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Revision 1.35 by root, Thu Mar 11 19:31:37 2010 UTC

1NAME 1NAME
2 JSON::XS - JSON serialising/deserialising, done correctly and fast 2 JSON::XS - JSON serialising/deserialising, done correctly and fast
3 3
4 JSON::XS - 正しくて高速な JSON 4 JSON::XS - 正しくて高速な JSON シリアライザ/デシリアライザ
5 シリアライザ/デシリアライザ
6 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) 5 (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html)
7 6
8SYNOPSIS 7SYNOPSIS
9 use JSON::XS; 8 use JSON::XS;
10 9
11 # exported functions, they croak on error 10 # exported functions, they croak on error
12 # and expect/generate UTF-8 11 # and expect/generate UTF-8
13 12
14 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 13 $utf8_encoded_json_text = encode_json $perl_hash_or_arrayref;
15 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 14 $perl_hash_or_arrayref = decode_json $utf8_encoded_json_text;
16 15
17 # OO-interface 16 # OO-interface
18 17
19 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 18 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
20 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 19 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
21 $perl_scalar = $coder->decode ($unicode_json_text); 20 $perl_scalar = $coder->decode ($unicode_json_text);
21
22 # Note that JSON version 2.0 and above will automatically use JSON::XS
23 # if available, at virtually no speed overhead either, so you should
24 # be able to just:
25
26 use JSON;
27
28 # and do the same things, except that you have a pure-perl fallback now.
22 29
23DESCRIPTION 30DESCRIPTION
24 This module converts Perl data structures to JSON and vice versa. Its 31 This module converts Perl data structures to JSON and vice versa. Its
25 primary goal is to be *correct* and its secondary goal is to be *fast*. 32 primary goal is to be *correct* and its secondary goal is to be *fast*.
26 To reach the latter goal it was written in C. 33 To reach the latter goal it was written in C.
34
35 Beginning with version 2.0 of the JSON module, when both JSON and
36 JSON::XS are installed, then JSON will fall back on JSON::XS (this can
37 be overridden) with no overhead due to emulation (by inheriting
38 constructor and methods). If JSON::XS is not available, it will fall
39 back to the compatible JSON::PP module as backend, so using JSON instead
40 of JSON::XS gives you a portable JSON API that can be fast when you need
41 and doesn't require a C compiler when that is a problem.
27 42
28 As this is the n-th-something JSON module on CPAN, what was the reason 43 As this is the n-th-something JSON module on CPAN, what was the reason
29 to write yet another JSON module? While it seems there are many JSON 44 to write yet another JSON module? While it seems there are many JSON
30 modules, none of them correctly handle all corner cases, and in most 45 modules, none of them correctly handle all corner cases, and in most
31 cases their maintainers are unresponsive, gone missing, or not listening 46 cases their maintainers are unresponsive, gone missing, or not listening
32 to bug reports for other reasons. 47 to bug reports for other reasons.
33 48
34 See COMPARISON, below, for a comparison to some other JSON modules.
35
36 See MAPPING, below, on how JSON::XS maps perl values to JSON values and 49 See MAPPING, below, on how JSON::XS maps perl values to JSON values and
37 vice versa. 50 vice versa.
38 51
39 FEATURES 52 FEATURES
40 * correct unicode handling 53 * correct Unicode handling
54
41 This module knows how to handle Unicode, and even documents how and 55 This module knows how to handle Unicode, documents how and when it
42 when it does so. 56 does so, and even documents what "correct" means.
43 57
44 * round-trip integrity 58 * round-trip integrity
59
45 When you serialise a perl data structure using only datatypes 60 When you serialise a perl data structure using only data types
46 supported by JSON, the deserialised data structure is identical on 61 supported by JSON and Perl, the deserialised data structure is
47 the Perl level. (e.g. the string "2.0" doesn't suddenly become "2" 62 identical on the Perl level. (e.g. the string "2.0" doesn't suddenly
48 just because it looks like a number). 63 become "2" just because it looks like a number). There *are* minor
64 exceptions to this, read the MAPPING section below to learn about
65 those.
49 66
50 * strict checking of JSON correctness 67 * strict checking of JSON correctness
68
51 There is no guessing, no generating of illegal JSON texts by 69 There is no guessing, no generating of illegal JSON texts by
52 default, and only JSON is accepted as input by default (the latter 70 default, and only JSON is accepted as input by default (the latter
53 is a security feature). 71 is a security feature).
54 72
55 * fast 73 * fast
56 Compared to other JSON modules, this module compares favourably in
57 terms of speed, too.
58 74
75 Compared to other JSON modules and other serialisers such as
76 Storable, this module usually compares favourably in terms of speed,
77 too.
78
59 * simple to use 79 * simple to use
80
60 This module has both a simple functional interface as well as an OO 81 This module has both a simple functional interface as well as an
61 interface. 82 object oriented interface interface.
62 83
63 * reasonably versatile output formats 84 * reasonably versatile output formats
85
64 You can choose between the most compact guarenteed single-line 86 You can choose between the most compact guaranteed-single-line
65 format possible (nice for simple line-based protocols), a pure-ascii 87 format possible (nice for simple line-based protocols), a pure-ASCII
66 format (for when your transport is not 8-bit clean, still supports 88 format (for when your transport is not 8-bit clean, still supports
67 the whole unicode range), or a pretty-printed format (for when you 89 the whole Unicode range), or a pretty-printed format (for when you
68 want to read that stuff). Or you can combine those features in 90 want to read that stuff). Or you can combine those features in
69 whatever way you like. 91 whatever way you like.
70 92
71FUNCTIONAL INTERFACE 93FUNCTIONAL INTERFACE
72 The following convinience methods are provided by this module. They are 94 The following convenience methods are provided by this module. They are
73 exported by default: 95 exported by default:
74 96
75 $json_text = to_json $perl_scalar 97 $json_text = encode_json $perl_scalar
76 Converts the given Perl data structure to a UTF-8 encoded, binary 98 Converts the given Perl data structure to a UTF-8 encoded, binary
77 string (that is, the string contains octets only). Croaks on error. 99 string (that is, the string contains octets only). Croaks on error.
78 100
79 This function call is functionally identical to: 101 This function call is functionally identical to:
80 102
81 $json_text = JSON::XS->new->utf8->encode ($perl_scalar) 103 $json_text = JSON::XS->new->utf8->encode ($perl_scalar)
82 104
83 except being faster. 105 Except being faster.
84 106
85 $perl_scalar = from_json $json_text 107 $perl_scalar = decode_json $json_text
86 The opposite of "to_json": expects an UTF-8 (binary) string and 108 The opposite of "encode_json": expects an UTF-8 (binary) string and
87 tries to parse that as an UTF-8 encoded JSON text, returning the 109 tries to parse that as an UTF-8 encoded JSON text, returning the
88 resulting reference. Croaks on error. 110 resulting reference. Croaks on error.
89 111
90 This function call is functionally identical to: 112 This function call is functionally identical to:
91 113
92 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 114 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
93 115
94 except being faster. 116 Except being faster.
95 117
96 $is_boolean = JSON::XS::is_bool $scalar 118 $is_boolean = JSON::XS::is_bool $scalar
97 Returns true if the passed scalar represents either JSON::XS::true 119 Returns true if the passed scalar represents either JSON::XS::true
98 or JSON::XS::false, two constants that act like 1 and 0, 120 or JSON::XS::false, two constants that act like 1 and 0,
99 respectively and are used to represent JSON "true" and "false" 121 respectively and are used to represent JSON "true" and "false"
… …
105A FEW NOTES ON UNICODE AND PERL 127A FEW NOTES ON UNICODE AND PERL
106 Since this often leads to confusion, here are a few very clear words on 128 Since this often leads to confusion, here are a few very clear words on
107 how Unicode works in Perl, modulo bugs. 129 how Unicode works in Perl, modulo bugs.
108 130
109 1. Perl strings can store characters with ordinal values > 255. 131 1. Perl strings can store characters with ordinal values > 255.
110 This enables you to store unicode characters as single characters in 132 This enables you to store Unicode characters as single characters in
111 a Perl string - very natural. 133 a Perl string - very natural.
112 134
113 2. Perl does *not* associate an encoding with your strings. 135 2. Perl does *not* associate an encoding with your strings.
114 Unless you force it to, e.g. when matching it against a regex, or 136 ... until you force it to, e.g. when matching it against a regex, or
115 printing the scalar to a file, in which case Perl either interprets 137 printing the scalar to a file, in which case Perl either interprets
116 your string as locale-encoded text, octets/binary, or as Unicode, 138 your string as locale-encoded text, octets/binary, or as Unicode,
117 depending on various settings. In no case is an encoding stored 139 depending on various settings. In no case is an encoding stored
118 together with your data, it is *use* that decides encoding, not any 140 together with your data, it is *use* that decides encoding, not any
119 magical metadata. 141 magical meta data.
120 142
121 3. The internal utf-8 flag has no meaning with regards to the encoding 143 3. The internal utf-8 flag has no meaning with regards to the encoding
122 of your string. 144 of your string.
123 Just ignore that flag unless you debug a Perl bug, a module written 145 Just ignore that flag unless you debug a Perl bug, a module written
124 in XS or want to dive into the internals of perl. Otherwise it will 146 in XS or want to dive into the internals of perl. Otherwise it will
125 only confuse you, as, despite the name, it says nothing about how 147 only confuse you, as, despite the name, it says nothing about how
126 your string is encoded. You can have unicode strings with that flag 148 your string is encoded. You can have Unicode strings with that flag
127 set, with that flag clear, and you can have binary data with that 149 set, with that flag clear, and you can have binary data with that
128 flag set and that flag clear. Other possibilities exist, too. 150 flag set and that flag clear. Other possibilities exist, too.
129 151
130 If you didn't know about that flag, just the better, pretend it 152 If you didn't know about that flag, just the better, pretend it
131 doesn't exist. 153 doesn't exist.
132 154
133 4. A "Unicode String" is simply a string where each character can be 155 4. A "Unicode String" is simply a string where each character can be
134 validly interpreted as a Unicode codepoint. 156 validly interpreted as a Unicode code point.
135 If you have UTF-8 encoded data, it is no longer a Unicode string, 157 If you have UTF-8 encoded data, it is no longer a Unicode string,
136 but a Unicode string encoded in UTF-8, giving you a binary string. 158 but a Unicode string encoded in UTF-8, giving you a binary string.
137 159
138 5. A string containing "high" (> 255) character values is *not* a UTF-8 160 5. A string containing "high" (> 255) character values is *not* a UTF-8
139 string. 161 string.
140 Its a fact. Learn to live with it. 162 It's a fact. Learn to live with it.
141 163
142 I hope this helps :) 164 I hope this helps :)
143 165
144OBJECT-ORIENTED INTERFACE 166OBJECT-ORIENTED INTERFACE
145 The object oriented interface lets you configure your own encoding or 167 The object oriented interface lets you configure your own encoding or
… …
155 177
156 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) 178 my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]})
157 => {"a": [1, 2]} 179 => {"a": [1, 2]}
158 180
159 $json = $json->ascii ([$enable]) 181 $json = $json->ascii ([$enable])
182 $enabled = $json->get_ascii
160 If $enable is true (or missing), then the "encode" method will not 183 If $enable is true (or missing), then the "encode" method will not
161 generate characters outside the code range 0..127 (which is ASCII). 184 generate characters outside the code range 0..127 (which is ASCII).
162 Any unicode characters outside that range will be escaped using 185 Any Unicode characters outside that range will be escaped using
163 either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL 186 either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL
164 escape sequence, as per RFC4627. The resulting encoded JSON text can 187 escape sequence, as per RFC4627. The resulting encoded JSON text can
165 be treated as a native unicode string, an ascii-encoded, 188 be treated as a native Unicode string, an ascii-encoded,
166 latin1-encoded or UTF-8 encoded string, or any other superset of 189 latin1-encoded or UTF-8 encoded string, or any other superset of
167 ASCII. 190 ASCII.
168 191
169 If $enable is false, then the "encode" method will not escape 192 If $enable is false, then the "encode" method will not escape
170 Unicode characters unless required by the JSON syntax or other 193 Unicode characters unless required by the JSON syntax or other
171 flags. This results in a faster and more compact format. 194 flags. This results in a faster and more compact format.
172 195
196 See also the section *ENCODING/CODESET FLAG NOTES* later in this
197 document.
198
173 The main use for this flag is to produce JSON texts that can be 199 The main use for this flag is to produce JSON texts that can be
174 transmitted over a 7-bit channel, as the encoded JSON texts will not 200 transmitted over a 7-bit channel, as the encoded JSON texts will not
175 contain any 8 bit characters. 201 contain any 8 bit characters.
176 202
177 JSON::XS->new->ascii (1)->encode ([chr 0x10401]) 203 JSON::XS->new->ascii (1)->encode ([chr 0x10401])
178 => ["\ud801\udc01"] 204 => ["\ud801\udc01"]
179 205
180 $json = $json->latin1 ([$enable]) 206 $json = $json->latin1 ([$enable])
207 $enabled = $json->get_latin1
181 If $enable is true (or missing), then the "encode" method will 208 If $enable is true (or missing), then the "encode" method will
182 encode the resulting JSON text as latin1 (or iso-8859-1), escaping 209 encode the resulting JSON text as latin1 (or iso-8859-1), escaping
183 any characters outside the code range 0..255. The resulting string 210 any characters outside the code range 0..255. The resulting string
184 can be treated as a latin1-encoded JSON text or a native unicode 211 can be treated as a latin1-encoded JSON text or a native Unicode
185 string. The "decode" method will not be affected in any way by this 212 string. The "decode" method will not be affected in any way by this
186 flag, as "decode" by default expects unicode, which is a strict 213 flag, as "decode" by default expects Unicode, which is a strict
187 superset of latin1. 214 superset of latin1.
188 215
189 If $enable is false, then the "encode" method will not escape 216 If $enable is false, then the "encode" method will not escape
190 Unicode characters unless required by the JSON syntax or other 217 Unicode characters unless required by the JSON syntax or other
191 flags. 218 flags.
219
220 See also the section *ENCODING/CODESET FLAG NOTES* later in this
221 document.
192 222
193 The main use for this flag is efficiently encoding binary data as 223 The main use for this flag is efficiently encoding binary data as
194 JSON text, as most octets will not be escaped, resulting in a 224 JSON text, as most octets will not be escaped, resulting in a
195 smaller encoded size. The disadvantage is that the resulting JSON 225 smaller encoded size. The disadvantage is that the resulting JSON
196 text is encoded in latin1 (and must correctly be treated as such 226 text is encoded in latin1 (and must correctly be treated as such
197 when storing and transfering), a rare encoding for JSON. It is 227 when storing and transferring), a rare encoding for JSON. It is
198 therefore most useful when you want to store data structures known 228 therefore most useful when you want to store data structures known
199 to contain binary data efficiently in files or databases, not when 229 to contain binary data efficiently in files or databases, not when
200 talking to other JSON encoders/decoders. 230 talking to other JSON encoders/decoders.
201 231
202 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] 232 JSON::XS->new->latin1->encode (["\x{89}\x{abc}"]
203 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) 233 => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not)
204 234
205 $json = $json->utf8 ([$enable]) 235 $json = $json->utf8 ([$enable])
236 $enabled = $json->get_utf8
206 If $enable is true (or missing), then the "encode" method will 237 If $enable is true (or missing), then the "encode" method will
207 encode the JSON result into UTF-8, as required by many protocols, 238 encode the JSON result into UTF-8, as required by many protocols,
208 while the "decode" method expects to be handled an UTF-8-encoded 239 while the "decode" method expects to be handled an UTF-8-encoded
209 string. Please note that UTF-8-encoded strings do not contain any 240 string. Please note that UTF-8-encoded strings do not contain any
210 characters outside the range 0..255, they are thus useful for 241 characters outside the range 0..255, they are thus useful for
211 bytewise/binary I/O. In future versions, enabling this option might 242 bytewise/binary I/O. In future versions, enabling this option might
212 enable autodetection of the UTF-16 and UTF-32 encoding families, as 243 enable autodetection of the UTF-16 and UTF-32 encoding families, as
213 described in RFC4627. 244 described in RFC4627.
214 245
215 If $enable is false, then the "encode" method will return the JSON 246 If $enable is false, then the "encode" method will return the JSON
216 string as a (non-encoded) unicode string, while "decode" expects 247 string as a (non-encoded) Unicode string, while "decode" expects
217 thus a unicode string. Any decoding or encoding (e.g. to UTF-8 or 248 thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or
218 UTF-16) needs to be done yourself, e.g. using the Encode module. 249 UTF-16) needs to be done yourself, e.g. using the Encode module.
250
251 See also the section *ENCODING/CODESET FLAG NOTES* later in this
252 document.
219 253
220 Example, output UTF-16BE-encoded JSON: 254 Example, output UTF-16BE-encoded JSON:
221 255
222 use Encode; 256 use Encode;
223 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); 257 $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object);
… …
242 2 276 2
243 ] 277 ]
244 } 278 }
245 279
246 $json = $json->indent ([$enable]) 280 $json = $json->indent ([$enable])
281 $enabled = $json->get_indent
247 If $enable is true (or missing), then the "encode" method will use a 282 If $enable is true (or missing), then the "encode" method will use a
248 multiline format as output, putting every array member or 283 multiline format as output, putting every array member or
249 object/hash key-value pair into its own line, identing them 284 object/hash key-value pair into its own line, indenting them
250 properly. 285 properly.
251 286
252 If $enable is false, no newlines or indenting will be produced, and 287 If $enable is false, no newlines or indenting will be produced, and
253 the resulting JSON text is guarenteed not to contain any "newlines". 288 the resulting JSON text is guaranteed not to contain any "newlines".
254 289
255 This setting has no effect when decoding JSON texts. 290 This setting has no effect when decoding JSON texts.
256 291
257 $json = $json->space_before ([$enable]) 292 $json = $json->space_before ([$enable])
293 $enabled = $json->get_space_before
258 If $enable is true (or missing), then the "encode" method will add 294 If $enable is true (or missing), then the "encode" method will add
259 an extra optional space before the ":" separating keys from values 295 an extra optional space before the ":" separating keys from values
260 in JSON objects. 296 in JSON objects.
261 297
262 If $enable is false, then the "encode" method will not add any extra 298 If $enable is false, then the "encode" method will not add any extra
… …
268 Example, space_before enabled, space_after and indent disabled: 304 Example, space_before enabled, space_after and indent disabled:
269 305
270 {"key" :"value"} 306 {"key" :"value"}
271 307
272 $json = $json->space_after ([$enable]) 308 $json = $json->space_after ([$enable])
309 $enabled = $json->get_space_after
273 If $enable is true (or missing), then the "encode" method will add 310 If $enable is true (or missing), then the "encode" method will add
274 an extra optional space after the ":" separating keys from values in 311 an extra optional space after the ":" separating keys from values in
275 JSON objects and extra whitespace after the "," separating key-value 312 JSON objects and extra whitespace after the "," separating key-value
276 pairs and array members. 313 pairs and array members.
277 314
… …
283 Example, space_before and indent disabled, space_after enabled: 320 Example, space_before and indent disabled, space_after enabled:
284 321
285 {"key": "value"} 322 {"key": "value"}
286 323
287 $json = $json->relaxed ([$enable]) 324 $json = $json->relaxed ([$enable])
325 $enabled = $json->get_relaxed
288 If $enable is true (or missing), then "decode" will accept some 326 If $enable is true (or missing), then "decode" will accept some
289 extensions to normal JSON syntax (see below). "encode" will not be 327 extensions to normal JSON syntax (see below). "encode" will not be
290 affected in anyway. *Be aware that this option makes you accept 328 affected in anyway. *Be aware that this option makes you accept
291 invalid JSON texts as if they were valid!*. I suggest only to use 329 invalid JSON texts as if they were valid!*. I suggest only to use
292 this option to parse application-specific files written by humans 330 this option to parse application-specific files written by humans
… …
295 If $enable is false (the default), then "decode" will only accept 333 If $enable is false (the default), then "decode" will only accept
296 valid JSON texts. 334 valid JSON texts.
297 335
298 Currently accepted extensions are: 336 Currently accepted extensions are:
299 337
300 * list items can have an end-comma 338 * list items can have an end-comma
339
301 JSON *separates* array elements and key-value pairs with commas. 340 JSON *separates* array elements and key-value pairs with commas.
302 This can be annoying if you write JSON texts manually and want 341 This can be annoying if you write JSON texts manually and want
303 to be able to quickly append elements, so this extension accepts 342 to be able to quickly append elements, so this extension accepts
304 comma at the end of such items not just between them: 343 comma at the end of such items not just between them:
305 344
… …
310 { 349 {
311 "k1": "v1", 350 "k1": "v1",
312 "k2": "v2", <- this comma not normally allowed 351 "k2": "v2", <- this comma not normally allowed
313 } 352 }
314 353
315 * shell-style '#'-comments 354 * shell-style '#'-comments
355
316 Whenever JSON allows whitespace, shell-style comments are 356 Whenever JSON allows whitespace, shell-style comments are
317 additionally allowed. They are terminated by the first 357 additionally allowed. They are terminated by the first
318 carriage-return or line-feed character, after which more 358 carriage-return or line-feed character, after which more
319 white-space and comments are allowed. 359 white-space and comments are allowed.
320 360
… …
322 1, # this comment not allowed in JSON 362 1, # this comment not allowed in JSON
323 # neither this one... 363 # neither this one...
324 ] 364 ]
325 365
326 $json = $json->canonical ([$enable]) 366 $json = $json->canonical ([$enable])
367 $enabled = $json->get_canonical
327 If $enable is true (or missing), then the "encode" method will 368 If $enable is true (or missing), then the "encode" method will
328 output JSON objects by sorting their keys. This is adding a 369 output JSON objects by sorting their keys. This is adding a
329 comparatively high overhead. 370 comparatively high overhead.
330 371
331 If $enable is false, then the "encode" method will output key-value 372 If $enable is false, then the "encode" method will output key-value
332 pairs in the order Perl stores them (which will likely change 373 pairs in the order Perl stores them (which will likely change
333 between runs of the same script). 374 between runs of the same script).
334 375
335 This option is useful if you want the same data structure to be 376 This option is useful if you want the same data structure to be
336 encoded as the same JSON text (given the same overall settings). If 377 encoded as the same JSON text (given the same overall settings). If
337 it is disabled, the same hash migh be encoded differently even if 378 it is disabled, the same hash might be encoded differently even if
338 contains the same data, as key-value pairs have no inherent ordering 379 contains the same data, as key-value pairs have no inherent ordering
339 in Perl. 380 in Perl.
340 381
341 This setting has no effect when decoding JSON texts. 382 This setting has no effect when decoding JSON texts.
342 383
384 This setting has currently no effect on tied hashes.
385
343 $json = $json->allow_nonref ([$enable]) 386 $json = $json->allow_nonref ([$enable])
387 $enabled = $json->get_allow_nonref
344 If $enable is true (or missing), then the "encode" method can 388 If $enable is true (or missing), then the "encode" method can
345 convert a non-reference into its corresponding string, number or 389 convert a non-reference into its corresponding string, number or
346 null JSON value, which is an extension to RFC4627. Likewise, 390 null JSON value, which is an extension to RFC4627. Likewise,
347 "decode" will accept those JSON values instead of croaking. 391 "decode" will accept those JSON values instead of croaking.
348 392
… …
355 "allow_nonref", resulting in an invalid JSON text: 399 "allow_nonref", resulting in an invalid JSON text:
356 400
357 JSON::XS->new->allow_nonref->encode ("Hello, World!") 401 JSON::XS->new->allow_nonref->encode ("Hello, World!")
358 => "Hello, World!" 402 => "Hello, World!"
359 403
404 $json = $json->allow_unknown ([$enable])
405 $enabled = $json->get_allow_unknown
406 If $enable is true (or missing), then "encode" will *not* throw an
407 exception when it encounters values it cannot represent in JSON (for
408 example, filehandles) but instead will encode a JSON "null" value.
409 Note that blessed objects are not included here and are handled
410 separately by c<allow_nonref>.
411
412 If $enable is false (the default), then "encode" will throw an
413 exception when it encounters anything it cannot encode as JSON.
414
415 This option does not affect "decode" in any way, and it is
416 recommended to leave it off unless you know your communications
417 partner.
418
360 $json = $json->allow_blessed ([$enable]) 419 $json = $json->allow_blessed ([$enable])
420 $enabled = $json->get_allow_blessed
361 If $enable is true (or missing), then the "encode" method will not 421 If $enable is true (or missing), then the "encode" method will not
362 barf when it encounters a blessed reference. Instead, the value of 422 barf when it encounters a blessed reference. Instead, the value of
363 the convert_blessed option will decide wether "null" 423 the convert_blessed option will decide whether "null"
364 ("convert_blessed" disabled or no "to_json" method found) or a 424 ("convert_blessed" disabled or no "TO_JSON" method found) or a
365 representation of the object ("convert_blessed" enabled and 425 representation of the object ("convert_blessed" enabled and
366 "to_json" method found) is being encoded. Has no effect on "decode". 426 "TO_JSON" method found) is being encoded. Has no effect on "decode".
367 427
368 If $enable is false (the default), then "encode" will throw an 428 If $enable is false (the default), then "encode" will throw an
369 exception when it encounters a blessed object. 429 exception when it encounters a blessed object.
370 430
371 $json = $json->convert_blessed ([$enable]) 431 $json = $json->convert_blessed ([$enable])
432 $enabled = $json->get_convert_blessed
372 If $enable is true (or missing), then "encode", upon encountering a 433 If $enable is true (or missing), then "encode", upon encountering a
373 blessed object, will check for the availability of the "TO_JSON" 434 blessed object, will check for the availability of the "TO_JSON"
374 method on the object's class. If found, it will be called in scalar 435 method on the object's class. If found, it will be called in scalar
375 context and the resulting scalar will be encoded instead of the 436 context and the resulting scalar will be encoded instead of the
376 object. If no "TO_JSON" method is found, the value of 437 object. If no "TO_JSON" method is found, the value of
… …
380 returns other blessed objects, those will be handled in the same 441 returns other blessed objects, those will be handled in the same
381 way. "TO_JSON" must take care of not causing an endless recursion 442 way. "TO_JSON" must take care of not causing an endless recursion
382 cycle (== crash) in this case. The name of "TO_JSON" was chosen 443 cycle (== crash) in this case. The name of "TO_JSON" was chosen
383 because other methods called by the Perl core (== not by the user of 444 because other methods called by the Perl core (== not by the user of
384 the object) are usually in upper case letters and to avoid 445 the object) are usually in upper case letters and to avoid
385 collisions with the "to_json" function. 446 collisions with any "to_json" function or method.
386 447
387 This setting does not yet influence "decode" in any way, but in the 448 This setting does not yet influence "decode" in any way, but in the
388 future, global hooks might get installed that influence "decode" and 449 future, global hooks might get installed that influence "decode" and
389 are enabled by this setting. 450 are enabled by this setting.
390 451
… …
431 492
432 As this callback gets called less often then the 493 As this callback gets called less often then the
433 "filter_json_object" one, decoding speed will not usually suffer as 494 "filter_json_object" one, decoding speed will not usually suffer as
434 much. Therefore, single-key objects make excellent targets to 495 much. Therefore, single-key objects make excellent targets to
435 serialise Perl objects into, especially as single-key JSON objects 496 serialise Perl objects into, especially as single-key JSON objects
436 are as close to the type-tagged value concept as JSON gets (its 497 are as close to the type-tagged value concept as JSON gets (it's
437 basically an ID/VALUE tuple). Of course, JSON does not support this 498 basically an ID/VALUE tuple). Of course, JSON does not support this
438 in any way, so you need to make sure your data never looks like a 499 in any way, so you need to make sure your data never looks like a
439 serialised Perl hash. 500 serialised Perl hash.
440 501
441 Typical names for the single object key are "__class_whatever__", or 502 Typical names for the single object key are "__class_whatever__", or
… …
466 527
467 { __widget__ => $self->{id} } 528 { __widget__ => $self->{id} }
468 } 529 }
469 530
470 $json = $json->shrink ([$enable]) 531 $json = $json->shrink ([$enable])
532 $enabled = $json->get_shrink
471 Perl usually over-allocates memory a bit when allocating space for 533 Perl usually over-allocates memory a bit when allocating space for
472 strings. This flag optionally resizes strings generated by either 534 strings. This flag optionally resizes strings generated by either
473 "encode" or "decode" to their minimum size possible. This can save 535 "encode" or "decode" to their minimum size possible. This can save
474 memory when your JSON texts are either very very long or you have 536 memory when your JSON texts are either very very long or you have
475 many short strings. It will also try to downgrade any strings to 537 many short strings. It will also try to downgrade any strings to
… …
493 converting strings that look like integers or floats into integers 555 converting strings that look like integers or floats into integers
494 or floats internally (there is no difference on the Perl level), 556 or floats internally (there is no difference on the Perl level),
495 saving space. 557 saving space.
496 558
497 $json = $json->max_depth ([$maximum_nesting_depth]) 559 $json = $json->max_depth ([$maximum_nesting_depth])
560 $max_depth = $json->get_max_depth
498 Sets the maximum nesting level (default 512) accepted while encoding 561 Sets the maximum nesting level (default 512) accepted while encoding
499 or decoding. If the JSON text or Perl data structure has an equal or 562 or decoding. If a higher nesting level is detected in JSON text or a
500 higher nesting level then this limit, then the encoder and decoder 563 Perl data structure, then the encoder and decoder will stop and
501 will stop and croak at that point. 564 croak at that point.
502 565
503 Nesting level is defined by number of hash- or arrayrefs that the 566 Nesting level is defined by number of hash- or arrayrefs that the
504 encoder needs to traverse to reach a given point or the number of 567 encoder needs to traverse to reach a given point or the number of
505 "{" or "[" characters without their matching closing parenthesis 568 "{" or "[" characters without their matching closing parenthesis
506 crossed to reach a given character in a string. 569 crossed to reach a given character in a string.
507 570
508 Setting the maximum depth to one disallows any nesting, so that 571 Setting the maximum depth to one disallows any nesting, so that
509 ensures that the object is only a single hash/object or array. 572 ensures that the object is only a single hash/object or array.
510 573
511 The argument to "max_depth" will be rounded up to the next highest
512 power of two. If no argument is given, the highest possible setting 574 If no argument is given, the highest possible setting will be used,
513 will be used, which is rarely useful. 575 which is rarely useful.
576
577 Note that nesting is implemented by recursion in C. The default
578 value has been chosen to be as large as typical operating systems
579 allow without crashing.
514 580
515 See SECURITY CONSIDERATIONS, below, for more info on why this is 581 See SECURITY CONSIDERATIONS, below, for more info on why this is
516 useful. 582 useful.
517 583
518 $json = $json->max_size ([$maximum_string_size]) 584 $json = $json->max_size ([$maximum_string_size])
585 $max_size = $json->get_max_size
519 Set the maximum length a JSON text may have (in bytes) where 586 Set the maximum length a JSON text may have (in bytes) where
520 decoding is being attempted. The default is 0, meaning no limit. 587 decoding is being attempted. The default is 0, meaning no limit.
521 When "decode" is called on a string longer then this number of 588 When "decode" is called on a string that is longer then this many
522 characters it will not attempt to decode the string but throw an 589 bytes, it will not attempt to decode the string but throw an
523 exception. This setting has no effect on "encode" (yet). 590 exception. This setting has no effect on "encode" (yet).
524 591
525 The argument to "max_size" will be rounded up to the next highest
526 power of two (so may be more than requested). If no argument is
527 given, the limit check will be deactivated (same as when 0 is 592 If no argument is given, the limit check will be deactivated (same
528 specified). 593 as when 0 is specified).
529 594
530 See SECURITY CONSIDERATIONS, below, for more info on why this is 595 See SECURITY CONSIDERATIONS, below, for more info on why this is
531 useful. 596 useful.
532 597
533 $json_text = $json->encode ($perl_scalar) 598 $json_text = $json->encode ($perl_scalar)
… …
558 and you need to know where the JSON text ends. 623 and you need to know where the JSON text ends.
559 624
560 JSON::XS->new->decode_prefix ("[1] the tail") 625 JSON::XS->new->decode_prefix ("[1] the tail")
561 => ([], 3) 626 => ([], 3)
562 627
628INCREMENTAL PARSING
629 In some cases, there is the need for incremental parsing of JSON texts.
630 While this module always has to keep both JSON text and resulting Perl
631 data structure in memory at one time, it does allow you to parse a JSON
632 stream incrementally. It does so by accumulating text until it has a
633 full JSON object, which it then can decode. This process is similar to
634 using "decode_prefix" to see if a full JSON object is available, but is
635 much more efficient (and can be implemented with a minimum of method
636 calls).
637
638 JSON::XS will only attempt to parse the JSON text once it is sure it has
639 enough text to get a decisive result, using a very simple but truly
640 incremental parser. This means that it sometimes won't stop as early as
641 the full parser, for example, it doesn't detect parenthese mismatches.
642 The only thing it guarantees is that it starts decoding as soon as a
643 syntactically valid JSON text has been seen. This means you need to set
644 resource limits (e.g. "max_size") to ensure the parser will stop parsing
645 in the presence if syntax errors.
646
647 The following methods implement this incremental parser.
648
649 [void, scalar or list context] = $json->incr_parse ([$string])
650 This is the central parsing function. It can both append new text
651 and extract objects from the stream accumulated so far (both of
652 these functions are optional).
653
654 If $string is given, then this string is appended to the already
655 existing JSON fragment stored in the $json object.
656
657 After that, if the function is called in void context, it will
658 simply return without doing anything further. This can be used to
659 add more text in as many chunks as you want.
660
661 If the method is called in scalar context, then it will try to
662 extract exactly *one* JSON object. If that is successful, it will
663 return this object, otherwise it will return "undef". If there is a
664 parse error, this method will croak just as "decode" would do (one
665 can then use "incr_skip" to skip the errornous part). This is the
666 most common way of using the method.
667
668 And finally, in list context, it will try to extract as many objects
669 from the stream as it can find and return them, or the empty list
670 otherwise. For this to work, there must be no separators between the
671 JSON objects or arrays, instead they must be concatenated
672 back-to-back. If an error occurs, an exception will be raised as in
673 the scalar context case. Note that in this case, any
674 previously-parsed JSON texts will be lost.
675
676 Example: Parse some JSON arrays/objects in a given string and return
677 them.
678
679 my @objs = JSON::XS->new->incr_parse ("[5][7][1,2]");
680
681 $lvalue_string = $json->incr_text
682 This method returns the currently stored JSON fragment as an lvalue,
683 that is, you can manipulate it. This *only* works when a preceding
684 call to "incr_parse" in *scalar context* successfully returned an
685 object. Under all other circumstances you must not call this
686 function (I mean it. although in simple tests it might actually
687 work, it *will* fail under real world conditions). As a special
688 exception, you can also call this method before having parsed
689 anything.
690
691 This function is useful in two cases: a) finding the trailing text
692 after a JSON object or b) parsing multiple JSON objects separated by
693 non-JSON text (such as commas).
694
695 $json->incr_skip
696 This will reset the state of the incremental parser and will remove
697 the parsed text from the input buffer so far. This is useful after
698 "incr_parse" died, in which case the input buffer and incremental
699 parser state is left unchanged, to skip the text parsed so far and
700 to reset the parse state.
701
702 The difference to "incr_reset" is that only text until the parse
703 error occured is removed.
704
705 $json->incr_reset
706 This completely resets the incremental parser, that is, after this
707 call, it will be as if the parser had never parsed anything.
708
709 This is useful if you want to repeatedly parse JSON objects and want
710 to ignore any trailing data, which means you have to reset the
711 parser after each successful decode.
712
713 LIMITATIONS
714 All options that affect decoding are supported, except "allow_nonref".
715 The reason for this is that it cannot be made to work sensibly: JSON
716 objects and arrays are self-delimited, i.e. you can concatenate them
717 back to back and still decode them perfectly. This does not hold true
718 for JSON numbers, however.
719
720 For example, is the string 1 a single JSON number, or is it simply the
721 start of 12? Or is 12 a single JSON number, or the concatenation of 1
722 and 2? In neither case you can tell, and this is why JSON::XS takes the
723 conservative route and disallows this case.
724
725 EXAMPLES
726 Some examples will make all this clearer. First, a simple example that
727 works similarly to "decode_prefix": We want to decode the JSON object at
728 the start of a string and identify the portion after the JSON object:
729
730 my $text = "[1,2,3] hello";
731
732 my $json = new JSON::XS;
733
734 my $obj = $json->incr_parse ($text)
735 or die "expected JSON object or array at beginning of string";
736
737 my $tail = $json->incr_text;
738 # $tail now contains " hello"
739
740 Easy, isn't it?
741
742 Now for a more complicated example: Imagine a hypothetical protocol
743 where you read some requests from a TCP stream, and each request is a
744 JSON array, without any separation between them (in fact, it is often
745 useful to use newlines as "separators", as these get interpreted as
746 whitespace at the start of the JSON text, which makes it possible to
747 test said protocol with "telnet"...).
748
749 Here is how you'd do it (it is trivial to write this in an event-based
750 manner):
751
752 my $json = new JSON::XS;
753
754 # read some data from the socket
755 while (sysread $socket, my $buf, 4096) {
756
757 # split and decode as many requests as possible
758 for my $request ($json->incr_parse ($buf)) {
759 # act on the $request
760 }
761 }
762
763 Another complicated example: Assume you have a string with JSON objects
764 or arrays, all separated by (optional) comma characters (e.g. "[1],[2],
765 [3]"). To parse them, we have to skip the commas between the JSON texts,
766 and here is where the lvalue-ness of "incr_text" comes in useful:
767
768 my $text = "[1],[2], [3]";
769 my $json = new JSON::XS;
770
771 # void context, so no parsing done
772 $json->incr_parse ($text);
773
774 # now extract as many objects as possible. note the
775 # use of scalar context so incr_text can be called.
776 while (my $obj = $json->incr_parse) {
777 # do something with $obj
778
779 # now skip the optional comma
780 $json->incr_text =~ s/^ \s* , //x;
781 }
782
783 Now lets go for a very complex example: Assume that you have a gigantic
784 JSON array-of-objects, many gigabytes in size, and you want to parse it,
785 but you cannot load it into memory fully (this has actually happened in
786 the real world :).
787
788 Well, you lost, you have to implement your own JSON parser. But JSON::XS
789 can still help you: You implement a (very simple) array parser and let
790 JSON decode the array elements, which are all full JSON objects on their
791 own (this wouldn't work if the array elements could be JSON numbers, for
792 example):
793
794 my $json = new JSON::XS;
795
796 # open the monster
797 open my $fh, "<bigfile.json"
798 or die "bigfile: $!";
799
800 # first parse the initial "["
801 for (;;) {
802 sysread $fh, my $buf, 65536
803 or die "read error: $!";
804 $json->incr_parse ($buf); # void context, so no parsing
805
806 # Exit the loop once we found and removed(!) the initial "[".
807 # In essence, we are (ab-)using the $json object as a simple scalar
808 # we append data to.
809 last if $json->incr_text =~ s/^ \s* \[ //x;
810 }
811
812 # now we have the skipped the initial "[", so continue
813 # parsing all the elements.
814 for (;;) {
815 # in this loop we read data until we got a single JSON object
816 for (;;) {
817 if (my $obj = $json->incr_parse) {
818 # do something with $obj
819 last;
820 }
821
822 # add more data
823 sysread $fh, my $buf, 65536
824 or die "read error: $!";
825 $json->incr_parse ($buf); # void context, so no parsing
826 }
827
828 # in this loop we read data until we either found and parsed the
829 # separating "," between elements, or the final "]"
830 for (;;) {
831 # first skip whitespace
832 $json->incr_text =~ s/^\s*//;
833
834 # if we find "]", we are done
835 if ($json->incr_text =~ s/^\]//) {
836 print "finished.\n";
837 exit;
838 }
839
840 # if we find ",", we can continue with the next element
841 if ($json->incr_text =~ s/^,//) {
842 last;
843 }
844
845 # if we find anything else, we have a parse error!
846 if (length $json->incr_text) {
847 die "parse error near ", $json->incr_text;
848 }
849
850 # else add more data
851 sysread $fh, my $buf, 65536
852 or die "read error: $!";
853 $json->incr_parse ($buf); # void context, so no parsing
854 }
855
856 This is a complex example, but most of the complexity comes from the
857 fact that we are trying to be correct (bear with me if I am wrong, I
858 never ran the above example :).
859
563MAPPING 860MAPPING
564 This section describes how JSON::XS maps Perl values to JSON values and 861 This section describes how JSON::XS maps Perl values to JSON values and
565 vice versa. These mappings are designed to "do the right thing" in most 862 vice versa. These mappings are designed to "do the right thing" in most
566 circumstances automatically, preserving round-tripping characteristics 863 circumstances automatically, preserving round-tripping characteristics
567 (what you put in comes out as something equivalent). 864 (what you put in comes out as something equivalent).
568 865
569 For the more enlightened: note that in the following descriptions, 866 For the more enlightened: note that in the following descriptions,
570 lowercase *perl* refers to the Perl interpreter, while uppcercase *Perl* 867 lowercase *perl* refers to the Perl interpreter, while uppercase *Perl*
571 refers to the abstract Perl language itself. 868 refers to the abstract Perl language itself.
572 869
573 JSON -> PERL 870 JSON -> PERL
574 object 871 object
575 A JSON object becomes a reference to a hash in Perl. No ordering of 872 A JSON object becomes a reference to a hash in Perl. No ordering of
576 object keys is preserved (JSON does not preserver object key 873 object keys is preserved (JSON does not preserve object key ordering
577 ordering itself). 874 itself).
578 875
579 array 876 array
580 A JSON array becomes a reference to an array in Perl. 877 A JSON array becomes a reference to an array in Perl.
581 878
582 string 879 string
… …
588 A JSON number becomes either an integer, numeric (floating point) or 885 A JSON number becomes either an integer, numeric (floating point) or
589 string scalar in perl, depending on its range and any fractional 886 string scalar in perl, depending on its range and any fractional
590 parts. On the Perl level, there is no difference between those as 887 parts. On the Perl level, there is no difference between those as
591 Perl handles all the conversion details, but an integer may take 888 Perl handles all the conversion details, but an integer may take
592 slightly less memory and might represent more values exactly than 889 slightly less memory and might represent more values exactly than
593 (floating point) numbers. 890 floating point numbers.
594 891
595 If the number consists of digits only, JSON::XS will try to 892 If the number consists of digits only, JSON::XS will try to
596 represent it as an integer value. If that fails, it will try to 893 represent it as an integer value. If that fails, it will try to
597 represent it as a numeric (floating point) value if that is possible 894 represent it as a numeric (floating point) value if that is possible
598 without loss of precision. Otherwise it will preserve the number as 895 without loss of precision. Otherwise it will preserve the number as
599 a string value. 896 a string value (in which case you lose roundtripping ability, as the
897 JSON number will be re-encoded toa JSON string).
600 898
601 Numbers containing a fractional or exponential part will always be 899 Numbers containing a fractional or exponential part will always be
602 represented as numeric (floating point) values, possibly at a loss 900 represented as numeric (floating point) values, possibly at a loss
603 of precision. 901 of precision (in which case you might lose perfect roundtripping
902 ability, but the JSON number will still be re-encoded as a JSON
903 number).
604 904
605 This might create round-tripping problems as numbers might become 905 Note that precision is not accuracy - binary floating point values
606 strings, but as Perl is typeless there is no other way to do it. 906 cannot represent most decimal fractions exactly, and when converting
907 from and to floating point, JSON::XS only guarantees precision up to
908 but not including the leats significant bit.
607 909
608 true, false 910 true, false
609 These JSON atoms become "JSON::XS::true" and "JSON::XS::false", 911 These JSON atoms become "JSON::XS::true" and "JSON::XS::false",
610 respectively. They are overloaded to act almost exactly like the 912 respectively. They are overloaded to act almost exactly like the
611 numbers 1 and 0. You can check wether a scalar is a JSON boolean by 913 numbers 1 and 0. You can check whether a scalar is a JSON boolean by
612 using the "JSON::XS::is_bool" function. 914 using the "JSON::XS::is_bool" function.
613 915
614 null 916 null
615 A JSON null atom becomes "undef" in Perl. 917 A JSON null atom becomes "undef" in Perl.
616 918
… …
639 an exception to be thrown, except for references to the integers 0 941 an exception to be thrown, except for references to the integers 0
640 and 1, which get turned into "false" and "true" atoms in JSON. You 942 and 1, which get turned into "false" and "true" atoms in JSON. You
641 can also use "JSON::XS::false" and "JSON::XS::true" to improve 943 can also use "JSON::XS::false" and "JSON::XS::true" to improve
642 readability. 944 readability.
643 945
644 to_json [\0,JSON::XS::true] # yields [false,true] 946 encode_json [\0, JSON::XS::true] # yields [false,true]
645 947
646 JSON::XS::true, JSON::XS::false 948 JSON::XS::true, JSON::XS::false
647 These special values become JSON true and JSON false values, 949 These special values become JSON true and JSON false values,
648 respectively. You can also use "\1" and "\0" directly if you want. 950 respectively. You can also use "\1" and "\0" directly if you want.
649 951
650 blessed objects 952 blessed objects
651 Blessed objects are not allowed. JSON::XS currently tries to encode 953 Blessed objects are not directly representable in JSON. See the
652 their underlying representation (hash- or arrayref), but this 954 "allow_blessed" and "convert_blessed" methods on various options on
653 behaviour might change in future versions. 955 how to deal with this: basically, you can choose between throwing an
956 exception, encoding the reference as if it weren't blessed, or
957 provide your own serialiser method.
654 958
655 simple scalars 959 simple scalars
656 Simple Perl scalars (any scalar that is not a reference) are the 960 Simple Perl scalars (any scalar that is not a reference) are the
657 most difficult objects to encode: JSON::XS will encode undefined 961 most difficult objects to encode: JSON::XS will encode undefined
658 scalars as JSON null value, scalars that have last been used in a 962 scalars as JSON "null" values, scalars that have last been used in a
659 string context before encoding as JSON strings and anything else as 963 string context before encoding as JSON strings, and anything else as
660 number value: 964 number value:
661 965
662 # dump as number 966 # dump as number
663 to_json [2] # yields [2] 967 encode_json [2] # yields [2]
664 to_json [-3.0e17] # yields [-3e+17] 968 encode_json [-3.0e17] # yields [-3e+17]
665 my $value = 5; to_json [$value] # yields [5] 969 my $value = 5; encode_json [$value] # yields [5]
666 970
667 # used as string, so dump as string 971 # used as string, so dump as string
668 print $value; 972 print $value;
669 to_json [$value] # yields ["5"] 973 encode_json [$value] # yields ["5"]
670 974
671 # undef becomes null 975 # undef becomes null
672 to_json [undef] # yields [null] 976 encode_json [undef] # yields [null]
673 977
674 You can force the type to be a string by stringifying it: 978 You can force the type to be a JSON string by stringifying it:
675 979
676 my $x = 3.1; # some variable containing a number 980 my $x = 3.1; # some variable containing a number
677 "$x"; # stringified 981 "$x"; # stringified
678 $x .= ""; # another, more awkward way to stringify 982 $x .= ""; # another, more awkward way to stringify
679 print $x; # perl does it for you, too, quite often 983 print $x; # perl does it for you, too, quite often
680 984
681 You can force the type to be a number by numifying it: 985 You can force the type to be a JSON number by numifying it:
682 986
683 my $x = "3"; # some variable containing a string 987 my $x = "3"; # some variable containing a string
684 $x += 0; # numify it, ensuring it will be dumped as a number 988 $x += 0; # numify it, ensuring it will be dumped as a number
685 $x *= 1; # same thing, the choise is yours. 989 $x *= 1; # same thing, the choice is yours.
686 990
687 You can not currently output JSON booleans or force the type in 991 You can not currently force the type in other, less obscure, ways.
688 other, less obscure, ways. Tell me if you need this capability. 992 Tell me if you need this capability (but don't forget to explain why
993 it's needed :).
689 994
690COMPARISON 995 Note that numerical precision has the same meaning as under Perl (so
691 As already mentioned, this module was created because none of the 996 binary to decimal conversion follows the same rules as in Perl,
692 existing JSON modules could be made to work correctly. First I will 997 which can differ to other languages). Also, your perl interpreter
693 describe the problems (or pleasures) I encountered with various existing 998 might expose extensions to the floating point numbers of your
694 JSON modules, followed by some benchmark values. JSON::XS was designed 999 platform, such as infinities or NaN's - these cannot be represented
695 not to suffer from any of these problems or limitations. 1000 in JSON, and it is an error to pass those in.
696 1001
697 JSON 1.07 1002ENCODING/CODESET FLAG NOTES
698 Slow (but very portable, as it is written in pure Perl). 1003 The interested reader might have seen a number of flags that signify
1004 encodings or codesets - "utf8", "latin1" and "ascii". There seems to be
1005 some confusion on what these do, so here is a short comparison:
699 1006
700 Undocumented/buggy Unicode handling (how JSON handles unicode values 1007 "utf8" controls whether the JSON text created by "encode" (and expected
701 is undocumented. One can get far by feeding it unicode strings and 1008 by "decode") is UTF-8 encoded or not, while "latin1" and "ascii" only
702 doing en-/decoding oneself, but unicode escapes are not working 1009 control whether "encode" escapes character values outside their
1010 respective codeset range. Neither of these flags conflict with each
1011 other, although some combinations make less sense than others.
1012
1013 Care has been taken to make all flags symmetrical with respect to
1014 "encode" and "decode", that is, texts encoded with any combination of
1015 these flag values will be correctly decoded when the same flags are used
1016 - in general, if you use different flag settings while encoding vs. when
1017 decoding you likely have a bug somewhere.
1018
1019 Below comes a verbose discussion of these flags. Note that a "codeset"
1020 is simply an abstract set of character-codepoint pairs, while an
1021 encoding takes those codepoint numbers and *encodes* them, in our case
1022 into octets. Unicode is (among other things) a codeset, UTF-8 is an
1023 encoding, and ISO-8859-1 (= latin 1) and ASCII are both codesets *and*
1024 encodings at the same time, which can be confusing.
1025
1026 "utf8" flag disabled
1027 When "utf8" is disabled (the default), then "encode"/"decode"
1028 generate and expect Unicode strings, that is, characters with high
1029 ordinal Unicode values (> 255) will be encoded as such characters,
1030 and likewise such characters are decoded as-is, no canges to them
1031 will be done, except "(re-)interpreting" them as Unicode codepoints
1032 or Unicode characters, respectively (to Perl, these are the same
1033 thing in strings unless you do funny/weird/dumb stuff).
1034
1035 This is useful when you want to do the encoding yourself (e.g. when
1036 you want to have UTF-16 encoded JSON texts) or when some other layer
1037 does the encoding for you (for example, when printing to a terminal
1038 using a filehandle that transparently encodes to UTF-8 you certainly
1039 do NOT want to UTF-8 encode your data first and have Perl encode it
1040 another time).
1041
1042 "utf8" flag enabled
1043 If the "utf8"-flag is enabled, "encode"/"decode" will encode all
1044 characters using the corresponding UTF-8 multi-byte sequence, and
1045 will expect your input strings to be encoded as UTF-8, that is, no
1046 "character" of the input string must have any value > 255, as UTF-8
1047 does not allow that.
1048
1049 The "utf8" flag therefore switches between two modes: disabled means
1050 you will get a Unicode string in Perl, enabled means you get an
1051 UTF-8 encoded octet/binary string in Perl.
1052
1053 "latin1" or "ascii" flags enabled
1054 With "latin1" (or "ascii") enabled, "encode" will escape characters
1055 with ordinal values > 255 (> 127 with "ascii") and encode the
1056 remaining characters as specified by the "utf8" flag.
1057
1058 If "utf8" is disabled, then the result is also correctly encoded in
1059 those character sets (as both are proper subsets of Unicode, meaning
1060 that a Unicode string with all character values < 256 is the same
1061 thing as a ISO-8859-1 string, and a Unicode string with all
1062 character values < 128 is the same thing as an ASCII string in
703 properly). 1063 Perl).
704 1064
705 No roundtripping (strings get clobbered if they look like numbers, 1065 If "utf8" is enabled, you still get a correct UTF-8-encoded string,
706 e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that 1066 regardless of these flags, just some more characters will be escaped
707 will decode into the number 2. 1067 using "\uXXXX" then before.
708 1068
709 JSON::PC 0.01 1069 Note that ISO-8859-1-*encoded* strings are not compatible with UTF-8
710 Very fast. 1070 encoding, while ASCII-encoded strings are. That is because the
1071 ISO-8859-1 encoding is NOT a subset of UTF-8 (despite the ISO-8859-1
1072 *codeset* being a subset of Unicode), while ASCII is.
711 1073
712 Undocumented/buggy Unicode handling. 1074 Surprisingly, "decode" will ignore these flags and so treat all
1075 input values as governed by the "utf8" flag. If it is disabled, this
1076 allows you to decode ISO-8859-1- and ASCII-encoded strings, as both
1077 strict subsets of Unicode. If it is enabled, you can correctly
1078 decode UTF-8 encoded strings.
713 1079
714 No roundtripping. 1080 So neither "latin1" nor "ascii" are incompatible with the "utf8"
1081 flag - they only govern when the JSON output engine escapes a
1082 character or not.
715 1083
716 Has problems handling many Perl values (e.g. regex results and other 1084 The main use for "latin1" is to relatively efficiently store binary
717 magic values will make it croak). 1085 data as JSON, at the expense of breaking compatibility with most
1086 JSON decoders.
718 1087
719 Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}" 1088 The main use for "ascii" is to force the output to not contain
720 which is not a valid JSON text. 1089 characters with values > 127, which means you can interpret the
1090 resulting string as UTF-8, ISO-8859-1, ASCII, KOI8-R or most about
1091 any character set and 8-bit-encoding, and still get the same data
1092 structure back. This is useful when your channel for JSON transfer
1093 is not 8-bit clean or the encoding might be mangled in between (e.g.
1094 in mail), and works because ASCII is a proper subset of most 8-bit
1095 and multibyte encodings in use in the world.
721 1096
722 Unmaintained (maintainer unresponsive for many months, bugs are not 1097 JSON and ECMAscript
723 getting fixed). 1098 JSON syntax is based on how literals are represented in javascript (the
1099 not-standardised predecessor of ECMAscript) which is presumably why it
1100 is called "JavaScript Object Notation".
724 1101
725 JSON::Syck 0.21 1102 However, JSON is not a subset (and also not a superset of course) of
726 Very buggy (often crashes). 1103 ECMAscript (the standard) or javascript (whatever browsers actually
1104 implement).
727 1105
728 Very inflexible (no human-readable format supported, format pretty 1106 If you want to use javascript's "eval" function to "parse" JSON, you
729 much undocumented. I need at least a format for easy reading by 1107 might run into parse errors for valid JSON texts, or the resulting data
730 humans and a single-line compact format for use in a protocol, and 1108 structure might not be queryable:
731 preferably a way to generate ASCII-only JSON texts).
732 1109
733 Completely broken (and confusingly documented) Unicode handling 1110 One of the problems is that U+2028 and U+2029 are valid characters
734 (unicode escapes are not working properly, you need to set 1111 inside JSON strings, but are not allowed in ECMAscript string literals,
735 ImplicitUnicode to *different* values on en- and decoding to get 1112 so the following Perl fragment will not output something that can be
736 symmetric behaviour). 1113 guaranteed to be parsable by javascript's "eval":
737 1114
738 No roundtripping (simple cases work, but this depends on wether the 1115 use JSON::XS;
739 scalar value was used in a numeric context or not).
740 1116
741 Dumping hashes may skip hash values depending on iterator state. 1117 print encode_json [chr 0x2028];
742 1118
743 Unmaintained (maintainer unresponsive for many months, bugs are not 1119 The right fix for this is to use a proper JSON parser in your javascript
744 getting fixed). 1120 programs, and not rely on "eval" (see for example Douglas Crockford's
1121 json2.js parser).
745 1122
746 Does not check input for validity (i.e. will accept non-JSON input 1123 If this is not an option, you can, as a stop-gap measure, simply encode
747 and return "something" instead of raising an exception. This is a 1124 to ASCII-only JSON:
748 security issue: imagine two banks transfering money between each
749 other using JSON. One bank might parse a given non-JSON request and
750 deduct money, while the other might reject the transaction with a
751 syntax error. While a good protocol will at least recover, that is
752 extra unnecessary work and the transaction will still not succeed).
753 1125
754 JSON::DWIW 0.04 1126 use JSON::XS;
755 Very fast. Very natural. Very nice.
756 1127
757 Undocumented unicode handling (but the best of the pack. Unicode 1128 print JSON::XS->new->ascii->encode ([chr 0x2028]);
758 escapes still don't get parsed properly).
759 1129
760 Very inflexible. 1130 Note that this will enlarge the resulting JSON text quite a bit if you
1131 have many non-ASCII characters. You might be tempted to run some regexes
1132 to only escape U+2028 and U+2029, e.g.:
761 1133
762 No roundtripping. 1134 # DO NOT USE THIS!
1135 my $json = JSON::XS->new->utf8->encode ([chr 0x2028]);
1136 $json =~ s/\xe2\x80\xa8/\\u2028/g; # escape U+2028
1137 $json =~ s/\xe2\x80\xa9/\\u2029/g; # escape U+2029
1138 print $json;
763 1139
764 Does not generate valid JSON texts (key strings are often unquoted, 1140 Note that *this is a bad idea*: the above only works for U+2028 and
765 empty keys result in nothing being output) 1141 U+2029 and thus only for fully ECMAscript-compliant parsers. Many
1142 existing javascript implementations, however, have issues with other
1143 characters as well - using "eval" naively simply *will* cause problems.
766 1144
767 Does not check input for validity. 1145 Another problem is that some javascript implementations reserve some
1146 property names for their own purposes (which probably makes them
1147 non-ECMAscript-compliant). For example, Iceweasel reserves the
1148 "__proto__" property name for it's own purposes.
1149
1150 If that is a problem, you could parse try to filter the resulting JSON
1151 output for these property strings, e.g.:
1152
1153 $json =~ s/"__proto__"\s*:/"__proto__renamed":/g;
1154
1155 This works because "__proto__" is not valid outside of strings, so every
1156 occurence of ""__proto__"\s*:" must be a string used as property name.
1157
1158 If you know of other incompatibilities, please let me know.
768 1159
769 JSON and YAML 1160 JSON and YAML
770 You often hear that JSON is a subset (or a close subset) of YAML. This 1161 You often hear that JSON is a subset of YAML. This is, however, a mass
771 is, however, a mass hysteria and very far from the truth. In general, 1162 hysteria(*) and very far from the truth (as of the time of this
772 there is no way to configure JSON::XS to output a data structure as 1163 writing), so let me state it clearly: *in general, there is no way to
773 valid YAML. 1164 configure JSON::XS to output a data structure as valid YAML* that works
1165 in all cases.
774 1166
775 If you really must use JSON::XS to generate YAML, you should use this 1167 If you really must use JSON::XS to generate YAML, you should use this
776 algorithm (subject to change in future versions): 1168 algorithm (subject to change in future versions):
777 1169
778 my $to_yaml = JSON::XS->new->utf8->space_after (1); 1170 my $to_yaml = JSON::XS->new->utf8->space_after (1);
779 my $yaml = $to_yaml->encode ($ref) . "\n"; 1171 my $yaml = $to_yaml->encode ($ref) . "\n";
780 1172
781 This will usually generate JSON texts that also parse as valid YAML. 1173 This will *usually* generate JSON texts that also parse as valid YAML.
782 Please note that YAML has hardcoded limits on (simple) object key 1174 Please note that YAML has hardcoded limits on (simple) object key
783 lengths that JSON doesn't have, so you should make sure that your hash 1175 lengths that JSON doesn't have and also has different and incompatible
1176 unicode character escape syntax, so you should make sure that your hash
784 keys are noticably shorter than the 1024 characters YAML allows. 1177 keys are noticeably shorter than the 1024 "stream characters" YAML
1178 allows and that you do not have characters with codepoint values outside
1179 the Unicode BMP (basic multilingual page). YAML also does not allow "\/"
1180 sequences in strings (which JSON::XS does not *currently* generate, but
1181 other JSON generators might).
785 1182
786 There might be other incompatibilities that I am not aware of. In 1183 There might be other incompatibilities that I am not aware of (or the
1184 YAML specification has been changed yet again - it does so quite often).
787 general you should not try to generate YAML with a JSON generator or 1185 In general you should not try to generate YAML with a JSON generator or
788 vice versa, or try to parse JSON with a YAML parser or vice versa: 1186 vice versa, or try to parse JSON with a YAML parser or vice versa:
789 chances are high that you will run into severe interoperability 1187 chances are high that you will run into severe interoperability problems
790 problems. 1188 when you least expect it.
1189
1190 (*) I have been pressured multiple times by Brian Ingerson (one of the
1191 authors of the YAML specification) to remove this paragraph, despite
1192 him acknowledging that the actual incompatibilities exist. As I was
1193 personally bitten by this "JSON is YAML" lie, I refused and said I
1194 will continue to educate people about these issues, so others do not
1195 run into the same problem again and again. After this, Brian called
1196 me a (quote)*complete and worthless idiot*(unquote).
1197
1198 In my opinion, instead of pressuring and insulting people who
1199 actually clarify issues with YAML and the wrong statements of some
1200 of its proponents, I would kindly suggest reading the JSON spec
1201 (which is not that difficult or long) and finally make YAML
1202 compatible to it, and educating users about the changes, instead of
1203 spreading lies about the real compatibility for many *years* and
1204 trying to silence people who point out that it isn't true.
1205
1206 Addendum/2009: the YAML 1.2 spec is still incomaptible with JSON,
1207 even though the incompatibilities have been documented (and are
1208 known to Brian) for many years and the spec makes explicit claims
1209 that YAML is a superset of JSON. It would be so easy to fix, but
1210 apparently, bullying and corrupting userdata is so much easier.
791 1211
792 SPEED 1212 SPEED
793 It seems that JSON::XS is surprisingly fast, as shown in the following 1213 It seems that JSON::XS is surprisingly fast, as shown in the following
794 tables. They have been generated with the help of the "eg/bench" program 1214 tables. They have been generated with the help of the "eg/bench" program
795 in the JSON::XS distribution, to make it easy to compare on your own 1215 in the JSON::XS distribution, to make it easy to compare on your own
796 system. 1216 system.
797 1217
798 First comes a comparison between various modules using a very short 1218 First comes a comparison between various modules using a very short
799 single-line JSON string: 1219 single-line JSON string (also available at
1220 <http://dist.schmorp.de/misc/json/short.json>).
800 1221
801 {"method": "handleMessage", "params": ["user1", "we were just talking"], \ 1222 {"method": "handleMessage", "params": ["user1",
802 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} 1223 "we were just talking"], "id": null, "array":[1,11,234,-5,1e5,1e7,
1224 1, 0]}
803 1225
804 It shows the number of encodes/decodes per second (JSON::XS uses the 1226 It shows the number of encodes/decodes per second (JSON::XS uses the
805 functional interface, while JSON::XS/2 uses the OO interface with 1227 functional interface, while JSON::XS/2 uses the OO interface with
806 pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). 1228 pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink.
807 Higher is better: 1229 JSON::DWIW/DS uses the deserialise function, while JSON::DWIW::FJ uses
1230 the from_json method). Higher is better:
808 1231
809 Storable | 15779.925 | 14169.946 |
810 -----------+------------+------------+
811 module | encode | decode | 1232 module | encode | decode |
812 -----------|------------|------------| 1233 --------------|------------|------------|
813 JSON | 4990.842 | 4088.813 | 1234 JSON::DWIW/DS | 86302.551 | 102300.098 |
814 JSON::DWIW | 51653.990 | 71575.154 | 1235 JSON::DWIW/FJ | 86302.551 | 75983.768 |
815 JSON::PC | 65948.176 | 74631.744 | 1236 JSON::PP | 15827.562 | 6638.658 |
816 JSON::PP | 8931.652 | 3817.168 | 1237 JSON::Syck | 63358.066 | 47662.545 |
817 JSON::Syck | 24877.248 | 27776.848 | 1238 JSON::XS | 511500.488 | 511500.488 |
818 JSON::XS | 388361.481 | 227951.304 | 1239 JSON::XS/2 | 291271.111 | 388361.481 |
819 JSON::XS/2 | 227951.304 | 218453.333 | 1240 JSON::XS/3 | 361577.931 | 361577.931 |
820 JSON::XS/3 | 338250.323 | 218453.333 | 1241 Storable | 66788.280 | 265462.278 |
821 Storable | 16500.016 | 135300.129 |
822 -----------+------------+------------+ 1242 --------------+------------+------------+
823 1243
824 That is, JSON::XS is about five times faster than JSON::DWIW on 1244 That is, JSON::XS is almost six times faster than JSON::DWIW on
825 encoding, about three times faster on decoding, and over fourty times 1245 encoding, about five times faster on decoding, and over thirty to
826 faster than JSON, even with pretty-printing and key sorting. It also 1246 seventy times faster than JSON's pure perl implementation. It also
827 compares favourably to Storable for small amounts of data. 1247 compares favourably to Storable for small amounts of data.
828 1248
829 Using a longer test string (roughly 18KB, generated from Yahoo! Locals 1249 Using a longer test string (roughly 18KB, generated from Yahoo! Locals
830 search API (http://nanoref.com/yahooapis/mgPdGg): 1250 search API (<http://dist.schmorp.de/misc/json/long.json>).
831 1251
832 module | encode | decode | 1252 module | encode | decode |
833 -----------|------------|------------| 1253 --------------|------------|------------|
834 JSON | 55.260 | 34.971 | 1254 JSON::DWIW/DS | 1647.927 | 2673.916 |
835 JSON::DWIW | 825.228 | 1082.513 | 1255 JSON::DWIW/FJ | 1630.249 | 2596.128 |
836 JSON::PC | 3571.444 | 2394.829 |
837 JSON::PP | 210.987 | 32.574 | 1256 JSON::PP | 400.640 | 62.311 |
838 JSON::Syck | 552.551 | 787.544 | 1257 JSON::Syck | 1481.040 | 1524.869 |
839 JSON::XS | 5780.463 | 4854.519 | 1258 JSON::XS | 20661.596 | 9541.183 |
840 JSON::XS/2 | 3869.998 | 4798.975 | 1259 JSON::XS/2 | 10683.403 | 9416.938 |
841 JSON::XS/3 | 5862.880 | 4798.975 | 1260 JSON::XS/3 | 20661.596 | 9400.054 |
842 Storable | 4445.002 | 5235.027 | 1261 Storable | 19765.806 | 10000.725 |
843 -----------+------------+------------+ 1262 --------------+------------+------------+
844 1263
845 Again, JSON::XS leads by far (except for Storable which non-surprisingly 1264 Again, JSON::XS leads by far (except for Storable which non-surprisingly
846 decodes faster). 1265 decodes a bit faster).
847 1266
848 On large strings containing lots of high unicode characters, some 1267 On large strings containing lots of high Unicode characters, some
849 modules (such as JSON::PC) seem to decode faster than JSON::XS, but the 1268 modules (such as JSON::PC) seem to decode faster than JSON::XS, but the
850 result will be broken due to missing (or wrong) unicode handling. Others 1269 result will be broken due to missing (or wrong) Unicode handling. Others
851 refuse to decode or encode properly, so it was impossible to prepare a 1270 refuse to decode or encode properly, so it was impossible to prepare a
852 fair comparison table for that case. 1271 fair comparison table for that case.
853 1272
854SECURITY CONSIDERATIONS 1273SECURITY CONSIDERATIONS
855 When you are using JSON in a protocol, talking to untrusted potentially 1274 When you are using JSON in a protocol, talking to untrusted potentially
… …
859 have any buffer overflows. Obviously, this module should ensure that and 1278 have any buffer overflows. Obviously, this module should ensure that and
860 I am trying hard on making that true, but you never know. 1279 I am trying hard on making that true, but you never know.
861 1280
862 Second, you need to avoid resource-starving attacks. That means you 1281 Second, you need to avoid resource-starving attacks. That means you
863 should limit the size of JSON texts you accept, or make sure then when 1282 should limit the size of JSON texts you accept, or make sure then when
864 your resources run out, thats just fine (e.g. by using a separate 1283 your resources run out, that's just fine (e.g. by using a separate
865 process that can crash safely). The size of a JSON text in octets or 1284 process that can crash safely). The size of a JSON text in octets or
866 characters is usually a good indication of the size of the resources 1285 characters is usually a good indication of the size of the resources
867 required to decode it into a Perl structure. While JSON::XS can check 1286 required to decode it into a Perl structure. While JSON::XS can check
868 the size of the JSON text, it might be too late when you already have it 1287 the size of the JSON text, it might be too late when you already have it
869 in memory, so you might want to check the size before you accept the 1288 in memory, so you might want to check the size before you accept the
… …
872 Third, JSON::XS recurses using the C stack when decoding objects and 1291 Third, JSON::XS recurses using the C stack when decoding objects and
873 arrays. The C stack is a limited resource: for instance, on my amd64 1292 arrays. The C stack is a limited resource: for instance, on my amd64
874 machine with 8MB of stack size I can decode around 180k nested arrays 1293 machine with 8MB of stack size I can decode around 180k nested arrays
875 but only 14k nested JSON objects (due to perl itself recursing deeply on 1294 but only 14k nested JSON objects (due to perl itself recursing deeply on
876 croak to free the temporary). If that is exceeded, the program crashes. 1295 croak to free the temporary). If that is exceeded, the program crashes.
877 to be conservative, the default nesting limit is set to 512. If your 1296 To be conservative, the default nesting limit is set to 512. If your
878 process has a smaller stack, you should adjust this setting accordingly 1297 process has a smaller stack, you should adjust this setting accordingly
879 with the "max_depth" method. 1298 with the "max_depth" method.
880 1299
881 And last but least, something else could bomb you that I forgot to think 1300 Something else could bomb you, too, that I forgot to think of. In that
882 of. In that case, you get to keep the pieces. I am always open for 1301 case, you get to keep the pieces. I am always open for hints, though...
883 hints, though...
884 1302
1303 Also keep in mind that JSON::XS might leak contents of your Perl data
1304 structures in its error messages, so when you serialise sensitive
1305 information you might want to make sure that exceptions thrown by
1306 JSON::XS will not end up in front of untrusted eyes.
1307
885 If you are using JSON::XS to return packets to consumption by javascript 1308 If you are using JSON::XS to return packets to consumption by JavaScript
886 scripts in a browser you should have a look at 1309 scripts in a browser you should have a look at
887 <http://jpsykes.com/47/practical-csrf-and-json-security> to see wether 1310 <http://blog.archive.jpsykes.com/47/practical-csrf-and-json-security/>
888 you are vulnerable to some common attack vectors (which really are 1311 to see whether you are vulnerable to some common attack vectors (which
889 browser design bugs, but it is still you who will have to deal with it, 1312 really are browser design bugs, but it is still you who will have to
890 as major browser developers care only for features, not about doing 1313 deal with it, as major browser developers care only for features, not
891 security right). 1314 about getting security right).
892 1315
893THREADS 1316THREADS
894 This module is *not* guarenteed to be thread safe and there are no plans 1317 This module is *not* guaranteed to be thread safe and there are no plans
895 to change this until Perl gets thread support (as opposed to the 1318 to change this until Perl gets thread support (as opposed to the
896 horribly slow so-called "threads" which are simply slow and bloated 1319 horribly slow so-called "threads" which are simply slow and bloated
897 process simulations - use fork, its *much* faster, cheaper, better). 1320 process simulations - use fork, it's *much* faster, cheaper, better).
898 1321
899 (It might actually work, but you ahve ben warned). 1322 (It might actually work, but you have been warned).
900 1323
901BUGS 1324BUGS
902 While the goal of this module is to be correct, that unfortunately does 1325 While the goal of this module is to be correct, that unfortunately does
903 not mean its bug-free, only that I think its design is bug-free. It is 1326 not mean it's bug-free, only that I think its design is bug-free. If you
904 still relatively early in its development. If you keep reporting bugs
905 they will be fixed swiftly, though. 1327 keep reporting bugs they will be fixed swiftly, though.
906 1328
907 Please refrain from using rt.cpan.org or any other bug reporting 1329 Please refrain from using rt.cpan.org or any other bug reporting
908 service. I put the contact address into my modules for a reason. 1330 service. I put the contact address into my modules for a reason.
1331
1332SEE ALSO
1333 The json_xs command line utility for quick experiments.
909 1334
910AUTHOR 1335AUTHOR
911 Marc Lehmann <schmorp@schmorp.de> 1336 Marc Lehmann <schmorp@schmorp.de>
912 http://home.schmorp.de/ 1337 http://home.schmorp.de/
913 1338

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