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

Comparing JSON-XS/README (file contents):
Revision 1.11 by root, Wed May 9 16:35:21 2007 UTC vs.
Revision 1.17 by root, Mon Aug 27 02:03:23 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
…		…
235		240
236	Example, space_before and indent disabled, space_after enabled:	241	Example, space_before and indent disabled, space_after enabled:
237		242
238	{"key": "value"}	243	{"key": "value"}
239		244
		245	$json = $json->relaxed ([$enable])
		246	If $enable is true (or missing), then "decode" will accept some
		247	extensions to normal JSON syntax (see below). "encode" will not be
		248	affected in anyway. *Be aware that this option makes you accept
		249	invalid JSON texts as if they were valid!*. I suggest only to use
		250	this option to parse application-specific files written by humans
		251	(configuration files, resource files etc.)
		252
		253	If $enable is false (the default), then "decode" will only accept
		254	valid JSON texts.
		255
		256	Currently accepted extensions are:
		257
		258	* list items can have an end-comma
		259	JSON separates array elements and key-value pairs with commas.
		260	This can be annoying if you write JSON texts manually and want
		261	to be able to quickly append elements, so this extension accepts
		262	comma at the end of such items not just between them:
		263
		264	[
		265	1,
		266	2, <- this comma not normally allowed
		267	]
		268	{
		269	"k1": "v1",
		270	"k2": "v2", <- this comma not normally allowed
		271	}
		272
240	$json = $json->canonical ([$enable])	273	$json = $json->canonical ([$enable])
241	If $enable is true (or missing), then the "encode" method will	274	If $enable is true (or missing), then the "encode" method will
242	output JSON objects by sorting their keys. This is adding a	275	output JSON objects by sorting their keys. This is adding a
243	comparatively high overhead.	276	comparatively high overhead.
244		277
…		…
268	Example, encode a Perl scalar as JSON value with enabled	301	Example, encode a Perl scalar as JSON value with enabled
269	"allow_nonref", resulting in an invalid JSON text:	302	"allow_nonref", resulting in an invalid JSON text:
270		303
271	JSON::XS->new->allow_nonref->encode ("Hello, World!")	304	JSON::XS->new->allow_nonref->encode ("Hello, World!")
272	=> "Hello, World!"	305	=> "Hello, World!"
		306
		307	$json = $json->allow_blessed ([$enable])
		308	If $enable is true (or missing), then the "encode" method will not
		309	barf when it encounters a blessed reference. Instead, the value of
		310	the convert_blessed option will decide wether "null"
		311	("convert_blessed" disabled or no "to_json" method found) or a
		312	representation of the object ("convert_blessed" enabled and
		313	"to_json" method found) is being encoded. Has no effect on "decode".
		314
		315	If $enable is false (the default), then "encode" will throw an
		316	exception when it encounters a blessed object.
		317
		318	$json = $json->convert_blessed ([$enable])
		319	If $enable is true (or missing), then "encode", upon encountering a
		320	blessed object, will check for the availability of the "TO_JSON"
		321	method on the object's class. If found, it will be called in scalar
		322	context and the resulting scalar will be encoded instead of the
		323	object. If no "TO_JSON" method is found, the value of
		324	"allow_blessed" will decide what to do.
		325
		326	The "TO_JSON" method may safely call die if it wants. If "TO_JSON"
		327	returns other blessed objects, those will be handled in the same
		328	way. "TO_JSON" must take care of not causing an endless recursion
		329	cycle (== crash) in this case. The name of "TO_JSON" was chosen
		330	because other methods called by the Perl core (== not by the user of
		331	the object) are usually in upper case letters and to avoid
		332	collisions with the "to_json" function.
		333
		334	This setting does not yet influence "decode" in any way, but in the
		335	future, global hooks might get installed that influence "decode" and
		336	are enabled by this setting.
		337
		338	If $enable is false, then the "allow_blessed" setting will decide
		339	what to do when a blessed object is found.
		340
		341	$json = $json->filter_json_object ([$coderef->($hashref)])
		342	When $coderef is specified, it will be called from "decode" each
		343	time it decodes a JSON object. The only argument is a reference to
		344	the newly-created hash. If the code references returns a single
		345	scalar (which need not be a reference), this value (i.e. a copy of
		346	that scalar to avoid aliasing) is inserted into the deserialised
		347	data structure. If it returns an empty list (NOTE: not "undef",
		348	which is a valid scalar), the original deserialised hash will be
		349	inserted. This setting can slow down decoding considerably.
		350
		351	When $coderef is omitted or undefined, any existing callback will be
		352	removed and "decode" will not change the deserialised hash in any
		353	way.
		354
		355	Example, convert all JSON objects into the integer 5:
		356
		357	my $js = JSON::XS->new->filter_json_object (sub { 5 });
		358	# returns [5]
		359	$js->decode ('[{}]')
		360	# throw an exception because allow_nonref is not enabled
		361	# so a lone 5 is not allowed.
		362	$js->decode ('{"a":1, "b":2}');
		363
		364	$json = $json->filter_json_single_key_object ($key [=>
		365	$coderef->($value)])
		366	Works remotely similar to "filter_json_object", but is only called
		367	for JSON objects having a single key named $key.
		368
		369	This $coderef is called before the one specified via
		370	"filter_json_object", if any. It gets passed the single value in the
		371	JSON object. If it returns a single value, it will be inserted into
		372	the data structure. If it returns nothing (not even "undef" but the
		373	empty list), the callback from "filter_json_object" will be called
		374	next, as if no single-key callback were specified.
		375
		376	If $coderef is omitted or undefined, the corresponding callback will
		377	be disabled. There can only ever be one callback for a given key.
		378
		379	As this callback gets called less often then the
		380	"filter_json_object" one, decoding speed will not usually suffer as
		381	much. Therefore, single-key objects make excellent targets to
		382	serialise Perl objects into, especially as single-key JSON objects
		383	are as close to the type-tagged value concept as JSON gets (its
		384	basically an ID/VALUE tuple). Of course, JSON does not support this
		385	in any way, so you need to make sure your data never looks like a
		386	serialised Perl hash.
		387
		388	Typical names for the single object key are "__class_whatever__", or
		389	"$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even
		390	things like "__class_md5sum(classname)__", to reduce the risk of
		391	clashing with real hashes.
		392
		393	Example, decode JSON objects of the form "{ "__widget__" => <id> }"
		394	into the corresponding $WIDGET{<id>} object:
		395
		396	# return whatever is in $WIDGET{5}:
		397	JSON::XS
		398	->new
		399	->filter_json_single_key_object (__widget__ => sub {
		400	$WIDGET{ $_[0] }
		401	})
		402	->decode ('{"__widget__": 5')
		403
		404	# this can be used with a TO_JSON method in some "widget" class
		405	# for serialisation to json:
		406	sub WidgetBase::TO_JSON {
		407	my ($self) = @_;
		408
		409	unless ($self->{id}) {
		410	$self->{id} = ..get..some..id..;
		411	$WIDGET{$self->{id}} = $self;
		412	}
		413
		414	{ __widget__ => $self->{id} }
		415	}
273		416
274	$json = $json->shrink ([$enable])	417	$json = $json->shrink ([$enable])
275	Perl usually over-allocates memory a bit when allocating space for	418	Perl usually over-allocates memory a bit when allocating space for
276	strings. This flag optionally resizes strings generated by either	419	strings. This flag optionally resizes strings generated by either
277	"encode" or "decode" to their minimum size possible. This can save	420	"encode" or "decode" to their minimum size possible. This can save
…		…
310	crossed to reach a given character in a string.	453	crossed to reach a given character in a string.
311		454
312	Setting the maximum depth to one disallows any nesting, so that	455	Setting the maximum depth to one disallows any nesting, so that
313	ensures that the object is only a single hash/object or array.	456	ensures that the object is only a single hash/object or array.
314		457
315	The argument to "max_depth" will be rounded up to the next nearest	458	The argument to "max_depth" will be rounded up to the next highest
316	power of two.	459	power of two. If no argument is given, the highest possible setting
		460	will be used, which is rarely useful.
		461
		462	See SECURITY CONSIDERATIONS, below, for more info on why this is
		463	useful.
		464
		465	$json = $json->max_size ([$maximum_string_size])
		466	Set the maximum length a JSON text may have (in bytes) where
		467	decoding is being attempted. The default is 0, meaning no limit.
		468	When "decode" is called on a string longer then this number of
		469	characters it will not attempt to decode the string but throw an
		470	exception. This setting has no effect on "encode" (yet).
		471
		472	The argument to "max_size" will be rounded up to the next highest
		473	power of two (so may be more than requested). If no argument is
		474	given, the limit check will be deactivated (same as when 0 is
		475	specified).
317		476
318	See SECURITY CONSIDERATIONS, below, for more info on why this is	477	See SECURITY CONSIDERATIONS, below, for more info on why this is
319	useful.	478	useful.
320		479
321	$json_text = $json->encode ($perl_scalar)	480	$json_text = $json->encode ($perl_scalar)
…		…
371	A JSON string becomes a string scalar in Perl - Unicode codepoints	530	A JSON string becomes a string scalar in Perl - Unicode codepoints
372	in JSON are represented by the same codepoints in the Perl string,	531	in JSON are represented by the same codepoints in the Perl string,
373	so no manual decoding is necessary.	532	so no manual decoding is necessary.
374		533
375	number	534	number
376	A JSON number becomes either an integer or numeric (floating point)	535	A JSON number becomes either an integer, numeric (floating point) or
377	scalar in perl, depending on its range and any fractional parts. On	536	string scalar in perl, depending on its range and any fractional
378	the Perl level, there is no difference between those as Perl handles	537	parts. On the Perl level, there is no difference between those as
379	all the conversion details, but an integer may take slightly less	538	Perl handles all the conversion details, but an integer may take
380	memory and might represent more values exactly than (floating point)	539	slightly less memory and might represent more values exactly than
381	numbers.	540	(floating point) numbers.
		541
		542	If the number consists of digits only, JSON::XS will try to
		543	represent it as an integer value. If that fails, it will try to
		544	represent it as a numeric (floating point) value if that is possible
		545	without loss of precision. Otherwise it will preserve the number as
		546	a string value.
		547
		548	Numbers containing a fractional or exponential part will always be
		549	represented as numeric (floating point) values, possibly at a loss
		550	of precision.
		551
		552	This might create round-tripping problems as numbers might become
		553	strings, but as Perl is typeless there is no other way to do it.
382		554
383	true, false	555	true, false
384	These JSON atoms become 0, 1, respectively. Information is lost in	556	These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
385	this process. Future versions might represent those values	557	respectively. They are overloaded to act almost exactly like the
386	differently, but they will be guarenteed to act like these integers	558	numbers 1 and 0. You can check wether a scalar is a JSON boolean by
387	would normally in Perl.	559	using the "JSON::XS::is_bool" function.
388		560
389	null	561	null
390	A JSON null atom becomes "undef" in Perl.	562	A JSON null atom becomes "undef" in Perl.
391		563
392	PERL -> JSON	564	PERL -> JSON
…		…
416	can also use "JSON::XS::false" and "JSON::XS::true" to improve	588	can also use "JSON::XS::false" and "JSON::XS::true" to improve
417	readability.	589	readability.
418		590
419	to_json [\0,JSON::XS::true] # yields [false,true]	591	to_json [\0,JSON::XS::true] # yields [false,true]
420		592
		593	JSON::XS::true, JSON::XS::false
		594	These special values become JSON true and JSON false values,
		595	respectively. You cna alos use "\1" and "\0" directly if you want.
		596
421	blessed objects	597	blessed objects
422	Blessed objects are not allowed. JSON::XS currently tries to encode	598	Blessed objects are not allowed. JSON::XS currently tries to encode
423	their underlying representation (hash- or arrayref), but this	599	their underlying representation (hash- or arrayref), but this
424	behaviour might change in future versions.	600	behaviour might change in future versions.
425		601
…		…
535	Does not generate valid JSON texts (key strings are often unquoted,	711	Does not generate valid JSON texts (key strings are often unquoted,
536	empty keys result in nothing being output)	712	empty keys result in nothing being output)
537		713
538	Does not check input for validity.	714	Does not check input for validity.
539		715
		716	JSON and YAML
		717	You often hear that JSON is a subset (or a close subset) of YAML. This
		718	is, however, a mass hysteria and very far from the truth. In general,
		719	there is no way to configure JSON::XS to output a data structure as
		720	valid YAML.
		721
		722	If you really must use JSON::XS to generate YAML, you should use this
		723	algorithm (subject to change in future versions):
		724
		725	my $to_yaml = JSON::XS->new->utf8->space_after (1);
		726	my $yaml = $to_yaml->encode ($ref) . "\n";
		727
		728	This will usually generate JSON texts that also parse as valid YAML.
		729	Please note that YAML has hardcoded limits on (simple) object key
		730	lengths that JSON doesn't have, so you should make sure that your hash
		731	keys are noticably shorter than the 1024 characters YAML allows.
		732
		733	There might be other incompatibilities that I am not aware of. In
		734	general you should not try to generate YAML with a JSON generator or
		735	vice versa, or try to parse JSON with a YAML parser or vice versa:
		736	chances are high that you will run into severe interoperability
		737	problems.
		738
540	SPEED	739	SPEED
541	It seems that JSON::XS is surprisingly fast, as shown in the following	740	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	741	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	742	in the JSON::XS distribution, to make it easy to compare on your own
544	system.	743	system.
545		744
546	First comes a comparison between various modules using a very short JSON	745	First comes a comparison between various modules using a very short
547	string:	746	single-line JSON string:
548		747
549	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}	748	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
		749	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
550		750
551	It shows the number of encodes/decodes per second (JSON::XS uses the	751	It shows the number of encodes/decodes per second (JSON::XS uses the
552	functional interface, while JSON::XS/2 uses the OO interface with	752	functional interface, while JSON::XS/2 uses the OO interface with
553	pretty-printing and hashkey sorting enabled). Higher is better:	753	pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink).
		754	Higher is better:
554		755
		756	Storable \| 15779.925 \| 14169.946 \|
		757	-----------+------------+------------+
555	module \| encode \| decode \|	758	module \| encode \| decode \|
556	-----------\|------------\|------------\|	759	-----------\|------------\|------------\|
557	JSON \| 11488.516 \| 7823.035 \|	760	JSON \| 4990.842 \| 4088.813 \|
558	JSON::DWIW \| 94708.054 \| 129094.260 \|	761	JSON::DWIW \| 51653.990 \| 71575.154 \|
559	JSON::PC \| 63884.157 \| 128528.212 \|	762	JSON::PC \| 65948.176 \| 74631.744 \|
		763	JSON::PP \| 8931.652 \| 3817.168 \|
560	JSON::Syck \| 34898.677 \| 42096.911 \|	764	JSON::Syck \| 24877.248 \| 27776.848 \|
561	JSON::XS \| 654027.064 \| 396423.669 \|	765	JSON::XS \| 388361.481 \| 227951.304 \|
562	JSON::XS/2 \| 371564.190 \| 371725.613 \|	766	JSON::XS/2 \| 227951.304 \| 218453.333 \|
		767	JSON::XS/3 \| 338250.323 \| 218453.333 \|
		768	Storable \| 16500.016 \| 135300.129 \|
563	-----------+------------+------------+	769	-----------+------------+------------+
564		770
565	That is, JSON::XS is more than six times faster than JSON::DWIW on	771	That is, JSON::XS is about five times faster than JSON::DWIW on
566	encoding, more than three times faster on decoding, and about thirty	772	encoding, about three times faster on decoding, and over fourty times
567	times faster than JSON, even with pretty-printing and key sorting.	773	faster than JSON, even with pretty-printing and key sorting. It also
		774	compares favourably to Storable for small amounts of data.
568		775
569	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	776	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
570	search API (http://nanoref.com/yahooapis/mgPdGg):	777	search API (http://nanoref.com/yahooapis/mgPdGg):
571		778
572	module \| encode \| decode \|	779	module \| encode \| decode \|
573	-----------\|------------\|------------\|	780	-----------\|------------\|------------\|
574	JSON \| 273.023 \| 44.674 \|	781	JSON \| 55.260 \| 34.971 \|
575	JSON::DWIW \| 1089.383 \| 1145.704 \|	782	JSON::DWIW \| 825.228 \| 1082.513 \|
576	JSON::PC \| 3097.419 \| 2393.921 \|	783	JSON::PC \| 3571.444 \| 2394.829 \|
577	JSON::Syck \| 514.060 \| 843.053 \|	784	JSON::PP \| 210.987 \| 32.574 \|
578	JSON::XS \| 6479.668 \| 3636.364 \|	785	JSON::Syck \| 552.551 \| 787.544 \|
579	JSON::XS/2 \| 3774.221 \| 3599.124 \|	786	JSON::XS \| 5780.463 \| 4854.519 \|
		787	JSON::XS/2 \| 3869.998 \| 4798.975 \|
		788	JSON::XS/3 \| 5862.880 \| 4798.975 \|
		789	Storable \| 4445.002 \| 5235.027 \|
580	-----------+------------+------------+	790	-----------+------------+------------+
581		791
582	Again, JSON::XS leads by far.	792	Again, JSON::XS leads by far (except for Storable which non-surprisingly
		793	decodes faster).
583		794
584	On large strings containing lots of high unicode characters, some	795	On large strings containing lots of high unicode characters, some
585	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the	796	modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
586	result will be broken due to missing (or wrong) unicode handling. Others	797	result will be broken due to missing (or wrong) unicode handling. Others
587	refuse to decode or encode properly, so it was impossible to prepare a	798	refuse to decode or encode properly, so it was impossible to prepare a
…		…
598	Second, you need to avoid resource-starving attacks. That means you	809	Second, you need to avoid resource-starving attacks. That means you
599	should limit the size of JSON texts you accept, or make sure then when	810	should limit the size of JSON texts you accept, or make sure then when
600	your resources run out, thats just fine (e.g. by using a separate	811	your resources run out, thats just fine (e.g. by using a separate
601	process that can crash safely). The size of a JSON text in octets or	812	process that can crash safely). The size of a JSON text in octets or
602	characters is usually a good indication of the size of the resources	813	characters is usually a good indication of the size of the resources
603	required to decode it into a Perl structure.	814	required to decode it into a Perl structure. While JSON::XS can check
		815	the size of the JSON text, it might be too late when you already have it
		816	in memory, so you might want to check the size before you accept the
		817	string.
604		818
605	Third, JSON::XS recurses using the C stack when decoding objects and	819	Third, JSON::XS recurses using the C stack when decoding objects and
606	arrays. The C stack is a limited resource: for instance, on my amd64	820	arrays. The C stack is a limited resource: for instance, on my amd64
607	machine with 8MB of stack size I can decode around 180k nested arrays	821	machine with 8MB of stack size I can decode around 180k nested arrays
608	but only 14k nested JSON objects (due to perl itself recursing deeply on	822	but only 14k nested JSON objects (due to perl itself recursing deeply on
…		…
613		827
614	And last but least, something else could bomb you that I forgot to think	828	And last but least, something else could bomb you that I forgot to think
615	of. In that case, you get to keep the pieces. I am always open for	829	of. In that case, you get to keep the pieces. I am always open for
616	hints, though...	830	hints, though...
617		831
		832	If you are using JSON::XS to return packets to consumption by javascript
		833	scripts in a browser you should have a look at
		834	<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
		835	you are vulnerable to some common attack vectors (which really are
		836	browser design bugs, but it is still you who will have to deal with it,
		837	as major browser developers care only for features, not about doing
		838	security right).
		839
618	BUGS	840	BUGS
619	While the goal of this module is to be correct, that unfortunately does	841	While the goal of this module is to be correct, that unfortunately does
620	not mean its bug-free, only that I think its design is bug-free. It is	842	not mean its bug-free, only that I think its design is bug-free. It is
621	still relatively early in its development. If you keep reporting bugs	843	still relatively early in its development. If you keep reporting bugs
622	they will be fixed swiftly, though.	844	they will be fixed swiftly, though.

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Comparing JSON-XS/README (file contents): Revision 1.11 by root, Wed May 9 16:35:21 2007 UTC vs. Revision 1.17 by root, Mon Aug 27 02:03:23 2007 UTC

Diff Legend

Comparing JSON-XS/README (file contents):
Revision 1.11 by root, Wed May 9 16:35:21 2007 UTC vs.
Revision 1.17 by root, Mon Aug 27 02:03:23 2007 UTC