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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 09:16:01 2007" /> 9 <meta name="created" content="Mon Nov 12 09:32:26 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_my_file_descripto"><code>ev_io</code> - is my 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 it</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="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the 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>
… …
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>
… …
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
157false. If it already was initialised it simply returns it (and ignores the 157false. If it already was initialised it simply returns it (and ignores the
158flags).</p> 158flags).</p>
159 <p>If you don't know what event loop to use, use the one returned from this 159 <p>If you don't know what event loop to use, use the one returned from this
160function.</p> 160function.</p>
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 then libev will <i>not</i> look 173 <p>If this flag bit is ored into the flag value (or the program runs setuid
174at the environment variable <code>LIBEV_FLAGS</code>. Otherwise (the default), this 174or setgid) then libev will <i>not</i> look at the environment variable
175environment variable will override the flags completely. This is useful 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
176to try out specific backends to tets their performance, or to work around 177useful to try out specific backends to test their performance, or to work
177bugs.</p> 178around bugs.</p>
178 </dd> 179 </dd>
179 <dt>EVMETHOD_SELECT portable select backend</dt> 180 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt>
180 <dt>EVMETHOD_POLL poll backend (everywhere except windows)</dt> 181 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
181 <dt>EVMETHOD_EPOLL linux only</dt> 182 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
182 <dt>EVMETHOD_KQUEUE some bsds only</dt> 183 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
183 <dt>EVMETHOD_DEVPOLL solaris 8 only</dt> 184 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
184 <dt>EVMETHOD_PORT solaris 10 only</dt> 185 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
185 <dd> 186 <dd>
186 <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
187backends 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
188specified, any backend will do.</p> 189specified, any backend will do.</p>
189 </dd> 190 </dd>
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199 </dd> 200 </dd>
200 <dt>ev_default_destroy ()</dt> 201 <dt>ev_default_destroy ()</dt>
201 <dd> 202 <dd>
202 <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
203etc.). This stops all registered event watchers (by not touching them in 204etc.). This stops all registered event watchers (by not touching them in
204any way whatsoever, although you cnanot rely on this :).</p> 205any way whatsoever, although you cannot rely on this :).</p>
205 </dd> 206 </dd>
206 <dt>ev_loop_destroy (loop)</dt> 207 <dt>ev_loop_destroy (loop)</dt>
207 <dd> 208 <dd>
208 <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
209earlier call to <code>ev_loop_new</code>.</p> 210earlier call to <code>ev_loop_new</code>.</p>
… …
215after 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
216again makes little sense).</p> 217again makes little sense).</p>
217 <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
218use 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
219have to call it.</p> 220have to call it.</p>
220 <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
221it 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
222quite nicely into a call to <code>pthread_atfork</code>:</p> 223quite nicely into a call to <code>pthread_atfork</code>:</p>
223<pre> pthread_atfork (0, 0, ev_default_fork); 224<pre> pthread_atfork (0, 0, ev_default_fork);
224 225
225</pre> 226</pre>
… …
233 <dt>unsigned int ev_method (loop)</dt> 234 <dt>unsigned int ev_method (loop)</dt>
234 <dd> 235 <dd>
235 <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
236use.</p> 237use.</p>
237 </dd> 238 </dd>
238 <dt>ev_tstamp = ev_now (loop)</dt> 239 <dt>ev_tstamp ev_now (loop)</dt>
239 <dd> 240 <dd>
240 <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
241got events and started processing them. This timestamp does not change 242got events and started processing them. This timestamp does not change
242as 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
243used 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
… …
250events.</p> 251events.</p>
251 <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
252no 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>
253 <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
254those 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
255case there are no events.</p> 256case there are no events and will return after one iteration of the loop.</p>
256 <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
257neccessary) and will handle those and any outstanding ones. It will block 258neccessary) and will handle those and any outstanding ones. It will block
258your 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>
259 <p>This flags value could be used to implement alternative looping 261 <p>This flags value could be used to implement alternative looping
260constructs, 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
261more generic mechanism.</p> 263more generic mechanism.</p>
262 </dd> 264 </dd>
263 <dt>ev_unloop (loop, how)</dt> 265 <dt>ev_unloop (loop, how)</dt>
264 <dd> 266 <dd>
265 <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
266must 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
267call 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>
268calls return.</p>
269 </dd> 271 </dd>
270 <dt>ev_ref (loop)</dt> 272 <dt>ev_ref (loop)</dt>
271 <dt>ev_unref (loop)</dt> 273 <dt>ev_unref (loop)</dt>
272 <dd> 274 <dd>
273 <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
274watcher keeps one reference. If you have a long-runing watcher you never 276loop: Every watcher keeps one reference, and as long as the reference
275unregister 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
276starting, 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
277example 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
278and 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
279also 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
280within third-party libraries. Just remember to unref after start and ref 282no event watchers registered by it are active. It is also an excellent
281before 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>
282 </dd> 285 </dd>
283</dl> 286</dl>
284 287
285</div> 288</div>
286<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>
287<div id="ANATOMY_OF_A_WATCHER_CONTENT"> 290<div id="ANATOMY_OF_A_WATCHER_CONTENT">
288<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
289interest 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
290become 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>
291<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)
292 { 295 {
293 ev_io_stop (w); 296 ev_io_stop (w);
294 ev_unloop (loop, EVUNLOOP_ALL); 297 ev_unloop (loop, EVUNLOOP_ALL);
295 } 298 }
… …
330third argument.</p> 333third argument.</p>
331<p>The rceeived events usually include a single bit per event type received 334<p>The rceeived events usually include a single bit per event type received
332(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
333are:</p> 336are:</p>
334<dl> 337<dl>
335 <dt>EV_READ</dt> 338 <dt><code>EV_READ</code></dt>
336 <dt>EV_WRITE</dt> 339 <dt><code>EV_WRITE</code></dt>
337 <dd> 340 <dd>
338 <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
339writable.</p> 342writable.</p>
340 </dd> 343 </dd>
341 <dt>EV_TIMEOUT</dt> 344 <dt><code>EV_TIMEOUT</code></dt>
342 <dd>
343 <p>The ev_timer watcher has timed out.</p>
344 </dd> 345 <dd>
345 <dt>EV_PERIODIC</dt> 346 <p>The <code>ev_timer</code> watcher has timed out.</p>
346 <dd> 347 </dd>
347 <p>The ev_periodic watcher has timed out.</p> 348 <dt><code>EV_PERIODIC</code></dt>
348 </dd> 349 <dd>
349 <dt>EV_SIGNAL</dt> 350 <p>The <code>ev_periodic</code> watcher has timed out.</p>
350 <dd> 351 </dd>
352 <dt><code>EV_SIGNAL</code></dt>
353 <dd>
351 <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>
352 </dd>
353 <dt>EV_CHILD</dt>
354 <dd> 355 </dd>
356 <dt><code>EV_CHILD</code></dt>
357 <dd>
355 <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>
356 </dd>
357 <dt>EV_IDLE</dt>
358 <dd> 359 </dd>
360 <dt><code>EV_IDLE</code></dt>
361 <dd>
359 <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>
360 </dd>
361 <dt>EV_PREPARE</dt>
362 <dt>EV_CHECK</dt>
363 <dd> 363 </dd>
364 <dt><code>EV_PREPARE</code></dt>
365 <dt><code>EV_CHECK</code></dt>
366 <dd>
364 <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
365to 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
366<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
367received events. Callbacks of both watcher types can start and stop as 370received events. Callbacks of both watcher types can start and stop as
368many 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
369(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
370<code>ev_loop</code> from blocking).</p> 373<code>ev_loop</code> from blocking).</p>
371 </dd> 374 </dd>
372 <dt>EV_ERROR</dt> 375 <dt><code>EV_ERROR</code></dt>
373 <dd> 376 <dd>
374 <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
375happen because the watcher could not be properly started because libev 378happen because the watcher could not be properly started because libev
376ran 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
377problem. 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
… …
423<div id="WATCHER_TYPES_CONTENT"> 426<div id="WATCHER_TYPES_CONTENT">
424<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
425information given in the last section.</p> 428information given in the last section.</p>
426 429
427</div> 430</div>
428<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_my_file_descripto"><code>ev_io</code> - is my file descriptor readable or writable</h2>
429<div id="struct_ev_io_is_my_file_descriptor_r-2"> 432<div id="code_ev_io_code_is_my_file_descripto-2">
430<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
431in each iteration of the event loop (This behaviour is called 434in each iteration of the event loop (This behaviour is called
432level-triggering because you keep receiving events as long as the 435level-triggering because you keep receiving events as long as the
433condition persists. Remember you cna stop the watcher if you don't want to 436condition persists. Remember you cna stop the watcher if you don't want to
434act on the event and neither want to receive future events).</p> 437act 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
439fd as you want (as long as you don't confuse yourself). Setting all file
440descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p>
442<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
444descriptors correctly if you register interest in two or more fds pointing
445to the same file/socket etc. description.</p>
446<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
448EVMETHOD_POLL).</p>
435<dl> 449<dl>
436 <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>
437 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 451 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
438 <dd> 452 <dd>
439 <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
440events 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 |
441EV_WRITE</code> to receive the given events.</p> 455EV_WRITE</code> to receive the given events.</p>
442 </dd> 456 </dd>
443</dl> 457</dl>
444 458
445</div> 459</div>
446<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>
447<div id="struct_ev_timer_relative_and_optiona-2"> 461<div id="code_ev_timer_code_relative_and_opti-2">
448<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
449given time, and optionally repeating in regular intervals after that.</p> 463given time, and optionally repeating in regular intervals after that.</p>
450<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
451times 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
452time, 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
453detecting time jumps is hard, and soem inaccuracies are unavoidable (the 467detecting time jumps is hard, and soem inaccuracies are unavoidable (the
454monotonic 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>
455<dl> 477<dl>
456 <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>
457 <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>
458 <dd> 480 <dd>
459 <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
… …
475value), or reset the running timer to the repeat value.</p> 497value), or reset the running timer to the repeat value.</p>
476 <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
477example: 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
478timeout, 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
479seconds 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
480configure 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
481time 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
482state 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
483the timer, and again will automatically restart it if need be.</p> 505the timer, and again will automatically restart it if need be.</p>
484 </dd> 506 </dd>
485</dl> 507</dl>
486 508
487</div> 509</div>
488<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 it</h2>
489<div id="ev_periodic_to_cron_or_not_to_cron_i-2"> 511<div id="code_ev_periodic_code_to_cron_or_not-2">
490<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
491(and unfortunately a bit complex).</p> 513(and unfortunately a bit complex).</p>
492<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)
493but on wallclock time (absolute time). You can tell a periodic watcher 515but on wallclock time (absolute time). You can tell a periodic watcher
494to 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
495periodic 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 ()
496+ 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
497take 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
498roughly 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
499again).</p> 521again).</p>
500<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
501triggering an event on eahc midnight, local time.</p> 523triggering an event on eahc midnight, local time.</p>
502<dl> 524<dl>
… …
531 <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,
532but 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
533full hour (UTC), or more correct, when the system time is evenly divisible 555full hour (UTC), or more correct, when the system time is evenly divisible
534by 3600.</p> 556by 3600.</p>
535 <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
536ev_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
537time 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>
538 </dd> 560 </dd>
539 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 561 <dt>* manual reschedule mode (reschedule_cb = callback)</dt>
540 <dd> 562 <dd>
541 <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
… …
573program when the crontabs have changed).</p> 595program when the crontabs have changed).</p>
574 </dd> 596 </dd>
575</dl> 597</dl>
576 598
577</div> 599</div>
578<h2 id="ev_signal_signal_me_when_a_signal_ge">ev_signal - signal me when a signal gets signalled</h2> 600<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
579<div id="ev_signal_signal_me_when_a_signal_ge-2"> 601<div id="code_ev_signal_code_signal_me_when_a-2">
580<p>Signal watchers will trigger an event when the process receives a specific 602<p>Signal watchers will trigger an event when the process receives a specific
581signal one or more times. Even though signals are very asynchronous, libev 603signal one or more times. Even though signals are very asynchronous, libev
582will try its best to deliver signals synchronously, i.e. as part of the 604will try it's best to deliver signals synchronously, i.e. as part of the
583normal event processing, like any other event.</p> 605normal event processing, like any other event.</p>
584<p>You cna configure as many watchers as you like per signal. Only when the 606<p>You cna configure as many watchers as you like per signal. Only when the
585first watcher gets started will libev actually register a signal watcher 607first watcher gets started will libev actually register a signal watcher
586with the kernel (thus it coexists with your own signal handlers as long 608with the kernel (thus it coexists with your own signal handlers as long
587as you don't register any with libev). Similarly, when the last signal 609as you don't register any with libev). Similarly, when the last signal
… …
595of the <code>SIGxxx</code> constants).</p> 617of the <code>SIGxxx</code> constants).</p>
596 </dd> 618 </dd>
597</dl> 619</dl>
598 620
599</div> 621</div>
600<h2 id="ev_child_wait_for_pid_status_changes">ev_child - wait for pid status changes</h2> 622<h2 id="code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</h2>
601<div id="ev_child_wait_for_pid_status_changes-2"> 623<div id="code_ev_child_code_wait_for_pid_stat-2">
602<p>Child watchers trigger when your process receives a SIGCHLD in response to 624<p>Child watchers trigger when your process receives a SIGCHLD in response to
603some child status changes (most typically when a child of yours dies).</p> 625some child status changes (most typically when a child of yours dies).</p>
604<dl> 626<dl>
605 <dt>ev_child_init (ev_child *, callback, int pid)</dt> 627 <dt>ev_child_init (ev_child *, callback, int pid)</dt>
606 <dt>ev_child_set (ev_child *, int pid)</dt> 628 <dt>ev_child_set (ev_child *, int pid)</dt>
… …
612contains the pid of the process causing the status change.</p> 634contains the pid of the process causing the status change.</p>
613 </dd> 635 </dd>
614</dl> 636</dl>
615 637
616</div> 638</div>
617<h2 id="ev_idle_when_you_ve_got_nothing_bett">ev_idle - when you've got nothing better to do</h2> 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>
618<div id="ev_idle_when_you_ve_got_nothing_bett-2"> 640<div id="code_ev_idle_code_when_you_ve_got_no-2">
619<p>Idle watchers trigger events when there are no other I/O or timer (or 641<p>Idle watchers trigger events when there are no other I/O or timer (or
620periodic) events pending. That is, as long as your process is busy 642periodic) events pending. That is, as long as your process is busy
621handling sockets or timeouts it will not be called. But when your process 643handling sockets or timeouts it will not be called. But when your process
622is idle all idle watchers are being called again and again - until 644is idle all idle watchers are being called again and again - until
623stopped, that is, or your process receives more events.</p> 645stopped, that is, or your process receives more events.</p>
… …
644watchers afterwards.</p> 666watchers afterwards.</p>
645<p>Their main purpose is to integrate other event mechanisms into libev. This 667<p>Their main purpose is to integrate other event mechanisms into libev. This
646could be used, for example, to track variable changes, implement your own 668could be used, for example, to track variable changes, implement your own
647watchers, integrate net-snmp or a coroutine library and lots more.</p> 669watchers, integrate net-snmp or a coroutine library and lots more.</p>
648<p>This is done by examining in each prepare call which file descriptors need 670<p>This is done by examining in each prepare call which file descriptors need
649to be watched by the other library, registering ev_io watchers for them 671to be watched by the other library, registering <code>ev_io</code> watchers for them
650and starting an ev_timer watcher for any timeouts (many libraries provide 672and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide
651just this functionality). Then, in the check watcher you check for any 673just this functionality). Then, in the check watcher you check for any
652events that occured (by making your callbacks set soem flags for example) 674events that occured (by making your callbacks set soem flags for example)
653and call back into the library.</p> 675and call back into the library.</p>
654<p>As another example, the perl Coro module uses these hooks to integrate 676<p>As another example, the perl Coro module uses these hooks to integrate
655coroutines into libev programs, by yielding to other active coroutines 677coroutines into libev programs, by yielding to other active coroutines
… …
676callback on whichever event happens first and automatically stop both 698callback on whichever event happens first and automatically stop both
677watchers. This is useful if you want to wait for a single event on an fd 699watchers. This is useful if you want to wait for a single event on an fd
678or timeout without havign to allocate/configure/start/stop/free one or 700or timeout without havign to allocate/configure/start/stop/free one or
679more watchers yourself.</p> 701more watchers yourself.</p>
680 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 702 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is
681ignored. Otherwise, an ev_io watcher for the given <code>fd</code> and <code>events</code> set 703ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set
682will be craeted and started.</p> 704will be craeted and started.</p>
683 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 705 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
684started. Otherwise an ev_timer watcher with after = <code>timeout</code> (and repeat 706started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat
685= 0) will be started.</p> 707= 0) will be started.</p>
686 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 708 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and
687gets passed an events set (normally a combination of EV_ERROR, EV_READ, 709gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>,
688EV_WRITE or EV_TIMEOUT) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 710<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p>
689<pre> static void stdin_ready (int revents, void *arg) 711<pre> static void stdin_ready (int revents, void *arg)
690 { 712 {
691 if (revents &amp; EV_TIMEOUT) 713 if (revents &amp; EV_TIMEOUT)
692 /* doh, nothing entered */ 714 /* doh, nothing entered */
693 else if (revents &amp; EV_READ) 715 else if (revents &amp; EV_READ)

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