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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.77 by root, Tue Dec 4 10:37:42 2007 UTC vs.
Revision 1.96 by root, Wed Mar 26 01:40:42 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
		2
		3	=encoding utf-8
2		4
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	5	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
10	use JSON::XS;	12	use JSON::XS;
11		13
12	# exported functions, they croak on error	14	# exported functions, they croak on error
13	# and expect/generate UTF-8	15	# and expect/generate UTF-8
14		16
15	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;	17	$utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
16	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;	18	$perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
17		19
18	# OO-interface	20	# OO-interface
19		21
20	$coder = JSON::XS->new->ascii->pretty->allow_nonref;	22	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
21	$pretty_printed_unencoded = $coder->encode ($perl_scalar);	23	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
…		…
58		60
59	=over 4	61	=over 4
60		62
61	=item * correct Unicode handling	63	=item * correct Unicode handling
62		64
63	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
64	it does so.	66	so, and even documents what "correct" means.
65		67
66	=item * round-trip integrity	68	=item * round-trip integrity
67		69
68	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only datatypes supported
69	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
71	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
72		75
73	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
74		77
75	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
76	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
77	feature).	80	feature).
78		81
79	=item * fast	82	=item * fast
80		83
81	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
82	of speed, too.	85	this module usually compares favourably in terms of speed, too.
83		86
84	=item * simple to use	87	=item * simple to use
85		88
86	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an objetc
87	interface.	90	oriented interface interface.
88		91
89	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
90		93
91	You can choose between the most compact guaranteed single-line format	94	You can choose between the most compact guaranteed-single-line format
92	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ascii format
93	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
94	Unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
95	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
96		99
…		…
100		103
101	package JSON::XS;	104	package JSON::XS;
102		105
103	use strict;	106	use strict;
104		107
105	our $VERSION = '2.0';	108	our $VERSION = '2.1';
106	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
107		110
108	our @EXPORT = qw(to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
		112
		113	sub to_json($) {
		114	require Carp;
		115	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");
		116	}
		117
		118	sub from_json($) {
		119	require Carp;
		120	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");
		121	}
109		122
110	use Exporter;	123	use Exporter;
111	use XSLoader;	124	use XSLoader;
112		125
113	=head1 FUNCTIONAL INTERFACE	126	=head1 FUNCTIONAL INTERFACE
…		…
115	The following convenience methods are provided by this module. They are	128	The following convenience methods are provided by this module. They are
116	exported by default:	129	exported by default:
117		130
118	=over 4	131	=over 4
119		132
120	=item $json_text = to_json $perl_scalar	133	=item $json_text = encode_json $perl_scalar
121		134
122	Converts the given Perl data structure to a UTF-8 encoded, binary string	135	Converts the given Perl data structure to a UTF-8 encoded, binary string
123	(that is, the string contains octets only). Croaks on error.	136	(that is, the string contains octets only). Croaks on error.
124		137
125	This function call is functionally identical to:	138	This function call is functionally identical to:
126		139
127	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
128		141
129	except being faster.	142	except being faster.
130		143
131	=item $perl_scalar = from_json $json_text	144	=item $perl_scalar = decode_json $json_text
132		145
133	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
134	to parse that as an UTF-8 encoded JSON text, returning the resulting	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
135	reference. Croaks on error.	148	reference. Croaks on error.
136		149
137	This function call is functionally identical to:	150	This function call is functionally identical to:
138		151
…		…
164	This enables you to store Unicode characters as single characters in a	177	This enables you to store Unicode characters as single characters in a
165	Perl string - very natural.	178	Perl string - very natural.
166		179
167	=item 2. Perl does I<not> associate an encoding with your strings.	180	=item 2. Perl does I<not> associate an encoding with your strings.
168		181
169	Unless you force it to, e.g. when matching it against a regex, or printing	182	... until you force it to, e.g. when matching it against a regex, or
170	the scalar to a file, in which case Perl either interprets your string as	183	printing the scalar to a file, in which case Perl either interprets your
171	locale-encoded text, octets/binary, or as Unicode, depending on various	184	string as locale-encoded text, octets/binary, or as Unicode, depending
172	settings. In no case is an encoding stored together with your data, it is	185	on various settings. In no case is an encoding stored together with your
173	I<use> that decides encoding, not any magical metadata.	186	data, it is I<use> that decides encoding, not any magical meta data.
174		187
175	=item 3. The internal utf-8 flag has no meaning with regards to the	188	=item 3. The internal utf-8 flag has no meaning with regards to the
176	encoding of your string.	189	encoding of your string.
177		190
178	Just ignore that flag unless you debug a Perl bug, a module written in	191	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
232		245
233	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
234	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
235	in a faster and more compact format.	248	in a faster and more compact format.
236		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
237	The main use for this flag is to produce JSON texts that can be	253	The main use for this flag is to produce JSON texts that can be
238	transmitted over a 7-bit channel, as the encoded JSON texts will not	254	transmitted over a 7-bit channel, as the encoded JSON texts will not
239	contain any 8 bit characters.	255	contain any 8 bit characters.
240		256
241	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
252	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
253	expects Unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
254		270
255	If C<$enable> is false, then the C<encode> method will not escape Unicode	271	If C<$enable> is false, then the C<encode> method will not escape Unicode
256	characters unless required by the JSON syntax or other flags.	272	characters unless required by the JSON syntax or other flags.
		273
		274	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		275	document.
257		276
258	The main use for this flag is efficiently encoding binary data as JSON	277	The main use for this flag is efficiently encoding binary data as JSON
259	text, as most octets will not be escaped, resulting in a smaller encoded	278	text, as most octets will not be escaped, resulting in a smaller encoded
260	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
261	in latin1 (and must correctly be treated as such when storing and	280	in latin1 (and must correctly be treated as such when storing and
…		…
280		299
281	If C<$enable> is false, then the C<encode> method will return the JSON	300	If C<$enable> is false, then the C<encode> method will return the JSON
282	string as a (non-encoded) Unicode string, while C<decode> expects thus a	301	string as a (non-encoded) Unicode string, while C<decode> expects thus a
283	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	302	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
284	to be done yourself, e.g. using the Encode module.	303	to be done yourself, e.g. using the Encode module.
		304
		305	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		306	document.
285		307
286	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
287		309
288	use Encode;	310	use Encode;
289	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
471	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>	493	The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
472	returns other blessed objects, those will be handled in the same	494	returns other blessed objects, those will be handled in the same
473	way. C<TO_JSON> must take care of not causing an endless recursion cycle	495	way. C<TO_JSON> must take care of not causing an endless recursion cycle
474	(== crash) in this case. The name of C<TO_JSON> was chosen because other	496	(== crash) in this case. The name of C<TO_JSON> was chosen because other
475	methods called by the Perl core (== not by the user of the object) are	497	methods called by the Perl core (== not by the user of the object) are
476	usually in upper case letters and to avoid collisions with the C<to_json>	498	usually in upper case letters and to avoid collisions with any C<to_json>
477	function.	499	function or method.
478		500
479	This setting does not yet influence C<decode> in any way, but in the	501	This setting does not yet influence C<decode> in any way, but in the
480	future, global hooks might get installed that influence C<decode> and are	502	future, global hooks might get installed that influence C<decode> and are
481	enabled by this setting.	503	enabled by this setting.
482		504
…		…
659	=> ([], 3)	681	=> ([], 3)
660		682
661	=back	683	=back
662		684
663		685
		686	=head1 INCREMENTAL PARSING
		687
		688	[This section is still EXPERIMENTAL]
		689
		690	In some cases, there is the need for incremental parsing of JSON
		691	texts. While this module always has to keep both JSON text and resulting
		692	Perl data structure in memory at one time, it does allow you to parse a
		693	JSON stream incrementally. It does so by accumulating text until it has
		694	a full JSON object, which it then can decode. This process is similar to
		695	using C<decode_prefix> to see if a full JSON object is available, but is
		696	much more efficient (JSON::XS will only attempt to parse the JSON text
		697	once it is sure it has enough text to get a decisive result, using a very
		698	simple but truly incremental parser).
		699
		700	The following two methods deal with this.
		701
		702	=over 4
		703
		704	=item [void, scalar or list context] = $json->incr_parse ([$string])
		705
		706	This is the central parsing function. It can both append new text and
		707	extract objects from the stream accumulated so far (both of these
		708	functions are optional).
		709
		710	If C<$string> is given, then this string is appended to the already
		711	existing JSON fragment stored in the C<$json> object.
		712
		713	After that, if the function is called in void context, it will simply
		714	return without doing anything further. This can be used to add more text
		715	in as many chunks as you want.
		716
		717	If the method is called in scalar context, then it will try to extract
		718	exactly I<one> JSON object. If that is successful, it will return this
		719	object, otherwise it will return C<undef>. If there is a parse error,
		720	this method will croak just as C<decode> would do (one can then use
		721	C<incr_skip> to skip the errornous part). This is the most common way of
		722	using the method.
		723
		724	And finally, in list context, it will try to extract as many objects
		725	from the stream as it can find and return them, or the empty list
		726	otherwise. For this to work, there must be no separators between the JSON
		727	objects or arrays, instead they must be concatenated back-to-back. If
		728	an error occurs, an exception will be raised as in the scalar context
		729	case. Note that in this case, any previously-parsed JSON texts will be
		730	lost.
		731
		732	If there is a parse
		733
		734	=item $lvalue_string = $json->incr_text
		735
		736	This method returns the currently stored JSON fragment as an lvalue, that
		737	is, you can manipulate it. This I<only> works when a preceding call to
		738	C<incr_parse> in I<scalar context> successfully returned an object. Under
		739	all other circumstances you must not call this function (I mean it.
		740	although in simple tests it might actually work, it I<will> fail under
		741	real world conditions). As a special exception, you can also call this
		742	method before having parsed anything.
		743
		744	This function is useful in two cases: a) finding the trailing text after a
		745	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		746	(such as commas).
		747
		748	=back
		749
		750	=head2 LIMITATIONS
		751
		752	All options that affect decoding are supported, except
		753	C<allow_nonref>. The reason for this is that it cannot be made to
		754	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		755	them back to back and still decode them perfectly. This does not hold true
		756	for JSON numbers, however.
		757
		758	For example, is the string C<1> a single JSON number, or is it simply the
		759	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		760	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		761	takes the conservative route and disallows this case.
		762
		763	=head2 EXAMPLES
		764
		765	Some examples will make all this clearer. First, a simple example that
		766	works similarly to C<decode_prefix>: We want to decode the JSON object at
		767	the start of a string and identify the portion after the JSON object:
		768
		769	my $text = "[1,2,3] hello";
		770
		771	my $json = new JSON::XS;
		772
		773	my $obj = $json->incr_parse ($text)
		774	or die "expected JSON object or array at beginning of string";
		775
		776	my $tail = $json->incr_text;
		777	# $tail now contains " hello"
		778
		779	Easy, isn't it?
		780
		781	Now for a more complicated example: Imagine a hypothetical protocol where
		782	you read some requests from a TCP stream, and each request is a JSON
		783	array, without any separation between them (in fact, it is often useful to
		784	use newlines as "separators", as these get interpreted as whitespace at
		785	the start of the JSON text, which makes it possible to test said protocol
		786	with C<telnet>...).
		787
		788	Here is how you'd do it (it is trivial to write this in an event-based
		789	manner):
		790
		791	my $json = new JSON::XS;
		792
		793	# read some data from the socket
		794	while (sysread $socket, my $buf, 4096) {
		795
		796	# split and decode as many requests as possible
		797	for my $request ($json->incr_parse ($buf)) {
		798	# act on the $request
		799	}
		800	}
		801
		802	Another complicated example: Assume you have a string with JSON objects
		803	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		804	[3]>). To parse them, we have to skip the commas between the JSON texts,
		805	and here is where the lvalue-ness of C<incr_text> comes in useful:
		806
		807	my $text = "[1],[2], [3]";
		808	my $json = new JSON::XS;
		809
		810	# void context, so no parsing done
		811	$json->incr_parse ($text);
		812
		813	# now extract as many objects as possible. note the
		814	# use of scalar context so incr_text can be called.
		815	while (my $obj = $json->incr_parse) {
		816	# do something with $obj
		817
		818	# now skip the optional comma
		819	$json->incr_text =~ s/^ \s* , //x;
		820	}
		821
		822	Now lets go for a very complex example: Assume that you have a gigantic
		823	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		824	but you cannot load it into memory fully (this has actually happened in
		825	the real world :).
		826
		827	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		828	can still help you: You implement a (very simple) array parser and let
		829	JSON decode the array elements, which are all full JSON objects on their
		830	own (this wouldn't work if the array elements could be JSON numbers, for
		831	example):
		832
		833	my $json = new JSON::XS;
		834
		835	# open the monster
		836	open my $fh, "<bigfile.json"
		837	or die "bigfile: $!";
		838
		839	# first parse the initial "["
		840	for (;;) {
		841	sysread $fh, my $buf, 65536
		842	or die "read error: $!";
		843	$json->incr_parse ($buf); # void context, so no parsing
		844
		845	# Exit the loop once we found and removed(!) the initial "[".
		846	# In essence, we are (ab-)using the $json object as a simple scalar
		847	# we append data to.
		848	last if $json->incr_text =~ s/^ \s* \[ //x;
		849	}
		850
		851	# now we have the skipped the initial "[", so continue
		852	# parsing all the elements.
		853	for (;;) {
		854	# in this loop we read data until we got a single JSON object
		855	for (;;) {
		856	if (my $obj = $json->incr_parse) {
		857	# do something with $obj
		858	last;
		859	}
		860
		861	# add more data
		862	sysread $fh, my $buf, 65536
		863	or die "read error: $!";
		864	$json->incr_parse ($buf); # void context, so no parsing
		865	}
		866
		867	# in this loop we read data until we either found and parsed the
		868	# separating "," between elements, or the final "]"
		869	for (;;) {
		870	# first skip whitespace
		871	$json->incr_text =~ s/^\s*//;
		872
		873	# if we find "]", we are done
		874	if ($json->incr_text =~ s/^\]//) {
		875	print "finished.\n";
		876	exit;
		877	}
		878
		879	# if we find ",", we can continue with the next element
		880	if ($json->incr_text =~ s/^,//) {
		881	last;
		882	}
		883
		884	# if we find anything else, we have a parse error!
		885	if (length $json->incr_text) {
		886	die "parse error near ", $json->incr_text;
		887	}
		888
		889	# else add more data
		890	sysread $fh, my $buf, 65536
		891	or die "read error: $!";
		892	$json->incr_parse ($buf); # void context, so no parsing
		893	}
		894
		895	This is a complex example, but most of the complexity comes from the fact
		896	that we are trying to be correct (bear with me if I am wrong, I never ran
		897	the above example :).
		898
		899
		900
664	=head1 MAPPING	901	=head1 MAPPING
665		902
666	This section describes how JSON::XS maps Perl values to JSON values and	903	This section describes how JSON::XS maps Perl values to JSON values and
667	vice versa. These mappings are designed to "do the right thing" in most	904	vice versa. These mappings are designed to "do the right thing" in most
668	circumstances automatically, preserving round-tripping characteristics	905	circumstances automatically, preserving round-tripping characteristics
…		…
696		933
697	A JSON number becomes either an integer, numeric (floating point) or	934	A JSON number becomes either an integer, numeric (floating point) or
698	string scalar in perl, depending on its range and any fractional parts. On	935	string scalar in perl, depending on its range and any fractional parts. On
699	the Perl level, there is no difference between those as Perl handles all	936	the Perl level, there is no difference between those as Perl handles all
700	the conversion details, but an integer may take slightly less memory and	937	the conversion details, but an integer may take slightly less memory and
701	might represent more values exactly than (floating point) numbers.	938	might represent more values exactly than floating point numbers.
702		939
703	If the number consists of digits only, JSON::XS will try to represent	940	If the number consists of digits only, JSON::XS will try to represent
704	it as an integer value. If that fails, it will try to represent it as	941	it as an integer value. If that fails, it will try to represent it as
705	a numeric (floating point) value if that is possible without loss of	942	a numeric (floating point) value if that is possible without loss of
706	precision. Otherwise it will preserve the number as a string value.	943	precision. Otherwise it will preserve the number as a string value (in
		944	which case you lose roundtripping ability, as the JSON number will be
		945	re-encoded toa JSON string).
707		946
708	Numbers containing a fractional or exponential part will always be	947	Numbers containing a fractional or exponential part will always be
709	represented as numeric (floating point) values, possibly at a loss of	948	represented as numeric (floating point) values, possibly at a loss of
710	precision.	949	precision (in which case you might lose perfect roundtripping ability, but
711		950	the JSON number will still be re-encoded as a JSON number).
712	This might create round-tripping problems as numbers might become strings,
713	but as Perl is typeless there is no other way to do it.
714		951
715	=item true, false	952	=item true, false
716		953
717	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	954	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
718	respectively. They are overloaded to act almost exactly like the numbers	955	respectively. They are overloaded to act almost exactly like the numbers
…		…
755	Other unblessed references are generally not allowed and will cause an	992	Other unblessed references are generally not allowed and will cause an
756	exception to be thrown, except for references to the integers C<0> and	993	exception to be thrown, except for references to the integers C<0> and
757	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	994	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
758	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	995	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
759		996
760	to_json [\0,JSON::XS::true] # yields [false,true]	997	encode_json [\0,JSON::XS::true] # yields [false,true]
761		998
762	=item JSON::XS::true, JSON::XS::false	999	=item JSON::XS::true, JSON::XS::false
763		1000
764	These special values become JSON true and JSON false values,	1001	These special values become JSON true and JSON false values,
765	respectively. You can also use C<\1> and C<\0> directly if you want.	1002	respectively. You can also use C<\1> and C<\0> directly if you want.
766		1003
767	=item blessed objects	1004	=item blessed objects
768		1005
769	Blessed objects are not allowed. JSON::XS currently tries to encode their	1006	Blessed objects are not directly representable in JSON. See the
770	underlying representation (hash- or arrayref), but this behaviour might	1007	C<allow_blessed> and C<convert_blessed> methods on various options on
771	change in future versions.	1008	how to deal with this: basically, you can choose between throwing an
		1009	exception, encoding the reference as if it weren't blessed, or provide
		1010	your own serialiser method.
772		1011
773	=item simple scalars	1012	=item simple scalars
774		1013
775	Simple Perl scalars (any scalar that is not a reference) are the most	1014	Simple Perl scalars (any scalar that is not a reference) are the most
776	difficult objects to encode: JSON::XS will encode undefined scalars as	1015	difficult objects to encode: JSON::XS will encode undefined scalars as
777	JSON null value, scalars that have last been used in a string context	1016	JSON C<null> values, scalars that have last been used in a string context
778	before encoding as JSON strings and anything else as number value:	1017	before encoding as JSON strings, and anything else as number value:
779		1018
780	# dump as number	1019	# dump as number
781	to_json [2] # yields [2]	1020	encode_json [2] # yields [2]
782	to_json [-3.0e17] # yields [-3e+17]	1021	encode_json [-3.0e17] # yields [-3e+17]
783	my $value = 5; to_json [$value] # yields [5]	1022	my $value = 5; encode_json [$value] # yields [5]
784		1023
785	# used as string, so dump as string	1024	# used as string, so dump as string
786	print $value;	1025	print $value;
787	to_json [$value] # yields ["5"]	1026	encode_json [$value] # yields ["5"]
788		1027
789	# undef becomes null	1028	# undef becomes null
790	to_json [undef] # yields [null]	1029	encode_json [undef] # yields [null]
791		1030
792	You can force the type to be a JSON string by stringifying it:	1031	You can force the type to be a JSON string by stringifying it:
793		1032
794	my $x = 3.1; # some variable containing a number	1033	my $x = 3.1; # some variable containing a number
795	"$x"; # stringified	1034	"$x"; # stringified
…		…
801	my $x = "3"; # some variable containing a string	1040	my $x = "3"; # some variable containing a string
802	$x += 0; # numify it, ensuring it will be dumped as a number	1041	$x += 0; # numify it, ensuring it will be dumped as a number
803	$x *= 1; # same thing, the choice is yours.	1042	$x *= 1; # same thing, the choice is yours.
804		1043
805	You can not currently force the type in other, less obscure, ways. Tell me	1044	You can not currently force the type in other, less obscure, ways. Tell me
806	if you need this capability.	1045	if you need this capability (but don't forget to explain why it's needed
		1046	:).
807		1047
808	=back	1048	=back
809		1049
810		1050
811	=head1 COMPARISON	1051	=head1 ENCODING/CODESET FLAG NOTES
812		1052
813	As already mentioned, this module was created because none of the existing	1053	The interested reader might have seen a number of flags that signify
814	JSON modules could be made to work correctly. First I will describe the	1054	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
815	problems (or pleasures) I encountered with various existing JSON modules,	1055	some confusion on what these do, so here is a short comparison:
816	followed by some benchmark values. JSON::XS was designed not to suffer	1056
817	from any of these problems or limitations.	1057	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1058	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1059	control whether C<encode> escapes character values outside their respective
		1060	codeset range. Neither of these flags conflict with each other, although
		1061	some combinations make less sense than others.
		1062
		1063	Care has been taken to make all flags symmetrical with respect to
		1064	C<encode> and C<decode>, that is, texts encoded with any combination of
		1065	these flag values will be correctly decoded when the same flags are used
		1066	- in general, if you use different flag settings while encoding vs. when
		1067	decoding you likely have a bug somewhere.
		1068
		1069	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1070	simply an abstract set of character-codepoint pairs, while an encoding
		1071	takes those codepoint numbers and I<encodes> them, in our case into
		1072	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1073	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1074	the same time, which can be confusing.
818		1075
819	=over 4	1076	=over 4
820		1077
821	=item JSON 1.07	1078	=item C<utf8> flag disabled
822		1079
823	Slow (but very portable, as it is written in pure Perl).	1080	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1081	and expect Unicode strings, that is, characters with high ordinal Unicode
		1082	values (> 255) will be encoded as such characters, and likewise such
		1083	characters are decoded as-is, no canges to them will be done, except
		1084	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1085	respectively (to Perl, these are the same thing in strings unless you do
		1086	funny/weird/dumb stuff).
824		1087
825	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1088	This is useful when you want to do the encoding yourself (e.g. when you
826	undocumented. One can get far by feeding it Unicode strings and doing	1089	want to have UTF-16 encoded JSON texts) or when some other layer does
827	en-/decoding oneself, but Unicode escapes are not working properly).	1090	the encoding for you (for example, when printing to a terminal using a
		1091	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1092	to UTF-8 encode your data first and have Perl encode it another time).
828		1093
829	No round-tripping (strings get clobbered if they look like numbers, e.g.	1094	=item C<utf8> flag enabled
830	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
831	decode into the number 2.
832		1095
833	=item JSON::PC 0.01	1096	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1097	characters using the corresponding UTF-8 multi-byte sequence, and will
		1098	expect your input strings to be encoded as UTF-8, that is, no "character"
		1099	of the input string must have any value > 255, as UTF-8 does not allow
		1100	that.
834		1101
835	Very fast.	1102	The C<utf8> flag therefore switches between two modes: disabled means you
		1103	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1104	octet/binary string in Perl.
836		1105
837	Undocumented/buggy Unicode handling.	1106	=item C<latin1> or C<ascii> flags enabled
838		1107
839	No round-tripping.	1108	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1109	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1110	characters as specified by the C<utf8> flag.
840		1111
841	Has problems handling many Perl values (e.g. regex results and other magic	1112	If C<utf8> is disabled, then the result is also correctly encoded in those
842	values will make it croak).	1113	character sets (as both are proper subsets of Unicode, meaning that a
		1114	Unicode string with all character values < 256 is the same thing as a
		1115	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1116	the same thing as an ASCII string in Perl).
843		1117
844	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1118	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
845	which is not a valid JSON text.	1119	regardless of these flags, just some more characters will be escaped using
		1120	C<\uXXXX> then before.
846		1121
847	Unmaintained (maintainer unresponsive for many months, bugs are not	1122	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
848	getting fixed).	1123	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1124	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1125	a subset of Unicode), while ASCII is.
849		1126
850	=item JSON::Syck 0.21	1127	Surprisingly, C<decode> will ignore these flags and so treat all input
		1128	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1129	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1130	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
851		1131
852	Very buggy (often crashes).	1132	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1133	they only govern when the JSON output engine escapes a character or not.
853		1134
854	Very inflexible (no human-readable format supported, format pretty much	1135	The main use for C<latin1> is to relatively efficiently store binary data
855	undocumented. I need at least a format for easy reading by humans and a	1136	as JSON, at the expense of breaking compatibility with most JSON decoders.
856	single-line compact format for use in a protocol, and preferably a way to
857	generate ASCII-only JSON texts).
858		1137
859	Completely broken (and confusingly documented) Unicode handling (Unicode	1138	The main use for C<ascii> is to force the output to not contain characters
860	escapes are not working properly, you need to set ImplicitUnicode to	1139	with values > 127, which means you can interpret the resulting string
861	I<different> values on en- and decoding to get symmetric behaviour).	1140	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
862		1141	8-bit-encoding, and still get the same data structure back. This is useful
863	No round-tripping (simple cases work, but this depends on whether the scalar	1142	when your channel for JSON transfer is not 8-bit clean or the encoding
864	value was used in a numeric context or not).	1143	might be mangled in between (e.g. in mail), and works because ASCII is a
865		1144	proper subset of most 8-bit and multibyte encodings in use in the world.
866	Dumping hashes may skip hash values depending on iterator state.
867
868	Unmaintained (maintainer unresponsive for many months, bugs are not
869	getting fixed).
870
871	Does not check input for validity (i.e. will accept non-JSON input and
872	return "something" instead of raising an exception. This is a security
873	issue: imagine two banks transferring money between each other using
874	JSON. One bank might parse a given non-JSON request and deduct money,
875	while the other might reject the transaction with a syntax error. While a
876	good protocol will at least recover, that is extra unnecessary work and
877	the transaction will still not succeed).
878
879	=item JSON::DWIW 0.04
880
881	Very fast. Very natural. Very nice.
882
883	Undocumented Unicode handling (but the best of the pack. Unicode escapes
884	still don't get parsed properly).
885
886	Very inflexible.
887
888	No round-tripping.
889
890	Does not generate valid JSON texts (key strings are often unquoted, empty keys
891	result in nothing being output)
892
893	Does not check input for validity.
894		1145
895	=back	1146	=back
896		1147
897		1148
898	=head2 JSON and YAML	1149	=head2 JSON and YAML
899		1150
900	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1151	You often hear that JSON is a subset of YAML. This is, however, a mass
901	however, a mass hysteria and very far from the truth. In general, there is	1152	hysteria(*) and very far from the truth (as of the time of this writing),
902	no way to configure JSON::XS to output a data structure as valid YAML.	1153	so let me state it clearly: I<in general, there is no way to configure
		1154	JSON::XS to output a data structure as valid YAML> that works in all
		1155	cases.
903		1156
904	If you really must use JSON::XS to generate YAML, you should use this	1157	If you really must use JSON::XS to generate YAML, you should use this
905	algorithm (subject to change in future versions):	1158	algorithm (subject to change in future versions):
906		1159
907	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1160	my $to_yaml = JSON::XS->new->utf8->space_after (1);
908	my $yaml = $to_yaml->encode ($ref) . "\n";	1161	my $yaml = $to_yaml->encode ($ref) . "\n";
909		1162
910	This will usually generate JSON texts that also parse as valid	1163	This will I<usually> generate JSON texts that also parse as valid
911	YAML. Please note that YAML has hardcoded limits on (simple) object key	1164	YAML. Please note that YAML has hardcoded limits on (simple) object key
912	lengths that JSON doesn't have, so you should make sure that your hash	1165	lengths that JSON doesn't have and also has different and incompatible
		1166	unicode handling, so you should make sure that your hash keys are
913	keys are noticeably shorter than the 1024 characters YAML allows.	1167	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1168	you do not have characters with codepoint values outside the Unicode BMP
		1169	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1170	strings (which JSON::XS does not I<currently> generate, but other JSON
		1171	generators might).
914		1172
915	There might be other incompatibilities that I am not aware of. In general	1173	There might be other incompatibilities that I am not aware of (or the YAML
		1174	specification has been changed yet again - it does so quite often). In
916	you should not try to generate YAML with a JSON generator or vice versa,	1175	general you should not try to generate YAML with a JSON generator or vice
917	or try to parse JSON with a YAML parser or vice versa: chances are high	1176	versa, or try to parse JSON with a YAML parser or vice versa: chances are
918	that you will run into severe interoperability problems.	1177	high that you will run into severe interoperability problems when you
		1178	least expect it.
		1179
		1180	=over 4
		1181
		1182	=item (*)
		1183
		1184	I have been pressured multiple times by Brian Ingerson (one of the
		1185	authors of the YAML specification) to remove this paragraph, despite him
		1186	acknowledging that the actual incompatibilities exist. As I was personally
		1187	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1188	educate people about these issues, so others do not run into the same
		1189	problem again and again. After this, Brian called me a (quote)I<complete
		1190	and worthless idiot>(unquote).
		1191
		1192	In my opinion, instead of pressuring and insulting people who actually
		1193	clarify issues with YAML and the wrong statements of some of its
		1194	proponents, I would kindly suggest reading the JSON spec (which is not
		1195	that difficult or long) and finally make YAML compatible to it, and
		1196	educating users about the changes, instead of spreading lies about the
		1197	real compatibility for many I<years> and trying to silence people who
		1198	point out that it isn't true.
		1199
		1200	=back
919		1201
920		1202
921	=head2 SPEED	1203	=head2 SPEED
922		1204
923	It seems that JSON::XS is surprisingly fast, as shown in the following	1205	It seems that JSON::XS is surprisingly fast, as shown in the following
924	tables. They have been generated with the help of the C<eg/bench> program	1206	tables. They have been generated with the help of the C<eg/bench> program
925	in the JSON::XS distribution, to make it easy to compare on your own	1207	in the JSON::XS distribution, to make it easy to compare on your own
926	system.	1208	system.
927		1209
928	First comes a comparison between various modules using a very short	1210	First comes a comparison between various modules using
929	single-line JSON string:	1211	a very short single-line JSON string (also available at
		1212	L<http://dist.schmorp.de/misc/json/short.json>).
930		1213
931	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1214	{"method": "handleMessage", "params": ["user1", "we were just talking"], \
932	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1215	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
933		1216
934	It shows the number of encodes/decodes per second (JSON::XS uses	1217	It shows the number of encodes/decodes per second (JSON::XS uses
…		…
953	about three times faster on decoding, and over forty times faster	1236	about three times faster on decoding, and over forty times faster
954	than JSON, even with pretty-printing and key sorting. It also compares	1237	than JSON, even with pretty-printing and key sorting. It also compares
955	favourably to Storable for small amounts of data.	1238	favourably to Storable for small amounts of data.
956		1239
957	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1240	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
958	search API (http://nanoref.com/yahooapis/mgPdGg):	1241	search API (L<http://dist.schmorp.de/misc/json/long.json>).
959		1242
960	module \| encode \| decode \|	1243	module \| encode \| decode \|
961	-----------\|------------\|------------\|	1244	-----------\|------------\|------------\|
962	JSON 1.x \| 55.260 \| 34.971 \|	1245	JSON 1.x \| 55.260 \| 34.971 \|
963	JSON::DWIW \| 825.228 \| 1082.513 \|	1246	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
1000		1283
1001	Third, JSON::XS recurses using the C stack when decoding objects and	1284	Third, JSON::XS recurses using the C stack when decoding objects and
1002	arrays. The C stack is a limited resource: for instance, on my amd64	1285	arrays. The C stack is a limited resource: for instance, on my amd64
1003	machine with 8MB of stack size I can decode around 180k nested arrays but	1286	machine with 8MB of stack size I can decode around 180k nested arrays but
1004	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1287	only 14k nested JSON objects (due to perl itself recursing deeply on croak
1005	to free the temporary). If that is exceeded, the program crashes. to be	1288	to free the temporary). If that is exceeded, the program crashes. To be
1006	conservative, the default nesting limit is set to 512. If your process	1289	conservative, the default nesting limit is set to 512. If your process
1007	has a smaller stack, you should adjust this setting accordingly with the	1290	has a smaller stack, you should adjust this setting accordingly with the
1008	C<max_depth> method.	1291	C<max_depth> method.
1009		1292
1010	And last but least, something else could bomb you that I forgot to think	1293	Something else could bomb you, too, that I forgot to think of. In that
1011	of. In that case, you get to keep the pieces. I am always open for hints,	1294	case, you get to keep the pieces. I am always open for hints, though...
1012	though...	1295
		1296	Also keep in mind that JSON::XS might leak contents of your Perl data
		1297	structures in its error messages, so when you serialise sensitive
		1298	information you might want to make sure that exceptions thrown by JSON::XS
		1299	will not end up in front of untrusted eyes.
1013		1300
1014	If you are using JSON::XS to return packets to consumption	1301	If you are using JSON::XS to return packets to consumption
1015	by JavaScript scripts in a browser you should have a look at	1302	by JavaScript scripts in a browser you should have a look at
1016	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1303	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1017	you are vulnerable to some common attack vectors (which really are browser	1304	you are vulnerable to some common attack vectors (which really are browser
1018	design bugs, but it is still you who will have to deal with it, as major	1305	design bugs, but it is still you who will have to deal with it, as major
1019	browser developers care only for features, not about doing security	1306	browser developers care only for features, not about getting security
1020	right).	1307	right).
1021		1308
1022		1309
1023	=head1 THREADS	1310	=head1 THREADS
1024		1311
1025	This module is I<not> guaranteed to be thread safe and there are no	1312	This module is I<not> guaranteed to be thread safe and there are no
1026	plans to change this until Perl gets thread support (as opposed to the	1313	plans to change this until Perl gets thread support (as opposed to the
1027	horribly slow so-called "threads" which are simply slow and bloated	1314	horribly slow so-called "threads" which are simply slow and bloated
1028	process simulations - use fork, its I<much> faster, cheaper, better).	1315	process simulations - use fork, it's I<much> faster, cheaper, better).
1029		1316
1030	(It might actually work, but you have been warned).	1317	(It might actually work, but you have been warned).
1031		1318
1032		1319
1033	=head1 BUGS	1320	=head1 BUGS
1034		1321
1035	While the goal of this module is to be correct, that unfortunately does	1322	While the goal of this module is to be correct, that unfortunately does
1036	not mean its bug-free, only that I think its design is bug-free. It is	1323	not mean it's bug-free, only that I think its design is bug-free. It is
1037	still relatively early in its development. If you keep reporting bugs they	1324	still relatively early in its development. If you keep reporting bugs they
1038	will be fixed swiftly, though.	1325	will be fixed swiftly, though.
1039		1326
1040	Please refrain from using rt.cpan.org or any other bug reporting	1327	Please refrain from using rt.cpan.org or any other bug reporting
1041	service. I put the contact address into my modules for a reason.	1328	service. I put the contact address into my modules for a reason.
…		…
1063	"--" => sub { $_[0] = ${$_[0]} - 1 },	1350	"--" => sub { $_[0] = ${$_[0]} - 1 },
1064	fallback => 1;	1351	fallback => 1;
1065		1352
1066	1;	1353	1;
1067		1354
		1355	=head1 SEE ALSO
		1356
		1357	The F<json_xs> command line utility for quick experiments.
		1358
1068	=head1 AUTHOR	1359	=head1 AUTHOR
1069		1360
1070	Marc Lehmann <schmorp@schmorp.de>	1361	Marc Lehmann <schmorp@schmorp.de>
1071	http://home.schmorp.de/	1362	http://home.schmorp.de/
1072		1363

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Revision 1.77 by root, Tue Dec 4 10:37:42 2007 UTC vs.
Revision 1.96 by root, Wed Mar 26 01:40:42 2008 UTC