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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; |
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8 | |
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9 | # exported functions, croak on error |
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10 | |
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11 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
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12 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
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13 | |
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14 | # oo-interface |
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15 | |
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16 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
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17 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
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18 | $perl_scalar = $coder->decode ($unicode_json_text); |
8 | |
19 | |
9 | =head1 DESCRIPTION |
20 | =head1 DESCRIPTION |
10 | |
21 | |
11 | This module converts Perl data structures to JSON and vice versa. Its |
22 | 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 |
23 | primary goal is to be I<correct> and its secondary goal is to be |
… | |
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18 | their maintainers are unresponsive, gone missing, or not listening to bug |
29 | their maintainers are unresponsive, gone missing, or not listening to bug |
19 | reports for other reasons. |
30 | reports for other reasons. |
20 | |
31 | |
21 | See COMPARISON, below, for a comparison to some other JSON modules. |
32 | See COMPARISON, below, for a comparison to some other JSON modules. |
22 | |
33 | |
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34 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
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35 | vice versa. |
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36 | |
23 | =head2 FEATURES |
37 | =head2 FEATURES |
24 | |
38 | |
25 | =over 4 |
39 | =over 4 |
26 | |
40 | |
27 | =item * correct handling of unicode issues |
41 | =item * correct handling of unicode issues |
28 | |
42 | |
29 | This module knows how to handle Unicode, and even documents how it does so. |
43 | This module knows how to handle Unicode, and even documents how and when |
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44 | it does so. |
30 | |
45 | |
31 | =item * round-trip integrity |
46 | =item * round-trip integrity |
32 | |
47 | |
33 | When you serialise a perl data structure using only datatypes supported |
48 | When you serialise a perl data structure using only datatypes supported |
34 | by JSON, the deserialised data structure is identical on the Perl level. |
49 | by JSON, the deserialised data structure is identical on the Perl level. |
35 | (e.g. the string "2.0" doesn't suddenly become "2"). |
50 | (e.g. the string "2.0" doesn't suddenly become "2"). |
36 | |
51 | |
37 | =item * strict checking of JSON correctness |
52 | =item * strict checking of JSON correctness |
38 | |
53 | |
39 | There is no guessing, no generating of illegal JSON strings by default, |
54 | 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). |
55 | and only JSON is accepted as input by default (the latter is a security |
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56 | feature). |
41 | |
57 | |
42 | =item * fast |
58 | =item * fast |
43 | |
59 | |
44 | compared to other JSON modules, this module compares favourably. |
60 | Compared to other JSON modules, this module compares favourably in terms |
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61 | of speed, too. |
45 | |
62 | |
46 | =item * simple to use |
63 | =item * simple to use |
47 | |
64 | |
48 | This module has both a simple functional interface as well as an OO |
65 | This module has both a simple functional interface as well as an OO |
49 | interface. |
66 | interface. |
50 | |
67 | |
51 | =item * reasonably versatile output formats |
68 | =item * reasonably versatile output formats |
52 | |
69 | |
53 | You can choose between the most compact format possible, a pure-ascii |
70 | 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 |
71 | possible (nice for simple line-based protocols), a pure-ascii format (for |
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72 | when your transport is not 8-bit clean), or a pretty-printed format (for |
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73 | when you want to read that stuff). Or you can combine those features in |
55 | whatever way you like. |
74 | whatever way you like. |
56 | |
75 | |
57 | =back |
76 | =back |
58 | |
77 | |
59 | =cut |
78 | =cut |
60 | |
79 | |
61 | package JSON::XS; |
80 | package JSON::XS; |
62 | |
81 | |
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82 | use strict; |
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83 | |
63 | BEGIN { |
84 | BEGIN { |
64 | $VERSION = '0.1'; |
85 | our $VERSION = '0.7'; |
65 | @ISA = qw(Exporter); |
86 | our @ISA = qw(Exporter); |
66 | |
87 | |
67 | @EXPORT = qw(to_json from_json); |
88 | our @EXPORT = qw(to_json from_json); |
68 | require Exporter; |
89 | require Exporter; |
69 | |
90 | |
70 | require XSLoader; |
91 | require XSLoader; |
71 | XSLoader::load JSON::XS::, $VERSION; |
92 | XSLoader::load JSON::XS::, $VERSION; |
72 | } |
93 | } |
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76 | The following convinience methods are provided by this module. They are |
97 | The following convinience methods are provided by this module. They are |
77 | exported by default: |
98 | exported by default: |
78 | |
99 | |
79 | =over 4 |
100 | =over 4 |
80 | |
101 | |
81 | =item $json_string = to_json $perl_scalar |
102 | =item $json_text = to_json $perl_scalar |
82 | |
103 | |
83 | Converts the given Perl data structure (a simple scalar or a reference to |
104 | Converts the given Perl data structure (a simple scalar or a reference to |
84 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
105 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
85 | octets only). Croaks on error. |
106 | octets only). Croaks on error. |
86 | |
107 | |
87 | This function call is functionally identical to C<< JSON::XS->new->utf8 |
108 | This function call is functionally identical to: |
88 | (1)->encode ($perl_scalar) >>. |
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89 | |
109 | |
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110 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
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111 | |
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112 | except being faster. |
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113 | |
90 | =item $perl_scalar = from_json $json_string |
114 | =item $perl_scalar = from_json $json_text |
91 | |
115 | |
92 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
116 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
93 | parse that as an UTF-8 encoded JSON string, returning the resulting simple |
117 | parse that as an UTF-8 encoded JSON text, returning the resulting simple |
94 | scalar or reference. Croaks on error. |
118 | scalar or reference. Croaks on error. |
95 | |
119 | |
96 | This function call is functionally identical to C<< JSON::XS->new->utf8 |
120 | This function call is functionally identical to: |
97 | (1)->decode ($json_string) >>. |
121 | |
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122 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
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123 | |
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124 | except being faster. |
98 | |
125 | |
99 | =back |
126 | =back |
100 | |
127 | |
101 | =head1 OBJECT-ORIENTED INTERFACE |
128 | =head1 OBJECT-ORIENTED INTERFACE |
102 | |
129 | |
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111 | strings. All boolean flags described below are by default I<disabled>. |
138 | strings. All boolean flags described below are by default I<disabled>. |
112 | |
139 | |
113 | The mutators for flags all return the JSON object again and thus calls can |
140 | The mutators for flags all return the JSON object again and thus calls can |
114 | be chained: |
141 | be chained: |
115 | |
142 | |
116 | my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]}) |
143 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
117 | => {"a": [1, 2]} |
144 | => {"a": [1, 2]} |
118 | |
145 | |
119 | =item $json = $json->ascii ($enable) |
146 | =item $json = $json->ascii ([$enable]) |
120 | |
147 | |
121 | If C<$enable> is true, then the C<encode> method will not generate |
148 | If C<$enable> is true (or missing), then the C<encode> method will not |
122 | characters outside the code range C<0..127>. Any unicode characters |
149 | 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 |
150 | unicode characters outside that range will be escaped using either a |
124 | characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627. |
151 | single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
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152 | as per RFC4627. |
125 | |
153 | |
126 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
154 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
127 | characters unless necessary. |
155 | characters unless required by the JSON syntax. This results in a faster |
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156 | and more compact format. |
128 | |
157 | |
129 | JSON::XS->new->ascii (1)->encode (chr 0x10401) |
158 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
130 | => \ud801\udc01 |
159 | => ["\ud801\udc01"] |
131 | |
160 | |
132 | =item $json = $json->utf8 ($enable) |
161 | =item $json = $json->utf8 ([$enable]) |
133 | |
162 | |
134 | If C<$enable> is true, then the C<encode> method will encode the JSON |
163 | If C<$enable> is true (or missing), then the C<encode> method will encode |
135 | string into UTF-8, as required by many protocols, while the C<decode> |
164 | the JSON result into UTF-8, as required by many protocols, while the |
136 | method expects to be handled an UTF-8-encoded string. Please note that |
165 | C<decode> method expects to be handled an UTF-8-encoded string. Please |
137 | UTF-8-encoded strings do not contain any characters outside the range |
166 | note that UTF-8-encoded strings do not contain any characters outside the |
138 | C<0..255>, they are thus useful for bytewise/binary I/O. |
167 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
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168 | versions, enabling this option might enable autodetection of the UTF-16 |
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169 | and UTF-32 encoding families, as described in RFC4627. |
139 | |
170 | |
140 | If C<$enable> is false, then the C<encode> method will return the JSON |
171 | If C<$enable> is false, then the C<encode> method will return the JSON |
141 | string as a (non-encoded) unicode string, while C<decode> expects thus a |
172 | string as a (non-encoded) unicode string, while C<decode> expects thus a |
142 | unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
173 | unicode string. Any decoding or encoding (e.g. to UTF-8 or UTF-16) needs |
143 | to be done yourself, e.g. using the Encode module. |
174 | to be done yourself, e.g. using the Encode module. |
144 | |
175 | |
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176 | Example, output UTF-16BE-encoded JSON: |
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177 | |
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178 | use Encode; |
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179 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
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180 | |
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181 | Example, decode UTF-32LE-encoded JSON: |
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182 | |
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183 | use Encode; |
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184 | $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); |
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185 | |
145 | =item $json = $json->pretty ($enable) |
186 | =item $json = $json->pretty ([$enable]) |
146 | |
187 | |
147 | This enables (or disables) all of the C<indent>, C<space_before> and |
188 | This enables (or disables) all of the C<indent>, C<space_before> and |
148 | C<space_after> (and in the future possibly more) flags in one call to |
189 | C<space_after> (and in the future possibly more) flags in one call to |
149 | generate the most readable (or most compact) form possible. |
190 | generate the most readable (or most compact) form possible. |
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191 | |
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192 | Example, pretty-print some simple structure: |
150 | |
193 | |
151 | my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
194 | my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
152 | => |
195 | => |
153 | { |
196 | { |
154 | "a" : [ |
197 | "a" : [ |
155 | 1, |
198 | 1, |
156 | 2 |
199 | 2 |
157 | ] |
200 | ] |
158 | } |
201 | } |
159 | |
202 | |
160 | =item $json = $json->indent ($enable) |
203 | =item $json = $json->indent ([$enable]) |
161 | |
204 | |
162 | If C<$enable> is true, then the C<encode> method will use a multiline |
205 | If C<$enable> is true (or missing), then the C<encode> method will use a multiline |
163 | format as output, putting every array member or object/hash key-value pair |
206 | format as output, putting every array member or object/hash key-value pair |
164 | into its own line, identing them properly. |
207 | into its own line, identing them properly. |
165 | |
208 | |
166 | If C<$enable> is false, no newlines or indenting will be produced, and the |
209 | If C<$enable> is false, no newlines or indenting will be produced, and the |
167 | resulting JSON strings is guarenteed not to contain any C<newlines>. |
210 | resulting JSON text is guarenteed not to contain any C<newlines>. |
168 | |
211 | |
169 | This setting has no effect when decoding JSON strings. |
212 | This setting has no effect when decoding JSON texts. |
170 | |
213 | |
171 | =item $json = $json->space_before ($enable) |
214 | =item $json = $json->space_before ([$enable]) |
172 | |
215 | |
173 | If C<$enable> is true, then the C<encode> method will add an extra |
216 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
174 | optional space before the C<:> separating keys from values in JSON objects. |
217 | optional space before the C<:> separating keys from values in JSON objects. |
175 | |
218 | |
176 | If C<$enable> is false, then the C<encode> method will not add any extra |
219 | If C<$enable> is false, then the C<encode> method will not add any extra |
177 | space at those places. |
220 | space at those places. |
178 | |
221 | |
179 | This setting has no effect when decoding JSON strings. You will also most |
222 | This setting has no effect when decoding JSON texts. You will also |
180 | likely combine this setting with C<space_after>. |
223 | most likely combine this setting with C<space_after>. |
181 | |
224 | |
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225 | Example, space_before enabled, space_after and indent disabled: |
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226 | |
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227 | {"key" :"value"} |
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228 | |
182 | =item $json = $json->space_after ($enable) |
229 | =item $json = $json->space_after ([$enable]) |
183 | |
230 | |
184 | If C<$enable> is true, then the C<encode> method will add an extra |
231 | If C<$enable> is true (or missing), then the C<encode> method will add an extra |
185 | optional space after the C<:> separating keys from values in JSON objects |
232 | optional space after the C<:> separating keys from values in JSON objects |
186 | and extra whitespace after the C<,> separating key-value pairs and array |
233 | and extra whitespace after the C<,> separating key-value pairs and array |
187 | members. |
234 | members. |
188 | |
235 | |
189 | If C<$enable> is false, then the C<encode> method will not add any extra |
236 | If C<$enable> is false, then the C<encode> method will not add any extra |
190 | space at those places. |
237 | space at those places. |
191 | |
238 | |
192 | This setting has no effect when decoding JSON strings. |
239 | This setting has no effect when decoding JSON texts. |
193 | |
240 | |
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241 | Example, space_before and indent disabled, space_after enabled: |
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242 | |
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243 | {"key": "value"} |
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244 | |
194 | =item $json = $json->canonical ($enable) |
245 | =item $json = $json->canonical ([$enable]) |
195 | |
246 | |
196 | If C<$enable> is true, then the C<encode> method will output JSON objects |
247 | If C<$enable> is true (or missing), then the C<encode> method will output JSON objects |
197 | by sorting their keys. This is adding a comparatively high overhead. |
248 | by sorting their keys. This is adding a comparatively high overhead. |
198 | |
249 | |
199 | If C<$enable> is false, then the C<encode> method will output key-value |
250 | If C<$enable> is false, then the C<encode> method will output key-value |
200 | pairs in the order Perl stores them (which will likely change between runs |
251 | pairs in the order Perl stores them (which will likely change between runs |
201 | of the same script). |
252 | of the same script). |
202 | |
253 | |
203 | This option is useful if you want the same data structure to be encoded as |
254 | This option is useful if you want the same data structure to be encoded as |
204 | the same JSON string (given the same overall settings). If it is disabled, |
255 | the same JSON text (given the same overall settings). If it is disabled, |
205 | the same hash migh be encoded differently even if contains the same data, |
256 | the same hash migh be encoded differently even if contains the same data, |
206 | as key-value pairs have no inherent ordering in Perl. |
257 | as key-value pairs have no inherent ordering in Perl. |
207 | |
258 | |
208 | This setting has no effect when decoding JSON strings. |
259 | This setting has no effect when decoding JSON texts. |
209 | |
260 | |
210 | =item $json = $json->allow_nonref ($enable) |
261 | =item $json = $json->allow_nonref ([$enable]) |
211 | |
262 | |
212 | If C<$enable> is true, then the C<encode> method can convert a |
263 | If C<$enable> is true (or missing), then the C<encode> method can convert a |
213 | non-reference into its corresponding string, number or null JSON value, |
264 | non-reference into its corresponding string, number or null JSON value, |
214 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
265 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
215 | values instead of croaking. |
266 | values instead of croaking. |
216 | |
267 | |
217 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
268 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
218 | passed an arrayref or hashref, as JSON strings must either be an object |
269 | passed an arrayref or hashref, as JSON texts must either be an object |
219 | or array. Likewise, C<decode> will croak if given something that is not a |
270 | or array. Likewise, C<decode> will croak if given something that is not a |
220 | JSON object or array. |
271 | JSON object or array. |
221 | |
272 | |
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273 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
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274 | resulting in an invalid JSON text: |
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275 | |
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276 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
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277 | => "Hello, World!" |
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278 | |
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279 | =item $json = $json->shrink ([$enable]) |
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280 | |
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281 | Perl usually over-allocates memory a bit when allocating space for |
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282 | strings. This flag optionally resizes strings generated by either |
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283 | C<encode> or C<decode> to their minimum size possible. This can save |
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284 | memory when your JSON texts are either very very long or you have many |
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285 | short strings. It will also try to downgrade any strings to octet-form |
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286 | if possible: perl stores strings internally either in an encoding called |
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287 | UTF-X or in octet-form. The latter cannot store everything but uses less |
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288 | space in general. |
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289 | |
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290 | If C<$enable> is true (or missing), the string returned by C<encode> will be shrunk-to-fit, |
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291 | while all strings generated by C<decode> will also be shrunk-to-fit. |
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292 | |
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293 | If C<$enable> is false, then the normal perl allocation algorithms are used. |
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294 | If you work with your data, then this is likely to be faster. |
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295 | |
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296 | In the future, this setting might control other things, such as converting |
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297 | strings that look like integers or floats into integers or floats |
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298 | internally (there is no difference on the Perl level), saving space. |
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299 | |
222 | =item $json_string = $json->encode ($perl_scalar) |
300 | =item $json_text = $json->encode ($perl_scalar) |
223 | |
301 | |
224 | Converts the given Perl data structure (a simple scalar or a reference |
302 | Converts the given Perl data structure (a simple scalar or a reference |
225 | to a hash or array) to its JSON representation. Simple scalars will be |
303 | to a hash or array) to its JSON representation. Simple scalars will be |
226 | converted into JSON string or number sequences, while references to arrays |
304 | converted into JSON string or number sequences, while references to arrays |
227 | become JSON arrays and references to hashes become JSON objects. Undefined |
305 | become JSON arrays and references to hashes become JSON objects. Undefined |
228 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
306 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
229 | nor C<false> values will be generated. |
307 | nor C<false> values will be generated. |
230 | |
308 | |
231 | =item $perl_scalar = $json->decode ($json_string) |
309 | =item $perl_scalar = $json->decode ($json_text) |
232 | |
310 | |
233 | The opposite of C<encode>: expects a JSON string and tries to parse it, |
311 | The opposite of C<encode>: expects a JSON text and tries to parse it, |
234 | returning the resulting simple scalar or reference. Croaks on error. |
312 | returning the resulting simple scalar or reference. Croaks on error. |
235 | |
313 | |
236 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
314 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
237 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
315 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
238 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
316 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
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317 | |
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318 | =back |
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319 | |
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320 | =head1 MAPPING |
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321 | |
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322 | This section describes how JSON::XS maps Perl values to JSON values and |
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323 | vice versa. These mappings are designed to "do the right thing" in most |
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324 | circumstances automatically, preserving round-tripping characteristics |
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325 | (what you put in comes out as something equivalent). |
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326 | |
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327 | For the more enlightened: note that in the following descriptions, |
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328 | lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> |
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329 | refers to the abstract Perl language itself. |
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330 | |
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331 | =head2 JSON -> PERL |
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332 | |
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333 | =over 4 |
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334 | |
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335 | =item object |
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336 | |
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337 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
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338 | keys is preserved (JSON does not preserver object key ordering itself). |
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339 | |
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340 | =item array |
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341 | |
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342 | A JSON array becomes a reference to an array in Perl. |
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343 | |
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344 | =item string |
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345 | |
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346 | A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON |
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347 | are represented by the same codepoints in the Perl string, so no manual |
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348 | decoding is necessary. |
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349 | |
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350 | =item number |
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351 | |
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352 | A JSON number becomes either an integer or numeric (floating point) |
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353 | scalar in perl, depending on its range and any fractional parts. On the |
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354 | Perl level, there is no difference between those as Perl handles all the |
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355 | conversion details, but an integer may take slightly less memory and might |
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356 | represent more values exactly than (floating point) numbers. |
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357 | |
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358 | =item true, false |
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359 | |
|
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360 | These JSON atoms become C<0>, C<1>, respectively. Information is lost in |
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361 | this process. Future versions might represent those values differently, |
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362 | but they will be guarenteed to act like these integers would normally in |
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363 | Perl. |
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364 | |
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365 | =item null |
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366 | |
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367 | A JSON null atom becomes C<undef> in Perl. |
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368 | |
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369 | =back |
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370 | |
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371 | =head2 PERL -> JSON |
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372 | |
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373 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
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374 | truly typeless language, so we can only guess which JSON type is meant by |
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375 | a Perl value. |
|
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376 | |
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377 | =over 4 |
|
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378 | |
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379 | =item hash references |
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380 | |
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381 | Perl hash references become JSON objects. As there is no inherent ordering |
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382 | in hash keys, they will usually be encoded in a pseudo-random order that |
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383 | can change between runs of the same program but stays generally the same |
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384 | within a single run of a program. JSON::XS can optionally sort the hash |
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385 | keys (determined by the I<canonical> flag), so the same datastructure |
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386 | will serialise to the same JSON text (given same settings and version of |
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387 | JSON::XS), but this incurs a runtime overhead. |
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388 | |
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389 | =item array references |
|
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390 | |
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391 | Perl array references become JSON arrays. |
|
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392 | |
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393 | =item blessed objects |
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394 | |
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395 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
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396 | underlying representation (hash- or arrayref), but this behaviour might |
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397 | change in future versions. |
|
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398 | |
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399 | =item simple scalars |
|
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400 | |
|
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401 | Simple Perl scalars (any scalar that is not a reference) are the most |
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402 | difficult objects to encode: JSON::XS will encode undefined scalars as |
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403 | JSON null value, scalars that have last been used in a string context |
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404 | before encoding as JSON strings and anything else as number value: |
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405 | |
|
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406 | # dump as number |
|
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407 | to_json [2] # yields [2] |
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408 | to_json [-3.0e17] # yields [-3e+17] |
|
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409 | my $value = 5; to_json [$value] # yields [5] |
|
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410 | |
|
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411 | # used as string, so dump as string |
|
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412 | print $value; |
|
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413 | to_json [$value] # yields ["5"] |
|
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414 | |
|
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415 | # undef becomes null |
|
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416 | to_json [undef] # yields [null] |
|
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417 | |
|
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418 | You can force the type to be a string by stringifying it: |
|
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419 | |
|
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420 | my $x = 3.1; # some variable containing a number |
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421 | "$x"; # stringified |
|
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422 | $x .= ""; # another, more awkward way to stringify |
|
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423 | print $x; # perl does it for you, too, quite often |
|
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424 | |
|
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425 | You can force the type to be a number by numifying it: |
|
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426 | |
|
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427 | my $x = "3"; # some variable containing a string |
|
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428 | $x += 0; # numify it, ensuring it will be dumped as a number |
|
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429 | $x *= 1; # same thing, the choise is yours. |
|
|
430 | |
|
|
431 | You can not currently output JSON booleans or force the type in other, |
|
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432 | less obscure, ways. Tell me if you need this capability. |
|
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433 | |
|
|
434 | =item circular data structures |
|
|
435 | |
|
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436 | Those will be encoded until memory or stackspace runs out. |
239 | |
437 | |
240 | =back |
438 | =back |
241 | |
439 | |
242 | =head1 COMPARISON |
440 | =head1 COMPARISON |
243 | |
441 | |
… | |
… | |
247 | followed by some benchmark values. JSON::XS was designed not to suffer |
445 | followed by some benchmark values. JSON::XS was designed not to suffer |
248 | from any of these problems or limitations. |
446 | from any of these problems or limitations. |
249 | |
447 | |
250 | =over 4 |
448 | =over 4 |
251 | |
449 | |
252 | =item JSON |
450 | =item JSON 1.07 |
253 | |
451 | |
254 | Slow (but very portable, as it is written in pure Perl). |
452 | Slow (but very portable, as it is written in pure Perl). |
255 | |
453 | |
256 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
454 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
257 | undocumented. One can get far by feeding it unicode strings and doing |
455 | undocumented. One can get far by feeding it unicode strings and doing |
… | |
… | |
259 | |
457 | |
260 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
458 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
261 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
459 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
262 | decode into the number 2. |
460 | decode into the number 2. |
263 | |
461 | |
264 | =item JSON::PC |
462 | =item JSON::PC 0.01 |
265 | |
463 | |
266 | Very fast. |
464 | Very fast. |
267 | |
465 | |
268 | Undocumented/buggy Unicode handling. |
466 | Undocumented/buggy Unicode handling. |
269 | |
467 | |
… | |
… | |
271 | |
469 | |
272 | Has problems handling many Perl values (e.g. regex results and other magic |
470 | Has problems handling many Perl values (e.g. regex results and other magic |
273 | values will make it croak). |
471 | values will make it croak). |
274 | |
472 | |
275 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
473 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
276 | which is not a valid JSON string. |
474 | which is not a valid JSON text. |
277 | |
475 | |
278 | Unmaintained (maintainer unresponsive for many months, bugs are not |
476 | Unmaintained (maintainer unresponsive for many months, bugs are not |
279 | getting fixed). |
477 | getting fixed). |
280 | |
478 | |
281 | =item JSON::Syck |
479 | =item JSON::Syck 0.21 |
282 | |
480 | |
283 | Very buggy (often crashes). |
481 | Very buggy (often crashes). |
284 | |
482 | |
285 | Very inflexible (no human-readable format supported, format pretty much |
483 | Very inflexible (no human-readable format supported, format pretty much |
286 | undocumented. I need at least a format for easy reading by humans and a |
484 | undocumented. I need at least a format for easy reading by humans and a |
287 | single-line compact format for use in a protocol, and preferably a way to |
485 | single-line compact format for use in a protocol, and preferably a way to |
288 | generate ASCII-only JSON strings). |
486 | generate ASCII-only JSON texts). |
289 | |
487 | |
290 | Completely broken (and confusingly documented) Unicode handling (unicode |
488 | Completely broken (and confusingly documented) Unicode handling (unicode |
291 | escapes are not working properly, you need to set ImplicitUnicode to |
489 | escapes are not working properly, you need to set ImplicitUnicode to |
292 | I<different> values on en- and decoding to get symmetric behaviour). |
490 | I<different> values on en- and decoding to get symmetric behaviour). |
293 | |
491 | |
… | |
… | |
305 | JSON. One bank might parse a given non-JSON request and deduct money, |
503 | JSON. One bank might parse a given non-JSON request and deduct money, |
306 | while the other might reject the transaction with a syntax error. While a |
504 | while the other might reject the transaction with a syntax error. While a |
307 | good protocol will at least recover, that is extra unnecessary work and |
505 | good protocol will at least recover, that is extra unnecessary work and |
308 | the transaction will still not succeed). |
506 | the transaction will still not succeed). |
309 | |
507 | |
310 | =item JSON::DWIW |
508 | =item JSON::DWIW 0.04 |
311 | |
509 | |
312 | Very fast. Very natural. Very nice. |
510 | Very fast. Very natural. Very nice. |
313 | |
511 | |
314 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
512 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
315 | still don't get parsed properly). |
513 | still don't get parsed properly). |
316 | |
514 | |
317 | Very inflexible. |
515 | Very inflexible. |
318 | |
516 | |
319 | No roundtripping. |
517 | No roundtripping. |
320 | |
518 | |
321 | Does not generate valid JSON (key strings are often unquoted, empty keys |
519 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
322 | result in nothing being output) |
520 | result in nothing being output) |
323 | |
521 | |
324 | Does not check input for validity. |
522 | Does not check input for validity. |
325 | |
523 | |
326 | =back |
524 | =back |
… | |
… | |
330 | It seems that JSON::XS is surprisingly fast, as shown in the following |
528 | It seems that JSON::XS is surprisingly fast, as shown in the following |
331 | tables. They have been generated with the help of the C<eg/bench> program |
529 | tables. They have been generated with the help of the C<eg/bench> program |
332 | in the JSON::XS distribution, to make it easy to compare on your own |
530 | in the JSON::XS distribution, to make it easy to compare on your own |
333 | system. |
531 | system. |
334 | |
532 | |
335 | First is a comparison between various modules using a very simple JSON |
533 | First comes a comparison between various modules using a very short JSON |
|
|
534 | string: |
|
|
535 | |
|
|
536 | {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} |
|
|
537 | |
336 | string, showing the number of encodes/decodes per second (JSON::XS is |
538 | It shows the number of encodes/decodes per second (JSON::XS uses the |
337 | the functional interface, while JSON::XS/2 is the OO interface with |
539 | functional interface, while JSON::XS/2 uses the OO interface with |
338 | pretty-printing and hashkey sorting enabled). |
540 | pretty-printing and hashkey sorting enabled). Higher is better: |
339 | |
541 | |
340 | module | encode | decode | |
542 | module | encode | decode | |
341 | -----------|------------|------------| |
543 | -----------|------------|------------| |
342 | JSON | 14006 | 6820 | |
544 | JSON | 11488.516 | 7823.035 | |
343 | JSON::DWIW | 200937 | 120386 | |
545 | JSON::DWIW | 94708.054 | 129094.260 | |
344 | JSON::PC | 85065 | 129366 | |
546 | JSON::PC | 63884.157 | 128528.212 | |
345 | JSON::Syck | 59898 | 44232 | |
547 | JSON::Syck | 34898.677 | 42096.911 | |
346 | JSON::XS | 1171478 | 342435 | |
548 | JSON::XS | 654027.064 | 396423.669 | |
347 | JSON::XS/2 | 730760 | 328714 | |
549 | JSON::XS/2 | 371564.190 | 371725.613 | |
348 | -----------+------------+------------+ |
550 | -----------+------------+------------+ |
349 | |
551 | |
350 | That is, JSON::XS is 6 times faster than than JSON::DWIW and about 80 |
552 | That is, JSON::XS is more than six times faster than JSON::DWIW on |
|
|
553 | encoding, more than three times faster on decoding, and about thirty times |
351 | times faster than JSON, even with pretty-printing and key sorting. |
554 | faster than JSON, even with pretty-printing and key sorting. |
352 | |
555 | |
353 | Using a longer test string (roughly 8KB, generated from Yahoo! Locals |
556 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
354 | search API (http://nanoref.com/yahooapis/mgPdGg): |
557 | search API (http://nanoref.com/yahooapis/mgPdGg): |
355 | |
558 | |
356 | module | encode | decode | |
559 | module | encode | decode | |
357 | -----------|------------|------------| |
560 | -----------|------------|------------| |
358 | JSON | 673 | 38 | |
561 | JSON | 273.023 | 44.674 | |
359 | JSON::DWIW | 5271 | 770 | |
562 | JSON::DWIW | 1089.383 | 1145.704 | |
360 | JSON::PC | 9901 | 2491 | |
563 | JSON::PC | 3097.419 | 2393.921 | |
361 | JSON::Syck | 2360 | 786 | |
564 | JSON::Syck | 514.060 | 843.053 | |
362 | JSON::XS | 37398 | 3202 | |
565 | JSON::XS | 6479.668 | 3636.364 | |
363 | JSON::XS/2 | 13765 | 3153 | |
566 | JSON::XS/2 | 3774.221 | 3599.124 | |
364 | -----------+------------+------------+ |
567 | -----------+------------+------------+ |
365 | |
568 | |
366 | Again, JSON::XS leads by far in the encoding case, while still beating |
569 | Again, JSON::XS leads by far. |
367 | every other module in the decoding case. |
|
|
368 | |
570 | |
369 | Last example is an almost 8MB large hash with many large binary values |
571 | On large strings containing lots of high unicode characters, some modules |
370 | (PNG files), resulting in a lot of escaping: |
572 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
|
|
573 | will be broken due to missing (or wrong) unicode handling. Others refuse |
|
|
574 | to decode or encode properly, so it was impossible to prepare a fair |
|
|
575 | comparison table for that case. |
|
|
576 | |
|
|
577 | =head1 RESOURCE LIMITS |
|
|
578 | |
|
|
579 | JSON::XS does not impose any limits on the size of JSON texts or Perl |
|
|
580 | values they represent - if your machine can handle it, JSON::XS will |
|
|
581 | encode or decode it. Future versions might optionally impose structure |
|
|
582 | depth and memory use resource limits. |
371 | |
583 | |
372 | =head1 BUGS |
584 | =head1 BUGS |
373 | |
585 | |
374 | While the goal of this module is to be correct, that unfortunately does |
586 | While the goal of this module is to be correct, that unfortunately does |
375 | not mean its bug-free, only that I think its design is bug-free. It is |
587 | not mean its bug-free, only that I think its design is bug-free. It is |