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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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333 <p>Instead of calling <code>ev_default_fork</code> or <code>ev_loop_fork</code> manually after 336 <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 337a fork, you can also make libev check for a fork in each iteration by
335enabling this flag.</p> 338enabling this flag.</p>
336 <p>This works by calling <code>getpid ()</code> on every iteration of the loop, 339 <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 340and 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 341iterations and little real work, but is usually not noticeable (on my
339Linux system for example, <code>getpid</code> is actually a simple 5-insn sequence 342Linux 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 343without a syscall and thus <i>very</i> fast, but my Linux system also has
341<code>pthread_atfork</code> which is even faster).</p> 344<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 345 <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 346forget about forgetting to tell libev about forking) when you use this
… …
480 <dt>ev_loop_fork (loop)</dt> 483 <dt>ev_loop_fork (loop)</dt>
481 <dd> 484 <dd>
482 <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
483<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
484after 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>
485 </dd> 497 </dd>
486 <dt>unsigned int ev_backend (loop)</dt> 498 <dt>unsigned int ev_backend (loop)</dt>
487 <dd> 499 <dd>
488 <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
489use.</p> 501use.</p>
… …
517one iteration of the loop. This is useful if you are waiting for some 529one iteration of the loop. This is useful if you are waiting for some
518external event in conjunction with something not expressible using other 530external event in conjunction with something not expressible using other
519libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is 531libev watchers. However, a pair of <code>ev_prepare</code>/<code>ev_check</code> watchers is
520usually a better approach for this kind of thing.</p> 532usually a better approach for this kind of thing.</p>
521 <p>Here are the gory details of what <code>ev_loop</code> does:</p> 533 <p>Here are the gory details of what <code>ev_loop</code> does:</p>
534<pre> - Before the first iteration, call any pending watchers.
522<pre> * If there are no active watchers (reference count is zero), return. 535 * If there are no active watchers (reference count is zero), return.
523 - Queue prepare watchers and then call all outstanding watchers. 536 - Queue all prepare watchers and then call all outstanding watchers.
524 - If we have been forked, recreate the kernel state. 537 - If we have been forked, recreate the kernel state.
525 - Update the kernel state with all outstanding changes. 538 - Update the kernel state with all outstanding changes.
526 - Update the &quot;event loop time&quot;. 539 - Update the &quot;event loop time&quot;.
527 - Calculate for how long to block. 540 - Calculate for how long to block.
528 - Block the process, waiting for any events. 541 - Block the process, waiting for any events.
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757 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt> 770 <dt>bool ev_is_pending (ev_TYPE *watcher)</dt>
758 <dd> 771 <dd>
759 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding 772 <p>Returns a true value iff the watcher is pending, (i.e. it has outstanding
760events but its callback has not yet been invoked). As long as a watcher 773events but its callback has not yet been invoked). As long as a watcher
761is pending (but not active) you must not call an init function on it (but 774is pending (but not active) you must not call an init function on it (but
762<code>ev_TYPE_set</code> is safe) and you must make sure the watcher is available to 775<code>ev_TYPE_set</code> is safe), you must not change its priority, and you must
763libev (e.g. you cnanot <code>free ()</code> it).</p> 776make sure the watcher is available to libev (e.g. you cannot <code>free ()</code>
777it).</p>
764 </dd> 778 </dd>
765 <dt>callback ev_cb (ev_TYPE *watcher)</dt> 779 <dt>callback ev_cb (ev_TYPE *watcher)</dt>
766 <dd> 780 <dd>
767 <p>Returns the callback currently set on the watcher.</p> 781 <p>Returns the callback currently set on the watcher.</p>
768 </dd> 782 </dd>
769 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt> 783 <dt>ev_cb_set (ev_TYPE *watcher, callback)</dt>
770 <dd> 784 <dd>
771 <p>Change the callback. You can change the callback at virtually any time 785 <p>Change the callback. You can change the callback at virtually any time
772(modulo threads).</p> 786(modulo threads).</p>
787 </dd>
788 <dt>ev_set_priority (ev_TYPE *watcher, priority)</dt>
789 <dt>int ev_priority (ev_TYPE *watcher)</dt>
790 <dd>
791 <p>Set and query the priority of the watcher. The priority is a small
792integer between <code>EV_MAXPRI</code> (default: <code>2</code>) and <code>EV_MINPRI</code>
793(default: <code>-2</code>). Pending watchers with higher priority will be invoked
794before watchers with lower priority, but priority will not keep watchers
795from being executed (except for <code>ev_idle</code> watchers).</p>
796 <p>This means that priorities are <i>only</i> used for ordering callback
797invocation after new events have been received. This is useful, for
798example, to reduce latency after idling, or more often, to bind two
799watchers on the same event and make sure one is called first.</p>
800 <p>If you need to suppress invocation when higher priority events are pending
801you need to look at <code>ev_idle</code> watchers, which provide this functionality.</p>
802 <p>You <i>must not</i> change the priority of a watcher as long as it is active or
803pending.</p>
804 <p>The default priority used by watchers when no priority has been set is
805always <code>0</code>, which is supposed to not be too high and not be too low :).</p>
806 <p>Setting a priority outside the range of <code>EV_MINPRI</code> to <code>EV_MAXPRI</code> is
807fine, as long as you do not mind that the priority value you query might
808or might not have been adjusted to be within valid range.</p>
809 </dd>
810 <dt>ev_invoke (loop, ev_TYPE *watcher, int revents)</dt>
811 <dd>
812 <p>Invoke the <code>watcher</code> with the given <code>loop</code> and <code>revents</code>. Neither
813<code>loop</code> nor <code>revents</code> need to be valid as long as the watcher callback
814can deal with that fact.</p>
815 </dd>
816 <dt>int ev_clear_pending (loop, ev_TYPE *watcher)</dt>
817 <dd>
818 <p>If the watcher is pending, this function returns clears its pending status
819and returns its <code>revents</code> bitset (as if its callback was invoked). If the
820watcher isn't pending it does nothing and returns <code>0</code>.</p>
773 </dd> 821 </dd>
774</dl> 822</dl>
775 823
776 824
777 825
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888this situation even with a relatively standard program structure. Thus 936this situation even with a relatively standard program structure. Thus
889it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning 937it is best to always use non-blocking I/O: An extra <code>read</code>(2) returning
890<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p> 938<code>EAGAIN</code> is far preferable to a program hanging until some data arrives.</p>
891<p>If you cannot run the fd in non-blocking mode (for example you should not 939<p>If you cannot run the fd in non-blocking mode (for example you should not
892play around with an Xlib connection), then you have to seperately re-test 940play around with an Xlib connection), then you have to seperately re-test
893wether a file descriptor is really ready with a known-to-be good interface 941whether a file descriptor is really ready with a known-to-be good interface
894such as poll (fortunately in our Xlib example, Xlib already does this on 942such as poll (fortunately in our Xlib example, Xlib already does this on
895its own, so its quite safe to use).</p> 943its own, so its quite safe to use).</p>
896<dl> 944<dl>
897 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 945 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
898 <dt>ev_io_set (ev_io *, int fd, int events)</dt> 946 <dt>ev_io_set (ev_io *, int fd, int events)</dt>
… …
1049but on wallclock time (absolute time). You can tell a periodic watcher 1097but on wallclock time (absolute time). You can tell a periodic watcher
1050to trigger &quot;at&quot; some specific point in time. For example, if you tell a 1098to trigger &quot;at&quot; some specific point in time. For example, if you tell a
1051periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () 1099periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now ()
1052+ 10.</code>) and then reset your system clock to the last year, then it will 1100+ 10.</code>) and then reset your system clock to the last year, then it will
1053take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 1101take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
1054roughly 10 seconds later and of course not if you reset your system time 1102roughly 10 seconds later).</p>
1055again).</p>
1056<p>They can also be used to implement vastly more complex timers, such as 1103<p>They can also be used to implement vastly more complex timers, such as
1057triggering an event on eahc midnight, local time.</p> 1104triggering an event on each midnight, local time or other, complicated,
1105rules.</p>
1058<p>As with timers, the callback is guarenteed to be invoked only when the 1106<p>As with timers, the callback is guarenteed to be invoked only when the
1059time (<code>at</code>) has been passed, but if multiple periodic timers become ready 1107time (<code>at</code>) has been passed, but if multiple periodic timers become ready
1060during the same loop iteration then order of execution is undefined.</p> 1108during the same loop iteration then order of execution is undefined.</p>
1061<dl> 1109<dl>
1062 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 1110 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
… …
1064 <dd> 1112 <dd>
1065 <p>Lots of arguments, lets sort it out... There are basically three modes of 1113 <p>Lots of arguments, lets sort it out... There are basically three modes of
1066operation, and we will explain them from simplest to complex:</p> 1114operation, and we will explain them from simplest to complex:</p>
1067 <p> 1115 <p>
1068 <dl> 1116 <dl>
1069 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 1117 <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt>
1070 <dd> 1118 <dd>
1071 <p>In this configuration the watcher triggers an event at the wallclock time 1119 <p>In this configuration the watcher triggers an event at the wallclock time
1072<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, 1120<code>at</code> and doesn't repeat. It will not adjust when a time jump occurs,
1073that is, if it is to be run at January 1st 2011 then it will run when the 1121that is, if it is to be run at January 1st 2011 then it will run when the
1074system time reaches or surpasses this time.</p> 1122system time reaches or surpasses this time.</p>
1075 </dd> 1123 </dd>
1076 <dt>* non-repeating interval timer (interval &gt; 0, reschedule_cb = 0)</dt> 1124 <dt>* non-repeating interval timer (at = offset, interval &gt; 0, reschedule_cb = 0)</dt>
1077 <dd> 1125 <dd>
1078 <p>In this mode the watcher will always be scheduled to time out at the next 1126 <p>In this mode the watcher will always be scheduled to time out at the next
1079<code>at + N * interval</code> time (for some integer N) and then repeat, regardless 1127<code>at + N * interval</code> time (for some integer N, which can also be negative)
1080of any time jumps.</p> 1128and then repeat, regardless of any time jumps.</p>
1081 <p>This can be used to create timers that do not drift with respect to system 1129 <p>This can be used to create timers that do not drift with respect to system
1082time:</p> 1130time:</p>
1083<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 1131<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
1084 1132
1085</pre> 1133</pre>
… …
1088full hour (UTC), or more correctly, when the system time is evenly divisible 1136full hour (UTC), or more correctly, when the system time is evenly divisible
1089by 3600.</p> 1137by 3600.</p>
1090 <p>Another way to think about it (for the mathematically inclined) is that 1138 <p>Another way to think about it (for the mathematically inclined) is that
1091<code>ev_periodic</code> will try to run the callback in this mode at the next possible 1139<code>ev_periodic</code> will try to run the callback in this mode at the next possible
1092time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 1140time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
1141 <p>For numerical stability it is preferable that the <code>at</code> value is near
1142<code>ev_now ()</code> (the current time), but there is no range requirement for
1143this value.</p>
1093 </dd> 1144 </dd>
1094 <dt>* manual reschedule mode (reschedule_cb = callback)</dt> 1145 <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt>
1095 <dd> 1146 <dd>
1096 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 1147 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
1097ignored. Instead, each time the periodic watcher gets scheduled, the 1148ignored. Instead, each time the periodic watcher gets scheduled, the
1098reschedule callback will be called with the watcher as first, and the 1149reschedule callback will be called with the watcher as first, and the
1099current time as second argument.</p> 1150current time as second argument.</p>
1100 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, 1151 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
1101ever, or make any event loop modifications</i>. If you need to stop it, 1152ever, or make any event loop modifications</i>. If you need to stop it,
1102return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by 1153return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
1103starting a prepare watcher).</p> 1154starting an <code>ev_prepare</code> watcher, which is legal).</p>
1104 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1155 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1105ev_tstamp now)</code>, e.g.:</p> 1156ev_tstamp now)</code>, e.g.:</p>
1106<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1157<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1107 { 1158 {
1108 return now + 60.; 1159 return now + 60.;
… …
1128 <dd> 1179 <dd>
1129 <p>Simply stops and restarts the periodic watcher again. This is only useful 1180 <p>Simply stops and restarts the periodic watcher again. This is only useful
1130when you changed some parameters or the reschedule callback would return 1181when you changed some parameters or the reschedule callback would return
1131a different time than the last time it was called (e.g. in a crond like 1182a different time than the last time it was called (e.g. in a crond like
1132program when the crontabs have changed).</p> 1183program when the crontabs have changed).</p>
1184 </dd>
1185 <dt>ev_tstamp offset [read-write]</dt>
1186 <dd>
1187 <p>When repeating, this contains the offset value, otherwise this is the
1188absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p>
1189 <p>Can be modified any time, but changes only take effect when the periodic
1190timer fires or <code>ev_periodic_again</code> is being called.</p>
1133 </dd> 1191 </dd>
1134 <dt>ev_tstamp interval [read-write]</dt> 1192 <dt>ev_tstamp interval [read-write]</dt>
1135 <dd> 1193 <dd>
1136 <p>The current interval value. Can be modified any time, but changes only 1194 <p>The current interval value. Can be modified any time, but changes only
1137take effect when the periodic timer fires or <code>ev_periodic_again</code> is being 1195take effect when the periodic timer fires or <code>ev_periodic_again</code> is being
… …
1358</pre> 1416</pre>
1359 1417
1360</div> 1418</div>
1361<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2> 1419<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do...</h2>
1362<div id="code_ev_idle_code_when_you_ve_got_no-2"> 1420<div id="code_ev_idle_code_when_you_ve_got_no-2">
1363<p>Idle watchers trigger events when there are no other events are pending 1421<p>Idle watchers trigger events when no other events of the same or higher
1364(prepare, check and other idle watchers do not count). That is, as long 1422priority are pending (prepare, check and other idle watchers do not
1365as your process is busy handling sockets or timeouts (or even signals, 1423count).</p>
1366imagine) it will not be triggered. But when your process is idle all idle 1424<p>That is, as long as your process is busy handling sockets or timeouts
1367watchers are being called again and again, once per event loop iteration - 1425(or even signals, imagine) of the same or higher priority it will not be
1426triggered. But when your process is idle (or only lower-priority watchers
1427are pending), the idle watchers are being called once per event loop
1368until stopped, that is, or your process receives more events and becomes 1428iteration - until stopped, that is, or your process receives more events
1369busy.</p> 1429and becomes busy again with higher priority stuff.</p>
1370<p>The most noteworthy effect is that as long as any idle watchers are 1430<p>The most noteworthy effect is that as long as any idle watchers are
1371active, the process will not block when waiting for new events.</p> 1431active, the process will not block when waiting for new events.</p>
1372<p>Apart from keeping your process non-blocking (which is a useful 1432<p>Apart from keeping your process non-blocking (which is a useful
1373effect on its own sometimes), idle watchers are a good place to do 1433effect on its own sometimes), idle watchers are a good place to do
1374&quot;pseudo-background processing&quot;, or delay processing stuff to after the 1434&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
1434are ready to run (it's actually more complicated: it only runs coroutines 1494are ready to run (it's actually more complicated: it only runs coroutines
1435with priority higher than or equal to the event loop and one coroutine 1495with priority higher than or equal to the event loop and one coroutine
1436of lower priority, but only once, using idle watchers to keep the event 1496of lower priority, but only once, using idle watchers to keep the event
1437loop from blocking if lower-priority coroutines are active, thus mapping 1497loop from blocking if lower-priority coroutines are active, thus mapping
1438low-priority coroutines to idle/background tasks).</p> 1498low-priority coroutines to idle/background tasks).</p>
1499<p>It is recommended to give <code>ev_check</code> watchers highest (<code>EV_MAXPRI</code>)
1500priority, to ensure that they are being run before any other watchers
1501after the poll. Also, <code>ev_check</code> watchers (and <code>ev_prepare</code> watchers,
1502too) should not activate (&quot;feed&quot;) events into libev. While libev fully
1503supports this, they will be called before other <code>ev_check</code> watchers did
1504their job. As <code>ev_check</code> watchers are often used to embed other event
1505loops those other event loops might be in an unusable state until their
1506<code>ev_check</code> watcher ran (always remind yourself to coexist peacefully with
1507others).</p>
1439<dl> 1508<dl>
1440 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 1509 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
1441 <dt>ev_check_init (ev_check *, callback)</dt> 1510 <dt>ev_check_init (ev_check *, callback)</dt>
1442 <dd> 1511 <dd>
1443 <p>Initialises and configures the prepare or check watcher - they have no 1512 <p>Initialises and configures the prepare or check watcher - they have no
1444parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 1513parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
1445macros, but using them is utterly, utterly and completely pointless.</p> 1514macros, but using them is utterly, utterly and completely pointless.</p>
1446 </dd> 1515 </dd>
1447</dl> 1516</dl>
1448<p>Example: To include a library such as adns, you would add IO watchers 1517<p>There are a number of principal ways to embed other event loops or modules
1449and a timeout watcher in a prepare handler, as required by libadns, and 1518into libev. Here are some ideas on how to include libadns into libev
1519(there is a Perl module named <code>EV::ADNS</code> that does this, which you could
1520use for an actually working example. Another Perl module named <code>EV::Glib</code>
1521embeds a Glib main context into libev, and finally, <code>Glib::EV</code> embeds EV
1522into the Glib event loop).</p>
1523<p>Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1450in a check watcher, destroy them and call into libadns. What follows is 1524and in a check watcher, destroy them and call into libadns. What follows
1451pseudo-code only of course:</p> 1525is pseudo-code only of course. This requires you to either use a low
1526priority for the check watcher or use <code>ev_clear_pending</code> explicitly, as
1527the callbacks for the IO/timeout watchers might not have been called yet.</p>
1452<pre> static ev_io iow [nfd]; 1528<pre> static ev_io iow [nfd];
1453 static ev_timer tw; 1529 static ev_timer tw;
1454 1530
1455 static void 1531 static void
1456 io_cb (ev_loop *loop, ev_io *w, int revents) 1532 io_cb (ev_loop *loop, ev_io *w, int revents)
1457 { 1533 {
1458 // set the relevant poll flags
1459 // could also call adns_processreadable etc. here
1460 struct pollfd *fd = (struct pollfd *)w-&gt;data;
1461 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1462 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1463 } 1534 }
1464 1535
1465 // create io watchers for each fd and a timer before blocking 1536 // create io watchers for each fd and a timer before blocking
1466 static void 1537 static void
1467 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1538 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1468 { 1539 {
1469 int timeout = 3600000;truct pollfd fds [nfd]; 1540 int timeout = 3600000;
1541 struct pollfd fds [nfd];
1470 // actual code will need to loop here and realloc etc. 1542 // actual code will need to loop here and realloc etc.
1471 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ())); 1543 adns_beforepoll (ads, fds, &amp;nfd, &amp;timeout, timeval_from (ev_time ()));
1472 1544
1473 /* the callback is illegal, but won't be called as we stop during check */ 1545 /* the callback is illegal, but won't be called as we stop during check */
1474 ev_timer_init (&amp;tw, 0, timeout * 1e-3); 1546 ev_timer_init (&amp;tw, 0, timeout * 1e-3);
1475 ev_timer_start (loop, &amp;tw); 1547 ev_timer_start (loop, &amp;tw);
1476 1548
1477 // create on ev_io per pollfd 1549 // create one ev_io per pollfd
1478 for (int i = 0; i &lt; nfd; ++i) 1550 for (int i = 0; i &lt; nfd; ++i)
1479 { 1551 {
1480 ev_io_init (iow + i, io_cb, fds [i].fd, 1552 ev_io_init (iow + i, io_cb, fds [i].fd,
1481 ((fds [i].events &amp; POLLIN ? EV_READ : 0) 1553 ((fds [i].events &amp; POLLIN ? EV_READ : 0)
1482 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0))); 1554 | (fds [i].events &amp; POLLOUT ? EV_WRITE : 0)));
1483 1555
1484 fds [i].revents = 0; 1556 fds [i].revents = 0;
1485 iow [i].data = fds + i;
1486 ev_io_start (loop, iow + i); 1557 ev_io_start (loop, iow + i);
1487 } 1558 }
1488 } 1559 }
1489 1560
1490 // stop all watchers after blocking 1561 // stop all watchers after blocking
… …
1492 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1563 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1493 { 1564 {
1494 ev_timer_stop (loop, &amp;tw); 1565 ev_timer_stop (loop, &amp;tw);
1495 1566
1496 for (int i = 0; i &lt; nfd; ++i) 1567 for (int i = 0; i &lt; nfd; ++i)
1568 {
1569 // set the relevant poll flags
1570 // could also call adns_processreadable etc. here
1571 struct pollfd *fd = fds + i;
1572 int revents = ev_clear_pending (iow + i);
1573 if (revents &amp; EV_READ ) fd-&gt;revents |= fd-&gt;events &amp; POLLIN;
1574 if (revents &amp; EV_WRITE) fd-&gt;revents |= fd-&gt;events &amp; POLLOUT;
1575
1576 // now stop the watcher
1497 ev_io_stop (loop, iow + i); 1577 ev_io_stop (loop, iow + i);
1578 }
1498 1579
1499 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1580 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1581 }
1582
1583</pre>
1584<p>Method 2: This would be just like method 1, but you run <code>adns_afterpoll</code>
1585in the prepare watcher and would dispose of the check watcher.</p>
1586<p>Method 3: If the module to be embedded supports explicit event
1587notification (adns does), you can also make use of the actual watcher
1588callbacks, and only destroy/create the watchers in the prepare watcher.</p>
1589<pre> static void
1590 timer_cb (EV_P_ ev_timer *w, int revents)
1591 {
1592 adns_state ads = (adns_state)w-&gt;data;
1593 update_now (EV_A);
1594
1595 adns_processtimeouts (ads, &amp;tv_now);
1596 }
1597
1598 static void
1599 io_cb (EV_P_ ev_io *w, int revents)
1600 {
1601 adns_state ads = (adns_state)w-&gt;data;
1602 update_now (EV_A);
1603
1604 if (revents &amp; EV_READ ) adns_processreadable (ads, w-&gt;fd, &amp;tv_now);
1605 if (revents &amp; EV_WRITE) adns_processwriteable (ads, w-&gt;fd, &amp;tv_now);
1606 }
1607
1608 // do not ever call adns_afterpoll
1609
1610</pre>
1611<p>Method 4: Do not use a prepare or check watcher because the module you
1612want to embed is too inflexible to support it. Instead, youc na override
1613their poll function. The drawback with this solution is that the main
1614loop is now no longer controllable by EV. The <code>Glib::EV</code> module does
1615this.</p>
1616<pre> static gint
1617 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1618 {
1619 int got_events = 0;
1620
1621 for (n = 0; n &lt; nfds; ++n)
1622 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1623
1624 if (timeout &gt;= 0)
1625 // create/start timer
1626
1627 // poll
1628 ev_loop (EV_A_ 0);
1629
1630 // stop timer again
1631 if (timeout &gt;= 0)
1632 ev_timer_stop (EV_A_ &amp;to);
1633
1634 // stop io watchers again - their callbacks should have set
1635 for (n = 0; n &lt; nfds; ++n)
1636 ev_io_stop (EV_A_ iow [n]);
1637
1638 return got_events;
1500 } 1639 }
1501 1640
1502 1641
1503 1642
1504 1643
… …
1701the callback model to a model using method callbacks on objects.</p> 1840the callback model to a model using method callbacks on objects.</p>
1702<p>To use it,</p> 1841<p>To use it,</p>
1703<pre> #include &lt;ev++.h&gt; 1842<pre> #include &lt;ev++.h&gt;
1704 1843
1705</pre> 1844</pre>
1706<p>(it is not installed by default). This automatically includes <cite>ev.h</cite> 1845<p>This automatically includes <cite>ev.h</cite> and puts all of its definitions (many
1707and puts all of its definitions (many of them macros) into the global 1846of them macros) into the global namespace. All C++ specific things are
1708namespace. All C++ specific things are put into the <code>ev</code> namespace.</p> 1847put into the <code>ev</code> namespace. It should support all the same embedding
1709<p>It should support all the same embedding options as <cite>ev.h</cite>, most notably 1848options as <cite>ev.h</cite>, most notably <code>EV_MULTIPLICITY</code>.</p>
1710<code>EV_MULTIPLICITY</code>.</p> 1849<p>Care has been taken to keep the overhead low. The only data member the C++
1850classes add (compared to plain C-style watchers) is the event loop pointer
1851that the watcher is associated with (or no additional members at all if
1852you disable <code>EV_MULTIPLICITY</code> when embedding libev).</p>
1853<p>Currently, functions, and static and non-static member functions can be
1854used as callbacks. Other types should be easy to add as long as they only
1855need one additional pointer for context. If you need support for other
1856types of functors please contact the author (preferably after implementing
1857it).</p>
1711<p>Here is a list of things available in the <code>ev</code> namespace:</p> 1858<p>Here is a list of things available in the <code>ev</code> namespace:</p>
1712<dl> 1859<dl>
1713 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt> 1860 <dt><code>ev::READ</code>, <code>ev::WRITE</code> etc.</dt>
1714 <dd> 1861 <dd>
1715 <p>These are just enum values with the same values as the <code>EV_READ</code> etc. 1862 <p>These are just enum values with the same values as the <code>EV_READ</code> etc.
… …
1726which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro 1873which is called <code>ev::sig</code> to avoid clashes with the <code>signal</code> macro
1727defines by many implementations.</p> 1874defines by many implementations.</p>
1728 <p>All of those classes have these methods:</p> 1875 <p>All of those classes have these methods:</p>
1729 <p> 1876 <p>
1730 <dl> 1877 <dl>
1731 <dt>ev::TYPE::TYPE (object *, object::method *)</dt> 1878 <dt>ev::TYPE::TYPE ()</dt>
1732 <dt>ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)</dt> 1879 <dt>ev::TYPE::TYPE (struct ev_loop *)</dt>
1733 <dt>ev::TYPE::~TYPE</dt> 1880 <dt>ev::TYPE::~TYPE</dt>
1734 <dd> 1881 <dd>
1735 <p>The constructor takes a pointer to an object and a method pointer to 1882 <p>The constructor (optionally) takes an event loop to associate the watcher
1736the event handler callback to call in this class. The constructor calls 1883with. If it is omitted, it will use <code>EV_DEFAULT</code>.</p>
1737<code>ev_init</code> for you, which means you have to call the <code>set</code> method 1884 <p>The constructor calls <code>ev_init</code> for you, which means you have to call the
1738before starting it. If you do not specify a loop then the constructor 1885<code>set</code> method before starting it.</p>
1739automatically associates the default loop with this watcher.</p> 1886 <p>It will not set a callback, however: You have to call the templated <code>set</code>
1887method to set a callback before you can start the watcher.</p>
1888 <p>(The reason why you have to use a method is a limitation in C++ which does
1889not allow explicit template arguments for constructors).</p>
1740 <p>The destructor automatically stops the watcher if it is active.</p> 1890 <p>The destructor automatically stops the watcher if it is active.</p>
1891 </dd>
1892 <dt>w-&gt;set&lt;class, &amp;class::method&gt; (object *)</dt>
1893 <dd>
1894 <p>This method sets the callback method to call. The method has to have a
1895signature of <code>void (*)(ev_TYPE &amp;, int)</code>, it receives the watcher as
1896first argument and the <code>revents</code> as second. The object must be given as
1897parameter and is stored in the <code>data</code> member of the watcher.</p>
1898 <p>This method synthesizes efficient thunking code to call your method from
1899the C callback that libev requires. If your compiler can inline your
1900callback (i.e. it is visible to it at the place of the <code>set</code> call and
1901your compiler is good :), then the method will be fully inlined into the
1902thunking function, making it as fast as a direct C callback.</p>
1903 <p>Example: simple class declaration and watcher initialisation</p>
1904<pre> struct myclass
1905 {
1906 void io_cb (ev::io &amp;w, int revents) { }
1907 }
1908
1909 myclass obj;
1910 ev::io iow;
1911 iow.set &lt;myclass, &amp;myclass::io_cb&gt; (&amp;obj);
1912
1913</pre>
1914 </dd>
1915 <dt>w-&gt;set&lt;function&gt; (void *data = 0)</dt>
1916 <dd>
1917 <p>Also sets a callback, but uses a static method or plain function as
1918callback. The optional <code>data</code> argument will be stored in the watcher's
1919<code>data</code> member and is free for you to use.</p>
1920 <p>The prototype of the <code>function</code> must be <code>void (*)(ev::TYPE &amp;w, int)</code>.</p>
1921 <p>See the method-<code>set</code> above for more details.</p>
1922 <p>Example:</p>
1923<pre> static void io_cb (ev::io &amp;w, int revents) { }
1924 iow.set &lt;io_cb&gt; ();
1925
1926</pre>
1741 </dd> 1927 </dd>
1742 <dt>w-&gt;set (struct ev_loop *)</dt> 1928 <dt>w-&gt;set (struct ev_loop *)</dt>
1743 <dd> 1929 <dd>
1744 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only 1930 <p>Associates a different <code>struct ev_loop</code> with this watcher. You can only
1745do this when the watcher is inactive (and not pending either).</p> 1931do this when the watcher is inactive (and not pending either).</p>
1746 </dd> 1932 </dd>
1747 <dt>w-&gt;set ([args])</dt> 1933 <dt>w-&gt;set ([args])</dt>
1748 <dd> 1934 <dd>
1749 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be 1935 <p>Basically the same as <code>ev_TYPE_set</code>, with the same args. Must be
1750called at least once. Unlike the C counterpart, an active watcher gets 1936called at least once. Unlike the C counterpart, an active watcher gets
1751automatically stopped and restarted.</p> 1937automatically stopped and restarted when reconfiguring it with this
1938method.</p>
1752 </dd> 1939 </dd>
1753 <dt>w-&gt;start ()</dt> 1940 <dt>w-&gt;start ()</dt>
1754 <dd> 1941 <dd>
1755 <p>Starts the watcher. Note that there is no <code>loop</code> argument as the 1942 <p>Starts the watcher. Note that there is no <code>loop</code> argument, as the
1756constructor already takes the loop.</p> 1943constructor already stores the event loop.</p>
1757 </dd> 1944 </dd>
1758 <dt>w-&gt;stop ()</dt> 1945 <dt>w-&gt;stop ()</dt>
1759 <dd> 1946 <dd>
1760 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p> 1947 <p>Stops the watcher if it is active. Again, no <code>loop</code> argument.</p>
1761 </dd> 1948 </dd>
… …
1785 1972
1786 myclass (); 1973 myclass ();
1787 } 1974 }
1788 1975
1789 myclass::myclass (int fd) 1976 myclass::myclass (int fd)
1790 : io (this, &amp;myclass::io_cb),
1791 idle (this, &amp;myclass::idle_cb)
1792 { 1977 {
1978 io .set &lt;myclass, &amp;myclass::io_cb &gt; (this);
1979 idle.set &lt;myclass, &amp;myclass::idle_cb&gt; (this);
1980
1793 io.start (fd, ev::READ); 1981 io.start (fd, ev::READ);
1794 } 1982 }
1795 1983
1796 1984
1797 1985
… …
1800 1988
1801</div> 1989</div>
1802<h1 id="MACRO_MAGIC">MACRO MAGIC</h1> 1990<h1 id="MACRO_MAGIC">MACRO MAGIC</h1>
1803<div id="MACRO_MAGIC_CONTENT"> 1991<div id="MACRO_MAGIC_CONTENT">
1804<p>Libev can be compiled with a variety of options, the most fundemantal is 1992<p>Libev can be compiled with a variety of options, the most fundemantal is
1805<code>EV_MULTIPLICITY</code>. This option determines wether (most) functions and 1993<code>EV_MULTIPLICITY</code>. This option determines whether (most) functions and
1806callbacks have an initial <code>struct ev_loop *</code> argument.</p> 1994callbacks have an initial <code>struct ev_loop *</code> argument.</p>
1807<p>To make it easier to write programs that cope with either variant, the 1995<p>To make it easier to write programs that cope with either variant, the
1808following macros are defined:</p> 1996following macros are defined:</p>
1809<dl> 1997<dl>
1810 <dt><code>EV_A</code>, <code>EV_A_</code></dt> 1998 <dt><code>EV_A</code>, <code>EV_A_</code></dt>
… …
1839 <dd> 2027 <dd>
1840 <p>Similar to the other two macros, this gives you the value of the default 2028 <p>Similar to the other two macros, this gives you the value of the default
1841loop, if multiple loops are supported (&quot;ev loop default&quot;).</p> 2029loop, if multiple loops are supported (&quot;ev loop default&quot;).</p>
1842 </dd> 2030 </dd>
1843</dl> 2031</dl>
1844<p>Example: Declare and initialise a check watcher, working regardless of 2032<p>Example: Declare and initialise a check watcher, utilising the above
1845wether multiple loops are supported or not.</p> 2033macros so it will work regardless of whether multiple loops are supported
2034or not.</p>
1846<pre> static void 2035<pre> static void
1847 check_cb (EV_P_ ev_timer *w, int revents) 2036 check_cb (EV_P_ ev_timer *w, int revents)
1848 { 2037 {
1849 ev_check_stop (EV_A_ w); 2038 ev_check_stop (EV_A_ w);
1850 } 2039 }
1851 2040
1852 ev_check check; 2041 ev_check check;
1853 ev_check_init (&amp;check, check_cb); 2042 ev_check_init (&amp;check, check_cb);
1854 ev_check_start (EV_DEFAULT_ &amp;check); 2043 ev_check_start (EV_DEFAULT_ &amp;check);
1855 ev_loop (EV_DEFAULT_ 0); 2044 ev_loop (EV_DEFAULT_ 0);
1856
1857
1858
1859 2045
1860</pre> 2046</pre>
1861 2047
1862</div> 2048</div>
1863<h1 id="EMBEDDING">EMBEDDING</h1> 2049<h1 id="EMBEDDING">EMBEDDING</h1>
… …
1905 ev_vars.h 2091 ev_vars.h
1906 ev_wrap.h 2092 ev_wrap.h
1907 2093
1908 ev_win32.c required on win32 platforms only 2094 ev_win32.c required on win32 platforms only
1909 2095
1910 ev_select.c only when select backend is enabled (which is by default) 2096 ev_select.c only when select backend is enabled (which is enabled by default)
1911 ev_poll.c only when poll backend is enabled (disabled by default) 2097 ev_poll.c only when poll backend is enabled (disabled by default)
1912 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2098 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1913 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2099 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1914 ev_port.c only when the solaris port backend is enabled (disabled by default) 2100 ev_port.c only when the solaris port backend is enabled (disabled by default)
1915 2101
… …
2080will have the <code>struct ev_loop *</code> as first argument, and you can create 2266will have the <code>struct ev_loop *</code> as first argument, and you can create
2081additional independent event loops. Otherwise there will be no support 2267additional independent event loops. Otherwise there will be no support
2082for multiple event loops and there is no first event loop pointer 2268for multiple event loops and there is no first event loop pointer
2083argument. Instead, all functions act on the single default loop.</p> 2269argument. Instead, all functions act on the single default loop.</p>
2084 </dd> 2270 </dd>
2271 <dt>EV_MINPRI</dt>
2272 <dt>EV_MAXPRI</dt>
2273 <dd>
2274 <p>The range of allowed priorities. <code>EV_MINPRI</code> must be smaller or equal to
2275<code>EV_MAXPRI</code>, but otherwise there are no non-obvious limitations. You can
2276provide for more priorities by overriding those symbols (usually defined
2277to be <code>-2</code> and <code>2</code>, respectively).</p>
2278 <p>When doing priority-based operations, libev usually has to linearly search
2279all the priorities, so having many of them (hundreds) uses a lot of space
2280and time, so using the defaults of five priorities (-2 .. +2) is usually
2281fine.</p>
2282 <p>If your embedding app does not need any priorities, defining these both to
2283<code>0</code> will save some memory and cpu.</p>
2284 </dd>
2085 <dt>EV_PERIODIC_ENABLE</dt> 2285 <dt>EV_PERIODIC_ENABLE</dt>
2086 <dd> 2286 <dd>
2087 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If 2287 <p>If undefined or defined to be <code>1</code>, then periodic timers are supported. If
2288defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2289code.</p>
2290 </dd>
2291 <dt>EV_IDLE_ENABLE</dt>
2292 <dd>
2293 <p>If undefined or defined to be <code>1</code>, then idle watchers are supported. If
2088defined to be <code>0</code>, then they are not. Disabling them saves a few kB of 2294defined to be <code>0</code>, then they are not. Disabling them saves a few kB of
2089code.</p> 2295code.</p>
2090 </dd> 2296 </dd>
2091 <dt>EV_EMBED_ENABLE</dt> 2297 <dt>EV_EMBED_ENABLE</dt>
2092 <dd> 2298 <dd>
… …
2157the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public 2363the <cite>libev/</cite> subdirectory and includes them in the <cite>EV/EVAPI.h</cite> (public
2158interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file 2364interface) and <cite>EV.xs</cite> (implementation) files. Only the <cite>EV.xs</cite> file
2159will be compiled. It is pretty complex because it provides its own header 2365will be compiled. It is pretty complex because it provides its own header
2160file.</p> 2366file.</p>
2161 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file 2367 <p>The usage in rxvt-unicode is simpler. It has a <cite>ev_cpp.h</cite> header file
2162that everybody includes and which overrides some autoconf choices:</p> 2368that everybody includes and which overrides some configure choices:</p>
2369<pre> #define EV_MINIMAL 1
2163<pre> #define EV_USE_POLL 0 2370 #define EV_USE_POLL 0
2164 #define EV_MULTIPLICITY 0 2371 #define EV_MULTIPLICITY 0
2165 #define EV_PERIODICS 0 2372 #define EV_PERIODIC_ENABLE 0
2373 #define EV_STAT_ENABLE 0
2374 #define EV_FORK_ENABLE 0
2166 #define EV_CONFIG_H &lt;config.h&gt; 2375 #define EV_CONFIG_H &lt;config.h&gt;
2376 #define EV_MINPRI 0
2377 #define EV_MAXPRI 0
2167 2378
2168 #include &quot;ev++.h&quot; 2379 #include &quot;ev++.h&quot;
2169 2380
2170</pre> 2381</pre>
2171 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p> 2382 <p>And a <cite>ev_cpp.C</cite> implementation file that contains libev proper and is compiled:</p>
… …
2181<h1 id="COMPLEXITIES">COMPLEXITIES</h1> 2392<h1 id="COMPLEXITIES">COMPLEXITIES</h1>
2182<div id="COMPLEXITIES_CONTENT"> 2393<div id="COMPLEXITIES_CONTENT">
2183 <p>In this section the complexities of (many of) the algorithms used inside 2394 <p>In this section the complexities of (many of) the algorithms used inside
2184libev will be explained. For complexity discussions about backends see the 2395libev will be explained. For complexity discussions about backends see the
2185documentation for <code>ev_default_init</code>.</p> 2396documentation for <code>ev_default_init</code>.</p>
2397 <p>All of the following are about amortised time: If an array needs to be
2398extended, libev needs to realloc and move the whole array, but this
2399happens asymptotically never with higher number of elements, so O(1) might
2400mean it might do a lengthy realloc operation in rare cases, but on average
2401it is much faster and asymptotically approaches constant time.</p>
2186 <p> 2402 <p>
2187 <dl> 2403 <dl>
2188 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt> 2404 <dt>Starting and stopping timer/periodic watchers: O(log skipped_other_timers)</dt>
2405 <dd>
2406 <p>This means that, when you have a watcher that triggers in one hour and
2407there are 100 watchers that would trigger before that then inserting will
2408have to skip those 100 watchers.</p>
2409 </dd>
2189 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt> 2410 <dt>Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)</dt>
2411 <dd>
2412 <p>That means that for changing a timer costs less than removing/adding them
2413as only the relative motion in the event queue has to be paid for.</p>
2414 </dd>
2190 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt> 2415 <dt>Starting io/check/prepare/idle/signal/child watchers: O(1)</dt>
2416 <dd>
2417 <p>These just add the watcher into an array or at the head of a list.
2191 <dt>Stopping check/prepare/idle watchers: O(1)</dt> 2418=item Stopping check/prepare/idle watchers: O(1)</p>
2419 </dd>
2192 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt> 2420 <dt>Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))</dt>
2421 <dd>
2422 <p>These watchers are stored in lists then need to be walked to find the
2423correct watcher to remove. The lists are usually short (you don't usually
2424have many watchers waiting for the same fd or signal).</p>
2425 </dd>
2193 <dt>Finding the next timer per loop iteration: O(1)</dt> 2426 <dt>Finding the next timer per loop iteration: O(1)</dt>
2194 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt> 2427 <dt>Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)</dt>
2428 <dd>
2429 <p>A change means an I/O watcher gets started or stopped, which requires
2430libev to recalculate its status (and possibly tell the kernel).</p>
2431 </dd>
2195 <dt>Activating one watcher: O(1)</dt> 2432 <dt>Activating one watcher: O(1)</dt>
2433 <dt>Priority handling: O(number_of_priorities)</dt>
2434 <dd>
2435 <p>Priorities are implemented by allocating some space for each
2436priority. When doing priority-based operations, libev usually has to
2437linearly search all the priorities.</p>
2438 </dd>
2196 </dl> 2439 </dl>
2197 </p> 2440 </p>
2198 2441
2199 2442
2200 2443

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