[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 1.61 by root, Wed Sep 12 17:42:36 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	=item * shell-style '#'-comments
		316
		317	Whenever JSON allows whitespace, shell-style comments are additionally
		318	allowed. They are terminated by the first carriage-return or line-feed
		319	character, after which more white-space and comments are allowed.
		320
		321	[
		322	1, # this comment not allowed in JSON
		323	# neither this one...
		324	]
		325
		326	=back
		327
251	=item $json = $json->canonical ([$enable])	328	=item $json = $json->canonical ([$enable])
252		329
253	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	330	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
254	by sorting their keys. This is adding a comparatively high overhead.	331	by sorting their keys. This is adding a comparatively high overhead.
255		332
…		…
280	resulting in an invalid JSON text:	357	resulting in an invalid JSON text:
281		358
282	JSON::XS->new->allow_nonref->encode ("Hello, World!")	359	JSON::XS->new->allow_nonref->encode ("Hello, World!")
283	=> "Hello, World!"	360	=> "Hello, World!"
284		361
		362	=item $json = $json->allow_blessed ([$enable])
		363
		364	If C<$enable> is true (or missing), then the C<encode> method will not
		365	barf when it encounters a blessed reference. Instead, the value of the
		366	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		367	disabled or no C<to_json> method found) or a representation of the
		368	object (C<convert_blessed> enabled and C<to_json> method found) is being
		369	encoded. Has no effect on C<decode>.
		370
		371	If C<$enable> is false (the default), then C<encode> will throw an
		372	exception when it encounters a blessed object.
		373
		374	=item $json = $json->convert_blessed ([$enable])
		375
		376	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		377	blessed object, will check for the availability of the C<TO_JSON> method
		378	on the object's class. If found, it will be called in scalar context
		379	and the resulting scalar will be encoded instead of the object. If no
		380	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		381	to do.
		382
		383	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		384	returns other blessed objects, those will be handled in the same
		385	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		386	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		387	methods called by the Perl core (== not by the user of the object) are
		388	usually in upper case letters and to avoid collisions with the C<to_json>
		389	function.
		390
		391	This setting does not yet influence C<decode> in any way, but in the
		392	future, global hooks might get installed that influence C<decode> and are
		393	enabled by this setting.
		394
		395	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		396	to do when a blessed object is found.
		397
		398	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		399
		400	When C<$coderef> is specified, it will be called from C<decode> each
		401	time it decodes a JSON object. The only argument is a reference to the
		402	newly-created hash. If the code references returns a single scalar (which
		403	need not be a reference), this value (i.e. a copy of that scalar to avoid
		404	aliasing) is inserted into the deserialised data structure. If it returns
		405	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		406	original deserialised hash will be inserted. This setting can slow down
		407	decoding considerably.
		408
		409	When C<$coderef> is omitted or undefined, any existing callback will
		410	be removed and C<decode> will not change the deserialised hash in any
		411	way.
		412
		413	Example, convert all JSON objects into the integer 5:
		414
		415	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		416	# returns [5]
		417	$js->decode ('[{}]')
		418	# throw an exception because allow_nonref is not enabled
		419	# so a lone 5 is not allowed.
		420	$js->decode ('{"a":1, "b":2}');
		421
		422	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		423
		424	Works remotely similar to C<filter_json_object>, but is only called for
		425	JSON objects having a single key named C<$key>.
		426
		427	This C<$coderef> is called before the one specified via
		428	C<filter_json_object>, if any. It gets passed the single value in the JSON
		429	object. If it returns a single value, it will be inserted into the data
		430	structure. If it returns nothing (not even C<undef> but the empty list),
		431	the callback from C<filter_json_object> will be called next, as if no
		432	single-key callback were specified.
		433
		434	If C<$coderef> is omitted or undefined, the corresponding callback will be
		435	disabled. There can only ever be one callback for a given key.
		436
		437	As this callback gets called less often then the C<filter_json_object>
		438	one, decoding speed will not usually suffer as much. Therefore, single-key
		439	objects make excellent targets to serialise Perl objects into, especially
		440	as single-key JSON objects are as close to the type-tagged value concept
		441	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		442	support this in any way, so you need to make sure your data never looks
		443	like a serialised Perl hash.
		444
		445	Typical names for the single object key are C<__class_whatever__>, or
		446	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		447	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		448	with real hashes.
		449
		450	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		451	into the corresponding C<< $WIDGET{<id>} >> object:
		452
		453	# return whatever is in $WIDGET{5}:
		454	JSON::XS
		455	->new
		456	->filter_json_single_key_object (__widget__ => sub {
		457	$WIDGET{ $_[0] }
		458	})
		459	->decode ('{"__widget__": 5')
		460
		461	# this can be used with a TO_JSON method in some "widget" class
		462	# for serialisation to json:
		463	sub WidgetBase::TO_JSON {
		464	my ($self) = @_;
		465
		466	unless ($self->{id}) {
		467	$self->{id} = ..get..some..id..;
		468	$WIDGET{$self->{id}} = $self;
		469	}
		470
		471	{ __widget__ => $self->{id} }
		472	}
		473
285	=item $json = $json->shrink ([$enable])	474	=item $json = $json->shrink ([$enable])
286		475
287	Perl usually over-allocates memory a bit when allocating space for	476	Perl usually over-allocates memory a bit when allocating space for
288	strings. This flag optionally resizes strings generated by either	477	strings. This flag optionally resizes strings generated by either
289	C<encode> or C<decode> to their minimum size possible. This can save	478	C<encode> or C<decode> to their minimum size possible. This can save
290	memory when your JSON texts are either very very long or you have many	479	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	480	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	481	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	482	UTF-X or in octet-form. The latter cannot store everything but uses less
294	space in general.	483	space in general (and some buggy Perl or C code might even rely on that
		484	internal representation being used).
295		485
		486	The actual definition of what shrink does might change in future versions,
		487	but it will always try to save space at the expense of time.
		488
296	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	489	If C<$enable> is true (or missing), the string returned by C<encode> will
297	while all strings generated by C<decode> will also be shrunk-to-fit.	490	be shrunk-to-fit, while all strings generated by C<decode> will also be
		491	shrunk-to-fit.
298		492
299	If C<$enable> is false, then the normal perl allocation algorithms are used.	493	If C<$enable> is false, then the normal perl allocation algorithms are used.
300	If you work with your data, then this is likely to be faster.	494	If you work with your data, then this is likely to be faster.
301		495
302	In the future, this setting might control other things, such as converting	496	In the future, this setting might control other things, such as converting
303	strings that look like integers or floats into integers or floats	497	strings that look like integers or floats into integers or floats
304	internally (there is no difference on the Perl level), saving space.	498	internally (there is no difference on the Perl level), saving space.
		499
		500	=item $json = $json->max_depth ([$maximum_nesting_depth])
		501
		502	Sets the maximum nesting level (default C<512>) accepted while encoding
		503	or decoding. If the JSON text or Perl data structure has an equal or
		504	higher nesting level then this limit, then the encoder and decoder will
		505	stop and croak at that point.
		506
		507	Nesting level is defined by number of hash- or arrayrefs that the encoder
		508	needs to traverse to reach a given point or the number of C<{> or C<[>
		509	characters without their matching closing parenthesis crossed to reach a
		510	given character in a string.
		511
		512	Setting the maximum depth to one disallows any nesting, so that ensures
		513	that the object is only a single hash/object or array.
		514
		515	The argument to C<max_depth> will be rounded up to the next highest power
		516	of two. If no argument is given, the highest possible setting will be
		517	used, which is rarely useful.
		518
		519	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		520
		521	=item $json = $json->max_size ([$maximum_string_size])
		522
		523	Set the maximum length a JSON text may have (in bytes) where decoding is
		524	being attempted. The default is C<0>, meaning no limit. When C<decode>
		525	is called on a string longer then this number of characters it will not
		526	attempt to decode the string but throw an exception. This setting has no
		527	effect on C<encode> (yet).
		528
		529	The argument to C<max_size> will be rounded up to the next B<highest>
		530	power of two (so may be more than requested). If no argument is given, the
		531	limit check will be deactivated (same as when C<0> is specified).
		532
		533	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
305		534
306	=item $json_text = $json->encode ($perl_scalar)	535	=item $json_text = $json->encode ($perl_scalar)
307		536
308	Converts the given Perl data structure (a simple scalar or a reference	537	Converts the given Perl data structure (a simple scalar or a reference
309	to a hash or array) to its JSON representation. Simple scalars will be	538	to a hash or array) to its JSON representation. Simple scalars will be
…		…
319		548
320	JSON numbers and strings become simple Perl scalars. JSON arrays become	549	JSON numbers and strings become simple Perl scalars. JSON arrays become
321	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	550	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>.	551	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
323		552
		553	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		554
		555	This works like the C<decode> method, but instead of raising an exception
		556	when there is trailing garbage after the first JSON object, it will
		557	silently stop parsing there and return the number of characters consumed
		558	so far.
		559
		560	This is useful if your JSON texts are not delimited by an outer protocol
		561	(which is not the brightest thing to do in the first place) and you need
		562	to know where the JSON text ends.
		563
		564	JSON::XS->new->decode_prefix ("[1] the tail")
		565	=> ([], 3)
		566
324	=back	567	=back
		568
325		569
326	=head1 MAPPING	570	=head1 MAPPING
327		571
328	This section describes how JSON::XS maps Perl values to JSON values and	572	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	573	vice versa. These mappings are designed to "do the right thing" in most
…		…
332		576
333	For the more enlightened: note that in the following descriptions,	577	For the more enlightened: note that in the following descriptions,
334	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	578	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
335	refers to the abstract Perl language itself.	579	refers to the abstract Perl language itself.
336		580
		581
337	=head2 JSON -> PERL	582	=head2 JSON -> PERL
338		583
339	=over 4	584	=over 4
340		585
341	=item object	586	=item object
…		…
353	are represented by the same codepoints in the Perl string, so no manual	598	are represented by the same codepoints in the Perl string, so no manual
354	decoding is necessary.	599	decoding is necessary.
355		600
356	=item number	601	=item number
357		602
358	A JSON number becomes either an integer or numeric (floating point)	603	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	604	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	605	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	606	the conversion details, but an integer may take slightly less memory and
362	represent more values exactly than (floating point) numbers.	607	might represent more values exactly than (floating point) numbers.
		608
		609	If the number consists of digits only, JSON::XS will try to represent
		610	it as an integer value. If that fails, it will try to represent it as
		611	a numeric (floating point) value if that is possible without loss of
		612	precision. Otherwise it will preserve the number as a string value.
		613
		614	Numbers containing a fractional or exponential part will always be
		615	represented as numeric (floating point) values, possibly at a loss of
		616	precision.
		617
		618	This might create round-tripping problems as numbers might become strings,
		619	but as Perl is typeless there is no other way to do it.
363		620
364	=item true, false	621	=item true, false
365		622
366	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	623	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
367	this process. Future versions might represent those values differently,	624	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	625	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
369	Perl.	626	the C<JSON::XS::is_bool> function.
370		627
371	=item null	628	=item null
372		629
373	A JSON null atom becomes C<undef> in Perl.	630	A JSON null atom becomes C<undef> in Perl.
374		631
375	=back	632	=back
		633
376		634
377	=head2 PERL -> JSON	635	=head2 PERL -> JSON
378		636
379	The mapping from Perl to JSON is slightly more difficult, as Perl is a	637	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	638	truly typeless language, so we can only guess which JSON type is meant by
…		…
383	=over 4	641	=over 4
384		642
385	=item hash references	643	=item hash references
386		644
387	Perl hash references become JSON objects. As there is no inherent ordering	645	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	646	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	647	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	648	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	649	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	650	the same datastructure will serialise to the same JSON text (given same
393	JSON::XS), but this incurs a runtime overhead.	651	settings and version of JSON::XS), but this incurs a runtime overhead
		652	and is only rarely useful, e.g. when you want to compare some JSON text
		653	against another for equality.
394		654
395	=item array references	655	=item array references
396		656
397	Perl array references become JSON arrays.	657	Perl array references become JSON arrays.
		658
		659	=item other references
		660
		661	Other unblessed references are generally not allowed and will cause an
		662	exception to be thrown, except for references to the integers C<0> and
		663	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		664	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		665
		666	to_json [\0,JSON::XS::true] # yields [false,true]
		667
		668	=item JSON::XS::true, JSON::XS::false
		669
		670	These special values become JSON true and JSON false values,
		671	respectively. You can also use C<\1> and C<\0> directly if you want.
398		672
399	=item blessed objects	673	=item blessed objects
400		674
401	Blessed objects are not allowed. JSON::XS currently tries to encode their	675	Blessed objects are not allowed. JSON::XS currently tries to encode their
402	underlying representation (hash- or arrayref), but this behaviour might	676	underlying representation (hash- or arrayref), but this behaviour might
…		…
435	$x *= 1; # same thing, the choise is yours.	709	$x *= 1; # same thing, the choise is yours.
436		710
437	You can not currently output JSON booleans or force the type in other,	711	You can not currently output JSON booleans or force the type in other,
438	less obscure, ways. Tell me if you need this capability.	712	less obscure, ways. Tell me if you need this capability.
439		713
440	=item circular data structures
441
442	Those will be encoded until memory or stackspace runs out.
443
444	=back	714	=back
		715
445		716
446	=head1 COMPARISON	717	=head1 COMPARISON
447		718
448	As already mentioned, this module was created because none of the existing	719	As already mentioned, this module was created because none of the existing
449	JSON modules could be made to work correctly. First I will describe the	720	JSON modules could be made to work correctly. First I will describe the
…		…
527		798
528	Does not check input for validity.	799	Does not check input for validity.
529		800
530	=back	801	=back
531		802
		803
		804	=head2 JSON and YAML
		805
		806	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		807	however, a mass hysteria and very far from the truth. In general, there is
		808	no way to configure JSON::XS to output a data structure as valid YAML.
		809
		810	If you really must use JSON::XS to generate YAML, you should use this
		811	algorithm (subject to change in future versions):
		812
		813	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		814	my $yaml = $to_yaml->encode ($ref) . "\n";
		815
		816	This will usually generate JSON texts that also parse as valid
		817	YAML. Please note that YAML has hardcoded limits on (simple) object key
		818	lengths that JSON doesn't have, so you should make sure that your hash
		819	keys are noticably shorter than the 1024 characters YAML allows.
		820
		821	There might be other incompatibilities that I am not aware of. In general
		822	you should not try to generate YAML with a JSON generator or vice versa,
		823	or try to parse JSON with a YAML parser or vice versa: chances are high
		824	that you will run into severe interoperability problems.
		825
		826
532	=head2 SPEED	827	=head2 SPEED
533		828
534	It seems that JSON::XS is surprisingly fast, as shown in the following	829	It seems that JSON::XS is surprisingly fast, as shown in the following
535	tables. They have been generated with the help of the C<eg/bench> program	830	tables. They have been generated with the help of the C<eg/bench> program
536	in the JSON::XS distribution, to make it easy to compare on your own	831	in the JSON::XS distribution, to make it easy to compare on your own
537	system.	832	system.
538		833
539	First comes a comparison between various modules using a very short JSON	834	First comes a comparison between various modules using a very short
540	string:	835	single-line JSON string:
541		836
542	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	837	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		838	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
543		839
544	It shows the number of encodes/decodes per second (JSON::XS uses the	840	It shows the number of encodes/decodes per second (JSON::XS uses
545	functional interface, while JSON::XS/2 uses the OO interface with	841	the functional interface, while JSON::XS/2 uses the OO interface
546	pretty-printing and hashkey sorting enabled). Higher is better:	842	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		843	shrink). Higher is better:
547		844
		845	Storable \| 15779.925 \| 14169.946 \|
		846	-----------+------------+------------+
548	module \| encode \| decode \|	847	module \| encode \| decode \|
549	-----------\|------------\|------------\|	848	-----------\|------------\|------------\|
550	JSON \| 11488.516 \| 7823.035 \|	849	JSON \| 4990.842 \| 4088.813 \|
551	JSON::DWIW \| 94708.054 \| 129094.260 \|	850	JSON::DWIW \| 51653.990 \| 71575.154 \|
552	JSON::PC \| 63884.157 \| 128528.212 \|	851	JSON::PC \| 65948.176 \| 74631.744 \|
553	JSON::Syck \| 34898.677 \| 42096.911 \|	852	JSON::PP \| 8931.652 \| 3817.168 \|
554	JSON::XS \| 654027.064 \| 396423.669 \|	853	JSON::Syck \| 24877.248 \| 27776.848 \|
555	JSON::XS/2 \| 371564.190 \| 371725.613 \|	854	JSON::XS \| 388361.481 \| 227951.304 \|
		855	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		856	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		857	Storable \| 16500.016 \| 135300.129 \|
556	-----------+------------+------------+	858	-----------+------------+------------+
557		859
558	That is, JSON::XS is more than six times faster than JSON::DWIW on	860	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	861	about three times faster on decoding, and over fourty times faster
560	faster than JSON, even with pretty-printing and key sorting.	862	than JSON, even with pretty-printing and key sorting. It also compares
		863	favourably to Storable for small amounts of data.
561		864
562	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	865	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
563	search API (http://nanoref.com/yahooapis/mgPdGg):	866	search API (http://nanoref.com/yahooapis/mgPdGg):
564		867
565	module \| encode \| decode \|	868	module \| encode \| decode \|
566	-----------\|------------\|------------\|	869	-----------\|------------\|------------\|
567	JSON \| 273.023 \| 44.674 \|	870	JSON \| 55.260 \| 34.971 \|
568	JSON::DWIW \| 1089.383 \| 1145.704 \|	871	JSON::DWIW \| 825.228 \| 1082.513 \|
569	JSON::PC \| 3097.419 \| 2393.921 \|	872	JSON::PC \| 3571.444 \| 2394.829 \|
570	JSON::Syck \| 514.060 \| 843.053 \|	873	JSON::PP \| 210.987 \| 32.574 \|
571	JSON::XS \| 6479.668 \| 3636.364 \|	874	JSON::Syck \| 552.551 \| 787.544 \|
572	JSON::XS/2 \| 3774.221 \| 3599.124 \|	875	JSON::XS \| 5780.463 \| 4854.519 \|
		876	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		877	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		878	Storable \| 4445.002 \| 5235.027 \|
573	-----------+------------+------------+	879	-----------+------------+------------+
574		880
575	Again, JSON::XS leads by far.	881	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		882	decodes faster).
576		883
577	On large strings containing lots of high unicode characters, some modules	884	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	885	(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	886	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	887	to decode or encode properly, so it was impossible to prepare a fair
581	comparison table for that case.	888	comparison table for that case.
582		889
583	=head1 RESOURCE LIMITS
584		890
585	JSON::XS does not impose any limits on the size of JSON texts or Perl	891	=head1 SECURITY CONSIDERATIONS
586	values they represent - if your machine can handle it, JSON::XS will	892
587	encode or decode it. Future versions might optionally impose structure	893	When you are using JSON in a protocol, talking to untrusted potentially
588	depth and memory use resource limits.	894	hostile creatures requires relatively few measures.
		895
		896	First of all, your JSON decoder should be secure, that is, should not have
		897	any buffer overflows. Obviously, this module should ensure that and I am
		898	trying hard on making that true, but you never know.
		899
		900	Second, you need to avoid resource-starving attacks. That means you should
		901	limit the size of JSON texts you accept, or make sure then when your
		902	resources run out, thats just fine (e.g. by using a separate process that
		903	can crash safely). The size of a JSON text in octets or characters is
		904	usually a good indication of the size of the resources required to decode
		905	it into a Perl structure. While JSON::XS can check the size of the JSON
		906	text, it might be too late when you already have it in memory, so you
		907	might want to check the size before you accept the string.
		908
		909	Third, JSON::XS recurses using the C stack when decoding objects and
		910	arrays. The C stack is a limited resource: for instance, on my amd64
		911	machine with 8MB of stack size I can decode around 180k nested arrays but
		912	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		913	to free the temporary). If that is exceeded, the program crashes. to be
		914	conservative, the default nesting limit is set to 512. If your process
		915	has a smaller stack, you should adjust this setting accordingly with the
		916	C<max_depth> method.
		917
		918	And last but least, something else could bomb you that I forgot to think
		919	of. In that case, you get to keep the pieces. I am always open for hints,
		920	though...
		921
		922	If you are using JSON::XS to return packets to consumption
		923	by javascript scripts in a browser you should have a look at
		924	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		925	you are vulnerable to some common attack vectors (which really are browser
		926	design bugs, but it is still you who will have to deal with it, as major
		927	browser developers care only for features, not about doing security
		928	right).
		929
589		930
590	=head1 BUGS	931	=head1 BUGS
591		932
592	While the goal of this module is to be correct, that unfortunately does	933	While the goal of this module is to be correct, that unfortunately does
593	not mean its bug-free, only that I think its design is bug-free. It is	934	not mean its bug-free, only that I think its design is bug-free. It is
594	still very young and not well-tested. If you keep reporting bugs they will	935	still relatively early in its development. If you keep reporting bugs they
595	be fixed swiftly, though.	936	will be fixed swiftly, though.
596		937
597	=cut	938	=cut
		939
		940	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		941	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		942
		943	sub true() { $true }
		944	sub false() { $false }
		945
		946	sub is_bool($) {
		947	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		948	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		949	}
		950
		951	XSLoader::load "JSON::XS", $VERSION;
		952
		953	package JSON::XS::Boolean;
		954
		955	use overload
		956	"0+" => sub { ${$_[0]} },
		957	"++" => sub { $_[0] = ${$_[0]} + 1 },
		958	"--" => sub { $_[0] = ${$_[0]} - 1 },
		959	fallback => 1;
598		960
599	1;	961	1;
600		962
601	=head1 AUTHOR	963	=head1 AUTHOR
602		964

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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 1.61 by root, Wed Sep 12 17:42:36 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 1.61 by root, Wed Sep 12 17:42:36 2007 UTC