faster).
512		872
513	Last example is an almost 8MB large hash with many large binary values	873	On large strings containing lots of high unicode characters, some modules
514	(PNG files), resulting in a lot of escaping:	874	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		875	will be broken due to missing (or wrong) unicode handling. Others refuse
		876	to decode or encode properly, so it was impossible to prepare a fair
		877	comparison table for that case.
		878
		879
		880	=head1 SECURITY CONSIDERATIONS
		881
		882	When you are using JSON in a protocol, talking to untrusted potentially
		883	hostile creatures requires relatively few measures.
		884
		885	First of all, your JSON decoder should be secure, that is, should not have
		886	any buffer overflows. Obviously, this module should ensure that and I am
		887	trying hard on making that true, but you never know.
		888
		889	Second, you need to avoid resource-starving attacks. That means you should
		890	limit the size of JSON texts you accept, or make sure then when your
		891	resources run out, thats just fine (e.g. by using a separate process that
		892	can crash safely). The size of a JSON text in octets or characters is
		893	usually a good indication of the size of the resources required to decode
		894	it into a Perl structure. While JSON::XS can check the size of the JSON
		895	text, it might be too late when you already have it in memory, so you
		896	might want to check the size before you accept the string.
		897
		898	Third, JSON::XS recurses using the C stack when decoding objects and
		899	arrays. The C stack is a limited resource: for instance, on my amd64
		900	machine with 8MB of stack size I can decode around 180k nested arrays but
		901	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		902	to free the temporary). If that is exceeded, the program crashes. to be
		903	conservative, the default nesting limit is set to 512. If your process
		904	has a smaller stack, you should adjust this setting accordingly with the
		905	C<max_depth> method.
		906
		907	And last but least, something else could bomb you that I forgot to think
		908	of. In that case, you get to keep the pieces. I am always open for hints,
		909	though...
		910
		911	If you are using JSON::XS to return packets to consumption
		912	by javascript scripts in a browser you should have a look at
		913	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		914	you are vulnerable to some common attack vectors (which really are browser
		915	design bugs, but it is still you who will have to deal with it, as major
		916	browser developers care only for features, not about doing security
		917	right).
		918
515		919
516	=head1 BUGS	920	=head1 BUGS
517		921
518	While the goal of this module is to be correct, that unfortunately does	922	While the goal of this module is to be correct, that unfortunately does
519	not mean its bug-free, only that I think its design is bug-free. It is	923	not mean its bug-free, only that I think its design is bug-free. It is
520	still very young and not well-tested. If you keep reporting bugs they will	924	still relatively early in its development. If you keep reporting bugs they
521	be fixed swiftly, though.	925	will be fixed swiftly, though.
522		926
523	=cut	927	=cut
		928
		929	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		930	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		931
		932	sub true() { $true }
		933	sub false() { $false }
		934
		935	sub is_bool($) {
		936	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		937	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		938	}
		939
		940	XSLoader::load "JSON::XS", $VERSION;
		941
		942	package JSON::XS::Boolean;
		943
		944	use overload
		945	"0+" => sub { ${$_[0]} },
		946	"++" => sub { $_[0] = ${$_[0]} + 1 },
		947	"--" => sub { $_[0] = ${$_[0]} - 1 },
		948	fallback => 1;
524		949
525	1;	950	1;
526		951
527	=head1 AUTHOR	952	=head1 AUTHOR
528		953

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Comparing JSON-XS/XS.pm (file contents): Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs. Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.10 by root, Fri Mar 23 17:40:29 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC