[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 1.33 by root, Wed May 9 16:10:37 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)->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. 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 or other flags. This results
		165	in a faster and more compact format.
128		166
		167	The main use for this flag is to produce JSON texts that can be
		168	transmitted over a 7-bit channel, as the encoded JSON texts will not
		169	contain any 8 bit characters.
		170
		171	JSON::XS->new->ascii (1)->encode ([chr 0x10401])
		172	=> ["\ud801\udc01"]
		173
		174	=item $json = $json->latin1 ([$enable])
		175
		176	If C<$enable> is true (or missing), then the C<encode> method will encode
		177	the resulting JSON text as latin1 (or iso-8859-1), escaping any characters
		178	outside the code range C<0..255>. The resulting string can be treated as a
		179	latin1-encoded JSON text or a native unicode string. The C<decode> method
		180	will not be affected in any way by this flag, as C<decode> by default
		181	expects unicode, which is a strict superset of latin1.
		182
		183	If C<$enable> is false, then the C<encode> method will not escape Unicode
		184	characters unless required by the JSON syntax or other flags.
		185
		186	The main use for this flag is efficiently encoding binary data as JSON
		187	text, as most octets will not be escaped, resulting in a smaller encoded
		188	size. The disadvantage is that the resulting JSON text is encoded
		189	in latin1 (and must correctly be treated as such when storing and
		190	transfering), a rare encoding for JSON. It is therefore most useful when
		191	you want to store data structures known to contain binary data efficiently
		192	in files or databases, not when talking to other JSON encoders/decoders.
		193
		194	JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
		195	=> ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
		196
129	=item $json = $json->utf8 ($enable)	197	=item $json = $json->utf8 ([$enable])
130		198
131	If C<$enable> is true, then the C<encode> method will encode the JSON	199	If C<$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>	200	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	201	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	202	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.	203	range C<0..255>, they are thus useful for bytewise/binary I/O. In future
		204	versions, enabling this option might enable autodetection of the UTF-16
		205	and UTF-32 encoding families, as described in RFC4627.
136		206
137	If C<$enable> is false, then the C<encode> method will return the JSON	207	If C<$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	208	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	209	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.	210	to be done yourself, e.g. using the Encode module.
141		211
		212	Example, output UTF-16BE-encoded JSON:
		213
		214	use Encode;
		215	$jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
		216
		217	Example, decode UTF-32LE-encoded JSON:
		218
		219	use Encode;
		220	$object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext);
		221
142	=item $json = $json->pretty ($enabla)	222	=item $json = $json->pretty ([$enable])
143		223
144	This enables (or disables) all of the C<indent>, C<space_before> and	224	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	225	C<space_after> (and in the future possibly more) flags in one call to
146	generate the most readable (or most compact) form possible.	226	generate the most readable (or most compact) form possible.
147		227
		228	Example, pretty-print some simple structure:
		229
		230	my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]})
		231	=>
		232	{
		233	"a" : [
		234	1,
		235	2
		236	]
		237	}
		238
148	=item $json = $json->indent ($enable)	239	=item $json = $json->indent ([$enable])
149		240
150	If C<$enable> is true, then the C<encode> method will use a multiline	241	If C<$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	242	format as output, putting every array member or object/hash key-value pair
152	into its own line, identing them properly.	243	into its own line, identing them properly.
153		244
154	If C<$enable> is false, no newlines or indenting will be produced, and the	245	If C<$enable> is false, no newlines or indenting will be produced, and the
155	resulting JSON strings is guarenteed not to contain any C<newlines>.	246	resulting JSON text is guarenteed not to contain any C<newlines>.
156		247
157	This setting has no effect when decoding JSON strings.	248	This setting has no effect when decoding JSON texts.
158		249
159	=item $json = $json->space_before ($enable)	250	=item $json = $json->space_before ([$enable])
160		251
161	If C<$enable> is true, then the C<encode> method will add an extra	252	If C<$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.	253	optional space before the C<:> separating keys from values in JSON objects.
163		254
164	If C<$enable> is false, then the C<encode> method will not add any extra	255	If C<$enable> is false, then the C<encode> method will not add any extra
165	space at those places.	256	space at those places.
166		257
167	This setting has no effect when decoding JSON strings. You will also most	258	This setting has no effect when decoding JSON texts. You will also
168	likely combine this setting with C<space_after>.	259	most likely combine this setting with C<space_after>.
169		260
		261	Example, space_before enabled, space_after and indent disabled:
		262
		263	{"key" :"value"}
		264
170	=item $json = $json->space_after ($enable)	265	=item $json = $json->space_after ([$enable])
171		266
172	If C<$enable> is true, then the C<encode> method will add an extra	267	If C<$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	268	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	269	and extra whitespace after the C<,> separating key-value pairs and array
175	members.	270	members.
176		271
177	If C<$enable> is false, then the C<encode> method will not add any extra	272	If C<$enable> is false, then the C<encode> method will not add any extra
178	space at those places.	273	space at those places.
179		274
180	This setting has no effect when decoding JSON strings.	275	This setting has no effect when decoding JSON texts.
181		276
		277	Example, space_before and indent disabled, space_after enabled:
		278
		279	{"key": "value"}
		280
182	=item $json = $json->canonical ($enable)	281	=item $json = $json->canonical ([$enable])
183		282
184	If C<$enable> is true, then the C<encode> method will output JSON objects	283	If C<$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.	284	by sorting their keys. This is adding a comparatively high overhead.
186		285
187	If C<$enable> is false, then the C<encode> method will output key-value	286	If C<$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	287	pairs in the order Perl stores them (which will likely change between runs
189	of the same script).	288	of the same script).
190		289
191	This option is useful if you want the same data structure to be encoded as	290	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,	291	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,	292	the same hash migh be encoded differently even if contains the same data,
194	as key-value pairs have no inherent ordering in Perl.	293	as key-value pairs have no inherent ordering in Perl.
195		294
196	This setting has no effect when decoding JSON strings.	295	This setting has no effect when decoding JSON texts.
197		296
		297	=item $json = $json->allow_nonref ([$enable])
		298
		299	If C<$enable> is true (or missing), then the C<encode> method can convert a
		300	non-reference into its corresponding string, number or null JSON value,
		301	which is an extension to RFC4627. Likewise, C<decode> will accept those JSON
		302	values instead of croaking.
		303
		304	If C<$enable> is false, then the C<encode> method will croak if it isn't
		305	passed an arrayref or hashref, as JSON texts must either be an object
		306	or array. Likewise, C<decode> will croak if given something that is not a
		307	JSON object or array.
		308
		309	Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
		310	resulting in an invalid JSON text:
		311
		312	JSON::XS->new->allow_nonref->encode ("Hello, World!")
		313	=> "Hello, World!"
		314
		315	=item $json = $json->shrink ([$enable])
		316
		317	Perl usually over-allocates memory a bit when allocating space for
		318	strings. This flag optionally resizes strings generated by either
		319	C<encode> or C<decode> to their minimum size possible. This can save
		320	memory when your JSON texts are either very very long or you have many
		321	short strings. It will also try to downgrade any strings to octet-form
		322	if possible: perl stores strings internally either in an encoding called
		323	UTF-X or in octet-form. The latter cannot store everything but uses less
		324	space in general (and some buggy Perl or C code might even rely on that
		325	internal representation being used).
		326
		327	The actual definition of what shrink does might change in future versions,
		328	but it will always try to save space at the expense of time.
		329
		330	If C<$enable> is true (or missing), the string returned by C<encode> will
		331	be shrunk-to-fit, while all strings generated by C<decode> will also be
		332	shrunk-to-fit.
		333
		334	If C<$enable> is false, then the normal perl allocation algorithms are used.
		335	If you work with your data, then this is likely to be faster.
		336
		337	In the future, this setting might control other things, such as converting
		338	strings that look like integers or floats into integers or floats
		339	internally (there is no difference on the Perl level), saving space.
		340
		341	=item $json = $json->max_depth ([$maximum_nesting_depth])
		342
		343	Sets the maximum nesting level (default C<512>) accepted while encoding
		344	or decoding. If the JSON text or Perl data structure has an equal or
		345	higher nesting level then this limit, then the encoder and decoder will
		346	stop and croak at that point.
		347
		348	Nesting level is defined by number of hash- or arrayrefs that the encoder
		349	needs to traverse to reach a given point or the number of C<{> or C<[>
		350	characters without their matching closing parenthesis crossed to reach a
		351	given character in a string.
		352
		353	Setting the maximum depth to one disallows any nesting, so that ensures
		354	that the object is only a single hash/object or array.
		355
		356	The argument to C<max_depth> will be rounded up to the next nearest power
		357	of two.
		358
		359	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
		360
198	=item $json_string = $json->encode ($perl_scalar)	361	=item $json_text = $json->encode ($perl_scalar)
199		362
200	Converts the given Perl data structure (a simple scalar or a reference	363	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	364	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	365	converted into JSON string or number sequences, while references to arrays
203	become JSON arrays and references to hashes become JSON objects. Undefined	366	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>	367	Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true>
205	nor C<false> values will be generated.	368	nor C<false> values will be generated.
206		369
207	=item $perl_scalar = $json->decode ($json_string)	370	=item $perl_scalar = $json->decode ($json_text)
208		371
209	The opposite of C<encode>: expects a JSON string and tries to parse it,	372	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.	373	returning the resulting simple scalar or reference. Croaks on error.
211		374
212	JSON numbers and strings become simple Perl scalars. JSON arrays become	375	JSON numbers and strings become simple Perl scalars. JSON arrays become
213	Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes	376	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>.	377	C<1>, C<false> becomes C<0> and C<null> becomes C<undef>.
215		378
216	=back	379	=back
217		380
		381
		382	=head1 MAPPING
		383
		384	This section describes how JSON::XS maps Perl values to JSON values and
		385	vice versa. These mappings are designed to "do the right thing" in most
		386	circumstances automatically, preserving round-tripping characteristics
		387	(what you put in comes out as something equivalent).
		388
		389	For the more enlightened: note that in the following descriptions,
		390	lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
		391	refers to the abstract Perl language itself.
		392
		393	=head2 JSON -> PERL
		394
		395	=over 4
		396
		397	=item object
		398
		399	A JSON object becomes a reference to a hash in Perl. No ordering of object
		400	keys is preserved (JSON does not preserver object key ordering itself).
		401
		402	=item array
		403
		404	A JSON array becomes a reference to an array in Perl.
		405
		406	=item string
		407
		408	A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON
		409	are represented by the same codepoints in the Perl string, so no manual
		410	decoding is necessary.
		411
		412	=item number
		413
		414	A JSON number becomes either an integer or numeric (floating point)
		415	scalar in perl, depending on its range and any fractional parts. On the
		416	Perl level, there is no difference between those as Perl handles all the
		417	conversion details, but an integer may take slightly less memory and might
		418	represent more values exactly than (floating point) numbers.
		419
		420	=item true, false
		421
		422	These JSON atoms become C<0>, C<1>, respectively. Information is lost in
		423	this process. Future versions might represent those values differently,
		424	but they will be guarenteed to act like these integers would normally in
		425	Perl.
		426
		427	=item null
		428
		429	A JSON null atom becomes C<undef> in Perl.
		430
		431	=back
		432
		433	=head2 PERL -> JSON
		434
		435	The mapping from Perl to JSON is slightly more difficult, as Perl is a
		436	truly typeless language, so we can only guess which JSON type is meant by
		437	a Perl value.
		438
		439	=over 4
		440
		441	=item hash references
		442
		443	Perl hash references become JSON objects. As there is no inherent ordering
		444	in hash keys (or JSON objects), they will usually be encoded in a
		445	pseudo-random order that can change between runs of the same program but
		446	stays generally the same within a single run of a program. JSON::XS can
		447	optionally sort the hash keys (determined by the I<canonical> flag), so
		448	the same datastructure will serialise to the same JSON text (given same
		449	settings and version of JSON::XS), but this incurs a runtime overhead
		450	and is only rarely useful, e.g. when you want to compare some JSON text
		451	against another for equality.
		452
		453	=item array references
		454
		455	Perl array references become JSON arrays.
		456
		457	=item other references
		458
		459	Other unblessed references are generally not allowed and will cause an
		460	exception to be thrown, except for references to the integers C<0> and
		461	C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
		462	also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
		463
		464	to_json [\0,JSON::XS::true] # yields [false,true]
		465
		466	=item blessed objects
		467
		468	Blessed objects are not allowed. JSON::XS currently tries to encode their
		469	underlying representation (hash- or arrayref), but this behaviour might
		470	change in future versions.
		471
		472	=item simple scalars
		473
		474	Simple Perl scalars (any scalar that is not a reference) are the most
		475	difficult objects to encode: JSON::XS will encode undefined scalars as
		476	JSON null value, scalars that have last been used in a string context
		477	before encoding as JSON strings and anything else as number value:
		478
		479	# dump as number
		480	to_json [2] # yields [2]
		481	to_json [-3.0e17] # yields [-3e+17]
		482	my $value = 5; to_json [$value] # yields [5]
		483
		484	# used as string, so dump as string
		485	print $value;
		486	to_json [$value] # yields ["5"]
		487
		488	# undef becomes null
		489	to_json [undef] # yields [null]
		490
		491	You can force the type to be a string by stringifying it:
		492
		493	my $x = 3.1; # some variable containing a number
		494	"$x"; # stringified
		495	$x .= ""; # another, more awkward way to stringify
		496	print $x; # perl does it for you, too, quite often
		497
		498	You can force the type to be a number by numifying it:
		499
		500	my $x = "3"; # some variable containing a string
		501	$x += 0; # numify it, ensuring it will be dumped as a number
		502	$x *= 1; # same thing, the choise is yours.
		503
		504	You can not currently output JSON booleans or force the type in other,
		505	less obscure, ways. Tell me if you need this capability.
		506
		507	=back
		508
		509
		510	=head1 COMPARISON
		511
		512	As already mentioned, this module was created because none of the existing
		513	JSON modules could be made to work correctly. First I will describe the
		514	problems (or pleasures) I encountered with various existing JSON modules,
		515	followed by some benchmark values. JSON::XS was designed not to suffer
		516	from any of these problems or limitations.
		517
		518	=over 4
		519
		520	=item JSON 1.07
		521
		522	Slow (but very portable, as it is written in pure Perl).
		523
		524	Undocumented/buggy Unicode handling (how JSON handles unicode values is
		525	undocumented. One can get far by feeding it unicode strings and doing
		526	en-/decoding oneself, but unicode escapes are not working properly).
		527
		528	No roundtripping (strings get clobbered if they look like numbers, e.g.
		529	the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will
		530	decode into the number 2.
		531
		532	=item JSON::PC 0.01
		533
		534	Very fast.
		535
		536	Undocumented/buggy Unicode handling.
		537
		538	No roundtripping.
		539
		540	Has problems handling many Perl values (e.g. regex results and other magic
		541	values will make it croak).
		542
		543	Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}>
		544	which is not a valid JSON text.
		545
		546	Unmaintained (maintainer unresponsive for many months, bugs are not
		547	getting fixed).
		548
		549	=item JSON::Syck 0.21
		550
		551	Very buggy (often crashes).
		552
		553	Very inflexible (no human-readable format supported, format pretty much
		554	undocumented. I need at least a format for easy reading by humans and a
		555	single-line compact format for use in a protocol, and preferably a way to
		556	generate ASCII-only JSON texts).
		557
		558	Completely broken (and confusingly documented) Unicode handling (unicode
		559	escapes are not working properly, you need to set ImplicitUnicode to
		560	I<different> values on en- and decoding to get symmetric behaviour).
		561
		562	No roundtripping (simple cases work, but this depends on wether the scalar
		563	value was used in a numeric context or not).
		564
		565	Dumping hashes may skip hash values depending on iterator state.
		566
		567	Unmaintained (maintainer unresponsive for many months, bugs are not
		568	getting fixed).
		569
		570	Does not check input for validity (i.e. will accept non-JSON input and
		571	return "something" instead of raising an exception. This is a security
		572	issue: imagine two banks transfering money between each other using
		573	JSON. One bank might parse a given non-JSON request and deduct money,
		574	while the other might reject the transaction with a syntax error. While a
		575	good protocol will at least recover, that is extra unnecessary work and
		576	the transaction will still not succeed).
		577
		578	=item JSON::DWIW 0.04
		579
		580	Very fast. Very natural. Very nice.
		581
		582	Undocumented unicode handling (but the best of the pack. Unicode escapes
		583	still don't get parsed properly).
		584
		585	Very inflexible.
		586
		587	No roundtripping.
		588
		589	Does not generate valid JSON texts (key strings are often unquoted, empty keys
		590	result in nothing being output)
		591
		592	Does not check input for validity.
		593
		594	=back
		595
		596	=head2 SPEED
		597
		598	It seems that JSON::XS is surprisingly fast, as shown in the following
		599	tables. They have been generated with the help of the C<eg/bench> program
		600	in the JSON::XS distribution, to make it easy to compare on your own
		601	system.
		602
		603	First comes a comparison between various modules using a very short JSON
		604	string:
		605
		606	{"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null}
		607
		608	It shows the number of encodes/decodes per second (JSON::XS uses the
		609	functional interface, while JSON::XS/2 uses the OO interface with
		610	pretty-printing and hashkey sorting enabled). Higher is better:
		611
		612	module \| encode \| decode \|
		613	-----------\|------------\|------------\|
		614	JSON \| 11488.516 \| 7823.035 \|
		615	JSON::DWIW \| 94708.054 \| 129094.260 \|
		616	JSON::PC \| 63884.157 \| 128528.212 \|
		617	JSON::Syck \| 34898.677 \| 42096.911 \|
		618	JSON::XS \| 654027.064 \| 396423.669 \|
		619	JSON::XS/2 \| 371564.190 \| 371725.613 \|
		620	-----------+------------+------------+
		621
		622	That is, JSON::XS is more than six times faster than JSON::DWIW on
		623	encoding, more than three times faster on decoding, and about thirty times
		624	faster than JSON, even with pretty-printing and key sorting.
		625
		626	Using a longer test string (roughly 18KB, generated from Yahoo! Locals
		627	search API (http://nanoref.com/yahooapis/mgPdGg):
		628
		629	module \| encode \| decode \|
		630	-----------\|------------\|------------\|
		631	JSON \| 273.023 \| 44.674 \|
		632	JSON::DWIW \| 1089.383 \| 1145.704 \|
		633	JSON::PC \| 3097.419 \| 2393.921 \|
		634	JSON::Syck \| 514.060 \| 843.053 \|
		635	JSON::XS \| 6479.668 \| 3636.364 \|
		636	JSON::XS/2 \| 3774.221 \| 3599.124 \|
		637	-----------+------------+------------+
		638
		639	Again, JSON::XS leads by far.
		640
		641	On large strings containing lots of high unicode characters, some modules
		642	(such as JSON::PC) seem to decode faster than JSON::XS, but the result
		643	will be broken due to missing (or wrong) unicode handling. Others refuse
		644	to decode or encode properly, so it was impossible to prepare a fair
		645	comparison table for that case.
		646
		647
		648	=head1 SECURITY CONSIDERATIONS
		649
		650	When you are using JSON in a protocol, talking to untrusted potentially
		651	hostile creatures requires relatively few measures.
		652
		653	First of all, your JSON decoder should be secure, that is, should not have
		654	any buffer overflows. Obviously, this module should ensure that and I am
		655	trying hard on making that true, but you never know.
		656
		657	Second, you need to avoid resource-starving attacks. That means you should
		658	limit the size of JSON texts you accept, or make sure then when your
		659	resources run out, thats just fine (e.g. by using a separate process that
		660	can crash safely). The size of a JSON text in octets or characters is
		661	usually a good indication of the size of the resources required to decode
		662	it into a Perl structure.
		663
		664	Third, JSON::XS recurses using the C stack when decoding objects and
		665	arrays. The C stack is a limited resource: for instance, on my amd64
		666	machine with 8MB of stack size I can decode around 180k nested arrays but
		667	only 14k nested JSON objects (due to perl itself recursing deeply on croak
		668	to free the temporary). If that is exceeded, the program crashes. to be
		669	conservative, the default nesting limit is set to 512. If your process
		670	has a smaller stack, you should adjust this setting accordingly with the
		671	C<max_depth> method.
		672
		673	And last but least, something else could bomb you that I forgot to think
		674	of. In that case, you get to keep the pieces. I am always open for hints,
		675	though...
		676
		677
		678	=head1 BUGS
		679
		680	While the goal of this module is to be correct, that unfortunately does
		681	not mean its bug-free, only that I think its design is bug-free. It is
		682	still relatively early in its development. If you keep reporting bugs they
		683	will be fixed swiftly, though.
		684
218	=cut	685	=cut
		686
		687	sub true() { \1 }
		688	sub false() { \0 }
219		689
220	1;	690	1;
221		691
222	=head1 AUTHOR	692	=head1 AUTHOR
223		693

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing JSON-XS/XS.pm (file contents): Revision 1.2 by root, Thu Mar 22 17:28:50 2007 UTC vs. Revision 1.33 by root, Wed May 9 16:10:37 2007 UTC

Diff Legend

Comparing JSON-XS/XS.pm (file contents):
Revision 1.2 by root, Thu Mar 22 17:28:50 2007 UTC vs.
Revision 1.33 by root, Wed May 9 16:10:37 2007 UTC