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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.85 by root, Wed Mar 19 02:55:23 2008 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 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
		104	no warnings;
106	use strict;	105	use strict;
107		106
108	our $VERSION = '2.01';	107	our $VERSION = '2.2222';
109	our @ISA = qw(Exporter);	108	our @ISA = qw(Exporter);
110		109
111	our @EXPORT = qw(encode_json decode_json to_json from_json);	110	our @EXPORT = qw(encode_json decode_json to_json from_json);
112		111
113	sub to_json($) {	112	sub to_json($) {
…		…
137		136
138	This function call is functionally identical to:	137	This function call is functionally identical to:
139		138
140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	139	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
141		140
142	except being faster.	141	Except being faster.
143		142
144	=item $perl_scalar = decode_json $json_text	143	=item $perl_scalar = decode_json $json_text
145		144
146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	145	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	146	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
149		148
150	This function call is functionally identical to:	149	This function call is functionally identical to:
151		150
152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	151	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
153		152
154	except being faster.	153	Except being faster.
155		154
156	=item $is_boolean = JSON::XS::is_bool $scalar	155	=item $is_boolean = JSON::XS::is_bool $scalar
157		156
158	Returns true if the passed scalar represents either JSON::XS::true or	157	Returns true if the passed scalar represents either JSON::XS::true or
159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	158	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
197		196
198	If you didn't know about that flag, just the better, pretend it doesn't	197	If you didn't know about that flag, just the better, pretend it doesn't
199	exist.	198	exist.
200		199
201	=item 4. A "Unicode String" is simply a string where each character can be	200	=item 4. A "Unicode String" is simply a string where each character can be
202	validly interpreted as a Unicode codepoint.	201	validly interpreted as a Unicode code point.
203		202
204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	203	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
205	Unicode string encoded in UTF-8, giving you a binary string.	204	Unicode string encoded in UTF-8, giving you a binary string.
206		205
207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	206	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
245		244
246	If C<$enable> is false, then the C<encode> method will not escape Unicode	245	If C<$enable> is false, then the C<encode> method will not escape Unicode
247	characters unless required by the JSON syntax or other flags. This results	246	characters unless required by the JSON syntax or other flags. This results
248	in a faster and more compact format.	247	in a faster and more compact format.
249		248
		249	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		250	document.
		251
250	The main use for this flag is to produce JSON texts that can be	252	The main use for this flag is to produce JSON texts that can be
251	transmitted over a 7-bit channel, as the encoded JSON texts will not	253	transmitted over a 7-bit channel, as the encoded JSON texts will not
252	contain any 8 bit characters.	254	contain any 8 bit characters.
253		255
254	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	256	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
265	will not be affected in any way by this flag, as C<decode> by default	267	will not be affected in any way by this flag, as C<decode> by default
266	expects Unicode, which is a strict superset of latin1.	268	expects Unicode, which is a strict superset of latin1.
267		269
268	If C<$enable> is false, then the C<encode> method will not escape Unicode	270	If C<$enable> is false, then the C<encode> method will not escape Unicode
269	characters unless required by the JSON syntax or other flags.	271	characters unless required by the JSON syntax or other flags.
		272
		273	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		274	document.
270		275
271	The main use for this flag is efficiently encoding binary data as JSON	276	The main use for this flag is efficiently encoding binary data as JSON
272	text, as most octets will not be escaped, resulting in a smaller encoded	277	text, as most octets will not be escaped, resulting in a smaller encoded
273	size. The disadvantage is that the resulting JSON text is encoded	278	size. The disadvantage is that the resulting JSON text is encoded
274	in latin1 (and must correctly be treated as such when storing and	279	in latin1 (and must correctly be treated as such when storing and
…		…
293		298
294	If C<$enable> is false, then the C<encode> method will return the JSON	299	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	300	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	301	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.	302	to be done yourself, e.g. using the Encode module.
		303
		304	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		305	document.
298		306
299	Example, output UTF-16BE-encoded JSON:	307	Example, output UTF-16BE-encoded JSON:
300		308
301	use Encode;	309	use Encode;
302	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	310	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
453	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,	461	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
454	resulting in an invalid JSON text:	462	resulting in an invalid JSON text:
455		463
456	JSON::XS->new->allow_nonref->encode ("Hello, World!")	464	JSON::XS->new->allow_nonref->encode ("Hello, World!")
457	=> "Hello, World!"	465	=> "Hello, World!"
		466
		467	=item $json = $json->allow_unknown ([$enable])
		468
		469	=item $enabled = $json->get_allow_unknown
		470
		471	If C<$enable> is true (or missing), then C<encode> will I<not> throw an
		472	exception when it encounters values it cannot represent in JSON (for
		473	example, filehandles) but instead will encode a JSON C<null> value. Note
		474	that blessed objects are not included here and are handled separately by
		475	c<allow_nonref>.
		476
		477	If C<$enable> is false (the default), then C<encode> will throw an
		478	exception when it encounters anything it cannot encode as JSON.
		479
		480	This option does not affect C<decode> in any way, and it is recommended to
		481	leave it off unless you know your communications partner.
458		482
459	=item $json = $json->allow_blessed ([$enable])	483	=item $json = $json->allow_blessed ([$enable])
460		484
461	=item $enabled = $json->get_allow_blessed	485	=item $enabled = $json->get_allow_blessed
462		486
…		…
603	=item $json = $json->max_depth ([$maximum_nesting_depth])	627	=item $json = $json->max_depth ([$maximum_nesting_depth])
604		628
605	=item $max_depth = $json->get_max_depth	629	=item $max_depth = $json->get_max_depth
606		630
607	Sets the maximum nesting level (default C<512>) accepted while encoding	631	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	632	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	633	data structure, then the encoder and decoder will stop and croak at that
610	stop and croak at that point.	634	point.
611		635
612	Nesting level is defined by number of hash- or arrayrefs that the encoder	636	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<[>	637	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	638	characters without their matching closing parenthesis crossed to reach a
615	given character in a string.	639	given character in a string.
616		640
617	Setting the maximum depth to one disallows any nesting, so that ensures	641	Setting the maximum depth to one disallows any nesting, so that ensures
618	that the object is only a single hash/object or array.	642	that the object is only a single hash/object or array.
619		643
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	644	If no argument is given, the highest possible setting will be used, which
622	used, which is rarely useful.	645	is rarely useful.
		646
		647	Note that nesting is implemented by recursion in C. The default value has
		648	been chosen to be as large as typical operating systems allow without
		649	crashing.
623		650
624	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	651	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
625		652
626	=item $json = $json->max_size ([$maximum_string_size])	653	=item $json = $json->max_size ([$maximum_string_size])
627		654
628	=item $max_size = $json->get_max_size	655	=item $max_size = $json->get_max_size
629		656
630	Set the maximum length a JSON text may have (in bytes) where decoding is	657	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>	658	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	659	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	660	attempt to decode the string but throw an exception. This setting has no
634	effect on C<encode> (yet).	661	effect on C<encode> (yet).
635		662
636	The argument to C<max_size> will be rounded up to the next B<highest>	663	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	664	C<0> is specified).
638	limit check will be deactivated (same as when C<0> is specified).
639		665
640	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	666	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
641		667
642	=item $json_text = $json->encode ($perl_scalar)	668	=item $json_text = $json->encode ($perl_scalar)
643		669
…		…
670		696
671	JSON::XS->new->decode_prefix ("[1] the tail")	697	JSON::XS->new->decode_prefix ("[1] the tail")
672	=> ([], 3)	698	=> ([], 3)
673		699
674	=back	700	=back
		701
		702
		703	=head1 INCREMENTAL PARSING
		704
		705	In some cases, there is the need for incremental parsing of JSON
		706	texts. While this module always has to keep both JSON text and resulting
		707	Perl data structure in memory at one time, it does allow you to parse a
		708	JSON stream incrementally. It does so by accumulating text until it has
		709	a full JSON object, which it then can decode. This process is similar to
		710	using C<decode_prefix> to see if a full JSON object is available, but
		711	is much more efficient (and can be implemented with a minimum of method
		712	calls).
		713
		714	JSON::XS will only attempt to parse the JSON text once it is sure it
		715	has enough text to get a decisive result, using a very simple but
		716	truly incremental parser. This means that it sometimes won't stop as
		717	early as the full parser, for example, it doesn't detect parenthese
		718	mismatches. The only thing it guarantees is that it starts decoding as
		719	soon as a syntactically valid JSON text has been seen. This means you need
		720	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		721	parsing in the presence if syntax errors.
		722
		723	The following methods implement this incremental parser.
		724
		725	=over 4
		726
		727	=item [void, scalar or list context] = $json->incr_parse ([$string])
		728
		729	This is the central parsing function. It can both append new text and
		730	extract objects from the stream accumulated so far (both of these
		731	functions are optional).
		732
		733	If C<$string> is given, then this string is appended to the already
		734	existing JSON fragment stored in the C<$json> object.
		735
		736	After that, if the function is called in void context, it will simply
		737	return without doing anything further. This can be used to add more text
		738	in as many chunks as you want.
		739
		740	If the method is called in scalar context, then it will try to extract
		741	exactly I<one> JSON object. If that is successful, it will return this
		742	object, otherwise it will return C<undef>. If there is a parse error,
		743	this method will croak just as C<decode> would do (one can then use
		744	C<incr_skip> to skip the errornous part). This is the most common way of
		745	using the method.
		746
		747	And finally, in list context, it will try to extract as many objects
		748	from the stream as it can find and return them, or the empty list
		749	otherwise. For this to work, there must be no separators between the JSON
		750	objects or arrays, instead they must be concatenated back-to-back. If
		751	an error occurs, an exception will be raised as in the scalar context
		752	case. Note that in this case, any previously-parsed JSON texts will be
		753	lost.
		754
		755	=item $lvalue_string = $json->incr_text
		756
		757	This method returns the currently stored JSON fragment as an lvalue, that
		758	is, you can manipulate it. This I<only> works when a preceding call to
		759	C<incr_parse> in I<scalar context> successfully returned an object. Under
		760	all other circumstances you must not call this function (I mean it.
		761	although in simple tests it might actually work, it I<will> fail under
		762	real world conditions). As a special exception, you can also call this
		763	method before having parsed anything.
		764
		765	This function is useful in two cases: a) finding the trailing text after a
		766	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		767	(such as commas).
		768
		769	=item $json->incr_skip
		770
		771	This will reset the state of the incremental parser and will remove the
		772	parsed text from the input buffer. This is useful after C<incr_parse>
		773	died, in which case the input buffer and incremental parser state is left
		774	unchanged, to skip the text parsed so far and to reset the parse state.
		775
		776	=item $json->incr_reset
		777
		778	This completely resets the incremental parser, that is, after this call,
		779	it will be as if the parser had never parsed anything.
		780
		781	This is useful if you want ot repeatedly parse JSON objects and want to
		782	ignore any trailing data, which means you have to reset the parser after
		783	each successful decode.
		784
		785	=back
		786
		787	=head2 LIMITATIONS
		788
		789	All options that affect decoding are supported, except
		790	C<allow_nonref>. The reason for this is that it cannot be made to
		791	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		792	them back to back and still decode them perfectly. This does not hold true
		793	for JSON numbers, however.
		794
		795	For example, is the string C<1> a single JSON number, or is it simply the
		796	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		797	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		798	takes the conservative route and disallows this case.
		799
		800	=head2 EXAMPLES
		801
		802	Some examples will make all this clearer. First, a simple example that
		803	works similarly to C<decode_prefix>: We want to decode the JSON object at
		804	the start of a string and identify the portion after the JSON object:
		805
		806	my $text = "[1,2,3] hello";
		807
		808	my $json = new JSON::XS;
		809
		810	my $obj = $json->incr_parse ($text)
		811	or die "expected JSON object or array at beginning of string";
		812
		813	my $tail = $json->incr_text;
		814	# $tail now contains " hello"
		815
		816	Easy, isn't it?
		817
		818	Now for a more complicated example: Imagine a hypothetical protocol where
		819	you read some requests from a TCP stream, and each request is a JSON
		820	array, without any separation between them (in fact, it is often useful to
		821	use newlines as "separators", as these get interpreted as whitespace at
		822	the start of the JSON text, which makes it possible to test said protocol
		823	with C<telnet>...).
		824
		825	Here is how you'd do it (it is trivial to write this in an event-based
		826	manner):
		827
		828	my $json = new JSON::XS;
		829
		830	# read some data from the socket
		831	while (sysread $socket, my $buf, 4096) {
		832
		833	# split and decode as many requests as possible
		834	for my $request ($json->incr_parse ($buf)) {
		835	# act on the $request
		836	}
		837	}
		838
		839	Another complicated example: Assume you have a string with JSON objects
		840	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		841	[3]>). To parse them, we have to skip the commas between the JSON texts,
		842	and here is where the lvalue-ness of C<incr_text> comes in useful:
		843
		844	my $text = "[1],[2], [3]";
		845	my $json = new JSON::XS;
		846
		847	# void context, so no parsing done
		848	$json->incr_parse ($text);
		849
		850	# now extract as many objects as possible. note the
		851	# use of scalar context so incr_text can be called.
		852	while (my $obj = $json->incr_parse) {
		853	# do something with $obj
		854
		855	# now skip the optional comma
		856	$json->incr_text =~ s/^ \s* , //x;
		857	}
		858
		859	Now lets go for a very complex example: Assume that you have a gigantic
		860	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		861	but you cannot load it into memory fully (this has actually happened in
		862	the real world :).
		863
		864	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		865	can still help you: You implement a (very simple) array parser and let
		866	JSON decode the array elements, which are all full JSON objects on their
		867	own (this wouldn't work if the array elements could be JSON numbers, for
		868	example):
		869
		870	my $json = new JSON::XS;
		871
		872	# open the monster
		873	open my $fh, "<bigfile.json"
		874	or die "bigfile: $!";
		875
		876	# first parse the initial "["
		877	for (;;) {
		878	sysread $fh, my $buf, 65536
		879	or die "read error: $!";
		880	$json->incr_parse ($buf); # void context, so no parsing
		881
		882	# Exit the loop once we found and removed(!) the initial "[".
		883	# In essence, we are (ab-)using the $json object as a simple scalar
		884	# we append data to.
		885	last if $json->incr_text =~ s/^ \s* \[ //x;
		886	}
		887
		888	# now we have the skipped the initial "[", so continue
		889	# parsing all the elements.
		890	for (;;) {
		891	# in this loop we read data until we got a single JSON object
		892	for (;;) {
		893	if (my $obj = $json->incr_parse) {
		894	# do something with $obj
		895	last;
		896	}
		897
		898	# add more data
		899	sysread $fh, my $buf, 65536
		900	or die "read error: $!";
		901	$json->incr_parse ($buf); # void context, so no parsing
		902	}
		903
		904	# in this loop we read data until we either found and parsed the
		905	# separating "," between elements, or the final "]"
		906	for (;;) {
		907	# first skip whitespace
		908	$json->incr_text =~ s/^\s*//;
		909
		910	# if we find "]", we are done
		911	if ($json->incr_text =~ s/^\]//) {
		912	print "finished.\n";
		913	exit;
		914	}
		915
		916	# if we find ",", we can continue with the next element
		917	if ($json->incr_text =~ s/^,//) {
		918	last;
		919	}
		920
		921	# if we find anything else, we have a parse error!
		922	if (length $json->incr_text) {
		923	die "parse error near ", $json->incr_text;
		924	}
		925
		926	# else add more data
		927	sysread $fh, my $buf, 65536
		928	or die "read error: $!";
		929	$json->incr_parse ($buf); # void context, so no parsing
		930	}
		931
		932	This is a complex example, but most of the complexity comes from the fact
		933	that we are trying to be correct (bear with me if I am wrong, I never ran
		934	the above example :).
		935
675		936
676		937
677	=head1 MAPPING	938	=head1 MAPPING
678		939
679	This section describes how JSON::XS maps Perl values to JSON values and	940	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	1029	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	1030	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	1031	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.	1032	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
772		1033
773	encode_json [\0,JSON::XS::true] # yields [false,true]	1034	encode_json [\0, JSON::XS::true] # yields [false,true]
774		1035
775	=item JSON::XS::true, JSON::XS::false	1036	=item JSON::XS::true, JSON::XS::false
776		1037
777	These special values become JSON true and JSON false values,	1038	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.	1039	respectively. You can also use C<\1> and C<\0> directly if you want.
…		…
816	my $x = "3"; # some variable containing a string	1077	my $x = "3"; # some variable containing a string
817	$x += 0; # numify it, ensuring it will be dumped as a number	1078	$x += 0; # numify it, ensuring it will be dumped as a number
818	$x *= 1; # same thing, the choice is yours.	1079	$x *= 1; # same thing, the choice is yours.
819		1080
820	You can not currently force the type in other, less obscure, ways. Tell me	1081	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	1082	if you need this capability (but don't forget to explain why it's needed
822	:).	1083	:).
823		1084
824	=back	1085	=back
825		1086
826		1087
…		…
828		1089
829	The interested reader might have seen a number of flags that signify	1090	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	1091	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:	1092	some confusion on what these do, so here is a short comparison:
832		1093
833	C<utf8> controls wether the JSON text created by C<encode> (and expected	1094	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	1095	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	1096	control whether C<encode> escapes character values outside their respective
836	codeset range. Neither of these flags conflict with each other, although	1097	codeset range. Neither of these flags conflict with each other, although
837	some combinations make less sense than others.	1098	some combinations make less sense than others.
838		1099
839	Care has been taken to make all flags symmetrical with respect to	1100	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	1101	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.	1181	proper subset of most 8-bit and multibyte encodings in use in the world.
921		1182
922	=back	1183	=back
923		1184
924		1185
925	=head1 COMPARISON
926
927	As already mentioned, this module was created because none of the existing
928	JSON modules could be made to work correctly. First I will describe the
929	problems (or pleasures) I encountered with various existing JSON modules,
930	followed by some benchmark values. JSON::XS was designed not to suffer
931	from any of these problems or limitations.
932
933	=over 4
934
935	=item JSON 2.xx
936
937	A marvellous piece of engineering, this module either uses JSON::XS
938	directly when available (so will be 100% compatible with it, including
939	speed), or it uses JSON::PP, which is basically JSON::XS translated to
940	Pure Perl, which should be 100% compatible with JSON::XS, just a bit
941	slower.
942
943	You cannot really lose by using this module, especially as it tries very
944	hard to work even with ancient Perl versions, while JSON::XS does not.
945
946	=item JSON 1.07
947
948	Slow (but very portable, as it is written in pure Perl).
949
950	Undocumented/buggy Unicode handling (how JSON handles Unicode values is
951	undocumented. One can get far by feeding it Unicode strings and doing
952	en-/decoding oneself, but Unicode escapes are not working properly).
953
954	No round-tripping (strings get clobbered if they look like numbers, e.g.
955	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
956	decode into the number 2.
957
958	=item JSON::PC 0.01
959
960	Very fast.
961
962	Undocumented/buggy Unicode handling.
963
964	No round-tripping.
965
966	Has problems handling many Perl values (e.g. regex results and other magic
967	values will make it croak).
968
969	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
970	which is not a valid JSON text.
971
972	Unmaintained (maintainer unresponsive for many months, bugs are not
973	getting fixed).
974
975	=item JSON::Syck 0.21
976
977	Very buggy (often crashes).
978
979	Very inflexible (no human-readable format supported, format pretty much
980	undocumented. I need at least a format for easy reading by humans and a
981	single-line compact format for use in a protocol, and preferably a way to
982	generate ASCII-only JSON texts).
983
984	Completely broken (and confusingly documented) Unicode handling (Unicode
985	escapes are not working properly, you need to set ImplicitUnicode to
986	I<different> values on en- and decoding to get symmetric behaviour).
987
988	No round-tripping (simple cases work, but this depends on whether the scalar
989	value was used in a numeric context or not).
990
991	Dumping hashes may skip hash values depending on iterator state.
992
993	Unmaintained (maintainer unresponsive for many months, bugs are not
994	getting fixed).
995
996	Does not check input for validity (i.e. will accept non-JSON input and
997	return "something" instead of raising an exception. This is a security
998	issue: imagine two banks transferring money between each other using
999	JSON. One bank might parse a given non-JSON request and deduct money,
1000	while the other might reject the transaction with a syntax error. While a
1001	good protocol will at least recover, that is extra unnecessary work and
1002	the transaction will still not succeed).
1003
1004	=item JSON::DWIW 0.04
1005
1006	Very fast. Very natural. Very nice.
1007
1008	Undocumented Unicode handling (but the best of the pack. Unicode escapes
1009	still don't get parsed properly).
1010
1011	Very inflexible.
1012
1013	No round-tripping.
1014
1015	Does not generate valid JSON texts (key strings are often unquoted, empty keys
1016	result in nothing being output)
1017
1018	Does not check input for validity.
1019
1020	=back
1021
1022
1023	=head2 JSON and YAML	1186	=head2 JSON and YAML
1024		1187
1025	You often hear that JSON is a subset of YAML. This is, however, a mass	1188	You often hear that JSON is a subset of YAML. This is, however, a mass
1026	hysteria(*) and very far from the truth. In general, there is no way to	1189	hysteria(*) and very far from the truth (as of the time of this writing),
		1190	so let me state it clearly: I<in general, there is no way to configure
1027	configure JSON::XS to output a data structure as valid YAML that works for	1191	JSON::XS to output a data structure as valid YAML> that works in all
1028	all cases.	1192	cases.
1029		1193
1030	If you really must use JSON::XS to generate YAML, you should use this	1194	If you really must use JSON::XS to generate YAML, you should use this
1031	algorithm (subject to change in future versions):	1195	algorithm (subject to change in future versions):
1032		1196
1033	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1197	my $to_yaml = JSON::XS->new->utf8->space_after (1);
…		…
1036	This will I<usually> generate JSON texts that also parse as valid	1200	This will I<usually> generate JSON texts that also parse as valid
1037	YAML. Please note that YAML has hardcoded limits on (simple) object key	1201	YAML. Please note that YAML has hardcoded limits on (simple) object key
1038	lengths that JSON doesn't have and also has different and incompatible	1202	lengths that JSON doesn't have and also has different and incompatible
1039	unicode handling, so you should make sure that your hash keys are	1203	unicode handling, so you should make sure that your hash keys are
1040	noticeably shorter than the 1024 "stream characters" YAML allows and that	1204	noticeably shorter than the 1024 "stream characters" YAML allows and that
1041	you do not have codepoints with values outside the Unicode BMP (basic	1205	you do not have characters with codepoint values outside the Unicode BMP
1042	multilingual page). YAML also does not allow C<\/> sequences in strings	1206	(basic multilingual page). YAML also does not allow C<\/> sequences in
1043	(which JSON::XS does not I<currently> generate).	1207	strings (which JSON::XS does not I<currently> generate, but other JSON
		1208	generators might).
1044		1209
1045	There might be other incompatibilities that I am not aware of (or the YAML	1210	There might be other incompatibilities that I am not aware of (or the YAML
1046	specification has been changed yet again - it does so quite often). In	1211	specification has been changed yet again - it does so quite often). In
1047	general you should not try to generate YAML with a JSON generator or vice	1212	general you should not try to generate YAML with a JSON generator or vice
1048	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1213	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
1051		1216
1052	=over 4	1217	=over 4
1053		1218
1054	=item (*)	1219	=item (*)
1055		1220
1056	This is spread actively by the YAML team, however. For many years now they	1221	I have been pressured multiple times by Brian Ingerson (one of the
1057	claim YAML were a superset of JSON, even when proven otherwise.	1222	authors of the YAML specification) to remove this paragraph, despite him
		1223	acknowledging that the actual incompatibilities exist. As I was personally
		1224	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1225	educate people about these issues, so others do not run into the same
		1226	problem again and again. After this, Brian called me a (quote)I<complete
		1227	and worthless idiot>(unquote).
1058		1228
1059	Even the author of this manpage was at some point accused of providing	1229	In my opinion, instead of pressuring and insulting people who actually
1060	"incorrect" information, despite the evidence presented (claims ranged	1230	clarify issues with YAML and the wrong statements of some of its
1061	from "your documentation contains inaccurate and negative statements about	1231	proponents, I would kindly suggest reading the JSON spec (which is not
1062	YAML" (the only negative comment is this footnote, and it didn't exist	1232	that difficult or long) and finally make YAML compatible to it, and
1063	back then; the question on which claims were inaccurate was never answered	1233	educating users about the changes, instead of spreading lies about the
1064	etc.) to "the YAML spec is not up-to-date" (the real and supposedly	1234	real compatibility for many I<years> and trying to silence people who
1065	JSON-compatible spec is apparently not currently publicly available)	1235	point out that it isn't true.
1066	to actual requests to replace this section by incorrect information,
1067	suppressing information about the real problem).
1068
1069	So whenever you are told that YAML was a superset of JSON, first check
1070	wether it is really true (it might be when you check it, but it certainly
1071	was not true when this was written). I would much prefer if the YAML team
1072	would spent their time on actually making JSON compatibility a truth
1073	(JSON, after all, has a very small and simple specification) instead of
1074	trying to lobby/force people into reporting untruths.
1075		1236
1076	=back	1237	=back
1077		1238
1078		1239
1079	=head2 SPEED	1240	=head2 SPEED
…		…
1081	It seems that JSON::XS is surprisingly fast, as shown in the following	1242	It seems that JSON::XS is surprisingly fast, as shown in the following
1082	tables. They have been generated with the help of the C<eg/bench> program	1243	tables. They have been generated with the help of the C<eg/bench> program
1083	in the JSON::XS distribution, to make it easy to compare on your own	1244	in the JSON::XS distribution, to make it easy to compare on your own
1084	system.	1245	system.
1085		1246
1086	First comes a comparison between various modules using a very short	1247	First comes a comparison between various modules using
1087	single-line JSON string:	1248	a very short single-line JSON string (also available at
		1249	L<http://dist.schmorp.de/misc/json/short.json>).
1088		1250
1089	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1251	{"method": "handleMessage", "params": ["user1",
1090	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1252	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1253	true, false]}
1091		1254
1092	It shows the number of encodes/decodes per second (JSON::XS uses	1255	It shows the number of encodes/decodes per second (JSON::XS uses
1093	the functional interface, while JSON::XS/2 uses the OO interface	1256	the functional interface, while JSON::XS/2 uses the OO interface
1094	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1257	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
1095	shrink). Higher is better:	1258	shrink). Higher is better:
…		…
1111	about three times faster on decoding, and over forty times faster	1274	about three times faster on decoding, and over forty times faster
1112	than JSON, even with pretty-printing and key sorting. It also compares	1275	than JSON, even with pretty-printing and key sorting. It also compares
1113	favourably to Storable for small amounts of data.	1276	favourably to Storable for small amounts of data.
1114		1277
1115	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1278	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1116	search API (http://nanoref.com/yahooapis/mgPdGg):	1279	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1117		1280
1118	module \| encode \| decode \|	1281	module \| encode \| decode \|
1119	-----------\|------------\|------------\|	1282	-----------\|------------\|------------\|
1120	JSON 1.x \| 55.260 \| 34.971 \|	1283	JSON 1.x \| 55.260 \| 34.971 \|
1121	JSON::DWIW \| 825.228 \| 1082.513 \|	1284	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
1163	to free the temporary). If that is exceeded, the program crashes. To be	1326	to free the temporary). If that is exceeded, the program crashes. To be
1164	conservative, the default nesting limit is set to 512. If your process	1327	conservative, the default nesting limit is set to 512. If your process
1165	has a smaller stack, you should adjust this setting accordingly with the	1328	has a smaller stack, you should adjust this setting accordingly with the
1166	C<max_depth> method.	1329	C<max_depth> method.
1167		1330
1168	And last but least, something else could bomb you that I forgot to think	1331	Something else could bomb you, too, that I forgot to think of. In that
1169	of. In that case, you get to keep the pieces. I am always open for hints,	1332	case, you get to keep the pieces. I am always open for hints, though...
1170	though...	1333
		1334	Also keep in mind that JSON::XS might leak contents of your Perl data
		1335	structures in its error messages, so when you serialise sensitive
		1336	information you might want to make sure that exceptions thrown by JSON::XS
		1337	will not end up in front of untrusted eyes.
1171		1338
1172	If you are using JSON::XS to return packets to consumption	1339	If you are using JSON::XS to return packets to consumption
1173	by JavaScript scripts in a browser you should have a look at	1340	by JavaScript scripts in a browser you should have a look at
1174	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1341	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1175	you are vulnerable to some common attack vectors (which really are browser	1342	you are vulnerable to some common attack vectors (which really are browser
…		…
1181	=head1 THREADS	1348	=head1 THREADS
1182		1349
1183	This module is I<not> guaranteed to be thread safe and there are no	1350	This module is I<not> guaranteed to be thread safe and there are no
1184	plans to change this until Perl gets thread support (as opposed to the	1351	plans to change this until Perl gets thread support (as opposed to the
1185	horribly slow so-called "threads" which are simply slow and bloated	1352	horribly slow so-called "threads" which are simply slow and bloated
1186	process simulations - use fork, its I<much> faster, cheaper, better).	1353	process simulations - use fork, it's I<much> faster, cheaper, better).
1187		1354
1188	(It might actually work, but you have been warned).	1355	(It might actually work, but you have been warned).
1189		1356
1190		1357
1191	=head1 BUGS	1358	=head1 BUGS
1192		1359
1193	While the goal of this module is to be correct, that unfortunately does	1360	While the goal of this module is to be correct, that unfortunately does
1194	not mean its bug-free, only that I think its design is bug-free. It is	1361	not mean it's bug-free, only that I think its design is bug-free. If you
1195	still relatively early in its development. If you keep reporting bugs they	1362	keep reporting bugs they will be fixed swiftly, though.
1196	will be fixed swiftly, though.
1197		1363
1198	Please refrain from using rt.cpan.org or any other bug reporting	1364	Please refrain from using rt.cpan.org or any other bug reporting
1199	service. I put the contact address into my modules for a reason.	1365	service. I put the contact address into my modules for a reason.
1200		1366
1201	=cut	1367	=cut
…		…
1221	"--" => sub { $_[0] = ${$_[0]} - 1 },	1387	"--" => sub { $_[0] = ${$_[0]} - 1 },
1222	fallback => 1;	1388	fallback => 1;
1223		1389
1224	1;	1390	1;
1225		1391
		1392	=head1 SEE ALSO
		1393
		1394	The F<json_xs> command line utility for quick experiments.
		1395
1226	=head1 AUTHOR	1396	=head1 AUTHOR
1227		1397
1228	Marc Lehmann <schmorp@schmorp.de>	1398	Marc Lehmann <schmorp@schmorp.de>
1229	http://home.schmorp.de/	1399	http://home.schmorp.de/
1230		1400

Diff Legend

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

Comparing JSON-XS/XS.pm (file contents): Revision 1.85 by root, Wed Mar 19 02:55:23 2008 UTC vs. Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.85 by root, Wed Mar 19 02:55:23 2008 UTC vs.
Revision 1.111 by root, Mon Jul 21 02:45:17 2008 UTC