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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;" />
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14<!-- INDEX START --> 14<!-- INDEX START -->
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119</pre> 119</pre>
120 120
121</div> 121</div>
122<h1 id="DESCRIPTION">DESCRIPTION</h1> 122<h1 id="DESCRIPTION">DESCRIPTION</h1>
123<div id="DESCRIPTION_CONTENT"> 123<div id="DESCRIPTION_CONTENT">
124<p>The newest version of this document is also available as a html-formatted
125web page you might find easier to navigate when reading it for the first
126time: <a href="http://cvs.schmorp.de/libev/ev.html">http://cvs.schmorp.de/libev/ev.html</a>.</p>
124<p>Libev is an event loop: you register interest in certain events (such as a 127<p>Libev is an event loop: you register interest in certain events (such as a
125file descriptor being readable or a timeout occuring), and it will manage 128file descriptor being readable or a timeout occuring), and it will manage
126these event sources and provide your program with events.</p> 129these event sources and provide your program with events.</p>
127<p>To do this, it must take more or less complete control over your process 130<p>To do this, it must take more or less complete control over your process
128(or thread) by executing the <i>event loop</i> handler, and will then 131(or thread) by executing the <i>event loop</i> handler, and will then
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133watcher.</p> 136watcher.</p>
134 137
135</div> 138</div>
136<h1 id="FEATURES">FEATURES</h1> 139<h1 id="FEATURES">FEATURES</h1>
137<div id="FEATURES_CONTENT"> 140<div id="FEATURES_CONTENT">
138<p>Libev supports <code>select</code>, <code>poll</code>, the linux-specific <code>epoll</code>, the 141<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 142BSD-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>), 143for file descriptor events (<code>ev_io</code>), the Linux <code>inotify</code> interface
144(for <code>ev_stat</code>), relative timers (<code>ev_timer</code>), absolute timers
141absolute timers with customised rescheduling (<code>ev_periodic</code>), synchronous 145with customised rescheduling (<code>ev_periodic</code>), synchronous signals
142signals (<code>ev_signal</code>), process status change events (<code>ev_child</code>), and 146(<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>, 147watchers 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 148<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 149file watchers (<code>ev_stat</code>) and even limited support for fork events
146(<code>ev_fork</code>).</p> 150(<code>ev_fork</code>).</p>
147<p>It also is quite fast (see this 151<p>It also is quite fast (see this
148<a href="http://libev.schmorp.de/bench.html">benchmark</a> comparing it to libevent 152<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 233might be supported on the current system, you would need to look at
230<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for 234<code>ev_embeddable_backends () &amp; ev_supported_backends ()</code>, likewise for
231recommended ones.</p> 235recommended ones.</p>
232 <p>See the description of <code>ev_embed</code> watchers for more info.</p> 236 <p>See the description of <code>ev_embed</code> watchers for more info.</p>
233 </dd> 237 </dd>
234 <dt>ev_set_allocator (void *(*cb)(void *ptr, size_t size))</dt> 238 <dt>ev_set_allocator (void *(*cb)(void *ptr, long size))</dt>
235 <dd> 239 <dd>
236 <p>Sets the allocation function to use (the prototype and semantics are 240 <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 241semantics is identical - to the realloc C function). It is used to
238memory (no surprises here). If it returns zero when memory needs to be 242allocate and free memory (no surprises here). If it returns zero when
239allocated, the library might abort or take some potentially destructive 243memory needs to be allocated, the library might abort or take some
240action. The default is your system realloc function.</p> 244potentially destructive action. The default is your system realloc
245function.</p>
241 <p>You could override this function in high-availability programs to, say, 246 <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, 247free 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> 248or 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 249 <p>Example: Replace the libev allocator with one that waits a bit and then
245retries).</p> 250retries).</p>
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324<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 329<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
325override the flags completely if it is found in the environment. This is 330override 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 331useful to try out specific backends to test their performance, or to work
327around bugs.</p> 332around bugs.</p>
328 </dd> 333 </dd>
334 <dt><code>EVFLAG_FORKCHECK</code></dt>
335 <dd>
336 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after
337a fork, you can also make libev check for a fork in each iteration by
338enabling this flag.</p>
339 <p>This works by calling <code>getpid ()</code> on every iteration of the loop,
340and thus this might slow down your event loop if you do a lot of loop
341iterations and little real work, but is usually not noticeable (on my
342Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence
343without a syscall and thus <i>very</i> fast, but my Linux system also has
344<code>pthread_atfork</code> which is even faster).</p>
345 <p>The big advantage of this flag is that you can forget about fork (and
346forget about forgetting to tell libev about forking) when you use this
347flag.</p>
348 <p>This flag setting cannot be overriden or specified in the <code>LIBEV_FLAGS</code>
349environment variable.</p>
350 </dd>
329 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt> 351 <dt><code>EVBACKEND_SELECT</code> (value 1, portable select backend)</dt>
330 <dd> 352 <dd>
331 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as 353 <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, 354libev tries to roll its own fd_set with no limits on the number of fds,
333but if that fails, expect a fairly low limit on the number of fds when 355but if that fails, expect a fairly low limit on the number of fds when
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461 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
462 <dd> 484 <dd>
463 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by 485 <p>Like <code>ev_default_fork</code>, but acts on an event loop created by
464<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop 486<code>ev_loop_new</code>. Yes, you have to call this on every allocated event loop
465after fork, and how you do this is entirely your own problem.</p> 487after fork, and how you do this is entirely your own problem.</p>
488 </dd>
489 <dt>unsigned int ev_loop_count (loop)</dt>
490 <dd>
491 <p>Returns the count of loop iterations for the loop, which is identical to
492the number of times libev did poll for new events. It starts at <code>0</code> and
493happily wraps around with enough iterations.</p>
494 <p>This value can sometimes be useful as a generation counter of sorts (it
495&quot;ticks&quot; the number of loop iterations), as it roughly corresponds with
496<code>ev_prepare</code> and <code>ev_check</code> calls.</p>
466 </dd> 497 </dd>
467 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
468 <dd> 499 <dd>
469 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in 500 <p>Returns one of the <code>EVBACKEND_*</code> flags indicating the event backend in
470use.</p> 501use.</p>
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738 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 769 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
739 <dd> 770 <dd>
740 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 771 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
741events but its callback has not yet been invoked). As long as a watcher 772events but its callback has not yet been invoked). As long as a watcher
742is pending (but not active) you must not call an init function on it (but 773is pending (but not active) you must not call an init function on it (but
743<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 774<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
744libev (e.g. you cnanot <code>free ()</code> it).</p> 775make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
776it).</p>
745 </dd> 777 </dd>
746 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 778 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
747 <dd> 779 <dd>
748 <p>Returns the callback currently set on the watcher.</p> 780 <p>Returns the callback currently set on the watcher.</p>
749 </dd> 781 </dd>
750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 782 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 783 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 784 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 785(modulo threads).</p>
786 </dd>
787 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
788 <dt>int ev_priority (ev_TYPE *watcher)</dt>
789 <dd>
790 <p>Set and query the priority of the watcher. The priority is a small
791integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
792(default: <code>-2</code>). Pending watchers with higher priority will be invoked
793before watchers with lower priority, but priority will not keep watchers
794from being executed (except for <code>ev_idle</code> watchers).</p>
795 <p>This means that priorities are <i>only</i> used for ordering callback
796invocation after new events have been received. This is useful, for
797example, to reduce latency after idling, or more often, to bind two
798watchers on the same event and make sure one is called first.</p>
799 <p>If you need to suppress invocation when higher priority events are pending
800you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
801 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
802pending.</p>
803 <p>The default priority used by watchers when no priority has been set is
804always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
805 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
806fine, as long as you do not mind that the priority value you query might
807or might not have been adjusted to be within valid range.</p>
808 </dd>
809 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
810 <dd>
811 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
812<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
813can deal with that fact.</p>
814 </dd>
815 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
816 <dd>
817 <p>If the watcher is pending, this function returns clears its pending status
818and returns its <code>revents</code> bitset (as if its callback was invoked). If the
819watcher isn't pending it does nothing and returns <code>0</code>.</p>
754 </dd> 820 </dd>
755</dl> 821</dl>
756 822
757 823
758 824
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869this situation even with a relatively standard program structure. Thus 935this situation even with a relatively standard program structure. Thus
870it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 936it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
871<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 937<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
872<p>If you cannot run the fd in non-blocking mode (for example you should not 938<p>If you cannot run the fd in non-blocking mode (for example you should not
873play around with an Xlib connection), then you have to seperately re-test 939play around with an Xlib connection), then you have to seperately re-test
874wether a file descriptor is really ready with a known-to-be good interface 940whether a file descriptor is really ready with a known-to-be good interface
875such as poll (fortunately in our Xlib example, Xlib already does this on 941such as poll (fortunately in our Xlib example, Xlib already does this on
876its own, so its quite safe to use).</p> 942its own, so its quite safe to use).</p>
877<dl> 943<dl>
878 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 944 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
879 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 945 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
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950 </dd> 1016 </dd>
951 <dt>ev_timer_again (loop)</dt> 1017 <dt>ev_timer_again (loop)</dt>
952 <dd> 1018 <dd>
953 <p>This will act as if the timer timed out and restart it again if it is 1019 <p>This will act as if the timer timed out and restart it again if it is
954repeating. The exact semantics are:</p> 1020repeating. The exact semantics are:</p>
1021 <p>If the timer is pending, its pending status is cleared.</p>
955 <p>If the timer is started but nonrepeating, stop it.</p> 1022 <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 1023 <p>If the timer is repeating, either start it if necessary (with the
957value), or reset the running timer to the repeat value.</p> 1024<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 1025 <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 1026example: 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, 1027timeout, 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 1028seconds 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 1029configure 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 1030<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 1031you 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 1032socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
966need be.</p> 1033automatically restart it if need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1034 <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> 1035altogether 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.); 1036<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer); 1037 ev_timer_again (loop, timer);
971 ... 1038 ...
972 timer-&gt;again = 17.; 1039 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer); 1040 ev_timer_again (loop, timer);
974 ... 1041 ...
975 timer-&gt;again = 10.; 1042 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer); 1043 ev_timer_again (loop, timer);
977 1044
978</pre> 1045</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want 1046 <p>This is more slightly efficient then stopping/starting the timer each time
980to modify its timeout value.</p> 1047you want to modify its timeout value.</p>
981 </dd> 1048 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt> 1049 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd> 1050 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1051 <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), 1052or <code>ev_timer_again</code> is called and determines the next timeout (if any),
… …
1246<p>The path does not need to exist: changing from &quot;path exists&quot; to &quot;path does 1313<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 1314not 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 1315not 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 1316otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p> 1317the stat buffer having unspecified contents.</p>
1318<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1319relative and your working directory changes, the behaviour is undefined.</p>
1251<p>Since there is no standard to do this, the portable implementation simply 1320<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 1321calls <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 1322can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1323a 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 1324unspecified default</i> value will be used (which you can expect to be around
… …
1336</pre> 1405</pre>
1337 1406
1338</div> 1407</div>
1339<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1408<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1340<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1409<div id="code_ev_idle_code_when_you_ve_got_no-2">
1341<p>Idle watchers trigger events when there are no other events are pending 1410<p>Idle watchers trigger events when no other events of the same or higher
1342(prepare, check and other idle watchers do not count). That is, as long 1411priority are pending (prepare, check and other idle watchers do not
1343as your process is busy handling sockets or timeouts (or even signals, 1412count).</p>
1344imagine) it will not be triggered. But when your process is idle all idle 1413<p>That is, as long as your process is busy handling sockets or timeouts
1345watchers are being called again and again, once per event loop iteration - 1414(or even signals, imagine) of the same or higher priority it will not be
1415triggered. But when your process is idle (or only lower-priority watchers
1416are pending), the idle watchers are being called once per event loop
1346until stopped, that is, or your process receives more events and becomes 1417iteration - until stopped, that is, or your process receives more events
1347busy.</p> 1418and becomes busy again with higher priority stuff.</p>
1348<p>The most noteworthy effect is that as long as any idle watchers are 1419<p>The most noteworthy effect is that as long as any idle watchers are
1349active, the process will not block when waiting for new events.</p> 1420active, the process will not block when waiting for new events.</p>
1350<p>Apart from keeping your process non-blocking (which is a useful 1421<p>Apart from keeping your process non-blocking (which is a useful
1351effect on its own sometimes), idle watchers are a good place to do 1422effect on its own sometimes), idle watchers are a good place to do
1352&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1423&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1442 1513
1443 // create io watchers for each fd and a timer before blocking 1514 // create io watchers for each fd and a timer before blocking
1444 static void 1515 static void
1445 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1516 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1446 { 1517 {
1447 int timeout = 3600000;truct pollfd fds [nfd]; 1518 int timeout = 3600000;
1519 struct pollfd fds [nfd];
1448 // actual code will need to loop here and realloc etc. 1520 // actual code will need to loop here and realloc etc.
1449 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1521 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1450 1522
1451 /* the callback is illegal, but won't be called as we stop during check */ 1523 /* the callback is illegal, but won't be called as we stop during check */
1452 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1524 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
… …
1679the callback model to a model using method callbacks on objects.</p> 1751the callback model to a model using method callbacks on objects.</p>
1680<p>To use it,</p> 1752<p>To use it,</p>
1681<pre> #include &lt;ev++.h&gt; 1753<pre> #include &lt;ev++.h&gt;
1682 1754
1683</pre> 1755</pre>
1684<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1756<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1685and puts all of its definitions (many of them macros) into the global 1757of them macros) into the global namespace. All C++ specific things are
1686namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1758put into the <code>ev</code> namespace. It should support all the same embedding
1687<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1759options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1688<code>EV_MULTIPLICITY</code>.</p> 1760<p>Care has been taken to keep the overhead low. The only data member the C++
1761classes add (compared to plain C-style watchers) is the event loop pointer
1762that the watcher is associated with (or no additional members at all if
1763you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1764<p>Currently, functions, and static and non-static member functions can be
1765used as callbacks. Other types should be easy to add as long as they only
1766need one additional pointer for context. If you need support for other
1767types of functors please contact the author (preferably after implementing
1768it).</p>
1689<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1769<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1690<dl> 1770<dl>
1691 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1771 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1692 <dd> 1772 <dd>
1693 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1773 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1704which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1784which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1705defines by many implementations.</p> 1785defines by many implementations.</p>
1706 <p>All of those classes have these methods:</p> 1786 <p>All of those classes have these methods:</p>
1707 <p> 1787 <p>
1708 <dl> 1788 <dl>
1709 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1789 <dt>ev::TYPE::TYPE ()</dt>
1710 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1790 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1711 <dt>ev::TYPE::~TYPE</dt> 1791 <dt>ev::TYPE::~TYPE</dt>
1712 <dd> 1792 <dd>
1713 <p>The constructor takes a pointer to an object and a method pointer to 1793 <p>The constructor (optionally) takes an event loop to associate the watcher
1714the event handler callback to call in this class. The constructor calls 1794with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1715<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1795 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1716before starting it. If you do not specify a loop then the constructor 1796<code>set</code> method before starting it.</p>
1717automatically associates the default loop with this watcher.</p> 1797 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1798method to set a callback before you can start the watcher.</p>
1799 <p>(The reason why you have to use a method is a limitation in C++ which does
1800not allow explicit template arguments for constructors).</p>
1718 <p>The destructor automatically stops the watcher if it is active.</p> 1801 <p>The destructor automatically stops the watcher if it is active.</p>
1802 </dd>
1803 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1804 <dd>
1805 <p>This method sets the callback method to call. The method has to have a
1806signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1807first argument and the <code>revents</code> as second. The object must be given as
1808parameter and is stored in the <code>data</code> member of the watcher.</p>
1809 <p>This method synthesizes efficient thunking code to call your method from
1810the C callback that libev requires. If your compiler can inline your
1811callback (i.e. it is visible to it at the place of the <code>set</code> call and
1812your compiler is good :), then the method will be fully inlined into the
1813thunking function, making it as fast as a direct C callback.</p>
1814 <p>Example: simple class declaration and watcher initialisation</p>
1815<pre> struct myclass
1816 {
1817 void io_cb (ev::io &amp;w, int revents) { }
1818 }
1819
1820 myclass obj;
1821 ev::io iow;
1822 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1823
1824</pre>
1825 </dd>
1826 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1827 <dd>
1828 <p>Also sets a callback, but uses a static method or plain function as
1829callback. The optional <code>data</code> argument will be stored in the watcher's
1830<code>data</code> member and is free for you to use.</p>
1831 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1832 <p>See the method-<code>set</code> above for more details.</p>
1833 <p>Example:</p>
1834<pre> static void io_cb (ev::io &amp;w, int revents) { }
1835 iow.set &lt;io_cb&gt; ();
1836
1837</pre>
1719 </dd> 1838 </dd>
1720 <dt>w-&gt;set (struct ev_loop *)</dt> 1839 <dt>w-&gt;set (struct ev_loop *)</dt>
1721 <dd> 1840 <dd>
1722 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1841 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1723do this when the watcher is inactive (and not pending either).</p> 1842do this when the watcher is inactive (and not pending either).</p>
1724 </dd> 1843 </dd>
1725 <dt>w-&gt;set ([args])</dt> 1844 <dt>w-&gt;set ([args])</dt>
1726 <dd> 1845 <dd>
1727 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1846 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1728called at least once. Unlike the C counterpart, an active watcher gets 1847called at least once. Unlike the C counterpart, an active watcher gets
1729automatically stopped and restarted.</p> 1848automatically stopped and restarted when reconfiguring it with this
1849method.</p>
1730 </dd> 1850 </dd>
1731 <dt>w-&gt;start ()</dt> 1851 <dt>w-&gt;start ()</dt>
1732 <dd> 1852 <dd>
1733 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1853 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1734constructor already takes the loop.</p> 1854constructor already stores the event loop.</p>
1735 </dd> 1855 </dd>
1736 <dt>w-&gt;stop ()</dt> 1856 <dt>w-&gt;stop ()</dt>
1737 <dd> 1857 <dd>
1738 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1858 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1739 </dd> 1859 </dd>
… …
1763 1883
1764 myclass (); 1884 myclass ();
1765 } 1885 }
1766 1886
1767 myclass::myclass (int fd) 1887 myclass::myclass (int fd)
1768 : io (this, &amp;myclass::io_cb),
1769 idle (this, &amp;myclass::idle_cb)
1770 { 1888 {
1889 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1890 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1891
1771 io.start (fd, ev::READ); 1892 io.start (fd, ev::READ);
1772 } 1893 }
1773 1894
1774 1895
1775 1896
… …
1778 1899
1779</div> 1900</div>
1780<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1901<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1781<div id="MACRO_MAGIC_CONTENT"> 1902<div id="MACRO_MAGIC_CONTENT">
1782<p>Libev can be compiled with a variety of options, the most fundemantal is 1903<p>Libev can be compiled with a variety of options, the most fundemantal is
1783<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1904<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1784callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1905callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1785<p>To make it easier to write programs that cope with either variant, the 1906<p>To make it easier to write programs that cope with either variant, the
1786following macros are defined:</p> 1907following macros are defined:</p>
1787<dl> 1908<dl>
1788 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1909 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1817 <dd> 1938 <dd>
1818 <p>Similar to the other two macros, this gives you the value of the default 1939 <p>Similar to the other two macros, this gives you the value of the default
1819loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 1940loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1820 </dd> 1941 </dd>
1821</dl> 1942</dl>
1822<p>Example: Declare and initialise a check watcher, working regardless of 1943<p>Example: Declare and initialise a check watcher, utilising the above
1823wether multiple loops are supported or not.</p> 1944macros so it will work regardless of whether multiple loops are supported
1945or not.</p>
1824<pre> static void 1946<pre> static void
1825 check_cb (EV_P_ ev_timer *w, int revents) 1947 check_cb (EV_P_ ev_timer *w, int revents)
1826 { 1948 {
1827 ev_check_stop (EV_A_ w); 1949 ev_check_stop (EV_A_ w);
1828 } 1950 }
1829 1951
1830 ev_check check; 1952 ev_check check;
1831 ev_check_init (&amp;check, check_cb); 1953 ev_check_init (&amp;check, check_cb);
1832 ev_check_start (EV_DEFAULT_ &amp;check); 1954 ev_check_start (EV_DEFAULT_ &amp;check);
1833 ev_loop (EV_DEFAULT_ 0); 1955 ev_loop (EV_DEFAULT_ 0);
1834
1835
1836
1837 1956
1838</pre> 1957</pre>
1839 1958
1840</div> 1959</div>
1841<h1 id="EMBEDDING">EMBEDDING</h1> 1960<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1883 ev_vars.h 2002 ev_vars.h
1884 ev_wrap.h 2003 ev_wrap.h
1885 2004
1886 ev_win32.c required on win32 platforms only 2005 ev_win32.c required on win32 platforms only
1887 2006
1888 ev_select.c only when select backend is enabled (which is by default) 2007 ev_select.c only when select backend is enabled (which is enabled by default)
1889 ev_poll.c only when poll backend is enabled (disabled by default) 2008 ev_poll.c only when poll backend is enabled (disabled by default)
1890 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2009 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1891 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2010 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1892 ev_port.c only when the solaris port backend is enabled (disabled by default) 2011 ev_port.c only when the solaris port backend is enabled (disabled by default)
1893 2012
… …
2058will have the <code>struct ev_loop *</code> as first argument, and you can create 2177will have the <code>struct ev_loop *</code> as first argument, and you can create
2059additional independent event loops. Otherwise there will be no support 2178additional independent event loops. Otherwise there will be no support
2060for multiple event loops and there is no first event loop pointer 2179for multiple event loops and there is no first event loop pointer
2061argument. Instead, all functions act on the single default loop.</p> 2180argument. Instead, all functions act on the single default loop.</p>
2062 </dd> 2181 </dd>
2182 <dt>EV_MINPRI</dt>
2183 <dt>EV_MAXPRI</dt>
2184 <dd>
2185 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2186<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2187provide for more priorities by overriding those symbols (usually defined
2188to be <code>-2</code> and <code>2</code>, respectively).</p>
2189 <p>When doing priority-based operations, libev usually has to linearly search
2190all the priorities, so having many of them (hundreds) uses a lot of space
2191and time, so using the defaults of five priorities (-2 .. +2) is usually
2192fine.</p>
2193 <p>If your embedding app does not need any priorities, defining these both to
2194<code>0</code> will save some memory and cpu.</p>
2195 </dd>
2063 <dt>EV_PERIODIC_ENABLE</dt> 2196 <dt>EV_PERIODIC_ENABLE</dt>
2064 <dd> 2197 <dd>
2065 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2198 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2199defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2200code.</p>
2201 </dd>
2202 <dt>EV_IDLE_ENABLE</dt>
2203 <dd>
2204 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2066defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2205defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2067code.</p> 2206code.</p>
2068 </dd> 2207 </dd>
2069 <dt>EV_EMBED_ENABLE</dt> 2208 <dt>EV_EMBED_ENABLE</dt>
2070 <dd> 2209 <dd>
… …
2135the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2274the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2136interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2275interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2137will be compiled. It is pretty complex because it provides its own header 2276will be compiled. It is pretty complex because it provides its own header
2138file.</p> 2277file.</p>
2139 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2278 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2140that everybody includes and which overrides some autoconf choices:</p> 2279that everybody includes and which overrides some configure choices:</p>
2280<pre> #define EV_MINIMAL 1
2141<pre> #define EV_USE_POLL 0 2281 #define EV_USE_POLL 0
2142 #define EV_MULTIPLICITY 0 2282 #define EV_MULTIPLICITY 0
2143 #define EV_PERIODICS 0 2283 #define EV_PERIODIC_ENABLE 0
2284 #define EV_STAT_ENABLE 0
2285 #define EV_FORK_ENABLE 0
2144 #define EV_CONFIG_H &lt;config.h&gt; 2286 #define EV_CONFIG_H &lt;config.h&gt;
2287 #define EV_MINPRI 0
2288 #define EV_MAXPRI 0
2145 2289
2146 #include &quot;ev++.h&quot; 2290 #include &quot;ev++.h&quot;
2147 2291
2148</pre> 2292</pre>
2149 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2293 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2159<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2303<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2160<div id="COMPLEXITIES_CONTENT"> 2304<div id="COMPLEXITIES_CONTENT">
2161 <p>In this section the complexities of (many of) the algorithms used inside 2305 <p>In this section the complexities of (many of) the algorithms used inside
2162libev will be explained. For complexity discussions about backends see the 2306libev will be explained. For complexity discussions about backends see the
2163documentation for <code>ev_default_init</code>.</p> 2307documentation for <code>ev_default_init</code>.</p>
2308 <p>All of the following are about amortised time: If an array needs to be
2309extended, libev needs to realloc and move the whole array, but this
2310happens asymptotically never with higher number of elements, so O(1) might
2311mean it might do a lengthy realloc operation in rare cases, but on average
2312it is much faster and asymptotically approaches constant time.</p>
2164 <p> 2313 <p>
2165 <dl> 2314 <dl>
2166 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2315 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2316 <dd>
2317 <p>This means that, when you have a watcher that triggers in one hour and
2318there are 100 watchers that would trigger before that then inserting will
2319have to skip those 100 watchers.</p>
2320 </dd>
2167 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2321 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2322 <dd>
2323 <p>That means that for changing a timer costs less than removing/adding them
2324as only the relative motion in the event queue has to be paid for.</p>
2325 </dd>
2168 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2326 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2327 <dd>
2328 <p>These just add the watcher into an array or at the head of a list.
2169 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2329=item Stopping check/prepare/idle watchers: O(1)</p>
2330 </dd>
2170 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2331 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2332 <dd>
2333 <p>These watchers are stored in lists then need to be walked to find the
2334correct watcher to remove. The lists are usually short (you don't usually
2335have many watchers waiting for the same fd or signal).</p>
2336 </dd>
2171 <dt>Finding the next timer per loop iteration: O(1)</dt> 2337 <dt>Finding the next timer per loop iteration: O(1)</dt>
2172 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2338 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2339 <dd>
2340 <p>A change means an I/O watcher gets started or stopped, which requires
2341libev to recalculate its status (and possibly tell the kernel).</p>
2342 </dd>
2173 <dt>Activating one watcher: O(1)</dt> 2343 <dt>Activating one watcher: O(1)</dt>
2344 <dt>Priority handling: O(number_of_priorities)</dt>
2345 <dd>
2346 <p>Priorities are implemented by allocating some space for each
2347priority. When doing priority-based operations, libev usually has to
2348linearly search all the priorities.</p>
2349 </dd>
2174 </dl> 2350 </dl>
2175 </p> 2351 </p>
2176 2352
2177 2353
2178 2354

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