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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="Thu Nov 22 13:26:17 2007" /> 9 <meta name="created" content="Fri Nov 23 09:26:40 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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123 <p>Usually, it's a good idea to terminate if the major versions mismatch, 123 <p>Usually, it's a good idea to terminate if the major versions mismatch,
124as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
125compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
126not a problem.</p> 126not a problem.</p>
127 </dd> 127 </dd>
128 <dt>unsigned int ev_supported_backends ()</dt>
129 <dd>
130 <p>Return the set of all backends (i.e. their corresponding <code>EV_BACKEND_*</code>
131value) compiled into this binary of libev (independent of their
132availability on the system you are running on). See <code>ev_default_loop</code> for
133a description of the set values.</p>
134 </dd>
135 <dt>unsigned int ev_recommended_backends ()</dt>
136 <dd>
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
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
141(assuming you know what you are doing). This is the set of backends that
142<code>EVFLAG_AUTO</code> will probe for.</p>
143 </dd>
128 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
129 <dd> 145 <dd>
130 <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
131realloc C function, the semantics are identical). It is used to allocate 147realloc C function, the semantics are identical). It is used to allocate
132and free memory (no surprises here). If it returns zero when memory 148and free memory (no surprises here). If it returns zero when memory
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164 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 180 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
165 <dd> 181 <dd>
166 <p>This will initialise the default event loop if it hasn't been initialised 182 <p>This will initialise the default event loop if it hasn't been initialised
167yet and return it. If the default loop could not be initialised, returns 183yet and return it. If the default loop could not be initialised, returns
168false. 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
169flags).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
170 <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
171function.</p> 187function.</p>
172 <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
173backends to use, and is usually specified as 0 (or EVFLAG_AUTO).</p> 189backends to use, and is usually specified as <code>0</code> (or EVFLAG_AUTO).</p>
174 <p>It supports the following flags:</p> 190 <p>It supports the following flags:</p>
175 <p> 191 <p>
176 <dl> 192 <dl>
177 <dt><code>EVFLAG_AUTO</code></dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
178 <dd> 194 <dd>
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186<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 202<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
187override the flags completely if it is found in the environment. This is 203override the flags completely if it is found in the environment. This is
188useful to try out specific backends to test their performance, or to work 204useful to try out specific backends to test their performance, or to work
189around bugs.</p> 205around bugs.</p>
190 </dd> 206 </dd>
191 <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt> 207 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
192 <dd> 208 <dd>
193 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 209 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
194libev tries to roll its own fd_set with no limits on the number of fds, 210libev tries to roll its own fd_set with no limits on the number of fds,
195but if that fails, expect a fairly low limit on the number of fds when 211but if that fails, expect a fairly low limit on the number of fds when
196using this backend. It doesn't scale too well (O(highest_fd)), but its usually 212using this backend. It doesn't scale too well (O(highest_fd)), but its usually
197the fastest backend for a low number of fds.</p> 213the fastest backend for a low number of fds.</p>
198 </dd> 214 </dd>
199 <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt> 215 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
200 <dd> 216 <dd>
201 <p>And this is your standard poll(2) backend. It's more complicated than 217 <p>And this is your standard poll(2) backend. It's more complicated than
202select, but handles sparse fds better and has no artificial limit on the 218select, but handles sparse fds better and has no artificial limit on the
203number of fds you can use (except it will slow down considerably with a 219number of fds you can use (except it will slow down considerably with a
204lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p> 220lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
205 </dd> 221 </dd>
206 <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt> 222 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
207 <dd> 223 <dd>
208 <p>For few fds, this backend is a bit little slower than poll and select, 224 <p>For few fds, this backend is a bit little slower than poll and select,
209but it scales phenomenally better. While poll and select usually scale like 225but it scales phenomenally better. While poll and select usually scale like
210O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 226O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
211either O(1) or O(active_fds).</p> 227either O(1) or O(active_fds).</p>
212 <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
213result in some caching, there is still a syscall per such incident 229result in some caching, there is still a syscall per such incident
214(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
215best 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
216well 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>
217 </dd> 236 </dd>
218 <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt> 237 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
219 <dd> 238 <dd>
220 <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
221was 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
222anything but sockets and pipes, except on Darwin, where of course its 241anything but sockets and pipes, except on Darwin, where of course its
223completely useless). For this reason its not being &quot;autodetected&quot; unless 242completely useless). For this reason its not being &quot;autodetected&quot; unless
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226kernel is more efficient (which says nothing about its actual speed, of 245kernel is more efficient (which says nothing about its actual speed, of
227course). While starting and stopping an I/O watcher does not cause an 246course). While starting and stopping an I/O watcher does not cause an
228extra syscall as with epoll, it still adds up to four event changes per 247extra syscall as with epoll, it still adds up to four event changes per
229incident, so its best to avoid that.</p> 248incident, so its best to avoid that.</p>
230 </dd> 249 </dd>
231 <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt> 250 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
232 <dd> 251 <dd>
233 <p>This is not implemented yet (and might never be).</p> 252 <p>This is not implemented yet (and might never be).</p>
234 </dd> 253 </dd>
235 <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt> 254 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
236 <dd> 255 <dd>
237 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris, 256 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
238it's really slow, but it still scales very well (O(active_fds)).</p> 257it's really slow, but it still scales very well (O(active_fds)).</p>
239 </dd> 258 <p>Please note that solaris ports can result in a lot of spurious
240 <dt><code>EVMETHOD_ALL</code></dt> 259notifications, so you need to use non-blocking I/O or other means to avoid
260blocking when no data (or space) is available.</p>
241 <dd> 261 </dd>
262 <dt><code>EVBACKEND_ALL</code></dt>
263 <dd>
242 <p>Try all backends (even potentially broken ones). Since this is a mask, you 264 <p>Try all backends (even potentially broken ones that wouldn't be tried
243can do stuff like <code>EVMETHOD_ALL &amp; ~EVMETHOD_KQUEUE</code>.</p> 265with <code>EVFLAG_AUTO</code>). Since this is a mask, you can do stuff such as
266<code>EVBACKEND_ALL &amp; ~EVBACKEND_KQUEUE</code>.</p>
244 </dd> 267 </dd>
245 </dl> 268 </dl>
246 </p> 269 </p>
247 <p>If one or more of these are ored into the flags value, then only these 270 <p>If one or more of these are ored into the flags value, then only these
248backends will be tried (in the reverse order as given here). If none are 271backends will be tried (in the reverse order as given here). If none are
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271 <dd> 294 <dd>
272 <p>This function reinitialises the kernel state for backends that have 295 <p>This function reinitialises the kernel state for backends that have
273one. Despite the name, you can call it anytime, but it makes most sense 296one. Despite the name, you can call it anytime, but it makes most sense
274after forking, in either the parent or child process (or both, but that 297after forking, in either the parent or child process (or both, but that
275again makes little sense).</p> 298again makes little sense).</p>
276 <p>You <i>must</i> call this function after forking if and only if you want to 299 <p>You <i>must</i> call this function in the child process after forking if and
277use the event library in both processes. If you just fork+exec, you don't 300only if you want to use the event library in both processes. If you just
278have to call it.</p> 301fork+exec, you don't have to call it.</p>
279 <p>The function itself is quite fast and it's usually not a problem to call 302 <p>The function itself is quite fast and it's usually not a problem to call
280it just in case after a fork. To make this easy, the function will fit in 303it just in case after a fork. To make this easy, the function will fit in
281quite nicely into a call to <code>pthread_atfork</code>:</p> 304quite nicely into a call to <code>pthread_atfork</code>:</p>
282<pre> pthread_atfork (0, 0, ev_default_fork); 305<pre> pthread_atfork (0, 0, ev_default_fork);
283 306
284</pre> 307</pre>
308 <p>At the moment, <code>EVBACKEND_SELECT</code> and <code>EVBACKEND_POLL</code> are safe to use
309without calling this function, so if you force one of those backends you
310do not need to care.</p>
285 </dd> 311 </dd>
286 <dt>ev_loop_fork (loop)</dt> 312 <dt>ev_loop_fork (loop)</dt>
287 <dd> 313 <dd>
288 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 314 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
289<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 315<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
290after fork, and how you do this is entirely your own problem.</p> 316after fork, and how you do this is entirely your own problem.</p>
291 </dd> 317 </dd>
292 <dt>unsigned int ev_method (loop)</dt> 318 <dt>unsigned int ev_backend (loop)</dt>
293 <dd> 319 <dd>
294 <p>Returns one of the <code>EVMETHOD_*</code> flags indicating the event backend in 320 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
295use.</p> 321use.</p>
296 </dd> 322 </dd>
297 <dt>ev_tstamp ev_now (loop)</dt> 323 <dt>ev_tstamp ev_now (loop)</dt>
298 <dd> 324 <dd>
299 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop 325 <p>Returns the current &quot;event loop time&quot;, which is the time the event loop
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397with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher 423with a watcher-specific start function (<code>ev_&lt;type&gt;_start (loop, watcher
398*)</code>), and you can stop watching for events at any time by calling the 424*)</code>), and you can stop watching for events at any time by calling the
399corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 425corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
400<p>As long as your watcher is active (has been started but not stopped) you 426<p>As long as your watcher is active (has been started but not stopped) you
401must not touch the values stored in it. Most specifically you must never 427must not touch the values stored in it. Most specifically you must never
402reinitialise it or call its set method.</p> 428reinitialise it or call its set macro.</p>
403<p>You can check whether an event is active by calling the <code>ev_is_active 429<p>You can check whether an event is active by calling the <code>ev_is_active
404(watcher *)</code> macro. To see whether an event is outstanding (but the 430(watcher *)</code> macro. To see whether an event is outstanding (but the
405callback for it has not been called yet) you can use the <code>ev_is_pending 431callback for it has not been called yet) you can use the <code>ev_is_pending
406(watcher *)</code> macro.</p> 432(watcher *)</code> macro.</p>
407<p>Each and every callback receives the event loop pointer as first, the 433<p>Each and every callback receives the event loop pointer as first, the
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519(the linux epoll backend is a notable example) cannot handle dup'ed file 545(the linux epoll backend is a notable example) cannot handle dup'ed file
520descriptors correctly if you register interest in two or more fds pointing 546descriptors correctly if you register interest in two or more fds pointing
521to the same underlying file/socket etc. description (that is, they share 547to the same underlying file/socket etc. description (that is, they share
522the same underlying &quot;file open&quot;).</p> 548the same underlying &quot;file open&quot;).</p>
523<p>If you must do this, then force the use of a known-to-be-good backend 549<p>If you must do this, then force the use of a known-to-be-good backend
524(at the time of this writing, this includes only EVMETHOD_SELECT and 550(at the time of this writing, this includes only <code>EVBACKEND_SELECT</code> and
525EVMETHOD_POLL).</p> 551<code>EVBACKEND_POLL</code>).</p>
526<dl> 552<dl>
527 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 553 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
528 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 554 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
529 <dd> 555 <dd>
530 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive 556 <p>Configures an <code>ev_io</code> watcher. The fd is the file descriptor to rceeive
531events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ | 557events for and events is either <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_READ |
532EV_WRITE</code> to receive the given events.</p> 558EV_WRITE</code> to receive the given events.</p>
559 <p>Please note that most of the more scalable backend mechanisms (for example
560epoll and solaris ports) can result in spurious readyness notifications
561for file descriptors, so you practically need to use non-blocking I/O (and
562treat callback invocation as hint only), or retest separately with a safe
563interface before doing I/O (XLib can do this), or force the use of either
564<code>EVBACKEND_SELECT</code> or <code>EVBACKEND_POLL</code>, which don't suffer from this
565problem. Also note that it is quite easy to have your callback invoked
566when the readyness condition is no longer valid even when employing
567typical ways of handling events, so its a good idea to use non-blocking
568I/O unconditionally.</p>
533 </dd> 569 </dd>
534</dl> 570</dl>
535 571
536</div> 572</div>
537<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 573<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>

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