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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.19 by root, Sat Mar 24 22:57:12 2007 UTC vs.
Revision 1.66 by root, Sun Oct 14 20:02:57 2007 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
		5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		7
5	=head1 SYNOPSIS	8	=head1 SYNOPSIS
6		9
7	use JSON::XS;	10	use JSON::XS;
8		11
9	# exported functions, croak on error	12	# exported functions, they croak on error
		13	# and expect/generate UTF-8
10		14
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
13		17
14	# oo-interface	18	# OO-interface
15		19
16	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
17	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
18	$perl_scalar = $coder->decode ($unicode_json_text);	22	$perl_scalar = $coder->decode ($unicode_json_text);
19		23
36		40
37	=head2 FEATURES	41	=head2 FEATURES
38		42
39	=over 4	43	=over 4
40		44
41	=item * correct handling of unicode issues	45	=item * correct unicode handling
42		46
43	This module knows how to handle Unicode, and even documents how and when	47	This module knows how to handle Unicode, and even documents how and when
44	it does so.	48	it does so.
45		49
46	=item * round-trip integrity	50	=item * round-trip integrity
47		51
48	When you serialise a perl data structure using only datatypes supported	52	When you serialise a perl data structure using only datatypes supported
49	by JSON, the deserialised data structure is identical on the Perl level.	53	by JSON, the deserialised data structure is identical on the Perl level.
50	(e.g. the string "2.0" doesn't suddenly become "2").	54	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		55	like a number).
51		56
52	=item * strict checking of JSON correctness	57	=item * strict checking of JSON correctness
53		58
54	There is no guessing, no generating of illegal JSON texts by default,	59	There is no guessing, no generating of illegal JSON texts by default,
55	and only JSON is accepted as input by default (the latter is a security	60	and only JSON is accepted as input by default (the latter is a security
…		…
66	interface.	71	interface.
67		72
68	=item * reasonably versatile output formats	73	=item * reasonably versatile output formats
69		74
70	You can choose between the most compact guarenteed single-line format	75	You can choose between the most compact guarenteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	76	possible (nice for simple line-based protocols), a pure-ascii format
72	when your transport is not 8-bit clean), or a pretty-printed format (for	77	(for when your transport is not 8-bit clean, still supports the whole
73	when you want to read that stuff). Or you can combine those features in	78	unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	79	stuff). Or you can combine those features in whatever way you like.
75		80
76	=back	81	=back
77		82
78	=cut	83	=cut
79		84
80	package JSON::XS;	85	package JSON::XS;
81		86
82	BEGIN {	87	use strict;
		88
83	$VERSION = '0.7';	89	our $VERSION = '1.51';
84	@ISA = qw(Exporter);	90	our @ISA = qw(Exporter);
85		91
86	@EXPORT = qw(to_json from_json);	92	our @EXPORT = qw(to_json from_json);
87	require Exporter;
88		93
89	require XSLoader;	94	use Exporter;
90	XSLoader::load JSON::XS::, $VERSION;	95	use XSLoader;
91	}
92		96
93	=head1 FUNCTIONAL INTERFACE	97	=head1 FUNCTIONAL INTERFACE
94		98
95	The following convinience methods are provided by this module. They are	99	The following convinience methods are provided by this module. They are
96	exported by default:	100	exported by default:
97		101
98	=over 4	102	=over 4
99		103
100	=item $json_text = to_json $perl_scalar	104	=item $json_text = to_json $perl_scalar
101		105
102	Converts the given Perl data structure (a simple scalar or a reference to	106	Converts the given Perl data structure to a UTF-8 encoded, binary string
103	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	107	(that is, the string contains octets only). Croaks on error.
104	octets only). Croaks on error.
105		108
106	This function call is functionally identical to:	109	This function call is functionally identical to:
107		110
108	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	111	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
109		112
110	except being faster.	113	except being faster.
111		114
112	=item $perl_scalar = from_json $json_text	115	=item $perl_scalar = from_json $json_text
113		116
114	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	117	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
115	parse that as an UTF-8 encoded JSON text, returning the resulting simple	118	to parse that as an UTF-8 encoded JSON text, returning the resulting
116	scalar or reference. Croaks on error.	119	reference. Croaks on error.
117		120
118	This function call is functionally identical to:	121	This function call is functionally identical to:
119		122
120	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	123	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
121		124
122	except being faster.	125	except being faster.
123		126
		127	=item $is_boolean = JSON::XS::is_bool $scalar
		128
		129	Returns true if the passed scalar represents either JSON::XS::true or
		130	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		131	and are used to represent JSON C<true> and C<false> values in Perl.
		132
		133	See MAPPING, below, for more information on how JSON values are mapped to
		134	Perl.
		135
124	=back	136	=back
		137
		138
		139	=head1 A FEW NOTES ON UNICODE AND PERL
		140
		141	Since this often leads to confusion, here are a few very clear words on
		142	how Unicode works in Perl, modulo bugs.
		143
		144	=over 4
		145
		146	=item 1. Perl strings can store characters with ordinal values > 255.
		147
		148	This enables you to store unicode characters as single characters in a
		149	Perl string - very natural.
		150
		151	=item 2. Perl does I<not> associate an encoding with your strings.
		152
		153	Unless you force it to, e.g. when matching it against a regex, or printing
		154	the scalar to a file, in which case Perl either interprets your string as
		155	locale-encoded text, octets/binary, or as Unicode, depending on various
		156	settings. In no case is an encoding stored together with your data, it is
		157	I<use> that decides encoding, not any magical metadata.
		158
		159	=item 3. The internal utf-8 flag has no meaning with regards to the
		160	encoding of your string.
		161
		162	Just ignore that flag unless you debug a Perl bug, a module written in
		163	XS or want to dive into the internals of perl. Otherwise it will only
		164	confuse you, as, despite the name, it says nothing about how your string
		165	is encoded. You can have unicode strings with that flag set, with that
		166	flag clear, and you can have binary data with that flag set and that flag
		167	clear. Other possibilities exist, too.
		168
		169	If you didn't know about that flag, just the better, pretend it doesn't
		170	exist.
		171
		172	=item 4. A "Unicode String" is simply a string where each character can be
		173	validly interpreted as a Unicode codepoint.
		174
		175	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		176	Unicode string encoded in UTF-8, giving you a binary string.
		177
		178	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		179
		180	Its a fact. Learn to live with it.
		181
		182	=back
		183
		184	I hope this helps :)
		185
125		186
126	=head1 OBJECT-ORIENTED INTERFACE	187	=head1 OBJECT-ORIENTED INTERFACE
127		188
128	The object oriented interface lets you configure your own encoding or	189	The object oriented interface lets you configure your own encoding or
129	decoding style, within the limits of supported formats.	190	decoding style, within the limits of supported formats.
…		…
145		206
146	If C<$enable> is true (or missing), then the C<encode> method will not	207	If C<$enable> is true (or missing), then the C<encode> method will not
147	generate characters outside the code range C<0..127> (which is ASCII). Any	208	generate characters outside the code range C<0..127> (which is ASCII). Any
148	unicode characters outside that range will be escaped using either a	209	unicode characters outside that range will be escaped using either a
149	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	210	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
150	as per RFC4627.	211	as per RFC4627. The resulting encoded JSON text can be treated as a native
		212	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		213	or any other superset of ASCII.
151		214
152	If C<$enable> is false, then the C<encode> method will not escape Unicode	215	If C<$enable> is false, then the C<encode> method will not escape Unicode
153	characters unless required by the JSON syntax. This results in a faster	216	characters unless required by the JSON syntax or other flags. This results
154	and more compact format.	217	in a faster and more compact format.
		218
		219	The main use for this flag is to produce JSON texts that can be
		220	transmitted over a 7-bit channel, as the encoded JSON texts will not
		221	contain any 8 bit characters.
155		222
156	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	223	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
157	=> ["\ud801\udc01"]	224	=> ["\ud801\udc01"]
		225
		226	=item $json = $json->latin1 ([$enable])
		227
		228	If C<$enable> is true (or missing), then the C<encode> method will encode
		229	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		230	outside the code range C<0..255>. The resulting string can be treated as a
		231	latin1-encoded JSON text or a native unicode string. The C<decode> method
		232	will not be affected in any way by this flag, as C<decode> by default
		233	expects unicode, which is a strict superset of latin1.
		234
		235	If C<$enable> is false, then the C<encode> method will not escape Unicode
		236	characters unless required by the JSON syntax or other flags.
		237
		238	The main use for this flag is efficiently encoding binary data as JSON
		239	text, as most octets will not be escaped, resulting in a smaller encoded
		240	size. The disadvantage is that the resulting JSON text is encoded
		241	in latin1 (and must correctly be treated as such when storing and
		242	transfering), a rare encoding for JSON. It is therefore most useful when
		243	you want to store data structures known to contain binary data efficiently
		244	in files or databases, not when talking to other JSON encoders/decoders.
		245
		246	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		247	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
158		248
159	=item $json = $json->utf8 ([$enable])	249	=item $json = $json->utf8 ([$enable])
160		250
161	If C<$enable> is true (or missing), then the C<encode> method will encode	251	If C<$enable> is true (or missing), then the C<encode> method will encode
162	the JSON result into UTF-8, as required by many protocols, while the	252	the JSON result into UTF-8, as required by many protocols, while the
…		…
238		328
239	Example, space_before and indent disabled, space_after enabled:	329	Example, space_before and indent disabled, space_after enabled:
240		330
241	{"key": "value"}	331	{"key": "value"}
242		332
		333	=item $json = $json->relaxed ([$enable])
		334
		335	If C<$enable> is true (or missing), then C<decode> will accept some
		336	extensions to normal JSON syntax (see below). C<encode> will not be
		337	affected in anyway. I<Be aware that this option makes you accept invalid
		338	JSON texts as if they were valid!>. I suggest only to use this option to
		339	parse application-specific files written by humans (configuration files,
		340	resource files etc.)
		341
		342	If C<$enable> is false (the default), then C<decode> will only accept
		343	valid JSON texts.
		344
		345	Currently accepted extensions are:
		346
		347	=over 4
		348
		349	=item * list items can have an end-comma
		350
		351	JSON I<separates> array elements and key-value pairs with commas. This
		352	can be annoying if you write JSON texts manually and want to be able to
		353	quickly append elements, so this extension accepts comma at the end of
		354	such items not just between them:
		355
		356	[
		357	1,
		358	2, <- this comma not normally allowed
		359	]
		360	{
		361	"k1": "v1",
		362	"k2": "v2", <- this comma not normally allowed
		363	}
		364
		365	=item * shell-style '#'-comments
		366
		367	Whenever JSON allows whitespace, shell-style comments are additionally
		368	allowed. They are terminated by the first carriage-return or line-feed
		369	character, after which more white-space and comments are allowed.
		370
		371	[
		372	1, # this comment not allowed in JSON
		373	# neither this one...
		374	]
		375
		376	=back
		377
243	=item $json = $json->canonical ([$enable])	378	=item $json = $json->canonical ([$enable])
244		379
245	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	380	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
246	by sorting their keys. This is adding a comparatively high overhead.	381	by sorting their keys. This is adding a comparatively high overhead.
247		382
…		…
272	resulting in an invalid JSON text:	407	resulting in an invalid JSON text:
273		408
274	JSON::XS->new->allow_nonref->encode ("Hello, World!")	409	JSON::XS->new->allow_nonref->encode ("Hello, World!")
275	=> "Hello, World!"	410	=> "Hello, World!"
276		411
		412	=item $json = $json->allow_blessed ([$enable])
		413
		414	If C<$enable> is true (or missing), then the C<encode> method will not
		415	barf when it encounters a blessed reference. Instead, the value of the
		416	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		417	disabled or no C<to_json> method found) or a representation of the
		418	object (C<convert_blessed> enabled and C<to_json> method found) is being
		419	encoded. Has no effect on C<decode>.
		420
		421	If C<$enable> is false (the default), then C<encode> will throw an
		422	exception when it encounters a blessed object.
		423
		424	=item $json = $json->convert_blessed ([$enable])
		425
		426	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		427	blessed object, will check for the availability of the C<TO_JSON> method
		428	on the object's class. If found, it will be called in scalar context
		429	and the resulting scalar will be encoded instead of the object. If no
		430	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		431	to do.
		432
		433	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		434	returns other blessed objects, those will be handled in the same
		435	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		436	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		437	methods called by the Perl core (== not by the user of the object) are
		438	usually in upper case letters and to avoid collisions with the C<to_json>
		439	function.
		440
		441	This setting does not yet influence C<decode> in any way, but in the
		442	future, global hooks might get installed that influence C<decode> and are
		443	enabled by this setting.
		444
		445	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		446	to do when a blessed object is found.
		447
		448	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		449
		450	When C<$coderef> is specified, it will be called from C<decode> each
		451	time it decodes a JSON object. The only argument is a reference to the
		452	newly-created hash. If the code references returns a single scalar (which
		453	need not be a reference), this value (i.e. a copy of that scalar to avoid
		454	aliasing) is inserted into the deserialised data structure. If it returns
		455	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		456	original deserialised hash will be inserted. This setting can slow down
		457	decoding considerably.
		458
		459	When C<$coderef> is omitted or undefined, any existing callback will
		460	be removed and C<decode> will not change the deserialised hash in any
		461	way.
		462
		463	Example, convert all JSON objects into the integer 5:
		464
		465	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		466	# returns [5]
		467	$js->decode ('[{}]')
		468	# throw an exception because allow_nonref is not enabled
		469	# so a lone 5 is not allowed.
		470	$js->decode ('{"a":1, "b":2}');
		471
		472	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		473
		474	Works remotely similar to C<filter_json_object>, but is only called for
		475	JSON objects having a single key named C<$key>.
		476
		477	This C<$coderef> is called before the one specified via
		478	C<filter_json_object>, if any. It gets passed the single value in the JSON
		479	object. If it returns a single value, it will be inserted into the data
		480	structure. If it returns nothing (not even C<undef> but the empty list),
		481	the callback from C<filter_json_object> will be called next, as if no
		482	single-key callback were specified.
		483
		484	If C<$coderef> is omitted or undefined, the corresponding callback will be
		485	disabled. There can only ever be one callback for a given key.
		486
		487	As this callback gets called less often then the C<filter_json_object>
		488	one, decoding speed will not usually suffer as much. Therefore, single-key
		489	objects make excellent targets to serialise Perl objects into, especially
		490	as single-key JSON objects are as close to the type-tagged value concept
		491	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		492	support this in any way, so you need to make sure your data never looks
		493	like a serialised Perl hash.
		494
		495	Typical names for the single object key are C<__class_whatever__>, or
		496	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		497	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		498	with real hashes.
		499
		500	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		501	into the corresponding C<< $WIDGET{<id>} >> object:
		502
		503	# return whatever is in $WIDGET{5}:
		504	JSON::XS
		505	->new
		506	->filter_json_single_key_object (__widget__ => sub {
		507	$WIDGET{ $_[0] }
		508	})
		509	->decode ('{"__widget__": 5')
		510
		511	# this can be used with a TO_JSON method in some "widget" class
		512	# for serialisation to json:
		513	sub WidgetBase::TO_JSON {
		514	my ($self) = @_;
		515
		516	unless ($self->{id}) {
		517	$self->{id} = ..get..some..id..;
		518	$WIDGET{$self->{id}} = $self;
		519	}
		520
		521	{ __widget__ => $self->{id} }
		522	}
		523
277	=item $json = $json->shrink ([$enable])	524	=item $json = $json->shrink ([$enable])
278		525
279	Perl usually over-allocates memory a bit when allocating space for	526	Perl usually over-allocates memory a bit when allocating space for
280	strings. This flag optionally resizes strings generated by either	527	strings. This flag optionally resizes strings generated by either
281	C<encode> or C<decode> to their minimum size possible. This can save	528	C<encode> or C<decode> to their minimum size possible. This can save
282	memory when your JSON texts are either very very long or you have many	529	memory when your JSON texts are either very very long or you have many
283	short strings. It will also try to downgrade any strings to octet-form	530	short strings. It will also try to downgrade any strings to octet-form
284	if possible: perl stores strings internally either in an encoding called	531	if possible: perl stores strings internally either in an encoding called
285	UTF-X or in octet-form. The latter cannot store everything but uses less	532	UTF-X or in octet-form. The latter cannot store everything but uses less
286	space in general.	533	space in general (and some buggy Perl or C code might even rely on that
		534	internal representation being used).
287		535
		536	The actual definition of what shrink does might change in future versions,
		537	but it will always try to save space at the expense of time.
		538
288	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	539	If C<$enable> is true (or missing), the string returned by C<encode> will
289	while all strings generated by C<decode> will also be shrunk-to-fit.	540	be shrunk-to-fit, while all strings generated by C<decode> will also be
		541	shrunk-to-fit.
290		542
291	If C<$enable> is false, then the normal perl allocation algorithms are used.	543	If C<$enable> is false, then the normal perl allocation algorithms are used.
292	If you work with your data, then this is likely to be faster.	544	If you work with your data, then this is likely to be faster.
293		545
294	In the future, this setting might control other things, such as converting	546	In the future, this setting might control other things, such as converting
295	strings that look like integers or floats into integers or floats	547	strings that look like integers or floats into integers or floats
296	internally (there is no difference on the Perl level), saving space.	548	internally (there is no difference on the Perl level), saving space.
		549
		550	=item $json = $json->max_depth ([$maximum_nesting_depth])
		551
		552	Sets the maximum nesting level (default C<512>) accepted while encoding
		553	or decoding. If the JSON text or Perl data structure has an equal or
		554	higher nesting level then this limit, then the encoder and decoder will
		555	stop and croak at that point.
		556
		557	Nesting level is defined by number of hash- or arrayrefs that the encoder
		558	needs to traverse to reach a given point or the number of C<{> or C<[>
		559	characters without their matching closing parenthesis crossed to reach a
		560	given character in a string.
		561
		562	Setting the maximum depth to one disallows any nesting, so that ensures
		563	that the object is only a single hash/object or array.
		564
		565	The argument to C<max_depth> will be rounded up to the next highest power
		566	of two. If no argument is given, the highest possible setting will be
		567	used, which is rarely useful.
		568
		569	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		570
		571	=item $json = $json->max_size ([$maximum_string_size])
		572
		573	Set the maximum length a JSON text may have (in bytes) where decoding is
		574	being attempted. The default is C<0>, meaning no limit. When C<decode>
		575	is called on a string longer then this number of characters it will not
		576	attempt to decode the string but throw an exception. This setting has no
		577	effect on C<encode> (yet).
		578
		579	The argument to C<max_size> will be rounded up to the next B<highest>
		580	power of two (so may be more than requested). If no argument is given, the
		581	limit check will be deactivated (same as when C<0> is specified).
		582
		583	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
297		584
298	=item $json_text = $json->encode ($perl_scalar)	585	=item $json_text = $json->encode ($perl_scalar)
299		586
300	Converts the given Perl data structure (a simple scalar or a reference	587	Converts the given Perl data structure (a simple scalar or a reference
301	to a hash or array) to its JSON representation. Simple scalars will be	588	to a hash or array) to its JSON representation. Simple scalars will be
…		…
311		598
312	JSON numbers and strings become simple Perl scalars. JSON arrays become	599	JSON numbers and strings become simple Perl scalars. JSON arrays become
313	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	600	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
314	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	601	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
315		602
		603	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		604
		605	This works like the C<decode> method, but instead of raising an exception
		606	when there is trailing garbage after the first JSON object, it will
		607	silently stop parsing there and return the number of characters consumed
		608	so far.
		609
		610	This is useful if your JSON texts are not delimited by an outer protocol
		611	(which is not the brightest thing to do in the first place) and you need
		612	to know where the JSON text ends.
		613
		614	JSON::XS->new->decode_prefix ("[1] the tail")
		615	=> ([], 3)
		616
316	=back	617	=back
		618
317		619
318	=head1 MAPPING	620	=head1 MAPPING
319		621
320	This section describes how JSON::XS maps Perl values to JSON values and	622	This section describes how JSON::XS maps Perl values to JSON values and
321	vice versa. These mappings are designed to "do the right thing" in most	623	vice versa. These mappings are designed to "do the right thing" in most
…		…
324		626
325	For the more enlightened: note that in the following descriptions,	627	For the more enlightened: note that in the following descriptions,
326	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	628	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
327	refers to the abstract Perl language itself.	629	refers to the abstract Perl language itself.
328		630
		631
329	=head2 JSON -> PERL	632	=head2 JSON -> PERL
330		633
331	=over 4	634	=over 4
332		635
333	=item object	636	=item object
…		…
345	are represented by the same codepoints in the Perl string, so no manual	648	are represented by the same codepoints in the Perl string, so no manual
346	decoding is necessary.	649	decoding is necessary.
347		650
348	=item number	651	=item number
349		652
350	A JSON number becomes either an integer or numeric (floating point)	653	A JSON number becomes either an integer, numeric (floating point) or
351	scalar in perl, depending on its range and any fractional parts. On the	654	string scalar in perl, depending on its range and any fractional parts. On
352	Perl level, there is no difference between those as Perl handles all the	655	the Perl level, there is no difference between those as Perl handles all
353	conversion details, but an integer may take slightly less memory and might	656	the conversion details, but an integer may take slightly less memory and
354	represent more values exactly than (floating point) numbers.	657	might represent more values exactly than (floating point) numbers.
		658
		659	If the number consists of digits only, JSON::XS will try to represent
		660	it as an integer value. If that fails, it will try to represent it as
		661	a numeric (floating point) value if that is possible without loss of
		662	precision. Otherwise it will preserve the number as a string value.
		663
		664	Numbers containing a fractional or exponential part will always be
		665	represented as numeric (floating point) values, possibly at a loss of
		666	precision.
		667
		668	This might create round-tripping problems as numbers might become strings,
		669	but as Perl is typeless there is no other way to do it.
355		670
356	=item true, false	671	=item true, false
357		672
358	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	673	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
359	this process. Future versions might represent those values differently,	674	respectively. They are overloaded to act almost exactly like the numbers
360	but they will be guarenteed to act like these integers would normally in	675	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
361	Perl.	676	the C<JSON::XS::is_bool> function.
362		677
363	=item null	678	=item null
364		679
365	A JSON null atom becomes C<undef> in Perl.	680	A JSON null atom becomes C<undef> in Perl.
366		681
367	=back	682	=back
		683
368		684
369	=head2 PERL -> JSON	685	=head2 PERL -> JSON
370		686
371	The mapping from Perl to JSON is slightly more difficult, as Perl is a	687	The mapping from Perl to JSON is slightly more difficult, as Perl is a
372	truly typeless language, so we can only guess which JSON type is meant by	688	truly typeless language, so we can only guess which JSON type is meant by
…		…
375	=over 4	691	=over 4
376		692
377	=item hash references	693	=item hash references
378		694
379	Perl hash references become JSON objects. As there is no inherent ordering	695	Perl hash references become JSON objects. As there is no inherent ordering
380	in hash keys, they will usually be encoded in a pseudo-random order that	696	in hash keys (or JSON objects), they will usually be encoded in a
381	can change between runs of the same program but stays generally the same	697	pseudo-random order that can change between runs of the same program but
382	within a single run of a program. JSON::XS can optionally sort the hash	698	stays generally the same within a single run of a program. JSON::XS can
383	keys (determined by the I<canonical> flag), so the same datastructure	699	optionally sort the hash keys (determined by the I<canonical> flag), so
384	will serialise to the same JSON text (given same settings and version of	700	the same datastructure will serialise to the same JSON text (given same
385	JSON::XS), but this incurs a runtime overhead.	701	settings and version of JSON::XS), but this incurs a runtime overhead
		702	and is only rarely useful, e.g. when you want to compare some JSON text
		703	against another for equality.
386		704
387	=item array references	705	=item array references
388		706
389	Perl array references become JSON arrays.	707	Perl array references become JSON arrays.
		708
		709	=item other references
		710
		711	Other unblessed references are generally not allowed and will cause an
		712	exception to be thrown, except for references to the integers C<0> and
		713	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		714	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		715
		716	to_json [\0,JSON::XS::true] # yields [false,true]
		717
		718	=item JSON::XS::true, JSON::XS::false
		719
		720	These special values become JSON true and JSON false values,
		721	respectively. You can also use C<\1> and C<\0> directly if you want.
390		722
391	=item blessed objects	723	=item blessed objects
392		724
393	Blessed objects are not allowed. JSON::XS currently tries to encode their	725	Blessed objects are not allowed. JSON::XS currently tries to encode their
394	underlying representation (hash- or arrayref), but this behaviour might	726	underlying representation (hash- or arrayref), but this behaviour might
…		…
427	$x *= 1; # same thing, the choise is yours.	759	$x *= 1; # same thing, the choise is yours.
428		760
429	You can not currently output JSON booleans or force the type in other,	761	You can not currently output JSON booleans or force the type in other,
430	less obscure, ways. Tell me if you need this capability.	762	less obscure, ways. Tell me if you need this capability.
431		763
432	=item circular data structures
433
434	Those will be encoded until memory or stackspace runs out.
435
436	=back	764	=back
		765
437		766
438	=head1 COMPARISON	767	=head1 COMPARISON
439		768
440	As already mentioned, this module was created because none of the existing	769	As already mentioned, this module was created because none of the existing
441	JSON modules could be made to work correctly. First I will describe the	770	JSON modules could be made to work correctly. First I will describe the
…		…
519		848
520	Does not check input for validity.	849	Does not check input for validity.
521		850
522	=back	851	=back
523		852
		853
		854	=head2 JSON and YAML
		855
		856	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		857	however, a mass hysteria and very far from the truth. In general, there is
		858	no way to configure JSON::XS to output a data structure as valid YAML.
		859
		860	If you really must use JSON::XS to generate YAML, you should use this
		861	algorithm (subject to change in future versions):
		862
		863	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		864	my $yaml = $to_yaml->encode ($ref) . "\n";
		865
		866	This will usually generate JSON texts that also parse as valid
		867	YAML. Please note that YAML has hardcoded limits on (simple) object key
		868	lengths that JSON doesn't have, so you should make sure that your hash
		869	keys are noticably shorter than the 1024 characters YAML allows.
		870
		871	There might be other incompatibilities that I am not aware of. In general
		872	you should not try to generate YAML with a JSON generator or vice versa,
		873	or try to parse JSON with a YAML parser or vice versa: chances are high
		874	that you will run into severe interoperability problems.
		875
		876
524	=head2 SPEED	877	=head2 SPEED
525		878
526	It seems that JSON::XS is surprisingly fast, as shown in the following	879	It seems that JSON::XS is surprisingly fast, as shown in the following
527	tables. They have been generated with the help of the C<eg/bench> program	880	tables. They have been generated with the help of the C<eg/bench> program
528	in the JSON::XS distribution, to make it easy to compare on your own	881	in the JSON::XS distribution, to make it easy to compare on your own
529	system.	882	system.
530		883
531	First comes a comparison between various modules using a very short JSON	884	First comes a comparison between various modules using a very short
532	string:	885	single-line JSON string:
533		886
534	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	887	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		888	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
535		889
536	It shows the number of encodes/decodes per second (JSON::XS uses the	890	It shows the number of encodes/decodes per second (JSON::XS uses
537	functional interface, while JSON::XS/2 uses the OO interface with	891	the functional interface, while JSON::XS/2 uses the OO interface
538	pretty-printing and hashkey sorting enabled). Higher is better:	892	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		893	shrink). Higher is better:
539		894
		895	Storable \| 15779.925 \| 14169.946 \|
		896	-----------+------------+------------+
540	module \| encode \| decode \|	897	module \| encode \| decode \|
541	-----------\|------------\|------------\|	898	-----------\|------------\|------------\|
542	JSON \| 11488.516 \| 7823.035 \|	899	JSON \| 4990.842 \| 4088.813 \|
543	JSON::DWIW \| 94708.054 \| 129094.260 \|	900	JSON::DWIW \| 51653.990 \| 71575.154 \|
544	JSON::PC \| 63884.157 \| 128528.212 \|	901	JSON::PC \| 65948.176 \| 74631.744 \|
545	JSON::Syck \| 34898.677 \| 42096.911 \|	902	JSON::PP \| 8931.652 \| 3817.168 \|
546	JSON::XS \| 654027.064 \| 396423.669 \|	903	JSON::Syck \| 24877.248 \| 27776.848 \|
547	JSON::XS/2 \| 371564.190 \| 371725.613 \|	904	JSON::XS \| 388361.481 \| 227951.304 \|
		905	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		906	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		907	Storable \| 16500.016 \| 135300.129 \|
548	-----------+------------+------------+	908	-----------+------------+------------+
549		909
550	That is, JSON::XS is more than six times faster than JSON::DWIW on	910	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
551	encoding, more than three times faster on decoding, and about thirty times	911	about three times faster on decoding, and over fourty times faster
552	faster than JSON, even with pretty-printing and key sorting.	912	than JSON, even with pretty-printing and key sorting. It also compares
		913	favourably to Storable for small amounts of data.
553		914
554	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	915	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
555	search API (http://nanoref.com/yahooapis/mgPdGg):	916	search API (http://nanoref.com/yahooapis/mgPdGg):
556		917
557	module \| encode \| decode \|	918	module \| encode \| decode \|
558	-----------\|------------\|------------\|	919	-----------\|------------\|------------\|
559	JSON \| 273.023 \| 44.674 \|	920	JSON \| 55.260 \| 34.971 \|
560	JSON::DWIW \| 1089.383 \| 1145.704 \|	921	JSON::DWIW \| 825.228 \| 1082.513 \|
561	JSON::PC \| 3097.419 \| 2393.921 \|	922	JSON::PC \| 3571.444 \| 2394.829 \|
562	JSON::Syck \| 514.060 \| 843.053 \|	923	JSON::PP \| 210.987 \| 32.574 \|
563	JSON::XS \| 6479.668 \| 3636.364 \|	924	JSON::Syck \| 552.551 \| 787.544 \|
564	JSON::XS/2 \| 3774.221 \| 3599.124 \|	925	JSON::XS \| 5780.463 \| 4854.519 \|
		926	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		927	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		928	Storable \| 4445.002 \| 5235.027 \|
565	-----------+------------+------------+	929	-----------+------------+------------+
566		930
567	Again, JSON::XS leads by far.	931	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		932	decodes faster).
568		933
569	On large strings containing lots of high unicode characters, some modules	934	On large strings containing lots of high unicode characters, some modules
570	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	935	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
571	will be broken due to missing (or wrong) unicode handling. Others refuse	936	will be broken due to missing (or wrong) unicode handling. Others refuse
572	to decode or encode properly, so it was impossible to prepare a fair	937	to decode or encode properly, so it was impossible to prepare a fair
573	comparison table for that case.	938	comparison table for that case.
574		939
575	=head1 RESOURCE LIMITS
576		940
577	JSON::XS does not impose any limits on the size of JSON texts or Perl	941	=head1 SECURITY CONSIDERATIONS
578	values they represent - if your machine can handle it, JSON::XS will	942
579	encode or decode it. Future versions might optionally impose structure	943	When you are using JSON in a protocol, talking to untrusted potentially
580	depth and memory use resource limits.	944	hostile creatures requires relatively few measures.
		945
		946	First of all, your JSON decoder should be secure, that is, should not have
		947	any buffer overflows. Obviously, this module should ensure that and I am
		948	trying hard on making that true, but you never know.
		949
		950	Second, you need to avoid resource-starving attacks. That means you should
		951	limit the size of JSON texts you accept, or make sure then when your
		952	resources run out, thats just fine (e.g. by using a separate process that
		953	can crash safely). The size of a JSON text in octets or characters is
		954	usually a good indication of the size of the resources required to decode
		955	it into a Perl structure. While JSON::XS can check the size of the JSON
		956	text, it might be too late when you already have it in memory, so you
		957	might want to check the size before you accept the string.
		958
		959	Third, JSON::XS recurses using the C stack when decoding objects and
		960	arrays. The C stack is a limited resource: for instance, on my amd64
		961	machine with 8MB of stack size I can decode around 180k nested arrays but
		962	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		963	to free the temporary). If that is exceeded, the program crashes. to be
		964	conservative, the default nesting limit is set to 512. If your process
		965	has a smaller stack, you should adjust this setting accordingly with the
		966	C<max_depth> method.
		967
		968	And last but least, something else could bomb you that I forgot to think
		969	of. In that case, you get to keep the pieces. I am always open for hints,
		970	though...
		971
		972	If you are using JSON::XS to return packets to consumption
		973	by javascript scripts in a browser you should have a look at
		974	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		975	you are vulnerable to some common attack vectors (which really are browser
		976	design bugs, but it is still you who will have to deal with it, as major
		977	browser developers care only for features, not about doing security
		978	right).
		979
		980
		981	=head1 THREADS
		982
		983	This module is I<not> guarenteed to be thread safe and there are no
		984	plans to change this until Perl gets thread support (as opposed to the
		985	horribly slow so-called "threads" which are simply slow and bloated
		986	process simulations - use fork, its I<much> faster, cheaper, better).
		987
		988	(It might actually work, but you ahve ben warned).
		989
581		990
582	=head1 BUGS	991	=head1 BUGS
583		992
584	While the goal of this module is to be correct, that unfortunately does	993	While the goal of this module is to be correct, that unfortunately does
585	not mean its bug-free, only that I think its design is bug-free. It is	994	not mean its bug-free, only that I think its design is bug-free. It is
586	still very young and not well-tested. If you keep reporting bugs they will	995	still relatively early in its development. If you keep reporting bugs they
587	be fixed swiftly, though.	996	will be fixed swiftly, though.
		997
		998	Please refrain from using rt.cpan.org or any other bug reporting
		999	service. I put the contact address into my modules for a reason.
588		1000
589	=cut	1001	=cut
		1002
		1003	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1004	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1005
		1006	sub true() { $true }
		1007	sub false() { $false }
		1008
		1009	sub is_bool($) {
		1010	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1011	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1012	}
		1013
		1014	XSLoader::load "JSON::XS", $VERSION;
		1015
		1016	package JSON::XS::Boolean;
		1017
		1018	use overload
		1019	"0+" => sub { ${$_[0]} },
		1020	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1021	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1022	fallback => 1;
590		1023
591	1;	1024	1;
592		1025
593	=head1 AUTHOR	1026	=head1 AUTHOR
594		1027

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Revision 1.66 by root, Sun Oct 14 20:02:57 2007 UTC