[ViewVC] Diff of: cvs/JSON-XS/README

Comparing JSON-XS/README (file contents):
Revision 1.12 by root, Wed Jun 6 18:17:13 2007 UTC vs.
Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC

…		…
7	# exported functions, they croak on error	7	# exported functions, they croak on error
8	# and expect/generate UTF-8	8	# and expect/generate UTF-8
9		9
10	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	10	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
11	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	11	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
12
13	# objToJson and jsonToObj aliases to to_json and from_json
14	# are exported for compatibility to the JSON module,
15	# but should not be used in new code.
16		12
17	# OO-interface	13	# OO-interface
18		14
19	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	15	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
20	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	16	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
…		…
91	This function call is functionally identical to:	87	This function call is functionally identical to:
92		88
93	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	89	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
94		90
95	except being faster.	91	except being faster.
		92
		93	$is_boolean = JSON::XS::is_bool $scalar
		94	Returns true if the passed scalar represents either JSON::XS::true
		95	or JSON::XS::false, two constants that act like 1 and 0,
		96	respectively and are used to represent JSON "true" and "false"
		97	values in Perl.
		98
		99	See MAPPING, below, for more information on how JSON values are
		100	mapped to Perl.
96		101
97	OBJECT-ORIENTED INTERFACE	102	OBJECT-ORIENTED INTERFACE
98	The object oriented interface lets you configure your own encoding or	103	The object oriented interface lets you configure your own encoding or
99	decoding style, within the limits of supported formats.	104	decoding style, within the limits of supported formats.
100		105
…		…
268	Example, encode a Perl scalar as JSON value with enabled	273	Example, encode a Perl scalar as JSON value with enabled
269	"allow_nonref", resulting in an invalid JSON text:	274	"allow_nonref", resulting in an invalid JSON text:
270		275
271	JSON::XS->new->allow_nonref->encode ("Hello, World!")	276	JSON::XS->new->allow_nonref->encode ("Hello, World!")
272	=> "Hello, World!"	277	=> "Hello, World!"
		278
		279	$json = $json->allow_blessed ([$enable])
		280	If $enable is true (or missing), then the "encode" method will not
		281	barf when it encounters a blessed reference. Instead, the value of
		282	the convert_blessed option will decide wether "null"
		283	("convert_blessed" disabled or no "to_json" method found) or a
		284	representation of the object ("convert_blessed" enabled and
		285	"to_json" method found) is being encoded. Has no effect on "decode".
		286
		287	If $enable is false (the default), then "encode" will throw an
		288	exception when it encounters a blessed object.
		289
		290	$json = $json->convert_blessed ([$enable])
		291	If $enable is true (or missing), then "encode", upon encountering a
		292	blessed object, will check for the availability of the "TO_JSON"
		293	method on the object's class. If found, it will be called in scalar
		294	context and the resulting scalar will be encoded instead of the
		295	object. If no "TO_JSON" method is found, the value of
		296	"allow_blessed" will decide what to do.
		297
		298	The "TO_JSON" method may safely call die if it wants. If "TO_JSON"
		299	returns other blessed objects, those will be handled in the same
		300	way. "TO_JSON" must take care of not causing an endless recursion
		301	cycle (== crash) in this case. The name of "TO_JSON" was chosen
		302	because other methods called by the Perl core (== not by the user of
		303	the object) are usually in upper case letters and to avoid
		304	collisions with the "to_json" function.
		305
		306	This setting does not yet influence "decode" in any way, but in the
		307	future, global hooks might get installed that influence "decode" and
		308	are enabled by this setting.
		309
		310	If $enable is false, then the "allow_blessed" setting will decide
		311	what to do when a blessed object is found.
		312
		313	$json = $json->filter_json_object ([$coderef->($hashref)])
		314	When $coderef is specified, it will be called from "decode" each
		315	time it decodes a JSON object. The only argument is a reference to
		316	the newly-created hash. If the code references returns a single
		317	scalar (which need not be a reference), this value (i.e. a copy of
		318	that scalar to avoid aliasing) is inserted into the deserialised
		319	data structure. If it returns an empty list (NOTE: not "undef",
		320	which is a valid scalar), the original deserialised hash will be
		321	inserted. This setting can slow down decoding considerably.
		322
		323	When $coderef is omitted or undefined, any existing callback will be
		324	removed and "decode" will not change the deserialised hash in any
		325	way.
		326
		327	Example, convert all JSON objects into the integer 5:
		328
		329	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		330	# returns [5]
		331	$js->decode ('[{}]')
		332	# throw an exception because allow_nonref is not enabled
		333	# so a lone 5 is not allowed.
		334	$js->decode ('{"a":1, "b":2}');
		335
		336	$json = $json->filter_json_single_key_object ($key [=>
		337	$coderef->($value)])
		338	Works remotely similar to "filter_json_object", but is only called
		339	for JSON objects having a single key named $key.
		340
		341	This $coderef is called before the one specified via
		342	"filter_json_object", if any. It gets passed the single value in the
		343	JSON object. If it returns a single value, it will be inserted into
		344	the data structure. If it returns nothing (not even "undef" but the
		345	empty list), the callback from "filter_json_object" will be called
		346	next, as if no single-key callback were specified.
		347
		348	If $coderef is omitted or undefined, the corresponding callback will
		349	be disabled. There can only ever be one callback for a given key.
		350
		351	As this callback gets called less often then the
		352	"filter_json_object" one, decoding speed will not usually suffer as
		353	much. Therefore, single-key objects make excellent targets to
		354	serialise Perl objects into, especially as single-key JSON objects
		355	are as close to the type-tagged value concept as JSON gets (its
		356	basically an ID/VALUE tuple). Of course, JSON does not support this
		357	in any way, so you need to make sure your data never looks like a
		358	serialised Perl hash.
		359
		360	Typical names for the single object key are "__class_whatever__", or
		361	"$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even
		362	things like "__class_md5sum(classname)__", to reduce the risk of
		363	clashing with real hashes.
		364
		365	Example, decode JSON objects of the form "{ "__widget__" => <id> }"
		366	into the corresponding $WIDGET{<id>} object:
		367
		368	# return whatever is in $WIDGET{5}:
		369	JSON::XS
		370	->new
		371	->filter_json_single_key_object (__widget__ => sub {
		372	$WIDGET{ $_[0] }
		373	})
		374	->decode ('{"__widget__": 5')
		375
		376	# this can be used with a TO_JSON method in some "widget" class
		377	# for serialisation to json:
		378	sub WidgetBase::TO_JSON {
		379	my ($self) = @_;
		380
		381	unless ($self->{id}) {
		382	$self->{id} = ..get..some..id..;
		383	$WIDGET{$self->{id}} = $self;
		384	}
		385
		386	{ __widget__ => $self->{id} }
		387	}
273		388
274	$json = $json->shrink ([$enable])	389	$json = $json->shrink ([$enable])
275	Perl usually over-allocates memory a bit when allocating space for	390	Perl usually over-allocates memory a bit when allocating space for
276	strings. This flag optionally resizes strings generated by either	391	strings. This flag optionally resizes strings generated by either
277	"encode" or "decode" to their minimum size possible. This can save	392	"encode" or "decode" to their minimum size possible. This can save
…		…
310	crossed to reach a given character in a string.	425	crossed to reach a given character in a string.
311		426
312	Setting the maximum depth to one disallows any nesting, so that	427	Setting the maximum depth to one disallows any nesting, so that
313	ensures that the object is only a single hash/object or array.	428	ensures that the object is only a single hash/object or array.
314		429
315	The argument to "max_depth" will be rounded up to the next nearest	430	The argument to "max_depth" will be rounded up to the next highest
316	power of two.	431	power of two. If no argument is given, the highest possible setting
		432	will be used, which is rarely useful.
		433
		434	See SECURITY CONSIDERATIONS, below, for more info on why this is
		435	useful.
		436
		437	$json = $json->max_size ([$maximum_string_size])
		438	Set the maximum length a JSON text may have (in bytes) where
		439	decoding is being attempted. The default is 0, meaning no limit.
		440	When "decode" is called on a string longer then this number of
		441	characters it will not attempt to decode the string but throw an
		442	exception. This setting has no effect on "encode" (yet).
		443
		444	The argument to "max_size" will be rounded up to the next highest
		445	power of two (so may be more than requested). If no argument is
		446	given, the limit check will be deactivated (same as when 0 is
		447	specified).
317		448
318	See SECURITY CONSIDERATIONS, below, for more info on why this is	449	See SECURITY CONSIDERATIONS, below, for more info on why this is
319	useful.	450	useful.
320		451
321	$json_text = $json->encode ($perl_scalar)	452	$json_text = $json->encode ($perl_scalar)
…		…
371	A JSON string becomes a string scalar in Perl - Unicode codepoints	502	A JSON string becomes a string scalar in Perl - Unicode codepoints
372	in JSON are represented by the same codepoints in the Perl string,	503	in JSON are represented by the same codepoints in the Perl string,
373	so no manual decoding is necessary.	504	so no manual decoding is necessary.
374		505
375	number	506	number
376	A JSON number becomes either an integer or numeric (floating point)	507	A JSON number becomes either an integer, numeric (floating point) or
377	scalar in perl, depending on its range and any fractional parts. On	508	string scalar in perl, depending on its range and any fractional
378	the Perl level, there is no difference between those as Perl handles	509	parts. On the Perl level, there is no difference between those as
379	all the conversion details, but an integer may take slightly less	510	Perl handles all the conversion details, but an integer may take
380	memory and might represent more values exactly than (floating point)	511	slightly less memory and might represent more values exactly than
381	numbers.	512	(floating point) numbers.
		513
		514	If the number consists of digits only, JSON::XS will try to
		515	represent it as an integer value. If that fails, it will try to
		516	represent it as a numeric (floating point) value if that is possible
		517	without loss of precision. Otherwise it will preserve the number as
		518	a string value.
		519
		520	Numbers containing a fractional or exponential part will always be
		521	represented as numeric (floating point) values, possibly at a loss
		522	of precision.
		523
		524	This might create round-tripping problems as numbers might become
		525	strings, but as Perl is typeless there is no other way to do it.
382		526
383	true, false	527	true, false
384	These JSON atoms become 0, 1, respectively. Information is lost in	528	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
385	this process. Future versions might represent those values	529	respectively. They are overloaded to act almost exactly like the
386	differently, but they will be guarenteed to act like these integers	530	numbers 1 and 0. You can check wether a scalar is a JSON boolean by
387	would normally in Perl.	531	using the "JSON::XS::is_bool" function.
388		532
389	null	533	null
390	A JSON null atom becomes "undef" in Perl.	534	A JSON null atom becomes "undef" in Perl.
391		535
392	PERL -> JSON	536	PERL -> JSON
…		…
416	can also use "JSON::XS::false" and "JSON::XS::true" to improve	560	can also use "JSON::XS::false" and "JSON::XS::true" to improve
417	readability.	561	readability.
418		562
419	to_json [\0,JSON::XS::true] # yields [false,true]	563	to_json [\0,JSON::XS::true] # yields [false,true]
420		564
		565	JSON::XS::true, JSON::XS::false
		566	These special values become JSON true and JSON false values,
		567	respectively. You cna alos use "\1" and "\0" directly if you want.
		568
421	blessed objects	569	blessed objects
422	Blessed objects are not allowed. JSON::XS currently tries to encode	570	Blessed objects are not allowed. JSON::XS currently tries to encode
423	their underlying representation (hash- or arrayref), but this	571	their underlying representation (hash- or arrayref), but this
424	behaviour might change in future versions.	572	behaviour might change in future versions.
425		573
…		…
535	Does not generate valid JSON texts (key strings are often unquoted,	683	Does not generate valid JSON texts (key strings are often unquoted,
536	empty keys result in nothing being output)	684	empty keys result in nothing being output)
537		685
538	Does not check input for validity.	686	Does not check input for validity.
539		687
		688	JSON and YAML
		689	You often hear that JSON is a subset (or a close subset) of YAML. This
		690	is, however, a mass hysteria and very far from the truth. In general,
		691	there is no way to configure JSON::XS to output a data structure as
		692	valid YAML.
		693
		694	If you really must use JSON::XS to generate YAML, you should use this
		695	algorithm (subject to change in future versions):
		696
		697	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		698	my $yaml = $to_yaml->encode ($ref) . "\n";
		699
		700	This will usually generate JSON texts that also parse as valid YAML.
		701	Please note that YAML has hardcoded limits on (simple) object key
		702	lengths that JSON doesn't have, so you should make sure that your hash
		703	keys are noticably shorter than the 1024 characters YAML allows.
		704
		705	There might be other incompatibilities that I am not aware of. In
		706	general you should not try to generate YAML with a JSON generator or
		707	vice versa, or try to parse JSON with a YAML parser or vice versa:
		708	chances are high that you will run into severe interoperability
		709	problems.
		710
540	SPEED	711	SPEED
541	It seems that JSON::XS is surprisingly fast, as shown in the following	712	It seems that JSON::XS is surprisingly fast, as shown in the following
542	tables. They have been generated with the help of the "eg/bench" program	713	tables. They have been generated with the help of the "eg/bench" program
543	in the JSON::XS distribution, to make it easy to compare on your own	714	in the JSON::XS distribution, to make it easy to compare on your own
544	system.	715	system.
…		…
549	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	720	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
550	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	721	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
551		722
552	It shows the number of encodes/decodes per second (JSON::XS uses the	723	It shows the number of encodes/decodes per second (JSON::XS uses the
553	functional interface, while JSON::XS/2 uses the OO interface with	724	functional interface, while JSON::XS/2 uses the OO interface with
554	pretty-printing and hashkey sorting enabled). Higher is better:	725	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
		726	Higher is better:
555		727
		728	Storable \| 15779.925 \| 14169.946 \|
		729	-----------+------------+------------+
556	module \| encode \| decode \|	730	module \| encode \| decode \|
557	-----------\|------------\|------------\|	731	-----------\|------------\|------------\|
558	JSON \| 7645.468 \| 4208.613 \|	732	JSON \| 4990.842 \| 4088.813 \|
559	JSON::DWIW \| 68534.379 \| 79437.576 \|	733	JSON::DWIW \| 51653.990 \| 71575.154 \|
560	JSON::PC \| 65948.176 \| 78251.940 \|	734	JSON::PC \| 65948.176 \| 74631.744 \|
561	JSON::Syck \| 23379.621 \| 28416.694 \|	735	JSON::PP \| 8931.652 \| 3817.168 \|
		736	JSON::Syck \| 24877.248 \| 27776.848 \|
562	JSON::XS \| 388361.481 \| 199728.762 \|	737	JSON::XS \| 388361.481 \| 227951.304 \|
563	JSON::XS/2 \| 218453.333 \| 192399.266 \|	738	JSON::XS/2 \| 227951.304 \| 218453.333 \|
564	JSON::XS/3 \| 338250.323 \| 192399.266 \|	739	JSON::XS/3 \| 338250.323 \| 218453.333 \|
565	Storable \| 15732.573 \| 28571.553 \|	740	Storable \| 16500.016 \| 135300.129 \|
566	-----------+------------+------------+	741	-----------+------------+------------+
567		742
568	That is, JSON::XS is about five times faster than JSON::DWIW on	743	That is, JSON::XS is about five times faster than JSON::DWIW on
569	encoding, about three times faster on decoding, and over fourty times	744	encoding, about three times faster on decoding, and over fourty times
570	faster than JSON, even with pretty-printing and key sorting. It also	745	faster than JSON, even with pretty-printing and key sorting. It also
…		…
573	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	748	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
574	search API (http://nanoref.com/yahooapis/mgPdGg):	749	search API (http://nanoref.com/yahooapis/mgPdGg):
575		750
576	module \| encode \| decode \|	751	module \| encode \| decode \|
577	-----------\|------------\|------------\|	752	-----------\|------------\|------------\|
578	JSON \| 254.685 \| 37.665 \|	753	JSON \| 55.260 \| 34.971 \|
579	JSON::DWIW \| 1014.244 \| 1087.678 \|	754	JSON::DWIW \| 825.228 \| 1082.513 \|
580	JSON::PC \| 3602.116 \| 2307.352 \|	755	JSON::PC \| 3571.444 \| 2394.829 \|
581	JSON::Syck \| 558.035 \| 776.263 \|	756	JSON::PP \| 210.987 \| 32.574 \|
582	JSON::XS \| 5747.196 \| 3543.684 \|	757	JSON::Syck \| 552.551 \| 787.544 \|
583	JSON::XS/2 \| 3968.121 \| 3589.170 \|	758	JSON::XS \| 5780.463 \| 4854.519 \|
584	JSON::XS/3 \| 6105.246 \| 3561.134 \|	759	JSON::XS/2 \| 3869.998 \| 4798.975 \|
585	Storable \| 4456.337 \| 5320.020 \|	760	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		761	Storable \| 4445.002 \| 5235.027 \|
586	-----------+------------+------------+	762	-----------+------------+------------+
587		763
588	Again, JSON::XS leads by far.	764	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		765	decodes faster).
589		766
590	On large strings containing lots of high unicode characters, some	767	On large strings containing lots of high unicode characters, some
591	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the	768	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
592	result will be broken due to missing (or wrong) unicode handling. Others	769	result will be broken due to missing (or wrong) unicode handling. Others
593	refuse to decode or encode properly, so it was impossible to prepare a	770	refuse to decode or encode properly, so it was impossible to prepare a
…		…
604	Second, you need to avoid resource-starving attacks. That means you	781	Second, you need to avoid resource-starving attacks. That means you
605	should limit the size of JSON texts you accept, or make sure then when	782	should limit the size of JSON texts you accept, or make sure then when
606	your resources run out, thats just fine (e.g. by using a separate	783	your resources run out, thats just fine (e.g. by using a separate
607	process that can crash safely). The size of a JSON text in octets or	784	process that can crash safely). The size of a JSON text in octets or
608	characters is usually a good indication of the size of the resources	785	characters is usually a good indication of the size of the resources
609	required to decode it into a Perl structure.	786	required to decode it into a Perl structure. While JSON::XS can check
		787	the size of the JSON text, it might be too late when you already have it
		788	in memory, so you might want to check the size before you accept the
		789	string.
610		790
611	Third, JSON::XS recurses using the C stack when decoding objects and	791	Third, JSON::XS recurses using the C stack when decoding objects and
612	arrays. The C stack is a limited resource: for instance, on my amd64	792	arrays. The C stack is a limited resource: for instance, on my amd64
613	machine with 8MB of stack size I can decode around 180k nested arrays	793	machine with 8MB of stack size I can decode around 180k nested arrays
614	but only 14k nested JSON objects (due to perl itself recursing deeply on	794	but only 14k nested JSON objects (due to perl itself recursing deeply on
…		…
619		799
620	And last but least, something else could bomb you that I forgot to think	800	And last but least, something else could bomb you that I forgot to think
621	of. In that case, you get to keep the pieces. I am always open for	801	of. In that case, you get to keep the pieces. I am always open for
622	hints, though...	802	hints, though...
623		803
		804	If you are using JSON::XS to return packets to consumption by javascript
		805	scripts in a browser you should have a look at
		806	<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		807	you are vulnerable to some common attack vectors (which really are
		808	browser design bugs, but it is still you who will have to deal with it,
		809	as major browser developers care only for features, not about doing
		810	security right).
		811
624	BUGS	812	BUGS
625	While the goal of this module is to be correct, that unfortunately does	813	While the goal of this module is to be correct, that unfortunately does
626	not mean its bug-free, only that I think its design is bug-free. It is	814	not mean its bug-free, only that I think its design is bug-free. It is
627	still relatively early in its development. If you keep reporting bugs	815	still relatively early in its development. If you keep reporting bugs
628	they will be fixed swiftly, though.	816	they will be fixed swiftly, though.

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Comparing JSON-XS/README (file contents): Revision 1.12 by root, Wed Jun 6 18:17:13 2007 UTC vs. Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC

Diff Legend

Comparing JSON-XS/README (file contents):
Revision 1.12 by root, Wed Jun 6 18:17:13 2007 UTC vs.
Revision 1.16 by root, Thu Jul 26 11:33:35 2007 UTC