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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.78 by root, Wed Dec 5 10:59:28 2007 UTC vs.
Revision 1.107 by root, Tue Jun 3 06:43:45 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
		4
		5	=encoding utf-8
4		6
5	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ	7	JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
6	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)	8	(http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7		9
8	=head1 SYNOPSIS	10	=head1 SYNOPSIS
35	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
36	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.
37		39
38	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
39	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
40	overriden) with no overhead due to emulation (by inheritign constructor	42	overridden) with no overhead due to emulation (by inheriting constructor
41	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
42	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
43	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
44	require a C compiler when that is a problem.	46	require a C compiler when that is a problem.
45		47
…		…
58		60
59	=over 4	61	=over 4
60		62
61	=item * correct Unicode handling	63	=item * correct Unicode handling
62		64
63	This module knows how to handle Unicode, and even documents how and when	65	This module knows how to handle Unicode, documents how and when it does
64	it does so.	66	so, and even documents what "correct" means.
65		67
66	=item * round-trip integrity	68	=item * round-trip integrity
67		69
68	When you serialise a perl data structure using only datatypes supported	70	When you serialise a perl data structure using only data types supported
69	by JSON, the deserialised data structure is identical on the Perl level.	71	by JSON, the deserialised data structure is identical on the Perl level.
70	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks	72	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
71	like a number).	73	like a number). There minor I<are> exceptions to this, read the MAPPING
		74	section below to learn about those.
72		75
73	=item * strict checking of JSON correctness	76	=item * strict checking of JSON correctness
74		77
75	There is no guessing, no generating of illegal JSON texts by default,	78	There is no guessing, no generating of illegal JSON texts by default,
76	and only JSON is accepted as input by default (the latter is a security	79	and only JSON is accepted as input by default (the latter is a security
77	feature).	80	feature).
78		81
79	=item * fast	82	=item * fast
80		83
81	Compared to other JSON modules, this module compares favourably in terms	84	Compared to other JSON modules and other serialisers such as Storable,
82	of speed, too.	85	this module usually compares favourably in terms of speed, too.
83		86
84	=item * simple to use	87	=item * simple to use
85		88
86	This module has both a simple functional interface as well as an OO	89	This module has both a simple functional interface as well as an object
87	interface.	90	oriented interface interface.
88		91
89	=item * reasonably versatile output formats	92	=item * reasonably versatile output formats
90		93
91	You can choose between the most compact guaranteed single-line format	94	You can choose between the most compact guaranteed-single-line format
92	possible (nice for simple line-based protocols), a pure-ascii format	95	possible (nice for simple line-based protocols), a pure-ASCII format
93	(for when your transport is not 8-bit clean, still supports the whole	96	(for when your transport is not 8-bit clean, still supports the whole
94	Unicode range), or a pretty-printed format (for when you want to read that	97	Unicode range), or a pretty-printed format (for when you want to read that
95	stuff). Or you can combine those features in whatever way you like.	98	stuff). Or you can combine those features in whatever way you like.
96		99
97	=back	100	=back
…		…
100		103
101	package JSON::XS;	104	package JSON::XS;
102		105
103	use strict;	106	use strict;
104		107
105	our $VERSION = '2.01';	108	our $VERSION = '2.21';
106	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
107		110
108	our @EXPORT = qw(encode_json decode_json to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
109		112
110	sub to_json($) {	113	sub to_json($) {
…		…
134		137
135	This function call is functionally identical to:	138	This function call is functionally identical to:
136		139
137	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)	140	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
138		141
139	except being faster.	142	Except being faster.
140		143
141	=item $perl_scalar = decode_json $json_text	144	=item $perl_scalar = decode_json $json_text
142		145
143	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries	146	The opposite of C<encode_json>: expects an UTF-8 (binary) string and tries
144	to parse that as an UTF-8 encoded JSON text, returning the resulting	147	to parse that as an UTF-8 encoded JSON text, returning the resulting
…		…
146		149
147	This function call is functionally identical to:	150	This function call is functionally identical to:
148		151
149	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)	152	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
150		153
151	except being faster.	154	Except being faster.
152		155
153	=item $is_boolean = JSON::XS::is_bool $scalar	156	=item $is_boolean = JSON::XS::is_bool $scalar
154		157
155	Returns true if the passed scalar represents either JSON::XS::true or	158	Returns true if the passed scalar represents either JSON::XS::true or
156	JSON::XS::false, two constants that act like C<1> and C<0>, respectively	159	JSON::XS::false, two constants that act like C<1> and C<0>, respectively
…		…
174	This enables you to store Unicode characters as single characters in a	177	This enables you to store Unicode characters as single characters in a
175	Perl string - very natural.	178	Perl string - very natural.
176		179
177	=item 2. Perl does I<not> associate an encoding with your strings.	180	=item 2. Perl does I<not> associate an encoding with your strings.
178		181
179	Unless you force it to, e.g. when matching it against a regex, or printing	182	... until you force it to, e.g. when matching it against a regex, or
180	the scalar to a file, in which case Perl either interprets your string as	183	printing the scalar to a file, in which case Perl either interprets your
181	locale-encoded text, octets/binary, or as Unicode, depending on various	184	string as locale-encoded text, octets/binary, or as Unicode, depending
182	settings. In no case is an encoding stored together with your data, it is	185	on various settings. In no case is an encoding stored together with your
183	I<use> that decides encoding, not any magical metadata.	186	data, it is I<use> that decides encoding, not any magical meta data.
184		187
185	=item 3. The internal utf-8 flag has no meaning with regards to the	188	=item 3. The internal utf-8 flag has no meaning with regards to the
186	encoding of your string.	189	encoding of your string.
187		190
188	Just ignore that flag unless you debug a Perl bug, a module written in	191	Just ignore that flag unless you debug a Perl bug, a module written in
…		…
194		197
195	If you didn't know about that flag, just the better, pretend it doesn't	198	If you didn't know about that flag, just the better, pretend it doesn't
196	exist.	199	exist.
197		200
198	=item 4. A "Unicode String" is simply a string where each character can be	201	=item 4. A "Unicode String" is simply a string where each character can be
199	validly interpreted as a Unicode codepoint.	202	validly interpreted as a Unicode code point.
200		203
201	If you have UTF-8 encoded data, it is no longer a Unicode string, but a	204	If you have UTF-8 encoded data, it is no longer a Unicode string, but a
202	Unicode string encoded in UTF-8, giving you a binary string.	205	Unicode string encoded in UTF-8, giving you a binary string.
203		206
204	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.	207	=item 5. A string containing "high" (> 255) character values is I<not> a UTF-8 string.
…		…
242		245
243	If C<$enable> is false, then the C<encode> method will not escape Unicode	246	If C<$enable> is false, then the C<encode> method will not escape Unicode
244	characters unless required by the JSON syntax or other flags. This results	247	characters unless required by the JSON syntax or other flags. This results
245	in a faster and more compact format.	248	in a faster and more compact format.
246		249
		250	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		251	document.
		252
247	The main use for this flag is to produce JSON texts that can be	253	The main use for this flag is to produce JSON texts that can be
248	transmitted over a 7-bit channel, as the encoded JSON texts will not	254	transmitted over a 7-bit channel, as the encoded JSON texts will not
249	contain any 8 bit characters.	255	contain any 8 bit characters.
250		256
251	JSON::XS->new->ascii (1)->encode ([chr 0x10401])	257	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
…		…
262	will not be affected in any way by this flag, as C<decode> by default	268	will not be affected in any way by this flag, as C<decode> by default
263	expects Unicode, which is a strict superset of latin1.	269	expects Unicode, which is a strict superset of latin1.
264		270
265	If C<$enable> is false, then the C<encode> method will not escape Unicode	271	If C<$enable> is false, then the C<encode> method will not escape Unicode
266	characters unless required by the JSON syntax or other flags.	272	characters unless required by the JSON syntax or other flags.
		273
		274	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		275	document.
267		276
268	The main use for this flag is efficiently encoding binary data as JSON	277	The main use for this flag is efficiently encoding binary data as JSON
269	text, as most octets will not be escaped, resulting in a smaller encoded	278	text, as most octets will not be escaped, resulting in a smaller encoded
270	size. The disadvantage is that the resulting JSON text is encoded	279	size. The disadvantage is that the resulting JSON text is encoded
271	in latin1 (and must correctly be treated as such when storing and	280	in latin1 (and must correctly be treated as such when storing and
…		…
290		299
291	If C<$enable> is false, then the C<encode> method will return the JSON	300	If C<$enable> is false, then the C<encode> method will return the JSON
292	string as a (non-encoded) Unicode string, while C<decode> expects thus a	301	string as a (non-encoded) Unicode string, while C<decode> expects thus a
293	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	302	Unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
294	to be done yourself, e.g. using the Encode module.	303	to be done yourself, e.g. using the Encode module.
		304
		305	See also the section I<ENCODING/CODESET FLAG NOTES> later in this
		306	document.
295		307
296	Example, output UTF-16BE-encoded JSON:	308	Example, output UTF-16BE-encoded JSON:
297		309
298	use Encode;	310	use Encode;
299	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);	311	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
…		…
450	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>,
451	resulting in an invalid JSON text:	463	resulting in an invalid JSON text:
452		464
453	JSON::XS->new->allow_nonref->encode ("Hello, World!")	465	JSON::XS->new->allow_nonref->encode ("Hello, World!")
454	=> "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.
455		483
456	=item $json = $json->allow_blessed ([$enable])	484	=item $json = $json->allow_blessed ([$enable])
457		485
458	=item $enabled = $json->get_allow_blessed	486	=item $enabled = $json->get_allow_blessed
459		487
…		…
600	=item $json = $json->max_depth ([$maximum_nesting_depth])	628	=item $json = $json->max_depth ([$maximum_nesting_depth])
601		629
602	=item $max_depth = $json->get_max_depth	630	=item $max_depth = $json->get_max_depth
603		631
604	Sets the maximum nesting level (default C<512>) accepted while encoding	632	Sets the maximum nesting level (default C<512>) accepted while encoding
605	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
606	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
607	stop and croak at that point.	635	point.
608		636
609	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
610	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<[>
611	characters without their matching closing parenthesis crossed to reach a	639	characters without their matching closing parenthesis crossed to reach a
612	given character in a string.	640	given character in a string.
613		641
614	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
615	that the object is only a single hash/object or array.	643	that the object is only a single hash/object or array.
616		644
617	The argument to C<max_depth> will be rounded up to the next highest power
618	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
619	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.
620		651
621	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.
622		653
623	=item $json = $json->max_size ([$maximum_string_size])	654	=item $json = $json->max_size ([$maximum_string_size])
624		655
625	=item $max_size = $json->get_max_size	656	=item $max_size = $json->get_max_size
626		657
627	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
628	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>
629	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
630	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
631	effect on C<encode> (yet).	662	effect on C<encode> (yet).
632		663
633	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
634	power of two (so may be more than requested). If no argument is given, the	665	C<0> is specified).
635	limit check will be deactivated (same as when C<0> is specified).
636		666
637	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.
638		668
639	=item $json_text = $json->encode ($perl_scalar)	669	=item $json_text = $json->encode ($perl_scalar)
640		670
…		…
669	=> ([], 3)	699	=> ([], 3)
670		700
671	=back	701	=back
672		702
673		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 is
		712	much more efficient (JSON::XS will only attempt to parse the JSON text
		713	once it is sure it has enough text to get a decisive result, using a very
		714	simple but truly incremental parser).
		715
		716	The following two methods deal with this.
		717
		718	=over 4
		719
		720	=item [void, scalar or list context] = $json->incr_parse ([$string])
		721
		722	This is the central parsing function. It can both append new text and
		723	extract objects from the stream accumulated so far (both of these
		724	functions are optional).
		725
		726	If C<$string> is given, then this string is appended to the already
		727	existing JSON fragment stored in the C<$json> object.
		728
		729	After that, if the function is called in void context, it will simply
		730	return without doing anything further. This can be used to add more text
		731	in as many chunks as you want.
		732
		733	If the method is called in scalar context, then it will try to extract
		734	exactly I<one> JSON object. If that is successful, it will return this
		735	object, otherwise it will return C<undef>. If there is a parse error,
		736	this method will croak just as C<decode> would do (one can then use
		737	C<incr_skip> to skip the errornous part). This is the most common way of
		738	using the method.
		739
		740	And finally, in list context, it will try to extract as many objects
		741	from the stream as it can find and return them, or the empty list
		742	otherwise. For this to work, there must be no separators between the JSON
		743	objects or arrays, instead they must be concatenated back-to-back. If
		744	an error occurs, an exception will be raised as in the scalar context
		745	case. Note that in this case, any previously-parsed JSON texts will be
		746	lost.
		747
		748	=item $lvalue_string = $json->incr_text
		749
		750	This method returns the currently stored JSON fragment as an lvalue, that
		751	is, you can manipulate it. This I<only> works when a preceding call to
		752	C<incr_parse> in I<scalar context> successfully returned an object. Under
		753	all other circumstances you must not call this function (I mean it.
		754	although in simple tests it might actually work, it I<will> fail under
		755	real world conditions). As a special exception, you can also call this
		756	method before having parsed anything.
		757
		758	This function is useful in two cases: a) finding the trailing text after a
		759	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		760	(such as commas).
		761
		762	=item $json->incr_skip
		763
		764	This will reset the state of the incremental parser and will remove the
		765	parsed text from the input buffer. This is useful after C<incr_parse>
		766	died, in which case the input buffer and incremental parser state is left
		767	unchanged, to skip the text parsed so far and to reset the parse state.
		768
		769	=item $json->incr_reset
		770
		771	This completely resets the incremental parser, that is, after this call,
		772	it will be as if the parser had never parsed anything.
		773
		774	This is useful if you want ot repeatedly parse JSON objects and want to
		775	ignore any trailing data, which means you have to reset the parser after
		776	each successful decode.
		777
		778	=back
		779
		780	=head2 LIMITATIONS
		781
		782	All options that affect decoding are supported, except
		783	C<allow_nonref>. The reason for this is that it cannot be made to
		784	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		785	them back to back and still decode them perfectly. This does not hold true
		786	for JSON numbers, however.
		787
		788	For example, is the string C<1> a single JSON number, or is it simply the
		789	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		790	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		791	takes the conservative route and disallows this case.
		792
		793	=head2 EXAMPLES
		794
		795	Some examples will make all this clearer. First, a simple example that
		796	works similarly to C<decode_prefix>: We want to decode the JSON object at
		797	the start of a string and identify the portion after the JSON object:
		798
		799	my $text = "[1,2,3] hello";
		800
		801	my $json = new JSON::XS;
		802
		803	my $obj = $json->incr_parse ($text)
		804	or die "expected JSON object or array at beginning of string";
		805
		806	my $tail = $json->incr_text;
		807	# $tail now contains " hello"
		808
		809	Easy, isn't it?
		810
		811	Now for a more complicated example: Imagine a hypothetical protocol where
		812	you read some requests from a TCP stream, and each request is a JSON
		813	array, without any separation between them (in fact, it is often useful to
		814	use newlines as "separators", as these get interpreted as whitespace at
		815	the start of the JSON text, which makes it possible to test said protocol
		816	with C<telnet>...).
		817
		818	Here is how you'd do it (it is trivial to write this in an event-based
		819	manner):
		820
		821	my $json = new JSON::XS;
		822
		823	# read some data from the socket
		824	while (sysread $socket, my $buf, 4096) {
		825
		826	# split and decode as many requests as possible
		827	for my $request ($json->incr_parse ($buf)) {
		828	# act on the $request
		829	}
		830	}
		831
		832	Another complicated example: Assume you have a string with JSON objects
		833	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		834	[3]>). To parse them, we have to skip the commas between the JSON texts,
		835	and here is where the lvalue-ness of C<incr_text> comes in useful:
		836
		837	my $text = "[1],[2], [3]";
		838	my $json = new JSON::XS;
		839
		840	# void context, so no parsing done
		841	$json->incr_parse ($text);
		842
		843	# now extract as many objects as possible. note the
		844	# use of scalar context so incr_text can be called.
		845	while (my $obj = $json->incr_parse) {
		846	# do something with $obj
		847
		848	# now skip the optional comma
		849	$json->incr_text =~ s/^ \s* , //x;
		850	}
		851
		852	Now lets go for a very complex example: Assume that you have a gigantic
		853	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		854	but you cannot load it into memory fully (this has actually happened in
		855	the real world :).
		856
		857	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		858	can still help you: You implement a (very simple) array parser and let
		859	JSON decode the array elements, which are all full JSON objects on their
		860	own (this wouldn't work if the array elements could be JSON numbers, for
		861	example):
		862
		863	my $json = new JSON::XS;
		864
		865	# open the monster
		866	open my $fh, "<bigfile.json"
		867	or die "bigfile: $!";
		868
		869	# first parse the initial "["
		870	for (;;) {
		871	sysread $fh, my $buf, 65536
		872	or die "read error: $!";
		873	$json->incr_parse ($buf); # void context, so no parsing
		874
		875	# Exit the loop once we found and removed(!) the initial "[".
		876	# In essence, we are (ab-)using the $json object as a simple scalar
		877	# we append data to.
		878	last if $json->incr_text =~ s/^ \s* \[ //x;
		879	}
		880
		881	# now we have the skipped the initial "[", so continue
		882	# parsing all the elements.
		883	for (;;) {
		884	# in this loop we read data until we got a single JSON object
		885	for (;;) {
		886	if (my $obj = $json->incr_parse) {
		887	# do something with $obj
		888	last;
		889	}
		890
		891	# add more data
		892	sysread $fh, my $buf, 65536
		893	or die "read error: $!";
		894	$json->incr_parse ($buf); # void context, so no parsing
		895	}
		896
		897	# in this loop we read data until we either found and parsed the
		898	# separating "," between elements, or the final "]"
		899	for (;;) {
		900	# first skip whitespace
		901	$json->incr_text =~ s/^\s*//;
		902
		903	# if we find "]", we are done
		904	if ($json->incr_text =~ s/^\]//) {
		905	print "finished.\n";
		906	exit;
		907	}
		908
		909	# if we find ",", we can continue with the next element
		910	if ($json->incr_text =~ s/^,//) {
		911	last;
		912	}
		913
		914	# if we find anything else, we have a parse error!
		915	if (length $json->incr_text) {
		916	die "parse error near ", $json->incr_text;
		917	}
		918
		919	# else add more data
		920	sysread $fh, my $buf, 65536
		921	or die "read error: $!";
		922	$json->incr_parse ($buf); # void context, so no parsing
		923	}
		924
		925	This is a complex example, but most of the complexity comes from the fact
		926	that we are trying to be correct (bear with me if I am wrong, I never ran
		927	the above example :).
		928
		929
		930
674	=head1 MAPPING	931	=head1 MAPPING
675		932
676	This section describes how JSON::XS maps Perl values to JSON values and	933	This section describes how JSON::XS maps Perl values to JSON values and
677	vice versa. These mappings are designed to "do the right thing" in most	934	vice versa. These mappings are designed to "do the right thing" in most
678	circumstances automatically, preserving round-tripping characteristics	935	circumstances automatically, preserving round-tripping characteristics
…		…
706		963
707	A JSON number becomes either an integer, numeric (floating point) or	964	A JSON number becomes either an integer, numeric (floating point) or
708	string scalar in perl, depending on its range and any fractional parts. On	965	string scalar in perl, depending on its range and any fractional parts. On
709	the Perl level, there is no difference between those as Perl handles all	966	the Perl level, there is no difference between those as Perl handles all
710	the conversion details, but an integer may take slightly less memory and	967	the conversion details, but an integer may take slightly less memory and
711	might represent more values exactly than (floating point) numbers.	968	might represent more values exactly than floating point numbers.
712		969
713	If the number consists of digits only, JSON::XS will try to represent	970	If the number consists of digits only, JSON::XS will try to represent
714	it as an integer value. If that fails, it will try to represent it as	971	it as an integer value. If that fails, it will try to represent it as
715	a numeric (floating point) value if that is possible without loss of	972	a numeric (floating point) value if that is possible without loss of
716	precision. Otherwise it will preserve the number as a string value.	973	precision. Otherwise it will preserve the number as a string value (in
		974	which case you lose roundtripping ability, as the JSON number will be
		975	re-encoded toa JSON string).
717		976
718	Numbers containing a fractional or exponential part will always be	977	Numbers containing a fractional or exponential part will always be
719	represented as numeric (floating point) values, possibly at a loss of	978	represented as numeric (floating point) values, possibly at a loss of
720	precision.	979	precision (in which case you might lose perfect roundtripping ability, but
721		980	the JSON number will still be re-encoded as a JSON number).
722	This might create round-tripping problems as numbers might become strings,
723	but as Perl is typeless there is no other way to do it.
724		981
725	=item true, false	982	=item true, false
726		983
727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	984	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
728	respectively. They are overloaded to act almost exactly like the numbers	985	respectively. They are overloaded to act almost exactly like the numbers
…		…
765	Other unblessed references are generally not allowed and will cause an	1022	Other unblessed references are generally not allowed and will cause an
766	exception to be thrown, except for references to the integers C<0> and	1023	exception to be thrown, except for references to the integers C<0> and
767	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can	1024	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
768	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.	1025	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
769		1026
770	encode_json [\0,JSON::XS::true] # yields [false,true]	1027	encode_json [\0, JSON::XS::true] # yields [false,true]
771		1028
772	=item JSON::XS::true, JSON::XS::false	1029	=item JSON::XS::true, JSON::XS::false
773		1030
774	These special values become JSON true and JSON false values,	1031	These special values become JSON true and JSON false values,
775	respectively. You can also use C<\1> and C<\0> directly if you want.	1032	respectively. You can also use C<\1> and C<\0> directly if you want.
776		1033
777	=item blessed objects	1034	=item blessed objects
778		1035
779	Blessed objects are not allowed. JSON::XS currently tries to encode their	1036	Blessed objects are not directly representable in JSON. See the
780	underlying representation (hash- or arrayref), but this behaviour might	1037	C<allow_blessed> and C<convert_blessed> methods on various options on
781	change in future versions.	1038	how to deal with this: basically, you can choose between throwing an
		1039	exception, encoding the reference as if it weren't blessed, or provide
		1040	your own serialiser method.
782		1041
783	=item simple scalars	1042	=item simple scalars
784		1043
785	Simple Perl scalars (any scalar that is not a reference) are the most	1044	Simple Perl scalars (any scalar that is not a reference) are the most
786	difficult objects to encode: JSON::XS will encode undefined scalars as	1045	difficult objects to encode: JSON::XS will encode undefined scalars as
787	JSON null value, scalars that have last been used in a string context	1046	JSON C<null> values, scalars that have last been used in a string context
788	before encoding as JSON strings and anything else as number value:	1047	before encoding as JSON strings, and anything else as number value:
789		1048
790	# dump as number	1049	# dump as number
791	encode_json [2] # yields [2]	1050	encode_json [2] # yields [2]
792	encode_json [-3.0e17] # yields [-3e+17]	1051	encode_json [-3.0e17] # yields [-3e+17]
793	my $value = 5; encode_json [$value] # yields [5]	1052	my $value = 5; encode_json [$value] # yields [5]
…		…
811	my $x = "3"; # some variable containing a string	1070	my $x = "3"; # some variable containing a string
812	$x += 0; # numify it, ensuring it will be dumped as a number	1071	$x += 0; # numify it, ensuring it will be dumped as a number
813	$x *= 1; # same thing, the choice is yours.	1072	$x *= 1; # same thing, the choice is yours.
814		1073
815	You can not currently force the type in other, less obscure, ways. Tell me	1074	You can not currently force the type in other, less obscure, ways. Tell me
816	if you need this capability.	1075	if you need this capability (but don't forget to explain why it's needed
		1076	:).
817		1077
818	=back	1078	=back
819		1079
820		1080
821	=head1 COMPARISON	1081	=head1 ENCODING/CODESET FLAG NOTES
822		1082
823	As already mentioned, this module was created because none of the existing	1083	The interested reader might have seen a number of flags that signify
824	JSON modules could be made to work correctly. First I will describe the	1084	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
825	problems (or pleasures) I encountered with various existing JSON modules,	1085	some confusion on what these do, so here is a short comparison:
826	followed by some benchmark values. JSON::XS was designed not to suffer	1086
827	from any of these problems or limitations.	1087	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1088	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1089	control whether C<encode> escapes character values outside their respective
		1090	codeset range. Neither of these flags conflict with each other, although
		1091	some combinations make less sense than others.
		1092
		1093	Care has been taken to make all flags symmetrical with respect to
		1094	C<encode> and C<decode>, that is, texts encoded with any combination of
		1095	these flag values will be correctly decoded when the same flags are used
		1096	- in general, if you use different flag settings while encoding vs. when
		1097	decoding you likely have a bug somewhere.
		1098
		1099	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1100	simply an abstract set of character-codepoint pairs, while an encoding
		1101	takes those codepoint numbers and I<encodes> them, in our case into
		1102	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1103	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1104	the same time, which can be confusing.
828		1105
829	=over 4	1106	=over 4
830		1107
831	=item JSON 1.07	1108	=item C<utf8> flag disabled
832		1109
833	Slow (but very portable, as it is written in pure Perl).	1110	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1111	and expect Unicode strings, that is, characters with high ordinal Unicode
		1112	values (> 255) will be encoded as such characters, and likewise such
		1113	characters are decoded as-is, no canges to them will be done, except
		1114	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1115	respectively (to Perl, these are the same thing in strings unless you do
		1116	funny/weird/dumb stuff).
834		1117
835	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1118	This is useful when you want to do the encoding yourself (e.g. when you
836	undocumented. One can get far by feeding it Unicode strings and doing	1119	want to have UTF-16 encoded JSON texts) or when some other layer does
837	en-/decoding oneself, but Unicode escapes are not working properly).	1120	the encoding for you (for example, when printing to a terminal using a
		1121	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1122	to UTF-8 encode your data first and have Perl encode it another time).
838		1123
839	No round-tripping (strings get clobbered if they look like numbers, e.g.	1124	=item C<utf8> flag enabled
840	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
841	decode into the number 2.
842		1125
843	=item JSON::PC 0.01	1126	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1127	characters using the corresponding UTF-8 multi-byte sequence, and will
		1128	expect your input strings to be encoded as UTF-8, that is, no "character"
		1129	of the input string must have any value > 255, as UTF-8 does not allow
		1130	that.
844		1131
845	Very fast.	1132	The C<utf8> flag therefore switches between two modes: disabled means you
		1133	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1134	octet/binary string in Perl.
846		1135
847	Undocumented/buggy Unicode handling.	1136	=item C<latin1> or C<ascii> flags enabled
848		1137
849	No round-tripping.	1138	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1139	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1140	characters as specified by the C<utf8> flag.
850		1141
851	Has problems handling many Perl values (e.g. regex results and other magic	1142	If C<utf8> is disabled, then the result is also correctly encoded in those
852	values will make it croak).	1143	character sets (as both are proper subsets of Unicode, meaning that a
		1144	Unicode string with all character values < 256 is the same thing as a
		1145	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1146	the same thing as an ASCII string in Perl).
853		1147
854	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1148	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
855	which is not a valid JSON text.	1149	regardless of these flags, just some more characters will be escaped using
		1150	C<\uXXXX> then before.
856		1151
857	Unmaintained (maintainer unresponsive for many months, bugs are not	1152	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
858	getting fixed).	1153	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1154	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1155	a subset of Unicode), while ASCII is.
859		1156
860	=item JSON::Syck 0.21	1157	Surprisingly, C<decode> will ignore these flags and so treat all input
		1158	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1159	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1160	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
861		1161
862	Very buggy (often crashes).	1162	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1163	they only govern when the JSON output engine escapes a character or not.
863		1164
864	Very inflexible (no human-readable format supported, format pretty much	1165	The main use for C<latin1> is to relatively efficiently store binary data
865	undocumented. I need at least a format for easy reading by humans and a	1166	as JSON, at the expense of breaking compatibility with most JSON decoders.
866	single-line compact format for use in a protocol, and preferably a way to
867	generate ASCII-only JSON texts).
868		1167
869	Completely broken (and confusingly documented) Unicode handling (Unicode	1168	The main use for C<ascii> is to force the output to not contain characters
870	escapes are not working properly, you need to set ImplicitUnicode to	1169	with values > 127, which means you can interpret the resulting string
871	I<different> values on en- and decoding to get symmetric behaviour).	1170	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
872		1171	8-bit-encoding, and still get the same data structure back. This is useful
873	No round-tripping (simple cases work, but this depends on whether the scalar	1172	when your channel for JSON transfer is not 8-bit clean or the encoding
874	value was used in a numeric context or not).	1173	might be mangled in between (e.g. in mail), and works because ASCII is a
875		1174	proper subset of most 8-bit and multibyte encodings in use in the world.
876	Dumping hashes may skip hash values depending on iterator state.
877
878	Unmaintained (maintainer unresponsive for many months, bugs are not
879	getting fixed).
880
881	Does not check input for validity (i.e. will accept non-JSON input and
882	return "something" instead of raising an exception. This is a security
883	issue: imagine two banks transferring money between each other using
884	JSON. One bank might parse a given non-JSON request and deduct money,
885	while the other might reject the transaction with a syntax error. While a
886	good protocol will at least recover, that is extra unnecessary work and
887	the transaction will still not succeed).
888
889	=item JSON::DWIW 0.04
890
891	Very fast. Very natural. Very nice.
892
893	Undocumented Unicode handling (but the best of the pack. Unicode escapes
894	still don't get parsed properly).
895
896	Very inflexible.
897
898	No round-tripping.
899
900	Does not generate valid JSON texts (key strings are often unquoted, empty keys
901	result in nothing being output)
902
903	Does not check input for validity.
904		1175
905	=back	1176	=back
906		1177
907		1178
908	=head2 JSON and YAML	1179	=head2 JSON and YAML
909		1180
910	You often hear that JSON is a subset (or a close subset) of YAML. This is,	1181	You often hear that JSON is a subset of YAML. This is, however, a mass
911	however, a mass hysteria and very far from the truth. In general, there is	1182	hysteria(*) and very far from the truth (as of the time of this writing),
912	no way to configure JSON::XS to output a data structure as valid YAML.	1183	so let me state it clearly: I<in general, there is no way to configure
		1184	JSON::XS to output a data structure as valid YAML> that works in all
		1185	cases.
913		1186
914	If you really must use JSON::XS to generate YAML, you should use this	1187	If you really must use JSON::XS to generate YAML, you should use this
915	algorithm (subject to change in future versions):	1188	algorithm (subject to change in future versions):
916		1189
917	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1190	my $to_yaml = JSON::XS->new->utf8->space_after (1);
918	my $yaml = $to_yaml->encode ($ref) . "\n";	1191	my $yaml = $to_yaml->encode ($ref) . "\n";
919		1192
920	This will usually generate JSON texts that also parse as valid	1193	This will I<usually> generate JSON texts that also parse as valid
921	YAML. Please note that YAML has hardcoded limits on (simple) object key	1194	YAML. Please note that YAML has hardcoded limits on (simple) object key
922	lengths that JSON doesn't have, so you should make sure that your hash	1195	lengths that JSON doesn't have and also has different and incompatible
		1196	unicode handling, so you should make sure that your hash keys are
923	keys are noticeably shorter than the 1024 characters YAML allows.	1197	noticeably shorter than the 1024 "stream characters" YAML allows and that
		1198	you do not have characters with codepoint values outside the Unicode BMP
		1199	(basic multilingual page). YAML also does not allow C<\/> sequences in
		1200	strings (which JSON::XS does not I<currently> generate, but other JSON
		1201	generators might).
924		1202
925	There might be other incompatibilities that I am not aware of. In general	1203	There might be other incompatibilities that I am not aware of (or the YAML
		1204	specification has been changed yet again - it does so quite often). In
926	you should not try to generate YAML with a JSON generator or vice versa,	1205	general you should not try to generate YAML with a JSON generator or vice
927	or try to parse JSON with a YAML parser or vice versa: chances are high	1206	versa, or try to parse JSON with a YAML parser or vice versa: chances are
928	that you will run into severe interoperability problems.	1207	high that you will run into severe interoperability problems when you
		1208	least expect it.
		1209
		1210	=over 4
		1211
		1212	=item (*)
		1213
		1214	I have been pressured multiple times by Brian Ingerson (one of the
		1215	authors of the YAML specification) to remove this paragraph, despite him
		1216	acknowledging that the actual incompatibilities exist. As I was personally
		1217	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1218	educate people about these issues, so others do not run into the same
		1219	problem again and again. After this, Brian called me a (quote)I<complete
		1220	and worthless idiot>(unquote).
		1221
		1222	In my opinion, instead of pressuring and insulting people who actually
		1223	clarify issues with YAML and the wrong statements of some of its
		1224	proponents, I would kindly suggest reading the JSON spec (which is not
		1225	that difficult or long) and finally make YAML compatible to it, and
		1226	educating users about the changes, instead of spreading lies about the
		1227	real compatibility for many I<years> and trying to silence people who
		1228	point out that it isn't true.
		1229
		1230	=back
929		1231
930		1232
931	=head2 SPEED	1233	=head2 SPEED
932		1234
933	It seems that JSON::XS is surprisingly fast, as shown in the following	1235	It seems that JSON::XS is surprisingly fast, as shown in the following
934	tables. They have been generated with the help of the C<eg/bench> program	1236	tables. They have been generated with the help of the C<eg/bench> program
935	in the JSON::XS distribution, to make it easy to compare on your own	1237	in the JSON::XS distribution, to make it easy to compare on your own
936	system.	1238	system.
937		1239
938	First comes a comparison between various modules using a very short	1240	First comes a comparison between various modules using
939	single-line JSON string:	1241	a very short single-line JSON string (also available at
		1242	L<http://dist.schmorp.de/misc/json/short.json>).
940		1243
941	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1244	{"method": "handleMessage", "params": ["user1",
942	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1245	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1246	true, false]}
943		1247
944	It shows the number of encodes/decodes per second (JSON::XS uses	1248	It shows the number of encodes/decodes per second (JSON::XS uses
945	the functional interface, while JSON::XS/2 uses the OO interface	1249	the functional interface, while JSON::XS/2 uses the OO interface
946	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1250	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
947	shrink). Higher is better:	1251	shrink). Higher is better:
…		…
963	about three times faster on decoding, and over forty times faster	1267	about three times faster on decoding, and over forty times faster
964	than JSON, even with pretty-printing and key sorting. It also compares	1268	than JSON, even with pretty-printing and key sorting. It also compares
965	favourably to Storable for small amounts of data.	1269	favourably to Storable for small amounts of data.
966		1270
967	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1271	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
968	search API (http://nanoref.com/yahooapis/mgPdGg):	1272	search API (L<http://dist.schmorp.de/misc/json/long.json>).
969		1273
970	module \| encode \| decode \|	1274	module \| encode \| decode \|
971	-----------\|------------\|------------\|	1275	-----------\|------------\|------------\|
972	JSON 1.x \| 55.260 \| 34.971 \|	1276	JSON 1.x \| 55.260 \| 34.971 \|
973	JSON::DWIW \| 825.228 \| 1082.513 \|	1277	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
1010		1314
1011	Third, JSON::XS recurses using the C stack when decoding objects and	1315	Third, JSON::XS recurses using the C stack when decoding objects and
1012	arrays. The C stack is a limited resource: for instance, on my amd64	1316	arrays. The C stack is a limited resource: for instance, on my amd64
1013	machine with 8MB of stack size I can decode around 180k nested arrays but	1317	machine with 8MB of stack size I can decode around 180k nested arrays but
1014	only 14k nested JSON objects (due to perl itself recursing deeply on croak	1318	only 14k nested JSON objects (due to perl itself recursing deeply on croak
1015	to free the temporary). If that is exceeded, the program crashes. to be	1319	to free the temporary). If that is exceeded, the program crashes. To be
1016	conservative, the default nesting limit is set to 512. If your process	1320	conservative, the default nesting limit is set to 512. If your process
1017	has a smaller stack, you should adjust this setting accordingly with the	1321	has a smaller stack, you should adjust this setting accordingly with the
1018	C<max_depth> method.	1322	C<max_depth> method.
1019		1323
1020	And last but least, something else could bomb you that I forgot to think	1324	Something else could bomb you, too, that I forgot to think of. In that
1021	of. In that case, you get to keep the pieces. I am always open for hints,	1325	case, you get to keep the pieces. I am always open for hints, though...
1022	though...	1326
		1327	Also keep in mind that JSON::XS might leak contents of your Perl data
		1328	structures in its error messages, so when you serialise sensitive
		1329	information you might want to make sure that exceptions thrown by JSON::XS
		1330	will not end up in front of untrusted eyes.
1023		1331
1024	If you are using JSON::XS to return packets to consumption	1332	If you are using JSON::XS to return packets to consumption
1025	by JavaScript scripts in a browser you should have a look at	1333	by JavaScript scripts in a browser you should have a look at
1026	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1334	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1027	you are vulnerable to some common attack vectors (which really are browser	1335	you are vulnerable to some common attack vectors (which really are browser
1028	design bugs, but it is still you who will have to deal with it, as major	1336	design bugs, but it is still you who will have to deal with it, as major
1029	browser developers care only for features, not about doing security	1337	browser developers care only for features, not about getting security
1030	right).	1338	right).
1031		1339
1032		1340
1033	=head1 THREADS	1341	=head1 THREADS
1034		1342
1035	This module is I<not> guaranteed to be thread safe and there are no	1343	This module is I<not> guaranteed to be thread safe and there are no
1036	plans to change this until Perl gets thread support (as opposed to the	1344	plans to change this until Perl gets thread support (as opposed to the
1037	horribly slow so-called "threads" which are simply slow and bloated	1345	horribly slow so-called "threads" which are simply slow and bloated
1038	process simulations - use fork, its I<much> faster, cheaper, better).	1346	process simulations - use fork, it's I<much> faster, cheaper, better).
1039		1347
1040	(It might actually work, but you have been warned).	1348	(It might actually work, but you have been warned).
1041		1349
1042		1350
1043	=head1 BUGS	1351	=head1 BUGS
1044		1352
1045	While the goal of this module is to be correct, that unfortunately does	1353	While the goal of this module is to be correct, that unfortunately does
1046	not mean its bug-free, only that I think its design is bug-free. It is	1354	not mean it's bug-free, only that I think its design is bug-free. If you
1047	still relatively early in its development. If you keep reporting bugs they	1355	keep reporting bugs they will be fixed swiftly, though.
1048	will be fixed swiftly, though.
1049		1356
1050	Please refrain from using rt.cpan.org or any other bug reporting	1357	Please refrain from using rt.cpan.org or any other bug reporting
1051	service. I put the contact address into my modules for a reason.	1358	service. I put the contact address into my modules for a reason.
1052		1359
1053	=cut	1360	=cut
…		…
1073	"--" => sub { $_[0] = ${$_[0]} - 1 },	1380	"--" => sub { $_[0] = ${$_[0]} - 1 },
1074	fallback => 1;	1381	fallback => 1;
1075		1382
1076	1;	1383	1;
1077		1384
		1385	=head1 SEE ALSO
		1386
		1387	The F<json_xs> command line utility for quick experiments.
		1388
1078	=head1 AUTHOR	1389	=head1 AUTHOR
1079		1390
1080	Marc Lehmann <schmorp@schmorp.de>	1391	Marc Lehmann <schmorp@schmorp.de>
1081	http://home.schmorp.de/	1392	http://home.schmorp.de/
1082		1393

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Comparing JSON-XS/XS.pm (file contents): Revision 1.78 by root, Wed Dec 5 10:59:28 2007 UTC vs. Revision 1.107 by root, Tue Jun 3 06:43:45 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.78 by root, Wed Dec 5 10:59:28 2007 UTC vs.
Revision 1.107 by root, Tue Jun 3 06:43:45 2008 UTC