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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="Fri Nov 23 06:14:47 2007" /> 9 <meta name="created" content="Fri Nov 23 16:26:06 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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137 <p>Return the set of all backends compiled into this binary of libev and also 137 <p>Return the set of all backends compiled into this binary of libev and also
138recommended for this platform. This set is often smaller than the one 138recommended for this platform. This set is often smaller than the one
139returned by <code>ev_supported_backends</code>, as for example kqueue is broken on 139returned by <code>ev_supported_backends</code>, as for example kqueue is broken on
140most BSDs and will not be autodetected unless you explicitly request it 140most BSDs and will not be autodetected unless you explicitly request it
141(assuming you know what you are doing). This is the set of backends that 141(assuming you know what you are doing). This is the set of backends that
142<code>EVFLAG_AUTO</code> will probe for.</p> 142libev will probe for if you specify no backends explicitly.</p>
143 </dd> 143 </dd>
144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
145 <dd> 145 <dd>
146 <p>Sets the allocation function to use (the prototype is similar to the 146 <p>Sets the allocation function to use (the prototype is similar to the
147realloc C function, the semantics are identical). It is used to allocate 147realloc C function, the semantics are identical). It is used to allocate
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184false. If it already was initialised it simply returns it (and ignores the 184false. If it already was initialised it simply returns it (and ignores the
185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
186 <p>If you don't know what event loop to use, use the one returned from this 186 <p>If you don't know what event loop to use, use the one returned from this
187function.</p> 187function.</p>
188 <p>The flags argument can be used to specify special behaviour or specific 188 <p>The flags argument can be used to specify special behaviour or specific
189backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p> 189backends to use, and is usually specified as <code>0</code> (or <code>EVFLAG_AUTO</code>).</p>
190 <p>It supports the following flags:</p> 190 <p>The following flags are supported:</p>
191 <p> 191 <p>
192 <dl> 192 <dl>
193 <dt><code>EVFLAG_AUTO</code></dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
194 <dd> 194 <dd>
195 <p>The default flags value. Use this if you have no clue (it's the right 195 <p>The default flags value. Use this if you have no clue (it's the right
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228 <p>While stopping and starting an I/O watcher in the same iteration will 228 <p>While stopping and starting an I/O watcher in the same iteration will
229result in some caching, there is still a syscall per such incident 229result in some caching, there is still a syscall per such incident
230(because the fd could point to a different file description now), so its 230(because the fd could point to a different file description now), so its
231best to avoid that. Also, dup()ed file descriptors might not work very 231best to avoid that. Also, dup()ed file descriptors might not work very
232well if you register events for both fds.</p> 232well if you register events for both fds.</p>
233 <p>Please note that epoll sometimes generates spurious notifications, so you
234need to use non-blocking I/O or other means to avoid blocking when no data
235(or space) is available.</p>
233 </dd> 236 </dd>
234 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt> 237 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
235 <dd> 238 <dd>
236 <p>Kqueue deserves special mention, as at the time of this writing, it 239 <p>Kqueue deserves special mention, as at the time of this writing, it
237was broken on all BSDs except NetBSD (usually it doesn't work with 240was broken on all BSDs except NetBSD (usually it doesn't work with
238anything but sockets and pipes, except on Darwin, where of course its 241anything but sockets and pipes, except on Darwin, where of course its
239completely useless). For this reason its not being &quot;autodetected&quot; unless 242completely useless). For this reason its not being &quot;autodetected&quot;
240you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p> 243unless you explicitly specify it explicitly in the flags (i.e. using
244<code>EVBACKEND_KQUEUE</code>).</p>
241 <p>It scales in the same way as the epoll backend, but the interface to the 245 <p>It scales in the same way as the epoll backend, but the interface to the
242kernel is more efficient (which says nothing about its actual speed, of 246kernel is more efficient (which says nothing about its actual speed, of
243course). While starting and stopping an I/O watcher does not cause an 247course). While starting and stopping an I/O watcher does not cause an
244extra syscall as with epoll, it still adds up to four event changes per 248extra syscall as with epoll, it still adds up to four event changes per
245incident, so its best to avoid that.</p> 249incident, so its best to avoid that.</p>
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250 </dd> 254 </dd>
251 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt> 255 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
252 <dd> 256 <dd>
253 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, 257 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
254it's really slow, but it still scales very well (O(active_fds)).</p> 258it's really slow, but it still scales very well (O(active_fds)).</p>
259 <p>Please note that solaris ports can result in a lot of spurious
260notifications, so you need to use non-blocking I/O or other means to avoid
261blocking when no data (or space) is available.</p>
255 </dd> 262 </dd>
256 <dt><code>EVBACKEND_ALL</code></dt> 263 <dt><code>EVBACKEND_ALL</code></dt>
257 <dd> 264 <dd>
258 <p>Try all backends (even potentially broken ones that wouldn't be tried 265 <p>Try all backends (even potentially broken ones that wouldn't be tried
259with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as 266with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
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263 </p> 270 </p>
264 <p>If one or more of these are ored into the flags value, then only these 271 <p>If one or more of these are ored into the flags value, then only these
265backends will be tried (in the reverse order as given here). If none are 272backends will be tried (in the reverse order as given here). If none are
266specified, most compiled-in backend will be tried, usually in reverse 273specified, most compiled-in backend will be tried, usually in reverse
267order of their flag values :)</p> 274order of their flag values :)</p>
275 <p>The most typical usage is like this:</p>
276<pre> if (!ev_default_loop (0))
277 fatal (&quot;could not initialise libev, bad $LIBEV_FLAGS in environment?&quot;);
278
279</pre>
280 <p>Restrict libev to the select and poll backends, and do not allow
281environment settings to be taken into account:</p>
282<pre> ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
283
284</pre>
285 <p>Use whatever libev has to offer, but make sure that kqueue is used if
286available (warning, breaks stuff, best use only with your own private
287event loop and only if you know the OS supports your types of fds):</p>
288<pre> ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
289
290</pre>
268 </dd> 291 </dd>
269 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 292 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
270 <dd> 293 <dd>
271 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 294 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
272always distinct from the default loop. Unlike the default loop, it cannot 295always distinct from the default loop. Unlike the default loop, it cannot
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325 <dt>ev_loop (loop, int flags)</dt> 348 <dt>ev_loop (loop, int flags)</dt>
326 <dd> 349 <dd>
327 <p>Finally, this is it, the event handler. This function usually is called 350 <p>Finally, this is it, the event handler. This function usually is called
328after you initialised all your watchers and you want to start handling 351after you initialised all your watchers and you want to start handling
329events.</p> 352events.</p>
330 <p>If the flags argument is specified as 0, it will not return until either 353 <p>If the flags argument is specified as <code>0</code>, it will not return until
331no event watchers are active anymore or <code>ev_unloop</code> was called.</p> 354either no event watchers are active anymore or <code>ev_unloop</code> was called.</p>
332 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle 355 <p>A flags value of <code>EVLOOP_NONBLOCK</code> will look for new events, will handle
333those events and any outstanding ones, but will not block your process in 356those events and any outstanding ones, but will not block your process in
334case there are no events and will return after one iteration of the loop.</p> 357case there are no events and will return after one iteration of the loop.</p>
335 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if 358 <p>A flags value of <code>EVLOOP_ONESHOT</code> will look for new events (waiting if
336neccessary) and will handle those and any outstanding ones. It will block 359neccessary) and will handle those and any outstanding ones. It will block
337your process until at least one new event arrives, and will return after 360your process until at least one new event arrives, and will return after
338one iteration of the loop.</p> 361one iteration of the loop. This is useful if you are waiting for some
339 <p>This flags value could be used to implement alternative looping 362external event in conjunction with something not expressible using other
340constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 363libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
341more generic mechanism.</p> 364usually a better approach for this kind of thing.</p>
342 <p>Here are the gory details of what ev_loop does:</p> 365 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
343<pre> 1. If there are no active watchers (reference count is zero), return. 366<pre> * If there are no active watchers (reference count is zero), return.
344 2. Queue and immediately call all prepare watchers. 367 - Queue prepare watchers and then call all outstanding watchers.
345 3. If we have been forked, recreate the kernel state. 368 - If we have been forked, recreate the kernel state.
346 4. Update the kernel state with all outstanding changes. 369 - Update the kernel state with all outstanding changes.
347 5. Update the &quot;event loop time&quot;. 370 - Update the &quot;event loop time&quot;.
348 6. Calculate for how long to block. 371 - Calculate for how long to block.
349 7. Block the process, waiting for events. 372 - Block the process, waiting for any events.
373 - Queue all outstanding I/O (fd) events.
350 8. Update the &quot;event loop time&quot; and do time jump handling. 374 - Update the &quot;event loop time&quot; and do time jump handling.
351 9. Queue all outstanding timers. 375 - Queue all outstanding timers.
352 10. Queue all outstanding periodics. 376 - Queue all outstanding periodics.
353 11. If no events are pending now, queue all idle watchers. 377 - If no events are pending now, queue all idle watchers.
354 12. Queue all check watchers. 378 - Queue all check watchers.
355 13. Call all queued watchers in reverse order (i.e. check watchers first). 379 - Call all queued watchers in reverse order (i.e. check watchers first).
380 Signals and child watchers are implemented as I/O watchers, and will
381 be handled here by queueing them when their watcher gets executed.
356 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 382 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
357 was used, return, otherwise continue with step #1. 383 were used, return, otherwise continue with step *.
358 384
359</pre> 385</pre>
360 </dd> 386 </dd>
361 <dt>ev_unloop (loop, how)</dt> 387 <dt>ev_unloop (loop, how)</dt>
362 <dd> 388 <dd>
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548 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 574 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
549 <dd> 575 <dd>
550 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 576 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
551events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 577events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
552EV_WRITE</code> to receive the given events.</p> 578EV_WRITE</code> to receive the given events.</p>
579 <p>Please note that most of the more scalable backend mechanisms (for example
580epoll and solaris ports) can result in spurious readyness notifications
581for file descriptors, so you practically need to use non-blocking I/O (and
582treat callback invocation as hint only), or retest separately with a safe
583interface before doing I/O (XLib can do this), or force the use of either
584<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
585problem. Also note that it is quite easy to have your callback invoked
586when the readyness condition is no longer valid even when employing
587typical ways of handling events, so its a good idea to use non-blocking
588I/O unconditionally.</p>
553 </dd> 589 </dd>
554</dl> 590</dl>
555 591
556</div> 592</div>
557<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 593<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>

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