[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 1.62 by root, Thu Oct 11 22:52:52 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:
…		…
121		125
122	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	126	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
123		127
124	except being faster.	128	except being faster.
125		129
		130	=item $is_boolean = JSON::XS::is_bool $scalar
		131
		132	Returns true if the passed scalar represents either JSON::XS::true or
		133	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		134	and are used to represent JSON C<true> and C<false> values in Perl.
		135
		136	See MAPPING, below, for more information on how JSON values are mapped to
		137	Perl.
		138
126	=back	139	=back
		140
127		141
128	=head1 OBJECT-ORIENTED INTERFACE	142	=head1 OBJECT-ORIENTED INTERFACE
129		143
130	The object oriented interface lets you configure your own encoding or	144	The object oriented interface lets you configure your own encoding or
131	decoding style, within the limits of supported formats.	145	decoding style, within the limits of supported formats.
…		…
147		161
148	If C<$enable> is true (or missing), then the C<encode> method will not	162	If C<$enable> is true (or missing), then the C<encode> method will not
149	generate characters outside the code range C<0..127> (which is ASCII). Any	163	generate characters outside the code range C<0..127> (which is ASCII). Any
150	unicode characters outside that range will be escaped using either a	164	unicode characters outside that range will be escaped using either a
151	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	165	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
152	as per RFC4627.	166	as per RFC4627. The resulting encoded JSON text can be treated as a native
		167	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		168	or any other superset of ASCII.
153		169
154	If C<$enable> is false, then the C<encode> method will not escape Unicode	170	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	171	characters unless required by the JSON syntax or other flags. This results
156	and more compact format.	172	in a faster and more compact format.
		173
		174	The main use for this flag is to produce JSON texts that can be
		175	transmitted over a 7-bit channel, as the encoded JSON texts will not
		176	contain any 8 bit characters.
157		177
158	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	178	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
159	=> ["\ud801\udc01"]	179	=> ["\ud801\udc01"]
		180
		181	=item $json = $json->latin1 ([$enable])
		182
		183	If C<$enable> is true (or missing), then the C<encode> method will encode
		184	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		185	outside the code range C<0..255>. The resulting string can be treated as a
		186	latin1-encoded JSON text or a native unicode string. The C<decode> method
		187	will not be affected in any way by this flag, as C<decode> by default
		188	expects unicode, which is a strict superset of latin1.
		189
		190	If C<$enable> is false, then the C<encode> method will not escape Unicode
		191	characters unless required by the JSON syntax or other flags.
		192
		193	The main use for this flag is efficiently encoding binary data as JSON
		194	text, as most octets will not be escaped, resulting in a smaller encoded
		195	size. The disadvantage is that the resulting JSON text is encoded
		196	in latin1 (and must correctly be treated as such when storing and
		197	transfering), a rare encoding for JSON. It is therefore most useful when
		198	you want to store data structures known to contain binary data efficiently
		199	in files or databases, not when talking to other JSON encoders/decoders.
		200
		201	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		202	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
160		203
161	=item $json = $json->utf8 ([$enable])	204	=item $json = $json->utf8 ([$enable])
162		205
163	If C<$enable> is true (or missing), then the C<encode> method will encode	206	If C<$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	207	the JSON result into UTF-8, as required by many protocols, while the
…		…
240		283
241	Example, space_before and indent disabled, space_after enabled:	284	Example, space_before and indent disabled, space_after enabled:
242		285
243	{"key": "value"}	286	{"key": "value"}
244		287
		288	=item $json = $json->relaxed ([$enable])
		289
		290	If C<$enable> is true (or missing), then C<decode> will accept some
		291	extensions to normal JSON syntax (see below). C<encode> will not be
		292	affected in anyway. I<Be aware that this option makes you accept invalid
		293	JSON texts as if they were valid!>. I suggest only to use this option to
		294	parse application-specific files written by humans (configuration files,
		295	resource files etc.)
		296
		297	If C<$enable> is false (the default), then C<decode> will only accept
		298	valid JSON texts.
		299
		300	Currently accepted extensions are:
		301
		302	=over 4
		303
		304	=item * list items can have an end-comma
		305
		306	JSON I<separates> array elements and key-value pairs with commas. This
		307	can be annoying if you write JSON texts manually and want to be able to
		308	quickly append elements, so this extension accepts comma at the end of
		309	such items not just between them:
		310
		311	[
		312	1,
		313	2, <- this comma not normally allowed
		314	]
		315	{
		316	"k1": "v1",
		317	"k2": "v2", <- this comma not normally allowed
		318	}
		319
		320	=item * shell-style '#'-comments
		321
		322	Whenever JSON allows whitespace, shell-style comments are additionally
		323	allowed. They are terminated by the first carriage-return or line-feed
		324	character, after which more white-space and comments are allowed.
		325
		326	[
		327	1, # this comment not allowed in JSON
		328	# neither this one...
		329	]
		330
		331	=back
		332
245	=item $json = $json->canonical ([$enable])	333	=item $json = $json->canonical ([$enable])
246		334
247	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	335	If C<$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.	336	by sorting their keys. This is adding a comparatively high overhead.
249		337
…		…
274	resulting in an invalid JSON text:	362	resulting in an invalid JSON text:
275		363
276	JSON::XS->new->allow_nonref->encode ("Hello, World!")	364	JSON::XS->new->allow_nonref->encode ("Hello, World!")
277	=> "Hello, World!"	365	=> "Hello, World!"
278		366
		367	=item $json = $json->allow_blessed ([$enable])
		368
		369	If C<$enable> is true (or missing), then the C<encode> method will not
		370	barf when it encounters a blessed reference. Instead, the value of the
		371	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		372	disabled or no C<to_json> method found) or a representation of the
		373	object (C<convert_blessed> enabled and C<to_json> method found) is being
		374	encoded. Has no effect on C<decode>.
		375
		376	If C<$enable> is false (the default), then C<encode> will throw an
		377	exception when it encounters a blessed object.
		378
		379	=item $json = $json->convert_blessed ([$enable])
		380
		381	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		382	blessed object, will check for the availability of the C<TO_JSON> method
		383	on the object's class. If found, it will be called in scalar context
		384	and the resulting scalar will be encoded instead of the object. If no
		385	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		386	to do.
		387
		388	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		389	returns other blessed objects, those will be handled in the same
		390	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		391	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		392	methods called by the Perl core (== not by the user of the object) are
		393	usually in upper case letters and to avoid collisions with the C<to_json>
		394	function.
		395
		396	This setting does not yet influence C<decode> in any way, but in the
		397	future, global hooks might get installed that influence C<decode> and are
		398	enabled by this setting.
		399
		400	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		401	to do when a blessed object is found.
		402
		403	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		404
		405	When C<$coderef> is specified, it will be called from C<decode> each
		406	time it decodes a JSON object. The only argument is a reference to the
		407	newly-created hash. If the code references returns a single scalar (which
		408	need not be a reference), this value (i.e. a copy of that scalar to avoid
		409	aliasing) is inserted into the deserialised data structure. If it returns
		410	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		411	original deserialised hash will be inserted. This setting can slow down
		412	decoding considerably.
		413
		414	When C<$coderef> is omitted or undefined, any existing callback will
		415	be removed and C<decode> will not change the deserialised hash in any
		416	way.
		417
		418	Example, convert all JSON objects into the integer 5:
		419
		420	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		421	# returns [5]
		422	$js->decode ('[{}]')
		423	# throw an exception because allow_nonref is not enabled
		424	# so a lone 5 is not allowed.
		425	$js->decode ('{"a":1, "b":2}');
		426
		427	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		428
		429	Works remotely similar to C<filter_json_object>, but is only called for
		430	JSON objects having a single key named C<$key>.
		431
		432	This C<$coderef> is called before the one specified via
		433	C<filter_json_object>, if any. It gets passed the single value in the JSON
		434	object. If it returns a single value, it will be inserted into the data
		435	structure. If it returns nothing (not even C<undef> but the empty list),
		436	the callback from C<filter_json_object> will be called next, as if no
		437	single-key callback were specified.
		438
		439	If C<$coderef> is omitted or undefined, the corresponding callback will be
		440	disabled. There can only ever be one callback for a given key.
		441
		442	As this callback gets called less often then the C<filter_json_object>
		443	one, decoding speed will not usually suffer as much. Therefore, single-key
		444	objects make excellent targets to serialise Perl objects into, especially
		445	as single-key JSON objects are as close to the type-tagged value concept
		446	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		447	support this in any way, so you need to make sure your data never looks
		448	like a serialised Perl hash.
		449
		450	Typical names for the single object key are C<__class_whatever__>, or
		451	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		452	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		453	with real hashes.
		454
		455	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		456	into the corresponding C<< $WIDGET{<id>} >> object:
		457
		458	# return whatever is in $WIDGET{5}:
		459	JSON::XS
		460	->new
		461	->filter_json_single_key_object (__widget__ => sub {
		462	$WIDGET{ $_[0] }
		463	})
		464	->decode ('{"__widget__": 5')
		465
		466	# this can be used with a TO_JSON method in some "widget" class
		467	# for serialisation to json:
		468	sub WidgetBase::TO_JSON {
		469	my ($self) = @_;
		470
		471	unless ($self->{id}) {
		472	$self->{id} = ..get..some..id..;
		473	$WIDGET{$self->{id}} = $self;
		474	}
		475
		476	{ __widget__ => $self->{id} }
		477	}
		478
279	=item $json = $json->shrink ([$enable])	479	=item $json = $json->shrink ([$enable])
280		480
281	Perl usually over-allocates memory a bit when allocating space for	481	Perl usually over-allocates memory a bit when allocating space for
282	strings. This flag optionally resizes strings generated by either	482	strings. This flag optionally resizes strings generated by either
283	C<encode> or C<decode> to their minimum size possible. This can save	483	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	484	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	485	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	486	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	487	UTF-X or in octet-form. The latter cannot store everything but uses less
288	space in general.	488	space in general (and some buggy Perl or C code might even rely on that
		489	internal representation being used).
289		490
		491	The actual definition of what shrink does might change in future versions,
		492	but it will always try to save space at the expense of time.
		493
290	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	494	If C<$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.	495	be shrunk-to-fit, while all strings generated by C<decode> will also be
		496	shrunk-to-fit.
292		497
293	If C<$enable> is false, then the normal perl allocation algorithms are used.	498	If C<$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.	499	If you work with your data, then this is likely to be faster.
295		500
296	In the future, this setting might control other things, such as converting	501	In the future, this setting might control other things, such as converting
297	strings that look like integers or floats into integers or floats	502	strings that look like integers or floats into integers or floats
298	internally (there is no difference on the Perl level), saving space.	503	internally (there is no difference on the Perl level), saving space.
		504
		505	=item $json = $json->max_depth ([$maximum_nesting_depth])
		506
		507	Sets the maximum nesting level (default C<512>) accepted while encoding
		508	or decoding. If the JSON text or Perl data structure has an equal or
		509	higher nesting level then this limit, then the encoder and decoder will
		510	stop and croak at that point.
		511
		512	Nesting level is defined by number of hash- or arrayrefs that the encoder
		513	needs to traverse to reach a given point or the number of C<{> or C<[>
		514	characters without their matching closing parenthesis crossed to reach a
		515	given character in a string.
		516
		517	Setting the maximum depth to one disallows any nesting, so that ensures
		518	that the object is only a single hash/object or array.
		519
		520	The argument to C<max_depth> will be rounded up to the next highest power
		521	of two. If no argument is given, the highest possible setting will be
		522	used, which is rarely useful.
		523
		524	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		525
		526	=item $json = $json->max_size ([$maximum_string_size])
		527
		528	Set the maximum length a JSON text may have (in bytes) where decoding is
		529	being attempted. The default is C<0>, meaning no limit. When C<decode>
		530	is called on a string longer then this number of characters it will not
		531	attempt to decode the string but throw an exception. This setting has no
		532	effect on C<encode> (yet).
		533
		534	The argument to C<max_size> will be rounded up to the next B<highest>
		535	power of two (so may be more than requested). If no argument is given, the
		536	limit check will be deactivated (same as when C<0> is specified).
		537
		538	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
299		539
300	=item $json_text = $json->encode ($perl_scalar)	540	=item $json_text = $json->encode ($perl_scalar)
301		541
302	Converts the given Perl data structure (a simple scalar or a reference	542	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	543	to a hash or array) to its JSON representation. Simple scalars will be
…		…
313		553
314	JSON numbers and strings become simple Perl scalars. JSON arrays become	554	JSON numbers and strings become simple Perl scalars. JSON arrays become
315	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	555	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>.	556	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
317		557
		558	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		559
		560	This works like the C<decode> method, but instead of raising an exception
		561	when there is trailing garbage after the first JSON object, it will
		562	silently stop parsing there and return the number of characters consumed
		563	so far.
		564
		565	This is useful if your JSON texts are not delimited by an outer protocol
		566	(which is not the brightest thing to do in the first place) and you need
		567	to know where the JSON text ends.
		568
		569	JSON::XS->new->decode_prefix ("[1] the tail")
		570	=> ([], 3)
		571
318	=back	572	=back
		573
319		574
320	=head1 MAPPING	575	=head1 MAPPING
321		576
322	This section describes how JSON::XS maps Perl values to JSON values and	577	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	578	vice versa. These mappings are designed to "do the right thing" in most
…		…
326		581
327	For the more enlightened: note that in the following descriptions,	582	For the more enlightened: note that in the following descriptions,
328	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	583	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
329	refers to the abstract Perl language itself.	584	refers to the abstract Perl language itself.
330		585
		586
331	=head2 JSON -> PERL	587	=head2 JSON -> PERL
332		588
333	=over 4	589	=over 4
334		590
335	=item object	591	=item object
…		…
347	are represented by the same codepoints in the Perl string, so no manual	603	are represented by the same codepoints in the Perl string, so no manual
348	decoding is necessary.	604	decoding is necessary.
349		605
350	=item number	606	=item number
351		607
352	A JSON number becomes either an integer or numeric (floating point)	608	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	609	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	610	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	611	the conversion details, but an integer may take slightly less memory and
356	represent more values exactly than (floating point) numbers.	612	might represent more values exactly than (floating point) numbers.
		613
		614	If the number consists of digits only, JSON::XS will try to represent
		615	it as an integer value. If that fails, it will try to represent it as
		616	a numeric (floating point) value if that is possible without loss of
		617	precision. Otherwise it will preserve the number as a string value.
		618
		619	Numbers containing a fractional or exponential part will always be
		620	represented as numeric (floating point) values, possibly at a loss of
		621	precision.
		622
		623	This might create round-tripping problems as numbers might become strings,
		624	but as Perl is typeless there is no other way to do it.
357		625
358	=item true, false	626	=item true, false
359		627
360	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	628	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
361	this process. Future versions might represent those values differently,	629	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	630	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
363	Perl.	631	the C<JSON::XS::is_bool> function.
364		632
365	=item null	633	=item null
366		634
367	A JSON null atom becomes C<undef> in Perl.	635	A JSON null atom becomes C<undef> in Perl.
368		636
369	=back	637	=back
		638
370		639
371	=head2 PERL -> JSON	640	=head2 PERL -> JSON
372		641
373	The mapping from Perl to JSON is slightly more difficult, as Perl is a	642	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	643	truly typeless language, so we can only guess which JSON type is meant by
…		…
377	=over 4	646	=over 4
378		647
379	=item hash references	648	=item hash references
380		649
381	Perl hash references become JSON objects. As there is no inherent ordering	650	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	651	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	652	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	653	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	654	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	655	the same datastructure will serialise to the same JSON text (given same
387	JSON::XS), but this incurs a runtime overhead.	656	settings and version of JSON::XS), but this incurs a runtime overhead
		657	and is only rarely useful, e.g. when you want to compare some JSON text
		658	against another for equality.
388		659
389	=item array references	660	=item array references
390		661
391	Perl array references become JSON arrays.	662	Perl array references become JSON arrays.
		663
		664	=item other references
		665
		666	Other unblessed references are generally not allowed and will cause an
		667	exception to be thrown, except for references to the integers C<0> and
		668	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		669	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		670
		671	to_json [\0,JSON::XS::true] # yields [false,true]
		672
		673	=item JSON::XS::true, JSON::XS::false
		674
		675	These special values become JSON true and JSON false values,
		676	respectively. You can also use C<\1> and C<\0> directly if you want.
392		677
393	=item blessed objects	678	=item blessed objects
394		679
395	Blessed objects are not allowed. JSON::XS currently tries to encode their	680	Blessed objects are not allowed. JSON::XS currently tries to encode their
396	underlying representation (hash- or arrayref), but this behaviour might	681	underlying representation (hash- or arrayref), but this behaviour might
…		…
429	$x *= 1; # same thing, the choise is yours.	714	$x *= 1; # same thing, the choise is yours.
430		715
431	You can not currently output JSON booleans or force the type in other,	716	You can not currently output JSON booleans or force the type in other,
432	less obscure, ways. Tell me if you need this capability.	717	less obscure, ways. Tell me if you need this capability.
433		718
434	=item circular data structures
435
436	Those will be encoded until memory or stackspace runs out.
437
438	=back	719	=back
		720
439		721
440	=head1 COMPARISON	722	=head1 COMPARISON
441		723
442	As already mentioned, this module was created because none of the existing	724	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	725	JSON modules could be made to work correctly. First I will describe the
…		…
521		803
522	Does not check input for validity.	804	Does not check input for validity.
523		805
524	=back	806	=back
525		807
		808
		809	=head2 JSON and YAML
		810
		811	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		812	however, a mass hysteria and very far from the truth. In general, there is
		813	no way to configure JSON::XS to output a data structure as valid YAML.
		814
		815	If you really must use JSON::XS to generate YAML, you should use this
		816	algorithm (subject to change in future versions):
		817
		818	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		819	my $yaml = $to_yaml->encode ($ref) . "\n";
		820
		821	This will usually generate JSON texts that also parse as valid
		822	YAML. Please note that YAML has hardcoded limits on (simple) object key
		823	lengths that JSON doesn't have, so you should make sure that your hash
		824	keys are noticably shorter than the 1024 characters YAML allows.
		825
		826	There might be other incompatibilities that I am not aware of. In general
		827	you should not try to generate YAML with a JSON generator or vice versa,
		828	or try to parse JSON with a YAML parser or vice versa: chances are high
		829	that you will run into severe interoperability problems.
		830
		831
526	=head2 SPEED	832	=head2 SPEED
527		833
528	It seems that JSON::XS is surprisingly fast, as shown in the following	834	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	835	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	836	in the JSON::XS distribution, to make it easy to compare on your own
531	system.	837	system.
532		838
533	First comes a comparison between various modules using a very short JSON	839	First comes a comparison between various modules using a very short
534	string:	840	single-line JSON string:
535		841
536	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	842	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		843	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
537		844
538	It shows the number of encodes/decodes per second (JSON::XS uses the	845	It shows the number of encodes/decodes per second (JSON::XS uses
539	functional interface, while JSON::XS/2 uses the OO interface with	846	the functional interface, while JSON::XS/2 uses the OO interface
540	pretty-printing and hashkey sorting enabled). Higher is better:	847	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		848	shrink). Higher is better:
541		849
		850	Storable \| 15779.925 \| 14169.946 \|
		851	-----------+------------+------------+
542	module \| encode \| decode \|	852	module \| encode \| decode \|
543	-----------\|------------\|------------\|	853	-----------\|------------\|------------\|
544	JSON \| 11488.516 \| 7823.035 \|	854	JSON \| 4990.842 \| 4088.813 \|
545	JSON::DWIW \| 94708.054 \| 129094.260 \|	855	JSON::DWIW \| 51653.990 \| 71575.154 \|
546	JSON::PC \| 63884.157 \| 128528.212 \|	856	JSON::PC \| 65948.176 \| 74631.744 \|
547	JSON::Syck \| 34898.677 \| 42096.911 \|	857	JSON::PP \| 8931.652 \| 3817.168 \|
548	JSON::XS \| 654027.064 \| 396423.669 \|	858	JSON::Syck \| 24877.248 \| 27776.848 \|
549	JSON::XS/2 \| 371564.190 \| 371725.613 \|	859	JSON::XS \| 388361.481 \| 227951.304 \|
		860	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		861	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		862	Storable \| 16500.016 \| 135300.129 \|
550	-----------+------------+------------+	863	-----------+------------+------------+
551		864
552	That is, JSON::XS is more than six times faster than JSON::DWIW on	865	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	866	about three times faster on decoding, and over fourty times faster
554	faster than JSON, even with pretty-printing and key sorting.	867	than JSON, even with pretty-printing and key sorting. It also compares
		868	favourably to Storable for small amounts of data.
555		869
556	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	870	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
557	search API (http://nanoref.com/yahooapis/mgPdGg):	871	search API (http://nanoref.com/yahooapis/mgPdGg):
558		872
559	module \| encode \| decode \|	873	module \| encode \| decode \|
560	-----------\|------------\|------------\|	874	-----------\|------------\|------------\|
561	JSON \| 273.023 \| 44.674 \|	875	JSON \| 55.260 \| 34.971 \|
562	JSON::DWIW \| 1089.383 \| 1145.704 \|	876	JSON::DWIW \| 825.228 \| 1082.513 \|
563	JSON::PC \| 3097.419 \| 2393.921 \|	877	JSON::PC \| 3571.444 \| 2394.829 \|
564	JSON::Syck \| 514.060 \| 843.053 \|	878	JSON::PP \| 210.987 \| 32.574 \|
565	JSON::XS \| 6479.668 \| 3636.364 \|	879	JSON::Syck \| 552.551 \| 787.544 \|
566	JSON::XS/2 \| 3774.221 \| 3599.124 \|	880	JSON::XS \| 5780.463 \| 4854.519 \|
		881	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		882	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		883	Storable \| 4445.002 \| 5235.027 \|
567	-----------+------------+------------+	884	-----------+------------+------------+
568		885
569	Again, JSON::XS leads by far.	886	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		887	decodes faster).
570		888
571	On large strings containing lots of high unicode characters, some modules	889	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	890	(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	891	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	892	to decode or encode properly, so it was impossible to prepare a fair
575	comparison table for that case.	893	comparison table for that case.
576		894
577	=head1 RESOURCE LIMITS
578		895
579	JSON::XS does not impose any limits on the size of JSON texts or Perl	896	=head1 SECURITY CONSIDERATIONS
580	values they represent - if your machine can handle it, JSON::XS will	897
581	encode or decode it. Future versions might optionally impose structure	898	When you are using JSON in a protocol, talking to untrusted potentially
582	depth and memory use resource limits.	899	hostile creatures requires relatively few measures.
		900
		901	First of all, your JSON decoder should be secure, that is, should not have
		902	any buffer overflows. Obviously, this module should ensure that and I am
		903	trying hard on making that true, but you never know.
		904
		905	Second, you need to avoid resource-starving attacks. That means you should
		906	limit the size of JSON texts you accept, or make sure then when your
		907	resources run out, thats just fine (e.g. by using a separate process that
		908	can crash safely). The size of a JSON text in octets or characters is
		909	usually a good indication of the size of the resources required to decode
		910	it into a Perl structure. While JSON::XS can check the size of the JSON
		911	text, it might be too late when you already have it in memory, so you
		912	might want to check the size before you accept the string.
		913
		914	Third, JSON::XS recurses using the C stack when decoding objects and
		915	arrays. The C stack is a limited resource: for instance, on my amd64
		916	machine with 8MB of stack size I can decode around 180k nested arrays but
		917	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		918	to free the temporary). If that is exceeded, the program crashes. to be
		919	conservative, the default nesting limit is set to 512. If your process
		920	has a smaller stack, you should adjust this setting accordingly with the
		921	C<max_depth> method.
		922
		923	And last but least, something else could bomb you that I forgot to think
		924	of. In that case, you get to keep the pieces. I am always open for hints,
		925	though...
		926
		927	If you are using JSON::XS to return packets to consumption
		928	by javascript scripts in a browser you should have a look at
		929	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		930	you are vulnerable to some common attack vectors (which really are browser
		931	design bugs, but it is still you who will have to deal with it, as major
		932	browser developers care only for features, not about doing security
		933	right).
		934
583		935
584	=head1 BUGS	936	=head1 BUGS
585		937
586	While the goal of this module is to be correct, that unfortunately does	938	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	939	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	940	still relatively early in its development. If you keep reporting bugs they
589	be fixed swiftly, though.	941	will be fixed swiftly, though.
590		942
591	=cut	943	=cut
		944
		945	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		946	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		947
		948	sub true() { $true }
		949	sub false() { $false }
		950
		951	sub is_bool($) {
		952	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		953	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		954	}
		955
		956	XSLoader::load "JSON::XS", $VERSION;
		957
		958	package JSON::XS::Boolean;
		959
		960	use overload
		961	"0+" => sub { ${$_[0]} },
		962	"++" => sub { $_[0] = ${$_[0]} + 1 },
		963	"--" => sub { $_[0] = ${$_[0]} - 1 },
		964	fallback => 1;
592		965
593	1;	966	1;
594		967
595	=head1 AUTHOR	968	=head1 AUTHOR
596		969

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Comparing JSON-XS/XS.pm (file contents): Revision 1.20 by root, Sun Mar 25 00:47:42 2007 UTC vs. Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.20 by root, Sun Mar 25 00:47:42 2007 UTC vs.
Revision 1.62 by root, Thu Oct 11 22:52:52 2007 UTC