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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 09:46:41 2007" /> 9 <meta name="created" content="Fri Nov 23 09:26:40 2007" />
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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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17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 19<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 20<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 27</ul>
27</li> 28</li>
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30<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
32<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#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>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the 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>
36</ul> 37</ul>
37</li> 38</li>
38<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>
39<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
40</li> 43</li>
41</ul><hr /> 44</ul><hr />
42<!-- INDEX END --> 45<!-- INDEX END -->
43 46
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87support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
88argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 91argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89will not have this argument.</p> 92will not have this argument.</p>
90 93
91</div> 94</div>
92<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
93<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
94<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
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the 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
97called <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
98to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
99<dl> 108<dl>
100 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
101 <dd> 110 <dd>
102 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. Please note that the
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you actually want to know.</p>
103 </dd> 114 </dd>
104 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
105 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
106 <dd> 117 <dd>
107 <p>You can find out the major and minor version numbers of the library 118 <p>You can find out the major and minor version numbers of the library
… …
112 <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,
113as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
114compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
115not a problem.</p> 126not a problem.</p>
116 </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>
117 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt> 144 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
118 <dd> 145 <dd>
119 <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
120realloc C function, the semantics are identical). It is used to allocate 147realloc C function, the semantics are identical). It is used to allocate
121and 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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142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 169<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 170<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144types of such loops, the <i>default</i> loop, which supports signals and child 171types of such loops, the <i>default</i> loop, which supports signals and child
145events, and dynamically created loops which do not.</p> 172events, and dynamically created loops which do not.</p>
146<p>If you use threads, a common model is to run the default event loop 173<p>If you use threads, a common model is to run the default event loop
147in your main thread (or in a separate thrad) and for each thread you 174in your main thread (or in a separate thread) and for each thread you
148create, you also create another event loop. Libev itself does no locking 175create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 176whatsoever, so if you mix calls to the same event loop in different
150threads, make sure you lock (this is usually a bad idea, though, even if 177threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because it's hideous and inefficient).</p> 178done correctly, because it's hideous and inefficient).</p>
152<dl> 179<dl>
153 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt> 180 <dt>struct ev_loop *ev_default_loop (unsigned int flags)</dt>
154 <dd> 181 <dd>
155 <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
156yet 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
157false. 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
158flags).</p> 185flags. If that is troubling you, check <code>ev_backend ()</code> afterwards).</p>
159 <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
160function.</p> 187function.</p>
161 <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
162backends 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>
163 <p>It supports the following flags:</p> 190 <p>It supports the following flags:</p>
164 <p> 191 <p>
165 <dl> 192 <dl>
166 <dt><code>EVFLAG_AUTO</code></dt> 193 <dt><code>EVFLAG_AUTO</code></dt>
167 <dd> 194 <dd>
… …
175<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 202<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
176override 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
177useful 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
178around bugs.</p> 205around bugs.</p>
179 </dd> 206 </dd>
180 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 207 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
181 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> 208 <dd>
182 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> 209 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
183 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> 210libev tries to roll its own fd_set with no limits on the number of fds,
184 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> 211but if that fails, expect a fairly low limit on the number of fds when
185 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> 212using this backend. It doesn't scale too well (O(highest_fd)), but its usually
213the fastest backend for a low number of fds.</p>
186 <dd> 214 </dd>
187 <p>If one or more of these are ored into the flags value, then only these 215 <dt><code>EVBACKEND_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
188backends will be tried (in the reverse order as given here). If one are 216 <dd>
189specified, any backend will do.</p> 217 <p>And this is your standard poll(2) backend. It's more complicated than
218select, but handles sparse fds better and has no artificial limit on the
219number of fds you can use (except it will slow down considerably with a
220lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
221 </dd>
222 <dt><code>EVBACKEND_EPOLL</code> (value 4, Linux)</dt>
223 <dd>
224 <p>For few fds, this backend is a bit little slower than poll and select,
225but it scales phenomenally better. While poll and select usually scale like
226O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
227either O(1) or O(active_fds).</p>
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
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
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>
236 </dd>
237 <dt><code>EVBACKEND_KQUEUE</code> (value 8, most BSD clones)</dt>
238 <dd>
239 <p>Kqueue deserves special mention, as at the time of this writing, it
240was broken on all BSDs except NetBSD (usually it doesn't work with
241anything but sockets and pipes, except on Darwin, where of course its
242completely useless). For this reason its not being &quot;autodetected&quot; unless
243you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
244 <p>It scales in the same way as the epoll backend, but the interface to the
245kernel is more efficient (which says nothing about its actual speed, of
246course). While starting and stopping an I/O watcher does not cause an
247extra syscall as with epoll, it still adds up to four event changes per
248incident, so its best to avoid that.</p>
249 </dd>
250 <dt><code>EVBACKEND_DEVPOLL</code> (value 16, Solaris 8)</dt>
251 <dd>
252 <p>This is not implemented yet (and might never be).</p>
253 </dd>
254 <dt><code>EVBACKEND_PORT</code> (value 32, Solaris 10)</dt>
255 <dd>
256 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
257it's really slow, but it still scales very well (O(active_fds)).</p>
258 <p>Please note that solaris ports can result in a lot of spurious
259notifications, so you need to use non-blocking I/O or other means to avoid
260blocking when no data (or space) is available.</p>
261 </dd>
262 <dt><code>EVBACKEND_ALL</code></dt>
263 <dd>
264 <p>Try all backends (even potentially broken ones that wouldn't be tried
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>
190 </dd> 267 </dd>
191 </dl> 268 </dl>
192 </p> 269 </p>
270 <p>If one or more of these are ored into the flags value, then only these
271backends will be tried (in the reverse order as given here). If none are
272specified, most compiled-in backend will be tried, usually in reverse
273order of their flag values :)</p>
193 </dd> 274 </dd>
194 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 275 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
195 <dd> 276 <dd>
196 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 277 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
197always distinct from the default loop. Unlike the default loop, it cannot 278always distinct from the default loop. Unlike the default loop, it cannot
… …
213 <dd> 294 <dd>
214 <p>This function reinitialises the kernel state for backends that have 295 <p>This function reinitialises the kernel state for backends that have
215one. 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
216after 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
217again makes little sense).</p> 298again makes little sense).</p>
218 <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
219use 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
220have to call it.</p> 301fork+exec, you don't have to call it.</p>
221 <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
222it 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
223quite nicely into a call to <code>pthread_atfork</code>:</p> 304quite nicely into a call to <code>pthread_atfork</code>:</p>
224<pre> pthread_atfork (0, 0, ev_default_fork); 305<pre> pthread_atfork (0, 0, ev_default_fork);
225 306
226</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>
227 </dd> 311 </dd>
228 <dt>ev_loop_fork (loop)</dt> 312 <dt>ev_loop_fork (loop)</dt>
229 <dd> 313 <dd>
230 <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
231<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
232after 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>
233 </dd> 317 </dd>
234 <dt>unsigned int ev_method (loop)</dt> 318 <dt>unsigned int ev_backend (loop)</dt>
235 <dd> 319 <dd>
236 <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
237use.</p> 321use.</p>
238 </dd> 322 </dd>
239 <dt>ev_tstamp ev_now (loop)</dt> 323 <dt>ev_tstamp ev_now (loop)</dt>
240 <dd> 324 <dd>
241 <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
… …
259your process until at least one new event arrives, and will return after 343your process until at least one new event arrives, and will return after
260one iteration of the loop.</p> 344one iteration of the loop.</p>
261 <p>This flags value could be used to implement alternative looping 345 <p>This flags value could be used to implement alternative looping
262constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 346constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
263more generic mechanism.</p> 347more generic mechanism.</p>
348 <p>Here are the gory details of what ev_loop does:</p>
349<pre> 1. If there are no active watchers (reference count is zero), return.
350 2. Queue and immediately call all prepare watchers.
351 3. If we have been forked, recreate the kernel state.
352 4. Update the kernel state with all outstanding changes.
353 5. Update the &quot;event loop time&quot;.
354 6. Calculate for how long to block.
355 7. Block the process, waiting for events.
356 8. Update the &quot;event loop time&quot; and do time jump handling.
357 9. Queue all outstanding timers.
358 10. Queue all outstanding periodics.
359 11. If no events are pending now, queue all idle watchers.
360 12. Queue all check watchers.
361 13. Call all queued watchers in reverse order (i.e. check watchers first).
362 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
363 was used, return, otherwise continue with step #1.
364
365</pre>
264 </dd> 366 </dd>
265 <dt>ev_unloop (loop, how)</dt> 367 <dt>ev_unloop (loop, how)</dt>
266 <dd> 368 <dd>
267 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 369 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
268has processed all outstanding events). The <code>how</code> argument must be either 370has processed all outstanding events). The <code>how</code> argument must be either
269<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or 371<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
270<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> 372<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
271 </dd> 373 </dd>
272 <dt>ev_ref (loop)</dt> 374 <dt>ev_ref (loop)</dt>
273 <dt>ev_unref (loop)</dt> 375 <dt>ev_unref (loop)</dt>
274 <dd> 376 <dd>
… …
321with 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
322*)</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
323corresponding 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>
324<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
325must 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
326reinitialise it or call its set method.</p> 428reinitialise it or call its set macro.</p>
327<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
328(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
329callback 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
330(watcher *)</code> macro.</p> 432(watcher *)</code> macro.</p>
331<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
… …
433<p>I/O watchers check whether a file descriptor is readable or writable 535<p>I/O watchers check whether a file descriptor is readable or writable
434in each iteration of the event loop (This behaviour is called 536in each iteration of the event loop (This behaviour is called
435level-triggering because you keep receiving events as long as the 537level-triggering because you keep receiving events as long as the
436condition persists. Remember you can stop the watcher if you don't want to 538condition persists. Remember you can stop the watcher if you don't want to
437act on the event and neither want to receive future events).</p> 539act on the event and neither want to receive future events).</p>
438<p>In general you can register as many read and/or write event watchers oer 540<p>In general you can register as many read and/or write event watchers per
439fd as you want (as long as you don't confuse yourself). Setting all file 541fd as you want (as long as you don't confuse yourself). Setting all file
440descriptors to non-blocking mode is also usually a good idea (but not 542descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p> 543required if you know what you are doing).</p>
442<p>You have to be careful with dup'ed file descriptors, though. Some backends 544<p>You have to be careful with dup'ed file descriptors, though. Some backends
443(the linux epoll backend is a notable example) cannot handle dup'ed file 545(the linux epoll backend is a notable example) cannot handle dup'ed file
444descriptors correctly if you register interest in two or more fds pointing 546descriptors correctly if you register interest in two or more fds pointing
445to the same file/socket etc. description.</p> 547to the same underlying file/socket etc. description (that is, they share
548the same underlying &quot;file open&quot;).</p>
446<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
447(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
448EVMETHOD_POLL).</p> 551<code>EVBACKEND_POLL</code>).</p>
449<dl> 552<dl>
450 <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>
451 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 554 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
452 <dd> 555 <dd>
453 <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
454events 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 |
455EV_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>
456 </dd> 569 </dd>
457</dl> 570</dl>
458 571
459</div> 572</div>
460<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>
461<div id="code_ev_timer_code_relative_and_opti-2"> 574<div id="code_ev_timer_code_relative_and_opti-2">
462<p>Timer watchers are simple relative timers that generate an event after a 575<p>Timer watchers are simple relative timers that generate an event after a
463given time, and optionally repeating in regular intervals after that.</p> 576given time, and optionally repeating in regular intervals after that.</p>
464<p>The timers are based on real time, that is, if you register an event that 577<p>The timers are based on real time, that is, if you register an event that
465times out after an hour and youreset your system clock to last years 578times out after an hour and you reset your system clock to last years
466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 579time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
467detecting time jumps is hard, and soem inaccuracies are unavoidable (the 580detecting time jumps is hard, and some inaccuracies are unavoidable (the
468monotonic clock option helps a lot here).</p> 581monotonic clock option helps a lot here).</p>
469<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 582<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
470time. This is usually the right thing as this timestamp refers to the time 583time. This is usually the right thing as this timestamp refers to the time
471of the event triggering whatever timeout you are modifying/starting. If 584of the event triggering whatever timeout you are modifying/starting. If
472you suspect event processing to be delayed and you *need* to base the timeout 585you suspect event processing to be delayed and you <i>need</i> to base the timeout
473ion the current time, use something like this to adjust for this:</p> 586on the current time, use something like this to adjust for this:</p>
474<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 587<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
475 588
476</pre> 589</pre>
590<p>The callback is guarenteed to be invoked only when its timeout has passed,
591but if multiple timers become ready during the same loop iteration then
592order of execution is undefined.</p>
477<dl> 593<dl>
478 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 594 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
479 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 595 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
480 <dd> 596 <dd>
481 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 597 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
483timer will automatically be configured to trigger again <code>repeat</code> seconds 599timer will automatically be configured to trigger again <code>repeat</code> seconds
484later, again, and again, until stopped manually.</p> 600later, again, and again, until stopped manually.</p>
485 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 601 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
486configure a timer to trigger every 10 seconds, then it will trigger at 602configure a timer to trigger every 10 seconds, then it will trigger at
487exactly 10 second intervals. If, however, your program cannot keep up with 603exactly 10 second intervals. If, however, your program cannot keep up with
488the timer (ecause it takes longer than those 10 seconds to do stuff) the 604the timer (because it takes longer than those 10 seconds to do stuff) the
489timer will not fire more than once per event loop iteration.</p> 605timer will not fire more than once per event loop iteration.</p>
490 </dd> 606 </dd>
491 <dt>ev_timer_again (loop)</dt> 607 <dt>ev_timer_again (loop)</dt>
492 <dd> 608 <dd>
493 <p>This will act as if the timer timed out and restart it again if it is 609 <p>This will act as if the timer timed out and restart it again if it is
… …
519take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 635take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
520roughly 10 seconds later and of course not if you reset your system time 636roughly 10 seconds later and of course not if you reset your system time
521again).</p> 637again).</p>
522<p>They can also be used to implement vastly more complex timers, such as 638<p>They can also be used to implement vastly more complex timers, such as
523triggering an event on eahc midnight, local time.</p> 639triggering an event on eahc midnight, local time.</p>
640<p>As with timers, the callback is guarenteed to be invoked only when the
641time (<code>at</code>) has been passed, but if multiple periodic timers become ready
642during the same loop iteration then order of execution is undefined.</p>
524<dl> 643<dl>
525 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 644 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
526 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 645 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
527 <dd> 646 <dd>
528 <p>Lots of arguments, lets sort it out... There are basically three modes of 647 <p>Lots of arguments, lets sort it out... There are basically three modes of
529operation, and we will explain them from simplest to complex:</p> 648operation, and we will explain them from simplest to complex:</p>
530
531
532
533
534 <p> 649 <p>
535 <dl> 650 <dl>
536 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 651 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
537 <dd> 652 <dd>
538 <p>In this configuration the watcher triggers an event at the wallclock time 653 <p>In this configuration the watcher triggers an event at the wallclock time
… …
562 <dd> 677 <dd>
563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 678 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
564ignored. Instead, each time the periodic watcher gets scheduled, the 679ignored. Instead, each time the periodic watcher gets scheduled, the
565reschedule callback will be called with the watcher as first, and the 680reschedule callback will be called with the watcher as first, and the
566current time as second argument.</p> 681current time as second argument.</p>
567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 682 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
568periodic watcher, ever, or make any event loop modifications</i>. If you need 683ever, or make any event loop modifications</i>. If you need to stop it,
569to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 684return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
570 <p>Also, <i>this callback must always return a time that is later than the 685starting a prepare watcher).</p>
571passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
572 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 686 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
573ev_tstamp now)</code>, e.g.:</p> 687ev_tstamp now)</code>, e.g.:</p>
574<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 688<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
575 { 689 {
576 return now + 60.; 690 return now + 60.;
… …
579</pre> 693</pre>
580 <p>It must return the next time to trigger, based on the passed time value 694 <p>It must return the next time to trigger, based on the passed time value
581(that is, the lowest time value larger than to the second argument). It 695(that is, the lowest time value larger than to the second argument). It
582will usually be called just before the callback will be triggered, but 696will usually be called just before the callback will be triggered, but
583might be called at other times, too.</p> 697might be called at other times, too.</p>
698 <p>NOTE: <i>This callback must always return a time that is later than the
699passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
584 <p>This can be used to create very complex timers, such as a timer that 700 <p>This can be used to create very complex timers, such as a timer that
585triggers on each midnight, local time. To do this, you would calculate the 701triggers on each midnight, local time. To do this, you would calculate the
586next midnight after <code>now</code> and return the timestamp value for this. How you do this 702next midnight after <code>now</code> and return the timestamp value for this. How
587is, again, up to you (but it is not trivial).</p> 703you do this is, again, up to you (but it is not trivial, which is the main
704reason I omitted it as an example).</p>
588 </dd> 705 </dd>
589 </dl> 706 </dl>
590 </p> 707 </p>
591 </dd> 708 </dd>
592 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 709 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
662believe me.</p> 779believe me.</p>
663 </dd> 780 </dd>
664</dl> 781</dl>
665 782
666</div> 783</div>
667<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 784<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
668<div id="prepare_and_check_your_hooks_into_th-2"> 785<div id="code_ev_prepare_code_and_code_ev_che-2">
669<p>Prepare and check watchers are usually (but not always) used in tandem: 786<p>Prepare and check watchers are usually (but not always) used in tandem:
670Prepare watchers get invoked before the process blocks and check watchers 787prepare watchers get invoked before the process blocks and check watchers
671afterwards.</p> 788afterwards.</p>
672<p>Their main purpose is to integrate other event mechanisms into libev. This 789<p>Their main purpose is to integrate other event mechanisms into libev. This
673could be used, for example, to track variable changes, implement your own 790could be used, for example, to track variable changes, implement your own
674watchers, integrate net-snmp or a coroutine library and lots more.</p> 791watchers, integrate net-snmp or a coroutine library and lots more.</p>
675<p>This is done by examining in each prepare call which file descriptors need 792<p>This is done by examining in each prepare call which file descriptors need
676to be watched by the other library, registering <code>ev_io</code> watchers for 793to be watched by the other library, registering <code>ev_io</code> watchers for
677them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 794them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
678provide just this functionality). Then, in the check watcher you check for 795provide just this functionality). Then, in the check watcher you check for
679any events that occured (by checking the pending status of all watchers 796any events that occured (by checking the pending status of all watchers
680and stopping them) and call back into the library. The I/O and timer 797and stopping them) and call back into the library. The I/O and timer
681callbacks will never actually be called (but must be valid neverthelles, 798callbacks will never actually be called (but must be valid nevertheless,
682because you never know, you know?).</p> 799because you never know, you know?).</p>
683<p>As another example, the Perl Coro module uses these hooks to integrate 800<p>As another example, the Perl Coro module uses these hooks to integrate
684coroutines into libev programs, by yielding to other active coroutines 801coroutines into libev programs, by yielding to other active coroutines
685during each prepare and only letting the process block if no coroutines 802during each prepare and only letting the process block if no coroutines
686are ready to run (its actually more complicated, it only runs coroutines 803are ready to run (it's actually more complicated: it only runs coroutines
687with priority higher than the event loop and one lower priority once, 804with priority higher than or equal to the event loop and one coroutine
688using idle watchers to keep the event loop from blocking if lower-priority 805of lower priority, but only once, using idle watchers to keep the event
689coroutines exist, thus mapping low-priority coroutines to idle/background 806loop from blocking if lower-priority coroutines are active, thus mapping
690tasks).</p> 807low-priority coroutines to idle/background tasks).</p>
691<dl> 808<dl>
692 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 809 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
693 <dt>ev_check_init (ev_check *, callback)</dt> 810 <dt>ev_check_init (ev_check *, callback)</dt>
694 <dd> 811 <dd>
695 <p>Initialises and configures the prepare or check watcher - they have no 812 <p>Initialises and configures the prepare or check watcher - they have no
… …
706 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 823 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
707 <dd> 824 <dd>
708 <p>This function combines a simple timer and an I/O watcher, calls your 825 <p>This function combines a simple timer and an I/O watcher, calls your
709callback on whichever event happens first and automatically stop both 826callback on whichever event happens first and automatically stop both
710watchers. This is useful if you want to wait for a single event on an fd 827watchers. This is useful if you want to wait for a single event on an fd
711or timeout without havign to allocate/configure/start/stop/free one or 828or timeout without having to allocate/configure/start/stop/free one or
712more watchers yourself.</p> 829more watchers yourself.</p>
713 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 830 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
714is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and 831is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
715<code>events</code> set will be craeted and started.</p> 832<code>events</code> set will be craeted and started.</p>
716 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 833 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
717started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and 834started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
718repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of 835repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
719dubious value.</p> 836dubious value.</p>
720 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 837 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
721passed an events set like normal event callbacks (with a combination of 838passed an <code>revents</code> set like normal event callbacks (a combination of
722<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> 839<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
723value passed to <code>ev_once</code>:</p> 840value passed to <code>ev_once</code>:</p>
724<pre> static void stdin_ready (int revents, void *arg) 841<pre> static void stdin_ready (int revents, void *arg)
725 { 842 {
726 if (revents &amp; EV_TIMEOUT) 843 if (revents &amp; EV_TIMEOUT)
… …
749 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 866 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
750 </dd> 867 </dd>
751</dl> 868</dl>
752 869
753</div> 870</div>
871<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
872<div id="LIBEVENT_EMULATION_CONTENT">
873<p>Libev offers a compatibility emulation layer for libevent. It cannot
874emulate the internals of libevent, so here are some usage hints:</p>
875<dl>
876 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
877 <dt>* The following members are fully supported: ev_base, ev_callback,
878ev_arg, ev_fd, ev_res, ev_events.</dt>
879 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
880maintained by libev, it does not work exactly the same way as in libevent (consider
881it a private API).</dt>
882 <dt>* Priorities are not currently supported. Initialising priorities
883will fail and all watchers will have the same priority, even though there
884is an ev_pri field.</dt>
885 <dt>* Other members are not supported.</dt>
886 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
887to use the libev header file and library.</dt>
888</dl>
889
890</div>
891<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
892<div id="C_SUPPORT_CONTENT">
893<p>TBD.</p>
894
895</div>
754<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 896<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
755<div id="AUTHOR_CONTENT"> 897<div id="AUTHOR_CONTENT">
756<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 898<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
757 899
758</div> 900</div>

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