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

Comparing JSON-XS/XS.pm (file contents):
Revision 1.4 by root, Thu Mar 22 21:13:58 2007 UTC vs.
Revision 1.32 by root, Thu Apr 12 07:25:29 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 = '1.12';
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)->space_after(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. The resulting encoded JSON text can be treated as a native
		160	unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string,
		161	or any other superset of ASCII.
125		162
126	If C<$enable> is false, then the C<encode> method will not escape Unicode	163	If C<$enable> is false, then the C<encode> method will not escape Unicode
127	characters unless necessary.	164	characters unless required by the JSON syntax. This results in a faster
		165	and more compact format.
128		166
129	JSON::XS->new->ascii (1)->encode (chr 0x10401)	167	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
130	=> \ud801\udc01	168	=> ["\ud801\udc01"]
131		169
132	=item $json = $json->utf8 ($enable)	170	=item $json = $json->utf8 ([$enable])
133		171
134	If C<$enable> is true, then the C<encode> method will encode the JSON	172	If C<$enable> is true (or missing), then the C<encode> method will encode
135	string into UTF-8, as required by many protocols, while the C<decode>	173	the JSON result into UTF-8, as required by many protocols, while the
136	method expects to be handled an UTF-8-encoded string. Please note that	174	C<decode> method expects to be handled an UTF-8-encoded string. Please
137	UTF-8-encoded strings do not contain any characters outside the range	175	note that UTF-8-encoded strings do not contain any characters outside the
138	C<0..255>, they are thus useful for bytewise/binary I/O.	176	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		177	versions, enabling this option might enable autodetection of the UTF-16
		178	and UTF-32 encoding families, as described in RFC4627.
139		179
140	If C<$enable> is false, then the C<encode> method will return the JSON	180	If C<$enable> is false, then the C<encode> method will return the JSON
141	string as a (non-encoded) unicode string, while C<decode> expects thus a	181	string as a (non-encoded) unicode string, while C<decode> expects thus a
142	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs	182	unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs
143	to be done yourself, e.g. using the Encode module.	183	to be done yourself, e.g. using the Encode module.
144		184
		185	Example, output UTF-16BE-encoded JSON:
		186
		187	use Encode;
		188	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		189
		190	Example, decode UTF-32LE-encoded JSON:
		191
		192	use Encode;
		193	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		194
145	=item $json = $json->pretty ($enable)	195	=item $json = $json->pretty ([$enable])
146		196
147	This enables (or disables) all of the C<indent>, C<space_before> and	197	This enables (or disables) all of the C<indent>, C<space_before> and
148	C<space_after> (and in the future possibly more) flags in one call to	198	C<space_after> (and in the future possibly more) flags in one call to
149	generate the most readable (or most compact) form possible.	199	generate the most readable (or most compact) form possible.
		200
		201	Example, pretty-print some simple structure:
150		202
151	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})	203	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
152	=>	204	=>
153	{	205	{
154	"a" : [	206	"a" : [
155	1,	207	1,
156	2	208	2
157	]	209	]
158	}	210	}
159		211
160	=item $json = $json->indent ($enable)	212	=item $json = $json->indent ([$enable])
161		213
162	If C<$enable> is true, then the C<encode> method will use a multiline	214	If C<$enable> is true (or missing), then the C<encode> method will use a multiline
163	format as output, putting every array member or object/hash key-value pair	215	format as output, putting every array member or object/hash key-value pair
164	into its own line, identing them properly.	216	into its own line, identing them properly.
165		217
166	If C<$enable> is false, no newlines or indenting will be produced, and the	218	If C<$enable> is false, no newlines or indenting will be produced, and the
167	resulting JSON strings is guarenteed not to contain any C<newlines>.	219	resulting JSON text is guarenteed not to contain any C<newlines>.
168		220
169	This setting has no effect when decoding JSON strings.	221	This setting has no effect when decoding JSON texts.
170		222
171	=item $json = $json->space_before ($enable)	223	=item $json = $json->space_before ([$enable])
172		224
173	If C<$enable> is true, then the C<encode> method will add an extra	225	If C<$enable> is true (or missing), then the C<encode> method will add an extra
174	optional space before the C<:> separating keys from values in JSON objects.	226	optional space before the C<:> separating keys from values in JSON objects.
175		227
176	If C<$enable> is false, then the C<encode> method will not add any extra	228	If C<$enable> is false, then the C<encode> method will not add any extra
177	space at those places.	229	space at those places.
178		230
179	This setting has no effect when decoding JSON strings. You will also most	231	This setting has no effect when decoding JSON texts. You will also
180	likely combine this setting with C<space_after>.	232	most likely combine this setting with C<space_after>.
181		233
		234	Example, space_before enabled, space_after and indent disabled:
		235
		236	{"key" :"value"}
		237
182	=item $json = $json->space_after ($enable)	238	=item $json = $json->space_after ([$enable])
183		239
184	If C<$enable> is true, then the C<encode> method will add an extra	240	If C<$enable> is true (or missing), then the C<encode> method will add an extra
185	optional space after the C<:> separating keys from values in JSON objects	241	optional space after the C<:> separating keys from values in JSON objects
186	and extra whitespace after the C<,> separating key-value pairs and array	242	and extra whitespace after the C<,> separating key-value pairs and array
187	members.	243	members.
188		244
189	If C<$enable> is false, then the C<encode> method will not add any extra	245	If C<$enable> is false, then the C<encode> method will not add any extra
190	space at those places.	246	space at those places.
191		247
192	This setting has no effect when decoding JSON strings.	248	This setting has no effect when decoding JSON texts.
193		249
		250	Example, space_before and indent disabled, space_after enabled:
		251
		252	{"key": "value"}
		253
194	=item $json = $json->canonical ($enable)	254	=item $json = $json->canonical ([$enable])
195		255
196	If C<$enable> is true, then the C<encode> method will output JSON objects	256	If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
197	by sorting their keys. This is adding a comparatively high overhead.	257	by sorting their keys. This is adding a comparatively high overhead.
198		258
199	If C<$enable> is false, then the C<encode> method will output key-value	259	If C<$enable> is false, then the C<encode> method will output key-value
200	pairs in the order Perl stores them (which will likely change between runs	260	pairs in the order Perl stores them (which will likely change between runs
201	of the same script).	261	of the same script).
202		262
203	This option is useful if you want the same data structure to be encoded as	263	This option is useful if you want the same data structure to be encoded as
204	the same JSON string (given the same overall settings). If it is disabled,	264	the same JSON text (given the same overall settings). If it is disabled,
205	the same hash migh be encoded differently even if contains the same data,	265	the same hash migh be encoded differently even if contains the same data,
206	as key-value pairs have no inherent ordering in Perl.	266	as key-value pairs have no inherent ordering in Perl.
207		267
208	This setting has no effect when decoding JSON strings.	268	This setting has no effect when decoding JSON texts.
209		269
210	=item $json = $json->allow_nonref ($enable)	270	=item $json = $json->allow_nonref ([$enable])
211		271
212	If C<$enable> is true, then the C<encode> method can convert a	272	If C<$enable> is true (or missing), then the C<encode> method can convert a
213	non-reference into its corresponding string, number or null JSON value,	273	non-reference into its corresponding string, number or null JSON value,
214	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON	274	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
215	values instead of croaking.	275	values instead of croaking.
216		276
217	If C<$enable> is false, then the C<encode> method will croak if it isn't	277	If C<$enable> is false, then the C<encode> method will croak if it isn't
218	passed an arrayref or hashref, as JSON strings must either be an object	278	passed an arrayref or hashref, as JSON texts must either be an object
219	or array. Likewise, C<decode> will croak if given something that is not a	279	or array. Likewise, C<decode> will croak if given something that is not a
220	JSON object or array.	280	JSON object or array.
221		281
		282	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		283	resulting in an invalid JSON text:
		284
		285	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		286	=> "Hello, World!"
		287
		288	=item $json = $json->shrink ([$enable])
		289
		290	Perl usually over-allocates memory a bit when allocating space for
		291	strings. This flag optionally resizes strings generated by either
		292	C<encode> or C<decode> to their minimum size possible. This can save
		293	memory when your JSON texts are either very very long or you have many
		294	short strings. It will also try to downgrade any strings to octet-form
		295	if possible: perl stores strings internally either in an encoding called
		296	UTF-X or in octet-form. The latter cannot store everything but uses less
		297	space in general (and some buggy Perl or C code might even rely on that
		298	internal representation being used).
		299
		300	The actual definition of what shrink does might change in future versions,
		301	but it will always try to save space at the expense of time.
		302
		303	If C<$enable> is true (or missing), the string returned by C<encode> will
		304	be shrunk-to-fit, while all strings generated by C<decode> will also be
		305	shrunk-to-fit.
		306
		307	If C<$enable> is false, then the normal perl allocation algorithms are used.
		308	If you work with your data, then this is likely to be faster.
		309
		310	In the future, this setting might control other things, such as converting
		311	strings that look like integers or floats into integers or floats
		312	internally (there is no difference on the Perl level), saving space.
		313
		314	=item $json = $json->max_depth ([$maximum_nesting_depth])
		315
		316	Sets the maximum nesting level (default C<512>) accepted while encoding
		317	or decoding. If the JSON text or Perl data structure has an equal or
		318	higher nesting level then this limit, then the encoder and decoder will
		319	stop and croak at that point.
		320
		321	Nesting level is defined by number of hash- or arrayrefs that the encoder
		322	needs to traverse to reach a given point or the number of C<{> or C<[>
		323	characters without their matching closing parenthesis crossed to reach a
		324	given character in a string.
		325
		326	Setting the maximum depth to one disallows any nesting, so that ensures
		327	that the object is only a single hash/object or array.
		328
		329	The argument to C<max_depth> will be rounded up to the next nearest power
		330	of two.
		331
		332	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		333
222	=item $json_string = $json->encode ($perl_scalar)	334	=item $json_text = $json->encode ($perl_scalar)
223		335
224	Converts the given Perl data structure (a simple scalar or a reference	336	Converts the given Perl data structure (a simple scalar or a reference
225	to a hash or array) to its JSON representation. Simple scalars will be	337	to a hash or array) to its JSON representation. Simple scalars will be
226	converted into JSON string or number sequences, while references to arrays	338	converted into JSON string or number sequences, while references to arrays
227	become JSON arrays and references to hashes become JSON objects. Undefined	339	become JSON arrays and references to hashes become JSON objects. Undefined
228	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>	340	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
229	nor C<false> values will be generated.	341	nor C<false> values will be generated.
230		342
231	=item $perl_scalar = $json->decode ($json_string)	343	=item $perl_scalar = $json->decode ($json_text)
232		344
233	The opposite of C<encode>: expects a JSON string and tries to parse it,	345	The opposite of C<encode>: expects a JSON text and tries to parse it,
234	returning the resulting simple scalar or reference. Croaks on error.	346	returning the resulting simple scalar or reference. Croaks on error.
235		347
236	JSON numbers and strings become simple Perl scalars. JSON arrays become	348	JSON numbers and strings become simple Perl scalars. JSON arrays become
237	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	349	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes
238	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.	350	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
239		351
240	=back	352	=back
		353
		354
		355	=head1 MAPPING
		356
		357	This section describes how JSON::XS maps Perl values to JSON values and
		358	vice versa. These mappings are designed to "do the right thing" in most
		359	circumstances automatically, preserving round-tripping characteristics
		360	(what you put in comes out as something equivalent).
		361
		362	For the more enlightened: note that in the following descriptions,
		363	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		364	refers to the abstract Perl language itself.
		365
		366	=head2 JSON -> PERL
		367
		368	=over 4
		369
		370	=item object
		371
		372	A JSON object becomes a reference to a hash in Perl. No ordering of object
		373	keys is preserved (JSON does not preserver object key ordering itself).
		374
		375	=item array
		376
		377	A JSON array becomes a reference to an array in Perl.
		378
		379	=item string
		380
		381	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		382	are represented by the same codepoints in the Perl string, so no manual
		383	decoding is necessary.
		384
		385	=item number
		386
		387	A JSON number becomes either an integer or numeric (floating point)
		388	scalar in perl, depending on its range and any fractional parts. On the
		389	Perl level, there is no difference between those as Perl handles all the
		390	conversion details, but an integer may take slightly less memory and might
		391	represent more values exactly than (floating point) numbers.
		392
		393	=item true, false
		394
		395	These JSON atoms become C<0>, C<1>, respectively. Information is lost in
		396	this process. Future versions might represent those values differently,
		397	but they will be guarenteed to act like these integers would normally in
		398	Perl.
		399
		400	=item null
		401
		402	A JSON null atom becomes C<undef> in Perl.
		403
		404	=back
		405
		406	=head2 PERL -> JSON
		407
		408	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		409	truly typeless language, so we can only guess which JSON type is meant by
		410	a Perl value.
		411
		412	=over 4
		413
		414	=item hash references
		415
		416	Perl hash references become JSON objects. As there is no inherent ordering
		417	in hash keys (or JSON objects), they will usually be encoded in a
		418	pseudo-random order that can change between runs of the same program but
		419	stays generally the same within a single run of a program. JSON::XS can
		420	optionally sort the hash keys (determined by the I<canonical> flag), so
		421	the same datastructure will serialise to the same JSON text (given same
		422	settings and version of JSON::XS), but this incurs a runtime overhead
		423	and is only rarely useful, e.g. when you want to compare some JSON text
		424	against another for equality.
		425
		426	=item array references
		427
		428	Perl array references become JSON arrays.
		429
		430	=item other references
		431
		432	Other unblessed references are generally not allowed and will cause an
		433	exception to be thrown, except for references to the integers C<0> and
		434	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		435	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		436
		437	to_json [\0,JSON::XS::true] # yields [false,true]
		438
		439	=item blessed objects
		440
		441	Blessed objects are not allowed. JSON::XS currently tries to encode their
		442	underlying representation (hash- or arrayref), but this behaviour might
		443	change in future versions.
		444
		445	=item simple scalars
		446
		447	Simple Perl scalars (any scalar that is not a reference) are the most
		448	difficult objects to encode: JSON::XS will encode undefined scalars as
		449	JSON null value, scalars that have last been used in a string context
		450	before encoding as JSON strings and anything else as number value:
		451
		452	# dump as number
		453	to_json [2] # yields [2]
		454	to_json [-3.0e17] # yields [-3e+17]
		455	my $value = 5; to_json [$value] # yields [5]
		456
		457	# used as string, so dump as string
		458	print $value;
		459	to_json [$value] # yields ["5"]
		460
		461	# undef becomes null
		462	to_json [undef] # yields [null]
		463
		464	You can force the type to be a string by stringifying it:
		465
		466	my $x = 3.1; # some variable containing a number
		467	"$x"; # stringified
		468	$x .= ""; # another, more awkward way to stringify
		469	print $x; # perl does it for you, too, quite often
		470
		471	You can force the type to be a number by numifying it:
		472
		473	my $x = "3"; # some variable containing a string
		474	$x += 0; # numify it, ensuring it will be dumped as a number
		475	$x *= 1; # same thing, the choise is yours.
		476
		477	You can not currently output JSON booleans or force the type in other,
		478	less obscure, ways. Tell me if you need this capability.
		479
		480	=back
		481
241		482
242	=head1 COMPARISON	483	=head1 COMPARISON
243		484
244	As already mentioned, this module was created because none of the existing	485	As already mentioned, this module was created because none of the existing
245	JSON modules could be made to work correctly. First I will describe the	486	JSON modules could be made to work correctly. First I will describe the
…		…
247	followed by some benchmark values. JSON::XS was designed not to suffer	488	followed by some benchmark values. JSON::XS was designed not to suffer
248	from any of these problems or limitations.	489	from any of these problems or limitations.
249		490
250	=over 4	491	=over 4
251		492
252	=item JSON	493	=item JSON 1.07
253		494
254	Slow (but very portable, as it is written in pure Perl).	495	Slow (but very portable, as it is written in pure Perl).
255		496
256	Undocumented/buggy Unicode handling (how JSON handles unicode values is	497	Undocumented/buggy Unicode handling (how JSON handles unicode values is
257	undocumented. One can get far by feeding it unicode strings and doing	498	undocumented. One can get far by feeding it unicode strings and doing
…		…
259		500
260	No roundtripping (strings get clobbered if they look like numbers, e.g.	501	No roundtripping (strings get clobbered if they look like numbers, e.g.
261	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will	502	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
262	decode into the number 2.	503	decode into the number 2.
263		504
264	=item JSON::PC	505	=item JSON::PC 0.01
265		506
266	Very fast.	507	Very fast.
267		508
268	Undocumented/buggy Unicode handling.	509	Undocumented/buggy Unicode handling.
269		510
…		…
271		512
272	Has problems handling many Perl values (e.g. regex results and other magic	513	Has problems handling many Perl values (e.g. regex results and other magic
273	values will make it croak).	514	values will make it croak).
274		515
275	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>	516	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
276	which is not a valid JSON string.	517	which is not a valid JSON text.
277		518
278	Unmaintained (maintainer unresponsive for many months, bugs are not	519	Unmaintained (maintainer unresponsive for many months, bugs are not
279	getting fixed).	520	getting fixed).
280		521
281	=item JSON::Syck	522	=item JSON::Syck 0.21
282		523
283	Very buggy (often crashes).	524	Very buggy (often crashes).
284		525
285	Very inflexible (no human-readable format supported, format pretty much	526	Very inflexible (no human-readable format supported, format pretty much
286	undocumented. I need at least a format for easy reading by humans and a	527	undocumented. I need at least a format for easy reading by humans and a
287	single-line compact format for use in a protocol, and preferably a way to	528	single-line compact format for use in a protocol, and preferably a way to
288	generate ASCII-only JSON strings).	529	generate ASCII-only JSON texts).
289		530
290	Completely broken (and confusingly documented) Unicode handling (unicode	531	Completely broken (and confusingly documented) Unicode handling (unicode
291	escapes are not working properly, you need to set ImplicitUnicode to	532	escapes are not working properly, you need to set ImplicitUnicode to
292	I<different> values on en- and decoding to get symmetric behaviour).	533	I<different> values on en- and decoding to get symmetric behaviour).
293		534
…		…
305	JSON. One bank might parse a given non-JSON request and deduct money,	546	JSON. One bank might parse a given non-JSON request and deduct money,
306	while the other might reject the transaction with a syntax error. While a	547	while the other might reject the transaction with a syntax error. While a
307	good protocol will at least recover, that is extra unnecessary work and	548	good protocol will at least recover, that is extra unnecessary work and
308	the transaction will still not succeed).	549	the transaction will still not succeed).
309		550
310	=item JSON::DWIW	551	=item JSON::DWIW 0.04
311		552
312	Very fast. Very natural. Very nice.	553	Very fast. Very natural. Very nice.
313		554
314	Undocumented unicode handling (but the best of the pack. Unicode escapes	555	Undocumented unicode handling (but the best of the pack. Unicode escapes
315	still don't get parsed properly).	556	still don't get parsed properly).
316		557
317	Very inflexible.	558	Very inflexible.
318		559
319	No roundtripping.	560	No roundtripping.
320		561
321	Does not generate valid JSON (key strings are often unquoted, empty keys	562	Does not generate valid JSON texts (key strings are often unquoted, empty keys
322	result in nothing being output)	563	result in nothing being output)
323		564
324	Does not check input for validity.	565	Does not check input for validity.
325		566
326	=back	567	=back
…		…
330	It seems that JSON::XS is surprisingly fast, as shown in the following	571	It seems that JSON::XS is surprisingly fast, as shown in the following
331	tables. They have been generated with the help of the C<eg/bench> program	572	tables. They have been generated with the help of the C<eg/bench> program
332	in the JSON::XS distribution, to make it easy to compare on your own	573	in the JSON::XS distribution, to make it easy to compare on your own
333	system.	574	system.
334		575
335	First is a comparison between various modules using a very simple JSON	576	First comes a comparison between various modules using a very short JSON
		577	string:
		578
		579	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
		580
336	string, showing the number of encodes/decodes per second (JSON::XS is	581	It shows the number of encodes/decodes per second (JSON::XS uses the
337	the functional interface, while JSON::XS/2 is the OO interface with	582	functional interface, while JSON::XS/2 uses the OO interface with
338	pretty-printing and hashkey sorting enabled).	583	pretty-printing and hashkey sorting enabled). Higher is better:
339		584
340	module \| encode \| decode \|	585	module \| encode \| decode \|
341	-----------\|------------\|------------\|	586	-----------\|------------\|------------\|
342	JSON \| 14006 \| 6820 \|	587	JSON \| 11488.516 \| 7823.035 \|
343	JSON::DWIW \| 200937 \| 120386 \|	588	JSON::DWIW \| 94708.054 \| 129094.260 \|
344	JSON::PC \| 85065 \| 129366 \|	589	JSON::PC \| 63884.157 \| 128528.212 \|
345	JSON::Syck \| 59898 \| 44232 \|	590	JSON::Syck \| 34898.677 \| 42096.911 \|
346	JSON::XS \| 1171478 \| 342435 \|	591	JSON::XS \| 654027.064 \| 396423.669 \|
347	JSON::XS/2 \| 730760 \| 328714 \|	592	JSON::XS/2 \| 371564.190 \| 371725.613 \|
348	-----------+------------+------------+	593	-----------+------------+------------+
349		594
350	That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80	595	That is, JSON::XS is more than six times faster than JSON::DWIW on
		596	encoding, more than three times faster on decoding, and about thirty times
351	times faster than JSON, even with pretty-printing and key sorting.	597	faster than JSON, even with pretty-printing and key sorting.
352		598
353	Using a longer test string (roughly 8KB, generated from Yahoo! Locals	599	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
354	search API (http://nanoref.com/yahooapis/mgPdGg):	600	search API (http://nanoref.com/yahooapis/mgPdGg):
355		601
356	module \| encode \| decode \|	602	module \| encode \| decode \|
357	-----------\|------------\|------------\|	603	-----------\|------------\|------------\|
358	JSON \| 673 \| 38 \|	604	JSON \| 273.023 \| 44.674 \|
359	JSON::DWIW \| 5271 \| 770 \|	605	JSON::DWIW \| 1089.383 \| 1145.704 \|
360	JSON::PC \| 9901 \| 2491 \|	606	JSON::PC \| 3097.419 \| 2393.921 \|
361	JSON::Syck \| 2360 \| 786 \|	607	JSON::Syck \| 514.060 \| 843.053 \|
362	JSON::XS \| 37398 \| 3202 \|	608	JSON::XS \| 6479.668 \| 3636.364 \|
363	JSON::XS/2 \| 13765 \| 3153 \|	609	JSON::XS/2 \| 3774.221 \| 3599.124 \|
364	-----------+------------+------------+	610	-----------+------------+------------+
365		611
366	Again, JSON::XS leads by far in the encoding case, while still beating	612	Again, JSON::XS leads by far.
367	every other module in the decoding case.
368		613
369	Last example is an almost 8MB large hash with many large binary values	614	On large strings containing lots of high unicode characters, some modules
370	(PNG files), resulting in a lot of escaping:	615	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		616	will be broken due to missing (or wrong) unicode handling. Others refuse
		617	to decode or encode properly, so it was impossible to prepare a fair
		618	comparison table for that case.
		619
		620
		621	=head1 SECURITY CONSIDERATIONS
		622
		623	When you are using JSON in a protocol, talking to untrusted potentially
		624	hostile creatures requires relatively few measures.
		625
		626	First of all, your JSON decoder should be secure, that is, should not have
		627	any buffer overflows. Obviously, this module should ensure that and I am
		628	trying hard on making that true, but you never know.
		629
		630	Second, you need to avoid resource-starving attacks. That means you should
		631	limit the size of JSON texts you accept, or make sure then when your
		632	resources run out, thats just fine (e.g. by using a separate process that
		633	can crash safely). The size of a JSON text in octets or characters is
		634	usually a good indication of the size of the resources required to decode
		635	it into a Perl structure.
		636
		637	Third, JSON::XS recurses using the C stack when decoding objects and
		638	arrays. The C stack is a limited resource: for instance, on my amd64
		639	machine with 8MB of stack size I can decode around 180k nested arrays but
		640	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		641	to free the temporary). If that is exceeded, the program crashes. to be
		642	conservative, the default nesting limit is set to 512. If your process
		643	has a smaller stack, you should adjust this setting accordingly with the
		644	C<max_depth> method.
		645
		646	And last but least, something else could bomb you that I forgot to think
		647	of. In that case, you get to keep the pieces. I am always open for hints,
		648	though...
		649
371		650
372	=head1 BUGS	651	=head1 BUGS
373		652
374	While the goal of this module is to be correct, that unfortunately does	653	While the goal of this module is to be correct, that unfortunately does
375	not mean its bug-free, only that I think its design is bug-free. It is	654	not mean its bug-free, only that I think its design is bug-free. It is
376	still very young and not well-tested. If you keep reporting bugs they will	655	still relatively early in its development. If you keep reporting bugs they
377	be fixed swiftly, though.	656	will be fixed swiftly, though.
378		657
379	=cut	658	=cut
		659
		660	sub true() { \1 }
		661	sub false() { \0 }
380		662
381	1;	663	1;
382		664
383	=head1 AUTHOR	665	=head1 AUTHOR
384		666

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Revision 1.32 by root, Thu Apr 12 07:25:29 2007 UTC