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4 | <head> |
4 | <head> |
5 | <title>libev</title> |
5 | <title>libev</title> |
6 | <meta name="description" content="Pod documentation for libev" /> |
6 | <meta name="description" content="Pod documentation for libev" /> |
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9 | <meta name="created" content="Mon Nov 12 09:32:51 2007" /> |
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12 | <body> |
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13 | <div class="pod"> |
13 | <div class="pod"> |
14 | <!-- INDEX START --> |
14 | <!-- INDEX START --> |
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17 | <ul><li><a href="#NAME">NAME</a></li> |
17 | <ul><li><a href="#NAME">NAME</a></li> |
18 | <li><a href="#SYNOPSIS">SYNOPSIS</a></li> |
18 | <li><a href="#SYNOPSIS">SYNOPSIS</a></li> |
19 | <li><a href="#DESCRIPTION">DESCRIPTION</a></li> |
19 | <li><a href="#DESCRIPTION">DESCRIPTION</a></li> |
20 | <li><a href="#FEATURES">FEATURES</a></li> |
20 | <li><a href="#FEATURES">FEATURES</a></li> |
21 | <li><a href="#CONVENTIONS">CONVENTIONS</a></li> |
21 | <li><a href="#CONVENTIONS">CONVENTIONS</a></li> |
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22 | <li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li> |
22 | <li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> |
23 | <li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li> |
23 | <li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> |
24 | <li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> |
24 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
25 | <li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> |
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26 | <ul><li><a href="#SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</a></li> |
25 | <ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
27 | <li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> |
26 | </ul> |
28 | </ul> |
27 | </li> |
29 | </li> |
28 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
30 | <li><a href="#WATCHER_TYPES">WATCHER TYPES</a> |
29 | <ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> |
31 | <ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> |
30 | <li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> |
32 | <li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> |
31 | <li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</a></li> |
33 | <li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> |
32 | <li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> |
34 | <li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> |
33 | <li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
35 | <li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> |
34 | <li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
36 | <li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> |
35 | <li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> |
37 | <li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> |
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38 | <li><a href="#code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</a></li> |
36 | </ul> |
39 | </ul> |
37 | </li> |
40 | </li> |
38 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
41 | <li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> |
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42 | <li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li> |
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43 | <li><a href="#C_SUPPORT">C++ SUPPORT</a></li> |
39 | <li><a href="#AUTHOR">AUTHOR</a> |
44 | <li><a href="#AUTHOR">AUTHOR</a> |
40 | </li> |
45 | </li> |
41 | </ul><hr /> |
46 | </ul><hr /> |
42 | <!-- INDEX END --> |
47 | <!-- INDEX END --> |
43 | |
48 | |
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87 | support for multiple event loops, then all functions taking an initial |
92 | support for multiple event loops, then all functions taking an initial |
88 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
93 | argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) |
89 | will not have this argument.</p> |
94 | will not have this argument.</p> |
90 | |
95 | |
91 | </div> |
96 | </div> |
92 | <h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
97 | <h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
93 | <div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> |
98 | <div id="TIME_REPRESENTATION_CONTENT"> |
94 | <p>Libev represents time as a single floating point number, representing the |
99 | <p>Libev represents time as a single floating point number, representing the |
95 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
100 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
96 | the beginning of 1970, details are complicated, don't ask). This type is |
101 | the beginning of 1970, details are complicated, don't ask). This type is |
97 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
102 | called <code>ev_tstamp</code>, which is what you should use too. It usually aliases |
98 | to the double type in C.</p> |
103 | to the <code>double</code> type in C, and when you need to do any calculations on |
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104 | it, you should treat it as such.</p> |
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105 | |
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106 | |
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107 | |
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108 | |
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109 | |
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110 | </div> |
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111 | <h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
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112 | <div id="GLOBAL_FUNCTIONS_CONTENT"> |
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113 | <p>These functions can be called anytime, even before initialising the |
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114 | library in any way.</p> |
99 | <dl> |
115 | <dl> |
100 | <dt>ev_tstamp ev_time ()</dt> |
116 | <dt>ev_tstamp ev_time ()</dt> |
101 | <dd> |
117 | <dd> |
102 | <p>Returns the current time as libev would use it.</p> |
118 | <p>Returns the current time as libev would use it. Please note that the |
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119 | <code>ev_now</code> function is usually faster and also often returns the timestamp |
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120 | you actually want to know.</p> |
103 | </dd> |
121 | </dd> |
104 | <dt>int ev_version_major ()</dt> |
122 | <dt>int ev_version_major ()</dt> |
105 | <dt>int ev_version_minor ()</dt> |
123 | <dt>int ev_version_minor ()</dt> |
106 | <dd> |
124 | <dd> |
107 | <p>You can find out the major and minor version numbers of the library |
125 | <p>You can find out the major and minor version numbers of the library |
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111 | version of the library your program was compiled against.</p> |
129 | version of the library your program was compiled against.</p> |
112 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
130 | <p>Usually, it's a good idea to terminate if the major versions mismatch, |
113 | as this indicates an incompatible change. Minor versions are usually |
131 | as this indicates an incompatible change. Minor versions are usually |
114 | compatible to older versions, so a larger minor version alone is usually |
132 | compatible to older versions, so a larger minor version alone is usually |
115 | not a problem.</p> |
133 | not a problem.</p> |
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134 | <p>Example: make sure we haven't accidentally been linked against the wrong |
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135 | version:</p> |
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136 | <pre> assert (("libev version mismatch", |
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137 | ev_version_major () == EV_VERSION_MAJOR |
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138 | && ev_version_minor () >= EV_VERSION_MINOR)); |
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139 | |
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140 | </pre> |
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141 | </dd> |
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142 | <dt>unsigned int ev_supported_backends ()</dt> |
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143 | <dd> |
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144 | <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code> |
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145 | value) compiled into this binary of libev (independent of their |
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146 | availability on the system you are running on). See <code>ev_default_loop</code> for |
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147 | a description of the set values.</p> |
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148 | <p>Example: make sure we have the epoll method, because yeah this is cool and |
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149 | a must have and can we have a torrent of it please!!!11</p> |
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150 | <pre> assert (("sorry, no epoll, no sex", |
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151 | ev_supported_backends () & EVBACKEND_EPOLL)); |
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152 | |
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153 | </pre> |
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154 | </dd> |
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155 | <dt>unsigned int ev_recommended_backends ()</dt> |
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156 | <dd> |
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157 | <p>Return the set of all backends compiled into this binary of libev and also |
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158 | recommended for this platform. This set is often smaller than the one |
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159 | returned by <code>ev_supported_backends</code>, as for example kqueue is broken on |
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160 | most BSDs and will not be autodetected unless you explicitly request it |
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161 | (assuming you know what you are doing). This is the set of backends that |
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162 | libev will probe for if you specify no backends explicitly.</p> |
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163 | </dd> |
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164 | <dt>unsigned int ev_embeddable_backends ()</dt> |
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165 | <dd> |
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166 | <p>Returns the set of backends that are embeddable in other event loops. This |
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167 | is the theoretical, all-platform, value. To find which backends |
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168 | might be supported on the current system, you would need to look at |
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169 | <code>ev_embeddable_backends () & ev_supported_backends ()</code>, likewise for |
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170 | recommended ones.</p> |
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171 | <p>See the description of <code>ev_embed</code> watchers for more info.</p> |
116 | </dd> |
172 | </dd> |
117 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
173 | <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> |
118 | <dd> |
174 | <dd> |
119 | <p>Sets the allocation function to use (the prototype is similar to the |
175 | <p>Sets the allocation function to use (the prototype is similar to the |
120 | realloc C function, the semantics are identical). It is used to allocate |
176 | realloc C function, the semantics are identical). It is used to allocate |
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122 | needs to be allocated, the library might abort or take some potentially |
178 | needs to be allocated, the library might abort or take some potentially |
123 | destructive action. The default is your system realloc function.</p> |
179 | destructive action. The default is your system realloc function.</p> |
124 | <p>You could override this function in high-availability programs to, say, |
180 | <p>You could override this function in high-availability programs to, say, |
125 | free some memory if it cannot allocate memory, to use a special allocator, |
181 | free some memory if it cannot allocate memory, to use a special allocator, |
126 | or even to sleep a while and retry until some memory is available.</p> |
182 | or even to sleep a while and retry until some memory is available.</p> |
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183 | <p>Example: replace the libev allocator with one that waits a bit and then |
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184 | retries: better than mine).</p> |
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185 | <pre> static void * |
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186 | persistent_realloc (void *ptr, long size) |
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187 | { |
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188 | for (;;) |
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189 | { |
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190 | void *newptr = realloc (ptr, size); |
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191 | |
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192 | if (newptr) |
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193 | return newptr; |
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194 | |
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195 | sleep (60); |
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196 | } |
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197 | } |
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198 | |
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199 | ... |
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200 | ev_set_allocator (persistent_realloc); |
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201 | |
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202 | </pre> |
127 | </dd> |
203 | </dd> |
128 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
204 | <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> |
129 | <dd> |
205 | <dd> |
130 | <p>Set the callback function to call on a retryable syscall error (such |
206 | <p>Set the callback function to call on a retryable syscall error (such |
131 | as failed select, poll, epoll_wait). The message is a printable string |
207 | as failed select, poll, epoll_wait). The message is a printable string |
132 | indicating the system call or subsystem causing the problem. If this |
208 | indicating the system call or subsystem causing the problem. If this |
133 | callback is set, then libev will expect it to remedy the sitution, no |
209 | callback is set, then libev will expect it to remedy the sitution, no |
134 | matter what, when it returns. That is, libev will generally retry the |
210 | matter what, when it returns. That is, libev will generally retry the |
135 | requested operation, or, if the condition doesn't go away, do bad stuff |
211 | requested operation, or, if the condition doesn't go away, do bad stuff |
136 | (such as abort).</p> |
212 | (such as abort).</p> |
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213 | <p>Example: do the same thing as libev does internally:</p> |
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214 | <pre> static void |
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215 | fatal_error (const char *msg) |
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216 | { |
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217 | perror (msg); |
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218 | abort (); |
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219 | } |
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220 | |
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221 | ... |
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222 | ev_set_syserr_cb (fatal_error); |
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223 | |
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224 | </pre> |
137 | </dd> |
225 | </dd> |
138 | </dl> |
226 | </dl> |
139 | |
227 | |
140 | </div> |
228 | </div> |
141 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
229 | <h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> |
142 | <div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> |
230 | <div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> |
143 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
231 | <p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two |
144 | types of such loops, the <i>default</i> loop, which supports signals and child |
232 | types of such loops, the <i>default</i> loop, which supports signals and child |
145 | events, and dynamically created loops which do not.</p> |
233 | events, and dynamically created loops which do not.</p> |
146 | <p>If you use threads, a common model is to run the default event loop |
234 | <p>If you use threads, a common model is to run the default event loop |
147 | in your main thread (or in a separate thrad) and for each thread you |
235 | in your main thread (or in a separate thread) and for each thread you |
148 | create, you also create another event loop. Libev itself does no locking |
236 | create, you also create another event loop. Libev itself does no locking |
149 | whatsoever, so if you mix calls to the same event loop in different |
237 | whatsoever, so if you mix calls to the same event loop in different |
150 | threads, make sure you lock (this is usually a bad idea, though, even if |
238 | threads, make sure you lock (this is usually a bad idea, though, even if |
151 | done correctly, because it's hideous and inefficient).</p> |
239 | done correctly, because it's hideous and inefficient).</p> |
152 | <dl> |
240 | <dl> |
153 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
241 | <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> |
154 | <dd> |
242 | <dd> |
155 | <p>This will initialise the default event loop if it hasn't been initialised |
243 | <p>This will initialise the default event loop if it hasn't been initialised |
156 | yet and return it. If the default loop could not be initialised, returns |
244 | yet and return it. If the default loop could not be initialised, returns |
157 | false. If it already was initialised it simply returns it (and ignores the |
245 | false. If it already was initialised it simply returns it (and ignores the |
158 | flags).</p> |
246 | flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> |
159 | <p>If you don't know what event loop to use, use the one returned from this |
247 | <p>If you don't know what event loop to use, use the one returned from this |
160 | function.</p> |
248 | function.</p> |
161 | <p>The flags argument can be used to specify special behaviour or specific |
249 | <p>The flags argument can be used to specify special behaviour or specific |
162 | backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> |
250 | backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p> |
163 | <p>It supports the following flags:</p> |
251 | <p>The following flags are supported:</p> |
164 | <p> |
252 | <p> |
165 | <dl> |
253 | <dl> |
166 | <dt><code>EVFLAG_AUTO</code></dt> |
254 | <dt><code>EVFLAG_AUTO</code></dt> |
167 | <dd> |
255 | <dd> |
168 | <p>The default flags value. Use this if you have no clue (it's the right |
256 | <p>The default flags value. Use this if you have no clue (it's the right |
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175 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
263 | <code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will |
176 | override the flags completely if it is found in the environment. This is |
264 | override the flags completely if it is found in the environment. This is |
177 | useful to try out specific backends to test their performance, or to work |
265 | useful to try out specific backends to test their performance, or to work |
178 | around bugs.</p> |
266 | around bugs.</p> |
179 | </dd> |
267 | </dd> |
180 | <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> |
268 | <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> |
181 | <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> |
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182 | <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> |
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183 | <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> |
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184 | <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> |
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185 | <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> |
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186 | <dd> |
269 | <dd> |
187 | <p>If one or more of these are ored into the flags value, then only these |
270 | <p>This is your standard select(2) backend. Not <i>completely</i> standard, as |
188 | backends will be tried (in the reverse order as given here). If one are |
271 | libev tries to roll its own fd_set with no limits on the number of fds, |
189 | specified, any backend will do.</p> |
272 | but if that fails, expect a fairly low limit on the number of fds when |
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273 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
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274 | the fastest backend for a low number of fds.</p> |
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275 | </dd> |
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276 | <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> |
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277 | <dd> |
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278 | <p>And this is your standard poll(2) backend. It's more complicated than |
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279 | select, but handles sparse fds better and has no artificial limit on the |
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280 | number of fds you can use (except it will slow down considerably with a |
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281 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> |
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282 | </dd> |
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283 | <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt> |
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284 | <dd> |
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285 | <p>For few fds, this backend is a bit little slower than poll and select, |
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286 | but it scales phenomenally better. While poll and select usually scale like |
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287 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
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288 | either O(1) or O(active_fds).</p> |
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289 | <p>While stopping and starting an I/O watcher in the same iteration will |
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290 | result in some caching, there is still a syscall per such incident |
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291 | (because the fd could point to a different file description now), so its |
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292 | best to avoid that. Also, dup()ed file descriptors might not work very |
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293 | well if you register events for both fds.</p> |
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294 | <p>Please note that epoll sometimes generates spurious notifications, so you |
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295 | need to use non-blocking I/O or other means to avoid blocking when no data |
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296 | (or space) is available.</p> |
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297 | </dd> |
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298 | <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> |
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299 | <dd> |
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300 | <p>Kqueue deserves special mention, as at the time of this writing, it |
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301 | was broken on all BSDs except NetBSD (usually it doesn't work with |
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302 | anything but sockets and pipes, except on Darwin, where of course its |
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303 | completely useless). For this reason its not being "autodetected" |
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304 | unless you explicitly specify it explicitly in the flags (i.e. using |
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305 | <code>EVBACKEND_KQUEUE</code>).</p> |
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306 | <p>It scales in the same way as the epoll backend, but the interface to the |
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307 | kernel is more efficient (which says nothing about its actual speed, of |
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308 | course). While starting and stopping an I/O watcher does not cause an |
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309 | extra syscall as with epoll, it still adds up to four event changes per |
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310 | incident, so its best to avoid that.</p> |
|
|
311 | </dd> |
|
|
312 | <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt> |
|
|
313 | <dd> |
|
|
314 | <p>This is not implemented yet (and might never be).</p> |
|
|
315 | </dd> |
|
|
316 | <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> |
|
|
317 | <dd> |
|
|
318 | <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, |
|
|
319 | it's really slow, but it still scales very well (O(active_fds)).</p> |
|
|
320 | <p>Please note that solaris ports can result in a lot of spurious |
|
|
321 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
322 | blocking when no data (or space) is available.</p> |
|
|
323 | </dd> |
|
|
324 | <dt><code>EVBACKEND_ALL</code></dt> |
|
|
325 | <dd> |
|
|
326 | <p>Try all backends (even potentially broken ones that wouldn't be tried |
|
|
327 | with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as |
|
|
328 | <code>EVBACKEND_ALL & ~EVBACKEND_KQUEUE</code>.</p> |
190 | </dd> |
329 | </dd> |
191 | </dl> |
330 | </dl> |
192 | </p> |
331 | </p> |
|
|
332 | <p>If one or more of these are ored into the flags value, then only these |
|
|
333 | backends will be tried (in the reverse order as given here). If none are |
|
|
334 | specified, most compiled-in backend will be tried, usually in reverse |
|
|
335 | order of their flag values :)</p> |
|
|
336 | <p>The most typical usage is like this:</p> |
|
|
337 | <pre> if (!ev_default_loop (0)) |
|
|
338 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
339 | |
|
|
340 | </pre> |
|
|
341 | <p>Restrict libev to the select and poll backends, and do not allow |
|
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342 | environment settings to be taken into account:</p> |
|
|
343 | <pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
344 | |
|
|
345 | </pre> |
|
|
346 | <p>Use whatever libev has to offer, but make sure that kqueue is used if |
|
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347 | available (warning, breaks stuff, best use only with your own private |
|
|
348 | event loop and only if you know the OS supports your types of fds):</p> |
|
|
349 | <pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
350 | |
|
|
351 | </pre> |
193 | </dd> |
352 | </dd> |
194 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
353 | <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> |
195 | <dd> |
354 | <dd> |
196 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
355 | <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is |
197 | always distinct from the default loop. Unlike the default loop, it cannot |
356 | always distinct from the default loop. Unlike the default loop, it cannot |
198 | handle signal and child watchers, and attempts to do so will be greeted by |
357 | handle signal and child watchers, and attempts to do so will be greeted by |
199 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
358 | undefined behaviour (or a failed assertion if assertions are enabled).</p> |
|
|
359 | <p>Example: try to create a event loop that uses epoll and nothing else.</p> |
|
|
360 | <pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
|
|
361 | if (!epoller) |
|
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362 | fatal ("no epoll found here, maybe it hides under your chair"); |
|
|
363 | |
|
|
364 | </pre> |
200 | </dd> |
365 | </dd> |
201 | <dt>ev_default_destroy ()</dt> |
366 | <dt>ev_default_destroy ()</dt> |
202 | <dd> |
367 | <dd> |
203 | <p>Destroys the default loop again (frees all memory and kernel state |
368 | <p>Destroys the default loop again (frees all memory and kernel state |
204 | etc.). This stops all registered event watchers (by not touching them in |
369 | etc.). This stops all registered event watchers (by not touching them in |
… | |
… | |
213 | <dd> |
378 | <dd> |
214 | <p>This function reinitialises the kernel state for backends that have |
379 | <p>This function reinitialises the kernel state for backends that have |
215 | one. Despite the name, you can call it anytime, but it makes most sense |
380 | one. Despite the name, you can call it anytime, but it makes most sense |
216 | after forking, in either the parent or child process (or both, but that |
381 | after forking, in either the parent or child process (or both, but that |
217 | again makes little sense).</p> |
382 | again makes little sense).</p> |
218 | <p>You <i>must</i> call this function after forking if and only if you want to |
383 | <p>You <i>must</i> call this function in the child process after forking if and |
219 | use the event library in both processes. If you just fork+exec, you don't |
384 | only if you want to use the event library in both processes. If you just |
220 | have to call it.</p> |
385 | fork+exec, you don't have to call it.</p> |
221 | <p>The function itself is quite fast and it's usually not a problem to call |
386 | <p>The function itself is quite fast and it's usually not a problem to call |
222 | it just in case after a fork. To make this easy, the function will fit in |
387 | it just in case after a fork. To make this easy, the function will fit in |
223 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
388 | quite nicely into a call to <code>pthread_atfork</code>:</p> |
224 | <pre> pthread_atfork (0, 0, ev_default_fork); |
389 | <pre> pthread_atfork (0, 0, ev_default_fork); |
225 | |
390 | |
226 | </pre> |
391 | </pre> |
|
|
392 | <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use |
|
|
393 | without calling this function, so if you force one of those backends you |
|
|
394 | do not need to care.</p> |
227 | </dd> |
395 | </dd> |
228 | <dt>ev_loop_fork (loop)</dt> |
396 | <dt>ev_loop_fork (loop)</dt> |
229 | <dd> |
397 | <dd> |
230 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
398 | <p>Like <code>ev_default_fork</code>, but acts on an event loop created by |
231 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
399 | <code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop |
232 | after fork, and how you do this is entirely your own problem.</p> |
400 | after fork, and how you do this is entirely your own problem.</p> |
233 | </dd> |
401 | </dd> |
234 | <dt>unsigned int ev_method (loop)</dt> |
402 | <dt>unsigned int ev_backend (loop)</dt> |
235 | <dd> |
403 | <dd> |
236 | <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in |
404 | <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in |
237 | use.</p> |
405 | use.</p> |
238 | </dd> |
406 | </dd> |
239 | <dt>ev_tstamp ev_now (loop)</dt> |
407 | <dt>ev_tstamp ev_now (loop)</dt> |
240 | <dd> |
408 | <dd> |
241 | <p>Returns the current "event loop time", which is the time the event loop |
409 | <p>Returns the current "event loop time", which is the time the event loop |
242 | got events and started processing them. This timestamp does not change |
410 | received events and started processing them. This timestamp does not |
243 | as long as callbacks are being processed, and this is also the base time |
411 | change as long as callbacks are being processed, and this is also the base |
244 | used for relative timers. You can treat it as the timestamp of the event |
412 | time used for relative timers. You can treat it as the timestamp of the |
245 | occuring (or more correctly, the mainloop finding out about it).</p> |
413 | event occuring (or more correctly, libev finding out about it).</p> |
246 | </dd> |
414 | </dd> |
247 | <dt>ev_loop (loop, int flags)</dt> |
415 | <dt>ev_loop (loop, int flags)</dt> |
248 | <dd> |
416 | <dd> |
249 | <p>Finally, this is it, the event handler. This function usually is called |
417 | <p>Finally, this is it, the event handler. This function usually is called |
250 | after you initialised all your watchers and you want to start handling |
418 | after you initialised all your watchers and you want to start handling |
251 | events.</p> |
419 | events.</p> |
252 | <p>If the flags argument is specified as 0, it will not return until either |
420 | <p>If the flags argument is specified as <code>0</code>, it will not return until |
253 | no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
421 | either no event watchers are active anymore or <code>ev_unloop</code> was called.</p> |
|
|
422 | <p>Please note that an explicit <code>ev_unloop</code> is usually better than |
|
|
423 | relying on all watchers to be stopped when deciding when a program has |
|
|
424 | finished (especially in interactive programs), but having a program that |
|
|
425 | automatically loops as long as it has to and no longer by virtue of |
|
|
426 | relying on its watchers stopping correctly is a thing of beauty.</p> |
254 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
427 | <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle |
255 | those events and any outstanding ones, but will not block your process in |
428 | those events and any outstanding ones, but will not block your process in |
256 | case there are no events and will return after one iteration of the loop.</p> |
429 | case there are no events and will return after one iteration of the loop.</p> |
257 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
430 | <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if |
258 | neccessary) and will handle those and any outstanding ones. It will block |
431 | neccessary) and will handle those and any outstanding ones. It will block |
259 | your process until at least one new event arrives, and will return after |
432 | your process until at least one new event arrives, and will return after |
260 | one iteration of the loop.</p> |
433 | one iteration of the loop. This is useful if you are waiting for some |
261 | <p>This flags value could be used to implement alternative looping |
434 | external event in conjunction with something not expressible using other |
262 | constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and |
435 | libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is |
263 | more generic mechanism.</p> |
436 | usually a better approach for this kind of thing.</p> |
|
|
437 | <p>Here are the gory details of what <code>ev_loop</code> does:</p> |
|
|
438 | <pre> * If there are no active watchers (reference count is zero), return. |
|
|
439 | - Queue prepare watchers and then call all outstanding watchers. |
|
|
440 | - If we have been forked, recreate the kernel state. |
|
|
441 | - Update the kernel state with all outstanding changes. |
|
|
442 | - Update the "event loop time". |
|
|
443 | - Calculate for how long to block. |
|
|
444 | - Block the process, waiting for any events. |
|
|
445 | - Queue all outstanding I/O (fd) events. |
|
|
446 | - Update the "event loop time" and do time jump handling. |
|
|
447 | - Queue all outstanding timers. |
|
|
448 | - Queue all outstanding periodics. |
|
|
449 | - If no events are pending now, queue all idle watchers. |
|
|
450 | - Queue all check watchers. |
|
|
451 | - Call all queued watchers in reverse order (i.e. check watchers first). |
|
|
452 | Signals and child watchers are implemented as I/O watchers, and will |
|
|
453 | be handled here by queueing them when their watcher gets executed. |
|
|
454 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
|
|
455 | were used, return, otherwise continue with step *. |
|
|
456 | |
|
|
457 | </pre> |
|
|
458 | <p>Example: queue some jobs and then loop until no events are outsanding |
|
|
459 | anymore.</p> |
|
|
460 | <pre> ... queue jobs here, make sure they register event watchers as long |
|
|
461 | ... as they still have work to do (even an idle watcher will do..) |
|
|
462 | ev_loop (my_loop, 0); |
|
|
463 | ... jobs done. yeah! |
|
|
464 | |
|
|
465 | </pre> |
264 | </dd> |
466 | </dd> |
265 | <dt>ev_unloop (loop, how)</dt> |
467 | <dt>ev_unloop (loop, how)</dt> |
266 | <dd> |
468 | <dd> |
267 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
469 | <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it |
268 | has processed all outstanding events). The <code>how</code> argument must be either |
470 | has processed all outstanding events). The <code>how</code> argument must be either |
269 | <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or |
471 | <code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or |
270 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
472 | <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> |
271 | </dd> |
473 | </dd> |
272 | <dt>ev_ref (loop)</dt> |
474 | <dt>ev_ref (loop)</dt> |
273 | <dt>ev_unref (loop)</dt> |
475 | <dt>ev_unref (loop)</dt> |
274 | <dd> |
476 | <dd> |
… | |
… | |
280 | example, libev itself uses this for its internal signal pipe: It is not |
482 | example, libev itself uses this for its internal signal pipe: It is not |
281 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
483 | visible to the libev user and should not keep <code>ev_loop</code> from exiting if |
282 | no event watchers registered by it are active. It is also an excellent |
484 | no event watchers registered by it are active. It is also an excellent |
283 | way to do this for generic recurring timers or from within third-party |
485 | way to do this for generic recurring timers or from within third-party |
284 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
486 | libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> |
|
|
487 | <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code> |
|
|
488 | running when nothing else is active.</p> |
|
|
489 | <pre> struct dv_signal exitsig; |
|
|
490 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
|
|
491 | ev_signal_start (myloop, &exitsig); |
|
|
492 | evf_unref (myloop); |
|
|
493 | |
|
|
494 | </pre> |
|
|
495 | <p>Example: for some weird reason, unregister the above signal handler again.</p> |
|
|
496 | <pre> ev_ref (myloop); |
|
|
497 | ev_signal_stop (myloop, &exitsig); |
|
|
498 | |
|
|
499 | </pre> |
285 | </dd> |
500 | </dd> |
286 | </dl> |
501 | </dl> |
287 | |
502 | |
288 | </div> |
503 | </div> |
289 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
504 | <h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> |
… | |
… | |
321 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
536 | with a watcher-specific start function (<code>ev_<type>_start (loop, watcher |
322 | *)</code>), and you can stop watching for events at any time by calling the |
537 | *)</code>), and you can stop watching for events at any time by calling the |
323 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
538 | corresponding stop function (<code>ev_<type>_stop (loop, watcher *)</code>.</p> |
324 | <p>As long as your watcher is active (has been started but not stopped) you |
539 | <p>As long as your watcher is active (has been started but not stopped) you |
325 | must not touch the values stored in it. Most specifically you must never |
540 | must not touch the values stored in it. Most specifically you must never |
326 | reinitialise it or call its set method.</p> |
541 | reinitialise it or call its <code>set</code> macro.</p> |
327 | <p>You cna check whether an event is active by calling the <code>ev_is_active |
|
|
328 | (watcher *)</code> macro. To see whether an event is outstanding (but the |
|
|
329 | callback for it has not been called yet) you cna use the <code>ev_is_pending |
|
|
330 | (watcher *)</code> macro.</p> |
|
|
331 | <p>Each and every callback receives the event loop pointer as first, the |
542 | <p>Each and every callback receives the event loop pointer as first, the |
332 | registered watcher structure as second, and a bitset of received events as |
543 | registered watcher structure as second, and a bitset of received events as |
333 | third argument.</p> |
544 | third argument.</p> |
334 | <p>The rceeived events usually include a single bit per event type received |
545 | <p>The received events usually include a single bit per event type received |
335 | (you can receive multiple events at the same time). The possible bit masks |
546 | (you can receive multiple events at the same time). The possible bit masks |
336 | are:</p> |
547 | are:</p> |
337 | <dl> |
548 | <dl> |
338 | <dt><code>EV_READ</code></dt> |
549 | <dt><code>EV_READ</code></dt> |
339 | <dt><code>EV_WRITE</code></dt> |
550 | <dt><code>EV_WRITE</code></dt> |
… | |
… | |
386 | programs, though, so beware.</p> |
597 | programs, though, so beware.</p> |
387 | </dd> |
598 | </dd> |
388 | </dl> |
599 | </dl> |
389 | |
600 | |
390 | </div> |
601 | </div> |
|
|
602 | <h2 id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS">SUMMARY OF GENERIC WATCHER FUNCTIONS</h2> |
|
|
603 | <div id="SUMMARY_OF_GENERIC_WATCHER_FUNCTIONS-2"> |
|
|
604 | <p>In the following description, <code>TYPE</code> stands for the watcher type, |
|
|
605 | e.g. <code>timer</code> for <code>ev_timer</code> watchers and <code>io</code> for <code>ev_io</code> watchers.</p> |
|
|
606 | <dl> |
|
|
607 | <dt><code>ev_init</code> (ev_TYPE *watcher, callback)</dt> |
|
|
608 | <dd> |
|
|
609 | <p>This macro initialises the generic portion of a watcher. The contents |
|
|
610 | of the watcher object can be arbitrary (so <code>malloc</code> will do). Only |
|
|
611 | the generic parts of the watcher are initialised, you <i>need</i> to call |
|
|
612 | the type-specific <code>ev_TYPE_set</code> macro afterwards to initialise the |
|
|
613 | type-specific parts. For each type there is also a <code>ev_TYPE_init</code> macro |
|
|
614 | which rolls both calls into one.</p> |
|
|
615 | <p>You can reinitialise a watcher at any time as long as it has been stopped |
|
|
616 | (or never started) and there are no pending events outstanding.</p> |
|
|
617 | <p>The callbakc is always of type <code>void (*)(ev_loop *loop, ev_TYPE *watcher, |
|
|
618 | int revents)</code>.</p> |
|
|
619 | </dd> |
|
|
620 | <dt><code>ev_TYPE_set</code> (ev_TYPE *, [args])</dt> |
|
|
621 | <dd> |
|
|
622 | <p>This macro initialises the type-specific parts of a watcher. You need to |
|
|
623 | call <code>ev_init</code> at least once before you call this macro, but you can |
|
|
624 | call <code>ev_TYPE_set</code> any number of times. You must not, however, call this |
|
|
625 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
626 | difference to the <code>ev_init</code> macro).</p> |
|
|
627 | <p>Although some watcher types do not have type-specific arguments |
|
|
628 | (e.g. <code>ev_prepare</code>) you still need to call its <code>set</code> macro.</p> |
|
|
629 | </dd> |
|
|
630 | <dt><code>ev_TYPE_init</code> (ev_TYPE *watcher, callback, [args])</dt> |
|
|
631 | <dd> |
|
|
632 | <p>This convinience macro rolls both <code>ev_init</code> and <code>ev_TYPE_set</code> macro |
|
|
633 | calls into a single call. This is the most convinient method to initialise |
|
|
634 | a watcher. The same limitations apply, of course.</p> |
|
|
635 | </dd> |
|
|
636 | <dt><code>ev_TYPE_start</code> (loop *, ev_TYPE *watcher)</dt> |
|
|
637 | <dd> |
|
|
638 | <p>Starts (activates) the given watcher. Only active watchers will receive |
|
|
639 | events. If the watcher is already active nothing will happen.</p> |
|
|
640 | </dd> |
|
|
641 | <dt><code>ev_TYPE_stop</code> (loop *, ev_TYPE *watcher)</dt> |
|
|
642 | <dd> |
|
|
643 | <p>Stops the given watcher again (if active) and clears the pending |
|
|
644 | status. It is possible that stopped watchers are pending (for example, |
|
|
645 | non-repeating timers are being stopped when they become pending), but |
|
|
646 | <code>ev_TYPE_stop</code> ensures that the watcher is neither active nor pending. If |
|
|
647 | you want to free or reuse the memory used by the watcher it is therefore a |
|
|
648 | good idea to always call its <code>ev_TYPE_stop</code> function.</p> |
|
|
649 | </dd> |
|
|
650 | <dt>bool ev_is_active (ev_TYPE *watcher)</dt> |
|
|
651 | <dd> |
|
|
652 | <p>Returns a true value iff the watcher is active (i.e. it has been started |
|
|
653 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
654 | it.</p> |
|
|
655 | </dd> |
|
|
656 | <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> |
|
|
657 | <dd> |
|
|
658 | <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
659 | events but its callback has not yet been invoked). As long as a watcher |
|
|
660 | is pending (but not active) you must not call an init function on it (but |
|
|
661 | <code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to |
|
|
662 | libev (e.g. you cnanot <code>free ()</code> it).</p> |
|
|
663 | </dd> |
|
|
664 | <dt>callback = ev_cb (ev_TYPE *watcher)</dt> |
|
|
665 | <dd> |
|
|
666 | <p>Returns the callback currently set on the watcher.</p> |
|
|
667 | </dd> |
|
|
668 | <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> |
|
|
669 | <dd> |
|
|
670 | <p>Change the callback. You can change the callback at virtually any time |
|
|
671 | (modulo threads).</p> |
|
|
672 | </dd> |
|
|
673 | </dl> |
|
|
674 | |
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675 | |
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676 | |
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677 | |
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678 | |
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679 | </div> |
391 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
680 | <h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> |
392 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
681 | <div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> |
393 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
682 | <p>Each watcher has, by default, a member <code>void *data</code> that you can change |
394 | and read at any time, libev will completely ignore it. This cna be used |
683 | and read at any time, libev will completely ignore it. This can be used |
395 | to associate arbitrary data with your watcher. If you need more data and |
684 | to associate arbitrary data with your watcher. If you need more data and |
396 | don't want to allocate memory and store a pointer to it in that data |
685 | don't want to allocate memory and store a pointer to it in that data |
397 | member, you can also "subclass" the watcher type and provide your own |
686 | member, you can also "subclass" the watcher type and provide your own |
398 | data:</p> |
687 | data:</p> |
399 | <pre> struct my_io |
688 | <pre> struct my_io |
… | |
… | |
425 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
714 | <h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> |
426 | <div id="WATCHER_TYPES_CONTENT"> |
715 | <div id="WATCHER_TYPES_CONTENT"> |
427 | <p>This section describes each watcher in detail, but will not repeat |
716 | <p>This section describes each watcher in detail, but will not repeat |
428 | information given in the last section.</p> |
717 | information given in the last section.</p> |
429 | |
718 | |
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719 | |
|
|
720 | |
|
|
721 | |
|
|
722 | |
430 | </div> |
723 | </div> |
431 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
724 | <h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> |
432 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
725 | <div id="code_ev_io_code_is_this_file_descrip-2"> |
433 | <p>I/O watchers check whether a file descriptor is readable or writable |
726 | <p>I/O watchers check whether a file descriptor is readable or writable |
434 | in each iteration of the event loop (This behaviour is called |
727 | in each iteration of the event loop (This behaviour is called |
435 | level-triggering because you keep receiving events as long as the |
728 | level-triggering because you keep receiving events as long as the |
436 | condition persists. Remember you cna stop the watcher if you don't want to |
729 | condition persists. Remember you can stop the watcher if you don't want to |
437 | act on the event and neither want to receive future events).</p> |
730 | act on the event and neither want to receive future events).</p> |
438 | <p>In general you can register as many read and/or write event watchers oer |
731 | <p>In general you can register as many read and/or write event watchers per |
439 | fd as you want (as long as you don't confuse yourself). Setting all file |
732 | fd as you want (as long as you don't confuse yourself). Setting all file |
440 | descriptors to non-blocking mode is also usually a good idea (but not |
733 | descriptors to non-blocking mode is also usually a good idea (but not |
441 | required if you know what you are doing).</p> |
734 | required if you know what you are doing).</p> |
442 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
735 | <p>You have to be careful with dup'ed file descriptors, though. Some backends |
443 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
736 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
444 | descriptors correctly if you register interest in two or more fds pointing |
737 | descriptors correctly if you register interest in two or more fds pointing |
445 | to the same file/socket etc. description.</p> |
738 | to the same underlying file/socket etc. description (that is, they share |
|
|
739 | the same underlying "file open").</p> |
446 | <p>If you must do this, then force the use of a known-to-be-good backend |
740 | <p>If you must do this, then force the use of a known-to-be-good backend |
447 | (at the time of this writing, this includes only EVMETHOD_SELECT and |
741 | (at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and |
448 | EVMETHOD_POLL).</p> |
742 | <code>EVBACKEND_POLL</code>).</p> |
449 | <dl> |
743 | <dl> |
450 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
744 | <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> |
451 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
745 | <dt>ev_io_set (ev_io *, int fd, int events)</dt> |
452 | <dd> |
746 | <dd> |
453 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
747 | <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive |
454 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
748 | events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | |
455 | EV_WRITE</code> to receive the given events.</p> |
749 | EV_WRITE</code> to receive the given events.</p> |
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|
750 | <p>Please note that most of the more scalable backend mechanisms (for example |
|
|
751 | epoll and solaris ports) can result in spurious readyness notifications |
|
|
752 | for file descriptors, so you practically need to use non-blocking I/O (and |
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|
753 | treat callback invocation as hint only), or retest separately with a safe |
|
|
754 | interface before doing I/O (XLib can do this), or force the use of either |
|
|
755 | <code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this |
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|
756 | problem. Also note that it is quite easy to have your callback invoked |
|
|
757 | when the readyness condition is no longer valid even when employing |
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|
758 | typical ways of handling events, so its a good idea to use non-blocking |
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|
759 | I/O unconditionally.</p> |
456 | </dd> |
760 | </dd> |
457 | </dl> |
761 | </dl> |
|
|
762 | <p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well |
|
|
763 | readable, but only once. Since it is likely line-buffered, you could |
|
|
764 | attempt to read a whole line in the callback:</p> |
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|
765 | <pre> static void |
|
|
766 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
767 | { |
|
|
768 | ev_io_stop (loop, w); |
|
|
769 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
|
|
770 | } |
|
|
771 | |
|
|
772 | ... |
|
|
773 | struct ev_loop *loop = ev_default_init (0); |
|
|
774 | struct ev_io stdin_readable; |
|
|
775 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
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|
776 | ev_io_start (loop, &stdin_readable); |
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|
777 | ev_loop (loop, 0); |
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|
778 | |
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|
779 | |
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780 | |
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|
781 | |
|
|
782 | </pre> |
458 | |
783 | |
459 | </div> |
784 | </div> |
460 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
785 | <h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> |
461 | <div id="code_ev_timer_code_relative_and_opti-2"> |
786 | <div id="code_ev_timer_code_relative_and_opti-2"> |
462 | <p>Timer watchers are simple relative timers that generate an event after a |
787 | <p>Timer watchers are simple relative timers that generate an event after a |
463 | given time, and optionally repeating in regular intervals after that.</p> |
788 | given time, and optionally repeating in regular intervals after that.</p> |
464 | <p>The timers are based on real time, that is, if you register an event that |
789 | <p>The timers are based on real time, that is, if you register an event that |
465 | times out after an hour and youreset your system clock to last years |
790 | times out after an hour and you reset your system clock to last years |
466 | time, it will still time out after (roughly) and hour. "Roughly" because |
791 | time, it will still time out after (roughly) and hour. "Roughly" because |
467 | detecting time jumps is hard, and soem inaccuracies are unavoidable (the |
792 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
468 | monotonic clock option helps a lot here).</p> |
793 | monotonic clock option helps a lot here).</p> |
469 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
794 | <p>The relative timeouts are calculated relative to the <code>ev_now ()</code> |
470 | time. This is usually the right thing as this timestamp refers to the time |
795 | time. This is usually the right thing as this timestamp refers to the time |
471 | of the event triggering whatever timeout you are modifying/starting. If |
796 | of the event triggering whatever timeout you are modifying/starting. If |
472 | you suspect event processing to be delayed and you *need* to base the timeout |
797 | you suspect event processing to be delayed and you <i>need</i> to base the timeout |
473 | ion the current time, use something like this to adjust for this:</p> |
798 | on the current time, use something like this to adjust for this:</p> |
474 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
799 | <pre> ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
475 | |
800 | |
476 | </pre> |
801 | </pre> |
|
|
802 | <p>The callback is guarenteed to be invoked only when its timeout has passed, |
|
|
803 | but if multiple timers become ready during the same loop iteration then |
|
|
804 | order of execution is undefined.</p> |
477 | <dl> |
805 | <dl> |
478 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
806 | <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> |
479 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
807 | <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> |
480 | <dd> |
808 | <dd> |
481 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
809 | <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is |
… | |
… | |
483 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
811 | timer will automatically be configured to trigger again <code>repeat</code> seconds |
484 | later, again, and again, until stopped manually.</p> |
812 | later, again, and again, until stopped manually.</p> |
485 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
813 | <p>The timer itself will do a best-effort at avoiding drift, that is, if you |
486 | configure a timer to trigger every 10 seconds, then it will trigger at |
814 | configure a timer to trigger every 10 seconds, then it will trigger at |
487 | exactly 10 second intervals. If, however, your program cannot keep up with |
815 | exactly 10 second intervals. If, however, your program cannot keep up with |
488 | the timer (ecause it takes longer than those 10 seconds to do stuff) the |
816 | the timer (because it takes longer than those 10 seconds to do stuff) the |
489 | timer will not fire more than once per event loop iteration.</p> |
817 | timer will not fire more than once per event loop iteration.</p> |
490 | </dd> |
818 | </dd> |
491 | <dt>ev_timer_again (loop)</dt> |
819 | <dt>ev_timer_again (loop)</dt> |
492 | <dd> |
820 | <dd> |
493 | <p>This will act as if the timer timed out and restart it again if it is |
821 | <p>This will act as if the timer timed out and restart it again if it is |
… | |
… | |
503 | time you successfully read or write some data. If you go into an idle |
831 | time you successfully read or write some data. If you go into an idle |
504 | state where you do not expect data to travel on the socket, you can stop |
832 | state where you do not expect data to travel on the socket, you can stop |
505 | the timer, and again will automatically restart it if need be.</p> |
833 | the timer, and again will automatically restart it if need be.</p> |
506 | </dd> |
834 | </dd> |
507 | </dl> |
835 | </dl> |
|
|
836 | <p>Example: create a timer that fires after 60 seconds.</p> |
|
|
837 | <pre> static void |
|
|
838 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
839 | { |
|
|
840 | .. one minute over, w is actually stopped right here |
|
|
841 | } |
508 | |
842 | |
|
|
843 | struct ev_timer mytimer; |
|
|
844 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
|
|
845 | ev_timer_start (loop, &mytimer); |
|
|
846 | |
|
|
847 | </pre> |
|
|
848 | <p>Example: create a timeout timer that times out after 10 seconds of |
|
|
849 | inactivity.</p> |
|
|
850 | <pre> static void |
|
|
851 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
|
|
852 | { |
|
|
853 | .. ten seconds without any activity |
|
|
854 | } |
|
|
855 | |
|
|
856 | struct ev_timer mytimer; |
|
|
857 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
|
|
858 | ev_timer_again (&mytimer); /* start timer */ |
|
|
859 | ev_loop (loop, 0); |
|
|
860 | |
|
|
861 | // and in some piece of code that gets executed on any "activity": |
|
|
862 | // reset the timeout to start ticking again at 10 seconds |
|
|
863 | ev_timer_again (&mytimer); |
|
|
864 | |
|
|
865 | |
|
|
866 | |
|
|
867 | |
|
|
868 | </pre> |
|
|
869 | |
509 | </div> |
870 | </div> |
510 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2> |
871 | <h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> |
511 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
872 | <div id="code_ev_periodic_code_to_cron_or_not-2"> |
512 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
873 | <p>Periodic watchers are also timers of a kind, but they are very versatile |
513 | (and unfortunately a bit complex).</p> |
874 | (and unfortunately a bit complex).</p> |
514 | <p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) |
875 | <p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) |
515 | but on wallclock time (absolute time). You can tell a periodic watcher |
876 | but on wallclock time (absolute time). You can tell a periodic watcher |
… | |
… | |
519 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
880 | take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger |
520 | roughly 10 seconds later and of course not if you reset your system time |
881 | roughly 10 seconds later and of course not if you reset your system time |
521 | again).</p> |
882 | again).</p> |
522 | <p>They can also be used to implement vastly more complex timers, such as |
883 | <p>They can also be used to implement vastly more complex timers, such as |
523 | triggering an event on eahc midnight, local time.</p> |
884 | triggering an event on eahc midnight, local time.</p> |
|
|
885 | <p>As with timers, the callback is guarenteed to be invoked only when the |
|
|
886 | time (<code>at</code>) has been passed, but if multiple periodic timers become ready |
|
|
887 | during the same loop iteration then order of execution is undefined.</p> |
524 | <dl> |
888 | <dl> |
525 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
889 | <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> |
526 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
890 | <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> |
527 | <dd> |
891 | <dd> |
528 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
892 | <p>Lots of arguments, lets sort it out... There are basically three modes of |
529 | operation, and we will explain them from simplest to complex:</p> |
893 | operation, and we will explain them from simplest to complex:</p> |
530 | |
|
|
531 | |
|
|
532 | |
|
|
533 | |
|
|
534 | <p> |
894 | <p> |
535 | <dl> |
895 | <dl> |
536 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
896 | <dt>* absolute timer (interval = reschedule_cb = 0)</dt> |
537 | <dd> |
897 | <dd> |
538 | <p>In this configuration the watcher triggers an event at the wallclock time |
898 | <p>In this configuration the watcher triggers an event at the wallclock time |
… | |
… | |
550 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
910 | <pre> ev_periodic_set (&periodic, 0., 3600., 0); |
551 | |
911 | |
552 | </pre> |
912 | </pre> |
553 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
913 | <p>This doesn't mean there will always be 3600 seconds in between triggers, |
554 | but only that the the callback will be called when the system time shows a |
914 | but only that the the callback will be called when the system time shows a |
555 | full hour (UTC), or more correct, when the system time is evenly divisible |
915 | full hour (UTC), or more correctly, when the system time is evenly divisible |
556 | by 3600.</p> |
916 | by 3600.</p> |
557 | <p>Another way to think about it (for the mathematically inclined) is that |
917 | <p>Another way to think about it (for the mathematically inclined) is that |
558 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
918 | <code>ev_periodic</code> will try to run the callback in this mode at the next possible |
559 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
919 | time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> |
560 | </dd> |
920 | </dd> |
… | |
… | |
562 | <dd> |
922 | <dd> |
563 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
923 | <p>In this mode the values for <code>interval</code> and <code>at</code> are both being |
564 | ignored. Instead, each time the periodic watcher gets scheduled, the |
924 | ignored. Instead, each time the periodic watcher gets scheduled, the |
565 | reschedule callback will be called with the watcher as first, and the |
925 | reschedule callback will be called with the watcher as first, and the |
566 | current time as second argument.</p> |
926 | current time as second argument.</p> |
567 | <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other |
927 | <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, |
568 | periodic watcher, ever, or make any event loop modificstions</i>. If you need |
928 | ever, or make any event loop modifications</i>. If you need to stop it, |
569 | to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> |
929 | return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
930 | starting a prepare watcher).</p> |
570 | <p>Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
931 | <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
571 | ev_tstamp now)>, e.g.:</p> |
932 | ev_tstamp now)</code>, e.g.:</p> |
572 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
933 | <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
573 | { |
934 | { |
574 | return now + 60.; |
935 | return now + 60.; |
575 | } |
936 | } |
576 | |
937 | |
577 | </pre> |
938 | </pre> |
578 | <p>It must return the next time to trigger, based on the passed time value |
939 | <p>It must return the next time to trigger, based on the passed time value |
579 | (that is, the lowest time value larger than to the second argument). It |
940 | (that is, the lowest time value larger than to the second argument). It |
580 | will usually be called just before the callback will be triggered, but |
941 | will usually be called just before the callback will be triggered, but |
581 | might be called at other times, too.</p> |
942 | might be called at other times, too.</p> |
|
|
943 | <p>NOTE: <i>This callback must always return a time that is later than the |
|
|
944 | passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p> |
582 | <p>This can be used to create very complex timers, such as a timer that |
945 | <p>This can be used to create very complex timers, such as a timer that |
583 | triggers on each midnight, local time. To do this, you would calculate the |
946 | triggers on each midnight, local time. To do this, you would calculate the |
584 | next midnight after <code>now</code> and return the timestamp value for this. How you do this |
947 | next midnight after <code>now</code> and return the timestamp value for this. How |
585 | is, again, up to you (but it is not trivial).</p> |
948 | you do this is, again, up to you (but it is not trivial, which is the main |
|
|
949 | reason I omitted it as an example).</p> |
586 | </dd> |
950 | </dd> |
587 | </dl> |
951 | </dl> |
588 | </p> |
952 | </p> |
589 | </dd> |
953 | </dd> |
590 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
954 | <dt>ev_periodic_again (loop, ev_periodic *)</dt> |
… | |
… | |
593 | when you changed some parameters or the reschedule callback would return |
957 | when you changed some parameters or the reschedule callback would return |
594 | a different time than the last time it was called (e.g. in a crond like |
958 | a different time than the last time it was called (e.g. in a crond like |
595 | program when the crontabs have changed).</p> |
959 | program when the crontabs have changed).</p> |
596 | </dd> |
960 | </dd> |
597 | </dl> |
961 | </dl> |
|
|
962 | <p>Example: call a callback every hour, or, more precisely, whenever the |
|
|
963 | system clock is divisible by 3600. The callback invocation times have |
|
|
964 | potentially a lot of jittering, but good long-term stability.</p> |
|
|
965 | <pre> static void |
|
|
966 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
|
|
967 | { |
|
|
968 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
|
|
969 | } |
|
|
970 | |
|
|
971 | struct ev_periodic hourly_tick; |
|
|
972 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
|
|
973 | ev_periodic_start (loop, &hourly_tick); |
|
|
974 | |
|
|
975 | </pre> |
|
|
976 | <p>Example: the same as above, but use a reschedule callback to do it:</p> |
|
|
977 | <pre> #include <math.h> |
|
|
978 | |
|
|
979 | static ev_tstamp |
|
|
980 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
|
|
981 | { |
|
|
982 | return fmod (now, 3600.) + 3600.; |
|
|
983 | } |
|
|
984 | |
|
|
985 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
|
|
986 | |
|
|
987 | </pre> |
|
|
988 | <p>Example: call a callback every hour, starting now:</p> |
|
|
989 | <pre> struct ev_periodic hourly_tick; |
|
|
990 | ev_periodic_init (&hourly_tick, clock_cb, |
|
|
991 | fmod (ev_now (loop), 3600.), 3600., 0); |
|
|
992 | ev_periodic_start (loop, &hourly_tick); |
|
|
993 | |
|
|
994 | |
|
|
995 | |
|
|
996 | |
|
|
997 | </pre> |
598 | |
998 | |
599 | </div> |
999 | </div> |
600 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
1000 | <h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> |
601 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
1001 | <div id="code_ev_signal_code_signal_me_when_a-2"> |
602 | <p>Signal watchers will trigger an event when the process receives a specific |
1002 | <p>Signal watchers will trigger an event when the process receives a specific |
603 | signal one or more times. Even though signals are very asynchronous, libev |
1003 | signal one or more times. Even though signals are very asynchronous, libev |
604 | will try it's best to deliver signals synchronously, i.e. as part of the |
1004 | will try it's best to deliver signals synchronously, i.e. as part of the |
605 | normal event processing, like any other event.</p> |
1005 | normal event processing, like any other event.</p> |
606 | <p>You cna configure as many watchers as you like per signal. Only when the |
1006 | <p>You can configure as many watchers as you like per signal. Only when the |
607 | first watcher gets started will libev actually register a signal watcher |
1007 | first watcher gets started will libev actually register a signal watcher |
608 | with the kernel (thus it coexists with your own signal handlers as long |
1008 | with the kernel (thus it coexists with your own signal handlers as long |
609 | as you don't register any with libev). Similarly, when the last signal |
1009 | as you don't register any with libev). Similarly, when the last signal |
610 | watcher for a signal is stopped libev will reset the signal handler to |
1010 | watcher for a signal is stopped libev will reset the signal handler to |
611 | SIG_DFL (regardless of what it was set to before).</p> |
1011 | SIG_DFL (regardless of what it was set to before).</p> |
… | |
… | |
616 | <p>Configures the watcher to trigger on the given signal number (usually one |
1016 | <p>Configures the watcher to trigger on the given signal number (usually one |
617 | of the <code>SIGxxx</code> constants).</p> |
1017 | of the <code>SIGxxx</code> constants).</p> |
618 | </dd> |
1018 | </dd> |
619 | </dl> |
1019 | </dl> |
620 | |
1020 | |
|
|
1021 | |
|
|
1022 | |
|
|
1023 | |
|
|
1024 | |
621 | </div> |
1025 | </div> |
622 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
1026 | <h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2> |
623 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
1027 | <div id="code_ev_child_code_wait_for_pid_stat-2"> |
624 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
1028 | <p>Child watchers trigger when your process receives a SIGCHLD in response to |
625 | some child status changes (most typically when a child of yours dies).</p> |
1029 | some child status changes (most typically when a child of yours dies).</p> |
… | |
… | |
628 | <dt>ev_child_set (ev_child *, int pid)</dt> |
1032 | <dt>ev_child_set (ev_child *, int pid)</dt> |
629 | <dd> |
1033 | <dd> |
630 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
1034 | <p>Configures the watcher to wait for status changes of process <code>pid</code> (or |
631 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
1035 | <i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look |
632 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
1036 | at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see |
633 | the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member |
1037 | the status word (use the macros from <code>sys/wait.h</code> and see your systems |
|
|
1038 | <code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the |
634 | contains the pid of the process causing the status change.</p> |
1039 | process causing the status change.</p> |
635 | </dd> |
1040 | </dd> |
636 | </dl> |
1041 | </dl> |
|
|
1042 | <p>Example: try to exit cleanly on SIGINT and SIGTERM.</p> |
|
|
1043 | <pre> static void |
|
|
1044 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1045 | { |
|
|
1046 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1047 | } |
|
|
1048 | |
|
|
1049 | struct ev_signal signal_watcher; |
|
|
1050 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1051 | ev_signal_start (loop, &sigint_cb); |
|
|
1052 | |
|
|
1053 | |
|
|
1054 | |
|
|
1055 | |
|
|
1056 | </pre> |
637 | |
1057 | |
638 | </div> |
1058 | </div> |
639 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
1059 | <h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> |
640 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
1060 | <div id="code_ev_idle_code_when_you_ve_got_no-2"> |
641 | <p>Idle watchers trigger events when there are no other I/O or timer (or |
1061 | <p>Idle watchers trigger events when there are no other events are pending |
642 | periodic) events pending. That is, as long as your process is busy |
1062 | (prepare, check and other idle watchers do not count). That is, as long |
643 | handling sockets or timeouts it will not be called. But when your process |
1063 | as your process is busy handling sockets or timeouts (or even signals, |
644 | is idle all idle watchers are being called again and again - until |
1064 | imagine) it will not be triggered. But when your process is idle all idle |
|
|
1065 | watchers are being called again and again, once per event loop iteration - |
645 | stopped, that is, or your process receives more events.</p> |
1066 | until stopped, that is, or your process receives more events and becomes |
|
|
1067 | busy.</p> |
646 | <p>The most noteworthy effect is that as long as any idle watchers are |
1068 | <p>The most noteworthy effect is that as long as any idle watchers are |
647 | active, the process will not block when waiting for new events.</p> |
1069 | active, the process will not block when waiting for new events.</p> |
648 | <p>Apart from keeping your process non-blocking (which is a useful |
1070 | <p>Apart from keeping your process non-blocking (which is a useful |
649 | effect on its own sometimes), idle watchers are a good place to do |
1071 | effect on its own sometimes), idle watchers are a good place to do |
650 | "pseudo-background processing", or delay processing stuff to after the |
1072 | "pseudo-background processing", or delay processing stuff to after the |
… | |
… | |
655 | <p>Initialises and configures the idle watcher - it has no parameters of any |
1077 | <p>Initialises and configures the idle watcher - it has no parameters of any |
656 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
1078 | kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, |
657 | believe me.</p> |
1079 | believe me.</p> |
658 | </dd> |
1080 | </dd> |
659 | </dl> |
1081 | </dl> |
|
|
1082 | <p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the |
|
|
1083 | callback, free it. Alos, use no error checking, as usual.</p> |
|
|
1084 | <pre> static void |
|
|
1085 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
|
|
1086 | { |
|
|
1087 | free (w); |
|
|
1088 | // now do something you wanted to do when the program has |
|
|
1089 | // no longer asnything immediate to do. |
|
|
1090 | } |
660 | |
1091 | |
|
|
1092 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
|
|
1093 | ev_idle_init (idle_watcher, idle_cb); |
|
|
1094 | ev_idle_start (loop, idle_cb); |
|
|
1095 | |
|
|
1096 | |
|
|
1097 | |
|
|
1098 | |
|
|
1099 | </pre> |
|
|
1100 | |
661 | </div> |
1101 | </div> |
662 | <h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> |
1102 | <h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> |
663 | <div id="prepare_and_check_your_hooks_into_th-2"> |
1103 | <div id="code_ev_prepare_code_and_code_ev_che-2"> |
664 | <p>Prepare and check watchers usually (but not always) are used in |
1104 | <p>Prepare and check watchers are usually (but not always) used in tandem: |
665 | tandom. Prepare watchers get invoked before the process blocks and check |
1105 | prepare watchers get invoked before the process blocks and check watchers |
666 | watchers afterwards.</p> |
1106 | afterwards.</p> |
667 | <p>Their main purpose is to integrate other event mechanisms into libev. This |
1107 | <p>Their main purpose is to integrate other event mechanisms into libev and |
668 | could be used, for example, to track variable changes, implement your own |
1108 | their use is somewhat advanced. This could be used, for example, to track |
669 | watchers, integrate net-snmp or a coroutine library and lots more.</p> |
1109 | variable changes, implement your own watchers, integrate net-snmp or a |
|
|
1110 | coroutine library and lots more.</p> |
670 | <p>This is done by examining in each prepare call which file descriptors need |
1111 | <p>This is done by examining in each prepare call which file descriptors need |
671 | to be watched by the other library, registering <code>ev_io</code> watchers for them |
1112 | to be watched by the other library, registering <code>ev_io</code> watchers for |
672 | and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide |
1113 | them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries |
673 | just this functionality). Then, in the check watcher you check for any |
1114 | provide just this functionality). Then, in the check watcher you check for |
674 | events that occured (by making your callbacks set soem flags for example) |
1115 | any events that occured (by checking the pending status of all watchers |
675 | and call back into the library.</p> |
1116 | and stopping them) and call back into the library. The I/O and timer |
|
|
1117 | callbacks will never actually be called (but must be valid nevertheless, |
|
|
1118 | because you never know, you know?).</p> |
676 | <p>As another example, the perl Coro module uses these hooks to integrate |
1119 | <p>As another example, the Perl Coro module uses these hooks to integrate |
677 | coroutines into libev programs, by yielding to other active coroutines |
1120 | coroutines into libev programs, by yielding to other active coroutines |
678 | during each prepare and only letting the process block if no coroutines |
1121 | during each prepare and only letting the process block if no coroutines |
679 | are ready to run.</p> |
1122 | are ready to run (it's actually more complicated: it only runs coroutines |
|
|
1123 | with priority higher than or equal to the event loop and one coroutine |
|
|
1124 | of lower priority, but only once, using idle watchers to keep the event |
|
|
1125 | loop from blocking if lower-priority coroutines are active, thus mapping |
|
|
1126 | low-priority coroutines to idle/background tasks).</p> |
680 | <dl> |
1127 | <dl> |
681 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
1128 | <dt>ev_prepare_init (ev_prepare *, callback)</dt> |
682 | <dt>ev_check_init (ev_check *, callback)</dt> |
1129 | <dt>ev_check_init (ev_check *, callback)</dt> |
683 | <dd> |
1130 | <dd> |
684 | <p>Initialises and configures the prepare or check watcher - they have no |
1131 | <p>Initialises and configures the prepare or check watcher - they have no |
685 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
1132 | parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> |
686 | macros, but using them is utterly, utterly pointless.</p> |
1133 | macros, but using them is utterly, utterly and completely pointless.</p> |
687 | </dd> |
1134 | </dd> |
688 | </dl> |
1135 | </dl> |
|
|
1136 | <p>Example: *TODO*.</p> |
|
|
1137 | |
|
|
1138 | |
|
|
1139 | |
|
|
1140 | |
|
|
1141 | |
|
|
1142 | </div> |
|
|
1143 | <h2 id="code_ev_embed_code_when_one_backend_"><code>ev_embed</code> - when one backend isn't enough</h2> |
|
|
1144 | <div id="code_ev_embed_code_when_one_backend_-2"> |
|
|
1145 | <p>This is a rather advanced watcher type that lets you embed one event loop |
|
|
1146 | into another (currently only <code>ev_io</code> events are supported in the embedded |
|
|
1147 | loop, other types of watchers might be handled in a delayed or incorrect |
|
|
1148 | fashion and must not be used).</p> |
|
|
1149 | <p>There are primarily two reasons you would want that: work around bugs and |
|
|
1150 | prioritise I/O.</p> |
|
|
1151 | <p>As an example for a bug workaround, the kqueue backend might only support |
|
|
1152 | sockets on some platform, so it is unusable as generic backend, but you |
|
|
1153 | still want to make use of it because you have many sockets and it scales |
|
|
1154 | so nicely. In this case, you would create a kqueue-based loop and embed it |
|
|
1155 | into your default loop (which might use e.g. poll). Overall operation will |
|
|
1156 | be a bit slower because first libev has to poll and then call kevent, but |
|
|
1157 | at least you can use both at what they are best.</p> |
|
|
1158 | <p>As for prioritising I/O: rarely you have the case where some fds have |
|
|
1159 | to be watched and handled very quickly (with low latency), and even |
|
|
1160 | priorities and idle watchers might have too much overhead. In this case |
|
|
1161 | you would put all the high priority stuff in one loop and all the rest in |
|
|
1162 | a second one, and embed the second one in the first.</p> |
|
|
1163 | <p>As long as the watcher is active, the callback will be invoked every time |
|
|
1164 | there might be events pending in the embedded loop. The callback must then |
|
|
1165 | call <code>ev_embed_sweep (mainloop, watcher)</code> to make a single sweep and invoke |
|
|
1166 | their callbacks (you could also start an idle watcher to give the embedded |
|
|
1167 | loop strictly lower priority for example). You can also set the callback |
|
|
1168 | to <code>0</code>, in which case the embed watcher will automatically execute the |
|
|
1169 | embedded loop sweep.</p> |
|
|
1170 | <p>As long as the watcher is started it will automatically handle events. The |
|
|
1171 | callback will be invoked whenever some events have been handled. You can |
|
|
1172 | set the callback to <code>0</code> to avoid having to specify one if you are not |
|
|
1173 | interested in that.</p> |
|
|
1174 | <p>Also, there have not currently been made special provisions for forking: |
|
|
1175 | when you fork, you not only have to call <code>ev_loop_fork</code> on both loops, |
|
|
1176 | but you will also have to stop and restart any <code>ev_embed</code> watchers |
|
|
1177 | yourself.</p> |
|
|
1178 | <p>Unfortunately, not all backends are embeddable, only the ones returned by |
|
|
1179 | <code>ev_embeddable_backends</code> are, which, unfortunately, does not include any |
|
|
1180 | portable one.</p> |
|
|
1181 | <p>So when you want to use this feature you will always have to be prepared |
|
|
1182 | that you cannot get an embeddable loop. The recommended way to get around |
|
|
1183 | this is to have a separate variables for your embeddable loop, try to |
|
|
1184 | create it, and if that fails, use the normal loop for everything:</p> |
|
|
1185 | <pre> struct ev_loop *loop_hi = ev_default_init (0); |
|
|
1186 | struct ev_loop *loop_lo = 0; |
|
|
1187 | struct ev_embed embed; |
|
|
1188 | |
|
|
1189 | // see if there is a chance of getting one that works |
|
|
1190 | // (remember that a flags value of 0 means autodetection) |
|
|
1191 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1192 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1193 | : 0; |
|
|
1194 | |
|
|
1195 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
1196 | if (loop_lo) |
|
|
1197 | { |
|
|
1198 | ev_embed_init (&embed, 0, loop_lo); |
|
|
1199 | ev_embed_start (loop_hi, &embed); |
|
|
1200 | } |
|
|
1201 | else |
|
|
1202 | loop_lo = loop_hi; |
|
|
1203 | |
|
|
1204 | </pre> |
|
|
1205 | <dl> |
|
|
1206 | <dt>ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
|
|
1207 | <dt>ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)</dt> |
|
|
1208 | <dd> |
|
|
1209 | <p>Configures the watcher to embed the given loop, which must be |
|
|
1210 | embeddable. If the callback is <code>0</code>, then <code>ev_embed_sweep</code> will be |
|
|
1211 | invoked automatically, otherwise it is the responsibility of the callback |
|
|
1212 | to invoke it (it will continue to be called until the sweep has been done, |
|
|
1213 | if you do not want thta, you need to temporarily stop the embed watcher).</p> |
|
|
1214 | </dd> |
|
|
1215 | <dt>ev_embed_sweep (loop, ev_embed *)</dt> |
|
|
1216 | <dd> |
|
|
1217 | <p>Make a single, non-blocking sweep over the embedded loop. This works |
|
|
1218 | similarly to <code>ev_loop (embedded_loop, EVLOOP_NONBLOCK)</code>, but in the most |
|
|
1219 | apropriate way for embedded loops.</p> |
|
|
1220 | </dd> |
|
|
1221 | </dl> |
|
|
1222 | |
|
|
1223 | |
|
|
1224 | |
|
|
1225 | |
689 | |
1226 | |
690 | </div> |
1227 | </div> |
691 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1228 | <h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> |
692 | <div id="OTHER_FUNCTIONS_CONTENT"> |
1229 | <div id="OTHER_FUNCTIONS_CONTENT"> |
693 | <p>There are some other fucntions of possible interest. Described. Here. Now.</p> |
1230 | <p>There are some other functions of possible interest. Described. Here. Now.</p> |
694 | <dl> |
1231 | <dl> |
695 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
1232 | <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> |
696 | <dd> |
1233 | <dd> |
697 | <p>This function combines a simple timer and an I/O watcher, calls your |
1234 | <p>This function combines a simple timer and an I/O watcher, calls your |
698 | callback on whichever event happens first and automatically stop both |
1235 | callback on whichever event happens first and automatically stop both |
699 | watchers. This is useful if you want to wait for a single event on an fd |
1236 | watchers. This is useful if you want to wait for a single event on an fd |
700 | or timeout without havign to allocate/configure/start/stop/free one or |
1237 | or timeout without having to allocate/configure/start/stop/free one or |
701 | more watchers yourself.</p> |
1238 | more watchers yourself.</p> |
702 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is |
1239 | <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events |
703 | ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set |
1240 | is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and |
704 | will be craeted and started.</p> |
1241 | <code>events</code> set will be craeted and started.</p> |
705 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
1242 | <p>If <code>timeout</code> is less than 0, then no timeout watcher will be |
706 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat |
1243 | started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and |
707 | = 0) will be started.</p> |
1244 | repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of |
|
|
1245 | dubious value.</p> |
708 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and |
1246 | <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets |
709 | gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>, |
1247 | passed an <code>revents</code> set like normal event callbacks (a combination of |
710 | <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p> |
1248 | <code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> |
|
|
1249 | value passed to <code>ev_once</code>:</p> |
711 | <pre> static void stdin_ready (int revents, void *arg) |
1250 | <pre> static void stdin_ready (int revents, void *arg) |
712 | { |
1251 | { |
713 | if (revents & EV_TIMEOUT) |
1252 | if (revents & EV_TIMEOUT) |
714 | /* doh, nothing entered */ |
1253 | /* doh, nothing entered */; |
715 | else if (revents & EV_READ) |
1254 | else if (revents & EV_READ) |
716 | /* stdin might have data for us, joy! */ |
1255 | /* stdin might have data for us, joy! */; |
717 | } |
1256 | } |
718 | |
1257 | |
719 | ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); |
1258 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
720 | |
1259 | |
721 | </pre> |
1260 | </pre> |
722 | </dd> |
1261 | </dd> |
723 | <dt>ev_feed_event (loop, watcher, int events)</dt> |
1262 | <dt>ev_feed_event (ev_loop *, watcher *, int revents)</dt> |
724 | <dd> |
1263 | <dd> |
725 | <p>Feeds the given event set into the event loop, as if the specified event |
1264 | <p>Feeds the given event set into the event loop, as if the specified event |
726 | has happened for the specified watcher (which must be a pointer to an |
1265 | had happened for the specified watcher (which must be a pointer to an |
727 | initialised but not necessarily active event watcher).</p> |
1266 | initialised but not necessarily started event watcher).</p> |
728 | </dd> |
1267 | </dd> |
729 | <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> |
1268 | <dt>ev_feed_fd_event (ev_loop *, int fd, int revents)</dt> |
730 | <dd> |
1269 | <dd> |
731 | <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> |
1270 | <p>Feed an event on the given fd, as if a file descriptor backend detected |
|
|
1271 | the given events it.</p> |
732 | </dd> |
1272 | </dd> |
733 | <dt>ev_feed_signal_event (loop, int signum)</dt> |
1273 | <dt>ev_feed_signal_event (ev_loop *loop, int signum)</dt> |
734 | <dd> |
1274 | <dd> |
735 | <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> |
1275 | <p>Feed an event as if the given signal occured (<code>loop</code> must be the default |
|
|
1276 | loop!).</p> |
736 | </dd> |
1277 | </dd> |
737 | </dl> |
1278 | </dl> |
|
|
1279 | |
|
|
1280 | |
|
|
1281 | |
|
|
1282 | |
|
|
1283 | |
|
|
1284 | </div> |
|
|
1285 | <h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p> |
|
|
1286 | <div id="LIBEVENT_EMULATION_CONTENT"> |
|
|
1287 | <p>Libev offers a compatibility emulation layer for libevent. It cannot |
|
|
1288 | emulate the internals of libevent, so here are some usage hints:</p> |
|
|
1289 | <dl> |
|
|
1290 | <dt>* Use it by including <event.h>, as usual.</dt> |
|
|
1291 | <dt>* The following members are fully supported: ev_base, ev_callback, |
|
|
1292 | ev_arg, ev_fd, ev_res, ev_events.</dt> |
|
|
1293 | <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is |
|
|
1294 | maintained by libev, it does not work exactly the same way as in libevent (consider |
|
|
1295 | it a private API).</dt> |
|
|
1296 | <dt>* Priorities are not currently supported. Initialising priorities |
|
|
1297 | will fail and all watchers will have the same priority, even though there |
|
|
1298 | is an ev_pri field.</dt> |
|
|
1299 | <dt>* Other members are not supported.</dt> |
|
|
1300 | <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need |
|
|
1301 | to use the libev header file and library.</dt> |
|
|
1302 | </dl> |
|
|
1303 | |
|
|
1304 | </div> |
|
|
1305 | <h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p> |
|
|
1306 | <div id="C_SUPPORT_CONTENT"> |
|
|
1307 | <p>TBD.</p> |
738 | |
1308 | |
739 | </div> |
1309 | </div> |
740 | <h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> |
1310 | <h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> |
741 | <div id="AUTHOR_CONTENT"> |
1311 | <div id="AUTHOR_CONTENT"> |
742 | <p>Marc Lehmann <libev@schmorp.de>.</p> |
1312 | <p>Marc Lehmann <libev@schmorp.de>.</p> |