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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.18 by root, Sat Mar 24 22:55:16 2007 UTC vs.
Revision 1.58 by root, Sun Aug 26 21:56:47 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
8		8
9	# exported functions, croak on error	9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
10		11
11	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
12	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
13		14
14	# oo-interface	15	# OO-interface
15		16
16	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	17	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
17	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	18	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
18	$perl_scalar = $coder->decode ($unicode_json_text);	19	$perl_scalar = $coder->decode ($unicode_json_text);
19		20
…		…
36		37
37	=head2 FEATURES	38	=head2 FEATURES
38		39
39	=over 4	40	=over 4
40		41
41	=item * correct handling of unicode issues	42	=item * correct unicode handling
42		43
43	This module knows how to handle Unicode, and even documents how and when	44	This module knows how to handle Unicode, and even documents how and when
44	it does so.	45	it does so.
45		46
46	=item * round-trip integrity	47	=item * round-trip integrity
47		48
48	When you serialise a perl data structure using only datatypes supported	49	When you serialise a perl data structure using only datatypes supported
49	by JSON, the deserialised data structure is identical on the Perl level.	50	by JSON, the deserialised data structure is identical on the Perl level.
50	(e.g. the string "2.0" doesn't suddenly become "2").	51	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		52	like a number).
51		53
52	=item * strict checking of JSON correctness	54	=item * strict checking of JSON correctness
53		55
54	There is no guessing, no generating of illegal JSON texts by default,	56	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	57	and only JSON is accepted as input by default (the latter is a security
…		…
66	interface.	68	interface.
67		69
68	=item * reasonably versatile output formats	70	=item * reasonably versatile output formats
69		71
70	You can choose between the most compact guarenteed single-line format	72	You can choose between the most compact guarenteed single-line format
71	possible (nice for simple line-based protocols), a pure-ascii format (for	73	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	74	(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	75	unicode range), or a pretty-printed format (for when you want to read that
74	whatever way you like.	76	stuff). Or you can combine those features in whatever way you like.
75		77
76	=back	78	=back
77		79
78	=cut	80	=cut
79		81
80	package JSON::XS;	82	package JSON::XS;
81		83
82	BEGIN {	84	use strict;
		85
83	$VERSION = '0.5';	86	our $VERSION = '1.5';
84	@ISA = qw(Exporter);	87	our @ISA = qw(Exporter);
85		88
86	@EXPORT = qw(to_json from_json);	89	our @EXPORT = qw(to_json from_json);
87	require Exporter;
88		90
89	require XSLoader;	91	use Exporter;
90	XSLoader::load JSON::XS::, $VERSION;	92	use XSLoader;
91	}
92		93
93	=head1 FUNCTIONAL INTERFACE	94	=head1 FUNCTIONAL INTERFACE
94		95
95	The following convinience methods are provided by this module. They are	96	The following convinience methods are provided by this module. They are
96	exported by default:	97	exported by default:
…		…
119		120
120	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	121	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
121		122
122	except being faster.	123	except being faster.
123		124
		125	=item $is_boolean = JSON::XS::is_bool $scalar
		126
		127	Returns true if the passed scalar represents either JSON::XS::true or
		128	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
		129	and are used to represent JSON C<true> and C<false> values in Perl.
		130
		131	See MAPPING, below, for more information on how JSON values are mapped to
		132	Perl.
		133
124	=back	134	=back
		135
125		136
126	=head1 OBJECT-ORIENTED INTERFACE	137	=head1 OBJECT-ORIENTED INTERFACE
127		138
128	The object oriented interface lets you configure your own encoding or	139	The object oriented interface lets you configure your own encoding or
129	decoding style, within the limits of supported formats.	140	decoding style, within the limits of supported formats.
…		…
145		156
146	If C<$enable> is true (or missing), then the C<encode> method will not	157	If C<$enable> is true (or missing), then the C<encode> method will not
147	generate characters outside the code range C<0..127> (which is ASCII). Any	158	generate characters outside the code range C<0..127> (which is ASCII). Any
148	unicode characters outside that range will be escaped using either a	159	unicode characters outside that range will be escaped using either a
149	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,	160	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
150	as per RFC4627.	161	as per RFC4627. The resulting encoded JSON text can be treated as a native
		162	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		163	or any other superset of ASCII.
151		164
152	If C<$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
153	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
154	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.
155		172
156	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	173	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
157	=> ["\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)
158		198
159	=item $json = $json->utf8 ([$enable])	199	=item $json = $json->utf8 ([$enable])
160		200
161	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
162	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
…		…
272	resulting in an invalid JSON text:	312	resulting in an invalid JSON text:
273		313
274	JSON::XS->new->allow_nonref->encode ("Hello, World!")	314	JSON::XS->new->allow_nonref->encode ("Hello, World!")
275	=> "Hello, World!"	315	=> "Hello, World!"
276		316
		317	=item $json = $json->allow_blessed ([$enable])
		318
		319	If C<$enable> is true (or missing), then the C<encode> method will not
		320	barf when it encounters a blessed reference. Instead, the value of the
		321	B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
		322	disabled or no C<to_json> method found) or a representation of the
		323	object (C<convert_blessed> enabled and C<to_json> method found) is being
		324	encoded. Has no effect on C<decode>.
		325
		326	If C<$enable> is false (the default), then C<encode> will throw an
		327	exception when it encounters a blessed object.
		328
		329	=item $json = $json->convert_blessed ([$enable])
		330
		331	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		332	blessed object, will check for the availability of the C<TO_JSON> method
		333	on the object's class. If found, it will be called in scalar context
		334	and the resulting scalar will be encoded instead of the object. If no
		335	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
		336	to do.
		337
		338	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
		339	returns other blessed objects, those will be handled in the same
		340	way. C<TO_JSON> must take care of not causing an endless recursion cycle
		341	(== crash) in this case. The name of C<TO_JSON> was chosen because other
		342	methods called by the Perl core (== not by the user of the object) are
		343	usually in upper case letters and to avoid collisions with the C<to_json>
		344	function.
		345
		346	This setting does not yet influence C<decode> in any way, but in the
		347	future, global hooks might get installed that influence C<decode> and are
		348	enabled by this setting.
		349
		350	If C<$enable> is false, then the C<allow_blessed> setting will decide what
		351	to do when a blessed object is found.
		352
		353	=item $json = $json->filter_json_object ([$coderef->($hashref)])
		354
		355	When C<$coderef> is specified, it will be called from C<decode> each
		356	time it decodes a JSON object. The only argument is a reference to the
		357	newly-created hash. If the code references returns a single scalar (which
		358	need not be a reference), this value (i.e. a copy of that scalar to avoid
		359	aliasing) is inserted into the deserialised data structure. If it returns
		360	an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
		361	original deserialised hash will be inserted. This setting can slow down
		362	decoding considerably.
		363
		364	When C<$coderef> is omitted or undefined, any existing callback will
		365	be removed and C<decode> will not change the deserialised hash in any
		366	way.
		367
		368	Example, convert all JSON objects into the integer 5:
		369
		370	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		371	# returns [5]
		372	$js->decode ('[{}]')
		373	# throw an exception because allow_nonref is not enabled
		374	# so a lone 5 is not allowed.
		375	$js->decode ('{"a":1, "b":2}');
		376
		377	=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
		378
		379	Works remotely similar to C<filter_json_object>, but is only called for
		380	JSON objects having a single key named C<$key>.
		381
		382	This C<$coderef> is called before the one specified via
		383	C<filter_json_object>, if any. It gets passed the single value in the JSON
		384	object. If it returns a single value, it will be inserted into the data
		385	structure. If it returns nothing (not even C<undef> but the empty list),
		386	the callback from C<filter_json_object> will be called next, as if no
		387	single-key callback were specified.
		388
		389	If C<$coderef> is omitted or undefined, the corresponding callback will be
		390	disabled. There can only ever be one callback for a given key.
		391
		392	As this callback gets called less often then the C<filter_json_object>
		393	one, decoding speed will not usually suffer as much. Therefore, single-key
		394	objects make excellent targets to serialise Perl objects into, especially
		395	as single-key JSON objects are as close to the type-tagged value concept
		396	as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
		397	support this in any way, so you need to make sure your data never looks
		398	like a serialised Perl hash.
		399
		400	Typical names for the single object key are C<__class_whatever__>, or
		401	C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
		402	things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
		403	with real hashes.
		404
		405	Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
		406	into the corresponding C<< $WIDGET{<id>} >> object:
		407
		408	# return whatever is in $WIDGET{5}:
		409	JSON::XS
		410	->new
		411	->filter_json_single_key_object (__widget__ => sub {
		412	$WIDGET{ $_[0] }
		413	})
		414	->decode ('{"__widget__": 5')
		415
		416	# this can be used with a TO_JSON method in some "widget" class
		417	# for serialisation to json:
		418	sub WidgetBase::TO_JSON {
		419	my ($self) = @_;
		420
		421	unless ($self->{id}) {
		422	$self->{id} = ..get..some..id..;
		423	$WIDGET{$self->{id}} = $self;
		424	}
		425
		426	{ __widget__ => $self->{id} }
		427	}
		428
277	=item $json = $json->shrink ([$enable])	429	=item $json = $json->shrink ([$enable])
278		430
279	Perl usually over-allocates memory a bit when allocating space for	431	Perl usually over-allocates memory a bit when allocating space for
280	strings. This flag optionally resizes strings generated by either	432	strings. This flag optionally resizes strings generated by either
281	C<encode> or C<decode> to their minimum size possible. This can save	433	C<encode> or C<decode> to their minimum size possible. This can save
282	memory when your JSON texts are either very very long or you have many	434	memory when your JSON texts are either very very long or you have many
283	short strings. It will also try to downgrade any strings to octet-form	435	short strings. It will also try to downgrade any strings to octet-form
284	if possible: perl stores strings internally either in an encoding called	436	if possible: perl stores strings internally either in an encoding called
285	UTF-X or in octet-form. The latter cannot store everything but uses less	437	UTF-X or in octet-form. The latter cannot store everything but uses less
286	space in general.	438	space in general (and some buggy Perl or C code might even rely on that
		439	internal representation being used).
287		440
		441	The actual definition of what shrink does might change in future versions,
		442	but it will always try to save space at the expense of time.
		443
288	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,	444	If C<$enable> is true (or missing), the string returned by C<encode> will
289	while all strings generated by C<decode> will also be shrunk-to-fit.	445	be shrunk-to-fit, while all strings generated by C<decode> will also be
		446	shrunk-to-fit.
290		447
291	If C<$enable> is false, then the normal perl allocation algorithms are used.	448	If C<$enable> is false, then the normal perl allocation algorithms are used.
292	If you work with your data, then this is likely to be faster.	449	If you work with your data, then this is likely to be faster.
293		450
294	In the future, this setting might control other things, such as converting	451	In the future, this setting might control other things, such as converting
295	strings that look like integers or floats into integers or floats	452	strings that look like integers or floats into integers or floats
296	internally (there is no difference on the Perl level), saving space.	453	internally (there is no difference on the Perl level), saving space.
		454
		455	=item $json = $json->max_depth ([$maximum_nesting_depth])
		456
		457	Sets the maximum nesting level (default C<512>) accepted while encoding
		458	or decoding. If the JSON text or Perl data structure has an equal or
		459	higher nesting level then this limit, then the encoder and decoder will
		460	stop and croak at that point.
		461
		462	Nesting level is defined by number of hash- or arrayrefs that the encoder
		463	needs to traverse to reach a given point or the number of C<{> or C<[>
		464	characters without their matching closing parenthesis crossed to reach a
		465	given character in a string.
		466
		467	Setting the maximum depth to one disallows any nesting, so that ensures
		468	that the object is only a single hash/object or array.
		469
		470	The argument to C<max_depth> will be rounded up to the next highest power
		471	of two. If no argument is given, the highest possible setting will be
		472	used, which is rarely useful.
		473
		474	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		475
		476	=item $json = $json->max_size ([$maximum_string_size])
		477
		478	Set the maximum length a JSON text may have (in bytes) where decoding is
		479	being attempted. The default is C<0>, meaning no limit. When C<decode>
		480	is called on a string longer then this number of characters it will not
		481	attempt to decode the string but throw an exception. This setting has no
		482	effect on C<encode> (yet).
		483
		484	The argument to C<max_size> will be rounded up to the next B<highest>
		485	power of two (so may be more than requested). If no argument is given, the
		486	limit check will be deactivated (same as when C<0> is specified).
		487
		488	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
297		489
298	=item $json_text = $json->encode ($perl_scalar)	490	=item $json_text = $json->encode ($perl_scalar)
299		491
300	Converts the given Perl data structure (a simple scalar or a reference	492	Converts the given Perl data structure (a simple scalar or a reference
301	to a hash or array) to its JSON representation. Simple scalars will be	493	to a hash or array) to its JSON representation. Simple scalars will be
…		…
311		503
312	JSON numbers and strings become simple Perl scalars. JSON arrays become	504	JSON numbers and strings become simple Perl scalars. JSON arrays become
313	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	505	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
314	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	506	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
315		507
		508	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
		509
		510	This works like the C<decode> method, but instead of raising an exception
		511	when there is trailing garbage after the first JSON object, it will
		512	silently stop parsing there and return the number of characters consumed
		513	so far.
		514
		515	This is useful if your JSON texts are not delimited by an outer protocol
		516	(which is not the brightest thing to do in the first place) and you need
		517	to know where the JSON text ends.
		518
		519	JSON::XS->new->decode_prefix ("[1] the tail")
		520	=> ([], 3)
		521
316	=back	522	=back
		523
317		524
318	=head1 MAPPING	525	=head1 MAPPING
319		526
320	This section describes how JSON::XS maps Perl values to JSON values and	527	This section describes how JSON::XS maps Perl values to JSON values and
321	vice versa. These mappings are designed to "do the right thing" in most	528	vice versa. These mappings are designed to "do the right thing" in most
…		…
324		531
325	For the more enlightened: note that in the following descriptions,	532	For the more enlightened: note that in the following descriptions,
326	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>	533	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
327	refers to the abstract Perl language itself.	534	refers to the abstract Perl language itself.
328		535
		536
329	=head2 JSON -> PERL	537	=head2 JSON -> PERL
330		538
331	=over 4	539	=over 4
332		540
333	=item object	541	=item object
…		…
345	are represented by the same codepoints in the Perl string, so no manual	553	are represented by the same codepoints in the Perl string, so no manual
346	decoding is necessary.	554	decoding is necessary.
347		555
348	=item number	556	=item number
349		557
350	A JSON number becomes either an integer or numeric (floating point)	558	A JSON number becomes either an integer, numeric (floating point) or
351	scalar in perl, depending on its range and any fractional parts. On the	559	string scalar in perl, depending on its range and any fractional parts. On
352	Perl level, there is no difference between those as Perl handles all the	560	the Perl level, there is no difference between those as Perl handles all
353	conversion details, but an integer may take slightly less memory and might	561	the conversion details, but an integer may take slightly less memory and
354	represent more values exactly than (floating point) numbers.	562	might represent more values exactly than (floating point) numbers.
		563
		564	If the number consists of digits only, JSON::XS will try to represent
		565	it as an integer value. If that fails, it will try to represent it as
		566	a numeric (floating point) value if that is possible without loss of
		567	precision. Otherwise it will preserve the number as a string value.
		568
		569	Numbers containing a fractional or exponential part will always be
		570	represented as numeric (floating point) values, possibly at a loss of
		571	precision.
		572
		573	This might create round-tripping problems as numbers might become strings,
		574	but as Perl is typeless there is no other way to do it.
355		575
356	=item true, false	576	=item true, false
357		577
358	These JSON atoms become C<0>, C<1>, respectively. Information is lost in	578	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
359	this process. Future versions might represent those values differently,	579	respectively. They are overloaded to act almost exactly like the numbers
360	but they will be guarenteed to act like these integers would normally in	580	C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
361	Perl.	581	the C<JSON::XS::is_bool> function.
362		582
363	=item null	583	=item null
364		584
365	A JSON null atom becomes C<undef> in Perl.	585	A JSON null atom becomes C<undef> in Perl.
366		586
367	=back	587	=back
		588
368		589
369	=head2 PERL -> JSON	590	=head2 PERL -> JSON
370		591
371	The mapping from Perl to JSON is slightly more difficult, as Perl is a	592	The mapping from Perl to JSON is slightly more difficult, as Perl is a
372	truly typeless language, so we can only guess which JSON type is meant by	593	truly typeless language, so we can only guess which JSON type is meant by
…		…
375	=over 4	596	=over 4
376		597
377	=item hash references	598	=item hash references
378		599
379	Perl hash references become JSON objects. As there is no inherent ordering	600	Perl hash references become JSON objects. As there is no inherent ordering
380	in hash keys, they will usually be encoded in a pseudo-random order that	601	in hash keys (or JSON objects), they will usually be encoded in a
381	can change between runs of the same program but stays generally the same	602	pseudo-random order that can change between runs of the same program but
382	within a single run of a program. JSON::XS can optionally sort the hash	603	stays generally the same within a single run of a program. JSON::XS can
383	keys (determined by the I<canonical> flag), so the same datastructure	604	optionally sort the hash keys (determined by the I<canonical> flag), so
384	will serialise to the same JSON text (given same settings and version of	605	the same datastructure will serialise to the same JSON text (given same
385	JSON::XS), but this incurs a runtime overhead.	606	settings and version of JSON::XS), but this incurs a runtime overhead
		607	and is only rarely useful, e.g. when you want to compare some JSON text
		608	against another for equality.
386		609
387	=item array references	610	=item array references
388		611
389	Perl array references become JSON arrays.	612	Perl array references become JSON arrays.
		613
		614	=item other references
		615
		616	Other unblessed references are generally not allowed and will cause an
		617	exception to be thrown, except for references to the integers C<0> and
		618	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		619	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		620
		621	to_json [\0,JSON::XS::true] # yields [false,true]
		622
		623	=item JSON::XS::true, JSON::XS::false
		624
		625	These special values become JSON true and JSON false values,
		626	respectively. You cna alos use C<\1> and C<\0> directly if you want.
390		627
391	=item blessed objects	628	=item blessed objects
392		629
393	Blessed objects are not allowed. JSON::XS currently tries to encode their	630	Blessed objects are not allowed. JSON::XS currently tries to encode their
394	underlying representation (hash- or arrayref), but this behaviour might	631	underlying representation (hash- or arrayref), but this behaviour might
…		…
427	$x *= 1; # same thing, the choise is yours.	664	$x *= 1; # same thing, the choise is yours.
428		665
429	You can not currently output JSON booleans or force the type in other,	666	You can not currently output JSON booleans or force the type in other,
430	less obscure, ways. Tell me if you need this capability.	667	less obscure, ways. Tell me if you need this capability.
431		668
432	=item circular data structures
433
434	Those will be encoded until memory or stackspace runs out.
435
436	=back	669	=back
		670
437		671
438	=head1 COMPARISON	672	=head1 COMPARISON
439		673
440	As already mentioned, this module was created because none of the existing	674	As already mentioned, this module was created because none of the existing
441	JSON modules could be made to work correctly. First I will describe the	675	JSON modules could be made to work correctly. First I will describe the
…		…
519		753
520	Does not check input for validity.	754	Does not check input for validity.
521		755
522	=back	756	=back
523		757
		758
		759	=head2 JSON and YAML
		760
		761	You often hear that JSON is a subset (or a close subset) of YAML. This is,
		762	however, a mass hysteria and very far from the truth. In general, there is
		763	no way to configure JSON::XS to output a data structure as valid YAML.
		764
		765	If you really must use JSON::XS to generate YAML, you should use this
		766	algorithm (subject to change in future versions):
		767
		768	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		769	my $yaml = $to_yaml->encode ($ref) . "\n";
		770
		771	This will usually generate JSON texts that also parse as valid
		772	YAML. Please note that YAML has hardcoded limits on (simple) object key
		773	lengths that JSON doesn't have, so you should make sure that your hash
		774	keys are noticably shorter than the 1024 characters YAML allows.
		775
		776	There might be other incompatibilities that I am not aware of. In general
		777	you should not try to generate YAML with a JSON generator or vice versa,
		778	or try to parse JSON with a YAML parser or vice versa: chances are high
		779	that you will run into severe interoperability problems.
		780
		781
524	=head2 SPEED	782	=head2 SPEED
525		783
526	It seems that JSON::XS is surprisingly fast, as shown in the following	784	It seems that JSON::XS is surprisingly fast, as shown in the following
527	tables. They have been generated with the help of the C<eg/bench> program	785	tables. They have been generated with the help of the C<eg/bench> program
528	in the JSON::XS distribution, to make it easy to compare on your own	786	in the JSON::XS distribution, to make it easy to compare on your own
529	system.	787	system.
530		788
531	First comes a comparison between various modules using a very short JSON	789	First comes a comparison between various modules using a very short
532	string:	790	single-line JSON string:
533		791
534	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	792	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		793	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
535		794
536	It shows the number of encodes/decodes per second (JSON::XS uses the	795	It shows the number of encodes/decodes per second (JSON::XS uses
537	functional interface, while JSON::XS/2 uses the OO interface with	796	the functional interface, while JSON::XS/2 uses the OO interface
538	pretty-printing and hashkey sorting enabled). Higher is better:	797	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
		798	shrink). Higher is better:
539		799
		800	Storable \| 15779.925 \| 14169.946 \|
		801	-----------+------------+------------+
540	module \| encode \| decode \|	802	module \| encode \| decode \|
541	-----------\|------------\|------------\|	803	-----------\|------------\|------------\|
542	JSON \| 11488.516 \| 7823.035 \|	804	JSON \| 4990.842 \| 4088.813 \|
543	JSON::DWIW \| 94708.054 \| 129094.260 \|	805	JSON::DWIW \| 51653.990 \| 71575.154 \|
544	JSON::PC \| 63884.157 \| 128528.212 \|	806	JSON::PC \| 65948.176 \| 74631.744 \|
545	JSON::Syck \| 34898.677 \| 42096.911 \|	807	JSON::PP \| 8931.652 \| 3817.168 \|
546	JSON::XS \| 654027.064 \| 396423.669 \|	808	JSON::Syck \| 24877.248 \| 27776.848 \|
547	JSON::XS/2 \| 371564.190 \| 371725.613 \|	809	JSON::XS \| 388361.481 \| 227951.304 \|
		810	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		811	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		812	Storable \| 16500.016 \| 135300.129 \|
548	-----------+------------+------------+	813	-----------+------------+------------+
549		814
550	That is, JSON::XS is more than six times faster than JSON::DWIW on	815	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
551	encoding, more than three times faster on decoding, and about thirty times	816	about three times faster on decoding, and over fourty times faster
552	faster than JSON, even with pretty-printing and key sorting.	817	than JSON, even with pretty-printing and key sorting. It also compares
		818	favourably to Storable for small amounts of data.
553		819
554	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	820	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
555	search API (http://nanoref.com/yahooapis/mgPdGg):	821	search API (http://nanoref.com/yahooapis/mgPdGg):
556		822
557	module \| encode \| decode \|	823	module \| encode \| decode \|
558	-----------\|------------\|------------\|	824	-----------\|------------\|------------\|
559	JSON \| 273.023 \| 44.674 \|	825	JSON \| 55.260 \| 34.971 \|
560	JSON::DWIW \| 1089.383 \| 1145.704 \|	826	JSON::DWIW \| 825.228 \| 1082.513 \|
561	JSON::PC \| 3097.419 \| 2393.921 \|	827	JSON::PC \| 3571.444 \| 2394.829 \|
562	JSON::Syck \| 514.060 \| 843.053 \|	828	JSON::PP \| 210.987 \| 32.574 \|
563	JSON::XS \| 6479.668 \| 3636.364 \|	829	JSON::Syck \| 552.551 \| 787.544 \|
564	JSON::XS/2 \| 3774.221 \| 3599.124 \|	830	JSON::XS \| 5780.463 \| 4854.519 \|
		831	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		832	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		833	Storable \| 4445.002 \| 5235.027 \|
565	-----------+------------+------------+	834	-----------+------------+------------+
566		835
567	Again, JSON::XS leads by far.	836	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		837	decodes faster).
568		838
569	On large strings containing lots of high unicode characters, some modules	839	On large strings containing lots of high unicode characters, some modules
570	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	840	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
571	will be broken due to missing (or wrong) unicode handling. Others refuse	841	will be broken due to missing (or wrong) unicode handling. Others refuse
572	to decode or encode properly, so it was impossible to prepare a fair	842	to decode or encode properly, so it was impossible to prepare a fair
573	comparison table for that case.	843	comparison table for that case.
574		844
575	=head1 RESOURCE LIMITS
576		845
577	JSON::XS does not impose any limits on the size of JSON texts or Perl	846	=head1 SECURITY CONSIDERATIONS
578	values they represent - if your machine can handle it, JSON::XS will	847
579	encode or decode it. Future versions might optionally impose structure	848	When you are using JSON in a protocol, talking to untrusted potentially
580	depth and memory use resource limits.	849	hostile creatures requires relatively few measures.
		850
		851	First of all, your JSON decoder should be secure, that is, should not have
		852	any buffer overflows. Obviously, this module should ensure that and I am
		853	trying hard on making that true, but you never know.
		854
		855	Second, you need to avoid resource-starving attacks. That means you should
		856	limit the size of JSON texts you accept, or make sure then when your
		857	resources run out, thats just fine (e.g. by using a separate process that
		858	can crash safely). The size of a JSON text in octets or characters is
		859	usually a good indication of the size of the resources required to decode
		860	it into a Perl structure. While JSON::XS can check the size of the JSON
		861	text, it might be too late when you already have it in memory, so you
		862	might want to check the size before you accept the string.
		863
		864	Third, JSON::XS recurses using the C stack when decoding objects and
		865	arrays. The C stack is a limited resource: for instance, on my amd64
		866	machine with 8MB of stack size I can decode around 180k nested arrays but
		867	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		868	to free the temporary). If that is exceeded, the program crashes. to be
		869	conservative, the default nesting limit is set to 512. If your process
		870	has a smaller stack, you should adjust this setting accordingly with the
		871	C<max_depth> method.
		872
		873	And last but least, something else could bomb you that I forgot to think
		874	of. In that case, you get to keep the pieces. I am always open for hints,
		875	though...
		876
		877	If you are using JSON::XS to return packets to consumption
		878	by javascript scripts in a browser you should have a look at
		879	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		880	you are vulnerable to some common attack vectors (which really are browser
		881	design bugs, but it is still you who will have to deal with it, as major
		882	browser developers care only for features, not about doing security
		883	right).
		884
581		885
582	=head1 BUGS	886	=head1 BUGS
583		887
584	While the goal of this module is to be correct, that unfortunately does	888	While the goal of this module is to be correct, that unfortunately does
585	not mean its bug-free, only that I think its design is bug-free. It is	889	not mean its bug-free, only that I think its design is bug-free. It is
586	still very young and not well-tested. If you keep reporting bugs they will	890	still relatively early in its development. If you keep reporting bugs they
587	be fixed swiftly, though.	891	will be fixed swiftly, though.
588		892
589	=cut	893	=cut
		894
		895	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
		896	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
		897
		898	sub true() { $true }
		899	sub false() { $false }
		900
		901	sub is_bool($) {
		902	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
		903	# or UNIVERSAL::isa $_[0], "JSON::Literal"
		904	}
		905
		906	XSLoader::load "JSON::XS", $VERSION;
		907
		908	package JSON::XS::Boolean;
		909
		910	use overload
		911	"0+" => sub { ${$_[0]} },
		912	"++" => sub { $_[0] = ${$_[0]} + 1 },
		913	"--" => sub { $_[0] = ${$_[0]} - 1 },
		914	fallback => 1;
590		915
591	1;	916	1;
592		917
593	=head1 AUTHOR	918	=head1 AUTHOR
594		919

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Comparing JSON-XS/XS.pm (file contents): Revision 1.18 by root, Sat Mar 24 22:55:16 2007 UTC vs. Revision 1.58 by root, Sun Aug 26 21:56:47 2007 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.18 by root, Sat Mar 24 22:55:16 2007 UTC vs.
Revision 1.58 by root, Sun Aug 26 21:56:47 2007 UTC