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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.84 by root, Wed Mar 19 02:52:15 2008 UTC vs.
Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC

…		…
		1	=head1 NAME
		2
		3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
1	=encoding utf-8	5	=encoding utf-8
2
3	=head1 NAME
4
5	JSON::XS - JSON serialising/deserialising, done correctly and fast
6		6
7	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
8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
9		9
10	=head1 SYNOPSIS	10	=head1 SYNOPSIS
37	primary goal is to be I<correct> and its secondary goal is to be	37	primary goal is to be I<correct> and its secondary goal is to be
38	I<fast>. To reach the latter goal it was written in C.	38	I<fast>. To reach the latter goal it was written in C.
39		39
40	Beginning with version 2.0 of the JSON module, when both JSON and	40	Beginning with version 2.0 of the JSON module, when both JSON and
41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be	41	JSON::XS are installed, then JSON will fall back on JSON::XS (this can be
42	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
43	and methods). If JSON::XS is not available, it will fall back to the	43	and methods). If JSON::XS is not available, it will fall back to the
44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS	44	compatible JSON::PP module as backend, so using JSON instead of JSON::XS
45	gives you a portable JSON API that can be fast when you need and doesn't	45	gives you a portable JSON API that can be fast when you need and doesn't
46	require a C compiler when that is a problem.	46	require a C compiler when that is a problem.
47		47
…		…
49	to write yet another JSON module? While it seems there are many JSON	49	to write yet another JSON module? While it seems there are many JSON
50	modules, none of them correctly handle all corner cases, and in most cases	50	modules, none of them correctly handle all corner cases, and in most cases
51	their maintainers are unresponsive, gone missing, or not listening to bug	51	their maintainers are unresponsive, gone missing, or not listening to bug
52	reports for other reasons.	52	reports for other reasons.
53		53
54	See COMPARISON, below, for a comparison to some other JSON modules.
55
56	See MAPPING, below, on how JSON::XS maps perl values to JSON values and	54	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
57	vice versa.	55	vice versa.
58		56
59	=head2 FEATURES	57	=head2 FEATURES
60		58
…		…
65	This module knows how to handle Unicode, documents how and when it does	63	This module knows how to handle Unicode, documents how and when it does
66	so, and even documents what "correct" means.	64	so, and even documents what "correct" means.
67		65
68	=item * round-trip integrity	66	=item * round-trip integrity
69		67
70	When you serialise a perl data structure using only datatypes supported	68	When you serialise a perl data structure using only data types supported
71	by JSON, the deserialised data structure is identical on the Perl level.	69	by JSON, the deserialised data structure is identical on the Perl level.
72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
73	like a number). There minor I<are> exceptions to this, read the MAPPING	71	like a number). There minor I<are> exceptions to this, read the MAPPING
74	section below to learn about those.	72	section below to learn about those.
75		73
…		…
84	Compared to other JSON modules and other serialisers such as Storable,	82	Compared to other JSON modules and other serialisers such as Storable,
85	this module usually compares favourably in terms of speed, too.	83	this module usually compares favourably in terms of speed, too.
86		84
87	=item * simple to use	85	=item * simple to use
88		86
89	This module has both a simple functional interface as well as an objetc	87	This module has both a simple functional interface as well as an object
90	oriented interface interface.	88	oriented interface interface.
91		89
92	=item * reasonably versatile output formats	90	=item * reasonably versatile output formats
93		91
94	You can choose between the most compact guaranteed-single-line format	92	You can choose between the most compact guaranteed-single-line format
95	possible (nice for simple line-based protocols), a pure-ascii format	93	possible (nice for simple line-based protocols), a pure-ASCII format
96	(for when your transport is not 8-bit clean, still supports the whole	94	(for when your transport is not 8-bit clean, still supports the whole
97	Unicode range), or a pretty-printed format (for when you want to read that	95	Unicode range), or a pretty-printed format (for when you want to read that
98	stuff). Or you can combine those features in whatever way you like.	96	stuff). Or you can combine those features in whatever way you like.
99		97
100	=back	98	=back
101		99
102	=cut	100	=cut
103		101
104	package JSON::XS;	102	package JSON::XS;
105		103
106	use strict;	104	use common::sense;
107		105
108	our $VERSION = '2.01';	106	our $VERSION = '2.25';
109	our @ISA = qw(Exporter);	107	our @ISA = qw(Exporter);
110		108
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	109	our @EXPORT = qw(encode_json decode_json to_json from_json);
112		110
113	sub to_json($) {	111	sub to_json($) {
…		…
137		135
138	This function call is functionally identical to:	136	This function call is functionally identical to:
139		137
140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	138	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141		139
142	except being faster.	140	Except being faster.
143		141
144	=item $perl_scalar = decode_json $json_text	142	=item $perl_scalar = decode_json $json_text
145		143
146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	144	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
147	to parse that as an UTF-8 encoded JSON text, returning the resulting	145	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
149		147
150	This function call is functionally identical to:	148	This function call is functionally identical to:
151		149
152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	150	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153		151
154	except being faster.	152	Except being faster.
155		153
156	=item $is_boolean = JSON::XS::is_bool $scalar	154	=item $is_boolean = JSON::XS::is_bool $scalar
157		155
158	Returns true if the passed scalar represents either JSON::XS::true or	156	Returns true if the passed scalar represents either JSON::XS::true or
159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	157	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
197		195
198	If you didn't know about that flag, just the better, pretend it doesn't	196	If you didn't know about that flag, just the better, pretend it doesn't
199	exist.	197	exist.
200		198
201	=item 4. A "Unicode String" is simply a string where each character can be	199	=item 4. A "Unicode String" is simply a string where each character can be
202	validly interpreted as a Unicode codepoint.	200	validly interpreted as a Unicode code point.
203		201
204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	202	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205	Unicode string encoded in UTF-8, giving you a binary string.	203	Unicode string encoded in UTF-8, giving you a binary string.
206		204
207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	205	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
245		243
246	If C<$enable> is false, then the C<encode> method will not escape Unicode	244	If C<$enable> is false, then the C<encode> method will not escape Unicode
247	characters unless required by the JSON syntax or other flags. This results	245	characters unless required by the JSON syntax or other flags. This results
248	in a faster and more compact format.	246	in a faster and more compact format.
249		247
		248	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		249	document.
		250
250	The main use for this flag is to produce JSON texts that can be	251	The main use for this flag is to produce JSON texts that can be
251	transmitted over a 7-bit channel, as the encoded JSON texts will not	252	transmitted over a 7-bit channel, as the encoded JSON texts will not
252	contain any 8 bit characters.	253	contain any 8 bit characters.
253		254
254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	255	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
265	will not be affected in any way by this flag, as C<decode> by default	266	will not be affected in any way by this flag, as C<decode> by default
266	expects Unicode, which is a strict superset of latin1.	267	expects Unicode, which is a strict superset of latin1.
267		268
268	If C<$enable> is false, then the C<encode> method will not escape Unicode	269	If C<$enable> is false, then the C<encode> method will not escape Unicode
269	characters unless required by the JSON syntax or other flags.	270	characters unless required by the JSON syntax or other flags.
		271
		272	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		273	document.
270		274
271	The main use for this flag is efficiently encoding binary data as JSON	275	The main use for this flag is efficiently encoding binary data as JSON
272	text, as most octets will not be escaped, resulting in a smaller encoded	276	text, as most octets will not be escaped, resulting in a smaller encoded
273	size. The disadvantage is that the resulting JSON text is encoded	277	size. The disadvantage is that the resulting JSON text is encoded
274	in latin1 (and must correctly be treated as such when storing and	278	in latin1 (and must correctly be treated as such when storing and
…		…
293		297
294	If C<$enable> is false, then the C<encode> method will return the JSON	298	If C<$enable> is false, then the C<encode> method will return the JSON
295	string as a (non-encoded) Unicode string, while C<decode> expects thus a	299	string as a (non-encoded) Unicode string, while C<decode> expects thus a
296	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	300	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
297	to be done yourself, e.g. using the Encode module.	301	to be done yourself, e.g. using the Encode module.
		302
		303	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		304	document.
298		305
299	Example, output UTF-16BE-encoded JSON:	306	Example, output UTF-16BE-encoded JSON:
300		307
301	use Encode;	308	use Encode;
302	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	309	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
434	the same hash might be encoded differently even if contains the same data,	441	the same hash might be encoded differently even if contains the same data,
435	as key-value pairs have no inherent ordering in Perl.	442	as key-value pairs have no inherent ordering in Perl.
436		443
437	This setting has no effect when decoding JSON texts.	444	This setting has no effect when decoding JSON texts.
438		445
		446	This setting has currently no effect on tied hashes.
		447
439	=item $json = $json->allow_nonref ([$enable])	448	=item $json = $json->allow_nonref ([$enable])
440		449
441	=item $enabled = $json->get_allow_nonref	450	=item $enabled = $json->get_allow_nonref
442		451
443	If C<$enable> is true (or missing), then the C<encode> method can convert a	452	If C<$enable> is true (or missing), then the C<encode> method can convert a
…		…
453	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	462	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
454	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
455		464
456	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
457	=> "Hello, World!"	466	=> "Hello, World!"
		467
		468	=item $json = $json->allow_unknown ([$enable])
		469
		470	=item $enabled = $json->get_allow_unknown
		471
		472	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		473	exception when it encounters values it cannot represent in JSON (for
		474	example, filehandles) but instead will encode a JSON C<null> value. Note
		475	that blessed objects are not included here and are handled separately by
		476	c<allow_nonref>.
		477
		478	If C<$enable> is false (the default), then C<encode> will throw an
		479	exception when it encounters anything it cannot encode as JSON.
		480
		481	This option does not affect C<decode> in any way, and it is recommended to
		482	leave it off unless you know your communications partner.
458		483
459	=item $json = $json->allow_blessed ([$enable])	484	=item $json = $json->allow_blessed ([$enable])
460		485
461	=item $enabled = $json->get_allow_blessed	486	=item $enabled = $json->get_allow_blessed
462		487
…		…
603	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
604		629
605	=item $max_depth = $json->get_max_depth	630	=item $max_depth = $json->get_max_depth
606		631
607	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
608	or decoding. If the JSON text or Perl data structure has an equal or	633	or decoding. If a higher nesting level is detected in JSON text or a Perl
609	higher nesting level then this limit, then the encoder and decoder will	634	data structure, then the encoder and decoder will stop and croak at that
610	stop and croak at that point.	635	point.
611		636
612	Nesting level is defined by number of hash- or arrayrefs that the encoder	637	Nesting level is defined by number of hash- or arrayrefs that the encoder
613	needs to traverse to reach a given point or the number of C<{> or C<[>	638	needs to traverse to reach a given point or the number of C<{> or C<[>
614	characters without their matching closing parenthesis crossed to reach a	639	characters without their matching closing parenthesis crossed to reach a
615	given character in a string.	640	given character in a string.
616		641
617	Setting the maximum depth to one disallows any nesting, so that ensures	642	Setting the maximum depth to one disallows any nesting, so that ensures
618	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
619		644
620	The argument to C<max_depth> will be rounded up to the next highest power
621	of two. If no argument is given, the highest possible setting will be	645	If no argument is given, the highest possible setting will be used, which
622	used, which is rarely useful.	646	is rarely useful.
		647
		648	Note that nesting is implemented by recursion in C. The default value has
		649	been chosen to be as large as typical operating systems allow without
		650	crashing.
623		651
624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	652	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
625		653
626	=item $json = $json->max_size ([$maximum_string_size])	654	=item $json = $json->max_size ([$maximum_string_size])
627		655
628	=item $max_size = $json->get_max_size	656	=item $max_size = $json->get_max_size
629		657
630	Set the maximum length a JSON text may have (in bytes) where decoding is	658	Set the maximum length a JSON text may have (in bytes) where decoding is
631	being attempted. The default is C<0>, meaning no limit. When C<decode>	659	being attempted. The default is C<0>, meaning no limit. When C<decode>
632	is called on a string longer then this number of characters it will not	660	is called on a string that is longer then this many bytes, it will not
633	attempt to decode the string but throw an exception. This setting has no	661	attempt to decode the string but throw an exception. This setting has no
634	effect on C<encode> (yet).	662	effect on C<encode> (yet).
635		663
636	The argument to C<max_size> will be rounded up to the next B<highest>	664	If no argument is given, the limit check will be deactivated (same as when
637	power of two (so may be more than requested). If no argument is given, the	665	C<0> is specified).
638	limit check will be deactivated (same as when C<0> is specified).
639		666
640	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	667	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
641		668
642	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
643		670
…		…
670		697
671	JSON::XS->new->decode_prefix ("[1] the tail")	698	JSON::XS->new->decode_prefix ("[1] the tail")
672	=> ([], 3)	699	=> ([], 3)
673		700
674	=back	701	=back
		702
		703
		704	=head1 INCREMENTAL PARSING
		705
		706	In some cases, there is the need for incremental parsing of JSON
		707	texts. While this module always has to keep both JSON text and resulting
		708	Perl data structure in memory at one time, it does allow you to parse a
		709	JSON stream incrementally. It does so by accumulating text until it has
		710	a full JSON object, which it then can decode. This process is similar to
		711	using C<decode_prefix> to see if a full JSON object is available, but
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	=item $lvalue_string = $json->incr_text
		757
		758	This method returns the currently stored JSON fragment as an lvalue, that
		759	is, you can manipulate it. This I<only> works when a preceding call to
		760	C<incr_parse> in I<scalar context> successfully returned an object. Under
		761	all other circumstances you must not call this function (I mean it.
		762	although in simple tests it might actually work, it I<will> fail under
		763	real world conditions). As a special exception, you can also call this
		764	method before having parsed anything.
		765
		766	This function is useful in two cases: a) finding the trailing text after a
		767	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		768	(such as commas).
		769
		770	=item $json->incr_skip
		771
		772	This will reset the state of the incremental parser and will remove
		773	the parsed text from the input buffer so far. This is useful after
		774	C<incr_parse> died, in which case the input buffer and incremental parser
		775	state is left unchanged, to skip the text parsed so far and to reset the
		776	parse state.
		777
		778	The difference to C<incr_reset> is that only text until the parse error
		779	occured is removed.
		780
		781	=item $json->incr_reset
		782
		783	This completely resets the incremental parser, that is, after this call,
		784	it will be as if the parser had never parsed anything.
		785
		786	This is useful if you want to repeatedly parse JSON objects and want to
		787	ignore any trailing data, which means you have to reset the parser after
		788	each successful decode.
		789
		790	=back
		791
		792	=head2 LIMITATIONS
		793
		794	All options that affect decoding are supported, except
		795	C<allow_nonref>. The reason for this is that it cannot be made to
		796	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		797	them back to back and still decode them perfectly. This does not hold true
		798	for JSON numbers, however.
		799
		800	For example, is the string C<1> a single JSON number, or is it simply the
		801	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		802	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		803	takes the conservative route and disallows this case.
		804
		805	=head2 EXAMPLES
		806
		807	Some examples will make all this clearer. First, a simple example that
		808	works similarly to C<decode_prefix>: We want to decode the JSON object at
		809	the start of a string and identify the portion after the JSON object:
		810
		811	my $text = "[1,2,3] hello";
		812
		813	my $json = new JSON::XS;
		814
		815	my $obj = $json->incr_parse ($text)
		816	or die "expected JSON object or array at beginning of string";
		817
		818	my $tail = $json->incr_text;
		819	# $tail now contains " hello"
		820
		821	Easy, isn't it?
		822
		823	Now for a more complicated example: Imagine a hypothetical protocol where
		824	you read some requests from a TCP stream, and each request is a JSON
		825	array, without any separation between them (in fact, it is often useful to
		826	use newlines as "separators", as these get interpreted as whitespace at
		827	the start of the JSON text, which makes it possible to test said protocol
		828	with C<telnet>...).
		829
		830	Here is how you'd do it (it is trivial to write this in an event-based
		831	manner):
		832
		833	my $json = new JSON::XS;
		834
		835	# read some data from the socket
		836	while (sysread $socket, my $buf, 4096) {
		837
		838	# split and decode as many requests as possible
		839	for my $request ($json->incr_parse ($buf)) {
		840	# act on the $request
		841	}
		842	}
		843
		844	Another complicated example: Assume you have a string with JSON objects
		845	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		846	[3]>). To parse them, we have to skip the commas between the JSON texts,
		847	and here is where the lvalue-ness of C<incr_text> comes in useful:
		848
		849	my $text = "[1],[2], [3]";
		850	my $json = new JSON::XS;
		851
		852	# void context, so no parsing done
		853	$json->incr_parse ($text);
		854
		855	# now extract as many objects as possible. note the
		856	# use of scalar context so incr_text can be called.
		857	while (my $obj = $json->incr_parse) {
		858	# do something with $obj
		859
		860	# now skip the optional comma
		861	$json->incr_text =~ s/^ \s* , //x;
		862	}
		863
		864	Now lets go for a very complex example: Assume that you have a gigantic
		865	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		866	but you cannot load it into memory fully (this has actually happened in
		867	the real world :).
		868
		869	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		870	can still help you: You implement a (very simple) array parser and let
		871	JSON decode the array elements, which are all full JSON objects on their
		872	own (this wouldn't work if the array elements could be JSON numbers, for
		873	example):
		874
		875	my $json = new JSON::XS;
		876
		877	# open the monster
		878	open my $fh, "<bigfile.json"
		879	or die "bigfile: $!";
		880
		881	# first parse the initial "["
		882	for (;;) {
		883	sysread $fh, my $buf, 65536
		884	or die "read error: $!";
		885	$json->incr_parse ($buf); # void context, so no parsing
		886
		887	# Exit the loop once we found and removed(!) the initial "[".
		888	# In essence, we are (ab-)using the $json object as a simple scalar
		889	# we append data to.
		890	last if $json->incr_text =~ s/^ \s* \[ //x;
		891	}
		892
		893	# now we have the skipped the initial "[", so continue
		894	# parsing all the elements.
		895	for (;;) {
		896	# in this loop we read data until we got a single JSON object
		897	for (;;) {
		898	if (my $obj = $json->incr_parse) {
		899	# do something with $obj
		900	last;
		901	}
		902
		903	# add more data
		904	sysread $fh, my $buf, 65536
		905	or die "read error: $!";
		906	$json->incr_parse ($buf); # void context, so no parsing
		907	}
		908
		909	# in this loop we read data until we either found and parsed the
		910	# separating "," between elements, or the final "]"
		911	for (;;) {
		912	# first skip whitespace
		913	$json->incr_text =~ s/^\s*//;
		914
		915	# if we find "]", we are done
		916	if ($json->incr_text =~ s/^\]//) {
		917	print "finished.\n";
		918	exit;
		919	}
		920
		921	# if we find ",", we can continue with the next element
		922	if ($json->incr_text =~ s/^,//) {
		923	last;
		924	}
		925
		926	# if we find anything else, we have a parse error!
		927	if (length $json->incr_text) {
		928	die "parse error near ", $json->incr_text;
		929	}
		930
		931	# else add more data
		932	sysread $fh, my $buf, 65536
		933	or die "read error: $!";
		934	$json->incr_parse ($buf); # void context, so no parsing
		935	}
		936
		937	This is a complex example, but most of the complexity comes from the fact
		938	that we are trying to be correct (bear with me if I am wrong, I never ran
		939	the above example :).
		940
675		941
676		942
677	=head1 MAPPING	943	=head1 MAPPING
678		944
679	This section describes how JSON::XS maps Perl values to JSON values and	945	This section describes how JSON::XS maps Perl values to JSON values and
…		…
768	Other unblessed references are generally not allowed and will cause an	1034	Other unblessed references are generally not allowed and will cause an
769	exception to be thrown, except for references to the integers C<0> and	1035	exception to be thrown, except for references to the integers C<0> and
770	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1036	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
771	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1037	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
772		1038
773	encode_json [\0,JSON::XS::true] # yields [false,true]	1039	encode_json [\0, JSON::XS::true] # yields [false,true]
774		1040
775	=item JSON::XS::true, JSON::XS::false	1041	=item JSON::XS::true, JSON::XS::false
776		1042
777	These special values become JSON true and JSON false values,	1043	These special values become JSON true and JSON false values,
778	respectively. You can also use C<\1> and C<\0> directly if you want.	1044	respectively. You can also use C<\1> and C<\0> directly if you want.
…		…
816	my $x = "3"; # some variable containing a string	1082	my $x = "3"; # some variable containing a string
817	$x += 0; # numify it, ensuring it will be dumped as a number	1083	$x += 0; # numify it, ensuring it will be dumped as a number
818	$x *= 1; # same thing, the choice is yours.	1084	$x *= 1; # same thing, the choice is yours.
819		1085
820	You can not currently force the type in other, less obscure, ways. Tell me	1086	You can not currently force the type in other, less obscure, ways. Tell me
821	if you need this capability (but don't forget to explain why its needed	1087	if you need this capability (but don't forget to explain why it's needed
822	:).	1088	:).
823		1089
824	=back	1090	=back
825		1091
826		1092
…		…
828		1094
829	The interested reader might have seen a number of flags that signify	1095	The interested reader might have seen a number of flags that signify
830	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be	1096	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
831	some confusion on what these do, so here is a short comparison:	1097	some confusion on what these do, so here is a short comparison:
832		1098
833	C<utf8> controls wether the JSON text created by C<encode> (and expected	1099	C<utf8> controls whether the JSON text created by C<encode> (and expected
834	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only	1100	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
835	control wether C<encode> escapes character values outside their respective	1101	control whether C<encode> escapes character values outside their respective
836	codeset range. Neither of these flags conflict with each other, although	1102	codeset range. Neither of these flags conflict with each other, although
837	some combinations make less sense than others.	1103	some combinations make less sense than others.
838		1104
839	Care has been taken to make all flags symmetrical with respect to	1105	Care has been taken to make all flags symmetrical with respect to
840	C<encode> and C<decode>, that is, texts encoded with any combination of	1106	C<encode> and C<decode>, that is, texts encoded with any combination of
…		…
920	proper subset of most 8-bit and multibyte encodings in use in the world.	1186	proper subset of most 8-bit and multibyte encodings in use in the world.
921		1187
922	=back	1188	=back
923		1189
924		1190
925	=head1 COMPARISON	1191	=head2 JSON and ECMAscript
926		1192
927	As already mentioned, this module was created because none of the existing	1193	JSON syntax is based on how literals are represented in javascript (the
928	JSON modules could be made to work correctly. First I will describe the	1194	not-standardised predecessor of ECMAscript) which is presumably why it is
929	problems (or pleasures) I encountered with various existing JSON modules,	1195	called "JavaScript Object Notation".
930	followed by some benchmark values. JSON::XS was designed not to suffer
931	from any of these problems or limitations.
932		1196
933	=over 4	1197	However, JSON is not a subset (and also not a superset of course) of
		1198	ECMAscript (the standard) or javascript (whatever browsers actually
		1199	implement).
934		1200
935	=item JSON 2.xx	1201	If you want to use javascript's C<eval> function to "parse" JSON, you
		1202	might run into parse errors for valid JSON texts, or the resulting data
		1203	structure might not be queryable:
936		1204
937	A marvellous piece of engineering, this module either uses JSON::XS	1205	One of the problems is that U+2028 and U+2029 are valid characters inside
938	directly when available (so will be 100% compatible with it, including	1206	JSON strings, but are not allowed in ECMAscript string literals, so the
939	speed), or it uses JSON::PP, which is basically JSON::XS translated to	1207	following Perl fragment will not output something that can be guaranteed
940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit	1208	to be parsable by javascript's C<eval>:
941	slower.
942		1209
943	You cannot really lose by using this module.	1210	use JSON::XS;
944		1211
945	=item JSON 1.07	1212	print encode_json [chr 0x2028];
946		1213
947	Slow (but very portable, as it is written in pure Perl).	1214	The right fix for this is to use a proper JSON parser in your javascript
		1215	programs, and not rely on C<eval> (see for example Douglas Crockford's
		1216	F<json2.js> parser).
948		1217
949	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1218	If this is not an option, you can, as a stop-gap measure, simply encode to
950	undocumented. One can get far by feeding it Unicode strings and doing	1219	ASCII-only JSON:
951	en-/decoding oneself, but Unicode escapes are not working properly).
952		1220
953	No round-tripping (strings get clobbered if they look like numbers, e.g.	1221	use JSON::XS;
954	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
955	decode into the number 2.
956		1222
957	=item JSON::PC 0.01	1223	print JSON::XS->new->ascii->encode ([chr 0x2028]);
958		1224
959	Very fast.	1225	Note that this will enlarge the resulting JSON text quite a bit if you
		1226	have many non-ASCII characters. You might be tempted to run some regexes
		1227	to only escape U+2028 and U+2029, e.g.:
960		1228
961	Undocumented/buggy Unicode handling.	1229	# DO NOT USE THIS!
		1230	my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
		1231	$json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
		1232	$json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
		1233	print $json;
962		1234
963	No round-tripping.	1235	Note that I<this is a bad idea>: the above only works for U+2028 and
		1236	U+2029 and thus only for fully ECMAscript-compliant parsers. Many existing
		1237	javascript implementations, however, have issues with other characters as
		1238	well - using C<eval> naively simply I<will> cause problems.
964		1239
965	Has problems handling many Perl values (e.g. regex results and other magic	1240	Another problem is that some javascript implementations reserve
966	values will make it croak).	1241	some property names for their own purposes (which probably makes
		1242	them non-ECMAscript-compliant). For example, Iceweasel reserves the
		1243	C<__proto__> property name for it's own purposes.
967		1244
968	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1245	If that is a problem, you could parse try to filter the resulting JSON
969	which is not a valid JSON text.	1246	output for these property strings, e.g.:
970		1247
971	Unmaintained (maintainer unresponsive for many months, bugs are not	1248	$json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
972	getting fixed).
973		1249
974	=item JSON::Syck 0.21	1250	This works because C<__proto__> is not valid outside of strings, so every
		1251	occurence of C<"__proto__"\s*:> must be a string used as property name.
975		1252
976	Very buggy (often crashes).	1253	If you know of other incompatibilities, please let me know.
977
978	Very inflexible (no human-readable format supported, format pretty much
979	undocumented. I need at least a format for easy reading by humans and a
980	single-line compact format for use in a protocol, and preferably a way to
981	generate ASCII-only JSON texts).
982
983	Completely broken (and confusingly documented) Unicode handling (Unicode
984	escapes are not working properly, you need to set ImplicitUnicode to
985	I<different> values on en- and decoding to get symmetric behaviour).
986
987	No round-tripping (simple cases work, but this depends on whether the scalar
988	value was used in a numeric context or not).
989
990	Dumping hashes may skip hash values depending on iterator state.
991
992	Unmaintained (maintainer unresponsive for many months, bugs are not
993	getting fixed).
994
995	Does not check input for validity (i.e. will accept non-JSON input and
996	return "something" instead of raising an exception. This is a security
997	issue: imagine two banks transferring money between each other using
998	JSON. One bank might parse a given non-JSON request and deduct money,
999	while the other might reject the transaction with a syntax error. While a
1000	good protocol will at least recover, that is extra unnecessary work and
1001	the transaction will still not succeed).
1002
1003	=item JSON::DWIW 0.04
1004
1005	Very fast. Very natural. Very nice.
1006
1007	Undocumented Unicode handling (but the best of the pack. Unicode escapes
1008	still don't get parsed properly).
1009
1010	Very inflexible.
1011
1012	No round-tripping.
1013
1014	Does not generate valid JSON texts (key strings are often unquoted, empty keys
1015	result in nothing being output)
1016
1017	Does not check input for validity.
1018
1019	=back
1020		1254
1021		1255
1022	=head2 JSON and YAML	1256	=head2 JSON and YAML
1023		1257
1024	You often hear that JSON is a subset of YAML. This is, however, a mass	1258	You often hear that JSON is a subset of YAML. This is, however, a mass
1025	hysteria(*) and very far from the truth. In general, there is no way to	1259	hysteria(*) and very far from the truth (as of the time of this writing),
		1260	so let me state it clearly: I<in general, there is no way to configure
1026	configure JSON::XS to output a data structure as valid YAML that works for	1261	JSON::XS to output a data structure as valid YAML> that works in all
1027	all cases.	1262	cases.
1028		1263
1029	If you really must use JSON::XS to generate YAML, you should use this	1264	If you really must use JSON::XS to generate YAML, you should use this
1030	algorithm (subject to change in future versions):	1265	algorithm (subject to change in future versions):
1031		1266
1032	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1267	my $to_yaml = JSON::XS->new->utf8->space_after (1);
1033	my $yaml = $to_yaml->encode ($ref) . "\n";	1268	my $yaml = $to_yaml->encode ($ref) . "\n";
1034		1269
1035	This will I<usually> generate JSON texts that also parse as valid	1270	This will I<usually> generate JSON texts that also parse as valid
1036	YAML. Please note that YAML has hardcoded limits on (simple) object key	1271	YAML. Please note that YAML has hardcoded limits on (simple) object key
1037	lengths that JSON doesn't have and also has different and incompatible	1272	lengths that JSON doesn't have and also has different and incompatible
1038	unicode handling, so you should make sure that your hash keys are	1273	unicode character escape syntax, so you should make sure that your hash
1039	noticeably shorter than the 1024 "stream characters" YAML allows and that	1274	keys are noticeably shorter than the 1024 "stream characters" YAML allows
1040	you do not have codepoints with values outside the Unicode BMP (basic	1275	and that you do not have characters with codepoint values outside the
1041	multilingual page). YAML also does not allow C<\/> sequences in strings	1276	Unicode BMP (basic multilingual page). YAML also does not allow C<\/>
1042	(which JSON::XS does not I<currently> generate).	1277	sequences in strings (which JSON::XS does not I<currently> generate, but
		1278	other JSON generators might).
1043		1279
1044	There might be other incompatibilities that I am not aware of (or the YAML	1280	There might be other incompatibilities that I am not aware of (or the YAML
1045	specification has been changed yet again - it does so quite often). In	1281	specification has been changed yet again - it does so quite often). In
1046	general you should not try to generate YAML with a JSON generator or vice	1282	general you should not try to generate YAML with a JSON generator or vice
1047	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1283	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1050		1286
1051	=over 4	1287	=over 4
1052		1288
1053	=item (*)	1289	=item (*)
1054		1290
1055	This is spread actively by the YAML team, however. For many years now they	1291	I have been pressured multiple times by Brian Ingerson (one of the
1056	claim YAML were a superset of JSON, even when proven otherwise.	1292	authors of the YAML specification) to remove this paragraph, despite him
		1293	acknowledging that the actual incompatibilities exist. As I was personally
		1294	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1295	educate people about these issues, so others do not run into the same
		1296	problem again and again. After this, Brian called me a (quote)I<complete
		1297	and worthless idiot>(unquote).
1057		1298
1058	Even the author of this manpage was at some point accused of providing	1299	In my opinion, instead of pressuring and insulting people who actually
1059	"incorrect" information, despite the evidence presented (claims ranged	1300	clarify issues with YAML and the wrong statements of some of its
1060	from "your documentation contains inaccurate and negative statements about	1301	proponents, I would kindly suggest reading the JSON spec (which is not
1061	YAML" (the only negative comment is this footnote, and it didn't exist	1302	that difficult or long) and finally make YAML compatible to it, and
1062	back then; the question on which claims were inaccurate was never answered	1303	educating users about the changes, instead of spreading lies about the
1063	etc.) to "the YAML spec is not up-to-date" (the real and supposedly	1304	real compatibility for many I<years> and trying to silence people who
1064	JSON-compatible spec is apparently not currently publicly available)	1305	point out that it isn't true.
1065	to actual requests to replace this section by incorrect information,
1066	suppressing information about the real problem).
1067		1306
1068	So whenever you are told that YAML was a superset of JSON, first check	1307	Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON, even
1069	wether it is really true (it might be when you check it, but it certainly	1308	though the incompatibilities have been documented (and are known to
1070	was not true when this was written). I would much prefer if the YAML team	1309	Brian) for many years and the spec makes explicit claims that YAML is a
1071	would spent their time on actually making JSON compatibility a truth	1310	superset of JSON. It would be so easy to fix, but apparently, bullying and
1072	(JSON, after all, has a very small and simple specification) instead of	1311	corrupting userdata is so much easier.
1073	trying to lobby/force people into reporting untruths.
1074		1312
1075	=back	1313	=back
1076		1314
1077		1315
1078	=head2 SPEED	1316	=head2 SPEED
…		…
1080	It seems that JSON::XS is surprisingly fast, as shown in the following	1318	It seems that JSON::XS is surprisingly fast, as shown in the following
1081	tables. They have been generated with the help of the C<eg/bench> program	1319	tables. They have been generated with the help of the C<eg/bench> program
1082	in the JSON::XS distribution, to make it easy to compare on your own	1320	in the JSON::XS distribution, to make it easy to compare on your own
1083	system.	1321	system.
1084		1322
1085	First comes a comparison between various modules using a very short	1323	First comes a comparison between various modules using
1086	single-line JSON string:	1324	a very short single-line JSON string (also available at
		1325	L<http://dist.schmorp.de/misc/json/short.json>).
1087		1326
1088	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1327	{"method": "handleMessage", "params": ["user1",
1089	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1328	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1329	true, false]}
1090		1330
1091	It shows the number of encodes/decodes per second (JSON::XS uses	1331	It shows the number of encodes/decodes per second (JSON::XS uses
1092	the functional interface, while JSON::XS/2 uses the OO interface	1332	the functional interface, while JSON::XS/2 uses the OO interface
1093	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1333	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1094	shrink). Higher is better:	1334	shrink). Higher is better:
…		…
1110	about three times faster on decoding, and over forty times faster	1350	about three times faster on decoding, and over forty times faster
1111	than JSON, even with pretty-printing and key sorting. It also compares	1351	than JSON, even with pretty-printing and key sorting. It also compares
1112	favourably to Storable for small amounts of data.	1352	favourably to Storable for small amounts of data.
1113		1353
1114	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1354	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1115	search API (http://nanoref.com/yahooapis/mgPdGg):	1355	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1116		1356
1117	module \| encode \| decode \|	1357	module \| encode \| decode \|
1118	-----------\|------------\|------------\|	1358	-----------\|------------\|------------\|
1119	JSON 1.x \| 55.260 \| 34.971 \|	1359	JSON 1.x \| 55.260 \| 34.971 \|
1120	JSON::DWIW \| 825.228 \| 1082.513 \|	1360	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
1162	to free the temporary). If that is exceeded, the program crashes. To be	1402	to free the temporary). If that is exceeded, the program crashes. To be
1163	conservative, the default nesting limit is set to 512. If your process	1403	conservative, the default nesting limit is set to 512. If your process
1164	has a smaller stack, you should adjust this setting accordingly with the	1404	has a smaller stack, you should adjust this setting accordingly with the
1165	C<max_depth> method.	1405	C<max_depth> method.
1166		1406
1167	And last but least, something else could bomb you that I forgot to think	1407	Something else could bomb you, too, that I forgot to think of. In that
1168	of. In that case, you get to keep the pieces. I am always open for hints,	1408	case, you get to keep the pieces. I am always open for hints, though...
1169	though...	1409
		1410	Also keep in mind that JSON::XS might leak contents of your Perl data
		1411	structures in its error messages, so when you serialise sensitive
		1412	information you might want to make sure that exceptions thrown by JSON::XS
		1413	will not end up in front of untrusted eyes.
1170		1414
1171	If you are using JSON::XS to return packets to consumption	1415	If you are using JSON::XS to return packets to consumption
1172	by JavaScript scripts in a browser you should have a look at	1416	by JavaScript scripts in a browser you should have a look at
1173	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1417	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1174	you are vulnerable to some common attack vectors (which really are browser	1418	you are vulnerable to some common attack vectors (which really are browser
…		…
1180	=head1 THREADS	1424	=head1 THREADS
1181		1425
1182	This module is I<not> guaranteed to be thread safe and there are no	1426	This module is I<not> guaranteed to be thread safe and there are no
1183	plans to change this until Perl gets thread support (as opposed to the	1427	plans to change this until Perl gets thread support (as opposed to the
1184	horribly slow so-called "threads" which are simply slow and bloated	1428	horribly slow so-called "threads" which are simply slow and bloated
1185	process simulations - use fork, its I<much> faster, cheaper, better).	1429	process simulations - use fork, it's I<much> faster, cheaper, better).
1186		1430
1187	(It might actually work, but you have been warned).	1431	(It might actually work, but you have been warned).
1188		1432
1189		1433
1190	=head1 BUGS	1434	=head1 BUGS
1191		1435
1192	While the goal of this module is to be correct, that unfortunately does	1436	While the goal of this module is to be correct, that unfortunately does
1193	not mean its bug-free, only that I think its design is bug-free. It is	1437	not mean it's bug-free, only that I think its design is bug-free. If you
1194	still relatively early in its development. If you keep reporting bugs they	1438	keep reporting bugs they will be fixed swiftly, though.
1195	will be fixed swiftly, though.
1196		1439
1197	Please refrain from using rt.cpan.org or any other bug reporting	1440	Please refrain from using rt.cpan.org or any other bug reporting
1198	service. I put the contact address into my modules for a reason.	1441	service. I put the contact address into my modules for a reason.
1199		1442
1200	=cut	1443	=cut
…		…
1220	"--" => sub { $_[0] = ${$_[0]} - 1 },	1463	"--" => sub { $_[0] = ${$_[0]} - 1 },
1221	fallback => 1;	1464	fallback => 1;
1222		1465
1223	1;	1466	1;
1224		1467
		1468	=head1 SEE ALSO
		1469
		1470	The F<json_xs> command line utility for quick experiments.
		1471
1225	=head1 AUTHOR	1472	=head1 AUTHOR
1226		1473
1227	Marc Lehmann <schmorp@schmorp.de>	1474	Marc Lehmann <schmorp@schmorp.de>
1228	http://home.schmorp.de/	1475	http://home.schmorp.de/
1229		1476

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Comparing JSON-XS/XS.pm (file contents): Revision 1.84 by root, Wed Mar 19 02:52:15 2008 UTC vs. Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.84 by root, Wed Mar 19 02:52:15 2008 UTC vs.
Revision 1.124 by root, Sun Aug 9 16:01:39 2009 UTC