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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC vs.
Revision 1.149 by root, Tue Oct 29 00:21:10 2013 UTC

…		…
64	so, and even documents what "correct" means.	64	so, and even documents what "correct" means.
65		65
66	=item * round-trip integrity	66	=item * round-trip integrity
67		67
68	When you serialise a perl data structure using only data types supported	68	When you serialise a perl data structure using only data types supported
69	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON and Perl, the deserialised data structure is identical on the Perl
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	level. (e.g. the string "2.0" doesn't suddenly become "2" just because
71	like a number). There minor I<are> exceptions to this, read the MAPPING	71	it looks like a number). There I<are> minor exceptions to this, read the
72	section below to learn about those.	72	MAPPING section below to learn about those.
73		73
74	=item * strict checking of JSON correctness	74	=item * strict checking of JSON correctness
75		75
76	There is no guessing, no generating of illegal JSON texts by default,	76	There is no guessing, no generating of illegal JSON texts by default,
77	and only JSON is accepted as input by default (the latter is a security	77	and only JSON is accepted as input by default (the latter is a security
…		…
83	this module usually compares favourably in terms of speed, too.	83	this module usually compares favourably in terms of speed, too.
84		84
85	=item * simple to use	85	=item * simple to use
86		86
87	This module has both a simple functional interface as well as an object	87	This module has both a simple functional interface as well as an object
88	oriented interface interface.	88	oriented interface.
89		89
90	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
91		91
92	You can choose between the most compact guaranteed-single-line format	92	You can choose between the most compact guaranteed-single-line format
93	possible (nice for simple line-based protocols), a pure-ASCII format	93	possible (nice for simple line-based protocols), a pure-ASCII format
…		…
99		99
100	=cut	100	=cut
101		101
102	package JSON::XS;	102	package JSON::XS;
103		103
104	no warnings;	104	use common::sense;
105	use strict;
106		105
107	our $VERSION = '2.23';	106	our $VERSION = '3.0';
108	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
109		108
110	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json);
111
112	sub to_json($) {
113	require Carp;
114	Carp::croak ("JSON::XS::to_json has been renamed to encode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
115	}
116
117	sub from_json($) {
118	require Carp;
119	Carp::croak ("JSON::XS::from_json has been renamed to decode_json, either downgrade to pre-2.0 versions of JSON::XS or rename the call");
120	}
121		110
122	use Exporter;	111	use Exporter;
123	use XSLoader;	112	use XSLoader;
		113
		114	use Types::Serialiser ();
124		115
125	=head1 FUNCTIONAL INTERFACE	116	=head1 FUNCTIONAL INTERFACE
126		117
127	The following convenience methods are provided by this module. They are	118	The following convenience methods are provided by this module. They are
128	exported by default:	119	exported by default:
…		…
149	This function call is functionally identical to:	140	This function call is functionally identical to:
150		141
151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	142	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
152		143
153	Except being faster.	144	Except being faster.
154
155	=item $is_boolean = JSON::XS::is_bool $scalar
156
157	Returns true if the passed scalar represents either JSON::XS::true or
158	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
159	and are used to represent JSON C<true> and C<false> values in Perl.
160
161	See MAPPING, below, for more information on how JSON values are mapped to
162	Perl.
163		145
164	=back	146	=back
165		147
166		148
167	=head1 A FEW NOTES ON UNICODE AND PERL	149	=head1 A FEW NOTES ON UNICODE AND PERL
…		…
433	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects	415	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
434	by sorting their keys. This is adding a comparatively high overhead.	416	by sorting their keys. This is adding a comparatively high overhead.
435		417
436	If C<$enable> is false, then the C<encode> method will output key-value	418	If C<$enable> is false, then the C<encode> method will output key-value
437	pairs in the order Perl stores them (which will likely change between runs	419	pairs in the order Perl stores them (which will likely change between runs
438	of the same script).	420	of the same script, and can change even within the same run from 5.18
		421	onwards).
439		422
440	This option is useful if you want the same data structure to be encoded as	423	This option is useful if you want the same data structure to be encoded as
441	the same JSON text (given the same overall settings). If it is disabled,	424	the same JSON text (given the same overall settings). If it is disabled,
442	the same hash might be encoded differently even if contains the same data,	425	the same hash might be encoded differently even if contains the same data,
443	as key-value pairs have no inherent ordering in Perl.	426	as key-value pairs have no inherent ordering in Perl.
444		427
445	This setting has no effect when decoding JSON texts.	428	This setting has no effect when decoding JSON texts.
		429
		430	This setting has currently no effect on tied hashes.
446		431
447	=item $json = $json->allow_nonref ([$enable])	432	=item $json = $json->allow_nonref ([$enable])
448		433
449	=item $enabled = $json->get_allow_nonref	434	=item $enabled = $json->get_allow_nonref
450		435
…		…
482		467
483	=item $json = $json->allow_blessed ([$enable])	468	=item $json = $json->allow_blessed ([$enable])
484		469
485	=item $enabled = $json->get_allow_blessed	470	=item $enabled = $json->get_allow_blessed
486		471
		472	See L<OBJECT SERIALISATION> for details.
		473
487	If C<$enable> is true (or missing), then the C<encode> method will not	474	If C<$enable> is true (or missing), then the C<encode> method will not
488	barf when it encounters a blessed reference. Instead, the value of the	475	barf when it encounters a blessed reference that it cannot convert
489	B<convert_blessed> option will decide whether C<null> (C<convert_blessed>	476	otherwise. Instead, a JSON C<null> value is encoded instead of the object.
490	disabled or no C<TO_JSON> method found) or a representation of the
491	object (C<convert_blessed> enabled and C<TO_JSON> method found) is being
492	encoded. Has no effect on C<decode>.
493		477
494	If C<$enable> is false (the default), then C<encode> will throw an	478	If C<$enable> is false (the default), then C<encode> will throw an
495	exception when it encounters a blessed object.	479	exception when it encounters a blessed object that it cannot convert
		480	otherwise.
		481
		482	This setting has no effect on C<decode>.
496		483
497	=item $json = $json->convert_blessed ([$enable])	484	=item $json = $json->convert_blessed ([$enable])
498		485
499	=item $enabled = $json->get_convert_blessed	486	=item $enabled = $json->get_convert_blessed
		487
		488	See L<OBJECT SERIALISATION> for details.
500		489
501	If C<$enable> is true (or missing), then C<encode>, upon encountering a	490	If C<$enable> is true (or missing), then C<encode>, upon encountering a
502	blessed object, will check for the availability of the C<TO_JSON> method	491	blessed object, will check for the availability of the C<TO_JSON> method
503	on the object's class. If found, it will be called in scalar context	492	on the object's class. If found, it will be called in scalar context and
504	and the resulting scalar will be encoded instead of the object. If no	493	the resulting scalar will be encoded instead of the object.
505	C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
506	to do.
507		494
508	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	495	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
509	returns other blessed objects, those will be handled in the same	496	returns other blessed objects, those will be handled in the same
510	way. C<TO_JSON> must take care of not causing an endless recursion cycle	497	way. C<TO_JSON> must take care of not causing an endless recursion cycle
511	(== crash) in this case. The name of C<TO_JSON> was chosen because other	498	(== crash) in this case. The name of C<TO_JSON> was chosen because other
512	methods called by the Perl core (== not by the user of the object) are	499	methods called by the Perl core (== not by the user of the object) are
513	usually in upper case letters and to avoid collisions with any C<to_json>	500	usually in upper case letters and to avoid collisions with any C<to_json>
514	function or method.	501	function or method.
515		502
516	This setting does not yet influence C<decode> in any way, but in the	503	If C<$enable> is false (the default), then C<encode> will not consider
517	future, global hooks might get installed that influence C<decode> and are	504	this type of conversion.
518	enabled by this setting.
519		505
520	If C<$enable> is false, then the C<allow_blessed> setting will decide what	506	This setting has no effect on C<decode>.
521	to do when a blessed object is found.	507
		508	=item $json = $json->allow_tags ([$enable])
		509
		510	=item $enabled = $json->allow_tags
		511
		512	See L<OBJECT SERIALISATION> for details.
		513
		514	If C<$enable> is true (or missing), then C<encode>, upon encountering a
		515	blessed object, will check for the availability of the C<FREEZE> method on
		516	the object's class. If found, it will be used to serialise the object into
		517	a nonstandard tagged JSON value (that JSON decoders cannot decode).
		518
		519	It also causes C<decode> to parse such tagged JSON values and deserialise
		520	them via a call to the C<THAW> method.
		521
		522	If C<$enable> is false (the default), then C<encode> will not consider
		523	this type of conversion, and tagged JSON values will cause a parse error
		524	in C<decode>, as if tags were not part of the grammar.
522		525
523	=item $json = $json->filter_json_object ([$coderef->($hashref)])	526	=item $json = $json->filter_json_object ([$coderef->($hashref)])
524		527
525	When C<$coderef> is specified, it will be called from C<decode> each	528	When C<$coderef> is specified, it will be called from C<decode> each
526	time it decodes a JSON object. The only argument is a reference to the	529	time it decodes a JSON object. The only argument is a reference to the
…		…
665		668
666	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	669	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
667		670
668	=item $json_text = $json->encode ($perl_scalar)	671	=item $json_text = $json->encode ($perl_scalar)
669		672
670	Converts the given Perl data structure (a simple scalar or a reference	673	Converts the given Perl value or data structure to its JSON
671	to a hash or array) to its JSON representation. Simple scalars will be	674	representation. Croaks on error.
672	converted into JSON string or number sequences, while references to arrays
673	become JSON arrays and references to hashes become JSON objects. Undefined
674	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
675	nor C<false> values will be generated.
676		675
677	=item $perl_scalar = $json->decode ($json_text)	676	=item $perl_scalar = $json->decode ($json_text)
678		677
679	The opposite of C<encode>: expects a JSON text and tries to parse it,	678	The opposite of C<encode>: expects a JSON text and tries to parse it,
680	returning the resulting simple scalar or reference. Croaks on error.	679	returning the resulting simple scalar or reference. Croaks on error.
681
682	JSON numbers and strings become simple Perl scalars. JSON arrays become
683	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
684	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
685		680
686	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)	681	=item ($perl_scalar, $characters) = $json->decode_prefix ($json_text)
687		682
688	This works like the C<decode> method, but instead of raising an exception	683	This works like the C<decode> method, but instead of raising an exception
689	when there is trailing garbage after the first JSON object, it will	684	when there is trailing garbage after the first JSON object, it will
690	silently stop parsing there and return the number of characters consumed	685	silently stop parsing there and return the number of characters consumed
691	so far.	686	so far.
692		687
693	This is useful if your JSON texts are not delimited by an outer protocol	688	This is useful if your JSON texts are not delimited by an outer protocol
694	(which is not the brightest thing to do in the first place) and you need
695	to know where the JSON text ends.	689	and you need to know where the JSON text ends.
696		690
697	JSON::XS->new->decode_prefix ("[1] the tail")	691	JSON::XS->new->decode_prefix ("[1] the tail")
698	=> ([], 3)	692	=> ([], 3)
699		693
700	=back	694	=back
…		…
712	calls).	706	calls).
713		707
714	JSON::XS will only attempt to parse the JSON text once it is sure it	708	JSON::XS will only attempt to parse the JSON text once it is sure it
715	has enough text to get a decisive result, using a very simple but	709	has enough text to get a decisive result, using a very simple but
716	truly incremental parser. This means that it sometimes won't stop as	710	truly incremental parser. This means that it sometimes won't stop as
717	early as the full parser, for example, it doesn't detect parenthese	711	early as the full parser, for example, it doesn't detect mismatched
718	mismatches. The only thing it guarantees is that it starts decoding as	712	parentheses. The only thing it guarantees is that it starts decoding as
719	soon as a syntactically valid JSON text has been seen. This means you need	713	soon as a syntactically valid JSON text has been seen. This means you need
720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop	714	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
721	parsing in the presence if syntax errors.	715	parsing in the presence if syntax errors.
722		716
723	The following methods implement this incremental parser.	717	The following methods implement this incremental parser.
…		…
739		733
740	If the method is called in scalar context, then it will try to extract	734	If the method is called in scalar context, then it will try to extract
741	exactly I<one> JSON object. If that is successful, it will return this	735	exactly I<one> JSON object. If that is successful, it will return this
742	object, otherwise it will return C<undef>. If there is a parse error,	736	object, otherwise it will return C<undef>. If there is a parse error,
743	this method will croak just as C<decode> would do (one can then use	737	this method will croak just as C<decode> would do (one can then use
744	C<incr_skip> to skip the errornous part). This is the most common way of	738	C<incr_skip> to skip the erroneous part). This is the most common way of
745	using the method.	739	using the method.
746		740
747	And finally, in list context, it will try to extract as many objects	741	And finally, in list context, it will try to extract as many objects
748	from the stream as it can find and return them, or the empty list	742	from the stream as it can find and return them, or the empty list
749	otherwise. For this to work, there must be no separators between the JSON	743	otherwise. For this to work, there must be no separators between the JSON
750	objects or arrays, instead they must be concatenated back-to-back. If	744	objects or arrays, instead they must be concatenated back-to-back. If
751	an error occurs, an exception will be raised as in the scalar context	745	an error occurs, an exception will be raised as in the scalar context
752	case. Note that in this case, any previously-parsed JSON texts will be	746	case. Note that in this case, any previously-parsed JSON texts will be
753	lost.	747	lost.
754		748
		749	Example: Parse some JSON arrays/objects in a given string and return
		750	them.
		751
		752	my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
		753
755	=item $lvalue_string = $json->incr_text	754	=item $lvalue_string = $json->incr_text
756		755
757	This method returns the currently stored JSON fragment as an lvalue, that	756	This method returns the currently stored JSON fragment as an lvalue, that
758	is, you can manipulate it. This I<only> works when a preceding call to	757	is, you can manipulate it. This I<only> works when a preceding call to
759	C<incr_parse> in I<scalar context> successfully returned an object. Under	758	C<incr_parse> in I<scalar context> successfully returned an object. Under
…		…
766	JSON object or b) parsing multiple JSON objects separated by non-JSON text	765	JSON object or b) parsing multiple JSON objects separated by non-JSON text
767	(such as commas).	766	(such as commas).
768		767
769	=item $json->incr_skip	768	=item $json->incr_skip
770		769
771	This will reset the state of the incremental parser and will remove the	770	This will reset the state of the incremental parser and will remove
772	parsed text from the input buffer. This is useful after C<incr_parse>	771	the parsed text from the input buffer so far. This is useful after
773	died, in which case the input buffer and incremental parser state is left	772	C<incr_parse> died, in which case the input buffer and incremental parser
774	unchanged, to skip the text parsed so far and to reset the parse state.	773	state is left unchanged, to skip the text parsed so far and to reset the
		774	parse state.
		775
		776	The difference to C<incr_reset> is that only text until the parse error
		777	occurred is removed.
775		778
776	=item $json->incr_reset	779	=item $json->incr_reset
777		780
778	This completely resets the incremental parser, that is, after this call,	781	This completely resets the incremental parser, that is, after this call,
779	it will be as if the parser had never parsed anything.	782	it will be as if the parser had never parsed anything.
780		783
781	This is useful if you want ot repeatedly parse JSON objects and want to	784	This is useful if you want to repeatedly parse JSON objects and want to
782	ignore any trailing data, which means you have to reset the parser after	785	ignore any trailing data, which means you have to reset the parser after
783	each successful decode.	786	each successful decode.
784		787
785	=back	788	=back
786		789
787	=head2 LIMITATIONS	790	=head2 LIMITATIONS
788		791
789	All options that affect decoding are supported, except	792	All options that affect decoding are supported, except
790	C<allow_nonref>. The reason for this is that it cannot be made to	793	C<allow_nonref>. The reason for this is that it cannot be made to work
791	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate	794	sensibly: JSON objects and arrays are self-delimited, i.e. you can
792	them back to back and still decode them perfectly. This does not hold true	795	concatenate them back to back and still decode them perfectly. This does
793	for JSON numbers, however.	796	not hold true for JSON numbers, however.
794		797
795	For example, is the string C<1> a single JSON number, or is it simply the	798	For example, is the string C<1> a single JSON number, or is it simply the
796	start of C<12>? Or is C<12> a single JSON number, or the concatenation	799	start of C<12>? Or is C<12> a single JSON number, or the concatenation
797	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS	800	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
798	takes the conservative route and disallows this case.	801	takes the conservative route and disallows this case.
…		…
977	If the number consists of digits only, JSON::XS will try to represent	980	If the number consists of digits only, JSON::XS will try to represent
978	it as an integer value. If that fails, it will try to represent it as	981	it as an integer value. If that fails, it will try to represent it as
979	a numeric (floating point) value if that is possible without loss of	982	a numeric (floating point) value if that is possible without loss of
980	precision. Otherwise it will preserve the number as a string value (in	983	precision. Otherwise it will preserve the number as a string value (in
981	which case you lose roundtripping ability, as the JSON number will be	984	which case you lose roundtripping ability, as the JSON number will be
982	re-encoded toa JSON string).	985	re-encoded to a JSON string).
983		986
984	Numbers containing a fractional or exponential part will always be	987	Numbers containing a fractional or exponential part will always be
985	represented as numeric (floating point) values, possibly at a loss of	988	represented as numeric (floating point) values, possibly at a loss of
986	precision (in which case you might lose perfect roundtripping ability, but	989	precision (in which case you might lose perfect roundtripping ability, but
987	the JSON number will still be re-encoded as a JSON number).	990	the JSON number will still be re-encoded as a JSON number).
988		991
		992	Note that precision is not accuracy - binary floating point values cannot
		993	represent most decimal fractions exactly, and when converting from and to
		994	floating point, JSON::XS only guarantees precision up to but not including
		995	the least significant bit.
		996
989	=item true, false	997	=item true, false
990		998
991	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	999	These JSON atoms become C<Types::Serialiser::true> and
992	respectively. They are overloaded to act almost exactly like the numbers	1000	C<Types::Serialiser::false>, respectively. They are overloaded to act
993	C<1> and C<0>. You can check whether a scalar is a JSON boolean by using	1001	almost exactly like the numbers C<1> and C<0>. You can check whether
994	the C<JSON::XS::is_bool> function.	1002	a scalar is a JSON boolean by using the C<Types::Serialiser::is_bool>
		1003	function (after C<use Types::Serialier>, of course).
995		1004
996	=item null	1005	=item null
997		1006
998	A JSON null atom becomes C<undef> in Perl.	1007	A JSON null atom becomes C<undef> in Perl.
		1008
		1009	=item shell-style comments (C<< # I<text> >>)
		1010
		1011	As a nonstandard extension to the JSON syntax that is enabled by the
		1012	C<relaxed> setting, shell-style comments are allowed. They can start
		1013	anywhere outside strings and go till the end of the line.
		1014
		1015	=item tagged values (C<< (I<tag>)I<value> >>).
		1016
		1017	Another nonstandard extension to the JSON syntax, enabled with the
		1018	C<allow_tags> setting, are tagged values. In this implementation, the
		1019	I<tag> must be a perl package/class name encoded as a JSON string, and the
		1020	I<value> must be a JSON array encoding optional constructor arguments.
		1021
		1022	See L<OBJECT SERIALISATION>, below, for details.
999		1023
1000	=back	1024	=back
1001		1025
1002		1026
1003	=head2 PERL -> JSON	1027	=head2 PERL -> JSON
…		…
1008		1032
1009	=over 4	1033	=over 4
1010		1034
1011	=item hash references	1035	=item hash references
1012		1036
1013	Perl hash references become JSON objects. As there is no inherent ordering	1037	Perl hash references become JSON objects. As there is no inherent
1014	in hash keys (or JSON objects), they will usually be encoded in a	1038	ordering in hash keys (or JSON objects), they will usually be encoded
1015	pseudo-random order that can change between runs of the same program but	1039	in a pseudo-random order. JSON::XS can optionally sort the hash keys
1016	stays generally the same within a single run of a program. JSON::XS can	1040	(determined by the I<canonical> flag), so the same datastructure will
1017	optionally sort the hash keys (determined by the I<canonical> flag), so	1041	serialise to the same JSON text (given same settings and version of
1018	the same datastructure will serialise to the same JSON text (given same	1042	JSON::XS), but this incurs a runtime overhead and is only rarely useful,
1019	settings and version of JSON::XS), but this incurs a runtime overhead	1043	e.g. when you want to compare some JSON text against another for equality.
1020	and is only rarely useful, e.g. when you want to compare some JSON text
1021	against another for equality.
1022		1044
1023	=item array references	1045	=item array references
1024		1046
1025	Perl array references become JSON arrays.	1047	Perl array references become JSON arrays.
1026		1048
1027	=item other references	1049	=item other references
1028		1050
1029	Other unblessed references are generally not allowed and will cause an	1051	Other unblessed references are generally not allowed and will cause an
1030	exception to be thrown, except for references to the integers C<0> and	1052	exception to be thrown, except for references to the integers C<0> and
1031	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1053	C<1>, which get turned into C<false> and C<true> atoms in JSON.
1032	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
1033		1054
		1055	Since C<JSON::XS> uses the boolean model from L<Types::Serialiser>, you
		1056	can also C<use Types::Serialiser> and then use C<Types::Serialiser::false>
		1057	and C<Types::Serialiser::true> to improve readability.
		1058
		1059	use Types::Serialiser;
1034	encode_json [\0, JSON::XS::true] # yields [false,true]	1060	encode_json [\0, Types::Serialiser::true] # yields [false,true]
1035		1061
1036	=item JSON::XS::true, JSON::XS::false	1062	=item Types::Serialiser::true, Types::Serialiser::false
1037		1063
1038	These special values become JSON true and JSON false values,	1064	These special values from the L<Types::Serialiser> module become JSON true
1039	respectively. You can also use C<\1> and C<\0> directly if you want.	1065	and JSON false values, respectively. You can also use C<\1> and C<\0>
		1066	directly if you want.
1040		1067
1041	=item blessed objects	1068	=item blessed objects
1042		1069
1043	Blessed objects are not directly representable in JSON. See the	1070	Blessed objects are not directly representable in JSON, but C<JSON::XS>
1044	C<allow_blessed> and C<convert_blessed> methods on various options on	1071	allows various ways of handling objects. See L<OBJECT SERIALISATION>,
1045	how to deal with this: basically, you can choose between throwing an	1072	below, for details.
1046	exception, encoding the reference as if it weren't blessed, or provide
1047	your own serialiser method.
1048		1073
1049	=item simple scalars	1074	=item simple scalars
1050		1075
1051	Simple Perl scalars (any scalar that is not a reference) are the most	1076	Simple Perl scalars (any scalar that is not a reference) are the most
1052	difficult objects to encode: JSON::XS will encode undefined scalars as	1077	difficult objects to encode: JSON::XS will encode undefined scalars as
…		…
1080		1105
1081	You can not currently force the type in other, less obscure, ways. Tell me	1106	You can not currently force the type in other, less obscure, ways. Tell me
1082	if you need this capability (but don't forget to explain why it's needed	1107	if you need this capability (but don't forget to explain why it's needed
1083	:).	1108	:).
1084		1109
		1110	Note that numerical precision has the same meaning as under Perl (so
		1111	binary to decimal conversion follows the same rules as in Perl, which
		1112	can differ to other languages). Also, your perl interpreter might expose
		1113	extensions to the floating point numbers of your platform, such as
		1114	infinities or NaN's - these cannot be represented in JSON, and it is an
		1115	error to pass those in.
		1116
1085	=back	1117	=back
		1118
		1119	=head2 OBJECT SERIALISATION
		1120
		1121	As JSON cannot directly represent Perl objects, you have to choose between
		1122	a pure JSON representation (without the ability to deserialise the object
		1123	automatically again), and a nonstandard extension to the JSON syntax,
		1124	tagged values.
		1125
		1126	=head3 SERIALISATION
		1127
		1128	What happens when C<JSON::XS> encounters a Perl object depends on the
		1129	C<allow_blessed>, C<convert_blessed> and C<allow_tags> settings, which are
		1130	used in this order:
		1131
		1132	=over 4
		1133
		1134	=item 1. C<allow_tags> is enabled and the object has a C<FREEZE> method.
		1135
		1136	In this case, C<JSON::XS> uses the L<Types::Serialiser> object
		1137	serialisation protocol to create a tagged JSON value, using a nonstandard
		1138	extension to the JSON syntax.
		1139
		1140	This works by invoking the C<FREEZE> method on the object, with the first
		1141	argument being the object to serialise, and the second argument being the
		1142	constant string C<JSON> to distinguish it from other serialisers.
		1143
		1144	The C<FREEZE> method can return any number of values (i.e. zero or
		1145	more). These values and the paclkage/classname of the object will then be
		1146	encoded as a tagged JSON value in the following format:
		1147
		1148	("classname")[FREEZE return values...]
		1149
		1150	For example, the hypothetical C<My::Object> C<FREEZE> method might use the
		1151	objects C<type> and C<id> members to encode the object:
		1152
		1153	sub My::Object::FREEZE {
		1154	my ($self, $serialiser) = @_;
		1155
		1156	($self->{type}, $self->{id})
		1157	}
		1158
		1159	=item 2. C<convert_blessed> is enabled and the object has a C<TO_JSON> method.
		1160
		1161	In this case, the C<TO_JSON> method of the object is invoked in scalar
		1162	context. It must return a single scalar that can be directly encoded into
		1163	JSON. This scalar replaces the object in the JSON text.
		1164
		1165	For example, the following C<TO_JSON> method will convert all L<URI>
		1166	objects to JSON strings when serialised. The fatc that these values
		1167	originally were L<URI> objects is lost.
		1168
		1169	sub URI::TO_JSON {
		1170	my ($uri) = @_;
		1171	$uri->as_string
		1172	}
		1173
		1174	=item 3. C<allow_blessed> is enabled.
		1175
		1176	The object will be serialised as a JSON null value.
		1177
		1178	=item 4. none of the above
		1179
		1180	If none of the settings are enabled or the respective methods are missing,
		1181	C<JSON::XS> throws an exception.
		1182
		1183	=back
		1184
		1185	=head3 DESERIALISATION
		1186
		1187	For deserialisation there are only two cases to consider: either
		1188	nonstandard tagging was used, in which case C<allow_tags> decides,
		1189	or objects cannot be automatically be deserialised, in which
		1190	case you can use postprocessing or the C<filter_json_object> or
		1191	C<filter_json_single_key_object> callbacks to get some real objects our of
		1192	your JSON.
		1193
		1194	This section only considers the tagged value case: I a tagged JSON object
		1195	is encountered during decoding and C<allow_tags> is disabled, a parse
		1196	error will result (as if tagged values were not part of the grammar).
		1197
		1198	If C<allow_tags> is enabled, C<JSON::XS> will look up the C<THAW> method
		1199	of the package/classname used during serialisation (it will not attempt
		1200	to load the package as a Perl module). If there is no such method, the
		1201	decoding will fail with an error.
		1202
		1203	Otherwise, the C<THAW> method is invoked with the classname as first
		1204	argument, the constant string C<JSON> as second argument, and all the
		1205	values from the JSON array (the values originally returned by the
		1206	C<FREEZE> method) as remaining arguments.
		1207
		1208	The method must then return the object. While technically you can return
		1209	any Perl scalar, you might have to enable the C<enable_nonref> setting to
		1210	make that work in all cases, so better return an actual blessed reference.
		1211
		1212	As an example, let's implement a C<THAW> function that regenerates the
		1213	C<My::Object> from the C<FREEZE> example earlier:
		1214
		1215	sub My::Object::THAW {
		1216	my ($class, $serialiser, $type, $id) = @_;
		1217
		1218	$class->new (type => $type, id => $id)
		1219	}
1086		1220
1087		1221
1088	=head1 ENCODING/CODESET FLAG NOTES	1222	=head1 ENCODING/CODESET FLAG NOTES
1089		1223
1090	The interested reader might have seen a number of flags that signify	1224	The interested reader might have seen a number of flags that signify
…		…
1115	=item C<utf8> flag disabled	1249	=item C<utf8> flag disabled
1116		1250
1117	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate	1251	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
1118	and expect Unicode strings, that is, characters with high ordinal Unicode	1252	and expect Unicode strings, that is, characters with high ordinal Unicode
1119	values (> 255) will be encoded as such characters, and likewise such	1253	values (> 255) will be encoded as such characters, and likewise such
1120	characters are decoded as-is, no canges to them will be done, except	1254	characters are decoded as-is, no changes to them will be done, except
1121	"(re-)interpreting" them as Unicode codepoints or Unicode characters,	1255	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
1122	respectively (to Perl, these are the same thing in strings unless you do	1256	respectively (to Perl, these are the same thing in strings unless you do
1123	funny/weird/dumb stuff).	1257	funny/weird/dumb stuff).
1124		1258
1125	This is useful when you want to do the encoding yourself (e.g. when you	1259	This is useful when you want to do the encoding yourself (e.g. when you
…		…
1181	proper subset of most 8-bit and multibyte encodings in use in the world.	1315	proper subset of most 8-bit and multibyte encodings in use in the world.
1182		1316
1183	=back	1317	=back
1184		1318
1185		1319
		1320	=head2 JSON and ECMAscript
		1321
		1322	JSON syntax is based on how literals are represented in javascript (the
		1323	not-standardised predecessor of ECMAscript) which is presumably why it is
		1324	called "JavaScript Object Notation".
		1325
		1326	However, JSON is not a subset (and also not a superset of course) of
		1327	ECMAscript (the standard) or javascript (whatever browsers actually
		1328	implement).
		1329
		1330	If you want to use javascript's C<eval> function to "parse" JSON, you
		1331	might run into parse errors for valid JSON texts, or the resulting data
		1332	structure might not be queryable:
		1333
		1334	One of the problems is that U+2028 and U+2029 are valid characters inside
		1335	JSON strings, but are not allowed in ECMAscript string literals, so the
		1336	following Perl fragment will not output something that can be guaranteed
		1337	to be parsable by javascript's C<eval>:
		1338
		1339	use JSON::XS;
		1340
		1341	print encode_json [chr 0x2028];
		1342
		1343	The right fix for this is to use a proper JSON parser in your javascript
		1344	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1345	F<json2.js> parser).
		1346
		1347	If this is not an option, you can, as a stop-gap measure, simply encode to
		1348	ASCII-only JSON:
		1349
		1350	use JSON::XS;
		1351
		1352	print JSON::XS->new->ascii->encode ([chr 0x2028]);
		1353
		1354	Note that this will enlarge the resulting JSON text quite a bit if you
		1355	have many non-ASCII characters. You might be tempted to run some regexes
		1356	to only escape U+2028 and U+2029, e.g.:
		1357
		1358	# DO NOT USE THIS!
		1359	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1360	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1361	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1362	print $json;
		1363
		1364	Note that I<this is a bad idea>: the above only works for U+2028 and
		1365	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1366	javascript implementations, however, have issues with other characters as
		1367	well - using C<eval> naively simply I<will> cause problems.
		1368
		1369	Another problem is that some javascript implementations reserve
		1370	some property names for their own purposes (which probably makes
		1371	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1372	C<__proto__> property name for its own purposes.
		1373
		1374	If that is a problem, you could parse try to filter the resulting JSON
		1375	output for these property strings, e.g.:
		1376
		1377	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
		1378
		1379	This works because C<__proto__> is not valid outside of strings, so every
		1380	occurrence of C<"__proto__"\s*:> must be a string used as property name.
		1381
		1382	If you know of other incompatibilities, please let me know.
		1383
		1384
1186	=head2 JSON and YAML	1385	=head2 JSON and YAML
1187		1386
1188	You often hear that JSON is a subset of YAML. This is, however, a mass	1387	You often hear that JSON is a subset of YAML. This is, however, a mass
1189	hysteria(*) and very far from the truth (as of the time of this writing),	1388	hysteria(*) and very far from the truth (as of the time of this writing),
1190	so let me state it clearly: I<in general, there is no way to configure	1389	so let me state it clearly: I<in general, there is no way to configure
…		…
1198	my $yaml = $to_yaml->encode ($ref) . "\n";	1397	my $yaml = $to_yaml->encode ($ref) . "\n";
1199		1398
1200	This will I<usually> generate JSON texts that also parse as valid	1399	This will I<usually> generate JSON texts that also parse as valid
1201	YAML. Please note that YAML has hardcoded limits on (simple) object key	1400	YAML. Please note that YAML has hardcoded limits on (simple) object key
1202	lengths that JSON doesn't have and also has different and incompatible	1401	lengths that JSON doesn't have and also has different and incompatible
1203	unicode handling, so you should make sure that your hash keys are	1402	unicode character escape syntax, so you should make sure that your hash
1204	noticeably shorter than the 1024 "stream characters" YAML allows and that	1403	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1205	you do not have characters with codepoint values outside the Unicode BMP	1404	and that you do not have characters with codepoint values outside the
1206	(basic multilingual page). YAML also does not allow C<\/> sequences in	1405	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1207	strings (which JSON::XS does not I<currently> generate, but other JSON	1406	sequences in strings (which JSON::XS does not I<currently> generate, but
1208	generators might).	1407	other JSON generators might).
1209		1408
1210	There might be other incompatibilities that I am not aware of (or the YAML	1409	There might be other incompatibilities that I am not aware of (or the YAML
1211	specification has been changed yet again - it does so quite often). In	1410	specification has been changed yet again - it does so quite often). In
1212	general you should not try to generate YAML with a JSON generator or vice	1411	general you should not try to generate YAML with a JSON generator or vice
1213	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1412	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1232	that difficult or long) and finally make YAML compatible to it, and	1431	that difficult or long) and finally make YAML compatible to it, and
1233	educating users about the changes, instead of spreading lies about the	1432	educating users about the changes, instead of spreading lies about the
1234	real compatibility for many I<years> and trying to silence people who	1433	real compatibility for many I<years> and trying to silence people who
1235	point out that it isn't true.	1434	point out that it isn't true.
1236		1435
		1436	Addendum/2009: the YAML 1.2 spec is still incompatible with JSON, even
		1437	though the incompatibilities have been documented (and are known to Brian)
		1438	for many years and the spec makes explicit claims that YAML is a superset
		1439	of JSON. It would be so easy to fix, but apparently, bullying people and
		1440	corrupting userdata is so much easier.
		1441
1237	=back	1442	=back
1238		1443
1239		1444
1240	=head2 SPEED	1445	=head2 SPEED
1241		1446
…		…
1248	a very short single-line JSON string (also available at	1453	a very short single-line JSON string (also available at
1249	L<http://dist.schmorp.de/misc/json/short.json>).	1454	L<http://dist.schmorp.de/misc/json/short.json>).
1250		1455
1251	{"method": "handleMessage", "params": ["user1",	1456	{"method": "handleMessage", "params": ["user1",
1252	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,	1457	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1253	true, false]}	1458	1, 0]}
1254		1459
1255	It shows the number of encodes/decodes per second (JSON::XS uses	1460	It shows the number of encodes/decodes per second (JSON::XS uses
1256	the functional interface, while JSON::XS/2 uses the OO interface	1461	the functional interface, while JSON::XS/2 uses the OO interface
1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1462	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1258	shrink). Higher is better:	1463	shrink. JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ
		1464	uses the from_json method). Higher is better:
1259		1465
1260	module \| encode \| decode \|	1466	module \| encode \| decode \|
1261	-----------\|------------\|------------\|	1467	--------------\|------------\|------------\|
1262	JSON 1.x \| 4990.842 \| 4088.813 \|	1468	JSON::DWIW/DS \| 86302.551 \| 102300.098 \|
1263	JSON::DWIW \| 51653.990 \| 71575.154 \|	1469	JSON::DWIW/FJ \| 86302.551 \| 75983.768 \|
1264	JSON::PC \| 65948.176 \| 74631.744 \|	1470	JSON::PP \| 15827.562 \| 6638.658 \|
1265	JSON::PP \| 8931.652 \| 3817.168 \|	1471	JSON::Syck \| 63358.066 \| 47662.545 \|
1266	JSON::Syck \| 24877.248 \| 27776.848 \|	1472	JSON::XS \| 511500.488 \| 511500.488 \|
1267	JSON::XS \| 388361.481 \| 227951.304 \|	1473	JSON::XS/2 \| 291271.111 \| 388361.481 \|
1268	JSON::XS/2 \| 227951.304 \| 218453.333 \|	1474	JSON::XS/3 \| 361577.931 \| 361577.931 \|
1269	JSON::XS/3 \| 338250.323 \| 218453.333 \|	1475	Storable \| 66788.280 \| 265462.278 \|
1270	Storable \| 16500.016 \| 135300.129 \|
1271	-----------+------------+------------+	1476	--------------+------------+------------+
1272		1477
1273	That is, JSON::XS is about five times faster than JSON::DWIW on encoding,	1478	That is, JSON::XS is almost six times faster than JSON::DWIW on encoding,
1274	about three times faster on decoding, and over forty times faster	1479	about five times faster on decoding, and over thirty to seventy times
1275	than JSON, even with pretty-printing and key sorting. It also compares	1480	faster than JSON's pure perl implementation. It also compares favourably
1276	favourably to Storable for small amounts of data.	1481	to Storable for small amounts of data.
1277		1482
1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1483	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).	1484	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1280		1485
1281	module \| encode \| decode \|	1486	module \| encode \| decode \|
1282	-----------\|------------\|------------\|	1487	--------------\|------------\|------------\|
1283	JSON 1.x \| 55.260 \| 34.971 \|	1488	JSON::DWIW/DS \| 1647.927 \| 2673.916 \|
1284	JSON::DWIW \| 825.228 \| 1082.513 \|	1489	JSON::DWIW/FJ \| 1630.249 \| 2596.128 \|
1285	JSON::PC \| 3571.444 \| 2394.829 \|
1286	JSON::PP \| 210.987 \| 32.574 \|	1490	JSON::PP \| 400.640 \| 62.311 \|
1287	JSON::Syck \| 552.551 \| 787.544 \|	1491	JSON::Syck \| 1481.040 \| 1524.869 \|
1288	JSON::XS \| 5780.463 \| 4854.519 \|	1492	JSON::XS \| 20661.596 \| 9541.183 \|
1289	JSON::XS/2 \| 3869.998 \| 4798.975 \|	1493	JSON::XS/2 \| 10683.403 \| 9416.938 \|
1290	JSON::XS/3 \| 5862.880 \| 4798.975 \|	1494	JSON::XS/3 \| 20661.596 \| 9400.054 \|
1291	Storable \| 4445.002 \| 5235.027 \|	1495	Storable \| 19765.806 \| 10000.725 \|
1292	-----------+------------+------------+	1496	--------------+------------+------------+
1293		1497
1294	Again, JSON::XS leads by far (except for Storable which non-surprisingly	1498	Again, JSON::XS leads by far (except for Storable which non-surprisingly
1295	decodes faster).	1499	decodes a bit faster).
1296		1500
1297	On large strings containing lots of high Unicode characters, some modules	1501	On large strings containing lots of high Unicode characters, some modules
1298	(such as JSON::PC) seem to decode faster than JSON::XS, but the result	1502	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
1299	will be broken due to missing (or wrong) Unicode handling. Others refuse	1503	will be broken due to missing (or wrong) Unicode handling. Others refuse
1300	to decode or encode properly, so it was impossible to prepare a fair	1504	to decode or encode properly, so it was impossible to prepare a fair
…		…
1336	information you might want to make sure that exceptions thrown by JSON::XS	1540	information you might want to make sure that exceptions thrown by JSON::XS
1337	will not end up in front of untrusted eyes.	1541	will not end up in front of untrusted eyes.
1338		1542
1339	If you are using JSON::XS to return packets to consumption	1543	If you are using JSON::XS to return packets to consumption
1340	by JavaScript scripts in a browser you should have a look at	1544	by JavaScript scripts in a browser you should have a look at
1341	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1545	L<http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/> to
1342	you are vulnerable to some common attack vectors (which really are browser	1546	see whether you are vulnerable to some common attack vectors (which really
1343	design bugs, but it is still you who will have to deal with it, as major	1547	are browser design bugs, but it is still you who will have to deal with
1344	browser developers care only for features, not about getting security	1548	it, as major browser developers care only for features, not about getting
1345	right).	1549	security right).
		1550
		1551
		1552	=head1 INTEROPERABILITY WITH OTHER MODULES
		1553
		1554	C<JSON::XS> uses the L<Types::Serialiser> module to provide boolean
		1555	constants. That means that the JSON true and false values will be
		1556	comaptible to true and false values of iother modules that do the same,
		1557	such as L<JSON::PP> and L<CBOR::XS>.
1346		1558
1347		1559
1348	=head1 THREADS	1560	=head1 THREADS
1349		1561
1350	This module is I<not> guaranteed to be thread safe and there are no	1562	This module is I<not> guaranteed to be thread safe and there are no
…		…
1353	process simulations - use fork, it's I<much> faster, cheaper, better).	1565	process simulations - use fork, it's I<much> faster, cheaper, better).
1354		1566
1355	(It might actually work, but you have been warned).	1567	(It might actually work, but you have been warned).
1356		1568
1357		1569
		1570	=head1 THE PERILS OF SETLOCALE
		1571
		1572	Sometimes people avoid the Perl locale support and directly call the
		1573	system's setlocale function with C<LC_ALL>.
		1574
		1575	This breaks both perl and modules such as JSON::XS, as stringification of
		1576	numbers no longer works correctly (e.g. C<$x = 0.1; print "$x"+1> might
		1577	print C<1>, and JSON::XS might output illegal JSON as JSON::XS relies on
		1578	perl to stringify numbers).
		1579
		1580	The solution is simple: don't call C<setlocale>, or use it for only those
		1581	categories you need, such as C<LC_MESSAGES> or C<LC_CTYPE>.
		1582
		1583	If you need C<LC_NUMERIC>, you should enable it only around the code that
		1584	actually needs it (avoiding stringification of numbers), and restore it
		1585	afterwards.
		1586
		1587
1358	=head1 BUGS	1588	=head1 BUGS
1359		1589
1360	While the goal of this module is to be correct, that unfortunately does	1590	While the goal of this module is to be correct, that unfortunately does
1361	not mean it's bug-free, only that I think its design is bug-free. If you	1591	not mean it's bug-free, only that I think its design is bug-free. If you
1362	keep reporting bugs they will be fixed swiftly, though.	1592	keep reporting bugs they will be fixed swiftly, though.
…		…
1364	Please refrain from using rt.cpan.org or any other bug reporting	1594	Please refrain from using rt.cpan.org or any other bug reporting
1365	service. I put the contact address into my modules for a reason.	1595	service. I put the contact address into my modules for a reason.
1366		1596
1367	=cut	1597	=cut
1368		1598
1369	our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };	1599	BEGIN {
1370	our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };	1600	*true = \$Types::Serialiser::true;
		1601	*true = \&Types::Serialiser::true;
		1602	*false = \$Types::Serialiser::false;
		1603	*false = \&Types::Serialiser::false;
		1604	*is_bool = \&Types::Serialiser::is_bool;
1371		1605
1372	sub true() { $true }	1606	JSON::XS::Boolean:: = Types::Serialiser::Boolean::;
1373	sub false() { $false }
1374
1375	sub is_bool($) {
1376	UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
1377	# or UNIVERSAL::isa $_[0], "JSON::Literal"
1378	}	1607	}
1379		1608
1380	XSLoader::load "JSON::XS", $VERSION;	1609	XSLoader::load "JSON::XS", $VERSION;
1381
1382	package JSON::XS::Boolean;
1383
1384	use overload
1385	"0+" => sub { ${$_[0]} },
1386	"++" => sub { $_[0] = ${$_[0]} + 1 },
1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
1388	fallback => 1;
1389
1390	1;
1391		1610
1392	=head1 SEE ALSO	1611	=head1 SEE ALSO
1393		1612
1394	The F<json_xs> command line utility for quick experiments.	1613	The F<json_xs> command line utility for quick experiments.
1395		1614
…		…
1398	Marc Lehmann <schmorp@schmorp.de>	1617	Marc Lehmann <schmorp@schmorp.de>
1399	http://home.schmorp.de/	1618	http://home.schmorp.de/
1400		1619
1401	=cut	1620	=cut
1402		1621
		1622	1
		1623

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing JSON-XS/XS.pm (file contents): Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC vs. Revision 1.149 by root, Tue Oct 29 00:21:10 2013 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.112 by root, Mon Sep 29 03:09:27 2008 UTC vs.
Revision 1.149 by root, Tue Oct 29 00:21:10 2013 UTC