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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs.
Revision 1.108 by root, Tue Jul 15 11:29:29 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 $VERSION = '2.22';
106	our @ISA = qw(Exporter);	109	our @ISA = qw(Exporter);
107		110
108	our @EXPORT = qw(encode_json decode_json to_json from_json);	111	our @EXPORT = qw(encode_json decode_json to_json from_json);
109		112
110	sub to_json($) {	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
		712	is much more efficient (and can be implemented with a minimum of method
		713	calls).
		714
		715	JSON::XS will only attempt to parse the JSON text once it is sure it
		716	has enough text to get a decisive result, using a very simple but
		717	truly incremental parser. This means that it sometimes won't stop as
		718	early as the full parser, for example, it doesn't detect parenthese
		719	mismatches. The only thing it guarantees is that it starts decoding as
		720	soon as a syntactically valid JSON text has been seen. This means you need
		721	to set resource limits (e.g. C<max_size>) to ensure the parser will stop
		722	parsing in the presence if syntax errors.
		723
		724	The following methods implement this incremental parser.
		725
		726	=over 4
		727
		728	=item [void, scalar or list context] = $json->incr_parse ([$string])
		729
		730	This is the central parsing function. It can both append new text and
		731	extract objects from the stream accumulated so far (both of these
		732	functions are optional).
		733
		734	If C<$string> is given, then this string is appended to the already
		735	existing JSON fragment stored in the C<$json> object.
		736
		737	After that, if the function is called in void context, it will simply
		738	return without doing anything further. This can be used to add more text
		739	in as many chunks as you want.
		740
		741	If the method is called in scalar context, then it will try to extract
		742	exactly I<one> JSON object. If that is successful, it will return this
		743	object, otherwise it will return C<undef>. If there is a parse error,
		744	this method will croak just as C<decode> would do (one can then use
		745	C<incr_skip> to skip the errornous part). This is the most common way of
		746	using the method.
		747
		748	And finally, in list context, it will try to extract as many objects
		749	from the stream as it can find and return them, or the empty list
		750	otherwise. For this to work, there must be no separators between the JSON
		751	objects or arrays, instead they must be concatenated back-to-back. If
		752	an error occurs, an exception will be raised as in the scalar context
		753	case. Note that in this case, any previously-parsed JSON texts will be
		754	lost.
		755
		756	=item $lvalue_string = $json->incr_text
		757
		758	This method returns the currently stored JSON fragment as an lvalue, that
		759	is, you can manipulate it. This I<only> works when a preceding call to
		760	C<incr_parse> in I<scalar context> successfully returned an object. Under
		761	all other circumstances you must not call this function (I mean it.
		762	although in simple tests it might actually work, it I<will> fail under
		763	real world conditions). As a special exception, you can also call this
		764	method before having parsed anything.
		765
		766	This function is useful in two cases: a) finding the trailing text after a
		767	JSON object or b) parsing multiple JSON objects separated by non-JSON text
		768	(such as commas).
		769
		770	=item $json->incr_skip
		771
		772	This will reset the state of the incremental parser and will remove the
		773	parsed text from the input buffer. This is useful after C<incr_parse>
		774	died, in which case the input buffer and incremental parser state is left
		775	unchanged, to skip the text parsed so far and to reset the parse state.
		776
		777	=item $json->incr_reset
		778
		779	This completely resets the incremental parser, that is, after this call,
		780	it will be as if the parser had never parsed anything.
		781
		782	This is useful if you want ot repeatedly parse JSON objects and want to
		783	ignore any trailing data, which means you have to reset the parser after
		784	each successful decode.
		785
		786	=back
		787
		788	=head2 LIMITATIONS
		789
		790	All options that affect decoding are supported, except
		791	C<allow_nonref>. The reason for this is that it cannot be made to
		792	work sensibly: JSON objects and arrays are self-delimited, i.e. you can concatenate
		793	them back to back and still decode them perfectly. This does not hold true
		794	for JSON numbers, however.
		795
		796	For example, is the string C<1> a single JSON number, or is it simply the
		797	start of C<12>? Or is C<12> a single JSON number, or the concatenation
		798	of C<1> and C<2>? In neither case you can tell, and this is why JSON::XS
		799	takes the conservative route and disallows this case.
		800
		801	=head2 EXAMPLES
		802
		803	Some examples will make all this clearer. First, a simple example that
		804	works similarly to C<decode_prefix>: We want to decode the JSON object at
		805	the start of a string and identify the portion after the JSON object:
		806
		807	my $text = "[1,2,3] hello";
		808
		809	my $json = new JSON::XS;
		810
		811	my $obj = $json->incr_parse ($text)
		812	or die "expected JSON object or array at beginning of string";
		813
		814	my $tail = $json->incr_text;
		815	# $tail now contains " hello"
		816
		817	Easy, isn't it?
		818
		819	Now for a more complicated example: Imagine a hypothetical protocol where
		820	you read some requests from a TCP stream, and each request is a JSON
		821	array, without any separation between them (in fact, it is often useful to
		822	use newlines as "separators", as these get interpreted as whitespace at
		823	the start of the JSON text, which makes it possible to test said protocol
		824	with C<telnet>...).
		825
		826	Here is how you'd do it (it is trivial to write this in an event-based
		827	manner):
		828
		829	my $json = new JSON::XS;
		830
		831	# read some data from the socket
		832	while (sysread $socket, my $buf, 4096) {
		833
		834	# split and decode as many requests as possible
		835	for my $request ($json->incr_parse ($buf)) {
		836	# act on the $request
		837	}
		838	}
		839
		840	Another complicated example: Assume you have a string with JSON objects
		841	or arrays, all separated by (optional) comma characters (e.g. C<[1],[2],
		842	[3]>). To parse them, we have to skip the commas between the JSON texts,
		843	and here is where the lvalue-ness of C<incr_text> comes in useful:
		844
		845	my $text = "[1],[2], [3]";
		846	my $json = new JSON::XS;
		847
		848	# void context, so no parsing done
		849	$json->incr_parse ($text);
		850
		851	# now extract as many objects as possible. note the
		852	# use of scalar context so incr_text can be called.
		853	while (my $obj = $json->incr_parse) {
		854	# do something with $obj
		855
		856	# now skip the optional comma
		857	$json->incr_text =~ s/^ \s* , //x;
		858	}
		859
		860	Now lets go for a very complex example: Assume that you have a gigantic
		861	JSON array-of-objects, many gigabytes in size, and you want to parse it,
		862	but you cannot load it into memory fully (this has actually happened in
		863	the real world :).
		864
		865	Well, you lost, you have to implement your own JSON parser. But JSON::XS
		866	can still help you: You implement a (very simple) array parser and let
		867	JSON decode the array elements, which are all full JSON objects on their
		868	own (this wouldn't work if the array elements could be JSON numbers, for
		869	example):
		870
		871	my $json = new JSON::XS;
		872
		873	# open the monster
		874	open my $fh, "<bigfile.json"
		875	or die "bigfile: $!";
		876
		877	# first parse the initial "["
		878	for (;;) {
		879	sysread $fh, my $buf, 65536
		880	or die "read error: $!";
		881	$json->incr_parse ($buf); # void context, so no parsing
		882
		883	# Exit the loop once we found and removed(!) the initial "[".
		884	# In essence, we are (ab-)using the $json object as a simple scalar
		885	# we append data to.
		886	last if $json->incr_text =~ s/^ \s* \[ //x;
		887	}
		888
		889	# now we have the skipped the initial "[", so continue
		890	# parsing all the elements.
		891	for (;;) {
		892	# in this loop we read data until we got a single JSON object
		893	for (;;) {
		894	if (my $obj = $json->incr_parse) {
		895	# do something with $obj
		896	last;
		897	}
		898
		899	# add more data
		900	sysread $fh, my $buf, 65536
		901	or die "read error: $!";
		902	$json->incr_parse ($buf); # void context, so no parsing
		903	}
		904
		905	# in this loop we read data until we either found and parsed the
		906	# separating "," between elements, or the final "]"
		907	for (;;) {
		908	# first skip whitespace
		909	$json->incr_text =~ s/^\s*//;
		910
		911	# if we find "]", we are done
		912	if ($json->incr_text =~ s/^\]//) {
		913	print "finished.\n";
		914	exit;
		915	}
		916
		917	# if we find ",", we can continue with the next element
		918	if ($json->incr_text =~ s/^,//) {
		919	last;
		920	}
		921
		922	# if we find anything else, we have a parse error!
		923	if (length $json->incr_text) {
		924	die "parse error near ", $json->incr_text;
		925	}
		926
		927	# else add more data
		928	sysread $fh, my $buf, 65536
		929	or die "read error: $!";
		930	$json->incr_parse ($buf); # void context, so no parsing
		931	}
		932
		933	This is a complex example, but most of the complexity comes from the fact
		934	that we are trying to be correct (bear with me if I am wrong, I never ran
		935	the above example :).
		936
		937
		938
674	=head1 MAPPING	939	=head1 MAPPING
675		940
676	This section describes how JSON::XS maps Perl values to JSON values and	941	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	942	vice versa. These mappings are designed to "do the right thing" in most
678	circumstances automatically, preserving round-tripping characteristics	943	circumstances automatically, preserving round-tripping characteristics
…		…
706		971
707	A JSON number becomes either an integer, numeric (floating point) or	972	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	973	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	974	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	975	the conversion details, but an integer may take slightly less memory and
711	might represent more values exactly than (floating point) numbers.	976	might represent more values exactly than floating point numbers.
712		977
713	If the number consists of digits only, JSON::XS will try to represent	978	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	979	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	980	a numeric (floating point) value if that is possible without loss of
716	precision. Otherwise it will preserve the number as a string value.	981	precision. Otherwise it will preserve the number as a string value (in
		982	which case you lose roundtripping ability, as the JSON number will be
		983	re-encoded toa JSON string).
717		984
718	Numbers containing a fractional or exponential part will always be	985	Numbers containing a fractional or exponential part will always be
719	represented as numeric (floating point) values, possibly at a loss of	986	represented as numeric (floating point) values, possibly at a loss of
720	precision.	987	precision (in which case you might lose perfect roundtripping ability, but
721		988	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		989
725	=item true, false	990	=item true, false
726		991
727	These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,	992	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	993	respectively. They are overloaded to act almost exactly like the numbers
…		…
765	Other unblessed references are generally not allowed and will cause an	1030	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	1031	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	1032	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.	1033	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
769		1034
770	encode_json [\0,JSON::XS::true] # yields [false,true]	1035	encode_json [\0, JSON::XS::true] # yields [false,true]
771		1036
772	=item JSON::XS::true, JSON::XS::false	1037	=item JSON::XS::true, JSON::XS::false
773		1038
774	These special values become JSON true and JSON false values,	1039	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.	1040	respectively. You can also use C<\1> and C<\0> directly if you want.
…		…
813	my $x = "3"; # some variable containing a string	1078	my $x = "3"; # some variable containing a string
814	$x += 0; # numify it, ensuring it will be dumped as a number	1079	$x += 0; # numify it, ensuring it will be dumped as a number
815	$x *= 1; # same thing, the choice is yours.	1080	$x *= 1; # same thing, the choice is yours.
816		1081
817	You can not currently force the type in other, less obscure, ways. Tell me	1082	You can not currently force the type in other, less obscure, ways. Tell me
818	if you need this capability (but don't forget to explain why its needed	1083	if you need this capability (but don't forget to explain why it's needed
819	:).	1084	:).
820		1085
821	=back	1086	=back
822		1087
823		1088
824	=head1 COMPARISON	1089	=head1 ENCODING/CODESET FLAG NOTES
825		1090
826	As already mentioned, this module was created because none of the existing	1091	The interested reader might have seen a number of flags that signify
827	JSON modules could be made to work correctly. First I will describe the	1092	encodings or codesets - C<utf8>, C<latin1> and C<ascii>. There seems to be
828	problems (or pleasures) I encountered with various existing JSON modules,	1093	some confusion on what these do, so here is a short comparison:
829	followed by some benchmark values. JSON::XS was designed not to suffer	1094
830	from any of these problems or limitations.	1095	C<utf8> controls whether the JSON text created by C<encode> (and expected
		1096	by C<decode>) is UTF-8 encoded or not, while C<latin1> and C<ascii> only
		1097	control whether C<encode> escapes character values outside their respective
		1098	codeset range. Neither of these flags conflict with each other, although
		1099	some combinations make less sense than others.
		1100
		1101	Care has been taken to make all flags symmetrical with respect to
		1102	C<encode> and C<decode>, that is, texts encoded with any combination of
		1103	these flag values will be correctly decoded when the same flags are used
		1104	- in general, if you use different flag settings while encoding vs. when
		1105	decoding you likely have a bug somewhere.
		1106
		1107	Below comes a verbose discussion of these flags. Note that a "codeset" is
		1108	simply an abstract set of character-codepoint pairs, while an encoding
		1109	takes those codepoint numbers and I<encodes> them, in our case into
		1110	octets. Unicode is (among other things) a codeset, UTF-8 is an encoding,
		1111	and ISO-8859-1 (= latin 1) and ASCII are both codesets I<and> encodings at
		1112	the same time, which can be confusing.
831		1113
832	=over 4	1114	=over 4
833		1115
834	=item JSON 1.07	1116	=item C<utf8> flag disabled
835		1117
836	Slow (but very portable, as it is written in pure Perl).	1118	When C<utf8> is disabled (the default), then C<encode>/C<decode> generate
		1119	and expect Unicode strings, that is, characters with high ordinal Unicode
		1120	values (> 255) will be encoded as such characters, and likewise such
		1121	characters are decoded as-is, no canges to them will be done, except
		1122	"(re-)interpreting" them as Unicode codepoints or Unicode characters,
		1123	respectively (to Perl, these are the same thing in strings unless you do
		1124	funny/weird/dumb stuff).
837		1125
838	Undocumented/buggy Unicode handling (how JSON handles Unicode values is	1126	This is useful when you want to do the encoding yourself (e.g. when you
839	undocumented. One can get far by feeding it Unicode strings and doing	1127	want to have UTF-16 encoded JSON texts) or when some other layer does
840	en-/decoding oneself, but Unicode escapes are not working properly).	1128	the encoding for you (for example, when printing to a terminal using a
		1129	filehandle that transparently encodes to UTF-8 you certainly do NOT want
		1130	to UTF-8 encode your data first and have Perl encode it another time).
841		1131
842	No round-tripping (strings get clobbered if they look like numbers, e.g.	1132	=item C<utf8> flag enabled
843	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
844	decode into the number 2.
845		1133
846	=item JSON::PC 0.01	1134	If the C<utf8>-flag is enabled, C<encode>/C<decode> will encode all
		1135	characters using the corresponding UTF-8 multi-byte sequence, and will
		1136	expect your input strings to be encoded as UTF-8, that is, no "character"
		1137	of the input string must have any value > 255, as UTF-8 does not allow
		1138	that.
847		1139
848	Very fast.	1140	The C<utf8> flag therefore switches between two modes: disabled means you
		1141	will get a Unicode string in Perl, enabled means you get an UTF-8 encoded
		1142	octet/binary string in Perl.
849		1143
850	Undocumented/buggy Unicode handling.	1144	=item C<latin1> or C<ascii> flags enabled
851		1145
852	No round-tripping.	1146	With C<latin1> (or C<ascii>) enabled, C<encode> will escape characters
		1147	with ordinal values > 255 (> 127 with C<ascii>) and encode the remaining
		1148	characters as specified by the C<utf8> flag.
853		1149
854	Has problems handling many Perl values (e.g. regex results and other magic	1150	If C<utf8> is disabled, then the result is also correctly encoded in those
855	values will make it croak).	1151	character sets (as both are proper subsets of Unicode, meaning that a
		1152	Unicode string with all character values < 256 is the same thing as a
		1153	ISO-8859-1 string, and a Unicode string with all character values < 128 is
		1154	the same thing as an ASCII string in Perl).
856		1155
857	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	1156	If C<utf8> is enabled, you still get a correct UTF-8-encoded string,
858	which is not a valid JSON text.	1157	regardless of these flags, just some more characters will be escaped using
		1158	C<\uXXXX> then before.
859		1159
860	Unmaintained (maintainer unresponsive for many months, bugs are not	1160	Note that ISO-8859-1-I<encoded> strings are not compatible with UTF-8
861	getting fixed).	1161	encoding, while ASCII-encoded strings are. That is because the ISO-8859-1
		1162	encoding is NOT a subset of UTF-8 (despite the ISO-8859-1 I<codeset> being
		1163	a subset of Unicode), while ASCII is.
862		1164
863	=item JSON::Syck 0.21	1165	Surprisingly, C<decode> will ignore these flags and so treat all input
		1166	values as governed by the C<utf8> flag. If it is disabled, this allows you
		1167	to decode ISO-8859-1- and ASCII-encoded strings, as both strict subsets of
		1168	Unicode. If it is enabled, you can correctly decode UTF-8 encoded strings.
864		1169
865	Very buggy (often crashes).	1170	So neither C<latin1> nor C<ascii> are incompatible with the C<utf8> flag -
		1171	they only govern when the JSON output engine escapes a character or not.
866		1172
867	Very inflexible (no human-readable format supported, format pretty much	1173	The main use for C<latin1> is to relatively efficiently store binary data
868	undocumented. I need at least a format for easy reading by humans and a	1174	as JSON, at the expense of breaking compatibility with most JSON decoders.
869	single-line compact format for use in a protocol, and preferably a way to
870	generate ASCII-only JSON texts).
871		1175
872	Completely broken (and confusingly documented) Unicode handling (Unicode	1176	The main use for C<ascii> is to force the output to not contain characters
873	escapes are not working properly, you need to set ImplicitUnicode to	1177	with values > 127, which means you can interpret the resulting string
874	I<different> values on en- and decoding to get symmetric behaviour).	1178	as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about any character set and
875		1179	8-bit-encoding, and still get the same data structure back. This is useful
876	No round-tripping (simple cases work, but this depends on whether the scalar	1180	when your channel for JSON transfer is not 8-bit clean or the encoding
877	value was used in a numeric context or not).	1181	might be mangled in between (e.g. in mail), and works because ASCII is a
878		1182	proper subset of most 8-bit and multibyte encodings in use in the world.
879	Dumping hashes may skip hash values depending on iterator state.
880
881	Unmaintained (maintainer unresponsive for many months, bugs are not
882	getting fixed).
883
884	Does not check input for validity (i.e. will accept non-JSON input and
885	return "something" instead of raising an exception. This is a security
886	issue: imagine two banks transferring money between each other using
887	JSON. One bank might parse a given non-JSON request and deduct money,
888	while the other might reject the transaction with a syntax error. While a
889	good protocol will at least recover, that is extra unnecessary work and
890	the transaction will still not succeed).
891
892	=item JSON::DWIW 0.04
893
894	Very fast. Very natural. Very nice.
895
896	Undocumented Unicode handling (but the best of the pack. Unicode escapes
897	still don't get parsed properly).
898
899	Very inflexible.
900
901	No round-tripping.
902
903	Does not generate valid JSON texts (key strings are often unquoted, empty keys
904	result in nothing being output)
905
906	Does not check input for validity.
907		1183
908	=back	1184	=back
909		1185
910		1186
911	=head2 JSON and YAML	1187	=head2 JSON and YAML
912		1188
913	You often hear that JSON is a subset of YAML. This is, however, a mass	1189	You often hear that JSON is a subset of YAML. This is, however, a mass
914	hysteria(*) and very far from the truth. In general, there is no way to	1190	hysteria(*) and very far from the truth (as of the time of this writing),
		1191	so let me state it clearly: I<in general, there is no way to configure
915	configure JSON::XS to output a data structure as valid YAML that works for	1192	JSON::XS to output a data structure as valid YAML> that works in all
916	all cases.	1193	cases.
917		1194
918	If you really must use JSON::XS to generate YAML, you should use this	1195	If you really must use JSON::XS to generate YAML, you should use this
919	algorithm (subject to change in future versions):	1196	algorithm (subject to change in future versions):
920		1197
921	my $to_yaml = JSON::XS->new->utf8->space_after (1);	1198	my $to_yaml = JSON::XS->new->utf8->space_after (1);
…		…
924	This will I<usually> generate JSON texts that also parse as valid	1201	This will I<usually> generate JSON texts that also parse as valid
925	YAML. Please note that YAML has hardcoded limits on (simple) object key	1202	YAML. Please note that YAML has hardcoded limits on (simple) object key
926	lengths that JSON doesn't have and also has different and incompatible	1203	lengths that JSON doesn't have and also has different and incompatible
927	unicode handling, so you should make sure that your hash keys are	1204	unicode handling, so you should make sure that your hash keys are
928	noticeably shorter than the 1024 "stream characters" YAML allows and that	1205	noticeably shorter than the 1024 "stream characters" YAML allows and that
929	you do not have codepoints with values outside the Unicode BMP (basic	1206	you do not have characters with codepoint values outside the Unicode BMP
930	multilingual page). YAML also does not allow C<\/> sequences in strings	1207	(basic multilingual page). YAML also does not allow C<\/> sequences in
931	(which JSON::XS does not I<currently> generate).	1208	strings (which JSON::XS does not I<currently> generate, but other JSON
		1209	generators might).
932		1210
933	There might be other incompatibilities that I am not aware of (or the YAML	1211	There might be other incompatibilities that I am not aware of (or the YAML
934	specification has been changed yet again - it does so quite often). In	1212	specification has been changed yet again - it does so quite often). In
935	general you should not try to generate YAML with a JSON generator or vice	1213	general you should not try to generate YAML with a JSON generator or vice
936	versa, or try to parse JSON with a YAML parser or vice versa: chances are	1214	versa, or try to parse JSON with a YAML parser or vice versa: chances are
…		…
939		1217
940	=over 4	1218	=over 4
941		1219
942	=item (*)	1220	=item (*)
943		1221
944	This is spread actively by the YAML team, however. For many years now they	1222	I have been pressured multiple times by Brian Ingerson (one of the
945	claim YAML were a superset of JSON, even when proven otherwise.	1223	authors of the YAML specification) to remove this paragraph, despite him
		1224	acknowledging that the actual incompatibilities exist. As I was personally
		1225	bitten by this "JSON is YAML" lie, I refused and said I will continue to
		1226	educate people about these issues, so others do not run into the same
		1227	problem again and again. After this, Brian called me a (quote)I<complete
		1228	and worthless idiot>(unquote).
946		1229
947	Even the author of this manpage was at some point accused of providing	1230	In my opinion, instead of pressuring and insulting people who actually
948	"incorrect" information, despite the evidence presented (claims ranged	1231	clarify issues with YAML and the wrong statements of some of its
949	from "your documentation contains inaccurate and negative statements about	1232	proponents, I would kindly suggest reading the JSON spec (which is not
950	YAML" (the only negative comment is this footnote, and it didn't exist	1233	that difficult or long) and finally make YAML compatible to it, and
951	back then; the question on which claims were inaccurate was never answered	1234	educating users about the changes, instead of spreading lies about the
952	etc.) to "the YAML spec is not up-to-date" (the real and supposedly	1235	real compatibility for many I<years> and trying to silence people who
953	JSON-compatible spec is apparently not currently publicly available)	1236	point out that it isn't true.
954	to actual requests to replace this section by incorrect information,
955	suppressing information about the real problem).
956
957	So whenever you are told that YAML was a superset of JSON, first check
958	wether it is really true (it might be when you check it, but it certainly
959	was not true when this was written). I would much prefer if the YAML team
960	would spent their time on actually making JSON compatibility a truth
961	(JSON, after all, has a very small and simple specification) instead of
962	trying to lobby/force people into reporting untruths.
963		1237
964	=back	1238	=back
965		1239
966		1240
967	=head2 SPEED	1241	=head2 SPEED
…		…
969	It seems that JSON::XS is surprisingly fast, as shown in the following	1243	It seems that JSON::XS is surprisingly fast, as shown in the following
970	tables. They have been generated with the help of the C<eg/bench> program	1244	tables. They have been generated with the help of the C<eg/bench> program
971	in the JSON::XS distribution, to make it easy to compare on your own	1245	in the JSON::XS distribution, to make it easy to compare on your own
972	system.	1246	system.
973		1247
974	First comes a comparison between various modules using a very short	1248	First comes a comparison between various modules using
975	single-line JSON string:	1249	a very short single-line JSON string (also available at
		1250	L<http://dist.schmorp.de/misc/json/short.json>).
976		1251
977	{"method": "handleMessage", "params": ["user1", "we were just talking"], \	1252	{"method": "handleMessage", "params": ["user1",
978	"id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}	1253	"we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
		1254	true, false]}
979		1255
980	It shows the number of encodes/decodes per second (JSON::XS uses	1256	It shows the number of encodes/decodes per second (JSON::XS uses
981	the functional interface, while JSON::XS/2 uses the OO interface	1257	the functional interface, while JSON::XS/2 uses the OO interface
982	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables	1258	with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
983	shrink). Higher is better:	1259	shrink). Higher is better:
…		…
999	about three times faster on decoding, and over forty times faster	1275	about three times faster on decoding, and over forty times faster
1000	than JSON, even with pretty-printing and key sorting. It also compares	1276	than JSON, even with pretty-printing and key sorting. It also compares
1001	favourably to Storable for small amounts of data.	1277	favourably to Storable for small amounts of data.
1002		1278
1003	Using a longer test string (roughly 18KB, generated from Yahoo! Locals	1279	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
1004	search API (http://nanoref.com/yahooapis/mgPdGg):	1280	search API (L<http://dist.schmorp.de/misc/json/long.json>).
1005		1281
1006	module \| encode \| decode \|	1282	module \| encode \| decode \|
1007	-----------\|------------\|------------\|	1283	-----------\|------------\|------------\|
1008	JSON 1.x \| 55.260 \| 34.971 \|	1284	JSON 1.x \| 55.260 \| 34.971 \|
1009	JSON::DWIW \| 825.228 \| 1082.513 \|	1285	JSON::DWIW \| 825.228 \| 1082.513 \|
…		…
1051	to free the temporary). If that is exceeded, the program crashes. To be	1327	to free the temporary). If that is exceeded, the program crashes. To be
1052	conservative, the default nesting limit is set to 512. If your process	1328	conservative, the default nesting limit is set to 512. If your process
1053	has a smaller stack, you should adjust this setting accordingly with the	1329	has a smaller stack, you should adjust this setting accordingly with the
1054	C<max_depth> method.	1330	C<max_depth> method.
1055		1331
1056	And last but least, something else could bomb you that I forgot to think	1332	Something else could bomb you, too, that I forgot to think of. In that
1057	of. In that case, you get to keep the pieces. I am always open for hints,	1333	case, you get to keep the pieces. I am always open for hints, though...
1058	though...	1334
		1335	Also keep in mind that JSON::XS might leak contents of your Perl data
		1336	structures in its error messages, so when you serialise sensitive
		1337	information you might want to make sure that exceptions thrown by JSON::XS
		1338	will not end up in front of untrusted eyes.
1059		1339
1060	If you are using JSON::XS to return packets to consumption	1340	If you are using JSON::XS to return packets to consumption
1061	by JavaScript scripts in a browser you should have a look at	1341	by JavaScript scripts in a browser you should have a look at
1062	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether	1342	L<http://jpsykes.com/47/practical-csrf-and-json-security> to see whether
1063	you are vulnerable to some common attack vectors (which really are browser	1343	you are vulnerable to some common attack vectors (which really are browser
…		…
1069	=head1 THREADS	1349	=head1 THREADS
1070		1350
1071	This module is I<not> guaranteed to be thread safe and there are no	1351	This module is I<not> guaranteed to be thread safe and there are no
1072	plans to change this until Perl gets thread support (as opposed to the	1352	plans to change this until Perl gets thread support (as opposed to the
1073	horribly slow so-called "threads" which are simply slow and bloated	1353	horribly slow so-called "threads" which are simply slow and bloated
1074	process simulations - use fork, its I<much> faster, cheaper, better).	1354	process simulations - use fork, it's I<much> faster, cheaper, better).
1075		1355
1076	(It might actually work, but you have been warned).	1356	(It might actually work, but you have been warned).
1077		1357
1078		1358
1079	=head1 BUGS	1359	=head1 BUGS
1080		1360
1081	While the goal of this module is to be correct, that unfortunately does	1361	While the goal of this module is to be correct, that unfortunately does
1082	not mean its bug-free, only that I think its design is bug-free. It is	1362	not mean it's bug-free, only that I think its design is bug-free. If you
1083	still relatively early in its development. If you keep reporting bugs they	1363	keep reporting bugs they will be fixed swiftly, though.
1084	will be fixed swiftly, though.
1085		1364
1086	Please refrain from using rt.cpan.org or any other bug reporting	1365	Please refrain from using rt.cpan.org or any other bug reporting
1087	service. I put the contact address into my modules for a reason.	1366	service. I put the contact address into my modules for a reason.
1088		1367
1089	=cut	1368	=cut
…		…
1109	"--" => sub { $_[0] = ${$_[0]} - 1 },	1388	"--" => sub { $_[0] = ${$_[0]} - 1 },
1110	fallback => 1;	1389	fallback => 1;
1111		1390
1112	1;	1391	1;
1113		1392
		1393	=head1 SEE ALSO
		1394
		1395	The F<json_xs> command line utility for quick experiments.
		1396
1114	=head1 AUTHOR	1397	=head1 AUTHOR
1115		1398
1116	Marc Lehmann <schmorp@schmorp.de>	1399	Marc Lehmann <schmorp@schmorp.de>
1117	http://home.schmorp.de/	1400	http://home.schmorp.de/
1118		1401

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Comparing JSON-XS/XS.pm (file contents): Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs. Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC

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Comparing JSON-XS/XS.pm (file contents):
Revision 1.83 by root, Sun Jan 20 19:19:07 2008 UTC vs.
Revision 1.108 by root, Tue Jul 15 11:29:29 2008 UTC