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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.20 by root, Sun Mar 25 00:47:42 2007 UTC vs.
Revision 1.64 by root, Thu Oct 11 23:57:24 2007 UTC

…		…
		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		6
		7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
		8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
		9
5	=head1 SYNOPSIS	10	=head1 SYNOPSIS
6		11
7	use JSON::XS;	12	use JSON::XS;
8		13
9	# exported functions, croak on error	14	# exported functions, they croak on error
		15	# and expect/generate UTF-8
10		16
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
13		19
14	# oo-interface	20	# OO-interface
15		21
16	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
17	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
18	$perl_scalar = $coder->decode ($unicode_json_text);	24	$perl_scalar = $coder->decode ($unicode_json_text);
19		25
36		42
37	=head2 FEATURES	43	=head2 FEATURES
38		44
39	=over 4	45	=over 4
40		46
41	=item * correct handling of unicode issues	47	=item * correct unicode handling
42		48
43	This module knows how to handle Unicode, and even documents how and when	49	This module knows how to handle Unicode, and even documents how and when
44	it does so.	50	it does so.
45		51
46	=item * round-trip integrity	52	=item * round-trip integrity
47		53
48	When you serialise a perl data structure using only datatypes supported	54	When you serialise a perl data structure using only datatypes supported
49	by JSON, the deserialised data structure is identical on the Perl level.	55	by JSON, the deserialised data structure is identical on the Perl level.
50	(e.g. the string "2.0" doesn't suddenly become "2").	56	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		57	like a number).
51		58
52	=item * strict checking of JSON correctness	59	=item * strict checking of JSON correctness
53		60
54	There is no guessing, no generating of illegal JSON texts by default,	61	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	62	and only JSON is accepted as input by default (the latter is a security
…		…
66	interface.	73	interface.
67		74
68	=item * reasonably versatile output formats	75	=item * reasonably versatile output formats
69		76
70	You can choose between the most compact guarenteed single-line format	77	You can choose between the most compact guarenteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	78	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	79	(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	80	unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	81	stuff). Or you can combine those features in whatever way you like.
75		82
76	=back	83	=back
77		84
78	=cut	85	=cut
79		86
80	package JSON::XS;	87	package JSON::XS;
81		88
82	use strict;	89	use strict;
83		90
84	BEGIN {
85	our $VERSION = '0.7';	91	our $VERSION = '1.5';
86	our @ISA = qw(Exporter);	92	our @ISA = qw(Exporter);
87		93
88	our @EXPORT = qw(to_json from_json);	94	our @EXPORT = qw(to_json from_json);
89	require Exporter;
90		95
91	require XSLoader;	96	use Exporter;
92	XSLoader::load JSON::XS::, $VERSION;	97	use XSLoader;
93	}
94		98
95	=head1 FUNCTIONAL INTERFACE	99	=head1 FUNCTIONAL INTERFACE
96		100
97	The following convinience methods are provided by this module. They are	101	The following convinience methods are provided by this module. They are
98	exported by default:	102	exported by default:
99		103
100	=over 4	104	=over 4
101		105
102	=item $json_text = to_json $perl_scalar	106	=item $json_text = to_json $perl_scalar
103		107
104	Converts the given Perl data structure (a simple scalar or a reference to	108	Converts the given Perl data structure to a UTF-8 encoded, binary string
105	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	109	(that is, the string contains octets only). Croaks on error.
106	octets only). Croaks on error.
107		110
108	This function call is functionally identical to:	111	This function call is functionally identical to:
109		112
110	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	113	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
111		114
112	except being faster.	115	except being faster.
113		116
114	=item $perl_scalar = from_json $json_text	117	=item $perl_scalar = from_json $json_text
115		118
116	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	119	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries
117	parse that as an UTF-8 encoded JSON text, returning the resulting simple	120	to parse that as an UTF-8 encoded JSON text, returning the resulting
118	scalar or reference. Croaks on error.	121	reference. Croaks on error.
119		122
120	This function call is functionally identical to:	123	This function call is functionally identical to:
121		124
122	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	125	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
123		126
124	except being faster.	127	except being faster.
125		128
		129	=item $is_boolean = JSON::XS::is_bool $scalar
		130
		131	Returns true if the passed scalar represents either JSON::XS::true or
		132	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		133	and are used to represent JSON C<true> and C<false> values in Perl.
		134
		135	See MAPPING, below, for more information on how JSON values are mapped to
		136	Perl.
		137
126	=back	138	=back
		139
		140
		141	=head1 A FEW NOTES ON UNICODE AND PERL
		142
		143	Since this often leads to confusion, here are a few very clear words on
		144	how Unicode works in Perl, modulo bugs.
		145
		146	=over 4
		147
		148	=item 1. Perl strings can store characters with ordinal values > 255.
		149
		150	This enables you to store unicode characters as single characters in a
		151	Perl string - very natural.
		152
		153	=item 2. Perl does I<not> associate an encoding with your strings.
		154
		155	Unless you force it to, e.g. when matching it against a regex, or printing
		156	the scalar to a file, in which case Perl either interprets your string as
		157	locale-encoded text, octets/binary, or as Unicode, depending on various
		158	settings. In no case is an encoding stored together with your data, it is
		159	I<use> that decides encoding, not any magical metadata.
		160
		161	=item 3. The internal utf-8 flag has no meaning with regards to the
		162	encoding of your string.
		163
		164	Just ignore that flag unless you debug a Perl bug, a module written in
		165	XS or want to dive into the internals of perl. Otherwise it will only
		166	confuse you, as, despite the name, it says nothing about how your string
		167	is encoded. You can have unicode strings with that flag set, with that
		168	flag clear, and you can have binary data with that flag set and that flag
		169	clear. Other possibilities exist, too.
		170
		171	If you didn't know about that flag, just the better, pretend it doesn't
		172	exist.
		173
		174	=item 4. A "Unicode String" is simply a string where each character can be
		175	validly interpreted as a Unicode codepoint.
		176
		177	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
		178	Unicode string encoded in UTF-8, giving you a binary string.
		179
		180	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
		181
		182	Its a fact. Learn to live with it.
		183
		184	=back
		185
		186	I hope this helps :)
		187
127		188
128	=head1 OBJECT-ORIENTED INTERFACE	189	=head1 OBJECT-ORIENTED INTERFACE
129		190
130	The object oriented interface lets you configure your own encoding or	191	The object oriented interface lets you configure your own encoding or
131	decoding style, within the limits of supported formats.	192	decoding style, within the limits of supported formats.
…		…
147		208
148	If C<$enable> is true (or missing), then the C<encode> method will not	209	If C<$enable> is true (or missing), then the C<encode> method will not
149	generate characters outside the code range C<0..127> (which is ASCII). Any	210	generate characters outside the code range C<0..127> (which is ASCII). Any
150	unicode characters outside that range will be escaped using either a	211	unicode characters outside that range will be escaped using either a
151	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	212	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
152	as per RFC4627.	213	as per RFC4627. The resulting encoded JSON text can be treated as a native
		214	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		215	or any other superset of ASCII.
153		216
154	If C<$enable> is false, then the C<encode> method will not escape Unicode	217	If C<$enable> is false, then the C<encode> method will not escape Unicode
155	characters unless required by the JSON syntax. This results in a faster	218	characters unless required by the JSON syntax or other flags. This results
156	and more compact format.	219	in a faster and more compact format.
		220
		221	The main use for this flag is to produce JSON texts that can be
		222	transmitted over a 7-bit channel, as the encoded JSON texts will not
		223	contain any 8 bit characters.
157		224
158	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	225	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
159	=> ["\ud801\udc01"]	226	=> ["\ud801\udc01"]
		227
		228	=item $json = $json->latin1 ([$enable])
		229
		230	If C<$enable> is true (or missing), then the C<encode> method will encode
		231	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		232	outside the code range C<0..255>. The resulting string can be treated as a
		233	latin1-encoded JSON text or a native unicode string. The C<decode> method
		234	will not be affected in any way by this flag, as C<decode> by default
		235	expects unicode, which is a strict superset of latin1.
		236
		237	If C<$enable> is false, then the C<encode> method will not escape Unicode
		238	characters unless required by the JSON syntax or other flags.
		239
		240	The main use for this flag is efficiently encoding binary data as JSON
		241	text, as most octets will not be escaped, resulting in a smaller encoded
		242	size. The disadvantage is that the resulting JSON text is encoded
		243	in latin1 (and must correctly be treated as such when storing and
		244	transfering), a rare encoding for JSON. It is therefore most useful when
		245	you want to store data structures known to contain binary data efficiently
		246	in files or databases, not when talking to other JSON encoders/decoders.
		247
		248	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		249	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
160		250
161	=item $json = $json->utf8 ([$enable])	251	=item $json = $json->utf8 ([$enable])
162		252
163	If C<$enable> is true (or missing), then the C<encode> method will encode	253	If C<$enable> is true (or missing), then the C<encode> method will encode
164	the JSON result into UTF-8, as required by many protocols, while the	254	the JSON result into UTF-8, as required by many protocols, while the
…		…
240		330
241	Example, space_before and indent disabled, space_after enabled:	331	Example, space_before and indent disabled, space_after enabled:
242		332
243	{"key": "value"}	333	{"key": "value"}
244		334
		335	=item $json = $json->relaxed ([$enable])
		336
		337	If C<$enable> is true (or missing), then C<decode> will accept some
		338	extensions to normal JSON syntax (see below). C<encode> will not be
		339	affected in anyway. I<Be aware that this option makes you accept invalid
		340	JSON texts as if they were valid!>. I suggest only to use this option to
		341	parse application-specific files written by humans (configuration files,
		342	resource files etc.)
		343
		344	If C<$enable> is false (the default), then C<decode> will only accept
		345	valid JSON texts.
		346
		347	Currently accepted extensions are:
		348
		349	=over 4
		350
		351	=item * list items can have an end-comma
		352
		353	JSON I<separates> array elements and key-value pairs with commas. This
		354	can be annoying if you write JSON texts manually and want to be able to
		355	quickly append elements, so this extension accepts comma at the end of
		356	such items not just between them:
		357
		358	[
		359	1,
		360	2, <- this comma not normally allowed
		361	]
		362	{
		363	"k1": "v1",
		364	"k2": "v2", <- this comma not normally allowed
		365	}
		366
		367	=item * shell-style '#'-comments
		368
		369	Whenever JSON allows whitespace, shell-style comments are additionally
		370	allowed. They are terminated by the first carriage-return or line-feed
		371	character, after which more white-space and comments are allowed.
		372
		373	[
		374	1, # this comment not allowed in JSON
		375	# neither this one...
		376	]
		377
		378	=back
		379
245	=item $json = $json->canonical ([$enable])	380	=item $json = $json->canonical ([$enable])
246		381
247	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	382	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
248	by sorting their keys. This is adding a comparatively high overhead.	383	by sorting their keys. This is adding a comparatively high overhead.
249		384
…		…
274	resulting in an invalid JSON text:	409	resulting in an invalid JSON text:
275		410
276	JSON::XS->new->allow_nonref->encode ("Hello, World!")	411	JSON::XS->new->allow_nonref->encode ("Hello, World!")
277	=> "Hello, World!"	412	=> "Hello, World!"
278		413
		414	=item $json = $json->allow_blessed ([$enable])
		415
		416	If C<$enable> is true (or missing), then the C<encode> method will not
		417	barf when it encounters a blessed reference. Instead, the value of the
		418	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		419	disabled or no C<to_json> method found) or a representation of the
		420	object (C<convert_blessed> enabled and C<to_json> method found) is being
		421	encoded. Has no effect on C<decode>.
		422
		423	If C<$enable> is false (the default), then C<encode> will throw an
		424	exception when it encounters a blessed object.
		425
		426	=item $json = $json->convert_blessed ([$enable])
		427
		428	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		429	blessed object, will check for the availability of the C<TO_JSON> method
		430	on the object's class. If found, it will be called in scalar context
		431	and the resulting scalar will be encoded instead of the object. If no
		432	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		433	to do.
		434
		435	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		436	returns other blessed objects, those will be handled in the same
		437	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		438	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		439	methods called by the Perl core (== not by the user of the object) are
		440	usually in upper case letters and to avoid collisions with the C<to_json>
		441	function.
		442
		443	This setting does not yet influence C<decode> in any way, but in the
		444	future, global hooks might get installed that influence C<decode> and are
		445	enabled by this setting.
		446
		447	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		448	to do when a blessed object is found.
		449
		450	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		451
		452	When C<$coderef> is specified, it will be called from C<decode> each
		453	time it decodes a JSON object. The only argument is a reference to the
		454	newly-created hash. If the code references returns a single scalar (which
		455	need not be a reference), this value (i.e. a copy of that scalar to avoid
		456	aliasing) is inserted into the deserialised data structure. If it returns
		457	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		458	original deserialised hash will be inserted. This setting can slow down
		459	decoding considerably.
		460
		461	When C<$coderef> is omitted or undefined, any existing callback will
		462	be removed and C<decode> will not change the deserialised hash in any
		463	way.
		464
		465	Example, convert all JSON objects into the integer 5:
		466
		467	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		468	# returns [5]
		469	$js->decode ('[{}]')
		470	# throw an exception because allow_nonref is not enabled
		471	# so a lone 5 is not allowed.
		472	$js->decode ('{"a":1, "b":2}');
		473
		474	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		475
		476	Works remotely similar to C<filter_json_object>, but is only called for
		477	JSON objects having a single key named C<$key>.
		478
		479	This C<$coderef> is called before the one specified via
		480	C<filter_json_object>, if any. It gets passed the single value in the JSON
		481	object. If it returns a single value, it will be inserted into the data
		482	structure. If it returns nothing (not even C<undef> but the empty list),
		483	the callback from C<filter_json_object> will be called next, as if no
		484	single-key callback were specified.
		485
		486	If C<$coderef> is omitted or undefined, the corresponding callback will be
		487	disabled. There can only ever be one callback for a given key.
		488
		489	As this callback gets called less often then the C<filter_json_object>
		490	one, decoding speed will not usually suffer as much. Therefore, single-key
		491	objects make excellent targets to serialise Perl objects into, especially
		492	as single-key JSON objects are as close to the type-tagged value concept
		493	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		494	support this in any way, so you need to make sure your data never looks
		495	like a serialised Perl hash.
		496
		497	Typical names for the single object key are C<__class_whatever__>, or
		498	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		499	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		500	with real hashes.
		501
		502	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		503	into the corresponding C<< $WIDGET{<id>} >> object:
		504
		505	# return whatever is in $WIDGET{5}:
		506	JSON::XS
		507	->new
		508	->filter_json_single_key_object (__widget__ => sub {
		509	$WIDGET{ $_[0] }
		510	})
		511	->decode ('{"__widget__": 5')
		512
		513	# this can be used with a TO_JSON method in some "widget" class
		514	# for serialisation to json:
		515	sub WidgetBase::TO_JSON {
		516	my ($self) = @_;
		517
		518	unless ($self->{id}) {
		519	$self->{id} = ..get..some..id..;
		520	$WIDGET{$self->{id}} = $self;
		521	}
		522
		523	{ __widget__ => $self->{id} }
		524	}
		525
279	=item $json = $json->shrink ([$enable])	526	=item $json = $json->shrink ([$enable])
280		527
281	Perl usually over-allocates memory a bit when allocating space for	528	Perl usually over-allocates memory a bit when allocating space for
282	strings. This flag optionally resizes strings generated by either	529	strings. This flag optionally resizes strings generated by either
283	C<encode> or C<decode> to their minimum size possible. This can save	530	C<encode> or C<decode> to their minimum size possible. This can save
284	memory when your JSON texts are either very very long or you have many	531	memory when your JSON texts are either very very long or you have many
285	short strings. It will also try to downgrade any strings to octet-form	532	short strings. It will also try to downgrade any strings to octet-form
286	if possible: perl stores strings internally either in an encoding called	533	if possible: perl stores strings internally either in an encoding called
287	UTF-X or in octet-form. The latter cannot store everything but uses less	534	UTF-X or in octet-form. The latter cannot store everything but uses less
288	space in general.	535	space in general (and some buggy Perl or C code might even rely on that
		536	internal representation being used).
289		537
		538	The actual definition of what shrink does might change in future versions,
		539	but it will always try to save space at the expense of time.
		540
290	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	541	If C<$enable> is true (or missing), the string returned by C<encode> will
291	while all strings generated by C<decode> will also be shrunk-to-fit.	542	be shrunk-to-fit, while all strings generated by C<decode> will also be
		543	shrunk-to-fit.
292		544
293	If C<$enable> is false, then the normal perl allocation algorithms are used.	545	If C<$enable> is false, then the normal perl allocation algorithms are used.
294	If you work with your data, then this is likely to be faster.	546	If you work with your data, then this is likely to be faster.
295		547
296	In the future, this setting might control other things, such as converting	548	In the future, this setting might control other things, such as converting
297	strings that look like integers or floats into integers or floats	549	strings that look like integers or floats into integers or floats
298	internally (there is no difference on the Perl level), saving space.	550	internally (there is no difference on the Perl level), saving space.
		551
		552	=item $json = $json->max_depth ([$maximum_nesting_depth])
		553
		554	Sets the maximum nesting level (default C<512>) accepted while encoding
		555	or decoding. If the JSON text or Perl data structure has an equal or
		556	higher nesting level then this limit, then the encoder and decoder will
		557	stop and croak at that point.
		558
		559	Nesting level is defined by number of hash- or arrayrefs that the encoder
		560	needs to traverse to reach a given point or the number of C<{> or C<[>
		561	characters without their matching closing parenthesis crossed to reach a
		562	given character in a string.
		563
		564	Setting the maximum depth to one disallows any nesting, so that ensures
		565	that the object is only a single hash/object or array.
		566
		567	The argument to C<max_depth> will be rounded up to the next highest power
		568	of two. If no argument is given, the highest possible setting will be
		569	used, which is rarely useful.
		570
		571	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		572
		573	=item $json = $json->max_size ([$maximum_string_size])
		574
		575	Set the maximum length a JSON text may have (in bytes) where decoding is
		576	being attempted. The default is C<0>, meaning no limit. When C<decode>
		577	is called on a string longer then this number of characters it will not
		578	attempt to decode the string but throw an exception. This setting has no
		579	effect on C<encode> (yet).
		580
		581	The argument to C<max_size> will be rounded up to the next B<highest>
		582	power of two (so may be more than requested). If no argument is given, the
		583	limit check will be deactivated (same as when C<0> is specified).
		584
		585	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
299		586
300	=item $json_text = $json->encode ($perl_scalar)	587	=item $json_text = $json->encode ($perl_scalar)
301		588
302	Converts the given Perl data structure (a simple scalar or a reference	589	Converts the given Perl data structure (a simple scalar or a reference
303	to a hash or array) to its JSON representation. Simple scalars will be	590	to a hash or array) to its JSON representation. Simple scalars will be
…		…
313		600
314	JSON numbers and strings become simple Perl scalars. JSON arrays become	601	JSON numbers and strings become simple Perl scalars. JSON arrays become
315	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	602	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
316	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	603	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
317		604
		605	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		606
		607	This works like the C<decode> method, but instead of raising an exception
		608	when there is trailing garbage after the first JSON object, it will
		609	silently stop parsing there and return the number of characters consumed
		610	so far.
		611
		612	This is useful if your JSON texts are not delimited by an outer protocol
		613	(which is not the brightest thing to do in the first place) and you need
		614	to know where the JSON text ends.
		615
		616	JSON::XS->new->decode_prefix ("[1] the tail")
		617	=> ([], 3)
		618
318	=back	619	=back
		620
319		621
320	=head1 MAPPING	622	=head1 MAPPING
321		623
322	This section describes how JSON::XS maps Perl values to JSON values and	624	This section describes how JSON::XS maps Perl values to JSON values and
323	vice versa. These mappings are designed to "do the right thing" in most	625	vice versa. These mappings are designed to "do the right thing" in most
…		…
326		628
327	For the more enlightened: note that in the following descriptions,	629	For the more enlightened: note that in the following descriptions,
328	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	630	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
329	refers to the abstract Perl language itself.	631	refers to the abstract Perl language itself.
330		632
		633
331	=head2 JSON -> PERL	634	=head2 JSON -> PERL
332		635
333	=over 4	636	=over 4
334		637
335	=item object	638	=item object
…		…
347	are represented by the same codepoints in the Perl string, so no manual	650	are represented by the same codepoints in the Perl string, so no manual
348	decoding is necessary.	651	decoding is necessary.
349		652
350	=item number	653	=item number
351		654
352	A JSON number becomes either an integer or numeric (floating point)	655	A JSON number becomes either an integer, numeric (floating point) or
353	scalar in perl, depending on its range and any fractional parts. On the	656	string scalar in perl, depending on its range and any fractional parts. On
354	Perl level, there is no difference between those as Perl handles all the	657	the Perl level, there is no difference between those as Perl handles all
355	conversion details, but an integer may take slightly less memory and might	658	the conversion details, but an integer may take slightly less memory and
356	represent more values exactly than (floating point) numbers.	659	might represent more values exactly than (floating point) numbers.
		660
		661	If the number consists of digits only, JSON::XS will try to represent
		662	it as an integer value. If that fails, it will try to represent it as
		663	a numeric (floating point) value if that is possible without loss of
		664	precision. Otherwise it will preserve the number as a string value.
		665
		666	Numbers containing a fractional or exponential part will always be
		667	represented as numeric (floating point) values, possibly at a loss of
		668	precision.
		669
		670	This might create round-tripping problems as numbers might become strings,
		671	but as Perl is typeless there is no other way to do it.
357		672
358	=item true, false	673	=item true, false
359		674
360	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	675	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
361	this process. Future versions might represent those values differently,	676	respectively. They are overloaded to act almost exactly like the numbers
362	but they will be guarenteed to act like these integers would normally in	677	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
363	Perl.	678	the C<JSON::XS::is_bool> function.
364		679
365	=item null	680	=item null
366		681
367	A JSON null atom becomes C<undef> in Perl.	682	A JSON null atom becomes C<undef> in Perl.
368		683
369	=back	684	=back
		685
370		686
371	=head2 PERL -> JSON	687	=head2 PERL -> JSON
372		688
373	The mapping from Perl to JSON is slightly more difficult, as Perl is a	689	The mapping from Perl to JSON is slightly more difficult, as Perl is a
374	truly typeless language, so we can only guess which JSON type is meant by	690	truly typeless language, so we can only guess which JSON type is meant by
…		…
377	=over 4	693	=over 4
378		694
379	=item hash references	695	=item hash references
380		696
381	Perl hash references become JSON objects. As there is no inherent ordering	697	Perl hash references become JSON objects. As there is no inherent ordering
382	in hash keys, they will usually be encoded in a pseudo-random order that	698	in hash keys (or JSON objects), they will usually be encoded in a
383	can change between runs of the same program but stays generally the same	699	pseudo-random order that can change between runs of the same program but
384	within a single run of a program. JSON::XS can optionally sort the hash	700	stays generally the same within a single run of a program. JSON::XS can
385	keys (determined by the I<canonical> flag), so the same datastructure	701	optionally sort the hash keys (determined by the I<canonical> flag), so
386	will serialise to the same JSON text (given same settings and version of	702	the same datastructure will serialise to the same JSON text (given same
387	JSON::XS), but this incurs a runtime overhead.	703	settings and version of JSON::XS), but this incurs a runtime overhead
		704	and is only rarely useful, e.g. when you want to compare some JSON text
		705	against another for equality.
388		706
389	=item array references	707	=item array references
390		708
391	Perl array references become JSON arrays.	709	Perl array references become JSON arrays.
		710
		711	=item other references
		712
		713	Other unblessed references are generally not allowed and will cause an
		714	exception to be thrown, except for references to the integers C<0> and
		715	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		716	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		717
		718	to_json [\0,JSON::XS::true] # yields [false,true]
		719
		720	=item JSON::XS::true, JSON::XS::false
		721
		722	These special values become JSON true and JSON false values,
		723	respectively. You can also use C<\1> and C<\0> directly if you want.
392		724
393	=item blessed objects	725	=item blessed objects
394		726
395	Blessed objects are not allowed. JSON::XS currently tries to encode their	727	Blessed objects are not allowed. JSON::XS currently tries to encode their
396	underlying representation (hash- or arrayref), but this behaviour might	728	underlying representation (hash- or arrayref), but this behaviour might
…		…
429	$x *= 1; # same thing, the choise is yours.	761	$x *= 1; # same thing, the choise is yours.
430		762
431	You can not currently output JSON booleans or force the type in other,	763	You can not currently output JSON booleans or force the type in other,
432	less obscure, ways. Tell me if you need this capability.	764	less obscure, ways. Tell me if you need this capability.
433		765
434	=item circular data structures
435
436	Those will be encoded until memory or stackspace runs out.
437
438	=back	766	=back
		767
439		768
440	=head1 COMPARISON	769	=head1 COMPARISON
441		770
442	As already mentioned, this module was created because none of the existing	771	As already mentioned, this module was created because none of the existing
443	JSON modules could be made to work correctly. First I will describe the	772	JSON modules could be made to work correctly. First I will describe the
…		…
521		850
522	Does not check input for validity.	851	Does not check input for validity.
523		852
524	=back	853	=back
525		854
		855
		856	=head2 JSON and YAML
		857
		858	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		859	however, a mass hysteria and very far from the truth. In general, there is
		860	no way to configure JSON::XS to output a data structure as valid YAML.
		861
		862	If you really must use JSON::XS to generate YAML, you should use this
		863	algorithm (subject to change in future versions):
		864
		865	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		866	my $yaml = $to_yaml->encode ($ref) . "\n";
		867
		868	This will usually generate JSON texts that also parse as valid
		869	YAML. Please note that YAML has hardcoded limits on (simple) object key
		870	lengths that JSON doesn't have, so you should make sure that your hash
		871	keys are noticably shorter than the 1024 characters YAML allows.
		872
		873	There might be other incompatibilities that I am not aware of. In general
		874	you should not try to generate YAML with a JSON generator or vice versa,
		875	or try to parse JSON with a YAML parser or vice versa: chances are high
		876	that you will run into severe interoperability problems.
		877
		878
526	=head2 SPEED	879	=head2 SPEED
527		880
528	It seems that JSON::XS is surprisingly fast, as shown in the following	881	It seems that JSON::XS is surprisingly fast, as shown in the following
529	tables. They have been generated with the help of the C<eg/bench> program	882	tables. They have been generated with the help of the C<eg/bench> program
530	in the JSON::XS distribution, to make it easy to compare on your own	883	in the JSON::XS distribution, to make it easy to compare on your own
531	system.	884	system.
532		885
533	First comes a comparison between various modules using a very short JSON	886	First comes a comparison between various modules using a very short
534	string:	887	single-line JSON string:
535		888
536	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	889	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		890	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
537		891
538	It shows the number of encodes/decodes per second (JSON::XS uses the	892	It shows the number of encodes/decodes per second (JSON::XS uses
539	functional interface, while JSON::XS/2 uses the OO interface with	893	the functional interface, while JSON::XS/2 uses the OO interface
540	pretty-printing and hashkey sorting enabled). Higher is better:	894	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		895	shrink). Higher is better:
541		896
		897	Storable \| 15779.925 \| 14169.946 \|
		898	-----------+------------+------------+
542	module \| encode \| decode \|	899	module \| encode \| decode \|
543	-----------\|------------\|------------\|	900	-----------\|------------\|------------\|
544	JSON \| 11488.516 \| 7823.035 \|	901	JSON \| 4990.842 \| 4088.813 \|
545	JSON::DWIW \| 94708.054 \| 129094.260 \|	902	JSON::DWIW \| 51653.990 \| 71575.154 \|
546	JSON::PC \| 63884.157 \| 128528.212 \|	903	JSON::PC \| 65948.176 \| 74631.744 \|
547	JSON::Syck \| 34898.677 \| 42096.911 \|	904	JSON::PP \| 8931.652 \| 3817.168 \|
548	JSON::XS \| 654027.064 \| 396423.669 \|	905	JSON::Syck \| 24877.248 \| 27776.848 \|
549	JSON::XS/2 \| 371564.190 \| 371725.613 \|	906	JSON::XS \| 388361.481 \| 227951.304 \|
		907	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		908	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		909	Storable \| 16500.016 \| 135300.129 \|
550	-----------+------------+------------+	910	-----------+------------+------------+
551		911
552	That is, JSON::XS is more than six times faster than JSON::DWIW on	912	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
553	encoding, more than three times faster on decoding, and about thirty times	913	about three times faster on decoding, and over fourty times faster
554	faster than JSON, even with pretty-printing and key sorting.	914	than JSON, even with pretty-printing and key sorting. It also compares
		915	favourably to Storable for small amounts of data.
555		916
556	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	917	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
557	search API (http://nanoref.com/yahooapis/mgPdGg):	918	search API (http://nanoref.com/yahooapis/mgPdGg):
558		919
559	module \| encode \| decode \|	920	module \| encode \| decode \|
560	-----------\|------------\|------------\|	921	-----------\|------------\|------------\|
561	JSON \| 273.023 \| 44.674 \|	922	JSON \| 55.260 \| 34.971 \|
562	JSON::DWIW \| 1089.383 \| 1145.704 \|	923	JSON::DWIW \| 825.228 \| 1082.513 \|
563	JSON::PC \| 3097.419 \| 2393.921 \|	924	JSON::PC \| 3571.444 \| 2394.829 \|
564	JSON::Syck \| 514.060 \| 843.053 \|	925	JSON::PP \| 210.987 \| 32.574 \|
565	JSON::XS \| 6479.668 \| 3636.364 \|	926	JSON::Syck \| 552.551 \| 787.544 \|
566	JSON::XS/2 \| 3774.221 \| 3599.124 \|	927	JSON::XS \| 5780.463 \| 4854.519 \|
		928	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		929	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		930	Storable \| 4445.002 \| 5235.027 \|
567	-----------+------------+------------+	931	-----------+------------+------------+
568		932
569	Again, JSON::XS leads by far.	933	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		934	decodes faster).
570		935
571	On large strings containing lots of high unicode characters, some modules	936	On large strings containing lots of high unicode characters, some modules
572	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	937	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
573	will be broken due to missing (or wrong) unicode handling. Others refuse	938	will be broken due to missing (or wrong) unicode handling. Others refuse
574	to decode or encode properly, so it was impossible to prepare a fair	939	to decode or encode properly, so it was impossible to prepare a fair
575	comparison table for that case.	940	comparison table for that case.
576		941
577	=head1 RESOURCE LIMITS
578		942
579	JSON::XS does not impose any limits on the size of JSON texts or Perl	943	=head1 SECURITY CONSIDERATIONS
580	values they represent - if your machine can handle it, JSON::XS will	944
581	encode or decode it. Future versions might optionally impose structure	945	When you are using JSON in a protocol, talking to untrusted potentially
582	depth and memory use resource limits.	946	hostile creatures requires relatively few measures.
		947
		948	First of all, your JSON decoder should be secure, that is, should not have
		949	any buffer overflows. Obviously, this module should ensure that and I am
		950	trying hard on making that true, but you never know.
		951
		952	Second, you need to avoid resource-starving attacks. That means you should
		953	limit the size of JSON texts you accept, or make sure then when your
		954	resources run out, thats just fine (e.g. by using a separate process that
		955	can crash safely). The size of a JSON text in octets or characters is
		956	usually a good indication of the size of the resources required to decode
		957	it into a Perl structure. While JSON::XS can check the size of the JSON
		958	text, it might be too late when you already have it in memory, so you
		959	might want to check the size before you accept the string.
		960
		961	Third, JSON::XS recurses using the C stack when decoding objects and
		962	arrays. The C stack is a limited resource: for instance, on my amd64
		963	machine with 8MB of stack size I can decode around 180k nested arrays but
		964	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		965	to free the temporary). If that is exceeded, the program crashes. to be
		966	conservative, the default nesting limit is set to 512. If your process
		967	has a smaller stack, you should adjust this setting accordingly with the
		968	C<max_depth> method.
		969
		970	And last but least, something else could bomb you that I forgot to think
		971	of. In that case, you get to keep the pieces. I am always open for hints,
		972	though...
		973
		974	If you are using JSON::XS to return packets to consumption
		975	by javascript scripts in a browser you should have a look at
		976	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		977	you are vulnerable to some common attack vectors (which really are browser
		978	design bugs, but it is still you who will have to deal with it, as major
		979	browser developers care only for features, not about doing security
		980	right).
		981
		982
		983	=head1 THREADS
		984
		985	This module is I<not> guarenteed to be thread safe and there are no
		986	plans to change this until Perl gets thread support (as opposed to the
		987	horribly slow so-called "threads" which are simply slow and bloated
		988	process simulations - use fork, its I<much> faster, cheaper, better).
		989
		990	(It might actually work, but you ahve ben warned).
		991
583		992
584	=head1 BUGS	993	=head1 BUGS
585		994
586	While the goal of this module is to be correct, that unfortunately does	995	While the goal of this module is to be correct, that unfortunately does
587	not mean its bug-free, only that I think its design is bug-free. It is	996	not mean its bug-free, only that I think its design is bug-free. It is
588	still very young and not well-tested. If you keep reporting bugs they will	997	still relatively early in its development. If you keep reporting bugs they
589	be fixed swiftly, though.	998	will be fixed swiftly, though.
		999
		1000	Please refrain from using rt.cpan.org or any other bug reporting
		1001	service. I put the contact address into my modules for a reason.
590		1002
591	=cut	1003	=cut
		1004
		1005	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		1006	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		1007
		1008	sub true() { $true }
		1009	sub false() { $false }
		1010
		1011	sub is_bool($) {
		1012	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		1013	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		1014	}
		1015
		1016	XSLoader::load "JSON::XS", $VERSION;
		1017
		1018	package JSON::XS::Boolean;
		1019
		1020	use overload
		1021	"0+" => sub { ${$_[0]} },
		1022	"++" => sub { $_[0] = ${$_[0]} + 1 },
		1023	"--" => sub { $_[0] = ${$_[0]} - 1 },
		1024	fallback => 1;
592		1025
593	1;	1026	1;
594		1027
595	=head1 AUTHOR	1028	=head1 AUTHOR
596		1029

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Revision 1.64 by root, Thu Oct 11 23:57:24 2007 UTC