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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, they croak on error |
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10 | # and expect/generate UTF-8 |
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11 | |
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12 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
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13 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
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14 | |
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15 | # objToJson and jsonToObj aliases to to_json and from_json |
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16 | # are exported for compatibility to the JSON module, |
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17 | # but should not be used in new code. |
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18 | |
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19 | # OO-interface |
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20 | |
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21 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
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22 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
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23 | $perl_scalar = $coder->decode ($unicode_json_text); |
8 | |
24 | |
9 | =head1 DESCRIPTION |
25 | =head1 DESCRIPTION |
10 | |
26 | |
11 | This module converts Perl data structures to JSON and vice versa. Its |
27 | This module converts Perl data structures to JSON and vice versa. Its |
12 | primary goal is to be I<correct> and its secondary goal is to be |
28 | primary goal is to be I<correct> and its secondary goal is to be |
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18 | their maintainers are unresponsive, gone missing, or not listening to bug |
34 | their maintainers are unresponsive, gone missing, or not listening to bug |
19 | reports for other reasons. |
35 | reports for other reasons. |
20 | |
36 | |
21 | See COMPARISON, below, for a comparison to some other JSON modules. |
37 | See COMPARISON, below, for a comparison to some other JSON modules. |
22 | |
38 | |
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39 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
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40 | vice versa. |
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41 | |
23 | =head2 FEATURES |
42 | =head2 FEATURES |
24 | |
43 | |
25 | =over 4 |
44 | =over 4 |
26 | |
45 | |
27 | =item * correct handling of unicode issues |
46 | =item * correct unicode handling |
28 | |
47 | |
29 | This module knows how to handle Unicode, and even documents how it does so. |
48 | This module knows how to handle Unicode, and even documents how and when |
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49 | it does so. |
30 | |
50 | |
31 | =item * round-trip integrity |
51 | =item * round-trip integrity |
32 | |
52 | |
33 | When you serialise a perl data structure using only datatypes supported |
53 | When you serialise a perl data structure using only datatypes supported |
34 | by JSON, the deserialised data structure is identical on the Perl level. |
54 | by JSON, the deserialised data structure is identical on the Perl level. |
35 | (e.g. the string "2.0" doesn't suddenly become "2"). |
55 | (e.g. the string "2.0" doesn't suddenly become "2" just because it looks |
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56 | like a number). |
36 | |
57 | |
37 | =item * strict checking of JSON correctness |
58 | =item * strict checking of JSON correctness |
38 | |
59 | |
39 | There is no guessing, no generating of illegal JSON strings by default, |
60 | There is no guessing, no generating of illegal JSON texts by default, |
40 | and only JSON is accepted as input (the latter is a security feature). |
61 | and only JSON is accepted as input by default (the latter is a security |
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62 | feature). |
41 | |
63 | |
42 | =item * fast |
64 | =item * fast |
43 | |
65 | |
44 | compared to other JSON modules, this module compares favourably. |
66 | Compared to other JSON modules, this module compares favourably in terms |
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67 | of speed, too. |
45 | |
68 | |
46 | =item * simple to use |
69 | =item * simple to use |
47 | |
70 | |
48 | This module has both a simple functional interface as well as an OO |
71 | This module has both a simple functional interface as well as an OO |
49 | interface. |
72 | interface. |
50 | |
73 | |
51 | =item * reasonably versatile output formats |
74 | =item * reasonably versatile output formats |
52 | |
75 | |
53 | You can choose between the most compact format possible, a pure-ascii |
76 | You can choose between the most compact guarenteed single-line format |
54 | format, or a pretty-printed format. Or you can combine those features in |
77 | possible (nice for simple line-based protocols), a pure-ascii format |
55 | whatever way you like. |
78 | (for when your transport is not 8-bit clean, still supports the whole |
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79 | unicode range), or a pretty-printed format (for when you want to read that |
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80 | stuff). Or you can combine those features in whatever way you like. |
56 | |
81 | |
57 | =back |
82 | =back |
58 | |
83 | |
59 | =cut |
84 | =cut |
60 | |
85 | |
61 | package JSON::XS; |
86 | package JSON::XS; |
62 | |
87 | |
63 | BEGIN { |
88 | use strict; |
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89 | |
64 | $VERSION = '0.1'; |
90 | our $VERSION = '1.4'; |
65 | @ISA = qw(Exporter); |
91 | our @ISA = qw(Exporter); |
66 | |
92 | |
67 | @EXPORT = qw(to_json from_json); |
93 | our @EXPORT = qw(to_json from_json objToJson jsonToObj); |
68 | require Exporter; |
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69 | |
94 | |
70 | require XSLoader; |
95 | use Exporter; |
71 | XSLoader::load JSON::XS::, $VERSION; |
96 | use XSLoader; |
72 | } |
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73 | |
97 | |
74 | =head1 FUNCTIONAL INTERFACE |
98 | =head1 FUNCTIONAL INTERFACE |
75 | |
99 | |
76 | The following convinience methods are provided by this module. They are |
100 | The following convinience methods are provided by this module. They are |
77 | exported by default: |
101 | exported by default: |
78 | |
102 | |
79 | =over 4 |
103 | =over 4 |
80 | |
104 | |
81 | =item $json_string = to_json $perl_scalar |
105 | =item $json_text = to_json $perl_scalar |
82 | |
106 | |
83 | Converts the given Perl data structure (a simple scalar or a reference to |
107 | Converts the given Perl data structure (a simple scalar or a reference to |
84 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
108 | a hash or array) to a UTF-8 encoded, binary string (that is, the string contains |
85 | octets only). Croaks on error. |
109 | octets only). Croaks on error. |
86 | |
110 | |
87 | This function call is functionally identical to C<< JSON::XS->new->utf8 |
111 | This function call is functionally identical to: |
88 | (1)->encode ($perl_scalar) >>. |
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89 | |
112 | |
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113 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
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114 | |
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115 | except being faster. |
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116 | |
90 | =item $perl_scalar = from_json $json_string |
117 | =item $perl_scalar = from_json $json_text |
91 | |
118 | |
92 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
119 | The opposite of C<to_json>: expects an UTF-8 (binary) string and tries to |
93 | parse that as an UTF-8 encoded JSON string, returning the resulting simple |
120 | parse that as an UTF-8 encoded JSON text, returning the resulting simple |
94 | scalar or reference. Croaks on error. |
121 | scalar or reference. Croaks on error. |
95 | |
122 | |
96 | This function call is functionally identical to C<< JSON::XS->new->utf8 |
123 | This function call is functionally identical to: |
97 | (1)->decode ($json_string) >>. |
124 | |
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125 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
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126 | |
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127 | except being faster. |
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128 | |
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129 | =item $is_boolean = JSON::XS::is_bool $scalar |
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130 | |
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131 | Returns true if the passed scalar represents either JSON::XS::true or |
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132 | JSON::XS::false, two constants that act like C<1> and C<0>, respectively |
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133 | and are used to represent JSON C<true> and C<false> values in Perl. |
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134 | |
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135 | See MAPPING, below, for more information on how JSON values are mapped to |
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136 | Perl. |
98 | |
137 | |
99 | =back |
138 | =back |
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139 | |
100 | |
140 | |
101 | =head1 OBJECT-ORIENTED INTERFACE |
141 | =head1 OBJECT-ORIENTED INTERFACE |
102 | |
142 | |
103 | The object oriented interface lets you configure your own encoding or |
143 | The object oriented interface lets you configure your own encoding or |
104 | decoding style, within the limits of supported formats. |
144 | decoding style, within the limits of supported formats. |
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111 | strings. All boolean flags described below are by default I<disabled>. |
151 | strings. All boolean flags described below are by default I<disabled>. |
112 | |
152 | |
113 | The mutators for flags all return the JSON object again and thus calls can |
153 | The mutators for flags all return the JSON object again and thus calls can |
114 | be chained: |
154 | be chained: |
115 | |
155 | |
116 | my $json = JSON::XS->new->utf8(1)->space_after(1)->encode ({a => [1,2]}) |
156 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
117 | => {"a": [1, 2]} |
157 | => {"a": [1, 2]} |
118 | |
158 | |
119 | =item $json = $json->ascii ($enable) |
159 | =item $json = $json->ascii ([$enable]) |
120 | |
160 | |
121 | If C<$enable> is true, then the C<encode> method will not generate |
161 | If C<$enable> is true (or missing), then the C<encode> method will not |
122 | characters outside the code range C<0..127>. Any unicode characters |
162 | 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 |
163 | unicode characters outside that range will be escaped using either a |
124 | characters) or a double \uHHHH\uLLLLL escape sequence, as per RFC4627. |
164 | single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL escape sequence, |
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165 | as per RFC4627. The resulting encoded JSON text can be treated as a native |
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166 | unicode string, an ascii-encoded, latin1-encoded or UTF-8 encoded string, |
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167 | or any other superset of ASCII. |
125 | |
168 | |
126 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
169 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
127 | characters unless necessary. |
170 | characters unless required by the JSON syntax or other flags. This results |
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171 | in a faster and more compact format. |
128 | |
172 | |
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173 | The main use for this flag is to produce JSON texts that can be |
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174 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
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175 | contain any 8 bit characters. |
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176 | |
129 | JSON::XS->new->ascii (1)->encode (chr 0x10401) |
177 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
130 | => \ud801\udc01 |
178 | => ["\ud801\udc01"] |
131 | |
179 | |
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180 | =item $json = $json->latin1 ([$enable]) |
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181 | |
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182 | If C<$enable> is true (or missing), then the C<encode> method will encode |
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183 | the resulting JSON text as latin1 (or iso-8859-1), escaping any characters |
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184 | outside the code range C<0..255>. The resulting string can be treated as a |
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185 | latin1-encoded JSON text or a native unicode string. The C<decode> method |
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186 | will not be affected in any way by this flag, as C<decode> by default |
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187 | expects unicode, which is a strict superset of latin1. |
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188 | |
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189 | If C<$enable> is false, then the C<encode> method will not escape Unicode |
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190 | characters unless required by the JSON syntax or other flags. |
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191 | |
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192 | The main use for this flag is efficiently encoding binary data as JSON |
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193 | text, as most octets will not be escaped, resulting in a smaller encoded |
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194 | size. The disadvantage is that the resulting JSON text is encoded |
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195 | in latin1 (and must correctly be treated as such when storing and |
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196 | transfering), a rare encoding for JSON. It is therefore most useful when |
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197 | you want to store data structures known to contain binary data efficiently |
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198 | in files or databases, not when talking to other JSON encoders/decoders. |
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199 | |
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200 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
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201 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
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202 | |
132 | =item $json = $json->utf8 ($enable) |
203 | =item $json = $json->utf8 ([$enable]) |
133 | |
204 | |
134 | If C<$enable> is true, then the C<encode> method will encode the JSON |
205 | If C<$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> |
206 | 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 |
207 | 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 |
208 | 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. |
209 | range C<0..255>, they are thus useful for bytewise/binary I/O. In future |
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210 | versions, enabling this option might enable autodetection of the UTF-16 |
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211 | and UTF-32 encoding families, as described in RFC4627. |
139 | |
212 | |
140 | If C<$enable> is false, then the C<encode> method will return the JSON |
213 | If C<$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 |
214 | 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 |
215 | 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. |
216 | to be done yourself, e.g. using the Encode module. |
144 | |
217 | |
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218 | Example, output UTF-16BE-encoded JSON: |
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219 | |
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220 | use Encode; |
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221 | $jsontext = encode "UTF-16BE", JSON::XS->new->encode ($object); |
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222 | |
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223 | Example, decode UTF-32LE-encoded JSON: |
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224 | |
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225 | use Encode; |
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226 | $object = JSON::XS->new->decode (decode "UTF-32LE", $jsontext); |
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227 | |
145 | =item $json = $json->pretty ($enable) |
228 | =item $json = $json->pretty ([$enable]) |
146 | |
229 | |
147 | This enables (or disables) all of the C<indent>, C<space_before> and |
230 | 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 |
231 | C<space_after> (and in the future possibly more) flags in one call to |
149 | generate the most readable (or most compact) form possible. |
232 | generate the most readable (or most compact) form possible. |
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233 | |
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234 | Example, pretty-print some simple structure: |
150 | |
235 | |
151 | my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
236 | my $json = JSON::XS->new->pretty(1)->encode ({a => [1,2]}) |
152 | => |
237 | => |
153 | { |
238 | { |
154 | "a" : [ |
239 | "a" : [ |
155 | 1, |
240 | 1, |
156 | 2 |
241 | 2 |
157 | ] |
242 | ] |
158 | } |
243 | } |
159 | |
244 | |
160 | =item $json = $json->indent ($enable) |
245 | =item $json = $json->indent ([$enable]) |
161 | |
246 | |
162 | If C<$enable> is true, then the C<encode> method will use a multiline |
247 | If C<$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 |
248 | format as output, putting every array member or object/hash key-value pair |
164 | into its own line, identing them properly. |
249 | into its own line, identing them properly. |
165 | |
250 | |
166 | If C<$enable> is false, no newlines or indenting will be produced, and the |
251 | If C<$enable> is false, no newlines or indenting will be produced, and the |
167 | resulting JSON strings is guarenteed not to contain any C<newlines>. |
252 | resulting JSON text is guarenteed not to contain any C<newlines>. |
168 | |
253 | |
169 | This setting has no effect when decoding JSON strings. |
254 | This setting has no effect when decoding JSON texts. |
170 | |
255 | |
171 | =item $json = $json->space_before ($enable) |
256 | =item $json = $json->space_before ([$enable]) |
172 | |
257 | |
173 | If C<$enable> is true, then the C<encode> method will add an extra |
258 | If C<$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. |
259 | optional space before the C<:> separating keys from values in JSON objects. |
175 | |
260 | |
176 | If C<$enable> is false, then the C<encode> method will not add any extra |
261 | If C<$enable> is false, then the C<encode> method will not add any extra |
177 | space at those places. |
262 | space at those places. |
178 | |
263 | |
179 | This setting has no effect when decoding JSON strings. You will also most |
264 | This setting has no effect when decoding JSON texts. You will also |
180 | likely combine this setting with C<space_after>. |
265 | most likely combine this setting with C<space_after>. |
181 | |
266 | |
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267 | Example, space_before enabled, space_after and indent disabled: |
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268 | |
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269 | {"key" :"value"} |
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270 | |
182 | =item $json = $json->space_after ($enable) |
271 | =item $json = $json->space_after ([$enable]) |
183 | |
272 | |
184 | If C<$enable> is true, then the C<encode> method will add an extra |
273 | If C<$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 |
274 | 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 |
275 | and extra whitespace after the C<,> separating key-value pairs and array |
187 | members. |
276 | members. |
188 | |
277 | |
189 | If C<$enable> is false, then the C<encode> method will not add any extra |
278 | If C<$enable> is false, then the C<encode> method will not add any extra |
190 | space at those places. |
279 | space at those places. |
191 | |
280 | |
192 | This setting has no effect when decoding JSON strings. |
281 | This setting has no effect when decoding JSON texts. |
193 | |
282 | |
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283 | Example, space_before and indent disabled, space_after enabled: |
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284 | |
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285 | {"key": "value"} |
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286 | |
194 | =item $json = $json->canonical ($enable) |
287 | =item $json = $json->canonical ([$enable]) |
195 | |
288 | |
196 | If C<$enable> is true, then the C<encode> method will output JSON objects |
289 | If C<$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. |
290 | by sorting their keys. This is adding a comparatively high overhead. |
198 | |
291 | |
199 | If C<$enable> is false, then the C<encode> method will output key-value |
292 | If C<$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 |
293 | pairs in the order Perl stores them (which will likely change between runs |
201 | of the same script). |
294 | of the same script). |
202 | |
295 | |
203 | This option is useful if you want the same data structure to be encoded as |
296 | 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, |
297 | 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, |
298 | the same hash migh be encoded differently even if contains the same data, |
206 | as key-value pairs have no inherent ordering in Perl. |
299 | as key-value pairs have no inherent ordering in Perl. |
207 | |
300 | |
208 | This setting has no effect when decoding JSON strings. |
301 | This setting has no effect when decoding JSON texts. |
209 | |
302 | |
210 | =item $json = $json->allow_nonref ($enable) |
303 | =item $json = $json->allow_nonref ([$enable]) |
211 | |
304 | |
212 | If C<$enable> is true, then the C<encode> method can convert a |
305 | If C<$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, |
306 | 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 |
307 | which is an extension to RFC4627. Likewise, C<decode> will accept those JSON |
215 | values instead of croaking. |
308 | values instead of croaking. |
216 | |
309 | |
217 | If C<$enable> is false, then the C<encode> method will croak if it isn't |
310 | If C<$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 |
311 | 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 |
312 | or array. Likewise, C<decode> will croak if given something that is not a |
220 | JSON object or array. |
313 | JSON object or array. |
221 | |
314 | |
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315 | Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, |
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316 | resulting in an invalid JSON text: |
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317 | |
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318 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
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319 | => "Hello, World!" |
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320 | |
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321 | =item $json = $json->allow_blessed ([$enable]) |
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322 | |
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323 | If C<$enable> is true (or missing), then the C<encode> method will not |
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324 | barf when it encounters a blessed reference. Instead, the value of the |
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325 | B<convert_blessed> option will decide wether C<null> (C<convert_blessed> |
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326 | disabled or no C<to_json> method found) or a representation of the |
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327 | object (C<convert_blessed> enabled and C<to_json> method found) is being |
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328 | encoded. Has no effect on C<decode>. |
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329 | |
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330 | If C<$enable> is false (the default), then C<encode> will throw an |
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331 | exception when it encounters a blessed object. |
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332 | |
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333 | =item $json = $json->convert_blessed ([$enable]) |
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334 | |
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335 | If C<$enable> is true (or missing), then C<encode>, upon encountering a |
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336 | blessed object, will check for the availability of the C<TO_JSON> method |
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337 | on the object's class. If found, it will be called in scalar context |
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338 | and the resulting scalar will be encoded instead of the object. If no |
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339 | C<TO_JSON> method is found, the value of C<allow_blessed> will decide what |
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340 | to do. |
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341 | |
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342 | The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON> |
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343 | returns other blessed objects, those will be handled in the same |
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344 | way. C<TO_JSON> must take care of not causing an endless recursion cycle |
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345 | (== crash) in this case. The name of C<TO_JSON> was chosen because other |
|
|
346 | methods called by the Perl core (== not the user of the object) are |
|
|
347 | usually in upper case letters and to avoid collisions with the C<to_json> |
|
|
348 | function. |
|
|
349 | |
|
|
350 | If C<$enable> is false, then the C<allow_blessed> setting will decide what |
|
|
351 | to do when a blessed object is found. |
|
|
352 | |
|
|
353 | =item $json = $json->shrink ([$enable]) |
|
|
354 | |
|
|
355 | Perl usually over-allocates memory a bit when allocating space for |
|
|
356 | strings. This flag optionally resizes strings generated by either |
|
|
357 | C<encode> or C<decode> to their minimum size possible. This can save |
|
|
358 | memory when your JSON texts are either very very long or you have many |
|
|
359 | short strings. It will also try to downgrade any strings to octet-form |
|
|
360 | if possible: perl stores strings internally either in an encoding called |
|
|
361 | UTF-X or in octet-form. The latter cannot store everything but uses less |
|
|
362 | space in general (and some buggy Perl or C code might even rely on that |
|
|
363 | internal representation being used). |
|
|
364 | |
|
|
365 | The actual definition of what shrink does might change in future versions, |
|
|
366 | but it will always try to save space at the expense of time. |
|
|
367 | |
|
|
368 | If C<$enable> is true (or missing), the string returned by C<encode> will |
|
|
369 | be shrunk-to-fit, while all strings generated by C<decode> will also be |
|
|
370 | shrunk-to-fit. |
|
|
371 | |
|
|
372 | If C<$enable> is false, then the normal perl allocation algorithms are used. |
|
|
373 | If you work with your data, then this is likely to be faster. |
|
|
374 | |
|
|
375 | In the future, this setting might control other things, such as converting |
|
|
376 | strings that look like integers or floats into integers or floats |
|
|
377 | internally (there is no difference on the Perl level), saving space. |
|
|
378 | |
|
|
379 | =item $json = $json->max_depth ([$maximum_nesting_depth]) |
|
|
380 | |
|
|
381 | Sets the maximum nesting level (default C<512>) accepted while encoding |
|
|
382 | or decoding. If the JSON text or Perl data structure has an equal or |
|
|
383 | higher nesting level then this limit, then the encoder and decoder will |
|
|
384 | stop and croak at that point. |
|
|
385 | |
|
|
386 | Nesting level is defined by number of hash- or arrayrefs that the encoder |
|
|
387 | needs to traverse to reach a given point or the number of C<{> or C<[> |
|
|
388 | characters without their matching closing parenthesis crossed to reach a |
|
|
389 | given character in a string. |
|
|
390 | |
|
|
391 | Setting the maximum depth to one disallows any nesting, so that ensures |
|
|
392 | that the object is only a single hash/object or array. |
|
|
393 | |
|
|
394 | The argument to C<max_depth> will be rounded up to the next nearest power |
|
|
395 | of two. |
|
|
396 | |
|
|
397 | See SECURITY CONSIDERATIONS, below, for more info on why this is useful. |
|
|
398 | |
222 | =item $json_string = $json->encode ($perl_scalar) |
399 | =item $json_text = $json->encode ($perl_scalar) |
223 | |
400 | |
224 | Converts the given Perl data structure (a simple scalar or a reference |
401 | 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 |
402 | 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 |
403 | converted into JSON string or number sequences, while references to arrays |
227 | become JSON arrays and references to hashes become JSON objects. Undefined |
404 | 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> |
405 | Perl values (e.g. C<undef>) become JSON C<null> values. Neither C<true> |
229 | nor C<false> values will be generated. |
406 | nor C<false> values will be generated. |
230 | |
407 | |
231 | =item $perl_scalar = $json->decode ($json_string) |
408 | =item $perl_scalar = $json->decode ($json_text) |
232 | |
409 | |
233 | The opposite of C<encode>: expects a JSON string and tries to parse it, |
410 | 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. |
411 | returning the resulting simple scalar or reference. Croaks on error. |
235 | |
412 | |
236 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
413 | JSON numbers and strings become simple Perl scalars. JSON arrays become |
237 | Perl arrayrefs and JSON objects become Perl hashrefs. C<true> becomes |
414 | 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>. |
415 | C<1>, C<false> becomes C<0> and C<null> becomes C<undef>. |
239 | |
416 | |
|
|
417 | =item ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
|
|
418 | |
|
|
419 | This works like the C<decode> method, but instead of raising an exception |
|
|
420 | when there is trailing garbage after the first JSON object, it will |
|
|
421 | silently stop parsing there and return the number of characters consumed |
|
|
422 | so far. |
|
|
423 | |
|
|
424 | This is useful if your JSON texts are not delimited by an outer protocol |
|
|
425 | (which is not the brightest thing to do in the first place) and you need |
|
|
426 | to know where the JSON text ends. |
|
|
427 | |
|
|
428 | JSON::XS->new->decode_prefix ("[1] the tail") |
|
|
429 | => ([], 3) |
|
|
430 | |
240 | =back |
431 | =back |
|
|
432 | |
|
|
433 | |
|
|
434 | =head1 MAPPING |
|
|
435 | |
|
|
436 | This section describes how JSON::XS maps Perl values to JSON values and |
|
|
437 | vice versa. These mappings are designed to "do the right thing" in most |
|
|
438 | circumstances automatically, preserving round-tripping characteristics |
|
|
439 | (what you put in comes out as something equivalent). |
|
|
440 | |
|
|
441 | For the more enlightened: note that in the following descriptions, |
|
|
442 | lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> |
|
|
443 | refers to the abstract Perl language itself. |
|
|
444 | |
|
|
445 | |
|
|
446 | =head2 JSON -> PERL |
|
|
447 | |
|
|
448 | =over 4 |
|
|
449 | |
|
|
450 | =item object |
|
|
451 | |
|
|
452 | A JSON object becomes a reference to a hash in Perl. No ordering of object |
|
|
453 | keys is preserved (JSON does not preserver object key ordering itself). |
|
|
454 | |
|
|
455 | =item array |
|
|
456 | |
|
|
457 | A JSON array becomes a reference to an array in Perl. |
|
|
458 | |
|
|
459 | =item string |
|
|
460 | |
|
|
461 | A JSON string becomes a string scalar in Perl - Unicode codepoints in JSON |
|
|
462 | are represented by the same codepoints in the Perl string, so no manual |
|
|
463 | decoding is necessary. |
|
|
464 | |
|
|
465 | =item number |
|
|
466 | |
|
|
467 | A JSON number becomes either an integer or numeric (floating point) |
|
|
468 | scalar in perl, depending on its range and any fractional parts. On the |
|
|
469 | Perl level, there is no difference between those as Perl handles all the |
|
|
470 | conversion details, but an integer may take slightly less memory and might |
|
|
471 | represent more values exactly than (floating point) numbers. |
|
|
472 | |
|
|
473 | =item true, false |
|
|
474 | |
|
|
475 | These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>, |
|
|
476 | respectively. They are overloaded to act almost exactly like the numbers |
|
|
477 | C<1> and C<0>. You can check wether a scalar is a JSON boolean by using |
|
|
478 | the C<JSON::XS::is_bool> function. |
|
|
479 | |
|
|
480 | =item null |
|
|
481 | |
|
|
482 | A JSON null atom becomes C<undef> in Perl. |
|
|
483 | |
|
|
484 | =back |
|
|
485 | |
|
|
486 | |
|
|
487 | =head2 PERL -> JSON |
|
|
488 | |
|
|
489 | The mapping from Perl to JSON is slightly more difficult, as Perl is a |
|
|
490 | truly typeless language, so we can only guess which JSON type is meant by |
|
|
491 | a Perl value. |
|
|
492 | |
|
|
493 | =over 4 |
|
|
494 | |
|
|
495 | =item hash references |
|
|
496 | |
|
|
497 | Perl hash references become JSON objects. As there is no inherent ordering |
|
|
498 | in hash keys (or JSON objects), they will usually be encoded in a |
|
|
499 | pseudo-random order that can change between runs of the same program but |
|
|
500 | stays generally the same within a single run of a program. JSON::XS can |
|
|
501 | optionally sort the hash keys (determined by the I<canonical> flag), so |
|
|
502 | the same datastructure will serialise to the same JSON text (given same |
|
|
503 | settings and version of JSON::XS), but this incurs a runtime overhead |
|
|
504 | and is only rarely useful, e.g. when you want to compare some JSON text |
|
|
505 | against another for equality. |
|
|
506 | |
|
|
507 | =item array references |
|
|
508 | |
|
|
509 | Perl array references become JSON arrays. |
|
|
510 | |
|
|
511 | =item other references |
|
|
512 | |
|
|
513 | Other unblessed references are generally not allowed and will cause an |
|
|
514 | exception to be thrown, except for references to the integers C<0> and |
|
|
515 | C<1>, which get turned into C<false> and C<true> atoms in JSON. You can |
|
|
516 | also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. |
|
|
517 | |
|
|
518 | to_json [\0,JSON::XS::true] # yields [false,true] |
|
|
519 | |
|
|
520 | =item JSON::XS::true, JSON::XS::false |
|
|
521 | |
|
|
522 | These special values become JSON true and JSON false values, |
|
|
523 | respectively. You cna alos use C<\1> and C<\0> directly if you want. |
|
|
524 | |
|
|
525 | =item blessed objects |
|
|
526 | |
|
|
527 | Blessed objects are not allowed. JSON::XS currently tries to encode their |
|
|
528 | underlying representation (hash- or arrayref), but this behaviour might |
|
|
529 | change in future versions. |
|
|
530 | |
|
|
531 | =item simple scalars |
|
|
532 | |
|
|
533 | Simple Perl scalars (any scalar that is not a reference) are the most |
|
|
534 | difficult objects to encode: JSON::XS will encode undefined scalars as |
|
|
535 | JSON null value, scalars that have last been used in a string context |
|
|
536 | before encoding as JSON strings and anything else as number value: |
|
|
537 | |
|
|
538 | # dump as number |
|
|
539 | to_json [2] # yields [2] |
|
|
540 | to_json [-3.0e17] # yields [-3e+17] |
|
|
541 | my $value = 5; to_json [$value] # yields [5] |
|
|
542 | |
|
|
543 | # used as string, so dump as string |
|
|
544 | print $value; |
|
|
545 | to_json [$value] # yields ["5"] |
|
|
546 | |
|
|
547 | # undef becomes null |
|
|
548 | to_json [undef] # yields [null] |
|
|
549 | |
|
|
550 | You can force the type to be a string by stringifying it: |
|
|
551 | |
|
|
552 | my $x = 3.1; # some variable containing a number |
|
|
553 | "$x"; # stringified |
|
|
554 | $x .= ""; # another, more awkward way to stringify |
|
|
555 | print $x; # perl does it for you, too, quite often |
|
|
556 | |
|
|
557 | You can force the type to be a number by numifying it: |
|
|
558 | |
|
|
559 | my $x = "3"; # some variable containing a string |
|
|
560 | $x += 0; # numify it, ensuring it will be dumped as a number |
|
|
561 | $x *= 1; # same thing, the choise is yours. |
|
|
562 | |
|
|
563 | You can not currently output JSON booleans or force the type in other, |
|
|
564 | less obscure, ways. Tell me if you need this capability. |
|
|
565 | |
|
|
566 | =back |
|
|
567 | |
241 | |
568 | |
242 | =head1 COMPARISON |
569 | =head1 COMPARISON |
243 | |
570 | |
244 | As already mentioned, this module was created because none of the existing |
571 | As already mentioned, this module was created because none of the existing |
245 | JSON modules could be made to work correctly. First I will describe the |
572 | JSON modules could be made to work correctly. First I will describe the |
246 | problems (or pleasures) I encountered with various existing JSON modules, |
573 | problems (or pleasures) I encountered with various existing JSON modules, |
247 | followed by some benchmark values. |
574 | followed by some benchmark values. JSON::XS was designed not to suffer |
|
|
575 | from any of these problems or limitations. |
248 | |
576 | |
249 | =over 4 |
577 | =over 4 |
250 | |
578 | |
251 | =item JSON |
579 | =item JSON 1.07 |
252 | |
580 | |
253 | Slow (but very portable, as it is written in pure Perl). |
581 | Slow (but very portable, as it is written in pure Perl). |
254 | |
582 | |
255 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
583 | Undocumented/buggy Unicode handling (how JSON handles unicode values is |
256 | undocumented. One can get far by feeding it unicode strings and doing |
584 | undocumented. One can get far by feeding it unicode strings and doing |
… | |
… | |
258 | |
586 | |
259 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
587 | No roundtripping (strings get clobbered if they look like numbers, e.g. |
260 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
588 | the string C<2.0> will encode to C<2.0> instead of C<"2.0">, and that will |
261 | decode into the number 2. |
589 | decode into the number 2. |
262 | |
590 | |
263 | =item JSON::PC |
591 | =item JSON::PC 0.01 |
264 | |
592 | |
265 | Very fast. |
593 | Very fast. |
|
|
594 | |
|
|
595 | Undocumented/buggy Unicode handling. |
|
|
596 | |
|
|
597 | No roundtripping. |
|
|
598 | |
|
|
599 | Has problems handling many Perl values (e.g. regex results and other magic |
|
|
600 | values will make it croak). |
|
|
601 | |
|
|
602 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
|
|
603 | which is not a valid JSON text. |
|
|
604 | |
|
|
605 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
606 | getting fixed). |
|
|
607 | |
|
|
608 | =item JSON::Syck 0.21 |
|
|
609 | |
|
|
610 | Very buggy (often crashes). |
266 | |
611 | |
267 | Very inflexible (no human-readable format supported, format pretty much |
612 | Very inflexible (no human-readable format supported, format pretty much |
268 | undocumented. I need at least a format for easy reading by humans and a |
613 | undocumented. I need at least a format for easy reading by humans and a |
269 | single-line compact format for use in a protocol, and preferably a way to |
614 | single-line compact format for use in a protocol, and preferably a way to |
270 | generate ASCII-only JSON strings). |
615 | generate ASCII-only JSON texts). |
271 | |
|
|
272 | Undocumented/buggy Unicode handling. |
|
|
273 | |
|
|
274 | No roundtripping. |
|
|
275 | |
|
|
276 | Has problems handling many Perl values. |
|
|
277 | |
|
|
278 | Does not even generate valid JSON (C<{1,2}> gets converted to C<{1:2}> |
|
|
279 | which is not a valid JSON string. |
|
|
280 | |
|
|
281 | Unmaintained (maintainer unresponsive for many months, bugs are not |
|
|
282 | getting fixed). |
|
|
283 | |
|
|
284 | =item JSON::Syck |
|
|
285 | |
|
|
286 | Very buggy (often crashes). |
|
|
287 | |
|
|
288 | Very inflexible. |
|
|
289 | |
616 | |
290 | Completely broken (and confusingly documented) Unicode handling (unicode |
617 | Completely broken (and confusingly documented) Unicode handling (unicode |
291 | escapes are not working properly, you need to set ImplicitUnicode to |
618 | escapes are not working properly, you need to set ImplicitUnicode to |
292 | I<different> values on en- and decoding to get symmetric behaviour). |
619 | I<different> values on en- and decoding to get symmetric behaviour). |
293 | |
620 | |
… | |
… | |
305 | JSON. One bank might parse a given non-JSON request and deduct money, |
632 | 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 |
633 | 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 |
634 | good protocol will at least recover, that is extra unnecessary work and |
308 | the transaction will still not succeed). |
635 | the transaction will still not succeed). |
309 | |
636 | |
310 | =item JSON::DWIW |
637 | =item JSON::DWIW 0.04 |
311 | |
638 | |
312 | Very fast. Very natural. Very nice. |
639 | Very fast. Very natural. Very nice. |
313 | |
640 | |
314 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
641 | Undocumented unicode handling (but the best of the pack. Unicode escapes |
315 | still don't get parsed properly). |
642 | still don't get parsed properly). |
316 | |
643 | |
317 | Very inflexible. |
644 | Very inflexible. |
318 | |
645 | |
319 | No roundtripping. |
646 | No roundtripping. |
320 | |
647 | |
|
|
648 | Does not generate valid JSON texts (key strings are often unquoted, empty keys |
|
|
649 | result in nothing being output) |
|
|
650 | |
321 | Does not check input for validity. |
651 | Does not check input for validity. |
322 | |
652 | |
323 | =back |
653 | =back |
324 | |
654 | |
|
|
655 | |
|
|
656 | =head2 JSON and YAML |
|
|
657 | |
|
|
658 | You often hear that JSON is a subset (or a close subset) of YAML. This is, |
|
|
659 | however, a mass hysteria and very far from the truth. In general, there is |
|
|
660 | no way to configure JSON::XS to output a data structure as valid YAML. |
|
|
661 | |
|
|
662 | If you really must use JSON::XS to generate YAML, you should use this |
|
|
663 | algorithm (subject to change in future versions): |
|
|
664 | |
|
|
665 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
|
|
666 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
|
|
667 | |
|
|
668 | This will usually generate JSON texts that also parse as valid |
|
|
669 | YAML. Please note that YAML has hardcoded limits on (simple) object key |
|
|
670 | lengths that JSON doesn't have, so you should make sure that your hash |
|
|
671 | keys are noticably shorter than the 1024 characters YAML allows. |
|
|
672 | |
|
|
673 | There might be other incompatibilities that I am not aware of. In general |
|
|
674 | you should not try to generate YAML with a JSON generator or vice versa, |
|
|
675 | or try to parse JSON with a YAML parser or vice versa: chances are high |
|
|
676 | that you will run into severe interoperability problems. |
|
|
677 | |
|
|
678 | |
325 | =head2 SPEED |
679 | =head2 SPEED |
326 | |
680 | |
|
|
681 | It seems that JSON::XS is surprisingly fast, as shown in the following |
|
|
682 | tables. They have been generated with the help of the C<eg/bench> program |
|
|
683 | in the JSON::XS distribution, to make it easy to compare on your own |
|
|
684 | system. |
|
|
685 | |
|
|
686 | First comes a comparison between various modules using a very short |
|
|
687 | single-line JSON string: |
|
|
688 | |
|
|
689 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
|
|
690 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
|
|
691 | |
|
|
692 | It shows the number of encodes/decodes per second (JSON::XS uses |
|
|
693 | the functional interface, while JSON::XS/2 uses the OO interface |
|
|
694 | with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables |
|
|
695 | shrink). Higher is better: |
|
|
696 | |
|
|
697 | module | encode | decode | |
|
|
698 | -----------|------------|------------| |
|
|
699 | JSON | 7645.468 | 4208.613 | |
|
|
700 | JSON::DWIW | 40721.398 | 77101.176 | |
|
|
701 | JSON::PC | 65948.176 | 78251.940 | |
|
|
702 | JSON::Syck | 22844.793 | 26479.192 | |
|
|
703 | JSON::XS | 388361.481 | 199728.762 | |
|
|
704 | JSON::XS/2 | 218453.333 | 192399.266 | |
|
|
705 | JSON::XS/3 | 338250.323 | 192399.266 | |
|
|
706 | Storable | 15779.925 | 14169.946 | |
|
|
707 | -----------+------------+------------+ |
|
|
708 | |
|
|
709 | That is, JSON::XS is about five times faster than JSON::DWIW on encoding, |
|
|
710 | about three times faster on decoding, and over fourty times faster |
|
|
711 | than JSON, even with pretty-printing and key sorting. It also compares |
|
|
712 | favourably to Storable for small amounts of data. |
|
|
713 | |
|
|
714 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
|
|
715 | search API (http://nanoref.com/yahooapis/mgPdGg): |
|
|
716 | |
|
|
717 | module | encode | decode | |
|
|
718 | -----------|------------|------------| |
|
|
719 | JSON | 254.685 | 37.665 | |
|
|
720 | JSON::DWIW | 843.343 | 1049.731 | |
|
|
721 | JSON::PC | 3602.116 | 2307.352 | |
|
|
722 | JSON::Syck | 505.107 | 787.899 | |
|
|
723 | JSON::XS | 5747.196 | 3690.220 | |
|
|
724 | JSON::XS/2 | 3968.121 | 3676.634 | |
|
|
725 | JSON::XS/3 | 6105.246 | 3662.508 | |
|
|
726 | Storable | 4417.337 | 5285.161 | |
|
|
727 | -----------+------------+------------+ |
|
|
728 | |
|
|
729 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
|
|
730 | decodes faster). |
|
|
731 | |
|
|
732 | On large strings containing lots of high unicode characters, some modules |
|
|
733 | (such as JSON::PC) seem to decode faster than JSON::XS, but the result |
|
|
734 | will be broken due to missing (or wrong) unicode handling. Others refuse |
|
|
735 | to decode or encode properly, so it was impossible to prepare a fair |
|
|
736 | comparison table for that case. |
|
|
737 | |
|
|
738 | |
|
|
739 | =head1 SECURITY CONSIDERATIONS |
|
|
740 | |
|
|
741 | When you are using JSON in a protocol, talking to untrusted potentially |
|
|
742 | hostile creatures requires relatively few measures. |
|
|
743 | |
|
|
744 | First of all, your JSON decoder should be secure, that is, should not have |
|
|
745 | any buffer overflows. Obviously, this module should ensure that and I am |
|
|
746 | trying hard on making that true, but you never know. |
|
|
747 | |
|
|
748 | Second, you need to avoid resource-starving attacks. That means you should |
|
|
749 | limit the size of JSON texts you accept, or make sure then when your |
|
|
750 | resources run out, thats just fine (e.g. by using a separate process that |
|
|
751 | can crash safely). The size of a JSON text in octets or characters is |
|
|
752 | usually a good indication of the size of the resources required to decode |
|
|
753 | it into a Perl structure. |
|
|
754 | |
|
|
755 | Third, JSON::XS recurses using the C stack when decoding objects and |
|
|
756 | arrays. The C stack is a limited resource: for instance, on my amd64 |
|
|
757 | machine with 8MB of stack size I can decode around 180k nested arrays but |
|
|
758 | only 14k nested JSON objects (due to perl itself recursing deeply on croak |
|
|
759 | to free the temporary). If that is exceeded, the program crashes. to be |
|
|
760 | conservative, the default nesting limit is set to 512. If your process |
|
|
761 | has a smaller stack, you should adjust this setting accordingly with the |
|
|
762 | C<max_depth> method. |
|
|
763 | |
|
|
764 | And last but least, something else could bomb you that I forgot to think |
|
|
765 | of. In that case, you get to keep the pieces. I am always open for hints, |
|
|
766 | though... |
|
|
767 | |
|
|
768 | If you are using JSON::XS to return packets to consumption |
|
|
769 | by javascript scripts in a browser you should have a look at |
|
|
770 | L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether |
|
|
771 | you are vulnerable to some common attack vectors (which really are browser |
|
|
772 | design bugs, but it is still you who will have to deal with it, as major |
|
|
773 | browser developers care only for features, not about doing security |
|
|
774 | right). |
|
|
775 | |
|
|
776 | |
|
|
777 | =head1 BUGS |
|
|
778 | |
|
|
779 | While the goal of this module is to be correct, that unfortunately does |
|
|
780 | not mean its bug-free, only that I think its design is bug-free. It is |
|
|
781 | still relatively early in its development. If you keep reporting bugs they |
|
|
782 | will be fixed swiftly, though. |
|
|
783 | |
327 | =cut |
784 | =cut |
|
|
785 | |
|
|
786 | our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" }; |
|
|
787 | our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" }; |
|
|
788 | |
|
|
789 | sub true() { $true } |
|
|
790 | sub false() { $false } |
|
|
791 | |
|
|
792 | sub is_bool($) { |
|
|
793 | UNIVERSAL::isa $_[0], "JSON::XS::Boolean" |
|
|
794 | # or UNIVERSAL::isa $_[0], "JSON::Literal" |
|
|
795 | } |
|
|
796 | |
|
|
797 | XSLoader::load "JSON::XS", $VERSION; |
|
|
798 | |
|
|
799 | package JSON::XS::Boolean; |
|
|
800 | |
|
|
801 | use overload |
|
|
802 | "0+" => sub { ${$_[0]} }, |
|
|
803 | "++" => sub { $_[0] = ${$_[0]} + 1 }, |
|
|
804 | "--" => sub { $_[0] = ${$_[0]} - 1 }, |
|
|
805 | fallback => 1; |
328 | |
806 | |
329 | 1; |
807 | 1; |
330 | |
808 | |
331 | =head1 AUTHOR |
809 | =head1 AUTHOR |
332 | |
810 | |