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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs.
Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC

…		…
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
		8
		9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
		11
		12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		14
		15	# OO-interface
		16
		17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		19	$perl_scalar = $coder->decode ($unicode_json_text);
8		20
9	=head1 DESCRIPTION	21	=head1 DESCRIPTION
10		22
11	This module converts Perl data structures to JSON and vice versa. Its	23	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	24	primary goal is to be I<correct> and its secondary goal is to be
…		…
18	their maintainers are unresponsive, gone missing, or not listening to bug	30	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	31	reports for other reasons.
20		32
21	See COMPARISON, below, for a comparison to some other JSON modules.	33	See COMPARISON, below, for a comparison to some other JSON modules.
22		34
		35	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		36	vice versa.
		37
23	=head2 FEATURES	38	=head2 FEATURES
24		39
25	=over 4	40	=over 4
26		41
27	=item * correct handling of unicode issues	42	=item * correct unicode handling
28		43
29	This module knows how to handle Unicode, and even documents how it does so.	44	This module knows how to handle Unicode, and even documents how and when
		45	it does so.
30		46
31	=item * round-trip integrity	47	=item * round-trip integrity
32		48
33	When you serialise a perl data structure using only datatypes supported	49	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	50	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		52	like a number).
36		53
37	=item * strict checking of JSON correctness	54	=item * strict checking of JSON correctness
38		55
39	There is no guessing, no generating of illegal JSON strings by default,	56	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	57	and only JSON is accepted as input by default (the latter is a security
		58	feature).
41		59
42	=item * fast	60	=item * fast
43		61
44	compared to other JSON modules, this module compares favourably.	62	Compared to other JSON modules, this module compares favourably in terms
		63	of speed, too.
45		64
46	=item * simple to use	65	=item * simple to use
47		66
48	This module has both a simple functional interface as well as an OO	67	This module has both a simple functional interface as well as an OO
49	interface.	68	interface.
50		69
51	=item * reasonably versatile output formats	70	=item * reasonably versatile output formats
52		71
53	You can choose between the most compact format possible, a pure-ascii	72	You can choose between the most compact guarenteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	73	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	74	(for when your transport is not 8-bit clean, still supports the whole
		75	unicode range), or a pretty-printed format (for when you want to read that
		76	stuff). Or you can combine those features in whatever way you like.
56		77
57	=back	78	=back
58		79
59	=cut	80	=cut
60		81
61	package JSON::XS;	82	package JSON::XS;
62		83
63	BEGIN {	84	use strict;
		85
64	$VERSION = '0.2';	86	our $VERSION = '1.5';
65	@ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
66		88
67	@EXPORT = qw(to_json from_json);	89	our @EXPORT = qw(to_json from_json);
68	require Exporter;
69		90
70	require XSLoader;	91	use Exporter;
71	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
72	}
73		93
74	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
75		95
76	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
77	exported by default:	97	exported by default:
78		98
79	=over 4	99	=over 4
80		100
81	=item $json_string = to_json $perl_scalar	101	=item $json_text = to_json $perl_scalar
82		102
83	Converts the given Perl data structure (a simple scalar or a reference to	103	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	104	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	105	octets only). Croaks on error.
86		106
87	This function call is functionally identical to C<< JSON::XS->new->utf8	107	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		108
		109	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		110
		111	except being faster.
		112
90	=item $perl_scalar = from_json $json_string	113	=item $perl_scalar = from_json $json_text
91		114
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	115	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	116	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	117	scalar or reference. Croaks on error.
95		118
96	This function call is functionally identical to C<< JSON::XS->new->utf8	119	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	120
		121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		122
		123	except being faster.
		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
98		133
99	=back	134	=back
		135
100		136
101	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
102		138
103	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	147	strings. All boolean flags described below are by default I<disabled>.
112		148
113	The mutators for flags all return the JSON object again and thus calls can	149	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	150	be chained:
115		151
116	my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]})	152	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a": [1, 2]}	153	=> {"a": [1, 2]}
118		154
119	=item $json = $json->ascii ([$enable])	155	=item $json = $json->ascii ([$enable])
120		156
121	If C<$enable> is true (or missing), then the C<encode> method will	157	If C<$enable> is true (or missing), then the C<encode> method will not
122	not generate characters outside the code range C<0..127>. Any unicode	158	generate characters outside the code range C<0..127> (which is ASCII). Any
123	characters outside that range will be escaped using either a single	159	unicode characters outside that range will be escaped using either a
124	\uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, as per	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
125	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.
126		164
127	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
128	characters unless necessary.	166	characters unless required by the JSON syntax or other flags. This results
		167	in a faster and more compact format.
129		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
130	JSON::XS->new->ascii (1)->encode (chr 0x10401)	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
131	=> \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)
132		198
133	=item $json = $json->utf8 ([$enable])	199	=item $json = $json->utf8 ([$enable])
134		200
135	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
136	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
137	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
138	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
139	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.
140		208
141	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
142	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
143	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
144	to be done yourself, e.g. using the Encode module.	212	to be done yourself, e.g. using the Encode module.
145		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
146	=item $json = $json->pretty ([$enable])	224	=item $json = $json->pretty ([$enable])
147		225
148	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
149	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
150	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:
151		231
152	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	232	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
153	=>	233	=>
154	{	234	{
155	"a" : [	235	"a" : [
…		…
163	If C<$enable> is true (or missing), then the C<encode> method will use a multiline	243	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
164	format as output, putting every array member or object/hash key-value pair	244	format as output, putting every array member or object/hash key-value pair
165	into its own line, identing them properly.	245	into its own line, identing them properly.
166		246
167	If C<$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
168	resulting JSON strings is guarenteed not to contain any C<newlines>.	248	resulting JSON text is guarenteed not to contain any C<newlines>.
169		249
170	This setting has no effect when decoding JSON strings.	250	This setting has no effect when decoding JSON texts.
171		251
172	=item $json = $json->space_before ([$enable])	252	=item $json = $json->space_before ([$enable])
173		253
174	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
175	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.
176		256
177	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
178	space at those places.	258	space at those places.
179		259
180	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
181	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"}
182		266
183	=item $json = $json->space_after ([$enable])	267	=item $json = $json->space_after ([$enable])
184		268
185	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
186	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
…		…
188	members.	272	members.
189		273
190	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
191	space at those places.	275	space at those places.
192		276
193	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	=item * shell-style '#'-comments
		316
		317	Whenever JSON allows whitespace, shell-style comments are additionally
		318	allowed. They are terminated by the first carriage-return or line-feed
		319	character, after which more white-space and comments are allowed.
		320
		321	[
		322	1, # this comment not allowed in JSON
		323	# neither this one...
		324	]
		325
		326	=back
194		327
195	=item $json = $json->canonical ([$enable])	328	=item $json = $json->canonical ([$enable])
196		329
197	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	330	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
198	by sorting their keys. This is adding a comparatively high overhead.	331	by sorting their keys. This is adding a comparatively high overhead.
…		…
200	If C<$enable> is false, then the C<encode> method will output key-value	333	If C<$enable> is false, then the C<encode> method will output key-value
201	pairs in the order Perl stores them (which will likely change between runs	334	pairs in the order Perl stores them (which will likely change between runs
202	of the same script).	335	of the same script).
203		336
204	This option is useful if you want the same data structure to be encoded as	337	This option is useful if you want the same data structure to be encoded as
205	the same JSON string (given the same overall settings). If it is disabled,	338	the same JSON text (given the same overall settings). If it is disabled,
206	the same hash migh be encoded differently even if contains the same data,	339	the same hash migh be encoded differently even if contains the same data,
207	as key-value pairs have no inherent ordering in Perl.	340	as key-value pairs have no inherent ordering in Perl.
208		341
209	This setting has no effect when decoding JSON strings.	342	This setting has no effect when decoding JSON texts.
210		343
211	=item $json = $json->allow_nonref ([$enable])	344	=item $json = $json->allow_nonref ([$enable])
212		345
213	If C<$enable> is true (or missing), then the C<encode> method can convert a	346	If C<$enable> is true (or missing), then the C<encode> method can convert a
214	non-reference into its corresponding string, number or null JSON value,	347	non-reference into its corresponding string, number or null JSON value,
215	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	348	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
216	values instead of croaking.	349	values instead of croaking.
217		350
218	If C<$enable> is false, then the C<encode> method will croak if it isn't	351	If C<$enable> is false, then the C<encode> method will croak if it isn't
219	passed an arrayref or hashref, as JSON strings must either be an object	352	passed an arrayref or hashref, as JSON texts must either be an object
220	or array. Likewise, C<decode> will croak if given something that is not a	353	or array. Likewise, C<decode> will croak if given something that is not a
221	JSON object or array.	354	JSON object or array.
222		355
		356	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		357	resulting in an invalid JSON text:
		358
		359	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		360	=> "Hello, World!"
		361
		362	=item $json = $json->allow_blessed ([$enable])
		363
		364	If C<$enable> is true (or missing), then the C<encode> method will not
		365	barf when it encounters a blessed reference. Instead, the value of the
		366	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		367	disabled or no C<to_json> method found) or a representation of the
		368	object (C<convert_blessed> enabled and C<to_json> method found) is being
		369	encoded. Has no effect on C<decode>.
		370
		371	If C<$enable> is false (the default), then C<encode> will throw an
		372	exception when it encounters a blessed object.
		373
		374	=item $json = $json->convert_blessed ([$enable])
		375
		376	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		377	blessed object, will check for the availability of the C<TO_JSON> method
		378	on the object's class. If found, it will be called in scalar context
		379	and the resulting scalar will be encoded instead of the object. If no
		380	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		381	to do.
		382
		383	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		384	returns other blessed objects, those will be handled in the same
		385	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		386	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		387	methods called by the Perl core (== not by the user of the object) are
		388	usually in upper case letters and to avoid collisions with the C<to_json>
		389	function.
		390
		391	This setting does not yet influence C<decode> in any way, but in the
		392	future, global hooks might get installed that influence C<decode> and are
		393	enabled by this setting.
		394
		395	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		396	to do when a blessed object is found.
		397
		398	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		399
		400	When C<$coderef> is specified, it will be called from C<decode> each
		401	time it decodes a JSON object. The only argument is a reference to the
		402	newly-created hash. If the code references returns a single scalar (which
		403	need not be a reference), this value (i.e. a copy of that scalar to avoid
		404	aliasing) is inserted into the deserialised data structure. If it returns
		405	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		406	original deserialised hash will be inserted. This setting can slow down
		407	decoding considerably.
		408
		409	When C<$coderef> is omitted or undefined, any existing callback will
		410	be removed and C<decode> will not change the deserialised hash in any
		411	way.
		412
		413	Example, convert all JSON objects into the integer 5:
		414
		415	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		416	# returns [5]
		417	$js->decode ('[{}]')
		418	# throw an exception because allow_nonref is not enabled
		419	# so a lone 5 is not allowed.
		420	$js->decode ('{"a":1, "b":2}');
		421
		422	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		423
		424	Works remotely similar to C<filter_json_object>, but is only called for
		425	JSON objects having a single key named C<$key>.
		426
		427	This C<$coderef> is called before the one specified via
		428	C<filter_json_object>, if any. It gets passed the single value in the JSON
		429	object. If it returns a single value, it will be inserted into the data
		430	structure. If it returns nothing (not even C<undef> but the empty list),
		431	the callback from C<filter_json_object> will be called next, as if no
		432	single-key callback were specified.
		433
		434	If C<$coderef> is omitted or undefined, the corresponding callback will be
		435	disabled. There can only ever be one callback for a given key.
		436
		437	As this callback gets called less often then the C<filter_json_object>
		438	one, decoding speed will not usually suffer as much. Therefore, single-key
		439	objects make excellent targets to serialise Perl objects into, especially
		440	as single-key JSON objects are as close to the type-tagged value concept
		441	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		442	support this in any way, so you need to make sure your data never looks
		443	like a serialised Perl hash.
		444
		445	Typical names for the single object key are C<__class_whatever__>, or
		446	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		447	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		448	with real hashes.
		449
		450	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		451	into the corresponding C<< $WIDGET{<id>} >> object:
		452
		453	# return whatever is in $WIDGET{5}:
		454	JSON::XS
		455	->new
		456	->filter_json_single_key_object (__widget__ => sub {
		457	$WIDGET{ $_[0] }
		458	})
		459	->decode ('{"__widget__": 5')
		460
		461	# this can be used with a TO_JSON method in some "widget" class
		462	# for serialisation to json:
		463	sub WidgetBase::TO_JSON {
		464	my ($self) = @_;
		465
		466	unless ($self->{id}) {
		467	$self->{id} = ..get..some..id..;
		468	$WIDGET{$self->{id}} = $self;
		469	}
		470
		471	{ __widget__ => $self->{id} }
		472	}
		473
223	=item $json = $json->shrink ([$enable])	474	=item $json = $json->shrink ([$enable])
224		475
225	Perl usually over-allocates memory a bit when allocating space for	476	Perl usually over-allocates memory a bit when allocating space for
226	strings. This flag optionally resizes strings generated by either	477	strings. This flag optionally resizes strings generated by either
227	C<encode> or C<decode> to their minimum size possible. This can save	478	C<encode> or C<decode> to their minimum size possible. This can save
228	memory when your JSON strings are either very very long or you have many	479	memory when your JSON texts are either very very long or you have many
229	short strings. It will also try to downgrade any strings to octet-form	480	short strings. It will also try to downgrade any strings to octet-form
230	if possible: perl stores strings internally either in an encoding called	481	if possible: perl stores strings internally either in an encoding called
231	UTF-X or in octet-form. The latter cannot store everything but uses less	482	UTF-X or in octet-form. The latter cannot store everything but uses less
232	space in general.	483	space in general (and some buggy Perl or C code might even rely on that
		484	internal representation being used).
233		485
		486	The actual definition of what shrink does might change in future versions,
		487	but it will always try to save space at the expense of time.
		488
234	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	489	If C<$enable> is true (or missing), the string returned by C<encode> will
235	while all strings generated by C<decode> will also be shrunk-to-fit.	490	be shrunk-to-fit, while all strings generated by C<decode> will also be
		491	shrunk-to-fit.
236		492
237	If C<$enable> is false, then the normal perl allocation algorithms are used.	493	If C<$enable> is false, then the normal perl allocation algorithms are used.
238	If you work with your data, then this is likely to be faster.	494	If you work with your data, then this is likely to be faster.
239		495
240	In the future, this setting might control other things, such as converting	496	In the future, this setting might control other things, such as converting
241	strings that look like integers or floats into integers or floats	497	strings that look like integers or floats into integers or floats
242	internally (there is no difference on the Perl level), saving space.	498	internally (there is no difference on the Perl level), saving space.
243		499
		500	=item $json = $json->max_depth ([$maximum_nesting_depth])
		501
		502	Sets the maximum nesting level (default C<512>) accepted while encoding
		503	or decoding. If the JSON text or Perl data structure has an equal or
		504	higher nesting level then this limit, then the encoder and decoder will
		505	stop and croak at that point.
		506
		507	Nesting level is defined by number of hash- or arrayrefs that the encoder
		508	needs to traverse to reach a given point or the number of C<{> or C<[>
		509	characters without their matching closing parenthesis crossed to reach a
		510	given character in a string.
		511
		512	Setting the maximum depth to one disallows any nesting, so that ensures
		513	that the object is only a single hash/object or array.
		514
		515	The argument to C<max_depth> will be rounded up to the next highest power
		516	of two. If no argument is given, the highest possible setting will be
		517	used, which is rarely useful.
		518
		519	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		520
		521	=item $json = $json->max_size ([$maximum_string_size])
		522
		523	Set the maximum length a JSON text may have (in bytes) where decoding is
		524	being attempted. The default is C<0>, meaning no limit. When C<decode>
		525	is called on a string longer then this number of characters it will not
		526	attempt to decode the string but throw an exception. This setting has no
		527	effect on C<encode> (yet).
		528
		529	The argument to C<max_size> will be rounded up to the next B<highest>
		530	power of two (so may be more than requested). If no argument is given, the
		531	limit check will be deactivated (same as when C<0> is specified).
		532
		533	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		534
244	=item $json_string = $json->encode ($perl_scalar)	535	=item $json_text = $json->encode ($perl_scalar)
245		536
246	Converts the given Perl data structure (a simple scalar or a reference	537	Converts the given Perl data structure (a simple scalar or a reference
247	to a hash or array) to its JSON representation. Simple scalars will be	538	to a hash or array) to its JSON representation. Simple scalars will be
248	converted into JSON string or number sequences, while references to arrays	539	converted into JSON string or number sequences, while references to arrays
249	become JSON arrays and references to hashes become JSON objects. Undefined	540	become JSON arrays and references to hashes become JSON objects. Undefined
250	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	541	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
251	nor C<false> values will be generated.	542	nor C<false> values will be generated.
252		543
253	=item $perl_scalar = $json->decode ($json_string)	544	=item $perl_scalar = $json->decode ($json_text)
254		545
255	The opposite of C<encode>: expects a JSON string and tries to parse it,	546	The opposite of C<encode>: expects a JSON text and tries to parse it,
256	returning the resulting simple scalar or reference. Croaks on error.	547	returning the resulting simple scalar or reference. Croaks on error.
257		548
258	JSON numbers and strings become simple Perl scalars. JSON arrays become	549	JSON numbers and strings become simple Perl scalars. JSON arrays become
259	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	550	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
260	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	551	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
261		552
		553	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		554
		555	This works like the C<decode> method, but instead of raising an exception
		556	when there is trailing garbage after the first JSON object, it will
		557	silently stop parsing there and return the number of characters consumed
		558	so far.
		559
		560	This is useful if your JSON texts are not delimited by an outer protocol
		561	(which is not the brightest thing to do in the first place) and you need
		562	to know where the JSON text ends.
		563
		564	JSON::XS->new->decode_prefix ("[1] the tail")
		565	=> ([], 3)
		566
262	=back	567	=back
		568
		569
		570	=head1 MAPPING
		571
		572	This section describes how JSON::XS maps Perl values to JSON values and
		573	vice versa. These mappings are designed to "do the right thing" in most
		574	circumstances automatically, preserving round-tripping characteristics
		575	(what you put in comes out as something equivalent).
		576
		577	For the more enlightened: note that in the following descriptions,
		578	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		579	refers to the abstract Perl language itself.
		580
		581
		582	=head2 JSON -> PERL
		583
		584	=over 4
		585
		586	=item object
		587
		588	A JSON object becomes a reference to a hash in Perl. No ordering of object
		589	keys is preserved (JSON does not preserver object key ordering itself).
		590
		591	=item array
		592
		593	A JSON array becomes a reference to an array in Perl.
		594
		595	=item string
		596
		597	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		598	are represented by the same codepoints in the Perl string, so no manual
		599	decoding is necessary.
		600
		601	=item number
		602
		603	A JSON number becomes either an integer, numeric (floating point) or
		604	string scalar in perl, depending on its range and any fractional parts. On
		605	the Perl level, there is no difference between those as Perl handles all
		606	the conversion details, but an integer may take slightly less memory and
		607	might represent more values exactly than (floating point) numbers.
		608
		609	If the number consists of digits only, JSON::XS will try to represent
		610	it as an integer value. If that fails, it will try to represent it as
		611	a numeric (floating point) value if that is possible without loss of
		612	precision. Otherwise it will preserve the number as a string value.
		613
		614	Numbers containing a fractional or exponential part will always be
		615	represented as numeric (floating point) values, possibly at a loss of
		616	precision.
		617
		618	This might create round-tripping problems as numbers might become strings,
		619	but as Perl is typeless there is no other way to do it.
		620
		621	=item true, false
		622
		623	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
		624	respectively. They are overloaded to act almost exactly like the numbers
		625	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
		626	the C<JSON::XS::is_bool> function.
		627
		628	=item null
		629
		630	A JSON null atom becomes C<undef> in Perl.
		631
		632	=back
		633
		634
		635	=head2 PERL -> JSON
		636
		637	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		638	truly typeless language, so we can only guess which JSON type is meant by
		639	a Perl value.
		640
		641	=over 4
		642
		643	=item hash references
		644
		645	Perl hash references become JSON objects. As there is no inherent ordering
		646	in hash keys (or JSON objects), they will usually be encoded in a
		647	pseudo-random order that can change between runs of the same program but
		648	stays generally the same within a single run of a program. JSON::XS can
		649	optionally sort the hash keys (determined by the I<canonical> flag), so
		650	the same datastructure will serialise to the same JSON text (given same
		651	settings and version of JSON::XS), but this incurs a runtime overhead
		652	and is only rarely useful, e.g. when you want to compare some JSON text
		653	against another for equality.
		654
		655	=item array references
		656
		657	Perl array references become JSON arrays.
		658
		659	=item other references
		660
		661	Other unblessed references are generally not allowed and will cause an
		662	exception to be thrown, except for references to the integers C<0> and
		663	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		664	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		665
		666	to_json [\0,JSON::XS::true] # yields [false,true]
		667
		668	=item JSON::XS::true, JSON::XS::false
		669
		670	These special values become JSON true and JSON false values,
		671	respectively. You can also use C<\1> and C<\0> directly if you want.
		672
		673	=item blessed objects
		674
		675	Blessed objects are not allowed. JSON::XS currently tries to encode their
		676	underlying representation (hash- or arrayref), but this behaviour might
		677	change in future versions.
		678
		679	=item simple scalars
		680
		681	Simple Perl scalars (any scalar that is not a reference) are the most
		682	difficult objects to encode: JSON::XS will encode undefined scalars as
		683	JSON null value, scalars that have last been used in a string context
		684	before encoding as JSON strings and anything else as number value:
		685
		686	# dump as number
		687	to_json [2] # yields [2]
		688	to_json [-3.0e17] # yields [-3e+17]
		689	my $value = 5; to_json [$value] # yields [5]
		690
		691	# used as string, so dump as string
		692	print $value;
		693	to_json [$value] # yields ["5"]
		694
		695	# undef becomes null
		696	to_json [undef] # yields [null]
		697
		698	You can force the type to be a string by stringifying it:
		699
		700	my $x = 3.1; # some variable containing a number
		701	"$x"; # stringified
		702	$x .= ""; # another, more awkward way to stringify
		703	print $x; # perl does it for you, too, quite often
		704
		705	You can force the type to be a number by numifying it:
		706
		707	my $x = "3"; # some variable containing a string
		708	$x += 0; # numify it, ensuring it will be dumped as a number
		709	$x *= 1; # same thing, the choise is yours.
		710
		711	You can not currently output JSON booleans or force the type in other,
		712	less obscure, ways. Tell me if you need this capability.
		713
		714	=back
		715
263		716
264	=head1 COMPARISON	717	=head1 COMPARISON
265		718
266	As already mentioned, this module was created because none of the existing	719	As already mentioned, this module was created because none of the existing
267	JSON modules could be made to work correctly. First I will describe the	720	JSON modules could be made to work correctly. First I will describe the
…		…
293		746
294	Has problems handling many Perl values (e.g. regex results and other magic	747	Has problems handling many Perl values (e.g. regex results and other magic
295	values will make it croak).	748	values will make it croak).
296		749
297	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	750	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
298	which is not a valid JSON string.	751	which is not a valid JSON text.
299		752
300	Unmaintained (maintainer unresponsive for many months, bugs are not	753	Unmaintained (maintainer unresponsive for many months, bugs are not
301	getting fixed).	754	getting fixed).
302		755
303	=item JSON::Syck 0.21	756	=item JSON::Syck 0.21
…		…
305	Very buggy (often crashes).	758	Very buggy (often crashes).
306		759
307	Very inflexible (no human-readable format supported, format pretty much	760	Very inflexible (no human-readable format supported, format pretty much
308	undocumented. I need at least a format for easy reading by humans and a	761	undocumented. I need at least a format for easy reading by humans and a
309	single-line compact format for use in a protocol, and preferably a way to	762	single-line compact format for use in a protocol, and preferably a way to
310	generate ASCII-only JSON strings).	763	generate ASCII-only JSON texts).
311		764
312	Completely broken (and confusingly documented) Unicode handling (unicode	765	Completely broken (and confusingly documented) Unicode handling (unicode
313	escapes are not working properly, you need to set ImplicitUnicode to	766	escapes are not working properly, you need to set ImplicitUnicode to
314	I<different> values on en- and decoding to get symmetric behaviour).	767	I<different> values on en- and decoding to get symmetric behaviour).
315		768
…		…
338		791
339	Very inflexible.	792	Very inflexible.
340		793
341	No roundtripping.	794	No roundtripping.
342		795
343	Does not generate valid JSON (key strings are often unquoted, empty keys	796	Does not generate valid JSON texts (key strings are often unquoted, empty keys
344	result in nothing being output)	797	result in nothing being output)
345		798
346	Does not check input for validity.	799	Does not check input for validity.
347		800
348	=back	801	=back
		802
		803
		804	=head2 JSON and YAML
		805
		806	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		807	however, a mass hysteria and very far from the truth. In general, there is
		808	no way to configure JSON::XS to output a data structure as valid YAML.
		809
		810	If you really must use JSON::XS to generate YAML, you should use this
		811	algorithm (subject to change in future versions):
		812
		813	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		814	my $yaml = $to_yaml->encode ($ref) . "\n";
		815
		816	This will usually generate JSON texts that also parse as valid
		817	YAML. Please note that YAML has hardcoded limits on (simple) object key
		818	lengths that JSON doesn't have, so you should make sure that your hash
		819	keys are noticably shorter than the 1024 characters YAML allows.
		820
		821	There might be other incompatibilities that I am not aware of. In general
		822	you should not try to generate YAML with a JSON generator or vice versa,
		823	or try to parse JSON with a YAML parser or vice versa: chances are high
		824	that you will run into severe interoperability problems.
		825
349		826
350	=head2 SPEED	827	=head2 SPEED
351		828
352	It seems that JSON::XS is surprisingly fast, as shown in the following	829	It seems that JSON::XS is surprisingly fast, as shown in the following
353	tables. They have been generated with the help of the C<eg/bench> program	830	tables. They have been generated with the help of the C<eg/bench> program
354	in the JSON::XS distribution, to make it easy to compare on your own	831	in the JSON::XS distribution, to make it easy to compare on your own
355	system.	832	system.
356		833
357	First is a comparison between various modules using a very simple JSON	834	First comes a comparison between various modules using a very short
		835	single-line JSON string:
		836
		837	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		838	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
		839
358	string, showing the number of encodes/decodes per second (JSON::XS is	840	It shows the number of encodes/decodes per second (JSON::XS uses
359	the functional interface, while JSON::XS/2 is the OO interface with	841	the functional interface, while JSON::XS/2 uses the OO interface
360	pretty-printing and hashkey sorting enabled).	842	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		843	shrink). Higher is better:
361		844
		845	Storable \| 15779.925 \| 14169.946 \|
		846	-----------+------------+------------+
362	module \| encode \| decode \|	847	module \| encode \| decode \|
363	-----------\|------------\|------------\|	848	-----------\|------------\|------------\|
364	JSON \| 14006 \| 6820 \|	849	JSON \| 4990.842 \| 4088.813 \|
365	JSON::DWIW \| 200937 \| 120386 \|	850	JSON::DWIW \| 51653.990 \| 71575.154 \|
366	JSON::PC \| 85065 \| 129366 \|	851	JSON::PC \| 65948.176 \| 74631.744 \|
367	JSON::Syck \| 59898 \| 44232 \|	852	JSON::PP \| 8931.652 \| 3817.168 \|
368	JSON::XS \| 1171478 \| 342435 \|	853	JSON::Syck \| 24877.248 \| 27776.848 \|
369	JSON::XS/2 \| 730760 \| 328714 \|	854	JSON::XS \| 388361.481 \| 227951.304 \|
		855	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		856	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		857	Storable \| 16500.016 \| 135300.129 \|
370	-----------+------------+------------+	858	-----------+------------+------------+
371		859
372	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	860	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
		861	about three times faster on decoding, and over fourty times faster
373	times faster than JSON, even with pretty-printing and key sorting.	862	than JSON, even with pretty-printing and key sorting. It also compares
		863	favourably to Storable for small amounts of data.
374		864
375	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	865	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
376	search API (http://nanoref.com/yahooapis/mgPdGg):	866	search API (http://nanoref.com/yahooapis/mgPdGg):
377		867
378	module \| encode \| decode \|	868	module \| encode \| decode \|
379	-----------\|------------\|------------\|	869	-----------\|------------\|------------\|
380	JSON \| 673 \| 38 \|	870	JSON \| 55.260 \| 34.971 \|
381	JSON::DWIW \| 5271 \| 770 \|	871	JSON::DWIW \| 825.228 \| 1082.513 \|
382	JSON::PC \| 9901 \| 2491 \|	872	JSON::PC \| 3571.444 \| 2394.829 \|
383	JSON::Syck \| 2360 \| 786 \|	873	JSON::PP \| 210.987 \| 32.574 \|
384	JSON::XS \| 37398 \| 3202 \|	874	JSON::Syck \| 552.551 \| 787.544 \|
385	JSON::XS/2 \| 13765 \| 3153 \|	875	JSON::XS \| 5780.463 \| 4854.519 \|
		876	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		877	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		878	Storable \| 4445.002 \| 5235.027 \|
386	-----------+------------+------------+	879	-----------+------------+------------+
387		880
388	Again, JSON::XS leads by far in the encoding case, while still beating	881	Again, JSON::XS leads by far (except for Storable which non-surprisingly
389	every other module in the decoding case.	882	decodes faster).
390		883
391	Last example is an almost 8MB large hash with many large binary values	884	On large strings containing lots of high unicode characters, some modules
392	(PNG files), resulting in a lot of escaping:	885	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		886	will be broken due to missing (or wrong) unicode handling. Others refuse
		887	to decode or encode properly, so it was impossible to prepare a fair
		888	comparison table for that case.
		889
		890
		891	=head1 SECURITY CONSIDERATIONS
		892
		893	When you are using JSON in a protocol, talking to untrusted potentially
		894	hostile creatures requires relatively few measures.
		895
		896	First of all, your JSON decoder should be secure, that is, should not have
		897	any buffer overflows. Obviously, this module should ensure that and I am
		898	trying hard on making that true, but you never know.
		899
		900	Second, you need to avoid resource-starving attacks. That means you should
		901	limit the size of JSON texts you accept, or make sure then when your
		902	resources run out, thats just fine (e.g. by using a separate process that
		903	can crash safely). The size of a JSON text in octets or characters is
		904	usually a good indication of the size of the resources required to decode
		905	it into a Perl structure. While JSON::XS can check the size of the JSON
		906	text, it might be too late when you already have it in memory, so you
		907	might want to check the size before you accept the string.
		908
		909	Third, JSON::XS recurses using the C stack when decoding objects and
		910	arrays. The C stack is a limited resource: for instance, on my amd64
		911	machine with 8MB of stack size I can decode around 180k nested arrays but
		912	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		913	to free the temporary). If that is exceeded, the program crashes. to be
		914	conservative, the default nesting limit is set to 512. If your process
		915	has a smaller stack, you should adjust this setting accordingly with the
		916	C<max_depth> method.
		917
		918	And last but least, something else could bomb you that I forgot to think
		919	of. In that case, you get to keep the pieces. I am always open for hints,
		920	though...
		921
		922	If you are using JSON::XS to return packets to consumption
		923	by javascript scripts in a browser you should have a look at
		924	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		925	you are vulnerable to some common attack vectors (which really are browser
		926	design bugs, but it is still you who will have to deal with it, as major
		927	browser developers care only for features, not about doing security
		928	right).
		929
393		930
394	=head1 BUGS	931	=head1 BUGS
395		932
396	While the goal of this module is to be correct, that unfortunately does	933	While the goal of this module is to be correct, that unfortunately does
397	not mean its bug-free, only that I think its design is bug-free. It is	934	not mean its bug-free, only that I think its design is bug-free. It is
398	still very young and not well-tested. If you keep reporting bugs they will	935	still relatively early in its development. If you keep reporting bugs they
399	be fixed swiftly, though.	936	will be fixed swiftly, though.
400		937
401	=cut	938	=cut
		939
		940	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		941	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		942
		943	sub true() { $true }
		944	sub false() { $false }
		945
		946	sub is_bool($) {
		947	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		948	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		949	}
		950
		951	XSLoader::load "JSON::XS", $VERSION;
		952
		953	package JSON::XS::Boolean;
		954
		955	use overload
		956	"0+" => sub { ${$_[0]} },
		957	"++" => sub { $_[0] = ${$_[0]} + 1 },
		958	"--" => sub { $_[0] = ${$_[0]} - 1 },
		959	fallback => 1;
402		960
403	1;	961	1;
404		962
405	=head1 AUTHOR	963	=head1 AUTHOR
406		964

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Comparing JSON-XS/XS.pm (file contents): Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs. Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.8 by root, Fri Mar 23 15:57:18 2007 UTC vs.
Revision 1.61 by root, Wed Sep 12 17:42:36 2007 UTC