[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 1.23 by root, Sun Mar 25 21:19:13 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.
		296
		297	If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit,
		298	while all strings generated by C<decode> will also be shrunk-to-fit.
		299
		300	If C<$enable> is false, then the normal perl allocation algorithms are used.
		301	If you work with your data, then this is likely to be faster.
		302
		303	In the future, this setting might control other things, such as converting
		304	strings that look like integers or floats into integers or floats
		305	internally (there is no difference on the Perl level), saving space.
		306
		307	=item $json = $json->max_depth ([$maximum_nesting_depth])
		308
		309	Sets the maximum nesting level (default C<8192>) accepted while encoding
		310	or decoding. If the JSON text or Perl data structure has an equal or
		311	higher nesting level then this limit, then the encoder and decoder will
		312	stop and croak at that point.
		313
		314	Nesting level is defined by number of hash- or arrayrefs that the encoder
		315	needs to traverse to reach a given point or the number of C<{> or C<[>
		316	characters without their matching closing parenthesis crossed to reach a
		317	given character in a string.
		318
		319	Setting the maximum depth to one disallows any nesting, so that ensures
		320	that the object is only a single hash/object or array.
		321
		322	The argument to C<max_depth> will be rounded up to the next nearest power
		323	of two.
		324
		325	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		326
198	=item $json_string = $json->encode ($perl_scalar)	327	=item $json_text = $json->encode ($perl_scalar)
199		328
200	Converts the given Perl data structure (a simple scalar or a reference	329	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	330	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	331	converted into JSON string or number sequences, while references to arrays
203	become JSON arrays and references to hashes become JSON objects. Undefined	332	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>	333	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
205	nor C<false> values will be generated.	334	nor C<false> values will be generated.
206		335
207	=item $perl_scalar = $json->decode ($json_string)	336	=item $perl_scalar = $json->decode ($json_text)
208		337
209	The opposite of C<encode>: expects a JSON string and tries to parse it,	338	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.	339	returning the resulting simple scalar or reference. Croaks on error.
211		340
212	JSON numbers and strings become simple Perl scalars. JSON arrays become	341	JSON numbers and strings become simple Perl scalars. JSON arrays become
213	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	342	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>.	343	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
215		344
216	=back	345	=back
217		346
		347
		348	=head1 MAPPING
		349
		350	This section describes how JSON::XS maps Perl values to JSON values and
		351	vice versa. These mappings are designed to "do the right thing" in most
		352	circumstances automatically, preserving round-tripping characteristics
		353	(what you put in comes out as something equivalent).
		354
		355	For the more enlightened: note that in the following descriptions,
		356	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		357	refers to the abstract Perl language itself.
		358
		359	=head2 JSON -> PERL
		360
		361	=over 4
		362
		363	=item object
		364
		365	A JSON object becomes a reference to a hash in Perl. No ordering of object
		366	keys is preserved (JSON does not preserver object key ordering itself).
		367
		368	=item array
		369
		370	A JSON array becomes a reference to an array in Perl.
		371
		372	=item string
		373
		374	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		375	are represented by the same codepoints in the Perl string, so no manual
		376	decoding is necessary.
		377
		378	=item number
		379
		380	A JSON number becomes either an integer or numeric (floating point)
		381	scalar in perl, depending on its range and any fractional parts. On the
		382	Perl level, there is no difference between those as Perl handles all the
		383	conversion details, but an integer may take slightly less memory and might
		384	represent more values exactly than (floating point) numbers.
		385
		386	=item true, false
		387
		388	These JSON atoms become C<0>, C<1>, respectively. Information is lost in
		389	this process. Future versions might represent those values differently,
		390	but they will be guarenteed to act like these integers would normally in
		391	Perl.
		392
		393	=item null
		394
		395	A JSON null atom becomes C<undef> in Perl.
		396
		397	=back
		398
		399	=head2 PERL -> JSON
		400
		401	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		402	truly typeless language, so we can only guess which JSON type is meant by
		403	a Perl value.
		404
		405	=over 4
		406
		407	=item hash references
		408
		409	Perl hash references become JSON objects. As there is no inherent ordering
		410	in hash keys, they will usually be encoded in a pseudo-random order that
		411	can change between runs of the same program but stays generally the same
		412	within a single run of a program. JSON::XS can optionally sort the hash
		413	keys (determined by the I<canonical> flag), so the same datastructure
		414	will serialise to the same JSON text (given same settings and version of
		415	JSON::XS), but this incurs a runtime overhead.
		416
		417	=item array references
		418
		419	Perl array references become JSON arrays.
		420
		421	=item blessed objects
		422
		423	Blessed objects are not allowed. JSON::XS currently tries to encode their
		424	underlying representation (hash- or arrayref), but this behaviour might
		425	change in future versions.
		426
		427	=item simple scalars
		428
		429	Simple Perl scalars (any scalar that is not a reference) are the most
		430	difficult objects to encode: JSON::XS will encode undefined scalars as
		431	JSON null value, scalars that have last been used in a string context
		432	before encoding as JSON strings and anything else as number value:
		433
		434	# dump as number
		435	to_json [2] # yields [2]
		436	to_json [-3.0e17] # yields [-3e+17]
		437	my $value = 5; to_json [$value] # yields [5]
		438
		439	# used as string, so dump as string
		440	print $value;
		441	to_json [$value] # yields ["5"]
		442
		443	# undef becomes null
		444	to_json [undef] # yields [null]
		445
		446	You can force the type to be a string by stringifying it:
		447
		448	my $x = 3.1; # some variable containing a number
		449	"$x"; # stringified
		450	$x .= ""; # another, more awkward way to stringify
		451	print $x; # perl does it for you, too, quite often
		452
		453	You can force the type to be a number by numifying it:
		454
		455	my $x = "3"; # some variable containing a string
		456	$x += 0; # numify it, ensuring it will be dumped as a number
		457	$x *= 1; # same thing, the choise is yours.
		458
		459	You can not currently output JSON booleans or force the type in other,
		460	less obscure, ways. Tell me if you need this capability.
		461
		462	=item circular data structures
		463
		464	Those will be encoded until memory or stackspace runs out.
		465
		466	=back
		467
		468
		469	=head1 COMPARISON
		470
		471	As already mentioned, this module was created because none of the existing
		472	JSON modules could be made to work correctly. First I will describe the
		473	problems (or pleasures) I encountered with various existing JSON modules,
		474	followed by some benchmark values. JSON::XS was designed not to suffer
		475	from any of these problems or limitations.
		476
		477	=over 4
		478
		479	=item JSON 1.07
		480
		481	Slow (but very portable, as it is written in pure Perl).
		482
		483	Undocumented/buggy Unicode handling (how JSON handles unicode values is
		484	undocumented. One can get far by feeding it unicode strings and doing
		485	en-/decoding oneself, but unicode escapes are not working properly).
		486
		487	No roundtripping (strings get clobbered if they look like numbers, e.g.
		488	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
		489	decode into the number 2.
		490
		491	=item JSON::PC 0.01
		492
		493	Very fast.
		494
		495	Undocumented/buggy Unicode handling.
		496
		497	No roundtripping.
		498
		499	Has problems handling many Perl values (e.g. regex results and other magic
		500	values will make it croak).
		501
		502	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		503	which is not a valid JSON text.
		504
		505	Unmaintained (maintainer unresponsive for many months, bugs are not
		506	getting fixed).
		507
		508	=item JSON::Syck 0.21
		509
		510	Very buggy (often crashes).
		511
		512	Very inflexible (no human-readable format supported, format pretty much
		513	undocumented. I need at least a format for easy reading by humans and a
		514	single-line compact format for use in a protocol, and preferably a way to
		515	generate ASCII-only JSON texts).
		516
		517	Completely broken (and confusingly documented) Unicode handling (unicode
		518	escapes are not working properly, you need to set ImplicitUnicode to
		519	I<different> values on en- and decoding to get symmetric behaviour).
		520
		521	No roundtripping (simple cases work, but this depends on wether the scalar
		522	value was used in a numeric context or not).
		523
		524	Dumping hashes may skip hash values depending on iterator state.
		525
		526	Unmaintained (maintainer unresponsive for many months, bugs are not
		527	getting fixed).
		528
		529	Does not check input for validity (i.e. will accept non-JSON input and
		530	return "something" instead of raising an exception. This is a security
		531	issue: imagine two banks transfering money between each other using
		532	JSON. One bank might parse a given non-JSON request and deduct money,
		533	while the other might reject the transaction with a syntax error. While a
		534	good protocol will at least recover, that is extra unnecessary work and
		535	the transaction will still not succeed).
		536
		537	=item JSON::DWIW 0.04
		538
		539	Very fast. Very natural. Very nice.
		540
		541	Undocumented unicode handling (but the best of the pack. Unicode escapes
		542	still don't get parsed properly).
		543
		544	Very inflexible.
		545
		546	No roundtripping.
		547
		548	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		549	result in nothing being output)
		550
		551	Does not check input for validity.
		552
		553	=back
		554
		555	=head2 SPEED
		556
		557	It seems that JSON::XS is surprisingly fast, as shown in the following
		558	tables. They have been generated with the help of the C<eg/bench> program
		559	in the JSON::XS distribution, to make it easy to compare on your own
		560	system.
		561
		562	First comes a comparison between various modules using a very short JSON
		563	string:
		564
		565	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
		566
		567	It shows the number of encodes/decodes per second (JSON::XS uses the
		568	functional interface, while JSON::XS/2 uses the OO interface with
		569	pretty-printing and hashkey sorting enabled). Higher is better:
		570
		571	module \| encode \| decode \|
		572	-----------\|------------\|------------\|
		573	JSON \| 11488.516 \| 7823.035 \|
		574	JSON::DWIW \| 94708.054 \| 129094.260 \|
		575	JSON::PC \| 63884.157 \| 128528.212 \|
		576	JSON::Syck \| 34898.677 \| 42096.911 \|
		577	JSON::XS \| 654027.064 \| 396423.669 \|
		578	JSON::XS/2 \| 371564.190 \| 371725.613 \|
		579	-----------+------------+------------+
		580
		581	That is, JSON::XS is more than six times faster than JSON::DWIW on
		582	encoding, more than three times faster on decoding, and about thirty times
		583	faster than JSON, even with pretty-printing and key sorting.
		584
		585	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		586	search API (http://nanoref.com/yahooapis/mgPdGg):
		587
		588	module \| encode \| decode \|
		589	-----------\|------------\|------------\|
		590	JSON \| 273.023 \| 44.674 \|
		591	JSON::DWIW \| 1089.383 \| 1145.704 \|
		592	JSON::PC \| 3097.419 \| 2393.921 \|
		593	JSON::Syck \| 514.060 \| 843.053 \|
		594	JSON::XS \| 6479.668 \| 3636.364 \|
		595	JSON::XS/2 \| 3774.221 \| 3599.124 \|
		596	-----------+------------+------------+
		597
		598	Again, JSON::XS leads by far.
		599
		600	On large strings containing lots of high unicode characters, some modules
		601	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		602	will be broken due to missing (or wrong) unicode handling. Others refuse
		603	to decode or encode properly, so it was impossible to prepare a fair
		604	comparison table for that case.
		605
		606
		607	=head1 SECURITY CONSIDERATIONS
		608
		609	When you are using JSON in a protocol, talking to untrusted potentially
		610	hostile creatures requires relatively few measures.
		611
		612	First of all, your JSON decoder should be secure, that is, should not have
		613	any buffer overflows. Obviously, this module should ensure that and I am
		614	trying hard on making that true, but you never know.
		615
		616	Second, you need to avoid resource-starving attacks. That means you should
		617	limit the size of JSON texts you accept, or make sure then when your
		618	resources run out, thats just fine (e.g. by using a separate process that
		619	can crash safely). The size of a JSON text in octets or characters is
		620	usually a good indication of the size of the resources required to decode
		621	it into a Perl structure.
		622
		623	Third, JSON::XS recurses using the C stack when decoding objects and
		624	arrays. The C stack is a limited resource: for instance, on my amd64
		625	machine with 8MB of stack size I can decode around 180k nested arrays
		626	but only 14k nested JSON objects. If that is exceeded, the program
		627	crashes. Thats why the default nesting limit is set to 8192. If your
		628	process has a smaller stack, you should adjust this setting accordingly
		629	with the C<max_depth> method.
		630
		631	And last but least, something else could bomb you that I forgot to think
		632	of. In that case, you get to keep the pieces. I am alway sopen for hints,
		633	though...
		634
		635
		636	=head1 BUGS
		637
		638	While the goal of this module is to be correct, that unfortunately does
		639	not mean its bug-free, only that I think its design is bug-free. It is
		640	still relatively early in its development. If you keep reporting bugs they
		641	will be fixed swiftly, though.
		642
218	=cut	643	=cut
219		644
220	1;	645	1;
221		646
222	=head1 AUTHOR	647	=head1 AUTHOR

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Revision 1.23 by root, Sun Mar 25 21:19:13 2007 UTC