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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.2 by root, Thu Mar 22 17:28:50 2007 UTC vs.
Revision 1.24 by root, Thu Mar 29 01:27:36 2007 UTC

…		…
3	JSON::XS - JSON serialising/deserialising, done correctly and fast	3	JSON::XS - JSON serialising/deserialising, done correctly and fast
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use JSON::XS;	7	use JSON::XS;
		8
		9	# exported functions, they croak on error
		10	# and expect/generate UTF-8
		11
		12	$utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
		13	$perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
		14
		15	# objToJson and jsonToObj aliases to to_json and from_json
		16	# are exported for compatibility to the JSON module,
		17	# but should not be used in new code.
		18
		19	# OO-interface
		20
		21	$coder = JSON::XS->new->ascii->pretty->allow_nonref;
		22	$pretty_printed_unencoded = $coder->encode ($perl_scalar);
		23	$perl_scalar = $coder->decode ($unicode_json_text);
8		24
9	=head1 DESCRIPTION	25	=head1 DESCRIPTION
10		26
11	This module converts Perl data structures to JSON and vice versa. Its	27	This module converts Perl data structures to JSON and vice versa. Its
12	primary goal is to be I<correct> and its secondary goal is to be	28	primary goal is to be I<correct> and its secondary goal is to be
…		…
18	their maintainers are unresponsive, gone missing, or not listening to bug	34	their maintainers are unresponsive, gone missing, or not listening to bug
19	reports for other reasons.	35	reports for other reasons.
20		36
21	See COMPARISON, below, for a comparison to some other JSON modules.	37	See COMPARISON, below, for a comparison to some other JSON modules.
22		38
		39	See MAPPING, below, on how JSON::XS maps perl values to JSON values and
		40	vice versa.
		41
23	=head2 FEATURES	42	=head2 FEATURES
24		43
25	=over 4	44	=over 4
26		45
27	=item * correct handling of unicode issues	46	=item * correct unicode handling
28		47
29	This module knows how to handle Unicode, and even documents how it does so.	48	This module knows how to handle Unicode, and even documents how and when
		49	it does so.
30		50
31	=item * round-trip integrity	51	=item * round-trip integrity
32		52
33	When you serialise a perl data structure using only datatypes supported	53	When you serialise a perl data structure using only datatypes supported
34	by JSON, the deserialised data structure is identical on the Perl level.	54	by JSON, the deserialised data structure is identical on the Perl level.
35	(e.g. the string "2.0" doesn't suddenly become "2").	55	(e.g. the string "2.0" doesn't suddenly become "2" just because it looks
		56	like a number).
36		57
37	=item * strict checking of JSON correctness	58	=item * strict checking of JSON correctness
38		59
39	There is no guessing, no generating of illegal JSON strings by default,	60	There is no guessing, no generating of illegal JSON texts by default,
40	and only JSON is accepted as input (the latter is a security feature).	61	and only JSON is accepted as input by default (the latter is a security
		62	feature).
41		63
42	=item * fast	64	=item * fast
43		65
44	compared to other JSON modules, this module compares favourably.	66	Compared to other JSON modules, this module compares favourably in terms
		67	of speed, too.
45		68
46	=item * simple to use	69	=item * simple to use
47		70
48	This module has both a simple functional interface as well as an OO	71	This module has both a simple functional interface as well as an OO
49	interface.	72	interface.
50		73
51	=item * reasonably versatile output formats	74	=item * reasonably versatile output formats
52		75
53	You can choose between the most compact format possible, a pure-ascii	76	You can choose between the most compact guarenteed single-line format
54	format, or a pretty-printed format. Or you can combine those features in	77	possible (nice for simple line-based protocols), a pure-ascii format
55	whatever way you like.	78	(for when your transport is not 8-bit clean, still supports the whole
		79	unicode range), or a pretty-printed format (for when you want to read that
		80	stuff). Or you can combine those features in whatever way you like.
56		81
57	=back	82	=back
58		83
59	=cut	84	=cut
60		85
61	package JSON::XS;	86	package JSON::XS;
62		87
		88	use strict;
		89
63	BEGIN {	90	BEGIN {
64	$VERSION = '0.1';	91	our $VERSION = '0.8';
65	@ISA = qw(Exporter);	92	our @ISA = qw(Exporter);
66		93
67	@EXPORT = qw(to_json from_json);	94	our @EXPORT = qw(to_json from_json objToJson jsonToObj);
68	require Exporter;	95	require Exporter;
69		96
70	require XSLoader;	97	require XSLoader;
71	XSLoader::load JSON::XS::, $VERSION;	98	XSLoader::load JSON::XS::, $VERSION;
72	}	99	}
…		…
76	The following convinience methods are provided by this module. They are	103	The following convinience methods are provided by this module. They are
77	exported by default:	104	exported by default:
78		105
79	=over 4	106	=over 4
80		107
81	=item $json_string = to_json $perl_scalar	108	=item $json_text = to_json $perl_scalar
82		109
83	Converts the given Perl data structure (a simple scalar or a reference to	110	Converts the given Perl data structure (a simple scalar or a reference to
84	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains	111	a hash or array) to a UTF-8 encoded, binary string (that is, the string contains
85	octets only). Croaks on error.	112	octets only). Croaks on error.
86		113
87	This function call is functionally identical to C<< JSON::XS->new->utf8	114	This function call is functionally identical to:
88	(1)->encode ($perl_scalar) >>.
89		115
		116	$json_text = JSON::XS->new->utf8->encode ($perl_scalar)
		117
		118	except being faster.
		119
90	=item $perl_scalar = from_json $json_string	120	=item $perl_scalar = from_json $json_text
91		121
92	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to	122	The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to
93	parse that as an UTF-8 encoded JSON string, returning the resulting simple	123	parse that as an UTF-8 encoded JSON text, returning the resulting simple
94	scalar or reference. Croaks on error.	124	scalar or reference. Croaks on error.
95		125
96	This function call is functionally identical to C<< JSON::XS->new->utf8	126	This function call is functionally identical to:
97	(1)->decode ($json_string) >>.	127
		128	$perl_scalar = JSON::XS->new->utf8->decode ($json_text)
		129
		130	except being faster.
98		131
99	=back	132	=back
		133
100		134
101	=head1 OBJECT-ORIENTED INTERFACE	135	=head1 OBJECT-ORIENTED INTERFACE
102		136
103	The object oriented interface lets you configure your own encoding or	137	The object oriented interface lets you configure your own encoding or
104	decoding style, within the limits of supported formats.	138	decoding style, within the limits of supported formats.
…		…
111	strings. All boolean flags described below are by default I<disabled>.	145	strings. All boolean flags described below are by default I<disabled>.
112		146
113	The mutators for flags all return the JSON object again and thus calls can	147	The mutators for flags all return the JSON object again and thus calls can
114	be chained:	148	be chained:
115		149
116	my $json = JSON::XS->new->utf8(1)->pretty(1)->encode ({a => [1,2]})	150	my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
117	=> {"a" : [1, 2]}	151	=> {"a": [1, 2]}
118		152
119	=item $json = $json->ascii ($enable)	153	=item $json = $json->ascii ([$enable])
120		154
121	If C<$enable> is true, then the C<encode> method will not generate	155	If C<$enable> is true (or missing), then the C<encode> method will not
122	characters outside the code range C<0..127>. Any unicode characters	156	generate characters outside the code range C<0..127> (which is ASCII). Any
123	outside that range will be escaped using either a single \uXXXX (BMP	157	unicode characters outside that range will be escaped using either a
124	characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627.	158	single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence,
		159	as per RFC4627.
125		160
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	161	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	162	characters unless required by the JSON syntax. This results in a faster
		163	and more compact format.
128		164
		165	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
		166	=> ["\ud801\udc01"]
		167
129	=item $json = $json->utf8 ($enable)	168	=item $json = $json->utf8 ([$enable])
130		169
131	If C<$enable> is true, then the C<encode> method will encode the JSON	170	If C<$enable> is true (or missing), then the C<encode> method will encode
132	string into UTF-8, as required by many protocols, while the C<decode>	171	the JSON result into UTF-8, as required by many protocols, while the
133	method expects to be handled an UTF-8-encoded string. Please note that	172	C<decode> method expects to be handled an UTF-8-encoded string. Please
134	UTF-8-encoded strings do not contain any characters outside the range	173	note that UTF-8-encoded strings do not contain any characters outside the
135	C<0..255>, they are thus useful for bytewise/binary I/O.	174	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		175	versions, enabling this option might enable autodetection of the UTF-16
		176	and UTF-32 encoding families, as described in RFC4627.
136		177
137	If C<$enable> is false, then the C<encode> method will return the JSON	178	If C<$enable> is false, then the C<encode> method will return the JSON
138	string as a (non-encoded) unicode string, while C<decode> expects thus a	179	string as a (non-encoded) unicode string, while C<decode> expects thus a
139	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	180	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
140	to be done yourself, e.g. using the Encode module.	181	to be done yourself, e.g. using the Encode module.
141		182
		183	Example, output UTF-16BE-encoded JSON:
		184
		185	use Encode;
		186	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		187
		188	Example, decode UTF-32LE-encoded JSON:
		189
		190	use Encode;
		191	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		192
142	=item $json = $json->pretty ($enabla)	193	=item $json = $json->pretty ([$enable])
143		194
144	This enables (or disables) all of the C<indent>, C<space_before> and	195	This enables (or disables) all of the C<indent>, C<space_before> and
145	C<space_after> (and in the future possibly more) settings in one call to	196	C<space_after> (and in the future possibly more) flags in one call to
146	generate the most readable (or most compact) form possible.	197	generate the most readable (or most compact) form possible.
147		198
		199	Example, pretty-print some simple structure:
		200
		201	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
		202	=>
		203	{
		204	"a" : [
		205	1,
		206	2
		207	]
		208	}
		209
148	=item $json = $json->indent ($enable)	210	=item $json = $json->indent ([$enable])
149		211
150	If C<$enable> is true, then the C<encode> method will use a multiline	212	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
151	format as output, putting every array member or object/hash key-value pair	213	format as output, putting every array member or object/hash key-value pair
152	into its own line, identing them properly.	214	into its own line, identing them properly.
153		215
154	If C<$enable> is false, no newlines or indenting will be produced, and the	216	If C<$enable> is false, no newlines or indenting will be produced, and the
155	resulting JSON strings is guarenteed not to contain any C<newlines>.	217	resulting JSON text is guarenteed not to contain any C<newlines>.
156		218
157	This setting has no effect when decoding JSON strings.	219	This setting has no effect when decoding JSON texts.
158		220
159	=item $json = $json->space_before ($enable)	221	=item $json = $json->space_before ([$enable])
160		222
161	If C<$enable> is true, then the C<encode> method will add an extra	223	If C<$enable> is true (or missing), then the C<encode> method will add an extra
162	optional space before the C<:> separating keys from values in JSON objects.	224	optional space before the C<:> separating keys from values in JSON objects.
163		225
164	If C<$enable> is false, then the C<encode> method will not add any extra	226	If C<$enable> is false, then the C<encode> method will not add any extra
165	space at those places.	227	space at those places.
166		228
167	This setting has no effect when decoding JSON strings. You will also most	229	This setting has no effect when decoding JSON texts. You will also
168	likely combine this setting with C<space_after>.	230	most likely combine this setting with C<space_after>.
169		231
		232	Example, space_before enabled, space_after and indent disabled:
		233
		234	{"key" :"value"}
		235
170	=item $json = $json->space_after ($enable)	236	=item $json = $json->space_after ([$enable])
171		237
172	If C<$enable> is true, then the C<encode> method will add an extra	238	If C<$enable> is true (or missing), then the C<encode> method will add an extra
173	optional space after the C<:> separating keys from values in JSON objects	239	optional space after the C<:> separating keys from values in JSON objects
174	and extra whitespace after the C<,> separating key-value pairs and array	240	and extra whitespace after the C<,> separating key-value pairs and array
175	members.	241	members.
176		242
177	If C<$enable> is false, then the C<encode> method will not add any extra	243	If C<$enable> is false, then the C<encode> method will not add any extra
178	space at those places.	244	space at those places.
179		245
180	This setting has no effect when decoding JSON strings.	246	This setting has no effect when decoding JSON texts.
181		247
		248	Example, space_before and indent disabled, space_after enabled:
		249
		250	{"key": "value"}
		251
182	=item $json = $json->canonical ($enable)	252	=item $json = $json->canonical ([$enable])
183		253
184	If C<$enable> is true, then the C<encode> method will output JSON objects	254	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
185	by sorting their keys. This is adding a comparatively high overhead.	255	by sorting their keys. This is adding a comparatively high overhead.
186		256
187	If C<$enable> is false, then the C<encode> method will output key-value	257	If C<$enable> is false, then the C<encode> method will output key-value
188	pairs in the order Perl stores them (which will likely change between runs	258	pairs in the order Perl stores them (which will likely change between runs
189	of the same script).	259	of the same script).
190		260
191	This option is useful if you want the same data structure to be encoded as	261	This option is useful if you want the same data structure to be encoded as
192	the same JSON string (given the same overall settings). If it is disabled,	262	the same JSON text (given the same overall settings). If it is disabled,
193	the same hash migh be encoded differently even if contains the same data,	263	the same hash migh be encoded differently even if contains the same data,
194	as key-value pairs have no inherent ordering in Perl.	264	as key-value pairs have no inherent ordering in Perl.
195		265
196	This setting has no effect when decoding JSON strings.	266	This setting has no effect when decoding JSON texts.
197		267
		268	=item $json = $json->allow_nonref ([$enable])
		269
		270	If C<$enable> is true (or missing), then the C<encode> method can convert a
		271	non-reference into its corresponding string, number or null JSON value,
		272	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
		273	values instead of croaking.
		274
		275	If C<$enable> is false, then the C<encode> method will croak if it isn't
		276	passed an arrayref or hashref, as JSON texts must either be an object
		277	or array. Likewise, C<decode> will croak if given something that is not a
		278	JSON object or array.
		279
		280	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		281	resulting in an invalid JSON text:
		282
		283	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		284	=> "Hello, World!"
		285
		286	=item $json = $json->shrink ([$enable])
		287
		288	Perl usually over-allocates memory a bit when allocating space for
		289	strings. This flag optionally resizes strings generated by either
		290	C<encode> or C<decode> to their minimum size possible. This can save
		291	memory when your JSON texts are either very very long or you have many
		292	short strings. It will also try to downgrade any strings to octet-form
		293	if possible: perl stores strings internally either in an encoding called
		294	UTF-X or in octet-form. The latter cannot store everything but uses less
		295	space in general (and some buggy Perl or C code might even rely on that
		296	internal representation being used).
		297
		298	The actual definition of what shrink does might change in future versions,
		299	but it will always try to save space at the expense of time.
		300
		301	If C<$enable> is true (or missing), the string returned by C<encode> will
		302	be shrunk-to-fit, while all strings generated by C<decode> will also be
		303	shrunk-to-fit.
		304
		305	If C<$enable> is false, then the normal perl allocation algorithms are used.
		306	If you work with your data, then this is likely to be faster.
		307
		308	In the future, this setting might control other things, such as converting
		309	strings that look like integers or floats into integers or floats
		310	internally (there is no difference on the Perl level), saving space.
		311
		312	=item $json = $json->max_depth ([$maximum_nesting_depth])
		313
		314	Sets the maximum nesting level (default C<8192>) accepted while encoding
		315	or decoding. If the JSON text or Perl data structure has an equal or
		316	higher nesting level then this limit, then the encoder and decoder will
		317	stop and croak at that point.
		318
		319	Nesting level is defined by number of hash- or arrayrefs that the encoder
		320	needs to traverse to reach a given point or the number of C<{> or C<[>
		321	characters without their matching closing parenthesis crossed to reach a
		322	given character in a string.
		323
		324	Setting the maximum depth to one disallows any nesting, so that ensures
		325	that the object is only a single hash/object or array.
		326
		327	The argument to C<max_depth> will be rounded up to the next nearest power
		328	of two.
		329
		330	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		331
198	=item $json_string = $json->encode ($perl_scalar)	332	=item $json_text = $json->encode ($perl_scalar)
199		333
200	Converts the given Perl data structure (a simple scalar or a reference	334	Converts the given Perl data structure (a simple scalar or a reference
201	to a hash or array) to its JSON representation. Simple scalars will be	335	to a hash or array) to its JSON representation. Simple scalars will be
202	converted into JSON string or number sequences, while references to arrays	336	converted into JSON string or number sequences, while references to arrays
203	become JSON arrays and references to hashes become JSON objects. Undefined	337	become JSON arrays and references to hashes become JSON objects. Undefined
204	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	338	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
205	nor C<false> values will be generated.	339	nor C<false> values will be generated.
206		340
207	=item $perl_scalar = $json->decode ($json_string)	341	=item $perl_scalar = $json->decode ($json_text)
208		342
209	The opposite of C<encode>: expects a JSON string and tries to parse it,	343	The opposite of C<encode>: expects a JSON text and tries to parse it,
210	returning the resulting simple scalar or reference. Croaks on error.	344	returning the resulting simple scalar or reference. Croaks on error.
211		345
212	JSON numbers and strings become simple Perl scalars. JSON arrays become	346	JSON numbers and strings become simple Perl scalars. JSON arrays become
213	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	347	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
214	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	348	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
215		349
216	=back	350	=back
217		351
		352
		353	=head1 MAPPING
		354
		355	This section describes how JSON::XS maps Perl values to JSON values and
		356	vice versa. These mappings are designed to "do the right thing" in most
		357	circumstances automatically, preserving round-tripping characteristics
		358	(what you put in comes out as something equivalent).
		359
		360	For the more enlightened: note that in the following descriptions,
		361	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		362	refers to the abstract Perl language itself.
		363
		364	=head2 JSON -> PERL
		365
		366	=over 4
		367
		368	=item object
		369
		370	A JSON object becomes a reference to a hash in Perl. No ordering of object
		371	keys is preserved (JSON does not preserver object key ordering itself).
		372
		373	=item array
		374
		375	A JSON array becomes a reference to an array in Perl.
		376
		377	=item string
		378
		379	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		380	are represented by the same codepoints in the Perl string, so no manual
		381	decoding is necessary.
		382
		383	=item number
		384
		385	A JSON number becomes either an integer or numeric (floating point)
		386	scalar in perl, depending on its range and any fractional parts. On the
		387	Perl level, there is no difference between those as Perl handles all the
		388	conversion details, but an integer may take slightly less memory and might
		389	represent more values exactly than (floating point) numbers.
		390
		391	=item true, false
		392
		393	These JSON atoms become C<0>, C<1>, respectively. Information is lost in
		394	this process. Future versions might represent those values differently,
		395	but they will be guarenteed to act like these integers would normally in
		396	Perl.
		397
		398	=item null
		399
		400	A JSON null atom becomes C<undef> in Perl.
		401
		402	=back
		403
		404	=head2 PERL -> JSON
		405
		406	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		407	truly typeless language, so we can only guess which JSON type is meant by
		408	a Perl value.
		409
		410	=over 4
		411
		412	=item hash references
		413
		414	Perl hash references become JSON objects. As there is no inherent ordering
		415	in hash keys, they will usually be encoded in a pseudo-random order that
		416	can change between runs of the same program but stays generally the same
		417	within a single run of a program. JSON::XS can optionally sort the hash
		418	keys (determined by the I<canonical> flag), so the same datastructure
		419	will serialise to the same JSON text (given same settings and version of
		420	JSON::XS), but this incurs a runtime overhead.
		421
		422	=item array references
		423
		424	Perl array references become JSON arrays.
		425
		426	=item blessed objects
		427
		428	Blessed objects are not allowed. JSON::XS currently tries to encode their
		429	underlying representation (hash- or arrayref), but this behaviour might
		430	change in future versions.
		431
		432	=item simple scalars
		433
		434	Simple Perl scalars (any scalar that is not a reference) are the most
		435	difficult objects to encode: JSON::XS will encode undefined scalars as
		436	JSON null value, scalars that have last been used in a string context
		437	before encoding as JSON strings and anything else as number value:
		438
		439	# dump as number
		440	to_json [2] # yields [2]
		441	to_json [-3.0e17] # yields [-3e+17]
		442	my $value = 5; to_json [$value] # yields [5]
		443
		444	# used as string, so dump as string
		445	print $value;
		446	to_json [$value] # yields ["5"]
		447
		448	# undef becomes null
		449	to_json [undef] # yields [null]
		450
		451	You can force the type to be a string by stringifying it:
		452
		453	my $x = 3.1; # some variable containing a number
		454	"$x"; # stringified
		455	$x .= ""; # another, more awkward way to stringify
		456	print $x; # perl does it for you, too, quite often
		457
		458	You can force the type to be a number by numifying it:
		459
		460	my $x = "3"; # some variable containing a string
		461	$x += 0; # numify it, ensuring it will be dumped as a number
		462	$x *= 1; # same thing, the choise is yours.
		463
		464	You can not currently output JSON booleans or force the type in other,
		465	less obscure, ways. Tell me if you need this capability.
		466
		467	=item circular data structures
		468
		469	Those will be encoded until memory or stackspace runs out.
		470
		471	=back
		472
		473
		474	=head1 COMPARISON
		475
		476	As already mentioned, this module was created because none of the existing
		477	JSON modules could be made to work correctly. First I will describe the
		478	problems (or pleasures) I encountered with various existing JSON modules,
		479	followed by some benchmark values. JSON::XS was designed not to suffer
		480	from any of these problems or limitations.
		481
		482	=over 4
		483
		484	=item JSON 1.07
		485
		486	Slow (but very portable, as it is written in pure Perl).
		487
		488	Undocumented/buggy Unicode handling (how JSON handles unicode values is
		489	undocumented. One can get far by feeding it unicode strings and doing
		490	en-/decoding oneself, but unicode escapes are not working properly).
		491
		492	No roundtripping (strings get clobbered if they look like numbers, e.g.
		493	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
		494	decode into the number 2.
		495
		496	=item JSON::PC 0.01
		497
		498	Very fast.
		499
		500	Undocumented/buggy Unicode handling.
		501
		502	No roundtripping.
		503
		504	Has problems handling many Perl values (e.g. regex results and other magic
		505	values will make it croak).
		506
		507	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		508	which is not a valid JSON text.
		509
		510	Unmaintained (maintainer unresponsive for many months, bugs are not
		511	getting fixed).
		512
		513	=item JSON::Syck 0.21
		514
		515	Very buggy (often crashes).
		516
		517	Very inflexible (no human-readable format supported, format pretty much
		518	undocumented. I need at least a format for easy reading by humans and a
		519	single-line compact format for use in a protocol, and preferably a way to
		520	generate ASCII-only JSON texts).
		521
		522	Completely broken (and confusingly documented) Unicode handling (unicode
		523	escapes are not working properly, you need to set ImplicitUnicode to
		524	I<different> values on en- and decoding to get symmetric behaviour).
		525
		526	No roundtripping (simple cases work, but this depends on wether the scalar
		527	value was used in a numeric context or not).
		528
		529	Dumping hashes may skip hash values depending on iterator state.
		530
		531	Unmaintained (maintainer unresponsive for many months, bugs are not
		532	getting fixed).
		533
		534	Does not check input for validity (i.e. will accept non-JSON input and
		535	return "something" instead of raising an exception. This is a security
		536	issue: imagine two banks transfering money between each other using
		537	JSON. One bank might parse a given non-JSON request and deduct money,
		538	while the other might reject the transaction with a syntax error. While a
		539	good protocol will at least recover, that is extra unnecessary work and
		540	the transaction will still not succeed).
		541
		542	=item JSON::DWIW 0.04
		543
		544	Very fast. Very natural. Very nice.
		545
		546	Undocumented unicode handling (but the best of the pack. Unicode escapes
		547	still don't get parsed properly).
		548
		549	Very inflexible.
		550
		551	No roundtripping.
		552
		553	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		554	result in nothing being output)
		555
		556	Does not check input for validity.
		557
		558	=back
		559
		560	=head2 SPEED
		561
		562	It seems that JSON::XS is surprisingly fast, as shown in the following
		563	tables. They have been generated with the help of the C<eg/bench> program
		564	in the JSON::XS distribution, to make it easy to compare on your own
		565	system.
		566
		567	First comes a comparison between various modules using a very short JSON
		568	string:
		569
		570	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
		571
		572	It shows the number of encodes/decodes per second (JSON::XS uses the
		573	functional interface, while JSON::XS/2 uses the OO interface with
		574	pretty-printing and hashkey sorting enabled). Higher is better:
		575
		576	module \| encode \| decode \|
		577	-----------\|------------\|------------\|
		578	JSON \| 11488.516 \| 7823.035 \|
		579	JSON::DWIW \| 94708.054 \| 129094.260 \|
		580	JSON::PC \| 63884.157 \| 128528.212 \|
		581	JSON::Syck \| 34898.677 \| 42096.911 \|
		582	JSON::XS \| 654027.064 \| 396423.669 \|
		583	JSON::XS/2 \| 371564.190 \| 371725.613 \|
		584	-----------+------------+------------+
		585
		586	That is, JSON::XS is more than six times faster than JSON::DWIW on
		587	encoding, more than three times faster on decoding, and about thirty times
		588	faster than JSON, even with pretty-printing and key sorting.
		589
		590	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		591	search API (http://nanoref.com/yahooapis/mgPdGg):
		592
		593	module \| encode \| decode \|
		594	-----------\|------------\|------------\|
		595	JSON \| 273.023 \| 44.674 \|
		596	JSON::DWIW \| 1089.383 \| 1145.704 \|
		597	JSON::PC \| 3097.419 \| 2393.921 \|
		598	JSON::Syck \| 514.060 \| 843.053 \|
		599	JSON::XS \| 6479.668 \| 3636.364 \|
		600	JSON::XS/2 \| 3774.221 \| 3599.124 \|
		601	-----------+------------+------------+
		602
		603	Again, JSON::XS leads by far.
		604
		605	On large strings containing lots of high unicode characters, some modules
		606	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		607	will be broken due to missing (or wrong) unicode handling. Others refuse
		608	to decode or encode properly, so it was impossible to prepare a fair
		609	comparison table for that case.
		610
		611
		612	=head1 SECURITY CONSIDERATIONS
		613
		614	When you are using JSON in a protocol, talking to untrusted potentially
		615	hostile creatures requires relatively few measures.
		616
		617	First of all, your JSON decoder should be secure, that is, should not have
		618	any buffer overflows. Obviously, this module should ensure that and I am
		619	trying hard on making that true, but you never know.
		620
		621	Second, you need to avoid resource-starving attacks. That means you should
		622	limit the size of JSON texts you accept, or make sure then when your
		623	resources run out, thats just fine (e.g. by using a separate process that
		624	can crash safely). The size of a JSON text in octets or characters is
		625	usually a good indication of the size of the resources required to decode
		626	it into a Perl structure.
		627
		628	Third, JSON::XS recurses using the C stack when decoding objects and
		629	arrays. The C stack is a limited resource: for instance, on my amd64
		630	machine with 8MB of stack size I can decode around 180k nested arrays
		631	but only 14k nested JSON objects. If that is exceeded, the program
		632	crashes. Thats why the default nesting limit is set to 8192. If your
		633	process has a smaller stack, you should adjust this setting accordingly
		634	with the C<max_depth> method.
		635
		636	And last but least, something else could bomb you that I forgot to think
		637	of. In that case, you get to keep the pieces. I am alway sopen for hints,
		638	though...
		639
		640
		641	=head1 BUGS
		642
		643	While the goal of this module is to be correct, that unfortunately does
		644	not mean its bug-free, only that I think its design is bug-free. It is
		645	still relatively early in its development. If you keep reporting bugs they
		646	will be fixed swiftly, though.
		647
218	=cut	648	=cut
219		649
220	1;	650	1;
221		651
222	=head1 AUTHOR	652	=head1 AUTHOR

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Revision 1.24 by root, Thu Mar 29 01:27:36 2007 UTC