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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="Wed Nov 28 12:27:27 2007" /> 9 <meta name="created" content="Thu Nov 29 18:28:02 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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133watcher.</p> 133watcher.</p>
134 134
135</div> 135</div>
136<h1 id="FEATURES">FEATURES</h1> 136<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 137<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 138<p>Libev supports <code>select</code>, <code>poll</code>, the Linux-specific <code>epoll</code>, the
139bsd-specific <code>kqueue</code> and the solaris-specific event port mechanisms 139BSD-specific <code>kqueue</code> and the Solaris-specific event port mechanisms
140for file descriptor events (<code>ev_io</code>), relative timers (<code>ev_timer</code>), 140for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
141(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 142with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 143(<code>ev_signal</code>), process status change events (<code>ev_child</code>), and event
143event watchers dealing with the event loop mechanism itself (<code>ev_idle</code>, 144watchers dealing with the event loop mechanism itself (<code>ev_idle</code>,
144<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as 145<code>ev_embed</code>, <code>ev_prepare</code> and <code>ev_check</code> watchers) as well as
145file watchers (<code>ev_stat</code>) and even limited support for fork events 146file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 147(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 148<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 149<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent
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229might be supported on the current system, you would need to look at 230might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 231<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 232recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 233 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 234 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 235 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 236 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 237 <p>Sets the allocation function to use (the prototype is similar - the
237identical to the realloc C function). It is used to allocate and free 238semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 239allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 240memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 241potentially destructive action. The default is your system realloc
242function.</p>
241 <p>You could override this function in high-availability programs to, say, 243 <p>You could override this function in high-availability programs to, say,
242free some memory if it cannot allocate memory, to use a special allocator, 244free some memory if it cannot allocate memory, to use a special allocator,
243or even to sleep a while and retry until some memory is available.</p> 245or even to sleep a while and retry until some memory is available.</p>
244 <p>Example: Replace the libev allocator with one that waits a bit and then 246 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 247retries).</p>
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323or setgid) then libev will <i>not</i> look at the environment variable 325or setgid) then libev will <i>not</i> look at the environment variable
324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 326<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 327override the flags completely if it is found in the environment. This is
326useful to try out specific backends to test their performance, or to work 328useful to try out specific backends to test their performance, or to work
327around bugs.</p> 329around bugs.</p>
330 </dd>
331 <dt><code>EVFLAG_FORKCHECK</code></dt>
332 <dd>
333 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
334a fork, you can also make libev check for a fork in each iteration by
335enabling this flag.</p>
336 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
337and thus this might slow down your event loop if you do a lot of loop
338iterations and little real work, but is usually not noticable (on my
339Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
340without a syscall and thus <i>very</i> fast, but my Linux system also has
341<code>pthread_atfork</code> which is even faster).</p>
342 <p>The big advantage of this flag is that you can forget about fork (and
343forget about forgetting to tell libev about forking) when you use this
344flag.</p>
345 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
346environment variable.</p>
328 </dd> 347 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 348 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 349 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 350 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
332libev tries to roll its own fd_set with no limits on the number of fds, 351libev tries to roll its own fd_set with no limits on the number of fds,
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950 </dd> 969 </dd>
951 <dt>ev_timer_again (loop)</dt> 970 <dt>ev_timer_again (loop)</dt>
952 <dd> 971 <dd>
953 <p>This will act as if the timer timed out and restart it again if it is 972 <p>This will act as if the timer timed out and restart it again if it is
954repeating. The exact semantics are:</p> 973repeating. The exact semantics are:</p>
974 <p>If the timer is pending, its pending status is cleared.</p>
955 <p>If the timer is started but nonrepeating, stop it.</p> 975 <p>If the timer is started but nonrepeating, stop it (as if it timed out).</p>
956 <p>If the timer is repeating, either start it if necessary (with the repeat 976 <p>If the timer is repeating, either start it if necessary (with the
957value), or reset the running timer to the repeat value.</p> 977<code>repeat</code> value), or reset the running timer to the <code>repeat</code> value.</p>
958 <p>This sounds a bit complicated, but here is a useful and typical 978 <p>This sounds a bit complicated, but here is a useful and typical
959example: Imagine you have a tcp connection and you want a so-called 979example: Imagine you have a tcp connection and you want a so-called idle
960idle timeout, that is, you want to be called when there have been, 980timeout, that is, you want to be called when there have been, say, 60
961say, 60 seconds of inactivity on the socket. The easiest way to do 981seconds of inactivity on the socket. The easiest way to do this is to
962this is to configure an <code>ev_timer</code> with <code>after</code>=<code>repeat</code>=<code>60</code> and calling 982configure an <code>ev_timer</code> with a <code>repeat</code> value of <code>60</code> and then call
963<code>ev_timer_again</code> each time you successfully read or write some data. If 983<code>ev_timer_again</code> each time you successfully read or write some data. If
964you go into an idle state where you do not expect data to travel on the 984you go into an idle state where you do not expect data to travel on the
965socket, you can stop the timer, and again will automatically restart it if 985socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
966need be.</p> 986automatically restart it if need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 987 <p>That means you can ignore the <code>after</code> value and <code>ev_timer_start</code>
968and only ever use the <code>repeat</code> value:</p> 988altogether and only ever use the <code>repeat</code> value and <code>ev_timer_again</code>:</p>
969<pre> ev_timer_init (timer, callback, 0., 5.); 989<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer); 990 ev_timer_again (loop, timer);
971 ... 991 ...
972 timer-&gt;again = 17.; 992 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer); 993 ev_timer_again (loop, timer);
974 ... 994 ...
975 timer-&gt;again = 10.; 995 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer); 996 ev_timer_again (loop, timer);
977 997
978</pre> 998</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want 999 <p>This is more slightly efficient then stopping/starting the timer each time
980to modify its timeout value.</p> 1000you want to modify its timeout value.</p>
981 </dd> 1001 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt> 1002 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd> 1003 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1004 <p>The current <code>repeat</code> value. Will be used each time the watcher times out
985or <code>ev_timer_again</code> is called and determines the next timeout (if any), 1005or <code>ev_timer_again</code> is called and determines the next timeout (if any),
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1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1266<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does
1247not exist&quot; is a status change like any other. The condition &quot;path does 1267not exist&quot; is a status change like any other. The condition &quot;path does
1248not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is 1268not exist&quot; is signified by the <code>st_nlink</code> field being zero (which is
1249otherwise always forced to be at least one) and all the other fields of 1269otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p> 1270the stat buffer having unspecified contents.</p>
1271<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1272relative and your working directory changes, the behaviour is undefined.</p>
1251<p>Since there is no standard to do this, the portable implementation simply 1273<p>Since there is no standard to do this, the portable implementation simply
1252calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You 1274calls <code>stat (2)</code> regularly on the path to see if it changed somehow. You
1253can specify a recommended polling interval for this case. If you specify 1275can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1276a polling interval of <code>0</code> (highly recommended!) then a <i>suitable,
1255unspecified default</i> value will be used (which you can expect to be around 1277unspecified default</i> value will be used (which you can expect to be around

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