1 | NAME |
1 | NAME |
2 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
2 | JSON::XS - JSON serialising/deserialising, done correctly and fast |
3 | |
3 | |
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4 | JSON::XS - 正しくて高速な JSON |
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5 | シリアライザ/デシリアライザ |
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6 | (http://fleur.hio.jp/perldoc/mix/lib/JSON/XS.html) |
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7 | |
4 | SYNOPSIS |
8 | SYNOPSIS |
5 | use JSON::XS; |
9 | use JSON::XS; |
6 | |
10 | |
7 | # exported functions, they croak on error |
11 | # exported functions, they croak on error |
8 | # and expect/generate UTF-8 |
12 | # and expect/generate UTF-8 |
9 | |
13 | |
10 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
14 | $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; |
11 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
15 | $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; |
12 | |
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13 | # objToJson and jsonToObj aliases to to_json and from_json |
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14 | # are exported for compatibility to the JSON module, |
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15 | # but should not be used in new code. |
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16 | |
16 | |
17 | # OO-interface |
17 | # OO-interface |
18 | |
18 | |
19 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
19 | $coder = JSON::XS->new->ascii->pretty->allow_nonref; |
20 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
20 | $pretty_printed_unencoded = $coder->encode ($perl_scalar); |
21 | $perl_scalar = $coder->decode ($unicode_json_text); |
21 | $perl_scalar = $coder->decode ($unicode_json_text); |
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22 | |
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23 | # Note that JSON version 2.0 and above will automatically use JSON::XS |
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24 | # if available, at virtually no speed overhead either, so you should |
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25 | # be able to just: |
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26 | |
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27 | use JSON; |
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28 | |
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29 | # and do the same things, except that you have a pure-perl fallback now. |
22 | |
30 | |
23 | DESCRIPTION |
31 | DESCRIPTION |
24 | This module converts Perl data structures to JSON and vice versa. Its |
32 | This module converts Perl data structures to JSON and vice versa. Its |
25 | primary goal is to be *correct* and its secondary goal is to be *fast*. |
33 | primary goal is to be *correct* and its secondary goal is to be *fast*. |
26 | To reach the latter goal it was written in C. |
34 | To reach the latter goal it was written in C. |
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35 | |
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36 | Beginning with version 2.0 of the JSON module, when both JSON and |
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37 | JSON::XS are installed, then JSON will fall back on JSON::XS (this can |
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38 | be overriden) with no overhead due to emulation (by inheritign |
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39 | constructor and methods). If JSON::XS is not available, it will fall |
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40 | back to the compatible JSON::PP module as backend, so using JSON instead |
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41 | of JSON::XS gives you a portable JSON API that can be fast when you need |
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42 | and doesn't require a C compiler when that is a problem. |
27 | |
43 | |
28 | As this is the n-th-something JSON module on CPAN, what was the reason |
44 | As this is the n-th-something JSON module on CPAN, what was the reason |
29 | to write yet another JSON module? While it seems there are many JSON |
45 | to write yet another JSON module? While it seems there are many JSON |
30 | modules, none of them correctly handle all corner cases, and in most |
46 | modules, none of them correctly handle all corner cases, and in most |
31 | cases their maintainers are unresponsive, gone missing, or not listening |
47 | cases their maintainers are unresponsive, gone missing, or not listening |
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35 | |
51 | |
36 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
52 | See MAPPING, below, on how JSON::XS maps perl values to JSON values and |
37 | vice versa. |
53 | vice versa. |
38 | |
54 | |
39 | FEATURES |
55 | FEATURES |
40 | * correct unicode handling |
56 | * correct Unicode handling |
41 | This module knows how to handle Unicode, and even documents how and |
57 | This module knows how to handle Unicode, and even documents how and |
42 | when it does so. |
58 | when it does so. |
43 | |
59 | |
44 | * round-trip integrity |
60 | * round-trip integrity |
45 | When you serialise a perl data structure using only datatypes |
61 | When you serialise a perl data structure using only datatypes |
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59 | * simple to use |
75 | * simple to use |
60 | This module has both a simple functional interface as well as an OO |
76 | This module has both a simple functional interface as well as an OO |
61 | interface. |
77 | interface. |
62 | |
78 | |
63 | * reasonably versatile output formats |
79 | * reasonably versatile output formats |
64 | You can choose between the most compact guarenteed single-line |
80 | You can choose between the most compact guaranteed single-line |
65 | format possible (nice for simple line-based protocols), a pure-ascii |
81 | format possible (nice for simple line-based protocols), a pure-ascii |
66 | format (for when your transport is not 8-bit clean, still supports |
82 | format (for when your transport is not 8-bit clean, still supports |
67 | the whole unicode range), or a pretty-printed format (for when you |
83 | the whole Unicode range), or a pretty-printed format (for when you |
68 | want to read that stuff). Or you can combine those features in |
84 | want to read that stuff). Or you can combine those features in |
69 | whatever way you like. |
85 | whatever way you like. |
70 | |
86 | |
71 | FUNCTIONAL INTERFACE |
87 | FUNCTIONAL INTERFACE |
72 | The following convinience methods are provided by this module. They are |
88 | The following convenience methods are provided by this module. They are |
73 | exported by default: |
89 | exported by default: |
74 | |
90 | |
75 | $json_text = to_json $perl_scalar |
91 | $json_text = to_json $perl_scalar |
76 | Converts the given Perl data structure (a simple scalar or a |
92 | Converts the given Perl data structure to a UTF-8 encoded, binary |
77 | reference to a hash or array) to a UTF-8 encoded, binary string |
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78 | (that is, the string contains octets only). Croaks on error. |
93 | string (that is, the string contains octets only). Croaks on error. |
79 | |
94 | |
80 | This function call is functionally identical to: |
95 | This function call is functionally identical to: |
81 | |
96 | |
82 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
97 | $json_text = JSON::XS->new->utf8->encode ($perl_scalar) |
83 | |
98 | |
84 | except being faster. |
99 | except being faster. |
85 | |
100 | |
86 | $perl_scalar = from_json $json_text |
101 | $perl_scalar = from_json $json_text |
87 | The opposite of "to_json": expects an UTF-8 (binary) string and |
102 | The opposite of "to_json": expects an UTF-8 (binary) string and |
88 | tries to parse that as an UTF-8 encoded JSON text, returning the |
103 | tries to parse that as an UTF-8 encoded JSON text, returning the |
89 | resulting simple scalar or reference. Croaks on error. |
104 | resulting reference. Croaks on error. |
90 | |
105 | |
91 | This function call is functionally identical to: |
106 | This function call is functionally identical to: |
92 | |
107 | |
93 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
108 | $perl_scalar = JSON::XS->new->utf8->decode ($json_text) |
94 | |
109 | |
95 | except being faster. |
110 | except being faster. |
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111 | |
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112 | $is_boolean = JSON::XS::is_bool $scalar |
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113 | Returns true if the passed scalar represents either JSON::XS::true |
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114 | or JSON::XS::false, two constants that act like 1 and 0, |
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115 | respectively and are used to represent JSON "true" and "false" |
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116 | values in Perl. |
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117 | |
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118 | See MAPPING, below, for more information on how JSON values are |
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119 | mapped to Perl. |
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120 | |
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121 | A FEW NOTES ON UNICODE AND PERL |
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122 | Since this often leads to confusion, here are a few very clear words on |
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123 | how Unicode works in Perl, modulo bugs. |
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124 | |
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125 | 1. Perl strings can store characters with ordinal values > 255. |
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126 | This enables you to store Unicode characters as single characters in |
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127 | a Perl string - very natural. |
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128 | |
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129 | 2. Perl does *not* associate an encoding with your strings. |
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130 | Unless you force it to, e.g. when matching it against a regex, or |
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131 | printing the scalar to a file, in which case Perl either interprets |
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132 | your string as locale-encoded text, octets/binary, or as Unicode, |
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133 | depending on various settings. In no case is an encoding stored |
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134 | together with your data, it is *use* that decides encoding, not any |
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135 | magical metadata. |
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136 | |
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137 | 3. The internal utf-8 flag has no meaning with regards to the encoding |
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138 | of your string. |
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139 | Just ignore that flag unless you debug a Perl bug, a module written |
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140 | in XS or want to dive into the internals of perl. Otherwise it will |
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141 | only confuse you, as, despite the name, it says nothing about how |
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142 | your string is encoded. You can have Unicode strings with that flag |
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143 | set, with that flag clear, and you can have binary data with that |
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144 | flag set and that flag clear. Other possibilities exist, too. |
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145 | |
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146 | If you didn't know about that flag, just the better, pretend it |
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147 | doesn't exist. |
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148 | |
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149 | 4. A "Unicode String" is simply a string where each character can be |
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150 | validly interpreted as a Unicode codepoint. |
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151 | If you have UTF-8 encoded data, it is no longer a Unicode string, |
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152 | but a Unicode string encoded in UTF-8, giving you a binary string. |
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153 | |
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154 | 5. A string containing "high" (> 255) character values is *not* a UTF-8 |
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155 | string. |
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156 | It's a fact. Learn to live with it. |
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157 | |
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158 | I hope this helps :) |
96 | |
159 | |
97 | OBJECT-ORIENTED INTERFACE |
160 | OBJECT-ORIENTED INTERFACE |
98 | The object oriented interface lets you configure your own encoding or |
161 | The object oriented interface lets you configure your own encoding or |
99 | decoding style, within the limits of supported formats. |
162 | decoding style, within the limits of supported formats. |
100 | |
163 | |
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108 | |
171 | |
109 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
172 | my $json = JSON::XS->new->utf8->space_after->encode ({a => [1,2]}) |
110 | => {"a": [1, 2]} |
173 | => {"a": [1, 2]} |
111 | |
174 | |
112 | $json = $json->ascii ([$enable]) |
175 | $json = $json->ascii ([$enable]) |
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176 | $enabled = $json->get_ascii |
113 | If $enable is true (or missing), then the "encode" method will not |
177 | If $enable is true (or missing), then the "encode" method will not |
114 | generate characters outside the code range 0..127 (which is ASCII). |
178 | generate characters outside the code range 0..127 (which is ASCII). |
115 | Any unicode characters outside that range will be escaped using |
179 | Any Unicode characters outside that range will be escaped using |
116 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
180 | either a single \uXXXX (BMP characters) or a double \uHHHH\uLLLLL |
117 | escape sequence, as per RFC4627. |
181 | escape sequence, as per RFC4627. The resulting encoded JSON text can |
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182 | be treated as a native Unicode string, an ascii-encoded, |
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183 | latin1-encoded or UTF-8 encoded string, or any other superset of |
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184 | ASCII. |
118 | |
185 | |
119 | If $enable is false, then the "encode" method will not escape |
186 | If $enable is false, then the "encode" method will not escape |
120 | Unicode characters unless required by the JSON syntax. This results |
187 | Unicode characters unless required by the JSON syntax or other |
121 | in a faster and more compact format. |
188 | flags. This results in a faster and more compact format. |
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189 | |
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190 | The main use for this flag is to produce JSON texts that can be |
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191 | transmitted over a 7-bit channel, as the encoded JSON texts will not |
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192 | contain any 8 bit characters. |
122 | |
193 | |
123 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
194 | JSON::XS->new->ascii (1)->encode ([chr 0x10401]) |
124 | => ["\ud801\udc01"] |
195 | => ["\ud801\udc01"] |
125 | |
196 | |
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197 | $json = $json->latin1 ([$enable]) |
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198 | $enabled = $json->get_latin1 |
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199 | If $enable is true (or missing), then the "encode" method will |
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200 | encode the resulting JSON text as latin1 (or iso-8859-1), escaping |
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201 | any characters outside the code range 0..255. The resulting string |
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202 | can be treated as a latin1-encoded JSON text or a native Unicode |
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203 | string. The "decode" method will not be affected in any way by this |
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204 | flag, as "decode" by default expects Unicode, which is a strict |
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205 | superset of latin1. |
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206 | |
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207 | If $enable is false, then the "encode" method will not escape |
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208 | Unicode characters unless required by the JSON syntax or other |
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209 | flags. |
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210 | |
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211 | The main use for this flag is efficiently encoding binary data as |
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212 | JSON text, as most octets will not be escaped, resulting in a |
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213 | smaller encoded size. The disadvantage is that the resulting JSON |
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214 | text is encoded in latin1 (and must correctly be treated as such |
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215 | when storing and transferring), a rare encoding for JSON. It is |
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216 | therefore most useful when you want to store data structures known |
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217 | to contain binary data efficiently in files or databases, not when |
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218 | talking to other JSON encoders/decoders. |
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219 | |
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220 | JSON::XS->new->latin1->encode (["\x{89}\x{abc}"] |
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221 | => ["\x{89}\\u0abc"] # (perl syntax, U+abc escaped, U+89 not) |
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222 | |
126 | $json = $json->utf8 ([$enable]) |
223 | $json = $json->utf8 ([$enable]) |
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224 | $enabled = $json->get_utf8 |
127 | If $enable is true (or missing), then the "encode" method will |
225 | If $enable is true (or missing), then the "encode" method will |
128 | encode the JSON result into UTF-8, as required by many protocols, |
226 | encode the JSON result into UTF-8, as required by many protocols, |
129 | while the "decode" method expects to be handled an UTF-8-encoded |
227 | while the "decode" method expects to be handled an UTF-8-encoded |
130 | string. Please note that UTF-8-encoded strings do not contain any |
228 | string. Please note that UTF-8-encoded strings do not contain any |
131 | characters outside the range 0..255, they are thus useful for |
229 | characters outside the range 0..255, they are thus useful for |
132 | bytewise/binary I/O. In future versions, enabling this option might |
230 | bytewise/binary I/O. In future versions, enabling this option might |
133 | enable autodetection of the UTF-16 and UTF-32 encoding families, as |
231 | enable autodetection of the UTF-16 and UTF-32 encoding families, as |
134 | described in RFC4627. |
232 | described in RFC4627. |
135 | |
233 | |
136 | If $enable is false, then the "encode" method will return the JSON |
234 | If $enable is false, then the "encode" method will return the JSON |
137 | string as a (non-encoded) unicode string, while "decode" expects |
235 | string as a (non-encoded) Unicode string, while "decode" expects |
138 | thus a unicode string. Any decoding or encoding (e.g. to UTF-8 or |
236 | thus a Unicode string. Any decoding or encoding (e.g. to UTF-8 or |
139 | UTF-16) needs to be done yourself, e.g. using the Encode module. |
237 | UTF-16) needs to be done yourself, e.g. using the Encode module. |
140 | |
238 | |
141 | Example, output UTF-16BE-encoded JSON: |
239 | Example, output UTF-16BE-encoded JSON: |
142 | |
240 | |
143 | use Encode; |
241 | use Encode; |
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163 | 2 |
261 | 2 |
164 | ] |
262 | ] |
165 | } |
263 | } |
166 | |
264 | |
167 | $json = $json->indent ([$enable]) |
265 | $json = $json->indent ([$enable]) |
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266 | $enabled = $json->get_indent |
168 | If $enable is true (or missing), then the "encode" method will use a |
267 | If $enable is true (or missing), then the "encode" method will use a |
169 | multiline format as output, putting every array member or |
268 | multiline format as output, putting every array member or |
170 | object/hash key-value pair into its own line, identing them |
269 | object/hash key-value pair into its own line, indenting them |
171 | properly. |
270 | properly. |
172 | |
271 | |
173 | If $enable is false, no newlines or indenting will be produced, and |
272 | If $enable is false, no newlines or indenting will be produced, and |
174 | the resulting JSON text is guarenteed not to contain any "newlines". |
273 | the resulting JSON text is guaranteed not to contain any "newlines". |
175 | |
274 | |
176 | This setting has no effect when decoding JSON texts. |
275 | This setting has no effect when decoding JSON texts. |
177 | |
276 | |
178 | $json = $json->space_before ([$enable]) |
277 | $json = $json->space_before ([$enable]) |
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278 | $enabled = $json->get_space_before |
179 | If $enable is true (or missing), then the "encode" method will add |
279 | If $enable is true (or missing), then the "encode" method will add |
180 | an extra optional space before the ":" separating keys from values |
280 | an extra optional space before the ":" separating keys from values |
181 | in JSON objects. |
281 | in JSON objects. |
182 | |
282 | |
183 | If $enable is false, then the "encode" method will not add any extra |
283 | If $enable is false, then the "encode" method will not add any extra |
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189 | Example, space_before enabled, space_after and indent disabled: |
289 | Example, space_before enabled, space_after and indent disabled: |
190 | |
290 | |
191 | {"key" :"value"} |
291 | {"key" :"value"} |
192 | |
292 | |
193 | $json = $json->space_after ([$enable]) |
293 | $json = $json->space_after ([$enable]) |
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294 | $enabled = $json->get_space_after |
194 | If $enable is true (or missing), then the "encode" method will add |
295 | If $enable is true (or missing), then the "encode" method will add |
195 | an extra optional space after the ":" separating keys from values in |
296 | an extra optional space after the ":" separating keys from values in |
196 | JSON objects and extra whitespace after the "," separating key-value |
297 | JSON objects and extra whitespace after the "," separating key-value |
197 | pairs and array members. |
298 | pairs and array members. |
198 | |
299 | |
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203 | |
304 | |
204 | Example, space_before and indent disabled, space_after enabled: |
305 | Example, space_before and indent disabled, space_after enabled: |
205 | |
306 | |
206 | {"key": "value"} |
307 | {"key": "value"} |
207 | |
308 | |
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309 | $json = $json->relaxed ([$enable]) |
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310 | $enabled = $json->get_relaxed |
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311 | If $enable is true (or missing), then "decode" will accept some |
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312 | extensions to normal JSON syntax (see below). "encode" will not be |
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313 | affected in anyway. *Be aware that this option makes you accept |
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314 | invalid JSON texts as if they were valid!*. I suggest only to use |
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315 | this option to parse application-specific files written by humans |
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316 | (configuration files, resource files etc.) |
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317 | |
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318 | If $enable is false (the default), then "decode" will only accept |
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319 | valid JSON texts. |
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320 | |
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321 | Currently accepted extensions are: |
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322 | |
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323 | * list items can have an end-comma |
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324 | JSON *separates* array elements and key-value pairs with commas. |
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325 | This can be annoying if you write JSON texts manually and want |
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326 | to be able to quickly append elements, so this extension accepts |
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327 | comma at the end of such items not just between them: |
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328 | |
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329 | [ |
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330 | 1, |
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331 | 2, <- this comma not normally allowed |
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332 | ] |
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333 | { |
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334 | "k1": "v1", |
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335 | "k2": "v2", <- this comma not normally allowed |
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336 | } |
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337 | |
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338 | * shell-style '#'-comments |
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339 | Whenever JSON allows whitespace, shell-style comments are |
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340 | additionally allowed. They are terminated by the first |
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341 | carriage-return or line-feed character, after which more |
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342 | white-space and comments are allowed. |
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343 | |
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344 | [ |
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345 | 1, # this comment not allowed in JSON |
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346 | # neither this one... |
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347 | ] |
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348 | |
208 | $json = $json->canonical ([$enable]) |
349 | $json = $json->canonical ([$enable]) |
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350 | $enabled = $json->get_canonical |
209 | If $enable is true (or missing), then the "encode" method will |
351 | If $enable is true (or missing), then the "encode" method will |
210 | output JSON objects by sorting their keys. This is adding a |
352 | output JSON objects by sorting their keys. This is adding a |
211 | comparatively high overhead. |
353 | comparatively high overhead. |
212 | |
354 | |
213 | If $enable is false, then the "encode" method will output key-value |
355 | If $enable is false, then the "encode" method will output key-value |
214 | pairs in the order Perl stores them (which will likely change |
356 | pairs in the order Perl stores them (which will likely change |
215 | between runs of the same script). |
357 | between runs of the same script). |
216 | |
358 | |
217 | This option is useful if you want the same data structure to be |
359 | This option is useful if you want the same data structure to be |
218 | encoded as the same JSON text (given the same overall settings). If |
360 | encoded as the same JSON text (given the same overall settings). If |
219 | it is disabled, the same hash migh be encoded differently even if |
361 | it is disabled, the same hash might be encoded differently even if |
220 | contains the same data, as key-value pairs have no inherent ordering |
362 | contains the same data, as key-value pairs have no inherent ordering |
221 | in Perl. |
363 | in Perl. |
222 | |
364 | |
223 | This setting has no effect when decoding JSON texts. |
365 | This setting has no effect when decoding JSON texts. |
224 | |
366 | |
225 | $json = $json->allow_nonref ([$enable]) |
367 | $json = $json->allow_nonref ([$enable]) |
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368 | $enabled = $json->get_allow_nonref |
226 | If $enable is true (or missing), then the "encode" method can |
369 | If $enable is true (or missing), then the "encode" method can |
227 | convert a non-reference into its corresponding string, number or |
370 | convert a non-reference into its corresponding string, number or |
228 | null JSON value, which is an extension to RFC4627. Likewise, |
371 | null JSON value, which is an extension to RFC4627. Likewise, |
229 | "decode" will accept those JSON values instead of croaking. |
372 | "decode" will accept those JSON values instead of croaking. |
230 | |
373 | |
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237 | "allow_nonref", resulting in an invalid JSON text: |
380 | "allow_nonref", resulting in an invalid JSON text: |
238 | |
381 | |
239 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
382 | JSON::XS->new->allow_nonref->encode ("Hello, World!") |
240 | => "Hello, World!" |
383 | => "Hello, World!" |
241 | |
384 | |
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385 | $json = $json->allow_blessed ([$enable]) |
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386 | $enabled = $json->get_allow_blessed |
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387 | If $enable is true (or missing), then the "encode" method will not |
|
|
388 | barf when it encounters a blessed reference. Instead, the value of |
|
|
389 | the convert_blessed option will decide whether "null" |
|
|
390 | ("convert_blessed" disabled or no "TO_JSON" method found) or a |
|
|
391 | representation of the object ("convert_blessed" enabled and |
|
|
392 | "TO_JSON" method found) is being encoded. Has no effect on "decode". |
|
|
393 | |
|
|
394 | If $enable is false (the default), then "encode" will throw an |
|
|
395 | exception when it encounters a blessed object. |
|
|
396 | |
|
|
397 | $json = $json->convert_blessed ([$enable]) |
|
|
398 | $enabled = $json->get_convert_blessed |
|
|
399 | If $enable is true (or missing), then "encode", upon encountering a |
|
|
400 | blessed object, will check for the availability of the "TO_JSON" |
|
|
401 | method on the object's class. If found, it will be called in scalar |
|
|
402 | context and the resulting scalar will be encoded instead of the |
|
|
403 | object. If no "TO_JSON" method is found, the value of |
|
|
404 | "allow_blessed" will decide what to do. |
|
|
405 | |
|
|
406 | The "TO_JSON" method may safely call die if it wants. If "TO_JSON" |
|
|
407 | returns other blessed objects, those will be handled in the same |
|
|
408 | way. "TO_JSON" must take care of not causing an endless recursion |
|
|
409 | cycle (== crash) in this case. The name of "TO_JSON" was chosen |
|
|
410 | because other methods called by the Perl core (== not by the user of |
|
|
411 | the object) are usually in upper case letters and to avoid |
|
|
412 | collisions with the "to_json" function. |
|
|
413 | |
|
|
414 | This setting does not yet influence "decode" in any way, but in the |
|
|
415 | future, global hooks might get installed that influence "decode" and |
|
|
416 | are enabled by this setting. |
|
|
417 | |
|
|
418 | If $enable is false, then the "allow_blessed" setting will decide |
|
|
419 | what to do when a blessed object is found. |
|
|
420 | |
|
|
421 | $json = $json->filter_json_object ([$coderef->($hashref)]) |
|
|
422 | When $coderef is specified, it will be called from "decode" each |
|
|
423 | time it decodes a JSON object. The only argument is a reference to |
|
|
424 | the newly-created hash. If the code references returns a single |
|
|
425 | scalar (which need not be a reference), this value (i.e. a copy of |
|
|
426 | that scalar to avoid aliasing) is inserted into the deserialised |
|
|
427 | data structure. If it returns an empty list (NOTE: *not* "undef", |
|
|
428 | which is a valid scalar), the original deserialised hash will be |
|
|
429 | inserted. This setting can slow down decoding considerably. |
|
|
430 | |
|
|
431 | When $coderef is omitted or undefined, any existing callback will be |
|
|
432 | removed and "decode" will not change the deserialised hash in any |
|
|
433 | way. |
|
|
434 | |
|
|
435 | Example, convert all JSON objects into the integer 5: |
|
|
436 | |
|
|
437 | my $js = JSON::XS->new->filter_json_object (sub { 5 }); |
|
|
438 | # returns [5] |
|
|
439 | $js->decode ('[{}]') |
|
|
440 | # throw an exception because allow_nonref is not enabled |
|
|
441 | # so a lone 5 is not allowed. |
|
|
442 | $js->decode ('{"a":1, "b":2}'); |
|
|
443 | |
|
|
444 | $json = $json->filter_json_single_key_object ($key [=> |
|
|
445 | $coderef->($value)]) |
|
|
446 | Works remotely similar to "filter_json_object", but is only called |
|
|
447 | for JSON objects having a single key named $key. |
|
|
448 | |
|
|
449 | This $coderef is called before the one specified via |
|
|
450 | "filter_json_object", if any. It gets passed the single value in the |
|
|
451 | JSON object. If it returns a single value, it will be inserted into |
|
|
452 | the data structure. If it returns nothing (not even "undef" but the |
|
|
453 | empty list), the callback from "filter_json_object" will be called |
|
|
454 | next, as if no single-key callback were specified. |
|
|
455 | |
|
|
456 | If $coderef is omitted or undefined, the corresponding callback will |
|
|
457 | be disabled. There can only ever be one callback for a given key. |
|
|
458 | |
|
|
459 | As this callback gets called less often then the |
|
|
460 | "filter_json_object" one, decoding speed will not usually suffer as |
|
|
461 | much. Therefore, single-key objects make excellent targets to |
|
|
462 | serialise Perl objects into, especially as single-key JSON objects |
|
|
463 | are as close to the type-tagged value concept as JSON gets (it's |
|
|
464 | basically an ID/VALUE tuple). Of course, JSON does not support this |
|
|
465 | in any way, so you need to make sure your data never looks like a |
|
|
466 | serialised Perl hash. |
|
|
467 | |
|
|
468 | Typical names for the single object key are "__class_whatever__", or |
|
|
469 | "$__dollars_are_rarely_used__$" or "}ugly_brace_placement", or even |
|
|
470 | things like "__class_md5sum(classname)__", to reduce the risk of |
|
|
471 | clashing with real hashes. |
|
|
472 | |
|
|
473 | Example, decode JSON objects of the form "{ "__widget__" => <id> }" |
|
|
474 | into the corresponding $WIDGET{<id>} object: |
|
|
475 | |
|
|
476 | # return whatever is in $WIDGET{5}: |
|
|
477 | JSON::XS |
|
|
478 | ->new |
|
|
479 | ->filter_json_single_key_object (__widget__ => sub { |
|
|
480 | $WIDGET{ $_[0] } |
|
|
481 | }) |
|
|
482 | ->decode ('{"__widget__": 5') |
|
|
483 | |
|
|
484 | # this can be used with a TO_JSON method in some "widget" class |
|
|
485 | # for serialisation to json: |
|
|
486 | sub WidgetBase::TO_JSON { |
|
|
487 | my ($self) = @_; |
|
|
488 | |
|
|
489 | unless ($self->{id}) { |
|
|
490 | $self->{id} = ..get..some..id..; |
|
|
491 | $WIDGET{$self->{id}} = $self; |
|
|
492 | } |
|
|
493 | |
|
|
494 | { __widget__ => $self->{id} } |
|
|
495 | } |
|
|
496 | |
242 | $json = $json->shrink ([$enable]) |
497 | $json = $json->shrink ([$enable]) |
|
|
498 | $enabled = $json->get_shrink |
243 | Perl usually over-allocates memory a bit when allocating space for |
499 | Perl usually over-allocates memory a bit when allocating space for |
244 | strings. This flag optionally resizes strings generated by either |
500 | strings. This flag optionally resizes strings generated by either |
245 | "encode" or "decode" to their minimum size possible. This can save |
501 | "encode" or "decode" to their minimum size possible. This can save |
246 | memory when your JSON texts are either very very long or you have |
502 | memory when your JSON texts are either very very long or you have |
247 | many short strings. It will also try to downgrade any strings to |
503 | many short strings. It will also try to downgrade any strings to |
248 | octet-form if possible: perl stores strings internally either in an |
504 | octet-form if possible: perl stores strings internally either in an |
249 | encoding called UTF-X or in octet-form. The latter cannot store |
505 | encoding called UTF-X or in octet-form. The latter cannot store |
250 | everything but uses less space in general. |
506 | everything but uses less space in general (and some buggy Perl or C |
|
|
507 | code might even rely on that internal representation being used). |
|
|
508 | |
|
|
509 | The actual definition of what shrink does might change in future |
|
|
510 | versions, but it will always try to save space at the expense of |
|
|
511 | time. |
251 | |
512 | |
252 | If $enable is true (or missing), the string returned by "encode" |
513 | If $enable is true (or missing), the string returned by "encode" |
253 | will be shrunk-to-fit, while all strings generated by "decode" will |
514 | will be shrunk-to-fit, while all strings generated by "decode" will |
254 | also be shrunk-to-fit. |
515 | also be shrunk-to-fit. |
255 | |
516 | |
… | |
… | |
260 | converting strings that look like integers or floats into integers |
521 | converting strings that look like integers or floats into integers |
261 | or floats internally (there is no difference on the Perl level), |
522 | or floats internally (there is no difference on the Perl level), |
262 | saving space. |
523 | saving space. |
263 | |
524 | |
264 | $json = $json->max_depth ([$maximum_nesting_depth]) |
525 | $json = $json->max_depth ([$maximum_nesting_depth]) |
|
|
526 | $max_depth = $json->get_max_depth |
265 | Sets the maximum nesting level (default 8192) accepted while |
527 | Sets the maximum nesting level (default 512) accepted while encoding |
266 | encoding or decoding. If the JSON text or Perl data structure has an |
528 | or decoding. If the JSON text or Perl data structure has an equal or |
267 | equal or higher nesting level then this limit, then the encoder and |
529 | higher nesting level then this limit, then the encoder and decoder |
268 | decoder will stop and croak at that point. |
530 | will stop and croak at that point. |
269 | |
531 | |
270 | Nesting level is defined by number of hash- or arrayrefs that the |
532 | Nesting level is defined by number of hash- or arrayrefs that the |
271 | encoder needs to traverse to reach a given point or the number of |
533 | encoder needs to traverse to reach a given point or the number of |
272 | "{" or "[" characters without their matching closing parenthesis |
534 | "{" or "[" characters without their matching closing parenthesis |
273 | crossed to reach a given character in a string. |
535 | crossed to reach a given character in a string. |
274 | |
536 | |
275 | Setting the maximum depth to one disallows any nesting, so that |
537 | Setting the maximum depth to one disallows any nesting, so that |
276 | ensures that the object is only a single hash/object or array. |
538 | ensures that the object is only a single hash/object or array. |
277 | |
539 | |
278 | The argument to "max_depth" will be rounded up to the next nearest |
540 | The argument to "max_depth" will be rounded up to the next highest |
279 | power of two. |
541 | power of two. If no argument is given, the highest possible setting |
|
|
542 | will be used, which is rarely useful. |
|
|
543 | |
|
|
544 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
|
|
545 | useful. |
|
|
546 | |
|
|
547 | $json = $json->max_size ([$maximum_string_size]) |
|
|
548 | $max_size = $json->get_max_size |
|
|
549 | Set the maximum length a JSON text may have (in bytes) where |
|
|
550 | decoding is being attempted. The default is 0, meaning no limit. |
|
|
551 | When "decode" is called on a string longer then this number of |
|
|
552 | characters it will not attempt to decode the string but throw an |
|
|
553 | exception. This setting has no effect on "encode" (yet). |
|
|
554 | |
|
|
555 | The argument to "max_size" will be rounded up to the next highest |
|
|
556 | power of two (so may be more than requested). If no argument is |
|
|
557 | given, the limit check will be deactivated (same as when 0 is |
|
|
558 | specified). |
280 | |
559 | |
281 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
560 | See SECURITY CONSIDERATIONS, below, for more info on why this is |
282 | useful. |
561 | useful. |
283 | |
562 | |
284 | $json_text = $json->encode ($perl_scalar) |
563 | $json_text = $json->encode ($perl_scalar) |
… | |
… | |
296 | |
575 | |
297 | JSON numbers and strings become simple Perl scalars. JSON arrays |
576 | JSON numbers and strings become simple Perl scalars. JSON arrays |
298 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
577 | become Perl arrayrefs and JSON objects become Perl hashrefs. "true" |
299 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
578 | becomes 1, "false" becomes 0 and "null" becomes "undef". |
300 | |
579 | |
|
|
580 | ($perl_scalar, $characters) = $json->decode_prefix ($json_text) |
|
|
581 | This works like the "decode" method, but instead of raising an |
|
|
582 | exception when there is trailing garbage after the first JSON |
|
|
583 | object, it will silently stop parsing there and return the number of |
|
|
584 | characters consumed so far. |
|
|
585 | |
|
|
586 | This is useful if your JSON texts are not delimited by an outer |
|
|
587 | protocol (which is not the brightest thing to do in the first place) |
|
|
588 | and you need to know where the JSON text ends. |
|
|
589 | |
|
|
590 | JSON::XS->new->decode_prefix ("[1] the tail") |
|
|
591 | => ([], 3) |
|
|
592 | |
301 | MAPPING |
593 | MAPPING |
302 | This section describes how JSON::XS maps Perl values to JSON values and |
594 | This section describes how JSON::XS maps Perl values to JSON values and |
303 | vice versa. These mappings are designed to "do the right thing" in most |
595 | vice versa. These mappings are designed to "do the right thing" in most |
304 | circumstances automatically, preserving round-tripping characteristics |
596 | circumstances automatically, preserving round-tripping characteristics |
305 | (what you put in comes out as something equivalent). |
597 | (what you put in comes out as something equivalent). |
306 | |
598 | |
307 | For the more enlightened: note that in the following descriptions, |
599 | For the more enlightened: note that in the following descriptions, |
308 | lowercase *perl* refers to the Perl interpreter, while uppcercase *Perl* |
600 | lowercase *perl* refers to the Perl interpreter, while uppercase *Perl* |
309 | refers to the abstract Perl language itself. |
601 | refers to the abstract Perl language itself. |
310 | |
602 | |
311 | JSON -> PERL |
603 | JSON -> PERL |
312 | object |
604 | object |
313 | A JSON object becomes a reference to a hash in Perl. No ordering of |
605 | A JSON object becomes a reference to a hash in Perl. No ordering of |
314 | object keys is preserved (JSON does not preserver object key |
606 | object keys is preserved (JSON does not preserve object key ordering |
315 | ordering itself). |
607 | itself). |
316 | |
608 | |
317 | array |
609 | array |
318 | A JSON array becomes a reference to an array in Perl. |
610 | A JSON array becomes a reference to an array in Perl. |
319 | |
611 | |
320 | string |
612 | string |
321 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
613 | A JSON string becomes a string scalar in Perl - Unicode codepoints |
322 | in JSON are represented by the same codepoints in the Perl string, |
614 | in JSON are represented by the same codepoints in the Perl string, |
323 | so no manual decoding is necessary. |
615 | so no manual decoding is necessary. |
324 | |
616 | |
325 | number |
617 | number |
326 | A JSON number becomes either an integer or numeric (floating point) |
618 | A JSON number becomes either an integer, numeric (floating point) or |
327 | scalar in perl, depending on its range and any fractional parts. On |
619 | string scalar in perl, depending on its range and any fractional |
328 | the Perl level, there is no difference between those as Perl handles |
620 | parts. On the Perl level, there is no difference between those as |
329 | all the conversion details, but an integer may take slightly less |
621 | Perl handles all the conversion details, but an integer may take |
330 | memory and might represent more values exactly than (floating point) |
622 | slightly less memory and might represent more values exactly than |
331 | numbers. |
623 | (floating point) numbers. |
|
|
624 | |
|
|
625 | If the number consists of digits only, JSON::XS will try to |
|
|
626 | represent it as an integer value. If that fails, it will try to |
|
|
627 | represent it as a numeric (floating point) value if that is possible |
|
|
628 | without loss of precision. Otherwise it will preserve the number as |
|
|
629 | a string value. |
|
|
630 | |
|
|
631 | Numbers containing a fractional or exponential part will always be |
|
|
632 | represented as numeric (floating point) values, possibly at a loss |
|
|
633 | of precision. |
|
|
634 | |
|
|
635 | This might create round-tripping problems as numbers might become |
|
|
636 | strings, but as Perl is typeless there is no other way to do it. |
332 | |
637 | |
333 | true, false |
638 | true, false |
334 | These JSON atoms become 0, 1, respectively. Information is lost in |
639 | These JSON atoms become "JSON::XS::true" and "JSON::XS::false", |
335 | this process. Future versions might represent those values |
640 | respectively. They are overloaded to act almost exactly like the |
336 | differently, but they will be guarenteed to act like these integers |
641 | numbers 1 and 0. You can check whether a scalar is a JSON boolean by |
337 | would normally in Perl. |
642 | using the "JSON::XS::is_bool" function. |
338 | |
643 | |
339 | null |
644 | null |
340 | A JSON null atom becomes "undef" in Perl. |
645 | A JSON null atom becomes "undef" in Perl. |
341 | |
646 | |
342 | PERL -> JSON |
647 | PERL -> JSON |
… | |
… | |
344 | truly typeless language, so we can only guess which JSON type is meant |
649 | truly typeless language, so we can only guess which JSON type is meant |
345 | by a Perl value. |
650 | by a Perl value. |
346 | |
651 | |
347 | hash references |
652 | hash references |
348 | Perl hash references become JSON objects. As there is no inherent |
653 | Perl hash references become JSON objects. As there is no inherent |
349 | ordering in hash keys, they will usually be encoded in a |
654 | ordering in hash keys (or JSON objects), they will usually be |
350 | pseudo-random order that can change between runs of the same program |
655 | encoded in a pseudo-random order that can change between runs of the |
351 | but stays generally the same within a single run of a program. |
656 | same program but stays generally the same within a single run of a |
352 | JSON::XS can optionally sort the hash keys (determined by the |
657 | program. JSON::XS can optionally sort the hash keys (determined by |
353 | *canonical* flag), so the same datastructure will serialise to the |
658 | the *canonical* flag), so the same datastructure will serialise to |
354 | same JSON text (given same settings and version of JSON::XS), but |
659 | the same JSON text (given same settings and version of JSON::XS), |
355 | this incurs a runtime overhead. |
660 | but this incurs a runtime overhead and is only rarely useful, e.g. |
|
|
661 | when you want to compare some JSON text against another for |
|
|
662 | equality. |
356 | |
663 | |
357 | array references |
664 | array references |
358 | Perl array references become JSON arrays. |
665 | Perl array references become JSON arrays. |
|
|
666 | |
|
|
667 | other references |
|
|
668 | Other unblessed references are generally not allowed and will cause |
|
|
669 | an exception to be thrown, except for references to the integers 0 |
|
|
670 | and 1, which get turned into "false" and "true" atoms in JSON. You |
|
|
671 | can also use "JSON::XS::false" and "JSON::XS::true" to improve |
|
|
672 | readability. |
|
|
673 | |
|
|
674 | to_json [\0,JSON::XS::true] # yields [false,true] |
|
|
675 | |
|
|
676 | JSON::XS::true, JSON::XS::false |
|
|
677 | These special values become JSON true and JSON false values, |
|
|
678 | respectively. You can also use "\1" and "\0" directly if you want. |
359 | |
679 | |
360 | blessed objects |
680 | blessed objects |
361 | Blessed objects are not allowed. JSON::XS currently tries to encode |
681 | Blessed objects are not allowed. JSON::XS currently tries to encode |
362 | their underlying representation (hash- or arrayref), but this |
682 | their underlying representation (hash- or arrayref), but this |
363 | behaviour might change in future versions. |
683 | behaviour might change in future versions. |
… | |
… | |
379 | to_json [$value] # yields ["5"] |
699 | to_json [$value] # yields ["5"] |
380 | |
700 | |
381 | # undef becomes null |
701 | # undef becomes null |
382 | to_json [undef] # yields [null] |
702 | to_json [undef] # yields [null] |
383 | |
703 | |
384 | You can force the type to be a string by stringifying it: |
704 | You can force the type to be a JSON string by stringifying it: |
385 | |
705 | |
386 | my $x = 3.1; # some variable containing a number |
706 | my $x = 3.1; # some variable containing a number |
387 | "$x"; # stringified |
707 | "$x"; # stringified |
388 | $x .= ""; # another, more awkward way to stringify |
708 | $x .= ""; # another, more awkward way to stringify |
389 | print $x; # perl does it for you, too, quite often |
709 | print $x; # perl does it for you, too, quite often |
390 | |
710 | |
391 | You can force the type to be a number by numifying it: |
711 | You can force the type to be a JSON number by numifying it: |
392 | |
712 | |
393 | my $x = "3"; # some variable containing a string |
713 | my $x = "3"; # some variable containing a string |
394 | $x += 0; # numify it, ensuring it will be dumped as a number |
714 | $x += 0; # numify it, ensuring it will be dumped as a number |
395 | $x *= 1; # same thing, the choise is yours. |
715 | $x *= 1; # same thing, the choice is yours. |
396 | |
716 | |
397 | You can not currently output JSON booleans or force the type in |
717 | You can not currently force the type in other, less obscure, ways. |
398 | other, less obscure, ways. Tell me if you need this capability. |
718 | Tell me if you need this capability. |
399 | |
|
|
400 | circular data structures |
|
|
401 | Those will be encoded until memory or stackspace runs out. |
|
|
402 | |
719 | |
403 | COMPARISON |
720 | COMPARISON |
404 | As already mentioned, this module was created because none of the |
721 | As already mentioned, this module was created because none of the |
405 | existing JSON modules could be made to work correctly. First I will |
722 | existing JSON modules could be made to work correctly. First I will |
406 | describe the problems (or pleasures) I encountered with various existing |
723 | describe the problems (or pleasures) I encountered with various existing |
… | |
… | |
408 | not to suffer from any of these problems or limitations. |
725 | not to suffer from any of these problems or limitations. |
409 | |
726 | |
410 | JSON 1.07 |
727 | JSON 1.07 |
411 | Slow (but very portable, as it is written in pure Perl). |
728 | Slow (but very portable, as it is written in pure Perl). |
412 | |
729 | |
413 | Undocumented/buggy Unicode handling (how JSON handles unicode values |
730 | Undocumented/buggy Unicode handling (how JSON handles Unicode values |
414 | is undocumented. One can get far by feeding it unicode strings and |
731 | is undocumented. One can get far by feeding it Unicode strings and |
415 | doing en-/decoding oneself, but unicode escapes are not working |
732 | doing en-/decoding oneself, but Unicode escapes are not working |
416 | properly). |
733 | properly). |
417 | |
734 | |
418 | No roundtripping (strings get clobbered if they look like numbers, |
735 | No round-tripping (strings get clobbered if they look like numbers, |
419 | e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that |
736 | e.g. the string 2.0 will encode to 2.0 instead of "2.0", and that |
420 | will decode into the number 2. |
737 | will decode into the number 2. |
421 | |
738 | |
422 | JSON::PC 0.01 |
739 | JSON::PC 0.01 |
423 | Very fast. |
740 | Very fast. |
424 | |
741 | |
425 | Undocumented/buggy Unicode handling. |
742 | Undocumented/buggy Unicode handling. |
426 | |
743 | |
427 | No roundtripping. |
744 | No round-tripping. |
428 | |
745 | |
429 | Has problems handling many Perl values (e.g. regex results and other |
746 | Has problems handling many Perl values (e.g. regex results and other |
430 | magic values will make it croak). |
747 | magic values will make it croak). |
431 | |
748 | |
432 | Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}" |
749 | Does not even generate valid JSON ("{1,2}" gets converted to "{1:2}" |
… | |
… | |
442 | much undocumented. I need at least a format for easy reading by |
759 | much undocumented. I need at least a format for easy reading by |
443 | humans and a single-line compact format for use in a protocol, and |
760 | humans and a single-line compact format for use in a protocol, and |
444 | preferably a way to generate ASCII-only JSON texts). |
761 | preferably a way to generate ASCII-only JSON texts). |
445 | |
762 | |
446 | Completely broken (and confusingly documented) Unicode handling |
763 | Completely broken (and confusingly documented) Unicode handling |
447 | (unicode escapes are not working properly, you need to set |
764 | (Unicode escapes are not working properly, you need to set |
448 | ImplicitUnicode to *different* values on en- and decoding to get |
765 | ImplicitUnicode to *different* values on en- and decoding to get |
449 | symmetric behaviour). |
766 | symmetric behaviour). |
450 | |
767 | |
451 | No roundtripping (simple cases work, but this depends on wether the |
768 | No round-tripping (simple cases work, but this depends on whether |
452 | scalar value was used in a numeric context or not). |
769 | the scalar value was used in a numeric context or not). |
453 | |
770 | |
454 | Dumping hashes may skip hash values depending on iterator state. |
771 | Dumping hashes may skip hash values depending on iterator state. |
455 | |
772 | |
456 | Unmaintained (maintainer unresponsive for many months, bugs are not |
773 | Unmaintained (maintainer unresponsive for many months, bugs are not |
457 | getting fixed). |
774 | getting fixed). |
458 | |
775 | |
459 | Does not check input for validity (i.e. will accept non-JSON input |
776 | Does not check input for validity (i.e. will accept non-JSON input |
460 | and return "something" instead of raising an exception. This is a |
777 | and return "something" instead of raising an exception. This is a |
461 | security issue: imagine two banks transfering money between each |
778 | security issue: imagine two banks transferring money between each |
462 | other using JSON. One bank might parse a given non-JSON request and |
779 | other using JSON. One bank might parse a given non-JSON request and |
463 | deduct money, while the other might reject the transaction with a |
780 | deduct money, while the other might reject the transaction with a |
464 | syntax error. While a good protocol will at least recover, that is |
781 | syntax error. While a good protocol will at least recover, that is |
465 | extra unnecessary work and the transaction will still not succeed). |
782 | extra unnecessary work and the transaction will still not succeed). |
466 | |
783 | |
467 | JSON::DWIW 0.04 |
784 | JSON::DWIW 0.04 |
468 | Very fast. Very natural. Very nice. |
785 | Very fast. Very natural. Very nice. |
469 | |
786 | |
470 | Undocumented unicode handling (but the best of the pack. Unicode |
787 | Undocumented Unicode handling (but the best of the pack. Unicode |
471 | escapes still don't get parsed properly). |
788 | escapes still don't get parsed properly). |
472 | |
789 | |
473 | Very inflexible. |
790 | Very inflexible. |
474 | |
791 | |
475 | No roundtripping. |
792 | No round-tripping. |
476 | |
793 | |
477 | Does not generate valid JSON texts (key strings are often unquoted, |
794 | Does not generate valid JSON texts (key strings are often unquoted, |
478 | empty keys result in nothing being output) |
795 | empty keys result in nothing being output) |
479 | |
796 | |
480 | Does not check input for validity. |
797 | Does not check input for validity. |
|
|
798 | |
|
|
799 | JSON and YAML |
|
|
800 | You often hear that JSON is a subset (or a close subset) of YAML. This |
|
|
801 | is, however, a mass hysteria and very far from the truth. In general, |
|
|
802 | there is no way to configure JSON::XS to output a data structure as |
|
|
803 | valid YAML. |
|
|
804 | |
|
|
805 | If you really must use JSON::XS to generate YAML, you should use this |
|
|
806 | algorithm (subject to change in future versions): |
|
|
807 | |
|
|
808 | my $to_yaml = JSON::XS->new->utf8->space_after (1); |
|
|
809 | my $yaml = $to_yaml->encode ($ref) . "\n"; |
|
|
810 | |
|
|
811 | This will usually generate JSON texts that also parse as valid YAML. |
|
|
812 | Please note that YAML has hardcoded limits on (simple) object key |
|
|
813 | lengths that JSON doesn't have, so you should make sure that your hash |
|
|
814 | keys are noticeably shorter than the 1024 characters YAML allows. |
|
|
815 | |
|
|
816 | There might be other incompatibilities that I am not aware of. In |
|
|
817 | general you should not try to generate YAML with a JSON generator or |
|
|
818 | vice versa, or try to parse JSON with a YAML parser or vice versa: |
|
|
819 | chances are high that you will run into severe interoperability |
|
|
820 | problems. |
481 | |
821 | |
482 | SPEED |
822 | SPEED |
483 | It seems that JSON::XS is surprisingly fast, as shown in the following |
823 | It seems that JSON::XS is surprisingly fast, as shown in the following |
484 | tables. They have been generated with the help of the "eg/bench" program |
824 | tables. They have been generated with the help of the "eg/bench" program |
485 | in the JSON::XS distribution, to make it easy to compare on your own |
825 | in the JSON::XS distribution, to make it easy to compare on your own |
486 | system. |
826 | system. |
487 | |
827 | |
488 | First comes a comparison between various modules using a very short JSON |
828 | First comes a comparison between various modules using a very short |
489 | string: |
829 | single-line JSON string: |
490 | |
830 | |
491 | {"method": "handleMessage", "params": ["user1", "we were just talking"], "id": null} |
831 | {"method": "handleMessage", "params": ["user1", "we were just talking"], \ |
|
|
832 | "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} |
492 | |
833 | |
493 | It shows the number of encodes/decodes per second (JSON::XS uses the |
834 | It shows the number of encodes/decodes per second (JSON::XS uses the |
494 | functional interface, while JSON::XS/2 uses the OO interface with |
835 | functional interface, while JSON::XS/2 uses the OO interface with |
495 | pretty-printing and hashkey sorting enabled). Higher is better: |
836 | pretty-printing and hashkey sorting enabled, JSON::XS/3 enables shrink). |
|
|
837 | Higher is better: |
496 | |
838 | |
497 | module | encode | decode | |
839 | module | encode | decode | |
498 | -----------|------------|------------| |
840 | -----------|------------|------------| |
499 | JSON | 11488.516 | 7823.035 | |
841 | JSON 1.x | 4990.842 | 4088.813 | |
500 | JSON::DWIW | 94708.054 | 129094.260 | |
842 | JSON::DWIW | 51653.990 | 71575.154 | |
501 | JSON::PC | 63884.157 | 128528.212 | |
843 | JSON::PC | 65948.176 | 74631.744 | |
|
|
844 | JSON::PP | 8931.652 | 3817.168 | |
502 | JSON::Syck | 34898.677 | 42096.911 | |
845 | JSON::Syck | 24877.248 | 27776.848 | |
503 | JSON::XS | 654027.064 | 396423.669 | |
846 | JSON::XS | 388361.481 | 227951.304 | |
504 | JSON::XS/2 | 371564.190 | 371725.613 | |
847 | JSON::XS/2 | 227951.304 | 218453.333 | |
|
|
848 | JSON::XS/3 | 338250.323 | 218453.333 | |
|
|
849 | Storable | 16500.016 | 135300.129 | |
505 | -----------+------------+------------+ |
850 | -----------+------------+------------+ |
506 | |
851 | |
507 | That is, JSON::XS is more than six times faster than JSON::DWIW on |
852 | That is, JSON::XS is about five times faster than JSON::DWIW on |
508 | encoding, more than three times faster on decoding, and about thirty |
853 | encoding, about three times faster on decoding, and over forty times |
509 | times faster than JSON, even with pretty-printing and key sorting. |
854 | faster than JSON, even with pretty-printing and key sorting. It also |
|
|
855 | compares favourably to Storable for small amounts of data. |
510 | |
856 | |
511 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
857 | Using a longer test string (roughly 18KB, generated from Yahoo! Locals |
512 | search API (http://nanoref.com/yahooapis/mgPdGg): |
858 | search API (http://nanoref.com/yahooapis/mgPdGg): |
513 | |
859 | |
514 | module | encode | decode | |
860 | module | encode | decode | |
515 | -----------|------------|------------| |
861 | -----------|------------|------------| |
516 | JSON | 273.023 | 44.674 | |
862 | JSON 1.x | 55.260 | 34.971 | |
517 | JSON::DWIW | 1089.383 | 1145.704 | |
863 | JSON::DWIW | 825.228 | 1082.513 | |
518 | JSON::PC | 3097.419 | 2393.921 | |
864 | JSON::PC | 3571.444 | 2394.829 | |
519 | JSON::Syck | 514.060 | 843.053 | |
865 | JSON::PP | 210.987 | 32.574 | |
520 | JSON::XS | 6479.668 | 3636.364 | |
866 | JSON::Syck | 552.551 | 787.544 | |
521 | JSON::XS/2 | 3774.221 | 3599.124 | |
867 | JSON::XS | 5780.463 | 4854.519 | |
|
|
868 | JSON::XS/2 | 3869.998 | 4798.975 | |
|
|
869 | JSON::XS/3 | 5862.880 | 4798.975 | |
|
|
870 | Storable | 4445.002 | 5235.027 | |
522 | -----------+------------+------------+ |
871 | -----------+------------+------------+ |
523 | |
872 | |
524 | Again, JSON::XS leads by far. |
873 | Again, JSON::XS leads by far (except for Storable which non-surprisingly |
|
|
874 | decodes faster). |
525 | |
875 | |
526 | On large strings containing lots of high unicode characters, some |
876 | On large strings containing lots of high Unicode characters, some |
527 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
877 | modules (such as JSON::PC) seem to decode faster than JSON::XS, but the |
528 | result will be broken due to missing (or wrong) unicode handling. Others |
878 | result will be broken due to missing (or wrong) Unicode handling. Others |
529 | refuse to decode or encode properly, so it was impossible to prepare a |
879 | refuse to decode or encode properly, so it was impossible to prepare a |
530 | fair comparison table for that case. |
880 | fair comparison table for that case. |
531 | |
881 | |
532 | SECURITY CONSIDERATIONS |
882 | SECURITY CONSIDERATIONS |
533 | When you are using JSON in a protocol, talking to untrusted potentially |
883 | When you are using JSON in a protocol, talking to untrusted potentially |
… | |
… | |
537 | have any buffer overflows. Obviously, this module should ensure that and |
887 | have any buffer overflows. Obviously, this module should ensure that and |
538 | I am trying hard on making that true, but you never know. |
888 | I am trying hard on making that true, but you never know. |
539 | |
889 | |
540 | Second, you need to avoid resource-starving attacks. That means you |
890 | Second, you need to avoid resource-starving attacks. That means you |
541 | should limit the size of JSON texts you accept, or make sure then when |
891 | should limit the size of JSON texts you accept, or make sure then when |
542 | your resources run out, thats just fine (e.g. by using a separate |
892 | your resources run out, that's just fine (e.g. by using a separate |
543 | process that can crash safely). The size of a JSON text in octets or |
893 | process that can crash safely). The size of a JSON text in octets or |
544 | characters is usually a good indication of the size of the resources |
894 | characters is usually a good indication of the size of the resources |
545 | required to decode it into a Perl structure. |
895 | required to decode it into a Perl structure. While JSON::XS can check |
|
|
896 | the size of the JSON text, it might be too late when you already have it |
|
|
897 | in memory, so you might want to check the size before you accept the |
|
|
898 | string. |
546 | |
899 | |
547 | Third, JSON::XS recurses using the C stack when decoding objects and |
900 | Third, JSON::XS recurses using the C stack when decoding objects and |
548 | arrays. The C stack is a limited resource: for instance, on my amd64 |
901 | arrays. The C stack is a limited resource: for instance, on my amd64 |
549 | machine with 8MB of stack size I can decode around 180k nested arrays |
902 | machine with 8MB of stack size I can decode around 180k nested arrays |
550 | but only 14k nested JSON objects. If that is exceeded, the program |
903 | but only 14k nested JSON objects (due to perl itself recursing deeply on |
|
|
904 | croak to free the temporary). If that is exceeded, the program crashes. |
551 | crashes. Thats why the default nesting limit is set to 8192. If your |
905 | to be conservative, the default nesting limit is set to 512. If your |
552 | process has a smaller stack, you should adjust this setting accordingly |
906 | process has a smaller stack, you should adjust this setting accordingly |
553 | with the "max_depth" method. |
907 | with the "max_depth" method. |
554 | |
908 | |
555 | And last but least, something else could bomb you that I forgot to think |
909 | And last but least, something else could bomb you that I forgot to think |
556 | of. In that case, you get to keep the pieces. I am alway sopen for |
910 | of. In that case, you get to keep the pieces. I am always open for |
557 | hints, though... |
911 | hints, though... |
|
|
912 | |
|
|
913 | If you are using JSON::XS to return packets to consumption by JavaScript |
|
|
914 | scripts in a browser you should have a look at |
|
|
915 | <http://jpsykes.com/47/practical-csrf-and-json-security> to see whether |
|
|
916 | you are vulnerable to some common attack vectors (which really are |
|
|
917 | browser design bugs, but it is still you who will have to deal with it, |
|
|
918 | as major browser developers care only for features, not about doing |
|
|
919 | security right). |
|
|
920 | |
|
|
921 | THREADS |
|
|
922 | This module is *not* guaranteed to be thread safe and there are no plans |
|
|
923 | to change this until Perl gets thread support (as opposed to the |
|
|
924 | horribly slow so-called "threads" which are simply slow and bloated |
|
|
925 | process simulations - use fork, its *much* faster, cheaper, better). |
|
|
926 | |
|
|
927 | (It might actually work, but you have been warned). |
558 | |
928 | |
559 | BUGS |
929 | BUGS |
560 | While the goal of this module is to be correct, that unfortunately does |
930 | While the goal of this module is to be correct, that unfortunately does |
561 | not mean its bug-free, only that I think its design is bug-free. It is |
931 | not mean its bug-free, only that I think its design is bug-free. It is |
562 | still relatively early in its development. If you keep reporting bugs |
932 | still relatively early in its development. If you keep reporting bugs |
563 | they will be fixed swiftly, though. |
933 | they will be fixed swiftly, though. |
564 | |
934 | |
|
|
935 | Please refrain from using rt.cpan.org or any other bug reporting |
|
|
936 | service. I put the contact address into my modules for a reason. |
|
|
937 | |
565 | AUTHOR |
938 | AUTHOR |
566 | Marc Lehmann <schmorp@schmorp.de> |
939 | Marc Lehmann <schmorp@schmorp.de> |
567 | http://home.schmorp.de/ |
940 | http://home.schmorp.de/ |
568 | |
941 | |