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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.22 by root, Sun Mar 25 02:37:00 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

…		…
9	# exported functions, they croak on error	9	# exported functions, they croak on error
10	# and expect/generate UTF-8	10	# and expect/generate UTF-8
11		11
12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
14
15	# objToJson and jsonToObj aliases to to_json and from_json
16	# are exported for compatibility to the JSON module,
17	# but should not be used in new code.
18		14
19	# OO-interface	15	# OO-interface
20		16
21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
…		…
85		81
86	package JSON::XS;	82	package JSON::XS;
87		83
88	use strict;	84	use strict;
89		85
90	BEGIN {
91	our $VERSION = '0.8';	86	our $VERSION = '1.5';
92	our @ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
93		88
94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);	89	our @EXPORT = qw(to_json from_json);
95	require Exporter;
96		90
97	require XSLoader;	91	use Exporter;
98	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
99	}
100		93
101	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
102		95
103	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
104	exported by default:	97	exported by default:
…		…
127		120
128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129		122
130	except being faster.	123	except being faster.
131		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
		133
132	=back	134	=back
		135
133		136
134	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
135		138
136	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
137	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
153		156
154	If C<$enable> is true (or missing), then the C<encode> method will not	157	If C<$enable> is true (or missing), then the C<encode> method will not
155	generate characters outside the code range C<0..127> (which is ASCII). Any	158	generate characters outside the code range C<0..127> (which is ASCII). Any
156	unicode characters outside that range will be escaped using either a	159	unicode characters outside that range will be escaped using either a
157	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
158	as per RFC4627.	161	as per RFC4627. The resulting encoded JSON text can be treated as a native
		162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		163	or any other superset of ASCII.
159		164
160	If C<$enable> is false, then the C<encode> method will not escape Unicode	165	If C<$enable> is false, then the C<encode> method will not escape Unicode
161	characters unless required by the JSON syntax. This results in a faster	166	characters unless required by the JSON syntax or other flags. This results
162	and more compact format.	167	in a faster and more compact format.
		168
		169	The main use for this flag is to produce JSON texts that can be
		170	transmitted over a 7-bit channel, as the encoded JSON texts will not
		171	contain any 8 bit characters.
163		172
164	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
165	=> ["\ud801\udc01"]	174	=> ["\ud801\udc01"]
		175
		176	=item $json = $json->latin1 ([$enable])
		177
		178	If C<$enable> is true (or missing), then the C<encode> method will encode
		179	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		180	outside the code range C<0..255>. The resulting string can be treated as a
		181	latin1-encoded JSON text or a native unicode string. The C<decode> method
		182	will not be affected in any way by this flag, as C<decode> by default
		183	expects unicode, which is a strict superset of latin1.
		184
		185	If C<$enable> is false, then the C<encode> method will not escape Unicode
		186	characters unless required by the JSON syntax or other flags.
		187
		188	The main use for this flag is efficiently encoding binary data as JSON
		189	text, as most octets will not be escaped, resulting in a smaller encoded
		190	size. The disadvantage is that the resulting JSON text is encoded
		191	in latin1 (and must correctly be treated as such when storing and
		192	transfering), a rare encoding for JSON. It is therefore most useful when
		193	you want to store data structures known to contain binary data efficiently
		194	in files or databases, not when talking to other JSON encoders/decoders.
		195
		196	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		197	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
166		198
167	=item $json = $json->utf8 ([$enable])	199	=item $json = $json->utf8 ([$enable])
168		200
169	If C<$enable> is true (or missing), then the C<encode> method will encode	201	If C<$enable> is true (or missing), then the C<encode> method will encode
170	the JSON result into UTF-8, as required by many protocols, while the	202	the JSON result into UTF-8, as required by many protocols, while the
…		…
246		278
247	Example, space_before and indent disabled, space_after enabled:	279	Example, space_before and indent disabled, space_after enabled:
248		280
249	{"key": "value"}	281	{"key": "value"}
250		282
		283	=item $json = $json->relaxed ([$enable])
		284
		285	If C<$enable> is true (or missing), then C<decode> will accept some
		286	extensions to normal JSON syntax (see below). C<encode> will not be
		287	affected in anyway. I<Be aware that this option makes you accept invalid
		288	JSON texts as if they were valid!>. I suggest only to use this option to
		289	parse application-specific files written by humans (configuration files,
		290	resource files etc.)
		291
		292	If C<$enable> is false (the default), then C<decode> will only accept
		293	valid JSON texts.
		294
		295	Currently accepted extensions are:
		296
		297	=over 4
		298
		299	=item * list items can have an end-comma
		300
		301	JSON I<separates> array elements and key-value pairs with commas. This
		302	can be annoying if you write JSON texts manually and want to be able to
		303	quickly append elements, so this extension accepts comma at the end of
		304	such items not just between them:
		305
		306	[
		307	1,
		308	2, <- this comma not normally allowed
		309	]
		310	{
		311	"k1": "v1",
		312	"k2": "v2", <- this comma not normally allowed
		313	}
		314
		315	=back
		316
251	=item $json = $json->canonical ([$enable])	317	=item $json = $json->canonical ([$enable])
252		318
253	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	319	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
254	by sorting their keys. This is adding a comparatively high overhead.	320	by sorting their keys. This is adding a comparatively high overhead.
255		321
…		…
280	resulting in an invalid JSON text:	346	resulting in an invalid JSON text:
281		347
282	JSON::XS->new->allow_nonref->encode ("Hello, World!")	348	JSON::XS->new->allow_nonref->encode ("Hello, World!")
283	=> "Hello, World!"	349	=> "Hello, World!"
284		350
		351	=item $json = $json->allow_blessed ([$enable])
		352
		353	If C<$enable> is true (or missing), then the C<encode> method will not
		354	barf when it encounters a blessed reference. Instead, the value of the
		355	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		356	disabled or no C<to_json> method found) or a representation of the
		357	object (C<convert_blessed> enabled and C<to_json> method found) is being
		358	encoded. Has no effect on C<decode>.
		359
		360	If C<$enable> is false (the default), then C<encode> will throw an
		361	exception when it encounters a blessed object.
		362
		363	=item $json = $json->convert_blessed ([$enable])
		364
		365	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		366	blessed object, will check for the availability of the C<TO_JSON> method
		367	on the object's class. If found, it will be called in scalar context
		368	and the resulting scalar will be encoded instead of the object. If no
		369	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		370	to do.
		371
		372	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		373	returns other blessed objects, those will be handled in the same
		374	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		375	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		376	methods called by the Perl core (== not by the user of the object) are
		377	usually in upper case letters and to avoid collisions with the C<to_json>
		378	function.
		379
		380	This setting does not yet influence C<decode> in any way, but in the
		381	future, global hooks might get installed that influence C<decode> and are
		382	enabled by this setting.
		383
		384	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		385	to do when a blessed object is found.
		386
		387	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		388
		389	When C<$coderef> is specified, it will be called from C<decode> each
		390	time it decodes a JSON object. The only argument is a reference to the
		391	newly-created hash. If the code references returns a single scalar (which
		392	need not be a reference), this value (i.e. a copy of that scalar to avoid
		393	aliasing) is inserted into the deserialised data structure. If it returns
		394	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		395	original deserialised hash will be inserted. This setting can slow down
		396	decoding considerably.
		397
		398	When C<$coderef> is omitted or undefined, any existing callback will
		399	be removed and C<decode> will not change the deserialised hash in any
		400	way.
		401
		402	Example, convert all JSON objects into the integer 5:
		403
		404	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		405	# returns [5]
		406	$js->decode ('[{}]')
		407	# throw an exception because allow_nonref is not enabled
		408	# so a lone 5 is not allowed.
		409	$js->decode ('{"a":1, "b":2}');
		410
		411	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		412
		413	Works remotely similar to C<filter_json_object>, but is only called for
		414	JSON objects having a single key named C<$key>.
		415
		416	This C<$coderef> is called before the one specified via
		417	C<filter_json_object>, if any. It gets passed the single value in the JSON
		418	object. If it returns a single value, it will be inserted into the data
		419	structure. If it returns nothing (not even C<undef> but the empty list),
		420	the callback from C<filter_json_object> will be called next, as if no
		421	single-key callback were specified.
		422
		423	If C<$coderef> is omitted or undefined, the corresponding callback will be
		424	disabled. There can only ever be one callback for a given key.
		425
		426	As this callback gets called less often then the C<filter_json_object>
		427	one, decoding speed will not usually suffer as much. Therefore, single-key
		428	objects make excellent targets to serialise Perl objects into, especially
		429	as single-key JSON objects are as close to the type-tagged value concept
		430	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		431	support this in any way, so you need to make sure your data never looks
		432	like a serialised Perl hash.
		433
		434	Typical names for the single object key are C<__class_whatever__>, or
		435	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		436	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		437	with real hashes.
		438
		439	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		440	into the corresponding C<< $WIDGET{<id>} >> object:
		441
		442	# return whatever is in $WIDGET{5}:
		443	JSON::XS
		444	->new
		445	->filter_json_single_key_object (__widget__ => sub {
		446	$WIDGET{ $_[0] }
		447	})
		448	->decode ('{"__widget__": 5')
		449
		450	# this can be used with a TO_JSON method in some "widget" class
		451	# for serialisation to json:
		452	sub WidgetBase::TO_JSON {
		453	my ($self) = @_;
		454
		455	unless ($self->{id}) {
		456	$self->{id} = ..get..some..id..;
		457	$WIDGET{$self->{id}} = $self;
		458	}
		459
		460	{ __widget__ => $self->{id} }
		461	}
		462
285	=item $json = $json->shrink ([$enable])	463	=item $json = $json->shrink ([$enable])
286		464
287	Perl usually over-allocates memory a bit when allocating space for	465	Perl usually over-allocates memory a bit when allocating space for
288	strings. This flag optionally resizes strings generated by either	466	strings. This flag optionally resizes strings generated by either
289	C<encode> or C<decode> to their minimum size possible. This can save	467	C<encode> or C<decode> to their minimum size possible. This can save
290	memory when your JSON texts are either very very long or you have many	468	memory when your JSON texts are either very very long or you have many
291	short strings. It will also try to downgrade any strings to octet-form	469	short strings. It will also try to downgrade any strings to octet-form
292	if possible: perl stores strings internally either in an encoding called	470	if possible: perl stores strings internally either in an encoding called
293	UTF-X or in octet-form. The latter cannot store everything but uses less	471	UTF-X or in octet-form. The latter cannot store everything but uses less
294	space in general.	472	space in general (and some buggy Perl or C code might even rely on that
		473	internal representation being used).
295		474
		475	The actual definition of what shrink does might change in future versions,
		476	but it will always try to save space at the expense of time.
		477
296	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	478	If C<$enable> is true (or missing), the string returned by C<encode> will
297	while all strings generated by C<decode> will also be shrunk-to-fit.	479	be shrunk-to-fit, while all strings generated by C<decode> will also be
		480	shrunk-to-fit.
298		481
299	If C<$enable> is false, then the normal perl allocation algorithms are used.	482	If C<$enable> is false, then the normal perl allocation algorithms are used.
300	If you work with your data, then this is likely to be faster.	483	If you work with your data, then this is likely to be faster.
301		484
302	In the future, this setting might control other things, such as converting	485	In the future, this setting might control other things, such as converting
303	strings that look like integers or floats into integers or floats	486	strings that look like integers or floats into integers or floats
304	internally (there is no difference on the Perl level), saving space.	487	internally (there is no difference on the Perl level), saving space.
		488
		489	=item $json = $json->max_depth ([$maximum_nesting_depth])
		490
		491	Sets the maximum nesting level (default C<512>) accepted while encoding
		492	or decoding. If the JSON text or Perl data structure has an equal or
		493	higher nesting level then this limit, then the encoder and decoder will
		494	stop and croak at that point.
		495
		496	Nesting level is defined by number of hash- or arrayrefs that the encoder
		497	needs to traverse to reach a given point or the number of C<{> or C<[>
		498	characters without their matching closing parenthesis crossed to reach a
		499	given character in a string.
		500
		501	Setting the maximum depth to one disallows any nesting, so that ensures
		502	that the object is only a single hash/object or array.
		503
		504	The argument to C<max_depth> will be rounded up to the next highest power
		505	of two. If no argument is given, the highest possible setting will be
		506	used, which is rarely useful.
		507
		508	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		509
		510	=item $json = $json->max_size ([$maximum_string_size])
		511
		512	Set the maximum length a JSON text may have (in bytes) where decoding is
		513	being attempted. The default is C<0>, meaning no limit. When C<decode>
		514	is called on a string longer then this number of characters it will not
		515	attempt to decode the string but throw an exception. This setting has no
		516	effect on C<encode> (yet).
		517
		518	The argument to C<max_size> will be rounded up to the next B<highest>
		519	power of two (so may be more than requested). If no argument is given, the
		520	limit check will be deactivated (same as when C<0> is specified).
		521
		522	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
305		523
306	=item $json_text = $json->encode ($perl_scalar)	524	=item $json_text = $json->encode ($perl_scalar)
307		525
308	Converts the given Perl data structure (a simple scalar or a reference	526	Converts the given Perl data structure (a simple scalar or a reference
309	to a hash or array) to its JSON representation. Simple scalars will be	527	to a hash or array) to its JSON representation. Simple scalars will be
…		…
319		537
320	JSON numbers and strings become simple Perl scalars. JSON arrays become	538	JSON numbers and strings become simple Perl scalars. JSON arrays become
321	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	539	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
322	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	540	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
323		541
		542	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		543
		544	This works like the C<decode> method, but instead of raising an exception
		545	when there is trailing garbage after the first JSON object, it will
		546	silently stop parsing there and return the number of characters consumed
		547	so far.
		548
		549	This is useful if your JSON texts are not delimited by an outer protocol
		550	(which is not the brightest thing to do in the first place) and you need
		551	to know where the JSON text ends.
		552
		553	JSON::XS->new->decode_prefix ("[1] the tail")
		554	=> ([], 3)
		555
324	=back	556	=back
		557
325		558
326	=head1 MAPPING	559	=head1 MAPPING
327		560
328	This section describes how JSON::XS maps Perl values to JSON values and	561	This section describes how JSON::XS maps Perl values to JSON values and
329	vice versa. These mappings are designed to "do the right thing" in most	562	vice versa. These mappings are designed to "do the right thing" in most
…		…
332		565
333	For the more enlightened: note that in the following descriptions,	566	For the more enlightened: note that in the following descriptions,
334	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	567	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
335	refers to the abstract Perl language itself.	568	refers to the abstract Perl language itself.
336		569
		570
337	=head2 JSON -> PERL	571	=head2 JSON -> PERL
338		572
339	=over 4	573	=over 4
340		574
341	=item object	575	=item object
…		…
353	are represented by the same codepoints in the Perl string, so no manual	587	are represented by the same codepoints in the Perl string, so no manual
354	decoding is necessary.	588	decoding is necessary.
355		589
356	=item number	590	=item number
357		591
358	A JSON number becomes either an integer or numeric (floating point)	592	A JSON number becomes either an integer, numeric (floating point) or
359	scalar in perl, depending on its range and any fractional parts. On the	593	string scalar in perl, depending on its range and any fractional parts. On
360	Perl level, there is no difference between those as Perl handles all the	594	the Perl level, there is no difference between those as Perl handles all
361	conversion details, but an integer may take slightly less memory and might	595	the conversion details, but an integer may take slightly less memory and
362	represent more values exactly than (floating point) numbers.	596	might represent more values exactly than (floating point) numbers.
		597
		598	If the number consists of digits only, JSON::XS will try to represent
		599	it as an integer value. If that fails, it will try to represent it as
		600	a numeric (floating point) value if that is possible without loss of
		601	precision. Otherwise it will preserve the number as a string value.
		602
		603	Numbers containing a fractional or exponential part will always be
		604	represented as numeric (floating point) values, possibly at a loss of
		605	precision.
		606
		607	This might create round-tripping problems as numbers might become strings,
		608	but as Perl is typeless there is no other way to do it.
363		609
364	=item true, false	610	=item true, false
365		611
366	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	612	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
367	this process. Future versions might represent those values differently,	613	respectively. They are overloaded to act almost exactly like the numbers
368	but they will be guarenteed to act like these integers would normally in	614	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
369	Perl.	615	the C<JSON::XS::is_bool> function.
370		616
371	=item null	617	=item null
372		618
373	A JSON null atom becomes C<undef> in Perl.	619	A JSON null atom becomes C<undef> in Perl.
374		620
375	=back	621	=back
		622
376		623
377	=head2 PERL -> JSON	624	=head2 PERL -> JSON
378		625
379	The mapping from Perl to JSON is slightly more difficult, as Perl is a	626	The mapping from Perl to JSON is slightly more difficult, as Perl is a
380	truly typeless language, so we can only guess which JSON type is meant by	627	truly typeless language, so we can only guess which JSON type is meant by
…		…
383	=over 4	630	=over 4
384		631
385	=item hash references	632	=item hash references
386		633
387	Perl hash references become JSON objects. As there is no inherent ordering	634	Perl hash references become JSON objects. As there is no inherent ordering
388	in hash keys, they will usually be encoded in a pseudo-random order that	635	in hash keys (or JSON objects), they will usually be encoded in a
389	can change between runs of the same program but stays generally the same	636	pseudo-random order that can change between runs of the same program but
390	within a single run of a program. JSON::XS can optionally sort the hash	637	stays generally the same within a single run of a program. JSON::XS can
391	keys (determined by the I<canonical> flag), so the same datastructure	638	optionally sort the hash keys (determined by the I<canonical> flag), so
392	will serialise to the same JSON text (given same settings and version of	639	the same datastructure will serialise to the same JSON text (given same
393	JSON::XS), but this incurs a runtime overhead.	640	settings and version of JSON::XS), but this incurs a runtime overhead
		641	and is only rarely useful, e.g. when you want to compare some JSON text
		642	against another for equality.
394		643
395	=item array references	644	=item array references
396		645
397	Perl array references become JSON arrays.	646	Perl array references become JSON arrays.
		647
		648	=item other references
		649
		650	Other unblessed references are generally not allowed and will cause an
		651	exception to be thrown, except for references to the integers C<0> and
		652	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		653	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		654
		655	to_json [\0,JSON::XS::true] # yields [false,true]
		656
		657	=item JSON::XS::true, JSON::XS::false
		658
		659	These special values become JSON true and JSON false values,
		660	respectively. You cna alos use C<\1> and C<\0> directly if you want.
398		661
399	=item blessed objects	662	=item blessed objects
400		663
401	Blessed objects are not allowed. JSON::XS currently tries to encode their	664	Blessed objects are not allowed. JSON::XS currently tries to encode their
402	underlying representation (hash- or arrayref), but this behaviour might	665	underlying representation (hash- or arrayref), but this behaviour might
…		…
435	$x *= 1; # same thing, the choise is yours.	698	$x *= 1; # same thing, the choise is yours.
436		699
437	You can not currently output JSON booleans or force the type in other,	700	You can not currently output JSON booleans or force the type in other,
438	less obscure, ways. Tell me if you need this capability.	701	less obscure, ways. Tell me if you need this capability.
439		702
440	=item circular data structures
441
442	Those will be encoded until memory or stackspace runs out.
443
444	=back	703	=back
		704
445		705
446	=head1 COMPARISON	706	=head1 COMPARISON
447		707
448	As already mentioned, this module was created because none of the existing	708	As already mentioned, this module was created because none of the existing
449	JSON modules could be made to work correctly. First I will describe the	709	JSON modules could be made to work correctly. First I will describe the
…		…
527		787
528	Does not check input for validity.	788	Does not check input for validity.
529		789
530	=back	790	=back
531		791
		792
		793	=head2 JSON and YAML
		794
		795	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		796	however, a mass hysteria and very far from the truth. In general, there is
		797	no way to configure JSON::XS to output a data structure as valid YAML.
		798
		799	If you really must use JSON::XS to generate YAML, you should use this
		800	algorithm (subject to change in future versions):
		801
		802	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		803	my $yaml = $to_yaml->encode ($ref) . "\n";
		804
		805	This will usually generate JSON texts that also parse as valid
		806	YAML. Please note that YAML has hardcoded limits on (simple) object key
		807	lengths that JSON doesn't have, so you should make sure that your hash
		808	keys are noticably shorter than the 1024 characters YAML allows.
		809
		810	There might be other incompatibilities that I am not aware of. In general
		811	you should not try to generate YAML with a JSON generator or vice versa,
		812	or try to parse JSON with a YAML parser or vice versa: chances are high
		813	that you will run into severe interoperability problems.
		814
		815
532	=head2 SPEED	816	=head2 SPEED
533		817
534	It seems that JSON::XS is surprisingly fast, as shown in the following	818	It seems that JSON::XS is surprisingly fast, as shown in the following
535	tables. They have been generated with the help of the C<eg/bench> program	819	tables. They have been generated with the help of the C<eg/bench> program
536	in the JSON::XS distribution, to make it easy to compare on your own	820	in the JSON::XS distribution, to make it easy to compare on your own
537	system.	821	system.
538		822
539	First comes a comparison between various modules using a very short JSON	823	First comes a comparison between various modules using a very short
540	string:	824	single-line JSON string:
541		825
542	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	826	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		827	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
543		828
544	It shows the number of encodes/decodes per second (JSON::XS uses the	829	It shows the number of encodes/decodes per second (JSON::XS uses
545	functional interface, while JSON::XS/2 uses the OO interface with	830	the functional interface, while JSON::XS/2 uses the OO interface
546	pretty-printing and hashkey sorting enabled). Higher is better:	831	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		832	shrink). Higher is better:
547		833
		834	Storable \| 15779.925 \| 14169.946 \|
		835	-----------+------------+------------+
548	module \| encode \| decode \|	836	module \| encode \| decode \|
549	-----------\|------------\|------------\|	837	-----------\|------------\|------------\|
550	JSON \| 11488.516 \| 7823.035 \|	838	JSON \| 4990.842 \| 4088.813 \|
551	JSON::DWIW \| 94708.054 \| 129094.260 \|	839	JSON::DWIW \| 51653.990 \| 71575.154 \|
552	JSON::PC \| 63884.157 \| 128528.212 \|	840	JSON::PC \| 65948.176 \| 74631.744 \|
553	JSON::Syck \| 34898.677 \| 42096.911 \|	841	JSON::PP \| 8931.652 \| 3817.168 \|
554	JSON::XS \| 654027.064 \| 396423.669 \|	842	JSON::Syck \| 24877.248 \| 27776.848 \|
555	JSON::XS/2 \| 371564.190 \| 371725.613 \|	843	JSON::XS \| 388361.481 \| 227951.304 \|
		844	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		845	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		846	Storable \| 16500.016 \| 135300.129 \|
556	-----------+------------+------------+	847	-----------+------------+------------+
557		848
558	That is, JSON::XS is more than six times faster than JSON::DWIW on	849	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
559	encoding, more than three times faster on decoding, and about thirty times	850	about three times faster on decoding, and over fourty times faster
560	faster than JSON, even with pretty-printing and key sorting.	851	than JSON, even with pretty-printing and key sorting. It also compares
		852	favourably to Storable for small amounts of data.
561		853
562	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	854	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
563	search API (http://nanoref.com/yahooapis/mgPdGg):	855	search API (http://nanoref.com/yahooapis/mgPdGg):
564		856
565	module \| encode \| decode \|	857	module \| encode \| decode \|
566	-----------\|------------\|------------\|	858	-----------\|------------\|------------\|
567	JSON \| 273.023 \| 44.674 \|	859	JSON \| 55.260 \| 34.971 \|
568	JSON::DWIW \| 1089.383 \| 1145.704 \|	860	JSON::DWIW \| 825.228 \| 1082.513 \|
569	JSON::PC \| 3097.419 \| 2393.921 \|	861	JSON::PC \| 3571.444 \| 2394.829 \|
570	JSON::Syck \| 514.060 \| 843.053 \|	862	JSON::PP \| 210.987 \| 32.574 \|
571	JSON::XS \| 6479.668 \| 3636.364 \|	863	JSON::Syck \| 552.551 \| 787.544 \|
572	JSON::XS/2 \| 3774.221 \| 3599.124 \|	864	JSON::XS \| 5780.463 \| 4854.519 \|
		865	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		866	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		867	Storable \| 4445.002 \| 5235.027 \|
573	-----------+------------+------------+	868	-----------+------------+------------+
574		869
575	Again, JSON::XS leads by far.	870	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		871	decodes faster).
576		872
577	On large strings containing lots of high unicode characters, some modules	873	On large strings containing lots of high unicode characters, some modules
578	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	874	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
579	will be broken due to missing (or wrong) unicode handling. Others refuse	875	will be broken due to missing (or wrong) unicode handling. Others refuse
580	to decode or encode properly, so it was impossible to prepare a fair	876	to decode or encode properly, so it was impossible to prepare a fair
581	comparison table for that case.	877	comparison table for that case.
582		878
583	=head1 RESOURCE LIMITS
584		879
585	JSON::XS does not impose any limits on the size of JSON texts or Perl	880	=head1 SECURITY CONSIDERATIONS
586	values they represent - if your machine can handle it, JSON::XS will	881
587	encode or decode it. Future versions might optionally impose structure	882	When you are using JSON in a protocol, talking to untrusted potentially
588	depth and memory use resource limits.	883	hostile creatures requires relatively few measures.
		884
		885	First of all, your JSON decoder should be secure, that is, should not have
		886	any buffer overflows. Obviously, this module should ensure that and I am
		887	trying hard on making that true, but you never know.
		888
		889	Second, you need to avoid resource-starving attacks. That means you should
		890	limit the size of JSON texts you accept, or make sure then when your
		891	resources run out, thats just fine (e.g. by using a separate process that
		892	can crash safely). The size of a JSON text in octets or characters is
		893	usually a good indication of the size of the resources required to decode
		894	it into a Perl structure. While JSON::XS can check the size of the JSON
		895	text, it might be too late when you already have it in memory, so you
		896	might want to check the size before you accept the string.
		897
		898	Third, JSON::XS recurses using the C stack when decoding objects and
		899	arrays. The C stack is a limited resource: for instance, on my amd64
		900	machine with 8MB of stack size I can decode around 180k nested arrays but
		901	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		902	to free the temporary). If that is exceeded, the program crashes. to be
		903	conservative, the default nesting limit is set to 512. If your process
		904	has a smaller stack, you should adjust this setting accordingly with the
		905	C<max_depth> method.
		906
		907	And last but least, something else could bomb you that I forgot to think
		908	of. In that case, you get to keep the pieces. I am always open for hints,
		909	though...
		910
		911	If you are using JSON::XS to return packets to consumption
		912	by javascript scripts in a browser you should have a look at
		913	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		914	you are vulnerable to some common attack vectors (which really are browser
		915	design bugs, but it is still you who will have to deal with it, as major
		916	browser developers care only for features, not about doing security
		917	right).
		918
589		919
590	=head1 BUGS	920	=head1 BUGS
591		921
592	While the goal of this module is to be correct, that unfortunately does	922	While the goal of this module is to be correct, that unfortunately does
593	not mean its bug-free, only that I think its design is bug-free. It is	923	not mean its bug-free, only that I think its design is bug-free. It is
594	still very young and not well-tested. If you keep reporting bugs they will	924	still relatively early in its development. If you keep reporting bugs they
595	be fixed swiftly, though.	925	will be fixed swiftly, though.
596		926
597	=cut	927	=cut
		928
		929	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		930	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		931
		932	sub true() { $true }
		933	sub false() { $false }
		934
		935	sub is_bool($) {
		936	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		937	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		938	}
		939
		940	XSLoader::load "JSON::XS", $VERSION;
		941
		942	package JSON::XS::Boolean;
		943
		944	use overload
		945	"0+" => sub { ${$_[0]} },
		946	"++" => sub { $_[0] = ${$_[0]} + 1 },
		947	"--" => sub { $_[0] = ${$_[0]} - 1 },
		948	fallback => 1;
598		949
599	1;	950	1;
600		951
601	=head1 AUTHOR	952	=head1 AUTHOR
602		953

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Comparing JSON-XS/XS.pm (file contents): Revision 1.22 by root, Sun Mar 25 02:37:00 2007 UTC vs. Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.22 by root, Sun Mar 25 02:37:00 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC