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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" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:20:02 2007" /> 9 <meta name="created" content="Mon Nov 12 09:47:14 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 26</ul>
27</li> 27</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</a></li> 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>
30<li><a href="#struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</a></li> 30<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="#ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</a></li> 31<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="#ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</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>
33<li><a href="#ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</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>
34<li><a href="#ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</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>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 35<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>
36</ul> 36</ul>
37</li> 37</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 39<li><a href="#AUTHOR">AUTHOR</a>
40</li> 40</li>
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107 <p>You can find out the major and minor version numbers of the library 107 <p>You can find out the major and minor version numbers of the library
108you linked against by calling the functions <code>ev_version_major</code> and 108you linked against by calling the functions <code>ev_version_major</code> and
109<code>ev_version_minor</code>. If you want, you can compare against the global 109<code>ev_version_minor</code>. If you want, you can compare against the global
110symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the 110symbols <code>EV_VERSION_MAJOR</code> and <code>EV_VERSION_MINOR</code>, which specify the
111version of the library your program was compiled against.</p> 111version of the library your program was compiled against.</p>
112 <p>Usually, its a good idea to terminate if the major versions mismatch, 112 <p>Usually, it's a good idea to terminate if the major versions mismatch,
113as this indicates an incompatible change. Minor versions are usually 113as this indicates an incompatible change. Minor versions are usually
114compatible to older versions, so a larger minor version alone is usually 114compatible to older versions, so a larger minor version alone is usually
115not a problem.</p> 115not a problem.</p>
116 </dd> 116 </dd>
117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
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146<p>If you use threads, a common model is to run the default event loop 146<p>If you use threads, a common model is to run the default event loop
147in your main thread (or in a separate thrad) and for each thread you 147in your main thread (or in a separate thrad) and for each thread you
148create, you also create another event loop. Libev itself does no locking 148create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 149whatsoever, so if you mix calls to the same event loop in different
150threads, make sure you lock (this is usually a bad idea, though, even if 150threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because its hideous and inefficient).</p> 151done correctly, because it's hideous and inefficient).</p>
152<dl> 152<dl>
153 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 153 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154 <dd> 154 <dd>
155 <p>This will initialise the default event loop if it hasn't been initialised 155 <p>This will initialise the default event loop if it hasn't been initialised
156yet and return it. If the default loop could not be initialised, returns 156yet and return it. If the default loop could not be initialised, returns
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161 <p>The flags argument can be used to specify special behaviour or specific 161 <p>The flags argument can be used to specify special behaviour or specific
162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 162backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p>
163 <p>It supports the following flags:</p> 163 <p>It supports the following flags:</p>
164 <p> 164 <p>
165 <dl> 165 <dl>
166 <dt>EVFLAG_AUTO</dt> 166 <dt><code>EVFLAG_AUTO</code></dt>
167 <dd> 167 <dd>
168 <p>The default flags value. Use this if you have no clue (its the right 168 <p>The default flags value. Use this if you have no clue (it's the right
169thing, believe me).</p> 169thing, believe me).</p>
170 </dd> 170 </dd>
171 <dt>EVFLAG_NOENV</dt> 171 <dt><code>EVFLAG_NOENV</code></dt>
172 <dd> 172 <dd>
173 <p>If this flag bit is ored into the flag value (or the program runs setuid 173 <p>If this flag bit is ored into the flag value (or the program runs setuid
174or setgid) then libev will <i>not</i> look at the environment variable 174or setgid) then libev will <i>not</i> look at the environment variable
175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override the flags completely if it is found in the environment. This is 176override the flags completely if it is found in the environment. This is
177useful to try out specific backends to test their performance, or to work 177useful to try out specific backends to test their performance, or to work
178around bugs.</p> 178around bugs.</p>
179 </dd> 179 </dd>
180 <dt>EVMETHOD_SELECT portable select backend</dt> 180 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
181 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 181 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
182 <dt>EVMETHOD_EPOLL linux only</dt> 182 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
183 <dt>EVMETHOD_KQUEUE some bsds only</dt> 183 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
184 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 184 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
185 <dt>EVMETHOD_PORT solaris 10 only</dt> 185 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
186 <dd> 186 <dd>
187 <p>If one or more of these are ored into the flags value, then only these 187 <p>If one or more of these are ored into the flags value, then only these
188backends will be tried (in the reverse order as given here). If one are 188backends will be tried (in the reverse order as given here). If one are
189specified, any backend will do.</p> 189specified, any backend will do.</p>
190 </dd> 190 </dd>
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200 </dd> 200 </dd>
201 <dt>ev_default_destroy ()</dt> 201 <dt>ev_default_destroy ()</dt>
202 <dd> 202 <dd>
203 <p>Destroys the default loop again (frees all memory and kernel state 203 <p>Destroys the default loop again (frees all memory and kernel state
204etc.). This stops all registered event watchers (by not touching them in 204etc.). This stops all registered event watchers (by not touching them in
205any way whatsoever, although you cnanot rely on this :).</p> 205any way whatsoever, although you cannot rely on this :).</p>
206 </dd> 206 </dd>
207 <dt>ev_loop_destroy (loop)</dt> 207 <dt>ev_loop_destroy (loop)</dt>
208 <dd> 208 <dd>
209 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an 209 <p>Like <code>ev_default_destroy</code>, but destroys an event loop created by an
210earlier call to <code>ev_loop_new</code>.</p> 210earlier call to <code>ev_loop_new</code>.</p>
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216after forking, in either the parent or child process (or both, but that 216after forking, in either the parent or child process (or both, but that
217again makes little sense).</p> 217again makes little sense).</p>
218 <p>You <i>must</i> call this function after forking if and only if you want to 218 <p>You <i>must</i> call this function after forking if and only if you want to
219use the event library in both processes. If you just fork+exec, you don't 219use the event library in both processes. If you just fork+exec, you don't
220have to call it.</p> 220have to call it.</p>
221 <p>The function itself is quite fast and its usually not a problem to call 221 <p>The function itself is quite fast and it's usually not a problem to call
222it just in case after a fork. To make this easy, the function will fit in 222it just in case after a fork. To make this easy, the function will fit in
223quite nicely into a call to <code>pthread_atfork</code>:</p> 223quite nicely into a call to <code>pthread_atfork</code>:</p>
224<pre> pthread_atfork (0, 0, ev_default_fork); 224<pre> pthread_atfork (0, 0, ev_default_fork);
225 225
226</pre> 226</pre>
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234 <dt>unsigned int ev_method (loop)</dt> 234 <dt>unsigned int ev_method (loop)</dt>
235 <dd> 235 <dd>
236 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 236 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in
237use.</p> 237use.</p>
238 </dd> 238 </dd>
239 <dt>ev_tstamp = ev_now (loop)</dt> 239 <dt>ev_tstamp ev_now (loop)</dt>
240 <dd> 240 <dd>
241 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 241 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
242got events and started processing them. This timestamp does not change 242got events and started processing them. This timestamp does not change
243as long as callbacks are being processed, and this is also the base time 243as long as callbacks are being processed, and this is also the base time
244used for relative timers. You can treat it as the timestamp of the event 244used for relative timers. You can treat it as the timestamp of the event
… …
251events.</p> 251events.</p>
252 <p>If the flags argument is specified as 0, it will not return until either 252 <p>If the flags argument is specified as 0, it will not return until either
253no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 253no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
254 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 254 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
255those events and any outstanding ones, but will not block your process in 255those events and any outstanding ones, but will not block your process in
256case there are no events.</p> 256case 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 257 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
258neccessary) and will handle those and any outstanding ones. It will block 258neccessary) and will handle those and any outstanding ones. It will block
259your process until at least one new event arrives.</p> 259your process until at least one new event arrives, and will return after
260one iteration of the loop.</p>
260 <p>This flags value could be used to implement alternative looping 261 <p>This flags value could be used to implement alternative looping
261constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 262constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
262more generic mechanism.</p> 263more generic mechanism.</p>
263 </dd> 264 </dd>
264 <dt>ev_unloop (loop, how)</dt> 265 <dt>ev_unloop (loop, how)</dt>
265 <dd> 266 <dd>
266 <p>Can be used to make a call to <code>ev_loop</code> return early. The <code>how</code> argument 267 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
268has processed all outstanding events). The <code>how</code> argument must be either
267must be either <code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> 269<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or
268call return, or <code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> 270<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
269calls return.</p>
270 </dd> 271 </dd>
271 <dt>ev_ref (loop)</dt> 272 <dt>ev_ref (loop)</dt>
272 <dt>ev_unref (loop)</dt> 273 <dt>ev_unref (loop)</dt>
273 <dd> 274 <dd>
274 <p>Ref/unref can be used to add or remove a refcount on the event loop: Every 275 <p>Ref/unref can be used to add or remove a reference count on the event
275watcher keeps one reference. If you have a long-runing watcher you never 276loop: Every watcher keeps one reference, and as long as the reference
276unregister that should not keep ev_loop from running, ev_unref() after 277count is nonzero, <code>ev_loop</code> will not return on its own. If you have
277starting, and ev_ref() before stopping it. Libev itself uses this for 278a watcher you never unregister that should not keep <code>ev_loop</code> from
278example for its internal signal pipe: It is not visible to you as a user 279returning, ev_unref() after starting, and ev_ref() before stopping it. For
279and should not keep <code>ev_loop</code> from exiting if the work is done. It is 280example, libev itself uses this for its internal signal pipe: It is not
280also an excellent way to do this for generic recurring timers or from 281visible to the libev user and should not keep <code>ev_loop</code> from exiting if
281within third-party libraries. Just remember to unref after start and ref 282no event watchers registered by it are active. It is also an excellent
282before stop.</p> 283way to do this for generic recurring timers or from within third-party
284libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
283 </dd> 285 </dd>
284</dl> 286</dl>
285 287
286</div> 288</div>
287<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 289<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
288<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 290<div id="ANATOMY_OF_A_WATCHER_CONTENT">
289<p>A watcher is a structure that you create and register to record your 291<p>A watcher is a structure that you create and register to record your
290interest in some event. For instance, if you want to wait for STDIN to 292interest in some event. For instance, if you want to wait for STDIN to
291become readable, you would create an ev_io watcher for that:</p> 293become readable, you would create an <code>ev_io</code> watcher for that:</p>
292<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 294<pre> static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
293 { 295 {
294 ev_io_stop (w); 296 ev_io_stop (w);
295 ev_unloop (loop, EVUNLOOP_ALL); 297 ev_unloop (loop, EVUNLOOP_ALL);
296 } 298 }
… …
320*)</code>), and you can stop watching for events at any time by calling the 322*)</code>), and you can stop watching for events at any time by calling the
321corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 323corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
322<p>As long as your watcher is active (has been started but not stopped) you 324<p>As long as your watcher is active (has been started but not stopped) you
323must not touch the values stored in it. Most specifically you must never 325must not touch the values stored in it. Most specifically you must never
324reinitialise it or call its set method.</p> 326reinitialise it or call its set method.</p>
325<p>You cna check whether an event is active by calling the <code>ev_is_active 327<p>You can check whether an event is active by calling the <code>ev_is_active
326(watcher *)</code> macro. To see whether an event is outstanding (but the 328(watcher *)</code> macro. To see whether an event is outstanding (but the
327callback for it has not been called yet) you cna use the <code>ev_is_pending 329callback for it has not been called yet) you can use the <code>ev_is_pending
328(watcher *)</code> macro.</p> 330(watcher *)</code> macro.</p>
329<p>Each and every callback receives the event loop pointer as first, the 331<p>Each and every callback receives the event loop pointer as first, the
330registered watcher structure as second, and a bitset of received events as 332registered watcher structure as second, and a bitset of received events as
331third argument.</p> 333third argument.</p>
332<p>The rceeived events usually include a single bit per event type received 334<p>The received events usually include a single bit per event type received
333(you can receive multiple events at the same time). The possible bit masks 335(you can receive multiple events at the same time). The possible bit masks
334are:</p> 336are:</p>
335<dl> 337<dl>
336 <dt>EV_READ</dt> 338 <dt><code>EV_READ</code></dt>
337 <dt>EV_WRITE</dt> 339 <dt><code>EV_WRITE</code></dt>
338 <dd> 340 <dd>
339 <p>The file descriptor in the ev_io watcher has become readable and/or 341 <p>The file descriptor in the <code>ev_io</code> watcher has become readable and/or
340writable.</p> 342writable.</p>
341 </dd> 343 </dd>
342 <dt>EV_TIMEOUT</dt> 344 <dt><code>EV_TIMEOUT</code></dt>
343 <dd>
344 <p>The ev_timer watcher has timed out.</p>
345 </dd> 345 <dd>
346 <dt>EV_PERIODIC</dt> 346 <p>The <code>ev_timer</code> watcher has timed out.</p>
347 <dd> 347 </dd>
348 <p>The ev_periodic watcher has timed out.</p> 348 <dt><code>EV_PERIODIC</code></dt>
349 </dd> 349 <dd>
350 <dt>EV_SIGNAL</dt> 350 <p>The <code>ev_periodic</code> watcher has timed out.</p>
351 <dd> 351 </dd>
352 <dt><code>EV_SIGNAL</code></dt>
353 <dd>
352 <p>The signal specified in the ev_signal watcher has been received by a thread.</p> 354 <p>The signal specified in the <code>ev_signal</code> watcher has been received by a thread.</p>
353 </dd>
354 <dt>EV_CHILD</dt>
355 <dd> 355 </dd>
356 <dt><code>EV_CHILD</code></dt>
357 <dd>
356 <p>The pid specified in the ev_child watcher has received a status change.</p> 358 <p>The pid specified in the <code>ev_child</code> watcher has received a status change.</p>
357 </dd>
358 <dt>EV_IDLE</dt>
359 <dd> 359 </dd>
360 <dt><code>EV_IDLE</code></dt>
361 <dd>
360 <p>The ev_idle watcher has determined that you have nothing better to do.</p> 362 <p>The <code>ev_idle</code> watcher has determined that you have nothing better to do.</p>
361 </dd>
362 <dt>EV_PREPARE</dt>
363 <dt>EV_CHECK</dt>
364 <dd> 363 </dd>
364 <dt><code>EV_PREPARE</code></dt>
365 <dt><code>EV_CHECK</code></dt>
366 <dd>
365 <p>All ev_prepare watchers are invoked just <i>before</i> <code>ev_loop</code> starts 367 <p>All <code>ev_prepare</code> watchers are invoked just <i>before</i> <code>ev_loop</code> starts
366to gather new events, and all ev_check watchers are invoked just after 368to gather new events, and all <code>ev_check</code> watchers are invoked just after
367<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any 369<code>ev_loop</code> has gathered them, but before it invokes any callbacks for any
368received events. Callbacks of both watcher types can start and stop as 370received events. Callbacks of both watcher types can start and stop as
369many watchers as they want, and all of them will be taken into account 371many watchers as they want, and all of them will be taken into account
370(for example, a ev_prepare watcher might start an idle watcher to keep 372(for example, a <code>ev_prepare</code> watcher might start an idle watcher to keep
371<code>ev_loop</code> from blocking).</p> 373<code>ev_loop</code> from blocking).</p>
372 </dd> 374 </dd>
373 <dt>EV_ERROR</dt> 375 <dt><code>EV_ERROR</code></dt>
374 <dd> 376 <dd>
375 <p>An unspecified error has occured, the watcher has been stopped. This might 377 <p>An unspecified error has occured, the watcher has been stopped. This might
376happen because the watcher could not be properly started because libev 378happen because the watcher could not be properly started because libev
377ran out of memory, a file descriptor was found to be closed or any other 379ran out of memory, a file descriptor was found to be closed or any other
378problem. You best act on it by reporting the problem and somehow coping 380problem. You best act on it by reporting the problem and somehow coping
… …
387 389
388</div> 390</div>
389<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 391<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
390<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 392<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
391<p>Each watcher has, by default, a member <code>void *data</code> that you can change 393<p>Each watcher has, by default, a member <code>void *data</code> that you can change
392and read at any time, libev will completely ignore it. This cna be used 394and read at any time, libev will completely ignore it. This can be used
393to associate arbitrary data with your watcher. If you need more data and 395to associate arbitrary data with your watcher. If you need more data and
394don't want to allocate memory and store a pointer to it in that data 396don't want to allocate memory and store a pointer to it in that data
395member, you can also &quot;subclass&quot; the watcher type and provide your own 397member, you can also &quot;subclass&quot; the watcher type and provide your own
396data:</p> 398data:</p>
397<pre> struct my_io 399<pre> struct my_io
… …
424<div id="WATCHER_TYPES_CONTENT"> 426<div id="WATCHER_TYPES_CONTENT">
425<p>This section describes each watcher in detail, but will not repeat 427<p>This section describes each watcher in detail, but will not repeat
426information given in the last section.</p> 428information given in the last section.</p>
427 429
428</div> 430</div>
429<h2 id="struct_ev_io_is_my_file_descriptor_r">struct ev_io - is my file descriptor readable or writable</h2> 431<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
430<div id="struct_ev_io_is_my_file_descriptor_r-2"> 432<div id="code_ev_io_code_is_this_file_descrip-2">
431<p>I/O watchers check whether a file descriptor is readable or writable 433<p>I/O watchers check whether a file descriptor is readable or writable
432in each iteration of the event loop (This behaviour is called 434in each iteration of the event loop (This behaviour is called
433level-triggering because you keep receiving events as long as the 435level-triggering because you keep receiving events as long as the
434condition persists. Remember you cna stop the watcher if you don't want to 436condition persists. Remember you can stop the watcher if you don't want to
435act on the event and neither want to receive future events).</p> 437act on the event and neither want to receive future events).</p>
436<p>In general you can register as many read and/or write event watchers oer 438<p>In general you can register as many read and/or write event watchers oer
437fd as you want (as long as you don't confuse yourself). Setting all file 439fd as you want (as long as you don't confuse yourself). Setting all file
438descriptors to non-blocking mode is also usually a good idea (but not 440descriptors to non-blocking mode is also usually a good idea (but not
439required if you know what you are doing).</p> 441required if you know what you are doing).</p>
… …
446EVMETHOD_POLL).</p> 448EVMETHOD_POLL).</p>
447<dl> 449<dl>
448 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
449 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 451 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
450 <dd> 452 <dd>
451 <p>Configures an ev_io watcher. The fd is the file descriptor to rceeive 453 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
452events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 454events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
453EV_WRITE</code> to receive the given events.</p> 455EV_WRITE</code> to receive the given events.</p>
454 </dd> 456 </dd>
455</dl> 457</dl>
456 458
457</div> 459</div>
458<h2 id="struct_ev_timer_relative_and_optiona">struct ev_timer - relative and optionally recurring timeouts</h2> 460<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
459<div id="struct_ev_timer_relative_and_optiona-2"> 461<div id="code_ev_timer_code_relative_and_opti-2">
460<p>Timer watchers are simple relative timers that generate an event after a 462<p>Timer watchers are simple relative timers that generate an event after a
461given time, and optionally repeating in regular intervals after that.</p> 463given time, and optionally repeating in regular intervals after that.</p>
462<p>The timers are based on real time, that is, if you register an event that 464<p>The timers are based on real time, that is, if you register an event that
463times out after an hour and youreset your system clock to last years 465times out after an hour and youreset your system clock to last years
464time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
465detecting time jumps is hard, and soem inaccuracies are unavoidable (the 467detecting time jumps is hard, and soem inaccuracies are unavoidable (the
466monotonic clock option helps a lot here).</p> 468monotonic clock option helps a lot here).</p>
469<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
470time. This is usually the right thing as this timestamp refers to the time
471of the event triggering whatever timeout you are modifying/starting. If
472you suspect event processing to be delayed and you *need* to base the timeout
473ion the current time, use something like this to adjust for this:</p>
474<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
475
476</pre>
467<dl> 477<dl>
468 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 478 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
469 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 479 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
470 <dd> 480 <dd>
471 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 481 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
487value), or reset the running timer to the repeat value.</p> 497value), or reset the running timer to the repeat value.</p>
488 <p>This sounds a bit complicated, but here is a useful and typical 498 <p>This sounds a bit complicated, but here is a useful and typical
489example: Imagine you have a tcp connection and you want a so-called idle 499example: Imagine you have a tcp connection and you want a so-called idle
490timeout, that is, you want to be called when there have been, say, 60 500timeout, that is, you want to be called when there have been, say, 60
491seconds of inactivity on the socket. The easiest way to do this is to 501seconds of inactivity on the socket. The easiest way to do this is to
492configure an ev_timer with after=repeat=60 and calling ev_timer_again each 502configure an <code>ev_timer</code> with after=repeat=60 and calling ev_timer_again each
493time you successfully read or write some data. If you go into an idle 503time you successfully read or write some data. If you go into an idle
494state where you do not expect data to travel on the socket, you can stop 504state where you do not expect data to travel on the socket, you can stop
495the timer, and again will automatically restart it if need be.</p> 505the timer, and again will automatically restart it if need be.</p>
496 </dd> 506 </dd>
497</dl> 507</dl>
498 508
499</div> 509</div>
500<h2 id="ev_periodic_to_cron_or_not_to_cron_i">ev_periodic - to cron or not to cron it</h2> 510<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
501<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 511<div id="code_ev_periodic_code_to_cron_or_not-2">
502<p>Periodic watchers are also timers of a kind, but they are very versatile 512<p>Periodic watchers are also timers of a kind, but they are very versatile
503(and unfortunately a bit complex).</p> 513(and unfortunately a bit complex).</p>
504<p>Unlike ev_timer's, they are not based on real time (or relative time) 514<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
505but on wallclock time (absolute time). You can tell a periodic watcher 515but on wallclock time (absolute time). You can tell a periodic watcher
506to trigger &quot;at&quot; some specific point in time. For example, if you tell a 516to trigger &quot;at&quot; some specific point in time. For example, if you tell a
507periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now () 517periodic watcher to trigger in 10 seconds (by specifiying e.g. c&lt;ev_now ()
508+ 10.&gt;) and then reset your system clock to the last year, then it will 518+ 10.&gt;) and then reset your system clock to the last year, then it will
509take a year to trigger the event (unlike an ev_timer, which would trigger 519take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
510roughly 10 seconds later and of course not if you reset your system time 520roughly 10 seconds later and of course not if you reset your system time
511again).</p> 521again).</p>
512<p>They can also be used to implement vastly more complex timers, such as 522<p>They can also be used to implement vastly more complex timers, such as
513triggering an event on eahc midnight, local time.</p> 523triggering an event on eahc midnight, local time.</p>
514<dl> 524<dl>
… …
540<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 550<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
541 551
542</pre> 552</pre>
543 <p>This doesn't mean there will always be 3600 seconds in between triggers, 553 <p>This doesn't mean there will always be 3600 seconds in between triggers,
544but only that the the callback will be called when the system time shows a 554but only that the the callback will be called when the system time shows a
545full hour (UTC), or more correct, when the system time is evenly divisible 555full hour (UTC), or more correctly, when the system time is evenly divisible
546by 3600.</p> 556by 3600.</p>
547 <p>Another way to think about it (for the mathematically inclined) is that 557 <p>Another way to think about it (for the mathematically inclined) is that
548ev_periodic will try to run the callback in this mode at the next possible 558<code>ev_periodic</code> will try to run the callback in this mode at the next possible
549time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
550 </dd> 560 </dd>
551 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
552 <dd> 562 <dd>
553 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
554ignored. Instead, each time the periodic watcher gets scheduled, the 564ignored. Instead, each time the periodic watcher gets scheduled, the
555reschedule callback will be called with the watcher as first, and the 565reschedule callback will be called with the watcher as first, and the
556current time as second argument.</p> 566current time as second argument.</p>
557 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other
558periodic watcher, ever, or make any event loop modificstions</i>. If you need 568periodic watcher, ever, or make any event loop modifications</i>. If you need
559to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 569to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p>
570 <p>Also, <i>this callback must always return a time that is later than the
571passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
560 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 572 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
561ev_tstamp now)&gt;, e.g.:</p> 573ev_tstamp now)</code>, e.g.:</p>
562<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 574<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
563 { 575 {
564 return now + 60.; 576 return now + 60.;
565 } 577 }
566 578
… …
585program when the crontabs have changed).</p> 597program when the crontabs have changed).</p>
586 </dd> 598 </dd>
587</dl> 599</dl>
588 600
589</div> 601</div>
590<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 602<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
591<div id="ev_signal_signal_me_when_a_signal_ge-2"> 603<div id="code_ev_signal_code_signal_me_when_a-2">
592<p>Signal watchers will trigger an event when the process receives a specific 604<p>Signal watchers will trigger an event when the process receives a specific
593signal one or more times. Even though signals are very asynchronous, libev 605signal one or more times. Even though signals are very asynchronous, libev
594will try its best to deliver signals synchronously, i.e. as part of the 606will try it's best to deliver signals synchronously, i.e. as part of the
595normal event processing, like any other event.</p> 607normal event processing, like any other event.</p>
596<p>You cna configure as many watchers as you like per signal. Only when the 608<p>You can configure as many watchers as you like per signal. Only when the
597first watcher gets started will libev actually register a signal watcher 609first watcher gets started will libev actually register a signal watcher
598with the kernel (thus it coexists with your own signal handlers as long 610with the kernel (thus it coexists with your own signal handlers as long
599as you don't register any with libev). Similarly, when the last signal 611as you don't register any with libev). Similarly, when the last signal
600watcher for a signal is stopped libev will reset the signal handler to 612watcher for a signal is stopped libev will reset the signal handler to
601SIG_DFL (regardless of what it was set to before).</p> 613SIG_DFL (regardless of what it was set to before).</p>
… …
607of the <code>SIGxxx</code> constants).</p> 619of the <code>SIGxxx</code> constants).</p>
608 </dd> 620 </dd>
609</dl> 621</dl>
610 622
611</div> 623</div>
612<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 624<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
613<div id="ev_child_wait_for_pid_status_changes-2"> 625<div id="code_ev_child_code_wait_for_pid_stat-2">
614<p>Child watchers trigger when your process receives a SIGCHLD in response to 626<p>Child watchers trigger when your process receives a SIGCHLD in response to
615some child status changes (most typically when a child of yours dies).</p> 627some child status changes (most typically when a child of yours dies).</p>
616<dl> 628<dl>
617 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 629 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
618 <dt>ev_child_set (ev_child *, int pid)</dt> 630 <dt>ev_child_set (ev_child *, int pid)</dt>
619 <dd> 631 <dd>
620 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 632 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
621<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 633<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
622at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 634at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
623the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 635the status word (use the macros from <code>sys/wait.h</code> and see your systems
636<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
624contains the pid of the process causing the status change.</p> 637process causing the status change.</p>
625 </dd> 638 </dd>
626</dl> 639</dl>
627 640
628</div> 641</div>
629<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 642<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
630<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 643<div id="code_ev_idle_code_when_you_ve_got_no-2">
631<p>Idle watchers trigger events when there are no other I/O or timer (or 644<p>Idle watchers trigger events when there are no other events are pending
632periodic) events pending. That is, as long as your process is busy 645(prepare, check and other idle watchers do not count). That is, as long
633handling sockets or timeouts it will not be called. But when your process 646as your process is busy handling sockets or timeouts (or even signals,
634is idle all idle watchers are being called again and again - until 647imagine) it will not be triggered. But when your process is idle all idle
648watchers are being called again and again, once per event loop iteration -
635stopped, that is, or your process receives more events.</p> 649until stopped, that is, or your process receives more events and becomes
650busy.</p>
636<p>The most noteworthy effect is that as long as any idle watchers are 651<p>The most noteworthy effect is that as long as any idle watchers are
637active, the process will not block when waiting for new events.</p> 652active, the process will not block when waiting for new events.</p>
638<p>Apart from keeping your process non-blocking (which is a useful 653<p>Apart from keeping your process non-blocking (which is a useful
639effect on its own sometimes), idle watchers are a good place to do 654effect on its own sometimes), idle watchers are a good place to do
640&quot;pseudo-background processing&quot;, or delay processing stuff to after the 655&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
647believe me.</p> 662believe me.</p>
648 </dd> 663 </dd>
649</dl> 664</dl>
650 665
651</div> 666</div>
652<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 667<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
653<div id="prepare_and_check_your_hooks_into_th-2"> 668<div id="code_ev_prepare_code_and_code_ev_che-2">
654<p>Prepare and check watchers usually (but not always) are used in 669<p>Prepare and check watchers are usually (but not always) used in tandem:
655tandom. Prepare watchers get invoked before the process blocks and check 670Prepare watchers get invoked before the process blocks and check watchers
656watchers afterwards.</p> 671afterwards.</p>
657<p>Their main purpose is to integrate other event mechanisms into libev. This 672<p>Their main purpose is to integrate other event mechanisms into libev. This
658could be used, for example, to track variable changes, implement your own 673could be used, for example, to track variable changes, implement your own
659watchers, integrate net-snmp or a coroutine library and lots more.</p> 674watchers, integrate net-snmp or a coroutine library and lots more.</p>
660<p>This is done by examining in each prepare call which file descriptors need 675<p>This is done by examining in each prepare call which file descriptors need
661to be watched by the other library, registering ev_io watchers for them 676to be watched by the other library, registering <code>ev_io</code> watchers for
662and starting an ev_timer watcher for any timeouts (many libraries provide 677them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
663just this functionality). Then, in the check watcher you check for any 678provide just this functionality). Then, in the check watcher you check for
664events that occured (by making your callbacks set soem flags for example) 679any events that occured (by checking the pending status of all watchers
665and call back into the library.</p> 680and stopping them) and call back into the library. The I/O and timer
681callbacks will never actually be called (but must be valid neverthelles,
682because you never know, you know?).</p>
666<p>As another example, the perl Coro module uses these hooks to integrate 683<p>As another example, the Perl Coro module uses these hooks to integrate
667coroutines into libev programs, by yielding to other active coroutines 684coroutines into libev programs, by yielding to other active coroutines
668during each prepare and only letting the process block if no coroutines 685during each prepare and only letting the process block if no coroutines
669are ready to run.</p> 686are ready to run (its actually more complicated, it only runs coroutines
687with priority higher than the event loop and one lower priority once,
688using idle watchers to keep the event loop from blocking if lower-priority
689coroutines exist, thus mapping low-priority coroutines to idle/background
690tasks).</p>
670<dl> 691<dl>
671 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 692 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
672 <dt>ev_check_init (ev_check *, callback)</dt> 693 <dt>ev_check_init (ev_check *, callback)</dt>
673 <dd> 694 <dd>
674 <p>Initialises and configures the prepare or check watcher - they have no 695 <p>Initialises and configures the prepare or check watcher - they have no
675parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 696parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
676macros, but using them is utterly, utterly pointless.</p> 697macros, but using them is utterly, utterly and completely pointless.</p>
677 </dd> 698 </dd>
678</dl> 699</dl>
679 700
680</div> 701</div>
681<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 702<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
682<div id="OTHER_FUNCTIONS_CONTENT"> 703<div id="OTHER_FUNCTIONS_CONTENT">
683<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 704<p>There are some other functions of possible interest. Described. Here. Now.</p>
684<dl> 705<dl>
685 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 706 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
686 <dd> 707 <dd>
687 <p>This function combines a simple timer and an I/O watcher, calls your 708 <p>This function combines a simple timer and an I/O watcher, calls your
688callback on whichever event happens first and automatically stop both 709callback on whichever event happens first and automatically stop both
689watchers. This is useful if you want to wait for a single event on an fd 710watchers. This is useful if you want to wait for a single event on an fd
690or timeout without havign to allocate/configure/start/stop/free one or 711or timeout without havign to allocate/configure/start/stop/free one or
691more watchers yourself.</p> 712more watchers yourself.</p>
692 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 713 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
693ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 714is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
694will be craeted and started.</p> 715<code>events</code> set will be craeted and started.</p>
695 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 716 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
696started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 717started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
697= 0) will be started.</p> 718repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
719dubious value.</p>
698 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 720 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
699gets passed an events set (normally a combination of EV_ERROR, EV_READ, 721passed an events set like normal event callbacks (with a combination of
700EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 722<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
723value passed to <code>ev_once</code>:</p>
701<pre> static void stdin_ready (int revents, void *arg) 724<pre> static void stdin_ready (int revents, void *arg)
702 { 725 {
703 if (revents &amp; EV_TIMEOUT) 726 if (revents &amp; EV_TIMEOUT)
704 /* doh, nothing entered */ 727 /* doh, nothing entered */;
705 else if (revents &amp; EV_READ) 728 else if (revents &amp; EV_READ)
706 /* stdin might have data for us, joy! */ 729 /* stdin might have data for us, joy! */;
707 } 730 }
708 731
709 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 732 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
710 733
711</pre> 734</pre>
712 </dd> 735 </dd>
713 <dt>ev_feed_event (loop, watcher, int events)</dt> 736 <dt>ev_feed_event (loop, watcher, int events)</dt>
714 <dd> 737 <dd>
715 <p>Feeds the given event set into the event loop, as if the specified event 738 <p>Feeds the given event set into the event loop, as if the specified event
716has happened for the specified watcher (which must be a pointer to an 739had happened for the specified watcher (which must be a pointer to an
717initialised but not necessarily active event watcher).</p> 740initialised but not necessarily started event watcher).</p>
718 </dd> 741 </dd>
719 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 742 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
720 <dd> 743 <dd>
721 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 744 <p>Feed an event on the given fd, as if a file descriptor backend detected
745the given events it.</p>
722 </dd> 746 </dd>
723 <dt>ev_feed_signal_event (loop, int signum)</dt> 747 <dt>ev_feed_signal_event (loop, int signum)</dt>
724 <dd> 748 <dd>
725 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 749 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
726 </dd> 750 </dd>

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