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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="Fri Dec 7 21:19:14 2007" />
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12<body> 12<body>
13<div class="pod"> 13<div class="pod">
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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750 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 781 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
751 <dd> 782 <dd>
752 <p>Change the callback. You can change the callback at virtually any time 783 <p>Change the callback. You can change the callback at virtually any time
753(modulo threads).</p> 784(modulo threads).</p>
754 </dd> 785 </dd>
786 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
787 <dt>int ev_priority (ev_TYPE *watcher)</dt>
788 <dd>
789 <p>Set and query the priority of the watcher. The priority is a small
790integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
791(default: <code>-2</code>). Pending watchers with higher priority will be invoked
792before watchers with lower priority, but priority will not keep watchers
793from being executed (except for <code>ev_idle</code> watchers).</p>
794 <p>This means that priorities are <i>only</i> used for ordering callback
795invocation after new events have been received. This is useful, for
796example, to reduce latency after idling, or more often, to bind two
797watchers on the same event and make sure one is called first.</p>
798 <p>If you need to suppress invocation when higher priority events are pending
799you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
800 <p>The default priority used by watchers when no priority has been set is
801always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
802 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
803fine, as long as you do not mind that the priority value you query might
804or might not have been adjusted to be within valid range.</p>
805 </dd>
755</dl> 806</dl>
756 807
757 808
758 809
759 810
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869this situation even with a relatively standard program structure. Thus 920this 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 921it 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> 922<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 923<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 924play 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 925whether 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 926such as poll (fortunately in our Xlib example, Xlib already does this on
876its own, so its quite safe to use).</p> 927its own, so its quite safe to use).</p>
877<dl> 928<dl>
878 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 929 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
879 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 930 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
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950 </dd> 1001 </dd>
951 <dt>ev_timer_again (loop)</dt> 1002 <dt>ev_timer_again (loop)</dt>
952 <dd> 1003 <dd>
953 <p>This will act as if the timer timed out and restart it again if it is 1004 <p>This will act as if the timer timed out and restart it again if it is
954repeating. The exact semantics are:</p> 1005repeating. The exact semantics are:</p>
1006 <p>If the timer is pending, its pending status is cleared.</p>
955 <p>If the timer is started but nonrepeating, stop it.</p> 1007 <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 1008 <p>If the timer is repeating, either start it if necessary (with the
957value), or reset the running timer to the repeat value.</p> 1009<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 1010 <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 1011example: 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, 1012timeout, 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 1013seconds 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 1014configure 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 1015<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 1016you 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 1017socket, you can <code>ev_timer_stop</code> the timer, and <code>ev_timer_again</code> will
966need be.</p> 1018automatically restart it if need be.</p>
967 <p>You can also ignore the <code>after</code> value and <code>ev_timer_start</code> altogether 1019 <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> 1020altogether 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.); 1021<pre> ev_timer_init (timer, callback, 0., 5.);
970 ev_timer_again (loop, timer); 1022 ev_timer_again (loop, timer);
971 ... 1023 ...
972 timer-&gt;again = 17.; 1024 timer-&gt;again = 17.;
973 ev_timer_again (loop, timer); 1025 ev_timer_again (loop, timer);
974 ... 1026 ...
975 timer-&gt;again = 10.; 1027 timer-&gt;again = 10.;
976 ev_timer_again (loop, timer); 1028 ev_timer_again (loop, timer);
977 1029
978</pre> 1030</pre>
979 <p>This is more efficient then stopping/starting the timer eahc time you want 1031 <p>This is more slightly efficient then stopping/starting the timer each time
980to modify its timeout value.</p> 1032you want to modify its timeout value.</p>
981 </dd> 1033 </dd>
982 <dt>ev_tstamp repeat [read-write]</dt> 1034 <dt>ev_tstamp repeat [read-write]</dt>
983 <dd> 1035 <dd>
984 <p>The current <code>repeat</code> value. Will be used each time the watcher times out 1036 <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), 1037or <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 1298<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 1299not 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 1300not 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 1301otherwise always forced to be at least one) and all the other fields of
1250the stat buffer having unspecified contents.</p> 1302the stat buffer having unspecified contents.</p>
1303<p>The path <i>should</i> be absolute and <i>must not</i> end in a slash. If it is
1304relative and your working directory changes, the behaviour is undefined.</p>
1251<p>Since there is no standard to do this, the portable implementation simply 1305<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 1306calls <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 1307can specify a recommended polling interval for this case. If you specify
1254a polling interval of <code>0</code> (highly recommended!) then a <i>suitable, 1308a 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 1309unspecified default</i> value will be used (which you can expect to be around
… …
1336</pre> 1390</pre>
1337 1391
1338</div> 1392</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> 1393<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"> 1394<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 1395<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 1396priority are pending (prepare, check and other idle watchers do not
1343as your process is busy handling sockets or timeouts (or even signals, 1397count).</p>
1344imagine) it will not be triggered. But when your process is idle all idle 1398<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 - 1399(or even signals, imagine) of the same or higher priority it will not be
1400triggered. But when your process is idle (or only lower-priority watchers
1401are pending), the idle watchers are being called once per event loop
1346until stopped, that is, or your process receives more events and becomes 1402iteration - until stopped, that is, or your process receives more events
1347busy.</p> 1403and becomes busy again with higher priority stuff.</p>
1348<p>The most noteworthy effect is that as long as any idle watchers are 1404<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> 1405active, the process will not block when waiting for new events.</p>
1350<p>Apart from keeping your process non-blocking (which is a useful 1406<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 1407effect 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 1408&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1442 1498
1443 // create io watchers for each fd and a timer before blocking 1499 // create io watchers for each fd and a timer before blocking
1444 static void 1500 static void
1445 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1501 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1446 { 1502 {
1447 int timeout = 3600000;truct pollfd fds [nfd]; 1503 int timeout = 3600000;
1504 struct pollfd fds [nfd];
1448 // actual code will need to loop here and realloc etc. 1505 // actual code will need to loop here and realloc etc.
1449 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1506 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1450 1507
1451 /* the callback is illegal, but won't be called as we stop during check */ 1508 /* the callback is illegal, but won't be called as we stop during check */
1452 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1509 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
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1679the callback model to a model using method callbacks on objects.</p> 1736the callback model to a model using method callbacks on objects.</p>
1680<p>To use it,</p> 1737<p>To use it,</p>
1681<pre> #include &lt;ev++.h&gt; 1738<pre> #include &lt;ev++.h&gt;
1682 1739
1683</pre> 1740</pre>
1684<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1741<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 1742of 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> 1743put 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 1744options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1688<code>EV_MULTIPLICITY</code>.</p> 1745<p>Care has been taken to keep the overhead low. The only data member the C++
1746classes add (compared to plain C-style watchers) is the event loop pointer
1747that the watcher is associated with (or no additional members at all if
1748you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1749<p>Currently, functions, and static and non-static member functions can be
1750used as callbacks. Other types should be easy to add as long as they only
1751need one additional pointer for context. If you need support for other
1752types of functors please contact the author (preferably after implementing
1753it).</p>
1689<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1754<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1690<dl> 1755<dl>
1691 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1756 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1692 <dd> 1757 <dd>
1693 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1758 <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 1769which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1705defines by many implementations.</p> 1770defines by many implementations.</p>
1706 <p>All of those classes have these methods:</p> 1771 <p>All of those classes have these methods:</p>
1707 <p> 1772 <p>
1708 <dl> 1773 <dl>
1709 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1774 <dt>ev::TYPE::TYPE ()</dt>
1710 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1775 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1711 <dt>ev::TYPE::~TYPE</dt> 1776 <dt>ev::TYPE::~TYPE</dt>
1712 <dd> 1777 <dd>
1713 <p>The constructor takes a pointer to an object and a method pointer to 1778 <p>The constructor (optionally) takes an event loop to associate the watcher
1714the event handler callback to call in this class. The constructor calls 1779with. 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 1780 <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 1781<code>set</code> method before starting it.</p>
1717automatically associates the default loop with this watcher.</p> 1782 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1783method to set a callback before you can start the watcher.</p>
1784 <p>(The reason why you have to use a method is a limitation in C++ which does
1785not allow explicit template arguments for constructors).</p>
1718 <p>The destructor automatically stops the watcher if it is active.</p> 1786 <p>The destructor automatically stops the watcher if it is active.</p>
1787 </dd>
1788 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1789 <dd>
1790 <p>This method sets the callback method to call. The method has to have a
1791signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1792first argument and the <code>revents</code> as second. The object must be given as
1793parameter and is stored in the <code>data</code> member of the watcher.</p>
1794 <p>This method synthesizes efficient thunking code to call your method from
1795the C callback that libev requires. If your compiler can inline your
1796callback (i.e. it is visible to it at the place of the <code>set</code> call and
1797your compiler is good :), then the method will be fully inlined into the
1798thunking function, making it as fast as a direct C callback.</p>
1799 <p>Example: simple class declaration and watcher initialisation</p>
1800<pre> struct myclass
1801 {
1802 void io_cb (ev::io &amp;w, int revents) { }
1803 }
1804
1805 myclass obj;
1806 ev::io iow;
1807 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1808
1809</pre>
1810 </dd>
1811 <dt>w-&gt;set (void (*function)(watcher &amp;w, int), void *data = 0)</dt>
1812 <dd>
1813 <p>Also sets a callback, but uses a static method or plain function as
1814callback. The optional <code>data</code> argument will be stored in the watcher's
1815<code>data</code> member and is free for you to use.</p>
1816 <p>See the method-<code>set</code> above for more details.</p>
1719 </dd> 1817 </dd>
1720 <dt>w-&gt;set (struct ev_loop *)</dt> 1818 <dt>w-&gt;set (struct ev_loop *)</dt>
1721 <dd> 1819 <dd>
1722 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1820 <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> 1821do this when the watcher is inactive (and not pending either).</p>
1724 </dd> 1822 </dd>
1725 <dt>w-&gt;set ([args])</dt> 1823 <dt>w-&gt;set ([args])</dt>
1726 <dd> 1824 <dd>
1727 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1825 <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 1826called at least once. Unlike the C counterpart, an active watcher gets
1729automatically stopped and restarted.</p> 1827automatically stopped and restarted when reconfiguring it with this
1828method.</p>
1730 </dd> 1829 </dd>
1731 <dt>w-&gt;start ()</dt> 1830 <dt>w-&gt;start ()</dt>
1732 <dd> 1831 <dd>
1733 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1832 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1734constructor already takes the loop.</p> 1833constructor already stores the event loop.</p>
1735 </dd> 1834 </dd>
1736 <dt>w-&gt;stop ()</dt> 1835 <dt>w-&gt;stop ()</dt>
1737 <dd> 1836 <dd>
1738 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1837 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1739 </dd> 1838 </dd>
… …
1763 1862
1764 myclass (); 1863 myclass ();
1765 } 1864 }
1766 1865
1767 myclass::myclass (int fd) 1866 myclass::myclass (int fd)
1768 : io (this, &amp;myclass::io_cb),
1769 idle (this, &amp;myclass::idle_cb)
1770 { 1867 {
1868 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1869 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1870
1771 io.start (fd, ev::READ); 1871 io.start (fd, ev::READ);
1772 } 1872 }
1773 1873
1774 1874
1775 1875
… …
1778 1878
1779</div> 1879</div>
1780<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1880<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1781<div id="MACRO_MAGIC_CONTENT"> 1881<div id="MACRO_MAGIC_CONTENT">
1782<p>Libev can be compiled with a variety of options, the most fundemantal is 1882<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 1883<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1784callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1884callbacks 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 1885<p>To make it easier to write programs that cope with either variant, the
1786following macros are defined:</p> 1886following macros are defined:</p>
1787<dl> 1887<dl>
1788 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1888 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1817 <dd> 1917 <dd>
1818 <p>Similar to the other two macros, this gives you the value of the default 1918 <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> 1919loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1820 </dd> 1920 </dd>
1821</dl> 1921</dl>
1822<p>Example: Declare and initialise a check watcher, working regardless of 1922<p>Example: Declare and initialise a check watcher, utilising the above
1823wether multiple loops are supported or not.</p> 1923macros so it will work regardless of whether multiple loops are supported
1924or not.</p>
1824<pre> static void 1925<pre> static void
1825 check_cb (EV_P_ ev_timer *w, int revents) 1926 check_cb (EV_P_ ev_timer *w, int revents)
1826 { 1927 {
1827 ev_check_stop (EV_A_ w); 1928 ev_check_stop (EV_A_ w);
1828 } 1929 }
1829 1930
1830 ev_check check; 1931 ev_check check;
1831 ev_check_init (&amp;check, check_cb); 1932 ev_check_init (&amp;check, check_cb);
1832 ev_check_start (EV_DEFAULT_ &amp;check); 1933 ev_check_start (EV_DEFAULT_ &amp;check);
1833 ev_loop (EV_DEFAULT_ 0); 1934 ev_loop (EV_DEFAULT_ 0);
1834
1835
1836
1837 1935
1838</pre> 1936</pre>
1839 1937
1840</div> 1938</div>
1841<h1 id="EMBEDDING">EMBEDDING</h1> 1939<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1883 ev_vars.h 1981 ev_vars.h
1884 ev_wrap.h 1982 ev_wrap.h
1885 1983
1886 ev_win32.c required on win32 platforms only 1984 ev_win32.c required on win32 platforms only
1887 1985
1888 ev_select.c only when select backend is enabled (which is by default) 1986 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) 1987 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) 1988 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) 1989 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) 1990 ev_port.c only when the solaris port backend is enabled (disabled by default)
1893 1991
… …
2058will have the <code>struct ev_loop *</code> as first argument, and you can create 2156will have the <code>struct ev_loop *</code> as first argument, and you can create
2059additional independent event loops. Otherwise there will be no support 2157additional independent event loops. Otherwise there will be no support
2060for multiple event loops and there is no first event loop pointer 2158for multiple event loops and there is no first event loop pointer
2061argument. Instead, all functions act on the single default loop.</p> 2159argument. Instead, all functions act on the single default loop.</p>
2062 </dd> 2160 </dd>
2161 <dt>EV_MINPRI</dt>
2162 <dt>EV_MAXPRI</dt>
2163 <dd>
2164 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2165<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2166provide for more priorities by overriding those symbols (usually defined
2167to be <code>-2</code> and <code>2</code>, respectively).</p>
2168 <p>When doing priority-based operations, libev usually has to linearly search
2169all the priorities, so having many of them (hundreds) uses a lot of space
2170and time, so using the defaults of five priorities (-2 .. +2) is usually
2171fine.</p>
2172 <p>If your embedding app does not need any priorities, defining these both to
2173<code>0</code> will save some memory and cpu.</p>
2174 </dd>
2063 <dt>EV_PERIODIC_ENABLE</dt> 2175 <dt>EV_PERIODIC_ENABLE</dt>
2064 <dd> 2176 <dd>
2065 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2177 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2178defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2179code.</p>
2180 </dd>
2181 <dt>EV_IDLE_ENABLE</dt>
2182 <dd>
2183 <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 2184defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2067code.</p> 2185code.</p>
2068 </dd> 2186 </dd>
2069 <dt>EV_EMBED_ENABLE</dt> 2187 <dt>EV_EMBED_ENABLE</dt>
2070 <dd> 2188 <dd>
… …
2135the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2253the <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 2254interface) 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 2255will be compiled. It is pretty complex because it provides its own header
2138file.</p> 2256file.</p>
2139 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2257 <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> 2258that everybody includes and which overrides some configure choices:</p>
2259<pre> #define EV_MINIMAL 1
2141<pre> #define EV_USE_POLL 0 2260 #define EV_USE_POLL 0
2142 #define EV_MULTIPLICITY 0 2261 #define EV_MULTIPLICITY 0
2143 #define EV_PERIODICS 0 2262 #define EV_PERIODIC_ENABLE 0
2263 #define EV_STAT_ENABLE 0
2264 #define EV_FORK_ENABLE 0
2144 #define EV_CONFIG_H &lt;config.h&gt; 2265 #define EV_CONFIG_H &lt;config.h&gt;
2266 #define EV_MINPRI 0
2267 #define EV_MAXPRI 0
2145 2268
2146 #include &quot;ev++.h&quot; 2269 #include &quot;ev++.h&quot;
2147 2270
2148</pre> 2271</pre>
2149 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2272 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2159<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2282<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2160<div id="COMPLEXITIES_CONTENT"> 2283<div id="COMPLEXITIES_CONTENT">
2161 <p>In this section the complexities of (many of) the algorithms used inside 2284 <p>In this section the complexities of (many of) the algorithms used inside
2162libev will be explained. For complexity discussions about backends see the 2285libev will be explained. For complexity discussions about backends see the
2163documentation for <code>ev_default_init</code>.</p> 2286documentation for <code>ev_default_init</code>.</p>
2287 <p>All of the following are about amortised time: If an array needs to be
2288extended, libev needs to realloc and move the whole array, but this
2289happens asymptotically never with higher number of elements, so O(1) might
2290mean it might do a lengthy realloc operation in rare cases, but on average
2291it is much faster and asymptotically approaches constant time.</p>
2164 <p> 2292 <p>
2165 <dl> 2293 <dl>
2166 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2294 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2295 <dd>
2296 <p>This means that, when you have a watcher that triggers in one hour and
2297there are 100 watchers that would trigger before that then inserting will
2298have to skip those 100 watchers.</p>
2299 </dd>
2167 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2300 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2301 <dd>
2302 <p>That means that for changing a timer costs less than removing/adding them
2303as only the relative motion in the event queue has to be paid for.</p>
2304 </dd>
2168 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2305 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2306 <dd>
2307 <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> 2308=item Stopping check/prepare/idle watchers: O(1)</p>
2309 </dd>
2170 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2310 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2311 <dd>
2312 <p>These watchers are stored in lists then need to be walked to find the
2313correct watcher to remove. The lists are usually short (you don't usually
2314have many watchers waiting for the same fd or signal).</p>
2315 </dd>
2171 <dt>Finding the next timer per loop iteration: O(1)</dt> 2316 <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> 2317 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2318 <dd>
2319 <p>A change means an I/O watcher gets started or stopped, which requires
2320libev to recalculate its status (and possibly tell the kernel).</p>
2321 </dd>
2173 <dt>Activating one watcher: O(1)</dt> 2322 <dt>Activating one watcher: O(1)</dt>
2323 <dt>Priority handling: O(number_of_priorities)</dt>
2324 <dd>
2325 <p>Priorities are implemented by allocating some space for each
2326priority. When doing priority-based operations, libev usually has to
2327linearly search all the priorities.</p>
2328 </dd>
2174 </dl> 2329 </dl>
2175 </p> 2330 </p>
2176 2331
2177 2332
2178 2333

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