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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 09:57:02 2007" /> 9 <meta name="created" content="Fri Nov 23 17:17:04 2007" />
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12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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35<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="#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_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li> 36<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>
37</ul> 37</ul>
38</li> 38</li>
39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
40<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
41</li> 43</li>
42</ul><hr /> 44</ul><hr />
43<!-- INDEX END --> 45<!-- INDEX END -->
44 46
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94<div id="TIME_REPRESENTATION_CONTENT"> 96<div id="TIME_REPRESENTATION_CONTENT">
95<p>Libev represents time as a single floating point number, representing the 97<p>Libev represents time as a single floating point number, representing the
96(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
97the beginning of 1970, details are complicated, don't ask). This type is 99the beginning of 1970, details are complicated, don't ask). This type is
98called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
99to the double type in C.</p> 101to the <code>double</code> type in C, and when you need to do any calculations on
102it, you should treat it as such.</p>
103
104
105
106
100 107
101</div> 108</div>
102<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 109<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103<div id="GLOBAL_FUNCTIONS_CONTENT"> 110<div id="GLOBAL_FUNCTIONS_CONTENT">
111<p>These functions can be called anytime, even before initialising the
112library in any way.</p>
104<dl> 113<dl>
105 <dt>ev_tstamp ev_time ()</dt> 114 <dt>ev_tstamp ev_time ()</dt>
106 <dd> 115 <dd>
107 <p>Returns the current time as libev would use it.</p> 116 <p>Returns the current time as libev would use it. Please note that the
117<code>ev_now</code> function is usually faster and also often returns the timestamp
118you actually want to know.</p>
108 </dd> 119 </dd>
109 <dt>int ev_version_major ()</dt> 120 <dt>int ev_version_major ()</dt>
110 <dt>int ev_version_minor ()</dt> 121 <dt>int ev_version_minor ()</dt>
111 <dd> 122 <dd>
112 <p>You can find out the major and minor version numbers of the library 123 <p>You can find out the major and minor version numbers of the library
… …
116version of the library your program was compiled against.</p> 127version of the library your program was compiled against.</p>
117 <p>Usually, it's a good idea to terminate if the major versions mismatch, 128 <p>Usually, it's a good idea to terminate if the major versions mismatch,
118as this indicates an incompatible change. Minor versions are usually 129as this indicates an incompatible change. Minor versions are usually
119compatible to older versions, so a larger minor version alone is usually 130compatible to older versions, so a larger minor version alone is usually
120not a problem.</p> 131not a problem.</p>
132 <p>Example: make sure we haven't accidentally been linked against the wrong
133version:</p>
134<pre> assert ((&quot;libev version mismatch&quot;,
135 ev_version_major () == EV_VERSION_MAJOR
136 &amp;&amp; ev_version_minor () &gt;= EV_VERSION_MINOR));
137
138</pre>
139 </dd>
140 <dt>unsigned int ev_supported_backends ()</dt>
141 <dd>
142 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
143value) compiled into this binary of libev (independent of their
144availability on the system you are running on). See <code>ev_default_loop</code> for
145a description of the set values.</p>
146 <p>Example: make sure we have the epoll method, because yeah this is cool and
147a must have and can we have a torrent of it please!!!11</p>
148<pre> assert ((&quot;sorry, no epoll, no sex&quot;,
149 ev_supported_backends () &amp; EVBACKEND_EPOLL));
150
151</pre>
152 </dd>
153 <dt>unsigned int ev_recommended_backends ()</dt>
154 <dd>
155 <p>Return the set of all backends compiled into this binary of libev and also
156recommended for this platform. This set is often smaller than the one
157returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
158most BSDs and will not be autodetected unless you explicitly request it
159(assuming you know what you are doing). This is the set of backends that
160libev will probe for if you specify no backends explicitly.</p>
121 </dd> 161 </dd>
122 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 162 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
123 <dd> 163 <dd>
124 <p>Sets the allocation function to use (the prototype is similar to the 164 <p>Sets the allocation function to use (the prototype is similar to the
125realloc C function, the semantics are identical). It is used to allocate 165realloc C function, the semantics are identical). It is used to allocate
… …
127needs to be allocated, the library might abort or take some potentially 167needs to be allocated, the library might abort or take some potentially
128destructive action. The default is your system realloc function.</p> 168destructive action. The default is your system realloc function.</p>
129 <p>You could override this function in high-availability programs to, say, 169 <p>You could override this function in high-availability programs to, say,
130free some memory if it cannot allocate memory, to use a special allocator, 170free some memory if it cannot allocate memory, to use a special allocator,
131or even to sleep a while and retry until some memory is available.</p> 171or even to sleep a while and retry until some memory is available.</p>
172 <p>Example: replace the libev allocator with one that waits a bit and then
173retries: better than mine).</p>
174<pre> static void *
175 persistent_realloc (void *ptr, long size)
176 {
177 for (;;)
178 {
179 void *newptr = realloc (ptr, size);
180
181 if (newptr)
182 return newptr;
183
184 sleep (60);
185 }
186 }
187
188 ...
189 ev_set_allocator (persistent_realloc);
190
191</pre>
132 </dd> 192 </dd>
133 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt> 193 <dt>ev_set_syserr_cb (void (*cb)(const char *msg));</dt>
134 <dd> 194 <dd>
135 <p>Set the callback function to call on a retryable syscall error (such 195 <p>Set the callback function to call on a retryable syscall error (such
136as failed select, poll, epoll_wait). The message is a printable string 196as failed select, poll, epoll_wait). The message is a printable string
137indicating the system call or subsystem causing the problem. If this 197indicating the system call or subsystem causing the problem. If this
138callback is set, then libev will expect it to remedy the sitution, no 198callback is set, then libev will expect it to remedy the sitution, no
139matter what, when it returns. That is, libev will generally retry the 199matter what, when it returns. That is, libev will generally retry the
140requested operation, or, if the condition doesn't go away, do bad stuff 200requested operation, or, if the condition doesn't go away, do bad stuff
141(such as abort).</p> 201(such as abort).</p>
202 <p>Example: do the same thing as libev does internally:</p>
203<pre> static void
204 fatal_error (const char *msg)
205 {
206 perror (msg);
207 abort ();
208 }
209
210 ...
211 ev_set_syserr_cb (fatal_error);
212
213</pre>
142 </dd> 214 </dd>
143</dl> 215</dl>
144 216
145</div> 217</div>
146<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p> 218<h1 id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</h1><p><a href="#TOP" class="toplink">Top</a></p>
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158 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 230 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
159 <dd> 231 <dd>
160 <p>This will initialise the default event loop if it hasn't been initialised 232 <p>This will initialise the default event loop if it hasn't been initialised
161yet and return it. If the default loop could not be initialised, returns 233yet and return it. If the default loop could not be initialised, returns
162false. If it already was initialised it simply returns it (and ignores the 234false. If it already was initialised it simply returns it (and ignores the
163flags).</p> 235flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
164 <p>If you don't know what event loop to use, use the one returned from this 236 <p>If you don't know what event loop to use, use the one returned from this
165function.</p> 237function.</p>
166 <p>The flags argument can be used to specify special behaviour or specific 238 <p>The flags argument can be used to specify special behaviour or specific
167backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 239backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
168 <p>It supports the following flags:</p> 240 <p>The following flags are supported:</p>
169 <p> 241 <p>
170 <dl> 242 <dl>
171 <dt><code>EVFLAG_AUTO</code></dt> 243 <dt><code>EVFLAG_AUTO</code></dt>
172 <dd> 244 <dd>
173 <p>The default flags value. Use this if you have no clue (it's the right 245 <p>The default flags value. Use this if you have no clue (it's the right
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180<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 252<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181override the flags completely if it is found in the environment. This is 253override the flags completely if it is found in the environment. This is
182useful to try out specific backends to test their performance, or to work 254useful to try out specific backends to test their performance, or to work
183around bugs.</p> 255around bugs.</p>
184 </dd> 256 </dd>
185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 257 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
186 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt>
187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt>
188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt>
189 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt>
190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt>
191 <dd> 258 <dd>
192 <p>If one or more of these are ored into the flags value, then only these 259 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
193backends will be tried (in the reverse order as given here). If one are 260libev tries to roll its own fd_set with no limits on the number of fds,
194specified, any backend will do.</p> 261but if that fails, expect a fairly low limit on the number of fds when
262using this backend. It doesn't scale too well (O(highest_fd)), but its usually
263the fastest backend for a low number of fds.</p>
264 </dd>
265 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
266 <dd>
267 <p>And this is your standard poll(2) backend. It's more complicated than
268select, but handles sparse fds better and has no artificial limit on the
269number of fds you can use (except it will slow down considerably with a
270lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
271 </dd>
272 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
273 <dd>
274 <p>For few fds, this backend is a bit little slower than poll and select,
275but it scales phenomenally better. While poll and select usually scale like
276O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
277either O(1) or O(active_fds).</p>
278 <p>While stopping and starting an I/O watcher in the same iteration will
279result in some caching, there is still a syscall per such incident
280(because the fd could point to a different file description now), so its
281best to avoid that. Also, dup()ed file descriptors might not work very
282well if you register events for both fds.</p>
283 <p>Please note that epoll sometimes generates spurious notifications, so you
284need to use non-blocking I/O or other means to avoid blocking when no data
285(or space) is available.</p>
286 </dd>
287 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
288 <dd>
289 <p>Kqueue deserves special mention, as at the time of this writing, it
290was broken on all BSDs except NetBSD (usually it doesn't work with
291anything but sockets and pipes, except on Darwin, where of course its
292completely useless). For this reason its not being &quot;autodetected&quot;
293unless you explicitly specify it explicitly in the flags (i.e. using
294<code>EVBACKEND_KQUEUE</code>).</p>
295 <p>It scales in the same way as the epoll backend, but the interface to the
296kernel is more efficient (which says nothing about its actual speed, of
297course). While starting and stopping an I/O watcher does not cause an
298extra syscall as with epoll, it still adds up to four event changes per
299incident, so its best to avoid that.</p>
300 </dd>
301 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
302 <dd>
303 <p>This is not implemented yet (and might never be).</p>
304 </dd>
305 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
306 <dd>
307 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
308it's really slow, but it still scales very well (O(active_fds)).</p>
309 <p>Please note that solaris ports can result in a lot of spurious
310notifications, so you need to use non-blocking I/O or other means to avoid
311blocking when no data (or space) is available.</p>
312 </dd>
313 <dt><code>EVBACKEND_ALL</code></dt>
314 <dd>
315 <p>Try all backends (even potentially broken ones that wouldn't be tried
316with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
317<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
195 </dd> 318 </dd>
196 </dl> 319 </dl>
197 </p> 320 </p>
321 <p>If one or more of these are ored into the flags value, then only these
322backends will be tried (in the reverse order as given here). If none are
323specified, most compiled-in backend will be tried, usually in reverse
324order of their flag values :)</p>
325 <p>The most typical usage is like this:</p>
326<pre> if (!ev_default_loop (0))
327 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
328
329</pre>
330 <p>Restrict libev to the select and poll backends, and do not allow
331environment settings to be taken into account:</p>
332<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
333
334</pre>
335 <p>Use whatever libev has to offer, but make sure that kqueue is used if
336available (warning, breaks stuff, best use only with your own private
337event loop and only if you know the OS supports your types of fds):</p>
338<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
339
340</pre>
198 </dd> 341 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 342 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 343 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 344 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202always distinct from the default loop. Unlike the default loop, it cannot 345always distinct from the default loop. Unlike the default loop, it cannot
203handle signal and child watchers, and attempts to do so will be greeted by 346handle signal and child watchers, and attempts to do so will be greeted by
204undefined behaviour (or a failed assertion if assertions are enabled).</p> 347undefined behaviour (or a failed assertion if assertions are enabled).</p>
348 <p>Example: try to create a event loop that uses epoll and nothing else.</p>
349<pre> struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
350 if (!epoller)
351 fatal (&quot;no epoll found here, maybe it hides under your chair&quot;);
352
353</pre>
205 </dd> 354 </dd>
206 <dt>ev_default_destroy ()</dt> 355 <dt>ev_default_destroy ()</dt>
207 <dd> 356 <dd>
208 <p>Destroys the default loop again (frees all memory and kernel state 357 <p>Destroys the default loop again (frees all memory and kernel state
209etc.). This stops all registered event watchers (by not touching them in 358etc.). This stops all registered event watchers (by not touching them in
… …
218 <dd> 367 <dd>
219 <p>This function reinitialises the kernel state for backends that have 368 <p>This function reinitialises the kernel state for backends that have
220one. Despite the name, you can call it anytime, but it makes most sense 369one. Despite the name, you can call it anytime, but it makes most sense
221after forking, in either the parent or child process (or both, but that 370after forking, in either the parent or child process (or both, but that
222again makes little sense).</p> 371again makes little sense).</p>
223 <p>You <i>must</i> call this function after forking if and only if you want to 372 <p>You <i>must</i> call this function in the child process after forking if and
224use the event library in both processes. If you just fork+exec, you don't 373only if you want to use the event library in both processes. If you just
225have to call it.</p> 374fork+exec, you don't have to call it.</p>
226 <p>The function itself is quite fast and it's usually not a problem to call 375 <p>The function itself is quite fast and it's usually not a problem to call
227it just in case after a fork. To make this easy, the function will fit in 376it just in case after a fork. To make this easy, the function will fit in
228quite nicely into a call to <code>pthread_atfork</code>:</p> 377quite nicely into a call to <code>pthread_atfork</code>:</p>
229<pre> pthread_atfork (0, 0, ev_default_fork); 378<pre> pthread_atfork (0, 0, ev_default_fork);
230 379
231</pre> 380</pre>
381 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
382without calling this function, so if you force one of those backends you
383do not need to care.</p>
232 </dd> 384 </dd>
233 <dt>ev_loop_fork (loop)</dt> 385 <dt>ev_loop_fork (loop)</dt>
234 <dd> 386 <dd>
235 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 387 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
236<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 388<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
237after fork, and how you do this is entirely your own problem.</p> 389after fork, and how you do this is entirely your own problem.</p>
238 </dd> 390 </dd>
239 <dt>unsigned int ev_method (loop)</dt> 391 <dt>unsigned int ev_backend (loop)</dt>
240 <dd> 392 <dd>
241 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 393 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
242use.</p> 394use.</p>
243 </dd> 395 </dd>
244 <dt>ev_tstamp ev_now (loop)</dt> 396 <dt>ev_tstamp ev_now (loop)</dt>
245 <dd> 397 <dd>
246 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 398 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
247got events and started processing them. This timestamp does not change 399received events and started processing them. This timestamp does not
248as long as callbacks are being processed, and this is also the base time 400change as long as callbacks are being processed, and this is also the base
249used for relative timers. You can treat it as the timestamp of the event 401time used for relative timers. You can treat it as the timestamp of the
250occuring (or more correctly, the mainloop finding out about it).</p> 402event occuring (or more correctly, libev finding out about it).</p>
251 </dd> 403 </dd>
252 <dt>ev_loop (loop, int flags)</dt> 404 <dt>ev_loop (loop, int flags)</dt>
253 <dd> 405 <dd>
254 <p>Finally, this is it, the event handler. This function usually is called 406 <p>Finally, this is it, the event handler. This function usually is called
255after you initialised all your watchers and you want to start handling 407after you initialised all your watchers and you want to start handling
256events.</p> 408events.</p>
257 <p>If the flags argument is specified as 0, it will not return until either 409 <p>If the flags argument is specified as <code>0</code>, it will not return until
258no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 410either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
411 <p>Please note that an explicit <code>ev_unloop</code> is usually better than
412relying on all watchers to be stopped when deciding when a program has
413finished (especially in interactive programs), but having a program that
414automatically loops as long as it has to and no longer by virtue of
415relying on its watchers stopping correctly is a thing of beauty.</p>
259 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 416 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
260those events and any outstanding ones, but will not block your process in 417those events and any outstanding ones, but will not block your process in
261case there are no events and will return after one iteration of the loop.</p> 418case there are no events and will return after one iteration of the loop.</p>
262 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 419 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
263neccessary) and will handle those and any outstanding ones. It will block 420neccessary) and will handle those and any outstanding ones. It will block
264your process until at least one new event arrives, and will return after 421your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 422one iteration of the loop. This is useful if you are waiting for some
266 <p>This flags value could be used to implement alternative looping 423external event in conjunction with something not expressible using other
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 424libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
268more generic mechanism.</p> 425usually a better approach for this kind of thing.</p>
426 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
427<pre> * If there are no active watchers (reference count is zero), return.
428 - Queue prepare watchers and then call all outstanding watchers.
429 - If we have been forked, recreate the kernel state.
430 - Update the kernel state with all outstanding changes.
431 - Update the &quot;event loop time&quot;.
432 - Calculate for how long to block.
433 - Block the process, waiting for any events.
434 - Queue all outstanding I/O (fd) events.
435 - Update the &quot;event loop time&quot; and do time jump handling.
436 - Queue all outstanding timers.
437 - Queue all outstanding periodics.
438 - If no events are pending now, queue all idle watchers.
439 - Queue all check watchers.
440 - Call all queued watchers in reverse order (i.e. check watchers first).
441 Signals and child watchers are implemented as I/O watchers, and will
442 be handled here by queueing them when their watcher gets executed.
443 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
444 were used, return, otherwise continue with step *.
445
446</pre>
447 <p>Example: queue some jobs and then loop until no events are outsanding
448anymore.</p>
449<pre> ... queue jobs here, make sure they register event watchers as long
450 ... as they still have work to do (even an idle watcher will do..)
451 ev_loop (my_loop, 0);
452 ... jobs done. yeah!
453
454</pre>
269 </dd> 455 </dd>
270 <dt>ev_unloop (loop, how)</dt> 456 <dt>ev_unloop (loop, how)</dt>
271 <dd> 457 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 458 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273has processed all outstanding events). The <code>how</code> argument must be either 459has processed all outstanding events). The <code>how</code> argument must be either
274<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or 460<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> 461<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 462 </dd>
277 <dt>ev_ref (loop)</dt> 463 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 464 <dt>ev_unref (loop)</dt>
279 <dd> 465 <dd>
… …
285example, libev itself uses this for its internal signal pipe: It is not 471example, libev itself uses this for its internal signal pipe: It is not
286visible to the libev user and should not keep <code>ev_loop</code> from exiting if 472visible to the libev user and should not keep <code>ev_loop</code> from exiting if
287no event watchers registered by it are active. It is also an excellent 473no event watchers registered by it are active. It is also an excellent
288way to do this for generic recurring timers or from within third-party 474way to do this for generic recurring timers or from within third-party
289libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p> 475libraries. Just remember to <i>unref after start</i> and <i>ref before stop</i>.</p>
476 <p>Example: create a signal watcher, but keep it from keeping <code>ev_loop</code>
477running when nothing else is active.</p>
478<pre> struct dv_signal exitsig;
479 ev_signal_init (&amp;exitsig, sig_cb, SIGINT);
480 ev_signal_start (myloop, &amp;exitsig);
481 evf_unref (myloop);
482
483</pre>
484 <p>Example: for some weird reason, unregister the above signal handler again.</p>
485<pre> ev_ref (myloop);
486 ev_signal_stop (myloop, &amp;exitsig);
487
488</pre>
290 </dd> 489 </dd>
291</dl> 490</dl>
292 491
293</div> 492</div>
294<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p> 493<h1 id="ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</h1><p><a href="#TOP" class="toplink">Top</a></p>
… …
326with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 525with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
327*)</code>), and you can stop watching for events at any time by calling the 526*)</code>), and you can stop watching for events at any time by calling the
328corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 527corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
329<p>As long as your watcher is active (has been started but not stopped) you 528<p>As long as your watcher is active (has been started but not stopped) you
330must not touch the values stored in it. Most specifically you must never 529must not touch the values stored in it. Most specifically you must never
331reinitialise it or call its set method.</p> 530reinitialise it or call its set macro.</p>
332<p>You can check whether an event is active by calling the <code>ev_is_active 531<p>You can check whether an event is active by calling the <code>ev_is_active
333(watcher *)</code> macro. To see whether an event is outstanding (but the 532(watcher *)</code> macro. To see whether an event is outstanding (but the
334callback for it has not been called yet) you can use the <code>ev_is_pending 533callback for it has not been called yet) you can use the <code>ev_is_pending
335(watcher *)</code> macro.</p> 534(watcher *)</code> macro.</p>
336<p>Each and every callback receives the event loop pointer as first, the 535<p>Each and every callback receives the event loop pointer as first, the
… …
430<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p> 629<h1 id="WATCHER_TYPES">WATCHER TYPES</h1><p><a href="#TOP" class="toplink">Top</a></p>
431<div id="WATCHER_TYPES_CONTENT"> 630<div id="WATCHER_TYPES_CONTENT">
432<p>This section describes each watcher in detail, but will not repeat 631<p>This section describes each watcher in detail, but will not repeat
433information given in the last section.</p> 632information given in the last section.</p>
434 633
634
635
636
637
435</div> 638</div>
436<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 639<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
437<div id="code_ev_io_code_is_this_file_descrip-2"> 640<div id="code_ev_io_code_is_this_file_descrip-2">
438<p>I/O watchers check whether a file descriptor is readable or writable 641<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 642in each iteration of the event loop (This behaviour is called
440level-triggering because you keep receiving events as long as the 643level-triggering because you keep receiving events as long as the
441condition persists. Remember you can stop the watcher if you don't want to 644condition persists. Remember you can stop the watcher if you don't want to
442act on the event and neither want to receive future events).</p> 645act on the event and neither want to receive future events).</p>
443<p>In general you can register as many read and/or write event watchers oer 646<p>In general you can register as many read and/or write event watchers per
444fd as you want (as long as you don't confuse yourself). Setting all file 647fd as you want (as long as you don't confuse yourself). Setting all file
445descriptors to non-blocking mode is also usually a good idea (but not 648descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 649required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 650<p>You have to be careful with dup'ed file descriptors, though. Some backends
448(the linux epoll backend is a notable example) cannot handle dup'ed file 651(the linux epoll backend is a notable example) cannot handle dup'ed file
449descriptors correctly if you register interest in two or more fds pointing 652descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 653to the same underlying file/socket etc. description (that is, they share
654the same underlying &quot;file open&quot;).</p>
451<p>If you must do this, then force the use of a known-to-be-good backend 655<p>If you must do this, then force the use of a known-to-be-good backend
452(at the time of this writing, this includes only EVMETHOD_SELECT and 656(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
453EVMETHOD_POLL).</p> 657<code>EVBACKEND_POLL</code>).</p>
454<dl> 658<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 659 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
456 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 660 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
457 <dd> 661 <dd>
458 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 662 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
459events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 663events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
460EV_WRITE</code> to receive the given events.</p> 664EV_WRITE</code> to receive the given events.</p>
665 <p>Please note that most of the more scalable backend mechanisms (for example
666epoll and solaris ports) can result in spurious readyness notifications
667for file descriptors, so you practically need to use non-blocking I/O (and
668treat callback invocation as hint only), or retest separately with a safe
669interface before doing I/O (XLib can do this), or force the use of either
670<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
671problem. Also note that it is quite easy to have your callback invoked
672when the readyness condition is no longer valid even when employing
673typical ways of handling events, so its a good idea to use non-blocking
674I/O unconditionally.</p>
461 </dd> 675 </dd>
462</dl> 676</dl>
677<p>Example: call <code>stdin_readable_cb</code> when STDIN_FILENO has become, well
678readable, but only once. Since it is likely line-buffered, you could
679attempt to read a whole line in the callback:</p>
680<pre> static void
681 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
682 {
683 ev_io_stop (loop, w);
684 .. read from stdin here (or from w-&gt;fd) and haqndle any I/O errors
685 }
686
687 ...
688 struct ev_loop *loop = ev_default_init (0);
689 struct ev_io stdin_readable;
690 ev_io_init (&amp;stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
691 ev_io_start (loop, &amp;stdin_readable);
692 ev_loop (loop, 0);
693
694
695
696
697</pre>
463 698
464</div> 699</div>
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 700<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
466<div id="code_ev_timer_code_relative_and_opti-2"> 701<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 702<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 703given time, and optionally repeating in regular intervals after that.</p>
469<p>The timers are based on real time, that is, if you register an event that 704<p>The timers are based on real time, that is, if you register an event that
470times out after an hour and youreset your system clock to last years 705times out after an hour and you reset your system clock to last years
471time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 706time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 707detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 708monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 709<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475time. This is usually the right thing as this timestamp refers to the time 710time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 711of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 712you suspect event processing to be delayed and you <i>need</i> to base the timeout
478ion the current time, use something like this to adjust for this:</p> 713on the current time, use something like this to adjust for this:</p>
479<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 714<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 715
481</pre> 716</pre>
717<p>The callback is guarenteed to be invoked only when its timeout has passed,
718but if multiple timers become ready during the same loop iteration then
719order of execution is undefined.</p>
482<dl> 720<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 721 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 722 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 723 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 724 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
488timer will automatically be configured to trigger again <code>repeat</code> seconds 726timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 727later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 728 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
491configure a timer to trigger every 10 seconds, then it will trigger at 729configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 730exactly 10 second intervals. If, however, your program cannot keep up with
493the timer (ecause it takes longer than those 10 seconds to do stuff) the 731the timer (because it takes longer than those 10 seconds to do stuff) the
494timer will not fire more than once per event loop iteration.</p> 732timer will not fire more than once per event loop iteration.</p>
495 </dd> 733 </dd>
496 <dt>ev_timer_again (loop)</dt> 734 <dt>ev_timer_again (loop)</dt>
497 <dd> 735 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 736 <p>This will act as if the timer timed out and restart it again if it is
… …
508time you successfully read or write some data. If you go into an idle 746time you successfully read or write some data. If you go into an idle
509state where you do not expect data to travel on the socket, you can stop 747state where you do not expect data to travel on the socket, you can stop
510the timer, and again will automatically restart it if need be.</p> 748the timer, and again will automatically restart it if need be.</p>
511 </dd> 749 </dd>
512</dl> 750</dl>
751<p>Example: create a timer that fires after 60 seconds.</p>
752<pre> static void
753 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
754 {
755 .. one minute over, w is actually stopped right here
756 }
757
758 struct ev_timer mytimer;
759 ev_timer_init (&amp;mytimer, one_minute_cb, 60., 0.);
760 ev_timer_start (loop, &amp;mytimer);
761
762</pre>
763<p>Example: create a timeout timer that times out after 10 seconds of
764inactivity.</p>
765<pre> static void
766 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
767 {
768 .. ten seconds without any activity
769 }
770
771 struct ev_timer mytimer;
772 ev_timer_init (&amp;mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
773 ev_timer_again (&amp;mytimer); /* start timer */
774 ev_loop (loop, 0);
775
776 // and in some piece of code that gets executed on any &quot;activity&quot;:
777 // reset the timeout to start ticking again at 10 seconds
778 ev_timer_again (&amp;mytimer);
779
780
781
782
783</pre>
513 784
514</div> 785</div>
515<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2> 786<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
516<div id="code_ev_periodic_code_to_cron_or_not-2"> 787<div id="code_ev_periodic_code_to_cron_or_not-2">
517<p>Periodic watchers are also timers of a kind, but they are very versatile 788<p>Periodic watchers are also timers of a kind, but they are very versatile
… …
524take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 795take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525roughly 10 seconds later and of course not if you reset your system time 796roughly 10 seconds later and of course not if you reset your system time
526again).</p> 797again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 798<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 799triggering an event on eahc midnight, local time.</p>
800<p>As with timers, the callback is guarenteed to be invoked only when the
801time (<code>at</code>) has been passed, but if multiple periodic timers become ready
802during the same loop iteration then order of execution is undefined.</p>
529<dl> 803<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 804 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 805 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 806 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 807 <p>Lots of arguments, lets sort it out... There are basically three modes of
534operation, and we will explain them from simplest to complex:</p> 808operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 809 <p>
540 <dl> 810 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 811 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 812 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 813 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 837 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 838 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569ignored. Instead, each time the periodic watcher gets scheduled, the 839ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 840reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 841current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 842 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573periodic watcher, ever, or make any event loop modifications</i>. If you need 843ever, or make any event loop modifications</i>. If you need to stop it,
574to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 844return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575 <p>Also, <i>this callback must always return a time that is later than the 845starting a prepare watcher).</p>
576passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 846 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 847ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 848<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 849 {
581 return now + 60.; 850 return now + 60.;
… …
584</pre> 853</pre>
585 <p>It must return the next time to trigger, based on the passed time value 854 <p>It must return the next time to trigger, based on the passed time value
586(that is, the lowest time value larger than to the second argument). It 855(that is, the lowest time value larger than to the second argument). It
587will usually be called just before the callback will be triggered, but 856will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 857might be called at other times, too.</p>
858 <p>NOTE: <i>This callback must always return a time that is later than the
859passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589 <p>This can be used to create very complex timers, such as a timer that 860 <p>This can be used to create very complex timers, such as a timer that
590triggers on each midnight, local time. To do this, you would calculate the 861triggers on each midnight, local time. To do this, you would calculate the
591next midnight after <code>now</code> and return the timestamp value for this. How you do this 862next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 863you do this is, again, up to you (but it is not trivial, which is the main
864reason I omitted it as an example).</p>
593 </dd> 865 </dd>
594 </dl> 866 </dl>
595 </p> 867 </p>
596 </dd> 868 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 869 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
600when you changed some parameters or the reschedule callback would return 872when you changed some parameters or the reschedule callback would return
601a different time than the last time it was called (e.g. in a crond like 873a different time than the last time it was called (e.g. in a crond like
602program when the crontabs have changed).</p> 874program when the crontabs have changed).</p>
603 </dd> 875 </dd>
604</dl> 876</dl>
877<p>Example: call a callback every hour, or, more precisely, whenever the
878system clock is divisible by 3600. The callback invocation times have
879potentially a lot of jittering, but good long-term stability.</p>
880<pre> static void
881 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
882 {
883 ... its now a full hour (UTC, or TAI or whatever your clock follows)
884 }
885
886 struct ev_periodic hourly_tick;
887 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 3600., 0);
888 ev_periodic_start (loop, &amp;hourly_tick);
889
890</pre>
891<p>Example: the same as above, but use a reschedule callback to do it:</p>
892<pre> #include &lt;math.h&gt;
893
894 static ev_tstamp
895 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
896 {
897 return fmod (now, 3600.) + 3600.;
898 }
899
900 ev_periodic_init (&amp;hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
901
902</pre>
903<p>Example: call a callback every hour, starting now:</p>
904<pre> struct ev_periodic hourly_tick;
905 ev_periodic_init (&amp;hourly_tick, clock_cb,
906 fmod (ev_now (loop), 3600.), 3600., 0);
907 ev_periodic_start (loop, &amp;hourly_tick);
908
909
910
911
912</pre>
605 913
606</div> 914</div>
607<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2> 915<h2 id="code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</h2>
608<div id="code_ev_signal_code_signal_me_when_a-2"> 916<div id="code_ev_signal_code_signal_me_when_a-2">
609<p>Signal watchers will trigger an event when the process receives a specific 917<p>Signal watchers will trigger an event when the process receives a specific
… …
640the status word (use the macros from <code>sys/wait.h</code> and see your systems 948the status word (use the macros from <code>sys/wait.h</code> and see your systems
641<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the 949<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
642process causing the status change.</p> 950process causing the status change.</p>
643 </dd> 951 </dd>
644</dl> 952</dl>
953<p>Example: try to exit cleanly on SIGINT and SIGTERM.</p>
954<pre> static void
955 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
956 {
957 ev_unloop (loop, EVUNLOOP_ALL);
958 }
959
960 struct ev_signal signal_watcher;
961 ev_signal_init (&amp;signal_watcher, sigint_cb, SIGINT);
962 ev_signal_start (loop, &amp;sigint_cb);
963
964
965
966
967</pre>
645 968
646</div> 969</div>
647<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 970<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
648<div id="code_ev_idle_code_when_you_ve_got_no-2"> 971<div id="code_ev_idle_code_when_you_ve_got_no-2">
649<p>Idle watchers trigger events when there are no other events are pending 972<p>Idle watchers trigger events when there are no other events are pending
… …
665 <p>Initialises and configures the idle watcher - it has no parameters of any 988 <p>Initialises and configures the idle watcher - it has no parameters of any
666kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless, 989kind. There is a <code>ev_idle_set</code> macro, but using it is utterly pointless,
667believe me.</p> 990believe me.</p>
668 </dd> 991 </dd>
669</dl> 992</dl>
993<p>Example: dynamically allocate an <code>ev_idle</code>, start it, and in the
994callback, free it. Alos, use no error checking, as usual.</p>
995<pre> static void
996 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
997 {
998 free (w);
999 // now do something you wanted to do when the program has
1000 // no longer asnything immediate to do.
1001 }
1002
1003 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1004 ev_idle_init (idle_watcher, idle_cb);
1005 ev_idle_start (loop, idle_cb);
1006
1007
1008
1009
1010</pre>
670 1011
671</div> 1012</div>
672<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 1013<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
673<div id="code_ev_prepare_code_and_code_ev_che-2"> 1014<div id="code_ev_prepare_code_and_code_ev_che-2">
674<p>Prepare and check watchers are usually (but not always) used in tandem: 1015<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 1016prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 1017afterwards.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 1018<p>Their main purpose is to integrate other event mechanisms into libev. This
678could be used, for example, to track variable changes, implement your own 1019could be used, for example, to track variable changes, implement your own
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 1020watchers, integrate net-snmp or a coroutine library and lots more.</p>
680<p>This is done by examining in each prepare call which file descriptors need 1021<p>This is done by examining in each prepare call which file descriptors need
681to be watched by the other library, registering <code>ev_io</code> watchers for 1022to be watched by the other library, registering <code>ev_io</code> watchers for
682them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 1023them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683provide just this functionality). Then, in the check watcher you check for 1024provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 1025any events that occured (by checking the pending status of all watchers
685and stopping them) and call back into the library. The I/O and timer 1026and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 1027callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 1028because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 1029<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 1030coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 1031during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 1032are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 1033with priority higher than or equal to the event loop and one coroutine
693using idle watchers to keep the event loop from blocking if lower-priority 1034of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 1035loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 1036low-priority coroutines to idle/background tasks).</p>
696<dl> 1037<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1038 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 1039 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 1040 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 1041 <p>Initialises and configures the prepare or check watcher - they have no
701parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1042parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
702macros, but using them is utterly, utterly and completely pointless.</p> 1043macros, but using them is utterly, utterly and completely pointless.</p>
703 </dd> 1044 </dd>
704</dl> 1045</dl>
1046<p>Example: *TODO*.</p>
1047
1048
1049
1050
705 1051
706</div> 1052</div>
707<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 1053<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
708<div id="OTHER_FUNCTIONS_CONTENT"> 1054<div id="OTHER_FUNCTIONS_CONTENT">
709<p>There are some other functions of possible interest. Described. Here. Now.</p> 1055<p>There are some other functions of possible interest. Described. Here. Now.</p>
… …
711 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 1057 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 1058 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 1059 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 1060callback on whichever event happens first and automatically stop both
715watchers. This is useful if you want to wait for a single event on an fd 1061watchers. This is useful if you want to wait for a single event on an fd
716or timeout without havign to allocate/configure/start/stop/free one or 1062or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 1063more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 1064 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and 1065is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720<code>events</code> set will be craeted and started.</p> 1066<code>events</code> set will be craeted and started.</p>
721 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 1067 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and 1068started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of 1069repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 1070dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 1071 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
726passed an events set like normal event callbacks (with a combination of 1072passed an <code>revents</code> set like normal event callbacks (a combination of
727<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> 1073<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728value passed to <code>ev_once</code>:</p> 1074value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 1075<pre> static void stdin_ready (int revents, void *arg)
730 { 1076 {
731 if (revents &amp; EV_TIMEOUT) 1077 if (revents &amp; EV_TIMEOUT)
… …
753 <dd> 1099 <dd>
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 1100 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
755 </dd> 1101 </dd>
756</dl> 1102</dl>
757 1103
1104
1105
1106
1107
1108</div>
1109<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
1110<div id="LIBEVENT_EMULATION_CONTENT">
1111<p>Libev offers a compatibility emulation layer for libevent. It cannot
1112emulate the internals of libevent, so here are some usage hints:</p>
1113<dl>
1114 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
1115 <dt>* The following members are fully supported: ev_base, ev_callback,
1116ev_arg, ev_fd, ev_res, ev_events.</dt>
1117 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
1118maintained by libev, it does not work exactly the same way as in libevent (consider
1119it a private API).</dt>
1120 <dt>* Priorities are not currently supported. Initialising priorities
1121will fail and all watchers will have the same priority, even though there
1122is an ev_pri field.</dt>
1123 <dt>* Other members are not supported.</dt>
1124 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
1125to use the libev header file and library.</dt>
1126</dl>
1127
1128</div>
1129<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
1130<div id="C_SUPPORT_CONTENT">
1131<p>TBD.</p>
1132
758</div> 1133</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 1134<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 1135<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 1136<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 1137

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